Battery cell casing, battery cell, and power device

Abstract

The present application relates to the technical field of battery cells, and discloses a battery cell casing, a battery cell, and a power device. The battery cell casing comprises a casing body. The casing body comprises a first connection edge and a second connection edge; the first connection edge and the second connection edge are connected by means of a weld seam; and a cavity used for accommodating an electrode assembly is defined inside. Along the width direction of the weld seam, the weld seam comprises a central zone and heat-affected zones located on two sides of the central zone. The tensile strength of the weld seam is K, with a unit of "MPa", and the tensile strength of the casing body is R, with a unit of "MPa", satisfying: 0.6≤K / R≤0.8. In a tensile test on a casing sample provided with a weld seam, the fracture position of the casing sample is not in the central zone. The present application can ensure that the weld seam has sufficient tensile strength, so that when the internal pressure of the battery cell rises, the battery cell casing would not crack in the central zone of the weld seam, thereby ensuring the safety performance of a battery and a vehicle.

Description

Battery cell shell, battery cell and power device

[0001] Cross-reference to related applications

[0002] The present application claims priority to the Chinese patent application No. 202410986658.8, filed on July 23, 2024, and entitled "Battery cell shell, battery cell and power device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of battery cells, in particular to a battery cell shell, a battery cell and a power device. BACKGROUND

[0004] The battery cell shell plays an important role in the safety of the battery cell.

[0005] Taking a blade battery cell shell as an example, the main forming process is laser welding after bending or high-frequency welding after rolling. The shell base material at the weld joint is fused and joined to form a battery cell shell with a cavity, and the electrode assembly is arranged in the battery cell shell.

[0006] After the battery cell works in an overcharged or high-temperature state, a large amount of gas is generated inside, causing the internal pressure to rise. The shell cannot bear the internal pressure of the battery cell, and cracking usually occurs at the weld joint, affecting the safety performance of the battery cell and the whole vehicle. SUMMARY

[0007] Therefore, the present application provides a battery cell shell, a battery cell and a power device to solve the problem that the battery cell is prone to cracking at the weld joint and has low safety.

[0008] In a first aspect, the present application provides a battery cell shell, comprising a shell body, the shell body comprising a first connecting edge and a second connecting edge, the first connecting edge and the second connecting edge being connected by a weld joint, and an internal cavity for accommodating an electrode assembly being surrounded by the weld joint; along the width direction of the weld joint, the weld joint comprises a central zone and a heat-affected zone on both sides of the central zone; the tensile strength of the weld joint is K, in units of "MPa", the tensile strength of the shell body is R, in units of "MPa", and satisfies: 0.6≤K / R≤0.8, and in the tensile test of the shell test sample with the weld joint, the fracture position of the shell test sample is not in the central zone.

[0009] Beneficial effects: the battery cell shell provided by the present application controls the ratio of the tensile strength K of the weld joint to the tensile strength R of the shell body in the range of 0.6 to 0.8, so that the weld joint has sufficient tensile strength, ensuring that when a large amount of gas is generated inside the battery cell after the battery cell works in an overcharged or high-temperature state, causing the internal pressure to rise, the battery cell shell will not crack at the central zone of the weld joint, thereby ensuring the safety performance of the battery and the whole vehicle, and being easy to weld, thereby controlling the welding cost.

[0010] In an optional embodiment, the tensile strength K of the weld is calculated by performing a tensile test on the shell sample, applying a tensile force along the width direction of the weld, K = F / (W x T), where F is the measured maximum tensile force value of the shell sample, in units of "N", W is the extension length of the weld, in units of "mm", and T is the thickness of the weld, in units of "mm".

[0011] In an optional embodiment, at least one side of the weld protrudes from the shell body, and the thickness of the shell body is t, in units of "mm", satisfying: 1.25 ≤ T / t ≤ 2.

[0012] In an optional embodiment, the thickness t of the shell body satisfies: 0.2 mm ≤ t ≤ 0.8 mm.

[0013] In an optional embodiment, the distance between any side of the central region and the center line of the weld is l, satisfying: 0.01 mm ≤ l ≤ 1 mm.

[0014] In an optional embodiment, the shell of the battery cell includes two oppositely arranged large faces and two oppositely arranged side faces, the area of the side face is smaller than the area of the large face, and the weld is located at any side face.

[0015] In an optional embodiment, the width of the shell sample is 20 mm ± 0.5 mm.

[0016] In an optional embodiment, the shell body is made of aluminum material.

[0017] In a second aspect, the present application further provides a battery cell, including an electrode assembly, a cover plate assembly, and the shell of the battery cell according to any one of the above technical solutions; the electrode assembly is arranged in the shell of the battery cell; and the cover plate assembly is arranged at the opening of the shell of the battery cell and encapsulates the electrode assembly in the shell of the battery cell.

[0018] Beneficial effects: Because the battery cell includes the shell of the battery cell, it has the same effects as the shell of the battery cell, which will not be repeated here.

[0019] In a third aspect, the present application further provides a power device, including the battery cell according to the above technical solutions.

[0020] Beneficial effects: Because the power device includes the battery cell, it has the same effects as the battery cell, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0022] Fig. 1 is a structural schematic view of an electric cell shell according to an embodiment of the present application;

[0023] Fig. 2 is a view of the electric cell shell shown in Fig. 1 along direction B;

[0024] Fig. 3 is an enlarged schematic view of part A in Fig. 2;

[0025] Fig. 4 is a structural schematic view of a weld of another electric cell shell according to an embodiment of the present application;

[0026] Fig. 5 is a structural schematic view of a shell sample according to an embodiment of the present application.

[0027] Legend of reference signs: 1, shell; 101, large face; 102, side face; 11, shell body; 2, weld; 201, central zone; 202, heat-affected zone; 3, shell sample. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0029] The following will describe the embodiments of the present application in combination with Figs. 1 to 5.

[0030] According to the embodiments of the present application, in one aspect, an electric cell shell 1 is provided, which comprises a shell body 11, the shell body 11 comprising a first connecting edge and a second connecting edge, the first connecting edge and the second connecting edge being connected by a weld 2, and the inside being surrounded to form a cavity for accommodating an electrode assembly; along the width direction of the weld 2, the weld 2 comprises a central zone 201 and heat-affected zones 202 located on both sides of the central zone 201; the tensile strength of the weld 2 is K, unit: "MPa", the tensile strength of the shell body 11 is R, unit: "MPa", and it is satisfied that 0.6≤K / R≤0.8, and in the tensile test of a shell sample 3 provided with the weld 2, the fracture position of the shell sample 3 is not in the central zone 201.

[0031] The ratio of the tensile strength K of the weld 2 to the tensile strength R of the shell body 11 is less than 0.6, the strength at the weld 2 cannot meet the use requirements of the battery cell, the ratio of the tensile strength K of the weld 2 to the tensile strength R of the shell body 11 is greater than 0.8, the effect of improving the strength is not obvious, and the welding difficulty is too high to be realized, and the cost will be greatly increased. Therefore, the battery cell shell 1 provided in the embodiments of the present application controls the ratio of the tensile strength K of the weld 2 to the tensile strength R of the shell body 11 in the range of 0.6 to 0.8, so that the weld 2 has sufficient tensile strength, and when a large amount of gas is generated inside the battery cell after working in an overcharged or high-temperature state to cause the internal pressure to rise, the battery cell shell 1 will not crack at the center area 201 of the weld 2, thereby ensuring the safety performance of the battery and the whole vehicle, and the welding is easy and the welding cost is controlled.

[0032] In some embodiments, the tensile strength K of the weld 2 is calculated by tensile test of the shell sample 3, the tensile force is applied along the width direction of the weld 2, K=F / (WxT), wherein F is the maximum tensile force value of the shell sample 3 actually measured, the unit is “N”, W is the extension length of the weld 2, the unit is “mm”, and T is the thickness of the weld 2, the unit is “mm”.

[0033] Specifically, the following is a test method for the welding strength of the shell 1, including the following steps:

[0034] The shell 1 high-frequency welding part is sampled, and the sampling size is required to be 100mmx20mm according to the standard shell sample 3 specification.

[0035] As shown in FIG. 5, the length of the shell sample 3 is L, L=100mm, and the width of the shell sample 3, i.e. the extension length W of the weld 2, is 25mm. Taking the shell 1 with a wall thickness of 0.35mm as an example, the material is Al3003H18, and the thickness of the weld 2 is 0.45mm.

[0036] The maximum tensile force value F of the weld 2 at the time of fracture is tested by a tensile testing machine, and then the actual tensile strength K of the weld 2 is F / (20x0.45). According to the actually measured K value and the tensile strength R of the shell body 11, it is judged whether the K / R value is within the range of 0.6-0.8, and at the same time, it is observed whether the fracture position of the shell sample 3 is located in the center area 201. Both conditions are met, then the tensile strength of the weld 2 of the battery cell shell 1 is qualified, if any condition is not met, then the tensile strength of the weld 2 of the battery cell shell 1 is unqualified.

[0037] In some embodiments, as shown in FIG. 4, the distance between any side edge of the center area 201 and the center line of the weld 2 is l, which satisfies: 0.01mm≤l≤1mm.

[0038] That is, along the width direction of the weld 2, the range of 0.01mm-1mm extending to both sides from the center line of the weld 2 is the center area 201. The numerical range can determine whether the fracture position of the shell sample 3 in the tensile test is located in the center area 201 of the weld 2. When the fracture position of the shell sample 3 is in the center area 201, it indicates that the welding strength of the cell shell 1 is unqualified, and when the fracture position of the shell sample 3 is in the heat-affected zone 202, it is acceptable.

[0039] In some embodiments, the surface of at least one side of the weld 2 protrudes from the shell body 11, and the thickness t of the shell body 11 is "mm", which satisfies: 1.25≤T / t≤2.

[0040] In order to ensure the strength of the shell 1 itself, the ratio of the thickness T of the weld 2 to the thickness t of the shell body 11 needs to be controlled within the range of 1.25 to 2. If the ratio of the thickness T of the weld 2 to the thickness t of the shell body 11 is too large, the thickness t of the shell body 11 will be too small, resulting in insufficient strength of the shell body 11; if the ratio of the thickness T of the weld 2 to the thickness t of the shell body 11 is too small, the total thickness of the protruding part of the weld 2 from the shell body 11 accounts for a small proportion of the thickness T of the weld 2, resulting in weak strength at the weld 2, and at the same time, the thickness of the shell body 11 is too large, the substrate is too thick, which affects the space utilization and battery capacity of the cell, and is not conducive to the weight reduction and cost reduction of the cell. Therefore, the cell shell 1 satisfies 1.25≤T / t≤2, which can not only ensure the strength of the weld 2, but also ensure the strength of the shell body 11, and at the same time, can ensure the space utilization and battery capacity of the cell, which is conducive to the weight reduction and cost reduction of the cell.

[0041] In some embodiments, the thickness t of the shell body 11 satisfies: 0.2mm≤t≤0.8mm.

[0042] By controlling the thickness t of the shell body 11 within the range of 0.2mm to 0.8mm, the thickness of the shell body 11 is not too small, which can further ensure the strength of the shell body 11, and at the same time, the thickness of the shell body 11 is not too large, which can ensure that the shell body 11 does not affect the capacity and weight reduction of the cell.

[0043] In some embodiments, as shown in FIG. 1, the cell shell 1 includes two oppositely arranged large faces 101 and two oppositely arranged side faces 102, the area of the side face 102 is smaller than the area of the large face 101, and the weld 2 is located at any side face 102.

[0044] In this way, the space occupied by the cell when packaged into a group can be reduced.

[0045] In some embodiments, the width of the shell sample 3 is 20mm±0.5mm.

[0046] In this way, the shell sample 3 can match the clamps of various types of tensile testing machines, and the width of the shell sample 3 is too large to completely cover the clamping, which can affect the test results. If the width of the shell sample 3 is too small, it is too easy to be pulled apart, and the measurement failure problem can occur.

[0047] In some embodiments, the shell body 11 is made of aluminum material.

[0048] In some embodiments, as shown in FIG. 4, the surfaces on both sides of the weld 2 protrude from the shell body 11.

[0049] Since the tensile strength R of the shell body 11 is the inherent physical property of the selected material, after selecting the material brand, there is a clear national standard or industry standard mechanical property requirement.

[0050] The following is a comparative description combined with examples.

[0051] Different shell bodies 1 are selected, the thickness t of the shell body 11 and the thickness T of the weld 2 are different, the maximum tensile force that the weld 2 can withstand is tested, and the tensile strength K of the weld 2 is calculated.

[0052] The specific test method is as follows:

[0053] Select the shell sample 3 with different wall thicknesses of the shell body 1 with the weld 2, clamp the two ends of the shell sample 3 in the length direction by the tensile testing machine, apply tension to the shell sample 3 by the tensile testing machine until the shell sample 3 is broken, record the maximum tensile force value and the breaking position when the shell sample 3 is broken, and the calculated weld 2 strength should satisfy 0.6≤K / R≤0.8, and the breaking position is not in the middle of the weld 2, which means that the strength of the weld 2 can meet the use requirements of the battery cell.

[0054] There are two notes here:

[0055] 1. The selected shell sample 3 should have the weld 2 in the center position of the shell sample 3, and should not be biased to one side to avoid errors in the tensile force measurement.

[0056] 2. Fold and unfold the shell sample 3 taken from the battery shell 1, and pay attention to avoid stress at the weld 2 when folding to avoid affecting the tensile test results.

[0057] The following will test and compare the battery shell 1 with the material brand Al 3003H18. The tensile strength R of this brand of aluminum material is 190 MPa. According to the ratio relationship between K and R, K should satisfy 114 MPa≤K≤152 MPa. Test each tensile force value and calculate the corresponding tensile strength. The examples and comparative examples are described in detail, and the details are shown in the following table.

[0058] Table 1: Tensile strength test results of examples.

[0059] Table 2: Tensile strength test results of the comparative examples.

[0060] From the comparison of Table 2 and Table 1, it can be seen that:

[0061] 1. According to Comparative Example 1 and Example 1, when t is constant, if T / t is too small, T will also be too small, that is, the thickness of weld 2 is too small, resulting in K being too small, and the strength of weld 2 does not meet the requirements.

[0062] 2. According to Comparative Example 6 and Example 7, when t is constant, if T / t is too large, T will also be too large, that is, the thickness of weld 2 is too large, and it is found through actual measurement and calculation that the increase of K is not obvious, but due to the too large T, the internal space of the battery cell is insufficient, affecting the capacity of the battery cell, and thus does not meet the requirements.

[0063] 3. According to Comparative Example 2 and Example 2, when T / t is constant, if t becomes smaller, T will also become smaller, that is, the thickness of weld 2 becomes smaller, and the actual measured and calculated K value becomes significantly smaller, indicating that the smaller T has a weakening effect on the strength of weld 2, and since the value of t does not exceed the lower limit, T will not be too small, and although K decreases in actual testing, K / R is still within the specified range.

[0064] 4. According to Comparative Example 5 and Example 6, when T / t is constant, if t becomes larger, T will also become larger, that is, the thickness of weld 2 becomes larger, and the actual measured and calculated K value also becomes larger, indicating that the larger T has a strengthening effect on the strength of weld 2, and since the value of t does not exceed the upper limit, T will not be too large, and thus K increases without affecting the internal space and capacity of the battery cell.

[0065] 5. According to Comparative Example 3 and Example 3, when t becomes smaller and even exceeds the lower limit, and T / t exceeds the upper limit value, T has already taken a relatively large value, at this time the fracture position is at the shell body 11, that is, the strength of weld 2 has already far exceeded the strength of the shell body 11, but the measured and calculated K value is too small, that is, the strength of the shell 1 itself is insufficient and still does not meet the requirements.

[0066] 6. According to Comparative Example 4 and Example 4, when t becomes larger, but T / t is too small and exceeds the lower limit, the value of T will become smaller, at this time the actual measured and calculated K value becomes larger, but the fracture position is at the center of weld 2, which is due to the fact that the shell body 11 occupies a large proportion of the thickness of weld 2, and accordingly, the total thickness of the protruding part of weld 2 occupies a small proportion of the thickness of weld 2, resulting in poor strength at weld 2, and the change in tensile strength of the shell body 11 is not obvious, and the increase in the thickness of the shell body 11 will result in a decrease in the internal space and capacity of the battery cell, and thus does not meet the requirements.

[0067] According to the embodiments of the present application, the second aspect further provides an electric core, comprising an electrode assembly, a cover plate assembly and the electric core shell 1 in any one of the above embodiments; the electrode assembly is arranged in the electric core shell 1; the cover plate assembly is arranged at the opening of the electric core shell 1 and encapsulates the electrode assembly in the electric core shell 1.

[0068] Because the electric core comprises the electric core shell 1 and the electric core shell 1 is safe and reliable, the electric core and the whole battery adopting the electric core shell 1 have high safety performance, and the remaining effects are the same, which will not be described here.

[0069] According to the embodiments of the present application, the third aspect further provides a power device, comprising the electric core in the above embodiments.

[0070] Because the power device comprises the electric core, it has the same effects as the electric core, which will not be described here.

[0071] Although the embodiments of the present application are described in combination with the drawings, various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electric cell housing, characterized by, The shell body includes a first connecting edge and a second connecting edge connected by a weld seam, and internally forms a cavity for accommodating an electrode assembly; The weld seam includes a central zone and heat-affected zones on both sides of the central zone along the width direction of the weld seam; the tensile strength of the weld seam is K, in units of "MPa", and the tensile strength of the shell body is R, in units of "MPa", satisfying: 0.6≤K / R≤0.8, and in a tensile test on a shell sample with the weld seam, the fracture position of the shell sample is not in the central zone; Wherein, The tensile strength K of the weld seam is calculated by a tensile test on a shell sample, a tensile force is applied along the width direction of the weld seam, K=F / (W×T), wherein F is the measured maximum tensile force value of the shell sample, in units of "N", W is the extension length of the weld seam, in units of "mm", and T is the thickness of the weld seam, in units of "mm"; The tensile strength R of the shell body is determined according to the corresponding national or industry standard mechanical property requirements after selecting the material grade.

2. The cell case of claim 1, wherein, The surface of at least one side of the weld seam protrudes from the shell body, the thickness of the shell body is t, in units of "mm", satisfying: 1.25≤T / t≤2.

3. The cell housing of claim 2, wherein, The thickness t of the shell body satisfies: 0.2mm≤t≤0.8mm.

4. The cell case according to any one of claims 1 to 3, characterized in that, The distance between any side of the central zone and the center line of the weld seam is l, satisfying: 0.01mm≤l≤1mm.

5. The cell case according to any one of claims 1 to 3, characterized in that, The shell body includes two oppositely arranged large faces and two oppositely arranged side faces, the area of the side face is smaller than that of the large face, and the weld seam is located at any of the side faces.

6. The cell case according to any one of claims 1 to 3, characterized in that, The width of the shell sample is 20mm±0.5mm.

7. The cell case according to any one of claims 1 to 3, characterized by, The shell body is made of aluminum material.

8. An electric cell characterized by Comprise: The shell body of any one of claims 1 to 7; The electrode assembly is arranged in the shell body; The cover plate assembly is arranged at the opening of the shell body and encapsulates the electrode assembly in the shell body.

9. A power plant characterized by The shell body of claim 8.

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