Study on the electrochemical characteristics of plasticized polymer Electrolyte based on the modified poly(vinyl chloride)

Abstract

The objective of this work is to find out and understand the electrochemical characteristics of plasticized polymer electrolyte based on poly(vinyl chloride)(PVC) and P(MMA-co-LiMA)(PMMA ionomer) blend. The polymer electrolytes were prepared by dipping polymer films extracted DBP into liquid electrolyte. The morphology of polymer films extracted DBP is very important due to determining the uptake of liquid electrolyte. When silica as a inorganic filler and DBP as a plasticizer coexisted, the complex 3D micropore structure was generated in PVC matrix. In order to enhance compatibility with liquid electrolyte (EC/DMC/ $LiClO_4$), the synthesized P(MMA-co-LiMA) ionomer was blended with PVC. The ion conductivity at low temperature (＜ 25℃) has optimum in polymer electrolyte based on PVC/P(MMA-co-LiMA) ionomer with 10mol% ion content. The conductivity was increased because P(MMA-co-LiMA) ionomer prevent EC(ethylene carbonate) in EC/DMC mixture from crystallization and the decrease of conductivity was due to decrease of charge carrier mobility and poor compatibility between ionomer and DMC. The interfacial stability for Li/polymer electrolyte/Li cell is dependent on the physical contact between polymer electrolyte and electrode and formation / growth of passive layer. The initial interfacial resistance was decreased from 141Ω to 73Ω by introduction of P(MMA-co-LiMA) ionomer with 16mol% ion content into PVC and interfacial stability was also enhanced as a function of storage time. The interfacial stability seemed to originate from stable contact between polymer electrolyte and electrode, and the suppression of formation /growth of passive layer. In order to investigate the electrochemical stability window, LSV (linear sweep voltammetry) experiment was carried. The decomposition voltage of polymer electrolytes on the stainless steel as a working electrode was delayed with increase of ion content in PVC/P(MMA-co-LiMA) blend. The electrochemical stability window of p...