Enhanced Li-ion Intercalation Kinetics and Lattice Oxygen Stability in Single-Crystalline Ni-rich Co-poor Layered Cathodes

Single-crystalline nickel-rich cobalt-poor layered oxides are promising cathode materials for lithium-ion batteries due to their high safety and competitive cost. However, the severe cation disorder and lithium/oxygen (Li/O) loss during the high-temperature calcination process result in slow Li-ion diffusion and inferior O stability. Herein, a LiNi0.85Co0.05Mn0.10O2 (NCM85) single-crystalline cathode was prepared at relatively lower lithiation temperatures by barium/aluminum (Ba/Al) co-doping. The increase in the c-axis caused by Ba doping with a larger ion radius and the reduction in Li/Ni disorder can enhance the Li-ion diffusion kinetics, while the strong Ba-O and Al-O bonds considerably boost the lattice O stability to alleviate O escape during the charging process. The optimized cathode exhibits a high reversible capacity of 206.5 mA h g-1 at 0.1C and 115.6 mA h g-1 at 5C. Impressively, 87.5% of initial capacity is still maintained after 500 cycles at 1C in a pouch-type full cell. This finding provides a viable and flexible method to resolve the kinetics and stability issues of other layered oxide cathodes. Ba/Al co-doping effectively lower the calcination temperature, greatly reduces Li/Ni mixing and expands the c-axis parameter, and stabilizes the lattice oxygen, resulting in enhanced Li-diffusion kinetics and excellent cycle life.