Electrochromic Supercapacitors Research Articles

Smart Energy Storage: W18O49 NW/Ti3C2Tx Composite-Enabled All Solid State Flexible Electrochromic Supercapacitors.

Developing a highly efficient electrochromic energy storage device with sufficient color fluctuation and significant electrochemical performance is highly desirable for practical energy-saving applications. Here, to achieve a highly stable material with a large electrochemical storage capacity, a W18O49 NW/Ti3C2Tx composite has been fabricated and deposited on a pre-assembled Ag and W18O49 NW conductive network by Langmuir-Blodgett technique. The resulting hybrid electrode composed of 15 layers of W18O49 NW/Ti3C2Tx composite exhibits an areal capacitance of 125mFcm-2, with a fast and reversible switching response. An optical modulation of 98.2% can be maintained at a current density of 5mAcm-2. Using this electrode, a bifunctional symmetric electrochromic supercapacitor device having an energy density of 10.26µWhcm-2 and a power density of 0.605mWcm-2 is fabricated, with high capacity retention and full columbic efficiency over 4000 charge-discharge cycles. Meanwhile, the device displays remarkable electrochromic characteristics, including fast switching time (5s for coloring and 7s for bleaching), and a significant coloration efficiency of 116cm2C-1 with good optical modulation stability. In addition, the device exhibits significant mechanical flexibility and fast switching while being stable over 100 bending cycles, which is promising for real-world applications.

Metal oxide-mixed polymer-based hybrid electrochromic supercapacitor: improved efficiency and dual band switching

The inclusion of charge storage properties in electrochromic devices (ECDs) has gained much interest and has evolved into a promising emerging energy-related field due to multifunctional smart device applications. Here, an organic–inorganic solid-state asymmetric electrochromic supercapacitor device (ESCD) containing nano-CoTiO3-mixed poly-3-hexylthiophene and WO3 as two electrodes has been designed to study electrochromic and supercapacitor properties. The electrochemical properties of CoTiO3 show a pseudocapacitive-type charge storage capability, which has been utilized to enhance the electrochromic performance of the ESCD with additional charge storage ability. The device shows charge storage properties with fast charging and slow discharging, giving very high coulombic efficiency with a specific capacitance of 6.4 mF cm−2 at 0.2 mA cm−2 current density. The device shows excellent electrochromic supercapacitive properties with a color contrast of ∼50% and a short switching time of ∼1 s at a 515 nm wavelength with excellent cyclic stability. The device exhibits the capability to cut near infrared wavelength (700 nm and 850 nm) and has a potential application as a heat filtering device. Thus, the addition of pseudocapacitive-type materials in ECDs enhances the capacitive performance along with electrochromic properties, which makes ECDs more suitable for real life applications.

One-step achieving high performance all-solid-state and all-in-one flexible electrochromic supercapacitor by polymer dispersed electrochromic device strategy

Electrochromic devices (ECD) are widely used to regulate the transmittance of sunlight by applying a small voltage, but the drawbacks like complex layer-by-layer preparation procedures and inconvenient assembling process still exist. To address these problems, gel or solution-type all-in-one ECDs were recently developed for the simple structure, however, the leakage risk and absence of flexible large-area production have limited real applications. Herein, a novel all-solid-state and all-in-one flexible ECD was reported by originally developed polymer dispersed electrochromic device (PDECD) strategy. This all-solid-state flexible ECD could be efficiently prepared only by one step of phase separation without any extra treatment, and demonstrated outstanding stability (92.1 % of original ΔT remained after 10,000 cycles), high coloration efficiency (197 cm2/C), low power consumption (86.4 μW/cm2) and satisfied response time (≤12 s). Meanwhile, the stored power in ECD during coloring process could drive a LED with excellent cyclic stability (93 % of original capacity remained after 3000 cycles), implying that ECD could also serve as an idea electrochromic supercapacitor. What’more, a reported largest viologen-based all-solid-state flexible ECD (17.8 × 13.2 cm2) with robust bending resistance (up to 1000 bending cycles) was successfully fabricated with industrial roller coating technique, which indicated the huge potential in real world.

Stoichiometrically Optimized Electrochromic Complex [V2 O2+ξ (OH)3-ξ ] Based Electrode: Prototype Supercapacitor with Multicolor Indicator.

The systematic structure modification of metal oxides is becoming more attractive, and effective strategies for structural tunning are highly desirable for improving their practical color-modulating energy storage performances. Here, the ability of a stoichiometrically tuned oxide-hydroxide complex of porous vanadium oxide, namely [V2 O2+ξ (OH)3-ξ ]ξ = 0:3 for multifunctional electrochromic supercapacitor application is demonstrated. Theoretically, the pre-optimized oxide complex is synthesized using a simple wet chemical etching technique in its optimized stoichiometry [V2 O2+ξ (OH)3-ξ ] with ξ=0, providing more electroactive surface sites. The multifunctional electrode shows a high charge storage property of 610Fg-1 at 1Ag-1 , as well as good electrochromic properties with high color contrast of 70% and 50% at 428 and 640nm wavelengths, faster switching, and high coloration efficiency. When assembled in a solid-state symmetric electrochromic supercapacitor device, it exhibits an ultrahigh power density of 1066mWcm-2 , high energy density of 246mWhcm-2 , and high specific capacitance of 290mFcm-2 at 0.2mAcm-2 . A prepared prototype device displays red when fully charged, green when half charged, and blue when fully discharged. A clear evidence of optimizing the multifunctional performance of electrochromic supercapacitor by stoichiometrical tuning is presented along with demonstrating a device prototype of a 25cm2 large device for real-life applications.

Electrode materials for electrochromic supercapacitors.

Smart energy storage systems, such as electrochromic supercapacitor (ECSC) integrated technology, have drawn a lot of attention recently, and numerous developments have been made owing to their reliable performance. Developing novel electrode materials for ECSCs that embed two different technologies in a material is an exciting and emerging field of research. To date, the research into ECSC electrode materials has been ongoing with excellent efforts, which need to be systematically reviewed so that they can be used to develop more efficient ECSCs. This mini-review provides a general composition, main evaluation parameters and future perspectives for electrode materials of ECSCs as well as a brief overview of the published reports on ECSCs and performance statistics on the existing literature in this field.

Self-Powered Dual-Band Electrochromic Supercapacitor Devices for Smart Window Based on Ternary Dielectric Triboelectric Nanogenerator.

A dual-band electrochromic supercapacitor device (DESCD) can be driven by an external power supply to modulate solar radiation, which is a promising energy-saving strategy and has broad application prospects in smart windows. However, traditional power supplies, such as batteries, supercapacitors, etc., usually face limited lifetimes and potential environmental issues. Hence, we propose a self-powered DESCD based on TiO2/WO3 dual-band electrochromic material and a ternary dielectric rotating triboelectric nanogenerator (TDR-TENG). The TDR-TENG can convert mechanical energy from the environment into electrical energy to obtain a high output of 840 V, 23.9 µA, and 327 nC. The as-prepared TDR-TENG can drive the TiO2/WO3 film to store energy with a high dual-band modulation amplitude of 41.6% in the visible (VIS) region and 84% in the near-infrared (NIR) region, decreasing the indoor-outdoor light-heat interaction and thereby reducing the building energy consumption. The self-powered DESCD demonstrated in this study has multiple functions of energy harvesting, energy storage, and energy saving, providing a promising strategy for the development of self-powered smart windows.

Design Strategies for High Reflectivity Contrast and Stability Adaptive Camouflage Electrochromic Supercapacitors.

The integration of an electrochromic (EC), energy storage, and adaptive camouflage system into a multifunctional electronic device is highly desirable and yet challenging. In this work, two carbazole-based conjugated polymers were prepared to achieve a reversible color change from transparent to yellow, green, and blue-green by easy electrochemical polymerization. Due to its dendritic geometry, the conjugated polymer p3CBCB exhibits a loosely packed structure with a relatively higher specific surface area than pCBCB, as well as a relatively better ionic conductivity. The kinetic and galvanostatic charge-discharge (GCD) study reveals that p3CBCB has superior properties with larger optical contrast and volumetric capacitance. Moreover, EC supercapacitors (ECSCs) are constructed with p3CBCB as the EC layer and ZnO@PEDOT:PSS as the ion storage layer. The dual function of a ZnO interface layer on improvement in reflectivity contrast (ΔR% > 35.1%) and cycling stability (over 40,000 cycles) using ZnO as a reflective and protective layer is demonstrated in an ion storage layer. Additionally, patterned prototype devices based on the design of double-sided ITO glass were successfully assembled, which can simulate conditions of various natural environments including forests, wilderness, and deserts. This study provides new ideas not only for the preparation of conjugated polymers that can simultaneously realize reversible transparent-yellow-green conversion but also for the achievement of high coloration efficiency, high reflectivity contrast, and good stability of ECSCs for adaptive camouflage.

Portable Visual Photoelectrochemical Biosensor Based on a MgTi2O5/CdSe Heterojunction and Reversible Electrochromic Supercapacitor for Dual-Modal Cry1Ab Protein Detection.

Reversible electrochromic supercapacitors (ESCs) have attracted considerable interest as visual display screens. The use of ESCs in combination with a photoelectrochemical (PEC) biosensor promises to improve the detection efficiency. Herein, a visual PEC biosensor is developed by introducing a circuit module between a PEC-sensing platform (PSP) and a reversible ESC for Cry1Ab protein detection. In PSP, a type II MgTi2O5/CdSe heterojunction effectively drives charge separation by their cross-matched band gap structures, generating an amplified photocurrent. Next, the circuit module is designed to connect the PSP and ESC, realizing the signal conversion from photocurrent to voltage. ESC, as a visual display screen, produces reversible color changes with different voltages. As the concentration of Cry1Ab increases, the photocurrent decreases due to the specific binding between the aptamer and Cry1Ab in PSP, while the color of the reversible ESC changes from green to blue. To improve the integrity of the device, a portable PEC biosensor is further constructed via three-dimensional printing for dual-modal Cry1Ab protein detection, thus collecting both PEC and visual signals. The linear ranges are 0.3-3000 ng mL-1 for PEC mode and 1-1000 ng mL-1 for visual mode. This work presents a portable, efficient, sensitive, and visualized detection system, providing an important reference for practical visualization applications.

Highly color tunable, electrochromic energy storage devices based on dye-modified ion gels

In this work, we proposed a facile strategy to achieve high color tunability of electrochromic supercapacitors (ECSs) with tungsten trioxide (WO3) and nickel oxide (NiO) combination as EC materials. To achieve high color tunability, we applied a small amount of rhodamine (1:103 wt%) as dyes and achieved a wide color map (e.g. blue, yellowish, and magenta). Hence, to expand the color map, we mixed dyes, controlled the concentration of dyes, and controlled the ratio of dye solutions therefore successfully expanding the color map (e.g. purple, navy, and red) and including highly reliable charging/discharging cyclic stability (83.6 % after 10,000 cycles), change in transmittance and galvanostatic charging/discharging curve synchronized well simultaneously and therefore energy storage amount is indicated visually For last, we fabricated practical feasibility of multicolor ECSs successfully. ECSs in this work have the potential to be ECSs applications for the next generation of smart windows as energy storage displays.

Dual-functional electrochromic supercapacitors with electrospun TiO2 ion storage layer

We have developed dual-functional electrochromic supercapacitors (ECSs) incorporating electrospun TiO2 nanofibers as an ion storage layer (ISL). The prepared ISL-ECSs exhibit excellent integrated electrochromic performances at low driving voltages due to high visible transparency and energy storage capabilities. This study describes direct electrospinning TiO2 on an FTO electrode and fabricating asymmetric electrochromic devices with viologen-based ion gel compositions. The electrospinning technique proved suitable for producing oxide nanostructures that facilitate efficient ion transport. The surface morphology of the fabricated nanoweb was analyzed using SEM and AFM images. The electrochromic performances were evaluated through cyclic voltammetry and spectroelectrochemical measurements, and charge storage properties were examined by galvanostatic charge–discharge curves. The optimized dual-functional devices demonstrated a large transmittance contrast of up to 87 %, high coloration efficiency of 175.7 cm2/C, areal capacitance of 20.53 mF/cm2, and good charging-discharging cyclic stability. Furthermore, the practical feasibility of the ISL-ECSs was demonstrated by evaluating their ability to serve as a power source for illuminating an LED lamp. The findings suggest the potential application of ISL-ECSs for dual-functional smart windows, in which the color intensity visualizes the real-time energy storage status.

Enhancing electrochromic supercapacitor electrode performance through different donor compartments in D-A-D type conjugated polymers

Conjugated polymers (CPs), particularly donor-acceptor-donor (D-AD) type polymers, have emerged as promising materials as supercapacitor electrode. In this study, 3-hexylthiophene and ethylenedioxythiophene (EDOT) as donor compartments in D-A-D type CPs, with an indenoquinoxalinone-based acceptor, were investigated for supercapacitor electrode performance. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and UV–Vis spectroscopy were employed to analyze the chemical structures and optical properties of the monomers, respectively. For surface characterization of the polymers, scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) analysis were used. Electrochromic behaviors were investigated via spectroelectrochemistry and kinetic studies. The electrochemical performance of the polymers was evaluated through cyclic voltammetry, galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The specific capacitance, energy density, and power density of the polymers were compared. Results showed that they were promising electrochromic material for supercapacitor application due to their high specific capacitance. Since EDOT containing polymer exhibited enhanced electrochemical properties, it was used to construct supercapacitor. Besides cyclic voltammetry and GCD characterization of device, the electrochemical cycling performance of it was assessed to evaluate the long-term reliability of the polymer as supercapacitor electrode material. This study provides valuable insights into the role of donor compartments, specifically 3-hexylthiophene and EDOT in D-A-D type CPs. The findings also highlight the potential of the indenoquinoxalinone-based acceptors in electrochromic supercapacitors. The results contribute to the design and development of enhanced supercapacitor materials with improved energy storage capabilities, offering new possibilities for utilizing D-A-D type polymers with indenoquinoxalinone-based acceptors.

Cu-doped W18O49 nanowire reticular films for electrochromic supercapacitors

The method of improving the electrochromic properties of tungsten oxide by doping has attracted great interest. In this study, we successfully fabricated nanostructured tungsten oxide with different copper doping concentrations by a solvothermal method using copper chloride dihydrate and tungsten hexachloride as precursors. We found that the area-specific capacitance of the films gradually increased with the increase in doping concentration. The products were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, cyclic voltammetry, and chronoamperometry. The results show that the films we fabricated are reticular structures composed of nanowires. The doping of copper can improve the electron conductivity and shorten the ion transmission distance, thus improving energy storage properties. When the doping concentration is 7% and the annealing temperature is 200 °C, the film had the largest surface capacitance of 17.89 mF/cm2 and the capacitance retention reached 58.23%.

Effect of precursor concentration on the electrochemical properties of nickel cobalt phosphate for high-performance electrochromic supercapacitors

This research focuses on developing a high-performance electrode material for sustainable energy applications. The study explores the electrochemical deposition of a nickel-cobalt phosphate composite (NCPC) on a conductive glass substrate. A systematic investigation is conducted to analyze the influence of precursor concentrations, including nickel chloride hexahydrate (NiCl2·6H2O), cobalt chloride hexahydrate (CoCl2·6H2O), and disodium hydrogen phosphate (Na2HPO4), on the electrochromic and energy storage properties of NCPC. Utilizing Design Expert (DoE) software, the optimization process results in a predictive quadratic model with a residual standard error below 5 %, effectively capturing the relationship between independent variables and specific capacitance (Csp). Under optimized conditions (0.1 M NiCl2·6H2O, 0.3 M CoCl2·6H2O, and 0.4 M Na2HPO4), NCPC exhibits remarkable attributes, including a high Csp of 878 F/g (equivalent to 439 mAh/g) for energy storage and an impressive coloration efficiency of 62 cm2/C for electrochromic applications. These exceptional outcomes are attributed to the synergistic effects of NCPC, enhancing electrical conductivity, active site availability, and surface area, collectively contributing to superior electrochemical performance. An electrochromic energy storage device (NCPC//AC) is made, utilizing the optimized NCPC as the positive electrode and activated carbon (AC) as the negative electrode. The NCPC//AC device demonstrates notable performance features, including a high Csp of 135 F/g at a 5 mV/s scan rate, specific power of 750 W/kg, and specific energy of 11 Wh/kg, showcasing an exceptional power-to-weight ratio. Moreover, the NCPC//AC device exhibits excellent stability, retaining 78 % of its capacitance after 5000 charge-discharge cycles, highlighting its durability and long-term viability. In summary, this study emphasizes the exceptional electrochemical properties and performance of the NCPC//AC device, positioning it as a promising sustainable energy technology aligned with SDG 7 of ensuring access to affordable, reliable, sustainable and modern energy for all.

Surface morphology engineering of WO3 films for increasing Li ion insertion area in electrochromic supercapacitors (ECSCs)

Two different dry deposition methods were used to deposit electrode films with different surface morphologies in relation to the performance of electrochromic supercapacitors (ECSCs): direct current (DC) magnetron sputtering and the nanoparticle deposition system (NPDS). The NPDS method, which sprays powders onto the substrate using pressure differences, deposited WO3 film with its roughness of 36 nm and its thickness of 383 nm, while the sputtered WO3 film had its roughness of 3 nm and its thickness of 262 nm. Due to its dramatic difference in surface roughness, the NPDS-WO3 thin film had larger reaction surface area as well as Li-ion diffusion coefficient than those of sputtered-WO3 films. As a result, the ECSC device with NPDS-WO3 exhibited 19 % higher coloration efficiency with greater charge capacity compared to those with sputtered-WO3. However, the ECSC device with NPDS-WO3 showed different charge/discharge with trapped Li ions during the coloring(charging)/bleaching(discharge) processes respectively, leading to rapid degradation of the device. This research highlights the clear difference between its characteristics of the thin films fabricated using the NPDS vs. sputtering methods in relation to its surface roughness so that this study would be potentially beneficial in engineering various properties of ECSC devices.

Surfactant integrated nanoarchitectonics for controlled morphology and enhanced functionality of tungsten oxide thin films in electrochromic supercapacitors

This research focuses on tungsten oxide (WO3) as a promising material, and the study investigates the electrodeposition of WO3 thin films on fluorine-doped tin oxide (FTO) coated glass substrates using three different surfactants: cationic hexamethylenetetramine (HMTA), anionic sodium dodecyl sulfate (SDS), and non-ionic polyethylene glycol (PEG). The X-ray diffraction analysis confirms that the resulting thin films exhibit amorphous structures. Raman analysis supports the identification of the pure WO3 phase based on the stretching and vibrational modes observed in the colored and bleached states. The X-ray photoelectron spectroscopic study examines the influence of cathodic and anodic potentials on the formation of oxidized and reduced tungsten species in surfactant-aided WO3 thin films. Field emission scanning electron microscopy is utilized to investigate the impact of different surfactants on the morphology of WO3 thin films, revealing the formation of porous, clumped, and dense nanogranules on the film surface. Electrochromic energy storage investigations highlight the superior performance of the W-PEG (polyethylene glycol assisted WO3) thin film, which exhibits efficient lithium-ion accommodation and desirable bifunctional characteristics. The optimized W-PEG sample demonstrates excellent electrochromic performance, including high optical modulation (84.39 %), good reversibility (98 %), and high coloration efficiency (117.95 cm2/C). Supercapacitive measurements reveal a high areal capacitance of 44.1 mF/cm2 at a current density of 0.1 mA/cm2, as well as an energy density of 0.024 mWh/cm2 at a power density of 0.1 mW/cm2, with 85 % capacitive retention over 8000 consecutive galvanostatic charge-discharge cycles. Furthermore, the application potential of nanogranular WO3 for electrochromic energy storage is demonstrated through the successful illumination of a red and green light-emitting diode (LED) using fully colored electrochromic supercapacitor devices (4 × 3 cm2), highlighting their energy storage capability.

Facile synthesis of oxygen-deficient MoO3-x nanosheets by light radiation for fast electrochromic supercapacitors

Facile synthesis of oxygen-deficient MoO3-x nanosheets by light radiation for fast electrochromic supercapacitors

High performance polythiophene derivative with good electrochromic and energy storage properties electrochemical synthesized in boron trifluoride diethyl etherate

In this study, novel poly(3,4-dibromothiophene) (PDBrTh) is firstly prepared through electrochemical polymerization method using boron trifluoride diethyl etherate (BF3·Et2O) as polymeric solvent. In BF3·Et2O, the electrochemical oxidation potential of 3,4-dibromothiophene is significantly reduced compared with in Acetonitrile/Tetrabutylammonium tetrafluoroborate (ACN/TBATFB) system, which provides conditions for high quality polymer preparation. The prepared PDBrTh in BF3·Et2O shows good electrochemical activity and thermal stability. The electrochromic and supercapacitive performance of the prepared PDBrTh are also studied. The color of the prepared PDBrTh can be reversibly changed between red and blue with fast response time and high optical contrast. Galvanostatic charge-discharge test shows that the prepared PDBrTh also has good electrochemical energy storage performance. The specific capacitance value of the PDBrTh can reach to 229.6 F g−1 under the current density of 1 A g−1, showing good energy storage capacity. An all-polythiophenes electrochromic supercapacitor device (ESD) is constructed by prepared PDBrTh and poly(3,4-ethylenedioxythiophene), the color of the device can change between red and dark blue. The ESD also shows good energy storage property and robust charge-discharge stability. Moreover, the ESD shows obvious color changes and corresponding light transmittance changes during the charging and discharging process, realizing intelligent visual monitoring of the energy storage state. This study shows that the prepared PDBrTh has good practical application potential in the field of intelligent wearable energy storage.

Polyoxometalate/poly(3,4-ethylenedioxythiophene) nanocomposites enabling visualization of energy storage status in multicolor electrochromic supercapacitors

Electrochromic supercapacitor devices (ESDs), which integrate electrochromism and energy storage functions, have garnered considerable attention in recent years. Polyoxometalates (POMs) are regarded as promising materials for electrochromic energy storage due to their intriguing structures and high electrochemical activities, while relatively low optical modulation limits their widespread application. Significant efforts have been dedicated to improve the electrochromic properties, with one of the most promising approaches being the combination of POMs with conducting polymers to harness the synergistic effect that enhances electrochemical performance. In this study, a novel K12.5Na1.5[NaP5W30O110]⋅15H2O/TiO2@Poly(3,4-ethylenedioxythiophene) (P5W30/TiO2@PEDOT) nanocomposites were successfully synthesized using a combination of screen-printing and electrochemical deposition methods. Benefiting from the synergistic effect between P5W30/TiO2 and PEDOT, the as prepared nanocomposites exhibit enhanced transmittance modulation (74%), shorter switching time (＜4.6 s) as well as higher areal capacitance (47.9 mF cm−2 at 0.1 mA cm−2) than pure P5W30/TiO2 film. Additionally, a multicolored ESD was demonstrated by integrating P5W30/TiO2@PEDOT film with an electrochemically polymerized PANI film. Furthermore, this ESD enabled an intelligent visual monitoring of the energy storage status and powered LED bulb after charging. This work holds great significance in developing electrode materials based on POMs for bifunctional ESDs while providing new possibilities for electronic display applications.

Microwave-assisted fabrication and optimization of nickel cobalt phosphate for high-performance electrochromic supercapacitors

This study uses response surface methodology and central composite design (RSM/CCD) to explore the optimization of nickel cobalt phosphate (NiCoPO4) composites as effective materials for electrodes in electrochromic supercapacitors. The synthesis of NiCoPO4 powder is achieved through microwave-assisted techniques, and spin coating is employed to fabricate the NiCoPO4 composite electrode. Two factors, namely spin speed and time, are simultaneously investigated to assess their impact on the specific capacity of NiCoPO4 composites. Statistical analysis using Design Expert software indicates a quadratic model with a residual standard error of less than 4 %. The NiCoPO4 composites are subjected to various characterization techniques, including FTIR, Raman, XRD, XPS, and FESEM with EDX. Additionally, comprehensive electrochromic energy storage performance analyses are conducted, encompassing EIS, CV, GCD, stability, optical, and kinetic studies. The NiCoPO4 electrode material exhibits distinct color changes, appearing black at 0.5 V and pale green at 0 V, which signify its electrochromic properties. Furthermore, NiCoPO4 electrode material demonstrates exceptional optical performance, with a specific capacitance of 48.95 cm2/C, and supercapacitive performance, with a specific capacity of 262.8C/g, thus highlighting the as-prepared NiCoPO4 potential as a promising electrode material for electrochromic supercapacitors.

Multicolor electrochromic polymers based on butterfly-shaped monomers for the visualization of energy storage

Electrochromic supercapacitors (ECSCs) enable visual indication of their energy storage, thus effectively preventing them from being overcharged or insufficient energy. The current studies mainly focus on improving its specific capacitance and cycling stability. Herein, two butterfly-shaped triphenylamine-thiophene derivatives with twisted molecular structures were designed and synthesized featuring an EDOT unit as the central core. Then, two conjugated polymers pBTTPAE and pETPAE were prepared through electrochemical polymerization. Both polymers exhibit distinct multicolor display behavior, faster response time and excellent cycling stability. GCD tests show that pBTTPAE exhibited a higher volumetric specific capacitance (324.4 F·cm−3) and GCD stability due to its high specific area. The prototype device based on pBTTPAE is remarkable for its impressive energy density of 17.94 mWh·cm−3 and power density of 6.32 W·cm−3, which can be switched reversibly from yellow to yellow-green and blue when the potential changes from -0.4 V to 1.5 V. The high-performance electrochromic supercapacitor materials demonstrate their extensive utilizations for intelligent energy-storage devices.