电极活性材料精细结构与MH-Ni电池性能关系研究的一些进展

RELATIONSHIP BETWEEN MICROSTRUCTURES OF ELECTRODE ACTIVE MATERIALS AND BATTERY PERFORMANCE IN MH-NI BATTERY:SOME PROGRESS

为了更深入地研究正负极活性材料精细结构与MH-Ni电池性能之间的关系,本文在介绍了简单而较适用的处理X射线衍射数据的方法之后,系统综述了电池活化前后、循环过程中正负极活性物质结构和微结构与电池性能之间关系研究的一些进展。主要包括:(1)具有适当晶粒大小和较大层错几率的β-Ni(OH)2物质,能获得较大的充放电容量;(2)没有观测到MH/Ni电池在充放电过程中有β-Ni(OH)2β-NiOOH的相变,只有满充和过充电时才发生部份β-Ni(OH)2γ-NiOOH的相变;MH/Ni电池的物理导电机制是在正负极活性物质中嵌入和脱嵌的氢离子形成固相质子在电极间定向运动。(3)循环性能的衰减、内阻、容量的变化与正负极活性物质的微结构变化有良好对应关系。微结构变化消耗电解液,并改变电解液的性能。正极、负极和电解液三者的共同作用是循环性能衰减的主导原因。(4)正极添加剂与电池性能之间的关系。由于正极添加剂Lu2O3和CaF2能抑制正极活性物质的微晶细化、减缓总的层错几率降低,对于储氢合金能抑制晶粒增大,特别能抑制A(OH)3和B的析出,故能提高了电池的循环性能和寿命。(5)电池储存前后的容量衰减和内阻增加是其在储存过程中CoOOH析出和晶粒细化双重作用的结果。

This article reviews some progress in researches on the relationships between the microstructures of electrode active materials and the battery performance for MH-Ni battery before and after the activation during circulation process. First, some simple and easily accessible methods for evaluating the X-ray diffraction data have been introduced. Subsequently, the major research results have been summarized. They includes： （1） The positive active material β-Ni（OH）2 of appropriate grain size and high fault probability can offer large charge-discharge capacity. （2） No β-Ni （OH）2←→β-NiOOH phase transformation during charging and discharging sequences is observed while phase transformation of partial β-Ni（OH）2 phase to β-NiOOH phase is identified at the full-charging or over-charging stage. The physical conduction mechanism of MH-Ni battery is ascribed to the directional motion of solid-state protons between the position and negative electrodes, and those protons are formed by hydrogen atoms deintercalated and intercalated in electrode active materials, β-Ni（OH）2 and AB5. （3） The dependence of circulation attenuation, inner resistance changes and capacity on the microstructural evolution of the anode and cathode active substances during circulation is established. The microstructural evolution may consume the electrolyte and deteriorate the performance of electrolyte. The microstructural evolutions of the anode, cathode and electrolyte are responsible for the attenuation of the circulation performance. （4） The additives of positive electrode, Lu2O3 and CaF2, can enhance the circulation performance and lifetime of MH Ni batter, because they can weaken the grain refining, maintain the fault probability in β-Ni（OH）2, and suppress the precipitation of A（OH）3 and B phases in particular. （5） The capacity fading and internal resistance enhancement of MH-Ni battery during storage are caused by the precipitation of CoOOH and grain refining.