Preparation and Electrochemical Performance of Niobium-Doped Modified LiNiO2 Cathode Materials
The layered nickel-rich oxide LiNiO2,characterized by its high theoretical specific capacity and relatively low cost,is considered one of the next-generation cathode materials for lithium-ion batteries.However,its cycling stability fails to meet requirements when applied in lithium-ion batteries,necessitating modification before practical use.Layered LiNi1-xNbxO2(x=0.005,0.01,0.015)cathode materials doped with Nb were synthesized via solid-state reaction.The effects of niobium doping level(in mole percentage)on the crystal structure,microstructure,and elemental distribution were investigated using techniques such as X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.Additionally,electrochemical tests were conducted to evaluate their electrochemical performance.The results indicate that with an increase in the Nb doping level,the interplanar spacing of the LiNi1-xNbxO2 material lattice gradually enlarges,while the primary particle size decreases.Introducing Nb5+ions into the LiNiO2 material enhances the lithium ion diffusion coefficient of LiNi1-xNbxO2 and stabilizes the crystal structure,suppressing phase transitions during charge-discharge processes,thereby improving electrochemical performance.When the Nb doping level is 1％,LiNi1-x Nb O2 exhibits excellent rate capability,with a discharge specific capacity of 134.1 mAh·g-1 at a high current density of 10 C.Moreover,the cycling stability of LiNi1-xNbxO2 improves with increasing Nb doping level.For instance,when the Nb doping level is 1.5％,the capacity retention of LiNi1-xNbxO2after 150 cycles is 73.3％,which is significantly higher than that of the undoped LiNiO2 sample at 36.2％.This study demonstrates that Nb doping can improve crystal structure and electrochemical properties of the LiNiO2 cathode material,providing a theoretical basis for its application.
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