Kinetic Suppression of Anion Intercalation into Cathode Conductive Carbon in High-Voltage Lithium Batteries

High-voltage lithium-ion batteries have been extensively studied to increase their energy density, yet long-term stability remains elusive due to oxidative electrolyte decomposition. A major obstacle to improving cycling stability is the unintended intercalation of electrolyte anions into the conductive carbon additive included in the cathode composite, occurring above 4.5 V versus Li/Li⁺, which generates defects or active sites on graphene surface layers that further accelerate decomposition. Here we show that manipulating multibody interactions among electrolyte components markedly suppresses anion intercalation into graphite. The rate-determining step of the anion intercalation process was analyzed to be the dissociation of ion pairs, the activation energy of which was indirectly but significantly enlarged by the introduction of a low-polarity solvent, calling an electrolyte engineering with reduced solvent polarity toward more stable high-voltage battery systems.