Design, Preparation, And Application Of Composite Polymer Electrolyte Membrance Used For Lithium Ion Battery

Aiming at developing advanced polymer lithium battery, preparation of polymer electrolyte, with higher ionic conductivity at room temperature and superior comprehensive properties, has been attracting considerable research attention in this field. In this paper, a type of specially designed ordered mesoporous silica (OMS) modified with polymer was synthesized and employed for modifying polymer electrolyte, including poly (methyl acrylate) (PMMA) and poly (ethylene oxide) (PEO) system, to explore a novel strategy for developing polymer electrolyte of high performance.(1) PMMA/PC/LiClO₄/OMS-g-PMMA system The PMMA-grafted OMS (OMS-g-PMMA) was first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl acrylate (MMA) from surface of OMS particle. The PMMA-matrix polymer electrolyte membrance, PMMA/PC/LiClO₄/ OMS-g-PMMA, was then prepared by solution casting process using the prepared OMS-g-PMMA as fillers and propylene carbonate (PC) as plasticizer. FTIR, TGA, SAXRD and HRTEM results confirmed that PMMA chains have been successfully grafted on the surface of OMS particles with a grafting ratio of 0.20 g PMMA/g OMS. It was found from alternating current (AC) impedance analysis that the OMS-g-PMMA-filled PMMA system shows higher ionic conductivity than the OMS-filled one. The highest ionic conductivity (25℃) for the OMS-g-PMMA-filled system reaches 1.06×10-4 S cm^-1, which higher by two grades than the filler-free parent PMMA system. Mechanical test and DSC analysis showed that both the mechanical properties and thermal stability of the modified PMMA system could be greatly improved upon modification with the OMS-g-PMMA.(2) PMMA/PC/LiClO₄/e-OMS-g-PMMA system A surface-initiated atom transfer radical polymerization of MMA was first performed selectively from the exterior surface of the OMS particles to synthesize the PMMA-grafted core-shell OMS (e-OMS-PMMA). The PMMA-matrix polymer electrolyte, PMMA/PC/ LiClO₄/e-OMS-g-PMMA, was further prepared by solution casting method using the prepared e-OMS-PMMA as fillers and PC as plasticizer. FTIR, TGA, SAXRD and HRTEM results confirmed that the PMMA chains have been successfully grafted onto the exterior surface the OMS particles as a core remaining the integrity of pore structure. As comparison with the OMS-filled PMMA system, the OMS-g-PMMA-filled one shows a higher ionic conductivity, better mechanical properties and improved thermal stability as well. The highest ionic conductivity at room temperature reaches 1.59×10-4 S cm^-1 for the OMS-g-PMMA-filled system, and the tensile strength and Young?s mold increased by 2.39 and 2.41 times, respectively, compared to the filler-free system, with an improvement in glass transition temperature (Tg) of 10℃.(3) PEO/LiClO₄/SBA15-g-HBPE system A hyperbranched polyethylene (HBPE) was first grafted onto the surface of SBA15 particles via ethylene polymerization catalyzed with a late transitional metal catalyst, Pd-Diimine, covalently immobilized on the SBA15 particles to synthesize the HBPE-grafted SBA15 (SBA15-g-HBPE). The prepared SBA15-g-HBPE was further used as filler to prepare the composite PEO-matrix polymer electrolyte, PEO/LiClO₄/ SBA15-g-HBPE, via solution casting process. It is confirmed by FTIR, TGA, SAXRD, BET and HRTEM results that the HBPE could be homogeneously grafted onto the surface of SBA15 particles. DSC analysis shows that the crystallinity of PEO as matrix could be greatly reduced upon addition of the SBA15-g-HBPE within a certain range of concentration. The SBA15-g-HBPE-filled PEO system exhibits a better ionic conductivity compared to the pristine SBA15-filled one. The highest ionic conductivity at 25℃for the SBA15-g-8hHBPE-filled system reaches 1.51×10-5 S cm^-1, which higher by one grade than the SBA15-filled system.