Preparation Of Flexible Wide Temperature Domain Organic Gel Electrolyte And Application In All-solid Supercapacitors

With the rapid development of energy storage equipment and the popularization of the concept of sustainable development,the development of green and clean electrochemical energy storage devices has become a hot issue in scientific research in recent years.Supercapacitors have attracted much attention because of their advantages such as high-power density,fast charging and discharging rate,long cycle life and simple structure.Like batteries,supercapacitors are made up of electrodes and electrolytes.In supercapacitors,electrolytes affect the safety factor of the device,operating voltage and working environment.Traditional liquid electrolytes are easy to leak during assembly and use,and are not easy to carry.Compared with other electrolytes,polymer gel electrolytes have attracted extensive attention in the field of supercapacitors because of their better flexibility and similar conductivity to liquid.However,traditional hydrogel electrolytes tend to freeze or dehydrate when the ambient temperature increases or decreases,which results in a very limited application environment.Therefore,improving the working temperature region and stability of gel electrolyte is an urgent problem to be solved.In this paper,an organic gel electrolyte（OGE）consisting of Acrylic acid n-hydroxyethyl acrylamide（AA-NHEA）network,glycol/water（EG/H₂O）solvent and sulfuric acid（H₂SO₄）was successfully prepared by radical polymerization initiated by UV light.The gel electrolyte crosslinked by a multiple hydrogen bond network has high compressive stress（200 k Pa）,good shape recovery performance and high proton conductivity（17 m S/cm,-40℃）.Because the EG/H2O binary solvent system effectively lowers the freezing point,ultracapacitors assembled with OGE can achieve nearly 76%capacitance retention at-40℃.In addition,the device has excellent long-term cycle stability,with capacitance retention rates of 90.73%（20℃）,80.68%（-20℃）,and 69.05%（-40℃）after 10,000 cycles at 1A/g.The hydrogen bond cross-linking between monomers can greatly reduce the mechanical properties of the gel.And,ethylene glycol as solvent was introduced into the system beforehand,which also had a certain influence on the polymerization of gel.Therefore,MXene was introduced as the inorganic filler and the gel was crosslinked.At the same time,the method of solvent replacement was used to remove excess free water molecules in the gel.Finally,the PAA-NHEA-MXene organic gel electrolyte prepared exhibits excellent mechanical strength（273 k Pa）.The specific capacitance of the device is 101F/g after assembling the PAA-NHEA-Mxene organogel electrolyte and activated carbon electrode.On the other hand,the gel electrolytes give the device a wider operating temperature range（-20℃ to 80℃）and excellent capacitive retention rates of 96.8%（80℃）and 94.9%（-20℃）for long cycles after solvent replacement.