Secondary battery electrode sheet, manufacturing method therefor, and use thereof

Abstract

The present application relates to a secondary battery electrode sheet, a manufacturing method therefor and the use thereof. The secondary battery electrode sheet provided in the present application comprises: a current collector, the current collector comprising an active layer coating region and a tab region which are connected, the tab region comprising an insulating layer coating region and a bare foil region, and the insulating layer coating region being a region between the bare foil region and the active layer coating region; an active layer, the active layer covering the active layer coating region; and an insulating layer, the insulating layer covering the insulating layer coating region. Raw materials for preparing the insulating layer comprise an insulating filler; the insulating filler satisfies the following conditions: pH is 10 to 12, Dv10 is 0.2 to 0.7 μm, Dv50 is 0.5 to 1.0 μm, Dv90 is 1.2 to 1.9 μm, and Dv99 is 2.8 to 4.0 μm.

Description

A secondary battery pole piece, a preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a secondary battery pole piece, a preparation method and application thereof. BACKGROUND

[0002] At present, the pole pieces in most lithium ion batteries in the industry all need to be welded with nickel tabs or copper tabs. The welding points are in the middle or tail of the pole piece, and there is no area coated with active material (also known as a groove). The nickel tab or copper tab, as a foreign substance, has the risk of piercing the separator, and the process of welding the tab is also relatively complex, and the preparation efficiency is relatively low.

[0003] In recent years, in order to improve the preparation efficiency and optimize the performance of the obtained lithium ion battery, researchers have designed a multi-tab cell structure. Specifically, the pole piece retains an empty foil in the coating direction in the tab area, and then in the laser die-cutting process, the empty foil is cut by laser to form a tab in the shape of a conventional tab. Each two layers of small pole pieces will have a pair of positive and negative tab. The small pole piece is a single pole piece according to the size of the cell. In the preparation process of the multi-tab cell structure, laser cutting technology is usually used. However, the laser cutting technology may generate burrs in the empty foil area (tab side edge). If the height of the burr is too high, it may pierce the separator, causing the cell to short circuit, and in severe cases, it may also cause the cell to catch fire.

[0004] In order to overcome the above technical problems, the related art has made many attempts, such as setting an insulating coating in part of the empty foil area, but the effect is still not good. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a secondary battery pole piece, which can effectively improve the flatness (thickness uniformity) of the insulating layer, thereby avoiding burrs in the laser die-cutting process or avoiding high burrs that affect the safety of the battery.

[0006] The present application also provides a preparation method of the above-mentioned secondary battery pole piece.

[0007] The present application also provides an application of the above-mentioned secondary battery pole piece.

[0008] According to an embodiment of the first aspect of the present application, a secondary battery pole piece is provided, which comprises:

[0009] a current collector comprising a connection setting active layer coating area and a tab area; the tab area comprises an insulating layer coating area and an empty foil area; the insulating layer coating area is the area between the empty foil area and the active layer coating area;

[0010] an active layer, the active layer being coated on the active layer coating area;

[0011] an insulation layer, the insulation layer being coated on the insulation layer coating area;

[0012] the raw material for preparing the insulation layer comprises an insulation filler;

[0013] the insulation filler satisfies the following conditions:

[0014] (1) pH is 10 to 12;

[0015] (2) Dv10 is 0.2 to 0.7 μm;

[0016] (3) Dv50 is 0.5 to 1.0 μm;

[0017] (4) Dv90 is 1.2 to 1.9 μm;

[0018] (5) Dv99 is 2.8 to 4.0 μm.

[0019] The secondary battery pole piece according to the embodiments of the present application has at least the following beneficial effects:

[0020] The present application controls the pH and particle size of the insulation filler, so that the thickness consistency of the insulation layer formed after coating is much greater than before, the thickness fluctuation is small, thereby greatly reducing the safety risk of the die cutting burr piercing the diaphragm causing the battery cell to catch fire, and effectively improving the safety performance of the battery cell.

[0021] According to some embodiments of the present application, the insulation filler comprises at least one of magnesium oxide, magnesium hydroxide, aluminum hydroxide and aluminum oxide. For example, it can be two, three or four kinds.

[0022] According to some embodiments of the present application, the insulation filler is selected from magnesium hydroxide.

[0023] According to some embodiments of the present application, the insulation filler is selected from aluminum hydroxide.

[0024] According to some embodiments of the present application, the insulation filler is selected from aluminum oxide.

[0025] According to some embodiments of the present application, the insulation filler is selected from a mixture of magnesium hydroxide and aluminum hydroxide. The mass ratio of the magnesium hydroxide and the aluminum hydroxide is 1:2 to 3. For example, it can be about 1:2.5.

[0026] According to some embodiments of the present application, the insulation filler is selected from a mixture of magnesium oxide, magnesium hydroxide and aluminum hydroxide. The mass ratio of the magnesium oxide, the magnesium hydroxide and the aluminum hydroxide is 1:(1.5 to 2.5):(1.5 to 2.5). For example, it can be about 1:2:2.

[0027] According to some embodiments of the present application, the insulating filler is selected from a mixture of magnesium oxide, magnesium hydroxide, aluminum hydroxide and aluminum oxide. The mass ratio of magnesium oxide, magnesium hydroxide, aluminum hydroxide and aluminum oxide is 1: (2.5 to 3.5): (3.5 to 4.5): (1.5 to 2.5). For example, it can be about 1:3:4:2.

[0028] According to some embodiments of the present application, the particle size of the insulating filler satisfies at least one of the following parameters:

[0029] (1) Dv10 0.3 to 0.6 μm;

[0030] For example, it can be about 0.4 μm, 0.45 μm or about 0.5 μm.

[0031] (2) Dv50 0.7 to 0.8 μm;

[0032] For example, it can be about 0.75 μm.

[0033] (3) Dv90 1.3 to 1.6 μm;

[0034] For example, it can be about 1.4 μm, 1.5 μm or about 1.55 μm.

[0035] (4) Dv99 3.1 to 3.6 μm;

[0036] For example, it can be about 3.2 μm, 3.3 μm, 3.4 μm or about 3.5 μm.

[0037] According to some embodiments of the present application, the pH of the insulating filler is 10.5 to 11.5. For example, it can be about 11.

[0038] Unless otherwise specified, the pH of the insulating filler in the present application is the pH of the slurry obtained by mixing the insulating filler and N-methyl pyrrolidone (NMP) at a mass ratio of 1:2.

[0039] According to some embodiments of the present application, the preparation raw material of the insulating layer further comprises a binder.

[0040] According to some embodiments of the present application, the binder comprises at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polyacrylic acid (PAA, water-based adhesive).

[0041] According to some embodiments of the present application, the mass percentage of the insulating filler in the insulating layer is 65% to 95%. For example, it can be about 80%, 82%, 85%, 87%, 88%, 89%, 90% or about 92%.

[0042] According to some embodiments of the present application, the preparation raw material of the insulation layer further comprises a solvent.

[0043] According to some embodiments of the present application, the solvent comprises at least one of water, NMP, dimethylformamide, dimethylacetamide and tetrahydrofuran. The selection of the solvent is determined by multiple factors such as the application environment of the secondary battery pole piece, the type of the binder, whether the preparation raw material of the secondary battery pole piece reacts with the solvent, etc.

[0044] According to some embodiments of the present application, the thickness of the insulation layer is 10% to 60% of the thickness of the active layer. For example, it can be about 20%, 30% or about 40% in particular. By limiting the thickness ratio between the insulation layer and the active layer, the melting of the current collector during laser film cutting can be significantly avoided, and the formation of beads, burrs and other phenomena that exceed the insulation layer can be avoided, thereby affecting the safety performance of the battery cell. That is, the limitation of this parameter can significantly improve the safety performance of the secondary battery pole piece.

[0045] According to some embodiments of the present application, the thickness of the insulation layer is between 20 to 30 μm. For example, it can be about 22 μm, 25 μm or about 28 μm in particular.

[0046] According to some embodiments of the present application, the secondary battery pole piece comprises at least one of a multi-tab pole piece and a stacked pole piece. The multi-tab pole piece refers to a plurality of tabs arranged on one pole piece, and the tabs are led out from the side. The stacked pole piece refers to one tab arranged on each pole piece, and the tabs are led out from the side. A plurality of pole pieces are arranged in a stacked manner, and the tab positions are substantially overlapped to form a battery cell.

[0047] According to some embodiments of the present application, the secondary battery pole piece comprises at least one of a positive electrode and a negative electrode.

[0048] According to some embodiments of the present application, when the secondary battery pole piece is a positive electrode, the active layer comprises a positive electrode active material.

[0049] According to some embodiments of the present application, the positive electrode active material comprises at least one of a polyanion material, a layered material and a spinel material.

[0050] The polyanion material comprises at least one of lithium iron phosphate, lithium manganese phosphate and lithium manganese iron phosphate.

[0051] The general formula of the layered material is LiMO2, wherein M comprises at least one of nickel, cobalt and manganese.

[0052] In the layered material, M further comprises a doping element; and the doping element comprises at least one of aluminum, zirconium, magnesium, titanium, boron and fluorine.

[0053] The spinel material includes lithium manganate (spinel phase).

[0054] Preferably, the positive active material is selected from lithium cobaltate.

[0055] According to some embodiments of the present application, when the secondary battery pole piece is a positive electrode, the active layer further includes a conductive agent and a binder. The mass percentage of the positive active material in the active layer is 90% to 98%; for example, it can be about 92%, 94%, 95%, 96%, or about 97%. The mass ratio of the conductive agent and the binder is 1:0.8 to 1.2; for example, it can be about 1:1.

[0056] According to some embodiments of the present application, when the secondary battery pole piece is a negative electrode, the active layer includes a negative active material.

[0057] According to some embodiments of the present application, the negative active material includes at least one of a carbon-based material, a silicon-based material, a lithium-based material, and a titanium-based material.

[0058] The carbon-based material includes at least one of artificial graphite and natural graphite.

[0059] The silicon-based material includes at least one of silicon-oxygen material and silicon-carbon material.

[0060] The lithium-based material includes at least one of lithium monomer and lithium-metal alloy.

[0061] The titanium-based material includes lithium titanate.

[0062] According to an embodiment of the second aspect of the present application, a preparation method of the secondary battery pole piece is provided, and the preparation method includes the following steps:

[0063] S1. Preparing an active slurry and an insulating slurry; the insulating slurry includes the insulating filler;

[0064] S2. Coating the active slurry on the active layer coating area to obtain the active layer;

[0065] Coating the insulating slurry on the insulating layer coating area to obtain the insulating layer;

[0066] S3. Laser die cutting the component obtained in step S2.

[0067] Since the preparation method adopts all the technical solutions of the secondary battery pole piece of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments. Further, compared with the traditional mechanical die cutting method, the laser die cutting method of the present application significantly improves the die cutting efficiency and die cutting effect.

[0068] According to some embodiments of the present application, the preparation of the insulating paste comprises mixing the insulating filler and the binder, and then mixing the obtained mixture with the solvent. In this way, the preparation time of the insulating paste can be significantly shortened.

[0069] According to some embodiments of the present application, the solid content of the insulating paste is 20% to 50%. For example, it can be about 30%, 31%, 32%, 33%, 34%, 35%, 36%, 38%, 39%, 40%, 42%, or about 45%.

[0070] According to some embodiments of the present application, the preparation of the active paste comprises mixing the raw materials for the active layer.

[0071] According to some embodiments of the present application, in step S2, the coating of the insulating layer and the active layer can be performed simultaneously or sequentially.

[0072] According to some embodiments of the present application, in step S2, the coating method comprises at least one of extrusion coating and dispensing coating.

[0073] According to some embodiments of the present application, in step S2, after the coating, drying, rolling and slitting are sequentially performed. The purpose of slitting is to cut the obtained component into the required size (profile); in step S3, the function of laser die cutting is mainly to die cut the shape of the tab.

[0074] According to some embodiments of the present application, in step S3, in the laser die cutting, the power of the laser used is 30% to 80% of the total power. For example, it can be about 35%, 40%, 45%, 50%, 60%, or about 70%. Unless otherwise specified, the laser used in the present application has a total power of 250W.

[0075] According to some embodiments of the present application, in step S3, in the laser die cutting, the frequency of the laser used is 200 to 1000 kHz. For example, it can be about 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, or about 900 kHz.

[0076] According to some embodiments of the present application, in step S3, in the laser die cutting, the walking speed is 30 to 50 m / min. For example, it can be about 35 m / min, 40 m / min, or about 45 m / min.

[0077] According to some embodiments of the third aspect of the present application, a secondary battery is provided, which comprises the battery tab as described.

[0078] Since the secondary battery adopts all the technical solutions of the battery pole piece of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments. That is, the obtained secondary battery has higher safety, service life and electrochemical performance.

[0079] According to some embodiments of the present application, the secondary battery comprises at least one of a lithium ion secondary battery, a sodium ion secondary battery and a potassium ion secondary battery.

[0080] Unless otherwise specified, in the present application, the particle size is measured by taking 4g of insulating filler sample and dissolving it in 40g of water, using a measuring device Malvern 3000, and testing the particle size of the material by laser diffraction method.

[0081] Unless otherwise specified, in the present application, "about" actually means that the allowed error is within ±2%, for example, about 100 actually means 100±2%*100.

[0082] Unless otherwise specified, in the present application, "between" includes the number, for example, "between 2 and 3" includes the end values 2 and 3.

[0083] Other features and advantages of the present application will be set forth in the subsequent description, and in part will become apparent from the description, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0084] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description, taken in conjunction with the following drawings, in which:

[0085] Figure 1 is the cross-sectional effect of the laser die cutting of the insulating layer region of the secondary battery pole piece obtained in Example 2 of the present application.

[0086] Figure 2 is the cross-sectional effect of the laser die cutting of the insulating layer region of the secondary battery pole piece obtained in Comparative Example 1 of the present application.

[0087] Figure 3 is a structural schematic diagram of the secondary battery pole piece obtained in Example 1 of the present application.

[0088] Reference signs: current collector 100, empty foil area 110; active layer 200; insulating layer 300. DETAILED DESCRIPTION

[0089] The concept and technical effects of the present application will be described in detail below in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0090] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in one or more embodiments or examples.

[0091] Embodiment 1

[0092] Referring to FIG. 3, a multi-tab secondary battery electrode sheet is prepared in this example; the secondary battery electrode sheet is a positive electrode, and specifically includes:

[0093] A current collector 100 including a connection provided active layer coating area and tab area; the tab area includes an insulating layer coating area and a blank foil area 110; the insulating layer coating area is the area between the blank foil area 110 and the active layer coating area;

[0094] An active layer 200, the active layer 200 is coated on the active layer coating area; the thickness of the active layer 200 is 80 μm;

[0095] An insulating layer 300, the insulating layer 300 is coated on the insulating layer coating area. The thickness of the insulating layer 300 is 25 μm.

[0096] The preparation process of the secondary battery electrode sheet in this example is as follows:

[0097] S1. Preparation stage:

[0098] Preparation of active slurry: mix positive active material lithium cobaltate, conductive agent (SP): PVDF according to the mass ratio of 97%: 1.5%: 1.5%, and add NMP homogenate to obtain active slurry.

[0099] Preparation of insulating slurry: mix insulating filler and PVDF according to the mass ratio of 90:10, and then mix with NMP to obtain insulating slurry with solid content of 35%. The parameters of the insulating filler used in this example are shown in Table 1.

[0100] S2. The above active slurry and insulating slurry are coated together on the surface of the aluminum current collector by extrusion die, and after drying, rolled, cut (into strips, but no tab shape is shown).

[0101] S3. Laser die cutting to remove excess parts, showing tabs, to obtain a secondary battery electrode sheet as a battery positive electrode sheet.

[0102] Examples 2 to 12 and Comparative Examples 1 to 18 each prepared a secondary battery pole piece, which is specifically different from Example 1 in that:

[0103] The parameters of the insulating fillers were different, and the specific differences are shown in Table 1.

[0104] Table 1 Parameters of insulating fillers used in examples and comparative examples

[0105] In Table 1, all proportions are mass ratios. The original particle size distribution of each type of insulating filler used is the same as that of magnesium hydroxide in Example 1; subsequent airflow classification is used to obtain insulating fillers with different particle size distributions for verifying the effect difference brought by particle size distribution. And the method of water washing is used to obtain insulating fillers with different pH values, same material and particle size, for verifying the effect of insulating filler pH.

[0106] Test Example

[0107] This example tests the burr condition of the die-cut edge side of the examples and comparative examples, and the specific test method is: using a microscope with measurement function (such as Keyence 3D microscope), observing the end face of the die-cut pole piece, and measuring the height of the melt bead exceeding the insulating coating.

[0108] This example also calculates the process capability parameters of the insulating layer thickness, and the specific method is: process capability parameter CPK = Min[(USL-Mu) / 3s,(Mu-LSL) / 3s]; wherein (USL, LSL are the upper and lower limit specification values of the thickness, Mu is the average value of the calculated insulating layer thickness, and s is the standard deviation of the calculated insulating layer thickness). The process capability parameter is a measure of the ability of the system to manufacture good products. In our industry, we usually consider process capability > 1.3 as meeting the current manufacturing needs. Then the larger the value is, the better.

[0109] The results of the above tests are shown in Figures 1 to 2 and Table 2.

[0110] Table 2 Performance results of secondary battery pole pieces obtained in examples and comparative examples

[0111] It can be known from Examples 1 to 12 that, within the scope provided by the present application, the insulation layer obtained by changing the type, particle size and pH of the insulation filler has almost no burr or a lower burr height after cutting. It can be further known that, within the scope provided by the present application, increasing the pH can reduce the burr height. This is because, in the insulation paste, as the pH increases (in the range of 10 to 12), the charge state of each particle in the paste can be changed, the electrostatic repulsion between particles is increased, the solution system is more stable, and the dispersibility is better. However, in general, a larger pH will affect the viscosity of the paste to some extent, especially when PVDF is used as the binder, which is more likely to appear as jelly, thereby deteriorating the construction process. The technical solution provided by the present application achieves an unexpected technical effect through the synergistic effect between the particle size and the pH of the insulation filler.

[0112] It can be known from Comparative Examples 1 to 2 and Comparative Examples 1 to 6 that, even if the same material insulation filler is used, if any one of the particle size or the pH is not within the scope required by the present application, the process capability parameter will decrease and the burr height will increase. The comparison of Examples 7 to 8 and Comparative Examples 7 to 10, or the comparison of Examples 9 to 10 and Comparative Examples 11 to 14, or the comparison of Examples 11 to 12 and Comparative Examples 15 to 18, can obtain similar results.

[0113] In summary, in the secondary battery pole piece provided by the present application, by limiting the particle size and the pH of the insulation filler, the thickness of the burr can be significantly reduced or the generation of the burr can be eliminated; further, the battery including the above-mentioned secondary battery pole piece has a significantly improved safety performance. Still further, the secondary battery with better safety performance is expected to be widely used in the field of electric vehicles, the field of 3C small household appliances and the field of energy storage.

[0114] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-mentioned embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A secondary battery electrode sheet, wherein, The secondary battery electrode sheet comprises: a current collector comprising a connection provided active layer coating area and tab area; the tab area comprises insulating layer coating area and empty foil area; the insulating layer coating area is the area between the empty foil area and the active layer coating area; an active layer coated on the active layer coating area; an insulating layer coated on the insulating layer coating area; the preparation raw material of the insulating layer comprises insulating filler; the insulating filler satisfies the following conditions: (1) pH is 10 to 12; (2) Dv10 is 0.2 to 0.7 μm; (3) Dv50 is 0.5 to 1.0 μm; (4) Dv90 is 1.2 to 1.9 μm; (5) Dv99 is 2.8 to 4.0 μm.

2. The secondary battery electrode sheet according to claim 1, wherein The insulating filler comprises at least one of magnesium oxide, magnesium hydroxide, aluminum hydroxide and aluminum oxide.

3. The secondary battery electrode sheet according to claim 1, wherein The pH of the insulating filler is 10.5 to 11.

5.

4. The secondary battery electrode sheet according to claim 1, wherein The particle size Dv10 of the insulating filler is 0.3 to 0.6 μm.

5. The secondary battery electrode sheet according to claim 1, wherein The particle size Dv50 of the insulating filler is 0.7 to 0.8 μm.

6. The secondary battery electrode sheet according to claim 1, wherein The particle size Dv90 of the insulating filler is 1.3 to 1.6 μm.

7. The secondary battery pole piece of claim 1, wherein, The particle size Dv99 of the insulating filler is 3.1 to 3.6 μm.

8. The secondary battery pole piece of claim 1, wherein, The mass percentage of the insulating filler in the insulating layer is 65% to 95%.

9. The secondary battery pole piece of claim 1, wherein, The thickness of the insulating layer is 10% to 60% of the thickness of the active layer.

10. The secondary battery electrode sheet according to claim 1, wherein The thickness of the insulating layer is 20% to 60% of the thickness of the active layer.

11. The secondary battery electrode sheet according to claim 1, wherein The thickness of the insulating layer is 30% to 60% of the thickness of the active layer.

12. The secondary battery pole piece of claim 1, wherein, The thickness of the insulating layer is 40% to 60% of the thickness of the active layer.

13. The secondary battery pole piece of claim 1, wherein, The thickness of the insulating layer is 20 to 30 μm.

14. The secondary battery pole piece of claim 1, wherein, The preparation raw material of the insulating layer further comprises binder and solvent.

15. The secondary battery electrode sheet of claim 14, wherein, The binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene and polyacrylic acid.

16. The secondary battery electrode of claim 14, wherein, The solvent comprises at least one of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide and tetrahydrofuran.

17. The secondary battery pole piece of any one of claims 1 to 16, wherein, The secondary battery electrode sheet comprises at least one of positive electrode and negative electrode.

18. A method of producing the secondary battery electrode sheet according to any one of claims 1 to 17, wherein The preparation method comprises the following steps: S1. preparing active slurry and insulating slurry; the insulating slurry comprises the insulating filler; S2. coating the active slurry on the active layer coating area to obtain the active layer; coating the insulating slurry on the insulating layer coating area to obtain the insulating layer; S3. laser die cutting the component obtained in step S2.

19. A secondary battery, wherein, The secondary battery comprises the secondary battery electrode sheet according to any one of claims 1 to 17.

20. The secondary battery of claim 19, wherein, The secondary battery comprises at least one of lithium ion secondary battery, sodium ion secondary battery and potassium ion secondary battery.

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