锂离子电池石墨负极微结构数值重建及特征化分析

Numerical Reconstruction and Characterization Analysis of Microstructure of Lithium-ion Battery Graphite Anode

实际锂离子电池石墨负极由鳞片状石墨层叠而成,具有明显的各向异性。本文基于椭球颗粒的模拟退火法对其进行三维微结构数值重建。重建微结构乃三相(孔或电解液、石墨和固体添加物)复合结构,很好地再现了实际电极各向异性特征。对重构电极进行特征化分析,得到了电极内固/孔相的连通率、比表面积以及孔径分布等信息;发现石墨颗粒尺寸对电极特性有重要的影响:椭球形石墨颗粒尺寸越大,则重建微结构的平均孔径越大,比表面积越小;相对于赤道半径,椭球颗粒的极半径对重建电极特性的影响更为明显。

The real graphite anode of lithium-ion battery is of evident non-isotropic characteristic due to its cascading graphite flakes. An ellipsoid particle-based simulated annealing method is developed to numerically reconstruct the three-dimensional microstructure of graphite anode. The reconstructed anode is a composite of three clearly distinguished phases： pore（or electrolyte）, graphite and solid additive, well representing the non-isotropic characteristic of real graphite anode. Characterization analysis of reconstructed electrodes gives information such as the connectivity, the specific surface area of solid or pore phase, and the pore size distribution. The results show that the size of graphite ellipsoids has important effects on the characteristics of electrode： 1） larger size graphite ellipsoids result in larger mean pore size and smaller specific surface area in the reconstructed electrode; 2） changing the polar radius of graphite ellipsoid particles has more pronounced influence on the characteristics of electrode than has changing its equatorial radius.