Electrochemical Energy Storage Elements

Abstract

To provide an array of several energy storage elements with improved safety. [Solution] An electrochemical energy storage element (12) has a winding assembly, the winding assembly having at least two electrode strips spirally wound around a winding axis and at least one separating separator disposed between the electrode strips. The winding assembly has a hollow cylindrical shape and has two end faces and an axially extending cavity at the center of the winding assembly. A winding core (50) is disposed within the cavity. To enhance the security of the energy storage element, an anchor element (52) is disposed on at least one of the two end faces of the winding assembly and is connected to the winding core. The anchor element protrudes laterally from the axial center of the winding assembly in at least a certain region on the end face of the winding assembly.

Description

[Technical Field]

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

[0002] The simplest form of electrochemical energy storage element is the electrochemical cell. An electrochemical cell contains at least one positive electrode and at least one negative electrode, connected via an ionically conductive electrolyte. In such a cell, an electrochemical energy-delivering reaction occurs, which consists of two electrically coupled but spatially separated partial reactions. One partial reaction occurs at a relatively low redox potential and occurs at the negative electrode, while the other partial reaction occurs at a relatively high redox potential and occurs at the positive electrode. The spatial separation is often ensured by a separator placed between the electrodes.

[0003] During discharge, electrons are released at the negative electrode as a result of the oxidation process, resulting in a flow of electrons to the positive electrode via an external load, and a corresponding amount of electrons are absorbed from the positive electrode. Thus, a reduction process occurs at the positive electrode. At the same time, an ionic current corresponding to the electrode reaction occurs in the electrochemical cell due to charge equalization. This is ensured by the ion-conducting electrolyte.

[0004] In secondary (rechargeable) electrochemical energy storage cells, the discharge reaction is reversible, i.e., the conversion of chemical energy to electrical energy during discharge can be reversed.

[0005] When the terms "anode" and "cathode" are used in connection with secondary electrochemical energy storage cells, the electrodes are generally named by their discharge function. Thus, in such cells, the negative electrode is the anode and the positive electrode is the cathode.

[0006] The electrochemical energy storage element may contain exactly one electrochemical energy cell, but may also contain two or more cells, preferably electrically connected in series or in parallel.

[0007] In energy storage elements, the electrodes and separators are often provided in the form of an assembly. Such an assembly can be a cell stack consisting of stacked electrodes. However, the assembly is usually structured with wound electrodes and separators (wound assembly).

[0008] Cylindrical designs are widely used for electrochemical energy storage elements, with electrodes typically arranged as part of a hollow cylindrical wound assembly within the interior space of a cylindrical housing, typically having a form factor of, for example, 21 x 70 mm (diameter x height). Cells with such a form factor are commonly known as cylindrical round cells.

[0009] For applications in the automotive sector, electric bikes, power tools, and other applications where high energy is required, lithium-ion cells with the highest possible energy density are preferred. Lithium-ion cells can be simultaneously subjected to high current loads during charging and discharging. Modern lithium-ion cells with this form factor can reach energy densities in the range of 300 Wh / kg or more.

[0010] A problem with electrochemical energy storage elements with extremely high energy densities is that strong thermal runaway can occur, for example, in the event of an electrical short circuit or other misuse condition. This can cause the cell's chemical materials, particularly the electrolyte and active material, to react violently and rapidly evaporate, potentially even causing the housing of the energy storage element to explode. Such thermal runaway of the energy storage element can pose a safety risk.

[0011] If several energy storage elements are combined to form an array, thermal failure of one energy storage element can propagate very quickly to adjacent energy storage elements, resulting in the failure of the entire array and posing a significant safety risk due to the associated heat generation.

[0012] It is also known that the use of active materials in cylindrical energy storage elements, which undergo significant volume changes, also known as volumetric thrust, during charging and discharging, is problematic. This is particularly evident for materials containing silicon (Si). The continuous growth of the solid electrolyte interface (SEI), a type of passivation layer on the anode, can also cause electrode swelling. That is, the volume change includes both reversible "breathing contributions" and continuous growth. Therefore, much effort has been made at the material, electrolyte, and electrode levels to minimize these volumetric effects. In winding assemblies, the windings can even collapse inward. To prevent / reduce this or stabilize the windings, prior art techniques have included, for example, the use of tubes as winding cores (also known as mandrels). The winding cores are either included as part of the winding process from the beginning or inserted later. The winding cores can be made of metallic materials, such as copper, but polymer-based materials are also often used.

[0013] An energy storage element with an improved wound core is known, for example, from EP 3945617 A1.

[0014] However, in the case of energy storage elements with wound cores, the safety risk is further increased by the fact that in the event of a thermal failure, the wound core may be projectile-like from inside the energy storage element to outside. Summary of the Invention [Problem to be solved by the invention]

[0015] In contrast, the present invention aims to provide an improved energy storage element that addresses the aforementioned problems. In particular, the energy storage element should be improved with regard to its safety.

[0016] Additionally, it provides an array of several energy storage elements with improved safety. [Means for solving the problem]

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

[0018] The energy storage element according to the invention has the following characteristics: (a) the energy storage element (12) has a hollow cylindrically shaped winding assembly (10), the winding assembly (10) having a spiral structure including at least two electrode strips (14, 24) spirally wound around a winding axis and at least one separator strip (38, 40) disposed between the electrode strips (14, 24); (b) a hollow cylindrically shaped wound assembly (10) including two end faces (34, 36), an outer assembly circumferential shell surface (42), and an inner assembly circumferential shell surface (44); (c) the assembly inner circumferential shell surface (44) defines an axially extending cavity (46) at the center of the wound assembly (10); (d) an essentially cylindrical or hollow cylindrical winding core (50) is disposed within the axially extending cavity (46), the winding core (50) having an outer circumferential surface, the outer circumferential surface preferably lying in intimate contact with the inner circumferential shell surface (44) of the assembly; An electrochemical energy storage element (12) having the following characteristics (e) and (f): (e) an anchor element (52) disposed on at least one (36) of the two end faces of the winding assembly (10) and connected to the winding core (50); (f) An anchor element (52) protrudes laterally from the axial center of the winding assembly (10) onto the end face (36) of the winding assembly (10) in at least a certain area.

[0019] The present invention recognizes that an anchor element connected to the winding core prevents the winding core from being ejected as a projectile from the cell in the event of a thermal failure of the energy storage element. The fact that the anchor element protrudes laterally on the end face of the winding assembly means that the winding core and the winding assembly form a single structural unit with respect to ejection out of the housing part. Due to the increased mass ejected during a thermal failure, the velocity of the ejected material is reduced for the same ejection pressure. This increases the safety of the energy storage element and eliminates the "projectile effect." However, above all, the thermally sensitive contents of the cell are removed from the plane of the cell array (see below for further explanation), ideally completely removed. This significantly reduces the possibility of thermal propagation within the cell array and greatly improves the safety of the overall system.

[0020] "Protruding above the end face of the winding assembly" essentially means that the anchor element extends radially above at least one region of the winding assembly, thereby creating an axial form-fit between the anchor element and the winding core connected to it, on the one hand, and between the anchor element and the winding assembly, on the other hand, so that the anchor element moves with the winding assembly as the winding core moves, thereby preventing any relative movement between the two components.

[0021] The feature "cylindrical" herein does not necessarily refer to a cylindrical shape, but is understood in its general mathematical sense and may therefore also include bodies with polygonal bases, e.g., hexagonal prisms, or non-circular cylindrical bases, e.g., compressed flat wound bodies.

[0022] Preferably, the electrochemical energy storage element according to the present invention is an electrochemical energy storage cell.

[0023] In a preferred embodiment, the anchor element is characterized by at least one of the following features (a) to (e):

[0024] (a) The anchor element (52) and the winding core (50) are integrally formed from the same material.

[0025] This offers advantages especially in manufacturing: the anchor element and the winding core can be manufactured as a single, integral component from a single material, e.g., a plastic injection-molded part, which is then inserted into the winding assembly without any further joining steps.

[0026] However, the anchor element and the winding core may also be initially separate components that are joined later. For example, the winding core may already be inserted into the winding assembly, and the anchor element may then be attached to the winding core, for example by gluing or welding. A mechanical or form-fit connection between the anchor element and the winding core is also conceivable.

[0027] (b) The anchor elements (52) are formed as one or more bent tabs (58) of the winding core (50).

[0028] A particularly efficient manufacturing method can be achieved by designing the winding core in the shape of a hollow cylinder with several protrusions on the end face of the winding assembly. In the area protruding from the end of the winding core, the winding core has at least two longitudinal notches, which are generally opposite each other. This provides two separate tabs that are bent outward to protrude over the end face of the winding assembly after the winding core is inserted into the winding assembly. The length of the notches determines the degree to which the anchor elements protrude from the center of the winding assembly over the end face.

[0029] A particularly efficient manufacturing method can be achieved by designing the hollow cylindrical winding core so that it protrudes slightly beyond the end face of the winding assembly. In this protruding region, the winding core has at least two generally opposing longitudinal slits extending inward from the free end. This forms two separate tabs that are bent outward to protrude above the end face of the winding assembly after the winding core is inserted into the winding assembly. The length of the slits determines the degree to which the anchor element protrudes from the center of the winding assembly beyond its end face.

[0030] (c) The anchor element (52) has two, three or four, preferably star-shaped arms (58).

[0031] If multiple longitudinal cuts are provided, this results in a correspondingly increased number of tabs, resulting in multiple tabs protruding on the end face of the winding assembly. However, the anchor element can also be formed as a cross-shaped component connected to the anchor element, for example, having four arms. The number of arms is therefore independent of the manufacturing method. Furthermore, the arms of the anchor element can have any shape. Thus, a leaf-shaped design is also conceivable.

[0032] (d) The anchor element (52) is formed as a disk.

[0033] A disk-shaped anchor element has the advantage that the end faces can be fitted over as large an area as possible, which provides a large area for a perfect fit between the anchor element and the winding assembly.

[0034] (e) The anchor elements (52) extend radially from the axial center of the winding assembly (10) to a range of 10 to 100%, preferably 30 to 98%, and particularly preferably 80 to 95% of the radius of the winding assembly (10).

[0035] To ensure the necessary form-fit between the anchor element and the winding assembly during ejection from the housing, it is not necessary for the anchor element to extend over the entire radius of the end face of the winding assembly. It has been found that it is already sufficient for the anchor element to extend only up to 10% of the radius of the winding assembly. Ideally, however, the coverage would be greater, for example, up to 60%, 80%, 90%, or even nearly complete coverage. The aforementioned radius values ​​are independent of the shape of the anchor element, and therefore, a disk-shaped anchor element or its arms or tabs may extend over the end face accordingly. Furthermore, it is also possible for the anchor element to extend beyond the radius of the winding assembly. However, such an arrangement is not advantageous in terms of the overall space requirements of the energy storage element.

[0036] According to a further preferred embodiment, the anchor element has the following characteristics:

[0037] (a) The anchor element (52) is an electrically conductive contact element that is in direct contact with one of the electrode strips (24) at the end face (36) of the winding assembly (10) on which the anchor element (52) is disposed.

[0038] Energy storage elements designed specifically for high current carrying capacity can include contact elements for contacting the electrode strips at the end faces of the winding assembly. Such energy storage elements are known, for example, from WO 2021 / 239492 A1. The contact elements can also serve as anchor elements for the winding core. For this purpose, the contact elements only need to be connected or bonded to the winding core during the manufacturing process. Since the contact elements are typically welded directly to the edges of the electrode strips with uncoated metal carriers of the electrode active material, the contact elements can also preferably be welded or mechanically connected to the winding core. In this way, the two particularly preferred functions of this component (as a contact element for the electrode strips and as an anchor element for the winding core) can be realized in a single manufacturing process.

[0039] According to a further preferred embodiment, the energy storage element has the following characteristics:

[0040] (a) Energy storage element (12) includes a housing (60), which includes a cup-shaped housing portion (62), preferably made of metal, which includes a bottom portion (64) and an end opening (65), which end opening (65) is closed by a lid assembly (66).

[0041] As will become apparent below, the fastening of the winding core to the winding assembly according to the invention is particularly advantageous in energy storage elements having a cup-shaped housing part closed by a lid assembly, in which the lid assembly can be opened in the event of a thermal fault, allowing the unit consisting of the winding core, the anchor element and the winding assembly to be released.

[0042] In such a housing, the energy storage element can have one of the following features:

[0043] (a) The winding core (50) is connected to the bottom (64) of the housing part (62) so that the bottom (64) of the housing part (62) forms the anchor element (52).

[0044] If the winding assembly is directly connected to the electrically conductive bottom part, for example by welding, the winding core may likewise be directly connected to the bottom part. In this case, the bottom part forms an anchor element, thereby preventing the winding core from being ejected from the housing (separated from the winding assembly) in the event of a thermal failure of the energy storage element. The advantage of this solution is that no separate components are required.

[0045] (b) The anchor element (52) is connected to the bottom (64) of the housing part (62).

[0046] Alternatively, the anchor element may be a separate component connected to the bottom of the housing part. This is particularly advantageous, for example, in combination with the above-mentioned feature in which the anchor element also functions as an electrically conductive contact element. Common practice is often to connect the contact element connected to the cathode current collector to the bottom of the cup-shaped housing part. In this way, the cup-shaped housing part functions as a terminal of the energy storage element. In such an embodiment, the contact element simultaneously functions as an anchor element when it is welded to the winding core. In this case, this connection (which may also be a welded connection) is designed to be more easily released than the connection to the winding core, which is ideally very strong.

[0047] According to further examples, the energy storage element has the following additional features:

[0048] (a) the anchor element (52) has a through opening (54) that allows gas pressure generated within the winding assembly (10) to be released into a space (74) between the bottom (64) and the anchor element (52); (b) This gas pressure presses the anchor element (52), together with the winding core (50) and winding assembly (10), against the lid assembly (66).

[0049] In the event of a thermal failure, the pressure generated within the winding assembly can quickly escape into the space between the anchor element and the bottom. Due to the accompanying release of material and the escape of gas from the through-opening, the winding assembly accelerates like a rocket and is ejected from the cup-shaped housing portion as soon as the lid assembly is opened. However, the velocity of the winding assembly upon ejection is relatively low, and therefore this does not pose an additional hazard. Essentially, most of the mass contained within the storage element should be ejected from the housing to prevent thermal propagation to adjacent storage elements.

[0050] According to an example of an advantageous embodiment, the electrochemical energy storage element may have at least one of the following additional features:

[0051] (a) The lid assembly (66) is attached to the cup-shaped housing portion (62), particularly by a crimp closure technique, such that the closure by the lid assembly (66) is released as soon as the internal pressure and / or the winding assembly (10) presses the lid assembly (66) with a predetermined threshold pressure.

[0052] If the closure of the lid assembly is arranged on the cup-shaped housing part, it is possible to prevent the cup-shaped housing part from bursting. This constitutes a controlled pressure release of the energy storage element. The threshold pressure at which the lid assembly opens is advantageously set to a pressure higher than the pressure at which so-called pressure release valves (PVRs) according to the prior art open. In addition, the opened lid assembly should preferably expose as large a net cross-sectional area as possible.

[0053] Thus, the following features are further additional or alternative features.

[0054] (b) The lid assembly (66) is attached to the cup-shaped housing portion (62), particularly by crimp closure techniques, such that the net cross-sectional area of ​​the cup-shaped housing portion (62) in the region below the lid assembly (66) is radially reduced by up to six times the wall thickness of the housing portion (62) compared to the remaining net cross-sectional area below that region.

[0055] In this way, the largest possible net cross-sectional area does not prevent the entire winding assembly from being ejected from the cup-shaped housing portion.

[0056] In the manufacture of energy storage elements, a crimping process is conventionally used to close a cup-shaped housing portion with a lid assembly. With the winding assembly already in place, the free end of the cup-shaped housing portion is bent radially inward over the area of ​​the lid assembly. To prevent the winding assembly from being damaged during the crimping process, conventional energy storage elements first create a tool engagement structure on the cup-shaped housing portion above the winding assembly. The function of the tool engagement structure is to allow a counter-tool of the crimping tool to be attached to the cup-shaped housing portion while the housing portion is closed during the crimping process. The counter-tool axially holds the lid assembly against the axial force applied during the crimping process and dissipates this force to minimize the force on the winding. Typically, a circumferential bead is provided in the cup-shaped housing portion at the time of closure, which remains after manufacture.

[0057] This bead projects radially into the interior space of the housing cup, resulting in a reduced cross-sectional area in the area where the bead is formed, which can complicate ejection of the wound assembly, since the assembly typically completely fills the housing cup radially.

[0058] In contrast to this conventional crimp closure technique, the crimp closure technique of the present invention described above makes it possible to dispense with the tool engagement structure typically required for a counter tool.

[0059] For details of the crimp closure technique, see applicant's patent application EP3916877A1.

[0060] Essentially, in this crimp closure technique, the winding assembly is inserted into a cup-shaped housing section that is provided with a step or cone, and then the step or cone is deformed into a circumferential recess by calibrating the outer diameter of the cup-shaped housing section. The lid assembly is then placed over this recess and only the upper protrusion of the cup-shaped housing section is radially bent or crimped. No axial counterfeiting is required.

[0061] Since the net cross-sectional area of ​​the cup-shaped housing section is only radially reduced in the area below the lid assembly, for example to six times the wall thickness of the housing section, the winding assembly can be ejected from the housing section together with the winding core and anchor element in the event of thermal failure of the energy storage element.

[0062] Here, the area under the lid assembly may be considered in particular to be the area directly under the lid assembly that rests on the cup-shaped housing portion.

[0063] Typical wall thicknesses range from 200 to 350 μm for 21700 type housings.

[0064] The area of ​​the inverted cup on the lid assembly can be larger to ensure retention for the seal or to allow contact between the peripheral edge of the cup and the end face of the storage element, however, this outer area can be more easily deformed if the cell opens.

[0065] The closure does not have to have a circumferential recess, but can have only individual contact points for the lid assembly. Therefore, the net cross-sectional penetration depth or reduction information is related to each element. Thus, in the case of a circumferential recess, the closure technique will also be under a protective area, which will protrude into the inner cross-section by up to six times the wall thickness on two opposite sides.

[0066] Further details of the closure technique with the largest possible net cross-sectional area can be found in the applicant's EP24194421.4, which has not yet been published at this time.

[0067] The housing of the energy storage element further has the following additional features:

[0068] (a) The bottom portion (64) has a predetermined break line (68) that defines the boundary between a bottom region (72) that is firmly connected to the housing portion (62) and a bottom region (70) that is separable therefrom.

[0069] This has the advantage that a punch can be placed in the separable bottom region and pressed into the separable bottom region by the punch, which can be used to manually remove the winding assembly and anchor element during the recycling process.

[0070] The above-mentioned energy storage element can preferably be designed such that by means of the anchoring element 10 to 100%, preferably 40 to 100%, particularly preferably 60% or more of the internal volume of the energy storage element is released from the housing in the event of a thermal failure.

[0071] With respect to arrays of electrochemical energy storage elements, the safety of the above energy storage elements can be further enhanced by the following additional features.

[0072] (a) A cell connector (82) connects the lid assemblies (66) of at least two energy storage elements (12) together, the cell connector (82) being deformable and / or separable such that when pressure within the energy storage elements (12) reaches a predetermined threshold pressure, the lid assembly (66) of one energy storage element (12) opens while the lid assemblies (66) of the other energy storage elements (12) remain closed.

[0073] The deformable or separable nature of the cell connectors allows the lid assembly of one energy storage element to be opened to eject its winding assembly in the event of a thermal failure of that energy storage element, even though the cell connectors are required to electrically connect adjacent elements.

[0074] Such cell connectors can have specific bending points, which are achieved, for example, by pinching the material, or the connection of the cell connector is stable enough to simply ensure electrical conductivity, but when a critical pressure is reached, the connection, such as a weld, is lost.

[0075] The above-described method for recycling electrochemical energy storage elements preferably has the following features:

[0076] (a) forcing a punch (90) into the bottom of the energy storage element (12) to eject the winding assembly (10), including the winding core (50), from the housing portion (62); (b) The housing portion (62) and the winding assembly (10) are processed separately.

[0077] Such manual removal of the wound assembly can make recycling of the energy storage element easier and safer. In particular, a punch can be pressed against the separable bottom area indicated by a predetermined break line. [Brief explanation of the drawings]

[0078] In the following, examples of the invention will be explained in more detail with reference to the drawings. [Figure 1] FIG. 1 is a schematic diagram of an electrode strip that has not yet been wound, in this case showing the anode. [Figure 2] FIG. 2 is a schematic diagram of an electrode strip not yet wound, in this case showing the cathode. [Figure 3] FIG. 3 shows a schematic diagram of the staggered arrangement of the anode, separator, and cathode in an unwound state. [Figure 4] FIG. 4 shows a perspective view of the winding assembly with the anode current collector protruding at the top, the cathode current collector protruding at the bottom, and the winding core on the inside. [Figure 5] FIG. 5 shows a perspective view of a winding assembly including an end face of a winding core and an anchor element according to a first example. [Figure 6] FIG. 6 shows a longitudinal cross section of the winding core of FIG. 5 and an anchor element assembled therewith. [Figure 7] FIG. 7 shows a plan view from below of the anchor element of FIGS. [Figure 8] FIG. 8 shows a perspective view of a winding assembly including an end face of a winding core and an anchor element according to a second example. [Figure 9] FIG. 9 shows a longitudinal cross section of the winding core of FIG. 8 and an anchor element assembled therewith. [Figure 10] FIG. 10 shows a plan view from below of the anchor element of FIGS. [Figure 11] FIG. 11 shows a longitudinal cross-sectional view of an electrochemical energy storage cell with a closed housing and an inserted winding assembly. [Figure 12] FIG. 12 shows a longitudinal cross-sectional view of the electrochemical energy storage cell with the lid assembly separated from the housing and the winding assembly released together with the winding core and anchoring elements. [Figure 13] FIG. 13 shows a cross-sectional view of a cell array having a plurality of energy storage cells according to the present invention, showing one of the energy storage elements discharged. [Figure 14] FIG. 14 shows a top view of a cell connector where two energy storage cells of a cell array are electrically connected. [Figure 15] FIG. 15 shows a cross-sectional view of a cell array during the disassembly process when recycling energy storage cells. DETAILED DESCRIPTION OF THE INVENTION

[0079] Figures 1 to 4 illustrate the structure of a winding assembly 10, which can be a component of an energy storage cell 12 (see Figures 11 to 15). Since the specification only shows examples of embodiments having only one electrochemical energy storage cell as an energy storage element according to the invention, the term "energy storage cell" will always be used below. However, as already explained above, other embodiments are also conceivable having a plurality of energy storage cells assembled to form an energy storage element according to the invention.

[0080] The winding assembly 10, as shown in FIG. 1, includes a strip-shaped anode 14 having a strip-shaped anode current collector 16, which has a first longitudinal end 18. The anode current collector 16 is a metal foil made of copper or nickel. For anodes with high potentials (>1 V vs. Li / Li+) or intended for Na-ion cells, aluminum can also be used. The metal foil includes a strip-shaped main region that is loaded with a layer of negative electrode material 20 and a free end strip 22 extending along the longitudinal end 18, which is free of electrode material 20. The end strip 22 can be partially coated with an electrically insulating material.

[0081] 2, the winding assembly 10 further includes a strip-shaped cathode 24 having a strip-shaped cathode current collector 26 having a second longitudinal end 28. The cathode current collector 26 is an aluminum metal foil. The metal foil includes a strip-shaped main region that is loaded with a layer of positive electrode material 30 and a free end strip 32 extending along the longitudinal end 28, the free end 28 being free of electrode material 30.

[0082] Both the anode 14 and cathode 24 electrodes are initially shown separately in an unwound state.

[0083] The anode 14 and cathode 24 are arranged offset from one another within the winding assembly 10 such that a first longitudinal end 18 of the anode current collector 16 protrudes from a first end face 34 of the winding assembly 10 and a second longitudinal end 28 of the cathode current collector 26 protrudes from a second end face 36 of the winding assembly 10. The offset arrangement is shown in FIG.

[0084] Two strip-shaped separators 38, 40 are also shown therein, which separate the anode 14 and cathode 24 from each other within the wound assembly. Therefore, in this context, they are often referred to as an electrode-separator assembly. The separators 38, 40 may comprise any material that electrically separates the electrodes. In addition, they can also be applied directly to the electrodes in the form of an insulating layer. For this purpose, electrically insulating and ionically conductive materials, such as ionically conductive polymers, are considered. Therefore, for the purposes of the scope of protection of the claims, such insulating layers can also be considered as separator tapes.

[0085] In Figure 4, the winding assembly 10 is shown in a wound form that can be used in an energy storage cell 12 according to any of Figures 11-15. The anode current collector 16 and the cathode current collector 26 can clearly be seen protruding from the end faces 34, 36.

[0086] Often, the wound assembly 10 remains surrounded by a winding shell 42, such as a plastic film. Alternatively, a strip of adhesive tape can be used for localized application, or a separator tape can be applied directly to the outermost winding.

[0087] As can be seen in FIG. 4 , the winding assembly 10 is hollow cylindrical in shape and has an outer assembly circumferential shell surface and an inner assembly circumferential shell surface 44 along which the winding shell 42 extends essentially, and the inner assembly circumferential shell surface 44 defines an axially extending cavity 46 in the center of the winding assembly 10.

[0088] The winding core 50 is disposed within the cavity 46. It functions to support the winding assembly 10 from the inside, preventing the cavity 46 from collapsing due to volume thrust during charging and discharging. The winding core 50 can be made of a metal material or a polymer material. Depending on the manufacturing process, the winding core 50 can be disposed within the winding assembly 10 before or after winding.

[0089] In most cases, the cavity 46 has a hollow cylindrical shape with a circular cross section. However, other hollow cylindrical shapes or cubic prism shapes such as a hexagonal prism are also possible depending on the geometry of the winding core 50. The winding core 50 is often formed as a circular cylindrical tube with longitudinal grooves so that the winding core 50 itself can tolerate the volume thrust of the electrode-separator assembly to some extent.

[0090] 5 to 7 show a first further development according to the invention.

[0091] 6 and 7 show a cross-sectional view and a plan view of the winding core 50 and the anchoring element 52 rigidly attached to the end face of the winding core 50. In FIG.

[0092] In the example shown here, anchor element 52 is disk-shaped and has four through openings 54. Although the through openings 54 are here oval, they can have other shapes and their number can be varied as desired.

[0093] In this example, the winding core 50 and the anchor element 52 are both made of metal and are therefore electrically conductive. The winding core 50 and the anchor element 52 are firmly connected to each other by a weld 56, as shown by the dashed line in FIG.

[0094] 5, the winding assembly 10 is shown with the winding core 50 inserted into the cavity 46 from the end face 36, on which the cathode current collector 26 protrudes, and such that the anchor element 52 protrudes on the end face 36 of the winding assembly 10. Thus, a form fit is formed between the winding core 50 and the anchor element 52, on the one hand, and between the winding core 50 and the winding assembly 10, on the other hand, for movement of the winding core 50 in the axial direction towards the end face 34. Accordingly, the winding core 50 can only move axially (upper side of FIG. 5) together with the winding assembly 10.

[0095] Due to the anchor element 52 being electrically conductive, it can also be used as a contact element for the cathode current collector 26 on which it rests. For good contact, the anchor element 52 is welded to the cathode current collector 26 at least in certain areas. The anchor element 52 is then welded to the winding core 50, which weld ensures an even closer connection between the winding core 50 and the winding assembly 10, allowing for movement together in the direction of the end face 36 on which the anchor element 52 is located.

[0096] 8-10 show a further example, in which the anchor element 52 is formed by making four longitudinal cuts in the end face of one end of the tube. The resulting tabs are each bent by 90° so that, as can be seen in FIGS. 8-10, they form star-shaped, radially protruding arms 58, which form the anchor element 52. The anchor element 52 and the winding core 50 are thus produced in one piece in a simple manner. Here too, the protruding arms can be welded along their length to the metal foil of the current collector to form contact elements that are electrically connected to the metal foil of the current collector.

[0097] FIG. 8 also shows how the anchor element 52 is positioned relative to the winding assembly 10.

[0098] FIG. 11 shows an electrochemical energy storage element 12 having a housing 60 within which the winding assembly 10 is disposed with a winding core 50 and anchor elements 52 .

[0099] Housing 60 includes a cup-shaped housing portion 62 having a bottom 64, an end opening 65 of housing portion 62 being closed by a lid assembly 66. Lid assembly 66 also includes an upper contact element 67, made, for example, of aluminum, which connects the remainder of lid assembly 66 to anode current collector 16 above the end face of the winding.

[0100] The bottom portion 64 has a predetermined break line 68 that defines the boundary between a bottom region 72 that is fixedly assembled to the remainder of the housing portion 62 and a bottom region 70 that is separable therefrom.

[0101] The lid assembly 66 is attached to the housing portion 62 using a novel crimp closure technique during manufacture of the energy storage cell 12. In contrast to conventional crimping of the cup-shaped housing portion 62 to close the lid assembly 66, the crimp closure technique of the present invention significantly reduces the net cross-sectional area of ​​the cup-shaped housing portion 62.

[0102] For details of this crimp closure technique, see applicant's patent application EP3916877A1.

[0103] Essentially, the crimp closure technique involves inserting the winding assembly 10 into a cup-shaped housing portion 62 that has a step or cone, and then calibrating the outer diameter of the housing portion 62 to deform the step or cone into a circumferential recess 74. The lid assembly 66 is then placed over this recess 74, and only the upper protrusion of the cup-shaped housing portion 62 is bent or crimped radially.

[0104] The recess 74 circumferentially surrounds the sidewall of the housing portion 62 in an annular shape, but does not have the depth of a recess used for conventional crimping, which requires significant depth to engage a crimping tool within the recess for axial opposition against the lid assembly 66.

[0105] The recess 74 in this example has a radial depth of about 2 to about 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.

[0106] The energy storage cell 12 according to the present invention operates as follows.

[0107] In FIG. 12, a thermal failure situation of the energy storage cell 12 is shown.

[0108] A thermal failure, caused for example by an internal short circuit, can cause excessive pressure to build up within the closed housing 60. The pressure rises so quickly that a pressure relief valve (PRV) located within a conventional lid assembly 66 is not sufficient to alleviate the dangerous situation.

[0109] 12, the excess pressure blows off the lid assembly 66 together with the upper contact element 67, and the resulting dynamics cause the excess pressure to flow downward through the through opening 54 into the region 76 below the anchor element 52. As a result, the entire unit consisting of the winding assembly 10, the winding core 50, and the anchor element 52 is ejected from the cup-shaped housing portion 62.

[0110] Alternatively, the ejection can occur in a manner that does not separate the lid assembly 66 and / or the upper contact element 67 from the windings, but merely opens the cell closure in the area of ​​the crimp. In general, various opening modes and combinations are possible, and the simplified diagram used here does not adequately reflect the failure patterns that occur in practice.

[0111] The axial form fit between the anchor element 52 and the winding assembly 10 prevents the winding core 50 from being ejected too quickly from the housing part 62 as a single projectile with a smaller mass. Instead, the ejected unit has a relatively large mass, resulting in a sufficiently slow velocity, which increases the safety of the energy storage cell 12. However, especially since a large portion of the cell's mass is ejected, the possibility of thermal propagation at the structural level of the cell is significantly reduced.

[0112] Additionally, the reduced radial depth of the recess 74 allows the winding assembly 10 to move more freely out of the cup-shaped housing portion 62 than would be the case with conventional bead closure techniques. As a result, pressure (or energy present in the system) is quickly released axially from the housing portion 62.

[0113] In FIG. 13, an energy storage cell 12 according to the present invention is shown within a cell array 80 that includes several energy storage cells 12 arranged side-by-side with one another.

[0114] The energy storage cells 12 of the cell array 80 are electrically connected to one another via cell connectors 82. Here, the lid assemblies 66 of two energy storage cells 12 are connected to one another via the cell connectors 82.

[0115] The cell connector 82 is designed to be able to separate or bend so that the lid assembly 66 of the energy storage cell 12 can be separated from the cup-shaped housing portion 62 in the event of a thermal failure.

[0116] A possible embodiment of such a cell connector 82 is shown in Figure 14. Here, the cell connector 82 has a base 84, the legs of which merge obliquely outward into contact protrusions 86. A constriction 88 between the legs and the contact protrusions 86 ensures sufficient axial deformability.

[0117] As mentioned above, in the event of a thermal failure of an energy storage cell 12 of the cell array 80, the flexible cell connector 82 allows its lid assembly 66 to separate and eject the winding assembly 10. Because the housing 60 opens axially and the problematic thermal load of the failed winding assembly 10 is also ejected by the anchoring element, the thermal problem does not spread to adjacent energy storage cells 12, or at least only to a small extent.

[0118] Therefore, the energy storage cell 12 according to the present invention, especially in the cell array 80, enhances its safety.

[0119] 15 shows the steps in the recycling process for the cell array 80. To facilitate emptying, the cell array 80 is placed upside down.

[0120] To remove the wound assembly 10 from the housing 60 of the energy storage cell 12, a plunger (punch) 90 is used to press the separable bottom region 70. By applying sufficient force along the predetermined break line 68, the separable bottom region 70 separates from the remaining bottom region 72. At the same time, the lid assembly 66 is opened because the crimp closure technology is configured to open the lid assembly 66 with a predetermined force or pressure. Thus, the wound assembly 10 can be easily pushed out of the housing 60.

[0121] The winding assembly 10 and the housing 60 are then separately fed to further recycling processes.

Claims

1. An electrochemical energy storage element (12) having the following characteristics (a) to (d): (a) the energy storage element (12) has a hollow cylindrically shaped winding assembly (10), the winding assembly (10) having a spiral structure including at least two electrode strips (14, 24) spirally wound around a winding axis and at least one separator strip (38, 40) disposed between the electrode strips (14, 24); (b) a hollow cylindrically shaped wound assembly (10) including two end faces (34, 36), an assembly outer circumferential shell surface (42), and an assembly inner circumferential shell surface (44); (c) the assembly inner circumferential shell surface (44) defines an axially extending cavity (46) at the center of the wound assembly (10); (d) an essentially cylindrical or hollow cylindrical winding core (50) is disposed within the axially extending cavity (46), the winding core (50) having an outer circumferential surface, the outer circumferential surface preferably lying in intimate contact with the inner circumferential shell surface (44) of the assembly; An electrochemical energy storage element (12) further having the following characteristics (e) and (f): (e) an anchor 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) An anchor element (52) projects laterally from the axial center of the winding assembly (10) onto the end face (36) of the winding assembly (10) in at least a certain area.

2. 10. The electrochemical energy storage element (12) of claim 1, having at least one of the following additional features (a) to (e): (a) the anchor element (52) and the winding core (50) are integrally formed from the same material; (b) the anchor element (52) is formed as one or more bent tabs (58) of the winding core (50); (c) the anchor element (52) has two, three, or four, preferably star-shaped arms (58); (d) the anchor element (52) is formed as a disk; (e) The anchor elements (52) extend radially from the axial center of the winding assembly (10) to a range of 10 to 100%, preferably 30 to 98%, and most preferably 80 to 95% of the radius of the winding assembly (10).

3. 3. An electrochemical energy storage element (12) according to claim 1 or 2, having the following additional features: (a) The anchor element (52) is an electrically conductive contact element that is in direct contact with one of the electrode strips (24) at the end face (36) of the winding assembly (10) where the anchor element (52) is located.

4. Electrochemical energy storage element (12) according to any one of claims 1 to 3, having the following additional features: (a) The energy storage element (12) includes a housing (60), which includes a cup-shaped housing portion (62), preferably made of metal, which includes a bottom portion (64) and an end opening (65), which end opening (65) is closed by a lid assembly (66).

5. 5. The electrochemical energy storage element (12) of claim 4, having one of the following additional features: (a) the winding core (50) is connected to the bottom (64) of the housing portion (62) such that the bottom (64) of the housing portion (62) forms the anchor element (52); (b) The anchor element (52) is connected to the bottom (64) of the housing part (62).

6. Electrochemical energy storage element (12) according to claim 4 or 5, having the following additional features: (a) the anchor element (52) has a through opening (54) that allows gas pressure generated within the winding assembly (10) to be released into a space (74) between the bottom (64) and the anchor element (52); (b) This gas pressure presses the anchor element (52), together with the winding core (50) and winding assembly (10), against the lid assembly (66).

7. Electrochemical energy storage element (12) according to any one of claims 4 to 6, having at least one of the following additional features: (a) the lid assembly (66) is attached to the cup-shaped housing portion (62), particularly by a crimp closure technique, such that the closure by the lid assembly (66) is released as soon as the internal pressure and / or the winding assembly (10) presses the lid assembly (66) with a predetermined threshold pressure; and / or (b) the lid assembly (66) is attached to the cup-shaped housing portion (62), particularly by crimp closure techniques, such that the net cross-sectional area of ​​the cup-shaped housing portion (62) in the region below the lid assembly (66) is radially reduced by up to six times the wall thickness of the housing portion (62) compared to the remaining net cross-sectional area below that region;

8. An electrochemical energy storage element (12) according to any one of claims 4 to 7, having the following additional characteristics: (a) The bottom portion (64) has a predetermined break line (68) that defines the boundary between a bottom region (72) that is firmly connected to the housing portion (62) and a bottom region (70) that is separable therefrom.

9. An array (80) comprising electrochemical energy storage elements (12) according to any of claims 1 to 8, with the following additional features: (a) A cell connector (82) connects the lid assemblies (66) of at least two energy storage elements (12) together, the cell connector (82) being deformable and / or separable such that when pressure within the energy storage elements (12) reaches a predetermined threshold pressure, the lid assembly (66) of one energy storage element (12) opens while the lid assemblies (66) of the other energy storage elements (12) remain closed.

10. A method for recycling an electrochemical energy storage element (12) according to any one of claims 1 to 8, characterized in that: (a) forcing a punch (90) into the bottom of the energy storage element (12) to eject the winding assembly (10), including the winding core (50), from the housing portion (62); (b) The housing portion (62) and the winding assembly (10) are processed separately.

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