Bottom protective plate, battery pack, and electric device

Abstract

The present application provides a bottom protective plate, a battery pack, and an electric device. The bottom protective plate comprises a protective outer layer, an impact-resistant layer, and an energy-absorbing layer. The protective outer layer comprises a first fiber-reinforced composite layer and a second fiber-reinforced composite layer arranged in a spaced apart manner, the impact-resistant layer is arranged between the first fiber-reinforced composite layer and the second fiber-reinforced composite layer, and the energy-absorbing layer is interposed between the first fiber-reinforced composite layer and the impact-resistant layer.

Description

Bottom guard plate, battery pack and electric device

[0001] The present application claims priority to Chinese Patent Application No. 202422199581.8, filed on September 6, 2024, and Chinese Patent Application No. 202422211865.4, filed on September 9, 2024, the contents of both of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a bottom guard plate, a battery pack and an electric device. BACKGROUND

[0003] In the related art, a bottom guard plate is arranged at the bottom of a battery pack to protect the battery cells inside the battery pack when the bottom of the battery pack is impacted by foreign matter, so as to avoid damage to the battery pack and cause safety accidents. SUMMARY

[0004] The current bottom guard plate has weak impact resistance, and the impact force is easily transmitted to the battery cells inside the battery pack through the bottom guard plate, causing damage to the battery cells.

[0005] In a first aspect, the embodiments of the present application provide a bottom guard plate, which includes a protective outer layer, an impact-resistant layer and an energy-absorbing layer. The protective outer layer includes a first fiber-reinforced composite layer and a second fiber-reinforced composite layer arranged at intervals, the impact-resistant layer is arranged between the first fiber-reinforced composite layer and the second fiber-reinforced composite layer, and the energy-absorbing layer is arranged between the first fiber-reinforced composite layer and the impact-resistant layer.

[0006] In a second aspect, the embodiments of the present application provide a battery pack, which includes the bottom guard plate according to any one of the above embodiments.

[0007] In a third aspect, the embodiments of the present application provide an electric device, which includes the battery pack described above. ADVANTAGEOUS EFFECTS

[0008] In the embodiment of the present application, by making the bottom protection plate include a protective outer layer, an impact-resistant layer and an energy-absorbing layer, the protective outer layer includes a first fiber-reinforced composite layer and a second fiber-reinforced composite layer, and the impact-resistant layer and the energy-absorbing layer are arranged between the first fiber-reinforced composite layer and the second fiber-reinforced composite layer, so that the bottom protection plate not only has the effects of insulation, wear resistance and puncture resistance, but also protects the impact-resistant layer and the energy-absorbing layer from being corroded. The impact-resistant layer can resist external impact force and disperse the external impact force concentrated at a certain position to different positions, avoiding foreign objects from directly piercing the bottom protection plate. The energy-absorbing layer can absorb the impact energy on the impact-resistant layer, avoiding the impact-resistant layer from being deformed or pierced, and avoiding the transmission of impact force to the battery cells in the battery pack, thereby improving the protection effect on the battery cells.

[0009] The battery pack provided in the present application has all the beneficial effects of the bottom protection plate described above, which will not be repeated here.

[0010] The use-of-electricity equipment provided in the present application has all the beneficial effects of the battery pack described above, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 is a perspective view of a bottom protection plate according to an embodiment of the present application;

[0012] FIG. 2 is an exploded view of the structure of the bottom protection plate according to an embodiment of the present application;

[0013] FIG. 3 is a sectional view of the structure of the bottom protection plate according to an embodiment of the present application;

[0014] FIG. 4 is a structural schematic view of an energy-absorbing layer in the bottom protection plate according to an embodiment of the present application;

[0015] FIG. 5 is a sectional view of the structure of a battery pack according to an embodiment of the present application.

[0016] BRIEF DESCRIPTION OF DRAWINGS

[0017] 100, bottom protection plate; 10, protective outer layer; 11, first fiber-reinforced composite layer; 12, second fiber-reinforced composite layer; 20, impact-resistant layer; 30, energy-absorbing layer; 31, drainage groove; 311, first drainage groove; 312, second drainage groove; 200, battery pack; 210, box body; 220, battery cell. Embodiments of the present application

[0018] To improve the fact that external impact force is easily transmitted to the battery cell in the battery pack through the bottom guard plate, according to the first aspect of the present application, as shown in FIGS. 1-3, a bottom guard plate 100 is provided, which comprises a protective outer layer 10, an impact-resistant layer 20 and an energy-absorbing layer 30. Among them, the protective outer layer 10 comprises a first fiber-reinforced composite layer 11 and a second fiber-reinforced composite layer 12, the impact-resistant layer 20 is arranged between the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12, and the energy-absorbing layer 30 is arranged between the first fiber-reinforced composite layer 11 and the impact-resistant layer 20.

[0019] Specifically, in the present embodiment, the protective outer layer 10 is composed of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12, the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 are the surface layer structure of the bottom guard plate 100, and the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 are both composite materials formed by winding, molding or pultrusion of reinforcing fibers and matrix materials. The reinforcing fibers can be glass fibers, carbon fibers, aramid fibers, etc., the matrix material can be resin, metal, ceramic, etc., the reinforcing fibers and matrix materials used in the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 can be the same or different, and the specific composition can be flexibly selected as needed.

[0020] It should be noted that the fiber-reinforced composite material has the characteristics of high strength, lightweight, corrosion resistance, etc., and when the reinforcing fibers in the fiber-reinforced composite material are glass fibers or aramid fibers and the matrix material is resin, the fiber-reinforced composite material also has good insulation. Therefore, when the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 are used as the surface layer structure of the bottom guard plate 100, not only can the bottom guard plate 100 have the effects of insulation, wear resistance and puncture resistance, but also can protect the impact-resistant layer 20 and the energy-absorbing layer 30, avoid corrosion of the impact-resistant layer 20 and the energy-absorbing layer 30, and thus there is no need to spray an insulating coating on the surface of the bottom guard plate 100, reducing production cost.

[0021] As shown in FIG. 5, when the bottom guard plate 100 is assembled on the box 210 of the battery pack 200, the first fiber-reinforced composite layer 11 can be closer to the battery cell 220 than the second fiber-reinforced composite layer 12, i.e. the battery cell 220 can be placed directly on the first fiber-reinforced composite layer 11.

[0022] As shown in FIG. 2 or FIG. 3, the bottom protection plate 100 further comprises an impact-resistant layer 20, which has certain strength and toughness to resist external impact force. The impact-resistant layer 20 can be made of a metal plate with certain strength, such as a steel plate, an alloy plate (such as a titanium alloy, a magnesium-aluminum alloy), etc. When the road surface through which the vehicle passes has protruding stones, the stones can scratch the bottom of the battery pack 200. At this time, the bottom protection plate 100 is subjected to the impact force from the stones. Because the impact-resistant layer 20 has certain strength, the bottom protection plate 100 can be prevented from being punctured when subjected to external impact force. In addition, because the impact-resistant layer 20 has certain toughness, the impact-resistant layer 20 can deform to some extent when subjected to external impact force, thereby dispersing the impact force to different positions.

[0023] Optionally, in an embodiment, the impact-resistant layer 20 is a steel plate. To improve the impact resistance, the impact-resistant layer 20 can be made of super-strong steel (such as a steel material with a model number of DP1470).

[0024] As shown in FIG. 2 or FIG. 3, the bottom protection plate 100 further comprises an energy-absorbing layer 30, which can absorb the impact energy on the impact-resistant layer 20, thereby avoiding the direct transmission of external impact force to the battery cell 220 in the battery pack 200, and improving the protection effect on the battery cell 220.

[0025] In the embodiment, the energy-absorbing layer 30 can be made of any one or more of basswood, high-density polyurethane foam, metal porous energy-absorbing materials (such as aluminum honeycomb, foamed aluminum), and high polymer materials (such as EVA foaming material). In general, the energy-absorbing layer 30 can be made of a material with certain deformation capability. When the impact force is transmitted to the energy-absorbing layer 30, the energy-absorbing layer 30 can absorb the impact energy through its own deformation, thereby avoiding the transmission of the impact force to the battery cell 220 in the battery pack 200.

[0026] As shown in FIG. 3 and FIG. 5, in the embodiment, the energy-absorbing layer 30 is located between the first fiber-reinforced composite layer 11 and the impact-resistant layer 20, that is, the energy-absorbing layer 30 is closer to the battery cell 220 than the impact-resistant layer 20. In this way, the transmission of the impact force on the impact-resistant layer 20 to the battery cell 220 can be better prevented.

[0027] In summary, in the embodiments of the present application, by making the bottom protection plate 100 include a protective outer layer, an impact-resistant layer 20 and an energy-absorbing layer 30, the protective outer layer includes a first fiber-reinforced composite layer 11 and a second fiber-reinforced composite layer 12, and the impact-resistant layer 20 and the energy-absorbing layer 30 are arranged between the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12, so that the bottom protection plate 100 not only has the effects of insulation, wear resistance and puncture resistance, but also protects the impact-resistant layer 20 and the energy-absorbing layer 30 from being corroded. The impact-resistant layer 20 can resist external impact force and disperse the external impact force concentrated at a certain position to different positions, avoiding foreign objects from directly piercing the bottom protection plate 100. The energy-absorbing layer 30 can absorb the impact energy on the impact-resistant layer 20, avoiding the impact-resistant layer 20 from being deformed or pierced, and avoiding the transmission of impact force to the battery cell 220 in the battery pack 200, thereby improving the protection effect on the battery cell 220.

[0028] Optionally, in an embodiment, the energy-absorbing layer 30 is made of balsa wood. Specifically, balsa wood is one of the lightest woods in the world, weighing only 0.1 grams per cubic centimeter. The lightweight property of balsa wood means that it can deform more easily when impacted, thereby absorbing and dispersing impact energy. In addition, the microstructure of balsa wood has porosity, and these voids and channels can act as "buffer zones" for energy absorption and dispersion when impacted, slowing down the transmission speed of the shock wave and reducing the destructive effect of impact energy on the material. Balsa wood can also undergo elastic or plastic deformation when impacted, and these deformation processes themselves will absorb a large amount of impact energy. It should be noted that although balsa wood is light in texture, it is structurally strong and not easily completely destroyed under impact, so it can absorb energy while maintaining a certain degree of structural integrity.

[0029] Therefore, by making the energy-absorbing layer 30 from balsa wood, the present embodiment not only better absorbs the impact energy on the impact-resistant layer 20, but also makes the structure of the bottom protection plate 100 more robust and less likely to be damaged.

[0030] Optionally, in an embodiment, the protective outer layer 10, the impact-resistant layer 20 and the energy-absorbing layer 30 are compounded into the bottom protection plate 100 by a resin transfer molding process. Specifically, in the present embodiment, the impact-resistant layer 20 is made of steel plate, the energy-absorbing layer 30 is made of balsa wood, and the protective outer layer 10, the impact-resistant layer 20 and the energy-absorbing layer 30 are compounded into the bottom protection plate 100 by a resin transfer molding process.

[0031] The resin transfer molding process is an advanced composite material molding technology, and its basic principle is to inject resin into a closed mold, infiltrate the reinforcing material, and solidify and form. Specifically, during molding, the protective outer layer 10, the impact-resistant layer 20, and the energy-absorbing layer 30 can be laid in the mold cavity, and then the resin glue can be injected into the mold cavity by a resin injection machine at a certain pressure. The resin fully infiltrates the fiber reinforced material and between the layers (i.e., the protective outer layer 10, the impact-resistant layer 20, and the energy-absorbing layer 30) under the action of pressure, and solidifies under certain conditions, and finally the composite material product is obtained, that is, the bottom guard plate 100 is obtained.

[0032] It can be understood that by the resin transfer molding process, the resin can be fully infiltrated between the first fiber reinforced composite layer 11 and the energy-absorbing layer 30, between the energy-absorbing layer 30 and the impact-resistant layer 20, and between the impact-resistant layer 20 and the second fiber reinforced composite layer 12, thereby enabling the layers in the bottom guard plate 100 to be firmly attached together, improving the structural strength and stability of the bottom guard plate 100.

[0033] It should be noted that in order to improve the composite effect of the layers in the bottom guard plate 100, a high-pressure resin transfer molding process (the glue injection pressure is usually between 1.0-6.0 MPa or even higher) can be used for production.

[0034] Optionally, in an embodiment, as shown in FIGS. 2 and 3, the surface of the energy-absorbing layer 30 facing the impact-resistant layer 20 is recessed with a drainage groove 31, the drainage groove 31 penetrates to the outer circumferential surface of the energy-absorbing layer 30, and the drainage groove 31 is provided for the resin to flow between the energy-absorbing layer 30 and the impact-resistant layer 20.

[0035] Specifically, in this embodiment, as described above, the protective outer layer 10, the impact-resistant layer 20, and the energy-absorbing layer 30 are combined into the bottom guard plate 100 by the resin transfer molding process, and in order to enable the resin to flow more fully between the energy-absorbing layer 30 and the impact-resistant layer 20, the energy-absorbing layer 30 is made of basswood, and the surface of the energy-absorbing layer 30 facing the impact-resistant layer 20 is recessed with a drainage groove 31, the drainage groove 31 penetrates to the outer circumferential surface of the energy-absorbing layer 30, and thus the resin can flow between the energy-absorbing layer 30 and the impact-resistant layer 20 through the drainage groove 31, that is, the resin can flow more fully between the energy-absorbing layer 30 and the impact-resistant layer 20, which can improve the composite effect of the energy-absorbing layer 30 and the impact-resistant layer 20.

[0036] Optionally, in an embodiment, as shown in FIG. 2 or FIG. 4, the plurality of flow grooves 31 are arranged in a staggered manner. It can be understood that, by arranging the plurality of flow grooves 31 in a staggered manner, more resin can be introduced between the energy-absorbing layer 30 and the impact-resistant layer 20, thereby improving the composite effect between the energy-absorbing layer 30 and the impact-resistant layer 20. By arranging the plurality of flow grooves 31 in a staggered manner, the efficiency of filling the flow grooves 31 with resin can be improved, and the situation that some flow grooves 31 are not filled with resin after molding is completed can be avoided. In addition, after the resin solidifies, a "resin grid structure" can be formed between the energy-absorbing layer 30 and the impact-resistant layer 20, which is conducive to improving the composite effect of the energy-absorbing layer 30 and the impact-resistant layer 20.

[0037] It should be noted that the extension direction of the plurality of flow grooves 31 can be designed flexibly according to requirements. For example, in an embodiment, as shown in FIG. 4, the energy-absorbing layer 30 is a rectangular plate and has a length direction and a width direction, and the plurality of flow grooves 31 include a plurality of first flow grooves 311 and a plurality of second flow grooves 312. The first flow grooves 311 extend along the length direction of the energy-absorbing layer 30, and the plurality of first flow grooves 311 are arranged in a staggered manner along the width direction of the energy-absorbing layer 30. The second flow grooves 312 extend along the width direction of the energy-absorbing layer 30, and the plurality of second flow grooves 312 are arranged in a staggered manner along the length direction of the energy-absorbing layer 30.

[0038] That is, in the embodiment, the plurality of first flow grooves 311 and the plurality of second flow grooves 312 are arranged in a staggered manner, and any one of the first flow grooves 311 and any one of the second flow grooves 312 are arranged in a perpendicular manner. In this way, the arrangement of the plurality of flow grooves 31 is relatively simple, which is conducive to processing, and the spacing between the flow grooves 31 can be better controlled.

[0039] Further, in an embodiment, as shown in FIG. 4, the plurality of first flow grooves 311 are uniformly spaced along the width direction of the energy-absorbing layer 30, and / or the plurality of second flow grooves 312 are uniformly spaced along the length direction of the energy-absorbing layer 30. In this way, the distribution of the resin between the energy-absorbing layer 30 and the impact-resistant layer 20 can be more uniform, thereby making the composite strength of the energy-absorbing layer 30 and the impact-resistant layer 20 at each position more uniform, and ensuring that the energy-absorbing effect of the energy-absorbing layer 30 at each position is more uniform.

[0040] Optionally, in an embodiment, the cross section of the flow groove 31 is a non-closed polygon with an opening on one side. Specifically, in the embodiment, the flow groove 31 can be provided with a plurality of side walls, and the plurality of side walls are sequentially connected in a head-to-tail manner. The first side wall and the last side wall in the connection sequence are not connected, thereby forming a non-closed polygonal structure with an opening on one side.

[0041] The number of side walls of the flow channel 31 can be flexibly selected as required. For example, in an embodiment, as shown in FIG. 3, the flow channel 31 is provided with two side walls arranged at an included angle, and the cross section of the flow channel 31 is V-shaped. In this way, the structure of the flow channel 31 is relatively simple and easy to process.

[0042] For another example, in another embodiment, the number of side walls of the flow channel 31 can be three, two of which are parallel to each other and spaced apart, and one of which is connected perpendicularly between the two parallel side walls. At this time, the cross section of the flow channel 31 is a square structure with one side open.

[0043] In general, the number of side walls of the flow channel 31 and the size of the included angle between the side walls can be flexibly selected as required.

[0044] Alternatively, in another embodiment, the cross section of the flow channel 31 is an arc with an arc less than 360°. Specifically, the inner wall of the flow channel 31 extends in an arc shape with an arc less than 360°. At this time, the cross section of the flow channel 31 is an arc with an arc less than 360°. In this way, the flow channel 31 has an opening, so that the resin in the flow channel 31 can be bonded to the impact-resistant layer 20.

[0045] Specifically, the cross section of the flow channel 31 can be semicircular, semi-elliptical, an arc with an arc of 90°, and the like.

[0046] Of course, in other embodiments, the cross section of the flow channel 31 can also be other shapes (for example, irregular shapes), and the specific shape can be flexibly designed as required.

[0047] Optionally, in an embodiment, the thickness of the energy-absorbing layer 30 is not less than 5 mm and not greater than 10 mm. Specifically, the thickness can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, and the like.

[0048] It can be understood that if the thickness of the energy-absorbing layer 30 is less than 5 mm, the energy-absorbing effect of the energy-absorbing layer 30 can not be good enough. If the thickness of the energy-absorbing layer 30 is greater than 10 mm, the thickness of the bottom guard plate 100 can be relatively thick. Therefore, by making the thickness of the energy-absorbing layer 30 not less than 5 mm and not greater than 10 mm, the energy-absorbing layer 30 can have a good buffering and energy-absorbing effect, and the bottom guard plate 100 can not be too thick.

[0049] It should be noted that, with reference to FIG. 3, the thickness direction of the energy-absorbing layer 30 is the stacking direction of the first fiber-reinforced composite layer 11, the energy-absorbing layer 30, the impact-resistant layer 20, and the second fiber-reinforced composite layer 12.

[0050] Optionally, in an embodiment, the impact-resistant layer 20 is made of a metal material, and the yield strength of the impact-resistant layer 20 is not less than 1200 MPa. Specifically, in the embodiment, the impact-resistant layer 20 is made of DP1470 super strong steel, and the yield strength of the impact-resistant layer 20 is 1200 MPa or even higher, so that the impact resistance of the impact-resistant layer 20 is improved, thereby providing better protection.

[0051] Optionally, in an embodiment, the thickness of the impact-resistant layer 20 is not less than 1 mm and not more than 2 mm, and the specific thickness can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.

[0052] It can be understood that if the thickness of the impact-resistant layer 20 is less than 1 mm, the impact resistance of the impact-resistant layer 20 can be weak, and if the thickness of the impact-resistant layer 20 is greater than 2 mm, the weight and cost of the bottom guard plate 100 can be increased. Therefore, by making the thickness of the impact-resistant layer 20 not less than 1 mm and not more than 2 mm, the impact-resistant layer 20 can have good impact resistance, and the weight and cost of the bottom guard plate 100 can be avoided.

[0053] Optionally, in an embodiment, the thickness of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 is not less than 0.6 mm and not more than 2 mm, and the specific thickness can be 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.

[0054] It can be understood that if the thickness of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 is less than 0.6 mm, the corrosion resistance and puncture resistance of the protective outer layer 10 can not be good enough, and if the thickness of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 is greater than 2 mm, the production difficulty can be increased. Therefore, by making the thickness of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 not less than 0.6 mm and not more than 2 mm, the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 can have good corrosion resistance and puncture resistance, and the production of the first fiber-reinforced composite layer 11 and the second fiber-reinforced composite layer 12 can be facilitated.

[0055] As shown in FIG. 5, the application also provides a battery pack 200, which comprises the bottom guard plate 100. The specific structure of the bottom guard plate 100 is referred to the above embodiments. Since the battery pack 200 adopts all the technical solutions of the above embodiments, the battery pack 200 at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0056] It should be noted that, as shown in FIG. 5, the battery pack 200 generally comprises a box 210 and a battery module installed in the box 210. The battery module comprises a plurality of battery cells 220. The bottom guard plate 100 in the application can be directly used as the bottom plate structure of the box 210, and the battery cells 220 are directly installed on the bottom guard plate 100.

[0057] Alternatively, in some other embodiments, the bottom of the box 210 is provided with a bottom plate, and the battery cells 220 are directly installed on the bottom plate of the box 210. The bottom guard plate 100 in the application is fixed at the bottom of the bottom plate of the box, so as to jointly protect the bottom of the battery cells 220 with the bottom plate of the box 210.

[0058] The application also provides a power consuming device, which comprises the above battery pack 200. Since the battery pack 200 adopts all the technical solutions of the above embodiments, the power consuming device at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0059] The power consuming device can be a car, a ship, an industrial device, a household device, etc.

Claims

1. A bottom protection plate, comprising a protective outer layer, an impact-resistant layer, and an energy-absorbing layer; the protective outer layer comprises a first fiber-reinforced composite layer and a second fiber-reinforced composite layer, the impact-resistant layer is arranged between the first fiber-reinforced composite layer and the second fiber-reinforced composite layer, and the energy-absorbing layer is arranged between the first fiber-reinforced composite layer and the impact-resistant layer.

2. The underguard of claim 1, wherein, The energy-absorbing layer is made of any one or more of basswood, high-density polyurethane foam, metal porous energy-absorbing material, and polymer material.

3. The underguard of claim 1, wherein, A surface of the energy-absorbing layer facing the impact-resistant layer is concavely provided with a drainage groove, the drainage groove penetrates to an outer circumferential surface of the energy-absorbing layer, and the drainage groove is configured to allow resin to flow between the energy-absorbing layer and the impact-resistant layer.

4. The underguard of claim 3, wherein, The drainage groove is provided in a plurality, and the plurality of drainage grooves are staggered and communicated.

5. The underguard of claim 4, wherein, The energy-absorbing layer is rectangular and has a length direction and a width direction, the drainage groove comprises a plurality of first drainage grooves and a plurality of second drainage grooves; the first drainage grooves extend along the length direction of the energy-absorbing layer, and the plurality of first drainage grooves are arranged at intervals along the width direction of the energy-absorbing layer; the second drainage grooves extend along the width direction of the energy-absorbing layer, and the plurality of second drainage grooves are arranged at intervals along the length direction of the energy-absorbing layer.

6. The underguard of claim 5 wherein, The plurality of first drainage grooves are uniformly spaced along the width direction of the energy-absorbing layer, and / or the plurality of second drainage grooves are uniformly spaced along the length direction of the energy-absorbing layer.

7. The underguard of claim 3 wherein, The cross section of the drainage groove is a non-closed polygon with an opening on one side, or the cross section of the drainage groove is an arc with an arc degree less than 360°.

8. The underguard of claim 3 wherein, The cross section of the drainage groove is V-shaped.

9. The underpan according to any one of claims 1-8, wherein, The thickness of the energy-absorbing layer is not less than 5 mm and not more than 10 mm.

10. The underpan according to any one of claims 1-8, wherein, The impact-resistant layer is made of a metal material, and the yield strength of the impact-resistant layer is not less than 1200 MPa.

11. The underpan according to any one of claims 1-8, wherein, The thickness of the impact-resistant layer is not less than 1 mm and not more than 2 mm.

12. The underpan according to any one of claims 1-8, wherein, The thickness of the first fiber-reinforced composite layer and the second fiber-reinforced composite layer is not less than 0.6 mm and not more than 2 mm.

13. The underpan according to any one of claims 1-8, wherein, The protective outer layer, the impact-resistant layer, and the energy-absorbing layer are compounded into the bottom protection plate by a resin transfer molding process.

14. A battery pack, wherein, A bottom protection plate according to any one of claims 1-13.

15. An electrical device, comprising: A battery pack according to claim 14.

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