Effect of hydrothermally doped-Nb on structure and cycling stability of Li(Ni0.96Co0.04)O2

Abstract

Nb5+ ions are hydrothermally incorporated into the hydroxide precursor of Li(Ni0.96Co0.04)O2 before lithiation. The hydrothermal doping of Nb results in particle size refinement and produces short- and long-ranged cation ordering that has not been observed in a Ni-rich layered cathode. The cation-ordered structure stabilizes the delithiated structure while the particle size refinement helps to absorb the strain energy generated during the H2 → H3 phase transformation near the charge end. 0.5 mol%-doped Li[Ni0.956Co0.039Nb0.005]O2 retains 96 % of the initial capacity after 100 cycles, which is remarkable despite its ultra-high Ni content. The cathode also delivers a discharge capacity of 227 mA h g−1. By contrast, the Li[Ni0.95Co0.04Al0.01]O2 maintains only 82 % of the initial capacity after 100 cycles. This finding highlights the importance of exploring different doping methods and the need to control and moderate the antisite defects which stabilize the delithiated structure to improve the cycling stability of ultra-high Ni-rich layered cathodes to a commercially viable level.