High-power Nickel-metal Hydride Battery

This work centered on the research and manufacture of Ni-MH high power battery, and the battery which could be charged/discharged at 10C were designed and manufactured. The impact of all kinds of factors on the high-rate charge performace was analyzed by studying nickel foam, cobalt-coated spherical Ni(OH)₂ and hydrogen storing alloys using constant current charge and discharge, CV, XRD and SEM.The result showed that the increase of surface density of nickel foam and PPi was beneficial to the improvement of high power discharge current and MPV. At 10C the discharge capacity and MPV of AA1600mAh battery reached 1475mAh and 1.03V repectively. But the nicklel foam with over 110 PPi played an negative role in the high power performance.It was an inverse proportion for capacity to surface area of spherical Ni(OH)₂ coated by cobalt in AA 1600mAh battery, with the value reduced from 240.1mAh/g to 224.2mAh/g; while it was an obverse proportion for the cycle life and Zn content, with the cycle number increased from 192 to 284. The proton diffusion coefficient in Ni(OH)₂ electrode was the most significant factor which affected the high power discharge MPV. The change trend of high power discharge MPV agreed well with that of diffusion coefficient, so did the variation relation between high power discharge MPV and hydrogen diffusion coefficient in hydrogen storing alloys. The increase of Ce sped up hydrogen diffusion in hydride and improved the dynamic performance of alloy, and the MPV reached up to 1.181V at 10C. Cycle life was related to the pulverization and cauterization of alloy. Pulverization caused a battery inner resistance reaching up to 7.03 mΩand a discharge flat reduced to 1.031V. Ce-rich alloy and hydrogen storing alloys with a proper increase of Co content were more suitable for high power batteries.At 10C the cycle life was almost in proportion with ventilation ability of separator, with the latter increased from 9 to 35 cm/sec and the former from 80 to 116 weeks. For the NH4⁺ absorption ability of sulfonated polypropylene separator, the highest charge retention of 78% was achieved after 7-day rest at 45℃, but the value for blended fabric and modified nylon were 56％and 60％repectively. The shuttle action between positive and negative electrode leads to a great decline of charge retention in separator. Hence modified nylon or blended fabric were better for batteries high power discharge performance.In the electrolyte consisting of K⁺, Na⁺ and Li⁺, the increase of NaOH and KOH concentration improved discharge flat and capacity respectively. But Cl^-,CO₃^2-,NO₃^- reduced the discharge flat, cycle life and charge retaintion.