Electrochemical properties of thin TiO2 electrode on Li1 + xAlxGe2 − x(PO4)3 solid electrolyte

A fabrication of all-solid-state thin-film rechargeable lithium ion batteries by sol–gel method is expected to achieve both the simplification and cost reduction for fabrication process. TiO2 thin film electrode was prepared by PVP (polyvinylpyrrolidone) sol–gel method combined with spin-coating on Li1 + xAlxGe2 − x(PO4)3 (LAGP) solid electrolyte which has wide electrochemical window. The thin film was composed of anatase TiO2 that is the most active phase for Li insertion and extraction and contacted well with LAGP substrate. In the cyclic voltammogram, a redox couple was observed at 1.8 V vs. Li/Li+ assigned to Li insertion/extraction into/from anatase TiO2, indicating that the thin film worked as electrode for lithium battery. The charge and discharge test in various charge and discharge rates revealed that the discharge process (delithiation) is thought to be faster than charge process (lithiation). It is attested that the sol–gel process, which derives both simplification and cost reduction for fabrication process, can be applied to thin film battery using LAGP solid electrolyte.

► TiO2 thin film on Li1 + xAlxGe2 − x(PO4)3 (LAGP) was prepared by sol-gel method.
► The thin film TiO2 showed clear charge and discharge behavior.
► The sol-gel process can be applied to fabricate thin film battery.