Influences of annealing on lithium-ion storage performance of thick germanium film anodes

•We demonstrated high performance Ge-based anode by air annealing post-treatment.•Annealed Ge had a specific capacity of 1186 mA h g−1 at 812 mA g−1 for 50 cycles.•Annealed Ge had a volumetric capacity of 5887.4 mA h cm−3 at 812 mA g−1 for 50 cycles.•Air annealing post-treatment is an effective, simple and low-cost method.•Better adhesion of SS/Ge due to interdiffusion at SS/Ge interface is attributed.

A high performance germanium (Ge) based anode is achieved through an appropriate air annealing post-treatment. Annealed Ge is fabricated by sputtering of Ge onto a stainless steel (SS) current collector and then annealed in air. It shows high specific and volumetric capacities of 1186 mA h g−1 and 5887.4 mA h cm−3, respectively, at the rate of 812 mA g−1 up to 50 cycles. These specific and volumetric capacities are approximately a factor of 20 higher than those from as-deposited Ge on the SS substrate. In addition, the annealed Ge has a higher initial Coulombic efficiency of 90.8% than the as-deposited Ge of 81%. The improved performance of the annealed Ge can be attributed to the enhanced adhesion of annealed Ge film to SS substrate through interdiffusion at the SS/Ge interface due to the annealing post-treatment.

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