Structural Evolution of Disordered Li_xV₂O₅ Bronzes in V₂O₅ Cathodes for Li-Ion Batteries

Abstract

Vanadium pentaoxide, V 2 O 5 is an attractive cathode material for Li-ion batteries, which can store up to three Li-ion per formula unit. At deep discharge an irreversible reconstructive phase transition occurs with formation the disordered ω-Li x V 2 O 5 bronze, which despite the lack of long range order exhibits a high reversible capacity (~310 mAh/g) without regaining the crystallinity upon recharge. Here, we utilize operando powder X-ray diffraction and total scattering (i.e. pair distribution function analysis) to investigate the atomic-scale structures of the deep-discharge phase ω-Li x V 2 O 5 (x ~ 3) and, for the first time, the highly disordered phase β-Li x V 2 O 5 (x ~0.3) formed during subsequent Li-extraction. Our studies reveal, that the deep discharge ω-Li 3 V 2 O 5 phase consists of ~60 Å domains rock salt structure with a local cation ordering on ~15 Å length scale. The charged β-Li x V 2 O 5 phase only exhibits very short range ordering (~10 Å). The phase transition between these phases is structurally reversible and appears unexpectedly to occur via a two-phase transition mechanism.

Order–disorder transition in nano-rutile TiO2 anodes: a high capacity low-volume change Li-ion battery material

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