Reversible Delithiation of Disordered Rock Salt LiVO₂

Abstract

A rigid crystal lattice, in which cations occupy specific positions, is generally regarded as a critical requirement to enable Li+ diffusion in the bulk of conventional cathode materials, whereas disorder is generally considered as detrimental. Herein, we demonstrate that facile and reversible insertion and extraction of Li+ is possible with LiVO2, a new cation‐disordered rock salt compound (space group: Fmtrue3‾ m), which is, to the best of our knowledge, described for the first time. This new polymorph of LiVO2 is synthesized by mechanical alloying. Rietveld refinements of the X‐ray diffractions patterns and SAED (selected‐area electron diffraction) patterns attested the formation of the disordered LiVO2 rock salt phase. Galvanostatic cycling experiments were employed to characterize the electrochemical performance of the material, demonstrating that reversible cycling over 100 cycles with a discharge capacity around 100 mAh g−1 is possible.

Superoxide formation in Li2VO2F cathode material – a combined computational and experimental investigation of anionic redox activity

“…The structure has a layered rocksalt-type structure, which is very similar to a closely-related oxide compound, LiVO 2 . 48,49 Although the layered structure being the most energetically stable Li 2 VO 2 F in a rocksalt lattice is consistent with the previous DFT simulation results, 47 it has higher energy compared to its decomposed product (i.e., LiVO 2 and LiF), suggesting that the layered rocksalt-type structure is metastable. The metastability of the layered Li 2 VO 2 F is consistent with the recent reports where the Li 2 VO 2 F operates in a metastable phase.…”

Short‐range ordering in the Li‐rich disordered rock salt cathode material Li2VO2F revealed by Raman spectroscopy

“…The Li 2 VO 2 F cathode material was synthesized following a high energy ball milling procedure as described elsewhere. [9,16] All steps were either conducted in a glovebox under argon atmosphere (water and oxygen levels below 0.1 ppm) or in sealed vials under argon atmosphere. Raman measurements on the Li 2 VO 2 F and Li x VO 2 F powders were performed in custom-made air-tight cells under argon atmosphere.…”

Determining the Criticality of Li‐Excess for Disordered‐Rocksalt Li‐Ion Battery Cathodes

“…For instance, while DRX-LiFeO 2 , LiCoO 2 , and LiNiO 2 showed limited capacity (<50 mAh g −1 ), [31,32] DRX-LiVO 2 , LiV 0.5 Co 0.2 O 2 , LiMnO 2 , and LiMoO 2 could still deliver high capacity (≈200 mAh g −1 ). [29,30,47,48] This suggests that the achievable capacity indeed does not depend entirely on the cycling kinetics, which is expected to be slow in all 0% Li-excess DRXs. To identify a possible correlation between the discharge capacity values with TM-redox voltage, we also plot in Figure 3c the calculated average voltage of various Li-TM oxides utilizing different TM-redox couples as extracted from the Materials Project database.…”

“…[15,16,25] Meanwhile, the charging voltage is predicted to be reasonable for both DRX LiMnO 3b). [29,30,47,48] In this case, the benefit of Li-excess would remain at the diffusivity-improvement-level (0-TM percolation), which becomes less important once the particle size is sufficiently reduced.…”