Cation-Dependent Hydrogel Template-Activation Strategy: Constructing 3D Anode and High Specific Surface Cathode for Dual-Carbon Potassium-Ion Hybrid Capacitor

Here, a universal template-activation strategy is proposed to prepare two different types of porous carbonaceous materials for potassium ion hybrid capacitor (PIHC) anode and cathode, which is realized by only changing the type of cation (Na+ and K+) in the polysilicic acid-organic mixed hydrogel precursor originating from adding organic acid into Na2SiO3 and K2SiO3 solution, respectively. TG-IR data demonstrate that K+ exhibits a stronger etching ability for activating carbonaceous materials during the annealing process. Accordingly, a 3D carbon anode obtained with the assistance of NaOH (NPC-500) exhibits abundant edge-N doping (8.14 at%), displaying a high K-storage capacity of 314.1 mA h g(-1) at 0.2 A g(-1) and a capacity of 219.3 mA h g(-1) at 10 A g(-1) after 10000 cycles. A porous carbon particles cathode prepared in the presence of KOH (KCP-800) shows a high specific surface area (1326.8 m(2) g(-1)), contributing to high PF6- (de)adsorb capacity of 103.0 mA h g(-1) at 1 A g(-1). Remarkably, the assembled NPC//KCP PIHC delivers a high energy density of 137.7 W h kg(-1) at a power density of 275.4 W kg(-1) even over 20 000 cycles.