Electrochemical storage cell and method for adjusting a compression pressure of an electrochemical storage cell

Abstract

The invention relates to an electrochemical storage cell comprising a housing (20) with a housing casing (21), as well as a housing underside and a housing upper side. An electrode stack (40) is arranged in an interior space of the housing (20), which is delimited by the housing casing (21), between the housing underside and the housing upper side. A bellows (10) is connected to the housing casing (21) on the housing underside and is designed to exert a compression pressure on the electrode stack (40) by means of elastic deformation.

Description

[0001] ELECTROCHEMICAL STORAGE CELL AND METHOD FOR ADJUSTING A

[0002] COMPRESSION PRESSURE OF AN ELECTROCHEMICAL STORAGE CELL

[0003] The following description relates to an electrochemical storage cell with a spring-loaded compression device for compensating for expansion of stacked electrochemical storage cells in the stacking direction. Furthermore, a method for adjusting a compression pressure of an electrochemical storage cell is described.

[0004] State of the art

[0005] Solid-state batteries are a special type of accumulator in which the electrodes and electrolyte are made of solid material. Solid-state batteries are increasingly seen as an important building block for the electrification of mobility. They are considered safer and enable greater range and shorter charging times than conventional lithium-ion batteries. Furthermore, lithium-silicon batteries are increasingly being developed, which use a silicon-based anode and lithium ions as charge carriers.

[0006] A well-known problem in battery technology for storage cells such as solid-state batteries and lithium-silicon batteries concerns variable layer thicknesses. For example, in anode-free all-solid-state batteries (ASSBs), there is initially no anode on the anode side in the discharged state, but only a current collector (e.g., a copper foil). In the charged state, an anode in the form of pure lithium is formed, which migrates from the cathode (lithium is stored in the cathode) through a separator during the charging process and deposits or forms on the copper foil. To put the cell into operation, the electrode layers must be pressed together. The necessary forces are in the kN range, or the pressures in the double-digit bar range.

[0007] The state of the art offers solutions to these problems. However, it remains a technical challenge to maintain the compression forces or pressures, once set, within certain limits, especially for electrode stacks with variable heights. For example, if the forces in the cell are designed for a charged state, the corresponding forces in the intermediate states between the charged and discharged states would be too low. The cell could not function properly. If the forces in the cell are designed for the discharged state, the compression forces or pressures in the intermediate states between the charged and discharged states would be too high. The cell could rupture.

[0008] Constant compression of the layers of an electrode stack can be achieved pneumatically or hydraulically. However, this requires either all cells to be supplied with a single pressure unit, or corresponding modules with multiple cells each with a pump or pressure unit. This is complex and requires a lot of space, for example, to compensate for the expansion of individual cells or multiple cells within the module. Hydraulic or pneumatic systems would need to be continuously supplied with energy to keep the compression forces constant even during extended downtimes. These systems are prone to leaks; a piping system must be supplied with oil, and they take up valuable installation space.

[0009] One object is to specify an electrochemical storage cell that can be operated with a compression pressure that is easier to adjust and maintain. Furthermore, a method for adjusting the compression pressure of an electrochemical storage cell is to be specified.

[0010] This object is achieved by an electrochemical storage cell and a storage cell module according to the independent and subordinate claims. Advantageous embodiments and further developments emerge from the dependent claims.

[0011] Summary

[0012] In the following, it is assumed that each feature described with reference to any embodiment can be used alone or in combination with other features described herein and can be used in combination with one or more features of any other embodiment or in any combination of any other embodiment, unless explicitly described as an alternative. Furthermore, equivalents and modifications not described below can be used without departing from the scope of the claimed subject matter. An electrochemical storage cell refers hereinafter to an electrochemically based energy storage device, in particular a rechargeable energy storage device, which is suitable for storing electrical energy and delivering it to a consumer, for example a consumer in a vehicle.A solid-state electrochemical cell is a solid-state battery, such as a lithium-ion battery, so the following description also refers to a solid-state lithium-ion battery. A solid is a chemical substance that is rigid at the temperatures typically found in an electrochemical storage cell or at least has a very low tendency to flow, as can be the case with polymers, for example.

[0013] In the following, the term "lithium-ion battery" is used synonymously for all terms commonly used in the art for lithium-containing galvanic elements and electrochemical storage cells (abbreviated to "cell"), such as lithium battery, lithium cell, lithium-ion cell, lithium polymer cell, lithium-ion battery cell, and lithium-ion accumulator. This particularly includes rechargeable batteries, so-called secondary batteries. The terms "battery" and "electrochemical storage cell" are also used synonymously with the terms "lithium-ion battery" and "lithium-ion cell."

[0014] The term "electrode stack" refers to a sequence of layers or films. In an electrochemical storage cell, the layers follow one another. However, this does not mean that the layers specified here must follow one another directly. Rather, intermediate layers may also be provided, such as a separator, insulator, electrode binder, coatings, and electrical conductivity additives, which can be applied to an electrically conductive carrier of the respective electrodes.

[0015] An electrochemical storage cell typically has various electrodes: a positive electrode (cathode) and a negative electrode (anode), which can be electrically contacted via current collectors. Each of these electrodes comprises at least one active material, optionally together with additives such as electrode binders and electrical conductivity additives, which is applied to an electrically conductive carrier (e.g., a metal foil) or to a current collector of the respective electrodes. Non-porous and solid collector foils made of aluminum (for the positive electrode) or copper (for the negative electrode) are typically used as the electrically conductive carrier. Such collector foils are typically impermeable to liquid electrolyte and gases.The electrochemical storage cells described below can be used with a liquid electrolyte or can be configured with a solid electrolyte as solid-state electrochemical storage cells, for example, as a ceramic or polymer-based solid-state battery. A solid-state electrochemical cell comprises a solid electrolyte.

[0016] Furthermore, an electrochemical storage cell is proposed which is designed to compensate for compression pressure changes due to an expansion of an electrode stack in the stacking direction.

[0017] According to one embodiment, an electrochemical storage cell comprises a housing. The housing further comprises a housing shell with a housing bottom and a housing top. An electrode stack is arranged in an interior space of the housing, defined by the housing shell, between the housing bottom and the housing top. A bellows is provided and connected to the housing shell at the housing bottom. The bellows is configured to exert a compressive pressure on the electrode stack through elastic deformation.

[0018] The housing of the electrochemical storage cell can be designed as a round housing (as a round cell). The housing is, for example, cylindrical and has a circular cross-section. The other components in the housing, in particular the electrode stack, can preferably also have a circular cross-section. The electrode stack can be filled with a liquid electrolyte. Alternatively, the electrode stack can be provided with a solid electrolyte, which is embossed into the layer sequence of the electrode stack. In this way, an electrochemical solid-state storage cell (ASSB for short, or all-solid-state battery) can be formed.

[0019] The bellows, also called a corrugated tube, has a casing with a wave-like, varying diameter. For example, the housing is made of metal, so the bellows is also designed as a metal bellows or metal corrugated tube. In one embodiment, the housing is designed as a round cell. The bellows has a circular cross-section and encloses a cylindrical housing volume on the underside of the housing. The housing volume comprises the interior of the housing in which the electrode stack is arranged.

[0020] The housing and bellows can have different cross-sections and geometries; for example, the housing and bellows can have a polygonal cross-section, such as a hexagonal cross-section. The storage cell, designed as a round cell, for example, is a storage cell that can be manufactured cost-effectively and quickly. The round cell enables surface contact between contacting elements and the respective electrode, which is electrically connected to the respective contacting element. The bellows can be described as a spring element with a Hook spring constant, which can be elastically deformed due to its material properties and geometry.

[0021] Depending on the state of charge of the electrochemical storage cell, the electrode stack can have different layer thicknesses. These layer thicknesses can "compress" or "relieve" the stack through the spring effect ("compress": the cell discharges, "relieve": the cell is charged; for example, the anode layers can be designed depending on the state of charge). The bellows is designed to track pressure changes in the electrochemical storage cell, for example, due to expansion and contraction of the electrode stack as a result of charging and discharging processes, and to adjust them to the desired compression pressure.

[0022] The description is based in particular on the considerations presented below. One aspect relates to an electrochemical storage cell that allows the layer height of the electrode stack to be continuously adjusted and tracked without the need for energy. The bellows represents a mechanical spring and can be elastically deformed according to its mechanical properties. In other words, the bellows corresponds to a spring-loaded compression device. With an initial deformation, a compression pressure of a specific magnitude can be set on the electrochemical storage cell. This is done, for example, during assembly or manufacture of the cell by inserting the bellows into the housing under pressure, thus deflecting the corrugations of the bellows into a position that corresponds to a specific deflection of the "spring" or a desired compression pressure.If the housing is closed in this adjusted state, the compression pressure acts on the electrode stack. Changes in the layer height of the electrode stack can be continuously adjusted using the spring action of the bellows, without the need for external power.

[0023] According to one embodiment, an electrochemical storage cell comprises a housing with a housing shell, as well as a housing bottom and a housing top. An electrode stack is arranged in an interior space of the housing, defined by the housing shell, between the housing bottom and the housing top. A bellows is connected to the housing shell at the housing bottom. The bellows is further configured to exert a compressive pressure on the electrode stack through elastic deformation.

[0024] According to one embodiment, the bellows is arranged entirely or partially within the interior of the housing and is movable within it. The bellows is connected to the housing shell on one side and is movable within the interior on the other. This allows the bellows to move, for example, into or out of the housing. The fixed point on the housing allows the bellows to build up compression pressure against the fixation.

[0025] According to one embodiment, the bellows is crimped, screwed, and / or welded to the housing bottom. Alternatively, or additionally, a lower housing cover is provided to close the housing.

[0026] According to one embodiment, the bellows has substantially parallel or spiral corrugations. The corrugations are substantially freely movable along an inner wall of the housing in the stacking direction.

[0027] According to one embodiment, the electrode stack and the bellows each have central openings through which an inner tube is guided to contact the electrode stack. The bellows is movable along the inner tube in the stacking direction in the housing. The inner tube serves to electrically contact the electrode layers of the electrode stack and as the central axis of the cell. Furthermore, the inner tube can assume a safety function and serve to direct gases. For example, in the event of a thermal event, gases can be specifically directed into a safety volume. According to one embodiment, the bellows has a pressure surface. The pressure surface is in operative contact with an underside of the electrode stack. The pressure surface is configured to exert the compression pressure on the underside of the electrode stack.For example, the pressure surface is moved by the elastic deformation of the bellows in the housing, so that the pressure surface exerts and adjusts the compression pressure on the electrode stack according to the deflection of the bellows.

[0028] According to one embodiment, the pressure surface and the lower housing cover enclose a safety volume in the area of ​​the bellows. This safety volume is connected to the inner tube for accommodating a gas from the electrode stack. The safety volume can, for example, absorb hot gases during a thermal event and thus defuse the cell.

[0029] According to one embodiment, a pressure plate is immovably connected to a housing cover on the top side of the housing. The pressure plate rests on the top side of the electrode stack. Furthermore, the pressure plate is configured to exert a pressure on the top side of the electrode stack that is opposite to the compression pressure. The pressure plate acts as a stop surface against which the electrode stack is pressed when the compression pressure is built up. The corresponding counterpressure compresses the electrode stack.

[0030] According to one embodiment, the pressure plate is designed to break and / or deform in a controlled manner during a thermal event. The pressure plate can be configured with a safety function through the choice of shape and / or material. For example, the pressure plate can deform in the event of a thermal event, so that the pressure from inside the electrochemical cell cambers the plate. Furthermore, additional safety systems can be provided. The pressure plate can have a PTC resistor or PTC thermistor. For example, the PTC resistor can form a ring on or in the pressure plate, which becomes an insulator at elevated temperatures and breaks the contact with the electrochemical cell.If the pressure plate deforms, the mechanical connection between the pressure plate and the PTC thermistor can become loose, disrupting the electrically conductive contact with the electrode stack and thus interrupting the current flow. According to one embodiment, the bellows can be replaced by a coil spring.

[0031] In such an implementation, the pressure surface can be sealed to the housing shell.

[0032] Furthermore, a method for adjusting the compression pressure of an electrochemical storage cell is proposed. The method first comprises the step of providing an electrochemical storage cell. The storage cell has a housing with a housing shell, a housing bottom, and a housing top. Furthermore, an electrode stack is arranged in an interior space of the housing, defined by the housing shell, between the housing bottom and the housing top.

[0033] In a further step, the compression pressure is adjusted. This is done using a bellows connected to the housing shell at the bottom. The bellows is elastically deformed by the compression pressure and subsequently exerts the compression pressure on the electrode stack. Finally, the housing is closed to maintain the adjusted compression pressure.

[0034] In the following, exemplary embodiments of the invention are described with reference to the accompanying drawings. Further details, preferred embodiments, and further developments emerge from them. Identical or similarly functioning components are provided with the same reference numerals in the figures. The illustrated components and their relative sizes are not to be considered to scale. To the extent that components and parts in the various figures have the same function, their description is not necessarily repeated for each of the following figures.

[0035] In detail:

[0036] Figure 1 shows an embodiment of an electrochemical storage cell,

[0037] Figures 2A, 2B, the embodiment of an electrochemical storage cell in different charge states, Figures 3A, 3B an embodiment of a bellows,

[0038] Figures 4A to 4C show an embodiment of an electrochemical storage cell,

[0039] Figure 5 shows another embodiment of an electrochemical storage cell,

[0040] Figure 6 shows the embodiment of an electrochemical storage cell in a state of charge, and

[0041] Figures 7A, 7B show an embodiment of an electrochemical storage cell.

[0042] Detailed description

[0043] Figure 1 shows an exemplary embodiment of an electrochemical storage cell. The drawing shows the electrochemical storage cell in an exploded view. The cell comprises a bellows 10 and a housing 20 with a contact disk 30 and an insulation disk 31. Furthermore, the cell comprises a pressure plate 32 and an electrode stack 40.

[0044] The housing 20 defines an internal receiving space with a circular cross-section, in which the electrode stack 40 is arranged. The housing comprises a housing shell 21 and a housing top with an upper housing cover 22. The receiving space is delimited by the housing cover on the housing top in the longitudinal direction of the cylindrical housing. In this example, the housing shell and the housing cover are made from a single piece. Alternatively, the housing cover can be screwed to the housing shell or otherwise mechanically connected (e.g., welded or crimped). Furthermore, the housing cover comprises a central cover opening 23, which allows access to the interior of the electrochemical storage cell, for example for filling with an electrolyte and / or as a pressure valve.

[0045] The contacting disk 30 is inserted into the housing and thus engages with the housing cover 22. For this purpose, the contacting disk is provided with a raised portion 33 that fits positively into the central cover opening 23. The housing can, for example, represent the positive pole (+) or negative pole (-) of the electrochemical storage cell, depending on how the cell is constructed and contacted. The polarity is predetermined, for example, by the electrode stack 40. The contacting disk provides contact to the electrode stack and corresponds to the positive pole or the negative pole. The annular insulating disk 31 can be arranged optionally on or below the contacting disk and serves to electrically insulate the poles of the electrochemical cell from one another. The contacting disk and the insulating disk can be screwed to the housing 20 or otherwise mechanically connected (e.g., welded or crimped).

[0046] The pressure plate 32 is configured to correspond to the cross-section of the housing 20, i.e., in this example, it is essentially circular. The pressure plate comprises a pressure plate base 34 and a pressure plate edge 35. The pressure plate base is configured to rest positively on an upper side 41 of the electrode stack. The pressure plate edge comprises a wall that extends in a plate-like manner along the circumference of the pressure plate and rises from the pressure plate base. In this exemplary embodiment, the pressure plate may not have a central opening, for example, for an inner ear 46. The pressure plate is inserted into the housing 20 and permanently connected to it at the housing shell 21, for example, welded, crimped, or screwed. "Permanently connected" here means that the connection is strong enough to withstand at least the compression pressure with which the electrode stack can be pressed. The compression pressure can reach values ​​in the double-digit kN range.The plate shape of the pressure plate, or rather the pressure plate edge, creates an upper, internal cavity between the housing cover and the pressure plate base. The pressure plate acts as a stop surface against which the electrode stack is pressed when the compression pressure is built up. The corresponding counterpressure compresses the electrode stack.

[0047] The pressure plate 32 can be equipped with a safety function through the choice of shape and / or material. For example, the pressure plate can deform in the event of a thermal event, so that the pressure from inside the electrochemical cell cambers the pressure plate. Furthermore, additional safety systems can be incorporated. The pressure plate can have a PTC thermistor, a PTC resistor, or a PTC thermistor. For example, the PTC thermistor can form a ring on or in the pressure plate that becomes an insulator at elevated temperatures and breaks the contact with the electrochemical cell or the electrode stack 40. If the pressure plate deforms, the mechanical connection between the pressure plate and the PTC thermistor can become loose, subsequently interrupting the electrically conductive contact with the electrode stack and thus interrupting the flow of current.

[0048] The electrode stack 40 comprises a plurality of stacks arranged one on top of the other, each stack having electrode layers arranged one on top of the other, namely at least one cathode layer 42, at least one anode layer 43, and at least one separator layer 44 arranged between the cathode layer and the anode layer. Furthermore, the stacks may have additional layers such as insulators and metallic conductor foils (e.g., made of aluminum or copper). The cathode layers and the anode layers are electrically connected to an inner tube 46 (not visible) and / or to the housing shell 21 via corresponding tabs 45. The upper side of the electrode stack engages the pressure plate 32 in a form-fitting manner. The pressure plate base, for example, lies essentially flat on the upper side 41 of the electrode stack. Since the pressure plate is mechanically firmly connected to the housing 20 or the housing shell, the pressure plate is immobile under pressure.An inner tube 46 (not shown) can be provided as a central axis and also serves to electrically contact the electrode layers of the electrode stack.

[0049] The bellows 10 is connected to the housing shell 21 on the underside. The bellows is screwed or otherwise mechanically connected to the housing shell over its entire circumference (for example welded or crimped). The bellows comprises a shell structured with a plurality of corrugations 11 which define an internal cavity 12. The corrugations are formed in the shell by wave-like, alternating diameters. The diameters are selected such that the bellows can be arranged inside the housing 20 and is essentially freely movable along an inner wall of the housing in the stacking direction. The diameters can be selected such that a desired spring strength of the bellows is achieved. The spring strength of the bellows also depends, among other things, on the material of the bellows, which is typically made of metal, and the geometry of the corrugations.In this exemplary embodiment, the bellows encloses a substantially cylindrical cavity. The bellows has a pressure surface 13. The pressure surface is in mechanical operative contact with the underside of the electrode stack. The underside of the electrode stack can be designed as a pressure plate. The pressure surface also has a central opening 14, into which, for example, the inner tube, which is guided through the electrode stack, engages. In the event of a thermal event, (hot) gases can be discharged in a controlled manner from the housing interior via the bellows into a safety volume through the inner tube 46 (see Figure 2A). In the event of a thermal event, the hot gases can be directed in a defined manner into a cavity 12 formed by the bellows, and the gas flow can be restricted. The cavity 12 thus serves as a safety volume.This saves space and alternative protective devices can be reduced or even eliminated.

[0050] The housing 20 as well as the bellows 10 can have a polygonal cross-section, such as a hexagonal cross-section. The storage cell, designed, for example, as a round cell, is a storage cell that can be manufactured cost-effectively and quickly. The round cell enables surface contact between contacting elements (for example, the tabs 45) and the respective electrode layer, which is electrically connected to the respective contacting element. The components of the electrochemical storage cell presented here can, unless explicitly stated, have a cross-section at least similar to that of the housing, so that the components can be connected to the housing or designed to be movable within it. In the case of a round housing or a round cell, the cross-section is essentially circular.

[0051] The electrochemical storage cell is assembled by inserting the components into one another, as shown in Figure 1 and described above. The inner tube 45 serves as the inner stack axis, which centrally brings the components together. When assembled in this way, a spring effect of the bellows 10 can exert a compression pressure on the electrode stack 40. For this purpose, the bellows can be elastically deformed during assembly. The compression pressure is adjusted by connecting the bellows to the housing 20 or closing the housing. The pressure surface 13 of the bellows thereby imparts the compression pressure against the electrode stack. Since the corrugations 11 are freely movable along the inner wall of the housing in the stacking direction, pressure fluctuations, for example due to changes in the layer thicknesses in the electrode stack, can be compensated or adjusted during cell operation.The pressure plate 32, on the other hand, is permanently connected to the housing and thus serves as a counterpressure surface for the compression pressure. The corresponding counterpressure compresses the electrode stack. The bellows functions as a spring element that adjusts the compression pressure through elastic deformation.

[0052] Figures 2A and 2B show the exemplary embodiment of an electrochemical storage cell in different states of charge. In contrast to Figure 1, the cell is shown in the assembled state and in section. The cell is designed, for example, as a solid-state cell, in particular as an anode-free all-solid-state battery (ASSB). The electrode stack 40 shown in section comprises several stacks arranged one on top of the other. Each stack has layers arranged one on top of the other, namely a cathode layer 42, an anode layer, and a separator layer arranged between the cathode layer and the anode layer. Furthermore, the stacks can have additional layers such as insulators and metallic conductor foils (for example made of aluminum or copper), which are not shown here. The cathode layers and the anode layers are electrically contacted with the inner tube or with the housing shell via corresponding tabs.

[0053] This example considers a lithium battery. Here, the cathode layers 42 have essentially the same layer thickness in the charged, partially discharged, and discharged states. In contrast, the layer thickness of the anode layers 43 changes depending on the state of charge. In the charged state, anode layers have been deposited. These are formed by the charging process, with lithium accumulating on conductor foils (e.g., copper foils). The electrode stack grows in height by the thickness of one anode layer x the number of layers. In the discharged state, no anode layer is formed. Lithium is stored in the cathode layers. The lithium migrates from the anode layers through the separator layers into the cathode layers and is stored there.

[0054] The different layer thicknesses are indicated in the drawings (see Figure 2A: the storage cell is charged, Figure 2B: the storage cell is discharged). In all states shown, a desired compression pressure is set, which acts on the electrode stack 40. This is mediated by the bellows 10, mediated by the movable pressure surface 13. As a result of the described charging and discharging processes, the electrode stack expands or contracts in length along the stacking direction. This is evident in the sectional views of Figures 2A and 2B by the varying longitudinal expansion of the bellows. A lower housing cover 24 forms the underside of the housing and closes the housing.

[0055] Figure 2A shows a charged state. The anode layers are formed, and in this state, the electrode stack has its greatest longitudinal extent (in the stacking direction). Accordingly, the bellows in the housing is compressed, and the compression pressure is adjusted according to the longitudinal extent of the bellows. The compression pressure is exerted on the electrode stack via the pressure surface. Also shown is the inner tube, which allows (hot) gases to be discharged from the housing interior via the bellows in a controlled manner during a thermal event. A possible flow is indicated by arrows in the drawing. For this purpose, the pressure surface of the bellows can have a central bulge 15 that coincides with the inner tube. A predetermined breaking point 16, notch, or valve is provided in the central bulge, which breaks, opens, or deforms in a controlled manner during a thermal event.This allows an opening to form on the underside of the housing through which the gas can escape. The gas is initially directed into the internal cavity 12 of the bellows 10, which forms a safety volume. This allows dangerous gases to remain in the housing and defuse the thermal event.

[0056] Figure 2B shows a discharged state. Here, the anode layers 43 are no longer formed, and the electrode stack 40 has a smallest longitudinal dimension in this state. Accordingly, the bellows 10 has the greatest longitudinal dimension, and the compression pressure is adjusted according to this longitudinal dimension of the bellows.

[0057] Figure 2B also shows a possible contact arrangement. The negative pole is designated (-) and the positive pole (+). The polarity shown is an example, whereby the negative pole and the positive pole are interchangeable. The cathode layers 42 of the electrode stack 40 are electrically connected to the housing shell 21 via tabs 45. The housing shell and the bellows 10 are placed on the same pole, in this example the negative pole (-). The upper housing cover 22 is also placed on the same pole, here the negative pole (-). The housing cover is connected to the housing shell and also to (-). The anode layers 43 of the electrode stack are electrically connected to the inner tube 46 via tabs, which is thus placed on the positive pole (+).This also applies to the pressure plate 32 and the contacting disc 30, which is insulated from the housing cover by the insulating disc 31 and is thus placed on the positive pole (+).

[0058] Figures 3A and 3B show an exemplary embodiment of a bellows. The drawings show an external view of a bellows with spiral corrugations. The corrugations are structured on the outer casing by wave-like, alternating diameters. Alternatively, the corrugations can also be arranged parallel. The corrugations give the bellows a spring effect with a Hookian spring constant.

[0059] Figures 4A to 4C show an external view of an exemplary embodiment of an electrochemical storage cell. In this example, the bellows 10 extends far into the housing 20. In the perspectives shown in Figures 4B and 4C, the bellows 10 can be seen in the charge states described above. Figure 4B shows the cell in the charged state (bellows is compressed). The lithium anode layers 43 are formed (the lithium from the cathode layers has, for example, been deposited on a copper conductor foil of the anode layers). Figure 4C shows the cell in the discharged state (bellows is "expanded"). Depending on the cell chemistry, the anode layers are weakly formed or not formed at all; the lithium is embedded in the cathode layers 42.

[0060] Figure 5 shows another embodiment of an electrochemical storage cell. This example is based on Figure 1. The structure is similar, differing only in modifications that allow for the provision of an inner tube 46 over substantially the entire height of the cell.

[0061] In this example, the inner tube 46 is guided from the bellows 10 to the housing cover 22 when the cell is assembled. The inner tube forms, for example, the positive pole (+) of the cell (or vice versa, depending on the structure of the electrode stack). Furthermore, the pressure plate 32 has a central pressure plate opening 36, which essentially coincides with the central cover opening 23 and can engage positively with the pressure plate opening. The pressure plate opening is large enough to accommodate the inner tube 46 or to allow the inner tube to be passed through the pressure plate opening. The inner tube is connected to the bellows 10 with an O-ring 18. The underside of the bellows 10 is provided with insulation 17, for example centrally between the positive (+) and negative pole (-) of the cell.The inner tube 46 extends further through the electrode stack 40 and contacts the electrode layers (anode or cathode layers 42, 43) via tabs 45. The insulating disc 31 rests on the electrode stack. The inner tube engages through a central opening in the insulating disc (which is annular) into a central protrusion 37 in the pressure plate 32. The pressure plate is plate-shaped. Furthermore, the inner tube is centrally connected to the housing cover via an O-ring 25 and an insulating ring 26.

[0062] Figure 6 shows the exemplary embodiment of an electrochemical storage cell in a state of charge. The drawing shows a sectional view of the electrochemical storage cell from Figure 5. The inner tube 46 runs from the upper to the lower housing cover 22, 24 and is guided through corresponding openings in the pressure plate 32, insulation disk 31, electrode stack 40, and bellows 10. The inner tube is centered by the O-rings 18, 25. The polarity reversal results from the electrical contact of the inner tube with the tabs 45 or the electrode layers 42, 43 of the electrode stack. In this example, the positive pole (+) lies on the inner tube or pressure plate. The negative pole (-) lies on the housing 20 and the bellows. Figures 7A and 7B show the assembled electrochemical storage cell from the outside and from above (Figure 7A) and from below (Figure 7B).

[0063] Although the invention has been illustrated and described in detail using exemplary embodiments, the invention is not limited by the exemplary embodiments. Rather, other variations of the invention may be derived therefrom by those skilled in the art without departing from the scope of the invention as defined by the claims.

[0064]

[0065] 10 bellows

[0066] 11 pleated wave

[0067] 12 internal cavity

[0068] 13 printing area

[0069] 14 central opening

[0070] 15 central vault

[0071] 16 Predetermined breaking point, notch or valve

[0072] 17 Isolation

[0073] 18 O-ring

[0074] 20 housings

[0075] 21 Housing shell

[0076] 22 upper housing cover

[0077] 23 central lid opening

[0078] 24 lower housing cover

[0079] 25 O-ring

[0080] 26 Insulation ring

[0081] 30 Contact disc

[0082] 31 Insulating disc

[0083] 32 printing plate

[0084] 33 Increase

[0085] 34 Printing plate base

[0086] 35 Printing plate edge

[0087] 36 Printing plate opening

[0088] 37 central survey

[0089] 40 electrode stacks

[0090] 41 Top

[0091] 42 Cathode layer

[0092] 43 Anode layer

[0093] 44 Separator layer

[0094] 45 tabs

[0095] 46 inner tube

Claims

1. An electrochemical storage cell comprising: - a housing (20) with a housing shell (21), as well as a housing bottom and a housing top, - an electrode stack (40) which is arranged in an interior space of the housing (20) delimited by the housing shell (21) between the housing bottom and the housing top, and - a bellows (10) which is connected to the housing shell (21) on the underside of the housing and is designed to exert a compression pressure on the electrode stack (40) by means of an elastic deformation.

2. The storage cell according to claim 1, wherein the bellows (10) is arranged entirely or partially in the interior and is movable therein.

3. The storage cell according to one of the preceding claims, wherein the bellows (10) is crimped, screwed and / or welded to the housing underside and / or a lower housing cover (24) closes the housing (20).

4. The memory cell according to any one of the preceding claims, wherein - the bellows (10) has substantially parallel or spiral-shaped corrugations (11), and - the pleated shafts (11) are substantially freely movable along an inner wall of the housing (20) in the stacking direction.

5. The memory cell according to any one of the preceding claims, wherein - the electrode stack (40) and the bellows (10) each have central openings through which an inner tube (46) is guided for contacting the electrode stack (40), and - the bellows (10) is movable along the inner tube (46) in the stacking direction in the housing (20).

6. The memory cell according to any one of the preceding claims, wherein - the bellows (10) has a pressure surface (13) which is in operative contact with an underside of the electrode stack (40), and - the pressure surface (31) is arranged to exert the compression pressure on the underside (21) of the electrode stack (40).

7. The storage cell according to one of the preceding claims, wherein the pressure surface (31) and the housing cover in the region of the bellows (10) enclose a safety volume (12) and the safety volume (12) is connected by means of the inner tube (46) for receiving a gas from the electrode stack (40).

8. The memory cell according to any one of the preceding claims, wherein - a pressure plate (15) is immovably connected to a housing cover (16) on the housing top side (13) in the housing (10) and rests on an upper side (22) of the electrode stack (40), and - the pressure plate (15) is arranged to exert a pressure opposite to the compression pressure on the upper side (22) of the electrode stack (20).

9. The memory cell according to one of the preceding claims, wherein the pressure plate (32) is configured to break and / or deform in a controlled manner during a thermal event.

10. A method for adjusting a compression pressure of an electrochemical storage cell, comprising the steps: - Providing an electrochemical storage cell with a housing (20) with a housing shell (21), a housing bottom and a housing top, wherein an electrode stack (40) is arranged in an interior of the housing (20) delimited by the housing shell (21) between the housing bottom and the housing top, - Adjusting the compression pressure by means of a bellows (10) which is connected to the housing shell (21) on the underside of the housing, wherein the bellows (10) is elastically deformed by the compression pressure and exerts the compression pressure on the electrode stack (40), and - Close the housing (20) so that the set compression pressure is maintained.

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