Molecular Dynamics Simulation of Lithium Ion Diffusion in Lithium Ion Battery

Molecular dynamics (MD) simulation can do research on the macroscopic properties of certain object and also the microscopic details which cannot be available through experiments. So the method is widely used in the fields of physics, chemistry, biology and materials science etc. This article is organized as follows. The widely use of lithium ion battery, its component, working principle is briefly introduced in the first chapter, as well as the important role cathode materials plays and their current research status. In the second chapter, we introduce the basic principles for MD simulation, the steps to achieve a molecular dynamics running, and some critical techniques utilized in it. Then in the third chapter, through choosing a specific potential model and MD simulation package after literature review, we run a MD simulation for the ion system using the ensemble of constant particle, constant temperature and constant pressure, to get the lattice parameter under the equilibrium after lattice relaxation, as well as radial distribution function for each pairs. Then we compare the simulation results with those from real experiment to verify the applicability of the chosen potential for the ionic crystal. From these, the structural and dynamical properties of spinel LiMn2O4 are achieved. Also, we observe the intercalation and de-intercalation of Lithium ions through viewing the trajectory. Next in the fourth chapter, we change the simulation conditions of temperature, lithium concentration and doping and we obtain the Mean Square Displacement (MSD) and 3-D diffusion coefficient of different ions to evaluate the dynamical properties. The simulation results indicates that Li ions have more significant movement than that of other ions and 3-D diffusion coefficient of Li ions increase linearly as higher temperature and decrease as higher concentration. But Ni doping does not show certain correlation with diffusion. Last in the fifth chapter, based on the Chemical Dynamics method and correlation between diffusion coefficient and temperature, we can make Arrhenius plot to get the activation energy during the process of lithium diffusion. Finally, we give an overall development trend for the cathode materials used in lithium battery, and its prospect to be widely used in many electronic products.