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

Abstract

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·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 ~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.