Malonic-acid-functionalized fullerene enables the interfacial stabilization of Ni-rich cathodes in lithium-ion batteries

High-capacity LiNi_1-x-yCo_xMn_yO₂ (NCM) (x + y ≤ 0.2) is a potential candidate for realizing high-energy-density lithium-ion batteries (LIBs). However, successful application of this cathode requires overcoming the irreversible phase transition (layered-to-spinel/rock-salt), interfacial instability caused by residual lithium compounds, and the electrolyte oxidation promoted by highly oxidized Ni⁴⁺. In this study, we investigate the roles of fullerene with malonic acid moieties (MA-C₆₀) as a superoxide dismutase mimetic (SODm) electrolyte additive in LIBs to deactivate reactive radical species (O₂^•-, LiOCO₃^•, and Li(CO₃)₂^•) induced by electrochemical oxidation of residual lithium compound, Li₂CO₃ on the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode surface and to scavenge trace water to avoid undesirable hydrolysis of LiPF₆. Further, MA-C₆₀ maintains the structural stability of NCM811 cathodes and mitigates the parasitic reaction of residual lithium compounds with LiPF₆ through the formation of a stable cathode–electrolyte interface. Our findings showed that MA-C₆₀ helps overcome the challenges associated with Li₂CO₃ oxidation at the NCM811 cathode, which produces CO₂ gas and O₂^•- that react with the solvent molecules.