Battery pack bottom protection plate, battery pack and vehicle

Abstract

The invention provides a battery pack bottom protection plate, a battery pack and a vehicle, and relates to the technical field of vehicles, the battery pack bottom protection plate comprises a base plate and a self-expansion layer; the substrate is used for being arranged below the battery cell module; the self-expansion layer is arranged on the top surface of the substrate; when the environment temperature of the self-expansion layer is lower than a first preset temperature, the self-expansion layer and the bottom surface of the battery cell module are arranged at an interval; and when the temperature of the environment where the self-expansion layer is located is higher than a first preset temperature, the self-expansion layer can be heated to expand and fill a gap between the self-expansion layer and the bottom surface of the battery cell module. When the battery pack is subjected to thermal runaway, the expansion layer is heated to expand to fill the gap between the self-expansion layer and the bottom surface of the battery cell module, so that air in the gap between the self-expansion layer and the bottom surface of the battery cell module is effectively isolated, and the spreading of thermal diffusion is hindered to achieve an inhibition effect on the thermal runaway; and flame is prevented from being jetted downwards through a gap between the self-expansion layer and the bottom surface of the battery cell module, so that a larger-range battery pack thermal runaway chain reaction is prevented, and the safety performance is improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and in particular to a battery pack bottom protection plate, a battery pack, and a vehicle. Background Technology

[0002] In recent years, new energy vehicles have developed rapidly, and with the popularization of new energy vehicles, battery pack safety issues have become increasingly prominent.

[0003] Under extreme conditions, battery packs may experience thermal runaway, generating large amounts of high-temperature gas and flames. Traditional battery pack bottom protection plates are mostly made of metal or rigid plastic materials, primarily serving to provide structural strength and durability for the battery pack. An unavoidable assembly gap exists between the battery pack and the cell modules.

[0004] When thermal runaway occurs, the underbody protection plate cannot effectively prevent the downward ejection of high-temperature gases and flames. Air in the assembly gaps can exacerbate thermal runaway, and flames can also be ejected downwards through the assembly gaps, causing a larger-scale chain reaction of thermal runaway in the battery pack, posing a great threat to passenger safety. Summary of the Invention

[0005] The purpose of this invention is to provide a battery pack bottom protection plate to solve the technical problem in the prior art that the assembly gap between the battery pack and the cell module will cause a larger-scale chain reaction of thermal runaway in the battery pack.

[0006] The battery pack bottom cover provided by the present invention includes a substrate and a self-expanding layer; The substrate is used to be disposed below the battery cell module; The self-expanding layer is disposed on the top surface of the substrate; when the ambient temperature of the self-expanding layer is lower than the first preset temperature, the self-expanding layer is spaced apart from the bottom surface of the battery cell module; when the ambient temperature of the self-expanding layer is higher than the first preset temperature, the self-expanding layer can be heated and expand to fill the gap between the self-expanding layer and the bottom surface of the battery cell module.

[0007] Furthermore, when the ambient temperature of the self-expanding layer is greater than the first preset temperature, the self-expanding layer can fill the gap between adjacent battery cell modules.

[0008] Furthermore, a thickening layer is provided on the top surface of the substrate, and the self-expanding layer is bonded to the thickening layer.

[0009] Furthermore, the substrate is provided with a plurality of through holes spaced apart; Each of the through holes is provided with a first pressure relief valve unit. When the ambient temperature of the first pressure relief valve unit is greater than a second preset temperature, the first pressure relief valve unit can be opened, and gas can pass through the self-expanding layer and enter the through hole.

[0010] Furthermore, the first pressure relief valve unit includes a valve body and a drive component; The valve body is interference-fitted with the through hole, and the drive member is connected to the valve cover of the valve body. When the ambient temperature of the valve body is greater than the second preset temperature, the drive member can extend to push open the valve cover of the valve body.

[0011] Furthermore, the top of the valve body protrudes from the top surface of the substrate.

[0012] Furthermore, an airtight layer is provided on the bottom surface of the substrate; A flow channel is provided between the substrate and the airtight layer, and the plurality of through holes are respectively connected to the flow channel. The end of the flow channel is connected to the outside of the bottom protective plate of the battery pack.

[0013] Furthermore, a second pressure relief valve unit is provided within the flow channel.

[0014] Another objective of this invention is to provide a battery pack, including the battery pack bottom protection plate provided by this invention.

[0015] Another objective of this invention is to provide a vehicle comprising a battery pack underbody protection plate or a battery pack as provided in this invention.

[0016] The battery pack bottom cover plate provided by the present invention includes a substrate and a self-expanding layer; the substrate is used to be disposed below the cell module; the self-expanding layer is disposed on the top surface of the substrate; when the ambient temperature of the self-expanding layer is lower than a first preset temperature, the self-expanding layer is spaced apart from the bottom surface of the cell module; when the ambient temperature of the self-expanding layer is higher than the first preset temperature, the self-expanding layer can be heated and expand to fill the gap between the self-expanding layer and the bottom surface of the cell module. The self-expanding layer is fixed on the top surface of the substrate. When the battery pack does not experience thermal runaway, the ambient temperature of the self-expanding layer is lower than a first preset temperature. The self-expanding layer is spaced apart from the bottom surface of the cell module. When the battery pack experiences thermal runaway, the ambient temperature of the self-expanding layer is lower than the first preset temperature. The expansion layer expands due to heat and fills the gap between the self-expanding layer and the bottom surface of the cell module, effectively isolating the air in the gap between the self-expanding layer and the bottom surface of the cell module, hindering the spread of heat diffusion. The self-expanding layer forms a sealing barrier under the cell module, which has a suppressive effect on thermal runaway and prevents flames from shooting downwards through the gap between the self-expanding layer and the bottom surface of the cell module, preventing a larger-scale chain reaction of battery pack thermal runaway and improving safety performance. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the battery pack bottom protective plate provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the battery pack bottom protective plate provided in an embodiment of the present invention; Figure 3 This is a partial structural schematic diagram of the battery pack bottom protection plate provided in an embodiment of the present invention.

[0019] Icons: 1-Cell module; 2-Self-expanding layer; 3-Substrate; 4-Airtight layer; 5-First pressure relief valve unit; 6-Through hole; 7-Second pressure relief valve unit; 8-Flow channel. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a battery pack bottom protector, a battery pack, and a vehicle. Several embodiments are given below to describe in detail the battery pack bottom protector, battery pack, and vehicle provided by this invention.

[0022] The battery pack bottom protection plate provided in this embodiment, such as Figures 1 to 3 As shown, it includes a substrate 3 and a self-expanding layer 2; the substrate 3 is used to be disposed below the battery cell module 1; the self-expanding layer 2 is disposed on the top surface of the substrate 3; when the ambient temperature of the self-expanding layer 2 is lower than a first preset temperature, the self-expanding layer 2 is spaced apart from the bottom surface of the battery cell module 1; when the ambient temperature of the self-expanding layer 2 is higher than the first preset temperature, the self-expanding layer 2 can be heated and expand to fill the gap between the self-expanding layer 2 and the bottom surface of the battery cell module 1.

[0023] The self-expanding layer 2 is fixed on the top surface of the substrate 3. When the battery pack does not experience thermal runaway, the ambient temperature of the self-expanding layer 2 is lower than the first preset temperature. The self-expanding layer 2 is spaced apart from the bottom surface of the cell module 1. When the battery pack experiences thermal runaway, the ambient temperature of the self-expanding layer 2 is lower than the first preset temperature. The expansion layer expands due to heat and fills the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, effectively isolating the air in the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, hindering the spread of heat diffusion. The self-expanding layer forms a sealing barrier under the cell module 1, which has a suppressive effect on thermal runaway and prevents flames from shooting downward through the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, preventing a larger-scale chain reaction of battery pack thermal runaway and improving safety performance.

[0024] The substrate of the self-expanding layer 2 can be an expandable mineral material, such as modified graphene aerogel, or other materials with a layered microstructure under normal temperature and pressure. The initial state of the self-expanding layer 2 is a dense film. Upon exposure to high temperatures (i.e., when the ambient temperature of the self-expanding layer 2 exceeds a first preset temperature), it self-expands into a porous thermal insulation structure, significantly increasing in volume to form a honeycomb-like porous thermal insulation structure. This porous thermal insulation structure has numerous tiny voids, providing thermal insulation properties and effectively filling the gaps between the substrate 3 and the battery module 1, hindering the spread of heat diffusion. The porous thermal insulation structure of the self-expanding layer 2, which fills the voids, can also effectively remove air from the gaps between the substrate 3 and the battery module 1, thereby fundamentally preventing the spread of thermal runaway.

[0025] A certain amount of fiber reinforcement can be added to the self-expanding layer 2, which is beneficial for the self-expanding layer 2 to build a spatial skeleton during the expansion process and maintain the stability of the porous thermal insulation structure.

[0026] When the self-expanding layer 2 is in its initial state and not triggered, the self-expanding layer 2 can be distributed in a part of the top surface of the substrate 3. After the self-expanding layer 2 is triggered, it can fill the gap between the self-expanding layer 2 and the bottom surface of the cell module 1. The self-expanding layer 2 can also be distributed in the entire top surface of the substrate 3. The specific distribution can be set according to the expansion capacity of the self-expanding layer 2.

[0027] The substrate 3, serving as the supporting frame for the battery pack's bottom cover, can be made of lightweight, high-strength materials, such as a high-strength metal substrate 3 or a glass fiber reinforced polyethylene substrate 3. Bolt mounting holes are provided around the perimeter of the substrate 3. The substrate 3 is connected to the battery pack frame via bolts, which pass through the mounting holes and are then secured to the frame. The design of the bolt mounting holes allows for thermal expansion displacement compensation, enabling the substrate 3 to freely expand and contract within a certain range, releasing thermal stress and ensuring connection stability and structural integrity.

[0028] Furthermore, when the ambient temperature of the self-expanding layer 2 is greater than the first preset temperature, the self-expanding layer 2 can fill the gap between adjacent battery cell modules 1.

[0029] Along the horizontal direction, there are gaps between adjacent cell modules 1. When thermal runaway occurs, the ambient temperature of the self-expanding layer 2 is greater than the first preset temperature. The self-expanding layer 2 fills the gaps between adjacent cell modules 1 through its own expansion characteristics, thereby directly constructing a thermal protection system between the thermal runaway cell module 1 and the adjacent cell module 1, which can effectively suppress the occurrence of thermal propagation between cell modules.

[0030] The self-expanding layer 2 can fill part of the gap between adjacent cell modules 1, or it can fill all the gap between adjacent cell modules 1.

[0031] Furthermore, a thickening layer is provided on the top surface of the substrate 3, and the self-expanding layer 2 is bonded to the thickening layer.

[0032] The top surface of substrate 3 is roughened to form a thickening layer, which improves the stability of the bonding between the self-expanding layer 2 and substrate 3.

[0033] The self-expanding layer 2 is bonded to the thickening layer through a high-temperature resistant adhesive film. The high-temperature resistant adhesive film can be a fluorosilicone high-temperature resistant adhesive film or other adhesive film that can maintain sufficient mechanical strength under high temperature conditions.

[0034] The thickening layer and the high-temperature resistant adhesive film work together to ensure that the self-expanding layer 2 is stably attached to the substrate 3 at room temperature and pressure, and allows directional expansion when thermal runaway occurs at high temperature.

[0035] Furthermore, the substrate 3 is provided with a plurality of through holes 6 at intervals; each through hole 6 is provided with a first pressure relief valve unit 5. When the ambient temperature of the first pressure relief valve unit 5 is greater than the second preset temperature, the first pressure relief valve unit 5 can be opened, and the gas can pass through the self-expanding layer 2 and enter the through hole 6.

[0036] Multiple through holes 6 can be evenly spaced on the substrate 3. In this embodiment, the multiple through holes 6 are distributed in an array on the substrate 3, which can both ensure the strength of the substrate 3 and provide a mounting base for subsequent functional layers. The through holes 6 can be round holes or irregularly shaped holes, and the edges of the through holes 6 can be chamfered to avoid stress concentration.

[0037] A reinforcing structure can be provided in the substrate 3. The mechanical strength of the substrate 3 structure can be improved by setting radial or grid-like reinforcing ribs. The direction of the reinforcing ribs should be consistent with the direction of force on the vehicle, so that the substrate 3 can better withstand various dynamic loads during vehicle operation, thereby ensuring the mechanical strength of the substrate 3 and improving the protection capability of the battery pack bottom guard plate for the battery pack under conditions such as bottom collision and scraping.

[0038] The through-holes 6 penetrate the top and bottom surfaces of the substrate 3, respectively. When the ambient temperature of the first pressure relief valve unit 5 is lower than the second preset temperature, the first pressure relief valve unit 5 remains closed, and the gas above the substrate 3 cannot flow out to the outside of the substrate 3 through the through-holes 6. When the ambient temperature of the first pressure relief valve unit 5 is higher than the second preset temperature, the first pressure relief valve unit 5 can open, making the through-holes 6 a pressure relief channel, and the gas above the substrate 3 can flow out to the outside of the substrate 3 through the through-holes 6, so that high-temperature products are kept away from the passenger compartment and critical vehicle components, thereby improving safety performance.

[0039] In the event of thermal runaway, the generated gas can pass through the self-expanding layer 2 and enter the through hole 6. Alternatively, the self-expanding layer 2 may expand without covering the through hole 6, allowing the gas to directly enter the through hole 6; or the self-expanding layer 2 may expand and cover the through hole 6, but the generated gas can still pass through the self-expanding layer 2 and enter the through hole 6.

[0040] Furthermore, the first pressure relief valve unit 5 includes a valve body and a drive component; the valve body is interference-fitted with the through hole 6, and the drive component is connected to the valve cover of the valve body. When the ambient temperature of the valve body is greater than the second preset temperature, the drive component can extend to push open the valve cover of the valve body.

[0041] The valve body can be made of high-temperature ceramic, such as Al2O3, and the drive component can be made of shape memory alloy. In this embodiment, the drive component is a shape memory alloy spring.

[0042] The valve body is press-fitted to the inner wall of the through hole 6, achieving sealing and force transmission through mechanical constraint. The valve body has an opening, and the valve cover can open or close the opening. The drive component is located between the valve cover and the valve body. Under normal temperature and pressure conditions, the compression force of the shape memory alloy spring keeps the valve cover closed. In the event of thermal runaway, the generated gas enters the valve body. When the ambient temperature of the valve body exceeds a second preset temperature, the shape memory alloy spring extends, generating thrust, thereby pushing open the valve cover and opening the opening. The entire process requires no electronic control and is characterized by rapid and reliable response.

[0043] The valve body can be located at the top of the through hole 6, at the bottom of the through hole 6, or in the middle of the through hole 6.

[0044] Furthermore, the top of the valve body protrudes from the top surface of the substrate 3.

[0045] The valve body is located at the top of the through hole 6, and the top of the valve body is higher than the top surface of the base plate 3 to prevent dust and debris from entering the through hole 6 and affecting the normal pressure relief operation of the through hole 6.

[0046] Furthermore, an airtight layer 4 is provided on the bottom surface of the substrate 3; a flow channel 8 is provided between the substrate 3 and the airtight layer 4, and multiple through holes 6 are respectively connected to the flow channel 8, and the end of the flow channel 8 is connected to the outside of the bottom protective plate of the battery pack.

[0047] The airtight layer 4 can be made of corrosion-resistant and high-temperature-resistant glass fiber polyethylene material or other materials with similar structural properties. The airtight layer 4 is used to ensure the airtightness of the bottom protective plate of the battery pack and improve the corrosion resistance of the battery pack.

[0048] A thickening layer can also be provided on the bottom surface of the substrate 3, and the airtight layer 4 is bonded to the thickening layer so that the airtight layer 4 is stably fixed on the substrate 3.

[0049] A flow channel 8 is provided between the substrate 3 and the airtight layer 4. The flow channel 8 conforms to aerodynamic principles and can be etched on the bottom surface of the substrate 3. In the event of thermal runaway, the generated gas enters the bottom of the substrate 3 through the through hole 6 and is discharged to the outside of the battery pack bottom guard plate through the flow channel 8 at the bottom of the substrate 3.

[0050] Furthermore, a second pressure relief valve unit 7 is provided in the flow channel 8.

[0051] The second pressure relief valve unit 7 can be located at any suitable position within the flow channel 8. In this embodiment, the second pressure relief valve unit 7 is located at the end of the flow channel 8 that communicates with the outside. This end of the flow channel 8 that communicates with the outside can be located on the side of the battery pack bottom guard plate. The end of the flow channel 8 that communicates with the outside is tightly connected to the flow channel at the bottom or side of the battery pack bottom guard plate. In the event of thermal runaway, the generated gas flows into the flow channel 8 through the through hole 6. At this time, the second pressure relief valve unit 7 is in the open state, and the generated gas flows out to the outside of the battery pack bottom guard plate through the flow channel 8. This allows for the controllable and safe guidance of high-temperature gas, flames, and projectiles to a designated area below or to the side of the vehicle, away from the passenger compartment, high-voltage lines, fuel tank (hybrid), and other critical components.

[0052] When thermal runaway occurs, the generated gas flows into the guide channel 8, and the second pressure relief valve unit 7 installed in the guide channel 8 can be opened. When the generated gas does not flow into the guide channel 8, the second pressure relief valve unit 7 is in the closed state.

[0053] The second pressure relief valve unit 7 can be a gas valve. When the generated gas flows into the guide channel 8, the generated gas pressure pushes the gas valve to open.

[0054] The second pressure relief valve unit 7 can also have the same structure as the first pressure relief valve unit 5. The second pressure relief valve unit 7 can open when the ambient temperature of the second pressure relief valve unit 7 is higher than the third preset temperature. The third preset temperature can be set according to the typical temperature range during battery pack thermal runaway. The inner wall of the flow channel 8 needs to be coated with a phase change heat-absorbing material layer to prevent damage to the flow channel 8 when high-temperature gas enters.

[0055] The working principle of the battery pack bottom protection plate provided in this embodiment when encountering thermal runaway is as follows: Stage 1: The sealing barrier of the self-expanding layer 2 is formed. When a flame or high-temperature gas comes into contact with the self-expanding layer 2, it triggers a physical expansion reaction in the material. The self-expanding layer 2 immediately undergoes a physical expansion reaction to form a porous thermal insulation structure, which fills the assembly gap between the battery pack bottom cover and the telecommunications module. The thermal insulation properties of the self-expanding layer 2 material can effectively prevent the propagation of thermal runaway. At the same time, the self-expanding layer 2 fills the gap between the battery pack bottom cover and the telecommunications module, expelling the air in the gap, thereby effectively suppressing the first path of heat propagation.

[0056] Phase 2: After the sealing barrier is formed, the high-temperature gas generated by thermal runaway will pass through the pressure relief channel in through-hole 6, opening the first pressure relief valve unit 5. This ensures that a controlled pressure relief mechanism is established after the sealing barrier is formed, preventing serious accidents such as explosions caused by excessive internal pressure in the battery pack, while also ensuring that the high-temperature gas can be discharged in an orderly manner, preparing for subsequent gas treatment and heat dissipation.

[0057] Stage 3: After the high-temperature gas generated by thermal runaway enters the guide channel 8, it triggers the second pressure relief valve unit 7 at the end of the guide channel 8, thereby guiding the orderly discharge of the gas. This allows the gas to be discharged from a safe area, effectively eliminating the risk of secondary hazards from the high-temperature gas and ensuring the safety of the battery pack and the surrounding environment.

[0058] The battery pack bottom protection plate provided in this embodiment has components that work together. When local thermal runaway occurs in the battery pack, the self-expanding layer 2 first responds to the high-temperature signal and rapidly expands to fill all assembly gaps (the gap between the battery pack bottom protection plate and the cell module 1), forming a physical isolation barrier. At the same time, the first pressure relief valve unit 5 automatically opens under temperature triggering, and the released high-temperature gas enters the guide channel 8. The guide channel 8 directs the gas to the side or rear of the vehicle for safe discharge. This triple protection works synergistically to effectively solve the problems of flame leakage and heat spread.

[0059] The battery pack bottom protector provided in this embodiment has a simple and straightforward manufacturing process, requiring no complex processes or high costs, and can be easily mass-produced, greatly meeting the market's urgent demand for efficient and safe battery pack bottom protectors. It has strong environmental adaptability; the integrated components of the bottom protector are purely mechanical structures, unaffected by electromagnetic interference. It maintains reliability under extreme temperature and vibration environments, and its service life matches the vehicle's lifespan. The functional integration design keeps the total thickness within a reasonable range, without altering the original battery pack installation space or vehicle ground clearance, effectively improving space utilization.

[0060] The battery pack provided in this embodiment includes a bottom protective plate. A self-expanding layer 2 is fixed to the top surface of the substrate 3. When the battery pack does not experience thermal runaway, the ambient temperature of the self-expanding layer 2 is lower than a first preset temperature. The self-expanding layer 2 is spaced apart from the bottom surface of the cell module 1. When the battery pack experiences thermal runaway, the ambient temperature of the self-expanding layer 2 is still lower than the first preset temperature. The expansion layer expands due to heat, filling the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, effectively isolating the air in the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, hindering the spread of heat diffusion. The self-expanding layer forms a sealing barrier below the cell module 1, suppressing thermal runaway and preventing flames from shooting downwards through the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, preventing a larger-scale chain reaction of battery pack thermal runaway, and improving safety performance.

[0061] The vehicle provided in this embodiment includes the battery pack bottom protection plate or the battery pack provided in this embodiment. The self-expanding layer 2 is fixed on the top surface of the substrate 3. When the battery pack does not experience thermal runaway, the ambient temperature of the self-expanding layer 2 is lower than a first preset temperature. The self-expanding layer 2 is spaced apart from the bottom surface of the cell module 1. When the battery pack experiences thermal runaway, the ambient temperature of the self-expanding layer 2 is lower than the first preset temperature. The expansion layer expands due to heat and fills the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, effectively isolating the air in the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, hindering the spread of heat diffusion. The self-expanding layer forms a sealing barrier under the cell module 1, which has a suppressive effect on thermal runaway and prevents flames from shooting downward through the gap between the self-expanding layer 2 and the bottom surface of the cell module 1, preventing a larger-scale chain reaction of battery pack thermal runaway and improving safety performance.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery pack bottom protective plate, characterized in that, It includes a substrate (3) and a self-expanding layer (2); The substrate (3) is used to be disposed below the battery cell module (1); The self-expanding layer (2) is disposed on the top surface of the substrate (3); when the ambient temperature of the self-expanding layer (2) is lower than the first preset temperature, the self-expanding layer (2) is spaced apart from the bottom surface of the battery cell module (1); when the ambient temperature of the self-expanding layer (2) is higher than the first preset temperature, the self-expanding layer (2) can be heated and expand to fill the gap between the self-expanding layer (2) and the bottom surface of the battery cell module (1).

2. The battery pack bottom protective plate according to claim 1, characterized in that, When the ambient temperature of the self-expanding layer (2) is greater than the first preset temperature, the self-expanding layer (2) can fill the gap between adjacent battery cell modules (1).

3. The battery pack bottom protective plate according to claim 1, characterized in that, The top surface of the substrate (3) is provided with a thickening layer, and the self-expanding layer (2) is bonded to the thickening layer.

4. The battery pack bottom protective plate according to claim 1, characterized in that, The substrate (3) is provided with a plurality of through holes (6) spaced apart; Each of the through holes (6) is provided with a first pressure relief valve unit (5). When the ambient temperature of the first pressure relief valve unit (5) is greater than the second preset temperature, the first pressure relief valve unit (5) can be opened, and the gas can pass through the self-expanding layer (2) and enter the through hole (6).

5. The battery pack bottom protective plate according to claim 4, characterized in that, The first pressure relief valve unit (5) includes a valve body and a drive component; The valve body is press-fitted with the through hole (6), the drive member is connected to the valve cover of the valve body, and when the ambient temperature of the valve body is greater than the second preset temperature, the drive member can extend to push open the valve cover of the valve body.

6. The battery pack bottom protective plate according to claim 5, characterized in that, The top of the valve body protrudes from the top surface of the substrate (3).

7. The battery pack bottom protective plate according to claim 4, characterized in that, The bottom surface of the substrate (3) is provided with an airtight layer (4); A flow channel (8) is provided between the substrate (3) and the airtight layer (4), and a plurality of through holes (6) are respectively connected to the flow channel (8). The end of the flow channel (8) is connected to the outside of the bottom protective plate of the battery pack.

8. The battery pack bottom protective plate according to claim 7, characterized in that, The flow channel (8) is equipped with a second pressure relief valve unit (7).

9. A battery pack, characterized in that, Includes the battery pack bottom cover plate according to any one of claims 1-8.

10. A vehicle, characterized in that, Includes the battery pack bottom cover plate according to any one of claims 1-8 or the battery pack according to claim 9.

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