Interfacial Regulation of Ni-Rich Cathode Materials with an Ion-Conductive and Pillaring Layer by Infusing Gradient Boron for Improved Cycle Stability.

Abstract

Ni-rich cathodes LiNixCoyAl1-x-yO2 (0.8 < x < 1) with high energy density, environmental benignity, and low cost are regarded as the most promising candidate materials for next-generation lithium batteries. Unfortunately, capacity fading derived from unstable surface properties and intrinsic structural instability under extreme conditions limits large-scale commercial utilization. Herein, an interface-regulated Ni-rich cathode material LiNi0.87Co0.10Al0.03O2 with a layer (R3̅m) core, a NiO salt-like (Fm3̅m) phase, and an ultrathin amorphous ion-conductive LiBO2 (LBO) layer is constructed by gradient boron incorporation and lithium-reactive coating during calcination. The ultrathin LBO layer not only exhausts residual lithium species but also acts as a layer for Li+ transport and insulation of detrimental reaction. The NiO salt-like phase in the subsurface could enhance the structural stability of the layer core for the pillar effects. With the positive role provided by the functional hybrid surface layer and boron doping, the modified cathode exhibits enhanced Li+ conductivity, structural stability, reversibility of the H2-H3 phase transition, suppressed side reactions, ameliorated transition-metal dissolution, and excellent electrochemical performance. Especially, a 1% wt boron-modified cathode delivers a discharge capacity of 211.99 mA h g-1 in the potential range of 3.0-4.3 V at 0.2 C and excellent cycle life with a capacity retention of 89.43% after 200 cycles at 1 C.