Composite foil current collector, electrode plate, battery cell, preparation method of composite foil current collector, electrode plate, battery cell and battery

Abstract

The invention belongs to the field of batteries, and particularly relates to a composite foil current collector, an electrode plate, a battery cell, a preparation method thereof and a battery. The preparation method of the composite foil current collector comprises the following steps: volatilizing an original insulating layer in an original welding region of an original composite foil current collector in a resistance welding manner to form the composite foil current collector; the original composite foil current collector comprises an original insulating layer and original conducting layers arranged on the two sides of the original insulating layer according to upper and lower layer distribution; the original composite foil current collector comprises an original coating area and an original welding area according to left and right side distribution. According to the preparation method of the composite foil current collector, the thickness of the transfer welding position is not increased, subsequent transfer welding is facilitated, the space occupation of the transfer welding position is reduced, and the preparation method is simple in process and convenient to implement and has great popularization value.

Description

Technical Field

[0001] The invention belongs to the field of batteries, and in particular relates to a composite foil current collector, an electrode sheet, a battery core and a preparation method thereof, and a battery. Background Art

[0002] As secondary lithium-ion batteries are increasingly used, battery performance requirements are becoming higher and higher. In order to effectively improve the safety performance and energy density of batteries, a composite foil current collector has gradually attracted attention in the industry. Ordinary current collectors are single-layer copper foil and aluminum foil, while composite foil current collectors are three-layer structures, with the middle layer being a polymer insulating layer. Currently, the insulating layer is generally made of PET material, and the upper and lower metal-plated layers serve as conductive layers. Since the middle layer is an insulating layer, the upper and lower metal layers are not conductive.

[0003] Composite foil current collectors have been gradually applied in the industry. There are various manufacturing methods. The connection method between the composite foil current collector and the tab is usually welding, such as rolling welding, inlaying, or hollow welding. Roll welding method: that is, a layer of metal foil is roll welded on the surface of the upper and lower metal layers of the composite foil. This method will cause the thickness of the current collector at the roll welding position to be too thick, which is not conducive to the subsequent transfer welding.

[0004] Inlay method: first make an empty space at an appropriate position of the composite foil current collector, and then inlay a conductive sheet. The conductive sheet is connected to the upper and lower surfaces of the composite foil, and the conductive sheet is epitaxially used for subsequent transfer welding. This method is complex and will also cause the current collector to thicken.

[0005] Hollow welding method: first make a hollow space at an appropriate position of the composite foil current collector, then connect the upper and lower metal sheets, weld the hollow space together, and then weld them to the upper and lower metal layers of the composite foil respectively. This method is complicated to operate and will also cause the current collector to thicken. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a composite foil current collector, an electrode sheet and a preparation method thereof, and a battery.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing a composite foil current collector comprises the following steps: using resistance welding to volatilize an original insulating layer from an original welding area of ​​an original composite foil current collector to form a composite foil current collector; the original composite foil current collector comprises an original insulating layer and original conductive layers arranged on both sides of the original insulating layer according to upper and lower layer distribution; the original composite foil current collector comprises an original coating area and an original welding area according to left and right side distribution.

[0008] Specifically, the method comprises the following steps: connecting two electrode columns to the original conductive layers on the upper and lower sides of the original welding area respectively, applying current to the original welding area until the melting temperature of the original conductive layer is reached so that the original insulating layer of the original welding area is volatilized, and the original conductive layers on the upper and lower sides are welded to form a welding area; the melting temperature of the conductive layer is greater than the melting temperature of the insulating layer.

[0009] The present invention also includes a composite foil current collector obtained by adopting the preparation method.

[0010] According to the distribution on the left and right sides, it includes a coating area and a welding area arranged on one side of the coating area; according to the distribution on the upper and lower layers, the coating area includes an insulating layer and a conductive layer arranged on both sides of the insulating layer; the welding area includes two conductive layers; the welding area is connected to the pole ear; the structure of the coating area retains the structure of the original coating area.

[0011] The insulating layer is a polymer insulating layer, and the conductive layer is a copper foil or an aluminum foil; the thickness of the conductive layer is ≥0.5um, preferably 1μm; the thickness of the insulating layer is ≥3μm, preferably 6μm.

[0012] Along the direction of the pole ear, the length of the welding zone is 1 / 30-1 / 10 of the length of the coating zone, preferably 1 / 15-1 / 25.

[0013] The present invention also includes a method for preparing an electrode sheet, which is prepared by one of the following methods: Method 1: coating an active material layer on the coating area of ​​the composite foil current collector to form an electrode sheet; Method 2: Prepared from an original electrode sheet; the original electrode sheet includes the original composite foil current collector and an active material layer coated on the original coating area; the original welding area of ​​the original composite foil current collector of the original electrode sheet adopts resistance welding to volatilize the original insulating layer to form an electrode sheet; the original electrode sheet includes an original positive electrode sheet and an original negative electrode sheet; The electrode sheet includes a positive electrode sheet or a negative electrode sheet.

[0014] The present invention also includes a battery core, including one or more battery core units; each of the battery core units includes the positive electrode sheet, the separator and the negative electrode sheet.

[0015] The present invention also includes a method for preparing a battery cell, which is used to prepare the battery cell by one of the following methods: Method 1: stacking the positive electrode sheet, negative electrode sheet and separator obtained in the method 1 of the electrode sheet preparation method, and then welding the positive electrode sheet with the welding area of ​​the negative electrode sheet; Method 2: Prepared from original battery cells; the original battery cells include original positive electrode sheets, original negative electrode sheets and separators; specifically include the following steps: stacking one or more layers of original battery cells together; using resistance welding to melt and volatilize the original insulating layers of the original positive electrode sheets and the original negative electrode sheets in the original welding areas and welding the original conductive layers together to form a welding area; welding the pole ears while welding the original conductive layers.

[0016] The present invention also includes a battery, characterized in that it includes the battery core.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of the composite foil current collector of the present application does not increase the thickness of the transfer welding position, is conducive to subsequent transfer welding, reduces the space occupied by the transfer welding position, and has a simple process and is easy to implement, and has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the original composite foil current collector of the present invention; Figure 2 It is a schematic diagram of the structure of the composite foil current collector of the present invention; Figure 3 It is a schematic diagram of the structure of the original electrode sheet of the present invention; Figure 4 It is a structural schematic diagram of the electrode sheet of the present invention; Figure 5 It is a schematic diagram of the structure of multiple battery core units of the present invention; DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiments. Example

[0020] A method for preparing a composite foil current collector comprises the following steps: Figure 1 The original welding area of ​​the composite foil is shown in FIG. 1 , wherein the original insulating layer is volatilized by resistance welding to form a composite foil current collector; the original composite foil current collector includes an original insulating layer 3-1-2 and an original conductive layer 3-1-1 arranged on both sides of the original insulating layer according to the upper and lower layers; the original composite foil current collector includes an original coating area and an original welding area according to the left and right sides. The resistance welding method is a conventional technology in the prior art.

[0021] Specifically, the steps include: connecting two electrode columns to the original conductive layers on the upper and lower sides of the original welding area respectively, applying current to the original welding area until the melting temperature of the original conductive layer is reached so that the original insulating layer of the original welding area is volatilized, and the original conductive layers on the upper and lower sides are welded to form a welding area ( Figure 2 As shown), a composite foil current collector is obtained; the melting temperature of the conductive layer is greater than the melting temperature of the insulating layer.

[0022] Figure 2 A composite foil current collector is shown, which includes a coating area and a welding area 2-1 arranged on one side of the coating area according to left and right side distribution; according to upper and lower layer distribution, the coating area includes an insulating layer 1-1-2 and a conductive layer 1-1-1 arranged on both sides of the insulating layer; the welding area 2-1 includes two conductive layers welded together; the welding area 2-1 is connected to the pole ear 2-2, and the structure of the coating area retains the structure of the original coating area.

[0023] The insulating layer is a polymer insulating layer, usually PET material, and the conductive layer is copper foil or aluminum foil. For the composite foil current collector used to prepare the positive electrode sheet, the conductive layer is aluminum foil; for the composite foil current collector used to prepare the negative electrode sheet, the conductive layer is copper foil.

[0024] The thickness of the conductive layer is ≥0.5um; in this embodiment, 1μm is used as a preferred example for illustration; the thickness of the insulating layer is ≥3μm; in this embodiment, 6μm is used as a preferred example for illustration.

[0025] Along the direction of the tab, the length of the welding zone is 1 / 30-1 / 10 of the length of the coating zone; preferably 1 / 15-1 / 25. In this embodiment, the length of the welding zone is 3 mm, and the length of the coating zone is 65 mm.

[0026] The present invention also includes an electrode sheet, which is prepared by one of the following methods: Method 1: coating an active material layer on the coating area of ​​the composite foil current collector to form an electrode sheet; Method 2: From the original electrode sheet ( Figure 3 The original electrode sheet includes the original composite foil current collector 3-1 and the active material layer 1-2 coated on the original coating area; the original welding area of ​​the original composite foil current collector of the original electrode sheet adopts resistance welding to volatilize the original insulating layer to form the electrode sheet ( Figure 4 As shown); the original electrode sheet includes an original positive electrode sheet and an original negative electrode sheet; The electrode sheet includes a positive electrode sheet or a negative electrode sheet.

[0027] The embodiment of the present invention also includes a battery cell, including one or more battery cell units; each of the battery cell units includes the positive electrode sheet, the separator and the negative electrode sheet.

[0028] The embodiment of the present invention also includes a method for preparing the battery cell, which is used to prepare the battery cell by one of the following methods: Method 1: stacking the positive electrode sheet, negative electrode sheet and separator obtained in the method 1 of the electrode sheet preparation method, and then welding the positive electrode sheet with the welding area of ​​the negative electrode sheet; Method 2: Prepared from original battery cells; the original battery cells include original positive electrode sheets, original negative electrode sheets and separators; specifically include the following steps: stacking one or more layers of original battery cells together; using resistance welding to melt and volatilize the original insulating layers of the original positive electrode sheets and the original negative electrode sheets in the original welding areas and welding the original conductive layers together to form a welding area; welding the pole ears while welding the original conductive layers.

[0029] The present invention also includes a battery, comprising the battery core.

[0030] In the actual production process, the original insulating layer of the original welding area is usually retained during the preparation of the electrode sheet. When preparing the battery cell, the original insulating layer of the original welding area of ​​the original composite foil current collector is melted and volatilized, and the original conductive layer is welded together and welded with the pole ear at the same time, that is, the preparation is carried out in the form of method 2 in the preparation method of the battery cell.

[0031] One battery cell unit is prepared in the following manner: the original coating area of ​​the original composite foil current collector is coated with active materials to form an original electrode sheet, and the original positive electrode sheet and the original negative electrode sheet are obtained according to the difference between the original conductive layer and the coated active material layer; the original positive electrode sheet, the separator and the original negative electrode sheet are superimposed in the form of the original positive electrode sheet, the separator and the original negative electrode sheet, and the original insulating layer of the original welding area of ​​the original composite foil current collector is melted and volatilized by resistance welding to obtain the battery cell unit; the steps include: connecting the original conductive layers on the upper and lower sides of the original welding area with two electrode columns respectively, applying current to the melting temperature of the original conductive layer so that the original conductive layers on the upper and lower sides are welded, and the original insulating layer is volatilized at this time; the melting temperature of the conductive layer is usually much higher than the melting temperature of the insulating layer. The resistance welding method is a conventional technology in the prior art, which first presses the two layers of the original composite foil current collector together, and then discharges. At this time, the pressed original composite foil current collector acts as a resistor, generates heat under the action of the current, and the temperature is as high as the melting point of the metal layer. At this melting point, the original insulating layer is volatilized, and the original conductive layer is melted to form a new welding area. The melting process is extremely short and is currently controlled to less than 1s.

[0032] For laminated or wound batteries, multiple cell units are usually used. The original coating area of ​​the original composite foil current collector is coated with active materials to form original electrode sheets. The original positive electrode sheet and the original negative electrode sheet are obtained according to the original conductive layer and the coated active material layer. The original positive electrode sheet, the separator, and the original negative electrode sheet are stacked to form multiple layers. Then, the original insulating layer of the original welding area of ​​the multi-layer original composite foil current collector is melted and volatilized by resistance welding to form a welding area ( Figure 5 As shown). In this embodiment, the thickness of the single-layer electrode sheet is 6μm, the thickness of the conductive layer is 1μm, and the thickness of the single-layer electrode sheet is 8μm. Usually, as a laminated battery, 26 layers need to be stacked, and the thickness of the welding area after welding is about 50μm (the thickness of each conductive layer is 1μm, and each electrode sheet contains two conductive layers); and if the roll welding method is adopted, that is, a layer of 4um metal foil is roll-welded on the upper and lower sides of the composite foil, the thickness of the single layer in the roll welding area has reached about 16um, and the thickness is too thick after stacking 26 layers. Therefore, compared with the traditional method, the preparation method of the composite foil current collector of the present application will not increase the thickness of the transfer welding position, which is conducive to subsequent transfer welding and reduces the space occupied by the transfer welding position. Moreover, its process is simple and easy to implement, and it has great promotion value.

[0033] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a composite foil current collector, characterized in that: The method comprises the following steps: the original welding area of ​​the original composite foil current collector is subjected to resistance welding to volatilize the original insulating layer to form a composite foil current collector; the original composite foil current collector comprises an original insulating layer and original conductive layers arranged on both sides of the original insulating layer according to the upper and lower layer distribution; the original composite foil current collector comprises an original coating area and an original welding area according to the left and right side distribution.

2. The method for preparing a composite foil current collector according to claim 1, characterized in that: Specifically, the method comprises the following steps: connecting two electrode columns to the original conductive layers on the upper and lower sides of the original welding area respectively, applying current to the original welding area until the melting temperature of the original conductive layer is reached so that the original insulating layer of the original welding area is volatilized, and the original conductive layers on the upper and lower sides are welded to form a welding area; the melting temperature of the conductive layer is greater than the melting temperature of the insulating layer.

3. A composite foil current collector, characterized in that: The preparation method according to claim 1 or 2 is used to obtain the 4. The composite foil current collector according to claim 3, characterized in that: According to the distribution on the left and right sides, it includes a coating area and a welding area arranged on one side of the coating area; according to the distribution on the upper and lower layers, the coating area includes an insulating layer and a conductive layer arranged on both sides of the insulating layer; the welding area includes two conductive layers; the welding area is connected to the pole ear; the structure of the coating area retains the structure of the original coating area.

5. The composite foil current collector according to claim 4, characterized in that: The insulating layer is a polymer insulating layer, and the conductive layer is a copper foil or an aluminum foil; the thickness of the conductive layer is ≥0.5um; and the thickness of the insulating layer is ≥3μm.

6. The composite foil current collector according to claim 4, characterized in that: Along the direction of the pole ear, the length of the welding area is 1 / 30-1 / 10 of the length of the coating area.

7. A method for preparing an electrode sheet, characterized in that: Prepared by one of the following methods: Method 1: coating an active material layer on the coating area of ​​the composite foil current collector according to any one of claims 3 to 6 to form an electrode sheet; Method 2: Prepared from an original electrode sheet; the original electrode sheet comprises the original composite foil current collector as described in any one of claims 1-2 and an active material layer coated on the original coating area; the original welding area of ​​the original composite foil current collector of the original electrode sheet is formed by volatilizing the original insulating layer by resistance welding; the original electrode sheet comprises an original positive electrode sheet and an original negative electrode sheet; The electrode sheet includes a positive electrode sheet or a negative electrode sheet.

8. A battery cell, characterized in that: It comprises one or more battery cell units; each of the battery cell units comprises the positive electrode sheet, separator and negative electrode sheet as described in claim 7.

9. A method for preparing a battery cell, used for preparing the battery cell according to claim 8, characterized in that: Prepared by one of the following methods: Method 1: stacking the positive electrode sheet, negative electrode sheet and separator obtained in method 1 of the electrode sheet preparation method of claim 7, and then welding the positive electrode sheet with the welding area of ​​the negative electrode sheet; Method 2: Prepared from original battery cells; the original battery cells include original positive electrode sheets, original negative electrode sheets and separators; specifically include the following steps: stacking one or more layers of original battery cells together; using resistance welding to melt and volatilize the original insulating layers of the original positive electrode sheets and the original negative electrode sheets in the original welding areas and welding the original conductive layers together to form a welding area; welding the pole ears while welding the original conductive layers.

10. A battery, characterized in that: Comprising the battery cell as claimed in claim 8.

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