Electrochemical Performances of Nickel-Rich Single-Crystal LiNi Co Mn O Cathode Material for Lithium-Ion Batteries Synthesized by Tuning Li /Ni Mixing.

Single-crystal nickel-rich materials are promising alternatives to polycrystalline cathodes owing to their excellent structure stability and cycle performance while the cathode material usually appears high cation mixing, which may have a negative effect on its electrochemical performance. The study presents the structural evolution of single-crystal LiNi Co Mn O in the temperature-composition space using temperature-resolved in situ XRD and the cation mixing is tuned to improve electrochemical performances. The as-synthesized single-crystal sample shows high initial discharge specific capacity (195.5 mAh g at 1 C), and excellent capacity retention (80.1 % after 400 cycles at 1 C), taking account of lower structure disorder (Ni occupying Li sites is 1.56 %) and integrated grains with an average of 2-3 μm. In addition, the single-crystal material also displays a superior rate capability of 159.1 mAh g at the rate of 5 C. This excellent performance is attributed to the rapid Li transportation within the crystal structure with fewer Ni cations in Li layer as well as intactly single grains. In sum, the regulation of Li /Ni mixing provides a feasible strategy for boosting single-crystal nickel-rich cathode material.