Tough and redox-mediated alkaline gel polymer electrolyte membrane for flexible supercapacitor with high energy density and low temperature resistance

A synergistic enhancement strategy for mechanical and conductive properties of hydrogels with dual ionically cross-linked κ-carrageenan/poly(sodium acrylate-co-acrylamide) network

Applying conductive hydrogels in electronic skin, health monitoring, and wearable devices has aroused great research interest. Yet, it remains a significant challenge to prepare conductive hydrogels simultaneously with superior mechanical, self-recovery, and conductivity performance. Herein, a dual ionically cross-linked double network (DN) hydrogel is fabricated based on K+ and Fe3+ ion cross-linked κ-carrageenan (κ-CG) and Fe3+ ion cross-linked poly(sodium acrylate-co-acrylamide) P(AANa-co-AM). Benefiting from the abundance of hydrogen bonds and metal coordination bonds, the conductive hydrogel has excellent mechanical properties (fracture strain up to 1420 %, fracture stress up to 2.30 MPa, and toughness up to 20.63 MJ/m3) and good self-recovery performance (the recovery rate of the toughness can reach 85 % after waiting for 1 h). Meanwhile, due to the introduction of dual metal ions of K+ and Fe3+, the ionic conductivity of conductive hydrogel is up to 1.42 S/m. Furthermore, the hydrogel strain sensor has good sensitivity with a gauge factor (GF) of 2.41 (0-100 %). It can be a wearable sensor that monitors different human motions, such as sit-ups. This work offers a new synergistic strategy for designing a hydrogel strain sensor with high mechanical, self-recovery, and conductive properties.

A Comparison of the Electrical Properties of Gel Polymer Electrolyte-Based Supercapacitors: A Review of Advances in Electrolyte Materials

Flexible solid-state-based supercapacitors are in demand for the soft components used in electronics. The increased attention paid toward solid-state electrolytes could be due to their advantages, including no leakage, special separators, and improved safety. Gel polymer electrolytes (GPEs) are preferred in the energy storage field, likely owing to their safety, lack of leakage, and compatibility with various separators as well as their higher ionic conductivity (IC) than traditional solid electrolytes. This review covers the classification, properties, and configurations of different GPE-based supercapacitors and recent advancements that have occurred in this area of energy storage. Ionic liquid (IL)-based materials are popular GPEs for electrochemical energy storage and can be used to prepare unprecedented flexible supercapacitors due to their great IC and wide potential range. A comparative assessment of the GPEs-based supercapacitors reveals that in a majority of them, the value of specific capacitance is generally under 1000 F g-1, energy density reaches around 125 Wh kg-1, and the power density is seen to be less than 1500 W kg-1. The results of this research serve as an essential reference for upcoming scholars, and could significantly improve our comprehension of the efficacy of GPE-containing supercapacitors.

Natural redox mediator anthraquinone aloe-emodin facilitated the in-situ mineralized γ-FeO(OH) membrane for the removal of tannic acid through photocatalytic-PMS activation

The growing utilization of Traditional Chinese Medicine (TCM) has resulted in an increase in wastewater. Herein, a new kind of organic-inorganic redox mediator membrane by immobilizing γ-FeO(OH) and aloe-emodin(AE) with the characteristic large π-conjugation anthraquinone structure on PVDF membrane was innovatively achieved. AE exhibiting both electron deficiency and redox activity possesses a co-catalyst role in degradation of tannic acid (TA), aiding in the separation of charge carriers through the sequential hydrogenation and dehydrogenation of AE. The removal rates of TA were 92.8 % in the tannic acid solution and 60.3 % in the simulated rhubarb wastewater by the AE-γ-FeO(OH) membrane under PMS+Vis conditions in 45 min. Also, they show a higher recovery of pure water flux and owning good fouling performance. Overall, this current work presents a novel approach for the design and preparation of organic-inorganic photocatalytic composite membrane using readily available natural products for the purification TCM wastewater.

Integrated supercapacitor with self-healing, arbitrary deformability and anti-freezing based on gradient interface structure from electrode to electrolyte

Flexible supercapacitors have attracted more and more attention because of their promising applications in wearable electronics, however, it is still important to harmonize their mechanical and electrochemical properties for practical applications. In the present work, a seamless transition between polyaniline (PANI) electrode and NH₄VO₃_FeSO₄ dual redox-mediated gel polymer electrolyte (GPE) is presented through in situ formation of gradient interface structure. Multiple physical interactions make the GPE excellent mechanical and self-healing properties. Meanwhile, double role functions of Fe²⁺ ions greatly relieve the traditional contradiction between mechanical and electrochemical properties of GPE. Moreover, benefiting from the structure and reversible redox reactions of VO^3- and Fe²⁺, the integrated supercapacitor delivers an exceptional specific capacitance of 441.8 mF/cm², a high energy density of 63.1 μWh/cm², remarkable cyclic stability. Simultaneously, the gradient structure from PANI electrode to GPE greatly improves the electrode/electrolyte interface compatibility and ion transport, which endows the supercapacitor with stable electrochemical performance. Furthermore, the supercapacitor well-maintains the specific capacitance even at -20 °C with over 89.19 % retention after 6 cutting/healing cycles. The gradient interface structure design will promote the development of high-performance supercapacitor.

Integrated photo-inspired antibacterial polyvinyl alcohol/carboxymethyl cellulose hydrogel dressings for pH real-time monitoring and accelerated wound healing

Recurrent infection of chronic wounds remains a major clinical challenge. Recently, the hydrogel antibacterial materials have attracted extensive attention for preventing infection in wound healing. In this study, a hybrid hydrogel made of polyvinyl alcohol - iodine (PAI), sodium carboxymethyl cellulose (CMC), and carbamino quantum dot (CQDs) was prepared by the cross-linking of hydrogen bonds, named as polyvinyl alcohol‑iodine/sodium carboxymethyl cellulose/carbon quantum dots (PAI/CMC/CQDs). The composite hydrogels exhibited the outstanding photothermal conversion efficiency with near infrared (NIR) light irradiation, and the high antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Meanwhile, the elevated temperature of the composite hydrogels up to ~45 °C was able to stimulate the migration of epidermal cell to accelerate skin repair. Given that PAI and CQDs could respond to different pH values (5-8), the real-time would pH information was provided by the visible light and fluorescent light dual monitoring system by naked eye. Moreover, the visible-fluorescent images could be collected and transformed into RGB signals to quantify the would pH levels, avoiding secondary injuries caused by frequent dressing changes. PAI/CMC/CQDs was demonstrated the significant therapeutic effect on chronic wounds by eliminating bacterial infections and promoting skin repair under the smart RGB monitoring system.

A polymer electrolyte design enables ultralow-work-function electrode for high-performance optoelectronics

Ambient solution-processed conductive materials with a sufficient low work function are essential to facilitate electron injection in electronic and optoelectronic devices but are challenging. Here, we design an electrically conducting and ambient-stable polymer electrolyte with an ultralow work function down to 2.2 eV, which arises from heavy n-doping of dissolved salts to polymer matrix. Such materials can be solution processed into uniform and smooth films on various conductors including graphene, conductive metal oxides, conducting polymers and metals to substantially improve their electron injection, enabling high-performance blue light-emitting diodes and transparent light-emitting diodes. This work provides a universal strategy to design a wide range of stable charge injection materials with tunable work function. As an example, we also synthesize a high-work-function polymer electrolyte material for high-performance solar cells.

Ambient-stable solution-processed conductive materials with a low work function are essential to facilitate electron injection. Here, the authors design and synthesise polymer electrolyte with work function down to 2.2 eV for applications in high-performance light-emitting diodes and solar cells.