Synergistically Active NiCo2S4 Nanoparticles Coupled with Holey Defect Graphene Hydrogel for High‐Performance Solid‐State Supercapacitors

• Published in: Chemistry : a European journal 2018-03, Vol.24 (13), p.3263-3270
• Main Authors: Tiruneh, Sintayehu Nibret, Kang, Bong Kyun, Kwag, Sung Hoon, Lee, YoungHun, Kim, MinSeob, Yoon, Dae Ho
• Format: Article
• Language: English
• Subjects: Capacitance; Chemistry; Cobalt; Electrical conductivity; Electrical resistivity; Electrode materials; Electrodes; Graphene; holey defect graphene hydrogel; Hydrogels; Hydrothermal crystal growth; Metal sulfides; Nanoparticles; Nickel; nickel cobalt sulfide; solid-state supercapacitors; Sulfides; Supercapacitors
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201705445

Nickel cobalt sulfide nanoparticles embedded in holey defect graphene hydrogel (HGH) that exhibit highly porous structures and uniform nickel cobalt sulfide nanoparticle sizes are successfully prepared by a facile solvothermal–hydrothermal method. As an electrode material for supercapacitors, the as‐prepared NiCo2S4@HGH shows ultra‐high specific capacitances of 1000 F g−1 and 800 F g−1 at 0.5 and 6 A g−1, respectively, owing to the outstanding electrical conductivity of HGH and high specific capacitance of NiCo2S4. After 2100 charge/discharge cycles at a current density of 6 A g−1, 96.6 % of the specific capacitance was retained, signifying the superb durability of NiCo2S4@HGH. Moreover, remarkable specific capacitance (312.6 F g−1) and capacity retention (87 % after 5000 cycles) at 6 A g−1 were displayed by the symmetric solid‐state supercapacitor fabricated by using NiCo2S4@HGH electrodes. These auspicious supercapacitor performances demonstrate that the as‐developed solvothermal–hydrothermal approach can be widely used to prepare graphene‐coupled binary metal sulfides for high‐performance supercapacitor applications. Holey defect, Batman! A facile solvothermal method encompassing an ion exchange process was used to imbed NiCo2S4 on holey defect graphene hydrogel. The resulting material showed remarkable electrochemical performance when used as a supercapacitor electrode free of binding and conducting agents.