High-Energy-Density Asymmetric Supercapacitor Based on a Nickel Cobalt Double Hydroxide/Reduced-Graphene-Oxide Fiber Electrode

Abstract

With high electrical conductivity, good mechanical strength, and excellent multidimensional flexibility, graphene fibers are more suitable for wearable devices than other flexible materials. However, challenges still exist in increasing their energy density. Here, we overcome this disadvantage by developing a fibrous supercapacitor loaded with battery-type active material. First, reduced-graphene-oxide fibers (rGOFs) with high conductivity and high toughness are fabricated from flake graphite by a series of redox reactions and wet-spinning processes. Second, Co-based zeolite imidazole framework (Co-ZIF) nanosheets are grown in situ on the surfaces of the rGOFs at room temperature and then converted into nickel cobalt layered double hydroxide (NCLDH) nanosheets by an etching codeposition method. The as-prepared NCLDH@rGOFs with a unique one-dimensional cladding structure exhibit an outstanding area specific capacitance of 2020 mF cm −2 at 5 mA cm −2 in a three-electrode system. When the NCLDH@ rGOFs and FeOOH@rGOFs are assembled into a flexible asymmetric supercapacitor (NF-FASC), the NF-FASC shows high area specific capacitance (351.6 mF cm −2 ), high energy density (max. 117.3 μWh cm −2 ), excellent power density (max. 34 000 μW cm −2 ), and acceptable cycle stability (75.5% capacitance retention after 5000 cycles).

Free-Standing Co(OH)2/Prussian Blue Analogue Nanostructured Electrodes for Flexible Na-Ion Supercapacitors with an Ultrawide Potential Window

“…Benefiting from the excellent electrochemical properties of the Co­(OH) 2 /PBA/CC electrodes and the wide potential window of the FSCs, they yield an energy density of 0.4 mWh cm –2 at a power density of 1.5 mW cm –2 . These results overmatch many similar devices reported previously, − and the specific values are summarized in Table .…”

Recent advances in Ni-materials/carbon nanocomposites for supercapacitor electrodes

“…Using NCLDH/rGOFs and FeOOH/rGOFs electrodes in the supercapacitor structure led to excellent properties. 117 Nickel selenide (NiSe) is used as an electrode in hybrid supercapacitors, although it is limited by poor conductivity and sluggish ion kinetics. The electrochemical performance of NiSe is improved by the addition of rGO, which can be attributed to the raised interfacial interaction and enhanced access to the active sites.…”

Synthesis and Electrochemical Studies of 3D Reduced Graphene Oxide for Efficient Energy Storage

“…Depending on the reduction method and synthesis conditions, various rGO morphologies may be attained (e.g., foams, sponges, hydrogels/aerogels, sheets, interconnected, fibers etc. ). ,− Li et al revealed that the initial oxidation in the preparation of graphene oxide had a potent influence on the capacitance of hydrothermally rGO . During the synthesis process, the GO sheets were reduced and self-assembled to form interconnected 3D architectures.…”