Non-foam nickel electrode with quasi-three-dimensional substrate for Ni-MH battery

New paste-type positive electrodes for nickel/metal-hydride (Ni/MH) batteries were prepared using low-cost quasi-three-dimensional (Q-3D) substrate replacing conventional Ni foam, and their electrochemical properties were studied. Q-3D substrate showed better packing efficiency of active material than punched metal. By using highly conductive CoOOH-coated Ni(OH)(2) as an active material, an unsealed cell with Q-3D substrate electrode showed relatively low resistance and 98% of utilization efficiency at 0.2 C discharging rate. A sealed cell with this positive electrode was slightly inferior to that with conventional Ni foam electrode in high rate capability and durability, but was able to discharge at 10 C rate and attained 510 cycles of cycle life. Swelling of the positive electrode and distribution of electrolyte in cells were investigated by means of X-ray computed tomography and atomic absorption spectrometry after cycle testing, and it was found that the cycle degradation was due to increase in cell resistance associated with transfer of electrolyte from the separator to the positive electrode. (C) 2004 The Electrochemical Society.