Porous electrodes in lithium-ion batteries: heterogeneity and performance
Institute for Materials Research (IMO-imomec), UHasselt, Martelarenlaan 42, B-3500 Hasselt, Belgium
Energyville, Thor Park 8320, B-3600 Genk, Belgium
IMEC division IMOMEC, BE-3590, Belgium
The presence of inhomogeneity in the porous electrodes of lithium-ion cells can significantly affect the active material utilization, energy/power density, and ageing dynamics of the cell, among others. Inhomogeneity might be defined as a non-zero directional gradient of the physical and/or chemical formulation in a porous electrode. In Li-ion cells, such inhomogeneity is caused by an uneven spatial distribution of the active material, carbon, binder, and electrolyte, or porous electrode micro/nanoscale properties such as the contact resistances, porosity and tortuosity. The existing literature suggests that the heterogeneity could inadvertently be introduced to the electrode with improper combination of design parameters and manufacturing steps, e.g. slurry formulation, thickness, mixing and drying. Important insights into the local microstructure of the porous electrodes have been provided by FIB-SEM , X-ray tomography or full simulation of electrode microstructure. Little attention has been paid, however, to develop formalisms to quantify the electrode heterogeneity and its correlation to the design parameters, manufacturing steps, and the battery performance. In this regard, the aim of this presentation is to spotlight the sensitivity of the energy and power density of the battery electrodes to the formulation and the microstructural indexes such as tortuosity, porosity, and effective conductivities.