Ge thin film anode in a flexible solid-state Li-ion microbattery

Abstract

Flexible solid-state lithium ion batteries (LIBs) have become an important part of the portable electronics due to their flexibility, lightweight, easy portability, security and the ability to be adjusted in large-scale energy storage microsystems, with significantly high power and long cycle life. Germanium (Ge) is a promising anode material for high-generation LIBs, with high theoretical capacity (1600 mAh/g corresponding to Li4.4Ge), fast Li ion diffusivity (i.e. 400 times faster than silicon) and good electronic conductivity (104 times higher than silicon) which allow high charge/discharge rates. Here, electrochemical performance of e-beam deposited Ge anode (300 nm thick) coupled with LiCoO2/LIPON (cathode/electrolyte) in a microbattery system was investigated. The battery (figure 1) was fabricated only by PVD techniques. LiCoO2 was deposited by RF-sputtering (120 W RF power; 17 sccm of Ar) and LIPON with the conditions explained in JF Ribeiro, et al. [1]. Open circuit potential (figure 2), charge/discharge cycles (figure 3) and electrochemical impedance spectroscopy (EIS), at room temperature, were performed.