Battery packs and devices containing them

Abstract

A battery pack according to an embodiment of the present invention includes a battery module including a battery cell stack in which a plurality of battery cells are stacked in one direction, a pack housing in which the battery module is housed, a cross beam disposed on a bottom of the pack housing, and a tube disposed inside the cross beam. The cross beam is located on one side of the battery module in the stacking direction of the battery cells and extends in a direction perpendicular to the stacking direction of the battery cells. A fluid is introduced into the tube.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0021377 filed February 18, 2022 and Korean Patent Application No. 10-2023-0018548 filed February 13, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a battery pack and a device including the same, and more particularly to a battery pack capable of controlling swelling of battery cells and a device including the same. [Background technology]

[0003] In modern society, the use of portable devices such as mobile phones, laptops, camcorders, and digital cameras has become commonplace, leading to active development of technologies related to these mobile devices. Furthermore, rechargeable secondary batteries are being used as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and other vehicles as a solution to air pollution caused by conventional gasoline-powered vehicles that use fossil fuels, and this has led to an increased need for development related to secondary batteries.

[0004] Currently available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries are attracting attention due to their advantages over nickel-based secondary batteries, such as almost no memory effect, freedom in charging and discharging, extremely low self-discharge rate, and high energy density.

[0005] Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as positive and negative electrode active materials, respectively, and include an electrode assembly in which positive and negative electrode plates coated with the positive and negative electrode active materials are arranged with a separator sandwiched between them, and a battery case that hermetically houses the electrode assembly together with an electrolyte.

[0006] Generally, lithium secondary batteries can be classified into can-type secondary batteries, in which an electrode assembly is housed in a metal can, and pouch-type secondary batteries, in which an electrode assembly is housed in a pouch made of an aluminum laminate sheet, depending on the shape of the exterior material.

[0007] In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices, but also in medium- to large-sized devices such as automobiles and power storage devices. To increase capacity and output for medium- to large-sized devices, multiple secondary batteries are electrically connected. Pouch-type secondary batteries are becoming more widely used due to their advantages, such as easy stacking and light weight.

[0008] Generally, a pouch-type secondary battery can be manufactured by injecting an electrolyte into a pouch-type outer casing in which an electrode assembly is housed, and then sealing the pouch-type outer casing.

[0009] A secondary battery may generate gas internally due to degradation during repeated charge and discharge. When gas is generated internally, the internal pressure increases, causing at least a portion of the exterior material to expand, resulting in a swelling phenomenon. In particular, in the case of a pouch-type secondary battery, the structural rigidity of the exterior material is weaker than in a can-type secondary battery, so this swelling phenomenon may occur more severely.

[0010] Conventionally, battery cells are housed in a module case and foam pads are placed on them to prevent the module case from excessively restricting the battery cells and to absorb swelling of the battery cells.

[0011] When swelling occurs in a battery cell, the pressure inside the battery increases, causing an increase in volume, which can adversely affect the structural stability of the battery module. Furthermore, battery modules often contain multiple secondary batteries. In particular, medium- to large-sized battery modules used in automobiles and energy storage systems (ESS) often contain and interconnect a large number of secondary batteries due to their high output and capacity. Even if the volume of each battery cell increases slightly due to swelling, the volume changes of the individual battery cells can add up to a significant level of deformation in the entire battery module. In particular, the module frame housing multiple secondary batteries may be deformed or the welded joints of the module frame may be damaged. In other words, the volume expansion caused by swelling of each secondary battery may reduce the overall structural stability of the battery module. Furthermore, if the swelling force increases significantly due to repeated charging and discharging, it may compress the separator within the battery cell, partially reducing battery performance.

[0012] Therefore, a method is needed that can absorb the swelling displacement when the battery cell swells and apply an appropriate pressure to the battery cell. Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a battery pack and a device including the same that can absorb swelling displacement due to swelling of battery cells and apply an appropriate pressure to the battery cells so that the battery cells can exhibit optimal performance.

[0014] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0015] A battery pack according to an embodiment of the present invention includes a battery module including a battery cell stack in which a plurality of battery cells are stacked in one direction; a pack housing in which the battery module is housed; a cross beam disposed on the bottom of the pack housing; and a tube disposed inside the cross beam. The cross beam is located on one side of the battery module in the stacking direction of the battery cells and extends in a direction perpendicular to the stacking direction of the battery cells. A fluid is introduced into the tube.

[0016] The battery cells may be stacked in one direction within the battery module while standing vertically on one surface of the bottom of the pack housing.

[0017] The cross beam may include a frame portion including a first side portion, a second side portion, and a ceiling portion.

[0018] The cross beam may be disposed such that one surface of the first side surface portion and one surface of the second side surface portion are parallel to both side surfaces of the battery module in a direction in which the battery cells are stacked.

[0019] An opening may be formed on at least one side of the first side portion or the second side portion, and the tube may be exposed through the opening and contact the battery module.

[0020] The tube into which the fluid is introduced may pressurize the battery module in a direction in which the battery cells are stacked.

[0021] The battery pack may further include a fluid supply device connected to the tube to supply the fluid to the tube.

[0022] The battery pack may further include a fluid control valve connecting the tube and the fluid supply device and controlling the amount of fluid flowing into the tube.

[0023] The battery pack may further include a pressure sensor connected to the tube and configured to measure a pressure in the tube.

[0024] The cross beam may include a frame portion including a first side portion, a second side portion, and a ceiling portion, and the first side portion, the second side portion, and the ceiling portion may form an n-shape on the cross section of the frame portion.

[0025] The fluid control valve may be located in a space surrounded by the first side portion, the second side portion, and the ceiling portion.

[0026] The tubes may be arranged in an n-shape within the n-shaped frame portion.

[0027] The tube may be made of a soft or elastic material, and the fluid flowing into the tube may be liquid or gel-like.

[0028] The battery module may further include a module frame that houses the battery cell stack, and the battery cells may be stacked in one direction from one side of the module frame to the other side. A compression pad may be interposed on at least one side between adjacent battery cells or between the outermost battery cell and the side of the module frame. In an end-of-life (EOL) state, the deformation rate in the stacking direction of the battery cells may be 12% or less, and a surface pressure applied to the battery cells may be 0.9 MPa or less.

[0029] The module stiffness curve of the battery module is calculated with a slope (MPa / %) in the range of 0.00417 or more and 0.225 or less, and the module stiffness curve of the battery module can correspond to the relationship between the deformation rate of the module frame and the surface pressure applied to the module frame.

[0030] The module stiffness curve of the battery module may be derived by reflecting the surface pressure applied to the compression pads, the degree of compression of the compression pads, and the number of the compression pads in the frame stiffness curve of the module frame.

[0031] A device according to one embodiment of the present invention includes the battery pack. [Effects of the Invention]

[0032] According to an embodiment of the present invention, in a battery pack in which battery modules are housed in a pack housing, a tube through which a fluid flows is provided inside a cross beam disposed adjacent to the battery modules. This effectively absorbs swelling displacement due to swelling of the battery cells, and applies an appropriate pressure that allows the battery cells to exhibit optimal performance.

[0033] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a perspective view showing a battery pack according to an embodiment of the present invention; [Figure 2] 2 is a perspective view showing a battery module included in the battery pack of FIG. 1. FIG. [Figure 3] FIG. 3 is an exploded perspective view of the battery module of FIG. 2. [Figure 4] 4 is a plan view showing one of the battery cells included in the battery module of FIG. 3. FIG. [Figure 5] 2 is a perspective view showing the configuration of the battery pack of FIG. 1 with a battery module removed. [Figure 6] 2 is a perspective view showing a cross beam included in the battery pack of FIG. 1. FIG. [Figure 7] 1 is a plan view schematically illustrating a battery pack according to an embodiment of the present invention; [Figure 8]FIG. 7 is a cross-sectional view showing a cross section taken along the line AA' in FIG. 6. [Figure 9] FIG. 7 is a cross-sectional view showing a cross section taken along the line BB' in FIG. 6. [Figure 10] FIG. 10 is an exploded perspective view showing a battery module according to another embodiment of the present invention. [Figure 11] 1 is a perspective view of a battery module according to an embodiment of the present invention; [Figure 12] FIG. 12 is an exploded perspective view of the battery module of FIG. [Figure 13] 13 is a plan view showing one of the battery cells included in the battery module of FIG. 12. FIG. [Figure 14] FIG. 12 is a cross-sectional view taken along the line AA' in FIG. [Figure 15] 10 is a graph showing a module stiffness curve and a PD curve of a battery cell stack for a battery module according to an embodiment of the present invention. [Figure 16] 10 is a graph showing a module stiffness curve and a PD curve of a battery cell stack for a battery module according to an embodiment of the present invention. [Figure 17] 10 is a graph showing a module stiffness curve and a PD curve of a battery cell stack for a battery module according to an embodiment of the present invention. [Figure 18] 1 is a graph showing a range of a module stiffness curve of a battery module according to an embodiment of the present invention. [Figure 19] 1 is a graph showing a PD curve for a single battery cell. [Figure 20] 1 is a graph showing a PD curve for a single battery cell and a PD curve for a battery cell stack. [Figure 21] 1 is a graph showing module stiffness curves for Examples 1 to 4 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0036] To clearly describe the present invention, portions unnecessary for the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0037] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. Thicknesses are exaggerated to clearly show multiple layers and regions in the drawings. In the drawings, the thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0038] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where the layer, film, region, plate, or other part in question is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the direction opposite to gravity.

[0039] Furthermore, throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, not excluding other elements, unless otherwise specified.

[0040] Also, throughout the specification, "in a plane" means a portion of the subject matter viewed from above, and "in cross section" means a portion of the subject matter viewed from the side along a vertical cross section.

[0041] FIG. 1 is a perspective view showing a battery pack according to an embodiment of the present invention.

[0042] 1, a battery pack 1000 according to an embodiment of the present invention includes a battery module 100a, a pack housing 1100 in which the battery module 100a is housed, and a cross beam 1200 disposed on the bottom of the pack housing 1100. One or more battery modules 100a may be housed in the pack housing 1100. FIG. 1 shows a configuration in which a plurality of battery modules 100a are housed.

[0043] First, the battery module 100a included in the battery pack 1000 according to this embodiment will be described in detail with reference to FIGS.

[0044] Fig. 2 is a perspective view showing a battery module included in the battery pack of Fig. 1. Fig. 3 is an exploded perspective view of the battery module of Fig. 2. Fig. 4 is a plan view showing one of the battery cells included in the battery module of Fig. 3.

[0045] 2 to 4, a battery module 100a according to this embodiment includes a battery cell stack 120 in which a plurality of battery cells 110 are stacked in one direction. The battery cells 110 may be pouch-type battery cells. The pouch-type battery cells may be formed by housing an electrode assembly in a pouch case made of a laminate sheet including a resin layer and a metal layer, and then bonding the outer periphery of the pouch case.

[0046] Specifically, the battery cell 110 may have a structure in which two electrode leads 111 and 112 face each other and protrude from one end 114a and the other end 114b of the battery body 113, respectively. The battery cell 110 may be manufactured by bonding both ends 114a and 114b of the pouch case 114 to one side 114c connecting them, with an electrode assembly (not shown) housed in the pouch case 114. That is, the battery cell 110 according to one embodiment of the present invention may have a total of three sealing portions, which are sealed by a method such as fusion, and the remaining side 114d may be formed as a folded portion. The battery cell 110 according to this embodiment may be a pouch battery cell in which an electrode assembly is housed inside the pouch case 114 and the outer periphery of the pouch case 114 is sealed. The battery cell 110 described above is an exemplary structure, and it goes without saying that a unidirectional battery cell in which two electrode leads protrude in the same direction is also possible.

[0047] The pouch-type battery cells 110 may be in a sheet shape, and such battery cells 110 are stacked in one direction to form the battery cell stack 120. As an example, the battery cells 110 may be stacked in a direction parallel to the y-axis with one surface of the battery bodies 113 facing each other.

[0048] The battery module 100 a may further include a pair of side plates 200 , a pair of bus bar frames 300 , and a band member 400 .

[0049] A pair of side plates 200 may be disposed on both sides of the battery cell stack 120 to support the battery cell stack 120. Specifically, a side plate 200 may be located on each side of the battery cell stack 120 in the stacking direction of the battery cells 110. As shown in FIG. 3 , the battery cells 110 may be stacked in a direction parallel to the y-axis, and the side plates 200 may be disposed on each side of the battery cell stack 120 in the stacking direction of the battery cells 110.

[0050] The pair of bus bar frames 300 may be located on one side and the other side of the battery cell stack 120. Specifically, the bus bar frames 300 may be located on one side and the other side of the battery cell stack 120 in a direction in which the electrode leads 111 and 112 of the battery cells 110 protrude. As the battery cells 110 are stacked along the y-axis direction, the electrode leads 111 and 112 may protrude in the x-axis direction and the negative x-axis direction, and the bus bar frames 300 may be located in the x-axis direction and the negative x-axis direction with respect to the battery cell stack 120. In addition, the bus bar frames 300 may be arranged to cover the battery cell stack 120.

[0051] The bus bar frame 300 may have bus bars 310 and module connectors 320 attached thereto.

[0052] The bus bar 310 can be electrically connected to the electrode leads 111, 112 of the battery cells 110 while being attached to the bus bar frame 300. A plurality of bus bars 310 can be provided. The battery cells 110 can be electrically connected in series or in parallel via the bus bars 310.

[0053] The module connector 320 may be electrically connected to an external device while being attached to the bus bar frame 300. For example, the module connector 320 may be provided with a high-voltage connector, a low-voltage connector, or the like, and may be connected to an external BMS (battery management system) to transmit temperature and voltage information of the battery module 100a.

[0054] Meanwhile, a sensing PCB 330 may be disposed to connect the pair of bus bar frames 300. The sensing PCB 330 may be formed of a flexible printed circuit board. The sensing PCB 330 may be provided to a predetermined length and disposed on the upper side of the battery cell stack 120.

[0055] The band member 400 may be connected to the pair of side plates 200 and at least partially cover the upper and lower sides of the battery cell stack 120. That is, the band member 400 may be positioned on the upper and lower sides of the battery cell stack 120 to connect the pair of side plates 200. One end of the band member 400 may be connected to one of the side plates 200, and the other end of the band member 400 may be connected to the other of the side plates 200. The band member 400 may be made of a metal member made of an elastic material. There are no particular limitations on the method of connecting the band member 400 and the pair of side plates 200, but as an example, they may be connected by welding. In particular, both end portions of the band member 400 may be bent and joined to the side plates 200.

[0056] The band members 400 may be arranged at predetermined intervals along the length direction of the battery module 100a on the upper or lower side of the battery cell stack 120. Here, the length direction of the battery module 100a is perpendicular to the direction in which the battery cells 110 are stacked, and corresponds to a direction parallel to the x-axis in the drawing.

[0057] Meanwhile, the battery module 100a may further include a heat sink 500. The heat sink 500 is for cooling the battery cell stack 120 and may be disposed below the battery cell stack 120. Such a heat sink 500 may be located on the bottom of a pack housing, which will be described later.

[0058] The pack housing 1100 and the cross beam 1200 according to this embodiment will be described in detail below with reference to Figs. 1, 5 to 7, and the like.

[0059] Fig. 5 is a perspective view showing the configuration of the battery pack of Fig. 1 excluding the battery modules. Fig. 6 is a perspective view showing a cross beam included in the battery pack of Fig. 1. Fig. 7 is a plan view schematically showing a battery pack according to an embodiment of the present invention. In particular, Fig. 7 is a plan view schematically showing the battery pack as viewed along the -z axis direction on the xy plane.

[0060] 1 and 5 to 7, the cross beam 1200 is disposed on the bottom 1100F of the pack housing 1100, is located on one side of the battery module 100a in the stacking direction of the battery cells 110, and extends in a direction perpendicular to the stacking direction of the battery cells 110.

[0061] The pack housing 1100 is a structure for accommodating the battery module 100a, and may have an open top while having an internal storage space. The battery module 100a is placed in the storage space, and a pack cover (not shown) may be assembled on the open top of the pack housing 1100.

[0062] As described above, the battery cells 110 are stacked in one direction within the battery module 100a. The cross beam 1200 is located on one side of the battery module 100a in the stacking direction of the battery cells 110 and extends in a direction perpendicular to the stacking direction of the battery cells 110. More specifically, the battery cells 110 may be stacked in one direction within the battery module 100a while standing upright perpendicular to one surface of the bottom 1100F of the pack housing 1100. As a result, one side of the cross beam 1200 may be positioned parallel to one surface of the battery body 113 (see FIG. 4 ) of the battery cell 110. As shown in the figure, the battery cells 110 are stacked in a direction parallel to the y-axis while being perpendicular to one surface of the bottom 1100F of the pack housing 1100. The cross beam 1200 is located on one side of any one battery module 100a in the y-axis or -y-axis direction. Alternatively, the cross beam 1200 may extend in a direction parallel to the x-axis. The cross beam 1200 is configured to support the swelling force when the battery cell 110 swells.

[0063] At this time, the battery pack 1000 according to this embodiment includes a tube 1300 disposed inside the cross beam 1200, and a fluid flows into the tube 1300. The tube 1300 may be made of a soft or elastic material. The tube 1300 may have a structure formed of a rubber material.

[0064] When the battery cells 110 are pouch-type battery cells in a sheet shape, swelling occurs, and the battery cells 110 swell primarily in the stacking direction. That is, the swelling force is applied in a direction parallel to the y-axis in the drawing. The cross beam 1200, located on one side of the battery module 100a in the stacking direction of the battery cells 110, can support the swelling force of the battery cells 110. In addition, the tubes 1300 inside the cross beam 1200 can absorb the swelling displacement of the battery cells 110. This can improve the pressure distribution effect between the battery cells 110.

[0065] Meanwhile, the fluid flowing into the tube 1300 may be liquid or gel-like. For example, the fluid may be cooling water or water. By filling the tube with cooling water or water, a cooling effect on the battery cell can be achieved. At the same time, if the fluid is hydrogel, it is advantageous for dispersing stress concentrated in a specific area and maintaining thermal equilibrium. Conversely, a gas may be used as the fluid, but if a gas is used as the fluid, there is a problem that the heated gas may increase the temperature of the battery cell 110 as a whole.

[0066] The battery pack 1000 according to this embodiment includes a tube 1300 inside the cross beam 1200 through which a fluid flows, thereby applying a constant force to the battery cells 110 and absorbing swelling displacement caused by swelling of the battery cells. Because this is a fluid-based control method, the surface pressure of the battery cells 110 can be maintained constant even if swelling of the battery cells 110 occurs.

[0067] Hereinafter, the detailed structure of the cross beam and the tubes according to this embodiment will be described in detail with reference to Figs.

[0068] Fig. 8 is a cross-sectional view taken along line A-A' in Fig. 6. Fig. 9 is a cross-sectional view taken along line B-B' in Fig. 6. For ease of explanation, Figs. 8 and 9 show a configuration in which the battery module 100a is disposed near the cross beam 1200.

[0069] 5, 6, 8, and 9, the cross beam 1200 according to this embodiment may include a frame portion 1200F including a first side portion 1210, a second side portion 1220, and a ceiling portion 1230. The tube 1300 may be located inside the frame portion 1200F.

[0070] The first side surface portion 1210 and the second side surface portion 1220 are arranged perpendicular to one surface of the bottom portion 1100F of the pack housing 1100, and the ceiling portion 1230 can connect such first side surface portion 1210 and second side surface portion 1220.

[0071] In this case, the cross beam 1200 may be disposed such that one surface of the first side surface portion 1210 and one surface of the second side surface portion 1220 are parallel to both sides of the battery module 100a in the stacking direction of the battery cells 110. One battery module 100a may be positioned on one surface of the first side surface portion 1210, and another battery module 100a may be positioned on one surface of the second side surface portion 1220. The first side surface portion 1210 and the second side surface portion 1220 of the cross beam 1200 may support the swelling force of the battery cells 110.

[0072] In this case, an opening 1200P may be formed on at least one side of the first side portion 1210 or the second side portion 1220. The opening 1200P may correspond to a shape in which a region of the frame portion 1200F is penetrated. The tube 1300 may be exposed through the opening 1200P and come into contact with one side of the battery module 100a, thereby applying a certain pressure to the battery module 100a.

[0073] In particular, one side of the first side portion 1210 and one side of the second side portion 1220 are arranged parallel to both sides of the battery module 100a in the direction in which the battery cells 110 are stacked, and the tube 1300 into which the fluid (F) flows can pressurize the battery module 100a in the direction in which the battery cells 110 are stacked through the opening 1200P.

[0074] With this structure, the tube 1300 can apply a constant pressure to the battery cell 110 using the pressure of the fluid (F) inside. The pressure and amount of the fluid (F) flowing into the tube 1300 can be adjusted to maintain an optimal pressure applied to the battery cell 110. In addition, in the case of an all-solid-state battery or a PureSi battery, a high initial pressure improves the performance of the battery cell. In order to increase the initial pressure, a pressure means using the fluid (F) can be used, as in this embodiment. In addition, even if swelling occurs in the battery cell 110 along the stacking direction, the fluid (F) inside the tube 1300 can absorb the swelling displacement of the battery cell 110.

[0075] Meanwhile, the battery pack 1000 according to this embodiment may include a fluid supply device 1400 connected to the tube 1300 to supply fluid to the tube 1300. The battery pack 1000 may further include a fluid control valve 1500 connecting the tube 1300 and the fluid supply device 1400 and controlling the amount of fluid (F) flowing into the tube 1300. The battery pack 1000 may further include a pressure sensor 1600 connected to the tube 1300 to measure the pressure of the tube 1300.

[0076] For example, the frame portion 1200F of the cross beam 1200 may include a first side portion 1210, a second side portion 1220, and a ceiling portion 1230, and the ceiling portion 1230 may connect an upper end of the first side portion 1210 to an upper end of the second side portion 1220. That is, the first side portion 1210, the second side portion 1220, and the ceiling portion 1230 may form an n-shape in the cross section of the frame portion 1200F. The tubes 1300 may be arranged in a corresponding n-shape within the n-shaped frame portion 1200F.

[0077] In this case, there is no particular limitation on the positions of the fluid control valve 1500 and the pressure sensor 1600, but they can be located in the inner space of the N-shaped frame unit 1200F as described above. That is, the fluid control valve 1500 can be located in the space surrounded by the first side surface unit 1210, the second side surface unit 1220, and the ceiling unit 1230. Similarly, the pressure sensor 1600 can be located in the space surrounded by the first side surface unit 1210, the second side surface unit 1220, and the ceiling unit 1230. Since the space inside the frame unit 1200F of the cross beam 1200 can be used as a space for arranging the fluid control valve 1500 and the pressure sensor 1600, the space utilization rate inside the pack housing 1100 can be improved.

[0078] Meanwhile, the fluid supply device 1400 according to this embodiment is a device that supplies fluid to the inside of the tube 1300, and may be a device that uses a general fluid pump or a pressure head.

[0079] The fluid supply device using the pressure head includes a fluid supply pipe connected to the tube 1300. In this case, the fluid supply pipe is located at a position higher than the fluid supply area of the tube 1300 and has a structure perpendicular to the ground. The amount of fluid (F) flowing into the tube 1300 can be determined by adjusting the height of the fluid inside the fluid supply pipe, thereby controlling the pressure of the tube 1300. In this case, the fluid supply device can apply fluid pressure to the tube without requiring a separate power source.

[0080] Meanwhile, the fluid control valve 1500 according to this embodiment may be a conventional valve connected between the fluid supply device 1400 and the tube 1300 to control the amount of fluid (F) flowing into the tube 1300. This allows the surface pressure of the battery cell 110 to be maintained constant. For example, the fluid control valve 1500 may be activated in response to a signal from the pressure sensor 1600 to open or close a flow path. Specifically, the fluid control valve 1500 may open the flow path to supply or discharge the fluid (F) when the pressure in the tube 1300 is above or below a reference value range, and may close the flow path when the pressure in the tube 1300 is within the reference value range.

[0081] In addition, the pressure sensor 1600 according to this embodiment is connected to the tube 1300 and can measure the pressure change in the tube 1300 when the fluid (F) flows in. The pressure sensor 1600 is also connected to the fluid control valve 1500 and can transmit pressure information of the tube 1300. Whether or not the fluid control valve 1500 is operated is determined based on the pressure measured by the pressure sensor 1600.

[0082] By supplying fluid (F) to the tubes 1300, the pressure in the tubes 1300 can be increased, and a desired initial pressure can be applied to the battery cells 110. That is, the battery pack 1000 according to this embodiment can be finally assembled in a state where appropriate pressure is applied to the battery cells 110 by applying fluid pressure to the tubes 1300 inside the cross beam 1200.

[0083] Meanwhile, when swelling occurs in the battery cells 110 inside the battery module 100a, the pressure received by the tube 1300 increases. In this case, the fluid supply device 1400 and the fluid control valve 1500 can be operated according to the pressure value of the tube 1300. That is, when the pressure in the tube 1300 exceeds a preset value, the fluid control valve 1500 opens until the pressure inside the tube 1300 reaches a reference value, and the fluid supply device 1400 can discharge the fluid (F) inside the tube 1300 to the outside of the tube 1300. This reduces the pressure. On the other hand, when the pressure in the tube 1300 is below a preset value, the fluid control valve 1500 opens, and the fluid supply device 1400 can supply the fluid (F) into the tube 1300. That is, the battery pack 1000 according to the present invention can control the amount of fluid flowing into the tube 1300 supporting the battery cell stack 120 based on the pressure of the tube 1300 measured by the pressure sensor 1600. This allows the battery cells 110 to maintain a constant surface pressure.

[0084] In the past, swelling of the battery cells 110 was controlled using compression pads arranged inside the battery module, but in this embodiment, swelling of the battery cells 110 is controlled by adjusting the amount of fluid in the tubes 1300 inside the cross beam 1200, and swelling displacement can be absorbed, allowing for a reduction in the number of compression pads. This has the effect of increasing battery capacity by the number of compression pads and reducing the number of parts.

[0085] In addition, in the conventional case, when the battery module 100a is housed, the initial pressurized state may change due to the tolerance of the battery cells 110, or the pressurized force may change under the EOL (End of Life) condition. However, in the present embodiment, even after the battery module 100a is placed in the pack housing 1100 and the assembly of the battery pack 1000 is completed, the applied pressurized force can be adjusted by controlling the amount of fluid, so that the change in the initial pressurized state due to the tolerance or the pressurized force under the EOL condition can be prevented.

[0086] In addition, the battery pack 1000 can be easily disassembled by discharging the fluid (F) inside the tube 1300 to reduce the pressure. Furthermore, since the amount of fluid (F) is adjusted based on the pressure of the tube 1300, there is no need to consider different swelling characteristics for each battery module 100a, and there is no need to perform swelling characteristic tests under various conditions.

[0087] Meanwhile, the tubes 1300 according to this embodiment are provided inside the cross beam 1200, rather than inside the individual battery modules 100a. When the number of battery modules 100a installed in the battery pack 1000 is large, providing tubes for each individual battery module increases the number of components and complicates the installation process. Meanwhile, the tubes 1300 according to this embodiment are provided in the cross beam 1200, enabling simultaneous control of the swelling of multiple battery modules 100a. Because the tubes 1300 inside the cross beam 1200 are capable of applying pressure to each battery module 100a in the stacking direction of the battery cells 110, there is no problem in controlling the swelling of each battery module 100a. Therefore, compared to providing tubes for each individual battery module, this embodiment has the advantages of requiring fewer components and being easier to install. Nevertheless, there is no problem in maintaining a constant pressure and surface pressure on the battery cells 110 and absorbing swelling displacement.

[0088] 10 is an exploded perspective view showing a battery module 100b according to another embodiment of the present invention. Referring to FIG. 10, the battery module 100b according to another embodiment of the present invention includes a battery cell stack 120 in which battery cells 110 are stacked in one direction, a module frame 210 in which the battery cell stack 120 is housed, and end plates 220 located on both open sides of the module frame 210.

[0089] Compared with the battery module 100 a described above, the configuration of the battery cell stack 120 is the same or similar to each other, except that the battery cell stack 120 is housed in a module frame 210 .

[0090] The module frame 210 may be a mono-frame with an integrated top, bottom, and both sides, as shown in the figure, or may be a module frame with an integrated bottom and both sides, in which an upper cover is welded to a U-shaped frame.

[0091] The module frame 210 has openings on both opposing sides, and the battery cell stack 120 is housed in these openings. After housing, the module frame 210 and the end plates 220 are coupled together so that the end plates 220 cover the openings of the module frame 210.

[0092] Like the battery module 100a described above, the battery module 100b of this embodiment can also be mounted in a pack housing together with a cross beam having a tube located therein to form a battery pack.

[0093] As the battery cells 110 are repeatedly charged and discharged, swelling occurs in the battery cells 110, and in the case of a battery module 100b having this configuration, the force applied to the module frame 210 gradually increases as the swelling occurs. In the past, the thickness of the module frame 210 had to be made thicker to withstand this. However, in the case of the battery pack according to this embodiment, the pressure applied to the battery cells 110 is maintained constant by using a fluid and the swelling displacement can be absorbed, so the thickness of the module frame 210 can be made thinner. This has the advantage of reducing the weight of the entire battery pack including the battery module 100b and increasing the battery capacity.

[0094] Furthermore, in the past, when the battery cell stack 120 was inserted into the module frame 210, in order to apply an appropriate initial pressure to the battery cells 110, the left and right sides of the U-shaped frame were widened as described above, or a certain amount of pressure was applied to both sides of the battery cell stack 120 while the battery was being inserted. However, in the battery pack according to this embodiment, the pressure to be applied can be adjusted by adjusting the amount of fluid inside the tubes 1300 after the battery module 100b is placed in the pack housing, eliminating the need for the conventional, difficult insertion of the battery cell stack 120 into the module frame 210. In other words, the initial pressure can be applied by simply inserting the battery cell stack 120 into the module frame 210, and then placing the battery module 100b near the cross beam 1200 and then increasing the pressure of the tubes 1300.

[0095] 5 and 7, the battery pack 1000 according to this embodiment may further include vertical beams 1700 extending in a direction perpendicular to the extension direction of the cross beams 1200. When a large number of battery modules are to be arranged, an appropriate number of vertical beams 1700 may be arranged to support the battery modules and form a sturdy structure.

[0096] Hereinafter, a design method for the battery module according to this embodiment will be described with reference to FIGS.

[0097] Fig. 11 is a perspective view of a battery module according to an embodiment of the present invention, Fig. 12 is an exploded perspective view of the battery module of Fig. 11, and Fig. 13 is a plan view showing one of the battery cells included in the battery module of Fig. 12.

[0098] 11 to 13, a battery module 100 according to an embodiment of the present invention includes a battery cell stack 120 in which a plurality of battery cells 110 are stacked in one direction, and a module frame 200 that houses the battery cell stack 120. The battery module 100 may further include at least one compression pad 400.

[0099] First, the battery cell 110 may be a pouch-type battery cell. A pouch-type battery cell may be formed by placing an electrode assembly in a pouch case made of a laminate sheet including a resin layer and a metal layer, and then joining the outer periphery of the pouch case. Such a battery cell 110 may have a rectangular sheet shape. Specifically, the battery cell 110 according to this embodiment has two electrode leads 111 and 112 that face each other and protrude from one end 114a and the other end 114b of a battery body 113, respectively. The battery cell 110 may be manufactured by joining both ends 114a and 114b of the battery case 114 and one side 114c connecting them, with the electrode assembly (not shown) placed in the battery case 114. In other words, the battery cell 110 according to this embodiment may have a total of three sealing portions, and the remaining side may be configured as a folding portion 115. The distance between both ends 114a, 114b of the battery case 114 can be defined as the length direction of the battery cell 110, and the distance between one side portion 114c connecting both ends 114a, 114b of the battery case 114 and the folding portion 115 can be defined as the width direction of the battery cell 110.

[0100] Although only the battery cell 110 having the electrode leads 111 and 112 protruding in both directions has been described, it is of course possible to provide a unidirectional pouch-type battery cell in which the electrode leads protrude in one direction together as another embodiment of the present invention.

[0101] A plurality of such battery cells 110 are stacked in one direction so as to be electrically connected to each other, forming a battery cell stack 120. The battery case 114 generally has a laminate structure of a resin layer / metal thin film layer / resin layer. For example, if the surface of the battery case is made of an O(oriented)-nylon layer, the battery cells tend to slip easily due to external impact when stacking them to form a medium- to large-sized battery module. Therefore, to prevent this and maintain a stable stack structure of the battery cells, an adhesive may be provided on the surface of the battery case to form the battery cell stack 120. The adhesive may be a pressure-sensitive adhesive such as double-sided tape or a chemical adhesive that bonds through a chemical reaction during adhesion. The adhesive will be described later.

[0102] When a plurality of battery cells 110 are stacked in one direction to form the battery cell stack 120, the battery cells 110 having rectangular sheet structures may be stacked in one direction with one side of each battery body 113 facing each other. More specifically, the battery cells 110 may be stacked in an upright position so that the one side of each battery cell 110 is parallel to side portions 210 and 220 of a module frame 200, which will be described later. FIG. 12 shows a configuration in which the battery cells 110 are stacked in a direction parallel to the y-axis to form the battery cell stack 120. This allows the electrode leads 111 and 112 in the battery cell stack 120 to protrude in the x-axis direction and the -x-axis direction.

[0103] The module frame 200 may be a frame having one and the other open sides. The battery cell stack 120 may be inserted through one or the other open side of the module frame 200, and the battery cell stack 120 may be accommodated in the internal space of the module frame 200.

[0104] The module frame 200 includes side portions 210, 220 that respectively cover both side surfaces of the battery cell stack 120 along the stacking direction of the battery cells 110. For battery cells 110 stacked along the y-axis direction, the side portions 210, 220 of the module frame 200 can respectively cover the side surface in the y-axis direction and the side surface in the -y-axis direction of the battery cell stack 120.

[0105] The module frame 200 may also include an upper surface portion 230 and a lower surface portion 240 that connect the side surfaces 210 and 220. The upper surface portion 230 and the lower surface portion 240 of the module frame 200 may cover the upper and lower surfaces of the battery cell stack 120 housed inside the module frame 200, respectively.

[0106] 12 has a form in which side portions 210, 220, top portion 230, and bottom portion 240 are integrated, but in another embodiment of the present invention, the module frame may have a form in which a U-shaped frame and an upper cover are joined together. The U-shaped frame, which covers both side surfaces and the bottom of the battery cell stack, and the upper cover, which covers the top of the battery cell stack, are joined at corresponding corners to form the module frame.

[0107] The battery module 100 according to this embodiment may include a bus bar frame 500 that is housed in the module frame 200 together with the battery cell stack 120. The bus bar frame 500 may include a front frame 510 and a rear frame 520 that are respectively located on one side and the other side of the battery cell stack 120 from which the electrode leads 111 and 112 protrude. The bus bar frame 500 may further include an upper frame 530 that is connected to the front frame 510 and the rear frame 520 and is located on the top of the battery cell stack 120.

[0108] Bus bars 540 for connecting the electrode leads 111, 112 of the battery cells 110 included in the battery cell stack 120 may be attached to the front frame 510 and the rear frame 520. Specifically, the electrode leads 111, 112 of the battery cells 110 may pass through slits formed in the front frame 510 and the rear frame 520, bend, and be joined to the bus bars 540 by welding or the like. In this manner, the battery cells 110 included in the battery cell stack 120 may be electrically connected in series or in parallel.

[0109] The battery module 100 according to this embodiment may include end plates 300 located on both opposing open sides of the module frame 200. The end plates 300 may be provided to cover one and the other open sides of the module frame 200. That is, two end plates 300 may be located on both open sides of the module frame 200 and joined to corresponding corners of the module frame 200 by a method such as welding. Such end plates 300 may physically protect the battery cell stack 120 and other electrical components from external impact.

[0110] FIG. 14 is a cross-sectional view taken along the line AA' in FIG.

[0111] 12 to 14, the battery module 100 according to this embodiment includes at least one compression pad 400 disposed on at least one side between adjacent battery cells 110 or between the outermost battery cell 110 and the side portion 210, 220.

[0112] The compression pad 400 can absorb some of the swelling of the battery cell with a foam-like member. Specifically, the battery cell 110 may generate gas internally due to degradation caused by repeated charging and discharging. When gas is generated internally, the internal pressure increases, causing a swelling phenomenon in which at least a portion of the exterior material expands. In particular, in the case of pouch-type secondary batteries, the structural rigidity of the exterior material is weaker than in can-type secondary batteries, so the swelling phenomenon may occur more severely.

[0113] When swelling occurs in a secondary battery, the pressure inside the battery increases, causing an increase in volume, which can adversely affect the structural stability of the battery module. Therefore, an attempt has been made to absorb some of the swelling of the battery cells 110 by disposing a compression pad 400 that compresses when pressure is applied inside the battery module 100. There are no particular limitations on the material of the compression pad 400 as long as it can absorb the swelling of the battery cells 110 when compressed, and one example includes a polyurethane material.

[0114] Hereinafter, a design method for the battery module according to this embodiment will be described with reference to FIGS.

[0115] 15 to 17 are graphs showing module stiffness curves and PD curves of battery cell stacks for a battery module according to an embodiment of the present invention, and Fig. 18 is a graph showing the range of the module stiffness curve for a battery module according to an embodiment of the present invention.

[0116] 12, 14, and 15 to 18, as described above, in a battery module 100 according to an embodiment of the present invention, a battery cell stack 120 in which battery cells 110 are stacked may be housed in a module frame 200. Within the battery module, the battery cells 110 may be stacked in one direction from a side portion 210 to the other side portion 220 of the module frame 200. In addition, a compression pad 400 may be interposed on at least one side of between adjacent battery cells 110 or between the outermost battery cell 110 and the side portions 210, 220 of the module frame 200.

[0117] At this time, the module stiffness curve (C1) due to the module frame 200 and the PD (Pressure-Displacement) curve (C3) of the battery cell stack 120 showing the swelling characteristics of the battery cells 110 are calculated and then fitted to a single graph. Then, the swelling behavior of the battery module can be predicted by finding the equilibrium point (intersection point) between the two curves.

[0118] 15 to 17 show intersections (P, P', P") between the module stiffness curves (C1, C1', C") and the PD curve (C3) of the battery cell stack. The PD curve (C3) of the battery cell stack is a graph showing the relationship between the surface pressure received by the battery cells 110 and the degree of change in thickness of the battery cells 110 due to swelling of the battery cells 110. The PD curve (C3) of the battery cell stack can be measured in the End of Life (EOL) state of the battery cells 110. Here, EOL refers to the state when the ratio of the current capacity of a battery to its initial capacity reaches a predetermined ratio, which may be 80%. In other words, EOL can refer to the state of a battery when the capacity of the battery reaches 80% of its initial capacity, and can correspond to the end of the battery's life or the need for replacement. Meanwhile, the module stiffness curves (C1, C1', C") are graphs showing the relationship between the degree of change in the width (W) of the module frame 200 depending on the stacking direction of the battery cells 110 and the load applied to the module frame 200. The stacking direction of the battery cells 110 corresponds to the direction from one side surface 210 to the other side surface 220 of the module frame 200, and hereinafter, the direction in which the battery cells 110 are stacked is referred to as the width direction. Furthermore, the width (W, W') of the module frame 200 refers to the distance from one side surface 210 to the other side surface 220. The module stiffness curve (C1) and the PD curve (C3) of the battery cell stack will be described in detail again below.

[0119] In each of the module stiffness curves (C1, C1', C") and the battery cell stack PD curve (C3), the X axis corresponds to the deformation rate in %, and the Y axis corresponds to the applied surface pressure in MPa.

[0120] The intersections (P, P', P") between the module stiffness curves (C1, C1', C") and the PD curve (C3) of the battery cell stack correspond to the points where the movement due to swelling of the battery cell stack 120 and the movement due to deformation of the module frame 200 are balanced. That is, in the End of Life (EOL) state, if a battery module is housed in a module frame 200 that exhibits a specific module stiffness curve (C1), the battery module can be predicted to have a deformation rate and surface pressure corresponding to the intersections (P, P', P") in the EOL state. That is, the battery module deforms in the width direction by an amount corresponding to the X-axis value of the intersections (P, P', P") in the EOL state, and the battery cells 110 and module frame 200 receive surface pressure by an amount corresponding to the Y-axis value of the intersections (P, P', P").

[0121] 15, the intersection point (P) is preferably located between the deformation limit point (x1) and the pressure limit point (y1). The deformation limit point (x1) is 12%, and the pressure limit point (y1) is 0.9 MPa. That is, it is preferable that the X-axis value of the intersection point (P) is less than 12%, which is the deformation limit point (x1), and the Y-axis value of the intersection point (P) is less than 0.9 MPa, which is the pressure limit point (y1). That is, in the EOL state, the battery module according to this embodiment may have a deformation rate of 12% or less in the stacking direction of the battery cells 110, and the surface pressure applied to the battery cells 110 may be 0.9 MPa or less.

[0122] 16, when the Y-axis value of the intersection point (P') exceeds the pressure limit point (y1), it is predicted that a surface pressure exceeding the pressure limit point (y1) will be applied to the battery cells 110 and module frame 200 of the battery module in the EOL state. When a pressure exceeding the pressure limit point (y1), 0.9 MPa, is applied to the battery cells 110, problems such as a sudden drop, which reduces the lifespan performance of the battery cells 110, may occur. Furthermore, when a pressure exceeding the pressure limit point (y1), 0.9 MPa, is applied to the module frame 200, a surface pressure exceeding the yield strength will be applied, which may damage and deform the module frame 200.

[0123] As shown in FIG. 17, if the X-axis value of the intersection point (P") exceeds the deformation limit point (x1), it is predicted that the battery module will deform further in the width direction than the deformation limit point (x1) in the EOL state. This means that excessive changes in thickness due to swelling of the battery cell 110 are tolerated, which may cause problems such as disconnection between the electrode lead and tab within the battery cell 110 and cracks in the pouch-type battery case of the battery cell 110. In addition, because it is predicted that the battery module will deform further than 12%, which is the deformation limit point (x1), the space occupied by the battery module within the battery pack will increase excessively, which will cause a decrease in the energy density of the battery module and the battery pack.

[0124] 18, for the battery module according to this embodiment, the module stiffness curve (C1) can be calculated with a slope (MPa / %) range of 0.00417 to 0.225. That is, the module stiffness curve (C1) of the battery module according to this embodiment can be formed in the range between a lower limit module stiffness curve (C1b) with a slope (Sb) value of 0.00417 MPa / % and an upper limit module stiffness curve (C1a) with a slope (Sa) value of 0.225 MPa / %. Since the intersection (P) between the module stiffness curve (C1) and the PD curve (C3) of the battery cell stack is located in the range between the deformation limit point (x1) and the pressure limit point (y1), it is preferable that the module stiffness curve (C1) be calculated with a slope (MPa / %) range of 0.00417 to 0.225.

[0125] The module rigidity curve (C1) will be described in detail below. As described above, the module rigidity curve (C1) is a graph showing the relationship between the degree of change in the width of the module frame 200 depending on the stacking direction of the battery cells 110 and the load applied to the module frame 200. From the perspective of the module rigidity curve (C1), the X-axis corresponds to the deformation rate (%) of the module frame 200 along the width direction. The deformation rate can be calculated based on the width (W') (see FIG. 14) of the module frame 200 deformed along the width direction compared to the width (W) of the module frame 200 before deformation (see FIG. 14). For example, the deformation rate can be calculated as the ratio of the degree of deformation of the width of the module frame 200 (W' - W) to the width (W) of the module frame 200 before deformation (see FIG. 14). From the perspective of the module rigidity curve (C1), the Y-axis corresponds to the surface pressure (MPa) applied to the side portions 210 and 220 of the module frame 200 depending on the deformation rate of the module frame 200.

[0126] To calculate the module stiffness curve (C1), a priority frame stiffness curve can be calculated. The frame stiffness curve is a graph showing the relationship between the deformation rate of the module frame 200 and the surface pressure applied to the module frame 200. Such a frame stiffness curve can be obtained through several actual tests or simulations. For example, an actual force is applied to the module frame 200, and the resulting widthwise deformation of the module frame 200 is measured. The frame stiffness curve can be derived by repeatedly performing this test while changing the applied force. The module stiffness curve (C1) can be derived by considering the influence of the compression pads 400 on such a frame stiffness curve. Specifically, the module stiffness curve (C1) can be finally derived by reflecting the surface pressure applied to the compression pads 400, the degree of compression of the compression pads 400, and the number of compression pads 400 on the frame stiffness curve.

[0127] The PD curve (C3) of the battery cell stack will be described in detail below. As described above, the PD curve (C3) of the battery cell stack is a graph showing the relationship between the degree of change in thickness of the battery cells 110 due to swelling and the surface pressure received by the battery cells 110. In terms of the PD curve (C3) of the battery cell stack, the X-axis may correspond to the deformation rate (%) in the width direction of the battery cell stack 120, and the Y-axis may correspond to the surface pressure (MPa) applied to the battery cells 110 included in the battery cell stack 120.

[0128] Hereinafter, the process of calculating the PD curve (C3) of such a battery cell stack will be described in detail with reference to FIGS.

[0129] FIG. 19 is a graph showing the PD curve for a single battery cell.

[0130] Referring to FIG. 19, the thickness change and surface pressure due to the charge / discharge cycle of a single battery cell 110 can be measured. Specifically, a single battery cell 110 is placed in a fixing jig that limits thickness change, and then the charge / discharge cycle is repeated. A load cell placed in the fixing jig measures the surface pressure value at a0. The measured a0 is displayed at P0 on the Y-axis. A single battery cell 110 is placed in an adjustable jig that allows thickness change using a spring or the like, and then the charge / discharge cycle is repeated. A load cell placed in the adjustable jig measures the surface pressure value at a1, and the increased thickness of the battery cell 110 is measured to calculate the thickness deformation rate at b1. The a1 and b1 are displayed at point P1. The spring constant of the adjustable jig is changed and the measurement process is repeated to measure the surface pressure values at a2, a3, and a4 and the deformation rates at b2, b3, and b4, respectively. Based on these values, coordinate points P2, P3, and P4 can be displayed, and a curve C2 can be derived. The curve (C2) thus derived corresponds to the PD (Pressure-Displacement) curve of a single battery cell.

[0131] Figure 20 is a graph showing the PD curve for a single battery cell and the PD curve for a battery cell stack. Referring to Figures 19 and 20 together, the PD curve (C3) for the battery cell stack 120 can be obtained by adding the number of battery cells 110 included in the battery cell stack 120 to the PD curve (C2) for a single battery cell obtained through the process described in Figure 19. As the number of battery cells 110 increases, the required surface pressure increases according to the degree of deformation, so the PD curve (C3) for the battery cell stack 120 naturally lies higher than the PD curve (C2) for a single battery cell.

[0132] FIG. 21 is a graph showing module stiffness curves for Examples 1 to 4 according to the present invention.

[0133] 21 shows the module stiffness curves for each of Examples 1 to 4. The PD curves for the battery cell stacks are not shown, but the equilibrium points (intersections) where the module stiffness curves for each of Examples 1 to 4 meet the PD curves for the battery cell stacks for each of Examples 1 to 4 are indicated.

[0134] Looking at the swelling behavior of the battery modules predicted using the above method, the battery module of Example 1 is predicted to deform by 5.4% in the width direction at the EOL state, with the internal battery cells and module frame subjected to a surface pressure of 0.8 MPa. The battery module of Example 2 is predicted to deform by 6.7% in the width direction at the EOL state, with the internal battery cells and module frame subjected to a surface pressure of 0.71 MPa. The battery module of Example 3 is predicted to deform by 6.1% in the width direction at the EOL state, with the internal battery cells and module frame subjected to a surface pressure of 0.29 MPa. Finally, the battery module of Example 4 is predicted to deform by 9.3% in the width direction at the EOL state, with the internal battery cells and module frame subjected to a surface pressure of approximately 0.44 MPa.

[0135] In all of the battery modules of Examples 1 to 4, in the EOL (End of Life) state, the deformation rate in the stacking direction of the battery cells is 12% or less, and the surface pressure applied to the battery cells is 0.9 MPa or less. Furthermore, the battery modules of Examples 1 to 4 have module stiffness curves calculated with a slope (MPa / %) range of 0.00417 to 0.225. That is, the module stiffness curves of the battery modules of Examples 1 to 4 can be formed in a range between a lower-limit module stiffness curve (C1b) with a slope (Sb) value of 0.00417 MPa / % and an upper-limit module stiffness curve (C1a) with a slope (Sa) value of 0.225 MPa / %.

[0136] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used for convenience of explanation, but these terms may differ depending on the position of the object of interest, the position of the observer, etc.

[0137] One or more battery modules according to the above-described embodiments may be mounted together with various control and protection systems such as a BMS (Battery Management System), a BDU (Battery Disconnect Unit), and a cooling system to form a battery pack.

[0138] The battery pack can be applied to various devices, specifically, but not limited to, transportation means such as electric bicycles, electric vehicles, and hybrid vehicles, and ESS (Energy Storage Systems), and can be applied to various devices that can use secondary batteries.

[0139] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0140] 100a, 100b battery modules 110 battery cells 120 Battery cell stack 1000 battery packs 1100 Pack Housing 1200 cross beam 1300 tubes

Claims

1. a battery module including a battery cell stack in which a plurality of battery cells are stacked in one direction; a pack housing in which the battery module is housed; a cross beam disposed on the bottom of the pack housing; and A battery pack including a tube disposed inside the cross beam, the cross beam is located on one side of the battery module in a stacking direction of the battery cells and extends in a direction perpendicular to the stacking direction of the battery cells, A fluid is introduced into the tube, The tube into which the fluid flows applies pressure to the battery module in a direction in which the battery cells are stacked.

2. The battery pack according to claim 1 , wherein the battery cells are stacked in one direction in the battery module while standing vertically on one surface of the bottom of the pack housing.

3. The battery pack of claim 1 , wherein the cross beam includes a frame portion including a first side portion, a second side portion, and a ceiling portion.

4. The battery pack according to claim 3 , wherein the cross beam is disposed so that one surface of the first side surface portion and one surface of the second side surface portion are parallel to both side surfaces of the battery module in a direction in which the battery cells are stacked.

5. an opening is formed in at least one of the first side surface portion or the second side surface portion; The battery pack according to claim 3 , wherein the tube is exposed through the opening and contacts the battery module.

6. The battery pack according to claim 1 , further comprising a fluid supply device connected to the tube to supply the fluid to the tube.

7. The battery pack according to claim 6 , further comprising a fluid control valve connecting the tube and the fluid supply device and controlling the amount of fluid flowing into the tube.

8. The battery pack of claim 7 , further comprising a pressure sensor connected to the tube for measuring a pressure in the tube.

9. the cross beam includes a frame portion including a first side portion, a second side portion, and a ceiling portion; The battery pack according to claim 7 , wherein the first side surface portion, the second side surface portion, and the ceiling portion form an n-shape in cross section of the frame portion.

10. The battery pack according to claim 9 , wherein the fluid control valve is located in a space surrounded by the first side surface portion, the second side surface portion, and the ceiling portion.

11. The battery pack of claim 9 , wherein the tubes are arranged in an n-shape within the n-shape of the frame portion.

12. The tube is made of a soft or elastic material, The battery pack according to claim 1 , wherein the fluid introduced into the tube is in a liquid or gel state.

13. the battery module further includes a module frame that houses the battery cell stack; the battery cells are stacked in one direction from one side surface of the module frame to another side surface of the module frame, a compression pad is interposed between adjacent battery cells or between the outermost battery cell and a side portion of the module frame; 2. The battery pack according to claim 1, wherein, in an end of life (EOL) state, a deformation rate in a stacking direction of the battery cells is 12% or less, and a surface pressure applied to the battery cells is 0.9 MPa or less.

14. the module stiffness curve of the battery module is calculated in a slope (MPa / %) range of 0.00417 or more and 0.225 or less; The battery pack according to claim 13 , wherein the module stiffness curve of the battery module corresponds to the relationship between the deformation rate of the module frame and the surface pressure applied to the module frame.

15. 15. The battery pack of claim 14, wherein the module stiffness curve of the battery module is derived by reflecting a frame stiffness curve of the module frame, a surface pressure applied to the compression pads, a degree of compression of the compression pads, and the number of the compression pads.

16. A device comprising the battery pack of claim 1.

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