CN117981149A - Battery pack and device comprising same - Google Patents

Abstract

A battery pack according to an embodiment of the present disclosure includes: a battery module including a plurality of battery cell stacks in which a plurality of battery cells are stacked in one direction; a battery pack case in which a battery module is accommodated; a cross member disposed at the bottom of the battery pack case; and a duct disposed inside the cross member. The cross member is located on one side of the stacking direction of the battery cells with respect to the battery module, and has a form extending in a direction perpendicular to the stacking direction of the battery cells. The fluid flows into the interior of the pipe.

Description

Battery pack and device comprising same

Technical Field

Cross Reference to Related Applications

The present application claims the benefits of korean patent application No. 10-2022-0021377, filed in the korean intellectual property office at 18 of 2 nd of 2022, and korean patent application No. 10-2023-0018548, filed in 13 of 2 nd of 2023, the disclosures of which are incorporated herein by reference in their entirety.

The present disclosure relates to a battery pack and an apparatus including the same, and more particularly, to a battery pack that can control expansion of battery cells and an apparatus including the same.

Background

In modern society, with the daily use of portable devices such as mobile phones, notebook computers, video cameras and digital cameras, development of technologies in the fields related to mobile devices as described above has begun. In addition, chargeable and dischargeable secondary batteries are used as energy sources for Electric Vehicles (EVs), hybrid Electric Vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and the like in an attempt to solve problems of air pollution and the like caused by existing gasoline vehicles using fossil fuel. Accordingly, the demand for development of secondary batteries is increasing.

The secondary batteries commercialized at present include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium secondary batteries. Among these secondary batteries, lithium secondary batteries are attracting attention because they have advantages of free charge and discharge, having a very low self-discharge rate and a high energy density, for example, exhibiting little memory effect as compared with nickel-based secondary batteries.

Such lithium secondary batteries mainly use lithium-based oxides and carbonaceous materials as positive electrode active materials and negative electrode active materials, respectively. The lithium secondary battery includes an electrode assembly in which positive and negative electrode plates coated with a positive and negative electrode active material, respectively, are arranged with a separator interposed therebetween, and a battery case sealing and accommodating the electrode assembly and an electrolyte.

Generally, lithium secondary batteries can be classified into can-type secondary batteries in which an electrode assembly is mounted in a metal can and soft pack-type secondary batteries in which an electrode assembly is mounted in a soft pack of an aluminum laminate sheet according to the shape of an external member.

Recently, secondary batteries are widely used not only for small devices such as smart phones but also for medium-or large-sized devices such as vehicles and energy storage systems. For the purpose of applying such a medium-sized device or large-sized device, a large number of secondary batteries may be electrically connected to improve capacity and output. Soft pack secondary batteries tend to be more widely used due to advantages such as easy stacking and light weight.

A soft pack type secondary battery may be generally manufactured through a process of injecting an electrolyte in a state in which an electrode assembly is received in a soft pack external member and sealing the soft pack external member.

When the charge and discharge are repeated, the secondary battery may generate gas inside due to degradation or the like. Also, when gas is generated from the inside in this way, the internal pressure increases, which may cause an expansion phenomenon in which the pressure resistance increases and at least a part of the external member expands. In particular, in the case of a soft pack type secondary battery, the structural rigidity of the external member is inferior to that of a can type secondary battery, so that the swelling phenomenon may occur more seriously.

Typically, the battery cells are housed in a module housing, and foam-shaped pads are arranged such that the module housing does not excessively constrain the battery cells, and the pads absorb the expansion of the battery cells.

When the swelling phenomenon of the battery cells progresses to a large extent, the pressure inside the battery increases and the volume increases, which may adversely affect the structural stability of the battery module. In addition, the battery module generally includes a plurality of secondary batteries. In particular, in the case of using a middle-or large-sized battery module in an automobile, an Energy Storage System (ESS), or the like, a large number of secondary batteries may be included and connected to each other for high output or high capacity. At this time, even if the volume of each secondary battery gradually increases due to swelling, the volume change of each secondary battery is accumulated to the battery module as a whole, and the degree of deformation may reach a serious level. In particular, the module frame accommodating the plurality of secondary batteries may be deformed, or the welded portion of the module frame may be broken. That is, a volume expansion (expansion) phenomenon due to expansion of each secondary battery may decrease the overall structural stability of the battery module. In addition, when the swelling force is greatly increased while the charge and discharge are repeated, the separator in the battery cell may be compressed, thereby partially degrading the battery performance.

Therefore, there is a need to develop a method capable of absorbing the expansion displacement during the swelling of the battery cell and applying an appropriate pressure to the battery cell.

Disclosure of Invention

Technical problem

It is an object of the present disclosure to provide a battery pack capable of absorbing an expansion displacement due to expansion of a battery cell and applying an appropriate pressure to the battery cell so that the battery cell may exhibit an optimal performance, and an apparatus including the battery pack.

However, the problems to be solved by the embodiments of the present disclosure are not limited to the above-described problems, and various extensions can be made within the scope of the technical ideas included in the present disclosure.

Technical proposal

According to one embodiment of the present disclosure, there is provided a battery pack including: a battery module including a battery cell stack in which a plurality of battery cells are stacked in one direction; a battery pack case in which a battery module is accommodated; a cross member disposed at the bottom of the battery pack case; and a duct disposed inside the cross member, wherein the cross member is located on one side of the stacking direction of the battery cells with respect to the battery module and has a form extending in a direction perpendicular to the stacking direction of the battery cells, and wherein the fluid flows into the duct inside.

The battery cells may be stacked in one direction in the battery module in a state of being vertically erected on one surface of the bottom of the battery pack case.

The cross beam may include a frame portion including a first side portion, a second side portion, and a top portion.

The cross member may be arranged such that one surface of the first side surface part and one surface of the second side surface part are parallel to both sides of the battery module in the direction in which the battery cells are stacked.

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

The duct into which the fluid flows may press the battery module in the stacking direction of the battery cells.

The battery pack may further include: and a fluid supply device connected to the pipe and supplying fluid to the pipe.

The battery pack may further include: a fluid control valve that connects the conduit with the fluid supply device and controls the amount of fluid flowing into the conduit.

The battery pack may further include: a pressure sensor connected to the pipe and measuring the pressure of the pipe.

The cross member may include a frame portion including a first side portion, a second side portion, and a top portion, and the first side portion, the second side portion, and the top portion may form an n-shape in a cross section of the frame portion.

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

The conduits may be arranged n-shaped within an n-shaped frame portion.

The tubing may be of a soft or elastic material and the fluid flowing into the tubing may be in a liquid or gel state.

The battery module may further include a module frame in which the battery cell stack is received, and the battery cells may be stacked in one direction from the side portion of the module frame to the other side portion. Compression pads may be interposed between adjacent battery cells or between the outermost battery cells and the side portions of the module frame at least one position. In an EOL (end of life) 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 may be 0.9MPa or less.

The module rigidity curve of the battery module may be calculated to be within a slope range (MPa/%) of 0.00417 or more and 0.225 or less, and the module rigidity curve of the battery module may correspond to a relationship between the deformation rate of the module frame and the surface pressure applied to the module frame.

The module rigidity curve of the battery module may be derived by reflecting the degree of compression of the compression pad with respect to the surface pressure applied to the compression pad and the number of compression pads on the module rigidity curve of the module frame.

According to another embodiment of the present disclosure, there is provided an apparatus including the above-described battery pack.

Advantageous effects

According to the embodiments of the present disclosure, the duct into which the fluid flows in the battery pack, in which the battery module is accommodated in the battery pack case, is provided inside the cross member disposed adjacent to the battery module, so that the expansion displacement due to the expansion of the battery cells can be effectively absorbed, and the appropriate pressure, which enables the battery cells to exhibit the optimal performance, can be applied.

The effects of the present disclosure are not limited to the above-described effects, and still other effects not described above will be clearly understood by those skilled in the art from the description of the appended claims.

Drawings

Fig. 1 is a perspective view illustrating a battery pack according to one embodiment of the present disclosure;

Fig. 2 is a perspective view illustrating 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 illustrating one battery cell included in the battery module of fig. 3;

fig. 5 is a perspective view illustrating components of the battery pack of fig. 1 except for a battery module;

fig. 6 is a perspective view illustrating a cross member included in the battery pack of fig. 1;

fig. 7 is a plan view schematically illustrating a battery pack according to an embodiment of the present disclosure;

FIG. 8 is a cross-sectional view showing a cross-section taken along section line A-A' of FIG. 6;

FIG. 9 is a cross-sectional view showing a cross-section taken along a section line B-B' of FIG. 6;

fig. 10 is an exploded perspective view illustrating a battery module according to another embodiment of the present disclosure;

fig. 11 is a perspective view of a battery module according to one embodiment of the present disclosure;

Fig. 12 is an exploded perspective view of the battery module of fig. 11;

Fig. 13 is a plan view illustrating any one of battery cells included in the battery module of fig. 12;

FIG. 14 is a cross-sectional view taken along section line A-A' of FIG. 11;

fig. 15 to 17 are graphs showing a module stiffness curve of a battery module and a P-D curve of a battery cell stack according to an embodiment of the present disclosure;

fig. 18 is a graph illustrating a range of module stiffness curves of a battery module according to one embodiment of the present disclosure;

FIG. 19 is a graph showing the P-D curve of a single cell;

Fig. 20 is a graph showing a P-D curve of a single cell and a P-D curve of a cell stack; and

Fig. 21 is a graph showing module stiffness curves according to examples 1 to 4 of the present disclosure.

Detailed Description

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the embodiments. The present disclosure may be modified in various different ways and is not limited to the embodiments set forth herein.

For clarity of description of the present disclosure, parts irrelevant to the description will be omitted, and like reference numerals denote like elements throughout the description.

Further, in the drawings, for convenience of description, the sizes and thicknesses of the respective elements are arbitrarily shown, and the present disclosure is not necessarily limited to those shown in the drawings. In the drawings, the thickness of layers, regions, etc. are exaggerated for clarity. In the drawings, the thickness of portions and regions are exaggerated for convenience of description.

In addition, it will be understood that when an element such as a layer, film, region or panel is referred to as being "on" or "over" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, it means that there are no other intervening elements present. Further, the word "upper" or "above" means disposed above or below the reference portion, and does not necessarily mean disposed at the upper end of the reference portion toward the opposite direction of gravity.

Furthermore, throughout the description, when a portion is referred to as "comprising" or "including" a particular element, this means that the portion may also include other elements, unless stated otherwise, other elements are not excluded.

Further, in the entire description, when referred to as a "plane", this means that when the target portion is viewed from the upper side, and when referred to as a "cross section", this means that the target portion is viewed from the side of the cross section that is vertically sectioned at this time.

Fig. 1 is a perspective view illustrating a battery pack according to one embodiment of the present disclosure.

Referring to fig. 1, a battery pack 1000 according to an embodiment of the present disclosure includes a battery module 100a, a battery pack case 1100 in which the battery module 100a is received, and a cross member 1200 disposed at the bottom of the battery pack case 1100. One or more battery modules 100a may be accommodated in the battery pack case 1100. Fig. 1 shows a form of accommodating a plurality of battery modules 100a.

First, referring to fig. 2 to 4, the battery module 100a included in the battery pack 1000 according to the present embodiment will be described in detail.

Fig. 2 is a perspective view illustrating 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 illustrating one battery cell included in the battery module of fig. 3.

Referring to fig. 2 to 4, the battery module 100a according to the present embodiment includes a cell stack 120 in which a plurality of battery cells 110 are stacked in one direction. The battery cell 110 may be a pouch-type battery cell. The pouch-type battery cell may be formed by accommodating the electrode assembly in a pouch case including a laminate sheet of a resin layer and a metal layer, and then bonding the outer peripheral portion of the pouch case.

In particular, 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 cell body 113, respectively. In a state in which an electrode assembly (not shown) is received in the soft can body 114, the battery cell 110 may be produced by joining both ends 114a and 114b of the battery cell case 114 and one side 114c connecting both ends 114a and 114 b. In other words, the battery cell 110 according to the present embodiment has a total of three sealing parts having a structure sealed by a method such as welding, and the remaining other side part 114d may be composed of folded parts. The battery cell 110 according to the present embodiment may be a pouch-type battery cell configured to accommodate the electrode assembly inside the pouch case 114 and to seal the outer circumferential side of the pouch case 114. The structure of the battery cell 110 described above is exemplary, and it is apparent that a unidirectional battery cell in which two electrode leads protrude in the same direction may be used.

The pouch-type battery cells 110 may have a sheet shape, and such battery cells 110 are stacked in one direction to form a battery cell stack 120. As an example, the battery cells 110 may be stacked in a direction parallel to the y-axis while facing the surface of the battery body 113.

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

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, in the battery cell stack 120, the side plates 200 may be located on both sides of the direction in which the battery cells 110 are stacked. As shown in fig. 3, the battery cells 110 are stacked in a direction parallel to the y-axis, and the side plates 200 may be respectively disposed on both sides of the battery cell stack 120 in the stacking direction of the battery cells 110.

A pair of bus bar frames 300 may be respectively located at one side and the other side of the battery cell stack 120. Specifically, the bus bar frame 300 may be located at one side and the other side of the battery cell stack 120 in the direction in which the electrode leads 111 and 112 of the battery cell 110 protrude. When the battery cells 110 are stacked in the y-axis direction, the electrode leads 111 and 112 may protrude in the x-axis direction and the-x-axis direction, and the bus bar frame 300 may be positioned in the x-axis direction and the-x-axis direction, respectively, with respect to the battery cell stack 120. Further, such a bus bar frame 300 may be arranged to cover the battery cell stack 120.

Bus bars 310 and module connectors 320 may be mounted on bus bar frame 300.

The bus bar 310 may be electrically connected with the electrode leads 111 and 112 of the battery cell 110 while being mounted on the bus bar frame 300. The bus bar 310 may be provided in a plurality of bars. The battery cells 110 may be electrically connected in series or in parallel via the bus bars 310.

The module connector 320 may be electrically connected with an external device while being mounted on the bus bar frame 300. As an example, the module connector 320 may be provided with a high voltage connector, a low voltage connector, etc., and may be connected with an external BMS (battery management system) to transmit temperature information and voltage information of the battery module 100 a.

Meanwhile, the sensing PCB 330 connecting the pair of bus bar frames 300 may be arranged. The sensing PCB 330 may be provided as a flexible printed circuit board. The sensing PCB 330 is provided with a predetermined length and may be disposed at the upper side of the battery cell stack 120.

The band member 400 is connected with the pair of side plates 200, and may at least partially cover the upper and lower sides of the battery cell stack 120. That is, the band member 400 may be positioned at 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 is connected with one side plate 200, and the other end of the band member 400 may be connected with the other side plate 200. Such a belt member 400 may be provided with a metal member of an elastic material. The connection method between the band member 400 and the pair of side plates 200 is not particularly limited, but may be joined by welding as an example. In particular, both ends of the band member 400 may be bent and engaged with the side plates 200.

On the upper side or the lower side of the battery cell stack 120, the belt members 400 may be respectively arranged at regular intervals in the longitudinal direction of the battery module 100 a. Here, the longitudinal direction of the battery module 100a is a direction perpendicular to the direction in which the battery cells 110 are stacked, and the longitudinal direction of the battery module 100a corresponds to a direction parallel to the x-axis in the drawing.

Meanwhile, the battery module 100a may further include a heat sink 500. The heat sink 500 serves to cool the battery cell stack 120 and may be disposed at the lower side of the battery cell stack 120. The heat sink 500 may be located at the bottom of the soft shell body, which will be described later.

Next, the battery pack case 1100 and the cross member 1200 according to the present embodiment will be described in detail with reference to fig. 1, 5 to 7, and the like.

Fig. 5 is a perspective view illustrating components of the battery pack of fig. 1 except for a battery module. Fig. 6 is a perspective view illustrating a cross member included in the battery pack of fig. 1. Fig. 7 is a plan view schematically illustrating a battery pack according to an embodiment of the present disclosure. In particular, fig. 7 is a plan view schematically showing a state in which the battery pack is viewed in the-z axis direction on the xy plane.

Referring to fig. 1, 5 to 7, the cross member 1200 is disposed at the bottom 1100F of the battery pack case 1100, is located on one side of the stacking direction of the battery cells 110 with respect to the battery module 100a, and has a shape extending in a direction perpendicular to the stacking direction of the battery cells 110.

The battery pack case 1100 is a structure in which the battery modules 100a are received, and for example, may be in the form of an upper part that is open while having an inner storage space. The battery module 100a is disposed in the storage space, although not specifically shown, a battery pack cover may be assembled on the open upper portion of the battery pack case 1100.

As described above, the battery cells 110 are stacked in one direction in the battery module 100a, and the cross member 1200 is located on one side of the stacking direction of the battery cells 110 with respect to the battery module 100a, and has a form extending 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 in a state of being vertically erected on one surface of the bottom 1100F of the battery pack case 1100 within the battery module 100 a. Accordingly, one side of the cross member 1200 may be disposed in parallel with one side of the battery body 113 (see fig. 4) of the battery cell 110. As shown in the drawings, the battery cells 110 are stacked in a direction parallel to the y-axis in a state perpendicular to one surface of the bottom 1100F of the battery pack case 1100. The cross member 1200 is located on one side of the y-axis direction or the-y-axis direction with respect to any one of the battery modules 100 a. Furthermore, the cross beam 1200 may have a form extending in a direction parallel to the x-axis. The cross member 1200 as described above is arranged to support an expansion force when the battery cell 110 expands due to expansion.

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

When the battery cell 110 is a pouch-type battery cell and has a sheet shape, the battery cell 110 mainly expands in the stacking direction during expansion. That is, an expansion force is applied in a direction parallel to the y-axis in the drawing. The cross member 1200 located on one side of the battery module 100a in the stacking direction of the battery cells 110 may support the expansion force of the battery cells 110. In addition, the tubes 1300 inside the cross beam 1200 can absorb the expansion displacement of the battery cells 110. Thus, the effect of the dispersion pressure between the battery cells 110 can be enhanced.

Meanwhile, the fluid flowing into the pipe 1300 may be in a liquid state or a gel state. For example, the fluid may be cooling water or water. Cooling water or water is filled in the pipe, so that the cooling effect of the battery cell can be achieved. In addition, when the fluid is a hydrogel, this is advantageous in dispersing stress concentrated in a specific region and maintaining thermal equilibrium. In contrast, it can be assumed that a gas is used as the fluid, but when a gas is used as the fluid, there may be a problem in that the heated gas increases the temperature of the battery cell 110 as a whole.

The battery pack 1000 according to the present embodiment is configured such that the pipe 1300 into which the fluid flows is provided inside, and thus, it is possible to apply a constant force to the plurality of battery cells 110 and absorb an expansion displacement due to the expansion of the battery cells. Since this is a control method using a fluid, the surface pressure of the battery cell 110 can be maintained constant even if the battery cell 110 swells.

Next, the detailed structure of the cross member and the pipe according to the present embodiment will be described in detail with reference to fig. 8 and 9, etc.

Fig. 8 is a cross-sectional view showing a cross-section taken along a section line A-A' of fig. 6. Fig. 9 is a sectional view showing a section taken along a section line B-B' of fig. 6. For convenience of explanation, fig. 8 and 9 show in a form in which the battery module 100a is disposed near the cross member 1200.

Referring collectively to fig. 5, 6, 8 and 9, a cross beam 1200 according to the present embodiment may include a frame portion 1200F, the frame portion 1200F including a first side portion 1210, a second side portion 1220 and a top portion 1230. The tube 1300 may be located inside the frame portion 1200F.

First and second side portions 1210 and 1220 may be disposed perpendicular to one surface of bottom 1100F of battery case 1100, and top portion 1230 may connect first and second side portions 1210 and 1220.

At this time, the cross member 1200 may be arranged 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 direction in which the battery cells 110 are stacked. Any one of the battery modules 100a may be located on one surface of the first side surface portion 1210, and another one of the battery modules 100a may be located on one surface of the second side surface portion 1220. The first and second side portions 1210 and 1220 of the cross beam 1200 may support the expansion force of the battery cell 110.

At this time, an opening 1200P may be formed on at least one of the first side surface portion 1210 or the second side surface portion 1220. The opening 1200P may correspond to a shape in which one region of the frame portion 1200F is penetrated. The duct 1300 may be exposed through the opening 1200P and contact one side of the battery module 100a, and may press the battery module 100a with a constant pressure.

In particular, one surface of the first side surface part 1210 and one surface of the second side surface part 1220 are arranged in parallel with both sides of the battery module 100a in the direction in which the battery cells 110 are stacked, and the duct 1300 into which the fluid F flows may press the battery module 100a in the direction in which the battery cells 110 are stacked via the opening 1200P.

With the above-described structure, the pipe 1300 may apply a constant pressure to the battery cell 110 using the pressure of the fluid F therein. By adjusting the pressure and amount of the fluid F flowing into the pipe 1300, the pressure applied to the battery cell 110 can be maintained at an optimal state. In addition, in the case of an all-solid-state battery or a pure Si battery, the performance of the battery cell is excellent when the initial pressure is high. In order to increase the initial pressure, a pressing device using a fluid may be used as in the present embodiment. In addition, even if the battery cells 110 expand in the stacking direction due to expansion, the fluid F in the pipe 1300 can absorb the expansion displacement of the battery cells 110.

Meanwhile, the battery pack 1000 according to the present embodiment may include a fluid supply device 1400 connected with the pipe 1300 to supply fluid to the pipe 1300. In addition, the battery pack 1000 may further include a fluid control valve 1500 that connects the pipe 1300 with the fluid supply device 1400 and controls the amount of the fluid F flowing into the pipe 1300. In addition, the battery pack 1000 may further include a pressure sensor 1600 connected to the pipe 1300 to measure the pressure of the pipe 1300.

As an example, the frame portion 1200F of the cross beam 1200 may include a first side portion 1210, a second side portion 1220, and a top portion 1230, wherein the top portion 1230 may connect an upper end of the first side portion 1210 with an upper end of the second side portion 1220. That is, the first side surface portion 1210, the second side surface portion 1220, and the top portion 1230 may form an n-shape in a cross section of the frame portion 1200F. The tubes 1300 may be correspondingly arranged n-shaped within the n-shaped frame portion 1200F.

At this time, the position of the fluid control valve 1500 or the pressure sensor 1600 is not particularly limited, but may be located in the inner space of the frame portion 1200F where the n-shape is formed as described above. That is, the fluid control valve 1500 may be located in a space surrounded by the first side surface portion 1210, the second side surface portion 1220, and the top portion 1230. Pressure sensor 1600 may similarly be located in a space surrounded by first side portion 1210, second side portion 1220, and top portion 1230. Since the space inside the frame portion 1200F of the cross member 1200 can be used as a space where the fluid control valve 1500 or the pressure sensor 1600 is arranged, the space utilization inside the battery pack case 1100 can be increased.

Meanwhile, the fluid supply apparatus 1400 according to the present embodiment may be an apparatus for supplying fluid to the inside of the pipe 1300, and the pipe 1300 is an apparatus using a conventional fluid pump or a ram.

The fluid supply apparatus using the ram includes a fluid supply pipe connected to the pipe 1300. At this time, the fluid supply pipe is located at a higher position than the fluid supply area of the pipe 1300, and has a structure formed to be perpendicular to the ground. In addition, the height of the fluid inside the fluid supply pipe may be adjusted to determine the amount of the fluid F flowing into the pipe 1300, thereby controlling the pressure of the pipe 1300. In such a case, the fluid supply device may apply fluid pressure to the conduit without the need for a separate energy source.

Meanwhile, the fluid control valve 1500 according to the present embodiment may be a conventional valve and connected between the fluid supply device 1400 and the pipe 1300, thereby being able to control the flow rate of the fluid F flowing into the pipe 1300. Thereby, the surface pressure of the battery cell 110 can be kept constant. For example, fluid control valve 1500 operates by receiving a signal from pressure sensor 1600 and may open or close a flow path. Specifically, the fluid control valve 1500 may open a flow path to supply or discharge the fluid F when the pressure in the pipe 1300 is greater than or less than a reference range, and the fluid control valve 1500 may close the flow path when the pressure in the pipe 1300 is within the reference range.

In addition, the pressure sensor 1600 according to the present embodiment is connected to the pipe 1300, and thus can measure a pressure change of the pipe 1300 into which the fluid F flows. Additionally, a pressure sensor 1600 may be coupled to the fluid control valve 1500 to communicate pressure information of the tubing 1300. Whether or not the fluid control valve 1500 is operated is set based on the measured pressure measured by the pressure sensor 1600.

By supplying the fluid F to the pipe 1300, the pressure of the pipe 1300 may be increased, and the initial pressure applied to the battery cell 110 may be reduced as needed. That is, the final assembly of the battery pack 1000 according to the present embodiment may be completed in a state in which fluid pressure is applied to the pipe 1300 inside the cross member 1200 to apply appropriate pressure to the battery cells 110.

Meanwhile, when swelling occurs in the battery cells 110 inside the battery module 100a, the pressure applied to the duct 1300 increases. In such a case, the fluid supply apparatus 1400 and the fluid control valve 1500 may operate according to the pressure value of the pipe 1300. That is, when the pressure of the pipe 1300 exceeds a predetermined value, the fluid control valve 1500 is opened until the pressure inside the pipe 1300 reaches a reference value, and the fluid supply device 1400 may discharge the fluid F inside the pipe 1300 to the outside of the pipe 1300. Thereby, the pressure can be reduced. Meanwhile, if the pressure of the pipe 1300 is less than a predetermined value, the fluid control valve 1500 is opened, and the fluid supply device 1400 may supply the fluid F into the pipe 1300. That is, the battery pack 1000 according to the present disclosure may control the inflow amount of fluid inside the pipe 1300 supporting the cell stack 120 based on the pressure of the pipe 1300 measured by the pressure sensor 1600. Thereby, the battery cell 110 can maintain a constant surface pressure.

In general, the expansion of the battery cells 110 is controlled using compression pads disposed within the battery module, but in the present embodiment, since the amount of fluid in the pipe 1300 inside the cross member 1200 can be adjusted, thereby controlling the expansion of the battery cells 110 and absorbing the expansion displacement, this can reduce the number of compression pads. The battery capacity is increased by reducing the number of compression pads, and the number of components is reduced.

Further, in the conventional case, the initial pressure state may vary during the accommodation of the battery module 100a due to the tolerance of the battery cells 110, or the pressure may vary under EOL (end of life) conditions. However, in the present embodiment, the battery module 100a is disposed in the battery pack case 1100, and the amount of fluid may be controlled to adjust the applied pressure even after the assembly of the battery pack 1000 is completed, so that it is possible to prevent a variation in the initial pressing state due to a tolerance or a variation in the pressure under EOL conditions.

Further, in the disassembly process of the battery pack 1000, the fluid F inside the pipe 1300 may be discharged to reduce the pressure, so that the battery pack 1000 may be easily disassembled. Further, since the amount of the fluid F is adjusted based on the pressure of the pipe 1300, it is not necessary to consider the expansion characteristics that vary for each battery module 100a, and it is not necessary to perform the expansion characteristic test for various conditions.

Meanwhile, the duct 1300 according to the present embodiment is disposed inside the cross member 1200, not inside a separate battery module. When the number of battery modules 100a mounted in the battery pack 1000 increases, there are problems in that the number of components increases and the mounting form becomes complicated in the form of arranging the duct for each individual battery module. On the other hand, the duct 1300 according to the present embodiment is provided on the cross member 1200, and the expansion of the plurality of battery modules 100a can be simultaneously controlled. Since the duct 1300 inside the cross member 1200 is configured to press each battery module 100a in the stacking direction of the battery cells 110, there is no problem in controlling the expansion of all of each battery module 100 a. Therefore, the present embodiment has the advantage of fewer parts and simpler installation form than arranging the duct in each individual battery module. Even so, there is no problem in maintaining the pressing force and the surface pressure of the battery cell 110 constant and absorbing the expansion displacement.

Meanwhile, fig. 10 is an exploded perspective view illustrating a battery module according to another embodiment of the present disclosure.

Referring to fig. 10, a battery module 100b according to another embodiment of the present disclosure may include 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 received, and end plates 220 at two open sides of the module frame 210.

The shapes of the battery cell stacks 120 are identical or similar to each other as compared to the above-described battery module 100a, but differ in that the battery cell stacks 120 are accommodated in the module frame 210.

The module frame 210 may be in the form of a single frame having an upper surface, a lower surface, and two sides integrally formed, as shown in the drawings. In another embodiment, a module frame in the form of a welded joint with a U-shaped frame with an upper cover integral with the lower surface and both sides may also be used.

The module frame 210 has a form in which two opposite sides are open, and the battery cell stack 120 is received in the open portion. After being accommodated, the module frame 210 is coupled with the end plate 220 such that the end plate 220 covers the open portion of the module frame 210.

Not only the battery module 100a as described above may be mounted in the battery pack case together with the cross member where the duct is located, but also the battery module 100b of the present embodiment may be mounted in the battery pack case together with the cross member where the duct is located to form a battery pack.

When the battery cell 110 is repeatedly charged and discharged, the battery cell 110 swells and expands. In the case of this type of battery module 100b, the force applied to the module frame 210 gradually increases with expansion. In general, in order to withstand such a situation, the thickness of the module frame 210 needs to be set to be thick. However, in the case of the battery pack according to the present embodiment, the pressing force of the battery cells 110 may be maintained constant using a fluid, and the expansion displacement is absorbed, so that the thickness of the module frame 210 may be set to be thin. Therefore, from the viewpoint of the entire battery pack including the battery module 100b, there are advantages in that the weight can be reduced and the battery capacity can be increased.

Further, in general, when the battery cell stack 120 is received in the module frame 210, in order to apply an appropriate initial pressure to the battery cells 110, the reception is performed while the left and right sides of the above-described U-shaped frame are spaced apart, or while a specific pressing force is applied to both sides of the battery cell stack 120. However, in the case of the battery pack according to the present embodiment, after the battery modules 100b are arranged in the battery pack case, the amount of fluid inside the duct 1300 may be adjusted to adjust the applied pressure, and thus, it is not necessary to accommodate the battery cell stack 120 inside the module frame 210 as in the conventional case. That is, after the battery cell stack 120 is conventionally received inside the module frame 210 and the battery module 100b is disposed near the cross member 1200, initial pressing may be performed in a manner to increase the pressure of the duct 1300.

Meanwhile, referring again to fig. 5 and 7, the battery pack 1000 according to the present embodiment may further include a vertical beam 1700 extending in a direction perpendicular to the extending direction of the cross beam 1200. As the number of arranged battery modules increases, an appropriate number of vertical beams 1700 may be arranged to support the battery modules and form a rigid structure.

Next, a method of designing a battery module according to the present embodiment will be described with reference to fig. 11 to 21.

Fig. 11 is a perspective view of a battery module according to one embodiment of the present disclosure. Fig. 12 is an exploded perspective view of the battery module of fig. 11. Fig. 13 is a plan view illustrating any one of the battery cells included in the battery module of fig. 12.

Referring to fig. 11 to 13, a battery module 100 according to an embodiment of the present disclosure may include a battery cell stack 120 in which a plurality of battery cells 110 are stacked in one direction and a module frame 200 in which the battery cell stack 120 is accommodated. In addition, the battery module 100 may further include at least one compression pad 400.

First, the battery cell 110 may be a pouch-type battery cell. The pouch-type battery cell may be formed by accommodating the electrode assembly in a pouch case including a laminate sheet of a resin layer and a metal layer, and then joining the outer peripheral portions of the pouch case. Such a battery cell 110 may be formed in a rectangular sheet-like structure. In particular, the battery cell 110 according to the present embodiment 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 cell body 113, respectively. In a state in which an electrode assembly (not shown) is received in the battery cell case 114, the battery cell 110 may be produced by joining both ends 114a and 114b of the battery cell case 114 and one side 114c connecting the both ends 114a and 114 b. In other words, the battery cell 110 according to one embodiment of the present disclosure has a total of three sealing parts, and the remaining other side part may be composed of the folded part 115. A longitudinal direction of the battery cell 110 may be defined between the both ends 114a and 114b of the battery case 114, and a width direction of the battery cell 110 may be defined between one side 114c connecting the both ends 114a and 114b of the battery case 114 and the folded portion 115.

Meanwhile, only the battery cell 110 having a structure in which the electrode leads 111 and 112 protrude in both directions of one side and the other side is described, but it is apparent that in another embodiment of the present disclosure, a one-way pouch type battery cell in which the electrode leads protrude together in one direction may be used.

The battery cell 110 may be composed of a plurality, and the plurality of battery cells 110 may be stacked to be electrically connected to each other, thereby forming the battery cell stack 120. The battery cell case 114 is generally formed in a stacked structure of a resin layer/a metal thin film layer/a resin layer. For example, when the surface of the battery case is formed of an O (orientation) -nylon layer, when a plurality of battery cells are stacked to form a middle-sized battery module and a large-sized battery module, it tends to easily slide due to external impacts. Accordingly, in order to prevent such a problem and maintain a stable stacked state of the battery cells, an adhesive part may be provided on the surface of the battery case to form the battery cell stack 120. The adhesive may be a self-adhesive such as double sided tape or a chemical adhesive that bonds by chemical reaction during bonding. The adhesion portion will be described later.

A plurality of battery cells 110 are stacked in one direction to form a battery cell stack 120, and battery cells 110 having a rectangular sheet-like structure may be stacked in one direction while facing one surface of the battery body 113. More specifically, the battery cells 110 may be stacked in a vertical configuration such that one surface of the battery cells 110 is parallel to the side portions 210 and 220 of the module frame 200, which will be described later. Fig. 12 illustrates a state in which the battery cells 110 are stacked in a direction parallel to the y-axis to form a battery cell stack 120. Accordingly, in the battery cell stack 120, the electrode leads 111 and 112 may protrude toward the x-axis direction and the-x-axis direction.

The module frame 200 may be a frame having a form in which one side and the other side are opened. The battery cell stack 120 is inserted through one side or the other open side of the module frame 200 such that the battery cell stack 120 can be received in the inner space of the module frame 200.

The module frame 200 includes side portions 210 and 220 that cover both sides of the battery cell stack 120 in the stacking direction of the battery cells 110, respectively. In the battery cells 110 stacked along the y-axis direction, each of the side parts 210 and 220 of the module frame 200 may cover the side surfaces 120 of the battery cell stack 120 in the y-axis direction and the-y-axis direction.

In addition, the module frame 200 may include an upper surface part 230 and a lower surface part 240 connecting the side surface parts 210 and 220. The upper surface part 230 and the lower surface part 240 of the module frame 200 may cover the upper surface and the lower surface of the battery cell stack 120, respectively, which is received inside the module frame 200.

Meanwhile, the module frame 200 shown in fig. 12 may have a form in which the side surface parts 210 and 220, the upper surface part 230, and the lower surface part 240 are integrated, but in another embodiment of the present disclosure, the module frame may have a form in which a U-shaped frame and an upper cover are coupled together. The U-shaped frames covering both sides and the lower surface of the battery cell stack and the upper cover covering the upper surface of the battery cell stack may be joined at the corresponding corners to form a module frame.

The battery module 100 according to the present embodiment may include a bus bar frame 500 accommodated 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 at one side and the other side of the battery cell stack 120, respectively, and the electrode leads 111 and 112 protrude from the front frame 510 and the rear frame 520. In addition, the bus bar frame 500 may further include an upper frame 530 connected to each of the front frame 510 and the rear frame 520 and located at the upper portion of the battery cell stack 120.

Bus bars 540 for connecting the electrode leads 111 and 112 of the battery cells 110 included in the battery cell stack 120 may be mounted on the front frame 510 and the rear frame 520. Specifically, the electrode leads 111 and 112 of the battery cell 110 are bent after penetrating the slits formed in the front and rear frames 510 and 520, and may be joined with the bus bar 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.

The battery module 100 according to the present embodiment may include end plates 300 at both open sides of the open module frame 200 facing each other. The end plate 300 may be disposed to cover the open one side and the other side of the module frame 200. That is, the two end plates 300 may be located at two open sides of the module frame 200 and joined at corresponding corners of the module frame 200 by welding or the like. The end plate 300 may physically protect the cell stack 120 and other electronic components from external impacts.

Fig. 14 is a cross-sectional view taken along section line A-A' of fig. 11.

Referring collectively to fig. 12 to 14, the battery module 100 according to the present embodiment includes at least one compression pad 400 disposed at least one position between adjacent battery cells 110 or between the outermost battery cell 110 and the side parts 210 and 220 among the battery cells 110.

The compression pad 400 is a foam-shaped member and may locally absorb the expansion of the battery cell. Specifically, when charge and discharge are repeated, the battery cell 110 may generate gas inside due to degradation or the like. Also, when gas is generated from the inside in this way, the internal pressure increases, which may cause an expansion phenomenon in which the pressure resistance increases and at least a part of the external member expands. In particular, in the case of a soft pack type secondary battery, the structural rigidity of the external member is weaker than that of a can type secondary battery, so that the swelling phenomenon may occur more seriously.

When the swelling phenomenon occurs in the secondary battery, the pressure inside the battery increases and the volume increases, which may adversely affect the structural stability of the battery module. Accordingly, by disposing the compression pad 400 compressed when pressure is applied to the inside of the battery module 100, it is attempted to locally absorb the expansion of the battery cell 110. The material of the compression pad 400 is not particularly limited as long as it can be compressed to absorb the expansion of the battery cell 110, and may include a polyurethane material as an example.

Next, a method of designing a battery module according to the present embodiment will be described with reference to fig. 15 to 21.

Fig. 15 to 17 are graphs showing a module rigidity curve of a battery module and a P-D curve of a battery cell stack according to an embodiment of the present disclosure. Fig. 18 is a graph illustrating a range of module stiffness curves of a battery module according to one embodiment of the present disclosure.

Referring collectively to fig. 12, 14, and 15 to 18, in the battery module 100 according to the embodiment of the present disclosure, as described above, the cell stack 120 in which the cells 110 are stacked may be accommodated in the module frame 200. Within the battery module, the battery cells 110 may be stacked in one direction from the side surface portion 210 to the other side surface portion 220 of the module frame 200. In addition, a compression pad 400 may be interposed between adjacent battery cells 110 or between the outermost battery cells 110 and the sides 210 and 220 of the module frame 200 at least one position.

At this time, a module stiffness curve C1 caused by the module frame 200 and a P-D (pressure-displacement) curve C3 of the cell stack 120 showing the expansion characteristics of the cells 110 are calculated, respectively, and fitted into one graph. Then, the swelling behavior of the battery module may be predicted by a method of finding a balance point (intersection point) between the two curves.

Fig. 15 to 17 show the intersections P, P 'and P "between the module stiffness curves C1, C1' and C" and the P-D curve C3 of the cell stack. The P-D curve C3 of the battery cell stack is a curve showing the relationship between the surface pressures to which the battery cells 110 are subjected according to the degree of variation when the thickness of the battery cells 110 is changed due to the swelling of the battery cells 110. The P-D curve C3 of the cell stack may be measured in an EOL (end of life) state of the cell 110. Here, EOL refers to a state when a ratio of a current capacity of the battery to an initial capacity of the battery reaches a predetermined ratio, and the ratio may be 80%. In other words, EOL may refer to a battery state when the capacity of the battery reaches 80% of an initial value, and may correspond to a state where the life of the corresponding battery expires or needs replacement. Meanwhile, the module rigidity curves C1, C1', and c″ are curves showing the relationship between the degree to which the width W of the module frame 200 is changed according to the direction in which the battery cells 110 are stacked and the amount applied to the module frame 200. The direction in which the battery cells 110 are stacked corresponds to the direction from one side 210 to the other side 220 of the module frame 200, and the direction in which the battery cells 110 are stacked is hereinafter referred to as the width direction. Further, widths W and W' of the module frame 200 represent distances from one side portion 210 to the other side portion 220. Each of the module stiffness curve C1 and the P-D curve C3 of the cell stack will be described in detail below.

In each of the module stiffness curves C1, C1' and c″ and the P-D curve C3 of the cell stack, the X-axis corresponds to the deformation rate, and the unit may be%. The Y-axis corresponds to the applied surface pressure and may be in MPa.

The points P, P 'and P "of intersection between the module stiffness curves C1, C1' and C" and the P-D curve C3 of the cell stack correspond to points where the behavior due to expansion of the cell stack 120 balances with the behavior due to deformation of the module frame 200. In other words, in the case where the battery cell stack 120 exhibiting the specific P-D curve C3 in the EOL (end of life) state is received in the battery module in the module frame 200 exhibiting the specific module stiffness curve C1, it can be predicted that the corresponding battery module has the deformation rate and the surface pressure corresponding to the intersection P, P' and p″ in the EOL state. That is, the battery module is deformed in the width direction by an amount corresponding to the X-axis value of the intersection P, P 'and p″ in the EOL state, and the battery cells 110 and the module frame 200 receive as much surface pressure as the Y-axis value of the intersection P, P' and p″.

At this time, as shown in fig. 15, the intersection point P is preferably located within the deformation limit point x1 and the pressure limit point y 1. The deformation limit point x1 is 12% and the pressure limit point y1 is 0.9MPa. That is, it is preferable that the X-axis value of the intersection point P is 12% or less (12% is the deformation limit point X1), and the Y-axis value of the corresponding intersection point P is 0.9MPa (0.9 MPa is the pressure limit point Y1) or less. That is, the battery module according to the present embodiment may have such features that: in the EOL state, the deformation rate in the direction in which the battery cells 110 are stacked is 12% or less, and the surface pressure applied to the battery cells 110 is 0.9MPa or less.

As shown in fig. 16, when the Y-axis value of the intersection P' exceeds the pressure limit point Y1, it is predicted that the surface pressure exceeding the pressure limit point Y1 is applied to the battery cells 110 and the module frames 200 of the corresponding battery modules in the EOL state. When a pressure exceeding 0.9MPa (0.9 MPa is the pressure limit point y 1) is applied to the battery cell 110, a problem of deterioration (e.g., abrupt decrease) in life performance of the battery cell may occur. Further, when a pressure exceeding 0.9MPa (0.9 MPa is the pressure limit point y 1) is applied to the module frame 200, a surface pressure exceeding the yield strength may be applied, so that the module frame 200 may be damaged and deformed.

As shown in fig. 17, when the X-axis value of the intersection p″ exceeds the deformation limit point X1, it is predicted that the battery module will be deformed more in the width direction than the deformation limit point X1 in the EOL state. This means that the thickness variation due to the swelling of the battery cell 110 is excessively allowed, which may cause problems such as disconnection between the electrode leads and the tabs in the battery cell 110 and occurrence of cracks in the pouch-type battery case of the battery cell 110. In addition, since the battery module is predicted to deform more than the deformation limit point x1 of 12%, the space occupied by the battery module inside the battery pack excessively increases, which results in a decrease in the energy density of the battery module and the battery pack.

Meanwhile, referring to fig. 18, in the case of the battery module according to the present embodiment, the module rigidity curve C1 may be calculated to be within a slope range of 0.00417 or more and 0.225 or less (MPa/%). That is, the module rigidity curve C1 of the battery module according to the present embodiment may be formed in a range between the lower limit module rigidity curve C1b having the slope Sb of 0.00417MPa/% and the upper limit module rigidity curve C1a having the slope Sa of 0.225 MPa/%. In order that the intersection point (P) between the module stiffness curve C1 and the P-D curve C3 of the cell stack is located in the range of the deformation limit point x1 and the pressure limit point y1, it is preferable that the module stiffness curve C1 is calculated to be in the slope range of 0.00417 or more and 0.225 or less (MPa/%).

The module stiffness curve C1 will be described in detail below. As described above, the module rigidity curve C1 is a curve showing the relationship between the degree to which the width of the module frame 200 is changed according to the direction in which the battery cells 110 are stacked and the load applied to the module frame 200. From the view of the module stiffness curve C1, the X-axis corresponds to the% deformation rate of the module frame 200 in the width direction. The deformation ratio may be calculated based on the width W' (see fig. 14) of the module frame 200 deformed in the width direction with respect to the width W (see fig. 14) of the module frame 200 before deformation. For example, the deformation ratio may be calculated as a ratio of the width W (see fig. 14) of the module frame 200 to the degree W' -W of the width deformation of the module frame 200 before the deformation. From the perspective of the module stiffness curve C1, the Y-axis may correspond to the surface pressure (MPa) applied to the sides 210 and 220 of the module frame 200 according to the deformation rate of the module frame 200.

To calculate the module stiffness curve C1, first, a frame stiffness curve may be calculated. The frame stiffness curve is a curve of 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 may be obtained through several practical tests or simulations. For example, an actual force is applied to the module frame 200 to measure the degree of deformation of the module frame 200 in the width direction. By repeating this process, while varying the applied force, a frame stiffness curve can be derived. By taking into account the impact of compression pad 400 on the frame stiffness curve, a module stiffness curve C1 can be derived. Specifically, the degree of compression pad 400 relative to the surface pressure applied to compression pad 400 and the number of compression pads 400 may be reflected in the frame stiffness curve to ultimately derive a module stiffness curve C1.

Next, the P-D curve C3 of the cell stack will be described in detail. As described above, the P-D curve C3 of the battery cell stack is a curve showing the relationship of the surface pressure that the battery cells 110 are subjected to according to the degree of variation when the thickness of the battery cells 110 is changed due to swelling. From the perspective of the P-D curve C3 of the cell stack, the X-axis may correspond to a deformation rate (%) along the width direction of the cell stack 120, and the Y-axis may correspond to a surface pressure (MPa) applied to the cells 110 included in the cell stack 120.

Next, a process of calculating the P-D curve C3 of the battery cell stack will be described in detail with reference to fig. 19 and 20.

Fig. 19 is a graph showing a P-D curve of a single battery cell.

Referring to fig. 19, the thickness variation and the surface pressure of the single battery cell 110 according to the charge-discharge cycle may be measured. Specifically, the single battery cell 110 is positioned in a fixing jig in which the thickness variation is limited, and then the charge and discharge cycles are repeated. After that, the surface pressure value a0 is measured by the load cells arranged in the corresponding fixing jigs. The measured a0 is denoted by P0 on the Y-axis. Next, the single battery cell 110 is positioned in a variable jig whose thickness can be changed by a spring or the like, and then the charge and discharge cycles are repeated. Then, the surface pressure value a1 is measured by a load cell arranged on the variable jig, and the increased thickness of the battery cell 110 is measured to calculate the thickness deformation rate b1. The corresponding a1 and b1 are represented by point P1. The spring constant of the variable jig is changed and the measurement process is repeated to measure the surface pressure values a2, a3 and a4 and the deformation values b2, b3 and b4, respectively. Based on such values, coordinate points P2, P3, and P4 can be displayed, and a curve C2 can be derived. And, the curve C2 thus derived corresponds to the P-D (pressure-displacement) curve of the single cell.

Fig. 20 is a graph showing a P-D curve of a single cell and a P-D curve of a cell stack.

Referring to fig. 19 and 20 in combination, the number of the battery cells 110 included in the battery cell stack 120 may be reflected in the P-D curve C2 of the individual battery cells obtained through the process described in fig. 19 to obtain the P-D curve C3 of the battery cell stack 120. As the number of the battery cells 110 increases, the surface pressure required according to the degree of deformation increases, so that the P-D curve C3 of the battery cell stack 120 naturally locates at the upper part, as compared to the P-D curve C2 of the single battery cell.

Fig. 21 is a graph showing module stiffness curves according to examples 1 to 4 of the present disclosure.

Referring to fig. 21, a module stiffness curve for each of examples 1-4 is shown. The P-D curves of the cell stacks are not shown, but the equilibrium points (intersection points) at which each of the module stiffness curves of examples 1 to 4 intersects the P-D curves of each of the cell stacks of examples 1 to 4 are shown.

The expansion behavior of the battery module predicted according to the above method was observed, the battery module of example 1 was predicted to be deformed 5.4% in the width direction in the EOL state, and the internal battery cells and the module frame were subjected to a surface pressure of 0.8 MPa. Further, it is predicted that the battery module of example 2 is deformed by 6.7% in the width direction in the EOL state, and the internal battery cells and the module frame are subjected to a surface pressure of 0.71 MPa. Further, it is predicted that the battery module of example 3 is deformed by 6.1% in the width direction in the EOL state, and the internal battery cells and the module frame are subjected to a surface pressure of 0.29 MPa. Finally, it was predicted that the battery module of example 4 was deformed by 9.3% in the width direction in the EOL state, and the internal battery cells and the module frame were subjected to a surface pressure of 0.44 MPa.

All of the battery modules of examples 1 to 4 exhibited such features: in an EOL (end of life) state, a deformation rate in a direction in which the battery cells are stacked is 12% or less, and a surface pressure applied to the battery cells is 0.9MPa or less. Further, the module rigidity curves of the battery modules of examples 1 to 4 were calculated to be in the slope range of 0.00417 or more and 0.225 or less (MPa/%). That is, the module stiffness curves of the battery modules of examples 1 to 4 may be formed in a range between the lower limit module stiffness curve C1b having a slope (Sb) value of 0.00417MPa/% and the upper limit module stiffness curve C1a having a slope (Sa) value of 0.225 MPa/%.

In the present embodiment, terms representing directions such as front side, rear side, left side, right side, upper side and lower side are used, but the terms used are provided for convenience of description and may become different depending on the position of an object, the position of a viewer, and the like.

One or more of the above-described battery modules according to the embodiments of the present disclosure 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.

The battery pack may be applied to various devices. For example, it may be applied to vehicle devices such as electric bicycles, electric vehicles, and hybrid electric vehicles, or ESS (energy storage system), and may be applied to various devices capable of using secondary batteries, and is not limited thereto.

Although the present disclosure has been described in detail with reference to the preferred embodiments thereof, the scope of the present disclosure is not limited thereto, and various modifications and improvements may be made by those skilled in the art using the basic concepts of the present disclosure as defined in the appended claims, which also fall within the scope of the present disclosure.

[ Description of reference numerals ]

100A, 100b: battery module

110: Battery cell

120: Battery cell stack

1000: Battery pack

1100: Battery pack case

1200: Cross beam

1300: Pipeline

Claims (17)

1. A battery pack, comprising:

A battery module including a battery cell stack in which a plurality of battery cells are stacked in one direction;

A battery pack case in which the battery module is accommodated;

A cross member arranged at the bottom of the battery pack case; and

A duct disposed inside the cross beam,

Wherein the cross member is located on one side of the stacking direction of the battery cells with respect to the battery module and has a form extending in a direction perpendicular to the stacking direction of the battery cells, and

Wherein fluid flows into the interior of the pipe.

2. The battery pack of claim 1, wherein:

The battery cells are stacked in one direction within the battery module in a state of being vertically erected on one surface of the bottom of the battery pack case.

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 top portion.

4. The battery pack of claim 3, wherein:

the cross member is arranged such that one surface of the first side surface portion and one surface of the second side surface portion are parallel to both sides of the battery module in the direction in which the battery cells are stacked.

5. The battery pack of claim 3, wherein:

an opening is formed on at least one of the first side surface portion or the second side surface portion, and

The duct is exposed through the opening and contacts the battery module.

6. The battery pack of claim 1, wherein:

The duct into which fluid flows presses the battery module in the stacking direction of the battery cells.

7. The battery pack of claim 1, further comprising:

A fluid supply device connected to the conduit and supplying fluid to the conduit.

8. The battery pack of claim 7, further comprising:

A fluid control valve that connects the conduit with the fluid supply and controls an amount of fluid flowing into the conduit.

9. The battery pack of claim 8, further comprising:

A pressure sensor connected to the pipe and measuring the pressure of the pipe.

10. The battery pack of claim 8, wherein:

the cross beam includes a frame portion including a first side portion, a second side portion, and a top portion, an

The first side portion, the second side portion, and the top portion form an n-shape in a cross section of the frame portion.

11. The battery pack of claim 10, wherein:

The fluid control valve is located in a space surrounded by the first side surface portion, the second side surface portion, and the top portion.

12. The battery pack of claim 10, wherein:

the conduits are arranged n-shaped within the n-shaped frame portion.

13. The battery pack of claim 1, wherein:

The pipe is of soft or elastic material, and

The fluid flowing into the pipe is in a liquid state or a gel state.

14. The battery pack of claim 1, wherein:

The battery module further includes a module frame in which the battery cell stack is accommodated,

The battery cells are stacked in one direction from the side surface portion to the other side surface portion of the module frame,

A compression pad is interposed between adjacent battery cells or between the outermost battery cell and the side face portion of the module frame, and

In EOL, i.e., end-of-life, a deformation rate in the stacking direction of the battery cells is 12% or less, and a surface pressure applied to the battery cells is 0.9MPa or less.

15. The battery pack of claim 14, wherein:

the module rigidity curve of the battery module is calculated to be within a slope range (MPa/%) of 0.00417 or more and 0.225 or less, and

The module rigidity curve of the battery module corresponds to a relationship between a deformation rate of the module frame and the surface pressure applied to the module frame.

16. The battery pack of claim 15, wherein:

The module rigidity curve of the battery module is derived by reflecting the compression degree of the compression pad with respect to the surface pressure applied to the compression pad and the number of the compression pads on the module rigidity curve of the module frame.

17. An apparatus comprising the battery pack of claim 1.