Sustainable Energy System Utilizing High‐Voltage‐Stable and Energy‐dense Supercapacitors Based on Porous Fe₂O₃@Graphene Electrode in Ionic Liquid Electrolyte

Abstract

Energy‐dense supercapacitors (SCs) based on metal oxides@graphene electrode and ionic liquid (IL) electrolyte hold great promise in sustainable energy system. However, these types of SCs suffer from poor cycling stability, especially at high working voltage. Herein, a porous ferric oxide/graphene (P−Fe2O3/G) electrode has been developed, in which Fe2O3 nanoparticles exhibit abundant and suitable mesoporous channels. This structure ensures the high ionic diffusion kinetics of the IL ions during the repeated charging‐discharging processes, thereby providing the P−Fe2O3/G electrode with outastanding capacitance behavior and cycling performance in IL electrolyte. As a result, an ingenious asymmetric electrode concept has been put forward to fabricate energy‐dense SCs based on this P−Fe2O3/G as negative electrode, carbon dodecahedrons/graphene (CDs/G) as positive electrode and IL electrolyte. Remarkably, the fabricated devices exhibit superior high‐voltage cycling stability with 95 % retention after 20 000 cycles, which are much better than that of most previously reported SCs based on metal oxides/graphene electrode and IL electrolyte. On this basis, a sustainable energy system combining wind harvesting with asymmetric SCs has been established, wherein the asymmetric SCs can be effectively recharged by harvesting sustainable wind power and repeatedly supply power without decline of electrochemical performance. Therefore, this work can provide a promising porous electrode for high performance SCs in sustainable energy system.

CuCo-Layered Double Hydroxide Nanosheet-Based Polyhedrons for Flexible Supercapacitor Cells

“…In this context, we tried to understand the possible pseudocapacitive mechanism of the CC-LDH with [EMIM]­[BF 4 ] IL electrolyte based on our characterization and previous studies. The observed high capacitance of the present cell is believed to be because of the EMIM + cation in [EMIM]­[BF 4 ] IL electrolyte and the high ionic liquid ion density onto the electrode surface as per Kornyshev theory as discussed for electrode materials such as Fe 2 O 3 , FeOOH, etc. , In these reports and in similar other materials, it was observed that the electrostatic interaction between a charged surface electrode forms a dense grim layer and loose diffuse layer because of large size of EMIM + . It is less mobile due to its large size, and in the present case, it overlaps with the electron density cloud from the OH – of LDH and finally gets adsorbed on the surface of the electrode .…”

“…Electrochemical charge storage characteristics of the CuCo-LDH material were further studied in a flexible cell using KOH as the electrolyte as described in the Experimental Section. The measured CV and GCD graphs, as shown in Figure S15 53,54 In these reports and in similar other materials, it was observed that the electrostatic interaction between a charged surface electrode forms a dense grim layer and loose diffuse layer because of large size of EMIM + . It is less mobile due to its large size, and in the present case, it overlaps with the electron density cloud from the OH − of LDH and finally gets adsorbed on the surface of the electrode.…”

“…Interestingly, pore size of our CC-LDH is high enough to intercalate the large size EMIM + cation (∼5.0 Å). The possible redox reactions of CuCo-LDH in [EMIM]­[BF 4 ] IL electrolyte can be given as , …”

Cu9S5/Fe2O3 Nanospheres as Advanced Negative Electrode Materials for High Performance Battery-like Hybrid Capacitors

“…The Raman spectra of Cu 9 S 5 /Fe 2 O 3 , Cu 9 S 5 and Fe 2 O 3 are displayed in Figure b. The peaks of Cu 9 S 5 /Fe 2 O 3 at 215 cm –1 correspond to the A 1g mode, and 281, 396, and 576 cm –1 correspond to the E g mode of the vibrations of Fe 2 O 3 . ,,, The peak at 482 cm –1 matches to Fe 2 O 3 and S–S stretching mode of Cu 9 S 5 . It is worth noting that the peak of pure Fe 2 O 3 shifts from 491 cm –1 to around 482 cm –1 of Cu 9 S 5 /Fe 2 O 3 , and the peak of pure Cu 9 S 5 shifts from 471 to 482 cm –1 of Cu 9 S 5 /Fe 2 O 3 .…”

Porous NiCo2O4–FeCo2O4 Nanowire Arrays as Advanced Electrodes for High-Performance Flexible Asymmetric Supercapacitors

“…Transition-metal oxides are being well studied for high-quality devices because of their low price and low toxicity. ,− For example, a single-crystal Co 3 O 4 nanowire array on nickel foam had a specific capacitance of 754 F/g at 2 A/g . A network of MnO 2 –ERGO exhibits an excellent capacitance of 422.5 F/g at 1 A/g .…”