Multivalent ion storage towards high-performance aqueous Mn-ion hybrid supercapacitors

Aqueous manganese-ion hybrid supercapacitors offer a promising pathway for safe and sustainable energy storage, yet their practical application is hindered by limited energy density and sluggish ion kinetics. To address these challenges, we develop a high-performance hybrid device through the strategic integration of a hierarchically porous carbon anode and a redox-active cathode. A series of silk-derived porous activated carbon (Silk-PAC) materials is synthesized via ZnCl 2 pre-activation and subsequent KOH secondary activation. The optimized Silk-PAC-6 exhibits a high specific surface area (2984.60 m 2 g −1 ) and enhanced hydrophilicity, facilitating rapid charge transfer. Concurrently, a nickel-iron Prussian blue analog (NiFe-PBA) cathode is prepared via room-temperature co-precipitation. Benefiting from reversible Ni 2+ /Ni 3+ and Fe 2+ /Fe 3+ redox reactions coupled with a Mn 2+ /Mn 4+ dissolution-deposition mechanism, the NiFe-PBA cathode delivers substantial pseudocapacitance. The assembled Silk-PAC-6//NiFe-PBA device achieves an outstanding specific capacitance of 400 F g −1 , a superior energy output of 125 Wh kg −1 at 750 W kg −1 , and maintains 93.6% capacity retention after 980 cycles. Furthermore, two series-connected devices successfully power an LED for 40 min, demonstrating practical viability. This work underscores the efficacy of combining biomass-derived carbon with Prussian blue analogs to overcome critical performance bottlenecks, providing a viable design strategy for high-performance, green aqueous energy storage systems.