High cycling stability graphite cathode modified by artificial CEI for potassium-based dual-ion batteries

Expanded graphite is the most common cathode for dual-ion batteries (DIBs), although graphite cathode suffers from a poor cycle life due to decomposition of the solid cathode electrolyte interface (CEI). Herein, a kind of surface modification strategy is developed to improve the cycling stability of graphite by forming artificial CEI on the cathode surface. Expanded graphite cathode modified by an artificial CEI layer can stably deliver a discharge capacity of 56.1 mAh g−1 after 100 cycles, which is obviously better than that of the pristine graphite cathode. The artificial CEI layer can still maintain a thin and uniform morphology after 100 cycles, which is beneficial to protect the interface between graphite and electrolyte and improve the stable intercalation/deintercalation of ions.