| Currently,energy issues provide both opportunities and challenges for the de-velopment of electric vehicles or hybrid electric vehicles.The state strongly supports the electric vehicle or hybrid electric vehicle industry.However,they still suffer from limited cruising kilometers and charging rates.Supercapacitors?SCs?are character-ized by their high power density,fast charge–discharge process,and long cycling life,showing great potential for vehicles.Electrolytes are one of crucial factors for achieving high performance of SCs.Although the most commonly used liquid elec-trolytes possess high conductivity and can operate at high voltages,they have a poten-tial leakage problem which causes safety issues.The polymer-based solid electrolytes for SCs can not only serve as the ionic conducting media but also as the electrode separators.The major advantages when using solid-state electrolytes are the simplifi-cation of packaging and fabrication processes of SCs and liquid-leakage free.Never-theless,they ususlly suffer from relatively poor mechanical strength and thermal sta-bility.Herein,we prepared polyvinylidene fluoride-hexafluoropropylene?PVDF-HFP?based gel polymer electrolytes,which were modified by the blend or copolymeriza-tion of polymers or incorporating additives into polymer hosts.Fourier transform in-frared spectroscopy?FTIR?,thermogravimetric analysis?TG?,and scanning electron microscope?SEM?were employed to determine their composition and structure.Moreover,their mechanical and electrochemical proterties were measured.The main results were summarized as follows:1.Polymethylmethacrylate?PMMA?was synthesized by emulsion polymerization and was blended with PVDF-HFP to obtain PVDF-HFP/PMMA gel polymer hosts.The optimum preparation condition was identified with respect to the electrochemical performance by the single factor experiments and the response surface method.The supercapacitor with the gel polymer electrolyte composed of PVDF-HFP/PMMA host synthesized under the optimized condition and 1 mol/L tetraethylammonium tetra-fluoroborate in acetonitrile/dimethyl carbonate/ethylene carbonate?1:1:1?V:V:V??shows a 83.70%retention of the initial capacitance over 1000 cycles at the current density of 0.5 A/g in a wide potential window of 0-2.5 V,and its electrical conductiv-ity can reach 2.61×10-3 S/cm.2.The crosslinked copolymer of butyl acrylate and methyl methacrylate?P?BA-co-MMA??was synthesized by emulsion copolymerization with butyl acry-late?BA?and methyl methacrylate?MMA?as monomers and then blended with PVDF-HFP to prepare the P?BA-co-MMA?/PVDF-HFP polymer hosts.The effect of the proportion of monomers on the properties of the as-prepared polymer films was studied.The results exhibit that the optimized P?BA-co-MMA?/PVDF-HFP film shows the tensile strength of 25.22%and the electrolyte uptake of 254.28%,when the ratio of BA to MMA was 3/2.After uptaking the electrolyte,the P?BA-co-MMA?/PVDF-HFP based electrolyte displays the electrical conductivity of1.84×10-3 S/cm and high thermal decomposition temperature of 235°C,which can meet the application requirements for SCs.Furthermore,the supercapacitor assembled with the as-obtained gel polymer electrolyte shows better electrochemical perfor-mance with a specific capacitance of 37.12 F/g,an energy density of 32.22 Wh/kg,and a 85.30%retention of the initial capacitance over 1000 cycles compared with that with PVDF-HFP/PMMA or commercial PP based electrolytes.3.If doped directly with nanoparticles,it is difficult to disperse,and the modifica-tion effect is not obvious.In this paper,P?BA-co-MMA?/PVDF-HFP film was modi-fied with polymethyl methacrylate surface-modified nano-silica?PKS?prepared by a two-step method.The effect of the content of PKS on the structure and the mechanical and electrochemical properties of polymers was investigated.When the gel polymer electrolyte synthesized with the addition of 10 wt%of PKS into P?BA-co-MMA?/PVDF-HFP was used for supercapacitors,the obtained electric dou-ble layer capacitor showed the best capacitive behavior with a specific capacitance of38.36 F/g,an energy density of 33.29 Wh/kg,a power density of 1.25 kW/kg,and a89.70 retention of the initial capacitance over 1000 cycles at a current density of1.0A/g in the potential window of 0-2.5V. |
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