mF Cm-2 Research Articles

Rhenium Sulfide Incorporated in Molybdenum Sulfide Nanosheets for High-Performance Symmetric Supercapacitors with Enhanced Capacitance.

Supercapacitors are considered potential energy storage devices and have drawn significant attention due to their superior intrinsic advantages. Herein, we report the synthesis of ReS2 embedded in MoS2 nanosheets (RMS-31) by a hydrothermal technique. The prepared RMS-31 electrode material demonstrated superior pseudocapacitive behavior in 1 M KOH electrolyte solution, which is confirmed by the heterostructure of RMS-31 nanosheet architectures. RMS-31 has a specific capacitance of 244 F g-1 at a current density of 1 A g-1 and a greater areal capacitance of 540 mF cm-2 at a current density of 5 mA cm-2. The symmetric supercapacitor device with the RMS-31 electrode delivers an energy density of 28 W h cm-2 with a power density of 1 W cm-2 and reveals long-term stability at a constant current density of 5 mA cm-2 for 10,000 cycles while accomplishing a retention of 66.5%. The high performance of this symmetric device is attributed to the synergistic effect of ReS2 and MoS2 and the presence of the metallic 1T-MoS2 phase in the RMS-31 electrode. To the best of our knowledge, this is the first report of increasing the interlayer spacing of 2H-MoS2 by incorporating ReS2 for symmetric supercapacitor applications.

Ternary NiCeCo-Layered Double Hydroxides Grown on CuBr2@ZIF-67 Nanowire Arrays for High-Performance Supercapacitors.

Ternary layered double-hydroxide-based active compounds are regarded as ideal electrode materials for supercapacitors because of their unique structural characteristics and excellent electrochemical properties. Herein, an NiCeCo-layered double hydroxide with a core-shell structure grown on copper bromide nanowire arrays (CuBr2@NCC-LDH/CF) has been synthesized through a hydrothermal strategy and calcination process and utilized to fabricate a binder-free electrode. Due to the unique top-tangled structure and the complex assembly of different active components, the prepared hierarchical CuBr2@NCC-LDH/CF binder-free electrode exhibits an outstanding electrochemical performance, including a remarkable areal capacitance of 5460 mF cm-2 at 2 mA cm-2 and a capacitance retention of 88% at 50 mA cm-2 as well as a low internal resistance of 0.163 Ω. Moreover, an all-solid-state asymmetric supercapacitor (ASC) installed with CuBr2@NCC-LDH/CF and activated carbon electrodes shows a high energy density of 118 Wh kg-1 at a power density of 1013 W kg-1. Three assembled ASCs connected in series can operate a multifunctional display for over three and a half hours. Therefore, this innovative work provides new inspiration for the preparation of electrode materials for supercapacitors.

Dry Synthesis of Binder-Free Ruthenium Nitride-Coated Carbon Nanotubes as a Flexible Supercapacitor Electrode.

Ruthenium nitride was successfully deposited on a multiwalled carbon nanotube (MWCNT) forest grown on a stainless-steel mesh substrate by radiofrequency plasma-assisted pulsed laser deposition. This novel dry fabrication method for flexible supercapacitor electrodes eliminates toxic byproducts and the need for any binder component. Experimental results show a successful thin film coating of the individual MWCNTs with RuNx under various synthesis conditions. The electrochemical characterization demonstrates a significant improvement in capacitance of the synthesized RuNx-MWCNT electrode compared to the bare MWCNT forest, with a large potential window of 1.2 V. Capacitance values as high as 818.2 F g-1 (37.9 mF cm-2) have been achieved.

Spin-Coated Heterogenous Stacked Electrodes for Performance Enhancement in CMOS-Compatible On-Chip Microsupercapacitors.

Integration of microsupercapacitors (MSCs) with on-chip sensors and actuators with nanoenergy harvesters can improve the lifetime of wireless sensor nodes in an Internet-of-Things (IoT) architecture. However, to be easy to integrate with such harvester technology, MSCs should be fabricated through a complementary-metal-oxide-semiconductor (CMOS) compatible technology, ubiquitous in electrode choice with the capability of heterogeneous stacking of electrodes for modulation in properties driven by application requirements. In this article, we address both these issues through fabrication of multielectrode modular, high energy density microsupercapacitors (MSC) containing reduced graphene oxide (GO), GO-heptadecane-9-amine (GO-HD9A), rGO-octadecylamine (rGO-ODA), and rGO-heptadecane-9-amine (rGO-HD9A) that stack through a scalable, CMOS compatible, high-wafer-yield spin-coating process. Furthermore, we compare the performance of the stack with individual electrode MSCs fabricated through the same process. The individual electrodes, in the presence of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfony)imide (EMIM-TFSI), demonstrate a capacitance of 38, 30, 36, and 105 μF cm–2 at 20 mV s–1 whereas the fabricated stack of electrodes demonstrates a high capacitance of 280 μF cm–2 at 20 mV s–1 while retaining and enhancing the material-dependent capacitance, charge retention, and power density.

Ultrafast Shaped Laser Induced Synthesis of MXene Quantum Dots/Graphene for Transparent Supercapacitors.

Ultratransparent electrodes have attracted considerable attention in optoelectronics and energy technology. However, balancing energy storage capability and transparency remains challenging. Herein, an in situ strategy employing a temporally and spatially shaped femtosecond laser is reported for photochemically synthesizing of MXene quantum dots (MQDs) uniformly attached to laser reduced graphene oxide (LRGO) with exceptional electrochemical capacitance and ultrahigh transparency. The mechanism and plasma dynamics of the synthesis process are analyzed and observed at the same time. The unique MQDs loaded on LRGO greatly improve the specific surface area of the electrode due to the nanoscale size and additional edge states. The MQD/LRGO supercapacitor has high flexibility and durability, ultrahigh energy density (2.04 × 10-3 mWhcm-2 ), long cycle life (97.6% after 12000 cycles), and excellent capacitance (10.42mF cm-2 ) with both high transparency (transmittance over 90%) and high performance. Furthermore, this method provides a means of preparing nanostructured composite electrode materials and exploiting quantum capacitance effects for energy storage.

Two Faces Under a Hood: Unravelling the Energy Harnessing and Storage Properties of 1T-MoS2 Quantum Sheets for Next-Generation Stand-Alone Energy Systems.

The two-dimensional 1T-MoS2 quantum sheets (QSs) continuously seek attention due to their extraordinary energy harnessing and storage properties towards designing an all-in-one self-charging power system (SCPS). Herein, we have utilized the superior dual-functional nature of exfoliated MoS2 QSs for SCPS via fabricating all-solid-state microsupercapacitors (MSC) as an energy storage device and triboelectric nanogenerator (TENG) with MoS2 QSs based charge-trapping interfacial layer as the energy harvester. The electrochemical analysis of MoS2 QSs MSC indicated their superior capacitive properties with a high areal capacitance (4.3 mF cm-2), energy density (0.38 μWh cm-2), and long cycle life. Furthermore, we emphasize the fabrication of MSC with shape diversity and performance uniformity via construction in several designable shapes, which exhibit superior electrochemical performances. The MoS2 QSs based charge-trapping layer enhances the output performance of TENG dramatically with a peak power density as large as 10 μW cm-2, which is 13-fold greater than that of the pristine TENG. As proof of the concept, we fabricated an all MoS2 based SCPS which showed their ability to self-charge up to a maximum of 1050 mV, outperforming many SCPS reported previously. Overall, this work creates a way to utilize the bifunctional properties of MoS2 QSs for the development of next-generation SCPS.

Sandwich-like MXene/α-Fe2O3-C-MoS2-PEDOT:PSS/MXene Film Electrodes with Ultrahigh Area Capacitance for Flexible Supercapacitors.

The restacking of the MXene film limits its development to the high energy density of flexible supercapacitors. In order to promote the application of MXene films in portable electronic devices and miniaturized energy storage devices, it is necessary to increase the area capacitance of MXene films for the pursuit of high energy density. The introduction of α-Fe2O3-C-MoS2-PEDOT:PSS (FMP) into MXene significantly increases the area capacitance. Considering the large number of active sites on the surface of MXene and its excellent hydrophilicity, FMP can be well-compounded with MXene, and the accumulation and loss of FMP can be prevented. Meanwhile, it can reduce the performance degradation caused by the accumulation of MXene's own structure and greatly increase its capacitance value. It is worth mentioning that the MXene/FMP/MXene (M/FMP/M) sandwich structure on the carbon cloth is reasonably designed to show excellent performance. Therefore, the best M/FMP/M electrode could attain a breakthrough in the area capacitance (2700 mF cm-2 and 541 F g-1). At the same time, the electrode maintains a fine rate capability and fabulous flexibility. In addition, the symmetrical supercapacitors also show a significant energy density of 371 μW h cm-2 (12.36 W h·kg-1), making this sandwich structure electrode a promising candidate for high-energy-density devices.

Graphene oxide-assisted electrochemical growth of Ni(OH)2 nanoflowers on nickel foam as electrode material for high-performance supercapacitors

Flower-like Ni(OH)2 nanostructures were electrochemically grown on nickel foam (NF) in an alkaline GO solution without adding nickel salts. The electrochemical deposition process was carried out using two modes of potentiostatic and galvanostatic to investigate the influences of the applied potential regime on the physicochemical and electrochemical properties of the resulting Ni(OH)2 nanostructures. Furthermore, to validate the promoting effect of GO on the electrochemical growth of Ni(OH)2, the same synthesis processes were performed in the absence of GO, using both the electrochemical modes. The chemical composition and morphological features of the electrodes, and the role of GO in the electrolyte greatly changed by altering the applied electrochemical mode. When a constant negative potential was applied, GO nanosheets were not reduced or deposited on the NF, and only flower-like Ni(OH)2 nanostructures were formed on the NF. Due to its hierarchical porous structure, this sample exhibited a significantly higher electrochemical performance compared to the samples prepared in the absence of GO and the sample prepared in the presence of GO by applying a constant cathodic current. Co-electrodeposition of reduced GO (rGO) nanosheets along with the Ni(OH)2 nanostructures occurred as a constant cathodic current was applied, leading to the formation of highly-packed rGO/Ni(OH)2 composite layer providing a considerably lower electrochemical performance. The electrode prepared by applying a constant potential to the NF in the alkaline solution containing GO exhibited specific capacitances of 2667.2 and 1586.8 mF cm-2 at the current densities of 4 and 40 mA cm-2, respectively. This electrode also showed a good rate capability with capacitance retention of 78% after 1000 charge/discharge cycles at the high current density of 40 mA cm-2. The assembled asymmetric supercapacitor device of Ni(OH)2/NF//AC/NF showed a high specific capacitance of 543.6 mF cm-2 at 2 mA cm-2, and the capacitance retention of 73.1% after 2000 cycles of charge/discharge at 16 mA cm-2. It also provided the highest energy density of 143 μWh cm-2 at power density of 1400 μW cm-2.

A high-performance electrode based on reduced graphene oxide/lignosulfonate/carbon microspheres film for flexible supercapacitors

Reduced graphene oxide (RGO) flexible film pillared with lignosulfonate (LS) and carbon microspheres (CM) was fabricated via a facile vacuum-filtration process to serve as a high-performance electrode material for supercapacitors. Composite electrodes comprising graphene and biomass materials have the advantages of being flexible, lightweight, cheap, and environmentally friendly. The addition of LS and CM between the RGO layers mitigated the self-restacking of reduced graphene oxide flakes. Composite film electrode displayed a high specific capacitance of 641 mF cm-2 at 0.2 mA cm-2, which was much higher than that of the RGO film (117.9 mF cm-2). The present findings indicate a great potential of the graphene films composited with biomass materials in fabricating flexible supercapacitor electrodes.

Hierarchical NiCo2S4/PANI/CNT nanostructures grown on graphene polyamide blend fiber as effective electrode for supercapacitors

Fiber-supercapacitors (FSCs) hold great promise in smart wearable energy textiles due to the advantages of security, excellent deformability and unique integration structure. However, the integration of electroactive materials into economically viable textile fibers to produce FSCs with high energy density and mechanical flexibility remains a huge challenge. Herein, we fabricated NiCo2S4/PANI/CNTs hierarchical nanostructures on graphene polyamide blend fiber (GPAF) as effective cathodes for FSCs. The prepared composite fiber electrode exhibited a specific capacity of 1290 mF cm-2 when the current density was 2 mA cm-2, which was benefitted from the delocalized conjugated system of PANI nanolayer and the unique nanostructure of NiCo2S4/PANI. Subsequently, the constructed asymmetrical fiber-supercapacitor (AFSC) delivered energy density up to 83.3 μWh cm-2 when the power density was 420 μW cm-2. In addition, the AFSC also exhibited satisfactory cycling stability, maintaining 80.13% of the initial capacity after 5000 cycles. This work provides new ideas to promote the further development and practical applications of flexible fiber-supercapacitors and accelerate the development process of wearable energy textiles.

Charge transfer and electrical double layer of an amphiphilic protic ionic liquid in bulk and when confined in nanochannels.

We report the behavior of the protic and surface active ionic liquid octylimidazolium bis(trifluoromethylsulfonyl)imide, [HC8Im][TFSI], in bulk and inside silica nanochannels, at the interface with the conductive substrate indium tin oxide (ITO) upon applied potential. The two distinct cases of the ionic liquid being in contact with a bare ITO substrate and an ITO substrate covered with a thin film of mesoporous silica containing vertically-aligned channel-like pores have been investigated. These correspond to the behavior of the bulk ionic liquid and the ionic liquid confined within nanochannels (approximately 3.5 nm wide and 65 nm long). Broadband dielectric spectroscopy (BDS) and electrochemical impedance spectroscopy (EIS) have been used as the experimental methods, while modelling with equivalent circuits has been applied to evaluate the experimental results. Thus, this study does not only show a functional ionic liquid/silica hybrid material, but also presents an in-depth electrochemical characterization revealing an enhanced specific capacitance at the confined-IL/ITO interface (∼16 μF cm-2) as compared to the case of bulk IL/ITO (∼6 μF cm-2). This suggests that local structure and ion ordering inside the nanochannels of silica are different from that of the bulk ionic liquid, favoring denser ionic packing and a higher specific capacitance at the metal interface.

Multi-step electrodeposited Ni-Co-P@LDH nanocomposites for high-performance interdigital asymmetric micro-supercapacitors.

The development of high-performance electrode materials and the rational design of asymmetric structures are the two main keys to fabricating micro-supercapacitors (MSCs) with high energy density. Transition metal compounds, especially nickel-cobalt phosphides and hydroxides, are promising electrode materials with excellent pseudo-capacitance. However, they are rarely used in fabricating asymmetric MSCs (AMSCs) due to the limitations of the preparation method. In this work, we constructed hierarchical Ni-Co-P@LDH nanocomposites with outstanding mass specific capacitance (1980 F g-1 at 1 A g-1) via a multi-step electrodeposition method, which is employed with FeOOH to fabricate an interdigital AMSC device (Ni-Co-P@LDHs//PVA-KOH//FeOOH). The as-prepared device exhibits a high working voltage (1.4 V), a large specific capacitance (24.0 mF cm-2 at 0.14 mA cm-2), a high energy density (6.54 μW h cm-2 at a power density of 100 μW cm-2) and good cycling stability (86.5% of capacitance retention after 5000 cycles). This work may provide novel methods for the synthesis of high-performance nickel-cobalt composite materials and their potential applications in interdigital AMSC devices.

In situ grown hierarchical NiO nanosheet@nanowire arrays for high-performance electrochromic energy storage applications.

Electrodes with hierarchical nanoarchitectures could promote electrochemical properties due to their largely exposed active sites and quick charge transfer. Herein, in situ grown hierarchical NiO nanosheet@nanowire films are reported by a one-step hydrothermal process followed by heat treatment. The unique NiO hierarchical nanostructures, which are composed of NiO nanowires grown on the surface of a nanosheet array, show improved electrochromic properties such as large optical modulation in different light regions (95% at 550 nm and 50.6% at 1000 nm), fast color change (9.8/5.4 s) and better coloring efficiency (91.2 cm2 C-1) with long-term cycling properties (82.2% after 700 cycles). Simultaneously, the hierarchical nanostructures possess optimal areal capacitance (117.2 mF cm-2), rate performance and cycling properties. The enhanced electrochemical properties are due to the pretreated seed layer and the synergistic effect between the unique in situ grown ultrathin nanowire and the underlying vertical nanosheet layer which can strengthen the mechanical adhesion of the nanoarray film to the substrate and make both nanosheets and nanowires more exposed to the electrolyte, enhancing charge transfer and mass diffusion. This work provides a promising pathway towards developing high quality electrochromic energy storage devices.

Thin-walled hollow fibers for flexible high energy density fiber-shaped supercapacitors

Fiber-shaped supercapacitors, which occupy minimal volume and possess remarkable flexibility, are particularly promising candidates for next-generation smart wearable devices. However, the state-of-the-art energy density and mechanical properties of fiber-shaped electrodes are far from satisfactory. Herein, hollow poly(3,4-ethylenedioxythiophene):polystyrene sulfonate thin-walled fibers (HPFs) are continuously prepared by coaxial wet-spinning. These HPFs combine a simple and high continuous preparation with high electrochemical performance and flexibility, owing to their hollow nature, small diameter (125 μm) and thin wall structure (8 μm). As a result, the HPFs display a specific areal capacitance of 115.2 mF cm-2 at a current density of 0.3 mA cm-2 with a high energy density of 9 μWh cm-2 at a power density of 0.112 mW cm-2. Furthermore, the HPFs maintain 81% of the initial capacitance after 10,000 cycles with ~100% Coulombic efficiency. More importantly, the specific capacitance is almost completely maintained after bending 3000 times at 180°.

Tin Oxide/Nitrogen‐Doped Graphene Quantum Dots Composite Nanotubes: An Efficient Electrode for Supercapacitors

Tin oxide (SnO2) and nitrogen‐doped graphene quantum dots (N‐GQDs) composite nanotubes (SnO2/N‐GQD NTs) were fabricated by the electrospinning technique and followed by the thermal annealing method for the application in supercapacitor as an electrode. SnO2/N‐GQD NTs with different ratio of N‐GQDs were prepared by adding different ratios of N‐GQDs along with tin chloride during the electrospinning process. The prepared composite's structure and morphological properties were characterized by using different techniques like XRD, FE‐SEM, TEM, and XPS. The supercapacitor performance of the SnO2/N‐GQD NTs composite was analyzed by the electrochemical studies such as cyclic voltammetry and galvanostatic charge‐discharge (GCD) measurement in 2 M KOH solution as electrolyte. The electrochemical analyses of SnO2/N‐GQD NTs was tested at different scan rates and current densities. SnO2/N‐GQD NTs prepared using 3 wt.% of N‐GQDs showed an excellent capacity retention even after 5000 GCD cycles and exhibited a maximum specific capacitance of 420 mF g-1 at a current density of 8 mA cm-2 in comparison to pure SnO2 NTs (230 mF cm-2).

Facile preparation of graphene@polyaniline nanofiber network/oxidized carbon cloth composites for high-performance flexible solid-state supercapacitors.

The complicated preparation process and low energy density of polyaniline (PANI)-based electrodes limit their wide applications in flexible energy storage devices. In this work, a reduced graphene (rGO)-wrapped polyaniline nanofiber network (PANI-NFN)/oxidized carbon cloth (OCC) (rGO@PANI-NFN/OCC) composite was prepared by a facile impregnation method using reactive templates of MnO2 on the surface of OCC. The as-prepared rGO@PANI-NFN/OCC composite exhibited a high area specific capacitance of 4438 mF cm-2 and maintained an initial capacitance of 88.2% after 3000 GCD cycles. It can be used as an independent electrode to construct flexible solid-state supercapacitors (FSSCs), and the FSSCs based on rGO@PANI-NFN/OCC also exhibit a high energy density of 117.9 μW h cm-2 and 88.39% retention after 500 bending cycles, which shows a great prospect for flexible energy storage device applications. The enhanced performance of rGO@PANI-NFN/OCC composites is mainly attributed to the synergistic effect of PANI-NFN structures with a large specific surface area and a rGO wrap layer to reduce the swelling and shrinking of PANI.

Membrane Potentials Trigger Molecular-Scale Rearrangements in the Outer Membrane of Gram-Negative Bacteria.

The structural complexity of the cell envelope of Gram-negative bacteria limits the fabrication of realistic models of bacterial cell membranes. A vertical Langmuir-Blodgett withdrawing was used to deposit a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) monolayer on the Au(111) surface. The second leaflet composed of di[3-deoxy-D-manno-octulosonyl]-lipid A (KLA) was deposited using Langmuir-Schaefer transfer. The use of an electrode material as a support for the POPE-KLA bilayer allowed electrochemical control of the membrane's stability, compactness, and structure. Capacitance-potential curves showed a typical pattern for the supported lipid bilayers electrochemical characteristic. The minimum membrane capacitance was ∼4 μF cm-2 and did not change in the following desorption-adsorption cycles, indicating the presence of a stable bilayer structure with an asymmetric composition of both leaflets. However, at a molecular scale, as elucidated in spectroelectrochemical experiments, large differences in the response of both leaflets to electric potentials were observed. The acyl chains in POPE and KLA existed in a liquid state. The quantitative analysis of the CH stretching modes indicated potential-driven reorientations in the hydrophobic fragment of the bilayer, already in the adsorbed state. To assign observed rearrangements to POPE and KLA lipids in both leaflets, per-deuterated d31-POPE was transferred into the inner leaflet. Since no potential-dependent changes of the CD2 stretching modes in the d31-POPE-KLA bilayer were observed, reorientations in the acyl chain region were assigned to the KLA molecules. Mg2+ ions were bound to the polar head groups of KLA. The strength of electrostatic interactions in the polar head group region of KLA was dependent on the direction of the electric field. At negative electric potentials, the binding of divalent cations weakened, which gave the KLA molecules increased orientational flexibility. This behavior in electric fields is peculiar for the outer membrane and indicates that the microbial cell membranes have different electrochemical properties than phospholipid bilayers.

Stereolithography-Derived Three-Dimensional Pyrolytic Carbon/Mn3O4 Nanostructures for Free-Standing Hybrid Supercapacitor Electrodes.

The development of permeable three-dimensional (3D) macroporous carbon architectures loaded with active pseudocapacitive nanomaterials offers hybrid supercapacitor (SC) materials with higher energy density, shortened diffusion length for ions, and higher charge–discharge rate capability and thereby is highly relevant for electrical energy storage (EES). Herein, structurally complex and tailorable 3D pyrolytic carbon/Mn3O4 hybrid SC electrode materials are synthesized through the self-assembly of MnO2 nanoflakes and nanoflowers onto the surface of stereolithography 3D-printed architectures via a facile wet chemical deposition route, followed by a single thermal treatment. Thermal annealing of the MnO2 nanostructures concurrent with carbonization of the polymer precursor leads to the formation of a 3D hybrid SC electrode material with unique structural integrity and uniformity. The microstructural and chemical characterization of the hybrid electrode reveals the predominant formation of crystalline hausmannite-Mn3O4 after the pyrolysis/annealing process, which is a favorable pseudocapacitive material for EES. With the combination of the 3D free-standing carbon architecture and self-assembled binder-free Mn3O4 nanostructures, electrochemical capacitive charge storage with very good rate capability, gravimetric and areal capacitances (186 F g–1 and 968 mF cm–2, respectively), and a long lifespan (>92% after 5000 cycles) is demonstrated. It is worth noting that the gravimetric capacitance value is obtained by considering the full mass of the electrode including the carbon current collector. When only the mass of the pseudocapacitive nanomaterial is considered, a capacitance value of 457 F g–1 is achieved, which is comparable to state-of-the-art Mn3O4-based SC electrode materials.

Interface Engineering on Cellulose-Based Flexible Electrode Enables High Mass Loading Wearable Supercapacitor with Ultrahigh Capacitance and Energy Density.

For practical energy storage devices, a bottleneck is to retain decent integrated performances while increasing the mass loading of active materials to the commercial level, which highlights an urgent need for novel electrode structure design strategies. Here, an active nitrogen-doped carbon interface with "high conductivity, high porosity, and high electrolyte affinity" on a flexible cellulose electrode surface is engineered to accommodate 1D active materials. The high conductivity of interface favors fast electron transport, while its high porosity and high electrolyte affinity properties benefit ion migration. As a result, the flexible anode accommodated by carbon nanotubes achieves an ultrahigh capacitance of 9501 mF cm-2 (315.6 F g-1 ) at a high mass loading of 30.1mg cm-2 , and the flexible cathode accommodated by polypyrrole nanotubes realizes a remarkably high capacitance of 6212 mF cm-2 (248 F g-1 , 25mg cm-2 ). The assembled flexible quasi-solid-state asymmetric supercapacitor delivers a maximum energy density of 1.42 mWh cm-2 (2.2V, 2105 mF cm-2 ), representing the highest value among all reported flexible supercapacitors. This versatile design concept provides a new way to prepare high performance flexible energy storage devices.

Electropolymerization of D-A-D type monomers consisting of thiophene and quionaxline moieties for electrochromic devices and supercapacitors

Three donor-acceptor-donor (D-A-D) type monomers (ThQ-Ph, ThQ-PhOMe and ThQ-Th) based on thiophene substituted quinoxaline derivates were synthesized and further electropolymerized for electrochromic and supercapacitor applications. The present redox-active monomers were electrodeposited on the ITO electrodes robustly from their solution through the oxidative coupling reactions between thiophene radical cations. The obtained conjugated polymers (PThQ-Ph, PThQ-PhOMe and PThQ-Th) exhibited tunable and multicolor electrochromism among the visible and near infrared region with good performances. Particularly, a high optical contrast (over 80%) was achieved around 1600 ​nm, with short response time (less than 1.5 ​s) and high coloration efficiency (over 300 ​cm2 ​C-1). Moreover, quasi-solid state electrochromic devices based on the present polymers employing gel-type electrolyte were fabricated, and exhibited specific capacitance of 0.81 ∼ 1.58 ​mF ​cm-2 at the current density of 0.01 ​mA ​cm-2, which guaranteed their potential applications in energy saving smart windows.