Simulation Study On The Microstructure Of Ionic Liquid In The Electric Double Layer And Its Effect On Capacitance

With the rapid development of the social economy,the demand for energy has become greater and greater.However,not only is the traditional depletion of energy faced by traditional fossil energy,but also the environmental problems caused by traditional fossil energy have become increasingly serious.Therefore,the development of new renewable energy and related energy storage devices has become more urgent.The continuous prosperity of the portable electronic device and electric vehicle industries has further created a huge demand for electrical energy storage.Supercapacitors based on electric double layer capacitors have gradually entered people's field of vision with their unique advantages.Compared with traditional capacitors,super capacitors have the advantages of high power density,rapid charge and discharge,and long service life.They have a wide market value and application prospects.Although the energy density of electric double layer capacitors has a qualitative leap compared to traditional dielectric capacitors,it still differs from the battery by an order of magnitude,making it the biggest bottleneck in its wide application.Because the electrochemical window of ionic liquid is wider,it can effectively increase its energy density,and it also has the advantages of stable properties,low saturated vapor pressure,and low toxicity.It is selected as the electrolyte for this work.Based on the method of molecular dynamics simulation,the adsorption,diffusion,and capacitance properties of ions on the surface of supercapacitor electrode materials are studied from the nanometer scale.It is hoped that the mechanism of its existence will be further explored from the micro scale to provide a reference for the improvement of the capacitance performance of super capacitors.The specific work is as follows:1.The electric double layer structure of four kinds of ionic liquids was studied by molecular dynamics simulation using a fixed charge method,that is,applying a charge on the graphene electrode surface.The discovery explores its impact on capacitor performance.With the increase of the applied voltage,the density and orientation of anions and cations have undergone considerable changes,and the effect on capacitance performance is further discussed2.Since the viscosity of ionic liquids is generally large,which affects the power density of supercapacitors,adding a solvent is a simple and effective method to reduce viscosity,which can improve the dielectric constant and conductivity of ions.In this paper,using acetonitrile as an example,the structure,kinetic properties and differential capacitance of the anion and cation at the interface of different concentrations of solvents in the supercapacitor are studied by molecular dynamics simulation.