High rate capability composite particles with root-inspired hierarchical channel structure

Abstract

Composite particle with high speed channels for delivering lithium is a promising candidate for the high performance electrode in electric vehicles. However, it still suffers from poor rate capability due to the long diffusion pathway caused by large particle size. Inspired by the efficient transporting ability of the hierarchical structure in tree roots, we design the channel structure to improve the rate capability using a diffuse interface model. This model enables us to simulate the fast lithium diffusion along the channel network and the electrochemical reaction on the particle surface. Our results demonstrate that two microstructure features of the channel network can efficiently enhance the rate capacity: One is the gradient distribution of the channel density with a higher channel density near the surface than that in the center; the other is the orientation of the channel structure parallel to lithium flux from the particle surface. The root-inspired hierarchical channel network displaying these two features can improve the capacity retention at large C-rates. Furthermore, our study can offer an efficient tool that can rationalize the topology design of channel structure in the purpose of achieving a high rate capability.