A high-stability battery separator, its preparation method and application

Abstract

This invention discloses a high-stability battery separator, its preparation method, and its applications, relating to the field of lithium-ion battery separator technology. A high-stability battery separator is made from raw materials comprising the following parts by weight: a base polymer: 70-95 parts, an oxidation-resistant modified polymer: 5-30 parts, an inorganic filler: 30-70 parts, a plasticizer: 1-10 parts, a coupling agent: 0.5-5 parts, an antistatic agent: 0.1-3 parts, and a stabilizer: 3-5 parts. The stabilizer is a specific structural compound containing electron-rich nitrogen heterocycles and active substituents, which synergistically improves separator performance by quenching free radicals, complexing metal ions, and inhibiting polymer chain slippage. Compared with existing technologies, this invention significantly improves the separator porosity and electrolyte absorption capacity, and greatly enhances the limiting oxygen index, indicating superior ion transport efficiency and flame retardant safety. This separator is suitable for power batteries, energy storage batteries, and other fields, effectively improving battery high-temperature stability and service life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery separator technology, specifically to a high-stability battery separator, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are key energy storage devices in portable electronic devices, electric vehicles, and energy storage systems, and their performance and safety are of great concern. The battery separator, as a crucial component of lithium-ion batteries, plays a vital role in preventing short circuits between the positive and negative electrodes and allowing lithium ions to move freely, thus having a critical impact on the overall performance of the battery.

[0003] While existing battery separators have achieved some success, many problems remain to be solved. Traditional battery separator materials often struggle to balance stability and performance. For example, some separators are prone to shrinkage or deformation at high temperatures, leading to damage to the internal battery structure and posing safety risks such as short circuits, fires, or even explosions. Their chemical corrosion resistance also needs improvement. During battery charging and discharging, chemicals in the electrolyte may corrode the separator, affecting its integrity and function, and shortening the battery's lifespan.

[0004] Furthermore, existing separators also have limitations in mechanical properties. When batteries are subjected to external impacts or prolonged use, the separator is prone to damage, causing direct contact between the positive and negative electrodes and resulting in battery failure. At the same time, to meet the diverse performance requirements of batteries in different application scenarios, such as high energy density and rapid charging and discharging, the performance improvement of traditional separators has gradually reached a bottleneck, making it difficult to meet the ever-increasing market demand.

[0005] Therefore, developing a highly stable battery separator that can maintain good performance over a wider temperature range, in more complex chemical environments, and under more demanding mechanical conditions is of great practical significance for promoting the advancement of lithium-ion battery technology and improving its application effectiveness and safety in various fields. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a highly stable battery separator that possesses excellent high-temperature resistance, chemical corrosion resistance, and superior mechanical properties, thereby significantly improving battery safety and lifespan and meeting the requirements for stable operation under high temperature and complex working conditions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a high-stability battery separator, made from raw materials comprising the following parts by weight: base polymer: 70-95 parts, oxidation-resistant modified polymer: 5-30 parts, inorganic filler: 30-70 parts, plasticizer: 1-10 parts, coupling agent: 0.5-5 parts, antistatic agent: 0.1-3 parts, and stabilizer: 3-5 parts;

[0008] The stabilizer is a compound represented by Formula 1:

[0009] Formula 1;

[0010] R1 is selected from: methyl, ethyl, propyl, tert-butyl, phenyl, methoxy.

[0011] Furthermore, the substrate polymer is selected from polypropylene or polyethylene.

[0012] Furthermore, the oxidation-resistant modified polymer is polyvinylidene fluoride.

[0013] Furthermore, the inorganic filler is a mixture of alumina and titanium dioxide, with a mass ratio of (3-5):1.

[0014] Furthermore, the plasticizer is dioctyl phthalate; the coupling agent is γ-aminopropyltriethoxysilane.

[0015] Furthermore, the antistatic agent is potassium perfluorobutyl sulfonate.

[0016] Furthermore, the stabilizer is any one of the compounds shown in the following structures:

[0017]

[0018] .

[0019] Furthermore, the method for synthesizing the stabilizer is as follows:

[0020] ;

[0021] Step 1: Raw material 1 and raw material 2 are synthesized into intermediate 1 via the Williamson reaction;

[0022] Step 2: Intermediate 1 and raw material 3 are synthesized into a stabilizer via a Buchwald-Hartwig aromatic amination reaction.

[0023] A method for preparing a high-stability battery separator includes the following steps:

[0024] S1. Add the base polymer, oxidation-resistant modified polymer, inorganic filler, plasticizer, coupling agent and antistatic agent to a high-speed mixer and mix at 60-80℃ for 10-30 minutes to obtain a mixture;

[0025] S2. The mixture is melt-blended using a twin-screw extruder at an extrusion temperature of 180-220°C. The melt is then extruded through a T-die and cooled by a cooling roller to form a base film with a thickness of 100-300 μm.

[0026] S3. The base film is stretched longitudinally by 1-2 times at 80-100℃ and transversely by 2-4 times at 100-110℃ to obtain a stretched base film;

[0027] S4. The stretched base film is heat-set at 105°C for 20 seconds and then cooled to room temperature to obtain a high-stability battery separator.

[0028] Furthermore, the temperature of the cooling roller is 20-50°C.

[0029] Application of a high-stability battery separator in lithium-ion battery separators.

[0030] Furthermore, the high-stability battery separator is used as an isolation layer between the positive and negative electrodes in a lithium-ion battery.

[0031] Furthermore, the lithium-ion battery is a power battery, an energy storage battery, or a consumer electronics battery.

[0032] The stabilizer described in this invention contains electron-rich nitrogen heterocycles and active substituents. During battery charging and discharging, the electrolyte may decompose to generate highly reactive free radicals. The hydroxyl groups in the stabilizer can quench these free radicals and block the oxidation chain reaction. Simultaneously, the nitrogen atoms on the heterocycle can complex metal ions, inhibiting their catalytic oxidation reaction, thereby significantly improving the chemical corrosion resistance and high-temperature stability of the separator. The rigid aromatic ring structure and sterically hindered substituents in the stabilizer interact with the polymer chains of the substrate through π-π stacking and / or van der Waals forces, inhibiting molecular chain movement at high temperatures. Its bulky substituents (such as tert-butyl groups) can physically block polymer chain slippage, reducing thermal shrinkage of the separator at high temperatures. The polar groups in the stabilizer form hydrogen bonds or chemical bonds with the surface of the inorganic filler through coupling agents, improving the filler-polymer interface compatibility. This reduces interface defects and improves the mechanical strength of the separator. The sulfonate groups in potassium perfluorobutyl sulfonate may generate ion-dipole interactions with the nitrogen-containing heterocycles of the stabilizer, optimizing charge distribution and jointly maintaining the durability of the antistatic properties of the separator surface.

[0033] This invention significantly improves the overall performance of the battery separator through the synergistic effect of its components: the phenolic hydroxyl groups in the stabilizer quench electrolyte free radicals, the nitrogen heterocyclic complexes metal ions, and its rigid aromatic rings and sterically hindered substituents (such as tert-butyl groups) inhibit high-temperature slippage of polymer chains through π-π stacking and physical barrier, reducing thermal shrinkage; the strong CF bonds of the oxidation-resistant modified polymer (polyvinylidene fluoride) (PVDF) enhance chemical corrosion resistance and melt-interpenetrate with the substrate polymer (polypropylene / polyethylene) (PP / PE), improving thermal stability; In the mechanical filler (alumina / titanium dioxide) mixture, alumina provides a rigid framework to enhance mechanical strength, while titanium dioxide shields against ultraviolet light and delays electrolyte decomposition. γ-aminopropyltriethoxysilane coupling agent forms hydrogen bonds with the stabilizer through amino groups, and the siloxane groups condense with the inorganic filler, bridging the organic-inorganic interface and reducing defects. Potassium perfluorobutyl sulfonate antistatic agent's sulfonate groups generate ion-dipole interactions with the stabilizer's nitrogen heterocycles, synergistically maintaining long-lasting antistatic properties. Dioctyl phthalate plasticizer optimizes melt flowability and promotes uniform dispersion of components. Combined with a biaxial stretching process, a uniform microporous structure is formed, ultimately achieving high stability of the diaphragm under high temperature, chemical corrosion, and mechanical stress.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. Significantly improves membrane structure performance: In the example group with the addition of the stabilizer described in this invention, the porosity of the membrane shows an overall upward trend, which helps to form a better porous structure.

[0036] 2. Significantly enhances electrolyte affinity: The invention effectively improves the membrane's ability to absorb and retain electrolyte, which is beneficial for ion transport inside the battery.

[0037] 3. Effectively improves flame retardant safety: This invention significantly enhances the thermal stability and flame retardant properties of the separator, reducing the risk of battery combustion under extreme conditions. Attached Figure Description

[0038] Figure 1 The stabilizer 1 described in this invention 1 HNMR image.

[0039] Figure 2 This is a method for synthesizing the stabilizer described in this invention. Detailed Implementation

[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and 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.

[0041] Synthesis example 1

[0042] Synthesis of Stabilizer 1:

[0043] ;

[0044] Step 1: Under a nitrogen atmosphere, 20 g of starting material 1, 19.25 g of starting material 2, 0.07 g of pyridine-2-carboxylic acid, 0.5 g of CuI, 32.85 g of potassium phosphate trihydrate, and 250 g of DMSO were added to the reaction system. The mixture was heated to 85 °C and reacted for 16 h. After cooling, the reaction mixture was extracted with ammonia solution and methyl tert-butyl ether. The organic phase was washed five times with water and then twice with saturated NaCl solution. Finally, the combined organic phases were dried over anhydrous magnesium sulfate, evaporated to dryness, and subjected to silica gel column chromatography using a mixture of petroleum ether and ethyl acetate as eluent to obtain 22.45 g of intermediate 1. MS [MS+1]: 504.

[0045] Step 2: Under a nitrogen atmosphere, add 22.45 g of intermediate 1, 12.85 g of starting material 3, 8.83 g of sodium tert-butoxide, 1.26 g of tris(dibenzylacetone)dipalladium, 0.4 g of tri-tert-butylphosphine and 250 g of toluene to the reaction system. Stir until homogeneous, heat to 110 °C, and reflux for 12 h. After the reaction is complete, lower the temperature slightly, filter with diatomaceous earth to remove salt and catalyst. After cooling the filtrate to room temperature, wash three times with water, retain the organic phase, and then extract the aqueous phase with ethyl acetate. After combining the organic phases, dry with anhydrous magnesium sulfate, evaporate to dryness, and perform silica gel column chromatography with a mixture of petroleum ether and ethyl acetate as eluent to obtain 23.79 g of stabilizer 1.

[0046] Final product structure identification:

[0047] MS[MS+1]: 656;

[0048] Stabilizer 1 1 HNMR-deuterated chloroform- Figure 1 : δ8.17(dd,2H),8.05(d,2H),7.89(m,1H),7.75-7.49(m,5H),7.30(d,2H),7.11(m,1H),7.00(dd,1H ),6.78(d,1H),6.39(p,1H),4.96(d,2H),4.78-4.69(m,2H),4.64(dd,1H),3.63(t,1H),2.49(d,3H).

[0049] Synthesis Example 2-Synthesis Example 6

[0050] Synthesis Examples 2-6 were performed to synthesize stabilizer 2-stabilizer 6 sequentially, following the same synthesis method as Synthesis Example 1, except that raw material 2 was replaced, while the rest remained the same as in Synthesis Example 1. The specific structures of raw material 2, stabilizer 2-stabilizer 6, and MS[MS+1] data are shown in the table below.

[0051]

[0052] Synthesis example 1

[0053] Preparation of a high-stability battery separator:

[0054] 1. Raw material ratio (parts by mass): Base polymer: polypropylene (85 parts), oxidation-resistant modified polymer: polyvinylidene fluoride (15 parts), inorganic filler: alumina (56 parts) and titanium dioxide (14 parts), mass ratio 4:1, plasticizer: dioctyl phthalate (5 parts), coupling agent: γ-aminopropyltriethoxysilane (2 parts), antistatic agent: potassium perfluorobutyl sulfonate (1 part), stabilizer: stabilizer 1 prepared by synthesis example 1 (4 parts).

[0055] 2. Preparation method:

[0056] S1. Add polypropylene, polyvinylidene fluoride, alumina, titanium dioxide, dioctyl phthalate, γ-aminopropyltriethoxysilane, potassium perfluorobutyl sulfonate and stabilizer 1 to a high-speed mixer and mix at 70°C for 20 minutes to obtain a uniform mixture.

[0057] S2. Feed the mixture into a twin-screw extruder and set the extrusion temperature to 200℃. After the melt is extruded through a T-die, it is cooled and solidified by a cooling roller with the temperature controlled at 35℃ to form a base film with a thickness of 200μm.

[0058] S3. The base film is stretched longitudinally by 1.5 times at 90°C and then stretched transversely by 3 times at 105°C to obtain a stretched base film;

[0059] S4. The stretched base film is heat-set at 105℃ for 20s and then cooled to room temperature to obtain a high-stability battery separator.

[0060] Examples 2-6

[0061] The preparation of a high-stability battery separator is carried out by referring to the preparation method of Example 1, except that the stabilizers are replaced sequentially with stabilizers 2-6 prepared in Synthesis Examples 2-6, and the rest is the same as in Example 1.

[0062] Comparative Example 1

[0063] The preparation of a highly stable battery separator is carried out by referring to the preparation method of Example 1, except that the stabilizer is replaced with comparative compound 1, and the rest is the same as in Example 1.

[0064] Comparative compound 1: .

[0065] Comparative Example 2

[0066] The preparation of a highly stable battery separator follows the same method as in Example 1, except that no stabilizer is added.

[0067] Comparative Example 3

[0068] A high-stability battery separator was prepared by referring to the preparation method of Example 1, except that the mass fraction of the substrate polymer was replaced with 100 parts, and the rest remained the same as in Example 1.

[0069] Comparative Example 4

[0070] The preparation of a high-stability battery separator is carried out by referring to the preparation method of Example 1, except that the mass fraction of plasticizer is replaced with 15 parts, and the rest is the same as in Example 1.

[0071] Performance testing:

[0072] 1. Porosity: The porosity of a high-stability battery separator prepared in the examples and comparative examples was tested according to standard GB / T21650.2-2008.

[0073] 2. Liquid absorption rate test: The high-stability battery separator prepared in the examples and comparative examples was immersed in the electrolyte. After 2 hours, it was taken out and weighed. The liquid absorption rate was calculated based on the change in weight before and after. The electrolyte composition was: 1 mol / L LiPF6 ethylene carbonate and dimethyl carbonate solution, wherein the volume ratio of the solvent ethylene carbonate to dimethyl carbonate was 1:1.

[0074] 3. Limiting Oxygen Index: The limiting oxygen index of a high-stability battery separator prepared in the examples and comparative examples was tested in accordance with standard JIS-K7201-3-2008.

[0075] The data is shown in the table below.

[0076]

[0077] The example membrane significantly outperformed the comparative example in porosity, liquid uptake, and limiting oxygen index. Specifically, the example membrane exhibited higher overall porosity, stronger liquid uptake, and a higher limiting oxygen index, reflecting a comprehensive improvement in membrane structure, electrolyte affinity, and flame retardant properties. In contrast, all indicators of the comparative example showed a downward trend, indicating that the absence of stabilizers or formulation imbalances could lead to performance degradation. Overall, the data trends highlight the positive role of stabilizers in improving the overall performance of the membrane.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-stability battery separator, characterized in that, It is made from raw materials comprising the following parts by weight: base polymer: 70-95 parts, oxidation-resistant modified polymer: 5-30 parts, inorganic filler: 30-70 parts, plasticizer: 1-10 parts, coupling agent: 0.5-5 parts, antistatic agent: 0.1-3 parts, stabilizer: 3-5 parts; The stabilizer is a compound represented by Formula 1: Formula 1; R1 is selected from: methyl, ethyl, propyl, tert-butyl, phenyl, methoxy.

2. The high-stability battery separator according to claim 1, characterized in that, The substrate polymer is selected from polypropylene or polyethylene.

3. The high-stability battery separator according to claim 1, characterized in that, The oxidation-resistant modified polymer is polyvinylidene fluoride.

4. The high-stability battery separator according to claim 1, characterized in that, The inorganic filler is a mixture of alumina and titanium dioxide, with a mass ratio of (3-5):

1.

5. A high-stability battery separator according to claim 1, characterized in that, The plasticizer is dioctyl phthalate; the coupling agent is γ-aminopropyltriethoxysilane.

6. The high-stability battery separator according to claim 1, characterized in that, The antistatic agent is potassium perfluorobutyl sulfonate.

7. A high-stability battery separator according to claim 1, characterized in that, The stabilizer is any one of the compounds shown in the following structures: 。 8. A method for preparing a high-stability battery separator according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Add the base polymer, oxidation-resistant modified polymer, inorganic filler, plasticizer, coupling agent and antistatic agent to a high-speed mixer and mix at 60-80℃ for 10-30 minutes to obtain a mixture; S2. The mixture is melt-blended using a twin-screw extruder at an extrusion temperature of 180-220°C. The melt is then extruded through a T-die and cooled by a cooling roller to form a base film with a thickness of 100-300 μm. S3. The base film is stretched longitudinally by 1-2 times at 80-100℃ and transversely by 2-4 times at 100-110℃ to obtain a stretched base film; S4. The stretched base film is heat-set at 105°C for 20 seconds and then cooled to room temperature to obtain a high-stability battery separator.

9. The method for preparing a high-stability battery separator according to claim 8, characterized in that, The temperature of the cooling roller is 20-50℃.

10. The application of a high-stability battery separator according to any one of claims 1-7 in lithium-ion battery separators.

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