Recent Development on the Preparation Processes of Co-Free Ni-Rich Layered Oxide Cathode Materials

Lithium-ion batteries (LIBs) are the dominant technology for electrochemical energy storage. However, the surging demand for LIBs has intensified concerns over cobalt (Co) scarcity, ethical sourcing, and cost volatility. To overcome these challenges, Co-free Ni-rich layered cathode materials have attracted growing attention. This review provides a comprehensive overview of recent developments in their preparation processes and performance optimization. The dual role of Co in conventional cathodes is first clarified: Co mitigates Li/Ni cation disorder but also induces lattice distortion, oxygen release, and microcrack formation. Eliminating Co, however, aggravates Rich-Ni-related issues such as structural phase transitions and severe Li/Ni cation mixing, which compromise structural and electrochemical stability. Recent progress in addressing these challenges is summarized, focusing on composition regulation, surface engineering, and structural design strategies. Preparation methodologies are discussed in detail, including wet chemical approaches that enable precise control over morphology and composition control, and solid-state techniques that offer scalability for industrial application. Optimized Co-free Ni-rich layered materials exhibit enhanced capacity retention, structural integrity, and thermal stability. Finally, the review highlights future research directions toward simplified processes, synergistic multi-technology coupling, and data-driven design to promote the commercialization of Co-free Ni-rich layered oxide cathodes for electric vehicles and large-scale energy storage systems.