Battery case

Abstract

It provides a lightweight battery case with high resistance to thermal blast. [Solution] The battery case of the present invention is a battery case that houses a battery module. Furthermore, since the outer wall of the battery case is formed of a resin outer shell, a plurality of flame-retardant sheets provided on the inner surface of the outer shell, and a resin protective layer provided on the inner surface of the flame-retardant sheets, a lightweight battery case with high thermal runaway blast resistance can be provided.

Description

Technical Field

[0001] The present invention relates to a battery case, and more particularly to a resin-made battery case.

Background Art

[0002] When a short circuit occurs between electrodes of a lithium ion battery for some reason, the temperature rises sharply, which may cause the battery to rupture due to thermal runaway blast, leading to scattering of fragments or ignition. The battery case is required to suppress the scattering of the fragments and the spread of fire.

[0003] Patent Document 1 describes that a battery case formed by integrally molding a resin and a flame-retardant mica sheet provided on the surface of the resin has improved adhesion between the resin and the mica sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] However, in recent years, along with the enlargement and higher density of battery modules, the power of thermal runaway blast has increased, requiring higher strength of battery cases, while further weight reduction is also demanded due to requirements such as extending the cruising range of electric vehicles.

[0006] The present invention has been made in view of the problems possessed by such conventional art, and an object thereof is to provide a lightweight battery case with high thermal runaway blast resistance.

Means for Solving the Problems

[0007] The inventors of this invention conducted extensive research to achieve the above objectives and discovered that these objectives can be achieved by providing a resin protective layer on the inner surface of the flame-retardant sheet, thus completing the present invention.

[0008] In other words, the battery case of the present invention is a battery case that houses a battery module. Furthermore, the outer wall of the battery case is characterized by being formed of a resin outer shell, a plurality of flame-retardant sheets provided on the inner surface of the outer shell, and a resin protective layer provided on the inner surface of the flame-retardant sheets. [Effects of the Invention]

[0009] According to the present invention, by providing a resin protective layer on the inner surface of the flame-retardant sheet, thermal runaway blast resistance is improved, and as a result, a lightweight battery case can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the battery case of the present invention. [Figure 2] This is a cross-sectional view of the main part of the outer wall of the battery case of the present invention. [Figure 3] This is a cross-sectional view of the main part of the exterior wall having ribs. [Figure 4] This is a schematic diagram of a battery case with a flame-retardant sheet installed in the corner of the wall. [Modes for carrying out the invention]

[0011] The battery case of the present invention will be described in detail. As shown in Figure 1, the battery case of the present invention is a battery case that houses a battery module inside, and the outer wall of the battery case that covers the battery module is mainly made of resin.

[0012] The battery case needs to withstand fragments (chipping) blown away by high-temperature, high-velocity gases to prevent the spread of fire.

[0013] Generally, resin battery cases consist of a resin that maintains the shape of the outer wall and a flame-retardant sheet that has heat insulation and fire resistance. The flame-retardant sheet prevents the resin constituting the outer wall from melting due to rising temperatures, thereby preventing rupture of the battery case.

[0014] Therefore, the flame-retardant sheet needs to be thick enough to withstand abrasion caused by the impact of high-speed fragments blown away by thermal runaway blasting and prevent holes from forming. Since the flame-retardant sheet is made of a material heavier than resin, such as inorganic minerals, the weight of the battery case increases.

[0015] The inventors analyzed the behavior of runaway thermal blasting and found that the amount of chipping and the scattering velocity are highest in the initial stages of runaway thermal blasting, and that both the amount of scattering and the scattering velocity decrease over time.

[0016] As shown in Figure 2, the battery case of the present invention has an outer wall comprising a resin outer shell and a plurality of flame-retardant sheets provided on the inner surface of the outer shell, and further comprises a resin protective layer provided on the inner surface of the flame-retardant sheets.

[0017] Therefore, during the initial stages of a runaway thermal blast, when its force is strongest, the protective layer protects the flame-retardant sheet from impacting fragments and suppresses wear on the flame-retardant sheet, thus allowing the thickness of the flame-retardant sheet to be reduced.

[0018] Furthermore, instead of applying the flame-retardant sheet to the entire outer wall of the battery case, the flame-retardant sheet is divided into multiple sections and placed only in locations where flame retardancy is required, such as positions facing the vent holes of the battery module, thereby reducing the content of the flame-retardant sheet.

[0019] In addition, the flame-retardant sheet is divided, the outer shell and the protective layer are connected to enclose the flame-retardant sheet between the outer shell and the protective layer, and ribs corresponding to the thickness of the flame-retardant sheet are formed on the outer shell, which improves the rigidity of the outer shell itself, so that the outer wall can be made thinner, and both improved thermal runaway blast resistance and weight reduction can be achieved.

[0020] Examples of the resin constituting the outer shell and the protective layer include thermoplastic resins such as polypropylene and polyamide, and thermosetting resins such as epoxy resin and polyurethane.

[0021] Moreover, examples of the flame-retardant sheet include sheets formed from resin or ceramic that contain 50% by volume or more of inorganic minerals such as glass fibers and mica. The content of inorganic minerals such as glass fibers and mica in the sheet is preferably 80% by volume or more.

[0022] The thickness of the outer shell is preferably greater than the thickness of the protective layer. As described above, the outer shell is a structural member that maintains the shape of the battery case, while the protective layer protects the flame-retardant sheet at the initial stage of thermal runaway blast occurrence and burns out after being exposed to the thermal runaway blast, so the thickness of the protective layer is sufficient as long as it can protect the flame-retardant sheet.

[0023] In this way, by clearly separating the roles of the outer shell and the protective layer and increasing the thickness of the outer shell, the decrease in strength and rigidity of the battery case after being exposed to thermal runaway blast can be minimized, and as a result, the thickness of the outer wall can be reduced.

[0024] The thickness of the protective layer depends on the size of the battery to be housed, that is, the assumed power of the thermal runaway blast and the material constituting the protective layer, but is preferably 50 μm to a value equivalent to the thickness of the outer shell.

[0025] Preferably, the outer shell and protective layer are made of fiber-reinforced resin. Reinforcement with fibers improves strength and rigidity, making it possible to reduce the thickness of the outer wall.

[0026] In other words, when the protective layer is made of fiber-reinforced resin, not only is abrasion resistance to flying debris improved, but even after the resin constituting the protective layer burns away, the reinforcing fibers remain and reduce the kinetic energy of the flying debris, thereby reducing damage to the flame-retardant sheet and outer shell.

[0027] Furthermore, if the outer shell is made of fiber-reinforced resin, thermal runaway can cause the inside of the battery case to become hot and high-pressure, increasing its resistance to bending input in the direction that would cause the battery case to expand. In addition, it also suppresses the decrease in material strength in high-temperature environments.

[0028] In addition to carbon fiber, glass fiber, and polypropylene fiber, natural fiber materials such as hemp can be used as reinforcing fibers.

[0029] The flame-retardant sheet is preferably arranged along the inner surface shape of the outer shell, and the thickness of the protective layer is constant.

[0030] Even when the rigidity is improved by changing the thickness of the outer shell in the in-plane direction, that is, when convex shapes such as ribs or bosses protruding outward or inward are provided, as shown in Figure 3, the thickness of the protective layer is kept constant by arranging the flame-retardant sheet along the inner surface shape of the outer shell, regardless of the change in the thickness of the outer shell.

[0031] This ensures that the thickness of the portion burned off by thermal runaway blasting remains constant, and the ribs and bosses of the outer shell remain even after exposure to thermal runaway blasting, thereby suppressing the reduction in the rigidity of the outer wall.

[0032] Furthermore, it is preferable that the flame-retardant sheet is provided at least in a position facing the vent holes of the battery module, as shown in Figure 1.

[0033] By selectively placing flame-retardant sheets in areas exposed to runaway thermal blasting, the amount of flame-retardant sheets used can be reduced, thereby lowering costs without compromising resistance to runaway thermal blasting.

[0034] Furthermore, it is preferable to install the flame-retardant sheet at the corners of the outer walls, or at the walls where the inner and outer walls intersect, as shown in Figure 4.

[0035] The thermal runaway blast ejected from the battery module hits the outer and inner walls and then spreads in the plane of those walls, so the corners of the walls are indirectly exposed to the thermal runaway blast. By installing flame-retardant sheets in these wall corners, the thermal runaway blast resistance of the battery case can be improved.

[0036] Preferably, the outer wall is formed by integrally molding the outer shell, the flame-retardant sheet, and the protective layer using a molding method such as press molding, injection molding, or overmolding.

[0037] Because the outer wall is integrally molded, the outer shell and the flame-retardant sheet, and the flame-retardant sheet and the protective layer are directly joined without the need for adhesives, etc. The flame-retardant sheet is embedded inside the outer wall, improving their adhesion and preventing peeling. Furthermore, the process of applying the flame-retardant sheet and evaluating its peelability are eliminated, resulting in increased productivity.

[0038] In addition, because a flame-retardant sheet is embedded inside the exterior wall, damage to the flame-retardant sheet can be prevented in subsequent processes such as assembly, thus improving work efficiency and reducing costs.

[0039] Furthermore, it is preferable that the outer shell and the protective layer are formed by integrally molding them from the same material.

[0040] Since the outer shell and the protective layer are integrally molded from the same material, there is no interface between the outer shell and the protective layer, thus preventing structural weaknesses and improving the strength of the battery case. [Explanation of symbols]

[0041] 1 Battery Case 2. Exterior walls 21 Outer shell 22 Flame-retardant sheet 23 Protective layer 3 Inner wall 4 Battery Modules 41 Benthole 5. Thermal Runaway Blast

Claims

1. A battery case containing a battery module, The outer wall of the above battery case, A resin outer shell, Multiple flame-retardant sheets are provided on the inner surface of the outer shell, A battery case characterized by being formed of a resin protective layer provided on the inner surface of the flame-retardant sheet mentioned above.

2. The battery case according to claim 1, characterized in that the thickness of the outer shell is greater than the thickness of the protective layer.

3. The battery case according to claim 2, characterized in that the protective layer is formed of fiber-reinforced resin.

4. The battery case according to claim 2, characterized in that the outer shell is formed of fiber-reinforced resin.

5. The above outer shell has a convex shape that protrudes outward and / or inward, The above flame-retardant sheet is arranged along the inner surface shape of the above outer shell, The battery case according to claim 1, characterized in that the thickness of the protective layer is constant.

6. The battery case according to claim 5, characterized in that the flame-retardant sheet is provided at least in a position facing the vent holes of the battery module.

7. The battery case according to claim 6, characterized in that the flame-retardant sheet is provided in the corner of the wall.

8. The battery case according to claim 1, characterized in that the outer wall is formed by integrally molding the outer shell, the flame-retardant sheet, and the protective layer.

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