High‐Performance 2.6 V Aqueous Asymmetric Supercapacitors based on In Situ Formed Na_0.5MnO₂ Nanosheet Assembled Nanowall Arrays

Abstract

The voltage limit for aqueous asymmetric supercapacitors is usually 2 V, which impedes further improvement in energy density. Here, high Na content Birnessite Na MnO nanosheet assembled nanowall arrays are in situ formed on carbon cloth via electrochemical oxidation. It is interesting to find that the electrode potential window for Na MnO nanowall arrays can be extended to 0-1.3 V (vs Ag/AgCl) with significantly increased specific capacitance up to 366 F g . The extended potential window for the Na MnO electrode provides the opportunity to further increase the cell voltage of aqueous asymmetric supercapacitors beyond 2 V. To construct the asymmetric supercapacitor, carbon-coated Fe O nanorod arrays are synthesized as the anode and can stably work in a negative potential window of -1.3 to 0 V (vs Ag/AgCl). For the first time, a 2.6 V aqueous asymmetric supercapacitor is demonstrated by using Na MnO nanowall arrays as the cathode and carbon-coated Fe O nanorod arrays as the anode. In particular, the 2.6 V Na MnO //Fe O @C asymmetric supercapacitor exhibits a large energy density of up to 81 Wh kg as well as excellent rate capability and cycle performance, outperforming previously reported MnO -based supercapacitors. This work provides new opportunities for developing high-voltage aqueous asymmetric supercapacitors with further increased energy density.

Stabilized Molybdenum Trioxide Nanowires as Novel Ultrahigh‐Capacity Cathode for Rechargeable Zinc Ion Battery

“…[1][2][3][4][5][6][7][8] As one of the most promising energy storage devices, aqueous zinc-ion batteries (ZIBs) has gained ever-increasing attention on account of its outstanding safety, high theoretical capacity (Zn: ≈820 mAh g −1 ), low cost as well as environmental benignity. [1][2][3][4][5][6][7][8] As one of the most promising energy storage devices, aqueous zinc-ion batteries (ZIBs) has gained ever-increasing attention on account of its outstanding safety, high theoretical capacity (Zn: ≈820 mAh g −1 ), low cost as well as environmental benignity.…”

Heterostructural Graphene Quantum Dot/MnO2 Nanosheets toward High‐Potential Window Electrodes for High‐Performance Supercapacitors

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Metal Oxide and Hydroxide–Based Aqueous Supercapacitors: From Charge Storage Mechanisms and Functional Electrode Engineering to Need‐Tailored Devices

“…For example, FeWO 4 ||MnO 2 (both electrodes are pseudocapacitive) were assembled in an asymmetric coin cell, working in 5 m LiNO 3 electrolyte. [121] Based on the formation of composite materials, containing carbon cloth with increased overpotential for oxygen and hydrogen evolution in neutral electrolytes, the Na 0.5 MnO 2 /carbon cloth could operate in a working potential range of 0-1.3 V and carbon-coated Fe 3 O 4 /carbon cloth could operate in a working potential range of −1.3 to 0 V (Figure 14b). α-Fe 2 O 3 nanoneedle/Ni nanotube||MnO 2 nanosheet/Ni nanotube cells operated in Na 2 SO 4 aqueous electrolyte or Na 2 SO 4 /PVA polymer gel electrolyte [82] and delivered better redox performance due to the higher ionic conductivity of the liquid form.…”