Lithium-ion battery separator with porous alumina-based composite coating and its preparation method

Abstract

This invention discloses a lithium-ion battery separator with a porous alumina-based composite material coating and its preparation method. The lithium-ion battery separator with the porous alumina-based composite material coating includes a base film and a coating on the base film. The coating includes modified porous alumina, which comprises porous alumina and lithium element supported on the porous alumina. The method for preparing the modified porous alumina includes: immersing the porous alumina in an aqueous solution of lithium salt, simultaneously stirring and sonicating under vacuum for 4-6 hours, drying, grinding into powder, and calcining at 400-600℃ for 2-4 hours under an inert gas atmosphere to obtain the modified porous alumina. The lithium-ion battery separator of this invention has high heat resistance, high wettability, and high ionic conductivity.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a lithium battery separator with a porous alumina-based composite material coating and its preparation method. Background Technology

[0002] As a core component of the lithium-ion battery structure, the separator plays a crucial dual role: on the one hand, it ensures physical isolation between the positive and negative electrodes, effectively preventing short circuits; on the other hand, it allows lithium ions to pass smoothly through, enabling the battery's charge-discharge cycles. This characteristic makes the separator's ionic conductivity and liquid absorption / retention capacity key factors affecting the battery's internal resistance, charge-discharge speed, and even its overall energy density and power performance. Therefore, improving the separator's ionic conductivity and liquid absorption / retention capacity is not only a strategic priority for optimizing lithium-ion battery performance but also a challenging and promising research frontier in materials science.

[0003] To meet the urgent demands of modern electronic devices for higher energy density and faster charging speeds, it is crucial to explore and implement effective strategies to enhance the ion transport efficiency and liquid retention capacity of lithium-ion battery separators. This requires researchers to conduct innovative studies in materials design and synthesis, microstructure control, and surface modification techniques, aiming to develop novel separator materials with superior overall performance.

[0004] In conclusion, conducting in-depth and meticulous scientific research and technological innovation on how to efficiently improve the ionic conductivity and liquid absorption and retention rate of lithium battery separators is of immeasurable value for promoting the development of high-performance lithium batteries and meeting the high standards required for future energy storage systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a lithium battery separator with a porous alumina-based composite material coating.

[0006] Another object of the present invention is to provide a method for preparing a lithium battery separator with the above-mentioned porous alumina-based composite material coating.

[0007] Another object of the present invention is to provide a slurry.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A lithium battery separator with a porous alumina-based composite material coating includes: a base film and a coating on the base film, wherein the coating includes: modified porous alumina, and the modified porous alumina includes: porous alumina and lithium element supported on the porous alumina.

[0010] In the above technical solution, the particle size of the porous alumina is: D10 = 0.225~0.356μm, D50 = 0.512~0.672μm, D90 = 1.356~1.478μm, and the specific surface area of ​​the porous alumina is 15~20m². 2 / g, the pore size of porous alumina is 10-50nm.

[0011] In the above technical solution, the particle size of the modified porous alumina is: D10 = 0.236~0.406μm, D50 = 0.552~0.772μm, D90 = 1.479~1.641μm, and the specific surface area of ​​the modified porous alumina is 15~20m². 2 / g.

[0012] In the above technical solution, the method for preparing modified porous alumina includes: immersing porous alumina in an aqueous solution of lithium salt, simultaneously stirring and sonicating under vacuum for 4–6 hours; drying the porous alumina and the aqueous solution of lithium salt used for immersion together; grinding the powder; and calcining the powder at 400–600℃ for 2–4 hours under an inert gas atmosphere to obtain modified porous alumina. The ratio of the porous alumina to the lithium salt in the aqueous solution is (20–50) by mass.

[0013] (50-80), wherein the concentration of lithium salt in the aqueous solution of the lithium salt is 10-20 wt%.

[0014] In the method for preparing modified porous alumina, the lithium salt is at least one selected from lithium chloride, lithium perchlorate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0015] In the method for preparing modified porous alumina, the porous alumina is dried at 60-80°C for 2-3 hours before being immersed in an aqueous solution of lithium salt.

[0016] In the method for preparing modified porous alumina, porous alumina is immersed in an aqueous solution of lithium salt and simultaneously stirred and sonicated under vacuum for 4–6 hours. The vacuum degree is 0.02–0.04 kPa, the rotation speed of the stirring is 200–300 r / min, the revolution speed is 20–30 r / min, and the ultrasonic frequency is 5–8 kHz.

[0017] The method for preparing the lithium battery separator with the porous alumina-based composite material coating includes: coating a slurry onto a base film, drying it, obtaining a coating on the base film, and obtaining a lithium battery separator with the porous alumina-based composite material coating, wherein the slurry includes modified porous alumina and water.

[0018] In the above technical solution, the coating thickness is 2-3 μm.

[0019] In the above technical solution, the coating speed is 10-20 m / min.

[0020] A slurry comprising: modified porous alumina, water, adhesive, and dispersant, wherein the ratio of modified porous alumina, water, adhesive, and dispersant by mass parts is (15-20):(60-80):(5-8):(0.5-0.8).

[0021] In the above technical solution, the adhesive is an acrylate copolymer solution, and the concentration of the acrylate copolymer in the acrylate copolymer solution is 10-30 wt%.

[0022] In the above technical solution, the dispersant is ammonium polyacrylate.

[0023] The method for preparing the above-mentioned slurry includes: mixing modified porous alumina, water, adhesive and dispersant until homogeneous to obtain the slurry.

[0024] The method for preparing the above-mentioned slurry specifically includes the following steps:

[0025] Step 1: Mix the dispersant, water, and modified porous alumina until homogeneous to obtain the first solution;

[0026] In step 1, the dispersant, water and modified porous alumina are mixed and stirred at a rotation speed of 2000-3000 r / min and a revolution speed of 40-50 r / min for 20-30 min until homogeneous, to obtain the first solution.

[0027] Step 2: Mix the first solution and adhesive until homogeneous to obtain a slurry. The ratio of modified porous alumina, water, adhesive and dispersant by mass is (15-20):(60-80):(5-8):(0.5-0.8).

[0028] In step 2, the first solution and the adhesive are mixed and simultaneously stirred and sonicated under vacuum for 30-40 minutes until homogeneous to obtain a slurry. The vacuum degree of the vacuum environment is 0.06-0.08 kPa, the rotation speed of the stirring is 2000-3000 r / min, the revolution speed is 40-60 r / min, and the ultrasonic frequency of the sonication is 5-8 kHz.

[0029] The application of modified porous alumina in improving the heat resistance, liquid absorption rate, liquid retention rate, air permeability and / or ionic conductivity of diaphragms, wherein the modified porous alumina comprises: porous alumina and lithium element supported on porous alumina.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. High Heat Resistance: The lithium battery separator of this invention exhibits excellent high heat resistance, which is a key factor in improving the safety and cycle stability of lithium batteries. This high-temperature resistance effectively prevents short circuits or thermal runaway caused by excessively high temperatures, thereby significantly improving battery safety performance.

[0032] 2. High wettability and high ionic conductivity: The lithium battery separator of this invention exhibits excellent wettability and ionic conductivity. The coating of this invention contains porous alumina, resulting in a rich pore structure that greatly enhances the separator's absorption and storage capacity for the electrolyte. This not only shortens the lithium-ion battery lifespan... + The improved transmission path also enhanced the ionic conductivity of the separator, thereby reducing the battery's internal resistance and increasing power density.

[0033] 3. High Safety: The high ionic conductivity effectively slows down lithium accumulation, allowing lithium ions to be distributed more evenly at the negative electrode, thereby slowing down lithium dendrite growth and preventing short circuits and thermal runaway. The lithium battery separator of this invention has a tortuous porous structure that can block the penetration of lithium dendrites, improve battery safety performance, and avoid the risks of overheating and combustion. Attached Figure Description

[0034] Figure 1 SEM image of the lithium battery separator prepared in Example 6. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0036] Porous alumina (powder): The particle size of porous alumina is: D10 = 0.306 μm, D50 = 0.595 μm, D90 = 1.388 μm, and the specific surface area of ​​porous alumina is 16.6 m². 2 / g, the pore size of porous alumina is 50nm;

[0037] Acrylic copolymer solution: Baoding Lucky Imaging Materials Technology Co., Ltd.;

[0038] Ammonium polyacrylate: Shanghai Sanrui Polymer Materials Technology Co., Ltd.

[0039] Dual planetary mixer: XFZH-30L.

[0040] In the following examples, the water used is pure water.

[0041] In the following examples, the base film is a PE film with a thickness of 7 micrometers.

[0042] Ionic conductivity: tested at 25°C and 60% relative humidity.

[0043] Example 1

[0044] A method for preparing a slurry includes the following steps:

[0045] Step 1: Mix the dispersant, water and modified porous alumina in a double planetary mixer at a rotation speed of 2000 r / min and a revolution speed of 40 r / min for 20 min until homogeneous to obtain the first solution. The dispersant is ammonium polyacrylate.

[0046] Step 2: Add adhesive (an acrylate copolymer solution with a concentration of 20 wt%, composed of acrylic acid and acrylamide copolymer) to the first solution. Stir and sonicate simultaneously under vacuum for 30 minutes in a dual planetary mixer with ultrasonic oscillation function until homogeneous, to obtain a slurry. The ratio of modified porous alumina, water, adhesive and dispersant by mass is 15:79.5:5:0.5. The vacuum degree is 0.06 kPa, the rotation speed of the mixer is 2000 r / min, the revolution speed is 40 r / min, and the ultrasonic frequency is 5 kHz.

[0047] The method for preparing modified porous alumina includes: immersing porous alumina in an aqueous solution of lithium salt (the porous alumina is dried in an oven at 60°C for 2 hours before immersion in the lithium salt solution), and simultaneously stirring and sonicating in a double planetary stirrer with ultrasonic oscillation function under vacuum for 4 hours (vacuum degree of 0.02 kPa, rotation speed of the stirrer is 200 r / min, revolution speed is 20 r / min, and ultrasonic frequency is 5 kHz); drying the porous alumina and the aqueous solution of lithium salt immersion together in an oven at 60°C for 2 hours; grinding into powder; placing in a tube furnace; and calcining at 400°C for 2 hours under an argon atmosphere to obtain modified porous alumina (the particle size of the modified porous alumina is D10 = 0.267 μm, D50 = 0.615 μm, D90 = 1.512 μm, and the average specific surface area of ​​the modified porous alumina is 17.2 m²). 2 / g), wherein, by mass parts, the ratio of lithium salt in the aqueous solution of porous alumina and lithium salt is 20:80, the concentration of lithium salt in the aqueous solution of lithium salt is 10wt%, and the lithium salt is lithium chloride.

[0048] Example 2

[0049] A method for preparing a slurry includes the following steps:

[0050] Step 1: Mix the dispersant, water and modified porous alumina in a double planetary mixer at a rotation speed of 2500 r / min and a revolution speed of 45 r / min for 25 min until homogeneous to obtain the first solution. The dispersant is ammonium polyacrylate.

[0051] Step 2: Add adhesive (an acrylate copolymer solution with a concentration of 20 wt%, composed of acrylic acid and acrylamide copolymer) to the first solution. Stir and sonicate simultaneously under vacuum for 35 minutes in a dual planetary mixer with ultrasonic oscillation function until homogeneous, to obtain a slurry. The ratio of modified porous alumina, water, adhesive and dispersant by mass is 17:75.3:7:0.7. The vacuum degree is 0.07 kPa, the rotation speed of the stirrer is 2500 r / min, the revolution speed is 50 r / min, and the ultrasonic frequency is 6 kHz.

[0052] The method for preparing modified porous alumina includes: immersing porous alumina in an aqueous solution of lithium salt (the porous alumina is dried in an oven at 70°C for 2.5 h before immersion in the lithium salt solution), and simultaneously stirring and sonicating in a double planetary stirrer with ultrasonic oscillation function under vacuum for 5 h (vacuum degree of 0.03 kPa, rotation speed of the stirrer is 250 r / min, revolution speed is 30 r / min, ultrasonic frequency is 5 kHz); drying the porous alumina and the aqueous solution of lithium salt immersion together in an oven at 70°C for 2.5 h; grinding into powder; placing in a tube furnace; and calcining at 500°C for 3 h under an argon atmosphere to obtain modified porous alumina (the particle size of the modified porous alumina is D10 = 0.289 μm, D50 = 0.587 μm, D90 = 1.625 μm, and the average specific surface area of ​​the modified porous alumina is 18.6 m²). 2 / g), wherein, by mass parts, the ratio of lithium salt in the aqueous solution of porous alumina and lithium salt is 30:70, the concentration of lithium salt in the aqueous solution of lithium salt is 15wt%, and the lithium salt is lithium chloride.

[0053] Example 3

[0054] A method for preparing a slurry includes the following steps:

[0055] Step 1: Mix the dispersant, water and modified porous alumina in a double planetary mixer at a rotation speed of 3000 r / min and a revolution speed of 50 r / min for 30 min until homogeneous to obtain the first solution. The dispersant is ammonium polyacrylate.

[0056] Step 2: Add adhesive (an acrylate copolymer solution with a concentration of 20 wt%, composed of acrylic acid and acrylamide copolymer) to the first solution. Stir and sonicate simultaneously under vacuum for 40 minutes in a dual planetary mixer with ultrasonic oscillation function until homogeneous, to obtain a slurry. The ratio of modified porous alumina, water, adhesive and dispersant by mass is 20:71.2:8:0.8. The vacuum degree is 0.08 kPa, the rotation speed of the stirrer is 3000 r / min, the revolution speed is 60 r / min, and the ultrasonic frequency is 8 kHz.

[0057] The method for preparing modified porous alumina includes: immersing porous alumina in an aqueous solution of lithium salt (the porous alumina is dried in an oven at 80°C for 3 hours before immersion in the lithium salt solution), and simultaneously stirring and sonicating in a double planetary stirrer with ultrasonic oscillation function under vacuum for 6 hours (vacuum degree of 0.04 kPa, rotation speed of the stirrer is 300 r / min, revolution speed is 20 r / min, and ultrasonic frequency is 5 kHz); drying the porous alumina and the aqueous solution of lithium salt immersion together in an oven at 80°C for 3 hours; grinding into powder; placing in a tube furnace; and calcining at 600°C for 4 hours under an argon atmosphere to obtain modified porous alumina (the particle size of the modified porous alumina is D10 = 0.299 μm, D50 = 0.633 μm, D90 = 1.586 μm, and the average specific surface area of ​​the modified porous alumina is 20 m²). 2 / g), wherein, by mass parts, the ratio of lithium salt in the aqueous solution of porous alumina and lithium salt is 50:50, the concentration of lithium salt in the aqueous solution of lithium salt is 20wt%, and the lithium salt is lithium chloride.

[0058] Example 4 (for comparison)

[0059] A method for preparing a slurry is basically the same as that in Example 1, except that the phrase "by mass parts, the ratio of porous alumina to lithium salt in the aqueous solution of lithium salt is 20:80" in the method for preparing modified porous alumina is replaced with "by mass parts, the ratio of porous alumina to lithium salt in the aqueous solution of lithium salt is 10:90".

[0060] Example 5 (for comparison)

[0061] A method for preparing a slurry is basically the same as that in Example 1, except that the phrase "by mass parts, the ratio of porous alumina to lithium salt in the aqueous solution of lithium salt is 20:80" in the method for preparing modified porous alumina is replaced with "by mass parts, the ratio of porous alumina to lithium salt in the aqueous solution of lithium salt is 60:40".

[0062] Comparative Example 1

[0063] A method for preparing a slurry includes the following steps:

[0064] Step 1: Mix the dispersant, water and porous alumina (the same porous alumina used in Example 1) in a double planetary mixer and stir for 25 minutes at a rotation speed of 3000 r / min and a revolution speed of 45 r / min until homogeneous to obtain solution A. The dispersant is ammonium polyacrylate.

[0065] Step 2: Add adhesive (an acrylate copolymer solution with a concentration of 20 wt%, composed of acrylic acid and acrylamide) to solution A. Stir and sonicate simultaneously under vacuum for 40 minutes in a dual planetary mixer with ultrasonic oscillation function until homogeneous, obtaining a slurry. The ratio of porous alumina, water, adhesive, and dispersant by mass is 20:73.5:6:0.5. The vacuum level is 0.07 kPa, the rotation speed of the mixer is 2500 r / min, the revolution speed is 60 r / min, and the ultrasonic frequency is 6 kHz.

[0066] Comparative Example 2

[0067] A method for preparing a slurry includes the following steps:

[0068] Step 1: Mix the dispersant, water, and alumina (D10 = 0.299 μm, D50 = 0.605 μm, D90 = 1.533 μm, non-porous alumina) in a double planetary mixer. First, stir at a rotation speed of 3000 r / min and a revolution speed of 50 r / min for 20 min, then sonicate at a frequency of 5 kHz for 20 min until homogeneous to obtain solution B. The dispersant is ammonium polyacrylate.

[0069] Step 2: Add adhesive (an acrylate copolymer solution with a concentration of 20 wt%, composed of acrylic acid and acrylamide) to solution B. Stir and sonicate simultaneously under vacuum for 30 minutes in a dual planetary mixer with ultrasonic oscillation function until homogeneous, to obtain a slurry. The ratio of alumina, water, adhesive, and dispersant by mass is 20:74.5:5:0.5. The vacuum level is 0.06 kPa, the rotation speed of the mixer is 2000 r / min, the revolution speed is 40 r / min, and the ultrasonic frequency is 5 kHz.

[0070] Examples 6-10 and Comparative Examples 3-4

[0071] A method for preparing a lithium battery separator includes: placing a base film on a coating machine containing slurry, coating one side of the base film with the slurry at a coating speed of X m / min, and then drawing the slurry into a drying equipment via a traction roller and drying it at Y °C for Z min to obtain a coating on the base film, thereby obtaining a lithium battery separator. The slurry is one of Examples 1-5 and Comparative Examples 1-2.

[0072] X, Y, and Z are shown in Table 1.

[0073] Table 1

[0074]

[0075] The parameters of the lithium battery separator prepared from the slurry of Example 1 are as follows:

[0076]

[0077]

[0078] The parameters of the lithium battery separator prepared from the slurry of Example 2 are as follows:

[0079]

[0080] The parameters of the lithium battery separator prepared from the slurry of Example 3 are as follows:

[0081]

[0082]

[0083] The parameters of the lithium battery separator prepared from the slurry of Example 4 are as follows:

[0084]

[0085] The parameters of the lithium battery separator prepared from the slurry of Example 5 are as follows:

[0086]

[0087] The parameters of the lithium battery separator prepared from the slurry of Comparative Example 1 are as follows:

[0088]

[0089] The parameters of the lithium battery separator prepared from the slurry of Comparative Example 2 are as follows:

[0090]

[0091] The pore structure of the lithium battery separator prepared from the slurry of Example 1 was tested, and the results are as follows:

[0092]

[0093] Traditional lithium-ion battery separators often suffer from low ion transport efficiency, limiting the overall performance of the battery. This invention modifies porous alumina with lithium salts. By introducing lithium salts with high ion conductivity onto the surface and pore walls of porous alumina, this strategy significantly improves the ionic conductivity of the lithium-ion battery separator. Specifically, utilizing the large specific surface area of ​​porous alumina as a supporting platform, a solution impregnation method is used to uniformly disperse lithium salts on the surface and within the pore structure of the porous alumina. The unique structure of porous alumina provides more active sites for the lithium salts, promoting rapid lithium-ion transport within the separator. Furthermore, the introduction of lithium salts enhances the compatibility between the separator and the electrolyte, further improving the ionic conductivity.

[0094] The test results of the examples and comparative examples show that the lithium battery separator prepared using modified porous alumina exhibits excellent ionic conductivity and liquid absorption / retention rate while maintaining good thermal shrinkage. This provides new ideas and methods for developing high-performance lithium battery separator materials, and is expected to promote the progress and development of lithium battery technology.

[0095] Figure 1 SEM image of the lithium battery separator prepared in Example 6.

[0096] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A lithium battery separator with a porous alumina-based composite material coating, characterized in that, include: A base film and a coating on the base film, the coating comprising: modified porous alumina, the modified porous alumina comprising: porous alumina and lithium element supported on the porous alumina; The coating is obtained by applying a slurry, which includes: modified porous alumina, water, adhesive and dispersant. By mass parts, the ratio of modified porous alumina, water, adhesive and dispersant is 15:79.5:5:0.

5. The adhesive is an acrylate copolymer solution and the dispersant is ammonium polyacrylate. The method for preparing modified porous alumina includes: immersing porous alumina in an aqueous solution of lithium salt, simultaneously stirring and sonicating under vacuum for 4-6 hours, drying, grinding into powder, and calcining at 400-600℃ for 2-4 hours under an inert gas atmosphere to obtain modified porous alumina, wherein, by mass fraction, the ratio of porous alumina to lithium salt in the aqueous solution is 20:80; The lithium salt is at least one of lithium chloride, lithium perchlorate, lithium hexafluorophosphate, and lithium tetrafluoroborate; The particle size of the porous alumina is: D10=0.225~0.356μm, D50=0.512~0.672μm, D90=1.356~1.478μm, the specific surface area of the porous alumina is 15~20 m 2 / g, and the pore size of the porous alumina is 10~50nm. The particle size of the modified porous alumina is: D10=0.236~0.406μm, D50=0.552~0.772μm, D90=1.479~1.641μm, and the specific surface area of the modified porous alumina is 15~20 m 2 / g. The coating contains porous alumina, resulting in a rich pore structure that greatly enhances the membrane's absorption and storage capacity for the electrolyte, thus shortening the Li... + The improved transmission path also enhanced the ionic conductivity of the separator, thereby reducing the battery's internal resistance and increasing power density.

2. The lithium battery separator with a porous alumina-based composite material coating according to claim 1, characterized in that, The concentration of lithium salt in the aqueous solution of the lithium salt is 10~20wt%.

3. The method for preparing a lithium battery separator with a porous alumina-based composite material coating as described in any one of claims 1 to 2, characterized in that, include: The slurry is coated onto the base film and dried to obtain a coating on the base film, resulting in a lithium battery separator with a porous alumina-based composite material coating.

4. The preparation method according to claim 3, characterized in that, The method for preparing the slurry includes: mixing modified porous alumina, water, adhesive and dispersant until homogeneous to obtain the slurry.

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