Significantly fastened redox kinetics in single crystal layered oxide cathode by gradient doping

Abstract

Nickel-rich layered cathode is a forefront candidate for lithium-ion batteries; however, structural degradation such as intragranular cracking and phase transition in polycrystals focus researchers’ attention towards single-crystals. Nevertheless, the sluggish ionic transport and redox kinetics in single-crystals hinder their rate capability and electrochemical performance in harsh conditions. Herein, a synergy of gradient Nb doping on single-crystal LiNi0.8Co0.1Mn0.1O2 stabilizes the core by strong Nb-O bond and induces Li/Ni antisite migration forming a disordered buffer layer on the surface. The disordered structure maintains the structural integrity by suppressing the phase transition and triggering the Li+ transport. Thus, the modified single-crystal (SNCM@Nb-2) delivers remarkable capacity retention of 92.54% after 100 cycles at 1 C between 2.7 and 4.3 V@ 25 °C (84.26% for SNCM, respectively) and 86.7% at an elevated temperature of 55 °C (SNCM 76.69%). The fast redox kinetics results in remarkably enhanced rate capability and ultra-stable high voltage performance at 4.5 V with SNCM@Nb-2 delivers an initial discharge capacity of 285.2 mAh g−1 with retention of 79.8% (SNCM with 192.1 mAh g−1, 64.1%). The findings of this study provide advancement for the inadequate kinetic properties of single-crystal Ni-rich cathodes under harsh operational conditions.