Enhanced Cathode and Anode Compatibility for Boosting Both Energy and Power Densities of Na/K-Ion Hybrid Capacitors

The kinetics and capacity mismatches between anode and cathode for the Na/K-ion hybrid capacitors (NIHC and KIHC) greatly hamper their overall performance output. Herein, we construct NIHC and KIHC using multilayer tungsten sulfide nanosheets anchored with nitrogen-doped carbon nanosheets (WS2@NCNs) composite as anode and hierarchical nitrogen-doped carbon hollow nano spheres (NCHS) as cathode. The strongly coupled sheet-on-sheet nanostructure of the anode can facilitate electron transport and alleviate volume change. In particular, the WS2-NCNB interface offers a more feasible channel for fast ion intercalation and deintercalation, which can improve kinetics. The hierarchical NCHS cathode provides numerous accessible active sites for reversible anion adsorption and desorption, dramatically enhancing the specific capacity. Consequently, due to the enhanced anode and cathode compatibility, the assembled NIHC and KIHC can deliver high energy densities of 134.7 and 103.4 Wh kg(-1) at 117.5 and 235 W kg(-1), respectively. Our electrode design strategy could offer guidance for the development of high-performance hybrid capacitors.