Md Simulation Studv On The Effects Of Electrolyte Solvent Properties In Graphene Based Supercapacitors

The advantages of electric double-layer capacitors(EDLCs)in terms of high power densities,fast charging times,and long cycling lifespans comparing with batteries make them increasingly attractive for energy storage applications.Organic electrolyte-based EDLCs are currently dominating the commercial market due to their higher operation potential window compared with the counterparts using aqueous electrolytes and their lower viscosity,higher conductivity,and wider operating temperature range than ionic liquid electrolytes.In this work,the microstructure of planar graphene-based EDLCs with different organic solvents are investigated with molecular dynamics simulations.Results show that an increase of solvent polarity could weaken the accumulation of counter-ions nearby the electrode surface,due to the screen of electrode charges and relatively lower ionic desolvation.It thus suggests that solvents with low polarity could be preferable to yield high EDL capacitance.Meanwhile,the significant effects of the size and structure of solvent molecules are reflected by non-electrostatic molecule-electrode interactions,further influencing the adsorption of solvent molecules on electrode surface.Compared with dimethyl carbonate,γ-butyrolactone,and propylene carbonate,acetonitrile with relatively small-size and linear structure owns weak non-electrostatic interactions,which favors the easy re-orientation of solvent molecules.Moreover,the shift of solvent orientation in surface layer,from parallel orientation to perpendicular orientation relative to the electrode surface,deciphers the solvent twin-peak behavior near negative electrode.The as-obtained insights into the roles of solvent properties on the interplays among particles and electrodes elucidate the solvent influences on the microstructure and capacitive behavior of EDLCs using organic electrolytes,which is instructive in selecting suitable solvents for EDLCs.