Urban air mobility (UAM) demands a Ni-rich cathode to balance the energy density, power, and stability; however, the synthesis of the cathode material struggles to optimize lithiation and the microstructure owing to the conflicting thermal requirements. Herein, we propose a strategic two-step calcination protocol that functionally decouples lithiation from structural evolution. Via a sequential process of intermediate-temperature lithiation, followed by cooling and high-temperature calcination with Nb doping to control the structural evolution, we fabricated a cathode material comprising fine, radially aligned primary particles. This strategy retarded complete phase transformation, establishing a unique multiphase structure, wherein rocksalt nanodomains coexisted within a layered matrix. This intentionally preserved intermediate phase facilitated a reversible spinel-like transformation upon charging, providing three-dimensional Li diffusion pathways. The optimized cathode demonstrated long-term power stability under harsh UAM flight profiles. This study presents a systematic approach for tailoring the physicochemical properties by precisely controlling the reaction pathway.
Seo et al. (Sun,) studied this question.