Xiong Shu, Linkai Tan, Kexiang Wei, Rundong Yan, Wenxian Yang
The mechanical safety of energy storage batteries is critical for their application in electric vehicles, smart grids, and portable electronics. While previous studies have primarily focused on thermal and electrical abuse, this work provides a systematic investigation into the mechanical failure mechanisms of lithium iron phosphate (LFP), nickel cobalt manganese oxide (NCM), and sodium-ion batteries (SIBs) under extrusion deformation at varying states of charge (SOC). The results reveal distinct differences in stress–strain behavior, open-circuit voltage (OCV), temperature evolution, and electrochemical impedance responses among battery types and SOC levels. Notably, LFP and NCM batteries exhibit increased yield stress at higher SOCs, whereas SIBs show greater voltage instability and a higher risk of thermal runaway. Electrochemical impedance spectroscopy (EIS) indicates that extrusion increases ohmic and diffusion resistance, while interfacial impedance decreases due to electrode densification. Scanning electron microscopy (SEM) shows that mechanical deformation induces interlayer detachment, cracking, and separator melting in LFP and NCM batteries, with severity increasing at higher SOCs. SIBs display microcrack expansion, particle fragmentation, and inter-particle delamination under similar conditions. This study offers new insights into SOC-dependent failure behaviors under mechanical abuse, contributing to safer battery design and performance optimization in real-world impact scenarios. • Failure mechanisms of LFP, NCM, and SIB batteries under extrusion are analyzed • Higher SOC increases stress and accelerates OCV drop in LFP and SIB batteries • EIS shows rising resistance and reduced interfacial impedance with deformation • SEM reveals severe electrode cracking and separator damage at higher SOCs