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  • 51. Lodge, Andrew W.
    et al.
    Lacey, Matthew J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Fitt, Matthew
    Garcia-Araez, Nuria
    Owen, John R.
    Critical appraisal on the role of catalysts for the oxygen reduction reaction in lithium-oxygen batteries2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 140, p. 168-173Article in journal (Refereed)
    Abstract [en]

    This work reports a detailed characterization of the reduction of oxygen in pyrrolidinium-based ionic liquids for application to lithium-oxygen batteries. It is found that, in the absence of Li+, all electron transfer kinetics are fast, and therefore, the reactions are limited by the mass transport rate. Reversible reduction of O-2 to O-2(center dot-) and O-2(center dot-) to O-2(2-) take place at E-0 = 2.1 V and 0.8 V vs. Li+/Li, respectively. In the presence of Li+, O-2 is reduced to LiO2 first and then to Li2O2. The solubility product constant of Li2O2 is found to be around 10(-51), corroborating the hypothesis that electrode passivation by Li2O2 deposition is an important issue that limits the capacity delivered by lithium-oxygen batteries. Enhancing the rate of Li2O2 formation by using different electrode materials would probably lead to faster electrode passivation and hence smaller charge due to oxygen reduction (smaller capacity of the battery). On the contrary, soluble redox catalysts can not only increase the reaction rate of Li2O2 formation but also avoid electrode passivation since the fast diffusion of the soluble redox catalyst would displace the formation of Li2O2 at a sufficient distance from the electrode surface.

  • 52.
    Maher, Kenza
    et al.
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Saadoune, Ismael
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Mansori, Mohammed
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Synthesis and characterization of carbon-coated Li0.5Ni0.25TiOPO4 anode material2009In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, no 23, p. 5531-5536Article, review/survey (Refereed)
    Abstract [en]

    Li0.5Ni0.25TiOPO4/C composite was synthesized by the co-precipitation method using polyethylene glycol as carbon source. X-ray diffraction study showed that the as-prepared material crystallizes in the monoclinic system (S.G. P21/c). This 3D structure exhibits an open framework favourable to intercalation reactions. The morphology and the microstructure characterisation was performed by scanning electron microscopy (SEM). Small particles (1 μm) coated by carbon were observed. Raman study confirms the presence of carbon graphite in the Li0.5Ni0.25TiOPO4/C composite. Cyclic voltammetry (CV) and charge–discharge galvanostatic cycling were used to characterize its electrochemical properties. The Li0.5Ni0.25TiOPO4/C composite exhibits excellent electrochemical performances with good capacity retention for 50 cycles. Approximately 200 mAh/g could be reached at C, C/2, C/5 and C/20 rates in the 0.5–3 V potential range. These results clearly evidenced the positive effect of the carbon coating on the electrochemical properties of the studied phosphate.

  • 53.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ciosek, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin für Materialien und Energie GmbH.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Comparing anode and cathode electrode/electrolyte interface composition and morphology using soft and hard X-ray photoelectron spectroscopy2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 97, p. 23-32Article in journal (Refereed)
    Abstract [en]

    Electrode/electrolyte interface depth profiling was performed on lithiated graphite and delithiated lithium iron phosphate electrodes after electrochemical cycling in a balanced full cell configuration containing a carbonate based LiPF6 electrolyte. The profiling was performed by synchrotron radiation based hard X‑ray photoelectron spectroscopy, HAXPES, and soft X‑ray photoelectron spectroscopy, SOXPES. In this way, the probing depth was varied over a wide range in the order of 2-50 nm. Both more surface and more bulk sensitive investigations than possible using traditional in-house X‑ray photoelectron spectroscopy (XPS) could thus be performed. The composition and morphology of the lithiated graphite anode/electrolyte interface (solid electrolyte interphase, SEI) and the delithiated lithium iron phosphate cathode/electrolyte interface (solid permeable interface, SPI) were compared. In the vicinity of the highly reductive graphite active material in the SEI, low binding energy components like Li2O were found while no obvious composition gradients were observed in the SPI. Both in the cathode SPI and the anode SEI, significant amounts of C-O and P‑F containing compounds were found to deposit during cycling. Evidence for mixing of the porous binder and other SEI/SPI components was observed in both the anode and cathode electrode/electrolyte interfaces. The lithiated graphite SEI was estimated to be of the order of two tens of nanometers, while the cathode SPI thickness was estimated to a few nanometers only. 

  • 54.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ciosek, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kühn, Julius
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Consequences of Air Exposure on the Lithiated Graphite SEI2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 105, p. 83-91Article in journal (Refereed)
    Abstract [en]

    In the present work, consequences of air exposure on the surface composition of one of the most reactive lithium-ion battery components, the lithiated graphite, was investigated using 280–835 eV soft X-ray photoelectron spectroscopy (SOXPES) as well as 1486.7 eV X-ray photoelectron spectroscopy (XPS) (∼2 and ∼10 nm probing depth, respectively). Different depth regions of the solid electrolyte interphase (SEI) of graphite cycled vs. LiFePO4 were thereby examined. Furthermore, the air sensitivity of samples subject to four different combinations of pre-treatments (washed/unwashed and exposed to air before or after vacuum treatment) was explored. The samples showed important changes after exposure to air, which were found to be largely dependent on sample pre-treatment. Changes after exposure of unwashed samples exposed before vacuum treatment were attributed to reactions involving volatile species. On washed, air exposed samples, as well as unwashed samples exposed after vacuum treatment, effects attributed to lithium hydroxide formation in the innermost SEI were observed and suggested to be associated with partial delithiation of the surface region of the lithiated graphite electrode. Moreover, effects that can be attributed to LiPF6 decomposition were observed. However, these effects were less pronounced than those attributed to reactions involving solvent species and the lithiated graphite.

  • 55.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ciosek, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kühn, Julius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Consequences of air exposure on the lithiated graphite SEI2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 105, p. 83-91Article in journal (Refereed)
    Abstract [en]

    In the present work, consequences of air exposure on the surface composition of one of the most reactive lithium-ion battery components, the lithiated graphite, was investigated using 280-835 eV soft X-ray photoelectron spectroscopy (SOXPES) as well as 1486.7 eV X-ray photoelectron spectroscopy (XPS) (similar to 2 and similar to 10 nm probing depth, respectively). Different depth regions of the solid electrolyte interphase (SEI) of graphite cycled vs. LiFePO4 were thereby examined. Furthermore, the air sensitivity of samples subject to four different combinations of pre-treatments (washed/unwashed and exposed to air before or after vacuum treatment) was explored. The samples showed important changes after exposure to air, which were found to be largely dependent on sample pre-treatment. Changes after exposure of unwashed samples exposed before vacuum treatment were attributed to reactions involving volatile species. On washed, air exposed samples, as well as unwashed samples exposed after vacuum treatment, effects attributed to lithium hydroxide formation in the innermost SEI were observed and suggested to be associated with partial delithiation of the surface region of the lithiated graphite electrode. Moreover, effects that can be attributed to LiPF6 decomposition were observed. However, these effects were less pronounced than those attributed to reactions involving solvent species and the lithiated graphite. 

  • 56.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Green, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Anomalous diffusion of ions in electrochromic tungsten oxide films2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 247, p. 252-257Article in journal (Refereed)
    Abstract [en]

    Amorphous tungsten oxide thinfilms were deposited by sputtering at different O2/Ar ratios onto conducting substrates. Ion intercalation and diffusion in thefilms was studied by electrochemical impedance spectroscopy measurements in the frequency range 10 mHz–100 kHz and for potentials between 1.0 and 3.2 V vs. Li/Li+, using the film as working electrode in a Li+ containing electrolyte. The impedance data were in very good agreement with anomalous diffusion models. Different models were found to be applicable at potentials >1.8 V and <1.8 V. At high potentials ion intercalation was found to be reversible and an anomalous diffusion model describing ion hopping was favored. At low potentials ion intercalation was found to be irreversible and ion trapping takes place. In this latter range an anomalous diffusion model for the case of non-conserved number of charge carriers gave the best fit to experimentaldata. We obtained potential dependent diffusion coefficients in the range from 109 to 1011cm2/s, and anomalous diffusion exponents in the range 0.1 to 0.4, with the films deposited at lower O2/Ar ratios exhibiting the higher values.

  • 57.
    Mindemark, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Imholt, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Synthesis of high molecular flexibility polycarbonates for solid polymer electrolytes2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 175, p. 247-253Article in journal (Refereed)
    Abstract [en]

    A new self-plasticizing aliphatic polycarbonate comprising flexible alkyl and alkyl ether side groups was designed and synthesized from six-membered cyclic carbonate monomers with the aim of producing a material with high molecular flexibility (low T-g)and concomitant high ionic conductivity when used as a polymer electrolyte. The T-g of the novel polycarbonate was determined to be -49.4 degrees C at a molecular weight of 34 400 g mol(-1), which is the lowest reported T-g to date for a substituted poly(trimethylene carbonate). UV-crosslinked polymer electrolytes were produced based on this novel material together with LiTFSI salt and showed ionic conductivities in the range of 2 x 10(-8) to 2 x 10(-7) S cm(-1) at room temperature and 1 x 10(-6) to 1 x 10(-5) S cm(-1) at 100 degrees C. The limited ionic conductivities of these electrolytes indicate that high molecular flexibility alone does not guarantee fast ion transport in solid polymer electrolytes and that other factors, such as the polarity of the polymer host material, will also influence the transport properties of the electrolyte.

  • 58.
    Mindemark, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sobkowiak, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Oltean, Gabriel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mechanical Stabilization of Solid Polymer Electrolytes through Gamma Irradiation2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 230, p. 189-195Article in journal (Refereed)
    Abstract [en]

    Attaining sufficient mechanical stability is a challenge for high-performance solid polymer electrolytes, particularly at elevated temperatures. We have here characterized the viscoelastic properties of the nonpolyether host material poly(epsilon-caprolactone-co-trimethylene carbonate) with and without incorporated LiTFSI salt. While this electrolyte material performs well at room temperature, at 80 degrees C the material is prone to viscous flow. Through gamma-irradiation at a dose of 25 kGy, the material stabilizes such that it behaves as a rubbery solid even at low rates of deformation while retaining a high ionic conductivity necessary for use in solid-state Li batteries. The performance of the irradiated electrolyte was investigated in Li polymer half-cells (Li vs. LiFePO4) at both 80 degrees C and room temperature. In Contrast with the notably stable battery performance at low temperatures using the non-irradiated material, during cycling of the irradiated electrolytes detrimental instabilities were noted at both 80 degrees C and room temperature. The possible effects of both radiation damage to the electrolyte and impaired interfacial contacts due to the crosslinking indicate that a different procedure may be necessary in order to stabilize these electrolytes for use in battery cells capable of stable long-term operation.

  • 59.
    Mogensen, Ronnie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brant, William R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Evolution of the solid electrolyte interphase on tin phosphide anodes in sodium ion batteries probed by hard x-ray photoelectron spectroscopy2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 245, p. 696-704Article in journal (Refereed)
    Abstract [en]

    In this work the high capacity anode material Sn4P3 for sodium ion batteries is investigated by electrochemical cycling and synchrotron-based hard x-ray photoelectron spectroscopy (HAXPES) in order to elucidate the solid electrolyte interphase (SEI) properties during the first 1.5 cycles. The electrochemical properties of tin phosphide (Sn4P3) when used as an anode material are first established in half cells versus metallic sodium in a 1 M NaFSI in EC: DEC electrolyte including 5 vol% FEC as SEI forming additive. The data from these experiments are then used to select the parameters for the samples to be analysed by HAXPES. A concise series of five cycled samples, as well as a soaked and pristine sample, were measured at different states of sodiation after the initial sodiation and after the following full cycle of sodiation and desodiation. Our results indicate that the SEI is not fully stable, as both significant thickness and composition changes are detected during cell cycling. (C) 2017 Elsevier Ltd. All rights reserved.

  • 60.
    Morcrette, M.
    et al.
    LRCS, Université de Picardie, France.
    Larcher, D.
    LRCS Université de Picardie, France.
    Tarascon, J.M.
    LRCS Université de Picardie Amiens France.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Vaughey, J.T.
    Argonne National Laboratory, US.
    Thackeray, M.M.
    Argonne National Laboratory US.
    Influence of electrode microstructure on the reactivity of Cu2Sb with lithium2007In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, no 17, p. 5339-5345Article in journal (Refereed)
    Abstract [en]

    The reactivity of lithium with Cu2Sb was recently described to be governed by displacement reactions of Cu similar to those occurring in Cu2.33V4O11. In order to complement the earlier work of Fransson et al., we have revisited the electrochemical reactivity of Cu2Sb with Li. Through a different arsenal of characterization techniques, we have emphasized the role of the particle size, electrode preparation and temperature on the reversibility of the electrochemical reaction. We have demonstrated that the structural reversibility of the Cu2Sb electrode can be obtained in two special cases: (1) when the particle size of Cu2Sb is small and when the powders are ball milled with carbon and (2) when Li2CuSb is used as the starting material and some Sb is lost from the electrode during charge.

  • 61.
    Nyström, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Rapid Potential Step Charging of Paper-based Polypyrrole Energy Storage Devices2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 70, p. 91-97Article in journal (Refereed)
    Abstract [en]

    Symmetric paper-based supercapacitor devices containing polypyrrole (PPy)-cellulose composite electrodes and aqueous electrolytes can be charged using either potential step or constant current charging. Potential step charging provides better control of the charging and can result in significantly shorter charging times, enabling charging in 22s for devices with cell capacitances of 12.2F when charged to 0.8 V. The paper-based electrode material was compatible with charging currents as large as 5.9 A g(-1) due to the rapid counter ion mass transport resulting from the porous composite structure and the thin PPy coatings. The charging times were controlled by the RC time constants of the devices and the cell resistance was found to decrease with increasing electrode area. For small cells, the cell resistance was determined to a large extent by the electrolyte resistance and contact resistances, whereas the resistance of the current collectors dominated for larger cells. The specific cell capacitance was 38.3 F g(-1) or 2.1 F cm(-2), normalized with respect to the total electrode weight and electrode cross section area respectively, and the devices showed 80-90% capacitance retention after 10 000 potential step charge and discharge cycles. These results, which demonstrate that potential step charging can be advantageous for conducting polymer based energy storage devices, are very encouraging for the development of new up-scalable paper-based energy storage devices.

  • 62.
    Oltean, Gabriel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Galvanostatic electrodeposition of aluminium nano-rods for Li-ion three-dimensional micro-battery current collectors2011In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, no 9, p. 3203-3208Article in journal (Refereed)
    Abstract [en]

    Constant current and pulsed current electrodeposition of aluminium nano-rods, for use as three-dimensional (3D) Li-ion micro-battery current collectors, have been studied using an ionic liquid electrolyte (1-ethyl-3-methylimidazolium chloride/aluminium chloride) and a template consisting of a commercial alumina membrane. It is shown that the homogeneity of the height of the rods can be improved significantly by inclusion of a short (i.e. 50 ms) potential pulse prior to the controlled current deposition step. The latter potential step increased the number of aluminium nuclei on the aluminium substrate and the best results were obtained for a potential of -0.9 V vs. Al/Al3+. The obtained nanostructured surfaces, which were characterized using electron microscopy and X-ray diffraction, consisted of parallel aligned aluminium nano-rods homogeneously distributed over the entire surface of the substrate. A narrower height distribution for the rods was obtained using a pulsed galvanostatic approach then when using a constant current, most likely due to the less favourable diffusion conditions in the latter case. The results also indicate that depletion and iR drop effects within the nano-pores result in a more homogeneous height distribution. It is concluded that the height distribution of the nano-rods is controlled by a combination of the nucleation probability in each pore at the start of the experiment, and the homogeneity of the diameters of the pores within the commercial alumina membranes employed as the electrodeposition template.

  • 63.
    Pazoki, Meysam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Stark effects in D35-sensitized mesoporous TiO2: influence of dye coverage and electrolyte composition2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, p. 174-178Article in journal (Refereed)
    Abstract [en]

    Strong Stark effects are visible in the spectra of the organic donor-pi-acceptor dye D35 when it is adsorbed onto mesoporous TiO2, both under steady state conditions and under modulated light conditions. The addition of lithium cations to the electrolyte results in a significant red shift of the D35 absorption spectrum, which is attributed to adsorption of Li+ at the TiO2 surface, resulting in a change of the electric field across the adsorbed dye molecules. The dye molecules must therefore be located inside the Helmholtz double layer at the TiO2/electrolyte interface. In photoinduced absorption (PIA) spectroscopy, modulated light is used to excite dye molecules. A significant Stark bleach is found in PIA spectra, which corresponds to a blue shift of the dye absorption spectrum upon addition of electrons to TiO2, due to an electric field across the dye monolayer. The observed bleach is reduced when the concentration of supporting electrolyte is increased, indicating local charge compensation of the electrons in TiO2 by adsorbed cations. Transient absorption studies reveal that screening of the interfacial electric field is faster at lower dye coverage compared to full monolayer coverage. Analysis of the Stark effect in dye-sensitized solar cell gives valuable information on the mechanism of charge compensation of electrons in mesoporous electrodes.

  • 64.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mahmoud, Abdelfattah
    Ledeuil, Jean-Bernard
    Chamas, Mohamad
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Dedryvère, Rémi
    Gonbeau, Danielle
    Université de Pau, France.
    Lippens, Pierre-Emmanuel
    MnSn2 electrodes for Li-ion batteries: Mechanisms at the nano scale and electrode/electrolyte interface2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 123, p. 72-83Article in journal (Refereed)
    Abstract [en]

    We have investigated the reaction mechanisms occurring upon the first discharge/charge cycle of a MnSn2//Li electrochemical cell, by using bulk- and surface-sensitive characterization techniques (Xray Diffraction, Sn-119 Mossbauer spectroscopy, magnetic measurements, X-ray photoelectron and Auger spectroscopies). Compared to other tin-transition metal alloys, MnSn2 displays an original behaviour. Lithium insertion into MnSn2 particles results in a nanocomposite consisting of Li7Sn2 phase, and of Mn nanoparticles which are immediately oxidized at their surface. Lithium extraction from this nanocomposite leads to the formation of magnetic MnSn2 particles and to our knowledge it is the first time such a mechanism is observed in tin-based intermetallic electrode materials due to electrochemical reaction with Li. The solid electrolyte interphase (SEI) is formed at the beginning of the first discharge and its thickness slightly increases upon further lithium insertion. A partial re-dissolution process occurs upon lithium extraction from the material, while its chemical composition is very stable over the whole cycle.

  • 65.
    Priimagi, Priit
    et al.
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia.
    Asfaw, Habtom Desta
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Srivastav, Shruti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kasemagi, Heiki
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia.
    Aabloo, Alvo
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Zadin, Vahur
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia.
    Modeling 3D-microbatteries based on carbon foams2018In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 281, p. 665-675Article in journal (Refereed)
    Abstract [en]

    Porous electrodes are considered attractive for potential use as 3D current collectors in Li-ion microbatteries. Carbon foams, in particular, can be coated with a variety of active materials to prepare electrodes which can maximize energy and power density simultaneously. Modeling such electrodes will aid the selection of microstructural parameters (e.g. porosity) required to optimize their electrochemical performance. Here, experimentally-validated Finite Element Methodology (FEM) is used to simulate a 3D Li-ion microbattery featuring a carbon foam electrode coated by layers of LiFePO4 nanoparticles. The electrodes are cycled against Li-metal at various current densities, and the electrochemical data obtained are used to benchmark and parametrize the simulations. By systematic variation of the LiFePO4 coating thickness and homogeneity and the foam substrate, it is revealed that LiFePO4 exhibits a uniform delithiation process and that the electrochemical reactions favor particles closer to the carbon structure, which is due to the poor electrical conductivity of LiFePO4. Therefore, the cell capacity (mAh cm(-2)) per footprint area can be increased by using lower charging currents, smaller carbon macropore sizes and thicker LiFePO4 coatings. The porous carbon structure provides an excellent template for loadings of LiFePO4 material, which in turn allows using thicker coatings with improved cell performance.

  • 66.
    Priimagi, Priit
    et al.
    Univ Tartu, Inst Technol, Nooruse 1, EE-50411 Tartu, Estonia..
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Srivastav, Shruti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Aabloo, Alvo
    Univ Tartu, Inst Technol, Nooruse 1, EE-50411 Tartu, Estonia..
    Kasemagi, Heiki
    Univ Tartu, Inst Technol, Nooruse 1, EE-50411 Tartu, Estonia..
    Zadin, Vahur
    Univ Tartu, Inst Technol, Nooruse 1, EE-50411 Tartu, Estonia..
    Optimizing the design of 3D-pillar microbatteries using finite element modelling2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 209, p. 138-148Article in journal (Refereed)
    Abstract [en]

    We here present finite element methodology simulations of current distribution, materials utilization and electrochemical cell behavior of a rechargeable Li-ion three dimensional microbattery (3D MB) with 'concentric' architecture, i.e., with one electrode material deposited through filling a 3D structured pillar template of the other electrode. The electrode materials modelled are LiCoO2 and lithiated graphite, respectively, where thin films of LiCoO2 are coated onto 3D-structured current collectors. Time dependent simulations of a range of template pillar heights (h) and interpillar distances (d) have been performed, and the ionic conduction pathways resulting from the different 3D MB concentric architecture design are analyzed. The dynamics of the discharge curves, Li-ion concentration and concentration gradient for each cell design are compared between the different structures and put into context of the state of charge in the electrodes during one full charge/discharge cycle. It is shown that the architecture with the shortest interpillar distance (d = 10 mu m) provides higher capacity per footprint area without displaying underutilization of the active material. Higher pillars, on the other hand, result in higher areal capacity, and an optimum height is considered to be ca. 70 mu m by balancing the active material utilization in the electrodes and the effective battery volumetric usage. Moreover, it is shown that there are significant differences in terms of cell capacity and power capabilities depending on if the anode or the cathode is coated onto the pillar current collectors.

  • 67.
    Priimagi, Priit
    et al.
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia..
    Kasemagi, Heiki
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia..
    Aabloo, Alvo
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia..
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Zadin, Vahur
    Univ Tartu, Inst Technol, IMS Lab, Nooruse 1, EE-50411 Tartu, Estonia..
    Thermal Simulations of Polymer Electrolyte 3D Li-Microbatteries2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 244, p. 129-138Article in journal (Refereed)
    Abstract [en]

    High charge and discharge rates are desired properties for Li-ion batteries of both macro- and micro-scale (i.e. a footprint area of < 1 mm(2)). Under these conditions, a rise of the cell temperature can take place, leading to performance limitations and safety issues. Investigations of thermal effects in battery cells provide possible explanations of the limiting factors of cell performance and can suggest improvements. We present here extensive simulations with a fully coupled 3D thermal-electrochemical model of 3D microbatteries (3D-MBs) using Finite Element Methodology (FEM). 3D-MB architectures comprising pillar shaped, plate shaped and concentric electrode arrangements are simulated, using LiCoO2 and graphite as electrodes and solid polymer electrolytes with LiTFSI salt. Sensitivity analysis of the electrolyte diffusion coefficient, depending on the C-rate, is used to benchmark the performance of these 3D-MB cells. FEM simulations of the 3D-MB during operation provide a complete 3D time-dependent description of the thermal behavior of the cells. Temperature gradients in the cell highlight critical regions which are likely causing performance bottlenecks and safety hazards. The simulations clearly demonstrate that the highest heat sources appear near the regions with most active charge transfer processes, thereby providing insights for optimization of the cell geometry in terms of both performance and safety.

  • 68. Protopapa, Elisabeth
    et al.
    Ringstad, Lovisa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Aggeli, Amalia
    Nelson, Andrew
    Interaction of self-assembling beta-sheet peptides with phospholipid monolayers: The effect of serine, threonine, glutamine and asparagine amino acid side chains2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 9, p. 3368-3375Article in journal (Refereed)
    Abstract [en]

    The dioleoyl phosphatidylcholine (DOPC) monolayer activities of 11 systematically altered 11 residue beta-sheet tape-forming peptides were studied. Peptide-DOPC interactions were characterised by electrochemical impedance spectroscopy (EIS). An impedance model combining the constant phase element approach with dielectric relaxation in the surface layer was used to analyse the data. The facilitation of DOPC layer permeability to ions by the peptides was monitored by both EIS and the Tl(l)/Tl(Hg) and Cd(II)/Cd(Hg)faradaic reactions. It was found that peptides with side chains of serine and threonine interact with DOPC layers more strongly and in a well characterised manner compared to peptides with side chains of glutamine and asparagine. Cationic and neutral peptides containing serine and threonine penetrate the DOPC to give a maximum plateau monolayer capacitance. At higher solution concentrations of these peptides the growth of a well-defined secondary element in the impedance data indicates the segregation of secondary DOPC-peptide phases. Cationic and neutral peptides containing serine and anionic peptides containing threonine interact with the DOPC layers leading to a selective increase in the layer's permeability to Tl+ ions. Impedance measurements at higher solution concentrations of anionic peptides with serine and threonine show that these peptide modified DOPC layers associate with electrolyte ions. (C) 2010 Elsevier Ltd. All rights reserved.

  • 69.
    Schmidt, Ina
    et al.
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Plettenberg, Inka
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Kimmich, Daniel
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Ellis, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Witt, Julia
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Dosche, Carsten
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Wittstock, Gunther
    Carl von Ossietzky Univ Oldenburg, Fac Math & Sci, Ctr Interface Sci, Inst Chem, D-26111 Oldenburg, Germany..
    Spatially Resolved Analysis of Screen Printed Photoanodes of Dye-Sensitized Solar Cells by Scanning Electrochemical Microscopy2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 222, p. 735-746Article in journal (Refereed)
    Abstract [en]

    Different approaches are compared for imaging local differences in the performance of nanostructured dye-sensitized solar cells (DSCs) using scanning electrochemical microscopy (SECM). The DSCs were fabricated from TiO2 and the triphenylamine dye (E)-3-(5-(4-(bis(2',4'-dibutoxy-[1,1'-biphenyl]-4-yl) amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid, called D35. The components of the redox electrolytes cobalt trisbipyridine ([Co(bpy)(3)](3+/2+)) and iodide/triiodide (I-/I-3(-)) were used as SECM mediators. Imaging was performed by the feedback (FB) mode and the substrate-generation/tip collection (SG/TC) mode of SECM with additional options of local and temporal illumination. In FB mode, the SECM microelectrode (ME) reduces the mediator which is re-oxidized at the illuminated photoanode. In the SG/TC mode, the reduced form of the mediator is oxidized at the photoanode and the oxidized form is detected at the ME. It is expected that the SG/TC is more sensitive than the FB mode but provides lower lateral resolution. However, imaging is complicated by the strong light scattering in the nanoporous photoanode and the long residence time of charge carriers under the conditions of SECM imaging with low mediator concentrations. This prevents approaches based on local illumination or temporal illumination. Using shear force SECM (SF-SECM) in the FB mode, local differences in the morphology and performance of screen-printed photoanodes could be resolved that resulted from screen printing process. The morphological variations are also corroborated by scanning force microscopy and optical phase contrast microscopy. Furthermore, isolated irregularities were detected in which morphology and local performance were not correlated.

  • 70.
    Scipioni, Roberto
    et al.
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark;Northwestern Univ, Dept Mat Sci & Engn, 2220 Campus Dr, Evanston, IL 60208 USA.
    Jorgensen, Peter S.
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Stroe, Daniel I.
    Aalborg Univ, Dept Energy Technol, Fredrik Bajers Vej 5, DK-9100 Aalborg, Denmark.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Simonsen, Soren B.
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Norby, Poul
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Hjelm, Johan
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Jensen, Soren H.
    Tech Univ Denmark, Dept Energy Convers & Storage, DTU Energy, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
    Complementary analyses of aging in a commercial LiFePO4/graphite 26650 cell2018In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 284, p. 454-468Article in journal (Refereed)
    Abstract [en]

    In this work we investigate the electrode degradation mechanisms in a commercial 2.5 Ah LiFePO4/ graphite 26650 cylindrical cell. Aged and fresh electrode samples were prepared by cycling two cells respectively five and 22 k times. Subsequently the cells were disassembled in a glovebox and the electrode samples were prepared for electrochemical testing in a 3-electrode setup, and for characterization with XRD, XPS and low-kV FIB/SEM tomography. A 1 mu m thick CEI (cathode electrolyte interface) layer was observed at the electrode/electrolyte interface of the aged LiFePO4 electrode. Relative to the fresh LiFePO4 electrode, the aged electrode exhibited a larger series resistance which indicates the observed degradation layer increases the ionic resistance. In addition, micron-sized agglomerates, probably a mixture of carbonaceous material and decomposition products from the electrolyte, were observed at the electrode/electrolyte interface of the aged graphite electrode. These layers may contribute significantly to the loss of lithium inventory (LLI) in the cell, and to the loss of active material (LAM) in the graphite electrode. Low-voltage FIB/SEM tomography was used to detect local charging effects of graphite particles in the carbon electrode, an effect of poor dissipation of the electric charge to the ground after the sample interaction with the electron beam. The charging effects were primarily observed in the aged electrode and most of the locally charged particles were found to be close to the electrode/electrolyte interface, indicating a poorly percolating graphite network near this interface.

  • 71. Soolo, Endel
    et al.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Liivat, Anti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Kasemagi, Heiki
    Tamm, Tarmo
    Aabloo, Alvo
    Force field generation and molecular dynamics simulations of Li+-Nafion2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 8, p. 2587-2591Article in journal (Refereed)
    Abstract [en]

    A new molecular dynamics force field for Nafion (R) containing Li+ ions has been generated using Density Functional Theory calculations (B3LYP) on a Nafion side-chain, a Li+ ion and a H2O molecule. The depth of the potential energy well between Li+ and the sulphonate group was decreased with similar to 10 kcal/mol and the optimal Li-S distance 0.5 angstrom shorter, as compared to force fields generated without water present. Molecular dynamics simulations based on the new force field result in a self-diffusion coefficient for Li+ of 8.0 x 10(-8) cm(2)/s at 353 K, which is closer to experimental result than previous simulations using force fields based on pure Nation-cation interactions.

  • 72.
    Srivastav, Shruti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tammela, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Understanding Ionic Transport in Polypyrrole/Nanocellulose Composite Energy Storage Devices2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 182, p. 1145-1152Article in journal (Refereed)
    Abstract [en]

    Abstract In this work, we aim to resolve different diffusion processes in polypyrrole/cellulose composites using a combination of impedance spectroscopy and finite element simulations. The computational model involves a coupled system of Ohm's law and Fickian diffusion to model electrode kinetics, non-linear boundary interactions at the electrode interfaces and ion transport inside the porous electrodes, thereby generating the impedance response. Composite electrodes are prepared via chemical polymerization of pyrrole on the surface of a nanocellulose fiber matrix, and the electrochemical properties are investigated experimentally using cyclic voltammetry, impedance spectroscopy and galvanostatic cycling. It is demonstrated that the onset frequency of the capacitive (or pseudocapacitive) process depends on the counter ion electrolyte diffusion, which is modulated by adding different amounts of sucrose to the aqueous electrolyte solution. Consequently, the electrochemical properties can be controlled by diffusion processes occurring at different length scales, and the critical diffusion processes can be resolved. It is shown that under normal operating conditions, the limiting process for charge transport in the device is diffusion within the electrolyte filled pores of the composite electrode.

  • 73.
    Srivastav, Shruti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Xu, Chao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Modelling the morphological background to capacity fade in Si-based lithium-ion batteries2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 258, p. 755-763Article in journal (Refereed)
    Abstract [en]

    Understanding the fundamental processes at the electrode/electrolyte interface during charge and discharge will aid the development of high-capacity Li-ion batteries (LIBs) with long lifetimes. Finite Element Methodology studies are here used to investigate the interplay between morphological changes and electrochemical performance in Si negative electrodes. A one-dimensional battery model including Solid Electrolyte Interphase (SEI) layer growth is constructed for porous Si electrodes in half-cells and used for simulating electrochemical impedance response during charge and discharge cycles. The computational results are then compared with experimental investigations. The SEI layer from the electrolyte decomposition products, different depending on the presence or absence of the fluoroethylene carbonate (FEC) additive, covers the electrode surface porous structure and is leading to an increasing polarization observed in the Nyquist plots during cycling. A continuous reformation of the SEI layer after each cycle can be observed, leading to consumption of Li-|. The electrolyte composition also results in a variation of electrode porosity, which affects the performance of the cell. A more stable porous network is formed when using the FEC additive, rendering a reduction in polarization due to improved Li diffusion inside the electrode composite.

  • 74.
    Sterby, Mia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Emanuelsson, Rikard
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Huang, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Characterization of PEDOT-Quinone Conducting Redox Polymers for Water Based Secondary Batteries2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 235, p. 356-364Article in journal (Refereed)
    Abstract [en]

    Lithium-ion technologies show great promise to meet the demands that the transition towards renewable energy sources and the electrification of the transport sector put forward. However, concerns regarding lithium-ion batteries, including limited material resources, high energy consumption during production, and flammable electrolytes, necessitate research on alternative technologies for electrochemical energy storage. Organic materials derived from abundant building blocks and with tunable properties, together with water based electrolytes, could provide safe, inexpensive and sustainable alternatives. In this study, two conducting redox polymers based on poly(3,4-ethylenedioxythiophene) (PEDOT) and a hydroquinone pendant group have been synthesized and characterized in an acidic aqueous electrolyte. The polymers were characterized with regards to kinetics, pH dependence, and mass changes during oxidation and reduction, as well as their conductance. Both polymers show redox matching, i.e. the quinone redox reaction occurs within the potential region where the polymer is conducting, and fast redox conversion that involves proton cycling during pendant group redox conversion. These properties make the presented materials promising candidates as electrode materials for water based all-organic batteries.

  • 75.
    Sterby, Mia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Emanuelsson, Rikard
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Investigating electron transport in a PEDOT/Quinone conducting redox polymer with in situ methods2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 308, p. 277-284Article in journal (Refereed)
    Abstract [en]

    A conducting redox polymer is investigated in acidic electrolyte using various in situ methods, including electron paramagnetic resonance (EPR), UV–vis spectroscopy, and conductance measurements. The quinone redox active pendant group has a formal potential of 0.67 V (vs. standard hydrogen electrode) where a 2e2H process occurs. By analyzing the rate constant at different temperatures, the rate-limiting step in the redox reaction was found to be a thermally activated process with an activation energy of 0.3 eV. The electron transport through the conducting polymerwas found to be non-thermally activated and, hence, not redox rate-limiting. This is also the first time a negative temperature dependence has been reported for a conducting redox polymer in the same potential region where the redox active pendant group has its formal potential. EPR and conductance data indicated that the conductivity is governed by both polarons and bipolarons but their ratio is shifting during oxidation and reduction of the polymer.

  • 76.
    Stjerndahl, Mårten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Bryngelsson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Vaughey, John T.
    Thackeray, Michael M.
    Argonne National Laboratory, US.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Surface chemistry of intermetallic AlSb-anodes for Li-ion batteries2007In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, no 15, p. 4947-4955Article in journal (Refereed)
    Abstract [en]

    The solid electrolyte interphase (SEI) layer on AlSb electrodes has been studied in Li/AlSb cells containing a LiPF6 EC/DEC electrolyte using X-ray photoelectron spectroscopy (XPS). Data were collected before SEI-formation, during formation, and after formation at 0.01 V versus Li0/Li+, and at full delithiation in cycled cells at 1.20 V. The thickness of the SEI layer increases during lithiation and decreases during delithiation. This dynamic behaviour occurs continuously on cycling the cells. The growth of the SEI layer can be attributed predominantly to the deposition of carbonaceous species below 0.50 V versus Li0/Li+; these species disappear almost completely during delithiation. The extra surface-layer formation is a consequence of the additional charge that is needed to lithiate the remaining Sb component of the micrometer-sized AlSb particles at low potentials as seen by synchrotron-based X-ray diffraction. Aluminium is not reactive to lithium alloying in this electrolyte. Relatively small amounts of LiF were detected in the AlSb SEI layers compared to that commonly found in the SEI layers on graphite electrodes.

  • 77.
    Sun, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Rehnlund, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lacey, Matthew J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrodeposition of thin poly(propylene glycol) acrylate electrolytes on 3D-nanopillar electrodes2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 137, p. 320-327Article in journal (Refereed)
  • 78.
    Valvo, Mario
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Doubaji, S.
    Univ Cadi Ayyad, FST Marrakech, LCME, Av A Khattabi,BP 549, Marrakech 40000, Morocco.
    Saadoune, I.
    Univ Cadi Ayyad, FST Marrakech, LCME, Av A Khattabi,BP 549, Marrakech 40000, Morocco;Mohamed VI Polytech Univ, Mat Sci & Nanoengn Dept, Lot 660 Hay Moulay Rachid, Benguerir 43150, Morocco.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Pseudocapacitive charge storage properties of Na2/3Co2/3Mn2/9Ni1/9O2 in Na-ion batteries2018In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 276, p. 142-152Article in journal (Refereed)
    Abstract [en]

    The behaviour of Na2/3Co2/3Mn2/9Ni1/9O2 in composite electrodes is studied via Na half-cells utilizing a dedicated cyclic voltammetry approach. The application of increasing sweep rates enabled a detailed analysis of the red-ox peaks of this material. All peak currents due to cathodic/anodic processes demonstrated clear capacitive properties. This finding widens the picture of classical Na+ insertion/ extraction in this complex oxide, as purely diffusive processes of Na+ through its layers do not fully explain the pseudocapacitance displayed by its red-ox peaks, which are typically linked to concomitant oxidation state changes for its transition metal atoms and/or phase transitions. No phase transition was observed during in operando X-Ray diffraction upon charge to 4.2 V vs. Na+/Na, proving good structural stability for P2-NaxCo2/3Mn2/9Ni1/9O2 upon Na+ removal. The origin of such pseudocapacitive properties is likely nested in strong electrostatic interactions among the metal oxide slabs and a tendency to release Na+ from its crystallites, e.g. to form surface by-products upon air exposure. Such a reactivity induces defects (e.g. vacancies) in its lattice and charge compensation mechanisms are required to maintain an overall charge neutrality, thus ultimately influencing the electrochemical properties. Possible limiting factors for the performances of this compound in composite coatings are also discussed.

  • 79.
    Valvo, Mario
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Check-Wai, Tai
    Arrhenius Laboratory, Department of Materials and Environmental Chemistry, Stockholm.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Insight into the processes controlling the electrochemical reactions of nanostructured iron oxide electrodes in Li- and Na-half cells2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 194, p. 74-83Article in journal (Refereed)
    Abstract [en]

    The kinetics and the processes governing the electrochemical reactions of various types of iron oxide nanostructures (i.e., nanopowders, nanowires and thin-films) have been studied via cyclic voltammetry in parallel with Li- and Na-half cells containing analogous electrolytes (Li+/Na+, ClO4 in EC:DEC). The particular features arising from each electrode architecture are discussed and compared to shed light on the associated behaviour of the reacting nanostructured active materials. The influence of their characteristic structure, texture and electrical wiring on the overall conversion reaction upon their respective lithiation and sodiation has been analyzed carefully. The limiting factors existing for this reaction upon uptake of Li+ and Na+ ions are highlighted and the related issues in both systems are addressed. The results of this investigation clearly prove that the conversion of iron oxide into metallic Fe and Na2O is severely impeded compared to its analogous process upon lithiation, independently of the type of nanostructure involved in such reaction. The diffusion mechanisms of the different ions (i.e., Li+vs. Na+) through the phases formed upon conversion, as well as the influence of various interfaces on the resulting reaction, appear to pose further constraints on an efficient use of these compounds.

  • 80. Vlachopoulos, Nick
    et al.
    Nissfolk, Jarl
    Moeller, Martin
    Briancon, Alain
    Corr, David
    Grave, Christian
    Leyland, Nigel
    Mesmer, Ralf
    Pichot, Francois
    Ryan, Michael
    Boschloo, Gerrit
    KTH, Dept. of Chemistry.
    Hagfeldt, Anders
    KTH, Dept. of Chemistry.
    Electrochemical aspects of display technology based on nanostructured titanium dioxide with attached viologen chromophores2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, ISSN 0013-4686, Vol. 53, no 11, p. 4065-4071Article in journal (Refereed)
    Abstract [en]

    Progress in recent years in the field of electrochromic displays based on viologen modified high-surface area TiO2 electrodes (Vio(2+)/TiO2) has moved the technology towards commercialisation. Viologen molecules (Vio(2+)), derivatised with phosphonic acid attachment groups can be chemisorbed on nanostructured TiO2 layers of thickness 2-10 mu m. Characterisation by cyclic voltammetry, spectroelectrochemistry and impedance spectroscopy demonstrates that colourless Vio(2+)/TiO2 is reversibly reduced to the strongly coloured cation radical species Vio(+center dot)/TiO2. This system can constitute the working electrode of an electrochromic display with a capacitive doped SnO2 electrode as counter electrode, the latter coated by an electrochemically inert white fight-reflecting layer. Such a device is stable upon repeated colouration-bleaching cycles with a bleached-to-coloured state contrast ratio exceeding 5. Multicolour displays can be achieved by patterning different electrochromophores onto different areas of one working electrode. (C) 2007 Elsevier Ltd. All rights reserved.

  • 81.
    Wang, Baoyuan
    et al.
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.;Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Cai, Yixiao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden.
    Xia, Chen
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.;Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Kim, Jung-Sik
    Loughborough Univ Technol, Dept Aero & Auto Engn, Ashby Rd, Loughborough LE11 3TU, Leics, England..
    Liu, Yanyan
    Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Dong, Wenjing
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China..
    Wang, Hao
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China..
    Afzal, Muhammad
    Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Li, Junjiao
    Nanjing Yunna Nanotech Lth, Heyan Rd 271, Nanjing 210037, Jiangsu, Peoples R China..
    Raza, Rizwan
    COMSATS Inst Informat Technol, Dept Phys, Islamabad, Pakistan..
    Zhu, Bin
    Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.;Royal Inst Technol, Dept Energy Technol, SE-10044 Stockholm, Sweden..
    Semiconductor-ionic Membrane of LaSrCoFe-oxide-doped Ceria Solid Oxide Fuel Cells2017In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 248, p. 496-504Article in journal (Refereed)
    Abstract [en]

    A novel semiconductor-ionic La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF)-Sm/Ca co-doped CeO2 (SCDC) nanocomposite has been developed as a membrane, which is sandwiched between two layers of Ni0.8Co0.15Al0.05Li-oxide (NCAL) to construct semiconductor-ion membrane fuel cell (SIMFC). Such a device presented an open circuit voltage (OCV) above 1.0 V and maximum power density of 814 mW cm(-2) at 550 degrees C, which is much higher than 0.84 V and 300 mW cm(-2) for the fuel cell using the SCDC membrane. Moreover, the SIMFC has a relatively promising long-term stability, the voltage can maintain at 0.966 V for 60 hours without degradation during the fuel cells operation and the open-circuit voltage (OCV) can return to 1.06 V after long-term fuel cell operation. The introduction of LSCF electronic conductor into the membrane did not cause any short circuit but brought significant enhancement of fuel cell performances. The Schottky junction is proposed to prevent the internal electrons passing thus avoiding the device short circuiting problem.

  • 82.
    Wang, Yanan
    et al.
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Shi, Liyi
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Zhou, Hualan
    University of Shanghai for Science and Technology, School of Medical Instrument and Food Engineering, Shanghai.
    Wang, Zhuyi
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Li, Rui
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Zhu, Jiefang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Qiu, Zhengfu
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Zhao, Yin
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Zhang, Meihong
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Yuan, Shuai
    Shanghai University, Research Center of Nanoscience and Nanotechnology, Shanghai.
    Polyethylene separators modified by ultrathin hybrid films enhancing lithium ion transport performance and Li-metal anode stability2018In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 259, p. 386-394Article in journal (Refereed)
    Abstract [en]

    Poor stability of lithium metal anodes in liquid electrolytes hinders its practical application in rechargeable batteries with very high energy density. Herein, we present an approach to tackle the intrinsic problems of Li metal anodes from the standpoint of separators. By a facile and versatile method based on mussel-inspired surface chemistry, a hybrid polydopamine/octaammonium POSS (PDA/POSS) coating was spontaneously formed on the surface of PE separators through the self-polymerization and strong adhesion feature of dopamine. This ultrathin PDA/POSS coating endows PE separators with different surface characteristics while keeping its microporous structure almost unchanged. The altered surface characteristics influence the separator/electrolyte interaction, and lead to remarkable enhanced ionic conductivity (from 0.36 mS cm−1 to 0.45 mS cm−1) and Li+ ion transference number (from 0.37 to 0.47) of PE separators as well as the improved stability of lithium/electrolyte interface, which effectively decreases the electrode polarization and suppresses the lithium dendrites formation, contributing to superior C-rates capability and cycling performance of cells.

  • 83.
    Wei, Wei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, Angstrom Adv Battery Ctr, SE-75121 Uppsala, Sweden..
    Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 176, p. 1393-1402Article in journal (Refereed)
    Abstract [en]

    Well-defined TiO2 nanotube size gradient thin films, manufactured using a bipolar electrochemistry approach, can be used as versatile monolithic hybrid electrodes for energy storage devices. The nanotube size distribution within the gradients can readily be controlled by altering the bipolar current and/or the length of the bipolar titanium sheet. As the electrochemical properties of the gradient electrodes can be carefully tailored by modifying the nanotube size gradient, this approach provides new possibilities for the manufacturing of hybrid electrodes with integrated energy and power density gradients. The freestanding anatase TiO2 nanotube size gradient electrodes provide unprecedented capacities at cycling rates from C/5 (i.e. 162 mAh cm(-2) or 169 mAh g(-1)) to 50C (i.e. 40 mAh cm(-2) or 42 mAh g(-1)). It is likewise shown that the size gradient electrodes facilitate fundamental studies of the charge/discharge process of TiO2 based electrodes. The results demonstrate that the different shapes of charge and discharge curves of TiO2 nanotube electrode can be explained by inherent differences between the lithiation and delithiation processes.

  • 84.
    Yang, Li
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Huang, Hao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Gogoll, Adolf
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Conducting Redox Polymer Based Anode Materials for High Power Electrical Energy Storage2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 204, p. 270-275Article in journal (Refereed)
    Abstract [en]

    Abstract In this report we present the synthesis and characterization of two conducting redox polymers (CRPs) with polythiophene backbone and diethyl terephthalate pendant groups for the use as anode materials in secondary batteries. The materials show excellent rate capability allowing 30 ÎŒm layers to be fully converted within seconds without the use of conductive additives. The high rate capability is traced to the open morphology of the materials that allows for fast ion transport, and to the mediation of electrons through the conducting polymer (CP) backbone. The requirements for the latter are i) that the redox chemistry of the pendant groups and the CP backbone overlaps and ii) that the CP conductivity is not compromised by the presence of the pendant groups. In the CRPs presented herein both these requirements are met and this is thus the first report on successful combination of the redox chemistry of organic redox molecules with the n-doping of conducting polymers.

  • 85.
    Yang, Li
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Huang, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Conducting Redox Polymer Based Anode Materials for High Power Electrical Energy Storage2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 204, p. 270-275Article in journal (Refereed)
    Abstract [en]

    In this report we present the synthesis and characterization of two conducting redox polymers (CRPs) with polythiophene backbone and diethyl terephthalate pendant groups for the use as anode materials in secondary batteries. The materials show excellent rate capability allowing 301,Lm layers to be fully converted within seconds without the use of conductive additives. The high rate capability is traced to the open morphology of the materials that allows for fast ion transport, and to the mediation of electrons through the conducting polymer (CP) backbone. The requirements for the latter are i) that the redox chemistry of the pendant groups and the CP backbone overlaps and ii) that the CP conductivity is not compromised by the presence of the pendant groups. In the CRPs presented herein both these requirements are met and this is thus the first report on successful combination of the redox chemistry of organic redox molecules with the n-doping of conducting polymers.

  • 86.
    Yang, Li
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Huang, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Effect of the Linker in Terephthalate-Functionalized Conducting Redox Polymers2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 222, p. 149-155Article in journal (Refereed)
    Abstract [en]

    Abstract The combination of high capacity redox active pendent groups and conducting polymers, realized in conducting redox polymers (CRPs), provides materials with high charge storage capacity that are electronically conducting which makes CRPs attractive for electrical energy storage applications. In this report, six polythiophene and poly(3,4-ethylenedioxythiophene)(PEDOT)-based CRPs with a diethyl terephthalate unit covalently bound to the polymer chain by various linkers have been synthesized and characterized electrochemically. The effects of the choice of polymer backbone and of the nature of the link on the electrochemistry, and in particular the cycling stability of these polymers, are discussed. All CRPs show both the doping of the polymer backbone as well as the redox behavior of the pendent groups and the redox potential of the pendent groups in the CRPs is close to that of corresponding monomer, indicating insignificant interaction between the pendant and the polymer backbone. While all CRPs show various degrees of charge decay upon electrochemical redox conversion, the PEDOT-based CRPs show significantly improved stability compared to the polythiophene counterparts. Moreover, we show that by the right choice of link the cycling stability of diethyl terephthalate substituted PEDOT-based CRPs can be significantly improved.

  • 87.
    Yang, Wenxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ghamgosar, Pedram
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Lulea Univ Technol, Dept Engn Sci & Math, Lulea, Sweden..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Thermal Stability Study of Dye-Sensitized Solar Cells with Cobalt Bipyridyl-based Electrolytes2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 213, p. 879-886Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSSCs) with cobalt bipyridyl-based electrolytes can display higher solar cell performance than their iodide/triiodide counterpart. There is, however, little knowledge on their long term stability, which is a crucial aspect for potential commercial application. Herein, we studied the thermal stability of DSSCs using Co(bpy)(3)(2+/3+) redox electrolyte at 70 degrees C in the dark for 50 days, combining 3 different additives, 4-tert-butylpyridine (TBP), 1-methylimidazole (MBI) and 2,2'-bipyridyl (BPY), in a nonvolatile solvent 3-methoxypropionitrile (MPN). Significant voltage decreases were found for all the studied solar cells, with a mechanism involving both a positive shift of the conduction band edge potential of TiO2 and a decreased electron lifetime, characterized by time resolved transient modulation techniques. Furthermore electrochemical impedance spectroscopy and differential pulse voltammetry studies indicate that the stability of Co(bpy)(3)(3+) is limited, causing an increased diffusion resistance in the electrolyte, but, surprisingly, no substantial change of the short-circuit current density (Jsc) in the devices. Overall, the DSSCs fabricated with the addition of both MBI and BPY in the electrolyte show the highest stability, maintaining 96% of its initial efficiency after 50 days, resulting from the overall compensation effects between the open circuit voltage decrease and the Jsc increase. These results provide insights about the degradation mechanism and emphasize the importance of the stability of TiO2/dye/electrolyte interface for the device stability under thermal stress.

  • 88. Zadin, Vahur
    et al.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Modelling polymer electrolytes for 3D-microbatteries using finite element analysis2011In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 57, p. 237-243Article in journal (Refereed)
    Abstract [en]

    Comparisons between a LiPF(6)center dot PEO(20) polymer electrolyte and a 1.5 M LiPF(6) liquid electrolyte in a 3D-microbattery of coated interdigitated current collector pillars is presented here, using Finite Element Analysis (FEA). Ionic transport in the electrolyte is modeled by the Nernst-Planck equation and electrode potentials by Ohm's law. Simulations were carried out in steady state. The height of the electrode pillars and the distance between them were systematically varied in the simulations to evaluate the effects on ionic transport in terms of concentration, concentration gradient and the minimum concentration in the electrolyte. The studies showed that the polarization in the electrolyte can be decreased by increasing the electrode pillar length, while increasing electrode distances led to a nonuniformity of the electrochemical activity. Indications of an optimum pillar length were also observed. Comparisons of the electrolytes showed that the polymer electrolyte was able to deliver a more uniform electrochemical activity for these cell designs, but not able to sustain as high currents as the liquid electrolytes. At the current density used (10 A/m(2)), concentration polarization in the polymer electrolyte led to concentration deviations from the mean value of up to 60%.

  • 89. Zadin, Vahur
    et al.
    Danilov, Dmitry
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Notten, Peter H. L.
    Aabloo, Alvo
    Finite element simulations of 3D ionic transportation properties in Li-ion electrolytes2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 65, p. 165-173Article in journal (Refereed)
    Abstract [en]

    In current work, the ionic transport limitations in the Li-ion battery liquid electrolyte with separator are studied by a finite element method. This theoretical approach is based on the Nernst-Planck equation. It is shown that instead of solving coupled PDE system for concentration and potential, it is sufficient to calculate only the concentration profile in a three-dimensional (3D) structure to obtain a full description of the diffusion-migration ionic transport in the electrolyte in the steady-state. Subsequently, the overpotential and electric field can be calculated by using the provided equations. It was found that diffusion and migration overpotentials are equal in the steady-state. Consequently, two algorithms exploiting electrolyte simulations are proposed and successfully used to calculate the limiting current for the simulated battery system. In the present study a single perforated layer of the separator is inserted into the electrolyte and the simulations are carried out by increasing the complexity of the membrane holes. The ionic transportation dependence on the pore shape was found to be local and limited by the spatial area around the perforated separator.

  • 90.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mohammadi, Hajar
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland.
    Sun, Licheng
    KTH Royal Inst Technol, Dept Chem Chem Sci & Engn, Ctr Mol Devices, Organ Chem, SE-10044 Stockholm, Sweden.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland.
    Sheibani, Esmaeil
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran.
    Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 300, p. 482-488Article in journal (Refereed)
    Abstract [en]

    A new conducting polymer poly (3, 4-phenylenedioxythiophene) is synthesized by the electrochemical polymerization technique with different solvents. We find that solvents used in electrochemical polymerization play important roles for the catalytic activity and morphology of the formed conducting polymers. The obtained poly (3, 4-phenylenedioxythiophene) is for the first time employed as counter electrode electrocatalyst in dye sensitized solar cells with cobalt-based electrolytes. We demonstrate that a polymer prepared from a mixed acetonitrile-dichloromethane solvent exhibit higher catalytic activity for redox reactions, as compared to that from a single solvent, dichloromethane. The devices based on this mixed solvent-based polymer from a mixed solvents show a high power conversion efficiency of 5.97%. An additional advantageous feature of the electrochemically polymerized poly (3, 4-phenylenedioxythiophene) for solar cell applications is the high transparency in the visible and nearinfrared region. We also investigate the beneficial effect of the poly (3, 4-phenylenedioxythiophene) layer thickness on device performance, and concluded that the series resistance and charge transfer resistance are greatly influenced by the thickness of polymer, as evidenced by electrochemical impedance spectroscopy measurements. The optimal thickness for poly (3, 4-phenylenedioxythiophene) is about 100 nm. Furthermore, the high catalytic activity and transparency of the new conducting polymer as counter electrode shows great promise for other optoelectronic applications.

  • 91.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Jarboui, Adel
    CNRS, Sorbonne Paris Cite, Inst Univ Paris Diderot Paris 7, ITODYS UMR 7086, F-75205 Paris 13, France..
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, FSB ISIC LSPM, CH-1015 Lausanne, Switzerland..
    Jouini, Mohamed
    CNRS, Sorbonne Paris Cite, Inst Univ Paris Diderot Paris 7, ITODYS UMR 7086, F-75205 Paris 13, France..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, FSB ISIC LSPM, CH-1015 Lausanne, Switzerland.;King Abdulaziz Univ, Ctr Excellence Adv Mat Res, Jeddah 21589, Saudi Arabia..
    Photoelectrochemical Polymerization of EDOT for Solid State Dye Sensitized Solar Cells: Role of Dye and Solvent2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, p. 220-227Article in journal (Refereed)
    Abstract [en]

    The aromatic-unit, commercially available, and cost-effective precursor 3, 4-ethylenedioxythiophene (EDOT), was employed instead of bis-EDOT to generate by in-situ photoelectrochemical polymerization (PEP) a conducting polymer-type hole conductor poly (3, 4-ethylenedioxythiophene) (PEDOT) for dye sensitized solar cell (DSC) devices. In order to conduct efficiently the PEP of EDOT, two electrolytic media, aqueous micellar and organic, and two Donor-pi-Acceptor sensitizers, were investigated. By using the electrolytic aqueous micellar medium, the PEP was efficient due to the low oxidation potential of the precursor in water. A DSC device based on PEDOT generated from aqueous PEP showed an energy conversion efficiency (eta) of 3.0% under 100 mWcm (2), higher by two orders of magnitude than that of a DSC device based on PEDOT from organic PEP (eta = 0.04%). The comparison of the properties of the as-obtained PEDOT polymers from aqueous and organic PEP by UV-VIS-NIR measurements shows the formation of PEDOT at a highly doped state from aqueous PEP. The thermodynamic and kinetic requirements for efficiency of PEP process in each medium are investigated and discussed on the basis of the light absorption abilities and electrochemical redox potentials measured for the two organic sensitizers.

  • 92.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Simiyu, Justus
    Univ Nairobi, Dept Phys, POB 30197-00100, Nairobi, Kenya.
    Johansson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cheung, Ocean
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Häggman, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    SB ISIC LSPM, Ecole Polytech Fed Lausanne, Lab Photomol Sci, Chemin Alamb,Stn 6,CH G1 523, CH-1015 Lausanne, Switzerland.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. SB ISIC LSPM, Ecole Polytech Fed Lausanne, Lab Photomol Sci, Chemin Alamb,Stn 6,CH G1 523, CH-1015 Lausanne, Switzerland.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    The effect of mesoporous TiO2 pore size on the performance of solid-state dye sensitized solar cells based on photoelectrochemically polymerized Poly(3,4-ethylenedioxythiophene) hole conductor2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 210, p. 23-31Article in journal (Refereed)
    Abstract [en]

    Photoelectrochemical polymerization of poly(3,4-ethylenedioxythiphene) (PEDOT) has recently been introduced and widely investigated for fabrication of the hole transporting material (HTM) in highly efficient solid state dye sensitized solar cells (sDSCs). In this work, the effects of the surface area and pore size of TiO2 film were for the first time investigated in the sDSCs employing the in-situ polymerizated PEDOT HTM. Three different varieties of mesoporous TiO2 particles with controllable surface area and pore size were synthesized through the basic route in order to study the corresponding sDSC photovoltaic performances. It was found that the pore size plays an important role in the kinetics of the photoelectrochemical polymerization (PEP) process and the formation of the PEDOT capping layer. Larger pore sizes provided a more favourable pathway for the precursor diffusion through the mesoporous pores during the PEP process, which contributed towards a more efficient PEP. However, the interfacial contact area between the formed polymer and the dyes on the surface of TiO2 particle would be lower in the case of larger pore sizes, which consequently caused a less efficient dye regeneration process. Electronic diffusion on the other hand was improved for larger particle sizes. Employing an organic dye LEG4 and the self-made TiO2 with an optimal pore size of 25 nm and particle size of 24 nm, the sDSCs showed a promising power conversion efficiency (PCE) of 5.2%, higher than 4.5% for the commercial TiO2 Dyesol DSL-30. By measuring the dye regeneration yield and the kinetics through photoinduced absorption, it was observed that the homemade TiO2 based device had more efficient dye regeneration compared to the Dyesol based device, which could result from the better interfacial contact between the PEDOT and the dye. This work provides important information on the effect of meso-pore size on sDSCs and points to the necessity of further photoanode optimization toward the enhancement of the PCE of polymeric hole conductor-based DSCs.

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