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

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 Si0.84Ge0.16 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 Si0.84Ge0.16/LiCoO2 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. (C) 2010 Elsevier B.V. All rights reserved.This work was financially supported by the Korean Science and Engineering Foundation (KOSEF) through the Research Center for Energy Conversion and Storage and by the Brain Korea 21 Project under the Ministry of Education and Human Resources Development, Republic of Korea