In situ tunable pillaring of compact and high-density graphite fluoride with pseudocapacitive diamines for supercapacitors with combined predominance in gravimetric and volumetric performancesElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ta09782h

• Main Authors: Zhao, Fu-Gang, Kong, Yu-Ting, Pan, Bingyige, Hu, Cheng-Min, Zuo, Biao, Dong, Xiaoping, Li, Benxia, Li, Wei-Shi
• Format: Journal Article
• Language: English
• Published: 12.02.2019
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta09782h

For most graphene electrodes, there is usually a disappointing trade-off relationship between gravimetric and volumetric capacitive characteristics, which is definitely a major stumbling block in the development of real-life supercapacitors with high energy density. Herein, we rationally designed a hierarchically porous and modestly packed diamine pillared graphene, which is achieved by a facile and straightforward reaction between commercialized bulk graphite fluoride and in situ generated diamine anions. Combined reliable characterization studies demonstrate that an advantageous reductive defluorination of the unsubstituted carbon-fluorine units (C-F x ) accompanies the foreseen substitution of C-F x by diamines, endowing the resultant products with recovered 2D π-conjugation and high conductivity. In comparison to ethylenediamine and p -phenylenediamine, pseudocapacitive 4,4′-oxydianiline (ODA) molecular pillars, having a bulky and rigid geometry, provide the ODA-G product with a greatly widened d -spacing (6.2 Å), large wettable and electrolyte-accessible specific surface area (1985 m 2 g −1 ), hierarchically porous and interconnected structuration, heavyweight nature (density of 1.08 g cm −3 ), etc. Consequently, the symmetric supercapacitor fabricated using ODA-G as both electrodes delivers an impressive gravimetric capacitance of 328.5 F g −1 and a maximized volumetric capacitance of 354.8 F cm −3 at a current density of 0.5 A g −1 , whilst exhibiting a remarkable rate capability and cycling stability. Apart from an exceptional gravimetric energy density, the volumetric energy density of the ODA-G device is as high as 19.5 W h L −1 at a large power density of 9093 W L −1 . It is notable that this contribution deepens our insight into the chemistry of graphite fluoride, and can guide the judicious design and synthesis of versatile functionalized graphene applicable to other electrochemical energy-storage systems, or the newly-emerging photothermal water evaporation, desalination, etc. Graphene electrodes with ultrahigh volumetric & gravimetric capacitances were prepared through pillaring fluorographite sheets with pseudocapacitive diamines.