Enabling Ambient Stability of LiNiO₂ Lithium-Ion Battery Cathode Materials via Graphene-Cellulose Composite Coatings

Nickel-rich layered oxides are widely used as cathodematerialsfor energy-dense lithium-ion batteries. These chemistries, based onthe parent compound LiNiO2 (LNO), are highly sensitiveto ambient environments and are known to readily react with moistureand carbon dioxide. As a result, impurities such as lithium hydroxidesand lithium carbonates are formed at the LNO surface, compromisingelectrochemical behavior. Here, we address this issue by coating LNOcathode particles with a hydrophobic barrier layer composed of grapheneand ethyl cellulose (GrEC). This coating limits contact between atmosphericmoisture and the LNO surface, which minimizes the generation of lithiumimpurities. This scheme is evaluated by exposing coated LNO to humidifiedCO(2) for 24 h as an accelerated ambient degradation test.Subsequent spectroscopy, microscopy, and electrochemical characterizationshow no detectable signatures of carbonates on the LNO surface, thusverifying that the GrEC coating prevents ambient degradation. By demonstratingthis methodology for the ultimate nickel-rich chemistry, this approachcan likely be generalized to a wide range of ambient-sensitive batterymaterials.