Enhanced Stability and Performance of High-Voltage LNMO Cathodes with Dual-Anion Niobium Oxyfluoride Coating

High energy cathodes with low environmental impact are critical for the development of next-generation lithium-ion batteries (LIBs). Lithium nickel manganese oxide (LNMO) cathode is a promising cathode candidate due to its high operating potential (≈4.7 V vs Li⁺/Li), energy density (≈650 Wh kg^-1), thermal stability, and cost-effectiveness. However, it suffers from interfacial degradation and processing limitations. This work pioneers the implementation of niobium oxyfluoride as a multifunctional protective coating on LNMO for high-voltage LIBs applications. A conformal, ultrathin NbO₂F layer (≈5 nm) is precisely engineered via atomic layer deposition, to improve cathode stability. The coating's dual-anion architecture (F^- and O^2-) and chemically inert Nb⁵⁺ state offers improved resistance to hydrofluoric acid-induced corrosion, suppressing transition-metal dissolution, and mitigating capacity degradation. In half-cell configuration, the niobium oxyfluoride coated LNMO (NbO₂F@LNMO) versus Li/Li⁺ achieves >91% capacity retention after 500 cycles. At high temperature (60 °C), the cathode demonstrates 92.8% retention at 0.1 C and 550 Wh kg^-1 energy density after 100 cycles. Full-cell comprising the NbO₂F@LNMO cathode exhibits >94% capacity retention after 100 cycles. Additionally, the NbO₂F@LNMO cathode exhibits a remarkable resilience under high-humidity environments, underscoring its robust long-term storage capabilities and processability. This approach provides a pathway toward practical LNMO cathodes for high-voltage, stable, and cost effective LIBs.