Korean Chemical Engineering Research, Vol.49, No.6, 758-763, December, 2011
TiO2 필러를 포함하는 PEO/PMMA 고분자 복합체 전해질의 이온전도도 및 결정화도
Study on Ionic Conductivity and Crystallinity of PEO/PMMA Polymer Composite Electrolytes containing TiO2 Filler
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초록
본 연구에서는 poly(ethylene oxide) (PEO)와 poly(methyl methacrylate) (PMMA) 블렌드를 고분자 매트릭스(matrix)로 사용하고, 가소제로propylene carbonate (PC), 리튬염인 LiClO4, 그리고 서로 다른 함량의 세라믹 필러인 TiO2를 이용하여 용액 캐스팅(solution casting)법에 의해 고분자 복합체 전해질 필름을 제조하였다. 고분자 전해질의 결정화도와 이온전도도는 각각, X선 회절분석기(XRD)와 AC임피던스법을 통해 분석하였고, 표면 형태학(morphology)을 조사하기 위해 주사전자현미경(SEM)으로 고찰하였다. 그 결과, TiO2의 함량을 증가시킴으로써 PEO의 결정화 영역이 감소하였고, 이온전도도는 증가하였다. 특히 TiO2의 함량이 15 wt%일 때 가장 높은 이온전도도가 관찰된 반면, 15 wt% 이상을 첨가한 경우, 이온전도도가 감소된 경향을 관찰할 수 있었다. 이는 표면 형태학를 통해 고분자와 필러간의 비혼합성 혹은 필러응집에 의해 불균일적인 형태학이 나타남으로써 이온전도도가 감소하는 현상을 확인할 수 있었다.
In this work, polymer composite electrolytes were prepared by a blend of pol (methyl methacrylate)(PMMA) and poly(ethylene oxide) (PEO) as a polymer matrix, propylene carbonate as a plasticizer, LiClO4 as a salt, and by containing a different content of TiO2, by using the solution casting method. The crystallinity and ionic conductivity of the polymer electrolytes was evaluated using X-ray diffraction(XRD) and AC impedance method, respectively. The morphology of composite electrolyte film was analyzed by SEM method. From the experimental results, by increasing the TiO2 content, crystallinity of PEO was reduced, and ionic conductivity was increased. In particular, the ionic conductivity was dependent on the content of TiO2 and showed the highest value 15 wt%. However, when TiO2 content exceeds 15 wt%, the ionic conductivity was decreased. According to the surface morphology, the ionic conductivity was decreased because the polymer composite electrolytes showed a heterogenous morphology of fillers due to immiscibility or aggregation of the filler within the polymer matrix.
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