Nitrogen‐Doped Accordion‐Like Soft Carbon Anodes with Exposed Hierarchical Pores for Advanced Potassium‐Ion Hybrid Capacitors

• Published in: Advanced functional materials 2021-06, Vol.31 (23), p.n/a
• Main Authors: Zhang, Chen, Liu, Xing, Li, Zhen, Zhang, Chenying, Chen, Zhiwen, Pan, Dengyu, Wu, Minghong
• Format: Article
• Language: English
• Subjects: accordion‐like architecture; Anodes; Capacitors; Carbon; Density functional theory; Electrochemical impedance spectroscopy; Electrode materials; Electrolytes; Energy storage; Exposure; Graphene; Materials science; Nitrogen; nitrogen doping type; Potassium; potassium‐ion hybrid capacitors; Quantum dots; soft carbon; Stability analysis
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202101470

Soft carbon (SC) is a promising anode material for potassium‐ion hybrid capacitors (PIHCs), but there are limited K+ storage sites in common SC due to a skin‐like carbon film covering on the surface. To address this issue, a simple oxidization method to completely remove the skin‐like carbon film is reported and a novel accordion‐like architecture of SC (ASC) is constructed with a hierarchical porous framework composed of micropores, mesopores, and macropores, all of which can be exposed to K+ electrolytes for enhanced energy storage. Importantly, this exposed structure facilitates pseudocapacitance modification by electro‐deposition of highly electrochemically active nitrogen‐doped graphene quantum dots (N‐GQDs) to enhance kinetic performance and additional K+ storage. After annealing treatment to regulate N‐doping type, the accordion‐like N‐GQD@ASC‐500 exhibits excellent reversible capacity of 360 mAh g−1 as well as superior rate capability and cycle stability. Kinetic, in situ Raman/electrochemical impedance spectroscopy analysis, and density functional theory calculation elucidate the K+ storage mechanism. As expected, the PIHC assembled with N‐GQD@ASC‐500 anode and porous carbon cathode delivers an ultrahigh energy/power density (171 Wh kg−1 and 20 000 W kg−1) with long cycle life. This work suggests that ASC is a promising anode material for designing of high‐performance PIHCs. A simple oxidization method to remove the skin‐like carbon film from soft carbon anodes is reported and a novel accordion‐like architecture of soft carbon (ASC) embedded with nitrogen‐doped graphene quantum dots is constructed. After annealing treatment to regulate N‐doping‐type, an assembled potassium‐ion hybrid capacitor using nitrogen‐doped ASC as the anode, delivers an ultrahigh energy/power density (171 Wh kg−1 and 20 000 W kg−1) with a long cycle life.