A porous structure red lead and its preparation method and application

Abstract

The present invention discloses a porous red lead and a preparation method and application thereof, and belongs to the technical field of lead-acid battery production. The preparation method of the present invention, by adding hydrophilic fibers, in the oxidation stage, the spherical particles retain the pore structure left after the fibers are ashed, and the structure provides a gas channel for the subsequent lead oxide conversion inside the spherical particles, reduces the time of powder oxidation, and improves production efficiency. The prepared porous red lead, after being added to the positive electrode, effectively improves the pore structure of the positive electrode active material, especially the abundance of micropores, increases the reaction area of ​​the active material, and improves the utilization rate of the active material.

Description

Technical Field

[0001] The invention belongs to the technical field of lead-acid battery production, and particularly relates to a porous red lead and a preparation method and application thereof. Background Art

[0002] Red lead, with the chemical formula Pb3O4, is an important raw material for manufacturing lead-acid batteries. It is widely used in the positive active material of valve-regulated lead-acid batteries, traction batteries, stationary batteries, electric vehicle lead-acid batteries and submarine batteries. In the production process of battery positive plates, it is often used as an additive, with an addition amount of 5% to 20% of the weight of lead powder. Its main function is to improve the efficiency of formation and reduce the power consumption of formation, especially for the formation (internal formation) process of the battery. In addition to adding red lead, antimony trioxide and stannous sulfate are also very critical additive materials for the positive electrode. In the paste stage, they are added according to the weight of the lead powder and the corresponding proportion, and then stirred to achieve the effect of uniform addition.

[0003] The processing method of red lead is relatively mature. One typical production method is: electrolytic lead is heated and melted in a lead melting furnace to become liquid. The liquid lead flows into a powder making furnace in a closed pipe and then undergoes primary oxidation using the Barton powder production method. The powder after primary oxidation is then crushed and screened to obtain irregular lead oxide powder. The powder is transported by an auger to a granulator for granulation. After screening, spherical particles with basically similar particle sizes are obtained, with a diameter of about 0.5 to 2 mm. Finally, they flow into a multi-stage oxidation furnace for heating and oxidation. After cooling and testing, they are crushed and packaged to obtain red lead for production.

[0004] For example, a patent application with publication number CN112694119A discloses a method for preparing red lead, comprising the following steps: step 1: desulfurizing the acid-leached lead mud, and performing solid-liquid separation to obtain desulfurized lead mud; step 2: transferring the desulfurized lead mud into a solidification chamber to convert the free lead therein into lead oxide; step 3: transferring the solidified lead mud obtained by solidification into a ball mill for high-temperature oxidation grinding to prepare red lead.

[0005] The patent application with publication number CN112694118A discloses a method for preparing red lead, comprising the following steps: desulfurizing the negative electrode active material to obtain negative electrode desulfurized lead mud and negative electrode desulfurized mother liquor; roasting the desulfurized lead mud to obtain crude lead oxide and carbon dioxide; purifying the crude lead oxide to obtain purified lead oxide; desulfurizing the positive electrode active material to obtain positive electrode desulfurized lead mud and positive electrode desulfurized mother liquor; and mixing and roasting the purified lead oxide with the positive electrode desulfurized lead mud.

[0006] The method for preparing red lead of the above invention is simple, but the prepared red lead has no effect on the pore structure of the active material of the positive electrode, and the initial capacity is limited. The red lead powder is similar to the lead powder in particle size and is also irregular in shape. After being added to the positive electrode, it has no effect on the pore structure of the active material of the positive electrode, and the initial capacity is limited. At present, there is a need for a red lead that can increase the reaction area of ​​the active material after the formation is completed and improve the initial capacity of the battery. Summary of the invention

[0007] Based on the deficiencies in the prior art, the present invention provides a porous structured red lead and a preparation method and application thereof. A porous structured red lead is prepared by adding hydrophilic fibers and multi-stage heating oxidation. The red lead is added to the positive electrode in an existing manner. After the formation is completed, the pore structure of the positive electrode active material can be significantly improved, especially the enrichment of micropores, thereby increasing the reaction area of ​​the active material and improving the initial capacity of the battery.

[0008] The technical solution of the present invention is as follows:

[0009] The present invention provides a method for preparing a porous structure red lead, comprising the following steps:

[0010] (1) melting electrolytic lead raw materials into lead liquid;

[0011] (2) pulverizing the lead liquid to obtain lead oxide powder;

[0012] (3) granulating the lead oxide powder, and adding hydrophilic fiber during the granulation process, wherein the mass of the hydrophilic fiber added is 0.08% to 0.10% of the mass of the lead oxide powder;

[0013] (4) heating and oxidizing the particles obtained after granulation in step (3), wherein the hydrophilic fibers are incinerated during the heating and oxidation process, and a pore structure is formed in the particles after the hydrophilic fibers are incinerated;

[0014] (5) Cooling the red lead obtained after the oxidation in step (4) and then crushing it to obtain the porous structure red lead.

[0015] Preferably, the hydrophilic fiber has a length of 1.0 to 1.5 mm, a diameter of 10 μm to 30 μm, and a thermal decomposition temperature of 325° C. to 375° C. The length is an absolute length, and the diameter is an absolute diameter.

[0016] By adding hydrophilic fibers, in the oxidation stage, the spherical particles retain the pore structure left after the fiber is ashed, and the structure provides a gas channel for the subsequent lead oxide conversion inside the spherical particles, which reduces the time of powder oxidation and improves production efficiency. The hydrophilic fibers used in the present invention include highly hydrophilic hollow polyester staple fibers, cotton-type polyester staple fibers, spunlace-type polyester staple fibers, vortex polyester staple fibers, etc. In the embodiments of the present invention, highly hydrophilic hollow polyester staple fibers are used as an example, but are not limited thereto. This type of hydrophilic fiber can achieve the effect of forming a pore structure in the particles after ashing.

[0017] On the other hand, in a preferred technical solution of the present invention, the lead oxide powder obtained in step (2) controls the free lead content by mass to be 2% to 5%.

[0018] In a preferred technical solution of the present invention, the particle size of the particles obtained by granulation in step (3) is 2.0 to 3.0 mm.

[0019] In a preferred technical solution of the present invention, during the heating oxidation in step (4), the heating temperature for incinerating the hydrophilic fiber is 460-480°C.

[0020] Specifically, during the heating oxidation in step (4), a multi-stage oxidation furnace is used, and the multi-stage oxidation furnace is divided into a first temperature zone, a second temperature zone, a third temperature zone and a fourth temperature zone from top to bottom. The granulated particles enter from the top of the multi-stage oxidation furnace and pass through the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone in sequence.

[0021] The temperature range of the first temperature zone is 105-120°C, the temperature range of the second temperature zone is 220-300°C, the temperature range of the third temperature zone is 490-500°C, and the temperature range of the fourth temperature zone is 400-420°C.

[0022] Furthermore, during the heating oxidation process, air is passed into the multi-stage oxidation furnace, wherein the air introduction rates into the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone are 6 L / min, 7 L / min, 12-14 L / min and 12-14 L / min respectively.

[0023] After entering the third temperature zone, in the early stage of this stage, the fibers are incinerated, and the spherical particles retain the pore structure left after the fibers are incinerated. This structure also provides a gas channel for the subsequent conversion of lead oxide inside the spherical particles. In the high temperature stage, lead oxide is oxidized into lead tetroxide. Because of the gas channels, the spherical particles can be quickly oxidized inside, thereby improving the conversion efficiency of red lead.

[0024] Compared with the existing conventional red lead production process, the porous structure red lead prepared by this method has larger spherical particles in the granulation stage. In the multi-stage oxidation furnace, more space can be reserved for the spherical particles to contact with the air, and it is not easy to cause powder blockage.

[0025] The present invention also provides a porous red lead prepared by the preparation method.

[0026] The present invention also provides the use of the porous structured red lead as an additive in preparing a positive electrode plate of a lead-acid battery.

[0027] After the red lead particles are crushed, the porous structure left by the fibers will still be retained in the powder. After being added to the positive electrode, the pore structure of the positive electrode active material is effectively improved.

[0028] Beneficial effects of the present invention:

[0029] The preparation method of the present invention, by adding hydrophilic fibers, in the oxidation stage, the spherical particles retain the pore structure left after the fibers are ashed, and the structure provides a gas channel for the subsequent lead oxide conversion inside the spherical particles, thereby reducing the oxidation time of the powder and improving production efficiency. The prepared porous red lead, after being added to the positive electrode, effectively improves the pore structure of the positive electrode active material, especially the abundance of micropores, increases the reaction area of ​​the active material, and improves the utilization rate of the active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an electron scanning microscope image of the porous structure red lead prepared in Example 1.

[0031] Figure 2 This is an electron scanning microscope image of the red lead prepared in Comparative Example 1. DETAILED DESCRIPTION

[0032] Example 1

[0033] A method for preparing porous red lead, the specific steps are as follows:

[0034] 1) One ton of electrolytic lead is sent to the lead melting furnace through a transmission belt for melting. Each lead bar weighs 50 kg, and there are 20 lead bars in total. The melting furnace is heated to 460°C, and the electrolytic lead is melted into liquid;

[0035] 2) Liquid lead flows into the powder making furnace through a closed pipe. The powder making furnace needs to be preheated before it is opened to prevent the lead liquid from cooling down quickly after it flows in. The preheating temperature stops when it reaches 500°C, and the lead liquid begins to flow into the powder making furnace. Heat is generated during the oxidation process of the lead powder, and heating is not required during the powder making stage. The transmission belt continuously feeds the material at a speed of one 50kg lead ingot every 3 minutes;

[0036] 3) Air is introduced into the powder making furnace at a speed of 8L / min. The lead liquid is rotated (200r / m) by high-speed centrifugal stirring in the powder making furnace. The temperature is controlled at 480°C. Under a negative pressure environment (0.3kPa), the outside air is sucked into the furnace. The impeller rotates to make the lead liquid and the air fully contact to generate fine lead powder with an oxidation degree of 96%. The lead on the surface of the lead liquid is oxidized to lead oxide. The powder obtained after primary oxidation in the powder making furnace is irregular lead oxide powder.

[0037] 4) The irregular powder is crushed and then screened by a secondary cyclone separator and a bag filter pipeline to obtain lead oxide powder without obvious large blocks, in which the free lead content is controlled at 4%, and the powder enters the powder bin and is collected;

[0038] 5) The powder is transported from the powder bin to the granulator by an auger conveyor for granulation. In the granulation stage, hydrophilic fibers (highly hydrophilic hollow polyester staple fibers) are slowly added to the powder during the auger feeding process. The added ratio is 0.08% of the mass of the lead oxide powder. The length of the highly hydrophilic hollow polyester staple fibers is 1.0 to 1.5 mm, the fiber diameter is 10 μm to 30 μm, and the thermal decomposition temperature is 325°C.

[0039] 6) The granulator is turned on, and the powder and the hydrophilic fiber are fully mixed during the powder feeding process. Subsequently, as the granulation is carried out, the powder and the hydrophilic fiber are continuously replenished, and the mixing is completed synchronously;

[0040] 7) During the granulation process, pure water is added to the granulator through the pure water pipeline, and the water flow rate is controlled at 1L / min. The amount of water added is determined according to the granulation condition of the powder and is controlled at 5% of the mass of the lead oxide powder. The granulation diameter range is Screening is performed simultaneously until the powder particle diameter meets the requirements;

[0041] 8) The qualified particles are heated and oxidized in a multi-stage oxidation furnace. The oxidation furnace is divided into the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone starting from the top feed port. After the powder passes through the first temperature zone, it is gradually squeezed into the second temperature zone, the third temperature zone and the fourth temperature zone under the gravity of the subsequent powder feed;

[0042] In the first temperature zone, the temperature is controlled in the range of 105℃~120℃, and air is introduced simultaneously at a speed of 6L / min for drying pretreatment to ensure that the powder can quickly and smoothly enter the later temperature zone;

[0043] In the second temperature zone, the temperature is controlled in the range of 280℃-300℃, and air is introduced simultaneously at a speed of 7L / min. After this stage, the spherical particles become harder and are not easy to break in the subsequent temperature zones;

[0044] The third temperature zone is controlled at a temperature range of 490°C-500°C, and air is introduced simultaneously at a speed of 14L / min;

[0045] The fourth temperature zone is controlled at a temperature range of 400°C-420°C, and air is introduced simultaneously at a speed of 12L / min;

[0046] 9) The oxidized red lead is cooled and flows into a pulverizer for pulverization. The pulverized red lead powder is screened through a 200-mesh sieve. The screened finished product is transported to a storage bin through a secondary cyclone separator and a bag filter pipeline for testing and packaging;

[0047] 10) Products that fail the test and products that have spilled from packaging will enter the oxidation furnace for re-oxidation.

[0048] 11) Observe the qualified porous red lead powder under an electron scanning microscope (5000 times). Figure 1 As shown, it can be observed that the red lead powder prepared by the method of the present invention has a porous structure feature.

[0049] Example 2

[0050] A method for preparing porous red lead, the specific steps are as follows:

[0051] 1) One ton of electrolytic lead is sent to the lead melting furnace through a transmission belt for melting. Each lead bar weighs 50 kg, and there are 20 lead bars in total. The melting furnace is heated to 480°C, and the electrolytic lead is melted into liquid;

[0052] 2) Liquid lead flows into the powder making furnace through a closed pipe. The powder making furnace needs to be preheated before it is opened to prevent the lead liquid from cooling down quickly after it flows in. The preheating temperature stops when it reaches 500°C, and the lead liquid begins to flow into the powder making furnace. Heat is generated during the oxidation process of the lead powder, and heating is not required during the powder making stage. The transmission belt continuously feeds the material at a speed of one 50kg lead ingot every 3 minutes;

[0053] 3) Air is introduced into the powder making furnace at a speed of 6L / min. The lead liquid is rotated (200r / m) by high-speed centrifugal stirring in the powder making furnace. The temperature is controlled at 460°C. Under a negative pressure environment (0.3kPa), the outside air is sucked into the furnace. The impeller rotates to make the lead liquid and the air fully contact to generate fine lead powder with an oxidation degree of 98%. The lead on the surface of the lead liquid is oxidized to lead oxide. The powder obtained after primary oxidation in the powder making furnace is irregular lead oxide powder.

[0054] 4) The irregular powder is crushed and then screened by a secondary cyclone separator and a bag filter pipeline to obtain lead oxide powder without obvious large lumps, in which the free lead content is controlled at 2%, and the powder enters the powder bin and is collected;

[0055] 5) The powder is transported from the powder bin to the granulator by an auger conveyor for granulation. In the granulation stage, hydrophilic fibers (highly hydrophilic hollow polyester staple fibers) are slowly added to the powder during the auger feeding process. The added ratio is 0.10% of the mass of the lead oxide powder. The length of the highly hydrophilic hollow polyester staple fibers is 1.0 to 1.5 mm, the fiber diameter is 10 μm to 30 μm, and the thermal decomposition temperature is 375°C.

[0056] 6) The granulator is turned on, and the powder and the hydrophilic fiber are fully mixed during the powder feeding process. Subsequently, as the granulation is carried out, the powder and the hydrophilic fiber are continuously replenished, and the mixing is completed synchronously;

[0057] 7) During the granulation process, pure water is added to the granulator through the pure water pipeline, and the water flow rate is controlled at 1L / min. The amount of water added is determined according to the granulation condition of the powder and is controlled at 5% of the mass of the lead oxide powder. The granulation diameter range is Screening is performed simultaneously until the powder particle diameter meets the requirements;

[0058] 8) The qualified particles are heated and oxidized in a multi-stage oxidation furnace. The oxidation furnace is divided into the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone starting from the top feed port. After the powder passes through the first temperature zone, it is gradually squeezed into the second temperature zone, the third temperature zone and the fourth temperature zone under the gravity of the subsequent powder feed;

[0059] In the first temperature zone, the temperature is controlled within the range of 110℃~120℃, and air is introduced simultaneously at a speed of 6L / min for drying pretreatment to ensure that the powder can quickly and smoothly enter the later temperature zone;

[0060] In the second temperature zone, the temperature is controlled in the range of 220℃-240℃, and air is introduced simultaneously at a speed of 7L / min. After this stage, the spherical particles become harder and are not easy to break in the subsequent temperature zones;

[0061] The third temperature zone is controlled at a temperature range of 490°C-500°C, and air is introduced simultaneously at a speed of 12L / min;

[0062] The fourth temperature zone is controlled at a temperature range of 400°C-420°C, and air is introduced simultaneously at a speed of 14L / min;

[0063] 9) The oxidized red lead is cooled and flows into a pulverizer for pulverization. The pulverized red lead powder is screened through a 200-mesh sieve. The screened finished product is transported to a storage bin through a secondary cyclone separator and a bag filter pipeline for testing and packaging;

[0064] 10) Products that fail the test and products that have spilled from packaging will enter the oxidation furnace for re-oxidation.

[0065] Comparative Example 1

[0066] The production method of the current red lead powder manufacturing enterprise was used to prepare red lead as a comparative example. The specific steps are as follows:

[0067] 1) One ton of electrolytic lead is sent to the lead melting furnace for melting through a transmission belt. Each lead bar weighs 50 kg, and there are 20 lead bars in total. The melting furnace is heated to 530°C, and the electrolytic lead is melted into liquid;

[0068] 2) Liquid lead flows into the powder making furnace through a closed pipe. The powder making furnace needs to be preheated before it is opened to prevent the lead liquid from cooling down quickly after it flows in. The preheating temperature stops when it reaches 550°C, and the lead liquid begins to flow into the powder making furnace. Heat is generated during the oxidation process of the lead powder. No heating is required during the powder making stage. The transmission belt continuously feeds the material at a speed of one 50kg lead ingot every 3 minutes;

[0069] 3) Air is introduced into the powder making furnace at a speed of 10L / min. The lead liquid is rotated (200r / m) by high-speed centrifugal stirring in the powder making furnace. The temperature is controlled at 510°C. Under a negative pressure environment (0.3kPa), the outside air is sucked into the furnace. The impeller rotates to make the lead liquid and the air fully contact to generate fine lead powder with an oxidation degree of 97%. The lead on the surface of the lead liquid is oxidized to lead oxide. The powder obtained after primary oxidation in the powder making furnace is irregular lead oxide powder.

[0070] 4) The irregular powder is crushed and then screened by a secondary cyclone separator and a bag filter pipeline to obtain lead oxide powder without obvious large lumps, in which the free lead content is controlled at 3%, and the powder enters the powder bin and is collected;

[0071] 5) The granulator is turned on. During the granulation process, pure water is added to the granulator through the pure water pipeline. The water flow rate is controlled at 1L / min. The amount of water added is determined according to the granulation condition of the powder and is controlled at 5% of the mass of the lead oxide powder. The granulation diameter range is Screening is performed simultaneously until the powder particle diameter meets the requirements;

[0072] 6) The qualified particles are heated and oxidized in a multi-stage oxidation furnace. The oxidation furnace is divided into the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone starting from the top feed port. After the powder passes through the first temperature zone, it is gradually squeezed into the second temperature zone, the third temperature zone and the fourth temperature zone under the gravity of the subsequent powder feed;

[0073] In the first temperature zone, the temperature is controlled within the range of 110℃~120℃, and air is introduced simultaneously at a speed of 6L / min for drying pretreatment to ensure that the powder can quickly and smoothly enter the later temperature zone;

[0074] In the second temperature zone, the temperature is controlled within the range of 300℃-320℃, and air is introduced simultaneously at a speed of 10L / min. After this stage, the spherical particles become harder and are not easy to break in the subsequent temperature zones;

[0075] The third temperature zone is controlled at a temperature range of 500°C-510°C, and air is introduced simultaneously at a speed of 14L / min;

[0076] The fourth temperature zone is controlled at a temperature range of 400°C-420°C, and air is introduced simultaneously at a speed of 12L / min;

[0077] 7) The oxidized red lead is cooled and flows into a pulverizer for pulverization. The pulverized red lead powder is screened through a 200-mesh sieve. The screened finished product is transported to a storage bin through a secondary cyclone separator and a bag filter pipeline for testing and packaging;

[0078] 8) Products that fail the test and products that have spilled from packaging will enter the oxidation furnace for re-oxidation.

[0079] 9) Observe the qualified red lead powder under an electron scanning microscope (5000 times) to see whether Figure 2 The structural characteristics of red lead powder can be observed in the

[0080] Test Example 1

[0081] The powders prepared in Example 1, Example 2 and Comparative Example 1 were selected for battery experiments. Three kinds of lead pastes were prepared using a vacuum paste machine. The weight of each pot of lead powder was 950 kg, and the amount of powder added was 50 kg, totaling 1000 kg. 91.5 kg of sulfuric acid (density 1.4 g / cm 3 ), 93kg pure water.

[0082] On the basis of the above existing formula, according to the weight of 1000kg lead powder, 5kg antimony trioxide, 5kg stannous sulfate and 0.7kg short fiber are added.

[0083] The three types of positive plates were prepared by coating, curing and slicing in the conventional way. The negative plate is the corresponding plate with the same dimensions as the positive plate. In the negative electrode formula, 0.2% lignin and 0.07% short fiber are added according to the mass percentage of lead powder. The lead paste is prepared by vacuum and paste. The pure water and sulfuric acid used in the paste process are added in an amount calculated by the mass percentage of lead powder, 8.6% sulfuric acid, and the density of sulfuric acid is 1.4g / cm 3 (25°C), 9.5% pure water. After coating, curing and slicing, the negative electrode plate is prepared and assembled into a 6-DZF-20 battery.

[0084] After the batteries of Examples 1 to 2 and Comparative Example 1 were assembled, they were formed using the same formation process, and the specific process is as follows:

[0085] Table 1 Formation process

[0086] step Technology Current (A) Time (h) 1 Stand 2 2 Charge 4 15 3 Discharge 4 1 4 Charge 4 13 5 Stand 2 6 Discharge 4 2.5 7 Charge 4 4 8 Charge 3 10 9 Discharge 5 3.5 10 Charge 4 4 11 Charge 3 8 12 Discharge 10 2 13 Charge 4 4 14 Charge 3 3 15 Charge 1 10 16 Charge 1 3 17 Finish

[0087] (1) Pore structure determination of positive electrode

[0088] After the formation, three types of batteries with similar capacities were selected and dissected respectively. The positive plates were taken out and soaked in pure water until the pH value of the plate surface was neutral. They were placed in a vacuum drying oven and dried at 80°C. After drying and cooling, samples were taken from the middle of the plate for mercury injection and specific surface area analysis. The pore structure data are shown in Table 2 below:

[0089] Table 2 Analysis of the pore structure of the positive electrode

[0090] category Pore ​​volume (ml / g) Porosity (%) <![CDATA[Specific surface area (BET; m 2 / g)]]> Example 1 0.1108 45.87 4.639 Example 2 0.1324 48.62 4.987 Comparative Example 1 0.0837 39.21 3.256

[0091] From the data in the above table, it can be seen that after adding porous red lead material, the pore volume, porosity and specific surface area of ​​the positive electrode plate are significantly increased. Compared with Example 1, since the amount of fiber added in Example 2 is larger, the prepared red lead material has more microporous structure, and the pore structure of the subsequent electrode plate is correspondingly richer.

[0092] (2) Battery performance testing

[0093] The lead-acid batteries after formation in Examples 1 to 2 and Comparative Example 1 were sampled, 10 each, and a two-hour rate capacity test was performed in accordance with GB / T22199.1-2017 "Valve-regulated Lead-acid Batteries for Electric Power-Assisted Vehicles". Table 3 is a comparison of the average two-hour rate capacities of the three types of batteries.

[0094] Table 3 Performance test comparison

[0095] Capacity Test Example 1 Battery Example 2 Battery Comparative Example 1 Battery First normal temperature capacity (min) 124.6 125.3 121.6 Second normal temperature capacity (min) 126.7 127.7 122.4 The third normal temperature capacity (min) 128.4 129.1 122.9

[0096] From the data in the above table, we can see that after adding porous red lead material, the capacity of the embodiments has increased significantly, and the capacity increase in the first three times is very obvious. This is mainly due to the change in the positive electrode pore structure, which improves the utilization rate of active materials.

Claims

1. A method for preparing porous red lead, characterized in that: The following steps are involved: (1) melting electrolytic lead raw materials into lead liquid; (2) pulverizing the lead liquid to obtain lead oxide powder; (3) granulating the lead oxide powder, and adding hydrophilic fiber during the granulation process, wherein the mass of the hydrophilic fiber added is 0.08% to 0.10% of the mass of the lead oxide powder; (4) heating and oxidizing the particles obtained after granulation in step (3), wherein the hydrophilic fibers are incinerated during the heating and oxidation process, and a pore structure is formed in the particles after the hydrophilic fibers are incinerated; (5) Cooling the red lead obtained after the oxidation in step (4) and then crushing it to obtain the porous structure red lead.

2. The method for preparing porous red lead according to claim 1, characterized in that: The hydrophilic fiber has a length of 1.0 to 1.5 mm, a diameter of 10 μm to 30 μm, and a thermal decomposition temperature of 325° C. to 375° C.

3. The method for preparing porous red lead according to claim 1, characterized in that: The lead oxide powder obtained in step (2) controls the free lead content by mass ratio to be 2% to 5%.

4. The method for preparing porous red lead according to claim 1, characterized in that: The particle size of the particles obtained by granulation in step (3) is 2.0 to 3.0 mm.

5. The method for preparing porous red lead according to claim 1, characterized in that: During the heating oxidation in step (4), the heating temperature for incinerating the hydrophilic fibers is 460-480°C.

6. The method for preparing porous red lead according to claim 5, characterized in that: During the heating oxidation in step (4), a multi-stage oxidation furnace is used, and the multi-stage oxidation furnace is divided into a first temperature zone, a second temperature zone, a third temperature zone and a fourth temperature zone from top to bottom. The granulated particles enter from the top of the multi-stage oxidation furnace and pass through the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone in sequence. The temperature range of the first temperature zone is 105-120°C, the temperature range of the second temperature zone is 220-300°C, the temperature range of the third temperature zone is 490-500°C, and the temperature range of the fourth temperature zone is 400-420°C.

7. The method for preparing porous red lead according to claim 6, characterized in that: During the heating oxidation process, air is introduced into the multi-stage oxidation furnace, wherein the air introduction rates into the first temperature zone, the second temperature zone, the third temperature zone and the fourth temperature zone are 6L / min, 7L / min, 12-14L / min and 12-14L / min respectively.

8. A porous red lead prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the porous red lead according to claim 8 as an additive in the preparation of positive plates of lead-acid batteries.

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