Investigating the Overdischarge Failure on Copper Dendritic Phenomenon of Lithium ion Batteries in Portable Electronics

Lithium-ion batteries (LIBs) have been widely applied in portable electronics as a power source. Nevertheless, LIBs also become the potential safety hazard for their high activity and flammable organic component, which threatens the safety of consumers. Failure analysis of LIBs is useful to discovery their defective technology and explore the failure mechanism, guiding the improvement of LIBs reliability. Herein, we report on the investigation of overdischarge failure phenomenon of LIBs and its internal short-circuit mechanism. A nondestructive X-ray computed tomography strategy in conjunction with microzone analysis has been employed to study the failure mechanisms. Firstly, nondestructive test shows that the failure initiating point is located at the bottom center of cell core with the most serious wrinkles. Secondly, microzone analysis and simulated tests display that dissolution of copper foil on anode occurs when cell voltage below 2.5 V. Then many copper dendrites generate during the recharge process. Additionally, growth of copper dendrite is the main reason leading to the internal microshort-circuit, the decomposition of SEI layers and closure of separator. As condition of LIBs continuously deteriorates, thermal runaway of LIBs occurs when the heat accumulates to a critical point. Moreover, the relationship between copper dissolution and cell voltage have been further investigated. Result offers information that designing cut-off voltage protection is an effective way to avoiding the overdischarge failure of LIBs.