Flexible and high surface area composites of carbon fiber, polypyrrole, and poly(DMcT) for supercapacitor electrodes

Conjugated Polymers for Flexible Energy Harvesting and Storage

Since the discovery of conjugated polymers in the 1970s, they have attracted considerable interest in light of their advantages of having a tunable bandgap, high electroactivity, high flexibility, and good processability compared to inorganic conducting materials. The above combined advantages make them promising for effective energy harvesting and storage, which have been widely studied in recent decades. Herein, the key advancements in the use of conjugated polymers for flexible energy harvesting and storage are reviewed. The synthesis, structure, and properties of conjugated polymers are first summarized. Then, their applications in flexible polymer solar cells, thermoelectric generators, supercapacitors, and lithium-ion batteries are described. The remaining challenges are then discussed to highlight the future direction in the development of conjugated polymers.

Assembly of flexible CoMoO4@NiMoO4·xH2O and Fe2O3 electrodes for solid-state asymmetric supercapacitors

In this work, CoMoO₄@NiMoO₄·xH₂O core-shell heterostructure electrode is directly grown on carbon fabric (CF) via a feasible hydrothermal procedure with CoMoO₄ nanowires (NWs) as the core and NiMoO₄ nanosheets (NSs) as the shell. This core-shell heterostructure could provide fast ion and electron transfer, a large number of active sites, and good strain accommodation. As a result, the CoMoO₄@NiMoO₄·xH₂O electrode yields high-capacitance performance with a high specific capacitance of 1582 F g^-1, good cycling stability with the capacitance retention of 97.1% after 3000 cycles and good rate capability. The electrode also shows excellent mechanical flexibility. Also, a flexible Fe₂O₃ nanorods/CF electrode with enhanced electrochemical performance was prepared. A solid-state asymmetric supercapacitor device is successfully fabricated by using flexible CoMoO₄@NiMoO₄·xH₂O as the positive electrode and Fe₂O₃ as the negative electrode. The asymmetric supercapacitor with a maximum voltage of 1.6 V demonstrates high specific energy (41.8 Wh kg^-1 at 700 W kg^-1), high power density (12000 W kg^-1 at 26.7 Wh kg^-1), and excellent cycle ability with the capacitance retention of 89.3% after 5000 cycles (at the current density of 3A g^-1).

Bendable solid-state supercapacitors with Au nanoparticle-embedded graphene hydrogel films

In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded GH supercapacitors (NP-GH SCs) exhibit excellent capacitive performances, with large specific capacitance (135 F/g) and high energy density (15.2 W·h/kg). Moreover, the NP-GH SCs exhibit comparable areal capacitance (168 mF/cm²) and operate under tensile/compressive bending.

Coaxial CoMoO4 nanowire arrays with chemically integrated conductive coating for high-performance flexible all-solid-state asymmetric supercapacitors

Flexible all-solid-state supercapacitors have offered promising applications as novel energy storage devices based on their merits, such as small size, low cost, light weight and high wearability for high-performance portable electronics. However, one major challenge to make flexible all-solid-state supercapacitors depends on the improvement of electrode materials with higher electrical conductivity properties and longer cycling stability. In this article, we put forward a simple strategy to in situ synthesize 1D CoMoO4 nanowires (NWs), using highly conductive CC and an electrically conductive PPy wrapping layer on CoMoO4 NW arrays for high performance electrode materials. The results show that the CoMoO4/PPy hybrid NW electrode exhibits a high areal specific capacitance of ca. 1.34 F cm(-2) at a current density of 2 mA cm(-2), which is remarkably better than the corresponding values for a pure CoMoO4 NW electrode of 0.7 F cm(-2). An excellent cycling performance of nanocomposites of up to 95.2% (ca. 1.12 F cm(-2)) is achieved after 2000 cycles compared to pristine CoMoO4 NWs. In addition, we fabricate flexible all-solid-state ASC which can be cycled reversibly in the voltage range of 0-1.7 V, and exhibits a maximum energy density of 104.7 W h kg(-1) (3.522 mW h cm(-3)), demonstrating great potential for practical applications in flexible energy storage electronics.

High-Performance Solid-State Supercapacitors Fabricated by Pencil Drawing and Polypyrrole Depositing on Paper Substrate

A solid-state powerful supercapacitor (SC) is fabricated with a substrate of Xerox paper. Its current collector based on a foldable electronic circuit is developed by simply pencil drawing. Thin graphite sheets on paper provide effective channels for electron transmission with a low resistance of 95 Ω sq^-1. The conductive organic material of polypyrrole coated on thin graphite sheets acts as the electrode material of the device. The as-fabricated SC exhibits a high specific capacitance of 52.9 F cm^-3 at a scan rate of 1 mV s^-1. An energy storage unit fabricated by three full-charged series SCs can drive a commercial light-emitting diode robustly. This work demonstrated a simple, versatile and cost-effective method for paper-based devices.

Electrochemical preparation and characterization of a polypyrrole/nickel-cobalt hexacyanoferrate nanocomposite for supercapacitor applications

A new electrode material for supercapacitor application is introduced based on polypyrrole conductive polymer and nickel-cobalt hexacyanoferrate poly-nuclear inorganic compound.

Freestanding nanocellulose-composite fibre reinforced 3D polypyrrole electrodes for energy storage applications

It is demonstrated that 3D nanostructured polypyrrole (3D PPy) nanocomposites can be reinforced with PPy covered nanocellulose (PPy@nanocellulose) fibres to yield freestanding, mechanically strong and porosity optimised electrodes with large surface areas. Such PPy@nanocellulose reinforced 3D PPy materials can be employed as free-standing paper-like electrodes in symmetric energy storage devices exhibiting cell capacitances of 46 F g(-1), corresponding to specific electrode capacitances of up to ∼185 F g(-1) based on the weight of the electrode, and 5.5 F cm(-2) at a current density of 2 mA cm(-2). After 3000 charge/discharge cycles at 30 mA cm(-2), the reinforced 3D PPy electrode material also showed a cell capacitance corresponding to 92% of that initially obtained. The present findings open up new possibilities for the fabrication of high performance, low-cost and environmentally friendly energy-storage devices based on nanostructured paper-like materials.

Solid-state high performance flexible supercapacitors based on polypyrrole-MnO2-carbon fiber hybrid structure

A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an “in situ growth for conductive wrapping” and an electrode material of polypyrrole (PPy)-MnO₂ nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3 F cm⁻³ at a discharge current density of 0.1 A cm⁻³ and an energy density of 6.16 × 10⁻³ Wh cm⁻³ at a power density of 0.04 W cm⁻³, the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the “in situ growth for conductive wrapping” method might be generalized to open up new strategies for designing next-generation energy storage devices.