Anti-bulging composite separator, preparation method and lead-acid storage battery

Abstract

The application belongs to the technical field of lead-acid storage batteries, and provides a bulge-preventing composite separator, a preparation method and a lead-acid storage battery, the composite separator comprising a first glass fiber layer, an intermediate layer and a second side glass fiber layer; the first glass fiber layer faces a positive plate, and the second glass fiber layer faces a negative plate; the intermediate layer comprises the following raw materials in parts by weight: high-density polyethylene 80-110 parts, glass fiber 8-15 parts, modified silicon dioxide 5-12 parts, a compatilizer 3-6 parts and an antioxidant 1-2 parts; wherein the modified silicon dioxide is modified and treated on the surface by a silane coupling agent, and is obtained after further loading a catalyst. The application provides a bulge-preventing composite separator, the method is simple and suitable for industrial production, the prepared composite separator is applied to a lead-acid storage battery, effectively reduces the battery bulging problem caused by gas accumulation and internal pressure rise, prolongs the service life of the lead-acid storage battery, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of lead-acid battery technology, and particularly to an anti-bulging composite separator, its preparation method, and a lead-acid battery. Background Technology

[0002] Lead-acid batteries are widely used in automotive starting systems, uninterruptible power supplies, energy storage systems, and electric vehicles due to their low cost, relatively high safety, excellent high-current discharge performance, and mature recycling technology. However, in actual use, lead-acid batteries commonly suffer from bulging and failure, which seriously affects their lifespan and safety.

[0003] Battery bulging is essentially caused by the rate of internal gas production (mainly hydrogen and oxygen) exceeding the venting rate of the safety valve, leading to a continuous increase in internal pressure and ultimately irreversible deformation of the casing. Research indicates that bulging is primarily related to the following factors: First, under overcharge conditions, oxygen is released from the positive electrode. If this oxygen cannot effectively recombine at the negative electrode, it accumulates and increases internal pressure. Second, battery thermal runaway, especially in high-temperature environments or when charging voltage is out of control, exacerbates water decomposition and gas production, creating a vicious cycle. Third, the safety valve may become clogged or malfunction due to aging, preventing timely gas release. Bubbling not only causes a sharp drop in battery capacity and increased internal resistance but can also lead to serious safety incidents such as electrolyte leakage, short circuits, and even explosions.

[0004] The separator is a key component of lead-acid batteries, primarily serving to isolate the positive and negative plates, prevent short circuits, absorb and retain electrolyte, and provide channels for gas recombination. Currently, ultrafine glass fiber (AGM) separators are widely used in valve-regulated sealed lead-acid batteries due to their excellent liquid absorption and porosity. However, existing AGM separators have significant shortcomings in suppressing bulging: firstly, their pore structure is relatively simple, resulting in greater resistance to oxygen diffusion from the positive to the negative electrode and lower gas recombination efficiency. Especially under overcharge or high-temperature conditions, the oxygen recombination reaction cannot consume the generated oxygen in time, leading to pressure accumulation. Secondly, traditional separators have poor compression resilience, and after long-term use, the thickness shrinks, reducing the pressure between the positive and negative plates and further deteriorating gas transport and recombination conditions. In addition, some separator materials have limited chemical stability in acidic electrolytes and high-temperature environments, making them prone to degradation or decreased porosity, accelerating battery water loss and bulging.

[0005] Therefore, developing a composite separator that can effectively promote oxygen recombination and suppress internal pressure accumulation is of great significance for improving the reliability and extending the service life of lead-acid batteries. Summary of the Invention

[0006] The purpose of this invention is to provide an anti-bulging composite separator, a preparation method, and a lead-acid battery to solve the bulging problem that exists in existing lead-acid batteries during use.

[0007] The objective of this invention can be achieved through the following technical solutions: The first aspect of the present invention provides an anti-bulging composite separator, the composite separator comprising a first glass fiber layer, an intermediate layer, and a second side glass fiber layer; the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate. The intermediate layer, by weight, comprises the following raw materials: 80-110 parts of high-density polyethylene, 8-15 parts of glass fiber, 5-12 parts of modified silica, 3-6 parts of compatibilizer, and 1-2 parts of antioxidant. The modified silica is obtained by modifying its surface with a silane coupling agent and then further loading a catalyst.

[0008] Furthermore, the modified silica is prepared by the following steps: Silica is added to a mixture of anhydrous ethanol and deionized water, sonicated for 0.5-1 h, and the pH is adjusted to 3.5-4.5. Then, a silane coupling agent is added and reacted at 70-80℃ for 4-8 h. After centrifugation and washing, and vacuum drying, it is impregnated in a catalyst solution, dried, and calcined at 400-500℃ for 3-4 h to obtain modified silica. This invention first modifies the surface of silica using a silane coupling agent, introducing active sites for catalytic oxygen recombination in the intermediate layer. This promotes efficient recombination of oxygen and hydrogen generated under overcharging or high temperatures within the separator, fundamentally inhibiting gas accumulation and shell bulging. Then, cerium oxide and / or cobalt oxide metal catalysts are loaded onto the silica surface. Cerium oxide and cobalt oxide provide catalytic active sites, further promoting the recombination reaction between oxygen evolved from the positive electrode and hydrogen ions diffused from the negative electrode in the intermediate layer of the composite separator, thereby reducing internal pressure and effectively preventing shell bulging and deformation caused by continuous increase in internal pressure. Furthermore, the introduction of silane coupling agents significantly improves the interfacial compatibility between silica and the polyethylene matrix, enabling the inorganic filler to be uniformly dispersed in the matrix. This avoids the negative impact of agglomeration on the mechanical properties and pore structure of the composite separator, thereby ensuring that the intermediate layer can maintain stable catalytic activity and structural integrity under long-term acidic electrolyte immersion and mechanical compression conditions.

[0009] Furthermore, the silane coupling agent is one of silane coupling agent KH-550 and silane coupling agent KH-570; the amount used is 5%-10% of the mass of silicon dioxide.

[0010] Furthermore, the catalyst is at least one of cerium oxide and cobalt oxide; the loading is 3%-8% of the mass of silicon dioxide.

[0011] Furthermore, the compatibilizer is at least one of maleic anhydride-grafted polyethylene and ethylene-acrylic acid copolymer.

[0012] Furthermore, the antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0013] Furthermore, the thickness of the first glass fiber layer is 0.3-0.5 mm and the porosity is 85%-90%; the thickness of the intermediate layer is 0.5-0.8 mm and the porosity is 60%-70%; and the thickness of the second glass fiber layer is 0.3-0.6 mm and the porosity is 75%-85%.

[0014] Furthermore, the pore size of the first glass fiber layer is 20-35 μm, the pore size of the intermediate layer is 10-20 μm, and the pore size of the second glass fiber layer is 5-10 μm. Along the direction from the positive electrode to the negative electrode, the pore size of the glass fiber layers decreases sequentially, forming a highly efficient directional gas diffusion network, which helps oxygen to quickly reach the catalytic site and prevents the battery from swelling and deforming due to local pressure accumulation.

[0015] A second aspect of the present invention provides a method for preparing an anti-bulging composite partition, comprising the following steps: Polyethylene, compatibilizer, and antioxidant are added to a mixer and plasticized at 160-180℃ for 5-8 minutes. Then, glass fiber and modified silica are added and the mixture is continued to be mixed for 10-15 minutes to obtain a mixture. The mixture is melt-extruded through a twin-screw extruder and cast into a film. Then, it is biaxially stretched to form an intermediate layer. Finally, the formed intermediate layer is hot-pressed with the glass fiber layers on both sides to obtain a composite partition.

[0016] A third aspect of the present invention provides a lead-acid battery, comprising a positive electrode plate, a negative electrode plate, an electrolyte, and the aforementioned composite separator disposed between the positive electrode plate and the negative electrode plate.

[0017] The beneficial effects of this invention are: This invention provides an anti-bulging composite separator, comprising a first glass fiber layer, an intermediate layer, and a second glass fiber layer; the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate. The intermediate layer uses high-density polyethylene as a skeleton, combined with glass fiber reinforcement, and incorporates modified silica, significantly improving the separator's resistance to compressive deformation and long-term cycle stability. It also enables the separator to remain stable in sulfuric acid electrolytes and high-temperature environments, resisting degradation or failure and extending battery life. Furthermore, by modifying silica with a silane coupling agent and loading a metal catalyst onto the silica surface, active sites for catalytic oxygen recombination are effectively introduced into the intermediate layer. This promotes efficient recombination of oxygen and hydrogen generated under overcharging or high temperatures within the separator, fundamentally inhibiting gas accumulation and casing bulging.

[0018] This invention also defines the pore size of each layer of the composite separator, controlling the pore size to decrease sequentially from the positive electrode to the negative electrode. The larger pore size on the positive electrode side reduces the mass transfer resistance of oxygen evolution from the positive electrode surface, the moderate pore size in the middle layer balances catalytic reaction space and mechanical support strength, and the smaller pore size on the negative electrode side increases the contact area between oxygen and the negative electrode active material, effectively inhibiting the shedding and migration of the negative electrode active material. Furthermore, the capillary pressure gradient formed by the decreasing pore size structure helps the electrolyte to distribute evenly from the middle layer to the glass fiber layers on both sides, avoiding the risk of increased internal resistance and thermal runaway caused by localized drying.

[0019] This invention provides a method for preparing an anti-bulging composite separator. The process is simple and suitable for industrial production. The resulting composite separator, when applied to lead-acid batteries, effectively reduces battery bulging caused by gas accumulation and increased internal pressure, extends the service life of lead-acid batteries, and improves safety performance, showing broad application prospects. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1 This embodiment provides an anti-bulging composite separator, which includes a first glass fiber layer (thickness 0.3 mm, porosity 85%, pore size 20-35 μm), an intermediate layer (thickness 0.5 mm, porosity 60%, pore size 10-20 μm), and a second side glass fiber layer (thickness 0.3 mm, porosity 75%, pore size 5-10 μm); the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate; The intermediate layer, by weight, comprises the following raw materials: 80 parts high-density polyethylene, 8 parts glass fiber, 5 parts modified silica, 3 parts maleic anhydride-grafted polyethylene, and 1 part antioxidant 1010. The modified silica is prepared through the following steps: Silica was added to a mixture of anhydrous ethanol and deionized water and sonicated for 0.5 h. The pH was adjusted to 3.5. Then, 6% of the mass of silica silane coupling agent KH-550 was added and reacted at 75 °C for 6 h. After centrifugation and washing, the silica was vacuum dried and then impregnated in a cerium oxide solution with a cerium oxide loading of 3% of the silica mass. After drying, the silica was calcined at 400 °C for 4 h to obtain modified silica.

[0022] This embodiment also provides a method for preparing an anti-bulging composite partition, including the following steps: Polyethylene, compatibilizer, and antioxidant are added to a mixer and plasticized at 160°C for 5 min. Then, glass fiber and modified silica are added and the mixture is continued to be mixed for 10 min to obtain a mixture. The mixture is melt-extruded through a twin-screw extruder and cast into a film. Then, it is biaxially stretched to form an intermediate layer. Finally, the formed intermediate layer is hot-pressed with the glass fiber layers on both sides to obtain a composite partition.

[0023] Example 2 The only difference from Example 1 is that: The modified silica is prepared through the following steps: Silica was added to a mixture of anhydrous ethanol and deionized water and sonicated for 0.5 h. The pH was adjusted to 3.5. Then, 8% of the mass of silica silane coupling agent KH-550 was added and reacted at 75 °C for 6 h. After centrifugation and washing, the silica was vacuum dried and then impregnated in a cerium oxide solution with a cerium oxide loading of 7% of the silica mass. After drying, the silica was calcined at 400 °C for 4 h to obtain modified silica.

[0024] Example 3 The only difference from Example 1 is that: A composite separator for preventing bulging, the composite separator comprising a first glass fiber layer (thickness 0.5 mm, porosity 85%, pore size 20-35 μm), an intermediate layer (thickness 0.7 mm, porosity 60%, pore size 10-20 μm), and a second side glass fiber layer (thickness 0.5 mm, porosity 75%, pore size 5-10 μm); the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate.

[0025] Example 4 The only difference from Example 1 is that: A composite separator for preventing bulging, the composite separator comprising a first glass fiber layer (thickness 0.3 mm, porosity 90%, pore size 20-35 μm), an intermediate layer (thickness 0.5 mm, porosity 70%, pore size 10-20 μm), and a second side glass fiber layer (thickness 0.3 mm, porosity 85%, pore size 5-10 μm); the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate.

[0026] Example 5 The only difference from Example 1 is that: The intermediate layer comprises, by weight, the following raw materials: 95 parts high-density polyethylene, 11 parts glass fiber, 8 parts modified silica, 4 parts maleic anhydride-grafted polyethylene, and 1.2 parts antioxidant 1010.

[0027] Example 6 The only difference from Example 1 is that: The intermediate layer comprises, by weight, the following raw materials: 110 parts high-density polyethylene, 15 parts glass fiber, 12 parts modified silica, 6 parts maleic anhydride-grafted polyethylene, and 1.9 parts antioxidant 1010.

[0028] Comparative Example 1 The only difference from Example 1 is that: The composite partition is an AGM (super glass fiber) partition (1.1 mm thick).

[0029] Comparative Example 2 The only difference from Example 1 is that: This comparative example provides a composite separator for preventing bulging. The composite separator includes a first glass fiber layer (thickness of 0.3 mm, porosity of 85%, and pore size of 20-35 μm) and a second glass fiber layer (thickness of 0.3 mm, porosity of 75%, and pore size of 5-10 μm); the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate.

[0030] Comparative Example 3 The only difference from Example 1 is that: This comparative example provides a composite separator for preventing bulging. The composite separator includes a first glass fiber layer (thickness 0.3 mm, porosity 85%, pore size 20-35 μm), an intermediate layer (thickness 0.5 mm, porosity 60%, pore size 10-20 μm), and a second side glass fiber layer (thickness 0.3 mm, porosity 75%, pore size 5-10 μm). The first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate. The intermediate layer comprises, by weight, the following raw materials: 80 parts high-density polyethylene, 8 parts glass fiber, 5 parts silicon dioxide, 3 parts maleic anhydride-grafted polyethylene, and 1 part antioxidant 1010.

[0031] Comparative Example 4 The only difference from Example 1 is that: The modified silica is prepared through the following steps: Silica was added to a mixture of anhydrous ethanol and deionized water and sonicated for 0.5 h. The pH was adjusted to 3.5. Then, 6% of the mass of silica was added with silane coupling agent KH-550 and the mixture was reacted at 75 °C for 6 h. After centrifugation, washing, and vacuum drying, modified silica was obtained.

[0032] Comparative Example 5 The only difference from Example 1 is that: A composite separator for preventing bulging, the composite separator comprising a first glass fiber layer (thickness 0.3 mm, porosity 85%, pore size 20-35 μm), an intermediate layer (thickness 0.5 mm, porosity 60%, pore size 20-35 μm), and a second side glass fiber layer (thickness 0.3 mm, porosity 75%, pore size 20-35 μm); the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate.

[0033] The composite separators prepared in Examples 1-6 and Comparative Examples 1-5 were tested and applied: (1) Compression rebound rate: The composite partition was compressed at 50 kPa for 24 h, and the thickness recovery rate of the composite partition was measured after the pressure was released.

[0034] The battery employs a valve-regulated sealed lead-acid (VRLA) structure with a rated capacity of 12 V / 6-Ah. The positive electrode is a PbO2 paste-coated plate; the negative electrode is a sponge-like Pb paste-coated plate; the separator is a composite separator prepared according to Examples 1-6 and Comparative Examples 1-5, wherein the first glass fiber layer faces the positive electrode and the second glass fiber layer faces the negative electrode; the electrolyte is a dilute sulfuric acid solution (density 1.28 g / cm³). 3 The lead-acid batteries obtained above were subjected to the following performance tests: (2) Overcharged casing expansion rate: According to the national standard GB / T 22473-2019, the battery was overcharged at a constant voltage of 2.45V / cell for 7 days, and the ratio of the expansion amount of the middle part of the side of the battery to the original thickness was measured.

[0035] (3) Cycle life: 100% deep discharge (1C discharge), termination voltage 1.75V / cell, number of cycles with capacity decay to 80% of the initial capacity.

[0036] The test results are shown in Table 1: Table 1

[0037] As can be seen from Table 1, the composite separators prepared in Examples 1-6 have excellent mechanical stability. They can effectively suppress overcharge bulging of lead-acid batteries and extend cycle life while improving the mechanical resilience of the separator, which is of positive significance for improving the long-term cycle stability of the battery.

[0038] 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 process, method, article, or apparatus.

[0039] 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 composite partition for preventing bulging, characterized in that, The composite separator includes a first glass fiber layer, an intermediate layer, and a second side glass fiber layer; the first glass fiber layer faces the positive electrode plate, and the second glass fiber layer faces the negative electrode plate. The intermediate layer, by weight, comprises the following raw materials: 80-110 parts of high-density polyethylene, 8-15 parts of glass fiber, 5-12 parts of modified silica, 3-6 parts of compatibilizer, and 1-2 parts of antioxidant. The modified silica is obtained by modifying its surface with a silane coupling agent and then further loading a catalyst.

2. The anti-bulging composite partition according to claim 1, characterized in that, The modified silica is prepared by the following steps: Add silica to a mixture of anhydrous ethanol and deionized water, sonicate for 0.5-1 h, adjust the pH to 3.5-4.5, then add silane coupling agent and react at 70-80℃ for 4-8 h. After centrifugation and washing, vacuum drying, impregnate in catalyst solution, dry, and calcine at 400-500℃ for 3-4 h to obtain modified silica.

3. The anti-bulging composite partition according to claim 2, characterized in that, The silane coupling agent is one of silane coupling agent KH-550 or silane coupling agent KH-570; the amount used is 5%-10% of the mass of silicon dioxide.

4. The anti-bulging composite partition according to claim 2, characterized in that, The catalyst is at least one of cerium oxide and cobalt oxide; the loading is 3%-8% of the mass of silicon dioxide.

5. The anti-bulging composite partition according to claim 1, characterized in that, The compatibilizer is at least one of maleic anhydride-grafted polyethylene and ethylene-acrylic acid copolymer.

6. The anti-bulging composite partition according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010 and antioxidant 168.

7. The anti-bulging composite partition according to claim 1, characterized in that, The thickness of the first glass fiber layer is 0.3-0.5 mm, and the porosity is 85%-90%; the thickness of the intermediate layer is 0.5-0.8 mm, and the porosity is 60%-70%; the thickness of the second glass fiber layer is 0.3-0.6 mm, and the porosity is 75%-85%.

8. The anti-bulging composite partition according to claim 1, characterized in that, The pore size of the first glass fiber layer is 20-35 μm, the pore size of the intermediate layer is 10-20 μm, and the pore size of the second glass fiber layer is 5-10 μm.

9. The method for preparing an anti-bulging composite partition according to claim 1, characterized in that, Includes the following steps: Polyethylene, compatibilizer, and antioxidant are added to a mixer and plasticized at 160-180℃ for 5-8 minutes. Then, glass fiber and modified silica are added and the mixture is continued to be mixed for 10-15 minutes to obtain a mixture. The mixture is melt-extruded through a twin-screw extruder and cast into a film. Then, it is biaxially stretched to form an intermediate layer. Finally, the formed intermediate layer is hot-pressed with the glass fiber layers on both sides to obtain a composite partition.

10. A lead-acid battery, characterized in that, It includes a positive electrode plate, a negative electrode plate, an electrolyte, and a composite separator as described in any one of claims 1-8, disposed between the positive electrode plate and the negative electrode plate.

Images