Effect of proton irradiation on anatase TiO₂ nanotube anodes for lithium-ion batteries

The role of defects in the charge transfer and transport properties of electrode materials for lithium-ion batteries has recently garnered increased interest. It is widely recognized that ion irradiation promotes the formation of defects within a crystalline solid. Among all ion species used for irradiation, protons are expected to create primarily simple Frenkel pair point defects without significantly changing the stoichiometry of the damaged region of the target material. This work investigates the effect of proton irradiation at varying temperatures on the electrochemical properties of anatase TiO₂ nanotube (TiO₂-NT) electrode for lithium-ion battery applications. Anatase TiO₂-NTs are irradiated at both room temperature (25 °C) and 250 °C and compared with non-irradiated control specimens. Characterization by Raman spectroscopy and XRD suggests that the irradiation at both temperatures does not alter the long-range order of the nanotubes. However, high-resolution TEM reveals that defect clusters are formed upon irradiation and increase in size with increasing temperature. Both irradiated samples exhibit increased capacity and enhanced rate capability compared with the non-irradiated control, which can be explained by increased storage sites as well as improved Li⁺ diffusivity due to the presence of irradiation-induced defects. This study presents a unique perspective on pathways to engineer functional nanostructured electrode materials by tailoring irradiation conditions.