Composite aluminum foil structure, pole piece and battery

Abstract

The utility model belongs to the field of battery materials, and particularly relates to a composite aluminum foil structure, a pole piece, and a battery. The composite aluminum foil structure includes an insulator and aluminum foil composited on two surfaces of the insulator in the thickness direction. The aluminum foil is provided with a coating portion and a reserved portion that is an integral structure with the coating portion; the thickness t1 of the reserved portion and the thickness t2 of the coating portion satisfy the relationship t1: t2 ≥ 2, the reserved portions are overlapped and welded with each other, the insulator is coated in the coating portion, and the reserved portion protrudes from the coating portion after overlap to form a groove on the coating portion. The composite aluminum foil structure provided by the utility model overlaps the insulator and the aluminum foil, and then the coating portion is thinned before directly welding the reserved portion. The process is simple and convenient to operate, and there is no need for step-by-step transfer welding, which is highly compatible with current large-scale mass production equipment; at the same time, the process is reduced and the cost is reduced; the reserved portion is thin after direct welding, which causes less pressure on the head space of the battery cell, improves the battery energy density, has a good welding effect, and enhances welding reliability.

Description

Technical Field

[0001] The utility model belongs to the field of battery materials, and in particular relates to a composite aluminum foil structure, a pole piece and a battery. Background Art

[0002] Under the current state of power battery technology, the weight of the current collector accounts for about 15% of the many components of lithium-ion batteries. Under the development trend of high-density and high-capacity power batteries, the current collector, as an inactive material, cannot provide energy for the battery during its operation. Therefore, reducing the proportion of the current collector in weight and volume and then increasing the application of active materials in the battery is one of the means to improve the energy density of power batteries. Based on this demand background, technical upgrades of the current collector are constantly proposed.

[0003] The contact short circuit between the aluminum foil and the anode in the current collector is the most dangerous mode of short circuit in lithium-ion batteries, and safety problems caused by it occur frequently. In recent years, composite aluminum foil with an aluminum-polymer film-aluminum sandwich structure has gradually come into the vision of lithium battery academia and industry. Composite aluminum foil has great potential in lithium battery applications due to its light and thin characteristics and high safety technical advantages. Since the conductive layer is separated by the insulating polymer film, it is impossible to use traditional welding technology to effectively guide the electrons on both sides of the pole piece. Therefore, the current welding of composite aluminum foil is mainly based on roll welding or riveting, which greatly reduces the production rhythm. At the same time, due to the increase in manufacturing processes, the battery preparation yield decreases exponentially, which brings great restrictions to the promotion of composite aluminum foil. Therefore, the current composite aluminum foil still cannot get rid of the dilemma of numerous processes. Utility Model Content

[0004] One of the purposes of the utility model is to address the deficiencies of the prior art and propose a composite aluminum foil structure, which can enable products based on the composite aluminum foil structure to be directly compatible with current welding processes, greatly facilitating the manufacture, application and promotion of the composite aluminum foil structure, so as to solve the dilemma that the current composite aluminum foil cannot get rid of the need to add processes.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A composite aluminum foil structure comprises an insulator and aluminum foils composited on two surfaces of the insulator in a thickness direction, wherein the aluminum foil is provided with a coating portion and a reserved portion which is an integral structure with the coating portion; the thickness of the reserved portion is t 1 The thickness t of the coating portion 2 Satisfies the relationship: t 1 :t 2≥2, the reserved parts are overlapped and welded with each other, the insulator is coated in the coating part, and the reserved parts protrude from the coating part after overlap to form a groove on the coating part. The reserved parts can be used to directly add the pole lugs for welding at the same time, effectively reducing the process, and the pole lugs can be placed on the outside of the reserved parts, or between the two reserved parts. The groove can be used to coat the active material layer. After coating the active material layer, its overall thickness is the same as the total thickness of the reserved parts after overlap welding, so as to form a flat and smooth pole piece.

[0007] Preferably, the coating thickness of the aluminum foil is 2 The thickness of the insulator t 3 The ratio is t 2 :t 3 ≤2 / 3, a coating portion is provided on both sides of the insulator in the thickness direction, and its total thickness is smaller than the thickness of the reserved portions after overlapping and welding, so as to form a groove for accommodating the active material layer on the coating portion. A chamfer may be provided at the junction of the reserved portion and the coating portion, so that the coating portion smoothly transitions to the reserved portion, and after the active material layer is filled in the groove, the reserved portion has no sharp corners that obviously protrude from the active material layer. The pole ear slot can be simultaneously placed in the pole ear sheet for integrated welding, and only one welding is required to simultaneously complete the welding of the upper and lower reserved portions and the welding of the pole ear sheet and the reserved portion. The gap can prevent the pole ear sheet from being in contact with the insulator at the welding point during welding, thereby reducing the impact on the insulator during welding. After welding, it can be equally cut at the middle depression of the X-shaped section.

[0008] Preferably, the reserved area S of the aluminum foil is 1 The coating area S of the aluminum foil 2 The ratio is 1 / 200≤S 1 :S 2 ≤1 / 3. The ratio can be appropriately adjusted according to the size of the tab provided on the reserved portion and the active material layer provided on the coating portion.

[0009] Preferably, the sheet resistance range of the coating portion is 5-50 mΩ, and the sheet resistance range of the reserved portion is 4-20 mΩ.

[0010] Preferably, the thickness of the insulator is 1-10 μm, more preferably 4 μm, 5 μm, 6 μm and 7 μm.

[0011] Preferably, the thickness of the reserved portion of the aluminum foil is 4-10 μm, more preferably 5 μm, 5.5 μm, 6 μm and 7 μm.

[0012] Preferably, the thickness of the coating portion of the aluminum foil is 0.5-2 μm, more preferably 0.8 μm, 1 μm, 1.2 μm and 1.4 μm.

[0013] Preferably, the reserved portion of the aluminum foil is provided with a chamfer, and the chamfer is a rounded corner or a beveled corner.

[0014] The second purpose of the utility model is to provide a pole piece with good electrochemical performance in view of the deficiencies of the prior art.

[0015] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0016] A pole piece comprises the above-mentioned composite aluminum foil structure and an electrode layer located on the surface of the composite aluminum foil structure.

[0017] The third purpose of the utility model is to provide a battery with less side reactions, high initial coulombic efficiency and long cycle life in view of the deficiencies in the prior art.

[0018] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0019] A battery comprises the above-mentioned pole piece.

[0020] Compared with the prior art, the beneficial effects of the utility model are as follows: the composite aluminum foil structure provided by the utility model includes an insulator and an aluminum foil, and an aluminum foil is respectively provided on the two surfaces in the thickness direction of the insulator, wherein the overlapping area of ​​the aluminum foil and the insulator is a coating part, and the overlapping area of ​​the aluminum foil side is a reserved part. After the insulator and the aluminum foil are overlapped and the coating part is thinned, the reserved part is directly welded. The process is simple and convenient to operate, and there is no need to perform step-by-step transfer welding, which is highly compatible with current large-scale mass production equipment. At the same time, the process is reduced, which can effectively reduce costs for enterprises. After the reserved part is directly welded, the thickness is thin, and the pressure on the head space of the battery cell is small, which can further improve the battery energy density, the welding effect is good, and the welding reliability is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the composite aluminum foil of the utility model.

[0022] Figure 2 It is another structural schematic diagram of the composite aluminum foil of the utility model.

[0023] Figure 3 It is a schematic cross-sectional structure diagram of embodiments 1-3 of the present utility model.

[0024] Figure 4 It is a schematic cross-sectional structure diagram of embodiment 4 of the present utility model.

[0025] Figure 5 It is a schematic cross-sectional structure diagram of Example 5 of the present utility model.

[0026] Figure 6It is a structural schematic diagram of comparative example 1 of the present utility model.

[0027] Figure 7 This is a continuous assembly effect diagram of the composite aluminum foil structure of the utility model.

[0028] Reference numerals:

[0029] 1. Insulator;

[0030] 2. aluminum foil, 21. coating portion, 22. reserved portion, 23. groove, 24. pole piece groove. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below in conjunction with specific implementations and the accompanying drawings, but the implementations of the present invention are not limited thereto.

[0032] like Figure 1-2 As shown, in a specific embodiment, the utility model provides a composite aluminum foil structure, including an insulator 1 and an aluminum foil 2, including an insulator 1 and an aluminum foil 2 composited on two surfaces of the insulator 1 in the thickness direction, and the aluminum foil 2 is provided with a coating portion 21 and a reserved portion 22 which is an integral structure with the coating portion 21. The reserved portion 22 can be overlapped on two opposite sides of the width of the insulator 1, or can be overlapped on two opposite sides of the length of the insulator 1; and the reserved portion 22 can be flush with the coating portion 21, or can protrude from the coating portion 21, and the specific setting can be determined according to production requirements. If it is flush, it is necessary to add a pole ear and a corresponding pole piece and then weld it synchronously with the reserved portion 22, and the preparation is completed by one welding. If a protruding portion is provided, it can be used as a pole ear, which is integrally formed with the reserved portion 22, and then welded synchronously with the reserved portion 22 after adding the corresponding pole piece.

[0033] In some embodiments, the thickness of the reserved portion 22 of the aluminum foil 2 is 1 The thickness t of the coating portion 21 of the aluminum foil 2 2 The ratio is t 1 :t 2 ≥2. Preferably, t 1 :t 2 =4, t 1 :t 2 =5, t 1 :t 2 =6.

[0034] In some embodiments, the coating portion 21 of the aluminum foil 2 has a thickness t 2 The thickness t of the insulator 1 3 The ratio is t 2 :t 3 ≤2 / 3. Preferably, t 2 :t 3 =0.5, t2 :t 3 =1 / 3, t 2 :t 3 =0.25.

[0035] After the reserved portion 22 is overlapped, it is sunken to form a pole ear groove 24 that can be used for synchronous welding with the pole ear sheet. A gap is formed between the mutually overlapped reserved portion 22 and the insulator 1, and the cross-section of the two connected reserved portions 22 is X-shaped. A coating portion 21 is provided on both sides of the thickness direction of the insulator 1, and its total thickness is smaller than the thickness of the reserved portion 22 after overlapping and welding, so as to form a groove 23 for accommodating the active material layer on the coating portion 21. A chamfer may be provided at the junction of the reserved portion 22 and the coating portion 21, so that the coating portion 21 smoothly transitions to the reserved portion 22, and after the active material layer is filled in the groove 23, the reserved portion 22 has no sharp corners that obviously protrude from the active material layer. The pole ear groove 24 can be synchronously placed in the pole ear sheet for integrated welding, and only one welding is required to simultaneously complete the welding of the upper and lower reserved portions 22 and the welding of the pole ear sheet and the reserved portion 22. The gap can prevent the welding point of the pole piece from contacting with the insulator 1 during welding, thereby reducing the impact on the insulator 1 during welding. After welding is completed, equal cutting can be made at the middle concave part of the X-shaped section, such as Figure 7 shown.

[0036] By respectively arranging a groove 23 for filling the active material layer on the coating portion 21 and a pole ear groove 24 for synchronously welding the pole ear on the reserved portion 22, when the preparation of the composite aluminum film is completed, the surface of the active material layer is flush with the pole ear, and a smooth and flat composite aluminum foil base surface can be formed, which is convenient for repeated stacking of multiple layers of composite aluminum foil to prepare battery cells.

[0037] In some embodiments, the area S of the reserved portion 22 of the aluminum foil 2 is 1 The area S of the coating portion 21 of the aluminum foil 2 2 The ratio is 1 / 200≤S 1 :S 2 ≤1 / 3. Preferably, S 1 :S 2 =1 / 30, S 1 :S 2 =1 / 20, S 1 :S 2 =1 / 10. When the above ratio is used, when the reserved portion 22 is flush with the upper and lower ends of the coating portion 21, the width of the reserved portion 22 is relatively narrow, which is convenient for welding the tabs and covering and fitting the insulator 1 inside the aluminum foil 2.

[0038] In some embodiments, the square resistance of the coating portion 21 is in the range of 5-50 mΩ, and the square resistance of the reserved portion 22 is in the range of 4-20 mΩ. Preferably, the square resistance of the coating portion 21 is 25 mΩ, 30 mΩ, 35 mΩ, and the square resistance of the reserved portion 22 is 6 mΩ, 8 mΩ, 10 mΩ. The adopted square resistance is low and the conductivity is high, so that the corresponding electrochemical performance of the lithium-ion battery is better.

[0039] In some embodiments, the thickness of the insulator 1 is 1-10 μm, preferably 4 μm, 5 μm, 6 μm and 7 μm.

[0040] In some embodiments, the thickness of the reserved portion 22 of the aluminum foil 2 is 4-10 μm, more preferably 5 μm, 5.5 μm, 6 μm and 7 μm.

[0041] In some embodiments, the thickness of the coating portion 21 of the aluminum foil 2 is 0.5-2 μm, more preferably 0.8 μm, 1 μm, 1.2 μm and 1.4 μm.

[0042] In some embodiments, the reserved portion 22 of the aluminum foil 2 is provided with a chamfer, and the chamfer is a rounded corner or a beveled corner.

[0043] In some embodiments of the utility model, a pole piece is also provided, comprising the above-mentioned composite aluminum foil structure and an electrode layer located on the surface of the composite aluminum foil structure, which has good electrochemical performance.

[0044] In some embodiments of the utility model, a battery is provided, including the above-mentioned electrode, and the battery has the advantages of less side reactions, high first coulomb efficiency and long cycle life.

[0045] Embodiment 1:

[0046] like Figure 3 As shown, a 6 μm PET film is selected as the insulator 1, and after the outer side of the insulator 1 is coated with glue, aluminum foil 2 is bonded on both sides. The aluminum foil 2 bonded on both sides is 5 μm aluminum foil 2. After stacking, the size of the foil substrate is that the total thickness of the coating part 21 is 16 μm, and the total thickness of the reserved part 22 is 10 μm.

[0047] The width W of the coating portion 21 is determined according to the cell design. 2 and the width W of the reserved portion 22 1 , the coating part 21 on both sides of the foil substrate is thinned by laser engraving, specifically, the coating part 21 of the aluminum foil is reduced to 1 μm, that is, the total thickness of the coating part 21 is 8 μm, and the reserved part 22 is slightly protruded from the coating part 21;

[0048] The composite aluminum foil structure with a square resistance of 30±5mΩ of the coating portion 21 required by the utility model is obtained above, and then the reserved portion 22 is welded to cover the PET film inside the aluminum foil 2. After the reserved portions 22 located on both sides of the insulator 1 are welded together, the edges thereof form upward sharp corners, which are inconvenient to affect subsequent processing, so the portion needs to be chamfered by laser, and the chamfer here is an oblique angle, and the inclined surface is parallel to the coating portion 21 after welding.

[0049] The insulator 1 and the coating portion 21 of the aluminum foil 2 have the same area size, the reserved portion 22 is arranged on both sides along the width of the insulator 1, and the reserved portion 22 and the coating portion 21 are flush with each other along the length direction of the insulator 1. Therefore, it is necessary to add pole ears on the upper and lower sides of the reserved portion 22. When the reserved portion 22 is welded, the pole ears are welded simultaneously. Compared with the existing process, it can be completed in one step, reducing the manufacturing process and speeding up the production speed.

[0050] Embodiment 2:

[0051] like Figure 3 As shown, the difference from Example 1 is that a 6μm PET film is selected as the insulator 1, a 6μm aluminum foil 2 is selected for bonding on both sides, and the coating part 21 is thinned to 1μm by laser. The rest of the operations are the same as those in Example 1 and will not be described in detail here.

[0052] Embodiment 3:

[0053] like Figure 3 As shown, the difference from Example 1 is that a 5μm PET film is selected as the insulator 1, a 5μm aluminum foil 2 is selected for bonding on both sides, and the coating part 21 is thinned to 1.2μm by laser. The rest of the operations are the same as those in Example 1 and will not be described in detail here.

[0054] Embodiment 4:

[0055] like Figure 4 As shown, a 6 μm PET film is selected as the insulator 1, and after the outer side of the insulator 1 is coated with glue, aluminum foil 2 is bonded on both sides. The aluminum foil 2 bonded on both sides is 5 μm aluminum foil 2. After stacking, the size of the foil substrate is that the total thickness of the coating part 21 is 16 μm, and the total thickness of the reserved part 22 is 10 μm.

[0056] The width W of the coating portion 21 according to the cell design 2 and the width W of the reserved portion 22 1 , prepare a 7% sodium hydroxide solution and apply it on the coating part 21, chemically corrode it, and obtain a composite aluminum foil structure with a square resistance of 30±5mΩ for the coating part 21, then weld the reserved part 22, and wrap the PET film inside the aluminum foil 2.

[0057] The insulator 1 and the aluminum foil 2 have the same area size of the coating portion 21, the reserved portion 22 is arranged on both sides along the length of the insulator 1, and the reserved portion 22 is protruding along the width direction of the insulator 1 with a pole ear, the pole ear and the reserved portion 22 are integrally formed, and the composite aluminum foil structure of the utility model can be obtained by welding the reserved portion 22, the process is simple, and the production efficiency is high.

[0058] Embodiment 5:

[0059] like Figure 5 As shown in the figure, a 6μm PET film is selected as the insulator 1, and an aluminum foil 2 is prepared on its surface by vacuum evaporation. When the coating part 21 covering the insulator 1 is prepared to a square resistance of 30±5mΩ, the width W of the coating part 21 designed according to the battery cell is 2 , the reserved portion 22 has a width W 1 , use the cover plate to block W 2 The reserved portion 22 is continuously prepared until its square resistance reaches 4-10 mΩ, thereby obtaining the composite aluminum foil structure of the utility model. The coating portion 21 and the reserved portion 22 are integrally formed, and the insulator 1 can be completely covered by the aluminum foil 2, and the aluminum foil 2 is uniform and dense, and has good electrochemical performance.

[0060] Comparative Example 1:

[0061] like Figure 6 As shown, a 6μm PET film is selected as the insulator 1, and aluminum foil 2 is bonded on both sides after the outer side of the insulator 1 is coated with glue. The aluminum foil 2 bonded on both sides is 5μm aluminum foil 2. After stacking, the size of the foil substrate is 16μm in total thickness of the middle stacking part and 10μm in total thickness of the welding parts on both sides. No thinning treatment is performed on the aluminum foil 2 on the middle stacking part. The composite aluminum foil formed in this way has a simple structure, uneven overall resistance distribution, large in the middle and small on the sides, and general electrochemical performance.

[0062] According to the disclosure and teaching of the above description, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the above specific implementation, and any obvious improvement, replacement or modification made by the technicians in this field on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in this specification, these terms are only for the convenience of explanation and do not constitute any limitation to the utility model.

Claims

1. A composite aluminum foil structure, characterized in that: It includes an insulator and aluminum foil compounded on two surfaces of the insulator in the thickness direction, the aluminum foil is provided with a coating portion and a reserved portion which is an integral structure with the coating portion; the thickness t1 of the reserved portion and the thickness t2 of the coating portion satisfy the relationship t1:t2≥2, the reserved portions are overlapped and welded with each other, the insulator is coated in the coating portion, and the reserved portion protrudes from the coating portion after overlap to form a groove on the coating portion.

2. The composite aluminum foil structure according to claim 1, characterized in that: The ratio of the thickness t2 of the coating part of the aluminum foil to the thickness t3 of the insulator is t2:t3≤2 / 3. After overlapping, the reserved part is sunken to form a pole ear groove which can be used for synchronous welding with the pole ear sheet. A gap is formed between the mutually overlapping reserved parts and the insulator, and the cross-section of the two connected reserved parts is X-shaped.

3. The composite aluminum foil structure according to claim 2, characterized in that: The ratio of the reserved area S1 of the aluminum foil to the coating area S2 of the aluminum foil is 1 / 200≤S1:S2≤1 / 3.

4. The composite aluminum foil structure according to claim 3, characterized in that: The square resistance range of the coating portion is 5-50 mΩ, and the square resistance range of the reserved portion is 4-20 mΩ.

5. The composite aluminum foil structure according to claim 1, characterized in that: The thickness of the insulator is 1-10 μm.

6. The composite aluminum foil structure according to claim 1, characterized in that: The thickness of the reserved portion of the aluminum foil is 4-10 μm.

7. The composite aluminum foil structure according to claim 6, characterized in that: The thickness of the coating portion of the aluminum foil is 0.5-2 μm.

8. The composite aluminum foil structure according to claim 1, characterized in that: The reserved portion of the aluminum foil is provided with a chamfer.

9. A pole piece, characterized in that: The pole piece comprises the composite aluminum foil structure as described in any one of claims 1 to 8 and an electrode layer located on the surface of the composite aluminum foil structure.

10. A battery, characterized in that: The battery comprises the pole piece as claimed in claim 9.

Images