“One stone, two birds”: Salt template enabling porosity engineering and single metal atom coordinating toward high-performance zinc-ion capacitors

Zinc-ion hybrid capacitors (ZIHCs) have received increasing attention as energy storage devices owing to their low cost, high safety, and environmental friendliness. However, their progress has been hampered by low energy and power density, as well as unsatisfactory long-cycle stability, mainly due to the lack of suitable electrode materials. In this context, we have developed manganese single atoms implanted in nitrogen-doped porous carbon nanosheets (MnSAs/NCNs) using a metal salt template method as cathodes for ZIHCs. The metal salt serves a dual purpose in the synthesis process: It facilitates the uniform dispersion of Mn atoms within the carbon matrix and acts as an activating agent to create the porous structure. When applied in ZIHCs, the MnSAs/NCNs electrode demonstrates exceptional performance, including a high capacity of 203 mAh g⁻¹, an energy density of 138 Wh kg⁻¹ at 68 W kg⁻¹, and excellent cycle stability with 91% retention over 10,000 cycles. Theoretical calculations indicate that the introduced Mn atoms modulate the local charge distribution of carbon materials, thereby improving the electrochemical property. This work demonstrates the significant potential of carbon materials with metal atoms in zinc-ion hybrid capacitors, not only in enhancing electrochemical performance but also in providing new insights and methods for developing high-performance energy storage devices.