Overcharging cycle aging-induced severe degradation of safety properties of lithium-ion pouch battery cells subjected to mechanical abuse

Revealing the effect of electrical abuse on service properties under external mechanical loading is essential for evaluating the safety of lithium-ion batteries. Batteries with different aging levels subjected to overcharging with a 4.65 V cut-off voltage are prepared for quasistatic indentation tests by using a hemispherical indenter. The mechanical-thermal-electrical coupling responses of these batteries are investigated and compared in-situ. The significant degradation of the mechanical properties after overcharge cycle aging is equivalently characterized by a decrease in the battery stiffness and peak force. The short circuit and voltage drop trigger simultaneously increase the intensity of the short circuit of the aging battery, decrease the energy release time, and increase the surface temperature. The Joule heat is concentrated in the indentation area, and the surface peak temperature of the 70 % SOH battery is 70 % higher than that of the fresh battery. The mechanical properties of the components decreased after aging, and the change in the mechanical behavior of the battery cells was mainly attributed to the anode. Moreover, the micromorphology of the aged anode changed dramatically. The sharp lithium dendrites formed during the process of overcharge aging on the surface of the anode result in a more severe internal short circuit. • The highlights are appended below: • The ability of overcharge cycle aging pouch cells to resist deformation decreases. • The changes in the mechanical behavior of the cells are mainly due to the anode. • Aging cells are more dangerous when subjected to mechanical abuse. • Lithium dendrites and larger separator melting area induce severe short circuit.