Stabilizing Zinc Electrodeposition in a Battery Anode by Controlling Crystal Growth

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.

Dual-functional ionic liquids additive enables dendrite-free Zn anode with ultra-long cycle life over one year

Zn anodes suffer from the formation of uncontrolled dendrites aggravated by the uneven electric field and the insulating by-product accumulation in aqueous zinc-ion batteries (AZIBs). Here, an effective strategy implemented by 1-butyl-3-methylimidazolium hydrogen sulfate (BMIHSO4) additive is proposed to synergistically tune the crystallographic orientation of zinc deposition and suppress the formation of zinc hydroxide sulfate for enhancing the reversibility on Zn anode surface. As a competing cation, BMI+ is proved to preferably adsorb on Zn-electrode compared with H2O molecules, which shields the "tip effect" and inhibits the Zn-deposition agglomerations to inducing the horizontal growth along Zn (002) crystallographic texture. Simultaneously, the protonated BMIHSO4 additives could remove the detrimental OH- in real-time to fundamentally eliminate the accumulation of 6Zn(OH)2·ZnSO4·4H2O and Zn4SO4(OH)6·H2O on Zn anode surface. Consequently, Zn anode exhibits an ultra-long cycling stability of one year (8762 h) at 0.2 mA cm-2/0.2 mAh cm-2, 3600 h at 2 mA cm-2/2 mAh cm-2 with a high plating cumulative capacity of 3.6 Ah cm-2, and a high average Coulombic efficiency of 99.6 % throughout 1000 cycles. This work of regulating Zn deposition texture combined with eliminating notorious by-products could offer a desirable way for stabilizing the Zn-anode/electrolyte interface in AZIBs.

Design Strategies toward High-Performance Zn Metal Anode

Rechargeable aqueous Zn-ion batteries (AZIBs) are one of the most promising alternatives for traditional energy-storage devices because of their low cost, abundant resources, environmental friendliness, and inherent safety. However, several detrimental issues with Zn metal anodes including Zn dendrite formation, hydrogen evolution, corrosion and passivation, should be considered when designing advanced AZIBs. Moreover, these thorny issues are not independent but mutually reinforcing, covering many technical and processing parameters. Therefore, it is necessary to comprehensively summarize the issues facing Zn anodes and the corresponding strategies to develop roadmaps for the development of high-performance Zn anodes. Herein, the failure mechanisms of Zn anodes and their corresponding impacts are outlined. Recent progress on improving the stability of Zn anode is summarized, including structurally designed Zn anodes, Zn alloy anodes, surface modification, electrolyte optimization, and separator design. Finally, this review provides brilliant and insightful perspectives for stable Zn metal anodes and promotes the large-scale application of AZIBs in power grid systems.

Electrolyte and Additive Engineering for Zn Anode Interfacial Regulation in Aqueous Zinc Batteries

Aqueous Zn-metal batteries (AZMBs) have gained great interest due to their low cost, eco-friendliness, and inherent safety, which serve as a promising complement to the existing metal-based batteries, e.g., lithium-metal batteries and sodium-metal batteries. Although the utilization of aqueous electrolytes and Zn metal anode in AZMBs ensures their improved safety over other metal batteries meanwhile guaranteeing their decent energy density at the cell level, plenty of challenges involved with metallic Zn anode still await to be addressed, including dendrite growth, hydrogen evolution reaction, and zinc corrosion and passivation. In the past years, several attempts have been adopted to address these problems, among which engineering the aqueous electrolytes and additives is regarded as a facile and promising approach. In this review, a comprehensive summary of aqueous electrolytes and electrolyte additives will be given based on the recent literature, aiming at providing a fundamental understanding of the challenges associated with the metallic Zn anode in aqueous electrolytes, meanwhile offering a guideline for the electrolytes and additives engineering strategies toward stable AZMBs in the future.

Advancements in aqueous zinc-iodine batteries: a review

Aqueous zinc-iodine batteries stand out as highly promising energy storage systems owing to the abundance of resources and non-combustible nature of water coupled with their high theoretical capacity. Nevertheless, the development of aqueous zinc-iodine batteries has been impeded by persistent challenges associated with iodine cathodes and Zn anodes. Key obstacles include the shuttle effect of polyiodine and the sluggish kinetics of cathodes, dendrite formation, the hydrogen evolution reaction (HER), and the corrosion and passivation of anodes. Numerous strategies aimed at addressing these issues have been developed, including compositing with carbon materials, using additives, and surface modification. This review provides a recent update on various strategies and perspectives for the development of aqueous zinc-iodine batteries, with a particular emphasis on the regulation of I2 cathodes and Zn anodes, electrolyte formulation, and separator modification. Expanding upon current achievements, future initiatives for the development of aqueous zinc-iodine batteries are proposed, with the aim of advancing their commercial viability.

Separator Design Strategies to Advance Rechargeable Aqueous Zinc Ion Batteries

With the increasing demand for low-cost and high-safety portable batteries, aqueous zinc-ion batteries (ZIBs) have been regarded as a potential alternative to the lithium-ion batteries, bringing about extensive research dedicated in the exploration of high-performance and highly reversible ZIBs. Although separators are generally considered as non-active components in conventional research on ZIBs, advanced separators designs seem to offer effective solutions to the majority of issues within ZIBs system. These issues encompass concerns related to the zinc anode, cathode, and electrolyte. Initially, we delve into the origins and implications of various inherent problems within the ZIBs system. Subsequently, we present the latest research advancements in addressing these challenges through separators engineering. This includes a comprehensive, detailed exploration of various strategies, coupled with instances of advanced characterizations to provide a more profound insight into the mechanisms that influence the separators. Finally, we undertake a multi-criteria evaluation, based on application standards for diverse substrate separators, while proposing guiding principles for the optimal design of separators in zinc batteries. This review aims to furnish valuable guidance for the future development of advanced separators, thereby nurturing progress in the field of ZIBs.

Mediating Triple Ions Migration Behavior via a Fluorinated Separator Interface toward Highly Reversible Aqueous Zn Batteries

Rampant dendrite growth, electrode passivation and severe corrosion originate from the uncontrolled ions migration behavior of Zn2+ , SO4 2- , and H+ , which are largely compromising the aqueous zinc ion batteries (AZIBs) performance. Exploring the ultimate strategy to eliminate all the Zn anode issues is challenging but urgent at present. Herein, a fluorinated separator interface (PVDF@GF) is constructed simply by grafting the polyvinylidene difluoride (PVDF) on the GF surface to realize high-performance AZIBs. Experimental and theoretical studies reveal that the strong interaction between C─F bonds in the PVDF and Zn2+ ions enables evenly redistributed Zn2+ ions concentration at the electrode interface and accelerates the Zn transportation kinetics, leading to homogeneous and fast Zn deposition. Furthermore, the electronegative separator interface can spontaneously repel the SO4 2- and anchor H+ ions to alleviate the passivation and corrosion. Accordingly, the Zn|Zn symmetric cell with PVDF@GF harvests a superior cycling stability of 500 h at 10 mAh cm-2 , and the Zn|VOX full cell delivers 76.8% capacity retention after 1000 cycles at 2 A g-1 . This work offers an all-round solution and provides new insights for the design of advanced separators with ionic sieve function toward stable and reversible Zn metal anode chemistry.

Critical triple roles of sodium iodide in tailoring the solventized structure, anode-electrolyte interface and crystal plane growth to achieve highly reversible zinc anodes for aqueous zinc-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) are promising for energy storage. However, the Zn dendrite and corrosive reactions on the surface of Zn anode limit the practical uses of ARZIBs. Herein, we present a valid electrolyte additive of NaI, in which I- can modulate the morphology of Zn crystal growth by adsorbing on specific crystal surfaces (002), and guide Zn deposition by inducing a negative charge on the Zn anode. Simultaneously, it enhances the reduction stability of water molecules by participating in the solvation structure of Zn(H2O)62+ by forming ZnI(H2O)5+. At 10 mA cm-2, the assembled Zn symmetrical batteries can run stably over 1,100 h, and the depth of discharge (DOD) can reach 51.3 %. At 1 A g-1, the VO2||Zn full-cell in 2 M ZnCl2 electrolyte with 0.4 M NaI (2 M ZnCl2-0.4 M NaI) maintains of the capacity retention of 75.7 % over 300 cycles. This work offers an insight into inorganic anions as electrolyte additives for achieving stable zinc anodes of ARZIBs.

Nonepitaxial Electrodeposition of (002)-Textured Zn Anode on Textureless Substrates for Dendrite-Free and Hydrogen Evolution-Suppressed Zn Batteries

Nontoxic and safe aqueous Zn batteries are largely restricted by the detrimental dendrite growth and hydrogen evolution of Zn metal anode. The (002)-textured Zn electrodeposition, demonstrated as an effective approach for solving these issues, is nevertheless achieved mainly by epitaxial or hetero-epitaxial deposition of Zn on pre-textured substrates. Herein, the electrodeposition of (002)-textured and compact Zn on textureless substrates (commercial Zn, Cu, and Ti foils) at a medium-high galvanostatic current density is reported. According to the systematic investigations on Zn nucleation and growth behaviors, this is ascribed to two reasons: i) the promoted nonepitaxial nucleation of fine horizontal (002) nuclei at increased overpotential and ii) the competitive growth advantages of (002)-orientated nuclei. The resulting freestanding (002)-textured Zn film exhibits significantly suppressed hydrogen evolution and prolonged Zn plating-stripping cycling life, achieving over 2100 mAh cm^-2 cumulative capacity under a current density of 10 mA cm^-2 and a high depth of discharge (DOD) of 45.5%. Therefore, this study provides both fundamental and practical insights into long-life Zn metal batteries.

Low-Concentration Redox-Electrolytes for High-Rate and Long-Life Zinc Metal Batteries

The uncontrolled zinc electrodeposition and side reactions severely limit the power density and lifespan of Zn metal batteries. Herein, the multi-level interface adjustment effect is realized with low-concentration redox-electrolytes (0.2 m KI) additives. The iodide ions adsorbed on the zinc surface significantly suppress water-induced side reactions and by-product formation and enhance the kinetics of zinc deposition. The distribution of relaxation times results reveal that iodide ions can reduce the desolvation energy of hydrated zinc ions and guide the deposition of zinc ions due to their strong nucleophilicity. As a consequence, the Zn||Zn symmetric cell achieves superior cycling stability (>3000 h at 1 mA cm^-2 , 1 mAh cm^-2 ) accompanied by a uniform deposition and a fast reaction kinetics with a low voltage hysteresis (<30 mV). Additionally, coupled with an activated carbon (AC) cathode, the assembled Zn||AC cell delivers a high-capacity retention of 81.64% after 2000 cycles at 4 A g^-1 . More importantly, the operando electrochemical UV-vis spectroscopies show that a small number of I₃ ^- can spontaneously react with the dead zinc as well as basic zinc saltsand regenerate iodide ions and zinc ions; thus, the Coulombic efficiency of each charge-discharge process is close to 100%.

Multifunctional Electrolyte Additive Enables Highly Reversible Anodes and Enhanced Stable Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are charming devices for large-scale power grid energy storage because of their characteristics of environment friendliness, low cost, high abundance, and safe operation. However, the inferior reversibility of the anode and the loss of cathode capacity always hinder the application of AZIBs. Herein, we propose a simple multifunctional electrolyte additive, diethylenetriamine (DETA), which can inhibit the formation of zinc dendrites and the occurrence of side reactions on the anode, reconstruct the solvated structure and uniform ion flux in the electrolyte, restrain the dissolution of active materials, and induce the crystal transformation on the cathode concurrently. Molecular dynamics Simulation and density functional theory both verified the extraordinary efficacy of DETA. With the assistance of DETA, the Zn anode gained a life of up to 2000 h, and the cathode with commercial V₂O₅ retained a capacity of 125.2 mA h g^-1 at the 1000th discharge process. From the perspective of practical application, this work can open up the application prospect of AZIBs in large-scale energy storage and provide reference for the subsequent works. The findings will greatly promote the application of AZIBs in large-scale energy storage and provide more inspiration for future research.

Recent Progress in High-voltage Aqueous Zinc-based Hybrid Redox Flow Batteries

The energy density of redox flow batteries (RFBs) is generally affected by the standard electrode potential and the solubility of the redox active species. These crucial factors are closely related to the solvent in which the active materials are dissolved. Aqueous RFBs have been widely studied due to their excellent reaction kinetics and high solubility of the redox couple in aqueous media. However, the low voltage of conventional aqueous RFBs has hindered them from being candidates for practical applications. Recently, high-voltage aqueous RFBs are implemented based on the low negative potential of the Zn/[Zn(OH)₄ ]^2- reaction in an alkaline solution. Here, we review recent progress in the design of high energy density RFBs in both aqueous and non-aqueous electrolytes, notably focusing on the Zn/MnO₂ hybrid RFBs in detail. Furthermore, strategies for inhibiting zinc dendritic growth and stabilizing manganese redox couple in the RFBs system are discussed.

Designing interphases for practical aqueous zinc flow batteries with high power density and high areal capacity

Aqueous zinc flow batteries (AZFBs) with high power density and high areal capacity are attractive, both in terms of cost and safety. A number of fundamental challenges associated with out-of-plane growth and undesirable side reactions on the anode side, as well as sluggish reaction kinetics and active material loss on the cathode side, limit practical deployment of these batteries. We investigated artificial interphases created using a simple electrospray methodology as a strategy for addressing each of these challenges. The effectiveness of the electrospray interphases in full cell zinc-iodine flow batteries was evaluated and reported; it is possible to simultaneously achieve high power density [115 milliwatts per square centimeter (mW/cm²)] and high areal capacity [25 milliampere hour per square centimeter (mA·hour/cm²)]. Last, we extended it to aqueous zinc-bromine and zinc-vanadium flow batteries of contemporary interest. It is again found that high power density (255 and 260 mW/cm², respectively) and high areal capacity (20 mA·hour/cm²) can be simultaneously achieved in AZFBs.

Biochar-seeded struvite precipitation for simultaneous nutrient recovery and chemical oxygen demand removal in leachate: From laboratory to pilot scale

Refuse transfer station (RTS) leachate treatment call for efficient methods to increase nutrient recovery (NH4+−N and PO43−−P) and chemical oxygen demand (COD) removal. In this study, the effects of various operational factors (seeding dose, pH, initial NH4+-N concentration, and reaction time) on biochar-seeded struvite precipitation were investigated at laboratory and pilot scales. Mealworm frass biochar (MFB) and corn stover biochar (CSB) were used as seeding materials to compare with traditional seed struvite. The maximum NH4+−N and PO43−−P recover efficiency of the MFB-seeded process reached 85.4 and 97.5%, higher than non-seeded (78.5 and 88.0%) and CSB-seeded (80.5 and 92.0%) processes and close to the struvite-seeded (84.5 and 95.1%) process. The MFB-seeded process also exhibited higher COD removal capacity (46.4%) compared to CSB-seeded (35.9%) and struvite-seeded (31.2%) processes and increased the average particle size of the struvite product from 33.7 to 70.2 μm for better sustained release. XRD, FT-IR, and SEM confirmed the orthorhombic crystal structure with organic matter attached to the struvite product. A pilot-scale test was further carried out in a custom-designed stirred tank reactor (20 L). In the pilot-scale test, the MFB-seeded process still spectacularly recovered 77.9% of NH4+−N and 96.1% of PO43−−P with 42.1% COD removal, which was slightly lower than the laboratory test due to insufficient and uniform agitation. On the whole, MFB-seeded struvite precipitation is considered to be a promising pretreatment method for rural RTS leachate.

Achieving Ultrahigh-Rate Planar and Dendrite-Free Zinc Electroplating for Aqueous Zinc Battery Anodes

Despite being one of the most promising candidates for grid-level energy storage, practical aqueous zinc batteries are limited by dendrite formation, which leads to significantly compromised safety and cycling performance. In this study, by using single-crystal Zn-metal anodes, reversible electrodeposition of planar Zn with a high capacity of 8 mAh cm^-2 can be achieved at an unprecedentedly high current density of 200 mA cm^-2 . This dendrite-free electrode is well maintained even after prolonged cycling (>1200 cycles at 50 mA cm^{- 2} ). Such excellent electrochemical performance is due to single-crystal Zn suppressing the major sources of defect generation during electroplating and heavily favoring planar deposition morphologies. As so few defect sites form, including those that would normally be found along grain boundaries or to accommodate lattice mismatch, there is little opportunity for dendritic structures to nucleate, even under extreme plating rates. This scarcity of defects is in part due to perfect atomic-stitching between merging Zn islands, ensuring no defective shallow-angle grain boundaries are formed and thus removing a significant source of non-planar Zn nucleation. It is demonstrated that an ideal high-rate Zn anode should offer perfect lattice matching as this facilitates planar epitaxial Zn growth and minimizes the formation of any defective regions.

Lanthanum nitrate as aqueous electrolyte additive for favourable zinc metal electrodeposition

Aqueous zinc batteries are appealing devices for cost-effective and environmentally sustainable energy storage. However, the zinc metal deposition at the anode strongly influences the battery cycle life and performance. To circumvent this issue, here we propose the use of lanthanum nitrate (La(NO3)3) as supporting salt for aqueous zinc sulfate (ZnSO4) electrolyte solutions. Via physicochemical and electrochemical characterizations, we demonstrate that this peculiar electrolyte formulation weakens the electric double layer repulsive force, thus, favouring dense metallic zinc deposits and regulating the charge distribution at the zinc metal|electrolyte interface. When tested in Zn||VS2 full coin cell configuration (with cathode mass loading of 16 mg cm-2), the electrolyte solution containing the lanthanum ions enables almost 1000 cycles at 1 A g-1 (after 5 activation cycles at 0.05 A g-1) with a stable discharge capacity of about 90 mAh g-1 and an average cell discharge voltage of ∼0.54 V.

Recent Advances of Aqueous Rechargeable Zinc-Iodine Batteries: Challenges, Solutions, and Prospects

Aqueous rechargeable zinc-iodine batteries (ZIBs), including zinc-iodine redox flow batteries and static ZIBs, are promising candidates for future grid-scale electrochemical energy storage. They are safe with great theoretical capacity, high energy, and power density. Nevertheless, to make aqueous rechargeable ZIBs practically feasible, there are quite a few hurdles that need to be overcome, including self-discharge, sluggish kinetics, low energy density, and instability of Zn metal anodes. This article first reviews the electrochemistry in aqueous rechargeable ZIBs, including the flow and static battery configurations and their electrode reactions. Then the authors discuss the fundamental questions of ZIBs and highlight the key strategies and recent accomplishments in tackling the challenges. Last, they share their thoughts on the future research development in aqueous rechargeable ZIBs.

Production of fast-charge Zn-based aqueous batteries via interfacial adsorption of ion-oligomer complexes

Aqueous zinc batteries are attracting interest because of their potential for cost-effective and safe electricity storage. However, metallic zinc exhibits only moderate reversibility in aqueous electrolytes. To circumvent this issue, we study aqueous Zn batteries able to form nanometric interphases at the Zn metal/liquid electrolyte interface, composed of an ion-oligomer complex. In Zn||Zn symmetric cell studies, we report highly reversible cycling at high current densities and capacities (e.g., 160 mA cm⁻²; 2.6 mAh cm⁻²). By means of quartz-crystal microbalance, nuclear magnetic resonance, and voltammetry measurements we show that the interphase film exists in a dynamic equilibrium with oligomers dissolved in the electrolyte. The interphase strategy is applied to aqueous Zn||I₂ and Zn||MnO₂ cells that are charged/discharged for 12,000 cycles and 1000 cycles, respectively, at a current density of 160 mA cm⁻² and capacity of approximately 0.85 mAh cm⁻². Finally, we demonstrate that Zn||I₂-carbon pouch cells (9 cm² area) cycle stably and deliver a specific energy of 151 Wh/kg (based on the total mass of active materials in the electrode) at a charge current density of 56 mA cm⁻².

Aqueous zinc batteries attract interest because of their potential for cost-effective and safe electricity storage. Here, the authors develop an in situ formed ion-oligomer nanometric interphase strategy to enable fast-charge aqueous Zn cells.

Gel Electrolyte Constructing Zn (002) Deposition Crystal Plane Toward Highly Stable Zn Anode

Zinc (Zn) metal anode has been widely evaluated in aqueous Zn batteries. Nevertheless, the dendrite formation issue and consecutive side reactions severely impede the practical applications of Zn metal at high current densities. Herein, it is reported that engineering the gel electrolyte with multifunctional charged groups by incorporating a zwitterionic gel poly(3-(1-vinyl-3-imidazolio) propanesulfonate) (PVIPS) can effectively address the abovementioned issues. The charged groups of sulfonate and imidazole in the gel electrolyte can texture the Zn2+ nucleation and deposition plane to (002), which possesses a high activation energy to resist side reactions and induce uniform growth of Zn metal for a dendrite-free structure. In addition, the Zn2+ solvation structure can be manipulated by the charged groups to further eliminate side reactions for high rate performance Zn batteries. Consequently, the polyzwitterionic gel electrolyte enables a stable cycling with a cumulative capacity of 3000 mA h cm-2 at high density of 7.5 mA cm-2 for the symmetrical Zn battery, and a long-term cycling life for more than 1000 cycles at 5 C of Zn/MnO2 full battery. It is envisioned that the design of the gel electrolyte will provide promising feasibility on safe, flexible, and wearable energy storage devices.

Highly reversible aqueous zinc-ion battery using the chelating agent triethanolamine as an electrolyte additive

The chelating agent triethanolamine (TEA) is introduced as an additive in the electrolyte to enhance the cycling stability of aqueous zinc-ion batteries.

Textured Electrodes: Manipulating Built-In Crystallographic Heterogeneity of Metal Electrodes via Severe Plastic Deformation

Control of crystallography of metal electrodeposit films has recently emerged as a key to achieving long operating lifetimes in next-generation batteries. It is reported that the large crystallographic heterogeneity, e.g., broad orientational distribution, that appears characteristic of commercial metal foils, results in rough morphology upon plating/stripping. On this basis, an accumulative roll bonding (ARB) methodology-a severe plastic deformation process-is developed. Zn metal is used as a first example to interrogate the concept. It is demonstrated that the ARB process is highly effective in achieving uniform crystallographic control on macroscopic materials. After the ARB process, the Zn grains exhibit a strong (002) texture (i.e., [002]_Zn //ND). The texture transitions from a classical bipolar pattern to a nonclassical unipolar pattern under large nominal strain eliminate the orientational heterogeneity of the foil. The strongly (002)-textured Zn remarkably improves the plating/stripping performance by nearly two orders of magnitude under practical conditions. The performance improvements are readily scaled to achieve pouch-type full batteries that deliver exceptional reversibility. The ARB process can, in principle, be applied to any metal chemistry to achieve similar crystallographic uniformity, provided the appropriate temperature and accumulated strains are employed. This concept is evaluated using commercial Li and Na foils, which, unlike Zn (HCP), are BCC crystals. The simple process for creating strong textures in both hexagonal and cubic metals and illustrating the critical role such built-in crystallography plays underscores opportunities for developing highly reversible thin metal anodes (e.g., hexagonal Zn, Mg, and cubic Li, Na, Ca, Al).