Achieving Highly Reversible Zinc Anodes via N, N-Dimethylacetamide Enabled Zn-Ion Solvation Regulation

Zinc Chemistries of Hybrid Electrolytes in Zinc Metal Batteries: From Solvent Structure to Interfaces

Along with the booming research on zinc metal batteries (ZMBs) in recent years, operational issues originated from inferior interfacial reversibility have become inevitable. Presently, single-component electrolytes represented by aqueous solution, "water-in-salt," solid, eutectic, ionic liquids, hydrogel, or organic solvent system are hard to undertake independently the task of guiding the practical application of ZMBs due to their specific limitations. The hybrid electrolytes modulate microscopic interaction mode between Zn2+ and other ions/molecules, integrating vantage of respective electrolyte systems. They even demonstrate original Zn2+ mobility pattern or interfacial chemistries mechanism distinct from single-component electrolytes, providing considerable opportunities for solving electromigration and interfacial problems in ZMBs. Therefore, it is urgent to comprehensively summarize the zinc chemistries principles, characteristics, and applications of various hybrid electrolytes employed in ZMBs. This review begins with elucidating the chemical bonding mode of Zn2+ and interfacial physicochemical theory, and then systematically elaborates the microscopic solvent structure, Zn2+ migration forms, physicochemical properties, and the zinc chemistries mechanisms at the anode/cathode interfaces in each type of hybrid electrolytes. Among of which, the scotoma and amelioration strategies for the current hybrid electrolytes are actively exposited, expecting to provide referenceable insights for further progress of future high-quality ZMBs.

N-methyl Formamide Electrolyte Additive Enabling Highly Reversible Zn Anodes

Parasitic side reactions and dendrites formation hinder the application of aqueous zinc ion batteries due to inferior cycling life and low reversibility. Against this background, N-methyl formamide (NMF), a multi-function electrolyte additive is applied to enhance the electrochemical performance. Studied via advanced synchrotron radiation spectroscopy and DFT calculations, the NMF additive simultaneously modifies the Zn2+ solvation structure and ensures uniform zinc deposition, thus suppressing both parasitic side reactions and dendrite formation. More importantly, an ultralong cycling life of 3115 h in the Zn||Zn symmetric cell at a current density of 0.5 mA cm-2 is achieved with the NMF additive. Practically, the Zn||PANI full cell utilizing NMF electrolyte shows better rate and cycling performance compared to the pristine ZnSO4 aqueous electrolyte. This work provides useful insights for the development of high-performance aqueous metal batteries.

Modulating solvated structure of Zn2+ and inducing surface crystallography by a simple organic molecule with abundant polar functional groups to synergistically stabilize zinc metal anodes for long-life aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their inherent security, low cost, abundant zinc (Zn) resources and high energy density. Nevertheless, the growth of zinc dendrites and side reactions on the surface of Zn anodes during repeatedly plating/stripping shorten the cycle life of AZIBs. Herein, a simple organic molecule with abundant polar functional groups, 2,2,2-trifluoroether formate (TF), has been proposed as a high-efficient additive in the ZnSO4 electrolyte to suppress the growth of Zn dendrites and side reaction during cycling. It is found that TF molecules can infiltrate the solvated sheath layer of the hydrated Zn2+ to reduce the number of highly chemically active H2O molecules owing to their strong binding energy with Zn2+. Simultaneously, TF molecules can preferentially adsorb onto the Zn surface, guiding the uniform deposition of Zn2+ along the crystalline surface of Zn(002). This dual action significantly inhibits the formation of Zn dendrites and side reactions, thus greatly extending the cycling life of the batteries. Accordingly, the Zn//Cu asymmetric cell with 2 % TF exhibits stable cycling for more than 3,800 cycles, achieving an excellent average Columbic efficiency (CE) of 99.81 % at 2 mA cm-2/1 mAh cm-2. Meanwhile, the Zn||Zn symmetric cell with 2 % TF demonstrates a superlong cycle life exceeding 3,800 h and 2,400 h at 2 mA cm-2/1 mAh cm-2 and 5 mA cm-2/2.5 mAh cm-2, respectively. Simultaneously, the Zn//VO2 full cell with 2 % TF possesses high initial capacity (276.8 mAh/g) and capacity retention (72.5 %) at 5 A/g after 500 cycles. This investigation provides new insights into stabilizing Zn metal anodes for AZIBs through the co-regulation of Zn2+ solvated structure and surface crystallography.

An Ion-Pumping Quasi-Solid Electrolyte Enabled by Electrokinetic Effects for Stable Aqueous Zinc Metal Batteries

The practical application of aqueous zinc (Zn) metal batteries (ZMBs) is hindered by the complicated hydrogen evolution, passivation reactions, and dendrite growth of Zn metal anodes. Here, an ion-pumping quasi-solid electrolyte (IPQSE) with high Zn2+ transport kinetics enabled by the electrokinetic phenomena to realize high-performance quasi-solid state Zn metal batteries (QSSZMBs) is reported. The IPQSE is prepared through the in situ ring-opening polymerization of tetramethylolmethane-tri-β-aziridinylpropionate in the aqueous electrolyte. The porous polymer framework with high zeta potential provides the IPQSE with an electrokinetic ion-pumping feature enabled by the electrokinetic effects (electro-osmosis and electrokinetic surface conduction), which significantly accelerates the Zn2+ transport, reduces the concentration polarization and overcomes the diffusion-limited current. Moreover, the Zn2+ affinity of the polymer and hydrogen bonding interactions in the IPQSE changes the Zn2+ coordination environment and reduces the amount of free H2O, which lowers the H2O activity and inhibits H2O-induced side reactions. Consequently, the highly reversible and stable Zn metal anodes are achieved. The assembled QSSZMBs based on the IPQSE display excellent cycling stability with high capacity retention and Coulombic efficiency. The high-performance quasi-solid state Zn metal pouch cells are demonstrated, showing great promise for the practical application of the IPQSE.

Quantifying Asymmetric Zinc Deposition: A Guide Factor for Designing Durable Zinc Anodes

Zinc metal is recognized as the most promising anode for aqueous energy storage but suffers from severe dendrite growth and poor reversibility. However, the coulombic efficiency lacks specificity for zinc dendrite growth, particularly in Zn||Zn symmetric cells. Herein, a novel indicator (fD) based on the characteristic crystallization peaks is proposed to evaluate the growth and distribution of zinc dendrites. As a proof of concept, triethylenetetramine (TETA) is adopted as an electrolyte additive to manipulate the zinc flux for uniform deposition, with a corroborating low fD value. A highly durable zinc symmetric cell is achieved, lasting over 2500 h at 10 mA cm-2 and 400 h at a large discharge of depth (10 mA cm-2, 10 mAh cm-2). Supported by the low fD value, the Zn||TETA-ZnSO4||MnO2 batteries overcome the sudden short circuit and fast capacity fading. The study provides a feasible method to evaluate zinc dendrites and sheds light on the design of highly reversible zinc anodes.

Carbonyl Chemistry for Advanced Electrochemical Energy Storage Systems

On the basis of the sustainable concept, organic compounds and carbon materials both mainly composed of light C element have been regarded as powerful candidates for advanced electrochemical energy storage (EES) systems, due to theie merits of low cost, eco-friendliness, renewability, and structural versatility. It is investigated that the carbonyl functionality as the most common constituent part serves a crucial role, which manifests respective different mechanisms in the various aspects of EES systems. Notably, a systematical review about the concept and progress for carbonyl chemistry is beneficial for ensuring in-depth comprehending of carbonyl functionality. Hence, a comprehensive review about carbonyl chemistry has been summarized based on state-of-the-art developments. Moreover, the working principles and fundamental properties of the carbonyl unit have been discussed, which has been generalized in three aspects, including redox activity, the interaction effect, and compensation characteristic. Meanwhile, the pivotal characterization technologies have also been illustrated for purposefully studying the related structure, redox mechanism, and electrochemical performance to profitably understand the carbonyl chemistry. Finally, the current challenges and promising directions are concluded, aiming to afford significant guidance for the optimal utilization of carbonyl moiety and propel practicality in EES systems.

In-Situ Ultrafast Construction of Zinc Tungstate Interface Layer for Highly Reversible Zinc Anodes

Constructing artificial solid electrolyte interface on the Zn anode surface is recognized as an appealing method to inhibit zinc dendrites and side reactions, whereas the current techniques are complex and time-consuming. Here, a robust and zincophilic zinc tungstate (ZnWO4) layer has been in situ constructed on the Zn anode surface (denoted as ZWO@Zn) by an ultrafast chemical solution reaction. Comprehensive characterizations and theoretical calculations demonstrate that the ZWO layer can effectively modulate the interfacial electric field distribution and promote the Zn2+ uniform diffusion, thus facilitating the uniform Zn2+ nucleation and suppressing zinc dendrites. Besides, ZWO layer can prevent direct contact between the Zn/water and increase the hydrogen evolution reaction overpotential to eliminate side reactions. Consequently, the in situ constructed ZWO layer facilitates remarkable reversibility in the ZWO@Zn||Ti battery, achieving an impressive Coulombic efficiency of 99.36 % under 1.0 mA cm-2, unprecedented cycling lifespan exceeding 1800 h under 1.0 mA cm-2 in ZWO@Zn||ZWO@Zn battery, and a steady and reliable operation of the overall ZWO@Zn||VS2 battery. The work provides a simple, low cost, and ultrafast pathway to crafting protective layers for driving advancements in aqueous zinc-metal batteries.

In Situ Spontaneous Construction of Zinc Phosphate Coating Layer Toward Highly Reversible Zinc Metal Anodes

Aqueous zinc ion batteries have received widespread attention due to their merits of high safety, high theoretical specific capacity, low cost, and environmental benignity. Nevertheless, the irreversible issues of Zn anode deriving from side reactions and dendrite growth have hindered its commercialization in large-scale energy storage systems. Herein, a zinc phosphate tetrahydrate (Zn3(PO4)2·4H2O, ZnPO) coating layer is in situ formed on the bare Zn by spontaneous redox reactions at room temperature to tackle the above issues. Particularly, the dense and brick-like ZnPO layer can effectively separate the anode surface from the aqueous electrolyte, thus suppressing the serious side reactions. Moreover, the ZnPO layer with high ionic conductivity, high Zn2+ transference number, and low nucleation barrier permits rapid Zn2+ transport and enables uniform Zn deposition, ensuring dendrite-free Zn deposition. As a result, the ZnPO@Zn symmetric battery achieves a high Coulombic efficiency of 99.8% and displays ultrahigh cycle stability over 6000 h (> 8 months), far surpassing its counterparts. Furthermore, the ZnPO@Zn||MnO2 full battery exhibits excellent electrochemical performances. Therefore, this work provides a new reference for simple and large-scale preparation of highly reversible Zn metal anodes, and has great potential for practical applications.

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.

Low-Cost Aqueous Electrolyte with MBA Additives for Uniform and Stable Zinc Deposition

Aqueous zinc ion batteries (AZIBs) are attracting increasing research interest due to their intrinsic safety, low cost, and scalability. However, the issues including hydrogen evolution, interface corrosion, and zinc dendrites at anodes have seriously limited the development of aqueous zinc ion batteries. Here, N,N-methylenebis(acrylamide) (MBA) additives with -CONH- groups are introduced to form hydrogen bonds with water and suppress H2O activity, inhibiting the occurrence of hydrogen evolution and corrosion reactions at the interface. In situ optical microscopy demonstrates that the MBA additive promotes the uniform deposition of Zn2+ and then suppresses the dendrite growth on the zinc anode. Therefore, Zn//Ti asymmetric batteries demonstrate a high plating/stripping efficiency of 99.5%, while Zn//Zn symmetric batteries display an excellent cycle stability for more than 1000 h. The Zn//MnO2 full cells exhibit remarkable cycling stability for 700 cycles in aqueous electrolytes with MBA additives. The additive engineering via MBA achieved the dendrite-free Zn anodes and stable full batteries, which is favorable for advanced AZIBs in practical applications.

Manipulating the Solvation Structure and Interface via a Bio-Based Green Additive for Highly Stable Zn Metal Anode

The practical application of aqueous zinc-ion batteries (AZIBs) is limited by serious side reactions, such as the hydrogen evolution reaction and Zn dendrite growth. Here, the study proposes a novel adoption of a biodegradable electrolyte additive, γ-Valerolactone (GVL), with only 1 vol.% addition (GVL-to-H2O volume ratio) to enable a stable Zn metal anode. The combination of experimental characterizations and theoretical calculations verifies that the green GVL additive can competitively engage the solvated structure of Zn2+ via replacing a H2O molecule from [Zn(H2O)6]2+, which can efficiently reduce the reactivity of water and inhibit the subsequent side reactions. Additionally, GVL molecules are preferentially adsorbed on the surface of Zn to regulate the uniform Zn deposition and suppress the Zn dendrite growth. Consequently, the Zn anode exhibits boosted stability with ultralong cycle lifespan (over 3500 h) and high reversibility with 99.69% Coulombic efficiency. The Zn||MnO2 full batteries with ZnSO4-GVL electrolyte show a high capacity of 219 mAh g-1 at 0.5 A g-1 and improved capacity retention of 78% after 550 cycles. This work provides inspiration on bio-based electrolyte additives for aqueous battery chemistry and promotes the practical application of AZIBs.

Rescuing zinc anode-electrolyte interface: mechanisms, theoretical simulations and in situ characterizations

The research interest in aqueous zinc-ion batteries (AZIBs) has been surging due to the advantages of safety, abundance, and high electrochemical performance. However, some technique issues, such as dendrites, hydrogen evolution reaction, and corrosion, severely prohibit the development of AZIBs in practical utilizations. The underlying mechanisms regarding electrochemical performance deterioration and structure degradation are too complex to understand, especially when it comes to zinc metal anode-electrolyte interface. Recently, theoretical simulations and in situ characterizations have played a crucial role in AZIBs and are exploited to guide the research on electrolyte engineering and solid electrolyte interphase. Herein, we present a comprehensive review of the current state of the fundamental mechanisms involved in the zinc plating/stripping process and underscore the importance of theoretical simulations and in situ characterizations in mechanism research. Finally, we summarize the challenges and opportunities for AZIBs in practical applications, especially as a stationary energy storage and conversion device in a smart grid.

A Holistic Additive Protocol Steers Dendrite-Free Zn(101) Orientational Electrodeposition

Orientation guidance has shown its cutting edges in electrodeposition modulation to promote Zn anode stability toward commercialized standards. Nevertheless, large-scale orientational deposition is handicapped by the competition between Zn-ion reduction and mass transfer. Herein, a holistic electrolyte additive protocol is put forward via incorporating bio-derived dextrin molecules into a zinc sulfate electrolyte bath. Electrochemical tests in combination with molecular dynamics simulations demonstrate the alleviation of concentration polarization throughout accelerating Zn2+ diffusion and retarding their reduction. The predominant (101) texture on inert current collectors (i.e., Cu, Ti, and stainless steel) and (101)/(002) textures on Zn foils afford homogeneous electrical field distribution, which is contributed by the work difference to form the 2D nucleus and the adsorption of dextrin molecules, respectively. Consequently, the symmetric cell harvests a longevous cycling lifespan of over 4000 h at 0.5 mA cm-2 /0.5 mAh cm-2 while the Zn@Cu electrode sustains for 240 h at a high depth of discharge of 40%.

Covalent Organic Framework with 3D Ordered Channel and Multi-Functional Groups Endows Zn Anode with Superior Stability

Achieving a highly robust zinc (Zn) metal anode is extremely important for improving the performance of aqueous Zn-ion batteries (AZIBs) for advancing "carbon neutrality" society, which is hampered by the uncontrollable growth of Zn dendrite and severe side reactions including hydrogen evolution reaction, corrosion, and passivation, etc. Herein, an interlayer containing fluorinated zincophilic covalent organic framework with sulfonic acid groups (COF-S-F) is developed on Zn metal (Zn@COF-S-F) as the artificial solid electrolyte interface (SEI). Sulfonic acid group (- SO3H) in COF-S-F can effectively ameliorate the desolvation process of hydrated Zn ions, and the three-dimensional channel with fluoride group (-F) can provide interconnected channels for the favorable transport of Zn ions with ion-confinement effects, endowing Zn@COF-S-F with dendrite-free morphology and suppressed side reactions. Consequently, Zn@COF-S-F symmetric cell can stably cycle for 1,000 h with low average hysteresis voltage (50.5 mV) at the current density of 1.5 mA cm-2. Zn@COF-S-F|MnO2 cell delivers the discharge specific capacity of 206.8 mAh g-1 at the current density of 1.2 A g-1 after 800 cycles with high-capacity retention (87.9%). Enlightening, building artificial SEI on metallic Zn surface with targeted design has been proved as the effective strategy to foster the practical application of high-performance AZIBs.

Key to High Performance Ion Hybrid Capacitor: Weakly Solvated Zinc Cations

Zinc ion hybrid capacitors suffer from lack of reversibility and dendrite formation. An electrolyte, based on a solution of a zinc salt in acetonitrile and tetramethylene sulfone, allows smooth zinc deposition with high coulombic efficiency in a Zn||stainless steel cell (99.6% for 2880 cycles at 1.0 mA cm-2 , 1.0 mAh cm-2 ). A Zn||Zn cell operates stably for at least 7940 h at 1.0 mA cm-2 with an area capacity of 10 mAh cm-2 , or 648 h at 90% depth of discharge and 1 mA cm-2 , 9.0 mAh cm-2 . Molecular dynamics simulations reveal the reason for the excellent reversibility: The zinc cation is only weakly solvated than in pure tetramethylene sulfone with the closest atoms at 3.3 to 3.8 Å. With this electrolyte, a zinc||activated-carbon hybrid capacitor exhibits an operating voltage of 2.0 to 2.5 V, an energy-density of 135 Wh kg-1 and a power-density of 613 W kg-1 at 0.5 A g-1 . At the very high current-density of 15 A g-1 , 29.3 Wh kg-1 and 14 250 W kg-1 are achieved with 81.2% capacity retention over 9000 cycles.

Recent progress of MOF-functionalized nanocomposites: From structure to properties

Metal-organic frameworks (MOFs) are novel crystalline porous materials assembled from metal ions and organic ligands. The adaptability of their design and the fine-tuning of the pore structures make them stand out in porous materials. Furthermore, by integrating MOF guest functional materials with other hosts, the novel composites have synergistic benefits in numerous fields such as batteries, supercapacitors, catalysis, gas storage and separation, sensors, and drug delivery. This article starts by examining the structural relationship between the host and guest materials, providing a comprehensive overview of the research advancements in various types of MOF-functionalized composites reported to date. The review focuses specifically on four types of spatial structures, including MOFs being (1) embedded in nanopores, (2) immobilized on surface, (3) coated as shells and (4) assembled into hybrids. In addition, specific design ideas for these four MOF-based composites are presented. Some of them involve in situ synthesis method, solvothermal method, etc. The specific properties and applications of these materials are also mentioned. Finally, a brief summary of the advantages of these four types of MOF composites is given. Hopefully, this article will help researchers in the design of MOF composite structures.

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.

Boosting Zn Anode Utilization by Trace Iodine Ions in Organic-Water Hybrid Electrolytes through Formation of Anion-rich Adsorbing Layers

Aqueous Zn batteries are attracting extensive attentions, but their application is still hindered by H2 O-induced Zn-corrosion and hydrogen evolution reactions. Addition of organic solvents into aqueous electrolytes to limit the H2 O activity is a promising solution, but at the cost of greatly reduced Zn anode kinetics. Here we propose a simple strategy for this challenge by adding 50 mM iodine ions into an organic-water (1,2-dimethoxyethane (DME)+water) hybrid electrolyte, which enables the electrolyte simultaneously owns the advantages of low H2 O activity and accelerated Zn kinetics. We demonstrate that the DME breaks the H2 O hydrogen-bond network and exclude H2 O from Zn2+ solvation shell. And the I- is firmly adsorbed on the Zn anode, reducing the Zn2+ de-solvation barrier from 74.33 kJ mol-1 to 32.26 kJ mol-1 and inducing homogeneous nucleation behavior. With such electrolyte, the Zn//Zn symmetric cell exhibits a record high cycling lifetime (14.5 months) and achieves high Zn anode utilization (75.5 %). In particular, the Zn//VS2 @SS full cell with the optimized electrolyte stably cycles for 170 cycles at a low N : P ratio (3.64). Even with the cathode mass-loading of 16.7 mg cm-2 , the full cell maintains the areal capacity of 0.96 mAh cm-2 after 1600 cycles.

A Liquid Metal Microdroplets Initialized Hemicellulose Composite for 3D Printing Anode Host in Zn-Ion Battery

Maintaining a steady affinity between gallium-based liquid metals (LM) and polymer binders, particularly under continuous mechanical deformation, such as extrusion-based 3D printing or plating/stripping of Zinc ion (Zn²⁺ ), is very challenging. Here, an LM-initialized polyacrylamide-hemicellulose/EGaIn microdroplets hydrogel is used as a multifunctional ink to 3D-print self-standing scaffolds and anode hosts for Zn-ion batteries. The LM microdroplets initiate acrylamide polymerization without additional initiators and cross-linkers, forming a double-covalent hydrogen-bonded network. The hydrogel acts as a framework for stress dissipation, enabling recovery from structural damage due to the cyclic plating/stripping of Zn²⁺ . The LM-microdroplet-initialized polymerization with hemicelluloses can facilitate the production of 3D printable inks for energy storage devices.

Achieving Ultralong-Cycle Zinc-Ion Battery via Synergistically Electronic and Structural Regulation of a MnO2 Nanocrystal-Carbon Hybrid Framework

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted burgeoning interests owing to the prospect in large-scale and safe energy storage application. Although manganese oxides are one of the typical cathodes of ZIBs, their practical usage is still hindered by poor service life and rate performance. Here, a MnO₂ -carbon hybrid framework is reported, which is obtained in a reaction between the dimethylimidazole ligand from a rational designed MOF array and potassium permanganate, achieving ultralong-cycle-life ZIBs. The unique structural feature of uniform MnO₂ nanocrystals which are well-distributed in the carbon matrix leads to a 90.4% capacity retention after 50 000 cycles. In situ characterization and theoretical calculations verify the co-ions intercalation with boosted reaction kinetics. The hybridization between MnO₂ and carbon endows the hybrid with enhanced electrons/ions transport kinetics and robust structural stability. This work provides a facile strategy to enhance the battery performance of manganese oxide-based ZIBs.

Triple-Function Electrolyte Regulation toward Advanced Aqueous Zn-Ion Batteries

The poor Zn reversibility has been criticized for limiting applications of aqueous Zn-ion batteries (ZIBs); however, its behavior in aqueous media is not fully uncovered yet. Here, this knowledge gap is addressed, indicating that Zn electrodes face a O₂ -involving corrosion, besides H₂ evolution and dendrite growth. Differing from aqueous Li/Na batteries, removing O₂ cannot enhance ZIB performance because of the aggravated competing H₂ evolution. To address Zn issues, a one-off electrolyte strategy is reported by introducing the triple-function C₃ H₇ Na₂ O₆ P, which can take effects during the shelf time of battery. It regulates H⁺ concentration and reduces free-water activity, inhibiting H₂ evolution. A self-healing solid/electrolyte interphase (SEI) can be triggered before battery operation, which suppresses O₂ adsorption corrosion and dendritic deposition. Consequently, a high Zn reversibility of 99.6% is achieved under a high discharge depth of 85%. The pouch full-cell with a lean electrolyte displays a record lifespan with capacity retention of 95.5% after 500 cycles. This study not only looks deeply into Zn behavior in aqueous media but also underscores rules for the design of active metal anodes, including Zn and Li metals, during shelf time toward real applications.

Artificial Interphase Layer for Stabilized Zn Anodes: Progress and Prospects

The burgeoning Li-ion battery is regarded as a powerful energy storage system by virtue of its high energy density. However, inescapable issues concerning safety and cost aspects retard its prospect in certain application scenarios. Accordingly, strenuous efforts have been devoted to the development of the emerging aqueous Zn-ion battery (AZIB) as an alternative to inflammable organic batteries. In particular, the instability from the anode side severely impedes the commercialization of AZIB. Constructing an artificial interphase layer (AIL) has been widely employed as an effective strategy to stabilize the Zn anode. This review specializes in the state-of-the-art of AIL design for Zn anode protection, encompassing the preparation methods, mechanism investigations, and device performances based on the classification of functional materials. To begin with, the origins of Zn instability are interpreted from the perspective of electrical field, mass transfer, and nucleation process, followed by a comprehensive summary with respect to functions of AIL and its designing criteria. In the end, current challenges and future outlooks based upon theoretical and experimental considerations are included.

Promoting Reversible Dissolution/Deposition of MnO2 for High-Energy-Density Zinc Batteries via Enhancing Cut-Off Voltage

Zn//MnO₂ batteries based on the MnO₂ /Mn²⁺ conversion reaction mechanism featuring high energy density, safety, and affordable cost are promising in large-scale energy storage application. Nonetheless, the continuous H⁺ intercalation at low potential reduces the average output voltage and the energy efficiency, impeding the development of the high-performance zinc battery. In this work, a strategy was proposed of enhancing the cut-off voltage from the perspective of electrochemical parameters, toward high energy efficiency and stable output voltage of the Zn//MnO₂ battery. This strategy was beneficial to promoting MnO₂ dissolution/deposition through the increase of acidity caused by the constant accumulation of MnO₂ and inhibiting H⁺ (de)intercalation during cycling process, thereby improving the energy efficiency (83.5 %) along with the stable average output voltage (1.88 V) under the cut-off voltage of 1.8 V. This work provides a new pathway to promote aqueous zinc batteries with high energy density and stable output voltage.

Multiscale modulation of vanadium oxides via one-step facile reduction to synergistically boost zinc-ion battery performance

Accordion-like V10O24·12H2O was prepared via one-step reduction of commercial V2O5. Benefiting from the interlayer spacing, mixed valence, and superstructure, a superior performance was obtained for V10O24·12H2O as compared to that of V2O5.