CAJ | 학술논문

采用高温固相反应,以NH4VO3为钒源合成了化学计量式为(1-x)LiFe0.5Mn0.5PO4-xLi3V2(PO4)3/C (x=0,0.1,0.2,0.25,1)的钒改性磷酸锰铁锂正极材料.电化学测试表明钒改性能明显提高磷酸锰铁锂材料的充放电性能,其中x=0.2时得到的0.8LiFe0.5Mn0.5PO4-0.2Li3V2(PO4)3/C(标记为LFMP-LVP/C)材料电化学性能最好,其0.1C倍率时的放电比容量为141 mAh·g-1.X射线衍射(XRD)分析指出LFMP-LVP/C材料的微观结构为橄榄石型LiFe0.5Mn0.5PO4/C和NASICON型Li3V2(PO4)3组成的双相结构.能量色射X射线谱(EDS)分析结果指出,Fe、Mn、V、P元素在所合成材料中的分布非常均匀,表明所制备材料成分的均一性.Li3V2(PO4)3改性使材料的电导率明显提高.LiFe0.5Mn0.5PO4的电导率为1.9×10-8 S· cm-1,而LFMP-LVP材料电导率提高到2.7×10-7 S·cm-1.与纯Li3V2(PO4)3的电导率(2.3×10-7 S·cm-1)相近.电化学测试表明钒改性使LFMP-LVP/C材料充放电过程电极极化明显减小,从而电化学性能得到显著提高.本文工作表明Li3V2(PO4)3改性可成为提高橄榄石型磷酸盐锂离子电池正极材料电化学性能的一种有效方法.
채용고온고상반응,이NH4VO3위범원합성료화학계량식위(1-x)LiFe0.5Mn0.5PO4-xLi3V2(PO4)3/C (x=0,0.1,0.2,0.25,1)적범개성린산맹철리정겁재료.전화학측시표명범개성능명현제고린산맹철리재료적충방전성능,기중x=0.2시득도적0.8LiFe0.5Mn0.5PO4-0.2Li3V2(PO4)3/C(표기위LFMP-LVP/C)재료전화학성능최호,기0.1C배솔시적방전비용량위141 mAh·g-1.X사선연사(XRD)분석지출LFMP-LVP/C재료적미관결구위감람석형LiFe0.5Mn0.5PO4/C화NASICON형Li3V2(PO4)3조성적쌍상결구.능량색사X사선보(EDS)분석결과지출,Fe、Mn、V、P원소재소합성재료중적분포비상균균,표명소제비재료성분적균일성.Li3V2(PO4)3개성사재료적전도솔명현제고.LiFe0.5Mn0.5PO4적전도솔위1.9×10-8 S· cm-1,이LFMP-LVP재료전도솔제고도2.7×10-7 S·cm-1.여순Li3V2(PO4)3적전도솔(2.3×10-7 S·cm-1)상근.전화학측시표명범개성사LFMP-LVP/C재료충방전과정전겁겁화명현감소,종이전화학성능득도현저제고.본문공작표명Li3V2(PO4)3개성가성위제고감람석형린산염리리자전지정겁재료전화학성능적일충유효방법.
Vanadium modified LiFe0.5Mn0.5PO4/C cathode materials with a nominal composition of (1-x)LiFe0.5Mn0.5PO4-xLi3V2(PO4)3/C (x=0,0.1,0.2,0.25,1)were prepared by a solid-state reaction using NH4VO3 as the vanadium source.The electrochemical performance of the LiFe0.5Mn0.5PO4-based compounds improved upon vanadium modification.The 0.8LiFe0.5Mn0.5PO4-0.2Li3V2(PO4)3/C (LFMP-LVP/C) sample exhibited the highest discharge capacity of 141 mAh· g-1 at 0.1C rate.X-ray diffraction analyses revealed a dual phase of the LFMP-LVP/C composite with the coexistence of an olivine-type LiFe0.5Mn0.5PO4/C phase and a NASICON-type Li3V2(PO4)3 phase.Energy dispersive X-ray spectroscopy (EDS) analysis indicates a uniform distribution of Fe,Mn,V,and P in the composite.The electronic conductivity of LFMP-LVP was found to be 2.7× 10-7 S· cm-1,which is much higher than the value (1.9× 10-8 S · cm-1) of LiFe0.5Mn0.5PO4 and similar to the value (2.3 × 10-7 S · cm-1) of pure Li3V2(PO4)3.Vanadium modification remarkably reduced the electrode polarization of the LFMP-LVP/C cathode during the charge-discharge procedure.This suggests that vanadium modification is an effective method to improve the electrochemical performance of olivine-type cathode materials.