3D Foam‐Based MXene Architectures: Structural and Electrolytic Engineering for Advanced Potassium‐Ion Storage

MXenes are emerging rapidly as promising electrode materials for energy storage due to their high electronic conductivity and rich surface chemistry, but their potassium storage performance is unsatisfactory because of the large size of K + and irreversible interfacial reaction. Here, a developed 3D foam‐like MXene scaffold (3D‐FMS) is constructed via an electrostatic neutralization of Ti 3 C 2 T x with positive‐charged melamine followed with calcination, which offers massive surface‐active sites and facilitates fast K + transfer for boosting the potassium‐ion storage capacity and dynamics. In addition, using KFSI‐based electrolyte, the formation of a robust solid electrolyte interface layer with more inorganic components on MXene anode is revealed for enhancing the Coulombic efficiency. Consequently, the 3D‐FMS with KFSI‐based electrolyte delivers enhanced potassium‐ion storage performance in terms of capacity (161.4 mAh g −1 at 30 mA g −1 ), rate capability (70 mAh g −1 at 2 A g −1 ), and cycling stability (80.5 mAh g −1 at 1 A g −1 after 2000 cycles). Moreover, the assembled 3D‐FMS//activated carbon potassium‐ion hybrid supercapacitor delivers a high energy density of 57 Wh kg −1 at a power density of 290 W kg −1 . These excellent performances demonstrate the great superiority of 3D‐FMS in KFSI‐based electrolyte and may accelerate the development of MXene‐based materials for potassium storage systems.