Pretreated aluminum foil as well as preparation method and application thereof

Abstract

The invention discloses a pretreated aluminum foil and a preparation method and application thereof.The preparation method comprises the steps that a conductive material, a high-molecular dispersing agent and N-methyl pyrrolidone are placed in a stirrer in proportion to be subjected to first stirring treatment, and first slurry is obtained after the conductive material, the high-molecular dispersing agent and the N-methyl pyrrolidone are evenly mixed; adding a lithium supplementing material and lithium nitride into the first slurry, and continuously carrying out second stirring treatment to obtain second slurry; transferring the second slurry into a sand mill, and carrying out sanding treatment to obtain third slurry; the granularity D50 of solid particles in the third slurry is less than 300nm; adding polyvinylidene fluoride into the third slurry, and carrying out third stirring treatment to obtain fourth slurry; coating the surface of the aluminum foil with the fourth slurry, drying, and forming a film from the coated fourth slurry to obtain a pretreated aluminum foil containing a coating; when the pretreated aluminum foil is applied to the lithium ion battery, the first-week coulombic efficiency, the cycle performance and the thermal safety of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and particularly relates to a pretreated aluminum foil, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, low cost, and long service life, and are an ideal choice for electric vehicles and various portable electronic products. However, in the first cycle of lithium-ion batteries, there is a first irreversible capacity loss of 5% - 15% in the formation of the SEI film on the surface of the graphite negative electrode, and a loss of 15% - 35% for high-capacity silicon-based materials. This is because a large amount of lithium is consumed in the formation of the SEI on the surface of the negative electrode material during the first cycle, resulting in a Coulombic efficiency (referred to as the first efficiency) of usually less than 80% in the first week, causing a significant decrease in the actual specific energy of the battery, and severely restricting the large-scale commercial application of graphite, especially silicon-based negative electrodes.

[0003] Current lithium supplementation schemes mainly include negative electrode lithium supplementation, positive electrode lithium supplementation, separator lithium supplementation, electrolyte lithium supplementation, etc. In the positive electrode lithium supplementation scheme, a positive electrode lithium supplementation additive is used to release Li during the charging process + to supplement the irreversible capacity loss during the first charge and discharge. The positive electrode lithium supplementation additive is a lithium salt. Since the typical positive electrode lithium supplementation scheme is to add a small amount of positive electrode lithium supplementation additive during the positive electrode slurry mixing process, or to coat the positive electrode lithium supplementation additive on the current collector first and then coat the positive electrode material. Using a lithium salt as a lithium supplementation additive in the above scheme will have a greater impact on the electrical conductivity of the positive electrode sheet, or affect the performance of the positive electrode specific capacity. Summary of the Invention

[0004] The embodiments of the present invention provide a pretreated aluminum foil, a preparation method thereof, and an application thereof, aiming to solve the problem that when the positive electrode lithium supplementation additive lithium salt is coated on the current collector and then the positive electrode material is coated in the existing lithium supplementation scheme, a small amount of positive electrode lithium supplementation additive is dispersed together at a higher viscosity during the positive electrode slurry mixing process, resulting in uneven dispersion of the positive electrode lithium supplementation additive, thereby affecting the electrical performance of the positive electrode sheet. Coating the positive electrode lithium supplementation additive on the current collector affects the electrical conductivity and ion conductivity of the current collector, thus affecting the cycle performance and the first-week Coulombic efficiency of the battery.

[0005] To this end, in a first aspect, the embodiments of the present invention provide a preparation method of a pretreated aluminum foil, and the preparation method includes:

[0006] Step S1, placing a conductive material, a polymer dispersant, and N-methylpyrrolidone in a blender according to a ratio for a first stirring treatment. After mixing evenly, a first slurry is obtained;

[0007] Step S2, adding a lithium supplementation material and lithium nitride to the first slurry, and continuing a second stirring treatment to obtain a second slurry;

[0008] Step S3: Transfer the second slurry to a sand mill for sanding treatment to obtain a third slurry. Among them, the diameter of the grinding beads for the sanding treatment is 0.3 mm; the particle size D of the solid particles in the third slurry 50 < 300 nm;

[0009] Step S4: Add polyvinylidene fluoride to the third slurry and perform a third stirring treatment to obtain a fourth slurry;

[0010] Step S5: Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0011] Preferably, the conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black SP;

[0012] The polymeric dispersant includes one or more of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester-amide) dispersants;

[0013] The mass percentage of the polymeric dispersant in the conductive material is from 0.1% to 5%;

[0014] The solid content of the first slurry is from 5% to 10%.

[0015] Preferably, the lithium supplementing material includes one or more of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4;

[0016] The mass of the lithium supplementing material is 1 to 1.5 times the mass of the conductive material;

[0017] The mass percentage of lithium nitride in the lithium supplementing material is from 0.1% to 10%.

[0018] Preferably, the mass percentage of polyvinylidene fluoride in the total mass of the third slurry is from 0.01% to 1%.

[0019] Preferably, the rotation speeds set for the first stirring treatment, the second stirring treatment, and the third stirring treatment are all between 2000 rpm and 5000 rpm; the dry dew point during the processes of the first stirring treatment, the second stirring treatment, and the third stirring treatment is ≤ -30 °C, and the temperature is ≤ 20 °C.

[0020] Preferably, the sand mill includes any one of a horizontal sand mill, a basket sand mill, and a vertical sand mill; the rotation speed of the sand mill is 500 rpm - 2000 rpm;

[0021] The grinding beads include any one of zirconia beads, alumina beads, and zirconium silicate beads.

[0022] Preferably, the drying treatment is air drying, and the temperature is 110°C - 150°C.

[0023] In a second aspect, an embodiment of the present invention provides a pretreated aluminum foil prepared by the preparation method described in the first aspect above. The pretreated aluminum foil includes an aluminum foil and a coating applied to the surface of the aluminum foil.

[0024] The mass ratio of the conductive material, the polymer type dispersant, the lithium supplement material, lithium nitride, and polyvinylidene fluoride is 100: [0.1 - 5]: [100 - 150]: [1 - 15]: [0.2 - 2.7].

[0025] Among them, the conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black SP.

[0026] The polymer type dispersant includes any one of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester - amide) dispersants.

[0027] The lithium supplement material includes any one of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4.

[0028] In a third aspect, an embodiment of the present invention provides a positive electrode sheet. The positive electrode sheet includes the pretreated aluminum foil described in the second aspect above and a positive electrode active material layer attached to the surface of the pretreated aluminum foil.

[0029] In a fourth aspect, an embodiment of the present invention provides a lithium - ion battery. The lithium - ion battery includes the positive electrode sheet described in the third aspect above.

[0030] An embodiment of the present invention provides a pretreated aluminum foil, its preparation method and application. By pre - mixing and dispersing a conductive agent and a polymer type dispersant with N - methylpyrrolidone (NMP) evenly, then adding a lithium supplement material and lithium nitride, after mixing evenly, performing sanding treatment until the particle size is less than 300 nm, and then adding polyvinylidene fluoride and stirring evenly to obtain an oily slurry, and coating it on the surface of the aluminum foil and drying, a pretreated aluminum foil is obtained.

[0031] The pre-treated aluminum foil provided by the embodiments of the present invention can improve the overall conductivity of the current collector aluminum foil after the slurry with better dispersion and more uniform particle size is obtained by subjecting the materials to high-speed stirring, grinding treatment, and then high-speed stirring treatment during the preparation process and coating the slurry on the surface of the aluminum foil. In addition, NMP is used as the solvent in the slurry of the present invention. As an oily slurry, it can greatly avoid side reactions between the materials in the slurry and the environment, ensure the stability of the lithium supplementing material in the slurry, and facilitate the full play of the lithium supplementing performance of the lithium supplementing material. When the pre-treated aluminum foil of the present invention is applied to a lithium-ion battery, lithium nitride in the surface coating of the pre-treated aluminum foil can provide a fast channel for the extraction of lithium ions, which is beneficial to improving the lithium supplementing efficiency of the lithium supplementing material, thereby improving the first-cycle Coulombic efficiency and cycle performance of the lithium-ion battery. Moreover, lithium nitride will generate LiNO2 during the formation process of the lithium-ion battery, which can inhibit the precipitation of oxygen in the lithium-ion battery and improve the thermal safety of the lithium-ion battery.

[0032] The preparation method of the pre-treated aluminum foil provided by the embodiments of the present invention is simple in operation and applicable to large-scale production. Brief Description of the Drawings

[0033] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and examples.

[0034] Figure 1 It is a flowchart of the preparation method of the pre-treated aluminum foil provided by the embodiments of the present invention.

[0035] Figure 2 It is a graph of the cycle capacity retention rate after 100 charge-discharge cycles at a 1C rate for Embodiments 1, 2, 3 and Comparative Example 1 of the present invention.

[0036] Figure 3 It is a graph of the cycle capacity retention rate after 50 cycles at a 3C charge / 1C discharge rate for Embodiments 1, 2, 3 and Comparative Example 1 of the present invention.

[0037] Figure 4 It is a comparison graph of the first-cycle Coulombic efficiency test at a 1C rate for Embodiments 1, 2, 3 and Comparative Example 1 of the present invention. Detailed Embodiments

[0038] The present invention will be further described in detail below with reference to the drawings and specific examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0039] The embodiments of the present invention provide a preparation method of a pre-treated aluminum foil, as Figure 1 shown, which specifically includes the following steps:

[0040] Step S1, place the conductive material, polymeric dispersant, and N-methylpyrrolidone in a blender in proportion for the first stirring treatment. After mixing evenly, the first slurry is obtained;

[0041] Among them, the conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black;

[0042] The polymeric dispersant includes one or more of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester-amide) dispersants; specifically includes methacrylamide, hydroxyethyl acrylate, alkylphenol polyoxyethylene ether, and fatty alcohol polyoxyethylene ether.

[0043] The mass percentage of the polymeric dispersant in the conductive material is 0.1%-5%, preferably 1%-5%;

[0044] The solid content of the first slurry is 5%-10%;

[0045] The equipment for the first stirring treatment is a high-speed blender, and the rotation speed is set between 2000 rpm and 5000 rpm; during the stirring treatment, the drying dew point ≤ -30°, and the temperature ≤ 20°C.

[0046] Step S2, add the lithium supplement material and lithium nitride to the first slurry, and continue with the second stirring treatment to obtain the second slurry;

[0047] Among them, the lithium supplement material includes one or more of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4;

[0048] The mass of the lithium supplement material is 1 to 1.5 times the mass of the conductive material;

[0049] The equipment for the second stirring treatment is a high-speed blender, and the rotation speed is set between 2000 rpm and 5000 rpm; during the stirring treatment, the drying dew point ≤ -30°, and the temperature ≤ 20°C.

[0050] The mass percentage of lithium nitride in the lithium supplement material is 0.1%-10%, preferably 1%-10%.

[0051] Step S3, transfer the second slurry to a sand mill for sanding treatment to obtain the third slurry; among them, the diameter of the grinding beads for the sanding treatment is 0.3 mm; the particle size D of the solid particles in the third slurry 50 <300 nm;

[0052] Among them, the sand mill includes any one of a horizontal sand mill, a basket sand mill, and a vertical sand mill; the rotation speed of the sand mill is 500 rpm - 2000 rpm;

[0053] The grinding beads include any one of zirconia beads, alumina beads, and zirconium silicate beads.

[0054] Step S4: Add polyvinylidene fluoride to the third slurry and perform a third stirring treatment to obtain a fourth slurry.

[0055] Among them, the percentage of the mass of polyvinylidene fluoride in the total mass of the third slurry is 0.01%-1%, preferably 0.1%-1%.

[0056] The equipment for the third stirring treatment is a high-speed mixer, and the rotation speed is set between 2000 rpm and 5000 rpm; during the stirring treatment, the drying dew point ≤ -30°C and the temperature ≤ 20°C.

[0057] Step S5: Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0058] Among them, the drying treatment method is air-blowing drying, and the temperature is 110°C - 150°C.

[0059] The pretreated aluminum foil prepared by the above preparation method in the embodiment of the present invention includes an aluminum foil and a coating coated on the surface of the aluminum foil.

[0060] Among them, the coating includes: a conductive material, a polymer dispersant, a lithium supplement material, lithium nitride, and polyvinylidene fluoride, and the mass ratio is 100: [0.1 - 5]: [100 - 150]: [1 - 15]: [0.2 - 2.7].

[0061] Specifically, the conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black SP; the polymer dispersant includes any one of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester - amide) dispersants; the lithium supplement material includes any one of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4. In the present invention, during the three high-speed stirring treatments, the drying dew point is set ≤ -30°C and the temperature ≤ 20°C. The purpose of such setting is to maintain a dry and low-temperature state during the stirring process to avoid other side reactions, which may cause the binder in the slurry to lose its binding effect.

[0062] The embodiment of the present invention provides a positive electrode plate, which includes a pretreated aluminum foil and a positive electrode active material layer attached to the surface of the pretreated aluminum foil.

[0063] In the present invention, the pretreated aluminum foil contains lithium nitride. During use, a part of the lithium nitride reacts with oxygen, and the other part fills the oxygen vacancies formed after oxygen evolution under the fully charged state, which can support the structure of the cathode material, thereby improving the stability of the cathode material and further enhancing the thermal safety performance of the battery.

[0064] The cathode electrode sheet containing the pretreated aluminum foil prepared in the present invention can be assembled with an anode electrode sheet, a separator, and an electrolyte to form a lithium-ion battery. Since the pretreated aluminum foil with pre-lithiation is used in the cathode electrode sheet, the initial Coulomb efficiency, cycle performance, and thermal safety performance of the lithium-ion battery can be improved without reducing the conductivity.

[0065] To better understand the technical solution provided by the present invention, the preparation method and characteristics of the pretreated aluminum foil of the present invention are described below with specific examples.

[0066] Example 1

[0067] This example provides a preparation process and performance test of a pretreated aluminum foil. The specific process is as follows:

[0068] (1) 1 kg of conductive carbon black, 2 g of polyvinylpyrrolidone, and 10 kg of NMP are placed in a blender and subjected to the first stirring treatment at a rotation speed of 2000 rpm for 60 min. After mixing evenly, the first slurry is obtained.

[0069] (2) 1.2 kg of Li2CuO2 and 10 g of lithium nitride are added to the first slurry, and the second stirring treatment is continued at a rotation speed of 2000 rpm for 120 min to obtain the second slurry.

[0070] (3) The second slurry is transferred to a horizontal sand mill for sanding treatment to obtain the third slurry. Among them, the rotation speed of the sanding treatment is 1000 rpm, and zirconia beads with a diameter of 0.3 mm are used. The particle size D of the solid particles in the obtained third slurry 50 is 300 nm.

[0071] (4) 20 g of polyvinylidene fluoride (PVDF) is added to the third slurry, and the third stirring treatment is carried out at a rotation speed of 2000 rpm for 90 min to obtain the fourth slurry.

[0072] (5) The fourth slurry is coated on the surface of the aluminum foil and dried. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0073] The drying dew point of the above three stirring treatment processes is -25°C, and the temperature is 18°C.

[0074] The pretreated aluminum foil of this example is used to assemble a lithium-ion full battery and tested. The specific process is as follows:

[0075] The specific process of battery assembly is as follows: The positive electrode material NCM523, conductive carbon black SP, and binder PVDF are weighed according to a mass ratio of 96:2:2, dissolved in NMP to prepare a positive electrode slurry. The positive electrode slurry is coated on the surface of the pretreated aluminum foil in this embodiment, and after drying, a positive electrode sheet is prepared; The copper foil coated with graphite slurry is used as the negative electrode sheet, where the graphite slurry contains graphite, sodium carboxymethylcellulose, conductive carbon black, and styrene-butadiene rubber with a mass ratio of 97:0.6:1.6:0.8; A 9μm polyethylene film is used as the separator, and a 1mol / L solution of lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the volume ratio of EC to DMC is 1:1) is used as the electrolyte, and a lithium-ion full battery is assembled by a conventional method.

[0076] Test 1: The charge cut-off voltage is 4.3V, the discharge cut-off voltage is 2.7V, the cycle test temperature is 25°C, and the charge and discharge cycles are carried out at a 1C rate for 100 weeks. The cycle capacity retention rate after 100 weeks of test cycles is as Figure 2 shown.

[0077] Test 2: The charge cut-off voltage is 4.3V, the discharge cut-off voltage is 2.7V, the cycle test temperature is 25°C, and the charge and discharge cycles are carried out at a 3C charge / 1C discharge rate for 50 weeks. The cycle capacity retention rate after 50 weeks of test cycles is as Figure 3 shown.

[0078] Test 3: The charge cut-off voltage is 4.3V, the discharge cut-off voltage is 2.7V, the cycle test temperature is 25°C, and the Coulomb efficiency of the first week is tested at a 1C rate, as Figure 4 shown.

[0079] The specific test data are shown in Table 1.

[0080] Example 2

[0081] This embodiment provides a preparation process and performance test of pretreated aluminum foil, and the specific process is as follows:

[0082] (1) 1 kg of conductive carbon black, 2 g of polyvinylpyrrolidone, and 10 kg of NMP are placed in a blender and subjected to the first stirring treatment at a rotation speed of 2000 rpm for 60 min. After mixing evenly, a first slurry is obtained.

[0083] (2) 1.2 kg of Li4FeO5 and 10 g of lithium nitride are added to the first slurry, and the second stirring treatment is continued at a rotation speed of 2000 rpm for 120 min to obtain a second slurry.

[0084] (3) Transfer the second slurry to a horizontal sand mill for sanding treatment to obtain a third slurry. Among them, the rotation speed of the sanding treatment is 1000 rpm, and zirconia beads with a diameter of 0.3 mm are used. The particle size D of the solid particles in the obtained third slurry 50 is 300 nm.

[0085] (4) Add 20 g of polyvinylidene fluoride (PVDF) to the third slurry and perform a third stirring treatment at a rotation speed of 2000 rpm for 90 min to obtain a fourth slurry.

[0086] (5) Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0087] The drying dew point in the above three stirring treatment processes is -28°, and the temperature is 16°C.

[0088] Assemble and test a lithium-ion full battery using the pretreated aluminum foil of this example. The assembly and testing processes are the same as those in Example 1. The cycle capacity retention rate after 100 charge-discharge cycles at a 1C rate is shown in Figure 2 as shown, the charge-discharge cycle 50 weeks at a 3C charge / 1C discharge rate is as shown in Figure 3 as shown, and the Coulomb efficiency in the first week of testing at a 1C rate is as shown in Figure 4 as shown. The specific test data are shown in Table 1.

[0089] Example 3

[0090] This example provides a preparation process and performance test of a pretreated aluminum foil. The specific process is as follows:

[0091] (1) Place 800 g of conductive carbon black, 2 g of polyvinylpyrrolidone, and 10 kg of N-methylpyrrolidone (NMP) in a blender and perform a first stirring treatment at a rotation speed of 2000 rpm for 60 min. After mixing evenly, a first slurry is obtained.

[0092] (2) Add 1.2 kg of Li4FeO5 and 12 g of lithium nitride to the first slurry and continue to perform a second stirring treatment at a rotation speed of 2000 rpm for 120 min to obtain a second slurry.

[0093] (3) Transfer the second slurry to a horizontal sand mill for sanding treatment to obtain a third slurry. Among them, the rotation speed of the sanding treatment is 1000 rpm, and zirconia beads with a diameter of 0.3 mm are used. The particle size D of the solid particles in the obtained third slurry 50 is 300 nm.

[0094] (4) Add 20 g of polyvinylidene fluoride (PVDF) to the third slurry, and perform the third stirring treatment at a rotation speed of 2000 rpm for 90 min to obtain the fourth slurry.

[0095] (5) Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0096] The drying dew point in the above three stirring treatment processes is -25°C, and the temperature is 15°C.

[0097] Use the pretreated aluminum foil of this example to assemble a lithium-ion full battery and conduct tests. The assembly and test processes are the same as those in Example 1. The cycle capacity retention rate after 100 charge-discharge cycles at a 1C rate is shown in Figure 2 as shown. The charge-discharge cycle is 50 weeks at a 3C charge / 1C discharge rate as shown in Figure 3 as shown. The Coulomb efficiency in the first week of testing at a 1C rate is shown in Figure 4 as shown. The specific test data are shown in Table 1.

[0098] Example 4

[0099] This example provides a preparation process and performance test of a pretreated aluminum foil. The specific process is as follows:

[0100] (1) Place 1 kg of carbon nanofibers, 2 g of ammonium polyacrylate, and 10 kg of N-methylpyrrolidone (NMP) in a blender and perform the first stirring treatment at a rotation speed of 2000 rpm for 60 min. After mixing evenly, obtain the first slurry.

[0101] (2) Add 1.2 kg of Li4FeO5 and 12 g of lithium nitride to the first slurry, and continue to perform the second stirring treatment at a rotation speed of 2000 rpm for 120 min to obtain the second slurry.

[0102] (3) Transfer the second slurry to a horizontal sand mill for sanding treatment to obtain the third slurry; among them, the rotation speed of the sanding treatment is 1000 rpm, and zirconia beads with a diameter of 0.3 mm are used; the particle size D of the solid particles in the obtained third slurry 50 is 300 nm.

[0103] (4) Add 20 g of polyvinylidene fluoride (PVDF) to the third slurry, and perform the third stirring treatment at a rotation speed of 2000 rpm for 90 min to obtain the fourth slurry.

[0104] (5) Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0105] The drying dew point of the above three stirring processes is -25°C, and the temperature is 18°C.

[0106] Using the pretreated aluminum foil of this example to assemble a lithium-ion full battery and conduct tests. The assembly and test processes are the same as those in Example 1. The cycle capacity retention rate after 100 charge-discharge cycles at a 1C rate is shown in Figure 2 as shown, the charge-discharge cycle for 50 weeks at a 3C charge / 1C discharge rate is as shown in Figure 3 as shown, the Coulombic efficiency in the first week of testing at a 1C rate is as shown in Figure 4 as shown. The specific test data are shown in Table 1.

[0107] Example 5

[0108] This example provides a preparation process and performance test of pretreated aluminum foil. The specific process is as follows:

[0109] (1) Place 1 kg of carbon nanofibers, 2 g of ammonium polyacrylate, and 10 kg of N-methylpyrrolidone (NMP) in a blender and conduct the first stirring process at a speed of 2000 rpm for 60 min. After mixing evenly, the first slurry is obtained.

[0110] (2) Add 1.2 kg of Li2NiO2 and 12 g of lithium nitride to the first slurry, and continue to conduct the second stirring process at a speed of 2000 rpm for 120 min to obtain the second slurry.

[0111] (3) Transfer the second slurry to a horizontal sand mill for sanding treatment to obtain the third slurry; among them, the rotation speed of the sanding treatment is 1000 rpm, and zirconia beads with a diameter of 0.3 mm are used; the particle size D of the solid particles in the obtained third slurry 50 is 300 nm.

[0112] (4) Add 20 g of polyvinylidene fluoride (PVDF) to the third slurry and conduct the third stirring process at a speed of 2000 rpm for 90 min to obtain the fourth slurry.

[0113] (5) Coat the fourth slurry on the surface of the aluminum foil and conduct drying treatment. After the coated fourth slurry forms a film, a pretreated aluminum foil with a coating is obtained.

[0114] The drying dew point of the above three stirring processes is -28°C, and the temperature is 18°C.

[0115] Using the pretreated aluminum foil of this example to assemble a lithium-ion full battery and conduct tests. The assembly and test processes are the same as those in Example 1. The cycle capacity retention rate after 100 charge-discharge cycles at a 1C rate is shown in Figure 2 as shown, the charge-discharge cycle for 50 weeks at a 3C charge / 1C discharge rate is as shown in Figure 3As shown, the Coulombic efficiency in the first week was tested at a rate of 1C as Figure 4 shown. The specific test data are shown in Table 1.

[0116] To better illustrate the effects of the embodiments of the present invention, Comparative Example 1 was compared with the above Embodiments 1-5.

[0117] Comparative Example 1

[0118] The difference between this comparative example and Embodiment 1 is that the positive electrode sheet was directly prepared using untreated aluminum foil, and the processes for preparing the lithium-ion full battery and the testing process were the same as those in Embodiment 1. The cycle capacity retention rate of the lithium-ion full battery in this comparative example during charge and discharge cycling 100 times at a rate of 1C is shown in Figure 2 shown, and during charge and discharge cycling 50 times at a rate of 3C charging / 1C discharging as Figure 3 shown. The Coulombic efficiency in the first week was tested at a rate of 1C as Figure 4 shown. The specific test data are shown in Table 1.

[0119] Table 1 summarizes the performance test results of the lithium-ion full batteries prepared in Embodiments 1-5 and Comparative Example 1:

[0120]

[0121] Table 1

[0122] From the comparison of the test data in Table 1, it can be seen that the cycle capacity retention rate and the Coulombic efficiency in the first week of the lithium-ion full batteries assembled with the pretreated aluminum foil in Embodiments 1-5 of the present invention are both better than those in Comparative Example 1. This is because in the preparation processes of Embodiments 1-5, the raw materials are subjected to high-speed stirring, grinding treatment, and then high-speed stirring treatment to obtain a slurry with better dispersion and more uniform particle size. After the slurry is coated on the surface of the aluminum foil, the overall conductivity of the current collector aluminum foil can be improved; in addition, NMP is used as the solvent in the slurry of the present invention. As an oily slurry, it can greatly avoid side reactions between the materials in the slurry and the environment, ensure the stability of the lithium supplementing material in the slurry, and facilitate the full play of the lithium supplementing performance of the lithium supplementing material; when the pretreated aluminum foil of the present invention is applied to a lithium-ion battery, lithium nitride in the surface coating of the pretreated aluminum foil can provide a fast channel for the extraction of lithium ions, which is beneficial to improving the lithium supplementing efficiency of the lithium supplementing material and thus improving the Coulombic efficiency in the first week and the cycle performance of the lithium-ion battery. Moreover, lithium nitride will generate LiNO2 during the formation process of the lithium-ion battery, which can inhibit the precipitation of oxygen in the lithium-ion battery and improve the thermal safety of the lithium-ion battery.

[0123] The specific embodiments described above further elaborate on the object, technical solution and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a pre-treated aluminum foil, characterized in that, The preparation method includes: Step S1: Place the conductive material, polymer dispersant, and N-methylpyrrolidone in a blender in proportion for the first stirring treatment. After mixing evenly, a first slurry is obtained. Step S2: Add the lithium supplement material and lithium nitride to the first slurry, and continue with the second stirring treatment to obtain a second slurry. Step S3, transfer the second slurry to a sand mill for sanding treatment to obtain a third slurry; wherein, the diameter of the grinding beads for the sanding treatment is 0.3 mm; the particle size D of the solid particles in the third slurry 50 ≤ 300 nm; Step S4: Add polyvinylidene fluoride to the third slurry and perform the third stirring treatment to obtain a fourth slurry. Step S5: Coat the fourth slurry on the surface of the aluminum foil and perform a drying treatment. After the coated fourth slurry forms a film, a pre-treated aluminum foil with a coating is obtained.

2. The preparation method according to claim 1, wherein The conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black SP. The polymer dispersant includes one or more of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester-amide) dispersants. The mass percentage of the polymer dispersant in the conductive material is 0.1%-5%. The solid content of the first slurry is 5%-10%.

3. The preparation method according to claim 1, characterized in that, The lithium supplement material includes one or more of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4. The mass of the lithium supplement material is 1 to 1.5 times the mass of the conductive material. The mass percentage of lithium nitride in the lithium supplement material is 0.1%-10%.

4. The preparation method according to claim 1, characterized in that, The mass percentage of polyvinylidene fluoride in the total mass of the third slurry is 0.01%-1%.

5. The preparation method according to claim 1, wherein, The rotation speeds of the first stirring treatment, the second stirring treatment, and the third stirring treatment are all set between 2000 rpm and 5000 rpm; the drying dew point during the processes of the first stirring treatment, the second stirring treatment, and the third stirring treatment is ≤ -30°C, and the temperature is ≤ 20°C.

6. The preparation method according to claim 1, wherein, The sand mill includes any one of a horizontal sand mill, a basket sand mill, and a vertical sand mill; the rotation speed of the sand mill is 500 rpm - 2000 rpm. The grinding beads include any one of zirconia beads, alumina beads, and zirconium silicate beads.

7. The preparation method according to claim 1, characterized in that, The drying treatment is air drying, and the temperature is 110°C - 150°C.

8. A pretreated aluminum foil prepared by the preparation method according to any one of claims 1-7 above, characterized in that, The pre-treated aluminum foil includes an aluminum foil and a coating coated on the surface of the aluminum foil. The coating includes a conductive material, a polymer dispersant, a lithium supplement material, lithium nitride, and polyvinylidene fluoride. The mass ratio of the conductive material, polymer dispersant, lithium supplement material, lithium nitride, and polyvinylidene fluoride is 100:[0.1 - 5]:[100 - 150]:[1 - 15]:[0.2 - 2.7]. Among them, the conductive material includes one or more of graphene, graphite, carbon nanotubes, nanofibrous carbon, and conductive carbon black SP. The polymer dispersant includes any one of acrylate dispersants, highly active polyether dispersants, polyester dispersants, and poly(ester-amide) dispersants. The lithium supplement material includes any one of Li4FeO5, Li2NiO2, Li6CoO4, Li2MnO3, Li2CuO2, and Li2C2O4.

9. A positive electrode plate, characterized in that, The positive electrode plate includes the pretreated aluminum foil described in claim 8 above, and a positive electrode active material layer attached to the surface of the pretreated aluminum foil.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the positive electrode plate described in claim 9 above.

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