Studies on the improvement in performance of nickel-metal hydride battery

以提高镍氢电池负极性能为目的，研究了化学镀、电镀、研究了含还原剂的碱性溶液处理和金属氧化物混合处理、用外来金属部分取代组成金属控制合金的本体组成以及合金成分与AB_2和AB_5等化学计量比的偏差对储氢合金电化学特性的影响。从这项工作中获得的信息可以概括如下。用外来金属取代部分成分金属，使合金成分偏离AB_5和AB_2.2等化学计量比，改善了储氢合金的电化学性能。对稀土储氢合金表面的各种金属和金属氧化物进行改性，提高了氢电极反应的催化活性和高倍率的可充电性。用还原剂对laes相储氢合金进行表面改性，使其初始活化更容易，并提高了高倍率的可放电性。用原子半径较小的外源金属代替组成金属后，用势步进法评价的储氢合金中氢的扩散系数增大。合金成分与化学计量比的额外偏差导致储氢合金中氢扩散活化能的降低和放电效率的提高。因此，可以为设计储氢合金和开发高性能二次电池负极提供一些指导方针。

For the purpose of improving the performance of negative electrode in a nickel-metal hydride battery, the effects of surface modification of alloys by electroless plating, electroplating, treatment with an alkaline solution containing a reducing agent and mixing of metal oxides and bulk-composition control of alloys by the partial substitution of foreign metals for constituent metals and the deviation of alloy composition from stoichiometric ratio such as AB_2 and AB_5 on the electrochemical characteristics of hydrogen storage alloys were investigated. The information obtained from this work can be summarized as follows.1. Electrochemical characteristics of the hydrogen storage alloys was improved by substituting foreign metals for a part of constituent metals and deviating alloy composition from stoichiometric ratio such as AB_5 and AB_2.2. Catalytic activity for hydrogen electrode reaction and high-rate chargeability increased by modifying various metals and metal oxides on the surface of the rare earth hydrogen storage alloys.3. Surface modification of the Laves-phase hydrogen storage alloys by a reducing agent resulted in easier initial activation and the increase in the high-rate dischargeability.4. Diffusion coefficient of hydrogen in the hydrogen storage alloys evaluated from the potential step method increased by substituting foreign metals having smaller atomic radius for constituent metals.5. Additional deviations of the alloy composition from the stoichiometric ratio lead to the decrease in activation energy for the hydrogen diffusion in the hydrogen storage alloys and the increase in discharge efficiency.Thus, several guidelines of designing the hydrogen storage alloys and developing the negative electrodes for high performance secondary batteries could be proposed.