High rate micron-sized niobium-doped LiMn1.5Ni0.5O4 as ultra high power positive-electrode material for lithium-ion batteries

Nb-doped LiMn1.5Ni0.5O4 materials have been synthesized through a solid-state reaction, and Nb doping achieves some encouraging results. Both crystal domain size and electronic conductivity are influenced by this kind of doping. The lattice parameter of the Nb-doped LiMn1.5Ni0.5O4 samples are slightly larger than that of pure LiMn1.5Ni0.5O4 samples, and Nb doping does not change the basic spinel structure. Even though the material has a particle size of 1-2 mu m, the capacity retention is improved remarkably compared to that of the undoped one when charge-discharged at high rates. The LiNi0.525Mn1.425Nb0.05O4 has a discharge capacity of 102.7 mAh g(-1) at 1 C charge-discharge rate after 100 cycles. Though all samples exhibit similar initial discharge capacities at various high C rates, the Nb-doped LiMn1.5Ni0.5O4 samples display remarkable cyclabilities. Capacity retention of Nb-doped LiMn1.5Ni0.5O4 is excellent without a significant capacity loss at various high C rates. This is ascribed to a smaller crystallite, a higher conductivity, and a higher lithium diffusion coefficient (D-Li) observed in this material. As a result, our microscale Nb-doped LiMn1.5Ni0.5O4 can be used for battery applications that require high power and long life, including HEVs and energy storage devices for renewable energy systems. (C) 2012 Elsevier B.V. All rights reserved.