Improved Cycling Performance of High‐Nickel NMC by Dry Powder Coating with Nanostructured Fumed Al2O3, TiO2, and ZrO2: A Comparison

Abstract Surface coating is an effective concept to protect layered cathode active materials (CAMs) in lithium ion batteries from detrimental side reactions. Dry powder coating is a fast and cost‐effective coating process, and here we transfer this coating approach from Al 2 O 3 to nanostructured fumed TiO 2 and ZrO 2 coatings on the same NMC (Li[Ni,Mn,Co]O 2 ) material. Using similar processing, this allows a direct comparison of the characteristics of the achieved coating layers and their influence on the cycling performance of high‐nickel NMC. The nanostructured small oxide aggregates result in a quite homogeneous coating layer with a certain porosity around each CAM particle. Significantly enhanced long‐term cycling stability is observed, with a trend of increasing stability in the series ZrO 2 <TiO 2 <Al 2 O 3 . Fumed Al 2 O 3 and TiO 2 coating layers prevent cathode particle cracking and disintegration successfully, while fumed ZrO 2 only shows a moderate protection effect. Each coating material enhances the rate performance compared to uncoated NMC in the row TiO 2 <ZrO 2 <Al 2 O 3 . XPS measurements of cycled electrodes indicate a partial incorporation of lithium ions in the crystalline TiO 2 and ZrO 2 coating layers, contributing to the enhanced lithium‐ion transport across the CAM surface layer, as observed before for fumed γ ‐Al 2 O 3 coatings. Summarizing the results, the best overall cycling performance was achieved by coating high‐nickel NMC with fumed Al 2 O 3 , providing the highest rate capability and the best long‐term cycling stability.