Lithium ion battery pole piece and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery pole piece and a preparation method thereof. The preparation method of the lithium ion battery pole piece comprises the following steps: uniformly coating two surfaces of a pre-configured current collector with a pre-prepared first layer of slurry by adopting a transfer type coating machine; carrying out drying treatment on the current collector coated with the first layer of slurry to enable the first layer of slurry to form a first film layer; uniformly coating a pre-prepared second layer of slurry on the two surfaces of the first film layer by adopting the extrusion type coating machine; carrying out drying and curing treatment on the current collector coated with the second layer of slurry, and forming a second film layer on each first film layer; and the first film layer and the second film layer form a double-sided double-layer diaphragm structure on the current collector. In this way, the coating uniformity, consistency and alignment can be improved.

Description

Technical Field

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

[0002] As the main energy source for modern electronic devices, the performance of lithium-ion batteries directly affects the operating efficiency and safety of the equipment. In the preparation process of lithium-ion batteries, the coating process is one of the key processes for the preparation of battery cells, and the quality of the coating is directly related to the performance of the battery. The coating process is a process in which the positive and negative electrode slurries are evenly coated on the current collector and the organic solvent in the slurry is dried. The electrode slurry is coated on the current collector, and then dried, rolled, and cut to obtain the pole piece.

[0003] At present, the coating process of lithium-ion batteries mainly adopts two methods: transfer coater and extrusion coater. Among them, the transfer coater controls the amount of slurry transfer by adjusting the gap between the scraper and the coating roller, while the extrusion coater uses a special extrusion die to extrude the slurry along the slit and coat it on the moving foil. However, all of the above methods have problems in coating uniformity, consistency, alignment, etc., which affect the overall performance of the battery. Summary of the invention

[0004] The present invention provides a lithium ion battery pole piece and a preparation method thereof, which can improve coating uniformity, consistency and alignment.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a method for preparing a lithium ion battery electrode, comprising:

[0006] The pre-prepared first layer of slurry is uniformly coated on both sides of the pre-prepared current collector using a transfer coater;

[0007] Drying the current collector after coating the first layer of slurry, so that the first layer of slurry forms a first film layer;

[0008] Using an extrusion coating machine to evenly coat the pre-formulated second layer of slurry on both sides of the first film layer;

[0009] The current collector coated with the second layer slurry is dried and cured to form a second film layer on each of the first film layers; the first film layer and the second film layer form a double-sided double-layer film structure on the current collector.

[0010] According to one embodiment of the present invention, the gap between the scraper and the coating roller of the transfer coater is 400-2000 μm; the speed ratio between the coating roller and the backing roller is 0.9-1.1; the coating speed is 15-30 m / min; the coating thickness is 80-500 μm; the coating surface density is 100-150 g / m 2 .

[0011] According to one embodiment of the present invention, the coating speed of the extrusion coater is 30-70 m / min; the coating thickness is 80-500 μm; the slurry feeding pump speed is 10-50 rpm / min; the coating surface density is 80-120 g / m 2 .

[0012] According to one embodiment of the present invention, the compaction density of the first layer of slurry is greater than the compaction density of the second layer of slurry.

[0013] According to one embodiment of the present invention, the first layer of slurry and the second layer of slurry are made of the same raw material.

[0014] According to one embodiment of the present invention, the first layer of slurry is lithium iron phosphate electrode slurry, and the second layer of slurry is lithium iron phosphate electrode slurry.

[0015] According to one embodiment of the present invention, the baking temperature for drying the current collector after coating the first layer of slurry is 90-110°C; the baking temperature for drying and curing the current collector after coating the second layer of slurry is 100-130°C.

[0016] According to one embodiment of the present invention, before the step of uniformly coating the pre-formulated first layer of slurry on both sides of the pre-formulated current collector using a transfer coater, the step further includes:

[0017] The pre-configured current collector is subjected to a surface cleaning treatment.

[0018] According to one embodiment of the present invention, after the step of drying and curing the current collector after coating the second layer of slurry and forming the second film layer on each of the first film layers, the step further includes:

[0019] The coated current collector is subjected to edge trimming treatment.

[0020] To solve the above technical problems, another technical solution adopted by the present invention is: to provide a lithium-ion battery pole piece, which includes a current collector and a double-layer membrane structure distributed on both sides of the current collector, and the double-layer membrane structure is prepared by the preparation method of the lithium-ion battery pole piece.

[0021] The beneficial effects of the present invention are as follows: a method for preparing a lithium-ion battery pole piece comprises: using a transfer coater to uniformly coat a pre-formulated first layer of slurry on both sides of a pre-formulated current collector; drying the current collector after coating the first layer of slurry, so that the first layer of slurry forms a first film layer; using an extrusion coater to uniformly coat a pre-formulated second layer of slurry on both sides of the first film layer; drying and curing the current collector after coating the second layer of slurry, forming a second film layer on each of the first film layers; the first film layer and the second film layer form a double-layer membrane structure on both sides of the current collector; by combining transfer coating and extrusion coating in the above manner, the coating quality (uniformity, consistency and alignment), production efficiency, production cost reduction and battery performance improvement can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow chart of a method for preparing a lithium-ion battery electrode sheet according to an embodiment of the present invention;

[0023] Figure 2 is a schematic flow chart of a method for preparing a lithium-ion battery electrode sheet according to another embodiment of the present invention;

[0024] Figure 3 It is a schematic flow chart of a method for preparing a lithium-ion battery electrode according to another embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The terms "first", "second" and "third" in the present invention are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second" and "third" can explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. All directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] Figure 1 FIG. 1 is a schematic flow chart of a method for preparing a lithium-ion battery electrode according to an embodiment of the present invention. It should be noted that the method of the present invention is not limited to the method of preparing a lithium-ion battery electrode according to an embodiment of the present invention. Figure 1 The process sequence shown is limited. Figure 1 As shown, the method comprises the steps of:

[0029] Step S101: using a transfer coater to evenly coat the pre-formulated first layer of slurry on both sides of the pre-formulated current collector.

[0030] In step S101, the current collector is copper foil or aluminum foil, and this embodiment performs double-layer coating on both sides of the current collector. The first layer of slurry is lithium iron phosphate electrode slurry. The gap between the scraper and the coating roller of the transfer coater is 400-2000μm; the gap can be adjusted according to the coating thickness and coating surface density. Among them, the coating thickness is 80-500μm; the coating surface density is 100-150g / m 2The speed ratio of the coating roller to the backing roller is 0.9-1.1; the speed ratio of the coating roller to the backing roller affects the transfer efficiency of the slurry on the coating roller and the uniformity of the coating layer. The coating speed is 15-30m / min; the coating speed directly affects the production efficiency and coating quality.

[0031] Step S102: drying the current collector after coating the first layer of slurry, so that the first layer of slurry forms a first film layer.

[0032] In step S102, the baking temperature of the drying process is 90-110°C.

[0033] Step S103: using an extrusion coating machine to evenly coat the pre-formulated second layer of slurry on both sides of the first film layer.

[0034] In step S103, the second layer of slurry is lithium iron phosphate electrode slurry. The coating speed of the extrusion coater is 30-70 m / min; the coating thickness is 80-500 μm; the slurry feeding pump speed is 10-50 rpm / min; the coating surface density is 80-120 g / m 2 The compaction density of the first layer of slurry is greater than that of the second layer of slurry. The compaction density of the second layer of slurry is relatively low, which is conducive to the rapid insertion and extraction of lithium ions, thereby improving the rate performance of the battery.

[0035] Step S104: drying and curing the current collector coated with the second layer of slurry to form a second film layer on each first film layer; the first film layer and the second film layer form a double-sided double-layer film structure on the current collector.

[0036] In step S104, the baking temperature of the drying process is 100-130°C.

[0037] This embodiment sequentially performs drying treatments on the first layer of slurry and the second layer of slurry, which can ensure that each coating layer is completely dried and forms a good film layer, while preventing cracking, falling off, and the like from occurring on the coating layer.

[0038] The transfer coater does not require high viscosity of the slurry and is easy to adjust the coating parameters, but the coating accuracy is lacking; the extrusion coater has high coating accuracy and high equipment accuracy requirements. This embodiment combines the transfer coater and the extrusion coater to give full play to the advantages of both, significantly improve the coating quality and production efficiency, reduce production costs and improve battery performance; through the parameter control of the transfer coater and the extrusion coater and the double-layer coating process, the coating uniformity, consistency and alignment can be improved; the multi-layer coating process reduces the waste of slurry and improves the material utilization rate, while effectively preventing the mixing of metal foreign matter and dust, and improving the safety performance of the battery.

[0039] As an example, based on the above example, see Figure 2 , before step S101, further comprising:

[0040] Step S100: performing surface cleaning treatment on the pre-configured current collector.

[0041] This embodiment performs surface cleaning treatment on the current collector to ensure that there is no particle, debris, dust, etc. mixed on the surface of the current collector, so as to improve the coating quality and the safety performance of the battery.

[0042] As an example, based on the above example, see Figure 3 , after step S104, further comprising:

[0043] Step S105: trimming the edges of the coated current collector.

[0044] This embodiment trims the edge of the current collector to improve the coating quality and the safety performance of the battery.

[0045] The embodiment of the present invention also provides a lithium-ion battery pole piece, which includes a current collector and a double-layer membrane structure distributed on both sides of the current collector, wherein the double-layer membrane structure is prepared by a preparation method of a lithium-ion battery pole piece. This embodiment combines transfer coating and extrusion coating in the above manner, which can significantly improve coating quality (uniformity, consistency and alignment), production efficiency, reduce production costs and improve battery performance.

[0046] Example 1

[0047] Pre-prepare lithium iron phosphate electrode slurry; use a transfer coater to coat the lithium iron phosphate electrode slurry on both sides of the aluminum foil; dry the coated current collector to obtain a first film layer; use an extrusion coater to evenly coat the lithium iron phosphate electrode slurry on both sides of the first film layer; dry the coated current collector to obtain a second film layer; the first film layer and the second film layer form a double-sided double-layer membrane structure on the current collector.

[0048] Comparative Example 1

[0049] The lithium iron phosphate electrode slurry is pre-prepared; the lithium iron phosphate electrode slurry is coated on both sides of the aluminum foil by a transfer coater; the coated current collector is dried to obtain a first film layer.

[0050] test

[0051] Coating surface density: Samples were taken at different positions of the lithium-ion battery pole pieces prepared in Example 1 and Comparative Example 1, and the coating surface density on both sides was tested; wherein, 12 samples were taken in Example 1, respectively marked as 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11#, and 12#; 12 samples were taken in Comparative Example 1, respectively marked as 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, 10#, 11#, and 12#; the coating surface density of Example 1 is the sum of the surface density of the first film layer and the surface density of the second film layer.

[0052] Discharge capacity retention rate: Three lithium-ion batteries were prepared using the lithium-ion battery pole pieces prepared in Example 1 and Comparative Example 1, and the discharge capacity retention rate of each lithium-ion battery at different discharge rates was tested.

[0053] The test data of Example 1 and Comparative Example 1 are shown in Tables 1 to 3 below.

[0054] Table 1: Coating area density data of Example 1 and Comparative Example 1.

[0055] Example 1 Comparative Example 1 <![CDATA[Coating surface density / g / m 2 (1#)]]> 389.2 389.2 <![CDATA[Coating areal density / g / m 2 (2#)]]> 388.5 387.5 <![CDATA[Coating areal density / g / m 2 (3#)]]> 388.9 388.9 <![CDATA[Coating areal density / g / m 2 (4#)]]> 390.4 391.4 <![CDATA[Coating areal density / g / m 2 (5#)]]> 392.4 392.3 <![CDATA[Coating areal density / g / m 2 (6#)]]> 392.1 392.3 <![CDATA[Coating areal density / g / m 2 (7#)]]> 392.6 392.6 <![CDATA[Coating areal density / g / m 2 (8#)]]> 390.2 387.0 <![CDATA[Coating areal density / g / m 2 (9#)]]> 390.4 393.4 <![CDATA[Coating areal density / g / m 2 (10#)]]> 389.2 389.2 <![CDATA[Coating areal density / g / m 2 (11#)]]> 390.5 390.5 <![CDATA[Coating areal density / g / m 2 (12#)]]> 391.8 393.8

[0056] Table 2: Battery performance data of Example 1.

[0057]

[0058] Table 3: Battery performance data of Comparative Example 1.

[0059]

[0060] Please refer to Table 1. The range of the single-layer coating surface density is 1.74%, and the range of the double-layer coating surface density is 1.05%. The range of the double-layer coating surface density is 0.69% smaller than the single-layer surface density range, indicating that the double-layer coating process of Example 1 can improve the coating uniformity, consistency, and alignment. In addition, it can be seen from Tables 2 and 3 that when the discharge rate is 1C, the discharge capacity retention rate of the lithium-ion battery of Example 1 is 0.46% greater than that of Comparative Example 1; when the discharge rate is 1.5C, the discharge capacity retention rate of the lithium-ion battery of Example 1 is 0.46% greater than that of Comparative Example 1; when the discharge rate is 2C, the discharge capacity retention rate of the lithium-ion battery of Example 1 is 0.39% greater than that of Comparative Example 1, indicating that the double-layer coating process of Example 1 can improve battery performance.

[0061] The above are only implementation modes of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a lithium-ion battery pole piece, characterized in that: include: The pre-prepared first layer of slurry is uniformly coated on both sides of the pre-prepared current collector using a transfer coater; Drying the current collector coated with the first layer of slurry to form a first film layer from the first layer of slurry; Using an extrusion coating machine to evenly coat the pre-formulated second layer of slurry on both sides of the first film layer; The current collector coated with the second layer slurry is dried and cured to form a second film layer on each of the first film layers; the first film layer and the second film layer form a double-sided double-layer film structure on the current collector.

2. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The gap between the scraper and the coating roller of the transfer coater is 400-2000 μm; the rotation speed ratio between the coating roller and the backing roller is 0.9-1.1; the coating speed is 15-30 m / min; the coating thickness is 80-500 μm; the coating surface density is 100-150 g / m 2 .

3. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The coating speed of the extrusion coater is 30-70 m / min; the coating thickness is 80-500 μm; the slurry feeding pump speed is 10-50 rpm / min; the coating surface density is 80-120 g / m 2 .

4. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The compaction density of the first layer of slurry is greater than the compaction density of the second layer of slurry.

5. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The first layer slurry and the second layer slurry are made of the same raw material.

6. The method for preparing a lithium-ion battery pole piece according to claim 5, characterized in that: The first layer of slurry is lithium iron phosphate electrode slurry, and the second layer of slurry is lithium iron phosphate electrode slurry.

7. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: The baking temperature for drying the current collector after coating the first layer of slurry is 90-110° C.; the baking temperature for drying and curing the current collector after coating the second layer of slurry is 100-130° C.

8. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: Before the step of uniformly coating the pre-formulated first layer slurry on both sides of the pre-formulated current collector using a transfer coater, the method further includes: The pre-configured current collector is subjected to a surface cleaning treatment.

9. The method for preparing a lithium-ion battery pole piece according to claim 1, characterized in that: After the step of drying and curing the current collector coated with the second layer of slurry to form the second film layer on each of the first film layers, the method further includes: The coated current collector is subjected to edge trimming treatment.

10. A lithium-ion battery pole piece, comprising a current collector and a double-layer membrane structure distributed on both sides of the current collector, characterized in that: The double-layer diaphragm structure is prepared by the method for preparing a lithium-ion battery pole piece as described in any one of claims 1 to 9.

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