A battery tray comprising fiber reinforced thermoplastic materials

Abstract

The present disclosure relates to a battery tray for housing battery module(s), the tray including a base part (1) having a length and a width, wherein the base part comprises at least a bottom wall (1') and side walls (2', 3', 4', 5') defining a receiving space for the battery module(s), wherein at least two opposing side walls of the side walls (2', 3', 4', 5') are each covered with side member(s) (2, 3, 4, 5), wherein the side member(s) (2, 3, 4, 5) comprises a continuous fiber reinforced thermoplastic material (CFRTP), and wherein the bottom wall (1') and the side walls (2', 3', 4', 5') comprise a fiber reinforced thermoplastic polymer composition, preferably a long glass fiber reinforced thermoplastic polymer composition, more preferably fire-retardant fiber reinforced thermoplastic polymer composition. The battery tray according to the invention achieves significantly reduced weight and can satisfy the safety requirements.

Description

[0001] A battery tray comprising fiber reinforced thermoplastic materials

[0002] Technical filed

[0003] The present invention relates to a vehicle battery tray for housing battery module(s), a process for preparing the battery tray, a vehicle battery pack comprising the battery tray and a vehicle, such as an electric vehicle, comprising the vehicle battery pack.

[0004] Background

[0005] A power battery is the core part of energy supply for electric vehicles (EV), where the EV battery pack enclosure plays a key role in the safety and protection of the internal units. The EV battery pack enclosure usually consists of a tray and a top cover where the tray plays a major role in providing sufficient mechanical strength to support the weight of the internal units and to cope with stress conditions such as crush, drop, collision, and bottom impact.

[0006] Metal materials, such as steel and aluminum alloy, are traditionally considered when designing the tray, and suitable forming processes are bending, stamping, welding, and die-casting. It is very difficult to achieve integrated design of a metal tray, and connecting components are necessary to combine several member parts, including bolt fastening, welding, bolt, buckle etc. This usually leads to heavy weight and complex assembly operations.

[0007] With the continuous popularization of electric vehicles, on the one hand higher manufacture efficiency of the battery pack is required; on the other hand, lightweight design of the battery pack enclosure will be conducive to obtaining better driving range performance. In any case, the premise is to satisfy the safety requirements (mechanical, fire, environment, etc.) of the battery pack.

[0008] There are attempts to design the tray with thermoset materials to reduce the weight. Most notable examples are the use of glass / carbon fiber reinforced thermosets, and to produce the tray in a compression or transfer molding process. The size and shape complexity are not usually limited but the process is labor-intensive and time consuming due to the curing characteristics of the material. Especially because the curing process is irreversible, high-volume production will bring huge society pressure / cost for material recovery.

[0009] In order to improve the economic viability of electric vehicles, as well as the driving range performance, the lightweight enclosure designed with fiber reinforced thermoplastic materials shall become a new field of technology development. SABIC is among the first to put forward the design concepts of using glass fiber reinforced thermoplastic materials for EV battery pack enclosure. Bounded by the available design space and material physical properties, the tray structure designed completely with thermoplastics will face large trade-offs in terms of the space occupied and mechanical strength.

[0010] US2012251863A1 discloses a reinforced polymer enclosure for a high voltage battery pack for an electric or hybrid vehicle, the enclosure comprising a support and a cover, each of the support and cover having a mating flange, the cover and support being secured together by mechanical fasteners along a joint line, one or both of the mating flanges incorporating an elastomeric seal, each of the support and cover being formed of a polymer consisting essentially of a formed thermoset or thermoplastic resin impregnating a woven fiber reinforcement and comprising a cavity shaped and proportioned to receive and retain the high voltage battery pack, the support and cover cooperating to retain and restrain the battery pack during vehicle operation.

[0011] US2014352886A1 disclosed a battery pack case assembly for an electric or hybrid vehicle. The battery pack case assembly includes a case body and a cover. The case body receives a battery pack, and the cover is coupled to the case body. The case body is formed of a plastic composite in which a long fiber or a blend of a long fiber and a continuous fiber is used as a reinforcing fiber in a plastic matrix. A separate reinforced member is bonded to both side bracket parts for coupling to a vehicle body, and is formed of a plastic composite in which a long fiber, a continuous, or a blend of a long fiber and a continuous fiber is used as the reinforcing fiber in the plastic matrix.

[0012] Therefore, it is desire to combine fiber reinforced thermoplastic materials with different materials to make full use of their respective characteristics and have appropriate processes for producing the vehicle lightweight battery tray that can satisfy the safety requirements.

[0013] Summary

[0014] It is an objective of the present invention to provide a vehicle battery tray for housing battery module(s) in which the above-mentioned and / or other needs are met.

[0015] Accordingly, the present invention provides a battery tray for housing battery module(s), the tray comprising a base part having a length and a width, wherein the base part comprises at least a bottom wall and side walls defining a receiving space for the battery module(s), wherein at least two opposing side walls of the side walls are each covered with side member(s), wherein the side member(s) comprises a continuous fiber reinforced thermoplastic material (CFRTP), and wherein the bottom wall and the side walls comprise a fiber reinforced thermoplastic polymer composition, such as a fire-retardant fiber reinforced thermoplastic polymer composition.

[0016] It was surprisingly found that, by combining a fiber reinforced thermoplastic polymer composition, a continuous fiber reinforced thermoplastic material, and / or metal materials in the design of EV battery tray, this invention can greatly reduce the weight of the tray and improves the integration of parts, without sacrificing the key mechanical safety performances (front crush, side crush, bottom impact) compared with the design of pure metal materials.

[0017] Brief description of the drawings

[0018] The following figures are exemplary embodiments, which are provided to illustrate the present invention, and wherein the like elements are numbered alike. The figures are not intended to limit the battery tray in accordance with the invention to the materials, structures, conditions, or process parameters set forth herein.

[0019] FIG. 1 shows an EV battery tray according to the present invention.

[0020] FIG. 2 shows a fiber reinforced thermoplastic base part of the EV battery tray of FIG.1 .

[0021] FIG. 3 shows side members of the EV battery tray of FIG.1 , which comprise a continuous glass fiber reinforced thermoplastic material.

[0022] FIG. 4 shows side reinforcements of the EV battery tray of FIG.1.

[0023] FIG. 5 shows connection of the side reinforcements to side flanges of the base part of FIG.2.

[0024] FIG. 6 shows cross-sections of surrounding beams of the EV battery tray of FIG.1.

[0025] FIG. 7 shows supporting ribs for side flanges of the base part of FIG.2.

[0026] FIG. 8 shows structural design at the base part of FIG.2 on the side opposite to the receiving space.

[0027] FIG. 9 shows a bottom sheet of the EV battery tray of FIG.1 , which covers the base part of FIG.2 on the side opposite to the receiving space. FIG. 10 shows fixations of the EV battery tray of FIG.1 to a body in white (BIW) and a battery cover.

[0028] FIG. 11 shows fixations of battery module(s) to the EV battery tray of FIG.1 .

[0029] FIG. 12 shows the maximum reaction force during front crush.

[0030] FIG. 13 shows front beam intrusion during front crush.

[0031] FIG. 14 shows the maximum reaction force during side crush.

[0032] FIG. 15 shows side beam intrusion during side crush.

[0033] FIG. 16 shows bottom impact description of the EV battery tray.

[0034] FIG. 17 shows bottom impact performance of the EV battery tray.

[0035] Detailed description

[0036] Reducing the weight of electric vehicles can extend their driving range, and therefore weight reduction is a key to the viability of the electric vehicles. One area of focus for weight reduction is the vehicle battery pack, e.g., including battery module(s) and a vehicle battery tray. In the present invention, much attention is drawn to the vehicle battery tray to provide a lightweight vehicle battery tray as an alternative to traditional one that is prepared completely from metal materials such as aluminum or high strength steel. In addition thereto, the battery tray according to the invention achieves the desired performances of front crush, side crush, bottom impact, which therefore complies with safety requirements for electric vehicles.

[0037] According to the invention, a lightweight vehicle battery tray for housing battery module(s) that is capable of protecting the battery module(s) when subject to stress conditions is provided herein, comprising a base part having a length and a width, wherein the base part comprises at least a bottom wall and side walls defining a receiving space for the battery module(s), wherein at least two opposing side walls of the side walls are each covered with side member(s), wherein the side member(s) comprises a continuous fiber reinforced thermoplastic composition (CFRTP), and wherein the bottom wall and the side walls comprise a fiber reinforced thermoplastic polymer composition, such as a fire-retardant fiber reinforced thermoplastic polymer composition. The vehicle battery tray according to the invention adapts the combination of multiple materials and specific structure of parts. The combination of multiple materials in the design of the battery tray requires making full use of the characteristics of different materials and designing the manufacturing process to connect them. Due to such design, the battery tray according to the invention has reduced weight while improving mechanical safety performances including front crush, side crush and bottom impact performances, as compared with the full metal battery tray. Besides, such design can provide improved structural integrity and part integration for the battery tray.

[0038] Battery tray

[0039] The vehicle battery tray according to the invention transverses at least a portion of the width of the vehicle, and also extends between the front suspension and the rear suspension. The size of the vehicle battery tray is not particularly limited and is dependent upon the size of the vehicle and dependent on the desired battery capacity and the size of battery modules. For example, the vehicle battery tray can be up to 3 meters (m) long (e.g., approximately 2.7 m long) and up to 1 .5 meters wide. The height of the vehicle battery tray can vary from 0.1 meters to 0.18 meters.

[0040] The vehicle battery tray according to the invention comprises a base part having a length and a width, for example, the base part (1) as shown in FIG. 1 . When the vehicle battery pack is installed in the vehicle, the length of the base part is in the length direction (“X”) of the vehicle, and the width of the base part is in the width direction (“Y”) of the vehicle. The base part comprises at least a bottom wall and side walls, which together define a receiving space for housing the battery module(s). For example, the base part (1) contains a bottom wall (1 ’) and four side walls (2’, 3’, 4’, 5’), as shown in FIG. 2.

[0041] The base part may have the same length and width respectively with the length and width of the bottom wall. The bottom wall may for example have a length of about 1 .7 m to 2.0 m, such as 1 .8 m, a width of about 1 .0 m to 1 .5 m, such as 1 .4 m, and a height of about 15 mm to 30 mm, such as 20 mm. The side walls may have a width of about 20 mm to 30 mm, such as 25 mm and a height of about 50 to 70 mm, such as 60 mm. The front or rear side wall may have a length that is identical or similar to the width of the bottom wall in the width direction of the base part, and the left or right side wall may have a length that is identical to similar to the length of the bottom wall in the length direction of the base part.

[0042] The bottom wall and the side walls of the base part comprise or consist of a fiber reinforced thermoplastic polymer composition, preferably a long glass fiber reinforced thermoplastic polymer composition, more preferably a fire-retardant fiber reinforced thermoplastic polymer composition. According to the invention, each of the bottom wall and the side walls may comprise at least 95 wt%, preferably at least 98 wt%, more preferably 100 wt% of the fiber reinforced thermoplastic polymer composition based on total weight of each of the bottom wall and the side walls. According to this invention, the base part may be produced from the fiber reinforced thermoplastic polymer composition by an injection molding process.

[0043] Preferably, the fiber reinforced thermoplastic polymer composition used in the vehicle battery tray according to the invention is a fire-retardant long glass fiber reinforced thermoplastic polymer composition, preferably a fire-retardant long glass fiber reinforced thermoplastic polypropylene composition, which renders the battery tray fire-retardant. The plastic battery tray using a PP-LGF fire retardant (FR) material is observed to satisfy all considered load cases.

[0044] In the battery tray of this invention, at least two opposing side walls of the side walls may be each covered with side members in order to retain structural integrity of the battery tray during a rigid pole impact according GB 38031-2020. Retention of structural integrity means that after impact, the rigid pole does not intrude into an inner space of the vehicle battery pack and battery modules within the vehicle battery pack are not compressed. In some embodiments, the side members may cover the two opposing side walls in the length direction of the base part. In some embodiments, the side members may cover the two opposing side walls in the width direction of the base part. In some embodiments, the side members may cover four side walls of the base part. The side walls may be partially or completely covered with the side members. Preferably, all four side walls may be covered with the side members, and more preferably the two opposing side walls in the length direction of the base part may be completely covered with the side members.

[0045] According to the invention, the side walls of the battery tray have an inner surface facing the receiving space, an opposite outer surface and a top surface. In some embodiments, the inner surface and optionally the top surface of the side walls are completely covered with the side members, that is, the side walls are partially covered with the side members. In some embodiments, the opposite outer surface and optionally the top surface of the side walls are completely covered with the side members, that is, the side walls are partially covered with the side members. In some embodiments, the inner surface, the opposite outer surface and the top surface of the side walls are completely covered with the side members, that is, the side walls are completely covered with the side members. Preferably, the inner surface and the top surface of the side walls are completely covered with the side members, and more preferably the outer surface of the side walls is further covered with the side members in the direction of the length of the base part. Preferably, the side members are symmetrical in the direction of the length of the base. Preferably, the side members are symmetrical in the direction of the width of the base.

[0046] When four side walls are covered with the side members, adjacent side members may overlap with each other at both ends, forming overlapping edges between the adjacent side members and therefore being integrated into a composite member having overlapping edges. As shown in FIG.s 1-3, the inner surface, the opposite outer surface and the top surface of two opposing side walls (3’, 5’) in the direction of the length of the base part are respectively covered with the side members (3, 5), and the inner surface and the top surface of two opposing side walls (2’, 4’) in the direction of the width of the base part are respectively covered with the side members (2, 4). The side members (2, 3, 4, 5) are formed as a quadrangle having overlapping edges.

[0047] According to the invention, in order for structural reinforcement of the battery tray, the side members may further be arranged on the bottom wall of the base part on the side facing the receiving space of the battery tray. In some embodiments, the side members may be covered around the bottom wall of the base part, for example on the edges of the bottom wall along the inner surface of the side walls. In particular, the side members on the edges of the bottom wall may be integrated together with the side members on the side walls of the base part. In some embodiments, the side members may be covered at the center axis of the bottom wall of the base part in the width direction. The size of covering the bottom wall is not particularly limited and depends on the desired mechanical strength of the battery tray. Preferably, the side members may be used to cover battery modules fixations (for fixing battery modules) located on the bottom wall, preferably on any of edges of the bottom wall, such as the side members (10) shown in FIG. 6.b.

[0048] The side members according to the invention comprise or consist of a continuous fiber reinforced thermoplastic material (CFRTP). According to the invention, the amount of the continuous fiber reinforced thermoplastic composite may be at least 95 wt%, preferably at least 98 wt%, more preferably 100 wt%, based on the total weight of the side members. CFRTP may offer good material performance in terms of strength and stiffness. Furthermore, CFRTP may offer excellent adhesion to the over-molded base material, if the base material is compatible.

[0049] According to the invention, the side members may be produced by a thermoforming process. In some embodiments, each of side members may be separately thermoformed, i.e., not joined, priorto over-molding of the base part of the battery tray. Longitudinal and latitudinal side members are adjacent or slightly overlapped at the corners. When the side members use the same matrix as the base part, the over-molding process allows excellent adhesion of the side members to the base part.

[0050] According to this invention, the bottom wall of the battery tray may further comprise side flange(s) extending away from any of the side walls. In some embodiments, the side flanges may extend away from two opposing side walls. For example, the side flanges may extend away from two opposing side walls in the direction of the length of the base part. For example, the side flanges may extend away from two opposing side walls in the direction of the width of the base part. In some embodiments, the side flanges may extend away from four side walls. As shown in FIG. 2, the base part (1) has two opposing side flanges (6’, 7’) in the direction of the width of the base part (1) and two opposing side flanges (8’, 9’) in the direction of the length of the base part (1).

[0051] The side flanges comprise a fiber reinforced thermoplastic polymer composition, which is preferably the same with that contained in the bottom wall, in the amount of at least 95 wt%, preferably at least 98 wt%, more preferably 100 wt%, based on the total weight of the side flanges. The side flanges are injection molded, including insert over-molded parts. Preferably, the side flanges and the bottom wall share the same composition and are integrated into one part. The side flange(s) have identical or similar length to that of the side walls attached thereto, and have identical or similar height to that of the bottom wall. The side flange(s) may have a width of about 70 mm to 100 mm, such as 82 mm.

[0052] According to this invention, the side flange(s) have a top surface, a bottom surface, and a side surface away from the receiving space. The side surface and the top surface of the side flanges may be covered with side reinforcements to form L-shaped reinforcements, wherein the side reinforcements are made of aluminum or a continuous fiber reinforced thermoplastic material (CFRTP).

[0053] In some embodiments, the side surface and the top surface of the side flanges may be covered with the side reinforcements in the direction of the width of the base part. Preferably, the side reinforcements are symmetrical in the direction of the width of the base. In some embodiments, the side surface and the top surface of the side flanges may be covered with the side reinforcements in the direction of the length of the base part. Preferably, the side reinforcements are symmetrical in the direction of the length of the base.

[0054] As shown in FIG. 4, the side reinforcements (6, 7) are L-shaped, which can be used as structural reinforcements for covering the side flanges (6’, 7’). According to this invention, the side flanges may be produced by an injection molding process, and the side reinforcements may be used as inserts for injection molding of the side flanges.

[0055] Alternatively, the side surface and the top surface of the side flanges may be covered with the side members to form L-shaped reinforcements. In some embodiments, the side surface and the top surface of the side flanges may be covered with the side members in the direction of the width of the base part. In some embodiments, the side surface and the top surface of the side flanges may be covered with the side members in the direction of the length of the base part, in which case preferably the side members covering both of the side walls and the side flanges may be integrated into a whole member in the direction of the length of the base part.

[0056] In some embodiments, the side surface and the top surface of the side flanges may be covered with the side reinforcements in the direction of the width of the base part, and the side surface and the top surface of the side flanges may be covered with the side members in the direction of the length of the base part, wherein the side members covering both of the side walls and the side flanges may be integrated into a whole member, such as the side members (3, 5) shown in FIG. 3.

[0057] In some embodiments, the side surface and the top surface of the side flanges may be covered with the side reinforcements in the direction of the width of the base part, and there may be no side flanges extending away from two opposing side walls in the direction of the length of the base part. For example, the base part (1) has two opposing side flanges (6’ 7’) in the direction of the width only, which are covered with respective L-shaped side reinforcements (6, 7), but has no side flanges (8’ 9’) in the direction of the length.

[0058] When L-shaped side reinforcements made of aluminum are arranged on the side flanges of the battery tray, in order to have good connection between the side reinforcements and the plastic battery tray, small holes (shown as holes 8 in FIG. 5) may be punched on the side reinforcements for plastics running therethrough during injection molding and being solidified as a connection between the side reinforcements and the plastic battery tray. In addition, the side reinforcements’ edges (shown as edges 9 in FIG. 5) may be covered with plastics.

[0059] When L-shape side reinforcements made of a continuous fiber reinforced thermoplastic material (CFRTP) are arranged on the side flanges of the battery tray, as CFRTP can offer excellent adhesion to the over-molded base material, no small holes are punched for plastics running therethrough during injection molding for connections between the side reinforcements and the plastic battery tray. The thickness of CFRTP can be optimized based on the need of mechanical performance.

[0060] In the context of the present application, the side walls and the side flanges (if any) after being covered are collectively referred to as side (left / right) beams in the direction of the width of the base part, and the side walls and the side flanges (if any) after being covered are collectively referred to as front / rear beams in the direction of the length of the base part. FIG. 6 shows crosssections of front / rear beams (a) and left / right beams (b) of the battery tray according to the invention.

[0061] According to the invention, the base part of the battery tray may further comprise one or more supporting ribs for reinforcing the side beams. The support ribs may be arranged for attaching the top surface of the side walls to the side flanges. Preferably, the supporting ribs may be arranged in the direction of the width of the base part. The supporting ribs may have a plastic wall thickness of about 2.0 mm to 4.0 mm, such as 3.5 mm. Various rib designs are possible, including triangular, rectangular, diagonal, crossed, and the like. As shown in FIG. 7, cross-shaped supporting ribs (11) are arranged between the top surface of the side walls and the side flanges, and are sideopen.

[0062] The supporting ribs comprise a fiber reinforced thermoplastic polymer composition, which is preferably the same with that contained in the base part, in the amount of at least 95 wt%, preferably at least 98 wt%, more preferably 100 wt%, based on the total weight of the supporting ribs. The supported ribs are injection molded, for example are integrally formed with the base part through injection molding of the base part.

[0063] According to the invention, the base part of the battery tray may further have a honeycomb structure that is attached to the bottom wall of the base part on the side opposite to the receiving space. The honeycomb structure is designed for crashworthiness regarding intrusion and impact and can provide protection against crushing forces experienced on the side of the battery tray, resulting in a reinforcing structure against deformation due to impact. The honeycomb structure may have a plastic wall thickness of about 2.0 mm to 4.0 mm, such as 3.5 mm.

[0064] The honeycomb structure has an array of columns with shapes having greater than or equal to 3 sides, such as triangular, pentagonal, hexagonal, heptagonal, and octagonal, and so forth, preferably a hexagonal geometry, for example the honeycomb zone with a hexagonal geometry in FIG. 8. Other geometries, for instance a geometry including channels, are possible as well. The columns and / or channels of a geometry may have one or more open end. As shown in FIG. 2, the base part has downward opening honeycomb structures. The dimension of the honeycomb structure and the thickness of the bottom wall can be optimized based on mechanical performance.

[0065] In addition to the honeycomb structure at the bottom side, reinforcing ribs may further be arranged at surrounding beams on the side opposite to the receiving space to reinforce the base part of the battery tray, as result of which, the reinforcing ribs may be arranged around the honeycomb structure such as to form together a reinforcing structure against bottom impact. The reinforcing ribs may have a plastic wall thickness of about 2.0 mm to 4.0 mm, such as 3.5 mm. As with the supporting ribs for side flanges, various rib designs are possible, including triangular, rectangular, diagonal, crossed, and the like. In FIG. 8, the base part of the battery tray is reinforced by crossshape ribs (12, 13, 14) at surrounding beams together with a honeycomb structure (honeycomb zone) at the bottom side.

[0066] According to this invention, the tray may further comprise a bottom sheet covering at least a part of the bottom wall of the base part on the side opposite to the receiving space. The bottom sheet may have the same dimension with the bottom wall of the tray. The bottom sheet may contribute to protecting the tray and prevent intrusion into and impact to the battery modules. Preferably, the bottom sheet may be covered on the side of the bottom wall having the reinforcing structure that contains the boney comb structure and the reinforcing ribs, wherein the bottom sheet may be attached to the reinforcing structure of the bottom wall. The bottom sheet is exemplified in FIG. 9, wherein several holes are arranged on the edge of the bottom sheet and used for fixation to the base part.

[0067] The bottom sheet according to the invention may be made of aluminum or a continuous fiber reinforced thermoplastic material (CFRTP). The definition as made above for the CFRTP used for the side members also applies to CFRTP used for the bottom sheet. When using the bottom sheet, it may be assembled to the base part of the battery tray through an adhesive and / or mounting via screws and the like. The skilled person in the art can select any adhesive that is suitable for use in a good adhesion between the plastic matrix of the base part and the bottom sheet.

[0068] As an example, the battery tray according to the present invention is exemplified in FIG. 1. The battery tray has a base part (1), four side members (2, 3, 4, 5), and two side reinforcements (6, 7) in the direction of the width of the base part (1). Two side members (2, 4) are respectively covered on two opposing side walls (2’, 4’) of the base part (1), and another two side members (3, 5), which are integrated as a whole, are respectively covered on two opposing side walls (3’, 5’) and side flanges (8’, 9’). The two side reinforcement (6, 7) are covered respectively on another two side flanges (6’, 7’) of the base part (1) in the direction of the width thereof. In addition, the battery tray further has a bottom sheet (15), which is not shown in FIG.1 but shown in FIG. 9.

[0069] Generally, the battery tray according to the present invention may be assembled to a body in white (BIW) through fixations at both side beams, i.e., left / right beams (in Y direction), and / or at front / rear beams (in X direction). In particular, the fixations may be located on the side flanges of the beams. In some embodiments, the battery tray may be assembled to the body in white only through the fixations at the left / right beams, provided that it is sufficiently strong and safe to install the battery tray. In addition, fixation points may be arranged for assembly of a battery cover into the battery tray. In some embodiments, the fixation points may be located on the top of the beams of the battery tray. As shown in FIG. 10, the battery tray is assembled to the body in white through several fixations on the side flanges of the left / right side beams and front / rear beams, and several fixation points are arranged on the top surface of the four side walls of the battery tray to fix the battery cover.

[0070] According to the invention, the battery modules fixations may be arranged in the receiving space of the battery tray in order to fix the battery modules. For example, the battery modules fixations may be arranged parallelly at the center axis (the position of Y=0) and two opposing edges of the bottom wall of the battery tray in the width direction, as shown in FIG. 11. The battery modules may be fixed by symmetrically using two fixations at the center axis and two fixations at either edge of the bottom wall. Larger battery modules may be fixed by symmetrically using four fixations at two opposing edges of the bottom wall. Besides, the side members may be used to cover the battery module fixations, which will improve stiffness and strength of the battery module fixations. The battery module fixations at the center axis (the position of Y=0) of the battery tray may be reinforced through a structural beam from the center of the front beam to the center of the rear beam.

[0071] Fiber reinforced thermoplastic polymer composition

[0072] According to the invention, the fiber reinforced thermoplastic polymer composition may comprise about 40 to 90 wt%, preferably about 50 to 85 wt%, more preferably about 60 to 80 wt% of a plastic matrix; about 10 to 60 wt%, preferably about 15 to 55 wt%, more preferably about 20 to 50 wt% of fibers, such as glass fibers; and about 0.0001 wt% to 30wt%, preferably about 0.001 to 20 wt%, more preferably about 0.01 to 10 wt% of additives; based on total weight of the fiber reinforced thermoplastic polymer composition. The total amount of the plastic matrix and the fibers may be preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt% based on the total amount of the fiber reinforced thermoplastic polymer composition. According to the invention, the plastic matrix may be selected from the group comprising polypropylene (PP), polybutylene tephthalate (PBT), polycarbonate (PC), polyamide (PA) or any combination thereof. The polypropylene may be a propylene homopolymer, a random propylene copolymer, a heterophasic propylene copolymer, or a propylene block-compolymer. The random propylene copolymer may comprise as the comonomer ethylene or an a-olefin chosen from the group of a-olefins having 4 to 10 C-atoms, preferably ethylene, 1 -butene, 1 -hexene or any mixtures thereof. The heterophasic propylene copolymer, also referred to as a propylene impact copolymer, consists of a propylene-based matrix and a dispersed ethylene-a-olefin copolymer, wherein the propylene-based matrix typically forms the continuous phase in the heterophasic propylene copolymer.

[0073] In general, a fiber is a cylindrical substance where its length is significantly longer than the diameter of its cross section. It is known that adding glass fibers are able to improve the mechanical performance (e.g. strength and stiffness) of polymeric matrix. The level of performance improvement depends heavily on the properties of the glass fibers, e.g. diameter, length and surface property of the glass fibers.

[0074] It is also known that long glass fibers (length from 0.5 to 50 mm) are able to provide superior performance improvement than short glass fibers (length shorter than 0.5 mm) to the composition. The length of glass fibers in the present invention depends heavily on the process used to prepare the said composition. Preferably the glass fibers in the polymer composition according to the invention are long glass fibers.

[0075] Glass fibers are known to those skilled in the art and are commercially available. The fibers can be of any size and shape suitable for use in the plastic battery tray of this invention. For example, the glass fibers may have a length of about 1 to about 50 mm, preferably about 1 to about 40 mm. In some embodiments, the fibers preferably have a length of from about 1 to about 30 mm, such as from about 5 to about 20 mm, from about 10 to about 18 mm and from about 2 to about 4 mm. The diameter of the glass fibers is not very critical. Generally, the fibers may have a diameter of about 5 to 50 pm, preferably about 10 to about 30 pm, such as 15 to 25 pm.

[0076] Other fiber types are contemplated as well in the invention, including carbon fibers, graphite fibers, synthetic organic fibers, particularly high modulus organic fibers such as para- and meta-aramid fibers, nylon fibers, polyester fibers, or any of the thermoplastic resins mentioned above that are suitable for use as fibers, natural fibers such as hemp, sisal, jute, flax, coir, kenaf and cellulosic fibers, mineral fibers such as basalt, mineral wool (e.g., rock or slag wool), Wollastonite, alumina, silica, and the like, or mixtures thereof, metal fibers, metalized natural and / or synthetic fibers, ceramic fibers, or mixtures thereof.

[0077] The additives contained in the fiber reinforced thermoplastic polymer composition may include but not be limited to stabilizers like antioxidants and UV stabilizers; fire retardants; colorants like pigments and dyes; adhesion promoters like modified polypropylene, in particular maleated polypropylene; antistatic agents; mold release agents; nucleating agents; impact modifiers, fillers and the like. In addition, the fiber reinforced thermoplastic polymer composition can contain further reinforcing additives like inorganic reinforcing agents such as talc, short glass fibers and glass, or organic reinforcing agents such as aramid fibers, polyester fibers, and carbon fibers. Preferably, the additives contain fire retardants.

[0078] The skilled person can readily select any suitable combination of additives and additive amounts without undue experimentation. For example, the fiber reinforced thermoplastic polymer composition may contain one or more of impact modifiers, fillers, fire retardants, antioxidants and reinforcing agents. The amount of the additives depends on their type and function and typically may be from about 0.0001 wt% to about 30 wt%, e.g. be from about 0.1 to about 20 wt%, from about 1 to about 10 wt% or from 2 to about 5 wt% based on the total fiber reinforced thermoplastic polymer composition.

[0079] The fiber reinforced thermoplastic polymer composition may be made by a process comprising subsequent steps of unwinding from a package of a continuous glass multifilament strand and applying a sheath of polymer around said multifilament strand to form a sheathed continuous multifilament strand. The fiber reinforced thermoplastic polymer compositions in the form of, for example, pellets or granules can be prepared from continuous lengths of fibers by a sheathing or wire-coating process, by crosshead extrusion or several pultrusion techniques. Using these technologies, fiber strands impregnated or coated with a polymer are formed; these may then be cut into lengths, and the pellets or granules thus obtained can be further processed, e.g. by injection molding or extrusion processes, into (semi)-finished articles.

[0080] One commercial source of long glass fiber reinforced polypropylene is SABIC’s STAMAX™ plastic. STAMAX is sold commercially with 20 to 60 wt% glass fiber content. Commercial products include those with 20, 30, 40 and 60 wt% glass fiber contents.

[0081] Continuous fiber reinforced thermoplastic material (CFRTP)

[0082] According to the invention, the continuous fiber reinforced thermoplastic material may comprise about 10 to 60 wt%, preferably about 20 to 50 wt%, more preferably about 30 to 45 wt% of a plastic matrix; about 30 to 80 wt%, preferably about 35 to 75 wt%, more preferably about 40 to 70 wt% of continuous fibers; and about 0.0001 wt% to 20wt%, preferably about 0.001 to about 15 wt%, more preferably about 0.01 to about 10 wt% of additives; based on total weight of the CFRTP. The total amount of the plastic matrix and the continuous fibers may be preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt% based on the total amount of the CFRTP.

[0083] According to the invention, the plastic matrix contained in the CFRTP may be selected from the group comprising polypropylene (PP), polybutylene tephthalate (PBT), polycarbonate (PC), polyamide (PA) or any combination thereof. The plastic matrix contained in the CFRTP and the plastic matrix contained in the fiber reinforced thermoplastic polymer composition may be the same or different. Preferably, the CFRTP uses the same plastic matrix, preferably polypropylene as the fiber reinforced thermoplastic polymer composition, which results in a good adhesion of the side members to the base part of the battery tray.

[0084] The continuous fibers used in the present invention may distinctly differ from the long fibers with respect to a certain length in that the continuous fibers have fiber structures without a break in one or mutually crossing directions.

[0085] Preferably, the continuous fibers contained in the CFRTP are continuous glass fibers. Other fiber types are contemplated as well in the invention, including carbon fibers, graphite fibers, synthetic organic fibers, particularly high modulus organic fibers such as para- and meta-aramid fibers, nylon fibers, polyester fibers, or any of the thermoplastic resins mentioned above that are suitable for use as fibers, natural fibers such as hemp, sisal, jute, flax, coir, kenaf and cellulosic fibers, mineral fibers such as basalt, mineral wool (e.g., rock or slag wool), Wollastonite, alumina, silica, and the like, or mixtures thereof, metal fibers, metalized natural and / or synthetic fibers, ceramic fibers, or mixtures thereof.

[0086] The definition as made above for the additives used in the fiber reinforced thermoplastic polymer composition also applies to the additives used in the CFRTP. The skilled person can readily select any suitable combination of additives and additive amounts without undue experimentation. For example, the CFRTP may contain one or more of impact modifiers, fillers, fire retardants, antioxidants and reinforcing agents. Preferably, the additives contain fire retardants. The amount of the additives typically may be from about 0.0001 wt% to about 20 wt%, e.g. be from about 0.1 to about 10 wt%, or from about 1 to about 5 wt% based on the total weight of the CFRTP. CFRTP may be produced in the form of an unidirectional tape (UD-tape). The unidirectional tape may have an arrangement in which many strands of continuous fiber longitudinally extend in the same direction (strand arrangement). CFRTP may be produced in the form of multi-ply laminates (UD- laminates) with a thickness in range of about 2.0 to 3.0 mm. The laminate lay-up is optimized based on material performance. Typically, it will be symmetrical lay-up. Specifically, CFRTP may be produced in unidirectional tapes and formed into UD-laminates to offer off-axis performance, post molded into complex shapes and over-molded with fiber reinforced thermoplastic polymer compositions to provide localized reinforcement in specific locations.

[0087] CFRTP may be produced in the form of a woven fabric. The fabric may have a woven structure in which the continuous fibers cross each other in the longitudinal and latitudinal directions. Some examples of the woven fabric may include plain weave, twill weave, and satin weave. CFRTP may also be produced in the form of a thermoplastic organosheet, which basically consist of several layers of thermoplastic prepreg or semipreg material which are stacked and then pressed into a sheet.

[0088] Process of preparing a battery tray

[0089] The invention further relates to a process for preparing the battery tray according to the invention, comprising the steps of: i) thermoforming the side member(s) with the continuous fiber reinforced thermoplastic material (CFRTP) according to the invention, ii) placing the thermoformed side member(s) in a mold, and iii) over-molding the battery tray with the fiber reinforced thermoplastic polymer composition according to the invention.

[0090] In the process according to the invention, the side members are manufactured by a thermoforming process, and subsequently over-molded to the battery tray through an injection molding process. For examples, the side members are thermoformed through a thermoforming mold. Considering that symmetrical side members are respectively arranged in the length direction and in the width direction of the base part of the battery tray, they are thermoformed through two thermoforming molds. Then they will be used as inserts for the next step of injecting molding.

[0091] The thermoforming may be performed by known thermoforming methods, such as vacuum forming, pressure forming, solid pressure forming, solid press forming, twin sheet forming and stamping forming. Such methods generally are carried out by heating CFRTP above its softening temperature in the plastic deformation range, for instance with rolls, heating plates or indirect heating means, like radiant electric heaters, and forcing CFRTP to fit the shape of the mold, for instance by sucking them against the mold.

[0092] The thermoforming may be performed under pressure or under vacuum. The pressure shall be sufficiently enough for CFRTP to conform to the final shape. The suitable temperature may be selected for the thermoforming process according to the continuous fiber reinforced thermoplastic material to be subjected to thermoforming.

[0093] The injection molding process, including insert injection molding, may be performed by any conventional technique known to the skilled person. Suitable pressure and temperature may be selected based on the desired mechanical performance and shape of the battery tray.

[0094] The invention further relates to a vehicle battery pack comprising the battery tray according to the invention. The invention further relates to a vehicle, such as an electric vehicle, comprising the vehicle battery pack according to the invention.

[0095] In the context of weight percentage, the term “about” represents a deviation between ±2% and ±5%.

[0096] It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

[0097] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process. When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0098] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0099] Examples

[0100] In the examples of the present invention, the following materials were used:

[0101] Continuous fiber reinforced thermoplastic material (CFRTP): GPP55Z-415, flame-retardant polypropylene composition comprising 55wt% of continuous glass fiber, available from QiYi Technology.

[0102] Fiber reinforced thermoplastic polymer composition: STAMAX™ 30YH570, high flow, halogen free flame retardant, propylene copolymer with 30wt% long glass fiber, available from SABIC.

[0103] A plastic EV battery tray with four side members and two symmetrical L-shape aluminum side reinforcements at the side beams was prepared, as shown in FIG. 1. The CFRTP material was used to manufacture the side members by a thermoforming process with one thermoforming mold for CFRTP side members 2 and 4 and another thermoforming mold for CFRTP side members 3 and 5. The aluminum side reinforcements 6 and 7 was prepared and punched with some holes for plastics running therethrough during injection molding. Then the thermoformed side members and the punched side reinforcements were used as inserts and placed in a injection molding mold, followed by over-molding the base part 1 having four side flanges in the mold by means of STAMAX™ 30YH570 to obtain the over-molded battery tray. The obtained battery tray can meet GB 38031-2020 standard in terms of c in X and Y directions.

[0104] The obtained battery tray was tested for its front crush performance, side crush performance and bottom impact performance.

[0105] The front crush performance of the plastic EV battery tray is evaluated through Finite Element Analysis (CAE method). As shown in FIG. 12, the plastic battery tray with the side members and side reinforcements can reach maximum reaction force 201 KN, which is higher than a testing standard 100 KN, without front beam contacting battery modules during crush, as shown in Figure 13. The side crush performance of the plastic EV battery tray is evaluated through Finite Element Analysis (CAE method). As shown in FIG. 14, the plastic EV battery tray with the side members and side reinforcements can reach maximum reaction force 250 KN, which is higher than a testing standard 100 KN, without side beam contacting battery module during crush (FIG. 15).

[0106] The bottom impact performance of the plastic EV battery tray is evaluated through Finite Element Analysis (CAE method). The plastic EV battery tray is impacted at two positions, i.e., position 1 and positon 2, as shown in FIG. 16. The plastic EV battery tray has comparable intrusion (with the maximum intrusion lower than 30 mm) as baseline model - a full metal battery tray. It is shown in FIG. 17 that:

[0107] • The maximum reaction force reached is 13.1 KN at position- 1. The maximum intrusion of the impactor is 16.8 mm. There is no damage of the plastic battery tray on the side of battery module.

[0108] • The maximum reaction force reached is 12.5 KN at position-2. The maximum intrusion of the impactor is 23.8 mm. There is no damage of the plastic battery tray on the side of battery module.

[0109] From the above, it can be observed that the plastic EV battery tray according to the invention has improved front crush and side crush performances and comparable bottom impact performance, while achieving significantly reduced weight of the battery tray, as compared with the full metal battery tray.

Claims

C L A I M S1 . A battery tray for housing battery module(s), the tray comprising a base part (1) having a length and a width, wherein the base part comprises at least a bottom wall (1 ’) and side walls (2’, 3’, 4’, 5’) defining a receiving space for the battery module(s), wherein at least two opposing side walls of the side walls (2’, 3’, 4’, 5’) are each covered with side member(s) (2, 3, 4, 5), wherein the side member(s) (2, 3, 4, 5) comprises a continuous fiber reinforced thermoplastic material (CFRTP), wherein the bottom wall (1 ’) and the side walls (2’, 3’, 4’, 5’) comprise a fiber reinforced thermoplastic polymer composition, preferably a long glass fiber reinforced thermoplastic polymer composition, more preferably fire-retardant fiber reinforced thermoplastic polymer composition, and wherein the side surface and the top surface of the side flange(s) (8’, 9’) are covered with the side member(s) (3, 5).

2. The battery tray according to claim 1 , wherein the side walls (2’, 3’, 4’, 5’) have an inner surface facing the receiving space, an opposite outer surface and a top surface, wherein the inner surface and the top surface of the side walls (2’, 3’, 4’, 5’) are covered with the side member(s) (2, 3, 4, 5), preferably wherein the outer surface of the side walls (3’, 5’) are further covered with the side member(s) (3, 5) in the direction of the length of the base part (1).

3. The battery tray according to any one of claims 1-2, wherein the bottom wall (1 ’) comprises side flange(s) (6’, 7’, 8’ 9’) extending away from any of the side walls and having a side surface away from the receiving space and a top surface, preferably the side flange(s) extending away from the two opposing side walls.

4. The battery tray according to claims 3, wherein the side surface and the top surface of the side flange(s) (6’, 7’) are covered with side reinforcements (6, 7) in the direction of the width of the base part (1) to form L-shaped reinforcements, wherein the side reinforcements (6, 7) are made of aluminum or a continuous fiber reinforced thermoplastic material (CFRTP).

5. The battery tray according to any one of claims 3-4, wherein the side surface and the top surface of the side flange(s) (8’, 9’) are covered with the side member(s) (3, 5) in the direction of the length of the base part (1).

6. The battery tray according to any one of claims 1-5, wherein the base part (1) further comprises one or more supporting ribs (11), preferably in the direction of the width of the base part, for attaching the top surface of the side walls to the side flanges, wherein the ribs (11) comprise a fiber reinforced thermoplastic polymer composition.

7. The battery tray according to any one of claims 1-6, wherein the base part (1) further has a honeycomb structure that is attached to the bottom wall (1’) of the base part (1) on the side opposite to the receiving space.

8. The battery tray according to any one of claims 1-7, wherein the tray further comprises a bottom sheet (15) covering at least a part of the bottom wall (1 ’) of the base part (1) on the side opposite to the receiving space, preferably wherein the bottom sheet (15) is made of aluminum or a continuous fiber reinforced thermoplastic material (CFRTP).

9. The battery tray according to any one of claims 1-8, wherein the continuous fiber reinforced thermoplastic material comprises about 10 to 60 wt%, preferably about 20 to 50 wt% of a plastic matrix; about 30 to 80 wt%, preferably about 35 to 75 wt% of continuous fibers; and about 0.0001 wt% to 20wt%, preferably about 0.001 to about 15 wt% of additives, such as fire retardants; based on total weight of the continuous fiber reinforced thermoplastic material, wherein the plastic matrix is selected from the group comprising polypropylene, polybutylene tephthalate (PBT), polycarbonate (PC), polyamide (PA) or any combination thereof.

10. The battery tray according to any one of claims 1-9, wherein the fiber reinforced thermoplastic polymer composition comprises about 40 to 90 wt%, preferably about 50 to 85 wt% of a plastic matrix; about 10 to 60 wt%, preferably about 15 to 55 wt% of fibers, such as glass fibers; and about 0.0001 wt% to 30wt%, preferably about 0.001 to about 20 wt% of additives, such as fire retardants; based on total weight of the fiber reinforced thermoplastic polymer composition, wherein the plastic matrix is selected from the group comprising polypropylene, polybutylene tephthalate (PBT), polycarbonate (PC), polyamide (PA) or any combination thereof.

11. The battery tray according to any one of claims 9-10, wherein the polypropylene is selected from the group comprising a propylene homopolymer, a random propylene-alpha olefin copolymer, such as a propylene-ethylene copolymer, and a heterophasic propylene copolymer, and preferably the polypropylene in the continuous fiber reinforced thermoplastic material is the same with that in the fiber reinforced thermoplastic polymer composition.

12. The battery tray according to any one of claims 1-11 , wherein the side member(s) (2, 3, 4, 5) are produced by a thermoforming process, and the base part (1) is produced by an injection molding process.

13. A process for preparing the battery tray according to any one of claims 1-12, comprising the steps of: i) thermoforming the side member(s) with the continuous fiber reinforced thermoplastic material, ii) placing the thermoformed side member(s) in a mold, and iii) over-molding the battery tray with the fiber reinforced thermoplastic polymer composition.

14. A vehicle battery pack comprising the battery tray according to any one of claims 1-12.

15. A vehicle, such as an electric vehicle, comprising the vehicle battery pack according to claim 14.

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