WO2022139265A1 - Battery cell cooling structure - Google Patents

Abstract

A battery cell cooling structure according to an embodiment of the present invention comprises: a cooling plate including an inlet through which cooling water flows in, a fluid pipe connected to the inlet and through which the cooling water flows, and an outlet connected to the fluid pipe and through which the cooling water is discharged; and a heat conduction module provided between a battery cell and the cooling plate to provide heat exchange between the cooling water and the battery cell, wherein the heat conduction module includes a first conductive layer formed toward the inlet, and a second conductive layer formed toward the outlet from the first conductive layer and having a higher thermal conductivity than the first conductive layer.

Description

battery cell cooling structure

The present invention relates to a battery cell cooling structure.

The present invention is a personal basic study of the Ministry of Science and ICT (Project Unique No.: 1711108021, Project No.: 2019R1C1C1011195, Research Project Name: Optimization of a thermal management system for a next-generation high energy density battery to which a complex phase change heat transfer package is applied, Project management institution: Korea It was derived from research conducted as part of the Research Foundation, research period: 2020.03.01. ~ 2021.02.28.).

Batteries are being used in various fields such as energy storage systems (ESS) and power sources for electric vehicles, and in particular, the energy density of electric vehicles is increasing.

As the energy density is improved, the battery generates heat locally due to heating in a situation where charging and discharging are repeated under high current, resulting in a temperature difference inside the battery. ) and cycle life. In addition, when the temperature of the battery increases, the efficiency and reliability of the battery decrease, so the battery cell needs to be properly cooled through heat exchange.

As a prior art related to battery cooling, there is registered Patent No. 10-2094709 (hereinafter referred to as prior art), which is a technique for reducing the temperature gradient between battery cells by applying additional components such as a heat pipe and a phase change material. is starting

However, in conventional technologies including the prior art, a very large temperature difference occurs in the battery cell due to the temperature difference between the inlet/outlet of the coolant, and the size and complexity of the system increase due to the addition of additional components such as a heat pipe and a phase change material. There is a problem in that the cost increases with the increase. In addition, in the case of a heat pipe, there is a limitation in operating only when the temperature difference between one side and the other side is very large. (See FIGS. 1A to 1C )

If the battery is continuously operated with a large temperature difference in the battery cell, there is a large possibility that the stability and lifespan of the battery will be greatly problematic, and considering the recent rapid increase in fire accidents in ESS and electric vehicles, it is more effective and reduces the complexity of the structure. The need for a cooling structure capable of cooling a battery cell without increasing the temperature is reconsidered.

The present invention provides a hybrid TIM (thermal interface material, heat transfer material) structure capable of minimizing the gradient between the inlet side temperature and the outlet side temperature of the battery cell in consideration of the temperature deviation within the battery cell due to the inlet/outlet temperature difference of the coolant. aim to

Another object of the present invention is to provide a cooling plate structure having a channel design capable of reducing temperature variations within a battery cell.

In addition, by providing such a cooling structure, it is an object to effectively reduce the temperature deviation within the cell without adding a cooling device, thereby reducing the size and complexity of the system, and providing a cost saving effect.

The present invention for the purpose of solving the above problems is a cooling plate including an inlet through which cooling water is introduced, a fluid pipe through which the cooling water flows through the inlet, and an outlet through which the cooling water is discharged through the fluid pipe, and a battery cell. and a heat conduction module provided between the cooling plate and providing heat exchange between the cooling water and the battery cell, wherein the heat conduction module includes a first conductive layer formed toward the inlet and the outlet side rather than the first conductive layer, and a second conductive layer having higher thermal conductivity than the first conductive layer.

The present invention having the above configuration and characteristics minimizes the gradient between the inlet side temperature and the outlet side temperature of the battery cell due to the difference in the inlet/outlet temperature of the coolant through the hybrid TIM composed of materials having different thermal conductivity.

In addition, the unique TIM layer and cooling plate design effectively prevent aggravation of temperature deviation due to heating caused by heat exchange of cooling water.

In addition, through the improvement of the cooling plate and heat conduction module, which are essential components of the battery cooling structure, the temperature deviation within the cell is effectively reduced without adding a cooling device, thereby reducing the size and complexity of the system and further reducing the cost.

1A to 1C are views of a conventional battery cooling structure.

Figure 2 is a diagram showing each configuration of the present invention separately.

3A to 3B are an embodiment of the heat conduction module of the present invention.

4A and 4B are diagrams for explaining the effect of applying a hybrid TIM.

5 is an embodiment of the cooling plate of the present invention.

6A and 6B are diagrams for explaining the effect according to the application of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

Examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is as follows It is not limited to an Example.

Rather, these examples are provided so that this disclosure will be more thorough and complete, and will fully convey the spirit of the invention to those skilled in the art.

In addition, in the following drawings, each configuration is exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term “and/or” includes any one and any combination of one or more of those listed items.

The terminology used herein is used to describe specific embodiments, not to limit the present invention.

As used herein, the singular form may include the plural form unless the context clearly dictates otherwise. Also, as used herein, “comprise” and/or “comprising” refers to specifying the presence of the recited shapes, numbers, steps, actions, members, elements, and/or groups thereof. will,

It does not exclude the presence or addition of one or more other shapes, numbers, movements, members, elements and/or groups.

Hereinafter, a battery cell (B) cooling structure (hereinafter this structure) according to the present invention will be described in detail with reference to the accompanying drawings.

1A to 1C are diagrams related to a conventional battery cooling structure.

1A to 1C , the simulation conditions are as follows.

Cooling water inlet temperature: 25℃

Coolant mass flow: 0.32 g/s

Heat dissipation of the battery: 130000 W/m3

Battery capacity: 32Ah

Specific heat of battery cell: 1070 J/kg K

Thermal conductivity of battery cells: anisotropic (15 W/m K in plane direction, 1 W/m K in thickness direction)

The conventional cooling method is a method of cooling the battery cell by supplying cooling water to the heat exchanger shown in FIG. The active method was used in the entire area.

However, when a TIM having a high heat transfer coefficient is attached to the entire area, there is a disadvantage in that the temperature difference inside the cell increases due to the temperature difference between the coolant inlet and the outlet. To solve this, the TIM having various thermal conductivity according to the present invention A hybrid TIM method that is attached to the

The present invention relates to a cooling structure of a battery cell (B), and as shown in FIG. 2, a cooling plate (1) through which cooling water for heat exchange flows and is provided between the battery cell (B) and the cooling plate (1). and a heat conduction module (2) providing heat exchange between the coolant and the battery cell (B).

A battery is a device that stores the electricity generated by an alternator and sends it out to power the electrical system of a vehicle (especially an electric vehicle). During the process of supplying electricity, heat is generated in the battery. For example, in a battery such as a lithium-ion battery having a high energy density, heat is locally generated due to Joule heating during charging and discharging, resulting in a temperature difference inside the battery. This temperature difference can adversely affect the performance (capacity degradation) and cycle life of the battery. In addition, when the temperature of the battery increases, the efficiency and reliability of the battery decrease, so the battery cell B needs to be properly cooled through heat exchange.

The present structure may be provided on one side or both sides of the battery cell B, and in particular, when the present structure is provided on both sides of the battery cell B, it is symmetrical about the battery cell B as shown in FIG. 2 . structure may be provided.

Specifically, the cooling plate 1, which is one configuration of the present structure, includes an inlet 11 through which the cooling water flows, a fluid pipe 12 through which the cooling water flows through the inlet 11, and a fluid pipe 12 through which the cooling water flows. and an outlet 13 for exhaust (see FIG. 5 ). The detailed structure of the cooling plate 1 will be described later.

Hereinafter, for convenience of explanation, the directions of the respective components will be described by referring to the directions of the inlet 11 as 'inlet side' and the outlet 13 side as 'outlet side' with reference to FIG. 2 .

Next, another configuration of the present structure, the heat conduction module 2, is a configuration that provides heat exchange between the coolant and the battery cell B, and may also be referred to as a thermal interface material (TIM), as shown in FIG. As shown, it is provided between the battery cell (B) and the cooling plate (1). The heat conduction module 2 is preferably provided so as to maximize heat exchange efficiency by contacting the cooling plate 1 on one surface and the battery cell B on the other surface, but is not necessarily limited to contact.

2-3, the heat conduction module 2 is composed of a plurality of materials having different thermal conductivity from each other. In the description of the present invention, the first embodiment composed of two materials and the second embodiment composed of three materials This will be described in detail through examples.

According to the first embodiment, as shown in FIG. 3A , the heat conduction module 2 moves toward the outlet 13 rather than the first conductive layer 21 formed toward the inlet 11 , and the first conductive layer 21 . The formed second conductive layer 22 may be included. In the above, the second conductive layer 22 is made of a material having higher thermal conductivity than the first conductive layer 21 .

Through this, heat exchange with the battery cell B occurs less in the first conductive layer 21 on the inlet side through which the coolant having a relatively low temperature flows, and the second conductive layer 22 on the outlet side through which the coolant having a relatively high temperature flows. ), a lot of heat exchange with the battery cell (B) occurs. This is because the battery cell (B) is excessively cooled at the inlet side through which coolant with a low temperature flows, and the temperature distribution of the battery cell (B) is concentrated, and the coolant is heated excessively from the inlet side more than necessary, so the role of the coolant at the outlet side prevent being unable to

In particular, there is room for cooling due to heat conduction in the battery cell B even if heat exchange by cooling water does not actively occur at the inlet side for exchanging heat with the first conductive layer 21 with low thermal conductivity, and the cooling plate 1 ) has an effect of heating the cooling water by its own heat conduction phenomenon, which can be confirmed in FIGS. 6A and 6B . Therefore, since heat exchange does not need to occur actively in the first conductive layer 21 , the first conductive layer 21 is preferably made of a material having a relatively low thermal conductivity, and the heat conduction of the first conductive layer 21 is The degree may be determined according to design specifications, and for example, may be made of a polymer material known to have low thermal conductivity.

In addition, in the second conductive layer 22 , heat exchange should be performed more actively compared to the first conductive layer 21 , which is the heating of the coolant that has already undergone heat exchange at the inlet side, and the coolant by heat conduction between the cooling plates 1 . This is because the cooling water at the outlet has a relatively higher temperature than the cooling water at the inlet due to the heating of Therefore, the second conductive layer 22 should have higher thermal conductivity than the first conductive layer 21 , and a metal material known to have high thermal conductivity may be added for example, but it is not necessarily limited in this way.

Additionally, as shown in FIG. 3A , in the heat conduction module 2 , the area of the first conductive layer 21 may be smaller than the area of the second conductive layer 22 . This is because, if the section of the first conductive layer 21 in which heat exchange is less is configured to be too long, the section in which heat exchange is less is too long, which may cause overheating of the battery cell (B), and the first conductive layer (21) The specific ratio between the area of the second conductive layer 22 and the area of the second conductive layer 22 may be appropriately selected through repeated experiments and design improvement, and for example, the area of the second conductive layer 22 is the area of the first conductive layer 21 . ) may be formed to be at least twice as large as the area of .

In FIG. 3A, when the width (horizontal length) of each conductive layer is assumed to be the same, the length (d21, vertical length) of the first conductive layer is shorter than the length (d22, vertical length) of the second conductive layer, so that the area is small You can check what is configured.

Next, according to the second embodiment, as shown in FIG. 3B , the heat conduction module 2 ′ is formed toward the outlet 13 rather than the second conductive layer 22 and has higher heat conduction than the second conductive layer 22 . It may further include a third conductive layer 23 having a degree. The second embodiment is an implementation in which the heat conduction module 2' is composed of three or more different materials, which implies that it may have four or more layers. In the above, the first to third conductive layers 21, 22, and 23 may be fabricated integrally or connected by bonding or the like.

In the second embodiment, the change in thermal conductivity according to heating of the cooling water is further subdivided. The most passive heat exchange is performed in the first conductive layer 21 with the lowest thermal conductivity, and more active heat exchange in the second conductive layer 22 . This is performed, and the third conductive layer 23 is configured to perform the most active heat exchange.

In the second embodiment, the heat conduction module 2' is preferably configured such that the area of the first conductive layer 21 is smaller than the area of the third conductive layer 23, which is the same as in the first embodiment described above. Similarly, this is to prevent the battery cell B from being overheated because the section of the first conductive layer 21 in which heat exchange is passively made is too long.

In particular, the area of the first conductive layer 21 through which the coldest cooling water flows is preferably smaller than the area of the third conductive layer 23 through which the hottest cooling water flows, and more preferably, the first conductive layer 21 ), the area of the second conductive layer 22 may be larger than the area of the second conductive layer 22 , and the area of the third conductive layer 23 may be larger than the area of the second conductive layer 22 .

In FIG. 3B, assuming that the width (horizontal length) of each conductive layer is the same, the length d22 of the second conductive layer is greater than the length d21 of the first conductive layer, and the length d22 of the second conductive layer is greater than the length d22 of the first conductive layer. As the length d23 of the third conductive layer is long, it can be seen that the area thereof increases toward the outlet side.

The above-described limitation on the area of each conductive layer is closely related to the design of the cross-sectional area of the fluid pipe 12 of the cooling plate 1 to be described later, and is particularly applicable with the structure of the fluid pipe 12 of the cooling plate 1 . can provide more effective improvement.

4A and 4B are diagrams for explaining the effect of applying a hybrid TIM.

The simulation conditions of FIGS. 4A and 4B are as follows.

Cooling water inlet temperature: 20℃

Coolant mass flow: 0.24 g/s

Heat output of battery: 10000W/m3

Battery capacity: 100Ah

Specific heat of battery cell: 1070 J/kg K

Thermal conductivity of battery cells: anisotropic (15 W/m K in plane direction, 1 W/m K in thickness direction)

The baseline graph of FIG. 4A and the simulation result of 'existing single Tim application' of FIG. 4B shows that a TIM (heat transfer material) with high thermal conductivity is attached over the entire area between the cooling plate and the battery cell in a conventional manner. However, in this case, the low inlet temperature of the coolant excessively cools a specific part of the battery cell, which causes a large temperature difference within the battery cell.

To solve this problem, the 'developed TIM attachment method application' graph of FIG. 4a and the 'developed hybrid TIM application' simulation result of Go 4b show the lower part of the battery that is in contact with the cooling water inlet of the cooling plate among the 265mm horizontal length of the battery. TIM having low thermal conductivity (0.1 W/m·K) is applied to 55mm, and TIM having high thermal conductivity (3 W/m·K) is applied to the remaining 210mm.

That is, referring to FIGS. 4A and 4B together, when the heat conduction module 2 of this structure composed of different materials is applied, it can be confirmed that the temperature deviation is reduced by 20% or more, and also in the heat distribution graphic It can be confirmed that the inlet side is not cooled excessively and has an appropriate temperature distribution.

Hereinafter, a detailed description of the above-mentioned cooling plate 1 will be continued.

First, as described above, the cooling plate 1 includes an inlet 11 through which coolant is introduced, a fluid pipe 12 connected to the inlet 11 through which the coolant flows, and an outlet connected to the fluid pipe 12 through which the coolant is discharged. (13) is included. As shown in FIG. 5 , the cooling plate 1 is configured such that the coolant circulated by the circulation driver 4 flows into the inlet 11 and is discharged to the outlet 13 along the fluid pipe 12 , and the outlet 13 ), the heated cooling water is cooled through the cooling unit 3 and flows back into the inlet 11 by the circulation driver 4 .

According to an embodiment, as shown in FIG. 5 , the fluid pipe 12 may include a converging channel part 121 connected to the inlet 11 and configured to have a smaller cross-sectional area toward the outlet 13 . This converging channel part 121 is formed in the form of a converging channel having the largest cross-sectional area on the inlet side and the smallest cross-sectional area on the outlet side. Sufficient heat exchange can be achieved through the slow flow rate, whereby sufficient heat exchange is achieved between the coolant and the battery cell B in the first conductive layer 21 having relatively low thermal conductivity.

This provides an effect of preventing the inlet-side portion of the battery cell B from being overheated because sufficient heat exchange does not occur because the first conductive layer 21 has low conductivity. In addition, in order for the coolant to receive sufficient heat flux in the preheating section, the cross-sectional area of the inlet side should be larger, that is, the contact area should be large.

Next, according to one embodiment, as shown in FIG. 5 , the fluid pipe 12 is connected to the outlet 13 and includes a diverging channel portion 122 configured to have a larger cross-sectional area toward the outlet 13 . can The diverging channel unit 122 is formed in the form of a diverging channel with the smallest inlet cross-sectional area and the largest outlet cross-sectional area. While the difference in heat flux received by the side becomes very small, in the case of a divergent channel, the heat flux increases at the inlet side with a small cross-sectional area, and decreases at the outlet side with a large cross-sectional area. That is, in a divergent channel, a large heat flux received by the inlet channel keeps the temperature of the cooling plate located at the inlet channel high, and a small heat flux received by the outlet channel keeps the temperature of the cooling plate located at the outlet channel relatively low. do it That is, the difference in heat flux due to the change in the cross-sectional area of the channel maintains the temperature uniformity of the cooling plate, and consequently contributes to reducing the temperature difference of the battery cell.

In addition, since the cross-sectional area of the diverging channel part 122 gradually increases toward the outlet side, a decrease in the flow rate may occur. A fin or a dimple that can speed up the flow rate may be inserted.

Alternatively, as shown in FIG. 5 , a converging channel part 121 is provided on the inlet side of the fluid pipe 12 and the diverging channel part 122 is connected to the outlet side of the converging channel part 121. That is, the fluid pipe 12 is connected to the inlet 11 and the cross-sectional area becomes smaller toward the outlet 13 side. That is, it may include a diverging channel portion 122 configured to increase the cross-sectional area.

In particular, in the implementation of connecting the diverging channel part 122 to the converging channel part 121, the existence of the converging channel part 121 does not have any difficulty in configuring the diverging channel part 122, and the implementation using a rapid contraction tube. It offers the advantage of less pressure drop.

5, it is preferable that the length d121 of the converging channel portion is shorter than the length d122 of the diverging channel portion, where the lengths d121 and d122 of the converging channel portion and the diverging channel portion are configured. The reference is based on the movement distance of the coolant, and in FIG. 5 , the length of the coolant can be simplified to a vertical length because it is a pipe in which the movement path of the coolant is configured in only one direction. This is because, for a reason similar to the area of each layer of the thermoelectric module, if the convergence channel part 121 with poor heat exchange is too long, the inlet side of the battery cell B may be overheated.

In addition, the cooling plate 1 may further include fins or dimples to increase the contact area or form turbulence.

6A and 6B are diagrams for explaining the effect according to the application of the present invention.

The simulation conditions of FIGS. 6A and 6B are as follows.

Cooling water inlet temperature: 25 ℃

Coolant mass flow: 0.32 g/s

Heat dissipation of the battery: 130000 W/m3

Battery capacity: 32Ah

Specific heat of battery cell: 1070 J/kg K

Thermal conductivity of battery cells: anisotropic (15 W/m K in plane direction, 1 W/m K in thickness direction)

The upper part of FIG. 6a is a simulation performed by applying TIM (3 W/m·K) having high thermal conductivity over the entire section. In addition, in the lower part of Fig. 6a, a TIM having low thermal conductivity (0.1W/mK) is applied to the area marked with low thermal conductivity (about 10 mm), and a TIM having relatively high thermal conductivity is applied to the remaining area to conduct a simulation. did it

Temp. stand. Dev refers to the standard deviation of the temperature within the battery cell, and by extracting the temperature value of each part of the battery cell from the simulation, the average temperature value of the battery and the temperature dispersion of the battery cell can be calculated. can be calculated

6A and 6B are views summarizing the effect of reducing the temperature gradient according to the present structure as a whole. As can be seen in FIGS. 6A and 6B , compared to the conventional cooling structure, the temperature difference and Temp. stand. It can be seen that Dev has decreased by more than 20%. In particular, in the temperature graph within the cell, it can be seen that the temperature at the inlet side of the battery cell B does not decrease rapidly, and the temperature gradient is reduced through this.

In order to reduce the temperature variation within the cell, the present structure effectively reduces the temperature variation within the cell without adding an excessive cooling device, thereby reducing the size and complexity of the system and providing a cost reduction effect. In particular, this structure can maximize the application effect when high-level thermal management is required for batteries such as electric vehicles and ESS systems.

Although the battery cell cooling structure according to the embodiment of the present invention has been described as a specific embodiment, this is merely an example, and the present invention is not limited thereto, and it is interpreted as having the widest scope according to the basic idea disclosed in the present specification. should be A person skilled in the art may implement a pattern of a shape not specified by combining or substituting the disclosed embodiments, but this also does not depart from the scope of the present invention. In addition, those skilled in the art can easily change or modify the disclosed embodiments based on the present specification, and it is clear that such changes or modifications also fall within the scope of the present invention.

Claims (9)

a cooling plate including an inlet through which the cooling water is introduced, a fluid pipe connected to the inlet through which the cooling water flows, and an outlet connected to the fluid pipe through which the cooling water is discharged; and a heat conduction module provided between the battery cell and the cooling plate to provide heat exchange between the cooling water and the battery cell; including, The heat-conducting module includes a first conductive layer formed toward the inlet and a second conductive layer formed toward the outlet rather than the first conductive layer and having higher thermal conductivity than the first conductive layer. The method according to claim 1, The heat-conducting module has a battery cell cooling structure in which an area of the first conductive layer is smaller than an area of the second conductive layer. The method according to claim 1, The heat-conducting module further includes a third conductive layer formed toward the outlet than the second conductive layer and having a higher thermal conductivity than the second conductive layer. 4. The method according to claim 3, The heat-conducting module has a battery cell cooling structure in which an area of the first conductive layer is smaller than an area of the third conductive layer. The method according to claim 1, The fluid pipe is connected to the inlet and the battery cell cooling structure including a converging channel portion configured to decrease in cross-sectional area toward the outlet. The method according to claim 1, The fluid pipe is connected to the outlet and the battery cell cooling structure includes a diverging channel portion configured to increase in cross-sectional area toward the outlet. The method according to claim 1, The fluid pipe includes a converging channel part connected to the inlet and configured to have a smaller cross-sectional area toward the outlet, and a diverging channel part connected to the converging channel and configured to have a larger cross-sectional area toward the outlet. 8. The method of claim 7, A battery cell cooling structure in which a length of the converging channel portion is shorter than a length of the diverging channel portion. A battery device comprising a battery cell and a battery cell cooling structure for cooling the battery cell, The battery cell cooling structure includes: a cooling plate including an inlet through which the cooling water is introduced, a fluid pipe connected to the inlet through which the cooling water flows, and an outlet connected to the fluid pipe through which the cooling water is discharged; and and a heat conduction module provided between the battery cell and the cooling plate to provide heat exchange between the cooling water and the battery cell, The heat-conducting module includes a first conductive layer formed toward the inlet, and a second conductive layer formed toward the outlet rather than the first conductive layer and having higher thermal conductivity than the first conductive layer.

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