Effects of addition of different carbon materials on the electrochemical performance of nickel hydroxide electrode

Nickel hydroxide is used as an active material in positive electrodes of rechargeable alkaline batteries. The capacity of nickel-metal hydride (Ni-MH) batteries depends on the specific capacity of the positive electrode and utilization of the active material because of the Ni(OH)₂/NiOOH electrode capacity limitation. The practical capacity of the positive nickel electrode depends on the efficiency of the conductive network connecting the Ni(OH)₂ particle with the current collector. As β-Ni(OH)₂ is a kind of semiconductor, the additives are necessary to improve the conductivity between the active material and the current collector. In this study the effect of adding different carbon materials (flake graphite, multi-walled carbon nanotubes (MWNT)) on the electrochemical performance of pasted nickel-foam electrode was established. A method of production of MWNT special type of catalysts had an influence on the performance of the nickel electrodes. The electrochemical tests showed that the electrode with added MWNT (110-170 nm diameter) exhibited better electrochemical properties in the chargeability, specific discharge capacity, active material utilization, discharge voltage and cycling stability. The nickel electrodes with MWNT addition (110-170 nm diameter) have exhibited a specific capacity close to 280 mAh g⁻¹ of Ni(OH)₂, and the degree of active material utilization was ∼96%.