Ternary cathode material LiNixCoyMnzO2(NCM)with a core-shell structure is one of the key materials for the development of lithium-ion batteries with high specific capacity and long term cycle stability.However,stress-induced mechanical failure is one of the main factors that would lead to the capacity decay of such types of electrode materials.In order to better understand the stress distribution and evolution in the core-shell structural cathode during the electrochemical reaction process,a three-dimensional multiphysics lithium-ion battery model for electrochemistry-mechanics coupling was constructed in this paper.The distribution and evolution of Li+concentration,strain and stress in the core-shell cathode during the discharge process were first obtained through the model,and then the effects of various discharge rates,shell thicknesses,and core radiuses on the strain-stress at the end of the discharge were investigated.The results show that stresses at the centre of the particle and the core-shell interface rapidly reach their maximum at the beginning of the discharge,and then undergo a gradual decreasing process with the prolonged diffusion process of Li+.The binder and neighboring particles have significant effects on the stress distribution in this cathode.Decreasing the discharge rate and core radius,as well as increasing the shell thickness,can reduce the stress in the cathode.The obtained conclusions can provide a reference for the design and optimization of core-shell cathode structures as well as discharge strategies for lithium-ion batteries.
维普
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