| As a new type of energy storage device,supercapacitors have the advantages of high power density,fast charge and discharge,long cycle life,and being environmentally friendly and so on,which has attracted extensive attention.At present,the liquid electrolyte commonly was used in commercial supercapacitors,which has the risk of leakage and explosion.In addition,in recent years,the demand for portable,miniaturized,and mechanically flexible electronic products has been increasing.The liquid electrolyte cannot meet the requirements of portable power supplies and wearable electronic products.Therefore,the new solid electrolyte has attracted everyone's attention.It has the advantages of higher safety performance,longer service life,more stable performance,thinner volume and so on,which provides an effective way for the development of miniaturization and mechanically flexible electronic equipment.PEO-based polymer electrolyte has attracted extensive attention at present,but it has the problems of low ionic conductivity at room temperature and poor mechanical strength.Therefore,how to improve the thermodynamic properties and ionic conductivity at room temperature of solid electrolyte has become the focus of current research.In order to solve this problem,under the guidance of the design idea of"Rigid and Flexible",a new type of high-performance poly(aryl ether ketone)-based solid polymer electrolyte was prepared,which was rationally designed and optimized.The morphological structure and electrical properties were tested,and then a new type of poly(aryl ether ketone)-based porous polymer electrolyte with excellent performance was prepared.The specific research contents of this work are as follows:(1)Based on molecular design,novel copolymer containing nitrogen heterocycle PAEK and PAEK-20%PEG were synthesized by random copolymerization.The two copolymer were used as solid electrolyte matrix materials.The rigid PAEK chain segment provided excellent thermal stability and mechanical strength,and the flexible PEG chain segment could further improve the ion transport capacity.By adjusting the composition ratio of the two polymers,the porous polymer electrolyte with excellent performance was prepared.The porosity reached73.7%.The hydrophilic carboxymethyl chitosan was added to increase the liquid absorption rate(292%)and reduce the leakage rate(38.8%).The ionic conductivity of the porous polymer electrolyte can reach 8.62×10-3 S cm-1 at 20oC.The porous polymer electrolyte was assembled into a solid symmetric supercapacitor,the capacitor behavior was similar to that of the liquid supercapacitor.At the current density of 1 A g-1,the specific capacitance of the solid symmetric supercapacitor could reach 87.20 F g-1.After 5000 cycles of charge and discharge,the capacity retention rate could still reach 97.3%.The solid symmetric supercapacitor was tested by self-discharge,and the voltage attenuation rates were 44%and 57%within 70000 s at the charging current density of 0.5 m A cm-2 and 1 m A cm-2.(2)On the basis of the above experiments,in order to further improve the electrochemical performance of porous polymer electrolyte,according to the design idea of“rigid and flexible”,the polymer PAEK-g-PEG was prepared by chemical grafting,and then blended it with PAEK.By adjusting the composition ratio of PAEK-g-PEG and PAEK,the porous polymer electrolyte with excellent performance was prepared.The“spongy”porous polymer electrolyte with high porosity was prepared,with porosity up to 84.2%,electrolyte absorption up to 323%,and liquid leakage rate down to 25%.The ionic conductivity of porous polymer electrolyte can reach2×10-2 S cm-1 at 20oC,which is about twice that of the traditional liquid electrolyte(1.03×10-2S cm-1).The porous polymer electrolyte was assembled into a solid state symmetric supercapacitor.The specific capacitance of solid state symmetric supercapacitor was 122.61 F g-1 at the current density of 1 A g-1.The important thing is,after 5000 cycles,the specific capacity retention of solid state symmetric supercapacitor could reach 104%.In the self-discharge test,the voltage attenuation rate of solid state symmetric supercapacitor within 70000s is only 33%and 36%at the charging current density of 0.5 m A cm-2 and 1 m A cm-2,respectively. |
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