Flexible MXene Framework as a Fast Electron/Potassium‐Ion Dual‐Function Conductor Boosting Stable Potassium Storage in Graphite Electrodes

Abstract Graphite anodes show great potential for potassium storage, however, their capacity fades quickly owing to substantial interlayer expansion/shrinkage (i.e., up to 60%) induced structural degradation. Here, Ti 3 C 2 T x MXene nanosheets are used as a fast electron/potassium‐ion dual‐function conductor to construct the framework of all‐integrated graphite nanoflake (GNF)/MXene (GNFM) electrodes. The continuous MXene framework constructs a 3D channel for fast electron/potassium‐ion transfer and endows GNFM electrodes with a high structural stability. Owing to this unique MXene framework, GNFM electrodes exhibit much enhanced potassium storage performances than that of the conventional polymer‐bonded electrodes even at high mass loadings. Moreover, GNFM electrodes also show impressive cyclability in non‐flammable electrolytes and are further used as anodes to assemble novel non‐flammable potassium‐ion capacitors that show an excellent cyclability and high energy/power densities (113.1 Wh kg –1 and 12.2 kW kg –1 ). New insights into phase transition mechanism in GNFM electrodes are verified by operando XRD. Density functional theory calculations demonstrate that MXene can promote electron transfer and potassium diffusion in the heterointerface between GNF and MXene. Therefore, the results demonstrate that all‐integrated GNFM electrodes designed with MXene as multifunctional frameworks provide a new paradigm for producing efficient potassium storage anodes.