| The novel gel polymer electrolytes (GPEs) for Secondary Lithium-ion Battery have been investigated. Four kinds of gel polymer electrolyte were prepared, including membrane supporting gel polymer electrolyte (MSGPE), modified dual-phase polymer electrolyte (DPE), semi-IPN gel polymer electrolyte and modified PVdF microporous gel polymer electrolyte. The chemical characteristics, surface morphology, thermal behavior, ionic conductivity, interfacial stability between lithium metal electrode have been investigated by using of FT-IR, Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Optical microscopic images, Alternating Current Impedance (AC Impedance) and Linear Sweep Voltammetry (LSV), respectively. Analysis the effects of preparation conditions and the proportions of raw materials on the properties of obtained GPEs, the aim of the paper is to develop the high ionic conductivity GPE with good mechanical strength.1. The membrane supporting gel polymer electrolytes (MSGPE), such as MSGPE-PPEGMA/PMMA, MSGPE-HBP/PEO and MSGPE-MAPTMS-MMA were prepared and investigated. For the polar prepolymers coated and cured PE membrane, the crystallinity property of PE, which imparted the mechanical strength to MSGPE was found to be almost maintenance. The coated polar copolymer presented a microporous structure, the absorbed liquid electrolyte could be trapped in the pores and formed gel polymer electrolyte due to good compatibility between them. In addition, the coated copolymer could increase the surface area in contact with the electrode, which would be benefit to the electrochemical stability between them. The ionic conductivity at room temperature reached 10-3S cm-1 and the electrochemical stability window was more than 4.5V.2. Dual-phase polymer electrolytes (DPEs) with enhanced phase compatibility, such as DPE-PMMA-g-NBR/PMMA and DPE-PMMA-g-PVC/PMMA were prepared. The polymer host NBR and PVC were modified with MMA by solution grafting polymerization. The grafted copolymer was first blend with PMMA and then absorbed the liquid electrolyte to prepare a new type DPE with enhanced phase compatibility. The films of DPE so obtained were homogeneous and transparent. In the DPE systems, the blending PMMA absorbed vastliquid electrolyte and formed ionic conduction channel to make the ionic conductivity at room temperature reach 10-3S cm-1 scale, while the PMMA-g-NBR or PMMA-g-PVC component kept excellent mechanical properties.3. Semi-IPN gel electrolytes such as SIN-(PPEG200MA-co-MMA/NBR), SIN-(MAPTMS -co-PEGDMA/NBR) and SIN-(XPEG/PMMA) were prepared by means of thermal polymerization or ultraviolet (UV) radiation. The surfaces of the semi-IPN polymer films were uniform and homogeneous, and hardly any cracks were observed. In the semi-IPN systems, the blending polymer chains tend to tangle with each other. The results of DSC and XRD analysis confirmed that the prepared hosts present amorphous state. The mechanical properties of the semi-IPN hosts varied with the proportion of the polymer blends. The phase compatibility of the semi-IPN gel electrolytes so obtained was better than the former blending type gel polymer electrolyte. This gel polymer electrolyte could not only retain the good mechanics, but also absorb a mass of liquid electrolyte to withstand a highly ionic conductivity. The ionic conductivity of gel polymer electrolyte reached 10-3S cm-1 and the electrochemical stability window was more than 4.5V.4. Modified PVdF microporous gel polymer electrolytes with enhanced properties were prepared by two methods. For the first method, PVdF microporous membranes were coated with polar cross-linked copolymer by means of UV radiation. For the second method, PVdF was blent with the polar copolymer which was prepared by means of dispersion polymerization, to prepare the microporous membrane. The images of the vacuum-dried films showed that micropores of 1-5μm were formed, which were influenced by concentration of the coated and the blending copolymer, respectively. PVdF kept good mechanical property and electrochemical stability in the GPE system. The addition of coated or blending copolymers helped to absorb the liquid electrolyte and gelatinize. In addition, the complexation effect of the copolymer and Li+ ion could promote the dissociation of the Li salt, which eventually increased the number of conductive ions and enhanced the ionic conductivities. The prepared microporous gel polymer electrolyte reached 10-3S cm-1 and the electrochemical stability window exceeded 4.5V.In a word, the above preparation methods of gel polymer electrolytes (GPEs) are quitesimple. GPEs so prepared have good properties, which made it possible to be used for secondary Lithium-ion battery in practice.
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