Flexible Symmetric Supercapacitor Research Articles

Construction of shrimp shell (SS) waste-based carbon electrode-gel polymer electrolyte (GPE) system for flexible symmetric supercapacitors

Shrimp shell waste based hierarchical porous carbon and gel polymer electrolytes (GPE) were prepared for supercapacitors.

A novel bilayer heterogeneous poly(ionic liquid) electrolyte for high-performance flexible supercapacitors with ultraslow self-discharge.

Flexible supercapacitors with high power density and long cyclic stability represent a promising candidate to be used as power supplies for portable electronics, but often suffer from the disadvantages of a limited working voltage and rapid self-discharge (spontaneous drop of open-circuit voltage). Here, we design a bilayer heterogeneous poly(ionic liquid) electrolyte (BHPE) consisting of a polycation complex and a polyanion complex with different zeta potentials to suppress the self-discharge of flexible symmetric supercapacitors. The resultant BHPE-based supercapacitors using active carbon/carbon nanotube composite electrodes exhibit a high working potential of 3.0 V and an energy density of 33 W h kg-1, which are comparable with those of devices obtained by using a homogeneous poly(ionic liquid) electrolyte (HPE). More significantly, the developed BHPE-based supercapacitor charged under forward bias exhibits a self-discharge time of 23.2 h, which is at least twice that of the device charged under reverse bias and is also much superior to those of HPE-based supercapacitors. The BHPE-based supercapacitors also possess excellent mechanical flexibility and stability, due to the stabilized interface contact between two layers of poly(ionic liquid)s.

Polyaniline wrapped graphene quantum dot decorated strontium titanate for robust high-performance flexible symmetric supercapacitors

Flexible supercapacitors: boosting performance with polyaniline-wrapped graphene quantum dots on strontium titanate.

Nanostructured zig-zag γ-Mo2N thin films produced by glancing angle deposition for flexible symmetrical solid-state supercapacitors

The performance of electrochemical capacitors strongly depends on their accessible surface area, chemical stability, and electrical conductivity. Simple columnar and zig-zag γ-Mo2N thin-film electrodes were prepared by magnetron sputtering. The latter is obtained by glancing angle deposition (GLAD), which is known for open porous structures due to the ballistic shadowing effect. As intended, the zig-zag structured γ-Mo2N electrode presents an outstanding area capacitance of 248 mF/cm2 at a scan speed of 50 mV/s, which is 4 times higher than that of the simple columnar one. Both of them exhibit excellent cycling stability of 95 % over 20,000 cycles (at 200 mV/s). The symmetrical solid-state supercapacitor prepared with the zig-zag structured γ-Mo2N thin film delivers an excellent power density of 107.1 W/cm3 at 33.8 mWh/cm3, and its volumetric capacitance is ∼ 3.5 times higher than the simple columnar structured γ-Mo2N device. Bending tests of such solid-state γ-Mo2N supercapacitors proved their mechanical flexibility to a bending angel of even 107°. Based on these studies we can conclude that the highly porous zig-zag structured γ-Mo2N-based electrodes prepared by GLAD combine outstanding electrochemical energy storage capabilities with excellent mechanical flexibility.

Cyclocrosslinked polyphosphazene modified MXene as aqueous supercapacitor

MXenes suffer from severe restacking and oxidative degradation, which may cause the loss of functional properties and hamper further applications in aqueous energy storage devices. It has been proven that MXenes' physical/electrochemical properties are strongly dependent on surface terminations. Establishing the relationship between the molecular configuration, electronic structure of surface modifier and the chemical/electrochemical properties is critical for designing MXene-based aqueous energy storage devices. Herein, a cyclocrosslinked polyphosphazene modified MXene (MXene/PZS) is fabricated by forming the Ti−O−P covalent bond through nucleophilic addition and successive condensation reaction. The MXene/PZS enables faster ion transport, enhanced ion accessibility and stronger oxidation resistance through the combined pillar, steric, and electronic effects provided by the cyclocrosslinked polyphosphazene, leading to pseudocapacitance of 380 F g−1 with superb rate performance. Moreover, the fabricated quasi-solid-state flexible symmetric supercapacitor shows an ultrahigh energy density of 12.26 Wh kg−1 at 0.125 kW kg−1, displaying remarkable flexibility and integrability. Our findings provide a holistic understanding of how the MXenes' physical/electrochemical properties influenced by the surface modifier, thus promoting the design of MXene-based aqueous energy devices.

Highly Efficient Solvothermal Synthesis of Poly(1,5-diaminoanthraquinone) Nanoflowers for Energy and Environmental Applications.

Poly(1,5-diaminoanthraquinone) (PDAA) has attracted more interest because of its unique molecular structure. However, the lower polymerization yield limits its practical application. Here, the solvothermal chemically oxidative polymerization of 1,5-diaminoanthraquinone (DAA) was developed, and the well-defined PDAA nanoflowers were obtained with a high yield of 72.6% within 16 h. The PDAA nanoflower-based flexible film electrodes were fabricated with expandable graphene as conductive support, delivering a capacitance of 277 F g-1 and 258 mF cm-2 at 0.5 A g-1 (1 mA cm-2) and superior cycling stability with retention of 99% after 10000 cycles. The flexible symmetric solid-state supercapacitors (SSSCs) possessed a high capacitance of 52.5 F g-1 at 0.25 A g-1 and 96.6 mF cm-2 at 1 mA cm-2 and had only a 14% capacitance loss after 10000 cycles at 0.1 V s-1 as well as excellent flexibility. Besides, the PDAA nanoflowers could be used as self-separable adsorbent for methylene blue (MB) with a capacity of 93.8 mg g-1 at pH 9.

High‐performance Flexible Symmetric Supercapacitor Based on Heterostructured PANI@MoS2 Nanocomposite Electrode

AbstractThree‐dimensional (3D) heterostructured molybdenum disulfide (MoS2) is used as base materials for aniline monomer in situ polymerization on its surface. It is found that the aniline addition has a remarkable effect on the energy storage of the final compounds due to the improvement of the conductivity and structure stability combined with the synergistic effect between the two types of species. The optimal compound of PANI@MoS2‐150 not only shows a high capacitance value of 801.4 F ⋅ g−1 at a current density of 0.5 A ⋅ g−1 but also provides a high retention rate of 77.4 % after 10,000 cycles. The capacitance fading may be due to the increase of the internal resistance analyzed by EIS. Furthermore, a flexible symmetric supercapacitor based on PANI@MoS2‐150 has also been fabricated and the specific capacitance reaches 105 F ⋅ g−1 at a current density of 1 A ⋅ g−1. Impressively, the capacitance retention is larger than 100 % undergoing 10,000 cycles. Besides, the highest energy density of 21 Wh ⋅ kg−1 was obtained. Additionally, the fabricated symmetric supercapacitor demonstrates excellent flexibility.

Wet oxidative functionalization of carbon nanotube cloth to boost its performance as a flexible supercapacitor electrode

Electrochemical recharging behavior of a binder-free flexible carbon nanotube cloth (CNTC) material in respect to aqueous supercapacitor applications is reported. To provide high enough pseudocapacitance, the surface of CNTC was exposed to wet oxidative functionalization by a KMnO4 treatment in an acidic medium. We report the effect of a KMnO4 to CNT molar ratio on capacitance, electrical resistivity and specific surface area of the CNTC material. The change in the composition of oxygen-containing interfacial functional groups attached to the carbon surface is also investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption methods. For the most oxidized CNTC sample the capacitance of ca. 71 F g−1 (29 µF cm−2BET) in 0.5 M H2SO4 (slightly decreasing with a scan rate up to 100 mV s−1) with the retention of ca. 99% during 30,000 recharging cycles as well as specific resistivity of ca. 31 µΩ m are achieved. Finally, two flexible symmetric supercapacitor prototypes based on a 38% H2SO4 solution and operating at 1.3 or 1.5 V were assembled from the freestanding and graphite foil supported functionalized CNTC electrodes, respectively. For the former device, the volumetric capacitance of ca. 22 F cm−3, power density of ca. 10 kW l−1 and energy density of ca. 3 Wh l−1 (per total volume of both electrodes) are demonstrated. The issues of the long-term stability and self-discharge behavior of assembled prototypes are also considered. Reported results allow us to consider the functionalized CNTC material as a promising electrode material for flexible aqueous supercapacitors.

Preparation of in-situ N/O co-doped lily-derived porous carbon framework material and its application in supercapacitors

The choice of an activator and activation method is crucial to the preparation of high-quality activated carbon. Herein, inspired by a foaming strategy, we selected KMnO4 as activator, and hierarchical porous framework carbon material was prepared via lily powder being fully foamed and activated in the KMnO4 hot solution. The Lily-derived Porous Carbon Material (LPCM) possesses the characteristics of in-situ co-doping of N and O. The maximum specific surface area of the obtained sample was 1852.5 m2g-1, and the corresponding total pore volume was 1.11 cm3g-1. Due to the interconnected hierarchical pore network structure and rich O (13.16 at%) & N (3.31 at%) contents, at 600 °C, the specific capacitance of the LPCM was 352 F g−1 at 0.5 A g1 and the cycling reliability was 100% after 10,000 charges and discharges. In addition, the voltage window of All-solid-state Symmetric Flexible Supercapacitor (ASFS) fabricated with PVA-KOH gel electrolyte was 1.4 V. And the fabricated ASFS device had energy density of 23.82 Wh kg−1 at 700 W kg−1. At the same time, two ASFSs in series could light up a small red bulb and maintained for more than 6 min.

Peripheral octamethyl-substituted nickel(II)-phthalocyanine-decorated carbon-nanotube electrodes for high-performance all-solid-state flexible symmetric supercapacitors

Construction of advanced electrode materials with unique performance for supercapacitors (SCs) is essential to achieving high implementation in the commercial market. Here, we report a novel peripheral octamethyl-substituted nickel(II) phthalocyanine (NiMe2Pc)-based nanocomposite as the electrode material of all-solid-state SCs. The highly redox-active NiMe2Pc/carboxylated carbon nanotube (CNT-COOH) dendritic nanocomposite provides rapid electron/electrolyte ion-transport pathways and exhibits excellent structural stability, resulting in high-capacity activity and impressive cycling stability. The composite prepared with the optimized weight ratio of NiMe2Pc:CNT-COOH (6:10) showed the highest specific capacitance of 330.5 F g−1 at 0.25 A g−1. The constructed NiMe2Pc/CNT-COOH-based all-solid-state symmetric SC device showed excellent performance with a maximum energy density of 22.8 Wh kg−1 and outstanding cycling stability (111.6% retained after 35,000 cycles). Moreover, flexible carbon cloth significantly enhanced the energy density of the NiMe2Pc/CNT-COOH all-solid-state symmetric device to 52.1 Wh kg−1 with 95.4% capacitance retention after 35,000 cycles, and it could be applied to high-performance flexible electronics applications. These findings provide a novel strategy to design phthalocyanine-based electrode materials for next-generation flexible SC devices.

A high-frequency flexible symmetric supercapacitor prepared by the laser-defocused ablation of MnO2 on a carbon cloth

A high-frequency flexible symmetric supercapacitor prepared by the laser-defocused ablation of MnO2 on a carbon cloth

Studies on fabrication of high-performance flexible printed supercapacitor using cobalt hydroxide nanowires

We report the successful fabrication and testing of a printed symmetric flexible supercapacitor based on cobalt hydroxide nanowire-carbon ink composite. The urea hydrolysis method provides a controlled way of cobalt hydroxide nanowire formation. The microscopic studies reveal nanowires with an average diameter of approximately 70 nm. Moreover, the material exhibited a high specific surface area of 13.08 m2g−1 and a pore volume of 0.060 cc g−1. Electrochemical studies with the nanocomposite revealed a very high areal capacitance. The cobalt hydroxide nanowire was used for fabricating a printed supercapacitor prototype using PVA/KOH gel as the electrolyte. It exhibited a high areal capacitance of 6.27 mF cm−2 with 0.7101 μWh cm−2 areal energy density and 32.7 μW cm−2 areal power density. Excellent capacitance retention was observed even after 8500 charge-discharge cycles. Series combination of printed capacitors yields summation of individual potentials, and its application was demonstrated using different LEDs and electronic devices. Furthermore, excellent capacitance retention at various bending angles and the performance remains the same even after 1500 bending cycles show high mechanical stability. Hence, it finds potential applications in flexible and wearable electronics.

RETRACTED ARTICLE: Polydopamine-modified MWCNT/graphene oxide hybrid 3D carbon nano-structure for flexible symmetric supercapacitor electrodes

The nanocarbon-based three-dimensional carbon nano-structure was prepared from the combination of one-dimensional multi-walled carbon nanotubes (MWCNTs) and two-dimensional graphene oxide by a simple hydrothermal method. The MWCNT/graphene hybrid hydrogel (CGOH) was used as electrode, and it exhibited higher specific capacitance (193.3 F g−1) compared to graphene oxide hydrogel (62.5 F g−1) due to the increase of electrical conductivity. Further enhancement of the capacitance was studied in this work by utilizing polydopamine (PDA) coating on the CGOH surface and heat treatment at 600 °C under argon gas condition for 2 h (PDA-CGOH-600). The specific capacitance of the PDA-CGOH-600 (217.4 F g−1) was enhanced by 12.5% compared to the CGOH. Using these hybrids, the flexible symmetric supercapacitor (FSS) devices were prepared with a solid polymer electrolyte (polyvinyl alcohol/sulfuric acid). The charge/discharge tests of FSS device confirmed that the highest capacitance of the FSS based on PDA-CGOH-600 because of the nitrogen-doping effect and the graphitic carbon formation. Furthermore, FSS device can be applied in the wire-shaped supercapacitor and good parameters of the energy storage device were achieved, such as specific capacitance of 50 mF cm−2, stability during 3000 times of charge/discharge, as well as stretchability and bending ability.

Solvothermal in-situ preparation of poly(1,5-diaminoanthraquinone) grafted graphene with superior electrochemical performance

Poly(1,5-diaminoanthraquinone) (PDAA) has attracted intense interests as electrode materials for supercapacitors. The interaction between PDAA and conductive frameworks plays an important role on the electrochemical performance of the flexible devices. Here, facile and efficient strategy was developed to covalently graft PDAA onto graphene oxide (GO) via solvothermal in-situ chemical oxidation polymerization, in which GO was oxidized and cut into pieces to produce more functional groups for PDAA grafting. Owing to the strong interaction, the PDAA-rGO/rEGO based flexible symmetric solid-state supercapacitors (SSSCs) possessed a capacitance of 203.1 mF cm−2, power density of 241.5 mW cm−2 and energy density of 18.0 mWh cm−2 at 0.50 mA cm−2, with superior capacitance retention of 92.5% and 93.3% after 10000 CV cycles and 300 cycles of 180°-bending.

Resilient bismuthene-graphene architecture for multifunctional energy storage and wearable ionic-type capacitive pressure sensor device

A facile resilient bismuthine-anchored graphene architecture is reported as multifunctional all-solid-state flexible supercapacitors and ionic-type capacitive sensor. Meanwhile, an electrons/ions dual transport channels design is achieved by inserting elaborately conductive bismuthene flakes into hierarchical porous aerogel framework. This strategy concurrently realizes the expansion of interlayer space for favoring electrolyte infiltration, and boost of interlayer conductivity to ensure interlayer electrons transport, endowing the device with attractive electrochemical energy storage and pressure sensing performance. As a result, the fabricated flexible symmetric supercapacitor device using bismuthene-graphene architecture as both negative and positive electrode delivers an excellent energy density of 45.55 Wh/kg at 400 W/kg along with cycling stability of 89.24% even after 3600 charge/discharge cycles. The bismuthene-graphene aerogel-based capacitive sensor with the hierarchical porous architecture demonstrates a high sensitivity of 0.326 kPa−1. Furthermore, the sensing mechanisms of ionic-type pressure sensor is explored. This work clearly demonstrates that the novel 3D hierarchical bismuthene-graphene architecture can be widely used in multifunctional devices of supercapacitors and tactile sensors.

Battery-like flexible supercapacitors from vertical 3D diamond/graphite composite films on carbon cloth

Flexible supercapacitors (SCs) based on carbon nanomaterials are one of the promising energy storage devices for wearable electron devices. However, their low energy density and cycle stability severely restrict further practical applications. The development of unique capacitor electrodes is expected largely to overcome these challenges. Herein, vertical 3D diamond/graphite (DG) composite films are directly grown on carbon cloth (CC) using a microwave plasma chemical vapor deposition (MPCVD) technique. Thin, straight nanosheets, consisted of diamond as core and graphite as shell, are interlaced with each other to form a 3D porous structure. As a binder- and additive-free electrode material, the DG/CC electrodes are used to construct electrical double layer capacitors (EDLCs) in diluted H2SO4 solution and pseudocapacitors (PCs) using Fe(CN)63−/4- redox electrolytes. Both EDLCs and PCs exhibit large specific capacitance and high capacitance retention. When assembled as all-solid-state flexible symmetric SCs, they offer high full-cell capacitances of 30.4 and 143.6 mF cm−2 at 10 mV s−1 for EDLCs and PCs, respectively. The power densities are 6.3 μW cm−2 and 3.0 mW cm−2 for EDLCs and PCs, together with their energy densities of 3.7 and 86.2 μWh cm−2, respectively. As flexible SCs, the specific capacitance can be completely recovered for EDLCs and has only about 6.7% loss for PCs even after the U-shape bending state. Such vertical 3D porous DG films are thus promising for the construction of high-performance battery-like SCs for an intelligent wearable energy supplier.

Ti3C2Tx/g-C3N4 heterostructure films with outstanding capacitance for flexible Solid-state supercapacitors

With the popularity of intelligent portable electronic devices, bendable and flexible electronic equipment, such as portable miniature devices, wearable electronics, smart clothing, electronics, display, skin flexible smartphones and implantable medical devices have become a development trend.As potential energy storage device, flexible supercapacitors have attracted extensive attention. Ti3C2Tx MXenes, which has high capacitance, mechanical strength and flexibility, perfectly meets the requirements of flexible energy storage devices.In order to avoid stacking, increase layer spacing, and enhance charge transfer efficiency, the Ti3C2Tx/g-C3N4 heterostructure is constructed by self-assembly method.The flexible self-supporting electrode is prepared by vacuum assisted filtration, which successfully widen the potential window and significantly improve the capacitance performance. The specific capacitance of the electrode in 1 M H2SO4 electrolyte reaches 414F/g at 1A/g.The electrode can simultaneously act as a fluid collector to construct a simple ultra-thin device.The flexible all-solid symmetric supercapacitor is assembled and the energy density reaches 23.98Wh/Kg when the power density is 139.66 W/Kg. Encouragingly, the device can maintain stable performance under 180° bending conditions.The above excellent performance confirms the applicability of supercapacitors based on Ti3C2Tx/g-C3N4 heterostructure films for future portable, flexible or wearable electronic energy storage devices.

Atmosphere‐free activation methodology for holey graphene/cellulose nanofiber‐based film electrode with highly efficient capacitance performance

AbstractAn efficient chamber‐induced activation method was applied for the preparation of holey graphene/cellulose nanofiber‐based film with high specific surface area (SSA) and multiple channels through the graphene nanosheets. With the cellulose nanofiber (CNF) simultaneously serving as “dispersing agent,” “spacer,” and “activating agent,” the graphene oxide (GO) nanosheets are perforated by the pyrolysis gas from CNF in the confined space inside the hybrid films, uniformly dispersed, and sandwiched between CNF networks with less agglomeration and restacking. Additionally, we have proved that H2O and H2 are primarily responsible for the activation and etching of GO/CNF film. As the CNF content increases, the mesoporosity of the activated reduced GO/CNF (A‐RGO/CNF) film increases, and the graphene nanosheets show more nanopore perforations. Benefitting from the high SSA, high density, moderate mesoporosity, and abundant channels for ion diffusion through the graphene nanosheets, the A‐RGO/CNF film exhibits the highest specific capacitance of 323 (236) F g−1 (F cm−3) at 1 A g−1. For the A‐RGO5/CNF5 film containing half CNF and half GO, an excellent comprehensive electrochemical performance including superior rate performance (208 (160) F g−1 (F cm−3) at 60 A g−1) is exhibited. Moreover, the A‐RGO5/CNF5 electrode in an all‐solid‐state flexible symmetric supercapacitor delivers a high specific capacitance of 250 (193) F g−1 (F cm−3) at 1 A g−1. This study provides a novel idea for the preparation of holey graphene‐based film for supercapacitor electrodes. The strategy of simultaneously employing CNF as “dispersing agent,” “spacer,” and “activating agent” also offers a new vision for the assembly of homogeneous nanohybrid material and the utilization of pyrolysis gas.

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

Polypyrrole (PPy)/bacterial cellulose (BC) composite membranes are a promising kind of lightweight and flexible electrodes for supercapacitors. Herein, we explored a facile and efficient electrostatic self-assembly approach to uniformly depositing anion-doped PPy onto positively charged SnCl2-modifed BC (SBC). The obtained PPy@SBC electrode exhibited a high areal capacitance of 5718 mF cm−2 at a current density of 0.5 mA cm−2, a desirable capacitance retention of 83.1% at 5.0 mA cm−2 and excellent cycling stability (a capacitance retention of 86.8% after 10,000 cycles at 10 mA cm−2). A symmetric flexible supercapacitor was further assembled with the PPy@SBC electrodes, which delivered outstanding mechanical flexibility with negligible capacitance decay under different bent states. This study shows impressive potential in fabricating high-performance electrodes for flexible supercapacitors.

A high-frequency flexible symmetric supercapacitor prepared by the laser-defocused ablation of MnO2 on a carbon cloth

The rapid development of flexible electronics has produced an enormous demand for supercapacitors. Compared to batteries, supercapacitors have great advantages in terms of power density and cycling stability. They can also respond well on a time scale of seconds, but most have a poor frequency response, and behave more like pure resistors when used at high frequencies (e.g., above 100 Hz). It is therefore challenging to develop supercapacitors that work at a frequency of over 100 Hz. We report a high-frequency flexible symmetrical supercapacitor composed of a MnO2@carbon cloth hybrid electrode (CC@MnO2), which is synthesized by the defocused-laser ablation method. This CC@MnO2-based symmetric supercapacitor has an excellent specific areal capacitance of 1.53 mF cm−2 at a frequency of 120 Hz and has good cycling stability with over 92.10% capacitance retention after 100 000 cycles at 100 V s−1. This remarkable electrochemical performance is attributed to the combined effect of the high conductivity of the 3D structure of the carbon cloth and the exceptional pseudo-capacitance of the laser-produced MnO2 nanosheets. The defocused laser ablation method can be used for large-scale production using roll-to-roll technology, which is promising for the wide use of the supercapacitor in high-frequency electronic devices.