Electrochemical characterizations of germanium and carbon-coated germanium composite anode for lithium-ion batteries

The electrochemical reaction mechanism of germanium with lithium at room temperature was investigated. Two distinct voltage plateaus corresponding to the formation of Li9Ge4 and Li7Ge2 were observed, and the final products were identified as a mixture of Li15Ge4 and Li22Ge5 phases. A three-step reaction mechanism of germanium with lithium was suggested. Carbon-coated germanium composites prepared by mechanical milling and pyrolysis were evaluated as anode materials for lithium-ion batteries. The composite materials, Ge-mesocarbon microbeads and Ge-poly(vinyl alcohol), showed good cyclability and retained fairly large capacities of 473 and 579 mAh/g, respectively, up to 50 cycles when cycled within a limited voltage window.