Abstract:storage systems are preferred due to their high safety and low capital cost. [2] However, commercial aqueous lead-and nickel-based rechargeable batteries possess low energy densities (≈45 Wh kg −1 for Pb-acid batteries; [3] ≈50 Wh kg −1 for Ni-Cd batteries [4]) and limited life spans, which increases the energy storage cost per unit energy output, [5,6] thus limits their practical applications. Zinc metal is considered as an ideal anode for aqueous energy storage devices because of its high theoretical capacit… Show more
“…[ 17–22 ] Zn‐ion hybrid capacitor (ZHC), has emerged as an attractive power supply system, which integrated the advantageous characteristics of supercapacitors and batteries. [ 23–29 ] It commonly consisted of a Zn metal as anode and a capacitive/pseudocapacitive electrode as cathode in a aqueous Zn‐ion electrolyte. The fast Zn plating/stripping kinetics of Zn anode together with these remarkable merits attract increasing research efforts in developing ZHC with high capacity and extreme stability.…”
Functionalizing carbon cathode surfaces with oxygen functional groups is an effective way to simultaneously tailor the fundamental properties and customize the electrochemical properties of aqueous Zn‐ion hybrid capacitors. In this work, the oxygen functional groups of chemically reduced graphene oxide (rGO) are systematically regulated via a series of reductants and varied experimental conductions. Carboxyl and carbonyl have been proven to significantly enhance the aqueous electrolyte wettability, Zn‐ion chemical adsorption, and pseudocapacitive redox activity by experimental study and computational analysis. The rGO cathode produced through hydrogen peroxide assisted hydrothermal reduction exhibits a specific capacitance of 277 F g−1 in 1 m ZnSO4 after optimization of surface oxygen functional groups. In addition, a quasi‐solid‐state flexible Zn‐ion hybrid capacitor (ZHC) with a polyacrylamide gel electrolyte and a high loading mass of 5.1 mg cm−2 are assembled. The as‐prepared quasi‐solid state ZHC can offer a superior areal capacitance of 1257 mF cm−2 and distinguished areal energy density of 342 µW h cm−2. The significant enhancement of redox activity and Zn‐ion storage capability by regulating the oxygen functional groups can shed light on the promotion of electrochemical charge storage properties even beyond protic electrolyte systems.
“…[ 17–22 ] Zn‐ion hybrid capacitor (ZHC), has emerged as an attractive power supply system, which integrated the advantageous characteristics of supercapacitors and batteries. [ 23–29 ] It commonly consisted of a Zn metal as anode and a capacitive/pseudocapacitive electrode as cathode in a aqueous Zn‐ion electrolyte. The fast Zn plating/stripping kinetics of Zn anode together with these remarkable merits attract increasing research efforts in developing ZHC with high capacity and extreme stability.…”
Functionalizing carbon cathode surfaces with oxygen functional groups is an effective way to simultaneously tailor the fundamental properties and customize the electrochemical properties of aqueous Zn‐ion hybrid capacitors. In this work, the oxygen functional groups of chemically reduced graphene oxide (rGO) are systematically regulated via a series of reductants and varied experimental conductions. Carboxyl and carbonyl have been proven to significantly enhance the aqueous electrolyte wettability, Zn‐ion chemical adsorption, and pseudocapacitive redox activity by experimental study and computational analysis. The rGO cathode produced through hydrogen peroxide assisted hydrothermal reduction exhibits a specific capacitance of 277 F g−1 in 1 m ZnSO4 after optimization of surface oxygen functional groups. In addition, a quasi‐solid‐state flexible Zn‐ion hybrid capacitor (ZHC) with a polyacrylamide gel electrolyte and a high loading mass of 5.1 mg cm−2 are assembled. The as‐prepared quasi‐solid state ZHC can offer a superior areal capacitance of 1257 mF cm−2 and distinguished areal energy density of 342 µW h cm−2. The significant enhancement of redox activity and Zn‐ion storage capability by regulating the oxygen functional groups can shed light on the promotion of electrochemical charge storage properties even beyond protic electrolyte systems.
“…Two characteristic peaks located at 1338 cm −1 (D band) and 1586 cm −1 (G band) are related to the defects and the graphitic carbons. Generally, the calculated I D /I G value is an effective indicator to evaluate the density of defects [7c] . The higher I D /I G ratio of D‐PC (0.992), ZU‐PC (1.072), Z‐PC (1.425), and U‐PC (1.042) than PC (0.991), implying more defects or disordered regions in carbons with ZnCl 2 or urea induced by the chemical interactions during pyrolysis.…”
Hierarchical porous carbon that possesses large surface area and high porosity has become an important electrode material for supercapacitors. However, some unavoidable issues like complex approach and environmental pollution involved in traditional chemical activation restrict the sustainable development of carbons. Herein, a green, low‐cost, and safe urea‐zinc chloride deep eutectic solvent (DES) is proposed to prepare polyacrylonitrile derived three‐dimensional carbon nanosphere (D‐PC). Specially, the D‐PC efficiently accelerates electrolyte ions migration and enhances charge storage due to its interconnected ionic pathways and large accessible active surfaces. When employing the D‐PC as positive electrode of zinc‐ion hybrid supercapacitors, a high specific capacitance of 261.5 F g−1 at 0.2 A g−1 along with a cycling stability of 91.3 % after 10000 cycles at 5 A g−1. Meanwhile, such device holds the maximum energy/power density of 93.9 Wh kg−1/16.7 kW kg−1 at 0.2 A g−1/20 A g−1, respectively. Thanks to the unique physicochemical properties of as‐obtained D‐PC, an ultrahigh areal capacitance of 2.2 F cm−2 also can be achieved at a mass loading of 23 mg cm−2. The satisfying structure and performance highlight the potential of DESs in the design of functional carbons.
“…Chemie Forschungsartikel 9700 www.angewandte.de previous reports, [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] we calculated the energy density (Wh kg À1 )o ft he MOF-PC//Zn cells only based on the mass of active material (i.e., MOF-PC) in cathode without considering the mass of Zn anode.A ss hown in Figure 4b,t he cell with the mass loading of 1mgcm À2 shows ah igh energy density of 58.1 Wh kg À1 at 112 Wkg À1 ,a nd the cell with the mass loading of 10 mg cm À2 exhibits an energy density of 48.6 Wh kg À1 at 113 Wkg À1 (see green lines in Figure 4b). Obviously,when calculated only based on the mass of MOF-PC in cathode,t he energy density achieved at al ow mass loading (1 mg cm À2 )issuperior to that achieved at ahigh mass loading (10 mg cm À2 ).…”
Zn‐based aqueous supercapacitors are attracting extensive attention. However, most of the reported long‐life and high‐power performances are achieved with low Zn‐utilization (<0.6 %) and low mass loading in cathode (<2 mg cm−2). And, many obtained high energy densities are generally evaluated without considering the mass of Zn‐anode. Herein, we propose a Zn‐based hybrid supercapacitor, involving a metal organic framework derived porous carbon cathode, a Zn‐anode and an N, N‐dimethylformamide (DMF)‐based electrolyte containing Zn2+. We demonstrate that the charge storage of cathode mainly occurs in macropores, showing high rate performance at high mass loading (40 mg cm−2). Furthermore, the aprotic nature of electrolyte and formation of Zn2+‐DMF complex avoid the Zn‐corrosion and dendrite formation. Therefore, the supercapacitor shows a long‐life (9,000 cycles) with a high Zn‐utilization (2.2 %). When calculated with the total mass of cathode (40 mg cm−2) and Zn‐anode, the energy density reaches 25.9 Wh kg−1.
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