The Research Of The Supercapacitors With Gel Polymer Electrolytes

Supercapacitors are new energy storage components between electrostatic capacitors and batteries, which have higher energy density than that of electrostatic capacitor and higher power density and longer cycle life than that of batteries. They can be used as assistant power sources for electric components, power sources for small electrical equipments or pulse power sources. In addition, they can be used as driving system of electric vehicles with batteries.Supercapacitors of liquid electrolyte are easy to leak and blast. Supercapacitors of gel polymer electrolyte are safe and non-leak, can adapt minitype and superthin wiring. Supercapacitors with poly acrylonitrile(PAN) based or poly methyl methacrylate(PMMA) based gel polymer electrolytes synthesized by in-situ polymerization were made. Propylene carbonate(PC), propylene carbonate and ethylene carbonate(EC), dimetyl carbonate(DMC) and ethylene carbonate, ethylmethylene carbonate(EMC) and ethylene carbonate were used as plasticizers, respectively. Lithium perchlorate was used as surpporting electrolyte. The performance of the gel polymer electrolyte, electrode materials and supercapacitors were tested with the aids of the measure methods such as impedance spectrum, X-rays diffraction, cyclic voltammetry, constant current charge/discharge, leakage current, and so on.The highest conductivity of PAN based gel polymer electrolyte is 9.10mS/cm at about room temperature, which is close to that of organic electrolyte, and the electrochemical stable window is 2.5V. The highest conductivity of PMMA based gel polymer electrolyte is 4.16mS/cm and the electrochemical stable window is 3V.The resistance of supercapacitor with gel polymer electrolyte by in-situ polymerization is small, which electrode materials are different specific surface area activated carbon. The resistance of PAN-based gel polymer electrolyte supercapacitor is less than that of PMMA-based. The highest double electrodes' specific capacitance of PAN-based gel polymer electrolyte supercapacitor is 48.88F/g and is close to that of organic electrolyte supercapacitor. The highest double electrodes' specific capacitance of PMMA-based gel polymer electrolyte supercapacitor is 46.52F/g and it has higher energy density. The capacitance of supercapacitor with gel polymer electrolyte by in-situ polymerization is higher than that of gel polymer electrolyte membrane supercapacitor according to referenced literatures. The leak current of PMMA-based gel polymer electrolyte supercapacitor is less than that of PAN-based. The conductivity of gel polymer electrolyte synthesized by in-situ polymerization is higher than that of PEO-based gel polymer electrolyte membrane. The highest double electrodes' specific capacitance of PEO-based gel polymer electrolyte membrane supercapacitor is 34.96F/g, but voltage drop is big and the performance is unstable.MnO₂ synthesized by the low temperatttre solid state reaction was anode material of supercapacitor with gel polymer electrolyte synthesized by in-situ polymerization and different specific surface area activated carbon was cathode material. The result is that the double electrodes' specific capacitance of MnO₂/AC is 27.3F/g and is higher than that of AC/AC by 32.2% when low specific surface area activated carbon is cathode material. The double electrodes' specific capacitance of MnO₂/AC is 36.26F/g when high specific surface area activated carbon is cathode material and is higher than that of MnO₂/AC with low specific surface area activated carbon by 32.8%. The leak current is 3.5mA.LiMn₂O₄ or LiCoO₂ with activated carbon was anode material of supercapacitor with gel polymer electrolyte synthesized by in-situ polymerization and high specific surface area activated carbon was cathode material. The result is that the specific capacitance increases with the content of activated carbon increasing. The specific capacitance of LiCoO₂ with activated carbon is higher than that of LiMn₂O₄ with activated carbon, and the specific capacitance is 40.53F/g when the content of of LiCoO₂ is 25%.