Bioinspired Tough Solid-State Electrolyte for Flexible Ultralong-Life Zinc-Air Battery

Engineered Wood-Derived Porous Hydrogel Composites for High-Performance Anisotropic Polyelectrolytes in Flexible Electronic Devices

Natural wood has long inspired the development of artificial biomimetic and bioinspired materials aimed at enhancing human life. However, a major challenge lies in developing straightforward and versatile approaches for producing high-performance, porous wood-derived materials. In this work, we introduce a space-confined porogen photochemistry strategy for engineering wood-derived porous hydrogel composites. Under light irradiation, the nitrogen gas release and the liquid precursor rapidly solidify into hydrogels within 30 s, facilitating in situ pore formation within the wood template. The integration of aligned wood structures with hydrogel multinetworks yields a composite material capable of sustaining a maximum stress of 7 MPa at a critical strain of 200%, with a high porosity of 70%. The anisotropic nature enhances directional ion transport and sensing with performance further tunable by adjusting porosity. This capability positions these materials as promising candidates for flexible zinc-air batteries, which demonstrate a higher output voltage and power density. Additionally, the superior mechanical integrity and water-retention abilities extend the battery life (up to ∼120 h) and support flexibility, as shown by 1000 cycles in bending tests. This space-confined porogen photochemistry approach and the resulting wood-derived composites are poised to make a significant impact in fields spanning energy storage, sensing technologies, and beyond.

Gelatin-based gel polymer electrolytes with high ionic conductivity for temperature adaptive flexible zinc-air batteries

Zinc-air batteries (ZABs) have gained increasing attention due to their high energy density and environmental sustainability. However, challenges such as dendrite formation on zinc anodes in flexible ZABs, particularly under highly alkaline conditions, have hindered their performance. In this study, we introduced a simple and effective approach to design a double-network gel polymer electrolyte (GPE) composed of polyacrylamide (PAM) and gelatin (PAG). The helical structure of the gelatin network facilitated uniform zinc ion transport, while the polar groups in PAG stabilized water molecules, reducing evaporation and freezing. Notably, the PAG GPE retained over 57 % of its water content after 240 h of air exposure. The ZABs incorporating the PAG GPE exhibited superior ionic conductivity (215 mS·cm-1) and an impressive maximum specific capacity of 737 mAh·g-1. Compared to PAM-only GPEs, the PAG-based batteries showed a 1.68-fold improvement in cycle life. Furthermore, the PAG GPE-based ZABs maintained exceptional stability over a wide temperature range from -40 °C to 60 °C, with an extended cycling lifespan of 140 h at -40 °C. These results underscored the suitability of PAG GPE for applications in extreme environments. Experimental results and simulations confirmed that the PAG GPE effectively promoted uniform zinc ion deposition, significantly suppressing dendrite growth. This innovative hydrogel electrolyte, integrated into flexible ZABs, provided a robust solution for next-generation flexible electronics.

Carboxymethyl chitosan modified double-skeleton hydrogel electrolyte enables high performance for flexible zinc-air batteries

Flexible Zn-air batteries (FZABs) are regarded as promising energy storage devices for wearable electronics because of their intrinsic safety and high energy densities. However, the low water absorption, low ionic conductivity, and poor water retention of hydrogel electrolytes lead to serious charge/discharge polarization, low discharge capacity, and a short lifespan of FZABs. A novel hydrogel, named polyvinyl alcohol-polyacrylamide-carboxymethyl chitosan (PVA-PAM-CMCS), is developed to address the aforementioned issues. Through the hydrogen bonds and electrostatic interactions, CMCS is connected with the PAM-PVA backbone, which induces a denser and finer porous structure in the hydrogel. Taking advantage of the structural modification, the PVA-PAM-CMCS hydrogel electrolyte shows enhanced ionic conductivity (108.65 mS cm-1) and improved tensile stress (244.1 kPa) and strain (410.7 %). 2D fabric FZABs with PVA-PAM-CMCS hydrogel electrolyte exhibit long cycle life (118 h), impressive discharge capacity (805.3 mAh g-1), and maximum power density (91.04 mW cm-2). Furthermore, 1D yarn FZABs with PVA-PAM-CMCS electrolyte are continuously produced in an integrated manner by the yarn-wrapping technique. These yarn batteries can maintain stable electrochemical performance under both bending and stretching conditions. The combined design methodology of PVA-PAM-CMCS hydrogel electrolyte and yarn-wrapping technique for 1D yarn FZABs opens a new avenue to power various portable electronics.

Regulating Interfacial Wettability for Fast Mass Transfer in Rechargeable Metal-Based Batteries

The interfacial wettability between electrodes and electrolytes could ensure sufficient physical contact and fast mass transfer at the gas-solid-liquid, solid-liquid, and solid-solid interfaces, which could improve the reaction kinetics and cycle stability of rechargeable metal-based batteries (RMBs). Herein, interfacial wettability engineering at multiphase interfaces is summarized from the electrolyte and electrode aspects to promote the interface reaction rate and durability of RMBs, which illustrates the revolution that is taking place in this field and thus provides inspiration for future developments in RMBs. Specifically, this review presents the principle of interfacial wettability at macro- and microscale and summarizes emerging applications concerning the interfacial wettability effect on mass transfer in RMBs. Moreover, deep insight into the future development of interfacial wettability is provided in the outlook. Therefore, this review not only provides insights into interfacial wettability engineering but also offers strategic guidance for wettability modification and optimization toward stable electrode-electrolyte interfaces for fast mass transfer in RMBs.

High-Density Accessible Iron Single-Atom Catalyst for Durable and Temperature-Adaptive Laminated Zinc-Air Batteries

Designing single-atom catalysts (SACs) with high density of accessible sites by improving metal loading and sites utilization is a promising strategy to boost the catalytic activity, but remains challenging. Herein, a high site density (SD) iron SAC (D-Fe-N/C) with 11.8 wt.% Fe-loading is reported. The in situ scanning electrochemical microscopy technique attests that the accessible active SD and site utilization of D-Fe-N/C reach as high as 1.01 × 1021 site g-1 and 79.8%, respectively. Therefore, D-Fe-N/C demonstrates superior oxygen reduction reaction (ORR) activity in terms of a half-wave potential of 0.918 V and turnover frequency of 0.41 e site-1 s-1. The excellent ORR property of D-Fe-N/C is also demonstrated in the liquid zinc-air batteries (ZABs), which exhibit a high peak power density of 306.1 mW cm-2 and an ultra-long cycling stability over 1200 h. Moreover, solid-state laminated ZABs prepared by presetting an air flow layer show a high specific capacity of 818.8 mA h g-1, an excellent cycling stability of 520 h, and a wide temperature-adaptive from -40 to 60 °C. This work not only offers possibilities by improving metal-loading and catalytic site utilization for exploring efficient SACs, but also provides strategies for device structure design toward advanced ZABs.

Constructing Artificial Zincophilic Interphases Based on Indium-Organic Frameworks as Zinc Dendrite Constraint for Rechargeable Zinc-Air Battery

The practical application of zinc (Zn)-air batteries is largely restricted by their inferior cyclability, especially under fast-charging conditions. Uneven Zn plating and dendrite formation result in their short circuits. In this work, an artificial solid-electrolyte interphase (SEI) is constructed using indium-organic frameworks (IOF) on the Zn anode. It contains a hybrid architecture that integrates chemical and morphological contributions to regulate Zn plating behaviors and constrain dendrite growth. The atomically dispersed In3+ provides zincophilic sites to tune Zn nucleation kinetics and promote preferential growth along (002) crystal facet. Meanwhile, IOF exhibits nanosheets-assembled microspheres with a well-ordered porous architecture, which promotes mass transfer and affords space for Zn electrodeposition. The influence of SEI microstructure on Zn plating/stripping behavior is further investigated and validated by the post-cycling characterizations. With IOF based SEI, Zn symmetric cells perform stable cycling for over 1750 h at 10 mA cm-2. When powering Zn-air batteries, their cycling life is extended to 800 h, which is approximately four times longer than that of pristine Zn foil.

Advanced Eutectogel Electrolyte for High-Performance and Wide-Temperature Flexible Zinc-Air Batteries

Despite ongoing challenges, achieving further breakthroughs in the development of gel polymer electrolytes with a wide temperature range, excellent liquid retention capability and enhanced anode compatibility in flexible zinc-air batteries (FZABs) remains a significant objective. This study presents a significant advancement in the development of choline chloride/ethylene glycol-polyvinyl alcohol (ChCl/EG-PVA) eutectogel electrolyte, tailored for high-performance operation across a wide temperature range. Systematic in-situ and ex-situ characterizations and theoretical simulations confirm the formation of robust hydrogen bonding and denser polymer cross-linked networks within the prepared eutectogel, leading to enhanced liquid retention ability (93.7 % after 96 h exposure to air) and ion transport capacity (ionic conductivity of 171.3 mS cm-1). Additionally, the zincophilicity nature of the choline cation in eutectogel effectively suppresses dendrites growth. The assembled FZAB utilizing this eutectogel electrolyte achieves a peak power density of 109.3 mW cm-2 and a cycle life of 90 h. Notably, the power density of FZAB is maintained as high as 38.2 mW cm-2 at -40 °C and 63.2 mW cm-2 at 50 °C, demonstrating its prominent suitability for applications in extreme temperature conditions. The design of eutectogel provides a novel way to achieve the high-performance FZAB.

High-Entropy Ag-Ru-Based Electrocatalysts with Dual-Active-Center for Highly Stable Ultra-Low-Temperature Zinc-Air Batteries

The development of advanced bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is significant for rechargeable zinc-air batteries (ZABs). Herein, a unique dual active center alloying strategy is proposed to achieve the efficient bifunctional oxygen catalysis, and the high entropy effect is further exploited to modulate the structure and performance of the catalysts. The MOF-assisted pyrolysis-replacement-alloying method was employed to construct the CoCuFeAgRu high-entropy alloy (HEA), which are uniformly anchored in porous nitrogen-doped carbon nanosheets. Notably, the obtained HEA catalyst exhibits excellent catalytic performance for both ORR and OER, and a peak power density of 136. 53 mW cm-2 and an energy density of 987.9 mAh gZn -1, surpassing the most of the previously reported bifunctional oxygen electrocatalysts. Moreover, the assembled flexible rechargeable ZAB enables excellent performance even at the ultralow temperature of -40 °C, with an energy density of 601.6 mAh gZn -1 and remarkable cycling stability up to 1,650 hours. Combined experimental and theoretical calculation results reveal that the excellent bifunctional catalytic activity of the HEA catalyst originated from the synergistic effect of the Ag and Ru dual active centers, and the optimization of the electronic structure by alloying effect.

Monodentate Acetate Anion Enhanced Hydrogel Electrolyte for Long-Term Lifespan Zn-Air Batteries

Flexible Zn-air batteries (FZABs) hold significant promise in diverse application scenarios with high safety and compatibility yet are still impeded by byproduct formation and poor water retention. Here, the neutral hydrogel electrolyte GAHE is engineered by in situ polymerizing acrylamide (AM) in a solution composed of cationic guar gum (CGG) and acetate salts to conquer the above challenges. The acetate anions (OAc-) exert a pH near 7 to effectively inhibit the side reactions triggered by H+. Meanwhile, the monodentate OAc- ions in LiOAc have fast ion diffusion kinetics and form hydrogen bonds between the released carbonyl groups and H2O to further suppress water activity for great side reaction prevention and water retention. Additionally, the in situ polymerization strategy realizes a polymer with high mechanical properties and great electrochemical interfacial stability and further improves the water retention property with hydrophilic groups. Consequently, GAHE gives the FZABs a lifespan of 2050 h at room temperature and 2940 h at -35 °C. This work provides concepts for electrolyte design for water retention and side reaction inhibition properties of aqueous devices.

Recent progress of flexible rechargeable batteries

The rapid popularization of wearable electronics, soft robots and implanted medical devices has stimulated extensive research in flexible batteries, which are bendable, foldable, knittable, wearable, and/or stretchable. Benefiting from these distinct characteristics, flexible batteries can be seamlessly integrated into various wearable/implantable devices, such as smart home systems, flexible displays, and implantable sensors. In contrast to conventional lithium-ion batteries necessitating the incorporation of stringent current collectors and packaging layers that are typically rigid, flexible batteries require the flexibility of each component to accommodate diverse shapes or sizes. Accordingly, significant advancements have been achieved in the development of flexible electrodes, current collectors, electrolytes, and flexible structures to uphold superior electrochemical performance and exceptional flexibility. In this review, typical structures of flexible batteries are firstly introduced and classified into mono-dimensional, two-dimensional, and three-dimensional structures according to their configurations. Subsequently, five distinct types of flexible batteries, including flexible lithium-ion batteries, flexible sodium-ion batteries, flexible zinc-ion batteries, flexible lithium/sodium-air batteries, and flexible zinc/magnesium-air batteries, are discussed in detail according to their configurations, respectively. Meanwhile, related comprehensive analysis is introduced to delve into the fundamental design principles pertaining to electrodes, electrolytes, current collectors, and integrated structures for various flexible batteries. Finally, the developments and challenges of flexible batteries are summarized, offering viable guidelines to promote the practical applications in the future.

"Seaweed Structure" design for solid gel electrolyte with hydroxide ion conductivity enabling flexible zinc air batteries

The construction of solid-state electrolytes for flexible zinc-air batteries is extremely challenging. A flexible and highly conductive solid electrolyte designed with a "seaweed structure" is reported in this work. Sodium alginate serves as the backbone to form a robust network structure, and the grafted quaternary ammonium groups provide channels for rapid ion transport, achieving excellent flexibility and hydroxide conductivity. The conductivity of the modified electrolyte membrane (QASA) is 5.23 × 10-2 S cm-1 at room temperature and reaches up to 8.51 × 10-2 S cm-1 at 75 °C. In the QASA based battery, bending at any angle is realized, and the power density is up to 57.28 mW cm-2. This work provides a new way to prepare high conductivity, green solid-state zinc-air batteries, and opens up a research line of thought for flexible energy storage materials.

Recent Progress on Advanced Flexible Lithium Battery Materials and Fabrication Process

Flexible energy storage devices have attracted wide attention as a key technology restricting the vigorous development of wearable electronic products. However, the practical application of flexible batteries faces great challenges, including the lack of good mechanical toughness of battery component materials and excellent adhesion between components, resulting in battery performance degradation or failure when subjected to different types of deformation. It is imperative to develop flexible batteries that can withstand deformation under different conditions and maintain stable battery performance. This paper reviews the latest research progress of flexible lithium batteries, from the research and development of new flexible battery materials, advanced preparation processes, and typical flexible structure design. First, the types of key component materials and corresponding modification technologies for flexible batteries are emphasized, mainly including carbon-based materials with flexibility, lithium anode materials, and solid-state electrolyte materials. In addition, the application of typical flexible structural designs (buckling, spiral, and origami) in flexible batteries is clarified, such as 3D printing and electrospinning, as well as advanced fabrication techniques commonly used in flexible materials and battery components. Finally, the limitations and coping strategies in the practical application of flexible lithium batteries are discussed, which provides new ideas for future research.

Development of flexible Zn/MnO2 secondary batteries using a fumed silica-doped hydrogel electrolyte

Hydrogel electrolytes have received tremendous research interest in designing flexible zinc-ion secondary batteries, making them highly promising for flexible energy storage and wearable electronic devices. Herein, we report a composite hydrogel electrolyte (CHE) prepared using a fumed silica-doped gelatin hydrogel. This electrolyte is specifically designed for use in rechargeable aqueous Zn/MnO2 batteries (ReAZMBs). Experimental results showed that after fumed silica was added, the porosity and ionic conductivity of the gelatin hydrogel electrolyte increased. Meanwhile, adding fumed silica to the hydrogel electrolyte contributed to reducing self-corrosion and promoting rapid and uniform deposition of zinc ions. When the addition of fumed silica to gelatin was 10 wt%, ReAZMBs with this CHE exhibited a superior rate and cycling performance. More specifically, ReAZMBs with this CHE achieved an initial specific capacity of 150 mA h g-1 at a current density of 1.5 A g-1 and a capacity retention rate of 67% after 1000 cycles, which was much higher than that of the battery with the pure gelatin hydrogel electrolyte (33%). This was because of the improved interface stability between the zinc anode and electrolyte and the reduced formation of by-products (3Zn(OH)2·ZnSO4·3H2O and 3Zn(OH)2·ZnSO4·5H2O), according to the results of the charge-discharge test of Zn//Zn symmetric batteries and SEM and XRD characterizations of post-run zinc anodes. In addition, the ReAZMBs with the CHE demonstrated good flexibility and could supply power reliably even when bent.

Vapor deposition strategy for implanting isolated Fe sites into papermaking nanofibers-derived N-doped carbon aerogels for liquid Electrolyte-/All-Solid-State Zn-Air batteries

Single-atom catalysts (SACs), with precisely controlled metal atom distribution and adjustable coordination architecture, have gained intensive concerns as efficient oxygen reduction reaction (ORR) electrocatalysts in Zn-air batteries (ZAB). The attainment of a monodispersed state for metallic atoms anchored on the carbonaceous substrate remains the foremost research priority; however, the persistent challenges lie in the relatively weak metal-support interactions and the instability of captured single atom active sites. Furthermore, in order to achieve rapid transport of O2 and other reactive substances within the carbon matrix, manufacturing SACs based on multi-stage porous carbon substrates is highly anticipated. Here, we propose a methodology for the fabrication of carbon aerogels (CA)-supported SACs utilizing papermaking nanofibers, which incorporates advanced strategies for N-atom self-doping, defect/vacancy introduction, and single-atom interface engineering. Specifically, taking advantages of using green and energy-efficient feedstocks, combining with a direct pore-forming template volatilization and chemical vapor deposition approach, we successfully developed N-doped carbon aerogels immobilized with separated iron sites (Fe-SAC@N/CA-Cd). The obtained Fe-SAC@N/CA-Cd exhibited substantially large specific surface area (SBET = 1173 m2/g) and a multi-level pore structure, which can effectively mitigate the random aggregation of Fe atoms during pyrolysis. As a result, it demonstrated appreciable activity and stability in catalyzing the ORR progress (E1/2 = 0.88 V, Eonset = 0.96 V). Furthermore, the assembled liquid electrolyte-state Zn-air batteries (LES-ZAB) and all-solid-state Zn-air battery (ASS-ZAB) also provides encouraging performance, with a peak power density of 169 mW cm-2 for LES-ZAB and a maximum power density of 124 mW cm-2 for ASS-ZAB.

N-P covalent bond regulation of mesoporous carbon-based catalyst for lowered oxygen reduction overpotential and enhanced zinc-air battery performance

Developing sustainable metal-free carbon-based electrocatalysts is essential for the deployment of metal-air batteries such as zinc-air batteries (ZABs), among which doping of heteroatoms has attracted tremendous interest over the past decade. However, the effect of the heteroatom covalent bonds in carbon matrix on catalysis was neglected in most studies. Here, an efficient metal-free oxygen reduction reaction (ORR) catalyst is demonstrated by the N-P bonds anchored carbon (termed N,P-C-1000). The N,P-C-1000 catalyst exhibits superior specific surface area of 1362 m2 g-1 and ORR activity with a half-wave potential of 0.83 V, close to that of 20 wt% Pt/C. Theoretical computations reveal that the p-band center for C-2p orbit in N,P-C-1000 has higher interaction strength with the intermediates, thus reducing the overall reaction energy barrier. The N,P-C-1000 assembled primary ZAB can attain a large peak power density of 121.9 mW cm-2 and a steady discharge platform of ∼1.20 V throughout 120 h. Besides, when served as the cathodic catalyst in a solid-state ZAB, the battery shows flexibility, conspicuous open circuit potential (1.423 V), and high peak power density (85.8 mW cm-2). Our findings offer a strategy to tune the intrinsic structure of carbon-based catalysts for improved electrocatalytic performance and shed light on future catalysts design for energy storage technologies beyond batteries.

An Overview and Future Perspectives of Rechargeable Flexible Zn-Air Batteries

Environmental friendliness and low-cost zinc-air batteries for flexible rechargeable applications have great potential in the field of flexible electronics and smart wearables owing to high energy density and long service life. However, the current technology of flexible rechargeable zinc-air batteries to meet the commercialization needs still facing enormous challenges due to the poor adaptability of each flexible component of the zinc-air batteries. This review focused on the latest progress over the past 5 years in designing and fabricating flexible self-standing air electrodes, flexible electrolytes and zinc electrodes of flexible Zn-air batteries, meanwhile the basic working principle of each component of flexible rechargeable zinc-air batteries and battery structures optimization are also described. Finally, challenges and prospects for the future development of flexible rechargeable zinc-air batteries are discussed. This work is intended to provide insights and general guidance for future exploration of the design and fabrication on high-performance flexible rechargeable zinc-air batteries.

Construction of Fully Integrated and Energy Self-Sufficient NO2 Gas Sensors Utilizing Zinc-Air Batteries

Exploration of novel self-powered gas sensors free of external energy supply restrictions, such as light illumination and mechanical vibration, for flexible and wearable applications is in urgent need. Herein, this work constructs a flexible and self-powered NO2 gas sensor based on zinc-air batteries (ZABs) with the cathode of the ZABs also acting as the gas-sensitive layer. Furthermore, the SiO2 coating film, serving as a hydrophobic layer, increases the three-phase interfaces for the NO2 reduction reaction. The constructed sensors exhibit a high sensing response (0.3 V @ 5 ppm), an ultralow detection limit (61 ppb), a fast sensing process (129 and 103 s), and excellent selectivity. Moreover, the sensors also possess a wide working temperature range and a low working temperature tolerance (0.34 V at -15 °C). Simulations indicate that the hydrophobic surface at the cathode-hydrogel interface will accommodate more NO2 gas molecules at the reaction sites and prevent the influence of inner water evaporation and direct dissolution of NO2 in the electrolyte, which is beneficial to the enhanced gas sensing abilities. Finally, the self-powered sensing device is incorporated into a smart sensing system for practical applications. This work will pave a new insight into the construction of integrated and energy self-sufficient smart gas sensing systems.

Flexible electrochemical energy storage devices and related applications: recent progress and challenges

Given the escalating demand for wearable electronics, there is an urgent need to explore cost-effective and environmentally friendly flexible energy storage devices with exceptional electrochemical properties. However, the existing types of flexible energy storage devices encounter challenges in effectively integrating mechanical and electrochemical performances. This review is intended to provide strategies for the design of components in flexible energy storage devices (electrode materials, gel electrolytes, and separators) with the aim of developing energy storage systems with excellent performance and deformability. Firstly, a concise overview is provided on the structural characteristics and properties of carbon-based materials and conductive polymer materials utilized in flexible energy storage devices. Secondly, the fabrication process and strategies for optimizing their structures are summarized. Subsequently, a comprehensive review is presented regarding the applications of carbon-based materials and conductive polymer materials in various fields of flexible energy storage, such as supercapacitors, lithium-ion batteries, and zinc-ion batteries. Finally, the challenges and future directions for next-generation flexible energy storage systems are proposed.

Biomass Solid-State Electrolyte with Abundant Ion and Water Channels for Flexible Zinc-Air Batteries

Flexible zinc-air batteries are the leading candidates as the next-generation power source for flexible/wearable electronics. However, constructing safe and high-performance solid-state electrolytes (SSEs) with intrinsic hydroxide ion (OH-) conduction remains a fundamental challenge. Herein, by adopting the natural and robust cellulose nanofibers (CNFs) as building blocks, the biomass SSEs with penetrating ion and water channels are constructed by knitting the OH--conductive CNFs and water-retentive CNFs together via an energy-efficient tape casting. Benefiting from the abundant ion and water channels with interconnected hydrated OH- wires for fast OH- conduction under a nanoconfined environment, the biomass SSEs reveal the high water-uptake, impressive OH- conductivity of 175 mS cm-1 and mechanical robustness simultaneously, which overcomes the commonly existed dilemma between ion conductivity and mechanical property. Remarkably, the flexible zinc-air batteries assemble with biomass SSEs deliver an exceptional cycle lifespan of 310 h and power density of 126 mW cm-2. The design methodology for water and ion channels opens a new avenue to design high-performance SSEs for 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.

Electric Eel Biomimetics for Energy Storage and Conversion

The electric eel is known as the most powerful creature to generate electricity with a discharge voltage up to 860 V and peak current up to 1 A. These surprising properties are the results of billions of years of evolution on the electrical biological structure and bulk, and now have triggered great research interest in electric eel biomimetics for designing innovated configurations and components of energy storage and conversion devices. In this review, first, the bioelectrical behavior of electric eels is surveyed, followed by the physiological structure to reveal the discharge characteristics and principles of electric organs and electrocytes. Additionally, underlying electrochemical mechanisms and models for calculating the potential and current of electrocytes are presented. Central to this review is the recent progress of electric-eel-inspired innovations and applications for energy storage and conversion, particularly including novel power sources, triboelectric nanogenerators, and nanochannel ion-selective membranes for salinity gradient energy harvesting. Finally, insights on the challenges at the moment and the perspectives on the future research prospects are critically compiled. It is suggested that energy-related electric eel biomimetics will greatly boost the development of next-generation high performance, green, and functional electronics.

A Biomimetic Cement-Based Solid-State Electrolyte with Both High Strength and Ionic Conductivity for Self-Energy-Storage Buildings

Cement-based materials are the foundation of modern buildings but suffer from intensive energy consumption. Utilizing cement-based materials for efficient energy storage is one of the most promising strategies for realizing zero-energy buildings. However, cement-based materials encounter challenges in achieving excellent electrochemical performance without compromising mechanical properties. Here, we introduce a biomimetic cement-based solid-state electrolyte (labeled as l-CPSSE) with artificially organized layered microstructures by proposing an in situ ice-templating strategy upon the cement hydration, in which the layered micropores are further filled with fast-ion-conducting hydrogels and serve as ion diffusion highways. With these merits, the obtained l-CPSSE not only presents marked specific bending and compressive strength (2.2 and 1.2 times that of traditional cement, respectively) but also exhibits excellent ionic conductivity (27.8 mS·cm-1), overwhelming most previously reported cement-based and hydrogel-based electrolytes. As a proof-of-concept demonstration, we assemble the l-CPSSE electrolytes with cement-based electrodes to achieve all-cement-based solid-state energy storage devices, delivering an outstanding full-cell specific capacity of 72.2 mF·cm-2. More importantly, a 5 × 5 cm2 sized building model is successfully fabricated and operated by connecting 4 l-CPSSE-based full cells in series, showcasing its great potential in self-energy-storage buildings. This work provides a general methodology for preparing revolutionary cement-based electrolytes and may pave the way for achieving zero-carbon buildings.

Steric-hindrance Effect Tuned Ion Solvation Enabling High Performance Aqueous Zinc Ion Batteries

Despite many additives have been reported for aqueous zinc ion batteries, steric-hindrance effect of additives and its correlation with Zn2+ solvation structure have been rarely reported. Herein, large-sized sucrose biomolecule is selected as a paradigm additive, and steric-hindrance electrolytes (STEs) are developed to investigate the steric-hindrance effect for solvation structure regulation. Sucrose molecules do not participate in Zn2+ solvation shell, but significantly homogenize the distribution of solvated Zn2+ and enlarge Zn2+ solvation shell with weakened Zn2+-H2O interaction due to the steric-hindrance effect. More importantly, STEs afford the water-shielding electric double layer and in situ construct the organic and inorganic hybrid solid electrolyte interface, which effectively boost Zn anode reversibility. Remarkably, Zn//NVO battery presents high capacity of 3.9 mAh ⋅ cm-2 with long cycling stability for over 650 cycles at lean electrolyte of 4.5 μL ⋅ mg-1 and low N/P ratio of 1.5, and the stable operation at wide temperature (-20 °C~+40 °C).

Design enhancement in hydroxide ion conductivity of viologen-bakelite organic frameworks for a flexible rechargeable zinc-air battery

Quasi-solid-state rechargeable zinc-air batteries (ZABs) are suitable for the generation of portable clean energy due to their high energy and power density, safety, and cost-effectiveness. Compared to the typical alkaline aqueous electrolyte in a ZAB, polymer or gel-based electrolytes can suppress the dissolution of zinc, preventing the precipitation of undesirable irreversible zinc compounds. Their low electronic conductivity minimizes zinc dendrite formation. However, gel electrolytes suffer from capacity fade due to the loss of the volatile solvent, failing to deliver high-energy and high-power ZABs. Consequently, developing polymers with high hydroxide ion conductivity and chemical durability is paramount. We report cationic C-C bonded robust polymers with stoichiometrically controlled mobile hydroxide ions as solid-state hydroxide ion transporters. To boot, we increased the viologen-hydroxide-ion concentration through "by-design" monomers. The polymers constructed with these designer monomers exhibit a commensurate increase in their ionic conductivity. The polymer prepared with 4 OH- ion-containing monomer was superior to the one with 3 OH-. The conductivity increases from 7.30 × 10-4 S cm-1 (30 °C) to 2.96 × 10-3 S cm-1 (30 °C) at 95% RH for IISERP-POF12_OH (2_OH) and IISERP-POF13_OH (3_OH), respectively. A rechargeable ZAB (RZAB) constructed using 3_OH@PVA (polyvinyl alcohol) as the electrolyte membrane and Pt/C + RuO2 catalyst delivers a power density of 158 mW cm-2. In comparison, RZABs with a PVA interlayer provided only 72 mW cm-2. Notably, the device suffered an initial charge-discharge voltage gap of merely 0.55 V at 10 mA cm-2, which increased by only 2 mV after 50 hours of running. The battery operated at 10 mA cm-2 and worked steadily for 67 hours. We accomplished a flexible and rechargeable zinc-air battery (F-RZAB) exhibiting a maximum power density of 79 mW cm-2. This demonstration of a cationic viologen-bakelite polymer-based flexible secondary ZAB with versatile stochiometric hydroxide-ion tunability marks an important achievement in hydroxide-ion conducting solid-state electrolyte development.

Fe, N-Inducing Interfacial Electron Redistribution in NiCo Spinel on Biomass-Derived Carbon for Bi-functional Oxygen Conversion

Herein, an interfacial electron redistribution is proposed to boost the activity of carbon-supported spinel NiCo2O4 catalyst toward oxygen conversion via Fe, N-doping strategy. Fe-doping into octahedron induces a redistribution of electrons between Co and Ni atoms on NiCo1.8Fe0.2O4@N-carbon. The increased electron density of Co promotes the coordination of water to Co sites and further dissociation. The generation of proton from water improves the overall activity for the oxygen reduction reaction (ORR). The increased electron density of Ni facilitates the generation of oxygen vacancies. The Ni-VO-Fe structure accelerates the deprotonation of *OOH to improve the activity toward oxygen evolution reaction (OER). N-doping modulates the electron density of carbon to form active sites for the adsorption and protonation of oxygen species. Fir wood-derived carbon endows catalyst with an integral structure to enable outstanding electrocatalytic performance. The NiCo1.8Fe0.2O4@N-carbon express high half-wave potential up to 0.86 V in ORR and low overpotential of 270 mV at 10 mA cm-2 in OER. The zinc-air batteries (ZABs) assembled with the as-prepared catalyst achieve long-term cycle stability (over 2000 cycles) with peak power density (180 mWcm-2). Fe, N-doping strategy drives the catalysis of biomass-derived carbon-based catalysts to the highest level for the oxygen conversion in ZABs.

Synergistic effect of surfactant and 1,10-decanedithiol as corrosion inhibitor for zinc anode in alkaline electrolyte of zinc-air batteries

The self-discharge by corrosion of zinc-air batteries (ZABs) will result in the reduced coulombic efficiency and lower energy efficiency. The additives in electrolyte should not only inhibit the occurrence of self-corrosion during battery dormancy, but also achieve a stable cycle of adsorption-desorption during battery operation, improving the durability of discharge cycles. But the former requires strong binding between additives and zinc to form a dense protective film, while the latter requires easy desorption of additives and zinc without affecting discharge power, which is contradictory to balance. In this study, a dynamic combination of additives and zinc, as well as a design of multi-channel strategy for the corresponding protective layer, have been proposed to solve the issues of self-corrosion and discharge cycle stability. Specifically, the surfactant (octylphenol polyoxyethylene ether phosphate (OP-10P)) and 1,10-decanedithiol (DD) have been selected as the combined anti-corrosion additives in ZABs with concentrated alkaline solution. The synergistic inhibition mechanism and the stabilization mechanism in zinc-air full cells have been studied systematically. The results indicated that the combined inhibitors inhibited the self-corrosion of Zn efficiently in the dormancy, and the inhibition efficiency reached 99.9 % at the optimized proportion. OP-10P achieve the preferential adsorption on the zinc surface, and then the chelates of DD with Zn2+ deposit on the outer layer to form the protective film with fine hydrophobic performance. The stability of ZABs in discharge and charging cycles has been improved owing to the multilayer adsorption film on zinc surface, which retains ion transport channels with the homogeneously pores to weaken the dendrites and side reactions during galvanostatic cycles. A probable model on zinc surface was established to discuss the actual working mechanism.

Theoretical investigation of electronic, energetic, and mechanical properties of polyvinyl alcohol/cellulose composite hydrogel electrolyte

Hydrogels are a new class of electrolytic materials employed in zinc-air batteries due to their significant on the battery's performance. However, the effectiveness of electrolytic hydrogel is affected by factors such as water content, temperature, additives, etc. Using DMol3 and molecular dynamics modeling techniques, this research aimed at investigating the electronic properties, effect of water content, and temperature on the binding energy, cohesive energy, and the mechanical properties of polyvinyl alcohol/cellulose-based composite hydrogel at the molecular level. The electronic optimized structures of the polymeric materials and parameters such as frontier molecular orbitals, band gap and electron density were analyzed. The results revealed that the binding energies of hydrogel polymer composite increased as the number of water molecules in the composite increased up to 60 % after which the binding energy decreased. In addition, the temperature increase led to a decrease in the binding energy of the composite. The cohesive energy density of the composite was highest at 40 % water content while higher temperatures decreased the cohesive energy density of the hydrogel. As the number of water molecules increased from 29 to 256, the tensile modulus increased from 0.707 × 10-3 to 2.821 × 10-3 Gpa; while the bulk modulus (K) increased in the order of K 40 > 50 > 30 > 20 > 10 respectively. These results serve as a theoretical enlightenment and a guide for experimental works in the field of energy conversion and storage devices.

Extending the Cycle Lifetime of Solid-State Zinc-Air Batteries by Arranging Stable Zinc Species Channels

The solid-state zinc-air batteries have attracted extensive attention due to their high theoretical energy density, high safety, and the compact structure. In this work, a novel hydrogel solid-state electrolyte was developed that was equipped with an interpenetrating network of zinc polyacrylate (PAZn) and polyacrylamide (PAM). At the same time, a cyclodextrin derivative with sulfonate groups was introduced as an additive. From the design of anionic groups in the network, effective and stable channels for zinc species have been established. The unique structure of the additives regulates the uniform deposition of zinc. After using this solid-state electrolyte, the cycle lifetime of solid-state zinc-air batteries assembled have been significantly extended. The byproducts were greatly suppressed and generated the smooth zinc electrode surface after the charge-discharge cycling.

Engineering Symmetry-Breaking Centers and d-Orbital Modulation in Triatomic Catalysts for Zinc-Air Batteries

Unraveling the configuration-activity relationship and synergistic enhancement mechanism (such as real active center, electron spin-state, and d-orbital energy level) for triatomic catalysts, as well as their intrinsically bifunctional oxygen electrocatalysis, is a great challenge. Here we present a triatomic catalyst (TAC) with a trinuclear active structure that displays extraordinary oxygen electrocatalysis for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), greatly outperforming the counterpart of single-atom and diatomic catalysts. The aqueous Zn-air battery (ZAB) equipped with a TAC-based cathode exhibits extraordinary rechargeable stability and ultrarobust cycling performance (1970 h/3940 cycles at 2 mA cm-2, 125 h/250 cycles at 10 mA cm-2 with negligible voltage decay), and the quasi-solid-state ZAB displays outstanding rechargeability and low-temperature adaptability (300 h/1800 cycles at 2 mA cm-2 at -60 °C), outperforming other state-of-the-art ZABs. The experimental and theoretical analyses reveal the symmetry-breaking CoN4 configuration under incorporation of neighboring metal atoms (Fe and Cu), which leads to d-orbital modulation, a low-shift d band center, weakened binding strength to the oxygen intermediates, and decreased energy barrier for bifunctional oxygen electrocatalysis. This rational tricoordination design as well as an in-depth mechanism analysis indicate that hetero-TACs can be promisingly applied in various electrocatalysis applications.

Gradient Quasi-Solid Electrolyte Enables Selective and Fast Ion Transport for Robust Aqueous Zinc-Ion Batteries

The quasi-solid electrolytes (QSEs) attract extensive attention due to their improved ion transport properties and high stability, which is synergistically based on tunable functional groups and confined solvent molecules among the polymetric networks. However, the trade-off effect between the polymer content and ionic conductivity exists in QSEs, limiting their rate performance. In this work, the epitaxial polymerization strategy is used to build the gradient hydrogel networks (GHNs) covalently fixed on zinc anode. Then, it is revealed that the asymmetric distribution of negative charges benefits GHNs with fast and selective ionic transport properties, realizing a higher Zn2+ transference number of 0.65 than that (0.52) for homogeneous hydrogel networks (HHNs) with the same polymer content. Meanwhile, the high-density networks formed at Zn/GHNs interface can efficiently immobilize free water molecules and homogenize the Zn2+ flux, greatly inhibiting the water-involved parasitic reactions and dendrite growth. Thus, the GHNs enable dendrite-free stripping/plating over 1000 h at 8 mA cm-2 and 1 mAh cm-2 in a Zn||Zn symmetric cell, as well as the evidently prolonged cycles in various full cells. This work will shed light on asymmetric engineering of ion transport channels in advanced quasi-solid battery systems to achieve high energy and safety.

Precise Design and Modification Engineering of Single-Atom Catalytic Materials for Oxygen Reduction

Due to their unique electronic and structural properties, single-atom catalytic materials (SACMs) hold great promise for the oxygen reduction reaction (ORR). Coordinating environmental and engineering strategies is the key to improving the ORR performance of SACMs. This review summarizes the latest research progress and breakthroughs of SACMs in the field of ORR catalysis. First, the research progress on the catalytic mechanism of SACMs acting on ORR is reviewed, including the latest research results on the origin of SACMs activity and the analysis of pre-adsorption mechanism. The study of the pre-adsorption mechanism is an important breakthrough direction to explore the origin of the high activity of SACMs and the practical and theoretical understanding of the catalytic process. Precise coordination environment modification, including in-plane, axial, and adjacent site modifications, can enhance the intrinsic catalytic activity of SACMs and promote the ORR process. Additionally, several engineering strategies are discussed, including multiple SACMs, high loading, and atomic site confinement. Multiple SACMs synergistically enhance catalytic activity and selectivity, while high loading can provide more active sites for catalytic reactions. Overall, this review provides important insights into the design of advanced catalysts for ORR.

Porous Cyclodextrin Polymer Enables Dendrite-Free and Ultra-Long Life Solid-State Zn-I2 Batteries

Zn-I2 batteries have attracted attention due to their low cost, safety, and environmental friendliness. However, their performance is still limited by the irreversible growth of Zn dendrites, hydrogen evolution reactions, corrosion, and shuttle effect of polyiodide. In this work, we have prepared a new porous polymer (CD-Si) by nucleophilic reaction of β-cyclodextrin with SiCl4 , and CD-Si is applied to the solid polymer electrolyte (denoted PEO/PVDF/CD-Si) to solve above-mentioned problems. Through the anchoring of the CD-Si, a conductive network with dual transmission channels was successfully constructed. Due to the non-covalent anchoring effect, the ionic conductivity of the solid polymer electrolytes (SPE) can reach 1.64×10-3  S cm-1 at 25 °C. The assembled symmetrical batteries can achieve highly reversible dendrite-free galvanizing/stripping (stable cycling for 7500 h at 5 mA cm-2 and 1200 h at 20 mA cm-2 ). The solid-state Zn-I2 battery shows an ultra-long life of over 35,000 cycles at 2 A g-1 . Molecular dynamics simulations are performed to elucidate the working mechanism of CD-Si in the polymer matrix. This work provides a novel strategy towards solid electrolytes for Zn-I2 batteries.

Strategies Toward Stretchable Aqueous Zn-based Batteries for Wearable Electronics from Components to Devices

Recently, aqueous Zn-based batteries (AZBs) are receiving increased attention in wearable and implantable electronics due to the low cost, high safety, high eco-efficiency, and relatively high energy density. However, it is still a big challenge to develop stretchable AZBs (SAZBs) which can be conformally folded, crumpled, and stretched with human body motions. Although a lot of efforts have been dedicated to constructions of SAZBs, a comprehensive review which focuses on summarizing stretchable materials, device configurations and challenges of SAZBs is needed. Herein, this review attempts to critically review the latest developments and progress in stretchable electrodes, electrolytes, packaging materials and device configurations in detail. Furthermore, these challenges and potential future research directions in the field of SAZBs are also discussed.

Self-Powered Integrated System with a Flexible Strain Sensor and a Zinc-Air Battery

At present, self-powered, lightweight, and flexible sensors are widely applied, especially in the fields of wearable devices and human health monitoring. Nevertheless, conventional self-powered flexible sensor systems rely on power supply components such as supercapacitors, nanofriction generators, and solar cells, which present certain limitations, such as high dependence on external environmental factors and the inability to provide long-term stable energy supply. Thus, a paramount exigency emerges for the development of wearable sensors endowed with enduring battery life to enable continuous monitoring of human motion for extended periods. In our academic study, we present an innovative self-powered sensing system that seamlessly combines a pliable zinc-air battery with a strain sensor. This approach offers a stable output signal over extended periods without an external energy device, which is crucial for long-term, continuous human motion monitoring. Through the incorporation of various carbon materials, we realized the multifunction of poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) dual network hydrogels and prepared zinc-air battery electrolytes and strain sensors. Notably, the batteries exhibit impressive power density (82.5 mW cm-2), high open-circuit voltage (1.42 V), and remarkable environmental stability. Even when subjected to puncture and breakage, the batteries remain operational without suffering from electrolyte leakage. Similarly, our strain sensor boasts a broad working range spanning from 0 to 1400%, coupled with a remarkable sensitivity (GF = 2.99) and exceptional capacity to accurately detect various mechanical deformations. When integrated into a single system, the integrated system can monitor human movement for up to 10 h, which has broad prospects in wearable sensor applications.

Bifunctional Single Atom Catalysts for Rechargeable Zinc-Air Batteries: From Dynamic Mechanism to Rational Design

Ever-growing demands for rechargeable zinc-air batteries (ZABs) call for efficient bifunctional electrocatalysts. Among various electrocatalysts, single atom catalysts (SACs) have received increasing attention due to the merits of high atom utilization, structural tunability, and remarkable activity. Rational design of bifunctional SACs relies heavily on an in-depth understanding of reaction mechanisms, especially dynamic evolution under electrochemical conditions. This requires a systematic study in dynamic mechanisms to replace current trial and error modes. Herein, fundamental understanding of dynamic oxygen reduction reaction and oxygen evolution reaction mechanisms for SACs is first presented combining in situ and/or operando characterizations and theoretical calculations. By highlighting structure-performance relationships, rational regulation strategies are particularly proposed to facilitate the design of efficient bifunctional SACs. Furthermore, future perspectives and challenges are discussed. This review provides a thorough understanding of dynamic mechanisms and regulation strategies for bifunctional SACs, which are expected to pave the avenue for exploring optimum single atom bifunctional oxygen catalysts and effective ZABs.

Single-Ion-Conducting Hydrogel Electrolytes Based on Slide-Ring Pseudo-Polyrotaxane for Ultralong-Cycling Flexible Zinc-Ion Batteries

Flexible zinc-ion batteries (ZIBs) with high capacity and long cycle stability are essential for wearable electronic devices. Hydrogel electrolytes have been developed to provide ion-transfer channels while maintaining the integrity of ZIBs under mechanical strain. However, hydrogel matrices are typically swollen with aqueous salt solutions to increase ionic conductivity, which can hinder intimate contact with electrodes and reduce mechanical properties. To address this, a single-Zn-ion-conducting hydrogel electrolyte (SIHE) is developed by integrating polyacrylamide network and pseudo-polyrotaxane structure. The SIHE exhibits a high Zn2+ transference number of 0.923 and a high ionic conductivity of 22.4 mS cm-1 at room temperature. Symmetric batteries with SIHE demonstrate stable Zn plating/stripping performance for over 160 h, with a homogenous and smooth Zn deposition layer. Full cells with La-V2 O5 cathodes exhibit a high capacity of 439 mA h g-1 at 0.1 A g-1 and excellent capacity retention of 90.2% after 3500 cycles at 5 A g-1 . Moreover, the flexible ZIBs display stable electrochemical performance under harsh conditions, such as bending, cutting, puncturing, and soaking. This work provides a simple design strategy for single-ion-conducting hydrogel electrolytes, which could pave the way for long-life aqueous batteries.

Sustainable zinc-air battery chemistry: advances, challenges and prospects

Sustainable zinc-air batteries (ZABs) are considered promising energy storage devices owing to their inherent safety, high energy density, wide operating temperature window, environmental friendliness, etc., showing great prospect for future large-scale applications. Thus, tremendous efforts have been devoted to addressing the critical challenges associated with sustainable ZABs, aiming to significantly improve their energy efficiency and prolong their operation lifespan. The growing interest in sustainable ZABs requires in-depth research on oxygen electrocatalysts, electrolytes, and Zn anodes, which have not been systematically reviewed to date. In this review, the fundamentals of ZABs, oxygen electrocatalysts for air cathodes, physicochemical properties of ZAB electrolytes, and issues and strategies for the stabilization of Zn anodes are systematically summarized from the perspective of fundamental characteristics and design principles. Meanwhile, significant advances in the in situ/operando characterization of ZABs are highlighted to provide insights into the reaction mechanism and dynamic evolution of the electrolyte|electrode interface. Finally, several critical thoughts and perspectives are provided regarding the challenges and opportunities for sustainable ZABs. Therefore, this review provides a thorough understanding of the advanced sustainable ZAB chemistry, hoping that this timely and comprehensive review can shed light on the upcoming research horizons of this prosperous area.

Interfacial Engineering of CoN/Co3 O4 Heterostructured Hollow Nanoparticles Embedded in N-Doped Carbon Nanowires as a Bifunctional Oxygen Electrocatalyst for Rechargeable Liquid and Flexible all-Solid-State Zn-Air Batteries

The design of economical, efficient, and robust bifunctional oxygen electrocatalysts is greatly imperative for the large-scale commercialization of rechargeable Zn-air battery (ZAB) technology. Herein, the neoteric design of an advanced bifunctional electrocatalyst composed of CoN/Co₃ O₄ heterojunction hollow nanoparticles in situ encapsulated in porous N-doped carbon nanowires (denoted as CoN/Co₃ O₄ HNPs@NCNWs hereafter) is reported. The simultaneous implementation of interfacial engineering, nanoscale hollowing design, and carbon-support hybridization renders the synthesized CoN/Co₃ O₄ HNPs@NCNWs with modified electronic structure, improved electric conductivity, enriched active sites, and shortened electron/reactant transport pathways. Density functional theory computations further demonstrate that the construction of a CoN/Co₃ O₄ heterojunction can optimize the reaction pathways and reduce the overall reaction barriers. Thanks to the composition and architectural superiorities, the CoN/Co₃ O₄ HNPs@NCNWs exhibit distinguished oxygen reduction reaction and oxygen evolution reaction performance with a low reversible overpotential of 0.725 V and outstanding stability in KOH medium. More encouragingly, the homemade rechargeable liquid and flexible all-solid-state ZABs utilizing CoN/Co₃ O₄ HNPs@NCNWs as the air-cathode deliver higher peak power densities, larger specific capacities, and robust cycling stability, exceeding the commercial Pt/C + RuO₂ benchmark counterparts. The concept of heterostructure-induced electronic modification herein may shed light on the rational design of advanced electrocatalysts for sustainable energy applications.

Versatile Electronic Textile Enabled by a Mixed-Dimensional Assembly Strategy

Electronic textiles (e-textiles) hold great promise for serving as next-generation wearable electronics owing to their inherent flexible, air-permeable, and lightweight characteristics. However, these e-textiles are of limited performance mainly because of lacking powerful materials combination. Herein, a versatile e-textile through a simple, high-efficiency mixed-dimensional assembly of 2D MXene nanosheets and 1D silver nanowires (AgNWs) are presented. The effective complementary actions of MXene and AgNWs endow the e-textiles with superior integrated performances including self-powered pressure sensing, ultrafast joule heating, and highly efficient electromagnetic interference (EMI) shielding. The textile-based self-powered smart sensor systems obtained through the screen-printed assembly of MXene-based supercapacitor and pressure sensor are flexible and lightweight, showing ultrahigh specific capacitance (2390 mF cm^-2 ), robust areal energy density (119.5 µWh cm^-2 ), excellent sensitivity (474.8 kPa^-1 ), and low detection limit (1 Pa). Furthermore, the interconnected conductive MXene/AgNWs network enables the e-textile with ultrafast temperature response (10.4 °C s^-1 ) and outstanding EMI shielding effectiveness of ≈66.4 dB. Therefore, the proposed mixed-dimensional assembly design creates a multifunctional e-textile that offers a practical paradigm for next-generation smart flexible electronics.

Flexible Solid-State Metal-Air Batteries: The Booming of Portable Energy Supplies

The rapid development of portable and wearable electronics has given rise to new challenges and provoked research in flexible, lightweight, and affordable energy storage devices. Flexible solid-state metal-air batteries (FSSMABs) are considered promising candidates, owing to their large energy density, mechanical flexibility, and durability. However, the practical applications of FSSMABs require further improvement to meet the demands of long-term stability, high power density, and large operating voltage. This Review presents a detailed discussion of innovative electrocatalysts for the air cathode, followed by a sequential overview of high-performance solid-state electrolytes and metal anodes, and a summary of the current challenges and future perspectives of FSSMABs to promote practical application and large-scale commercialization in the near future.

Regulation of Released Alkali from Gel Polymer Electrolyte in Quasi-Solid State Zn-Air Battery

Gel polymer electrolyte (GPE) in quasi-solid state Zn-air battery (QSZAB) will release alkali during cycling, resulting in gradual dehydration of GPE, corrosion of Zn electrode, Zn dendrites growth, and therefore inferior performance. Here, hollow Sn microspheres are prepared on Zn substrate by the technique of colloidal self-assembly. The inner surfaces of hollow Sn microspheres are modified by 2-hydroxypropyl-β-cyclodextrin (hollow Sn-inner HPβCD) to regulate the released alkali at GPE|anode interface. The hollow Sn-inner HPβCD can lessen the leakage of released alkali, make stored alkali diffuse back to GPE during the charging process, and mitigate the loss of soluble Zn(OH)₄ ^2- to suppress Zn dendrites growth. Resultantly, GPE in QSZAB with hollow Sn-inner HPβCD exhibits a high retention capacity for alkaline solution. The cell also exhibits a long cyclic lifespan of 127 h due to the effective regulation of released alkali, which outperforms QSZAB without hollow Sn-inner HPβCD by 7.94 times. This work rivets the regulation of released alkali at GPE|anode interface, providing new insight to improve QSZABs' performance.

Rational Design of Flexible Zn-Based Batteries for Wearable Electronic Devices

The advent of 5G and the Internet of Things has spawned a demand for wearable electronic devices. However, the lack of a suitable flexible energy storage system has become the "Achilles' Heel" of wearable electronic devices. Additional problems during the transformation of the battery structure from conventional to flexible also present a severe challenge to the battery design. Flexible Zn-based batteries, including Zn-ion batteries and Zn-air batteries, have long been considered promising candidates due to their high safety, eco-efficiency, substantial reserve, and low cost. In the past decade, researchers have come up with elaborate designs for each portion of flexible Zn-based batteries to improve the ionic conductivities, mechanical properties, environment adaptabilities, and scalable productions. It would be helpful to summarize the reported strategies and compare their pros and cons to facilitate further research toward the commercialization of flexible Zn-based batteries. In this review, the current progress in developing flexible Zn-based batteries is comprehensively reviewed, including their electrolytes, cathodes, and anodes, and discussed in terms of their synthesis, characterization, and performance validation. By clarifying the challenges in flexible Zn-based battery design, we summarize the methodology from previous investigations and propose challenges for future development. In the end, a research paradigm of Zn-based batteries is summarized to fit the burgeoning requirement of wearable electronic devices in an iterative process, which will benefit the future development of Zn-based batteries.

Candied Haws-Like Fe-N-C Catalysts with Broadened Carbon Interlayer Spacing for Efficient Zinc-Air Battery

As efficient nonprecious metal catalysts for oxygen reduction reaction (ORR), Fe-N-C materials are one of the most promising alternatives to Pt-based catalysts for fuel cells and metal-air batteries. However, the intrinsically low density of key active sites like FeN₄ moieties hampers their commercial applications. Herein, we provide a smart strategy to construct a candied haws-like Fe-N-C catalyst (CH-FeNC) with broadened carbon interplanar spacing (>4 Å), starting with trehalose as a structure-built brick coupled with a zinc-zeolite imidazole framework (ZIF-8) and polyaniline (PANI) and then followed by copyrolysis carbonization of them. The obtained CH-FeNC exhibits half-wave potentials of 0.92 and 0.90 V (vs RHE) before and after 10,000 cycles in 0.1 M KOH, which are superior to the 0.90 and 0.85 V obtained by commercial Pt/C for ORR. The power density of a homemade zinc-air battery equipped with the catalyst is up to 131 mW cm^-2, greater than that of Pt/C (124 mW cm^-2). The extended X-ray absorption fine structure (EXAFS) results and density functional theory (DFT) theoretical calculations reveal that there exists enriched zigzag or armchair edge-hosted FeN₄ active sites, located at the abundant interface between carbon components in this composite. Furthermore, the unique broadened carbon interlayer spacing plays a key role in deciding the ORR rate in alkaline but not in acidic environments because there exists a fifth ligand of active Fe in the form of FeN₄ centers coupled with SO₄^2- and ClO₄^- from acids.

"Tree-Trunk" Design for Flexible Quasi-Solid-State Electrolytes with Hierarchical Ion-Channels Enabling Ultralong-Life Lithium-Metal Batteries

The construction of robust (quasi)-solid-state electrolyte (SSE) for flexible lithium-metal batteries is desirable but extremely challenging. Herein, a novel, flexible, and robust quasi-solid-state electrolyte (QSSE) with a "tree-trunk" design is reported for ultralong-life lithium-metal batteries (LMBs). An in-situ-grown metal-organic framework (MOF) layer covers the cellulose-based framework to form hierarchical ion-channels, enabling rapid ionic transfer kinetics and excellent durability. A conductivity of 1.36 × 10^-3  S cm^-1 , a transference number of 0.72, an electrochemical window of 5.26 V, and a good rate performance are achieved. The flexible LMBs fabricated with as-designed QSSEs deliver areal capacity of up to 3.1 mAh cm^-2 at the initial cycle with high mass loading of 14.8 mg cm^-2 in Li-NCM811 cells and can retain ≈80% capacity retention after 300 cycles. An ultralong-life of 3000 cycles (6000 h) is also achieved in Li-LiFePO₄ cells. This work presents a promising route in constructing a flexible QSSE toward ultralong-life LMBs, and also provides a design rationale for material and structure development in the area of energy storage and conversion.