β-球形氢氧化镍的微结构与热分解特征

Microstructures of spherical β-nickel hydroxides and their thermal decomposition characteristics

利用热分析方法和扫描电子显微镜(SEM)对湿法制备的β-球形氢氧化镍的热分解特征及其与微晶形貌和大小之间的关系进行了研究。基于热分析数据,应用Arrhenius方程对氢氧化镍的失水热分解反应动力学进行了研究,结果表明:反应过程可能包括早期的由反应控制的阶段和后期的由扩散控制的阶段。随着组成氢氧化镍的球粒表面微晶大小和形态由粗粒片状至微细粒状变化,失水热分解温度降低,失水速率增大。因此,具有微细粒状边界模糊特征的氢氧化镍有更好的热传导性能并经测试证明具有更好的电化学活性。同时,良好的热传导性能将有利于MH-Ni蓄电池的高低温充放电特性的改善。

Thermal decomposition characteristics of hydro-synthesized spherical β-Ni(OH)2 were researched and the relationship between the thermal decomposition characteristics and the microstructures of nickel hydroxides was established. Thermal decomposition reaction kinetics of β-Ni(OH)2 was also discussed by use of the Arrhenius equation from thermal analysis data. The results show that the reaction kinetic approach may include two parts: the first part is controlled by reaction and the consequent second part is controlled by diffusion. The thermal decomposition temperature decreases and the decomposition rate increases with the decrease of crystalline size and the shape of the β-Ni(OH)2 changing from layer-like to sphere-like. So the β-Ni(OH)2 characterized with superfine crystallites and unclear interfaces may have better thermal conductivities and testified superior electrochemical activities. Moreover, the excellent thermal conductivity will contribute to the improvement of charging and discharging performance of MH-Ni cells under wide temperature range.