Lithium battery and lithium battery assembly process

Abstract

The present application relates to the field of lithium battery technology, and in particular to a lithium battery and a lithium battery assembly process. The lithium battery assembly process includes the following steps: first, lay out two pole groups so that the pole ears of the two pole groups with the same polarity are opposite to each other, and weld the two pole ears with the same polarity to the surface of one side of the connecting piece; the next step is to combine the two pole groups; the next step is to assemble the pole bottom plate of the connecting piece and the cover plate, and perform seam welding on both sides of the connecting piece and the pole bottom plate; the next step is to install the two pole groups into the battery housing. The lithium battery assembly process of the present application can effectively shorten the pole ear length and the folding pole ear space reserved in the battery housing, so as to increase the internal space of the battery cell and improve the design capacity of the battery cell; at the same time, the pole ear can be directly arranged at a position opposite to the pole bottom plate, avoiding the situation where the length of the cover plate is short, and the position of the pole ear blocks the electrolyte injection port and the explosion-proof valve vent on the cover plate, thereby reducing the risk of thermal runaway of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a lithium battery and a lithium battery assembly process. Background Art

[0002] As lithium-ion battery technology becomes increasingly mature, lithium-ion batteries are widely used as power batteries in electric vehicles and energy storage fields. Lithium-ion power batteries generally include an internal battery structure and an external battery structure. The internal battery structure mainly includes a pole group, and the external battery structure mainly includes a cover plate and a shell. The shell provides a storage space for the pole group, and the cover plate and the shell are welded together to fix the pole group in the internal space.

[0003] At present, when assembling lithium-ion batteries, it is necessary to lay the two pole groups flat first, and weld the pole ears of the same polarity of the two pole groups to the connecting piece, and then weld the connecting piece to the pole column of the cover plate. After welding, the two pole combination cores are installed into the shell. In order to avoid interference between the pole group and the cover plate during welding, this assembly method requires the pole ears of the pole group to be designed to be longer, which increases the processing difficulty and material cost. After the pole combination core is placed in the shell, it is also necessary to sacrifice the internal space of the battery cell and reserve enough space for folding the pole ears to prevent the pole ears from being inserted upside down, torn or short-circuited, which affects the battery cell capacity. Summary of the invention

[0004] The object of the present invention is to provide a lithium battery and a lithium battery assembly process, so as to solve the technical problems in the prior art that the pole tabs are long and the reserved folding pole tab space is large to a certain extent.

[0005] The present invention provides a lithium battery assembly process, comprising the following steps:

[0006] Step 100, laying out two electrode groups so that the electrode tabs of the two electrode groups with the same polarity face each other, and welding the two electrode tabs with the same polarity to the connecting sheet;

[0007] Step 200, closing the two pole groups;

[0008] Step 300, assembling the connection piece and the pole bottom plate of the cover plate, and performing seam welding on both sides of the connection piece and the pole bottom plate;

[0009] Step 400: Assemble two electrodes into a battery housing.

[0010] Furthermore, the thickness of the pole group is T, and the pole lug has an eccentricity P, where P=T / 2.

[0011] Furthermore, in the step 300, the weld between the connecting piece and the pole bottom plate has a weld width w, w≥0.3 mm.

[0012] Furthermore, in the step 300, the weld between the connecting piece and the pole bottom plate has a penetration depth h, where h≥0.2 mm.

[0013] Furthermore, the thickness of the connecting sheet is x, w / 2+0.3≤x≤5mm.

[0014] Furthermore, a lower plastic is provided on one side of the cover plate facing the pole group, and the lower plastic forms a plastic edge on both sides of the pole bottom plate in a first direction, and the first direction extends along the thickness direction of the pole group;

[0015] The height of the plastic edge is j, j≥0.5mm.

[0016] Furthermore, the thickness of the pole bottom plate is y, w / 2+j+0.3≤y≤5mm.

[0017] Furthermore, the lower plastic is provided with protrusions on both sides of the pole bottom plate in a second direction, and the second direction is perpendicular to the first direction;

[0018] The protrusions on both sides of the pole bottom plate and the plastic edging form a lower plastic opening, and the distance between the welding seam between the connecting piece and the pole bottom plate and the lower plastic opening is n, where n≥1mm.

[0019] Furthermore, there is a welding mark between the connecting piece and the two pole tabs, the distance between the outer edges of the two welding marks is Z, and the pole tabs have an eccentricity P, 1mm≤2P-Z≤5mm.

[0020] The present invention further provides a lithium battery, comprising a pole group, a connecting piece and a cover plate; the pole group, the connecting piece and the cover plate are assembled using any of the above-mentioned lithium battery assembly processes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a lithium battery assembly process, comprising the following steps: first, laying two electrode groups flat so that the electrode ears with the same polarity of the two electrode groups face each other, and welding the two electrode ears with the same polarity to one side surface of a connecting piece; next, joining the two electrode groups; next, assembling the connecting piece and the pole bottom plate of the cover plate, and performing seam welding on both sides of the connecting piece and the pole bottom plate; next, installing the two electrode groups into a battery casing.

[0023] Since the connecting piece and the cover plate are welded by seam welding, the electrode group can be assembled first, and then the connecting piece and the pole bottom plate on the cover plate are welded. The pole ear length and the folded pole ear space reserved in the battery shell can be effectively shortened, thereby increasing the internal space of the battery cell and improving the design capacity of the battery cell. At the same time, the pole ear can be directly arranged at a position opposite to the pole bottom plate, avoiding the situation where the pole ear position blocks the electrolyte injection port and the explosion-proof valve vent on the cover plate when the cover plate is short, thereby reducing the risk of thermal runaway of the battery.

[0024] The present invention also provides a lithium battery, which is assembled using the lithium battery assembly process, so the lithium battery also has the beneficial effects of the lithium battery assembly process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of welding the electrode group flat and the connecting piece in the traditional solution;

[0027] Figure 2 It is a schematic diagram of welding the pole bottom plate of the connecting piece and the cover plate in the conventional solution when the pole group is laid flat;

[0028] Figure 3 It is a schematic diagram of the pole combination core in the traditional scheme;

[0029] Figure 4 This is a schematic diagram of the conventional solution in which the electrode assembly core is installed into the battery housing;

[0030] Figure 5 A schematic diagram of the welding state of the pole lug and the connecting piece of the pole group in the traditional solution;

[0031] Figure 6 A schematic diagram of welding the electrode group flat and the connecting piece in the lithium battery assembly process provided by an embodiment of the present invention;

[0032] Figure 7 A schematic diagram of a pole assembly core in a lithium battery assembly process provided by an embodiment of the present invention;

[0033] Figure 8 A schematic diagram of a lithium battery assembly process after a cover plate is assembled in an embodiment of the present invention;

[0034] Fig. 9 for Figure 8Schematic diagram of the AA position in the middle;

[0035] Fig.10 for Figure 8 Enlarged view of point C in the middle;

[0036] Fig.11 A schematic diagram of the assembly of a battery into a battery housing in a lithium battery assembly process provided by an embodiment of the present invention;

[0037] Fig.12 for Fig. 9 Enlarged view of point B in the middle;

[0038] Fig.13 A schematic diagram of the welding state of the electrode tab and the connecting piece in the lithium battery assembly process provided by an embodiment of the present invention.

[0039] Reference numerals:

[0040] 1-pole group, 11-pole ear, 2-connecting piece, 21-welding stamp, 3-cover plate, 31-pole bottom plate, 32-plastic edging, 33-lower plastic, 34-lower plastic opening, 35-protrusion, 4-battery shell. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0042] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0043] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0044] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Refer to the following Figures 1 to 13 Describe the lithium battery and lithium battery assembly process according to some embodiments of the present application.

[0047] The present application provides a lithium battery assembly process, such as Figures 6 to 11 As shown, the following steps are included:

[0048] Step 100: Complete welding between the electrode group and the connecting piece.

[0049] Specifically, if Figure 6 As shown, firstly, two electrode groups 1 are laid flat, so that the sides of the two electrode groups 1 with the pole ears 11 are opposite to each other, and the pole ears 11 of the two electrode groups 1 with the same polarity are opposite to each other, that is, the positive pole ears of the two electrode groups 1 are opposite to each other, and the negative pole ears of the two electrode groups 1 are opposite to each other; then, a connecting piece 2 is placed at each group of two pole ears 11 with the same polarity, and the two pole ears 11 are welded to one side surface of the connecting piece 2. Laser welding is used for welding between the connecting piece 2 and the pole ears 11, and the weld mark 21 formed by welding is located on the surface where the connecting piece 2 and the pole ears 11 are attached.

[0050] Step 200: closing the core.

[0051] Specifically, if Figure 7 As shown, the pole ears 11 of the two pole groups 1 are bent away from the connecting sheet 2 so that the large surfaces of the two pole groups 1 are in contact with each other; the large surface of the pole group 1 refers to the surface of the pole group 1 perpendicular to its own thickness direction.

[0052] Step 300: Complete the welding of the connecting piece and the cover plate.

[0053] Specifically, if Figure 8 , Fig. 9 As shown, first, two poles are provided on the cover plate 3, namely, a positive pole and a negative pole. The cover plate 3 is assembled with the two pole groups 1 so that the pole bottom plates 31 of the two poles are respectively attached to the connecting pieces 2 with the same polarity, that is, the pole bottom plate 31 of the positive pole is attached to the connecting piece 2 at the positive pole ear of the two pole groups 1, and the pole bottom plate 31 of the negative pole is attached to the connecting piece 2 at the negative pole ear of the two pole groups 1; then, the attached connecting pieces 2 and the pole bottom plates 31 are seam-welded.

[0054] Step 400: Fig.11 As shown, two pole groups 1 are installed in a battery housing 4 , and the subsequent connection between the cover plate 3 and the battery housing 4 is performed.

[0055] Figures 1 to 4 The conventional lithium battery assembly process is shown. Figure 1 As shown, the pole group is laid flat and the connecting piece is welded, and then Figure 2 As shown, keep the pole group flat, assemble and weld the connecting piece and the cover plate, and then Figure 3 As shown, the pole combination core, finally Figure 4 As shown, insert into the battery housing.

[0056] In the traditional lithium battery assembly process, after the electrode group is welded to the connecting piece, it needs to continue to be laid flat and welded to the cover plate, and then the core is assembled and installed into the battery case. Figure 2 As shown in the figure, the welding between the connecting piece and the pole bottom plate is surface welding. If the core is closed first, the welding area will be blocked. In order to avoid interference between the flat pole group and the cover plate, as shown in the figure, the connection plate and the pole bottom plate are connected to the surface of the pole. Figure 5 As shown, a gap G should be left between the pole group and the cover plate.

[0057] At the same time, if Figure 5 As shown, the pole group includes multiple pole pieces, and the pole ears of the pole group are formed by gathering and compacting the pole ears of multiple pole pieces together. The length of the pole ear of each pole piece is L. The pole ears of the pole group formed after gathering have a gathering height e. The length of the pole ear of each pole piece in the gathering area is a, and the length of the compaction area is b. The pole ears of the pole group formed after gathering have an eccentricity P, that is, the distance of the pole ears of the gathered pole group away from the edge of the pole group, where L=a+b, a 2 =p 2 +e 2 .

[0058] However, since it is necessary to consider leaving a gap G between the electrode group and the cover plate and ensure that the two electrode groups can fit together after the core is assembled, in traditional lithium batteries, the eccentricity P of the electrode group ear is greater than T / 2, where T is the thickness of the electrode group. This also results in the outermost electrode sheet among the multiple electrode sheets having the shortest length of the compacted area after being folded, that is, the b value is the smallest.

[0059] Combination Figure 1 As shown, after welding two pole ears with the same polarity of the pole group and the connecting sheet, welding marks are formed. The distance between the edges of the two welding marks away from each other is Z. In order to ensure that the two pole groups can fit together after being assembled into a core, 2P>Z must be ensured.

[0060] like Figure 1 and Figure 5As shown, the tab needs to be as short as possible, but it is also necessary to ensure that the tab of the pole piece with the smallest b value can also cover the weld mark range. Therefore, in traditional lithium batteries, the weld mark between the connecting piece and the tab is designed to be close to the edge of the connecting piece, that is, the Z value is larger, but the larger Z is, the larger P is, and the larger a is.

[0061] Compared with the traditional process, the lithium battery assembly process of the present application adopts the method of patch welding to weld the connecting piece 2 and the cover plate 3, so that the electrode group 1 can be firstly cored, and then the connecting piece 2 and the pole bottom plate 31 on the cover plate 3 are welded; at the same time, there is no need to consider the gap G between the electrode group and the cover plate in the traditional solution, so that the welding mark 21 of the pole ear 11 and the connecting piece 2 can be close to the center of the connecting piece 2, and the eccentricity P of the pole ear 11 can be designed according to half of the thickness of the electrode group 1, that is, Fig.13 As shown, P=T / 2, so that the length of the pole ear 11 is minimized. At the same time, since the length of the pole ear 11 is shortened, the folding pole ear space reserved in the battery housing 4 can also be reduced, thereby increasing the internal space of the battery cell and improving the design capacity of the battery cell. There will be no situation where the pole ear 11 is torn or inserted upside down into the pole group 1 to cause a short circuit.

[0062] At the same time, if Figure 1 and Figure 2 As shown, in the traditional lithium battery assembly process, since the welding of the connecting piece to the pole ear and the welding to the pole bottom plate are all surface welding, the welding mark between the connecting piece and the pole ear needs to avoid the welding mark between the connecting piece and the pole bottom plate, that is, the pole bottom plate cannot be directly opposite to the pole ear, and needs to be staggered, and then one end of the connecting piece is welded to the pole ear, and the other end of the connecting piece is welded to the pole bottom plate.

[0063] Since the present application adopts the method of patchwork welding, the above-mentioned problem does not exist. The pole ear 11 can be directly arranged at a position opposite to the pole bottom plate 31. This avoids the situation where the pole ear 11 blocks the electrolyte injection port and the explosion-proof valve vent on the cover plate 3 when the cover plate 3 is short, thereby reducing the risk of thermal runaway of the battery.

[0064] In this embodiment, preferably, in step 300, as Fig.12 As shown, the weld formed by the butt welding between the connecting piece 2 and the pole bottom plate 31 has a weld width w and a weld depth h, wherein the weld width w≥0.3 mm and the weld depth h≥0.2 mm, thereby ensuring the connection strength between the connecting piece 2 and the pole bottom plate 31 .

[0065] In this embodiment, preferably, Fig.12 As shown, the thickness of the connecting sheet 2 is x, w / 2+0.3≤x≤5 mm, so that the thickness of the connecting sheet 2 is neither too small to meet the welding requirements nor too large to cause excessive weight and material waste.

[0066] In this embodiment, if Figure 8 and 12 As shown, preferably, a lower plastic 33 is provided on the side of the cover plate 3 facing the pole group 1, and a plastic edging 32 is formed on both sides of the pole bottom plate 31 in a first direction of the lower plastic 33, and the first direction is the thickness direction of the pole group 1; the plastic edging 32 has a height j, and the pole bottom plate 31 has a thickness y, wherein the height j of the plastic edging 32 is ≥0.5mm to avoid insufficient anti-rotation strength of the pole bottom plate 31; w / 2+j+0.3≤y≤5mm, so that the thickness of the pole bottom plate 31 will not be too small to meet the welding requirements, nor too large to cause excessive weight and material waste.

[0067] In this embodiment, preferably, Figure 8 and Fig.10 As shown, the lower plastic 33 forms protrusions 35 on both sides of the second direction of the pole bottom plate 31, and the second direction is perpendicular to the first direction. Specifically, two poles are provided on the cover plate 3, and the two poles are spaced along the second direction. The lower plastic 33 is provided with protrusions at both ends and the middle of the second direction, that is, two end protrusions and one middle protrusion. The two poles are located between the two end protrusions, and the middle protrusion is located between the two poles, so that each pole and its pole bottom plate 31 are provided with two protrusions on both sides, that is, one end protrusion and one middle protrusion.

[0068] For any pole, the protrusions 35 on both sides and the plastic edging 32 surround a U-shaped lower plastic opening 34, and the distance between the joint weld (the weld between the connecting piece 2 and the pole bottom plate 31) and the lower plastic opening 34 is n, n ≥ 1mm, so that when the connecting piece 2 and the pole bottom plate 31 are joint welded by laser welding, the lower plastic can be prevented from blocking the laser welding path.

[0069] It should be noted that if Figure 8 and Fig.10 As shown, the two protrusions 35 and the plastic package surface 32 surrounding the lower plastic opening 34 constitute the three side walls of the lower plastic opening 34. The distances between the three side walls and the splicing weld are all n. The n values ​​at these three locations can be the same or different, as long as n≥1mm.

[0070] As described above, after welding the two pole tabs 11 of the pole group 1 with the same polarity to the connecting sheet 2, a weld mark 21 is formed. The distance between the edges of the two weld marks 21 away from each other is Z. In order to ensure that the two pole groups 1 can fit together after being cored, it is necessary to ensure that 2P>Z. In this embodiment, preferably, 1mm≤2P-Z≤5mm, so as to avoid tearing of the pole tab 11 when it is bent.

[0071] In order to verify that the welding matching structure of the connecting piece and the pole bottom plate of the present application can better play a fixing and processing role, the present application conducted a cell vibration test and a cover plate pole torque test on the matching structure of the connecting piece and the pole bottom plate with different parameters. The specific parameters are shown in Table 1:

[0072] Table 1

[0073]

[0074]

[0075] The present application also provides a lithium battery, which is assembled using the above-mentioned lithium battery assembly process. Therefore, the lithium battery has all the beneficial effects of the battery assembly process, which will not be described one by one here.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery assembly process, characterized in that: The following steps are involved: Step 100, laying out two electrode groups so that the electrode tabs of the two electrode groups with the same polarity face each other, and welding the two electrode tabs with the same polarity to one side surface of the connecting piece; Step 200, closing the two pole groups; Step 300, assembling the connection piece and the pole bottom plate of the cover plate, and performing seam welding on both sides of the connection piece and the pole bottom plate; Step 400: Assemble two electrodes into a battery housing.

2. The lithium battery assembly process according to claim 1, characterized in that: The thickness of the pole group is T, and the pole ear has an eccentricity P, where P=T / 2.

3. The lithium battery assembly process according to claim 1, characterized in that: In step 300, the weld between the connecting piece and the pole bottom plate has a weld width w, where w≥0.3 mm.

4. The lithium battery assembly process according to claim 1, characterized in that: In step 300, the weld between the connecting piece and the pole bottom plate has a penetration depth h, where h≥0.2 mm.

5. The lithium battery assembly process according to claim 3, characterized in that: The thickness of the connecting sheet is x, w / 2+0.3≤x≤5mm.

6. The lithium battery assembly process according to claim 1, characterized in that: A lower plastic is provided on one side of the cover plate facing the pole group, and the lower plastic forms a plastic edge on both sides of the pole bottom plate in a first direction, and the first direction extends along the thickness direction of the pole group; The height of the plastic edge is j, j≥0.5mm.

7. The lithium battery assembly process according to claim 6, characterized in that: The thickness of the pole bottom plate is y, w / 2+j+0.3≤y≤5mm.

8. The lithium battery assembly process according to claim 6, characterized in that: The lower plastic is provided with protrusions on both sides of the pole bottom plate in a second direction, and the second direction is perpendicular to the first direction; The protrusions on both sides of the pole bottom plate and the plastic edging form a lower plastic opening, and the distance between the welding seam between the connecting piece and the pole bottom plate and the lower plastic opening is n, where n≥1mm.

9. The lithium battery assembly process according to claim 1, characterized in that: There is a welding mark between the connecting piece and the two pole ears, the distance between the outer edges of the two welding marks is Z, and the pole ears have an eccentricity P, 1mm≤2P-Z≤5mm.

10. A lithium battery, characterized in that: It comprises a pole group, a connecting piece and a cover plate; the pole group, the connecting piece and the cover plate are assembled by using the lithium battery assembly process described in any one of claims 1 to 9.

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