Flexible Solid-state Supercapacitors Research Articles

Using the amorphous‑carbon derived from cigarette filters for the fabrication of highly efficient flexible supercapacitors and role of the Sr3.2Y0.8Fe1.5Co1.5O10 layered perovskite to enhance their electrochemical performance

Eco-friendly solid-state supercapacitors (SCs) were fabricated using recycled cigarette filters and their electrochemical performance was studied. Firstly, new and smoked cigarette filters were pyrolyzed at 250 °C and obtained an amorphous‑carbon material, which consisted in particles of irregular shape mixed with other ones with folded sheet-like morphology. The amorphous‑carbon was mixed with graphene micro-flakes and it was employed to fabricate the energy storage devices. The flexible SC made with pyrolyzed new filter (PNF) had capacitance and energy density values of 623.4 F g−1 and 55.5 Wh kg−1, respectively, while the SC device made with pyrolyzed used filters (PUF) exhibited a capacitance and energy density of 1124.30 F g−1 and 188.9 Wh kg−1, respectively. The analysis by EDS demonstrated the presence of extra elements such as Ca, K, Mg and P in the PUF (which improved the ionic conductivity and electronic transport on the electrodes), therefore, the devices made with this PUF had 80 % more capacitance than the devices made with PNF. Later, the Sr3.2Y0.8Fe1.5Co1.5O10 (SYFECO) layered perovskite was incorporated on the SC electrodes made with PUF and obtained a higher capacitance and energy density of 2051.2 F g−1 and 210.3 Wh kg−1, respectively. Thus, the capacitance was enhanced by 82 % after adding the perovskite to the devices. Moreover, absorbance, Raman and XPS spectra were measured on the SC electrodes containing the SYFECO perovskite and they revealed the presence of oxygen vacancies, Co2+/Co3+ and Fe2+/Fe3+/Fe4+ species. Those ones were responsible for the charge storage by redox reactions. Hence, the results reported here corroborates that using recycled cigarette filters is a viable alternative for the manufacture of efficient SCs for portable/wearable applications.

Redox mediator-enhanced charge storage in dimensionally tailored nanostructures towards flexible hybrid solid-state supercapacitors.

Although extensive research has been performed on metal oxide-based supercapacitors during recent years, they remain lacking in their intrinsic conductivity and stability. To resolve this, 1D/2D heterostructure materials are being utilized, which significantly improves the performance and stability of both materials while employing their synergistic advantage consisting of morphologically tuned surfaces and superior electroactive sites. However, the performance remains unsatisfactory due to the sluggish faradaic reaction at the electrode/electrolyte interface. To address this challenge, we combined the synergistic advantage of morphological nanoengineering and the fast reaction kinetics of redox mediators, thus anticipating superior energy storage performance. A novel 1D/2D heterostructure of ZnCo2O4 (ZCO) and GaN was designed and implemented for the first time, and it demonstrated an excellent specific capacitance of 1693 F g-1 in the mixed electrolyte of KOH and K4[Fe(CN)6]. The all-solid-state flexible hybrid supercapacitor delivered an energy density of 92.63 W h kg-1 at a power density of 1287.52 W kg-1, with superb stability and mechanical endurance that outperformed previously reported ZCO-based materials. Additionally, we delineated the underlying mechanism governing the utilization of redox mediators along with morphological nanoengineering, which will facilitate the current development of state-of-the-art energy storage systems.

Enhancing electrochemical performance of ultrasmall Fe2O3-embedded carbon nanotubes via combusting-induced high-valence dopants

• Ti 4+ , Sn 4+ , and Zr 4+ were successfully incorporated in Fe 2 O 3 by a flame synthesis. • The Fe 2 O 3 /CNTs nanocomposite was directly obtained by a flame synthesis. • Combustion reaction generating oxygen functional groups favor the wettability of electrode. • High-valence metal ions optimize the electron structure and enhance Na + adsorption. • The flexible Ti-FeO-CNT//MnO 2 achieved an exceeding high operating potential of 2.0 V. Doping is a reasonable solution to improve the electronic structure and surface properties of nanomaterials. Herein, we propose a rapid and simple methodology, flame synthesis, as an effective preparation strategy for incorporating high-valence metal ions (Ti 4+ , Sn 4+ , and Zr 4+ ) into ultrasmall Fe 2 O 3 on carbon nanotube support (i.e., M-FeO-CNT). The resulting materials exhibit not only a boosted Na + adsorption as shown by density functional theory (DFT) calculations, but also display an increased oxygen deficiency. The electrochemical activity and charge transfer efficiency of Fe 2 O 3 can be improved by reasonably substituting Fe 3+ with Ti 4+ , Sn 4+ , and Zr 4+ . The electrochemical investigation of Ti-doped Fe 2 O 3 (Ti-FeO-CNT) electrode demonstrates a splendid specific capacitance of 1.25 F cm −2 at 1 mA cm −2 in 1 M Na 2 SO 4 . This is significantly higher as compared to the capacitance of 0.48 F cm −2 . Flexible solid-state asymmetric supercapacitor Ti-FeO-CNT//MnO 2 is verified with operating voltage of 2.0 V and stability over 3000 cycles, and delivers a high energy density of 2.14 mWh cm −3 at power density of 25 mW cm −3 . The flame synthesis is expected to be widely applicable for the preparation of high-valence metal ions doped nanosized Fe 2 O 3 functionalized materials, thus opening up new avenues for energy and catalysis research.

High ionic conductivity and toughness hydrogel electrolyte for high-performance flexible solid-state zinc-ion hybrid supercapacitors enabled by cellulose-bentonite coordination interactions

The lamellar structure of BT and coordination interaction with cellulose make cellulose hydrogel electrolytes have both high ionic conductivity and mechanical strength, and assembled ZHSCs can be applied in the field of wearable electronic devices.

From energy storage to pathogen eradication: unveiling the antibacterial and antiviral capacities of flexible solid-state carbon cloth supercapacitors.

With the emergence of deadly viral and bacterial infections, preventing the spread of microorganisms on surfaces has gained ever-increasing importance. This study investigates the potential of solid-state supercapacitors as antibacterial and antiviral devices. We developed a low-cost and flexible carbon cloth supercapacitor (CCSC) with highly efficient antibacterial and antiviral surface properties. The CCSC comprised two parallel layers of carbon cloth (CC) electrodes assembled in a symmetric, electrical double-layer supercapacitor structure that can be charged at low potentials between 1 to 2 V. The optimized CCSC exhibited a capacitance of 4.15 ± 0.3 mF cm-2 at a scan rate of 100 mV s-1, high-rate capability (83% retention of capacitance at 100 mV s-1 compared to its value at 5 mV s-1), and excellent electrochemical stability (97% retention of the initial capacitance after 1000 cycles). Moreover, the CCSC demonstrated outstanding flexibility and retained its full capacitance even when bent at high angles, making it suitable for wearable or flexible devices. Using its stored electrical charge, the charged CCSC disinfects bacteria effectively and neutralizes viruses upon surface contact with the positive and negative electrodes. The charged CCSC device yielded a 6-log CFU reduction of Escherichia coli bacterial inocula and a 5-log PFU reduction of HSV-1 herpes virus. Antibacterial and antiviral carbon cloth supercapacitors represent a promising platform technology for various applications, including electronic textiles and electronic skins, health monitoring or motion sensors, wound dressings, personal protective equipment (e.g., masks) and air filtration systems.

Tightly intercalated Ti3C2Tx/MoO3-x/PEDOT:PSS free-standing films with high volumetric/gravimetric performance for flexible solid-state supercapacitors.

Ti3C2Tx-MXenes have extremely promising applications in electrochemistry, but the development of Ti3C2Tx is limited due to severe self-stacking problem. Here, we introduced oxygen vacancy-enriched molybdenum trioxide (MoO3-x) with pseudocapacitive properties as the intercalator of Ti3C2Tx and PEDOT with high electronic conductivity as the co-intercalator and conductive binder of Ti3C2Tx to synthesize Ti3C2Tx/MoO3-x/PEDOT:PSS (TMP) free-standing films by vacuum-assisted filtration and H2SO4 soaking. The tightly intercalated free-standing film structure can effectively improve the self-stacking phenomenon of Ti3C2Tx, expose more active sites and facilitate electron/ion transport, thus making TMP show excellent electrochemical performance. The volumetric and gravimetric capacitance of optimized TMP-2 can reach 1898.5 F cm-3 and 523.0 F g-1 at 1 A g-1 with a rate performance of 90.5% at the current density from 1 A g-1 to 20 A g-1, which is significantly better than those of MXene-based composites reported in the literature. The directly-assembled TMP-2//TMP-2 flexible solid-state supercapacitor displays high energy/power output performances (25.1 W h L-1 at 6383.1 W L-1, 6.9 W h kg-1 at 1758.4 W kg-1) and there is no obvious change after 100 cycles at a bending angle of 180°. As a result, the tightly intercalated TMP-2 free-standing film with high volumetric/gravimetric capacitances is a promising material for flexible energy storage devices.

Strong and tough conductive PVA hydrogels based on the synergistic effect of acetic acid induction and salting-out for flexible solid-state supercapacitors

A synergistic strategy of acetic acid induction and salting-out is proposed for optimizing the microstructure, mechanical properties, and ionic conductivity, thus constructing strong and tough conductive PVA hydrogels for flexible supercapacitors.

A MXene-BiFeO3-ZnO nanocomposite photocatalyst served as a high-performance supercapacitor electrode.

MXenes have attracted considerable attention in the field of energy storage and conversion due to their high surface area, excellent electrical conductivity, and ability to intercalate various ions. However, simultaneously achieving high capacitance, rate capability, cycling stability, and mechanical flexibility is a significant challenge for designing MXene-based supercapacitors. In this article, we explored MXene-BiFeO3-ZnO nanocomposites for both photocatalytic and electric double-layer supercapacitor applications. While the BiFeO3-ZnO nanohybrid heterostructure improves the charge separation properties in nanocomposite photocatalysts, it was applied as an interlayer spacer between the MXene layers to prevent the stacking effect of electrodes in the supercapacitor. Furthermore, the optimization of MXene content in the nanocomposite was established by photocatalytic studies on methylene blue dye, which revealed a maximum of 98.72% degradation under direct sunlight with superior stability. The electrochemical studies on the best composition material reveal a maximum areal capacitance (Ccv) of 142.8 mF cm-2, an energy density (E) of 1.65 μW h cm-2, and a capacitive retention of 99.98% after 8000 cycles at 7 μA cm-2. Additionally, the flexible solid-state supercapacitor fabricated with the same material demonstrates an areal capacitance of 47.6 mF cm-2 and a capacitive retention of 66% after 8000 cycles at 7 μA cm-2, with potential for high-performance flexible supercapacitors.

Facile synthesis of the SnTe/SnSe binary nanocomposite via a hydrothermal route for flexible solid-state supercapacitors.

Environmental degradation and energy shortage are the two biggest problems facing the world right now. Because of the limited supply of non-renewable sources, the production of environment-friendly energy and its storage has gained significant importance. Pseudocapacitors have lately caught the interest of energy specialists due to their greater energy/power density and prolonged cycle life. In this work, binding-free SnTe/SnSe (STSS) electrodes deposited onto Ni foam (NF) as the conductive substrate have been developed by a facile hydrothermal route for supercapacitor applications. Several analytical tools were utilized to study the morphological, structural and textural characteristics. The electrochemical results obtained from a three-electrode system suggest that the STSS electrode material exhibits great specific capacitance (C s) of 1276 F g-1, specific energy (E d) of 46.45 W h kg-1 and specific power (P d) of 256 W kg-1 @ 1 A g-1. The results of C dl indicate that the STSS (31.28 mF) has a larger C dl value than those of SnTe (23.22 mF) and SnSe (26.35 mF). The analysis of electrochemical stability indicates that the STSS displays structural stability over 5000 cycles with a maximum capacitance retention of 96%. The Nyquist plot profile displayed a smaller R ct value for STSS (0.89 Ω) than SnSe (1.13 Ω) and SnTe (1.97 Ω). The symmetric behavior of STSS was determined in 2.0 M potassium hydroxide. The results reveal that this material has a specific capacitance of 537.72 F g-1 and specific energy of 78.32 W h kg-1. These findings suggest that the STSS electrode might serve as a potential candidate for supercapacitors and other energy-saving equipment.

Vertically aligned 1T-2H MoS2 on 3D porous carbon for ultrahigh-performance flexible energy storage device

Construct vertically ordered MS nanosheets with large interlayer spacing on the surface of B, N co-doped porous carbon BNC, and use them as electrode materials for all solid-state flexible supercapacitors.

Ni3P2O8 nanodots anchored multiwalled carbon nanotubes composite for flexible all-solid-state symmetric supercapacitor

Flexible solid-state supercapacitors embedded the fast charge rate of electric double-layer capacitive materials with high capacity pseudocapacitive type materials to exhibit better storage capacity and cycle life, hold great potential for portable microelectronic devices in the present days. Herein, we propose analogues state of the art through the facile solution synthesis of multi-walled carbon nanotubes decorated by Ni3P2O8 nanodots (Ni3P2O8/MWCNT) on a flexible substrate for supercapacitor application. Designed composite benefits from inter component synergistic effects wherein redox-enriched Ni3P2O8 nanodots contribute 26- fold high-performance energy storage capability with reference to bare MWCNT, while MWCNT acts as a one dimensional conductive as well as mechanical support for Ni3P2O8 growth. The corresponding flexible all-solid-sate symmetric supercapacitor designed from carboxymethyl cellulose-Na2SO4 (CMC-Na2SO4) neutral gel electrolyte holds a maximum specific energy of 72.3 Wh kg−1 with a power density of 6.4 kW kg−1 across an extended voltage window of 1.8 V. In addition, the device's excellent deformation tolerance (103 % at mechanical bending of 170o) indicates promising potential for enhanced flexible energy storage.

Synergistic effect of two-dimensional additives on carbon nanotube film electrodes towards high-performance all-solid-state flexible supercapacitors

Flexible supercapacitors (SCs) have attracted growing interest as the power source for portable and wearable electronics. In the present work, we report the CNTs (Carbon Nanotubes) buckypaper integrated with electroactive 2D materials including graphene, graphene oxide (GO), and transition metal sulphides (TMDs), especially tin sulphide (SnS2). The flexible and free-standing, interface-enhanced CNT paper having homogeneously dispersed 2D materials was prepared using a traditional scalable casting method. The hybridized CNT films were thoroughly characterized to elucidate their structural and surface properties. Finally, such hybrid CNT films were used as free-standing electrodes without any binder for the fabrication of flexible-solid-state supercapacitor (FSSSs) devices. In the FSSS, the electrochemical interactions between hybrid CNT paper electrodes and a polymer gel electrolyte were studied. In the symmetric configuration, the CNT-SnS2 electrodes reach the highest areal and volumetric capacitance of 533 mF/cm2 and 63 mF/cm3, respectively, almost four times that of pristine CNT electrodes, whereas CNT-GO-based electrodes display high-rate capability. The CNT-SnS2-based symmetric FSSS devices exhibit an extended voltage window of 1.5 V with a high capacitance of 133 mF/cm2 and show high cyclic stability for 5000 cycles under 180 0 bendings.

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.

Chitosan/graphene oxide hybrid hydrogel electrode with porous network boosting ultrahigh energy density flexible supercapacitor

To overcome the low energy density and poor conductivity of conventional electrode materials for building supercapacitor, herein, a hybrid hydrogel prepared from compositing bio-based chitosan with holey graphene oxide by microwave-assisted hydrothermal is proposed. This binary hydrogel is endowed with heteroatomic functional groups and conductive porous network by chemical pretreatments, where amides and carboxyl groups are introduced during the acylation modification of chitosan to enable it soluble in water for sufficient reaction, while the oxidation etching for graphene oxide in the defect area by H2O2 facilitates in-plane nanopores network to provide abundant active surface and short ion diffusion pathway. Benefited from the high conductivity and flexibility, this hydrogel present promising performance when used as additive-free electrode in a three-electrode, with a high specific capacitance of 377 F/g at 5 A/g. The rich nitrogen and oxygen groups on surface of the hydrogel contribute to high capacitance directly, while the in-plane nanopores and hierarchically porous network benefit to promote their wettability, accelerate the charge transfer and enhance their charge storage ability. When the hydrogel composite is adopted into a flexible solid-state supercapacitor employing lignin hydrogel electrolyte, it unfolds a specific capacitance of 210 F/g at 0.5 A/g, with an ultrahigh energy density of 31 Wh/kg at the power density of 150 W/kg. The solid-state supercapacitor exhibits promising potential in applications such as signal sensor and portable energy storage.

Multifunctional, bicontinuous, flexible comb copolymer electrolyte for solid-state supercapacitors

Solid electrolytes with high safety, good flexibility, and wide potential windows have attracted significant interest as alternatives to conventional liquid electrolytes, which have the disadvantages of flammability and leakage. Herein, we report a high-performance polymer electrolyte comprising a poly(isobornyl methacrylate)-co-poly(ethylene glycol) methyl ether methacrylate (PIBMA-co-PEGMA) (PIBEG) amphiphilic comb copolymer for solid-state supercapacitors (SCs). The PIBEG comb copolymer was synthesized via facile, inexpensive, and scalable free radical polymerization, followed by the incorporation of an ionic liquid (IL) to fabricate an ion-conducting flexible polymer electrolyte. Owing to the microphase-separated structure, the PIBEG films showed homogeneity and good flexibility up to 85 wt% of IL loading. The PIBEG/IL electrolytes had a bicontinuous, worm-like nanostructure with an ionic conductivity of 4.35 mS cm−1. The solid SC with PIBEG/IL electrolytes exhibited a specific capacitance of 48.6 F/g and an energy density of 37.12 Wh kg−1 at a power density of 1174 W kg−1, which are among the highest values reported for flexible solid SCs with conventional activated carbon electrodes. Furthermore, SCs could be fabricated without the use of separators or adhesives due to the multifunctional properties of PIBEG/IL electrolytes, including strong adhesion, high conductivity, and good mechanical strength.

Self-supporting electrode for flexible supercapacitors: NiCo-layered double hydroxide derived from metal organic frameworks wrapped on graphene/polyaniline nanotubes@cotton cloth

Nowadays, constructing hetero-structure materials is an efficacious procedure to uplift the electrochemical performance of layered double hydroxide (LDH) materials. The logical design of such elegant nanostructures is still challenging. Herein, NiCo-LDH nanosheets derived from Co-ZIF grown on graphene/polyaniline nanotube (G/PANI-NT)@cotton cloth (CC) was synthesized by a facile and novel two-step strategy for supercapacitors. Such hetero-structures give a 30.63 m2 g−1 surface area and more subjected electrochemical active sites. The supercapacitor performance results exhibit that the NiCo-LDH/G/PANI-NT@CC electrode has the best supercapacitor performance when it is used as a pseudocapacitor. By the ratio of Ni/Co = 2:1 in the precursor solution, the electrode shows an areal specific capacitance of 88.15 mF cm−2 at a current density of 0.075 mA cm−2. The electrochemical performance of the electrodes was perused using a redox-additive electrolyte. The electrochemical performance of the NiCo-LDH/G/PANI-NT@CC electrode was amended using K2S2O8 in a 3 M KOH solution. Considerably, the areal specific capacitance of NiCo-LDH/G/PANI-NT@CC (181.17 mF cm−2) increased to 431.30 mF cm−2, by changing the K2S2O8 concentration in KOH solution at a current density of 0.075 mA cm−2. Long-term stability test demonstrates that 84.05 % of the original capacitance remains after 10,000 cycles at the current density of 0.2 mA cm−2. The results indicate that NiCo-LDH/G/PANI-NT@CC will be an appropriate candidate for high-performance supercapacitors. The NiCo-LDH/G/PANI-NT@CC//NiCo-LDH/G/PANI-NT@CC flexible solid-state supercapacitor was assembled with the PVA/KOH gel electrolyte.

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.

Design of hierarchical porous carbon nanofibrous membrane for better electrochemical performance in solid-state flexible supercapacitors

The pore structure dramatically influences the electrochemical behavior of carbon nanofibers. The electrochemical performance of flexible carbon nanofibers as electrode materials for supercapacitors can be controlled by changing the size and quantity of pores. Hollow porous carbon nanofibers (HPCNFs) are prepared by coaxial electrostatic spinning and high-temperature carbonization. According to the nitrogen adsorption/desorption curve, HPCNF has a large specific surface area and good pore size distribution. In addition, cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) are used to analyze the electrochemical performance of HPCNF. Results show that the specific capacitance of hollow porous carbon nanofibers is 168.8 F/g at the current density of 1 A/g. Moreover, the specific capacitance retention of HPCNF is 95.61 % after 2000 cycles of charge and discharge at the current density of 5 A/g, exhibiting a stable cycle performance. In addition, solid-state supercapacitors assembled without any adhesives or conductive agents also show good cycle stability and excellent flexibility. As a result, HPCNF with flexibility, high specific surface area, and excellent electrochemical performance has broad prospects as an excellent electrode material for supercapacitors. Therefore, HPCNF has the advantages of good flexibility, high specific surface area, and excellent electrochemical performance. This paper proposes reasonable methods and creates more possibilities for future research and the application of flexible electrode materials for supercapacitors and flexible wearable electronic devices. • Different levels of hierarchical porous carbon nanofibrous membranes are constructed. • The effect of pores in carbon nanofibers on electrochemical performance are deeply studied. • Symmetric solid-state supercapacitors exhibit excellent stability and flexibility. • The charge distribution in supercapacitor are simulated by finite element method.

Effect of Two Dimensional Additives on the Charge Storage Performance of All Solid-State Carbon Nanotube Based Flexible Supercapacitors.

Flexible and miniaturized electronic devices have attracted widespread attention due to their potential for future hand-held, portable consumer, and wearable electronics. This has incited a growing interest in the development of compact yet efficient power sources that are flexible and holds the potential to be implemented in confined space for newer applications. In the present work, we report the CNT (Carbon NanoTubes) buckypaper integrated with electroactive 2D materials such as graphene, graphene oxide (GO), and the transition metal sulphides (TMDs) especially, tin sulphide (SnS2). The flexible and free-standing, interface-enhanced CNT paper having homogeneously dispersed 2D materials was prepared using a traditional scalable casting method. The hybridized CNT films were thoroughly characterized to elucidate their structural and surface properties. Finally, such hybrid CNT films were used as, free-standing electrodes without any binder for the fabrication of flexible-solid-state supercapacitor (FSSSs) devices. In the FSSS, the electrochemical interactions between hybrid CNT paper electrodes and polymer gel electrolyte were studied. In the symmetric configuration, the CNT-SnS2 electrodes reach the highest areal and volumetric capacitance, and almost 4 times that of pristine CNT electrodes, whereas CNT-GO-based electrodes display high-rate capability. The CNT-SnS2-based symmetric FSSS devices exhibit an extended voltage window of 1.5 V with a high capacitance of 133 mF/cm2 and show high cyclic stability for 5000 cycles under 180 ⁰ bending.

Functionalized Metallic 2D Transition Metal Dichalcogenide-Based Solid-State Electrolyte for Flexible All-Solid-State Supercapacitors.

Highly efficient and durable flexible solid-state supercapacitors (FSSSCs) are emerging as low-cost devices for portable and wearable electronics due to the elimination of leakage of toxic/corrosive liquid electrolytes and their capability to withstand elevated mechanical stresses. Nevertheless, the spread of FSSSCs requires the development of durable and highly conductive solid-state electrolytes, whose electrochemical characteristics must be competitive with those of traditional liquid electrolytes. Here, we propose an innovative composite solid-state electrolyte prepared by incorporating metallic two-dimensional group-5 transition metal dichalcogenides, namely, liquid-phase exfoliated functionalized niobium disulfide (f-NbS2) nanoflakes, into a sulfonated poly(ether ether ketone) (SPEEK) polymeric matrix. The terminal sulfonate groups in f-NbS2 nanoflakes interact with the sulfonic acid groups of SPEEK by forming a robust hydrogen bonding network. Consequently, the composite solid-state electrolyte is mechanically/dimensionally stable even at a degree of sulfonation of SPEEK as high as 70.2%. At this degree of sulfonation, the mechanical strength is 38.3 MPa, and thanks to an efficient proton transport through the Grotthuss mechanism, the proton conductivity is as high as 94.4 mS cm-1 at room temperature. To elucidate the importance of the interaction between the electrode materials (including active materials and binders) and the solid-state electrolyte, solid-state supercapacitors were produced using SPEEK and poly(vinylidene fluoride) as proton conducting and nonconducting binders, respectively. The use of our solid-state electrolyte in combination with proton-conducting SPEEK binder and carbonaceous electrode materials (mixture of activated carbon, single/few-layer graphene, and carbon black) results in a solid-state supercapacitor with a specific capacitance of 116 F g-1 at 0.02 A g-1, optimal rate capability (76 F g-1 at 10 A g-1), and electrochemical stability during galvanostatic charge/discharge cycling and folding/bending stresses.