Battery cell tab connection structure, preparation method thereof and secondary battery

Abstract

The invention discloses a battery cell tab connection structure and a preparation method thereof, and a secondary battery. The battery cell tab connection structure comprises a battery cell body, one end of the first tab is electrically connected with at least one end part of the battery cell body, the other end of the first tab is divided into N parts along the thickness direction, and N is greater than or equal to 2; the second tab comprises a welding end and an external connection end, and the welding end is cut into N parts along the thickness direction; wherein the N parts of first tabs and the N parts of second tabs are welded and connected in a one-to-one correspondence manner. According to the battery cell tab connecting structure provided by the invention, one-time tab welding is changed into multi-time welding, and only the welding end of the second tab is cut, so that the welding effectiveness is improved, the abnormities of foil breakage and insufficient welding during welding are reduced, the problem of welding failure caused by too thick tabs and foils is effectively improved, and the battery cell tab connecting structure is suitable for large-scale production. And the problem of packaging liquid leakage caused by traditional multi-tab packaging is avoided.

Description

Technical Field

[0001] The present invention relates to the field of secondary batteries, and in particular to a battery cell pole ear connection structure and a preparation method thereof, and a secondary battery. Background Art

[0002] At present, the stacking process battery cells mainly form conductors by reserving blank areas in the current collector for welding with the pole lugs. The welding mainly uses ultrasound to overlap the blank areas of the pole collector with the pole lugs, and connects the pole lugs and the pole collectors through ultrasonic energy.

[0003] With the demand for energy density in the consumer market, the development of large-capacity battery cells has become a trend. For some thick and large battery cells, the more electrode layers there are, the higher the power required for welding. However, in actual use, there will still be over-welding or foil welding cracks on the surface directly in contact with the welding head. The side farther away from the welding head will have insufficient welding power, resulting in welding and the electrode not being bonded, which seriously affects the quality of the battery cell.

[0004] Therefore, an innovative technical solution is needed to improve the connection structure of the battery cell tabs. The design for such thick battery cells can effectively ensure welding reliability, reduce the abnormalities of welding foil cracking and welding cold joints, improve product quality and safety, and improve production efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a battery cell tab connection structure to address the deficiencies of the prior art and reduce the anomalies of foil cracking and cold welding during welding.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A battery cell tab connection structure,

[0008] Battery cell body;

[0009] A first pole lug, one end of which is electrically connected to at least one end of the battery cell body, and the other end of which is divided into N parts along the thickness direction, where N≥2;

[0010] The second electrode tab comprises a welding end and an external connection end, wherein the welding end is cut into N parts along the thickness direction;

[0011] The N first pole tabs and the N second pole tabs are welded and connected in a one-to-one correspondence.

[0012] Preferably, the other end of the first pole tab is divided into N equal parts along the thickness direction, and the welding end of the second pole tab is cut into N equal parts along the thickness direction.

[0013] Preferably, a packaging area is further provided between the welding end and the external connection end, and the packaging area is provided with a tab glue, and the distance between the lower edge of the tab glue and the upper edge of the welding end is h, wherein h satisfies the relationship: 3mm≤h≤8mm.

[0014] Preferably, the total thickness of the first electrode tab is 300-2000 μm.

[0015] Preferably, the total thickness of the second electrode tab is 300-2000 μm.

[0016] Preferably, the thickness of each of the first electrode tabs is 100-200 μm.

[0017] Preferably, the thickness of each of the second electrode tabs is 100-200 μm.

[0018] Preferably, the width of the first pole tab is 10-500 mm, and the width of the second pole tab is 10-500 mm.

[0019] In addition, the present invention also provides a method for preparing the battery cell tab connection structure, comprising the following steps:

[0020] 1) cutting the welding end of the second pole lug into N parts along the thickness direction, and polishing the edge of each second pole lug;

[0021] 2) dividing the other end of the first electrode tab into N parts along the thickness direction;

[0022] 3) N first electrode tabs and N second electrode tabs are connected by welding in a one-to-one correspondence.

[0023] In addition, the present invention also provides a secondary battery, comprising the above-mentioned battery cell tab connection structure.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The battery cell tab connection structure provided by the present invention changes the tab welding from one time to multiple times, and only the welding end of the second tab is cut, which improves the welding effectiveness, reduces the abnormality of foil cracking and welding cold solder joints during welding, effectively improves the welding failure problem caused by the tab and foil being too thick, and avoids the packaging leakage problem caused by traditional multi-tab packaging. When assembling the PACK, only the external connection end of the second tab needs to be welded, which can avoid welding multiple tabs during PACK assembly.

[0026] 2) In the battery cell tab connection structure provided by the present invention, the spacing between the lower edge of the tab glue of the second tab and the upper edge of the welding end is set to h, and h is controlled to be 3-8mm. If h is too large, the cutting area will be relatively small, and the contact area during the trace connection will be relatively small, which will increase the difficulty of welding; if h is too small, the tab glue may be damaged during the cutting of the second tab, thereby affecting the battery cell packaging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the connection structure of the battery cell tabs according to an embodiment of the present invention.

[0028] Figure 2 FIG. 4 is a schematic cross-sectional view of a second electrode tab welding end according to an embodiment of the present invention.

[0029] Figure 3 FIG. 4 is a top view of a second electrode tab according to an embodiment of the present invention.

[0030] Among them, 1-battery cell; 2-first pole ear; 3-second pole ear; 31-pole ear glue; 32-welding end; 33-external connection end. DETAILED DESCRIPTION

[0031] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be described in further detail below in conjunction with specific implementation methods and accompanying drawings, but the implementation methods of the present invention are not limited thereto.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0033] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be described in further detail below in conjunction with specific implementation methods and accompanying drawings, but the implementation methods of the present invention are not limited thereto.

[0034] like Figure 1-3 As shown, according to the first aspect of the present application, the present application aims to provide a battery cell tab connection structure, comprising:

[0035] Battery cell body 1;

[0036] A first pole lug 2, one end of which is electrically connected to at least one end of the battery cell body, and the other end of the first pole lug is divided into N parts along the thickness direction, N ≥ 2;

[0037] The second electrode tab 3 comprises a welding end 32 and an external connection end 33, wherein the welding end 32 is cut into N parts along the thickness direction;

[0038] The N first electrode tabs 2 and the N second electrode tabs 3 are welded and connected in a one-to-one correspondence.

[0039] The other end of the first pole lug is divided into N parts along the thickness direction, and the welding end 32 of the second pole lug 3 is cut into N parts along the welding direction and then welded and connected one by one, changing from one-time welding to multiple welding, and only the welding end 32 of the second pole lug 3 is cut, which improves the welding effectiveness and improves the welding failure problem caused by the excessive thickness of the pole lug and foil.

[0040] In some embodiments, the other end of the first electrode tab is divided into N equal parts along the thickness direction, and the welding end of the second electrode tab is cut into N equal parts along the thickness direction.

[0041] In some embodiments, a packaging area is further provided between the welding end 32 and the external connection end 33, and a tab glue 31 is provided in the packaging area, and the distance between the lower edge of the tab glue 31 and the upper edge of the welding end 32 is h, where h satisfies the relationship: 3mm≤h≤8mm, for example, it can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm. If h is too large, the cutting area will be relatively small, and the contact area during the trace connection will be relatively small, and the welding difficulty will increase; if h is too small, the tab glue may be damaged when the second tab is cut, thereby affecting the packaging performance of the battery cell.

[0042] In some embodiments, the total thickness of the first electrode tab 2 is 300-2000 μm, for example, 300 μm, 500 μm, 1000 μm, 1500 μm, or 2000 μm.

[0043] In some embodiments, the total thickness of the second electrode tab 3 is 300-2000 μm, for example, 300 μm, 500 μm, 1000 μm, 1500 μm, or 2000 μm.

[0044] In some embodiments, the thickness of each first electrode tab 2 is 100-200 μm, for example, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 110 μm, 120 μm, 130 μm, 140 μm.

[0045] In some embodiments, the thickness of each second electrode tab 3 is 100-200 μm. If the thickness is too small, it will be difficult to split and difficult to shape. If the thickness is too large, it will increase the difficulty of welding.

[0046] In some embodiments, the width of the first pole tab 2 is 10-500 mm, and the width of the second pole tab 3 is 10-500 mm.

[0047] In some embodiments, the material of the first electrode tab 2 is a conductive material, for example, any one of copper, aluminum, nickel, nickel-plated copper, tin-plated copper, and gold-plated copper.

[0048] In some embodiments, the second electrode tab 3 is made of a conductive material, such as copper, aluminum, nickel, nickel-plated copper, tin-plated copper, or gold-plated copper.

[0049] According to the second aspect of the present application, the present application provides a method for preparing the above-mentioned battery cell tab connection structure, comprising the following steps:

[0050] 1) cutting the welding end 33 of the second electrode tab into N parts along the thickness direction, and polishing the edge of each second electrode tab;

[0051] 2) dividing the other end of the first electrode tab into N parts along the thickness direction;

[0052] 3) N first electrode tabs and N second electrode tabs are connected by welding in a one-to-one correspondence.

[0053] The tab welding is changed from one time welding to multiple welding, and only the welding end of the second tab is cut, which improves the welding effectiveness, reduces the abnormality of foil cracking and welding cold joints during welding, effectively improves the welding failure problem caused by the tab and foil being too thick, and avoids the packaging leakage problem caused by traditional multi-tab packaging. When assembling the PACK, only one metal sheet needs to be welded, which can avoid welding multiple tabs during PACK assembly.

[0054] In some embodiments, the welding of the first electrode tab and the second electrode tab in step 3) may be carried out by any one of ultrasonic welding, laser welding, resistance welding, soft soldering, hard soldering, pulse welding, friction welding and cold pressure welding.

[0055] In some embodiments, the area of ​​the first electrode tab and the second electrode tab when welded in step 3) is ≥50 mm2. If the welding range is too small, the welding tension may be small, resulting in welding failure.

[0056] In some embodiments, in step 3), the power during welding of the first electrode tab and the second electrode tab is 500W-3000W.

[0057] According to a third aspect of the present application, the present application provides a secondary battery, comprising a battery cell and an electrolyte, wherein the battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator separated between the positive electrode sheet and the negative electrode sheet, and the above-mentioned battery cell tab connection structure.

[0058] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material. The positive electrode active material may include but is not limited to a chemical formula such as Li a Nix Co y M z O 2-b N b (wherein 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from a combination of one or more of Mn and Al, and N is selected from a combination of one or more of F, P, and S) The positive electrode active material may also be, but is not limited to, LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 , Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 , CuS 2 , FeS 2 、MoS 2 、NiS、TiS 2 The positive electrode active material may also be subjected to a modification treatment. The method for modifying the positive electrode active material should be known to those skilled in the art. For example, the positive electrode active material may be modified by coating, doping, etc. The material used for the modification treatment may include but is not limited to a combination of one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. The positive electrode current collector is usually a structure or part for collecting current. The positive electrode current collector may be any material suitable for use as a positive electrode current collector for lithium-ion batteries in the art. For example, the positive electrode current collector may include but is not limited to metal foil, etc., and more specifically may include but is not limited to aluminum foil, etc.

[0059] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode active material layer can be one or more of, including but not limited to, graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium.

[0060] Among them, graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; silicon-based materials can be selected from one or more of elemental silicon, silicon oxide compounds, silicon carbon composites, and silicon alloys; tin-based materials can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode current collector is usually a structure or part that collects current. The negative electrode current collector can be any material suitable for use as a negative electrode current collector for lithium-ion batteries in the art. For example, the negative electrode current collector can include but is not limited to metal foil, and more specifically can include but is not limited to copper foil.

[0061] The separator can be any material suitable for lithium-ion battery separators in the art, for example, it can be a combination of one or more materials including but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

[0062] The lithium-ion battery also includes an electrolyte, which includes an organic solvent, an electrolyte lithium salt and an additive. The electrolyte lithium salt can be LiPF used in high-temperature electrolytes. 6 and / or LiBOB; it can also be LiBF used in low temperature electrolytes 4 、LiBOB、LiPF 6 It can also be LiBF used in the overcharge-proof electrolyte 4 、LiBOB、LiPF 6 , LiTFSI; it can also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of the above. The organic solvent may be a cyclic carbonate, including PC, EC; it may also be a chain carbonate, including DFC, DMC, or EMC; it may also be a carboxylic acid ester, including MF, MA, EA, MP, etc. The additives include but are not limited to film-forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and additives for controlling H in the electrolyte. 2 At least one of an additive for increasing the content of O and HF, an additive for improving low temperature performance, and a multifunctional additive.

[0063] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A battery cell tab connection structure, It is characterized by; including: Battery cell body; A first pole lug, one end of which is electrically connected to at least one end of the battery cell body, and the other end of which is divided into N parts along the thickness direction, where N≥2; The second electrode tab comprises a welding end and an external connection end, wherein the welding end is cut into N parts along the thickness direction; The N first pole tabs and the N second pole tabs are welded and connected in a one-to-one correspondence.

2. The battery cell tab connection structure according to claim 1, characterized in that: The other end of the first pole tab is divided into N equal parts along the thickness direction, and the welding end of the second pole tab is cut into N equal parts along the thickness direction.

3. The battery cell tab connection structure according to claim 1, characterized in that: A packaging area is also provided between the welding end and the external connection end, and the packaging area is provided with a tab glue. The distance between the lower edge of the tab glue and the upper edge of the welding end is h, wherein h satisfies the relationship: 3mm≤h≤8mm.

4. The battery cell tab connection structure according to claim 1, characterized in that: The total thickness of the first electrode tab is 300-2000 μm.

5. The battery cell tab connection structure according to claim 1, characterized in that: The total thickness of the second electrode tab is 300-2000 μm.

6. The battery cell tab connection structure according to claim 1, characterized in that: The thickness of each of the first electrode tabs is 100-200 μm.

7. The battery cell tab connection structure according to claim 1, characterized in that: The thickness of each of the second electrode tabs is 100-200 μm.

8. The battery cell tab connection structure according to claim 1, characterized in that: The width of the first pole tab is 10-500 mm, and the width of the second pole tab is 10-500 mm.

9. A method for preparing a battery cell tab connection structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) cutting the welding end of the second pole lug into N parts along the thickness direction, and polishing the edge of each second pole lug; 2) dividing the other end of the first electrode tab into N parts along the thickness direction; 3) N first electrode tabs and N second electrode tabs are connected by welding in a one-to-one correspondence.

10. A secondary battery, characterized in that; The invention comprises the battery cell tab connection structure as described in any one of claims 1 to 8.

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