thermal runaway

heat generation

capacity fade

state charge

Cell Reports Physical Science

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) (ΔT int = +2°C) and 100% capacity fade when the PE is warmer than the NE (ΔT int = −2°C). Incremental capacity analysis diagnoses PE degradation for ΔT int = +2°C and NE degradation for ΔT int = −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. Directionality of interelectrode thermal gradient dictates which electrode degrades At elevated temperature (35°C), Li-ion batteries degrade under thermal gradients (±2°C) Thermal gradients expedite degradation, providing an accelerated aging strategy Simulated incremental capacity corroborates experiments and diagnoses degradation modes Carter et al. demonstrate that Li-ion batteries operating at elevated temperature exhibit rapid degradation with the presence of interelectrode thermal gradients. Using incremental capacity analysis and simulations as well as postmortem electrochemical and optical analyses, it is determined that the directionality of the interelectrode thermal gradient dictates whether degradation is prominent at the positive or negative electrode.

Directionality of thermal gradients in lithium-ion batteries dictates diverging degradation modes