Promotion of the Nucleation of Ultrafine Ni-Rich Layered Oxide Primary Particles by an Atomic Layer-Deposited Thin Film for Enhanced Mechanical Stability

Understanding the atomistic mechanisms of non-equilibriumprocessesduring solid-state synthesis, such as nucleation and grain structureformation of a layered oxide phase, is a critical challenge for developingpromising cathode materials such as Ni-rich layered oxide for Li-ionbatteries. In this study, we found that the aluminum oxide coatinglayer transforms into lithium aluminate as an intermediate, whichhas favorable low interfacial energies with the layered oxide to promotethe nucleation of the latter. The fast and uniform nucleation andformation of the layered oxide phase at relatively low temperatureswere evidenced using solid-state nuclear magnetic resonance and insitu synchrotron X-ray diffraction. The resulting Ni-rich layeredoxide cathode has fine primary particles, as visualized by three-dimensionaltomography constructed using a focused-ion beam and scanning electronmicroscopy. The densely packed fine primary particles enable the excellentmechanical strength of the secondary particles, as demonstrated byin situ compression tests. This strategy provides a new approach fordeveloping next-generation, high-strength battery materials.

Automated summary

This research reveals the formation mechanism of Ni-rich layered oxide through the use of various characterization techniques. It has been found that the aluminum oxide coating layer transforms into lithium aluminate and promotes the nucleation of the layered oxide. High-resolution imaging techniques have observed the formation of layered oxide with fine primary particles. This study provides a new approach for developing high-strength battery materials.