Electrochemical Zinc Ion Capacitors Enhanced by Redox Reactions of Porous Carbon Cathodes

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 capacity (gravimetric, 820 mAh g −1 ; volumetric, 5851 mAh cm −3), low potential (−0.76 V vs standard hydrogen electrode (SHE)), and high hydrogen evolution overpotential. [7] Zinc-based rechargeable batteries and capacitors are expected to be low-cost, long-life energy storage devices since they utilize inexpensive zinc metal anode and aqueous electrolytes. [8,9] However, most transition-metal oxide cathodes display limited cycle life due to dissolution and parasitic reactions, which deteriorate the cycling performance of zinc ion batteries. [10] Electrochemical zinc ion capacitors (ZICs) are hybrid supercapacitors consisting of zinc anodes and porous carbon cathodes. [11,12] On the one hand, theoretically, a porous carbon cathode has unlimited cycle life due to the adsorption/desorption charge storage mechanism without phase transition. [13] On the other hand, the zinc anode shows Faradaic reactions with infinite theoretical capacitance compared with a porous carbon cathode, which exerts the maximum electric double-layer capacitance (EDLC) of porous carbon cathode. [14] Nevertheless, in an aqueous ZIC system, commercial porous carbon has low capacity, energy density and power density (typical values are ≈55 mAh g −1 , 43.1 Wh kg −1 , and 12.0 kW kg −1 for YP-50F, Kuraray Chemical, Japan) [15] due to its EDLC dominated charge storage mechanism. [16,17] Therefore, novel porous carbon cathodes are designed to boost the electrochemical performances of full-cell ZIC. [18] Kang and coworkers reported a ZIC with activated carbon cathode and Zn anode in an aqueous ZnSO 4 electrolyte. [19] The assembled ZIC delivered a capacity of 272.3 F g −1 and a high power density of 14.9 kW kg −1 with a corresponding energy density of 30 Wh kg −1 in the operational voltage window of 0.2-1.8 V. Liu and coworkers employed a porous carbon cathode to assemble ZIC. The as-fabricated ZIC delivered a capacitance of 298.6 F g −1 , a maximum energy density of 82.36 Wh kg −1 , and a maximum power density of up to 3.76 kW kg −1 in the operating voltage Aqueous electrochemical zinc ion capacitors (ZICs) are promising next-generation energy storage devices because of their high safety, inexpensive raw materials, and long cycle life. Herein, an aqueous ZIC with superior performance is fabricated by employing an oxygen-rich porous carbon cathode. Excellent capacitance and energy density are obtained thanks to the electric double-layer capacitance of porous carbon, and additional pseudocapacitances originating from the variation in oxidation states ...

Regulating Oxygen Substituents with Optimized Redox Activity in Chemically Reduced Graphene Oxide for Aqueous Zn‐Ion Hybrid Capacitor

“…[ 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.…”

Deep Eutectic Solvent‐Induced Polyacrylonitrile‐Derived Hierarchical Porous Carbon for Zinc‐Ion Hybrid Supercapacitors

“…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.…”

Towards High‐Performance Zinc‐Based Hybrid Supercapacitors via Macropores‐Based Charge Storage in Organic Electrolytes

“…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 ).…”