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

Abstract

An electrochemical storage cell comprises a housing (20) with a housing shell (21), as well as a housing bottom and a housing top. An electrode stack (40) is arranged in an interior space of the housing (20), bounded by the housing shell (21), between the housing bottom and the housing top. A bellows (10) is connected to the housing shell (21) at the housing bottom and is configured to exert a compressive pressure on the electrode stack (40) by means of elastic deformation.

Description

[0001] The following description concerns an electrochemical storage cell with a spring-loaded compression device for compensating for the expansion of stacked electrochemical storage cells in the stacking direction. Furthermore, a method for setting the compression pressure of an electrochemical storage cell is described. State of the art

[0002] Solid-state batteries are a special type of rechargeable battery in which the electrodes and electrolyte are made of solid material. Solid-state batteries are increasingly seen as a key component 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.

[0003] 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), no anode is initially formed on the anode side in the discharged state; instead, only a current collector (e.g., a copper foil) is present. In the charged state, an anode forms in the form of pure lithium, which migrates from the cathode (where lithium is stored) through a separator during the charging process and is deposited or forms on the copper foil. To activate the cell, the electrode layers must be compressed. The necessary forces are in the kN range, and the pressures are in the double-digit bar range.

[0004] The state of the art offers solutions to these problems. However, maintaining the set compression forces or pressures within certain limits remains a technical challenge, especially with electrode stacks of variable height. For example, if the forces in the cell are designed for a charged state, the corresponding forces in the intermediate states between charged and discharged would be too low. The cell might not function correctly. Conversely, if the forces in the cell are designed for a discharged state, the compression forces or pressures in the intermediate states between charged and discharged would be too high. The cell might rupture.

[0005] Constant compression of the layers of an electrode stack can be achieved pneumatically or hydraulically. However, this means that either all cells must be supplied with a single pressure unit, or corresponding modules with multiple cells must each have their own pump or pressure unit. This is complex and requires considerable space to compensate for the expansion of individual cells or multiple cells within the module. Hydraulic or pneumatic systems would need a continuous power supply to maintain constant compression forces, even during extended periods of inactivity. These systems are prone to leaks, require a piping system filled with oil, and occupy valuable installation space.

[0006] One task 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 should be provided.

[0007] This problem is solved by an electrochemical storage cell and a storage cell module according to the independent and dependent claims. Advantageous embodiments and further developments are described in the dependent claims. Summary

[0008] It is hereby assumed that each feature described in relation to any embodiment may be used alone or in combination with other features described herein, and may 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 may be used without departing from the scope of the claimed subject matter.

[0009] In the following, an electrochemical storage cell refers to an energy storage device based on electrochemical principles, in particular a rechargeable energy storage device, that is suitable for storing electrical energy and supplying it to a consumer, for example, a consumer in a vehicle. An electrochemical solid-state cell is a solid-state battery, such as a lithium-ion battery, so the following description also refers to a lithium-ion solid-state battery. A solid is understood to be a chemical substance that is rigid at the temperatures typically found in an electrochemical storage cell or at least exhibits a very low tendency to flow, as can be the case, for example, with polymers.

[0010] In the following, the term "lithium-ion battery" is used synonymously for all terms commonly used in the prior art for lithium-containing galvanic cells and electrochemical storage cells (or simply "cell"), such as lithium battery, lithium cell, lithium-ion cell, lithium polymer cell, lithium-ion battery cell, and lithium-ion accumulator. Rechargeable batteries, so-called secondary batteries, are included in particular. The terms "battery" and "electrochemical storage cell" are also used synonymously with "lithium-ion battery" and "lithium-ion cell."

[0011] 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 listed here must follow each other directly. Intermediate layers can also be included, such as a separator, insulator, electrode binder, coatings, and electrically conductive additives, which can be applied to an electrically conductive substrate for the respective electrodes.

[0012] An electrochemical storage cell typically has several electrodes: a positive electrode (cathode) and a negative electrode (anode), which can be electrically contacted via current collectors. Each of these electrodes contains at least one active material, optionally together with additives such as electrode binders and electrically conductive additives, which are applied to an electrically conductive substrate (for example, a metal foil) or to a current collector of the respective electrode. Typically, non-porous and solid conductive substrates made of aluminum (for the positive electrode) or copper (for the negative electrode) are used. Such conductive substrates are typically impermeable to liquid electrolyte and gases.The electrochemical storage cells described below can be used with a liquid electrolyte or, with a solid electrolyte, can be designed as solid-state electrochemical storage cells, for example, as ceramic or polymer-based solid-state batteries. A solid-state electrochemical cell comprises a solid electrolyte.

[0013] Furthermore, an electrochemical storage cell is proposed which is designed to compensate for compression pressure changes resulting from an expansion of an electrode stack in the stack direction.

[0014] According to one embodiment, an electrochemical storage cell comprises a housing. The housing further comprises a housing shell with a lower and a housing upper surface. An electrode stack is arranged in an interior space of the housing, bounded by the housing shell, between the lower and upper surfaces. A bellows is provided and connected to the housing shell at the lower surface. The bellows is designed to exert a compressive pressure on the electrode stack by means of elastic deformation.

[0015] The housing of the electrochemical storage cell can be designed as a round housing (as a cylindrical cell). For example, the housing is cylindrical and has a circular cross-section. The other components within the housing, particularly 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 filled with a solid electrolyte, which is incorporated into the layer sequence of the electrode stack. In this way, an electrochemical solid-state storage cell (ASSB or all-solid-state battery) can be formed.

[0016] 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 known as a metal bellows or metal corrugated tube. In one embodiment, the housing is designed as a cylindrical cell. The bellows has a circular cross-section and encloses a cylindrical housing volume at its base. This housing volume comprises the interior of the housing in which the electrode stack is arranged.

[0017] The housing and bellows can have different cross-sections and geometries; for example, they can have a polygonal cross-section, such as a hexagonal one. A storage cell designed as a cylindrical cell, for instance, is a cost-effective and time-efficient storage cell to manufacture. The cylindrical cell enables planar contact between contact elements and the respective electrode, which is electrically connected to the contact element. The bellows can be described as a spring element with a Hooke's law spring constant, which can be elastically deformed due to its material properties and geometry.

[0018] Depending on the state of charge of the electrochemical storage cell, the electrode stack can have different layer thicknesses. These layer thicknesses can, through the spring action, either compress or release the stack ("compression": the cell discharges; "release": the cell is charged; for example, the anode layers can be designed depending on the state of charge). The bellows is designed to compensate for 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 the pressure to the desired compression pressure.

[0019] The description is based in particular on the considerations outlined below. One aspect concerns an electrochemical storage cell that allows the layer height of the electrode stack to be continuously adjusted and maintained without requiring energy. The bellows acts as 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 specific compression pressure can be set at the electrochemical storage cell. This is achieved, for example, during the assembly or manufacturing of the cell by inserting the bellows into the housing under pressure, thus deflecting the bellows' corrugations into a position corresponding to a specific deflection of the "spring" or a desired compression pressure.When the housing is closed in this adjusted position, the compression pressure acts on the electrode stack. Changes in the layer height of the electrode stack can be continuously readjusted by the spring action of the bellows without requiring external energy.

[0020] 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, bounded by the housing shell, between the housing bottom and the housing top. A bellows is connected to the housing shell at the bottom. The bellows is further configured to exert a compressive pressure on the electrode stack by means of elastic deformation.

[0021] According to one embodiment, the bellows is arranged wholly or partially inside the housing and is movable within it. The bellows is connected to the housing shell on one side and is also movable within the housing. In this way, the bellows can, for example, move inwards or outwards. The fixed point on the housing allows the bellows to exert compression pressure against this point.

[0022] According to one embodiment, the bellows is crimped, screwed, and / or welded to the underside of the housing. Alternatively, or additionally, a lower housing cover is provided to close the housing.

[0023] According to one embodiment, the bellows has essentially parallel or spiral-shaped corrugations. The corrugations are essentially freely movable along an inner wall of the housing in the stacking direction.

[0024] According to one embodiment, the electrode stack and the bellows each have central openings through which an inner tube is guided for contacting the electrode stack. The bellows is movable along the inner tube in the stack direction within the housing. The inner tube serves for the electrical contacting of the electrode layers of the electrode stack and as the central axis of the cell. Furthermore, the inner tube can perform a safety function and serve to direct gases. For example, in the event of a thermal incident, gases can be directed into a safety volume.

[0025] 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 compression pressure on the underside of the electrode stack. For example, the pressure surface is moved by the elastic deformation of the bellows within the housing, so that the pressure surface exerts and adjusts the compression pressure on the electrode stack according to the deflection of the bellows.

[0026] 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 receiving gas from the electrode stack. The safety volume can, for example, absorb hot gases in the event of a thermal incident, thus mitigating the cell's risk.

[0027] According to one embodiment, a pressure plate is rigidly connected to a housing cover at the top of the housing. The pressure plate rests on the upper side of the electrode stack. Furthermore, the pressure plate is configured to exert pressure on the upper side of the electrode stack in the opposite direction to the compression pressure. The pressure plate acts as a stop surface against which the electrode stack is pressed when the compression pressure is applied. The corresponding counter-pressure compresses the electrode stack.

[0028] According to one embodiment, the pressure plate is designed to break and / or deform in a controlled manner in the event of a thermal event. The pressure plate can be equipped with a safety function through the choice of its shape and / or material. For example, in the event of a thermal event, the pressure plate can deform so that the pressure from inside the electrochemical cell causes the plate to buckle. Furthermore, additional safety systems can be provided. The pressure plate can incorporate a PTC thermistor, such as a PTC resistor or PTC resistor. For example, the PTC thermistor can form a ring on or within the pressure plate that becomes an insulator at elevated temperatures, thus breaking the contact with the electrochemical cell.If the pressure plate is deformed, the mechanical connection between the pressure plate and the PTC thermistor can break, thereby interrupting the electrically conductive contact with the electrode stack and thus interrupting the current flow.

[0029] According to one embodiment, the bellows can be replaced by a coil spring. In such an implementation, the pressure surface can be sealed to the housing shell.

[0030] Furthermore, a method for setting the compression pressure of an electrochemical memory cell is proposed. The method initially comprises the step of providing an electrochemical memory cell. The memory cell has a housing with a casing shell, a bottom, and a top. Additionally, an electrode stack is arranged in an interior space of the housing, bounded by the casing shell, between the bottom and top.

[0031] In a further step, the compression pressure is set. 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 this pressure on the electrode stack. Finally, the housing is closed to maintain the set compression pressure.

[0032] Exemplary embodiments of the invention are described below with reference to the accompanying drawings. Further details, preferred embodiments, and further developments will be derived from these. Identical or similarly functioning components are identified by the same reference numerals in the figures. The components shown, as well as their relative sizes, are not to be considered to scale. Where components and parts function identically in different figures, their descriptions will not necessarily be repeated for each subsequent figure. Brief description of the drawings

[0033] In detail: Fig. 1 an embodiment of an electrochemical storage cell, Fig. 2A, Fig. 2B, an embodiment of an electrochemical storage cell in different states of charge, Fig. 3A, Fig. 3B an embodiment of a bellows, Fig. 4A to 4C is an embodiment of an electrochemical storage cell, Fig. 5 another embodiment of an electrochemical storage cell, Fig. 6 the embodiment of an electrochemical storage cell in a state of charge, and Fig. 7A, Fig. 7B is an embodiment of an electrochemical storage cell. Detailed description

[0034] The Fig. Figure 1 shows an 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 disc 30 and an insulating disc 31. Furthermore, the cell includes a pressure plate 32 and an electrode stack 40.

[0035] The housing 20 defines an internal receiving chamber 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 a housing cover 22. The receiving chamber is bounded at the housing top by the housing cover in the longitudinal direction of the cylindrical housing. In this example, the housing shell and the housing cover are manufactured as a single piece. Alternatively, the housing cover can be screwed or otherwise mechanically connected to the housing shell (for example, welded or crimped). Furthermore, the housing cover includes a central opening 23 that allows access to the interior of the electrochemical storage cell, for example, for filling with an electrolyte and / or as a pressure relief valve.

[0036] The contact disc 30 is inserted into the housing and thus engages with the housing cover 22. For this purpose, the contact disc is provided with a raised section 33 that fits snugly into the central opening 23 of the cover. The housing can, for example, represent the positive terminal (+) or negative terminal (-) of the electrochemical storage cell, depending on the cell's configuration and contact arrangement. The polarity is determined, for example, by the electrode stack 40. The contact disc facilitates contact with the electrode stack and corresponds to either the positive or the negative terminal. The annular insulating disc 31 can be arranged either on top of or below the contact disc and serves to electrically isolate the terminals of the electrochemical cell from one another. The contact disc and the insulating disc can be screwed to the housing 20 or otherwise mechanically connected (for example, by welding or crimping).

[0037] The pressure plate 32 is shaped according to the cross-section of the housing 20, in this example essentially circular. The pressure plate comprises a pressure plate base 34 and a pressure plate rim 35. The pressure plate base is designed to rest positively on a top surface 41 of the electrode stack. The pressure plate rim comprises a wall that extends in a disc-like shape along the circumference of the pressure plate and rises from the pressure plate base. In this embodiment, the pressure plate cannot 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, 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 can be compressed. The compression pressure can reach values ​​in the tens of kN range.The plate-like shape of the pressure plate, or rather its edge, creates an upper internal cavity between the housing cover and the base of the pressure plate. The pressure plate acts as a stop against which the electrode stack is pressed when compression pressure is applied. The corresponding counter-pressure compresses the electrode stack.

[0038] The pressure plate 32 can be equipped with a safety function through the choice of its shape and / or material. For example, in the event of a thermal event, the pressure plate can deform so that the pressure from inside the electrochemical cell causes the pressure plate to buckle. 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 within the pressure plate that becomes an insulator at elevated temperatures, thus interrupting 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 break, consequently interrupting the electrically conductive contact with the electrode stack and thus interrupting the current flow.

[0039] The electrode stack 40 comprises several stacks arranged one above the other, each stack having electrode layers arranged one above 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 (for example, made of aluminum or copper). The cathode layers and the anode layers are electrically contacted via corresponding tabs 45 with an inner tube 46 (not visible) and / or with the housing shell 21. The top surface of the electrode stack engages the pressure plate 32 in a form-fitting manner. The base of the pressure plate, for example, lies substantially flat on the top surface 41 of the electrode stack. Since the pressure plate is mechanically fixed to the housing 20 or the housing shell, the pressure plate is not movable under pressure.An inner tube 46 (not shown) can be provided as a central axis and also serves for the electrical contacting of the electrode layers of the electrode stack.

[0040] The bellows 10 is connected to the housing shell 21 at the bottom of the housing. The bellows is screwed or otherwise mechanically connected (e.g., welded or crimped) to the housing shell around its entire circumference. The bellows comprises a shell structured with several corrugated sections 11, which defines an internal cavity 12. The corrugated sections are formed in the shell by varying diameters in a wave-like pattern. The diameters are selected such that the bellows can be arranged inside the housing 20 and is essentially free to move along an inner wall of the housing in the stacking direction. The diameters can be selected to achieve a desired spring force of the bellows. The spring force 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 corrugated sections.In this exemplary embodiment, the bellows encloses a substantially cylindrical cavity. The bellows has a pressure surface 13. The pressure surface is in mechanical 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. Through the inner tube 46, (hot) gases can be discharged in a controlled manner from the interior of the housing via the bellows into a safety volume during a thermal event (see [reference]). Fig. 2A). In the event of a thermal incident, the hot gases can be directed into a cavity 12 formed by the bellows, thus limiting the gas flow. The cavity 12 therefore serves as a safety volume. This saves space and allows alternative protective devices to be reduced or even eliminated.

[0041] The housing 20 and the bellows 10 can have a polygonal cross-section, such as a hexagonal cross-section. The storage cell, designed, for example, as a cylindrical cell, is a cost-effective and time-efficient storage cell to manufacture. The cylindrical cell enables planar contact between contact elements (for example, the tabs 45) and the respective electrode layer, which is electrically connected to the respective contact element. Unless explicitly stated otherwise, the components of the electrochemical storage cell presented here can 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 cylindrical housing or cell, the cross-section is essentially circular.

[0042] The electrochemical storage cell is assembled by combining the components as shown in the Fig. The components shown in Figure 1 and described above are guided into one another. The inner tube 45 serves as the inner stacking axis, which centers and brings the components together. Once assembled in this way, a compression pressure can be exerted on the electrode stack 40 by means of the spring action of the bellows 10. The bellows can be elastically deformed during assembly. The compression pressure is adjusted by connecting the bellows to the housing 20 or by closing the housing. The pressure surface 13 of the bellows then transmits the compression pressure against the electrode stack. Since the corrugated sections 11 are freely movable along the inner wall of the housing in the stacking direction, pressure fluctuations during cell operation, for example, due to changes in the layer thicknesses in the electrode stack, can be compensated for or adjusted.The pressure plate 32, on the other hand, is permanently connected to the housing and thus serves as a counter-pressure surface for the compression pressure. The corresponding counter-pressure compresses the electrode stack. The bellows functions as a spring element, adjusting the compression pressure through elastic deformation.

[0043] The Fig. 2A and Fig. Figure 2B shows an exemplary embodiment of an electrochemical storage cell in different states of charge. In contrast to Fig. Figure 1 shows the cell in its assembled state and in cross-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 cross-section comprises several stacks arranged one above the other. Each stack has layers arranged one above the other, namely a cathode layer 42, an anode layer, and a separator layer arranged between the cathode and anode layers. Furthermore, the stacks may have additional layers such as insulators and metallic conductor foils (for example, made of aluminum or copper), which are not shown here. The cathode and anode layers are electrically contacted with the inner tube or the casing via corresponding tabs.

[0044] This example considers a lithium battery. Here, the cathode layers 42 have essentially the same thickness in the charged, partially discharged, and discharged states. In contrast, the thickness of the anode layers 43 changes depending on the state of charge. In the charged state, anode layers have formed. These are created during the charging process as lithium accumulates on conductive foils (for example, copper foils). The electrode stack grows in height by the thickness of an anode layer multiplied by 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.

[0045] The different layer thicknesses are indicated in the drawings (see below). Fig. 2A: the memory cell is charged, Fig. 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 achieved mediated by the bellows 10 and the movable pressure surface 13. As a result of the described charging and discharging processes, the electrode stack expands or contracts lengthwise along its length. This is shown in the sectional views of the Fig. 2A and Fig. 2B is recognizable by a different longitudinal expansion of the bellows. A lower housing cover 24 forms the underside of the housing and closes the housing.

[0046] In Fig. Figure 2A shows a charged state. The anode layers are formed, and the electrode stack has its greatest longitudinal extent (in the stack direction) in this state. Accordingly, the bellows in the housing is compressed, and the compression pressure adjusts itself according to the longitudinal extent of the bellows. The compression pressure is exerted on the electrode stack via the pressure surface. The inner tube is also shown, which allows (hot) gases to be discharged from the inside of the housing via the bellows in a controlled manner during a thermal event. A possible flow is indicated by arrows in the drawing. 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.In this way, an opening can form on the underside of the housing through which the gas can escape. The gas is first directed into the inner cavity 12 of the bellows 10, which forms a safety volume. This allows hazardous gases to remain within the housing and mitigate the thermal event.

[0047] In Fig. Figure 2B shows a discharged state. Here, the anode layers 43 are no longer formed, and the electrode stack 40 has its smallest longitudinal extent in this state. Accordingly, the bellows 10 has its greatest longitudinal extent, and the compression pressure adjusts itself according to this longitudinal extent of the bellows.

[0048] In the Fig. Figure 2B also shows a possible connection. The negative terminal is labeled (-) and the positive terminal (+). The polarity shown is an example, where the negative and positive terminals 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 connected to the same terminal, in this example the negative terminal (-). The upper housing cover 22 is also connected to the same terminal, here the negative terminal (-). 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 connected to the positive terminal (+).This also applies to the pressure plate 32 and the contact disc 30 shown, which is insulated from the housing cover by the insulating disc 31 and is thus placed on the positive pole (+).

[0049] The Fig. 3A and Fig. Figure 3B shows an embodiment of a bellows. The drawings show an external view of a bellows with helical corrugations. The corrugations are structured on the outer casing by wave-like, alternating diameters. Alternatively, the corrugations can also be designed in parallel. The corrugations give the bellows a spring action with a Hookean spring constant.

[0050] The Fig. Figures 4A to 4C show an embodiment of an electrochemical storage cell in an external view. In this example, the bellows 10 extends far into the housing 20. In the Fig. 4B and Fig. The perspectives shown in 4C reveal the bellows 10 in the charging states described above. Fig. 4B the cell in the charged state (bellows are 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). Fig. Figure 4C shows the cell in its discharged state (the bellows are "expanded"). Depending on the cell chemistry, the anode layers are weakly formed or not formed at all; the lithium is stored in the cathode layers (Figure 42).

[0051] Fig. Figure 5 shows another embodiment of an electrochemical storage cell. This example is based on Fig. 1. The structure is similar and differs only in modifications that allow an inner tube 46 to be provided over essentially the entire height of the cell.

[0052] In this example, the inner tube 46, when the cell is assembled, extends from the bellows 10 to the housing cover 22. The inner tube forms, for example, the positive terminal (+) of the cell (or vice versa, depending on the electrode stack configuration). 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 pass through the pressure plate opening. The inner tube is connected to the bellows 10 by an O-ring 18.

[0053] The underside of the bellows 10 is provided with insulation 17, for example, midway between the positive (+) and negative (-) terminals of the cell. The inner tube 46 extends through the electrode stack 40 and is contacted with 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 projection 37 in the pressure plate 32. The pressure plate is disc-shaped. Furthermore, the inner tube is connected centrally to the housing cover via an O-ring 25 and an insulating ring 26.

[0054] Fig. Figure 6 shows an embodiment of an electrochemical storage cell in a charged state. The drawing shows a sectional view of the electrochemical storage cell. Fig. Figure 5 shows the inner tube 46 extending from the upper to the lower housing cover 22, 24, passing through corresponding openings in the pressure plate 32, insulating disc 31, electrode stack 40, and bellows 10. The inner tube is centered by the O-rings 18, 25. The reverse polarity 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 (+) is located on the inner tube or pressure plate. The negative pole (-) is located on the housing 20 and the bellows. Fig. 7A, Fig. 7B shows the assembled electrochemical storage cell from the outside and from above ( Fig. 7A) as well as from below ( Fig. 7B).

[0055] Although the invention has been illustrated and described in detail with reference to exemplary embodiments, the invention is not limited by these embodiments. Rather, other variations of the invention can be derived by a person skilled in the art without departing from the scope of protection of the invention as defined by the claims. List of reference symbols 10 bellows 11. Wrinkle wave 12 internal cavity 13 printing area 14 central opening 15 central bulge 16. Break point, notch or valve 17 Insulation 18 O-ring 20 cases 21 Housing shell 22 upper case cover 23 central lid opening 24 lower case cover 25 O-ring 26 Insulation ring 30 contact discs 31 insulating disc 32 Printing plate 33 Increase 34 pressure plate floor 35 Printing plate edge 36 Pressure plate opening 37 central survey 40 electrode stacks 41 Top 42 Cathode layer 43 Anode layer 44 Separator layer 45 tabs 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 housing underside 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 enclose a safety volume (12) in the region of the bellows (10) 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 any 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 of: - 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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