Carbonated MOF-based graphene hydrogel for hierarchical all‑carbon supercapacitors with ultra-high areal and volumetric energy density

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2020-11, Vol.876, p.114489, Article 114489
• Main Authors: Li, Zhen, Ren, Jing, Bu, Jingting, Wang, Liang, Shi, Wenyan, Pan, Dengyu, Wu, Minghong
• Format: Article
• Language: English
• Subjects: Areal energy density; Capacitance; Carbon; Carbonation; cZIF-8; Electrical resistivity; Electrode materials; Electrodes; Flux density; Graphene; Graphene hydrogel; Hydrogels; Ion transport; N-doped graphene quantum dots; Porous materials; Quantum dots; Supercapacitors; Volumetric energy density; Wettability
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2020.114489

Graphene hydrogel (GH) has been widely explored as electrode material for supercapacitors due to its three-dimensional porous network structure. However, poor conductivity and low capacitance activity have limited practical application. Herein, we design and fabricate a hierarchical all‑carbon GH-based electrode material decorated with MOF-derived porous carbon (cZIF-8) and highly N-doped graphene quantum dots. In this N-GQD@cZIF-8/GH composite, GH constructs an interconnected porous structure which benefits rapid electron/ion transport, and cZIF-8 provides a large specific surface area and enhances electrical conductivity, while N-GQDs contribute pseudo-capacitance and improve the wettability. The supercapacitor based on N-GQD@cZIF-8/GH shows a high areal capacitance (617.1 mF cm−2) and areal energy density (85.7 μWh cm−2) at 1 mA cm−2. It also has good rate capability (81.5% at 20 mA cm−2) and excellent cycling stability (93.1% after 10,000 cycles). Moreover, the assembled all-solid-state flexible supercapacitor can deliver a high energy density of 18.1 mWh cm−3 at high power density of 4907.3 mW cm−3. This rational-designed all‑carbon electrode opens up opportunities in the fabrication of next-generation wearable electronic equipments. [Display omitted] •We report a hierarchical all-carbon graphene hydrogel (GH) based electrode decorated with MOF-derived porous carbon (cZIF-8) and N-doped graphene quantum dots (N-GQDs).•The all-solid-state supercapacitor based on N-GQD@cZIF-8/GH electrode can deliver ultrahigh energy density with an excellent cycling stability and flexibility.