Device and method for preparing tetrabasic lead sulfate ultrafine seed crystal

Abstract

The invention discloses a preparation device and a preparation method of superfine tetrabasic lead sulfate crystal seeds, and relates to the field of lead-acid batteries. The preparation device comprises a continuous flow reaction system, wherein the continuous flow reaction system comprises three reaction units, namely a nucleation area, a growth area and a stabilization area which are respectively composed of a reaction channel and a heat exchange device and are connected end to end. According to the preparation method, on the basis of the preparation device, the mass transfer efficiency of reaction liquid is improved by utilizing a high flow speed and a turbulent flow device in a continuous flow reaction system, formation of fine grains and long-strip-shaped 4BS seed crystals is promoted through a confinement effect and a directional shearing field, and the temperature is accurately controlled in a segmented manner, so that help is provided for particle size and morphology control and side reaction inhibition. The tetrabasic lead sulfate seed crystal prepared according to the device and the method disclosed by the invention is used as a positive electrode additive of a lead-acid battery, has extremely small influence on the initial capacity of the battery, and can greatly prolong the cycle life.

Description

Technical Field

[0001] The present invention relates to the field of lead-acid batteries, and in particular to a device and method for preparing ultrafine tetrabasic lead sulfate seeds. Background Art

[0002] Lead-acid batteries are widely used traditional secondary batteries, boasting advantages such as low cost, mature technology, and high safety. In the new energy era, they continue to play a vital role in applications such as automotive starting power supplies, energy storage systems, and uninterruptible power supplies. However, the positive electrode material in lead-acid batteries is susceptible to corrosion and shedding, resulting in a short service life. Adding tetrabasic lead sulfate (4BS) seed crystals to the positive electrode paste can improve the cycle life of lead-acid batteries. The smaller the seed crystal size and the larger the aspect ratio within a certain range, the better the resulting battery performance.

[0003] Among the common 4BS preparation methods, the hydrothermal synthesis method can better control the product morphology, but the product usually has a large particle size; if it undergoes subsequent grinding, it is difficult to maintain the rod-shaped structure of the crystal, and the hydrothermal method is generally difficult to directly obtain high-purity 4BS crystals.

[0004] A Chinese invention patent application with publication number CN109867302A discloses a high-purity, ultrafine tetrabasic lead sulfate product and its preparation method. By adding a suitable catalyst and particle size control agent, rod-shaped 4BS crystals with an average particle size of ≤10 μm are obtained, while also shortening the reaction time and improving the product purity.

[0005] A Chinese invention patent application with publication number CN113880133A discloses a method for preparing tetrabasic lead sulfate for lead-acid batteries. Using a crystallization promoter composed of EDTA and glycolic acid, an ultrapure 4BS product with a length of approximately 10 μm and a diameter of approximately 1 μm was obtained in a relatively short time and at normal pressure.

[0006] Tetrabasic lead sulfate of this particle size is typically used as a direct additive in lead-acid battery positive electrodes. However, tetrabasic lead sulfate used as seed crystals to induce the formation of fine 4BS crystals in the positive electrode and paste is typically smaller in particle size, resulting in higher formation efficiency and cycle life. Conventional methods have proven difficult to produce submicron (particle size <1μm) tetrabasic lead sulfate seed crystals with high aspect ratios (≥10). Summary of the Invention

[0007] The present invention aims to provide a device and method for preparing ultrafine tetrabasic lead sulfate seeds. 4BS seeds are continuously prepared using a continuous flow reaction system, the temperature is controlled in stages, and the confinement effect and periodic turbulence of narrow channels are utilized to precisely control the size and morphology of the obtained 4BS seeds.

[0008] One of the purposes of the present invention is to disclose a device for preparing ultrafine tetrabasic lead sulfate seeds, which comprises a mixing system 1, a continuous flow reaction system 2 and a post-processing system 3.

[0009] The mixing system 1 includes a lead oxide mixing tank 11 and a sulfuric acid mixing tank 12 .

[0010] The continuous flow reaction system 2 includes three reaction units: a nucleation zone 21 , a growth zone 22 and a stabilization zone 23 . Each reaction unit includes a reaction channel 210 , 220 , 230 and a heat exchange device 211 , 221 , 231 .

[0011] The reaction channels 210, 220, and 230 of each reaction unit are connected end to end in the order listed. The front end of the reaction channel 210 in the nucleation zone 21 has two feed ports connected to the lead oxide mixing tank 11 and the sulfuric acid mixing tank 12, respectively. The rear end of the reaction channel 230 in the stabilization zone 23 has a discharge port connected to the post-processing system 3.

[0012] Preferably, the reaction channels 210 , 220 , 230 are composed of a plurality of sub-channels connected in parallel, each sub-channel is provided with a flow disturbance structure, and the equivalent diameter of a single sub-channel is 100 to 500 μm.

[0013] More preferably, in the nucleation zone 21 , the equivalent diameter of a single sub-channel is 300-500 μm; in the growth zone 22 , the equivalent diameter of a single sub-channel is 100-300 μm.

[0014] Preferably, the two feed inlets are arranged in a Y shape at their confluence, and the branching angle is 90 to 120°.

[0015] A second object of the present invention is to disclose a method for preparing ultrafine tetrabasic lead sulfate seeds, using the above-mentioned preparation device and comprising the following steps:

[0016] S1: Mix lead oxide, dispersant, chelating agent and water in a lead oxide mixing tank 11 to obtain a lead oxide suspension; mix sulfuric acid, catalyst and water in a sulfuric acid mixing tank 12 to obtain a sulfuric acid solution.

[0017] S2: Lead oxide suspension and sulfuric acid solution are continuously and uniformly fed into the continuous flow reaction system 2 through two feed ports, and sequentially pass through reaction channels 210, 220, and 230;

[0018] S3: The reaction liquid is fed into the post-processing system 3 from the discharge port, where it is separated, washed, and dried to obtain the tetrabasic lead sulfate ultrafine crystal seeds.

[0019] Preferably, the dispersant is selected from one or more of anionic surfactants and nonionic surfactants, and the amount of the dispersant used is 0.3-1.5% of the mass of the lead oxide. The chelating agent is selected from ethylenediaminetetraacetic acid, citric acid, tartaric acid, alkali metal salts of the above three substances, or a combination thereof, and the amount of the chelating agent used is 0.1-1.0% of the mass of the lead oxide.

[0020] Preferably, the catalyst is selected from formic acid, acetic acid, nitric acid, citric acid or a combination thereof, and the amount of the catalyst used is 0.5-6.0% of the mass of the sulfuric acid.

[0021] Preferably, the concentration of the lead oxide suspension is 0.4 to 0.9 mol / L, and the concentration of the sulfuric acid solution is 0.1 to 0.3 mol / L. The lead oxide suspension is fed into the continuous flow reaction system 2 at a flow rate of 1.0 to 2.0 mL / min, and the sulfuric acid solution is fed into the continuous flow reaction system 2 at a flow rate of 0.6 to 1.6 mL / min. The molar ratio of lead oxide to sulfuric acid fed simultaneously is 4.95 to 5.10:1.

[0022] Preferably, the temperatures in the nucleation zone 21, the growth zone 22 and the stabilization zone 23 are controlled at 60-70°C, 85-95°C and 50-60°C respectively.

[0023] Preferably, the residence time of the reaction liquid in the nucleation zone 21, the growth zone 22 and the stabilization zone 23 is 30-60 s, 180-300 s and 60-120 s respectively.

[0024] The technical solution of the present invention has the following beneficial effects:

[0025] 1. The apparatus for preparing ultrafine tetrabasic lead sulfate seeds of the present invention is based on a continuous flow reaction system, and each reaction unit consists of three zones with independently controlled tube diameter, tube length, and temperature. Compared with conventional kettle reactions, the properties of the product can be better controlled.

[0026] 2. The method for preparing ultrafine tetrabasic lead sulfate seeds of the present invention achieves instantaneous, stable and uniform mixing of lead oxide and sulfuric acid through a continuous flow reaction system, inhibits the agglomeration and sedimentation of lead oxide and 4BS particles, improves product purity and raw material conversion rate, and greatly reduces reaction time and energy consumption.

[0027] 3. The narrow channel of the continuous flow reaction system produces a confinement effect, while the high-speed directional liquid flow promotes the directional arrangement of the grains during movement, so that the preparation method described in the present invention can better control the particle size of the obtained 4BS seed crystals in liquid phase synthesis, and promote them to form uniform slender strips, thereby improving their performance.

[0028] Reference numerals

[0029] Figure 1 This is a schematic diagram of the device for preparing ultrafine tetrabasic lead sulfate seeds described in Device Example 1.

[0030] In the figure: 1 is a mixing system, 2 is a continuous flow reaction system, 3 is a post-treatment system, 11 is a lead oxide mixing tank, 12 is a sulfuric acid mixing tank, 21 is a nucleation zone, 22 is a growth zone, 23 is a stabilization zone, 210, 220, 230 are reaction channels in the nucleation zone, the growth zone and the stabilization zone respectively, 211, 221, 231 are heat exchange devices in the nucleation zone, the growth zone and the stabilization zone respectively. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the implementation methods of the present invention and should be understood as illustrative rather than limiting of the technical solutions of the present invention.

[0032] The present invention discloses a device for preparing ultrafine tetrabasic lead sulfate seeds:

[0033] It consists of a mixing system 1, a continuous flow reaction system 2 and a post-processing system 3.

[0034] The mixing system 1 includes a lead oxide mixing tank 11 and a sulfuric acid mixing tank 12 .

[0035] The continuous flow reaction system 2 includes three reaction units: a nucleation zone 21 , a growth zone 22 and a stabilization zone 23 . Each reaction unit includes reaction channels 210 , 220 , 230 and heat exchange devices 211 , 221 , 231 .

[0036] The reaction channels 210, 220, and 230 of each reaction unit are connected end to end in the order listed. The front end of the reaction channel 210 in the nucleation zone 21 has two feed ports connected to the lead oxide mixing tank 11 and the sulfuric acid mixing tank 12, respectively. The rear end of the reaction channel 230 in the stabilization zone 23 has a discharge port connected to the post-processing system 3.

[0037] The core of the preparation device described in this invention is a continuous flow reaction system consisting of three sequentially arranged reaction units, each independently controlled in terms of reaction channel size, length, and temperature. This allows for precise control of temperature, flow rate, and flow pattern during the three reaction stages of hydrothermal synthesis of tetrabasic lead sulfate seeds from lead oxide and sulfuric acid: (1) lead sulfate formation and 4BS nucleation, (2) 4BS nucleus growth, and (3) 4BS seed maturation and morphology stabilization. Compared to conventional hydrothermal synthesis methods that rely on magnetic stirring to control mixing, the method described in this invention provides a more stable and robust directional shear field, resulting in crystals with superior morphology.

[0038] Preferably, the reaction channels 210 , 220 , and 230 are composed of a plurality of sub-channels connected in parallel, each sub-channel is provided with a flow disturbance structure, and the equivalent diameter of a single sub-channel is 100 to 500 μm.

[0039] The flow-disrupting structures include, but are not limited to, flow-disrupting columns and plates disposed within the subchannels, as well as diamond-shaped flow-disrupting elements, spiral or serpentine structures within the subchannels themselves. The diameter of the subchannels must be such that the 4BS grains are physically confined and maintain a high directional shear force, forcing the grains to align longitudinally and inhibiting their lateral growth. Furthermore, the diameter cannot be too small, otherwise clogging may occur even with nanoscale raw materials.

[0040] More preferably, in the nucleation zone 21 , the equivalent diameter of a single sub-channel is 300-500 μm; in the growth zone 22 , the equivalent diameter of a single sub-channel is 100-300 μm.

[0041] The nucleation zone is where the reaction solutions mix, lead oxide converts to lead sulfate, and 4BS micronuclei begin to form. This reaction step takes a very short time and has low requirements for mass transfer rate, confinement, and high shear force. Therefore, a slightly larger diameter is used to expand the mixing space and reduce the risk of clogging. In the growth zone, a narrow diameter and high flow rate are required to strictly control the morphology of the 4BS seed product.

[0042] Preferably, the two feed inlets are arranged in a Y shape at their confluence, and the branching angle is 90 to 120°.

[0043] The branch angle of 90 to 120 degrees controls particle breakage, agglomeration, and friction adsorption with the tube wall while ensuring mixing efficiency.

[0044] In addition, it is also preferred to use a polymer reaction channel with a silanized inner wall (such as PDMS, PMMA, etc.) to ensure the channel strength while reducing the adsorption of lead salts on the tube wall.

[0045] The present invention further discloses a method for preparing ultrafine tetrabasic lead sulfate seeds, which uses the above-mentioned preparation device and includes the following steps:

[0046] S1: Mix lead oxide, dispersant, chelating agent and water in a lead oxide mixing tank 11 to obtain a lead oxide suspension; mix sulfuric acid, catalyst and water in a sulfuric acid mixing tank 12 to obtain a sulfuric acid solution.

[0047] S2: Lead oxide suspension and sulfuric acid solution are continuously and uniformly fed into the continuous flow reaction system 2 through two feed ports, and pass through the reaction channels 210, 220, and 230 in sequence;

[0048] S3: The reaction liquid is fed into the post-processing system 3 from the discharge port, where it is separated, washed, and dried to obtain the tetrabasic lead sulfate ultrafine crystal seeds.

[0049] The lead oxide is lead monoxide (PbO). Due to the relatively mild reaction conditions, nano-lead oxide with a smaller particle size is preferably used as a reactant to increase the reaction rate and conversion rate, control the particle size of the product and reduce the risk of clogging; the equivalent particle size of the nano-lead oxide is less than 200 nm, preferably less than 100 nm.

[0050] Preferably, the dispersant is selected from one or more of anionic surfactants and nonionic surfactants, and the amount of the dispersant used is 0.3-1.5% of the mass of the lead oxide. The chelating agent is selected from ethylenediaminetetraacetic acid, citric acid, tartaric acid, alkali metal salts of the above three substances, or a combination thereof, and the amount of the chelating agent used is 0.1-1.0% of the mass of the lead oxide.

[0051] The anionic surfactant includes but is not limited to sodium dodecyl sulfate SDS, sodium dodecylbenzene sulfonate SDBS, and the nonionic surfactant includes but is not limited to polyvinyl alcohol PVA, polyvinyl pyrrolidone PVP. More preferably, the dispersant includes both anionic surfactants and nonionic surfactants; when the dispersant includes anionic surfactants, it is preferred to use a small amount of sulfuric acid solution to adjust the pH of the lead oxide suspension to 4.0-5.0. The role of the chelating agent is to slow down the Pb 2+ Ions and SO4 2+ In order to reduce the reaction rate, it is preferred to use a weaker chelating agent, or add a small amount of a strong chelating agent (EDTA) in combination.

[0052] Preferably, the catalyst is selected from formic acid, acetic acid, nitric acid, citric acid or a combination thereof, and the amount of the catalyst used is 0.5-6.0% of the mass of the sulfuric acid.

[0053] The acid catalyst of the present invention mainly promotes the initial mixing stage of Pb in the nucleation zone. 2+ The formation of , while some organic weak acids can stabilize pH or play a role in complexation. The lower the additional acidity provided by the catalyst, the longer the reaction liquid needs to stay, but it is beneficial to the purity and fineness of the product.

[0054] Preferably, the concentration of the lead oxide suspension is 0.4 to 0.9 mol / L, and the concentration of the sulfuric acid solution is 0.1 to 0.3 mol / L. The lead oxide suspension is fed into the continuous flow reaction system 2 at a flow rate of 1.0 to 2.0 mL / min, and the sulfuric acid solution is fed into the continuous flow reaction system 2 at a flow rate of 0.6 to 1.6 mL / min. The molar ratio of lead oxide to sulfuric acid fed simultaneously is 4.95 to 5.10:1.

[0055] Lead oxide suspensions have a high solids content, so a high flow rate is required to maintain particle suspension. However, if the flow rate is too high, the solid particles will impact the channel walls at the bends with strong forces, which can lead to sedimentation or desorption. At the same time, the flow rate difference between the two channels should not be too large to prevent stratified flow and affect the uniformity of the mixed solution. During operation, the flow rates of the two reaction solutions must correspond to their concentrations to keep the Pb / S ratio close to stoichiometric (5:1).

[0056] Preferably, the temperatures in the nucleation zone 21, the growth zone 22 and the stabilization zone 23 are controlled at 60-70°C, 85-95°C and 50-60°C respectively.

[0057] During the initial stages of reactant mixing, lead salt production, and 4BS nucleation, the reaction temperature should be kept low to prevent excessive nucleation, agglomeration, or encapsulation by hydrolyzed Pb(OH)2 colloids. Once the 4BS nuclei reach a certain number and volume, the temperature should be raised to accelerate the ripening rate and maximize the thermodynamic advantage of the 4BS product. Furthermore, a stepwise ramping of the temperature can prevent the formation of bubbles and localized crystallization, while also stabilizing the grain size.

[0058] Preferably, the residence time of the reaction liquid in the nucleation zone 21, the growth zone 22 and the stabilization zone 23 is 30-60 s, 180-300 s and 60-120 s respectively.

[0059] As mentioned above, the reaction rate in the nucleation zone is relatively fast, while crystal growth and dimensional stabilization require more time. However, overall, existing research has demonstrated that in microchannels with high shear and intense mixing, the temperature of certain hydrothermal reactions can be significantly reduced, and the reaction rate can be increased by 1 to 2 orders of magnitude.

[0060] The following is a detailed description with reference to the accompanying drawings and examples. The experimental methods are conventional unless otherwise specified, and the raw materials are from conventional sources unless otherwise specified. The raw lead oxide is a nano-α-PbO prepared according to the method described in Chinese invention CN102616833B, with a diameter of less than 10 nm and a length of less than 500 nm.

[0061] Device Example 1

[0062] like Figure 1 The preparation device of tetrabasic lead sulfate ultrafine crystal seeds is shown.

[0063] It should be noted that the scale in the figure has nothing to do with the actual scale. The continuous flow reaction system is enlarged to show the details, and the post-processing system is only represented by a box.

[0064] In the preparation device described in this embodiment, the reaction channel is made of PDMS and is composed of 900 sub-channels. The equivalent diameters of single sub-channels in the nucleation zone, growth zone and stabilization zone are 400 μm, 150 μm and 250 μm, respectively; the disturbance structure in the nucleation zone and the stabilization zone is a serpentine channel, and the disturbance structure in the growth zone is a serpentine channel and a spoiler (for schematic purposes only); the branching angle of the two feed ports is 100°.

[0065] Preparation Example 1

[0066] All preparation examples adopt the preparation apparatus described in Apparatus Example 1.

[0067] (1) Prepare lead oxide suspension (0.65 mol / L): Dissolve 137.1 g of nano-lead oxide, 0.4 g of sodium dodecylbenzenesulfonate, 0.83 g of polyvinylpyrrolidone, 0.2 g of disodium ethylenediaminetetraacetic acid, and 0.49 g of sodium citrate in 930 mL of water. Ultrasonicate and homogenize in a lead oxide mixing tank, stirring slowly to maintain dispersion.

[0068] (2) Prepare sulfuric acid solution (0.2 mol / L): Dissolve 12.0 g of concentrated sulfuric acid (98%) and 0.4 g of glacial acetic acid in 600 mL of water and stir evenly in a sulfuric acid mixing tank.

[0069] (3) Lead oxide suspension and sulfuric acid solution were fed into the continuous flow reaction system through the feed port at a rate of 1.4 mL / min and 0.9 mL / min, respectively, with Pb / S = 5.06:1; the temperatures in the nucleation zone, growth zone, and stabilization zone were controlled at 65°C, 90°C, and 55°C, respectively, and the residence times were 45 s, 240 s, and 90 s, respectively.

[0070] (4) The reaction liquid discharged from the discharge port enters a post-processing system and is washed twice with ammonium chloride solution and then water. After each wash, the solid is filtered and separated. The resulting solid is dried at 70°C for 8 hours to obtain ultrafine tetrabasic lead sulfate seeds. X-ray fluorescence spectroscopy analysis shows a Pb / S ratio of 5.004 and a purity of 99.6% (impurities are calculated as PbO). SEM imaging shows that the product is in the form of elongated strips with an average diameter of 31 nm and an average length of 440 nm.

[0071] Preparation Example 2

[0072] (1) Prepare lead oxide suspension (0.9 mol / L): Dissolve 205.3 g of nano-lead oxide, 1.0 g of sodium lauryl sulfate, 2.1 g of polyethylene glycol-400, 0.6 g of disodium ethylenediaminetetraacetic acid, and 1.5 g of potassium sodium tartrate in 1000 mL of water, and mix them in a lead oxide mixing tank by ultrasonic homogenization while stirring slowly to maintain dispersion.

[0073] (2) Prepare sulfuric acid solution (0.3 mol / L): Dissolve 18.0 g of concentrated sulfuric acid (98%) and 1.0 g of formic acid in 600 mL of water and stir evenly in a sulfuric acid mixing tank.

[0074] (3) Lead oxide suspension and sulfuric acid solution were fed into the continuous flow reaction system through the feed port at rates of 1.0 mL / min and 0.6 mL / min, respectively, with Pb / S = 5:1; the temperatures in the nucleation zone, growth zone, and stabilization zone were controlled at 70°C, 95°C, and 60°C, respectively, and the residence times were 60 s, 300 s, and 120 s, respectively.

[0075] (4) The reaction liquid discharged from the outlet of the serpentine channel was subjected to a post-treatment device and washed twice with ammonium chloride solution and water, respectively. After each wash, the solid was filtered and separated. The resulting solid was dried at 70°C for 8 hours to obtain ultrafine tetrabasic lead sulfate seeds. X-ray fluorescence spectroscopy analysis showed that the product had a Pb / S ratio of 4.980 and a purity of 99.5% (impurities were calculated as PbSO4). SEM imaging showed that the product was in the form of elongated strips with an average diameter of 40 nm and an average length of 530 nm.

[0076] Preparation Example 3

[0077] (1) Prepare lead oxide suspension (0.4 mol / L): Dissolve 90.1 g of nano-lead oxide, 0.07 g of sodium dodecylbenzene sulfonate, 0.2 g of polyvinyl alcohol, and 0.09 g of sodium citrate in 1000 mL of water, ultrasonically homogenize the mixture in a lead oxide mixing tank, and stir slowly to maintain dispersion.

[0078] (2) Prepare sulfuric acid solution (0.1 mol / L): Dissolve 8.0 g of concentrated sulfuric acid (98%) and 0.04 g of nitric acid (calculated as NO2) in 800 mL of water and stir evenly in a sulfuric acid mixing tank.

[0079] (3) Lead oxide suspension and sulfuric acid solution were fed into the continuous flow reaction system through the feed port at a rate of 2.0 mL / min and 1.6 mL / min, respectively, with Pb / S = 5:1; the temperatures in the nucleation zone, growth zone, and stabilization zone were controlled at 60°C, 85°C, and 50°C, respectively, and the residence times were 30 s, 180 s, and 60 s, respectively.

[0080] (4) The reaction liquid exiting the serpentine channel was subjected to a post-treatment device, washed twice with an ammonium chloride solution and then with water. After each wash, the solid was filtered and separated. The resulting solid was dried at 60°C for 12 hours to obtain ultrafine tetrabasic lead sulfate seeds. X-ray fluorescence spectroscopy analysis revealed a Pb / S ratio of 4.992 and a purity of 99.8% (impurities calculated as PbSO4). SEM imaging revealed the product to be elongated strips with an average diameter of 27 nm and an average length of 340 nm.

[0081] The 4BS seed crystals obtained in the above examples were subjected to battery and paste performance tests: the positive plate of the 3-D-180 electric road vehicle lead-acid battery was used as the experimental object, 0.5wt% of 4BS seed crystals were added to its formula, and then the paste was mixed at 60°C in a vacuum paste mixing machine, applied to the surface of the same electrode plate, and cured at a temperature of 75°C and a relative humidity of 95% for 8 hours. In addition, a control group 1 (commercially available 4BS seed crystals, synthesized and ground by a hydrothermal method, with an average particle size of 200nm and an addition amount of 1wt%) and a control group 2 (no 4BS seed crystals were added) were also set up. The matching negative plates were taken and assembled into a lead-acid battery in an alternating arrangement of 9 positive and 10 negative. The initial capacity and cycle life of the battery were tested using three-stage charging and constant current discharge (expressed as the number of cycles at which the battery capacity remained 70%, and the cycle at which the battery capacity just began to stabilize was used as the starting point for calculation). The test results are shown in Table 1.

[0082] Table 1 Initial capacity and cycle life of lead-acid batteries

[0083]

[0084] It can be seen that the 4BS seed crystals obtained by the preparation device and method of the present invention achieve a better effect of improving the battery cycle life with a smaller addition amount, and have a relatively low impact on the initial capacity.

[0085] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description, and such obvious variations or modifications should still be considered within the scope of protection of the present invention.

Claims

1. A device for preparing ultrafine tetrabasic lead sulfate seeds, characterized in that: It consists of a mixing system (1), a continuous flow reaction system (2) and a post-processing system (3); The mixing system (1) includes a lead oxide mixing tank (11) and a sulfuric acid mixing tank (12); The continuous flow reaction system (2) includes three reaction units: a nucleation zone (21), a growth zone (22), and a stabilization zone (23); the reaction units include reaction channels (210, 220, 230) and heat exchange devices (211, 221, 231); The reaction channels (210, 220, 230) of each reaction unit are connected end to end in the order listed. The front end of the reaction channel (210) of the nucleation zone (21) has two feed ports connected to the lead oxide mixing tank (11) and the sulfuric acid mixing tank (12) respectively. The rear end of the reaction channel (230) of the stabilization zone (23) has a discharge port connected to the post-processing system (3).

2. The device for preparing ultrafine tetrabasic lead sulfate seeds according to claim 1, wherein: The reaction channels (210, 220, 230) are composed of a plurality of sub-channels connected in parallel, each sub-channel is provided with a flow disturbance structure, and the equivalent diameter of a single sub-channel is 100 to 500 μm.

3. The device for preparing ultrafine tetrabasic lead sulfate seeds according to claim 2, wherein: In the nucleation zone (21), the equivalent diameter of a single sub-channel is 300 to 500 μm; and in the growth zone (22), the equivalent diameter of a single sub-channel is 100 to 300 μm.

4. The device for preparing ultrafine tetrabasic lead sulfate seeds according to claim 1, wherein: The two feed ports are arranged in a Y shape at their confluence, and the branching angle is 90-120 degrees.

5. A method for preparing ultrafine tetrabasic lead sulfate seeds, characterized in that: The preparation device according to any one of claims 1 to 4 is used, and comprises the following steps: S1: mixing lead oxide, a dispersant, a chelating agent and water in a lead oxide mixing tank (11) to obtain a lead oxide suspension; Sulfuric acid, a catalyst and water are mixed in a sulfuric acid mixing tank (12) to obtain a sulfuric acid solution; S2: The lead oxide suspension and the sulfuric acid solution are continuously and uniformly fed into the continuous flow reaction system (2) through two feed ports, and sequentially pass through the reaction channels (210, 220, 230); S3: The reaction liquid is fed into a post-processing system (3) from the discharge port, where it is separated, washed, and dried to obtain the tetrabasic lead sulfate ultrafine crystals.

6. The method for preparing ultrafine tetrabasic lead sulfate seeds according to claim 5, wherein: The dispersant is selected from one or more of anionic surfactants and nonionic surfactants, and the amount of the dispersant is 0.3-1.5% of the mass of the lead oxide; the chelating agent is selected from ethylenediaminetetraacetic acid, citric acid, tartaric acid, alkali metal salts of the above three substances or a combination thereof, and the amount of the chelating agent is 0.1-1.0% of the mass of the lead oxide.

7. The method for preparing ultrafine tetrabasic lead sulfate seeds according to claim 5, wherein: The catalyst is selected from formic acid, acetic acid, nitric acid, citric acid or a combination thereof, and the amount of the catalyst is 0.5-6.0% of the mass of the sulfuric acid.

8. The method for preparing ultrafine tetrabasic lead sulfate seeds according to claim 5, wherein: The concentration of the lead oxide suspension is 0.4-0.9 mol / L, and the concentration of the sulfuric acid solution is 0.1-0.3 mol / L; the flow rate of the lead oxide suspension input into the continuous flow reaction system (2) is 1.0-2.0 mL / min, and the flow rate of the sulfuric acid solution input into the continuous flow reaction system (2) is 0.6-1.6 mL / min; and the molar ratio of the lead oxide to the sulfuric acid inputted at the same time is 4.95-5.10:

1.

9. The method for preparing ultrafine tetrabasic lead sulfate seeds according to claim 5, wherein: The temperatures in the nucleation zone (21), the growth zone (22) and the stabilization zone (23) are controlled at 60-70°C, 85-95°C and 50-60°C respectively.

10. The method for preparing ultrafine tetrabasic lead sulfate seeds according to claim 5, characterized in that: The residence time of the reaction liquid in the nucleation zone (21), the growth zone (22) and the stabilization zone (23) is 30 to 60 seconds, 180 to 300 seconds and 60 to 120 seconds respectively.

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