Molecular Dynamics-based Charging Simulation Of Multilayer Fullerene Electrodes

Lithium-ion batteries have been widely used as energy storage equipment with the increasing demand for energy storage equipment.Multi-layer fullerenes have become the popular electrode materials in the field of Lithium-ion batteries.Aiming at the mechanism of performance degradation of multilayer fullerene electrode,a lot of experiments have been carried out from macroscopic point of view,and various reasons have been summed up,such as electrode material damage or shedding,diaphragm damage,etc.However,due to the limitations of experimental means,there is still no clear understanding of the microstructural defects of multilayer fullerenes and their effects on lithium ion diffusion.In this paper,molecular dynamics(MD)simulation method is used to analyze the mechanism of structural defects in multilayer fullerenes as electrode materials during charging,and the effect of structural defects on lithium ion diffusion and battery capacity is also analyzed.The detailed content is as follows: 1.This paper simulated the diffusion process of lithium ion on the surface of multilayer fullerenes by establishing multilayer fullerenes model using MD simulator.the influence of lithium ion diffusion on the carbon ring stress is examined.Factors such as diffusion speed,lithium ion concentrations and layers are considered.Then the Cauchy stress of the local carbon ring was calculated according to the transformation relationship between Virial stress and Cauchy stress.The movement of carbon atoms was observed by visual software.The relationship between stress and diffusion speed,concentration of lithium ion and layer number of multilayer fullerenes is discussed,and the loading conditions and geometrical conditions in which carbon rings can break through energy barrier are analyzed(Vibrations with high frequencies and large amplitudes activate carbon atoms,increasing their ability to break through energy barriers,resulting in the rupture of carbon rings.)2.Considering the squeezing effect of electrode expansion on the internal structure,we established simplified model in which the multilayer fullerene electrode suffers the unidirectional extrusion process.Then,the process of structural defects caused by the extrusion is analyzed.Additionally,different changes in the structure of multilayer fullerenes and single-layer fullerenes after being extruded are compared,and the loading conditions and locations where defects occur are analyzed.The results show that multilayer fullerenes are more prone to defects at the apex than single layer fullerenes.3.Finally,a defect-containing multilayer fullerene MD model was established and the lithium ion diffusion and extraction simulation was performed;the visual software was used to observe and analyze the effect of defects on the diffusion of lithium ions;and the number of lithium ions captured by the multilayer fullerene was counted to explore the impact of defects on battery capacity.