Highly Reversible Zn Metal Anodes Enabled by Freestanding, Lightweight, and Zincophilic MXene/Nanoporous Oxide Heterostructure Engineered Separator for Flexible Zn-MnO2 Batteries

Biomass-derived polymer as a flexible "zincophilic-hydrophobic" solid electrolyte interphase layer to enable practical Zn metal anodes

Aqueous zinc ion batteries (AZIBs) face significant challenges stemming from Zn dendrite growth and water-contact attack, primarily due to the lack of a well-designed solid electrolyte interphase (SEI) to safeguard the Zn anode. Herein, we report a bio-mass derived polymer of chitin on Zn anode (Zn@chitin) as a novel and robust artificial SEI layer to boost the Zn anode rechargeability. The polymeric chitin SEI layer features both zincophilic and hydrophobic characteristics to target the suppressed dendritic Zn formation as well as the water-induced side reactions, thus harvesting a dendrite-free and corrosion-resistant Zn anode. More importantly, this polymeric interphase layer is strong and flexible accommodating the volume changes during repeated cycling. Based on these benefits, the Zn@chitin anode demonstrates prolonged cycling performance surpassing 1300 h under an ultra-large current density of 20 mA cm-2, and a long cycle life of 680 h with a record-high zinc utilization rate of 80 %. Besides, the assembled Zn@chitin/V2O5 full batteries reveal excellent capacity retention and rate performance under practical conditions, proving the reliability of our proposed strategy for industrial AZIBs. Our research offers valuable insights for constructing high-performance AZIBs, and simultaneously realizes the high-efficient use of cheap biomass from a "waste-to-wealth" concept.

Universal Strike-Plating Strategy to Suppress Hydrogen Evolution for Improving Zinc Metal Reversibility

The development of highly reversible zinc (Zn) metal anodes is pivotal for determining the feasibility of rechargeable aqueous Zn batteries. Our research quantitively evalulates how the hydrogen evolution reaction (HER) adversely affects Zn reversibility in batteries and emphasizes the importance of substrate design in modulating HER and its associated side reactions. When the cathodic reaction is dominated by HER, the Zn electrode exhibits low plating/stripping efficiency, characterized by extensive coverage of a passivation layer that encompasses the electrochemical inactive Zn. Therefore, we propose a strike-plating strategy that modifies the pristine substrate by initiating Zn plating at a high current density for a short time. This straightforward and effective approach has been proven to suppress hydrogen evolution and transform the electrodeposition mode into one dominated by Zn reduction. Notably, Zn metal exhibits exceptionally high average reversibility of 98.80% over 200 h on a stainless steel substrate, which was typically precluded in aqueous electrolytes because of their favorable HER capability. Additionally, our strike-plating strategy demonstrates an appliable pathway to achieve high Zn reversibility on Cu substrate, showing an average efficiency of 99.83% over 540 h at a high areal capacity of 10 mAh cm-2 and high-performance Zn full cells with low N/P ratios. This research provides a foundation for future investigations into the underlying mechanisms of HER and strategies to optimize Zn-based battery performance.

Accelerated and Guided Zn2+ Diffusion via Polarized Interface Engineering Toward High Performance Wearable Zinc-Ion Batteries

Rechargeable aqueous Zn-ion batteries (ZIBs) are considered as a new energy storage device for wearable electronic equipment. Nowadays, dendrite growth and uneven deposition of zinc have been the principal problems to suppress the development of high-performance wearable zinc-ion batteries. Herein, a perovskite material of LaAlO3 nanoparticle has been applied for interface engineering and zinc anode protection. By adjusting transport channels and accelerating the Zn2+ diffusion, the hydrogen evolution reaction potential is improved, and electric field distribution on the Zn electrode surface is regulated to navigate the fast and uniform deposition of Zn2+. As a proof of demonstration, the assembled LAO@Zn||MnO2 batteries can display the highest capacity of up to 140 mAh g-1 without noticeable decay even after 1000 cycles. Moreover, a motor-driven fan and electronic wristwatch powered by wearable ZIBs can demonstrate the practical feasibility of LAO@Zn||MnO2 in wearable electronic equipment.

Crystalline MnCO3@Amorphous MnOx Composite as Cathode Material for High-Performance Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) have received extensive attention because of their advantages of low cost, high safety, and nontoxicity. However, problems such as dissolution of the active cathode material, dendrites/passivation of the zinc anode, and slow reaction kinetics hindered their further applications. In this work, a crystalline/amorphous composite-type material composed of crystalline MnCO3 and amorphous MnOx was prepared and used as the cathode material for RAZIBs. The MnCO3@amorphous MnOx (MnCO3@A-MnOx) composite possesses the merits of both the pure crystalline phase of MnCO3 and the amorphous phase of MnOx, which can deliver better electrochemical performance than the corresponding single component in repeated cycles. In addition, crystalline MnCO3 undergoes a complex phase transition to the active MnO2 during the first charge process, providing the composite with a stable structure and additional electrochemical capacity. The electrochemical measurement results indicate that the MnCO3@A-MnOx electrode can display high reversible discharge capacity at 0.1 A g-1, excellent rate performance at 5.0 A g-1, and long cycling stability over 2000 cycles, showing great potential as a cathode material for high-performance RAZIBs.

Scalable fabrication of free-standing and integrated electrodes with commercial level of areal capacity for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) present a highly promising avenue for the deployment of grid-scale energy storage systems. However, the electrodes fabricated through conventional methodologies not only suffer from insufficient mass loadings, but also are susceptible to exfoliation under deformations. Herein, a scalable and cost-effective freezing-thawing method is developed to construct free-standing and integrated electrode, comprising H11Al2V6O23.2, carboxymethyl cellulose, and carbon nanotubes. Benefiting from the synergistic effect of these components, the resultant electrode exhibits superior flexibility and robustness, large tensile strength, exceptional electrical conductivity, and favorable electrolyte wettability. Under a large mass loading of 8 mg cm-2 (corresponding to a negative/positive electrode capacity ratio of 2.09), the electrode achieves remarkable capacity of 345.2 mAh/g (2.76 mAh cm-2) at 0.2 A/g and maintains 235.2 mAh/g (1.88 mAh cm-2) at 4 A/g, while sustaining an impressive capacity retention of 97.7 % over 5000 cycles. These considerably outperform conventional electrodes employing traditional binders. Even at an elevated mass loading of 14 mg cm-2 or when operated at a low temperature of - 30 °C, the electrode continues to deliver excellent electrochemical performance (e.g., extraordinary areal capacity of 4.32 mAh cm-2). In addition, the electrode owns outstanding tolerance to external forces. This research contributes to our understanding of the pivotal challenges within the realm of AZIB technology.

Versatile MXenes for Aqueous Zinc Batteries

Aqueous zinc-ion batteries (AZIBs) are gaining popularity for their cost-effectiveness, safety, and utilization of abundant resources. MXenes, which possess outstanding conductivity, controllable surface chemistry, and structural adaptability, are widely recognized as a highly versatile platform for AZIBs. MXenes offer a unique set of functions for AZIBs, yet their significance has not been systematically recognized and summarized. This review article provides an up-to-date overview of MXenes-based electrode materials for AZIBs, with a focus on the unique functions of MXenes in these materials. The discussion starts with MXenes and their derivatives on the cathode side, where they serve as a 2D conductive substrate, 3D framework, flexible support, and coating layer. MXenes can act as both the active material and a precursor to the active material in the cathode. On the anode side, the functions of MXenes include active material host, zinc metal surface protection, electrolyte additive, and separator modification. The review also highlights technical challenges and key hurdles that MXenes currently face in AZIBs.

Nanofiber-Reinforced Composite Gel Enabling High Ionic Conductivity and Ultralong Cycle Life for Zn Ion Batteries

Despite the impressive merits of gel electrolytes for aqueous Zn-ion batteries, it remains a significant challenge to design and develop the gel electrolyte with high ionic conductivity, excellent dimensional stability, and long cycle life. Herein, a composite electrolyte (PTP) with thermolastic polyurethane -poly(m-phenylene isophthalamide)  nanofiber-reinforced polyvinyl alcohol gel strategy is proposed for highly reversible Zn plating/stripping. Mechanically robust and ultrathin PTP contains functional groups for building ion migration channels and immobilizing water molecules, which accelerates Zn2+ migration and mitigates water-related side reactions. Thus, the Zn anodes exhibit excellent electrochemical performance involving high cycling stability (6500 h at 5 mA cm-2 , 5 mA h cm-2 ) and achieving an exceptional cumulative capacity of more than 16 000 mA h cm-2 . This enhancement is well maintained when combined with MnO2 cathode. This work provides a reasonable solution for stabilizing Zn anodes and also provides new ideas for the modification of nanofiber-reinforced gel electrolytes.

Preventing Dissolution of Cathode Active Materials by Ion-anchoring Zeolite-based Separators for Durable Aqueous Zinc Batteries

Aqueous zinc batteries have emerged as promising energy storage devices due to their safety and low cost. However, they face challenges such as anodic dendrite formation and cathodic compound dissolution. Here, we present the development of a polymer-matrixed zeolite separator (SZ) by synthesizing zeolite materials on a flexible polymeric membrane. This separator acts as an effective ionic barrier, preventing the leaching and shuttling of vanadium from the cathode, while significantly inhibiting the formation of by-products and zinc dendrites. The SZ cells demonstrate stable operation for more than 400 cycles at 0.5 A g-1 , with an initial capacity of 375.4 mAh g-1 , and over 10,000 cycles at 15 A g-1 . Notably, when pre-anchored with vanadium ions, the SZ-V cells exhibited excellent capacity retention of up to 94.6 % over 1000 cycles. The SZ separator featuring an ion barrier represents a crucial advancement towards the commercialization of zinc storage devices.

Synergistically regulating the separator pore structure and surface property toward dendrite-free and high-performance aqueous zinc-ion batteries

As an emerging electrochemical device, aqueous zinc-ion batteries (ZIBs) present promising potential in safe and large-scale energy storage. However, the large pores of commercial glass fiber (GF) separators result in uneven Zn2+ ion flux, leading to severe dendrite growth issues of Zn metal anodes. Herein, we integrated a multifunctional layer on the GF separator that can synergistically regulate the pore feature and surface property of commercial GF separators. Such modification layer, composed of nanocellulose and SiO2 nanoparticles, exhibited uniform nanoporous structure and abundant negatively charged polar functional groups. These features allow regulating the distribution of Zn2+ ions at the separator-anode interface, facilitating stable and uniform Zn nucleation and growth. Moreover, the electrostatic interaction between the negatively charged functional groups and Zn2+ ions enhanced the Zn2+ ion transport kinetics, preventing the Zn dendrites formation and adverse reactions. Consequently, the modified electrolyte-filled GF separator showed an increased Zn2+ ion transference number of 0.65. The symmetric Zn//Zn batteries utilizing such a separator achieved an impressive cycling life of 500 h at a high current density/capacity of 10 mA cm-2/4 mAh cm-2, nearly nine times longer than the battery using the unmodified GF separator (<55 h). The superior electrochemical performance was verified in both Zn//AC and Zn//LiMn2O4 full battery evaluations. This work presents a novel synergistic modification strategy for developing advanced separators for aqueous ZIBs.

A Reversible Six-Electron Transfer Cathode for Advanced Aqueous Zinc Batteries

The electrochemical reactions for the storage of Zn2+ while embracing more electron transfer is a foundation of the future high-energy aqueous zinc batteries. Herein, we report a six-electron transfer electrochemistry of nano-sized TeO2 /C (n-TeO2 /C) cathode by facilitating the reversible conversion of TeO2 ↔Te and Te↔ZnTe. Benefitting from the integrated conductive nanostructure and the proton-rich environment in providing optimized electrochemical kinetics (facilitated Zn2+ uptake and high electronic conductivity) and feasible thermodynamic process (low Gibbs free energy change), the as-prepared n-TeO2 /C with stable cycling performance exhibits a superior reversible capacity of over 800 mAh g-1 at 0.1 A g-1 . A precise understanding of the reaction mechanism via ex situ and in situ characterizations presents that the reversible six-electron transfer reaction is proton-dependent, and a proton generating and consuming mechanism of three-phase conversion n-TeO2 /C in the weakly acidic electrolyte is thoroughly revealed.

Flexible Silica/MXene/Natural rubber film strain sensors with island chain structure for Healthcare monitoring

The demand for flexible strain sensors with high sensitivity and durability has increased significantly. However, traditional sensors are limited in terms of their detection ranges and fabrications. In this work, a space stacking method was proposed to fabricate natural rubber (NR)/ Ti3C2Tx (MXene)/silica (SiO2) films that possessed exceptional electrical conductivity, sensitivity and reliability. The introduction of SiO2 into the NR/MXene composite enabled the construction of an "island-chain structure", which promoted the formation of conductive pathways and significantly improved the conductivity of the composite. Specifically, the electrical conductivity of the NR/MXene/10 wt%SiO2 composite was enhanced by about 200 times compared to that of the NR/MXene composite alone (from 0.07 to 13.4 S/m). Additionally, the "island-chain structure" further enhanced the sensing properties of the NR/MXene/10 wt%SiO2 composite, as evidenced by its excellent sensitivity (GF = 189.2), rapid response time (102 ms), and good repeatability over 10,000 cycles. The fabricated device demonstrates an outstanding mechanical sensing performance and can accurately detect human physiological signals. Specifically, the device serves as a strain detector, recognizing different strain signals by monitoring the movement of fingers, arms, and thighs. This study provides critical insights into composite manufacturing with exceptional conductivity, flexibility and stability, which are essential properties for creating high-performance flexible sensors.

Highly Reversible Zn Anodes Achieved by Enhancing Ion-Transport Kinetics and Modulating Zn (002) Deposition

Uncontrolled dendrite growth and water-related side reactions in mild electrolytes are the main causes of poor cycling stability of zinc anodes, resulting in the deterioration of aqueous zinc-based batteries. Herein, a multifunctional fluorapatite (Ca5(PO4)3F) aerogel (FAG) interface layer is proposed to realize highly stable zinc anodes via the integrated regulation of Zn2+ migration kinetics and Zn (002) orientation deposition. Owing to the well-defined aerogel nanochannels and the rich Zn2+ adsorption sites resulting from the ion exchange between Ca2+ and Zn2+, the FAG interface layer could significantly accelerate the Zn2+ migration and effectively homogenize the Zn2+ flux and nucleation sites, thus promoting rapid and uniform Zn2+ migration at the electrode/electrolyte interface. Additionally, during the cycling process, the F atoms from FAG promote the in situ generation of ZnF2, which facilitates the manipulation of the preferred Zn (002) orientation deposition, thus efficiently suppressing dendrite growth and side reactions by combining with the above synergistic effects. Consequently, the FAG-modified Zn anode displays a stable cycle life of over 4000 h at 1 mA cm-2 and exhibits highly reversible Zn plating/stripping behavior. Meanwhile, the Zn||MnO2 full cells exhibit improved cycle stability over 2000 cycles compared with that of the bare Zn, highlighting the virtues of the FAG protective layer for highly reversible Zn anodes. Our work brings the insight in to stabilize Zn anodes and power the commercial applications of aqueous zinc-based batteries.

Zincophilic Interfacial Manipulation against Dendrite Growth and Side Reactions for Stable Zn Metal Anodes

Constructing multifunctional interphases to suppress the rampant Zn dendrite growth and detrimental side reactions is crucial for Zn anodes. Herein, a phytic acid (PA)-ZnAl coordination compound is demonstrated as a versatile interphase layer to stabilize Zn anodes. The zincophilic PA-ZnAl layer can manipulate Zn2+ flux and promote rapid desolvation kinetics, ensuring the uniform Zn deposition with dendrite-free morphology. Moreover, the robust PA-ZnAl protective layer can effectively inhibit the hydrogen evolution reaction and formation of byproducts, further contributing to the reversible Zn plating/stripping with high Coulombic efficiency. As a result, the Zn@PA-ZnAl electrode shows a lower Zn nucleation overpotential and higher Zn2+ transference number compared with bare Zn. The Zn@PA-ZnAl symmetric cell exhibits a prolonged lifespan of 650 h tested at 5 mA cm-2 and 5 mAh cm-2 . Furthermore, the assembled Zn battery full cell based on this Zn@PA-ZnAl anode also delivers decent cycling stability even under harsh conditions.

Salting-Out Effect Realizing High-Strength and Dendrite-Inhibiting Cellulose Hydrogel Electrolyte for Durable Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries are limited by poor Zn stripping/plating reversibility. Not only can hydrogel electrolytes address this issue, but also they are suitable for constructing flexible batteries. However, there exists a contradiction between the mechanical strength and the ionic conductivity for hydrogel electrolytes. Herein, high-concentration kosmotropic ions are introduced into the cellulose hydrogel electrolyte to take advantage of the salting-out effect. This can significantly improve both the mechanical strength and ionic conductivity. Additionally, the obtained cellulose hydrogel electrolyte (denoted as Con-CMC) has strong adhesion, a wide electrochemical stability window, and good water retaining ability. The Con-CMC is also found to accelerate the desolvation process, improve Zn deposition kinetics, promote Zn deposition along the (002) plane, and suppress parasitic reactions. Accordingly, the Zn/Zn cell with Con-CMC demonstrates dendrite-free behavior with prolonged lifespan and can endure extremely large areal capacity of 25 mAh cm-2. The Con-CMC also enables a large average Coulombic efficiency of 99.54% over 500 cycles for the Zn/Cu cell. Furthermore, the assembled pouch-type Zn/polyaniline full battery provides great rate capability, superior cyclability (even with limited Zn anode excess), a slow self-discharge rate, and outstanding affordability to external forces. Overall, this work extends our knowledge of the rational design of hydrogel electrolytes.

Fluorescent Fiber-Shaped Aqueous Zinc-Ion Batteries for Bifunctional Multicolor-Emission/Energy-Storage Textiles

Wearable smart textiles are natural carriers to enable imperceptible and highly permeable sensing and response to environmental conditions via the system integration of multiple functional fibers. However, the existing massive interfaces between different functional fibers significantly increase the complexity and reduce the wearability of the textile system. Thus, it is significant yet challenging to achieve all-in-one multifunctional fibers for realizing miniaturized and lightweight smart textiles with high reliability. Herein, as bifunctional electrolyte additives, fluorescent carbon dots with abundant zincophilic functional groups are introduced into electrolytes to develop fluorescent fiber-shaped aqueous zinc-ion batteries (FFAZIBs). Originating from effective dendrite suppression of Zn anodes and multiple active sites of freestanding Prussian blue cathodes, high energy density (0.17 Wh·cm-3) and long-term cyclability (78.9% capacity retention after 1500 cycles) are achieved for FFAZIBs. More importantly, the one-dimensional structure ensures the same luminance in all directions of FFAZIBs, enabling the form of multicolor display-in-battery textiles.

Oriented Zinc Metal Anode Based on Directional Recognition and Assembly

The practical application of aqueous zinc batteries are highly limited by unsatisfied Zn anodes for the unavoidable dendrite growth and side reactions. Crystal orientation engineering is an effective way to overcome these inherent drawbacks. However, how to achieve Zn plating with manipulated crystallographic orientation is still a great challenge. Herein, a uniform (002)-oriented Zn metal anode is reported based on a directional cation recognition and crystal assembly strategy. The activated layered double hydroxide (Act-LDH) exhibits favorable adsorption energy with Zn2+ and high lattice matching with Zn (002) plane, which can be served as directional recognition layer to anchor Zn2+ and regulate crystallographic orientation of Zn as well. As demonstration, Zn crystals with ultrahigh ratio of (002)/(100) plane of 15.7 are assembled parallelly on horizontal Act-LDH, in which high CE of 99.85% maintains over 18 000 cycles. The symmetric battery with (002)-oriented Zn shows stable plating/stripping process over 1650 and 420 h at 1 mA cm-2 /0.5 mA h cm-2 and 10 mA cm-2 /5 mA h cm-2 , respectively, which is 9 and 12 times higher than unoriented polycrystalline Zn. Moreover, as-assembled full battery displays high specific capacity of 120 mA h g-1 at 2 A g-1 over 1800 cycles.

Two-dimensional materials for high density, safe and robust metal anodes batteries

With a high specific capacity and low electrochemical potentials, metal anode batteries that use lithium, sodium and zinc metal anodes, have gained great research interest in recent years, as a potential candidate for high-energy-density storage systems. However, the uncontainable dendrite growth during the repeated charging process, deteriorates the battery performance, reduces the battery life and more importantly, raises safety concerns. With their unique properties, two-dimensional (2D) materials, can be used to modify various components in metal batteries, eventually mitigating the dendrite growth, enhancing the cycling stability and rate capability, thus leading to safe and robust metal anodes. In this paper, we review the recent advances of 2D materials and summarize current research progress of using 2D materials in the applications of (i) anode design, (ii) separator engineering, and (iii) electrolyte modifications by guiding metal ion nucleation, increasing ion conductivity, homogenizing the electric field and ion flux, and enhancing the mechanical strength for safe metal anodes. The 2D material modifications provide the ultimate solution for obtaining dendrite-free metal anodes, realizes the high energy storage application, and indicates the importance of 2D materials development. Finally, in-depth understandings of subsequent metal growth are lacking due to research limitations, while more advanced characterizations are welcome for investigating the metal deposition mechanism. The more facile and simplified preparation of 2D materials possess great prospects in high energy density metal anode batteries, and thus fulfils the development of EVs.

Interfacial Designs of MXenes for Mild Aqueous Zinc-Ion Storage

Limited Li resources, high cost, and safety risks of using organic electrolytes have stimulated a strong motivation to develop non-Li aqueous batteries. Aqueous Zn-ion storage (ZIS) devices offer low-cost and high-safety solutions. However, their practical applications are at the moment restricted by their short cycle life arising mainly from irreversible electrochemical side reactions and processes at the interfaces. This review sums up the capability of using 2D MXenes to increase the reversibility at the interface, assist the charge transfer process, and thereby improve the performance of ZIS. First, they discuss the ZIS mechanism and irreversibility of typical electrode materials in mild aqueous electrolytes. Then, applications of MXenes in different ZIS components are highlighted, including as electrodes for Zn2+ intercalation, protective layers of Zn anode, hosts for Zn deposition, substrates, and separators. Finally, perspectives are put forward on further optimizing MXenes to improve the ZIS performance.

Flexible Electronic Systems via Electrohydrodynamic Jet Printing: A MnSe@rGO Cathode for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) are promising candidates to power flexible integrated functional systems because they are safe and environmentally friendly. Among the numerous cathode materials proposed, Mn-based compounds, particularly MnO₂, have attracted special attention because of their high energy density, nontoxicity, and low cost. However, the cathode materials reported so far are characterized by sluggish Zn²⁺ storage kinetics and moderate stabilities. Herein, a ZIB cathode based on reduced graphene oxide (rGO)-coated MnSe nanoparticles (MnSe@rGO) is proposed. After MnSe was activated to α-MnO₂, the ZIB exhibits a specific capacity of up to 290 mAh g^-1. The mechanism underlying the improvement in the electrochemical performance of the MnSe@rGO based electrode is investigated using a series of electrochemical tests and first-principles calculations. Additionally, in situ Raman spectroscopy is used to track the phase transition of the MnSe@rGO cathodes during the initial activation, proving the structural evolution from the LO to MO₆ mode. Because of the high mechanical stability of MnSe@rGO, flexible miniaturized energy storage devices can be successfully printed using a high-precision electrohydrodynamic (EHD) jet printer and integrated with a touch-controlled light-emitting diode array system, demonstrating the application of flexible EHD jet-printed microbatteries.

Nucleophilic deposition behavior of metal anodes

Nucleophilic materials play important roles in the deposition behavior of high-energy-density metal batteries (Li, Na, K, Zn, and Ca), while the principle and determination method of nucleophilicity are lacking. In this review, we summarize the metal extraction/deposition process to find out the mechanism of nucleophilic deposition behavior. The key points of the most critical nucleophilic behavior were found by combining the potential change, thermodynamic analysis, and active metal deposition behavior. On this basis, the inductivity and affinity of the material have been determined by Gibbs free energy directly. Thus, the inducibility of most materials has been classified: (a) induced nuclei can reduce the overpotential of active metals; (b) not all materials can induce active metal deposition; (c) the induced reaction is not changeless. Based on these results, the influencing factors (temperature, mass, phase state, induced reaction product, and alloying reactions) were also taken into account during the choice of inducers for active metal deposition. Finally, the critical issues, challenges, and perspectives for further development of high-utilization metal electrodes were considered comprehensively.

Hierarchical amorphous vanadium oxide and carbon nanotubes microspheres with strong interface interaction for Superior performance aqueous Zinc-ion batteries

Aqueous zinc-ion batteries have attracted more and more attention due to their safety, environmental benignity and high theoretical capacity. However, the lack of appropriate cathode materials with high capacity and long cycle life have become an obstacle to the development of aqueous zinc-ion batteries. Herein, the hierarchical amorphous vanadium oxide and carbon nanotubes (a-V₂O₅@CNTs) microspheres with strong interface interaction were successfully prepared by combing facile spray drying technique with annealing treatment. Benefiting from the a-V₂O₅ amorphous characters, CNTs framework high conductivity and hierarchical microspheres with strong interface interaction, the a-V₂O₅@CNTs exhibited abundant active sites, fast reaction kinetics as well as eminent structure stability. As a promising electrode material, the a-V₂O₅@CNTs displayed high specific capacity (480 mAh g^-1 at 0.5 A g^-1), good rate capability and long-term stability under high current density (158 mAh g^-1 at 30 A g^-1 over 1000 cycles). Meanwhile, the corresponding mechanism was further illustrated through different characterizations. Furthermore, the as-assembled flexible pouch battery based on the a-V₂O₅@CNTs delivered outstanding flexibility and feasibility. Hence, this work provides a new idea for developing high performance cathode materials of aqueous zinc-ion batteries.

A Nature-Inspired Separator with Water-Confined and Kinetics-Boosted Effects for Sustainable and High-Utilization Zn Metal Batteries

Uncontrollable dendrite growth and sluggish ion-transport kinetics are considered as the main obstacles for the further development of high-performance aqueous zinc ion batteries (AZIBs). Here, a nature-inspired separator (ZnHAP/BC) is developed to tackle these issues via the hybridization of the biomass-derived bacterial cellulose (BC) network and nano-hydroxyapatite particles (HAP). The as-prepared ZnHAP/BC separator not only regulates the desolvation process of the hydrated Zn²⁺ ions (Zn(H₂ O)₆ ²⁺ ) by suppressing the water reactivity through the surface functional groups, alleviating the water-induced side-reactions, but also boosts the ion-transport kinetics and homogenize the Zn²⁺ flux, resulting in a fast and uniform Zn deposition. Remarkably, the Zn|Zn symmetric cell with ZnHAP/BC separator harvests a long-term stability over 1600 h at 1 mA cm^-2 , 1 mAh cm^-2 and endures stable cycling over 1025 and 611 h even at a high depth of discharge (DOD) of 50% and 80%, respectively. The Zn|V₂ O₅ full cell with a low negative/positive (N/P) capacity ratio of 2.7 achieves a superior capacity retention of 82% after 2500 cycles at 10 A g^-1 . Furthermore, the Zn/HAP separator can be totally degraded within 2 weeks. This work develops a novel nature-derived separator and provides insights in constructing functional separators toward sustainable and advanced AZIBs.

Oriented Zn plating guided by aligned ZnO hexagonal columns realizing dendrite-free Zn metal electrodes

Aqueous zinc-ion batteries (AZIBs), featuring low cost and high safety, have become a research hotspot in recent years. However, the low Zn stripping/plating reversibility, caused by dendritic growth, harmful side reactions, and Zn metal corrosion, severely influences the applicability of AZIBs. Zincophilic materials have shown great potential to form protective layers at the surface of Zn metal electrodes, whereas those protective layers are usually thick, lack fixed crystalline orientation, and require binders. Herein, a facile, scalable, and cost-effective solution method is used to grow vertically aligned ZnO hexagonal columns with (002) top surface and low thickness of 1.3 µm onto Zn foil. Such oriented protective layer can promote homogenous and nearly horizontal Zn plating not only on the top but also at the side of ZnO columns due to the low lattice mismatch between Zn (002) and ZnO (002) facets and between Zn (110) and ZnO (110) facets. Accordingly, the modified Zn electrode exhibits dendrite-free behavior with considerably suppressed corrosion issue, inert byproduct growth, and hydrogen evolution. Thanks to that, the Zn stripping/plating reversibility is significantly improved in Zn//Zn cell, Zn//Ti cell, and Zn//MnO₂ battery. This work provides a promising avenue for guiding metal plating process via oriented protective layer.

Challenges and Strategies in the Development of Zinc-Ion Batteries

Although promising, the practical use of zinc-ion batteries (ZIBs) remains plagued with uncontrollable dendrite growth, parasitic side reactions, and the high intercalation energy of divalent Zn²⁺ ions. Hence, much work has been conducted to alleviate these issues to maximize the energy density and cyclic life of the cell. In this holistic review, the mechanisms and rationale for the stated challenges shall be summarized, followed by the corresponding strategies employed to mitigate them. Thereafter, a perspective on present research and the outlook of ZIBs would be put forth in hopes to enhance their electrochemical properties in a multipronged approach.

Interfacial Engineering Boosts Highly Reversible Zinc Metal for Aqueous Zinc-Ion Batteries

Zinc metal is emerging as the promising anode for aqueous Zn-ion batteries. However, corrosion and undesirable Zn dendrite growth limit their practical application in the large-scale energy storage area. Herein, a mountain-valley micro/nanostructure is successfully fabricated on the surface of the Zn anode via a femtosecond-laser filament texturing (FsLFT) technique. Beneficial from the large surface area and spontaneously generated ZnO coating layer, the FsLFT-Zn electrode demonstrates a slow corrosion rate with a current density of 0.62 mA cm^-2 and a stable cycle life over 3000 h under 1 mA cm^-2, superior to the original Zn anode. Simulation of the electric fields reveals that the enlarged surface area is responsible for the outstanding performance of the FsLFT-Zn electrode. This study not only proposes a novel strategy to suppress dendrite growth toward highly stable AZIBs but also opens a new avenue to solve similar issues in other metal batteries.

Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators

Zinc ion hybrid capacitors (ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applications. Carbon-based materials are deemed the competitive candidates for cathodes of ZIHC due to their cost-effectiveness, high electronic conductivity, chemical inertness, controllable surface states, and tunable pore architectures. In recent years, great research efforts have been devoted to further improving the energy density and cycling stability of ZIHCs. Reasonable modification and optimization of carbon-based materials offer a remedy for these challenges. In this review, the structural design, and electrochemical properties of carbon-based cathode materials with different dimensions, as well as the selection of compatible, robust current collectors and separators for ZIHCs are discussed. The challenges and prospects of ZIHCs are showcased to guide the innovative development of carbon-based cathode materials and the development of novel ZIHCs.

2D Materials Boost Advanced Zn Anodes: Principles, Advances, and Challenges

Aqueous zinc-ion battery (ZIB) featuring with high safety, low cost, environmentally friendly, and high energy density is one of the most promising systems for large-scale energy storage application. Despite extensive research progress made in developing high-performance cathodes, the Zn anode issues, such as Zn dendrites, corrosion, and hydrogen evolution, have been observed to shorten ZIB's lifespan seriously, thus restricting their practical application. Engineering advanced Zn anodes based on two-dimensional (2D) materials are widely investigated to address these issues. With atomic thickness, 2D materials possess ultrahigh specific surface area, much exposed active sites, superior mechanical strength and flexibility, and unique electrical properties, which confirm to be a promising alternative anode material for ZIBs. This review aims to boost rational design strategies of 2D materials for practical application of ZIB by combining the fundamental principle and research progress. Firstly, the fundamental principles of 2D materials against the drawbacks of Zn anode are introduced. Then, the designed strategies of several typical 2D materials for stable Zn anodes are comprehensively summarized. Finally, perspectives on the future development of advanced Zn anodes by taking advantage of these unique properties of 2D materials are proposed.

Rationally designing a Ti3C2Tx/CNTs-Co9S8 heterostructure as a sulfur host with multi-functionality for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have been regarded as potential next-generation batteries owing to their ultrahigh theoretical capacity and abundance of sulfur. However, polysulfide shuttling, poor electronic conductivity, and severe volume expansion limit their commercial prospects. In this work, we rationally constructed a 3D porous Ti₃C₂T_x/CNTs-Co₉S₈ heterostructure derived from a zeolite imidazole framework (ZIF)/Ti₃C₂T_x MXene composite via carbonization and subsequent sulfidation. In this 3D porous Ti₃C₂T_x/CNTs-Co₉S₈ heterostructure, the 3D porous Ti₃C₂T_x MXene structure can provide facilitated ion and electron transport, good structural stability, and polar bonds to anchor sulfur and polysulfides. The formed CNTs can enhance ion diffusion and electron transport. The Co₉S₈ nanoparticles can accelerate the conversion reaction of polysulfides to Li₂S, which can further prevent polysulfide shuttling. The 3D porous structure can buffer the electrode volume change upon cycling. This rationally designed Ti₃C₂T_x/CNTs-Co₉S₈/S cathode exhibits a high initial capacity of 1389.8 mA h g^-1 at 0.1C, good cyclic stability (730.7 mA h g^-1 at 0.2C after 100 cycles), and excellent rate capacities (530.7 mA h g^-1 at 1C). When the S loading was 2.5 mg cm^-2, the Ti₃C₂T_x/CNTs-Co₉S₈/S cathode still exhibited a reversible capacity of 472.8 mA h g^-1 at 0.5C after 300 cycles.

Long Shelf-Life Efficient Electrolytes Based on Trace l-Cysteine Additives toward Stable Zinc Metal Anodes

The unstable anode/electrolyte interface (AEI) triggers the corrosion reaction and dendrite formation during cycling, hindering the practical application of zinc metal batteries. Herein, for the first time, l-cysteine (Cys) is employed to serve as an electrolyte additive for stabilizing the Zn/electrolyte interface. It is revealed that Cys additives tend to initially approach the Zn surface and then decompose into multiple effective components for suppressing parasitic reactions and Zn dendrites. As a consequence, Zn|Zn symmetric cells using trace Cys additives (0.83 mm) exhibit a steady cycle life of 1600 h, outperforming that of prior studies. Additionally, an average Coulombic efficiency of 99.6% for 250 cycles is also obtained under critical test conditions (10 mA cm^-2 /5 mAh cm^-2 ). Cys additives also enable Zn-V₂ O₅ and Zn-MnO₂ full cells with an enhanced cycle stability at a low N/P ratio. More importantly, Cys/ZnSO₄ electrolytes are demonstrated to be still effective after resting for half year, favoring the practical production.

Constructing hollow nanotube-like amorphous vanadium oxide and carbon hybrid via in-situ electrochemical induction for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries receive more and more attentions on account of their low cost, high theoretical density and inherent safety. Nevertheless, the lack of suitable cathode materials with excellent performance still severely impedes the development of aqueous zinc-ion batteries. Herein, an in-situ electrochemical induction strategy is developed to prepare hollow nanotube-like amorphous vanadium oxide and carbon (a-V₂O₅@C) hybrid and its electrochemical performance is investigated comprehensively as cathode materials for aqueous zinc-ion batteries. Benefitting from the unique amorphous structure of V₂O₅ and intimate contact between amorphous V₂O₅ and carbon, the a-V₂O₅@C hybrid possess the abundant ion storage sites, isotropic ion diffusion routes and excellent conductivity. As a result, the a-V₂O₅@C hybrid cathode shows outstanding specific capacity of 448 mAh g^-1 at 0.15 A g^-1. Impressively, the a-V₂O₅@C hybrid cathode exhibits superior cycling stability, even when cycling at high current density of 10 A g^-1, that the 96.5% specific capacity retention can be gained over 1500 cycles, corresponding to an average specific capacity loss of only 0.0023% per cycle. Furthermore, the mechanism involved is illustrated by systematical characterizations. Therefore, this work affords a new way for developing high-performance cathode materials for aqueous zinc-ion batteries.

From spent alkaline batteries to active Zn||ZnxMn2O4 aqueous batteries: a mild process of cathode recycling and crystal engineering

A mild, efficient, and low-cost method was designed for recycling cathode materials from spent alkaline batteries into advanced aqueous zinc batteries.