Solid-state diffusion limitations on pulse operation of a lithium ion cell for hybrid electric vehicles

A 1D model based on physical and electrochemical processes of a lithium ion cell is used to describe constant current and hybrid pulse power haracterization (HPPC) data from a 6 Ah cell designed for hybrid electric vehicle (HEV) application. An approximate solution method for the iffusion of lithium ions within active material particles is formulated using the finite element method and implemented in the previously developed D electrochemical model as an explicit difference equation. Reaction current distribution and redistribution processes occurring during discharge nd current interrupt, respectively, are driven by gradients in equilibrium potential that arise due to solid diffusion limitations. The model is xtrapolated to predict voltage response at discharge rates up to 40 C where end of discharge is caused by negative electrode active material surface oncentrations near depletion. Simple expressions are derived from an analytical solution to describe solid-state diffusion limited current for short uration, high-rate pulses. 2006 Elsevier B.V. All rights reserved.