Tailoring nanoporous structures of Ge anodes for stable potassium-ion batteries

We present here for the first time the electrochemical behavior of germanium anodes in potassium-ion batteries (KIBs). Nanoporous germanium (np-Ge) samples were fabricated by the chemical-dealloying method using Al as the sacrificial metal. Galvanostatic tests identified the reversible potassiation of the np-Ge anodes and the optimal sample with tuned porosities and ligaments demonstrated stable capacities of ~120 mAh g−1 over 400 cycles. Further analysis of the np-Ge electrode revealed amorphous KGe alloys were formed upon discharge. This study suggest germanium can be a potential anode in KIBs, but the structural tailoring is critical to overcome the kinetics problems of the large K-ions. •Nanoporous germanium with different porous structures have been fabricated via a facile chemical-dealloying approach.•Reversible potassiation have been identified with the Ge anodes in potassium ion cells.•The tailored Ge electrodes with interconnected porosity and small ligaments demonstrate a stable long-term cycling over 400 cycles.