Potassium Metal Underpotential Deposition in Crystalline Carbon of Potassium‐Ion Batteries

Abstract Carbon materials, owing to their low cost, high conductivity, and good thermal and chemical stability, have been deemed as a promising anode candidate for potassium‐ion batteries. However, anomalous low‐voltage discharge situations in crystalline carbon materials imply uncertainty in the potassium storage mechanism. Herein, an overlooked scenario, i.e., potassium metal underpotential deposition (PMUPD), is disclosed in crystalline carbon materials for the first time. The study unveils the induction of interlayer pores on desolvation and PMUPD by insights from thermodynamics, kinetics, and experimental analyses. By manipulating the cutoff voltage to utilize partial PMUPD, a novel synergistic mechanism of co‐intercalation and PMUPD is revealed. A remarkable initial coulombic efficiency of 92% and a 65% capacity retention at 30C (80 mAh g −1 ) are realized in crystalline carbon anode. This work provides a new insight into the potassium storage mechanism of carbon anode and contributes to further research and application of the UPD behavior in other alkaline metal ion batteries.