TiO₂(B) Epitaxial Thin Film Electrode for All-Solid-State Nanobattery

Due to its pseudocapacitive, one-dimensional, rapid ion channels, TiO₂(B) holds promise as a Li-ion rechargeable battery anode electrode. Despite its potential for high capacity and superior rate capability, realizing its theoretical capacity and full rate capability remained challenging. Partly owing to its metastability, instead of pure or single crystalline TiO₂(B) materials, multiphase or polycrystalline samples are synthesized. In this study, assisted by an isostructural VO₂(B) template layer, we successfully synthesized single-phase TiO₂(B) films epitaxially, with well-aligned ion diffusion channels. Using a liquid electrolyte, TiO₂(B) epitaxial electrode demonstrates a capacity close to the theoretical value of 335 mA h g–1 and exceptional charge–discharge cyclability for ≥200 cycles, surpassing the performance of other TiO₂(B) or alternative phase nanostructures. Moreover, by applying LiPON as a solid electrolyte, we demonstrated the feasibility of an all-solid-state configuration, showing excellent stability. These findings suggest significant potential for downsizing all-solid-state nanobatteries for application in self-powered integrated circuits.