KR102618649B1 - A battery module comprising a device for applying pressure to a battery cell stack and a battery pack thereof - Google Patents

Abstract

The purpose of the present invention is to provide a battery module with a structure that can compensate for the vulnerability of battery cells to deformation and pressure changes and a battery pack including the same.
An embodiment of the present invention provides a battery module equipped with a device capable of applying a constant pressure to the cells in response to pressure changes and deformation acting on the cells arranged in the battery module, and a battery pack including the same, thereby improving the charging and discharging efficiency of the battery. It can improve the lifespan and prevent fire hazards such as ignition.

Description

A battery module comprising a device for applying pressure to a battery cell stack and a battery pack thereof}

The present invention relates to a device that improves the performance and safety of secondary lithium battery cells. In particular, the present invention relates to a device that improves the performance and safety of secondary battery lithium battery cells. In particular, it protects the cells from mechanical vulnerabilities that may occur as the number of lithium battery cells stacked increases in accordance with the demand for high capacity of batteries for electric vehicles. This relates to a cell stack pressurization device that can improve the efficiency and lifespan of batteries.

In recent secondary lithium batteries, the number of stacked battery cells is increasing in response to demands for higher capacity.

As the number of cells stacked increases, a stacking method that can improve cell performance and safety while increasing the cell loading ratio in a battery module or pack has become an important technical task.

In order to increase the space coverage of at least two or more battery cells, the cell stack is subjected to compressive force.

Cannarella et al. reported the effect of compression force on the capacity of lithium-ion pouch cells, and many research results have been published showing that compression force affects cell capacity in liquid electrolyte lithium metal battery cells and solid electrolyte lithium metal battery cells.

The capacity of a cell decreases with repeated charge and discharge cycles, and many studies have published results showing that the rate of decrease in cell capacity when an appropriate compression force is applied is slower than the rate of decrease in cell capacity in a state where no pressure is applied. .

However, if the compression force increases beyond a certain value, the negative result is that the rate of cell capacity decrease is accelerated.

US Patent US2019/0027797A1 devised a method of applying compressive force to the cells by placing leaf springs at the ends of the cell stack, and Korean Patent No. 10-2229410 arranged an elastic member made of a plurality of coil springs in the cell stack. A method of applying compressive force to cells is presented.

European patent EP3886202A1 proposes a method of applying compressive force to cells by placing a fluid spring in a cell stack.

The above methods have the effect of limiting cell expansion and contraction by applying pressure to the cell stack in response to the spring elastic force as expansion and contraction of the cell stack are repeated according to the charging and discharging cycle.

However, according to the charging and discharging cycle, the pressure increases rapidly due to abnormalities such as gas generation in at least one cell inside the laminate, and volume expansion such as swelling occurs due to the elasticity of the above patents bound to the laminate. When acting on a member, the elastic member suppresses the expansion of the laminate and rapidly applies an abnormal expansion response force to the laminate, ultimately causing the cells in the laminate to expand in a direction that has no restrictions on cell deformation, for example, the swing expansion direction. When the cell thickness direction is referred to as the z-direction, deformation stress is concentrated in the x- or y-direction, causing damage at vulnerable places such as the heat-sealed portion of the pouch cell or the square joint, which may lead to a serious accident.

In addition, when vibration or impact from the outside is applied to the elastic unit, the vibration energy and impact energy are directly transferred to the laminate and overlap with the pressure acting on the cell, resulting in excessive pressure and deterioration of cell performance. It can cause serious safety problems.

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US Patent US2019/0027797A1 Republic of Korea registered patent 10-2229410 European Patent EP3886202A1

1. “Stress evolution and capacity fade in constrained lithium-ion pouch cells”, John Cannarella, Craig B. Arnold, Journal of Power Sources, Vol 245, 2014, Pages 745-751. 2. "Analysis of the effect of applying external mechanical pressure on next generation silicon alloy lithium-ion cells", Gert Berckmans et al, Electrochimica Acta, Volume 306, 20 May 2019, Pages 387-395 3. “Editors’ Choice-Methods-Pressure Control Apparatus for Lithium Metal Batteries", Bingyu Lu et al, Journal of The Electrochemical Society, 2022 169 070537 4. “Volume, Pressure and Thickness Evolution of Li-Ion Pouch Cells with Silicon-Composite Negative Electrodes” A. J. Louli et al, Journal of The Electrochemical Society, 164 (12) A2689-A2696 (2017) 5. "Stress evolution and thickness change of a lithium-ion pouch cell under various cycling conditions" Congrui Jin et al, Journal of Power Sources Advances Volume 16, August 2022, 100103

Therefore, the purpose of the present invention is to apply a certain pressure to the laminate in response to the normal expansion and contraction of battery cells that occur during charging and discharging cycles, as well as to prevent abnormal expansion from inside the laminate, such as swelling, and from the outside. To provide a laminate pressurizing device that can improve the performance life and safety of battery cells by preventing excessive pressure from being suddenly applied to battery cells even in vibration and impact, and to provide battery modules equipped with the same and battery packs containing the same. there is.

As a means of solving the above problem, a battery module of a secondary battery according to the present invention includes a stack of the cells 10 in which a plurality of secondary battery cells 10 are stacked in one direction while facing a wide surface ( 20);

Two end plates (30a) and (30b) respectively facing both end surfaces of the laminate 20, which are parallel to the wide surface of the cell 10;

A pressure applying device (40) provided between one of the end plates (30a) and one side (70a) of the battery module case;

Battery module cases (70a), (70b) storing the laminate (20), end plates (30a), (30b), and pressure applying device (40); It consists of,

The pressure applying device 40 includes a superelastic spring 41,

The end plates (30a), (30b), and battery module cases (70a) and (70b) are formed of a rigid material with an elastic modulus of 100 GPa or more.

The end plate (30a) is mechanically connected to the pressure applying device (40),

The pressure applying device 40 is mechanically connected to one side 70a of the case of the battery module,

The other end plate (30b) is fixed to one side (70b) of the case opposite to the one side (70a) of the case, so that the multilayer body (20) is viewed from a direction perpendicular to the wide surface of the multilayer body (20). Provides counterforce to increase or decrease pressure from

The end plate 30a moves in both directions horizontally to the pressure direction according to the increase or decrease of the pressure from the direction perpendicular to the large surface of the laminate 20, and is connected to the pressure applying device 40 or the laminate. and transmit the pressure change to (20).

The pressure applying device 40 absorbs the pressure change and applies a constant pressure to the laminate 20,

The case 70a provides a counter force to the pressure applying device 40 to

A module 100 or module 200 is provided, which manages pressure changes and deformation amounts of the cells 10 within the laminate 20.

Additionally, a battery pack according to the present invention includes one or more modules 100; Control unit 93; It consists of a battery pack case;

The pack case is formed of at least four walls,

In addition, the case may include one or more inner walls,

Additionally, each wall can be used as a case for the one or more modules 100,

In addition, each of the walls may be mechanically connected by contacting the chassis or body of the automobile,

Additionally, a battery pack 1000 is provided in which the chassis or body of the vehicle itself can be used as one wall of the case.

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Embodiments of the present invention not only apply a constant pressure appropriate to the normal expansion and contraction behavior that occurs according to the charging and discharging cycle of cells placed in a battery module, but also prevent abnormal expansion of cells such as swelling and the exterior of the stack. By preventing excessive pressure from vibration and impact from being applied to the cell stack, the charging/discharging efficiency and lifespan of the battery can be improved and fire hazards such as ignition can be prevented.

Since these drawings are for reference in explaining exemplary embodiments of the present invention, the technical idea of the present invention should not be interpreted as limited to the attached drawings.
Figure 1 is a diagram schematically showing a cross section of a battery module 100 according to an embodiment of the present invention.
Figure 2 is a schematic cross-sectional view of a pressure applying device 40 according to an embodiment of the present invention.
Figure 5 is a configuration diagram of a battery pack 1000 according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail according to embodiments.

Prior to this, the terms or words used in this specification should not be construed as limited to their general or dictionary meaning, and the inventor may appropriately define the concept of the term in order to explain his or her invention in the best way. It must be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent the entire technical idea of the present invention, so at the time of filing the present application, various alternatives may be used to replace them. It should be understood that equivalents and variations may exist.

Additionally, in this specification and drawings, components having substantially the same functional configuration are assigned the same reference numerals, thereby omitting redundant description. In addition, each component in the drawings is appropriately enlarged or reduced for ease of explanation, and the size and ratio of each component in the drawings are different from the actual ones.

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Referring to FIGS. 1 to 3, the battery module 100 according to an embodiment of the present invention includes at least two or more secondary battery cells 10 facing a wide surface in one direction, where the cell thickness When the vertical direction is referred to as the z direction, a stack 20 of the cells 10 stacked in the z direction;

Two end plates (30a) and (30b) respectively facing both end surfaces of the laminate (20);

Both sides (70a) and (70b) of the battery module case storing the stacked body (20) and the end plates (30a) and (30b); It consists of

Two end plates (30a) and (30b) respectively facing both end surfaces of the cell stack (20);

Both sides (70a) and (70b) of the battery module case storing the cell stack (20) and end plates (30a) and (30b); It consists of

The battery module cases (70a) and (70b) may be formed of a general rigid material such as a steel plate, and in the case of a prismatic type case, the elastic modulus value of aluminum metal, which is mainly used as a case material, is 100 GPa, which is greater than about 70 GPa. It is preferable that it is formed of a rigid body with an elastic modulus equal to or higher.

A pressure applying device 40 is provided between one of the end plates 30a and one side 70a of the battery module case.

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As the pressure applying device, devices using elastic body, hydraulic pressure, pneumatic pressure, electric motor driving force, etc. may be used, but as described above, elastic body has the disadvantage of being difficult to respond to a rapid increase in pressure from inside and outside the laminate, and other methods are It is difficult to adopt in terms of cost and weight.

In the present invention, the purpose of the present invention is achieved by designing a pressure application device equipped with a superelastic body, which exhibits characteristics different from the elastic limit and elastic energy characteristics of conventional elastic bodies.

The superelastic body undergoes a phase transformation as it is deformed by an applied force, and when the applied force is removed, a certain amount of momentum is dissipated as heat, and the amount of deformation is elastically recovered and returned to the state before deformation, thereby attenuating vibration and impact energy from the outside of the hyperelastic body. There is a characteristic that allows it.

Representative materials that exhibit superelastic properties include nickel-titanium alloy and copper alloy, known as shape memory alloys. Conventional materials used as elastic springs show an elastic limit where they lose elasticity when the tensile strain is above 0.5%, whereas shape memory alloys show elasticity even when the tensile strain is above 5 to 10%. Elastic springs not only feature an elastic range that is more than 10 times wider than that of conventional elastic springs, but also use a portion of the strain energy absorbed from the outside as a phase transformation and perform elastic deformation to restore their original form, making them resistant to external vibrations or shocks. It can display the function of attenuating energy.

Meanwhile, a strain gauge that measures the force applied to the laminate 20 on one side of the end plate 30a, one side of the end plate 30b, or one side of each of the end plates 30a and 30b. A pressure sensor 31 may be installed that converts the mechanical movement of the back into an electrical signal, and the electrical signal of the pressure sensor 31 may be transmitted to the control unit 93 for processing.

The pressure application device 40 includes a super-elastic spring 41 and a shaft 42 installed and mechanically connected to one side 70a of the battery module within the inner diameter of the spring for structural stability of the spring and the outer diameter of the shaft. + It may be composed of a plain washer (43) having an inner diameter of tolerance.

Meanwhile, a strain gauge measures the force applied to the cell stack 20 on one side of the end plate 30a, one side of the end plate 30b, or one side of each of the end plates 30a and 30b. A pressure sensor 31 that converts the mechanical movement of the back into an electrical signal may be installed, and the electrical signal of the pressure sensor 31 may be transmitted to the control unit 93 for processing.

Additionally, an electrically connected swelling detection device 44 may be provided on the end surface of the shaft 42 installed at any location within the pressure device.

As the swelling detection device, observation and measurement devices such as image sensors, pressure sensors, strain gauges, limit switches, and optical sensors using infrared rays may be used. The swelling detection device in an embodiment of the present invention is ( 44) is provided with a limit switch that is relatively simple in installation.

The number of superelastic springs 41 provided in the pressure applying device 40 may be at least one, and the stress exerted on the shaft 42 on the end plate 70a is uniform as much as the number of superelastic springs. Install so that they are evenly distributed.

Meanwhile, the superelastic spring 41 can be completed by forcing a cold worked wire into a spring shape and subjecting it to shape memory heat treatment at 400 to 600°C.

At this time, when processing into a spring shape, a twist of an appropriate angle can be applied to the wire to strengthen the force, speed, shrinkage rate, etc. of the spring.

At this time, the wires can be assembled or combined into at least two wires to form a single wire or cable, and then subjected to the shape memory heat treatment to form a spring and used as the superelastic spring 41.
The superelastic spring 41 in one embodiment of the present invention is presented in the shape of a coil spring, but can be used in various forms such as a plate spring, leaf spring, torsion spring, and spiral spring. It can also be implemented in the form

Meanwhile, the end plates (30a) and (30b); When defining the pressure applying device 40 as a pressurizing unit device that applies a constant pressure to the laminate 20, the pressurizing unit device is applied to the wide surface of the laminate 20 for a change in pressure in the z direction and A pressurized pressure unit that manages the amount of deformation is installed by default.

Additionally, a pressing pressure unit that manages pressure changes and deformations in the x-direction or y-direction can be additionally installed on the wide surface of the laminate 20. That is, the deformation direction of the superelastic spring 41 provided in the added pressing unit device may be in the x or y direction.

Additionally, a pressing pressure unit that manages pressure changes and deformations in the x-direction or y-direction can be additionally installed on the wide surface of the cell stack 20. That is, the deformation direction of the superelastic spring 41 provided in the added pressing unit device may be in the x or y direction.

Below, the operating mechanisms of each of the above-described components will be described in detail.

First, for physical and mechanical connection between each component, the end plate 30a faces the pressure applying device 40 and is mechanically connected by a fastening method such as welding,

The pressure applying device 40 faces one side 70a of the case of the battery module and is mechanically connected by welding or bolting, etc.,

The other end plate (30b) is mechanically connected and fixed to one side (70b) of the case opposite to one side (70a) of the battery case by welding or bolting, etc. to form a wide space of the cell stack (20). It provides a counter force to the increase or decrease in pressure from the direction perpendicular to the surface.

The other end plate (30b) is mechanically connected and fixed to one side (70b) of the case opposite to one side (70a) of the battery case by welding or bolting, thereby forming a large surface of the cell stack 20. and provides a counterforce to the increase or decrease in pressure from the perpendicular direction.

Finally, the main assembly of the battery module according to an embodiment of the present invention can be completed by applying an arbitrarily set constant pressure to the cell stack 20 by the pressure applying device 40 connected to the end plate 70a. .

At this time, the pressure applying device is installed while checking the pressure value from the pressure sensor 31.

A pressure of less than 0.02 MPa has little effect on the change in thickness of the cells 10 constituting the laminate 20 and causes layer separation within the cells 10, thereby reducing the efficiency and efficiency of the cells 10. It can have negative consequences on lifespan. A pressure of 5 MPa or more may cause excessive pressure on the cell 10 when external vibration and shock are applied, resulting in adverse results in the efficiency and lifespan of the cell 10.

A pressure of less than 0.02 MPa has little effect on the change in thickness of the cell 10 and may cause delamination of layers within the cell 10, resulting in bad results in the efficiency and lifespan of the cell 10. A pressure of 5 MPa or more may cause excessive pressure on the cell 10 when external vibration and shock are applied, resulting in adverse results in the efficiency and lifespan of the cell 10.

At this time, the pressure applied is adjusted by checking the pressure value from the pressure sensor 31 and varying the wire diameter, number of turns, shape, etc. of the superelastic spring 41 to determine the position of the superelastic spring 41. It can be adjusted in various ways, such as by adjusting the pressure applied by adjustment. For example, as shown in FIG. 2, in one embodiment of the present invention, the specifications and location of the superelastic spring 41, etc. It is possible to use a method of adjusting the pressure of the superelastic spring 41 by setting and adjusting the thickness of the flat washer 43.

At this time, the deformable length of the hyperelastic spring 41 may be a hyperelastic spring having a value that satisfies the inequality defined by Equation 1 below.

[Equation 1]

For example, if the thickness of the cells 10 is 15 mm and the number of cells 10 in the stack 20 is 12, the deformable length of the superelastic spring 41 must be longer than 1.8 mm and shorter than 90 mm.

If the deformable length of the hyperelastic spring/(number of cells stacked A rapid response force is applied to normal deformation behavior, which may have a negative impact on the performance, lifespan, and safety of the cell 10.

If the deformable length of the hyperelastic spring/(number of cell stacks A rapid response force is applied to the normal deformation behavior of the cell 10, which may adversely affect the performance, lifespan, and safety of the cell 10.

Preferably, the amount of deformation of the laminate 20 can be controlled by setting the deformable length of the superelastic spring/(number of cell stacks x cell thickness) value to be greater than 0.02 and less than 0.2.

More preferably, the deformable length of the superelastic spring/(number of cell stacks

At this time, appendages such as compression pads and insulating pads may be placed in the space between the cells 10 within the laminate 20, but the deformation effect of these appendages is not considered in the above equation.

At this time, appendages such as compression pads and insulating pads may be placed in the spaces between cells in the cell stack, but the deformation effect of these appendages is not considered in the above equation.

As discussed above, the pressure applying device 40 attenuates the pressure change on the battery cell 10 constituting the laminate 20 by deformation and deformation recovery of the superelastic spring 41, thereby 10) The pressure applied can be kept constant at an arbitrarily set value within the range of 0.02 MPa to 5 Mpa, and the deformable length of the hyperelastic spring/(number of cells stacked x cell thickness) value is within the range of 0.02 to 0.5. Since the amount of deformation of the cell stack 20 can be controlled, the pressure acting on the stack 20 from pressure changes such as vibration and shock from the outside as well as expansion and contraction from the inside of the cell 10 is within a desirable range. By managing it to a constant value, it is possible to solve the problem of reduced efficiency and shortened lifespan of the cell 10 due to unstable pressure.

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In addition, when swelling or excessive volume expansion occurs in one cell or a plurality of cells constituting the laminate 20, the pressure on the end plate 70a increases significantly, and thus the pressure sensor 31 If it is measured and exceeds the safety setting value, the control unit 93, such as a BMS provided in the battery pack, can immediately take countermeasures to ensure safety, such as turning off the power.

In addition, when swelling or excessive volume expansion occurs in one cell or a plurality of cells of the cell stack 20, the pressure on the end plate 70a increases significantly, and thus the pressure sensor 31 If the measured pressure value exceeds an arbitrarily set safety threshold, the control unit 93, such as a BMS provided in the battery pack, can immediately take countermeasures to ensure safety, such as turning off the power.

In addition, when excessive deformation such as swelling occurs, the superelastic spring 41 is compressed, thereby ensuring safety by allowing the end plate 70a to detect excessive deformation such as swelling within the pressure applying device. When the limit switch 44 provided at an arbitrary safety limit position is touched and activated and the limit switch 44 generates a signal, the control unit 93, such as a BMS provided in the battery pack, immediately takes countermeasures to ensure safety. You can command.

For example, the electricity supply to the cell 10 can be cut off or, although not shown in the drawing, additional thermal runaway or fire can be prevented by operating a fire extinguishing device provided in the battery pack.

Additionally, a battery pack according to the present invention includes one or more modules 100; Control unit 93; It consists of a battery pack case;

The pack case is formed of at least four walls (70a), (70a), (70c), and (70d),

In addition, the case may include one or more inner walls 70b,

In addition, each wall can be used as a case for one or more modules 100 or modules 200,

In addition, each of the walls may be mechanically connected by contacting the chassis or body of the automobile,

Additionally, a battery pack 1000 is provided in which the chassis or body of the vehicle itself can be used as one wall of the case.

Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the claims described below. It will be possible to implement it. Therefore, if the modified implementation basically includes the elements of the claims of the present invention, it should be considered to be included in the technical scope of the present invention.

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1000: Battery pack according to an embodiment of the present invention
100: Module provided in a battery pack according to an embodiment of the present invention
200: Module provided in a battery pack according to another embodiment of the present invention
10: battery cell
20: A stack of secondary battery cells 10 in which a plurality of secondary battery cells 10 are stacked in one direction with a wide surface facing them.
30a, 30b: End plate
31: pressure sensor
40: pressure applying device
44: Cell swelling detection device
70a, 70b, 70c, 70d: Battery pack wall
93: Battery pack control unit

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1000: Battery pack according to an embodiment of the present invention
100: Module provided in a battery pack according to an embodiment of the present invention
200: Module provided in a battery pack according to another embodiment of the present invention
10: battery cell
20: Battery cell laminate
30a, 30b: End plate
31: pressure sensor
40: pressure applying device
44: Cell swelling detection device
70a, 70b, 70c, 70d: Battery pack wall
93: Battery pack control unit

Claims (7)

In the battery module,
A stack of cells in which a plurality of secondary battery cells are stacked in one direction with a wide surface facing them;
Two end plates facing each end surface of the laminate;
a pressure applying device provided between one of the end plates and one side of the battery module case;
a battery module case storing the laminate, end plate, and pressure applying device; It consists of,
one of the end plates is mechanically connected to the pressure applying device,
The pressure applying device is mechanically connected while facing one side of the case of the battery module,
The other end plate is fixed to one side of the case opposite the one side of the case to provide a counter force to the increase or decrease in pressure from the laminate in a direction perpendicular to the wide surface of the laminate,
The end plate facing the pressure applying device moves in both directions horizontally to the pressure direction according to the increase or decrease of the pressure from the direction perpendicular to the wide surface of the laminate and is attached to the pressure applying device or the laminate. transmitting pressure changes.
The pressure applying device absorbs the pressure change and applies a constant pressure of 0.02 MPa or more to less than 5 MPa to the laminate,
The pressure applying device is characterized in that it includes a superelastic spring formed of a shape memory alloy,
The deformable length of the hyperelastic spring is defined by Equation 1 below and is 0.01 to 0.5,
[Equation]
0.01<Deformable length of superelastic spring / (Number of cell stacks x Cell thickness) < 0.5
The battery module, characterized in that the case facing the pressure applying device provides a counter force to the pressure applying device to manage pressure changes in the laminate.
The battery module according to claim 1, comprising a limit switch device installed within the pressure applying device to detect swelling of the laminate. The battery module according to claim 1, wherein a pressure sensor is installed on one surface of at least one of the end plates and includes a device capable of measuring the pressure acting on the laminate.
At least one battery module according to claim 1;
control unit; and a pack case serving as a case for the battery module. The battery pack according to claim 4, comprising a control unit that takes safety measures such as turning off the power when a pressure sensor or a limit switch detects an abnormal increase in pressure and deformation acting on the laminate.
According to clause 4,
A battery pack, characterized in that the chassis or body of an automobile is used as one wall of the pack case. A motor vehicle comprising at least one battery pack according to claim 4.