Secondary battery and automobile

Abstract

The invention relates to a secondary battery and an automobile. A secondary battery includes an electrode assembly, a case, and a cap assembly. The housing has an opening. The top cover assembly is connected to the opening of the shell and forms a packaging space, the electrode assembly is packaged in the packaging space, the top cover assembly comprises a top cover piece and an anti-explosion valve connected to the top cover piece, the anti-explosion valve comprises a flat base part and a protruding part connected to the flat base part, and the protruding part protrudes in the direction away from the electrode assembly relative to the flat base part. The protruding part is provided with a transverse straight nick and a branch nick connected to one end of the transverse straight nick, and a non-zero angle is formed between the transverse straight nick and the branch nick.

Description

[0001] This application is a divisional application of the application with the application number 201810020462.8, the application date of January 9, 2018, the applicant of CATL New Energy Technology Co., Ltd., and the application name of "Explosion-proof valve for secondary battery top cover, top cover assembly, secondary battery and vehicle". Technical Field

[0002] This application relates to the technical field of energy storage devices, and particularly to a secondary battery and a vehicle. Background Art

[0003] A secondary battery can be charged and discharged. If the secondary battery is in the following situations, such as overcharging, being pierced by a metal conductor through the electrode plate, and during a hot box test, heat and gas will rapidly accumulate inside the secondary battery, resulting in an increase in the internal pressure of the secondary battery, and in severe cases, causing the secondary battery to expand and explode.

[0004] A secondary battery is usually provided with an explosion-proof valve. When the internal pressure of the secondary battery increases to the opening pressure of the explosion-proof valve, the internal gas is released from the explosion-proof valve, thereby avoiding dangerous accidents such as the explosion of the secondary battery. Summary of the Invention

[0005] This application provides a secondary battery and a vehicle, aiming to improve the safety of the secondary battery.

[0006] This application provides a secondary battery, which includes an electrode assembly, a housing, and a top cover assembly. The housing has an opening. The top cover assembly is connected to the opening of the housing and forms a sealed space, and the electrode assembly is encapsulated in the sealed space. The top cover assembly includes a top cover sheet and an explosion-proof valve connected to the top cover sheet. The explosion-proof valve includes a flat base portion and a raised portion connected to the flat base portion. The raised portion protrudes away from the electrode assembly relative to the flat base portion. The raised portion is provided with a horizontal straight notch and a branch notch connected to one end of the horizontal straight notch, and the horizontal straight notch and the branch notch form a non-zero angle.

[0007] Optionally, the raised portion has a ridge-shaped sharp corner, and the inner surface of the explosion-proof valve opposite to the raised portion has a concave portion corresponding to the shape of the raised portion.

[0008] Optionally, both the horizontal straight notch and the branch notch are provided at the top of the ridge-shaped sharp corner, and / or

[0009] Both the horizontal straight notch and the branch notch are provided at the bottom of the concave portion corresponding to the ridge-shaped sharp corner.

[0010] Optionally, there are at least two branch notches. The two branch notches are connected to the same end of the horizontal straight notch and form a Y-shaped structure with the horizontal straight notch.

[0011] Optionally, two branch notches are connected to both ends of the horizontal and vertical notch; the two branch notches connected to the same end of the horizontal and vertical notch are symmetrical.

[0012] Optionally, in the width direction of the explosion-proof valve, a part of the flat base is located between the two branch notches.

[0013] Optionally, the angle between the branch notch and the horizontal and vertical notch is 120°-150°.

[0014] Optionally, the length of the horizontal and vertical notch is 1.5 to 2.5 times the length of the branch notch.

[0015] Optionally, the explosion-proof valve further includes a transition portion, the raised portion is connected to the flat base through the transition portion, and the transition portion is inclined relative to the flat base.

[0016] Optionally, the inclination angle of the transition portion is 2°-15°.

[0017] Optionally, the transition portion surrounds the raised portion, and the flat base surrounds the transition portion.

[0018] Optionally, the explosion-proof valve includes an edge connection portion surrounding the flat base, the edge connection portion is connected to the top cover sheet, and the thickness of the edge connection portion is greater than the thickness of the flat base.

[0019] This application also provides an automobile, including the secondary battery described above.

[0020] The technical solution provided by this application can achieve the following beneficial effects:

[0021] This application provides an explosion-proof valve for a secondary battery top cover assembly. The explosion-proof valve includes a raised portion protruding outward relative to the flat base. A horizontal and vertical notch and a branch notch connecting the horizontal and vertical notch are provided on the raised portion. When the pressure inside the housing is excessively increased, stress concentration occurs at the raised portion and the explosion-proof valve is torn from the horizontal and vertical notch and the branch notch, so that the gas inside the housing can be released, thereby reducing the risk of explosion of the secondary battery and improving the safety of the secondary battery.

[0022] It should be understood that the above general description and the following detailed description are only exemplary and do not limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is an exploded view of the secondary battery provided by the embodiment of this application;

[0024] Figure 2 is a top view of the secondary battery top cover assembly provided by the embodiment of this application;

[0025] Figure 3 is an exploded view of the secondary battery top cover assembly provided by the embodiment of this application;

[0026] Figure 4 Schematic diagram of the explosion-proof valve of the secondary battery top cover assembly provided by the embodiment of the present application;

[0027] Figure 5 Cross-sectional view of a partial structure of the explosion-proof valve provided by the embodiment of the present application;

[0028] Figure 6 Cross-sectional view of a partial structure of the explosion-proof valve provided by another embodiment of the present application.

[0029] Reference numerals:

[0030] 1000 - secondary battery;

[0031] 100 - housing;

[0032] 200 - top cover assembly;

[0033] 202 - top cover sheet;

[0034] 202a - explosion-proof port;

[0035] 204 - first terminal board;

[0036] 206 - second terminal board;

[0037] 208 - explosion-proof valve;

[0038] 2082 - edge connection part;

[0039] 2084 - central exhaust part;

[0040] 20842 - flat base part;

[0041] 20844 - raised part;

[0042] 20844a - horizontal and vertical notch;

[0043] 20844b - branch notch;

[0044] 20846 - transition part;

[0045] 300 - electrode assembly;

[0046] 302 - first pole tab;

[0047] 304 - second pole tab;

[0048] 400 - insulating film;

[0049] 500 - first current collector;

[0050] 502 - first pole tab connection part;

[0051] 600 - The second current collector;

[0052] 602 - The second tab connection part.

[0053] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application. Detailed embodiments

[0054] The following will further describe this application in detail through specific embodiments in conjunction with the accompanying drawings.

[0055] It should be noted that the orientation words such as "upper", "lower", "left", and "right" described in the embodiments of this application are described from the angles shown in the accompanying drawings and should not be construed as limitations on the embodiments of this application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0056] Please refer to Figure 1 , Figure 1 , which shows an exploded view of a secondary battery.

[0057] The secondary battery 1000 includes a housing 100, a secondary battery top cover assembly 200 (hereinafter referred to as the top cover assembly), an electrode assembly 300, and an insulating film 400. Among them, the electrode assembly 300 and the insulating film 400 are accommodated in the housing 100, the electrode assembly 300 is wrapped by the insulating film 400, the opening of the housing 100 can be sealed by the top cover assembly 200, and the contact part between the top cover assembly 200 and the housing 100 can be connected to each other by, for example, welding.

[0058] The electrode assembly 300 is made by winding or laminating, and it includes a first pole piece, a second pole piece, and a separator for separating the first pole piece and the second pole piece. Here, the first pole piece can be used as the negative electrode piece, and the second pole piece can be used as the positive electrode piece, and vice versa.

[0059] Both the first pole piece and the second pole piece include a coated part coated with active material and an uncoated part not coated with active material. Since the materials of the active materials coated on the first pole piece and the second pole piece are different, the first pole piece and the second pole piece can have different polarities from each other.

[0060] For example, the first pole piece is the positive electrode piece, and the active material coated on the positive electrode piece can be lithium iron phosphate, lithium cobaltate, lithium manganate, etc. The second pole piece is the negative electrode piece, and the active material coated on the negative electrode piece can be carbon or silicon. The uncoated part of the first pole piece forms the first tab 302, and the uncoated part of the second pole piece forms the second tab 304.

[0061] The secondary battery further includes a first current collector 500 and a second current collector 600. The first electrode tab and the second electrode tab of the electrode assembly 300 can be respectively connected to the first current collector 500 and the second current collector 600. The first current collector 500 is made of a conductive material and is connected to the first electrode tab 302 located at one end of the electrode assembly 300 so as to be connected to the first electrode tab.

[0062] The first current collector 500 includes a first terminal connection portion and a first electrode tab connection portion 502. The first electrode tab connection portion 502 is connected to the first electrode tab 302, and the first terminal connection portion is connected to a first electrode terminal (not shown in the drawings) of the top cover assembly 200. A connection hole is provided on the first terminal connection portion, and the first electrode terminal is arranged to match the connection hole so as to accommodate the first electrode terminal in the connection hole. The first electrode terminal and the first terminal connection portion can be connected to each other by, for example, welding.

[0063] The second current collector 600 is made of a conductive material and is connected to the second electrode tab 304 located at one end of the electrode assembly 300 so as to be connected to the second electrode tab.

[0064] The second current collector 600 includes a second terminal connection portion and a second electrode tab connection portion 602. The second electrode tab connection portion 602 is connected to the second electrode tab 304, and the second terminal connection portion is connected to a second electrode terminal (not shown in the drawings) of the top cover assembly 200. A connection hole is provided on the second terminal connection portion, and the second electrode terminal is arranged to match the connection hole so as to accommodate the second electrode terminal in the connection hole. The second electrode terminal and the second terminal connection portion can be connected to each other by, for example, welding.

[0065] It should be noted that Figure 1 Although the case where the first electrode tab 302 and the second electrode tab 304 protrude from the side of the electrode assembly 300 is shown, the structure of the electrode assembly 300 is not limited thereto.

[0066] Please refer to Figure 2 , Figure 2 which shows a top view of the top cover assembly.

[0067] The top cover assembly 200 includes a top cover sheet 202, a first electrode terminal, and a second electrode terminal (not shown in the drawings). A terminal hole (not shown in the drawings) is formed in the top cover sheet 202 to allow the first electrode terminal and the second electrode terminal to protrude outward. Exemplarily, the portion of the first electrode terminal protruding from the top cover sheet 202 is connected to the first terminal plate 204 and then connected to an external conductive terminal.

[0068] A similar structure can also be applied to the second electrode terminal, that is, the portion of the second electrode terminal protruding from the top cover sheet 202 is connected to the second terminal plate 206.

[0069] The top cover assembly 200 further includes an explosion-proof valve 208, which is connected to the top cover sheet 202 and is connected to a portion approximately in the center of the top cover sheet 202.

[0070] Please refer to Figure 3 , Figure 3 which shows an exploded view of the top cover assembly.

[0071] The top cover sheet 202 is provided with an explosion-proof opening 202a, and the explosion-proof valve 208 seals the explosion-proof opening 202a. Exemplarily, the explosion-proof opening 202a is set as an oval opening, and the outer shape of the explosion-proof valve 208 matches the outer shape of the explosion-proof opening 202a. The explosion-proof valve 208 includes an edge connection portion 2082 and a central exhaust portion 2084. Among them, the edge connection portion 2082 is hermetically connected to the top cover sheet 202 and is connected to the perimeter of the explosion-proof opening 202a, and the central exhaust portion 2084 allows the gas inside the housing 100 to be discharged after being torn.

[0072] In an exemplary embodiment, the thickness of the edge connection portion 2082 can be greater than the thickness of the central exhaust portion 2084, so as to form a more reliable connection between the edge connection portion 2082 and the top cover sheet 202. The edge connection portion 2082 is connected to the inner surface of the top cover sheet 202, and the connection method can be welding, such as laser welding.

[0073] Please refer to Figure 4 , Figure 4 which shows a top view of the explosion-proof valve.

[0074] The central exhaust portion 2084 includes a flat base portion 20842 and a raised portion 20844 that protrudes outward relative to the flat base portion 20842. Among them, the flat base portion 20842 has a flat surface, and the raised portion 20844 bulges from the flat base portion 20842 toward the side away from the electrode assembly 300 (toward the outside of the top cover assembly 200) to form a protruding structure.

[0075] The raised portion 20844 is provided with a straight horizontal notch 20844a in a straight line shape and a branch notch 20844b connected to the end of the straight horizontal notch 20844a. The straight horizontal notch 20844a extends along the length direction of the oval explosion-proof valve 208, and the angle formed by the branch notch 20844b and the straight horizontal notch 20844a is not zero. When the internal pressure in the housing 100 is greater than the preset pressure (for example, when excessive gas is generated due to overcharging), at this time, the straight horizontal notch 20844a and the branch notch 20844b can be opened faster than other parts of the housing 100 to form a tear opening for gas ejection. This tear opening can quickly release the gas inside the housing 100 to relieve the internal pressure of the housing 100, thereby reducing the risk of explosion of the secondary battery.

[0076] Please refer to Figure 5 ,Figure 5 A cross-sectional view of the explosion-proof valve is shown.

[0077] The raised portion 20844 bulges toward the side away from the inner space of the housing 100 and is ridge-shaped. Both the horizontal straight notch 20844a and the branch notch 20844b are provided at the top of the ridge-shaped sharp corner. Since a recessed portion is formed at the corresponding position on the inner surface after the raised portion 20844 bulges, when there is sufficient internal pressure in the housing 100, the internal pressure of the housing 100 can act concentratedly within the recessed portion, that is, at the top of the ridge-shaped sharp corner. At this time, the horizontal straight notch 20844a and the branch notch 20844b provided at the top of the raised portion 20844 can be quickly torn under the action of a preset pressure to instantaneously respond to the excessively increased gas pressure within the housing 100.

[0078] Optionally, please refer to Figure 6 , the horizontal straight notch 20844a and the branch notch 20844b can also be provided on the inner surface of the raised portion 20844 facing the electrode assembly 300, that is, at the bottom of the recessed portion. Similarly, under the action of the internal pressure of the housing 100, gas accumulates within the recessed portion and stress concentration is formed at the horizontal straight notch 20844a and the branch notch 20844b. After the horizontal straight notch 20844a and the branch notch 20844b are torn, the gas quickly ejects.

[0079] It is known that the raised portion 20844 bulges outward relative to the flat base portion 20842 instead of bending toward the inner space of the housing 100. This setting is to avoid fatigue fracture of the central exhaust portion 2084 due to repeated expansion under internal pressure and to prevent the defect of the opening pressure of the explosion-proof valve 280 from decreasing.

[0080] Please continue to refer to Figure 4 , in order to increase the area of the tear opening formed at the horizontal straight notch 20844a and the branch notch 20844b, at the same end of the horizontal straight notch 20844a, the branch notch 20844b can be provided in two. In this way, the two branch notches 20844b and one horizontal straight notch 20844a can form a notch approximately in the shape of a Y. The Y-shaped notch can increase the opening area after tearing, thereby increasing the flow rate when the gas is discharged.

[0081] Further, in order to quickly open the explosion-proof valve 208, both ends of the horizontal and vertical notch 20844a can be respectively configured as Y-shaped notches, that is, two branch notches 20844b are connected to both ends of the horizontal and vertical notch 20844a. After such a configuration, two intersections are formed between both ends of the horizontal and vertical notch 20844a and the two branch notches 20844b. The central exhaust portion 2084 can be first torn from the two intersections and quickly form a torn opening that is connected and penetrates the flat base portion 20842. At this time, the torn opening allows gas to release the pressure inside the housing 100 with a larger exhaust volume.

[0082] The two branch notches 20844b provided at the same end of the horizontal and vertical notch 20844a can be symmetrically arranged with respect to the straight line where the horizontal and vertical notch 20844a is located. In this way, the lengths of the respective branch notches 20844b are equal, and the angles between the branch notches 20844b and the horizontal and vertical notch 20844a are equal. Under the action of the internal pressure of the housing 100, the intersection of the two branch notches 20844b and the horizontal and vertical notch 20844a is the starting point of tearing. Starting from this starting point of tearing, the central exhaust portion 2084 can be synchronously torn along the two branch notches 20844b and a horizontal and vertical notch 20844a until the torn opening is completely opened, thereby shortening the time for releasing the gas inside the housing 100 and improving the safety of the secondary battery.

[0083] According to an exemplary embodiment, the angle θ between each branch notch 20844b and the horizontal and vertical notch 20844a can be selected within the range of 120° to 150°. Through analysis, it can be known that within this range, when the torn opening extends along three paths from the intersection of the three, the three notches can maintain synchronization when opened when the angles formed are approximately equal. This is because when the gas jets out quickly, the stress concentration point is the intersection of the three notches. This intersection is opened first and radially tears the central exhaust portion 2084 with this point as the center. If the angles between the three notches are approximately equal, the impact force of the gas received at each notch is basically equal, and the three notches can be synchronously torn under the same gas impact force.

[0084] In an alternative embodiment, the angle between each branch notch 20844b and the horizontal and vertical notch 20844a can be further selected within the range of 130° to 140°. At this time, the interval angles of the three notches are more equal. When the central exhaust portion 2084 is torn at the notch, the tearing process of the branch notch 20844b and the horizontal and vertical notch 20844a will be faster, smoother, and the area of the torn opening is larger.

[0085] On the other hand, in terms of improving the synchronization of tearing, the present application also sets the length of the horizontal and vertical score line 20844a to be 1.5 to 2.5 times the length of the branch score line 20844b. The length of the horizontal and vertical score line 20844a refers to the length of the horizontal and vertical score line 20844a along its extending direction (as Figure 2 shown, the extending direction of the horizontal and vertical score line 20844a is parallel to the length direction of the top cover sheet), and the length of the branch score line 20844b refers to the length of the branch score line 20844b along its extending direction (as Figure 2 shown, the extending direction of the branch score line 20844b forms a non-zero angle with the extending direction of the horizontal and vertical score line 20844a). For the solution where the branch score lines 20844b are respectively arranged at both ends of the horizontal and vertical score line 20844a, there is a situation where tearing starts simultaneously from two initial tearing points. At each initial tearing point, if tearing is performed along three score lines with approximately equal lengths respectively, the three tearing paths are basically equal, and thus the time required for tearing the two Y-shaped score lines is approximately equal, and they are almost simultaneously torn, so that it can be ensured that the explosion-proof valve 208 takes less time to fully open.

[0086] In an optional embodiment, the length of the horizontal and vertical score line 20844a can be further set to be 1.8 to 2.2 times the length of the branch score line 20844b. In this way, the lengths of the three score lines intersecting at the same initial tearing point are closer, and the synchronization of opening the two Y-shaped score lines is higher.

[0087] Please refer to Figure 4 again. The central exhaust part 2084 further includes a transition part 20846. The raised part 20844 is connected to the flat base part 20842 via the transition part 20846, and the transition part 20846 is inclined relative to the flat base part 20842. The transition part 20846 can make the raised part 20844 gradually protrude relative to the flat base part 20842 and form a ridge-like protrusion with a gradually increasing height. At the same time, the transition part 20846 can also play a role in guiding the gas in the housing 100 to accumulate in the concave part, and finally a stress concentration phenomenon of tearing the horizontal and vertical score line 20844a and the branch score line 20844b is formed in the concave part.

[0088] In an exemplary embodiment, the inclination angle α of the transition part 20846 can be set to 2° to 15° (see Figure 6 ). The explosion-proof valve 208 is processed by a stamping process. The transition part 20846 can provide an auxiliary function for the raised part 20844 to protrude a preset height relative to the flat base part 20842. At the same time, the setting of the transition part 20846 can improve the processability of the raised part 20844 and avoid the central exhaust part 2084 from cracking due to the excessive raising of the raised part 20844.

[0089] Optionally, the inclination angle α of the transition portion 20846 can be further set to 3° to 6°.

[0090] The present application also provides an automobile, which includes the secondary battery in any of the above embodiments.

[0091] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A secondary battery, characterized in that, Comprising: An electrode assembly; A housing having an opening; And A top cover assembly connected to the opening of the housing and forming a packaging space, the electrode assembly being encapsulated in the packaging space. The top cover assembly includes a top cover sheet and an explosion-proof valve connected to the top cover sheet. The explosion-proof valve includes a flat base portion and a raised portion connected to the flat base portion. The raised portion protrudes away from the electrode assembly relative to the flat base portion. The raised portion is provided with a horizontal straight notch and a branch notch connected to one end of the horizontal straight notch. The horizontal straight notch and the branch notch form a non-zero angle.

2. The secondary battery according to claim 1, characterized in that, The raised portion has a ridge-shaped sharp corner, and the inner surface of the explosion-proof valve opposite to the raised portion has a recess corresponding to the shape of the raised portion.

3. The secondary battery according to claim 2, characterized in that, Both the horizontal straight notch and the branch notch are provided at the top of the ridge-shaped sharp corner, and / or Both the horizontal straight notch and the branch notch are provided at the bottom of the recess corresponding to the ridge-shaped sharp corner.

4. The secondary battery according to claim 1, characterized in that, There are at least two branch notches. The two branch notches are connected to the same end of the horizontal straight notch and form a Y-shaped structure with the horizontal straight notch.

5. The secondary battery according to claim 4, characterized in that, Two branch notches are connected to both ends of the horizontal straight notch; The two branch notches connected to the same end of the horizontal straight notch are symmetric.

6. The secondary battery according to claim 4, characterized in that, In the width direction of the explosion-proof valve, a part of the flat base portion is located between the two branch notches.

7. The secondary battery according to claim 1, characterized in that, The angle between the branch notch and the horizontal straight notch is 120° - 150°.

8. The secondary battery according to claim 1, characterized in that, The length of the horizontal straight notch is 1.5 times to 2.5 times the length of the branch notch.

9. The secondary battery according to any one of claims 1-8, characterized in that, The explosion-proof valve further includes a transition portion. The raised portion is connected to the flat base portion via the transition portion. The transition portion is inclined relative to the flat base portion.

10. The secondary battery according to claim 9, characterized in that, The inclination angle of the transition portion is 2° - 15°.

11. The secondary battery according to claim 9, characterized in that, The transition portion surrounds the raised portion, and the flat base portion surrounds the transition portion.

12. The secondary battery according to claim 1, characterized in that, The explosion-proof valve includes an edge connection portion surrounding the flat base portion. The edge connection portion is connected to the top cover sheet, and the thickness of the edge connection portion is greater than the thickness of the flat base portion.

13. An automobile, characterized in that, Including a secondary battery according to any one of claims 1 - 12.

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