e - beam 증발법으로 제조된 비정질 WO3 박막과 전해질 계면으로 삽입되는 리튬의 층간 반응에 관한 전기화학적 특성 = Electrochemical Characteristic on Lithium Intercalation into the Interface between Organic Electrolyte and Amorphous WO3 Thin Film Prepared by e - beam Evaporation Method

국문 초록 (Abstract)

본 연구에서는 1M LiClO₄/PC 유기 용액 중에 존재하는 리튬 이온의 층간 반응에 의하여 전기 발색 현상을 나타내는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서의 전기화학적 특성들을 연구하기 위하여 음극 Tafel 분극법, 순환 전류-전위법 및 전기량 적정법 등의 전기화학 측정법과 X선 회절 분석법을 이용한 박막의 결정 상태 조사 등이 수행되었다. 특히 다중 순환 전류-전위 곡선으로부터 리튬 이온의 층간 반응은 발색 반응에 대한 인가 과전압이 약 1.0V 이내에서는 안정된 소 · 발색의 가역적 현상을 나타내었으나, 발색 반응에 대한 인가 과전압이 1.5V일 때는 발색 시 삽입된 박막 내부의 리튬이 소색 시 완전히 빠져 나오지 못하여, 박막 내부에 리튬이 축적되는 현상을 나타내었으며, 적은 순환 횟수임에도 불구하고 소 ·발색의 전류 밀도가 감소되는 것이 조사되어 발색에 필요한 인가 과전압의 한계가 존재함을 알 수 있었다.

다국어 초록 (Multilingual Abstract)

This work was performed to study the characteristics of electrochanical intercalation reactions occurring at the interface between the organic electrolyte and tungsten trioxide thin film (thickness of 4000Å) prepared by e-beam evaporation method as cathodically coloring oxide with regard to the electrochromism by the intercalating reactions of the lithium cation in the 1M LiClO₄/PC organic solution. The characteristics of electrochemical intercalation reactions were investigated by various DC electrochemical methods such as cathodic Tafel polarization test, multiple and the single sweep cyclic voltammetry and the coulometry titrations method. The surfaces of thin films were observed with the patterns of X ray diffraction after the coloring and bleaching reactions. In comparison with the previous results that WO₃ thin film intensely detached from the surface of electrode when the hydrogen cation was intercalated into WO₃ thin film in the O.1N H₂SO₄ aqueous solution, the intercalation reaction of lithium cation into WO₃ thin film in the 1M LiClO₄/PC organic solution was shown that the stable bleaching and coloration was appeared within 1.0V of the applied overpotential. When the overpotential of electrochromic reaction for lithium cation in the 1M LiClO₄/PC organic solution had been applied up to 1.5V, the accumulation phenomenon of lithium in amorphous WO₃ thin film layer occurred because the inserted lithium into amorphous WO₃ thin layer for coloring process was not fully removed from the thin layer to the electrolyte during bleaching process. It was found that there is a limitation of applied overpotential for coloring process by the reduction of the current densities of bleaching and coloration after few number of coloring and bleaching cycles.