Surface treatment for hydrogen storage alloy of nickel/metal hydride battery

The electrochemical performance of AB(2)-type (Ti0.35Zr0.65Ni1.2V0.6Mn0.2Cr 0.2) and AB(s)-type (MmB(4.3)(Al0.3Mn0.4)(0.5)) hydrogen storage alloys mod ified by hot KOH etching and electroless nickel coating has been investigat ed. It is found that the alloy modified with hot KOH solution shows quick a ctivation but at the expense of cycle-life stability. The alloy coated with nickel was effectively improved in both cycle-life stability and discharge capacity. Both the exchange and limiting current densities were increased by modifying the alloys by hot KOH solution dipping or electroless nickel c oating as compared with untreated alloy electrode. The electrode with highe r exchange current density and limiting current density leads to increased high-rate dischargeability. A duplex surface modified alloy (i.e., alloy fi rst treated with hot KOH solution and then coated with nickel) has been dev eloped, which performs satisfactorily with respect to both quick activation and long cycle life. In addition, the high-rate dischargeability for the e lectrode with duplex surface modification is superior to that of electrode solely treated with KOH etching or Ni plating. (C) 2000 Elsevier Science S. A. All rights reserved.