Silicon-based, tin-based electrode materials have become ideal electrode materials for lithium-ion batteries due to their high capacitance density. However, mechanically this type of material is often accompanied by large volume deformation during charging and discharging, resulting in a high stress state. And lead to the destruction of the electrode structure and other issues, which seriously affect the service life of lithium-ion batteries.
In order to reasonably design the electrode structure and avoid the mechanical damage that may occur in the structure, it is necessary to establish the force-electro-chemical coupling constitutive relation of the electrode material in the charge and discharge process. The usual practice is to obtain the in-situ measurement experiment and the Stoney formula. The stress evolution of the electrode material during charge and discharge. However, the method must rely on the thickness of the film is much less than the thickness of the substrate, the film thickness changes in the deformation process can be ignored, the film and the substrate is good adhesion between the three hypotheses, High-performance batteries are often difficult to meet these conditions.
In order to solve this problem, the research team of the State Key Laboratory of Nonlinear Mechanics at the Institute of Mechanics, Chinese Academy of Sciences based on the force-electro-chemical coupling theory developed a set of finite element calculation methods that can accurately characterize the electrode material during charge and discharge. Plastic deformation and intrinsic stress evolution. This method was used for finite element simulation. The error analysis of Stoney's formula caused by the large elastic-plastic deformation of the electrode film was described. The large deformation of the electrode film, elasto-plastic constitutive relation and interface material The influence of properties on the stress-charge-discharge state curve, and the correspondence between electrode material parameters and stress-charge-discharge state-curve characteristics. This work is to investigate the force-electro-chemical coupling constitutive relation of electrode materials during charge and discharge processes. Provided help.
Related research results have been published in the International Journal of power sources (Wen, J., Wei, Y., Cheng, YT, 2018. Examining the validity of Stoney-equation for in-situ stress measurements in thin film electrodes using large -deformation finite-element procedure. J.Power Sources, 387,126-134.) and Journal of the Mechanics and Physics of Solids (Wen, J., Wei, Y., Cheng, YT, 2018. Stress evolution in elastic plastic During the electrochemical processes: A numerical method and its applications.J.Mech.Phys.Solids,116,403-415.). The study was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences Class B pilot project and the National Science Foundation of the United States.
Fig.: Typical layered battery structure and its deformation. (a) Electrode thin film-adhesive-substrate structure; (b) Comparison between numerical model and experimental results, showing changes in stress in the electrode film during charge and discharge processes; (c) Elasto-plasticity of the electrode material and the internal shear stress distribution of the film under interface failure conditions.
