Method for producing thin film lithiated materials

Abstract

The present invention relates to a manufacturing method for producing a lithiated material suitable for three-dimensional or 3D batteries or a positive electrode layer based on a lithiated material suitable for 3D batteries, in order to obtain a lithiated material on a substrate, the lithiated material comprising several thin layers, i.e. layers having a thickness between 1 nm and 1 μm, composed of an electrochemically active composite material, and in particular being homogeneous and suitable to fit into the more or less complex bump pattern of the surface of the substrate on which the lithiated material is deposited.

Description

[Technical Field]

[0001] The present invention relates to a method for producing lithiated materials, and more particularly to a method for producing lithium-containing materials deposited in a thin layer on the surface of a substrate. [Background technology]

[0002] The current prior art is known for methods of forming thin layers of materials on various types of substrates, in particular for producing layers of lithiated materials, i.e., materials containing lithium. These lithiated materials are used, in particular, in batteries, for example, to form electrolyte barriers or electrodes, or in any other electrical storage device. These layers can be deposited from precursors by atomic layer deposition (commonly referred to by the acronym ALD), atomic layer chemical vapor deposition (commonly referred to by the acronym ALCVD), or atomic layer epitaxy (commonly referred to by the acronym ALE). In particular, ALD is a thin film deposition technique based on gas-surface reactions to expose a surface on which it is desired to deposit a layer of material with different successive chemical precursors.

[0003] However, currently, no prior art method exists for producing lithiated materials comprising thin layers, i.e., layers having a thickness of 1 nm to 1 μm, composed of electrochemically active composite materials, which are particularly homogeneous and suitable for conforming to the more or less complex raised pattern of the surface of the substrate on which the lithiated material is deposited.

[0004] For the purposes of the present invention, the term "complex raised pattern" is understood to mean a substrate having cavities, tubes, or pillars machined into it to form a three-dimensional framework that creates a surface-to-volume ratio of greater than 10.

[0005] Furthermore, the prior art lacks manufacturing methods for producing cathode layers based on lithiated materials suitable for three-dimensional or 3D batteries.

[0006] For the purposes of the present invention, the term "three-dimensional battery or 3D battery" is understood to mean a battery having a pattern defined by a thickness greater than 5 μm. For example, a three-dimensional battery or 3D battery can have a microbattery consisting of at least six layers of material conformally deposited on a pre-structured substrate to form a three-dimensional mat that generates a predetermined specific surface area. These six layers are an insulating layer, two current collector layers, an anode layer, and a cathode layer. These two electrode layers are separated by a solid electrolyte. These six layers may optionally be protected by an additional encapsulation layer that prevents the 3D battery from aging.

[0007] The object of the present invention is, inter alia, to overcome all or some of the above-mentioned drawbacks. Summary of the Invention

[0008] To this end, according to a first aspect, the invention relates to a method for producing a lithiated material on a substrate, the lithiated material comprising a plurality of thin layers, the method comprising the steps of: a) placing a substrate made of a material intended for use in a battery in a reaction chamber; c1) atomic layer depositing a precursor of a first metal selected from nickel, manganese, cobalt, chromium, lanthanum, niobium, vanadium, iron, titanium, and aluminum onto at least a portion of a surface of a substrate through a reaction chamber at least once; c2) purging the reaction chamber at least once; c3) diffusing the first oxidizing species through the reaction chamber at least once to obtain a thin layer of oxide of the first metal; c4) purging the reaction chamber at least once; f1) atomic layer deposition of a lithium precursor through a reaction chamber onto the thin layer of oxide of the first metal at least once to form a thin lithiated layer; f2) purging the reaction chamber at least once; The method is characterized in that after step f2), it further comprises a crystallization annealing step g) at a temperature between 600°C and 800°C for 1 to 4 hours to obtain a lithiated material.

[0009] For purposes of this invention, by "material intended for use in a battery" is meant any type of material that has sufficient mechanical strength to be mechanically unaltered by the heat treatments typically performed in the battery manufacturing process, is chemically inert, and is electrochemically stable with respect to temperature.

[0010] Thus, according to this first aspect of the present invention, it is possible to produce an electrochemically active material comprising at least one thin layer of an oxide of the first metal described above and a thin lithiated layer on a substrate. Thus, it is possible to deposit electrochemically active composite materials on a substrate that can provide electrochemical performance suitable for three-dimensional batteries. For example, this method makes it possible to produce lithiated materials comprising a thin layer that is homogeneous, particularly over an area greater than 7.5 cm on a side.

[0011] It should be noted that the lithiated material can be used, for example, in electrochemical storage devices. In particular, such lithiated material can be used to fabricate two-dimensional or three-dimensional batteries, in particular three-dimensional microbatteries, such as lithium-ion microbatteries, for various applications. In two-dimensional or three-dimensional batteries, the substrate can take the form of a two-dimensional or three-dimensional object.

[0012] For the purposes of the present invention, the term "two-dimensional object" is understood to mean a flat object, for example made of silicon, or any object that can act as a mechanical base for receiving layers of material to produce a two-dimensional battery.

[0013] For the purposes of the present invention, the term "three-dimensional object" is understood to mean an object covered with a material, for example a stack of materials deposited in the form of thin layers by ALD. For example, the three-dimensional object may have, on at least one of its surfaces, a structuring that may be produced by using microelectronic etching techniques or techniques for the growth of micro / nano objects.

[0014] Thus, in such a method according to the invention, if the substrate is microstructured, i.e. if the substrate exhibits a certain degree of surface roughness on at least one of its surfaces, the deposited lithiated material will conform to this microstructure and it is therefore possible to easily form a lithiated material that perfectly follows the microstructure of the substrate so as to obtain a homogeneous material having the same thickness over the entire area on which the material is formed.

[0015] In particular, microstructured substrates have a larger specific surface area than flat (i.e., non-microstructured) substrates. The surface area of ​​a substrate can be increased, for example, by disposing microstructures with high aspect ratios on the surface of the substrate. The aspect ratio of a microstructure corresponds, for example, to the ratio of its vertical dimension to its smallest lateral dimension (e.g., the smallest lateral distance between two consecutive microstructures on the substrate).

[0016] For example, a microstructured substrate can include a substrate that includes microstructures such as grooves, pillars, and channels, or microstructures such as those taught in WO 2015052412. It is noted that the substrate may also be machinable using microfabrication techniques and must be able to withstand the heat treatments applied during the method for its manufacture, for example, during the deposition and annealing steps.

[0017] For example, the substrate may be selected from the group consisting of silicon, SiO2, Al2O3, Ti, glass, and Kapton®. Furthermore, the substrate may be flexible or rigid.

[0018] The precursor of the first metal may be in liquid or powder form, and may be selected from, but not limited to, the following precursors: FeCl2, FeCp2, Fe(thd)3, La(thd)3, CoCp2, MnCp2, Mn(thd)3, NiCp2, TiCl4, NbOEt5, and Cr(OCI)2.

[0019] It should be noted that step c3) of diffusing a first oxidizing species allows the breaking of chemical bonds of the elements located on the surface after carrying out step c1). This first oxidizing species is selected according to the strength of the chemical bonds of the elements in question. For example, ozone is preferably used to promote the oxidation of manganese, resulting in the formation of MnO2.

[0020] Preferably, the thin layer of oxide of the first metal has a thickness of 5 to 15 nm. This first layer may also preferably be deposited at a rate of 0.5 to 1 A per ALD cycle.

[0021] The lithium precursor may be in the form of a powder, for example, LiOtBu, but is not limited thereto.

[0022] Preferably, the lithiated thin layer has a thickness of 5 to 1000 nm. This first layer may also preferably be deposited at a rate of 0.5 to 1 A per ALD cycle.

[0023] In one particular embodiment, it is advantageous to functionalize the substrate to facilitate subsequent deposition steps, in particular to promote the bonding of the first atomic monolayer of the precursor of the first metal to the substrate. Such functionalization also makes it possible to obtain a substrate whose surface is free of or contains only very few contaminating elements, with the aim of obtaining a surface state conducive to the desired chemical reaction during the subsequent deposition step. Therefore, in this embodiment, the method further comprises, between steps a) and c1), at least one step b1) of functionalizing the substrate, which comprises diffusing water through the reaction chamber, followed by step b2) of purging the water from the reaction chamber.

[0024] Preferably, the functionalization step b1) is carried out at a temperature between 180°C and 220°C.

[0025] Preferably, the method further comprises a step b3) of the n1 first repetitions of steps b1) and b2), step b3) being carried out between steps b2) and c1), which makes it possible to significantly limit or even completely eliminate contaminants that may be present on the surface of the substrate before a subsequent deposition step is carried out.

[0026] In one particular embodiment, it is advantageous to produce a lithiated material that includes not only a single thin layer of an oxide of a first metal, but also at least one thin layer of an oxide of a first metal and a thin layer of an oxide of a second metal. Specifically, the presence of at least two thin layers of oxides of two different (transition) metals in the lithiated material provides significant advantages over currently used This allows for the production of lithiated materials that are electrochemically active at higher potentials. In particular, such lithiated materials can be used to operate at high potentials, i.e., Li / Li + It is therefore possible to produce a positive electrode for a three-dimensional battery operating at a potential higher than 4 V with respect to the electrode. In this embodiment, the method therefore further comprises, between steps c2) and f1), - step d1) of atomic layer deposition, at least once, of a precursor of a second metal selected from nickel, manganese, cobalt, chromium, lanthanum, titanium and aluminum, or of a phosphate precursor, through a reaction chamber onto at least a portion of the thin layer of oxide of the first metal; - step d2) of purging the reaction chamber at least once; - step d3) of diffusing a second oxidizing species through the reaction chamber at least once to obtain a thin layer of oxide or phosphate of the second metal; - step d4) of purging the reaction chamber at least once.

[0027] Similar to step c3) of diffusing a first oxidizing species, step d3) of diffusing a second oxidizing species makes it possible to break the chemical bonds of the elements located on the surface after carrying out step d1), this second oxidizing species being selected according to the strength of the chemical bonds of the elements.

[0028] It should be noted that the first oxidizing species may be, but is not necessarily, the same as the second oxidizing species.

[0029] Thus, for example, the first and / or second oxidizing species can include ozone, water, or any other gaseous compound containing oxygen, such as CO. Combinations of oxygen precursors can also be used in separate steps of diffusing the oxidizing species or simultaneously in the same step of diffusing the first or second oxidizing species.

[0030] It is also possible to carry out further steps similar to the above steps d1) to d4) in order to obtain thin layers of oxides of additional metals. Thus, for example, in this way, the following materials can be obtained: Li x M1 y M2 z M3 s O t , wherein M1, M2, and M3 are transition metals selected from Ni, Mn, Co, Cr, and Al, for example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Lix Ni y Co z Al t O2 (where y+z+t=1), it is possible to obtain

[0031] Preferably, the thin layer of second metal oxide or phosphate may have a thickness of 5 to 15 nm. This layer may also preferably be deposited at a rate of 0.5 to 1 A per ALD cycle.

[0032] It should be noted that the second metal precursor or phosphate precursor may be the same as or different from that deposited in step c1), and it is therefore possible to form, for example, ternary, quaternary, or pentary lithiated materials by forming thin layers derived from different transition metal precursors.

[0033] It should be noted that the second metal precursor or phosphate precursor may be in liquid or powder form. For example, the second metal precursor or phosphate precursor may be selected from, but not limited to, the following precursors: La(thd)3, CoCp2, MnCp2, Mn(thd)3, NiCp2, TiCl4, Cr(OCI)2.

[0034] Preferably, the method further comprises a step c5) of n2 second repetitions of steps c1) to c4). It should be noted that this step c5) is preferably carried out between steps c4) and d1), thus making it possible to obtain a homogeneous growth of the oxide of the first metal described by these steps c1) to c4) and to control the final stoichiometry of the desired lithiated material produced. It is possible to both control the

[0035] Preferably, the method further comprises a step d5) of a third repetition of steps d1) to d4) ns times, step d5) being carried out between steps d4) and f1), thus making it possible both to obtain a homogeneous growth of the oxide of the second metal described by these steps d1) to d4) and to control the final stoichiometry of the desired lithiated material produced.

[0036] Preferably, the method further comprises a fourth repetition (n4) of steps c1) to d4), step e). Note that this step e) is preferably carried out between steps d5) and f1). It is therefore possible to increase the thickness of each of the thin layers of oxides of the first and second metals, and thus the thickness of the active material, in order to improve the performance of a three-dimensional battery comprising such a lithiated material.

[0037] In one particular embodiment, it is advantageous to significantly limit or even eliminate carbon species that may have formed after step f1) of atomic layer deposition of the lithium precursor.Accordingly, in this embodiment, the method further comprises, between steps f2) and g), at least one forced oxidation step f3) of the thin lithiated layer, wherein the forced oxidation step f3) consists of diffusing water into the reaction chamber, followed by a step f4) of purging the reaction chamber.

[0038] Preferably, the forced oxidation step f3) is carried out at a temperature between 180°C and 220°C.

[0039] In steps b1) and f3), the water is preferably deionized.

[0040] Preferably, the method further comprises a fifth repetition of steps f1) to f4) n5 times, step f5) being carried out between steps f4) and g), thereby increasing the atomic layer thickness of the lithium precursor.

[0041] Preferably, n5 is defined as n5 = 0.05 * (n2 + n3) * n4. For example, in this manner, the ratio of manganese to nickel in an ALD cycle can be optimized to allow the formation of lithiated materials while limiting the presence of lithium oxide (NiO) and Li2MnO3.

[0042] Therefore, by adjusting the values ​​of n1 to n5, it is possible to obtain different stoichiometric ratios of materials containing lithium, nickel, manganese and oxygen (hereinafter referred to as LNMO materials).

[0043] It should further be noted that the purge step consists of drawing an inert gas through the reaction chamber, in particular after each precursor pulse or simultaneously with the precursor pulse. Alternatively, multiple purge pulses may be performed between each precursor pulse. The purge step is intended to remove all unreacted reagents, thereby ensuring that the production of the lithiated material occurs according to a self-limiting gas-surface reaction. Therefore, the reaction chamber may be purged by flowing a purge gas through the chamber or by flushing the chamber by reducing the pressure. Suitable purge gases include inert gases such as nitrogen, argon, etc., although any suitable gas or gas mixture that does not react with the deposited thin layer of precursor-containing material may be pulsed.

[0044] According to a second aspect, the present invention relates to a lithiated material obtainable by the process defined above. [Brief explanation of the drawings]

[0045] The invention will be better understood on reading the following description, given purely by way of example, and on referring to the accompanying drawings, in which:

[0046] [Figure 1] 1A to 1C are diagrams schematically illustrating an embodiment of a manufacturing method according to the present invention.

[0047] [Figure 2] 1 shows a TEM image of a cross section of the material of Example 1 before annealing obtained according to one embodiment of the present invention, on which a protective layer of alumina (Al) 2 O 3 has been further deposited.

[0048] [Figure 3]1 shows a TEM image of a cross section of the material of Example 1 after annealing obtained according to one embodiment of the present invention, where a protective layer of alumina (Al) 2 O 3 has been further deposited on the material. DETAILED DESCRIPTION OF THE INVENTION

[0049] Devices / Products device: -Reaction chamber: PICOSUN R200 ALD reactor.

[0050] product: -Substrate: BT Electronics, Siltronix (Si(100), 5~10ohm.cm, 2”~4”, 1 polished surface) -ALD precursors: For platinum: Trimethyl)methylcyclopentadienylplatinum(IV), 99%, Merck, StremChemicals For phosphate: Trimethyl phosphate, minimum 97%, Merck, Strem Chemicals For lithium: Lithium t-butoxide, 98+%, Merck, Strem Chemicals For alumina: Trimethylaluminum, 98% minimum, Merck, Strem Chemicals For nickel: Bis(cyclopentadienyl)nickel, 99% (nickelocene), Merck, Strem Chemicals Manganese: Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)manganese(III), 99% Mn(TMHD)3), Merck, Strem Chemicals. [Example]

[0051] Example 1: Preparation of a first lithiated material according to the present invention

[0052] The lithiated material produced in this example is LiNi applied to a two-dimensional substrate. 0.5 Mn 1.5O4(LNMO), which is obtained using atomic layer deposition (ALD) techniques as shown below.

[0053] The method according to this example comprises four main steps. forming a thin film of MnO2; forming a thin film of NiO; forming a thin lithiated film on the surface; - a crystallization annealing step that allows the formation of an LNMO material.

[0054] More specifically, the successive steps carried out in this example are as follows (as shown in FIG. 1): vinegar). a) placing a two-dimensional silicon substrate in a reaction chamber; b1) functionalizing the substrate by diffusing deionized water through the reaction chamber at a temperature of 195°C; b2) purging the reaction chamber; b3) a first iteration of steps b1) and b2) performed 10 times; c1) atomic layer deposition of a manganese (Mn) precursor by drawing Mn(thd) through a high temperature reaction chamber at a temperature of 195°C to form a thin layer containing Mn on the surface of the substrate; c2) purging the reaction chamber; c3) diffusing ozone by drawing it through a high-temperature reaction chamber at a temperature of 195°C to promote the reaction of the ozone with the thin layer containing Mn pre-formed on the surface of the substrate at the end of step c1), thereby forming a thin layer of MnO2; c4) purging the reaction chamber; c5) a second iterative step of performing steps c1) to c4) 27 times; d1) atomic layer deposition of a nickel (Ni) precursor by drawing Ni(Cp) through a high temperature reaction chamber at a temperature of 195°C to form a thin layer containing Ni on the surface of the thin layer of MnO; d2) purging the reaction chamber; d3) diffusing ozone by drawing it through a high-temperature reaction chamber at a temperature of 195°C to promote the reaction of the ozone with a thin layer containing Ni previously formed on the surface of the thin layer of MnO formed at the end of step d1), thereby forming a thin layer of NiO; d4) purging the reaction chamber; d5) a third repeating step of performing steps d1) to d4) 10 times; e) a fourth iteration of steps c1) to d4) performed 52 times to obtain a layer of MnO2-NiO; f1) atomic layer deposition of a Li precursor by drawing LiOtBu through a high temperature reaction chamber at a temperature of 225°C to form a thin layer containing Li on the surface of the MnO2-NiO layer; f2) purging the reaction chamber; f3) oxidizing the thin lithiated layer by drawing deionized water through a high-temperature reaction chamber at a temperature of 225°C to promote the reaction of the water with the Li-containing layer previously formed on the surface of the MnO2-NiO layer formed at the end of step f1), thereby forming a thin layer of lithium oxide; f4) purging the reaction chamber; f5) a fifth iterative process of performing steps f1) to f4) 96 times; g) crystallization annealing in air at a temperature of about 700° C. for 2 hours;

[0055] By proceeding in this manner, a lithiated material LiNi with a thickness of 100 nm was deposited on a silicon substrate. 0.5 Mn 1.5 O4 is obtained.

[0056] It should be noted that the above process can also be applied to microstructured substrates such as those described in WO2015052412. test

[0057] The lithiated material obtained according to Example 1 was analyzed by transmission electron microscopy (commonly referred to by the acronym TEM) (see Figures 2 and 3) before (see Figure 2) and after (see Figure 3) the annealing carried out in step g). The lithiated material is deposited on a layer of platinum applied from a platinum precursor capable of acting as a battery collector layer. 80 ... A 5 nm layer protects the assembly of platinum layer and lithiated material from cutting by a focused ion beam (commonly referred to by the acronym FIB), and this alumina layer is applied from an alumina precursor.

[0058] An analysis of the material before annealing is shown in Figure 2. Cells A, B, C, and D show the various stacked layers mentioned above (A and B are at a first scale, and C and D are at a second scale, as shown). In cells A and B of Figure 2, from bottom to top, one can see a first layer of alumina, a first layer of platinum, a layer of manganese-nickel, a second layer of alumina, and a second layer of platinum. In cells C and D of Figure 2, one can see, from bottom to top, a first layer of platinum, a layer of manganese-nickel, and a second layer of alumina.

[0059] Furthermore, note that there are no spaces between the various layers described above before annealing. This absence of spaces is a hallmark of good adhesion between the layers. Furthermore, in cells E-L, no interdiffusion is observed between the alumina or platinum and the lithiated material (here, the manganese-nickel layer, since lithium is invisible under a transmission electron microscope and the lithium layer is invisible in photographs). The platinum layer to which the lithiated material is applied exhibits surface roughness, and its grain orientation influences the orientation of the lithiated material deposited on top, which then acts as the positive electrode layer, in the case of a battery where this layer may be the collector layer. It can also be seen that the manganese and nickel are intimately mixed, forming a homogeneous layer, indicating good elemental distribution during deposition by ALD. Thus, the thin layer of Ni formed on top of the thin layer of Mn after its deposition diffuses into the Mn layer to form the manganese-nickel layer.

[0060] Analysis of the material after annealing is shown in Figure 3. In Figure 3, cells A and B show, from bottom to top, a first layer of alumina, a layer of platinum, a layer of manganese-nickel, and a second layer of alumina. In cells C and D of Figure 2, from bottom to top, a layer of platinum, a layer of manganese-nickel, and a second layer of alumina are shown. Furthermore, it is now possible to further discern the influence of the grain orientation of the collector layer, the platinum layer, on the preferred grain orientation of the LNMO material. Generally, segregation between manganese and nickel is observed. Specifically, nickel-depleted zones are observed to be enriched in manganese, and vice versa, but in different proportions. Note also that NiO is observed after annealing and the formation of the LNMO material.

[0061] Each cell in Figures 2 and 3 corresponds to a chemical map of a layer deposited on a silicon substrate. The chemical elements are indicated in the legend of each cell E-L. A color (or grayscale level) is assigned to each chemical element. The analytical techniques used also make it possible to overlay the colors or grayscale levels of the various elements (see cells B and C in Figure 2 and cells B and D in Figure 3).

[0062] In these two figures (2 and 3), two different scales are present (one for cells A and B, the other for cells C and D). The TEM analysis and subsequent chemical maps with all elements superimposed are shown on the cell images. In cells E-L in Figure 2 and cells E-L in Figure 3, each chemical element (Al, Pt, Ni, Mn) is shown alone. This allows for more precise access to information such as the interdiffusion or lack thereof of elements between successive layers, or the distribution of these various elements. In cells G and H, as well as K and L in Figure 3, manganese-nickel element segregation is observed for the manganese-nickel ratios considered in Figure 1. Furthermore, in cells F-H or I, K, and L in Figure 3, no interdiffusion is observed between the platinum and alumina layers or between the platinum and manganese-nickel layers.

Claims

1. 1. A method for producing a lithiated material on a substrate, the lithiated material comprising a plurality of thin layers, the method comprising: a) placing a substrate made of a material intended to be used in a battery in a reaction chamber; c1) atomic layer depositing a precursor of a first metal selected from nickel, manganese, cobalt, chromium, lanthanum, niobium, vanadium, iron, titanium, and aluminum onto at least a portion of a surface of the substrate through the reaction chamber at least once; c2) purging the reaction chamber at least once; c3) diffusing a first oxidizing species through the reaction chamber at least once to obtain a thin layer of oxide of the first metal; c4) purging the reaction chamber at least once; f1) atomic layer depositing a lithium precursor through the reaction chamber onto the thin layer of oxide of a first metal at least once to form a thin lithiated layer; f2) purging the reaction chamber at least once; 10. The method according to claim 9, further comprising, after step f2), a crystallization annealing step g) at a temperature between 600° C. and 800° C. for 1 to 4 hours to obtain a lithiated material.

2. 2. The method of claim 1, further comprising at least one step b1) of functionalizing the substrate between steps a) and c1), wherein the functionalizing step b1) comprises diffusing water through the reaction chamber, followed by step b2) of purging water from the reaction chamber.

3. n of steps b1) and b2) １ The method of claim 2 , further comprising a first iteration step b3) performed between steps b2) and c1).

4. n in steps c1) to c4) ２ The method according to any one of claims 1 to 3, further comprising a second iteration step c5).

5. Between steps c2) and f1), - step d1) of atomic layer deposition, at least once, of a precursor of a second metal selected from nickel, manganese, cobalt, chromium, lanthanum, titanium and aluminum, or a phosphate precursor, through the reaction chamber onto at least a portion of the layer of oxide of the first metal; - step d2) of purging the reaction chamber at least once; - a step d3) of diffusing a second oxidizing species through said reaction chamber at least once to obtain a thin layer of oxide or phosphate of said second metal; The method according to any one of claims 1 to 4, further comprising a step d4) of purging the reaction chamber at least once.

6. Steps d1) to d4) n ５ 6. The method of claim 5, further comprising a third iteration step d5), said step d5) being performed between steps d4) and f1).

7. Steps c1) to d4) n ４ 7. The method of claim 5 or 6, further comprising a fourth iteration step e).

8. Between steps f2) and g), a step f3) of forcibly oxidizing the lithiated thin layer at least once is further included, and the forcible oxidation step f3) is carried out by oxidizing the lithiated thin layer ...

8. The method of any one of claims 1 to 7, comprising: a) purging the reaction chamber; and b) purging the reaction chamber.

9. Steps f1) to f4) n ５ 9. The method of claim 8, further comprising a fifth iteration step f5), wherein step f5) is performed between steps f4) and g).

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