A ternary lithium battery separator slurry and a preparation method thereof

Abstract

This invention discloses a ternary lithium battery separator slurry and its preparation method, belonging to the field of lithium battery technology. It comprises the following raw materials in parts by weight: 50-70 parts composite binder, 200-300 parts N-methylpyrrolidone, 0.4-0.6 parts modified graphene oxide, 60-65 parts aromatic additives, 2-5 parts ceramic powder, and 300-400 parts DMF. The preparation method includes the following steps: dissolving the composite binder in N-methylpyrrolidone, then adding modified graphene oxide, reacting, precipitating with methanol and filtering, washing and drying the filter residue with methanol and water, then dissolving it in DMF, and ultrasonically obtaining the ternary lithium battery separator slurry. The composite binder is used to improve the thermal stability of the polymer, and its incompatibility with aromatic additives and the addition of modified graphene oxide can improve the ion permeability of the lithium battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a ternary lithium battery separator slurry and its preparation method. Background Technology

[0002] The booming development of the new energy industry has brought unprecedented opportunities to the lithium-ion battery industry, while also placing higher demands on it. Traditional lithium-ion battery separators are mostly polyolefin separators. However, due to the poor thermal stability of polyolefins, they are prone to thermal shrinkage, which can easily lead to safety hazards during the use of lithium-ion batteries. Therefore, heat-resistant polymers are often coated on the surface of polyolefin separators to form a heat-resistant three-dimensional network structure. However, the dense network structure greatly reduces the ion permeability, thus affecting the battery's capacity and efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a ternary lithium battery separator slurry to solve the problems of poor thermal stability and low ion permeability of lithium battery separators in the prior art.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A ternary lithium battery separator slurry comprises the following raw materials in parts by weight: 50-70 parts of composite binder, 200-300 parts of N-methylpyrrolidone, 0.4-0.6 parts of modified graphene oxide, 60-65 parts of aromatic additives, 2-5 parts of ceramic powder, and 300-400 parts of DMF.

[0006] Furthermore, the preparation of the modified graphene oxide includes the following steps:

[0007] Step A1: Add graphene oxide and (3-mercaptopropyl)trimethylsilane to tetrahydrofuran and react at 55-65℃ for 20-22 h to obtain mixture A;

[0008] Step A2: Cool mixture A to room temperature, filter it, and soak the resulting filter residue in a 30-35% hydrogen peroxide solution for 20-22 hours to fully convert the thiol groups into sulfonic acid groups, thus obtaining mixture B;

[0009] Step A3: After filtering the mixture B, place the resulting filter residue in a 0.15-0.25 mol / L LiOH aqueous solution for 3-4 hours for lithium exchange to obtain mixture C;

[0010] Step A4: Filter the mixture C, wash it three times with water and methanol respectively, and dry it under vacuum for 20-22 hours to obtain modified graphene oxide. Since graphene oxide has a high specific surface area and good electrochemical, mechanical and thermal stability, adding it to lithium battery separator slurry can significantly improve the thermal stability of lithium battery separator.

[0011] Furthermore, the mass ratio of the graphene oxide, (3-mercaptopropyl)trimethylsilane, tetrahydrofuran, hydrogen peroxide solution, and LiOH aqueous solution is 8-12:95-105:95-105:100-110:100-110.

[0012] Furthermore, the composite adhesive is obtained by mixing polyimide P84 and PVDF-HFP in a mass ratio of 4:6.

[0013] Furthermore, the aromatic additive is obtained by mixing 4,4-diaminodiphenyl sulfone and diphenylsulfonyl imide in a mass ratio of 3.5:1.4. The aliphatic flexible PVDF-HFP adhesive is incompatible with the aromatic rigid polymer diphenylsulfonyl imide, and the strongly polar lithium sulfonate groups on the modified graphene oxide interact strongly with the strongly polar diphenylsulfonyl imide groups in the composite adhesive. Therefore, during the solvent evaporation process in the preparation of the lithium battery separator, the aliphatic flexible PVDF-HFP adhesive and the aromatic rigid polymer diphenylsulfonyl imide will undergo microphase separation to generate a porous structure, thereby improving the ion permeability of the lithium battery.

[0014] A method for preparing a ternary lithium battery separator slurry includes the following steps:

[0015] Step B1: Add the composite adhesive and N-methylpyrrolidone to the reaction vessel. After they are completely dissolved, add the aromatic additives and modified graphene oxide. React at 100-120℃ under argon protection for 6-8 hours to obtain the reaction solution.

[0016] Step B2: Cool the reaction solution to 60-65℃, transfer it to methanol, filter after the precipitate has completely precipitated, wash the filter residue with methanol and water 3-4 times respectively, dry it at 60-65℃ for 10-12h, and finally vacuum dry it at 100-105℃ for 20-22h for later use to obtain the modified composite electrolyte.

[0017] Step B3: Dissolve the modified composite electrolyte in DMF at 60-65℃, sonicate for 15-20 min, and then add ceramic powder to the modified electrolyte to obtain a ternary lithium battery separator slurry.

[0018] Furthermore, in step B2, the volume ratio of the reaction solution to methanol is 1:10.

[0019] The beneficial effects of this invention are:

[0020] This invention utilizes PVDF-HFP and polyimide P84 as a composite adhesive. PVDF-HFP possesses advantages such as good affinity with organic solvents and excellent chemical and electrochemical stability. Furthermore, the addition of aromatic additives, modified graphene oxide, and ceramic powder significantly improves its thermal stability and mechanical strength. Simultaneously, the graphene oxide is modified with (3-mercaptopropyl)trimethylsilane, hydrogen peroxide solution, and LiOH. Graphene oxide has a high specific surface area and excellent electrochemical, mechanical, and thermal stability. The modified graphene oxide contains strongly polar lithium sulfonate groups on its surface, which can strongly interact with the strongly polar disulfonylimide groups in the composite adhesive. This facilitates microphase separation between the inherently incompatible aliphatic flexible PVDF-HFP adhesive and the aromatic rigid polymer diphenylsulfonylimide, thereby increasing the porosity of the composite material and consequently improving its ion permeability. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] A method for preparing modified graphene oxide includes the following steps:

[0024] Step A1: Add 8 parts of graphene oxide and 95 parts of (3-mercaptopropyl)trimethylsilane to 95 parts of tetrahydrofuran, and react at 55-65℃ for 20-22 hours to obtain mixture A;

[0025] Step A2: Cool mixture A to room temperature, filter it, and soak the resulting filter residue in 30% hydrogen peroxide solution for 20 hours to fully convert the thiol groups into sulfonic acid groups, thus obtaining mixture B;

[0026] Step A3: After filtering the mixture B, place the resulting filter residue in a 0.15 mol / L LiOH aqueous solution for 3 hours for lithium exchange to obtain mixture C;

[0027] Step A4: Filter the mixture C, wash it three times with water and methanol respectively, and dry it under vacuum for 20 hours to obtain modified graphene oxide.

[0028] Example 2

[0029] A method for preparing modified graphene oxide includes the following steps:

[0030] Step A1: Add 10 parts of graphene oxide and 100 parts of (3-mercaptopropyl)trimethylsilane to 100 parts of tetrahydrofuran, and react at 60°C for 21 hours to obtain mixture A;

[0031] Step A2: Cool mixture A to room temperature, filter it, and soak the resulting filter residue in 32.5% hydrogen peroxide solution for 21 hours to fully convert the thiol groups into sulfonic acid groups, thus obtaining mixture B;

[0032] Step A3: After filtering the mixture B, place the resulting filter residue in a 0.2 mol / L LiOH aqueous solution for 3.5 h for lithium exchange to obtain mixture C;

[0033] Step A4: Filter the mixture C, wash it three times with water and methanol respectively, and dry it under vacuum for 21 hours to obtain modified graphene oxide.

[0034] Example 3

[0035] A method for preparing modified graphene oxide includes the following steps:

[0036] Step A1: Add 12 parts of graphene oxide and 105 parts of (3-mercaptopropyl)trimethylsilane to 105 parts of tetrahydrofuran, and react at 65°C for 22 hours to obtain mixture A;

[0037] Step A2: Cool mixture A to room temperature, filter it, and soak the resulting filter residue in 35% hydrogen peroxide solution for 22 hours to fully convert the thiol groups into sulfonic acid groups, thus obtaining mixture B;

[0038] Step A3: After filtering the mixture B, place the resulting filter residue in a 0.25 mol / L LiOH aqueous solution for 4 hours for lithium exchange to obtain mixture C;

[0039] Step A4: Filter the mixture C, wash it three times with water and methanol respectively, and dry it under vacuum for 22 hours to obtain modified graphene oxide.

[0040] Example 4

[0041] A method for preparing a ternary lithium battery separator slurry includes the following steps:

[0042] Step B1: Add 50 parts of composite adhesive and 200 parts of N-methylpyrrolidone to a reaction vessel, stir evenly at room temperature until completely dissolved, then add 60 parts of aromatic auxiliaries and 0.4 parts of modified graphene oxide prepared in Example 1, and react for 6 hours under argon protection at 100°C to obtain the reaction solution.

[0043] Step B2: Cool the reaction solution to 60°C, transfer it to 3000 parts of methanol, filter after the precipitate has completely precipitated, wash the filter residue with methanol and water three times, dry it at 60°C for 10 hours, and finally vacuum dry it at 100°C for 20 hours for later use to obtain the modified composite electrolyte.

[0044] Step B3: Dissolve the modified composite electrolyte in 300 parts of DMF at 60°C, sonicate for 15 min, and then add 2 parts of ceramic powder to the modified electrolyte to obtain a ternary lithium battery separator slurry.

[0045] Example 5

[0046] A method for preparing a ternary lithium battery separator slurry includes the following steps:

[0047] Step B1: Add 60 parts of composite adhesive and 250 parts of N-methylpyrrolidone to a reaction vessel, stir evenly at room temperature until completely dissolved, then add 62.5 parts of aromatic additive and 0.5 parts of modified graphene oxide prepared in Example 2, and react for 7 hours under argon protection at 110°C to obtain the reaction solution.

[0048] Step B2: Cool the reaction solution to 62.5℃, transfer it to 3700 parts of methanol, filter after the precipitate has completely precipitated, wash the filter residue with methanol and water three times respectively, dry it at 62.5℃ for 11h, and finally vacuum dry it at 102.5℃ for 21h for later use to obtain the modified composite electrolyte.

[0049] Step B3: Dissolve the modified composite electrolyte in 350 parts of DMF at 62.5℃, sonicate for 17.5 min, and then add 3.5 parts of ceramic powder to the modified electrolyte to obtain a ternary lithium battery separator slurry.

[0050] Example 6

[0051] A method for preparing a ternary lithium battery separator slurry includes the following steps:

[0052] Step B1: Add 70 parts of composite adhesive and 300 parts of N-methylpyrrolidone to a reaction vessel, stir evenly at room temperature until completely dissolved, then add 65 parts of aromatic auxiliaries and 0.6 parts of modified graphene oxide prepared in Example 3, and react for 8 hours under argon protection at 120°C to obtain a reaction solution.

[0053] Step B2: Cool the reaction solution to 65°C, transfer it to 4300 parts of methanol, filter after the precipitate has completely precipitated, wash the filter residue with methanol and water three times, dry it at 65°C for 12 hours, and finally vacuum dry it at 105°C for 22 hours for later use to obtain the modified composite electrolyte.

[0054] Step B3: Dissolve the modified composite electrolyte in 400 parts of DMF at 65°C, sonicate for 20 min, and then add 5 parts of ceramic powder to the modified electrolyte to obtain a ternary lithium battery separator slurry.

[0055] Comparative Example 1:

[0056] Compared with Example 4, this comparative example only replaces "modified graphene oxide" with "commonly available graphene oxide". All other steps and parameters are the same, and will not be repeated here. The final result is a ternary lithium battery separator slurry.

[0057] Comparative Example 2:

[0058] Compared with Example 5, this comparative example did not add aromatic additives in the preparation process of the ternary lithium battery separator slurry. All other steps and parameters were the same, and will not be repeated here. The final ternary lithium battery separator slurry was obtained.

[0059] The ternary lithium battery separator slurry prepared in Examples 4-6 and Comparative Examples 1-2 was coated on both sides of a polyolefin-based membrane with a thickness of 15-20 μm, with the coating thickness on each side being 2-3 μm, to form a lithium battery separator.

[0060] The thermal stability of the lithium battery separator was analyzed using a differential scanning calorimeter (DSC3, METTLER-TOLEDO). The test conditions were N2 atmosphere, 60-330℃, and heating rate of 50℃ / min.

[0061] The tensile strength and elongation at break of the lithium battery separator were tested using an intelligent electronic tensile testing machine (XLW-PC). The sample was a rectangle with a length of 40 mm and a width of 10 mm, and the displacement rate was 25 mm / min.

[0062] The porosity test procedure is as follows: Measure the mass of the dry film and the saturated adsorbed n-butanol, and calculate the porosity using Formula 1:

[0063] Porosity(%)=(Δm / ρ) / V0×100%

[0064] Where Δm is the change in mass of the lithium battery separator before and after saturation adsorption of n-butanol, ρ is the density of n-butanol, and V0 is the volume of the membrane.

[0065] The results are shown in Table 1:

[0066] Table 1

[0067] project Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Thermal decomposition temperature / °C 320 313 326 298 301 Tensile strength / MPa 14.5 15 14.7 8.9 9.0 Elongation at break / % 630 609 612 314 326 Porosity / % 56 55.9 57.2 41 40.8

[0068] As can be seen from Table 1, the lithium battery separators obtained using the ternary lithium battery separator slurries prepared in Examples 4-6 have significantly higher thermal decomposition temperature, tensile strength, elongation at break, and porosity than those obtained using the ternary lithium battery separator slurries prepared in Comparative Examples 1 and 2.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A ternary lithium battery separator slurry, characterized in that, By weight, it includes the following raw materials: 50-70 parts of composite adhesive, 200-300 parts of N-methylpyrrolidone, 0.4-0.6 parts of modified graphene oxide, 60-65 parts of aromatic additives, 2-5 parts of ceramic powder, and 300-400 parts of DMF. The preparation of the modified graphene oxide includes the following steps: Step A1: Add graphene oxide and (3-mercaptopropyl)trimethylsilane to tetrahydrofuran and react at 55-65℃ for 20-22 h to obtain mixture A; Step A2: Cool mixture A to room temperature, filter it, and soak the resulting filter residue in a 30-35% hydrogen peroxide solution for 20-22 hours to obtain mixture B; Step A3: After filtering the mixture B, the resulting filter residue is treated in a 0.15-0.25 mol / L LiOH aqueous solution for 3-4 hours to obtain mixture C; Step A4: Filter the mixture C, wash it three times with water and methanol respectively, and dry it under vacuum for 20-22 hours to obtain modified graphene oxide. The composite adhesive is obtained by mixing polyimide P84 and PVDF-HFP in a mass ratio of 4:6; The aromatic auxiliaries are obtained by mixing 4,4-diaminodiphenyl sulfone and diphenylsulfonyl imide in a mass ratio of 3.5:1.

4.

2. The ternary lithium battery separator slurry according to claim 1, characterized in that: The mass ratio of the graphene oxide, (3-mercaptopropyl)trimethylsilane, tetrahydrofuran, hydrogen peroxide solution, and LiOH aqueous solution is 8-12:95-105:95-105:100-110:100-110.

3. The method for preparing a ternary lithium battery separator slurry according to claim 1, characterized in that: Includes the following steps: Step B1: Add the composite adhesive and N-methylpyrrolidone to the reaction vessel, stir evenly at room temperature until completely dissolved, add aromatic additives and modified graphene oxide, and react under argon protection at 100-120℃ for 6-8 hours to obtain the reaction solution. Step B2: Cool the reaction solution to 60-65℃, transfer it to methanol, filter after the precipitate has completely precipitated, wash the filter residue with methanol and water 3-4 times respectively, dry it at 60-65℃ for 10-12h, and finally vacuum dry it at 100-105℃ for 20-22h for later use to obtain the modified composite electrolyte. Step B3: Dissolve the modified composite electrolyte in DMF at 60-65℃, sonicate for 15-20 minutes, and then add ceramic powder to the modified composite electrolyte solution to obtain ternary lithium battery separator slurry.

4. The method for preparing a ternary lithium battery separator slurry according to claim 3, characterized in that: In step B2, the volume ratio of the reaction solution to methanol is 1:10.