Li insertion into V6O13 battery cathodes studied by soft x-ray spectroscopies

Abstract

Changes in the electronic structure of V6O13 on lithium-ion insertion into battery cathodes 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 changes 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 lithiation, x=6. Nevertheless, further lithiation may be possible, in view of the linear development of the vanadium and oxygen bands on charge uptake.

Local environment dependentGGA+Umethod for accurate thermochemistry of transition metal compounds

“…Constant-U and LD-GGA+U methods both produce similar results up to x = 2 (i.e., up to reduction of all V 5+ to V 4+ ), in good agreement with the experimental profile. 112 The agreement of both methods with the experiment in this region implies that V 4+ and V 5+ require U values close enough such that they can be treated accurately with the same constant-U value.…”

Recent Progress in the Applications of Vanadium‐Based Oxides on Energy Storage: from Low‐Dimensional Nanomaterials Synthesis to 3D Micro/Nano‐Structures and Free‐Standing Electrodes Fabrication

“…Moreover, V 6 O 13 can electrochemically incorporate up to 8 Li per formula unit, which results in a high theoretical specific capacity of 417 mA h g −1 (8 Li + intercalation). [74,[117][118][119][120][121][122][123][124] For example, Zhou and his co-workers synthesized a V 6 O 13 nanostructure from hydrated aerogel. [74,[117][118][119][120][121][122][123][124] For example, Zhou and his co-workers synthesized a V 6 O 13 nanostructure from hydrated aerogel.…”

Electronic structure of Li-inserted V6O13 battery cathodes: Rigid band behavior and effects of hybridization

“…2 The electrochemical lithiation process of V 6 O 13 is characterized by a stepwise transition between phases of Li x V 6 O 13 with x =0,2/3,1,...,6 resulting in a "staircase" shape of the electrode potential as a function of lithium content. 3,4 So far, only sparse information exists about their electronic structure, such as, V K-edge x-ray absorption fine structure spectroscopy 5 and x-ray diffraction ͑XRD͒. 6,7 Although V 6 O 13 requires the use of Lifoils in battery applications, interesting prospects for taking advantage of the discrete phase transition behavior exist and promise new materials that are technically easier to handle.…”

“…Elsewhere, we report on oxidation state changes during the lithiation process in a soft x-ray absorption ͑SXA͒ study. 3 During charging of a Li-ion battery, 1 lithium ions are extracted from the cathode and inserted into the anode, and the reverse reaction takes place upon discharge. If the cathode material does not contain lithium as-synthesized as in V 6 O 13 , a lithium foil is generally used as anode.…”