LiCoO_2电极中锂离子的扩散性能

Diffusion performance of lithium ions in LiCoO_2 electrode

为使锂离子电池在较高的充、放电倍率下满足动力型电源的需要,对LiCoO2中锂离子的扩散性能进行了理论推导及试验测定。以球状电极模型对LiCoO2电极进行了处理,在简化的假设条件下,推导出LiCoO2电极的扩散电流表达式,并可求得锂离子在LiCoO2电极中的固相扩散系数DLi+。研究结果表明:I对t-1/2在10～150s表现出很好的线性关系,与理论分析结果相符合;不同晶粒大小的LiCoO2样品扩散系数有很大差别,相差1个数量级以上;锂离子扩散动力学特征是由LiCoO2的晶粒尺寸决定的,与其粒径分布、比表面积及表面形貌等参数基本无关。

In order to make lithium ion batteries applicable for higher charge/discharge performance in heavy drain and satisfy the requirement of electric vehicle power source, the diffusion performance of lithium ions in LiCoO_2 electrode was studied theoretically and experimentally. Based on a spherical electrode model and under the simple hypothesis, the equation of diffusion current density of LiCoO_2 electrode was deduced. There exists a linear relationship between I and t ^(-1/2). According to the slope and the intercept, the diffusion coefficient D _(Li^+) in LiCoO_2 electrode could be calculated. The results show that there is a linear relationship between I and t ^(-1/2) when time is in the range of 10150 s, which is in agreement with the theoretical analysis. The difference of diffusion coefficient of LiCoO_2 samples with different sizes can reach more than 10 times, which indicates that the diffusion dynamical characters of lithium ions are determined by the structure of LiCoO_2 (the grain size), independent of particle distribution, specific surface area and morphology.