Numerical Prediction of Multiscale Electronic Conductivity of Lithium-Ion Battery Positive Electrodes

The electronic conductivity, at the multiscale, of lithium-ion positive composite electrodes based on LiNi1/3Mn1/3Co1/3O2 and/or carbon-coated LiFePO4, carbon black and poly(vinylidene fluoride) mixture is modeled. The electrode microstructures are acquired numerically in 3D by X-ray tomography and FIB/SEM nanotomography and numerically segmented to perform electrostatic simulations using Fast Fourier Transform (FFT) method. Such simulations are easy and quick to perform because they are directly computed on the grid represented by the voxels in the 3D volumes. Numerical results are compared with experimental measurements of the multiscale electronic conductivity by broadband dielectric spectroscopy (BDS). A good prediction is realized for the bulk conductivities of the C/LiFePO4 phase and the CB/PVdF mixture. The combination of X-ray and FIB/SEM tomography, FFT simulation method, and BDS is thus well adapted to understand the influence of the electrode composition and microstructure on its electronic conductivity. (C) 2019 The Electrochemical Society.