Study on the surface modification of the MH electrode with cobalt

The metal-hydride electrode of the MH/Ni batteries was modified with a thin cobalt film using vacuum evaporate plating technology. The discharge capacity, high-rate dischargeability, cyclic stability and inner pressure of the batteries were tested. The XPS and XRD were used to analyze the surface and structure of the electrode. Experimental results indicated that the surface modification could decrease the resistance and increase the discharge capacity and voltage of the batteries. After surface modification, the discharge capacity at 5C (8.5 A) was increased by 120 mAh and discharge voltage was increased by 0.05 V, the resistance of the batteries was also decreased by 19.3%. The cyclic stability of the batteries was remarkably improved after surface modification. The remaining capacity of the modified batteries was 94.0% of the initial capacity even after 500 cycles. The inner pressure of the batteries during overcharging was lowered and the charging efficiency of the batteries was enhanced.