Preparation of Li<Sub>4</Sub>Ti<Sub>5</Sub>O<Sub>12</Sub> Thin Film Electrode with PVP Sol-Gel for a Rechargeable Lithium Microbattery

Abstract

A Li4Ti5O12 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 Li4Ti5O12 oxide. Optimized conditions for preparation of uniform film without any cracks were firstly a heating temperature of 600oC, 3000 rpm, and secondly a sol with 5 mol% 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% at 60th cycle. The Li+ ion diffusion coefficient at a potential of 1.57 V was estimated to be 6.5×10−10 cm2 s−1, indicating that the thin film exhibited a fast electrochemical response. From these results, it can be said that the Li4Ti5O12 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.