A slurry mixing process of high-dispersibility positive electrode slurry and a positive electrode sheet preparation method

Abstract

This invention provides a slurry mixing process for highly dispersible positive electrode slurry and a method for preparing positive electrode sheets. This slurry mixing process and method for preparing positive electrode sheets significantly improves slurry dispersibility through a three-stage process: pre-dispersion of conductive agent, dual planetary gradient mixing, and ultrasonic optimization. The slurry fineness is reduced to 2-3 μm, and the uniformity of distribution of active material and conductive agent exceeds 95%, solving the problems of local enrichment and agglomeration in traditional processes. The conductivity of the electrode sheets is optimized, with a well-constructed three-dimensional conductive network and a resistivity as low as 3.5-4.0 Ω·cm, a reduction of 30%-40% compared to traditional processes. Interfacial adhesion is enhanced, with the binder uniformly adsorbed on the particle surface, achieving a peel strength of 22-25 N / m, while reducing binder usage by 8%, avoiding the contradiction between increased resistance and powdering. Production efficiency and stability are improved, with the total mixing time shortened to 65-80 minutes. Combined with online detection and precise temperature control, batch consistency is better, and indicators such as electrode burrs and solvent residue meet high standards.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, and more specifically, to a slurry mixing process for highly dispersible positive electrode slurry and a method for preparing positive electrode sheets. Background Technology

[0002] With the rapid development of new energy vehicles, energy storage power stations, and other fields, the market demand for lithium-ion batteries continues to rise, and the industry's requirements for battery energy density, fast charging performance, and cycle life are becoming increasingly stringent. The positive electrode, as the core component for charge storage and transfer in lithium-ion batteries, directly determines the overall quality and service reliability of the battery. The slurry mixing process, as a crucial pre-process in positive electrode preparation, not only affects the stability of subsequent processes such as coating, drying, and rolling, but also plays a decisive role in the final electrode's dispersion uniformity, conductivity, and interfacial bonding strength. It is one of the core technological bottlenecks restricting the improvement of lithium-ion battery performance.

[0003] Currently, the mainstream cathode slurry mixing process in the industry mostly adopts a single-tank stirring mode. Although this process is simple to operate, it has three major technical problems that are difficult to overcome: First, conductive agents (such as carbon nanotubes, SuperP, etc.) are prone to agglomeration during the mixing process, which cannot form a continuous and uniform three-dimensional conductive network in the slurry, directly leading to an increase in the resistivity of the cathode sheet and a decrease in the battery charge transfer efficiency. Second, the binder (such as PVDF, aqueous PVA and acrylate copolymer composite system, etc.) is unevenly dispersed. When the content is too low in some areas, it will cause insufficient peel strength between the electrode and the current collector, and powdering will easily occur during charge and discharge cycles. When the content is too high, it will increase the interfacial impedance and affect the lithium ion migration rate. Third, traditional single-tank stirring equipment has a stirring dead zone, which leads to uneven mixing of the cathode active material and various auxiliary materials. The fineness of the prepared slurry is usually greater than 5μm, which in turn causes an imbalance in the current distribution during the charge and discharge of the electrode sheet and aggravates the degradation of battery performance.

[0004] To address the shortcomings of the single-tank stirring process, some patents have proposed a multi-tank, staged stirring approach. However, existing multi-tank processes still have significant technical limitations, failing to meet the demands of industrial production and high-performance batteries. Firstly, current solutions lack a clear quantitative correlation between key process parameters such as stirring speed, dispersion time, and temperature at each stage and the slurry dispersibility and electrode conductivity. This results in poor process repeatability and significant performance fluctuations between different batches, failing to meet the stringent stability requirements of large-scale industrial production. Secondly, no effective solution has been proposed for protecting the molecular chains during binder dispersion. In pursuing dispersion efficiency, excessive shearing can easily lead to binder molecular chain breakage, which in turn reduces electrode adhesion performance, making it difficult to achieve synergistic optimization of slurry dispersibility, electrode conductivity, and adhesion. Furthermore, with the widespread application of new high-energy-density cathode materials such as high-nickel ternary materials (e.g., NCM811, NCA92, NCMA91) and lithium manganese iron phosphate (LMFP), these materials exhibit higher surface activity and more complex particle morphologies, placing higher demands on the precision of the slurry mixing process. Existing processes are no longer adequate to meet the performance requirements of these new materials.

[0005] This invention can achieve a positive electrode slurry fineness ≤3μm, an electrode peel strength ≥20N / m, and a resistivity ≤4Ω・cm by controlling the stirring intensity, the order of material addition, and the dispersion time, while reducing the amount of binder by 5%-10%. Summary of the Invention

[0006] The present invention aims to solve the technical problems mentioned in the background art and provide a slurry mixing process for highly dispersible positive electrode slurry and a method for preparing positive electrode sheets.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a slurry mixing process for highly dispersible positive electrode slurry, comprising the following steps: Step 1: Select the following components by mass percentage: positive electrode active material, dispersant, composite conductive agent, binder, functional additive, and solvent. The specific components are as follows: positive electrode active material mass fraction 88-97%; composite conductive agent mass fraction 1.5-3%; binder mass fraction 1-2%; solvent mass fraction 3-8%; functional additive mass fraction 0.1-0.5%. The sum of the mass percentages of the above components is 100%. Step 2, First Stage: Add 50% solvent to the first dispersion tank, start the high-speed shear disperser, set the speed to 3000-4000 rpm, and control the temperature at 25-30℃; add the composite conductive agent in 3 batches, with an interval of 2 minutes between each batch, and continue dispersing for 15-20 minutes to form a conductive slurry (particle size D90≤100nm); the key mechanism is to break up the carbon nanotube agglomeration through high-frequency shearing, and SuperP fills the gaps between the carbon nanotubes to initially construct a three-dimensional conductive network; Step 3, Second Stage: Active Material Composite and Macroscopic Uniform Mixing. The conductive slurry is transported to a dual planetary mixer, and the positive electrode active material and lithium supplement are added. The revolution speed is set to 500-800 rpm and the rotation speed to 1500-2000 rpm, and the mixture is stirred for 20-30 minutes. 30% solvent is added by spraying, controlling the spraying speed to 1-2 mL / s to avoid sudden increases in local viscosity. The key mechanism is that the dual planetary mixer eliminates dead zones, and the spraying of solvent achieves gradient wetting of the material, reducing the agglomeration of active materials. Step 4, Third Stage: Binder Shaping and Interface Bonding Optimization. The mixed slurry is transported to an ultrasonic dispersion tank, and the binder and dispersant are added. The ultrasonic power is set to 500-800W and the frequency to 20-40kHz, while stirring at a low speed of 1000-1500rpm for 10-15min. The remaining 20% ​​solvent is added to adjust the viscosity to 3000-5000mPa・s. After passing the online viscometer test, ultrasonic defoaming is performed in the pipeline at a power of 300W for 5min. The key mechanism is that ultrasonic dispersion promotes the uniform adsorption of binder molecular chains on the particle surface, and low-speed stirring avoids molecular chain breakage, ensuring adhesion performance.

[0008] Further preferred options: The positive electrode active material can be lithium iron phosphate, ternary material NCM811 / NCA92 or NCMA91, with a particle size D50 of 2-8μm and a water content ≤500ppm.

[0009] A further preferred embodiment: the composite conductive agent may be a mixture of SuperP, ECP and carbon nanotubes at a mass ratio of 3:1, with the carbon nanotubes having an aspect ratio ≥500.

[0010] A further preferred embodiment: the adhesive may be PVDF with a molecular weight of 500,000-800,000, or a waterborne PVA and acrylate copolymer compound system.

[0011] A further preferred embodiment: the solvent is NMP or deionized water with a purity ≥99.5%.

[0012] A further preferred embodiment: the functional additive may be a mixture of dispersant BYK-163 and lithium supplementer Li2CO3 at a mass ratio of 2:1.

[0013] A method for preparing highly dispersible positive electrode sheets using the above-mentioned slurry includes the following steps: The prepared positive electrode slurry is coated onto an aluminum foil current collector at a speed of 10-15 m / min, with a thickness of 12 μm and a wet film thickness of 80-120 μm; the drying process during coating adopts a three-stage drying method, with temperatures of 80℃, 120℃, and 150℃ respectively, for a total time of 15-20 min, and the solvent residue is ≤0.5%; the compaction density after coating is controlled at 3.0-3.5 g / cm³, and the pressure is 5-8 MPa; after rolling, the electrode sheets are cut into widths of 50-200 mm, with burr length ≤5 μm. Beneficial effects

[0014] 1. By incorporating a conductive agent pre-dispersion step, high-speed shear dispersion breaks up carbon nanotube agglomerations, and SuperP fills the gaps, initially constructing a continuous three-dimensional conductive network. This lays the foundation for the formation of subsequent conductive pathways. This step avoids the agglomeration problem caused by direct mixing of the conductive agent with other materials, ensuring that the conductive agent is uniformly dispersed in the slurry. This significantly reduces the electrode resistivity to as low as 3.5-4.0 Ω・cm, which is more than 1.9 Ω・cm lower than without the pre-dispersion step. At the same time, the pre-dispersed conductive agent has more sufficient contact with the active material. Combined with subsequent process optimization, this further improves the slurry dispersion uniformity, with a distribution uniformity of ≥95%. It avoids localized enrichment or absence of conductive agent, ensuring stable electrode conductivity and creating conditions for uniform adsorption of the binder, indirectly contributing to improved peel strength. This solves the synergistic contradiction between conductivity and adhesion in traditional processes. 2. By incorporating a dual planetary tank, the combined stirring function of its revolution and rotation effectively eliminates the dead zone problem inherent in traditional single-tank stirring, significantly improving the uniformity of material mixing. In the second stage, a spray-type gradient solvent addition achieves gradient wetting of active materials, effectively preventing localized viscosity spikes and agglomeration, laying the foundation for subsequent dispersion optimization. The equipment's strong mixing capability ensures full contact between active materials, pre-dispersed conductive agents, and other components, reducing micro-agglomeration and resulting in a finer slurry with a particle size as low as 2.8 μm. Simultaneously, it maintains a stable electrode resistivity of approximately 3.8 Ω·cm. Furthermore, the uniform mixing environment facilitates the subsequent uniform adsorption of the binder, maintaining electrode peel strength above 21 N / m. Balancing conductivity and interfacial adhesion, this solution addresses the performance fluctuation problem caused by uneven mixing in traditional single-tank stirring, improving batch stability. 3. In summary, the mixing process and electrode preparation method of this highly dispersible positive electrode slurry employ a three-stage gradient mixing process. The mixing process is based on the pre-dispersion of the conductive agent, utilizing high-speed shearing to construct a continuous three-dimensional conductive network. Next, a dual planetary tank with synergistic rotation and revolution is used for stirring, combined with gradient spraying of solvent to eliminate mixing dead zones and prevent material agglomeration. Finally, ultrasonic dispersion optimizes interface bonding, coupled with online viscosity detection and defoaming, ensuring a slurry fineness of 2-3 μm and a stable viscosity of 3000-5000 mPa·s, resulting in a suitable electrode. The preparation process employs a three-stage drying, precise rolling, and slitting process, strictly controlling compaction density, solvent residue, and burr indicators. This method optimizes the entire process from material dispersion, mixing uniformity, interface bonding to molding, reducing electrode resistivity by 30%-40% and peel strength to 22-25 N / m. It also shortens the slurry mixing time, improves batch stability, and reduces binder usage. This solves the pain points of uneven dispersion and the contradiction between conductivity and bonding in traditional processes, providing an efficient and reliable technical solution for the large-scale production of high-performance power batteries. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the SEM images of the embodiments and comparative examples of the present invention. Detailed Implementation

[0016] The following will refer to the appendices in the embodiments of the present invention. Figure 1 The technical solutions in the embodiments of the present invention will be clearly and completely described.

[0017] Please see Figure 1 In this embodiment of the invention, a slurry mixing process for a highly dispersible positive electrode slurry includes the following steps: Step 1: Select the following components by mass percentage: positive electrode active material, dispersant, composite conductive agent, binder, functional additive, and solvent. The specific components are as follows: positive electrode active material mass fraction 88-97%; composite conductive agent mass fraction 1.5-3%; binder mass fraction 1-2%; solvent mass fraction 3-8%; functional additive mass fraction 0.1-0.5%. The sum of the mass percentages of the above components is 100%. Step 2, First Stage: Add 50% solvent to the first dispersion tank, start the high-speed shear disperser, set the speed to 3000-4000 rpm, and control the temperature at 25-30℃; add the composite conductive agent in 3 batches, with an interval of 2 minutes between each batch, and continue dispersing for 15-20 minutes to form a conductive slurry (particle size D90≤100nm); the key mechanism is to break up the carbon nanotube agglomeration through high-frequency shearing, and SuperP fills the gaps between the carbon nanotubes to initially construct a three-dimensional conductive network; Step 3, Second Stage: Active Material Composite and Macroscopic Uniform Mixing. The conductive slurry is transported to a dual planetary mixer, and the positive electrode active material and lithium supplement are added. The revolution speed is set to 500-800 rpm and the rotation speed to 1500-2000 rpm, and the mixture is stirred for 20-30 minutes. 30% solvent is added by spraying, controlling the spraying speed to 1-2 mL / s to avoid sudden increases in local viscosity. The key mechanism is that the dual planetary mixer eliminates dead zones, and the spraying of solvent achieves gradient wetting of the material, reducing the agglomeration of active materials. Step 4, Third Stage: Binder Shaping and Interface Bonding Optimization. The mixed slurry is transported to an ultrasonic dispersion tank, and the binder and dispersant are added. The ultrasonic power is set to 500-800W and the frequency to 20-40kHz, while stirring at a low speed of 1000-1500rpm for 10-15min. The remaining 20% ​​solvent is added to adjust the viscosity to 3000-5000mPa・s. After passing the online viscometer test, ultrasonic defoaming is performed in the pipeline at a power of 300W for 5min. The key mechanism is that ultrasonic dispersion promotes the uniform adsorption of binder molecular chains on the particle surface, and low-speed stirring avoids molecular chain breakage, ensuring adhesion performance.

[0018] The positive electrode active material can be lithium iron phosphate, ternary materials NCM811 / NCA92 or NCMA91, with a particle size D50 of 2-8μm and a water content ≤500ppm; the composite conductive agent can be a mixture of SuperP, ECP and carbon nanotubes at a mass ratio of 3:1, with the carbon nanotubes having an aspect ratio ≥500; the binder can be PVDF with a molecular weight of 500,000-800,000, or a composite system of aqueous PVA and acrylate copolymer; the solvent is NMP or deionized water with a purity ≥99.5%; the functional additive can be a mixture of dispersant BYK-163 and lithium supplementer Li2CO3 at a mass ratio of 2:1. The specific steps for preparing highly dispersible positive electrode sheets using the above slurry are as follows: The prepared positive electrode slurry was coated onto the aluminum foil current collector at a speed of 10-15 m / min, with a thickness of 12 μm and a wet film thickness of 80-120 μm. The drying process during coating was carried out in three stages, with temperatures of 80℃, 120℃, and 150℃ respectively, for a total time of 15-20 min, and the solvent residue was ≤0.5%. The compaction density of the roller after coating was controlled at 3.0-3.5 g / cm³, and the pressure was 5-8 MPa. After roller pressing, the plates were cut into electrode sheets with a width of 50-200 mm and a burr length of ≤5 μm. Example

[0019] The positive electrode slurry is prepared using ternary material NCA92 active material with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%. The positive electrode slurry mixing process parameters refer to the three-stage gradient process in steps two to four of this invention. The coating, rolling and slitting processes refer to the positive electrode sheet preparation method in this invention. Example

[0020] The positive electrode slurry is prepared using ternary material NCA92 active material with a mass fraction of 97%, composite conductive agent with a mass fraction of 1.2%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.3%. The positive electrode slurry mixing process parameters refer to the three-stage gradient process in steps two to four of this invention. The coating, rolling and slitting processes refer to the positive electrode sheet preparation method in this invention.

[0021] Comparative Example 1 The composition of the positive electrode sheet is the same as in Example 1: the positive electrode slurry is prepared using ternary material NCA92 active material with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%. The slurry mixing process adopts the traditional single-tank stirring process: all NMP is added at once to a 100L (5L-1400L) single-tank stirring equipment (equipped with an anchor-type stirring paddle), stirring is started, the speed is set to 800-1200rpm, and the temperature is at room temperature (the slurry temperature is controlled by condensate, usually fluctuating between 20-35℃); then all PVDF preparation solution is added at once, and stirring is continued for 90-120min until the PVDF is initially dissolved (no obvious solid particles, but uneven local dissolution is likely to occur). Keep the stirring speed constant (800-1200 rpm), add all the conductive agent (such as SuperP) at once, and stir for 30-45 minutes. After the conductive agent is initially dispersed, add all the ternary active material NCA at once. At this time, the viscosity of the material in the tank increases sharply, and agglomeration is likely to occur. The stirring speed needs to be increased to 1500-1800 rpm, and stirring should be continued for 90-120 minutes for high-viscosity mixing. During this period, the mixing state is judged by visual observation (if there are no obvious lumps of material, it is considered qualified). There is no intermediate sampling and testing. After stirring, if the slurry viscosity is too high (e.g., exceeding 6000 mPa·s), add solvent (NMP) at once to adjust it to the target viscosity (3000-5000 mPa·s). Then turn off the stirring and let it stand for 15-20 minutes for natural defoaming (or vacuum defoaming) to finally obtain the positive electrode slurry. The coating, rolling and slitting processes are the same as the positive electrode preparation method in this invention.

[0022] Comparative Example 2 The composition of the positive electrode sheet is the same as in Example 1: the positive electrode slurry is prepared using ternary material NCA92 active material with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%. The positive electrode slurry mixing process parameters refer to the three-stage gradient process of steps two to four in this invention, except that the ultrasonic dispersion step in the third stage is removed. The coating, rolling and slitting processes refer to the positive electrode sheet preparation method in this invention.

[0023] Comparative Example 3 The composition of the positive electrode sheet is the same as in Example 1: the positive electrode slurry is prepared using ternary material NCA92 active material with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%. The positive electrode slurry mixing process parameters refer to the three-stage gradient process of steps two to four in this invention, omitting the first stage of conductive adhesive preparation and the composite conductive agent pre-dispersion step. The coating, rolling and slitting processes refer to the positive electrode sheet preparation method in this invention.

[0024] Comparative Example 4 The composition of the positive electrode sheet is the same as in Example 1: the positive electrode slurry is prepared using ternary material NCA92 with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%. The slurry mixing process parameters refer to the three-stage gradient process in steps two to four of this invention, wherein the order of adding composite conductive agent and binder is reversed, the binder is pre-dispersed first, and then the conductive agent and active material are added. The coating, rolling and slitting processes refer to the positive electrode sheet preparation method in this invention.

[0025] Comparative Example 5 The composition of the positive electrode sheet is the same as in Example 1: the positive electrode slurry preparation uses ternary material NCA92 active material with a mass fraction of 96.3%, composite conductive agent with a mass fraction of 1.8%, PVDF with a mass fraction of 1.5%, and functional additives with a mass fraction of 0.4%; the positive electrode slurry mixing process parameters refer to the three-stage gradient process of steps two to four in the present invention, wherein the double planetary stirring tank used in the second stage is replaced with a traditional single-tank stirring device, and the coating, rolling and slitting processes refer to the positive electrode sheet preparation method in the present invention.

[0026] The parameters of the positive electrode sheets prepared in the above embodiments and comparative examples are shown in the following table: Indicator Example Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example 1 2 1 2 3 4 5 Slurry fineness (pm) 2.8 3.4 6.2 4.5 4.8 5.2 4.1 Slurry viscosity (mPa-s) 4022 3871 5872 4952 4523 6211 4333 Eccentricity (pm) 3.8 4.5 6.5 5.2 5.7 6.1 4.9 Peeling strength (N / m) 23.5 21.4 15.2 18.1 20.3 17.8 21.1 Combination Figure 1 The SEM images and the positive electrode parameters in the table above can be seen as follows: Traditional single-tank mixing processes result in high viscosity and fineness of the positive electrode slurry, leading to poor dispersion and low peel strength of the final positive electrode sheet. In a three-stage mixing process, ultrasonic dispersion is crucial for further reducing slurry fineness and eliminating micro-agglomerations. This prevents the binder from damaging the conductive network, ensuring uniform binder adsorption and improving interfacial stability. Conductive agent pre-dispersion is a prerequisite for building a continuous conductive network; its absence directly leads to binder agglomeration and a 1.9 Ω·cm increase in resistivity. The order of material addition determines the interfacial bonding effect; reversing the order of the conductive agent and binder causes double degradation, reducing peel strength by 5.7 N / m. The revolution and rotation functions of the dual planetary tanks eliminate dead zones in the mixing process and improve mixing uniformity.

[0027] In summary, this implementation method can improve the dispersibility of the positive electrode slurry: the slurry fineness is reduced to 2-3 μm, the uniformity of distribution of active material and conductive agent is ≥95%, and SEM characterization shows no obvious agglomeration, solving the problem of local enrichment in traditional processes; optimize the conductivity of the positive electrode sheet: the electrode resistivity is reduced to 3.5-4.0 Ω・cm, a reduction of 30%-40% compared to traditional processes; enhance the adhesion between the positive electrode slurry and the current collector: the electrode peel strength reaches 22-25 N / m, the amount of binder is reduced by 8%, avoiding the contradiction of excessive resistance increase and insufficient powder removal; and improve actual production efficiency: the total time of the slurry mixing process is shortened to 65-80 min, and online monitoring ensures batch stability.

[0028] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A slurry mixing process for a highly dispersible positive electrode slurry, characterized in that: Includes the following steps: Step 1: Select the following components by mass percentage: positive electrode active material, dispersant, composite conductive agent, binder, functional additive, and solvent. The specific components are as follows: positive electrode active material mass fraction 88-97%; composite conductive agent mass fraction 1.5-3%; binder mass fraction 1-2%; solvent mass fraction 3-8%; functional additive mass fraction 0.1-0.5%. The sum of the mass percentages of the above components is 100%. Step 2, First Stage: Add 50% solvent to the first dispersion tank, start the high-speed shear disperser, set the speed to 3000-4000 rpm, and control the temperature at 25-30℃; add the composite conductive agent in 3 batches, with an interval of 2 minutes between each batch, and continue dispersing for 15-20 minutes to form a conductive slurry (particle size D90≤100nm); the key mechanism is to break up the carbon nanotube agglomeration through high-frequency shearing, and SuperP fills the gaps between the carbon nanotubes to initially construct a three-dimensional conductive network; Step 3, Second Stage: Active Material Composite and Macroscopic Uniform Mixing. The conductive slurry is transported to a dual planetary mixer, and the positive electrode active material and lithium supplement are added. The revolution speed is set to 500-800 rpm and the rotation speed to 1500-2000 rpm, and the mixture is stirred for 20-30 minutes. 30% solvent is added by spraying, controlling the spraying speed to 1-2 mL / s to avoid sudden increases in local viscosity. The key mechanism is that the dual planetary mixer eliminates dead zones, and the spraying of solvent achieves gradient wetting of the material, reducing the agglomeration of active materials. Step 4, Third Stage: Binder Shaping and Interface Bonding Optimization. The mixed slurry is transported to an ultrasonic dispersion tank, and the binder and dispersant are added. The ultrasonic power is set to 500-800W and the frequency to 20-40kHz, while stirring at a low speed of 1000-1500rpm for 10-15min. The remaining 20% ​​solvent is added to adjust the viscosity to 3000-5000mPa・s. After passing the online viscometer test, ultrasonic defoaming is performed in the pipeline at a power of 300W for 5min. The key mechanism is that ultrasonic dispersion promotes the uniform adsorption of binder molecular chains on the particle surface, and low-speed stirring avoids molecular chain breakage, ensuring adhesion performance.

2. The slurry mixing process for a highly dispersible positive electrode slurry according to claim 1, characterized in that: The positive electrode active material can be lithium iron phosphate, ternary material NCM811 / NCA92 or NCMA91, with a particle size D50 of 2-8μm and a water content ≤500ppm.

3. The slurry mixing process for a highly dispersible positive electrode slurry according to claim 1, characterized in that: The composite conductive agent can be selected from SuperP, ECP and carbon nanotubes mixed at a mass ratio of 3:1, and the carbon nanotubes have an aspect ratio ≥500.

4. The slurry mixing process for a highly dispersible positive electrode slurry according to claim 1, characterized in that: The adhesive may be PVDF with a molecular weight of 500,000-800,000, or a waterborne PVA and acrylate copolymer compound system.

5. The slurry mixing process for a highly dispersible positive electrode slurry according to claim 1, characterized in that: The solvent is NMP or deionized water with a purity ≥99.5%.

6. The slurry mixing process for a highly dispersible positive electrode slurry according to claim 1, characterized in that: The functional additive can be a mixture of dispersant BYK-163 and lithium supplementer Li2CO3 at a mass ratio of 2:

1.

7. A method for preparing highly dispersible positive electrode sheets using the slurry described in claims 1-6, characterized in that: The specific steps are as follows: The prepared positive electrode slurry is coated onto the aluminum foil current collector at a speed of 10-15 m / min, with a thickness of 12 μm and a wet film thickness of 80-120 μm; the drying process during coating adopts a three-stage drying method, with temperatures of 80℃, 120℃, and 150℃ respectively, for a total time of 15-20 min, and the solvent residue is ≤0.5%; the compaction density of the roller after coating is controlled at 3.0-3.5 g / cm³, and the pressure is 5-8 MPa; after roller pressing, it is cut into electrode sheets with a width of 50-200 mm and a burr length of ≤5 μm.

Images