Electrochemical energy storage element

Abstract

An electrochemical energy storage element. An electrochemical energy storage element (12) has a winding assembly (10) having a helical structure comprising at least two electrode strips (14, 24) helically wound about a winding axis and at least one diaphragm strip (38, 40) arranged between the electrode strips (14, 24). A hollow cylindrical winding assembly (10) includes two terminal end faces (34, 36) and axially aligned cavities (46) at the center of the winding assembly (10). The winding core (50) is arranged in the cavity (46). In order to increase the safety of the energy storage element (12), an anchoring element (52) is arranged on at least one (36) of the two end faces of the winding assembly (10), the anchoring element (52) being connected to the winding core (50). The anchoring element (52) projects laterally from an axial center of the winding assembly (10) over an end face (36) of the winding assembly (10) at least in some regions.

Description

Technical Field

[0001] The present invention relates to an electrochemical energy storage element having a cylindrical shell and a hollow cylindrical winding assembly, and a method for manufacturing such an electrochemical energy storage element. Background Technology

[0002] The simplest form of electrochemical energy storage device is the electrochemical cell. An electrochemical cell comprises at least one positive electrode and at least one negative electrode, connected via an ion-conducting electrolyte. In this type of cell, an electrochemical, energy-supplying reaction occurs, consisting of two electrically coupled but spatially separated partial reactions. One partial reaction, occurring at a relatively low redox potential, takes place at the negative electrode, while another partial reaction, occurring at a relatively high redox potential, takes place at the positive electrode. Spatial separation is often ensured by a membrane arranged between the electrodes.

[0003] During discharge, as a result of the oxidation process, electrons are released at the negative electrode, causing electrons to flow to the positive electrode via the external load, where a corresponding amount of electrons are absorbed. Therefore, a reduction process occurs at the positive electrode. Simultaneously, for charge balance, an ionic current corresponding to the electrode reaction appears within the electrochemical cell. This is ensured by ion-conducting electrolyte.

[0004] In secondary (rechargeable) electrochemical energy storage cells, the discharge reaction is reversible, meaning that it is possible to convert chemical energy into electrical energy during discharge.

[0005] When the terms "anode" and "cathode" are used together in the context of secondary electrochemical energy storage cells, the electrodes are typically named according to their discharge function. Therefore, in such cells, the negative electrode is the anode, and the positive electrode is the cathode.

[0006] An electrochemical energy storage element may include exactly one electrochemical energy storage cell. However, it may also include two or more cells, which are preferably connected in series or in parallel.

[0007] In energy storage devices, electrodes and separators are often provided in the form of assemblies. Such assemblies can be cell stacks consisting of stacked electrodes. However, assemblies typically have a structure with wound electrodes and separators (winding assemblies).

[0008] Cylindrical designs are widely used in electrochemical energy storage devices, where electrodes are typically housed as part of a hollow cylindrical winding assembly within a cylindrical casing with a form factor of, for example, 21 x 70 (diameter * height, in mm). Cells with this form factor are commonly referred to as cylindrical circular cells.

[0009] For applications in the automotive industry, for e-bikes, or for other applications with high energy demands (such as in power tools), lithium-ion cells with the highest possible energy density are preferred, while simultaneously being able to carry high currents during charging and discharging. Modern lithium-ion cells with this form factor can achieve energy densities ranging from 300 Wh / kg.

[0010] For example, a problem with electrochemical energy storage devices with very high energy density is the strong thermodynamics that can occur under conditions of electrical short circuits or other misuse. This can cause violent reactions and sudden evaporation of the cell's chemical materials, especially the electrolyte and active materials, potentially even leading to the explosion of the energy storage device's casing. Such thermal runaway in energy storage devices poses a safety risk.

[0011] If several energy storage elements are combined to form an array, the thermal failure of one energy storage element can propagate very quickly to neighboring energy storage elements, causing the array to fail as a whole and posing a considerable safety risk due to the associated heat generation.

[0012] It is also known that using active materials in such cylindrical energy storage elements is problematic, namely, these elements undergo significant volume changes (also known as volume thrust) during charging or discharging. This is particularly pronounced, for example, in the case of materials containing Si. Continuous growth of the solid electrolyte interface (SEI) (a type of passivation layer on the anode) also contributes to electrode swelling. Thus, volume changes include both reversible “breathing contributions” and continuous growth. Consequently, considerable effort has been made at the material, electrolyte, and electrode levels to minimize these volume effects. In winding assemblies, the winding can even collapse towards the interior. To prevent / reduce this or stabilize the winding, existing technologies use, for example, tubes as winding cores (also known as mandrels). The winding core is either included from the outset as part of the winding process or inserted subsequently. The winding core can be composed of metallic materials (e.g., Cu), but polymer-based materials are also frequently used.

[0013] For example, energy storage elements with improved winding cores are known from EP 3 945 617 A1.

[0014] However, in the case of energy storage elements with winding cores, the safety risks are further increased in the event of thermal failure because the winding cores can be ejected from the inside of the energy storage element like a projectile. Summary of the Invention

[0015] In contrast, the present invention aims to provide an improved energy storage element that solves the aforementioned problems. In particular, the energy storage element should be improved in terms of its safety properties.

[0016] In addition, an array of several energy storage elements with improved safety features will be provided.

[0017] This objective is achieved by an array of electrochemical energy storage elements having the features of claim 1 and electrochemical energy storage elements having the features of claim 9. The method according to claim 10 is also part of this invention.

[0018] The energy storage element according to the present invention has the following characteristics:

[0019] a) The energy storage element has a hollow cylindrical winding assembly with a helical structure comprising at least two electrode strips spirally wound around the winding axis and at least one diaphragm strip disposed between the electrode strips.

[0020] b) The hollow cylindrical winding assembly includes two terminal faces, a circumferential outer shell surface, and a circumferential inner shell surface.

[0021] c) The inner component housing surface defines an axially aligned cavity at the center of the winding assembly.

[0022] d) A winding core having a basic cylindrical or hollow cylindrical shape is arranged in an axially aligned cavity, wherein the winding core has an outer peripheral surface, which preferably rests flat against the surface of the inner component housing.

[0023] Energy storage elements are characterized in particular by the following features:

[0024] e) An anchoring elements connected to the winding core are arranged on at least one of the two end faces of the winding assembly.

[0025] f) The anchoring element protrudes laterally from the axial center of the winding assembly over the end face of the winding assembly, at least in certain areas.

[0026] This invention recognizes that, in the event of thermal failure of an energy storage element, an anchoring element connected to the winding core prevents the winding core from being ejected from the cell as a projectile. The fact that the anchoring element protrudes laterally from the end face of the winding assembly means that the winding core and the winding assembly form a structural unit that ejects from the housing portion. Due to the increased mass ejected during thermal failure, the velocity of the ejected material is reduced under the same ejection pressure. This improves the safety of the energy storage element by eliminating the "projectile effect." However, most importantly, the thermally critical contents of the cell are removed from the plane of the cell array (see further explanation below) – ideally completely removed. This significantly reduces the probability of heat propagation within the cell array and significantly improves the safety of the entire system.

[0027] In essence, by protruding above the end face of the winding assembly, we mean the radial extension of the anchoring element over at least one region of the winding assembly, which creates a form-fit in the axial direction between the anchoring element and (on the one hand) the winding core to which it is connected, and (on the other hand) the winding assembly. Thus, as the winding core moves, the anchoring portion moves together with the winding composite, thereby preventing any relative movement between the two parts.

[0028] The feature “cylindrical” here is not necessarily considered to be circular-cylindrical, but is understood in a general mathematical sense, and therefore may also include a body with a polygonal base surface (e.g., a hexagonal prism) or a non-circular-cylindrical base surface (e.g., a compressed flat winding).

[0029] Preferably, the electrochemical energy storage element according to the present invention is an electrochemical energy storage cell.

[0030] In a preferred example of the embodiment, the anchoring element is characterized by at least one of the following features a) to e).

[0031] a) The anchoring element and the winding core are integrally formed from the same material.

[0032] This offers particular advantages in manufacturing. Therefore, the anchoring portion and the winding core can be manufactured as a single, integral part of a single material, for example, as an injection-molded part. This part is then inserted into the winding composite without any further connection process steps.

[0033] However, the anchoring portion and the winding core can also initially be separate components that are subsequently joined. For example, the winding core may have already been inserted into the winding composite, and the anchoring portion may then be attached to the winding core, for example, by gluing or welding. A form-fit connection with mechanical interlocking between the anchoring portion and the winding core is also conceivable.

[0034] b) The anchoring element is formed as one or more curved tabs of the winding core.

[0035] A particularly efficient manufacturing method can be achieved by designing the hollow cylindrical winding core to have a protrusion above the end face of the winding assembly. In the region protruding from the end of the winding core, the winding core has at least two longitudinal cuts that are generally opposite each other. This provides two separate tabs that bend outwards after the winding core has been inserted into the winding assembly, causing them to protrude above the end face of the winding assembly. The length of the cuts determines the extent to which the anchoring element protrudes above the end face from the center of the winding assembly.

[0036] A particularly efficient manufacturing method can be achieved by designing the hollow cylindrical winding core to protrude slightly beyond the end face of the winding assembly. In the region of this protrusion, the winding core includes at least two generally opposing longitudinal slits extending inward from its free end. This creates two separate tabs that bend outward after the winding core is inserted into the winding composite to protrude beyond the end face of the winding assembly. The length of the slits determines the extent to which the anchoring element protrudes beyond the end face from the center of the winding assembly.

[0037] c) The anchoring element has two, three, or four arms, which are preferably arranged in a star shape.

[0038] If several longitudinal cuts are provided, this results in a correspondingly higher number of tabs, such that multiple tabs protrude above the end face of the winding assembly. However, the anchoring element can also be formed as, for example, a cross member connected to the anchoring element with four arms. Therefore, the number of arms is independent of the manufacturing method. Furthermore, the arms of the anchoring element can be of any shape. Thus, a design with leaf-shaped arms is also conceivable.

[0039] d) The anchoring element is formed as a disc.

[0040] Disc-shaped anchoring elements have the advantage that their end faces can be contacted over the largest possible area. This results in a large area for positive fit between the anchoring element and the winding assembly.

[0041] e) The anchoring element extends from the axial center of the winding assembly to a radius ranging between 10% and 100% of the radius of the winding assembly, preferably between 30% and 98%, and particularly between 80% and 95%.

[0042] To ensure the necessary form fit between the anchor portion and the winding assembly during ejection from the housing, it is not essential that the anchor portion extend across the entire radius of the winding assembly's end face. It has been found that extending the anchor portion up to 10% of the winding assembly's radius is sufficient. However, ideally, a larger coverage area, such as up to 60%, 80%, or 90%, or near-complete coverage, is desirable. The stated radial values ​​are independent of the anchor portion's shape, allowing disc-shaped anchor portions, or their arms or tabs, to protrude considerably beyond the end face. Furthermore, it is possible for the anchor portion to extend beyond the winding assembly's radius. However, this configuration is not advantageous in terms of the overall space requirements of the energy storage element.

[0043] According to another preferred example, the anchoring element is characterized by the following features.

[0044] a) The anchoring element is a conductive contact element that is in direct contact with one of the electrode strips at the end face of the winding assembly on which the anchoring element is arranged.

[0045] Energy storage elements specifically designed for high current carrying capacity may include contact elements for contacting electrode strips at the end faces of the winding composite. Such energy storage elements are known, for example, from WO 2021 / 239492 A1. This contact element can also serve as an anchoring portion for the winding core. For this purpose, it simply needs to be connected to the winding core or coupled to it during the manufacturing process. Since the contact element is typically welded directly to the edge of the electrode strip over an uncoated metal carrier of the active electrode material, it can also preferably be welded or mechanically connected to the winding core. In this way, the particularly preferred dual function of the component—as a contact element for the electrode strip and as an anchoring portion for the winding core—can be achieved in a single manufacturing step.

[0046] According to another preferred example, the energy storage element is characterized by the following features.

[0047] a) The energy storage element includes a housing, which includes a cup-shaped housing portion having a bottom and a terminal opening, the cup-shaped housing portion preferably being metallic, the terminal opening being closed by a cap assembly.

[0048] As will become apparent below, in energy storage elements having a cup-shaped housing portion enclosed by a cover assembly, the anchoring of the winding core to the winding assembly according to the invention is particularly advantageous. In such a housing, in the event of thermal failure, the cover assembly can be opened, thereby allowing the unit consisting of the winding core, the anchoring portion, and the winding assembly to be ejected.

[0049] In such housings, the energy storage element can be characterized by one of the following characteristics:

[0050] a) The winding core is connected to the bottom of the housing portion by forming an anchoring element at the bottom.

[0051] If the winding assembly is directly connected to the conductive bottom, for example, by welding, the winding core can also be directly connected to the bottom. In this case, the bottom forms an anchoring portion, preventing the winding core from being ejected from the housing (removed from the winding assembly) in the event of thermal failure of the energy storage element. The advantage of this solution is that no separate component is required.

[0052] b) The anchoring element is connected to the bottom of the housing section.

[0053] Alternatively, the anchoring portion can be a separate component attached to the bottom of the housing portion. This is particularly advantageous (e.g., in conjunction with the features described above), whereby the anchoring portion also serves as a conductive contact element. A common practice is to attach the contact element, which connects to the cathode current collector, to the bottom of the cup-shaped housing portion. In this way, the cup-shaped housing portion acts as a terminal for the energy storage element. In such embodiments, if the contact element is welded to the winding core, the contact element can also serve as the anchoring portion. Thus, the connection (which can also be a welded connection) is designed to be easier to release than the connection to the winding core, which is ideally very robust.

[0054] According to another example, energy storage elements have the following additional characteristics.

[0055] a) The anchoring element has through openings through which the gas pressure generated in the winding assembly can be released into the space between the bottom and the anchoring element in the following manner:

[0056] b) Gas pressure presses the anchoring element, along with the winding core and winding assembly, against the cover assembly.

[0057] In the event of thermal failure, the pressure generated in the winding assembly can rapidly escape into the space between the anchoring element and the bottom. Due to the ejection of entrained material and the escape of gas through the through-opening, the winding assembly accelerates like a rocket and ejects from the cup-shaped housing section as soon as the cover assembly opens. However, the speed of the winding assembly during ejection is relatively low, preventing any further danger. Essentially, most of the mass contained in the energy storage element should eject from the housing to prevent heat propagation to adjacent energy storage elements.

[0058] According to an advantageous example of the embodiments, the electrochemical energy storage element may have at least one of the following additional features.

[0059] a) The cover assembly is attached to the cup-shaped housing portion in such a manner that the closure of the cover assembly opens as long as the internal pressure and / or the winding composite is pressed against the cover assembly at a predetermined threshold pressure, particularly by means of a press-fit closure technique.

[0060] If the closure of the cover assembly is correspondingly configured on the cup-shaped housing portion, it is possible to prevent the cup-shaped housing portion from rupturing. This constitutes controlled pressure release of the energy storage element. The threshold pressure at which the cover assembly opens is advantageously set to be higher than the pressure at which a so-called pressure relief valve (PRV) according to the prior art opens. In addition, the opened cover assembly should preferably expose the maximum possible net cross-section.

[0061] Therefore, the following features are additional or alternative features.

[0062] b) The cover assembly (66) is attached to the cup-shaped housing portion (62) in such a way that the net cross-section of the cup-shaped housing portion (62) is radially reduced in the region below the cover assembly (66) by no more than six times the wall thickness of the housing portion (62) compared to the remaining net cross-section, particularly by means of a press-fit closure technique.

[0063] In this way, the maximum possible cross section is freely ejected from the cup-shaped housing portion to form the complete winding assembly.

[0064] In the manufacture of energy storage devices, a crimping process is conventionally used to close the cup-shaped housing portion with a cap assembly. With the winding assembly already in place, the free end section of the cup-shaped housing is radially bent inward over the area of ​​the cap assembly. To prevent damage to the winding assembly during the crimping process, in conventional energy storage devices, a tool engagement structure is first formed on the cup-shaped housing portion above the winding assembly. The function of the tool engagement structure is that, when the housing is closed by the crimping process, an opposing tool of the crimping tool can be attached to the cup-shaped housing portion. The opposing tool overcomes the axial force applied during the crimping process, holding the cap assembly axially and dissipating this force, thus largely protecting the winding from force application. Typically, a circumferential bead is provided in the cup-shaped housing portion at closing, and this circumferential bead is retained after manufacturing.

[0065] When the rolled edge protrudes radially into the interior space of the housing cup, the area where the rolled edge is formed has a reduced cross-section. This complicates the ejection of the winding assembly, as the assembly typically completely fills the housing cup radially.

[0066] In contrast to this conventional crimp-sealing technique, the crimp-sealing technique mentioned above makes it possible to eliminate the tool engagement structure that is usually required for opposing tools.

[0067] For details on the crimp sealing technology, please refer to the applicant's application EP 3 916 877 A1.

[0068] Essentially, in this crimp-sealing technique, after the winding assembly has been inserted into the cup-shaped housing portion with steps or cones, the steps or cones are transferred into a circumferential recess by aligning the outer diameter of the cup-shaped housing portion. The cover assembly is then placed on this recess, and only the upper protrusion of the cup-shaped housing portion is radially bent, i.e., crimped. Axial opposition is not necessary.

[0069] Because the net cross-section of the cup-shaped housing portion decreases radially only in the region below the cover assembly, for example, by up to 6 times the wall thickness of the housing portion, the winding assembly, along with the winding core and anchoring elements, can be ejected from the housing portion in the event of thermal failure of the energy storage element.

[0070] Here, the area below the lid assembly can be specifically considered as the area directly below the lid assembly, in which the lid assembly rests on the cup-shaped housing portion.

[0071] For the 21700 housing, the typical wall thickness ranges from 200 μm to 350 μm.

[0072] The area of ​​the inverted cup above the cap assembly can be larger to ensure retention of the seal or to allow the end face of the energy storage element to contact the circumferential edge of the cup. However, this outer area is more prone to deformation if the cell is opened.

[0073] The closure need not have a circumferential recess, but can also have only a single contact point for the cover assembly. Therefore, information regarding the penetration depth or reduction in net cross-section is relevant to the corresponding element. In the case of a circumferential recess, the closure technology will therefore also fall below the protected area, which will protrude on both opposite sides into the inner cross-section by up to 6 times the wall thickness.

[0074] Further details regarding the closure technique with the maximum possible net cross-section can be found in the applicant's unpublished EP24194421.4.

[0075] The housing of the energy storage element is further characterized by the following additional features.

[0076] a) The bottom has a predetermined break line that separates the removable bottom area from the bottom area of ​​the rest of the housing portion that is securely assembled to the housing portion.

[0077] This has the following advantages: a punch can be placed there, which can be used to press into the removable base area. This can be used to manually eject the winding assembly and anchoring elements during the recycling process.

[0078] The energy storage element mentioned above can preferably be designed in such a way that, in the event of thermal failure, due to the anchoring element, a volume fraction of the energy storage element between 10% and 100%, preferably between 40% and 100%, and particularly greater than 60%, ejects from the housing.

[0079] Regarding arrays of electrochemical energy storage elements, the following additional features can be used to further enhance the safety of these energy storage elements:

[0080] a) A cell connector connects a cover assembly of at least two energy storage elements, wherein the cell connector is deformable and / or detachable such that the cover assembly of one energy storage element can be opened when a predetermined threshold pressure is reached within the energy storage element, while the cover assembly of the other energy storage element remains closed.

[0081] The deformability or detachability of the cell connector is advantageous because, although it is necessary to make an electrical connection to adjacent components, the cell connector allows the cover assembly to be opened from a single energy storage element where thermal failure has occurred, so as to pop out the winding assembly.

[0082] Such cell connectors may have special bends, achieved, for example, through material shrinkage. Alternatively, the connection of the cell connector may be just stable enough to ensure conductivity, but the connection (e.g., solder joint) loosens when extreme pressure is reached.

[0083] A method for recycling the electrochemical energy storage element mentioned above preferably has the following characteristics.

[0084] a) The winding assembly, including the winding core, is pressed out of the housing portion by pressing a punch into the bottom of the energy storage element.

[0085] b) Treat the housing section and winding assembly separately.

[0086] This manual ejection of the winding assembly allows for easier and safer recovery of the energy storage element. In particular, the punch can be pressed into a removable base area outlined by a predetermined break line. Attached Figure Description

[0087] Hereinafter, examples of the invention will be explained in more detail with reference to the accompanying drawings. These drawings illustrate:

[0088] Figure 1 It is a schematic sketch of the still-unfolded electrode strip (in this case, the anode);

[0089] Figure 2 It is a schematic sketch of the still-unfolded electrode strip (in this case, the cathode);

[0090] Figure 3 It is a schematic sketch of the alternating arrangement of the anode, diaphragm, and cathode in an unfolded state;

[0091] Figure 4 This is a perspective view of a winding assembly with a prominent anode current collector at the top and a prominent cathode current collector at the bottom, and a winding core inside.

[0092] Figure 5 It is a perspective view of a winding assembly including a winding core and end face anchoring elements according to the first example;

[0093] Figure 6 It is through from Figure 5 Longitudinal section of the winding core and the anchoring elements assembled therewith;

[0094] Figure 7 It comes from Figure 5 and Figure 6 A top view of the anchoring element from below;

[0095] Figure 8 It is a perspective view of a winding assembly including a winding core and end face anchoring elements according to the second example;

[0096] Figure 9 It is through from Figure 8 Longitudinal section of the winding core and the anchoring elements assembled therewith;

[0097] Figure 10 It comes from Figure 8 and Figure 9 A top view of the anchoring element from below;

[0098] Figure 11 It is a longitudinal section through an electrochemical energy storage cell with a closed housing and inserted winding assembly;

[0099] Figure 12 The longitudinal section of the electrochemical energy storage cell is traversed in the following condition: the cover assembly has been removed from the housing and the winding assembly, along with the winding core and anchoring elements, has been ejected;

[0100] Figure 13 It is a cross-section of a cell array having several energy storage cells according to the present invention, wherein one of the energy storage cells is ejected;

[0101] Figure 14 This is a top view of the cell connector between two energy storage cells in an array of cells that are electrically connected.

[0102] Figure 15 This is a cross-sectional view of the cell array during the dismantling process in the recycling of energy storage cells. Detailed Implementation

[0103] Figures 1 to 4 The diagram illustrates the structure of winding assembly 10, which can be energy storage cell 12 (see diagram). Figures 11 to 15 The components of the energy storage element according to the invention are described in this description only as an example of an embodiment of an energy storage element with only one electrochemical energy storage cell. Therefore, the term energy storage cell will always be used in the following text. However, as explained above, variations having several energy storage cells assembled to form an energy storage element according to the invention are also conceivable.

[0104] The winding assembly 10 includes a strip anode 14 (in Figure 1(Shown in the image) and a strip-shaped anode current collector 16 having a first longitudinal edge 18. The anode current collector 16 is a foil made of copper or nickel. Aluminum can also be used in the case of an anode with a higher potential (>1V vs. Li / Li+) or for Na-ion cells. The foil includes a strip-shaped main region loaded with a layer of negative electrode material 20 and a free edge strip 22 extending along the longitudinal edge 18, which is not loaded with electrode material 20. The edge strip 22 may be partially coated with a material for electrical insulation.

[0105] In addition, the winding assembly 10 includes a strip cathode 24 (in Figure 2 (shown in the figure) and a strip-shaped cathode current collector 26 having a second longitudinal edge 28. The cathode current collector 26 is an aluminum foil. It includes a strip-shaped main region loaded with a layer of positive electrode material 30 and a free edge strip 32 extending along the longitudinal edge 28, which is not loaded with electrode material 30.

[0106] The two electrodes (anode 14 and cathode 24) are initially shown individually in the deployed state.

[0107] The anode 14 and cathode 24 are arranged offset from each other within the winding assembly 10 such that the first longitudinal edge 18 of the anode current collector 16 protrudes from the first terminal face 34 and the second longitudinal edge 28 of the cathode current collector 26 protrudes from the second terminal face 36 of the winding assembly 10. Figure 3 The offset arrangement is shown in the figure.

[0108] Two strip-shaped diaphragms 38 and 40 are also shown there, separating the anode 14 and cathode 24 from each other in the winding assembly 10. In this context, the term electrode-diaphragm assembly is therefore often referred to. Diaphragm strips 38 and 40 may comprise any material used for electrically separating the electrodes. Alternatively, these diaphragm strips may also be applied directly to the electrodes as a type of insulating layer. For this purpose, electrically insulating ion-conducting materials (such as ion-conducting polymers) are conceivable. Such insulating layers are therefore also considered diaphragm strips for the purposes of this claim.

[0109] exist Figure 4 The winding assembly 10 is shown in a wound form because it can be used according to... Figures 11 to 15 In one of the energy storage cells 12, the anode current collector 16 and cathode current collector 26 protruding from end faces 34 and 36 are clearly visible.

[0110] Often, the winding assembly 10 is still enclosed by the winding housing 42, for example, by a plastic film. Alternatively, locally applied strip-shaped adhesive tape may be used, or the diaphragm tape may be glued together directly in the outermost winding.

[0111] like Figure 4 As can be seen, the winding assembly 10 is a hollow cylinder and has a circumferential outer component shell surface and a circumferential inner component shell surface 44. The winding shell 42 extends substantially along the circumferential outer component shell surface, and the circumferential inner component shell surface defines an axially aligned cavity 46 at the center of the winding assembly 10.

[0112] The winding core 50 is arranged within the cavity 46. This serves to support the winding assembly 10 from the inside. This prevents the cavity 46 from collapsing due to volumetric thrust during loading and unloading. The winding core 50 may be made of metal or polymer material. Depending on the manufacturing process, the winding core 50 may be placed inside the winding assembly 10 before or after winding.

[0113] In most cases, cavity 46 has a hollow cylindrical shape with a circular cross-section. However, depending on the geometry of winding core 50, other hollow or solid cylindrical shapes (such as hexagonal prism shapes) are also conceivable. Winding core 50 is often formed as a longitudinally slotted cylindrical tube, so that winding core 50 itself can yield to some extent to the volumetric thrust of the electrical separator assembly.

[0114] Figures 5 to 7 A first example of a further development according to the invention is now shown.

[0115] Figure 6 and Figure 7 The winding core 50 and the anchoring element 52, which is securely attached to the end face of the winding core 50, are shown in a sectional or plan view.

[0116] In the example shown here, the anchoring element 52 is disc-shaped and has four through openings 54. The through openings 54 are elliptical here, but can also have other shapes, and their number can vary as needed.

[0117] In this example, both the winding core 50 and the anchoring element 52 are metallic and therefore both conductive. The winding core 50 and the anchoring element 52 are along what is shown as... Figure 7 The dotted weld seams 56 in the diagram are firmly connected to each other.

[0118] exist Figure 5 In the diagram, the winding assembly 10 is shown having a winding core 50, which is inserted into the cavity 46 from the end face 36 (on which the cathode current collector 26 protrudes) by means of an anchoring element 52 protruding above the end face 36 of the winding assembly 10. Therefore, with respect to the axial movement of the winding core 50 toward the end face 34, a form-fit is formed between the winding core 50 and (on the one hand) the anchoring element 52 and (on the other hand) the winding assembly 10. Thus, the winding core 50 can only be axially (in...) Figure 5 Move upwards (from the center).

[0119] Because the anchoring element 52 is conductive, it also serves as a contact element to the cathode current collector 26, against which it rests. For better contact, the anchoring element 52 is welded to the cathode current collector 26 in at least certain areas. The anchoring element 52 is further welded to the winding core 50, ensuring an even closer connection between the winding core 50 and the winding assembly 10, since movement along the end face 36 (on which the anchoring element 52 is disposed) can only occur together.

[0120] Figures 8 to 10 Another example is shown. There, as a result of making four longitudinal cuts at the end face of one end of the tube, an anchoring element 52 is formed. The resulting tabs are then each bent 90°, such that... Figures 8 to 10 As can be seen, these form star-shaped radial protrusions 58, which in turn form anchoring elements 52. Therefore, the anchoring elements 52 and the winding core 50 are manufactured in a single piece and in a simple manner. Similarly, the protrusions can be welded along their length to the current collector foil to form contact elements that electrically connect to the current collector foil.

[0121] Figure 8 It also shows how the anchoring element 52 abuts against the winding assembly 10.

[0122] Figure 11 An electrochemical energy storage cell 12 with a housing 60 is shown, in which a winding assembly 10, together with a winding core 50 and an anchoring element 52, is arranged.

[0123] The housing 60 includes a cup-shaped housing element 62 having a bottom 64, the terminal opening 65 of which is closed by a cover assembly 66. The cover assembly 66 also includes an upper contact element 67, for example made of aluminum, which connects the anode current collector 16 to the remainder of the cover assembly 66 at the upper winding end face.

[0124] The bottom 64 has a predetermined break line 68 that defines a removable bottom portion 70 from the remaining portion of the bottom portion 72 that is fixedly assembled to the housing portion 62.

[0125] During the manufacturing of the energy storage cell 12, a novel press-fit sealing technique is used to attach the cover assembly 66 to the housing portion 62. Compared to conventional press-fitting of the cup-shaped housing portion 62 to seal the cover assembly 66, the press-fit sealing technique results in a significantly narrower net cross-section of the cup-shaped housing portion 62.

[0126] For details on the crimp sealing technology, please refer to the applicant's parallel application EP 3 916 877 A1.

[0127] Essentially, in the crimp sealing technique, after the winding assembly 10 is inserted into the cup-shaped housing portion 62 provided with a step or cone, the step or cone is transferred into the circumferential recess 74 by calibrating the outer diameter of the housing portion 62. Then, the cover assembly 66 is placed on the recess 74, and only the upper protrusion of the cup-shaped housing portion 62 is radially bent, i.e., crimped.

[0128] The recess 74 circumferentially surrounds the sidewall of the housing portion 62 in an annular manner, but does not have the depth that a recess for conventional crimping would have (the crimping tool would engage in the recess to oppose the cover assembly 66 in the axial direction).

[0129] In this example, the recess 74 has a radial depth of approximately 2 to approximately 6 times the wall thickness of the cup-shaped housing portion 62 in the region of the recess 74. This leaves a large net cross-section in the cup-shaped housing portion 62.

[0130] The energy storage cell 12 according to the present invention operates as follows:

[0131] exist Figure 12 The image shows the thermal failure of the energy storage cell 12.

[0132] Due to thermal failure (e.g., caused by an internal short circuit), overpressure has gradually built up in the enclosed housing 60. The pressure rises so rapidly that the pressure relief valve (PRV) conventionally arranged in the cover assembly 66 is insufficient to mitigate the dangerous situation.

[0133] like Figure 12 As can be seen, due to overpressure, the cover assembly 66, including the upper contact element 67, is blown off, and due to the resulting dynamics, the overpressure also flows downward through the through opening 54 into the region 76 below the anchoring element 52. As a result, the entire unit of the winding assembly 10, the winding core 50, and the anchoring element 52 is ejected from the cup-shaped housing portion 62.

[0134] Alternatively, popping can occur without separating the cover assembly 66 and / or the upper contact element 67 from the winding. In this case, only a closed opening of the cell exists in the crimped area. Generally, different variations of the opening and mixtures thereof are possible, and the simplified illustrations used herein do not adequately reflect the actual failure modes that occur.

[0135] The axial form fit between the anchoring element 52 and the winding assembly 10 prevents the winding core 50 from ejecting very quickly from the housing portion 62 as a single projectile with its lower mass. Instead, the ejected unit has a relatively large mass and therefore a significantly lower velocity, which improves the safety of the energy storage cell 12. Most importantly, a larger portion of the cell mass is ejected, thus significantly reducing the probability of heat propagation at the cell composite level.

[0136] Furthermore, the reduced radial depth of the recess 74 allows the winding assembly 10 to move out of the cup-shaped housing portion 62 more freely than with conventional crimped closing techniques. This allows pressure (or energy present in the system) to be rapidly axially released from the housing portion 62.

[0137] exist Figure 13 In the present invention, the energy storage cell 12 is shown in a cell array 80, which includes several energy storage cells 12 arranged laterally adjacent to each other.

[0138] The energy storage cells 12 of the cell array 80 are electrically connected to each other via cell connectors 82. Here, the cover assemblies 66 of the two energy storage cells 12 are each connected via cell connectors 82.

[0139] The cell connector 82 is designed to be bent or disassembled in a manner that allows the cover assembly 66 of the energy storage cell 12, in which thermal failure occurs, to be removed from the cup-shaped housing portion 62.

[0140] Figure 14 A possible embodiment of such a cell connector 82 is shown. Here, the cell connector 82 has a base 84, the legs of which merge into an angled, outwardly pointing contact lug 86. A contraction 88 between the legs and the contact lug 86 ensures sufficient deformability in the axial direction.

[0141] As described above, in the event of a thermal failure of the energy storage cell 12 in the cell array 80, the flexible cell connector 82 allows for the removal of its cover assembly 66 and the ejection of the winding assembly 10. Because the housing 60 is open in the axial direction and the problematic load of the failed winding assembly 10 is also ejected due to the anchoring elements, the thermal problem does not spread to adjacent energy storage cells 12, or at least spreads to a lesser extent.

[0142] Therefore, the energy storage cell 12 according to the present invention improves safety, especially in the cell array 80.

[0143] Figure 15 The steps in the recycling process of the cell array 80 are shown. For ease of emptying, the cell assembly 80 is arranged in an inverted orientation.

[0144] To remove the winding assembly 10 from the housing 60 of the energy storage cell 12, a plunger 90 is used to press the removable base region 70. With sufficient force along a predetermined break line 68, the winding assembly is detached from the remaining base region 72. Simultaneously, the cover assembly 66 is released because the press-fit closure technology is configured to open according to a predetermined force or pressure. Therefore, the winding assembly 10 can be easily pressed out of the housing 60.

[0145] Then, the winding assembly 10 and the housing 60 are fed separately to another recycling step.

Claims

1. An electrochemical energy storage element (12), said electrochemical energy storage element having the following characteristics: a) The energy storage element (12) has a hollow cylindrical winding assembly (10) with a helical structure, the helical structure comprising at least two electrode strips (14, 24) spirally wound around the winding axis and at least one diaphragm strip (38, 40) disposed between the electrode strips (14, 24). b) The hollow cylindrical winding assembly (10) includes two terminal end faces (34, 36), a circumferential outer component shell surface (42), and a circumferential inner component shell surface (44). c) The inner component housing surface (44) defines an axially aligned cavity (46) at the center of the winding assembly (10), and d) A winding core (50) having a basic cylindrical or hollow cylindrical shape is arranged in the axially aligned cavity (46), the winding core having an outer peripheral surface, the outer peripheral surface preferably lying flat against the inner component housing surface (46). Furthermore, the electrochemical energy storage element has the following characterization features: e) An anchoring element (52) is disposed on at least one (36) of the two end faces of the winding assembly (10) and connected to the winding core (50). f) The anchoring element (52) protrudes laterally from the axial center of the winding assembly (10) over the end face (36) of the winding assembly (10) in at least some areas.

2. The electrochemical energy storage element according to claim 1, wherein the electrochemical energy storage element has at least one of the following additional features: a) The anchoring element (52) and the winding core (50) are integrally formed from the same material. b) The anchoring element (52) is formed as one or more curved tabs (58) of the winding core (50). c) The anchoring element (52) has two, three, or four arms (58), the arms preferably being star-shaped. d) The anchoring element (52) is formed as a disk. e) The anchoring element (52) extends from the axial center of the winding assembly (10) to a radius ranging between 10% and 100% of the radius of the winding assembly (10), preferably between 30% and 98%, and particularly between 80% and 95%.

3. The electrochemical energy storage element according to any one of the preceding claims, wherein the electrochemical energy storage element has the following additional features: a) The anchoring element (52) is a conductive contact element that is in direct contact with one of the electrode strips (24) at the end face (36) on which the anchoring element (52) is arranged in the winding assembly (10).

4. The electrochemical energy storage element according to any one of the preceding claims, wherein the electrochemical energy storage element has the following additional features: a) The energy storage element (12) includes a housing (60) having a cup-shaped housing portion (62) having a bottom (64) and a terminal opening (65), the cup-shaped housing portion preferably being metallic, and the terminal opening being closed by a cap assembly (66).

5. The electrochemical energy storage element according to claim 4, wherein the electrochemical energy storage element has one of the following additional features: a) The winding core (50) is connected to the bottom (64) of the housing portion, such that the bottom (64) forms the anchoring element (52), or b) The anchoring element (52) is connected to the bottom (64) of the housing portion (62).

6. The electrochemical energy storage element according to any one of claims 4 to 5, wherein the electrochemical energy storage element has the following additional features: a) The anchoring element (52) has a through opening (54) through which the gas pressure generated in the winding assembly (10) can be released into the space (74) between the bottom (64) and the anchoring element (52), so that b) The gas pressure presses the anchoring element (52), together with the winding core (50) and the winding assembly (10), against the cover assembly (66).

7. The electrochemical energy storage element according to any one of claims 4 to 6, wherein the electrochemical energy storage element has at least one of the following additional features: a) The lid assembly (66) is attached to the cup-shaped housing portion (62) in such a manner that the closure of the lid assembly (66) opens as soon as the internal pressure and / or the winding composite (10) presses against the lid assembly (66) at a predetermined threshold pressure; and / or b) The lid assembly (66) is attached to the cup-shaped housing portion (62) in such a way that the net cross-section of the cup-shaped housing portion (62) is radially reduced in the region below the lid assembly (66) by no more than six times the wall thickness of the housing portion (62) compared to the remaining net cross-section, particularly by means of a press-fit closure technique.

8. The electrochemical energy storage element according to any one of claims 4 to 7, wherein the electrochemical energy storage element has the following additional features: a) The bottom (64) has a predetermined break line (68) that defines a removable bottom region (70) from the bottom region (72) which is securely connected to the remaining housing portion (62).

9. An array (80) of an electrochemical energy storage element (12) according to any one of the preceding claims, the array having the following additional features: a) A cell connector (82) connects a cover assembly (66) to at least two energy storage elements (12), wherein, The cell connector (82) is deformable and / or removable in such a way that the cover assembly (66) of one energy storage element (12) can be opened when a predetermined threshold pressure is reached within the energy storage element (12), while the cover assembly (66) of the other energy storage element (12) remains closed.

10. A method for recycling an electrochemical energy storage element (12) according to any one of claims 1 to 8, the method having the following characteristics: a) The winding assembly (10) including the winding core (50) is pressed out of the housing portion (62) by pressing the punch (90) into the bottom of the energy storage element (12); b) Process the housing portion (62) and the winding assembly (10) separately.

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