Competition between discharge reaction and side reaction for anode's lithium during internal short circuit in lithium-ion batteries

The dynamic evolution mechanism of internal short circuit (ISC) leading to the thermal runaway (TR) during battery overheating was studied by analyzing materials inside batteries. The results showed that the ISC during overheating was caused by contact between the aluminum current collector and the anode on the surface of the battery cell. Four typical ISC experiments were designed to analyze the ISC process of the battery. There were two processes competing for anode's lithium after the ISC. One was the self-discharge reaction of the battery, and the other was the side reaction. Both processes can be affected by temperature. The ISC was interrupted when the side reaction was dominant, causing the anode to retain a part of the lithium for the next side reaction, which ultimately led to the battery TR. The TR risk was reduced when the self-discharge reaction was dominant, and experimental evidence was given. Finally, equivalent circuit diagram of ISC was proposed, and the evolution mechanism of ISC and TR of the battery was analyzed in detail based on it. The research in this paper provided a new insight for the comprehensive understanding of ISC and a new idea for the development of high safety batteries.