Abstract
Understanding the mechanism of mechanical deformation/stress-induced electrical failure of lithium–ion batteries (LIBs) is important in crash-safety design of power LIBs. The state of charge (SOC) of LIBs is a critical factor in their electrochemical performance; however, the influence of SOC with mechanical integrity of LIBs remains unclear. This study investigates the electrochemical failure behaviors of LIBs with various SOCs under both compression and bending loadings, underpinned by the short circuit phenomenon. Mechanical behaviors of the whole LIB body, which is regarded as an intact structure, were analyzed in terms of structure stiffness. Results showed that the mechanical behaviors of LIBs depend highly on SOC. Experimental verification on the cathode and anode sheet compression tests show that higher SOC with more lithium inserted in the anode leads to higher structure stiffness. In the bending tests, failure strain upon occurrence of short circuit has an inverse linear relationship with the SOC value. These results may shed light on the fundamental physical mechanism of mechanical integrity LIBs in relation to inherent electrochemical status.
Highlights
Lithium–ion batteries (LIBs) have become the most popular commercial choice as power source for non-gasoline vehicles[1,2,3]
Constitutive behaviors of aluminum and steel can both be expressed by Johnson-Cook model, which is expressed as σ = Aεn + B; they may share the same mechanical behavior form
In previous studies[11,12,14], the mechanical model of the jellyroll is given as σ = Aεn + B or σ = Aεn, confirming that the parameters A and B by compression tests can describe the mechanical behavior of jellyrolls
Summary
Lithium–ion batteries (LIBs) have become the most popular commercial choice as power source for non-gasoline vehicles[1,2,3]. Understanding the mechanical behavior of LIBs at various values of state of charge (SOC) is extremely important because vehicle crashes usually occur when SOC varies during driving. The results have proven that insertion of lithium–ion in anodes may cause elastic softening of the silicon anode, probably because of the formation of Li-rich areas in the grain boundary regions[26] This finding further supports our idea to examine the electrochemically dependent mechanical behavior of LIBs and investigate the short circuit occurrence at various SOC values subjected to extreme mechanical loadings. Relationships of failure strain/stress to the SOC values at both compression and bending loadings are established
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