电解液组成对LiFePO_4电池低温性能的影响

Effect of electrolyte component on low-temperature performance of LiFePO_4 batteries

研究了低温(-20℃)下磷酸铁锂正极材料与电解液的相容性。采用不同溶剂组成的电解液与磷酸铁锂正极组装成LiFePO4/Li半电池,进行电化学测试。结果表明:低温下电池界面阻抗是影响磷酸铁锂电池性能的关键因素;随着界面阻抗的增大,LiFePO4/Li半电池的放电容量显著下降,同时极化加重,放电平台降低,并且其界面阻抗的变化直接与电解液中线性酯和环状酯溶剂的比例相关。在-20℃下,环状酯类溶剂含量(体积分数)为33%的电解液界面阻抗最小,其组装的LiFePO4/Li半电池0.1C倍率下放电容量为113.9 mA·h/g,是常温放电容量的75%。

The compatibility of LiFePO 4 cathode with electrolyte at low temperatur-e （ 20 ℃） was studied. Electrochemical analysis was employed to investigate a series of electrolytes with different compositions for the LiFePO 4/Li half cells. The results show that the interface impendence at low temperature is the key factor affecting the performance of LiFePO 4 batteries. The discharging capacity of the LiFePO 4/Li cells significantly decreases, and the polarization and resistance increase due to an increase in the interface impedance between the electrode and electrolyte. In addition, the interface impedance change is directly related to the ratio of the linear and cyclic carbonate solvents. At-20℃, the electrolyte with 33%（volume fraction） cyclic carbonate has the lowest interface impedance. The discharging capacity of the corresponding LiFePO 4/Li half cells is 113.9 mA·h/g and about 75%as that of the room temperature one.