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

Abstract

High-capacity LiNi1-x-yCoxMnyO2 (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 LiNi0.8Co0.1Mn0.1O2 (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.