Research On The Mechanism Of Lithiation Deformation And Failure Of Electrode Materials For Lithium Battery Under Irradiation Environment

Lithium-ion batteries?LIBs?,as a new generation of green,efficient and pollution-free energy,has the advantages of high voltage,high-energy density,long-cycle life and so on.it has shown a good applied prospect in the field of aerospace and satellite.However,the service environment of LIBs actually covers the coupling of the electric field,chemical field,force field,irradiation field and other multiple physical fields in space.On the one hand,Under the action of the electric field and chemical field,the intercalation and deintercalation of lithium-ion between anode and cathode could cause a serious volume deformation even fracture of electrode material.On the other hand,the failure which results the coupling multivariable with irradiation is more complicated,it greatly restricts the application of LIBs in space.Thus,it is urgent to research the failure mechanism of lithiation under irradiation so as to understand and solve this crucial problem.In order to solve the electrochemical and mechanical failure of high-capacity electrode materials for LIBs under irradiation,by neutron irradiation experiment,electrochemical performance tests,the theoretical analysis,and finite element numerical simulation,we have established an electrochemical-irradiated plasticity model for metallic electrodes in LIBs,a constitutive model coupling irradiation with two-phase lithiation for electrodes and the prediction model of electrochemical failure for electrode materials at different irradiation doses.We aim to analyze the evolution of microstructures and stress of electrode materials during lithiation with irradiation,clarify the effect of irradiation on the electrochemical properties of electrode materials for LIBs.There are some brief introductions for our main efforts:We have established an analytical solution of the stress evolution by introducing an electrochemical reaction layer into the plastic model,which deeply analyzes the dynamic evolution of concentration and stress during two-phase lithiation for spherical electrode particle.It finds that there is a mutation of the lithiation stress in the phase boundary,and the hoop stress in the surface of a spherical particle,which converts from compression into tension,implies a great threaten of fracture.Furthermore,we depict the critical state of failure for electrode material during the first lithiation based on the energy failure criteria.?1?The experiments are carried out under different irradiation doses,different charge states and different temperatures,which find that the elastic modulus decreases and the yield stress decreases with the increase of state of charge?SOC?.Irradiation hardening appeares with the increase of irradiation dose.The yield stress decreases with the increase of irradiation temperature.Based on these,we establish an irradiation-electrochemical coupled elastoplastic model that considered SOC,radiation dose and temperature as internal variables.Also,a constitutive model coupling irradiated defects with electrochemical dislocations is built.It shows that the irradiation hardening is caused by the obstacle of defects to dislocation,and when the defect density is greater than 10^-4 nm^-2,it appears as over-yield point softening.?2?We have established the prediction model of electrochemical failure for electrode materials under irradiation.By finite element numerical simulation,we analyze the influence of irradiation dose on the electrochemical properties of electrode material.It is found that the defect caused by irradiation damage in electrode material might result in a decrease of the diffusion coefficient of lithium-ion and the deterioration of electrochemical properties.Moreover,the neutron irradiation experiments are conducted on film-tin electrodes using the different radiation dose of10¹¹,10¹²,10¹³ and 10¹⁴ n·cm^-2,respectively.The results show that the particle size grows with the increasing radiation does by scanning electron microscope?SEM?.In addition,the degressive trend of specific capacity of tin anodes after neutron radiations increases with the increase of radiation dose.