Positive electrode active material for power battery and production process of positive electrode active material

Abstract

The invention discloses a positive active material for a power battery and a production process thereof, the positive active material for the power battery comprises major materials and auxiliary additives, the major materials comprise 80-85% of lead powder; 4%-9% of sulfuric acid; 7.5%-11.5% of pure water; the auxiliary additive comprises the following components in percentage by weight: 0.1%-0.20% of graphite; 0.08%-0.12% of short fibers; 0.08% to 0.1% of antimony trioxide; 0.09% to 0.14% of stannous mono-sulphate; 0.3%-0.7% of glass fiber; and 0.2%-0.5% of lithium hydroxide. Medium-long glass fibers are arranged to construct a macroscopic framework to provide millimeter-level support, the overall deformation resistance of the lead plaster is effectively improved, microcosmic pores of the lead plaster are accurately filled with superfine short fibers, microcosmic bonding among particles is effectively enhanced, the superfine short fibers and the microcosmic pores are combined to form a continuous'micro-medium-macro 'three-level reinforced network, and the microcosmic bonding is effectively enhanced. The contradiction that traditional fibers are difficult to disperse if being long and weak in support if being short is solved, so that the bonding force between the adjusted lead paste and the grid is greatly improved, the falling rate of active substances is reduced, and the lead paste is more suitable for being used in a high-frequency vibration scene.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to positive electrode active materials for power batteries, as well as the production process of positive electrode active materials for power batteries. Background Technology

[0002] Power batteries are "high-power output batteries" specifically designed for new energy vehicles, electric equipment, etc. Their core purpose is to "drive loads" and they must simultaneously meet stringent requirements such as high-power discharge (such as vehicle acceleration), vibration resistance, and rapid charging and discharging.

[0003] The positive electrode active material (PbO2 after formation) is the core carrier for storing and releasing electrical energy in a battery. The bumps and vibrations during the operation of an electric vehicle will continuously impact the active material. If the adhesion is insufficient, it will directly cause the particles to detach. The detachment of active material is an irreversible process. The detached particles cannot re-attach to the grid, which will not only lead to rapid capacity decay but also significantly shorten the battery cycle life and reduce its service life. Summary of the Invention

[0004] This invention addresses the problem in existing technologies where insufficient adhesive strength of active materials leads to detachment due to continuous external mechanical impact, and proposes the following technical solution: The positive electrode active material used in power batteries includes main components and auxiliary additives, and the following components are measured by mass percentage: the main components include: lead powder 80%-85%; sulfuric acid 4%-9%; pure water 7.5%-11.5%; the auxiliary additives include: graphite 0.1%-0.20%; short fibers 0.08%-0.12%; antimony trioxide 0.08%-0.1%; stannous sulfate 0.09%-0.14%; glass fiber 0.3%-0.7%; lithium hydroxide 0.2%-0.5%.

[0005] As a preferred embodiment of the above technical solution, the short fiber is an ultrafine short fiber with a length of 5-10 μm, and the glass fiber is a medium-length glass fiber with a length of 30-50 μm.

[0006] As a preferred embodiment of the above technical solution, the antimony trioxide contains mixed nano-bismuth oxide, and the volume ratio of the nano-bismuth oxide to the antimony trioxide is 1:3-1:2, thereby forming an "antimony-bismuth" composite corrosion inhibition system.

[0007] The production process of positive electrode active materials for power batteries includes the following steps: S1. Dry mixing pretreatment; Add lead powder and all auxiliary additives into the paste mixer, and use a method of premixing at low stirring speed and dispersing at high speed to mix the materials. The auxiliary additives and lead powder are mixed at the molecular level through shear force. S2, gradient wet mixing; Add pure water into the paste mixing machine, first use medium speed to stir so that the water initially coats the lead powder particles, then perform vacuum degassing and switch to low speed to remove the air from the pores of the lead powder so that the water can fully penetrate. S3. Add acid in steps; a. First addition of acid: Add 40%-50% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. The temperature will naturally rise to 65-68℃. The initial exothermic reaction will promote the initial reaction between PbO and sulfuric acid to generate basic PbSO4 crystal nuclei. b. Secondary acid addition: Add 25%-35% of the total sulfuric acid to the paste mixer, stir at 55r / min for 3-4min, and turn on the exhaust system to maintain a stable temperature when the temperature rises to 70-72℃. c. Three additions of acid: Finally, add 20%-30% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. When the temperature exceeds 72℃, the jacket water cooling and exhaust will be automatically turned on to form a coordinated temperature control to ensure that the reaction endpoint temperature is still stable at 70-72℃, and promote the uniform growth of PbSO4 crystals. S4. Segmented cooling; After adding acid, gradually lower the temperature to the paste discharge temperature. When the temperature drops below 50°C, maintain a low stirring speed for 2-3 minutes to fully stabilize the lead paste structure. After discharge, the production of active substances is complete.

[0008] As a preferred embodiment of the above technical solution, S5 and visual density closed-loop control are also included; Three minutes before the ointment is dispensed, real-time monitoring is performed using an online visual density meter to achieve the final desired effect. If the apparent density is >4.60 g / cm³, automatically add some pure water and stir for 1 minute at a low stirring speed to reduce density; If the apparent density is <4.50 g / cm³, increase the stirring speed to medium and extend the stirring time by 2 minutes to improve the density through shear force.

[0009] As a preferred embodiment of the above technical solution, the gradual cooling in step S4 includes the following: First stage (5 min): Stir at a speed of 45 r / min, and use ventilation and water cooling to quickly cool down to 60℃; Second stage (5-8 min): Gradually reduce the rotation speed from 45 r / min to 30 r / min, decreasing the speed by 5 r / min every 2 min, while intermittent stirring reduces shear damage to the fiber network.

[0010] As a preferred embodiment of the above technical solution, the initial low-speed stirring speed is 25 r / min, the medium-speed stirring speed is 40 r / min, and the high-speed stirring speed is 60 r / min.

[0011] The beneficial effects of this invention are as follows: 1. The medium-length glass fiber structure provides millimeter-level support to the macroscopic framework, effectively improving the overall deformation resistance of the lead paste. Meanwhile, the ultra-fine short fiber precisely fills the microscopic pores of the lead paste, effectively enhancing the microscopic adhesion between particles. The combination of the two forms a continuous "micro-meta-macro" three-level reinforcement network, which solves the contradiction of traditional fibers being "difficult to disperse when long and weak to support when short". This significantly improves the adhesion between the adjusted lead paste and the grid, reduces the active material shedding rate, and is more suitable for the use of power batteries in high-frequency vibration scenarios, ensuring the battery's range and cycle life. 2. Based on the inhibition of grid corrosion by antimony trioxide, nano-bismuth oxide improves crystal stability by refining the crystals of active materials; the two form a synergistic effect of "corrosion inhibition + crystal optimization". After adjusting the pH value, lithium hydroxide works with the "antimony-bismuth" system to stabilize the structure of active materials and delay cycle decay. 3. The dry mixing mode of "low-speed premixing + high-speed dispersion" is adopted. Low-speed premixing can avoid the formation of agglomerates of ultrafine short fibers due to excessive shear force, while high-speed dispersion can make medium and long glass fibers spread evenly through strong shear force, ensuring that the two form "encapsulated dispersion" on the surface of lead powder. This solves the characteristics of "ultrafine short fibers are easy to agglomerate and medium and long glass fibers are difficult to disperse", laying a physical foundation for the formation of the three-level network and the uniformity of subsequent wet mixing and reaction. 4. Add acid once (40%-50%) and control the temperature at 65-68℃ to avoid the initial violent exothermic reaction that could damage the nano-bismuth particles. Add acid a second and third time to maintain a stable temperature range of 70-72℃. This ensures that the lead powder (PbO) and sulfuric acid react fully to form uniform PbSO4 crystal nuclei. Combined with dual temperature control of ventilation and water cooling, this also prevents the "antimony-bismuth" composite system from failing due to high temperature. Attached Figure Description

[0012] Figure 1 The diagram shown is a production process flow chart of an embodiment; Figure 2 The diagram shown is a comparison of the cycle curves in the embodiment. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings.

[0014] The positive electrode active material used in power batteries includes main components and auxiliary additives, and the following components are measured by mass percentage: the main components include: lead powder 80%-85%; sulfuric acid 4%-9%; pure water 7.5%-11.5%; the auxiliary additives include: graphite 0.1%-0.20%; short fibers 0.08%-0.12%; antimony trioxide 0.08%-0.1%; stannous sulfate 0.09%-0.14%; glass fiber 0.3%-0.7%; lithium hydroxide 0.2%-0.5%.

[0015] The short fiber is an ultrafine short fiber with a length of 5-10 μm, and the glass fiber is a medium-length glass fiber with a length of 30-50 μm.

[0016] Medium and long glass fibers form the macroscopic framework, while ultra-fine short fibers are used to fill the microscopic pores, forming a three-level reinforcement network of "micro-meso-macro". This significantly improves the adhesion while avoiding uneven dispersion caused by single fiber length.

[0017] The medium-length glass fibers form a macroscopic framework that provides millimeter-level support, effectively improving the overall deformation resistance of the lead paste. Meanwhile, the ultra-fine short fibers precisely fill the microscopic pores of the lead paste, effectively enhancing the microscopic adhesion between particles. The combination of the two forms a continuous "micro-medium-macro" three-level reinforcement network, which solves the contradiction of traditional fibers being "difficult to disperse when long and weak in support when short". This significantly improves the adhesion between the adjusted lead paste and the grid, reduces the active material shedding rate, and is more suitable for the use of power batteries in high-frequency vibration scenarios.

[0018] The antimony trioxide contains nano-bismuth oxide, and the volume ratio of the nano-bismuth oxide to the antimony trioxide is 1:3-1:2. The antimony trioxide and the nano-bismuth oxide form an "antimony-bismuth" composite corrosion inhibition system.

[0019] Based on the inhibition of grid corrosion by antimony trioxide, nano-bismuth oxide improves the crystal stability by refining the crystals of active materials; the two form a synergistic effect of "corrosion inhibition + crystal optimization". After adjusting the pH value, lithium hydroxide works with the "antimony-bismuth" system to stabilize the structure of active materials and delay cycle decay. Under the premise that graphite and stannous sulfate synergistically improve conductivity, it forms a closed loop of "structure enhancement - conductivity optimization - performance stabilization" with medium and long glass fibers and ultra-fine short fibers, further optimizing the active materials.

[0020] Figure 1 The production process of the positive electrode active material used in power batteries includes the following steps: S1. Dry mixing pretreatment; Add lead powder and all auxiliary additives into the paste mixer, and use a method of premixing at low stirring speed and dispersing at high speed to mix the materials. The auxiliary additives and lead powder are mixed at the molecular level through shear force. Lead powder is mixed with auxiliary materials such as graphite, short fibers, and glass fibers at different rotation speeds to break up the agglomerates of the auxiliary materials. The high-speed shear force enables the auxiliary material particles to adhere evenly to the surface of the lead powder, forming a dispersion system with "lead powder as the core and auxiliary materials as the outer layer". This lays the physical foundation for the uniformity of the subsequent wet mixing reaction.

[0021] The dry mixing mode of "low-speed premixing + high-speed dispersion" is adopted. Low-speed premixing can avoid the formation of agglomerates of ultrafine short fibers due to excessive shear force, while high-speed dispersion can make medium and long glass fibers spread evenly through strong shear force, ensuring that the two form "encapsulated dispersion" on the surface of lead powder. This solves the characteristics of "ultrafine short fibers are easy to agglomerate and medium and long glass fibers are difficult to disperse", and lays the physical foundation for the formation of the three-level network and the uniformity of subsequent wet mixing and reaction.

[0022] S2, gradient wet mixing; Add pure water into the paste mixing machine, first use medium speed to stir so that the water initially coats the lead powder particles, then perform vacuum degassing and switch to low speed to remove the air from the pores of the lead powder so that the water can fully penetrate. Preheated pure water at 42°C rapidly penetrates the gaps and surface of lead powder particles, wetting the lead powder surface and reducing the resistance to the subsequent reaction between sulfuric acid and lead powder. Vacuum degassing forces the air out of the pores of the lead powder, preventing air from blocking the contact between moisture and sulfuric acid with the lead powder and eliminating the "local dry area" in the subsequent reaction.

[0023] S3. Add acid in steps; a. First addition of acid: Add 40%-50% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. The temperature will naturally rise to 65-68℃. The initial exothermic reaction will promote the initial reaction between PbO and sulfuric acid to generate basic PbSO4 crystal nuclei. When the PbO layer on the surface of the lead powder comes into contact with sulfuric acid, it triggers an initial reaction, generating a thin layer of PbSO4 crystal nuclei, and the temperature naturally rises to 67℃ (a physical phenomenon caused by the exothermic reaction).

[0024] b. Secondary acid addition: Add 25%-35% of the total sulfuric acid to the paste mixer, stir at 55r / min for 3-4min, and turn on the exhaust system to maintain a stable temperature when the temperature rises to 70-72℃. Sulfuric acid penetrates into the inner layer of lead powder, PbO continues to react, crystal nuclei grow rapidly, and the temperature rises to 70-72℃ (the peak of the exothermic reaction). At this point, temperature control is required to avoid the reaction from being too fast and resulting in coarse crystals.

[0025] c. Three additions of acid: Finally, add 20%-30% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. When the temperature exceeds 72℃, the jacket water cooling and exhaust will be automatically turned on to form a coordinated temperature control to ensure that the reaction endpoint temperature is still stable at 70-72℃, and promote the uniform growth of PbSO4 crystals. The remaining PbO reacts completely, and PbSO4 crystals grow uniformly, forming a stable crystal structure. The exothermic reaction gradually weakens, and the temperature is maintained at 70-72℃.

[0026] The first addition of acid (40%-50%) controls the temperature at 65-68℃ to avoid the initial violent exothermic reaction that could damage the nano-bismuth particles. The second and third additions of acid maintain a stable temperature range of 70-72℃, which ensures that the lead powder (PbO) and sulfuric acid react fully to form uniform PbSO4 crystal nuclei. Combined with dual temperature control of ventilation and water cooling, this also prevents the "antimony-bismuth" composite system from failing due to high temperature, thus solving the problem of nano-bismuth oxide easily agglomerating and failing at high temperatures (>75℃).

[0027] S4. Segmented cooling; After adding acid, gradually lower the temperature to the paste discharge temperature. When the temperature drops below 50°C, maintain a low stirring speed for 2-3 minutes to fully stabilize the lead paste structure. After discharge, the production of active substances is complete.

[0028] The gradual cooling process in S4 includes the following: First stage (5 min): Stir at a speed of 45 r / min, and use ventilation and water cooling to quickly cool down to 60℃; Second stage (5-8 min): Gradually reduce the rotation speed from 45 r / min to 30 r / min, decreasing the speed by 5 r / min every 2 min, while intermittent stirring reduces shear damage to the fiber network.

[0029] The viscosity of lead paste gradually increases as the temperature decreases, and PbSO4 crystals stop growing rapidly and enter a stable stage. By gradually reducing the speed and intermittent stirring, the damage of shear force to the fiber network can be reduced, allowing short fibers and glass fibers to form a three-dimensional support structure in the lead paste, thereby allowing PbSO4 crystals to be evenly distributed in the fiber network.

[0030] It also includes S5 and visual density closed-loop control; Three minutes before the ointment is dispensed, real-time monitoring is performed using an online visual density meter to achieve the final desired effect. If the apparent density is >4.60 g / cm³, some pure water will be automatically added and stirred for 1 minute at a low stirring speed to reduce the density, increase the water content of the lead paste, reduce the friction between particles, and thus decrease the apparent density. If the apparent density is <4.50 g / cm³, increase the stirring speed to medium and extend the stirring time by 2 minutes. This will improve the density through shear force, compress the internal pores of the lead paste through mechanical shear force, increase the particle packing density, and thus increase the apparent density.

[0031] Through physical adjustments, the apparent density of the lead paste was stabilized at 4.55±0.03 g / cm³, balancing the "particle contact density" and the "electrolyte permeability porosity".

[0032] The initial low-speed stirring speed is 25 r / min, the medium-speed stirring speed is 40 r / min, and the high-speed stirring speed is 60 r / min.

[0033] The formulation builds performance potential through innovations such as fiber grading and composite corrosion inhibition, while the process optimizes potential through uniform dispersion and precise temperature control, ultimately achieving a triple improvement in the positive electrode active material of power batteries: "high adhesion, long life, and high consistency". It is especially suitable for scenarios with stringent requirements for reliability and cycle performance, such as new energy vehicles and energy storage. Example

[0034] Based on 1000g of lead powder, the following formula was used: 1000g lead powder (82%), 85g sulfuric acid (6.8%), 130g pure water (10.4%), 1.8g graphite (0.14%), 1.2g short fiber (0.1%), 1.0g antimony trioxide (0.08%), 1.3g stannous sulfate (0.1%), 6g glass fiber (0.48%), and 4g lithium hydroxide (0.32%), for a total weight of 1231.3g.

[0035] Production steps: S1. Dry mixing pretreatment: Add 1000g of lead powder to the paste mixer, add all the auxiliary materials, first premix at a low speed of 25r / min for 2min, then disperse at a high speed of 60r / min for 4min to ensure that the auxiliary materials are evenly attached to the surface of the lead powder.

[0036] S2, Gradient wet mixing: Add 130g of pure water preheated to 42℃, stir at a medium speed of 40r / min for 2min, then evacuate to -0.06MPa and stir at a low speed of 25r / min for 3min to remove air from the pores of the lead powder.

[0037] S3, Stepwise addition of acid: Take 1.33 g / cm³ 3 85g of sulfuric acid, added in 3 portions: a. Add 34g (40%) for the first time, stir at 50r / min for 4min, and let the temperature rise naturally to 67℃; b. Add 25.5g (30%) for the second time, stir at 55 rpm for 3 minutes, and turn on the exhaust fan (200m) when the temperature rises to 71℃. 3Temperature control ( / h); c. Add 25.5g (30%) for the third time, stir at 50r / min for 6min, and stabilize the temperature at 70-72℃. If the temperature exceeds the limit, turn on the jacket water cooling auxiliary temperature control.

[0038] S4. Segmented cooling and stirring: After adding acid, stir at 45r / min for 5min (with ventilation and water cooling) to cool down to 60℃; then gradually reduce the speed to 30r / min (5r / min every 2min), stir intermittently (stir for 3min + stop for 30s) for 6min, and finally cool down to 48℃.

[0039] S5, Visual Density Modulation: Detected visual density was 4.56 g / cm³. 3 (Meets 4.55±0.03g / cm³), dispense the ointment directly.

[0040] Instruction manual illustrations Figure 2 The battery cycle curves for the normal and experimental excipient formulations differ by 226 cycles. The battery model is 6-DZF-22H, and the curves are 2-hour discharge curves. The test method is as follows: 1. The fully charged batteries (4 in series) are discharged at 11A in an environment of (25±2)℃ until the battery pack terminal voltage is 42V. 2. Constant voltage 59.2V, current limit 11A, charging time 4 hours; 3. The above constitutes one cycle. Repeat steps 1-2 until the discharge time is less than 1.6 hours for three consecutive times, at which point the experiment will be terminated.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A positive electrode active material for power batteries, characterized in that, The product comprises main components and auxiliary additives, and the following components are measured by mass percentage: the main components include: lead powder 80%-85%; sulfuric acid 4%-9%; pure water 7.5%-11.5%; the auxiliary additives include: graphite 0.1%-0.20%; short fibers 0.08%-0.12%; antimony trioxide 0.08%-0.1%; stannous sulfate 0.09%-0.14%; glass fiber 0.3%-0.7%; and lithium hydroxide 0.2%-0.5%.

2. The positive electrode active material for power batteries according to claim 1, characterized in that, The short fiber is an ultrafine short fiber with a length of 5-10 μm, and the glass fiber is a medium-length glass fiber with a length of 30-50 μm.

3. The positive electrode active material for power batteries according to claim 1, characterized in that, The antimony trioxide contains nano-bismuth oxide, and the volume ratio of the nano-bismuth oxide to the antimony trioxide is 1:3-1:

2. The antimony trioxide and the nano-bismuth oxide form an "antimony-bismuth" composite corrosion inhibition system.

4. The production process for the positive electrode active material of a power battery according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Dry mixing pretreatment; Add lead powder and all auxiliary additives into the paste mixer, and use a method of premixing at low stirring speed and dispersing at high speed to mix the materials. The auxiliary additives and lead powder are mixed at the molecular level through shear force. S2, gradient wet mixing; Add pure water into the paste mixing machine, first use medium speed to stir so that the water initially coats the lead powder particles, then perform vacuum degassing and switch to low speed to remove the air from the pores of the lead powder so that the water can fully penetrate. S3. Add acid in steps; a. First addition of acid: Add 40%-50% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. The temperature will naturally rise to 65-68℃. The initial exothermic reaction will promote the initial reaction between PbO and sulfuric acid to generate basic PbSO4 crystal nuclei. b. Secondary acid addition: Add 25%-35% of the total sulfuric acid to the paste mixer, stir at 55r / min for 3-4min, and turn on the exhaust system to maintain a stable temperature when the temperature rises to 70-72℃. c. Three additions of acid: Finally, add 20%-30% of the total amount of sulfuric acid into the paste mixer and stir at 50r / min for 6-8min. When the temperature exceeds 72℃, the jacket water cooling and exhaust will be automatically turned on to form a coordinated temperature control to ensure that the reaction endpoint temperature is still stable at 70-72℃, and promote the uniform growth of PbSO4 crystals. S4. Segmented cooling; After adding acid, gradually lower the temperature to the paste discharge temperature. When the temperature drops below 50°C, maintain a low stirring speed for 2-3 minutes to fully stabilize the lead paste structure. After discharge, the production of active substances is complete.

5. The production process for the positive electrode active material of a power battery according to claim 4, characterized in that, It also includes S5 and visual density closed-loop control; Three minutes before the ointment is dispensed, real-time monitoring is performed using an online visual density meter to achieve the final desired effect. If the apparent density is >4.60 g / cm³ 3 Automatically add some pure water and stir for 1 minute at a low stirring speed to reduce density; If the apparent density is <4.50 g / cm³ 3 Increase the stirring speed to medium and extend the stirring time by 2 minutes to improve density through shear force.

6. The production process for the positive electrode active material of a power battery according to claim 4, characterized in that, The gradual cooling process in S4 includes the following: First stage (5 min): Stir at a speed of 45 r / min, and use ventilation and water cooling to quickly cool down to 60℃; Second stage (5-8 min): Gradually reduce the rotation speed from 45 r / min to 30 r / min, decreasing the speed by 5 r / min every 2 min, while intermittent stirring reduces shear damage to the fiber network.

7. The production process for the positive electrode active material of a power battery according to claim 4, characterized in that, The initial low-speed stirring speed is 25 r / min, the medium-speed stirring speed is 40 r / min, and the high-speed stirring speed is 60 r / min.

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