LiFePO4单颗粒电化学本征性能的快速精确评测

通常需要将电活性材料与导电剂、粘接剂等辅助物质混合后，制成复合电极来评测材料的电化学性能，但辅助物质和复合电极结构可能影响评测结果的准确性. 由于单颗粒微电极可选取单一颗粒进行测试，无需加入添加剂材料，因此，采用单颗粒微电极评测材料性能可以得到材料的本征性能. 同时，单颗粒微电极还可以实现对材料的快速、精确评测. 本文利用单颗粒微电极方法测试了球形LiFePO4颗粒的循环伏安特性、循环稳定性和动力学性能. 结果表明，单颗粒微电极可以20 mV?s-1的速率快速扫描、精确测试，测得锂离子在该颗粒中的扩散系数约为2.4 ~ 3.2?10-11 cm2?s-1，电化学反应的控制步骤为锂离子的固相扩散控制. 另外，LiFePO4颗粒在该单颗粒微电极构成的电池中表现出良好的循环稳定性. 这些显示了单颗粒微电极在电极材料特性研究中的可行性.

Fast and Accurate Evaluation of LiFePO4 Cathode Materials by Single Particle Microelectrode

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.