Investigation of interfacial resistance between LiCoO2 cathode and LiPON electrolyte in thin-film battery

초록

Microenergy sources are required to drive small electronic devices such as CMOS backup, smart cards, and microelectromechanical systems. Thin film microbattery is the best candidate to supply the energy for the operation of these elctronic applications. Li ion conducting solid electrolyte lithium phosphorous oxynitride(LiPON) has a high ionic conductiity, stability window up to 5.5 V and LiCoO2 cathode has a high energy density and good cycling-life performance. In this work, all solid-state thin film battery using LiCoO2 cathode/LiPON electrolyte was fabricated with RF sputtering and Li deposition by thermal evaporation. It has been known that performance of the thin film battery strongly depends on the interfacial resistance between cathode/electrolyte during intercalation and deintercalation of Li ions and metal oxide coating on cathode enhances the cell performance by suppressing Co dissolution in liquid electrolyte. In order to decrease the interfacial resistance, nanometer-thick Al2O3 interlayer was prepared between cathode and LiPON electrolyte. The effect of thermal treatment and sputtering conditions of interlayer materials on the cell performance was analyzed with impedance spectroscopy and electrochemical measurements. Insertion of Al2O3 interlayer shows a higher discharge capacity and enhanced cyclability.