Tortuosity estimation and microstructure optimization of non-uniform porous heterogeneous electrodes

The design optimization of lithium-ion battery (LIB) electrode microstructures is key to improving the rate capability of the batteries. In this work, two-dimensional heterogeneous electrodes with different microstructures, which are generated based on particle packing model proposed in our previous work, are investigated for their rate performance. In order to quantify the influence of the tortuosity of the microstructure in a straightforward manner, a topological tessellation-based method is proposed to estimate the tortuosity. As an example, the rate capability of NMC111 electrode is studied with different microstructures. Specifically, we analyze the two competing factors that influence performance of electrodes: the solid-state Li diffusion in particles and Li diffusion the pore phase. The results show that for the electrodes with the same particle size and different porosity, the tortuosity is the key to the rate performance. For the electrodes with the same porosity and different particle sizes, the diffusion of Li ions in the particles has the greatest impact on the rate performance. Based on the above study, gradient electrodes are designed with different particle sizes and porosity compositions. The results show that better performance can be achieved through gradient designs for different usage scenarios.