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

doi:10.15541/jim20150051

Abstract

Abstract:

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.

Key words: lithium-ion battery, graphite anode, microstructure reconstruction, simulated annealing method, ellipsoid particles

CLC Number:

TQ174

HE Shao-Yang, ZENG Jian-Bang, JIANG Fang-Ming. Numerical Reconstruction and Characterization Analysis of Microstructure of Lithium-ion Battery Graphite Anode[J]. Journal of Inorganic Materials, 2015, 30(9): 906-912.

Figures/Tables 7

Fig. 1 FIB/SEM images of lithium-ion battery electrodes (a) LiCoO2 cathode; (b) Graphite anode

Fig. 2 Ellipsoid particle The a, b and c are the three semi axial lengths of ellipsoid. The α, β and γ are the three rotation angles for the X’-Y’-Z’ coordinates relative to the X-Y-Z coordinates

Fig. 3 3D microstructure of reconstructed graphite anode (a) Spatial distribution of graphite; (b) Spatial distribution of solid additive; (c) Spatial distribution and topological relation of graphite anode microstructureconsisting of 3 components. Yellow denotes graphite, blue solid additive and transparent pore or electrolyte

Fig. 4 Distribution of volume fraction of each component along X direction (i.e. the electrode thickness direction)

Fig. 5 Pore size distribution inside the reconstructed graphite anode

Table 1 Effects of particle size on microstructural characteristics of the reconstructed anode

Particle size (2a/ 2b/ 2c) /μm	Average pore diameter /μm	Specific surface area /m^-1	Connectivity /%
Particle size (2a/ 2b/ 2c) /μm	Average pore diameter /μm	Specific surface area /m^-1	Solid	Pore
4/8/16	3.88	539430	99.62	98.68
4/8/24	3.98	479619	99.73	98.42
4/16/24	4.45	456897	99.60	98.00
4/16/32	4.80	437198	99.04	98.35
4/24/32	4.87	418739	99.62	97.66
2/16/24	3.26	563154	99.86	95.86

Fig. 6 Pore size distribution for microstructures reconstructed with particles of different sizes

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