Solid-state battery system

Abstract

The present invention relates to a solid-state battery system (1, 2), having at least one solid-state battery (1) with a preferred size-changing direction (A), and having at least one solid-state battery holder (2) which is designed to counteract the size change of the solid-state battery (1) in the size-changing direction (A) by means of at least one variable fluid volume (23).

Description

[0001] Description

[0002] Solid-state accumulator system

[0003] The present invention relates to a solid-state accumulator system and a solid-state accumulator holder for use in such a solid-state accumulator system.

[0004] It is known to store electrical energy for later and / or mobile use. Mobile applications can include electronic entertainment and communication devices such as mobile phones, as well as vehicles that can be partially or fully electrically powered.

[0005] In any case, rechargeable electrical energy storage devices, also known as accumulators, can be used for this purpose. Accumulators are also known as secondary batteries and colloquially abbreviated to accumulator. An accumulator is a rechargeable galvanic cell with two electrodes and an electrolyte that can store electrical energy electrochemically. The electrolyte serves to conduct ions between the anode and cathode.

[0006] Rechargeable batteries can be manufactured in various sizes and shapes depending on the application. For example, the batteries of mobile phones are usually flat and cuboid-shaped to minimize installation space. If the required installation space is less important, batteries are often cylindrical. Cylindrical and cuboid-shaped batteries are used in many electrical household appliances. Cylindrical batteries, in particular, are usually used in multiples and connected in series and / or arranged one behind the other in direct contact, for example, in remote controls for electronic devices and the like.

[0007] Battery electric vehicles (BEVs), which can also be referred to as electric cars, typically combine a variety of batteries, particularly cylindrical ones. The batteries are often arranged parallel to each other in the floor of the vehicle's chassis. The interconnection of the individual batteries can vary depending on the application and the manufacturer.

[0008] Accumulators differ primarily in the technology used to store electrical energy, which essentially depends on the electrolyte used. Lithium-ion batteries, which are based on lithium compounds in all three phases of the electrochemical cell, are now widely used. Lithium-ion batteries have a comparatively high specific energy, i.e., a comparatively high energy per unit mass, and are typically used in mobile phones, but also in battery-electric vehicles. Lead- or nickel-based batteries are also used in battery-electric vehicles. What these batteries have in common is that they use a liquid electrolyte.

[0009] A disadvantage of batteries with liquid electrolytes is that they typically require cooling to extend the lifespan of the electrodes. This represents a significant additional expense.

[0010] In particular, the required cooling and other devices can account for more than half the volume of, for example, a lithium-ion battery. To extend the lifespan of the batteries, it is also important to avoid fully charging or discharging them.

[0011] Another disadvantage of batteries with liquid electrolytes is that most liquid electrolytes are flammable, which may require additional safety precautions. Furthermore, the liquid electrolyte can leak if damaged, which may also require additional safety measures. A further safety risk can arise with batteries with liquid electrolytes from very low or very high ambient temperatures, as the liquid electrolytes can then freeze or boil.

[0012] Accumulators with an electrolyte made of solid material are also known, which can also be referred to as solid-state batteries. Because the electrolytes are made of solid materials, they cannot leak if damaged, which can increase the safety of using solid-state batteries or eliminate the need for additional safety measures. The solid materials of the electrolytes are also generally non-flammable. Furthermore, solid-state batteries typically have a longer service life than batteries with liquid electrolytes and are easier to store. Solid-state batteries are also easier to miniaturize and can be manufactured, in particular, in the form of a thin film. Furthermore, solid-state batteries generally do not exhibit safety problems or abrupt changes in performance when exposed to temperature fluctuations.

[0013] A disadvantage of solid-state batteries, however, is that they currently have a lower power density and a higher energy density than batteries with liquid electrolytes. This can have a correspondingly adverse impact on applications, as it can limit the acceleration capabilities of battery-electric vehicles. Another disadvantage is that solid-state batteries, or rather their anodes, can experience a significant change in size of, for example, 20% during charging and discharging. This change in size can occur particularly along the longitudinal axis of the solid-state battery, for example, in the case of cylindrical solid-state batteries, in the direction of the longitudinal axis, in which the electrodes also lie opposite each other. This change in size, or this change in length, between the charged and discharged or uncharged states of the solid-state battery can also be referred to as "breathing."

[0014] A further disadvantage is that solid-state batteries must be compressed at a comparatively high pressure of over approximately 10 bar, particularly between approximately 10 bar and approximately 30 bar, to achieve acceptable, particularly good, efficiency, since the applied pressure can lead to better contact between the solid particles and thus increase electrical conductivity. In solid-state batteries with an elongated extension direction, this pressure is usually applied in the elongated extension direction, for example, in the case of cylindrical solid-state batteries, in the direction of the longitudinal axis.

[0015] In any case, this places special demands on solid-state accumulators or on the housings and the like that surround the solid-state accumulators.

[0016] One object of the present invention is to improve the potential uses of solid-state batteries. This should be achieved in a way that is as simple, robust, versatile, cost-effective, and / or space-saving as possible.

[0017] According to the invention, this object is achieved by a solid-state accumulator system and a solid-state accumulator holder having the features of the independent patent claims. Advantageous further developments are described in the subclaims.

[0018] Thus, the present invention relates to a solid-state accumulator system comprising at least one solid-state accumulator with a preferred size change direction and comprising at least one solid-state accumulator holder which is designed to counteract the size change of the solid-state accumulator in the size change direction by means of at least one variable fluid volume.

[0019] The present invention is based on the finding that, as described above, solid-state accumulators or their anodes generally tend to shrink when the stored electrical charge is discharged and to expand again when recharging, which can also be referred to as the "breathing" of the solid-state accumulator. This occurs essentially in one spatial direction, which can thus be referred to as the preferred direction of size change, since the greatest change in size due to the "breathing" of the solid-state accumulator or its accumulator cell(s) occurs in this spatial direction. This change in size has a particular effect in the direction of the elongated extent of the solid-state accumulator, so that the direction of the elongated extent can also be referred to as the preferred direction of size change.This usually also represents the direction in which the two electrodes of the solid-state accumulator are spaced from each other or separated by a separating layer.

[0020] In order to be able to hold or fix a solid-state accumulator in the preferred direction of size change despite the regular, significant change in size, which can easily amount to 20% of the elongated extent of the solid-state accumulator, the invention proposes a solid-state accumulator holder which can counteract this change in size by means of at least one variable fluid volume. For this purpose, the variable fluid volume can be at least almost or completely forceless, or can rest loosely against the solid-state accumulator, when the solid-state accumulator is at its minimum size in the preferred direction of size change, i.e., in the fully or largely discharged state.and, by means of the pressure of the fluid of the variable fluid volume during charging, counteract the resulting increase in the size of the solid-state accumulator in the preferred direction of size change, so that the solid-state accumulator can be held along the direction of the preferred size change even when "breathing," but can still expand in the preferred direction of size change due to its nature. Thus, a secure hold of the solid-state accumulator can be achieved despite the "breathing."

[0021] However, the counteracting of the change in size or the breathing when the battery cell grows can also be achieved in such a way that, in the fully or largely discharged state, when the smallest expansion of the battery cells occurs in the preferred direction of change in size, a predetermined force is exerted on the battery cell by the solid-state battery holder according to the invention, which force is maintained as constant as possible even when the battery cell expands during charging. By means of such pre-tensioning, i.e. by a force acting on the battery cells even when they are not expanded, the uncharged battery cell can also be subjected to force or pressure and compressed, which can support the functioning of solid-state battery cells or, if necessary, even enable it in the first place.

[0022] In any case, the counteracting of the size change or breathing during enlargement of the battery cell according to the invention does not prevent the change in size at all, but merely opposes the change in size or breathing, so that the change in size or breathing can occur against a predetermined force. In particular, this occurs against a predetermined force that is as constant as possible over the entire distance of the change in size. Counteracting the increasing change in size during breathing of the battery cell can also be understood as balancing the force exerted by the increasing change in size during breathing of the battery cell in order to establish an equilibrium between the forces, which can also exist with different battery cell sizes.

[0023] In any case, when the battery cell expands, the counteracting force can be reduced or kept constant to prevent excessive pressure on the battery cell. This can be achieved, for example, by draining the fluid.

[0024] In any case, this force also acts in the opposite direction and compresses the battery cell again when it is discharged and thus shrinks in the preferred direction of size change.

[0025] In any case, this can preferably ensure that a defined pre-voltage is sufficiently high, but not too high, at every charge level, i.e., at every size of the accumulator. In particular, the pre-voltage can remain within a defined pressure range.

[0026] To achieve this, the fluid in the variable fluid volume of the solid-state accumulator holder exerts a force on the solid-state accumulator opposite to the preferred direction of size change of the solid-state accumulator, in particular in order to exert a force on the accumulator cell that is as constant as possible, regardless of the size or charge state of the accumulator cell. In other words, a change in size of the solid-state accumulator or its anode in the preferred direction of size change during charging acts on the solid-state accumulator holder or on its at least one variable fluid volume in such a way that the solid-state accumulator expanding in the preferred direction of size change compressibly compresses the fluid in the variable fluid volume or, in the case of an incompressible fluid, presses it out of the variable fluid volume against a force, so that the compressibility of the fluid orthe counterforce of the incompressible fluid counteracts this expansion, in particular with a force that is as constant as possible.

[0027] The variable fluid volume is therefore fundamentally to be understood functionally in the sense that, according to the invention, by means of a fluid, which can be a (compressible) gas or an (incompressible) liquid, the volume occupied by the fluid relative to the solid-state accumulator or its at least one accumulator cell, which changes size in the preferred direction of change in size, can be varied in such a way that, contrary to the increasing change in size of the solid-state accumulator or its accumulator cell, a force, as constant as possible, can be exerted on the accumulator cell. This also applies to the decreasing change in size of the solid-state accumulator or its accumulator cell during shrinkage.

[0028] To this end, the fluid can be compressed as a compressible gas by the expanding solid-state accumulator or its accumulator cell, thereby exerting a force that counteracts the change in size of the solid-state accumulator or its accumulator cell. Similarly, a force can also be exerted on the contracting solid-state accumulator or its accumulator cell by the gas. In any case, a prestress or preload force can be exerted on the minimal solid-state accumulator or its accumulator cell by filling it with gas at a predetermined pressure.

[0029] Alternatively, the fluid can be forced out of the space between the solid-state accumulator or its accumulator cell and the solid-state accumulator mount as an incompressible liquid by the expanding solid-state accumulator or its accumulator cell. An additional compensating volume can be used for this purpose, as explained in more detail below. Accordingly, a force can also be exerted on the contracting solid-state accumulator or its accumulator cell by the liquid. In any case, a prestress or preload force can be exerted on the minimal solid-state accumulator or its accumulator cell by appropriately designing the compensating volume or the entire fluid space, including the lines.

[0030] In any case, a casing for the variable fluid volume can be formed by a housing of the solid-state accumulator holder, in which the solid-state accumulator or its accumulator cell is movable as a piston, or by an additional, particularly elastic, element that can be compressed from the outside by the solid-state accumulator or its accumulator cell and automatically expand again. The variable fluid volume can thus also structurally designate the casing or element that at least substantially encompasses the functionally variable fluid volume, and can also be referred to as a fluid cushion, a hydraulic cushion, or an air cushion.

[0031] In any case, the use of a variable fluid volume can facilitate a compact arrangement or construction of the solid-state accumulator holder. To this end, the variable fluid volume can be arranged on one or both sides of the solid-state accumulator, acting in the preferred direction of size change of the solid-state accumulator.

[0032] In particular, a variable fluid volume can have a degressive course of the characteristic curve of the spring stiffness due to the compressibility of the gas or the counterforce of the compensation volume of the fluid upon expansion of the solid-state accumulator or its accumulator cell in the preferred direction of change in size, so that over the entire range of the change in size of the solid-state accumulator or its accumulator cell, a counterforce or a pressure that is as constant as possible can be exerted by the variable fluid volume on the solid-state accumulator or its accumulator cell.

[0033] In any case, according to the invention, the solid-state accumulator or its accumulator cell can be securely held by the solid-state accumulator holder, both in the discharged and charged states, as well as during the discharging and charging process. This can be achieved despite the significant change in size in the preferred direction of change in size during the discharging and charging process. By means of the solid-state accumulator holder, the solid-state accumulator or its accumulator cell can be connected to a device or a device, which can be electrically powered or operated by the solid-state accumulator, and thus securely held there.

[0034] Preferably, the variable fluid volume or its casing comprises or consists of an elastomeric material such as ethylene-propylene-diene rubber, natural rubber, or silicone. These can represent particularly simple, cost-effective, and / or durable implementation options.

[0035] According to one aspect of the invention, the variable fluid volume is formed by a gas, preferably air, or the variable fluid volume is filled by a gas. This can represent a possible implementation, as described above. According to a further aspect of the invention, the solid-state accumulator holder has at least one compressor, which is designed and configured to generate a predetermined pressure of the gas. As a result, the fluid volume or the amount of gas within the fluid volume can be increased in order to exert a higher pressure on the solid-state accumulator or on its accumulator cell and / or to maintain a constant pressure on the solid-state accumulator or on its accumulator cell. This can represent a possible implementation, as described above.

[0036] According to a further aspect of the invention, the solid-state accumulator holder comprises at least one check valve, which is designed and configured to open at a predetermined pressure of the variable fluid volume. This allows the fluid volume, the pressure, or the amount of gas within the fluid volume to be reduced in order to exert a slight pressure on the solid-state accumulator or its accumulator cell or to counteract its change in size. This can represent one possible implementation, as described above.

[0037] According to a further aspect of the invention, the variable fluid volume is formed by a liquid, preferably a hydraulic fluid, wherein the solid-state accumulator holder has at least one variable compensation volume, which is fluidly connected to the variable fluid volume and is designed to exert a force on the fluid. This can represent a further possible implementation, as described above.

[0038] According to a further aspect of the invention, the variable compensation volume is designed as an elastic compensation volume with an elastic outer shell that accommodates the liquid in an inner volume. This can represent a possible implementation of a compensation volume. In particular, this can be achieved particularly easily, since active or moving elements such as drives and the like can be dispensed with.

[0039] According to a further aspect of the invention, the elastic outer shell comprises, preferably consists of, an elastomeric material, preferably fiber-reinforced and / or provided with tensile members, or a textile material provided with a sealing membrane. These can be specific implementation options to utilize the respective properties and advantages. This can, in particular, improve the transmission of tensile forces by the elastic outer shell and thereby, in particular, increase the durability of the elastic outer shell.

[0040] According to a further aspect of the invention, the variable compensation volume is designed as a rigid compensation volume with a compensation chamber, the volume of which can be varied by means of a movable spring-loaded or pressure-loaded piston or by means of an elastic membrane. These may be alternative implementation options.

[0041] According to a further aspect of the invention, the variable fluid volume is designed to exert a prestress on the solid-state accumulator. This can be achieved by appropriately designing the variable fluid volume, in that even when the solid-state accumulator is at its minimum size and completely discharged in the preferred direction of size change, a counterforce or pressure of the variable fluid volume can be exerted on the solid-state accumulator or its accumulator cell, which compresses the solid-state accumulator in the direction of the preferred size change and thereby prestresses it. In other words, a prestress as uniform as possible can be exerted on the solid-state accumulator or its accumulator cell, regardless of the state of charge of the solid-state accumulator or its accumulator cell.on its accumulator cell, so that the conductivity and thus the maximum performance of the accumulator cell is not affected or influenced as little as possible by “breathing”.

[0042] This counterforce or pressure of the variable fluid volume of the tension spring can be considered the preload of the variable fluid volume and is preferably at least approximately 10 bar, particularly preferably between approximately 10 bar and approximately 30 bar. In this way, the solid-state accumulator, or its anode, cathode, and electrolyte, can be compressed to increase efficiency, since the applied pressure can lead to better contact between the solid particles and thus increase electrical conductivity.

[0043] According to a further aspect of the invention, the solid-state accumulator holder has at least one fluid inlet designed and configured to allow the fluid quantity of the variable fluid volume to be refilled. This can enable or simplify the refilling or maintaining a constant fluid quantity. Fluid losses that may occur due to leaks, etc., during operation can thus be compensated.

[0044] According to a further aspect of the invention, the solid-state accumulator holder has at least one pressure sensor, which is designed and configured to detect a pressure of the fluid within the variable fluid volume. Based on the pressure values ​​detected by the sensor, it can be detected, for example, whether or when the fluid needs to be refilled, for example in order to keep the amount of fluid within the variable fluid volume constant or to increase the pressure, for example by means of a compressor, within the variable fluid volume. According to a further aspect of the invention, the variable fluid volume has, or preferably consists of, an elastomeric material, preferably one that is fiber-reinforced and / or provided with tensile reinforcement, or a textile material provided with a sealing membrane. These can be concrete implementation options in order to utilize the respective properties and advantages.This can in particular improve the transmission of tensile forces from the variable fluid volume and thereby increase the longevity of the variable fluid volume.

[0045] According to a further aspect of the invention, the solid-state accumulator comprises a plurality of accumulator cells arranged in the preferred size-change direction and / or perpendicular to the preferred size-change direction, wherein the solid-state accumulator holder is configured to counteract the size change of all accumulator cells in the size-change direction by means of at least the variable fluid volume. This can increase the design flexibility for utilizing the present invention.

[0046] In particular, the effort required to implement the present invention can be kept correspondingly low.

[0047] According to a further aspect of the invention, the solid-state accumulator holder comprises a plurality of variable fluid volumes, which are designed and arranged to counteract the change in size of one or more accumulator cells of the solid-state accumulator on one or both sides in the direction of change in size. This can increase the design flexibility for utilizing the present invention. In particular, the effort required to implement the present invention can be kept correspondingly low.

[0048] According to a further aspect of the invention, the

[0049] The solid-state accumulator holder has at least one variable additional volume arranged parallel to the variable fluid volume. The variable additional volume is connected to an ambient fluid, preferably to the ambient air, by means of a first check valve in order to receive ambient fluid when the pressure drops. The variable additional volume is connected to the variable fluid volume by means of a second check valve in order to release fluid to the variable fluid volume when the pressure increases, so that a constant pressure can be maintained in the variable additional volume. This allows pressure equalization of the variable additional volume without active measures, comparable to inflating an air pump.

[0050] Preferably, a spring-loaded check valve can be provided on the side of the variable fluid volume to avoid overpressure there.

[0051] The present invention also relates to a solid-state accumulator holder for use in a solid-state accumulator system as described above. This makes it possible to provide a solid-state accumulator holder for implementing a solid-state accumulator system according to the invention as described above.

[0052] In other words, the present invention is based on the object of suitably preloading a solid-state battery or multiple solid-state batteries with the smallest possible volume and / or the lowest possible weight, while allowing the cells to breathe or expand during charging and discharging. The permissible maximum pressure on the cell should not be exceeded. In particular, the preload element should have a degressive characteristic curve in order to keep the preload change during charging and discharging as small as possible. The solution to this problem involves the use of a hydraulic cushion or an air cushion on one or both end plates of the cell.

[0053] The medium-filled cushion can be connected to a compensating volume. When the cell expands, the cushion can be compressed, and with sufficient force, the volume can be pushed into the compensating volume. If the cell's expansion decreases, the pressure on the end plates decreases, and the volume from the compensating chamber is pushed back into the cushion.

[0054] A compressor or a preloaded cylinder (e.g., preloaded with a disc spring) can be used to maintain the pressure. Alternatively, the compensating volume itself can be an elastic chamber, such as an elastomer bladder (similar to a balloon), so that the increasing expansion with an increase in pressure reduces the wall thickness, resulting in a degressive behavior. When the load decreases, the volume is pumped back from the elastic chamber into the cushion.

[0055] By using an air chamber or a hydraulic chamber, a degressive characteristic curve can be created. In extreme cases, the preload on the cell remains constant.

[0056] Because the pressure within the air cushion is constant, the preload force is evenly distributed across the end plate. A further advantage is that when the cell expands, the cushion can be compressed to a minimum height of the cushion wall, thus offering a significant space saving.

[0057] The compensation volume can be flexibly integrated anywhere in the battery. Using a compressor reduces the installation space only by its volume. An air cushion offers the advantage that air is compressible, allowing the compensation volume, the degressiveness of the characteristic curve, and the applied preload during expansion and contraction to be adjusted to optimal conditions. Optionally, the end plate can be very thin (e.g., a thin metal / plastic plate) or omitted entirely (the air cushion applies the preload directly and evenly), thus saving additional installation space and reducing weight.

[0058] For example, one embodiment could be the cushion as an air chamber defined by an elastomer. This cushion can be supplied with a constant pressure via a compressor and have a pressure relief valve so that the pressure applied to the cell precisely corresponds to the required preload force of the cell. The air cushion and the cell (or cells) can be integrated into a housing or tensioned by a belt.

[0059] In another variant, several air cushions can be connected to the same compressor (e.g. air conditioning compressor) and the same pressure relief valve.

[0060] In another variant, the compressor and the pressure relief valve can be replaced by an elastic compensation volume.

[0061] In another variant, a central elastic compensation volume can be used for two or more cells, to which the individual air cushions are connected.

[0062] In another variant, the compressor and pressure relief valve can be replaced by a preloaded piston and a rigid compensation volume. The piston can be preloaded in such a way that it creates a degressive characteristic curve.

[0063] In another variant, the compressor and the pressure relief valve can be replaced by a pressure equalization chamber with an integrated elastomeric pressure regulating membrane.

[0064] Optionally, a compressor can be used in addition to the compensation volume to compensate for air losses over the lifetime and temperature influences.

[0065] Optionally, an air refilling device can be provided, where the air pressure is checked at regular intervals and corrected if necessary (e.g. during an inspection or by the TÜV (Technical Inspection Association)).

[0066] Optionally, an air refilling device and a pressure sensor can be provided, which determines the air pressure and, if necessary, informs the driver about the need for refilling (similar to a tire pressure sensor).

[0067] The elastomer shell of the air cushion can be fiber-reinforced or made with tensile members.

[0068] The air cushion can also be made without elastomer and instead, for example, from textile with a sealing membrane.

[0069] Another option is to pre-tension two or more cells with a cushion, thus reducing the assembly effort.

[0070] One possible approach is to insert the cells into the battery case, followed by the application of a large air cushion and the case lid. After the lid is installed, the preload can be applied to the individual cells by filling the cushion. The above-mentioned options are available for designing the compensation volume or similar.

[0071] Another possible compensation volume is a pressure vessel with two or more chambers separated by one or more membranes. A force equilibrium exists between the two sides of each membrane. One or more fluid cushions are connected to one side, and the other side is filled with air at a defined pressure, for example. When the air cushions are compressed, fluid is directed into the compensation chamber, increasing the force on the membrane. The air on the other side is compressed, creating a counterforce. A new equilibrium is established, so that the system returns to its original state when the pressure is removed.

[0072] Another possibility is to use cell expansion to generate the necessary air volume. This can be achieved either directly by overstretching an elastic chamber to a certain extent or by using an energy harvesting principle, in which the harvested energy is later converted into fluid pressure. One way to use cell expansion for energy harvesting or to integrate pressure regulation is an additional air cushion, which is compressed during cell expansion and connected to at least one air cushion or the compensation volume via a pressure relief valve (e.g., 3 MPa). The additional air cushion is also equipped with a one-way valve facing the atmosphere, so that air at atmospheric pressure can flow in when the cell decompresses.The advantage is that the system operates without a compressor or additional energy and can automatically compensate for small leaks and settlement of the elastic chamber. It is conceivable that this solution could be applied to applications involving the preloading of stationary solid-state batteries or fuel cells.

[0073] Several exemplary embodiments and further advantages of the invention are explained below in conjunction with the following figures. Figures 1 to 10 each show a schematic representation of a solid-state accumulator system according to the invention with a solid-state accumulator holder according to the invention according to a first to tenth exemplary embodiment.

[0074] The above figure is described in Cartesian coordinates with a longitudinal direction (not shown), a transverse direction Y perpendicular to the longitudinal direction, and a vertical direction Z perpendicular to both the longitudinal direction and the transverse direction Y. The longitudinal direction can also be referred to as depth, the transverse direction Y as width Y, and the vertical direction Z as height Z. The longitudinal direction and the transverse direction Y together form the horizontal, which can also be referred to as the horizontal plane. The longitudinal direction, the transverse direction Y, and the vertical direction Z can together be referred to as spatial directions Y, Z or Cartesian spatial directions Y, Z.

[0075] A solid-state accumulator 1 is always considered, each of which has at least one accumulator cell 10. The accumulator cell 10 represents a rechargeable galvanic element having two electrodes (not shown), i.e., an anode and a cathode, and an electrolyte (not shown) which can store electrical energy on an electrochemical basis and serves to conduct ions between the electrodes. The electrolyte is a solid material. The two electrodes lie opposite each other in the vertical direction Z and enclose the electrolyte between them. In accumulator cells 10 with a solid electrolyte, it is known that a significant change in size of, for example, approximately 20% can occur during charging and discharging. This change in size or length can also be referred to as "breathing."The change in size can occur essentially in an elongated direction of extension of the accumulator cell 10, which in the exemplary embodiments considered corresponds to the vertical direction Z, in which the electrodes are also opposite each other. The preferred direction of change in size A thus corresponds to the elongated direction of extension of the accumulator cell 10 (schematically shown differently for clarity) and thus to the vertical direction Z. The preferred direction of change in size A can also be referred to as the expansion-compression direction A.

[0076] For accumulator cells 10 with a solid electrolyte, it is advantageous to compress the accumulator cells 10 with a comparatively high pressure of more than approximately 10 bar, in particular between approximately 10 bar and approximately 30 bar, since the applied pressure can lead to better contact between the solid particles of the electrolyte and thereby increase electrical conductivity. In the exemplary embodiments considered, the direction of this pressure application corresponds to the longitudinal extension direction of the accumulator cell 10 and thus to the vertical direction Z or the preferred dimension change direction A.

[0077] Figure 1 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a first exemplary embodiment. The accumulator cell 10 of the solid-state accumulator 1 is enclosed by a solid-state accumulator holder 2, which has a frame 20 that accommodates or encloses the solid-state accumulator 1 and other elements of the solid-state accumulator holder 2. Other elements of the solid-state accumulator holder 2 can also be arranged externally on the frame 20. The frame 20 can also be referred to or designed as a holder 20 or as a housing 20.

[0078] Arranged within the frame 20 are a pair of support elements 21, 22, each of which rests flat against the solid-state accumulator 1, parallel to one of the electrodes. The support elements 21, 22 can also be referred to as holding plates 21, 22 or as end plates 21, 22. The first support element 21 can also be referred to as the upper support element 21, and the second support element 22 can also be referred to as the lower support element 22.

[0079] In the first embodiment of Figure 1, the second, lower holding element 22 lies flat against the inside (not designated) of the bottom (not designated) of the housing 20, ie the second, lower holding element 22 is arranged in the vertical direction Z in direct contact between the housing 20 and the accumulator cell 10 or one of its electrodes.

[0080] The first, upper support element 21 is arranged opposite the other electrode of the accumulator cell 10 in the vertical direction Z. Arranged there, also in a plane-parallel manner, is a variable fluid volume 23 in the form of an elastic fluid cushion 23, which is filled with air and is therefore also referred to as an air cushion 23. Alternatively, the use of hydraulic fluid would also be possible. Furthermore, a compressor 24 is connected to the variable fluid volume 23 to increase the air pressure there. A check valve 25 or a one-way valve 25 is also present as a pressure relief valve 25, which opens at a predetermined pressure and releases pressure from the variable fluid volume 23.

[0081] According to the first embodiment of Figure 1, a sufficiently high air pressure can be generated within the variable fluid volume 23 by means of the compressor 24 in order to apply a predetermined force to the accumulator cell 10 in the vertical direction Z from above or along its preferred size-changing direction A, and thus to apply the predetermined force or a corresponding predetermined pressure to the accumulator cell 10. This can bring about a desired preload.

[0082] Furthermore, if the accumulator cell 10 expands or "breathes" in the vertical direction Z as its preferred size change direction A, the air pressure in the variable fluid volume 23 can be reduced by means of the check valve 25, which is designed accordingly, in order to keep the pressure on the accumulator cell 10 constant and yet allow the accumulator cell 10 to expand.

[0083] Conversely, when the accumulator cell 10 shrinks, the force or pressure on the accumulator cell 10 can be kept constant by increasing the air pressure within the variable fluid volume 23 accordingly by means of the compressor 24.

[0084] Thus, according to the invention, a variable air-filled fluid volume 23 enables a change in the size of the accumulator cell 10 and, at the same time, a constant force or a constant pressure of, for example, approximately 10 bar can be exerted on the accumulator cell 10 in order to improve the contact between the solid particles of the electrolyte and thus increase the electrical conductivity. By means of the variable air quantity within the variable fluid volume 23, which can be increased by the compressor 24 and reduced by the check valve 25, a degressive course of the characteristic curve of the spring stiffness of the variable fluid volume 23 can be achieved, so that the most constant pressure force possible can be exerted by the variable fluid volume 23 on the accumulator cell 10 over the entire range of the size change.

[0085] Accordingly, the compressive force or pressure for compressing the solid particles of the electrolyte can be exerted comparatively constantly despite the significant change in size of the accumulator cell 10 or its anode during “breathing”.

[0086] Figure 2 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to a second exemplary embodiment. In this case, a pair of variable fluid volumes 23 are arranged in the vertical direction Z on either side of the accumulator cell 10, so that the previously described properties can be implemented on both sides. The two variable fluid volumes 23 are connected to one another in a fluid-conducting manner (not labeled).

[0087] Figure 3 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a third exemplary embodiment. In this case, a pair of variable fluid volumes 23 are arranged next to one another on the same side of the accumulator cell 10 and are each connected to the compressor 24. Each variable fluid volume 23 has its own check valve 25 with the same opening threshold. This can represent an alternative implementation. More accumulator cells 10 can also be operated in this manner.

[0088] Figure 4 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a fourth exemplary embodiment. In this case, two accumulator cells 10 are arranged next to one another or parallel to one another, on which a variable fluid volume 23 can act, as described with reference to the first exemplary embodiment in Figure 1. This can represent an alternative implementation possibility. More than two accumulator cells 10 can also be used, and / or they can also be arranged differently or in any desired manner.

[0089] Figure 5 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a fifth exemplary embodiment. In this case, two arrangements of accumulator cells 10 and variable fluid volumes 23 are arranged parallel to one another, as described with reference to the first exemplary embodiment in Figure 1, but which have a common compressor 24 and a common check valve 25. This can represent an alternative implementation possibility. More than two accumulator cells 10 can also be used and / or these can also be arranged differently or in any desired manner.

[0090] Figure 6 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a sixth exemplary embodiment. This exemplary embodiment corresponds to the first exemplary embodiment of Figure 1, with the difference that in this case, an elastic compensation volume 26 is used, which has an elastic outer shell 26a in the form of an elastomer bladder 26a, which encloses an inner volume 26b in the form of an elastic chamber 26b. The inner volume 26b of the elastic compensation volume 26 is fluidly connected to the inner volume of the variable fluid volume 23.

[0091] The internal volume of the variable fluid volume 23 and the internal volume 26b of the elastic compensation volume 26 are filled with a hydraulic fluid, so that a constant pressure prevails within the internal volume of the variable fluid volume 23 and the internal volume 26b of the elastic compensation volume 26. If the variable fluid volume 23 is now compressed by the expanding accumulator cell 10, the hydraulic fluid, which is thereby displaced from the variable fluid volume 23, is absorbed by the elastic compensation volume 26 by its elastic outer shell 26a in the form of the elastomer bladder 26a expanding accordingly. This elastic deformation of the elastomer bladder 26a of the elastic compensation volume 26 also causes the hydraulic fluid to be pushed back out of the elastomer bladder 26a into the variable fluid volume 23 if the accumulator cell 10 shortens again.Thus, the invention can also be implemented as described above using a hydraulic fluid as the fluid. A gas such as air could also be used as the fluid.

[0092] Figure 7 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a seventh exemplary embodiment. In this case, instead of an elastic compensation volume 26, as in the sixth exemplary embodiment of Figure 6, a rigid compensation volume 27 is used, which is fluidically connected to the variable fluid volume 23. For this purpose, the rigid compensation volume 27 has a cylinder housing (not labeled), which, together with a linearly movable piston 27b (see arrow), forms a compensation chamber 27a, which is fluidically connected to the variable fluid volume 23.

[0093] As the accumulator cell 10 expands, the movable piston 27b can be pushed away from the hydraulic fluid against the force of a preload spring 27c in the form of a disc spring 27c, which is arranged on the opposite side of the movable piston 27b within a spring chamber 27d. When the accumulator cell 10 contracts again, the hydraulic fluid is pushed by the preload spring 27c, by means of the movable piston 27b, back from the compensation chamber 27a of the rigid compensation volume 27 into the variable fluid volume 23. This also allows the invention to be implemented as described above using a hydraulic fluid as the fluid.

[0094] Figure 8 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to an eighth exemplary embodiment. In this case, instead of the movable piston 27b with preload spring 27c, an elastic membrane 27e in the form of an integrated elastomeric pressure regulating membrane 27e is used, comparable to the sixth exemplary embodiment of Figure 6 of the elastic compensation volume 26 or its elastomer bladder 26a.

[0095] Figure 9 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to a ninth exemplary embodiment. In this case, the movable piston 27b is arranged between the compensation chamber 27a and a pressure compensation chamber 27f, which in turn is fluidically connected to a rigid or elastic compensation volume. This may represent an alternative implementation option.

[0096] Figure 10 shows a schematic representation of a solid-state accumulator system 1, 2 according to the invention with a solid-state accumulator holder 2 according to the invention according to a tenth exemplary embodiment. The variable fluid volume 23 surrounds an additional volume 28 in the form of an additional cushion 28 in an annular manner. A defined amount of air is located in the additional cushion 28 as fluid. The additional cushion 28 is compressed by the expansion of the accumulator cell 10. As a result, the pressure in the air cushion 28 increases. If the pressure in the air cushion 28 is higher than the pressure in the variable fluid volume 23 or in the compensation volume 26, the check valve 25 arranged between the two air volumes of the variable fluid volume 23 and the additional cushion 28 opens. Pressure equalization takes place.

[0097] If, after this pressure equalization, the total system pressure exceeds or approaches a critical value, a spring-loaded check valve 25a opens. The excess air is released, and the pressure in the system drops to the permissible range. This allows small air losses in the system to be compensated. If the accumulator cell 10 contracts, air from outside at the currently prevailing air pressure or pressure level passes through the check valve 25, which is located between the additional cushion 28 and the environment.

[0098] Ambient pressure into the additional cushion 28. For this purpose, the air cushion 28 is firmly connected to the first, upper support element 21. The effect is comparable to an air pump inflating a tire (each discharge / charge corresponds to one pump stroke).

[0099] List of reference symbols (part of the description)

[0100] A preferred direction of size change; stretch-Zcompression direction

[0101] Y transverse direction; width

[0102] Z vertical direction; height

[0103] 1 , 2 Solid-state accumulator system

[0104] 1 solid-state accumulator

[0105] 10 battery cells

[0106] 2 solid-state battery holder

[0107] 20 frame; bracket; housing

[0108] 21 first upper support elements; first upper support plates; first upper end plate

[0109] 22 second, lower support elements; second, lower support plates; second, lower end plate

[0110] 23 variable fluid volumes; fluid cushions; air cushions

[0111] 24 compressor

[0112] 25 Check valve; one-way valve; pressure relief valve

[0113] 25a spring-loaded check valve

[0114] 26 (elastic) compensation volume

[0115] 26a elastic outer shell; elastomer bladder

[0116] 26b Internal volume; elastic chamber

[0117] 27 (rigid) compensation volume

[0118] 27a Compensation chamber

[0119] 27b piston

[0120] 27c Preload spring; disc spring

[0121] 27d spring chamber

[0122] 27e elastic membrane; integrated elastomeric pressure regulating membrane 27f pressure equalization chamber

[0123] 28 variable additional volume; additional cushion

Claims

Patent claims 1. Solid-state accumulator system (1, 2) with at least one solid-state accumulator (1) with a preferred size change direction (A) and with at least one solid-state accumulator holder (2) which is designed to counteract the size change of the solid-state accumulator (1) in the size change direction (A) by means of at least one variable fluid volume (23).

2. Solid-state accumulator system (1, 2) according to claim 1, wherein the variable fluid volume (23) is formed by a gas, preferably air.

3. Solid-state accumulator system (1, 2) according to claim 2, wherein the solid-state accumulator holder (2) has at least one compressor (24) which is designed and configured to generate a predetermined pressure of the gas.

4. Solid-state accumulator system (1, 2) according to claim 2 or 3, wherein the solid-state accumulator holder (2) has at least one check valve (25) which is designed and configured to open at a predetermined pressure of the variable fluid volume (23).

5. Solid-state accumulator system (1, 2) according to claim 1, wherein the variable fluid volume (23) is formed by a liquid, preferably by a hydraulic fluid, wherein the solid-state accumulator holder (2) has at least one variable compensation volume (26; 27) which is fluid-conductingly connected to the variable fluid volume (23) and is designed to exert a force on the liquid. Solid-state accumulator system (1, 2) according to claim 5, wherein the variable compensation volume (26) is designed as an elastic compensation volume (26) with an elastic outer shell (26a) that accommodates the liquid in an inner volume (26b). Solid-state accumulator system (1, 2) according to claim 6, wherein the elastic outer shell (26a) comprises, preferably consists of, an elastomeric material that is fiber-reinforced and / or provided with tensile members, or a textile material provided with a sealing membrane.Solid-state accumulator system (1, 2) according to claim 5, wherein the variable compensation volume (27) is designed as a rigid compensation volume (27) with a compensation chamber (27d), the volume of which can be varied by means of a movable spring-loaded or pressure-loaded piston (27b) or by means of an elastic membrane (27e). Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the variable fluid volume (23) is designed to exert a prestress on the solid-state accumulator (1). Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the solid-state accumulator holder (2) has at least one fluid inlet designed and configured to enable the fluid quantity of the variable fluid volume (23) to be filled. Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the solid-state accumulator holder (2) has at least one pressure sensor designed and configured to detect a pressure of the fluid within the variable fluid volume (23). Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the variable fluid volume (23) comprises, preferably consists of, an elastomeric material, preferably one that is fiber-reinforced and / or provided with tensile members, or a textile material provided with a sealing membrane.Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the solid-state accumulator (1) has a plurality of accumulator cells (10) arranged in the preferred size-change direction (A) and / or perpendicular to the preferred size-change direction (A), wherein the solid-state accumulator holder (2) is designed to counteract the size change of all accumulator cells (10) in the size-change direction (A) by means of at least the variable fluid volume (23). Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the solid-state accumulator holder (2) has a plurality of variable fluid volumes (23) designed and arranged to counteract the size change of one accumulator cell (10) or of a plurality of accumulator cells (10) of the solid-state accumulator (1) on one side or on both sides in the size-change direction (A). Solid-state accumulator system (1, 2) according to one of the preceding claims, wherein the solid-state accumulator holder (2) has at least one variable additional volume (28) arranged parallel to the variable fluid volume (23), wherein the variable additional volume (28) is connected to an ambient fluid, preferably to the ambient air, by means of a first check valve (25) in order to receive ambient fluid when the pressure decreases, and wherein the variable additional volume (28) is connected to the variable fluid volume (23) by means of a second check valve (25) in order to release fluid to the variable fluid volume (23) when the pressure increases, so that a constant pressure can be maintained in the variable additional volume (28). Solid-state accumulator holder (2) for use in a Solid-state accumulator system (1, 2) according to one of the preceding claims.

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