关键词: LiFePO4, 单颗粒微电极, 循环伏安曲线, 锂离子扩散系数

Abstract:

Single particle microelectrode enables to evaluate the electrochemical responses for single particle of active material without binder and conductive agent. Thus, the influences of additive and electrode structure on the electrochemical performance of active materials can be ignored. Furthermore, this technology can be used to evaluate active materials fast. Therefore, single particle microelectrode allows fast and accurate determination of the intrinsic performance of active material. Cyclic voltammogram (CV), cycle performance, and kinetic behavior of LiFePO4 cathode materials were evaluated by the single particle microelectrode. CV curve of LiFePO4 particle with a pair of oxidation and reduction peaks was obtained with scan rates of 20 mV?s-1, which is 400 times larger than that of composite electrode. Besides, it is found that Li+ diffusion in LiFePO4 particle is the bottleneck of electrochemical process, and the Li+ diffusion coefficient in LiFePO4 particle is about 2.4 ~ 3.2 ? 10-11 cm2?s-1. Excellent cycle performance was also proved to be the intrinsic properties of LiFePO4 cathode materials by single particle microelectrode. Therefore, single particle microelectrode is an effective method for evaluation of active materials for lithium ion batteries.

Key words: LiFePO₄, single particle microelectrode, cyclic voltammograms, Li⁺ diffusion coefficient