Method for protecting the surface of an electrode and electrode obtained thereby

Abstract

The invention relates to a method for modifying the surface of an alkali metal, such as lithium, for use in electrochemical cells and batteries. The described method alters the surface of the alkali metal by means of at least one organic compound previously deposited on a support. The organic compounds belong to the family of polycyclic aromatic molecules, quinones and / or vat dyes.

Description

[0001] METHOD FOR PROTECTING THE SURFACE OF AN ELECTRODE AND ELECTRODE OBTAINED BY THIS METHOD

[0002] RELATED APPLICATION

[0003] This application claims priority, under applicable law, from U.S. Provisional Application No. 63 / 724,636, filed on November 25, 2024, the contents of which being incorporated by reference in its entirety and for all purposes.

[0004] TECHNICAL FIELD

[0005] This technology generally relates to electrode materials and processes for their preparation, for example, electrode materials comprising an electrochemically active metallic material and an organic passivation layer. This technology also relates to electrodes and their use in electrochemical cells.

[0006] STATE OF THE ART

[0007] Metallic lithium is one of the elements exhibiting very high reactivity towards many chemicals and gases (even inert gases such as nitrogen). This high reactivity makes it very unstable, rendering its handling in uncontrolled atmospheres extremely dangerous and hindering its use as a negative electrode material for batteries. Various strategies have been proposed for the passivation of metallic lithium surfaces, depending on the physical form of the metallic lithium (strip, powder, etc.) or its production process.

[0008] For example, in the case of lithium powder produced from dispersed molten lithium, the use of small amounts of CO2 has been proposed (see US 5,567,474). In the case of lithium strip produced by cold rolling, the passivating agent can be added to a solvent and used as a lubricant and passivating agent during the production of thin lithium sheets (see EP06926691A1).

[0009] It has been observed that when a lithium layer is produced by depositing a thin layer of molten lithium onto a substrate, the lithium surface is so reactive that it reacts even at room temperature when exposed to pure nitrogen. It also reacts unpredictably when exposed to very dry air (dew point of -45°C). Therefore, it is important to be able to passivate the surface very early in its production to prevent any possible reaction of the lithium due to its exposure to reactive elements (such as H₂O, O₂, or N₂), even at very low concentrations.Treating lithium produced from molten lithium with passivating agents proposed in the literature, which must be dissolved in solvents or have a low vapor pressure, is not feasible because molten lithium deposition is carried out in highly controlled atmospheres. These atmospheres are very often achieved using purification reactors with zeolites and titanium sponge-based reagents to remove traces of H₂O and N₂. The presence of solvents and / or volatile reagents causes them to react with these zeolites and titanium sponge-based reagents in the purification reactors, leading to their deactivation and / or the formation of other byproducts.

[0010] One possible approach to avoid the use of solvents and dispersing agents is to deposit a thin layer of passivating agent onto the same polymer used as the coating after the lithium layer has been deposited. This allows the passivation process to begin a few seconds after the lithium layer is produced. The Chinese patent (CN109638235B, filed in November 2018) describes a roll-to-roll method for transferring a lithium salt or solvent using a lithium strip and a reagent strip wound together. The lithium salt solution or solvent reacts with the lithium to form a passivation layer composed of a lithium alloy (with Au, Ag, Mg, Al, Zn, Pt, Sn, In, Co, Si, or carbon) or a lithium phosphide, sulfide, chloride, or fluoride.However, this technology uses reagents dissolved in a solvent that interferes with the purification reactors and also contaminates the controlled atmosphere required during the deposition of a molten lithium layer. Furthermore, most of the agents proposed for forming lithium alloys on the lithium surface are relatively expensive reagents.

[0011] Another approach involved using a fluoropolymer with a side chain containing labile CF groups (French patent FR3134396B1). This polymer acts as a fluorine donor through a solid-solid reaction. This only involves the transfer of a portion of the molecules. Furthermore, these polymers involve a relatively complex polymerization process and a certain cost compared to simpler molecules.

[0012] Therefore, there is a need to develop a new process for passivating the surface of an alkali metal film, such as a lithium film, that eliminates at least one of the drawbacks of other known processes, as well as to identify the films obtained or obtainable by such a new process. SUMMARY

[0013] In certain respects, the embodiments of this technology include the following items:

[0014] Item 1. Process for preparing an electrode material, the process comprising the steps of:

[0015] (a) obtaining a lithium film or a lithium alloy comprising a first and a second surface;

[0016] (b) preparation of a transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free;

[0017] (c) bringing the first surface of the active lithium film into contact with the layer of organic protective agent in order to produce a protective layer on the first surface of the active lithium film; and

[0018] (d) optionally the removal of the transfer film; wherein the organic protective agent is preferably a non-volatile organic compound.

[0019] Item 2. The process of item 1, wherein the organic protecting agent is a passivating agent and the protective layer is a passivation layer.

[0020] Item 3. The process of item 1 or 2, in which the organic protecting agent is selected from polyaromatic compounds, vat dyes (vat), polycyclic compounds containing a quinone and their combinations.

[0021] Item 4. The process of item 3, wherein the organic protecting agent is a polyaromatic compound, preferably selected from anthracene, phenanthrene, phenanthroline, tetracene, pyrene, perylene and their derivatives.

[0022] Item 5. The process of item 3, wherein the organic protecting agent is a vat dye (vat), preferably selected from indigoids (e.g. indigo, thio-indigo, etc.) and their derivatives, dyes based on anthraquinone derivatives, and others similar.

[0023] Item 6. The process of item 3, wherein the organic protective agent is a polycyclic compound containing a quinone, preferably selected from anthraquinone, phenanthrenequinone, tetracenequinone, perylenequinone, alizarin, and their derivatives. Item 7. The process of any one of items 1 to 6, wherein step (b) comprises applying the organic protective agent to the transfer film.

[0024] Item 8. The process of any one of items 1 to 6, wherein step (b) includes preparing a solution or suspension of the organic protective agent in a solvent, applying the solution or suspension to the surface of the transfer film and removing the solvent.

[0025] Item 9. The process of item 8, wherein the solution is applied by drop-casting, mold casting, dip coating, spin coating, spray coating, printing (for example, an etching-type process), slot-die coating, doctor blade coating, preferably by spray coating.

[0026] Item 10. The process of any one of items 1 to 9, wherein the contacting step includes calendering, rolling or rolling the lithium film or lithium alloy with the transfer film comprising the organic protective agent layer.

[0027] Item 11. The process of any one of items 1 to 10, wherein the second surface of the lithium film or lithium alloy of step (a) is on a current collector.

[0028] Item 12. The method of item 11, wherein the lithium or lithium alloy film is a first lithium or lithium alloy film, and a second lithium or lithium alloy film is present on the current collector surface opposite the current collector surface in contact with the first lithium or lithium alloy film.

[0029] Item 13. The process of item 12, wherein step (c) further comprises bringing the free surface of the second active lithium film into contact with a second layer of organic protective agent in order to produce a protective layer on the free surface of the second active lithium film.

[0030] Item 14. The process of any one of items 1 to 10, wherein the process further comprises applying the second surface of the lithium film or lithium alloy to a current collector in step (a). Item 15. The process of any one of items 1 to 10, wherein the process further comprises applying the second surface of the lithium film or lithium alloy to a current collector after step (c).

[0031] Item 16. The process of any one of items 1 to 10, wherein the process further comprises applying the second surface of the lithium film or lithium alloy to a current collector during step (c), at the same time as or just before the first surface of the active lithium film is brought into contact with the layer of organic protective agent.

[0032] Item 17. The process of any one of items 1 to 10, wherein the process further comprises bringing the second surface of the lithium film or of a lithium alloy into contact with a second transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free.

[0033] Item 18. The method of item 17, in which said contacting of the second surface occurs simultaneously with step (c).

[0034] Item 19. The process of any one of items 1 to 18, wherein the lithium film or lithium alloy film is a lithium film having a purity of at least 99% by weight, or at least 99.9

[0035] % by weight, or at least 99.99% by weight, or at least 99.999% by weight.

[0036] Item 20. The process of any of items 1 to 18, wherein the lithium or lithium alloy film comprises a lithium alloy comprising at least 50% by weight, at least 75% by weight, at least 90% by weight, at least 95% by weight or at least 98% by weight of lithium.

[0037] Item 21. The process of item 20, wherein the lithium alloy comprises lithium and at least one element selected from the alkali metals other than lithium, the alkaline earth metals, the rare earth metals, zirconium, copper, silver, bismuth, cobalt, manganese, zinc, aluminium, silicon, tin, antimony, cadmium, mercury, lead, molybdenum, iron, boron, indium, thallium, nickel and germanium.

[0038] Item 22. The process of any one of items 1 to 21, wherein the lithium or lithium alloy film has a thickness of between about 1 pm and about 200 pm, or between about 5 pm and about 100 pm, or between about 10 pm and about 50 pm.

[0039] Item 23. The process of any one of items 1 to 22 in which at least a portion of the process is carried out by a roll-to-roll process. Item 24. The process of any one of items 1 to 23, in which the process further includes step (d) of removing the transfer film.

[0040] Item 25. Electrode material obtained or obtainable by the process of any of items 1 to 24.

[0041] Item 26. The electrode material of item 25, in which said electrode material comprises the protective layer on the first surface of the lithium or lithium alloy film.

[0042] Item 27. The electrode material of item 26, wherein said protective layer provides improved protection against moisture and reactive gases compared to a lithium film or lithium alloy without said protective layer.

[0043] Item 28. Electrochemical cell comprising an electrode, a counter electrode and an electrolyte between the electrode and the counter electrode, in which the electrode comprises the electrode material as defined in any one of items 25 to 27.

[0044] Item 29. The electrochemical cell of item 28, in which said electrolyte is a solid electrolyte comprising a polymer, inorganic particles or a combination thereof.

[0045] Item 30. The electrochemical cell of item 28, in which said electrolyte is a gel or liquid electrolyte and further comprises a separator.

[0046] Item 31. Battery comprising at least one electrochemical cell as defined in one of items 28 to 30.

[0047] Other aspects and characteristics of the present processes, materials and uses will become more apparent upon reading the following non-restrictive description of embodiments and illustrative examples, which should not be interpreted as limiting the scope of the invention.

[0048] BRIEF DESCRIPTION OF THE FIGURES

[0049] Figure 1 shows photographs taken in daylight (top) and under UV light (bottom) of a transfer film with the passivating agent (left), a lithium film including a passivation layer (center), and the transfer film after removal of the lithium film, according to Example 1. Figure 2 shows photographs of a reference film (Li A, top) and a treated film (Li B, bottom) taken at 0 seconds, 30 seconds, and at 1, 2, 3, 4, and 7 minutes, as described in Example 2.

[0050] Figure 3 shows the discharge capacity (in mAh / g of LiFePCL) as a function of the number of cycles (in number) for Li A, Li C, Li D and Li E, as described in Example 3.

[0051] Figure 4 shows a photograph of an ultrathin lithium film with the PP film with thioindigo sprayed on its surface, according to Example 4.

[0052] Figure 5 shows photographs (a) of the surface of a lithium film following thio-indigo transfer, and (b) of the transfer film after removal of the lithium film, according to Example 4.

[0053] Figure 6 shows the capacity and coulombic efficiency of unprotected lithium (solid symbols) and with transferred protection (empty symbols) relative to NCM in an ether-based liquid electrolyte according to Example 5.

[0054] Figure 7 shows the state of health (SOH) and coulombic efficiency of unprotected lithium (solid symbols) and with transferred protection (empty symbols) compared to NCM in a liquid ether electrolyte according to Example 5.

[0055] Figure 8 shows impedance measurements with button cells containing (a) unprotected lithium and (b) lithium with transferred protection as described in Example 5.

[0056] Figure 9 shows in (a) unprotected lithium exposed to a dew point of -15°C, and in (b) the same lithium with the protective layer.

[0057] DETAILED DESCRIPTION

[0058] All technical and scientific terms and expressions used herein have the same definitions as those generally understood by a person versed in the art of this technology. The definitions of certain terms and expressions used are nevertheless provided below. To the extent that the definitions of terms in publications, patents, and patent applications incorporated herein by reference are contrary to the definitions stated in this specification, the definitions in this specification shall prevail. The section headings used herein are for organizational purposes only and shall not be construed as limiting the subject matter described. When the term "about" is used herein, it means approximately, in the region of, or around. For example, when the term "about" is used in connection with a numerical value, it may modify it above or below by a variation of 10% from its nominal value.This term can also take into account, for example, the experimental error of a measuring device or rounding.

[0059] The chemical structures described here are drawn according to conventional standards. Furthermore, when an atom, such as a carbon atom as drawn, appears to include an incomplete valence, then the valence is assumed to be satisfied by one or more hydrogen atoms, even if these are not explicitly shown. The hydrogen atoms should be considered as part of the compound.

[0060] The terminology used here is intended to describe particular embodiments and is not meant to be exhaustive. It should be noted that the singular forms "a," "an," and "the" also include plural forms, unless the context clearly indicates otherwise. Thus, for example, a reference to a composition containing "a compound" also considers a mixture of two or more compounds. It should also be noted that the term "or" is generally used in its sense including "and / or," unless the context clearly indicates otherwise. Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variants thereof are used in the detailed description and / or claims, these terms are intended to be inclusive in a manner similar to the term "comprising."

[0061] The number of carbon atoms in a hydrocarbyl substituent can be indicated by the prefix "Cx-Cy" or "Cx-y", where x is the minimum number and y the maximum number of carbon atoms in the substituent. However, when the prefix "Cx-Cy" is used, the number of carbon atoms in a hydrocarbyl substituent is not the same as the number of carbon atoms in a hydrocarbyl substituent. x -C y » or « C x-y " is associated with a group incorporating one or more heteroatom(s) by definition (e.g., heterocycloalkyl, heteroaryl, etc.), x and y then respectively define the minimum and maximum number of atoms in the ring, including carbon atoms as well as heteroatom(s).

[0062] The term "alkyl" as used here refers to saturated hydrocarbons with one to twelve carbon atoms, including linear or branched alkyl groups. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, tert-butyl, sec-butyl, and isobutyl. When the alkyl group is located between two functional groups, the term "alkyl" also encompasses alkylene groups such as methylene, ethylene, and propylene. The term "lower alkyl" refers to an alkyl group with one to six carbon atoms.

[0063] The term "alkenyl" as used here refers to a linear or branched hydrocarbon radical containing one or more double bonds and typically 2 to 20 carbon atoms. For example, a "C2-salkenyl" contains two to eight carbon atoms. Alkenyl groups include, but are not limited to, ethenyl, propenyl, butenyl, 1-methyl-2-butene-1-yl, heptenyl, octenyl, etc.

[0064] The term "alkynyl" as used here refers to a linear or branched hydrocarbon radical containing one or more triple bonds and generally 2 to 20 carbon atoms. For example, "C2-salkynyl" contains two to eight carbon atoms. Representative alkynyl groups include, but are not limited to, ethynyl, propyn-1-yl, butyn-1-yl, heptynyl, octynyl, etc.

[0065] The terms "cycloalkyl," "alicyclic," "carbocycle," "carbocyclic," and equivalent expressions refer to a group comprising a saturated or partially unsaturated (non-aromatic) carbocyclic ring in a monocyclic or polycyclic system, including spiro (sharing one atom), fused (sharing at least one bond), or bridged (sharing two or more bonds) carbocyclic systems, with three to fifteen ring members. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentene-1-yl, cyclopentene-2-yl, cyclopentene-3-yl, cyclohexyl, cyclohexene-1-yl, cyclohexene-2-yl, cyclohexene-3-yl, cycloheptyl, bicyclo[4,3,0]nonanyl, norbornyl, etc. The term cycloalkyl includes both unsubstituted and substituted cycloalkyl groups.The term "Cs-Cycloalkyl" refers to a cycloalkyl group having from 3 to the specified number "n" of carbon atoms in its cyclic structure. Unless otherwise stated, "lower cycloalkyl" groups as used here have at least 3 and at most 8 carbon atoms in their cyclic structure.

[0066] In this document, the terms "heterocycle," "heterocycloalkyl," "heterocyclyl," "heterocyclic radical," and "heterocyclic ring" are used interchangeably and refer to a chemically stable, saturated or partially unsaturated monocyclic heterocyclic fragment of 3 to 7 members or a bicyclic fragment of 7 to 10 members, comprising, in addition to carbon atoms, one or more, preferably one to four, heteroatoms, as defined above. When used with reference to a ring atom of a heterocycle, the term "nitrogen" includes a substituted nitrogen. For example, in a saturated or partially unsaturated ring comprising 1 to 3 heteroatoms selected from oxygen, sulfur, or nitrogen, the nitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl), or NR (as in N-substituted pyrrolidinyl).A heterocyclic ring can be attached to its pendant group at any heteroatom or carbon atom, in a chemically stable structure, and any of the ring atoms can optionally be substituted.Examples of heterocycloalkyl groups include, but are not limited to, 1,3-dioxolanyl, pyrrolidinyl, pyrrolidonyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothiopyranyl, tetrahydrodithienyl, tetrahydrothienyl, thiomorpholino, thioxanyl, azetidinyl, oxetanyl, thietanyl, homopiperidinyl, oxepanyl, thiepanyl, oxazepinyl, diazepinyl, thiazepinyl, 1,2,3,6- tetrahydropyridinyl, 2-pyrrolinyl, 3-pyrrolinyl, 2H-pyranyl, 4H-pyranyl, dioxanyl, dithianyl, dithiolanyl, dihydropyranyl, dihydrothienyl, dihydrofuranyl, 3-azabicyclo[3,1,0]hexanyl, 3-azabicyclo[4,1,0]heptanyl, quinolizinyl, quinuclidinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, etc.Heterocyclic groups also include groups in which a heterocyclic ring is fused to one or more aryl, heteroaryl, or cycloaliphatic rings, such as indolinyl, 3H-indolyl, chromanyl, chromenyl, phenanthridinyl, 2-azabicyclo[2.2.1]heptanyl, octahydroindolyl, or tetrahydroquinolinyl, where the radical or attachment point is on the heterocyclyl ring. A heterocyclyl group may be monocyclic or bicyclic. The term "heterocyclylalkyl" refers to an alkyl group substituted by a heterocyclyl, in which the alkyl and heterocyclyl portions are independently and optionally substituted. The term "Cs-nheterocycloalkyl" refers to a heterocycloalkyl group having from 3 to the specified number "n" of atoms in the cyclic structure, including carbon atoms and heteroatoms.

[0067] As used here, the term "partially unsaturated" refers to a cyclic fragment that includes at least one double or triple bond between the ring atoms but is not aromatic. The term "partially unsaturated" is intended to encompass rings with multiple unsaturation sites but is not intended to include aryl or heteroaryl fragments as defined here.

[0068] The term "aryl," used alone or as part of a larger group such as "aralkyl," "aralcoxy," "aryloxy," or "aryloxyalkyl," refers to aromatic groups having 4n+2 conjugated TT(pi) electrons, where n is an integer from 1 to 3, in a monocyclic group or a fused bicyclic or tricyclic system comprising a total of six to 15 ring members, in which at least one ring of the system is aromatic and in which each ring of the system contains three to seven ring members. The term "aryl" may be used interchangeably with the term "aryl ring." In some embodiments of this description, "aryl" refers to an aromatic cyclic system that includes, but is not limited to, phenyl, biphenyl, naphthyl, azulenyl, anthracyl, and the like, which may bear one or more substituents. The term "aralkyl" or "arylalkyl" refers to an alkyl residue attached to an aryl ring.Examples of aralkyl include, but are not limited to, benzyl, phenethyl, etc. The term "aryl," as used here, also includes a group in which an aromatic ring is fused to one or more non-aromatic rings, such as indanyl, indenyl, phthalimidyl, naphtimidyl, fluorenyl, phenanthridinyl, tetrahydronaphthyl, etc. The term "C6-. n "aryl" denotes an aryl group containing from 6 to the specified number "n" of atoms in the cyclic structure.

[0069] The term "heteroaryl," used alone or as part of a larger group, for example, "heteroaralkyl" or "heteroaralkoxy," refers to aromatic groups having 4n+2 conjugated ir(pi) electrons, where n is an integer from 1 to 3 (e.g., having 5 to 18 ring atoms, preferably 5, 6, or 9 cyclic atoms; having 6, 10, or 14 TT electrons shared in a cyclic lattice); and having, in addition to carbon atoms, one to five heteroatoms. The term "heteroatom" includes, but is not limited to, nitrogen, oxygen, or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quaternized form of basic nitrogen. A heteroaryl may be a single ring or two or more fused rings. The term "heteroaryl", as used here, also includes groups in which a heteroaromatic ring is condensed to one or more aryl, cycloaliphatic, or heterocyclic rings.where the radical or point of attachment is located on the heteroaromatic ring. Non-limiting examples of heteroaryl groups include thienyl, furanyl (furyl), pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, indolyl, 3H-indolyl, isoindolyl, indolizinyl, benzothienyl (benzothiophenyl), benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzotriazolyl, pyrrolopyridinyl (e.g., pyrrolo[3,2-b]pyridinyl or pyrrolo[3,2-c]pyridinyl), pyrazolopyridinyl (e.g., pyrazolo[1,5-a]pyridinyl), furopyridinyl, purinyl, imidazopyrazinyl (e.g., imidazo[4,5-b]pyrazinyl), quinolyl (quinolinyl), isoquinolyl (isoquinolinyl), quinolonyl, isoquinolonyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl,naphthyridinyl and pteridinyl carbazolyl, acridinyl, phenanthridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-l,4-oxazine-3(4H)-one. A heteroaryl group can be mono- or bicyclic. Heteroaryl groups comprise rings that are optionally substituted. The term "heteroaryl" refers to an alkyl group substituted by a heteroaryl, in which the alkyl and heteroaryl portions are independently and possibly substituted. Examples include, but are not limited to, pyridinylmethyl, pyrimidinylethyl, and others like them. For example, the term "Cs-nheteroaryl" refers to a heteroaryl group having from 5 to the specified number "n" of atoms in the cyclic structure, including carbon atoms and heteroatoms.

[0070] As described herein, the compounds in this description may contain "possibly substituted" fragments. In general, the term "substituted," whether or not preceded by "possibly," means that one or more hydrogen atoms of the designated fragment are replaced by a suitable substituent. Unless otherwise specified, a "possibly substituted" group may have a suitable substituent at each substitutable position of the group, and where several positions in a given structure may be substituted by several substituents chosen from a specified group, the substituent may be the same or different at each position. The combinations of substituents considered in this description are preferably those that result in the formation of chemically stable or chemically feasible compounds.The term "chemically stable", as used here, refers to compounds that are not substantially altered when subjected to conditions permitting their production, detection and, in certain embodiments, their recovery, purification and use for one or more of the purposes described herein.

[0071] The term "halo" refers to a halogen atom, that is, an atom of fluorine, chlorine, bromine or iodine, preferably fluorine or chlorine.

[0072] The term "possibly substituted" refers to groups that are substituted or unsubstituted by the independent replacement of one, two, three, or more hydrogen atoms by substituents including, but not limited to, F, Cl, Br, I, OH, CO2H, alkoxy, oxo, thiooxo, NO2, CN, CF3, NH2, NHalkyl, NHalkenyl, NHalkynyl, NHcycloalkyl, N-Haryl, NH-heteroaryl, NH-heterocycloalkyl, dialkylamino, diarylamino, diheteroarylamino, O-alkyl, O-alkenyl, O-alkynyl, O-cycloalkyl, O-aryl, O-heteroaryl, O-haloalkyl, O-heterocycloalkyl, C(O)alkyl, C(O)alkenyl, C(O)alkynyl, C(O)cycloalkyl, C(O)aryl, C(O)heteroaryl, C(O)heterocycloalkyl, CChalkyl, CChalcenyl, CChalcynyl, CChcycloalkyl, CCharyl, CChheteroaryl, CChheterocycloalkyl, OC(O)alkyl, OC(O)alkenyl, OC(O)alkynyl, OC(O)cycloalkyl, OC(O)aryl, OC(O)heteroaryl, OC(O)heterocycloalkyl, C(O)NH2, C(O)NHalkyl, C(O)NHalcenyl, C(O)NHalcynyl, C(O)NHcycloalkyl, C(O)NHaryl, C(O)NHheteroaryl

[0073] C(O)NHheterocycloalkyle, OCCalkyle, OCCalcenyle, OCCalcynyle, OCChcycloalkyle,

[0074] OCCharyle, OCCheteroaryle, OCCheterocycloalkyle, OC(O)NH2, OC(O)NHalkyle,

[0075] OC(O)NHalcenyle, OC(O)NHalcynyle, OC(O)NHcycloalkyle, OC(O)NHaryle,

[0076] OC(O)NHheteroaryle, OC(O)NHheterocycloalkyl, NHC(O)alkyl, NHC(O)alkenyl,

[0077] NHC(O)alcynyle, NHC(O)cycloalkyle, NHC(O)aryle, NHC(O)heteroaryle,

[0078] NHC(O)heterocycloalkyle, NHCC^alkyle, NHCC^alcenyle, NHCC^alcynyle, NHCO2cycloalkyle,

[0079] NHCO2aryle, NHCO2heteroaryle, NHCO2heterocycloalkyl, NHC(O)NH2, NHC(O)NHalkyle,

[0080] NHC(O)NHalcenyle, NHC(O)NHalcynyl, NHC(O)NHcycloalkyle, NHC(O)NHaryle,

[0081] NHC(O)NHheteroaryle, NHC(O)NHheterocycloalkyl, NHC(S)NH2, NHC(S)NHalkyle,

[0082] NHC(S)NHalcenyle, NHC(S)NHalcynyle, NHC(S)NHcycloalkyle, NHC(S)NHaryle,

[0083] NHC(S)NHheteroaryl, NHC(S)NHheterocycloalkyl, NHC(NH)NH2, NHC(NH)NHalkyl,

[0084] NHC(NH)NHalkenyl, NHC(NH)NHalkynyl, NHC(NH)NHcycloalkyl, NHC(NH)NHaryl,

[0085] NHC(NH)NHheteroaryl, NHC(NH)NHheterocycloalkyl, NHC(NH)alkyl, NHC(NH)alkenyl,

[0086] NHC(NH)alkynyl, NHC(NH)cycloalkyl, NHC(NH)aryl, NHC(NH)heteroaryl, NHC(NH)heterocycloalkyl, C(NH)NHalkyl, C(NH)NHalkenyl, C(NH)NHalkynyl, C(NH)NHcycloalkyl, C(NH)NHaryl, C(NH)NHheteroaryl, C(NH)NHheterocycloalkyl, S(O)alkyl, S(O)alkenyl, S(O)alkynyl, S(O)cycloalkyl, S(O)aryl, S(O)2alkyl, S(O)2alkenyl, S(O)2alkynyl, S(O)2cycloalkyl, S(O)2aryl, S(O)heteroaryl, S(O)heterocycloalkyl, SO2NH2,

[0087] SChNHalkyl, SChNHalkenyl, SChNHalkynyl, SChNHcycloalkyl, SChNHaryl,

[0088] SChNHheteroaryl, SChNHheterocycloalkyl, NHSChalkyl, NHSChalcenyl, NHSChalcynyl, NHSChcycloalkyl, NHSCharyl, NHSChheteroaryl, NHSChheterocycloalkyl, CH2NH2, CH2SO2CH3, alkyl, alkenyl, alkynyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, heterocycloalkyl, cycloalkyl, carbocyclic, heterocyclic, polyalkoxyalkyl, polyalkoxy, methoxymethoxy, methoxyethoxy, SH, S-alkyl, S-alkenyl, S-alkynyl, S-cycloalkyl, S-aryl, S-heteroaryl, S-heterocycloalkyl, or methylthiomethyl.

[0089] The inclusion of a list of chemical groups in any variable definition in this document includes definitions of that variable as a single group or as a combination of the listed groups. The mention of an embodiment of a variable in this document includes that embodiment alone or in combination with any other embodiment or part thereof. Thus, the following embodiments are presented alone or in combination, as appropriate.

[0090] The term "polyaromatic compound" as used herein defines a compound comprising at least two, preferably three, conjugated aryl and / or heteroaryl groups as defined herein. The term polyaromatic compound specifically excludes polyaromatic carbon materials such as graphene or graphite and their forms and derivatives.

[0091] The term "vat dyes" as used here refers to a class of compounds that are normally water-insoluble polycyclic compounds and are applied to a fabric using a redox reaction, for example, applied to fibers under reducing conditions and then oxidized again to form an insoluble color. Vat dyes include, for example, indigoids and anthraquinone-based dyes.

[0092] The expression "quinone-containing polycyclic compound" as used here refers to a polycyclic compound comprising quinone groups in a polycyclic skeleton comprising at least two aryl and / or heteroaryl groups and possibly non-aromatic rings.

[0093] The present technology relates to a process for preparing an electrode material containing an alkali metal film or an alkali metal alloy and an organic compound acting as a protective (or passivating) agent and forming a protective (or passivating) layer on the surface of the film. The organic compound is non-volatile and has a low vapor pressure.

[0094] Although the following text and the attached claims refer to lithium and lithium alloys, it should be noted that lithium can be replaced by another alkali metal in the present process, the electrode material, the electrochemical cell, and the battery, including in any of their embodiments and combinations thereof. However, in a preferred embodiment, the alkali metal film or an alkali metal alloy film is a lithium film or an alloy thereof.

[0095] In one embodiment, the process relates to the preparation of an electrode material and includes the following steps: (a) obtaining a lithium film or a lithium alloy comprising a first and a second surface;

[0096] (b) preparation of a transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free;

[0097] (c) bringing the first surface of the active lithium film into contact with the layer of organic protective agent in order to produce a protective layer on the first surface of the active lithium film; and

[0098] (d) optionally the removal of the transfer film; wherein the organic protective agent is preferably a non-volatile organic compound.

[0099] According to one embodiment, the organic protective agent is a passivating agent and the protective layer forms a passivation layer.

[0100] For example, the organic preservative is preferably chosen from polyaromatic compounds, vat dyes (vats), polycyclic compounds containing a quinone, or a combination of two or more of these. Non-limiting examples of polyaromatic compounds include anthracene, phenanthrene, phenanthroline, tetracene, pyrene, perylene, and their derivatives. Examples of vat dyes include, but are not limited to, indigoids (e.g., indigo, thio-indigo, etc.) and their derivatives, dyes based on anthraquinone derivatives, and the like. Non-limiting examples of polycyclic compounds containing a quinone include anthraquinone, phenanthrenequinone, tetracenequinone, perylenequinone, alizarin, and their derivatives. For example, an anthraquinone derivative might include methyl- or ethylanthraquinone, etc.

[0101] The transfer film can be made of any material that will not react with the surface of the lithium or lithium alloy film, preferably a polymer film. Examples of such a polymer include polypropylene, polyethylene, or a combination or copolymer thereof.

[0102] In one embodiment of the process, step (b) includes applying the organic protective agent to the transfer film. For example, step (b) preferably includes preparing a solution or suspension of the organic protective agent in a solvent, applying the solution or suspension to the surface of the transfer film, and removing the solvent. Non-limiting examples of application methods include dropcasting, mold casting, dip coating, spin coating, spray coating, printing (e.g., an etching process), slot-die coating, doctor blade coating, preferably by spray coating.

[0103] In preferred embodiments, the contacting step includes calendering, rolling, or pressing the lithium film or lithium alloy between rolls with the transfer film comprising the organic protective agent layer. For example, calendering, rolling, or pressing can be carried out hot or cold, for example, by hot rolling or cold rolling.

[0104] According to some embodiments of the process, the second surface of the lithium or lithium alloy film in step (a) is on a current collector. For example, the lithium or lithium alloy film can be considered the first lithium or lithium alloy film, where a second lithium or lithium alloy film is present on the current collector surface opposite the current collector surface in contact with the first lithium or lithium alloy film. In this embodiment, preferably, step (c) further includes contacting the free surface of the second active lithium film with a second layer of organic protective agent to produce a protective layer on the free surface of the second active lithium film.

[0105] In some embodiments, the process may further include applying the second surface of the lithium or lithium alloy film to a current collector in step (a). Alternatively, the process may further include applying the second surface of the lithium or lithium alloy film to a current collector after step (c). In other embodiments, the process further includes applying the second surface of the lithium or lithium alloy film to a current collector during step (c), either simultaneously with or just before contacting the first surface of the active lithium film with the organic protective layer. The current collector may be a compatible current collector such as is commonly known in the field (e.g., Cu, Ni, conductive polymer, etc.).Alternatively, the process may further include bringing the second surface of the lithium or lithium alloy film into contact with a second transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free, for example said contacting of the second surface preferably occurring simultaneously with step (c).

[0106] In some examples, the lithium or lithium alloy film is a lithium film having a purity of at least 99% by weight, or at least 99.9% by weight, or at least 99.99% by weight, or at least 99.999% by weight. In other examples, the lithium or lithium alloy film comprises a lithium alloy containing at least 50% by weight, at least 75% by weight, at least 90% by weight, at least 95% by weight, or at least 98% by weight of lithium. For example, lithium alloy includes lithium and at least one element selected from alkali metals other than lithium, alkaline earth metals (e.g. Mg), rare earth metals, zirconium, copper, silver, bismuth, cobalt, manganese, zinc, aluminum, silicon, tin, antimony, cadmium, mercury, lead, molybdenum, iron, boron, indium, thallium, nickel, and germanium.

[0107] In one embodiment, the lithium or lithium alloy film has a thickness of between about 1 pm and about 200 pm, or between about 5 pm and about 100 pm, or between about 10 pm and about 50 pm.

[0108] The process can be carried out at least partially using a rolling process. For example, at least part of the process can be carried out using a roll-to-roll process. The process is preferably carried out at least partially in an anhydrous environment and / or an inert atmosphere, in particular steps (a) and (c).

[0109] In some cases, step (d) can be carried out only before assembly with other components of an electrochemical cell. For example, the transfer film can be retained on the lithium or alloy film to serve as protection (protective film) during transport to a cell assembly unit, for example in the form of lithium or lithium alloy rolls.

[0110] This technology also relates to an electrode material, for example, one obtained by this process and comprising the characteristics defined in the steps above. This electrode material includes a protective (or passivation) layer on the first surface of the lithium or lithium alloy film. For example, the protective (or passivation) layer provides improved protection against moisture and reactive gases compared to a lithium or lithium alloy film without said protective layer.

[0111] The present technology also proposes an electrochemical cell comprising an electrode, a counter electrode and an electrolyte between the electrode and the counter electrode, where the electrode comprises the electrode material as defined herein.

[0112] Examples of counter-electrode materials include particles of an electrochemically active material such as oxides and complex oxides of metals, lithiased oxides and complex oxides of metals, metal phosphates and lithiased metal phosphates.Examples of electrochemically active counter-electrode materials include, but are not limited to, lithiated metal phosphates (e.g., LiM'PCU where M' is Fe, Ni, Mn, Co, or a combination thereof), vanadium oxides (e.g., LiVaOs, V2O5, UV2O5, and others like them), and other lithiated metal oxides such as LiM^Cl, LiM”C>2 (M’ being Mn, Co, Ni, or a combination thereof) and Li(NiM”’)C>2 (M’’ being Mn, Co, Al, Fe, Cr, Ti, Zr, and others like them, or a combination thereof), as well as the lithiated forms of the above lithiated metal oxides and phosphates, electrochemically active organic cathode materials, sulfur, air (oxygen), or a combination thereof, or any of the above materials further including a compatible doping element chosen from groups 2 to 15 of the periodic table of elements.For example, the active material of the counter electrode is chosen from lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP) and lithium nickel manganese cobalt oxide (NMC).

[0113] In another example, the electrochemically active material of the counter electrode corresponds to the formula LiM'PCL, in which M' is Fe, Ni, Mn, Co, or a combination thereof, possibly doped with a compatible element, for example, possibly doped with an element chosen from Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr, and W, or a combination thereof. For example, the electrochemically active material is LiFePCL or LiMn x Fei. xPO4, where 0 < x < 1, possibly doped with a compatible element, for example, possibly doped with an element chosen from Co, Ni, Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr, and W, or a combination thereof, for example, possibly doped with magnesium. Compounds of the formula LiM”C>2, in which M” represents Mn, Co, Ni, or a combination thereof, are also examples of electrochemically active counter-electrode materials. For example, the electrochemically active counter-electrode material is UNi w Mn y COzO2, where w + y + z = 1. The electrochemically active material particles of the counter electrode are freshly formed or sourced commercially. They may be in the form of microparticles or nanoparticles and may also include a carbon coating.

[0114] The counter electrode material may include additional components such as electronically conductive materials, inorganic particles, glass or ceramic particles, salts (e.g., lithium salts), and the like. Examples of electronically conductive materials include carbon black, Ketjen Black™, acetylene black, graphite, graphene, carbon fibers or nanofibers (e.g., VGCF), or nanotubes, or a combination thereof. In another example, the counter electrode material as defined above may also include an organic compound as defined herein.

[0115] The counter-electrode material may also include at least one binder. Examples of binders include water-soluble binders such as SBR (styrene-butadiene rubber), NBR (acrylonitrile butadiene rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), ACM (acrylate rubber), and others similar, and cellulose-based binders (e.g., carboxyalkylcellulose, hydroxyalkylcellulose, and combinations thereof), or any combination of two or more of these. For example, carboxyalkylcellulose may be carboxymethylcellulose (CMC) or carboxyethylcellulose. Hydroxypropylcellulose is an example of hydroxyalkylcellulose. Other examples of binders include fluorine-containing polymer binders such as PVDF and PTFE, and ion-conducting polymer binders such as block copolymers composed of at least one lithium-ion-solvating segment and at least one crosslinkable segment.For example, the binder is a polyether-type polymer such as those based on poly(ethylene oxide) (PEO), which may further include crosslinkable fragments. In one embodiment, the binder comprises a water-soluble binder and a cellulose-based binder, for example, a combination of SBR and CMC.

[0116] The counter electrode material is typically applied to a substrate film, such as a current collector. The counter electrode material can be applied as a slurry or suspension to the substrate film in continuous mode using various methods, such as the comma coating method, the doctor blade coating method, or slot-die coating. The electrolyte can be liquid, gel, or solid and, in the case of a lithium or lithium-ion battery, comprises a lithium salt and / or conducts lithium ions.Non-limiting examples of liquid electrolytes include organic liquid electrolytes comprising a polar aprotic solvent such as ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), γ-butyrolactone (γ-BL), vinyl carbonate (VC), ethers (e.g., 1,2-dimethoxyethane (DME), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE)), and mixtures of two or more of these, and a lithium salt. Other examples of compatible liquid electrolytes include molten salt-based electrolytes. A separator can also be impregnated with the liquid or gel electrolyte, for example a polymer separator (e.g., of polypropylene, polyethylene or a copolymer of propylene and ethylene).

[0117] Gel electrolytes typically comprise a compatible polymer and a salt, and may also include a solvent and / or a separator. Examples of gel electrolytes are described in PCT publications W02009 / 111860 (Zaghib et al.) and WO2004 / 068610 (Zaghib et al.).

[0118] Solid electrolytes can be solid polymer electrolytes, composite electrolytes, or ceramic electrolytes, comprising, for example, a polymer, inorganic particles (e.g., ceramic), or a combination thereof.

[0119] Solid polymer electrolytes (SPEs) typically comprise one or more solid polar polymers, possibly crosslinked, and a salt. Polyether-type polymers, such as those based on poly(ethylene oxide) (PEO), can be used, but several other compatible polymers are also known for the preparation of SPEs. The polymer may also be crosslinked. Examples of such polymers include star- or comb-shaped multibranch polymers such as those described in PCT Publication W02003 / 063287 (Zaghib et al.).

[0120] For example, electrochemical cells can be used in capacitors or supercapacitors, or in alkali or alkaline earth metal batteries such as lithium, sodium, or magnesium batteries. EXAMPLES

[0121] The following examples are illustrative embodiments and should not be interpreted as further limiting the scope of the present invention. These examples will be better understood by referring to the accompanying figures. on lithium film

[0122] In this example, an indirect method for transferring a passivating agent onto a metallic lithium foil is described. A 25 µm thick polypropylene (PP) film was spray-coated with a saturated solution of anthracene in ethanol (at 20 °C) at a flow rate of 0.4 mL / min and then dried in a dry atmosphere. The presence of the deposited anthracene can be easily detected by its fluorescence under UV light (see Figure 1, left-hand images, top in daylight, bottom under UV light).

[0123] The film was then used to transfer anthracene onto the surface of a 2 cm lithium foil disc2 (40 µm laminated Li sheet) by calendering the Li sheet sandwiched between the PP-anthracene film on one side and a copper sheet (10 µm thick) on the other. The PP film is then removed. The central photographs in Figure 1 show the surface of the lithium film obtained on the copper sheet, where the presence of anthracene is readily visible on the lithium disk, particularly under UV light (bottom photograph).

[0124] Examination of the PP-anthracene film used in Figure 1 (right-hand photos) after the calendering step shows that all the anthracene has been transferred to the lithium surface, since anthracene can only be detected under UV light in areas outside the zone that was in contact with the 2 cm lithium disc. 2during calendering. This demonstrates the possibility of achieving a virtually complete transfer of the passivating agent onto a lithium foil surface by a single roll-to-roll calendering step.

[0125] Example 2 - Formation of a passivation layer on a lithium film and stability

[0126] In an anhydrous chamber (dew point of at least -40 °C), a 2 cm disc of metallic lithium foil 2 (thickness 40 pm) (Li A) was laminated between two polymer sheets to produce a newly formed unprotected surface on the lithium sheet used as a reference.

[0127] In an anhydrous chamber (dew point of at least -40 °C), another 40 µm thick lithium (Li B) sheet was laminated with anthracene, which had been spray-coated as a thin film onto a polymer substrate as a transfer film (in this example, a 25 µm thick polypropylene sheet). This coated polymer substrate was prepared beforehand using a sprayer and an anthracene solution saturated in ethanol, by spray-coating at a flow rate of 0.4 mL / min on a 30 cm² sample. 2 , then dried under a dry atmosphere.

[0128] The two lithium samples were placed in a climate chamber with a dew point of -10 °C. The polypropylene sheet(s) were removed, and the lithium samples were exposed for 7 minutes. Considered an accelerated aging test, this test confirms that anthracene protects lithium. Figure 2 shows photographs of the reference film (Li A, top) and the treated film (Li B, bottom) taken at 0 seconds, 30 seconds, and then at 1, 2, 3, 4, and 7 minutes. As can be seen, in the case of the unpassivated Li sheet (Li A), the surface color begins to darken after only 1 minute, and after 4 minutes, most of the surface is covered with a very dark layer that is most likely composed of lithium hydroxide, oxide, nitride, and carbonate. In the case of the passivated lithium sheet, no color change is observed, even after 7 minutes.

[0129] Example 3 - Formation of a passivation layer on a lithium film and stability

[0130] In an anhydrous chamber (dew point of at least -40 °C), a lithium (Li A) film was laminated between two polymer sheets. In a similar anhydrous chamber (dew point of at least -40 °C), lithium (Li C, D, and E) films were laminated with anthracene films of varying thicknesses onto a polymer substrate used as a transfer film. These films had been previously produced, as in Example 2, using a spray dryer with the parameters shown in Table 1.

[0131] Table 1: Parameters for the preparation of the coated substrate film

[0132] For each lithium film, an electrochemical cell was assembled with a LiFePCL electrode as the cathode and cycled at C / 3-1C using a 1,2-dimethoxyethane (DME)-1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) electrolyte containing LiTFSi (1.5 M) as the lithium salt (Figure 3). In the case of the Li A film, the lithium film was handled only in a glove box under argon to prevent deterioration in the dry room atmosphere, as no passivation agent had been transferred to the surface of the lithium film. As can be seen, the presence of increasing amounts of anthracene on the surface of lithium (in the range studied) did not prevent the possibility of having a stable cycle and, in the case of Li D and Li E sheets, the capacity obtained appears to be greater than that of Li A without anthracene, but which was handled in a glove box.

[0133] Example 4 - Formation of a layer on lithium film with the thio-indigo dye

[0134] An 8 µm copper foil was treated by electrodeposition of a 500 nm nickel (Ni) layer, followed by a 40 nm tin (Sn) layer in a roll-to-roll configuration. The prepared foil was then used in another roll-to-roll device (in a glove box containing purified argon (Ar) with less than 1 ppm of H₂O, O₂, and N₂) in which molten metallic lithium was applied to the Cu-Ni-Sn surface according to the method described in US patent application number US 2023 / 0223546 A1. The thickness of the deposited Li layer was measured to be approximately 5 µm with a standard deviation of about 10% in thickness.

[0135] The Cu-Ni-Sn-Li sample was laminated in contact with a layer of thio-indigo (pink color) previously deposited by spraying at a flow rate of 1.5 ml / min using a saturated solution (at 25 °C) of thio-indigo in THF and at a speed of 35 mm / sec (4 passes in total) on a polypropylene (PP) substrate (Figure 4).

[0136] Figure 5(a) shows the lithium surface after thio-indigo transfer, while Figure 5(b) shows the PP substrate after the process.

[0137] The absence of thio-indigo (pink color) in the area that was in contact with the lithium on the PP surface (Figure 5b) confirms that the transfer was successful. Residual thio-indigo spots remain on the PP substrate, corresponding to the colorless voids observed on the lithium surface (Figure 5a).

[0138] It is thus possible to transfer a protective layer onto the surface of melt-deposited lithium metal using a simple lamination process. In this approach, the lithium foil is brought into intimate contact with the pre-coated substrate under controlled pressure, ensuring adhesion of the protective layer without requiring additional chemical treatments or complex processing steps. This method leverages the mechanical bond at the interface, enabling uniform coverage while preserving the integrity of the lithium surface.

[0139] Example 5 - Effect of the thio-indigo protective layer on electrochemical performance

[0140] To evaluate the impact of the protective layer on electrochemical performance, button cells were assembled using standard NCM811-based cathodes and Cu-Ni-Sn-Li anodes, either unprotected or coated with a transferred thio-indigo layer. The liquid electrolyte consisted of an ether-based formulation containing LiFSI salt. After an initial formation step, cycling tests were performed at 25 °C, followed by aging at a C / 3 rate during charge and discharge.

[0141] The cycling performance, illustrated in Figure 6, compares unprotected lithium (solid squares) to lithium with a transferred protective layer (empty squares). This evaluation aims to determine whether the laminated coating improves interfacial stability, mitigates parasitic reactions, and enhances long-term capacity retention under practical conditions. Coulombic efficiency is more stable with the transferred protection, as shown in the enlarged image in Figure 7.

[0142] To better understand the evolution of stability during cycling, impedance measurements were performed at the initial cell stage and then every 10 cycles. Figure 8(a) shows the impedance response of unprotected lithium in a complete cell configuration relative to the NCM, while Figure 8(b) corresponds to the cell with the protective layer transferred. An additional component is observed in Figure 8(b), which can be attributed to the presence of the organic coating introducing additional interfacial resistance. This feature likely reflects the formation of a stable passivation layer that reduces interactions between lithium and the electrolyte.During cycling, the impedance of the protected lithium stabilizes over time (Figure 8(b)), unlike the cell with unprotected lithium, where the impedance fluctuates continuously, indicating non-homogeneous plating / stripping in the absence of the transferred protection. This stabilization is correlated with better capacitance retention, confirming that the protective layer contributes to improved electrochemical durability. The transferred thio-indigo thus acts as a protective interfacial layer on the metallic lithium. Its molecular structure, characterized by conjugated aromatic rings and sulfur atoms, offers several advantages, including:

[0143] Passivation effect: by creating a uniform coating, thio-indigo limits dendrite nucleation and suppresses parasitic side reactions, which are the main causes of capacity loss; and

[0144] Mechanical integrity: the laminated layer acts as a physical barrier, mitigating volume changes during cycling and preserving the electrode morphology.

[0145] Overall, thio-indigo improves interfacial stability, enhances cycle life, and helps make lithium metal batteries safer and more durable.

[0146] Example 6 - Effect of the thio-indigo layer on the stability of lithium during handling

[0147] Two lithium samples, one treated with thio-indigo and the other without thio-indigo, were introduced into a climate chamber with a dew point of -15 °C, and the lithium samples were exposed for a period of 30 minutes.

[0148] Figure 9(a) shows unprotected lithium exposed to a dew point of -15 °C, while Figure 9(b) shows the same lithium with a protective thio-indigo coating. The unprotected lithium darkened and became unusable, whereas the protected sample remained clean. This demonstrates that the thio-indigo coating effectively protects lithium from environmental degradation, facilitates its handling, and simultaneously improves its electrochemical performance. The organic coating acts as a physical and chemical barrier against moisture and oxygen, preventing rapid surface oxidation and preserving the integrity of the metallic lithium.

[0149] The examples above demonstrate that a simple lamination process enables the efficient transfer of a vat dye molecule (such as thio-indigo) or an aromatic compound (such as anthracene) as a protective layer onto metallic lithium. This coating offers multiple advantages: it acts as a physical and chemical barrier against moisture and oxygen, facilitates safe handling, and significantly improves electrochemical performance. In the case of thio-indigo, impedance analysis confirms the formation of a stable interfacial layer, which mitigates inhomogeneous plating / stripping and is correlated with improved cycling stability and capacity retention. These results highlight the potential of interfacial organic engineering as a practical strategy for overcoming the inherent challenges of metallic lithium anodes, paving the way for safer and more durable high-energy batteries.

[0150] Several modifications could be made to any of the embodiments described above without departing from the scope of the present invention. All references, patents, or scientific literature referenced in this document are incorporated herein in their entirety and for all purposes.

Claims

DEMANDS 1. A process for preparing an electrode material, the process comprising the steps of: (a) obtaining a lithium film or a lithium alloy comprising a first and a second surface; (b) preparation of a transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free; (c) bringing the first surface of the active lithium film into contact with the layer of organic protective agent in order to produce a protective layer on the first surface of the active lithium film; and (d) optionally the removal of the transfer film; wherein the organic protective agent is preferably a non-volatile organic compound.

2. The process of claim 1, wherein the organic protective agent is a passivating agent and the protective layer is a passivation layer.

3. The process of claim 1 or 2, wherein the organic protecting agent is selected from polyaromatic compounds, vat dyes (vat), polycyclic compounds containing a quinone and combinations thereof.

4. The process of claim 3, wherein the organic protecting agent is a polyaromatic compound, preferably selected from anthracene, phenanthrene, phenanthroline, tetracene, pyrene, perylene and their derivatives.

5. The process of claim 3, wherein the organic protecting agent is a vat dye (vat), preferably selected from indigoids (e.g. indigo, thio-indigo, etc.) and their derivatives, dyes based on anthraquinone derivatives, and others similar.

6. The process of claim 3, wherein the organic protecting agent is a polycyclic compound containing a quinone, preferably selected from anthraquinone, phenanthrenequinone, tetracenequinone, perylenequinone, alizarin and their derivatives.

7. The method of any one of claims 1 to 6, wherein step (b) comprises the application of the organic protective agent to the transfer film.

8. The method of any one of claims 1 to 6, wherein step (b) comprises preparing a solution or suspension of the organic protective agent in a solvent, applying the solution or suspension to the surface of the transfer film and removing the solvent.

9. The process of claim 8, wherein the solution is applied by drop-casting, mold casting, dip coating, spin coating, spray coating, printing (for example, an engraving-type process), slot-die coating, doctor blade coating, preferably by spray coating.

10. The method of any one of claims 1 to 9, wherein the contacting step includes calendering, rolling or rolling the lithium film or lithium alloy with the transfer film comprising the organic protective agent layer.

11. The method of any one of claims 1 to 10, wherein the second surface of the lithium film or lithium alloy of step (a) is on a current collector.

12. The process of step 11, wherein the lithium film or lithium alloy is a first lithium film or lithium alloy, and a second lithium film or lithium alloy is present on the surface of the current collector opposite the surface of the current collector in contact with the first lithium film or lithium alloy.

13. The process of step 12, wherein step (c) further comprises bringing the free surface of the second active lithium film into contact with a second layer of organic protective agent in order to produce a protective layer on the free surface of the second active lithium film.

14. The method of any one of claims 1 to 10, wherein the method further comprises applying the second surface of the lithium film or lithium alloy to a current collector in step (a).

15. The method of any one of claims 1 to 10, wherein the method further comprises applying the second surface of the lithium film or lithium alloy to a current collector after step (c).

16. The method of any one of claims 1 to 10, wherein the method further comprises applying the second surface of the lithium film or lithium alloy to a current collector during step (c), at the same time as or just before the first surface of the active lithium film is brought into contact with the layer of organic protective agent.

17. The method of any one of claims 1 to 10, wherein the method further comprises bringing the second surface of the lithium film or of a lithium alloy into contact with a second transfer film comprising a layer of an organic protective agent on one of its surfaces, the layer being solvent-free.

18. The method of claim 17, wherein said contacting of the second surface occurs simultaneously with step (c).

19. The process of any one of claims 1 to 18, wherein the lithium film or lithium alloy film is a lithium film having a purity of at least 99% by weight, or at least 99.9% by weight, or at least 99.99% by weight, or at least 99.999% by weight.

20. The method of any one of claims 1 to 18, wherein the lithium or lithium alloy film comprises a lithium alloy comprising at least 50% by weight, at least 75% by weight, at least 90% by weight, at least 95% by weight or at least 98% by weight of lithium.

21. The process of claim 20, wherein the lithium alloy comprises lithium and at least one element selected from alkali metals other than lithium, alkaline earth metals, rare earth metals, zirconium, copper, silver, bismuth, cobalt, manganese, zinc, aluminum, silicon, tin, antimony, cadmium, mercury, lead, molybdenum, iron, boron, indium, thallium, nickel and germanium.

22. The method of any one of claims 1 to 21, wherein the lithium or lithium alloy film has a thickness of between about 1 pm and about 200 pm, or between about 5 pm and about 100 pm, or between about 10 pm and about 50 pm.

23. The process of any one of claims 1 to 22 wherein at least a part of the process is carried out according to a roll-to-roll process.

24. The method of any one of claims 1 to 23, wherein the method further comprises step (d) of removing the transfer film.

25. Electrode material obtained or obtainable by the process of any one of claims 1 to 24.

26. The electrode material of claim 25, wherein said electrode material comprises the protective layer on the first surface of the lithium or lithium alloy film.

27. The electrode material of claim 26, wherein said protective layer provides improved protection against moisture and reactive gases compared to a lithium film or lithium alloy without said protective layer.

28. Electrochemical cell comprising an electrode, a counter electrode and an electrolyte between the electrode and the counter electrode, wherein the electrode comprises the electrode material as defined in any one of claims 25 to 27.

29. The electrochemical cell of claim 28, wherein said electrolyte is a solid electrolyte comprising a polymer, inorganic particles or a combination thereof.

30. The electrochemical cell of claim 28, wherein said electrolyte is a gel or liquid electrolyte and further comprises a separator.

31. Battery comprising at least one electrochemical cell as defined in any one of claims 28 to 30.

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