Structure and Electrochemistry of LiV₃O₈ Thin Film Electrode: Effect of Diffusion Rate and Concentration on Cell Polarization

Electrochemistry of lithium trivanadate (LiV3O8, LVO) has been extensively studied due to its large capacity and high rate capability. The material undergoes both insertion/extraction and phase transform reactions during discharge and charge in a Li-ion battery. However, the rate limiting factors of the material are unclear over the cycling window of 2.0 -3.8 V. In this work, LVO thin films are fabricated from RF magnetron sputtering and annealed at different temperatures of 260, 350, 400 and 500°C. Crystallinity, crystallite size and preferred orientation of the thin films are analyzed by x-ray diffraction. All solid-state thin film batteries are fabricated with LVO cathodes annealed at different temperatures of 260, 350 and 400°C. The electrochemical properties are investigated at two different test temperatures to compare the rate limiting process for discharge and charge. AC impedance is applied on the 260 and 350°C cells to characterize the voltage dependence of the diffusion coefficient during both discharge and charge. Our work correlates the cell polarization with both the diffusion coefficient and the Li+ concentration, showing that these parameters play different roles in the insertion and phase transform reactions, and shows the structural dependence of these parameters. Figure 1