Research On PVDF-based Gel Polymer Electrolyte For Dual-ion Battery Syste

Dual-ion batteries(DIBs)are a new type of energy storage device that has higher capacity characteristics than supercapacitors and higher rate characteristics than traditional lithium-ion batteries.DIB using pure ionic liquid(IL)as electrolyte(ILDIB)have the advantage of being metal-free,which effectively avoids the problem of metal dendrites.Moreover,ILs are not as sensitive to air and water as the electrolytes of traditional lithium-ion batteries,making them uniquely safe.Additionally,the recycling process of these batteries is easier and more convenient.Despite these advantages,it cannot be denied that ILDIBs suffer from severe self-discharge effects.This work aims to improve the structural stability of ILDIBs,mitigate their self-discharge effects and increase their specific capacity.Using literature reports and experimental methods as guides,graphite-based dual-ion batteries(DGBs)and polyimide-based dual-ion batteries(PGI-DIBs)were studied,and new ideas and innovations were explored.Polyvinylidene fluoride-based ionic liquid gel polymer electrolytes(ILGPEs),ILGPE graphite dual-ion batteries(IGDGBs)and ILGPE polyimide dual-ion batteries(IGDIBs)were prepared,and their physical and chemical properties were analyzed.The improvement effects of these materials on the cyclic performance,rate performance and self-discharge effect of ILDIBs were investigated,and their mechanisms were analyzed.The detailed research contents are as follows:(1)Preparation and performance analysis of ILGPE.Two types of ILGPE were prepared using solution casting method with two polymer matrices and two types of ILs.The effect of IL content(50%,100%,150%,200% and 250%)on the ionic conductivity of ILGPE was studied,and the change of the ionic conductivity of ILGPE was analyzed by related characterization methods.Finally,the ionic conduction mechanism of ILGPE was analyzed.(2)Study of ILGPE for DGB.The influence of IL and ILGPE,as well as the charge and discharge cutoff window,on the cyclic stability of DGB was analyzed.The effect of IL content on the cyclic performance,rate performance,and self-discharge of IGDGB was studied,and electrochemical impedance spectroscopy(EIS)was used for analysis.The effect of static time and cycle number on the self-discharge of IGDGB was discussed,and the mechanism of ILGPE in mitigating the self-discharge effect of DGB was analyzed using EIS.(3)Study of ILGPE for PGI-DIB.Polyimide(PGI)was synthesized using the solvent thermal method,and PGI-DIB was constructed.The physical and chemical properties of PGI and the energy storage process of PGI-DIB were analyzed by relevant characterization methods.The effect of IL content on the cyclic performance,rate performance,and self-discharge of IGDIB was discussed,and EIS was used for analysis.