High-Energy-Density 3.5 V Carbon Supercapacitor Fabricated with Ionic-Liquid-Incorporated Redox-Active Gel Polymer Electrolyte

Abstract

Introducing redox-active species in the electrolyte component is an effective approach to improving the energy density of carbon supercapacitors via additional pseudocapacitive redox activities at the electrode–electrolyte interfaces. Herein, we report a quasisolid-state supercapacitor fabricated with symmetrical activated carbon electrodes and an ionic liquid (IL, 1-butyl-1-methylpyrrolidinium bis­(trifluoromethylsulfonyl)­imide, BMPTFSI)-incorporated nonaqueous, redox-active gel polymer electrolyte (R-GPE) added with a redox-additive IL (BMPBr), entrapped in a polymer matrix of poly­(vinylidene fluoride-co-hexafluoropropylene). The R-GPE film with an optimum composition of an additive (BMPBr) showing a high mechanical stability (tensile strength ∼0.32 MPa and elongation at break ∼154%), a wide thermal stability range (up to ∼385 °C), and excellent electrochemical properties (an ionic conductivity of ∼1.2 × 10–3 S cm–1 at room temperature and an electrochemical stability window of ∼6.5 V) is found as an excellent substitute of liquid electrolytes in supercapacitors. The quasisolid-state supercapacitor is fabricated from biomass (pollen-cone)-derived activated carbon electrodes separated by the R-GPE film and characterized via electrochemical techniques, namely, electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge tests. The Br–-related redox activities at the interfaces lead to a significant improvement in specific capacitance (from ∼164 to ∼248 F g–1), specific energy (from ∼65 to ∼105 W h kg–1), and maximum power (from ∼15 to 31 kW kg–1). With a moderate rate capability, the supercapacitor demonstrates a good cycling performance with an initial ∼23% fading in the specific capacitance and a ∼100% Coulombic efficiency for ∼10 000 charge–discharge cycles.

Bubble Up Induced Graphene Microspheres for Engineering Capacitive Energy Storage

“…The solid‐state supercapacitor has a specific capacity of 220.5 F g −1 at a current density of 0.5 mA cm −2 , thus delivering an energy density as high as 92.3 Wh kg −1 (calculation based on the electrode only, with areal mass loading of 5 mg cm −2 ), which is higher than the values for most of the state‐of‐the‐art solid‐state supercapacitors reported previously [ 10,17,42–55 ] (Figure S21, Table S2, Supporting Information). For example, functionalized graphene [ 43 ] showed a specific capacitance of 242 F g −1 and an energy density of 33 Wh kg −1 with potential window of (0, 2.0 V) using ionogel electrolyte of PVDF‐HFP/BMIMBF 4 ; the hierarchical graphene [ 44 ] delivered specific capacitance of 180 F g −1 and energy density of 75 Wh kg −1 with potential window of (0, 3.5 V) using ionogel electrolyte of PVDF‐HFP/BMIMBF 4 ; the graphene‐doped carbon exhibited a specific capacitance of 190 F g −1 and energy density of 76 Wh kg −1 at potential window of (0, 3.5 V) using ionogel electrolyte of PVDF‐HFP/EMIMBF 4 /GO; the activated carbon [ 50 ] exhibited a specific capacitance of 248 F g −1 and an energy density of 105 Wh kg −1 with potential window of (0, 3.75 V), the 3D printed MXene [ 55 ] provided a specific capacitance of 242.5 F g −1 and an energy density of 8.5 Wh kg −1 with potential window of (0, 0.6 V).…”

Directly Sputtered Molybdenum Disulfide Nanoworms Decorated with Binder-less VN and W2N Nanoarrays for Bendable Large-Scale Asymmetric Supercapacitor

“…The complex capacitance method was applied to probe the frequency (ω) response of the asymmetrical cell in the 0.1 MHz to 10 mHz range. Both real and imaginary parts ( C ′ and C ″) are defined by italicC ′ ( ω ) = − Z ″ ( ω ) 2 π f | Z ( ω ) | 2 and italicC ″ ( ω ) = Z ′ ( ω ) 2 π f | Z ( ω ) | 2 expressions, separately (Figures c,d) where ω, Z ′, and Z ″ specify the angular frequency, real impedance, and imaginary impedance, respectively. The experimental data was fitted (χ 2 = ∼0.01) by employing the above expressions to examine the response parameters of our device.…”

“…expressions, separately (Figures 6c,d) 55 where ω, Z′, and Z″ specify the angular frequency, real impedance, and imaginary impedance, respectively. The experimental data was fitted (χ 2 = ∼0.01) by employing the above expressions to examine the response parameters of our device.…”

Poly(ionic liquid)s: an emerging platform for green chemistry

“…The advantages of ionic liquids (ILs), such as low vapor pressure and volatility, and high thermal and chemical stability, have made them widely used in supercapacitors. [227][228][229] However, their low ionic conductivity and high viscosity limit the development space. When coupling them with polymer backbone to PILs, their thermal/electrochemical stability can be further enhanced and their dielectric constants can be improved.…”