| Ionic liquids, which consist only of cations and anions, due to their excellent properties, such as high ionic conductivity, immeasurably low vapor pressure, good thermal and electrochemical stability, benign to environment, are suitable for incorporation into polymers. The obtained ionic liquid-polymer electrolytes afford the completely compatible combination of ionic liquid and polymer, so the safety and stability of batteries will be improved further. Evidently, the promising application foreground of them in lithium batteries and capacitors is brought forth. In this paper, the ionic liquid-polymer electrolytes based on 1-ethyl-3-methylimida-zolium tetrafluoroborate (EMIBF4) and poly(vinylidene fluoride-co-hexafluoropropane) (P(VDF-HFP)) were prepared on the basis of the existing results. The main study contents were as follows:Firstly, EMIBF4-TiO2 gels were prepared in ionic liquid EMIBF4 by precipitation in situ. The composite ionic liquid-polymer electrolytes were prepared by the solvent-free method with EMIBF4-TiO2 gels as both plasticizer and charge carrier. Then the resultant gel ionic liquid-polymer electrolytes were studied by DSC, TG, SEM and electrochemical measurement. The results show that the ionic liquid-polymer electrolytes have high decomposition temperature (above 300°C). And the TiO2 fillers added in P(VDF-HFP)/EMIBF4 served to improve ionic conductivity as well as mechanical properties of the composite polymer electrolytes. High ionic conductivity was originated from the reduced crystallinity of P(VDF-HFP) and the fast sequential ion migration of ionic liquid phase in the ceramic fillers modified electrolytes. The P(VDF-HFP)/EMIBF4(mass ratio:1.0) -TiO2 polymer electrolyte possesses 4.1×10-3 S·cm-1 of ionic conductivity at room temperature when composite polymer electrolyte contain 3 wt% of TiO2 .Secondly, Non-woven membranes based on P(VDF-HFP) copolymer which contain micro-porous structure were prepared by electrospinning method. The resulting polymer-ionic liquid electrolytes, P(VDF-HFP)/EMIBF4 possess an ionic conductivity of 8.43×10-3 S·cm-1 at room temperature, which is close to that of pure ionic liquid. The electric double-layer capacitors applying the obtained ionic liquid-polymer electrolytes were prepared and tested. They exhibited comparatively excellent electrochemical performance at higher temperature, such as maintaining a specific capacity of 109.5 F·g-1 even after 500 cycles at 5.0 mA·cm-2 constant current charge-discharge density and enjoying the cycling efficiency of 96.4% at 80℃. However, the electric double-layer capacitors maintained a lower specific capacity of 76.9 F·g-1 after 500 cycles at 5.0mA·cm-2 constant current charge-discharge and showed a poor cycling efficiency of 81.3% at room temperature .In addition, a kind of Zwitterionic ionic liquid, 1-methyl-3-(butylsul-fonate)-2- imidazolium, which has higher melting point(219℃) and decomposition temperature(320℃), was synthesized. The modified gel ionic liquid-polymer electrolytes were prepared by incorporating the ionic liquid EMIBF4 as polymer plasticizers, lithium salt and zwitterion salt with P(VDF-HFP). The resulting polymer electrolyte possesses 1.57×10-3 S·cm-1 of ionic conductivity at room temperature when it contain 5wt% of LiBF4 and 1wt% of zwitterion salt. At this component, the ionic liquid- polymer electrolyte P(VDF-HFP)/EMIBF4(mass ratio:1.0) has 0.35 of Li+ ions transference numbers and 30.93 kJ·mol-1 of activation energy for ion transport.Finally, we primarily applied the ionic liquid-polymer electrolyte [P(VDF- HFP)/EMIBF4/ LiBF4/Zwitterion] to the LiCoO2 /Li[Li1/3Ti5/3]O4 batteries. These batteries show a discharge specific capacity of 91 mAh·g-1 and voltage plateau of 2.2V at a rate of 0.05 C in the first cycle. But after 10 cycles, their discharging capacity decreases rapidly, only delivering a discharge specific capacity of 23 mAh·g-1.
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