Interfacial Radical Reaction Enables High‐Performance Graphite Anode for Potassium‐Ion Batteries

The reversible K-intercalation chemistry in graphite anode plays a critical role in advancing the development of potassium-ion batteries (PIBs) for large-scale energy storage systems. However, the poor stability of natural solid electrolyte interface (SEI) on graphite anode as well as the co-intercalation of K⁺-solvent into graphite has caused poor cycling stability and sluggish reaction kinetics. Herein, a mechanochemical-induced radical reaction between graphite and open-shell Spiro-O8 radicals has been discovered and applied to construct a uniform organic layer on graphite, in which the phenoxy radicals can efficiently facilitate the decomposition of KFSI salt to generate outer inorganic-rich layer when the graphite was evaluated as anode for PIBs. The outer inorganic film can enhance K⁺ transport kinetics and inhibit the co-intercalation of K⁺-solvent, while the inner Spiro-O8 film can effectively accommodate the volume change during the cycling process. As a result, the highly ion-conductive Spiro-O8 modified graphite exhibited reversible capacity of 241.0 mAh g^-1 at 100 mA g^-1, high-rate capability (147.2 mAh g^-1 at 1 A g^-1) and stable cycles more than 600 cycles with a capacity retention of 89.4 %. The interfacial radical reaction in our work provides a new avenue to solve the interface problems of graphite anode for high-performance PIBs.