Degradation mechanism of lithium-ion battery under appropriate in-plane temperature gradient

Temperature significantly affects battery performance. However, the mechanism of in-plane temperature gradient caused by high current on battery degradation is still unclear. In this study, the in-plane temperature gradient is artificially constructed between battery tab and bottom region. Then, the fast-charging cycling test is performed. Post-mortem analysis after battery cycling is carried out to obtain the anode surface morphology and elemental distribution. A three-dimensional electrochemical model is developed to obtain the internal parameter distributions during fast charging. The results indicate that the battery degradation process can be divided into three stages: in-plane current density gradient stage, in-plane temperature gradient stage, and emergence of degradation factors stage. A spatial matching criterion between in-plane temperature gradient and in-plane current density gradient is proposed to suppress battery degradation, where optimal performance is achieved when high current density region coincide with high temperature region. Specifically, the in-plane temperature gradient with high temperature at the high current density tabs and low temperature at the low current density bottom region enhances battery fast charging performance, maintaining over 90% capacity after 50 cycles at 2C charging rate. However, an in-plane temperature gradient in the opposite direction can lead to lithium plating and material cracking, with a 34.3% capacity loss after just 5 cycles. Additionally, the low-temperature discharge tests demonstrate that achieving the spatial matching criterion can enhance battery discharge performance. Specifically, the discharge capacity increases by 8% at -20°C. This study provides a novel temperature-regulation-based approach for reducing battery polarization. • In-plane temperature gradient is constructed for battery thermal management. • A 3D electrochemical model is developed for fast charging simulation. • Inhomogeneous temperature leads to inhomogeneous lithium plating. • The battery degradation process can be divided into three stages. • A matching criterion between temperature gradient and current density is proposed.