Atomic Layer Deposition Derived Zirconia Coatings on Ni‐Rich Cathodes in Solid‐State Batteries: Correlation Between Surface Constitution and Cycling Performance

Protective coatings are required to address interfacial incompatibility issues in composite cathodes made from Ni-rich layered oxides and lithium thiophosphate solid electrolytes (SEs), one of the most promising combinations of materials for high energy and power density solid-state battery (SSB) applications. Herein, the preparation of conformal ZrO2 nanocoatings on a LiNi0.85Co0.10Mn0.05O2 (NCM85) cathode-active material (CAM) by atomic layer deposition (ALD) is reported and the structural and chemical evolution of the modified NCM85 upon heat treatment—a post-processing step often required to boost battery performance—is investigated. The coating properties are shown to have a strong effect on the cyclability of high-loading SSB cells. After mild annealing (≈400 °C), the CAM delivers high specific capacities (≈200 mAh g−1 at C/10) and exhibits improved rate capability (≈125 mAh g−1 at 1C) and stability (≈78% capacity retention after 200 cycles at 0.5C), enabled by effective surface passivation. In contrast, annealing temperatures above 500 °C lead to the formation of an insulating interphase that negatively affects the cycling performance. The results of this study demonstrate that the preparation conditions for a given SE/CAM combination need to be tailored carefully and ALD is a powerful surface-engineering technique toward this goal

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

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$_x$Co$_y$Mn$_z$O$_2$ cathode material, NCM-851005 (85 % Ni), was modified by applying a coating containing Li, Nb and Zn, aiming at a composition Li$_6$ZnNb$_4$O$_14$, 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 O$_2$ at 500 °C contains Li$_3$NbO$_4$ nanocrystals and Li$_2$CO$_3$, 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 Li$_6$PS$_5$Cl as solid electrolyte. Interestingly, the level of improvement is superior to that achieved with conventional LiNbO$_3$ coatings

Interface and Electrode Microstructure Engineering for Optimizing Performance of the LiNiO₂ Cathode in All-Solid-State Batteries

Solid-state batteries (SSBs) utilizing superionic thiophosphate solid electrolytes (SEs), such as argyrodite Li6PS5Cl, are attracting great interest as a potential solution for safe, high-energy-density electrochemical energy storage. However, the development of high-capacity cathodes remains a major challenge. Herein, we present an effective design strategy to improve the cyclability of the layered Co-free oxide cathode active material (CAM) LiNiO2, consisting of surface modification and electrode microstructure engineering. After optimization, the SSB cells were found to deliver high capacities (qdis ≈ 200 mAh/gCAM) and to cycle stably for hundreds of hours. A combination of operando and ex situ characterization techniques was employed to reveal the mechanism of optimization in overcoming several issues of LiNiO2, including poor SE compatibility, outgassing, and state-of-charge heterogeneity. Tailoring the microstructure of the composite cathode and increasing the CAM|SE interface stability enable superior electrochemical performance