Polyimide / lithium aluminum titanium phosphate composite battery diaphragm and preparation method thereof

Abstract

The invention provides a polyimide / titanium-aluminum-lithium phosphate composite battery diaphragm and a preparation method thereof, and relates to the technical field of diaphragm preparation, the polyimide / titanium-aluminum-lithium phosphate composite battery diaphragm comprises a polyimide base membrane and a titanium-aluminum-lithium phosphate coating located on one surface of the polyimide base membrane, the polyimide base membrane comprises a polyimide matrix and lithium titanium aluminum phosphate embedded in the polyimide matrix, and the polyimide / lithium titanium aluminum phosphate composite battery diaphragm can effectively avoid the growth of lithium dendrites.

Description

Technical Field

[0001] This invention relates to the field of separator preparation technology, specifically to a polyimide / lithium aluminum titanium phosphate composite battery separator and its preparation method. Background Technology

[0002] Lithium-ion batteries possess advantages such as high operating voltage, high energy density, and long cycle life, leading to their increasing application as energy storage media. They are widely used not only in various consumer electronics products but also in electric vehicles and electrochemical energy storage. While lithium-ion batteries using metallic lithium as the negative electrode material exhibit high energy density and excellent cycle performance, lithium metal batteries inevitably suffer from lithium dendrite formation. Dendritic lithium metal has a high specific surface area, which can cause side reactions with the electrolyte, leading to gas production and capacity reduction. Furthermore, dendritic lithium metal can potentially puncture the separator, causing short circuits and even combustion or explosion. Therefore, suppressing lithium dendrite growth is a crucial problem that must be solved in the research and manufacturing of lithium batteries. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a polyimide / lithium aluminum titanium phosphate composite battery separator and its preparation method, solving the technical problem of lithium dendrite formation in lithium metal batteries.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] On one hand, the present invention provides a polyimide / lithium titanium aluminum phosphate composite battery separator, comprising a polyimide base film and a lithium titanium aluminum phosphate coating on one surface of the polyimide base film, wherein the polyimide base film comprises a polyimide matrix and lithium titanium aluminum phosphate particles with a size D50 of 0.1-0.3 μm embedded in the polyimide matrix, and the thickness of the lithium titanium aluminum phosphate coating is 0.5-4 μm.

[0006] The aforementioned polyimide / lithium titanium aluminum phosphate composite battery separator includes a polyimide base film and a lithium titanium aluminum phosphate coating on one surface of the polyimide base film. The polyimide base film includes a polyimide matrix and lithium titanium aluminum phosphate particles with a size D50 of 0.1-0.3 μm embedded in the polyimide matrix. The thickness of the lithium titanium aluminum phosphate coating is 0.5-4 μm. Under low potential conditions, lithium dendrites easily form in the lithium metal anode layer. In this application, the 0.5-4 μm thick lithium titanium aluminum phosphate coating and the 0.1-0.3 μm thick lithium titanium aluminum phosphate particles embedded in the polyimide matrix in the polyimide / lithium titanium aluminum phosphate composite battery separator are reduced at low anode potentials. The Ti in the lithium titanium aluminum phosphate is reduced by Ti... 4+ Restore to Ti 3+During this reduction reaction, the lithium dendrites generated are combined to form lithium-containing compounds, thereby consuming the lithium dendrites. Therefore, in the lithium metal battery prepared with the polyimide / lithium titanium aluminum phosphate composite battery separator of this application, the synergistic effect of the 0.5-4 μm thick lithium titanium aluminum phosphate coating and the lithium titanium aluminum phosphate particles with a D50 of 0.1-0.3 μm embedded in the substrate rapidly consumes the tiny lithium dendrites formed on the surface of the lithium metal anode, preventing further growth. This effectively avoids lithium dendrite growth and prevents lithium dendrites from piercing the separator and causing battery failure, thus inhibiting the growth of lithium dendrites on the anode of the lithium metal battery. In addition, the lithium titanium aluminum phosphate embedded in the polyimide matrix can serve as a lithium-ion transport channel, improving the ion permeability of the separator and enhancing battery performance.

[0007] Preferably, the polyimide-based film has a thickness of 9-20 μm.

[0008] Preferably, the polyimide-based film has a porous structure with a porosity of 30-60%.

[0009] Preferably, the D50 of the lithium titanium aluminum phosphate particles embedded in the polyimide matrix is ​​0.1 μm. The lithium titanium aluminum phosphate embedded in the polyimide matrix enhances lithium-ion transport, eliminating the need for additional liquid electrolyte and reducing the overall electrolyte content in the battery. Furthermore, the reduction of lithium titanium aluminum phosphate solidifies a portion of the electrolyte without affecting battery performance, further reducing the electrolyte content and significantly improving the battery's high-temperature safety.

[0010] Preferably, the thickness of the lithium titanium aluminum phosphate coating is 0.5 μm.

[0011] Preferably, the lithium titanium aluminum phosphate coating contains lithium titanium aluminum phosphate particles, and the particle size D50 is 0.3-1 μm.

[0012] In a second aspect, the present invention provides a method for preparing the polyimide / lithium titanium aluminum phosphate composite battery separator as described in the first aspect, comprising the following steps: dissolving p-phenylenediamine and pyromellitic dianhydride in a solvent at a molar ratio of 1:1-3 to prepare a polyamic acid solution; adding lithium titanium aluminum phosphate to the polyamic acid solution and mixing evenly to obtain a polyamic acid / lithium titanium aluminum phosphate blend slurry; forming the polyamic acid / lithium titanium aluminum phosphate blend slurry into a film on a plane to obtain a polyamic acid / lithium titanium aluminum phosphate blend wet film; solidifying, drying, and dehydrating the polyamic acid / lithium titanium aluminum phosphate blend wet film at high temperature to obtain a polyimide-based film; coating a lithium titanium aluminum phosphate coating slurry on one surface of the polyimide-based film and drying to obtain the polyimide / lithium titanium aluminum phosphate composite battery separator.

[0013] Preferably, the lithium titanium aluminum phosphate coating slurry includes lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water.

[0014] Preferably, the mass ratio of lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water is 10-30:2-5:0.1-0.3:0.2-0.4:0.2-0.3:74-88.

[0015] Preferably, the mass ratio of lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water is 15:2.5:0.2:0.3:0.3:81.7. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the polyimide / lithium aluminum titanium phosphate composite battery separator structure of the present invention.

[0018] Among them, 1-polyimide matrix, 2-LATP particles, 3-base film pores, 4-lithium aluminum titanium phosphate coating, 5-polyimide base film;

[0019] Figure 2 These are the cycle stability test results of the batteries prepared in Example 3 and Comparative Example 3. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0022] I. Preparation Method

[0023] Example 1

[0024] This embodiment provides a polyimide / lithium aluminum titanium phosphate composite battery separator, such as Figure 1 As shown, it includes a polyimide-based film 5 and a lithium aluminum titanium phosphate coating 4 located on one side of the base film. The polyimide-based film 5 includes a polyimide matrix 1 and lithium aluminum titanium phosphate (LATP) particles 2 embedded in the matrix.

[0025] The polyimide-based film 5 has the following characteristics: a thickness of 9 μm, a pore structure 3, a porosity of 30%, and an LATP particle size D50 of 0.1 μm.

[0026] The lithium aluminum titanium phosphate coating has the following characteristics: a thickness of 0.5 μm and a D50 size of 0.3 μm for LATP particles in the coating.

[0027] A method for preparing a polyimide / lithium aluminum titanium phosphate composite battery separator includes the following steps:

[0028] S1. Weigh p-phenylenediamine and pyromellitic dianhydride according to a molar ratio of 1:2. Then, under nitrogen protection, fully dissolve p-phenylenediamine in dehydrated N-methylpyrrolidone to obtain a first mixed solution. After cooling the first mixed solution to 7°C, add pyromellitic dianhydride to obtain a second mixed solution. Gradually heat the second mixed solution and control the temperature at 15°C. After reacting for 20 minutes, obtain a polyamic acid solution. In the polyamic acid solution, the mass fraction of N-methylpyrrolidone is 90 wt%, and the total mass fraction of other substances is 10 wt%.

[0029] S2. Add dried and dehydrated LATP particles with a size D50 of 0.1 μm to the polyamic acid solution, wherein the amount of LATP added is 3% of the mass of polyamic acid. After thorough stirring and uniform dispersion, a polyamic acid / LATP particle blend slurry is obtained.

[0030] S3. At an ambient temperature of 15°C, the polyamic acid / LATP particle blend slurry is first cooled to 15°C, and then uniformly flowed onto a horizontal conveyor membrane with a conveying speed of 20 m / min. The thickness of the polyamic acid / LATP particle blend slurry on the horizontal conveyor membrane is controlled to be 60 μm to obtain a polyamic acid / LATP particle blend wet membrane.

[0031] S4. The polyamic acid / LATP particle blend wet membrane was sequentially passed through 10 coagulation baths. The first three coagulation baths contained N-methylpyrrolidone deionized water with mass percentage concentrations of 60wt%, 45wt%, and 10wt%, respectively. The fourth to tenth coagulation baths contained deionized water. The sequential passage of the polyamic acid / LATP particle blend wet membrane through different coagulation baths achieved phase separation. It was then dried to obtain the membrane precursor. The drying process consisted of three stages: the first stage had a drying temperature of 40℃, an exhaust frequency of 13Hz, an inlet frequency of 14Hz, and a drying time of 10s; the second stage had a drying temperature of 50℃, an exhaust frequency of 15Hz, an inlet frequency of 16Hz, and a drying time of 10s; and the third stage had a drying temperature of 60℃, an exhaust frequency of 15Hz, an inlet frequency of 16Hz, and a drying time of 10s.

[0032] S5. The diaphragm precursor is sequentially passed through a preheating roller with a diameter of 500 mm, two heating rollers, and a cooling roller for high-temperature dehydration to obtain a polyimide-based film with a thickness of 9 μm. The temperature of the preheating roller is 50℃, the temperature of the heating roller is 100℃, and the temperature of the cooling roller is 30℃.

[0033] S6. Ten parts of LATP powder with a D50 of 0.3 μm, two parts of binder, 0.1 parts of dispersant, 0.2 parts of wetting agent, and 0.2 parts of thickener are uniformly dispersed in 87.5 parts of deionized water to prepare a lithium titanium aluminum phosphate coating slurry. The slurry is then coated onto the upper surface of a polyimide-based film using a microgravure plate. After drying, a stable lithium titanium aluminum phosphate coating with a thickness of 0.5 μm is formed, resulting in a polyimide / lithium titanium aluminum phosphate composite battery separator.

[0034] Example 2

[0035] This embodiment provides a polyimide / lithium aluminum titanium phosphate composite battery separator, including a polyimide base film and a lithium aluminum titanium phosphate coating located on one side surface of the base film. The polyimide base film includes a polyimide matrix and lithium aluminum titanium phosphate (LATP) particles embedded in the matrix.

[0036] The polyimide-based film has the following characteristics: a thickness of 20 μm and a porosity of 60%. The LATP particle size is 0.3 μm.

[0037] The lithium aluminum titanium phosphate coating has the following characteristics: a thickness of 4 μm and a LATP particle size of 1 μm in the coating.

[0038] A method for preparing a polyimide / lithium aluminum titanium phosphate composite battery separator includes the following steps:

[0039] S1. Weigh p-phenylenediamine and pyromellitic dianhydride according to a molar ratio of 1:2. Then, under nitrogen protection, fully dissolve p-phenylenediamine in dehydrated N-methylpyrrolidone to obtain a first mixed solution. After cooling the first mixed solution to 12°C, add pyromellitic dianhydride to obtain a second mixed solution. Gradually heat the second mixed solution and control the temperature at 20°C. After reacting for 30 minutes, obtain a polyamic acid solution. In the polyamic acid solution, the mass fraction of N-methylpyrrolidone is 95 wt%, and the total mass fraction of other substances is 5 wt%.

[0040] S2. Add dried LATP particles with a size D50 of 0.3 μm to the polyamic acid solution. After thorough stirring and uniform dispersion, a polyamic acid / LATP particle blend slurry is obtained.

[0041] S3. At an ambient temperature of 20°C, the polyamic acid / LATP particle blend slurry is first cooled to 20°C, and then it is uniformly flowed onto a horizontal conveyor membrane with a conveying speed of 30 m / min. The thickness of the polyamic acid / LATP particle blend slurry on the horizontal conveyor membrane is controlled to obtain a polyamic acid / LATP particle blend wet membrane.

[0042] S4. The polyamic acid / LATP particle blend wet membrane was sequentially passed through 15 coagulation baths. The first three coagulation baths contained N-methylpyrrolidone deionized water with mass percentage concentrations of 70wt%, 55wt%, and 20wt%, respectively. The fourth to tenth coagulation baths contained deionized water. The sequential passage of the polyamic acid / LATP particle blend wet membrane through different coagulation baths achieved phase separation. It was then dried to obtain the membrane precursor. The drying process consisted of three stages: the first stage had a drying temperature of 50℃, an exhaust frequency of 20Hz, an inlet frequency of 20Hz, and a drying time of 15s; the second stage had a drying temperature of 60℃, an exhaust frequency of 20Hz, an inlet frequency of 20Hz, and a drying time of 15s; and the third stage had a drying temperature of 70℃, an exhaust frequency of 20Hz, an inlet frequency of 20Hz, and a drying time of 15s.

[0043] S5. The diaphragm precursor is sequentially passed through a preheating roller with a diameter of 500 mm, two heating rollers, and a cooling roller for high-temperature dehydration to obtain a polyimide-based film with a thickness of 20 μm. The temperature of the preheating roller is 60℃, the temperature of the heating roller is 110℃, and the temperature of the cooling roller is 50℃.

[0044] S6. 30 parts of LATP powder with a D50 of 1 μm, 5 parts of binder, 1 part each of dispersant, wetting agent, and thickener are uniformly dispersed in 74 parts of deionized water to prepare a lithium titanium aluminum phosphate coating slurry. The slurry is then coated onto the surface of a polyimide-based film using a microgravure plate. After drying, a stable lithium titanium aluminum phosphate coating with a thickness of 4 μm is formed, resulting in a polyimide / lithium titanium aluminum phosphate composite battery separator.

[0045] Example 3

[0046] This embodiment provides a polyimide / lithium aluminum titanium phosphate composite battery separator, including a polyimide base film and a lithium aluminum titanium phosphate coating located on one side surface of the base film. The polyimide base film includes a polyimide matrix and lithium aluminum titanium phosphate (LATP) particles embedded in the matrix.

[0047] The polyimide-based film has the following characteristics: a thickness of 14 μm, a porous structure, a porosity of 45%, and an LATP particle size D50 of 0.2 μm.

[0048] The lithium aluminum titanium phosphate coating has the following characteristics: a thickness of 2 μm and a D50 of 0.5 μm for LATP particles in the coating.

[0049] A method for preparing a polyimide / lithium aluminum titanium phosphate composite battery separator includes the following steps:

[0050] S1. Weigh p-phenylenediamine and pyromellitic dianhydride according to a molar ratio of 1:2. Then, under nitrogen protection, fully dissolve p-phenylenediamine in dehydrated N-methylpyrrolidone to obtain a first mixed solution. After cooling the first mixed solution to 10°C, add pyromellitic dianhydride to obtain a second mixed solution. Gradually heat the second mixed solution and control the temperature at 17°C. After reacting for 25 minutes, obtain a polyamic acid solution. In the polyamic acid solution, the mass fraction of N-methylpyrrolidone is 92 wt%, and the total mass fraction of other substances is 8 wt%.

[0051] S2. Add dried LATP particles with a particle size D50 of 0.2 μm to the polyamic acid solution. After thorough stirring and uniform dispersion, a polyamic acid / LATP particle blend slurry is obtained.

[0052] S3. At an ambient temperature of 17°C, the polyamic acid / LATP particle blend slurry is first cooled to 17°C, and then it is uniformly flowed onto a horizontal conveyor membrane with a conveying speed of 25 m / min. The thickness of the polyamic acid / LATP particle blend slurry on the horizontal conveyor membrane is controlled to obtain a polyamic acid / LATP particle blend wet membrane.

[0053] S4. The polyamic acid / LATP particle blend wet membrane was sequentially passed through 12 coagulation baths. The first three coagulation baths contained N-methylpyrrolidone deionized water with mass percentage concentrations of 65wt%, 48wt%, and 15wt%, respectively. The fourth to tenth coagulation baths contained deionized water. The sequential passage of the polyamic acid / LATP particle blend wet membrane through these different coagulation baths achieved phase separation. It was then dried to obtain the membrane precursor. The drying process consisted of three stages: the first stage had a drying temperature of 45℃, an exhaust frequency of 16Hz, an inlet frequency of 17Hz, and a drying time of 13s; the second stage had a drying temperature of 55℃, an exhaust frequency of 16Hz, an inlet frequency of 18Hz, and a drying time of 12s; and the third stage had a drying temperature of 65℃, an exhaust frequency of 18Hz, an inlet frequency of 18Hz, and a drying time of 14s.

[0054] S5. The diaphragm precursor is sequentially passed through a preheating roller with a diameter of 560 mm, two heating rollers, and a cooling roller for high-temperature dehydration to obtain a polyimide-based film with a thickness of 14 μm. The temperature of the preheating roller is 55℃, the temperature of the heating roller is 105℃, and the temperature of the cooling roller is 40℃.

[0055] S6. 15 parts of LATP powder with a D50 of 0.5 μm, 2.5 parts of BASF S400 binder, 0.2 parts of BASF Ultra PX 4580 dispersant, 0.3 parts of Evonik Wet 270 wetting agent, and 0.3 parts of sodium carboxymethyl cellulose thickener are uniformly dispersed in 81.7 parts of deionized water to prepare a lithium titanium aluminum phosphate coating slurry. The slurry is then coated onto the upper surface of a polyimide-based membrane using a microgravure plate. After drying, a stable lithium titanium aluminum phosphate coating with a thickness of 2 μm is formed, resulting in a polyimide / lithium titanium aluminum phosphate composite battery separator.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 3 is that the polyimide / lithium titanium aluminum phosphate composite battery separator only includes the polyimide base film and does not include the lithium titanium aluminum phosphate coating located on one side of the base film. Otherwise, it is the same as Example 3.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 3 is that the polyimide-based membrane of the polyimide / lithium aluminum titanium phosphate composite battery separator only includes the polyimide matrix and does not include lithium aluminum titanium phosphate (LATP) particles embedded in the matrix; otherwise, it is the same as Example 3.

[0060] Comparative Example 3

[0061] This comparative example provides a PE / alumina composite separator, comprising a PE base film and an alumina ceramic coating on one side surface of the base film. The PE base film is a commercially available wet-process biaxially oriented polyolefin separator with a thickness of 12 μm and a porosity of 45%. The alumina particles in the ceramic coating have a size of 700 nm and a coating thickness of 3 μm.

[0062] II. Testing Methods

[0063] The performance of the composite membranes prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The specific test items and methods are as follows:

[0064] 1. Diaphragm thickness: Tested using a Malvern thickness gauge.

[0065] 2. Membrane air permeability: Tested using the Wang Yan-style air permeability method (Gurley method).

[0066] 3. Thermal shrinkage rate of the diaphragm: Refer to GB / T 36363 for testing.

[0067] 4. Diaphragm rupture temperature: TMA thermomechanical method

[0068] 5. Ionic conductivity of the diaphragm: Tested according to GB / T 36363

[0069] 6. Battery Capacity Retention Rate: Lithium-ion batteries were prepared by stacking, assembling, baking, electrolyte injection, and formation of the composite separators prepared in Examples 1-3 and Comparative Examples 1-3 together with the positive and negative electrode sheets. The lithium titanium aluminum phosphate coating in the polyimide / lithium titanium aluminum phosphate composite battery separator and the ceramic coating in the PE / alumina composite separator both faced the lithium metal negative electrode. The positive electrode active material was lithium nickel cobalt manganese oxide (NCM). Other components of the positive electrode sheet were determined according to conventional battery chemistry systems. The negative electrode material was lithium metal. The electrolyte composition included solvent, lithium salt (lithium hexafluorophosphate), and additives, with specific components determined according to conventional battery chemistry systems. The battery structure was a square pouch cell with a capacity of 5 Ah. The prepared batteries were subjected to a 25°C room temperature cycling test with a charge / discharge rate of 1C to test the battery capacity retention rate.

[0070] III. Test Results

[0071] The performance test results of the composite membranes prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0072] Table 1. Performance test results of composite separators and batteries in the examples and comparative examples.

[0073]

[0074] Note: In Comparative Example 3, the battery assembled with a PE / alumina composite membrane as the separator developed lithium dendrites leading to an internal short circuit after 110 cycles, resulting in a sharp drop in capacity retention (see...). Figure 2 The test was stopped due to safety concerns.

[0075] As shown in Table 1, the thickness and air permeability of the polyimide / lithium aluminum titanium phosphate composite battery separator prepared in this application are not significantly different from those of Comparative Example 3, but the heat resistance is significantly improved, and it also has a high ionic conductivity.

[0076] From Table 1 and Figure 2 It can be seen that the lithium metal battery assembled with the polyimide / lithium titanium aluminum phosphate composite battery separator prepared in Example 3 exhibits excellent cycle performance, retaining more than 99% of its capacity even after 300 cycles. However, as shown in Table 1, the lithium metal batteries assembled with the polyimide / lithium titanium aluminum phosphate composite battery separators prepared in Comparative Examples 1 and 2 cannot achieve optimal battery cycle performance when lacking a lithium titanium aluminum phosphate coating or lithium titanium aluminum phosphate (LATP) particles embedded in the substrate. This is because the synergistic effect of the 0.5-4 μm thick lithium titanium aluminum phosphate coating and the lithium titanium aluminum phosphate particles with a D50 of 0.1-0.3 μm embedded in the substrate improves the separator's ability to suppress lithium dendrite growth. Therefore, the polyimide / lithium titanium aluminum phosphate composite battery separator of this application can improve the cycle stability of lithium metal batteries.

[0077] 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 a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0079] The present invention has been illustrated with the above embodiments to describe the detailed process flow of the present invention. However, the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyimide / lithium aluminum titanium phosphate composite battery separator, characterized in that, The invention includes a polyimide-based film and a lithium titanium aluminum phosphate coating on one surface of the polyimide-based film. The polyimide-based film includes a polyimide matrix and lithium titanium aluminum phosphate particles with a size D50 of 0.1-0.3 μm embedded in the polyimide matrix. The thickness of the lithium titanium aluminum phosphate coating is 0.5-4 μm.

2. The polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 1, characterized in that, The polyimide-based film has a thickness of 9-20 μm.

3. The polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 1, characterized in that, The polyimide-based film has a porous structure with a porosity of 30-60%.

4. The polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 1, characterized in that, The size D50 of the lithium titanium aluminum phosphate particles embedded in the polyimide matrix is ​​0.1 μm.

5. The polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 1, characterized in that, The thickness of the lithium titanium aluminum phosphate coating is 0.5 μm.

6. The polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 1, characterized in that, The lithium titanium aluminum phosphate coating contains lithium titanium aluminum phosphate particles, and the particle size D50 is 0.3-1μm.

7. A method for preparing the polyimide / lithium aluminum titanium phosphate composite battery separator according to any one of claims 1-6, characterized in that, The process includes the following steps: preparing a polyamic acid solution by dissolving p-phenylenediamine and pyromellitic dianhydride in a solvent at a molar ratio of 1:1-3; adding lithium titanium aluminum phosphate to the polyamic acid solution and mixing evenly to obtain a polyamic acid / lithium titanium aluminum phosphate blend slurry; forming a film of the polyamic acid / lithium titanium aluminum phosphate blend slurry on a plane to obtain a polyamic acid / lithium titanium aluminum phosphate blend wet film; solidifying, drying, and dehydrating the polyamic acid / lithium titanium aluminum phosphate blend wet film at high temperature to obtain a polyimide-based film; coating a surface of the polyimide-based film with a lithium titanium aluminum phosphate coating slurry and drying to obtain a polyimide / lithium titanium aluminum phosphate composite battery separator.

8. The method for preparing the polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 7, characterized in that, The lithium titanium aluminum phosphate coating slurry includes lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water.

9. The method for preparing the polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 8, characterized in that, The mass ratio of lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water is 10-30:2-5:0.1-0.3:0.2-0.4:0.2-0.3:74-88.

10. The method for preparing the polyimide / lithium aluminum titanium phosphate composite battery separator as described in claim 9, characterized in that, The mass ratio of lithium titanium aluminum phosphate, binder, dispersant, wetting agent, thickener, and deionized water is 15:2.5:0.2:0.3:0.3:81.7.

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