Method for treating a surface of a material web having at least one alkali metal, material web and use thereof

Abstract

The invention relates to a method for treating a surface of a material web (3) having at least one alkali metal, the method having the following steps: - providing the material web (3, 8), which has the at least one alkali metal and is covered at least on one side by a layer of a first type (13) in the form of a passivation layer, - introducing the material web (3, 8) into a treatment chamber (2), - at least partially removing the layer of the first type (13) by evaporation with the aid of at least one laser (6) to form a laser-treated surface of the material web (3, 9), wherein, at the same time, at least one gassing with at least one process gas containing at least one reactive gas component takes place, wherein - at least one layer of the second type (14) is produced by reacting the laser-treated surface of the material web (3, 9) with the at least one reactive gas component in the at least one process gas in the treatment chamber (2) in combination with the energy input brought about by laser (6), wherein a modified material web (3, 10) is formed with the at least one second layer of the second type (14) instead of the layer of the first type (13) in the region of the laser-treated surface, and - discharging the material web (3, 10) from the treatment chamber (2).

Description

[0001] Methods for treating the surface of a material web containing at least one alkali metal, material web and its use

[0002] The invention relates to a method for treating the surface of a material web comprising at least one alkali metal, in particular lithium, also as a component of an alloy. The invention further relates to a material web and its use.

[0003] Lithium-containing electrodes can be used as alkali metal anodes in battery cells. Lithium is known to be a highly reactive metal. At various stages of manufacturing and during the subsequent use of a finished product, lithium surfaces can be covered by a layer, either desired or undesired. Such a layer could, for example, be a passivation layer in the form of lithium carbonate.

[0004] A battery cell disclosed in US patent 2004 / 0126653 A1 comprises a lithium-containing anode with a protective composite membrane on its surface that is conductive for lithium ions. A first layer of the composite membrane, which contacts the anode, is chemically compatible with lithium. The second layer forms a barrier against battery electrolytes and solvents. Possible materials for the second layer mentioned in US patent 2004 / 0126653 A1 include ceramic active metal ion conductors and glass-ceramic active metal ion conductors.

[0005] CN 217709646 U describes a method for producing a lithium carbonate protective layer on the surface of a lithium-containing material. This protective layer is intended to prevent the lithium from reacting with water and oxygen in the air. The method according to CN 217709646 U is said to be feasible using a treatment chamber into which argon, oxygen, and carbon dioxide can be introduced. Possibilities for laser treatment of lithium-containing workpieces intended for use in batteries are described, for example, in the following publication:

[0006] Kriegler, Johannes et al.: Surface Reconditioning of Lithium Metal Electrodes by Laser Treatment for the Industrial Production of Enhanced Lithium Metal Batteries, Advanced Functional Material Journal 2024, 34, 23 13766, published February 19, 2024, DOI: 10.1002 / afm.202313766

[0007] Chemical treatments of lithium surfaces are the subject of the following publication:

[0008] Tang, Wei et al.: Chemically polished lithium metal anode for high energy lithium metal batteries, Energy Storage Materials, Volume 14, September 2018, pages 289 -296, DOI: 10.1016 / j.ensm.2O18.05.009

[0009] The possibility of sandblasting lithium surfaces is discussed in the following publication:

[0010] Wolf, Andreas et al.: Abrasive Blasting of Lithium Metal Surfaces Yields Clean and 3D-Structured Lithium Metal Anodes with Superior Properties, Energy Technology, Volume 9, Issue 11, published September 8, 2021, DOI: 10.1002 / ente.202100455

[0011] The pretreatment of the surface of a lithium foil to improve the lifespan of lithium metal batteries is described below:

[0012] Delaporte, Nicolas et al.: Pre-treatments of lithium foil surface for improving the cycling life of Li metal batteries, Frontiers in Materials, Vol. 6, Nov. 2019, Article-No. 267, S. 1-22, ISSN 2296-8016; https: / / doi.org / 10.3389 / fmats.2019.00267

[0013] German patent application DE 102023 124847 A1, published after the priority date of this application, discloses a method for processing a lithium surface and a processing device. In this process, a web of material whose surface is formed by lithium is processed in a roll-to-roll process under a protective gas atmosphere. The surface is exposed to laser radiation, thereby selectively altering the surface morphology and chemical state. The laser radiation is suitable for either melting, vaporizing, or ablating material from the surface. Uneven surface morphology can be smoothed by generating a continuous melt pool with a laser, utilizing surface tension. Furthermore, passivating surface layers can be removed by laser-induced vaporization of material layers in the nanometer or micrometer range.The formation of a new passivation layer can be prevented by using a protective gas or dry air. Alternatively, laser processing can be carried out in an atmosphere specifically designed to induce the formation of a passivation layer. This process is suitable for the production of lithium metal anodes and batteries, i.e., primary or secondary batteries.

[0014] US Patent 2024 / 0079543 ​​A1 describes a surface fluorination process for lithium metal using elemental fluorine to produce a uniform, impurity-free LiF surface layer over the entire surface of the Li metal. The process involves treating the lithium metal surface with fluorine gas, optionally mixed with an inert gas such as helium, argon, perfluoroalkanes, or SFe, at a pressure between 0.01 mbar and 10 bar and at a temperature between -78 and 180°C. The resulting material is suitable for use as an anode in a lithium battery.

[0015] US Patent 2019 / 0379056 A1 discloses a metal anode comprising a metal layer containing an alkali metal in the form of lithium, sodium, or potassium, and a protective layer of a composite material comprising an oxide or fluoride of the alkali metal. The composite materials listed for a lithium metal layer include LiF-Li₂O, LiF-Li₂COs, LiF-LiPFe, LiF-LiPO₄, LiF-LiBF₄, LiF-CF₄, or a combination of these materials. Further composite materials listed include Li₂O-Ü₂CO₃, Li₂O-LiF, Li₂O-LiPO₄, Li₂O-LiBF₄, Li₂O-CF₄, HfO₂, and Li₂. x HfO2, SiO2, LiF - NbO2, LisN - AIN, Li x SisN4, Li x NbsN4, where x > 0, or a combination of these materials. On a sodium metal layer, a composite material consisting of, among other things, NaF - Na2Ü, and on a potassium metal layer, a composite material consisting of, among other things, KF - K2O, is called.

[0016] US Patent 2023 / 0343940 A1 describes a method for treating the surface of a strip or layer of lithium or a lithium-based alloy with laser radiation in an anhydrous, controlled atmosphere. The laser irradiation can take place under vacuum or in an atmosphere containing oxygen, nitrogen, argon, helium, or mixtures thereof. Furthermore, the laser irradiation can take place in an atmosphere reactive with respect to lithium, containing, in particular, a substance containing fluorine, sulfur, phosphorus, carbon, or mixtures thereof.

[0017] The invention is based on the objective of providing methods for the surface treatment of workpieces containing at least one alkali metal, in particular lithium, on which a passivation layer may be located, which are further developed compared to the prior art, whereby a rational and at the same time particularly process-reliable treatment is sought.

[0018] This problem is solved according to the invention by a method designed according to claim 1 for treating the surface of a material web comprising at least one alkali metal. In particular, a material web according to claim 12 can be produced by means of the method. Use of the material web is claimed in claim 15.

[0019] Insofar as the present text refers to alkali metals, the corresponding statements apply, within the limits of technical feasibility, to lithium as well as to the alkali metals sodium and potassium and to alloys based on alkali metals.

[0020] The inventive method starts with the provision of a material web which contains the at least one alkali metal and which is covered at least on one side by a layer of the first kind in the form of a passivation layer, and comprises the following steps: - introducing the material web into a treatment chamber,

[0021] - At least partial removal of the layer of the first kind by evaporation using at least one laser, forming a laser-treated surface of the material web, wherein gassing with at least one process gas containing at least one reactive gas component is carried out simultaneously, wherein

[0022] - at least one second-order layer is formed by the reaction of the laser-treated surface of the material web with the at least one reactive gas component in the treatment chamber in combination with the energy input induced by the laser, wherein a modified material web with the at least one second-order layer is formed instead of the first-order layer in the area of ​​the laser-treated surface, and

[0023] - Draining the altered material stream from the treatment chamber.

[0024] The laser irradiation of the material web can be performed on one or both sides. The production of the second type of layer is accordingly also performed on one or both sides.

[0025] The invention is based on the consideration that the presence of a passivation layer can have advantageous properties with regard to the possibilities of transporting and processing a material web containing at least one alkali metal, in particular lithium, and that it can be removed from the material web in various ways. Simultaneously, a second type of layer, which differs from the original passivation layer, can be applied to the surface of the material web in the treatment chamber after the passivation layer has been removed.

[0026] With the solution according to the invention, the two process steps "removing a layer" and "applying at least one new layer" are not only carried out immediately one after the other, but are also linked in such a way that they transition seamlessly into one another. Here, the laser has a multiple function, in that it both removes material and, practically at the same moment, forms at least one new layer, generally referred to as a second layer, from the material being removed together with the at least one reactive gas component in the process gas used for purging. This results in a combination of cleaning and converting the surface composition.The material that is heated with the aid of the laser and thus put into a delamination process, which is at least partially interrupted by the gassing, can be at least one alkali metal, in particular lithium, or a mixture of at least one alkali metal, in particular lithium, and other substances.

[0027] The generation of at least one layer of the second kind by targeted gassing of the laser-treated surface in the treatment chamber therefore occurs simultaneously with the laser-induced energy input required to remove the layer of the first kind, creating a highly reactive surface on the material web. The processes of removing the layer of the first kind and forming the at least one layer of the second kind cannot thus be considered separately in time. The formation of at least one layer of the second kind can be influenced by the targeted selection of at least one reactive gas component, which is supplied to the laser-treated surface of the material web via at least one process gas.

[0028] A first-order layer can be either a layer deliberately applied to the material web or a passivation layer that forms naturally in the ambient air. The latter arises from the oxidation of the material web at its exposed surface by the surrounding atmosphere.

[0029] The passivation layer on a web containing at least one alkali metal in the form of lithium can contain components such as lithium carbonate, lithium oxide, lithium hydroxide, or lithium nitride, which are reaction products of lithium and air (containing oxygen, carbon dioxide, and nitrogen). This type of passivation layer, formed in air, offers no advantages for subsequent applications of the web, for example, in battery cells. A layer of the first kind, produced under parameters deviating from natural environmental conditions, differs in its stoichiometric composition. For example, a favorable ratio between carbon dioxide and oxygen can be chosen to create a mixture of lithium carbonate and lithium oxide with a Pilling-Bedworth ratio close to 1. This results in the formation of a dense layer of the first kind, which is particularly suitable for shipping the web.For later applications in a battery cell, however, this deliberately created layer of the first kind can be just as disruptive as a passivation layer formed under natural environmental conditions in air and should also be removed if necessary.

[0030] Preferably, in the inventive method, in a first step, the layer of the first kind is removed in a first partial area by evaporation using at least one first laser, forming a first laser-treated surface of the material web, wherein gassing with a first process gas containing at least one first reactive gas component takes place simultaneously, wherein in the first partial area a layer of the second kind is formed by reaction of the first laser-treated surface of the material web with the first reactive gas component in the treatment chamber in combination with the energy input effected by the first laser.In a second step, the first-type layer is subsequently removed from a further sub-area by vaporization using the laser or at least one additional laser, forming a second laser-treated surface of the material web. Simultaneously, the material is treated with a second process gas containing at least one second reactive gas component. In this further sub-area, another second-type layer forms through the reaction of the second laser-treated surface of the material web with the second reactive gas component in the treatment chamber, in combination with the energy input from the laser. This results in the formation of a modified material web with the second-type layers instead of the first-type layer in the area of ​​the first and second laser-treated surfaces.Alternatively, in a preferred method, the laser-treated surface can be locally exposed to different process gases, so that the layer of the second type is produced having at least two different surface areas in which different chemical compositions of the layer of the second type are formed.

[0031] In this way, locally differently composed layers of the second type can be formed on a material web instead of the layer of the first type, whereby the formation of patterns or structures by the different layers of the second type is also possible.

[0032] The at least one reactive gas component is preferably formed by a chlorofluorocarbon, a hydrochlorofluorocarbon, a hydrofluorocarbon, sulfur hexafluoride, a perfluorocarbon, ammonia, a hydrofluoroolefin, sulfur difluoride, methyl mercaptan, sulfur tetrafluoride, carbon dioxide, hydrogen, oxygen, nitrogen, fluorine, sulfur dioxide, iodine, hydrogen iodine, an iodine fluoride, an iodine chloride, an iodine cyanide, bromine, a bromine fluoride, hydrogen bromide, hexabromocyclododecane, or an organophosphorus compound. The aforementioned substances can be present in the process gas in any combination.

[0033] When using such a process gas containing, in particular, at least one of the above-mentioned reactive gas components, a second type of layer containing at least one of the following compounds is formed in an alkali metal layer made of lithium: LiF, LiCI, Li2S, LiNH2, Li2CO3, LiH, Li2Ü, LisN, Li2SO3, Li2SO4, Lil, LiCN, LiBr, Li3P.

[0034] When the aforementioned reactive gas components are used, for example with lithium as an alkali metal layer, the following reaction products are formed, which form the layer of the second type:

[0035]

[0036]

[0037] Table 1

[0038] A process gas containing at least one reactive gas component and, in particular, an inert gas such as krypton and / or argon, is typically used to dilute the reactive gas component. These inert gases can be added to control the reaction kinetics and the resulting formation of the second type layer. This is necessary, for example, when fluorine gas is used as the reactive gas. However, the inert gases are not incorporated into the formed second type layer.

[0039] The process gas can preferably be used containing two or more different reactive gas components.

[0040] When using a combination of, for example, two of the following reactive gas components, the following reaction products are formed with lithium as an alkali metal layer, which form the layer of the second type:

[0041]

[0042] Table 2. Using at least one laser, alkali metal, in particular lithium, contained in the material web including a passivation layer, is vaporized. The vaporized and / or vaporizing alkali metal, still bonded to the workpiece surface or already detached from the workpiece surface or the passivation layer, then reacts with the at least one reactive gas component used for gassing in the process gas, forming at least one layer of the second kind. Not all of the vaporized alkali metal, in particular lithium, is necessarily deposited in the at least one layer of the second kind. The same applies to other atoms that are initially contained in the layer of the first kind and ideally should no longer be found in the at least one layer of the second kind.In any case, alkali metal, in particular the exposed alkali metal located below the layer of the first kind, can react with the laser with the at least one reactive gas component in the process gas used for gassing, whereby a reaction product in the form of at least one layer of the second kind is formed on the surface of the material web, which adheres firmly to the material web.

[0043] Preferably, at least one closed layer of the second type is produced in the area of ​​the laser-treated surface(s) instead of the layer of the first type.

[0044] It has proven advantageous for the process if the material web is locally heated to a temperature of at least 900 °C using the at least one laser. This accelerates the evaporation of the layer of the first kind and initiates the reaction with the at least one reactive gas component.

[0045] In particular, at least one laser removes 0.01 pm to a maximum of 10 pm from the surface of the material web.

[0046] The operating parameters of the at least one laser can be adjusted so that the energy input is limited to the surface and near-surface regions of the material web. Shallow material removal depths can be achieved by pulsed operation of the at least one laser. In particular, a femtosecond, picosecond, or nanosecond laser can be used in the surface treatment process. The short pulse duration can be combined with a high instantaneous laser power. This provides good conditions for transitions between the solid and gaseous phases that are abruptly halted by the process settings, i.e., for so-called "quasi-solid-gas" transitions.

[0047] It has proven effective to introduce a liquid and / or a solid into the treatment chamber which transitions into the gas phase under the partial pressure prevailing in the treatment chamber and provides at least one reactive gas component of the process gas.

[0048] Regarding the structure of the at least one second-order layer, which is produced using laser radiation and at least one process gas, a wide variety of options are possible. For example, a continuous second-order layer of uniform composition and thickness can be produced. Alternatively, the at least one second-order layer can be structured so that it is formed only in certain areas or in a pattern on the material web. This structuring can take the form of a variation in layer thickness or, depending on the application, by leaving defined surface areas uncoated, which can later be covered with another second-order layer.

[0049] A material web produced using the inventive method, which has at least one alkali metal in the form of lithium and which comprises at least one layer of the second type on at least one side, has

[0050] at least two different surface areas in which differing chemical compositions of the second type of layer are formed, and / or exhibits

[0051] The material web contains at least two of the following compounds: LiF, LiCl, Li₂S, LiNH₂, Li₂CO₃, LiH, Li₂O, Li₃N, Li₂SO₃, Li₂SO₄, Li₂, LiCN, LiBr, Li₃P. In particular, the material web has a second-type layer which, in a first surface area, contains LiF and / or LiCl and / or Li₂ and / or LiBr. The material web further comprises the second-type layer in at least one other surface area which contains at least one compound from the group comprising Li₂S, LiNFh, Li₂CO₃, LiH, Li₂O, Li₃N, Li₂SO₃, Li₂SO₄, LiCN, Li₃P.

[0052] The use of a material web according to the invention for the formation of anode material for battery cells of secondary batteries has proven to be particularly advantageous.

[0053] The at least one layer of the second type, also referred to as the "top layer" or top layer, counteracts in particular the formation and growth of alkali metal dendrites or lithium dendrites. The top layer, as a so-called "solid electrolyte interphase" (abbreviated SEI), is an electrically insulating, ion-conducting layer suitable for separating metallic alkali metal, especially lithium, from an adjacent electrolyte, particularly within a battery cell. This separation is formed from a portion of the material web. Furthermore, the top layer is capable of accommodating volume changes occurring at the anode during charging or discharging of a battery cell.

[0054] Regarding the structure of the at least one second-order layer, which is produced using laser radiation and at least one process gas, the material web according to the invention can be realized in a wide variety of configurations. For example, at least one continuous second-order layer of uniform composition and thickness can be produced. Alternatively, the second-order layer can be structured so that it is formed only in certain areas or in a pattern on the material web. The structuring can take the form of a variation in layer thickness or, depending on the application, also by leaving defined surface areas uncovered, which can then be provided with another second-order layer. In all cases, metrological monitoring of the entire treatment process is possible.Geometric, electrical or other properties of the manufactured product, that is, the material web covered with at least one layer of the second type, can be determined not only by direct analysis of this product, but also by recording parameters of the integrated cleaning and coating process in combination with a simulation.

[0055] In all process variants, the direct and / or indirect introduction of process gas during the cleaning process prevents an undesirable side reaction between the laser-cleaned surface and the removed substances, which, at least at this stage of the process, should no longer react with the material web. Desired reactions, on the other hand, can be triggered or catalyzed by the energy input from the laser, depending on the atmosphere. Overall, the process circumvents the problem of the low melting point of alkali metals, especially lithium, while simultaneously providing the energy input required for the intended reactions, which, depending on the reaction conditions, sometimes necessitates temperatures exceeding 1000 °C.

[0056] A system for treating the surface of a material web containing at least one alkali metal generally comprises a treatment chamber designed to hold the material web, at least one laser designed to irradiate the material web located in the treatment chamber, and at least one gassing device. The gassing device is designed to introduce at least one process gas into the treatment chamber, wherein the process gas reacts both with solid alkali metal, in particular lithium, exposed by the laser and with vaporizing alkali metal, in particular lithium.

[0057] The material web comprises, in particular, a carrier layer on which an alkali metal layer, containing at least one alkali metal, is located on one or both sides. In this case, the layer of the first kind is located on the free surface of the alkali metal layer facing away from the carrier layer. An electrically conductive carrier layer, for example made of copper, is preferred. In particular, the material web used comprises a copper carrier layer covered on one or both sides with an alkali metal layer, in particular lithium. The layer of the first kind, located on the free surface of the alkali metal layer facing away from the carrier layer, is formed, for example, of lithium carbonate and / or lithium oxide.

[0058] In the case of the use of nitrogen as a reactive gas component for the formation of at least one layer of the second kind, as mentioned here, a porous layer of the second kind made of lithium nitride (LisN) is formed in-situ during laser treatment of the material web. Lithium nitride has a Pilling-Bedworth ratio of approximately 0.6, which explains the porosity of the layer. Furthermore, lithium nitride is conductive for lithium ions. Due to the pores present, these serve as spaces or free spaces for volume changes that occur during the charging and discharging of metallic lithium anodes in battery cells.

[0059] Furthermore, the use of iodine pentafluoride as a reactive gas in the treatment chamber is cited as an example. Here, fluorine and iodine are present in a 5:1 ratio, resulting in a dense and compact second-order layer of lithium iodide and lithium fluoride in a 5:1 ratio with a Pilling-Bedworth ratio of approximately 1.2. Lithium iodide and lithium fluoride exhibit high electrochemical stability and are ideally suited for use in a battery cell.

[0060] The use of a material web produced according to the inventive method, comprising at least one layer of the second type, has proven particularly advantageous for the formation of anode material for battery cells of secondary batteries. The layer of the second type can be provided on one side or on both sides of the material web.

[0061] Overall, the treatment system is designed primarily as a roll-to-roll system. This means that the material web to be processed is in roll form, i.e., a coil, and the processed material web is then wound back into a coil. The rolls can be located outside the treatment chamber, which necessitates a gas-tight introduction and discharge of the material web into and out of the treatment chamber, within the limits of what is technically feasible and economically viable.

[0062] An embodiment of the invention is explained in more detail below with reference to the drawings. These show, in some cases idealized:

[0063] Fig. 1 shows a schematic representation of a system for treating a web of material containing at least one alkali metal.

[0064] Fig. 2 shows a cross-sectional view of a material web to be treated with the system according to Fig. 1.

[0065] Fig. 3 shows the material web with a laser-treated surface on one side,

[0066] Fig. 4 shows the material web with a newly formed layer of the second type,

[0067] Fig. 5 shows a further system for treating a material web containing at least one alkali metal in a schematic representation, Fig. 6 shows the treated material web in a sectional view Vl-Vl,

[0068] Fig. 7 shows the treated material web in a sectional view VII-VII, and Fig. 8 shows the treated material web in a sectional view VIII-VIII with two differently formed layers of the second type.

[0069] The production plant designated 1 is a plant for treating a web of material 3, which will be discussed in more detail below. The production plant 1, i.e., the treatment plant, comprises a treatment chamber 2, indicated by dashed lines in Fig. 1. The treatment chamber 2, together with all other components of the production plant 1 visible in Fig. 1, is arranged in a room with a protective gas atmosphere, which is designated as the outer treatment chamber 15. This applies, among other things, to the web of material 3, designated regardless of its processing state. At the inlet side of the treatment chamber 2, the web of material 3 is unwound from a roll 4, i.e., a coil, and at the outlet side of the treatment chamber 2, it is wound onto another roll 5, i.e., another coil. The conveying direction of the web of material 3 is designated FR in Fig. 1.

[0070] In its initial state, that is, on the input coil 4, the material web 3, as shown in Figure 2 (which depicts a section through the material web 3, 8), consists of a support layer 11, here made of copper, with an alkali metal layer 12, here made of lithium, applied to one side of it. On the side of the alkali metal layer 12 facing away from the support layer 11, a first-order layer in the form of a passivation layer 13 is present. The material web 3 with a passivated surface is additionally designated by the reference numeral 8. In this embodiment, the first-order layer is a natural passivation layer 13, which forms when the material web 3 is stored in ambient air. In this state, the material web 3, 8 is introduced into the treatment chamber 2.

[0071] In treatment chamber 2, the material web 3, 8 is superficially cleaned by means of a laser 6, which is located outside the treatment chamber 2, thereby removing the first-order layer in the form of the passivation layer 13. Fig. 3 shows an idealized representation of a cleaned material web 3, 9, from which the first-order layer in the form of the passivation layer 13 has been completely detached and vaporized. A suction device may be present in the laser treatment zone to remove the vaporized material before it can react again with the laser-treated surface. The laser radiation indicated in Fig. 1, designated LS, acts only in near-surface regions of the material web 3. The laser radiation LS is pulsed radiation with high-energy pulses in the pico-, femto-, or nanosecond range. The ablation depth is no more than 10 pm.The use of a continuous laser source is also possible. In contrast to the setup sketched in Fig. 1, or rather the setup of the material web 3, additional lasers 6 can be located above and below the material web 3; see also Fig. 5. At least one additional laser is located below the material web 3, particularly if an alkali metal layer is also present there and is to be treated. The laser irradiation process is combined with gassing using a process gas PG containing a reactive gas component, which is introduced into the treatment chamber 2 by means of a gassing device 7. For this purpose, a mixture of at least one reactive gas component with an unreactive gas, here argon and / or krypton, is used as the process gas.

[0072] The process gas PG encounters the surface of the alkali metal layer 12, which is exposed by the first-order layer in the form of the passivation layer 13 and which was / is exposed to the laser radiation LS. The process gas used is a gas mixture containing krypton and / or argon, which further contains at least one of the following substances: chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, sulfur hexafluoride, perfluorocarbons, ammonia, hydrofluoroolefins, sulfur difluoride, methyl mercaptan, sulfur tetrafluoride, carbon dioxide, hydrogen, oxygen, nitrogen, fluorine, sulfur dioxide, iodine, hydrogen iodine, iodine fluorides, iodine chlorides, iodine cyanides, bromine, bromine fluorides, bromine hydrogen, hexabromocyclododecane, organophosphorus compounds.

[0073] This triggers a reaction involving both the lithium of the alkali metal layer 12 and the process gas. Here, evaporating or heated lithium reacts with the at least one reactive gas component in the process gas PG, without having to have already detached from the surface of the material web 3, 9. This means that rapid evaporation or sublimation is stopped by a chemical reaction at the point of evaporation or sublimation. It is also possible that lithium evaporates, reacts, and precipitates. Furthermore, it should be mentioned that after the removal of the first type of layer in the form of the passivation layer 13, the lithium of the alkali metal layer 12 exposed reacts with the at least one reactive gas component in the process gas PG.

[0074] A layer of the second type 14, which is firmly bonded to the metallic lithium of the alkali metal layer 12, is present in the current embodiment as a LisN layer when gassed with a reactive gas component in the form of nitrogen. With this layer of the second type 14, the material web 3, additionally designated by reference numeral 10 in this state (see Figure 4), is suitable for use as anode material in battery cells of secondary batteries. If required, a geometrically defined structure of the layer of the second type 14 can be generated by appropriately controlling the laser 6.

[0075] By using additional lasers 6, 6a or additional gassing devices 7, 7a for different process gases, different layers of the second type can be produced side by side or sequentially on the material web 3 in a defined pattern. For this purpose, several treatment chambers, optionally atmospherically separated from one another, can be provided in the treatment chamber 2. These can optionally be separated from each other by extraction systems and / or bulkheads.

[0076] Fig. 5 shows a further system 1 for treating a web of material 3, 8 containing at least one alkali metal in a schematic representation. The same reference numerals as in Fig. 1 denote identical elements. For the sake of clarity, the rollers 4, 5, the treatment chamber 2, and the outer processing area 15 have been omitted here. The conveying direction of the web of material 3 is also designated FR in Fig. 5.

[0077] In its initial state, that is, on the input side, the material web 3 again consists of a support layer 11, here made of copper, with an alkali metal layer 12, here made of lithium, applied to one side of it, as shown in Figure 2. On the side of the alkali metal layer 12 facing away from the support layer 11, a layer of the first kind in the form of a passivation layer 13 is present. The material web 3 with a passivated surface is additionally designated by reference numeral 8. In this embodiment, the layer of the first kind is a natural passivation layer 13, which forms when the material web 3 is stored in ambient air.

[0078] The material web 3, 8 is superficially cleaned using a laser 6, thereby removing only the first-order layer in the form of the passivation layer 13 locally. Figure 5 shows an idealized representation of a material web 3, 9 cleaned in the center of a strip, from which the first-order layer in the form of the passivation layer 13 has been detached and vaporized in a strip. An extraction device can be present in the laser treatment zone to remove the vaporized material before it can react again with the laser-treated surface. The laser radiation indicated in Fig. 5, designated LS, acts only in near-surface regions of the material web 3. The laser radiation LS is pulsed radiation with high-energy pulses in the pico-, femto-, or nanosecond range. The ablation depth is no more than 10 pm. The use of a continuous laser source is also possible.

[0079] The process of laser irradiation with laser 6 is combined with gassing using a process gas PGi containing a first reactive gas component, which is supplied by means of a gassing device 7. For this purpose, a mixture of at least one reactive gas component with an unreactive gas, here argon and / or krypton, is used as the process gas PGi.

[0080] The process gas PGi encounters the surface of the alkali metal layer 12, which was exposed by the layer of the first kind and was / is exposed to the laser radiation LS. The process gas PGi is a gas mixture containing krypton and / or argon, which also contains sulfur hexafluoride (SFe) as a reactive gas component.

[0081] This triggers a reaction involving both the lithium of the alkali metal layer 12 and the process gas. Here, evaporating or heated lithium reacts with the at least one reactive gas component in the process gas PGi, without having to have already detached from the surface of the material web 3, 9. This means that rapid evaporation or sublimation is stopped by a chemical reaction at the point of evaporation or sublimation. It is also possible that lithium evaporates, reacts, and precipitates. Furthermore, it should be mentioned that after removal of the layer of the first type, the lithium exposed in the alkali metal layer 12 reacts with the at least one reactive gas component in the process gas PGi.A layer of the second type 14, which is firmly bonded to the strip-shaped exposed metallic lithium of the alkali metal layer 12, is present in the current embodiment and consists of a mixture of Li₂S and LiF. In addition, strip-shaped areas of the layer of the first type, in the form of the passivation layer 13, are present on both sides. A section V1-V1 according to Figure 6 shows the structure of the material layer 3 at this point.

[0082] Unlike the setup sketched in Fig. 1, here, due to the conveying direction FR of the material web 3, an additional laser 6a is present above the material web 3. Alternatively, the laser 6 could be used a second time without requiring an additional laser. The additional laser 6a now removes the strip-shaped remnants of the first type of layer, in the form of the passivation layer 13, from the material web 3, while the already formed second type of layer 14 remains on it. A section VII-VIII according to Figure 7 shows the structure of the material layer 3 at this point.

[0083] The process of laser irradiation with the additional laser 6a is combined with gassing with a further process gas PG2 containing a second reactive gas component, which is supplied by means of a gassing device 7a. For this purpose, a mixture of at least one further reactive gas component with an unreactive gas, here argon and / or krypton, is used as the second process gas PG2, which is different from the process gas PG1.

[0084] The process gas PG2 encounters the surfaces of the alkali metal layer 12, which were exposed by the layer of the first kind and which were / are exposed to the laser radiation LS. The process gas PG2 is a gas mixture containing krypton and / or argon, which also contains iodine fluoride (IF5) and nitrogen (N2) as reactive gas components.

[0085] This triggers a reaction involving both the lithium of the alkali metal layer 12 and the process gas PG2. Here, evaporating or heated lithium reacts with the reactive gas components in the process gas PG2, even if it has not yet detached from the surface of the material web 3, 9. This means that rapid evaporation or sublimation is stopped by a chemical reaction at the point of evaporation or sublimation. It is also possible that lithium evaporates, reacts, and precipitates. Furthermore, it should be noted that after the removal of the layer of the first type, the lithium exposed in the alkali metal layer 12 reacts with the reactive gas components in the process gas PG2.

[0086] The resulting layers of the second type 14', which are firmly bonded to the twice strip-shaped exposed metallic lithium of the alkali metal layer 12, consist in the present embodiment of a mixture of LisN, LiI, and LiF. In addition, a further strip-shaped layer of the second type 14 is present between the two strip-shaped regions of the layers of the second type 14'. A section VIII-VI 11 according to Figure 8 shows the structure of the material layer 3, 10 at this point.

[0087] With these different second-order layers 14, 14', the material web 3, additionally designated with reference numeral 10 in this state (see Figure 8), is suitable for use as anode material in battery cells of secondary batteries. By appropriately controlling the lasers 6, 6a, a geometrically defined structuring of the second-order layers 14, 14' can be generated if required.

[0088] In such a system, multiple lasers 6, 6a or multiple gas purging units 7, 7a for different process gases PG, PG1, PG2 can be used to produce different second-order layers 14, 14' in a defined pattern, either side-by-side or sequentially, on the material web 3. For this purpose, several treatment chambers, optionally atmospherically separated from one another, can be provided in the treatment chamber(s) 2. These can optionally be separated from one another by extraction devices and / or barriers. The second-order layer 14, 14' is characterized by electrically insulating properties and / or ionic conductivity. After exiting the material web 3, 10 from the treatment chamber(s) 2, it, like the roll 5, is located in the so-called outer processing chamber 15, in which a protective gas atmosphere is maintained.The pressure of the protective gas atmosphere can be slightly lower than the pressure in the treatment chamber(s) 2 to prevent unintentional introduction of protective gas into the treatment chamber(s) 2.

[0089] Active and / or passive devices for venting residual process gas and any gaseous components of the removed passivation layer 13 from the treatment chamber(s) 2, as well as for the possible post-treatment of the vented gas stream, are generally available and can be used as required. However, for the sake of simplicity, these are not shown in detail in Figures 1 and 5. (List of reference symbols)

[0090] 1. Production plant, plant for treating a material web; 2. Treatment chamber

[0091] 3 Material track

[0092] 4 rolls, coil, input side

[0093] 5 rolls, coils, output side

[0094] 6, 6a Laser

[0095] 7, 7a Fumigation device

[0096] 8 Material web with layer of first type

[0097] 9 Material web, laser treated

[0098] 10 Material web with layer(s) of the second type

[0099] 11 Carrier layer

[0100] 12 Alkali metal layer

[0101] 13. Passivation layer, first type layer

[0102] 14, 14' Layer of the second kind

[0103] 15 outer processing area

[0104] FR Direction of Conveyance

[0105] LS laser beam

[0106] PG, PGi, PG2 process gas

Claims

Patent claims 1. Method for treating a surface of a material web containing at least one alkali metal (3), comprising the following steps: - Provision of the material web (3, 8) which contains the at least one alkali metal and which is covered on at least one side by a layer of the first kind (13) in the form of a passivation layer, - Introducing the material web (3, 8) into a treatment chamber (2), - at least partial removal of the layer of the first kind (13) by evaporation using at least one laser (6) forming a laser-treated surface of the material web (3, 9), wherein Simultaneously, gassing with at least one process gas containing at least one reactive gas component takes place, wherein at least one layer of the second type (14) is formed by reaction of the laser-treated surface of the material web (3, 9) with the at least one reactive gas component in the at least one process gas in the treatment chamber (2) in combination with the energy input effected by laser (6), wherein a modified material web (3, 10) with at least one layer of the second type (14) instead of the layer of the first type (13) is formed in the area of ​​the laser-treated surface, and -Ejection of the altered material web (3, 10) from the treatment chamber (2).

2. Treatment method according to claim 1, characterized in that in a first step the layer of the first type (13) is removed in a first partial area by evaporation using at least one first laser (6) to form a first laser-treated surface of the material web (3, 9), wherein gassing with a first process gas containing at least one first reactive gas component is carried out simultaneously, wherein in the first partial area a layer of the second type (14) is formed by reaction of the first laser-treated surface of the material web (3, 9) with the first reactive gas component in the treatment chamber (2) in combination with the energy input effected by the first laser (6), and that subsequently, in a second step, a further removal of the first-type layer (13) in a further sub-area is carried out by evaporation using the laser (6) or at least one further laser (6a) to form a second laser-treated surface of the material web (3, 9), wherein at the same time gassing with a second process gas containing at least a second reactive gas component takes place, wherein in the further sub-area a further second-type layer (14') is formed by reaction of the second laser-treated surface of the material web (3, 9) with the second reactive gas component in the treatment chamber (2) in combination with the energy input effected by the laser (6, 6a), forming a modified material web (3, 10) with the layers of the second type (14, 14') instead of the layer of the first type (13) in the area of ​​the first and second laser-treated surfaces.

3. Treatment method according to claim 1, characterized in that the laser-treated surface is locally exposed to different process gases, so that the layer of the second type (14) is produced having at least two different surface areas (14a, 14b) in which different chemical compositions of the layer of the second type (14) are formed.

4. Treatment method according to one of claims 1 to 3, characterized in that the at least one reactive gas component is formed by a chlorofluorocarbon or a hydrochlorofluorocarbon or a hydrofluorocarbon or sulfur hexafluoride or a perfluorocarbon or ammonia or a hydrofluoroolefin or sulfur difluoride or methyl mercaptan or sulfur tetrafluoride or carbon dioxide or hydrogen or oxygen or nitrogen or fluorine or sulfur dioxide or iodine or hydrogen iodine or an iodine fluoride or an iodine chloride or an iodine cyanide or bromine or a bromine fluoride or hydrogen bromide or hexabromocyclododecane or an organophosphorus compound.

5. Treatment method according to any one of claims 1 to 4, characterized in that the process gas contains at least one reactive gas component and further an inert gas in the form of krypton and / or argon.

6. Treatment method according to claim 4 or according to claims 4 and 5, characterized in that the alkali metal is present in the form of lithium and the layer of the second type (14, 14') is formed containing at least one of the following compounds: LiF, LiCl, Li₂S, LiNFh, Ü₂CO₃, LiH, Li₂Ü, LisN, Li₂SO₄, Li₂SO₄, LiCl, LiCN, LiBr, Li₃P.

7. Treatment method according to one of claims 1 to 6, characterized in that the process gas is used containing two or more different reactive gas components.

8. Treatment method according to one of claims 1 to 7, characterized in that the material web (3, 9) is heated locally to a temperature of at least 900 °C by means of the at least one laser (6, 6a).

9. Treatment method according to one of claims 1 to 8, characterized in that at least one closed layer of the second type (14, 14') is produced in the area of ​​the laser-treated surface(s) instead of the layer of the first type (13).

10. Treatment method according to one of claims 1 to 9, characterized in that 0.01 pm to a maximum of 10 pm is removed from the surface of the material web (3) by the at least one laser (6, 6a).

11. Treatment method according to one of claims 1 to 10, characterized in that a liquid and / or a solid, which transitions into the gas phase under the partial pressure prevailing in the treatment chamber (2) and provides the at least one reactive gas component of the process gas, is introduced into the treatment chamber (2).

12. Material web (3, 10) produced according to a method according to one of claims 1 to 11, comprising at least one alkali metal in the form of lithium and comprising at least one layer of the second type (14, 14') on at least one side, which has at least two different surface areas (14a, 14b) in which differing chemical compositions of the layer of the second type (14, 14') are formed, and / or - contains at least two of the following compounds: LiF, LiCI, Li2S, LiNH2, Li2CO3, LiH, Li2O, Li3N, Li2SO3, Li2SO4, Lil, LiCN, LiBr, Li3P.

13. Material web (3, 10) according to claim 12, wherein the layer of the second type (14) has LiF and / or LiCI and / or Lil and / or LiBr in a first surface area (14a).

14. Material web (3, 10) according to claim 13, wherein the layer of the second type (14) has in at least one further surface area (14b) at least one compound of the group comprising Li2S, LiNH2, Li2CO3, LiH, Li2O, Li3N, Li2SO3, Li2SO4, LiCN, Li3P.

15. Use of a material web (3, 10) according to one of claims 12 to 14 for the formation of anode material for battery cells of secondary batteries.

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