Study On Preparation And Energy Storage Performance Of PVA/Partially Reduced Graphene Oxide Based Electrolyte

Supercapacitors have received widespread attention once they came out because of their fast charge and discharge,good cycle stability,high power density,and environmental friendliness.It is applied to the backup power supply of electronic products,the auxiliary power supply of electric vehicles and hybrid vehicles,solar and wind power generation devices,as well as military,aerospace and other fields.With the advancement of science and technology,the requirements for energy storage devices are getting higher and higher.Therefore,the development of electrode materials with excellent performance and electrolytes are inevitable.Graphene has always been regarded as one of the first materials for ideal electric double layer capacitors due to its high electrical conductivity,excellent chemical stability and large theoretical specific surface area.The fully reduced graphene oxide（RGO） is hydrophobic,and there is an obvious agglomeration phenomenon,which hinders ion diffusion.In order to overcome this phenomenon,we chose to control the reduction degree and prepare the partially reduced graphene oxide（PRGO） with both electrical conductivity and hydrophilicity.In recent years,polyvinyl alcohol（PVA） has been widely used as a hydrogel electrolyte due to its excellent physical and chemical properties.In this paper,PVA is selected as the supporting matrix,and the PVA/PRGO composite material is doped with electrolyte NaClO₄ to achieve integration,and an electrolyte containing partially reduced graphene in a critical state of solid precipitation is prepared,which effectively improves the specific surface area and capacitance performance of the electrode material.The main research contents of this paper are as follows:（1）The PVA/PRGO composite was prepared by a one-step hydrothermal method,and then mechanically mixed with NaClO₄,KOH and NaCl to prepare different electrolytes PRGO@NaClO₄,PRGO@KOH,PRGO@NaCl,compare its capacitance performance after assembling into super capacitor.Through testing,it is found that the supercapacitors assembled with PRGO@NaClO₄ electrolyte can reach 360 mF cm^-2 in terms of area specific capacitance,with the best performance,and the capacitance retention rate can still reach 99% after 1000 cycles of charging and discharging,and has good cycle stability.（2）Comparing the electrochemical performance of the device assembled with pure NaClO₄ electrolyte,it is confirmed that the doping of graphene does increase the electrochemical performance of the device.Also mainly explored the influence of electrolytes prepared with different concentrations of graphene on the capacitance performance of the overall device.The conclusion drawn is that the 4-PRGO@NaClO₄ electrolyte prepared with a graphene concentration of 4 mg ml^-1 has the best performance of the assembled device.At a current density of 0.5 mA cm^-2,the capacitance can reach913 mF cm^-2.In addition,the energy density and power density of the device were compared.The energy density of the device assembled with 4-PRGO@NaClO₄ electrolyte reached 40.667μWh cm^-2,and the power density was 0.2 mW cm^-2.（3）In order to further improve the capacitance performance of the device,the PVA/PRGO composite material was chemically oxidized to polymerize pyrrole to prepare the PRGO/Ppy@NaClO₄ electrolyte.The comparison of the electrochemical performance of the PRGO/Ppy@NaClO₄ electrolytes prepared from graphene at different reduction temperatures and assembled into supercapacitors confirms that partially reduced graphene oxide not only ensures hydrophilicity,but also improves conductivity,and the compound of polypyrrole provides pseudocapacitance and improves electrochemical performance.By formula calculation,the symmetrical supercapacitor assembled with PRGO/Ppy@NaClO₄ electrolyte can reach 1525 mF cm^-2 in area specific capacitance under the condition of current density of 10 mA cm^-2.And the capacitance retention rate can still reach 110.64% under 10000 times of charge and discharge,showing the excellent cycle stability of the device.The electrolyte prepared in this paper provides a new idea for energy storage devices.