Directionality of thermal gradients in lithium-ion batteries dictates diverging degradation modes
Rachel Carter, Todd A. Kingston, Robert W. Atkinson, Mukul Parmananda, Matthieu Dubarry, Conner Fear, Partha P. Mukherjee, Corey T. Love
Abstract
Intentionally applied interelectrode thermal gradients (ITGs) accelerate capacity loss in 35°C cells, and the directionality of the thermal gradient dictates the responsible degradation mode. By simulating cell self-heating at various temperatures and C-rates, we identify 35°C and C/5 as a condition that does not typically exhibit lithium (Li) plating under isothermal conditions but is sensitive to thermal gradients. When subjected to an ITG, we observe 77% capacity fade over 20 cycles when the negative electrode (NE) is warmer than the positive electrode (PE) (ΔTint = +2°C) and 100% capacity fade when the PE is warmer than the NE (ΔTint = −2°C). Incremental capacity analysis diagnoses PE degradation for ΔTint = +2°C and NE degradation for ΔTint = −2°C. Electrochemical impedance spectroscopy and postmortem optical investigation corroborate these findings. We identify ITGs as a means to achieve accelerated aging of Li-ion cells with the capability to dictate a limiting electrode and/or decouple degradation of each electrode.