Effect of Defects on Diffusion Behaviors of Lithium-Ion Battery Electrodes: In Situ Optical Observation and Simulation.
Effect of Defects on Diffusion Behaviors of Lithium-Ion Battery Electrodes: In Situ Optical Observation and Simulation.
复制标题
DOI：
10.1021/acsami.8b15260
复制
发表时间：
2018-11
影响因子：
9.5
通讯作者：
Le Yang;Haosen Chen;Weili Song;D. Fang
中科院分区：
文献类型：
--
作者：
Le Yang;Haosen Chen;Weili Song;D. Fang
具有高能效的锂离子电池在各个领域都有迫切的需求。对于LIBs电极来说，在制造过程和机械降解过程中会产生缺陷，严重影响LIBs的稳定性和性能。然而，电极缺陷对电化学过程的影响尚不清楚。本文开发了一种原位光学观测系统，用于监测商业石墨电极中预引入缺陷周围的Li扩散。实验表明，垂直于Li扩散方向的充气缺陷会明显减缓Li的扩散，而平行于Li扩散方向的充液缺陷会加速Li的扩散。此外，有限元分析（FEA）表明，缺陷周围局部Li浓度分布不均匀，与实验结果一致。通过有限元分析得到的等效扩散系数也依赖于缺陷的结构。充液平行缺陷和充气垂直缺陷的扩散系数分别为12.6%和11.0%。对于充气缺陷，尺寸效应计算表明，等效扩散系数随着缺陷尺寸的增大而减小，缺陷形状对等效扩散系数的减小速率有较大影响。通过新的等效二维实验，直接揭示了缺陷诱导电极扩散行为变化的机理，等效扩散系数对优化LIBs中电极的设计具有重要意义。
Lithium-ion batteries (LIBs) with high energy efficiency are urgently needed in various fields. For the LIBs electrodes, defects would be generated during the manufacturing processes and mechanical degradation and significantly impact the stability and performance of the LIBs. However, the effects of electrode defects on the electrochemical processes are still not clear. Herein, an in situ optical observation system is developed for monitoring the Li diffusion around the preintroduced defects in the commercial graphite electrodes. The experiments show that the gas-filled defects vertical to the direction of the Li diffusion would obviously decelerate the Li diffusion, whereas the electrolyte-filled defects parallel to the direction of the Li diffusion would accelerate the Li diffusion. In addition, finite element analysis (FEA) suggests, consistent with the experiments, a nonuniform distribution of local Li concentration around the defect. The equivalent diffusivity obtained by the FEA is also dependent on the configuration of the defects. The diffusivities of the electrolyte-filled parallel defect and gas-filled vertical defect are 12.6 and 11.0%, respectively. For the gas-filled defects, the size-effect calculation manifests that the equivalent diffusivity would decrease with the enlarged defect size, and the shape of the defects would substantially impact the decrease rate. The results directly reveal the mechanisms of the defect-induced diffusion behavior change in the electrodes by the new equivalent two-dimensional experiments, and the equivalent diffusivity would be useful for optimizing the electrode designs in LIBs.