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Publications (10 of 27) Show all publications
Aktekin, B., Valvo, M., Smith, R. I., Sörby, M. H., Marzano, F. L., Zipprich, W., . . . Brant, W. (2019). Cation Ordering and Oxygen Release in LiNi0.5-xMn1.5+xO4-y (LNMO): In Situ Neutron Diffraction and Performance in Li Ion Full Cells. ACS APPLIED ENERGY MATERIALS, 2(5), 3323-3335
Open this publication in new window or tab >>Cation Ordering and Oxygen Release in LiNi0.5-xMn1.5+xO4-y (LNMO): In Situ Neutron Diffraction and Performance in Li Ion Full Cells
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2019 (English)In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 5, p. 3323-3335Article in journal (Refereed) Published
Abstract [en]

Lithium ion cells utilizing LiNi0.5Mn1.5O4 (LNMO) as the positive electrode are prone to fast capacity fading, especially when operated in full cells and at elevated temperatures. The crystal structure of LNMO can adopt a P4(3)32 (cation-ordered) or Fd (3) over barm (disordered) arrangement, and the fading rate of cells is usually mitigated when samples possess the latter structure. However, synthesis conditions leading to disordering also lead to oxygen deficiencies and rock-salt impurities and as a result generate Mn3+. In this study, in situ neutron diffraction was performed on disordered and slightly Mn-rich LNMO samples to follow cation ordering-disordering transformations during heating and cooling. The study shows for the first time that there is not a direct connection between oxygen release and cation disordering, as cation disordering is observed to start prior to oxygen release when the samples are heated in a pure oxygen atmosphere. This result demonstrates that it is possible to tune disordering in LNMO without inducing oxygen deficiencies or forming the rock-salt impurity phase. In the second part of the study, electrochemical testing of samples with different degrees of ordering and oxygen content has been performed in LNMO vertical bar vertical bar LTO (Li4Ti5O12) full cells. The disordered sample exhibits better performance, as has been reported in other studies; however, we observe that all cells behave similarly during the initial period of cycling even when discharged at a 10 C rate, while differences arise only after a period of cycling. Additionally, the differences in fading rate were observed to be time-dependent rather than dependent on the number of cycles. This performance degradation is believed to be related to instabilities in LNMO at higher voltages, that is, in its lower lithiation states. Therefore, it is suggested that future studies should target the individual effects of ordering and oxygen content. It is also suggested that more emphasis during electrochemical testing should be placed on the stability of samples in their delithiated state.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
Keywords
high-voltage spinel, neutron diffraction, LNMO, cation ordering, oxygen deficiency
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-387975 (URN)10.1021/acsaem.8b02217 (DOI)000469885300040 ()
Funder
Swedish Energy Agency, 42758-1Swedish Energy Agency, 39043-1StandUp
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-07-29Bibliographically approved
Slawinski, W. A., Playford, H. Y., Hull, S., Norberg, S. T., Eriksson, S. G., Gustafsson, T., . . . Brant, W. R. (2019). Neutron Pair Distribution Function Study of FePO4 and LiFePO4. Chemistry of Materials, 31(14), 5024-5034
Open this publication in new window or tab >>Neutron Pair Distribution Function Study of FePO4 and LiFePO4
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 14, p. 5024-5034Article in journal (Refereed) Published
Abstract [en]

Neutron powder diffraction studies of the compounds FePO4 and LiFePO4 are reported. Rietveld refinement of the diffraction data provides averaged structures for both materials that are in good agreement with the published structures. In addition, detailed investigations of the short-range ion-ion correlations within each compound have been performed using the reverse Monte Carlo (RMC) modeling of the total scattering (Bragg plus diffuse) data. Although the short-range structural information for LiFePO4 is consistent with the long-range (averaged) picture, a small, but statistically significant, proportion of the anions is displaced away from their ideal sites within the RMC configurations of FePO4. These anion displacements are discussed in terms of a small concentration of Li+/Fe2+ occupying the empty octahedral sites, probably arising from incomplete delithiation of the LiFePO4 and/or antisite (Li+-Fe2+) defects introduced during the delithiation process.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-391371 (URN)10.1021/acs.chemmater.9b00552 (DOI)000477093000007 ()
Funder
Swedish Research Council, VR-2012-5240
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-03Bibliographically approved
Brant, W., Mogensen, R., Colbin, S., Ojwang, D. O., Schmid, S., Häggstrom, L., . . . Younesi, R. (2019). Selective Control of Composition in Prussian White for Enhanced Material Properties. Chemistry of Materials, 31(18), 7203-7211
Open this publication in new window or tab >>Selective Control of Composition in Prussian White for Enhanced Material Properties
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 18, p. 7203-7211Article in journal (Refereed) Published
Abstract [en]

Sodium-ion batteries based on Prussian blue analogues (PBAs) are ideal for large-scale energy storage applications due to the ability to meet the huge volumes and low costs required. For Na2-xFe[Fe(CN)(6)](1-y)center dot zH(2)O, realizing its commercial potential means fine control of the concentration of sodium, Fe(CN)(6) vacancies, and water content. To date, there is a huge variation in the literature of composition leading to variable electrochemical performance. In this work, we break down the synthesis of PBAs into three steps for controlling the sodium, vacancy, and water content via an inexpensive, scalable synthesis method. We produce rhombohedral Prussian white Na1.88(5)Fe[Fe-(CN)(6)]center dot 0.18(9)H2O with an initial capacity of 158 mAh/g retaining 90% capacity after 50 cycles. Subsequent characterization revealed that the increased polarization on the 3 V plateau is coincident with a phase transition and reduced utilization of the high-spin Fe(III)/Fe(II) redox couple. This reveals a clear target for subsequent improvements of the material to boost long-term cycling stability. These results will be of great interest for the myriad of applications of PBAs, such as catalysis, magnetism, electrochromics, and gas sorption.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-395840 (URN)10.1021/acs.chemmater.9b01494 (DOI)000487859200012 ()
Funder
StandUpSwedish Research Council, 2016-03441ÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Björklund, E., Naylor, A. J., Brant, W., Brandell, D., Younesi, R. & Edström, K. (2019). Temperature dependence of electrochemical degradation in LiNi1/3Mn1/3Co1/3O2/Li4Ti5O12 cells. Energy Technology, 7(9), Article ID 1900310.
Open this publication in new window or tab >>Temperature dependence of electrochemical degradation in LiNi1/3Mn1/3Co1/3O2/Li4Ti5O12 cells
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2019 (English)In: Energy Technology, ISSN 2194-4288, Vol. 7, no 9, article id 1900310Article in journal (Refereed) Published
Abstract [en]

Aging mechanisms in lithium‐ion batteries are dependent on the operational temperature, but the detailed mechanisms on what processes take place at what temperatures are still lacking. The electrochemical performance and capacity fading of the common cell chemistry LiNi1/3Mn1/3Co1/3O2 (NMC)/Li4Ti5O12 (LTO) pouch cells are studied at temperatures 10, 30, and 55 °C. The full cells are cycled with a moderate upper cutoff potential of 4.3 V versus Li+/Li. The electrode interfaces are characterized postmortem using photoelectron spectroscopy techniques (soft X‐ray photoelectron spectroscopy [SOXPES], hard X‐ray photoelectron spectroscopy [HAXPES], and X‐ray absorption near edge structure [XANES]). Stable cycling at 30 °C is explained by electrolyte reduction forming a stabilizing interphase, thereby preventing further degradation. This initial reaction, between LTO and the electrolyte, seems to be beneficial for the NMC–LTO full cell. At 55 °C, continuous electrolyte reduction and capacity fading are observed. It leads to the formation of a thicker surface layer of organic species on the LTO surface than at 30 °C, contributing to an increased voltage hysteresis. At 10 °C, large cell‐resistances are observed, caused by poor electrolyte conductivity in combination with a relatively thicker and LixPFy‐rich surface layer on LTO, which limit the capacity.

Keywords
aging, lithium-ion batteries, photoelectron spectroscopy
National Category
Energy Engineering Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-381545 (URN)10.1002/ente.201900310 (DOI)000483721900011 ()
Available from: 2019-04-11 Created: 2019-04-11 Last updated: 2019-12-09Bibliographically approved
Liu, C., Qiu, Z., Brant, W., Younesi, R., Ma, Y., Edström, K., . . . Zhu, J.-F. (2018). A free standing Ru–TiC nanowire array/carbon textile cathode with enhanced stability for Li–O2 batteries. Journal of Materials Chemistry A, 6, 23659-23668
Open this publication in new window or tab >>A free standing Ru–TiC nanowire array/carbon textile cathode with enhanced stability for Li–O2 batteries
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2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, p. 23659-23668Article in journal (Refereed) Published
Abstract [en]

The instability of carbon cathode materials is one of the key problems that hinder the development of lithium–air/lithium–oxygen (Li–O2) batteries. In this contribution, a type of TiC-based cathode is developed as a suitable alternative to carbon based cathodes, and its stability with respect to its surface properties is investigated. Here, a free-standing TiC nanowire array cathode was in situ grown on a carbon textile, covering its exposed surface. The TiC nanowire array, via deposition with Ru nanoparticles, showed enhanced oxygen reduction/evolution activity and cyclability, compared to the one without Ru modification. The battery performance of the Li–O2cells with Ru–TiC was investigated by using in operando synchrotron radiation powder X-ray diffraction (SR-PXD) during a full cycle. With the aid of surface analysis, the role of the cathode substrate and surface modification is demonstrated. The presented results are a further step toward a wise design of stable cathodes for Li–O2 batteries.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-369118 (URN)DOI: 10.1039/c7ta10930j (DOI)000451813300047 ()
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2019-03-19Bibliographically approved
Aktekin, B., Brant, W., Valvo, M., Marzano, F., Zipprich, W., Brandell, D. & Edström, K. (2018). Cation Ordering and Oxygen Release in LiNi0.5-xMn1.5+xO4-y (LNMO)—In Situ Neutron Diffraction and Performance in Li-Ion Full Cells. In: : . Paper presented at 2018 MRS Fall Meeting, Boston, MA, USA, November 25-30, 2018. Boston, MA, USA
Open this publication in new window or tab >>Cation Ordering and Oxygen Release in LiNi0.5-xMn1.5+xO4-y (LNMO)—In Situ Neutron Diffraction and Performance in Li-Ion Full Cells
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

LiNi0.5Mn1.5O4 (LNMO) is a promising spinel-type positive electrode for lithium ion batteries as it operates at high voltage and possesses high power capability. However, rapid performance degradation in full cells, especially at elevated temperatures, is a problem. There has been a considerable interest in its crystal structure as this is known to affect its electrochemical performance. LNMO can adopt a P4332 (cation ordered) or Fd-3m (cation disordered) arrangement depending on the synthesis conditions. Most of the studies in literature agree on better electrochemical performance for disordered LNMO [1], however, a clear understanding of the reason for this behaviour is still lacking. This partly arises from the fact that synthesis conditions leading to disordering also lead to oxygen deficiency, rock-salt impurities and therefore generate some Mn3+ [2]. Most commonly, X-ray diffraction is used to characterize these materials, however, accurate structural analysis is difficult due to the near identical scattering lengths of Mn and Ni. This is not the case for neutron diffraction. In this study, an in-situ neutron diffraction heating-cooling experiment was conducted on slightly Mn-rich LNMO under pure oxygen atmosphere in order to investigate relationship between disordering and oxygen deficiency. The study shows for the first time that there is no direct relationship between oxygen loss and cation disordering, as disordering starts prior to oxygen release. Our findings suggest that it is possible to obtain samples with varying degrees of ordering, yet with the same oxygen content and free from impurities. In the second part of the study, highly ordered, partially ordered and fully disordered samples have been tested in LNMO∥LTO (Li4Ti5O12) full cells at 55 °C. It is shown that differences in their performances arise only after repeated cycling, while all the samples behave similarly at the beginning of the test. The difference is believed to be related to instabilities of LNMO at higher voltages, that is, in its lower lithiation states.

[1] A. Manthiram, K. Chemelewski, E.-S. Lee, Energy Environ. Sci. 7 (2014) 1339.

[2] M. Kunduraci, G.G. Amatucci, J. Power Sources. 165 (2007) 359–367.

Place, publisher, year, edition, pages
Boston, MA, USA: , 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-375838 (URN)
Conference
2018 MRS Fall Meeting, Boston, MA, USA, November 25-30, 2018
Funder
StandUp
Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-09-25Bibliographically approved
Brant, W. (2018). Controlling Cation Ordering and Oxygen Release in LiNi0.5Mn1.5O4. In: : . Paper presented at 16th European Powder Diffraction Conference.
Open this publication in new window or tab >>Controlling Cation Ordering and Oxygen Release in LiNi0.5Mn1.5O4
2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

LiNi0.5Mn1.5O4 (LNMO) is a promising spinel-type positive electrode (cathode) material for lithium-ion batteries (LiBs), with a theoretical capacity of 147 mAh/g and an operating voltage around 4.7 V (vs. Li/Li+). With both high ionic and electronic conductivity it is regarded as a suitable cathode material for high power applications. LMNO can adopt two different structural arrangements, P4332 (cation ordered) or Fd-3m (disordered) [1]. Generally speaking, it has been observed that batteries incorporating the latter structure exhibit reduced capacity fading during electrochemical cycling. However, synthesis conditions leading to disordering also lead to oxygen deficiency, rock-salt impurities and as a result generate Mn3+ [2,3]. Furthermore, while many literature reports categorise the material as either “ordered” or “disordered”, the material can adopt varying degrees of ordering. Thus, isolating the exact cause of capacity fade is challenging. In this study, in-situ neutron diffraction is performed on disordered and slightly Mn-rich LNMO samples (Mn:Ni ratio of 1.56:0.44) to follow cation ordering-disordering transformations during heating and cooling (see figure). The study shows for the first time that there is not a direct connection between oxygen deficiency and cation disordering. This demonstrates that it is possible to tune disordering in LNMO without inducing oxygen deficiencies or forming the rock-salt impurity phase. Electrochemical testing of samples with different degrees of ordering and oxygen deficiency (i.e. highly ordered, partially ordered and fully disordered) have been performed in LNMO-LTO (Li4Ti5O12) full cells. It was shown that all cells behave similarly during the initial period of cycling even when discharged at 10C rate, however, over time the disordered sample exhibited the best performance.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-376557 (URN)
Conference
16th European Powder Diffraction Conference
Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-02-06
Brant, W. (2018). Decoupling cation ordering and oxygen release: An in situ neutron study of LiNi0.5Mn1.5O4 positive electrode materials. In: : . Paper presented at Swedish Neutron Scattering Society Annual Meeting 2018.
Open this publication in new window or tab >>Decoupling cation ordering and oxygen release: An in situ neutron study of LiNi0.5Mn1.5O4 positive electrode materials
2018 (English)Conference paper, Oral presentation only (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-376559 (URN)
Conference
Swedish Neutron Scattering Society Annual Meeting 2018
Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-02-06
Chien, Y.-C., Menon, A. S., Brant, W., Brandell, D. & Lacey, M. (2018). Development of operando XRD coin cells for lithium-sulfur batteries. In: : . Paper presented at RACIRI Summer School 2018, 25 aug - 1 sept 2018, Rügen, Germany.
Open this publication in new window or tab >>Development of operando XRD coin cells for lithium-sulfur batteries
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2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Lithium-sulfur (Li-S) batteries has been regarded as one of the promising technology for the next generation of rechargeable batteries due to its high theoretical energy density (2600 Wh/kg [1]). Several works [2–7] on operando X-ray diffraction (XRD) of the Li-S system have been published; however, their experimental setups showed one or more of the following drawbacks. First, the amount of electrolyte was often not reported or would be considered too high for a common Li-S cell, which has been demonstrated to have a significant impact on the behavior of the system [8]. Another issue is the non-uniform stack pressure and electron conductivity of the operando cell setup, whose effects were found by both experiments and simulations [9].

This work aims to tackle with the above-mentioned issues by modifying commercial coin cells and using X-ray transparent metal, beryllium, as the spacers. By doing so, the electron conductivity and stack pressure can be expected to be uniform throughout the electrodes. The amount of electrolyte can also be precisely controlled since no vacuum-sealing is required for coin cells. A preliminary diffraction pattern obtained with the cell setup can be seen in Fig. 1. With electrochemical properties similar to common Li-S cells, ‘online’ electrochemical characterization techniques, e.g. Intermittent Current Interruption (ICI) method for following cell resistance [10], will be applicable with operando XRD, revealing more information about this complex system.

Figure 1 XRD patterns of alpha-S and electrode material in the modified coin cell.

References

[1] J. Tan, et al., Nanoscale (2017) 19001–19016.

[2] J. Nelson, et al., J. Am. Chem. Soc. 134 (2012) 6337–6343.

[3] N.A. Cañas, et al., J. Power Sources 226 (2013) 313–319.

[4] S. Waluś, et al., Chem. Commun. 49 (2013) 7899.

[5] M. a. Lowe, et al., RSC Adv. 4 (2014) 18347.

[6] J. Kulisch, et al., Phys. Chem. Chem. Phys. 16 (2014) 18765–18771.

[7] J. Conder, et al., Nat. Energy 2 (2017) 1–7.

[8] M.J. Lacey, ChemElectroChem (2017) 1–9.

[9] O.J. Borkiewicz, et al., J. Phys. Chem. Lett. 6 (2015) 2081–2085.

[10] M.J. Lacey, et al., Chem. Commun. 51 (2015) 16502–16505.

Keywords
lithium-sulfur, operando X-ray diffraction, online resistance measurement
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-375406 (URN)
Conference
RACIRI Summer School 2018, 25 aug - 1 sept 2018, Rügen, Germany
Funder
Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-10-25Bibliographically approved
Brant, W. (2018). Electrochemical Cells for Neutron Diffraction. In: : . Paper presented at Neutron and Synchrotron Sample Environment Workshop.
Open this publication in new window or tab >>Electrochemical Cells for Neutron Diffraction
2018 (English)Conference paper, Oral presentation only (Other academic)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-376561 (URN)
Conference
Neutron and Synchrotron Sample Environment Workshop
Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-02-06
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8658-8938

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