All-Solid-State Fiber-Shaped Asymmetric Supercapacitors with Ultrahigh Energy Density Based on Porous Vanadium Nitride Nanowires and Ultrathin Ni(OH)₂ Nanosheet Wrapped NiCo₂O₄ Nanowires Arrays Electrode

Abstract

Fiber-shaped supercapacitors (FSC), among the most promising next-generation flexible energy storage devices, attract tremendous attention due to their high power density and rapid charging and discharging. However, their practical application is hindered by the low energy density that results from inferior specific capacitance and a limited voltage window. Herein, we design a flexible fiber-shaped asymmetric supercapacitor (FASC) with high energy density using vanadium nitride (VN) nanowires (NWs) on carbon nanotube fiber (CNTF) as negative electrode and ultrathin Ni(OH) 2 nanosheet wrapped nickel cobalt oxide (NiCo 2 O 4 ) to form a hierarchical nanowire array (HNWA) structure on CNTF as positive electrode. As-assembled FASC device has a maximum operational voltage of 1.6 V, with a highest areal capacitance of 291.9 mF/cm 2 (106.1 F/cm 3 ) and an energy density of 103.8 μWh/ cm 2 (37.7 mW/cm 3 ). The FASC device possesses excellent reliability and achieves a retaining capacitance of more than 90% after 3000 bending cycles, which boosts practical applications for next-generation flexible energy storage devices.

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

“…This can provide unique synergistic effects to facilitate the transfer of ions and electrons during electrochemical reactions process. In this context, ultrathin Ni(OH) 2 nanosheet wrapped NiCo 2 O 4 nanowires were grown on carbon nanotube fibers (CNTF) as the positive electrode, which provides a large accessible surface area in the electrolyte and improved ionic transportation, [ 207 ] as shown in Figure a. Unlike typical carbon‐negative electrode, highly conducting and porous vanadium nitride (VN) nanowires on CNTF were utilized as a pseudocapacitive negative electrode to assemble HSSC with a NiCo 2 O 4 @Ni(OH) 2 /CNTF positive electrode.…”

“…Reproduced with the permission. [ 207 ] Copyright, 2018, American Chemical Society. b) Schematic illustration of the synthesis procedure of metal silicate.…”

Atomic Modulation of 3D Conductive Frameworks Boost Performance of MnO2 for Coaxial Fiber-Shaped Supercapacitors

“…VN nanowires array was synthesized on CNT film by our previous method [ 25 ]. The Na 2 SO 4 /PVA sol–gel electrolyte was firstly prepared by mixing 10 g of PVA and 10 g of Na 2 SO 4 into 100 mL of deionized water under vigorous stirring at 85 °C for 2 h. The Zn–CuO@MnO 2 core–shell nanowires on Cu wires electrode were soaked into the Na 2 SO 4 /PVA sol–gel electrolyte for 5 min and then maintained at 60 °C for 2 h to evaporate excess moisture.…”

Recent Advances of Asymmetric Supercapacitors

“…[ 29,152–154 ] Recently, a variety of researches regarding the synthesis and electrochemical performance of metal nitrides including titanium nitride (TiN), and vanadium nitride (VN) were reported. [ 155–160 ] Compared with their oxide counterparts, the metal nitrides could exhibit enhanced conductivities and capacitance originating from the reversible redox reaction. [ 140 ] Wang et al.…”

“…synthesized VN nanowires through electrostatic spinning approach followed by calcination under NH 3 atmosphere. [ 156 ] The conductivities and electrochemical performance of VN were further improved with the combination of carbon nanotube fibers (VN NWs/CNTF). Meanwhile, Ni(OH) 2 nanosheet wrapped NiCo 2 O 4 composites (NiCo 2 O 4 @ Ni(OH) 2 ) with core–shell structure were adopted as cathode.…”