Aging Mechanisms and Thermal Characteristics of Commercial 18650 Lithium-Ion Battery Induced by Minor Mechanical Deformation

Abstract

Lithium-ion batteries (LIBs) inevitably encounter abusive mechanical loading during engineering applications and result in mechanical deformation, internal short circuit, and even thermal runaway. A 18650 LIB under minor mechanical deformation is subjected to cyclic charge/discharge experiments in this study to analyze its aging behavior. Aging mechanism of the battery with minor deformation is qualitatively investigated through the incremental capacity analysis (ICA). ICA, a commonly used method for exploring degradation mechanism of LIBs, can transform flat voltage plateaus into peaks in the capacity increase curve (IC curve). Experimental data during the battery charging/discharging cycle can be used to calculate the IC curve, which can reflect the characteristics of electrochemical changes inside the battery. Results showed that the LIB suffers from deterioration in the state of health (SOH) in the entire charge/discharge cycle upon minor mechanical deformation. Possible explanations for the slight decrease in SOH with the increasing number of cycles in the early stages and the rapid decrease in the charge/discharge capacity in the late stages were provided. However, precise mechanisms for these phenomena require further detailed research. Moreover, damaged cells demonstrate considerably higher temperature increments than original ones. This temperature difference will increase if additional charging/discharging cycles are conducted. This research infers that additional metallic lithium deposits in damaged cells compared with the original ones cause serious exothermic reactions and lead to enhanced heat accumulation.