采用分子动力学方法, 模拟充电过程中锂离子在石墨层间的扩散行为. 研究了300 K温度下石墨阳极材料的锂离子扩散性质; 计算了Einstein 关系下LiC6, LiC12 和LiC18 的扩散系数, 得到了LixC6 扩散系数与锂离子浓度的关系曲线. 结果表明, 在充电过程中锂离子电池的扩散系数随嵌锂浓度的变化而变化. 在二阶段和一阶段, 扩散系数分别随浓度的增大而减小, 而在LiC12 附近, 扩散系数由于结构相变而发生较大变化. 此外, 通过分子动力学可视化图像显示了LixC6 晶体的微观结构. 实验结果为锂离子电池电极变形的连续尺度模型研究提供了基础数据.
Simulation of the Li-ion diffusion behavior in graphite during the charging process is performed by using molecular dynamics. The Li-ion diffusion properties of the graphite anode material are studied at 300 K. Diffusion coefficients of LiC6, LiC12 and LiC18 are calculated by Einstein relationship. The relationship between diffusion coefficients of LixC6 and Li concentration is obtained. The results show that diffusion coefficient changes with Li concentrations in the charging process. Stage Ⅰ and stage Ⅱ diffusion coefficient decreases with the increasing Li concentration. The diffusion coefficient near LiC12 changes greatly because of the structural phase transition. The simulation results show visual images of the atomic configuration LixC6. The results of the study provide data for Li modelling of Li electrode deformation.
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