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

Abstract 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.