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  • 1.
    Blidberg, Andreas
    et al.
    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.
    Tengstedt, Carl
    Scania CV AB, Södertälje, Sweden.
    Björefors, Fredrik
    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.
    Monitoring LixFeSO4F (x = 1, 0.5, 0) Phase Distributions in Operando To Determine Reaction Homogeneity in Porous Battery Electrodes2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 17, p. 7159-7169Article in journal (Refereed)
    Abstract [en]

    Increasing the energy and power density simultaneously remains a major challenge for improving electrochemical energy storage devices such as Li-ion batteries. Understanding the underlying processes in operating electrodes is decisive to improve their performance. Here, an extension of an in operando X-ray diffraction technique is presented, wherein monitoring the degree of coexistence between crystalline phases in multiphase systems is used to investigate reaction homogeneity in Li-ion batteries. Thereby, a less complicated experimental setup using commercially available laboratory equipment could be employed. By making use of the intrinsic structural properties of tavorite type LiFeSO4F, a promising cathode material for Li-ion batteries, new insights into its nonequilibrium behavior are gained. Differences in the reaction mechanism upon charge and discharge are shown; the influence of adequate electronic wiring for the cycling stability is demonstrated, and the effect of solid state transport on rate performance is highlighted. The methodology is an alternative and complementary approach to the expensive and demanding techniques commonly employed for time-resolved studies of structural changes in operating battery electrodes. The multiphase behavior of LiFeSO4F is commonly observed for other insertion type electrode materials, making the methodology transferable to other new energy storage materials. By expanding the possibilities for investigating complex processes in operating batteries to a larger community, faster progress in both electrode development and fundamental material research can be realized.

  • 2.
    Blidberg, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Tengstedt, Carl
    Gustafsson, Torbjorn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Structural and Electronic Changes in Li2FeP2O7 during Electrochemical Cycling2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 11, p. 3801-3804Article in journal (Refereed)
  • 3.
    Blidberg, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala universitet.
    Sobkowiak, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tengstedt, Carl
    Scania CV AB.
    Valvo, Mario
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Battery Performance of PEDOT Coated LiFeSO4F Cathodes with Controlled PorosityManuscript (preprint) (Other academic)
  • 4.
    Blidberg, Andreas
    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.
    Tengstedt, Carl
    Scania CV AB, Södertälje.
    Valvo, Mario
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Identifying the Electrochemical Processes in LiFeSO4F Cathodes for Lithium Ion Batteries2017In: Chemelectrochem, Vol. 4, no 8, p. 1896-1907Article in journal (Other academic)
    Abstract [en]

    The electrochemical performance of tavorite LiFeSO4F can be considerably improved by coating the material with a conducting polymer (poly(3,4-ethylenedioxythiophene); PEDOT). Herein, the mechanisms behind the improved performance are studied systematically by careful electrochemical analysis. It is shown that the PEDOT coating improves the surface reaction kinetics for the Li-ion insertion into LiFeSO4F. For such coated materials no kinetic limitations remain, and a transition from solid state to solution-based diffusion control was observed at 0.6 mA cm−2 (circa C/2). Additionally, the quantity of PEDOT is optimized to balance the weight added by the polymer and the improved electrochemical function. Post mortem analysis shows excellent stability for the LiFeSO4F-PEDOT composite, and maintaining the electronic wiring is the most important factor for stable electrochemical cycling of LiFeSO4F. The insights and the methodology used to determine the rate-controlling steps are readily transferable to other ion-insertion-based electrodes, and the findings are important for the development of improved battery electrodes.

  • 5.
    Blidberg, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Alfredsson, Maria
    Univ Kent, Sch Phys Sci, Canterbury CT2 7NH, Kent, England.
    Tengstedt, Carl
    Scania CV AB, SE-15187 Sodertalje, Sweden.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electronic changes in poly(3,4-ethylenedioxythiophene)-coated LiFeSO4F during electrochemical lithium extraction2019In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 418, p. 84-89Article in journal (Refereed)
    Abstract [en]

    The redox activity of tavorite LiFeSO4F coated with poly (3,4-ethylenedioxythiophene), i.e. PEDOT, is investigated by means of several spectroscopic techniques. The electronic changes and iron-ligand redox features of this LiFeSO4F-PEDOT composite are probed upon delithiation through X-ray absorption spectroscopy. The PEDOT coating, which is necessary here to obtain enough electrical conductivity for the electrochemical reactions of LiFeSO4F to occur, is electrochemically stable within the voltage window employed for cell cycling. Although the electronic configuration of PEDOT shows also some changes in correspondence of its reduced and oxidized forms after electrochemical conditioning in Li half-cells, its p-type doping is fully retained between 2.7 and 4.1 V with respect to Li+/Li during the first few cycles. An increased iron-ligand interaction is observed in LixFeSO4F during electrochemical lithium extraction, which appears to be a general trend for polyanionic insertion compounds. This finding is crucial for a deeper understanding of a series of oxidation phenomena in Li-ion battery cathode materials and helps paving the way to the exploration of new energy storage materials with improved electrochemical performances.

  • 6.
    Boman, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Björefors, Fredrik
    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.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Corrosion of copper in water free from molecular oxygen2014In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 49, no 6, p. 431-434Article in journal (Refereed)
    Abstract [en]

    The possibility of copper reacting with O-2-free water has been investigated by analysis of primary corrosion products, as well as by monitoring gas pressure change by time, in long term experiments for up to 6 months in a glove box environment. We establish hydrogen production, but being of the same magnitude irrespective whether copper is present or not. Although low, the hydrogen production rate is considerably larger than what would directly correspond to the amount of analysed copper oxidation products. Our analyses encompass the changes to the surface cleaned copper (99.9999%), the water phase and the Duran glass in contact with the water (ppt quality). We have used very sensitive methods (XPS, AES, ICP-MS, XRF) while keeping contamination risks to a minimum. We conclude that the oxidation rate of copper is very low, yielding only parts of a monolayer of Cu2O after 6 months of exposure at 50 degrees C together with an accompanying very low concentration of copper species (4-5 mu g L-1) in the water phase.

  • 7.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    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.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Inorganic and organometallic materials for novel Li-ion batteries2013Conference paper (Other academic)
  • 8.
    Eriksson, Rickard
    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.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gustafsson, Torbjörn
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Formation of Tavorite-Type LiFeSO4F Followed by In Situ X-ray Diffraction2015In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 298, p. 363-368Article in journal (Refereed)
    Abstract [en]

    The tavorite-type polymorph of LiFeSO4F has recently attracted substantial attention as a positive elec- trode material for lithium ion batteries. The synthesis of this material is generally considered to rely on a topotactic exchange of water (H2O) for lithium (Li) and fluorine (F) within the structurally similar hy- drated iron sulfate precursor (FeSO4·H2O) when reacted with lithium fluoride (LiF). However, there have also been discussions in the literature regarding the possibility of a non-topotactic reaction mechanism between lithium sulfate (Li2SO4) and iron fluoride (FeF2) in tetraethylene glycol (TEG) as reaction medium. In this work, we use in situ X-ray diffraction to continuously follow the formation of LiFeSO4F from the two suggested precursor mixtures in a setup aimed to mimic the conditions of a solvothermal autoclave synthesis. It is demonstrated that LiFeSO4F is formed directly from FeSO4·H2O and LiF, in agreement with the proposed topotactic mechanism. The Li2SO4 and FeF2 precursors, on the other hand, are shown to rapidly transform into FeSO4·H2O and LiF with the water originating from the highly hygroscopic TEG before a subsequent formation of LiFeSO4F is initiated. The results highlight the importance of the FeSO4·H2O precursor in obtaining the tavorite-type LiFeSO4F, as it is observed in both reaction routes.

  • 9.
    Fredriksson, Wendy
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Petrini, Daniel
    Erasteel Kloster AB, Box 100, Söderfors SE-815 82, Sweden.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural 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.
    Corrosion Resistances and Passivation of Powder Metallurgical and Conventionally Cast 316L and 2205 Stainless Steels2013In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 67, p. 268-280Article in journal (Refereed)
    Abstract [en]

    The corrosion resistances and passivation of austenitic 316L and duplex 2205 powder metallurgical (P/M) steels, produced by employing gas atomizing and hot isostatic pressing (HIP), have been compared with those of their conventional cast and forged counterparts. The P/M 316L steel is shown to have a significantly higher pitting corrosion resistance than the conventional 316L steel in 0.5 M HCl. Since the chemical composition and the total amount of inclusions were analogous for the two steels, the effect is ascribed to the finer grained microstructure for the P/M 316L steel yielding a better passive layer. This is supported by photoelectron spectroscopy data demonstrating differences between the thickness and composition of the passive layers for the two 316 L steels. Differences in the passivation process were also found for the different steels as three mixed potentials were observed in the polarization curves for the P/M and conventional 316L steels whereas only one mixed potential at about +0.7 V vs. Ag/AgCl was observed for the two duplex steels in 0.5 M HCl. The results indicate that discussions of the shapes of polarization curves and mixed potentials should be based on the anodic and cathodic partial currents, including the reduction of oxygen. HIP:ed P/M steels are clearly well-suited for applications requiring high pitting corrosion resistances.

  • 10.
    Hedman, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Morát, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Johansson, David
    Langhammer, Elin
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nanoplasmonics for online monitoring of lithium-ion batteries2018Conference paper (Other academic)
  • 11.
    Högström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Matilda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    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, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    On the evaluation of corrosion resistances of amorphous chromium carbide thin-films2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 122, no SI, p. 224-233Article in journal (Refereed)
    Abstract [en]

    The possibilities of evaluating the corrosion resistance of amorphous chromium carbide (Cr-C) films containing nanometre-sized carbide grains embedded in an amorphous carbon matrix on the basis of polarization curves, voltammograms and the oxidation charge have been studied for Cr-C films with different carbon concentrations. The films, which were manufactured by non-reactive directcurrent magnetron sputtering, were studied in 1.0 mM H2SO4 at both 22 °C and 80 °C, and with scanning electron microscopy and X-ray photoelectron spectroscopy prior to and after the electrochemical experiments. It is demonstrated that the oxidation of these Cr-C films gives rise to a surface composed of Cr2O3 and partially oxidized carbon and that the non-corroding oxidation current due to the carbon oxidation increases with increasing carbon concentration in the films as well as with the electrolyte temperature. Since the oxidation current is composed of contributions from both Cr-C and carbon oxidation it is not straightforward to evaluate the corrosion resistances of these films based on the current in the passive region, the mixed potential (i.e., the corrosion potential) or the open circuit potential. The present results in fact indicate that Cr-C films with high carbon concentrations may have better corrosion resistances than the corresponding films with lower carbon concentrations although larger currents in the passive region can be seen in polarization curves.

  • 12.
    Högström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fredriksson, Wendy
    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.
    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.
    Olsson, Claes-O. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 284, p. 700-714Article in journal (Refereed)
    Abstract [en]

    An approach for determining depth gradients of metal-ion concentrations in passive films on stainlesssteel using angle-resolved X-ray photoelectron spectroscopy (ARXPS) is described. The iterative method,which is based on analyses of the oxidised metal peaks, provides increased precision and hence allowsfaster ARXPS measurements to be carried out. The method was used to determine the concentrationdepth profiles for molybdenum, iron and chromium in passive films on 316L/EN 1.4432 stainless steelsamples oxidised in 0.5 M H2SO4 and acetic acid diluted with 0.02 M Na2B4O7 · 10H2O and 1 M H2O,respectively. The molybdenum concentration in the film is pin-pointed to the oxide/metal interface andthe films also contained an iron-ion-enriched surface layer and a chromium-ion-dominated middle layer.Although films of similar composition and thickness (i.e., about 2 nm) were formed in the two electrolytes,the corrosion currents were found to be three orders of magnitude larger in the acetic acid solution.The differences in the layer composition, found for the two electrolytes as well as different oxidationconditions, can be explained based on the oxidation potentials of the metals and the dissolution rates ofthe different metal ions.

  • 13.
    Johansson, David
    et al.
    Insplor AB, Medicinaregatan 8A, S-41390 Gothenburg, Sweden..
    Andersson, Jenny
    Insplor AB, Medicinaregatan 8A, S-41390 Gothenburg, Sweden..
    Wickman, Bjorn
    Chalmers Univ Technol, Dept Phys, Kemivagen 9, S-41296 Gothenburg, Sweden..
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sobkowiak, Adam
    Uppsala Univ, Angstrom Lab, Dept Chem, Lagerhyddsvagen 1, S-75121 Uppsala, Sweden..
    Kasemo, Bengt
    Chalmers Univ Technol, Dept Phys, Kemivagen 9, S-41296 Gothenburg, Sweden..
    Nanoplasmonic Sensing of Pb-acid and Li-ion Batteries2016In: Sensors And Electronic Instrumentation Advances (SEIA) / [ed] Yurish, SY Malayeri, AD, INT FREQUENCY SENSOR ASSOC-IFSA , 2016, p. 57-59Conference paper (Refereed)
    Abstract [en]

    The increasing sophistication and performance of batteries are connected with more complex chemical and physical battery processes and increase the need of more direct and informative measurements, both in the R&D phase and for monitoring and control during operation of vehicles. Todays potentiometric based measurement sensors are not sufficiently accurate for optimal battery sensing. To avoid the built in wide safety margins new, more informative monitoring signals are therefore desired or needed. In this study the optical technology NanoPlasmonic Sensing (NPS) has been used to in-situ monitor the charge and discharge processes of lead-acid and Li-ion batteries. The optical signals were found to correlate well with charging/discharging of both battery technologies.

  • 14.
    Lee, Kian Keat
    et al.
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Hao, Wenming
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Gustafsson, Mikaela
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Tai, Cheuk-Wai
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Morin, Daniel
    ABB Corp Res, Forskargrand 7, SE-72178 Vasteras, Sweden..
    Bjorkman, Eva
    Biokol Lilliestrale & Co KB, Sibyllegatan 53, SE-11443 Stockholm, Sweden..
    Lilliestrale, Malte
    Biokol Lilliestrale & Co KB, Sibyllegatan 53, SE-11443 Stockholm, Sweden..
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Anna M.
    ABB Corp Res, Forskargrand 7, SE-72178 Vasteras, Sweden..
    Hedin, Niklas
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Tailored activated carbons for supercapacitors derived from hydrothermally carbonized sugars by chemical activation2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 112, p. 110629-110641Article in journal (Refereed)
    Abstract [en]

    Activated carbons (ACs) are actively researched as electrode materials for supercapacitors and there is a significant interest to produce ACs from sustainable and low cost precursors. In this study, various ACs were prepared from hydrothermally carbonized sugars by KOH activation. Both the hydrothermal carbonization and activation processes were optimized to tailor the properties (e.g. textural properties, chemical composition, N-doping, electrical conductivity) of the ACs. For instance, the Brunauer-Emmett-Teller (BET) surface areas (S-BET) were tuned in the range of 800-3000 m(2) g(-1) with associated variation in the extent of microporosity and pore size distributions (PSDs). The ACs were evaluated electrochemically as materials for supercapacitor electrodes in a symmetrical two-electrode cell using an aqueous electrolyte. The relationship between the electrochemical, textural, electrical, and physicochemical properties were analyzed systematically to understand the key factors determining the electrochemical performance. A high specific capacitance (C-m) of similar to 260 F g(-1) was achieved at a moderately high S-BET of similar to 1300 m(2) g(-1), which was equivalent to a C-m/S-BET of 20 mu F cm(-2), for an optimal AC prepared from hydrothermally carbonized glucose. The very high surface-specific capacitance highlights that the specific surface area is certainly not the sole limiting parameter for effective electrode materials.

  • 15.
    Lettieri, Raffaella
    et al.
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    Di Giorgio, Floriana
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    Colella, Alessandra
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    Magnusson, Roger
    Linkoping Univ, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden..
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Placidi, Ernesto
    Univ Roma Tor Vergata, Dept Phys, CNR, Inst Struct Matter, I-00133 Rome, Italy..
    Palleschi, Antonio
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    Venanzi, Mariano
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    Gatto, Emanuela
    Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy..
    DPPTE Thiolipid Self-Assembled Monolayer: A Critical Assay2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 44, p. 11560-11572Article in journal (Refereed)
    Abstract [en]

    Supported lipid membranes represent an elegant way to design a fluid interface able to mimic the physicochemical properties of biological membranes, with potential biotechnological applications. In this work, a diacyl phospholipid, the 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE), functionalized with a thiol group, was immobilized on a gold surface. In this molecule, the thiol group, responsible for the Au S bond (45 kJ/mol) is located on the phospholipid polar head, letting the hydrophobic chain protrude from the film. This system is widely used in the literature but is no less challenging, since its characterization is not complete, as several discordant data have been obtained. In this work, the film was characterized by cyclic voltammetry blocking experiments, to verify the SAM formation, and by reductive desorption measurements, to estimate the molecular density of DPPTE on the gold surface. This value has been compared to that obtained by quartz crystal microbalance measurements. Ellipsometry and impedance spectroscopy measurements have been performed to obtain information about the monolayer thickness and capacitance. The film morphology was investigated by atomic force microscopy. Finally, Monte Carlo simulations were carried out, in order to gain molecular information about the morphologies of the DPPTE SAM and compare them to the experimental results. We demonstrate that DPPTE molecules, incubated 18 h below the phase transition temperature (T = 41.1 +/- 0.4 degrees C) in ethanol solution, are able to form a self-assembled monolayer on the gold surface, with domain structures of different order, which have never been reported before. Our results make possible rationalization of the scattered results so far obtained on this system, giving a new insight into the formation of phospholipids SAMs on a gold surface.

  • 16.
    Lindgren, Fredrik
    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.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Anna M.
    Marcinek, Marek
    Niedzicki, Leszek
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    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.
    A hard X-ray photoelectron spectroscopy study on the solid electrolyte interphase of a lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide based electrolyte for Si-electrodes2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 301, p. 105-112Article in journal (Refereed)
    Abstract [en]

    This report focuses on the relatively new salt, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), and its functionality together with a silicon based composite electrode in a half-cell lithium ion battery context. LiTDI is a promising alternative to the commonly used LiPF6 salt because it does not form HF which can decompose the oxide layer on Si. The formation of a solid electrolyte interphase (SEI) as well as the development of the active Si-particles are investigated during the first electrochemical lithiation and de-lithiation. Characterizations are carried out at different state of charge with scanning electron microscopy (SEM) as well as hard x-ray photoelectron spectroscopy (HAXPES) at two different photon energies. This enables a depth resolved picture of the reaction processes and gives an idea of the chemical buildup of the SEI. The SEI is formed by solvent and LiTDI decomposition products and its composition is similar to SEI formed by other carbonate based electrolytes. The LiTDI salt or its decomposition products are not in itself reactive towards the active Si-material and no unwanted side reactions occurs with the active Si-particles. Despite some decomposition of the LiTDI salt, it is a promising alternative for electrolytes aimed towards Si-based electrodes.

  • 17.
    Lindgren, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Xu, Chao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Niedzicki, Leszek
    Warsaw Univ Technol, Fac Chem, Noakowskiego 3, PL-00664 Warsaw, Poland..
    Marcinek, Marek
    Warsaw Univ Technol, Fac Chem, Noakowskiego 3, PL-00664 Warsaw, Poland..
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    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.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    SEI Formation and Interfacial Stability of a Si Electrode in a LiTDI-Salt Based Electrolyte with FEC and VC Additives for Li-Ion Batteries2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 24, p. 15758-15766Article in journal (Refereed)
    Abstract [en]

    An electrolyte based on the new salt, lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), is evaluated in combination with nano-Si composite electrodes for potential use in Li-ion batteries. The additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are also added to the electrolyte to enable an efficient SEI formation. By employing hard X-ray photoelectron spectroscopy (HAXPES), the SEI formation and the development of the active material is probed during the first 100 cycles. With this electrolyte formulation, the Si electrode can cycle at 1200 mAh g(-1) for more than 100 cycles at a coulombic efficiency of 99%. With extended cycling, a decrease in Si particle size is observed as well as an increase in silicon oxide amount. As opposed to LiPF6 based electrolytes, this electrolyte or its decomposition products has no side reactions with the active Si material. The present results further acknowledge the positive effects of SEI forming additives. It is suggested that polycarbonates and a high LiF content are favorable components in the SEI over other kinds of carbonates formed by ethylene carbonate (EC) and dimethyl carbonate (DMC) decomposition. This work thus confirms that LiTDI in combination with the investigated additives is a promising salt for Si electrodes in future Li-ion batteries.

  • 18.
    Lundgren, Anders
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Munktell, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lacey, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Berglin, Mattias
    SP Tech Res Inst Sweden, Chem Mat & Surfaces, Box 857, SE-50115 Boras, Sweden; Gothenburg Univ, Dept Chem & Mol Biol, Box 462, SE-40530 Gothenburg, Sweden.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Formation of Gold Nanoparticle Size and Density Gradients via Bipolar Electrochemistry2016In: ChemElectroChem, ISSN 2196-0216, Vol. 3, no 3, p. 378-382Article in journal (Refereed)
    Abstract [en]

    Bipolar electrochemistry is employed to demonstrate the formation of gold nanoparticle size gradients on planar surfaces. By controlling the electric field in a HAuCl4-containing electrolyte, gold was reduced onto 10 nm diameter particles immobilized on pre-modified thiolated bipolar electrode (BPE) templates, resulting in larger particles towards the more cathodic direction. As the gold deposition was the dominating cathodic reaction, the increased size of the nanoparticles also reflected the current distribution on the bipolar electrode. The size gradients were also combined with a second gradient-forming technique to establish nanoparticle surfaces with orthogonal size and density gradients, resulting in a wide range of combinations of small/large and few/many particles on a single bipolar electrode. Such surfaces are valuable in, for example, cell-material interaction and combinatorial studies, where a large number of conditions are probed simultaneously.

  • 19.
    Munktell, Sara
    et al.
    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.
    Bjorefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Towards high throughput corrosion screening using arrays of bipolar electrodes2015In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY, ISSN 1572-6657, Vol. 747, p. 77-82Article in journal (Refereed)
    Abstract [en]

    In this work we demonstrate the possibility of combining bipolar electrochemistry with arrays of samples as a fast and versatile method for comparing their corrosion resistances at a wide range of potentials. Several steel samples of different grades were arranged in a bipolar electrochemical cell and exposed to an electric field by applying a constant current. The gradient in electrochemical potential difference across each sample resulted in a pitting corrosion gradient on the anodic parts which was used as a simple, straightforward and qualitative method of screening the corrosion properties of several samples in one single experiment. In the cell, all samples acted as individual bipolar electrodes but interestingly, the current density for each sample was also found to be influenced by the corrosion resistances of its neighbours. Results from the bipolar array were also compared with standard polarisation curves and the pitting resistance equivalent number (PREN) for each steel type.

  • 20.
    Munktell, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tydén, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Högström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    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.
    Bipolar electrochemistry for high-throughput corrosion screening2013In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 34, p. 274-277Article in journal (Refereed)
    Abstract [en]

    It is demonstrated that bipolar electrochemistry can be used for high-throughput corrosion testing covering a wide potential range in one single experiment and that this, combined with rapid image analysis, constitutes a simple and convenient way to screen the corrosion behaviour of conducting materials and corrosion protective coatings. Stainless steel samples (SS304), acting as bipolar electrodes, were immersed in sulphuric and hydrochloric acid and exposed to an electric field to establish a potential gradient along the surface. In this way, the same steel sample was exposed to a wide range of cathodic and anodic conditions, ranging from potentials yielding hydrogen evolution to potentials well into the transpassive region. This wireless approach enables rapid simultaneous comparison of numerous samples, and also provides the opportunity to perform experiments on samples that are of a complex shape, or which otherwise are difficult to employ in standard electrochemical corrosion tests.

  • 21. Nilsson, Sara
    et al.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Robinson, Nathaniel D.
    Electrochemical quartz crystal microbalance study of polyelectrolyte film growth under anodic conditions2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 280, p. 783-790Article in journal (Refereed)
    Abstract [en]

    Coating hard materials such as Pt with soft polymers like poly-l-lysine is a well-established technique for increasing electrode biocompatibility. We have combined quartz crystal microgravimetry with dissipation with electrochemistry (EQCM-D) to study the deposition of PLL onto Pt electrodes under anodic potentials. Our results confirm the change in film growth over time previously reported by others. However, the dissipation data suggest that, after the short initial phase of the process, the rigidity of the film increases with time, rather than decreasing, as previously proposed. In addition to these results, we discuss how gas evolution from water electrolysis and Pt etching in electrolytes containing Cl- affect EQCM-D measurements, how to recognize these effects, and how to reduce them. Despite the challenges of using Pt as an anode in this system, we demonstrate that the various electrochemical processes can be understood and that PLL coatings can be successfully electrodeposited. 

  • 22. Samuelsson, Mattias
    et al.
    Lundin, Daniel
    Sarakinos, Kostas
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Walivaara, Bengt
    Ljungcrantz, Henrik
    Helmersson, U.
    Influence of ionization degree on film properties when using high power impulse magnetron sputtering2012In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 30, no 3, p. 031507-Article in journal (Refereed)
    Abstract [en]

    Chromium thin films are deposited by combining direct current magnetron sputtering and high power impulse magnetron sputtering (HiPIMS) on a single cathode in an industrial deposition system. While maintaining a constant deposition rate and unchanged metal ion energy distribution function, the fraction of the total power supplied by either deposition technique is altered, and thereby also the metal ion to metal neutral ratio of the deposition flux. It is observed that the required total average power needed to be proportionally increased as the HiPIMS fraction is increased to be able to keep a constant deposition rate. The influence on microstructure, electrical, and electrochemical properties of the films is investigated and shows improvements with the use of HiPIMS. However, considerable influence of the studied properties occurs already when only some 40% of the total power is supplied by the HiPIMS technique. Further increase of the HiPIMS power fraction results in comparatively minor influence of the studied properties yet significant deposition rate efficiency reduction. The results show that the degree of ionization can be controlled separately, and that the advantages associated with using HiPIMS can be obtained while much of the deposition rate reduction, often reported for HiPIMS, can be avoided.

  • 23.
    Sobkowiak, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ericsson, Tore
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    A Mössbauer spectroscopy study of polyol synthesized tavorite LiFeSO4F.2014In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, ISSN 0304-3843, Vol. 226, no 1-3, p. 229-236Article in journal (Refereed)
    Abstract [en]

    The tavorite polymorph of LiFeSO4F has attracted considerable attention as a cathode material for lithium ion batteries due to interesting structural and electrochemical characteristics. For the analysis of such iron-based electrode materials, Mössbauer spectroscopy has become an important and highly useful tool. In this work, we perform a detailed Mössbauer study of pristine tavoriteLiFeSO4F prepared by an optimized synthesis in tetraethylene glycol as reaction media. In contrast to many reported results, we demonstrate the use of an asymmetric fitting model for the inner doublet of the spectrum, which is coupled to the structural properties of the compound. Moreover, we discuss a new approach of ascribing the Fe2 + -doublets to the two distinct crystallographic iron sites of tavorite LiFeSO4F by comparing the Mössbauer signal intensities with the expected f-factors for the corresponding iron atom.

  • 24.
    Sobkowiak, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Anna M.
    ABB.
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Identification of an Intermediate Phase, Li1/2FeSO4F, Formed during Electrochemical Cycling of Tavorite LiFeSO4F2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 15, p. 4620-4628Article in journal (Refereed)
    Abstract [en]

    Many compounds adopting the tavorite-type crystal structure have attracted considerable attention as cathode materials for lithium ion batteries due to the favorable structural characteristics, facilitating promising electrochemical performance. Recent reports have highlighted the complex mechanism of lithium insertion/extraction in some of these compounds, such as the stabilization of intermediate phases in the LiFeSO4OH and LiVPO4F systems. In the case of tavorite LiFeSO4F, reported density functional theory (DFT) calculations have suggested the possibility of a similar behavior, but thus far, no experimental verification of such a process has, to the best of our knowledge, been successfully demonstrated. In this work, we investigate the structural evolution of LiFeSO4F upon extraction/insertion of lithium ions from/into the host framework. By thorough ex situ characterizations of chemically and electrochemically prepared LixFeSO4F-samples (0 ≤ x ≤ 1), we demonstrate the stabilization of an intermediate phase, Li1/2FeSO4F, for which one possible structural model is proposed. However, results indicating charge ordering on the iron-sites, suggesting the formation of a super structure with a larger unit cell, are also highlighted. Moreover, the degree of formation of Li1/2FeSO4F is shown to be highly dependent on the rate of lithium extraction as a result of an exceptionally small potential separation (similar to 15 mV during charging) of the two subsequently occurring biphasic processes, LiFeSO4F/Li1/2FeSO4F and Li1/2FeSO4F/FeSO4F. Finally, the intermediate phase is shown to be formed both on charge and discharge during battery cycling, even though an apparent asymmetrical electrochemical trace suggests the contrary.

  • 25.
    Sobkowiak, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew R.
    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.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Haggstrom, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Tai, Cheuk-Wai
    Stockholm University.
    Andersson, Anna M.
    ABB.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjorn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Understanding and Controlling the Surface Chemistry of LiFeSO4F for an Enhanced Cathode Functionality2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 15, p. 3020-3029Article in journal (Refereed)
    Abstract [en]

    The tavorite polymorph of LiFeSO4F has recently attracted a lot of interest as a cathode material for lithium ion batteries stimulated by its competitive specific capacity, high potential for the Fe2+/Fe3+ redox couple, and low-temperature synthesis. However, the synthesis routes explored to date have resulted in notably varied electrochemical performance. This inconsistency is difficult to understand given the excellent purity, crystallinity, and similar morphologies achieved via all known methods. In this work, we examine the role of the interfacial chemistry on the electrochemical functionality of LiFeSO4F. We demonstrate that particularly poor electrochemical performance may be obtained for pristine materials synthesized in tetraethylene glycol (TEG), which represents one of the most economically viable production methods. By careful surface characterization, we show that this restricted performance can be largely attributed to residual traces of TEG remaining on the surface of pristine materials, inhibiting the electrochemical reactions. Moreover, we show that optimized cycling performance of LiFeSO4F can be achieved by removing the unwanted residues and applying a conducting polymer coating, which increases the electronic contact area between the electrode components and creates a highly percolating network for efficient electron transport throughout the composite material. This coating is produced using a simple and scalable method designed to intrinsically favor the functionality of the final product.

  • 26. Ulrich, Christian
    et al.
    Louthander, Dan
    Martensson, Per
    Kluftinger, Andre
    Gawronski, Michael
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Evaluation of industrial cutting fluids using electrochemical impedance spectroscopy and multivariate data analysis2012In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 97, p. 468-472Article in journal (Refereed)
    Abstract [en]

    In this paper we explore the combination of electrochemical impedance spectroscopy (EIS) and multivariate data analysis to evaluate the concentration and pH of an industrial cutting fluid. These parameters are vital for the performance of for instance tooling processes, and an on-line quality monitoring system would in such applications be very beneficial. It is shown that both the total impedance and the phase angle contain information that allows the simultaneous discrimination of the concentration and the pH. The final evaluation was conducted using the regression technique partial least squares (PLS), and this approach provided a way to quickly and easily find the correlation between EIS data and the sought parameters. The possibility to estimate both the concentration and pH level clearly indicates the potential of this method to be implemented for on-line evaluation.

  • 27.
    Valvo, Mario
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lafont, Ugo
    Björefors, Fredrik
    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.
    Towards more sustainable negative electrodes in Na-ion batteries via nanostructured iron oxide2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 245, p. 967-978Article in journal (Refereed)
    Abstract [en]

    Na-ion technology could emerge as an alternative to Li-ion batteries due to limited costs and vast availability of sodium, as well as its similar chemistry. Several Na-rich compounds have been proposed as positive electrodes, whereas suitable negative counterparts have not been found yet. Nanostructured iron oxide is reported here for the first time as a potentially viable negative electrode for Na-ion cells based on conventional electrolytes and composite coatings with carboxymethyl cellulose. Electrochemical reactions of Na+ and Li+ ions with nanostructured Fe2O3 are analysed and compared. Initial sodiation of Fe2O3 yields a sloping profile in a voltage range characteristic for oxide conversion, which instead generates a typical plateau upon lithiation. Application of such earth-abundant, nontoxic material in upcoming Na-ion batteries is potentially groundbreaking, since it offers important advantages, namely: i. simple and cost-effective synthesis of Fe2O3 nanostructures at low temperatures; ii. cheaper and more sustainable cell fabrication with higher energy densities, e.g., use of natural, water-soluble binders, as well as Al for both current collectors; iii. electrochemical performances with specific gravimetric capacities exceeding 400 mAh g(-1) at 40 mA g(-1), accompanied by decent specific volumetric energy densities, e.g., approximate to 1.22 Wh cm(-3), provided that cycle inefficiencies and long-term durability are addressed.

  • 28.
    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.

  • 29.
    Wei, Wei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Oltean, Gabriel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm University.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural 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.
    High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 28, p. 8160-8169Article in journal (Refereed)
    Abstract [en]

    Highly ordered anodic TiO2 nanotube arrays with a tube length of 9 [small mu ]m are shown to provide areal capacities of 0.24 mA h cm-2 (i.e. 96 mA h g-1) at a charge/discharge current density of 2.5 mA cm-2 (corresponding to a rate of 5 C) and 0.46 mA h cm-2 (i.e. 184 mA h g-1) at 0.05 mA cm-2, when used as 3D free-standing anodes in Li-ion microbatteries. The present nanotube electrodes, which could be cycled for 500 cycles with only 6% loss of capacity, exhibited significantly higher energy and power densities, as well as an excellent cycling stability compared to previously reported TiO2-based Li-ion microbattery electrodes. The influence of parameters such as ordering, geometry and crystallinity of the nanotubes on the microbattery performance was investigated. A two-step anodization process followed by annealing of the nanotubes was found to yield the best microbattery performance. It is also demonstrated that the rate capability of the electrode depends mainly on the rate of the structural rearrangements associated with the lithiation/delithiation reaction and that the areal capacity at various charge/discharge rates can be increased by increasing the tube wall thickness or the length of the nanotubes, up to 0.6 mA h cm-2 for 100 cycles.

  • 30.
    Xu, Chao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindgren, Fredrik
    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.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin Germany.
    Björefors, Fredrik
    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.
    Improved Performance of the Silicon Anode for Li-Ion Batteries: Understanding the Surface Modification Mechanism of Fluoroethylene Carbonate as an Effective Electrolyte Additive2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 7, p. 2591-2599Article in journal (Refereed)
    Abstract [en]

    Silicon as a negative electrode material for lithium-ion batteries has attracted tremendous attention due to its high theoretical capacity, and fluoroethylene carbonate (FEC) was used as an electrolyte additive, which significantly improved the cyclability of silicon-based electrodes in this study. The decomposition of the FEC additive was investigated by synchrotron-based X-ray photoelectron spectroscopy (PES) giving a chemical composition depth-profile. The reduction products of FEC were found to mainly consist of LiF and -CHF-OCO2-type compounds. Moreover, FEC influenced the lithium hexafluorophosphate (LiPF6) decomposition reaction and may have suppressed further salt degradation. The solid electrolyte interphase (SEI) formed from the decomposition of ethylene carbonate (EC) and diethyl carbonate (DEC), without the FEC additive present, covered surface voids and lead to an increase in polarization. However, in the presence of FEC, which degrades at a higher reduction potential than EC and DEC, instantaneously a conformal SEI was formed on the silicon electrode. This stable SEI layer sufficiently limited the emergence of large cracks and preserved the original surface morphology as well as suppressed the additional SEI formation from the other solvent. This study highlights the vital importance of how the chemical composition and morphology of the SEI influence battery performance.

  • 31.
    Younesi, Reza
    et al.
    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.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Johansson, Patrik
    Department of Applied Physics, Chalmers University of Technology.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Li-O2 Battery Degradation by Lithium Peroxide (Li2O2): A Model Study2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 1, p. 77-84Article in journal (Refereed)
    Abstract [en]

    The chemical stability of the Li-O2 battery components (cathode and electrolyte) in contact with lithiumperoxide (Li2O2) was investigated using X-ray photoelectron spectroscopy (XPS). XPS is a versatile method to detect amorphous as well as crystalline decomposition products of both salts and solvents. Two strategies were employed. First, cathodes including carbon, α‑MnO2 catalyst, and Kynar binder (PVdF-HFP) were exposed to Li2O2 and LiClO4 in propylenecarbonate (PC) or (tetraethylene glycol dimethyl ether) TEGDME electrolytes. The results indicated that Li2O2 degrades TEGDME to carboxylate containing species and that the decomposition products in turn degraded the Kynar binder. The α‑MnO2 catalyst was unaffected. Second, Li2O2 model surfaces were kept in contact with different electrolytes to investigate the chemical stability, and also the resulting surface layer on Li2O2. Further, the XPS experiments revealed that the Li salts LiPF6, LiBF4, and LiClO4 decomposed to form LiF or LiCl together with P-O or B-O bond containing compounds when exposed to Li2O2. PC decomposed to carbonate and ether based species. The degradation of the electrolytes increased from short to long exposure time indicating that the surface layer on Li2O2 became thicker by increasing time. Overall, it was shown that a mixture of ethylene carbonate and diethyl carbonate (EC/DEC) is more robust in contact with Li2O2 compared to PC.

  • 32.
    Younesi, S Reza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Urbonaite, Sigita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Influence of the Cathode Porosity on the Discharge Performance of the Lithium-Oxygen Battery2011In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, no 22, p. 9835-9838Article in journal (Refereed)
    Abstract [en]

    By varying the ratio between the amount of carbon and Kynar binder in the cathode of a lithium-oxygen battery, it could be shown that an increasing amount of binder resulted in a decrease in the discharge capacity, mainly as a result of the decrease in the cathode porosity. It was shown that the Kynar binder blocked the majority of the pores with a width below 300 angstrom as determined by studying the pore volume and pore size distribution by nitrogen adsorption. Three carbonate based electrolytes (PC, PC:DEC (1:1), and EC:DEC (2:1) with 1 M LiPF(6)) were tested with the various cathode film compositions. Generally, the PC:DEC and EC:DEC based electrolytes provided higher capacities than PC. The results indicated that the air electrode composition and its effect on the porosity of the cathode, as well as electrolyte properties, are important when optimizing the discharge capacity.

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