Research On Electrochemical Performance And Optimization Of Lithium Ion Batterries Based On The Mechanism Model

Li-ion batteries have been attracted for their excellent performance and they are widely used in ekectronic devives,power energy sources,energy reserves and so on.However,it's difficult to obtain the working state of the battery through experimental means for its complex structure,and it can't obtain the performance of the battery.Therefore,it's of great significance to ensure the optimal and safe operation of the battery.In this paper,the battery was studied based on the mechanism model of Li-ion battery,we obtained the model parameters,analysised the electrochemical performance and optimized the battery.For Li Co O2/mesocarbon microbeads cells,the solid phase diffusion coefficient of positive and negative electrode was obtained by experimental means of PITT,we obtained the initial lithium concentration and other parameters of electrode by the method of identification.The above parameters were embedded into the mechanism model.The simulation results were in good agreement with the experimental results and the error was only 4%,which proved the mechanism had a high accuracy.On this basis,the internal working process of the battery under different conditions was simulated.The simulation results showed that the lithium ion transfer to the positive electrode from negative electrode during discharge process,and led to the increase of the negative liquid concentration and the decrease of the positive liquid concentration,the greater the ratio of the discharge at end of the discharge,the greater the concentration difference between the two electrodes;Menawhile,the solid concentration of the negative electrode and the positive electrode decreased and increased respectively,and the greater the ratio of the discharge at end of the discharge,the smaller the concentration difference between the two electrodes.The smaller the particle radius,the more fully diffuse of the lithium ion and the more superior performance.We proposed the methods to optimize the specific energy and volume energy density respectively,we improved the battery performance by design the internal parameters of the battery such as the thickness of the electrode,the porosity of the electrode,the ratio of positive and negative electrode capacity,and so on.The results showed that the performance of the battery was increased after the optimization.The specific energy and the volume energy density of the battery was increased by 104 Wh/kg and 173 Wh/L respectively.Meanwhile,the graphite negative electrode had the phenomenon of lithium plating in charging process,which threated the safety of the battery.We optimized the particle radius,electrode thickness and other paramaters under different working conditions,the results showed that increasing the thickness of the negative electrode and reducing the size of active particle can effectively slow down the generation of lithium plating.Finally,in view of the particularity of the expansion of silicon electrode,we developed the mechanism model and systematically researched the change of electrode thickness,particle radius and electrode porosity under different working conditions in the discharge process.Besides,we anlaysed the effects of various parameters on the performance of the battery,which provided the basis for the optimization of the silicon electrode.