Cu粉粒径及含量对Ni/MH电池负极放电性能的影响

为了提高Ni/MH电池中储氢电极的放电性能,以电解Cu粉为充填材料与活性物质混合制备电极,研究Cu粉粒径及含量对电极性能的影响。研究发现,Cu粉粒径越小,含量越高,电极的放电容量、高倍率放电性能、及在低温和高温下的放电能力均提高,且Cu充填电极的性能优于Ni充填电极。Cu充填电极中析氢反应的交换电流密度较大,过电势较小,说明其电催化活性好,电极反应阻力小。SEM分析发现,充放电循环后的Cu充填电极,其储氢合金颗粒表面覆盖着一层细小Cu颗粒和丝状物,这是电极性能提高的主要原因。

Effect of Cu Power as Compacting Material on the Discharge Characteristics of Negative Electrode in Ni/MH Batteris

In order to investigate the effect of Cu powder as a compacting material on the electrode performance, negative electrodes are prepared by mixing Ml( NiCoMnTi)5 Alloy powder with copper powder of various sizes and contents,and are analyzed with electrochemical techniques and by scanning electron microscopy ( SEM) after cycling. The electrode performances such as the rate capability and the low - temperature and high - temperature dischargeability of the Cu - compacted electrode are improved as the size of Cu powder decreases or its content increases. These performances are better than those of the Ni - compacted electrode. The Cu -compacted electrode shows a high exchange current density and a low reaction overpotential for the hydrogen evolution reaction. From SEM analysis of the cycled electrode compacted with copper powder, it is also found that the surface of the metal hydride particles of the cycled Cu - compacted electrode is covered with copper grains and whiskers. Therefore, it is suggested that the improved electrode characteristics are attributed to the copper layer deposited on the MH particles by the dissolution and precipitation process.