Highly Stable Supercapacitors Enabled by a New Conducting Polymer Complex PEDOT:CF3 SO2(x) PSS(1-x)

Herein, a novel conducting polymer complex PEDOT:CF₃ SO_2(x) PSS_(1-x) [denoted as S-PEDOT:CF₃ SO_2(x) PSS_(1-x) , where PEDOT is poly(3,4-ethylenedioxythiophene) and PSS is poly(styrene sulfonate)], is fabricated with the assistance of zinc di[bis(trifluoromenthylsulfonyl) imide][Zn(TFSI)₂ ] (CFE). The introduction of CF₃ SO₂ ^- group is expected to bring better stability of PEDOT:CF₃ SO₂ than PEDOT:PSS due to its strong Coulomb force. Electrochemical measurement shows that a high specific capacitance of 194 F cm^-3 was achieved from the novel complex S-PEDOT:CF₃ SO_2(x) PSS_(1-x) , the highest value reported so far. An all-solid-state supercapacitor assembly with a structure of S-PEDOT:CF₃ SO_2(x) PSS_(1-x) /H₂ SO₄ :polyvinyl alcohol (PVA)/S-PEDOT:CF₃ SO_2(x) PSS_(1-x) shows a record specific capacitance of 70.9 F cm^-3 and a maximum energy density of 6.02 mWh cm^-3 at a power density of 397 mW cm^-3 . This supercapacitor device demonstrates excellent electrochemical stability with a capacitance retention rate of 98 % after 10 000 cycles and extreme air stability of 96 % capacitance retention rate after 10 000 cycles, even if the device is exposed to air over 2880 h, much better than that of PEDOT:PSS based supercapacitors. Excellent capacitance can be achieved from PEDOT:CF₃ SO_2(x) PSS_(1-x) electrode under electrolyte-free conditions. This work provides a novel method for high performance stable supercapacitors and may pave the way for the commercialization of PEDOT based supercapacitors.

Excellent rate capability supercapacitor based on a free-standing PEDOT:PSS film enabled by the hydrothermal method

For the first time, herein, the hydrothermal method with H₂SO₄ as the solvent is introduced to enhance the rate capability of free-standing pristine PEDOT:PSS films. The film with a record conductivity of 3188 S cm^-1 displays a rectangular characteristic at an ultrahigh scan rate of 1300 mV s^-1 and a stable specific capacitance of 110 F cm^-3 from 0.1 to 100 A cm^-3, with a capacitance retention of up to 94.8%. The flexible supercapacitor based on the films delivers a comparable energy density of 2.96 mW h cm^-3 even at a high power density of 36 685 mW cm^-3. This study provides an effective method to prepare PEDOT:PSS films with outstanding electrochemical properties and potentially expand its applications in flexible devices.

High-Conductivity, Flexible and Transparent PEDOT:PSS Electrodes for High Performance Semi-Transparent Supercapacitors

Herein, we report a flexible high-conductivity transparent electrode (denoted as S-PH1000), based on conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and itsapplication to flexible semi-transparentsupercapacitors. A high conductivity of 2673 S/cm was achieved for the S-PH1000 electrode on flexible plastic substrates via a H₂SO₄ treatment with an optimized concentration of 80 wt.%. This is among the top electrical conductivities of PEDOT:PSS films processed on flexible substrates. As for the electrochemical properties,a high specific capacitance of 161F/g was obtained from the S-PH1000 electrode at a current density of 1 A/g. Excitingly, a specific capacitance of 121 F/g was retained even when the current density increased to 100 A/g, which demonstrates the high-rate property of this electrode. Flexible semi-transparent supercapacitors based on these electrodes demonstrate high transparency, over 60%, at 550 nm. A high power density value, over 19,200 W/kg,and energy density, over 3.40 Wh/kg, was achieved. The semi-transparent flexible supercapacitor was successfully applied topower a light-emitting diode.

Self-Standing Hydrogels Composed of Conducting Polymers for All-Hydrogel-State Supercapacitors

Conducting polymer hydrogels that are capable of contacting with electrolytes at the molecular level, represent an important electrode material. However, the fabrication of self-standing hydrogels merely composed of conducting polymers is still challenging owing to the absence of reliable methods. Herein, a novel and facile macromolecular interaction assisted route is reported to fabricate self-standing hydrogels consisting of polyaniline (PANi: providing high electrochemical activity) and poly(3,4-ethylenedioxythiophene) (PEDOT: enabling high electronic conductivity). Owing to the synergistic effect between them, the self-standing hydrogels possess good mechanical properties and electronic/electrochemical performances, making them an excellent potential electrode for solid-state energy storage devices. A proof-of-concept all-hydrogel-state supercapacitor is fabricated, which exhibits a high areal capacitance of 808.2 mF cm^-2 , and a high energy density of 0.63 mWh cm^-3 at high power density of 28.42 mW cm^-3 , superior to many recently reported conducting polymer hydrogels based supercapacitors. This study demonstrates a novel promising strategy to fabricate self-standing conducting polymer hydrogels.

Highly Conductive Ti3 C2 Tx MXene Hybrid Fibers for Flexible and Elastic Fiber-Shaped Supercapacitors

Fiber-shaped supercapacitors (FSCs) are promising energy storage solutions for powering miniaturized or wearable electronics. However, the scalable fabrication of fiber electrodes with high electrical conductivity and excellent energy storage performance for use in FSCs remains a challenge. Here, an easily scalable one-step wet-spinning approach is reported to fabricate highly conductive fibers using hybrid formulations of Ti₃ C₂ T_x MXene nanosheets and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate. This approach produces fibers with a record conductivity of ≈1489 S cm^-1 , which is about five times higher than other reported Ti₃ C₂ T_x MXene-based fibers (up to ≈290 S cm^-1 ). The hybrid fiber at ≈70 wt% MXene shows a high volumetric capacitance (≈614.5 F cm^-3 at 5 mV s^-1 ) and an excellent rate performance (≈375.2 F cm^-3 at 1000 mV s^-1 ). When assembled into a free-standing FSC, the energy and power densities of the device reach ≈7.13 Wh cm^-3 and ≈8249 mW cm^-3 , respectively. The excellent strength and flexibility of the hybrid fibers allow them to be wrapped on a silicone elastomer fiber to achieve an elastic FSC with 96% capacitance retention when cyclically stretched to 100% strain. This work demonstrates the potential of MXene-based fiber electrodes and their scalable production for fiber-based energy storage applications.

Freestanding flexible polymer films based on bridging of two EDOT units with functionalized chains for use in long-term-stable supercapacitors

Freestanding flexible films were prepared by cross-linking two EDOT unit with fictionalized flexible chains, the application of these films in supercapacitors showed excellent cycling life.

Achieving Ultrahigh Energy Density and Long Durability in a Flexible Rechargeable Quasi-Solid-State Zn-MnO2 Battery

Advanced flexible batteries with high energy density and long cycle life are an important research target. Herein, the first paradigm of a high-performance and stable flexible rechargeable quasi-solid-state Zn-MnO₂ battery is constructed by engineering MnO₂ electrodes and gel electrolyte. Benefiting from a poly(3,4-ethylenedioxythiophene) (PEDOT) buffer layer and a Mn²⁺ -based neutral electrolyte, the fabricated Zn-MnO₂ @PEDOT battery presents a remarkable capacity of 366.6 mA h g^-1 and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl₂ /MnSO₄ gel as electrolyte, the as-fabricated quasi-solid-state Zn-MnO₂ @PEDOT battery remains highly rechargeable, maintaining more than 77.7% of its initial capacity and nearly 100% Coulombic efficiency after 300 cycles. Moreover, this flexible quasi-solid-state Zn-MnO₂ battery achieves an admirable energy density of 504.9 W h kg^-1 (33.95 mW h cm^-3 ), together with a peak power density of 8.6 kW kg^-1 , substantially higher than most recently reported flexible energy-storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn-MnO₂ battery opens new opportunities for powering portable and wearable electronics.

Metal-Organic Coaxial Nanowire Array Electrodes Combining Large Energy Capacity and High Rate Capability

Pseudocapacitors have been widely studied in the context of their potential applications in portable electronics and energy regeneration. However, the internal resistance within these devices hampers charge transport and limits their performance. As a result, maximum charge/discharge rates are typically limited to a few hundred mV s^-1 for pseudocapacitors. Beyond this limit, capacitance rapidly decreases and devices become incapable of storing energy. Here, we design electrodes in which coaxial nanowires made of highly conductive metal cores and pseudocapacitive organic shells are fabricated into a seamless, monolithic, and vertically aligned structure. The design of this structure reduces its internal resistance, and devices fabricated using these electrodes exhibit excellent energy capacity even when charged/discharged at high rates of more than a few hundred mV s^-1 . The energy density obtained in these devices corresponds to the maximum energy density predicted by the Trasatti method, and the coaxial-nanowire structure of the electrodes enhances the charge storage capacity and rate capability simultaneously.