LiFePO_4锂离子电池放电行为理论研究

Theoretical study on discharge behavior of LiFePO_4 battery

使用多孔电极理论对LiFePO_4(LFP)锂离子电池的放电行为进行了研究,发现随着放电过程进行,电极内部的电化学反应从隔膜侧向集流体侧移动,并且移动过去之后LFP基本完成放电过程。随后对放电速率、电极导电性和电解液电导率对放电过程的影响进行了研究。随着放电倍率增加,电化学反应推进的距离不断减少,并且锂化峰值不断增大。提高电极电导率可以保证电化学反应从隔膜侧开始进行,较高的电解液离子导电性可以保证所有的活性材料都能发生电化学反应。以上结论可对高性能LFP锂离子电池的设计有指导作用。

The discharge behavior of a LiFePO4（LFP） battery was investigated using the porous electrode theory. It is found that the electrochemical reaction happens from the separator side to the curent collector side with the discharge process, untio LFP is almost fully lithiated. The effects of discharge rate, conductivities of the electrode and electrolyte on the discharge process were studied. With the increase of discharge rate, the affected distance of the electrochemical reaction is decreased, and the level of lithiation at the separatoe side increased. The increase of the electrode conductivity can ensure that the electrochemical reaction starts from the separator side, and the higher ionic conductivity is necessary for a fully lithiation. The above conclusions can provide an effective guide for the design of high performance LFP lithium batteries.