Design And Performance Research Of High Specific Energy Double-layer Capacitors

Electric double layer capacitors(EDLCs)have many advantages,such as long cycle life,fast charging and discharging speed,high power density,low cost,environmental friendliness,etc..The biggest drawback of EDLCs,however,is that the lower energy density,than that of batteries and pseudo-capacitors.According to the energy density formula of the supercapacitor,the electrochemical properties of the capacitor are improved by widen the potential window and rise the specific capacity of the capacitor,and the high specific energy EDLCs are prepared.The main research contents include:(1)A useful strategy was adopted to improve the performance of PAA-based GPEs by incorporating sulfonated poly(ether ether ketone)(SPEEK)chains.The prepared gel not only has improved mechanical properties,but its ion conductivity has also been increased to 100m S cm^-1.The assembled EDLC by the gel electrolyte has a potential window of 1.6 V,a maximum specific capacity of 26.74 F g^-1;and an energy density of 9.04 k W kg^-1.After10,000 cycles of constant current charge and discharge,the capacity retention rate is close to100%.(2)A series of novel supramolecular hydrogel electrolytes were proposed and fabricated by a facile process at room temperature.They show good elongation at break and moderate ultimate tensile strength.The optimum hydrogel electrolyte exhibits an ionic conductivity of81.27 m S cm^-1,which endows a carbon-based supercapacitor with a stable voltage window of2.0 V.And the EDLC assembled by it can operate stably at a voltage of 2.0V,with a specific capacity of 24 F g^-1 and an energy density of 12.6 Wh kg^-1.After introducing potassium ferricyanide as a redox active material,the energy density of the EDLC is further increased to18.2Wh kg^-1,and the cycle stability is good.(3)A series of deep eutectic solvent(DES)-based supramolecular GPEs were firstly developed for carbon-based EDLCs with wide voltage windows.The as-fabricated DES-based GPE shows an ionic conductivity of?58 m S cm^-1,which makes the stable voltage window of a carbon-based EDLC reach 2.4 V.The carbon-based EDLC exhibits a specific capacitance of 32.1 F g^-1,an energy density of 24.6 Wh kg^-1 and a capacitance retention of?90%after 15000 charge-discharge cycles.Moreover,when quinhydrone is added into the DES-based GPE,the specific capacitance and energy density of the corresponding EDLC can be further expanded to 60 F g^-1 and 43.6 Wh kg^-1,respectively.