An electrochemical-thermal model was developed to quantitative analysis ohmic polarization, concentration polarization and activation polarization of positive and negative electrodes at different discharge rates. The results show that concentration polarization of positive is the main constituent part at the beginning of 1C rate discharge, which also shows the biggest fluctuation range. Various polarizations change less in the middle of 1C rate discharge, but at the end ohmic polarization and activation polarization of negative rapidly increase. Concentration polarization of solid phase in positive electrode increases dramatically to 715mV at the end of 8C rate discharge. The aggravation of activation polarization is the main cause of large polarization with discharge rate raised, and the activation polarization of negative electrode is worse than that of positive. It is effective to remit activation polarization of negative by reducing particle sizes of negative electrode.%基于电化学热耦合模型,定量分析了磷酸铁锂动力电池不同倍率放电下正负极欧姆极化、浓差极化和活化极化.结果表明:1C放电初期,正极固相浓差极化波动最大,峰值达到147 mV;放电中期,各类型极化变化曲线较为平稳,活化极化最大,约为48 mV;放电末期,负极活化极化和负极固相浓差极化迅速增大;8C放电末期,正极固相浓差极化急剧增加,达到715 mV.提高放电倍率,活化极化的大幅增加是高倍率下极化严重的最主要原因,且负极活化极化的增加幅度比正极活化极化更大;而减小负极颗粒粒径可以有效减小负极活化极化.
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