导电剂镍粉对La0.7Mg0.3Ni2.6Co0.7合金电极电化学性能的影响

采用放电容量、循环寿命、伏安特性、高倍率放电、交流阻抗等方法研究不同导电剂镍粉含量对La0.7Mg0.3Ni2.6Co0.7合金电极电化学性能的影响。结果表明:La0.7Mg0.3Ni2.6Co0.7+xwt%Ni(x=0.0,5.0,7.5,10.0,12.5)合金电极的放电容量分别为388.0、410.7、409.6、412.2、421.3 mAh/g,高倍率放电性能HRD1200从40.2%(x=0.0)增大到75.7%(x=12.5),同时合金电极的电荷转移阻抗明显降低,添加导电剂镍粉有利于电流在电极中分布趋于均匀化,增大了活性物质的填充量,促使合金电极的放电容量增加。电荷转移阻抗的降低有利于氢原子在合金内部扩散,从而有效地改善合金电极的高倍率放电性能。

Effects of nickel powder conductive agent on electrochemical properties of La0.7Mg0.3Ni2.6Co0.7 alloy electrodes

Effects of nickel powder content on the electrochemical characteristics of the La0.7Mg0.3Ni2.6Co0.7 alloy electrode were investigated by means of discharge capacity,cycle life,volt-ampere characteristic,high-rate discharge and electrochemical impedance spectroscopy measurement.The results showed that the discharge capability of La0.7Mg0.3Ni2.6Co0.7+xwt% Ni(x=0.0,5.0,7.5,10.0,12.5) alloy electrodes were 388.0 mAh/g,410.7 mAh/g,409.6 mAh/g,412.2 mAh/g and 421.3 mAh/g,respectively.The high rate dischargeability(HRD1200) of the alloy electrodes increased from 40.2%(x=0) to 75.7%(x=12.5) and the charge-transfer resistance decreased significantly.When the nickel powder conductive agent was introduced,the uniformity of current distribution in the electrodes was improved greatly,and the filling quantity of the active material increased,resulting in the increase of discharge capacity.Moreover,the decrease of charge-transfer resistance was beneficial to the diffusion of hydrogen atoms into the alloy electrodes,leading to an obvious improvement on high rate dischargeability of the alloy electrodes.