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) having an outer housing casing (24), the outer housing casing (24) having a bellows (10). An electrode stack (40) is arranged in the interior of the housing (20). A first pressure plate (50), which is connected to the outer housing casing (11), is designed to exert a compression pressure on the electrode stack (40) with the aid of elastic deformation of the bellows (10).

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 offer 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 layer thicknesses. 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 would 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 burst.

[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, 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 has means to compensate for compression pressure changes due to an expansion of an electrode stack in the stacking direction.

[0017] According to one embodiment of the invention, an electrochemical storage cell comprises a housing. The housing has an outer housing shell comprising a bellows. An electrode stack is arranged in an interior space of the housing. A first pressure plate is connected to the outer housing shell and is configured to exert a compressive pressure on the electrode stack via elastic deformation of the bellows.

[0018] The electrochemical storage cell can be arranged in 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 mixed with a liquid electrolyte, or the electrode stack can be provided with a solid electrolyte that is embossed into the layer sequence of the electrode stack. In this way, an electrochemical solid-state storage cell (abbreviated to ASSB or all-solid-state battery) can be formed.

[0019] The bellows, also called a corrugated tube, has an outer housing shell which has a wave-like, changing diameter. For example, the housing is made of metal, so the bellows is also referred to 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, together with the outer housing shell, encloses a cylindrical housing volume in which the electrode stack is arranged. The housing and thus the bellows can have other cross-sections and geometries; for example, the housing and the 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 produced cost-effectively and quickly.The round cell enables surface contact between the contact elements and the respective electrode, which is electrically connected to the respective contact 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.

[0020] 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.

[0021] The invention 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 achieved, for example, by a pressing tool that engages corresponding corrugations of the bellows on the housing during assembly or manufacture of the cell and thus deflects 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.

[0022] According to one embodiment, the first pressure plate is movably arranged in the housing along a stacking direction of the electrode stack and firmly connected to a housing base. The first pressure plate is configured to exert the compression pressure on an underside of the electrode stack via the elastic deformation of the bellows. For example, the first pressure plate is connected to the outer housing shell. The outer housing shell and the first pressure plate can be made from a single piece or, alternatively, can be screwed together or otherwise mechanically connected (e.g., welded or crimped). The bellows can thus move the pressure plate in the housing along the stacking direction of the electrode stack. This movement occurs as a function of the elastic deformation of the bellows, i.e., its spring action or deflection. The pressure plate thus imparts the compression pressure to the electrode stack.The first printing plate can be described as a movable “printing plate”.

[0023] According to one embodiment, a second pressure plate is immovably connected to a housing cover in the housing and rests on an upper side of the electrode stack. The second pressure plate is configured to exert a pressure on the electrode stack that is opposite to the compression pressure.

[0024] The outer housing shell and the housing cover can be made from a single piece or, alternatively, can be screwed together or otherwise mechanically connected (e.g., welded or crimped). The second pressure plate is mechanically fixed within the housing, so that the pressure plate is in mechanical contact with an upper side of the electrode stack and is configured to exert a counterpressure to the compression pressure on the upper side of the electrode stack. The electrode stack can thus be pressed between the two pressure plates according to the compression pressure in the housing set by the bellows.

[0025] According to one embodiment, the housing is double-walled and comprises a housing intermediate space defined by the outer housing shell and an inner housing shell. The electrode stack is arranged in an interior space of the housing defined by the inner housing shell. Furthermore, the housing intermediate space is configured to accommodate a temperature control medium.

[0026] The housing comprises, for example, an outer wall formed by the outer housing shell. The outer wall thus at least partially has the shape and function of the bellows. The outer wall is a spring that compresses the layers of the electrode stack according to the compression pressure. An inner wall is formed, for example, by the inner housing shell. In the example of a round cell, the inner wall encloses a cylindrical housing volume in which the electrode stack is arranged. In other words, the inner wall is at least partially the surface area of ​​a cylindrical cell. The housing space forms a cavity between the inner and outer walls and can accommodate a temperature control medium. This allows, for example, immersion cooling to be realized. The electrochemical storage cell can be cooled particularly effectively via the outer housing shell, which has an enlarged surface area due to the bellows.

[0027] According to one embodiment, the housing base is double-walled and designed to accommodate the temperature control medium. An inner wall of the double-walled housing base is connected to the inner housing shell. An outer wall of the double-walled housing base is connected to the outer housing shell. The first pressure plate is connected to the inner and outer walls of the double-walled housing base via a common connection point.

[0028] The double-walled housing base expands the capacity of the temperature control medium and thus the surface area available for cooling. The pressure plate is connected to the double-walled housing base via the common connection point and can be moved by the bellows according to the set compression pressure. For this purpose, the inner wall of the housing base can be designed to be flexible, for example, through a material and / or structure to support movement.

[0029] According to one embodiment, the inner wall of the double-walled housing base comprises a wave-shaped membrane plate.

[0030] The underside of the storage cell, or the inner wall of the double-walled housing base, is a wave-shaped membrane plate (preferably made of metal). The membrane plate is wave-shaped, ensuring elasticity between different charge states of the cell. One advantage of the membrane plate is that the plate can be mechanically connected, for example, welded, to the bellows via the common connection point with the inner housing shell and the outer housing shell. This allows the electrodes of the electrode stack to be separated from the cooling medium; no rubber seals are required. The movable pressure plate allows hot gases (in the event of a thermal event) to be precisely and specifically directed through a deliberately weakened predetermined breaking point in the membrane plate (or notches).

[0031] According to one embodiment, the housing has a first connection on a top side for receiving the temperature control medium. The housing further has a second connection on a bottom side for receiving the temperature control medium. The housing is configured for a temperature control medium flow between the first connection and the second connection.

[0032] During operation of the electrochemical storage cell, the temperature control or cooling medium can flow between the first terminal and the second terminal, thus implementing immersion cooling. The heat is dissipated at the cell's outer surface. The bellows supports heat conduction by allowing the cell to be cooled indirectly. In particular, the cell's contacts (or terminals), such as the cathode, can be more effectively cooled, even though the immersion essentially takes place at the outer surface.

[0033] According to one embodiment, the bellows has essentially parallel corrugations. The corrugations are structured on the outer casing by wave-like, alternating diameters. This increases the surface area of ​​the casing, which can lead to better heat transfer between the terminals.

[0034] According to one embodiment, the bellows has essentially spiral-shaped corrugations. The corrugations form, for example, one or more spirals along the housing shell in the stacking direction. The temperature control medium can preferably flow along the spirals, so that a linear flow can develop.

[0035] Furthermore, a method for adjusting a compression pressure of an electrochemical storage cell is proposed.

[0036] According to one embodiment, the method comprises the following steps. First, an electrochemical storage cell is provided. The storage cell has a housing with an outer housing shell configured as a bellows and an electrode stack arranged in an interior of the housing. A compression pressure is set by engaging a pressing tool in the bellows, with a first pressure plate connected to the outer housing shell imparting the compression pressure and exerting it on the electrode stack through elastic deformation of the bellows. Finally, the housing is closed at the set compression pressure.

[0037] The crimping tool can, for example, engage the corrugations and deflect the bellows to set a desired compression pressure. By closing the housing (e.g., by welding or crimping), the compression pressure is applied and maintained by the spring action of the bellows.

[0038] 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.

[0039] Brief description of the drawings

[0040] In detail:

[0041] Figures 1 A, 1 B show an embodiment of an electrochemical storage cell,

[0042] Figures 2A, 2B, 2C show an embodiment of an electrochemical storage cell in different charge states,

[0043] Figures 3A, 3B show embodiments of a housing for an electrochemical

[0044] Storage cell with a bellows, and

[0045] Figures 4A to 4C show another embodiment of an electrochemical

[0046] memory cell.

[0047] Detailed Description Figures 1A and 1B show an exemplary embodiment of an electrochemical storage cell. The figures show an exploded view of the electrochemical storage cell, with the illustration divided into Figures 1A and 1B, and the electrochemical storage cell shown in the combined view of both figures. Figure 1A shows a bellows 10 and a housing 20. Also shown are a contact disk 21 and an insulating disk 22. Figure 1B shows an upper pressure plate 30 and an electrode stack 40. Also shown are a lower pressure plate 50, a membrane plate 60, and a lower housing cover 23. The insulating disk has an opening 28.

[0048] The bellows 10 comprises an outer housing shell 11 and a plurality of corrugations 12. The corrugations are structured into the outer housing shell by wave-like, alternating diameters. The inner diameters are selected so that the housing 20 can be arranged inside the bellows. In this example, the inner diameters are selected so that the bellows encloses an inner cylindrical volume. The outer diameters can be selected to achieve a desired spring strength of the bellows. 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.

[0049] The bellows 10 has a ring-shaped, structured upper side 13, which is designed to receive the (cell) housing 20. An upper opening 14 is provided in the upper side. Furthermore, the bellows has a first connection 15 on the upper side, via which the housing can receive a temperature control medium. The bellows has a ring-shaped, structured lower side 16. The bellows has a second connection 17 on the lower side for receiving the temperature control medium. In this example, the housing 20 is designed as a round housing or cylinder and is made, for example, of metal or another pressure-resistant material. Alternatively, the electrochemical storage cell can also be designed as a prismatic cell, wherein the housing is also constructed of a solid material, usually metal.

[0050] Figure 1A shows an external view of the housing 20. The housing defines an internal receiving space (not shown) with a circular cross-section, into which the electrode stack 40 can be accommodated. The housing comprises an inner housing shell 24 and a housing cover 25. The receiving space is defined on a first side by the housing cover in the longitudinal direction of the cylindrical housing. In this example, the inner housing shell and the housing cover are made from a single piece. Alternatively, the housing cover can be screwed to the inner housing shell or otherwise mechanically connected (e.g., welded or crimped). Furthermore, the housing cover comprises a central cover opening 26, which allows access to the interior of the electrochemical storage cell, for example, for filling with an electrolyte and / or as a pressure valve.

[0051] Together, the bellows 10 and the housing 20 form a double-walled cell housing. An outer housing wall encompasses the outer housing shell 11 of the bellows. An inner housing wall encompasses the inner housing shell 24. The housing walls enclose a housing cavity that can accommodate the temperature control medium, which can be supplied and / or discharged via the connections 15 and 17. As discussed further below, the corrugations 12 can support heat exchange with the environment and, depending on the design, also enable laminar flow between the connections.

[0052] 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 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. Various additional components of the electrochemical storage cell are presented below. Unless explicitly stated, these components have at least a similar cross-section 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.

[0053] The contacting disk 21 can be inserted into the housing and thus engage the housing cover 25. For this purpose, the contacting disk is provided with a raised portion 27 that fits positively into the central cover opening 26. The housing can, for example, represent the positive or negative pole of the electrochemical storage cell, depending on how the cell is constructed. 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 or negative pole. The insulating disk 22 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 or otherwise mechanically connected (e.g., welded or crimped).

[0054] Figure 1B shows the upper pressure plate 30. The upper pressure plate 20 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 31 and a pressure plate edge 32. The pressure plate base is configured to rest positively on an upper side of the electrode stack 40. 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. Furthermore, the pressure plate has a central pressure plate opening 33, which essentially coincides with the central cover opening 26 and can engage positively with the pressure plate opening 33. The pressure plate opening is large enough to accommodate an inner tube or to allow the inner tube to be passed through the pressure plate opening.

[0055] The upper pressure plate 30 is inserted into the housing 20 and permanently connected to the inner housing shell 24, for example by welding, crimping, or screwing. “Permanently connected” here means that the connection is strong enough to withstand at least the compression pressure with which the electrode stack 40 can be pressed. The compression pressure can reach values ​​in the double-digit kN range. Due to the plate shape of the pressure plate or the pressure plate edge 32, an upper, internal cavity is formed between the housing cover 25 and the pressure plate base 31. The upper pressure plate thus 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. In other words, the upper pressure plate has the technical effect of absorbing the compression pressure orto transfer the pressing force from the electrode layers of the electrode stack into the bellows.

[0056] The electrode stack 40 comprises a plurality of stacks arranged one upon the other, each stack having electrode layers arranged one upon the other, namely at least one cathode layer 41, at least one anode layer 42, and at least one separator layer 43 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). The cathode layers and the anode layers are electrically connected to an inner tube (not visible) and / or to the inner housing shell 24 via corresponding tabs 44.

[0057] An upper side of the electrode stack 40 engages the upper pressure plate 30 in a form-fitting manner. The pressure plate base 31, for example, lies essentially flat on the upper side of the electrode stack. Since the upper pressure plate 30 is mechanically firmly connected to the housing 20 or the housing shell 24, the pressure plate is immobile under pressure.

[0058] The lower pressure plate 50 is designed to match the cross-section of the housing 20, i.e., in this example, it is essentially circular. The lower pressure plate comprises a pressure plate base 52 and a pressure plate rim 51. The pressure plate rim optionally includes a seal that extends along the circumference of the pressure plate and seals the pressure plate 50 from the inner housing shell 24, but holds the pressure plate movable within the housing in the stacking direction. In the illustrated embodiment, no seal is necessary because the membrane plate 60 takes over the sealing. Furthermore, the pressure plate has a central pressure plate opening 53, which essentially coincides axially with the cover opening 23, so that, for example, the inner tube can be guided into the central pressure plate opening 53 and ends in this area.

[0059] The pressure plate edge can be flattened relative to the pressure plate base, like a piston in an internal combustion engine, to prevent the pressure plate from tilting in the housing. Tilting is also prevented by the electrode stack 40. Furthermore, the pressure plate opening is large enough to accommodate, for example, the inner tube, or to allow the inner tube to be passed through the pressure plate opening. The lower pressure plate 50 is inserted into the housing and is movable along the inner housing shell 24 and the inner tube in the stacking direction. The lower pressure plate 50 comprises a pipe socket 54 on a side facing away from the electrode stack.

[0060] The diaphragm plate 60 closes off the housing at its underside and thus forms the inner wall of the double-walled housing at the housing base. For this purpose, the diaphragm plate is screwed to the housing or the inner housing shell 24 or is otherwise mechanically connected (e.g., welded or crimped). Alternatively, the diaphragm plate and the housing shell can be made from a single piece. The diaphragm plate can be made from the same material as the housing (e.g., metal) or from a different material, such as plastic. The diaphragm plate has a wavy structure similar to a bellows, i.e., it has waves and valleys. Unlike a bellows, the diaphragm plate is not designed to transmit force. The introduction of the compression force on one side of the diaphragm plate is transferred to the opposite side of the diaphragm plate, so that the plate is subjected to compression.In other words, the diaphragm plate—similar to a photo bellows—can follow a longitudinal deflection of the bellows 10 or a movement of the lower pressure plate 50. The diaphragm plate has a central recess 61 into which the pipe socket 54 can engage and is mechanically connected.

[0061] The lower housing cover 23 closes off the double-walled housing at its underside. For this purpose, the lower housing cover is screwed to the housing or the outer housing shell 11 or is mechanically connected in some other way (e.g., welded or crimped). Alternatively, the lower housing cover and the outer housing shell can be made from a single piece. The diaphragm plate closes off the housing base from the inside to the electrode stack 40, so that the temperature control medium remains in the cavity between the inner and outer walls of the housing despite the compensating movement of the bellows. The lower housing cover 23 forms the underside of the bellows 10 and encloses the second connection 17. A central elevation 28 is mechanically connected to the pipe socket 54 via the central recess 61 of the diaphragm plate.

[0062] The electrochemical storage cell is assembled by inserting the components, as shown in Figures 1A and 1B and described above, into one another. The inner tube serves as the inner stacking axis, which brings together and stacks the bellows 10 and the housing 20 with the two pressure plates 30, 50, and the electrode stack 40. For this purpose, the inner tube 40 is guided, in particular, through the upper opening 14, the cover opening 26, the pressure plate opening 33, and the pressure plate opening 53. The inner tube ends in the central recess 61, into which the pipe socket 54 engages and is mechanically connected.

[0063] Assembled in this way, a spring action of the bellows 10 can exert a compressive pressure on the electrode stack 30. For this purpose, the bellows can be elastically deformed by a pressing tool, in which the tool engages with the bellows or the corrugations 12. As a result, the lower pressure plate 50, which is connected to the outer housing shell 11, transmits the compressive pressure against the upper pressure plate 30 and thus onto the electrode stack 40. The lower pressure plate is movable within the housing and can thus compensate for or adjust pressure fluctuations resulting from changes in the layer thicknesses in the electrode stack. The upper pressure plate 30, on the other hand, is permanently connected to the housing and thus serves as a counterpressure surface for the compressive pressure. The electrode stack is pressed together by the corresponding counterpressure.

[0064] Despite the compensating movement of the bellows 10 (which corresponds to the deflection of a mechanical spring), the diaphragm plate 60 ensures that the temperature control medium remains in the cavity between the inner and outer walls of the housing. The double-walled housing enables both a constant compression pressure and effective heat conduction or cooling during operation of the electrochemical storage cell.

[0065] Figures 2A to 2C show an embodiment of an electrochemical storage cell in a charged, partially discharged, and discharged state in a sectional view. This example corresponds to the embodiment shown in Figures 1A and 1B and described above in the assembled state. In Figure 2A, the storage cell is charged; in Figures 2B and 2C, the storage cell is discharged.

[0066] 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 41, an anode layer 42, and a separator layer 43 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 24 via corresponding tabs 44.

[0067] This example considers a lithium battery. Here, the cathode layers 41 have essentially the same layer thickness in the charged, partially discharged, and discharged states. In contrast, the layer thickness of the anode layers 42 changes depending on the state of charge. In the charged state, anode layers are 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 42 is formed. Lithium is stored in the cathode layers. The lithium migrates from the anode layers through the separator layers 43 into the cathode layers and is stored there. The different layer thicknesses are indicated in the drawings (seeFigure 2A: the storage cell is charged, Figure 2B: the storage cell is partially discharged, and Figure 2C: the storage cell is discharged. In all states shown, a desired compression pressure is set, which acts on the electrode stack 40. This is achieved by the lower pressure plate 50, which is attached to the bellows and can be moved within the housing.

[0068] As a result of the described charging and discharging processes, the electrode stack 40 expands or contracts in length along the stacking direction. This can be seen in the sectional views of Figures 2A to 2C by a different position of the lower pressure plate 50, for example, relative to the lower housing cover 23. The lower housing cover forms the underside of the bellows 10 and closes the double-walled housing. The lower housing cover is connected to the pipe socket 54 via the central elevation 24. The pipe socket engages in the central recess 61 of the membrane plate 60. The central recess is closed during normal operation and can break in the event of a thermal event. For this purpose, the central recess can have a notch 55, which serves as a predetermined breaking point in the event of a thermal event (see Figure 1C).

[0069] For example, the diaphragm plate is welded around the circumference of the housing. The bottom of the pipe socket may be circular and welded to the diaphragm plate. The bottom of the diaphragm plate may be welded in a circular manner to the central protrusion 24 of the lower housing cover.

[0070] In the charged state shown in Figure 2A, the anode layers 42 are formed, and the electrode stack 40 has its greatest longitudinal dimension (in the stacking direction) in this state. Accordingly, the bellows 10 also has its greatest longitudinal dimension. Due to the mechanical connection via the pipe socket 54, the lower pressure plate 50 moves into a position within the inner housing shell 24 that corresponds to the compression pressure.

[0071] The compression pressure is adjusted according to the longitudinal expansion of the bellows. Since the pipe socket is also connected to the diaphragm plate 60 and the diaphragm plate is connected to the housing 20, the diaphragm plate bulges outward, i.e., toward the housing base 23.

[0072] In the partially charged state shown in Figure 2B, the anode layers 42 are partially formed, and in this state the electrode stack 40 has a reduced (average) longitudinal extent compared to the largest longitudinal extent. Accordingly, the bellows 10 also has an average longitudinal extent. Due to the mechanical connection via the pipe socket 54, the lower pressure plate 50 moves to a central position within the inner housing shell, which corresponds to the compression pressure. The compression pressure is adjusted according to the longitudinal extent of the bellows. Since the pipe socket is also connected to the diaphragm plate 60 and the diaphragm plate is connected to the housing 20, the diaphragm plate bulges outward less; in the example shown, the diaphragm is not bulged at all.

[0073] In the discharged state shown in Figure 2C, the anode layers 42 are no longer formed, and the electrode stack 40 has a minimum longitudinal dimension in this state. Accordingly, the bellows 10 also has a minimum longitudinal dimension. Due to the mechanical connection via the pipe socket 54, the lower pressure plate 50 moves into a position within the inner housing shell that corresponds to the compression pressure. The compression pressure is adjusted according to the longitudinal dimension of the bellows. Since the pipe socket is also connected to the diaphragm plate 60 and the diaphragm plate is connected to the housing 20, the diaphragm plate bulges inward, i.e., toward the housing cover 25.

[0074] In the different charge states, a hollow space is formed that accommodates the temperature control medium. Cooling is ensured despite the movement by the bellows 10. Furthermore, the membrane plate 60 or the lower housing cover can each have a notch 55 in the area of ​​the pipe socket 54. The notch is indicated by way of example in Figure 2C and can be configured to break in the event of a thermal event. This makes it possible to precisely direct hot gases from the electrode stack 40 out of the housing via the pipe socket and the notch. In this way, the electrochemical storage cell can be enhanced with an improved safety function in addition to the functions of compensating the compression pressure and effective cooling.

[0075] Figures 3A and 3B show embodiments of a housing for an electrochemical storage cell with a bellows. Figure 3A shows an external view of a bellows with essentially parallel corrugations. The corrugations are structured on the outer housing shell by wave-like, alternating diameters. This increases the surface area of ​​the housing, which can lead to better heat transfer between the connections. This embodiment is also shown in Figures 2A to 2C. There, a possible flow of the temperature control medium between the connections is indicated by arrows. In the case of parallel corrugations, the flow can be set to be laminar if the flow velocity does not exceed a certain value. Figure 3A shows an external view of a bellows with essentially spiral-shaped corrugations. The corrugations form, for example, one or more spirals along the housing shell in the stacking direction.The temperature control medium can flow preferentially along the spirals, allowing a linear flow to develop. This has the additional advantage that the flow can be adjusted to a laminar flow pattern even at higher flow velocities.

[0076] Figures 4A to 4C show another embodiment of an electrochemical storage cell. The figures show, in particular, a possible electrical polarity of the storage cell. In the drawings, the negative pole is designated (-) and the positive pole is designated (+). The polarity shown is an example, with the negative and positive poles being interchangeable.

[0077] Figure 4A shows the housing 20. The inner housing shell 24 and the membrane plate 60 are placed on the same pole, in this example, the negative pole (-). The housing cover is also placed on the same pole, in this case, the negative pole (-), as shown in Figure 4B. Also shown is the contact disk 21, which is placed on the positive pole (+).

[0078] Figure 4C shows a cross-sectional view of the electrochemical storage cell with the polarity reversal introduced in Figures 4A and 4B. It can be seen that the electrode stack is electrically connected to the inner tube via the tabs. As a result, the inner tube rests, for example, on the positive pole (+). The upper pressure plate rests on the electrode stack and is in contact with the inner tube. The upper pressure plate therefore also rests on the positive pole (+). The insulation plate 22 insulates the upper pressure plate and the inner tube from the housing and bellows. The contacting disk 21 is also insulated from the housing and bellows and rests on the positive pole (+). The electrode stack is electrically connected to the inner and outer housing shell via the tabs. Therefore, the housing 20 and the bellows 10 rest on the negative pole (-).The lower pressure plate 50 is in electrical contact with the electrode stack and, due to its layer sequence, also on the negative pole (-). Due to the selected contacting, the electrochemical storage cell is reversed in such a way that the positive pole (+) can be tapped via the top side with the contact disk 21 and the negative pole (-) can be tapped via the bottom side with the housing cover.

[0079] 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.

[0080] List of reference symbols

[0081] 10 bellows

[0082] 11 outer casing

[0083] 12 pleated waves

[0084] 13 ring-shaped structured top

[0085] 14 upper opening

[0086] 15 first connection

[0087] 16 ring-shaped structured underside

[0088] 17 second connection

[0089] 20 housings

[0090] 21 Contact disc

[0091] 22 Insulating disc

[0092] 23 lower housing cover

[0093] 24 inner housing shell

[0094] 25 housing cover

[0095] 26 central lid opening

[0096] 27 Increase

[0097] 28 Increase

[0098] 29 Opening of the insulation plate

[0099] 30 upper pressure plate

[0100] 31 Printing plate base

[0101] 32 printing plate edge

[0102] 33 central printing plate opening

[0103] 40 electrode stacks

[0104] 41 Cathode layer

[0105] 42 Anode layer

[0106] 43 Separator layer

[0107] 44 tabs

[0108] 50 lower pressure plate

[0109] 51 Printing plate edge

[0110] 52 Printing plate base

[0111] 53 central printing plate opening

[0112] 54 Pipe socket notch membrane plate central recess

Claims

1. An electrochemical storage cell comprising: - a housing (20) with an outer housing shell (24), wherein the outer housing shell (24) comprises a bellows (10), - an electrode stack (40) arranged in an interior of the housing (20), and - a first pressure plate (50) which is connected to the outer housing shell (11) and is arranged to exert a compression pressure on the electrode stack (40) by means of an elastic deformation of the bellows (10).

2. The memory cell according to claim 1, wherein - the first pressure plate (50) is arranged in the housing so as to be movable along a stacking direction of the electrode stack (40) and is fixedly connected to a housing base (23), - the first pressure plate (50) is arranged to exert the compression pressure on an underside of the electrode stack (40) by means of the elastic deformation of the bellows (10).

3. The memory cell according to one of the preceding claims, wherein - a second pressure plate (30) is immovably connected to a housing cover (25) in the housing (20) and rests on an upper side of the electrode stack (40), and - the second pressure plate (30) is arranged to exert a pressure on the electrode stack (40) which is opposite to the compression pressure.

4. The memory cell according to any one of the preceding claims, wherein - the housing (20) is double-walled and comprises a housing space which is delimited by the outer housing shell (11) and an inner housing shell (24), - the electrode stack (40) is arranged in an interior space of the housing (20) delimited by the inner housing shell (24), and - the space between the housings is designed to accommodate a temperature control medium.

5. The memory cell according to any one of the preceding claims, wherein - the housing base is double-walled and designed to accommodate the temperature control medium, - an inner wall of the double-walled housing base is connected to the inner housing shell (24), - an outer wall of the double-walled housing base is connected to the outer housing shell (11) and - the first pressure plate (30) is connected to the inner and outer walls of the double-walled housing base via a common connection point.

6. The storage cell according to claim 5, wherein the inner wall of the double-walled housing base comprises a membrane plate (60).

7. The memory cell according to any one of the preceding claims, wherein - the housing has a first connection (15) on an upper side for receiving the temperature control medium, - the housing has a second connection (17) on a bottom side for receiving the temperature control medium, and - the housing (20) is arranged for a temperature control medium flow between the first connection and the second connection.

8. The storage cell according to any one of the preceding claims, wherein the bellows has substantially parallel corrugations (12).

9. The storage cell according to any one of the preceding claims, wherein the bellows has substantially spiral-shaped corrugations (12).

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 an outer housing shell (11) designed as a bellows (10) and an electrode stack (40) arranged in an interior of the housing (20), - Adjusting the compression pressure by engaging a pressing tool in the bellows (10), wherein a first pressure plate (30) connected to the outer housing shell (11) exerts the compression pressure on the electrode stack (40) by means of an elastic deformation of the bellows (10) and - Closing the housing (20) at the set compression pressure.

Images