Enhancing the cycling stability of full-concentration-gradient Ni-rich layered cathodes via in-situ Zr doping

Abstract

Full-concentration-gradient (FCG) Ni-rich layered cathodes suffers from severe structural deterioration caused by the high-Ni content in the cores of the particles. Herein, an in-situ doping strategy is proposed to remove the structural deterioration in the cores of the particles, and a Zr-doped FCG LiNi0.80-xZrxCo0.05Mn0.15O2 (FNCMZ) cathode is successfully prepared. In-situ doping achieved a gradient distribution of Zr inside the particles, and induced the Li+/Ni2+mixing into an order structure. The order structure and Zr–O strong bonds reduced the degree of lattice contraction in the cores of the particles during the H2–H3 phase transition. Density functional theory calculations further proved that Zr doping and the order structure improved the electronic conductivity and structural stability of the cathodes. The improvement of structural stability and ion/electron migration environment enhanced the cycling stability and thermal stability of the FCG cathodes. Therefore, The FNCMZ0.2 cathode (doped with 0.2 mol% Zr) exhibited a high initial discharge specific capacity (181.7 mAh/g) with excellent capacity retention (91.9 %) after 200 cycles (1 C, 2.7–4.3 V). Even at a high cutoff voltage (4.5 V) and high temperature (50 °C), the capacity retention remained high at 83.7 % and 85.2 %, respectively, after 200 cycles. Overall, in-situ Zr doping effectively resolves structural deterioration in the cores of the particles and improves the electrochemical properties of FCG Ni-rich layered cathodes.