Hierarchical Nanosheets/Walls Structured Carbon‐Coated Porous Vanadium Nitride Anodes Enable Wide‐Voltage‐Window Aqueous Asymmetric Supercapacitors with High Energy Density

Abstract

The energy density of aqueous asymmetric supercapacitors (ASCs) is usually limited by low potential windows and capacitances of both anode and cathode. Herein, a facile strategy to fabricate hierarchical carbon‐coated porous vanadium nitride nanosheet arrays on vertically aligned carbon walls (CC/CW/p‐VN@C) as anode for aqueous ASCs is reported. The potential window of CC/CW/p‐VN@C electrode can be stably extended to –1.3 to 0 V (vs Ag/AgCl) with greatly improved specific capacitance (604.8 F g −1 at 1 A g −1 ), excellent rate capability (368 F g −1 at 60 A g −1 ), and remarkable electrochemical stability. To construct ASCs, a Birnessite Na 0.5 MnO 2 nanosheet arrays (CC/CW/Na 0.5 MnO 2 ) cathode is similarly built. Benefiting from the matchable potential windows and high specific capacitances of the rationally designed anode and cathode, aqueous CC/CW/p‐VN@C||CC/CW/Na 0.5 MnO 2 ASCs with a wide voltage window of 2.6 V are fabricated. Moreover, the ASCs showcase an ultrahigh energy density up to 96.7 W h kg −1 at a high power density of 1294 W kg −1 , and excellent cycling stability (92.5% retention after 10 000 cycles), outperforming most of previously reported ASCs and even comparable to that of organic electrolyte supercapacitors (SCs). This efficient strategy for fabricating 2.6 V aqueous ASCs suggests a promising research system for high energy density SCs.

Coupling PEDOT on Mesoporous Vanadium Nitride Arrays for Advanced Flexible All‐Solid‐State Supercapacitors

“…[28] Accordingly, several modification strategies have been adopted on VN to obtain enhanced performance. [29] One way is to dope heteroatoms (metal ion or nonmetal element) into VN to stabilize its intrinsic cell structure. Another popular way is to coat a protective shell or layer on VN.…”

NiCoSe2/Ni3Se2 lamella arrays grown on N-doped graphene nanotubes with ultrahigh-rate capability and long-term cycling for asymmetric supercapacitor

“…With the significant increase in the consumption of portable electronic devices, electric vehicles and mobile phones, supercapacitors (SCs) have recently drawn much attention due to their ultrahigh power density, long-span cycle life, lightweight and environment friendliness [1][2][3][4][5]. The currently available SCs, although able to possess versatile features, only have an energy density that is one to two orders of magnitude lower than that of a typical rechargeable ion battery [6,7]. The electrode materials are the key components of SCs, which determine their electrochemical performances.…”

Surface and Interface Engineering of Nanoarrays toward Advanced Electrodes and Electrochemical Energy Storage Devices

“…Using a VN NS array anode instead of AC, a solid-state SC based on fully 3D-NAs was also designed with excellent flexibility. [133] We also reported a non-polar quasi-solid-state asymmetrical SC using Ni-CNT NAs as both the cathode and anode. [134] The integration of the PVA-KOH hydrogel into 3D electrodes enabled a long cyclability of 10 000 times (nearly 100% capacitance retention); the CV profile was also kept unchanged under different bending degrees (Figure 9f,g).…”