Method for manufacturing electrodes for solid-state battery cells

Abstract

A method for manufacturing a first electrode (1) of a battery cell (2), the method comprising at least the following steps: a) providing a substrate (3) for the first electrode (1) comprising at least an active material (4) of the first electrode (1) and a copolymer (5); and b) wetting the substrate (3) with a liquid electrolyte (6) and forming a gel polymer electrolyte (7) by reacting the copolymer (5) with the liquid electrolyte (6) to form the first electrode (1).

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electrode for a solid-state battery cell.The term "solid-state battery cell" is hereinafter also included in the term "battery cell".

[0002] Batteries, especially lithium-ion batteries, are increasingly being used to drive automobiles. For example, automobiles have electric machines that can be driven by electrical energy stored in battery cells. Batteries typically consist of battery cells, each of which has a stack of anode, cathode, and separator sheets. At least some of the anode and cathode sheets are configured as conductors that conduct electrical current from the cell to an electrical load located outside the cell. Battery cells with liquid or solid electrolytes (solid-state batteries) are known.

[0003] The electrodes described herein are used in solid-state battery cells (all-solid-state battery cells and polymer gel battery cells), i.e., the solid-state battery cells contain exclusively solid components (e.g., polymers, including semi-solid electrolytes, i.e., solid or gel electrolytes, and thus not just liquid electrolytes). These solid or gel electrolytes are arranged not only as ion-conducting separators between the electrodes, but also for ion conduction within the electrodes. These separators are typically made of ceramic materials or polymers, glass, or hybrid materials.

[0004] A solid-state battery cell comprises a particularly gastight casing in which at least one stack of electrode films or layers, also referred to as electrodes, arranged one on top of the other, is arranged. The casing can be configured as a shape-fixed casing (prismatic cell) or at least partially made of an elastically deformable film material (pouch cell). The two types of casing can also be combined.

[0005] When producing electrodes for solid-state battery cells, so-called support materials, in particular strip-shaped support materials, such as support films, are at least partially coated on one or both sides with active materials (in particular additionally containing a solid electrolyte, with a gel electrolyte optionally being provided later). Electrical conductors (conductor leads) formed in the electrodes are formed in particular by uncoated areas of the support material. Support materials include, for example, copper, copper alloys, aluminum, or aluminum alloys.

[0006] The coating formed from the active material in this way is initially porous, which is reduced by calendering, as the coating is then compressed, which is required to increase the specific capacitance (by volume) and conductivity, or to ensure charge transport through materials in contact with the active material.

[0007] During calendering, the active material of a solid-state battery cell is compressed to a porosity of less than 1%, with gel electrolytes retaining a particularly large porosity. In this case, the porosity is reduced by 20-50% as a result of calendering. The calendering process is similar to a rolling process. The active material is compressed by applying a calendering force in a deformation zone. The calendering device includes multiple rollers that form at least one gap, through which the electrodes are conveyed along the conveying direction.

[0008] Polymer electrolytes that have been earmarked for application in lithium cells fall into two main categories: (1) based on pure high polymers that are used both as solvents to dissolve lithium salts and as mechanical matrices to aid processability; and (2) those based on polymers gelled by conventional electrolyte solutions, in which small organic molecules are used as the main solvent, while a small proportion of high polymers fully swollen by these solvents is used only to ensure shape stability; can be distinguished as follows.

[0009] The first polymer electrolyte is usually called a solid polymer electrolyte (SPE), and the second is called a gel polymer electrolyte (GPE). Due to their poor ionic conductivity at room temperature, SPEs have little potential for application. On the other hand, GPEs have proven to be useful in practical applications, and second-generation lithium-ion cells (e.g., solid-state or all-solid-state batteries) are already being fabricated using these new electrolytes.

[0010] GPEs are primarily used in the cathode of solid-state batteries and are therefore also called catholytes. For this purpose, a high-temperature (approximately 90°C) polymer solution consisting of a polymer (e.g., a poly(vinylidene fluoride-co-hexafluoropropylene) based polymer, i.e., PVdF-HFP) is mixed with a convective electrolyte, e.g., propylene carbonate (PC), dimethyl carbonate (DMC), and a lithium salt such as lithium hexafluorophosphate (LiPF6) or a new lithium salt such as lithium bis(fluorosulfonyl)imide (LiFSi).

[0011] Conventional methods for incorporating GPEs into the cathode can have the following drawbacks: Typically, GPEs are deposited at high temperatures after calendering with an excess of conventional electrolyte to reduce their viscosity and enhance wetting of the porous electrode structure. After cooling, the GPE-coated electrodes' gel-like behavior makes lamination of the cathode with the anode and separator difficult. The sticky nature of the gel coating also makes the cathode difficult to handle for further processing. Conventional methods for producing GPEs require heating a liquid electrolyte with a polymer to form a gel. The thermal instability of the lithium salt (LiPF or LiBF) and the volatility of the solvent (DMC, EMC, etc.) can lead to deviations from the desired composition or even decomposition of the resulting GPE. Furthermore, conventional electrolytes, such as LiPF / EC (ethylene carbonate) / DMC, are unusable because the lithium salt LiPF is not stable above 55°C. DMC also begins to boil at 90°C, necessitating the use of expensive lithium salts, such as lithium bis(fluorosulfonyl)imide (LiFSi), which is thermally stable at this temperature. Since LiPF6 forms hydrofluoric acid (HF) very quickly in the presence of even traces of water, the entire process must be carried out in a dry space after inserting the GPE into the cathode, which increases production costs. Although it is important for the liquid electrolyte to swell the polymer to form GPEs, the swelling of PVdF-HFP by liquid electrolytes is not complete due to the semi-crystalline nature of the copolymer, which tends to lead to the formation and separation of microphases after activation with liquid electrolytes, and the multiphase nature of GPEs (liquid, gel, and crystalline solid) makes them difficult to handle in subsequent processes such as cutting and lamination. During calendering, the porosity in the active material of the electrode decreases. GPE is currently applied to the cathode after calendering, but the small pore size makes it difficult for the liquid electrolyte and GPE to penetrate into the pores of the active material. High temperatures are required to reduce the viscosity so that the electrolyte and GPE can penetrate into the pores. High temperatures here result in further degradation of the electrolyte.

[0012] In summary, it can be seen that the current methods for introducing GPE into or onto the cathode are not efficient methods.

[0013] To avoid the above problems in the conventional application of GPE, the following measures can be considered: Uses expensive lithium salts such as lithium bis(fluorosulfonyl)imide (LiFSi), which is thermally stable at temperatures around 90°C. Increasing the amount of low viscosity solvent (e.g., dimethyl carbonate (DMC) in the liquid electrolyte) as excess electrolyte to improve the wettability of the electrodes or active materials, although this has the drawback of requiring an additional drying step (which is inefficient and time-consuming). Increasing the process temperature to reduce viscosity. In this case, other solvents or additives must be used to avoid boiling of DMC at, for example, about 90°C. Note that while a low processing temperature can contribute to a stable DMC, it also has a negative effect, as it increases the viscosity of the liquid electrolyte, making it difficult for the active material to penetrate the pores. Since LiPF6 is sensitive to moisture, the entire process of manufacturing the GPE and its application to the cathode must be carried out in a dry space, and all subsequent processes must also be carried out in a dry space. · The handling of GPE-coated cathodes in later processes such as cutting and lamination remains an unresolved issue.

[0014] The most important drawbacks of the above measures are, in some cases: · Expensive lithium salts further increase the cost of GPE. Dry space leads to high production costs. The high temperatures required for GPE (approximately 90°C) decompose the other components of the liquid electrolyte, namely the lithium salt LiPF6 and dimethyl carbonate (DMC). The gel surface of the cathode creates handling problems in later processes such as cutting and laminating the electrodes.

[0015] From DE 10020031 A1 a method for producing lithium polymer batteries is known, in which a polymer gel electrolyte is laminated together with the active material for the anode and the active material for the cathode onto a successive collector film.

[0016] From WO 01 / 82403 a method for producing a lithium polymer battery is known.

[0017] From WO 02 / 19450 a method for producing a laminate component of a battery cell is known, the laminate component comprising a layer of gel polymer electrolyte and a layer of active material.

[0018] The object of the present invention is to at least partially solve the problems mentioned in connection with the prior art. In particular, a method for producing electrodes for solid-state battery cells is proposed, in which cutting and / or stacking of the individual electrodes is particularly simplified.

[0019] To achieve this object, a method having the features of the independent claims contributes. Advantageous developments are the subject of the respective dependent claims. The features individually recited in the claims can be combined with one another in a technically significant manner and can be supplemented by facts stated in the description and / or details of the drawings, leading to further variant embodiments of the invention.

[0020] A method for manufacturing a first electrode of a solid-state battery cell (hereinafter referred to as battery cell) is proposed, which method comprises at least the following steps: a) providing a first electrode substrate comprising at least an active material of the electrode and a copolymer; b) wetting the substrate with a liquid electrolyte and reacting the copolymer with the liquid electrolyte to form a gel polymer electrolyte to form a first electrode; Includes.

[0021] Known methods for producing uniform GPE coatings on electrodes are inefficient and are particularly replaced by a two-stage method, in which an electrode substrate is first prepared containing only the copolymer as the starting material for the gel polymer electrolyte. At least the electrode material is cut into the geometric shape of the electrode to be present in the solid-state battery cell. Only then are the electrodes preferably stacked together to form a stack, and only after placing the stack in the casing of the solid-state battery cell does the electrolyte addition and the formation of the gel polymer electrolyte take place.

[0022] In step a), in particular, an active material is prepared and optionally placed on a support material. When producing electrodes for solid-state battery cells, one or both sides of the support material, in particular a strip-shaped support material, such as a support film, can be at least partially coated with the active material. Electrical conductors (conductor leads) formed at the electrode sites are formed in particular by uncoated areas of the support material. The support material can, for example, comprise copper or a copper alloy for the anode, and aluminum or an aluminum alloy for the cathode. Thus, the substrate can comprise the active material, the support material, and the copolymer.

[0023] In particular, in step a), the copolymer is mixed with the active material to form a material mixture, which is then applied to a support material. In particular, the copolymer is substantially uniformly dispersed in the material mixture. If the formation of a gel polymer electrolyte is performed in step b), the gel polymer electrolyte is also uniformly dispersed in the material mixture of the subsequently formed first electrode.

[0024] However, such blending of copolymers can sometimes have drawbacks. For example, the reaction of the copolymer with NMP (N-methyl-2-pyrrolidone; a solvent for preparing the coating material with the active material of the first electrode) can result in an increase in density and therefore viscosity of the coating material. This can cause problems when coating the support material of the first electrode (i.e., for example, an aluminum substrate and / or a copper substrate) with the coating material, or can irreversibly damage the copolymer of the subsequent gel polymer electrolyte.

[0025] It is desirable for the surface of the first electrode to be completely covered with the gel polymer electrolyte, which allows for good contact with the solid electrolyte separator used in the battery cell, facilitating ion transfer. Such a gel polymer electrolyte layer on the surface of the first electrode is particularly difficult to fabricate when the copolymer and the active material are mixed to form a material mixture.

[0026] Therefore, preferably, the copolymer is deposited on the active material as a coating in step a1) carried out during step a). In particular, the copolymer is additionally disposed in the active material in the form of a material mixture. Alternatively, the copolymer is disposed exclusively in the coating.

[0027] In solid-state batteries, typically, only the cathode is coated with a gel polymer electrolyte, while the anode is made of lithium metal. In other polymer-gel or solid-state battery cells, both the anode and cathode can be coated with a gel polymer electrolyte. Because both the cathode and anode compound materials on the support material are coated with the same copolymer (e.g., PVdF-HFP) as a binder, the three elements of the battery cell (anode, cathode, and gel polymer electrolyte separator) are effectively fused into an integrated multilayer wafer without any physical boundaries through gelation after electrolyte activation. This allows the anode-electrolyte interface or cathode-electrolyte interface to extend deep within the porous structure of these electrodes, much like a liquid electrolyte reaching the interface. This also improves the ionic conductivity and dimensional stability of the gel polymer electrolyte.

[0028] In particular, when lithium metal is used as the anode, a liquid electrolyte can be added only to the substrate formed as the cathode to form a gel polymer electrolyte from the reaction of the copolymer with the liquid electrolyte. If the battery cell is fabricated without lithium metal, the same method can be used for the anode, and a liquid electrolyte can also be added to the anode to form a gel polymer electrolyte.

[0029] The first electrode is in particular a cathode, but can also be configured as an anode.

[0030] In one configuration of the method, the active material as a microporous coating is (first) calendered, after which a copolymer, e.g., PVdF-HFP, is deposited onto the active material, in which case calendering can be carried out as a two-stage calendering process with an integrated coating.

[0031] Copolymers (e.g., PVdF-HFP) can be deposited as coatings in various ways. For example, they can be sprayed onto the surface of the substrate (i.e., onto the active material only) using, for example, a Venturi-based nozzle (also known as high-velocity spray or high-velocity jet method). The nozzle is typically pressurized with dry air at high pressure (about 6 bar). When copolymer particles are introduced into the nozzle, the high air pressure is converted into high air velocity, which drives the copolymer particles at high speeds (up to 0.3-4 Ma) into the substrate, especially onto the already calendered surface. In this way, thin coatings of a few micrometers thick can be formed.

[0032] Alternatively or additionally, the copolymer particles are taken up by a deposition roller and pressed onto the substrate, particularly onto the already calendered surface.

[0033] After the substrate has been coated with a coating, for example a thin microporous layer consisting of PVdF-HFP, the substrate consisting of at least the active material and the copolymer is calendered in step a2), in particular (for a second time), before step b).

[0034] In the second calendering process, only the copolymer coating is pressed onto the substrate, especially the active material, so that the copolymer coating adheres well to the surface of the substrate. The density of the (PVdF-HFP) coating does not increase significantly. After the second calendering, the copolymer (PVdF-HFP) adheres strongly to the surface of the substrate and also has a sufficient porosity, which is important for the formation of the gel polymer electrolyte in step b).

[0035] In particular, the active material is calendered in step a0) before step a1) during step a). Calendering has already been explained at the beginning. The calendering process is similar to a rolling process. The active material (i.e. the material possibly not yet containing the copolymer) is subjected to a calendering force in the deformation zone and is compressed.

[0036] The calendering device comprises a number of rollers forming at least one gap, through which the substrate of the first electrode (here in particular only the active material and optionally also the support material coated with the active material) is conveyed along the conveying direction.

[0037] In particular, the active material is wetted with the pore-forming material during step a), in this case before or during step a0).

[0038] In particular, the coating is wetted by the pore-forming material during step a).

[0039] For example, the pore-forming material can be evaporated at a predetermined temperature, so that the pore-forming material can be formed from the substrate, i.e., from the coating and / or active material or material mixture, by heating the substrate. During evaporation, pores are particularly formed within the substrate. The space occupied by the pore-forming material within the substrate becomes empty after evaporation, especially if the pore-forming material boils at a low temperature. In this way, the porosity required for the formation of a gel polymer electrolyte can be maintained.

[0040] Another way to create porosity is to use a pore-forming material that is soluble in DMC, for example. The pore-forming material dissolves into the DMC on the surface of the substrate or coating (e.g., into the microporosity formed by a wetting roller). This DMC on the surface can be removed by washing the substrate with a wiping roller, which removes the pore-forming agent, and now creates pores in the copolymer coating on the substrate.

[0041] This means, in particular, that there are at least two ways to create pores in the coating: one is by thermal processes and the other is by chemical dissolution processes, although such creation of pores is only necessary if the copolymer coating has a low porosity.

[0042] The substrate is guided through a tank filled with a pore-forming material, for example, DMC (dimethyl carbonate), for wetting with the pore-forming material. The tank filled with DMC is kept under pressure with nitrogen gas, so that outside air cannot penetrate. As the first electrode passes through the tank, the pore-forming material penetrates into the pores of the active material.

[0043] A pressure roller or wetting roller can be provided to apply pressure to the substrate, and the mechanical pressure will drive more of the DMC into the active material of the substrate. The wetting roller will particularly create a microstructure on the surface of the substrate. In this way, more of the DMC will be deposited in the pores or micropores of the substrate surface.

[0044] Additionally, a wiping roller can be provided to remove excess pore-forming material from the surface of the substrate, which can in particular be returned to the tank.

[0045] The pores of the substrate are then filled, in particular with a pore-forming material.The substrate can then be calendered, in particular in step a2).

[0046] In step a2), the substrate is subjected to a final density, e.g. 3.6 g / cm for a typical NMC material (i.e., material for lithium-nickel-cobalt-manganese battery cells). 3 (grams per cubic centimeter).

[0047] DMC is particularly chosen as the pore-forming material because it has a boiling point of 90° C. The DMC is removed again from the substrate at a later point in the process, particularly by evaporation.

[0048] When DMC leaves the surface of the substrate, it creates new pores on the surface or increases the pore diameter, thereby increasing the porosity, allowing the copolymer deposited in the form of a coating to penetrate relatively easily into the pores of the first electrode or substrate.

[0049] The microstructure created by the wetting roller particularly contributes to the adhesion of the subsequent copolymer coating to the surface of the substrate.

[0050] During the calendering process in step a2), a protective film, for example a polyurethane film, can be used on one or both sides. This prevents the DMC from spreading to the sides of the substrate. The polyurethane film can be placed on the substrate before it is introduced into the calender rollers and can be unwound again after it leaves the calendering device. In this way, the same film can be reused.

[0051] In particular, the material mixture is wetted with a pore-forming material during step a).

[0052] In particular, the pore-forming material is at least partially removed from the substrate before step b).

[0053] In particular, the substrate consisting of at least the active material and the copolymer is calendered in step a2) before step b).

[0054] In particular, the substrate does not contain a gel polymer electrolyte immediately prior to step b).

[0055] In particular, the first electrode is cut prior to step b) into a predetermined geometric shape for operation within the battery cell.

[0056] Cutting of a substrate, in particular formed as a continuous material, includes in particular slitting (cut lines extending along the extension direction of the continuous material, i.e., the x-direction, to divide the wide starting material of the substrate into a plurality of narrow continuous material strips), notching (cut lines cutting conductors out of the continuous material; the cut lines extending longitudinally along the extension direction of the continuous material and transversely to this extension direction, i.e., for example along the y-direction and the x-direction), and / or separation (cut lines extending transversely to the extension direction of the continuous material along the y-direction; here separation cuts the substrate out of the continuous material to form individual layers or electrodes of the stack).

[0057] Before step b), only the copolymer and in particular no gel polymer electrolyte is present, ie in particular no gelling has yet taken place, so that the substrate can be handled particularly easily.

[0058] In particular, the substrate or the first electrode is dried between steps a) and b).

[0059] In particular, the substrate is heated to a temperature of about 90°C and dried at that time. If a pore-forming material is disposed in the active material and / or material mixture, this pore-forming material boils and evaporates. When bubbles of the pore-forming material are released from the surface of the substrate, new pores are formed or the diameter of existing pores is increased. This increases the porosity in the active material and, if present, in the coating.

[0060] If a pore-forming material is disposed within the coating, the pore-forming material is released and removed from the coating by heating, thereby increasing the porosity of the coating.

[0061] Pore-forming materials that are released from the substrate or coating upon drying can be captured and optionally recycled for reuse.

[0062] After heating, the pore-forming material may still remain in the pores of the substrate or coating, which is not particularly detrimental, since the pore-forming material, e.g., DMC, may optionally become part of the liquid electrolyte used to wet the first electrode in step b).

[0063] Therefore, in particular DMC or an equivalent suitable pore-forming material is used, i.e. a material that can be used to form pores and that also serves as an electrolyte component, which is also free from health concerns and does not contain VOCs (volatile organic compounds).

[0064] After cutting into a predetermined geometric shape, the first electrode can be arranged in a stack, particularly with other electrodes, and since there is no gel material on the first electrode at this point, the first electrode can be easily handled during stacking.

[0065] In particular, the first electrode is arranged after step a) and before step b) stacked together with at least one second electrode, these electrodes forming a stack.

[0066] In particular, the stack is placed in a casing of the battery cell before step b).

[0067] The lamination can be carried out in a known manner, for example, by Z-folding, i.e., by forming successive layers with alternating folded edges, or by a pick-and-drop method, i.e., by using individual layers, in which a cathode-separator-anode stack is produced.

[0068] After lamination, the conductors on the anode side are interconnected or welded to one another, in particular using nickel-based connecting elements, and likewise, on the cathode side, the aluminum conductors are interconnected or welded to one another, in particular by aluminum connecting elements.

[0069] The stack, in particular including the respective connected conductors, is then placed in a battery cell casing. The casing can be formed as a pouch cell casing or as a plastically deformable casing (prismatic battery cell). If the casing is a pouch cell casing, the edges of the pouch cell casing are sealed in a known manner to ensure an airtight seal. In particular, the casing has, in a known manner, gas pockets that can collect gases released during the formation of the battery cell.

[0070] A liquid electrolyte is then introduced into the casing after at least partial sealing of the casing.

[0071] In particular in step b), a liquid electrolyte, for example PC (polypropylene carbonate) and / or DMC (dimethyl carbonate) containing a dissolved lithium salt (for example lithium hexafluorophosphate, LiPF6, or lithium bis(fluorosulfonyl)imide, LiFSi), is supplied to at least the first electrode, in particular the stack. In this case, the amount of liquid electrolyte is very small, since its main function is to form a gel polymer electrolyte together with the copolymer.

[0072] After being filled with electrolyte, the still open edges of the casing, e.g., pouch cell casing, are closed or sealed.

[0073] The electrolyte filling is preferably carried out under a nitrogen atmosphere and / or under vacuum, which allows air to escape from the battery cell or casing during electrolyte filling.

[0074] In particular, the formation of the gel polymer electrolyte is activated by the supply of at least thermal or mechanical energy.

[0075] At least the first electrode is wetted, allowing the liquid electrolyte to penetrate into the pores of the first electrode, the substrate, or the coating. The liquid electrolyte reacts with the copolymer and becomes activated. Activation requires energy, which can be provided, inter alia, by heat or mechanical force. After activation, the liquid electrolyte swells the original microporous film (substrate and / or coating), ultimately forming a gel polymer electrolyte.

[0076] Wetting and activation are typically achieved by applying mechanical force to the first electrode or stack. For example, the stack, placed in a pouch cell casing, can be compressed between two rotating rollers. The mechanical force causes the liquid electrolyte to penetrate into the pores. This method may be suitable because it is relatively unlikely to damage the casing or separator.

[0077] Wetting and activation may (optionally additionally) be achieved by thermal energy. For this purpose, thermal energy is supplied to at least the first electrode or stack and / or the casing with the stack, for example by placing it in an oven. For this purpose, at least the first electrode is heated to approximately 50°C. If LiFSi is used as the lithium salt, heating can also be achieved up to 80°C. By heating, thermal energy is utilized by the electrolyte, which penetrates into the pores and activates the copolymer, producing a gel polymer electrolyte.

[0078] After the wetting process, the solid-state or polymer battery is ready for molding: the copolymer is in particular at least 90%, preferably at least 95%, particularly preferably completely converted into a gel polymer electrolyte.

[0079] In particular, the stack can be activated with a liquid electrolyte (especially containing a lithium salt) during the electrolyte filling process, similar to how a conventional polyolefin separator is activated by a liquid electrolyte. Depending on the porosity of the coating or substrate, the liquid electrolyte can penetrate into the coating or substrate. After activation, the liquid electrolyte swells the original microporous coating or substrate, ultimately forming a gel polymer electrolyte with the copolymer.

[0080] To accelerate the wetting process of the copolymer, a portion of the liquid electrolyte can be added, especially before calendering.

[0081] In the proposed method, the only step that has to be performed in a humidity-controlled environment is the supply of liquid electrolyte to the stack, so the advantages of the proposed method in terms of manufacturing and equipment costs are clear.

[0082] In battery cells, typically, only the cathode is coated with a gel polymer electrolyte, while the anode is made of lithium metal. In other polymer-gel batteries, both the anode and cathode can be coated with a gel polymer electrolyte. In particular, because both the cathode and anode compound materials on a substrate or support material are coated with the same PVdF-HFP copolymer, for example, as a binder, the three elements of the battery cell are effectively fused into an integrated multilayer wafer by gelation after electrolytic activation without any physical boundaries. This allows the anode-electrolyte interface or cathode-electrolyte interface to extend deep within the porous structure of these electrodes, much like a liquid electrolyte reaching the interface. This also improves the ionic conductivity and dimensional stability of the gel polymer electrolyte.

[0083] In particular, the method can be used for both solid-state batteries and polymer gel battery cells. In the case of battery cells, lithium metal is used as the anode, so the proposed method is particularly used only for manufacturing the cathode. In the case of polymer gel battery cells, the method can be used to manufacture both the cathode and the anode. Therefore, if the battery cell is manufactured without lithium metal, the method can be used for both electrodes.

[0084] In battery cells with lithium as the metal anode, applying the liquid electrolyte and wetting the first electrode is typically done before lamination of the electrodes. Problems can arise if the liquid electrolyte comes into contact with the lithium metal of the anode, the adhesive film, the nickel plate, and the copper substrate. Wetting of the electrodes can also be done after lamination, especially if the liquid electrolyte does not negatively affect the lithium metal on the anode.

[0085] In particular, the proposed method differs from known methods for manufacturing solid-state battery cells in at least the following respects: In this method, the gel polymer electrolyte is not formed immediately after calendering, but only after electrolyte filling and activation. The known methods do not provide for filling the casing with a liquid electrolyte. The present method proposes providing a liquid electrolyte that activates the copolymer to form a gel polymer electrolyte. Only the coating of the active material with the copolymer is a new process for producing at least a battery cell, the other method steps being already known in particular but now proposed for the first time in a different combination. The coating with the copolymer can be carried out in particular by high-speed spraying or by pressing with a deposition roller. In particular, the first electrode configured as a cathode does not have a gelled electrolyte coating during cutting of the electrode, during connection of the electrode to the conductor element, and also during the lamination process. The gel polymer electrolyte does not need to be manufactured externally and then deposited onto the cathode. The gel polymer electrolyte is manufactured within the battery cell. The porosity of the substrate or coating can be increased by the addition of a pore-forming material. In known methods, the porosity is maintained at a relatively low density during calendering. In this method, the calendering of the active material is not altered, and the first electrode is compressed completely to the desired density. Pore-forming materials are released, especially during the drying process, and can be captured and recycled. The gel polymer electrolyte does not need to be applied at high temperatures (approximately 90°C) onto, for example, the cathode. The gel polymer electrolyte is distributed uniformly at a lower temperature after wetting at least the first electrode. Since wetting here lasts, in particular, 3 to 4 hours, a temperature of approximately 50°C may be sufficient. "Regular" cost-effective lithium salts, such as lithium hexafluorophosphate, can be used instead of expensive lithium salts, such as LiFSi. Other copolymers can also be used, such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. The method proposes the use of a copolymer of polyvinylidene fluoride (PVdF) with hexafluoropropylene (HFP) as a preferred composition.

[0086] Compared to known methods, the following advantages can be realized in particular: The first electrode can be easily handled during the various steps of the method, since the formation of the gel polymer electrolyte occurs at a later phase. · Dry atmosphere for electrode production is no longer required, thus saving significant energy costs. The gel polymer electrolyte and the liquid electrolyte can penetrate (as in known methods) into the pores of the first electrode or the substrate or the coating without the need to supply excessive heat energy. No need for expensive lithium salts such as LiFSi. Most of the conventional methods for manufacturing batteries can be used, which reduces the effort required to implement the proposed method. In particular, the stack can be activated with liquid electrolyte (especially containing lithium salts) during the electrolyte filling process, similar to conventional polyolefin separators with liquid electrolyte. The method is better suited to the mass production of solid-state battery cells than currently known methods. The relatively low temperatures required to produce the gel polymer electrolyte in the battery cell result in no or only minor electrolyte degradation. - No thermal decomposition of lithium salts occurs. The gel polymer electrolyte inhibits the formation of dendrites in the lithium metal, reducing the risk of thermal runaway. Conventional calendering can be used to compress the first electrode to a high density, which results in a high volumetric energy density. The higher porosity of the first electrode allows for higher current (higher C-rate) and therefore higher power delivery.

[0087] In short, producing a gel polymer electrolyte in an already assembled battery cell (i.e., when the first electrode is already placed in a stack and this stack is already present in the battery cell casing) can significantly simplify the production of solid-state or polymer gel batteries.

[0088] The method can in particular be carried out by a data processing system, for example a control device, which system has means that are suitably arranged or configured or programmed to carry out the steps of the method or means for carrying out the method, and which system allows at least closed-loop control of the components of the device used in the method.

[0089] The means here include, for example, a processor, a memory that stores instructions executed by the processor, and a data line or transmission device that can transmit instructions, measurements, data, etc. between the listed components of the device used in the method.

[0090] Furthermore, a computer program is proposed comprising instructions for causing a computer to carry out the above-mentioned method or the above-mentioned method steps when the program is executed by the computer.

[0091] Furthermore, a computer-readable storage medium is proposed, comprising instructions which, when executed by a computer, cause the computer to perform the above-mentioned method or the above-mentioned method steps.

[0092] Furthermore, a battery cell is proposed, which comprises at least a casing and an electrode stack arranged in the casing, which includes at least one electrode, in particular manufactured by the method described above.

[0093] A battery cell specifically includes a casing surrounding a volume, at least one first electrode of a first electrode type and a second electrode of a second electrode type disposed within the volume, and a separator material or a solid (which may be gelled) electrolyte disposed therebetween.

[0094] The battery cells are in particular pouch cells (with a deformable casing made of a pouch film) or prismatic cells (with a shape-fixed casing). Pouch films are known deformable casing materials used as casings for so-called pouch cells. They are composite materials, for example, containing plastic and aluminum.

[0095] The battery cells are in particular lithium-ion battery cells.

[0096] The individual layers of the electrodes are arranged one on top of the other, in particular forming a stack, and the electrodes are each associated with a different electrode type, i.e., configured as anodes or cathodes, where the anodes and cathodes are arranged alternately and separated from each other by a separator material or an electrolyte, respectively.

[0097] Furthermore, a motor vehicle is proposed which comprises at least a traction drive and a battery with at least one battery cell as described, the traction drive being able to be supplied with energy by the at least one battery cell.

[0098] Descriptions of methods are particularly applicable to battery cells, automobiles, data processing systems, and computer-implemented methods (ie, computers or processors, computer-readable storage media), and vice versa.

[0099] In particular, the use of indefinite articles ("a" and "an") in the claims and descriptions reflecting them should not be understood as numerals per se, and therefore the concepts or elements introduced in response to such indefinite articles should be understood as meaning that there is at least one of these concepts or elements, and in particular that there may be a plurality of these concepts or elements.

[0100] As a reminder, the use of numerals ("first," "second," ...) in this specification is primarily (and only) used to distinguish between multiple similar objects, quantities, or processes; that is, they do not specifically impose a dependency and / or order between these objects, quantities, or processes. Where a dependency and / or order is required, it is either explicitly stated in this specification or will become apparent to those skilled in the art upon consideration of the specifically described configuration. Where components appear multiple times ("at least one"), a description of one of these components may, but need not, apply to all or some of these components as well.

[0101] The present invention and its technical environment will be described in detail below with reference to the accompanying drawings. Please note that the present invention is not limited to the described embodiments. In particular, unless otherwise specified, partial aspects of the facts shown in the drawings can be extracted and combined with other components and findings from this specification. It should be noted that the drawings, especially the illustrated scales, are merely approximate. [Brief explanation of the drawings]

[0102] [Figure 1] FIG. 10 shows the flow of a first variant embodiment of the method. [Figure 2] FIG. 10 shows the flow of a second variant embodiment of the method. [Figure 3] FIG. 10 shows the flow of a third variant embodiment of the method. [Figure 4] FIG. 1 is a side view of a first alternative embodiment of an apparatus for applying a coating. [Figure 5] FIG. 10 is a side view of a second alternative embodiment of an apparatus for applying a coating. [Figure 6] FIG. 2 is a side cross-sectional view showing a battery cell. [Figure 7] FIG. 10 shows a battery cell during step b) of the method. [Figure 8] FIG. 8 shows the battery cell of FIG. 7 after step b). [Figure 9] FIG. [Figure 10] FIG. 10 is a view showing the wetting roller of FIG. 9 along the conveying direction. [Figure 11] FIG. 11 is a side view of the wetting roller of FIG. [Figure 12] FIG. 12 shows the microstructure of the wetting roller of FIGS. 10 and 11.

[0103] 1 shows the flow chart of a first variant embodiment of the method. In step a) 27, the active material 4 is prepared and optionally placed on a support material 9. The substrate 3 comprises the active material 4 and the support material 9. The active material 4 is moistened with a pore-forming material 11 before step a0) 28. The active material 4 is calendered in step a0) 28 during step a) 27 and before step a1) 29. Calendering has already been described at the beginning. The calendering device 16 comprises a number of calender rollers 17. A calendering force is applied to the active material 4 in the deformation zone via the calender rollers 17, causing it to be compressed.

[0104] In a subsequent step a1) 29, the copolymer 5 is deposited on the active material 4 as a coating 10. The coating 10 is wetted with a pore-forming material 11 during step a) 27. The coating 10 wetted with material 11 is calendered again in step a2) 30.

[0105] Prior to step b) 31, the first electrode 1 is cut in step a3) 32 into a predetermined geometric shape 12 for operation within the battery cell 2. Cutting of the substrate 3 formed as a continuous material 39 can include slitting (cut lines extending along the elongation direction of the continuous material 39, i.e., the x-direction or conveying direction 46, to divide the wide starting material of the substrate 3 into a plurality of narrow strips of the continuous material 39), notching (cut lines cutting out the conductors 38 from the continuous material 39; the cut lines extending longitudinally along the elongation direction of the continuous material 39 and transversely to this elongation direction, i.e., along the y-direction and the x-direction, for example), and / or separation (cut lines extending transversely to the elongation direction of the continuous material 39 along the y-direction; separation here cuts the substrate 3 from the continuous material 39 to form the individual layers or electrodes 1, 13 of the stack 14).

[0106] In a next step a4) 33, the cut first electrode 1 or substrate 3 is dried, where the pore-forming material 11 evaporates and pores are formed in the active material 4 and in the coating 10.

[0107] In a next step a5) 34, the electrodes 1, 13 and possibly separators 40 are stacked to form the stack 14.

[0108] In the next step a6) 35, the placement of the stack 14 in the casing 15 takes place.

[0109] The next step b) 31 is divided into a step b1) 36 of adding a liquid electrolyte 6 and a step b2) 37 of reacting the copolymer 5 with the liquid electrolyte 6 to form a gel polymer electrolyte 7 to form the first electrode 1.

[0110] It should be mentioned here that the addition of the pore-forming material 11 may be carried out as an optional measure.

[0111] 2 shows the flow of a second variant of the method, in which the second electrode 13 is a lithium metal anode not supplemented by a liquid electrolyte 6 (see also the description of FIG. 1).

[0112] Unlike the first variant embodiment, here the method produces only the cathode as the first electrode 1. Therefore, step b) 31 is performed after step a3) 32, i.e. after cutting. Step b) 31 involves adding a liquid electrolyte 6 and reacting the copolymer 5 with the liquid electrolyte 6 to form a gel polymer electrolyte 7, thereby forming the first electrode 1.

[0113] In a next step a5) 34, the electrodes 1, 13 and possibly separators 40 are stacked to form the stack 14.

[0114] In the next step a6) 35, the placement of the stack 14 in the casing 15 takes place.

[0115] The flow of a third variant of the method is shown in Figure 3. See also the explanations for Figures 1 and 2.

[0116] In contrast to the other variants, here the copolymer 5 is mixed with the active material 4 in step a) 27 to form a material mixture 8, which is then applied to a support material 9. The copolymer 5 is homogeneously dispersed in the material mixture 8. When the formation of the gel polymer electrolyte 7 then takes place in the framework of step b) 31, the gel polymer electrolyte 7 is also homogeneously dispersed in the material mixture 8 of the subsequently formed first electrode 1.

[0117] The active material 4 is wetted with a pore-forming material 11 prior to step a0) 28. The active material 4 is calendered in step a0) 28 during step a) 27 and prior to step a1) 29. The first electrode 1 is cut to a predetermined geometric shape 12 for operation within the battery cell 2 in step a3) 32 prior to step b) 31.

[0118] In a next step a4) 33, the cut first electrode 1 or substrate 3 is dried, where the pore-forming material 11 evaporates and pores are formed in the material mixture 8.

[0119] Unlike the first variant embodiment, here the method produces only the cathode as the first electrode 1. Therefore, step b) 31 is performed after step a3) 32, i.e. after cutting. Step b) 31 involves adding a liquid electrolyte 6 and reacting it with the copolymer 5 to form a gel polymer electrolyte 7, thereby forming the first electrode 1.

[0120] In a next step a5) 34, the electrodes 1, 13 and possibly separators 40 are stacked to form the stack 14.

[0121] Step a1) 29, ie placing the copolymer 5 on the material mixture 8 as a coating 10, does not necessarily have to take place here.

[0122] In FIG. 4, a side view of a first alternative embodiment of an apparatus for applying the coating 10 is shown.

[0123] The copolymer 5 is sprayed onto the surface of the substrate 3 (i.e., only onto the active material 4) using a Venturi-based nozzle 21 (also known as high-velocity spray or high-velocity jet method). The nozzle 21 is supplied with dry air 24 at high pressure (approximately 6 bar). For this purpose, the air 24 is compressed in a compressor 22. The supply of the copolymer 5 is controlled via a valve 23. The copolymer particles flow into the nozzle 21. The high air pressure is converted into a high air velocity. The high velocity air (up to 0.3 Ma to 4 Ma) entrains the copolymer particles and drives them into the substrate 3, in particular onto the already calendered surface. In this way, thin coatings 10 of a few micrometers thick can be formed.

[0124] 5 shows a side view of a second variant embodiment of an apparatus for applying a coating 10. The substrate is fed as a continuous material 39 to a pair of pressure rollers 26. Copolymer 5 is fed via each of the pressure rollers 26 through one outlet 25 and is bonded to the support material 9. Further transport of the first electrode 1 takes place via transport rollers 20 to the calendering device 16 and step a2) 30. The coating 10, moistened with material 11, is calendered again in step a2) 30.

[0125] 6 shows a cross-sectional side view of a battery cell 2. The battery cell 2 includes a casing 15 that encloses a volume, and further includes, disposed within the volume, a plurality of first electrodes 1 of a first electrode type, a plurality of second electrodes 13 of a second electrode type, and a separator 40 or solid (or gel) electrolyte 6 disposed therebetween. Electrical conductors 38 of the electrodes 1 and 13 extend outward from the casing 15. The casing 15 is hermetically closed.

[0126] 7 shows the battery cell 2 during method step b) 31. The casing 15 is already partially closed by the sealing seam 41. The electrical conductors 38 extend beyond the casing 15 to the outside.

[0127] In step a6) 35, the stack 14 is placed in the casing 15. In step b1) 36, the liquid electrolyte 6 is added via the face of the casing 15 that is not yet closed.

[0128] 8 shows the battery cell 2 of FIG. 7 after step b) 31, in which the casing 15 is now finally closed. Step b2) 37 involves the formation of a gel polymer electrolyte 7 by reacting the copolymer 5 with the liquid electrolyte 6 to form the first electrode 1.

[0129] FIG. 9 shows a part of the method, showing step a0) 28, i.e., the (first) calendering and wetting of the active material 4 with the pore-forming material 11 before step a0) 28. The active material 4 is calendered in step a0) 28 during step a) 27 and before step a1) 29. The substrate 3 is guided through a tank 42 filled with the pore-forming material 11 for wetting with the pore-forming material 11. The pore-forming material 11 comprises, for example, DMC (dimethyl carbonate). The tank 42 filled with DMC is kept under a predetermined pressure by nitrogen gas 43, so that outside air cannot enter. When the first electrode 1 passes through the tank 42 as a continuous material 39, the pore-forming material 11 penetrates into the pores of the active material 4. A wetting roller 18 is provided which applies pressure to the substrate 3, and this mechanical pressure causes more of the pore-forming material 11 to penetrate into the active material 4 of the substrate 3. The wetting roller 18 creates a microstructure 44 on the surface of the substrate 3 (see FIG. 12 ). In this way, more of the material 11 is deposited in the pores or micropores on the surface of the substrate 3.

[0130] Additionally, a wiping roller 19 is provided to remove excess pore-forming material from the surface of the substrate 3. Excess pore-forming material 11 can be returned into the tank .

[0131] The pores of the substrate 3 are then filled with a pore-forming material. Subsequently, the substrate 3 is calendered in step a2)30.

[0132] During the calendering in step a2) 30, a protective film 45, for example (polyurethane), is used on both sides, so that the material 11 does not spread over the sides of the substrate 3. The polyurethane protective film 45 is placed on the substrate 3 before it is introduced into the calender rollers 17 and is unwound again after it has been led out of the calendering device 16. In this way, the same protective film 45 can be used repeatedly.

[0133] Figure 10 shows the wetting roller 18 of Figure 9 in a view along the conveying direction 46. Figure 11 shows the wetting roller 18 of Figure 10 in a side view. Figure 12 shows the microstructure 44 of the wetting roller 18 of Figures 10 and 11. Figures 10-12 are discussed together below. See also the discussion of Figure 9.

[0134] The wetting roller 18 is additionally excited by an excitation device 47 to produce vibrations 48. The wetting roller 18 exerts pressure on the substrate 3, and this mechanical pressure causes more of the pore-forming material 11 to reach the active material 4 of the substrate 3. The wetting roller 18 has a microstructure 44, which forms a microstructure 44 on the surface of the substrate 3 (see FIG. 12). The individual shapes of the microstructure 44 have a depth of about 20 μm and a width of up to about 5 μm. In this way, more of the material 11 is deposited in the pores or micropores on the surface of the substrate 3. [Explanation of symbols]

[0135] 1. First electrode 2 (solid state) battery cells 3 Base 4 Active materials 5. Copolymer 6 Electrolytes 7. Gel polymer electrolyte 8 Material mixture 9 Support material 10 Coating 11 Material 12 Geometric shapes 13 Second electrode 14 stacks 15 Casing 16 Calendar device 17 Calendar Roller 18 Wetting roller 19 Wiping roller 20 Conveyor roller 21 nozzles 22 Compressor 23 Valve 24 Air 25 Exit 26 Pressure roller 27 Step a) 28 Step a0) 29 Step a1) 30 Step a2) 31 Step b) 32 Step a3) 33 Step a4) 34 Step a5) 35 Step a6) 36 Step b1) 37 Step b2) 38 Conductors 39 Continuous Materials 40 Separator 41 Sealed Seam 42 Tank 43 Nitrogen gas 44 Microstructure 45 Polyurethane protective film 46 Conveying direction 47 Excitation Device 48 vibrations

Claims

1. A method for manufacturing a first electrode (1) of a battery cell (2), comprising the steps of: The method comprises at least the following steps: a) producing a substrate (3) of said first electrode (1) comprising at least the active material (4) of said first electrode (1) and a copolymer (5); b) wetting the substrate (3) with a liquid electrolyte (6) and reacting the copolymer (5) with the liquid electrolyte (6) to form a gel polymer electrolyte (7) to form the first electrode (1); Including, In step a), Mixing the copolymer (5) with the active material (4) to form a material mixture (8), placing the material mixture (8) on a support material (9), and wetting the material mixture (8) with a pore-forming material (11), or Depositing the copolymer (5) as a coating (10) on the active material (4) and wetting the coating (10) with a pore-forming material (11), or wetting the active material (4) with a pore-forming material (11), calendering the active material (4), and depositing the copolymer (5) as a coating (10) onto the active material (4); Prior to step b), the pore-forming material (11) is at least partially removed from the substrate (3), method.

2. The method described in claim 1, wherein the substrate (3) does not contain a gel polymer electrolyte before being wetted with the liquid electrolyte (6).

3. A method as described in claim 1 or 2, wherein before removing the porous-forming material (11), the first electrode (1) is cut into a predetermined geometric shape (12) for operation within a battery cell (2).

4. A method as described in claim 1 or 2, wherein after removing the porous forming material (11), the first electrode (1) and at least one second electrode (13) are stacked and arranged so as to overlap each other, and each electrode (1, 13) forms a stack (14).

5. A method as described in claim 4, wherein the stack (14) is placed within a casing (15) of the battery cell (2).

6. 3. The method according to claim 1, wherein the formation of the gel polymer electrolyte (7) is activated by supplying at least thermal or mechanical energy.

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