State of the art commercial lithium ion batteries (LIBs) use graphite as a low-cost anode material to store lithium ions safely and reversibly. Recently, alloying anodes such germanium (Ge, 1600 mAh g–1), silicon and tin have been proposed as alternatives to replace low capacity graphite anode (372 mAh g–1), mainly due to their outstanding theoretical capacities. However, germanium-based anode suffers from huge volume changes (~300%) during lithiation and de-lithiation, resulting in pulverization and fast capacity fading. In this study, the large volume change issue was tackled by etching asymmetric porous germanium membrane with hydrogen peroxide solutions. Non-etched Ge asymmetric membrane electrode demonstrated a mediocre improvement in cyclability over micron powder Ge control electrode with a capacity retention less than 30% in 50 cycles at 160 mA g–1. After being etched with concentrated H2O2 at 90 °C for 30 s, the cyclability was dramatically enhanced to above 80% in 50 cycles at 160 mA g–1. To prevent the still inevitable capacity loss from the membrane surface, the etched Ge membrane was coated with porous carbonaceous membranes to create a sandwich structure. As a result, not only can more than 95% capacity be retained in 50 cycles but the electrode capacity is also raised. Ge membranes were also systematically characterized by using scanning electron microscope, energy dispersive X-ray analyzer, powder X-ray diffractometer, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric, and surface area analyzers. It was found there is a clear correlation between the electrochemical performance, membrane geometry, carbonaceous membrane coating, and concentration of Ge.

H2O2-etched germanium membranes for cyclable lithium ion battery anode

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.