Enhanced Copolymer Gel Modified by Dual Surfactants for Flexible Zinc-Air Batteries

Self-Healing Ionogel-Enabled Self-Healing and Wide-Temperature Flexible Zinc-Air Batteries with Ultra-Long Cycling Lives

Hydrogel-based zinc-air batteries (ZABs) are promising flexible rechargeable batteries. However, the practical application of hydrogel-based ZABs is limited by their short service life, narrow operating temperature range, and repair difficulty. Herein, a self-healing ionogel is synthesized by the photopolymerization of acrylamide and poly(ethylene glycol) monomethyl ether acrylate in 1-ethyl-3-methylimidazolium dicyanamide with zinc acetate dihydrate and first used as an electrolyte to fabricate self-healing ZABs. The obtained self-healing ionogel has a wide operating temperature range, good environmental and electrochemical stability, high ionic conductivity, satisfactory mechanical strength, repeatable and efficient self-healing properties enabled by the reversibility of hydrogen bonding, and the ability to inhibit the production of dendrites and by-products. Notably, the self-healing ionogel has the highest ionic conductivity and toughness compared to other reported self-healing ionogels. The prepared self-healing ionogel is used to assemble self-healing flexible ZABs with a wide operating temperature range. These ZABs have ultra-long cycling lives and excellent stability under harsh conditions. After being damaged, the ZABs can repeatedly self-heal to recover their battery performance, providing a long-lasting and reliable power supply for wearable devices. This work opens new opportunities for the development of electrolytes for ZABs.

Constructing amphipathic molecular layer to assists de-solvation process for dendrite-free Zn anode

Due to the excellent safety feature, substantial theoretical capacity and abundant zinc reserves in the earth's crust, Aqueous Zn-ion batteries (AZIBs) are promising as the next generation energy storage system. However, the problem of dendrite growth and the related side reactions in Zn surface limit their further development and application. Herein, an amphipathic molecular layer (Polyacrylic Acid, named as PAA) is constructed on Zn surface to hinder the side reactions and zinc dendrites by intervening the de-solvation process. It is found that the rich hydroxyl group in polyacrylic acid is very hydrophilic. On the contrary, hydrocarbon group on the other side is nearly hydrophobic. The amphiphilic PAA molecular layer on Zn surface results in lower de-solvation energy barrier, thus inhibits the decomposition of water and related side reactions. Additionally, the accumulate abundant negative charge at the interface of polyacrylic acid and Zn surface can attract homogeneous deposition of Zn atoms. Using only 0.01 M PAA as additive in 2.0 M ZnSO4 electrolyte. Zn||Zn symmetric cells expresses a superior cycling stability of 4643 h (5 mA cm-2, 1 mAh cm-2). This study provides new insights into the long-life AZIBs modulated by amphipathic molecular layer.

Biomass-Derived Bifunctional Cathode Electrocatalyst and Multiadaptive Gel Electrolyte for High-Performance Flexible Zn-Air Batteries in Wide Temperature Range

High-efficiency and low-cost bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as gel electrolytes with high thermal and mechanical adaptability are required for the development of flexible batteries. Herein, abundant Setaria Viridis (SV) biomass is selected as the precursor to prepare porous N-doped carbon tubes with high specific surface area and the 900 °C calcination product of SV (SV-900) shows the optimum ORR/OER activities with a small EOER -EORR of 0.734 V. Meanwhile, a new multifunctional gel electrolyte named C20E2G5 is prepared using cellulose extracted from another widely distributed biomass named flax as the skeleton, epichlorohydrin as the cross-linker and glycerol as the antifreezing agent. C20E2G5 possesses high ionic conductivity from -40 to + 60 °C, excellent tensile and compressive resistance, high adhesion, strong freezing and heat resistance. Moreover, the symmetrical cell assembled with C20E2G5 can significantly inhibit Zn dendrite growth. Finally, flexible solid-state Zn-air batteries assembled with SV-900 and C20E2G5 show high open circuit voltage, large energy density, and long-term operation stability between -40 and + 60 °C. This biomass-based approach is generic and can be used for the development of diverse next-generation electrochemical energy conversion and storage devices.

Recent progress in structural modification of polymer gel electrolytes for use in solid-state zinc-ion batteries

Zinc-ion batteries are one of the promising energy storage devices, which have the advantages of environmental friendliness, high safety and low price and are expected to be used in large-scale battery application fields. However, four prominent water-induced adverse reactions, including zinc dendrite formation, zinc corrosion, passivation and the hydrogen evolution reaction in aqueous systems, seriously shorten the cycling life of zinc-ion batteries and greatly hinder their development. Based on this, polymer gel electrolytes have been developed to alleviate these issues due to their unique network structure, which can reduce water activity and suppress water-induced side reactions. Based on the challenges of polymer gel electrolytes, this review systematically summarizes the latest research progress in the use of additives in them and explores new perspectives in response to the existing problems with polymer electrolytes. In order to expand the performance of polymer gel electrolytes in zinc-ion batteries, a range of different types of additives are added via physical/chemical crosslinking, such as organic or inorganic substances, natural plants, etc. In addition, different types of additives and polymerization crosslinking from different angles essentially improve the ionic conductivity of the gel electrolyte, inhibit the growth of zinc dendrites, and reduce hydrogen evolution and oxygen-absorbed corrosion. After these modifications of polymer gel electrolytes, a more stable and superior electrochemical performance of zinc-ion batteries can be obtained, which provides some strategies for solid-state zinc-ion batteries.

Highly stretchable, supersensitive, and self-adhesive ionohydrogels using waterborne polyurethane micelles as cross-linkers for wireless strain sensors

Due to the rapid development of multi-functional flexible wearable sensors, the development prospects of ionohydrogels with excellent mechanical properties and high sensitivity are necessary. In this work, a novel waterborne polyurethane (WPU) micelle with reactive groups on the surface has been prepared as a crosslinker and then reacted with polyacrylamide (PAM) to obtain a polyacrylamide-polyurethane/ionic liquid (PAM-WPU/IL) ionohydrogel. With the aid of ion-dipole interaction and crosslinks in the composite, the ionohydrogel exhibited ultrastretchability (up to 2927%), good mechanical resilience, and excellent self-adhesion strength (46.01 kPa). Furthermore, the ionohydrogel was used as a strain sensor for monitoring human movement with high strain sensitivity (gauge factor = 35). It is believed that this study provides a new idea for designing a multifunctional ionohydrogel for use in wearable electronics.