A high-heat-resistant battery separator and a method for preparing the same

Abstract

The application discloses a high-heat-resistance battery diaphragm and a preparation method thereof, and relates to the technical field of lithium ion battery diaphragms. The high-heat-resistance battery diaphragm comprises the following components in a mass ratio: 40-60 parts of a heat-resistant polymer matrix, 20-40 parts of inorganic heat-resistant fillers, 5-15 parts of pore-forming agents, 3-10 parts of toughening agents, 2-10 parts of stabilizers and 0.5-5 parts of coupling agents. The synergistic effect of the stabilizers with specific structures and the formula can significantly enhance the high-temperature resistance of the diaphragm, inhibit high-temperature deformation and thermal degradation, and greatly improve the flame retardancy. The synergistic effect of the stabilizers and the coupling agents improves the dispersibility of the inorganic fillers, and the reasonable proportioning of the pore-forming agents and the toughening agents forms a more uniform through-pore structure, thereby significantly improving the porosity and the liquid absorption rate. While maintaining high heat resistance, the application avoids the problems of mechanical strength reduction or ion channel blockage caused by traditional modification techniques, and realizes the synchronous optimization of heat resistance, electrolyte wettability and mechanical flexibility.

Description

Technical Field

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

[0002] With the rapid development of new energy technologies, lithium-ion batteries, as efficient and rechargeable energy storage devices, have been widely used in electric vehicles, energy storage systems, and consumer electronics. However, battery safety and reliability remain key factors restricting their further development. The battery separator, as a crucial component of lithium-ion batteries, plays a vital role in battery performance, safety, and lifespan.

[0003] Traditional battery separators typically use polyolefin materials, such as polypropylene (PP) and polyethylene (PE), which possess good chemical stability and a certain level of mechanical strength. However, under high-temperature environments, polyolefin separators are prone to shrinkage, deformation, and even melting, leading to internal short circuits within the battery. This can trigger thermal runaway, causing battery fires, explosions, and other safety accidents, seriously threatening the lives and property of users. Furthermore, polyolefin separators have limited oxidation resistance, making it difficult to meet the stringent requirements of high-energy-density batteries during charge and discharge processes.

[0004] During the development of high-energy-density batteries, the redox reactions inside the battery become more intense, generating more heat and oxidizing substances. The separator needs to possess higher heat resistance and oxidation resistance to maintain the stability of the battery's internal structure and ensure unobstructed lithium-ion transport channels. Simultaneously, with the continuous expansion of battery applications, such as fast charging of electric vehicles, operation in high-temperature environments, and long-term charge-discharge cycles in energy storage systems, the comprehensive performance requirements for battery separators are becoming increasingly stringent.

[0005] Currently, industry research on improving the heat resistance and oxidation resistance of battery separators mainly focuses on material modification and composite technologies. For example, adding inorganic heat-resistant fillers to a polyolefin matrix can improve the heat resistance of the separator, while surface coating technology can enhance its oxidation resistance. However, existing technologies still have many shortcomings: on the one hand, some modification methods are complex and costly, making large-scale industrial production difficult; on the other hand, some composite separators, while improving one performance, often lead to a decline in other properties, such as reduced mechanical strength and lithium-ion conductivity, failing to achieve a performance balance and thus limiting their widespread application in high-end battery fields.

[0006] Therefore, developing a battery separator with high heat resistance and oxidation resistance, excellent comprehensive performance, and suitable for large-scale production, as well as its preparation method, has become a key issue that urgently needs to be addressed in the field of battery separator technology. It is of great practical significance for promoting the sustainable development of the new energy industry. Summary of the Invention

[0007] The purpose of this invention is to provide a battery separator with high heat resistance and oxidation resistance, while taking into account both mechanical strength and ionic conductivity, so as to solve the performance degradation problem of existing separators under high temperature and oxidation environment, and improve the safety and service life of the battery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a high heat-resistant battery separator, comprising the following components in the indicated mass ratios: heat-resistant polymer matrix: 40-60 parts, inorganic heat-resistant filler: 20-40 parts, pore-forming agent: 5-15 parts, toughening agent: 3-10 parts, stabilizer: 2-10 parts, coupling agent: 0.5-5 parts; The stabilizer is a compound represented by Formula 1; Formula 1; R1 is selected from: methyl, ethyl, propyl, tert-butyl, phenyl, methoxy.

[0009] Furthermore, the heat-resistant polymer matrix is ​​selected from polyimide or polyetheretherketone.

[0010] Furthermore, the inorganic heat-resistant filler is selected from alumina and / or silica, with an average particle size range of 50-500 nm.

[0011] Furthermore, the pore-forming agent is selected from polyethylene glycol or polyvinylpyrrolidone.

[0012] Furthermore, the toughening agent is selected from dioctyl phthalate.

[0013] Furthermore, the stabilizer is selected from any one of the compounds shown in the following structures: ; .

[0014] Furthermore, the method for synthesizing the stabilizer is as follows: ; Step 1: Raw material 1 and raw material 2 are synthesized into intermediate 1 via the Williamson reaction; Step 2: Intermediate 1 and raw material 3 are synthesized into a stabilizer via a Buchwald-Hartwig aromatic amination reaction.

[0015] Furthermore, the coupling agent is selected from γ-aminopropyltriethoxysilane.

[0016] A method for preparing a high heat-resistant battery separator includes the following steps: S1. Dissolve the heat-resistant polymer matrix in a solvent at 80-100°C to form a 10-20% (w / w) adhesive solution; S2. Add inorganic heat-resistant filler, pore-forming agent, toughening agent, stabilizer and coupling agent to the adhesive solution, and homogenize and disperse to obtain coating slurry; S3. The coating slurry is coated onto the substrate and dried to form a film; S4. After extracting the pore-forming agent, the membrane is dried to obtain a high heat-resistant battery separator.

[0017] Furthermore, the solvent is N-methylpyrrolidone.

[0018] Furthermore, the homogenization and dispersion are performed using a shear emulsifier at 1500-2000 rpm for 0.5-2 hours.

[0019] Furthermore, the drying temperature is 80-150℃, and the drying time is 1-3 hours.

[0020] Furthermore, the solvent for extraction is deionized water or ethanol, and the extraction time is 10-30 min.

[0021] The stabilizer described in this invention comprises a rigid aromatic ring and electron-donating groups in its molecular structure. The phenolic hydroxyl groups and / or nitrogen-containing heterocyclic structures in the molecular structure can provide hydrogen atoms, quenching free radicals generated during battery charging and discharging, and interrupting the oxidation chain reaction. Steric hindrance groups (such as tert-butyl and phenyl) slow down the molecular chain breakage of the polymer matrix at high temperatures through steric hindrance, inhibiting the thermal degradation of the separator. The polar groups in the stabilizer form hydrogen bonds with the surface of the inorganic filler, and through the synergistic effect of the coupling agent, achieve the following: reduced filler agglomeration and improved dispersion uniformity; strengthened the filler-polymer interfacial bonding force, preventing separator structural failure caused by interfacial peeling at high temperatures. The low oxidation potential of the stabilizer preferentially causes passivation reactions on the electrode surface, forming a stable solid electrolyte interfacial film, reducing electrolyte side reactions, and extending battery cycle life.

[0022] The heat-resistant polymer matrix described in this invention provides a rigid framework with a glass transition temperature far exceeding that of traditional polyolefins. As a continuous phase, it supports the stability of the membrane structure and resists high-temperature deformation. The inorganic heat-resistant filler inhibits heat conduction through physical barriers, reducing the risk of melting. It forms hydrogen bonds with the polar groups of the stabilizer, improving dispersibility. The coupling agent enhances the bonding with the polymer interface, preventing filler detachment at high temperatures. The stabilizer, containing phenolic hydroxyl groups / nitrogen-containing heterocyclic structures, provides triple protection: the phenolic hydroxyl groups capture free radicals generated during battery charging and discharging, interrupting the oxidation chain reaction; sterically hindered groups such as tert-butyl / phenyl groups shield the polymer backbone, inhibiting high-temperature chain breakage; the polar groups form a hydrogen bond network with the filler surface; and together with the coupling agent, they optimize the filler-matrix interface, reducing interfacial thermal stress failure. After hydrolysis, the siloxane groups of the coupling agent bond with the filler, bridging the inorganic filler and organic phase, improving interfacial compatibility at high temperatures. After extraction, the pore-forming agent and toughening agent form interconnected micropores, ensuring ionic conductivity; the plasticizing effect counteracts the brittleness caused by fillers, maintaining the flexibility of the membrane. The pores formed by the pore-forming agent work synergistically with the toughening agent to avoid ion channel blockage and mechanical property degradation caused by high filler content.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. Synergistic enhancement of thermal stability and flame retardancy: Through the synergistic effect of stabilizers with specific structures and formulations, the high-temperature resistance of the diaphragm is significantly enhanced, high-temperature deformation and thermal degradation are inhibited, and flame retardancy is greatly improved.

[0024] 2. Optimize pore structure and electrolyte wettability: The synergistic effect of stabilizers and coupling agents improves the dispersibility of inorganic fillers. Combined with the reasonable ratio of pore-forming agents and toughening agents, a more uniform through-pore structure is formed, which significantly improves porosity and liquid absorption rate.

[0025] 3. Breaking through the performance balance bottleneck: While maintaining high heat resistance, it avoids the problems of decreased mechanical strength or ion channel blockage caused by traditional modification techniques, and achieves simultaneous optimization of heat resistance, electrolyte wettability and mechanical flexibility. Attached Figure Description

[0026] Figure 1 The stabilizer 1 described in this invention 1 HNMR image.

[0027] Figure 2 This is the stabilizer synthesis method described in this invention. Detailed Implementation

[0028] 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.

[0029] Synthesis example 1 Synthesis of Stabilizer 1: ; Step 1: Under a nitrogen atmosphere, 20 g of raw material 1, 17.65 g of raw material 2, 0.07 g of pyridine-2-carboxylic acid, 0.6 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 with a mixture of petroleum ether and ethyl acetate as eluent to obtain 22.12 g of intermediate 1.

[0030] Step 2: Under a nitrogen atmosphere, add 22.45 g of intermediate 1, 23.95 g of starting material 3, 8.44 g of sodium tert-butoxide, 1.21 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 salts and catalysts. 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 29.91 g of stabilizer 1.

[0031] Product structure identification: MS[MS+1] of intermediate 1: 504; MS[MS+1] of stabilizer 1: 918; 1H NMR of stabilizer 1-deuterated chloroform- Figure 1: δ8.17(dd,2H),8.05(d,2H),7.87-7.79(m,1H),7.73(m,1H),7.68-7.55(m,6H),7.44-7.31(m,6H),7.23(m,2H),7.09(m,1H) ,6.94(dd,1H),6.39(p,1H),4.80(d,1H),4.56-4.48(m,1H),4.39(d,1H),4.06-3.55(m,9H),2.49(d,3H),1.07-1.00(m,9H).

[0032] Synthesis Example 2-Synthesis Example 6 Synthesis Examples 2-6 were used 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 Table 2.

[0033] Table 2. Structures of raw material 2, stabilizer 2 to stabilizer 6, and MS [MS+1] data involved in Synthesis Examples 2-6.

[0034]

[0035] Example 1 Preparation of a high heat-resistant battery separator: 1. Raw material mass ratio: 50 parts of heat-resistant polymer matrix (polyimide), 30 parts of inorganic heat-resistant filler (alumina, average particle size range 200 nm), 10 parts of pore-forming agent (polyethylene glycol), 5 parts of toughening agent (dioctyl phthalate), 5 parts of stabilizer (stabilizer 1 prepared in Synthesis Example 1), and 2 parts of coupling agent (γ-aminopropyltriethoxysilane). 2. Preparation method: S1. Add the heat-resistant polymer matrix to the reactor, add 400 parts of N-methylpyrrolidone (NMP) solvent, stir and dissolve at 90°C for 2 hours to form a 12.5% ​​mass concentration adhesive solution; S2. Add inorganic heat-resistant filler, pore-forming agent, toughening agent, stabilizer and coupling agent to the adhesive solution, and homogenize and disperse it at 1800 rpm for 1.5 hours using a shear emulsifier to obtain a uniform and stable coating slurry; S3. The coating slurry is coated onto a polyethylene terephthalate (PET) substrate, and the wet film thickness is controlled at 200 μm; it is then dried at 120°C for 2 hours to form an initial diaphragm. S4. Immerse the initial separator in deionized water and extract at room temperature for 20 minutes to remove the polyethylene glycol pore-forming agent; after removal, vacuum dry at 100°C for 1 hour to obtain the final high heat-resistant battery separator.

[0036] Examples 2-6 The preparation of a high heat-resistant 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.

[0037] Comparative Example 1 The preparation of a high heat-resistant battery separator is carried out according 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.

[0038] Comparative compound 1: .

[0039] Comparative Example 2 The preparation of a high heat-resistant battery separator is the same as in Example 1, except that no stabilizer is added.

[0040] Comparative Example 3 The preparation of a high heat-resistant battery separator is carried out by referring to the preparation method of Example 1, except that the mass fraction of the heat-resistant polymer matrix is ​​replaced with 65 parts, and the rest is the same as in Example 1.

[0041] Performance testing: 1. Porosity: The porosity of a high heat-resistant battery separator prepared in the examples and comparative examples was tested according to standard GB / T21650.2-2008.

[0042] 2. Liquid absorption rate test: The high heat-resistant 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.

[0043] 3. Limiting Oxygen Index: The limiting oxygen index of a high heat-resistant battery separator prepared in the examples and comparative examples was tested in accordance with standard JIS-K7201-3-2008.

[0044] The data is shown in Table 2.

[0045] Table 2. Porosity, liquid absorption rate, and limiting oxygen index data of a high heat-resistant battery separator prepared in the examples and comparative examples.

[0046]

[0047] The embodiments of the present invention exhibit significantly superior performance compared to the comparative examples in terms of porosity, liquid uptake, and limiting oxygen index. The embodiments generally demonstrate higher porosity and liquid uptake, while the comparative examples show significantly lower values. The limiting oxygen index of the embodiments is generally much higher than that of the comparative examples, indicating superior thermal stability. In the comparative examples, performance deteriorated across the board when no stabilizer was added or an ineffective stabilizer was used; adjusting the matrix ratio resulted in a sharp decrease in liquid uptake. This demonstrates that the stabilizer and formulation design of the present invention synergistically enhance the overall performance of the membrane, showing significant advantages in maintaining high porosity, electrolyte wettability, and flame retardancy.

[0048] 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 heat-resistant battery separator, characterized in that, It is composed of the following components in the indicated mass ratios: heat-resistant polymer matrix: 40-60 parts, inorganic heat-resistant filler: 20-40 parts, pore-forming agent: 5-15 parts, toughening agent: 3-10 parts, stabilizer: 2-10 parts, coupling agent: 0.5-5 parts; The stabilizer is a compound represented by Formula 1; Formula 1; R1 is selected from: methyl, ethyl, propyl, tert-butyl, phenyl, methoxy; The method for preparing a high heat-resistant battery separator includes the following steps: S1. Dissolve the heat-resistant polymer matrix in a solvent at 80-100°C to form a 10-20% (w / w) adhesive solution; S2. Add inorganic heat-resistant filler, pore-forming agent, toughening agent, stabilizer and coupling agent to the adhesive solution, and homogenize and disperse to obtain coating slurry; S3. The coating slurry is coated onto the substrate and dried to form a film; S4. After extracting the pore-forming agent, the membrane is dried to obtain a high heat-resistant battery separator.

2. The high heat-resistant battery separator according to claim 1, characterized in that, The heat-resistant polymer matrix is ​​selected from polyimide or polyetheretherketone.

3. The high heat-resistant battery separator according to claim 1, characterized in that, The inorganic heat-resistant filler is selected from alumina and / or silica, with an average particle size range of 50-500 nm.

4. The high heat-resistant battery separator according to claim 1, characterized in that, The pore-forming agent is selected from polyethylene glycol or polyvinylpyrrolidone.

5. A high heat-resistant battery separator according to claim 1, characterized in that, The toughening agent is selected from dioctyl phthalate.

6. The high heat-resistant battery separator according to claim 1, characterized in that, The stabilizer is selected from any one of the compounds shown in the following structures: ； 。 7. A high heat-resistant battery separator according to claim 1, characterized in that, The coupling agent is selected from γ-aminopropyltriethoxysilane.

8. A high heat-resistant battery separator according to claim 1, characterized in that, The solvent is N-methylpyrrolidone; the homogenization is performed using a shear emulsifier at 1500-2000 rpm for 0.5-2 hours.

9. A high heat-resistant battery separator according to claim 1, characterized in that, The drying temperature is 80-150℃, and the drying time is 1-3h; the extraction solvent is deionized water or ethanol, and the extraction time is 10-30min.

Images