Modeling lithium diffusion in nickel composite graphite

A simple theoretical model is presented to simulate the galvanostatic discharge behavior of the Ni-composite graphite electrode. The discharge profiles predicted by using a constant diffusion coefficient (CDC) and by a varied diffusion coefficient (VDC) are compared in this paper. The results show that, the VDC model can be simplified to the CDC for discharge rates less than 2C for a 5 μm particle. Also, an approximate analytical solution is presented for VDC model, which is found to be valid for discharge rates up to 6C. Exchange current and diffusion coefficient for the lithium-diffusion are predicted.