Research On The Performance Of Low Temperature Resistant Supercapacitor Based On Reduced Graphene Oxide

In the last decade,the development of portable and wearable electronic devices has greatly stimulated the research of miniature energy storage devices that has both flexibility and small size.As an energy storage device with a wide range of applications,the supercapacitor has the advantages of high power density,safe operation,longer cycle life and simple configuration,etc.,and it has been widely developed and researched.However,the supercapacitor can be inactivated at low temperature due to the solidification of the electrolyte during use,and its capacitance performance would be greatly attenuated.Therefore,the application of supercapacitors in low temperature environments is greatly restricted.In order to overcome this shortcoming,in this paper,reduced graphene oxide（rGO） film with good flexibility was prepared,a low-temperature resistant electrolyte was designed and prepared,and a sandwich-like supercapacitor composed of rGO electrode material and low-temperature resistant electrolyte was assembled.The main content and the results include:（1）A rGO film with a honeycomb porous layered structure with good flexibility was prepared.The annealed rGO film could be folded well under liquid nitrogen conditions and quickly restored to its original shape.The supercapacitor combined with Li₂SO₄ aqueous electrolyte could work in a low temperature environment of -40℃,and the specific capacitance tested by two electrodes could reach 25.1 F/g,which was 33.03%of the performance at room temperature（76.0 F/g）.When the current density was 0.2 A/g,the capacity retention rate was 83.3% after 5000 charge/discharge cycles at-20℃,which proved that the supercapacitor composed of the honeycomb porous layered rGO film had good low temperature resistance.（2）An organohydrogel electrolyte containing LiCl/PVA/glycerol was prepared.The organohydrogel electrolyte had good flexibility and mechanical properties.It could work normally at a very low temperature of -60℃ without solidification,and had good conductivity,ionic conductivity reached 0.0016 S/cm.The supercapacitor composed of the rGO film prepared above,tested in a two-electrode system,could operate stably at a low temperature of -60℃,with a specific capacitance of 7.73 F/g.Not only that,it could also be bent within a range of 180°,showing good flexibility and mechanical properties,and its electrochemical performance was stable.（3）The rGO/CC electrode material based on carbon cloth（CC） with high porosity was prepared,which effectively increased the surface porosity of the rGO film.Combining this rGO/CC electrode material with the above-mentioned organohydrogel electrolyte to prepare an organohydrogel electrolyte low-temperature resistant supercapacitor,which could be operated at ultra-low temperature（-60℃） to complete energy storage.After the two-electrode system tested,the specific capacitance at -60℃was 30.5 F/g,which greatly improved the specific capacitance of this electrode material at low temperature.After 5000 charge/discharge cycles,the capacitance retention rate was 81.4%.