Low-viscosity high-solid-content negative electrode slurry efficient preparation method, slurry and application thereof

Abstract

The application belongs to the field of lithium ion batteries, and discloses a high-efficiency preparation method of a negative electrode slurry with low viscosity and high solid content, the slurry and application thereof, and comprises the following steps: adding pre-mixed and stirred powder into a stirring tank; adding corresponding deionized water into a solvent storage tank; preparing slurry and circulating the slurry; adding SBR, stirring, mixing, adjusting viscosity, discharging, sieving and obtaining the negative electrode slurry. The obtained slurry has the characteristics of low viscosity and high solid content, effectively improves the surface load of the electrode sheet and the capacity of the lithium ion battery. Compared with the traditional process, the high-efficiency preparation method only needs 1.5-2.5 hours, shortens the production cycle and improves the efficiency by 2-3 times. Through the control of process conditions, the internal circulation of the slurry is realized, the conductive agent aggregation can be fully broken, the active material, the conductive agent and the binder can be uniformly mixed, the consistency and stability of the slurry are improved, and the preparation process is simple and can be scaled up.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an efficient preparation method of low-viscosity, high-solids-content negative electrode slurry, the slurry, and its applications. Background Technology

[0002] With economic and social development and the excessive consumption of traditional fossil fuels, the demand for efficient energy storage systems is constantly increasing. Among existing electrochemical energy storage devices, lithium-ion batteries dominate the information technology, aerospace, portable 3C products, energy storage products, and electric vehicle markets due to their advantages such as high energy density and long cycle life.

[0003] As one of the core components of lithium-ion batteries, the negative electrode material directly affects the battery's initial efficiency, energy, and lifespan. The slurry homogenization process plays a crucial role in ensuring the battery's consistency and stability during battery fabrication. Currently, in actual production, wet homogenization is generally used. During this process, the slurry remains wet, resulting in a long kneading time, which can easily lead to poor dispersion of the negative electrode active material and low production efficiency.

[0004] To address the aforementioned issues, CN109509868A discloses a high-efficiency homogenization process for lithium-ion battery anodes, comprising the following steps: (1) mixing active material, powdered conductive agent, and powder binder; (2) adding slurry-like conductive agent and 40-70% deionized water, and mixing; (3) evacuating to -0.085 to -0.1 MPa and continuing to stir; (4) adding 20-30% deionized water, evacuating to -0.085 to -0.1 MPa, and mixing; (5) adding styrene-butadiene rubber to the mixing tank, evacuating to -0.085 to -0.1 MPa, and mixing; (6) adding the remaining deionized water, evacuating to -0.085 to -0.1 MPa, and mixing to obtain a lithium-ion battery anode slurry. This method, through control of the feeding sequence and mixing process conditions, ensures thorough mixing of powdered materials, thereby improving the stability and mixing efficiency of the slurry.

[0005] Publication No. CN109378446A discloses a method for preparing a negative electrode slurry for lithium-ion batteries, including the following steps: Step 1: Dry mixing of various dry materials to obtain a dry mixture; Step 2: Adding a solvent to the dry mixture and stirring again to obtain a wet mixture; Step 3: Adding a binder to the wet mixture to obtain the negative electrode slurry. This method employs a highly efficient homogenization process. The shear force generated by the stirring mechanism can fully disperse some of the agglomerated conductive agents. Furthermore, high-speed stirring enables microscopic mixing, depositing a fine, dispersed conductive agent layer on the surface of larger active material particles, thereby forming a good conductive network. This method shortens the stirring process time and improves the stability and dispersion uniformity of the slurry.

[0006] The aforementioned patent discloses a method of pre-mixing active materials, powdered conductive agents, and powder binders to obtain a mixed powder, followed by the addition of a slurry-like conductive agent and a dispersant to obtain a mixed slurry. While this method can thoroughly mix the powdered materials and shorten the mixing time, its homogenization efficiency remains low, the binder utilization rate is low, and the active materials and conductive agents cannot fully bond, ultimately leading to excessive resistance in the negative electrode. Furthermore, the solid content of the slurry is one of the key factors determining the capacity of lithium batteries. Higher solid content means a higher mass of active material loaded on the current collector per unit area, resulting in a larger achievable capacity. Currently, the solid content of lithium-ion battery slurries is generally around 40-55%. Increasing the solid content of the slurry while maintaining appropriate viscosity is one approach to improving lithium battery capacity.

[0007] Existing lithium-ion battery anode slurries still suffer from problems such as complex processes. Therefore, how to develop a lithium-ion battery anode slurry that simultaneously possesses characteristics such as high solid content, good stability, high mixing efficiency, and mass production capability while ensuring a simple preparation process has become an urgent problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and to provide an efficient preparation method for low-viscosity, high-solids-content negative electrode slurry, the slurry and its application, solving the problems of low solids content in existing wet mixing methods and the long time required for dry mixing.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry, characterized by comprising the following steps:

[0011] Step (1): Weigh the active powder, binder and conductive agent in a mass ratio of 96%:0.5%:1%, stir them in advance to make the color uniform, and obtain the pre-mixed powder.

[0012] Step (2): Add deionized water to the solvent storage tank in the high-efficiency pulper. The mass ratio of deionized water to the pre-mixed powder is 30-35%: 65-70%.

[0013] Step (3): Add the pre-mixed powder into the mixing tank of the high-efficiency pulper, pulp, stir and mix, add conductive binder SONE with a mass ratio of 1.5% to that in step (1), stir and mix, and start the pulp circulation of the high-efficiency pulper;

[0014] Step (4): Add styrene-butadiene rubber at a mass ratio of 1% to that in step (1) to the mixing tank of the high-efficiency pulping machine and mix.

[0015] Step (5): Discharge, sieve, and obtain slurry.

[0016] Preferably, the pre-stirring and mixing in step (1) is done manually for 5-10 minutes until the color is uniform and there are no obvious large particles. The active powder material is silicon carbide and graphite; the binder is carboxymethyl cellulose; the conductive agent is conductive carbon black; and the mass ratio of silicon carbide to graphite in the active powder material is 5%:91%.

[0017] Preferably, the deionized water mentioned in step (2) is weighed by mass weighing; the deionized water is automatically pumped into the mixing tank during the stirring and mixing process until it is completely consumed.

[0018] Preferably, in step (3), during the pulping process, the revolution speed of the stirring is 20-50 r / min; the rotation speed of the stirring is 1300-4000 r / min; the stirring time is 20-30 min; the conductive binder SONE is a conductive binder of carbon nanotubes with carboxymethyl cellulose solution as dispersant, and its solid content is 3.6%; during the pulp circulation process, the revolution speed of the stirring is 20-50 r / min; the rotation speed of the stirring is 1300-4000 r / min; the stirring time is 2-5 min, the above conditions are for one cycle, the number of cycles is 20-40, the total pulping time is 40-70 min, after the cycle is completed, the upper and lower parts of the pulp are exchanged, and the resulting pulp is more uniform and stable; after step (3), the pulp viscosity is 3000-4000. mPa∙s; Carboxymethyl cellulose molecules have a high molecular chain structure. The carboxymethyl and hydroxyl groups are hydrophilic. When dissolved in water, the hydrophilic groups first swell with water molecules, and the molecular chains aggregate. Therefore, a high linear velocity is required to overcome the interaction force between carboxymethyl cellulose and water molecules to disperse the carboxymethyl cellulose. The pulp circulation of the high-efficiency pulper is driven by pressure / pump. After each cycle of stirring, the pulp circulates between the mixing tank and the pipes inside the high-efficiency pulper and finally returns to the mixing tank to complete one cycle.

[0019] Preferably, the revolution speed of the stirring in step (4) is 20-40 r / min; the rotation speed of the stirring is 800-1500 r / min; the stirring time is 20-40 min; the viscosity of the slurry after step (4) is 1200-2000 mPa∙s; the styrene-butadiene rubber is a high molecular elastomer material synthesized by copolymerization reaction of butadiene and styrene as the main monomers, which plays the role of auxiliary binder, and its solid content is 48.5%; if the rotation speed after adding styrene-butadiene rubber is set too high, it will cause excessive shear force, which will cause certain damage to the chain structure of styrene-butadiene rubber and produce demulsification phenomenon; in addition, styrene-butadiene rubber organically combines graphite through hydrophobicity on the one hand, and forms chemical bonds by condensation reaction between the hydrophilic groups on the surface and the groups on the surface of copper foil on the other hand, thereby enhancing the adhesion to copper foil.

[0020] Preferably, the material is sieved using a 150-mesh screen in step (5); the resulting slurry has a fineness of 8-10 μm, a viscosity of 1200-2000 mPa∙s, and a solid content of 60-70%.

[0021] Preferably, the active powder, binder, and conductive agent in step (1) are combined, and the total mass percentage of the conductive binder SONE in step (3) and the styrene-butadiene rubber in step (4) is 100%.

[0022] Preferably, the required active powder, binder, and conductive agent in step (1) are combined with the total mass of the conductive binder SONE in step (3) and the styrene-butadiene rubber powder in step (4) of 4 kg.

[0023] Preferably, the corresponding masses in step (1) are as follows: silicon carbon and graphite in the active powder are 0.2 Kg and 3.64 Kg, respectively, carboxymethyl cellulose as binder is 0.02 Kg and conductive carbon black as conductive agent is 0.04 Kg.

[0024] Preferably, the mass of the deionized water in step (2) is 0.019 to 0.448 kg.

[0025] Preferably, the mass of the conductive adhesive SONE in step (3) is 1.67 Kg, calculated as follows:

[0026] Required mass = (Total powder mass x Percentage of solids) / Solid content = (4 kg x 1.5%) / 3.6% = 1.67 kg

[0027] Preferably, the mass of the styrene-butadiene rubber in step (4) is 0.082 kg, calculated as follows:

[0028] Required mass = (total mass of powder x percentage of mass) / solid content = (4 kg x 1%) / 48.5% = 0.082 kg.

[0029] This invention also discloses a negative electrode slurry, which is prepared by the above-described preparation method. The slurry is characterized by: graphite appearing as irregular lumps, silicon carbon appearing as irregular lumps with a particle size smaller than graphite, and the adhesion force generated by the aggregation of molecular chains of carboxymethyl cellulose when dissolved in water binding the materials together; conductive carbon black having a chain-like structure, coating the surfaces of graphite and silicon carbon materials, filling the gaps between graphite particles, and playing a role in conducting electrons, while also improving the electrolyte retention of the electrode; during later electrode cycling processes, as the number of charge-discharge cycles increases, graphite and silicon carbon gradually fragment, and the spacing gradually increases, while styrene-butadiene rubber binds the graphite, and conductive carbon black connects the materials for conductivity; the resulting negative electrode slurry has a fineness of 8–10 μm, a viscosity of 1200–2000 mPa∙s, and a solid content of 60–70%.

[0030] This invention also discloses a negative electrode sheet, characterized in that: the negative electrode sheet further includes a current collector; a negative electrode slurry is disposed on the current collector; the slurry is the aforementioned negative electrode slurry; the current collector is copper foil; the negative electrode sheet obtained after the coating and die-cutting process is as follows: Figure 3 As shown; the single-sided density of the negative electrode sheet is ≥83.9 g / m². 2 . Beneficial effects

[0031] 1. This invention uses SONE, a slurry-like binder, as the main source of deionized water. Without adding excessive amounts of deionized water, it increases the solid content of the slurry (conventional slurries are around 40-55%) while meeting viscosity requirements. This increases the mass of active material loaded on the current collector per unit area, effectively improving the actual capacity of the lithium-ion battery.

[0032] 2. This invention achieves more uniform mixing of active materials and binders through multiple internal circulation of the slurry, and fully bonds the active materials and conductive agents, thereby greatly reducing the resistance of the negative electrode sheet.

[0033] 3. By utilizing a high-efficiency pulping machine, this invention overcomes the complex process problems of traditional negative electrode pulp preparation methods, while ensuring simple equipment processes and features high solid content, good stability, high mixing efficiency, and mass production capability. Attached Figure Description

[0034] Figure 1 This is a comparison diagram showing the time required in Embodiments 1-2 and Comparative Examples 1-2 of the present invention;

[0035] Figure 2 This is a graph showing the comparison of solid content in Examples 1-2 and Comparative Examples 1-2 of the present invention;

[0036] Figure 3 This is an optical photograph of the negative electrode sheet obtained by coating the negative electrode slurry according to Example 1 of the present invention.

[0037] Figure 4 The images shown are scanning electron microscope (SEM) images of the negative electrode sheet obtained by coating the negative electrode slurry according to Example 2 of the present invention; wherein (a) is a scanning electron microscope image of the lower electrode sheet at 500x magnification, (b) is a scanning electron microscope image of the lower electrode sheet at 2000x magnification, (c) is a scanning electron microscope image of the lower electrode sheet at 5000x magnification, and (d) is a cross-sectional view of the lower electrode sheet at 2000x magnification.

[0038] Figure 5 The internal resistance before formation of the soft-pack battery assembled with electrode sheets corresponding to the slurry in Examples 1-2 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0039] To address the problems of low solid content and low efficiency in existing mixing processes, this invention provides a highly efficient preparation method for low-viscosity, high-solid-content negative electrode slurry, the slurry itself, and its applications, comprising the following steps:

[0040] (1) Weigh the active powder (silicon carbon: graphite = 5%: 91%), binder (carboxymethyl cellulose) and conductive agent (conductive carbon black) in a mass ratio of 96%: 0.5%: 1%, and stir them for 5 to 10 minutes until the color is uniform and there are no obvious large particles to obtain the pre-mixed powder.

[0041] (2) Weigh deionized water by mass weighing and add it to the solvent storage tank in the high-efficiency pulping machine. The mass ratio of deionized water to pre-mixed powder is 30-35%: 65-70%. Deionized water is automatically pumped into the mixing tank during the mixing process until it is completely consumed.

[0042] (3) Add the pre-mixed powder to the mixing tank of the high-efficiency pulper. During the pulping process, stir for 20-30 min at a revolution speed of 20-50 r / min and a rotation speed of 1300-4000 r / min. Carboxymethyl cellulose molecules have a high molecular chain structure. The carboxymethyl and hydroxyl groups are hydrophilic. When dissolved in water, the hydrophilic groups first swell with the water molecules and the molecular chains aggregate. Therefore, a high linear velocity is required to overcome the interaction between carboxymethyl cellulose and water molecules and disperse the carboxymethyl cellulose. Add conductive binder SONE at a mass ratio of 1.5% to that in step (1). After stirring and mixing, start the pulp circulation of the high-efficiency pulper. During the pulp circulation process, stir for 2-5 min at a revolution speed of 20-50 r / min and a rotation speed of 1300-4000 r / min. This is set as one cycle. The cycle is 20-40 times, and the total pulp circulation time is 40-70 minutes. After the cycle is completed, the upper and lower parts of the slurry can be exchanged, and the resulting slurry is more uniform. After step (3), the viscosity of the slurry is 3000-4000 mPa∙s. Under the drive of the pressure / pump, after each cycle of stirring, the slurry circulates between the mixing tank and the pipeline in the internal pipeline of the high-efficiency pulper, and finally returns to the mixing tank to complete one cycle.

[0043] (4) Add 1% of styrene-butadiene rubber (SBR) in the mixing tank of the high-efficiency pulping machine at a mass ratio of 1% to that in step (1), and stir for 20 to 40 minutes at a revolution speed of 20 to 40 r / min and a rotation speed of 800 to 1500 r / min. After step (4), the viscosity of the slurry is 1200 to 2000 mPa∙s. If the rotation speed is set too high after adding SBR, the shear force will be too large, which will cause certain damage to the chain structure of SBR and produce demulsification. In addition, SBR organically combines graphite through hydrophobicity and forms chemical bonds with the groups on the surface of copper foil through condensation reaction of surface hydrophilic groups, which enhances the adhesion to copper foil. If demulsification occurs, the adhesion between the slurry and copper foil will be too low or even fall off during the subsequent coating process.

[0044] (5) Discharge: The material is sieved through a 150-mesh sieve to obtain negative electrode slurry. The fineness of the slurry is 8-10 μm, the viscosity is 1200-2000 mPa∙s, and the solid content is 60-70%.

[0045] The present invention also provides a negative electrode slurry, which is prepared by the above-described preparation method. The resulting negative electrode slurry has a fineness of 8-10 μm, a viscosity of 1200-2000 mPa∙s, and a solid content of 60-70%.

[0046] The present invention also provides a negative electrode sheet, which further includes a current collector copper foil; the current collector is provided with the aforementioned negative electrode slurry; the single-sided density of the negative electrode sheet is ≥83.9 g / m³. 2 .

[0047] To make the technical means, creative features, objectives, and effects of this invention easily understood, the invention is further illustrated below with specific embodiments. The sources of all raw materials used in this invention are not particularly limited; they can be purchased from the market or prepared using conventional methods known to those skilled in the art. Their purity is not particularly limited, but this invention preferably uses analytical grade or conventional purity used in the field of composite materials. Example

[0048] The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry, the slurry itself, and its applications provided in this embodiment include the following steps:

[0049] (1) Weigh the active powder (silicon carbon: graphite = 0.2 Kg: 3.64 Kg), binder (carboxymethyl cellulose) 0.02 Kg and conductive agent (conductive carbon black) in a mass ratio of 96%:0.5%:1%, and stir and mix for 6 min until the mixture is uniform in color and there are no obvious large particles to obtain the pre-mixed powder.

[0050] (2) Weigh 0.268 kg of deionized water by mass weighing and add it to the solvent storage tank in the high-efficiency pulping machine; the mass ratio of deionized water to pre-mixed powder is 33%:67%; the deionized water is automatically pumped into the mixing tank during the mixing process until it is completely consumed.

[0051] (3) Add the pre-mixed powder to the mixing tank of the high-efficiency pulper. During the pulping process, stir for 25 min at a revolution speed of 35 r / min and a rotation speed of 3000 r / min. Add 1.67 kg of conductive binder SONE with a mass ratio of 1.5% to that in step (1). Stir and mix for 8 min at a revolution speed of 35 r / min and a rotation speed of 3000 r / min. Start the pulp circulation of the high-efficiency pulper. During the pulp circulation process, stir for 2 min at a revolution speed of 45 r / min and a rotation speed of 3500 r / min. Set as one cycle. Circulate 30 times. The total pulp circulation time is 60 min. After step (3), the pulp viscosity is 3521 mPa∙s. After the circulation is completed, the upper and lower parts of the pulp can be exchanged, and the resulting pulp is more uniform.

[0052] (4) Add 0.082 kg of styrene-butadiene rubber (SBR) at a mass ratio of 1% to that in step (1) to the mixing tank of the high-efficiency pulping machine, and stir for 30 min at a revolution speed of 25 r / min and a rotation speed of 1300 r / min. After step (4), the viscosity of the slurry is 1508 mPa∙s. Setting the rotation speed too high after adding SBR will cause excessive shear force, which will damage the chain structure of SBR and cause demulsification, resulting in slurry detachment during subsequent coating.

[0053] (5) Discharge: The material is sieved through a 150-mesh sieve to obtain negative electrode slurry. The fineness of the obtained slurry is 9 μm, the viscosity is 1508 mPa∙s, and the solid content is 67%.

[0054] The present invention also provides a negative electrode slurry, which is prepared by the above-described preparation method; the resulting negative electrode slurry has a fineness of 9 μm, a viscosity of 1508 mPa∙s, and a solid content of 67%.

[0055] The present invention also provides a negative electrode sheet, the optical image of which is shown below. Figure 3 As shown, the surface is smooth without wrinkles or pits. The negative electrode sheet also includes a current collector copper foil; the aforementioned negative electrode paste is disposed on the current collector; the single-sided density of the negative electrode sheet is ≥83.9 g / m³. 2 . Example

[0056] The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry, the slurry itself, and its application provided in this embodiment differ from the slurry preparation method described in Example 1 in that the revolution speed, rotation speed, and stirring time of the stirring are modified, while the remaining operating parameters are the same as in Example 1. The method includes the following steps:

[0057] (1) Weigh the active powder (silicon carbon: graphite = 0.2 Kg: 3.64 Kg), binder (carboxymethyl cellulose) 0.02 Kg and conductive agent (conductive carbon black) in a mass ratio of 96%:0.5%:1%, and manually stir and mix for 10 min until the color is uniform and there are no obvious large particles to obtain the pre-mixed powder.

[0058] (2) Weigh 0.268 kg of deionized water by mass weighing and add it to the solvent storage tank in the high-efficiency pulping machine; the mass ratio of deionized water to pre-mixed powder is 33%:67%; the deionized water is automatically pumped into the mixing tank during the mixing process until it is completely consumed.

[0059] (3) Add the pre-mixed powder to the mixing tank of the high-efficiency pulper. During the pulping process, stir for 25 min at a revolution speed of 45 r / min and a rotation speed of 3500 r / min. Add 1.67 kg of conductive binder SONE at a mass ratio of 1.5% to that in step (1). Stir and mix for 15 min at a revolution speed of 45 r / min and a rotation speed of 3500 r / min. Start the pulp circulation of the high-efficiency pulper. During the pulp circulation process, stir for 2 min at a revolution speed of 45 r / min and a rotation speed of 3500 r / min. Set as one cycle. Circulate 35 times. The total pulp circulation time of the high-efficiency pulper is 70 min. After step (3), the pulp viscosity is 3256 mPa∙s. After the circulation is completed, the upper and lower parts of the pulp can be exchanged, and the resulting pulp is more uniform.

[0060] (4) Add 0.082 kg of styrene-butadiene rubber (SBR) at a mass ratio of 1% to that in step (1) to the mixing tank of the high-efficiency pulping machine, and stir for 30 min at a revolution speed of 25 r / min and a rotation speed of 1300 r / min. After step (4), the viscosity of the slurry is 1351 mPa∙s. Setting the rotation speed too high after adding SBR will cause excessive shear force, which will damage the chain structure of SBR and cause demulsification, resulting in slurry detachment during subsequent coating.

[0061] (5) Discharge: The material is sieved through a 150-mesh sieve to obtain negative electrode slurry. The fineness of the obtained slurry is 10 μm, the viscosity is 1351 mPa∙s, and the solid content is 68%.

[0062] The present invention also provides a negative electrode slurry, which is prepared by the above-described preparation method; the resulting negative electrode slurry has a fineness of 10 μm, a viscosity of 1351 mPa∙s, and a solid content of 68%.

[0063] The present invention also provides a negative electrode sheet, which further includes a current collector copper foil; the current collector is provided with the aforementioned negative electrode slurry; the single-sided density of the negative electrode sheet is ≥81 g / m³. 2 .

[0064] This comparative example provides a method for preparing lithium-ion battery negative electrode slurry, the slurry itself, and its application. Compared with Example 1, the difference lies in the use of a conventional slurry preparation method with a planetary mixer, including the following steps:

[0065] (1) Weigh 3.8 kg of active powder (graphite), 0.06 kg of binder (carboxymethyl cellulose), 0.06 kg of conductive agent (conductive carbon black) and 1.96 kg of deionized water in a mass ratio of 95%:1.5%:1.5% and add them to the mixing tank of a planetary mixer. The mixing speed is 25 r / min and the rotation speed is 800 r / min. Mix for 60 min.

[0066] (2) Evacuate to -0.085 MPa and stir for 180 min at a revolution speed of 35 r / min and a rotation speed of 1650 r / min.

[0067] (3) Add 0.165 kg of styrene-butadiene rubber at a mass ratio of 2% (calculated according to the calculation method of styrene-butadiene rubber in the invention content), evacuate to -0.085 MPa, and stir for 90 min at a revolution speed of 35 r / min and a rotation speed of 1600 r / min.

[0068] (4) Add the remaining 1.96 kg of deionized water, evacuate to -0.085 MPa, and stir for 90 min at a revolution speed of 22 r / min and a rotation speed of 500 r / min.

[0069] (5) Discharge: The material is sieved through a 150-mesh sieve to obtain negative electrode slurry. The fineness of the slurry is 12μm, the viscosity is 1453mPa∙s, and the solid content is 50%.

[0070] This comparative example also provides a negative electrode slurry, which is prepared by the above-described preparation method; the slurry has a fineness of 12 μm, a viscosity of 1453 mPa∙s, and a solid content of 50%.

[0071] This comparative example also provides a negative electrode sheet, which further includes a current collector copper foil; the current collector is coated with the aforementioned negative electrode slurry; the single-sided density of the negative electrode sheet is ≥80.5 g / m³. 2 .

[0072] This comparative example provides a method for preparing negative electrode slurry, the slurry itself, and its application. Compared with Example 1, the difference lies in the use of a conventional slurry preparation method with a planetary mixer, including the following steps:

[0073] (1) Weigh 3.8 kg of active powder (graphite), 0.06 kg of binder (carboxymethyl cellulose), and 0.06 kg of conductive agent (conductive carbon black) in a mass ratio of 95%:1.5%:1.5% and add them to the mixing tank of a planetary mixer. The mixing speed is 23 r / min and the rotation speed is 1500 r / min. Mix for 30 min.

[0074] (2) Add 1.95 kg of deionized water, which accounts for 46% of the total weight of deionized water, to the mixing tank, evacuate to -0.085 MPa, stir at 35 r / min, disperse at 650 r / min, and stir for 30 min.

[0075] (3) Evacuate to -0.085 MPa and stir for 300 min at a revolution speed of 35 r / min and a rotation speed of 1540 r / min;

[0076] (4) Add 0.935 kg of deionized water, which accounts for 22% of the total weight of deionized water, into the mixing tank, evacuate to -0.085 MPa, and stir for 30 min at a revolution speed of 38 r / min and a rotation speed of 1500 r / min.

[0077] (5) Add 0.165 kg of styrene-butadiene rubber at a mass ratio of 2% to the mixing tank (calculated according to the calculation method of styrene-butadiene rubber in the invention content), evacuate to -0.085 MPa, and stir for 30 min at a revolution speed of 38 r / min and a rotation speed of 1000 r / min.

[0078] (6) Add 1.365 kg of the remaining deionized water, evacuate to -0.085 MPa, and stir for 30 min at a revolution speed of 32 r / min and a rotation speed of 500 r / min.

[0079] (7) Discharge: The material is sieved through a 150-mesh sieve to obtain negative electrode slurry. The fineness of the slurry is 11 μm, the viscosity is 996 mPa∙s, and the solid content is 48%.

[0080] This comparative example also provides a negative electrode slurry, which is prepared by the above-described preparation method; the slurry has a fineness of 11 μm, a viscosity of 996 mPa∙s, and a solid content of 48%.

[0081] This comparative example also provides a negative electrode sheet, which further includes a current collector copper foil; the current collector is provided with the aforementioned negative electrode slurry; the single-sided density of the negative electrode sheet is ≥82 g / m³. 2 .

[0082] Figure 1 The diagram shows the time required for mixing in Examples 1-2 and Comparative Examples 1-2 of the present invention. Compared with the traditional pulping method which takes 6-8 hours, the efficient preparation method for low-viscosity, high-solids-content negative electrode slurry provided by the present invention significantly shortens the pulping time, saves production costs, and increases efficiency by 2-3 times. Figure 2 The low-viscosity, high-solids-content negative electrode slurry shown exhibits a high solids content, with Example 1 showing an effective increase in solids content compared to Comparative Examples 1 and 2. This increases the loading of active material per unit area on the electrode sheet, thereby enhancing the overall capacity of the lithium battery, aligning with future development trends. Figure 4 The scanning electron microscope images and cross-sectional images of the electrode film coated with the slurry obtained in Example 1 of the present invention at different magnifications all show irregular block shapes, and the blocks are tightly bonded together. The cross-sectional thickness is 60 μm, and the surface of the electrode sheet shows uniformity. Figure 5 The diagrams show the internal resistance relationships of lithium-ion batteries obtained from the slurries of Examples 1-2 and Comparative Examples 1-2 before formation. By controlling the circulation conditions of the high-efficiency slurry mixer, the conductive agent agglomerates can be fully broken up, and the active material, conductive agent, and binder can be thoroughly and uniformly mixed, reducing the internal resistance of the electrode and improving the consistency and stability of the slurry. Compared with Comparative Examples 1-2, Examples 1-2 exhibit lower internal resistance values, which is related to the tight bonding between the electrode material and the conductive carbon black and binder in the scanning electron microscope. In addition, as shown in Table 1, the slurries obtained from Examples 1-2 of this invention are significantly better than those from Comparative Examples 1-2 in terms of viscosity change rate, viscosity, solid content, and mixing time.

[0083] Table 1. Results of mixing time and slurry performance tests.

[0084] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Mixing time (h) 2.16 2.5 7 7.5 Viscosity (mPa∙s) 1508 1351 1453 996 Viscosity (mPa∙s) after 24 hours 1297 1175 1264 787 Viscosity change rate (%) 14 13 13 21 Fineness (μm) 9 10 12 11 Solid content (%) 67 68 50 48 Internal resistance before conversion (mΩ) 1.6214 1.6327 2.6784 2.932

[0085] It should be understood that the above-described embodiments are merely exemplary and not restrictive. Various obvious or equivalent modifications or substitutions made by those skilled in the art regarding the above details without departing from the basic principles of the invention are all included within the scope of the claims of this invention.

[0086] This invention uses SONE binder as the main source of deionized water, eliminating the need for large amounts of additional deionized water. This effectively solves the problem of low solid content in negative electrode slurry in traditional mixing methods, thereby increasing the actual capacity of lithium-ion batteries. The use of a high-efficiency slurry mixer enables multiple internal circulation of the slurry, ensuring thorough mixing of the powders and reducing electrode resistance. Furthermore, the efficient negative electrode slurry preparation method, the slurry itself, and its applications provided by this invention feature simple processing, high solid content, good stability, high mixing efficiency, and suitability for mass production.

[0087] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry, characterized in that, Includes the following steps: Step (1): Weigh the active powder, binder and conductive agent in a mass ratio of 96%:0.5%:1%, stir them in advance to make the color uniform, and obtain the pre-mixed powder. Step (2): Add deionized water to the solvent storage tank in the high-efficiency pulper. The mass ratio of deionized water to the pre-mixed powder is 30-35%: 65-70%. Step (3): Add the pre-mixed powder into the mixing tank of the high-efficiency pulper, pulp, stir and mix, add conductive binder SONE with a mass ratio of 1.5% to that in step (1), stir and mix, and start the pulp circulation of the high-efficiency pulper; During pulping, the revolution speed of the stirring is 20-50 r / min; the rotation speed of the stirring is 1300-4000 r / min; the stirring time is 20-30 min; the conductive binder SONE is a conductive binder of carbon nanotubes with carboxymethyl cellulose solution as dispersant, and its solid content is 3.6%; during pulp circulation, the revolution speed of the stirring is 20-50 r / min; the rotation speed of the stirring is 1300-4000 r / min; the stirring time is 2-5 min. The above conditions constitute one cycle, the number of cycles is 20-40, and the total pulping time is 40-70 min; the pulp circulation of the high-efficiency pulper is carried out by the pulp circulating between the stirring tank and the pipes inside the high-efficiency pulper under the drive of pressure / pump. After each cycle of stirring, the pulp finally returns to the stirring tank, completing one cycle; Step (4): Add styrene-butadiene rubber (SBR) at a mass ratio of 1% to that in step (1) to the mixing tank of the high-efficiency pulping machine, and mix. The revolution speed of the stirring is 20-40 r / min; the rotation speed of the stirring is 800-1500 r / min; the stirring time is 20-40 min; the SBR is a high-molecular elastomer material synthesized by copolymerization reaction of butadiene and styrene as the main monomers, which plays the role of auxiliary binder, and its solid content is 48.5%; the viscosity of the slurry after step (4) is 1200-2000. ; Step (5): Discharge, sieve, and obtain slurry with a viscosity of 1200-2000. The solid content is 60-70%.

2. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 1, characterized in that: The pre-stirring and mixing in step (1) is done manually for 5 to 10 minutes until the color is uniform. The active material in the powder is silicon carbide and graphite. The binder is carboxymethyl cellulose. The conductive agent is conductive carbon black.

3. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 1, characterized in that: The deionized water mentioned in step (2) is weighed by mass weighing; the deionized water is automatically pumped into the mixing tank during the stirring and mixing process until it is completely consumed.

4. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 1, characterized in that: In step (5), a 150-mesh sieve is used for sieving the output material; the fineness of the resulting slurry is 8-10 μm.

5. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 1, characterized in that: In step (1), the mass ratio of silicon carbide to graphite in the active powder material is 5%:91%.

6. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 1, characterized in that: The corresponding masses in step (1) are as follows: silicon carbon: graphite = 0.2 Kg: 3.64 Kg in the active material of the powder, carboxymethyl cellulose as binder = 0.02 Kg and conductive carbon black as conductive agent = 0.04 Kg.

7. The method for efficiently preparing low-viscosity, high-solids-content negative electrode slurry according to claim 6, characterized in that: In step (2), the mass of deionized water is 0.019–0.448 Kg; in step (3), the mass of conductive adhesive SONE is 1.67 Kg; and in step (4), the mass of styrene-butadiene rubber is 0.082 Kg.

8. A negative electrode slurry, wherein the slurry is prepared by any one of the preparation methods according to claims 1-7, characterized in that: Graphite appears as irregular blocks, while silicon carbon appears as irregular blocks with a particle size smaller than graphite. When carboxymethyl cellulose dissolves in water, the adhesion generated by the aggregation of molecular chains binds the materials together. Conductive carbon black has a chain structure that coats the surface of graphite and silicon carbon materials, fills the gaps between graphite, and plays a role in conducting electrons, while also improving the liquid retention of the electrode. During later electrode cycling processes, as the number of charge-discharge cycles increases, the graphite and silicon carbon gradually fragment, and the intermaterial spacing gradually increases. Styrene-butadiene rubber binds the graphite, while conductive carbon black connects the materials for electrical conductivity. The resulting negative electrode slurry has a fineness of 8–10 μm and a viscosity of 1200–2000 μL. The solid content is 60-70%.

9. A negative electrode sheet, characterized in that: The negative electrode sheet further includes a current collector, on which a negative electrode slurry is disposed; the slurry is the negative electrode slurry according to claim 8; the current collector is copper foil; the single-sided density of the negative electrode sheet is ≥83.9 g / m2.

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