Simulation Study Of Polythiophene As The Artificial Solid Electrolyte Interface In Lithium Ion Batteries

At present,the development of portable electronic equipment and electric vehicle makes lithium-ion battery have a huge market demand.However,especially for the application of electric vehicles,new challenges,such as the life cycle,capability,safety,and irreversible capacity have to be overcome.The unstable solid electrolyte interface(SEI)formed on the anode surface during the charge-discharge cycle of lithium-ion batteries is one of the most important factors restricting the development of lithium-ion batteries.The unstable SEI formed during the cycle of lithium-ion battery is easy to rupture and fall off,which affects the Columbic efficiency,cycle life and safety of lithium-ion battery.Therefore,the design of a stable artificial solid electrolyte interface(A-SEI)is an important way to improve the life and performance of lithium-ion batteries.In this paper,molecular dynamics simulation is used to study the adhesion between polythiophene(PTh)and graphite anode(graphene oxide),the utility of polythiophene(PTh)as an A-SEI,and the diffusion dynamics of lithium ions in the polythiophene matrix.First,the adhesion interaction between polythiophene and graphene oxide is studied,and the polythiophene and different surface density of carboxyl-graphene oxide(FG-COOH),hydroxyl-graphene oxide(FG-OH),amino-graphene oxide(FG-NH₂)and methyl-graphene oxide(FG-CH₃)are calculated via direct energy method.The enhanced adhesion behavior between PTh and graphene oxide substituted with different functional groups is mainly dominated by the electronegativity of the functional groups.The adhesion between carboxyl-graphene(FG-COOH)and PTh is the strongest,and the methyl group with the weakest electronegativity have the weakest adhesion interaction behavior.In addition,the adhesion of the adjoining system is also affected by the surface roughness of the interface between graphene oxide and PTh.With the increase of the density of the surface functional groups of the methyl-graphene oxide(FG-CH₃),the interaction energy of the adhesion system gradually strengthens and tends to be stable,which indicates that the surface roughness of the contact interface weakens the adhesion interaction between PTh and graphene oxide.After confirming the strong adhesion between PTh and graphene oxide,lithium-ion battery model is constructed to explore the effect of PTh as an A-SEI in lithium-ion battery.PTh is used as an artificial solid electrolyte interface(A-SEI)to isolate the electrolyte solvent molecules(EC)in the lithium-ion battery from contact with the graphite negative electrode,reducing the probability of the electrolyte solvent molecules being reduced and decomposed.In addition,a special hopping transport mechanism is verified by the diffusion rate of lithium ions through the PTh layer and the diffusion kinetics of lithium ions between PTh matrix.Therefore,this article confirms the strong adhesion between PTh and graphene oxide and the utility of PTh as an A-SEI in lithium-ion batteries.The results provide new insight to develop A-SEI for high-performance lithium-ion batteries.