(694g) Reversible Disorder-to-Order Transition Induced By Aqueous Lithiation in Vanadate Electrode Materials

Aqueous lithium-ion batteries provide a promising solution for sustainable and safe energy storage. Vanadium-based oxides existing in various valence states (+2 to +5) are intriguing electrode materials in aqueous owing to their low cost and high theoretical capacity for lithium ions. Two-dimensional (2D) vanadium pentoxide (V₂O₅) has been a widely used cathode material in compact commercial cells for decades. However, V₂O₅ is soluble in aqueous solutions, leading to potential capacity loss over time. Additionally, it undergoes phase transformations and irreversible structural distortions upon Li-ion intercalation, compromising its long-term stability, which is an ongoing challenge for vanadium oxide electrodes.

In this study, a disordered lithium vanadate (Li-V₃O₈) was investigated as a strategy to suppress phase transitions in vanadium oxide within aqueous electrolytes. Our research using electrokinetic analysis, in situ X-ray diffraction (XRD), and Debye scattering simulations revealed a monophase of Li-V₃O₈ experiencing reversible disorder-to-order structural transition throughout the (de-)lithiation process, unlike its crystalline V₂O₅ polymorph. This transition indicated a sequential interlayer and intralayer lithiation process. The absence of distortive phase transitions and multilithiation pathways facilitates Li-ion diffusion in vanadate electrode materials, improving storage capacity. This work opens a new dimension for vanadium-based disordered oxides, advancing the development of low-cost, aqueous electrochemical energy storage systems.