Thick Electrodes of a Self‐Assembled MXene Hydrogel Composite for High‐Rate Energy Storage

Supercapacitors based on two‐dimensional MXene (Ti₃C₂T_z) have shown extraordinary performance in ultrathin electrodes with low mass loading, but usually there is a significant reduction in high‐rate performance as the thickness increases, caused by increasing ion diffusion limitation. Further limitations include restacking of the nanosheets, which makes it challenging to realize the full potential of these electrode materials. Herein, we demonstrate the design of a vertically aligned MXene hydrogel composite, achieved by thermal‐assisted self‐assembled gelation, for high‐rate energy storage. The highly interconnected MXene network in the hydrogel architecture provides very good electron transport properties, and its vertical ion channel structure facilitates rapid ion transport. The resulting hydrogel electrode show excellent performance in both aqueous and organic electrolytes with respect to high capacitance, stability, and high‐rate capability for up to 300 μm thick electrodes, which represents a significant step toward practical applications.