Study on the electrochemical characteristics of the polymer electrolytes based on porous P(VdF-co-HFP)/PMMA Ionomer blend

Abstract

The goal of the research in this thesis is to extend the understanding of the physics involved in the electrochemical characteristics of the polymer electrolytes based on porous matrix polymer and to develop the novel polymer electrolytes applicable to plastic lithium ion batteries (PLIB). A new preparation method for a polymer electrolyte system based on a copolymer of vinylidene fluoride and hexafluoropropylene, P(VdF-co-HFP) had been proposed for PLIB. The plasticization of P(VdF-co-HFP) copolymers, subsequent removal of the plasticizer from the polymer matrix and immersion in a liquid electrolyte solution is of critical importance in this process. However, the studies on the plasticized polymer electrolyte based on the porous P(VdF-co-HFP) matrix have been quite rare and thus the effects of the plasticizer and inorganic filler on the host polymer and ionic conductive behavior has not been clarified yet. In addition, since the P(VdF-co-HFP) polymer does not show the good compatibility with high polar organic solvent such as ethylene carbonate (EC) within the liquid electrolyte, thus, the uptake amount of liquid electrolyte is limited and the absorbed liquid electrolytes leak from matrix polymer during the storage or charge/discharge cycles. Therefore, it would be very important to enhance the uptake amount of liquid electrolyte and to sustain the absorbed liquid electrolyte within the matrix polymer. These consideration motivated us to modify the P(VdF-co-HFP) matrix by introducing the ion-containing polymer which can contribute to enhancing the interaction between the matrix polymer and liquid electrolyte. In this study, we synthesized the series of poly(methyl methacrylate-co-lithium methacrylate) ionomer, P(MMA-co-Li MA) with variation of the ion content and prepared the plasticized polymer electrolytes composed of the blend of P(VdF-co-HFP)/P(MMA-co-Li MA), the mixed solvent of EC and dimethyl carbonate (DMC), and $LiPF_6$ salt. In Chapter III & IV,...