Coupling Effect of State-of-Health and State-of-Charge on the Mechanical Integrity of Lithium-Ion Batteries
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Two governing factors that influence the electrochemical behaviors of lithium-ion batteries (LIBs), namely, state of charge (SOC) and state of health (SOH), are constantly interchanged, thus hindering the understanding of the mechanical integrity of LIBs. This study investigates the electrochemical failure of LIBs with various SOHs and SOCs subjected to abusive mechanical loading. Comprehensive experiments on LiNi0.8CoO15Al0.05O2 (NCA) LIB show that SOH reduction leads to structural stiffness and that the change trend varies with SOC value. Low SOH, however, may mitigate this phenomenon. Electrochemical failure strain at short circuit has no relationship with SOC or SOH, whereas failure stress increases with the increase of SOC value. Experiments on three types of batteries, namely, NCA, LiCoO2 (LCO), and LiFePO4 (LFP) batteries, indicate that their mechanical behaviors share similar SOH-dependency properties. SOH also significantly influences failure stress, temperature increase, and stiffness, whereas its effect on failure strain is minimal. Results may provide valuable insights for the fundamental understanding of the electrochemically and mechanically coupled integrity of LIBs and establish a solid foundation for LIB crash-safety design in electric vehicles.
KeywordsLithium-ion batteries State of charge State of health Mechanical integrity Coupling effect
This work is financially supported by start-up funds of “The Recruitment Program of Global Experts” awardee from Beihang University (YWF-17-BJ-Y-28), Opening project of State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology) (KFJJ17-13 M), Research Project of the State Key Laboratory of Vehicle NVH and Safety Technology under Grant NVHSKL-201610 and Excellence Foundation of BUAA for PhD Students.
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