Battery case assembly and battery pack

Abstract

The embodiment of the utility model provides a battery shell assembly and a battery pack. The battery shell assembly comprises a plurality of battery monomer shells, positive pole pieces for electrically connecting the adjacent battery monomer shells and negative pole pieces for electrically connecting the adjacent battery monomer shells; each battery monomer shell comprises a shell body, a positive pole, a sealing structure and a bottom cover; the top end of the shell body is provided with a positive pole mounting port, the positive pole is arranged at the positive pole mounting port, and the sealing structure is arranged between the positive pole and the shell body and used for sealing a gap between the positive pole and the shell body; an opening is formed in the bottom end of the shell body, the bottom cover is arranged at the opening, and the bottom cover and the shell body are not electrically conducted; the positive pole piece is welded with the positive pole of the battery monomer shell; the negative pole piece is welded with the top end of the battery monomer shell, and the thickness of the negative pole piece is 0.5-1.2 mm; or the negative pole piece is welded with the bottom cover. After the battery case assembly is assembled into a battery pack, the possibility of thermal runaway of the battery pack is low, and the safety of the battery pack is high.

Description

Technical Field

[0001] The utility model relates to the field of battery structures, and in particular to a battery shell assembly and a battery pack. Background Art

[0002] When a lithium-ion battery encounters an external short circuit, according to Joule's law, it will generate huge amounts of heat to heat the battery itself, which will then cause thermal runaway and eventually lead to battery explosion and fire. Compared to square batteries, cylindrical batteries are more prone to fire failure due to external short circuits because it is difficult to design internal fuse devices. In addition, due to the special structure of cylindrical batteries, they are prone to thermal runaway when external short circuits occur, leading to fire and explosion. At present, there is no effective solution for external short circuits of single cylindrical batteries with high nickel ternary systems. Possible mitigation measures include: (1) adjusting the material system to reduce the heat generated during thermal runaway, such as using 5-series nickel-cobalt-manganese ternary positive electrode materials, but this will significantly reduce the battery capacity and energy density; (2) changing the design of the current collector or current collector plate, such as designing a fuse structure, but this will limit the battery's high power output.

[0003] In view of this, this application is hereby filed. Utility Model Content

[0004] The purpose of the utility model is to provide a battery shell assembly and a battery pack, aiming to improve the safety performance of the battery.

[0005] The embodiment of the present utility model is achieved as follows:

[0006] In a first aspect, the present invention provides a battery housing assembly, comprising a plurality of battery cell housings, a positive electrode tab for electrically connecting adjacent battery cell housings, and a negative electrode tab for electrically connecting adjacent battery cell housings;

[0007] Each battery cell shell includes a shell body, a positive electrode column, a sealing structure and a bottom cover;

[0008] The top of the shell body is provided with a positive electrode post installation opening, the positive electrode post is arranged at the positive electrode post installation opening, and a sealing structure is arranged between the positive electrode post and the shell body to seal the gap between the two;

[0009] The bottom end of the shell body is open, the bottom cover is arranged at the opening position, and the bottom cover and the shell body are not electrically connected to each other;

[0010] Welding the positive electrode tab to the positive electrode column of the battery cell shell;

[0011] The negative electrode tab is welded to the top of the battery cell shell. The thickness of the negative electrode tab is 0.5 to 1.2 mm.

[0012] Alternatively, the negative electrode tab is welded to the bottom cover.

[0013] In an optional embodiment, when the negative electrode tab is welded to the bottom cover, the thickness of the negative electrode tab is 0.5 to 1 mm.

[0014] In an optional embodiment, the positive electrode column includes a column body passing through the positive electrode column installation port and an inner current collecting disk located in the shell body, and one end of the column body is connected to the inner current collecting disk;

[0015] The sealing structure includes a first sealing ring and an inner plastic ring. At least a portion of the first sealing ring is located in the positive electrode column mounting opening and isolated between the column body and the shell body. The inner plastic ring is arranged between the inner collecting plate and the inner top wall of the shell body.

[0016] In an optional embodiment, a second sealing ring is provided between the bottom cover and the shell body.

[0017] In an optional embodiment, the positive electrode column further includes an outer current collecting disk, which is located outside the shell body and connected to an end of the column body away from the inner current collecting disk;

[0018] The sealing structure further comprises an outer plastic ring, which is arranged between the outer collecting plate and the outer top wall of the shell body.

[0019] In an optional embodiment, a mounting groove is provided on the inner plastic ring, the mounting groove being opened on a side of the inner plastic ring away from the inner top wall of the shell body and being located at the inner edge of the inner plastic ring;

[0020] The sealing ring includes a first sealing portion and a second sealing portion. The first sealing portion is located in the positive electrode mounting opening, and the second sealing portion is arranged in the mounting groove to isolate the inner plastic ring and the inner current collecting plate from each other.

[0021] In a second aspect, the present invention provides a battery pack, comprising a battery shell assembly according to any one of the aforementioned embodiments and a battery cell disposed in each shell body.

[0022] The beneficial effects of the embodiments of the present utility model are:

[0023] The battery shell assembly provided by the embodiment of the present invention can improve the problem of melting of the inner plastic ring by increasing the thickness of the negative electrode tab or changing the welding position of the negative electrode tab to the bottom cover of the shell body, thereby reducing the possibility of thermal runaway of the battery pack and further improving the safety of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A schematic structural diagram of a battery housing assembly provided in the first embodiment of the present invention;

[0026] Figure 2 Comparison of the thickness of the negative electrode tab in the prior art and the thickness of the tab in the embodiment of the present invention;

[0027] Figure 3 This is a schematic structural diagram of a battery housing assembly provided in the second embodiment of the present invention.

[0028] Icons: 100-battery shell assembly; 110-battery cell shell; 111-shell body; 111a-positive pole mounting port; 112-positive pole; 112a-column body; 112b-inner current collecting plate; 112c-outer current collecting plate; 113-first sealing ring; 113a-first sealing part; 113b-second sealing part; 114-inner plastic ring; 115-outer plastic ring; 116-second sealing ring; 117-bottom cover; 120-positive pole piece; 130-negative pole piece. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0032] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the utility model product is typically placed when in use. These terms are intended solely to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0034] It should also be noted that, in the description of this utility model, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0035] By studying the thermal runaway phenomenon of cylindrical batteries during external short circuit, the following external short circuit failure process of cylindrical batteries is proposed:

[0036] (1) Heat generated by external short-circuit resistance: According to Joule's law, a small external short-circuit resistor will generate a lot of Joule heat.

[0037] (2) The positive and negative electrode tabs 130 transfer heat on the same side: Joule heat is transferred to the positive and negative electrodes through the tabs. The positive and negative electrode tabs 130 are on the same side, and the heat is concentrated to heat the top cover of the cylindrical battery; especially the negative electrode tab 130, due to its high thermal conductivity and small heat capacity, the negative electrode tab 130 heats up much faster.

[0038] (3) The sealing structure includes PP plastic (i.e., the inner plastic ring 114 mentioned later), and the resistance of the shell body 111 (<0.5mΩ) participates in the short-circuit process: when the temperature rises to the melting point of the PP plastic (165°C), the PP plastic melts and breaks, and the internal collector or tab comes into contact with the top of the shell body 111, causing insulation failure. At this point, the short-circuit resistance is no longer the external resistor (2-5mΩ), but the parallel resistance of the cylindrical shell body 111 and the external resistor (<0.5mΩ). According to Joule's law, the smaller the short-circuit resistance, the greater the Joule heat released, and the more likely the battery is to thermal runaway. A short-circuit resistance below 0.5mΩ is very likely to cause thermal runaway of the battery.

[0039] (4) Heat generation surges, triggering thermal runaway: The extremely small external short-circuit resistance (<0.5mΩ) causes the Joule heat generated to surge in a short period of time. The huge amount of heat triggers thermal runaway of the battery, accompanied by the generation of a large amount of flammable gas.

[0040] (5) The internal air pressure breaks open the positive pole 112 / explosion-proof valve of the battery, and an explosion occurs at the same time: a large amount of combustible gas accumulated inside the battery breaks open the explosion-proof valve / positive pole 112, and at the same time the combustible gas reaches the explosion limit, causing the battery to explode.

[0041] In view of this, the following proposal is proposed.

[0042] First embodiment

[0043] like Figure 1 As shown, in order to clearly show the structure of the battery housing assembly 100, only one battery cell shell 110 is drawn in the figure. The embodiment of the present utility model provides a battery housing assembly 100, including multiple battery cell shells 110, a positive electrode tab 120 for electrically connecting adjacent battery cell shells 110, and a negative electrode tab 130 for electrically connecting adjacent battery cell shells 110;

[0044] Each battery cell housing 110 includes a housing body 111 , a positive electrode column 112 , a sealing structure, and a bottom cover 117 ;

[0045] The top of the shell body 111 has a positive electrode mounting opening 111a, and the positive electrode 112 is arranged at the positive electrode mounting opening 111a. A sealing structure is provided between the positive electrode 112 and the shell body 111 to seal the gap therebetween.

[0046] The bottom end of the shell body 111 is open, and the bottom cover 117 is arranged at the opening position. The bottom cover 117 and the shell body 111 are not electrically connected to each other;

[0047] The positive electrode tab 120 is welded to the positive electrode post 112 of the battery cell shell 110;

[0048] The negative electrode tab 130 is welded to the top of the battery cell shell 110 , and the thickness h of the negative electrode tab 130 is 0.5-1.2 mm.

[0049] The thickness of the tabs in the embodiment of the present invention is greater than that of the currently available tabs.

[0050] Under the premise that the material of the tab remains unchanged, increasing the thickness of the tab is equivalent to increasing its mass. From the perspective of heat transfer, by increasing the mass of the negative tab 130, the heat capacity of the negative tab 130 can be significantly improved. Heat capacity calculation formula: C = m*Cs, where C is heat capacity, m is mass, and Cs is specific heat capacity. For example, if the mass m of the negative tab 130 is increased from the original 3 to 10g to 20 to 60g, the heat capacity becomes 2 to 20 times the original. This means that when the external short-circuit resistor generates the same amount of heat, the temperature rise of the negative tab 130 will become 5% to 50% of the original, greatly delaying the melting of the PP material parts in the sealing structure.

[0051] From the perspective of heat generation, increasing the thickness of the tab is equivalent to increasing the cross-sectional area of ​​the negative tab 130 (e.g. Figure 2 As shown), the resistance of the negative electrode sheet 130 can be reduced, thereby reducing the heat generated by the negative electrode sheet 130. The resistance calculation formula is R=ρL / S, where R is resistance, ρ is resistivity, L is length, and S is cross-sectional area. For example, if the length of the negative electrode sheet 130 is 50mm and the thickness of the negative electrode sheet 130 in the prior art is 0.1-0.2mm, then this application is equivalent to reducing the cross-sectional area of ​​the negative electrode sheet 130 from the original 5-10mm. 2 , expanded to 25~100mm 2 , the resistance of the negative electrode tab 130 decreases from 0.1-0.2mΩ to 0.04-0.01mΩ, and the resistance becomes 5%-40% of the original resistance. According to Joule's law: Q=I2Rt (where I is current, R is resistance, and t is time), the heat generated by the negative electrode tab 130 will also be reduced to 5%-40% of the original resistance. Although the heat generated by the external short-circuit resistor is dominant at this time, the reduced heat generation of the negative electrode tab 130 can also partially reduce the temperature of the top of the shell body 111, thereby delaying the melting of the lower plastic.

[0052] Furthermore, because battery capacity is closely related to short-circuit current and heat generation power, the best design solution is to determine the mass and cross-sectional area (i.e., thickness) of the tabs based on the battery capacity. For example, starting from 10Ah, for every 2Ah increase in capacity, the mass of the tabs needs to start from 20g and increase by 1g accordingly. Similarly, for every 1Ah increase in capacity, the thickness of the tabs needs to start from 25mm. 2 Start by increasing by 25mm 2 .

[0053] Therefore, the battery shell assembly 100 provided in the embodiment of the present invention can effectively reduce the heat generation of the negative electrode tab 130 by increasing the thickness of the tab, thereby delaying the melting of the PP material parts in the sealing structure, and thus improving the safety of the battery.

[0054] Optionally, the positive electrode column 112 includes a column body 112a passing through the positive electrode column installation port 111a and an inner current collecting plate 112b located in the shell body 111, and one end of the column body 112a is connected to the inner current collecting plate 112b;

[0055] The sealing structure includes a first sealing ring 113 and an inner plastic ring 114. At least a portion of the first sealing ring 113 is located within the positive electrode column mounting opening 111a, isolated between the column body 112a and the shell body 111. The inner plastic ring 114 is disposed between the inner collecting plate 112b and the inner top wall of the shell body 111.

[0056] Optionally, a method for achieving electrical disconnection between the bottom cover 117 and the shell body 111 is as follows: a second sealing ring 116 is provided between the bottom cover 117 and the shell body 111 .

[0057] Optionally, the positive electrode column 112 further includes an outer current collecting plate 112 c, which is located outside the shell body 111 and connected to an end of the column body 112 a away from the inner current collecting plate 112 b;

[0058] The sealing structure further includes an outer plastic ring 115 , which is disposed between the outer collecting plate 112 c and the outer top wall of the shell body 111 .

[0059] Optionally, a mounting groove is provided on the inner plastic ring 114 , which is opened on a side of the inner plastic ring 114 away from the inner top wall of the shell body 111 and is located at the inner edge of the inner plastic ring 114 ;

[0060] The sealing ring includes a first sealing portion 113a and a second sealing portion 113b. The first sealing portion 113a is located in the positive electrode mounting opening 111a, and the second sealing portion 113b is disposed in the mounting groove to isolate the inner plastic ring 114 and the inner current collecting plate 112b from each other.

[0061] Optionally, the shell body 111 is a steel shell.

[0062] Second embodiment

[0063] This embodiment is basically the same as the first embodiment, and for matters not described, refer to the content of the first embodiment.

[0064] like Figure 3As shown, in order to clearly show the structure of the battery housing assembly 100, only one battery cell shell 110 is drawn in the figure. In the battery housing assembly 100 provided in this embodiment, the negative electrode tab 130 is welded to the bottom cover 117.

[0065] When the negative electrode tab 130 is welded to the bottom cover 117, the positive and negative electrode tabs 130 are located on different sides. In this way, the top of the shell body 111 only bears the heat of the positive electrode tab 120 and no longer bears the heat of the negative electrode tab 130. This can effectively prevent the inner plastic ring 114 from melting, thereby reducing the possibility of thermal runaway of the battery and improving the safety of the battery.

[0066] Preferably, when the negative electrode tab 130 is welded to the bottom cover 117 , the thickness of the negative electrode tab 130 is 0.5-1 mm.

[0067] When the thickness of the negative electrode tab 130 is 0.5 to 1 mm, it is equivalent to increasing the thickness of the existing negative electrode tab 130 , which can further reduce the possibility of thermal runaway of the battery, thereby further improving the safety of the battery.

[0068] In summary, the battery shell assembly 100 provided in the embodiment of the present invention can improve the problem of melting of the inner plastic ring 114 by increasing the thickness of the negative electrode tab 130 or changing the welding position of the negative electrode tab 130 to the bottom cover 117 of the shell body 111, thereby reducing the possibility of thermal runaway of the battery pack and further improving the safety of the battery pack.

[0069] The embodiment of the present invention further provides a battery pack, including the battery shell assembly 100 provided in the embodiment of the present invention and a battery cell arranged in each shell body 111.

[0070] Since the battery pack includes the battery housing assembly 100 provided by the embodiment of the present invention, it has the characteristic of high safety.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A battery shell assembly, characterized in that: The battery comprises a plurality of battery cell shells, a positive electrode tab for electrically connecting adjacent battery cell shells, and a negative electrode tab for electrically connecting adjacent battery cell shells; Each of the battery cell shells includes a shell body, a positive electrode column, a sealing structure and a bottom cover; The top of the shell body is provided with a positive electrode post installation opening, the positive electrode post is arranged at the positive electrode post installation opening, and the sealing structure is arranged between the positive electrode post and the shell body to seal the gap therebetween; The bottom end of the shell body is open, the bottom cover is arranged at the opening position, and the bottom cover and the shell body are not electrically connected to each other; The positive electrode tab is welded to the positive electrode post of the battery cell shell; The negative electrode tab is welded to the top of the battery cell shell, and the thickness of the negative electrode tab is 0.5 to 1.2 mm; Alternatively, the negative electrode tab is welded to the bottom cover.

2. The battery housing assembly according to claim 1, wherein: When the negative electrode tab is welded to the bottom cover, the thickness of the negative electrode tab is 0.5 to 1 mm.

3. The battery housing assembly according to claim 1, wherein: The positive electrode column comprises a column body passing through the positive electrode column installation port and an inner current collecting disk located in the shell body, and one end of the column body is connected to the inner current collecting disk; The sealing structure includes a first sealing ring and an inner plastic ring. At least a portion of the first sealing ring is located in the positive electrode column mounting opening, isolated between the column body and the shell body, and the inner plastic ring is arranged between the inner collecting plate and the inner top wall of the shell body.

4. The battery housing assembly according to claim 3, wherein: A second sealing ring is provided between the bottom cover and the shell body.

5. The battery housing assembly according to claim 3, wherein: The positive electrode column further includes an outer current collecting disk, which is located outside the shell body and connected to an end of the column body away from the inner current collecting disk; The sealing structure further includes an outer plastic ring, which is arranged between the outer collecting plate and the outer top wall of the shell body.

6. The battery housing assembly according to claim 3, wherein: The inner plastic ring is provided with a mounting groove, which is opened on a side of the inner plastic ring away from the inner top wall of the shell body and is located at the inner edge of the inner plastic ring; The sealing ring includes a first sealing portion and a second sealing portion. The first sealing portion is located in the positive electrode column installation opening, and the second sealing portion is arranged in the installation groove to isolate the inner plastic ring and the inner current collecting plate from each other.

7. A battery pack, characterized in that: The invention comprises a battery shell assembly according to any one of claims 1 to 6 and a battery cell arranged in each shell body.

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