A hybrid glass fiber battery separator, method of making and system

Abstract

This invention provides a hybrid glass fiber battery separator, a separator manufacturing method, and a system, belonging to the field of battery separator manufacturing technology. Its main components are: biomimetic multi-level ultrafine glass fibers, core-shell hydrophobic fibers, composite nanofillers, and additives. The hybrid glass fiber separator, by employing core-shell hydrophobic fibers, solves the problem of insufficient aging and corrosion resistance of existing hydrophobic fibers, improving the separator's long-term acid resistance and mechanical strength, and extending the battery's cycle life. The addition of composite nanofillers improves the uneven dispersion of nanofillers, enhancing the separator's dry / wet puncture resistance and tensile strength, and improving high-temperature pore size stability. The biomimetic multi-level ultrafine glass fibers optimize porosity, increasing liquid absorption and oxygen diffusion efficiency. Combined with supercritical pulping and vacuum-hot pressing processes, the separator's performance consistency is ensured, thereby significantly improving the overall performance of the separator, adapting it to the harsh operating conditions of batteries, and enhancing battery operational reliability.

Description

Technical Field

[0001] This invention relates to the field of battery separator manufacturing technology, and in particular to a hybrid glass fiber battery separator, a separator manufacturing method and system. Background Technology

[0002] With the rapid expansion of new energy storage, electric vehicles, and emergency backup power, lead-acid batteries remain one of the mainstream energy storage and power sources in both industrial and civilian sectors due to their core advantages such as controllable cost, excellent safety performance, and stable rate discharge performance. The industry's technological development trend has clearly focused on the research and development of battery products with high cycle life and resistance to harsh operating conditions (high temperature environment, long-term acid corrosion, high load charging and discharging). The separator, as a key component that isolates the positive and negative electrodes and ensures electrolyte ion migration and gas recombination, directly determines the battery's internal resistance control, sealing efficiency, and long-term operational stability. Therefore, developing separators with excellent aging resistance, temperature resistance, uniform component dispersion, and structural stability has become the main technological direction for adapting lead-acid batteries to more demanding application scenarios and is also a key area for technological breakthroughs in the industry.

[0003] In the field of battery separator technology, existing technologies have gradually evolved from early single-glass fiber separators to multi-component hybrid fiber separators. For example, the invention patent with publication number CN102496689A proposes a mixed system of ultrafine glass fiber cotton, hydrophobic fiber materials, and fumed silica. By introducing hydrophobic fibers (such as polypropylene and polyethylene), the tensile strength and liquid absorption capacity of the separator are improved, while fumed silica enhances the puncture resistance of the separator in both dry and wet conditions. This improves to some extent the problems of insufficient porosity and easy decomposition and drift due to the expansion and contraction of the plates in traditional pure glass fiber separators. Currently, the industry generally adopts a process route of hydraulic pulping and vacuum dehydration molding. By adjusting the fiber component ratio and slurry concentration parameters, the basic performance of the separator can be controlled. Hybrid fiber separators have become the mainstream supporting components for mid-to-high-end lead-acid batteries.

[0004] However, existing hybrid fiber separator technology still has significant drawbacks, making it difficult to meet the industry's demand for high-reliability batteries. Specifically: First, the hydrophobic fibers lack sufficient aging and corrosion resistance. Existing technologies use single hydrophobic fibers such as polypropylene and polyethylene, which are prone to molecular chain degradation under long-term exposure to the acidic electrolyte environment inside the battery and temperature fluctuations during operation. This leads to a significant decrease in the mechanical strength of the separator over time, potentially causing short circuits in the battery's internal plates. Second, the nanofiller dispersion is poor. Current processes only achieve mixing of fumed silica and fibers through hydraulic crushing, resulting in nanoscale... Other types of fumed silica tend to agglomerate, forming blockages in the separator's pores or causing uneven mechanical strength, leading to fluctuations in battery performance. Thirdly, their temperature resistance is limited; existing fiber systems are prone to thermal shrinkage under high-temperature conditions (such as fast charging and high-load operation), resulting in smaller separator pores and affecting oxygen diffusion and gas recombination efficiency, making them unsuitable for high-temperature applications. Fourthly, their process stability is insufficient; the pH of the slurry during pulping is easily affected by fluctuations in the amount of sulfuric acid added, leading to decreased fiber dispersibility. Furthermore, the uneven porosity distribution of the separator after vacuum dehydration further affects the battery's internal resistance consistency and sealing performance. These defects severely restrict the application of lead-acid batteries in demanding scenarios, becoming a technological bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a hybrid glass fiber battery separator, a separator manufacturing method, and a system. By employing core-shell structured hydrophobic fibers, the problem of insufficient aging and corrosion resistance of existing hydrophobic fibers is solved, improving the long-term acid resistance and mechanical strength of the separator and extending the battery cycle life. By adding composite nanofillers, the uneven dispersion of nanofillers is improved, enhancing the dry / wet puncture resistance and tensile strength of the separator, and improving high-temperature pore size stability. The porosity is optimized through biomimetic multi-level ultrafine glass fibers, improving liquid absorption and oxygen diffusion efficiency. Combined with supercritical pulping and vacuum-hot pressing processes, the consistency of separator performance is ensured, thereby significantly improving the overall performance of the separator, adapting it to the harsh operating conditions of batteries, and improving battery operational reliability.

[0006] To achieve the above objectives, the present invention provides the following solution: One objective of this invention is to provide a hybrid glass fiber battery separator, disposed between each positive and negative electrode plate in a battery electrode group structure. The hybrid glass fiber battery separator comprises biomimetic multi-level ultrafine glass fibers, core-shell hydrophobic fibers, composite nanofillers, and additives. The biomimetic multi-level ultrafine glass fibers include primary fibers with a diameter of 0.6-0.9 μm, secondary fibers with a diameter of 1-2 μm, and tertiary fibers with a diameter of 3-4 μm. The core-shell hydrophobic fibers are composed of a core layer of polyolefin fibers and a shell layer of fluoropolymers containing acid-resistant additives and antioxidants. The composite nanofillers include modified fumed silica and montmorillonite nanosheets. The additives include dispersants and pH stabilizers.

[0007] Preferably, in the biomimetic multi-level ultrafine glass fiber, the primary fiber accounts for 60%-70% of the total mass of the separator, the secondary fiber accounts for 8%-12% of the total mass of the separator, and the tertiary fiber accounts for 18%-22% of the total mass of the separator; the core-shell structure hydrophobic fiber accounts for 14%-16% of the total mass of the hybrid glass fiber battery separator.

[0008] Preferably, the core layer of the core-shell hydrophobic fiber is a polyolefin fiber, which is polypropylene or polyethylene, with a diameter of 8-18 μm; the shell layer is a fluoropolymer, which is polyvinylidene fluoride or polytetrafluoroethylene, with a thickness of 0.8-2.2 μm; the acid-resistant additive is perfluorooctylphosphonic acid or perfluorohexylphosphonic acid; and the antioxidant is antioxidant 1010 or antioxidant 168.

[0009] Preferably, in the composite nanofiller, the modified fumed silica is modified with a silane coupling agent and has a particle size of 12-25 nm; the montmorillonite nanosheets have a particle size of 3-12 nm; the mass ratio of modified fumed silica to montmorillonite nanosheets is 2-4:1; and the composite nanofiller accounts for 0.5%-0.9% of the total mass of the mixed glass fiber battery separator.

[0010] Preferably, in the additives, the dispersant is polyethylene glycol 4000-8000, and the pH stabilizer is a citrate-sodium citrate buffer pair or an acetate-sodium acetate buffer pair; the additives account for 0.1%-0.3% of the total mass of the mixed glass fiber battery separator.

[0011] Preferably, the porosity of the hybrid glass fiber battery separator is 85%-92%, the tensile strength retention rate after soaking in sulfuric acid at 60°C for 1000 hours is not less than 90%, and the pore size retention rate at 80°C is not less than 92%.

[0012] The second objective of this invention is to provide a method for manufacturing the above-mentioned hybrid glass fiber battery separator, comprising the following steps: Prefabricated core-shell structure hydrophobic fiber: The core layer polyolefin fiber is surface activated, and the activated core layer fiber is immersed in a fluoropolymer solution containing acid-resistant additives and antioxidants. After coating and drying, the core-shell structure hydrophobic fiber is obtained. Supercritical synergistic pulping: Biomimetic multi-level ultrafine glass fiber, core-shell structured hydrophobic fiber, composite nanofiller and additives are added to a pulping device, and after pretreatment with supercritical fluid, water and sulfuric acid are added to adjust the pH of the pulp to 2.0-2.5, and the pulp is stirred and dispersed to obtain glass fiber pulp; Vacuum-hot pressing: After adjusting the concentration and flow rate, the glass fiber slurry is transported to the forming device, where it is first dehydrated by vacuum and then hot-pressed to form a separator paper with a humidity of 25%-35%. Modification and drying: The diaphragm paper is subjected to plasma surface modification and then dried until the moisture content is no more than 0.5%; Cutting: Cut the dried separator paper according to the battery specifications to obtain a mixed glass fiber battery separator.

[0013] Preferably, in the supercritical synergistic pulping process, the supercritical fluid is supercritical CO2, and the supercritical state parameters include: pressure of 20-25 MPa, temperature of 31-35℃, flow rate of 4-6 L / min, pretreatment time of 8-12 min, stirring speed of 1600-2000 rpm, and stirring time of 25-35 min.

[0014] Preferably, in the vacuum-hot pressing process, the vacuum degree for vacuum dehydration is -0.08 to -0.09 MPa, and the dehydration time is 1.5 to 2.5 min; the hot pressing temperature is 110 to 130°C, the pressure is 0.4 to 0.6 MPa, and the time is 0.8 to 1.2 min. During the modification and drying process, the plasma modification gas is oxygen or air, the power is 120-180W, the time is 2-4min, the drying temperature is 100-120℃, the wind speed is 2-4m / s, and the drying time is 25-35min.

[0015] A third objective of this invention is to provide a system for producing the aforementioned hybrid glass fiber battery separator, comprising a supercritical synergistic pulping unit, a pH-stabilized slurry storage unit, an online monitoring unit, a vacuum-hot pressing unit, a plasma-modified drying unit, a closed-loop white water recycling unit, and a slitting unit; the discharge end of the supercritical synergistic pulping unit is connected to the feed end of the pH-stabilized slurry storage unit for conveying the prepared glass fiber slurry to the storage unit; the discharge end of the pH-stabilized slurry storage unit is connected to the feed end of the vacuum-hot pressing unit, and the two are connected... An online monitoring unit is provided to detect the concentration and agglomerated particle size of the glass fiber pulp. The discharge end of the vacuum-hot pressing unit is connected to the feed end of the plasma-modified drying unit to transport the formed diaphragm paper to the modified drying unit. The vacuum-hot pressing unit is also connected to a closed-loop white water recycling unit to transport the white water generated during the production process to the closed-loop white water recycling unit for treatment and reuse. The discharge end of the plasma-modified drying unit is connected to a slitting unit to transport the dried diaphragm paper to the slitting unit for cutting.

[0016] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) This invention significantly improves the long-term aging and corrosion resistance of the battery separator, extending the battery cycle life. By using core-shell structured hydrophobic fibers, acid-resistant fluoropolymers (such as polyvinylidene fluoride) as the shell layer, and combining acid-resistant additives and antioxidants, a dual protection mechanism of physical barrier and chemical protection is formed: the shell layer fluoropolymer itself has excellent sulfuric acid corrosion resistance, which can block the electrolyte from directly contacting the core layer polyolefin fibers, avoiding acid-induced degradation of the fiber molecular chains; the antioxidant can inhibit the oxidative aging reaction of the fibers under high temperature conditions, reducing the attenuation of mechanical strength. This core-shell structure breaks through the limitation of insufficient corrosion resistance of existing single hydrophobic fibers, enabling the separator to maintain stable tensile strength under long-term acidic and high-temperature conditions, effectively avoiding the problem of short circuit of the plates caused by separator decomposition and drift, thereby significantly extending the cycle life of the battery.

[0017] (2) This invention optimizes the dispersion and pore structure of the membrane components, improves mechanical properties and ion migration efficiency, and achieves performance breakthroughs through the synergistic design of composite nanofillers and biomimetic multi-level ultrafine glass fibers: On the one hand, montmorillonite nanosheets in the composite nanofillers can be interspersed between modified fumed silica through a sheet-like structure, and the steric hindrance effect of the sheet space can be used to block the aggregation of silica nanoparticles, forming a uniform three-dimensional network support structure, which significantly improves the dry / wet puncture resistance and tensile strength of the membrane; On the other hand, the biomimetic multi-level ultrafine glass fibers imitate the multi-level channel design of plant leaf veins, and through the optimization of the gradation of fibers of different diameters, a continuous and uniform pore system is constructed, which not only ensures sufficient liquid absorption space to increase electrolyte storage, but also provides a smooth channel for the diffusion of oxygen from the positive electrode to the negative electrode, taking into account both ion migration efficiency and battery sealing performance, and avoiding battery performance fluctuations caused by local pore density or blockage.

[0018] (3) This invention enhances process stability and membrane temperature resistance, adapting to the demanding operating conditions of batteries. Through a combination of supercritical synergistic pulping, vacuum-hot pressing molding, and plasma modification, the entire chain from preparation to finished product performance is optimized: Supercritical fluid, with its high permeability and low surface tension, can loosen the initial agglomerates of fibers and fillers, ensuring uniform mixing of components during the pulping stage, thus solving the problem of insufficient dispersion in traditional hydraulic pulping; Vacuum-hot pressing synergistic molding, through a process logic of dehydration followed by densification, ensures high porosity of the membrane while allowing fibers to tightly bind together to form a stable structure, avoiding local density unevenness in the membrane after vacuum dehydration; Plasma modification forms micro-nano pits through surface etching, improving the hydrophilicity of the membrane to ensure electrolyte wettability without damaging the bonding structure of fibers and fillers. These process innovations not only improve the stability and consistency of membrane production but also endow the membrane with excellent temperature resistance. The synergistic effect of core-shell fibers and composite nanofillers at high temperatures can suppress pore shrinkage, ensuring that the diaphragm can maintain stable performance under harsh conditions such as fast charging and high load, and significantly improving the operational reliability of the battery. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0020] Figure 1 A schematic diagram of a hybrid glass fiber battery separator applied to a battery electrode group structure provided by the present invention; Figure 2 A flowchart of a manufacturing method for preparing a hybrid glass fiber battery separator provided by the present invention; Figure 3 This invention provides a system block diagram for producing hybrid glass fiber battery separators. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, this invention provides a hybrid glass fiber battery separator, disposed between each positive and negative electrode plate in a battery electrode group structure. The hybrid glass fiber battery separator comprises biomimetic multi-level ultrafine glass fibers, core-shell hydrophobic fibers, composite nanofillers, and additives. The biomimetic multi-level ultrafine glass fibers include primary fibers with a diameter of 0.6-0.9 μm, secondary fibers with a diameter of 1-2 μm, and tertiary fibers with a diameter of 3-4 μm. The core-shell hydrophobic fibers are composed of a core layer of polyolefin fibers and a shell layer of fluoropolymers containing acid-resistant additives and antioxidants. The composite nanofillers include modified fumed silica and montmorillonite nanosheets. The additives include dispersants and pH stabilizers.

[0024] According to the above, in the biomimetic multi-level ultrafine glass fiber, primary fibers account for 60%-70% of the total mass of the separator, secondary fibers account for 8%-12% of the total mass of the separator, and tertiary fibers account for 18%-22% of the total mass of the separator; the core-shell structure hydrophobic fiber accounts for 14%-16% of the total mass of the hybrid glass fiber battery separator. The core layer of the core-shell structure hydrophobic fiber is a polyolefin fiber, which is polypropylene or polyethylene, with a diameter of 8-18 μm; the shell layer is a fluoropolymer, which is polyvinylidene fluoride or polytetrafluoroethylene, with a thickness of 0.8-2.2 μm; the acid-resistant additive is perfluorooctylphosphonic acid or perfluorohexylphosphonic acid; and the antioxidant is antioxidant 1010 or antioxidant 168.

[0025] The fluoropolymer shell itself possesses excellent resistance to sulfuric acid corrosion, preventing direct contact between the electrolyte and the core polyolefin fibers and avoiding acid-induced degradation of the fiber molecular chains. Antioxidants inhibit the oxidative aging reaction of the fibers under high-temperature conditions, reducing mechanical strength degradation. This core-shell structure overcomes the limitations of existing single hydrophobic fibers in terms of corrosion resistance, enabling the separator to maintain stable tensile strength under long-term acidic and high-temperature conditions. This effectively avoids short-circuit problems caused by separator decomposition and drift, thus significantly extending the battery's cycle life.

[0026] According to the above, in the composite nanofiller, the modified fumed silica is modified with a silane coupling agent and has a particle size of 12-25 nm; the montmorillonite nanosheets have a particle size of 3-12 nm; the mass ratio of modified fumed silica to montmorillonite nanosheets is 2-4:1; and the composite nanofiller accounts for 0.5%-0.9% of the total mass of the mixed glass fiber battery separator.

[0027] On the one hand, montmorillonite nanosheets in the composite nanofiller can be interspersed between modified fumed silica through a sheet-like structure, utilizing the steric hindrance effect of the sheets to prevent the aggregation of silica nanoparticles, forming a uniform three-dimensional network support structure, which significantly improves the dry / wet puncture resistance and tensile strength of the separator. On the other hand, the biomimetic multi-level ultrafine glass fiber mimics the multi-level channel design of plant leaf veins. Through the optimization of the gradation of fibers with different diameters, a continuous and uniform pore system is constructed, which not only ensures sufficient liquid absorption space to increase electrolyte storage capacity, but also provides a smooth channel for oxygen diffusion from the positive electrode to the negative electrode, taking into account both ion migration efficiency and battery sealing performance, and avoiding battery performance fluctuations caused by local pore density or blockage.

[0028] Furthermore, in the additives, the dispersant is polyethylene glycol 4000-8000, and the pH stabilizer is a citrate-sodium citrate buffer pair or an acetate-sodium acetate buffer pair; the additives account for 0.1%-0.3% of the total mass of the mixed glass fiber battery separator. The porosity of the mixed glass fiber battery separator is 85%-92%, the tensile strength retention rate after soaking in sulfuric acid at 60℃ for 1000h is not less than 90%, and the pore size retention rate at 80℃ is not less than 92%.

[0029] like Figure 2 As shown, the present invention also provides a method for manufacturing the above-mentioned hybrid glass fiber battery separator, comprising the following steps: Step 100: Prefabrication of core-shell structured hydrophobic fiber: Surface activation of the core layer polyolefin fiber, immersion of the activated core layer fiber in a fluoropolymer solution containing acid-resistant additives and antioxidants, coating and drying to obtain core-shell structured hydrophobic fiber; Step 200, Supercritical Synergistic Pulping: Biomimetic multi-level ultrafine glass fiber, core-shell structure hydrophobic fiber, composite nanofiller and additives are added to the pulping device, and after pretreatment with supercritical fluid, water and sulfuric acid are added to adjust the pH of the slurry to 2.0-2.5, and the mixture is stirred and dispersed to obtain glass fiber slurry; Step 300, Vacuum-Hot Press Forming: After adjusting the concentration and flow rate, the glass fiber slurry is transported to the forming device, where it is first dehydrated by vacuum and then hot-pressed to form a membrane paper with a humidity of 25%-35%. Step 400, Modification and Drying: The diaphragm paper is subjected to plasma surface modification and then dried until the moisture content is no more than 0.5%; Step 500: Cutting: Cut the dried separator paper according to the battery specifications to obtain a mixed glass fiber battery separator.

[0030] In step 200 above, the supercritical fluid is supercritical CO2, and the supercritical state parameters include: pressure of 20-25 MPa, temperature of 31-35℃, flow rate of 4-6 L / min, pretreatment time of 8-12 min, stirring speed of 1600-2000 rpm, and stirring time of 25-35 min.

[0031] In step 300 above, the vacuum degree of vacuum dehydration is -0.08 to -0.09 MPa, and the dehydration time is 1.5 to 2.5 min; the temperature of hot pressing is 110 to 130℃, the pressure is 0.4 to 0.6 MPa, and the time is 0.8 to 1.2 min. In step 400 above, the plasma-modified gas is oxygen or air, the power is 120-180W, the time is 2-4min, the drying temperature is 100-120℃, the wind speed is 2-4m / s, and the drying time is 25-35min.

[0032] like Figure 3As shown, the present invention also provides a system for producing the above-mentioned hybrid glass fiber battery separator, comprising a supercritical synergistic pulping unit, a pH-stabilized slurry storage unit, an online monitoring unit, a vacuum-hot pressing unit, a plasma-modified drying unit, a closed-loop white water recycling unit, and a slitting unit; the discharge end of the supercritical synergistic pulping unit is connected to the feed end of the pH-stabilized slurry storage unit for conveying the prepared glass fiber slurry to the slurry storage unit; the discharge end of the pH-stabilized slurry storage unit is connected to the feed end of the vacuum-hot pressing unit, and a connection is provided between the two. An online monitoring unit is provided to detect the concentration and agglomerated particle size of the glass fiber pulp. The discharge end of the vacuum-hot pressing unit is connected to the feed end of the plasma-modified drying unit to transport the formed diaphragm paper to the modified drying unit. The vacuum-hot pressing unit is also connected to a closed-loop white water recycling unit to transport the white water generated during the production process to the closed-loop white water recycling unit for treatment and reuse. The discharge end of the plasma-modified drying unit is connected to a slitting unit to transport the dried diaphragm paper to the slitting unit for cutting.

[0033] The above content will be further explained below through specific implementation methods. The described embodiments are only some embodiments of the present invention.

[0034] Example 1 This embodiment provides a hybrid glass fiber battery separator, which is composed of the following components in the indicated mass percentages: Biomimetic multi-level ultrafine glass fiber: 84.1%, including primary fibers with a diameter of 0.6-0.9μm, secondary fibers with a diameter of 1-2μm, and tertiary fibers with a diameter of 3-4μm, with the three types of fibers accounting for 65%, 10%, and 19.1% of the mass, respectively; Core-shell structure hydrophobic fiber: 15.0%, with a core layer of 12μm diameter polypropylene fiber and a shell layer of 1.5μm thickness polyvinylidene fluoride, containing 0.8% antioxidant 1010 and 0.5% perfluorooctylphosphonic acid, and the addition of these two additives... All additions are calculated based on the shell mass; Composite nanofiller: 0.7%, including fumed silica modified with silane coupling agent KH-550 and montmorillonite nanosheets, wherein the particle size of the modified fumed silica is 15-20nm and accounts for 0.5% by mass, and the particle size of the montmorillonite nanosheets is 5-10nm and accounts for 0.2% by mass, with a mass ratio of 3:1; Additives: 0.2%, including polyethylene glycol 6000 and citric acid-sodium citrate buffer pair, with each additive accounting for 0.1% by mass.

[0035] The hybrid glass fiber battery separator in this embodiment utilizes... Figure 3 The hybrid glass fiber battery separator shown is prepared using the production system, and the specific steps are as follows: First, prefabricate the core-shell structured hydrophobic fiber: Take a 12μm diameter polypropylene fiber and place it in a plasma treatment instrument for surface activation. Set the activation power to 200W and the activation time to 5min. Prepare a 15% (w / w) polyvinylidene fluoride solution using N-methylpyrrolidone as the solvent. Add 0.8% antioxidant 1010 and 0.5% perfluorooctylphosphonic acid to the solution. The amount of both additives is calculated based on the mass of polyvinylidene fluoride. Stir until completely dissolved. Immerse the activated polypropylene fiber in the above polyvinylidene fluoride solution and coat it using the dip-coating method. Control the coating speed to 5mm / s. Then, place the coated fiber in an 80℃ vacuum drying oven and dry for 2h to obtain the core-shell structured hydrophobic fiber.

[0036] Next, supercritical co-processing was performed: Biomimetic multi-stage ultrafine glass fibers, pre-fabricated core-shell hydrophobic fibers, composite nanofillers, and additives were sequentially added to the supercritical co-processing unit of the system. After shutting down the supercritical co-processing unit, supercritical CO2 was introduced, and the supercritical state parameters were set to pressure 22 MPa, temperature 32℃, and flow rate 5 L / min for pretreatment for 10 min. After pretreatment, deionized water and sulfuric acid were added to the unit to adjust the pH of the slurry to 2.2. The stirring device in the unit was turned on, and the stirring speed was set to 1800 rpm. The supercritical state was maintained for stirring for 30 min to obtain glass fiber slurry. The slurry was monitored by the system's online monitoring unit. After confirming that the agglomerated particle size in the slurry was ≤5 μm, the glass fiber slurry was transferred to the system's pH-stabilized storage unit for temporary storage.

[0037] Then, vacuum-hot pressing co-forming is performed: the glass fiber slurry in the pH-stabilized slurry storage unit is transported to the slurry conditioning tank. After the concentration and flow rate are adjusted in the slurry conditioning tank, it is then transported to the long-wire machine of the vacuum-hot pressing forming unit of the system. First, the vacuum dewatering module of the vacuum-hot pressing forming unit is started, and the vacuum degree is set to -0.09MPa and the dewatering time is 2min to remove about 60% of the water in the slurry. Then, the hot pressing module of the unit is started, and the hot pressing temperature is set to 120℃, the hot pressing pressure is set to 0.5MPa, and the hot pressing time is 1min to form a membrane paper with a humidity of 30%.

[0038] Next, plasma modification and drying are carried out: the formed diaphragm paper is sent into the plasma modification and drying unit of the system. The diaphragm paper is first transported to the plasma modification chamber of the unit, and the modification gas is set to oxygen, the modification power is 150W, and the modification time is 3min to complete the surface modification. After the modification is completed, the diaphragm paper is transported to the hot air drying chamber of the unit, and the drying temperature is set to 110℃, the wind speed is 3m / s, and the drying time is 30min to control the final moisture content of the diaphragm paper to ≤0.5%.

[0039] Finally, the slitting and white water recycling processes are carried out: the dried separator paper is conveyed to the slitting unit of the system and cut into finished separators of 148mm×94mm according to the specifications of the 12V20Ah battery; at the same time, the white water generated in the vacuum-hot pressing unit during the forming process is conveyed to the closed-loop white water recycling unit of the system for treatment, and the treated recycled white water is conveyed back to the supercritical co-pulping unit for subsequent glass fiber pulp preparation.

[0040] Example 2 The difference from Example 1 is that the shell layer of the core-shell hydrophobic fiber is 1.0 μm thick with polyvinylidene fluoride, while the other components and processes are the same as in Example 1.

[0041] Example 3 The difference from Example 1 is that the modified fumed silica accounts for 0.4% and montmorillonite nanosheets account for 0.3% in the composite nanofiller, while the remaining components and processes are the same as in Example 1.

[0042] Comparative Example 1 This comparative example adopts the technical solution published under CN102496689A, which specifically includes the following: The membrane composition consists of: ultra-fine glass fiber cotton (0.6-0.9μm), polypropylene fiber (12μm in diameter), and fumed silica (unmodified, with a particle size of 15-20nm). The polypropylene fiber accounts for 15%, the fumed silica accounts for 0.7%, and the remainder is glass fiber. Manufacturing method: The pulping process is carried out using a hydraulic pulping machine (without supercritical treatment), vacuum dehydration molding (without hot pressing), and no plasma modification. The remaining processes are the same as those for conventional lead-acid membrane manufacturing.

[0043] The performance of the diaphragms in Examples 1-3 and Comparative Example 1 was tested below. The test items and results are shown in Table 1.

[0044] Table 1 Test Results

[0045] As can be seen from Table 1, the embodiments 1-3 provided by the present invention have the following characteristics compared with Comparative Example 1: Long-term aging resistance and corrosion resistance: In the core-shell structure of the hydrophobic fiber in the mixed glass fiber battery separators of Examples 1-3, the shell layer of fluoropolymer (such as polyvinylidene fluoride) forms a physical barrier, blocking the direct contact between sulfuric acid and the core layer polyolefin fiber. At the same time, the antioxidant inhibits oxidative aging. Therefore, the tensile strength retention rate after immersion in sulfuric acid at 60°C is significantly higher than that of Comparative Example 1. This is because the polypropylene fiber in Comparative Example 1 is directly corroded by acid, and the molecular chain is severely degraded.

[0046] Temperature resistance: The three-dimensional network support of the composite nanofiller and the thermal stability of the core-shell fiber work together to make the pore size retention rate of the mixed glass fiber battery separators in Examples 1-3 much higher than that in Comparative Example 1 at a high temperature of 80°C. This is because the conventional fiber in Comparative Example 1 has obvious thermal shrinkage, which leads to a sharp reduction in pore size.

[0047] Cycle life: The improved stability and corrosion resistance of the diaphragm structure effectively avoids plate short circuits and electrolyte loss, resulting in the cycle life of the batteries using the mixed glass fiber battery diaphragms in Examples 1-3 being nearly doubled compared to Comparative Example 1.

[0048] Dispersion uniformity: The high permeability of supercritical CO2 and the steric hindrance effect of composite nanofillers result in extremely low agglomeration rate of fumed silica in the mixed glass fiber battery separators of Examples 1-3, while in Comparative Example 1, which was only broken down by hydraulic means, the nanoparticles agglomerated severely, leading to fluctuations in separator performance.

[0049] In summary, the hybrid glass fiber battery separator, its manufacturing method, and system described above address the shortcomings of existing hydrophobic fibers in terms of aging and corrosion resistance by employing core-shell structured hydrophobic fibers. This improves the separator's long-term acid resistance and mechanical strength, extending the battery's cycle life. The addition of composite nanofillers improves the uneven dispersion of nanofillers, enhancing the separator's dry / wet puncture resistance and tensile strength, and improving high-temperature pore size stability. Biomimetic multi-level ultrafine glass fibers optimize porosity, increasing liquid absorption and oxygen diffusion efficiency. Combined with supercritical slurry preparation and vacuum-hot pressing processes, the consistency of separator performance is ensured. Therefore, the overall performance of the separator is significantly improved, making it suitable for harsh battery operating conditions and enhancing battery reliability.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0051] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A hybrid glass fiber battery separator, disposed between each positive and negative electrode plate in a battery electrode group structure, characterized in that, The hybrid glass fiber battery separator comprises biomimetic multi-level ultrafine glass fibers, core-shell hydrophobic fibers, composite nanofillers, and additives. The biomimetic multi-level ultrafine glass fibers include primary fibers with a diameter of 0.6-0.9 μm, secondary fibers with a diameter of 1-2 μm, and tertiary fibers with a diameter of 3-4 μm. The core-shell hydrophobic fibers are composed of a core layer of polyolefin fibers and a shell layer of fluoropolymers containing acid-resistant additives and antioxidants. The composite nanofillers include modified fumed silica and montmorillonite nanosheets. The additives include dispersants and pH stabilizers. The core layer of the hydrophobic fiber with a core-shell structure is a polyolefin fiber, which is polypropylene or polyethylene, with a diameter of 8-18 μm; the shell layer is a fluoropolymer, which is polyvinylidene fluoride or polytetrafluoroethylene, with a thickness of 0.8-2.2 μm; the acid-resistant additive is perfluorooctylphosphonic acid or perfluorohexylphosphonic acid; and the antioxidant is antioxidant 1010 or antioxidant 168.

2. The hybrid glass fiber battery separator according to claim 1, characterized in that, In the biomimetic multi-level ultrafine glass fiber, the primary fiber accounts for 60%-70% of the total mass of the separator, the secondary fiber accounts for 8%-12% of the total mass of the separator, and the tertiary fiber accounts for 18%-22% of the total mass of the separator; the core-shell structure hydrophobic fiber accounts for 14%-16% of the total mass of the hybrid glass fiber battery separator.

3. The hybrid glass fiber battery separator according to claim 1, characterized in that, In the composite nanofiller, the modified fumed silica is modified with a silane coupling agent and has a particle size of 12-25 nm; the montmorillonite nanosheets have a particle size of 3-12 nm; the mass ratio of modified fumed silica to montmorillonite nanosheets is 2-4:1; and the composite nanofiller accounts for 0.5%-0.9% of the total mass of the mixed glass fiber battery separator.

4. The hybrid glass fiber battery separator according to claim 1, characterized in that, In the additives, the dispersant is polyethylene glycol 4000-8000, and the pH stabilizer is a citrate-sodium citrate buffer pair or an acetate-sodium acetate buffer pair; the additives account for 0.1%-0.3% of the total mass of the mixed glass fiber battery separator.

5. The hybrid glass fiber battery separator according to claim 1, characterized in that, The hybrid glass fiber battery separator has a porosity of 85%-92%, a tensile strength retention rate of not less than 90% after being soaked in sulfuric acid at 60°C for 1000 hours, and a pore size retention rate of not less than 92% at 80°C.

6. A method for preparing a hybrid glass fiber battery separator as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Prefabricated core-shell structure hydrophobic fiber: The core layer polyolefin fiber is surface activated, and the activated core layer fiber is immersed in a fluoropolymer solution containing acid-resistant additives and antioxidants. After coating and drying, the core-shell structure hydrophobic fiber is obtained. Supercritical synergistic pulping: Biomimetic multi-level ultrafine glass fiber, core-shell structured hydrophobic fiber, composite nanofiller and additives are added to a pulping device, and after pretreatment with supercritical fluid, water and sulfuric acid are added to adjust the pH of the pulp to 2.0-2.5, and the pulp is stirred and dispersed to obtain glass fiber pulp; Vacuum-hot pressing: After adjusting the concentration and flow rate, the glass fiber slurry is transported to the forming device, where it is first dehydrated by vacuum and then hot-pressed to form a separator paper with a humidity of 25%-35%. Modification and drying: The diaphragm paper is subjected to plasma surface modification and then dried until the moisture content is no more than 0.5%; Cutting: Cut the dried separator paper according to the battery specifications to obtain a mixed glass fiber battery separator.

7. The method for manufacturing a hybrid glass fiber battery separator according to claim 6, characterized in that, In the supercritical synergistic pulping process, the supercritical fluid is supercritical CO2, and the supercritical state parameters include: pressure of 20-25 MPa, temperature of 31-35℃, flow rate of 4-6 L / min, pretreatment time of 8-12 min, stirring speed of 1600-2000 rpm, and stirring time of 25-35 min.

8. The method for manufacturing a hybrid glass fiber battery separator according to claim 6, characterized in that, During the vacuum-hot pressing process, the vacuum degree for vacuum dehydration is -0.08 to -0.09 MPa, and the dehydration time is 1.5 to 2.5 min; the hot pressing temperature is 110 to 130℃, the pressure is 0.4 to 0.6 MPa, and the time is 0.8 to 1.2 min. During the modification and drying process, the plasma modification gas is oxygen or air, the power is 120-180W, the time is 2-4min, the drying temperature is 100-120℃, the wind speed is 2-4m / s, and the drying time is 25-35min.

9. A system for producing a hybrid glass fiber battery separator as described in any one of claims 1 to 5, characterized in that, The system includes a supercritical co-pulping unit, a pH-stabilized pulp storage unit, an online monitoring unit, a vacuum-hot pressing unit, a plasma-modified drying unit, a closed-loop white water recycling unit, and a slitting unit. The discharge end of the supercritical co-pulping unit is connected to the feed end of the pH-stabilized pulp storage unit, used to transport the prepared glass fiber pulp to the storage unit. The discharge end of the pH-stabilized pulp storage unit is connected to the feed end of the vacuum-hot pressing unit, and an online monitoring unit is provided between them to detect the concentration and agglomerated particle size of the glass fiber pulp. The discharge end of the vacuum-hot pressing unit is connected to the feed end of the plasma-modified drying unit, used to transport the formed separator paper to the modification and drying unit. The vacuum-hot pressing unit is also connected to the closed-loop white water recycling unit, used to transport the white water generated during production to the closed-loop white water recycling unit for treatment and reuse. The discharge end of the plasma-modified drying unit is connected to the slitting unit, used to transport the dried separator paper to the slitting unit for cutting.

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