Method for synthesizing crystalline layers of manganese oxides, in particular for rechargeable batteries

Abstract

The invention relates to a method (100) for synthesizing at least one crystalline layer of manganese oxides that can contain zinc, of formula ZnxMnyOz, where x is greater than or equal to 0, y is greater than 0, and z is greater than 0, the method being implemented in a chamber of a low-pressure plasma reactor, kept between 10 Pa and 105 Pa, the method comprising forming a plasma discharge (110) from a plasma-generating gas; adding (120), in the form of a nebulizate, a predetermined amount of a manganese precursor; adding (130) a reactive gas so as to create oxygen vacancy defects in the layer of manganese oxides, and / or so as to maintain a controlled redox environment; synthesizing and depositing (140), on a substrate, the at least one crystalline layer of manganese oxides that can contain zinc, these operations being carried out at a substrate temperature of 400°C or less, advantageously 200°C or less.

Description

Process for the synthesis of crystalline layers of manganese oxides, in particular for rechargeable batteries Prior art - technical problem

[0001] Lithium Ion Batteries (LIBs) occupy a dominant position in the electricity storage market. However, the depletion of available lithium resources and the increase in its price make alternative solutions with similar performance particularly necessary. Zinc is considered as an alternative material with equivalent performance to lithium. Several recent studies show that materials based on ZnMn2C>4 spinel as cathode material have characteristics tending to approach those of lithium-based batteries, in terms of cyclability and electrochemical properties (mass or volume capacity, etc., e.g. Cai et al 2022).

[0002] However, there are challenges to overcome before zinc can be substituted for lithium and zinc-ion batteries (ZIBs) produced. One of the major challenges is the development of stoichiometrically controlled ZnxMnyOz oxide layers that can create oxygen vacancies at low temperatures while preserving its spinel crystallographic structure. Conventional development processes described in the literature, such as solvothermal, colloidal, sol-gel, or emulsion synthesis, all require a succession of multiple, long, and complex steps and, at the end of the development process, high annealing temperatures (500 °C or more, for several hours), which are highly energy- and time-consuming.In addition, the powder resulting from these processes, which includes manganese oxide crystals, then requires the use of a binder and / or an adhesive for its application to a substrate surface supporting the electrode (called the current collector) and / or a protective coating, which can alter the electrochemical performance of the ZIB.

[0003] There are ZIBs whose cathode materials are formed solely by manganese oxides (without zinc oxide); a disadvantage of these ZIBs is the instability of these cathodes related to the dissolution of MnO2 in the electrolyte, which preempts the number of charge-discharge cycles possible for these batteries. Carbon materials such as graphene mixed with the cathode material or the application of a protective graphene layer on the electrodes have been used to overcome this drawback (Wu et al., 2018). However, such materials are expensive, can reduce electrochemical performance and are therefore incompatible with the production of efficient ZIBs at a reasonable cost. Application WO 2020 / 176787 describes a cathode comprising a layer of manganese oxide for ZIBs on which is deposited a protective coating, in particular based on oxides which are not zinc oxides. Said coating aims to protect the manganese electrode from dissolution.

[0004] Given the promising performance of manganese oxides, the increasing need for electrical energy storage solutions and the need to save scarce environmental resources, there is a need to find a simple and rapid process for producing stable and efficient ZI B battery cathodes, to facilitate the development of manganese oxide-based ZI B batteries. The process of Mollar et al. (2009) is a liquid phase electrochemical deposition technique and its authors are targeting applications in magnetic semiconductors; the process of Mollar et al. involves doping the layers with Mn. Mollar et al. is also completely silent about any electrochemical performance.

[0005] Faced with the aforementioned current need, the inventors have developed a process using a low-pressure, low-temperature plasma which allows the deposition of layers of manganese oxides which may include zinc and of formula Znx Mny Oz (x greater than or equal to 0, y and z greater than 0) in a single step, at a temperature not exceeding 200°C. The layers deposited directly, without the addition of binder(s) or carbon other than that produced in situ, on the substrate and resulting from the process of the invention have electrochemical properties (cyclic voltammetry, measurement of charge capacity) meeting those required to form rechargeable batteries, allowing a satisfactory number of charge / discharge cycles, and similar to those of the materials obtained by state-of-the-art techniques which involve an annealing step. This process also makes it possible to control the stoichiometry of the layers produced and thus to control their electrochemical performances. Summary of the invention

[0006] Thus, according to a first aspect, the invention relates to a method for synthesizing at least one crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz, with x greater than or equal to 0, y greater than 0, z greater than 0, said method for synthesizing at least one crystalline layer of manganese oxides which may contain zinc, being carried out in an enclosure of a low-pressure plasma reactor, said pressure in said enclosure being maintained between 10 Pa and 10 5 Pa, advantageously between 10 Pa and 100 Pa, said method of synthesizing at least one crystalline layer of manganese oxides, comprising: • the formation of a plasma discharge from a plasmagenic gas, • at least one injection into the reactor enclosure in the form of a nebulizer, of a predetermined quantity of at least one manganese precursor and optionally of a predetermined quantity of at least one additional precursor such as zinc, simultaneously or successively, the precursors being dissolved in a solvent to be introduced in the form of a nebulizer, into the plasma reactor, • at least one injection into the reactor enclosure of a reactive gas which mixes with the precursor so as to create oxygen defects in the manganese oxide layer, and / or so as to maintain a controlled redox environment in the reactor enclosure, • the precursors being dissolved in a solvent to be introduced in the form of a nebulizer, into the plasma reactor, • the synthesis and deposition of at least one crystalline layer of manganese oxides which may contain zinc, of formula Zn x Mn y O zon a substrate, said synthesis and said deposition (140) being carried out at a substrate temperature less than or equal to 400°C, advantageously less than or equal to 200°C.

[0007] Unlike the methods of the state of the art, the method according to the invention allows direct deposition of said layer on, for example, a conductive support. It also makes it possible to control the composition of these layers of manganese oxides of a Zn composition. x Mn y O z and thus optimize their electrochemical properties and durability.

[0008] According to other optional features of the process, included alone or in combination: - to create oxygen defects in the manganese oxide layer, at least one carbon precursor such as acetates or acetylacetonates is injected, - to create oxygen defects in the manganese oxide layer, a predetermined quantity of at least one reducing gas is injected, - the synthesis and said deposition of the Zn layer x Mn y Oz Are carried out at a substrate temperature below 100°C, advantageously below 50°C, the process thus allows deposition on heat-sensitive supports, and thus broadens the possible supports, in particular for electrochemical applications, - at the precursor injection stage the ratio of quantity of manganese precursor / quantity of zinc precursor greater than or equal to 2, or even greater than or equal to 10, - the step of injecting the manganese and possibly zinc precursors further comprises the injection of a precursor of a doping element comprising salts of: copper and / or vanadium, said precursors being solid under normal temperature and pressure conditions, and injected into the reactor dissolved in a solvent in the form of a nebulisate, - the precursors of Mn, optionally of Zn, and of optional doping elements are in the form of nitrate, chloride, acetate, acetylacetonate, acetonate or any other salts, and in that the precursors are soluble in a solvent such as water, ethanol, methanol, propanol, hexane, heptane or octane. - the method (100) is carried out without a step of annealing the at least one crystalline layer of manganese oxides which may contain zinc of a composition Zn x Mn y O z, doing without such a step is particularly advantageous both in terms of energy savings and the speed of the process, since such steps can last several hours and require subsequent treatments depending on the chosen applications, in particular for the production of electrodes (for example, reduction to powder then application with a binder), - the reactive or plasmagenic gas contains oxygen, - the carrier gas is chosen for example from the following list: Argon, Helium, Krypton. - the reactive or plasmagenic gas comprises reducing molecules chosen from a hydrocarbon such as an alcohol or an aliphatic hydrocarbon. - the reducing gas is chosen from carbon monoxide, carbon dioxide, CH4, H2, NH3, methanol, propanol, methane, ethane, propane, or any other hydrocarbon capable of reacting with oxygen in the plasma, or mixtures thereof, - the composition of reactive or plasmagenic gas is chosen so as to allow the formation of graphene and / or oxygraphene in the at least one crystalline layer of manganese oxides, - the process is carried out in a single step, for example lasting less than 1 hour, - the plasma is produced by an alternating electric generator, by inductive or capacitive radiofrequency, or an ECR microwave source (electron cyclotron resonance), or by the application of a direct electric voltage, - in the process: • the nebulisates comprising the precursors are carried by the reactive gases or a carrier gas, in the case of a carrier gas, the latter also being mixed with the reactive gases; • the reactive gases and the nebulizates are introduced simultaneously or successively through one or more ends of the reactor, and react together in the plasma, • the vapor or gaseous by-products which come out through one or more other ends are sucked up by a pump coupled to the reactor, and / or • -the substrate is placed in the reactor between one or more inlet ends and one or more outlet ends of the reactor and is thus exposed to the passage of gases and nebulizates, - in the process: - the reactive gas or plasma gas contains oxygen - the carrier gas is chosen for example from the following list: Argon, Helium, Krypton.

[0009] Thus, depending on the composition of the reducing gas, the method according to the invention can make it possible to obtain a layer of composition: ZnxMnyOz, where x and z represent stoichiometric coefficients greater than 0, and y greater than or equal to 1 and / or MnyOz where y is greater than or equal to 1 and z represents stoichiometric coefficients greater than 0.

[0010] More specifically, when the precursor mixture contains a manganese salt and a zinc salt, and the percentage of O2 in the reactor enclosure: - is equal to 0%, by applying the method of the invention a crystalline layer of manganese oxides is obtained only with the following oxide Mn y Oz (with x=0, y is greater than or equal to 1 and z greater than zero), - is greater than 0% and less than 10%, by applying the method of the invention a crystalline layer of manganese oxides comprising the following oxides is obtained: Zn x Mn y O z (with x greater than 0, y greater than or equal to 1 and z greater than zero), Mn y Oz (with y greater than or equal to 1 and z greater than zero), - is greater than 17%, by applying the method of the invention a crystalline layer of manganese oxides of composition ZnxMnyOz is obtained.

[0011] In a particular embodiment, said method allows the synthesis of at least one crystalline layer of manganese and zinc oxides of a composition ZnxMnyOz, where x, y and z represent stoichiometric coefficients greater than 0, said method for the synthesis of at least one crystalline layer of manganese and zinc oxides of a composition Zn x Mn y O z , being implemented in an enclosure of a low pressure plasma reactor, said pressure in said enclosure being maintained between 10 Pa and 10 5 Pa, advantageously between 50 Pa and 100 Pa, said method of synthesizing at least one crystalline layer of manganese and zinc oxides of a composition Zn x Mn y O z , including: - the formation of a plasma discharge from a plasmagenic gas, - at least one injection into the reactor enclosure of a reactive gas which comprises a predetermined quantity: • at least one reducing gas or • at least one oxidizing gas so as to maintain a controlled redox environment in the reactor enclosure, - an injection in the form of a nebulizer, and / or vapor: of a predetermined quantity of manganese precursors and a predetermined quantity of zinc precursors, simultaneously or successively, - the synthesis and deposition of the Zn layer x Mn y Oz on a substrate, at a substrate temperature less than or equal to 400°C, advantageously less than or equal to 200°C.

[0012] In an even more particular embodiment, said method allows the synthesis of at least one crystalline layer of manganese and zinc oxides of a composition ZnxMnyOz, where x, y and z represent stoichiometric coefficients greater than 0, or equal to 0 for one of the coefficients with the other coefficients being greater than 0, said method of synthesis (100) of at least one crystalline layer of mixed oxides of manganese and zinc of a composition Zn x Mn y O z , being implemented in an enclosure of a low pressure plasma reactor, said pressure in said enclosure being maintained between 10 Pa and 10 5 Pa, advantageously between 10 Pa and 100 Pa, said method of synthesizing at least one crystalline layer of manganese and zinc oxides of a composition Zn x Mn y O z , including: - the formation of a plasma discharge (1 10) from a plasmagenic gas, - at least one injection (120) into the reactor enclosure of a reactive gas which comprises a predetermined quantity: • at least one reducing gas or • at least one oxidizing gas so as to maintain a controlled redox environment in the reactor enclosure, - an injection (130) in the form of a nebulizer, and / or vapor: of a predetermined quantity of manganese precursors and of a predetermined quantity of zinc precursors, simultaneously or successively, - the synthesis and deposition (140) of the Zn layer x Mn y Oz on a substrate, at a substrate temperature less than or equal to 400°C, advantageously less than or equal to 200°C.

[0013] According to a second aspect, the invention relates to an assembly comprising at least one crystalline layer of manganese oxides which may contain zinc of a composition ZnxMnyOz, where x is greater than or equal to 0, y greater than or equal to 1 and z greater than 0, obtained according to the method according to the first aspect of the invention, said layer of manganese oxides having a thickness of the order of a nanometer to a thickness of the order of a micrometer. These layers have in particular oxygen vacancies, in controllable proportions, and are, due to these vacancies, of particular interest for electrochemical applications. Furthermore, such thicknesses are particularly advantageous for applications such as batteries or rechargeable cells.

[0014] According to other optional characteristics of said assembly comprising at least one crystalline layer of manganese oxides which may contain zinc, alone or in combination: - the layer of manganese Zn oxides x Mn y O z includes graphene and / or oxygraphene, - the ratio of quantity of Zn / quantity of Mn is less than 0.5, preferably less than 0.1 and advantageously less than 0.05, - the manganese oxides of the at least one crystalline layer of manganese oxides are of formula Mn y O z where y represents stoichiometric coefficients greater than or equal to 1, z represents stoichiometric coefficients greater than 0, - the manganese oxides of the at least one crystalline layer of manganese oxides are of formula: • Zn x Mn y O z , where x and z represent stoichiometric coefficients greater than 0, and y greater than or equal to 1 and • Mn y O zwhere y represents stoichiometric coefficients greater than or equal to 1 and z represents stoichiometric coefficients greater than 0, said set comprises • a crystalline layer composed solely of manganese oxide of formula MnO, • a crystalline layer of manganese oxides in which the manganese oxides of formula ZnMnsCU and MnO, or • a layer with only the following oxide ZnMn2O4.

[0015] According to a third aspect, the invention therefore relates to a cathode of a zinc-ion battery (ZIB) comprising, on a conductive substrate, at least one layer of manganese oxides which may contain zinc of formula ZnxMnyOz or x equal to or greater than 0, y and z greater than 0, resulting from the method according to the first aspect.

[0016] According to other optional features of this cathode according to this third aspect, included alone or in combination: - the substrate on which said at least one layer is deposited is a conductive metal, for example chosen from the following list: Al, Cu, Pt, Ag, steel, stainless steel or one of their alloys, - x=1, y=2 and z=4. As demonstrated in the experimental part, such a cathode is present effective, - the substrate is a conductive metal, for example chosen from the following list: Al, Cu, Pt, Ag, steel, stainless steel, or one of their alloys of these metals, - the substrate is a conductive polymer or a polymer covered with a layer of conductive material, in the form of sheets or plates, - said cathode not comprising a protective layer, covering said layer of manganese oxide, and in which said at least one layer of manganese oxides not comprising glue or binder. These characteristics contribute to the electrochemical efficiency of the cathode according to the invention to optimize its lifespan.

[0017] According to a fourth aspect, the invention also relates to a Zn-ion battery (ZIB) comprising: - at least one cathode according to the third aspect of the invention, - at least one anode comprising zinc, and - at least one electrolyte of at least one manganese salt.

[0018] As mentioned, such batteries, which comprise at least one cathode according to the invention, constitute valid alternatives to LiBs batteries, allowing the saving of rare resources, with adequate electrochemical performances. Figures

[0019] Other objectives, characteristics and advantages will emerge from the detailed description which follows with reference to the drawings given for illustrative and non-limiting purposes among which Figure 1: Method according to one embodiment of the invention. Figure 2A: Raman spectra of ZnMn2C>4 produced at low temperature (200 °C) with or without annealing at 500 °C for 4 h. Figure 2B: X-ray diffraction pattern of tetragonal ZnMn2O4 layers without annealing, showing the crystal structure of the layers produced at 200 °C, and after annealing at 500 °C for 4 h. The reference ZnMn2C>4 comes from the CIF mp- database Figure 3A: Cyclic voltammetric curves for crystalline layers of manganese oxides of ZnMn2O4 obtained according to the method of the invention. The number of charge-discharge cycles is indicated. Figure 3B: Cyclic voltammetric curves for ZnMn2O4 manganese oxide crystalline layers obtained by a state-of-the-art method (Sinian Yang et al. (2019)). The data show similar electrochemical properties to that of Figure 3A. The number of charge-discharge cycles is indicated. Figure 4: a representation of the device allowing the implementation of the method according to the invention. Figure 5: Result of Raman spectroscopy analysis of a ZnMnO layer obtained according to the method of the invention. Depending on the amount of oxygen present in the reactive mixture and in the presence of the carbon element, the presence of graphene or oxygraphene sheets can be observed, highlighted by the G (G) and D (D) bands, specific signatures of graphene and oxygraphene. The specific signatures of ZnxMnyOz on the one hand and of graphene and oxygraphene on the other hand are boxed. It is observed that the more oxygen there is in the reaction mixture, the less graphene layers there are: At 70mL / min of oxygen, no graphene layers are detected in the ZnMnO layer. Figure 6: image obtained by electron microscopy of a layer of manganese oxides doped with zinc according to the invention, deposited on a silicon substrate, and obtained according to the method of the invention: under the conditions tested, a layer with a thickness of 1.4 pM is obtained. Description of the embodiments

[0020] A first subject of the invention therefore relates to a plasma process for synthesizing at least one crystalline layer of manganese oxides. The process developed advantageously makes it possible to control the stoichiometry, in particular the oxygen stoichiometry, of a crystalline layer of manganese oxides of formula Zn x Mn yOz, which makes it possible to vary and optimize its electrochemical properties and the doping possibilities of the layers. This process also has the particularity of being implemented in a low-pressure plasma reactor and at low temperatures, which is particularly advantageous from the point of view of the energy cost of the synthesis of the crystalline layers. This also allows implementation on heat-sensitive supports. The process of the invention also makes it possible to: to promote the doping of the layers of a crystalline layer of manganese oxides of formula Zn x Mn y Oz by elements such as N, Cu, Ag, V, etc. from the periodic table of elements.

[0021] For the purposes of the invention, a crystalline layer of manganese oxides of formula Zn x Mn yOz, means a crystalline layer in which the elements Zn, Mn and O are linked together covalently and / or by ionic bonds and / or are present interstitially in the crystalline lattice. Thus, a layer of manganese oxides produced according to the process of the invention may comprise manganese oxides and zinc and / or another cation, depending on the reaction mixture produced in the reactor, one embodiment of which is described below.

[0022] Thus, this first subject of the invention relates to a method for synthesizing at least one crystalline layer of manganese oxides of a composition ZnxMnyOz, where x is greater than or equal to 0, y greater than 0, z greater than 0, said method for synthesizing at least one crystalline layer of manganese oxides of a composition Zn x Mn y O z, being implemented in an enclosure of a low pressure plasma reactor, said pressure in said enclosure being maintained between 10 Pa and 10 5 Pa, 25 Pa and 10 4 Pa, advantageously between 50 Pa and 100 Pa, said method of synthesizing at least one crystalline layer of manganese oxides of a Zn composition x Mn y O z , including: - the formation of a plasma discharge from a plasmagenic gas, - at least one injection in the form of a nebulisate, of a predetermined quantity of manganese precursors and optionally of a predetermined quantity of zinc precursors, simultaneously or successively, the precursors being dissolved in a solvent to be introduced in the form of a nebulisate, into the plasma reactor, - at least one injection into the reactor enclosure of a reactive gas which mixes with the precursor so as to create oxygen defects in the manganese oxide layer, and / or so as to maintain a controlled redox environment in the reactor enclosure - the synthesis and deposition of at least one layer of manganese oxides of formula Zn x MnyOz On a substrate, said synthesis and said deposition being able to be carried out at a substrate temperature less than or equal to 400°C, advantageously less than or equal to 200°C.

[0023] Obviously, as long as the reactive gas and the precursor(s) mix adequately in the reactor to allow the reaction and the deposition of the manganese oxide layer on the support in the plasma reactor, the order of injections of the reactive gas on the one hand and of the precursor(s) on the other hand is not important. In one embodiment, these injections may be concomitant.

[0024] In a particular embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides of formula ZnxMnyOz, where x is greater than or equal to 0, y is greater than or equal to 1, z greater than 0.

[0025] In a particular embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides of formula ZnxMnyOz, where x is greater than 0, y is greater than 0, z is greater than 0.

[0026] In another particular embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides of a formula ZnxMnyOz, where x is greater than 0, y greater than or equal to 1, z is greater than 0.

[0027] In one embodiment, said at least one layer of manganese oxides comprises manganese oxides at least one layer of manganese oxides of formula ZnxMnyOz where x=1, y=2 and z=4.

[0028] In one embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides comprising manganese oxides of formulas ZnxMnyOz where x is greater than 0, y is greater than 0, z is greater than 0 and / or MnyOz (x then being equal to 0 and Zn consequently absent) where y is greater than 0, z is greater than 0.

[0029] In another particular embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides of formula ZnxMnyOz, where x equal to 0, y greater than 0, z is greater than 0. The at least one crystalline layer of manganese oxides therefore being of formula MnyOz with y greater than 0, and z greater than 0.

[0030] In another particular embodiment, the synthesis method according to the invention is a method for synthesizing at least one crystalline layer of manganese oxides of formula ZnxMnyOz, where x equal to 0, y greater than or equal to 1, and z greater than 0. The at least one crystalline layer of manganese oxides therefore being of formula MnyOz with y greater than or equal to 1, and z greater than 0.

[0031] It is understood that the predetermined quantities of precursors are defined so as to allow the obtaining of said crystalline layer of a composition according to the aforementioned stoichiometric coefficients.

[0032] The plasma gas is advantageously chosen from argon, helium, neon, xenon, dihydrogen or mixtures thereof. It can be mixed with at least one other gas such as N2, CO, CO2, CH4, H2, Cl2, F2, H2O or other gaseous hydrocarbons (such as C2H2, C2H4, C2H6, or organic vapors) or mixtures thereof. In the method according to this first subject of the invention, the plasma can be produced by an alternating electric generator, by inductive or capacitive radiofrequency, or an ECR microwave source (for electron cyclotron resonance, in English terminology ECR for Electron Cyclotron Resonance), or by the application of a direct electric voltage, according to means known to those skilled in the art.

[0033] The reactive gas comprising a predetermined quantity of at least one reducing gas is chosen so as to maintain a controlled redox environment in the reactor enclosure and thus to control the oxygen stoichiometry of the oxide layers, and, consequently, to modulate the presence in said at least one crystalline layer of oxygen vacancies advantageous for the electrochemistry applications of these layers. One of the effects of the creation of vacancies is in particular to make it possible to reduce the loss of capacity of the material observed in conventional materials during charge-discharge cycles.

[0034] The molar ratio of the reactor enclosure between oxygen and the reducing gas advantageously varies between 0% and 30%, the variation of this ratio makes it possible to vary the coefficient z of the at least one Zn crystalline layer x Mn y O zto order and according to the desired electrochemical properties. For example, the higher the oxygen gas / plasma gas ratio or the higher the reducing gas / plasma gas ratio, the lower z and the more gaps in the crystalline structure of the layer the layer has. Advantageously, this ratio is between 0% and 20%, even more advantageously between 0% and 10%.

[0035] Any reducing gas capable of reacting with oxygen in the plasma may be used in the method according to the first subject of the invention. In a particular embodiment, the reducing gas may comprise carbon monoxide, carbon dioxide, CH4, H2, NH3, methane, ethane, propane, methanol, propanol or any other hydrocarbon, such as a suitable aliphatic hydrocarbon or alcohol or mixtures thereof.

[0036] Oxidizing gases can be used, which may include molecular oxygen, ozone, or water vapor or mixtures thereof. These gases provide the plasma reactive medium with molecular oxygen and hydroxyl radicals.

[0037] The Zn / Mn molar ratio in the precursor mixture makes it possible in particular to control the x and y coefficients of the at least one ZnxMnyOz crystalline layer resulting from the implementation of the process. It may be less than or equal to 0.5, preferably less than or equal to 0.1, and advantageously less than 0.05.

[0038] The inventors also discovered that the presence of reducing gas in the precursor mixture contributes to the reduction of Zn in the crystalline layer: For reducing gas / plasma gas ratios greater than 1 the value of x decreases.

[0039] In the method according to the invention, the precursor mixture(s) is (are) advantageously injected in the form of nebulisate(s) (i.e. in English terminology a spray) produced, for example, using ultrasound or any other suitable means such as electrospray or injection needles. According to the common acceptance and the definition above, a nebulisate is defined as a set or a cloud of liquid droplets in suspension; the droplets may be microdroplets. This injection may be continuous or pulsed.

[0040] In the method according to the present invention, the precursors are dissolved in a solvent to be introduced in liquid form into the plasma reactor. These may be salts that are solid in their natural state, under atmospheric pressure and room temperature conditions, whose boiling points are very high; they are dissolved in a solvent to be introduced in liquid form into the plasma reactor. These precursors are salts of metals Mn, Cu, Zn, V, solid under room temperature and atmospheric pressure conditions. The device for implementing the method according to the invention allows the formation of a fine mist of droplets or even microdroplets which is introduced into the enclosure by means of a carrier gas (chosen for example from argon, helium, krypton, advantageously argon).

[0041] The manganese and optionally zinc precursors may be of any composition suitable for the synthesis of crystalline layers by plasma and for the method according to the first subject of the invention. More particularly, in a particular embodiment of this first subject, the precursors are in the form of nitrate, chloride, acetate, acetylacetonate, acetonate or any other zinc or manganese salts. Even more particularly, to create oxygen defects into the layer of manganese oxides, a precursor is injected in the form of a carbon precursor such as an acetate or an acetylacetonate.

[0042] The precursors are soluble in a solvent such as water, ethanol, methanol, propanol, hexane, heptane or octane.

[0043] The method according to the first subject of the invention allows the synthesis of said at least one crystalline layer and the deposition on the support in a single step, which is particularly advantageous in terms of yield and resource savings. In particular, the formation of a crystalline layer in the method according to the invention does not require an annealing step which is characterized by the exposure of the mixture to high temperatures (usually between 500°C and 800°C, or even more) for a duration of several hours. This step makes these processes particularly long and energy-consuming, and they also do not allow the direct deposition of a crystalline layer directly onto a support which would not withstand exposure to such temperatures.Furthermore, the absence of further processing such as grinding and then application in paste with a binder, in the case for example of application on a conductive support, makes it possible to avoid any negative influence of these on the electrochemical properties of the manganese oxide crystals and the loss of material. The experimental data below confirm the crystalline structure of the layers produced according to the process which is the first subject of the invention.

[0044] This process is particularly suitable for the generation of material comprising several crystalline layers i, different or not, of composition Zn xi Mn yi O Z i, with xi, yi and zi representing stoichiometric coefficients of each crystalline layer of manganese oxides i. In a particular embodiment, different layers i of composition Zn xi Mn yi O Zican be obtained, by varying for the different injections: the characteristics of the reactive gas (for example, the oxygen gas / reducing gas ratio and / or composition and nature of the reducing gas) and / or the characteristics of the mixture of manganese precursors possibly including zinc precursors (for example, the ratio of precursors and / or the composition of the manganese precursor). The succession of crystalline layers also makes it possible to control and optimize the thickness of the deposited crystalline material, the latter comprising layers of identical or different composition and / or stoichiometry.

[0045] In a particular embodiment of the method which constitutes the first subject of the invention, at least one doping element is injected at the at least one precursor injection step. The presence of vacancies in the crystalline layer makes the layers obtained by this method particularly suitable for doping. This doping element may be any element of the periodic table, including, but not limited to, N, Cu, Ag, or V. Even more particularly, this at least one doping element is selected from nitrate, sulfate, chloride, acetate, acetylacetonate, acetonate, and / or organometallic compounds of metals such as copper or aluminum. The precursor of the at least one doping element may be added to the mixture of Mn precursors optionally comprising Zn. In a particular embodiment, in the event, for example, of incompatibility between the at least one precursor of the doping element and the at least one manganese precursor, the at least one precursor of the doping element may be injected in the form of a nebulizer or spray by a route parallel to the route of the main mixture of precursors. These doping elements are solid under normal temperature and pressure conditions (i.e., usually ambient temperature and pressure).To enable their use in the process, these elements are dissolved in a solvent and then introduced into the reactor in the form of a nebulisate (i.e. in the form of a cloud of droplets or even a cloud of microdroplets) at the low temperatures described.

[0046] This method therefore makes it possible to easily and quickly generate crystalline layers with controlled stoichiometry and / or improved and / or controlled electrochemical properties. In one embodiment, the method according to the invention is a method for synthesizing at least one crystalline layer (and its deposition on the substrate) in a single step. In one embodiment, the method is a method for synthesizing at least one crystalline layer (and its deposition on the substrate) in a single step. With a duration of less than 5 hours, 4 hours, 3 hours, 2 hours or even less than 1 hour. In a particular embodiment, the method is a method for synthesizing at least one crystalline layer (and its deposition on the substrate) in a single step is advantageously of a duration of less than one hour and varies according to the thickness of the crystalline layer that is desired.In any case, this duration is much shorter than that of conventional synthesis methods which generally require a multitude of long steps which can last several days.

[0047] In the method according to the invention, the deposition time is variable. Advantageously, it can be modulated according to the thickness of the desired crystalline layer. The method allows deposition rates of at least 0.1 pm per minute, advantageously this rate is greater than 0.2 pm per minute, 0.3 pm per minute, 0.4 pm per minute, 0.5 pm per minute, or even much higher. Thus this process is rapid and can last one hour or less. It can last longer if a thicker layer is desired.

[0048] In addition to the lower chamber temperature, the method according to this first subject of the invention allows deposition of the at least one crystalline layer on a substrate maintained at a particularly low temperature. Deposition at a low substrate temperature is particularly advantageous because it makes it possible to envisage deposition on heat-sensitive substrates, which degrade or are denatured at the high temperatures of conventional methods. In a particular embodiment of this first subject, the deposition takes place at a substrate temperature below 100°C, advantageously below 50°C, even more advantageously below 30°C.

[0049] In a particular embodiment, the substrate is a conductive substrate. This conductive substrate can be of any type provided that it is suitable for the plasma synthesis method of the invention. It can be, for example, metallic or polymeric, conductive or comprising a metallized layer. In an even more particular embodiment, the conductive substrate comprises a conductive metal selected from Al, Cu, Pt, Ag, alloys such as steel, stainless steel or one of their alloys. The deposition on such conductive substrates makes the crystalline layers produced by the method of the invention particularly suitable for use in the field of electrochemistry, and in particular, in a non-limiting manner, in cells, rechargeable cells, or batteries.The process is suitable for the deposition of crystalline layers of manganese oxides of formula ZnxMnyOz as described above on supports of any shape and variable size, which can subsequently be used themselves on any support such as a polymer, fabrics, leather, organic materials, etc.

[0050] A second subject of the invention relates to a crystalline layer of manganese oxides of a Zn composition x Mn y O z, x, y and z being stoichiometric coefficients where x is greater than or equal to 0, and y and z represent stoichiometric coefficients greater than 0, obtained according to the method which is the first subject of the invention, or any of its particular embodiments or their combinations. In a particular embodiment, x is greater than or equal to 0, y greater than or equal to 1, and z greater than 0. In another embodiment, x is greater than 0, y is greater than or equal to 1 and z greater than 0. The method of the invention is particularly suitable for producing layers with a thickness of the order of a nanometer, a hundred nanometers or several hundred nanometers or even of the order of ten micrometers while controlling, as explained above, the oxygen stoichiometry and the Zn / Mn ratio, which is particularly advantageous in particular in the electrochemical applications of these layers crystalline oxide layers. Thus, in a particular embodiment, said crystalline layer of manganese oxides of a Zn composition x Mn y O z, x, y and z being stoichiometric coefficients where x is greater than or equal to 0, and y and z represent stoichiometric coefficients greater than 0; where x is equal to 0, y greater than or equal to 1, and z greater than 0; or where x is greater than or equal to 0, y greater than or equal to 1, and z greater than 0, ; or x=1, y=2 and z=4, is obtained according to the aforementioned process and with a thickness of the order of hundreds of nanometers or even several tens of micrometers. More particularly, said layer has a thickness of at least 100 nm, a thickness of at least 200 nm, a thickness of at least 300 nm, a thickness of at least 400 nm, a thickness of at least 500 nm, a thickness of at least 600 nm, a thickness of at least 700 nm, a thickness of at least 800 nm, a thickness of at least 900 nm, or even at least 1 pm, or even at least 2 pm, or even at least 10 pm micrometers or several tens of micrometers.This variability in the thickness of the crystalline layers is obtained in particular by modulating the deposition time of the crystalline layer during the process. It can also be obtained by successive applications of layers one above the other.

[0051] These layers are particularly suitable for electrochemical applications, as indicated above. In view of what is known in the state of the art, as shown by the experimental data, the crystalline oxide layers obtained according to the invention have charge capacities whose values ​​are among the highest of what is known for ZIB battery materials.

[0052] A third subject of the invention relates to a cathode of a zinc-ion battery (ZIB) comprising, on a conductive substrate, at least one layer of manganese oxide of formula ZnxMnyOz, x, y and z being stoichiometric coefficients where x is greater than or equal to 0, and y and z represent stoichiometric coefficients greater than 0, and resulting from the method described above in any one of its embodiments. In a particular embodiment, said cathode of a zinc-ion battery (ZIB) comprises, on a conductive substrate, at least one layer of manganese oxide of formula ZnxMnyOz, x, y and z being stoichiometric coefficients where x is greater than or equal to 0, and y represents stoichiometric coefficients greater than or equal to 1 and z represents stoichiometric coefficients greater than 0, and resulting from the method described above in any one of its embodiments

[0053] The characterization of the composition of the at least one oxide layer and in particular of its composition in Zn, Mn and O can be done by any means known to those skilled in the art. In particular, inductively coupled plasma spectrometry (Inductive Coupled Plasma) is particularly suitable for the detection of elements in small quantities in the crystalline layers according to the invention.

[0054] In a particular embodiment, the cathode according to this third subject of the invention comprises at least one layer of manganese oxides of formula ZnxMnyOz where x=1, y=2 and z=4.

[0055] In another particular embodiment, the conductive substrate comprises a conductive metal selected from Al, Cu, Pt, Ag, alloys such as steel, stainless steel, or an alloy thereof.

[0056] As mentioned above, in the cathode according to the third subject of the invention the conductive substrate may be a conductive polymer or a polymer covered with a layer of conductive material; this layer may take any form, for example sheets or layers.

[0057] The absence of annealing to obtain the crystalline layer according to the invention makes it possible to avoid subsequent processing steps for applying the oxide layer to the conductive substrate layer. Thus, the oxides are not in powder form, the cathode according to this third subject therefore does not contain glue or binder. In addition, the crystalline structure obtained is particularly stable and does not require, like the cathodes currently under development, a protective layer aimed at preventing the dissolution of the oxide layer in the electrolyte.

[0058] A fourth subject of the invention relates to a Zn-ion cell or battery (ZIB) comprising: -at least one cathode as described previously in any of its embodiments, -at least one anode comprising zinc, and -at least one electrolyte of at least one manganese salt

[0059] In a particular embodiment, the anode is made of solid zinc. In another particular embodiment, the anode comprises a substrate on which a zinc film is deposited.

[0060] The electrochemical performances of these cells or batteries are remarkable; for example, they have a charge capacity very close to the initial charge capacities, even after numerous charge and discharge cycles. They can also have charge capacities corresponding to the highest values ​​known in the state of the art for ZIB batteries. Thus, rechargeable batteries according to this fourth object can be used in many fields such as, for example, the optimization of energy use. intermittent renewables, the use of electric vehicles to limit hydrocarbon emissions, the use of mobile electronic and electrical devices.

[0061] In a particular embodiment, a rechargeable Zn-ion battery (ZIB) according to the fourth subject of the invention achieves a number of charge-discharge cycles greater than or equal to 500, greater than 800, greater than 1000, preferably greater than 1500, preferably greater than 2000, preferably greater than 2400, preferably greater than 3000, even more preferably greater than 3500, even more preferably greater than 5000. As demonstrated in the experimental part, the crystalline layers obtained according to the method of the invention withstand a particularly large number of charge-discharge cycles without detectable modification of the crystalline structure of the layer.

[0062] A fifth object of the invention relates to a plasma reactor 200 adapted to implement the method according to the first object of the invention.

[0063] In a particular embodiment, the plasma reactor comprises - a silica glass enclosure (or “quartz glass”) 201 or any other material allowing the formation and maintenance of an inductive radiofrequency plasma or a microwave plasma by electron cyclotron resonance (or in English terminology ECR (for Electron Cyclotron Resonance), - a radiofrequency electrical source (ideally 13.5 MHz inductive frequency) 202, - an inductive coil 203 for applying the electromagnetic energy emitted by the source, alternatively, in cases where the source is a microwave source, an applicator makes it possible to inject the energy into the plasma enclosure. - a pumping group 204 and pressure gauge 205 adapted to create an average vacuum between 0.1 and 100 mbar in the plasma reactor. - a substrate holder 206 whose temperature can be controlled and regulated.

[0064] In this reactor, it will be understood that the electromagnetic energy emitted by the source is applied using the inductive coil 203.

[0065] The plasma gas is as defined above, in particular it can be argon, or other gases such as helium or neon. The reactive or plasma gas can also include oxygen. As also mentioned above, it is also possible to use other gases, such as CH4, these gases making it possible in particular to modulate the redox character of the plasma medium. It is also possible to use a gas mixture previously prepared with a predefined composition, for example an Argon + CH4 mixture. In one embodiment In particular, the reactor 200 is associated with means for controlling the flow rates 209 of the gases used. Thus, in a particular embodiment, the plasma reactor is associated with flow meters making it possible to control the flow rate(s) of the gas(es) used. In an even more particular embodiment, the plasma reactor is associated with mass flow meters making it possible to control the flow rate(s) of the gas(es) used.

[0066] This reactor comprises two ends, one of which is through which the reactive gases and precursors are introduced. This arrangement allows the deposition of the layer of manganese oxides which may include zinc on the support 206 present in the reactor. This also makes it possible to possibly connect the other end to the pumping means 204 arranged to extract the by-products such as vapors or gases which come out through the other end, by sucking them up.

[0067] In one embodiment, the reactor is associated with at least one device 207 for preparing and injecting liquid or gaseous precursors.

[0068] In a particular embodiment, the plasma reactor comprises several parallel injection paths 208. These parallel injection paths can in particular allow the injection of precursors separately at the same time. They can also allow, by means of successive injections, the creation of homogeneous layers in concentration and thus the formation of multi-layer strata.

[0069] Typically, the substrate holder 206 is coupled to means 210 for maintaining the temperature of the substrate and the deposition at a predetermined value. Typically, 200°C or less.

[0070] Preferably, the enclosure is cylindrical in shape and is surrounded by a metallic inductive coil 203, preferably made of copper, to induce electromagnetic energy into the enclosure to form and maintain the plasma.

[0071] An embodiment of the plasma reactor suitable for implementing the method according to the invention is presented in Figure 5.

[0072] As mentioned, the injection of precursors, mineral or organic, of zinc and manganese is carried out in the process of the invention and in the enclosure of the plasma reactor in the form of nebulisate (i.e. finely divided droplets) in a plasma advantageously at low pressure (for example between 0.1 and 100 mbar). The precursor can be in the form of nitrates, chlorides, acetates, acetylacetonate or any other metallic salts of zinc or manganese soluble in a solvent such as water, ethanol, methanol, propanol, etc.

[0073] As also mentioned, in varying proportions, the plasma gas can be supplemented with oxygen, and / or reducing gas such as for example CO2, CH4, H2, OR any other hydrocarbon. Such mixtures make it possible to control the oxygen stoichiometry of the final deposition of the ZnxMnyOz layer, or even as illustrated in Figure 5 to obtain layers comprising layers of graphene or oxygraphene. Example: electrochemical properties of crystalline layers obtained using the process according to the invention.

[0074] The plasma process according to the invention for the production of manganese oxide layers of formula Zn x Mn y Oz made it possible to produce layers of the order of one micron in thickness while controlling the oxygen stoichiometry and the Zn / Mn ratio.

[0075] The analysis of the deposits by SEM, TEM, DRX, RAMAN of the layers produced on the surface of the substrates shows results that agree with those found in the literature for substrates produced according to conventional processes (for example, Figure 2A Raman data, Figure 2B X-ray diffraction data): The results confirm the crystalline structure of the layers produced at 200 °C according to the process of the invention. In addition, the cyclic voltammetry data presented in Figure 3A concerning the layers obtained according to the invention are, for their performances, comparable to those presented Yang et al (2019). The data presented in Figure 3A were obtained for a sample of a ZnMnsCU layer using as electrolyte a solution of composition Zn SO4 + Mn SO4.The evaluation of the electrochemical characteristics of charge and discharge shows that the layers obtained according to the method of the invention give results comparable to those of the layers obtained with the methods of the literature (Figures 3A and B).

[0076] Furthermore, it is observed that the electrochemical performances of the layers of oxides obtained according to the process of the invention are quite remarkable: - properties are identical to 96% of the initial charge capacity after more than 500 charge and discharge cycles. - a charge capacity of the order of 150 mAh / g is obtained, which varies depending on the experimental deposition conditions, in relation to the oxygen level in the plasma. The values ​​announced in the literature are between 80 and 180 mAh / g. - after more than 3500 charging cycles, no alteration of the crystalline layers formed according to the process is observed.

[0077] In conclusion, the plasma medium is a reactive gas composed of electrons, radicals, molecules and ionized or excited atoms capable of rapid chemical transformations. The energy required for chemical transformation is provided by electrons at the molecular level rather than by heat transfer. The plasma medium is made reducing by the introduction or in-situ formation of reducing molecules such as carbon monoxide.

[0078] Controlling the concentration of oxidizing or reducing species allows, in the process of the invention, to control the oxygen stoichiometry in the material deposits. The RAMAN and RDX characterization methods show that the stoichiometry of the deposited layers varies with the concentration of oxygen in the plasma gas. This operation of controlling the oxygen stoichiometry constitutes one of the specificities of this process. This control of the presence of oxygen also allows, as shown in Figure 5, to modulate the presence of other structures in the ZnxMnyOz layers of the invention: the higher the oxygen content of the reaction mixture, the fewer graphenic layers the manganese oxide layers contain.

[0079] The method of the invention also makes it possible to produce crystalline layers at a temperature below 200°C without annealing, whereas layers produced by conventional methods require temperatures above 500°C to obtain crystalline layers.

[0080] This process allows layers to be doped with other elements of the periodic table; doping can be carried out over a wide range of concentrations. The production of a ZnxMnyOz layer takes place in a single step of relatively short duration which may not exceed one hour, obviously depending on the thickness of the layer to be produced, while conventional synthesis methods generally require a multitude of long steps which can reach several days. Figure 6 shows an electron microscopy image of a layer with a thickness of 1.4 mm obtained according to the process of the invention. The production of the deposits can be carried out in a fully automated manner under a controlled atmosphere. The management of the chemical compounds involved in the ZnxMnyOz layer deposition operations can be carried out in such a way as to have a neutral impact on the environment. References Kexing Cai, Shao-hua, Jun Cong, Kun Li, Sheng-xue Yan, Peng-qing Hou, Qing Wang, Yahui Zhang, Xin Liu and Xuefei Lei, Journal of The Electrochemical Society, Volume 169, Number 3, March 2022. Mollar M, Tortosa M, Casasûs R, Man B, Electrodepositing ZnxMnyOz alloys from zinc oxide to manganese oxide, Microelectronics Journal 40 (2009) pp 276-279. Sinian Yang, Manshu Zhang, Xianwen Wu, Xiangsi Wu, Fanghong Zeng, Yuting Li, Shiye Duan, Dihua Fan, Yan Yang, Xianming Wu The excellent electrochemical performances of ZnMn2O4 / Mn2O3: The composite cathode material for potential aqueous zinc ion batteries, Journal of Electroanalytical Chemistry 832 (2019) 69-74. Wu B, Zhang G, Yan M, Xiong T, He P, He L, Xu X, Mai L. Graphene Scroll-Coated a-MnO2 Nanowires as High-Performance Cathode Materials for Aqueous Zn-lon Battery. Small. 2018 Mar;14(13):e1703850.

Claims

31 AMENDED CLAIMS received by the International Bureau on April 1, 2024 (01.04.24) 1. Method for synthesizing (100) at least one crystalline layer of manganese oxides which may contain zinc, of formula Zn x Mn y O z , with x greater than or equal to 0, y greater than 5 0, z greater than 0, said method of synthesis (100) of at least one crystalline layer of manganese oxides which may contain zinc, being carried out in an enclosure of a low pressure plasma reactor, said pressure in said enclosure being maintained 10 between 10 Pa and 10 5 Pa, advantageously between 10 Pa and 100 Pa, said method of synthesizing at least one crystalline layer of manganese oxides, comprising: 15 - the formation of a plasma discharge (1 10) from a plasmagenic gas, - at least one injection (120) into the reactor enclosure in the form of a nebulisate, of a predetermined quantity of at least one manganese precursor and optionally of a predetermined quantity of at least one additional precursor such as zinc, simultaneously or successively, 20 the precursors being dissolved in a solvent to be introduced in the form of a nebulisate, into the plasma reactor, - at least one injection (130) into the reactor enclosure of a reactive gas which mixes with the precursor so as to create oxygen defects in the layer of manganese oxides, and / or so as to maintain an environment 25 controlled redox in the reactor enclosure, - the synthesis and deposition (140) of at least one crystalline layer of manganese oxides which may contain zinc, of formula Zn x Mn y O zon a substrate, at a substrate temperature less than or equal to 400°C, advantageously less than or equal to 200°C. 30 2. Method (100) according to claim 1, in which to create oxygen defects in the layer of manganese oxides, at least one carbon precursor such as acetates or acetylacetonates is injected. AMENDED SHEET (ARTICLE 19) 32 3. Method (100) according to one of claims 1 to 2, in which to create oxygen defects in the layer of manganese oxides, a predetermined quantity of at least one reducing gas is injected. 5 4. Method (100) according to one of claims 1 to 3, in which the injection step 130 comprises the injection of zinc precursor in a ratio of quantity of manganese precursor / quantity of zinc precursor greater than or equal to 2.

5. Method (100) according to one of claims 1 to 4, in which the injection step 130 10 includes the injection of zinc precursor, in a ratio of quantity of manganese precursor / quantity of zinc precursor greater than or equal to 10.

6. Method (100) according to one of claims 1 to 5, in which the injection step (130) further comprises the injection of a precursor of a doping element comprising salts 15 of: copper and / or vanadium, said precursors being solid under normal temperature and pressure conditions, and injected into the reactor dissolved in a solvent in the form of a nebulisate.

7. Method (100) according to one of the preceding claims, wherein said synthesis and 20 said deposition (140) are carried out at a substrate temperature less than or equal to 100°C, advantageously less than 50°C.

8. Method (100) according to one of the preceding claims, said method (100) being carried out without a step of annealing the at least one crystalline layer of Zn composition.x Mn y O z . 25 9. Method (100) according to one of the preceding claims, in which: - the nebulisates comprising the precursors are carried by the reactive gases or a carrier gas, in the case of a carrier gas, the latter also being mixed with the reactive gases; 30 - the reactive gases and the nebulizates are introduced simultaneously or successively through one or more inlet ends of the reactor, and react together in the plasma.

10. Method (100) according to the preceding claim, in which: 35 - the vapor or gaseous by-products which come out through one or more outlet ends are sucked up by a pump coupled to the reactor, and / or AMENDED SHEET (ARTICLE 19) 33 - the substrate is placed in the reactor between one or more inlet ends and one or more outlet ends of the reactor and is thus exposed to the passage of gases and nebulizates. 5 11. Method (100) according to one of the preceding claims, in which: - the reactive gas or plasma gas contains oxygen - the carrier gas is chosen for example from the following list: Argon, Helium, Krypton.

12. Method (100) according to one of the preceding claims, in which the at least one 10 reducing gas comprises reducing molecules selected from a hydrocarbon such as an alcohol or an aliphatic hydrocarbon.

13. Method (100) according to one of the preceding claims, in which the at least one reducing gas is chosen from carbon monoxide, carbon dioxide, CH4, H2, 15 NH3, methanol, propanol, methane, ethane, propane, or any other hydrocarbon that can react with oxygen in the plasma, or mixtures thereof.

14. Method (100) according to one of the preceding claims, in which the composition of reactive or plasmagenic gas is chosen so as to allow the formation of graphene and / or 20 of oxygraphene in the at least one crystalline layer of manganese oxides.

15. Method (100) according to one of the preceding claims, characterized in that the method is carried out in a single step, for example lasting less than 1 hour. 25 16. Method (100) according to one of the preceding claims, in which depending on the composition of the reducing gas, the following are obtained: - a layer of composition: Zn x Mn y O z , where x and z represent stoichiometric coefficients greater than 0, and y greater than or equal to 1 and / or - Mn yOz Where y is greater than or equal to 1 and z represents stoichiometric coefficients 30 greater than 0.

17. Method (100) according to the preceding claim, wherein when the precursor mixture contains a manganese salt and a zinc salt, and the percentage of O2 in the reactor enclosure: 35 - is equal to 0%, a crystalline layer of manganese oxides is obtained only with the following oxide Mn y Oz with x=0, y greater than or equal to 1 and z greater than zero. AMENDED SHEET (ARTICLE 19) 34 - is greater than 0% and less than 10%, a crystalline layer of manganese oxides is obtained comprising the following oxides: Zn x Mn y O z with x greater than 0, y greater than or equal to 1 and z greater than zero, Mn y Oz with y greater than or equal to 1 and z greater than zero, 5 - is greater than 17%, a crystalline layer of manganese oxides of composition Zn is obtained x Mn y O z .

18. Method (100) according to one of the preceding claims, in which the plasma is produced by an alternating electric generator, by inductive or capacitive radiofrequency, 10 or an ECR (electron cyclotron resonance) microwave source, or by applying a direct electrical voltage.

19. Method (100) according to one of the preceding claims, in which the precursors of Mn, optionally of Zn, and of optional doping elements are in the form of 15 nitrate, chloride, acetate, acetylacetonate, acetonate or any other salts, and in that the precursors are soluble in a solvent such as water, ethanol, methanol, propanol, hexane, heptane or octane.

20. Assembly comprising at least one crystalline layer of manganese oxides which can 20 contain zinc, of formula Zn x Mn y O z , where x, y and z represent stoichiometric coefficients with x greater than or equal to 0, y greater than 0, z greater than 0, obtained according to the method as defined in any one of claims 1 to 19 and using a plasma, said layer of manganese oxides being of a thickness of the order of a nanometer to a thickness of the order of ten micrometers and having defects 25 in oxygen.

21. An assembly according to claim 20, wherein the layer of manganese Zn oxides x Mn y O z comprises within it graphene and / or oxygraphene formed in the at least one crystalline layer of manganese oxides during the synthesis process 30 (100) using plasma.

22. Assembly according to one of claims 20 to 21, in which the Zn / Mn ratio is less than 0.5, preferably less than 0.1 and advantageously less than 0.

05. 35 23. Assembly according to one of claims 20 to 22, in which the manganese oxides of the at least one crystalline layer of manganese oxides are of formula Mn y O z Or AMENDED SHEET (ARTICLE 19) 35 y represents stoichiometric coefficients greater than or equal to 1, z represents stoichiometric coefficients greater than 0.

24. Assembly according to one of claims 20 to 23, in which the manganese oxides 5 of the at least one crystalline layer of manganese oxides are of formula: ZnxMnyOz, where x and z represent stoichiometric coefficients greater than 0, and y greater than or equal to 1 and MnyOz where y represents stoichiometric coefficients greater than or equal to 1 and z represents stoichiometric coefficients greater than 0. 10 25. Assembly according to one of claims 20 to 24, comprising: a crystalline layer composed solely of manganese oxide of formula MnO, a crystalline layer of manganese oxides in which the manganese oxides of formula ZnMnsCU and MnO, or 15 a layer with only the following oxide ZnMn2O4.

26. Cathode of a zinc-ion battery (ZIB) comprising, on a conductive substrate, at least one layer of manganese oxides which may contain zinc, of formula Zn x Mn y O z , where y and z represent stoichiometric coefficients greater than 0, and x being equal to or 20 greater than 0, resulting from the implementation of the method according to one of claims 1 to 19.

27. Cathode according to the preceding claim, the at least one layer of manganese oxides which may contain zinc, is of formula ZniMn2O4. 25 28. Cathode according to one of claims 26 or 27, in which the substrate on which said at least one layer is deposited is a conductive metal, for example chosen from the following list: Al, Cu, Pt, Ag, steel, stainless steel or one of their alloys. 30 29. Cathode according to one of claims 26 or 27, in which the substrate is a conductive polymer or a polymer covered with a layer of conductive material, in the form of sheets or plates.

30. Cathode according to one of claims 26 to 29, in which 35 said cathode does not comprise a protective layer covering said at least one layer of manganese oxides which may contain zinc, and in which AMENDED SHEET (ARTICLE 19) 36 said at least one layer of manganese oxides which may contain zinc does not comprise glue or binder.

31. Zn-ion battery (ZIB) comprising: 5 at least one cathode according to one of claims 26 to 30, and at least one anode comprising zinc, and at least one electrolyte of at least one manganese salt. AMENDED SHEET (ARTICLE 19) DECLARATION UNDER ARTICLE 19 (1) 1. Declaration according to Article 19.1 i) Reminder of the invention The process according to the invention is a low-pressure plasma process according to the invention a particular reactivity and leads to the formation of non-stoichiometric compounds. The gaseous medium of the plasma allows, by controlling the flows of oxidants or reducers, to lead to a reducing medium in which oxygen defects can appear in the at least one crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz final deposited. Such control of the oxygen stoichiometry in the metal oxides is not easy in conventional processes in liquid or gaseous media which have not reached the formation of a plasma within them and is the heart of the process of the invention which allows easy control of the oxygen stoichiometry and thereby to create oxygen defects crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz ([0005]). Under certain conditions, the method of the invention also makes it possible to create in situ within at least one crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz, graphene and / or oxygraphene. This is of particular advantage since it can contribute to increasing the number of charge-discharge cycles. However, in the prior art, these materials are mixed a posteriori with the electrode materials or applied in a layer at certain production costs. ([0003]) Currently in the state of the art, it is known that graphene compounds are formed under particular conditions, in the presence of copper and at high temperature 1084 °C by thermal processes. The documents do not mention the formation of such material, within it these compounds without requiring post-treatment. 1 ii) Novelty We note that the ISA considers the process which is the subject of claims 1 to 19 to be new and involving an inventive step with regard to documents DI to D8. We also note that the ISA considers the whole subject matter of claims 21 to 25 to be new in light of documents D1 to D8 but devoid of inventive step. Regarding claim 20, we wish to draw the following points to the attention of the Examiner. The DI document describes a thermal process (see Scheme 1) for the production of MnxOy and does not describe the possibility of producing ZnxMnyOz. In the thermal process of Dl, the energy required for the transformation is supplied in the form of heat by electrical resistors. Clearly the process of Dl is not a plasma process such as that of the present invention, in which the energy is supplied by an inductive plasma and in which the electrons are accelerated by the electromagnetic field. During electron collusions the kinetic energy of the electrons is transferred to the precursor molecules. Furthermore, the DI document does not mention at any point the injection of precursor in the form of a nebulisate. It concerns the injection of a steam into the thermal reactor described. This thermal process, therefore very different from the plasma process of the invention, cannot result in the formation of at least one crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz and which includes oxygen defects. Document D2 does not describe any plasma process. On the other hand, on page 1 paragraph 10 of D2, an alkyl organometallic compound is mentioned: 2 Clearly, this compound is not a manganese oxide that may contain zinc. Document D2 describes, in its paragraphs 1 1 to 22, formulas of organometallic complexes and not processes for forming oxide layers. None of the compounds proposed in this document are used by the plasma process described in our application. This document is silent about any process for obtaining a crystalline layer of manganese oxides that may contain zinc, of formula ZnxMnyOz including oxygen defects. Consequently, the relevance of document D2 is not demonstrated, and this document does not describe such a layer. Document D3 uses a gas that is nitrogen dioxide potentially with dinitrogen, which are not reducing gases. D3 thus obtains a p-type conductivity (provided by the positive charges) in a thin layer of ZnO, which is clearly not MnO. Thus the layers obtained at the end of the D3 process are certainly not a crystalline layer of manganese oxides that may contain zinc, of formula ZnxMnyOz, where x, y and z represent stoichiometric coefficients with x greater than or equal to 0, y greater than 0, z greater than 0 with a thickness of the order of a nanometer to a thickness of the order of ten micrometers and having oxygen defects. Document D4 describes the properties of ZnMnO layers obtained by the Atomic Layer Deposition (ALD) method, which is a relatively low-temperature thermal process (160-200 °C) under a reduced atmosphere of very pure nitrogen gas (99.9999%). The Zn and Mn oxide layers are produced alternately, cycle by cycle. These processes do not allow the presence of reducing gas such as methane. The document is completely silent about the formation of oxygen defects or graphene or oxy-graphene, and for good reason: the thermodynamic conditions proposed in this document do not allow the formation of oxygen vacancies in the crystal lattice of the deposited layers, and even less graphene or oxy-graphene. The conditions for the formation of these compounds are absolutely not met. Document D5 describes a MOCVD process for the growth of structured layers of Zm.x Mn xO (crystal orientation controlled by the use of oriented crystal substrates such as sapphire). In the D5 process, the precursors are introduced in vapor form and then growth takes place at 450 °C. This document is completely silent about the presence of oxygen defects or graphene or oxygraphene, in a manner identical to previously the conditions for the formation of graphene compounds or oxygen vacancies are not met in this process. This document does not specify in particular the introduction of reducing gas or an oxygen-deficient plasma medium in order to create oxygen vacancies in the crystal lattice of the deposits. Thus the structured layers of D5 cannot contain such vacancies. Document D6 describes a process for electrodeposition of ZnMn2O4. This is a liquid phase electrodeposition process at 60 °C by applying an electric potential between 3 two conductors placed in a liquid bath containing ZnSO4 and MnSO4 salts. This document does not cite the presence of oxygen defects or graphene or oxygraphene. The conditions for the formation of graphenic compounds are not met in this process. This method is very far from the plasma method which is the subject of the present application. In any case, this electrochemical method in a liquid medium certainly does not allow the creation of oxygen defects. Document D7 describes a method of chemical synthesis from zinc and manganese nitrates in liquid phase. In this method, carbon is added to the solution and then the whole mixture reacts in an ammonia solution for one hour. After evaporation of the liquid, the mixture is calcined at 160 °C. The conditions for the formation of graphene compounds are not met in this process. This method is very different from the plasma method that is the subject of this application. It is a conventional method in a liquid medium that does not allow the creation of oxygen defects. Document D8 describes the formation of ZnMn2O4 from Zn and Mn precursors mixed with spherical carbon in a solvothermal process where a liquid can be brought to a supercritical state. The conditions for the formation of oxygen defects or graphenic compounds are not met in this process. This is a completely conventional method which does not allow the creation of oxygen defects. Thus, none of the documents cited in the RRI discloses "a crystalline layer of manganese oxides which may contain zinc, of formula ZnxMnyOz, where x, y and z represent stoichiometric coefficients with x greater than or equal to 0, y greater than 0, z greater than 0, obtained according to the method of any one of claims 1 to 19, said layer of manganese oxides being of a thickness of the order of a nanometer to a thickness of the order of ten micrometers and having oxygen defects. Thus, the subject matter of claim 20 is novel with respect to the prior art. Therefore, the cathode subject matter of claim 26 or the battery of claim 31 which comprise this layer are also novel. Consequently, the objects of dependent claims 27-29 are also. Thus, all of the objects covered by the claims submitted here are new with regard to the prior art identified in the RRI. 4 (iii) Inventive step. Claim 20 The closest document should be one that uses a plasma process to obtain ZnxMnyOz layers and gives these layers specific properties. As mentioned previously, none of the layers made in these documents have oxygen defects because the necessary conditions are not met in the described processes which are not plasma processes. Furthermore, prior art materials require post-treatment after their formation to integrate binders or carbon. Whereas, on the contrary, the layers of the invention present, from their synthesis, electrochemical properties (cyclic voltammetry, measurement of charge capacity) meeting those required to form rechargeable batteries, directly on a substrate, which also presents a cost advantage and a time saving for their synthesis. This is even more true for the layers comprising graphene and oxygraphene, the presence of which makes it possible to obtain materials with even better properties. Nothing in these documents suggests arriving at such compounds. Therefore, starting from these documents, the person of the profession could not arrive at the element object of claim 1. The element which is the subject of the claim therefore clearly involves an inventive step. Claims 26 and 31 The same reasoning applies mutatis mutandis to the cathode which is the subject of claim 26 or to the battery of claim 31 which comprise the crystalline layer of manganese oxides which may contain zinc and which is obtained at the end of the process of the invention. Therefore, the subjects of dependent claims 21-25 and 27-30 also involve an inventive step. 5 2. Conclusions It is therefore submitted that the subject-matter covered by claims 20-31 as amended meets the criteria of novelty and inventive step. Group No. 783 6

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