LiFePO_4/活性炭复合材料的储能机理

Energy storage mechanisms of LiFePO_4/activated carbon composite

用交流阻抗、循环伏安和恒流充放电实验,考察了LiFePO4/活性炭(AC)复合材料的储能机理,以及LiFePO4、AC含量对电化学性能的影响。加入AC可提高电极的电导率和比表面积,增加可发生Li+嵌脱反应的活性点位。复合电极能利用法拉第准电容效应和双电层电容效应的协同作用储能。当LiFePO4和AC含量分别为55%和25%时,协同作用达到最佳,复合电极以0.2C和30.0C在2～4 V放电,首次放电比容量分别为163 mAh/g和60 mAh/g。

Energy storage mechanisms of LiFePO4/activated carbon（AC） composite and effects of LiFePO4, AC content on the electrochemical performance of the cathode were investigated by experiments of A. C. impedance, cyclic vohammetry and galvanostatic charge/discharge. The addition of AC could increase the electronic conductivity and specific surface area of the electrode, increase the reactive sites of Li＋ insertion and extraction taken place. The composite electrode could store energy by the synergy effect of pseudo-capacitance effect and double layer capacitance effect. The synergy effect reached the best when the content of LiFePO4 and AC was 55% and 25% ,respectively. When discharged at 2- 4 V with 0.2 C and 30.0 C, the initial specific discharge capacity of the composite electrode was 163 mAh/g and 60 mAh/g, respectively.