Electrochemical characterizations of multi-layer and composite silicon–germanium anodes for Li-ion batteries using magnetron sputtering

Abstract

To improve the electrochemical performance of Si film, we investigate the addition of two film forms of Ge. Si/Ge multi-layered and Si–Ge composite electrodes that are fabricated by magnetron sputtering onto Cu current collector substrates are investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and extended X-ray absorption fine structure (EXAFS) are employed to analyze the structures of the Si–Ge electrodes. When used as an anode electrode for a lithium ion battery, the first discharge capacity of a Si/Ge 150 multi-layer cell with a ratio of Si 15 nm/Ge 3 nm is 2099 mAh g −1 between 1.1 and 0.01 V. A stable reversible capacity of 1559 mAh g −1 is maintained after 100 cycles with a capacity retention rate of 74.25%. Additionally, the Si 0.84Ge 0.16 composite has an initial discharge capacity of 1915 mAh g −1 and a capacity retention of 74.25%. In full cell tests of Si–Ge electrodes, the Si 0.84Ge 0.16/LiCoO 2 cell delivers a specific capacity of approximatly 160 mAh g −1 and a capacity retention of 52.4% after 100 cycles. The results reveal that these two systems of sputtered Si–Ge electrodes can be used as anodes in lithium ion batteries with higher energy densities.