XANES analysis for cation-vacancy distribution induced by doping Al ions in transition-metal-oxide anodes of lithium battery (original) (raw)
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In situ X-ray absorption spectroscopy—A probe of cathode materials for Li-ion cells
Fluid Phase Equilibria, 2006
In situ X-ray absorption spectroscopy is a powerful emerging technique that has the capability to observe the changes in ongoing electrochemical reactions. It is already well established in materials science, and it is becoming a significant tool for the electrochemical community. As with all X-ray absorption spectroscopies, extended X-ray absorption fine structure (EXAFS) has the advantage of being element specific. Interpretation of the spectra at different states of charge can provide very useful quantitative and qualitative information about the valence change of the constituent elements in the cathode material during the ongoing electrochemical reaction, the degree of distortion or changes in structure from the initial state of charge to the final state of charge and provide valuable information about the extent of degradation of the cathode material during continuous cycling. It can also provide valuable insight about how the nature of the electrochemical reactions changes when one of the transition metal constituents is removed or increased in content in the cathode material. It is often important to adjust the composition of the cathode material in order to achieve high specific capacity and long-term stability in Li-ion cells. This article details the development of the in situ XAS techniques to study electrochemical reactions using various X-ray absorption spectroscopies which are now possible with the advent of third generation synchrotron radiation sources and improved end stations. The strength of in situ EXAFS techniques is illustrated using examples of various interesting transition metal oxides. In this way, we aim to encourage chemists, chemical engineers and materials scientists to consider in situ X-ray absorption spectroscopy as an effective tool for developing an understanding the electronic structure of materials and the changes that it undergoes during electrochemical reactions. (A. Deb).
In Operando XANES Imaging of High Capacity Intermetallic Anodes for Lithium Ion Batteries
Journal of The Electrochemical Society, 2020
In operando 2D X-ray absorption near edge structure (XANES) imaging was performed near the Cu K-edge during cycling of Cu 6 Sn 5 composite anodes for lithium ion batteries. Galvanostatic lithiation and delithiation with intermittent constant voltage holds near reaction plateaus show evolution of absorption spectra for active material particles. XANES spectra obtained from images taken during cycling were compared to standard spectra for Cu, Cu 6 Sn 5 , and Li 2 CuSn. Chemical composition was assessed for Cucontaining phases. Distinct Cu, Cu 6 Sn 5 , and Li 2 CuSn regions were identified for each voltage plateau. Mechanical degradation, electrode particle fracture and expansion were observed during delithiation. Movement of particles during cycling suggests that expansion also impacts the supporting secondary phases and the transport networks therein. These results demonstrate that spectroscopic X-ray imaging methods can clearly distinguish chemically distinct phases in alloy electrodes and have the versatility to observe the evolution of these phases during lithiation and delithiation.
e-Journal of Surface Science and Nanotechnology
For analysis of lithium ion batteries, the soft X-ray grating monochromator beamline BL-2 at SR center of Ritsumeikan University has been upgraded: adding a new grating (900 l/mm) to extend the available energy up to 1000 eV, and constructing a XAFS (X-ray Absorption Fine Structure)-PES (photoelectron spectroscopy) chamber equipped with in-situ transfer vessel systems. With this beamline, Li K-, O K-and 3d transition metal (TM) L-XAFS and Li 1s PES spectra were measured for several compounds related to Li ion batteries. For precise analysis of the Li chemical state, some of Li compounds, as well as Li metal were prepared by vacuum deposition.
Designing High-Capacity, Lithium-Ion Cathodes Using X-ray Absorption Spectroscopy
Chemistry of Materials, 2011
We have taken advantage of the element specific nature of X-ray absorption spectroscopy to elucidate the chemical and structural details of a surface treatment intended for the protection of high-capacity cathode materials. Electrochemical data have shown that surface treatments of 0.5Li 2 MnO 3 •0.5LiCoO 2 (Li 1.2 Mn 0.4 Co 0.4 O 2) with an acidic solution of lithium− nickel-phosphate significantly improves electrode capacity, rate, and cycling stability. XAS data reveal that the surface treatment results in a modification of the composite structure itself, where Ni 2+ cations, intended to be present in a lithium−nickel-phosphate coating, have instead displaced lithium in the transition metal layers of Li 2 MnO 3-like domains within the 0.5Li 2 MnO 3 •0.5LiCoO 2 structure. X-ray diffraction data show the presence of Li 3 PO 4 , suggesting that phosphate ions from the acidic solution are responsible for lithium extraction and nickel insertion with the formation of vacancies and/or manganese reduction for charge compensation. Furthermore, we show that the above effects are not limited to lithium−nickelphosphate treatments. The studies described are consistent with a novel approach for synthesizing and tailoring the structures of high-capacity cathode materials whereby a Li 2 MnO 3 framework is used as a precursor for synthesizing a wide variety of composite metal oxide insertion electrodes for Li-ion battery applications.
Materials Letters, 2020
In this paper, we discussed about the electrochemical behavior of the Li(Ni 1/3 Co 1/3 Mn 1/3)O 2 battery using X-ray absorption spectroscopy and transmission X-ray microscopy techniques. Ni ions in the cathode material undergoes change of oxidation in charging and discharging state, however, metal ions like Co and Mn do not exhibit this phenomenon. Simulation of Ni K-edge XAS spectra reflect change of coordination environment during charging and discharging. The experimental result from TXM imaging visualized the chemical distribution map for charging and discharging states at Ni K-edge.
2022
Solid electrolyte interphase (SEI) formation is critical to the long-term performance of Li-ion battery anodes, however probing the decomposition processes occurring at the buried electrode-electrolyte interface is a significant challenge. We demonstrate here for the first time, the use of operando soft X-ray Absorption spectroscopy in total electron yield (TEY) mode to resolve the chemical evolution of the SEI during electrochemical formation in a Li-ion cell. Interface-sensitive O, F, and Si K-edge spectra, acquired as a function of potential, reveal when key reactions occur on high capacity amorphous Si anodes cycled in conventional carbonate-based electrolytes (LP30) with and with- out fluoroethylene carbonate (FEC) as an additive. Density functional theory (DFT) calculations provide insight into the species observed and the origins of their spectral features. LiF is observed as the dominant F-containing SEI product, forming at ∼0.6 V for LP30 and at a higher potential of ∼1.0 V...
Journal of Solid State Chemistry, 1998
Structural changes accompanying the electrochemical Li deintercalation of Li 1؊x NiO 2 and Li 1؊x CoO 2 were studied by the transmission X-ray absorption fine structure (XAFS) technique using an in situ X-ray cell of original design. Our results revealed that the Jahn-Teller distortion of the Ni-O octahedra found in LiNiO 2 decreased as the Li ion was removed from the cathode. The observed X-ray absorption near-edge structures (XANES) of Li 1؊x NiO 2 and Li 1؊x CoO 2 as a function of x are consistent with the phase transitions found by powder-diffraction studies. The Ni-O, CoO , and Ni-Ni interatomic distances decreased almost linearly as the Li content decreased to x ؍ 0.8, while the Co-Co distance slightly decreased to x ؍ 0.5 and increased up to x ؍ 0.8. The local distortion of NiO 6 octahedra also decrease with increasing y in a Li(Ni 1؊y , Co y)O 2 solid solution.