Carbon-coated current collector, preparation method therefor, and use thereof

Abstract

Disclosed herein are a carbon-coated current collector, a preparation method therefor, and a use thereof. The preparation method comprises the following steps: (1) performing pre-treatment and dispersion on a conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then performing homogenization treatment, to obtain a conductive carbon material premix; (2) mixing the conductive carbon material premix with deionized water, a binder, a wetting dispersant, and lithium carbonate, and performing dispersion to obtain a conductive slurry; and (3) coating the conductive slurry prepared in step (2) on a surface of a current collector and baking same, to obtain the carbon-coated current collector. In the present application, homogenization treatment is first performed on the conductive carbon material, and then same is mixed with the binder and dispersed, so that the compatibility between the conductive carbon material and the binder can be improved and the adaptability of a slurry formulation is improved. The lithium carbonate is added to the conductive slurry, such that the carbon coating layer, during formation, can provide a raw material for SEI formation, thereby reducing the consumption of a positive electrode material and ensuring the electrical performance and safety performance of a battery.

Description

A carbon-coated current collector and its preparation method and application Technical Field

[0001] The embodiments of the present application relate to the field of current collector technology, for example, a carbon-coated current collector and a preparation method and application thereof, and specifically relate to a carbon-coated aluminum foil current collector and a preparation method and application thereof. Background Art

[0002] Due to their high energy density, lithium-ion batteries are widely used in many fields, including automobiles and mobile phones. Lithium-ion batteries are primarily composed of positive and negative electrode active materials, electrolytes, separators, and positive and negative electrode current collectors. Currently, aluminum foil, copper foil, composite aluminum foil, composite copper foil, and carbon-coated aluminum foil, carbon-coated copper foil, composite carbon-coated aluminum foil, and composite carbon-coated copper foil with improved surface carbon coating are the primary materials used to transmit electrons. However, traditional aluminum or copper foil current collectors suffer from high interfacial resistance. While carbon-coated current collectors can improve interfacial resistance and enhance battery charging and discharging, when the current collector is made of aluminum foil, the carbon coating is easily affected by the amount and type of oil on the aluminum foil surface during the manufacturing process, resulting in defects such as white spots and exposed foil spots. Furthermore, different customers may have different requirements for the appearance of the carbon coating, necessitating frequent changes to the carbon coating slurry formula.

[0003] Therefore, it is desired in the art to develop a carbon-coated current collector whose carbon coating layer is less prone to defects such as white spots and exposed foil spots, and which can greatly improve the adaptability of the conductive paste formulation.

[0004] Summary of the Invention

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] The embodiments of the present application provide a carbon-coated current collector, a preparation method and application thereof, and specifically provide a carbon-coated aluminum foil current collector, a preparation method and application thereof.

[0007] In a first aspect, an embodiment of the present application provides a method for preparing a carbon-coated current collector, the method comprising the following steps:

[0008] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing the mixture to obtain a conductive carbon material premix;

[0009] (2) mixing the conductive carbon material premix with deionized water, a binder, a wetting dispersant, and lithium carbonate, and dispersing the mixture to obtain a conductive slurry;

[0010] (3) coating the conductive slurry obtained in step (2) on the surface of the current collector and baking it to obtain the carbon-coated current collector.

[0011] Compared with the traditional method of directly mixing and dispersing the conductive carbon material with the binder, the present application first performs a homogenization pretreatment on the conductive carbon material, and then mixes and disperses it with the binder. On the one hand, it can increase the compatibility between the conductive carbon material and the binder and improve the bonding strength. On the other hand, it can improve the surface tension of the conductive slurry, thereby greatly improving the adaptability of the slurry formulation; through homogenization treatment, the carbon coating layer can have different colors, thereby meeting the color requirements of different customers and avoiding defects such as white spots and exposed foil spots in the carbon coating layer; the present application adds lithium carbonate to the conductive slurry, so that the carbon coating layer can provide raw materials for SEI formation during formation, thereby providing good interface strength for the positive electrode active material, reducing the consumption of positive electrode materials, improving battery energy density, and ensuring the electrical performance and safety performance of lithium-ion batteries.

[0012] Preferably, the pressure of the homogenization treatment in step (1) is 100-1600 bar, for example, 100 bar, 200 bar, 300 bar, 400 bar, 500 bar, 600 bar, 700 bar, 800 bar, 900 bar, 1000 bar, 1100 bar, 1200 bar, 1300 bar, 1400 bar, 1500 bar or 1600 bar, etc., preferably 600-1000 bar.

[0013] Preferably, the homogenization treatment in step (1) is performed 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times. The homogenization treatment in the present application is performed by a homogenizer.

[0014] Preferably, the D90 of the conductive carbon material in the conductive carbon material premix in step (1) is 5-15 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm, etc.

[0015] Preferably, the raw materials for preparing the conductive carbon material premix in step (1) include, by weight: 1-50 parts (e.g., 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts, 43 parts, 45 parts, 48 ​​parts or 50 parts) of conductive carbon material, 1 part of deionized water ... -50 parts (e.g., 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts, 43 parts, 45 parts, 48 ​​parts or 50 parts, etc.), dispersant 1-20 parts (e.g., 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts or 20 parts, etc.).

[0016] Preferably, the conductive carbon material includes any one of conductive carbon powder, acetylene black, graphene or conductive graphite (such as natural graphite or artificial graphite) or a combination of at least two thereof.

[0017] Preferably, the dispersant includes any one of polyvinyl alcohol, hydroxypropyl methylcellulose, chitosan or polyvinyl pyrrolidone, or a combination of at least two thereof.

[0018] Preferably, the raw materials for preparing the conductive paste in step (2) include, by weight: 10-60 parts (e.g., 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 35 parts, 38 parts, 40 parts, 43 parts, 45 parts, 48 ​​parts, 50 parts, 53 parts, 55 parts, 58 parts or 60 parts) of a conductive carbon material premix, 10-20 parts (e.g., 10 parts, 13 parts, 15 parts, 18 parts or 20 parts) of deionized water, etc.), binder 10-30 parts (for example, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts or 30 parts, etc.), wetting and dispersing agent 0.03-1 part (for example, 0.03 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts or 1 parts, etc.), lithium carbonate 0.5-5 parts (for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, etc.).

[0019] Compared to other lithium salts, adding lithium carbonate to the conductive paste allows the lithium ions dissolved in the electrolyte to replenish the SEI film during battery charging and discharging. However, if the amount of lithium carbonate added to the conductive paste is too small, it will not be able to replenish the lithium ions lost during SEI film formation. If the amount of lithium carbonate added to the conductive paste is too large, the excess amount will not play any additional role in the battery.

[0020] Preferably, the binder includes any one of polytetrafluoroethylene (PTFE) emulsion, styrene-butadiene (SBR) emulsion, water-based polyacrylate or polyvinyl acetate, or a combination of at least two thereof.

[0021] Preferably, the solid content of the binder is 20-80%, for example, 20%, 30%, 40%, 50%, 60%, 70% or 80%.

[0022] Preferably, the wetting and dispersing agent includes any one of n-pentanol, ethanol, methanol, isopropanol or sodium dodecylbenzenesulfonate, or a combination of at least two thereof.

[0023] Preferably, the dispersion speed in step (2) is 500-1500 rpm, for example, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm or 1500 rpm, and the dispersion time is 0.5-2 hours, for example, 0.5 hour, 1 hour, 1.5 hours or 2 hours, etc.

[0024] Preferably, the material of the current collector in step (3) includes aluminum foil.

[0025] Preferably, the coating in step (3) includes gravure coating or slit coating.

[0026] Preferably, the baking temperature in step (3) is 90-100°C, for example, 90°C, 93°C, 95°C, 98°C or 100°C, and the baking time is 20s to 3min, for example, 20s, 40s, 1min, 2min or 3min. After the baking step, moisture can be removed and the conductive slurry forms a carbon coating layer on the surface of the current collector.

[0027] It should be noted that in step (3), the conductive slurry is coated on the surface of the current collector. It can be coated on one surface of the current collector or on both surfaces of the current collector.

[0028] Preferably, the thickness of the single-sided carbon-coated layer in the carbon-coated current collector in step (3) is 0.5-2 μm, such as 0.5 μm, 1 μm, 1.5 μm or 2 μm.

[0029] In a second aspect, an embodiment of the present application provides a carbon-coated current collector, which is prepared using the preparation method described in the first aspect.

[0030] In a third aspect, an embodiment of the present application provides an application of the carbon-coated current collector as described in the second aspect in a lithium-ion battery.

[0031] Compared with the related art, the embodiments of the present application have at least the following beneficial effects:

[0032] Compared with the traditional method of directly mixing and dispersing the conductive carbon material with the binder, the embodiment of the present application first performs a homogenization pretreatment on the conductive carbon material, and then mixes and disperses it with the binder. On the one hand, the compatibility between the conductive carbon material and the binder can be increased and the bonding strength can be improved. On the other hand, the surface tension of the conductive slurry can be improved, thereby greatly improving the adaptability of the slurry formula, so that the same formula can be used in a variety of ways, improving the consistency of lithium-ion battery production, and reducing the raw material import cost of battery manufacturers; through homogenization treatment, the carbon coating layer can have different colors, thereby meeting the color requirements of different customers and avoiding defects such as white spots and exposed foil spots in the carbon coating layer; the present application adds lithium carbonate to the conductive slurry, so that the carbon coating layer can provide raw materials for SEI formation during formation, thereby providing good interface strength for the positive electrode active material, reducing the consumption of positive electrode materials, improving the battery energy density, and ensuring the electrical performance and safety performance of the lithium-ion battery.

[0033] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0034] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0035] Example 1

[0036] In this embodiment, a method for preparing a carbon-coated current collector is provided, and the preparation method comprises the following steps:

[0037] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing once at 800 bar to obtain a conductive carbon material premix;

[0038] (2) mixing the conductive carbon material premix prepared in step (1) with deionized water, a binder, a wetting dispersant, and lithium carbonate, and stirring and dispersing the mixture at 1000 rpm for 1 hour to obtain a conductive slurry;

[0039] (3) The conductive paste prepared in step (2) was coated on one surface of the current collector (aluminum foil with a thickness of 13 μm) by gravure coating, and baked at 100° C. for 1 min to obtain the carbon-coated current collector (with a total thickness of 13.5 μm).

[0040] Wherein, the raw materials for preparing the conductive carbon material premix in step (1) include, by weight, 25 parts of conductive carbon material, 25 parts of deionized water, and 10 parts of dispersant; the conductive carbon material is conductive carbon powder, and the dispersant is hydroxypropyl methylcellulose;

[0041] The raw materials for preparing the conductive slurry in step (2) include, by weight: 30 parts of a conductive carbon material premix, 15 parts of deionized water, 20 parts of a binder, 0.5 parts of a wetting and dispersing agent, and 3 parts of lithium carbonate; the binder is a water-based polyacrylate (ADY-801, purchased from Hubei Kediya Technology Co., Ltd.), and the wetting and dispersing agent is n-pentanol.

[0042] Example 2

[0043] In this embodiment, a method for preparing a carbon-coated current collector is provided, and the preparation method comprises the following steps:

[0044] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing the mixture 5 times at 100 bar to obtain a conductive carbon material premix;

[0045] (2) mixing the conductive carbon material premix prepared in step (1) with deionized water, a binder, a wetting dispersant, and lithium carbonate, and stirring and dispersing the mixture at 500 rpm for 2 hours to obtain a conductive slurry;

[0046] (3) The conductive paste prepared in step (2) was coated on one surface of the current collector (aluminum foil with a thickness of 13 μm) by gravure coating, and baked at 100° C. for 1 min to obtain the carbon-coated current collector (with a total thickness of 13.5 μm).

[0047] The raw materials for preparing the conductive carbon material premix in step (1) include, by weight, 1 part of conductive carbon material, 50 parts of deionized water, and 15 parts of dispersant; the conductive carbon material is conductive graphite, and the dispersant is polyvinyl alcohol;

[0048] The raw materials for preparing the conductive slurry in step (2) include, by weight, 10 parts of a conductive carbon material premix, 10 parts of deionized water, 10 parts of a binder, 0.03 parts of a wetting and dispersing agent, and 0.5 parts of lithium carbonate; the binder is polytetrafluoroethylene (PTFE) emulsion (DuPont TE-3893), and the wetting and dispersing agent is isopropyl alcohol.

[0049] Example 3

[0050] In this embodiment, a method for preparing a carbon-coated current collector is provided, and the preparation method comprises the following steps:

[0051] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing once at 1200 bar to obtain a conductive carbon material premix;

[0052] (2) mixing the conductive carbon material premix prepared in step (1) with deionized water, a binder, a wetting dispersant, and lithium carbonate, and stirring and dispersing at 1500 rpm for 0.5 hours to obtain a conductive slurry;

[0053] (3) The conductive paste prepared in step (2) was coated on one surface of the current collector (aluminum foil with a thickness of 13 μm) by gravure coating, and baked at 100° C. for 1 min to obtain the carbon-coated current collector (with a total thickness of 13.5 μm).

[0054] The raw materials for preparing the conductive carbon material premix in step (1) include, by weight, 50 parts of conductive carbon material, 1 part of deionized water, and 5 parts of dispersant; the conductive carbon material is conductive carbon powder and conductive graphite (25 parts each), and the dispersant is hydroxypropyl methylcellulose;

[0055] The raw materials for preparing the conductive slurry in step (2) include, by weight: 50 parts of a conductive carbon material premix, 15 parts of deionized water, 15 parts of a binder, 0.8 parts of a wetting and dispersing agent, and 2 parts of lithium carbonate; the binder is a water-based polyacrylate (ADY-801, purchased from Hubei Kediya Technology Co., Ltd.), and the wetting and dispersing agent is n-pentanol.

[0056] Example 4

[0057] In this embodiment, a method for preparing a carbon-coated current collector is provided, and the preparation method comprises the following steps:

[0058] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing once at 1600 bar to obtain a conductive carbon material premix;

[0059] (2) mixing the conductive carbon material premix prepared in step (1) with deionized water, a binder, a wetting dispersant, and lithium carbonate, and stirring and dispersing the mixture at 1500 rpm for 2 hours to obtain a conductive slurry;

[0060] (3) The conductive paste prepared in step (2) was coated on one surface of the current collector (aluminum foil with a thickness of 13 μm) by gravure coating, and baked at 100° C. for 1 min to obtain the carbon-coated current collector (with a total thickness of 13.5 μm).

[0061] The raw materials for preparing the conductive carbon material premix in step (1) include, by weight, 10 parts of conductive carbon material, 40 parts of deionized water, and 20 parts of dispersant; the conductive carbon material is acetylene black, and the dispersant is polyvinyl alcohol;

[0062] The raw materials for preparing the conductive slurry in step (2) include, by weight, 60 parts of a conductive carbon material premix, 20 parts of deionized water, 30 parts of a binder, 1 part of a wetting and dispersing agent, and 5 parts of lithium carbonate; the binder is styrene-butadiene (SBR) emulsion (ZEON BM-451B, Japan), and the wetting and dispersing agent is ethanol.

[0063] Example 5

[0064] The only difference between this embodiment and embodiment 1 is that the pressure of the homogenization treatment in step (1) is 600 bar.

[0065] Example 6

[0066] The only difference between this embodiment and embodiment 1 is that the pressure of the homogenization treatment in step (1) is 1000 bar.

[0067] Example 7

[0068] The only difference between this embodiment and embodiment 1 is that the weight portion of lithium carbonate in the raw materials for preparing the conductive paste in step (2) is 0.2 parts.

[0069] Example 8

[0070] The only difference between this embodiment and embodiment 1 is that the weight portion of lithium carbonate in the raw materials for preparing the conductive paste in step (2) is 8 parts.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that the homogenization treatment in step (1) is replaced by ordinary stirring dispersion, as follows:

[0073] (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then stirring and dispersing at 1000 rpm for 1 hour to obtain a conductive carbon material premix;

[0074] The other steps and raw materials used are the same as those in Example 1.

[0075] Comparative Example 2

[0076] The only difference between this comparative example and Example 1 is that lithium carbonate is not added to the raw materials for preparing the conductive paste in step (2).

[0077] Comparative Example 3

[0078] The only difference between this comparative example and Example 1 is that, in the raw materials for preparing the conductive paste in step (2), lithium carbonate is replaced by lithium chloride in equal parts by weight.

[0079] The performance of the carbon-coated current collectors provided in Examples 1-8 and Comparative Examples 1-3 was tested using the following method:

[0080] (1) Color of carbon coating and whether there are white spots or exposed foil spots: Confirm the color of carbon coating by visual method and observe whether there are white spots or exposed foil spots;

[0081] (2) First charge and discharge efficiency: After the carbon-coated aluminum foil is made into a half-cell, the first charge and discharge efficiency is obtained through testing = first discharge capacity / first charge capacity.

[0082] The performance test results are shown in Table 1.

[0083] Table 1

[0084] As can be seen from Table 1, the carbon-coated layers of the carbon-coated current collectors provided in the embodiments of the present application do not have defects such as white spots and exposed foil spots, and the carbon-coated layers have different colors to meet the color requirements of different customers; and the addition of lithium carbonate to the slurry can significantly improve the initial charge and discharge efficiency. As the lithium carbonate content increases, the initial charge and discharge efficiency increases and reaches a stable range.

[0085] Compared with Example 1, the initial charge and discharge efficiencies of the carbon-coated current collectors provided in Comparative Examples 1-3 were all reduced.

[0086] The applicant declares that this application uses the above-mentioned embodiments to illustrate the carbon-coated current collector, its preparation method, and application. However, this application is not limited to the above-mentioned embodiments, which does not mean that this application must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent replacements for various raw materials in the product of this application, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of this application.

Claims

1. A method for preparing a carbon-coated current collector, comprising the following steps: (1) Pre-treating and dispersing the conductive carbon material: mixing the conductive carbon material with deionized water and a dispersant, and then homogenizing the mixture to obtain a conductive carbon material premix; (2) mixing the conductive carbon material premix with deionized water, a binder, a wetting dispersant, and lithium carbonate, and dispersing the mixture to obtain a conductive slurry; (3) coating the conductive slurry obtained in step (2) on the surface of the current collector and baking to obtain the carbon-coated current collector.

2. The preparation method according to claim 1, wherein The pressure of the homogenization treatment in step (1) is 100-1600 bar, preferably 600-1000 bar.

3. The preparation method according to claim 1 or 2, wherein The homogenization treatment in step (1) is performed 1 to 5 times.

4. The preparation method according to any one of claims 1 to 3, wherein The D90 of the conductive carbon material in the conductive carbon material premix in step (1) is 5-15 μm.

5. The preparation method according to any one of claims 1 to 4, wherein The raw materials for preparing the conductive carbon material premix in step (1) include, by weight: 1-50 parts of conductive carbon material, 1-50 parts of deionized water, and 1-20 parts of dispersant.

6. The preparation method according to any one of claims 1 to 5, wherein The conductive carbon material includes any one of conductive carbon powder, acetylene black, graphene or conductive graphite, or a combination of at least two of them.

7. The preparation method according to any one of claims 1 to 6, wherein The dispersant includes any one of polyvinyl alcohol, hydroxypropyl methylcellulose, chitosan or polyvinyl pyrrolidone, or a combination of at least two thereof.

8. The preparation method according to any one of claims 1 to 7, wherein The raw materials for preparing the conductive paste in step (2) include, by weight: 10-60 parts of conductive carbon material premix, 10-20 parts of deionized water, 10-30 parts of binder, 0.03-1 parts of wetting dispersant, and 0.5-5 parts of lithium carbonate.

9. The preparation method according to any one of claims 1 to 8, wherein The binder includes any one of polytetrafluoroethylene emulsion, styrene-butadiene emulsion, water-based polyacrylate or polyvinyl acetate, or a combination of at least two thereof; Preferably, the solid content of the binder is 20 to 80%; Preferably, the wetting and dispersing agent includes any one of n-pentanol, ethanol, methanol, isopropanol or sodium dodecylbenzene sulfonate, or a combination of at least two thereof.

10. The preparation method according to any one of claims 1 to 9, wherein The dispersion speed in step (2) is 500-1500 rpm, and the dispersion time is 0.5-2 hours.

11. The preparation method according to any one of claims 1 to 10, wherein The material of the current collector in step (3) includes aluminum foil.

12. The preparation method according to any one of claims 1 to 11, wherein The coating in step (3) includes gravure coating or slit coating.

13. The preparation method according to any one of claims 1 to 12, wherein The baking temperature in step (3) is 90-100° C., and the baking time is 20 seconds to 3 minutes.

14. A carbon-coated current collector, wherein: The carbon-coated current collector is prepared by the preparation method according to any one of claims 1 to 13.

15. Use of the carbon-coated current collector as claimed in claim 14 in a lithium-ion battery.

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