Ionic Liquid Assisted Synthesis Of Reduced Graphene Oxide For High-performance Supercapacitors

Supercapacitors,also known as electrochemical capacitors,with longer cycle life and higher power density,play important roles in energy storage and conversion systems.Accompanying the growing requirement for intelligent electronic devices,various flexible wearable electronic devices are gradually appearing in our life and attracting more and more attentions.Environment-friendly ionic liquids play great roles in material preparation,such as solvent,stabilizer and structure guide agent.Therefore,we investigated the great effect of ionic liquid on GO including the mass and types,then we constructed flexible all-solid-state symmetric supercapacitor.The main research work includes the following three aspects:1?Hydrophobic ionic liquid?BmimFeCl₄?,hydrophilic and acidic ionic liquid?BmimH₂PO₄?,ionic liquids with different cationic?BmimCl,BmimCl?were used to prepare kinds of electrode materials.The results indicate that the type shows almost no difference.The electrostatic interaction between ionic liquid and the oxygen-containing functional groups on the graphene sheets plays a real role in the reduction process.Moreover,electrochemical tests of various reduced graphene oxide materials prepared by adding different amounts of ionic liquid were carried out.The results show that the electrochemical performance of ILG-150 is the best.2?In this chapter,ionic liquid?BmimCl?is used to induce the electrostatic self-assemble of reduced graphene oxide,which can not only effectively inhibit the agglomeration between sheets,but also retain part of oxygen-containing functional groups,so as to have good electrochemical properties.At the current density of 0.5 A g^-1,the specific capacitance of ILG is 195 F g^-1.Moreover,ILG material shows superior rate capability(62%from 0.5 to 100 A g^-1),outstanding energy density(9.03 W h kg^-11 at 125 W kg^-1)and cyclic performance(98.31%capacitance retention after 30000 cycles at 2 A g^-1)in 6 M KOH electrolyte.3?In this chapter,ILG material was used as flexible electrode material and successfully assembled into a flexible all-solid-state symmetric supercapacitor with PVA/KOH gel as solid electrolyte,and the outer layer was encapsulated by PDMS to obtain a transparent and highly flexible all-solid-state symmetric supercapacitor.When the current density is 0.5 A g^-1,the specific capacitance is 195 F g^-1,and the capacitance retention rate is almost 100%when the capacitors are tested in different bending states.In addition,after 10,000 cycles of charge and discharge,the capacitance retention rate is 84.69%,reflecting that the capacitor device has good electrochemical stability.