Long-life flexible supercapacitors based on nitrogen-doped porous graphene@π-conjugated polymer film electrodes and porous quasi-solid-state polymer electrolyte

Integrated Construction Improving Electrochemical Performance of Stretchable Supercapacitors Based on Ant-Nest Amphiphilic Gel Electrolytes

Aqueous integrated stretchable supercapacitors (ISSCs) have attracted extensive attention due to the intrinsic safety in future wearable electronics. However, aqueous ISSCs usually suffer from low energy density and poor dynamic deformation stability owing to the conventional hydrogel electrolytes' narrow electrochemical stability window (ESW) and dissatisfied interface bonding. Herein, an ant-nest amphiphilic polyurethane hydro/organogel electrolyte (sAPUGE) with a wide ESW (≈2.2 V) and superb self-adhesion is prepared by electrospinning, which interacts with carbon-based stretchable electrodes for the construction of flame-retardant PU-based sAPUGE-ISSC. Benefitting from the synergistic effect of chemical bonding and mechanical meshing between the electrode and gel electrolyte interface, as-assembled sAPUGE-ISSC delivers a high energy density of 13.7 mWh cm^-3 (at a power density of 0.126 W cm^-3 ) and outstanding dynamic deformation stability (98.3% capacitance retention after 500 stretching cycles under 100% strain). This unique hydro/organogel electrolyte provides a pathway toward the next generation of wearable energy products in modern electronics.

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.

Layer-by-Layer Electrode Fabrication for Improved Performance of Porous Polyimide-Based Supercapacitors

Nanoporous polymers are becoming increasingly interesting materials for electrochemical applications, as their large surface areas with redox-active sites allow efficient adsorption and diffusion of ions. However, their limited electrical conductivity remains a major obstacle in practical applications. The conventional approach that alleviates this problem is the hybridisation of the polymer with carbon-based additives, but this directly prevents the utilisation of the maximum capacity of the polymers. Here, we report a layer-by-layer fabrication technique where we separated the active (porous polymer, top) layer and the conductive (carbon, bottom) layer and used these “layered” electrodes in a supercapacitor (SC). Through this approach, direct contact with the electrolyte and polymer material is greatly enhanced. With extensive electrochemical characterisation techniques, we show that the layered electrodes allowed a significant contribution of fast faradic surface reactions to the overall capacitance. The electrochemical performance of the layered-electrode SC outperformed other reported porous polymer-based devices with a specific gravimetric capacitance of 388 F·g⁻¹ and an outstanding energy density of 65 Wh·kg⁻¹ at a current density of 0.4 A·g⁻¹. The device also showed outstanding cyclability with 90% of capacitance retention after 5000 cycles at 1.6 A·g⁻¹, comparable to the reported porous polymer-based SCs. Thus, the introduction of a layered electrode structure would pave the way for more effective utilisation of porous organic polymers in future energy storage/harvesting and sensing devices by exploiting their nanoporous architecture and limiting the negative effects of the carbon/binder matrix.

A review of π-conjugated polymer-based nanocomposites for metal-ion batteries and supercapacitors

Owing to their extraordinary properties of π-conjugated polymers (π-CPs), such as light weight, structural versatility, ease of synthesis and environmentally friendly nature, they have attracted considerable attention as electrode material for metal-ion batteries (MIBs) and supercapacitors (SCPs). Recently, researchers have focused on developing nanostructured π-CPs and their composites with metal oxides and carbon-based materials to enhance the energy density and capacitive performance of MIBs and SCPs. Also, the researchers recently demonstrated various novel strategies to combine high electrical conductivity and high redox activity of different π-CPs. To reflect this fact, the present review investigates the current advancements in the synthesis of nanostructured π-CPs and their composites. Further, this review explores the recent development in different methods for the fabrication and design of π-CPs electrodes for MIBs and SCPs. In review, finally, the future prospects and challenges of π-CPs as an electrode materials for strategies for MIBs and SCPs are also presented.

Synthesis of a Three-Dimensional Interconnected Oxygen-, Boron-, Nitrogen-, and Phosphorus Tetratomic-Doped Porous Carbon Network as Electrode Material for the Construction of a Superior Flexible Supercapacitor

To construct a high-performance next-generation carbon-based flexible supercapacitor, high porosity, large mass density, and high flexibility are three significant challenging goals. However, one side always affects another. Herein, high-density tetratomic-doped porous composite carbon derived from sustainable biomaterials is achieved via two-step processes of carbonization and acid-washing treatment. The assembled carbon-based electrodes are highly doped with various heteroatoms (B, O, N, and P) for 33.59 atom %, resulting in abundant porosity, high densities, high pseudocapacitive contribution for 84.5%, and superior volumetric capacitive performance. The fabricated flexible electrode exhibits high flexibility, high mass loading (316 mg cm^-3), and remarkable tensile strength (44.6 MPa). Generally, the volumetric performance is key and a significant parameter to appraise the electrochemical characteristics of flexible supercapacitors within a limited space. The aqueous symmetric supercapacitor demonstrates a high volumetric energy density and an excellent power density of 2.08 mWh cm^-3 and 498.4 mW cm^-3, respectively, along with 99.6% capacitance retention after 20 000 cycles, making it competitive to even some pseudocapacitors.