Electrochemical energy storage element and production method

Abstract

An electrochemical energy storage element (100) comprises a housing which encloses an interior (103) and has a housing base (104) and a housing cover (102), each of which has an inner side facing the interior (103) and an outer side, and a single-walled housing casing (105). At least one positive electrode (122) and at least one negative electrode (121), which are connected to each other via an electrolyte, are arranged in the interior (103). The housing base (104) has a hole (107). An insulating layer (108) is arranged around the hole (107) on the inner side of the housing base (104). A small metal plate (109), which rests against this inner side, only separated by the insulating layer (108), forms a perforated base which closes the hole (107) on the inner side. A current conductor (110), which is electrically connected to one of the electrodes, is attached to the side of the small metal plate (109) facing away from the hole (107). The current conductor (110) and the small metal plate (109) are preferably connected to each other by means of a punctiform or linear weld seam (117), the current conductor (110) preferably being a metal foil having a thickness in the range of from 40 µm to 120 µm and the small metal plate (109) preferably having a thickness in the range of from 50 µm to 250 µm. In addition to the energy storage element (100), a method for producing it is also described.

Description

[0001] Electrochemical energy storage element and manufacturing process

[0002] The present invention relates to an electrochemical energy storage element and to methods for manufacturing electrochemical energy storage elements.

[0003] SCOPE OF APPLICATION AND STATE OF THE ART

[0004] Electrochemical energy storage devices are capable of converting stored chemical energy into electrical energy through a redox reaction. The simplest electrochemical energy storage device is the electrochemical cell with a positive and a negative electrode. During discharge, electrons are released at the negative electrode through an oxidation process. This results in an electron current that can be drawn from an external electrical load. Simultaneously, an ion current corresponding to the electrode reaction occurs within the cell. This ion current is made possible by an ion-conducting electrolyte.

[0005] If the discharge is reversible, meaning it's possible to reverse the conversion of chemical energy into electrical energy during discharge and thus recharge the cell, it's called a secondary cell. The common designation of the negative electrode as the anode and the positive electrode as the cathode for secondary cells refers to the discharge function of the electrochemical cell.

[0006] Lithium-ion cells are used in many applications today because they can provide high currents and are characterized by a comparatively high energy density. They are based on the use of lithium, which can move back and forth between the cell's electrodes in the form of ions.

[0007] The negative and positive electrodes of energy storage elements are often combined to form a composite body. For example, ribbon-shaped electrodes can be wound up to form a composite body that spirally encompasses the electrodes. In other embodiments, electrodes are stacked. Separators or solid electrolyte layers are placed between the positive and negative electrodes. Therefore, the composite bodies typically comprise the sequence positive electrode / separator or solid electrolyte / negative electrode.

[0008] Energy storage devices often have a cylindrical shape. A distinction is made between cylindrical cells and button cells. Cylindrical cells are characterized not only by their cylindrical shape but also by the fact that their height is greater than their diameter. Button cells, on the other hand, have a height that is smaller than their diameter. Furthermore, cylindrical cells are typically larger than button cells. The nominal capacity of a button cell is typically less than 1500 mAh. Cylindrical cells, in their lithium-ion versions, can achieve capacities of, for example, 90,000 mAh.

[0009] Button cells are sometimes offered in very small form factors. They are suitable, for example, for powering small electronic devices such as watches, hearing aids, wireless headphones, or similar items.

[0010] Button cells typically consist of a casing made up of two cup-shaped parts, one of which is inserted into the other with its opening facing forward. A plastic ring between the two casing parts serves as a sealing element and simultaneously ensures that the two casing parts are electrically isolated from each other. The two casing parts can therefore function as electrical poles. Such cells are known, for example, from US patent 2013 / 0216881 A1.

[0011] The casing of such button cells has a multi-layered outer layer in which the cell cup, the seal, and the cell lid overlap. Given fixed external dimensions, this necessarily results in a limitation of the internal volume available for the cell's electrodes.

[0012] Button cells are also known in which a pole connected to one of the electrodes passes through a wall of a housing. For example, EP 3813171 A1 and CN 106159350 A describe button cells in which a housing consists of a housing cup and a housing lid, the lid closing the opening of the housing cup. Since both housing parts have the same polarity, a pole feedthrough is required to connect both electrodes within the housing. In both cases, this feedthrough passes through the housing lid, and the described solutions each require a radial sequence of pole, seal, and housing, which complicates the cell's design.

[0013] From EP 3920297 A1, a button cell is known in which a conductor is led through a hole in the lid of a metal housing and welded to a metal disc located on the outside of the lid. The metal disc closes the hole. However, direct contact between the conductor and the edge of the hole must be strictly avoided.

[0014] TASK AND SOLUTION

[0015] In contrast, the invention aims to provide an energy storage element, and in particular a button cell, with a simple design and a particularly high energy density.

[0016] This problem is solved by an electrochemical energy storage element with the features of claim 1. Advantageous embodiments of the energy storage element are defined in the dependent claims. Furthermore, this problem is solved by the method for manufacturing an energy storage element according to claim 14. An advantageous embodiment of the energy storage element is defined in the dependent claim of claim 14.

[0017] The electrochemical energy storage element according to the invention is preferably designed as a button cell, i.e., it has a cylindrical shape with a height that is smaller than its diameter. As a button cell, its maximum diameter is generally up to 3 cm, preferably less than 2 cm.

[0018] In other preferred embodiments, the electrochemical energy storage element according to the invention can have a cylindrical shape with a height greater than its diameter. Such an energy storage element can, for example, have a diameter of up to 2 cm and a height of up to 3 cm. Electrochemical energy storage elements according to the invention with a cylindrical shape and the aforementioned dimensions are particularly preferred if they have a nominal capacity of up to 1500 mAh. For example, the nominal capacity can be in the range of 100 mAh to 1000 mAh.

[0019] All energy storage elements with a cylindrical design and a nominal capacity < 1500 mAh are referred to as miniature cells within the scope of this application.

[0020] In further embodiments, the electrochemical energy storage element according to the invention can have a cylindrical shape with a height greater than its diameter and a capacity > 1500 mAh. Such energy storage elements are referred to herein as cylindrical cells. With a form factor of 21 x 70 (21 mm diameter at 70 mm height), such a cell, in one embodiment as a lithium-ion cell, can, for example, have a preferred nominal capacity in the range of 3000 mAh to 7000 mAh.

[0021] However, it may also be preferable for the energy storage element to have a different design, for example a prismatically shaped housing.

[0022] The electrochemical energy storage element according to the invention is always characterized by the following features a. to f.: a. It comprises a housing enclosing an interior space, with a housing base having an inner surface facing the interior space and an outer surface, a housing cover having an inner surface facing the interior space and an outer surface, and a single-walled housing jacket. b. At least one positive and at least one negative electrode are arranged in the interior space and are connected to each other via an electrolyte. c. The housing base has a hole. d. An insulating layer is arranged around the hole on the inner surface of the housing base. e. A metal plate rests against this inner surface, separated from it only by the insulating layer, and forms a hole bottom that closes the hole on the inner surface. f.A conductor electrically connected to one of the electrodes is welded to the side of the metal plate facing away from the hole.

[0023] Compared to solutions known from the prior art, the electrochemical energy storage element according to the invention is distinguished by the fact that the single-walled housing shell offers advantages with regard to the desired high energy density. The aforementioned radial sequence of pole, seal, and housing is not required in the solution according to the invention; the claimed cell has a very simple structure, and its assembly is correspondingly very simple. A short-circuit problem such as that encountered in EP 3920297 A1 does not exist.

[0024] The housing is preferably cylindrical. The housing base and the housing cover are preferably circular or oval.

[0025] Preferably, the base and the lid of the housing are aligned parallel to each other. Both the base and the lid of the housing preferably form an angle of 90° with the housing shell.

[0026] In accordance with the above statements, the base of the housing and the cover of the housing particularly preferably have a minimum diameter in the range of 0.5 cm to 1 cm and a maximum diameter in the range of 2 cm to 3 cm.

[0027] The casing preferably has a height in the range of 0.3 cm to 3 cm.

[0028] In particularly preferred embodiments, the energy storage element according to the invention is characterized by a combination of the following features: g. The conductor and the metal plate are connected via a point- or line-shaped

[0029] The weld seam connects the components. h. The conductor is a metal foil with a thickness in the range of 20 pm to 120 pm, preferably in the range of 20 pm to 120 pm, more preferably from 40 pm to 120 pm, and the metal plate has a thickness in the range of 50 pm to 250 pm.

[0030] It is preferred that the weld penetrates the metal plate. Particularly preferred is the weld being formed using a laser.

[0031] The cell configuration according to the invention, with the hole in the bottom and the metal plate located on the inside of the bottom, enables the formation of the weld seam in a very advantageous way, especially also by means of a laser.

[0032] If the hole is positioned in the lid, welding the conductor to the metal plate would only be possible under one of the following conditions: (1) Using a sufficiently long conductor to allow welding to the metal plate before the lid is fitted. (2) Welding the conductor after the lid is closed. Option (1) presents problems due to the required conductor length, which usually necessitates folding the conductor when fitting the lid. Option (2) is even more complicated, especially when using cells whose electrodes require electrolyte impregnation. Either the housing is filled with electrolyte before the lid is fitted, or...In this case, laser welding, which generally produces very good results, presents problems because the electrolyte inside the housing heats up during welding and can cause a pressure increase within the housing. Since laser welding completely melts the metal plate within the laser's effective range, the pressure increase can cause molten metal to be ejected. Therefore, in these cases, a less complex external resistance welding process is necessary (the welding electrodes are applied to the metal plate on the outside of the lid). Alternatively, the housing can be filled with the electrolyte after the lid has been fitted. While this allows for laser welding from outside the housing, it requires a subsequent step of introducing the electrolyte into the housing through a suitable opening, which involves considerably more effort.However, if the hole is located in the base, the welding can be carried out with the housing open, and this can easily be done with a laser. Laser welding is preferably performed from the outside. The laser first welds the metal plate, penetrates it, and then melts the conductor within its effective range. This results in a molten zone of metal during the melting process, which solidifies into the weld seam after cooling. The weld seam is surrounded by a heat-affected zone where no melting occurs, but where structural changes, for example due to phase transformations and grain growth, can take place in the metallic structure.

[0033] Welding, especially using a laser, is not trivial, regardless of the positioning of the hole and thus the metal plate. It has been shown that very good welding results are only achieved when the substrates to be welded—the metal plate and the conductor—have defined thicknesses, as defined above in features g and h. Outside of these ranges, the defect rate increased, sometimes significantly.

[0034] The ratio of the thickness of the metal plate to the thickness of the surge arrester is preferably in the range of 3:1 to 1:3, more preferably in the range of 2:1 to 1:2, and more preferably in the range of 2:1 to 1:1. A ratio in the range of 2.0:1 to 1.1:1 is particularly preferred, ideally in the range of 1.6:1 to 1.2:1, which means that ideally the thickness of the metal plate exceeds the thickness of the conductor by at least 10%, better by at least 20%, and by a maximum of 100%, better by a maximum of 60%.

[0035] The conductor preferably has a thickness in the range of 50 pm to 100 pm, while the metal plate preferably has a thickness in the range of 80 pm to 150 pm.

[0036] This applies in particular if the following material combination is present: a. The conductor is made of aluminum or an aluminum alloy. b. The metal plate is made of stainless steel.

[0037] Within the scope of the invention, a metal plate made of stainless steel with a thickness in the range of 50 pm to 250 pm, preferably in the range of 80 pm to 150 pm, is therefore particularly preferably welded to a conductor made of aluminum or an aluminum alloy with a thickness in the range of 20 pm to 120 pm, preferably in the range of 40 pm to 120 pm, particularly preferably in the range of 50 pm to 100 pm.

[0038] While the choice of aluminum or an aluminum alloy for the conductor may be necessary for electrochemical reasons, stainless steel was chosen primarily for its corrosion resistance and mechanical stability. However, welding substrates made of different materials is never trivial, and success cannot be guaranteed.

[0039] If an aluminum alloy is used, it preferably has an aluminum content of > 95 wt.%.

[0040] With regard to the housing, the energy storage element is preferably characterized by at least one of the following additional features a. to e.: a. The housing comprises a housing cup with the housing base and the housing shell. b. The housing cover is a disc. c. The housing cover closes an end opening of the housing cup. d. The housing cover is welded, soldered, or glued into the opening. e. The housing cover is welded, soldered, or glued to the edge of the opening.

[0041] Particularly preferred are the features a. to d. immediately preceding or the features a. to c. and e. immediately preceding are realized in combination.

[0042] The housing cup and the housing lid preferably have the same polarity, especially in the case of a welded connection between the two housing parts.

[0043] The housing cup and the housing lid are preferably joined to each other via a weld line along the opening edge of the housing cup. The bottom of the housing cup preferably has a thickness in the range of 50 pm to 1000 pm, particularly preferably a thickness in the range of 50 pm to 500 pm. The thickness of the housing bottom defines the depth of the hole arranged therein.

[0044] The housing cover preferably has a thickness in the range of 50 pm to 1000 pm, particularly preferably a thickness in the range of 50 pm to 500 pm.

[0045] The casing preferably has a thickness in the range of 50 pm to 1000 pm, particularly preferably a thickness in the range of 50 pm to 500 pm.

[0046] Preferably, the housing cup is formed by a deep-drawing process.

[0047] The housing cup and the housing lid can be made of materials such as nickel, steel, or aluminum. Multi-layered sheets, for example with one layer of steel and one layer of nickel, can also be used to manufacture the housing parts.

[0048] As mentioned above, the housing can also be prismatic, for example. The base and top of the housing can then be rectangular or have an alternative polygonal shape (such as a hexagon or octagon). In the case of an octagon, the housing can then comprise, for example, eight side walls connected by edges.

[0049] With regard to the electrodes, the energy storage element is preferably characterized by one of the following additional features a. and b.: a. The at least one positive and the at least one negative electrode are part of a cylindrical electrode-separator winding or are designed as such. b. The at least one positive and the at least one negative electrode are parts of a stack or are designed as a stack.

[0050] Cylindrical electrode-separator windings often have an axial cavity in their center due to their manufacturing process, which may contain a winding core. This cavity is often partially filled with a separator film. In the present case, it is particularly preferred that the cylindrical electrode-separator windings used have an axial cavity with a maximum diameter of < 2 mm, preferably < 1.5 mm. Cavities with such diameters are generally too narrow to serve as passages for welding electrodes, such as those used in resistance welding, and are also not well suited as passages for a laser beam in laser welding, especially if they are filled with the aforementioned separator material. In these cases in particular, the laser welding described above is advantageously applicable from the outside.

[0051] The energy storage element is not limited with regard to electrochemistry either. In particularly preferred embodiments, the energy storage element comprises lithium-ion-based electrodes. In further embodiments, the energy storage element can also be a sodium-ion cell, a potassium-ion cell, a calcium-ion cell, a magnesium-ion cell, or an aluminum-ion cell.

[0052] The electrochemical energy storage element according to the invention is therefore particularly preferred as a lithium-ion cell or a sodium-ion cell.

[0053] Preferably, the energy storage element according to the invention comprises so-called composite electrodes as negative and positive electrodes, which include electrochemically active components as well as electrochemically inactive components.

[0054] In principle, all materials that can absorb and release lithium ions are suitable as electrochemically active components (active materials) for lithium-ion energy storage devices. For the negative electrode, carbon-based or silicon-based particles, such as graphitic carbon, are used. For the positive electrode, NMC materials (LiNi) are examples of suitable active materials. x Mn x Co x Lithium cobalt oxide (LiCoC), lithium manganese oxide (LiMnzC), lithium iron phosphate (LiFePC), or derivatives thereof are used. The electrochemically active materials are usually contained in particle form within the electrodes.

[0055] The active materials are typically part of a mixture applied as a layer to a ribbon-shaped current collector. The current collector represents an electrochemically inactive component of the energy storage element. Metallic foils are particularly suitable as current collectors, serving as a substrate for the respective active material. In lithium-ion-based energy storage elements, the current collector for the negative electrode (anode current collector) can be made of copper or nickel, for example, and the current collector for the positive electrode (cathode current collector) of aluminum, for example. The layer preferably comprises, as electrochemically inactive components, an electrode binder (e.g., polyvinylidene fluoride (PVDF) or another polymer, such as carboxymethylcellulose), conductivity-enhancing additives, and other admixtures.The electrode binder ensures the mechanical stability of the electrodes and also ensures the adhesion of the active material to the current collectors.

[0056] Suitable electrolytes for a lithium-ion-based energy storage element include, for example, solutions of lithium salts such as lithium hexafluorophosphate (LiPFe) in organic solvents (e.g., ethers and esters of carbonic acid).

[0057] In the coil and the stack, the at least one positive and at least one negative electrode are preferably separated from each other by a separator or a layer of a solid electrolyte. In simple cases, the separator is, for example, a microporous plastic film.

[0058] With regard to the hole, the energy storage element is preferably characterized by at least one of the following additional features a. to c.: a. The housing base is bounded by a circular edge formed by the hole. b. The hole is located in the center of the housing base. c. The hole is preferably circular or polygonal. d. The hole has a minimum diameter in the range of 1 mm to 1 cm, preferably from 2 mm to 4 mm, and a maximum diameter in the range of 2 cm to 3 cm.

[0059] The features a. to c. immediately preceding this are preferably implemented in combination. The features a. to d. immediately preceding this are particularly preferably implemented in combination. The hole can, for example, be formed by a punching process.

[0060] With regard to the insulating layer, the energy storage element is preferably characterized by at least one of the following additional features a. to i.: a. The insulating layer is bonded to the inside of the housing base with the hole via an adhesive. b. The insulating layer is a layer of an adhesive, in particular a hot melt adhesive. c. The insulating layer consists of or is based on a polyolefin. d. The insulating layer consists of a material that melts at a temperature in the range of 100 °C to 180 °C, in particular above 170 °C. e. The insulating layer has a thickness in the range of 10 pm to 500 pm. f. The insulating layer is designed as an O-ring. g. The insulating layer has a three-layer structure and comprises two outer adhesive layers and one inner layer. h. The inner layer melts at a temperature above 170 °C. i. The inner layer is a metal layer.

[0061] Particularly preferred are the features b. to e. immediately preceding, and especially features b. to f. immediately preceding, implemented in combination. In further preferred embodiments, features a., d., e., g., h. and optionally f. are implemented in combination with one another. In further preferred embodiments, features a., d., e., g., i. and optionally f. are implemented in combination with one another.

[0062] The insulating layer can be a component, for example an O-ring made of a thermoplastic polymer, in particular a polyolefin, one side of which is bonded to the inside of the housing base by means of an adhesive and the other side of which is bonded to the metal plate by means of an adhesive. Preferably, however, the insulating layer itself is a layer of adhesive, according to the preceding feature b. Preferably, the insulating layer has a uniform thickness within the aforementioned preferred thickness range.

[0063] A film made of a meltable polymer material, heated, especially melted, is particularly preferred for producing the insulating layer. A film made of an adhesion-modified polyolefin is especially suitable for this purpose.

[0064] The foil is melted and, upon solidification, forms an adhesive bond between the inside of the case base or lid and the metal plate. Preferably, the surfaces to be joined are pressed together during this process.

[0065] To improve the adhesion of the foil to the inside and / or the metal plate, grooves, undercuts, or similar features may be incorporated. In particular, the relevant surfaces may also be deliberately roughened.

[0066] The meltability according to characteristics d. and h. can advantageously represent a safety feature of the cell. Since the metal plate is larger than the hole it covers, it cannot be forced out when pressure builds up in the housing. However, since the build-up of pressure is almost always associated with a temperature increase, the complete melting of the insulating layer can cause the metal plate to be forced by the pressure through the molten insulating layer against the base of the housing, creating direct contact and thus generating a desired short circuit to discharge the cell. Furthermore, the cell can vent through the molten insulating layer and release its internal pressure. By using a suitable material for the insulating layer, a "thermal fuse" can therefore be integrated into the cell.

[0067] The use of the metal layer as an inner layer may be preferred if particular importance is placed on a diffusion barrier.

[0068] With regard to the metal plate, the energy storage element is preferably characterized by at least one of the following additional features a. to c.: a. The metal plate has a minimum diameter in the range of 2 mm to 1 cm and a maximum diameter in the range of 5 mm to 2.55 cm. b. The metal plate has a thickness in the range of 90 pm to 120 pm. c. The metal plate is made of one of the following materials: steel, stainless steel, aluminum, stainless steel coated with aluminum, stainless steel coated with aluminum and nickel, or nickel and copper.

[0069] The features a. to c. immediately preceding this document are particularly preferred when implemented in combination.

[0070] Preferably, the metal plate has a uniform thickness within the aforementioned preferred thickness ranges. It can be very thin, which is why the invention can provide housings with optimized internal volume. This larger internal volume can be used for more electrochemically active material.

[0071] In particularly preferred embodiments, the metal plate has a corrosion-preventing, electrically conductive layer on its side facing away from the hole. This layer can be, for example, an aluminum or copper layer. In the case of a lithium-ion cell, aluminum is particularly preferred if the metal plate is electrically connected to a positive electrode. Copper or nickel are particularly preferred if the metal plate is electrically connected to a negative electrode.

[0072] The corrosion-preventive layer can be formed, for example, by electroplating, sputtering, or a conventional gas-phase metal deposition process. It can have a thickness of, for example, < 1 pm.

[0073] In preferred embodiments, the energy storage element is characterized by at least one of the following additional features a. to e.: a. The metal plate is a disk with a circular edge. b. The hole is circular. c. The housing base is bounded by a circular edge. d. The diameter of the metal plate is in the range of 20% to 99%, preferably in the range of 40% to 90%, of the diameter of the housing base. e. The diameter of the metal plate is in the range of 120% to 200%, preferably in the range of 140% to 180%, of the diameter of the hole 107.

[0074] Preferably, the features a., b., c., e. and e. immediately preceding are implemented in combination.

[0075] The aforementioned sizes and proportions offer a good compromise, ensuring both sufficient mechanical stability of the base and a sufficiently large contact surface on the outside to, for example, fix an electrical contact to the metal plate.

[0076] It is further particularly preferred if a. the metal plate and the housing base enclose an annular overlap area and / or b. the annular overlap area has a ring width of 1 mm to 4 mm, preferably 1 mm to 3 mm.

[0077] The insulating layer is located in the overlap area between the metal plate and the base of the housing.

[0078] With regard to the conductor, the energy storage element is preferably characterized by at least one of the following additional features a. and b.: a. The metal foil has a thickness in the range of 60 pm to 90 pm. b. The conductor consists of one of the following materials: copper, nickel, and aluminum, with aluminum being particularly preferred in some cases.

[0079] The features a. and b. immediately preceding it are particularly preferred when implemented in combination.

[0080] The conductor could, for example, be a metal strip, one end of which is welded to the current collector of one of the electrodes. Alternatively, the conductor could also be an end piece of a current collector that has been folded to reach the metal plate.

[0081] Of course, instead of (or in addition to) a welded connection, there can also be an adhesive connection or a soldered connection between the conductor and the metal plate.

[0082] In some particularly preferred embodiments, the energy storage element is characterized by at least one of the following additional features a. and b.: a. It comprises an additional conductor that electrically connects one of the electrodes and the housing. b. The additional conductor is welded to the housing.

[0083] This additional conductor can also be a metal strip, one end of which is welded to the current collector of one of the electrodes, possibly the end piece of a current collector.

[0084] Feature b. can be very advantageous insofar as the welding to the housing shell can be carried out very easily before the lid is fitted. This means it can also be done before the electrolyte is added and thus also be performed using a laser. The additional conductor and the housing shell are then connected to each other – analogous to the conductor connected to the metal plate – via a spot or line weld.

[0085] In a preferred embodiment, the at least one positive electrode is electrically connected to the metal plate via the conductor. Particularly in these cases, the current collector of the at least one positive electrode, the conductor, and the metal plate or the corrosion-preventing, electrically conductive layer are preferably made of aluminum. The at least one negative electrode is then preferably electrically connected to the housing, in particular the housing cup or the housing cover, via the additional conductor. If the at least one negative electrode is electrically connected to the metal plate via the conductor, then the at least one positive electrode is preferably also electrically connected to the housing, in particular the housing cup or the housing cover, via the additional conductor.

[0086] In further particularly preferred embodiments, the energy storage element is characterized by at least one of the following additional features a. to c.: a. A metallic pole is arranged in the hole, which rests on the metal plate and is spaced apart from the edge of the hole. b. The metallic pole is a metal disc, in particular with a diameter in the range of 1 mm to 3 cm and / or a thickness in the range of 50 pm to 1000 pm. c. The metallic pole is welded to the metal plate.

[0087] However, the metallic pole as a metal disc is not absolutely necessary for the invention; even without this metal disc, the current can be tapped via the underlying metal plate.

[0088] The features a. to c. immediately preceding this document are particularly preferred when implemented in combination.

[0089] In principle, the metal plate can serve as the pole, and a voltage can be tapped at the bottom of the hole. In other embodiments, it may be preferable to arrange the metal disc in the hole and weld it to the metal plate.

[0090] The invention further comprises a method for manufacturing the described electrochemical energy storage element. This method comprises at least the following steps a. to e.: a. Providing a housing cup with a housing base and a housing shell, as well as a housing lid, wherein the housing base has an inner surface and a hole. b. Inserting a metal plate into the housing cup so that it closes the hole on the inner surface, wherein an insulating layer is arranged between the metal plate and the housing base, separating the metal plate from the housing base. c. Inserting at least one positive electrode and at least one negative electrode, as well as a conductor connected to one of the electrodes, into the housing cup. d. Welding the conductor to the metal plate. e. Mounting the lid to close the housing.

[0091] This method is used to manufacture an electrochemical energy storage element with a housing cup whose bottom has a hole that is closed by the metal plate, as described above.

[0092] Another current collector, also as described above, may be provided to connect the electrode not connected to the aforementioned current conductor to the housing or a pole passing through the housing.

[0093] The insulating layer not only serves as an electrical insulator but also seals the housing. It is therefore bifunctional. The metal plate can be inserted into the housing cup together with the insulating layer, or it can be positioned in the housing cup before the metal plate is inserted.

[0094] Preferably, the insulating layer undergoes heat treatment as part of the process to bond it to the metal plate and / or the inside of the housing base. Such heating can be generated, for example, inductively or locally using a laser or by pressing a heated tool against the outside of the housing base in the area where the insulating layer is located on the inside. Before step c, it is of course also possible to heat the insulating layer from both sides.

[0095] As described above, the at least one positive electrode and the at least one negative electrode are preferably inserted into the housing cup in the form of a coil or stack. To weld the conductor to the metal plate, a coil or stack comprising the at least one positive electrode and the at least one negative electrode is preferably inserted into the housing cup such that the conductor connected to one of the electrodes is in direct contact with the metal plate. Welding is then preferably carried out from the outside, i.e., through the metal plate, for example, using a laser or resistance welding, as described above. A contact between another conductor and the housing can also be established in a similar manner, preferably, however, only after the lid has been fitted, except in the aforementioned case of contact with the housing shell.

[0096] The lid assembly preferably includes inserting the housing lid into the opening of the housing cup or placing the housing lid on the edge of the housing cup and then welding it together.

[0097] BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Further features and advantages of the invention will become apparent from the following description of preferred embodiments in conjunction with the drawing. The features shown can be implemented individually or in combination with other features.

[0099] The figures show:

[0100] Fig. 1 schematic sectional view of a possible embodiment of the housing of an energy storage element according to the invention.

[0101] Fig. 2 schematic sectional view of an energy storage element according to the invention with a further possible embodiment of the housing.

[0102] DESCRIPTION OF PREFERRED EXAMPLES

[0103] The electrochemical energy storage element 100 comprises a cylindrical housing consisting of a housing cup 101 and a housing cover 102, enclosing an interior 103, see Fig. 1. The housing cup 101 is a deep-drawn metal part and includes the housing base 104 and the single-walled housing shell 105. The opening rim 106 of the housing cup 101 defines a circular opening that is closed by the housing cover 102. The housing cover 102 is a circular metal disc. The housing cup 101 and the housing cover 102 are connected to each other along the opening rim 106 by a circumferential weld 115.

[0104] The base plate 104 and the cover plate 102 each have an inner side and an outer side facing the interior 103. The inner side of the base plate is marked with reference numeral 104a, and the inner side of the cover plate with reference numeral 102a.

[0105] In the interior space 103 of energy storage elements according to the invention, one or more positive and one or more negative electrodes are always arranged, which are connected to each other via an electrolyte and are usually arranged as a coil or stack. For the sake of clarity, their illustration has been omitted here.

[0106] The housing base 104 has a circular hole 107. On the inner side 104a of the housing base with the hole 107, an insulating layer 108, designed as an O-ring, is arranged around the hole 107. A metal plate 109, which rests against the inner side 104a, separated from it only by the insulating layer 108, forms a hole base and closes the hole 107 on the inner side 104a. A conductor 110, which is electrically connected to one of the electrodes (not shown), is attached to the side 111 of the metal plate 109 facing away from the hole 107 (see schematically represented weld bead 117). The side 111 is formed by the corrosion-preventing aluminum layer 112.

[0107] A metal disc 113 is arranged in hole 107, resting on the metal plate 109 and spaced apart from the edge of hole 107a. The metal disc 113 is welded to the metal plate 109 (see schematically depicted weld bead 116) and serves as a pole for tapping an electrical voltage.

[0108] The metal disc 113 is not strictly necessary. The metal plate 109 can also be used to tap into or apply current and voltage. The energy storage element 100 shown in Fig. 2 differs from the one shown in Fig. 1 in the following aspects:

[0109] A metal disc 113 was omitted here. The outer surface of the metal plate 109 serves as the pole for tapping an electrical voltage. Inside the interior 103, a coil 120 comprising a positive electrode 122 and a negative electrode 121 is arranged, which are connected to each other via an electrolyte. The positive electrode 122 is electrically connected to the metal plate 109 via the conductor 110.

[0110] Additionally, it is shown that the negative electrode 121 is electrically connected to the casing of the housing 101 via another conductor 119.

[0111] The corrosion-preventive aluminium layer 112 was omitted here.

Claims

PATENT CLAIMS 1. Electrochemical energy storage element (100), in particular a button cell, comprising a. a housing enclosing an interior space (103) with a housing base (104) having an inner side (104a) facing into the interior space (103) and an outer side, a housing cover (102) having an inner side (102a) facing into the interior space (103) and an outer side, and a single-walled housing jacket (105), and b. at least one positive electrode (122) and at least one negative electrode (121) arranged in the interior space (103), which are connected to each other via an electrolyte, wherein c. the housing base (104) has a hole (107), d. an insulating layer (108) is arranged around the hole (107) on the inner side (104a) of the housing base (104) or the housing cover (102) with the hole (107), and e.a metal plate (109) which rests against this inner surface (104a), separated only by the insulating layer (108), forming a hole bottom which closes the hole (107) on the inner surface (104a), and f. a conductor (110) which is electrically connected to one of the electrodes (121; 122) is welded to the side of the metal plate (109) facing away from the hole (107), wherein it is preferred that g. the conductor (110) and the metal plate (109) are connected to each other via a spot or line weld (117) and h. the conductor (110) is a metal foil with a thickness in the range of 20 pm to 120 pm and the metal plate (109) has a thickness in the range of 50 pm to 250 pm.

2. Energy storage element according to claim 1 with at least one of the following additional features: a. The weld (117) penetrates the metal plate (109). b. The weld (117) is formed by means of a laser.

3. Energy storage element according to claim 1 or claim 2 with at least one of the following additional features: a. The conductor (110) is made of aluminum or an aluminum alloy. b. The metal plate (109) is made of stainless steel.

4. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The housing comprises a housing cup (101) with the housing base (104) and the housing shell (105). b. The housing cover (102) is a disc. c. The housing cover (102) closes an end opening of the housing cup (101). d. The housing cover (102) is welded, soldered, or glued into the opening. e. The housing cover (102) is welded, soldered, or glued to the edge of the opening.

5. Energy storage element according to claim 1 or claim 2 with at least one of the following additional features: a. The at least one positive electrode (122) and the at least one negative electrode (121) are part of a cylindrical electrode-separator winding. b. The at least one positive and the at least one negative electrode are configured as a stack.

6. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The housing base (104) is bounded by a circular rim. b. The hole (107) is located in the center of the housing base (104). c. The hole (107) is preferably circular or polygonal. d. The hole (107) has a minimum diameter in the range of 1 mm to 1 cm, preferably from 2 mm to 4 mm, and a maximum diameter in the range of 2 cm to 3 cm.

7. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The insulating layer (108) is bonded to the inner surface (104a) of the housing base (104) via an adhesive. b. The insulating layer (108) is a layer of an adhesive, in particular a hot melt adhesive. c. The insulating layer (108) consists of or is based on a polyolefin. d. The insulating layer (108) consists of a material that melts at a temperature in the range of 100 °C to 180 °C, in particular above 170 °C. e. The insulating layer (108) has a thickness in the range of 10 pm to 500 pm. f. The insulating layer (108) is designed as an O-ring. g. The insulating layer has a three-layer structure and comprises two outer adhesive layers and one inner layer. h. The inner layer melts at a temperature above 170 °C. i. The inner layer is a metal layer.

8. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The metal plate (109) has a minimum diameter in the range of 2 mm to 1 cm and a maximum diameter in the range of 5 mm to 2.5 cm. b. The metal plate (109) has a thickness in the range of 90 pm to 120 pm. c. The metal plate (109) is made of one of the following materials: steel, stainless steel, aluminum, stainless steel coated with aluminum, stainless steel coated with aluminum and nickel, or nickel and copper.

9. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The metal plate (109) is a disk with a circular edge. b. The hole (107) is circular. c. The housing base (104) is bounded by a circular edge. d. The diameter of the metal plate (109) is in the range of 20% to 99%, preferably in the range of 40% to 90%, of the diameter of the housing base. e. The diameter of the metal plate (109) is in the range of 120% to 200%, preferably in the range of 140% to 180%, of the diameter of the hole (107).

10. Energy storage element according to claim 9 with the following additional feature: a. The metal plate (109) and the housing base (104) enclose an annular overlapping area. b. The annular overlapping area has a ring width of 1 mm to 4 mm, preferably 1 mm to 3 mm.

11. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. The metal foil forming the current conductor (110) has a thickness in the range of 60 pm to 90 pm. b. The conductor (110) is made of one of the following materials: copper, nickel and Aluminum.

12. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. It comprises a further conductor (119) that electrically connects one of the electrodes and the housing. b. The further conductor is welded to the housing shell (105).

13. Energy storage element according to one of the preceding claims with at least one of the following additional features: a. A metallic pole (113) is arranged in the hole (107), which rests on the metal plate (109) and is spaced apart from the edge of the hole (107). b. The metallic pole (113) is a metal disc, in particular with a diameter in the range of 1 mm to 3 cm and / or a thickness in the range of 50 pm to 1000 pm. c. The metallic pole (113) is welded to the metal plate (109).

14. A method for manufacturing an electrochemical energy storage element, in particular an energy storage element (100) according to one of the preceding claims, characterized by the following steps: a. Providing a housing cup (101) with a housing base (104) and a housing shell (105) as well as a housing lid (102), wherein the housing base (104) has an inner surface (104a) and a hole (107). b. Inserting a metal plate (109) into the housing cup (101) so that it closes the hole (107) on the inner surface (104a), wherein an insulating layer (108) is arranged between the metal plate (109) and the housing base (104), separating the metal plate (109) from the housing base (104). c. Insert at least one positive electrode (122) and at least one negative electrode (121), as well as a conductor (110) connected to one of the electrodes, into the housing cup (101). d. Weld the conductor (110) to the metal plate (109). e. Mount the lid (102) to close the housing.

15. Method according to claim 14, characterized by the following additional features: a. Welding a further conductor (119) connected to one of the electrodes (121; 122) to the housing shell (105), particularly preferably before step e. of claim 14.

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