Investigation of Particle Size and Coating Thickness for Pulse Performance of Automotive Lithium Ion Batteries

Optimization of the performance of Micro-hybrid Electric Vehicles (MHEV) requires a close match between the demands of the driving profile and the chemical and engineering characteristics of the material. Typical driving patterns present the opportunity for regenerative braking pulses that may be over 30 seconds in some cases. Our goal is to provide more opportunity for regenerative braking, particularly for high-speed, long deceleration pulses. In this work we have used electrochemical modeling of NMC 1:1:1 cells to investigate the effects of particle size, coating thickness, and system capability on the energy and power capability of lithium ion batteries. We demonstrate a novel metric for evaluating the regeneration capability of a cell - recovered energy per volume, Wh(recov)/L - against which these effects are optimized. Finally, we have modeled lithium concentration gradients in both the electrolyte and particle surface and have identified conditions under which regeneration capability is affected.