An effective doping strategy to improve the cyclic stability and rate capability of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) is considered as a promising cathode material for high-capacity power batteries. Nevertheless, the rapid capacity fading during the charge/discharge process and inferior rate capability hinder their successful realization. Elemental doping plays a critical role in stabilizing the structure, inhibiting Li/Ni disorder, reducing polarization, improving electronic conductivity and enhancing Li-diffusion coefficient from the viewpoints of dopant radius, valence state and bonding energy. Herein, niobium (Nb), with optimal radius (0.64 angstrom), high valence state (Nb5+) and strong Nb-O bonding energy (753 kJ/mol), is introduced into NCM811 structure to improve the electrochemical performance and to evaluate this strategy. Then, X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical characterization are carried out to comprehensively evaluate the influence of Nb-doping on structure and electrochemical performance of NCM811 cathodes. Consequently, NCM811 cathode, with 1 at.% Nb, exhibited the highest capacity retention of 94.55% after 100 charge/discharge cycles (1 C) and rendered a superior charge storage capacity of 151.46 mAh/g at a high current rate of 5 C, demonstrating the effectiveness of the proposed strategy.