Battery bottom protection plate, battery pack and vehicle

Abstract

The application discloses a battery bottom protection plate, a battery pack and a vehicle, and relates to the technical field of batteries. The battery bottom protection plate comprises a fiber framework and a resin matrix; the fiber framework comprises a plurality of fiber woven layers which are sequentially stacked; and the resin matrix is filled and solidified in the fiber framework. The fiber woven layer is made of one or more kinds of fiber filaments selected from rigid fibers and flexible fibers; the breaking elongation of the rigid fibers is less than that of the flexible fibers; and the content of the flexible fibers in the fiber woven layer located at the outermost side of the fiber framework is greater than that in the fiber woven layer located at the inner side of the fiber framework. The battery bottom protection plate, the battery pack and the vehicle have the advantages that good impact resistance can be ensured, and light weight can be realized.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and more specifically, to a battery underbody plate, a battery pack, and a vehicle. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the safety and reliability of battery systems have become a focus of industry attention. As a core component of new energy vehicles, the battery pack's bottom protective structure directly faces complex conditions such as road impacts and stone collisions, making its performance crucial.

[0003] In related technologies, high-strength steel and ultra-high-strength steel with high strength and rigidity are usually used to make the bottom protection plate. However, this approach limits the lightweighting of the battery pack. Utility Model Content

[0004] This disclosure provides a battery underbody protection plate, a battery pack, and a vehicle, which helps to achieve lightweighting while ensuring good impact resistance.

[0005] According to one aspect of this disclosure, a battery bottom protection plate is provided, comprising: The fiber skeleton includes multiple layers of fiber braided layers stacked sequentially. Resin matrix, filled and cured in fiber skeleton; The fiber braided layer is made of one or more fibers, including rigid fibers and flexible fibers; the breaking elongation of rigid fibers is less than that of flexible fibers; the content of flexible fibers in the fiber braided layer located on the outermost side of the fiber skeleton is greater than that in the fiber braided layer located inside the fiber skeleton.

[0006] In one exemplary embodiment of this disclosure, the outermost fiber braided layer of the fiber skeleton is made of flexible fiber braiding.

[0007] In one exemplary embodiment of this disclosure, the fiber braided layer located inside the fiber skeleton is made of rigid fiber braiding.

[0008] In one exemplary embodiment of this disclosure, the content of flexible fibers in the fiber braid layer increases from the inside of the fiber skeleton to the outermost side.

[0009] In one exemplary embodiment of this disclosure, each fiber braid layer is made of a mixture of rigid and flexible fibers.

[0010] In one exemplary embodiment of this disclosure, the fiber braided layer includes at least two types of rigid fibers, wherein the difference in filament diameter between the two types of rigid fibers is not less than 3 micrometers.

[0011] In one exemplary embodiment of this disclosure, the flexible fiber includes ultra-high molecular weight polyethylene fiber.

[0012] In one exemplary embodiment of this disclosure, the rigid fiber includes at least one of glass fiber, carbon fiber, ceramic fiber, basalt fiber, and aramid fiber.

[0013] In one exemplary embodiment of this disclosure, the resin matrix comprises a thermosetting polyurethane resin.

[0014] In one exemplary embodiment of this disclosure, the fiber skeleton and the resin matrix are integrally composited through a resin transfer molding process.

[0015] In one exemplary embodiment of this disclosure, the fiber skeleton has a local reinforcement region, where the fiber areal density is greater than that outside the local reinforcement region.

[0016] In one exemplary embodiment of this disclosure, the battery bottom cover has bolt connection holes located in a localized reinforcement area.

[0017] In one exemplary embodiment of this disclosure, the breaking elongation of the rigid fiber is less than 10%; the breaking elongation of the flexible fiber is greater than or equal to 10%.

[0018] In one exemplary embodiment of this disclosure, the tensile strength of the rigid fiber is greater than 1000 MPa; the elongation at break of the flexible fiber is greater than or equal to 10%.

[0019] According to another aspect of this disclosure, a battery pack is provided, including the battery bottom protection plate of any of the foregoing.

[0020] According to another aspect of this disclosure, a vehicle is provided, including the battery pack of any of the foregoing.

[0021] The battery bottom protector disclosed herein contains a higher content of flexible fibers in the outermost fiber skeleton layer, i.e., the fiber braided layer closest to the impact surface and back surface, compared to the layer located inside the fiber skeleton, i.e., the fiber braided layer between the impact surface and back surface. This results in excellent toughness for the impact surface and back surface, effectively resisting puncture by sharp objects. Upon impact, it undergoes plastic deformation, absorbing a large amount of energy and preventing fiber detachment due to brittle fracture of rigid fibers. Furthermore, the outer fiber braided layer can constrain the internal structure of the fiber skeleton under extreme impact, preventing overall fragmentation. Meanwhile, the inner layer utilizes the high strength and high modulus of rigid fibers to effectively disperse impact energy throughout the entire bottom protector area, suppressing localized deformation. Together, these factors ensure the excellent protective performance and lightweight design of the bottom protector.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] Figure 1 This is an exploded view of the fiber skeleton in an exemplary embodiment of the battery bottom protection plate of this disclosure.

[0025] Figure 2 This is a schematic diagram of the fiber braided layer in an exemplary embodiment of the battery bottom cover plate of this disclosure.

[0026] Figure 3 This is a schematic diagram of the fiber braided layer in another exemplary embodiment of the battery bottom cover of this disclosure.

[0027] Explanation of reference numerals in the attached figures: 11. First fiber layer; 12. Second fiber layer; 13. Third fiber layer; 14. Fourth fiber layer; 15. Fifth fiber layer; 21. First fiber; 22. Second fiber. Detailed Implementation

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0029] Unless otherwise specified or stated, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “a,” “an,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “comprising” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to those listed; the terms “first” and “second” are used only as illustrative marks and are not intended to limit the number, importance, or order of the objects.

[0030] Furthermore, in this application, directional terms such as "upper" and "lower" are used only to indicate relative positional relationships. For example, for convenience, they are defined based on the actual position and state during operation, or relative to the indicated placement of components in the accompanying drawings. It should be understood that these directional terms are relative concepts and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0031] According to one aspect of this disclosure, a battery bottom cover plate is provided, comprising a fiber skeleton and a resin matrix. The fiber skeleton includes multiple layers of fiber braided layers stacked sequentially. The resin matrix fills and cures the fiber skeleton. The fiber braided layers are woven from one or more types of fibers, specifically rigid fibers and flexible fibers; the breaking elongation of the rigid fibers is less than that of the flexible fibers; the content of flexible fibers in the outermost fiber braided layer of the fiber skeleton is greater than the content of flexible fibers in the inner fiber braided layers of the fiber skeleton.

[0032] The battery bottom protector has an impact-resistant surface and a back surface facing inwards towards the battery pack. The battery bottom protector of this disclosure comprises a fiber skeleton formed by multiple layers of stacked fiber braids, filled and cured with a resin matrix, which allows the multiple fiber braids to be firmly bonded into a single unit, forming the final battery bottom protector.

[0033] The outermost fiber braided layer, closest to the impact surface and back, has a higher content of flexible fibers than the inner fiber braided layer between the impact surface and back. This gives the impact surface and back excellent toughness, effectively resisting punctures from sharp objects. Under impact, it can undergo plastic deformation, absorbing a large amount of energy and preventing fiber detachment due to brittle fracture of rigid fibers. Furthermore, the outer fiber braided layer can constrain the internal structure of the fiber skeleton under extreme impact, preventing overall fragmentation. The inner layer, utilizing the high strength and high modulus of rigid fibers, effectively disperses impact energy throughout the entire bottom plate area, suppressing localized deformation. Together, these factors ensure the excellent protective performance and lightweight design of the bottom plate.

[0034] Specifically, the fiber skeleton is composed of multiple layers of fiber braids stacked sequentially. Each fiber braid layer can be made from fiber filaments through weaving processes such as plain weave, twill weave, and satin weave. (Reference) Figures 1 to 3 As shown, Figure 1 A schematic diagram is shown showing multiple layers of fiber braided fabric stacked sequentially to form a fiber skeleton; Figure 2 and Figure 3A schematic diagram of a single-layer fiber braided layer is shown. A resin matrix is ​​filled and cured within the fiber skeleton; for example, the resin is filled into the gaps in the fiber skeleton under vacuum or pressure conditions and then cured, thereby firmly bonding the multiple fiber braided layers into a single unit to form the battery bottom cover. The fiber braided layer is formed by weaving fiber filaments, which can be classified as rigid fibers and flexible fibers according to their mechanical properties. In an exemplary embodiment of this disclosure, rigid fibers refer to fiber filaments with high tensile strength, such as those with a tensile strength greater than 1000 MPa, thereby providing a robust skeletal support for the bottom cover and ensuring structural rigidity. Exemplarily, rigid fibers can be selected from fibers with low elongation at break, such as fibers with an elongation at break of less than 10%, to ensure that impact energy can be rigidly dispersed within the fiber skeleton. For example, rigid fibers may include, but are not limited to, glass fibers, carbon fibers, ceramic fibers, basalt fibers, and aramid fibers.

[0035] Flexible fibers refer to fiber filaments with high elongation at break, such as fiber filaments with an elongation at break greater than or equal to 10%, thus possessing good toughness and strong energy absorption capacity. Upon impact, they can absorb and dissipate energy through significant deformation. For example, flexible fibers may include ultra-high molecular weight polyethylene (UHMWPE) fibers, which can have an elongation at break of 300% or more, thus improving the puncture resistance of the battery bottom protector. When mixed with rigid fibers during weaving, the toughness of the battery bottom protector can be ensured. In some embodiments, flexible fibers may include polyester fibers, spandex fibers, polyamide fibers, polyimide fibers, etc.

[0036] It should be noted that the "content of a certain fiber in the fiber braid layer" mentioned in this disclosure is relatively high or low, which can be understood as mass fraction, volume fraction or its proportion in the total fiber content of the fiber braid layer.

[0037] In one exemplary embodiment of this disclosure, the outermost fiber braided layer of the fiber skeleton is made of flexible fibers. The outermost layer may be woven using only ultra-high molecular weight polyethylene fibers, without using rigid fibers such as carbon fiber. This arrangement allows the impact face and back of the bottom guard plate to have good surface toughness and puncture resistance, providing initial protection for the inner fiber braided layer. Furthermore, the outermost layer being made of flexible fibers facilitates the full utilization of the energy absorption function of flexible fibers in the initial impact phase.

[0038] In one exemplary embodiment of this disclosure, the fiber braided layer located inside the fiber skeleton is made of rigid fiber braiding. For example, refer to... Figure 1As shown, the fiber skeleton can be made of five fiber woven layers stacked sequentially, namely the first fiber layer 11, the second fiber layer 12, the third fiber layer 13, the fourth fiber layer 14, and the fifth fiber layer 15. Among them, the two outermost layers, namely the first fiber layer 11 and the fifth fiber layer 15, can be made of ultra-high molecular weight polyethylene fiber; the three middle layers, namely the second fiber layer 12, the third fiber layer 13, and the fourth fiber layer 14, can all be made of glass fiber, thereby ensuring the high strength and rigidity of the fiber skeleton, which is beneficial to improving the overall rigidity and bending resistance of the battery bottom plate, and ensuring that the impact force can be quickly and effectively rigidly dispersed.

[0039] refer to Figure 2 The diagram illustrates a fiber braided layer. For example, the fiber braided layer is woven from a single first fiber 21. The orientation of the first fiber 21 within the fiber braided layer can be either 90° or 0°, forming a crisscrossing mesh structure, thereby better dispersing stress and bearing impact energy. In the fiber braided layer located on the outermost side of the fiber skeleton, the first fiber 21 can be a flexible fiber; in the fiber braided layer inside the fiber skeleton, the first fiber 21 can be a rigid fiber.

[0040] Those skilled in the art will understand that in the description of exemplary embodiments of this disclosure, the description that the fiber braided layer is "made" or "woven" from a certain type or class of fibers should be understood as the dominant component in terms of technology, rather than absolute chemical purity. Due to factors such as actual production processes, raw materials, and environment, unavoidable trace amounts of other fibers, auxiliaries (such as sizing agents, impregnating agents), or impurities are permissible. The presence of these non-dominant components, as long as they do not substantially affect the core mechanical properties desired by the fiber braided layer in which they are located—for example, for a fiber braided layer woven from flexible fibers, not substantially affecting its high toughness and energy absorption characteristics; for a fiber braided layer woven from rigid fibers, not substantially affecting its high modulus—should still be considered to fall within the scope of "made from..." described above.

[0041] For example, in a certain fiber braided layer, when the number or volume of the specified fiber (e.g., flexible fiber or rigid fiber) accounts for more than 95% of the total number or volume of all fibers in the layer, the layer can be considered to satisfy the condition of being "woven from the fiber".

[0042] In some embodiments, all fiber braided layers can be made of a blend of rigid and flexible fibers. This ensures that each fiber braided layer possesses a certain degree of toughness and rigidity, preventing the formation of weak layers and promoting uniform stress distribution. (Reference) Figure 3The diagram shows a schematic of a fiber braided layer. For example, the fiber braided layer is made of two kinds of fibers, a first fiber 21 and a second fiber 22. The orientation of the first fiber 21 in the fiber braided layer can be either 90° or 0°, and the orientation of the second fiber 22 can also be either 90° or 0°, forming a mesh structure through interlacing.

[0043] For example, refer to Figure 3 As shown, in the same direction, the first fiber 21 and the second fiber 22 can be staggered. For example, in any direction, all the second fibers 22 are disposed between two adjacent first fibers 21, such that the first fibers 21 are on the outside and the second fibers 22 are on the inside. Through the cross-weaving of the first fibers 21 and the second fibers 22 in two directions, the content of the second fibers 22 in the central region of the fiber weave layer is greater than that in the edge region, and the content of the first fibers 21 in the edge region is greater than that in the central region. The central part of the fiber weave layer has higher strength and stiffness, which is beneficial to improving the stiffness and bending resistance of the central part of the battery bottom protector; at the same time, the edge region has greater toughness, which is beneficial to maintaining the energy absorption function of the plastic deformation of the battery bottom protector.

[0044] In some embodiments, the fiber braided layer is made of a mixture of rigid and flexible fibers, but is not limited to two specific types of fibers. For example, the fiber braided layer can be made of a mixture of four types of fibers: ultra-high molecular weight polyethylene fiber, spandex fiber, glass fiber, and carbon fiber. The braiding method can be referred to the description of the aforementioned exemplary embodiments, and will not be repeated here.

[0045] In one exemplary embodiment of this disclosure, the content of flexible fibers in the fiber braided layers increases from the inside of the fiber skeleton to the outermost layer. For example, a gradient change in the content of flexible fibers can be achieved by adjusting the ratio of the two types of fibers when each fiber braided layer is mixed.

[0046] In one embodiment, the innermost one or two fiber braided layers of the fiber skeleton have the lowest flexible fiber content, for example, it can be 0. Then, from the inside out, the flexible fiber content in the fiber braided layers gradually increases until the outermost layer has the highest content, for example, 100%. The gradient change in flexible fiber content can make the transition of the material's mechanical properties smoother, which helps to further optimize stress distribution and avoid stress concentration caused by abrupt changes in performance between layers, thereby improving the impact resistance and fatigue life of the battery bottom plate.

[0047] For example, consider a fiber skeleton constructed by sequentially stacking a first fiber layer 11, a second fiber layer 12, a third fiber layer 13, a fourth fiber layer 14, and a fifth fiber layer 15. The third fiber layer 13 has the lowest content of flexible fibers, for example, it can be 0; the second fiber layer 12 and the fourth fiber layer 14 have a higher content of flexible fibers than the third fiber layer 13, for example, the second fiber layer 12 and the fourth fiber layer 14 are made of a mixture of flexible and rigid fibers, with the content of flexible fibers accounting for 50%; the first fiber layer 11 and the fifth fiber layer 15 have the highest content of flexible fibers, for example, they are made entirely of flexible fibers.

[0048] For example, the content of flexible fibers in the fiber braided layer closer to the inner region is not higher than that in the fiber braided layer closer to the outer region. Take, for instance, a fiber skeleton constructed by sequentially stacking a first fiber layer 11, a second fiber layer 12, a third fiber layer 13, a fourth fiber layer 14, and a fifth fiber layer 15. The second fiber layer 12, the third fiber layer 13, and the fourth fiber layer 14 can all be woven from rigid fibers, or from a mixture of rigid and flexible fibers; the first fiber layer 11 and the fifth fiber layer 15 can be entirely woven from flexible fibers.

[0049] In some exemplary embodiments of this disclosure, the fiber braided layer comprises at least two types of fiber filaments with different diameters. For example, the fiber braided layer comprises flexible fibers and rigid fibers. Specifically, for example, the fiber braided layer comprises ultra-high molecular weight polyethylene (UHMWPE) fibers and glass fibers. The diameter of the UHMWPE fibers can be 10-30 micrometers, and the diameter of the glass fibers can be 10-15 micrometers. When selecting fiber filaments to weave into the fiber braided layer, the diameter of the UHMWPE fibers can be larger than the diameter of the glass fibers, and the difference between the two can be no less than 3 micrometers. When the composite material is subjected to impact, microcracks tend to propagate along the interface between the fiber filaments and the resin matrix, leading to delamination or breakage. The mixed weaving of fiber filaments with different diameters can help to hinder crack propagation, causing cracks to deflect or branch rather than penetrate in a straight line, thus protecting the integrity of the battery bottom plate.

[0050] For example, the fiber braided layer may include at least two types of rigid fibers with different diameters. For instance, the fiber braided layer may be made of a blend of glass fibers with different diameters.

[0051] In one exemplary embodiment of this disclosure, the fiber braided layer comprises at least two types of rigid fibers, wherein the difference in filament diameter between the two types of rigid fibers is not less than 3 micrometers. For example, mixing and weaving glass fibers with a diameter of 10-15 micrometers with carbon fibers with a diameter of 5-7 micrometers to form a multi-scale fiber structure can make the bond between the resin matrix and the fibers tighter, thereby further improving the intra-layer and inter-layer bonding strength. Furthermore, the fiber braided layer with rigid fibers has lower toughness than the fiber braided layer with a higher content of flexible fibers, making it more prone to brittle fracture under impact. Mixing and weaving rigid fibers of different diameters can effectively hinder crack propagation and reduce the risk of brittle fracture in layers with a higher content of rigid fibers.

[0052] Furthermore, the properties of different fibers can also have a synergistic effect. For example, although both carbon fiber and glass fiber are rigid fibers, carbon fiber has a higher tensile strength and a lower elongation at break compared to glass fiber; glass fiber has a lower tensile strength than carbon fiber, but its elongation at break can be twice that of carbon fiber. By weaving carbon fiber and glass fiber together, cracking caused by minute deformation can be avoided.

[0053] In one exemplary embodiment of this disclosure, the resin matrix may include a thermosetting polyurethane resin. Thermosetting polyurethane has good elasticity, toughness, adhesion, and impact resistance, which is beneficial for bonding with the fiber skeleton to form a robust composite battery bottom cover.

[0054] For example, the fiber skeleton and resin matrix are integrally composited using a resin transfer molding (RTM) process. The RTM process helps ensure that the resin fully impregnates each fiber braid layer, resulting in good interlayer bonding and a high surface area of ​​the molded part, which improves the surface quality of the battery bottom cover.

[0055] In one exemplary embodiment of this disclosure, the fiber skeleton has a locally reinforced region, where the fiber areal density is greater than that outside the locally reinforced region. Specifically, within the locally reinforced region, the fiber filament arrangement density is higher than that outside the locally reinforced region, thereby specifically improving the performance of the battery bottom protector in the locally reinforced area, thus locally reinforcing the battery bottom protector while ensuring cost and lightweight design.

[0056] For example, the battery bottom protector is provided with bolt holes for connection to the battery pack housing or frame. The bolt holes are located in a localized reinforced area on the battery bottom protector, thereby improving the structural strength and tear resistance at the bolt fastening points of the battery bottom protector and preventing damage and cracking around the bolt holes during long-term vibration or accidental impact.

[0057] For example, within a locally reinforced region, the spacing between fibers can be half the spacing between fibers outside the region, thereby increasing the fiber areal density. For instance, within a locally reinforced region, the spacing between fibers can be 0.5 mm, while outside the region, the spacing between fibers can be 1 mm.

[0058] In some implementations, the location of the local reinforcement area can be determined based on the specific vehicle model and after-sales data. For example, the local reinforcement area on the battery underbody protection plate of the corresponding vehicle model can be located at the part of the bottom that is most severely impacted according to after-sales data.

[0059] This disclosure also provides a battery pack that may include the battery bottom protection plate described in any of the foregoing embodiments and possible combinations. The bottom protection plate of the battery pack of this disclosure has excellent impact and puncture resistance, and is conducive to achieving lightweight design, thereby improving the overall safety, reliability, and lightweight performance of the battery pack.

[0060] This disclosure also provides a vehicle including the battery pack of any of the foregoing embodiments. The vehicle of this disclosure, particularly in the chassis area facing complex road conditions, effectively reduces the risk of damage to its power battery system from bottom impacts, thereby improving the overall vehicle safety performance. Furthermore, the lightweighting of the battery pack contributes to the overall vehicle weight reduction and improves energy efficiency.

[0061] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the utility models disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A battery undertray characterized by, include: The fiber skeleton includes multiple layers of fiber braided layers stacked sequentially. A resin matrix is ​​filled and cured into the fiber skeleton; The fiber braided layer is made of one or more fibers, namely rigid fibers and flexible fibers; the breaking elongation of the rigid fibers is less than that of the flexible fibers; the content of flexible fibers in the fiber braided layer located on the outermost side of the fiber skeleton is greater than the content of flexible fibers in the fiber braided layer located inside the fiber skeleton.

2. The battery bottom protection plate according to claim 1, characterized in that, The fiber braided layer located on the outermost side of the fiber skeleton is made of the flexible fibers.

3. The battery under-shield of claim 1, wherein, The fiber braided layer located inside the fiber skeleton is made of the rigid fibers.

4. The battery undertray of any one of claims 1 to 3, wherein, The content of flexible fibers in the fiber braided layer increases from the inside of the fiber skeleton to the outermost side.

5. The battery bottom protection plate according to claim 4, characterized in that, Each of the fiber braided layers is made of a mixture of the rigid fibers and the flexible fibers.

6. The battery undertray of claim 5, wherein, The fiber braided layer comprises at least two types of rigid fibers, wherein the difference in filament diameter between the two types of rigid fibers is not less than 3 micrometers.

7. The battery undertray of claim 1, wherein, The flexible fiber includes ultra-high molecular weight polyethylene fiber.

8. The battery undertray of claim 1, wherein, The rigid fiber includes at least one of glass fiber, carbon fiber, ceramic fiber, basalt fiber, and aramid fiber.

9. The battery undertray of claim 1, wherein, The resin matrix includes thermosetting polyurethane resin.

10. The battery undertray of claim 9, wherein, The fiber skeleton and the resin matrix are integrally composited through a resin transfer molding process.

11. The battery bottom protection plate according to claim 1, characterized in that, The fiber skeleton has a localized reinforcement region, where the fiber surface density is greater than that outside the localized reinforcement region.

12. The battery undertray of claim 11, wherein, The battery bottom cover plate has bolt connection holes, which are located in the local reinforcement area.

13. The battery undertray of claim 1, wherein, The elastic elongation at break of the flexible fiber is greater than or equal to 10%; the elastic elongation at break of the rigid fiber is less than 10%; and / or the tensile strength of the rigid fiber is greater than 1000 MPa.

14. A battery pack, characterized in that, Includes the battery bottom protection plate according to any one of claims 1 to 13.

15. A vehicle characterized by comprising: Includes the battery pack as described in claim 14.

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