Rationalized Electroepitaxy toward Scalable Single-Crystal Zn Anodes

A solid solution alloy current collector to stabilize zinc metal anodes

Dendrite growth limits the performance of aqueous zinc-metal batteries. Here, we present a Cu-In solid solution alloy current collector, where indium enhances zinc affinity and lowers nucleation overpotential, enabling dendrite-free zinc deposition. The Zn@Cu-In anode demonstrates stable cycling at high current densities.

Low Strain Mediated Zn (0002) Plane Epitaxial Plating for Highly Stable Zinc Metal Batteries

Optimizing the crystalline orientation to achieve stable Zn (0002) plane growth is pursued for highly reversible zinc metal batteries (ZMBs). However, the lattice strain of Zn substrate hinders stable Zn2+ plating/stripping and sustainable epitaxial growth of Zn (0002) texture. Herein, we present a low-strain strategy to mediate nucleated-Zn grains for stabilizing Zn2+ electrodeposition/stripping process and guiding sustainable Zn2+ growth along (0002) surfaces. Fluorinated anthracene triptycene polymer (FATP) photopolymerized on Zn exhibits nanocrystalline structure with highly ordered nanochannels (1.5 nm), enabling oriented nucleation and sustainable epitaxial stacking of Zn (0002) plane due to low nucleation energy (0.2 vs. 1.1 e- Å-3 of pure Zn) and low grain strain (-0.2 to 0.4 vs. -0.9 to 0.9 MPa). Besides, the ordered porous FATP nanofilm refines electroplating Zn grains (9.4 vs. 26.7 µm), alleviating strain accumulation (3.7 vs. 28.2 MPa) and lattice distortion. Consequently, FATP-Zn||Cu cell achieves a high average Coulombic efficiency of 99.6% over 6000 cycles, while FATP-Zn||FATP-Zn cell shows stable plating/stripping after 5000 h. Notably, FATP-Zn||MnO2 pouch cell (2.77 Ah) demonstrates stable operation over 1000 cycles. This work presents a new approach to designing Zn anodes with refined nucleated-Zn grains and sustainable Zn (0002) plane stacking for advanced ZMBs.

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.

Multifunctional Polymer Interphase with Fast Kinetics for Ultrahigh-rate Zn Metal Anode

Polymer interphase on Zn anodes obviates dendrite growth and significant side reactions including corrosion and hydrogen evolution in aqueous zinc ion batteries (AZIBs), however has drawbacks of slow kinetics and large overpotential for Zn plating/stripping that prevent practical application especially under high-rate conditions. Here, a multifunctional polymer interphase with fast kineticsis reported, using poly(phenazine-alt-pyromellitic anhydride) (PPPA) as an electrolyte additive. PPPA, with linear π-conjugated structure and enriched polar pyridine (conjugated cyclic -C=N-) and carbonyl (C=O) groups, preferentially adsorbs on the Zn anode to form a stable solid-electrolyte interphase (SEI) layer in situ. The PPPA SEI is efficient to block direct contact between water molecules and Zn anode, and regulate the interfacial solvation structure and Zn depostion. Importantly, the expanding π-conjugated structure of PPPA is shown to provide abundant 2D open channels for rapid Zn2+ transport, and the delocalized π electrons form a space electrostatic field to facilitate de-solvation and diffusion of Zn2+. As a result, the Zn metal anode with PPPA/ZnSO4 electrolyte exhibits high Coulombic efficiency of 98.3 % at current density of 20 mA  cm-2, and excellent cycle lifespan for over 2000 cycles (400 h) at current density 50 mA cm-2 and plating/stripping capacity of 5 mAh cm-2. The Zn||MnO2 full battery exhibited a discharge capacity of 74.4 mAh g-1 after 5000 cycles at the current density of 2000 mA g-1, demonstrating practical feasibility. It is concluded that judicious engineering of polymer additives and interphase will benefit the development of commercial AZIBs with fast kinetics for high-rate applications.

Regulating Water Molecules via Bioinspired Covalent Organic Framework Membranes for Zn Metal Anodes

The Zn metal anode in aqueous zinc-ion batteries (AZIBs) faces daunting challenges including undesired water-induced parasitic reactions and sluggish ion migration kinetics. Herein, we develop three-dimensional covalent organic framework (COF) membranes with bioinspired ion channels toward stabilized Zn anodes. These COFs, featured by zincophilic pyridine-N sites, enable effective regulation of water molecules at the anode-electrolyte interphase. Systematic experimental analysis and theoretical simulations reveal the optimized COF-320N membrane functions as ion pumps, accordingly facilitating Zn2+ transport and inhibiting direct contact between Zn anode and free water molecules. Consequently, the bio-inspired strategy achieves improved Zn2+ transference number (0.61), rapid de-solvation kinetics, and suppressed hydrogen evolution. The assembled Zn||MnO2 pouch cell integrated with COF-320N membrane exhibits favorable electrochemical performances. Such a bioinspired concept for optimizing Zn anodes opens new pathways in developing advanced energy storage devices.

Ordered zinc electrodeposition from single-crystal units to polycrystalline stacking within solid-electrolyte interphase in battery anodes

Controlling Zinc (Zn) nucleation and subsequent crystal growth are critical for long lifespan aqueous zinc metal batteries. However, the concurrent side reactions and unstable solid-electrolyte interphase (SEI) formations impedes the continuous Zn metal electrodeposition. Herein, induced by a well-designed organic/inorganic dual-phase SEI, we realize ordered zinc electrodeposition of polycrystalline stackings from single-crystal building blocks. The uncommon SEI with appropriate ion transport kinetics and thermodynamic stability protects deposited zinc from side reactions of hydrogen evolution and metal corrosion, enabling rapid and long single crystal Zn nucleation, followed by mitigated crystal growth, and ultimately dense polycrystalline stacking without dendrites. Benefited from the above advantages, the Zn | |Zn symmetric batteries exhibit long lifespan exceeding 5600 h and high depth of discharge of 85.0 %, and the Zn | |I2 full cell delivers a high capacity of 201.9 mAh g-1 at -30 oC. Furthermore, the practical 0.1 Ah Zn | |I2 bilayer pouch cell can stably operate for 113 cycles with a high specific energy of 122.1 Wh kg-1 with a low N/P capacity ratio of 1.5. Our findings advance the understanding of critical roles of SEI on zinc electrodeposition behaviors and provide valuable insights into crystal structure regulation during electrodeposition in other metal batteries.

Popularizing Holistic High-Index Crystal Plane via Nonepitaxial Electrodeposition Toward Hydrogen-Embrittlement-Relieved Zn Anode

Electrodeposition is promising to fabricate Zn electrodes affording nonepitaxial single-crystal textures. Previous research endeavors focus on achieving Zn(002) faceted deposition, nevertheless, the popularization of a high-index Zn plane with favorable electrochemical activity remains poorly explored. There also exists a deficiency in the assessment of the electrodeposited quality of Zn. Here, a straightforward strategy to address such concerns by cultivating predominant Zn(112) texture via a potentiostatic electrodeposition mode is reported. By precisely identifying the "limiting" conditions for electrodeposition, a striking balance between improved deposition quality, tailored deposition kinetics, and suppressed hydrogen evolution is found. (002) Faceted Zn electrode is shown that be indeed produced, yet the rampant hydrodynamic convection and hydrogen embrittlement issue under such "over-limiting" preparation conditions pose challenges in the electrode lifespan. In contrast, an optimized deposition minimizes hydrodynamic disturbances and mitigates the hydrogen embrittlement effect, where the thus-generated high-index (112)-textured Zn electrode manifests impressive deposition quality and demonstrates holistic cycling stability. The pouch cell by pairing a ZnxV2O5 (ZnVO) cathode manages a reversible capacity of ≈130 mAh and a capacity retention of 98.42%. This study offers guidance for the development of dendrite-free and hydrogen-embrittlement-relieved Zn anodes, unleashing the potential of high-index plane textures for advanced Zn batteries.

Epitaxial Electrodeposition of Zinc on Different Single Crystal Copper Substrates for High Performance Aqueous Batteries

The aqueous zinc metal battery holds great potential for large-scale energy storage due to its safety, low cost, and high theoretical capacity. However, challenges such as corrosion and dendritic growth necessitate controlled zinc deposition. This study employs epitaxy to achieve large-area, dense, and ultraflat zinc plating on textured copper foil. High-quality copper foils with Cu(100), Cu(110), and Cu(111) facets were prepared and systematically compared. The results show that Cu(111) is the most favorable for zinc deposition, offering the lowest nucleation overpotential, diffusion energy, and interfacial energy with a Coulombic efficiency (CE) of 99.93%. The study sets a record for flat-zinc areal loading at 20 mAh/cm2. These findings provide some clarity on the best-performing copper and zinc crystalline facets, with Cu(111)/Zn(0002) ranking the highest. Using a MnO2-Zn full cell model, the research achieved an exceptional cycle life of over 800 cycles in a cathode-anode-free battery configuration.

Dual-Induced Directed Deposition Mechanism Based on Anionic Surfactants Enables Long Cycle Aqueous Zinc Ion Batteries

Aqueous zinc-ion battery has low cost, and environmental friendliness, emerging as a promising candidate for next-generation battery systems. However, it still suffers from a limited cycling life, caused by dendritic Zn growth and severe side reactions. Recent research highlights that the Zn (002) crystal plane exhibits superior anti-corrosive properties and a horizontal growth pattern. However, achieving uniform deposition on the Zn (002) plane remains a formidable challenge. Here, preferential rapid growth of the Zn (002) plane is manipulated via the dual-induced deposition effect of anionic surfactant (2-acrylamido-2-methylpropanesulfonic acid, AMPS), achieving Zn metal anode with ultralong cycle life. AMPS can preferentially adsorb on the Zn (100) and Zn (101) crystal planes, exposing the Zn (002) plane as a nucleation site for Zn2+ ions, while the abundant presence of amide groups in AMPS can form fast ion channels, inducing rapid and uniform Zn deposition. Thus, even using 30 µm Zn foils, the symmetric cells can maintain a stable plating-stripping process over 5000 h, and Zn.

Customizing H2O-Poor Electric Double Layer and Boosting Texture Exposure of Zn (101) Plane towards Super-High Areal Capacity Zinc Metal Batteries

The catastrophic dendrite hyperplasia and parasitic reactions severely impede the future deployment of aqueous Zn-ion batteries. Controlling zinc orientation growth is considered to be an effective method to overcome the aforementioned concerns, especially for regulating the (002) plane of deposited Zn. Unfortunately, Zn (002) texture is difficult to obtain stable cycling under high deposition capacity resulting from its large lattice distortion and nonuniform distribution in electric field. Herein, different from traditional cognition, a crystallization orientation regulation tactic is proposed to boost Zn (101) texture exposure and inhibit zinc dendrite proliferation during plating/stripping. Experimental results and theoretical calculations demonstrate the malate molecules preferentially adsorb on the Zn (002) facet, leading to the texture exposure of distinctive Zn (101) plane. Meanwhile, the -COOH and -OH groups of malate molecules exhibit strong adsorption on the Zn anode surface and chelate with Zn2+, achieving H2O-poor electrical double layer. Very impressively, the multifunctional malate additive enlists zinc anode to survive for 600 h under a harsh condition of 15 mA cm-2/15 mAh cm-2. Moreover, the symmetric cell harvests highly-reversible cycling life of 6600 h at 5 mA cm-2/1.25 mAh cm-2, remarkably outperforming the ZnSO4 electrolyte. The assembled Zn//MnO2 full cells also demonstrate prominent electrochemical reversibility.

Emulating "Curvature-Enhanced Adsorbate Coverage" for Superconformal and Orientated Zn Electrodeposition in Zinc-ion-Batteries

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature-enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure directs superconformal Zn deposition by controlling the spatial deposition rate of the rearranged crystal planes, thereby promoting bottom-up "superfilling" of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra-long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12 %. The Zn|Na2V6O16 ⋅ 3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high-performance zinc-ion batteries.

Breaking Mass Transport Limit for Hydrogen Evolution-Inhibited and Dendrite-Free Aqueous Zn Batteries

It is commonly accepted that batteries perform better at low current densities below the mass-transport limit, which restricts their current rate and capacity. Here, it is demonstrated that the performance of Zn metal electrodes can be dramatically enhanced at current densities and cut-off capacities exceeding the mass-transport limit by using pulsed-current protocols. These protocols achieve cumulative plating/stripping capacities of 11.0 Ah cm-2 and 3.8 Ah cm-2 at record-high current densities of 80 and 160 mA cm-2, respectively. The study identifies and understands the promoted (002)-textured Zn growth and suppressed hydrogen evolution based on the thermodynamics and kinetics of competing reactions. Furthermore, the over-limiting pulsed-current protocol enables long-life Zn batteries with high mass loading (29 mgcathode cm-2) and high areal capacity (7.9 mAh cm-2), outperforming cells using constant-current protocols at equivalent energy and time costs. The work provides a comprehensive understanding of the current-capacity-performance relationship in Zn plating/stripping and offers an effective strategy for dendrite-free metal batteries that meet practical requirements for high capacity and high current rates.

Achieving high-durability aqueous Zn-ion batteries enabled by reanimating inactive Zn on Zn anodes

The heavy by-products generated on Zn anode surface decrease the active surface of Zn anodes and thus induce uneven Zn deposition, seriously reducing the service life of aqueous Zn-ion batteries (AZIBs). Herein, we propose an elimination strategy enabled by the coordination chemistry to dissolve the main by-products (Zn4SO4(OH)6·xH2O). Urea as a proof-of-concept has been applied as the reactivator in the electrolyte to catalytically produce highly active NH3 on the surface of the by-products. Then the NH3 can powerfully coordinate with the Zn2+ ion in the by-products to form the soluble complex [Zn(NH3)4]2+. Consequently, the proposed electrolyte can not only lead to the timely decomposition of the by-products to prevent the Zn anode from inactivation during cycling, but also repair the waste Zn anodes for reutilization. The action mechanism has been systematically demonstrated via theoretical simulation and experimental study. As a result, the high durability with ultrahigh cumulative capacity of 10,600 mAh cm-2 for the Zn||Zn symmetric cell has been achieved at 40 mA cm-2. Particularly, the dead Zn||Zn symmetric cells and Zn||LiFePO4 full cells have been successfully reactivated. This study lights a new route to extend the cell lifespan and reuse waste Zn-ion batteries.

Microscopic Insights into Zn (002) Epitaxial Electrodeposition in Aqueous Zinc Metal Batteries

Dendrite growth, corrosion, passivation, and other side reactions during Zn plating and stripping have consistently hindered the capacity and lifespan of Zn metal batteries. In this study, we employ first-principles calculations to unravel the epitaxial electroplating mechanism of Zn (002) planes on various substrate surfaces. We identify six critical factors, including interfacial stability, zincophilicity, surface atomic arrangement, lattice mismatch, responsiveness, and adaptability, that profoundly influence the electrochemical behavior of zinc deposition. Our findings reveal that substrates with hexagonal surface atomic arrangements and strong metallic bonding with zinc, such as (002)-Zn, (111)-Cu, and Ti3C2 MXenes, facilitate uniform and dendrite-free zinc deposition. Notably, lattice contraction induced by substrate lattice mismatch exerts a greater impact on the deposition stability than lattice expansion. Kinetic analyses demonstrate that substrates exhibiting high responsiveness and adaptability can tolerate higher current densities and larger areal capacities, which are crucial for practical applications.

Crystallographic Reorientation Induced by Gradient Solid-Electrolyte Interphase for Highly Stable Zinc Anode

Oriented zinc (Zn) electrodeposition is critical for the long-term performance of aqueous Zn metal batteries. However, the intricate interfacial reactions between the Zn anode and electrolytes hinder a comprehensive understanding of Zn metal deposition. Here, the reaction pathways of Zn deposition and report the preferential formation of Zn single-crystalline nuclei followed by dense Zn(002) deposition is elucidated, which is induced by a gradient solid-electrolyte interphase (SEI). The gradient SEI composed of abundant B-O and C species facilitates faster Zn2+ nucleation rate and smaller nucleus size, promoting the formation of Zn single-crystalline nuclei. Additionally, the homogeneity and mechanical stability of SEI ensure the crystallographic reorientation of Zn anodes from Zn(101) to (002) planes, efficiently inhibiting dendrite growth and metal corrosion during the Zn2+ stripping/plating process. These advantages significantly enhance the stability of the Zn anode, as demonstrated by the prolonged cycling lifespan of symmetric Zn batteries and exceptional reversibility (>99.5%) over 5000 cycles in Zn//Cu asymmetric batteries. Notably, this strategy also enables the stable operation of anode-free Zn//I2 batteries with a long lifespan of 3000 cycles. This work advances the understanding of Zn electrochemical behaviors, encompassing Zn nucleation, growth, and Zn2+ stripping/plating.

High-Entropy Multiple-Anion Aqueous Electrolytes for Long-Life Zn-Metal Anodes

Aqueous zinc-ion batteries (AZIBs) hold great promise for large-scale energy storage applications, however, their practical use is significantly hindered by issues such as zinc dendrite growth and hydrogen evolution. To address these challenges, we propose a high-entropy (HE) electrolyte design strategy that incorporates multiple zinc salts, aimed at enhancing ion kinetics and improving the electrochemical stability of the electrolyte. The interactions between multiple anions and Zn2+ increase the complexity of the solvation structure, resulting in smaller ion clusters while maintaining weakly anion-rich solvation structures. This leads to improved ion mobility and the formation of robust interphase layers on the electrode-electrolyte interface. Moreover, the HE electrolyte effectively suppresses hydrogen evolution and corrosion side reactions while facilitating uniform and reversible Zn plating/stripping processes. Impressively, the optimized electrolyte enables dendrite-free Zn plating/stripping for over 3000 h in symmetric cells and achieves a high Coulombic efficiency of 99.5% at 10 mA cm-2 in asymmetric cells. Inspiringly, full cells paired with Ca-VO2 cathodes demonstrate excellent performance, retaining 81.5% of the initial capacity over 1800 cycles at 5 A g-1. These significant findings highlight the potential of this electrolyte design strategy to improve the performance and lifespan of Zn-metal anodes in AZIBs.

Grain Boundary Filling Empowers (002)-Textured Zn Metal Anodes with Superior Stability

Aqueous Zn battery is promising for grid-level energy storage due to its high safety and low cost, but dendrite growth and side reactions at the Zn metal anode hinder its development. Designing Zn with (002) orientation improves the stability of the Zn anode, yet grain boundaries remain susceptible to corrosion and dendrite growth. Addressing these intergranular issues is crucial for enhancing the electrochemical performance of (002)-textured Zn. Here, a strategy based on grain boundary wetting to fill intergranular regions and mitigate these issues is reported. By systematically investigating boundary fillers and filling conditions, In metal is chosen as the filler, and one-step annealing is used to synergistically convert commercial Zn foils into single (002)-textured Zn while filling In into the boundaries. The inter-crystalline-modified (002)-textured Zn (IM(002) Zn) effectively inhibits corrosion and dendrite growth, resulting in excellent stability in batteries. This work offers new insights into Zn anode protection and the development of high-energy Zn batteries.

Non-Epitaxial Electrodeposition of Overall 99 % (002) Plane Achieves Extreme and Direct Utilization of 95 % Zn Anode and By-Product as Cathode

Zn anode protection in Zn-ion batteries (ZIBs) face great challenges of high Zn utilization rate (i.e., depth of discharge, DOD) and high current density due to the large difficulty in obtaining an extreme overall RTC (relative texture coefficient) of Zn (002) plane. Through the potent interaction of Mn(III)aq and H+ with distinct Zn crystal planes under an electric field, large-size Zn foils with a breakthrough (002) plane RTC of 99 % (i.e., close to Zn single crystal) are electrodeposited on texture-less substrates, which is also applicable from recycled Zn. The ultra-high (002) plane RTC remarkably enhances cyclic performance of the Zn anode (70 % DOD @ 45.5 mA cm-2), and the DOD is even up to 95 % (@ 28.1 mA cm-2) with an electrolyte additive of polyaniline. Furthermore, MnO2, the by-product of electrodeposition, is directly used as cathode of both coin cell and pouch battery, surpassing the cyclic performance exhibited by the majority of Zn||MnO2 batteries in previous instances. These results demonstrate the great potential of our strategy for high-performance, low-cost and large-scale ZIBs.

Interfacial chemistry in multivalent aqueous batteries: fundamentals, challenges, and advances

As one of the most promising electrochemical energy storage systems, aqueous batteries are attracting great interest due to their advantages of high safety, high sustainability, and low costs when compared with commercial lithium-ion batteries, showing great promise for grid-scale energy storage. This invited tutorial review aims to provide universal design principles to address the critical challenges at the electrode-electrolyte interfaces faced by various multivalent aqueous battery systems. Specifically, deposition regulation, ion flux homogenization, and solvation chemistry modulation are proposed as the key principles to tune the inter-component interactions in aqueous batteries, with corresponding interfacial design strategies and their underlying working mechanisms illustrated. In the end, we present a critical analysis on the remaining obstacles necessitated to overcome for the use of aqueous batteries under different practical conditions and provide future prospects towards further advancement of sustainable aqueous energy storage systems with high energy and long durability.

Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries

Manipulating the crystallographic orientation of zinc (Zn) metal to expose more (002) planes is promising to stabilize Zn anodes in aqueous electrolytes. However, there remain challenges involving the non-epitaxial electrodeposition of highly (002) textured Zn metal and the maintenance of (002) texture under deep cycling conditions. Herein, a novel organic imidazolium cations-assisted non-epitaxial electrodeposition strategy to texture electrodeposited Zn metals is developed. Taking the 1-butyl-3-methylimidazolium cation (Bmim+) as a paradigm additive, the as-prepared Zn film ((002)-Zn) manifests a compact structure and a highly (002) texture without containing (100) signal. Mechanistic studies reveal that Bmim+ featuring oriented adsorption on the Zn-(002) plane can reduce the growth rate of (002) plane to render the final exposure of (002) texture, and homogenize Zn nucleation and suppress H2 evolution to enable the compact electrodeposition. In addition, the formulated Bmim+-containing ZnSO4 electrolyte effectively sustains the (002) texture even under deep cycling conditions. Consequently, the combination of (002) texture and Bmim+-containing electrolyte endows the (002)-Zn electrode with superior cycling stability over 350 h under 20 mAh cm-2 with 72.6% depth-of-discharge, and assures the stable operation of full Zn batteries with both coin-type and pouch-type configurations, significantly outperforming the (002)-Zn and commercial Zn-based batteries in Bmim+-free electrolytes.

Converting Commercial Zn Foils into Single (002)-Textured Zn with Millimeter-Sized Grains for Highly Reversible Aqueous Zinc Batteries

Rechargeable aqueous zinc batteries are promising but hindered by unfavorable dendrite growth and side reactions on zinc anodes. In this study, we demonstrate a fast melting-solidification approach for effectively converting commercial Zn foils into single (002)-textured Zn featuring millimeter-sized grains. The melting process eliminates initial texture, residual stress, and grain size variations in diverse commercial Zn foils, guaranteeing the uniformity of commercial Zn foils into single (002)-textured Zn. The single (002)-texture ensures large-scale epitaxial and dense Zn deposition, while the reduction in grain boundaries significantly minimizes intergranular reactions. These features enable large grain single (002)-textured Zn shows planar and dense Zn deposition under harsh conditions (100 mA cm-2, 100 mAh cm-2), impressive reversibility in Zn||Zn symmetric cell (3280 h under 1 mA cm-2, 830 h under 10 mAh cm-2), and long cycling stability over 180 h with a high depth of discharge value of 75 %. This study successfully addresses the issue of uncontrollable texture formation in Zn foils following routine annealing treatments with temperatures below the Zn melting point. The findings of this study establish a highly efficient strategy for fabricating highly reversible single (002)-textured Zn anodes.

Modulation of Interfacial Characteristics of Copper Electrode by Electrodeposited Cu@Ti for High-Performance Anode-Free Zinc Ion Batteries

Preparation of the NC-Cu@Ti electrode involved electrochemical deposition of nanocrystalline copper on the surface of titanium foil using a constant potential method, intended for high stability anode-free zinc ion battery (ZIB) anode material applications. This paper examines the effect of Cu2+ concentration in the electrodeposition solution on the structure and morphology of copper crystals on the NC-Cu@Ti electrode surface. The study also assesses how the interfacial properties of the NC-Cu@Ti electrode affect the process of anodic zinc deposition without anodic ZIBs. Our data suggest that with a voltage setting of -0.95 V and a copper ion concentration of 0.5 M in the solution, the deposition rate of copper crystals on the NC-Cu@Ti-0.5 electrode remains consistent. The resultant crystal phase surface appears smooth with a fine grain size. The NC-Cu@Ti-0.5 electrodes have increased hydrogen potentials and superior corrosion resistance; noting zinc nucleation sites at a mere 21.4 mV, it can provide stable electrochemical conditions for the zinc deposition interface of ZIBs and accelerate the process of zinc desolvation and nucleation. The constructed Zn//NC-Cu@Ti-0.5 asymmetric cell displays swift zinc deposition/stripping kinetics, elevated Coulombic efficiency, and prolonged stability (maintaining nearly 99% after 200 cycles). This performance significantly extends the service life relative to the Zn//Zn symmetric cell, which operates stably for 400 h at 1 mA/cm2. Moreover, the NC-Cu@Ti-0.5//MnO2 ZIBs offer enhanced conductivity and magnification performance to the pure zinc anode ZIBs. This study presents a novel approach for the low-cost and rapid preparation of anode materials for high-performance free-anode ZIBs.

Tailoring Localized Electrolyte via a Dual-Functional Protein Membrane toward Stable Zn Anodes

Considerable attention has been by far paid to stabilizing metallic Zn anodes, where side reactions and dendrite formation still remain detrimental to their practical advancement. Electrolyte modification or protected layer design is widely reported; nonetheless, an effective maneuver to synergize both tactics has been rarely explored. Herein, we propose a localized electrolyte optimization via the introduction of a dual-functional biomass modificator over the Zn anode. Instrumental characterization in conjunction with molecular dynamics simulation indicates local solvation structure transformation owing to the limitation of bound water with intermolecular hydrogen bonds, effectively suppressing hydrogen evolutions. Meanwhile, the optimized nucleation throughout the protein membrane allows uniform Zn deposition. Accordingly, the symmetric cell exhibits an elongated lifespan of 3280 h at 1.0 mA cm-2/1.0 mAh cm-2, while the capacity retention of the full cell sustains 91.1% after 2000 cycles at 5.0 A g-1. The localized electrolyte tailoring via protein membrane introduction might offer insights into operational metal anode protection.

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%.

Screening Selection of Hydrogen Evolution-Inhibiting and Zincphilic Alloy Anode for Aqueous Zn Battery

The hydrogen evolution reaction (HER) and Zn dendrites growth are two entangled detrimental effects hindering the application of aqueous Zn batteries. The alloying strategy is studied to be a convenient avenue to stabilize Zn anodes, but there still lacks global understanding when selecting reliable alloy elements. Herein, it is proposed to evaluate the Zn alloying elements in a holistic way by considering their effects on HER, zincphilicity, price, and environmental-friendliness. Screening selection sequence is established through the theoretical evaluation of 17 common alloying elements according to their effects on hydrogen evolution and Zn nucleation thermodynamics. Two alloy electrodes with opposite predicted effects are prepared for experimental demonstration, i.e., HER-inhibiting Bi and HER-exacerbating Ni. Impressively, the optimum ZnBi alloy anode exhibits one order of magnitude lower hydrogen evolution rate than that of the pure Zn, leading to an ultra-long plating/stripping cycling life for more than 11 000 cycles at a high current density of 20 mA cm-2 and 81% capacity retention for 170 cycles in a Zn-V2O5 pouch cell. The study not only proposes a holistic alloy selection principle for Zn anode but also identifies a practically effective alloy element.

Practicable Zn metal batteries enabled by ultrastable ferromagnetic interface

Rechargeable zinc (Zn) metal batteries (RZMBs) are demonstrated as sustainable and low-cost alternative in the energy storage industry of the future. However, the elusive Zn deposition behavior and water-originated parasitic reactions bring significant challenges to the fabrication and commercialization of Zn anodes, especially under high plating/stripping capacity. In this work, the ferromagnetic interface in conjunction with the magnetic field (MF) to effectively address these fabrication hurdles is proposed. The introduction of ferromagnetic layer with high chemical durability not only maintains the long-term regulating deposition steadily by magnetic field, but also plays a significant role in preventing side reactions, hence reducing gas production. These merits allow Zn-anode to achieve over 350 h steady Zn-deposition with a depth of discharge (DODZn) up to 82% and translates well to ZnFe-MF||V2O5 full cells, supporting stable cycling at high mass loading of 13.1 mg/cm2, which makes RZMBs configurations promising for commercial applications.

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.

Conformal poly 3,4-ethylene dioxythiophene skin stabilized ε-type manganese dioxide microspheres for zinc ion batteries with high volumetric energy density

Manganese dioxide (MnO2) is an important active material for energy storage. Constructing microsphere-structured MnO2 is key for practical application due to the high tapping density for high volumetric energy density. However, the unstable structure and poor electrical conductivity hinder the development of MnO2 microspheres. Herein, Poly 3,4-ethylene dioxythiophene (PEDOT) is painted conformally on ε-MnO2 microspheres to stabilize the structure and enhance the electrical conductivity via in-situ chemical polymerization. When used for Zinc ion batteries (ZIBs), the obtained material (named MOP-5) with high tapping density (1.04 g cm-3) delivers a superior volumetric energy density (342.9 mWh cm-3) and excellent cyclic stability (84.5% after 3500 cycles). Moreover, we find the structure transformation of ε-MnO2 to ZnMn3O7 during the initial few cycles of charge and discharge, and the ZnMn3O7 provides more reaction sites for Zinc ions from analysis of the energy storage mechanism. The material design and theoretical analysis of MnO2 in this work may provide a new idea for future commercial applications of aqueous ZIBs.

A Functional Janus Ag Nanowires/Bacterial Cellulose Separator for High-Performance Dendrite-Free Zinc Anode Under Harsh Conditions

Aqueous zinc-ion batteries (AZIBs) offer promising prospects for large-scale energy storage due to their inherent abundance and safety features. However, the growth of zinc dendrites remains a primary obstacle to the practical industrialization of AZIBs, especially under harsh conditions of high current densities and elevated temperatures. To address this issue, a Janus separator with an exceptionally ultrathin thickness of 29 µm is developed. This Janus separator features the bacterial cellulose (BC) layer on one side and Ag nanowires/bacterial cellulose (AgNWs/BC) layer on the other side. High zincophilic property and excellent electric/thermal conductivity of AgNWs make them ideal for serving as an ion pump to accelerate Zn2+ transport in the electrolyte, resulting in greatly improved Zn2+ conductivity, deposition of homogeneous Zn nuclei, and dendrite-free Zn. Consequently, the Zn||Zn symmetrical cells with the Janus separator exhibit a stable cycle life of over 1000 h under 80 mA cm-2 and are sustained for over 600 h at 10 mA cm-2 under 50 °C. Further, the Janus separator enables excellent cycling stability in AZIBs, aqueous zinc-ion capacitors (AZICs), and scaled-up flexible soft-packaged batteries. This study demonstrates the potential of functional separators in promoting the application of aqueous zinc batteries, particularly under harsh conditions.