Enabling high-rate discharge capability and stable cycling for Ni-rich layered cathodes via multi-functional modification strategy

Abstract

Nickel-rich layered cathodes have received extensive attention because of their relatively high energy density. However, the poor rate performance and inadequate cycling stability severely hinder its large-scale applications. Herein, a multi-functional modification strategy combining dual-site Mg/Nb co-doping with in-situ derived LiNbO3 coating layer is proposed. Mg2+ doped as pillar ions at Li sites can reduce the disorder of Li+/Ni2+, while Nb5+ doped at transition metal sites can improve structural stability due to its stronger Nb-O binding energy. Moreover, LiNbO3 ionically conductive nano-scale coating layer can effectively improve interface properties of the material. Benefitting from the synergistic effect of multi-functional modification strategy, the LiNi0.83Co0.12Mn0.05O2 cathode material co-modified with 2 mol% Mg and 1.4 mol% Nb exhibits extraordinarily enhanced electrochemical performance, which can display an excellent capacity retention of 84.1% after 200 cycles at 1 C and a high specific capacity of 132.9 mAh g−1 at the ultra-high rate of 30 C. Furthermore, the multi-functional modification strategy can also effectively alleviate grain-level intergranular cracks and structural degradation during long-term cycling. These results demonstrate that simultaneously using two types of doping cations together with in situ derived coating layer is an efficient and feasible modification strategy for Ni-rich layered cathodes.