Polypyrrole/SnCl2 modified bacterial cellulose electrodes with high areal capacitance for flexible supercapacitors

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm−2 at 1 mA cm−2, good flexibility with a higher value (204.6 mF cm−2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg−1 (with a power density of 3.2 kW kg−1) and a maximum power density of 4.2 kW kg−1 (with an energy density of 3.1 Wh kg−1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

All‐Solid‐State Cable‐Type Supercapacitors with Ultrahigh Rate Capability

Facile strategy for mass production of polymer-supported film electrodes for high performance flexible symmetric solid-state supercapacitors

Agar-based porous electrode and electrolyte for flexible symmetric supercapacitors with ultrahigh energy density

Construction of extensible and flexible supercapacitors from covalent organic framework composite membrane electrode

Carbon nanotubes (CNTs) grown on the carbon fiber paper (CFP) via chemical vapor deposition system is used as flexible substrate. NiO nanoparticles are electrodeposited onto CNTs/CFP flexible substrate by electrochemical deposition technique, which is used as a flexible electrode for supercapacitors. The NiO@CNTs/CFP electrode displays specific capacitance as high as 1317 F g−1 at a current density of 1.2 A g−1, which can preserve a capacitance retention of 90.6 % with a high current density of 9.6 A g−1. After 3000 cycles, the composite electrode can retain 90 % of initial capacitance, showing good cyclability. Meanwhile, the 3D porous nanostructure of NiO@CNTs/CFP electrode can offer a great opportunity to fabricate a high-performance flexible binder-free supercapacitor electrode, in which all of the materials could take part in the charge-storage process with their surface in direct contact with the electrolyte.

We report a strategy to employ two-dimensional Ti3C2Tx MXene as a flexible, conductive, and electrochemically active binder for one-step fabrication of MXene-bonded activated carbon as a flexible electrode for supercapacitors in an organic electrolyte. In this electrode, the activated carbon particles are encapsulated between the MXene layers, eliminating the need for insulative polymer binders. MXene plays a multifunctional role in the electrode, including as a binder, a flexible backbone, a conductive additive, and an additional active material. The synergetic effect of MXene and activated carbon constructs a three-dimensional conductive network and enlarges the distance between the MXene layers, greatly enhancing the electrode capacitance and rate capability. As a result, the flexible MXene-bonded activated carbon electrode exhibits a high capacitance of 126 F g–1 at 0.1 A g–1 and a retention of 57.9% at 100 A g–1 in an organic electrolyte, which is required for developing high-performance, flexible supercapacitors.

A morphology control engineered strategy of Ti3C2Tx/sulfated cellulose nanofibril composite film towards high-performance flexible supercapacitor electrode

Supercapacitors (SCs) have drawn considerable attention as one of the energy storage devices. The key to fabricating flexible supercapacitors lies in the acquirement of flexible electrodes. In this study, the manganese oxide (MnO2) and reduced graphene oxide (RGO) hybrid films (MnO2/RGO) were prepared by a filtration deposition and thermal reduction technique. Electrochemical measurements show that the hybrid films exhibit a specific capacitance of 333.9 F g−1 at 0.5 A g−1, and 87% capacitance after 3000 cycles at 0.5 A g−1. The flexible symmetric SCs was further fabricated with two pieces of MnO2/RGO hybrid films as electrodes. The fabricated flexible and sandwich type symmetrical SCs exhibited a safe working range with a potential window of 0–0.7 V with a maximum energy density of 23.5 Wh kg−1 at 0.5 A g−1 and the maximum power density of 1716.9 W kg−1 at 2.25 A g−1.

A facile strategy for the preparation of N-doped carbon/FeOx-decorated carbon cloth (CC@NC/FeOx) as supercapacitor electrode is reported in this work. In this strategy, the oxidant Fe3+ used for oxidizing pyrrole to polypyrrole (PPy) on the cotton cloth simultaneously acts as the precursor of FeOx in CC@NC/FeOx. N-doped carbon derived from the carbonization of PPy coated on the carbonized cotton cloth is obtained during the heat treatment. The as-prepared integrated, binder-free, and flexible CC@NC/FeOx electrode shows a good specific supercapacitance (1594.0 F g−1 at the scan rate of 1 mV s−1 and 739.0 F g−1 at 10 mV s−1). The assembled CC@NC/FeOx-based solid-state symmetrical supercapacitor (CC@NC/FeOx-SSC) exhibits 1.35 F cm−2 at the scan rate of 1 mV s−1. The high surface area from the nanosheet structure and the excellent conductivity due to the existence of Fe3O4 contributes to their rate capability and the cyclability. This simple strategy offers an environmentally friendly, cost-effective and easily scaled-up route for the integrated, binder-free, and flexible supercapacitor electrode.

Synergistic combination of carbon conductive and flexural additives for flexible screen-printed supercapacitor electrodes

A low-cost and simple approach involving soaking and electrochemical deposition is employed to deposit carbon nanotubes (CNTs) and Ni-Co-S (NCS) on papers to prepare paper-based electrodes for flexible solid-state symmetric supercapacitors. The as-prepared Paper-CNTs-NCS electrode shows excellent electrochemical performance such as high areal capacitance and good rate capability. In addition, the electrode possesses good mechanical stability even after bending for 100 cycles. The symmetric supercapacitor (SC) based on the NCS-CNTs paper electrode is fabricated and exhibits a maximum energy density of 4.2 mWh Wh/m2 and power density of 1.26 W/m2.

Nowadays, rationally preparing heterostructure materials can not only make up for the shortage of individual components, but also exert unexpected performance through synergistic interactions between the components. Herein, a core–shell of WS2@NiCo2O4 screw-like heterostructure arrays grown on carbon cloth (CC) was prepared by a two-step solvothermal method for supercapacitors. As a binder-free flexible electrode, a high areal capacitance of 2449.9 mF cm–2 can be achieved for WS2@NiCo2O4/CC at a current density of 1 mA cm–2. Benefiting from the core–shell of the WS2@NiCo2O4 heterostructure, the capacitive property of the flexible WS2@NiCo2O4/CC electrode is better than those of WS2/CC and NiCo2O4/CC electrodes. Based on WS2@NiCo2O4/CC electrodes, the assembled flexible solid-state symmetric supercapacitor (FSS) device shows a high energy density of ∼45.67 W h kg–1 at a power density of 992.83 W kg–1. Meantime, the WS2@NiCo2O4/CC-assembled FSS device also exhibits high cycling stability with an excellent capacity retention of ∼85.59% after 5000 cycles.

Flexible supercapacitors have attracted great interest as energy storage devices because of their promise in applications such as wearable and smart electronic devices. Herein, a novel flexible supercapacitor electrode based on gallium nitride nanowire (GaN NW)/graphite paper (GP) nanocomposites is reported. The outstanding electrical conductivities of the GaN NW (6.36 × 102 S m-1 ) and GP (7.5 × 104 S m-1 ) deliver a synergistically enhanced electrochemical performance that cannot be achieved by either of the components alone. The composite electrode exhibits excellent specific capacitance (237 mF cm-2 at 0.1 mA cm-2 ) and outstanding cycling performance (98% capacitance retention after 10 000 cycles). The flexible symmetric supercapacitor also manifests high energy and power densities (0.30 mW h cm-3 and 1000 mW cm-3 ). These findings demonstrate that the GaN/GP composite electrode has significant potential as a candidate for the flexible energy storage devices.

Boosting the electrochemical performance of polyaniline based all-solid-state flexible supercapacitor using NiFe2O4 as adjuvant