A Seamless Metal-Organic Framework Interphase with Boosted Zn2+ Flux and Deposition Kinetics for Long-Living Rechargeable Zn Batteries

Synergistic Effects of CuZn Nanoparticles and Graphene for Advanced Zinc Anodes in Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have garnered significant attention as promising next-generation energy storage devices due to their advantages of low cost, operational safety, and high theoretical specific capacity. Nevertheless, interface instability issues including dendrite growth, hydrogen evolution, and corrosion severely compromise zinc anode reversiblity. This study presents a novel strategy employing CuZn alloy nanoparticles anchored on graphene sheets (CZPG) as a multifuctional protective coating. The CZPG architecture establishes a dual-functional interface: graphene provides high-conductivity pathways and abundant nucleation sites, while CuZn nanoparticles demonstrate expecetional zincophilicity and hydrogen evolution suppression. The alloy's elevated dezincification potential synergizes with graphene's conductive network to regulate Zn2+ flux distribution and deposition kinetics. Systematic characterization reveals that the CZPG coating enable homogeneous zinc nucleation while suppressing parasitic reactions. Consequently, CZPG@Zn symmetric cells achieve remarkable cycling stability exceeding 1300 h at a 5.0 mA·cm-2 and 2.5 mAh·cm-2, providing a 24-fold increase in cycle life compared to bare Zn. When paired with KVO cathodes, full cells maintain 81.9% capacity retention after 1000 cycles, demonstrating 10-fold improvement over conventional Zn anodes. This interfacial engineering approach through alloy-graphene hybrid coatings provides new insights for developing high-preformance AZIBs, showing significant potential for grid-scale enegy storage applications.

Spatial Confinement and Induced Deposition of ZnHCF in 3D Structure for Ultrahigh-Rate and Dendrite-Free Zn Anodes

Aqueous Zn-metal batteries (AZBs) are thought as highly prospective candidates for large-scale energy-storage systems because of their abundant natural resources, low cost, high safety, and environmentally friendly. Nevertheless, the key problems of AZBs are the uncontrollable zinc dendrites growth and water-induced erosion faced by zinc anodes. Therefore, reducing the hydrophilicity of zinc anode and introducing the zincophilic sites are the availably strategy. Herein, 3D highly-conductive host is developed to inhibit Zn dendrites growth, which have a porous structure consisting of graphene and carbon nanotubes embedded with a zincophilic nucleation sites of Zn Prussian blue analogs (ZnHCF@3D-GC). The inner ZnHCF possess minimized nucleation barriers, which can serve as favorable nucleation sites, and 3D host provide a buffer interspace to allow for even more high-capacity Zn plating. Additionally, density functional theory results show that ZnHCF exhibits a strong Zn binding energy and high adsorption energy of Zn (002) plane, which can guide Zn horizontal deposition in the 3D host. As a result, the assembled symmetrical cell is able to stabilize 900 cycles at an ultrahigh current density of 100 mA cm-2. Zn-ZnHCF@3D-GC//MnO2 and Zn-ZnHCF@3D-GC//ZnHCF full cells can be stably cycled 1000 cycles at 2.0 A g-1.

Single (002)-Textured Zinc Anode via Nonepitaxial Electrodeposition with In Situ Texture Maintenance for Stable Aqueous Zinc Batteries

Crystallography regulation of a zinc (Zn) metal substrate to expose more (002) textures holds great promise for stabilizing Zn anodes. However, significant challenges remain in directly constructing a single (002)-plane-textured Zn metal anode (S-(002)-Zn) and realizing a sustainable (002)-texture exposure in working batteries. Herein, we report an anion and cation coregulated nonepitaxial electrodeposition to fabricate S-(002)-Zn by introducing 1-ethyl-3-methylimidazolium iodide (EmimI) additives in low-cost ZnSO4 aqueous electrolyte (ZS). Mechanistic studies reveal that the cooperation of Emim+ and I- with oriented adsorption behaviors on Zn can synergistically boost the (100) plane growth, depress the (002) plane growth, and suppress H2 evolution, thus enabling compact S-(002)-Zn electrodeposition. Moreover, other similar organic iodides (e.g., dimethyl-imidazolium iodide and 1-propyl-3-methylimidazolium iodide) are applicable to this scalable electrodeposition. On the other hand, the as-designed ZS-EmimI electrolyte can be directly applied in working Zn batteries, thus effectively sustaining the smooth (002) texture of S-(002)-Zn and inhibiting HER during cycling. Consequently, the combination of single-(002)-texture and ZS-EmimI electrolyte endows the S-(002)-Zn anode with an ultralong lifespan over 10,100 h (>14 months) at 1 mAh cm-2 and superior deep-cycling stability under 88.0% utilization (25 mAh cm-2) over 500 h and assures the stable operation of full Zn batteries.

Novel organic additives with high dipole moments: Improving the anode interface structure to enhance the performance of zinc ion aqueous batteries

The reversibility and stability of aqueous zinc-ion batteries (AZIBs) are largely limited by free-water-induced side reactions (e.g., hydrogen evolution and zinc corrosion) and negative zinc dendrite growth. To address these issues, we introduced triethyl 2-phosphonopropionate (Tp), a novel high-dipole-moment electrolyte additive. Tp effectively replaces free water in the electrolyte through strong ion-dipole interactions, altering the solvation structure and suppressing hydrogen evolution and zinc corrosion at the zinc anode. Additionally, the high binding energy between Tp and zinc foil ensures that Tp adheres firmly to the zinc anode surface, while the hydrophobic alkyl chains repel free water, modifying the interfacial structure of the zinc anode, promoting reversible zinc deposition, and effectively suppressing zinc dendrite growth. With these excellent properties, the optimal concentration of Tp enables a cycle time of over 770 h for 1 mA cm-2 and 1 mAh cm-2 symmetric cells, which is 7.7 times longer than that of pure electrolyte. Furthermore, the cycle number of Zn//Na2V6O16 full cells increased from 600 to 4000 cycles compared to pure electrolyte, with capacity retention improved from 70 % to 92 %. These results highlight the significance of high-dipole moment electrolyte additives, provide new insights into electrolyte modification strategies, and are expected to accelerate the commercialization of AZIBs for practical applications.

Surface engineering activation of mixed valence copper selenide: A high-performance anode for long life zinc-ion rock-chair batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) are an attractive alternative to lithium-ion batteries (LIBs) for large-scale energy storage, which offer high ionic conductivity and environmental advantages. However, challenges such as dendrite growth and limited coulombic efficiency (CE) limit electrochemical performance of AZIBs thus hindering their practical application. This study designs a polypyrrole (PPy)-coated copper selenide composite (CuxSey@PPy) that works via Zn2+ insertion/extraction mechanism. Density Functional Theory (DFT) calculations reveal the PPy layer modifies the surface charge distribution of CuxSey, introducing additional electrochemical active sites. Consequently, the novel composite anode achieving specific capacity of 308.2 mAh g-1 at 100 mA g-1 and capacity retain of 96 %after 10,000 cycles at 2000 mA g-1, in half cell configuration. In full cell configuration, the rock-chair batteries with a ZnMn2O4 cathode retained 65.4 % capacity after 20,000 cycles, maintaining a CE consistently above 99 %.

Delocalized Electron Engineering of MXene-Immobilized Atomic Catalysts toward Fast Desolvation and Dendritic Inhibition for Low-Temperature Zn Metal Batteries

Rechargeable low-temperature aqueous zinc metal batteries (LT-AZMBs) are considered as a competitive candidate for next-generation energy storage systems owing to increased safety and low cost. Unfortunately, sluggish desolvation kinetics of hydrated [Zn(H2O)x]2+ and inhomogeneous ion flux cause detrimental hydrogen evolution reactions (HER) and Zn dendrite growth. Herein, the atomic iron well-implanted onto MXene via defect capture (SAFe@MXene) has been initially proposed to modulate Zn plating. The SAFe@MXene serves as kinetic promoters to enhance interfacial desolvation of [Zn(H2O)x]2+ to prevent HER and uniformizes Zn2+ flux for smooth deposition, as confirmed by theoretical simulation, Raman and electrochemical tests. Consequently, under 0 °C, the SAFe@MXene-modulated Zn electrodes deliver long-term stability of 800 h with lower overpotentials even at 5 mA cm-2 or higher plating/stripping capacity. The full cell with a MnO2 cathode stabilizes a high capacity-retention of nearly 100% after 1000 cycles at 1 A g-1, suggesting great promise for high-performance LT-AZMBs.

Low-Temperature Lithium Metal Batteries Achieved by Synergistically Enhanced Screening Li+ Desolvation Kinetics

Lithium metal anode is desired by high capacity and low potential toward higher energy density than commercial graphite anode. However, the low-temperature Li metal batteries suffer from dendrite formation and dead Li resulting from uneven Li behaviors of flux with huge desolvation/diffusion barriers, thus leading to short lifespan and safety concern. Herein, differing from electrolyte engineering, a strategy of delocalizing electrons with generating rich active sites to regulate Li+ desolvation/diffusion behaviors are demonstrated via decorating polar chemical groups on porous metal-organic frameworks (MOFs). As comprehensively indicated by theoretical simulations, electrochemical analysis, in situ spectroscopies, electron microscope, and time-of-flight secondary-ion mass spectrometry, the sieving kinetics of desolvation is not merely relied on pore size morphology but also significantly affected by the ─NH2 polar chemical groups, reducing energy barriers for realizing non-dendritic and smooth Li metal plating. Consequently, the optimal cells stabilize for long lifespan of 2000 h and higher average Coulombic efficiency, much better than the-state-of-art reports. Under a lower negative/positive ratio of 3.3, the full cells with NH2-MIL-125 deliver a high capacity-retention of 97.0% at 0.33 C even under -20 °C, showing the great potential of this kind of polar groups on boosting Li+ desolvation kinetics at room- and low-temperatures.

Advancing Anode Performance in Aqueous Zinc-Ion Batteries: A Review of Metal-Organic Framework-Based Strategies

Aqueous zinc-ion batteries (AZIBs) are garnering substantial research interest in electric vehicles, energy storage systems, and portable electronics, primarily for the reason that the inexpensive cost, high theoretical specific capacity, and environmental sustainability of zinc metal anodes, which are an essential component to their design. Nonetheless, the progress of AZIBs is hindered by significant obstacles, such as the occurrence of anodic side reactions (SR) and the formation of zinc dendrites. Metal-organic framework (MOF)-based materials are being explored as promising alternatives owing to homogeneous porous structure and large specific surface areas. There has been a rare overview and discussion on strategies for protecting anodes using MOF-based materials. This review specifically aims to investigate cutting-edge strategies for the design of highly stable MOF-based anodes in AZIBs. Firstly, the mechanisms of dendrites and SR are summarized. Secondly, the recent advances in MOF-based anodic protection including those of pristine MOFs, MOF composites, and MOF derivatives are reviewed. Furthermore, the strategies involving MOF-based materials for zinc anode stabilization are presented, including the engineering of surface coatings, three-dimensional zinc structures, artificial solid electrolyte interfaces, separators, and electrolytes. Finally, the ongoing challenges and prospective directions for further enhancement of MOF-based anodic protection technologies in AZIBs are highlighted.

Constructing 3D Crosslinked Macromolecular Networks as a Highly Efficient Interface Layer for Ultra-Stable Zn Metal Anodes

Aqueous zinc ion batteries (AZIBs) are experiencing rapid development due to their high theoretical capacity, abundant zinc resources, and intrinsic safety. However, the progress of AZIBs is hindered by uncontrollable parasitic reactions and excessive dendrite growth, which compromise the durability and effective utilization of zinc metal anodes. To address these challenges, the study has constructed a 3D crosslinked macromolecular network composed of zinc ion-bonded potato starch (StZ) as an interface layer on Zn foil (StZ-Zn) to inhibit hydrogen evolution, regulate Zn2+ flux, and ensure uniform Zn deposition. Density functional theory calculations, molecular dynamics simulations, COMSOL Multiphysics simulations, and in situ Raman spectra demonstrate that the 3D StZ interface layer facilitates Zn2+ desolvation by restructuring the solvation shells. This process reduces the concentration of H2O at the anode, thereby inhibiting the hydrogen evolution reaction. Consequently, Zn2+ transport is more efficient, promoting a homogeneous Zn2+ flux and enabling dendrite-free Zn deposition. As a result, StZ-Zn||StZ-Zn symmetric cell delivers a superb lifespan of 4800 h at the current density of 5 mA cm-2, and the corresponding cumulative capacity is as high as 12000 mAh cm-2. Notably, StZ-Zn||NaV3O8·1.5H2O full cell can stably operate for 2500 cycles at 5 A g-1 with an outstanding capacity retention of 92%.

Designing Multi-functional Separators With Regulated Ion Flux and Selectivity for Macrobian Zinc Ion Batteries

The success of achieving scale-up deployment of zinc ion batteries is to selectively regulate the rapid and dendrite-free growth of zinc anodes. Herein, this is proposed that a creative design strategy of constructing multi-functional separators (MFS) to stabilize the zinc anodes. By in situ decorating metal-organic-framework coating on commercial glass fiber, the upgraded separator is of remarkable benefit for strong anion (SO4 2-) anchoring, uniform ion flux across the interface, and boosted Zn2+ desolvation. Such a feature selectively promotes the Zn2+ transportation efficiency, which enables a high Zn2+ transference number of 0.81, enhanced ionic conductivity, and a superb exchange current density of 12.80 mA cm-2. Consequently, the zinc anode can be operated stably with an ultra-long service lifetime of over 4800 h in symmetric cells and improved cycling endurance in full batteries. This work paves an attractive pathway to design multi-functional separators with regulated ion flux and selectivity toward high-energy metal batteries beyond zinc chemistry.

Realizing the Electrode Engineering Significance Through Porous Organic Framework Materials for High-Capacity Aqueous Zn-Alkaline Battery

Energy storage technologies are eminently developed to address renewable energy utilization efficiently. Porous framework materials possess high surface area and pore volume, allowing for efficient ion transportation and storage. Their unique structure facilitates fast electron transfer, leading to improved battery kinetics. Porous organic framework materials like metal-organic (MOF) and covalent organic (COF) frameworks have immense potential in enhancing the charge/discharge performances of aqueous Zn-alkaline batteries. Organic frameworks and their derivatives can be modified feasibly to exhibit significant chemical stability, enabling them to tolerate the harsh battery environment. Zn-alkaline batteries can achieve enhanced energy density, longer lifespan, and improved rechargeability by incorporating MOFs and COFs, such as electrodes, separators, or electrolyte additives, into the battery architecture. The present review highlights the significant electrode design strategies based on porous framework materials for aqueous Zn-alkaline batteries, such as Zn-Ni, Zn-Mn, Zn-air, and Zn-N2/NO3 batteries. Besides, the discussion on the issues faced by the Zn anode and the essential anode design strategies to solve the issues are also included.

Tailoring Zn2+ Flux by an Ion Acceleration Layer Modified Separator for High-Rate Long-Lasting Zn Metal Anodes

A large concentration gradient originating from sluggish ion transport on the surface of Zn metal anodes will result in uneven Zn2+ flux, giving rise to severe dendrite growth, especially at high current density. Herein, an ion acceleration layer is introduced by a facile separator engineering strategy to realize modulated Zn2+ flux and dendrite-free deposition. Zinc hexacyanoferrate as the modifying agent featuring strong zincophilicity and rapid diffusion tunnel can enable fast trap for Zn2+ near the electrode surface and immediate transport onto deposition sites, respectively. The ion acceleration effect is substantiated by improved ion conductivity, decreased activated energy, and promoted Zn2+ transference number, which can moderate concentration gradient to guide homogenous Zn2+ flux distribution. As a result, the separator engineering guarantees Zn||Zn symmetrical cells with long-term stability of 2700 h at 2 mA cm-2, and 1770 h at a large current density of 10 mA cm-2. Moreover, cycling stability and rate capability for full cells with different cathodes can be substantially promoted by the modified separator, validating its superior practical feasibility. This study supplies a new scalable approach to tailoring ion flux near the electrode surface to enable robust Zn metal anodes at a high current density.

Modulating Interfacial Zn2+ Desolvation and Transport Kinetics through Coordination Interaction toward Stable Anodes in Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (AZIBs) are promising candidates for grid-scale energy-storage applications, but uneven Zn2+ flux distribution and undesirable water-related interfacial side reactions seriously hinder their practical application. Herein, a strategy of regulating the coordination interaction between Zn2+ and artificial interphase layers (AILs) to modulate the interfacial Zn2+ desolvation/transport behaviors and relieve side reactions for building stable Zn anodes is proposed. By selectively choosing appropriate polymers with different functional groups, it is shown that compared with the strong interaction offered by aryl groups in polystyrene-based AILs, cyano groups in polyacrylonitrile (PAN)-based AILs provide a moderate coordination interaction with Zn2+, which not only accelerates interfacial Zn2+desolvation kinetics but also enables efficient Zn2+ transport within AILs. Moreover, the Zn2+ transport kinetics of PAN-based AILs can be further enhanced with the incorporation of an ionic conductor, zinc phosphate (ZP). Because of these advantages, the Zn anodes decorated with the hybrid AILs composed of PAN and ZP can steadily operate for >2000 h at 0.2 mA cm-2 and >350 h at a high current density of 10 mA cm-2. This work provides a valuable guideline for selective design of AILs at the molecular level for durable AZIBs.

Recent Functionalized Strategies of Metal-Organic Frameworks for Anode Protection of Aqueous Zinc-Ion Battery

The inherent benefits of aqueous Zn-ion batteries (ZIBs), such as environmental friendliness, affordability, and high theoretical capacity, render them promising candidates for energy storage systems. Nevertheless, the Zn anodes of ZIBs encounter severe challenges, including dendrite formation, hydrogen evolution reaction, corrosion, and surface passivation. These would result in the infeasibility of ZIBs in practical situations. To this end, artificial interfaces with functionalized materials are crafted to protect the Zn anode. They have the capability to modulate the zinc ion flux in proximity to the electrode surface and shield it from aqueous electrolytes by leveraging either size effects or charge effects. Considering metal-organic frameworks (MOFs) with tunable pore size, chemical composition, and stable framework structures, they have emerged as effective materials for building artificial interfaces, prolonging the lifespan, and improving the unitization of Zn anode. In this review, the contributions of MOFs for protecting Zn anode, which mainly involves facilitating homogeneous nucleation, manipulating selective deposition, regulating ion and charge flux, accelerating Zn desolvation, and shielding against free water and anions are comprehensively summarized. Importantly, the future research trajectories of MOFs for the protection of the Zn anode are underscored, which may propose new perspectives on the practical Zn anode and endow the MOFs with high-value applications.

Zincophilic Nanospheres Assembled as Solid-Electrolyte Interphase on Zn Metal Anodes for Reversible High-rate Zn-Ion Storage

Aqueous Zn-ion batteries (ZIBs) are considered to be one of the most promising energy storage devices in the post-lithium-ion era with fast ionic conductivity, safety, and low cost. However, excessive accumulation of zinc dendrites will fracture and produce dead zinc, resulting in the unsatisfied utilization rate of Zn anodes, which greatly restricts the lifespan of the battery and reduces the reversibility. In this paper, by constructing a protective layer of ZnSnO3 hollow nanospheres in situ growth on the surface of the Zn anode, more zincophilic sites are established on the electrode surface. It demonstrates that uniform deposition of Zn ions by deepening the binding energy with Zn ion and its unique hollow structure shortens the diffusion distance of Zn ions and enhances the reaction kinetics. The assembled Zn-ion hybrid supercapacitor (ZHSC) of ZnSnO3@Zn//AC achieved a long-term lifespan with 4000 cycles at a current density of 10 mA cm-2 with a Coulombic efficiency of 99.31% and capacity retention of 79.6%. This work offers a new path for advanced Zn anodes interphase supporting the long cycle life with large capacities and improving electrochemical reversibility.

MOFs-Based Materials with Confined Space: Opportunities and Challenges for Energy and Catalytic Conversion

Metal-Organic Frameworks (MOFs) are a very promising material in the fields of energy and catalysis due to their rich active sites, tunable pore size, structural adaptability, and high specific surface area. The concepts of "carbon peak" and "carbon neutrality" have opened up huge development opportunities in the fields of energy storage, energy conversion, and catalysis, and have made significant progress and breakthroughs. In recent years, people have shown great interest in the development of MOFs materials and their applications in the above research fields. This review introduces the design strategies and latest progress of MOFs are included based on their structures such as core-shell, yolk-shell, multi-shelled, sandwich structures, unique crystal surface exposures, and MOF-derived nanomaterials in detail. This work comprehensively and systematically reviews the applications of MOF-based materials in energy and catalysis and reviews the research progress of MOF materials for atmospheric water harvesting, seawater uranium extraction, and triboelectric nanogenerators. Finally, this review looks forward to the challenges and opportunities of controlling the synthesis of MOFs through low-cost, improved conductivity, high-temperature heat resistance, and integration with machine learning. This review provides useful references for promoting the application of MOFs-based materials in the aforementioned fields.

Anode-Free Aqueous Aluminum Ion Batteries

Aqueous aluminum ion batteries (AAIBs) possess the advantages of high safety, cost-effectiveness, eco-friendliness and high theoretical capacity. However, the Al2O3 film on the Al anode surface, a natural physical barrier to the plating of hydrated aluminum ions, is a key factor in the decomposition of the aqueous electrolyte and the severe hydrogen precipitation reaction. To circumvent the obnoxious Al anode, a proof-of-concept of an anode-free AAIB is first proposed, in which Al2TiO5, as a cathode pre-aluminum additive (Al source), can replenish Al loss by over cycling. The Al-Cu alloy layer, formed by plating Al on the Cu foil surface during the charge process, possesses a reversible electrochemical property and is paired with a polyaniline (cathode) to stimulate the battery to exhibit high initial discharge capacity (175 mAh g-1), high power density (≈410 Wh L-1) and ultra-long cycle life (4000 cycles) with the capacity retention of ≈60% after 1000 cycles. This work will act as a primer to ignite the enormous prospective researches on the anode-free aqueous Al ion batteries.

Superfast Zincophilic Ion Conductor Enables Rapid Interfacial Desolvation Kinetics for Low-Temperature Zinc Metal Batteries

Low-temperature rechargeable aqueous zinc metal batteries (AZMBs) as highly promising candidates for energy storage are largely hindered by huge desolvation energy barriers and depressive Zn2+ migration kinetics. In this work, a superfast zincophilic ion conductor of layered zinc silicate nanosheet (LZS) is constructed on a metallic Zn surface, as an artificial layer and ion diffusion accelerator. The experimental and simulation results reveal the zincophilic ability and layer structure of LZS not only promote the desolvation kinetics of [Zn(H2O)6]2+ but also accelerate the Zn2+ transport kinetics across the anode/electrolyte interface, guiding uniform Zn deposition. Benefiting from these features, the LZS-modified Zn anodes showcase long-time stability (over 3300 h) and high Coulombic efficiency with ≈99.8% at 2 mA cm-2, respectively. Even reducing the environment temperature down to 0 °C, ultralong cycling stability up to 3600 h and a distinguished rate performance are realized. Consequently, the assembled Zn@LZS//V2O5-x full cells deliver superior cyclic stability (344.5 mAh g-1 after 200 cycles at 1 A g-1) and rate capability (285.3 mAh g-1 at 10 A g-1) together with a low self-discharge rate, highlighting the bright future of low-temperature AZMBs.

Electrolyte Solvation Chemistry for Stabilizing the Zn Anode via Functionalized Organic Agents

As a potential candidate for grid-scale energy storage technology, aqueous Zn-ion batteries (ZIBs) have attracted considerable attention due to their intrinsic safety, environmental friendliness, and ease of fabrication. Nevertheless, the road to industry for this technique is hindered by serious issues, including undesired side reactions, random growth of the Zn dendrites, electrode passivation, and anode corrosion, which are associated with the high reactivity of water molecules during the electrochemical reactions. These challenges are strongly dependent on electrolyte solvation chemistry (ESC), which subsequently determines the electrochemical behavior of the metal ions and water molecules on the electrode surface. In this work, a comprehensive understanding of optimized ESC with specified functional groups on the mixing agents to stabilize the Zn anode is provided. First, the challenges facing the ZIBs and their chemical principles are outlined. Specific attention is paid to the working principles of the mixing agents with different functional groups. Then the recent progress is summarized and compared. Finally, perspectives on future research for the aqueous Zn batteries are presented from the point of view.

Activating and Stabilizing a Reversible four Electron Redox Reaction of I-/I+ for Aqueous Zn-Iodine Battery

Low capacity and poor cycle stability greatly inhibit the development of zinc-iodine batteries. Herein, a high-performance Zn-iodine battery has been reached by designing and optimizing both electrode and electrolyte. The Br- is introduced as the activator to trigger I+, and coupled with I+ forming interhalogen to stabilize I+ to achieve a four-electron reaction, which greatly promotes the capacity. And the Ni-Fe-I LDH nanoflowers serve as the confinement host to enable the reactions of I-/I+ occurring in the layer due to the spacious and stable interlayer spacing of Ni-Fe-I LDH, which effectively suppresses the iodine-species shuttle ensuring high cycling stability. As a result, the electrochemical performance is greatly enhanced, especially in specific capacity (as high as 350 mAh g-1 at 1 A g-1 far higher than two-electron transfer Zn-iodine batteries) and cycling performance (94.6 % capacity retention after 10000 cycles). This strategy provides a new way to realize high capacity and long-term stability of Zn-iodine batteries.

Ultrasmall, Amorphous V2O3 Intimately Anchored on a Carbon Nanofiber Aerogel Toward High-Rate Zinc-Ion Batteries

When considered as a cathode candidate for aqueous Zn-ion batteries, V2O3 faces several problems, such as inherently unsuitable structure, fast structural degradation, and sluggish charge transport kinetics. In this paper, we report the synthesis of a V2O3 intimately coupled carbon aerogel by a controllable ion impregnation and solid-state reaction strategy using bacterial cellulose and ammonium metavanadate as raw materials. In this newly designed structure, the carbonized carbon fiber network provides fast ion and electron transport channels. More importantly, the cellulose aerogel functions as a dispersing and supporting skeleton to realize the particle size reduction, uniform distribution, and amorphous features of V2O3. These advantages work together to realize adequate electrochemical activation during the initial charging process and shorter transport distance and faster transport kinetics of Zn2+. The batteries based on the V2O3/CNF aerogel exhibit a high-rate performance and an excellent cycling stability. At a current density of 20 A g-1, the V2O3/CNF aerogel delivers a specific capacity of 159.8 mAh g-1, and it demonstrates an exceptionally long life span over 2000 cycles at 12 A g-1. Furthermore, the electrodes with active material loadings as high as 10 mg cm-2 still deliver appreciable specific capacities of 257 mAh g-1 at 0.1 A g-1.

Achieving Long-Cycle-Life Zinc-Ion Batteries through a Zincophilic Prussian Blue Analogue Interphase

The practical application of rechargeable aqueous zinc-ion batteries (ZIBs) has been severely hindered by detrimental dendrite growth, uncontrollable hydrogen evolution, and unfavorable side reactions occurring at the Zn metal anode. Here, we applied a Prussian blue analogue (PBA) material K2Zn3(Fe(CN)6)2 as an artificial solid electrolyte interphase (SEI), by which the plentiful -C≡N- ligands at the surface and the large channels in the open framework structure can operate as a highly zincophilic moderator and ion sieve, inducing fast and uniform nucleation and deposition of Zn. Additionally, the dense interface effectively prevents water molecules from approaching the Zn surface, thereby inhibiting the hydrogen-evolution-resultant side reactions and corrosion. The highly reversible Zn plating/stripping is evidenced by an elevated Coulombic efficiency of 99.87% over 600 cycles in a Zn/Cu cell and a prolonged lifetime of 860 h at 5 mA cm-2, 2 mAh cm-2 in a Zn/Zn symmetric cell. Furthermore, the PBA-coated Zn anode ensures the excellent rate and cycling performance of an α-MnO2/Zn full cell. This work provides a simple and effective solution for the improvement of the Zn anode, advancing the commercialization of aqueous ZIBs.

Tandem Chemistry with Janus Mesopores Accelerator for Efficient Aqueous Batteries

A reliable solid electrolyte interphase (SEI) on the metallic Zn anode is imperative for stable Zn-based aqueous batteries. However, the incompatible Zn-ion reduction processes, scilicet simultaneous adsorption (capture) and desolvation (repulsion) of Zn2+(H2O)6, raise kinetics and stability challenges for the design of SEI. Here, we demonstrate a tandem chemistry strategy to decouple and accelerate the concurrent adsorption and desolvation processes of the Zn2+ cluster at the inner Helmholtz layer. An electrochemically assembled perforative mesopore SiO2 interphase with tandem hydrophilic -OH and hydrophobic -F groups serves as a Janus mesopores accelerator to boost a fast and stable Zn2+ reduction reaction. Combining in situ electrochemical digital holography, molecular dynamics simulations, and spectroscopic characterizations reveals that -OH groups capture Zn2+ clusters from the bulk electrolyte and then -F groups repulse coordinated H2O molecules in the solvation shell to achieve the tandem ion reduction process. The resultant symmetric batteries exhibit reversible cycles over 8000 and 2000 h under high current densities of 4 and 10 mA cm-2, respectively. The feasibility of the tandem chemistry is further evidenced in both Zn//VO2 and Zn//I2 batteries, and it might be universal to other aqueous metal-ion batteries.

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

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

Orientational Electrodeposition of Highly (002)-Textured Zinc Metal Anodes Enabled by Iodide Ions for Stable Aqueous Zinc Batteries

Regulating the crystallographic texture of the zinc (Zn) metal anode is promising to promote Zn reversibility in aqueous electrolytes, but the direct fabrication of specific textured Zn still remains challenging. Herein, we report a facile iodide ion (I-)-assisted electrodeposition strategy that can scalably fabricate highly (002) crystal plane-textured Zn metal anode (H-(002)-Zn). Theoretical and experimental characterizations demonstrate that the presence of I- additives can significantly elevate the growth rate of the Zn (100) plane, homogenize the Zn nucleation, and promote the plating kinetics, thus enabling the uniform H-(002)-Zn electrodeposition. Taking the electrolytic cell with the conventional ZnSO4-based electrolyte and commercial Cu substrate as a model system, the Zn texture gradually transforms from (101) to (002) as the increase of NaI additive concentration. In the optimized 1 M ZnSO4 + 0.8 M NaI electrolyte, the as-prepared H-(002)-Zn features a compact structure and an ultrahigh intensity ratio of (002) to (101) signal without containing the (100) signal. The free-standing H-(002)-Zn electrode manifests stronger resistance to interfacial side reactions than the conventional (101)-textured Zn electrode, thus delivering a high efficiency of 99.88% over 400 cycles and ultralong cycling lifespan over 6700 h (>9 months at 1 mA cm-2) and assuring the stable operation of full Zn batteries. This work will enlighten the efficient electrosynthesis of high-performance Zn anodes for practical aqueous Zn batteries.

Fine-Tuning Electrolyte Concentration and Metal-Organic Framework Surface toward Actuating Fast Zn2+ Dehydration for Aqueous Zn-Ion Batteries

Functional porous coating on zinc electrode is emerging as a powerful ionic sieve to suppress dendrite growth and side reactions, thereby improving highly reversible aqueous zinc ion batteries. However, the ultrafast charge rate is limited by the substantial cation transmission strongly associated with dehydration efficiency. Here, we unveil the entire dynamic process of solvated Zn2+ ions' continuous dehydration from electrolyte across the MOF-electrolyte interface into channels with the aid of molecular simulations, taking zeolitic imidazolate framework ZIF-7 as proof-of-concept. The moderate concentration of 2 M ZnSO4 electrolyte being advantageous over other concentrations possesses the homogeneous water-mediated ion pairing distribution, resulting in the lowest dehydration energy, which elucidates the molecular mechanism underlying such concentration adopted by numerous experimental studies. Furthermore, we show that modifying linkers on the ZIF-7 surface with hydrophilic groups such as -OH or -NH2 can weaken the solvation shell of Zn2+ ions to lower the dehydration free energy by approximately 1 eV, and may improve the electrical conductivity of MOF. These results shed light on the ions delivery mechanism and pave way to achieve long-term stable zinc anodes at high capacities through atomic-scale modification of functional porous materials.

Subnanocyclic Molecule of 15-Crown-5 Inhibiting Interfacial Water Decomposition and Stabilizing Zinc Anodes via Regulation of Zn2+ Solvation Shell

Aqueous zinc ion batteries exhibit a promising application prospect for next-generation energy storage devices. However, the decomposition of active H2O molecules on the Zn anode induces drastic dendrite formation, thereby impairing the performance for entire devices. To solve this challenge, we introduce subnanocyclic molecules of 15-Crown-5 as an additive into ZnSO4 electrolyte to stabilize the Zn anode. Owing to the binding property of crown ethers with alkali metal ions and the size-fit rule, the 15-Crown-5 additives enable effective regulation of the solvation structure of hydrated Zn2+ and reduce the efficient contact between Zn anode and active H2O, which are validated by the experimental analysis and theoretical calculations. Under the assistance of the 15-Crown-5 additive, the as-assembled Zn-based batteries deliver superior performance compared with ZnSO4 and 18-Crown-6contaning ZnSO4 electrolytes. This work shows a bright direction toward progress in aqueous batteries.

Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High-Performance Zinc Anode: Principles, Strategies, and Challenges

The last several years have witnessed the prosperous development of zinc-ion batteries (ZIBs), which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety. However, the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth, hydrogen evolution, and corrosion passivation on anode side. A functionally and structurally well-designed anode current collectors (CCs) is believed as a viable solution for those problems, with a lack of summarization according to its working mechanisms. Herein, this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs, which can be divided into zincophilic modification, structural design, and steering the preferred crystal facet orientation. The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

Progress and Prospect of Zn Anode Modification in Aqueous Zinc-Ion Batteries: Experimental and Theoretical Aspects

Aqueous zinc-ion batteries (AZIBs), the favorite of next-generation energy storage devices, are popular among researchers owing to their environmental friendliness, low cost, and safety. However, AZIBs still face problems of low cathode capacity, fast attenuation, slow ion migration rate, and irregular dendrite growth on anodes. In recent years, many researchers have focused on Zn anode modification to restrain dendrite growth. This review introduces the energy storage mechanism and current challenges of AZIBs, and then some modifying strategies for zinc anodes are elucidated from the perspectives of experiments and theoretical calculations. From the experimental point of view, the modification strategy is mainly to construct a dense artificial interface layer or porous framework on the anode surface, with some research teams directly using zinc alloys as anodes. On the other hand, theoretical research is mainly based on adsorption energy, differential charge density, and molecular dynamics. Finally, this paper summarizes the research progress on AZIBs and puts forward some prospects.