Zinc Electrodeposition Research Articles

Efficient extraction and separation of zinc and iron from electric arc furnace dust by roasting with FeSO4·7H2O followed by water leaching

Electric arc furnace dust (EAFD) formed during steelmaking in electric arc furnace is rich in iron and zinc. Due to the negative effects of zinc, directly recycling as raw materials for ironmaking does not work so that it is still mostly accumulated. In this study, a novel process was proposed, wherein EAFD was roasted with FeSO4·7H2O followed by water leaching for the effective and selective extraction and separation of zinc and iron from EAFD. The optimal roasting conditions were determined as mass ratio of FeSO4·7H2O/EAFD of 1.5, roasting temperature of 675 °C, holding time of 3 h. The transfer mechanism of elements in EAFD was analyzed. 98.79% of zinc and only 0.11% of iron were dissolved in the leaching solution, respectively, avoiding the iron-removing step before the subsequent zinc electrodeposition. Meanwhile, most of Ca, Mg and Mn ions transformed into corresponding sulfates during roasting experiments and then entered leaching solution after water leaching. Thus, the leaching residue with 91.36% mass ratio of Fe2O3 could be applied as raw material for ironmaking industry. In addition, the majority of heavy metals (Pb and Cr) were remained and immobilized in the leaching residue, meeting the requirement of leaching toxicity standard. Results from this work provide a new insight into selective recovery of valuable metals from EAFD while at the same time exploiting the solid waste of Copperas.

Lattice Matching and Halogen Regulation for Synergistically Induced Uniform Zinc Electrodeposition by Halogenated Ti3C2 MXenes

Dendrite growth and low Coulombic efficiency caused by uneven diffusion and electrodeposition of Zn2+ ions have emerged as a barrier to exploit the Zn metal anode. In this work, we demonstrate the stoichiometric halogenated MXenes (Ti3C2Cl2, Ti3C2Br2, and Ti3C2I2) as an artificial layer that can induce the uniform Zn deposition. The efficient redistribution effect results from the coherent heterogeneous interface reconstruction and regulated ion tiling by halogen surficial termination. The synergetic effects of high lattice matching (90%) between the adopted MXenes and Zn, as well as the positive halogen regulation, Zn2+ ions are guided to nucleate uniformly on the most extensive (000l) crystal plane of the MXene matrix and grow in a planar manner. In terms of Zn ion regulation, Cl termination is found to be more effective than O/F, Br, and I due to its moderate adsorption and diffusion coefficiency for Zn2+ ions. The Ti3C2Cl2-Zn anode achieves a life extension of over 12 times (840 h at 2 mA cm-2//1 mAh cm-2) over that of the bare Zn anode and serves more than 9000 cycles in a battery with a Ti3C2I2 cathode at a high rate of 3 A g-1. Given the abundance of lattice parameters and terminations of MXene materials, the developed strategy is expected to be extended to other metal anode systems.

Separator Effect on Zinc Electrodeposition Behavior and Its Implication for Zinc Battery Lifetime.

Uncontrolled zinc electrodeposition is an obstacle to long-cycling zinc batteries. Much has been researched on regulating zinc electrodeposition, but rarely are the studies performed in the presence of a separator, as in practical cells. Here, we show that the microstructure of separators determines the electrodeposition behavior of zinc. Porous separators direct zinc to deposit into their pores and leave "dead zinc" upon stripping. In contrast, a nonporous separator prevents zinc penetration. Such a difference between the two types of separators is distinguished only if caution is taken to preserve the attachment of the separator to the zinc-deposited substrate during the entire electrodeposition-morphological observation process. Failure to adopt such a practice could lead to misinformed conclusions. Our work reveals the mere use of porous separators as a universal yet overlooked challenge for metal anode-based rechargeable batteries. Countermeasures to prevent direct exposure of the metal growth front to a porous structure are suggested.

Relation between Faradic Yields, Hydrogen Evolution and Pulsed Currents: Morphological and Fe Content Control in Zn and ZnFe Coatings

Long-term protection of metallic parts from atmospheric exposure is an important challenge and one of the most frequent way to ensure their corrosion resistance is the application of sacrificial zinc alloys coatings [1]. Among the various zinc electroplating baths, the alkaline zincate solutions has gained a wide range of applications thanks to its simple bath composition, good dispersion and efficient coverage ability. Nevertheless, its efficiency is very low in absence of additives, which affects the performances of the coatings by modifying the crystal growth and therefore the structural and mechanical properties. This is a result from the competition between dihydrogen production and the reduction of the metallic species present in the bath.The present study deals with the optimization of ZnFe sacrificial coating on steel and aluminum substrate in the frame of the ATLAS project -Alternative TechnoLogies for improved Anticorrosion Solutions- managed by the IRT M2P. After the analysis of the electrochemical behavior of the ZnFe electrolyte patented by the Coventya company and the UTINAM institute, pulsed currents will be implemented to extend the versatility of the coatings. Indeed, pulsed currents are known to act on various parameters such as improving the faradic yield or modifying morphologies and structures [2].The determination of a first panel of pulsed sequences (average current densities, cathodic peak current, cathodic pulse time and off-time) have been based on transient curves analysis from a zincate bath. Three sequences have been selected as they resulted in very different patterns in terms of electrochemical behavior and coatings characteristics. These sequences have been replicated and compared to DC current in several electrolytes, from the zincate bath to the commercial formula. For each set of parameters, the faradic yield has been measured and compared to the hydrogen generated during the electrolysis distributed between the absorbed one (measured by hot extraction) and the dihydrogen released into the reactor atmosphere (measured by mass spectrometry with a dedicated set- up). It is interesting to note that the obtained values strongly depend on pulsed sequences as well as electrolytes composition. Coatings were systematically produced and characterized. Morphology was observed using SEM and microstructure determined from XRD diffractograms: preferential orientation and crystal lattice and crystalline phases. The latest has required a specific methodological development.Finally, the identification of nucleation parameters by model simulation has been undertaken to describe the mechanisms involved in the first steps of zinc electrodeposition [3].[1] B. Chatterjee, « Electrodeposition of Zinc Alloys », p. 31.[2] X. Zhang, K. Tsay, J. Fahlman, and W. Qu, « Journal of Energy Storage, 26 p. 100966 (2019)[3] A. Milche, Electrochimica Acta, 48 p.2903-2913 (2003)

A high areal capacity solid-state zinc-air battery via interface optimization of electrode and electrolyte

Solid-state zinc-air batteries (SZABs) are regarded as a promising energy source for next-generation wearable electronic devices due to their high theoretical energy density and reliability. However, practical development of solid-state zinc-air batteries is hindered by the low specific areal capacity and poor contact between solid-state electrolyte and electrode caused by zinc passivation and electrolyte aging. Herein, we report a new strategy for optimizing the solid-state electrolyte/electrode interface coupling by combining porous zinc electrode and thermal-sensitive solid-state electrolyte F127 to improve the areal-capacity of solid-state zinc-air batteries. The porous Zn anode prepared by zinc electrodeposition on the zinc substrate is used to alleviate zinc passivation and improve the specific area capacity of SZAB. In addition, to enhance the contact between the solid-state electrolyte and the zinc anode, the F127 surfactant is selected as the solid-state electrolyte due to its fluidity at low temperatures. Benefiting from the porous structure and excellent contact, the SZAB using porous zinc anode and the solid-state electrolyte F127 exhibits high areal capacity of 133 mAh cm−2 at the current density of 4 mA cm−2, which is 100 times higher than that of the solid zinc-air battery using zinc foil as the anode. Moreover, the results show that the use of porous zinc electrodes is conducive to achieving high current discharge, which is critical for the practical application of solid-state zinc-air batteries.

Protective Efficiency of ZrO2/Chitosan “Sandwich” Coatings on Galvanized Low-Carbon Steel

Enhanced corrosion efficiency of low-carbon steel was achieved by newly developed hybrid multilayers, composed of low-carbon steel coated with an electrodeposited zinc sublayer (1 µm), a chitosan (CS) middle layer and ZrO2 coating by the sol–gel method (top-layer). The middle chitosan layer was obtained by dipping galvanized steel substrate in 3% tartatic acid water solution of medium molecular-weight chitosan, composed of β-(1–4)-linked D-glucosamine and N-acetyl-D-glucosamine with a deacetylation degree of about 75–85% (CS). The substrates were dipped into CS solution and withdrawn at a rate of 30 mm/min. One part of the samples with the CS layer was dried at room temperature for 2 weeks, and another part at 100 °C for 1 h, respectively. After CS deposition treatment, the substrates were dipped into an isopropanol sol of zirconium butoxide with small quantity of polyethylene glycol (PEG400). The dipping-drying cycles of the ZrO2 coatings were repeated three times. After the third cycle, the final structures were treated at 180 °C. The samples were denoted as T25, which consists of the CS middle layer, and dried at RT and T100 with the CS middle layer treated at 100 °C, respectively. The samples were characterized by means of differential thermal analysis (DTA-TG), XRD analyses, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Hydrophobicity properties were evaluated by measuring the contact angle with a ramé-hart automated goniometer. Two electrochemical tests—potentiodynamic polarization technique (PD) and electrochemical impedance spectroscopy (EIS)—have been used to determine the corrosion resistance and protective ability of the coatings in a 5% NaCl solution. The results obtained by both methods revealed that the applied “sandwich” multilayer systems demonstrate sacrificial character and will hopefully protect the steel substrate in corrosion medium containing chloride ions as corrosion activators. The newly obtained hybrid multilayer coating systems have dense structure and a hydrophobic nature. They demonstrated positive effects on the corrosion behavior at conditions of external polarization independent of their various characteristics: morphology, grain sizes, surface roughness and contact angle. They extend the service life of galvanized steel in a chloride-containing corrosion medium due to their amorphous structure, hydrophobic surface and the combination of the positive features of both the chitosan middle layer and the zirconia top layer.

High-voltage K/Zn dual-ion battery with 100,000-cycles life using zero-strain ZnHCF cathode

Rechargeable zinc-based batteries (RZBs) using low-cost zinc metal anodes are feasible for large-scale energy storage, but the developments currently are restricted by the poor performances. Here we constructed a particular dual-ion battery (DIB) based on zinc hexacyanoferrate (ZnHCF) cathode, zinc metal anode, and non-aqueous K+/Zn2+ hybrid ions electrolyte. It was revealed that K+-ions occupied almost all the cavities in ZnHCF at high voltage over 1.7 V (vs. Zn2+/Zn), which effectively blocked Zn2+-ions insertion. The ZnHCF showed a zero-strain characteristic during the repeated K+-ions intake/removal. Meanwhile, the charge screening effect of additive K+-ions on optimizing the zinc electrodeposition process ensured the reversible and dendrite-free Zn plating/stripping. The DIBs demonstrated excellent rate performances (57 and 47 mAh gcathode‒1 at 2000 and 5000 mA g‒1, respectively) and incredibly 100,000-cycles life with 74% capacity retention.

Electrodeposition of Zinc onto Au(111) and Au(100) from the Ionic Liquid [MPPip][TFSI

AbstractThe improvement of rechargeable zinc/air batteries was a hot topic in recent years. Predominantly, the influence of water and additives on the structure of the Zn deposit and the possible dendrite formation were studied. However, the effect of the surface structure of the underlying substrate was not focused on in detail, yet. We now show the differences in electrochemical deposition of Zn onto Au(111) and Au(100) from the ionic liquid N‐methyl‐N‐propylpiperidinium bis(trifluoromethanesulfonyl)imide. The fundamental processes were initially characterized via cyclic voltammetry and in situ scanning tunnelling microscopy. Bulk deposits were then examined using Auger electron spectroscopy and scanning electron microscopy. Different structures of Zn deposits are observed during the initial stages of electrocrystallisation on both electrodes, which reveals the strong influence of the crystallographic orientation on the metal deposition of zinc on gold.

Electrodeposition of Zinc onto Au(111) and Au(100) from the Ionic Liquid [MPPip][TFSI

The improvement of rechargeable zinc/air batteries was a hot topic in recent years. Predominantly, the influence of water and additives on the structure of the Zn deposit and the possible dendrite formation were studied. However, the effect of the surface structure of the underlying substrate was not focused on in detail, yet. We now show the differences in electrochemical deposition of Zn onto Au(111) and Au(100) from the ionic liquid N‐methyl‐N‐propylpiperidinium bis(trifluoromethanesulfonyl)imide. The fundamental processes were initially characterized via cyclic voltammetry and in situ scanning tunnelling microscopy. Bulk deposits were then examined using Auger electron spectroscopy and scanning electron microscopy. Different structures of Zn deposits are observed during the initial stages of electrocrystallisation on both electrodes, which reveals the strong influence of the crystallographic orientation on the metal deposition of zinc on gold.

Ionometallurgical Step-Electrodeposition of Zinc and Lead and its Application in a Cycling-Stable High-Voltage Zinc-Graphite Battery.

Ionometallurgy is a new development aiming at the sustainable low-temperature conversion of naturally occurring metal ores and minerals to their metals or valuable chemicals in ionic liquids (ILs) or deep eutectic solvents. The IL betainium bis((trifluoromethyl)sulfonyl)imide, [Hbet][NTf2 ], is especially suited for this process due to its redox-stability and specific-functionalization. The potentiostatic electrodeposition of zinc and lead starting directly from ZnO and PbO, which dissolve in [Hbet][NTf2 ] in high concentrations is reported. The initial reduction potentials of zinc(II) and lead(II) are about -1.5 and -1.0V, respectively. The ionic conductivity of the solution of ZnO in [Hbet][NTf2 ] is measured and the effect of various temperatures and potentials on the morphology of the deposited material is explored. The IL proves to be stable under the chosen conditions. From IL-solutions, where ZnO, PbO, and MgO have been dissolved, metallic Zn and Pb are deposited under potentiostatic control either consecutively by step-electrodeposition or together in a co-electrodeposition. Using the method, Zn is also deposited on 3D copper foam and assembles into high-voltage zinc-graphite battery. It exhibits a working-voltage up to 2.7V, an output midpoint discharge-voltage of up to 2.16V, up to 98.6% capacity-retention after 150 cycles, and good rate performance.

Zinc Electrodeposition in Acetate‐based Water‐in‐Salt Electrolyte: Experimental and Theoretical Studies

AbstractZinc electroplating has found applications in many fields. The chemical composition of the electrodeposition bath can have a great impact on the final coating quality and the economics of the process. In traditional aqueous electrolytes, zinc deposition competes with the hydrogen evolution and oxygen reduction reactions, which can lead to hydrogen embrittlement of the substrate as well as decrease in efficiency. Highly concentrated water‐in‐salt electrolytes can suppress these reactions significantly. Here, we show that electrodeposition of zinc with high efficiencies can be achieved using an acetate‐based water‐in‐salt electrolyte at room temperature. Nucleation studies confirm that at potentials more negative than −1.30 V vs. Ag/AgCl, the three‐dimensional (3D) nucleation process becomes instantaneous, while at more positive potentials it is progressive. Using two of the most common nucleation and growth models, Scharifker‐Mostany and Mirkin‐Nilov‐Heerman‐Tarallo, nucleation parameters such as the nucleation rate constant and nuclei density are found, showing a good agreement between the two models.

Stabilizing Zinc Electrodeposition in a Battery Anode by Controlling Crystal Growth.

Reversible electrodeposition of metals at liquid-solid interfaces is a requirement for long cycle life in rechargeable batteries that utilize metals as anodes. The process has been studied extensively from the perspective of the electrochemical transformations that impact reversibility, however, the fundamental challenges associated with maintaining morphological control when a intrinsically crystalline solid metal phase emerges from an electrolyte solution have been less studied, but provide important opportunities for progress. A crystal growth stabilization method to reshape the initial growth and orientation of crystalline metal electrodeposits is proposed here. The method takes advantage of polymer-salt complexes (PEG-Zn2+ -aX- ) (a= 1,2,3) formed spontaneously in aqueous electrolytes containing zinc (Zn2+ ) and halide (X- ) ions to regulate electro-crystallization of Zn. It is shown that when X = Iodine (I), the complexes facilitate electrodeposition of Zn in a hexagonal closest packed morphology with preferential orientation of the (002) plane parallel to the electrode surface. This facilitates exceptional morphological control of Zn electrodeposition at planar substrates and leads to high anode reversibility and unprecedented cycle life. Preliminary studies of the practical benefits of the approach are demonstrated in Zn-I2 full battery cells, designed in both coin cell and single-flow battery cell configurations.

НЕКОТОРЫЕ ОСОБЕННОСТИ ЭЛЕКТРООСАЖДЕНИЯ МЕТАЛЛОВ ИЗ ЭЛЕКТРОЛИТОВ С ПАВ

for a long time, the use of various surfactants in the composition of simple electrolytes by researchers to improve the quality of metal coatings with cadmium and zinc has been an urgent task.Surfactants contribute to the grinding of the coating structure, the elimination of their porosity and the appearance of anticorrosion properties of coatings. For example, cadmium electroplated coatings require corrosion resistance, since they are operated in tropical climates, in underground tunnels. Zinc coatings are widely used in building structures and roofing, on electrified railways and high-voltage power lines, in the mining industry and water pipes, as well as for galvanizing the body material in modern all-terrain vehicles to pass in hard-to-reach places without being subjected to corrosion. The object of our research is the process of electrodeposition of cadmium and zinc from simple acidic electrolytes with surfactants, which are thiourea derivatives of dialkyl-phosphorous acids in the current density range of 0.5-3.5 A /dm2, at room temperature. To confirm the quality of the obtained electroplating, we used a JSM-6490LV scanning electron microscope with INSA Energu energy–dispersion microanalysis and HKL-Basicc structural analysis systems with a useful magnification of 300000.

Control of Texture and Morphology of Zinc Films through Pulsed Methods from Additive‐Free Electrolytes

AbstractWe investigate the electrodeposition of zinc on steel substrates using pulsed methods from additive‐free electrolytes in an industrially scalable parallel plate flow cell. We demonstrate that variables such as peak current and duty cycle can be used to independently control the morphology and preferential texture of the crystalline structure, which is, in turn, desirable for a variety of applications. Specifically, we have observed a transition of the preferential (002) facets at low peak current density (or low duty cycle) to (101) preferring facets at higher peak current density (or high duty cycle) as determined by the analysis of texture coefficients. Further analysis using scanning electron microscopy reveals a transition from the conventional hexagonal‐shaped particles of zinc to needle‐shaped structures, accompanied by a change in average crystallite size from 33 to 19 nanometers, determined from X‐ray diffraction studies. The variation in morphology is also correlated to crystallographic textures through the analysis of texture coefficients and an understanding of crystallization mechanisms occurring during deposition. Collectively, these results demonstrate that the morphology and crystalline orientation of zinc can be easily manipulated through tuning of the pulse parameters without the use of complex and expensive additives that have been traditionally used to achieve similar effects.

The effect of zinc oxide coating morphology on corrosion performance of Ti-6Al-4 V alloys

The release of aluminum and vanadium is one of the major issues affecting the service life of permanent orthopedic devices made of Ti6Al4V. This study aims to improve the corrosion resistance of Ti6Al4V using electrodeposited zinc oxide coatings. Moreover, the effects of bath temperature and applied potential on the morphology, roughness, porosity, wettability, and corrosion performance of zinc oxide coatings were evaluated. The results showed that by controlling the process parameters, zinc oxide coatings with various morphologies including spherical, worm-like, irregular porous network and flower-like were created. The coating changed the hydrophilic nature of Ti6Al4V substrate (wettability of ~46°) to a hydrophobic one. The wettability of the zinc oxide films varied from ~83° for the spherical to ~67° for the flower-like morphology. The long-term corrosion performance of the zinc oxide coatings was estimated in phosphate-buffered saline solution using electrochemical impedance spectroscopy. The results revealed that the spherical morphology provides higher corrosion performance at the initial stage of immersion, however, the corrosion behavior of both spherical and worm-like morphologies became the same after 4 weeks. On the other hand, zinc oxide coating with an irregular porous network of nanoflakes and flower-like morphologies reduced the corrosion performance of Ti6Al4V substrate.

Electrodeposition of Zinc for Redox Flow Batteries

The redox flow batteries (RFBs) have received great attention due to their attractive features for large-scale energy storage applications. A RFB is a type of flow-based energy storage device capable of providing reversible conversion between electrical and chemical energy through two redox half-cell reactions. Nowadays the most common RFBs exploit the vanadium chemistry, followed by the zinc-bromine chemistries. Though RFB technology has advantage for energy storage and has successful demonstration of systems up to MWh levels, they have not enjoyed broad market penetration. Some of the reasons are relatively high capital and life-cycle costs. New applications are envisaged for RFBs, including the electric mobility which is becoming increasingly important. Zinc based redox flow batteries (Zn-RFBs) based on new chemistries with respect to the chlorine and bromine ones can be the answer to new market success devices, not only in the large storage field but also in the medium and mobility sector.In this presentation, the electrodeposition of zinc will be discussed in light of its exploitation in the new generation of zinc based RFBs. Alkaline and acidic baths will be presented in combination with proper chemistries for the other half cells. The role of additives and pulse plating will be discussed in terms of nucleation and growth of the metallic layer and its dissolution during charging/discharging cycles. A zinc-iron RFB with low cost and high energy density will be presented. In particular, inorganic electrolytes based on high soluble salts have been developed, achieving a charge density of 30-70 Wh/l. Moreover, in order to enhance the capacity of Zn-Fe flow battery, the use of slurry dispersed electrodes to decuple capacity from the power rating have been studied. As another example, zinc electrodeposition and its optimization will be introduced in combination with the iodine chemistry for high energy efficiency Zn-I RFBs, in the order of 70% at 20 mA cm-2, with high energy density ranging from 25 to 60 Wh/l.

Comparative Study to Investigate the Role of SEI Layer on the Formation of Dendrites on Lithium, Sodium and Zinc Metals

The huge theoretical capacities of metal anodes provide the potential for high energy density batteries that could have widespread applications in consumer devices. However, metallic anodes are plagued by challenges caused by the formation of unstable solid electrolyte interphase (SEI) layers, surface pitting, and dendritic plating morphologies leading to reductions in cycle life, low Coulombic efficiencies, and potential safety hazards. There currently exists a gap in understanding within the literature concerning the nucleation and morphology growth of dendrites upon metallic anodes during cycling. These dendritic morphologies lead to increased SEI layer formation, generation of “dead” metal which is no longer is physical or electrical contact with the electrode, and the potential for internal short circuits. So far, these drawbacks have prevented the widespread implementation of metallic anodes in secondary batteries. A better understanding of when dendrites nucleate and how plating morphologies evolve over cycling is needed for increasing reversibility of metallic anodes and facilitating next-generation battery technologies such as metal-air and metal-sulfur batteries.In this study, we employed various electrochemical methods including galvanostatic cycling and impedance spectroscopy as well as imaging tools such as scanning electron microscopy to investigate the dendrite formations on Li, Na and Zn metals. Herein, we compare the performances of symmetric cells comprised of three metals M (Li, Na, and Zn) in analogous perchlorate (M(ClO4)x) electrolytes and draw connections between voltage profile variations and metal morphology evolution using SEM. These 3 metal anodes where chosen owing to their range of reactivities, electrons involved in their charge transfer reactions, SEI layer composition, and electrolyte compatibilities. Additionally, recent research based on modeling the onset of lithium dendrite growth as a diffusion-limited process using Sand’s equation has correlated the appearance of lithium dendrites to the reduction in Li + ion concentration at the lithium-SEI interface to zero. This hypothesis has been further evaluated by comparison of lithium electrodeposition in an organic electrolyte (wherein an SEI layer is formed) to zinc electrodeposition in an aqueous electrolytes (which involves the formation of a minimal SEI layer) using a custom 3-electrode cell. The results of this study provide insights into the analysis of symmetric cell voltage profiles and the nucleation mechanism of dendrites during charging.

Mathematical modeling and simulation of the dissolution of zinc anodes in industrial electroplating

The simulation of large-scale industrial electrodeposition of zinc is of major importance, since through the simulation, important data about the positioning of electrodes, thickness of layers, etc. can be generated. But the models used in practical applications indirectly assume small anodes and cathodes for which the electrical potential or the charge-transfer current are constant over the cathode, resp. anode. In this paper, a new type of model for the dissolution of zinc anodes is described. Furthermore, a numerical scheme to treat the model will be described and verified. The new model will be compared to a commonly known model. The paper gives an alternative model for the calculation of the current density on anodes and formulates a FEM for the approximation of Poisson equations on multiple domains with Robin-interfaces. Besides the application to the dissolution of zinc-anodes during electro-plating, the basic model and FEM can be applied to the dissolution of anodes made of a different material and to the modelling of corrosion processes.

Dynamic Windows Using Reversible Zinc Electrodeposition in Neutral Electrolytes with High Opacity and Excellent Resting Stability

AbstractDynamic windows, which electronically switch between clear and dark states, can play a vital role in energy‐efficient buildings by reducing lighting, heating, and cooling demands. In this manuscript, reversible Zn electrodeposition on tin‐doped indium oxide electrodes is studied and a mechanism is proposed that explains the deposition and dissolution processes. This mechanistic understanding enables the construction of 100 cm2 two‐electrode devices that transition from clear (80% transmission at 600 nm) to highly opaque (<0.1% transmission at 600 nm) in less than 20 s. Additionally, the dynamic windows utilize a pH‐neutral electrolyte, which enables them to switch without degradation over the course of four weeks. The high opacity and stability of the Zn‐based devices represent significant improvements over existing switchable thin films based on the reversible electrodeposition of more noble metals such as Bi and Cu.

Reducing Zinc Redistribution and Extending Cycle Life Via Electrochemical Synthesis of Zinc/Zinc Oxide Anodes in Rechargeable Alkaline Batteries

Redistribution of zinc over the electrode surface, also known as shape change, is a major problem and a cause of failure in alkaline zinc anode batteries. To mitigate this phenomenon, we propose a scalable approach based on an in situ formed, highly porous electrochemically synthesized ZnO matrix with uniformly electrodeposited zinc particles. This results in ∼70% improvement in cycle life performance at a rate of 10 mA cm−2 compared to control Zn anodes, which have not gone through the formation process. A quantitative electrolyte analysis revealed under-saturated zincate ion concentration in the electrochemically synthesized ZnO/Zn cells indicating reduced zincate movement. Post mortem analysis of the anodes indicated higher retention of both Zn and ZnO on the electrochemically synthesized ZnO anodes signifying reduced redistribution of active material. Image analysis of the cycled anodes revealed a narrower Zn particle size distribution (62−79 μm) in contrast to a wider particle size distribution of 51–96 μm observed in the control anodes. The formation approach results in electrochemically synthesized ZnO/Zn anodes providing a stable ZnO matrix in which Zn particles retain their localized distribution on cycling better than control electrodes conventionally made by pasting zinc particles together with a binder.