Preparation method of high-solid-content and high-flowability sodium ion aqueous positive electrode slurry

Abstract

The invention discloses a preparation method of high-solid-content and high-flowability sodium ion aqueous positive electrode slurry, which comprises the following steps: S1, preparation of a glue solution: adding a binder into deionized water, and stirring to obtain the glue solution; s2, preparation of a high-fluidity glue solution: adding a first glue solution flow regulator into the glue solution, and stirring at a high speed to obtain the high-fluidity glue solution; s3, preparing a weakly alkaline glue solution, namely adding a second pH flow regulator into the high-flowability glue solution, and stirring to obtain the weakly alkaline glue solution; s4, preparation of a conductive adhesive solution: adding a first conductive agent into the alkalescent adhesive solution, and stirring to obtain the conductive adhesive solution; s5, preparation of first slurry: adding the active substance material into the conductive adhesive solution in batches, stirring and dispersing, and adjusting the viscosity to obtain the first slurry; and S6, preparation of finished slurry: adding the second conductive agent into the first slurry, and stirring and dispersing at a medium-low speed to obtain the final slurry. The invention has the characteristics of good fluidity, high solid content and green and environment-friendly process.

Description

Preparation method of high solids content and high fluidity sodium ion aqueous cathode slurry Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry. Background Technology

[0002] With the rapid development of renewable energy and the continuous growth in demand for energy storage, sodium-ion batteries have broad development prospects. Sodium resources are abundant and widely distributed, and the raw material cost is much lower than that of lithium, giving it a significant cost advantage and making it a suitable supplement to lithium-ion batteries.

[0003] Currently, the three main systems of sodium-ion cathode materials are: polyanionic compounds, layered oxides, and Prussian blue compounds. In particular, polyanionic cathode materials (NFPP) primarily contain Fe and P, two elements that are extremely abundant in the Earth's crust, inexpensive, and stable. Due to their structural safety advantages, along with good thermal stability, long cycle life, and high safety, NFPP occupies a unique niche in the sodium battery cathode material system.

[0004] NFPP material is an ideal cathode material for sodium-ion batteries due to its stable structure and good thermal stability. In the manufacturing process, sodium-ion batteries and lithium-ion batteries share highly similar processes and equipment, resulting in strong compatibility. During the slurry preparation process, the sodium-ion battery cathode slurry can utilize an oil-based system: polyvinylidene fluoride (PVDF) as a binder and N-methylpyrrolidone (NMP) as a solvent. While oil-based systems offer advantages such as wide applicability, mature technology, and good material compatibility, they also have disadvantages in terms of environmental protection, energy consumption, and cost.

[0005] For example, coating and drying processes are energy-intensive and costly. The high boiling point of NMP in oil-based slurries leads to huge energy consumption during electrode drying during the coating process. At the same time, an expensive NMP waste gas recovery system is required, which increases the cost of battery production.

[0006] This can cause pollution to the ecological environment. Even with expensive heat recovery systems, a small portion of NMP cannot be recovered during production and is released into the atmosphere as vapor. It is not easily purified in the environment and, after mixing with air, enters water bodies or soil through rainfall, persisting in the environment for a long time and exhibiting characteristics of persistent organic pollutants. If pretreatment is inadequate, residual NMP can produce toxic gases and complex volatile organic compounds, exacerbating the risk of secondary pollution. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a high-solids-content, high-flowability sodium ion aqueous cathode slurry, which features good flowability, high solids content, and a green and environmentally friendly process.

[0008] This invention can be achieved through the following technical solutions:

[0009] The present invention discloses a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, comprising the following steps:

[0010] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution;

[0011] S2. Preparation of high-flowability adhesive: Add the first flow conditioner to the adhesive and stir at high speed to obtain a high-flowability adhesive;

[0012] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high flowability adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution.

[0013] S4. Preparation of conductive adhesive: Add the first conductive agent to the weak alkaline adhesive and stir to completely disperse the first conductive agent in the weak alkaline adhesive to obtain the conductive adhesive.

[0014] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches, stirred until completely dispersed, and deionized water is added to adjust the viscosity to obtain the first slurry.

[0015] S6. Preparation of finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and slowly stir under vacuum to remove bubbles to obtain the final slurry.

[0016] Further, in step S1, the binder is PAANa (sodium polyacrylate), and the mass concentration of this adhesive solution is 4-6%. If the adhesive concentration is too low, the resulting adhesive solution has low viscosity, which is insufficient in contributing to the thickening and bonding ability of the high-solids content slurry, resulting in weak bonding between the active material and conductive agent particles, and insufficient adhesion between the particles and the current collector. If the adhesive concentration is too high, firstly, the binder may not completely dissolve, and secondly, the adhesive solution is extremely viscous (almost gel-like), easily forming clumps. During the homogenization process, if the slurry viscosity is too high, the fluidity is poor, the slurry is difficult to stir, and air bubbles are difficult to remove, resulting in defects such as tailing, streaks, and uneven thickness during coating.

[0017] Further, in step S2, the first flow conditioner is C2H5OH (ethanol), and the amount of this flow conditioner added is 8%-15% of the weight of the binder (dry powder). Ethanol has a low surface tension, and its addition can significantly reduce the surface tension of the adhesive, which helps to more quickly and thoroughly coat and wet active substances, conductive agents, and other powder particles, reduce agglomeration, and improve dispersion uniformity. In the coating process, ethanol can weaken the temporary network structure formed between PAANa molecular chains through hydration, making the slurry easier to spread on the aluminum foil surface, forming a more uniform and thinner initial wet film, reducing "pinhole" coating defects, and improving wetting and spreading properties. Since PAANa is a water-soluble polymer and insoluble in ethanol, when the proportion of ethanol added is too high, it may cause PAANa to "salt out," producing colloidal particles or flocculent matter, which seriously affects the dispersion and adhesion of the adhesive; when the proportion added is too low, good physical effects cannot be produced.

[0018] Further, in step S2, the high-speed stirring conditions are: revolution 30-35 Hz, rotation 30-35 Hz, and stirring time 35-45 min. A dual planetary mixer is preferred as the stirring machine. When ethanol is added to the PAANa adhesive, high-speed stirring provides strong shear force, causing the ethanol to be instantly dispersed into the adhesive. The intense fluid motion accelerates the exchange process between water and ethanol molecules around the PAANa molecular chains, helping the polymer chains quickly adapt to the new solvent environment and reach a new dissolution equilibrium, thereby stabilizing the viscosity and rheological properties of the adhesive. If the stirring speed is low or the stirring time is insufficient, uneven mixing of the adhesive may occur, forming localized areas of high ethanol concentration. This may lead to salting out of the PAANa molecular chains, resulting in microgel particles in the adhesive that damage the adhesive's bonding effect.

[0019] Further, in step S3, the second pH flow regulator is ammonia and / or organic amine, and the pH of the alkaline slurry is 9-11. The functional group on the PAANa molecular chain is sodium carboxylate (-COONa). In an alkaline environment of pH 9-11, -COONa completely ionizes into -COO⁻ and Na⁺. The -COO⁻ generated by ionization is negatively charged. Due to the repulsion of like charges, the PAANa molecular chain fully extends from its coiled state, more effectively isolating particles through steric hindrance and preventing agglomeration. At the same time, the large amount of negative charge it carries makes the Zeta potential of the particle (carbon black, active material) surface more negative through electrostatic stabilization mechanism, causing mutual repulsion. During the homogenization process, the polyanionic material is more stable on the surface under alkaline conditions, which can inhibit the dissolution of transition metal ions, thereby avoiding the gelation caused by irreversible ionic crosslinking between transition metal ions and -COO⁻ of PAANa, ensuring the fluidity and processability of the slurry.

[0020] Furthermore, in step S3, the high-speed stirring conditions are: revolution 30-35Hz, rotation 30-35Hz, and stirring time 30-40min. After adding the pH flow regulator, a locally extremely high pH zone will form around the adhesive, while the pH in areas far away will remain low. The strong convection and shear forces generated by the high-speed stirring of the dual planetary mixer will disperse the pH flow regulator to every corner of the adhesive within a certain time, eliminating the pH gradient and ensuring that the adhesive uniformly reaches the target pH value. This gives the adhesive a strong and uniform negative charge. When conductive agents and active substances are added, the particles entering the adhesive are protected by strong electrostatic repulsion, inhibiting agglomeration from the source and laying a good foundation for a high-flowability slurry.

[0021] Further, in step S4, the first conductive agent is one or more of Super P, Ketjen Black, acetylene black, and KS-6, and the mass of the first conductive agent added accounts for 0.3-0.8% of the dry powder mass of the slurry. Adding the first conductive agent (conductive carbon black) and mixing it with the binder solution during the homogenization of the aqueous cathode slurry is the core of constructing a highly efficient and uniform conductive network. Conductive carbon black consists of tiny primary particles, but its surface energy is enormous, causing it to tightly aggregate into micron-sized aggregates. These aggregates are a detrimental factor contributing to the viscosity increase of the slurry. After the initial addition of the binder solution, high shear force is used to thoroughly disperse the aggregates, restoring them to or near the state of primary particles. While dispersing the conductive carbon, binder molecules quickly adsorb onto the surface of the newly dispersed carbon black particles. The steric hindrance formed by this polymer adsorption layer effectively prevents the carbon black particles from re-aggregating due to van der Waals forces. Subsequently added active material particles are uniformly coated and connected to this network during stirring. This construction results in a conductive network with better continuity and lower resistance, making it easier for each surface of the active material particles to access the conductive pathway, thus greatly reducing the ohmic impedance of the electrode.

[0022] Further, in step S6, the second conductive agent is carbon nanotubes (CNTs), and the mass percentage of this second conductive agent added is 0.2-0.7% of the dry powder mass of the slurry. Adding CNT (carbon nanotube) slurry in the final stage of the homogenization process optimizes process controllability and maximizes the conductivity efficiency of CNTs. Because CNTs have a huge specific surface area and surface energy, adding them at the initial stage of homogenization, especially in environments with high solid content and high viscosity, can easily cause localized agglomeration and entanglement, leading to a surge in slurry viscosity and even gelation. By optimizing the order of material addition, the risks of gelation, tube breakage, and process control difficulties caused by CNT dispersion are effectively avoided, ensuring that the active material, binder, and other main components are fully mixed and homogeneous, forming a stable slurry. Finally, CNTs are added and mixed at low speed to maximize the preservation of the intact fiber structure of CNTs. CNTs can more easily distribute on the surface and between the active material particles and cover the entire electrode structure. This structure can efficiently collect and transport electrons between particles, improve the rate performance of the battery and reduce electrode impedance. It is also beneficial to improve the high fluidity and high solids content of the slurry.

[0023] Further, in step S6, the conditions for medium-low speed stirring are: revolution 20-25Hz, rotation 10-15Hz, and stirring time 30-45min. CNTs are seamless, hollow tubes made by rolling up single or multiple layers of graphene sheets. Due to their extremely strong van der Waals forces, they easily agglomerate into bundles. Adding CNTs to this slurry at the end avoids the long fibers of the CNTs being broken or damaged by shear forces during long-term, high-intensity dispersion, thus preventing a decrease in their aspect ratio. Adding them last allows for efficient dispersion in the already uniformly mixed slurry system, ultimately constructing a highly efficient and stable three-dimensional conductive network covering the entire electrode.

[0024] Further, in step S5, the viscosity of the first slurry is 3000-4000 mPa·s. If the viscosity of the first slurry is high, the CNT slurry is difficult to mix evenly in a short time, easily forming local agglomeration of CNTs, resulting in uneven coating density. To improve the homogenization effect, the stirring speed or time needs to be increased. High shear force will damage the long fiber structure of CNTs and weaken their conductivity. If the viscosity of the first slurry is too low, the active material and other particles will settle more rapidly during mixing and settling, leading to slurry layering coating failure. The active material is a polyanionic active material, including one or more of (Na2Fe2(SO4)3, Na4Fe3(PO4)2(P2O7), Na3V2(PO4)3, NaFeSiO4, NaMnSiO4). The mass ratio of the active material to the first conductive agent is 95-97: 0.3-0.8.

[0025] This invention provides a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, which has the following beneficial effects:

[0026] First, it has good fluidity. This invention improves the uniform dispersion of the slurry through a first flow regulator. The positive electrode active material and conductive agent have hydrophobic and high surface energy. Ethanol can significantly reduce the surface tension of the slurry, reduce the "soft agglomeration" of particles in the slurry, achieve more uniform dispersion, and improve the uniformity and fluidity of the slurry. When the electrode is in the oven during coating, ethanol evaporates preferentially, which can accelerate the "setting" of the slurry surface, help suppress the re-aggregation and sedimentation of the active material during the coating process, and improve drying efficiency.

[0027] Secondly, the high solids content is achieved by adding a second pH flow regulator, ensuring the binder remains in an extended molecular chain state and providing a strong steric hindrance effect. This allows the slurry to maintain a low viscosity even with a solids content as high as 60-70%, which is beneficial for high-efficiency coating. The addition of the second pH flow regulator inhibits slurry gelation at its source. It maintains the overall slurry in a weakly alkaline state, inhibiting the dissolution of metal ions from the surface of the polyanionic material and completely destroying the conditions that lead to irreversible gelation.

[0028] Third, the process is green and environmentally friendly. The polymer chains of the binder enable Na+ to absorb the volume stress of Na+ through viscoelastic deformation during the insertion and extraction process, thereby inhibiting the volume expansion of the electrode and improving the cycle life of the battery (Figure 1). Water is used as a solvent in the homogenization process, and ethanol is added as the first flow regulator and volatile alkali as the second pH regulator to ensure that it can be volatilized and removed during the subsequent electrode drying process, without pollution or residual hazards. Attached Figure Description

[0029] Figure 1 shows the cycle performance test curves of the sodium-ion battery (25°C, current density 1C, voltage 3.4V-1.5V) assembled from the aqueous positive electrode and hard carbon negative electrode prepared in Application Example 1. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0031] The present invention discloses a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, comprising the following steps:

[0032] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution;

[0033] S2. Preparation of high-flowability adhesive: Add the first flow conditioner to the adhesive and stir at high speed to obtain a high-flowability adhesive;

[0034] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high flowability adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution.

[0035] S4. Preparation of conductive adhesive: Add the first conductive agent to the weak alkaline adhesive and stir to completely disperse the first conductive agent in the weak alkaline adhesive to obtain the conductive adhesive.

[0036] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches, stirred until completely dispersed, and deionized water is added to adjust the viscosity to obtain the first slurry.

[0037] S6. Preparation of finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and slowly stir under vacuum to remove bubbles to obtain the final slurry.

[0038] Furthermore, in step S1, the adhesive is PAANa (sodium polyacrylate), and the mass concentration of the adhesive solution is 4%-6%.

[0039] Furthermore, in step S2, the first flow modifier is C2H5OH (ethanol), and the amount of the flow modifier added is 8%-15% of the weight of the adhesive (dry powder).

[0040] Furthermore, in step S2, the conditions for high-speed stirring are: revolution 30-35Hz, rotation 30-35Hz, and stirring time 35-45min.

[0041] Further, in step S3, the second pH flow regulator is ammonia and / or organic amine, and the pH of the alkaline solution is 9-11.

[0042] Furthermore, in step S3, the conditions for high-speed stirring are: revolution 30-35Hz, rotation 30-35Hz, and stirring time 30-40min.

[0043] Further, in step S4, the first conductive agent is one or more of Super P, Ketjen Black, acetylene black, and KS-6, and the mass of the first conductive agent added is 0.3-0.8% of the mass ratio of the dry powder in the slurry.

[0044] Furthermore, in step S6, the second conductive agent is carbon nanotubes (CNTs), and the mass of the second conductive agent added is 0.2%-0.7% of the dry powder mass ratio of the slurry.

[0045] Furthermore, in step S6, the stirring conditions are: revolution 20-25Hz, rotation 10-15Hz, and stirring time 30-45min.

[0046] Further, in step S5, the viscosity of the first slurry is 3000-4000 mPa·s; the active material is a polyanionic active material, including one or more of (Na2Fe2(SO4)3, Na4Fe3(PO4)2(P2O7), Na3V2(PO4)3, NaFeSiO4, NaMnSiO4); the mass ratio of the active material to the first conductive agent is 95-97: 0.3-0.8.

[0047] Example 1

[0048] This embodiment relates to a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, which includes the following steps:

[0049] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution; specifically, the adhesive is PAANa and the mass concentration of the adhesive solution is 6%.

[0050] S2. Preparation of high-flowability adhesive: Add the first flow modifier to the adhesive and stir at high speed to obtain a high-flowability adhesive; specifically, the first flow modifier is C2H5OH, and the amount of the flow modifier added is 11% of the weight of the adhesive (dry powder); the conditions for high-speed stirring are: revolution 30Hz, rotation 35Hz, and stirring time 40min.

[0051] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high-flow adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution; specifically, the second pH flow regulator is ammonia water, and the pH of the alkaline adhesive solution is 9-11; the high-speed stirring conditions are: revolution 30Hz, rotation 35Hz, and stirring time 35min.

[0052] S4. Preparation of conductive adhesive: The first conductive agent is added to the weakly alkaline adhesive and stirred to completely disperse the first conductive agent in the weakly alkaline adhesive to obtain the conductive adhesive; specifically, the first conductive agent is Super P, Ketjen Black, acetylene black, or KS-6, and the mass ratio of the first conductive agent added to the dry powder of the slurry is 0.3%.

[0053] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches and stirred until completely dispersed. Deionized water is added to adjust the viscosity to obtain the first slurry. Specifically, the viscosity of the first slurry is 3000-4000 mPa.s; the active material is Na2Fe2(SO4)3; and the mass ratio of the active material to the first conductive agent is 97:0.3.

[0054] S6. Preparation of the finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and then slowly stir under vacuum to remove bubbles to obtain the final slurry. Specifically, the second conductive agent is carbon nanotubes (CNTs), and the mass ratio of the second conductive agent added to the dry powder of the slurry is 0.7%; the stirring conditions are: revolution at 23 Hz, rotation at 10 Hz, and stirring time of 45 min.

[0055] Example 2

[0056] This embodiment relates to a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, which includes the following steps:

[0057] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution; specifically, the adhesive is PAANa and the mass concentration of the adhesive solution is 5%.

[0058] S2. Preparation of high-flowability adhesive: Add the first flow modifier to the adhesive and stir at high speed to obtain a high-flowability adhesive; specifically, the first flow modifier is C2H5OH, and the amount of the flow modifier added is 8% of the weight of the adhesive (dry powder); the high-speed stirring conditions are: revolution 35Hz, rotation 33Hz, and stirring time 35min.

[0059] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high-flow adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution; specifically, the second pH flow regulator is ammonia water, and the pH of the alkaline adhesive solution is 9-11; the conditions for high-speed stirring are: revolution 35Hz, rotation 33Hz, and stirring time 30min.

[0060] S4. Preparation of conductive adhesive: The first conductive agent is added to the weakly alkaline adhesive and stirred to completely disperse the first conductive agent in the weakly alkaline adhesive to obtain the conductive adhesive; specifically, the first conductive agent is Super P or KS-6, and the mass ratio of the first conductive agent added is 0.8% of the dry powder mass ratio of the slurry.

[0061] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches and stirred until completely dispersed. Deionized water is added to adjust the viscosity to obtain the first slurry. Specifically, the viscosity of the first slurry is 3000-4000 mPa·s. The active material is Na4Fe3(PO4)2(P2O7). The mass ratio of the active material to the first conductive agent is 96:0.8.

[0062] S6. Preparation of the finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and then slowly stir under vacuum to remove bubbles to obtain the final slurry. Specifically, the second conductive agent is carbon nanotubes (CNTs), and the mass ratio of the second conductive agent added to the dry powder of the slurry is 0.7%; the stirring conditions are: revolution at 25 Hz, rotation at 13 Hz, and stirring time of 30 min.

[0063] Example 3

[0064] This embodiment relates to a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, which includes the following steps:

[0065] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution; specifically, the adhesive is PAANa and the mass concentration of the adhesive solution is 4%.

[0066] S2. Preparation of high-flowability adhesive: Add the first flow modifier to the adhesive and stir at high speed to obtain a high-flowability adhesive; specifically, the first flow modifier is C2H5OH, and the amount of the flow modifier added is 15% of the weight of the adhesive (dry powder); the conditions for high-speed stirring are: revolution 33Hz, rotation 30Hz, and stirring time 45min.

[0067] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high-flow adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution; specifically, the second pH flow regulator is ammonia water, and the pH of the alkaline adhesive solution is 9-11; the high-speed stirring conditions are: revolution 33Hz, rotation 30Hz, and stirring time 40min.

[0068] S4. Preparation of conductive adhesive: The first conductive agent is added to the weakly alkaline adhesive and stirred to completely disperse the first conductive agent in the weakly alkaline adhesive to obtain the conductive adhesive; specifically, the first conductive agent is Super P, Ketjen Black, acetylene black, or KS-6, and the mass ratio of the first conductive agent added to the dry powder of the slurry is 0.3%.

[0069] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches and stirred until completely dispersed. Deionized water is added to adjust the viscosity to obtain the first slurry. Specifically, the viscosity of the first slurry is 3000-4000 mPa·s; the active material is Na3V2(PO4)3; and the mass ratio of the active material to the first conductive agent is 95:0.3.

[0070] S6. Preparation of the finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and then slowly stir under vacuum to remove bubbles to obtain the final slurry. Specifically, the second conductive agent is carbon nanotubes (CNTs), and the mass ratio of the second conductive agent added to the dry powder of the slurry is 0.4%; the stirring conditions are: revolution at 20 Hz, rotation at 15 Hz, and stirring time of 38 min.

[0071] Example 4

[0072] This embodiment relates to a method for preparing a high-solids-content, high-flowability aqueous sodium-ion cathode slurry, which includes the following steps:

[0073] S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution; specifically, the adhesive is PAANa and the mass concentration of the adhesive solution is 4.6%.

[0074] S2. Preparation of high-flowability adhesive: Add the first flow modifier to the adhesive and stir at high speed to obtain a high-flowability adhesive; specifically, the first flow modifier is C2H5OH, and the amount of the flow modifier added is 11% of the weight of the adhesive (dry powder); the conditions for high-speed stirring are: revolution 32Hz, rotation 34Hz, and stirring time 39min.

[0075] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator to the high-flow adhesive solution and stir at high speed to obtain a weakly alkaline adhesive solution; specifically, the second pH flow regulator is an organic amine, and the pH of the alkaline adhesive solution is 9-11; the high-speed stirring conditions are: revolution 35Hz, rotation 31Hz, and stirring time 36min.

[0076] S4. Preparation of conductive adhesive: The first conductive agent is added to the weakly alkaline adhesive and stirred to completely disperse the first conductive agent in the weakly alkaline adhesive to obtain the conductive adhesive; specifically, the first conductive agent is Super P, Ketjen Black, acetylene black, or KS-6, and the mass ratio of the first conductive agent added to the dry powder of the slurry is 0.5%.

[0077] S5. Preparation of the first slurry: The active material is added to the conductive adhesive in batches and stirred until completely dispersed. Deionized water is added to adjust the viscosity to obtain the first slurry. Specifically, the viscosity of the first slurry is 3000-4000 mPa·s. The active material is NaFeSiO4 or NaMnSiO4. The mass ratio of the active material to the first conductive agent is 95:0.5.

[0078] S6. Preparation of the finished slurry: Add the second conductive agent to the first slurry, stir to completely disperse the carbon nanotubes in the slurry, and then slowly stir under vacuum to remove bubbles to obtain the final slurry. Specifically, the second conductive agent is carbon nanotubes (CNTs), and the mass ratio of the second conductive agent added to the dry powder of the slurry is 0.4%; the stirring conditions are: revolution at 21 Hz, rotation at 14 Hz, and stirring time of 35 min.

[0079] Application Example 1

[0080] In this embodiment, the mass ratio of active material, binder, conductive agent, and flow conditioner is 96.8:2:1:0.2. Deionized water is used as the solvent; the binder is sodium polyacrylate (PAANa); the mass ratio of the first conductive agent SP (0.5% dry powder in the slurry) to the second conductive agent MWCNT is 1:1; the first flow conditioner is ethanol, the first pH flow conditioner is ammonia, and the mass ratio of the first flow conditioner to the second pH flow conditioner is 1:1.

[0081] The slurry homogenization process is as follows:

[0082] S1. Preparation of adhesive solution: Add the adhesive PAANa to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0083] S2. Preparation of high-flowability adhesive: Add the first adhesive flow conditioner (ethanol) to the adhesive and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 45 min) to obtain a high-flowability adhesive;

[0084] S3. Preparation of weakly alkaline adhesive solution: Add the second pH flow regulator (ammonia water) to the high flowability adhesive solution and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 30 min) to obtain the weakly alkaline adhesive solution.

[0085] S4. Preparation of conductive adhesive: Add SP to S3 adhesive and stir to completely disperse SP in the weakly alkaline adhesive to obtain conductive adhesive.

[0086] S5. Preparation of the first slurry: The active material NFPP (sodium iron pyrophosphate) is added to the conductive adhesive in two batches and stirred until completely dispersed. An appropriate amount of deionized water is added to adjust the viscosity to obtain the first slurry.

[0087] S6. Preparation of finished slurry: Add MWCNT to the first slurry and stir at medium-low speed (20Hz revolution, 15Hz rotation, stirring for 30 minutes) to completely disperse MWCNT in the slurry. Vacuum slow stirring and degassing will yield the final slurry.

[0088] Application Example 2

[0089] The active material, binder, conductive agent, and flow conditioner are present in a ratio of 96%:2%:1.5%:0.5%. Deionized water is used as the solvent. The binder is sodium polyacrylate (PAANa). The conductive agents include SP (1%) and MWCNT (0.5%). The flow conditioners are ethanol (0.1%) and ammonium carbonate (0.4%).

[0090] The slurry homogenization process is as follows:

[0091] S1. First, add the adhesive PAANa to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0092] S2. Add the flow conditioner (ethanol) to the adhesive solution in S1 and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 45 min) to obtain a high-flow adhesive solution.

[0093] S3. Add pH flow regulator (ammonium carbonate) to S2 adhesive solution and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 40 min) to obtain a weakly alkaline adhesive solution.

[0094] S4. Add SP to the S3 adhesive solution and stir to completely disperse SP in the adhesive solution to obtain a conductive adhesive solution.

[0095] S5. Add the active material NFPP (sodium iron pyrophosphate) to the S4 conductive adhesive in two batches, stir until completely dispersed, and add an appropriate amount of deionized water to adjust the viscosity.

[0096] S6. Add MWCNT to the S5 slurry and stir at medium-low speed (20 Hz revolution, 10 Hz rotation, stir for 30 min) to completely disperse MWCNT in the slurry.

[0097] S7. Vacuum slow stirring and degassing for 30 minutes, then test the slurry viscosity, fineness, solid content, discharge, and coating.

[0098] Application Example 3

[0099] The active material, binder, conductive agent, and flow conditioner are present in a ratio of 95.5% : 2.5% : 1.5% : 0.5%. Deionized water is used as the solvent. The binder is sodium polyacrylate (PAANa). The conductive agents include SP (1%) and MWCNT (0.5%). The flow conditioners are ethanol (0.2%) and ammonium carbonate (0.3%).

[0100] The slurry homogenization process is as follows:

[0101] S1. First, add the adhesive PAANa to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0102] S2. Add the flow conditioner (ethanol) to the adhesive solution in S1 and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 30 min) to obtain a high-flow adhesive solution.

[0103] S3. Add pH flow regulator (ammonium carbonate) to S2 adhesive solution and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 30 min) to obtain a weakly alkaline adhesive solution.

[0104] S4. Add SP to the S3 adhesive solution and stir to completely disperse SP in the adhesive solution to obtain a conductive adhesive solution.

[0105] S5. Add the active material NFPP (sodium iron pyrophosphate) to the S4 conductive adhesive in two batches, stir until completely dispersed, and add an appropriate amount of deionized water to adjust the viscosity.

[0106] S6. Add MWCNT to the S5 slurry and stir at medium-low speed (25 Hz revolution, 15 Hz rotation, stir for 45 min) to completely disperse MWCNT in the slurry.

[0107] S7. Vacuum slow stirring and degassing for 30 minutes, then test the slurry viscosity, fineness, solid content, discharge, and coating.

[0108] Comparative Example 1

[0109] The active material, binder, and conductive agent are in a ratio of 96%:2.5%:1.5%. Deionized water is used as the solvent. The binder is sodium polyacrylate (PAANa). The conductive agents include SP (1%) and MWCNT (0.5%).

[0110] The slurry homogenization process is as follows:

[0111] S1. First, add the adhesive PAANa to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0112] S2. Add SP to the S1 adhesive solution and stir to completely disperse SP in the adhesive solution to obtain a conductive adhesive solution.

[0113] S3. Add MWCNT to the S2 slurry and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 60 min) to completely disperse MWCNT in the slurry and obtain conductive adhesive solution.

[0114] S4. Add the active material NFPP (sodium iron pyrophosphate) to the conductive adhesive solution in two batches, stir until completely dispersed, and add an appropriate amount of deionized water to adjust the viscosity.

[0115] S7. Vacuum slow stirring and degassing for 30 minutes, then test the slurry viscosity, fineness, solid content, discharge, and coating.

[0116] Comparative Example 2

[0117] The active material, binder, and conductive agent are in a ratio of 95%:3%:2%. Deionized water is used as the solvent. The binder is sodium polyacrylate (PAANa). The conductive agents include SP (1.5%) and MWCNT (0.5%).

[0118] The slurry homogenization process is as follows:

[0119] S1. First, add the adhesive PAANa to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0120] S2. Add SP to the S1 adhesive solution and stir to completely disperse SP in the adhesive solution to obtain a conductive adhesive solution.

[0121] S3. Add MWCNT to the S2 slurry and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 60 min) to completely disperse MWCNT in the slurry and obtain conductive adhesive solution.

[0122] S4. Add the active material NFPP (sodium iron pyrophosphate) to the conductive adhesive solution in two batches, stir until completely dispersed, and add an appropriate amount of deionized water to adjust the viscosity.

[0123] S7. Vacuum slow stirring and degassing for 30 minutes, then test the slurry viscosity, fineness, solid content, discharge, and coating.

[0124] Comparative Example 3

[0125] The active material, thickener, binder, and conductive agent are in the following proportions: 94%, 2%, 2.5%, and 1.5%, respectively. Deionized water is used as the solvent. The thickener is sodium carboxymethyl cellulose (CMC); the binder is styrene-butadiene rubber (SBR); and the conductive agents include SP (1%) and MWCNT (0.5%).

[0126] The slurry homogenization process is as follows:

[0127] S1. First, add the thickener CMC to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution.

[0128] S2. Add SP to the S1 adhesive solution and stir to completely disperse SP in the adhesive solution to obtain a conductive adhesive solution.

[0129] S3. Add MWCNT to the S2 slurry and stir at high speed (30 Hz revolution, 35 Hz rotation, stirring for 60 min) to completely disperse MWCNT in the slurry and obtain conductive adhesive solution.

[0130] S4. Add the active material NFPP (sodium iron pyrophosphate) to the conductive adhesive solution in two batches, stir until completely dispersed, and add an appropriate amount of deionized water to adjust the viscosity.

[0131] S7. Vacuum slow stirring and degassing for 30 minutes, then test the slurry viscosity, fineness, solid content, discharge, and coating.

[0132] The performance of the slurries from Application Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1:

[0133] Table 1 Performance Test Results

[0134]

[0135] Table 1 shows that Application Example 1 used PAANa adhesive with the addition of a first flow modifier and a second pH flow modifier, while Comparative Examples 1, 2, and 3 did not add any modifiers, and Comparative Example 3 used a CMC+SBR system. Comparative Examples 1 and 2 required the addition of deionized water before discharge to adjust the discharge viscosity, but the discharge viscosity and fineness were still higher than in Application Example 1, while the solid content of the slurry was reduced. Although the discharge viscosity of the slurry in Comparative Example 3 was lower than that in Comparative Examples 1 and 2, the solid content of the slurry was significantly lower than that in Application Example 1. The addition of ethanol as the first flow conditioner to the PAANa slurry significantly reduces the surface tension of the slurry, allowing it to more quickly and thoroughly encapsulate and wet active materials, conductive agents, and other powder particles during homogenization, reducing agglomeration and improving dispersion uniformity. The second pH flow conditioner, ammonia, makes the slurry overall alkaline, effectively inhibiting the dissolution of transition metal ions during NFPP homogenization. This avoids irreversible ionic crosslinking between transition metal ions and PAANa's -COO⁻, resulting in gel formation and ensuring the slurry's high fluidity and high solids content.

[0136] As shown in Figure 1, Application Example 1, using PAANa slurry, achieved a capacity retention of 95.52% after 300 cycles at 1C. PAANa can construct a high-porosity electrode. During cycling, PAANa, with its flexible polymer chains and dynamic hydrogen bond network, can buffer volume stress, allowing Na+ to absorb volume stress through viscoelastic deformation during insertion / extraction, effectively suppressing electrode volume expansion and ensuring long-term battery cycling.

[0137] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-solids-content, high-flowability aqueous sodium ion cathode slurry, characterized in that... Includes the following steps: S1. Preparation of adhesive solution: Add the adhesive to deionized water and stir to completely dissolve the adhesive in the deionized water to obtain the adhesive solution; S2. Preparation of high-flowability adhesive: Add the first flow regulator to the adhesive and stir at high speed to obtain a high-flowability adhesive; S3. Preparation of weakly alkaline adhesive: Add the second pH flow regulator to the high-flowability adhesive and stir at high speed to obtain a weakly alkaline adhesive; S4. Preparation of conductive adhesive: Add the first conductive agent to the weakly alkaline adhesive and stir to completely disperse the first conductive agent in the weakly alkaline adhesive to obtain a conductive adhesive; S5. Preparation of the first slurry: Add the active material to the conductive adhesive in batches and stir until completely dispersed. Add deionized water to adjust the viscosity to obtain the first slurry; S6. Preparation of the finished slurry: Add the second conductive agent to the first slurry and stir to completely disperse the carbon nanotubes in the slurry. Vacuum slow stirring degasses the slurry to obtain the final slurry.

2. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S1, the adhesive is sodium polyacrylate, and the mass concentration of the adhesive solution is 4-6%.

3. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S2, the first flow modifier is ethanol, and the amount of the flow modifier added is 8%-15% of the weight of the adhesive.

4. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S2, the conditions for high-speed stirring are: revolution 30-35Hz, rotation 30-35Hz, and stirring time 35-45min.

5. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S3, the second pH flow conditioner is ammonia and / or organic amine, and the pH of the alkaline solution is 9-11.

6. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S3, the conditions for high-speed stirring are: revolution 30-35Hz, rotation 30-35Hz, and stirring time 30-40min.

7. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S4, the first conductive agent is one or more of Super P, Ketjen Black, acetylene black, and KS-6, and the mass of the first conductive agent added is 0.3-0.8% of the mass ratio of the dry powder in the slurry.

8. The method for preparing high-solids-content, high-flowability aqueous sodium ion cathode slurry according to claim 1, characterized in that: In step S6, the second conductive agent is carbon nanotubes, and the mass of the second conductive agent added is 0.2-0.7% of the dry powder mass ratio of the slurry.

9. The method for preparing high-solids-content, high-flowability aqueous sodium-ion cathode slurry according to claim 8, characterized in that: In step S6, the stirring conditions are: revolution 20-25Hz, rotation 10-25Hz, and stirring time 30-45min.

10. The method for preparing high-solids-content, high-flowability aqueous sodium-ion cathode slurry according to claim 1, characterized in that: In step S5, the viscosity of the first slurry is 3000-4000 mPa·s; the active material is an anionic active material; and the mass ratio of the active material to the first conductive agent is 95-97: 0.3-0.8.

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