Twisted ladder-like donor-acceptor polymers as electrode materials for flexible electrochromic supercapacitors

Ultra-Stable High-Capacity Polythiophene Derivative for Wide-Potential-Window Supercapacitors

Conducting polymer (CP)-based supercapacitors show great promise for applications in the field of wearable and portable electronics. However, these supercapacitors face persistent challenges, notably low energy density and inadequate stability. In this study, we introduce a polythiophene derivative, designated as poly(EPE), synthesized via the electrochemical polymerization of 8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (EPE). The resulting poly(EPE) polymer exhibits an exemplary 3D porous network-like structure, significantly enhancing its capacitance performance. When employed as the electrode material, the symmetric supercapacitor demonstrates an exceptionally high specific capacitance of 1342 F g-1 at a current density of 4.0 A g-1, along with impressive energy and power densities of 119.3 W h kg-1 and 38.83 kW kg-1, respectively. These capacitance values surpass those of previously reported pristine CP-based supercapacitors. Notably, the supercapacitor showcases outstanding stability, maintaining a retention rate of 92.5% even after 50,000 charge-discharge cycles. These findings underscore the substantial potential of poly(EPE) as an electrode material for the advancement of the supercapacitor technology.

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.

Energy Storage Application of Conducting Polymers Featuring Dual Acceptors: Exploring Conjugation and Flexible Chain Length Effects

Solution-processable conducting polymers (CPs) are a compelling alternative to inorganic counterparts because of their potential for tuning chemical properties and creating flexible organic electronics. CPs, which typically comprise either only an electron donor (D) or its alternative combinations with an electron acceptor (A), exhibit charge transfer behavior between the units, resulting in an electrical conductivity suitable for utilization in electronic devices and for energy storage applications. However, the energy storage behavior of CPs with a sequence of electron acceptors (A-A), has rarely been investigated, despite their promising lower band gap and higher charge carrier mobility. Utilizing the aforesaid concept herein, four CPs featuring benzodithiophenedione (BDD), and diketopyrrolepyrrole (DPP) are synthesized. Among them, the BDDTH-DPPEH polymer exhibited the highest specific capacitance of 126.5 F g^-1 at a current density of 0.5 A g^-1 in an organic electrolyte over a wide potential window of -0.6-1.4 V. Notably, the supercapacitor properties of the polymeric electrode materials improved with increasing conjugation length by adding thiophene donor units and shortening the alkyl chain lengths. Furthermore, a symmetric supercapacitor device fabricated using BDDTH-DPPEH exhibited a high-power density of 4000 W kg^-1 and an energy density of 31.66 Wh kg^-1 .

Sea-Cucumber-like Microstructure Polyoxometalate/TiO2 Nanocomposite Electrode for High-Performance Electrochromic Energy Storage Devices

The key challenge in the practical application of electrochromic energy storage devices (EESDs) is the fabrication of high-performance electrode materials. Herein, we deposited K7[La(H2O)x(α2-P2W17O61)] (P2W17La) onto TiO2 nanowires (NW) to construct an NW–P2W17La nanocomposite using a layer-by-layer self-assembly method. In contrast to the pure P2W17La films, the nanocomposite exhibits enhanced electrochromic and electrochemical performance owing to the 3D sea-cucumber-like microstructure. An EESD using the NW–P2W17La film as the cathode exhibited outstanding electrochromic and energy storage properties, with high optical modulation (48.6% at 605 nm), high switching speeds (tcoloring = 15 s, tbleaching = 4 s), and high area capacitance (5.72 mF cm−2 at 0.15 mA cm−2). The device can reversibly switch between transparent and dark blue during the charge/discharge process, indicating that electrochromic contrast can be used as a quantitative indicator of the energy storage status.

Recent Progress and Future Prospects on All-Organic Polymer Dielectrics for Energy Storage Capacitors

With the development of advanced electronic devices and electric power systems, polymer-based dielectric film capacitors with high energy storage capability have become particularly important. Compared with polymer nanocomposites with widespread attention, all-organic polymers are fundamental and have been proven to be more effective choices in the process of scalable, continuous, and large-scale industrial production, leading to many dielectric and energy storage applications. In the past decade, efforts have intensified in this field with great progress in newly discovered dielectric polymers, fundamental production technologies, and extension toward emerging computational strategies. This review summarizes the recent progress in the field of energy storage based on conventional as well as heat-resistant all-organic polymer materials with the focus on strategies to enhance the dielectric properties and energy storage performances. The key parameters of all-organic polymers, such as dielectric constant, dielectric loss, breakdown strength, energy density, and charge-discharge efficiency, have been thoroughly studied. In addition, the applications of computer-aided calculation including density functional theory, machine learning, and materials genome in rational design and performance prediction of polymer dielectrics are reviewed in detail. Based on a comprehensive understanding of recent developments, guidelines and prospects for the future development of all-organic polymer materials with dielectric and energy storage applications are proposed.

Physical and Electrochemical Properties of Soluble 3,4-Ethylenedioxythiophene (EDOT)-Based Copolymers Synthesized via Direct (Hetero)Arylation Polymerization

Over the past decades, π-conjugated polymers (CPs) have drawn more and more attention and been essential materials for applications in various organic electronic devices. Thereinto, conjugated polymers based on the 3,4-ethylenedioxythiophene (EDOT) backbone are among the high-performance materials. In order to investigate the structure-property relationships of EDOT-based polymers and further improve their electrochemical properties, a series of organic solvent-soluble EDOT-based alternative copolymers consisting of electron-rich fragments (fluorene P1, carbazole P2, and 3,4-alkoxythiophene P3) or electron-deficient moieties (benzotriazole P4 and thieno[3,4-c]pyrrole-4,6-dione P5) were synthesized via direct C-H (hetero)arylation polymerization (DHAP) in moderate to excellent yields (60-98%) with medium to high molecular weights (M n = 3,100-94,000 Da). Owing to their various electronic and structural properties, different absorption spectra (λ max = 476, 380, 558, 563, and 603 nm) as well as different specific capacitances of 70, 68, 75, 51, and 25 F/g with 19, 10, 21, 26, and 69% of capacity retention after 1,000 cycles were observed for P1-P5, respectively. After careful study through multiple experimental measurements and theoretical calculation, appropriate electronic characteristics, small molecular conformation differences between different oxidative states, and well-ordered molecular stacking could improve the electrochemical performance of CPs.

Preparation and application of a D–A conjugated electrochromic flexible electrode with side chain carbazole active groups in supercapacitors

Electrochromic power storage devices (ESCs) integrate energy storage and electrochromic behaviour into a single full cell that can enable the visualization of the energy status by the naked eye.

Highly Stable Indacenodithieno[3,2-b]thiophene-Based Donor-Acceptor Copolymers for Hybrid Electrochromic and Energy Storage Applications

Stable doping of indacenodithieno[3,2-b]thiophene (IDTT) structures enables easy color tuning and significant improvement in the charge storage capacity of electrochromic polymers, making use of their full potential as electrochromic supercapacitors and in other emerging hybrid applications. Here, the IDTT structure is copolymerized with four different donor-acceptor-donor (DAD) units, with subtle changes in their electron-donating and electron-withdrawing characters, so as to obtain four different donor-acceptor copolymers. The polymers attain important form factor requirements for electrochromic supercapacitors: desired switching between achromatic black and transparent states (L*a*b* 45.9, -3.1, -4.2/86.7, -2.2, and -2.7 for PIDTT-TBT), high optical contrast (72% for PIDTT-TBzT), and excellent electrochemical redox stability (Ired/Iox ca. 1.0 for PIDTT-EBE). Poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(2-hexyldecyl)-2H-benzo[d][1,2,3]triazole-7,7'-diyl] (PIDTT-EBzE) stands out as delivering simultaneously a high contrast (69%) and doping level (>100%) and specific capacitance (260 F g-1). This work introduces IDTT-based polymers as bifunctional electro-optical materials for potential use in color-tailored, color-indicating, and self-regulating smart energy systems.