Preparation of Li_4Ti_5O_(12) Thin Film Electrode with PVP Sol-Gel for a Rechargeable Lithium Microbattery

摘要

A Li_4Ti_5O_(12) thin film electrode for rechargeable lithium microbatteries was prepared on Au substrate by a sol-gel method. A stable sol was successfully prepared by adding poly(vinylpyrrolidone) (PVP) into 2-propanol solvent, in which PVP prevented a crack formation. The sol was coated on Au substrates with a spin coater, and was converted to gel during the spin coating process. The gel was then heated to form Li_4Ti_5O_(12) oxide. Optimized conditions for preparation of uniform film without any cracks were firstly a heating temperature of 600 deg C, 3000 rpm and secondly a sol with S mol percent of PVP. An electrochemical cell was constructed with polymethylmethacrylate gel-polymer electrolyte, which was electrochemically evaluated using a cyclic voltammetry and a discharge and charge test. The discharge and charge curves were very flat around 1.55 V and the rechargeability increased up to 97.5 percent at 60th cycle. The Li~+ ion diffusion coefficient at a potential of 1.57 V was estimated to be 6.5 X 10~(-10) cm~2 s~(-1) indicating that the thin film exhibited a fast electrochemical response. From these results, it can be said that the Li_4Ti_5O_(12) thin film with a fast electrochemical response is a prospect of an active electrode material, and that PVP sol-gel method is very useful for thin film preparation.