Battery cooling member and manufacturing method thereof

Abstract

The present invention relates to a method for manufacturing a battery cooling member and a battery manufactured thereby, the method comprising the steps of: preparing an upper plate and a lower plate in which a cooling channel is formed; applying a flux on the upper plate and the lower plate; disposing the lower plate under the upper plate and then interposing an aluminum insert material between the upper plate and the lower plate; and brazing the upper plate and the lower plate with the insert material interposed therebetween, wherein each of the upper plate and the lower plate includes: a base steel sheet; and an aluminum-based plating layer formed on the base steel sheet, and, during the brazing, the brazing heat input in the temperature range of 570 to 650°C is 330,000 to 700,000°C sec.

Description

Cooling element for battery and method of manufacturing the same

[0001] The present invention relates to a cooling member for a battery and a method for manufacturing the same.

[0002] Generally, an automobile refers to a machine that uses a prime mover as a power source to drive, transport people or cargo, or perform various tasks. Automobiles can be classified according to the type of prime mover. Automobiles can be categorized into gasoline automobiles powered by gasoline engines, diesel automobiles powered by diesel engines, LPG automobiles powered by liquefied petroleum gas, gas turbine automobiles powered by gas turbines, and electric vehicles (EVs) powered by motors and electricity stored in batteries.

[0003] Electric vehicles are gaining attention as eco-friendly cars because they utilize drive motors powered by electricity supplied from batteries, resulting in zero carbon dioxide emissions compared to engines powered by fossil fuels such as gasoline or diesel. Stricter exhaust gas regulations are accelerating the development of electric vehicles, and the market is growing rapidly.

[0004] An electric vehicle is equipped with a battery that serves as an electric power source, and a cooling member is provided at the bottom of the cell or module of the battery, for example, by brazing an upper plate and a lower plate as shown in Fig. 1. Generally, aluminum-based plates with a high heat transfer coefficient are used as the material for the upper and lower plates, and the upper plate has a flat shape, while the lower plate has a cooling water channel formed to allow the flow of a refrigerant to effectively dissipate heat from the battery cell or module. These upper and lower plates are brazed together to form a cooling member. However, the aluminum-based plates have the disadvantage of being very expensive.

[0005] In addition, due to the recent increase in weight resulting from the increase in battery capacity, there is a demand for high strength in cooling material for batteries, but in the case of aluminum-based sheet metal, there is a problem in that the yield strength and tensile strength are significantly reduced after brazing at about 600°C.

[0006] Accordingly, there have been attempts to use steel materials as substitutes for existing aluminum-based plates, but when manufacturing cooling members using the above steel materials, Ni or Cu foil is used as an insert during brazing, and the above Ni or Cu foil has the disadvantage of being expensive and requiring a vacuum atmosphere or reducing atmosphere at a high temperature (about 900~1100℃).

[0007] One aspect of the present invention is to provide a cooling member for a battery and a method for manufacturing the same.

[0008] A preferred aspect of the present invention is to provide a cooling member for a battery with excellent bonding performance and a method for manufacturing the same.

[0009] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0010] One embodiment of the present invention provides a cooling member for a battery comprising: an upper plate; a lower plate having a cooling water channel formed therein, provided on the lower side of the upper plate; and a brazing joint between the upper plate and the lower plate, wherein the upper plate and the lower plate comprise a base steel plate; and an intermetallic compound layer formed on the base steel plate, and wherein the average thickness of the intermetallic compound layer is 10 to 60 μm.

[0011] The above-mentioned base steel plate may be carbon steel or stainless steel.

[0012] The above stainless steel may be an austenitic or ferritic stainless steel.

[0013] The above intermetallic compound layer may be an Fe-Al-Si-based intermetallic compound layer or an Fe-Al-Cr-Si-based intermetallic compound layer.

[0014] Another embodiment of the present invention provides a method for manufacturing a cooling member for a battery, comprising the steps of: preparing an upper plate and a lower plate having a cooling water channel formed therein; applying flux on the upper plate and the lower plate; providing the lower plate on the lower side of the upper plate and then providing an aluminum-based insert between the upper plate and the lower plate; and brazing joining the upper plate and the lower plate having the insert; wherein the upper plate and the lower plate comprise a base steel plate; and an aluminum-based plating layer formed on the base steel plate, and when brazing joined, the brazing heat input is 330,000 to 700,000℃sec in the range of 570 to 650℃.

[0015] The average thickness of the above aluminum-based plating layer may be 10 to 40 μm.

[0016] The average thickness of the above aluminum-based insert may be 50 to 150 μm.

[0017] A method for manufacturing a cooling member for a battery in which the above brazing joint is performed in a heating furnace having four zones.

[0018] According to one aspect of the present invention, a cooling member for a battery and a method for manufacturing the same can be provided.

[0019] According to a preferred aspect of the present invention, a cooling member for a battery with excellent bonding performance and a method for manufacturing the same can be provided.

[0020] FIG. 1 is an example of photographs of the top and bottom plates of a cooling member provided at the bottom of a cell or module of an electric vehicle battery. (a) is the top plate, and (b) is the bottom plate.

[0021] FIG. 2 is a perspective view of a cooling member for a battery according to one embodiment of the present invention.

[0022] FIG. 3 is a schematic diagram showing a brazed upper plate and a lower plate according to one embodiment of the present invention.

[0023] FIG. 4 is an electron microscope photograph of a brazed upper plate and a lower plate according to one embodiment of the present invention, (a) is a photograph of Invention Example 2 and (b) is a photograph of Invention Example 3.

[0024] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0025] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0026] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0027] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0028] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0029] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0030] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0031] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0032] FIG. 2 is a perspective view of a cooling member for a battery according to an embodiment of the present invention. As shown in FIG. 2, a cooling member (1) for a battery according to an embodiment of the present invention includes an upper plate (10) and a lower plate (20) having a cooling water channel (22) formed therein, which is provided on the lower side of the upper plate (10). The upper plate (10) is in contact with a battery cell or module and serves to transfer heat generated from the battery cell or module to a refrigerant. Within the lower plate (22), the refrigerant can flow through the cooling water channel (22). An embossed (bead) (24) may be formed within the cooling water channel (22) of the lower plate (20), and the upper plate (10) and the lower plate (20) are brazed together at the periphery of the cooling water channel (22) and at the embossed (bead) (24) portion. That is, a brazed joint may be included between the upper plate (10) and the lower plate (20). In the present invention, the shape and number of the cooling water channel (12) and the emboss (beads) (24) or the brazing joining method are not specifically limited, and any method commonly used in the relevant technical field may be used. Meanwhile, although FIG. 2 shows that the emboss (beads) (24) are formed on the lower plate (20), the emboss (beads) (24) may not be formed. Also, in FIG. 2, a refrigerant inlet (12) and a refrigerant outlet (14) are formed in the cooling water channel (12) on the upper plate (10), but the refrigerant inlet (12) and the refrigerant outlet (14) may be formed on the lower plate (20) instead of the upper plate (10). Furthermore, although FIG. 2 shows that the upper plate (10) has the shape of a flat plate, the cooling water channel may be formed on the upper plate (10) as on the lower plate (20).

[0033] FIG. 3 is a schematic diagram showing a brazed upper plate and a lower plate according to an embodiment of the present invention. As shown in FIG. 3, the upper plate (100) and the lower plate (200) may include a base steel plate (110, 210); and an intermetallic compound layer (120, 220) formed on the base steel plate (110, 210). The intermetallic compound layer (120, 220) is formed as the aluminum-based plating layer formed on the base steel plate (110, 210), which is the raw material, is alloyed during brazing. The thickness of the intermetallic compound layer (120, 220) may be increased compared to the aluminum-based plating layer as the base steel plate or the insert material is alloyed together with the aluminum-based plating layer. The upper plate (100) and the lower plate (200) may be brazed and include a brazed joint portion (300) between them. Meanwhile, an unalloyed aluminum-based plating layer may remain on the intermetallic compound layer (120, 220). However, since the alloy composition of the aluminum-based plating layer and the brazing joint (300) may be the same or similar, making it difficult to distinguish between them, the present invention does not specifically distinguish between the aluminum-based plating layer and the brazing joint. The present invention does not specifically limit the alloy composition of the aluminum-based plating layer and the brazing joint, but as an example, it may include Si: 10% or less by weight, the remainder being Al and other unavoidable impurities. Meanwhile, a rod-shaped Al-Si compound formed during the melting and solidification process of the aluminum-based plating layer formed on the aluminum-based insert and the upper and lower plates may exist in the brazing joint.

[0034] The upper and lower plates of the present invention have the advantage of being not only cheaper than conventional aluminum-based plates but also having high rigidity. In particular, the upper and lower plates of the present invention have the advantage that the decrease in yield strength or tensile strength is not significant even after brazing, that is, after heat treatment at high temperatures. The base steel plates of the upper and lower plates may be carbon steel or stainless steel. The present invention does not specifically limit the type of carbon steel or stainless steel. However, as an example, one or more types of austenitic or ferritic stainless steel may be used as the stainless steel. In this case, considering formability and cost aspects, it is more advantageous to use ferritic stainless steel. In the present invention, steel of the same type may be used as the material for the upper and lower plates, or steel of a different type may be used.

[0035] It is preferable that the average thickness of the intermetallic compound layer be 10 to 60 μm. If the average thickness of the intermetallic compound layer is less than 10 μm, the bonding strength is inferior due to insufficient metallurgical bonding, and problems such as refrigerant leakage or fracture of the bonding site may occur when applied to a battery. If the average thickness of the intermetallic compound layer exceeds 60 μm, problems such as fracture of the bonding site may occur when applied to a battery due to the brittleness of the intermetallic compound. The intermetallic compound layer may be an Fe-Al-Si based intermetallic compound layer or an Fe-Al-Cr-Si based intermetallic compound layer, wherein the Fe and Cr, etc., may diffuse from the base steel sheet and be included in the intermetallic compound layer.

[0036] As described above, the cooling member of the present invention has the advantage of excellent adhesion between the upper plate and the lower plate, as well as the advantage of being able to be manufactured without changing the existing manufacturing process. That is, the present invention does not specifically limit the manufacturing method, and the manufacturing method of a cooling member using an existing aluminum-based plate can be utilized.

[0037] However, a preferred example of a method for manufacturing a cooling member for a battery according to the present invention will be described below.

[0038] First, an upper plate and a lower plate formed with a cooling channel are prepared. A cooling channel of an appropriate shape may be machined into the lower plate depending on the type or size of the battery of the electric vehicle to which it is applied. The upper plate and the lower plate may comprise a base steel plate; and an aluminum-based plating layer formed on the base steel plate. In the present invention, the average thickness of the aluminum-based plating layer is not specifically limited. However, as an example, the average thickness of the aluminum-based plating layer may be 10 to 40 μm. If the average thickness of the aluminum-based plating layer is less than 10 μm, it may be difficult to ensure uniformity across the entire length and width during the manufacturing of the upper plate and the lower plate. If the average thickness of the aluminum-based plating layer exceeds 40 μm, there may be a disadvantage of increased manufacturing costs for the upper plate and the lower plate. As the aluminum-based plating layer is heat-treated in the subsequent brazing step, some or all of it is converted into an intermetallic compound layer.

[0039] Subsequently, a flux is applied to the upper and lower plates. The flux can help prevent brazing from being easily performed due to the oxide layer formed on the aluminum-based plating layer. In the present invention, the type of flux is not specifically limited, and any type used in the relevant technical field may be used. However, as an example, the flux may be a flux containing one or more of K, Al, and F.

[0040] Subsequently, the lower plate is provided on the lower side of the upper plate, and an aluminum-based insert is provided between the upper plate and the lower plate. In the present invention, the average thickness of the aluminum-based insert is not specifically limited. However, as an example, the average thickness of the aluminum-based insert may be 50 to 150 μm. If the average thickness of the aluminum-based insert is less than 50 μm, it may not be possible to sufficiently fill the gap between the upper plate and the lower plate caused by surface roughness of the upper plate and the lower plate or errors during forming, and thus a sound brazing joint may not be formed. If the average thickness of the aluminum-based insert exceeds 150 μm, there may be a disadvantage of increased brazing joint costs. Meanwhile, the present invention does not specifically limit the type of the aluminum-based insert. However, as an example, the above aluminum-based insert may use an aluminum-based alloy with a melting point of 570 to 650°C, and more specifically, AA4045 (melting point 573 to 599°C) or AA4047 (577 to 585°C), etc. may be used.

[0041] Subsequently, the upper and lower plates equipped with the aforementioned insert are brazed together. It is common practice to use furnace brazing for the brazing joint. In the case of furnace brazing, while it may be performed in a single chamber as in vacuum furnace brazing, the furnace may be divided into four zones, such as a heating zone and a cracking zone, and configured to enable continuous production by allowing the workpiece to pass through these zones. Meanwhile, regardless of the brazing furnace equipment, if a thermocouple is attached to the workpiece passing through the furnace to measure the temperature, a graph showing the temperature curve according to the heating time can be obtained. In the above graph, the integral value between the heating time range and the temperature curve can be defined as the brazing heat input. In the present invention, it is preferable that the brazing heat input be 330,000 to 700,000°C / sec in the range of 570 to 650°C during the brazing joint. If the brazing temperature is less than 570°C, the flux does not melt, making it impossible to remove aluminum oxide from the surfaces of the joined materials and the insert, which may result in inferior brazing performance. If the brazing temperature exceeds 650°C, it may be disadvantageous in terms of brazing equipment and process costs. If the brazing heat input is less than 330,000°C / sec, sufficient metallurgical bonding between the aluminum-based plating layer and the insert is not achieved, which may result in inferior joint strength. If the brazing heat input exceeds 700,000°C / sec, the thickness of the intermetallic compound at the interface between the top and bottom plates exceeds 60 μm, which may cause leakage or fracture in the brazing joint.

[0042] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0043] (Example)

[0044] An upper plate and a lower plate having an aluminum-based plating layer (10 wt% Si-Al) formed on both sides as described in Table 1 below were prepared. Then, NOCOLOK flux was applied to the upper and lower plates, an aluminum-based insert (Al4047 foil) was provided, and the upper and lower plates were brazed together under the conditions described in Table 1 below to manufacture a cooling member. At this time, ferritic stainless steel (STS409) containing 11 wt% Cr and carbon steel containing 0.15 wt% C were used as the base steel plates for the upper and lower plates. The thickness of the upper and lower plates was 0.8 mm each. The upper plate was in the form of a flat plate, and the lower plate was in the form of a cooling water channel. The brazing was performed through a heating furnace divided into four zones, such as a heating zone and a cracking zone, and the heating was performed in an N2 atmosphere. The average thickness and bonding performance of the intermetallic compound layer and the brazing joint of the cooling member manufactured in this way were measured, and the results are shown in Table 2 below.

[0045] The average thickness of the intermetallic compound layer and the brazing joint was calculated by cutting the joint of the above-manufactured cooling member and measuring the cross-section at 10 random locations using a scanning electron microscope (SEM).

[0046] The bonding performance was determined by whether leakage or fracture occurred when a pressure of 2 Bar was applied to the above-manufactured cooling member.

[0047] Classification Top Plate Bottom Plate Brazing Heat Input (°C / sec) in the Range of 570~650°C Base Steel Plate Type Aluminum-based Plating Layer Average Thickness (㎛) Base Steel Plate Type Aluminum-based Plating Layer Average Thickness (㎛) Invention Example 1 STS40921 STS40921332909 Invention Example 2 STS40921 STS40921454733 Invention Example 3 STS40921 STS40921697500 Invention Example 4 Carbon Steel 25 Carbon Steel 25548500 Comparative Example 1 STS40921 STS40921750000 Comparative Example 2 Carbon Steel 25 Carbon Steel 25200000

[0048] Classification Cooling Element Bonding Performance (Whether Leak or Fracture Occurs When 2 Bar Pressure is Applied) Average Thickness of Upper Plate Intermetallic Compound Layer (㎛) Average Thickness of Lower Plate Intermetallic Compound Layer (㎛) Invention Example 1 26 22 Not Occurred Invention Example 2 33 25 Not Occurred Invention Example 3 42 50 Not Occurred Invention Example 4 40 45 Not Occurred Comparative Example 1 70 72 Occurred Comparative Example 2 10 8 Occurred

[0049] FIG. 4 is an electron microscope image of a brazed upper plate and a lower plate according to an embodiment of the present invention, where (a) is a photograph of Invention Example 2 and (b) is a photograph of Invention Example 3. As can be seen from Tables 1 and 2 and FIG. 4, in the case of Invention Examples 1 to 4 manufactured to satisfy the manufacturing conditions proposed by the present invention, it can be seen that the bonding performance is good as the average thickness of the intermetallic compound layer proposed by the present invention is satisfied.

[0050] On the other hand, in the case of Comparative Examples 1 and 2, the manufacturing conditions proposed by the present invention are not satisfied, and the average thickness of the intermetallic compound layer proposed by the present invention is not satisfied, so it can be seen that the bonding performance is poor.

[0051] [Explanation of the symbol]

[0052] 1: Cooling element for battery

[0053] 10: Top plate

[0054] 20: Bottom plate

[0055] 12: Refrigerant filler

[0056] 14: Refrigerant outlet

[0057] 22: With coolant

[0058] 24: Embossed (Bead)

[0059] 100: Top plate

[0060] 200: Bottom plate

[0061] 110, 210: Base steel plate

[0062] 120, 220: Intermetallic compound layer

[0063] 300: Brazing joint

Claims

1. Top plate; A lower plate having a cooling water channel formed therein, provided on the lower side of the upper plate; and It includes a brazing joint between the upper plate and the lower plate, and The above upper plate and lower plate comprise a base steel plate; and an intermetallic compound layer formed on the base steel plate. A cooling member for a battery having an average thickness of 10 to 60 μm of the above-mentioned intermetallic compound layer.

2. In Paragraph 1, The above-mentioned base steel plate is a cooling member for a battery, which is carbon steel or stainless steel.

3. In Paragraph 2, The above stainless steel is an austenitic or ferritic stainless steel, a cooling member for a battery.

4. In Paragraph 1, The above intermetallic compound layer is a Fe-Al-Si-based intermetallic compound layer or a Fe-Al-Cr-Si-based intermetallic compound layer, and is a cooling member for a battery.

5. A step of preparing an upper plate and a lower plate having a cooling water channel formed therein; A step of applying flux onto the upper and lower plates; A step of providing the lower plate on the lower side of the upper plate, and then providing an aluminum-based insert between the upper plate and the lower plate; and The method includes the step of brazing the upper plate and the lower plate equipped with the above-mentioned insert; The upper and lower plates above comprise a base steel plate; and an aluminum-based plating layer formed on the base steel plate, and A method for manufacturing a cooling member for a battery, wherein, during the above brazing joining, the brazing heat input is 330,000 to 700,000℃sec in the range of 570 to 650℃.

6. In Paragraph 5, A method for manufacturing a cooling member for a battery, wherein the average thickness of the aluminum-based plating layer is 10 to 40 μm.

7. In Paragraph 5, A method for manufacturing a cooling member for a battery, wherein the average thickness of the aluminum-based insert is 50 to 150 μm.

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