Investigation of structure and cycling performance of Nb5+ doped high-nickel ternary cathode materials

Nickel-rich layered LiNi0.8Co0.1Mn0.1O2 is a promising cathode material due to its high specific capacity. However, commercial application of this material is impeded by its rapid capacity degradation associated with structural instability. In this work, 0.5-2 mol% Nb5+ doped LiNi0.8Co0.1Mn0.1O2 cathode material is prepared by heat treatment of a mixture of stoichiometric amounts of nano-sized Nb2O5 powders, co-precipitated NixMn1-x(OH)(2) precursors, and LiOH center dot H2O. The results show that Nb5+ doping significantly improves the cycling properties of LiNi0.8Co0.1Mn0.1O2 cathode material and that the optimal Nb5+ content in the structure is 1 mol%. Under a voltage range of 2.75-4.3 V, 1 mol% Nb5+ doped LiNi0.8Co0.1Mn0.1O2 cathode material shows an initial discharge capacity of 180.2 mAh/g at 0.1C, with a capacity retention of 96.9% for subsequent 300 cycles at 1C at room temperature. In contrast, bare LiNi0.8Co0.1Mn0.1O2 shows a capacity retention of only similar to 79.8% under the same conditions, with an initial specific discharge capacity of 184.9 mAh/g. The improvement in cycling performance is attributed to stabilization of the layered structure by Nb5+, mitigated migration of Ni2+ to the Li layer, improved lithium diffusion kinetics and reduced lattice expansion/shrinkage during cycling. Stabilization of the layered structure by Nb5+ doping is further reflected by the observation of fewer cracks in cathode electrodes after prolonged cycling.

Automated summary

Doping with 1 mol% Nb5+ significantly improves the cycling performance of LiNi0.8Co0.1Mn0.1O2 cathode material, showing a 96.9% capacity retention after 300 cycles at 1C. The enhancement is attributed to stabilization of the layered structure, mitigation of Ni2+ migration, improved lithium diffusion kinetics, and reduced lattice expansion/shrinkage during cycling.