Method for mounting an electrode winding having a pressure element, electrode winding having the pressure element, and use of the pressure element

Abstract

The invention relates to a method for mounting an electrode winding for stored energy sources, comprising the method steps of: A) providing an electrode winding which comprises a wound current collector layer and an electrode layer applied to the current collector layer; and B) placing a pressure element circumferentially around the entire circumference of the electrode winding, the pressure element exerting a pressure on the outer surface of the electrode winding. Such a method for mounting an electrode winding is particularly suitable for preventing bending deformation of the outer surfaces of the electrode winding during mounting.

Description

[0001] Method for storing an electrode winding with a pressure element, electrode winding with the pressure element and use of the pressure element

[0002] The present invention relates to a method for storing an electrode winding with a pressure element, an electrode winding with the pressure element and a use of the pressure element.

[0003] To manufacture electrodes for energy storage devices, such as lithium-ion batteries or solid-state batteries, electrode materials are applied to a current collector film using either a wet chemical process or a dry chemical process with a dry binder, employing doctor blades or slot dies. To achieve the high energy density required for the electrodes, the electrode materials on the current collector film are compacted by calendering. Current collector films often have uncoated areas along the length of the current collector strip, which can serve as contact points for current collectors during the manufacturing process. During calendering, different forces are exerted on the areas of the current collector film coated with electrode material and the uncoated areas.This can lead to a saber-shaped bending of the electrode paths due to differing voltages.

[0004] From WO 2022 / 128788 A1, a method is known in which, during the calendering of the areas of a current collector film coated with electrode material, a corresponding deformation is carried out in the uncoated areas of the current collector film in order to reduce deforming bending of the current collector strip during calendering. No statements are made regarding the storage of the current collector film after calendering.

[0005] It is an object of the present invention to provide a method for storing an electrode winding that is improved with respect to the aforementioned disadvantages. Furthermore, it is an object of the present invention to provide an electrode winding with a pressure element that can be stored particularly well. A further object of the present invention is to provide a use for the pressure element.

[0006] One aspect of the invention provides a method for storing an electrode winding for energy storage devices. The method comprises the following process steps:

[0007] A) Providing an electrode winding comprising a wound current collector layer and an electrode layer applied to the current collector layer, and B) Applying a pressure element around the entire circumference of the electrode winding, the pressure element exerting pressure on the outer surface of the electrode winding.

[0008] The inventors have found that in electrode windings containing wound electrode foils, which are used to manufacture electrodes in energy storage devices, the outer areas of the electrode winding in particular exhibit a bending deformation after storage, so that these outer areas of the electrode winding are not readily suitable for the manufacture of electrode foils for energy storage devices and often have to be discarded or reworked.

[0009] Different forces act on the electrode winding during storage. In particular, different forces occur in the core of an electrode winding compared to its outer edges. Towards the core, the compressive stress perpendicular to the foil surface on the electrode material coating increases, while at the end of the winding, where the compressive stress on the electrode surfaces is low or nonexistent. Conversely, the tensile stresses on the outer areas of the electrode winding increase along the longitudinal direction of the strip, while they decrease towards the core. This effect is particularly pronounced in electrode windings that have uncoated areas of the current collector layer along the longitudinal direction of the current collector strip for later contact with current collectors.These electrode windings are subjected to tensile stresses, resulting in elongation, particularly in the areas of the current collector layer coated with electrode material, while this elongation does not occur, or is less pronounced, in the uncoated areas. This difference in elongation between the coated and uncoated areas of the current collector layer leads to bending deformation.

[0010] Furthermore, the inventors have determined that bending deformation and elongation occur particularly during the transport of the electrode windings. During transport, the electrode windings are exposed to varying temperatures in warehouses or transport vehicles, which can lead to increased bending deformation.

[0011] By applying the pressure element, which encircles the entire circumference of the electrode winding, pressure can be exerted on the outer surface of the electrode winding particularly easily and reliably, counteracting the deforming bending of the outer areas of the electrode winding observed by the inventors. In particular, the pressure element can reduce or prevent deformation of the electrode layer in the outer areas of the electrode winding during storage.

[0012] The pressure element is applied during the storage of the electrode coil, whereby storage also includes the transport and drying of the electrode coil, for example in a vacuum oven, after calendering, roll cutting (longitudinal cutting), or contour cutting (laser notching or punching). Storage specifically refers to the safekeeping of the electrode coil. In particular, storage can extend over a longer period, for example, at least one week or at least 14 days.

[0013] The electrode winding has an electrode layer applied to the current collector layer, wherein the electrode layer may be applied to one main surface of the current collector layer or to both main surfaces of the current collector layer.

[0014] The current collector layer can, for example, comprise a metal layer, in particular a metal foil such as aluminum foil or copper foil. The current collector layer can also comprise coated metal foils, for example, metal foils coated with carbon. The current collector layer can also comprise metal grids, for example, metal grids made of copper. The current collector layer can also comprise carbon-containing materials, such as carbon-containing papers. The current collector layer can also comprise a metal-coated polymer film.

[0015] In the electrode winding, the number of windings increases from the core towards the end of the winding. An electrode layer of one winding contacts the electrode layer of an adjacent winding if an electrode layer is applied to both main surfaces of the current collector layer. Conversely, an electrode layer of one winding can also contact the current collector layer of an adjacent winding if an electrode layer is applied to only one main surface of the current collector layer. Therefore, the electrode winding with the pressure element lacks a separator layer, which is present in a finished energy storage device to separate electrodes of different polarities.

[0016] Such an electrode winding thus has either a wound anode electrode or a wound cathode electrode and can be used to manufacture electrode windings in storage cells, for example, lithium-ion batteries. An "electrode" is understood to be a current collector layer with the electrode layer applied to it.

[0017] The electrode winding can either comprise an electrode that has already been cut, for example, by longitudinal and / or contour cutting, and can be installed in a single energy storage cell. Alternatively, the electrode winding can comprise a master coil that can be unwound and cut into individual electrodes, the daughter coils, to manufacture the energy storage devices. The master coil can be a continuous coil and have a length of, for example, 100 meters to several thousand meters. Such a continuous coil is particularly well-suited for manufacturing electrode windings for individual energy storage cells by cutting the continuous coil.

[0018] The pressure element is, in particular, a pressure-exerting element. The pressure element is especially suitable for generating a radially inward-directed pressure on the outer surface of the electrode winding.

[0019] After the electrode winding has been stored, the pressure element can be removed in process step C), which takes place after process step B). Subsequently, the electrode winding can be unwound to manufacture an energy storage device and processed into a finished electrode within the energy storage device.

[0020] In a further embodiment of the method according to the invention, the electrode layer is applied only to a portion of the current collector layer. In particular, peripheral areas of the current collector layer can be free of the electrode layer. These peripheral areas can be used, in particular, as uncoated areas for contacting a current collector. With such an electrode winding, in process step B), the pressure element can be applied at least to these coated portions of the outer surface of the electrode winding. As already described, during storage of the electrode winding, the portions of the current collector layer on which an electrode layer is applied can deform. Therefore, it is advantageous to apply a pressure element circumferentially around the entire circumference of the electrode winding in these portions.

[0021] The mother roll may have edge areas of the current collector layer that are already cut (notched) for better connection of current collectors.

[0022] Furthermore, the pressure element can comprise a band that at least partially encircles the electrode winding. Advantageously, the band can encircle the entire electrode winding. In particular, the band can exhibit a lower creep tendency than the electrode material. Creep is understood as the time- and temperature-dependent viscoelastic or plastic deformation of the band under constant load. The creep tendency can be described by the creep modulus E. cThe creep modulus of the electrode material can be denoted as (t) = o / s(t), where o represents the mechanical stress and s the time-dependent strain. The creep modulus of the electrode material can be determined, for example, using the standard DIN EN ISO 899, which was introduced for plastic materials. The creep modulus of the band encircling the electrode winding can also be determined using the standard DIN EN ISO 899 if the band is made of plastic. The creep modulus of a metal band can be determined using the standard DIN EN ISO 204. The creep modulus of titanium, for example, is 0.5–1.5 x 10⁻⁵. 8 N / mm 2 per hour at 500°C and 100 MPa load, and the creep modulus of aluminium is 1-3 x 10' 8 N / mm 2 per hour at 200°C and 100 MPa load. The creep modulus of carbon-reinforced or glass-fiber-reinforced plastics can be in the range of 1 x 10⁻⁶. 9 up to 1 x 10' 12 N / mm 2per hour under stress at elevated temperatures.

[0023] If the electrode winding is dried after calendering, for example in a vacuum oven, the tape can also include a material with the same or a lower coefficient of thermal expansion than the electrode material. This can particularly easily reduce or prevent expansion of the electrode material during drying. The coefficients of thermal expansion of plastics can be determined, for example, according to the standard ISO 11359-2:2021-11. In general, the changes in length of all solid bodies can be determined according to the standard DIN 51045-1:2005-08. The coefficient of thermal expansion of aluminum, for example, is 22.2 x 10⁻⁶. 6 up to 2.6 x 10' 6 per °C and the coefficient of thermal expansion of copper is 16.5 x 10' 6 up to 17.0 x 10 -6 per °C.

[0024] In carbon fiber reinforced plastics, the coefficient of thermal expansion of the carbon fibers can be negative. Such carbon fiber reinforced plastics can, for example, be used as tensioning straps during the drying of electrode windings, whereby the tensioning strap contracts as it heats up during drying and thus exerts force on the electrode winding.

[0025] The tape can be made from a material selected from the following group: carbon-reinforced or glass-fiber-reinforced plastic and metal. The carbon-reinforced or glass-fiber-reinforced plastic can be selected from epoxies, polyamides, polyetherimides, or polyaryletherketones. For example, carbon-reinforced or glass-fiber-reinforced PA6, PEI, or polyetheretherketone (PEEK) can be used. The proportion of carbon fibers or glass fibers in the carbon-reinforced or glass-fiber-reinforced plastic can range from 30% to 75% by weight of the total weight of the plastic. Suitable metals include, for example, steel, aluminum, copper, and other metals. The thickness of a tape made from carbon-reinforced or glass-fiber-reinforced plastic can range from 0.5 mm to 20 mm.The thickness of a band made of metal can range from 0.3 to 3 mm.

[0026] The pressure element can further include a clamping device designed to apply pressure from the outside, circumferentially around the entire circumference of the electrode winding, towards the core of the electrode winding. In particular, in process step B), the clamping device can then be used to apply pressure directed towards the interior of the electrode winding when the pressure element is applied.

[0027] The clamping device can, for example, be used together with the band encircling the circumference of the electrode winding and serve to build up tension on the outer surface of the electrode winding via the band.

[0028] Furthermore, the tape can partially encircle the electrode coil and have two opposite ends. The tensioning device can be connected to both ends and serves to move both ends of the tape towards each other when the tensioning device is tightened, so that pressure can be applied to the outer surfaces of the coil.

[0029] Preferably, the clamping device may comprise a clamping screw, a clamping lock, a strap or a ratchet.

[0030] The pressure element can also include a pressure sleeve or a heat-shrink tube. In process step B), the pressure directed on the interior of the electrode winding can then be built up by applying pressure or a vacuum.

[0031] The pressure element can also comprise a web-shaped, flexible material, such as a plastic film or a sheet of metal. This material can then be drawn around the entire circumference of the electrode winding under high web tensions of 1 N / mm to 5 N / mm relative to the width of the web, i.e., under high tensile stress on the ribbon-shaped flexible material, thus generating pressure on the outer surfaces of the electrode winding.

[0032] The following polymers, selected from a group consisting of, are particularly suitable as materials for a hosiery tube: Polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polycarbonate (PC), polyamide (nylon), polyethylene (PE), polyoxymethylene (POM), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK).

[0033] The band encircling the electrode winding, which can be used together with the clamping device, can be made of steel, for example. Alternatively, the band can be made of carbon fiber reinforced plastic (CFRP), such as reinforced PA6 or polyethyleneimine (PEI).

[0034] The electrode layer may include components selected from a group consisting of: electrically conductive additives, electrically conductive polymers, electrochemically active material, and binders.

[0035] The electrically conductive additives can be selected from a group consisting of: carbon powder, carbon nanotubes (CNTs), carbon nanoparticles, and metal particles. Preferably, carbon nanotubes and / or carbon nanoparticles are used as electrically conductive additives.

[0036] The electrically conductive polymers can include, for example, poly(3,4-ethylenedioxythiophene)- :poly(styrenesulfonate) (PEDOT:PSS).

[0037] The binders can be selected from a group consisting of: cellulose, cellulose derivatives, rubbers, polyolefins, and polyperfluoroolefins.

[0038] The binders can be, in particular, dry binders. These dry binders can be selected from a group consisting of: polytetrafluoroethylene, ultra-high molecular weight polypropylene, polyethylene, their copolymers, and their polymer mixtures. These dry binders are fibrillable, especially without the addition of process solvents, and thus allow the production of dry electrodes without the addition of process solvents.

[0039] The binders can also be conventional binders used in conjunction with process solvents in the wet-chemical fabrication of electrodes. These binders can be, for example, cellulose, cellulose derivatives, rubbers, or thermoplastic fluoropolymers. In particular, the binders can be carboxymethyl cellulose, styrene-butadiene rubber, and polyvinylidene fluoride, or a combination of these compounds.

[0040] The electrochemically active material includes, in particular, electrochemically active materials capable of absorbing and releasing metal ions, especially lithium ions. For example, the electrode material can be graphite if the electrode is to be used as the anode in a lithium-ion battery. Lithium ions can intercalate in the graphite. For the cathode in a lithium-ion battery used as an energy storage device, oxides containing lithium, nickel, manganese, and cobalt, or phosphates such as UCOO2, LiNiO, 33COO, 33Mno, 33O2, and / or LiFePO4 are used as active materials. Nickel-rich manganese-cooxides (NMC) are typically used for high-energy cells. Silicon, silicon-carbon compounds, and / or silicon oxides capable of absorbing lithium ions can also be used as active materials.

[0041] The electrode material can, in particular, comprise 80% to 99.5% by weight of electrochemically active material, 0% to 10% by weight of conductive carbon, and 3% to 15% by weight of binder. The percentages by weight refer to the total weight of the electrode material. The conductive carbon is preferably selected from the group consisting of: carbon / carbon black, carbon nanotubes, carbon nanoparticles, and graphite.

[0042] Another embodiment of the present invention relates to an electrode winding for energy storage. The electrode winding comprises a wound current collector layer and an electrode layer applied to the current collector layer. A pressure element is provided circumferentially around the entire circumference of the electrode winding. The pressure element is designed to exert pressure on the outer surface of the electrode winding.

[0043] Such an electrode winding with a pressure element is particularly well suited for long storage without deformation of the electrodes occurring in the outer areas of the electrode winding.

[0044] The electrode coil can further be wrapped with a protective film, for example made of polyethylene, to improve storage and prevent the introduction of suspended particles.

[0045] The electrode winding can, in particular, be an endless roll, as described above. The electrode winding can be specifically designed to serve as a means of producing a large number of electrode layers in a final energy storage device.

[0046] In particular, the electrode winding can comprise an increasing number of turns from the core to the outer end. Within the electrode winding, an electrode layer of one winding contacts the electrode layer of an adjacent winding if an electrode layer is applied to both main surfaces of the current collector layer. Conversely, an electrode layer of one winding can also contact the current collector layer of an adjacent winding if an electrode layer is applied to only one main surface of the current collector layer.

[0047] The electrode winding with the pressure element does not have a separator layer, which is present in a finished energy storage device for separating electrodes of different polarity.

[0048] The electrode winding can, for example, include a current collector layer made of copper with a thickness between 4 pm and 10 pm, forming the anode winding. The thickness of the anode layer on the current collector layer can range from 40 pm to 250 pm.

[0049] The electrode winding can include a current collector layer, for example made of aluminum, as the cathode winding. The thickness of the current collector layer can range from 10 pm to 15 pm. The thickness of the cathode layer on top of the current collector layer can range from 40 pm to 250 pm.

[0050] The pressure element can comprise a band encircling the circumference of the electrode coil.

[0051] The pressure element can also include all pressure elements and their components described above in connection with the storage method.

[0052] The electrode winding can comprise an electrode layer applied in a strip shape to the current collector layer. The circumferential band of the pressure element can extend at least over the strip-shaped electrode layer, preferably covering the entire strip-shaped electrode layer. This can ensure that increased pressure is exerted on the areas of the current collector layer covered by the electrode layer via the pressure element, reducing or preventing deforming bending of these areas.

[0053] The electrode winding can be used to manufacture electrodes for energy storage devices without problems arising from deformation, particularly of the outer areas of the winding, during production. The energy storage device could be, for example, a lithium-ion battery or a solid-state battery.

[0054] In a lithium-ion battery, an electrode according to the invention can be an anode and / or a cathode. The separator prevents an electrical short circuit between the electrode and the counter electrode and can be a porous, electrically insulating layer of polyethylene or propylene, glass fibers, a polyolefin membrane, or another porous, electrically insulating material. In particular, an electrolyte solution containing an aprotic solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or 1,2-dimethoxyethane and a conducting salt, for example, lithium hexafluorophosphate (LiPFe), lithium tetrafluoroborate (UBF4), or lithium bis(oxalato)borate, dissolved in the aprotic solvent, can be used as the electrolyte.

[0055] An electrode made from an electrode winding according to the invention can also be used in a solid-state battery. In such an energy storage device, lithium can be used as the anode, and an electrode according to the invention can be used as the cathode. A ceramic permeable to lithium ions, for example lithium orthosilicate, or glass can be used as the solid-state electrolyte.

[0056] The present invention also relates to the use of a pressure-exerting element encircling the entire circumference of an electrode winding to reduce or prevent deformation of the electrode layer in the outer areas of the electrode winding during storage. The electrode winding comprises a wound current collector layer and an electrode layer applied to the current collector layer.

[0057] In the following, aspects of the present invention will be explained in more detail with reference to figures and exemplary embodiments. The figures show:

[0058] Figure 1A is a schematic top view of a printing element with a belt and a tensioning device.

[0059] Figure 1B is a schematic perspective drawing of the printing element of Figure 1A, which is placed around an electrode coil.

[0060] Figure 2 is a schematic cross-sectional drawing of an electrode winding with a pressure element.

[0061] Figure 3 shows a schematic perspective drawing of another embodiment of a pressure element as a pressure sleeve.

[0062] Figure 4 is a schematic perspective drawing of another embodiment of a pressure element, comprising two half-cylinders with a clamping device, and

[0063] Figure 5 is a schematic perspective drawing of an electrode coil around which the pressure element shown in Figure 4 is placed. Figure 1A shows a top view of an embodiment of a pressure element 1. The pressure element 1 comprises a strip 2, for example a thin sheet, with a clamping device 3, for example a ratchet closure, at each of its opposite ends 2A and 2B. At one end 2A, the ratchet closure 3 has a grid 3A, and at the opposite end 2B of the strip, a spring-loaded tab 3B that can engage in the grid 3A to close the strip.

[0064] Figure 1B shows how the pressure element 1 of Figure 1A is placed around the electrode coil 4 and how the spring-loaded tab 3B engages in the grid 3A to serve as a clamping device for the pressure element.

[0065] Figure 2 shows a schematic cross-sectional drawing of an electrode winding 4 with a sleeve 7 in the winding core, which is surrounded by a pressure element 1. The electrode winding 4 has a plurality of windings of a current collector layer 5, wherein the current collector layer 5 is coated in strips with electrode material 6. Furthermore, edge regions 5A of the current collector layer are visible, which are free of the electrode material 6 and can, for example, serve for contacting current collectors. The pressure element 1 has a band 2 encircling the winding 4. This band 2 can be tightened by means of the clamping device 3, for example a screw clamp, so that pressure is exerted on the outer regions of the electrode winding 4.The circumferential band 2 of the pressure element covers at least those areas of the current collector layer 5 that are coated with electrode material 6 and are particularly susceptible to bending deformation during storage, especially in the outer areas of the electrode winding. Electrode material 6 is applied to both main surfaces of the current collector layer 5 in the electrode winding 4. Therefore, the electrode layer 6A of winding 4A contacts the electrode layer 6B of the adjacent winding 4B of the electrode winding.

[0066] Figure 3 shows a schematic perspective drawing of another embodiment of a pressure element 1 as a pressure sleeve. The pressure element 1 has a pressure ring 8 which can be inflated with air or filled with water via a hose 9, so that pressure can be exerted on an electrode coil. Additionally, the pressure element 1 has a clamping screw 3 which can be used to exert additional pressure on the electrode coil. Alternatively, the pressure element can also have only a pressure sleeve or only a clamping screw. If the pressure element has only a clamping screw, a slot is advantageously provided in the annular pressure element, which can be narrowed by the clamping screw (slot not shown in Fig. 3). Figure 4 shows a perspective schematic drawing of another embodiment of a pressure device 1 according to the invention.Printing device 1 has two separate bands 2 as half-cylinders, wherein one half-cylindrical band 2' has screws 3A of a clamping screw 3 and the other half-cylindrical band 2" has holes 3B for receiving the screws 3A of the clamping screw 3.

[0067] Figure 5 shows a perspective schematic drawing of an electrode winding 4 around which the pressure device 1 according to the invention of Figure 4 is placed. The screws 3A of one semi-cylindrical band 2' engage in the holes 3B of the second semi-cylindrical band 2" so that a clamping screw connection is formed.

[0068] The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the patent claims, even if this feature or combination itself is not explicitly specified in the patent claims or exemplary embodiments.

Claims

Patent claims 1. Method for storing an electrode winding for energy storage, comprising the process steps: A) Providing an electrode winding comprising a wound current collector layer and an electrode layer applied to the current collector layer, and B) Applying a pressure element around the entire circumference of the electrode winding, wherein the pressure element exerts pressure on the outer surface of the electrode winding.

2. Method according to the preceding claim, wherein the electrode layer is applied only to a partial area of ​​the current collector layer and wherein in process step B) the pressure element is applied at least to this partial area of ​​the outer surface of the electrode winding.

3. Method according to one of the preceding claims, wherein the pressure element comprises a band circumferentially circulating the electrode winding, wherein the band has a lower tendency to creep than the electrode material and / or wherein the band has a coefficient of thermal expansion which is less than or equal to the coefficient of thermal expansion of the electrode material.

4. Method according to the preceding claim, wherein the belt is made of a material selected from a group consisting of: carbon fiber reinforced or glass fiber reinforced plastic and metal.

5. Method according to one of the preceding claims, wherein the pressure element comprises a clamping device, preferably a clamping screw, a clamping fastener, a strap or a ratchet, and wherein in method step B) the pressure directed towards the interior of the electrode winding is built up via the clamping device when the pressure element is applied.

6. Method according to one of the preceding claims, wherein the pressure element comprises a pressure sleeve or a shrink tube and wherein in method step B) the pressure directed on the interior of the electrode winding is built up by applying pressure or vacuum.

7. Electrode winding for energy storage, comprising a wound current collector layer and an electrode layer applied to the current collector layer, wherein a pressure element is provided circumferentially around the entire circumference of the electrode winding, wherein the pressure element is configured to exert pressure on the outer surface of the electrode winding.

8. Electrode coil according to the preceding claim, wherein the electrode coil is packaged in a protective packaging.

9. Electrode winding according to one of the preceding claims 7 or 8, wherein the electrode winding is an endless roll.

10. Electrode winding according to one of the preceding claims 7 to 9, wherein the pressure element comprises a band circumferentially around the circumference of the electrode winding.

11. Electrode winding according to the preceding claim, wherein the electrode layer is applied in a strip shape to the current collector layer and wherein the circumferential band of the pressure element extends at least over the strip-shaped electrode layer, preferably wherein the band completely covers the strip-shaped electrode layer.

12. Use of a pressure-exerting element circumferentially around the entire circumference of an electrode winding, wherein the electrode winding comprises a wound current collector layer and an electrode layer applied to the current collector layer, in order to reduce or prevent deformation of the electrode layer in the outer areas of the electrode winding during storage.

Images