Mechanical Analysis Of Si Anodes For Lithium-ion Battery And Test Validation

Si has the highest theoretical specific capacity(4200mAh/g)and has been regarded as the competitive candidate of the anode for the next generation advanced lithium-ion battery.But during the lithium-ion insertion/extraction,Si experiences big volume change,the huge volume change will cause the pulverization failure of Si electrode which will cause the capacity and life of lithium-ion battery will fade fast during the repeated charge and discharge process.Preparation of Si composite thin film with inert metal material can relieve the volume effect less and more.In this article,we use Abaqus first to analyze the failure mechanism of Si thin film,then analyze the influence of the inert metal(Mn and Zr)and the thickness of the metal(Zr)on the failure of Si thin film,from which the charge and discharge properties can be forecasted.Then,we prepared and analyzed the corresponding Si thin films discussed in the finite element analysis.The detailed research content and conclusions are as follows:Firstly,we used finite element software Abaqus to analyze the failure mechanism,and then analyzed the influence of the inert metal(Mn and Zr)on the maximum stress and strain of the Si thin film after totally lithium-ion insertion/extraction.The results indicated that during the process of lithium-ion insertion/extraction,the maximum stress and strain occurs in the region close to the edge surface of the interface between Si thin film and Cu foil,the failure of the Si thin film may first occurs in this region.With the use of inert metal,the maximum stress and strain occurred in the same region,while the maximum valus decreased,maximum stress and strain of Si-Zr thin film is less than that of Si-Mn thin film.Secondly,magnetron sputtering was used to fabricate the Si thin films,and their electrochemical performance were evaluated.The electrochemical performance reveals that the cycle and rate performance of Si thin film were improved with the use of inert metal.In comparison with Si-Mn thin film,Si-Zr thin film behaved better.Furthermore,based on the finite element model set up ahead,the effect of thickness of inert metal on the maximum stress and strain caused by lithium-ion insertion/extraction is then considered,in the case where the Si-Zr thin film behaved better than Si-Mn thin film,we chose the Si-Zr thin film as an research object.We fabricated the Si-Zr thin film by magnetron sputtering and analyzed their cycling performance.The simulation results showed that the maximum stress and strain caused by insertion/extraction decreased with the increase of the thickness of Zr even though the change is light.The testing results showed that the cycling and rate performance of the Si-Zr thin film were better with the thickness of thin film.The experimental results matched with the simulation results.