Pressing device for battery cell stacks

Abstract

A press device for a battery cell stack (10) comprising a plurality of prismatic or pouch-shaped battery cells (11), wherein the press device (1) comprises a first pressure plate (2) and a second pressure plate (3) configured to be positioned at each end of the battery cell stack (10), and is manufactured from a shape memory alloy, the austenite phase (A) of the alloy. f A press device comprising a first pressure plate (2) and a second pressure plate (3) with a pressure element (4) fixed to them, which are kept at a temperature higher than the final transformation temperature of the battery cell (11), thereby the press device (1) expands as the thickness of the battery cell (11) increases and compresses as the thickness of the battery cell (11) decreases.

Description

[Technical Field]

[0001] This invention relates to a pressing device for battery cell stacks. [Background technology]

[0002] Today, energy storage systems consisting of multiple battery cells arranged adjacent to each other to form a stack are known. However, it is known that the thickness of battery cells tends to change due to various factors such as temperature, charge state, or aging. It is known that pressure is applied to the battery cells forming the cell stack, and given that the pressure applied to the aforementioned cells directly affects their efficiency and degradation, the more uniform the pressure applied to the battery cells is throughout their life cycle, the better the behavior of the battery cells and the less degradation they will experience.

[0003] German Patent Application Publication No. 102010012930 describes a battery having a stack of substantially flat single battery cells. The battery cells are arranged between two plates attached to each other by a tensioning device having at least one elastic element arranged in the stacking direction. The tensioning device is configured as a tie rod, each tie rod comprising a spring and a pre-tension element. The battery cells can be manufactured using lithium-ion technology. However, the tensioning device does not exert a constant force on the battery cells; the force is variable and proportional to the expansion of the spring of the aforementioned tensioning device at any given time. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102010012930 Specification [Overview of the project]

[0005] The object of the present invention is to provide a pressing device as defined in the claims.

[0006] The present invention relates to a press device for a battery cell stack comprising a plurality of prismatic or pouch-type battery cells. The press device comprises a first pressure plate and a second pressure plate configured to be positioned at each end of the battery cell stack, wherein a plurality of battery cells are stacked and positioned between the first pressure plate and the second pressure plate, and a pressure element fixed to the first pressure plate and the second pressure plate so that the distance between the first pressure plate and the second pressure plate can be variable. The pressure element is manufactured from a shape memory alloy, wherein the austenite phase (A) of the shape memory alloy is used. f The press is kept at a temperature higher than the final transformation temperature of the battery cell, thereby expanding as the thickness of the battery cell increases and compressing as the thickness of the battery cell decreases.

[0007] In a second aspect, the present invention also relates to a press device 1 for a battery cell stack 10 comprising a plurality of prismatic or pouch-type battery cells 11. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 configured to be positioned at each end of the battery cell stack 10, wherein the plurality of battery cells 11 are stacked and positioned between the first pressure plate 2 and the second pressure plate 3, and pressure elements 4, 5 fixed to the first pressure plate 2 and the second pressure plate 3 so that the distance between the first pressure plate 2 and the second pressure plate 3 may be variable. The pressure elements 4, 5 are manufactured from a shape memory alloy, wherein the austenite phase (A) of the shape memory alloy is used. f The press device 1 is kept at a temperature lower than the final transformation temperature of the battery cell 11, thereby expanding as the thickness of the battery cell 11 increases and compressing as the temperature of the pressure elements 4 and 5 increases.

[0008] In a third aspect, the present invention also relates to a method for monitoring the charge level of a battery. The battery comprises a battery cell stack having a plurality of prismatic or pouch-type battery cells, and a press device. The press device comprises a first pressure plate and a second pressure plate configured to be positioned at each end of the battery cell stack, wherein a plurality of battery cells are stacked and positioned between the first and second pressure plates. The press device also comprises pressure elements fixed to the first and second pressure plates such that the distance between the first and second pressure plates may be variable. The pressure elements are manufactured from a shape memory alloy, thereby causing the press device to expand as the thickness of the battery cells increases and to compress as the thickness of the battery cells decreases. The monitoring method is characterized by measuring the internal resistance or stiffness of the pressure elements and determining the charge state and / or health state of the battery cells based on the internal resistance or stiffness.

[0009] In a fourth aspect, the present invention also relates to a method for controlling a battery. The battery comprises a battery cell stack having a plurality of prismatic or pouch-type battery cells, and a press device. The press device comprises a first pressure plate and a second pressure plate configured to be positioned at each end of the battery cell stack, wherein a plurality of battery cells are stacked and positioned between the first pressure plate and the second pressure plate. The press device comprises pressure elements fixed to the first pressure plate and the second pressure plate such that the distance between the first pressure plate and the second pressure plate may be variable. The pressure elements are manufactured from a shape memory alloy, thereby causing the press device to expand as the thickness of the battery cells increases and to compress as the thickness of the battery cells decreases. The control method is characterized by adjusting the force exerted on the battery cells by the pressure elements by changing the temperature of the pressure elements.

[0010] Unlike the press devices known in the prior art, the press device of the present invention applies a constant force to the battery cells regardless of the expansion of the pressure elements at any given time, and thus improves the behavior of the battery cells throughout their entire life cycle and reduces their degradation.

[0011] These and other advantages and features of the present invention will become apparent upon consideration of the drawings and detailed description of the present invention.

Brief Description of the Drawings

[0012] [Figure 1] The superelastic behavior of the shape memory alloy is shown in a stress-temperature diagram. [Figure 2] A stress-strain diagram of a shape memory alloy having superelastic behavior is shown. [Figure 3] A three-dimensional stress-strain-temperature diagram of the shape memory alloy is shown. [Figure 4] A perspective view of a first embodiment of the press device within a prismatic battery cell stack is shown. [Figure 5] A perspective view of a second embodiment of the press device within a prismatic battery cell stack is shown. [Figure 6] A perspective view of a third embodiment of the press device within a pouch-type battery cell stack in which the second pressure plate is not shown is shown. [Figure 7] A perspective view of the embodiment of FIG. 3 in which the second pressure plate is disposed within the press device is shown. [Figure 8] A perspective view of a fourth embodiment of the press device within a pouch-type battery cell stack in which the second pressure plate is not shown is shown. [Figure 9] A perspective view of the embodiment of FIG. 5 in which the second pressure plate is disposed within the press device is shown. [Figure 10] A schematic view of an embodiment of the control unit is shown.

Modes for Carrying Out the Invention

[0013] Figs. 3 to 9 show four preferred embodiments of the press device 1 of the present invention.

[0014] The press device 1 of the present invention is a press device for a battery cell stack 10 comprising a plurality of prismatic or pouch-type battery cells 11. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 configured to be positioned at each end of the battery cell stack 10, wherein the plurality of battery cells 11 are stacked and positioned between the first pressure plate 2 and the second pressure plate 3. The press device 1 comprises pressure elements 4 and 5 fixed to the first pressure plate 2 and the second pressure plate 3 so that the distance between the first pressure plate 2 and the second pressure plate 3 may be variable. The pressure elements 4 and 5 are manufactured from a shape memory alloy, and the austenite phase (A) of the shape memory alloy is used. f The press device 1 is kept at a temperature higher than the final transformation temperature of the battery cell 11, thereby expanding as the thickness of the battery cell 11 increases and compressing as the thickness of the battery cell 11 decreases.

[0015] In energy storage systems, battery cells are stacked by arranging them adjacent to each other in the stacking direction to form a battery cell stack, and pressure is applied to the battery cells. The force or pressure applied to the battery cells directly affects their efficiency and degradation. As a result, the more uniform the force applied to the battery cells throughout their entire life cycle, the better the behavior of the battery cells, the less degradation occurs, and the longer-lasting the battery cell stack becomes.

[0016] However, battery cells tend to change thickness due to various factors such as temperature, charge state, or aging. On the one hand, in each charge-discharge cycle, the battery increases or decreases in thickness due to battery expansion, and on the other hand, the battery also expands over time (the more battery cells are used, the more they expand). In the press apparatus 1 of the present invention, a first pressure plate 2 and a second pressure plate 3 are placed at each end of the battery cell stack 10, thereby stacking battery cells 11 between the first pressure plate 2 and the second pressure plate 3. The first pressure plate 2 is fixed to both the first pressure plate 2 and the second pressure plate 3 and attached to the second pressure plate by pressure elements 4 and 5 which are arranged longitudinally in the direction of expansion of the battery cells 11, i.e., in the direction of stacking the battery cells 11. As the thickness of the battery cell 11 increases, the cell exerts a mechanical load, namely pressure on the first pressure plate 2 and the second pressure plate 3. Since the first pressure plate 2 and the second pressure plate 3 are attached by pressure elements 4 and 5, the pressure elements 4 and 5 also experience the aforementioned mechanical load.

[0017] Shape memory alloys (SMAs) are metallic alloys that can recover their original shape after being deformed. This property of shape memory alloys is due to a phase change called martensitic transformation that occurs in the aforementioned materials. Martensitic transformation is defined as a crystallographically reversible and instantaneous phase transformation in which atoms move in a coordinated manner, similar to that in shear mechanisms (Otsuka, K., Weyman, C., 1999, Shape Memory Materials. Cambridge University Press, UK). The main characteristic of the aforementioned shape memory alloys is their ability to recover from fairly large strains (up to 8%) through a reversible transformation between phases (austenite and martensite). This transformation can be induced in two ways: by stress that brings about the superelastic properties or superelastic effect of these materials, or by temperature that brings about the shape memory effect.

[0018] Hyperelastic behavior, hyperelastic effect, or hyperelasticity is associated with stress-induced martensitic transformation, where the final temperature of the austenite transformation is Af When the temperature is higher than [a certain value], it results in strain induced by applying a mechanical load that can be removed and recovered. Therefore, the superelastic strain cycle starts at a temperature high enough for the stable phase to become the austenite phase. A f Temperature is a characteristic of each shape memory alloy. As a result, for a shape memory alloy to exhibit superelastic properties, A f the pressure elements 4 and 5 are manufactured from a shape memory alloy that is lower than the working temperature of the pressing device 1.

[0019] Figure 1 shows a typical stress-temperature curve of the SMA, M s 、M f 、A s and A f represent the start temperature (s) and final temperature (f) of the martensite transformation (M), and the start temperature (s) and final temperature (f) of the austenite phase (A), respectively. As shown in Figure 2, when the temperature of the shape memory alloy is higher than A f starting from the austenite structure, when a load is applied, it deforms until it reaches the critical stress level σ Ms for the start of the martensite transformation and ends when it reaches the stress level σ Mf . Macroscopically, this martensite transformation or conversion is characterized by uniform strain of the shape memory alloy at a given temperature with a constant load and at the rate at which the battery cell 11 expands. When the load is removed, as the material enters the martensite phase, recovery from the strain occurs until it reaches the stress level σ As at which the martensite phase is thermodynamically unstable, and nucleation of the austenite phase starts. When it reaches the stress level σ Af , this reverse transformation is completed and the original shape is restored. The ability of the shape memory alloy to deform under stress and recover from the aforementioned strain when at a temperature higher than A f is known as superelastic behavior, the superelastic effect, or superelasticity.

[0020] Unlike press devices known in the latest technology, the press device 1 of the present invention applies a constant force to the battery cell 11 regardless of its thickness at any given time, and is characterized by improving the behavior of the battery cell 11 throughout its entire life cycle and reducing the degradation of the battery cell 11. This effect is due to the fact that the pressure element is manufactured from a shape memory alloy, and the pressure element is A f This is due to the hyperelastic behavior of pressure elements 4 and 5 at temperatures higher than σ. For this purpose, first, pressure elements 4 and 5 are assembled prestressed, and at the most compressed position of the battery cell 11, pressure elements 4 and 5 initiate martensitic transformation, that is, pressure elements 4 and 5 undergo σ Ms and σ Mf This ensures that there is a stress level between the above. Therefore, during the charging cycle of the battery cells 11, as described above, the battery cells 11 expand and thereby increase their thickness, exert a mechanical load on the pressure elements 4 and 5, which, since the pressure elements 4 and 5 are made from shape memory alloy, increase their strain, i.e., elongation, but keep their stress constant. Assuming that the pressure elements 4 and 5 are fixed to the first pressure plate 2 and the second pressure plate 3, the stress on the pressure elements 4 and 5 causes the first pressure plate 2 and the second pressure plate 3 to exert a force on the battery cells 11 that is kept constant during the phase transformation.

[0021] Similarly, during the discharge cycle of the battery cell 11, as described above, the thickness of the cell decreases, a reverse transformation of the shape-effect alloy from martensite to austenite occurs, again exerting a constant force on the battery cell 11. The superelastic behavior of the alloy has a certain hysteresis such that the force exerted by the pressure elements 4 and 5 does not have to be the same during the charging cycle of the battery cell 11 and during the discharge cycle of the battery cell 11, but the aforementioned force is kept constant during the charging cycle and also kept constant during the discharge cycle.

[0022] In one embodiment of the present invention, a shape memory alloy exhibiting minimal hysteresis is used so as to minimize the pressure fluctuations exerted on the battery cell 11 by the pressure elements 4 and 5 during the charging and discharging cycles of the battery cell 11.

[0023] Therefore, the press device 1 of the present invention can passively apply a constant force to the battery cell 11. Furthermore, the press device 1 of the present invention is compact, occupies a very small space, and allows the battery cell stack 11 to have a higher energy density than pressure-compensated battery cell stacks known in the latest technology. Moreover, since the press device 1 does not require the introduction of additional elements between the battery cells 11, it enables the same solution in terms of volume as a pressure-uncompensated battery cell stack. Finally, the press device 1 is cost-effective and easy to implement.

[0024] In one embodiment, pressure elements 4 and 5 exert a constant force when the press device is expanded or compressed. As described above, the austenite phase (A) of the shape memory alloy is f If the temperature is maintained above the final transformation temperature of the battery, the force exerted on the battery cell 11 by the pressure elements 4 and 5 is constant relative to that temperature.

[0025] In one embodiment, the press device 1 includes control means that changes the temperature of the pressure elements 4 and 5, thereby controlling the force exerted by the pressure elements 4 and 5 on the battery cell 11. As described above, the pressure elements 4 and 5 are manufactured from a shape memory alloy. The temperature of the aforementioned pressure elements 4 and 5 is A f As long as the temperature is higher than [a certain value], the pressure elements 4 and 5 exhibit hyperelastic behavior. Furthermore, as shown in Figure 1, as the temperature of the pressure elements 4 and 5 rises, the stress at which constant force conversion occurs in the pressure elements 4 and 5 increases, and as the temperature of the pressure elements 4 and 5 decreases, the stress at which constant force conversion occurs decreases. Assuming that the stress in the pressure elements 4 and 5 is converted into force exerted by the press device 1 of the present invention on the battery cell 11 via the first pressure plate 2 and the second pressure plate 3, the force exerted on the battery cell 11 by the press device 1 can be actively controlled so that the force can take on a desired value for each specific embodiment of the present invention.

[0026] Some possible shape memory alloys that can be used in the press apparatus 1 of the present invention are described below. In one embodiment, the pressure elements 4 and 5 are made from a nickel-titanium (NiTi) alloy containing 49 to 57% by weight of nickel.

[0027] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-titanium-copper (NiTiCu) alloy containing 8 to 20% by weight of copper.

[0028] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-titanium-chromium (NiTiCr) alloy in which the weight of chromium is less than 1%.

[0029] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-titanium-cobalt (NiTiCo) alloy in which the weight of cobalt is less than 4%.

[0030] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-aluminum (NiAl) alloy containing 36-38% by weight of aluminum.

[0031] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-titanium-palladium (NiTiPd) alloy containing 0 to 40% by weight of nickel.

[0032] In one embodiment, the pressure elements 4 and 5 are manufactured from a nickel-titanium-niobium (NiTiNb) alloy containing 0 to 40% by weight of nickel.

[0033] In one embodiment, the pressure elements 4 and 5 are manufactured from a copper-zinc (CuZn) alloy containing 38.5 to 51.5% by weight of zinc.

[0034] In one embodiment, the pressure elements 4 and 5 are manufactured from a copper-zinc (CuZn) alloy and a third element selected from silicon, tin, aluminum, or gallium.

[0035] In one embodiment, the pressure elements 4 and 5 are manufactured from a copper-aluminum-nickel (CuAlNi) alloy containing 28-29% by weight of aluminum and 3-4.5% by weight of nickel.

[0036] In one embodiment, the pressure elements 4 and 5 are manufactured from a copper-aluminum-manganese (CuAlMn) alloy containing 16-18% by weight of aluminum and 9-13% by weight of manganese.

[0037] In one embodiment, the pressure elements 4 and 5 are manufactured from a copper-aluminum-beryllium (CuAlBe) alloy containing 22-25% by weight of aluminum and 0.5-8% by weight of beryllium.

[0038] In one embodiment, the control means of the press device 1 includes an internal resistance sensor and a control unit 500 that communicates with the internal resistance sensor. The internal resistance sensor is configured to measure the internal resistance of the pressure elements 4 and 5 and transmit it to the control unit, and the control unit 500 is configured to determine the strain of the pressure elements 4 and 5 based on their internal resistance. The resistivity of the pressure elements 4 and 5 changes with their strain, and a correlation between both values ​​is known for a particular shape memory alloy. Therefore, based on the measured resistivity of the pressure elements 4 and 5, it is possible to determine the strain of the pressure elements 4 and 5, i.e., how much the pressure elements have expanded or stretched, or how much the pressure elements have been compressed or contracted. Knowing the strain of the pressure elements 4 and 5 also allows us to know how much the thickness of the battery cell 11 has increased.

[0039] In one embodiment, the control unit 500 is configured to determine the charge state and / or health state or remaining life of the battery cell 11 based on the aforementioned internal resistance. The correlation between variations in the thickness of the battery cell 11 and its charge state (i.e., "SOC") and health state (i.e., "SOH") is known. Therefore, by knowing the resistivity of the pressure elements 4 and 5, it is possible to determine the charge state and / or health state of the battery cell 11 by the monitoring method of the present invention. The paper "Experimental Characterization of Lithium-Ion Cell Strain Using Laser Sensors" in the publication Energies 2021, 14, 6281, https: / / doi.org / 10.3390 / en14196281 describes a possible method for obtaining the aforementioned charge state (i.e., "SOC") and health state (i.e., "SOH") based on measurements of the thickness of a battery cell. Therefore, it is known that the charge state and health state of a battery cell can be determined from the thickness of the battery cell. However, by measuring the internal resistance of the pressure elements 4 and 5 manufactured from shape memory alloy, the press device 1 of the present invention can indirectly determine the aforementioned charge state and / or soundness state.

[0040] In one embodiment, the control unit 500 is configured to determine the force applied to the battery cell 11 at any given time based on the internal resistance of the pressure elements 4 and 5, and to change the temperature of the pressure elements 4 and 5 based on that force. The ratio of the stress of the pressure elements 4 and 5 to the strain of the pressure elements 4 and 5 as a function of the temperature of the pressure elements 4 and 5 is known. Therefore, from the measured resistivity of the pressure elements 4 and 5, it is possible to determine the stress of the pressure elements 4 and 5 and the temperature rise of the pressure elements 4 and 5 that are performed to adjust the pressure applied to the battery cell 11 to a desired level. As a result, the pressure elements 4 and 5 have a dual function in the present invention, as they allow for the selection of the pressure applied to the battery cell 11 in addition to applying a constant pressure to the battery cell 11.

[0041] In one embodiment of the present invention, the control unit 500 may include one or more processing units 502, one or more memory elements 504, a bus 508, one or more I / O interfaces 514, and a plurality of instructions, when executed by the processing unit 502, that enable the processing unit 502 to determine the internal resistance of the pressure elements 4, 5 and the temperature of the pressure elements 4, 5, which are performed so that the pressure applied to the battery cell 11 reaches a desired pressure. The control unit 500 may also include a storage device 506 and one or more network processing units 510 interconnected with one or more network input / output (I / O) interfaces 512. Figure 10 shows a schematic diagram of one embodiment of the control unit 500.

[0042] In one embodiment, where the battery stack 10 is located within the battery module of the battery pack, the control unit 500 is implemented in a battery management system (i.e., "BMS") that is either a slave BMS or a master BMS.

[0043] In one embodiment, the control means is configured to supply current to the pressure elements 4 and 5 in order to raise their temperature. In one embodiment, the two ends of the pressure elements 4 and 5 are connected to two power cables, which can supply either current or voltage to the pressure elements 4 and 5. Thus, when current is supplied, the voltage is read, and conversely, when voltage is supplied, the current flowing through the aforementioned pressure elements 4 and 5 is read. By knowing both values, the internal resistance of the pressure elements 4 and 5 can be obtained.

[0044] In one embodiment, the control means is configured to divert heat stored in a thermal management system associated with the battery cell stack 10 to the pressure elements 4 and 5 in order to increase the temperature of the pressure elements 4 and 5.

[0045] However, in other embodiments, other modes can be used to increase the temperature of the pressure elements 4 and 5, based on the Peltier effect, or by radiation, induction, etc.

[0046] In one embodiment, the pressure elements 4, 5 comprise a plurality of wires 5, plates 4, preferably tubes manufactured by extrusion, or straps manufactured from a shape memory alloy, with the first end of each wire 5, plate 4, tube, or strap fixed to the first pressure plate 2, and the second end of each wire 5, plate 4, tube, or strap fixed to the second pressure plate 3.

[0047] In one embodiment of the present invention, the wire 5 or tube has a cross-section such that the diameter of the circle circumscribing the cross-section is 7 mm or less. In another embodiment, the cross-section of the wire 5, plate 4, tube, or strap is such that, considering the dimensions of the cross-section on two perpendicular axes in the plane of the cross-section, the minimum dimension of the cross-section on one of the axes is less than 5 mm.

[0048] In one embodiment of the present invention, the pressure elements 4, 5 comprise a plurality of wires 5 or tubes, the wires 5 or tubes passing through at least two pulleys. This makes it possible to have wires 5 or tubes longer than the separation distance between the first pressure plate 2 and the second pressure plate 3. Therefore, if the maximum strain allowed by the wires 5 or tubes is insufficient to accommodate the expansion of the battery cell 11 which requires greater strain, the aforementioned system of pulleys or pulley guides makes it possible to increase the separation distance between the wires 5 or tubes for the wires 5 or tubes for the wires 5 or tubes for the wires 5 or tubes for the expansion of the battery cell 11 which requires greater strain, compared to when the pulleys are not used.

[0049] Figure 4 shows a first embodiment of the press device 1 of the present invention. In this embodiment, the press device 1 is placed in a battery cell stack 10 comprising a plurality of prismatic battery cells 11. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 positioned at each end of the battery cell stack 10, and the plurality of battery cells 11 are stacked between the first pressure plate 2 and the second pressure plate 3. The press device 1 comprises a pressure element 4, which is manufactured from a shape memory alloy and fixed to the first pressure plate 2 and the second pressure plate 3. The pressure elements 4 and 5 are the austenite phase (A) of the shape memory alloy. f The press device 1 is kept at a temperature higher than the final transformation temperature of the battery cell 11, thereby expanding as the thickness of the battery cell 11 increases and compressing as the thickness of the battery cell 11 decreases, thereby allowing the distance between the first pressure plate 2 and the second pressure plate 3 to be varied.

[0050] In this first embodiment, the pressure element 4 comprises a plurality of plates 4 made from a shape memory alloy, the first end of each plate 4 being fixed to the first pressure plate 2, and the second end of each plate 4 being fixed to the second pressure plate 3.

[0051] In the first embodiment, the press device 1 comprises six plates 4 such that three plates 4 are arranged on the first side of the battery cell stack 10 and three other plates 4 are arranged on the second side of the battery cell stack 1, where the first side and the second side are both sides of the battery cell stack 10. In other embodiments, the press device 1 may have one, two, or another number of plates 4 on each of the first and second sides.

[0052] In the first embodiment, the terminals of the prismatic battery cells 11 are all located on the same side of the battery cell stack 10. Considering the arrangement of the battery cells 11 in Figure 4, the terminals of the battery cells 11 are located on the upper side of the cell stack 10. Preferably, the plates 4 are located on both sides of the battery cell stack 10 where the terminals of the battery cells 10 are not located. Specifically, considering the arrangement of the battery cells in Figure 4, three plates 4 are located on the left side of the cell stack 10 and three other plates 4 are located on the right side.

[0053] Figure 5 shows a second embodiment of the press apparatus 1 of the present invention, in which the plate 4 of the first embodiment is replaced with a wire 5, which is also made from a shape memory alloy.

[0054] In a second embodiment, the press device 1 comprises 10 wires 5 such that 5 wires 5 are arranged on a first side of the battery cell stack 10 and 5 other wires 5 are arranged on a second side of the battery cell stack 1, the first side and the second side being the sides of the battery cell stack 10 where the terminals of the battery cells 11 are not located. In other embodiments, the press device 1 may have one, two, three, or another number of wires 5 on each of the first and second sides.

[0055] Figures 6 and 7 show a third embodiment of the press device 1 of the present invention. In this embodiment, the press device 1 is placed in a battery cell stack 10 comprising a plurality of pouch-type battery cells 11. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 positioned at each end of the battery cell stack 10, and the plurality of battery cells 11 are stacked between the first pressure plate 2 and the second pressure plate 3. The press device 1 comprises a pressure element 4, which is manufactured from a shape memory alloy and fixed to the first pressure plate 2 and the second pressure plate 3. The pressure elements 4 and 5 are the austenite phase (A) of the shape memory alloy. fThe press device 1 is kept at a temperature higher than the final transformation temperature of the battery cells, thereby expanding as the thickness of the battery cells 11 increases and compressing as the thickness of the battery cells 11 decreases, thereby allowing the distance between the first pressure plate 2 and the second pressure plate 3 to be variable. In this third embodiment, each battery cell 11 is placed in a cartridge 6 that acts as a separator between the battery cells 11, and the terminals of each battery cell 11 protrude from the contour of the cartridge 6 through at least one opening 61 located on one side of the cartridge 6 for such purposes.

[0056] In this third embodiment, the pressure element 4 comprises a plurality of plates 4 made from a shape memory alloy, the first end of each plate 4 being fixed to the first pressure plate 2 and the second end of each plate 4 being fixed to the second pressure plate 3.

[0057] In a third embodiment, the press device 1 comprises six plates 4 such that three plates 4 are positioned on a first side of the battery cell stack 10 and three other plates 4 are positioned on a second side of the battery cell stack 1, where the first and second sides are both sides of the battery cell stack 10. In other embodiments, the press device 1 may have one, two, or another number of plates 4 on each of the first and second sides.

[0058] In the third embodiment, the terminals of each pouch-type battery cell 11 are located on both sides of each battery cell 10. However, in other embodiments, both terminals of each battery cell 11 can be located on the same side of the battery cell 11. Considering the arrangement of the battery cell 11 in Figure 3, the terminals of the battery cell 10 are located on the left and right sides of the cell stack 10. Preferably, the plates 4 are located on both sides of the battery cell stack 10 where the terminals of the battery cell 11 are not located. Specifically, considering the arrangement of the battery cell 11 in Figure 6, three plates 4 are located on the upper side of the cell stack 10, and three other plates 4 are located on the lower side.

[0059] As shown in Figures 6 and 7, the cartridge 6 has a plurality of through holes 62 through which a plate 4 passes, so that it is housed inside the cartridge 6 when the cell stack 10 is assembled together with the press device 1 of the present invention. In other embodiments, the plate 4 can be located outside the cartridge 6.

[0060] Figures 8 and 9 show a press apparatus 1 according to a fourth embodiment of the present invention, in which the plate 4 of the third embodiment is replaced with a wire 5, which is also made from a shape memory alloy.

[0061] In the fourth embodiment, the press device 1 comprises 12 wires 5, similar to the third embodiment of the present invention, such that 6 wires 5 are arranged on the first side of the battery cell stack 10 and 6 other wires 5 are arranged on the second side of the battery cell stack 1, where the first and second sides are the sides of the battery cell stack 10 where the terminals of the battery cells 11 are not located. In other embodiments, the press device 1 may have a different number of wires 5 on each of the first and second sides.

[0062] Similar to the third embodiment, the wire is housed inside the cartridge 6 by passing through the through hole 62 of the cartridge 6. In other embodiments, the wire 5 can be located outside the cartridge 6.

[0063] In the fourth embodiment, a pair of wires 5 pass through each through hole 62. However, in other embodiments, one, three, or another number of wires 5 can pass through each through hole 62.

[0064] In the four embodiments described above, the pressure element is the austenite phase (A) of the shape memory alloy. f When kept at a temperature higher than the final transformation temperature of the battery cell, the press device 1 expands as the thickness of the battery cell 11 increases and compresses as the thickness of the battery cell 11 decreases. Furthermore, for a given temperature, the pressure elements 4 and 5 exert a constant force on the battery cell 11 when the press device expands or compresses.

[0065] Furthermore, in four embodiments, the press device includes control means that changes the temperature of the pressure elements 4 and 5, thereby controlling the force exerted by the pressure elements 4 and 5, and this makes it possible to determine the force exerted by the pressure elements 4 and 5 on the battery cell 11.

[0066] A second aspect of the present invention relates to a press device 1 for a battery cell stack 10 comprising a plurality of prismatic or pouch-type battery cells 11. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 configured to be positioned at each end of the battery cell stack 10, wherein the plurality of battery cells 11 are stacked and positioned between the first pressure plate 2 and the second pressure plate 3, and pressure elements 4 and 5 fixed to the first pressure plate 2 and the second pressure plate 3 so that the distance between the first pressure plate 2 and the second pressure plate 3 may be variable. The pressure elements 4 and 5 are manufactured from a shape memory alloy, and the austenite phase (A) of the shape memory alloy is used. f The press device 1 is kept at a temperature lower than the final transformation temperature of the battery cell 11, thereby expanding as the thickness of the battery cell 11 increases and compressing as the temperature of the pressure elements 4 and 5 increases.

[0067] The temperature of pressure elements 4 and 5 is A f When the temperature is below a certain level, shape memory alloys exhibit a characteristic behavior in which the transformation between the austenite and martensite phases of pressure elements 4 and 5 is induced by temperature, resulting in a shape memory effect. Shape memory refers to the ability of a particular material to "remember" its shape, even after severe strain. Once deformed at low temperatures (martensite phase), these materials remain deformed until heated, at which point they return to their original shape before straining.

[0068] Figure 3 shows the three-dimensional stress-strain-temperature diagram of the shape memory alloy, allowing observation of its behavior at different temperatures. d Since this is the highest temperature at which stress-induced martensite can be obtained, the temperature at which stress-induced martensite can be obtained is M s(From the starting temperature of martensitic transformation) d The temperature becomes M d At higher temperatures, the material behaves like a conventional metal that fractures under stress. f (Final temperature of the austenite phase) is higher than M d At lower temperatures, the material exhibits hyperelastic behavior, i.e., stress-induced martensite is generated, as described above in this application. Finally, the last figure shows temperature M f It exhibits martensite strain below (final temperature of the martensite phase). This strain occurs after the stress applied to the shape-effect material is removed. s Temperature and A f When the material recovers between the temperature (the starting temperature and the final temperature of the austenite phase, respectively), that is, when the stress on the material disappears, the strain of the material decreases due to heating, i.e., the material is compressed.

[0069] In one embodiment, pressure elements 4 and 5 exert a constant force when the press device is expanded or compressed. As shown in Figure 3, the austenite phase (A) of the shape memory alloy is f If the temperature is kept below the final transformation temperature of the battery, the force exerted on the battery cell 11 by the pressure elements 4 and 5 is constant relative to that temperature.

[0070] In one embodiment, the press device 1 includes a control means that changes the temperature of the pressure elements 4 and 5, thereby controlling the force exerted by the pressure elements 4 and 5.

[0071] The temperature of the shape memory alloy is A f If it is less than A, when the mechanical load applied to the shape memory alloy is removed, the temperature of the alloy will be A fIt is known that the shape memory alloy can recover from deformation by raising its temperature to a certain value. In this sense, as the expansion of the battery cell 11 decreases during the discharge phase and its thickness decreases, the press device 1 of the present invention can actively control the deformation of the pressure elements 4 and 5 by raising their temperature, so that the pressure elements 4 and 5 are no longer subjected to stress due to the expansion of the battery cell 11. As shown in Figure 3, the deformation, stress, and temperature of the shape memory alloy are related. The press device 1 can change the temperature of the pressure elements 4 and 5 so that they have deformation such that the stress of the pressure elements 4 and 5 remains constant over time. Since this stress is converted into the force that the press device 1 exerts on the battery cell, the press device 1 of the present invention changes the temperature of the pressure elements 4 and 5 so that the force exerted by the pressure elements 4 and 5 on the battery cell 11 remains constant. Furthermore, by changing the temperature of the pressure elements 4 and 5, the force exerted by the pressure elements 4 and 5 on the battery cell 11 is corrected. Therefore, it is possible not only to control the pressure elements 4 and 5 so that they exert a constant force on the battery cell 11, but also to determine the force that the pressure elements 4 and 5 exert on the battery cell 11.

[0072] In one embodiment, the control means includes an internal resistance sensor and a control unit 500 that communicates with the internal resistance sensor. The internal resistance sensor is configured to measure the internal resistance of the pressure elements 4 and 5 and transmit it to the control unit. The control unit 500 is configured to determine the strain of the pressure elements 4 and 5 based on the measured internal resistance.

[0073] In one embodiment of the present invention, the control unit 500 is configured to determine the force exerted on the battery cell 11 at any given time based on the internal resistance of the pressure elements 4 and 5, and to change the temperature of the pressure elements 4 and 5 based on that force.

[0074] In one embodiment of the present invention, the control means is configured to pass an electric current through the pressure elements 4 and 5 in order to raise the temperature of the pressure elements 4 and 5.

[0075] In one embodiment of the present invention, the control means is configured to divert heat stored in a thermal management system associated with the battery cell stack 10 to the pressure elements 4 and 5 in order to increase the temperature of the pressure elements 4 and 5.

[0076] In one embodiment of the present invention, the pressure elements 4 and 5 comprise a plurality of wires 5 or plates 4 made from a shape memory alloy, the first end of each wire 5 or plate 4 being fixed to the first pressure plate 2, and the second end of each wire 5 or plate 4 being fixed to the second pressure plate 3.

[0077] In one embodiment of the present invention, the pressure elements 4 and 5 include a plurality of wires 5, the wires 5 passing through at least two pulleys.

[0078] The first, second, third, and fourth embodiments of the press apparatus 1 of the present invention are also applicable to this second embodiment of the present invention, in which case the pressure elements 4 and 5 are the austenite phase (A) of the shape memory alloy. f The press device 1 is kept at a temperature lower than the final transformation temperature of the battery cells, and there is a difference in that the press device 1 expands as the thickness of the battery cells 11 increases and compresses as the temperature of the pressure elements 4 and 5 increases. Furthermore, in this case, for a given temperature, the pressure elements 4 and 5 exert a constant force on the battery cells 11 when the press device expands or compresses.

[0079] Furthermore, in four embodiments, the press device includes control means that changes the temperature of the pressure elements 4 and 5, thereby controlling the force exerted by the pressure elements 4 and 5, and this makes it possible to determine the force exerted by the pressure elements 4 and 5 on the battery cell 11.

[0080] Given that the technology used in battery cells can be used with lithium-ion battery cells, all-solid-state battery cells, or any other type of battery cell, i.e., prismatic, pouch-type, etc., the aforementioned press apparatus does not represent any limitation on the use of the press apparatus of the present invention.

[0081] Another aspect of the present invention relates to a battery comprising a battery cell stack 10 having a plurality of prismatic or pouch-shaped battery cells 11, and a press device 1 according to the present invention.

[0082] In a third aspect, the present invention relates to a method for monitoring the charge level of a battery, the battery comprising a battery cell stack 10 having a plurality of prismatic or pouch-type battery cells 11, and a press device 1. The press device 1 comprises a first pressure plate 2 and a second pressure plate 3 configured to be positioned at each end of the battery cell stack 10, the plurality of battery cells 11 being stacked and positioned between the first pressure plate 2 and the second pressure plate 3, and pressure elements 4, 5 fixed to the first pressure plate 2 and the second pressure plate 3 so that the distance between the first pressure plate 2 and the second pressure plate 3 may be variable. The pressure elements 4, 5 are manufactured from a shape memory alloy, thereby the press device 1 expands as the thickness of the battery cells 11 increases and compresses as the thickness of the battery cells 11 decreases. The monitoring method is characterized by measuring the internal resistance of the pressure elements 4, 5 and determining the charge state and / or health state of the battery cells 11 based on the internal resistance. The present invention provides a monitoring method for shape memory alloys, specifically for their austenite phase (A f It is effective whether the final temperature is above or below that of the product.

[0083] The resistivity of pressure elements 4 and 5 changes with the strain of the elements, and a correlation between the two values ​​for a particular shape memory alloy is known. Therefore, based on the measured resistivity of pressure elements 4 and 5, it is possible to determine how much the pressure elements 4 and 5 have been deformed, i.e., how much the pressure elements have expanded or stretched, or how much the pressure elements have been compressed or contracted. Similarly, by knowing how much the pressure elements 4 and 5 have been deformed, it is possible to determine the variation in the thickness of the battery cell 11. Furthermore, the correlation between the variation in the thickness of the battery cell 11 and its charge state (i.e., "SOC") and soundness state (i.e., "SOH") is known. Therefore, by knowing the resistivity of pressure elements 4 and 5, it is possible to determine the charge state and / or soundness state of the battery cell 11 by the monitoring method of the present invention. The paper "Experimental Characterization of Lithium-Ion Cell Strain Using Lases Sensors" in the publication Energies 2021, 14, 6281, https: / / doi.org / 10.3390 / en14196281 describes a possible method for obtaining the aforementioned charge state (i.e., "SOC") and state of health (i.e., "SOH") based on measurements of the thickness of a battery cell. Thus, it is known that the charge state and state of health of a battery cell are determined from the thickness of the battery cell. However, the monitoring method of the present invention makes it possible to indirectly determine the charge state and / or state of health by measuring the internal resistance of pressure elements 4, 5 manufactured from shape memory alloy.

[0084] In another embodiment, the monitoring method is characterized by measuring the stiffness of the pressure elements 4 and 5 and determining the charge state and / or health state of the battery cell 11 based on the stiffness. The stiffness is determined as the ratio between the force exerted by the pressure elements 4 and 5 and the displacement of the battery cell 11 during the charge-discharge cycle.

[0085] In one embodiment of the monitoring method, the voltage between the terminals of each battery cell 11 is measured, and the charge state and / or health state of the battery cell 11 is determined based on the voltage and the internal resistance or stiffness of the pressure elements 4, 5. The correlation between the voltage of a battery cell and its charge state is also known. However, since the voltage of a battery cell remains substantially flat during significant fluctuations in the level of charge state, a measurement of voltage alone does not allow for an accurate determination of the charge state. The method of the present invention makes it possible to obtain a more accurate measurement of the charge state of a battery cell by combining the charge state of the battery cell obtained from the voltage reading with the charge state obtained based on a measurement of the internal resistance of the pressure elements.

[0086] The method for monitoring the charge level of a battery according to the present invention is configured to be performed in a battery comprising a battery cell stack 10 having a plurality of prismatic or pouch-type battery cells 11, and a press device 1 according to the present invention in any of its possible embodiments.

[0087] A fourth aspect of the present invention relates to a battery control method comprising a battery cell stack 10 having a plurality of prismatic or pouch-shaped battery cells 11, and a press device 1 having a first pressure plate 2 and a second pressure plate 3 configured to be positioned at each end of the battery cell stack 10, wherein the plurality of battery cells 11 are stacked and arranged between the first pressure plate 2 and the second pressure plate 3, and pressure elements 4 and 5 are fixed to the first pressure plate 2 and the second pressure plate 3 such that the distance between the first pressure plate 2 and the second pressure plate 3 can be variable, and the pressure elements 4 and 5 are manufactured from a shape memory alloy, thereby causing the press device 1 to expand as the thickness of the battery cells 11 increases and to compress as the thickness of the battery cells 11 decreases. The control method adjusts the force exerted by the pressure elements 4 and 5 on the battery cells 11 by changing the temperature of the pressure elements 4 and 5.

[0088] Furthermore, as shown in Figure 1, the austenite phase (A) of the shape memory alloy fIt is known that when pressure elements 4 and 5 are held at a temperature higher than their final transformation temperature, the stress in the pressure elements 4 and 5 increases as their temperature rises, and decreases as their temperature falls. Assuming that the stress in the pressure elements 4 and 5 is converted into the force that the aforementioned press device 1 exerts on the battery cell 11 via the first pressure plate 2 and the second pressure plate 3, the force exerted on the battery cell 11 by the press device 1 can be actively controlled by the control method of the present invention.

[0089] Shape memory alloys are the austenite phase of the alloy (A f When the temperature of the pressure elements 4 and 5 is kept below the final transformation temperature, as the temperature of the pressure elements 4 and 5 rises, the strain of the pressure elements 4 and 5 decreases, thereby allowing the pressure elements 4 and 5 to exert a constant force on the battery cell 11. Similarly, when the aforementioned temperature rises, it is possible to control the force exerted by the pressure elements 4 and 5, thereby making it possible to determine the force exerted by the pressure elements 4 and 5 on the battery cell 11.

[0090] In one embodiment of the control method of the present invention, the temperature of the pressure elements 4 and 5 is increased by passing an electric current through the pressure elements 4 and 5.

[0091] The battery control method of the present invention is configured to be performed in a battery comprising a battery cell stack 10 having a plurality of prismatic or pouch-type battery cells 11, and a press device 1 according to the present invention in any of its possible embodiments.

Claims

1. A press device for a battery cell stack (10) comprising a plurality of prismatic or pouch-shaped battery cells (11), wherein the press device (1) A first pressure plate (2) and a second pressure plate (3) are configured to be positioned at each end of the battery cell stack (10), wherein the plurality of battery cells (11) are stacked and positioned between the first pressure plate (2) and the second pressure plate (3), The system includes pressure elements (4, 5) fixed to the first pressure plate (2) and the second pressure plate (3) so that the distance between the first pressure plate (2) and the second pressure plate (3) can be varied, The pressure elements (4, 5) are manufactured from a shape memory alloy, and the austenite phase (A) of the shape memory alloy is manufactured from a shape memory alloy. ｆ A press device characterized in that it is kept at a temperature higher than the final transformation temperature of the battery cell (11), thereby causing the press device (1) to expand as the thickness of the battery cell (11) increases and to compress as the thickness of the battery cell (11) decreases.

2. The press apparatus according to claim 1, wherein the pressure elements (4, 5) exert a constant force when the press apparatus is expanded or compressed.

3. The press apparatus according to claim 1 or 2, further comprising control means for changing the temperature of the pressure elements (4, 5) and thereby controlling the force exerted by the pressure elements (4, 5).

4. The press apparatus according to claim 3, wherein the control means comprises an internal resistance sensor and a control unit (500) that communicates with the internal resistance sensor, the internal resistance sensor is configured to measure the internal resistance of the pressure elements (4, 5) and transmit the internal resistance to the control unit, and the control unit (500) is configured to determine the strain of the pressure elements (4, 5) based on the measured value of the internal resistance.

5. The press apparatus according to claim 4, wherein the control unit (500) is configured to determine the charge state and / or health state of the battery cell (11) based on the internal resistance.

6. The press apparatus according to claim 4, wherein the control unit (500) is configured to determine the force applied to the battery cell (11) for an arbitrary given time based on the internal resistance of the pressure elements (4, 5), and to change the temperature of the pressure elements (4, 5) based on the force.

7. The press apparatus according to claim 6, wherein the control means is configured to pass an electric current through the pressure elements (4, 5) in order to raise the temperature of the pressure elements (4, 5).

8. The press apparatus according to claim 6, wherein the control means is configured to divert heat stored in a thermal management system associated with the battery cell stack (10) to the pressure elements (4, 5) in order to increase the temperature of the pressure elements (4, 5).

9. The press apparatus according to claim 1 or 2, wherein the pressure elements (4, 5) comprise a plurality of wires (5) or plates (4) manufactured from the shape memory alloy, the first end of each wire (5) or plate (4) being fixed to the first pressure plate (2), and the second end of each wire (5) or plate (4) being fixed to the second pressure plate (3).

10. The press apparatus according to claim 9, wherein the pressure elements (4, 5) comprises a plurality of wires (5), and the wires (5) pass through at least two pulleys.

11. A press device for a battery cell stack (10) comprising a plurality of prismatic or pouch-shaped battery cells (11), wherein the press device (1) A first pressure plate (2) and a second pressure plate (3) are configured to be positioned at each end of the battery cell stack (10), wherein the plurality of battery cells (11) are stacked and positioned between the first pressure plate (2) and the second pressure plate (3), The system includes pressure elements (4, 5) fixed to the first pressure plate (2) and the second pressure plate (3) so that the distance between the first pressure plate (2) and the second pressure plate (3) can be varied, The pressure elements (4, 5) are manufactured from a shape memory alloy, and the austenite phase (A) of the shape memory alloy is manufactured from a shape memory alloy. ｆ A press device characterized in that it is kept at a temperature lower than the final transformation temperature of the battery cell (11), thereby expanding as the thickness of the battery cell (11) increases, and being compressed as the temperature of the pressure elements (4, 5) rises.

12. The press apparatus according to claim 11, wherein the pressure elements (4, 5) exert a constant force when the press apparatus is expanded or compressed.

13. The press apparatus according to claim 11 or 12, further comprising control means for changing the temperature of the pressure elements (4, 5) and thereby controlling the force exerted by the pressure elements (4, 5).

14. The press apparatus according to claim 13, wherein the control means comprises an internal resistance sensor and a control unit (500) that communicates with the internal resistance sensor, the internal resistance sensor is configured to measure the internal resistance of the pressure elements (4, 5) and transmit the internal resistance to the control unit, and the control unit (500) is configured to determine the strain of the pressure elements (4, 5) based on the measured internal resistance.

15. The press apparatus according to claim 14, wherein the control unit (500) is configured to determine the force applied to the battery cell (11) for an arbitrary given time based on the internal resistance of the pressure elements (4, 5), and to change the temperature of the pressure elements (4, 5) based on the force.

16. The press apparatus according to claim 15, wherein the control means is configured to pass an electric current through the pressure elements (4, 5) in order to raise the temperature of the pressure elements (4, 5).

17. The press apparatus according to claim 15, wherein the control means is configured to divert heat stored in a thermal management system associated with the battery cell stack (10) to the pressure elements (4, 5) in order to increase the temperature of the pressure elements (4, 5).

18. The press apparatus according to claim 11, wherein the pressure elements (4, 5) comprise a plurality of wires (5) or plates (4) manufactured from the shape memory alloy, the first end of each wire (5) or plate (4) being fixed to the first pressure plate (2), and the second end of each wire (5) or plate (4) being fixed to the second pressure plate (3).

19. The press apparatus according to claim 18, wherein the pressure elements (4, 5) comprises a plurality of wires (5), and the wires (5) pass through at least two pulleys.

20. A battery comprising a battery cell stack (10) having a plurality of prismatic or pouch-shaped battery cells (11), and a press device (1) according to claim 1 or 2.

21. A monitoring method for monitoring the charge level of a battery, wherein the battery comprises a battery cell stack (10) having a plurality of prismatic or pouch-type battery cells (11), and a press device (1), A first pressure plate (2) and a second pressure plate (3) are configured to be positioned at each end of the battery cell stack (10), wherein the plurality of battery cells (11) are stacked and positioned between the first pressure plate (2) and the second pressure plate (3), The press device (1) includes pressure elements (4, 5) fixed to the first pressure plate (2) and the second pressure plate (3), such that the distance between the first pressure plate (2) and the second pressure plate (3) can be varied. A monitoring method characterized in that the pressure elements (4, 5) are manufactured from a shape memory alloy, thereby causing the press device (1) to expand as the thickness of the battery cell (11) increases and to compress as the thickness of the battery cell (11) decreases, the internal resistance or stiffness of the pressure elements (4, 5) is measured, and the charge state and / or soundness state of the battery cell (11) is determined based on the internal resistance or stiffness.

22. The monitoring method according to claim 21, wherein the voltage between the terminals of each battery cell (11) is measured, and the charge state and / or health state of the battery cell (11) is determined based on the voltage and the internal resistance or stiffness of the pressure elements (4, 5).

23. A battery cell stack (10) comprising a plurality of prismatic or pouch-shaped battery cells (11), and a press device (1), A first pressure plate (2) and a second pressure plate (3) are configured to be positioned at each end of the battery cell stack (10), wherein the plurality of battery cells (11) are stacked and positioned between the first pressure plate (2) and the second pressure plate (3), A battery control method comprising a press device (1) having pressure elements (4, 5) fixed to the first pressure plate (2) and the second pressure plate (3) such that the distance between the first pressure plate (2) and the second pressure plate (3) can be varied, A control method characterized in that the pressure elements (4, 5) are manufactured from a shape memory alloy, thereby causing the press device (1) to expand as the thickness of the battery cell (11) increases and to compress as the thickness of the battery cell (11) decreases, and the force exerted on the battery cell (11) by the pressure elements (4, 5) is adjusted by changing the temperature of the pressure elements (4, 5).

24. The control method according to claim 23, wherein the temperature of the pressure elements (4, 5) increases by passing an electric current through the pressure elements (4, 5).

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