Preparation method of boehmite microcrystalline modified polyvinyl alcohol lithium battery diaphragm
Through the preparation of thin-water aluminite microcrystal modified polyvinyl alcohol separators, the problem of insufficient wetting and thermal stability of the lithium battery separator is solved, and the normal operation and environmental protection performance of the battery at high temperatures is achieved.
Patent Information
- Application Number
- CN202510439171.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2025-07-18
AI Technical Summary
The wetting and thermal stability of existing lithium battery separators are insufficient, resulting in low ion transmission rate and safety hazards, and the non-degradable polyolefin material causes environmental pollution.
Thin water limeite microcrystals are mixed with polyvinyl alcohol solution and composite separators are made by electrospinning to ensure that the lithium-ion battery is charged and discharged normally at high temperatures.
It improves the mechanical properties and thermal stability of lithium batteries, prevents thermal runaway, and the material can be degraded and reduces environmental pollution.
Smart Images
Figure CN120341498A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of new energy lithium battery materials and relates to a preparation method of a boehmite microcrystal modified polyvinyl alcohol lithium battery separator. Background Art
[0002] A lithium ion battery mainly consists of core components such as a positive electrode, a negative electrode, an electrolyte, and a separator. At present, the lithium battery separators widely used in the market are mainly made of polyolefin materials. The polyolefin separators have poor wettability, which is not conducive to the absorption and retention of the electrolyte, thereby affecting ion transport; their thermal stability is limited, and they are prone to shrinkage or even melting under high temperature conditions, increasing the safety risk. In addition, polyolefin materials are non-degradable, bringing potential environmental pollution problems. Polyvinyl alcohol has multiple hydroxyl groups on its surface, with good hydrophilicity, degradability, and certain mechanical properties, making it a potential alternative material for polyolefin separators. However, the lithium battery separator made of a single polyvinyl alcohol material has a low porosity, which limits the ion transport rate inside the battery; secondly, there are many non-crystalline regions in polyvinyl alcohol, which will lead to problems such as reduced mechanical strength and poor thermal stability of the separator, affecting the overall performance of the separator. Using inorganic powder fillers (such as SiO2, Al2O3, TiO2) to compound with PVA can optimize the performance of the polyvinyl alcohol separator, such as improving the mechanical strength, thermal stability, and electrolyte wettability of the separator. However, the dispersion of the powder filler in the PVA matrix is poor, and the particles are prone to agglomeration, which may lead to uneven local conductivity and affect the overall electrochemical performance of the battery. Summary of the Invention
[0003] Aiming at the above problems and deficiencies, the present invention synthesizes a sol of boehmite through a simple and effective method, mixes it with a polyvinyl alcohol solution to form a stable system, and then prepares a boehmite microcrystal modified polyvinyl alcohol lithium battery separator by electrospinning. On the premise of ensuring the electrochemical performance of the lithium ion battery, the mechanical performance and thermal stability of the battery are improved, and the thermal runaway of the battery is effectively prevented.
[0004] The technical solution of the present invention:
[0005] A preparation method of a boehmite microcrystal modified polyvinyl alcohol lithium battery separator comprises the following steps:
[0006] (1) Mix and disperse boehmite and water in a certain proportion, and subject the obtained mixture to hydrothermal treatment at 200 °C to 280 °C for 2 to 24 h; the hydrothermal product is dried to obtain boehmite microcrystals;
[0007] Wherein,
[0008] The mass ratio of boehmite to water is 1:3 to 1:20.
[0009] (2) Boehmite microcrystals are added to a nitric acid solution and dispersed evenly. The resulting mixture is subjected to hydrothermal treatment at 80°C to 180°C for 2 to 24 hours. The hydrothermal product is cooled, and then the resulting mixture is centrifuged at a high speed of not less than 3000 r / min to obtain a boehmite sol.
[0010] Among them,
[0011] The molar ratio of nitric acid to aluminum in the boehmite microcrystals is 1:10 to 1:50.
[0012] The mass ratio of the boehmite microcrystals to the 1.7 mol / L nitric acid solution is 1:3 to 1:20.
[0013] (3) Polyvinyl alcohol and water are dissolved at 85 to 90°C for 2 to 8 hours, cooled and left standing to remove bubbles to obtain a polyvinyl alcohol solution. The boehmite sol obtained in step (2) is mixed with the polyvinyl alcohol solution and stirred into a uniform colloid, and a composite separator is prepared by electrospinning. The composite separator is dried in vacuum to remove residual solvents. The separator is hot-pressed to obtain a boehmite-modified polyvinyl alcohol composite lithium battery separator.
[0014] Among them,
[0015] The mass ratio of polyvinyl alcohol to water is 1:10 to 1:4.
[0016] The mass ratio of the boehmite sol to the 10% polyvinyl alcohol solution is 1:10 to 1:1.
[0017] Furthermore, the degree of alcoholysis of the polyvinyl alcohol is 88 to 99%.
[0018] Furthermore, the temperature of the hot-pressing process is 60 to 120°C, the pressure is 100 Pa to 100 kPa, and the hot-pressing time is 0.5 to 12 hours.
[0019] Furthermore, the pseudo-boehmite is prepared by methods such as hydrolysis of aluminum alkoxide and precipitation of inorganic aluminum salts. Preferably, the peptization index of the pseudo-boehmite is not less than 85%, the mass content of Na impurities is not higher than 0.10%, the mass content of Fe impurities is not higher than 0.015%, and the mass content of Si impurities is not higher than 0.015%.
[0020] Furthermore, the hydrothermal reaction is static hydrothermal or stirred hydrothermal.
[0021] Furthermore, the mixing and dispersion of the boehmite sol and the polyvinyl alcohol solution is one of conventional high-speed dispersion disk stirring, ultrasonic dispersion, and ultrasonic-assisted stirring dispersion.
[0022] Furthermore, the electrospinning process uses conventional electrospinning equipment.
[0023] A lithium battery separator modified with boehmite microcrystals and polyvinyl alcohol is applied to a lithium battery. After the battery is heat-treated at 120 °C, the battery can be charged and discharged normally.
[0024] Advantages of the present invention: The selected raw materials are pseudo-boehmite and polyvinyl alcohol, which are easily available; the boehmite sol and the polyvinyl alcohol aqueous solution can form a homogeneous and stable system. After film formation, the boehmite is evenly distributed in the polyvinyl alcohol fibers without large particle agglomeration, which is beneficial to the migration of lithium ions; the battery separator obtained by the electrospinning technology has a large number of pores, which improves the electrolyte absorption rate of the battery and is beneficial to the transmission of lithium ions; the introduction of boehmite can improve the wettability of the battery, making the separator have lower resistance and better cycle and rate performance; the high thermal stability of boehmite and polyvinyl alcohol makes the separator have good thermal stability. After the battery is heat-treated at 120 °C, the battery can still be charged and discharged normally. Brief Description of the Drawings
[0025] Figure 1 It is the XRD pattern of the product after the obtained boehmite sol is dried.
[0026] Figure 2 It is the scanning electron micrograph of Celgard 2325 separator.
[0027] Figure 3 It is the scanning electron micrograph of the PVA composite separator.
[0028] Figure 4 It is the scanning electron micrograph of the BM / PVA composite separator.
[0029] Figure 5 It is BM 160 / PVA composite separator scanning electron micrograph.
[0030] Figure 6 It is BM 200 / PVA composite separator scanning electron micrograph.
[0031] Figure 7 It is BM 240 / PVA composite separator scanning electron micrograph.
[0032] Figure 8 It is the cycle performance graph of batteries assembled with different boehmite / polyvinyl alcohol separators after heat treatment. Detailed Embodiments
[0033] The following describes in detail the specific embodiments of the present invention in conjunction with the drawings and technical solutions.
[0034] Example 1
[0035] Weigh 15 g of pseudo-boehmite and put it into 60 g of deionized water, and stir and disperse it at 400 r / min for 30 min. Then put the obtained mixture into a 100 mL hydrothermal autoclave and carry out static hydrothermal reaction at 240 °C for 6 h. The cooled product is dried in a blast dryer at 80 °C for 12 h to obtain boehmite microcrystals. Measure 0.15 mL of concentrated nitric acid (65%) and 54 g of deionized water, put them into a beaker and stir for 30 min, weigh 6 g of boehmite microcrystals and put them into the nitric acid solution, and stir and disperse them at 400 r / min for 30 min. Then put the obtained mixture into a 100 mL hydrothermal autoclave and carry out dynamic hydrothermal reaction at 120 °C for 4 h. The obtained product is centrifuged at 4000 r / min for 10 min, and the supernatant is boehmite sol (average particle size is 188 nm). Weigh 1.2 g of polyvinyl alcohol (type 1788) and 6.8 g of deionized water, heat them in a three-necked flask at 95 °C for 4 h, cool it and let it stand at room temperature for 12 h to remove bubbles to obtain a polyvinyl alcohol solution; weigh 2 g of boehmite colloid, drop it into the polyvinyl alcohol solution, stir and disperse it, the stirring speed is 400 r / min, after stirring for 12 h, then carry out ultrasonic dispersion for 30 min; inject the obtained mixture into a 10 mL syringe, the distance between the needle and the collector is 16 cm, and carry out electrospinning at a feeding rate of 0.8 mL / h under a high voltage of 20 kV to obtain a composite separator. Then vacuum-dry the obtained composite membrane at 60 °C for 12 h to remove the residual solvent; finally, hot-press the separator at 120 °C for 1 h under a pressure of 200 Pa to obtain a boehmite microcrystal modified polyvinyl alcohol separator (BM 240 / PVA membrane), and the membrane thickness is 90 microns. The dried product (BM 240 ) XRD pattern is shown in Appendix Figure 1 , and the scanning electron microscope image of the prepared composite separator is shown in Appendix Figure 7 . It can be seen from Figure 1 that the crystallinity of the obtained boehmite is improved compared with that of pseudo-boehmite, Figure 7 shows that the surface of the fibers of the composite separator obtained by electrospinning is smooth, indicating that polyvinyl alcohol and boehmite microcrystals are completely compounded together.
[0036] Assembly into a battery and electrical performance testing are as follows: Prepare a positive electrode material slurry with a mass ratio of LiFePO4:PVDF:Super-p = 8:1:1, then scrape it onto an aluminum foil with a thickness of 150 μm, vacuum dry it at 100 °C for 12 h, and then cut it into circular pieces with a diameter of 12 mm for use as the positive electrode sheet of the battery. A lithium sheet is used as the negative electrode, and a Celgard 2325 commercial separator is selected as the comparative separator. A CR2032 half-cell (LiFePO4 / / separator / / Li) was used to study the battery performance in a voltage range of 2.0 - 4.2 V in a battery testing system. To test the battery performance in a high-temperature environment, for the high-temperature performance test, the assembled battery was treated at 120 °C for 0.5 h, and then charged and discharged at a rate of 0.1C (1C = 170 mAg -1 ) for 100 cycles. Figure 8 Shows the cycling performance graph of the lithium battery assembled with the BM 240 / PVA composite separator after treatment at 120 °C, while the capacity of the lithium battery assembled with the commercial separator Celgard 2325 is 0 after 17 cycles of operation.
[0037] Comparative Example 1
[0038] Prepare a pure PVA separator: Weigh 1.2 g of polyvinyl alcohol (PVA, type 1788) and 8.8 g of deionized water, heat it in a three-necked flask at 95 °C for 4 h, cool it and let it stand at room temperature for 12 h to remove bubbles to obtain a polyvinyl alcohol solution; the remaining steps and parameters for preparing the film are the same as in Example 1, but no boehmite sol is added; the film thickness is 100 microns.
[0039] Assembly of the battery and testing refer to Example 1, Figure 3 Showing the cycling performance of the lithium battery assembled with the pure PVA separator after treatment at 120 °C.
[0040] Comparative Example 2
[0041] Measure 0.14 mL of nitric acid and 54 g of deionized water, put them into a beaker and stir for 30 min, weigh 6 g of boehmite and put it into the nitric acid solution, stir and disperse it at 400 r / min for 30 min. Then put the obtained mixture into a 100 mL hydrothermal autoclave and carry out dynamic hydrothermal reaction at 120 °C for 4 h. The obtained product is centrifuged at 4000 r / min for 10 min, and the supernatant is the boehmite sol (average particle size is 54 nm). Figure 1 Showing the XRD pattern of the product (BM) after drying the boehmite sol, and the scanning electron micrograph of the prepared composite separator is shown in the appendix Figure 4 . Other preparation conditions are the same as in Example 1, replace the boehmite sol with the boehmite sol to obtain a low-crystallinity boehmite-modified polyvinyl alcohol separator (BM / PVA membrane), and the membrane thickness is 85 microns.
[0042] The assembled battery and the test were carried out according to Reference Example 1. Figure 8 The cycle performance of a lithium battery assembled with a modified polyvinyl alcohol separator (BM / PVA) of pseudo-boehmite with low crystallinity after being treated at 120 °C was shown.
[0043] Comparative Example 3
[0044] The preparation process of the boehmite microcrystals was the same as that of Example 1, but the hydrothermal temperature was 160 °C. The other conditions and parameters were the same as those of Example 1. Figure 1 The XRD pattern of the dried product (BM 160 ) of the 160 °C boehmite microcrystal sol (average particle size of 62 nm) was shown. The scanning electron micrograph of the prepared composite separator is shown in the appendix Figure 5 .
[0045] The manufacturing conditions of the lithium battery and the battery testing equipment were the same as those of Example 1. Figure 8 The cycle performance of a lithium battery assembled with a 160 °C boehmite microcrystal modified polyvinyl alcohol separator (BM 160 / PVA film) after being treated at 120 °C was shown.
[0046] Example 2
[0047] The preparation process of the boehmite microcrystals was the same as that of Example 1, but the hydrothermal temperature was 200 °C. The other parameters and conditions were the same as those of Example 1. Figure 1 The XRD pattern of the dried product (BM 200 ) of the 200 °C boehmite sol (average particle size of 133 nm) was shown. The scanning electron micrograph of the prepared composite separator is shown in the appendix Figure 6 .
[0048] The manufacturing conditions of the lithium battery and the battery testing equipment were the same as those of Example 1. Figure 8 The cycle performance of a lithium battery assembled with a 200 °C boehmite modified polyvinyl alcohol separator (BM 200 / PVA film) after being treated at 120 °C was shown.
[0049] Example 3
[0050] The preparation process of the boehmite microcrystals was the same as that of Example 1, but the ratio of boehmite to water was 1:3, that is, 18.75 g of boehmite and 56.25 g of deionized water. The other parameters and conditions were the same as those of Example 1.
[0051] The manufacturing conditions of the lithium battery and the battery testing equipment were the same as those of Example 1.
[0052] Example 4
[0053] The preparation process of the boehmite microcrystals is the same as that in Example 1, but the ratio of boehmite to water is 1:20, that is, 3.57 g of boehmite and 71.43 g of deionized water. The remaining parameters and conditions are the same as those in Example 1.
[0054] The manufacturing conditions of the lithium battery and the battery testing equipment are the same as those in Example 1.
[0055] Example 5
[0056] The preparation process of the boehmite microcrystals is the same as that in Example 1. The preparation process of the boehmite sol is the same as that in Example 1, but the molar ratio of nitric acid to aluminum in the boehmite microcrystals is 1:10, that is, 0.62 mL of concentrated nitric acid and 6 g of boehmite microcrystals. The remaining parameters and conditions are the same as those in Example 1.
[0057] The manufacturing conditions of the lithium battery and the battery testing equipment are the same as those in Example 1.
[0058] Example 6
[0059] The preparation process of the boehmite microcrystals is the same as that in Example 1. The preparation process of the boehmite sol is the same as that in Example 1, but the molar ratio of nitric acid to aluminum in the boehmite microcrystals is 1:50, that is, 0.12 mL of concentrated nitric acid and 6 g of boehmite microcrystals. The remaining parameters and conditions are the same as those in Example 1.
[0060] The manufacturing conditions of the lithium battery and the battery testing equipment are the same as those in Example 1.
[0061] Example 7
[0062] The preparation process of the boehmite microcrystals is the same as that in Example 1. The preparation process of the boehmite sol is the same as that in Example 1. The preparation process of the composite separator is the same as that in Example 1, but the mass ratio of the boehmite sol to polyvinyl alcohol is 1:10, that is, 0.91 g of boehmite sol and 9.09 g of polyvinyl alcohol solution. The remaining parameters and conditions are the same as those in Example 1.
[0063] The manufacturing conditions of the lithium battery and the battery testing equipment are the same as those in Example 1.
[0064] Example 8
[0065] The preparation process of the boehmite microcrystals is the same as that in Example 1. The preparation process of the boehmite sol is the same as that in Example 1. The preparation process of the composite separator is the same as that in Example 1, but the mass ratio of the boehmite sol to polyvinyl alcohol is 1:1, that is, 5 g of boehmite sol and 5 g of polyvinyl alcohol solution. The remaining parameters and conditions are the same as those in Example 1.
[0066] The manufacturing conditions of the lithium battery and the battery testing equipment are the same as those in Example 1.
[0067] From the above examples and comparative examples, the conclusion is drawn that the boehmite microcrystal composite PVA separator does not introduce new metal ions, reducing environmental pollution; the boehmite microcrystals are evenly distributed in the polyvinyl alcohol fibers without obvious particle agglomeration, which helps the transmission of lithium ions; as the hydrothermal temperature of the pseudo-boehmite increases, the crystallinity of the obtained boehmite microcrystals improves, and the battery performance after treatment at 120 °C is better retained, and it can be maintained better after the hydrothermal temperature exceeds 200 °C.
Claims
1. A preparation method of a boehmite microcrystal modified polyvinyl alcohol lithium battery separator, characterized in that, The steps are as follows: (1) Pseudoboehmite and water are mixed and dispersed in a certain proportion, and the obtained mixture is hydrothermally treated at 200 °C to 280 °C for 2 to 24 h; the hydrothermal product is dried to obtain boehmite microcrystals; (2) Boehmite microcrystals are added to a nitric acid solution and dispersed evenly, and the obtained mixture is hydrothermally treated at 80 °C to 180 °C for 2 to 24 h; the hydrothermal product is cooled, and then the obtained mixture is centrifuged at a high speed of not less than 3000 r / min to obtain a boehmite sol; (3) Polyvinyl alcohol and water are dissolved at 85 to 90 °C for 2 to 8 h, cooled and left to remove bubbles to obtain a polyvinyl alcohol solution; the boehmite sol obtained in step (2) is mixed and stirred with the polyvinyl alcohol solution to form a uniform colloid, and a composite separator is prepared by electrospinning. The composite separator is vacuum dried to remove residual solvents; the separator is hot pressed to obtain a boehmite-modified polyvinyl alcohol composite lithium battery separator.
2. The preparation method according to claim 1, wherein in step (1), the mass ratio of pseudoboehmite to water is 1:3 to 1:
20.
3. The preparation method according to claim 1, wherein in step (2), the molar ratio of nitric acid to aluminum in the boehmite microcrystals is 1:10 to 1:50; the mass ratio of the boehmite microcrystals to the 1.7 mol / L nitric acid solution is 1:3 to 1:
20.
4. The preparation method according to claim 1, wherein in step (3), the mass ratio of polyvinyl alcohol to water is 1:10 to 1:4; the mass ratio of the boehmite sol to the 10% polyvinyl alcohol solution is 1:10 to 1:1; the degree of alcoholysis of polyvinyl alcohol is 88 to 99%.
5. The preparation method according to claim 1, wherein in step (3), the temperature of the hot pressing process is 60 to 120 °C, the pressure is 100 Pa to 100 kPa, and the hot pressing time is 0.5 to 12 h.
6. The preparation method according to claim 1, wherein the hydrothermal reaction is static hydrothermal or stirring hydrothermal.