우레아 가수분해법에 의한 리튬이차전지용 LiCoO2의 합성과 전기화학적 특성
Synthesis and electrochemical properties of LiCoO2 powders by ureahydrolysis
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초록
우레아 가수분해법을 이용하여 리튬이차전지용 LiCoO2 양극 분말을 합성하였다. Li/Co 몰 비가 다르고 가수분 해에 의해 얻어진 전구체는 다양한 온도에서 열처리되었다. 저온상 LiCoO2(LT-LiCoO2)와 고온상 LiCoO2(HT-LiCoO2)는 500oC에서 2시간 열처리 후 합성되었고, 저온상에서 고온상으로 상전이는 700oC 이상에서 완전히 일어났다. 열처리 온도가 증가함에 따라 LiCoO2의 층상구조가 잘 발달하였다. 충방전 실험결과 Li/Co의 몰비가 1.2이고 800oC에서 열처리한 LiCoO2 의 초기용량이 152 mAh/g으로 높았으며, 40회 충․방전 후에는 9.2 %의 용량감소를 나타내는 상대적으로 안정한 충방전 특 성을 나타내었다.
Abstract
Lithium cobalt oxide (LiCoO2) cathode powders for rechargeable battery have been successfully prepared using urea hydrolysis method. The obtained hydrolysis-derived precursors with different Li/Co molar ratio were calcined at various temperatures. Low temperature phase (LT-LiCoO2) and high temperature phase (HT-LiCoO2) were obtained after calcination at 500oC for 2 hr, and phase transformation from LT-LiCoO2 to HT-LiCoO2 was completely occurred over 700oC. The layered structure of LiCoO2 was well developed with a rise in the calcination temperature. Charge-discharge test show that the lithium cobalt oxide with 1.2 molar ratio prepared at 800oC has an initial discharge capacity as high as 152 mAh/g, and the relatively stable cycling characteristic with 9.2 % of capacity fading was obtained after 40th charge-discharge test.
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