Co/CMK-3 composites are synthesized via a facile hydrothermal route. The electrochemical performances of Co/CMK-3 composite as the negative electrode material for alkaline rechargeable Ni/Co batteries have been systemically investigated. Electrochemical measurements show that the CMK-3 can remarkably enhance the electrochemical activity of Co, leading to a notable improvement of the discharge capacity, cycle stability and rate capability. Interestingly, the discharge capacity of Co/CMK-3 (25 mg CMK-3) electrode can reach 519.3 mAh g−1 and retains about 365.8 mAh g−1 after 100 cycles at discharge current of 100 mA g−1. The electrochemical reaction mechanism of Co/CMK-3 composite electrode can be attributed to the electrochemical redox reaction between Co and Co(OH)2.