Current collectors and electrodes containing them, and their preparation methods

Abstract

This invention discloses a current collector, an electrode containing the same, and a method for preparing the same. The current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer along its thickness direction. At least one surface of the support layer in contact with the conductive layer has a first texture, and the surface of the conductive layer in contact with the support layer has a second texture. The first and second textures are concave-convex and mutually conforming. The current collector of this invention has conforming textures on the surfaces of the support layer and the conductive layer in contact, which effectively enables conductivity between the conductive layers on both sides, improving the current-carrying capacity of the current collector; it also prevents cracking of the conductive layer, improving the welding capability between the external electrode tab and the conductive layer; the energy density of the battery cell is increased by approximately 10%; and the safety performance of the battery cell is improved.

Description

Technical Field

[0001] This invention relates to a current collector and an electrode containing the same, and a method for preparing the same. Background Technology

[0002] With the rapid development of the lithium-ion battery industry, the requirements for battery cost and performance are becoming increasingly stringent. Copper foil accounts for about 13% of the total weight of lithium batteries. Composite current collectors significantly reduce the weight of foil materials and improve battery energy density. In addition, the copper / aluminum content in PET composite current collectors is significantly lower than that of ordinary copper foil, which is expected to significantly reduce costs.

[0003] Composite current collectors generally include a support layer and functional metal composite layers on both sides of the support layer. Since the outer layer of the composite current collector is a metal layer with good electrical and thermal conductivity, and the inner layer is a support layer with poor electrical conductivity, the welding of the composite current collector and the internal resistance after welding affect a series of battery performance characteristics.

[0004] Composite current collectors are generally welded using ultrasonic roll welding. They are pre-welded using a method of sandwiching a support layer with two functional metal composite layers, and then mainly welded to the external tabs of the battery. Alternatively, a single functional metal composite layer is pre-welded to the support foil, and then mainly welded to the external tabs of the battery.

[0005] The pre-welding method of sandwiching the support layer between two functional metal composite layers leads to serious waste of functional metal composite layers, increases the thickness of the tab area, causes difficulties for subsequent main welding and cell assembly, and increases the weight of the cell to a certain extent.

[0006] Pre-welding of single-sided functional metal composite layers, such as conductive foil, can lead to breakage and damage of the foil due to its thinness, affecting the subsequent welding effect with external tabs and deteriorating the cell performance. Summary of the Invention

[0007] To overcome the shortcomings of existing composite current collectors, such as the tendency for functional metal composite layers to fracture and break after pre-welding, affecting cell performance, this invention provides a current collector, an electrode containing the current collector, and a method for its preparation. This current collector, by having matching textures on the surfaces where the support layer and conductive layer contact, effectively achieves conductivity between the conductive layers on both sides, improving the current collector's current-carrying capacity; it also prevents cracking in the conductive layer, improving the welding capability between the external electrode tab and the conductive layer; the energy density of the cell is increased by approximately 10%; and the safety performance of the cell is improved.

[0008] In a first aspect, the present invention provides a current collector comprising a support layer and a conductive layer disposed on at least one surface of the support layer along the thickness direction, wherein at least one surface of the support layer in contact with the conductive layer has a first texture, and the surface of the conductive layer in contact with the support layer has a second texture, wherein the first texture and the second texture are concave-convex in shape and conform to each other.

[0009] Secondly, the present invention provides a method for preparing the current collector as described above, which includes the following steps:

[0010] S1. Surface-treat at least one surface of the support layer to form a first texture; and / or, surface-treat one surface of the conductive layer to form a second texture;

[0011] S2. The conductive layer is disposed on at least one surface of the support layer along the thickness direction and hot-pressed to form a first texture on at least one surface of the support layer that is in contact with the conductive layer, and a second texture on the surface of the conductive layer that is in contact with the support layer. The first texture and the second texture are concave-convex in shape and match each other.

[0012] Thirdly, the present invention provides an electrode comprising a current collector as described above, and an active material layer.

[0013] Fourthly, the present invention provides a battery comprising the electrodes as described above.

[0014] The positive and progressive effects of this invention are as follows:

[0015] The current collector of this invention has matching textures on the surface where the support layer and the conductive layer are in contact, which can effectively realize the conduction of the conductive layers on both sides, improve the current carrying capacity of the current collector, prevent cracks in the conductive layer, and improve the welding ability between the external electrode and the conductive layer; the energy density of the battery cell is increased by about 10%; and the safety performance of the battery cell is improved compared to the previous version.

[0016] The current collector preparation method of the present invention can reduce the cost of the conductive layer by about 30% by riveting the surfaces of the support layer and the conductive layer that have matching textures. The raw material cost of the overall battery cell is expected to be reduced by 1-2%. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the support layer in Example 1 before surface treatment.

[0018] Figure 2 This is a schematic diagram of the structure of the support layer after the texture is formed in Example 1. Detailed Implementation

[0019] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0020] In the current collector of the first aspect of the present invention:

[0021] In this invention, the absolute depth of the recess in the first texture refers to the vertical distance from the lowest point to the end edge of the recess in the longitudinal direction. Preferably, the absolute depth of the recess in the first texture is 0.2-1.0 μm, for example, 0.5 μm.

[0022] In this invention, preferably, the ratio of the absolute depth of the recess of the first texture to the thickness of the support layer is 0.02-0.5, for example, 0.125.

[0023] In this invention, preferably, the texture of the concave and convex shape is a spark pattern, a wavy pattern, or a thread.

[0024] In this invention, preferably, the area of ​​the first texture on the surface of the support layer accounts for 60-100% of the surface area of ​​the support layer.

[0025] In this invention, preferably, on one surface of the conductive layer, the area of ​​the second texture accounts for 60-100% of the surface area of ​​the conductive layer.

[0026] In this invention, preferably, the material of the support layer is selected from one or more of polyamide, polyimide, polyester, polyolefin, polyacetylene, siloxane polymer, polyether, polyol, polysulfone, polysaccharide polymer, amino acid polymer, polysulfide, aromatic ring polymer, aromatic heterocyclic polymer, epoxy resin, phenolic resin, and their derivatives, crosslinks and copolymers; the polyester is preferably polyethylene terephthalate (PET).

[0027] In this invention, preferably, the material of the conductive layer is selected from one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0028] In this invention, preferably, the thickness of the support layer is 2μm-10μm, for example 4μm.

[0029] In this invention, preferably, the thickness of the conductive layer is 1μm-3μm, for example 2μm.

[0030] In this invention, the widths of the support layer and the conductive layer can be selected according to conventional methods in the art.

[0031] In a preferred embodiment of the present invention, the conductive layer is disposed on two surfaces of the support layer, and one surface of the support layer has a first texture.

[0032] In the method for preparing the current collector according to the second aspect of the present invention:

[0033] In a preferred embodiment of the present invention, the method for preparing the current collector includes the following steps:

[0034] S1. At least one surface of the support layer is surface treated to form a first texture with an uneven shape;

[0035] S2. The conductive layer is disposed along the thickness direction on the surface of the support layer having the first texture, and hot-pressed to form a second texture that matches the first texture on the surface of the conductive layer in contact with the support layer.

[0036] The method of depositing the conductive layer on the support layer before the hot pressing is conventional in the art, such as coating the conductive layer onto the support layer. The coating can be a conventional coating method in the art, such as multi-arc ion plating surface metallization or electroplating.

[0037] Specifically, the multi-arc ion plating surface metallization method can be described as performing multi-arc ion plating on the support layer to metallize its surface, with a vacuum degree of 4×10⁻⁶. -3 Pa or above. The specific operating conditions for multi-arc ion plating surface metallization can be as follows: substrate deposition temperature 130℃, target source current 80A, substrate negative bias voltage 20V, substrate deposition time 10min, inert protective gas is argon, reaction gas pressure to flow rate ratio is 80sccm, and a conductive layer material such as Cu is used as the cathode target. The cathode target emits metal vapor, forming plasma in space to deposit on the surface of the support layer to form a conductive layer such as a Cu coating, thereby metallizing the surface of the support layer.

[0038] Specifically, the electroplating method can be a conventional electroplating method in the art. The plating solution used in the electroplating can be conventional in the art, such as a high-acid, low-copper plating solution. The raw materials of the high-acid, low-copper plating solution generally include copper sulfate salt, sulfuric acid, brightener, and wetting agent. In particular, the composition of the high-acid, low-copper plating solution can be: CuSO4 80g / L, H2SO4 150g / L, polyethylene glycol as a wetting agent 1ml / L, and sodium phenyl dithiopropane sulfonate as a brightener 3ml / L. Taking copper electroplating on a support layer as an example, the specific electroplating operating conditions can be: selecting a high-acid, low-copper plating solution, operating temperature of 45℃, and current density of 3500A / m 2 The circulating flow rate is 10m³. 3 / h; the anode is a copper plate, the cathode is a metallized plastic film, and the electroplating time is 10min.

[0039] In another preferred embodiment of the present invention, the method for preparing the current collector includes the following steps:

[0040] S1. Perform surface treatment on one surface of the conductive layer to form a second texture with an uneven shape;

[0041] S2. The conductive layer is disposed on at least one surface of the support layer along the thickness direction, and the surface of the conductive layer having the second texture is in contact with the support layer. The surface is hot-pressed to form a first texture that matches the second texture on the surface of the support layer in contact with the conductive layer.

[0042] In this invention, preferably, the surface treatment is performed by pressing at least one surface of the support layer and / or the conductive layer with a textured work roller.

[0043] Preferably, the pressing temperature is 45-100℃; the pressing pressure is 10-30T; and the pressing time is 5-20s, for example, 4s.

[0044] In this invention, preferably, the hot pressing temperature is 25-35°C.

[0045] In this invention, preferably, the pressure of the hot pressing is 50-80T.

[0046] In this invention, preferably, the hot pressing time is 30-90 seconds.

[0047] In this invention, preferably, during the hot pressing process, the hot pressing temperature and pressure are both high, which will cause the support layer to partially melt, thereby completing the connection between the support layer and the two conductive layers.

[0048] In the electrode sheet of the third aspect of the present invention:

[0049] This invention can be divided into positive electrode current collectors and negative electrode current collectors based on the material of the conductive layer. The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The negative electrode includes a negative electrode current collector and a negative electrode active material layer.

[0050] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0051] The reagents and raw materials used in this invention are all commercially available.

[0052] Example 1

[0053] Example 1 provides a current collector and a method for preparing the current collector.

[0054] The preparation method of the current collector includes the following steps:

[0055] (1) A surface treatment is performed on one surface of the support layer 1 to form a raised / lowered spark pattern 2, such as... Figure 2 As shown. A schematic diagram of the structure of support layer 1 before surface treatment is shown below. Figure 1 As shown. The surface treatment method involves pressing with a work roller bearing a spark pattern. The thickness of the support layer 1 is 4 μm, and the absolute depth of the spark pattern 2 is 0.5 μm. The pressing temperature is 60℃; the pressing pressure is 25T; and the pressing time is 5s. The area of ​​the spark pattern 2 occupies 100% of the surface area of ​​the support layer 1. The material of the support layer 1 is PET.

[0056] (2) A conductive layer (made of copper with a thickness of 2 μm) is placed on the surface of the support layer 1 with the above-mentioned spark pattern 2, and hot-pressed to form a second pattern that matches the above-mentioned spark pattern 2 on the surface of the conductive layer in contact with the support layer 1, thereby obtaining a negative electrode current collector.

[0057] Hot pressing is a method of hot pressing riveting. The hot pressing temperature is 30℃, the hot pressing pressure is 60T, and the hot pressing time is 40s.

[0058] The conductive layer is disposed on the support layer 1 by multi-arc ion plating surface metallization. Specifically, the support layer 1 is subjected to multi-arc ion plating to metallize its surface, with a vacuum degree of 4×10⁻⁶. -3 Pa or higher. The specific operating conditions are: substrate deposition temperature 130℃, target source current 80A, substrate negative bias voltage 20V, substrate deposition time 10min, inert protective gas is argon, reaction gas pressure to flow rate ratio is 80sccm, Cu is used as cathode target material, the cathode target material emits metal vapor, forming plasma in space to deposit on the surface of support layer 1 to form a Cu coating, thereby metallizing the surface of support layer 1.

[0059] Comparative Example 1:

[0060] The difference between Comparative Example 1 and Example 1 is that the negative electrode current collector is only a conductive layer.

[0061] Effect Example

[0062] Welding tensile strength and welding resistance were tested on the negative electrode sheets formed by the negative electrode current collectors in Example 1 and Comparative Example 1 using welding testing methods.

[0063] (1) The negative electrode material is coated on the negative electrode current collector to obtain the negative electrode sheet. The negative electrode sheet is then stacked in a Z-shape with the positive electrode sheet and the separator. Then, pre-welding is performed. The negative electrode pre-welding pressure is 0.1 MPa, the pre-welding energy is 60 J, and the pre-welding amplitude is 65%, to obtain the welded stack.

[0064] (2) Weld the weld stack to the external negative electrode tab with a welding pressure of 0.1 MPa, a pre-welding energy of 220 J, and a pre-welding amplitude of 70% to complete the welding.

[0065] Welding tensile test: One robotic arm of the tensile tester holds the negative electrode sheet, while another robotic arm holds the overlap between the negative electrode sheet and the adhesive tape. Then, equal and opposite tensile forces are applied to test the welding tensile strength of the negative electrode sheet.

[0066] Welding resistance test: Place the negative electrode plate on the placement platform of the welding resistance test device; adjust the actual temperature of the sample to be tested to the target temperature; send a measuring current to the welding resistance test device and receive the measuring voltage fed back by the measuring current; calculate the resistance value of the negative electrode plate based on the measuring current and the measuring voltage.

[0067] The test results of the negative electrode sheets prepared in Example 1 and Comparative Example 1 are shown in Table 1.

[0068] Table 1. Welding test results of Example 1 and Comparative Example 1

[0069] Group Welding tensile force / N Welding resistance / mΩ Welding interface Example 1 650 0.026 The interface is smooth, with no foil cracks or poor soldering. Comparative Example 1 700 0.021 The interface is smooth, with no foil cracks or poor soldering.

[0070] As shown in Table 1, the interface of the negative electrode sheet in Example 1 is smooth, without foil cracks or poor soldering. Although the welding pull force is slightly lower and the welding resistance is slightly higher compared to the conventional negative electrode current collector (pure metal current collector) in Comparative Example 1, the raw material costs of the actual conductive layer and the overall cell can be reduced. By setting matching patterns on the surfaces where the support layer and the conductive layer contact for riveting, the cost of the conductive layer can be reduced by about 30%, the raw material cost of the overall cell is expected to be reduced by 1-2%, and the current carrying capacity of the current collector is improved; and cracks in the conductive layer are prevented.

Claims

1. A method for preparing a current collector, characterized in that, It includes the following steps: S1. Surface-treat at least one surface of the support layer to form a first texture; and / or, surface-treat one surface of the conductive layer to form a second texture; S2. The conductive layer is disposed on at least one surface of the support layer along the thickness direction and hot-pressed to form such that at least one surface of the support layer in contact with the conductive layer has a first texture and the surface of the conductive layer in contact with the support layer has a second texture, wherein the first texture and the second texture are concave-convex shapes and match each other. The current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer along the thickness direction. At least one surface of the support layer in contact with the conductive layer has a first texture, and the surface of the conductive layer in contact with the support layer has a second texture. The first texture and the second texture are concave-convex in shape and match each other.

2. The method for preparing the current collector as described in claim 1, characterized in that, It includes the following steps: S1. At least one surface of the support layer is surface treated to form a first texture with an uneven shape; S2. The conductive layer is disposed along the thickness direction on the surface of the support layer having the first texture, and hot-pressed to form a second texture that matches the first texture on the surface of the conductive layer in contact with the support layer.

3. The method for preparing the current collector as described in claim 1, characterized in that, It includes the following steps: S1. Perform surface treatment on one surface of the conductive layer to form a second texture with an uneven shape; S2. The conductive layer is disposed on at least one surface of the support layer along the thickness direction, and the surface of the conductive layer having the second texture is in contact with the support layer. The surface is hot-pressed to form a first texture that matches the second texture on the surface of the support layer in contact with the conductive layer.

4. The method for preparing the current collector as described in claim 1, characterized in that, The method for preparing the current collector satisfies one or more of the following conditions: a. The temperature for hot pressing is 25-35℃; b. The pressure for hot pressing is 50-80T; c. The surface treatment method is to press at least one surface of the support layer and / or the conductive layer using a textured work roller.

5. The method for preparing the current collector as described in claim 4, characterized in that, The pressing temperature is 45-100℃; the pressing pressure is 10-30T.

6. The method for preparing the current collector as described in claim 1, characterized in that, The absolute depth of the recess in the first texture is 0.2μm - 1.0μm.

7. The method for preparing the current collector as described in claim 1, characterized in that, The current collector satisfies one or more of the following conditions: a. The ratio of the absolute depth of the recess in the first texture to the thickness of the support layer is 0.02-0.5; b. On the surface of the support layer, the area of ​​the first texture accounts for 60%-100% of the surface area of ​​the support layer; c. On one surface of the conductive layer, the area of ​​the second texture accounts for 60%-100% of the surface area of ​​the conductive layer; d. The first texture is a spark pattern, a wavy pattern, or a spiral pattern.

8. The method for preparing the current collector as described in claim 1, characterized in that, The current collector satisfies one or more of the following conditions: a. The thickness of the support layer is 2μm - 10μm; b. The thickness of the conductive layer is 1μm - 3μm.

9. A current collector prepared by the method of any one of claims 1-8.

10. An electrode sheet, characterized in that, It includes the current collector as described in claim 9 and the active material layer.

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