State of Charge Dependent Constitutive Model of the Jellyroll of Cylindrical Lithium-Ion Cells

Most literature on the mechanical properties of Lithium-ion battery cells is concerned with the mechanical behavior of jellyroll or Lithium-ion battery when the state of charge (SOC) is 0%. Recent evidence shows that the mechanical properties of Lithium-ion batteries change as the SOC value changes. In this paper, several quasi-static mechanical tests on 18650 battery cells with various SOC values are performed to reveal the SOC-dependent mechanical and electrochemical failure behavior of Lithium-ion batteries. The SOC-dependent constitutive model of the jellyroll is proposed. Experimental results indicate that the ability of Lithium-ion batteries to resist deformation increase as the SOC value increases. An increase in the SOC value may facilitate thermal runaway after an internal short circuit. An explicit finite-element model of a Lithium-ion battery is established to validate the proposed approach. The simulation results of various loading cases are in good agreement with the corresponding experimental results. The established SOC-dependent finite-element model of a Lithium-ion battery may be beneficial to produce accurate simulations of an entire battery pack during operation.

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