| 1. |
- Hollmark, Håkan M., et al.
(författare)
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Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O2
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:8, s. A962-A966
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the charge-state behavior of the Li-ion battery cathode material LixNi(0.65)Co(0.25)Mn(0.1)O(2) as observed by X-ray absorption spectroscopy (XAS) and resonant soft X-ray emission (RSXE). A set of six identical Li//LixNi0.65Co0.25Mn0.1O2 batteries has been cycled and is studied in different states of charge in the range of x = 1.0, ... ,0.2 before disassembly in an Ar glove box. Site and symmetry selective information about the electronic structure of the conduction and valence bands reveals that Ni as well as Co ions participate in the uptake and release of the extra electron charge that the inserted Li ions provide, but the Ni ion is much less than expected. The net amount of charge on the oxygen varies approximately 0.24 charge units in the range of x, and dramatic changes in the hybridization are evident in XAS and in particular in RSXE at the O K edge. We attribute this to a strong screening behavior of the Li ions between the oxide layers. Structural integrity effects limit the extraction of Li ions to a value of about x = 0.2-0.4. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454739] All rights reserved.
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| 2. |
- Oltean, Gabriel, et al.
(författare)
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Towards Li-ion batteries operating at 80 °C: Ionic liquid versus conventional liquid electrolytes
- 2018
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Ingår i: Batteries. - : MDPI AG. - 2313-0105. ; 4, s. 2-6
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Tidskriftsartikel (refereegranskat)abstract
- Li-ion battery (LIB) full cells comprised of TiO2-nanotube (TiO2-nt) and LiFePO4 (LFP)electrodes and either a conventional organic solvent based liquid electrolyte or an ionic liquid basedelectrolyte have been cycled at 80 °C. While the cell containing the ionic liquid based electrolyteexhibited good capacity retention and rate capability during 100 cycles, rapid capacity fading was found for the corresponding cell with the organic electrolyte. Results obtained for TiO2-nt and LFP half-cells indicate an oxidative degradation of the organic electrolyte at 80 °C. In all, ionic liquidbased electrolytes can be used to significantly improve the performance of LIBs operating at 80 °C.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Svane, Maria, 1957, et al.
(författare)
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On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry
- 2009
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 43:7, s. 653-661
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Tidskriftsartikel (refereegranskat)abstract
- An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50-500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.
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| 7. |
- Kam, Kinson C., et al.
(författare)
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Synthesis and electrochemical properties of nanostructured Li(2)FeSiO(4)/C cathode material for Li-ion batteries
- 2011
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 192:1, s. 356-359
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured Li(2)FeSiO(4)/C was synthesized by high-energy ball-milling and the amorphous citrate-assisted techniques. Similar redox behaviour is observed for samples prepared by the amorphous citrate-assisted route followed by a 4 h heat treatment: 0.3 V polarization and more sloping behaviour was observed when cycling between 2.0 V and 3.7 V at 60 degrees C; lower capacity fade is also observed compared to Li(2)FeSiO(4)/C prepared by the solid-state reaction technique. A discharge capacity of 102 mA h g(-1) is obtained for samples prepared by the high-energy ball-milling method, while capacities decrease from 95 to 77 mA h g(-1) using the amorphous citrate method for heat-treatment times increasing successively from 4 h to 18 h.
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| 8. |
- 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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| 9. |
- Ma, Yue, et al.
(författare)
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Iron Doping in Spinel NiMn2O4 : Stabilization of the Mesoporous Cubic Phase and Kinetics Activation toward Highly Reversible Li+ Storage
- 2015
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 27:22, s. 7698-7709
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Tidskriftsartikel (refereegranskat)abstract
- Quaternary oxide structures with a three-dimensional macro/mesoporous network are synthesized via a facile nanocasting method followed by a calcination process. Structural engineering integrates multiscale pores by using a hydrophilic membrane with tunable-porosity as the sacrificial template. Through tailoring the metal precursor ratio, the tetragonal sites of spinel oxide are preferentially occupied by iron, resulting in a stabilized mesoporous cubic phase. Crystal field theory together with compositional characterizations from energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Mossbauer, and electron energy loss spectroscopy (EELS) direct our detailed analysis of the cation distribution in the spinel structures. Galvanostatic tests based on the best performing electrode exhibits a robust cycle life stable for 1200 cycles at a high current density of 1500 mA g(-1). This good Li+ storage performance could be attributed to the mutually beneficial synergy of the optimal level of iron doping which improves the electrical conductivity and structural robustness, as well as the presence of extended, hierarchical macro/mesoporous network. Finally, we demonstrate three feasible surface modification strategies for the oxide anodes toward better reversibility of Li+ storage.
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| 10. |
- Ojwang, Dickson O., et al.
(författare)
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Structure Characterization and Properties of K-Containing Copper Hexacyanoferrate
- 2016
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 55:12, s. 5924-5934
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Tidskriftsartikel (refereegranskat)abstract
- Copper hexacyanoferrate, Cu-II[Fe-III(CN)(6)](2/3)center dot nH(2)O, was synthesized, and varied amounts of IC ions were inserted via reduction by K2S2O3 (aq). Ideally, the reaction can be written as Cu-II[Fe-III(CN)(6)](2/3)-nH(2)O + 2x/3K(+) + 2x/3e(-)K(+) <-> K-2x/3 Cu-II[Fe-x(II).Fe-1-x(II),(CN)(6)](2/3)-nH(2)O. Infrared, Raman, and Mossbauer spectroscopy studies show that Fe-II is continuously reduced to Fell with increasing x, accompanied by a decrease of the a-axis of the cubic Fn (3) over barm unit cell. Elemental analysis of K by inductively coupled plasma shows that the insertion only begins when a significant fraction similar to 10% of the Fe-III, has already been reduced. Thermogravimetric analysis shows a fast exchange of water with ambient atmosphere and a total weight loss of similar to 26 wt % upon heating to 180 degrees C, above which the structure starts to decompose. The crystal structures of Cu-III[Fe-III(CN)(6)](2/3)center dot nH(2)O and K2/3Cu[Fe(CN)(6)](2/3)center dot nH(2)O were refined using synchrotron X-ray powder diffraction data. In both, one-third of the Fe(CN)(6) groups are vacant, and the octahedron around Cull is completed by water molecules. In the two structures, difference Fourier maps reveal three additional zeolitic water sites (8c, 32f, and 48g) in the center of the cavities formed by the-Cu-N-C-Fe- framework. The K-containing compound shows an increased electron density at two of these sites (32f and 48g), indicating them to be the preferred positions for the K+ ions.
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