Effects of high-energy ball milling (HEBM) on the structure and electrochemical performance of nickel hydroxide

A method of high-energy ball milling (HEBM) was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of Ni/MH battery. The experimental results showed that HEBM is an effective method to improve the electrochemical performance of β-Ni(OH)2 such as specific discharge capacity, discharge potential and cycle performance. But the performance of α-Ni(OH)2 was greatly reduced by HEBM processing. The results of electrochemical impedance spectroscopy, powder X-ray diffraction and particle size distribution indicated that the improvement of the performance of β-Ni(OH)2 through HEBM was attributed to the reduction of the charge-transfer resistance (Rt), the diffusion impedance (Zw), which was resulted from the decrease of the crystallite and particle size and the increase of interlayer spacing. However, for α-Ni(OH)2 samples, those structure changes after HEBM resulted in the increase of the Rt and Zw and the deterioration of its electrochemical performance.