고에너지밀도 리튬전지를 위한 망간이 첨가된 LiFePO4 양극재료
Manganese Doped LiFePO4 as a Cathode for High Energy Density Lithium Batteries
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초록
다공성 LiMn0.6Fe0.4PO4 (LMFP)를 졸-겔법을 이용하여 합성하였고, 원료물질을 양론비로 혼합한 후 혼합물을 600oC에서 10시간 동안 가열하여 입자 표면 전체에 전도성 탄소물질이 균일하게 형성된 LMFP을 제조하였다. LMFP의 결정구조는 리트펠트법에 의해 조사하였고, 표면구조와 기공특성은 주사전자현미경, 투과전자현미경, BET로 분석하였다. 제조된 LMFP는 표면적이 크고, 입자 표면에는 웹(web) 형태의 다공성 탄소층이 균일하게 형성되어 있는 것을 확인하였다. 상온에서 LMFP를 양극으로 사용하여 0.1 C의 전류밀도에서 초기방전용량은 152 mAh/g, 에너지밀도는 570 Wh/kg로 높았고 사이클 성능도 장기적으로 안정적이었다. 졸-겔법에 의해 제조된 LMFP는 높은 기공도와 균일한 탄소코팅에 의한 시너지효과로 이온확산이 용이하여 우수한 전기화학적 특성을 나타내었다.
Abstract
Porous LiMn0.6Fe0.4PO4 (LMFP) was synthesized by a sol-gel process. Uniform dispersionof the conductive carbon source throughout LMFP with uniform carbon coating wasachieved by heating a stoichiometric mixture of raw materials at 600oC for 10 h. The crystalstructure of LMFP was investigated by Rietveld refinement. The surface structure and poreproperties were investigated by SEM, TEM and BET. The LMFP so obtained has a high specificsurface area with a uniform, porous, and web-like nano-sized carbon layer at the surface. The initial discharge capacity and energy density were 152 mAh/g and 570 Wh/kg, respectively,at 0.1 C current density, and showed stable cycle performance. The combined effect of highporosity and uniform carbon coating leads to fast lithium ion diffusion and enhanced electrochemicalperformance
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