Facile, Scalable, Eco-Friendly Fabrication of High-Performance Flexible All-Solid-State Supercapacitors

A highly porous freestanding supercapacitor electrode has been fabricated through a simple, inexpensive, bulk-scalable, and environmentally friendly method, without using any extra current collector, binder, or conducting additive. Benefiting from its unique micro-tubular hollow structure with a thin cell wall and large lumen, kapok fiber (KF) was used herein as a low-cost template for the successive growth of polypyrrole (PPy) through in situ chemical polymerization. This PPy-coated KF (KF@PPy) was blended with functionalized carbon nanotubes (f-CNTs) to form freestanding conductive films (KF@PPy/f-CNT) through a simple dispersion and filtration method. The hybrid film featuring the optimal composition exhibited an outstanding areal capacitance of 1289 mF cm−2 at a scan rate of 5 mV s−1. Moreover, an assembled all-solid-state symmetric supercapacitor featuring a PVA/H2SO4 gel electrolyte exhibited not only areal capacitances as high as 258 mF cm−2 (at a scan rate of 5 mV s−1) but also excellent cycling stability (97.4% of the initial capacitance after 2500 cycles). Therefore, this efficient, low-cost, scalable green synthesis strategy appears to be a facile and sustainable way of fabricating high-performance flexible supercapacitors incorporating a renewable cellulose material

Green synthesis of polypyrrole tubes using curcumin template for excellent electrochemical performance in supercapacitors

In this study, polypyrrole (PPy) having a unique hollow tubular structure was prepared through a simple and scalable one-step method of in situ chemical oxidative polymerization, employing curcumin, a plant-derived material, as a readily removable and eco-friendly template. PPy tubes (PPyT: PPyC1T1, PPyC1T2, PPyC1T4, PPyC2T2, and PPyC3T2) prepared under various conditions were then combined with functionalized carbon nanotubes (f-CNTs) to form freestanding electrodes. Among the tested composite electrodes, the PPyC3T2/f-CNT freestanding electrode exhibited the greatest morphological uniformity, a favorable hierarchical porous structure, the largest surface area, and excellent electrochemical properties. A record areal capacitance of 11 830.4 mF cm−2 at a current density of 2 mA cm−2 was obtained for the PPyC3T2/f-CNT-thick freestanding electrode at a high mass loading of 30 mg cm−2. In addition, a symmetric supercapacitor fabricated using the PPyC3T2/f-CNT-thick freestanding electrode exhibited an excellent areal capacitance (2732 mF cm−2 at a current density of 2 mA cm−2), an outstanding cycling stability (retention of 118.18% of its initial capacitance after 12 500 charge/discharge cycles), and a high energy density (242.84 μW h cm−2) and maximum power density (129.35 mW cm−2). These characteristics highlight the potential applicability of PPyT/f-CNT freestanding electrodes in high-performance supercapacitors

Flexible and freestanding electrodes based on polypyrrole/carbon nanotube/cellulose composites for supercapacitor application

In this study, freestanding paper-like composite films were fabricated using a simple, but scalable and efficient, approach: an environmentally friendly freeze-and-thaw process giving a porous fibrous matrix of cellulose and functionalized carbon nanotubes (f-CNTs), followed by in situ chemical polymerization for the incorporation of polypyrrole (PPy). A homogeneous porous fibrous matrix was formed as a result of strong hydrogen bonding between the f-CNTs and the regenerated cellulose; this material served as an excellent template for the uniform coating of PPy. The structural, morphological, thermal, and electrochemical properties of the as-prepared PPy/f-CNT/cellulose composite films were investigated to evaluate their potential for use as flexible, lightweight, and inexpensive freestanding electrode materials within flexible supercapacitors. The unique microstructure—with high electrical conductivity, good wettability, and a porous architecture—provided large interfacial areas for the storage/release of charge carriers and for the facile diffusion of electrolyte ions in the prepared composite electrodes. With these attributes, the freestanding electrode having the optimal PPy loading exhibited not only an excellent areal capacitance (2147 mF cm−2 at a current density of 1 mA cm−2) but also a good rate capability and an outstanding cycling stability. Moreover, the flexibility, environmental friendliness, and biodegradability of the PPy/f-CNT/cellulose composite films suggest that they will be suitable for use as green and sustainable electrode materials within flexible supercapacitors

Facile, Scalable, Eco-Friendly Fabrication of High-Performance Flexible All-Solid-State Supercapacitors

A highly porous freestanding supercapacitor electrode has been fabricated through a simple, inexpensive, bulk-scalable, and environmentally friendly method, without using any extra current collector, binder, or conducting additive. Benefiting from its unique micro-tubular hollow structure with a thin cell wall and large lumen, kapok fiber (KF) was used herein as a low-cost template for the successive growth of polypyrrole (PPy) through in situ chemical polymerization. This PPy-coated KF (KF@PPy) was blended with functionalized carbon nanotubes (f-CNTs) to form freestanding conductive films (KF@PPy/f-CNT) through a simple dispersion and filtration method. The hybrid film featuring the optimal composition exhibited an outstanding areal capacitance of 1289 mF cm-2 at a scan rate of 5 mV s-1. Moreover, an assembled all-solid-state symmetric supercapacitor featuring a PVA/H₂SO₄ gel electrolyte exhibited not only areal capacitances as high as 258 mF cm-2 (at a scan rate of 5 mV s-1) but also excellent cycling stability (97.4% of the initial capacitance after 2500 cycles). Therefore, this efficient, low-cost, scalable green synthesis strategy appears to be a facile and sustainable way of fabricating high-performance flexible supercapacitors incorporating a renewable cellulose material

Polypyrrole/Carbon Nanotube Freestanding Electrode with Excellent Electrochemical Properties for High-Performance All-Solid-State Supercapacitors

In this study, a facile and environmentally friendly method was used to prepare a freestanding supercapacitor electrode displaying excellent areal capacitance and good cycle life performance. First, we prepared polypyrrole nanoparticles (PPyNP) through a simple in situ chemical polymerization using the plant-derived material curcumin as a bioavailable template. A PPyNP/f-CNT freestanding composite electrode of high mass loading (ca. 14 mg cm–2) was prepared after blending the mixtures of the prepared PPyNP and functionalized CNTs (f-CNTs). The performance of the as-prepared material as a supercapacitor electrode was evaluated in a three-electrode setup using aqueous 1 M H2SO4 as the electrolyte. The PPyNP/f-CNT freestanding composite electrode exhibited a high areal capacitance of 4585 mF cm–2 and a corresponding volumetric capacitance of 176.35 F cm–3 at a current density of 2 mA cm–2. A symmetric all-solid-state supercapacitor assembled using two identical pieces of PPyNP/f-CNT composite electrodes exhibited maximum areal energy and power density of 129.24 μW h cm–2 and 12.5 mW cm–2, respectively. Besides, this supercapacitor device exhibited good cycle life performance, with 79.03% capacitance retention after 10,000 charge/discharge cycles. These results suggest practical applications for these PPyNP/f-CNT freestanding composite electrode-based symmetric all-solid-state supercapacitors

Lignin-Derived Quinone Redox Moieties for Bio-Based Supercapacitors

Because of their rapid charging and discharging, high power densities, and excellent cycling life stabilities, supercapacitors have great potential for use in electric vehicles, portable electronics, and for grid frequency modulation. The growing need for supercapacitors that are both efficient and ecologically friendly has generated curiosity in developing sustainable biomass-based electrode materials and electrolytes. Lignin, an aromatic polymer with remarkable electroactive redox characteristics and a large number of active functional groups, is one such candidate for use in renewable supercapacitors. Because its chemical structure features an abundance of quinone groups, lignin undergoes various surface redox processes, storing and releasing both electrons and protons. Accordingly, lignin and its derivatives have been tested as electroactive materials in supercapacitors. This review discusses recent examples of supercapacitors incorporating electrode materials and electrolytes derived from lignin, focusing on the pseudocapacitance provided by the quinone moieties, with the goal of encouraging the use of lignin as a raw material for high-value applications. Employing lignin and its derivatives as active materials in supercapacitor electrodes and as a redox additive in electrolytes has the potential to minimize environmental pollution and energy scarcity while also providing economic benefits

Synthesis of a series of novel imidazolium-containing ionic liquid copolymers for dye-sensitized solar cells

A series of imidazolium-containing ionic liquid copolymers has been synthesized through free radical copolymerizations of an imidazolium-containing ionic liquid monomer (MEBIm-I), poly(ethylene glycol) methyl ether methacrylate (POEM), and acrylonitrile at various molar ratios. A thorough investigation has been conducted to study the effects of the chemical structure on the ionic conductivities, ionic diffusion coefficients, and catalytic activities of the ionic liquid copolymers. The presence of the ethylene oxide segments enhanced the ionic diffusion coefficients and conductivities of the POEM-containing ionic liquid copolymers. The incorporation of suitable contents of acrylonitrile units enhanced the catalytic activities of the ionic liquid copolymers. The photovoltaic and electrochemical impedance properties of dye-sensitized solar cells (DSSCs) assembled from these ionic liquid copolymer–based electrolytes have been evaluated. A maximum power conversion efficiency of 7.57%, with a maximum short-circuit current density of 16.0 mA cm−2, an open-circuit voltage of 0.84 mV, and a fill factor of 57.0%, has been achieved for DSSCs based on the ionic liquid copolymers (architecture: fluorine-doped tin oxide (FTO) glass/TiO2/N719 dye/ionic liquid polymer–based electrolyte/Pt/FTO glass) under AM 1.5 illumination with an intensity of 100 mW cm−2