• Mixed Anion Effect in PEO/Salt Polymer Electrolytes
  • Shin KH, Choi BK
  • PEO/염 고분자 전해질에서의 혼합 음이온 효과
  • 신경희, 최병구
Abstract
The mixed anion effect in [(1-x)NH4C1O4 +xNH4M](PEO)l6 (M=I, CF3SO3) polymer electrolytes has been studied by using impedance spectroscopy and differential scanning calorimetry. In the CIO4-/I- systems, the plasticizing effect, which favors the formation of an amorphous phase, appeared when salt was mixed, and hence the ionic conductivity was enhanced revealing an occurrence of the mixed anion effect. In the CIO4- /CF3SO3 - systems, on the other hand, several physical properties were found to be changed linearly between two single-salt complexes. These results were caused by the facts that the ionic size and lattice energy of ClO4- ions are similar to those of CF3SO3- ions but very different to those of I- ions. At high temperatures above the melting temperature (Tm) of poly(ethylene oxide) (PEO), the conductivities of both systems were varied linearly with x. It indicated that the ionic conductions in polymer/salt systems were not affected appreciably by the ion-ion interactions between dissimilar ions, which are frequently assigned to be the major source of the mixed alkali effect in ion-conducting glasses. In the PEO/mixed-salt systems, the crystallinity was changed due to disordering of ions and consequently an weak mixed anion effect on the ionic conductivity might appear according to the changes in the phase formation properties below Tm.

[(1-x)NH4C1O4+xNH4M](PEO)16 (M=I, CF3SO3) 고분자 전해질에 대한 혼합 음이온 효과를 Impedance spectroscopy법과 differential scanning calorimetry로 분석하였다. ClO4-/I- 계는 염이 흔합될 때 비정질상이 증대되는 plasticizing 효과가 나타나고, 따라서 이온 전도도가 증대되는 혼합 음이온 효과를 나타낸다. 그러나 ClO4-/CF3SO3 -계는 여러 물리적 성질이 두 단일 염계 사이에서 선형적으로 변하는 것으로 나타났다. 이는 ClO4-와 I- 이온의 이온 반경 및 격자에너지는 큰 차이가 나지만 ClO4-와 CF3SO 3- 이온은 비슷한 값을 갖기 때문인 것으로 분석하였다. 그러나 고분자 복합체가 전체적으로 비정질상이 되는 PEO의 융점 (약 60℃) 위에서는 이온 전도도는 두 종류의 시료 모두 선형적인 변화를 나타낸다. 따라서 고분자/염계는 특이한 혼합염 효과를 나타내는 이온전도성 유리의 경우와는 달리 서로 다른 이온과 이온 사이의 상호작용이 전도에 큰 영향을 미치지 않음을 나타낸다. PEO/흔합염 계에서는 이온들의 부정렬로 인하여 결정화도에 변화가 일어나고, 이에 따라 이온전도성의 비선형적 변화가 유발되는 약한 혼합 음이온 효과가 나타난다.

Keywords: polymer electrolyte; mixed anion effect; ionic conductivity

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This Article

  • 1998; 22(2): 269-274

    Published online Mar 25, 1998