결정화도에 따른 Li3V2(PO4)3 음극의 전기화학적 특성
Electrochemical Characteristics of Li3V2(PO4)3Negative Electrode as a Function of Crystallinity
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초록
열처리 온도를 600oC와 800oC로 다르게 하여 비정질 및 결정질구조의 탄소를 포함하는Li3V2(PO4)3/C분말을 각각 합성하였으며, 결정성에 따른 리튬 이차전지용 음극으로의 특성을 비교하였다. 결정질 Li3V2(PO4)3/C은 추가반응에 의하여 리튬이 저장되기 때문에 260 mAh g−1의제한된 용량만을 지니고 있음에 비하여, 비정질 Li3V2(PO4)3/C는 3가의 바나듐이 금속상태에 근접할 정도로 가역적으로 반응되어 460 mAh g−1의 큰가역용량을 발현함을 확인하였다. 이는 비정질구조에서 기인하는 특성으로 유연한 구조로 인한 새로운 리튬의 저장공간이 확보되는 것 때문이라할 수 있다. 또한, 비정질 Li3V2(PO4)3/C는 비정질 구조에 기인하는 선형적인 충방전 곡선을 지니고있어 정확한 충전심도의 예측이 용이할 뿐만 아니라, 결함구조에서 유발된 리튬이온의 향상된 확산성으로 인하여 우수한 속도 특성도 나타내고 있다.
Abstract
Li3V2(PO4)3/carbon composite materials are synthesized from a sucrose-containing precursor. Amorphous Li3V2(PO4)3/C (a-LVP/C) and crystalline Li3V2(PO4)3/C (c-LVP/C) are obtained by calcining at 600oC and 800oC, respectrively, and electrochemical performance as the negative electrode for lithium secondary batteries is compared for two samples. The a-LVP electrode shows much larger reversible capacity than c-LVP, which is ascribed to the spatial Li+channels and flexible structure of amorphous material. In addition, this electrode shows an excellent rate capability, which can be accounted for by the facilitated Li+ diffusion through the defect sites. The sloping voltage profile is another advantageous feature for easy SOC (state of charge) estimation.
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