Device and method for reversible electrodeposition of a zinc film on an electrode with a transparent semi-conductive or conductive surface and electrochromic glazing obtained

Abstract

An electrochromic device (1, 11) comprising: - a device for reversible electrodeposition of a zinc film Zn at the negative electrode, the device comprising a negative electrode, a positive electrode, a volume containing an electrolyte (4, 14) with Zn2+ ions, the negative electrode having a transparent semi-conductive or conductive surface comprising a conductive or semi-conductive material which is a transparent metal oxide, the electrolyte being aqueous or in gel form, the electrolyte containing ethylene glycol, polyethylene glycol or derivatives of these compounds, the pH of the electrolyte being between 4 and 7, - a means for applying a current imposed between the negative electrode and the positive electrode, in order to pass, at each galvanostatic step of the cycle, from a transparent state to a coloured or even opaque state of the device, the device for reversible electrodeposition of the zinc film Zn making it possible to pass during each cycle, at a second step that follows the galvanostatic step, from the coloured or even opaque state from the galvanostatic step to a transparent state of the entire transparent semi-conductive or conductive surface.

Description

[0001] Device and method for reversible electrodeposition of a zinc film on an electrode with a transparent semiconducting or conductive surface and electrochromic glazing obtained

[0002] Technical field

[0003] The invention relates to methods and devices for reversible electrodeposition of a zinc film on an electrode with a transparent semiconducting or conductive surface, for the manufacture of glazing.

[0004] State of the art

[0005] In state-of-the-art systems, a device can be proposed comprising a single electrode having electrochromic properties, with a counter electrode which is a grid or a zinc plate and which is not used for electrochromism.

[0006] The energy efficiency of buildings is a lever for the energy transition, essential in sustainable development strategies and the fight against global warming.

[0007] A relevant way to increase the comfort and energy efficiency of buildings is to use smart windows.

[0008] A window is a window with a glass enclosure that allows lighting into a room, for example a residential or commercial space. A smart window is a window whose optical properties can be adapted to suit your needs. The glazing is referred to as smart glazing, switchable glazing or dynamic glazing.

[0009] By regulating both light and heat transfer, smart windows improve the energy efficiency of a building's heating, ventilation, and air conditioning (HVAC) system.

[0010] Replacing static low-E windows with such smart windows would deliver energy savings of 20% on average, and up to 45%, significantly reducing carbon emissions associated with the built environment.

[0011] Smart windows can be classified into different categories, depending on the parameter modulating the optical properties of the glazing, or depending on the materials used for the glazing. In liquid crystal windows and windows with glazing equipped with suspended particles (Suspended Particle Device SPD), the optical properties of the glazing are modified by applying an electric field. In windows with chromic material, the optical properties of the glazing are modified depending on the light intensity (photochromic glazing), heat (thermochromic glazing), the injection of a gas (gasochromic glazing), or electrical voltage (electrochromic glazing).

[0012] The invention relates more particularly to smart windows with electrochromic glazing.

[0013] Electrochromic glazing currently on the market uses electrochromism, which is a change in the optical properties of a material when an electrical potential difference is applied, a reversal of the polarization allowing it to return to the initial state, in a reversible manner.

[0014] The principle of electrochromism is conventionally illustrated using a device comprising five layers, namely two layers of transparent and conductive oxides (Transparent Conducting Oxides TCO), two layers of electrochromic material forming a working electrode and a counter-electrode, and an electrolyte placed between the two electrodes. When a voltage is applied, electrons migrate through the TCOs and ions pass through the electrolyte to insert themselves into one of the electrochromic materials. This transfer of ions (for example H + , Li + , N / A +) and electrons causes redox reactions of the transition metals of the electrochromic layers, which leads to a color change. For example, thin layers of tungsten oxide WO3 switch from a transparent state to blue, by insertion of lithium ions Li + , sodium ions Na + or protons. The combination of WO3 and nickel oxide NiO x allows you to obtain neutral, gray colored glazing.

[0015] Performance indicators for electrochromic devices are optical contrast, optical efficiency, memory effect, switching or response time, cycling life or durability, operating temperature range, and applied potential range. Optical contrast is the ratio of optical reflection or transmission between the colored state and the transparent state, this contrast is often calculated for the wavelength corresponding to the maximum sensitivity of the human eye (550 nm). Memory effect is the time during which the electrochromic device retains its coloring, after stopping the application of a potential difference. Switching time is the time required for the material to change from coloring to discoloration, a time of about ten minutes being accepted for smart windows of about one square meter.The electrolyte can be liquid, solid (e.g. metal oxide such as Ta2O5), or in the form of a polymer membrane. Electrochromic materials can be organic or inorganic. Organic electrochromic materials are either conductive polymers (polyaniline PAN I, polypyrrole PPy, polythiophene PTh and their derivatives such as poly(3,4-(ethylenedioxy)thiophene) PEDOT), or viologen-based materials, or Prussian blue-based materials. Inorganic electrochromic materials can be cathodically colored (e.g. WO3, Nb2O5, M0O3, lnO2:Sn, V2O5, TiO2), or anodically colored (e.g. lrO. x , Li xCo02, MnO2, C03O4, NiO). A state of the art of inorganic electrochromic materials is presented by Granqvist (Handbook of inorganic electrochromic materials, ISBN 978-0-444-89930-9, 1995; Electrochromics for smart windows: oxide-based thin films and devices, Thin Solid Films, 2014).

[0016] Electrochromic materials can be distinguished based on their change of state. A first type of electrochromic material includes soluble molecules, particularly based on viologens, which change color when an electric current is applied, while remaining in the liquid state. A second type of electrochromic material includes soluble molecules that form a colored solid film when an electric current is applied. A third type of electrochromic material includes solid films, based on transition metal oxides (Transparent Conductive Oxides TCO, most often ln2C>3:Sn ITO or SnO2:P FTO), or based on Prussian blue or polymeric materials.

[0017] In recent decades, research and development activities on smart windows have focused on low-power electrochromic devices, taking advantage of active materials such as ion-inserted transition metal oxides (mainly WO3 and NiO x ), Prussian blue derivatives or conductive organic polymers. Several companies market electrochromic glazing, for example Saint-Gobain (SageGlass®), ChromoGenics AB, Pleotint LLC (Suntuitive self-tinting Glass), View Inc. (ViewGlass®).

[0018] Only a few systems are commercially available, however, due to their inability to simultaneously achieve durable, color-neutral, and fast switching with a wide dynamic range, at large scale, and at low cost.

[0019] In electrochromic glazings currently on the market, color tones are rarely neutral, and maximum opacity does not exceed 70%. For example, commercial WO3-based devices transmitting blue-green light exhibit moderate optical contrast (typically 40-60% for SageGlass® dynamic glass), without achieving total opacification, making them unsatisfactory for many applications. In addition, material degradation due to repeated ion intercalation is responsible for the persistence of some coloration in the bleached state.

[0020] In an attempt to obtain glazing with high optical contrast, less expensive, and without persistent coloring, it has been proposed, in the laboratory, to use reversible metal electrodeposition (RME) on the negative electrode.

[0021] According to the RME technique, optical tint is induced by the electrodeposition of a solid metal film on an electrode with a transparent semiconducting or conductive surface, by electrochemical reduction of a colorless metal ion present in the electrolyte. The inversion of the polarity allows the re-oxidation of the metal film and its dissolution in the electrolyte, which allows the window to regain the initial transparency of the electrode. Reference may be made, for example, to documents W02023 / 004973 (Hainan University, 2023), WO2022 / 221 094 (University of Nevada, 2022), EP3958051 (Stanley Electric Co, 2022), WO2021 / 1 55247 (University of Colorado, 2021), WO2019 / 018667 (Leland Stanford Junior University, 2019), US2005248825, W02004 / 099863.

[0022] The RME technique was initially proposed, in the laboratory, with the reversible electrodeposition of bismuth (Bi) on ITO (indium tin oxide) and FTO (fluorine-doped tin oxide) substrates, with a view to applications for smart absorbing windows.

[0023] Hernandez et al. proposed, in the laboratory, the reversible co-electrodeposition of copper and bismuth on ITO electrodes modified by platinum nanoparticles to achieve electrochromic windows with a maximum size of 225 cm 2(Electrolyte for improved durability of dynamic windows based on reversible metal electrodeposition, Joule, 2020). The durability of these systems was initially limited by the slow corrosion of the ITO support during cathodic cycles in acidic aqueous (pH = 2) and corrosive halide-based electrolytes. By adjusting the chemical nature of the electrolyte anion, it is possible, according to these authors, to carry out 10,000 RM E cycles over 20 days, without any sign of electrode degradation.

[0024] Tao et al. (Reversible Metal Electrodeposition Devices: An Emerging Approach to Effective Light Modulation and Thermal Management, 2021 Adv. Optical Mater. 9, 2001847, doi.org / 10.1002 / adom.202001847) present a state of the art of the RM E technique, and indicate that the deposited metal is silver, bismuth or copper, the most used electrodes being made of transparent conductive oxide, such as indium tin oxide ITO or fluorine-doped tin oxide FTO. According to these authors, the devices tested in the laboratory have dimensions that do not exceed, most often, a few square centimeters.

[0025] The invention relates to the reversible electrodeposition of a zinc film, on an electrode with a transparent semiconducting or conductive surface, for the manufacture of smart windows with electrochromic glazing.

[0026] The invention further relates to the ability of such a smart window with electrochromic glazing to temporarily and reversibly store electrical energy, like a battery. When the smart window is charged, the optical tint of the glazing of these windows is modified by the electrodeposition of a zinc film. When the window is discharged, the spontaneous re-oxidation of the zinc film returns the electrode to its transparent state, while releasing the electrical energy temporarily stored in the device, which can therefore be considered an electrochromic battery.

[0027] In most of the electrodeposition devices proposed in the prior art for the production of electrochromic glazing, the electrolyte is non-aqueous and corrosive.

[0028] Madu et al. ( Electrolytes for reversible zinc electrodeposition for dynamic windows J. Mat. Chem. 2021, A 9, 6297-6307) describe the use of transparent ITO electrodes pre-functionalized with platinum. A gel electrolyte is used (hydroxyethylcellulose 3%).

[0029] The method proposed by Madu et al., in this 2021 publication, has many drawbacks.

[0030] It is necessary to pre-functionalize the electrodes with platinum nanoparticles, with the resulting complexity and costs.

[0031] The electrolyte leading to the best performance produces a film containing a very high proportion of ZnO (about 90%).

[0032] In this electrolyte, cycling performance is modest, with accumulation of residual electrode coloration in its discharged state (initial transmittance of 85%, drops to 75% after 50 cycles and 18% after 250 cycles).

[0033] Using the same device as that proposed in the 2021 publication, Madu et al., in a 2022 publication, (Investigating Formate, Sulfate and Halide Anions in Reversible Zinc Electrodeposition Dynamic Windows, 2022, ACS Appl. Mater. Interfaces 14, 47810-47821), study the influence of the nature of the zinc salt counterion (electrolyte 0.5 M ZnSC>4, Zn(NOs)2, Zn(CIC>4), Zn Br2, ZnCI2) as well as the presence of formate (0.5 M HCOONa) on the efficiency of the reversible electrodeposition process, mainly in a three-electrode setup.

[0034] The process described by Madu et al., in this 2022 publication, has many drawbacks.

[0035] It is necessary to pre-functionalize the electrodes with platinum nanoparticles, with the resulting complexity and costs.

[0036] Electrochemical and optical reversibility degrades very rapidly, which the authors attribute to the precipitation of zinc hydroxides at the ITO electrode.

[0037] Islam et al. (Dynamic windows using reversible zinc electrodeposition in neutral electrolytes with high opacity and excellent resting stability, 2021, Adv. Energy Mater., 2100417) propose a symmetrical device with the use of an ITO electrode and a zinc grid. The aqueous electrolyte contains 0.5 M zinc acetate + 0.9 M KOI and 2% hydroxyethylcellulose, without then with 1 mM copper acetate.

[0038] The process proposed by Islam et al., in this 2021 publication, has several drawbacks. The cyclability is modest, with progressive residual coloration of the electrode in its discharged state (initial transmittance of 80%, drops to 65% after 100 cycles and about 10% after 250 cycles), which the authors attribute to the co-precipitation of zinc oxides (ZnO, Zn(OH)2) at the electrode, whose solubility is low and which accumulate during cycling. To address this problem in this state of the art, a redox-active additive (1 mM copper acetate) is added to the electrolyte, to assist zinc nucleation, which allows 2500 cycles to be achieved with a decrease in optical contrast from 80 to about 65%. However, the Cu additive 2+is incompatible with some electrochromic materials of the positive electrode, notably Prussian blue (Islam et al., Dual Tinting Dynamic Windows Using Reversible Metal Electrodeposition and Prussian Blue, 2019, ACS Appl. Mater. Interfaces, 1 1, 10043). Also, the chronoamperometric cycling used consumes electrical energy for both coloring and discoloration of the electrode, and is therefore not suitable for battery-type operation.

[0039] Objects of the invention

[0040] A first object of the invention is to provide a device and a method for reversible electrodeposition of a zinc film, on an electrode with a transparent semiconducting or conductive surface, for the manufacture of smart windows with electrochromic glazing, the electrodeposition being carried out directly on a commercial electrode, for example ITO or FTO.

[0041] A second object of the invention is to provide a device and a method for reversible electrodeposition of a zinc film, on an electrode with a transparent semiconducting or conductive surface, for the manufacture of smart windows with electrochromic glazing, with a non-corrosive aqueous electrolyte.

[0042] A third object of the invention is to provide a device and a method according to at least one of the above objects, in combination with temporary storage of electrical charge.

[0043] General presentation of the invention

[0044] For these purposes, the invention relates, according to a first aspect, to an electrochromic device such as an electrochromic window comprising: a device for reversible electrodeposition of a zinc Zn film at the negative electrode, to produce an electrochromic electrode at the negative electrode, the device comprising a negative electrode, a positive electrode, a volume arranged between the negative electrode and the positive electrode and containing an electrolyte with Zn ions 2+, the negative electrode having a transparent semiconducting or conductive surface, the transparent semiconducting or conductive surface of the negative electrode comprising a conductive or semiconducting material which is a transparent metal oxide, the electrolyte being aqueous or in gel form, the electrolyte containing ethylene glycol, polyethylene glycol or derivatives of these compounds, the pH of the electrolyte being between 4 and 7, a means for applying an imposed current between the negative electrode and the positive electrode, to pass at each galvanostatic step of the cycle, from a transparent state to a colored, or even advantageously opaque, state of the device, by homogeneous electro-deposition of the zinc film on the entire transparent semiconducting or conductive surface of the negative electrode, the device for reversible electro-deposition of the zinc film Zn making it possible to pass during each cycle, to a second step which follows the galvanostatic step,from the colored, or even advantageously opaque, state of the galvanostatic step to a transparent state of the entire transparent semiconducting or conducting surface by electro-dissolution of the zinc film in the electrolyte.,

[0045] The variations in state, from the transparent state to the colored state, or even advantageously opaque, as if it were a deposit of the Zinc metal, correspond to significant variations in transmittance, which remain during at least N cycles, for example greater than 30%, advantageously greater than 40%.

[0046] For example, with N = 600, a retention of the discharged electrode transmittance T633 > 80%, is associated with a coloration of the electrode which remains high.

[0047] According to various embodiments, the device has the following characteristics, possibly combined.

[0048] The electrolyte is without additives intended for pre-functionalization of the negative electrode, in particular for the nucleation and growth of the homogeneous deposition of the zinc film during electrodeposition on the transparent semiconductor or conductive surface.

[0049] The negative electrode is without pre-functionalization or chemical modification of its transparent semiconducting or conductive surface, in particular for the nucleation and growth of the homogeneous deposition of the zinc film during electrodeposition on its transparent semiconducting or conductive surface.

[0050] In some implementations, the transparent conductive or semiconductive material of the negative electrode comprises an indium tin-doped oxide ITO and the electrolyte is unbuffered.

[0051] In some implementations, the transparent conductive or semiconductive material of the negative electrode comprises a fluorine-doped tin dioxide FTO and the electrolyte is buffered.

[0052] In certain embodiments, the device is said to be asymmetrical, and the positive electrode is an electrochromic electrode with a transparent semiconducting or conducting surface, the means of applying an electric current imposed at each galvanostatic step of the cycle, between the negative electrode and the positive electrode, to pass from a discharged configuration to a charged configuration, making it possible to pass: at the transparent semiconducting or conducting surface of the negative electrode from a transparent state to a colored state, or even advantageously opaque, and at the transparent semiconducting or conducting surface of the positive electrode from a transparent state to a colored state, or even advantageously opaque, the passage from a charged configuration to a discharged configuration by circulation in a discharge circuit of a current from the positive electrode to the negative electrode,allowing to pass during the second stage of each cycle: for the transparent semi-conductor or conductive surface of the negative electrode from a colored state, or even advantageously opaque, to a transparent state; and for the transparent semi-conductor or conductive surface of the positive electrode from a colored state, or even advantageously opaque, to a transparent state.,

[0053] In certain embodiments, the asymmetric device has materials chosen at the positive electrode and at the negative electrode to deliver electrical energy in the discharge circuit, with a voltage greater than 0.5 V, advantageously greater than 1 V, the device being qualified in this case as an electrochromic battery. In various implementations, the device has the following characteristics, where appropriate combined.

[0054] The electrolyte contains a reagent capable of electrodepositing on the surface of the positive electrode and which allows it to change from a transparent state to a colored state, or even advantageously opaque.

[0055] The positive electrode has on its transparent surface an electrochromic material which allows it to pass from a transparent state to a colored state, or even advantageously opaque, by disinsertion of ions. The electrolyte contains one or more reagents capable of electroprecipitating on the transparent semiconducting or conducting surface of the positive electrode and which allows it to pass from a transparent state to a colored state, or even advantageously opaque. The transparent semiconducting or conducting surface of the negative electrode is nanostructured by a thin film deposited on the surface. The surface of the positive electrode is nanostructured by a thin film deposited on the surface.

[0056] The nanostructured thin film is a semiconducting or conducting metal oxide, such as: ITO, FTO, TiOs, SnOs.

[0057] The electrolyte includes Mn ions 2+ and the positive electrode involves the couple Mn 2+ / MnC>2 during charging and discharging, with MnOs being deposited by electrodeposition on its transparent surface, for example based on ITO, during charging.

[0058] The positive electrode is coated on its transparent surface during discharge with Prussian white and during charge with Prussian blue. The electrolyte contains Br ions and a quaternary amine. The device is said to be symmetrical and the positive electrode is a grid comprising zinc opposite the negative electrode. The electrolyte is free of organic Bronsted acid. The electrolyte comprises zinc acetate or zinc chloride, for example the electrolyte comprises between 0.1 and 1 mol per liter of zinc acetate, advantageously 0.5 mol per liter. The electrolyte comprises glyceroL The electrolyte contains glucose. The electrolyte is buffered, preferably with an acetate buffer. The pH of the electrolyte is between 5 and 6.

[0059] The electrolyte comprises 5 to 30% PEG by volume of the electrolyte, preferably between 5% and 15%. The electrolyte comprises 10 to 70% glycerol by volume of the electrolyte, preferably between 40% and 70%.

[0060] Polyethylene glycol has the formula H(OCH2CH2) n OH, with n between 1 and 200, and preferably n between 1 and 30.

[0061] The electrolyte comprises glycerol and PEG, advantageously with a glycerol / PEG ratio greater than 2.

[0062] The transparent surface S of the negative electrode and the transparent surface S' of the positive electrode are equal and opposite, allowing a uniform variation in transmittance.

[0063] The invention is based on various aspects, including: the compatibility of the electrolytes and protocols developed with transparent current collectors (negative electrode) such as ITO and FTO; the absence of pre-functionalization of the transparent current collectors by metallic particles (e.g. Pt) that can serve as nucleation sites; the use of a non-corrosive aqueous electrolyte (slightly acidic to neutral pH), containing an additive (notably PEG) to improve not only the nucleation / growth of the zinc film and its homogeneous deposition but also the coulombic efficiency (CE); the use of an additive (notably glycerol) to improve the coulombic efficiency and long-term cyclability, and to maintain good transparency of the discharged state, while limiting self-discharge in open circuit;the implementation of galvanostatic cycling (chronopotentiometric technique with imposed current) compatible with a battery application; the use of a buffered aqueous electrolyte, compatible with the operation of an electron-proton coupled electrochromic process at the positive electrode; the use of an unbuffered aqueous electrolyte, compatible with the operation of an insertion electrochromic process at the positive electrode; the compatibility of the electrolytes and protocols developed with electrochromic positive electrode materials for the assembly of bi-functional devices combining charge storage and electrochromism. Description of embodiments;

[0064] Other objects and advantages of the invention will appear in the light of the description of embodiments, given below with reference to the appended drawings in which:

[0065] - Figure 1 is a schematic diagram of reversible opacification of an electrode with a transparent semiconducting or conductive surface by electrodeposition / electrodissolution of a zinc film;

[0066] - Figure 2 is a schematic representation of a symmetrical electrochromic window exploiting the reversible electrodeposition of zinc on an electrode with a transparent semiconducting or conductive surface, coupled to a positive zinc electrode;

[0067] - Figure 3 is a schematic representation of an asymmetric electrochromic window exploiting the reversible electrodeposition of zinc on an electrode with a transparent semiconducting or conductive surface, coupled to a positive electrochromic electrode involving either the Mn couple 2+ / MnC>2 is a Prussian blue film;

[0068] - Figure 4 is a schematic representation of an asymmetric electrochromic device, of the zinc / Prussian blue type, the device being shown in charge mode, on the left of the figure

[0069] 4, and in discharge mode, on the right of figure 4;

[0070] - Figure 5 is a schematic representation of an asymmetric electrochromic device, of the zinc / MnOs type, the device being represented in electrodeposition charge mode, on the left of the figure

[0071] 5, and in electro-dissolution discharge mode, on the right in figure 5;

[0072] - Figure 6 is a set of three curves showing the galvanostatic cycling, the change in transmittance at 633 nm (T633) during the first 10 cycles and the coulombic efficiency (CE) for 1250 consecutive cycles for a symmetrical device comprising an ITO electrode, a zinc frame and an electrolyte containing 0.5M Zn acetate + 0.9M KCl + 10% PEG-200 + 50% Glycerol, the cycling intensity being 1 mA / cm 2 , the fixed charge being at 100 mC / cm 2 ; - Figure 7 is a set of curves showing (left) the galvanostatic cycling and (right) the variation in transmittance between the initial state (solid curve) and the charged / colored state (dotted curve) for an asymmetric device which comprises an FTO electrode, a nanostructured ITO electrode, and an electrolyte consisting of 0.4M Zn acetate + 0.1M Mn acetate + 1M acetate buffer + 10% PEG-200 of pH = 5.2, the cycling intensity being 1 mA / cm 2, the fixed charge being at 100 mC / cm 2 ;

[0073] - Figure 8 is a set of three curves showing (left) the galvanostatic cycling, (center) the change in transmittance at 633 nm (T633) during the first 15 cycles and (right) the coulombic efficiency (CE) for 8 consecutive cycles for an asymmetric device which comprises an ITO electrode, a nanostructured ITO electrode containing a Prussian white deposit, and an electrolyte consisting of 0.5M Zn acetate + 0.9M KCl + 5%PEG + 5M Glucose of pH = 5.2, the cycling intensity being 1 mA / cm 2 , the charge controlled by a voltage limit value set at 1.65 V;

[0074] - Figure 9 is a schematic diagram of a variant of the asymmetric device with sacrificial zinc electrode and described in Example 5. The device is shown in normal cycling mode on the left, and in cathode regeneration mode on the right;

[0075] - Figure 10 is a set of three curves showing (top left) the galvanostatic cycling, (bottom) the transmittance variation at 633 nm and (top right) the coulombic efficiency for a variant of the asymmetric device comprising an FTO electrode, a nanostructured ITO electrode and a sacrificial zinc electrode, an electrolyte consisting of 0.4M Zn acetate + 0.1M Mn acetate + 1M acetate buffer + 10% PEG-200 of pH = 5.2, the cycling intensity being 1 mA / cm 2 , the charge fixed at 50 mC / cm 2 .

[0076] Figure 1 is a schematic diagram of reversible opacification of a device 1 such as an electrochromic window, comprising a transparent electrode 2, based on ITO or FTO.

[0077] In Figure 1, the circles symbolize the chemical species contained in an electrolyte, and in particular the Zn ions 2+. Device 1 is shown schematically in a transparent discharged state, on the left in Figure 1, and in a charged state, in which device 1 is more or less opaque, on the right in Figure 1.

[0078] In the charged state, a film 3 of zinc Zn is deposited on the transparent semiconductor or conductive surface electrode 2, and a large part of the light incident on the device 1 is absorbed and reflected, and does not pass through the device 1.

[0079] In the discharged state, light, particularly in the visible wavelengths, passes through the transparent semiconductor or conductive surface electrode 2 and the electrolyte 4.

[0080] Symmetrical device

[0081] Figure 2 shows a symmetrical electrochromic window 1, exploiting the reversible electrodeposition of zinc on an electrode with a transparent semiconducting or conductive surface, coupled to a positive zinc electrode.

[0082] Window 1 comprises an electrode 2, forming the negative electrode, on which the zinc is reversibly electrodeposited.

[0083] Electrode 2 comprises a transparent conductive metal oxide film, deposited on a transparent inert support, for example glass.

[0084] In some implementations, electrode 2 is based on ITO.

[0085] For example, electrode 2 is formed from a transparent conductive material marketed by the company Solems, under the reference ITO SOL 12 / 1 .1 , this material comprising a layer of indium oxide doped with tin ITO deposited on a soda-lime glass support, by physical vapor deposition PVD. The thickness of the glass support is 1 .1 mm. The thickness of the ITO layer is approximately 370 nm . The square resistance is between 8 and 12 £) / □. During the tests, electrode 2 is a square with sides of 2.5 cm.

[0086] In other implementations, electrode 2 is based on FTO.

[0087] For example, electrode 2 is formed from a transparent conductive material marketed by the company Solems, this material comprising a layer of fluorine-doped tin oxide FTO, deposited on a soda-lime glass support, by chemical vapor deposition CVD. The thickness of the glass support is for example 1.1 mm. The thickness of the FTO layer is between 80 and 600 nm. The square resistance is between 8 and 12 £) / □. During the tests, electrode 2 is a square with sides of 2.5 cm.

[0088] Window 1 comprises a positive zinc electrode 5, a generator 6 connecting electrode 2 and counter-electrode 5.

[0089] In this symmetrical device, the positive electrode 5 is in the form of a zinc grid.

[0090] Window 1 includes 7 glazing.

[0091] Between the electrode 2 forming the negative electrode and the positive electrode 5, the window 1 comprises a first separator 8.

[0092] Between the positive electrode 3 and the glazing 4, the window 1 comprises a second separator 9.

[0093] The separators 8, 9 ensure separation between the two electrodes 2, 5.

[0094] In certain implementations, the first separator 8 and the second separator 9 are substantially identical, for example produced in the form of a silicone frame, with a thickness of between 1.5 and 3 mm, for example of the order of 1.5 mm.

[0095] The separators 8, 9 delimit an internal volume containing an aqueous, non-corrosive electrolyte 4.

[0096] During the tests carried out, the volume of the electrolyte is of the order of 1.2 mL, the size of the electrodes 2, 5 being 2.5 x 2.5 cm 2This dimension of the electrodes was chosen for comparison purposes with the results of the devices proposed in the laboratory tests for the devices of the prior art.

[0097] Advantageously, when the electrode 2 is made of ITO, the aqueous electrolyte 4 does not contain or contains only very little Bronsted acid, with pKa < 5.

[0098] In the state of the art, to avoid the precipitation of zinc hydroxides, reported to be responsible for the progressive coloration of the ITO electrode in unbuffered aqueous electrolytes, it has been proposed to use a weakly acidic buffered solution in which it is no longer possible to generate a pH gradient.

[0099] The inventors found that it is preferable not to use a buffered aqueous electrolyte in the presence of ITO because the presence of a Bronsted acid such as acetic acid (pKa = 5) induces a damaging reduction of the ITO, which is moreover at a potential thermodynamically very close to that of the reduction of Zn ions. 2+ This process being hardly reversible, this has the effect of inducing a progressive and irreversible coloration of the electrode.

[0100] Advantageously, electrolyte 4 contains polyethylene glycol PEG. This arrangement allows the formation of a homogeneous and uniform zinc deposit.

[0101] For testing, window 1 was prepared as follows.

[0102] Firstly, the electrodes 2, 5 are cleaned chemically, for a period of five minutes, using ultrasound, successively in dichloromethane, acetone and then ethanol.

[0103] The electrodes 2, 5 are then dried, then a copper adhesive tape 10 is affixed to the periphery of the electrodes 2, 5.

[0104] The 10 copper tape is then covered with an insulating varnish.

[0105] The transparent semiconducting or conductive surface electrode 2 is then assembled in a window device 1, and associated with a zinc counter-electrode 5.

[0106] The symmetrical device obtained (ITO / Zn or FTO / Zn) forms a window 1, exploiting the reversible electrodeposition of zinc at the two electrodes 2, 5.

[0107] The performance of a window 1 as shown in figure 2 will be illustrated by examples.

[0108] Example 1 (figure 6)

[0109] In the case of using a transparent ITO-based electrode 2, window 1 forms a symmetrical ITO / Zn device, and exhibits the best performance when using an aqueous electrolyte 4 containing 0.5 M Zn(acetate)s + 0.9 M KCI + 10%(vol) PEG-200 + 50%(vol) glycerol (pH = 5.9) and galvanostatic cycling at 1 mA / cm 2 for a maximum deposited charge of 100 mC / cm 2 .

[0110] Under these conditions, 1,250 cycles were performed, with an average CE coulombic efficiency of 98 ± 0.7%.

[0111] The transmittance variation (633 nm) associated with zinc electrodeposition is initially 60% (decrease from 80% to 20%), then stabilizes at 50%, as measured for cycles 256, 620 and 716.

[0112] Subsequent cycles show a progressive degradation of the CE (86% after 1500 cycles). A slight decrease in the transmittance of the discharged state (without zinc deposit) is observed during cycling, ranging from 80% to 61% for cycle 71 6.

[0113] The potentiometric charge / discharge curves show a low hysteresis of 84 mV for the first cycle, which increases slightly during cycling, rising to 110 mV for cycle 71 6, then to 163 mV for cycle 1200.

[0114] These results are significantly better than those published for example by Islam et al. in 2021 (Dynamic windows using reversible zinc electrodeposition in neutral electrolytes with high opacity and excellent resting stability, 2021, Adv. Energy Mater., 2100417). In these prior art tests, the transmittance properties of the ITO electrode degrade rapidly during chronoamperometric cycling, decreasing from 80% to < 10% after 250 cycles. An improvement was observed with the addition of 1 mM copper (II) acetate. The use of this electrolyte (0.5 M Zn(acetate)s + 0.9 M KCI + 1 mM Cu(acetate)2 + 2% hydroxyethylcellulose) in our operating conditions of the present invention shows that this electrolyte does not lead to satisfactory results (25 cycles were carried out with an average CE coulombic efficiency of 62%, while the variation in transmittance (633 nm) associated with the electrodeposition of zinc, initially 34% (decrease from 46% to 13%), decreases rapidly to reach a value of less than 2% from the 5th cycle).

[0115] Example 2

[0116] In the case of using a transparent electrode 2 made of FTO, window 1 forms a symmetrical FTO / Zn device with the best performance when using an aqueous electrolyte 4 containing 0.5 M Zn(acetate)s + 1 M acetate buffer + 10%(vol) PEG-200 + 50%(vol) glycerol (pH = 5.2) and galvanostatic cycling at 1 mA / cm 2 for a maximum deposited charge of 50 mC / cm 2 .

[0117] Under these conditions, 1320 cycles were carried out, with an average coulombic efficiency of 96.5 ± 1%.

[0118] The transmittance variation (633 nm) associated with zinc electrodeposition is initially 45% (decrease from 85% to 40%), then quickly stabilizes at 40% as measured for the 1315 cycle. The transmittance of the discharged state (without zinc deposition) remains very stable during cycling, with a transmittance loss of only 6% between the initial state and the 131 5 cycle.

[0119] The potentiometric curves show a hysteresis of 270 mV for the first cycle, which increases during cycling, rising to 410 mV for cycle 1315.

[0120] Asymmetric device

[0121] We now refer to Figure 3, which schematically illustrates an asymmetric electrochromic window 11, exploiting the reversible electrodeposition of zinc on a transparent electrode 12, forming the negative electrode, coupled to a positive electrochromic electrode 15.

[0122] The negative electrode 1 2 and the positive electrode 1 5 are connected by a charging circuit, on which is placed a means of producing electrical energy, switchable as required with a discharge circuit comprising one or more resistive systems. For testing, a galvanostat makes it possible to control the electrical intensity injected into the charging and discharging circuit.

[0123] The electrode 12 comprises a transparent conductive metal oxide film, deposited on a transparent inert support, for example glass.

[0124] In some implementations, electrode 12 is ITO-based.

[0125] For example, electrode 1 2 is formed from a transparent conductive material marketed by the company Solems, under the reference ITO SOL 12 / 1 .1 , this material comprising a layer of indium oxide doped with tin ITO deposited on a soda-lime glass support, by physical vapor deposition PVD. The thickness of the glass support is 1 .1 mm. The thickness of the ITO layer is approximately 370 nm . The square resistance is between 8 and 12 £) / □. During the tests, electrode 2 is a square with sides of 2.5 cm.

[0126] In other implementations, the electrode 1 2 is based on FTO.

[0127] For example, electrode 1 2 is formed from a transparent conductive material marketed by the company Solems, this material comprising a layer of fluorine-doped tin dioxide FTO, deposited on a soda-lime glass support, by chemical vapor deposition CVD. The thickness of the glass support is for example 3.1 mm. The thickness of the FTO layer is between 80 and 600 nm. The square resistance is between 8 and 12 £) / □. During the tests, electrode 1 2 is a square with sides of 2.5 cm.

[0128] Advantageously, the electrode 15 comprises a transparent conductive metal oxide film, deposited on a transparent inert support, for example glass, on which a transparent and conductive nanostructured ITO film has been deposited. During the tests, the electrode 15 comprises a nanostructured ITO film with a thickness of between 1 and 1.7 μm deposited under vacuum on a commercial flat ITO electrode.

[0129] Between the negative electrode 12 and the positive electrode 15, the window 11 comprises a separator 18.

[0130] In some implementations, the separator 18 is made in the form of a silicone frame, with a thickness of between 1.5 and 3 mm, for example of the order of 1.5 mm. In other implementations, the separator 18 is gas-tight and made in the form of a butyl rubber frame, with a thickness of between 1.5 and 3 mm, for example of the order of 2 mm.

[0131] Between the negative electrode and the positive electrode extends an internal volume containing a non-corrosive, aqueous electrolyte.

[0132] Window 11 is advantageously capable of delivering a voltage during the bleaching process.

[0133] In certain implementations, the positive electrochromic electrode 15 involves the Mn couple 2+ / MnC>2, the transition from a transparent state to a colored state for window 1 1 corresponding to a charge of the battery, according to the following reaction:

[0134] Mn 2+ + 4A- + Zn 2+ -> MnO2+ Zn + 4AH where AH / A- corresponds to a Bronsted acid / base pair. In other implementations, the electrochromic positive electrode 1 5 involves a Prussian white-based film, the transition from a transparent state to a colored state for the window 1 1 corresponding to a charge of the battery, according to the following reaction:

[0135] Battery charging is reversible. The transition from the colored / charged state to the transparent / discolored state of window 1 1 corresponds to the reverse reactions.

[0136] For the tests, the window 11 was prepared as follows. First, the electrode 12 is chemically cleaned for a period of five minutes using ultrasound, successively in dichloromethane, acetone and then ethanol. First, the nanostructured electrode 15 is chemically cleaned for a period of fifteen minutes and at 50°C, successively in dichloromethane, acetone and then ethanol. The electrodes 12, 15 are then dried, and then a copper tape 20 is glued to the periphery of the electrodes 12, 15.

[0137] The copper tape 20 is then covered with an insulating varnish.

[0138] The negative electrode with transparent semiconducting or conductive surface 1 2 is then assembled in a window device 1 1 , and associated with the positive electrode 1 5, an electrical connection connecting the two electrodes, a galvanostat 40 on this circuit makes it possible to control the electrical intensity injected into the charging and discharging circuit of the tests.

[0139] The performance of a 1 1 window as shown in Figure 3 will be illustrated by examples.

[0140] Example 3

[0141] Window 11 comprises a nanostructured ITO electrode 15 covered with a thin film of Prussian white (PW), in which potassium ions reversibly disintegrate, and an unbuffered electrolyte, the negative electrode 12 being made of ITO on which zinc is reversibly electrodeposited from Zn 2+ in solution.

[0142] The composition of electrolyte 14 is as follows: 0.5M Zn(OAc)s + 0.9M KCI + 5%PEG + 50% glyceroL

[0143] The voltage delivered to the discharge is 1.1 2 V

[0144] The amount of charge stored is 85 mC / cm 2

[0145] The initial transmission variation at 633 nm is 58% (change from 58% to 0%, total opacification of the device).

[0146] Cyclability: 25 cycles with CE = 98.5% ± 0.8

[0147] Alternatively, the glycerol additive can be replaced by glucose (5 M concentration), see Figure 8. Window 1 1 implements two conversion reactions, with on one side a negative electrode 1 2 based on ITO on which zinc is reversibly electrodeposited from Zn 2+ in solution, and on the other a positive electrode 1 5 on which MnOs is reversibly electrodeposited from Mn 2+ in solution.

[0148] The MnOs electrodeposition reaction is advantageously carried out in a buffered electrolyte containing Mn 2+ , which has the advantage of avoiding the formation of pH gradients at the interface and therefore allowing perfect reversibility of the process.

[0149] Electrolyte 14 has the following composition: 0.4M Zn(OAc)s + 0.1 M Mn(OAc)2 + 1 M acetate buffer + 10% PEG-200 pH = 5.2

[0150] The delivered voltage is 1.6 V.

[0151] The amount of charge stored is 50 mC / cm 2 .

[0152] The initial transmittance variation at 633 nm is 50% (change from 65% to 15%).

[0153] Cyclability: 50 cycles with CE = 94% ± 0.5

[0154] Different implementation variants can be implemented.

[0155] In the embodiment of Figure 4, an electrochromic device comprises two transparent electrodes, based on ITO.

[0156] A buffered aqueous electrolyte, containing Zn ions 2+ , is contained in an internal space delimited by the two electrodes, and joints. The positive electrode coated, on its face facing the electrolyte, with a transparent film based on nanostructured ITO, containing Prussian white.

[0157] The movements of the ions are represented in Figure 4, when the device is in charge mode (left of Figure 4), or in discharge mode (right of Figure 4), a circuit connecting the two electrodes. A zinc deposit is obtained on the negative electrode, a Prussian blue forming on the positive electrode.

[0158] In the embodiment of Figure 5, an asymmetric electrochromic device is implemented, the device comprising two transparent electrodes, one based on FTO, the other based on ITO.

[0159] A buffered aqueous electrolyte, comprising Zn ions 2+ and Mn ions2+ , is contained in an internal space delimited by the two electrodes, and joints. One of the two electrodes, based on ITO, is coated, on its face facing the electrolyte, with a transparent film based on nanostructured ITO.

[0160] The ion movements are shown in Figure 5, when the device is in charge mode, electrodeposition mode (left of Figure 5), or in electro-dissolution discharge mode (right of Figure 5).

[0161] A zinc deposit is obtained on the negative electrode based on FTO, and a MnOs deposit is obtained on the positive electrode based on nanostructured ITO.

[0162] In some implementations, the sulfolane additive can be added to the electrolyte, the results being however inferior, for the FTO electrode, to those obtained by the addition of polyethylene glycol PEG.

[0163] Tests were carried out to assess reproducibility, as well as the effect of different parameters.

[0164] The tables below present the test conditions for a symmetrical FTO (negative electrode) - Zn (grid, positive electrode) type assembly, of the type shown in figure 2.

[0165] In the symmetrical setup tests, the electrolyte comprises 0.5 mol / L of Zn(OAc)s.

[0166] The electrolyte contains 1 mol / L acetate buffer except in test 8 where the electrolyte is not buffered.

[0167] The pH of the electrolyte is between 5.02 and 6.34.

[0168] Galvanostatic cycling is performed in most tests at a rate of 1 mA / cm 2 , for a deposited charge of 50 mC / cm 2 .

[0169] Comparative tests are carried out, in which the electrolyte does not contain polyethylene glycol (tests 1 and 12).

[0170] In the tables below, the transmittance at 633 nm of the discharged device is denoted T633 (%) and its variation during a charge is denoted AT633 (%), the average coulombic efficiency is denoted CE (%). The initial transmittance of the device at 633 nm is 82 ± 7%.

[0171] The initial values ​​and the values ​​at 100, 400 and 1000 cycles (or for the cycle whose number is specified in parentheses) are shown in the table below.

[0172] The addition of PEG-200 (runs 2 to 11) is associated with an improvement in electrode coloration during charging (initial AT633) and in the CE coulombic efficiency. The addition of glycerol (runs 9, 10 and 11) is associated with very good results, with a high CE coulombic efficiency and an initial transmittance variation (initial AT633) of 50 ± 1% for a charge of 50 mC / cm 2, with a conservation of the transmittance of the discharged electrode (T633 > 85%) after 682 or 1000 cycles, associated with a coloration of the electrode which remains high.

[0173] The tables below present the test conditions for a symmetrical assembly of the ITO (negative electrode) - Zn (grid, positive electrode) type, of the type shown in figure 3.

[0174] In the symmetrical setup tests, the electrolyte comprises 0.5 mol / L of Zn(OAc)s, except for test 27 in which zinc chloride ZnCls is used.

[0175] The electrolyte does not contain Bronsted acid with pKa < 5, except in tests 28 and 29.

[0176] The pH of the electrolyte is between 4.83 and 6.46.

[0177] Galvanostatic cycling is performed in most tests at a rate of 1 mA / cm 2 , for a deposited charge of 100 mC / cm 2 .

[0178] Comparative tests are carried out, in which the electrolyte does not contain polyethylene glycol (tests 13 and 26). In the tables below, the transmittance at 633 nm of the discharged device is denoted T633 (%) and its variation during a charge is denoted AT633 (%), the average coulombic efficiency is denoted CE (%). The initial transmittance of the device at 633 nm is 78 ± 2%.

[0179] The initial values ​​and the values ​​at 100, 400 and 1000 cycles (or for the cycle whose number is specified in parentheses) are shown in the table below. The addition of PEG-200 (runs 14–25 and 27–29) is associated with improved electrode coloration upon charging (initial AT633) and CE coulombic efficiency.

[0180] The tests show the beneficial effect of the addition of glycerol (tests 20 to 29), in particular for the electrolyte conditions of tests 21 to 23 which lead to very good cyclability (high coulombic efficiency CE over 1000 cycles and high transmittance variation after 620-700 cycles).

[0181] Example 5

[0182] A variant of the symmetrical devices consists of producing a device as described previously, but which incorporates a sacrificial zinc electrode.

[0183] Initially, the sacrificial electrode is not connected to the circuit, and galvanostatic cycling applies to the two transparent electrodes located opposite each other.

[0184] During this cycling, if a color accumulates at an electrode, transparency can be regenerated by connecting this electrode (which has become colored) to the sacrificial electrode and applying a current to electrodissolve the material accumulated at the transparent electrode.

[0185] As a proof of concept, a 3-electrode FTO / Zn / ITO1 smart window was constructed, incorporating a zinc frame as a sacrificial anode.

[0186] The following sequential protocol was used:

[0187] (i) The ITO1 cathode was first coupled to the FTO anode and subjected to a series of 20 galvanostatic charge / discharge cycles with a charge rate fixed at 1 mA / cm 2 and a charge fixed at 0.05 C / cm 2 ;

[0188] (ii) the FTO anode was interchanged with the Zn frame anode, and the device was subjected to two successive steps of galvanostatic discharge regeneration, first at 1 mA / cm2 then at 0.3 mA / cm 2 .

[0189] This two-step process was repeated 5 times, always every 20 cycles, for a total of 100 charge / discharge cycles.

[0190] Advantages of the invention

[0191] The invention has numerous advantages. The invention provides symmetrical electrochromic devices (in particular by coupling with a semi-transparent zinc grid) or asymmetrical ones (in particular by coupling with a positive electrochromic electrode to combine electrochromism and reversible charge storage).

[0192] Reversible electroplating allows high performance to be achieved compared to the use of conventional electrochromic materials.

[0193] Electrodeposited metal films have high coloring efficiency, which results in high opacity at thicknesses of only a few tens of nanometers.

[0194] Electrodeposited metal films have light reflectance properties, redirecting heat away from the building, which can lead to greater energy savings than prior art electrochromic devices based on light absorption.

[0195] Among the metal cations that can be electrodeposited in the form of a metal film, the Zn ion 2+ is particularly interesting in several respects.

[0196] First, it is abundant, inexpensive, and non-toxic.

[0197] Second, the Zn couple 2+ / Zn is associated with a potential of -0.76 V vs NHE, which allows it to operate in aqueous media while presenting a high charge storage capacity (volumetric: 5855 mAh / cm 3 ; gravimetric: 820 mAh / g).

[0198] The deposition of metallic zinc is carried out reversibly, directly on an electrode with a transparent semiconductor or conductive surface, without requiring functionalization of the electrode, which can be a commercial ITO or FTO electrode.

[0199] The absence of pre-functionalization of transparent current collectors by metallic particles (e.g. platinum) allows a significant reduction in costs.

[0200] The aqueous electrolyte also does not contain any metal ion salts (such as Cu salts 2+ or Ag +) as is the case in the state of the art and which are used to form metal alloys with zinc to promote its nucleation. These additives based on metal ion salt are also incompatible with certain materials used at the positive electrode of asymmetric devices. A complex manufacture of semi-transparent zinc grids used in the prior art is avoided, the reversible electrodeposition of a metallic zinc film being obtained directly on an electrode with a commercial transparent semiconducting or conductive metal oxide surface (typically ITO or FTO).

[0201] The development of reversible zinc electrodeposition on FTO allows the use of buffered (or acidic) electrolytes, in which rapid degradation of ITO is observed.

[0202] The use of a non-corrosive aqueous electrolyte (slightly acidic to neutral pH), containing an additive (PEG), improves not only the nucleation / growth of the zinc film and its homogeneous deposition, but also improves the coulombic efficiency.

[0203] The use of glycerol improves coulombic efficiency, long-term cyclability and maintains good transparency of the discharged state, while limiting self-discharge.

[0204] The combination of the use of glycerol and polyethylene glycol PEG with transparent electrodes allows high performance to be achieved.

[0205] The invention proposes bifunctional smart windows, coupling electrochromism and reversible charge storage. These windows thus have the capacity to become colored when a battery is charged, and to return to a completely transparent state when the temporarily stored energy, Le., is released during discharge.

[0206] The invention finds application in the field of civil engineering, and can also find application in the construction of vehicles, for example land vehicles, in particular for the interiors of motor vehicles.

[0207] Advantageously, the windows implement galvanostatic cycling (chronopotentiometric technique), making it possible to deliver a constant current, unlike prior art tests using cyclic voltammetry or chronoamperometry.

[0208] FTO is advantageously combined with the use of a buffered aqueous electrolyte, which offers the possibility of exploiting the reversible electrodeposition of MnOs and makes it possible to avoid the formation of Zn or ZnO hydroxides, via the control of the pH at the interfaces.

[0209] In the state-of-the-art zinc-based systems combining electrochromism and reversible charge storage, a device is proposed comprising a single electrode having electrochromic properties, the negative electrode being a zinc grid or plate and not used for electrochromism.

[0210] Furthermore, by associating two electrochromic electrodes positioned opposite each other, face to face, in a symmetrical manner, the asymmetrical devices proposed by the invention allow:

[0211] (i) greater opacification over a wide range of energy density;

[0212] (ii) more homogeneous and reversible colorations by optimizing the field lines within the device, and

[0213] (iii) reflective properties at the negative electrode, limiting absorption phenomena and therefore an increase in local temperature.

[0214] The electrochromic windows proposed by the invention operate in mild aqueous electrolytes, composed of abundant and non-toxic chemical constituents. The performance of these windows is improved compared to the state of the art, particularly in terms of reversibly stored energy density and optical contrast.

[0215] The invention finds application in the field of intelligent windows or glazing, capable of reversibly becoming opaque, and possibly of temporarily storing electrical energy.

[0216] The invention provides suitable compositions of non-corrosive aqueous electrolytes, allowing the uniform and reversible electrodeposition of a zinc film on a commercial transparent semiconductor or conductive surface electrode, consisting of a transparent conductive metal oxide film deposited on a transparent inert support (typically glass), and compatible with the operation of smart windows combining charge storage and electrochromism.

[0217] In conclusion, the invention proposes asymmetric devices, associating a transparent negative electrode with a positive electrode made of an electrochromic material, so as to be able to deliver a direct current, during the discharge / discoloration process.

[0218] The invention also proposes symmetrical devices, combining a transparent negative electrode with a positive electrode consisting of a semi-transparent zinc grid. These devices exploit the reversible electrodeposition of zinc at both electrodes. They therefore do not allow energy to be stored, but nevertheless remain interesting for electrochromic aspects due to the low cost of zinc, its high opacity and the low energy cost linked to the coloring / discoloration process.

Claims

AMENDED CLAIMS received by the International Bureau on July 22, 2024 (22.07.2024) 1. Electrochromic device (1, 11), such as an electrochromic window comprising: - a device for reversible electrodeposition of a zinc Zn film at the negative electrode, to produce an electrochromic electrode at the negative electrode, the device comprising a negative electrode, a positive electrode, a volume arranged between the negative electrode and the positive electrode and containing an electrolyte (4, 14) with Zn ions 2+, the negative electrode has a transparent semiconducting or conductive surface, the transparent semiconducting or conductive surface of the negative electrode comprising a conductive or semiconducting material which is a transparent metal oxide, the electrolyte (4, 14) being aqueous or in gel form, the electrolyte (4, 14) containing ethylene glycol, polyethylene glycol or derivatives of these compounds, the pH of the electrolyte (4, 14) being between 4 and 7, - a means for applying a current which is imposed between the negative electrode and the positive electrode, in order to control the electrical intensity injected into the circuit, this current making it possible to pass at each galvanostatic step of the cycle, from a transparent state to a colored state of the device, by homogeneous electro-deposition of the zinc film on the entire transparent semi-conductor or conductive surface of the negative electrode, and from a transparent state to a colored state on the transparent semi-conductor or conductive surface of the positive electrode, the device for reversible electro-deposition of the zinc Zn film making it possible to pass during each cycle, at a second step which follows the galvanostatic step, from the colored state of the galvanostatic step to a transparent state of the entire transparent semi-conductor or conductive surface by electro-dissolution of the zinc film in the electrolyte (4, 14), AMENDED SHEET (ARTICLE 19) and wherein the negative electrode is without pre-functionalization or chemical modification of its transparent semiconducting or conductive surface in order to promote the nucleation and homogeneous growth of the deposition of the zinc film during the electrodeposition on its transparent semiconducting or conductive surface, the electrochromic device (1 1) being said to be asymmetric, the positive electrode being an electrochromic electrode with a transparent semiconducting or conductive surface, the asymmetric device comprising a sacrificial zinc electrode, which makes it possible to regenerate the initial transparency of the device after cycling via an electrical coupling to the negative or positive electrode, for example in the event of accumulation of a color at one of the two transparent electrodes, the transition from a charged configuration to a discharged configuration by circulation in a discharge circuit of a current from the positive electrode to the negative electrode,allowing to pass during the second stage of each cycle: for the transparent semiconducting or conducting surface of the negative electrode from a colored state to a transparent state; and for the transparent semiconducting or conducting surface of the positive electrode from a colored state to a transparent state., 2. Electrochromic device according to claim 1, characterized in that the electrolyte is without the addition of additives which are metal ions to promote the pre-nucleation of the zinc film during electrodeposition on the transparent semiconducting or conducting surface on the negative electrode.

3. Electrochromic device according to one of claims 1 to 2, characterized in that: the negative electrode is without pre-functionalization or chemical modification of its transparent semiconducting or conducting surface, by metallic particles such as nanoparticles of platinum, silver, copper, bismuth, and AMENDED SHEET (ARTICLE 19) the electrolyte being without the addition of other metal ions, and in particular without the addition of other metal ions such as bismuth 2+ or copper 2+ ions intended for pre-nucleation of the zinc film during electrodeposition on the transparent semiconducting or conducting surface on the negative electrode.

4. Electrochromic device according to one of claims 1 to 3, characterized in that the transparent conductive or semi-conductive material of the negative electrode comprises a tin-doped indium oxide (or ITO) and the electrolyte (4, 14) is unbuffered.

5. Electrochromic device according to one of claims 1 to 3, characterized in that the transparent conductive or semiconductive material of the negative electrode comprises a fluorine-doped tin dioxide (or FTO) and the electrolyte (4, 14) is buffered.

6. Electrochromic device according to any one of claims 1 to 5, characterized in that the imposed current has values between 0.1 and 10 mA / cm 2 and in that the potential measured following the passage of the imposed current between the two electrodes is between + 1 and +2 V.

7. Electrochromic device (11) according to any one of claims 1 to 6, characterized in that the asymmetrical device has materials chosen at the positive electrode and at the negative electrode to deliver electrical energy in the discharge circuit, with a voltage greater than 0.5 V, advantageously greater than 1 V, the device being qualified in this case as an electrochromic battery.

8. Electrochromic device (1, 11) according to any one of claims 1 to 6, characterized in that the electrolyte contains a reagent capable of electrodepositing on the surface of the positive electrode and which allows it to pass from a transparent state to a colored state.

9. Electrochromic device (1, 11) according to claim 7 or 8, characterized in that the positive electrode has on its surface AMENDED SHEET (ARTICLE 19) transparent an electrochromic material which allows to pass from a transparent state to a colored state, by disinsertion of ions.

10. Electrochromic device (1, 11) according to any one of claims 1 to 9, characterized in that the electrolyte contains one or more reagents capable of electroprecipitating on the transparent semiconducting or conducting surface of the positive electrode and which allows it to pass from a transparent state to a colored state. 1 1 . Electrochromic device (1 , 1 1 ) according to any one of claims 1 to 1 0, characterized in that the transparent semiconducting or conducting surface of the negative electrode is nano-structured by a thin film deposited on the surface. 1 2. Electrochromic device (1, 1 1) according to any one of claims 1 to 1 0, characterized in that the surface of the positive electrode is nano-structured by a thin film deposited on the surface.

13. Electrochromic device (1, 11) according to claim 11 or 12, characterized in that the nano-structured thin film is a semiconducting or conducting metal oxide, such as: ITO, FTO, TiC>2, SnC>2.

14. Electrochromic device (1, 11) according to any one of claims 1 to 13, characterized in that the electrolyte comprises Mn ions 2+ and the positive electrode involves the couple Mn 2+ / MnC>2 during charging and discharging, the MnC>2 being deposited by electrodeposition on its transparent surface, for example based on ITO, during charging. 1 5. Electrochromic device (1, 11) according to any one of claims 1 to 13, characterized in that the positive electrode is covered on its transparent surface during discharge with Prussian white and during charging with Prussian blue. AMENDED SHEET (ARTICLE 19) 16. Electrochromic device (1, 11) according to any one of claims 1 to 13, characterized in that the electrolyte contains Br- ions and a quaternary amine.

17. Electrochromic device (1, 11) according to any one of claims 1 to 16, characterized in that the electrolyte is free of an organic Bronsted acid.

18. Electrochromic device (1, 11) according to any one of claims 1 to 17, characterized in that the electrolyte comprises zinc acetate or zinc chloride, or zinc sulfate or zinc triflate, for example the electrolyte comprises between 0.1 and 1 mol per liter of zinc acetate, advantageously 0.5 mol per liter.

19. Electrochromic device (1, 11) according to any one of claims 1 to 18, characterized in that the electrolyte comprises glycerol.

20. Electrochromic device (1, 11) according to any one of claims 1 to 19, characterized in that the electrolyte (4, 14) contains glucose.

21. Electrochromic device (1, 11) according to any one of claims 1 to 20, characterized in that the electrolyte (4, 14) contains a guanidinium salt.

22. Electrochromic device (1, 11) according to any one of claims 1 to 21, characterized in that the electrolyte (4, 14) is buffered, preferably by an acetate buffer.

23. Electrochromic device (1, 11) according to any one of claims 1 to 22, characterized in that the pH of the electrolyte (4, 14) is between 5 and 6.

24. Electrochromic device (1, 11) according to any one of claims 1 to 23, characterized in that the electrolyte comprises 5% AMENDED SHEET (ARTICLE 19) at 30% PEG by volume of the electrolyte, advantageously between 5% and 1 5%.

25. Electrochromic device (1, 11) according to any one of claims 1 to 24, characterized in that the electrolyte comprises 10% to 70% of glycerol by volume of the electrolyte, advantageously between 40% and 70%.

26. Electrochromic device (1, 11) according to any one of claims 1 to 25, characterized in that the polyethylene glycol is of formula H(OCH2CH2) n OH, with n between 1 and 200, and preferably n between 1 and 30.

27. Electrochromic device (1, 11) according to any one of claims 1 to 26, characterized in that the electrolyte comprises glycerol and PEG, advantageously with a glycerol / PEG ratio greater than 2.

28. Electrochromic device (1, 11) according to any one of claims 1 to 27, characterized in that the transparent surface S of the negative electrode and the transparent surface S' of the positive electrode are equal and opposite, allowing a uniform variation in transmittance.

29. Electrochromic device according to one of claims 1 to 28, characterized in that the application of the imposed current is between 40 seconds and 5 minutes. AMENDED SHEET (ARTICLE 19) DECLARATION UNDER ARTICLE 19 (1) In response to the search report, a set of amended claims is filed. Claim 1 is amended as follows:

1. Electrochromic device (1, 11), such as an electrochromic window comprising: - a device for reversibly electrodepositing a zinc Zn film at the negative electrode, to produce an electrochromic electrode at the negative electrode, the device comprising a negative electrode, a positive electrode, a volume arranged between the negative electrode and the positive electrode and containing an electrolyte (4, 14) with Zn2+ ions, the negative electrode has a transparent semiconducting or conducting surface, the transparent semiconducting or conducting surface of the negative electrode comprising a conducting or semiconducting material which is a transparent metal oxide, the electrolyte (4, 14) being aqueous or in the form of a gel, the electrolyte (4, 14) containing ethylene glycol, polyethylene glycol or derivatives of these compounds, the pH of the electrolyte (4, 14) being between 4 and 7, the device for reversible electroplating of the zinc Zn film making it possible to pass during each cycle, in a second step which follows the galvanostatic step, from the colored state of the galvanostatic step to a transparent state of the entire transparent semiconducting or conductive surface by electro-dissolution of the zinc film in the electrolyte (4, 14), and in which the negative electrode is without pre-functionalization or chemical modification of its transparent semiconducting or conductive surface in order to promote the nucleation and homogeneous growth of the deposition of the zinc film during the electroplating on its transparent semiconducting or conductive surface. Claim 1 combines claims 1, 6 and 8 as filed. The claimed electrochromic device is asymmetrical, claim 7 as filed being amended accordingly, claims 19 and 20 being deleted. The claims are renumbered accordingly. The amended claims are thus supported by the content of the application as filed. As the Examiner acknowledges, none of the prior art documents discloses or suggests a configuration comprising a sacrificial zinc electrode, nor proposes to solve the problem of material accumulation at the transparent electrode, thus making claim 8 as filed novel and inventive. Amended claim 1, incorporating claim 8 as filed, is therefore novel and inventive.

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