(The) effects of the inorganic particles on the electrochemical characteristics of the composite polymer electrolytes based on poly(ethylene oxide)

Abstract

In order to discover the effects of the inorganic particles on the polymer electrolytes, the composite polymer electrolytes(CPE) were prepared using poly(ethylene oxide)(PEO)(MW 600,000)/$LiCF_3SO_3$/particles. The inorganic particles used are alumina (5㎛ size), alumina(11nm size), and silica (11nm size). We focused on two properties of CPE, that is, the bulk properties and the interfacial properties. Additionally, the effect of particle size, kind, and content are considered as variables. In the all experiments, the effect of particle kind experimented on the properties of CPE is not so much significant. The ionic conductivity is maintained upto 20 wt% particle content and then decrease over 20 wt% in the all systems. The weight fraction of the amorphous region of PEO within CPE shows similar trend with that of ionic conductivity and thus is considered as dominant factor to determine the ion conduction behavior. The glass transition temperatures are not so much changed with particle contents. The heat of fusion of PEO was decreased with particle content in the micrometer-particle system, but was decreased and then increased with particle content in the nm-particle system. In the 11nm particle systems, considerable agglomeration of particles are observed at 25 wt%, which explain the increase of the crystallinity of PEO at 25 wt%. Contrarily, few agglomeration is found at 40 wt% particle in the micrometer-particle system, which illustrates well-dispersed particle as proved in the SEM. The interfacial resistance(Ri) at the interface of Li/CPE is maintained with similar value as a function of the storage time under storage at 75℃ As particle content is increased, Ri is increased except for the CPEs containing small particle content, which have similar Ri values with polymer electrolytes of PEO/$LiCF_3SO_3$. The rate of increasing in Ri with particle content is larger in the nm-particle systems than that in the micrometer-one, due to the difference of surfac...