具有超晶格结构的La-Mg-Ni型合金的高低温电化学性能研究

Nickel-metal hydride (Ni-MH) batteries with hydrogen storage alloys as the negative electrode materials have been the focus of attention due to their high discharge capacity, high energy and power density, non-toxicity, and environmental friendliness. Therefore, it is one of the most promising candidates for the development of secondary batteries with reversible and efficient electrochemical energy storage and conversion. However, it is well-known that the operating temperature has striking effect on the electrochemical performance. That is to say, Ni-MH batteries could suffer substantial deterioration of the electrochemical performance at temperatures below ca. 273 K (winter conditions) or above ca. 313 K (summer conditions). In this research proposal, the rare-earth La-Mg-Ni-type hydrogen storage alloys with superlattice structure are selected as negative electrode for Ni-MH batteries and the material failure analysis of negative electrode is investigated over a wide temperature range (253-323 K). The composition and structure of alloy will be adjusted and the physical and/or chemical modification of alloy particles (such as microencapsulation) will be conducted in order to improve the overall electrochemical performance over a wide temperature range. Furthermore, the optimal Ni(OH)2 positive electrode will be picked out and the components of KOH alkaline electrolyte will be adjusted for optimum combination of Ni-MH batteries. Through the investigation of the essential roles of negative electrode, positive electrode and electrolyte in Ni-MH batteries, the effect of temperature on the electrochemical performance will be further understood and the theoretical model of the influence of temperature on the electrochemical performance will be established. In the meanwhile, the fundamental data and information will be obtained, on which the Ni-MH batteries over a wide temperature are investigated in the future. This research proposal will help us to further understand the effect of temperature on La-Mg-Ni-type alloys with superlattice structure as negative electrode in Ni-MH batteries, on which the Ni-MH power batteries will be investigated in the future.

以储氢合金为负极的镍氢电池是一种绿色环保电池，由于具有高容量、大功率、无污染等特点而备受青睐，是当今二次电池的重要发展方向之一。但是，电池性能受温度影响较大，高低温下的性能严重偏离室温下的性能，使用的温度范围受限制。本项目拟以具有超晶格结构的La-Mg-Ni系储氢合金作为负极材料，探索负极材料在电池高低温运行时的失效机制，调节合金材料的组成和结构并做进一步的改性处理（如微胶囊化），同时匹配合适的氢氧化镍正极材料以及调节KOH 碱性电解质溶液的组成和成分，以期达到电池各部分的优化组合，改善其在宽温区范围内(253～323 K)的综合性能。通过研究正负极材料和电解质溶液在镍氢电池中的作用本质，深入理解温度对电池性能的影响机制，建立温度对电化学性能影响的理论模型。本项目的实施对于深入认识高低温对具有超晶格结构的La-Mg-Ni型合金的影响机制有普遍指导意义，为镍氢动力电池的后续研究奠定基础。

以储氢合金为负极的镍氢电池是一种绿色环保电池，由于具有高容量、大功率、无污染等特点而备受青睐，是当今二次电池的重要发展方向之一。但是，电池性能受温度影响较大，高低温下的性能严重偏离室温下的性能，使用的温度范围受限制。本项目拟以具有超晶格结构的La-Mg-Ni系储氢合金和CoB非晶合金作为负极材料，调节KOH碱性电解质溶液的组成和成分，改善了其在宽温区范围内(253～323 K)的综合性能。用NaBH4溶液分别还原CoCl2·6H2O，CoSO4·7H2O和Co(NO3)2·6H2O溶液制备了CoB非晶合金，实验结果表明：由CoCl2·6H2O制备所得的CoB合金具有较高的放电比容量，在100 mA/g的电流密度下，最大放电容量高达844.6 mAh/g，经过几个循环之后基本稳定在450 mAh/g左右。添加La0.7Mg0.3Ni3.5合金能明显改善CoB合金电极的循环稳定性和高倍率放电性能。HRD900由48.6% (x = 0 wt.%)提高到 82.5% (x = 30 wt.%)，而容量保持率C100/Cmax先由37.1% (x = 0)提高到45.6% (x = 5 wt.%)。另外，添加5 wt.% La0.7Mg0.3Ni3.5合金后，合金电极的动力学性能明显改善，低温放电容量和高倍率放电性能明显提高。采用液相沉积法制备了三元Co-Ni-B非晶合金，作为碱性电池的负极材料，合金展示出优异的宽温区（-30 ~ 50 ℃）电化学性能。特别是在-15 ~ 25 ℃，经过100个充放电循环后电化学容量都还保持在400 mAh/g左右。即使是在-30 ℃时，合金的最大放电容量仍有408.3 mAh/g，经过100个循环后缓慢降到317.1 mAh/g。另外，在-30 ℃时，HRD900为29.6%。本项目的实施对于深入认识高低温对具有超晶格结构的La-Mg-Ni型合金和CoB非晶合金的影响机制有普遍指导意义，为镍氢动力电池的后续研究奠定基础。