A modified pvdf material preparation method, a diaphragm preparation method and a battery
By grafting PAMAM hyperbranched precursors onto the surface of PVDF materials to form polar functional groups, the problem of PVDF material loss of bonding force in the battery cell is solved, thereby improving the cycle performance and service life of the battery cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG GEELY HLDG GRP CO LTD
- Filing Date
- 2026-01-27
- Publication Date
- 2026-05-29
AI Technical Summary
During the use of battery cells, as the electrolyte is gradually lost, the bonding force between the separator and the electrode is gradually lost, affecting the electrode interface performance and leading to a loss of battery cell cycle performance.
The hyperbranched precursor structure in PAMAM material is used to modify PVDF material. By forming a large number of polar functional groups on the PVDF surface, the adhesion to the electrode is enhanced, and the electrolyte is adsorbed during the cell baking process to form a gel structure to improve the adhesion.
It enhances the adhesion of PVDF material during the cell recycling process, thereby improving the lifespan of the cell.
Smart Images
Figure CN122103799A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and in particular to a method for preparing modified PVDF material, a method for preparing a separator, and a battery. Background Technology
[0002] PVDF, a widely used material in battery separators, plays a crucial role in providing adhesion between the separator and the electrode, improving the interface between the cell electrode and the separator, and offering a certain degree of shapeability. Simultaneously, PVDF exhibits stable chemical properties and strong inertness during cell use, minimizing the likelihood of side reactions affecting cell lifespan.
[0003] In recent years, with the development and application of high-energy-density power batteries in the power battery market, various high-energy-density materials have been widely developed and applied in cell materials, resulting in a gradual decrease in the electrolyte injection coefficient of the battery and a gradual decrease in the amount of electrolyte injected into a single cell.
[0004] However, during the use of PVDF materials in battery cells, as the electrolyte is gradually lost, the bonding force between the separator and the electrode will gradually be lost, affecting the electrode interface performance and thus causing a certain loss in the cycle performance of the battery cell. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a method for preparing modified PVDF material, a method for preparing a separator, and a battery, so as to solve the above technical problems.
[0006] This invention provides a method for preparing modified PVDF materials, comprising the following steps: PVDF and anhydrous ethanol were added to a NaOH solution with a concentration of 1 mol / L-3 mol / L to obtain alkali-treated PVDF powder. The mass ratio of NaOH solution was 1040-1680 parts, PVDF was 100-200 parts, and anhydrous ethanol was 39.5-79 parts. The alkali-treated PVDF powder was dissolved in NMP solution, and AA monomer and oil-soluble thermal initiator were added to the solution to obtain AA-modified PVDF powder. The alkali-treated PVDF powder was 100-200 parts, the oil-soluble thermal initiator was 0.1-0.5 parts, and the AA monomer was 10-40 parts by mass. A modified PVDF material is obtained by adding DMTMM solution and AA-modified PVDF powder to a mixed solution of methanol and PAMAM. The mass ratio of methanol is 792-1584 parts, PAMAM is 50-100 parts, DMTMM is 1.4-4.4 parts, and AA-modified PVDF powder is 100-200 parts.
[0007] Optionally, when adding PVDF and anhydrous ethanol to the NaOH solution, the temperature is raised to 60℃-80℃.
[0008] Optionally, when adding PVDF and anhydrous ethanol to the NaOH solution, the addition is carried out at a stirring speed of 700 rpm-900 rpm, and stirring is stopped after 30 min-40 min.
[0009] Optionally, when dissolving the alkali-treated PVDF powder in NMP solution, nitrogen is introduced and the temperature is raised to 50°-70°C.
[0010] Optionally, the oil-soluble thermal initiator is AIBN. After adding AA monomer and oil-soluble thermal initiator to the solution, the solution is stirred for 8-12 hours.
[0011] Optionally, the concentration of the DMTMM solution is 0.05 mol / L - 0.08 mol / L.
[0012] Optionally, in the step of obtaining the modified PVDF material, the solution is stirred at a speed of 700 rpm-900 rpm at a temperature of 20℃-30℃ for 8 h-12 h. After stirring, the product is filtered to obtain the modified PVDF material.
[0013] Optionally, in the step of obtaining the modified PVDF material, the solution is stirred at a speed of 700 rpm-900 rpm at a temperature of 20℃-30℃ for 8 h-12 h. After stirring, the product is filtered to obtain the modified PVDF material.
[0014] This invention also provides a method for preparing a diaphragm, using the modified PVDF material obtained by the above method, comprising the following steps: After the modified PVDF material is slurried, it is sprayed onto the base membrane to obtain the modified diaphragm.
[0015] Optionally, the coating thickness of the PVDF slurry on the base film is 1μm-3μm, and the base film coated with the PVDF slurry is dried in an environment of 60℃-80℃ for 48h-72h.
[0016] The present invention also provides a battery comprising a separator prepared by the separator preparation method described above.
[0017] The beneficial effects of this invention are as follows: In preparing modified PVDF, this invention utilizes the hyperbranched precursor structure of PAMAM material, which possesses a large contact area and numerous potential sites, enabling the formation of a large number of polar functional groups (terminal amino groups (-NH2) of PAMAM) on the PVDF surface. During the cell baking process after electrolyte injection, a large amount of electrolyte is adsorbed and permeates into the PAMAM-modified PVDF interface. The lithium salt of the electrolyte forms a complex with the amino groups of PAMAM, thereby forming a gel structure on the PVDF surface. Furthermore, the large number of polar functional groups on the PVDF material surface allows for a relatively stable adhesion to the electrode surface, enhancing the stability of the adhesion during cell cycling and thus improving the cell's lifespan. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the PAMAM structure for generation 1.0.
[0020] Figure 2 This is a schematic diagram of the PAMAM structure for generation 2.0. Detailed Implementation
[0021] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way. Unless otherwise specified, the reagents described in the embodiments are commercially available.
[0022] This embodiment provides a method for preparing modified PVDF materials. It involves synthesizing hyperbranched PAMAM (polyamide-amine dendritic polymer) precursors of different generation numbers, and then grafting these hyperbranched PAMAM precursors onto the surface of PVDF (polyvinylidene fluoride), thereby modifying PVDF. The specific steps include: Take 1040-1680 parts of a NaOH solution with a concentration of 1mol / L-3mol / L according to the mass ratio, and heat it to 60℃-80℃. Add 100-200 parts of PVDF and 39.5-79 parts of anhydrous ethanol to the NaOH solution while stirring at 700rpm-900rpm, and stop stirring after 30min-40min. After stirring, filter the solution, and then wash the filtrate three times with ultrapure water to obtain alkali-treated PVDF powder. NaOH is used in this embodiment instead of other alkalis because other alkaline components may affect the performance of the battery cell. Anhydrous ethanol is used because its solubility differs significantly from that of NMP added in subsequent steps.
[0023] Dissolve 100-200 parts of alkali-treated PVDF powder in 1000-2000 parts of NMP (N-methylpyrrolidone) solution, purge with nitrogen, and heat to 50°-70°C. Then, add 10-40 parts of AA (acrylic acid) monomer and 0.1-0.5 parts of AIBN (azobisisobutyronitrile) to the solution, and react for 8-12 hours. AIBN can be replaced with other oil-soluble thermal initiators such as BPO (benzoyl peroxide). After stirring, add methanol to precipitate the product, obtaining AA-modified PVDF powder.
[0024] Take 1000-2000 parts of methanol and 50-100 parts of PAMAM, and dissolve PAMAM in methanol. After PAMAM is completely dissolved, add 1.4-4.4 parts of DMTMM (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholine chloride) with a concentration of 0.05mol / L-0.08mol / L and 100-200 parts of AA-modified PVDF powder to the methanol and PAMAM mixture. Then stir the solution at 700-900 rpm at 20℃-30℃ for 8-12 hours. After stirring, filter the product and wash it three times with ultrapure water to obtain the modified PVDF material. Methanol has a significantly different solubility than NMP and can promote the precipitation of PAMAM from the solvent. Its low boiling point also makes it easy to remove.
[0025] In this process, 792-1584 parts of methanol and 50-100 parts of PAMAM are taken. When dissolving PAMAM in methanol, different generations of PAMAM are added according to the performance requirements of the modified PVDF material.
[0026] The specific preparation methods for different generations of PAMAM are as follows: Synthesis of 0.5 generation PAMAM: Under ice-water bath conditions, 10-15 parts of ethylenediamine and 23.8-31.7 parts of methanol were added to a three-necked flask, and nitrogen was purged for 10 min with stirring to ensure complete dissolution. Simultaneously, 130-150 parts of methyl acrylate were dissolved in 79.2-118.8 parts of methanol to form a homogeneous solution; this homogeneous solution was pumped into the three-necked flask using a peristaltic pump over a period of 1-1.5 h. After the addition was complete, the temperature was raised to 20-30 °C and the reaction proceeded for 24-48 h. Following the reaction, the product was transferred to a rotary evaporator, and unreacted monomers and solvents were removed by rotary evaporation at a pressure of 0.1-0.5 MPa and a temperature of 20-60 °C. After rotary evaporation, 0.5 generation PAMAM (G0.5-PAMAM) was obtained.
[0027] Synthesis of 1.0 generation PAMAM: Under ice-water bath conditions, 60-70 parts of ethylenediamine and 47.5-63.3 parts of methanol solution were added to a three-necked flask. Nitrogen was bubbled through the flask for 10 minutes with stirring to ensure complete dissolution. Simultaneously, 15-25 parts of G0.5-PAMAM were dissolved in 39.6-79.2 parts of methanol solution to form a homogeneous solution. The homogeneous solution was pumped into the three-necked flask using a peristaltic pump over a period of 1-1.5 hours. After the addition was complete, the temperature was raised to 20-30°C and the reaction proceeded for 24-48 hours. After the reaction, the reactants were transferred to a rotary evaporator and subjected to rotary evaporation at 0.2 MPa and 70°C to remove unreacted monomers and solvent. After rotary evaporation, 1.0 generation PAMAM (G1.0-PAMAM) was obtained, with the structure shown below. Figure 1 As shown in the image.
[0028] Other generations of PAMAM synthesis methods are based on 1.0 generation PAMAM, with ethylenediamine and methyl acrylate added alternately in certain proportions as described above. This process is repeated to obtain 1.5 generation PAMAM and 2.0 generation PAMAM (their structures are shown below). Figure 2 (as shown in the image), as well as higher-generation PAMAM materials.
[0029] Higher generation PAMAM materials have more terminal functional groups, higher density, and stronger viscosity. Subsequently, different generations of PAMAM are added according to the performance requirements of the PVDF material to be modified. A lower injection coefficient requires a higher generation number of the matching PAMAM.
[0030] Furthermore, in batteries using modified PVDF materials, the lower the liquid injection coefficient, the higher the generation number of the PAMAM required to match the PVDF material.
[0031] The modified PVDF material provided in this embodiment is synthesized using two functional monomers, ethylenediamine and methyl acrylate, to produce PAMAM hyperbranched precursors of different generations. These precursors are then chemically grafted onto the PVDF surface, thereby modifying the PVDF. By synthesizing PAMAM hyperbranched precursors of different generations, the number of functional groups and contact sites on the PVDF surface can be effectively adjusted. Different generations of PAMAM hyperbranched precursors can be appropriately matched according to the liquid injection coefficient requirements to impart high adhesion to the electrode sheets during cell cycling. Furthermore, the modification improves the liquid retention performance of the PVDF material, thus extending the lifespan of the cell.
[0032] This embodiment also provides a method for preparing a diaphragm, using the modified PVDF material prepared by the method described above, comprising the following steps: The modified PVDF material was pulverized using a solid pulverizer to achieve a fineness of 200-500 mesh.
[0033] At 300 rpm, 0.5 parts of BYK-ET3000 (wetting and dispersing agent), 20 parts of modified PVDF material, and 10 parts of AA were added sequentially to 69.5 parts of ultrapure water. After the addition was complete, the speed was adjusted to 500 rpm and dispersed for 20 minutes. After dispersion, vacuum degassing was performed to obtain the final slurry.
[0034] After the modified PVDF material is slurried, it is coated onto the polyolefin membrane by spraying. The coating thickness is controlled between 1μm and 3μm. The polyolefin membrane coated with PVDF slurry is then dried in an environment of 60℃-80℃ for 48h-72h to obtain the modified polyolefin membrane.
[0035] This embodiment also provides a battery, including a separator prepared by the separator preparation method described above.
[0036] Example 1: This example provides a method for preparing modified PVDF material and a method for preparing a diaphragm, including the following steps: Synthesis of 0.5 generation PAMAM: Under ice-water bath conditions, 12 parts by mass of ethylenediamine and 23.8 parts by mass of methanol solution were added to a three-necked flask. Nitrogen was bubbled through the flask for 10 min under stirring to ensure complete dissolution. Simultaneously, 140 parts by mass of methyl acrylate were dissolved in 79.2 parts by mass of methanol solution to form a homogeneous solution. The methyl acrylate solution was pumped into the three-necked flask using a peristaltic pump over a period of 1 h. After the addition was complete, the temperature was raised to 25 °C and the reaction proceeded for 24 h. The product was then transferred to a rotary evaporator and subjected to rotary evaporation at 0.2 MPa and 45 °C to remove unreacted monomers and solvents. After rotary evaporation, 0.5 generation PAMAM (G0.5-PAMAM) was obtained.
[0037] PVDF alkali treatment: Prepare 1116 parts of 3.0 mol / L NaOH solution, heat to 60℃, add 150 parts of PVDF and 39.6 parts of anhydrous ethanol at a stirring speed of 700 rpm, stop stirring after stirring for 30 min, filter the solution, and then wash the filtrate three times with ultrapure water to obtain alkali-treated PVDF powder.
[0038] Alkali-treated PVDF was modified with AA: 100 parts of alkali-treated PVDF powder were dissolved in 1000 parts of NMP, nitrogen was introduced, and the temperature was raised to 70°C. 10 parts of AA monomer and 0.1 parts of AIBN initiator were added, and the mixture was stirred for 8 hours. After the reaction was completed, a large amount of methanol was added to precipitate the product. The precipitated product was filtered and washed three times with ultrapure water to obtain PAA-modified PVDF powder.
[0039] PVDF grafted with hyperbranched precursor: 792 parts of methanol solution and 50 parts of PAMAM with a generation of 0.5 were added sequentially to a three-necked flask. After complete dissolution, 100 parts of AA-modified PVDF powder and 1.4 parts of 0.05 mol / L DMTMM solution were added. The stirring speed was set to 700-900 rpm, and the mixture was stirred at 25℃ for 8 hours. After 8 hours, stirring was stopped, the product was filtered, and washed three times with ultrapure water to obtain the PVDF material modified with the hyperbranched precursor.
[0040] The PVDF material was pulverized using a solid pulverizer to achieve a fineness of 200-500 mesh. At 300 rpm, 0.5 parts of BYK-ET3000, 20 parts of modified PVDF material, and 10 parts of AA were added sequentially to 69.5 parts of ultrapure water. After addition, the speed was adjusted to 500 rpm and dispersed for 20 minutes. Vacuum degassing was then performed to obtain the final slurry.
[0041] The prepared PVDF material is sprayed onto a polyolefin membrane, and the slurry is prepared using the synthetic PVDF material, including the following steps: The prepared slurry was coated onto a polyolefin membrane with a coating thickness controlled at 2 μm. The polyolefin membrane coated with the slurry was then dried at 80°C for 52 hours to obtain the final modified polyolefin membrane material.
[0042] This embodiment also provides a battery, including a separator prepared by the separator preparation method described above.
[0043] Example 2: This embodiment provides a method for preparing modified PVDF material and a method for preparing a membrane, including the following steps: Synthesis of 1.0 generation PAMAM: Under ice-water bath conditions, 70 parts of ethylenediamine and 55.4 parts of methanol solution were added to a three-necked flask. Nitrogen was bubbled through the flask for 10 min with stirring until complete dissolution. Simultaneously, 20 parts of G0.5-PAMAM were dissolved in 39.6 parts of methanol solution to form a homogeneous solution. The homogeneous solution was pumped into the three-necked flask using a peristaltic pump over a period of 1 h. After the addition was complete, the temperature was raised to 25 °C and the reaction proceeded for 48 h. After the reaction, the reactants were transferred to a rotary evaporator and subjected to rotary evaporation at 0.2 MPa and 70 °C to remove unreacted monomers and solvent. The 1.0 generation PAMAM (G1.0-PAMAM) was obtained after rotary evaporation.
[0044] PVDF alkali treatment: Prepare 1300 parts of 2.0 mol / L NaOH solution, heat to 70℃, add 130 parts of PVDF and 55.3 parts of anhydrous ethanol while stirring at 800 rpm, stop stirring after stirring for 35 min, filter the solution, and then wash the filtrate three times with ultrapure water to obtain alkali-treated PVDF powder.
[0045] Alkali-treated PVDF was modified with AA: 130 parts of alkali-treated PVDF powder were dissolved in 1300 parts of NMP, nitrogen was introduced, and the temperature was raised to 60℃. 20 parts of AA monomer and 0.3 parts of AIBN initiator were added, and the mixture was stirred for 9 hours. After the reaction was completed, a large amount of methanol was added to precipitate the product. The precipitate was filtered and washed three times with ultrapure water to obtain AA-modified PVDF powder.
[0046] PVDF grafted with hyperbranched precursor: 950 parts of methanol solution and 70 parts of 1.0 generation PAMAM were added to a three-necked flask in sequence. After complete dissolution, 130 parts of AA-modified PVDF powder and 2.46 parts of 0.06 mol / L DMTMM solution were added. The mixture was stirred at 800 rpm at 27°C for 10 h. After 10 h, stirring was stopped, the product was filtered, and washed three times with ultrapure water to obtain PVDF material modified with hyperbranched precursor.
[0047] The prepared PVDF material is sprayed onto a polyolefin membrane, and the slurry is prepared using the synthetic PVDF material, including the following steps: The modified PVDF material was pulverized using a solid pulverizer to achieve a fineness of 300 mesh. At 300 rpm, 0.5 parts BYK-ET3000, 20 parts modified PVDF material, and 10 parts PAA were added sequentially to 69.5 parts ultrapure water. After addition, the speed was adjusted to 500 rpm and dispersed for 20 minutes. Subsequently, vacuum degassing was performed to obtain the final slurry.
[0048] The prepared slurry was coated onto a polyolefin membrane with a coating thickness controlled at 1 μm. The polyolefin membrane coated with the slurry was then dried at 70°C for 48 hours to obtain the final modified polyolefin membrane material.
[0049] This embodiment also provides a battery, including a separator prepared by the separator preparation method described above.
[0050] Example 3: The PAMAM generation used in this example is 2.0, and the other parts are the same as in Example 2.
[0051] After modifying the separator material with the modified PVDF material prepared in Examples 1 to 3, the modified separator material was used to stack the battery cells, and then the battery cells were hot-pressed. The appearance of the battery cells after hot pressing was evaluated, and the test results are shown in Table (1). The PVDF coating thickness deviated from the coating thickness in the above examples by less than 0.3 μm. The hot pressing conditions were set to 95℃, 12t, and 150s.
[0052]
[0053] Table (1) The cells from Examples 1 to 3 were used to prepare corresponding batteries, which were then cycled 300 times at a 1C rate. The test results are shown in Table (2). The control sample was a membrane battery using unmodified ordinary PVDF material. The cycling results show that the cells prepared in Examples 1-3 have significantly better cycle performance than the control group.
[0054]
[0055] Table (2) The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing modified PVDF material, characterized in that, Includes the following steps: PVDF and anhydrous ethanol were added to a NaOH solution with a concentration of 1 mol / L-3 mol / L to obtain alkali-treated PVDF powder. The mass ratio of NaOH solution was 1040-1680 parts, PVDF was 100-200 parts, and anhydrous ethanol was 39.5-79 parts. The alkali-treated PVDF powder was dissolved in NMP solution, and AA monomer and oil-soluble thermal initiator were added to the solution to obtain AA-modified PVDF powder. The alkali-treated PVDF powder was 100-200 parts, the oil-soluble thermal initiator was 0.1-0.5 parts, and the AA monomer was 10-40 parts by mass. A modified PVDF material is obtained by adding DMTMM solution and AA-modified PVDF powder to a mixed solution of methanol and PAMAM. The mass ratio of methanol is 792-1584 parts, PAMAM is 50-100 parts, DMTMM is 1.4-4.4 parts, and AA-modified PVDF powder is 100-200 parts.
2. The method for preparing modified PVDF material according to claim 1, characterized in that: When adding PVDF and anhydrous ethanol to the NaOH solution, the temperature is raised to 60℃-80℃.
3. The method for preparing modified PVDF material according to claim 2, characterized in that: When adding PVDF and anhydrous ethanol to the NaOH solution, add them at a stirring speed of 700 rpm-900 rpm, and stop stirring after stirring for 30 min-40 min.
4. The method for preparing modified PVDF material according to claim 1, characterized in that: When dissolving the alkali-treated PVDF powder in NMP solution, nitrogen is introduced and the temperature is raised to 50°-70°C.
5. The method for preparing modified PVDF material according to claim 1, characterized in that: The oil-soluble thermal initiator is AIBN. After adding AA monomer and oil-soluble thermal initiator to the solution, the solution is stirred for 8-12 hours.
6. The method for preparing modified PVDF material according to claim 1, characterized in that: The concentration of the DMTMM solution is 0.05 mol / L - 0.08 mol / L.
7. The method for preparing modified PVDF material according to claim 1, characterized in that: In the step of obtaining the modified PVDF material, the solution is stirred at a speed of 700 rpm-900 rpm at a temperature of 20℃-30℃ for 8-12 hours. After stirring, the product is filtered to obtain the modified PVDF material.
8. A method for preparing a diaphragm, using a modified PVDF material obtained by the method of claim 1, characterized in that, Includes the following steps: After the modified PVDF material is slurried, it is sprayed onto the base membrane to obtain the modified diaphragm.
9. The method for preparing a diaphragm according to claim 8, characterized in that: The PVDF slurry coating thickness on the base film is 1μm-3μm, and the base film coated with PVDF slurry is placed in an environment of 60℃-80℃ to dry for 48h-72h.
10. A battery, characterized in that: This includes the diaphragm prepared by the diaphragm preparation method as described in claim 8.