Flexible Supercapacitors Based on CNT/MnO₂-BP Composite Yarn Synthesized by In Situ Reduction

Abstract

Solid-state flexible supercapacitors are considered significant prospective energy storage devices, and carbon nanotube (CNT) yarn is an ideal electrode material for constructing linear flexible supercapacitors because of its high electrical conductivity and flexibility. However, the relatively low specific capacitance and energy density of a supercapacitor made of pure CNT yarn limits its application. Here, we prepared a CNT/MnO2-BP composite yarn via a facile one-step liquid deposition method by the innovative introduction of few-layer black phosphorous (BP) nanosheets. The redox reaction between the BP and the potassium permanganate forms MnO2 and an electrolyte of phosphorus acids (HxPOy). The two-ply yarn supercapacitor composed of the CNT/MnO2-BP composite yarn shows excellent electrochemical properties with a volumetric capacitance of 441.79 F cm−3 at the scanning rate of 0.01 V s−1 and an energy density of 9.82 mWh cm−3 at a power density of 441.79 mW cm−3. Herein, this work provides a way to improve the electrochemical performance of CNT yarn-based supercapacitors that can act as flexible energy storage devices for wearable electronics.

Anti-Shedding Nickel-Protection-Layer Boosting an Ultrahigh Loading Carbon Fiber@Co–NiSx Electrode to Deliver Superior Areal/Volumetric/Gravimetric Capacitance

“…As shown in Figure g, Ni-CP@Co 8% –NiS x achieves capacitance retention of 89.4% after 10,000 cycles. Moreover, compared with other recently reported electrodes as shown in Figures h and S14, the Ni-CP@Co 8% –NiS x in this work not only has a very high loading of active material but could also deliver a very high gravimetric and areal capacitance under high loading conditions. ,– The specific volumetric capacitance and corresponding areal capacitance of this electrode are much higher than any of the work reported at this stage. ,– Owing to the decrease in the impedance derived from the Co-doping and the external electroplated nickel layer and the inhibition effect of the external electroplated Ni layer on the shedding of active substances, the modified electrode could display good electrochemical performance.…”

Improved Capacitive Behavior of Birnessite Type Mn Oxide Coated on Activated Carbon Fibers

“…[22][23][24] Because of its abundance, high carbon content and mainly polyaromatic nature, asphaltene represents a promising precursor for carbon fibers which can be utilized in EDLCs as well as pseudocapacitors. [25][26][27][28][29][30][31][32][33] In this study, efforts are made to increase the specific capacitance of potassium birnessite type MnO 2 (referred to as birnessite type MnO 2 or δ-MnO 2 in this work) closer to its theoretical value by taking advantage of the high carbon content and conductivity of asphaltene based activated carbon fibers (ACF). Other Mn oxide/ carbon composite electrodes have been studied in the literature; e.g., MnO 2 /PANI by Zhu et al 25 and MnO 2 /carbon nanotubes (CNT) by Zhou et al 31 The effect of annealing in N 2 on the pseudocapacitive performance of δ-MnO 2 , as well as the charge storage mechanism of this material, are also investigated.…”

“…[25][26][27][28][29][30][31][32][33] In this study, efforts are made to increase the specific capacitance of potassium birnessite type MnO 2 (referred to as birnessite type MnO 2 or δ-MnO 2 in this work) closer to its theoretical value by taking advantage of the high carbon content and conductivity of asphaltene based activated carbon fibers (ACF). Other Mn oxide/ carbon composite electrodes have been studied in the literature; e.g., MnO 2 /PANI by Zhu et al 25 and MnO 2 /carbon nanotubes (CNT) by Zhou et al 31 The effect of annealing in N 2 on the pseudocapacitive performance of δ-MnO 2 , as well as the charge storage mechanism of this material, are also investigated. Carbon fibers activated using a chemical agent (KOH pellets), with a mass ratio of KOH/ACF = 3, were chosen based on previous work due to their high conductivity, high BET specific surface area (2290 m 2 g −1 ) and total pore volume of 1.27 cm 3 g −1 and good capacitive performance.…”

High Areal Capacitance of Flexible Supercapacitors Fabricated with Carbon Cloth-Carbon Fiber-TiO2 Electrodes and Different Hydrogel Polymer Electrolytes

“…Flexible electrodes used for SCs should be customarily electrically conducting, chemically stable, light weight, environmental-friendly and sufficiently mechanically stable without compromising with their flexibility. [21][22][23] Carbon fabric namely carbon cloth (CC) is considered as one of the most attracted electrode substrates for flexible SCs due to its light weight, low-cost, good flexibility, electrical conductivity, large surface area, and high mechanical stability. There are also other flexible electrode substrates known in the literature such as polyester textile, plastics, cotton fabrics, and cellulose papers.…”