Co 치환량에 따른 LiNi(1-x)Co(x)O2 (x=0.0~1.0)의 결정구조 및 전기화학 특성
Crystal Structure and Electrochemical Performance of LiNi(1-x)Co(x)O2 (x=0.0~1.0) According to Co Substitution

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홍진규; 오승모
Issue Date
한국전기화학회 = The Korean Electrochemical Society (KECS)
J. Korean Electrochem. Soc., 6, 1 (2003)
Li secondary batteriesRietveld refinementSolid solutionsElectrochemical voltage spectroscopy
LiNi_1-xCo_xO_2(x=0.0, 0.3, 05, 0.7, 1.0) 을 구연산법을 이용하여 합성하고, Co 치환량에 따른 결정구조와 리튬 이차전지 양극특성을 조사하였다 X-선 회절분석 결과로부터 Co치환량에 무관하게 모든 조성에서 단일상의 고용체를 형성함을 알 수 있었다. 또한 Rietveld 구조정산을 통하여 고용체의 결정구조가 Co 치환량에 따라 크게 변화함을 확인하였다. 즉, Co치환량이 적은 경우는 (x=0~0.5)는 격자상수의 비가 작은(c/a<4.98) 입방구조에 가까웠으며, Co치환량이 큰 경우(x >0.7)는 격자상수의 비가 큰(c/a ≥4.98) 층상구조를 보였다. 이와 같은 차이는 electrochemical voltage spectroscopy를 통하여 확인할 수 있었는데, 고용체를 형성하고 있는 Co성분은 Co치환량이 적을 경우는 3.7 V(vs. Li/Li+) , 그리고 치환량이 클 경우는 3.92 V(vs. Li/Li+) 에서 충전되는 현상을 보였다.
LiNi_1-xCo_xO_2(x=0.0, 0.3, 05, 0.7, 1.0) powders were synthesized by citrate method, and their crystal structures and electrochemical performance as the cathode material in Li secondary batteries were analyzed. X-ray diffraction analysis revealed that all the samples carry a single phase regardless of the Co substitution. The results of Rietveld refinement suggested that the crystal structure of solid solutions varies according to the Co substitution. When the Co substitution is low (x=0.3~0.5), the solid solutions carry a cubic-like structure with a relatively small value in the ratio of lattice parameters (c/a). The solid solutions made with a higher Co substitution (x=0.7), however, exhibit a layered structure with a higher c/a ratio. This difference was also observed in the electrochemical voltage spectroscopy (EVS) profiles, whereby the Co component in scarcely substituted materials shows a charging reaction at 3.7 V(vs. Li/Li+), but in the heavily substituted ones at 3.92V.
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Journal Papers (저널논문_화학생물공학부)
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