LiCr_(0.05)Ni_(0.15)Mn_(1.8)O_4的合成和电化学性能

Synthesis and Electrochemical Characterization of LiCr_(0.05)Ni_(0.15)Mn_(1.8)O_4

通过溶胶-凝胶法合成尖晶石型锂离子电池正极材料LiCr0.05Ni0.15Mn1.8O4,并用XRD,SEM,FTIR,TGA表征其形貌和结构,采用电化学测试考察材料的电化学性能。结果表明,所合成的LiCr0.05Ni0.15Mn1.8O4具有与母体LiMn2O4同样完整的尖晶石结构,Cr3+(d3)和Ni2+(d8)部分取代了尖晶石结构八面体骨架中的Mn3+(d3)。LiCrxNiyMn2-x-yO4(x=0.05,y=0.15)电极的良好容量归功于尖晶石结构中Cr和Ni对Mn位的掺杂而使主体结构得到了稳定。其首次充放电容量为120/100(mA.h.g-1),循环41次后容量保持率为98%。与单一LiMn2O4相比,在800℃合成的目标产物结构稳定性和循环可逆性好,循环伏安和充放电曲线表明该物种在充放电过程中Li+两步脱嵌过程有转变为一步的趋向。

The lithium transition-metals oxides LiCr0.05Ni0.15Mn1.8O4 as lithium ions cell anodes materials is synthesized with Sol-Gel method, the morphology and the microstructure of the products are described by X-ray, SEM and FTIR, and the electrochemical performances are investigated by electrochemical tests. The results show that the spinel structure of synthesized LiCr0.05Ni0.15Mn1.8O4 is completely same as the LiMn2O4, the Mn^3＋ （d^4） ions are partially replaced by Cr^3 ＋ （d^3） and Ni^2 ＋ （d^8 ） ions in the octahedral framework of the spinel structure. The good capacity retention of LiCr0.05Ni0.15Mn1.8O4 electrode is attributed to the stabilization of the spinel structure by Cr and Ni doping for Mn ion sites. The chemical substitution of Cr^3＋ and Ni^2＋ for Mn^3＋ in LiMn2O4 improves the efficiency in maintaining electrochemical capacity a large number. The charge-discharge capacity in the doped Li/LiCr0.05Ni0.15Mn1.8O4 cell is about 120/100 （mA· h· g^- 1 ）. For the cell after 41 cycles, the capacity still have 98 mA·h·g^-1. Compare with LiMn2O4, LiCr0.05Ni0.15Mn1.8O4 have more stability of structure and cycle reversibility, the cyclic voltammetry and charge-discharge cycling curve of LiCr0.05Ni0.15Mn1.8O4 shown that the Li^＋ insertion and extraction process have the tend from two steps to one step, this is larruping compare with else doped compounds.