MH/Ni电池充放电过程导电物理机制的研究

借助X射线衍射等方法, 研究了MH/Ni电池在充放电过程中电极活性材料β-Ni(OH)2和AB5合金的结构和微结构变化, 进而讨论了两种电极活性材料在充放电过程中的物理行为和导电的物理机制. 研究发现, 在充电过程中确实未观测到β-Ni(OH)2→β-NiOOH的相变, 只有在满充和过充时, 才发生部分β-Ni(OH)2转变成γ-NiOOH, 且一直是β-Ni(OH)2和γ-NiOOH两相共存; 在充电过程不是由β-Ni(OH)2→β-NiOOH相变来提供氢离子, 而是由氢原子离开β-Ni(OH)2的点阵位置提供氢离子; 在负极这一边, 开始时氢原子是以间隙式嵌入AB5点阵形成固溶体, 只有当AB5因氢原子的嵌入使其体积变化达一定百分数后才析出AB5Hx氢化物. 这些过程使电极活性材料的微结构也发生变化, 而且这种变化不是完全可逆的. 简言之, MH/Ni电池的物理导电机制是在正负极活性材料中嵌入和脱嵌的氢离子在电极间的定向迁移运动.

Investigation of Physical Mechanism for Electric Conduction during Charge-discharge Process in MH/Ni Battery

The structure and microstructure changes of electrode active materials, β-Ni(OH)2 and AB5 alloy, during the charge and discharge processes have been studied detailed by means of X-ray diffraction (XRD). Physical behavior of electrode active materials and the physical conductive mechanism have been discussed. It has been found that the phase transformation from β-Ni(OH)2 to β-NiOOH do not be observed during the charge process. Until full charge or over charge, partial β-Ni(OH)2 is transformed into γ-NiOOH and both the phases β-Ni(OH)2 and γ-NiOOH always co-existed. During the process of charge, H＋ is not offered by the phase transformation from β-Ni(OH)2 to β-NiOOH, but by the hydrogen atom disengaging from lattice position of β-Ni(OH)2. In the side of negative electrode, solid solution of AB5-H is formed by hydrogen atom inserting into interstitial positions of the AB5 lattice. AB5Hx is formed only when volume change of AB5 reached certain percent. These processes make microstructure of the electrode active materials to occur change and such changes are not fully reversible. To be brief, the physical conductive mechanism of MH/Ni batteries is the directional migrating and moving of hydrogen ions between the positive and negative electrodes because hydrogen atoms are inserting into and deviating from the β-Ni(OH)2 and AB5.