Study on the electrochemical characteristics of high ion-conductive solid polymer electrolyte based on non-woven matrix

Abstract

Solid polymer electrolytes (SPEs) based on poly(ethylene glycol) (PEO) have attracted considerable attention since 1970s due to their potential application in solid-state rechargeable lithium batteries. However, they show low ion conductivity and high interfacial resistance at room temperature due to high crystallinity of PEO. There have been various efforts to resolve these problems. However, high ionic conductive SPEs by structure modification and introduction of new materials have poor dimensional and mechanical stability. In this study, we designed SPEs consisting of two separate phases. One is the phase to support polymer electrolyte mechanically and the other is the phase to conduct lithium cation. The main advantage of this system is that the ion conductivity of ion conduction phase can be highly enhanced by making polymer matrix as flexible as possible within a range of sustaining dimensional stability. So various cross-linking agents and plasticizers to enhance the ionic conductivity can be introduced. So in this study, we introduced non-woven matrix and synthesized new cross-linking agents based on the polysiloxane and PEGB_acrylate to increase the ionic conductivity, electrochemical stability and transfer number of lithium cation. In addition, we synthesized PEG borate as an anion receptor. And we added PEGDME as a plasticizer and PEG borate to the polymer electrolyte in order to enhance the cationic conductivity and electrochemical stability. Flexible and transparent polymer electrolyte films were obtained by UV-irradiation and casting of polymer solution over porous matrix like PE or PP. The mechanical strength of films increased as the contents of cross-linking agent increase but its ionic conductivity had a tendency to decrease. SPEs showed no thermal hysterisis when the ratio of plasticizer over cross-linking agent was 80/20. The ionic conductivity of SPE based on PEGDMA as a cross-linking agent was $2.7x10^{-4}$ S/cm at room temperature and it ...