Study On Mechanical Behavior Of Porous Electrode Materials Based On UMAT

Lithium metal batteries have the advantages of high energy density,light weight,and environmental friendliness,and are expected to become the next generation of new secondary batteries.However,during the charging and discharging process of a lithium metal battery,the irregular deposition of lithium ions on the electrode surface will generate lithium dendrites of various shapes.The formation of dendrites will not only consume a large amount of active materials(Li~+)inside the battery,but also cause the battery capacity to be reduced.Attenuation,and may cause serious safety problems.Current studies have shown that the stress state of the lithium metal electrode during the charging process will affect the deposition of lithium ions,and applying appropriate mechanical stress can effectively inhibit the formation of lithium dendrites.Experiments show that moss-like lithium dendrites are porous structures composed of micro-lithium dendrites,so it is necessary to select a suitable constitutive to describe its mechanical behavior.In addition,the porous structure is widely used in batteries,the changes of electrode materials during electrochemical cycling are worthy of research and attention.Based on the theory of porous plasticity,this paper has compiled the corresponding User Defined Material Subroutine(UMAT)in ABAQUS.By finite element method,this paper analyzes the deformation behavior of mossy lithium dendrites under mechanical load,and based on the electrochemical-mechanical coupling theory,the corresponding numerical simulation of the lithiation of the porous electrode material is carried out.Mainly completed the following work:Firstly,using the theory of degraded porous plasticity,a numerical simulation was carried out for the nanoindentation experiment of bulk metal lithium,and the simulation results were compared with the displacement-load curve obtained from the experiment.The results showed that the degraded porous plasticity was adjusted by the corresponding parameters.The theory can accurately describe the mechanical response of metallic lithium in the nanoindentation process.Secondly,numerical simulation is carried out on the nanoindentation experiment of moss-like lithium dendrites.Based on the morphological characteristics of the mossy lithium dendrites,a corresponding simulation model was established,combined with the theory of porous plasticity,and the numerical simulation of the nanoindentation experiment of the mossy lithium dendrites under a flat indenter was completed.Finally,the electrochemical-mechanical coupling problem of porous electrodes is simulated.Considering the influence of the in and out of lithium ions on the volume and stress state of the electrode,the existing porous plasticity theory is revised.Then use the modified porous plasticity theory to write a subroutine to complete the numerical simulation of the porous electrode under the electrochemical-mechanical coupling.