Edge-Oriented Graphene on Carbon Nanofiber for High-Frequency Supercapacitors

Abstract

High-frequency supercapacitors are being studied with the aim to replace the bulky electrolytic capacitors for current ripple filtering and other functions used in power systems. Here, 3D edge-oriented graphene (EOG) was grown encircling carbon nanofiber (CNF) framework to form a highly conductive electrode with a large surface area. Such EOG/CNF electrodes were tested in aqueous and organic electrolytes for high-frequency supercapacitor development. For the aqueous and the organic cell, the characteristic frequency at − 45° phase angle was found to be as high as 22 and 8.5 kHz, respectively. At 120 Hz, the electrode capacitance density was 0.37 and 0.16 mF cm−2 for the two cells. In particular, the 3 V high-frequency organic cell was successfully tested as filtering capacitor used in AC/DC converter, suggesting the promising potential of this technology for compact power supply design and other applications. Electronic supplementary materialThe online version of this article (doi:10.1007/s40820-017-0162-4) contains supplementary material, which is available to authorized users.

Hierarchical, Vertically‐Oriented Carbon Nanowall Foam Supercapacitor using Room Temperature Ionic Liquid Mixture for AC Line Filtering with Ultrahigh Energy Density

“…The specific capacitance C areal of CWF was calculated to be ∼0.557 mF cm −2 at 120 Hz, substantially higher than those of commercial AEC (around 0.019 mF cm −2 ) and supercapacitor used for filtering applications (0.12 mF cm −2 , 0.172 mF cm −2 , and 0.316 mF cm −2[11] ). Most importantly, it exhibits a recorded‐high specific energy density of 1.23 μWh cm −2 at 120 Hz, which is almost ∼10 times and ∼2 times higher than those of aqueous, and organic,, electrolyte‐based supercapacitors, respectively (Figure d and Table S3). The as‐obtained superior energy storage capability is closely correlated with the hierarchical structure of CWF and the wide voltage window, improved wettability and electrical conductivity of RTIL mixture (4.0 V), which is much larger than those of conventional aqueous (∼1.23 V) and organic solutions (∼2.7 V).…”

The electrochemical properties of reduced graphene oxide film with capsular pores prepared by using oxalic acid as template

“…It is clear that the sequence of the equivalent series resistances is C-rGOF12-T160 < C-rGOF12-T150 < C-rGOF12-T170 < rGOF. 56 The small τ 0 value implies the good rate capability, and the obtained τ 0 value for C-rGOF12-T160 is smaller than those of porous graphene materials previously reported, 34,36,54,55,57 indicating excellent rate performance of C-rGOF12-T160. The values of f 0 for the devices fabricated by rGOF, C-rGOF12-T150, C-rGOF12-T160, and C-rGOF12-T170 are 0.99, 2.43, 5.30, and 1.21 Hz ( Figure 8C) which correspond to the characteristic relaxation time constants τ 0 (1/ f 0 ) of about 1.01, 0.41, 0.19, and 0.83 second, respectively.…”

“…The values of f 0 for the devices fabricated by rGOF, C-rGOF12-T150, C-rGOF12-T160, and C-rGOF12-T170 are 0.99, 2.43, 5.30, and 1.21 Hz ( Figure 8C) which correspond to the characteristic relaxation time constants τ 0 (1/ f 0 ) of about 1.01, 0.41, 0.19, and 0.83 second, respectively. 56 The small τ 0 value implies the good rate capability, and the obtained τ 0 value for C-rGOF12-T160 is smaller than those of porous graphene materials previously reported, 34,36,54,55,57 indicating excellent rate performance of C-rGOF12-T160. Cycling stability is of vital importance to evaluate the practical electrochemical performance.…”

Hierarchically Macroporous Graphitic Nanowebs Exhibiting Ultra-fast and Stable Charge Storage Performance

“…Therefore, surface-induced charge storage performances can be improved in HM-GNWs, showing exceptionally high rate capabilities and cycling stabilities by sweep rates of 100 V s −1 and 1,000,000 cycles, respectively. The rate and cycling performances of HM-GNWs surpass them of other similar carbonbased electrode materials for supercapacitors [18][19][20][21][22][23][24][25].…”

“…These ultra-stable cycling behaviors confirm that the surface charge adsorption/desorption mechanism on the HM-GNWs is highly reversible and semi-permanent after repetitive cycling. The high rate and cycling performances of HM-GNWs were induced by their unique morphological and microstructural features based on three-dimensionally entangled graphitic nanofibers (~20 nm in diameter) which is much smaller and well ordered than carbon nanofibers prepared from electrospinning or template method [18][19][20][21]. Therefore, surface-induced charge storage performances can be improved in HM-GNWs, showing exceptionally high rate capabilities and cycling stabilities by sweep rates of 100 V s −1 and 1,000,000 cycles, respectively.…”