Impact of particle size on the kinetics and structure stability of single-crystal Li-rich cathode materials

Abstract

High-energy-density single-crystal (SC) Li-rich materials with high stability have great potential to be next-generation high-performance cathodes because of their stable anionic redox and excellent mechanical strength. However, the synthesis of SC Li-rich cathodes with controllable size, and their impact on electrochemical performances have rarely been investigated yet. In the research reported herein, the co-free, Li-rich SC Li_1.2Ni_0.2Mn_0.6O₂ cathodes with regulated particle sizes from nano-to micro-meter levels were synthesized, and the electrode with a particle size of D₅₀ ≈ 413 nm displayed an optimized Li⁺ diffusion coefficient of 10^−8.88 cm² s⁻¹. The favorable kinetic process greatly promotes the rate performance of Li-rich cathodes, yielding a high reversible capacity of 216 mA h g⁻¹ at 1C (250 mA h g⁻¹). Moreover, the SC Li-rich cathode with the optimal particle size exhibited a high capacity retention of 98.6% and a high energy density of 691 W h kg⁻¹ after 250 cycles in the full cell. These findings not only give insight into the impact of particle size on the structural and electrochemical stability of SC Li-rich electrodes, but also provide effective guidance for the design of high-performance cathode materials.