溶胶-凝胶法制备LiCoPO_4及其电化学性能

Synthesis and Electrochemical Performance of LiCoPO_4 by Sol-Gel Method

采用溶胶-凝胶法合成了高电位正极材料LiCoPO4,并通过X射线衍射(XRD)、扫描电镜(SEM)以及充放电测试考察了不同烧结条件下产物的晶体结构、微观形貌以及电化学性能.实验结果表明:在650°C下烧结12h所制备的样品为单一橄榄石型结构的LiCoPO4,产物颗粒细小(0.2-0.4μm)且分布均匀,同时具有最佳的电化学性能,其在1C倍率下的放电比容量可达到122.7mAh.g-1.此外,产物在充放电过程中均呈现两个电压平台,且随着放电倍率的增加,两个电压平台之间的区分逐渐明显,分析认为,这与充放电过程中锂离子的两步脱嵌行为有关.

High potential cathode material LiCoPO4 was synthesized by sol-gel method. The effects of different sintering conditions on the crystal structure, surface morphology and electrochemical performance of LiCoPO4 were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and charge-discharge tests. The results show that the sample synthesized at 650 ℃ for 12 h has a good crystalline orthorhombic olivine-type structure and a uniform particle distribution （0.2-0.4 μm）, which delivers the best electrochemical performance. The discharge capacity of the sample at 1C rate can reach 122.7 mAh·g-1. Moreover, from the charge and discharge profiles, two charge/discharge plateaus are presented and they become more obvious with the increase of charge/discharge rate. This phenomenon can be interpreted by considering the two-step extraction/insertion behavior of Li＋ in LiCoPO4.