Method for preparing multi-layer current collector with latticed active region, electrode plate and battery

Abstract

The invention discloses a multi-layer current collector with a latticed active region and a preparation method thereof, and the method comprises the following steps: carrying out the evaporation of two side surfaces of a base material belt, and forming a first metal layer; roll welding is carried out on the middle area of the base material belt after the first metal layer is evaporated, so that the metal layers on the two faces of the middle area of the base material belt are riveted; rolling the middle area of the base material strip subjected to roll welding; and respectively carrying out evaporation on the surfaces of the two sides of the base material belt again to form a second metal layer. Metal layers on the front side and the back side of the base material form a riveting connection mode, then the thickness of the metal layers is increased through secondary evaporation, and metal is deposited at the light-transmitting positions of the metal layers to form secondary riveting. The middle part of the prepared multi-layer current collector is the metal riveted latticed active region, so that the metal layer can be obviously prevented from falling off from the polymer layer.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a multilayer current collector method with a grid-shaped active area, an electrode sheet and a battery. Background Art

[0002] Lithium-ion batteries have rapidly occupied the global new energy market due to their high energy density, good cycle stability, and environmental friendliness. They have been used in a variety of fields, from 3C products to electric vehicles and ships. In order to further expand their advantages and reduce the cost of battery use, it is necessary to optimize the design of battery materials, structures, and other aspects.

[0003] As an important component of lithium-ion batteries, the current collector made of metal foil currently accounts for about 15% of the battery weight, which not only accounts for a large amount of cost, but also restricts the further improvement of battery energy density. The commonly used functional current collector (multi-layer current collector) is a three-layer structure, and its specific structure is metal conductive layer-polymer support layer-metal conductive layer. It uses insulating polymer film as the support material, and covers the metal layer on both sides of the support material as the middle layer by one or more evaporation methods to obtain a multi-layer current collector. The middle of the multi-layer current collector is plastic, and its density is much lower than that of metal, which can improve the energy density of the battery.

[0004] However, after the existing multilayer current collector is made into a battery, it is easy for the surface metal layer and polymer layer to fall off and peel off after being immersed in electrolyte, activated pre-charged, and cycled, causing the battery capacity to drop and fail. Summary of the invention

[0005] The object of the present invention is to provide a multilayer current collector having a grid-like active area and a preparation method thereof, an electrode sheet and a battery capable of inhibiting the metal layer from falling off from the polymer layer.

[0006] To achieve the above purpose, the technical solution provided by the present invention is:

[0007] The first aspect of the present application provides a method for preparing a multilayer current collector having a grid-shaped active region, characterized in that it comprises the following steps:

[0008] Step (1): performing a first evaporation deposition on both sides of the base material strip to form a first metal layer;

[0009] Step (2): roller welding the base material strip having the first metal layer on both sides of the strip, so that the first metal layers on both sides of the base material strip are partially pressed down to form a grid-like riveted structure;

[0010] Step (3): pressing the grid-shaped riveted structure after roller welding;

[0011] Step (4): performing a second evaporation on both side surfaces of the pressed grid-shaped riveted structure to form a second metal layer.

[0012] To optimize the above technical solutions, the specific measures taken also include:

[0013] In step (1), the thickness of the first metal layer evaporated is 40 to 100 nm, and the first metal layer is evaporated using a multiple evaporation molding device.

[0014] In step (2), the base material strip after the first metal layer is evaporated is roller welded, and the riveting of the metal layers on both sides of the base material strip is made to form a light transmittance that meets the requirements, and the light transmittance requirement is 0.5% to 1.0%.

[0015] Unprocessed blank areas are set at both side edges of the base material strip along the width direction. The blank areas are strip-shaped and extend along the length direction of the base material strip. The width of the roller welding is the same as the width of the area between the blank areas on both sides.

[0016] In step (3), the pressing adopts constant roll gap pressing, and the gap of the constant roll gap is 0 to 20 μm, excluding 0; the maximum height of the grid-like riveted structure protrusions pressed by the constant roll gap does not exceed the thickness of the second metal layer formed by vapor deposition on both sides of the base material strip; the grid-like riveted structure protrusions on both sides of the base material strip are staggered.

[0017] In step (4), the thickness of the evaporated second metal layer is 600-1300 nm; and the second metal layer is evaporated using a one-step evaporation molding device.

[0018] The second metal layer is formed by the second evaporation on both sides of the surface, and riveting is formed again at the position where the light transmittance meets the requirements after roller welding.

[0019] A second aspect of the present application provides a multilayer current collector having a grid-shaped active region, comprising a base material strip and metal riveted grid-shaped active regions on both sides of the base material strip.

[0020] The third aspect of the present application provides an electrode sheet, comprising a multilayer current collector having a grid-shaped active area prepared by the method described in the first aspect of the present application or described in the second aspect of the present application.

[0021] The fourth aspect of the present application provides a battery, comprising the electrode sheet described in the third aspect of the present application.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention adopts the method of evaporation + roller welding + pressing + evaporation, so that the evaporated metal layer is welded by a welding head during roller welding, so that the metal layers on the front and back sides of the substrate form a riveted connection, and then the thickness of the metal layer is thickened by a second evaporation, and metal is deposited at its light-transmitting position to form a secondary riveting, so as to solve the problem of easy separation and delamination of the metal layer and the polymer layer after electrolyte immersion and circulation.

[0024] The present invention can reduce the metal layer from falling off the polymer substrate, because there are two layers of riveting points in the grid-shaped active area of ​​the current collector, which can greatly inhibit the delamination and falling off between the metal layer and the polymer layer.

[0025] The method of the present invention can also increase the peeling force of the active material by forming a grid-like uneven film surface, thereby obtaining a functional current collector that is easy to peel off the active material.

[0026] The use of the multi-layer current collector with a grid-shaped active area of ​​the present invention can reduce the square resistance of the current collector and improve the battery cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : Schematic diagram of the process of preparing a multilayer current collector having a grid-shaped active area of ​​the present invention.

[0028] Figure 2 : Schematic diagram of the structure of a multilayer current collector with a grid-like active area prepared by the present invention.

[0029] Figure 3 : Welding effect diagram of the middle area of ​​the base material strip after roller welding in an embodiment of the present invention.

[0030] Figure 4 : The finished product effect diagram of the multilayer current collector with a grid-shaped active area prepared in an embodiment of the present invention.

[0031] Figure 5 : Schematic diagram of pressing the grid riveted structure after roller welding.

[0032] Figure 6 : Schematic diagram after the second evaporation.

[0033] In the figure: 1-upper pressing roller, 2-lower pressing roller, 3-base material strip, 4-first metal layer, 5-blank area, 6-grid-like riveted structure protrusions, 7-second metal layer. DETAILED DESCRIPTION

[0034] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0035] In the description of the present invention, it is also necessary to explain:

[0036] For the sake of simplicity, this document only specifically discloses some numerical values ​​and optional ranges. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range; the optional items in the optional range can also be combined arbitrarily.

[0037] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0038] The present application provides a method for preparing a multilayer current collector, such as Figure 1 As shown, the following steps are included:

[0039] Step (1): performing a first evaporation deposition on both sides of the base material strip 3 to form a first metal layer 4;

[0040] Step (2): roller welding the base material strip 3 having the first metal layer 4 on both sides of the base material strip 3, so that the first metal layers 4 on both sides of the base material strip 3 are partially pressed down to form a grid-like riveted structure;

[0041] Step (3): pressing the grid-shaped riveted structure after roller welding;

[0042] Step (4): performing a second evaporation deposition on both side surfaces of the pressed grid-shaped riveted structure to form a second metal layer 7.

[0043] The riveting referred to in this application is not the rivet connection in the field of mechanical devices in the macroscopic sense, but refers to the local metal depression of the metal layer through roller welding, and the metal layers on both sides and the substrate therebetween are closely connected at a relatively microscopic level at the depression.

[0044] The pressing referred to in the present application is to use two rollers to press the grid-like riveted structure protrusions 7 by controlling the gap between the rollers.

[0045] The base material band 3 involved in the present application is an insulating material, and can be any one of high molecular polymer materials such as polyethylene terephthalate (PET), polypropylene (PP), polyamide (PA), polyimide (PI), polyvinyl chloride (PVC) and polystyrene (PS).

[0046] The base material strip 3 of the present application is in the form of a film and plays a supporting role, and its thickness h0 is generally between 3 μm and 12 μm.

[0047] The metal layer formed by vapor deposition in the present application plays a conductive role; the thickness h1 of the first metal layer 4 vapor-deposited for the first time in the present application is 40 to 100 nm; it is preferred to use a multiple vapor deposition molding device to vapor-deposit the first metal layer 4; the thickness h2 of the second metal layer 7 vapor-deposited for the second time is 600 to 1300 nm; it is preferred to use a single vapor deposition molding device to vapor-deposit the second metal layer 7.

[0048] When the current collector of the present application is used as a positive electrode current collector, the material of the metal layer can be aluminum or an aluminum alloy; wherein the metal layer can also be a multilayer composite structure with a mass ratio of aluminum of not less than 80%.

[0049] The base material strip 3 is generally unwound in the form of a material strip, which may be prepared in advance and stored on an unwinding shaft.

[0050] The base material tape 3 provided in the embodiment of the present application travels along a preset direction, where the traveling direction is the length direction of the base material tape 3 , and the direction perpendicular to the length direction is the width direction of the base material tape 3 .

[0051] The middle area of ​​the base material strip 3 is: blank areas 5 are formed on both side edges of the base material strip 3 along the width direction, and the middle area is between the blank areas 5 on both sides; the blank areas 5 and the middle area are both strip-shaped and extend along the length direction of the base material strip 3.

[0052] The present application performs roller welding on the base material strip 3 after the first metal layer 4 is evaporated, and the riveting of the metal layers on both sides of the base material strip 3 is performed by roller welding to form a light transmittance that meets the requirements, and the light transmittance requirement is 0.5% to 1.0%.

[0053] The width of the roller welding is the same as the width of the middle area between the blank areas 5 on both sides, so that the welding head can cover the middle area. The depth of the welding teeth for roller welding is 20-60μm.

[0054] The roller gap of the constant roller gap pressing is 0-20 μm, excluding 0; the maximum height of the grid-like riveted structure protrusions 6 pressed by the constant roller gap does not exceed the thickness of the second metal layer 7 formed by vapor deposition on both sides of the base material strip 3.

[0055] The grid-like riveting structure protrusions 6 on both sides of the base material strip are arranged alternately.

[0056] The two sides of the base material strip 3 are respectively subjected to vapor deposition and the two sides of the metal are riveted again at the locations that meet the light transmittance requirements.

[0057] The present application also provides a multilayer current collector with a grid-shaped active area, including a base material strip 3 and metal riveted grid-shaped active areas on both sides of the base material strip 3 .

[0058] The present application also provides an electrode sheet, comprising the above-mentioned multilayer current collector with a grid-shaped active area.

[0059] The present application also provides a battery, comprising the above-mentioned electrode sheet.

[0060] The present invention is further described in detail below in conjunction with specific embodiments:

[0061] Example 1

[0062] like Figure 2 As shown, the base material band 3 is made of polyethylene terephthalate (PET) film with a thickness of 6 μm. One side surface of the base material band 3 is side A, and the other side surface is side B. The middle area of ​​the base material band 3 is A2 and B2 respectively, and the blank areas 5 on both side edges of the base material band 3 are A1 and B1 and A3 and B3 respectively.

[0063] The first aluminum evaporation is performed on the A side of the base material strip 3 by multiple evaporation equipment, and a vacuum aluminum deposition layer of about 60nm is deposited; and an aluminum layer of about 60nm is deposited on the B side in the same way.

[0064] Roller welding was performed on the middle areas A2 and B2 of the current collector surface after the aluminum layer was plated, respectively, with welding teeth of 30 μm depth, welding energy of 20 kJ, amplitude of 10%, and welding pressure of 0.15 MPa; after welding, the welding tooth strip foil material ensured a welding transmittance of 0.8%, and the welding effect diagram is shown in FIG. Figure 3 shown.

[0065] Then, the middle areas A2 and B2 are further pressed by a rolling device with a constant roll gap, and the rolling thickness does not exceed the 940nm thickness of the second evaporation aluminum coating.

[0066] Then, the entire A surface is subjected to a second aluminum evaporation coating using a one-time forming evaporation device, and the aluminum coating thickness is about 940nm; the B surface is subjected to aluminum coating using the same method with a thickness of about 940nm.

[0067] The multilayer current collector with a grid-like active area is prepared. Figure 4 , the blue area simulates the aluminum foil after the second evaporation.

[0068] Comparative Example 1

[0069] By using the existing technology, the surface of the base material strip 3 is multi-evaporated by a multiple aluminum plating device, and multiple evaporations are performed on both the front and back sides of the substrate until the thickness reaches 1 μm.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that no roller welding and pressing are performed between the two evaporation depositions. For the first evaporation aluminum plating: the first evaporation aluminum plating is performed on the A side of the base material strip 3 through a multiple evaporation deposition equipment, and a vacuum aluminum plating deposits an aluminum layer of about 60nm; an aluminum layer of about 60nm is deposited on the B side in the same way; for the second evaporation aluminum plating: the second evaporation aluminum plating is performed on the entire A side using a one-time forming evaporation deposition equipment, and the aluminum plating thickness is about 940nm; the aluminum plating thickness is about 940nm on the B side in the same way; after the two evaporation aluminum platings are completed, the middle areas A2 and B2 on the surface of the collector where the aluminum layer is plated are respectively roller welded with welding teeth with a depth of 30μm, with a roller welding energy of 20 kJ, an amplitude of 10%, and a welding pressure of 0.15 MPa; then the middle areas A2 and B2 are continued to be pressed by a roller pressing device with a constant roller gap, and the rolling thickness does not exceed the thickness of the second evaporation aluminum plating.

[0072] Comparative Example 3

[0073] The difference between this comparative example and Example 1 is that the first evaporation is not performed to form the first metal layer 4, and the remaining steps are the same as Example 1, that is, the base material strip 3 is directly roll-welded, and then the subsequent steps are performed. The comparative example has the material drop phenomenon in the rolling process.

[0074] The following are the test results of the embodiments and comparative examples:

[0075] Table 1 Test results of embodiments and comparative examples

[0076]

[0077] From the above data comparison, it can be seen that the test results of Example 1 are significantly better than those of the comparative example. The multilayer current collector with a grid-shaped active area prepared by the method of evaporation + roller welding + roller pressing + evaporation in the scheme of the present application is superior to the multilayer current collector prepared by the traditional process in terms of square resistance, resistance to electrolyte immersion, electrode peeling force and cycle performance.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a multilayer current collector having a grid-like active area, characterized in that: The following steps are involved: Step (1): performing a first evaporation deposition on both sides of the base material strip to form a first metal layer; Step (2): roller welding the base material strip having the first metal layer on both sides of the strip, so that the first metal layers on both sides of the base material strip are partially pressed down to form a grid-like riveted structure; Step (3): pressing the grid-shaped riveted structure after roller welding; Step (4): performing a second evaporation on both side surfaces of the pressed grid-shaped riveted structure to form a second metal layer.

2. The method for preparing a multilayer current collector having a grid-like active area according to claim 1, characterized in that: In step (1), the thickness of the first metal layer evaporated is 40 to 100 nm, and the first metal layer is evaporated using a multiple evaporation molding device.

3. The method for preparing a multilayer current collector having a grid-like active area according to claim 1, characterized in that: In step (2), the base material strip after the first metal layer is evaporated is roller welded, and the riveting of the metal layers on both sides of the base material strip is made to form a light transmittance that meets the requirements, and the light transmittance requirement is 0.5% to 1.0%.

4. The method for preparing a multilayer current collector having a grid-like active area according to claim 1, characterized in that: Unprocessed blank areas are set at both side edges of the base material strip along the width direction. The blank areas are strip-shaped and extend along the length direction of the base material strip. The width of the roller welding is the same as the width of the area between the blank areas on both sides.

5. The method for preparing a multilayer current collector having a grid-like active region according to claim 1, characterized in that: In step (3), the pressing adopts constant roll gap pressing, and the gap of the constant roll gap is 0 to 20 μm, excluding 0; the maximum height of the grid-like riveted structure protrusions pressed by the constant roll gap does not exceed the thickness of the second metal layer formed by vapor deposition on both sides of the base material strip; the grid-like riveted structure protrusions on both sides of the base material strip are staggered.

6. The method for preparing a multilayer current collector having a grid-like active region according to claim 1, characterized in that: In step (4), the thickness of the second metal layer deposited is 600-1300 nm, and the second metal layer is deposited using a one-step evaporation molding device.

7. The method for preparing a multilayer current collector having a grid-like active region according to claim 3, characterized in that: The second metal layer is formed by the second evaporation on both sides of the surface, and riveting is formed again at the position where the light transmittance meets the requirements after roller welding.

8. A multilayer current collector having a grid-like active region, characterized in that: It includes a base material belt and metal riveted grid-shaped active areas on both sides of the base material belt.

9. An electrode sheet, characterized in that: A multilayer current collector having a grid-shaped active area prepared by the method of any one of claims 1 to 7 or as described in claim 8.

10. A battery, characterized in that: The electrode sheet comprising claim 9.

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