Effect of germanium on electrochemical performance of chain-like Co–P anode material for Ni/Co rechargeable batteries

Co–P (4.9% P) powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co–P and germanium powders were mixed at various mass ratios to form Co–P composite electrodes. Charge and discharge test and electrochemical impedance spectroscopy (EIS) were carried out to investigate the electrochemical performance, which can be significantly improved by the addition of germanium. For instance, when the mass ratio of Co–P powders to germanium is 5:1, the sample electrode shows a reversible discharge capacity of 350.3 mA·h/g and a high capacity retention rate of 95.9% after 50 cycles. The results of cyclic voltammmetry (CV) show the reaction mechanism of Co/Co(OH)2 within Co–P composite electrodes and EIS indicates that this electrode shows a low charge-transfer resistance, facilitating the oxidation of Co to Co(OH)2.