MH-Ni蓄电池正负极阻抗分布的电化学研究

应用电流阶越法、线性电位扫描法及电化学交流阻抗法分析了MH-Ni蓄电池正负极的阻抗分布,考察了电极阻抗在放电过程中的变化,对比了正负极的各个阻抗参数,讨论了上述三种电化学方法在电极体系阻抗分析中的优点及缺陷。测试结果表明,在放电初期,负极的欧姆阻抗和电化学阻抗远大于正极,是电池欧姆阻抗的主要组成部分。随着放电程度的加深,负极的阻抗减小,正极的欧姆阻抗与电化学阻抗不断增大,最终接近或超过负极。正极的浓差极化远大于负极,且随放电深度的增大显著增加,是影响电池性能的主要因素。通过成品电极的阻抗分析为提高电池各项性能提供了有效途径。

Electrochemical study on the resistance distribution of positive and negative electrodes in Ni-MH battery

The resistance distribution of positive and negative electrodes in nickel metal hydride battery was analyzed by current-step method, linear voltage sweep technique and electrochemical impedance spectroscopy(EIS). The changes of resistance values at various depth of discharge (DOD) were discussed, and the results of the positive and negative electrodes were compared. The advantages and disadvantages of these electrochemical techniques applied in electrode system were also discussed. Testing results showed that the ohmic and electrochemical resistance of negative electrode is larger than that of the positive at the beginning of discharge, which is the main part of battery resistance. The ohmic resistance and polarized resistance of the positive electrode increased with the increase of DOD, and finally reached the values of negative ones. The diffusion polarization of positive electrode was much larger than that of the negative, and it remarkably increased with enhancing DOD, so the diffusion polarization of positive electrode is the main factor influencing battery performances.