Battery box body, manufacturing method thereof and battery pack

Abstract

The invention provides a battery box body, a manufacturing method thereof and a battery pack, the battery box body comprises a box body, the box body comprises a middle plate and a first end plate, the first end plate is arranged at one end of the middle plate in the length direction of the box body, and at least one part of a battery mounting cavity is defined by the middle plate and the first end plate; wherein a first bonding wire is arranged at the joint of the middle plate and the first end plate, and the middle plate and the first end plate are located on the two opposite sides of the first bonding wire in the length direction of the box body.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery case and a manufacturing method thereof, and a battery pack. Background Art

[0002] New energy vehicles have various specifications, and accordingly, the battery pack cases used for new energy vehicles will have different lengths. In order to make the battery pack case adapt to vehicle models of different lengths, the battery pack case is designed to be a middle plate and two end plates. The middle plate and the two end plates are designed as case sections of different lengths and then spliced, so as to adjust the size of the battery pack case. In the related art, the middle plate and the two end plates are connected by resistance welding. Since there are overlapping lap areas in resistance welding, it is necessary to apply sealant to seal the welding joint area after welding. However, some welding joint areas will have gaps after welding due to poor flatness of the case, and there will still be a situation where the battery pack case seal fails, which makes it difficult for the battery pack to pass the air tightness test. Summary of the invention

[0003] The embodiments of the present invention provide a battery case and a manufacturing method thereof, and a battery pack, which can improve the technical problem of failure in airtightness detection of the battery pack.

[0004] In a first aspect, an embodiment of the present invention provides a battery box, comprising:

[0005] A box body, the box body includes a middle plate and a first end plate, the first end plate is arranged at one end of the middle plate in the length direction of the box body, and the middle plate and the first end plate enclose at least a part of the battery installation cavity; wherein a first welding line is arranged at the connection between the middle plate and the first end plate, and the middle plate and the first end plate are located on opposite sides of the first welding line in the length direction of the box body.

[0006] In one embodiment, the box body also includes a second end plate, which is arranged at the other end of the middle plate in the length direction of the box body, and a second welding line is arranged at the connection between the middle plate and the second end plate, and the middle plate and the second end plate are located on opposite sides of the second welding line in the length direction of the box body.

[0007] In one embodiment, the orthographic projection of the first welding line and / or the second welding line on the plane where the bottom wall of the battery installation cavity is located is set to be a continuous straight line.

[0008] In one embodiment, the width of the first welding line and / or the second welding line is 2 mm to 4 mm.

[0009] In one embodiment, the first end plate includes a first end plate plane area and a first end plate arc surface area, a first end plate dividing line extending along the height direction of the box body is arranged between the first end plate plane area and the first end plate arc surface area, and the minimum distance between the first end plate dividing line and the first welding line is set to be not less than 90 mm; and / or, the second end plate includes a second end plate plane area and a second end plate arc surface area, a second end plate dividing line extending along the height direction of the box body is arranged between the second end plate plane area and the second end plate arc surface area, and the minimum distance between the second end plate dividing line and the second welding line is set to be not less than 90 mm.

[0010] In one embodiment, along the width direction of the box body, the middle plate includes a first part, a second part and a third part, and the second part is arranged between the first part and the third part in the width direction of the box body; wherein the thickness of the first part is greater than the thickness of the second part, and the thickness of the third part is greater than the thickness of the second part.

[0011] In one embodiment, a third welding wire is provided at the connection between the first part and the second part, the first part and the second part are located on opposite sides of the third welding wire in the width direction of the box, and the third welding wire is connected between the first welding wire and the second welding wire; and / or a fourth welding wire is provided at the connection between the third part and the second part, the second part and the third part are located on opposite sides of the fourth welding wire in the width direction of the box, and the fourth welding wire is connected between the first welding wire and the welding wire.

[0012] In one embodiment, the middle plate, the first end plate and the second end plate together include a substrate layer and a first protective layer formed on the substrate layer in the thickness direction of the box body, the substrate layer includes a steel plate or an aluminum plate, and the first protective layer includes a zinc coating.

[0013] In one embodiment, the middle plate, the first end plate and the second end plate further jointly include a second protective layer, the second protective layer is arranged on a side of the first protective layer away from the substrate layer, and the second protective layer includes an organic coating.

[0014] In one embodiment, the thickness of the middle plate, the first end plate and the second end plate are all set to be less than 3 mm, and the thickness of the middle plate, the first end plate and the second end plate are set to be greater than 0.5 mm.

[0015] In one embodiment, the length of the battery case is set to d, the length of the middle plate extending along the length direction of the battery case is set to d1, the ratio of d1 to d is 0.5 to 0.8, the length of the orthographic projection of the first end plate or the second end plate on the plane where the bottom wall of the battery mounting cavity is located extending along the length direction of the battery case is d2, the ratio of d2 to d is 0.1 to 0.25; and / or, the ratio of d1+2d2 to d is 1.

[0016] In one embodiment, the box body includes a first supporting longitudinal beam and a second supporting longitudinal beam and a supporting cross beam connected between the first supporting longitudinal beam and the second supporting longitudinal beam, wherein the first supporting longitudinal beam is connected to the first end plate, the second supporting longitudinal beam is connected to the second end plate, one end of the supporting cross beam extends to the outer side of the first welding line away from the second welding line, and the other end of the supporting cross beam extends to the outer side of the second welding line away from the first welding line.

[0017] In a second aspect, an embodiment of the present invention provides a battery pack, comprising the above-mentioned battery case, and a plurality of batteries disposed in the battery case.

[0018] In a third aspect, the present invention provides a method for manufacturing the battery case, the method comprising:

[0019] Welding a flat first end plate to one end of a flat middle plate by laser welding, and welding a flat second end plate to the other end of the flat middle plate by laser welding to form a welded part;

[0020] The welding piece is formed into the box body by stamping.

[0021] In one embodiment, the welding piece is punched into the box body by a punching die, and the punching die is configured to be adjustable according to the length of the middle plate.

[0022] In one embodiment, before the step of forming the box body by stamping the welded part, the step further includes: performing electrophoresis treatment on the welded part.

[0023] Beneficial effects of the embodiments of the present invention:

[0024] In an embodiment of the present invention, a first welding line is set at the connection between the middle plate and the first end plate, for example, the first welding line is formed by laser welding, wherein the first end plate and the middle plate are respectively located on both sides of the first welding line, so that the first end plate and the middle plate do not overlap in the thickness direction of the box body. Compared with the related art in which the resistance welding process requires the first end plate and the middle plate to overlap in the thickness direction, the gap of the box body in the thickness direction can be reduced, thereby improving the air tightness of the box body. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a top view of a battery box formed by resistance welding provided by the related art;

[0027] Figure 2 It is a cross-sectional view of a battery box formed by resistance welding provided by the related art;

[0028] Figure 3 yes Figure 2 A partial enlarged view of

[0029] Figure 4 is a top view of a battery box provided by an embodiment of the present invention;

[0030] Figure 5 is a front view of a battery box provided by an embodiment of the present invention;

[0031] Figure 6a yes Figure 5 A magnified view of the local area A;

[0032] Figure 6b yes Figure 5 A partial enlarged view of B;

[0033] Figure 7 is a three-dimensional diagram of a welded part of a battery box after welding provided by an embodiment of the present invention;

[0034] Figure 8 is a cross-sectional structural diagram of a molding material of a battery case provided by an embodiment of the present invention;

[0035] Fig. 9 is a manufacturing process flow chart of a battery box provided by an embodiment of the present invention;

[0036] Related technical figures:

[0037] 3. Box body; 31. Left end plate; 32. Middle plate; 33. Right end plate; 341. Left reinforced longitudinal beam; 342. Right reinforced longitudinal beam; 343. Cross beam; 35. Welding overlap area;

[0038] Figure numbers of the embodiments of the present application:

[0039] 1. Box body; 11. First end plate; 12. Middle plate; 121. First part; 122. Second part; 123. Third part; 13. Second end plate; 14. Battery installation cavity; 151. First welding line; 152. Second welding line; 153. Third welding line; 154. Fourth welding line; 161. First end plate plane area; 162. First end plate arc surface area; 163. First end plate dividing line; 164. Second end plate plane area; 165. Second end plate arc surface area; 166. Second end plate dividing line; 17. Reinforcement; 181. Base material layer; 182. Anti-corrosion layer;

[0040] 21. First supporting longitudinal beam; 22. Second supporting longitudinal beam; 23. Supporting cross beam;

[0041] 4. Welding parts; DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the drawings; while "inside" and "outside" refer to the outline of the device.

[0043] New energy vehicles have various specifications, and the battery packs used in new energy vehicles have different lengths. In order to adapt the battery pack to different lengths of vehicles, the battery pack is designed to be a middle plate and two end plates. The middle plate and the two end plates are designed as box sections of different lengths and then spliced ​​together to adjust the size of the battery pack.

[0044] In the related art, reference Figures 1 to 3The two end plates of the box body 3 include a left end plate 31 and a right end plate 33. The left end plate 31 and the middle plate 32, as well as the middle plate 32 and the right end plate 33 are connected by resistance welding. Resistance welding is to weld the overlapping middle plate and the end plate together by melting them with an electric current under the condition of overlapping. The length of the welding overlap area 35 between the middle plate and the end plate is 40mm to 60mm. A plurality of circular welding spots are formed in the welding overlap area 35. The diameter of each circular welding spot is about 6mm. The resistance welding method can only ensure the connection strength, but cannot achieve the sealing connection between the middle plate 32 and the end plate. Therefore, the edge of the welding overlap area 35 is usually fully sealed by coating the sealant. On the one hand, coating the sealant will increase the production cost. On the other hand, some welding overlap areas will have gaps after welding due to the poor flatness of the box body. The sealant cannot be 100% filled and sealed. There will still be a situation where the battery pack box seal fails, which makes it difficult for the battery pack to pass the airtightness test. In addition, the sealant itself has fluidity and aging failure properties. Therefore, in the actual production process, the sealant needs to be applied and tested multiple times before the battery box can pass the air tightness test.

[0045] Continue to refer Figure 2 and Figure 3 The box body 3 in the related art also includes two longitudinal reinforcing beams and a reinforcing cross beam 343 connected between the two longitudinal reinforcing beams, which are respectively a left reinforcing longitudinal beam 341 and a right reinforcing longitudinal beam 342, wherein the left reinforcing longitudinal beam 341 is fixed close to the left end plate 31, and the right reinforcing longitudinal beam 342 is fixed close to the right end plate 33, one side of the left reinforcing longitudinal beam 341 close to the left end plate 31 is fixed on the left end plate 31, and the other side of the left reinforcing longitudinal beam 341 is fixed on the middle plate 32, so that a height difference structure is formed between the bottom end surfaces where the two sides of the left reinforcing longitudinal beam 341 are located, and the two sides of the right reinforcing longitudinal beam 342 close to the right end plate 33 are fixed on the middle plate 32, so that the left reinforcing longitudinal beam 341 and the right reinforcing longitudinal beam 342 are set to an asymmetric structure, so the left reinforcing longitudinal beam 341 and the right reinforcing longitudinal beam 342 need to be molded and manufactured separately, thereby increasing the mold making cost of the battery box.

[0046] The embodiment of the present application provides a battery pack, which includes a battery box and multiple batteries arranged inside the battery box. The battery pack can be an energy storage battery pack, and multiple energy storage battery packs are combined to form an energy storage battery cabinet or an energy storage container. The battery pack can also be a power battery pack, which provides electric drive for new energy vehicles.

[0047] like Figure 4 and Figure 5As shown, the battery box includes a box body 1 and a box cover (not shown in the figure), and the box body 1 includes a first end plate 11, a middle plate 12, and a second end plate 13. The first end plate 11 is spliced ​​to one end of the middle plate 12 by laser welding, and the second end plate 13 is spliced ​​to the other end of the middle plate 12 by laser welding. The first end plate 11, the middle plate 12, and the second end plate 13 enclose a battery installation cavity 14, and a first welding line 151 is formed at the connection between the middle plate 12 and the first end plate 11, and a second welding line 152 is formed at the connection between the middle plate 12 and the second end plate 13, wherein the first end plate 11 and the middle plate 12 are located on opposite sides of the first welding line 151 in the length direction of the box, and the middle plate 12 and the second end plate 13 are located on opposite sides of the second welding line 152 in the length direction of the box, so that the first end plate 11 and the middle plate 12 do not overlap along the thickness direction of the box, and the middle plate 12 and the second end plate 13 do not overlap along the thickness direction of the box. Wherein, the length of the box is as shown in FIG. Figure 4 The X direction is shown, and the thickness direction of the box is as follows Figure 5 The Z direction is shown.

[0048] Compared with the welding points formed by resistance welding between the two end plates and the middle plate in the related art, and a welding overlap area needs to be set between the end plates and the middle plate, the box body 1 provided in the embodiment of the present application uses laser welding to splice the first end plate 11 to one end of the middle plate 12, and splice the second end plate 13 to the other end of the middle plate 12. Since there is no welding overlap area between the first end plate 11 and the middle plate 12, and between the middle plate 12 and the second end plate 13, the sealing performance of the connection between the first end plate 11 and the middle plate 12, and the connection between the middle plate 12 and the second end plate 13 is better. The inventor found through airtightness test that the battery box formed by splicing the first end plate 11, the middle plate 12 and the second end plate 13 by laser welding can pass the airtightness test.

[0049] Air tightness test method: After sealing the battery box, inflate the battery box with air at a pressure of 6.5KPa±0.5KPa until the stable pressure reaches 3.5KPa±0.3KPa. Maintain the pressure for 50 seconds. The pressure difference before and after the test is no more than 0.03KPa.

[0050] Example 1: The first end plate 11, the middle plate 12 and the second end plate 13 of the battery box 1 provided in Example 1 are spliced ​​together by laser welding to form the battery box 1, the first end plate 11 and the middle plate 12 form a first welding line 151 extending in a straight line, and the middle plate 12 and the second end plate 13 form a second welding line 152 extending in a straight line.

[0051] Comparative Example 1: The left end plate 31, the middle plate 32 and the right end plate 33 of the battery box body 3 provided in Comparative Example 1 are connected by resistance welding. The left end plate 31, the middle plate 32 and the right end plate 33 are connected by resistance welding at the welding overlap area of ​​the left end plate 31 and the middle plate 32, and the welding overlap area of ​​the middle plate 32 and the right end plate 33 are connected, and sealant is applied to the welding overlap area.

[0052] The battery case of Example 1 and the battery case of Comparative Example 1 were respectively placed on airtight testing equipment and subjected to airtightness testing according to the airtightness testing method.

[0053] Test results: The battery case provided in Example 1 passed the air tightness test, while the battery case provided in Comparative Example 1 failed the air tightness test.

[0054] In some embodiments, the projections of the first welding line 151 and the second welding line 152 on the plane where the bottom wall of the battery installation cavity 14 is located are both set to be continuous straight lines.

[0055] It is understandable that the first welding line 151 connecting the first end plate 11 and the middle plate 12 is set as a continuously extending straight line structure, and the second welding line 152 connecting the middle plate 12 and the second end plate 13 is set as a continuously extending straight line structure. Therefore, compared with the use of resistance welding to form dispersed welding points, the use of laser welding to form a continuously extending straight line structure of the first welding line 151 and the second welding line 152 has a more stable welding structure. At the same time, compared with the first welding line and the second welding line of the curved structure, the first welding line and the second welding line of the straight structure are more convenient to splice the first end plate and the second end plate on both sides of the middle plate, thereby improving the efficiency of the welding operation.

[0056] In some implementations, the width of the first welding line 151 or the second welding line 152 is set to 2 mm to 4 mm. In a specific implementation, the width of the first welding line 151 or the second welding line 152 can be 2.0 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3.0 mm, 3.2 mm, 2.5 mm, 3.7 mm, 4.0 mm, and a value between any two of the above values ​​or a range between any two of the above values.

[0057] The inventors have found through research that when the width of the first welding line 151 or the second welding line 152 is set to be less than 2 mm, the welding strength between the first end plate 11 and the middle plate 12, or between the middle plate 12 and the second end plate 13 is insufficient, resulting in insufficient connection strength of the battery box formed by splicing. When the width of the first welding line 151 or the second welding line 152 is set to be greater than 4 mm, the surface flatness of the first welding line 151 or the second welding line 152 is poor, resulting in a large deviation in the flatness of the battery box, which is not conducive to the stable installation of multiple batteries in the battery installation cavity 14.

[0058] Continue to refer Figure 4 and Figure 5 The box body 1 formed by stamping after welding the first end plate 11, the middle plate 12 and the second end plate 13 comprises two opposite side walls, two opposite end walls and a bottom wall, wherein the two end walls are arranged between the two side walls, and the bottom wall is connected to the two side walls and the bottom of the two end walls. The two side walls comprise a left side wall and a right side wall, and the two end walls comprise a front end wall and a rear end wall. The first welding line 151 and the second welding line 152 are arranged in parallel along the width direction of the box body, and the first welding line 151 and the second welding line 152 both extend from the top of the front end wall to the bottom of the front end wall, and from the front end of the bottom wall to the rear end of the bottom wall, and from the bottom of the rear end wall to the top of the rear end wall, wherein the width direction of the box body is as shown in FIG. Figure 4 Y direction shown.

[0059] Since the first welding wire 151 and the second welding wire 152 extend along the width direction Y of the battery case on the entire front end wall, bottom wall and rear end wall, the overall structure of the case is basically symmetrical along the length direction x and the width direction Y of the battery case, which is beneficial to maintaining the stability of the overall structural strength of the case 1.

[0060] Continue to refer Figure 5 , a reinforcing beam is also provided inside the box 1, and the reinforcing beam includes two supporting longitudinal beams extending along the width direction of the battery box and a supporting cross beam 23 extending along the length direction of the battery box, wherein the supporting cross beam 23 is connected between the two supporting longitudinal beams. The two supporting cross beams include a first supporting longitudinal beam 21 and a second supporting longitudinal beam 22 arranged at intervals, wherein the first supporting longitudinal beam 21 is connected to the first end plate 11, and the second supporting longitudinal beam 22 is connected to the second end plate 13, and the length of the supporting cross beam 23 along the length direction of the battery box is greater than the length of the middle plate 12, one end of the supporting cross beam 23 extends to the outside of the first welding line 151 and is connected to the first supporting longitudinal beam 21, and the other end of the supporting cross beam 23 extends to the outside of the second welding line 152 and is connected to the second supporting longitudinal beam 22.

[0061] Since there is no need to set a welding overlap area between the first end plate 11 and the middle plate 12 and between the middle plate 12 and the second end plate 13, the first supporting longitudinal beam 21 and the second supporting longitudinal beam 22 are configured as a completely symmetrical structure, so that the first supporting longitudinal beam 21 and the second supporting longitudinal beam 22 can be prepared by using a set of molds, thereby effectively reducing the preparation cost of the first supporting longitudinal beam 21 and the second supporting longitudinal beam 22.

[0062] refer to Figure 5 , Figure 6a and Figure 6b, the first end plate 11 includes a first end plate plane area 161, a first end plate curved area 162, and a first end plate dividing line 163 for connecting the first end plate plane area 161 and the first end plate curved area 162, wherein the minimum distance d3 between the first end plate dividing line 163 and the first welding line 151 is set to be not less than 90 mm. And / or, the second end plate 13 includes a second end plate plane area 164, a second end plate curved area 165, and a second end plate dividing line 166 for connecting the second end plate plane area 164 and the second end plate curved area 165, and the minimum distance d4 between the second end plate dividing line 166 and the second welding line 152 is set to be not more than 90 mm. It should be noted that the minimum distance d3 between the first end plate dividing line 163 and the first welding line 151 is set to be the minimum distance between the edge of the first end plate dividing line 163 close to the curved area 162 and the edge of the first welding line 151 close to the plane area 161. The minimum distance d3 between the second end plate boundary line 166 and the second welding line 152 is set to be the minimum distance between the edge of the boundary line 163 of the second end plate 13 close to the arc surface area 162 and the edge of the second welding line 152 close to the plane area 161 .

[0063] Since the box body 1 firstly uses laser welding to splice the first end plate 11, the middle plate 12 and the second end plate 13 into a whole, and then forms the two side walls and the two end walls of the box body 1 by stamping, if the distance between the boundary line 163 of the first end plate 11 and the first welding line 151 is less than 90 mm, the stamping process will affect the first welding line 151 and reduce the connection strength of the first welding line 151. Similarly, if the distance between the boundary line 163 of the second end plate 13 and the second welding line 152 is less than 90 mm, the stamping process will affect the second welding line 152 and reduce the connection strength of the second welding line 152.

[0064] Continue to refer Figure 6a The wall thickness at the boundary line 163 is smaller than the wall thickness at the plane area 161 . The box body 1 further includes a reinforcing member 17 , which is disposed near the boundary line 163 .

[0065] Continue to refer Figure 4, along the width direction of the box body 1, the middle plate 12 includes a first part 121, a second part 122 and a third part 123 of different thicknesses, wherein the first part 121 is connected to one end of the second part 122, and the third part 123 is connected to the other end of the second part 122, the first part 121 is configured as a part of the front end wall of the box body 1, the second part 122 is configured as a part of the front end wall, a part of the bottom wall and a part of the rear end wall of the box body 1, and the third part 123 is configured as a part of the rear end wall of the box body 1. The first part 121 and the third part 123 serve as the pressure-bearing parts of the box body 1, so the thickness of the first part 121 and the third part 123 is greater than the thickness of the second part 122. In one example, the average thickness of the first part 121 and the third part 123 is set to 2.7 mm, and the average thickness of the second part 122 is set to 1.2 mm.

[0066] Along the width direction of the box body 1, the first part 121 is spliced ​​to one side of the second part 122 by laser welding, and the connection between the first part 121 and the second part 122 forms a third welding line 153. The third part 123 is spliced ​​to the other side of the second part 122 by laser welding, and the connection between the second part 122 and the third part 123 forms a fourth welding line 154. The third welding line 153 is connected between the first welding line 151 and the second welding line 152, and the fourth welding line 154 is connected between the first welding line 151 and the second welding line 152.

[0067] By setting the middle plate 12 to be a first part 121, a second part 122 and a third part 123, and setting the thickness of the first part 121 and the third part 123 as the pressure-bearing body to be greater than the thickness of the second part 122, the box body 1 can provide sufficient pressure-bearing force while also reducing the total weight of the box body 1, which is beneficial to the lightweight design of the battery pack.

[0068] Continue to refer Figure 8 The first end plate 11, the middle plate 12 and the second end plate 13 all include a substrate layer 181 and a first protective layer 182 formed on the substrate layer 181, wherein the substrate layer 181 includes a steel plate or an aluminum plate, and the first protective layer 182 includes a galvanized layer. The melting point of zinc is about 420°C, and the melting point of the steel plate is about 1500°C or higher. Therefore, during the laser welding process, the galvanized layer will first reach the melting point and melt, and then fill the weld, playing a role similar to welding wire, thereby reducing the need for additional welding wire during the laser welding process. At the same time, the material properties of the galvanized layer itself help to form a continuous and stable weld.

[0069] Continue to refer Figure 8The first end plate 11, the middle plate 12, and the second end plate 13 all include a substrate layer 181, a first protective layer 182, and a second protective layer 183. The first protective layer 182 is formed on the substrate layer 181, and the second protective layer 183 is formed on the first protective layer 182, wherein the first protective layer 182 includes a galvanized layer, and the second protective layer 183 includes an organic coating. The second protective layer 183 is configured as an organic coating formed by electrophoresis treatment of the entire welded part after the first end plate 11 and the middle plate 12 are laser welded to form a first weld line 151, and the second end plate 13 and the middle plate 12 are laser welded to form a second weld line 152 to form a welded part. The organic coating includes at least one of a film-forming resin, a cross-linking agent, a dispersant, a leveling agent, and a defoaming agent.

[0070] Since the first end plate 11 and the middle plate 12, and the middle plate 12 and the second end plate 13 are laser welded without filling welding wire, the first protective layer 182 will be partially damaged during the welding process. Therefore, after the welding is completed, the welded parts are electrophoretically treated to form a second protective layer 183, so as to compensate for the damage to the first protective layer 182, thereby enhancing the corrosion resistance of the box body 1 formed by welding.

[0071] Continue to refer Figure 5 , the thickness of the first end plate 11, the middle plate 12 and the second end plate 13 are all set to be greater than 0.5 mm, and the thickness of the first end plate 11, the middle plate 12 and the second end plate 13 is set to be less than 3 mm. In a specific implementation, the thickness of the first end plate 11, the middle plate 12 and the second end plate 13 is set to 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2.0 mm, 2.3 mm, 2.5 mm, 2.8 mm, 2.9 mm, and a value between any two of the above values ​​or a range between any two of the above values.

[0072] The inventors have found through research that when the thickness of the first end plate 11, the middle plate 12, and the second end plate 13 is set to be less than 0.5 mm, although the first end plate 11, the middle plate 12, and the second end plate 13 can be spliced ​​by laser welding to form a box body, the thickness of the box body 1 is not enough, which will lead to insufficient strength of the box body 1, thereby affecting the safety performance of the battery pack. When the thickness of the first end plate 11, the middle plate 12, and the second end plate 13 is set to be greater than 3 mm, it is difficult for high-energy lasers to penetrate the first end plate 11, the middle plate 12, and the second end plate 13, so there will be gaps on the back of the welded parts formed by laser welding, thereby affecting the connection strength of the first welding line 151 and the second welding line 152 formed.

[0073] Continue to refer Figure 4, the length of the battery case 1 is set to d, the length of the middle plate 12 extending along the length direction of the battery case is set to d1, the ratio of d1 to d is 0.5-0.8, the length of the first end plate 11 or the second end plate 13 extending along the length direction of the battery case is d2, and the ratio of d2 to d is 0.1-0.25. The ratio of d1+2d2 to d is 1. In a specific implementation, the length d of the battery case 1 is set to 1000mm-2500mm, the length d1 of the middle plate 12 is set to 500mm-2000mm, and the length d2 of the first end plate 11 or the second end plate 13 is set to 250mm-400mm.

[0074] When the battery box is adapted to vehicles of different lengths, it is usually configured to change the length d of the battery box 1 by changing the length d1 of the middle plate 12. For vehicles of different lengths, the ratio between d1 and d can be set to 0.5, 0.6, 0.7, 0.8, and a value between any two of the above values ​​or a range between any two of the above values. Correspondingly, the ratio between the length d2 of the first end plate 11 or the second end plate 13 and d can be set to 0.1, 0.15, 0.2, 0.25, and a value between any two of the above values ​​or a range between any two of the above values.

[0075] The embodiment of the present application also provides a method for manufacturing the box 1, such as Fig. 9 As shown, the manufacturing method of the box body 1 includes:

[0076] like Figure 7 As shown, a flat first end plate 11 is spliced ​​to one end of a flat middle plate 12 by laser welding, and a flat second end plate 13 is spliced ​​to the other end of the flat middle plate 12 by laser welding to form a welded part 4;

[0077] The welding 4 is punched through a punching die to form a box body 1 having two side walls, two end walls and a bottom wall structure.

[0078] Compared with the manufacturing method of the box body in the related art, which is first stamped and then welded, the embodiment of the present application adopts the method of first laser welding the flat first end plate 11, the middle plate 12 and the second end plate 13 to form a flat welded part 4, and then stamping the welded part 4 to form the box body 1. It is understandable that if the flat first end plate 11, the middle plate 12 and the second end plate 13 are first stamped to form a box structure with a side wall, an end wall and a bottom wall structure, and then the non-planar first end plate 11, the middle plate 12 and the second end plate 13 are spliced ​​by laser welding, it will be unfavorable to form a first welding line 151 and a second welding line 152 structure with consistent flatness, and it will also increase the difficulty of welding, thereby affecting the stability of the battery box structure and reducing the manufacturing efficiency of the box.

[0079] In some embodiments, the flat plate-shaped weldment is punched into a box body by a punching die, and the punching die is configured to be adjusted according to the length of the middle plate, so that the punching die can be used to prepare boxes of different length specifications.

[0080] Continue to refer Figure 8 The flat welding piece 4 is first subjected to electrophoresis treatment and then punched to form a box body.

[0081] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A battery box, characterized in that: include: A box body, the box body includes a middle plate and a first end plate, the first end plate is arranged at one end of the middle plate in the length direction of the box body, and the middle plate and the first end plate enclose at least a part of the battery installation cavity; wherein a first welding line is arranged at the connection between the middle plate and the first end plate, and the middle plate and the first end plate are located on opposite sides of the first welding line in the length direction of the box body.

2. The battery box according to claim 1, characterized in that: The box body also includes a second end plate, which is arranged at the other end of the middle plate in the length direction of the box body, and a second welding line is arranged at the connection between the middle plate and the second end plate, and the middle plate and the second end plate are located on opposite sides of the second welding line in the length direction of the box body.

3. The battery box according to claim 2, characterized in that: The orthographic projection of the first welding line and / or the second welding line on the plane where the bottom wall of the battery installation cavity is located is set to be a continuous straight line.

4. The battery box according to claim 2, characterized in that: The width of the first welding line and / or the second welding line is 2 mm to 4 mm.

5. The battery box according to claim 2, characterized in that: The first end plate comprises a first end plate plane area and a first end plate arc surface area, a first end plate dividing line extending along the height direction of the box body is arranged between the first end plate plane area and the first end plate arc surface area, and the minimum distance between the first end plate dividing line and the first welding line is set to be not less than 90 mm; and / or, the second end plate comprises a second end plate plane area and a second end plate arc surface area, a second end plate dividing line extending along the height direction of the box body is arranged between the second end plate plane area and the second end plate arc surface area, and the minimum distance between the second end plate dividing line and the second welding line is set to be not less than 90 mm.

6. The battery box according to claim 2, characterized in that: Along the width direction of the box body, the middle plate includes a first part, a second part and a third part, and the second part is arranged between the first part and the third part in the width direction of the box body; wherein the thickness of the first part is greater than the thickness of the second part, and the thickness of the third part is greater than the thickness of the second part.

7. The battery case according to claim 6, characterized in that: A third welding wire is provided at the connection between the first part and the second part, the first part and the second part are located on opposite sides of the third welding wire in the width direction of the box, and the third welding wire is connected between the first welding wire and the second welding wire; and / or a fourth welding wire is provided at the connection between the third part and the second part, the second part and the third part are located on opposite sides of the fourth welding wire in the width direction of the box, and the fourth welding wire is connected between the first welding wire and the welding wire.

8. The battery box according to claim 2, characterized in that: The middle plate, the first end plate and the second end plate together include a substrate layer and a first protective layer formed on the substrate layer in the thickness direction of the box body, the substrate layer includes a steel plate or an aluminum plate, and the first protective layer includes a zinc coating.

9. The battery case according to claim 8, characterized in that: The middle plate, the first end plate and the second end plate also jointly include a second protective layer, which is arranged on a side of the first protective layer away from the substrate layer, and includes an organic coating.

10. The battery case according to claim 8, characterized in that: The thickness of the middle plate, the first end plate and the second end plate are all set to be less than 3 mm, and the thickness of the middle plate, the first end plate and the second end plate are set to be greater than 0.5 mm.

11. The battery case according to any one of claims 2 to 10, characterized in that: The length of the battery case is set to d, the length of the middle plate extending along the length direction of the battery case is set to d1, the ratio of d1 to d is 0.5 to 0.8, the length of the orthographic projection of the first end plate or the second end plate on the plane where the bottom wall of the battery mounting cavity is located extending along the length direction of the battery case is d2, the ratio of d2 to d is 0.1 to 0.25; and / or, the ratio of d1+2d2 to d is 1.

12. The battery box according to claim 2, characterized in that: The box body includes a first supporting longitudinal beam, a second supporting longitudinal beam, and a supporting cross beam connected between the first supporting longitudinal beam and the second supporting longitudinal beam, wherein the first supporting longitudinal beam is connected to the first end plate, the second supporting longitudinal beam is connected to the second end plate, one end of the supporting cross beam extends to the outer side of the first welding line away from the second welding line, and the other end of the supporting cross beam extends to the outer side of the second welding line away from the first welding line.

13. A battery pack, characterized in that: The battery pack comprises the battery case according to any one of claims 1 to 12, and a plurality of batteries arranged in the battery case.

14. A method for manufacturing the battery case according to claim 1, characterized in that: The manufacturing method of the battery box comprises: Welding a flat first end plate to one end of a flat middle plate by laser welding, and welding a flat second end plate to the other end of the flat middle plate by laser welding to form a welded part; The welding piece is formed into the box body by stamping.

15. The method for manufacturing a battery case according to claim 14, characterized in that: The welding piece is punched by a punching die to form the box body, and the punching die is configured to be adjustable according to the length of the middle plate.

16. The method for manufacturing a battery case according to claim 14, characterized in that: Before the step of forming the box body by stamping the welded part, the method further includes: performing electrophoresis treatment on the welded part.

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