| 1. |
- Renman, Viktor, et al.
(författare)
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Manganese Hexacyanomanganate as a Positive Electrode for Nonaqueous Li-, Na-, and K-Ion Batteries
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:36, s. 22040-22049
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Tidskriftsartikel (refereegranskat)abstract
- K2Mn[Mn(CN)(6)] is synthesized, characterized, and evaluated as possible positive electrode material in nonaqueous Li-, Na-, and K-ion batteries. This compound belongs to the rich and versatile family of hexacyanometallates displaying distinctive structural properties, which makes it interesting for ion insertion purposes. It can be viewed as a perovskite-like compound in which CN-bridged Mn(CN)(6) octahedra form an open framework structure with sufficiently large diffusion channels able to accommodate a variety of insertion cations. By means of galvanostatic cycling and cyclic voltammetry tests in nonaqueous alkali metal half-cells, it is demonstrated that this material is able to reversibly host Li+, Na+, and K+ ions via electrochemical insertion/deinsertion within a wide voltage range. The general electrochemical features are similar for all of these three ion insertion chemistries. An in operando X-ray diffraction investigation indicates that the original monoclinic structure is transformed into a cubic one during charging (i.e., removal of cations from the host framework) and that such a process is reversible upon subsequent cell discharge and cation reuptake.
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| 2. |
- Blidberg, Andreas, 1987-, et al.
(författare)
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Electronic changes in poly(3,4-ethylenedioxythiophene)-coated LiFeSO4F during electrochemical lithium extraction
- 2019
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Ingår i: Journal of Power Sources. - : ELSEVIER SCIENCE BV. - 0378-7753 .- 1873-2755. ; 418, s. 84-89
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Brant, William R., et al.
(författare)
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In Operando X-ray and Neutron Diffraction for Lithium Ion Batteries
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- To find new materials for lithium-ion batteries (LIBs) or to improve existing materials is a huge field of research. The positive electrode material in these devices is a bottleneck for increasing the energy density for the LIB and numerous oxides, phosphates, and silicates based on transition metals have been suggested. The crystallinity, chemical composition and structure of the bulk and the surface of a potential material are some important parameters influencing battery performance. In this presentation, we will show some examples of iron and Mn/Ni based cathode materials, and how in operando X-ray and neutron diffraction results have contributed to the understanding of how these materials function in batteries. In operando X-ray and neutron diffraction are extremely powerful techniques for investigating reaction mechanisms in battery materials in general. To date, the vast majority of these experiments have been performed using synchrotron X-ray diffraction, predominantly due to the fast data collection times possible. Is it so that synchrotron based X-ray diffraction always is the best choice? We will discuss this and show why in house in operando diffraction still is powerful. In operando neutron diffraction experiments are becoming increasingly popular due to a range of new cell designs increasing the accessibility of the technique [1], [2]. This presentation will discuss two different approaches to in operando neutron diffraction: a larger format wound cell and a cheaper modified a coin type cell. The wound cell design contains a large quantity of active material (up to 4 g) enabling high quality diffraction patterns to be collected down to small d-spacings. When used to investigate the positive electrode material LiMn1.5Ni0.5O4, reflections arising from Mn/Ni ordering could be observed to change during battery cycling. The modified coin cell design utilizes a completely different approach to in operando neutron diffraction experiments. The modified coin cells contain a large quantity of active material (~300-400 mg) to a much smaller amount of electrolyte (~10‑50 μL), separator and lithium metal. The smaller volume of electrolyte is particularly vital as it substantially reduces the cost of the experiment, as deuteration may no longer be necessary. The modified coin cell exhibited favourable electrochemistry when cycled at C/12 and enabled unit cell and phase fraction information to be extracted from in operando data collection conditions (5-15 min data sets). [1] M. Bianchini, E. Suard, L. Croguennec, C. Masquelier, J. Phys. Chem. C, 2014, 118, 25947. [2] R. Petibon, J. Li, N. Sharma, W.K. Pang, V.K. Peterson, J.R. Dahn, Electrochim. Acta, 2015, 174, 417.
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| 4. |
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| 5. |
- Lindgren, Fredrik, et al.
(författare)
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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-electrodes
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 301, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Schmitt, Thorsten, et al.
(författare)
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Electronic structure of Li-inserted V6O13 battery cathodes: Rigid band behavior and effects of hybridization
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:6, s. 064101-
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Tidskriftsartikel (refereegranskat)abstract
- Resonant soft x-ray emission (SXE) spectroscopy was used to study the electronic structure of LixV6O13 battery cathodes. We observe that the V 3d-bands of V6O13 exhibit a rather rigid behavior. Upon lithiation, electrons enter the top of the valence band and add intensity to the corresponding part of the V L-emission spectrum without significantly distorting the lower lying bands. We perform ab initio calculations which are in good agreement with the experimental results. Moreover, we find that lithiation leads to an overall decrease of the V 3d–O 2p hybridization. In contrast to x-ray diffraction, it is possible to study charge transfer effects in Li-batteries with SXE spectroscopy over the entire lithiation range.
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| 7. |
- Schmitt, Thorsten, et al.
(författare)
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Li insertion into V6O13 battery cathodes studies by soft x-ray spectroscopies
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:11, s. 6444-6449
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the electronic structure of V6O13 on lithium-ion insertion into battery cathod were studied by soft x-ray absorption (SXA) spectroscopy and resonant soft x-ray emission (SXE) spectroscopy. SXA and resonant SXE spectra were recorded ex situ for cycled battery cathodes discharged to different potentials corresponding closely to distinct lithiated stages (LixV6O13,x=0,1,...,6).Large systematic change were observed in the vanadium and oxygen x-ray spectra, reflecting the effects of electrochemical reduction associated with the Li-ion insertion. Spectral shape analysis indicates that a large fraction of the vanadium ions have been reduced to V3+ ions for the highest degree of, x=6. Neverrtheless, further lithiation may be possible, in view of the linear development of the vanadium and oxygen bands on charge uptake.
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| 8. |
- Slawinski, Wojciech Andrzej, 1980, et al.
(författare)
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Neutron Pair Distribution Function Study of FePO4 and LiFePO4
- 2019
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 31:14, s. 5024-5034
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Xu, Chao, 1988-, et al.
(författare)
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The Role of LiTDI Additive in LiNi1/3Mn1/3Co1/3O2/ Graphite Lithium-Ion Batteries at Elevated Temperatures
- 2018
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Ingår i: Journal of the Electrochemical Society. - : ELECTROCHEMICAL SOC INC. - 0013-4651 .- 1945-7111. ; 165:2, s. A40-A46
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Tidskriftsartikel (refereegranskat)abstract
- The poor thermal stability of conventional LiPF6-based electrolytes is one of the major obstacles for today's lithium-ion batteries. Recently, lithium 4,5-dicyano-2-( trifluoromethyl) imidazolide (LiTDI) has demonstrated to be highly efficient in scavenging moisture from the electrolyte and thereby improving electrolyte stability. In this context, effects of the LiTDI additive on LiNi1/3Mn1/3Co1/3O2 (NMC)/graphite cells are evaluated at a temperature of 55 degrees C. With the incorporation of LiTDI, an improved cycling performance of NMC/graphite cells was achieved, and the impedance increase at the NMC/electrolyte interface was significantly mitigated. Furthermore, LiTDI exhibited a profound influence on the interfacial chemistries in the full cell, and LiTDI-derived species were found on the surfaces of both the cathode and the anode. The SEI layer formed on graphite anodes was more homogenous in morphology and consisted of larger amounts of LiF and fewer oxygen-containing species, as compared to graphite in additive-free cells. This study shows that LiTDI is a promising electrolyte additive for NMC/graphite cells operated at elevated temperatures, highlighting that the influence of the LiTDI additive is worth exploring also in other battery chemistries.
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| 10. |
- Liu, Chenjuan, et al.
(författare)
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Towards an Understanding of Li2O2 Evolution in Li-O2 Batteries : An In-operando Synchrotron X-ray Diffraction Study
- 2017
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 10:7, s. 1592-1599
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Tidskriftsartikel (refereegranskat)abstract
- One of the major challenges in developing high-performance Li-O-2 batteries is to understand the Li2O2 formation and decomposition during battery cycling. In this study, this issue was investigated by synchrotron radiation powder X-ray diffraction. The evolution of Li2O2 morphology and structure was observed under actual electrochemical conditions of battery operation. By quantitatively tracking Li2O2 during discharge and charge, a two-step process was suggested for both growth and oxidation of Li2O2 owing to different mechanisms during two stages of both oxygen reduction reaction and oxygen evolution reaction. From an observation of the anisotropic broadening of Li2O2 in XRD patterns, it was inferred that disc-like Li2O2 grains are formed rapidly in the first step of discharge. These grains can stack together so that they facilitate the nucleation and growth of toroidal Li2O2 particles with a LiO2-like surface, which could cause parasitic reactions and hinder the formation of Li2O2. During the charge process, Li2O2 is firstly oxidized from the surface, followed by a delithiation process with a faster oxidation of the bulk by stripping the interlayer Li atoms to form an off-stoichiometric intermediate. This fundamental insight brings new information on the working mechanism of Li-O-2 batteries.
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