Multi‐Element Surface Coating of Layered Ni‐Rich Oxide Cathode Materials and Their Long‐Term Cycling Performance in Lithium‐Ion Batteries

The energy density of layered oxide cathode materials increases with their Ni content, while the stability decreases and degradation becomes more severe. A common strategy to mitigate or prevent degradation is the application of protective coatings on the particle surfaces. In this article, a room-tem-perature, liquid-phase reaction of trimethylaluminum (TMA) and tetraethyl orthosilicate (TEOS) with adsorbed moisture on either LiNi0.85Co0.10Mn0.05O2or LiNiO2, yielding a hybrid coating that shows synergetic benefits compared to coatings from TMA and TEOS individually, is reported. The surface layer is investigated in long-term pouch full-cell studies as well as by electron micros-copy, X-ray photoelectron spectroscopy, and differential electrochemical mass spectrometry, demonstrating that it prevents degradation primarily by a fluorine-scavenging effect, and by reducing the extent of rock salt-type phase formation.