A multilayer composite separator for lead-carbon batteries

Abstract

The application provides a composite separator for a colloidal lead-carbon battery. The composite separator comprises a PE separator and two layers of screen meshes, and the PE separator is sandwiched between the two layers of screen meshes to form a sandwich structure. The PE separator is used for separating positive and negative active materials, and the screen meshes are used for storing colloids. The introduction of the screen meshes can not only increase the colloidal storage capacity of the separator, but also provide a channel for the injection of sol, thereby reducing the injection resistance of colloids. Experiments show that the colloidal injection amount of the battery can be increased to the injection amount of liquid acid electrolyte by using the composite separator, and the discharge capacity of the battery can be increased to more than 95% of the discharge capacity of a lead-carbon battery using liquid acid as electrolyte.

Description

Technical Field

[0001] This invention relates to the field of lead-carbon batteries, and particularly to lead-carbon battery separators. Background Technology

[0002] With the increasing demand for hybrid vehicles and the expanding scale of renewable energy utilization, the development of safe, low-cost, and high-performance advanced energy storage systems is urgently needed. Lead-acid batteries have advantages such as good safety, good low-temperature performance, high cost-effectiveness, and mature technology, making them one of the most widely used electrochemical energy storage technologies. However, lead-acid batteries suffer from low energy density, low power density, and poor cycle performance. Lead-carbon batteries are an advanced type of lead-acid battery developed in recent years, overcoming some of the performance defects of lead-acid batteries. On the one hand, carbon materials form a conductive network in the active material lead paste, which can promote the conversion between Pb and PbSO4, thereby increasing the power density of the negative electrode. On the other hand, carbon materials can prevent the growth of lead sulfate crystal particles and their large accumulation on the surface of the active material, slowing down the irreversible sulfation process of the lead paste, reducing the capacity decay rate of the negative electrode, and thus extending the cycle life of the lead-carbon battery. Lead-carbon batteries are divided into three types: internally hybrid, internally parallel, and pure carbon negative electrode. Among them, the internally hybrid lead-carbon battery belongs to the energy-type lead-carbon battery and has broad application prospects in the field of stationary energy storage, especially in the field of large-scale energy storage. In internally mixed lead-carbon batteries, the purpose of introducing carbon materials is to improve the effective utilization rate of active materials and extend the battery's charge-discharge cycle life. In internally mixed lead-carbon batteries, carbon materials are mixed into the lead paste, allowing for full contact between the carbon materials and the active materials, which is beneficial for the carbon materials' conductivity, steric hindrance, and electrocatalytic effects. Studies have shown that adding carbon materials to the negative electrode of lead-carbon batteries can significantly improve the overall performance of the battery. Specifically, the energy density, charge acceptance capacity, and cycle life of lead-carbon batteries are increased by 20%, 1 time, and 2-3 times respectively compared to lead-acid batteries.

[0003] Although lead-carbon batteries offer significantly improved energy density, charge acceptance, and cycle life compared to lead-acid batteries, their application in energy storage still faces substantial challenges from other types of electrochemical energy storage technologies. For example, compared to lithium-ion batteries, lead-carbon batteries have significantly lower energy density and cycle life. However, compared to other types of electrochemical energy storage technologies, lead-carbon batteries possess outstanding advantages in terms of high safety and low energy storage cost. Further improvements in cycle life would significantly enhance their market competitiveness in large-scale energy storage. While introducing carbon materials into the negative electrode active material can suppress irreversible sulfation of the negative electrode and extend the battery's cycle life, the failure of lead-carbon batteries remains primarily due to severe sulfation at the bottom of the negative electrode. The cause of irreversible sulfation in the lower part of the negative electrode active material is acid stratification; under the influence of gravity, H₂SO₄ gradually migrates to the bottom of the battery, leading to a continuous increase in acid concentration. This increased sulfuric acid concentration causes the lead sulfate crystals to gradually enlarge, resulting in the loss of electrochemical activity.

[0004] One effective method to solve acid stratification in lead-carbon batteries is to use a gel electrolyte instead of sulfuric acid solution. In the production of gel batteries, efficient gel filling is a crucial technical challenge. Silica sol has a higher viscosity and poorer flowability than electrolyte solutions, making it difficult to penetrate the separators between the electrodes and ensure sufficient wetting of the positive and negative plates. Insufficient gel filling will affect subsequent formation, leading to reduced utilization of electrode active materials and decreased battery capacity. Summary of the Invention

[0005] The technical problem to be solved by this invention (the purpose of the invention):

[0006] This invention provides a composite separator for colloidal lead-carbon batteries. The composite separator comprises a PE separator layer and two layers of screens, with the PE separator sandwiched between the two screens to form a sandwich structure. The PE separator separates the positive and negative electrode active materials, while the mesh of the screens stores the colloidal material.

[0007] A composite partition is made of polyester screen, PE partition and polyester screen stacked together.

[0008] A PE partition is sandwiched between two layers of polyester screen to form a sandwich structure. The mesh density of the polyester screen is 5-500 mesh, preferably 10-100 mesh, and the screen thickness is 0.1-5mm. The thickness of the PE partition is 0.1-5mm.

[0009] The composite separator described herein is used as a separator in lead-carbon batteries.

[0010] The composite separator is used as a separator for colloidal lead-carbon batteries.

[0011] The preparation process of the colloidal lead-carbon battery is as follows:

[0012] A、(1) By weight, 500-800 parts of lead powder, 0.01-20 parts of carbon material, 6-10 parts of barium sulfate, and 0.1-0.5 parts of polypropylene short fibers with a length of 0.1-5mm and a diameter of 100nm-5μm are stirred and premixed. While stirring, 50-100 parts of deionized water are added to the premixed powder and stirred continuously for 1-60 minutes to obtain lead paste;

[0013] (2) Apply lead paste to the metal lead grid, filling the through holes on the metal lead grid. After curing and drying, the negative electrode of the lead-carbon battery is obtained. The curing temperature is 30-50℃, the humidity is 70-95%, and the curing time is 10-30 hours. The drying temperature is 60-120℃ and the time is 10-30 hours.

[0014] B. Preparation of the positive electrode: The positive electrode of the lead-acid battery is prepared according to the same process steps (1) and (2) in the preparation of the negative electrode in A above. The difference is that no carbon material is added to the positive electrode.

[0015] C. After assembling into a lead-carbon battery, the electrolyte added to the lead-carbon battery is a colloidal electrolyte with a mass concentration of 1.1 g / ml-1.4 g / ml, preferably 1.275 g / ml, and the mass ratio of sulfuric acid electrolyte to the total mass of active material of the negative electrode excluding the metal lead grid is 60-120:50, preferably 83:57.2.

[0016] The dimensions of the metal lead grid are 50-1000mm in length, 20-80mm in width, and 0.5-4mm in thickness;

[0017] The hydroxyapatite membrane prepared in step 1 has a length of 50-1000 mm, a width of 20-80 mm, and a thickness of 0.5-4 mm.

[0018] The colloidal electrolyte is a sulfuric acid solution with a mass fraction of 0.01%-20% fumed silica, preferably 0.5%-5%.

[0019] The length, width, and height of the square screens on both sides of the PE partition are equal to or greater than the length, width, and height of the corresponding lead-carbon solar cell grid.

[0020] Beneficial effects of this invention:

[0021] This invention, by incorporating sieves on both sides of the separator, not only increases the amount of adhesive stored in the separator but also provides a channel for sol injection, reducing the resistance to adhesive injection. Experimental results show that using the composite separator of this invention can increase the amount of adhesive injected into the battery to that of liquid acid electrolytes and improve wettability, thereby increasing the battery's discharge capacity to over 95% of that of lead-carbon batteries using liquid acid electrolytes. Detailed Implementation

[0022] Example 1

[0023] Lead-carbon batteries are prepared using the following steps:

[0024] 1. Preparation of the negative electrode: (1) 600g of lead powder, 9g of activated carbon, 8.4g of barium sulfate, and 0.3g of polypropylene short fibers with a length of 5mm and a diameter of 0.5-1.5μm were premixed using a high-speed mixer. While stirring, 84g of deionized water was added to the premixed powder, and stirring was continued for 10min to obtain lead paste; (2) The lead paste was scraped onto a metal lead grid with a grid size of 70mm in length, 50mm in width, and 2mm in thickness. After curing and drying, the negative electrode of the lead-carbon battery was obtained. The curing temperature was 40℃, the humidity was 80%, and the curing time was 20 hours; the drying temperature was 80℃ and the drying time was 24 hours.

[0025] 2. Preparation of the positive electrode: The positive electrode of the lead-acid battery is prepared according to the same process steps as the negative electrode preparation steps (1) and (2), except that no carbon material is added to the positive electrode;

[0026] 3. Preparation of lead-carbon battery: Three positive electrode plates and two negative electrode plates are arranged alternately in parallel. A composite separator for gel lead-carbon battery (as a separator) is placed between the positive and negative electrode plates. The separator structure uses 1mm thick PE separator with 10 mesh polyester mesh on both sides, and the screen thickness is 1mm (the PE separator is sandwiched between two layers of polyester screen to form a sandwich structure, and the PE separator thickness is 2mm). The two negative electrode plates are welded in parallel and the three positive electrode plates are welded in parallel. The total mass of positive electrode active material of lead-acid battery (the total mass of lead paste on the three positive electrode plates after drying) is 20.0g. The total mass of positive electrode active material refers to the total mass of lead paste contained in the three parallel welded positive electrode plates. The total mass of negative electrode active material (the total mass of lead paste on the two negative electrode plates after drying) is 14.3g. The total mass of negative electrode active material refers to the total mass of lead paste contained in the two parallel welded negative electrode plates. The positive and negative electrode grids use conventional lead grids with dimensions of 70mm in length, 50mm in width, and 2mm in thickness. The positive and negative electrodes are placed in a tightly assembled battery box, which is 76mm in length, 40mm in width, and 100mm in height. 83g of a colloidal electrolyte with a density of 1.275g / ml and a silica mass fraction of 1% is injected into the battery box. The conductivity of the colloidal electrolyte between the positive and negative electrodes under these conditions is 690mS / cm.

[0027] The battery was subjected to a room temperature life test: a constant current discharge of 4.2A for 59 seconds, a discharge of 18A for 1 second, and a constant current and constant voltage charge of 6.3A current and 2.3V voltage for 60 seconds. This charge and discharge condition was cycled 3600 times, followed by a resting period of 40 hours. After 40 hours, the cycle was restarted. The life test was terminated when the battery voltage dropped below 1.2V.

[0028] The assembled hybrid battery has an initial voltage of 2.1765V when fully charged at room temperature, and can run 18,153 cycles in a room temperature life test. Compared with the test results of a regular lead-acid battery with the same lead content under the same test conditions (7,223 cycles), the room temperature cycle life of the hybrid lead-carbon battery can reach 2.5 times that of a traditional lead-acid battery.

[0029] Example 2

[0030] The process is the same as in Example 1, except that for the lead-carbon battery: following the requirements of Example 1 without changing other conditions, the mesh size of the polyester mesh used on both sides of the PE separator in the separator structure is changed to 100 mesh. Testing showed that under these conditions, the conductivity of the gel electrolyte between the positive and negative electrodes was 695 mS / cm. The assembled hybrid battery had an initial voltage of 2.1293V at full charge at room temperature, and could run 17,824 cycles in the room temperature life test. Compared with the test results of a conventional lead-acid battery with the same lead content under the same test conditions (7,223 cycles), the room temperature cycle life of the hybrid lead-carbon battery is 2.5 times that of a traditional lead-acid battery.

[0031] Example 3

[0032] The process is the same as in Example 1, except that, without changing other conditions, the polyester mesh used on both sides of the PE separator in the separator structure is changed from 10 mesh to a 10 mesh polyester mesh placed only on one side. Testing showed that the conductivity of the gel electrolyte between the positive and negative electrodes under these conditions was 680 mS / cm. The assembled hybrid battery had an initial voltage of 2.1843V at full charge at room temperature, and it could run 14742 cycles in the room temperature life test. Compared with the test results of a conventional lead-acid battery with the same lead content under the same test conditions (7223 cycles), the room temperature cycle life of the hybrid lead-carbon battery is twice that of a traditional lead-acid battery.

[0033] Comparative Example 1

[0034] The process is the same as in Example 1, except that the lead-carbon battery is prepared using a conventional single-layer AGM separator, following the requirements of Example 1 without changing other conditions. Testing showed that the conductivity of the gel electrolyte between the positive and negative electrodes under these conditions was 660 mS / cm. The assembled internal hybrid battery had an initial voltage of 2.1939V at room temperature when fully charged, and its operational life test at room temperature lasted for 10415 cycles.

[0035] Comparative Example 2

[0036] The process is the same as in Example 1, except that for the lead-carbon battery: following the requirements of Example 1 without changing other conditions, a polyester screen with a mesh density of 3000 is used to construct the composite separator. Testing showed that under these conditions, the conductivity of the gel electrolyte between the positive and negative electrodes was 450 mS / cm. The assembled internal hybrid battery had an initial voltage of 2.1734V under full charge at room temperature, and its operational life test at room temperature lasted for 3563 cycles.

[0037] The conclusions drawn from the above examples and comparative examples show that the appropriate sieve mesh size determines the conductivity of the colloidal electrolyte, and the cycle life of batteries with electrolytes that have too low conductivity is severely affected.

Claims

1. The application of a composite separator as a separator in a colloidal lead-carbon battery, characterized in that: the composite separator is composed of a polyester screen, a PE separator, and a polyester screen layered together; The electrolyte added to the lead-carbon battery is a colloidal electrolyte with a mass concentration of: 1.1 g / ml - 1.4 g / ml; The colloidal electrolyte is a sulfuric acid solution with a mass fraction of 0.01%-20% for fumed silica; A PE partition is sandwiched between two layers of polyester screen to form a sandwich structure. The polyester screen has a mesh density of 5-500 mesh and a thickness of 0.1-5 mm.

2. The application according to claim 1, characterized in that: The mesh density of the polyester screen is 10-100 mesh; the thickness of the PE partition is 0.1-5 mm.

3. The application according to claim 1, characterized in that: The preparation process of the colloidal lead-carbon battery is as follows: A. (1) By weight, 500-800 parts of lead powder, 0.01-20 parts of carbon material, 6-10 parts of barium sulfate, and 0.1-0.5 parts of polypropylene short fibers with a length of 0.1-5 mm and a diameter of 100 nm-5 μm are stirred and premixed. While stirring, 50-100 parts of deionized water are added to the premixed powder and stirred continuously for 1-60 min to obtain lead paste. (2) Apply lead paste to the metal lead grid, fill the through holes on the metal lead grid with lead paste, and obtain the negative electrode of lead-carbon battery after curing and drying; curing temperature 30-50℃, humidity 70-95%, curing time 10-30 hours; drying temperature 60-120℃, time 10-30 hours. B. Preparation of the positive electrode: The positive electrode of the lead-acid battery is prepared according to the same process steps (1) and (2) in the preparation of the negative electrode in A above. The difference is that no carbon material is added to the positive electrode. C. After assembling into a lead-carbon battery, the electrolyte added to the lead-carbon battery is a colloidal electrolyte with a mass concentration of 1.275 g / ml, and the mass ratio of sulfuric acid electrolyte to the total mass of active material in the negative electrode excluding the metal lead grid is 60-120:

50.

4. The application according to claim 3, characterized in that: The dimensions of the metal lead grid are 50-1000 mm in length, 20-80 mm in width, and 0.5-4 mm in thickness; The hydroxyapatite membrane prepared in step 1 has a length of 50-1000 mm, a width of 20-80 mm, and a thickness of 0.5-4 mm.

5. The application according to claim 3, characterized in that: After assembling the lead-carbon battery in step C, the electrolyte added to the lead-carbon battery is a colloidal electrolyte with a mass concentration of 1.275 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active material of the negative electrode excluding the metal lead grid is 83:57.

2.

6. The application according to claim 3, characterized in that: The colloidal electrolyte is a sulfuric acid solution with a mass fraction of 0.5-5% fumed silica.

7. The application according to claim 3, characterized in that: The length, width, and height of the square screens on both sides of the PE partition are equal to or greater than the length, width, and height of the corresponding lead-carbon solar cell grid.