High capacity cobalt boride prepared via vacuum freeze-drying method and used as anode material for alkaline secondary battery

In recent years, some metal borides, especially cobalt boride, have been regarded as anode candidates of high energy alkaline secondary batteries for their potential of carrying out multi-electron reactions. So far, there are some reports on the synthesis of metal borides, such as ball milling method, arc melting method, high-temperature solid-phase method, and so on. Herein, a vacuum freeze-drying method is adopted to synthesize cobalt boride with small size, uniform particle size distribution, high specific surface area, as well as excellent electrochemical activity. The crystal structures, particle size, and specific surface area of the as-prepared Co-B alloys were characterized and analyzed via X-ray diffraction, scanning electron microscopy, and nitrogen adsorption-desorption test. The electrochemical activities of the Co-B samples were examined by cyclic voltammetry (CV) and charge-discharge test. It is found that the Co-B alloy synthesized via the vacuum freeze-drying method exhibits good reversibility and cycle stability, and achieves a maximum discharge capacity of 437 mAh/g at the current density of 300 mA/g, which is much superior to that of the sample prepared via traditional chemical reduction method.