A composite current collector for a lithium-ion battery and a preparation method thereof

Abstract

The present invention provides a composite current collector for a lithium ion battery pole piece and a preparation method thereof, relating to the field of lithium ion batteries. The composite current collector comprises two layers of foil materials arranged up and down and a composite layer arranged between the foil materials, wherein the composite layer is a sandwich between the two layers of foil materials, a plurality of through holes are opened on the surface of the composite foil material, the foil material and the composite layer are pressed into one by external pressure, the thickness of the single-layer foil material is 0.2μm-1μm, the inner wall of the through hole is provided with a connecting portion, the outer contour of the extension portion is in contact with the composite layer, and the two foil materials are welded through the connecting portion, and the composite layer is further fixed between the foil materials. The foil material is lighter and thinner than the traditional 10μm foil material, which is beneficial to improving the lightness and thinness of the later battery core manufacturing material. The tensile strength of the microporous composite foil material can be improved by the composite layer sandwich, the tension of the microporous composite foil material is strengthened, and the quality of the battery core material can be improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium ion batteries, and in particular to a pole piece composite current collector for lithium ion batteries and a preparation method thereof. Background Art

[0002] In the lithium battery manufacturing industry, foil is required as the positive electrode. As batteries develop towards being lighter and thinner, battery cells are also required to have high energy density, low space occupancy, high battery capacity, and high safety performance.

[0003] Currently, some laminated foils are used in digital 3C battery cells. Compared to standard foils, laminated foils have better tensile strength. However, due to the presence of interlayer materials, laminated foils are relatively heavy. Despite their excellent tensile strength, they often increase the weight of the battery cell during production. Summary of the Invention

[0004] The present invention aims to provide a composite current collector for a lithium-ion battery electrode and a method for preparing the same to address the aforementioned technical issues. To achieve this objective, the present invention employs the following technical solutions:

[0005] A composite current collector for a lithium-ion battery electrode. The composite current collector comprises two layers of foil material arranged vertically and a composite layer disposed between the foil materials. The composite layer is a sandwich layer between the two layers of foil material. A plurality of through holes are formed on the surface of the composite current collector. The foil material and the composite layer are combined to form a composite foil material, thereby improving the stretchability of subsequent battery core materials. The weight of the foil material after the punching treatment is reduced, which is beneficial to reducing the weight of the battery core materials.

[0006] A further preferred solution is that the foil material and the composite layer are pressed together by external pressure, wherein the pressure source includes but is not limited to rolling, punching or pressing.

[0007] A further preferred solution is that the thickness of a single layer of the foil is 0.2 μm-1 μm.

[0008] A further preferred solution: the composite layer is made of a conductive film material.

[0009] Furthermore, a connecting portion is provided on the inner wall of the through hole, and both ends of the connecting portion are respectively connected to the two layers of foil. The edge of the connecting portion is vacuum plated or laser welded to the foil, which is beneficial to increase the connection area. Similarly, the connection area between the two layers of foil is increased, and the two layers of foil are welded and fixed to increase connectivity.

[0010] Furthermore, the connecting portion is tubular.

[0011] Furthermore, the connecting portion is an extension portion of the foil material, and the foil material has a deformable characteristic. The through hole opening of the foil material is deformed by utilizing the compliance stress of the punching and extends downward to form the extension portion.

[0012] Furthermore, the extension portion is punched to extend through the through hole.

[0013] Furthermore, the outer contour of the extension portion contacts the composite layer, and the composite layer is further fixed between the two foils after welding through the connecting portion, thereby improving the firmness of the composite between the two foils and the composite layer.

[0014] A method for preparing a composite current collector for a lithium-ion battery, the method comprising the following steps:

[0015] Step 1: Using a lamination technique to press the foil and the composite layer to obtain a composite foil;

[0016] Step 2: Punch a number of through holes on the surface of the foil;

[0017] Step 3: Connect the two layers of foil along the inner wall of the through hole by welding, and the welding method is vacuum plating or laser.

[0018] Beneficial effects of the present invention:

[0019] The foil is thinner and lighter than the traditional 10μm foil, which is beneficial to improving the lightness and thinness of the later battery cell manufacturing materials;

[0020] The end of the connection part is welded by vacuum plating or laser dot welding, or a connection ring with the same material as the foil is used to connect the connection part and the foil. Both connection methods of the connection part and the foil 1 can effectively expand the connection area between the connection part and the foil. The connection part is melted to the foil or the edge of the connection ring, which is conducive to the transition between the two layers of foil. The connection part passes through the through hole, and the outer contour of the connection part is connected to the composite layer, which can further fix the foil and the composite layer and improve the composite effect.

[0021] The connection between the connecting part and the foil is transitioned by a connecting ring, which has an anti-cracking effect and the connecting part between the connecting part and the foil is not easy to break.

[0022] The through-holes are 45μm-90μm, which effectively reduces the weight of the battery material while avoiding leakage and seepage of lithium batteries in the later stage due to large pore diameters. The hole spacing is controlled within 1-10mm. The holes are punched according to the spacing within this planned range to avoid the through-holes being too dense and affecting the strength of the composite foil, and the through-holes being too sparse and affecting the performance.

[0023] The composite layer interlayer can improve the tensile strength of the microporous composite foil and strengthen the tension of the microporous composite foil, which can improve the quality of battery cell materials and effectively avoid the problem of traditional foil easily breaking and affecting production. The microporous composite foil is not easy to crack and can also solve the problem that the tensile strength of traditional foil is too low to support coating.

[0024] When a through hole is punched at the edge of the microporous composite foil, an incomplete notch will appear in the through hole. The notch position of the microporous composite foil can increase the surface tension of the battery material. The microporous composite foil has a relatively high tensile strength, which helps to prevent the battery material from cracking.

[0025] The two layers of foil conduct electricity through the connection part, which helps to enhance the conductivity and ensure the stable operation of the battery cell;

[0026] When high temperature is generated during the operation of the battery cell, the composite layer melts due to the high temperature, reducing the conductivity of the electrode, thereby reducing the possibility of the battery cell catching fire.

[0027] Batteries such as lithium iron phosphate, lithium cobalt oxide, or lithium manganese oxide can all adopt the composite foil material of the present invention, which can especially protect the operation safety of lithium cobalt oxide batteries, effectively protect the battery from short circuit, thereby improving the battery safety performance, and also protect the cycle life of lithium manganese oxide batteries. The composite foil can effectively reduce the temperature, improve the heat dissipation capacity, and extend the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the overall structure of a composite current collector for a lithium-ion battery of the present invention;

[0029] Figure 2 Schematic diagram of the foil and composite layer structure of the present invention (unperforated state);

[0030] Figure 3 Schematic diagram of the foil and composite layer structure of the present invention (punched state);

[0031] Figure 4 This is a partial schematic diagram of the interior of the microporous composite foil structure of the present invention;

[0032] Figure 5 A reference diagram for the specifications of the microporous composite foil of the present invention for preparing a combined structure;

[0033] Figure 6 This is a schematic diagram of welding the connecting portion and the foil structure of the present invention;

[0034] Figure 7 It is a schematic diagram of welding the connecting portion, connecting ring and foil structure of the present invention.

[0035] In the figure: foil (1), composite layer (2), through hole (3). DETAILED DESCRIPTION

[0036] The following combination Figure 1-Figure 7 The accompanying drawings further illustrate embodiments of the present invention:

[0037] First see Figure 1-Figure 3 A composite current collector for a lithium-ion battery electrode, the composite current collector comprising two layers of foil material 1 arranged one above the other and a composite layer 2 disposed between the foil materials 1, wherein the composite layer 2 is an interlayer between the two layers of the foil material 1;

[0038] The foil 1 can be made of aluminum foil or copper foil, and the thickness of the foil 1 is 0.2 μm-1 μm. Compared with the traditional 10 μm foil, the foil 1 is lighter and thinner, which improves the lightness and thinness of the later battery cell manufacturing material.

[0039] The foil 1 and the composite layer 2 are pressed together by external pressure. Before the foil 1 and the composite layer 2 are pressed together, an adhesive can be used to adhere the foil 1 and the composite layer 2. The mechanical force for pressing the foil 1 and the composite layer 2 together includes but is not limited to rolling, punching or pressing. Any mechanical device that can generate a pressing force is suitable for the composite work of the foil 1 and the composite layer 2. The foil 1 and the composite layer 2 are preliminarily composited in this process.

[0040] The composite current collector surface is provided with a plurality of through holes 3; after the foil 1 and the composite layer 2 are initially composited, they are subjected to a punching process. In the punching process, the A-side foil 1 or the B-side foil 1 can be selected as the punching surface, wherein the punching method is selected from punching, stamping or drilling, etc., which are conventional technical means in this field and belong to the common knowledge of technicians and will not be described in detail. A plurality of through holes 3 are punched on the surface of the composite foil, wherein the shape of the through holes 3 can be circular, rectangular or triangular, etc. After the punching is completed, a microporous composite foil (such as Figure 3 shown).

[0041] See also Figure 3-Figure 5 , the inner wall of the through hole 3 is provided with a connecting portion, which is an extension of the foil 1. The extension is punched and extends through the through hole 3; the hole punched on the foil 1 is the through hole 3, wherein the composite layer 2 as the sandwich is punched through, the punched foil 1 is partially broken and deformed by the stress of the punching and drilling to enter the through hole 3, forming a connecting portion, and the end of the extension of the foil 1 extends to another layer of foil 1. At this time, the punched foil 1 forms a tubular shape (such as Figure 3 、 Figure 4 shown);

[0042] See also Figure 6-Figure 7 , both ends of the connecting portion are connected to the two layers of foil 1 respectively;

[0043] Regarding the method for connecting the connecting portion and the foil 1, the present invention provides two embodiments:

[0044] Example 1: The end of the connection part is welded by vacuum plating or laser dot welding, so that the end of the connection part is welded to the edge of the through hole 3 in another layer of foil 1 (such as Figure 6 (As shown in the electroplating section), the welding between the two layers of foil 1 is completed, wherein the vacuum electroplating method includes but is not limited to magnetron sputtering, vacuum evaporation, ion plating and other electroplating methods;

[0045] Example 2: Use a connecting ring with the same material as the foil to connect the transition connecting part to the foil 1, place the connecting ring at the end of the connecting part at the position corresponding to the periphery of the through hole 3, and the connecting ring is located on the surface of the foil 1 without the perforation (such as Figure 7 The connecting ring is then welded to the end of the connecting portion and the surface of the non-perforated foil 1 by laser dot matrix welding. At this time, the connecting ring, the connecting portion and the foil 1 are welded and fixed as one, and the connecting portion is welded through the connecting ring.

[0046] The above two connection methods of the connection part and the foil 1 can both effectively expand the connection area between the connection part and the foil 1. The edge of the connection part is welded. Similarly, the connection part is melted to the foil 1 or the edge of the connection ring. The two layers of foil 1 are indirectly welded. The area of ​​the welded connection part is large, which is conducive to the transition between the two layers of foil. The connection part passes through the through hole 3, and the outer contour of the connection part is connected to the composite layer 2, which can further fix the foil 1 and the composite layer 2 and improve the composite effect.

[0047] The connection between the connecting part and the foil material 1 is connected by a connecting ring, which has an anti-cracking effect, and the connecting part between the connecting part and the foil material 1 is not easy to break.

[0048] A method for preparing a composite current collector for a lithium-ion battery, the method comprising the following steps:

[0049] Step 1: Use a lamination technique to press the foil 1 and the composite layer 2 to obtain a composite foil. The mechanical devices that generate the pressing force are all suitable for the composite work of the foil 1 and the composite layer 2. The foil 1 and the composite layer 2 are preliminarily composited in this process.

[0050] Step 2: Punch a number of through holes 3 on the surface of the foil 1. The inner diameter of the through holes 3 should be controlled within 45 μm-90 μm. The through holes 3 within this specification range effectively reduce the weight of the battery material while avoiding leakage and seepage of the lithium battery in the later stage due to larger pore diameters. The hole spacing is controlled within 1-10 mm. Punch according to the spacing within this planned range to avoid the through holes 3 being too dense and affecting the strength of the composite foil, and to avoid the through holes 3 being too sparse and affecting the use effect.

[0051] Step 3: Connect the two layers of foil 1 along the inner wall of the through hole 3 by welding. The welding method is vacuum plating or laser welding. Direct welding can also be used to weld the transition connecting part with the foil 1 using a connecting ring. The end of the connecting part is welded to the edge of the through hole 3 in the other layer of foil 1 (such as Figure 6 、 Figure 7 shown);

[0052] Furthermore, in order to improve the success rate of welding, the welding head can be preheated before the welding work is carried out. After the welding head temperature reaches 660°C-700°C, the foil 1 is welded, so that the welding work is completed in one step. After the composite foil is cooled, the production of the microporous composite foil is completed;

[0053] Furthermore, during the cooling process of the composite foil, it is possible to observe whether it has cracked, so as to prevent defective composite foil materials from flowing into the battery cell processing process. After the composite foil cools to the room temperature, the work is completed.

[0054] The composite layer 2 is a conductive film material such as polyethylene terephthalate or polybutylene terephthalate. As an interlayer, the composite layer 2 has good tensile properties. When the microporous composite foil is used in the production of battery cells in the future, the interlayer of the composite layer 2 can improve the tensile strength of the microporous composite foil, strengthen the tension of the microporous composite foil, improve the quality of the battery cell material, and effectively avoid the problem of traditional foil easily breaking and affecting production. The microporous composite foil is not easy to crack, and can also solve the problem that the tensile strength of traditional foil is too low to support coating.

[0055] When the through hole 3 is punched at the edge of the microporous composite foil, the through hole 3 will appear in an incomplete notch shape (such as Figure 3 As shown), at this time, the surface tension of the battery material can be increased by the notch position of the microporous composite foil. The microporous composite foil has a relatively high tensile strength, which is beneficial to prevent the battery material from cracking.

[0056] The two layers of foil 1 are stably conductive through the connection portion, which is beneficial to enhance the conductivity and ensure the stable operation of the battery cell;

[0057] When the battery cell generates high temperature during operation, the composite layer 2 melts due to the high temperature, reducing the conductivity of the electrode and greatly reducing the possibility of fire in the battery cell.

[0058] Furthermore, batteries such as lithium iron phosphate, lithium cobalt oxide, or lithium manganese oxide can all use the composite foil material of the present invention. In particular, lithium cobalt oxide has a higher capacity than lithium iron phosphate batteries, and its charge and discharge structure is easily changed, resulting in low safety performance. The use of this composite foil material can effectively protect the battery from short circuits, thereby improving battery safety performance.

[0059] However, lithium manganese oxide batteries have a high operating voltage, and Mn is easily dissolved at high temperatures, which affects the battery cycle life. This composite foil can effectively reduce the temperature, improve the heat dissipation capacity, and extend the battery life.

Claims

1. A composite current collector for a lithium-ion battery, characterized in that: The composite current collector comprises two layers of foil materials (1) arranged one above the other and a composite layer (2) arranged between the foil materials (1), wherein the composite layer (2) is a sandwich layer between the two layers of the foil materials (1), the foil materials (1) and the composite layer (2) are pressed together by external pressure, and a plurality of through holes (3) are opened on the surface of the composite current collector; The composite layer (2) is made of a conductive film material, and a connecting portion is provided on the inner wall of the through hole (3). Both ends of the connecting portion are respectively connected to the two layers of foil (1). The connecting portion is tubular and is an extension of the foil (1). The extension is punched and extends through the through hole (3). A connecting ring made of the same material as the foil (1) is used to connect the transition connecting portion and the foil (1), and the connecting ring is placed at a position corresponding to the periphery of the through hole (3) at the end of the connecting portion.

2. The composite current collector for a lithium-ion battery according to claim 1, characterized in that: The thickness of a single layer of the foil (1) is 0.2 μm-1 μm.

3. The composite current collector for a lithium-ion battery according to claim 1, wherein: The outer contour of the extension portion is in contact with the composite layer (2).

4. A method for preparing a composite current collector for a lithium-ion battery according to any one of claims 1 to 3, the method comprising the following steps: Step 1: Using a lamination technique to press the foil (1) and the composite layer (2) to obtain a composite foil; Step 2: punching a plurality of through holes (3) on the surface of the foil (1); Step 3: Connect the two layers of foil (1) along the inner wall of the through hole (3) by welding, wherein the welding method is vacuum plating or laser.

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