A novel approach for battery longevity through controlled surface lithium concentration gradient

One of the key challenges in battery degradation is mechanical failure, such as cracks and delamination, caused by stress from lithium concentration gradients inside active particles. In conventional charging protocols, such as constant current constant voltage (CCCV) charging, the concentration gradient and corresponding stress levels vary, and reaching critical levels can lead to mechanical failure. This paper introduces a new charging methodology called constant gradient constant voltage (CGCV), which regulates the charging current to maintain a constant lithium gradient at the surface of active particles, thereby limiting stress development and mechanical crack propagation. To control the concentration gradient, factors such as charging current, lithium diffusivity, and particle geometry must be considered. Two scenarios are considered to demonstrate CGCV effectiveness. For scenario 1, the CGCV shows a significant reduction in charging time, with a 50% reduction compared to 0.1 C CCCV, while exhibiting slightly slower degradation rates. In scenario 2, 0.5 C CCCV, which has roughly equivalent charging time to CGCV, shows significantly more capacity fade; it takes CCCV 66 cycles for 20% capacity fade, while CGCV takes 100 cycles to reach only a 12% capacity fade. These 2 scenarios show that the CGCV methodology effectively mitigates degradation while shortening charging time.