A Quasi‐Multinary Composite Coating on a Nickel‐Rich NCM Cathode Material for All‐Solid‐State Batteries

Abstract Inorganic solid‐state batteries are attracting significant interest as a contender to conventional liquid electrolyte‐based lithium‐ion batteries but still suffer from several limitations. The search for advanced coatings for protecting cathode materials in solid‐state batteries to achieve interfacial stability is a continuing challenge. In the present work, the surface of an industrially relevant Ni‐rich LiNi_xCo_yMn_zO₂ cathode material, NCM‐851005 (85 % Ni), was modified by applying a coating containing Li, Nb and Zn, aiming at a composition Li₆ZnNb₄O₁₄, by means of sol‐gel chemistry. Detailed characterization using scanning transmission electron microscopy combined with energy‐dispersive X‐ray spectroscopy and nano‐beam electron diffraction showed that the surface layer after heating in O₂ at 500 °C contains Li₃NbO₄ nanocrystals and Li₂CO₃, with Zn presumably acting as a dopant. The protective coating on the NCM‐851005 secondary particles significantly increased the cycling performance (reversible capacity, rate capability etc.) and stability of full cells using argyrodite Li₆PS₅Cl as solid electrolyte. Interestingly, the level of improvement is superior to that achieved with conventional LiNbO₃ coatings.