Battery housing part, battery housing, traction battery, and method for producing battery housing part

Abstract

The present application relates a battery housing part, a battery housing, a traction battery, and a method for producing a battery housing part, in particular discloses a battery housing part comprising a composite, characterized in that said composite is comprising: a polymer composition comprising polyamide 6 and amorphous polyamide; and fiber material.

Description

[0001] Battery housing part, battery housing, traction battery, and method for producing battery housing part

[0002] The present invention relates to a battery housing part and to a battery housing containing a battery housing part for a traction battery of a motor vehicle . Furthermore, the present invention relates to a method for producing a battery housing part . Finally, the present invention relates to a traction battery .

[0003] Warpage is one of the common issues for fiber reinforced thermal plastic composites , especially for resin with crystalline behavior like polyamide 6 (polyamide6 ) . Many approaches have been directed at improving both the used material and used process to reduce warpage .

[0004] The use of flat fiber, i . e . fiber with a non-circular cross-section, was one promising method to reduce warpage and improve the flatness of a part , and applied in many cases especially when applying an inj ection molding forming process . The improvement of flatness with flat fiber is achieved due to the oval shape of flat fiber in cross section . This non-circular cross section contributes to reducing the difference between the shrinkage of the material in the flowing direction and the transverse direction . In this way, less internal stress is generated and the flatness of the molded part is improved .

[0005] Forming process parameters were further critical influencing factors on warpage , such as forming temperature, mold temperature, cooling pressure, cooling time, application of post-cooling etc . Normally, a series of different process parameters were tried to maximize the flatness even when this meant compromising on other properties .

[0006] Equipping a molded structure with ribs , a reinforcing geometry, or with a continuous fiber reinforced composite sheet sandwich structure was also a useful method for flatness improvement .

[0007] Albeit, these approaches may result in additional space occupation by ribs or the reinforcing geometry . Moreover, the forming of continuous fiber reinforced composite sheet sandwich structures can be a complex process .

[0008] The obj ect of the present invention is to provide a battery housing part with increased stability and improved flatness .

[0009] This obj ect of the present invention is achieved by a battery housing part having the features as described herein . Advantageous embodiments of the battery housing part are described herein in details .

[0010] More specifically, the obj ect of the present invention is achieved by a battery housing part comprising a composite, characteri zed in that said composite is comprising a polymer composition comprising polyamide 6 and amorphous polyamide, and fiber material .

[0011] The battery housing part according to the invention exhibits improved stability and flatness . In particular, it has been surprisingly found that the addition of amorphous polyamide to a resin results in an improved stability and flatness of the battery housing part .

[0012] The amorphous polyamide is preferably made from aromatic amine monomers , for example, di-amine monomers . The aromatic parts of the monomers may prevent the forming of a crystalline structure in the polymer and thus provide an amorphous polymer . Preferably the amorphous polyamide is made from a resin mixture comprising two dif ferent (di-amine ) monomers . Preferably the amorphous polyamide is made from a resin mixture comprising hexamethylene diamine isophthalic acid and hexamethylene diamine terephthalic acid . In preferred embodiments , the resin mixture comprises a (weight / weight ) -% ratio (wt% ) of hexamethylene diamine isophthalic acid to hexamethylene diamine terephthalic acid of 90 / 10 to 50 / 50 , 80 / 20 to 60 / 40 , or 75 / 25 to 65 / 35.

[0013] I f not otherwise stated all values indicated as wt% in this description use the weight of the total composite as reference .

[0014] The weight values are to be understood in the following way : For example, if the total composite comprises 10 wt% of substance A and the total composite has a weight of 1 kg then this means that the 10 wt% value corresponds to 100 g . In a further example, a composition comprising a 90 / 10 wt% ratio of substance A and substance B means that the composition may comprise 90 g of substance A and 10 g of substance B .

[0015] The composite of the battery housing part according to the invention preferably comprises 5-50 wt% , 10-45 wt% , 10-35 wt% , 15-35 wt% , or 15-25 wt% amorphous polyamide .

[0016] Amorphous polyamide present in the above concentrations was particularly suitable for improving the flatness of the battery housing part of the invention .

[0017] The composite of the battery housing part according to the invention alternatively preferably comprises 5-15 wt% mica powder and 5-40 wt% , 10-35 wt% , 10-25 wt% , 5-25 wt% , or 5-15 wt% amorphous polyamide .

[0018] It has been surprisingly found that about half of the mass of amorphous polyamide can be replaced with a corresponding mass of mica powder which is less expensive than amorphous polyamide. For example, it has been found that 5-15 wt% of amorphous polyamide can be replaced with 5-15 wt% of mica powder, in particular 8-12 wt%, 9-11 wt% or 10 wt% of mica powder.

[0019] Mica powder comprises a group of complex hydrous aluminosilicate minerals, with the general formula X2Y4_6Z802o (OH, F)4where X is (mainly) K, Na or Ca; Y is (mainly) Al, Mg or Fe; and Z is (mainly) Si or Al. Mica powder material is monoclinic, with a tendency towards pseudohexagonal crystals. Mica powder material has a hexagonal sheet-like arrangement of its atoms. The mica powder material can be, for example, muscovite or phlogopite. The mica powder has a mesh of at least 80 mesh, 100 mesh, or 150 mesh or a particle diameter of up to 0.100 mm, 0.150 mm, or 0.180 mm. The particle diameter can be between 0.001 and 0.180 mm, 0.010 and 0.180 mm, or 0.050 and 0.180 mm.

[0020] Polyamide 6 is polycaprolactam. The relative viscosity of the polyamide 6 can be 1.0 to 4.0 or 1.8 to 3.6.

[0021] The battery housing part according to the invention advantageously has a flatness of a less than 6 mm, 5 mm, or 4 mm in a planar region of the battery housing part that extends over a length of 30 cm.

[0022] The composite of the battery housing part according to the invention preferably comprises 10-70 wt%, 55-60 wt%, 20-50 wt%, 25-45 wt%, or 30-40 wt% of the polymer composition comprising polyamide 6.

[0023] The polymer composition of the composite of the battery housing part according to the invention preferably comprises 70-100 wt%, 75-90 wt%, 75-85 wt% polyamide 6.

[0024] Preferably, the composite may further comprise additives, wherein said additives may comprise antioxidants (e.g. a hindered phenol) , lubricants (e.g. ethylene bis stearamide, EBS; zinc stearate) , coloring agents and / or molding release agents. The additives can be provided in the polymer composition or separate from the polymer composition .

[0025] If the additives are comprised in the polymer composition, the polymer composition comprises 0-30 wt%, 10-27 wt%, or 15-25 wt% additives .

[0026] If the additives are provided separate from the polymer composition, the polymer composition comprises 99-100 wt% polyamide 6 and the composite comprises 0-6 wt%, 2-5 wt%, or 3-5 wt% additives .

[0027] Polyamide 6 having the above concentrations was particularly suitable for improving the flatness of the battery housing part of the invention.

[0028] The composite of the battery housing part according to the invention preferably comprises 15-80 wt%, 20-75 wt%, 25-70 wt%, 40-60 wt%, 35-55 wt%, or 40-50 wt% fiber material.

[0029] Fiber material having the above concentrations was particularly suitable for improving the flatness of the battery housing part of the invention.

[0030] The fiber material can exhibit glass fibers and / or aramid fibers and / or carbon fibers, preferentially glass fibers.

[0031] The fiber diameter of the fiber material used in the composite of the battery housing part according to the invention preferably is 5-25 micrometer, 8-23 micrometer, 10-23 micrometer, 12-21 micrometer, 14- 19 micrometer, or 16-18 micrometer .

[0032] Fiber material exhibiting the above fiber diameters was particularly suitable for improving the flatness of the battery housing part of the invention .

[0033] The fiber material used in the composite of the battery housing part according to the invention can have a circular or non-circular cross-section . It has been surprisingly found that the use of amorphous polyamide allows to improve the flatness and strength of battery housing parts even when using fiber material with circular cross-section .

[0034] The fiber material used to produce the composite of the battery housing part according to the invention can be in the form of a chopped strand, roving or any other suitable form.

[0035] The fiber material used to produce the composite of the battery housing part according to the invention can have a coating improving the binding to the polyamide 6 and / or amorphous polyamide . The coating (or sizing) is not particularly limited and can be a fiber mechanical reinforcement impregnating agent, woving impregnating agent, silanes or a polymer, e . g . thermoset plastic or / and a polymer comprising maleic acid or maleic anhydride .

[0036] Preferably, the composite may further comprise antioxidants , lubricants , and / or molding release agents .

[0037] The extruded part is preferably designed such that the fiber grid is embedded in a matrix material , wherein the matrix material is integrally bonded to the polymer melt ( s ) . The correspondingly designed extruded part has even greater stability . This is because by embedding the fiber material in the matrix material , the forces can be better transferred from the extruded part to the fibers thereof in the component . With the correspondingly designed extruded part, better penetration of the fiber grid with plastics material is achieved, so that the stability of the extruded part is increased .

[0038] The invention is also directed to a molded battery housing part made from the battery housing part according to the invention and having the features as described herein, wherein the molded battery housing part is obtainable from the battery housing part by compressing molding or inj ection molding .

[0039] Advantageously, the battery housing part of the invention can be formed by compressing molding or inj ection molding .

[0040] A further obj ect of the present invention is the provision of a battery housing which has increased stability and reduced production costs .

[0041] This obj ect of the present invention is achieved by a battery housing having the features as described herein . More precisely, this obj ect of the present invention is achieved by a battery housing for a traction battery, wherein the battery housing has at least one extruded part as described above in this description .

[0042] The extruded part is preferably designed as a battery housing shell , which in turn is designed as a battery housing upper shell or as a battery housing lower shell . Even more preferably, the battery housing has a first extruded part designed as a battery housing upper shell and a second extruded part designed as a battery housing lower shell .

[0043] Another obj ect of the present invention is to provide a traction battery that has increased stability and reduced production costs .

[0044] The obj ect of the present invention is achieved by a traction battery having the features as described herein . More precisely, this obj ect of the present invention is achieved by a traction battery for a motor vehicle, wherein the traction battery has a battery housing as described above in this description, wherein at least one battery component is contained in the interior of the battery housing .

[0045] The battery component can be designed as a battery module and / or a battery cell .

[0046] It is also an obj ect of the invention of providing a method for producing a battery housing part as defined in the description . This obj ect of the invention is achieved by the method as described herein .

[0047] More precisely, this obj ect of the present invention is achieved by a method for producing a battery housing part by means of an extrusion tool , the method having the following method steps : mixing and melting a polymer composition comprising polyamide 6 and amorphous polyamide to provide a melt ; mixing the melt with fiber material in an extrusion tool to provide a mixture ; extruding the mixture at a temperature below 280 °C .

[0048] The method advantageously provides a battery housing part with improved stability and flatness . A further advantage is that the extrusion temperature can be lower than in extrusion processes without amorphous polyamide and thus the energy demand and consequently production costs are reduced . This may be due to the fact that amorphous polyamide has a lower melting point ( about 130- 160 °C) than polyamide 6 ( about 215 °C) .

[0049] The extrusion tool can be any suitable extrusion tool , e . g . a twin- screw extruder .

[0050] In the method according the invention, the mixture may be extruded via any suitable die, e . g . die providing a rectangular shape in cross-section for the extruded die .

[0051] In the method according to the invention the mixture can be extruded at a temperature below 270 ° C, 260 °C, 250 °C, or 245 °C .

[0052] It has been surprisingly found that the extrusion temperature can be reduced to the values indicated above thereby further reducing energy demand and production costs .

[0053] The method according to the invention can further comprise the following steps :

[0054] Cutting the extruded mixture into pieces with a predetermined weight ; transferring at least one piece of the pieces to a molding press at a temperature between 200 °C and 300 °C; placing the at least one piece into the molding press ; compressing molding the at least one piece in the molding press .

[0055] An advantage associated with this additional step is that the pieces can be transported at a lower temperature to the molding press than required when using a mixture without amorphous polyamide and thus the energy consumption and consequently the production costs are reduced . This may be due to the fact that amorphous polyamide has a lower melting point ( about 130-160 °C) than polyamide 6 ( about 215 °C) .

[0056] In the method according to the invention the mixture can be transferred at a temperature between 210 ° and 280 °C, between 215 ° and 270 °C, between 220 ° and 260 °C, or 235 ° - 245 ° C .

[0057] It has been surprisingly found that the transfer temperature can be even further reduced to the values indicated above thereby further reducing energy demand and production costs .

[0058] The predetermined weight can substantially or completely correspond to the weight of the finally obtained battery housing part .

[0059] In the method according the invention, the extruded mixture can be cut into pieces with a predetermined weight and a predetermined length .

[0060] The predetermined length can depend on the dimensions of the mold of the molding press .

[0061] Instead of including a step of compression molding into the method of the invention the method can further comprise the step of :

[0062] - inj ection molding the mixture to provide a battery housing part .

[0063] Further advantages , details , and features of the invention can be found below in the described embodiments . In the drawings , in detail :

[0064] Fig . 1 : schematically shows the production process of the battery housing part ; Fig . 2 : schematically shows how a ruler is applied to a battery housing part to determine the flatness of the battery housing part .

[0065] In the following description, the same reference signs denote the same components or features , so that a description of a component with reference to one drawing also applies to the other drawings , thus avoiding repeating the description . Furthermore , individual features that have been described in connection with one embodiment can also be used separately in other embodiments .

[0066] Fig . 1 illustrates a compression molding process , in this case a direct long fiber technology ( D-LFT , here thermoplastic molding, ) process . However, a granular-long fiber technology (G-LFT ) process could also be used . After drying, polyamide 6 and amorphous polyamide resin in amounts as indicated below, were fed via a feeder 2 into an extruder 3 , mixed and melted to provide a melt comprising a polymer composition comprising polyamide 6 and amorphous polyamide . The melt was transported to an extruder 6 ( e . g . an twin-screw extruder ) and mixed with fiber material 4 obtained from at least one fiber material roving 5. The mixture was extruded by the extruder 6 via a die providing a rectangular cross-sectional shape to the extruded mixture .

[0067] The mixture was loaded onto a conveying belt 7 . On the conveying belt 7 the extruded mixture was cut into pieces 8 with a certain weight and length . The weight corresponds to the intended weight of the battery housing part 1 that is to be formed from each of the pieces 8 . The length depends on the dimension of the mold . After exit from the extruder 6 the temperature of the mixture and the pieces 8 are controlled to be within a certain range until they are trans ferred to a compression molding press 9 ( transport temperature) .

[0068] After arrival at the compression molding press 9, one of the pieces 8 is transferred into the mold of the compression molding press 9 as indicated by the dashed arrow 10. This transport can be achieved, e.g. by a handling robot.

[0069] The temperature of molds of the compression molding press 9 is also maintained at a predetermined temperature (tool temperature) .

[0070] After transport into the mold the halves of the mold close as indicated by arrow 11. After closing and opening of the mold halves a battery housing part 1 is removed from the mold as indicated by arrow 12. This transport can be achieved in any suitable way, e.g. by the same or a further handling robot as before.

[0071] Using the process described in reference to Fig. 1 the following compositions were tested:

[0072] Table 1

[0073] Amorphous polyamide had material grade A1315 and was obtained from Beijing energy (China) . Amorphous polyamide was made from Hexamethylene diamine isophthalic acid / Hexamethylene diamine terephthalic acid: 70 / 30 wt% .

[0074] Polyamide 6 had material grade BN0FBK-S03Y and was obtained from

[0075] Nan ing Julong (China) . This polyamide 6 composition contained polyamide6 ( relative viscosity 1 . 8 to 3 . 6 ) : 79 wt%

[0076] Hindered phenol antioxidant : 4 wt%

[0077] Phosphite antioxidant : 4 wt%

[0078] Ethylene Bis Stearamide lubricant : 5 wt%

[0079] Zinc Stearate lubricant : 5 wt%

[0080] Black coloring agent : 3 wt%

[0081] Glass fiber had material grade ECT4301R-2400 and was obtained from CPIC (China) . The diameter of the glass fiber was 17 pm and the cross-section was circular .

[0082] For conducting the process described with regard to Fig . 1 , the following processing conditions were identified and used :

[0083] Table 2

[0084] As can be derived from Table 2 , compared to the Reference Example without amorphous polyamide, the battery housing part of the disclosure has a lower heating temperature during extrusion and during conveyer belt sections .

[0085] Next the tensile and flexural strength and modulus of the battery housing part of the Example and the Reference Example were determined (under dry conditions ) : Table 3

[0086] As can be derived from Table 3 , compared to the Reference Example without amorphous polyamide, the battery housing part of the disclosure exhibits a higher strength and stiffness .

[0087] Next the flatness of the battery housing part 1 was determined . In brief the flatness was determined as illustrated in Fig . 2 .

[0088] Fig . 2 shows the battery housing part 1 in cross-section . The curvature of the battery housing part is illustrated in an exaggerated way to better illustrate the measuring method .

[0089] One end of a ruler 13 with a length L ( e . g . 30 cm) is aligned with its long side to a planar area of the battery housing part 1 . Since the planar region of the battery housing part 1 is not completely flat this alignment is only possible for one of the ends ( the first end close to the value 0 ) of the ruler . Then the smallest distance between the second end of ruler ( at the 30 cm value ) and the surface of the planar area of the battery housing part 1 is determined .

[0090] The flatness is determined as d at the 30 cm mark of the ruler in mm.

[0091] The following results were obtained :

[0092] Table 4

[0093] As can be derived from Table 4 , the flatness of a battery housing part with 20% amorphous polyamide improved significantly from a value of 6. 65 mm to a value 3 . 75 mm.

[0094] The experiments described above were repeated with the following composition which differs from the composition of Example 1 only by the amount of amorphous polyamide and the incorporation of mica powder :

[0095] Table 5

[0096] The composition of Example 2 was subj ected to the same tests as described above . The battery housing part obtained from the composition of Example 2 exhibited the same advantageous properties with regard to heating temperature during extrusion and during conveyer belt sections , tensile and flexural strength, and flatness as the composition of Example 1 (data not shown) . List of reference signs

[0097] 1 Battery housing part

[0098] 2 Feeder

[0099] 3 ( First ) Extruder

[0100] 4 Glass fiber

[0101] 5 Glass fiber roving

[0102] 6 ( Second) Extruder

[0103] 7 Conveying belt

[0104] 8 (Extruded) Piece

[0105] 9 Compression molding press

[0106] 10 dashed arrow indicating trans fer to compression molding press

[0107] 11 direction of applied pressure

[0108] 12 dashed arrow indicating trans fer from compression molding press

[0109] L Length of ruler d distance from end of ruler to surface of battery housing part

Claims

Claims1. Battery housing part comprising a composite, characterized in that said composite is comprising:- a polymer composition comprising polyamide 6 and amorphous polyamide; and- fiber material.

2. Battery housing part according to claim 1, characterized in that the composite comprises 5-50 wt%, 10-45 wt%, 10-35 wt%, 15-35 wt%, or 15-25 wt% amorphous polyamide.

3.

2. Battery housing part according to claim 1, characterized in that the composite comprises 5-15 wt% mica powder and 5-40 wt%, 10-35 wt%, 10-25 wt%, 5-25 wt%, or 5-15 wt% amorphous polyamide.

4. Battery housing part according to any of the preceding claims, characterized in that the polymer composition comprises 10-70 wt%, 55-60 wt%, 20-50 wt%, 25-45 wt%, or 30-40 wt% polyamide6.

5. Battery housing part according to any of the preceding claims, characterized in that the composite comprises 15-80 wt%, 20-75 wt%, 25-70 wt%, 40-60 wt%, 35-55 wt%, or 40-50 wt% fiber material .

6. Battery housing part according to any of the preceding claims, characterized in that the diameter of the fiber material is 5-25 micrometer, 8-23 micrometer, 10-23 micrometer, 12-21 micrometer, 14-19 micrometer, or 16-18 micrometer.

7. Battery housing part according to any of the preceding claims, characterized in that the composite further comprises8. antioxidants, lubricants, and / or molding release agents.

9. Battery housing part according to any of the preceding claims, characterized in that the fiber material is embedded in the polymer composition.

10. Molded battery housing part made from the battery housing part according to any of the preceding claims, wherein the molded battery housing part is obtainable from the battery housing part by compressing molding or injection molding.

11. Battery housing for a traction battery, wherein the battery housing has at least one battery housing part according to any claims 1-8 or at least one molded battery housing part according to claim 9.

12. Traction battery for a motor vehicle, wherein the traction battery has a battery housing according to claim 10, wherein at least one battery component is contained in the interior of the battery housing.

13. Method for producing a battery housing part by means of an extrusion tool, the method having the following method steps :- mixing and melting polyamide 6 and amorphous polyamide to provide a melt;- mixing the melt with fiber material in an extrusion tool to provide a mixture;- extruding the mixture at a temperature below 280°C.

14. Method according to claim 12, characterized in that the mixture is extruded at a temperature below 270°C, 260°C, 250°C, or 245°C.

15. Method according to claims 12 or 13, characterized in that the method further comprises:- Cutting the extruded mixture into pieces with a predetermined weight; - transferring at least one piece of the pieces to a molding press at a temperature between 200°C and 300°C;- placing the at least one piece into the molding press;- compressing molding the at least one piece in the molding press .

16. Method according to claim 14, characterized in that the mixture is transferred at a temperature between 210° and 280°C, between 215° and 270°C, between 220° and 260 °C, or 235° - 245°C.

Images