Silicon negative electrode slurry and kneading method thereof, negative electrode sheet, secondary battery, and electric device

Abstract

The application discloses a silicon negative electrode slurry and a kneading method thereof, a negative electrode sheet, a secondary battery and an electric device, and relates to the technical field of batteries.The application comprises the following steps: mixing a silicon-based active material, a binder, a conductive agent and a first part of water to obtain a first mixture; kneading the first mixture with a second part of water to obtain a second mixture; mixing the second mixture with a third part of water to obtain a third mixture; mixing the third mixture with a fourth part of water to obtain a silicon negative electrode slurry; wherein the mass ratio of the first part of water, the second part of water, the third part of water and the fourth part of water is (1-1.5):(20-25):(66-75):(3-7.5); and in the first mixture, the mass percentage of the first part of water is 0.4%-0.6%. By adding deionized water in batches and in different proportions, the problem of powder flying in the dry mixing process can be effectively reduced, and the problem of inconsistent material ratio caused by the adhesion of some powder to the wall can be avoided.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a silicon anode slurry and its kneading method, an anode sheet, a secondary battery, and an electrical device. Background Technology

[0002] Silicon anode materials have become a research hotspot for next-generation lithium-ion battery anode materials due to their high theoretical specific capacity (4200 mAh / g) and low discharge plateau. However, the huge volume effect (up to 300%) that accompanies silicon materials during charge and discharge hinders their large-scale application. In industrial production, silicon materials are often mixed with graphite to combine the advantages and disadvantages of both. Graphite can provide higher initial efficiency and better conductivity, while silicon can provide higher specific capacity.

[0003] The preparation of negative electrode slurry is one of the key steps in the lithium-ion battery production process. Traditional methods for preparing lithium-ion battery negative electrode slurry suffer from uneven binder dispersion, leading to problems such as insufficient bonding strength, large particles, and sticking to rollers during slurry application. Meanwhile, premixing powder methods can cause dust dispersion and powder loss, affecting slurry consistency. Existing kneading and mixing methods also suffer from uneven binder dispersion, causing problems during slurry application. Summary of the Invention

[0004] This application provides a silicon anode slurry and its kneading method, an anode sheet, a secondary battery, and an electrical device to improve the problem of poor slurry stability.

[0005] In a first aspect, this application provides a method for kneading silicon anode slurry, comprising the following steps: A first mixture is obtained by mixing a silicon-based active material, a binder, a conductive agent, and a first portion of water. The first mixture is kneaded together with the second portion of water to obtain the second mixture; The second mixture is mixed with the third portion of water to obtain the third mixture; The third mixture is mixed with the fourth part of water to obtain a silicon anode slurry; The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is (1~1.5):(20~25):(66~75):(3~7.5). In the first mixture, the mass percentage of water in the first part is 0.4% to 0.6%.

[0006] This application utilizes a phased approach, adding deionized water in varying proportions. During the dry powder mixing stage (forming the first mixture), 1%–1.5% deionized water is added. This effectively reduces powder scattering during dry mixing, preventing some powder from adhering to the walls and causing inconsistent component ratios. During the kneading stage (forming the second mixture), 20%–25% deionized water is added. This appropriate solvent amount ensures sufficient wetting of the powder surface, uniform bonding between components, and prevents uneven binder dispersion and localized enrichment. Good kneading also improves the consistency of the finished slurry's viscosity and solids content. During the dilution stage (forming the third mixture), 66%–75% deionized water is added, while reserving 3%–7.5% for subsequent viscosity adjustment (forming the silicon anode slurry). This avoids excessively low viscosity due to a single solvent addition and further improves slurry consistency.

[0007] It should be noted that the conventional silicon anode slurry kneading process usually involves adding deionized water in two steps: first, mixing it with the pre-mixed dry mix, and second, diluting it to the target solid content. The drawback of this process is that silicon particles have a large specific surface area, high surface energy, and are prone to hard agglomeration. The binder is not completely wetted, and localized excessive thinning or dry clumps are likely to occur, resulting in insufficient adhesion.

[0008] The conventional kneading method did not consider adding a small amount of water in the dry powder mixing step due to the inertia of the industry's graphite system process, and did not take into account the special characteristics of silicon's high specific surface area, strong agglomeration, and large expansion.

[0009] In some embodiments, the solid content of the silicon anode slurry is 45% to 48%. Under the same formulation, conventional silicon anode slurry kneading methods can only obtain slurries with a solid content of less than 45%. This is because the slurry dispersion effect is not ideal, and the binder and conductive agent fail to form a uniform network, resulting in excessively high viscosity. At the same viscosity, it is necessary to increase solvent dilution, resulting in a lower solid content.

[0010] In some embodiments, the viscosity of the silicon anode slurry is 3000 mPa·s to 6000 mPa·s. Under the same formulation, conventional silicon anode slurry kneading methods can achieve a viscosity of 6000 mPa·s to 8000 mPa·s, while the viscosity of the slurry obtained using the silicon anode slurry kneading method of this application can reach 3000 mPa·s to 6000 mPa·s. This is because the kneading speed is differentiated in both directions, forming a reverse strong shear flow field, combined with high-speed circulating dispersion, resulting in a more uniform distribution of the slurry components.

[0011] In some embodiments, the silicon-based active material contains 28% to 35% silicon by mass. Conventional silicon anode slurries contain 5% to 15% silicon by mass, while the silicon-based anode slurry produced using the kneading method of this application can reach 28% to 35% silicon by mass. This is due to the adoption of a positive electrode-matched ultra-high nickel ternary system and a high-pressure compaction design for the anode. It should be noted that, apart from silicon, the remaining components of the silicon-based active material can be natural flake graphite, artificial graphite (needle coke / petroleum coke-based), graphitized mesophase carbon microspheres, etc.

[0012] In some embodiments, the mass ratio of silicon-based active material, binder, and conductive agent in the silicon anode slurry is (94~96):(3~5):(0.5~1.5). Maintaining this mass ratio within this range can improve the cell's energy density, cycle life, and other performance characteristics.

[0013] In some embodiments, the mixing of the silicon-based active material, binder, conductive agent, and a first portion of water to obtain a first mixture includes: The mixing speed is 15 rpm to 30 rpm; and / or, The dispersion rate of the mixture is 10 m / s to 20 m / s; and / or, Mixing time is 20-30 minutes.

[0014] When forming the first mixture, dry powder is mixed in a kneading tank. By adding a small amount of deionized water, dust can be reduced, dry powder flying and sticking to the wall can be reduced. The stirring speed is 15 rpm to 30 rpm, the dispersion speed is 10 m / s to 20 m / s, and the stirring time is 20 to 30 min, which can make the powder particles evenly mixed and improve the consistency of the slurry.

[0015] In some embodiments, the process of kneading the first mixture with a second portion of water to obtain a second mixture involves the use of a rotor and blades moving in opposite directions to form a cyclonic shearing mixture, wherein: The rotor speed is 10 m / s to 15 m / s; and / or, The impeller stirring speed is 15 rpm to 25 rpm; and / or, The mixing time is 30 min to 45 min.

[0016] During the formation of the second mixture, efficient kneading is performed in a kneading tank. An appropriate amount of deionized water is added and thoroughly stirred with the first mixture to ensure effective wetting of the powder surface. A high-viscosity kneading high-speed rotor and low-speed impeller move in opposite directions, creating cyclonic shearing to rapidly break up agglomerates and form a high-viscosity slurry. The rotor speed is 10 m / s to 15 m / s, the impeller stirring speed is 15 rpm to 25 rpm, and the stirring time is 30 min to 45 min. This results in a slurry with good properties, higher solids content, and moderate viscosity, thereby improving battery performance.

[0017] In some embodiments, the mixing of the second mixture with the third portion of water to obtain the third mixture is performed using a shear dispersion method, wherein: Shear rate greater than or equal to 18 m / s; and / or, Mixing time is 20-30 minutes.

[0018] When forming the third mixture, deionized water is added to the kneaded high-viscosity slurry second mixture for dilution. The diluted slurry is then transferred to a dispersion tank and circulated online using a high-shear disperser with a shear rate ≥18m / s and a circulation time of 20~30min. This allows for further shear dispersion of the slurry and a more uniform distribution.

[0019] In some embodiments, if the binder in the mixture of the third mixture and the fourth portion of water to obtain the silicon anode slurry contains styrene-butadiene rubber, then: The mixing rate is 6 m / s to 8 m / s; and / or, The mixing time is 15 min to 30 min.

[0020] During the viscosity adjustment stage, i.e. the process of forming silicon anode slurry, if the binder contains styrene-butadiene rubber, it has the characteristic of being prone to demulsification due to high-speed shearing. Therefore, it is necessary to use low-speed dispersion to adjust the viscosity, with a dispersion speed of 6m / s to 8m / s and a mixing time of 15min to 30min, in order to reduce the risk of demulsification.

[0021] In some embodiments, if the binder in the mixture of the third mixture and the fourth portion of water to obtain the silicon anode slurry does not contain styrene-butadiene rubber, then: The mixing rate is 15 m / s to 20 m / s; and / or, The mixing time is 15 min to 30 min.

[0022] During the viscosity adjustment stage, i.e. the process of forming silicon anode slurry, if the binder does not contain styrene-butadiene rubber, it has high viscosity characteristics and requires high-speed shear dispersion for viscosity adjustment. The dispersion speed is 15m / s~20m / s and the mixing time is 15min~30min, so as to make the slurry more uniformly dispersed.

[0023] In some embodiments, the silicon-based active material includes at least one of nano-silicon particles, silicon-carbon composite material (Si / C), and silicon monoxide (SiOx, 0 < x < 2); and / or, the binder includes at least one of polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyimide (PI) flexible binder; and / or, the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, conductive graphite, vapor-grown carbon fiber, carbon nanotube, and graphene.

[0024] In some embodiments, the total time used for the kneading process is less than or equal to 180 min. Usually, the conventional silicon negative electrode slurry takes 360 min to 480 min because of the insufficient high-speed shearing efficiency. However, the total time used for the kneading process of this application is less than or equal to 180 min, which is achieved by efficient kneading and continuous cyclic dispersion.

[0025] In a second aspect, this application provides a silicon negative electrode slurry prepared by the silicon negative electrode slurry kneading method described in the first aspect.

[0026] In a third aspect, this application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer disposed at least on one side of the negative electrode current collector. The negative electrode active material layer is coated with the silicon negative electrode slurry described in the second aspect.

[0027] In a fourth aspect, this application provides a secondary battery, which includes a positive electrode sheet, a separator, and the negative electrode sheet described in the third aspect.

[0028] In some embodiments, the energy density of the battery is greater than or equal to 340 Wh / kg.

[0029] In some embodiments, the 3C rate discharge capacity of the battery is greater than or equal to 85%.

[0030] In some embodiments, the capacity retention rate of the battery after 500 cycles at 25 °C is greater than or equal to 93%.

[0031] In a fifth aspect, this application provides an electrical device, which includes the secondary battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1The image shows the flow curve of the silicon anode slurry prepared by the kneading method of Example 3 of this application.

[0034] Figure 2 This is a stability test diagram of the silicon anode slurry prepared by the silicon anode slurry kneading method of Example 3 of this application.

[0035] Figure 3 The graph shows the cycle performance of the battery cell prepared from the silicon anode slurry obtained by the silicon anode slurry kneading method of Example 3 of this application.

[0036] Figure 4 This is a comparison chart of the battery cell performance of the embodiments and comparative examples in this application. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0038] Silicon anode materials have become a research hotspot for next-generation lithium-ion battery anode materials due to their high theoretical specific capacity (4200 mAh / g) and low discharge plateau. However, the huge volume effect (up to 300%) that accompanies silicon materials during charge and discharge hinders their large-scale application. In industrial production, silicon materials are often mixed with graphite to combine the advantages and disadvantages of both. Graphite can provide higher initial efficiency and better conductivity, while silicon can provide higher specific capacity.

[0039] The preparation of negative electrode slurry is one of the key steps in the lithium-ion battery production process. Traditional methods for preparing lithium-ion battery negative electrode slurry suffer from uneven binder dispersion, leading to problems such as insufficient bonding strength, large particles, and sticking to rollers during slurry application. Meanwhile, premixing powder methods can cause dust dispersion and powder loss, affecting slurry consistency. Existing kneading and mixing methods also suffer from uneven binder dispersion, causing problems during slurry application.

[0040] The solid content and stability of a slurry are closely related. For the same process and formulation, the higher the solid content, the greater the viscosity, and vice versa. Within a certain range, higher viscosity generally leads to higher slurry stability. However, high solid content slurries can also affect their flowability, posing significant challenges to equipment and technicians in the coating process.

[0041] In view of this, this application provides a silicon anode slurry and its kneading method, an anode sheet, a secondary battery, and an electrical device to improve the problem of poor slurry stability.

[0042] In a first aspect, this application provides a method for kneading silicon anode slurry, comprising the following steps: A first mixture is obtained by mixing a silicon-based active material, a binder, a conductive agent, and a first portion of water. The first mixture is kneaded together with the second portion of water to obtain the second mixture; The second mixture is mixed with the third portion of water to obtain the third mixture; The third mixture is mixed with the fourth part of water to obtain a silicon anode slurry; The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is (1~1.5):(20~25):(66~75):(3~7.5). In the first mixture, the mass percentage of water in the first part is 0.4% to 0.6%.

[0043] This application utilizes a phased approach, adding deionized water in varying proportions. During the dry powder mixing stage (forming the first mixture), 1%–1.5% deionized water is added. This effectively reduces powder scattering during dry mixing, preventing some powder from adhering to the walls and causing inconsistent component ratios. During the kneading stage (forming the second mixture), 20%–25% deionized water is added. This appropriate solvent amount ensures sufficient wetting of the powder surface, uniform bonding between components, and prevents uneven binder dispersion and localized enrichment. Good kneading also improves the consistency of the finished slurry's viscosity and solids content. During the dilution stage (forming the third mixture), 66%–75% deionized water is added, while reserving 3%–7.5% for subsequent viscosity adjustment (forming the silicon anode slurry). This avoids excessively low viscosity due to a single solvent addition and further improves slurry consistency.

[0044] It should be noted that the conventional silicon anode slurry kneading process usually involves adding deionized water in two steps: first, mixing it with the pre-mixed dry mix, and second, diluting it to the target solid content. The drawback of this process is that silicon particles have a large specific surface area, high surface energy, and are prone to hard agglomeration. The binder is not completely wetted, and localized excessive thinning or dry clumps are likely to occur, resulting in insufficient adhesion.

[0045] The conventional kneading method did not consider adding a small amount of water in the dry powder mixing step due to the inertia of the industry's graphite system process, and did not take into account the special characteristics of silicon's high specific surface area, strong agglomeration, and large expansion.

[0046] In conjunction with the first aspect, in some embodiments provided in this application, the solid content of the silicon anode slurry is 45% to 48%. Under the same formulation, conventional silicon anode slurry kneading methods can achieve a solid content of less than 45%. This is because the slurry dispersion effect is not ideal, and the binder and conductive agent fail to form a uniform network, resulting in excessively high viscosity. At the same viscosity, it is necessary to increase solvent dilution, resulting in a lower solid content.

[0047] In conjunction with the first aspect, in some embodiments provided in this application, the viscosity of the silicon anode slurry is 3000 mPa·s to 6000 mPa·s. Under the same formulation, the viscosity of conventional silicon anode slurry kneading methods can reach 6000 mPa·s to 8000 mPa·s, while the viscosity of the slurry obtained by the silicon anode slurry kneading method of this application can reach 3000 mPa·s to 6000 mPa·s. This is because the kneading speed is differentiated in both directions, forming a reverse strong shear flow field, combined with high-speed circulation dispersion, resulting in a more uniform distribution of the slurry components.

[0048] In conjunction with the first aspect, in some embodiments provided in this application, the silicon-based active material contains 28% to 35% silicon by mass. In conventional silicon anode slurries, the silicon by mass is 5% to 15%, while the silicon by mass in the slurry produced using the silicon anode slurry kneading method of this application can reach 28% to 35%. This is due to the use of a positive electrode-matched ultra-high nickel ternary system and a high-pressure compaction design for the anode. It should be noted that, apart from silicon, the remaining components of the silicon-based active material can be natural flake graphite, artificial graphite (needle coke / petroleum coke-based), graphitized mesophase carbon microspheres, etc.

[0049] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of silicon-based active material, binder, and conductive agent in the silicon anode slurry is (94~96):(3~5):(0.5~1.5). Maintaining this mass ratio within this range can improve the energy density, cycle life, and other performance characteristics of the battery cell.

[0050] In conjunction with the first aspect, in some embodiments provided in this application, the mixing of silicon-based active material, binder, conductive agent and a first portion of water to obtain a first mixture involves: a stirring speed of 15 rpm to 30 rpm; a dispersion speed of 10 m / s to 20 m / s; and a mixing time of 20 min to 30 min.

[0051] When forming the first mixture, dry powder is mixed in a kneading tank. By adding a small amount of deionized water, dust can be reduced, dry powder flying and sticking to the wall can be reduced. The stirring speed is 15 rpm to 30 rpm, the dispersion speed is 10 m / s to 20 m / s, and the stirring time is 20 to 30 min, which can make the powder particles evenly mixed and improve the consistency of the slurry.

[0052] In conjunction with the first aspect, in some embodiments provided in this application, the first mixture is kneaded with a second portion of water to obtain a second mixture, in which a rotor and a paddle move in opposite directions to form a vortex shear mixing, wherein: the rotor speed is 10m / s~15m / s; the paddle stirring speed is 15rpm~25rpm; and the mixing time is 30min~45min.

[0053] During the formation of the second mixture, efficient kneading is performed in a kneading tank. An appropriate amount of deionized water is added and thoroughly stirred with the first mixture to ensure effective wetting of the powder surface. A high-viscosity kneading high-speed rotor and low-speed impeller move in opposite directions, creating cyclonic shearing to rapidly break up agglomerates and form a high-viscosity slurry. The rotor speed is 10 m / s to 15 m / s, the impeller stirring speed is 15 rpm to 25 rpm, and the stirring time is 30 min to 45 min. This results in a slurry with good properties, higher solids content, and moderate viscosity, thereby improving battery performance.

[0054] In conjunction with the first aspect, in some embodiments provided in this application, the second mixture is mixed with the third portion of water to obtain the third mixture, which is mixed by shear dispersion, wherein: the shear rate is greater than or equal to 18 m / s; and the mixing time is 20 min to 30 min.

[0055] When forming the third mixture, deionized water is added to the kneaded high-viscosity slurry second mixture for dilution. The diluted slurry is then transferred to a dispersion tank and circulated online using a high-shear disperser with a shear rate ≥18m / s and a circulation time of 20~30min. This allows for further shear dispersion of the slurry and a more uniform distribution.

[0056] In conjunction with the first aspect, in some embodiments provided in this application, when the third mixture is mixed with the fourth part of water to obtain a silicon anode slurry, if the binder contains styrene-butadiene rubber, the mixing rate is 6 m / s to 8 m / s; the mixing time is 15 min to 30 min.

[0057] During the viscosity adjustment stage, i.e. the process of forming silicon anode slurry, if the binder contains styrene-butadiene rubber, it has the characteristic of being prone to demulsification due to high-speed shearing. Therefore, it is necessary to use low-speed dispersion to adjust the viscosity, with a dispersion speed of 6m / s to 8m / s and a mixing time of 15min to 30min, in order to reduce the risk of demulsification.

[0058] In conjunction with the first aspect, in some embodiments provided in this application, when the third mixture is mixed with the fourth part of water to obtain a silicon anode slurry, if the binder does not contain styrene-butadiene rubber, the mixing rate is 15 m / s to 20 m / s; the mixing time is 15 min to 30 min.

[0059] In the viscosity adjustment stage, that is, during the formation of the silicon negative electrode slurry, if the binder does not contain styrene-butadiene rubber, it has high viscosity characteristics and requires high-speed shear dispersion for viscosity adjustment. The dispersion speed is 15 m / s to 20 m / s, and the mixing time is 15 min to 30 min, so as to make the slurry more evenly dispersed.

[0060] In some embodiments provided in the present application in combination with the first aspect, the silicon-based active material includes at least one of nano-silicon particles, silicon-carbon composite material (Si / C), or silicon suboxide (SiOx, 0 < x < 2); the binder includes at least one of a composite binder of polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) (the mass ratio is (1 to 2):1) and a polyimide (PI) flexible binder; the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, conductive graphite, vapor grown carbon fiber, carbon nanotube, and graphene.

[0061] In some embodiments provided in the present application in combination with the first aspect, the total time used in the kneading process is less than or equal to 180 min. Usually, the conventional silicon negative electrode slurry takes 360 min to 480 min, which is due to insufficient high-speed shear efficiency. However, the total time used in the kneading process of the present application is less than or equal to 180 min, which is achieved by efficient kneading and continuous cyclic dispersion.

[0062] In the second aspect, the present application provides a silicon negative electrode slurry prepared by the silicon negative electrode slurry kneading method described in the first aspect.

[0063] In the third aspect, the present application provides a negative electrode sheet, including a negative electrode current collector and at least a negative electrode active material layer provided on one side of the negative electrode current collector, and the negative electrode active material layer is coated with the silicon negative electrode slurry described in the second aspect.

[0064] In the fourth aspect, the present application provides a secondary battery, including a positive electrode sheet, a separator, and the negative electrode sheet described in the third aspect.

[0065] In some embodiments provided in the present application in combination with the fourth aspect, the energy density of the battery is greater than or equal to 340 Wh / kg.

[0066] In some embodiments provided in the present application in combination with the fourth aspect, the 3C rate discharge capacity of the battery is greater than or equal to 85%.

[0067] In some embodiments provided in the present application in combination with the fourth aspect, the capacity retention rate of the battery after 500 cycles at 25 °C is greater than or equal to 93%.

[0068] In the fifth aspect, the present application provides an electrical device including the secondary battery described in the fourth aspect.

[0069] The technical solution provided in this application will be described in detail below with reference to embodiments, wherein the silicon-oxygen material is pre-lithiated silicon suboxide (SiO2). x (x≈1), particle size D50 5μm, specific surface area BET 5m² 2 Taking / g as an example, the graphite material is artificial graphite with a particle size Dv50 of 15μm and a specific surface area BET of 2.0m². 2 Let's take / g as an example for explanation.

[0070] Example 1 Embodiment 1 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0071] 94 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.2), 4.5 parts of binder (polyacrylic acid: styrene-butadiene rubber = 1:1.6), 1.5 parts of conductive agent (conductive carbon black: carbon nanotubes = 1:2.1), and 0.4 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 15 rpm, the dispersion speed was 10 m / s, and the stirring was carried out for 30 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 6.7 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 10 m / s, the impeller stirring speed is 15 rpm, and the stirring time is 45 min to obtain the second mixture. 17.6 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 18 m / s and a circulation time of 20 min to obtain the third mixture. Two parts of deionized water were used to adjust the viscosity of the third mixture. The dispersion speed was 6 m / s and the dispersion time was 30 min. The viscous slurry was then vacuum degassed to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0072] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:25:66:7.5.

[0073] Example 2 Embodiment 2 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0074] 96 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.2), 3 parts of binder (polyacrylic acid: styrene-butadiene rubber = 1:1.6), 1 part of conductive agent (conductive carbon black: carbon nanotubes = 1:2.1), and 0.6 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 30 rpm, the dispersion speed was 20 m / s, and the stirring was carried out for 30 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 12 parts of deionized water to the first mixture and stir thoroughly to ensure that the powder surface is effectively wetted. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly break up the agglomerates, and form a high-viscosity slurry. The rotor speed is 15 m / s, the impeller stirring speed is 25 rpm, and the stirring time is 40 min to obtain the second mixture. 45 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 25 m / s and a circulation time of 25 min to obtain the third mixture. The viscosity of the third mixture was adjusted using 2.4 parts of deionized water at a dispersion speed of 8 m / s and a dispersion time of 15 min. The viscous slurry was then vacuum degassed to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0075] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1:20:75:4.

[0076] Example 3 Embodiment 3 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0077] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.2), 4 parts of binder (polyacrylic acid: styrene-butadiene rubber = 1:1.6), 1 part of conductive agent (conductive carbon black: carbon nanotubes = 1:2.1), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 25 rpm, the dispersion speed was 15 m / s, and the stirring was carried out for 40 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 7.5 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 14 m / s, the impeller stirring speed is 20 rpm, and the stirring time is 30 min to obtain the second mixture. 24.3 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 25 m / s and a circulation time of 25 min to obtain the third mixture. The viscosity of the third mixture was adjusted using 1 part deionized water at a dispersion speed of 7 m / s and a dispersion time of 20 min. The viscous slurry was then vacuum degassed to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0078] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:22.5:73:3.

[0079] Example 4 Embodiment 4 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0080] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.1), 3.5 parts of binder (sodium carboxymethyl cellulose: polyacrylic acid = 1:1.5), 1.5 parts of conductive agent (conductive carbon black: carbon nanotubes = 1:2.2), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 40 rpm, the dispersion speed was 30 m / s, and the stirring was carried out for 25 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 8.7 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 15 m / s, the impeller stirring speed is 25 rpm, and the stirring time is 30 min to obtain the second mixture. 28 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 18 m / s and a circulation time of 20 min to obtain the third mixture. The third mixture was adjusted to a viscosity using 1.2 parts of deionized water at a dispersion speed of 15 m / s and a dispersion time of 30 min. The viscous slurry was then degassed under vacuum to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0081] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.3:22.7:73:3.

[0082] Example 5 Embodiment 5 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0083] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.1), 4 parts of binder (sodium carboxymethyl cellulose: polyacrylic acid = 1:1.7), 1 part of conductive agent (conductive graphite: carbon nanotubes = 1:2.3), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 30 rpm, the dispersion speed was 20 m / s, and the stirring was carried out for 30 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 7.5 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 8 m / s, the impeller stirring speed is 12 rpm, and the stirring time is 60 min to obtain the second mixture. 24.3 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 18 m / s and a circulation time of 20 min to obtain the third mixture. The third mixture was adjusted with 1 part deionized water at a dispersion speed of 20 m / s and a dispersion time of 20 min. The adjusted slurry was then degassed under vacuum to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0084] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:22.5:73:3.

[0085] Example 6 Embodiment 6 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0086] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.3), 4 parts of binder (polyacrylic acid: styrene-butadiene rubber = 1:1.7), 1 part of conductive agent (acetylene black: carbon nanotubes = 1:2.3), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 30 rpm, the dispersion speed was 20 m / s, and the stirring was carried out for 30 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 7.5 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 20 m / s, the impeller stirring speed is 35 rpm, and the stirring time is 20 min to obtain the second mixture. 24.3 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 18 m / s and a circulation time of 20 min to obtain the third mixture. The third mixture was adjusted to a viscosity using 1 part deionized water at a dispersion speed of 5 m / s for 30 min. The slurry was then degassed under vacuum to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0087] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:22.5:73:3.

[0088] Example 7 Embodiment 7 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0089] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.2), 4 parts of binder (sodium carboxymethyl cellulose: polyacrylic acid = 1:1.4), 1 part of conductive agent (Ketjen black: carbon nanotubes = 1:2), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 30 rpm, the dispersion speed was 20 m / s, and the stirring was carried out for 30 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 7.5 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 15 m / s, the impeller stirring speed is 25 rpm, and the stirring time is 30 min to obtain the second mixture. 24.3 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 15 m / s and a circulation time of 40 min to obtain the third mixture. The third mixture was adjusted to a viscosity using 1 part deionized water at a dispersion speed of 25 m / s and a dispersion time of 20 min. The viscous slurry was then vacuum degassed to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0090] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:22.5:73:3.

[0091] Example 8 Embodiment 8 of this application provides a method for kneading silicon anode slurry, including the following steps.

[0092] 95 parts of silicon-based active material (silicon-oxygen material: graphite material = 1:2.3), 4 parts of binder (polyacrylic acid: styrene-butadiene rubber = 1:1.4), 1 part of conductive agent (conductive carbon black: carbon nanotubes = 1:2), and 0.5 parts of deionized water were added to a kneading jar for dry powder mixing. The stirring speed was 40 rpm, the dispersion speed was 30 m / s, and the stirring was carried out for 25 min to make the powder particles uniformly mixed, thus obtaining the first mixture. Add 7.3 parts of deionized water to the first mixture and stir thoroughly to ensure effective wetting of the powder surface. Use a high-viscosity kneading high-speed rotor and a low-speed impeller moving in opposite directions to form a cyclonic shearing effect, quickly breaking up the agglomerates to form a high-viscosity slurry. The rotor speed is 8 m / s, the impeller stirring speed is 12 rpm, and the stirring time is 60 min to obtain the second mixture. 24.3 parts of deionized water were added to the second mixture for dilution. The diluted slurry was then transferred to a dispersion tank and dispersed online using a high-shear circulating disperser at a shear rate of 15 m / s and a circulation time of 40 min to obtain the third mixture. The third mixture was adjusted to a viscosity using 1.2 parts of deionized water at a dispersion speed of 5 m / s and a dispersion time of 30 min. The viscous slurry was then degassed under vacuum to remove air bubbles. The degassed slurry was then sieved to obtain a uniform silicon anode slurry.

[0093] The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is 1.5:22.5:73:3.

[0094] Comparative Example 1 Comparative Example 1 of this application provides a method for kneading silicon anode slurry, which is similar to Example 8, except that deionized water is added to the slurry in four equal parts.

[0095] Comparative Example 2 Comparative Example 2 of this application provides a method for kneading silicon anode slurry, which is similar to Example 8, except that deionized water is added twice. The first time is added to the dry-mixed material, and the second time is added to the slurry after kneading. The ratio of the two additions is 1:9.

[0096] Comparative Example 3 Comparative Example 3 of this application provides a method for kneading silicon anode slurry, which is similar to Example 8, except that deionized water is not added when forming the first mixture, but is added together when forming the second mixture.

[0097] Comparative Example 4 Comparative Example 4 of this application provides a method for kneading silicon anode slurry, which is similar to Example 8, except that all deionized water has been added when forming the third mixture, and no viscosity adjustment is performed.

[0098] Performance testing The silicon anode slurries prepared by the silicon anode slurry kneading method in Examples 1 to 8 and the silicon anode slurries prepared by the silicon anode slurry kneading method in Comparative Examples 1 to 4 were subjected to performance tests. The specific test methods are as follows: Solid content: Under constant temperature of 25℃, a certain mass of slurry sample is taken, and the solvent is completely removed by constant temperature drying. The mass of the remaining solids after drying is weighed, and the mass of the remaining solids is the percentage of the initial mass of the sample.

[0099] Viscosity: Under constant temperature of 25℃, a rotational viscometer was used. The 3# rotor was rotated in the slurry at a constant speed of 12rpm. After the rotation was stable, the viscosity value was read.

[0100] Kneading status: Under a constant temperature of 25℃, take the kneaded slurry and observe its consistency and feel. If the paste is fine, has moderate yielding, and a smooth film surface, the kneading is good; if it is slightly rough and has particles, the kneading is insufficient and too dry; if it is sticky, has severe stringing, or has residue on the wall, the kneading is excessive and too thin.

[0101] The test results are shown in Table 1.

[0102] The silicon anode slurries prepared by the silicon anode slurry kneading method in Examples 1 to 8 and the silicon anode slurries prepared by the silicon anode slurry kneading method in Comparative Examples 1 to 4 were used to prepare batteries, and performance tests were conducted. The specific test methods are as follows: The battery assembly process is as follows: Positive electrode: A 12μm aluminum foil is used as the current collector. The surface is uniformly coated with a slurry made of 9-series high-nickel ternary active material, conductive carbon black and carbon nanotube composite conductive agent (mass ratio 1:2), PVDF binder and NMP solvent in a mass ratio of 96:3:1. The coating thickness on one side is controlled at 60 μm, and the overall thickness of the electrode is 125 μm. It is cut into a circular sheet with a diameter of 15 mm, and a 2 mm blank aluminum foil current collector area is reserved at the edge.

[0103] Negative electrode: Using 6μm copper foil as the current collector, the slurry of this scheme is uniformly coated and cut into a circular electrode that matches the positive electrode or is 0.5mm smaller.

[0104] Separator: A modified polyolefin separator is used, with PP / PE microporous membrane as the base membrane and a heat-resistant alumina ceramic coating on the surface. The base membrane thickness is 18 μm, the single-sided ceramic coating thickness is 2 μm, the total separator thickness is 5 μm, and the cutting diameter is 1 mm larger than that of the positive and negative electrode sheets, so as to completely cover the electrode sheets.

[0105] Assembly: The pre-treated, dried, and deburred positive electrode sheet is placed flat and centered on the bottom of the battery casing. A measured amount of electrolyte is added to fully wet the pores of the electrode sheet. Then, a neatly cut separator is placed centered on the surface of the positive electrode sheet, ensuring no wrinkles, no misalignment, and complete coverage of the positive electrode area. Next, the negative electrode sheet is placed centered, ensuring complete overlap and no misalignment. Stainless steel gaskets and spring contacts are then inserted to buffer electrode expansion during battery cycling and ensure tight current collection. Finally, the battery cover is snapped shut, and the battery assembly is completed by stamping and sealing with a sealing machine. After assembly, the battery is allowed to stand at room temperature for 12-24 hours to allow the electrolyte to fully wet the microporous structure of the electrode sheet and separator, ensuring unobstructed ion transport channels. Subsequent formation, capacity testing, and electrochemical performance testing are then performed.

[0106] Capacity retention: The ratio of remaining capacity to initial stable capacity after 500 cycles under a constant temperature environment of 25℃, using 1C constant current and constant voltage charging + 1C constant current discharging.

[0107] Energy density: The ratio of discharge energy to the net weight of the cell after charging to the upper voltage limit at 0.2C constant current and constant voltage under a constant temperature environment of 25℃, and then discharging to the lower voltage limit at 0.2C constant current.

[0108] Rate performance: The ratio of the discharge capacity obtained by measuring the reference capacity under a constant temperature environment of 25℃ with a standard charge and discharge of 0.2C, and then discharging at a constant current of 1C to the reference capacity.

[0109] The results are shown in Table 2: Table 1 Performance results of silicon anode slurries in Examples 1 to 8 and Comparative Examples 1 to 4

[0110] Table 2 Battery performance results of Examples 1 to 8 and Comparative Examples 1 to 4

[0111] As can be seen from Tables 1 and 2, in Examples 1 to 3, by adding water in stages and controlling the amount, and matching the combination of rotation speed / time / linear speed, the shear dispersion and powder protection were perfectly balanced, resulting in a more uniform slurry composition and better battery cell performance.

[0112] The slurry flow curve of Example 3 is as follows: Figure 1 As shown, by Figure 1 It can be seen that the slurry has shear-thinning properties, resulting in more uniform dispersion, good fluidity, and stable viscosity.

[0113] The slurry stability test results of Example 3 are as follows: Figure 2 As shown, by Figure 2 It can be seen that the slurry has good settling stability.

[0114] The cell cycle performance results of Example 3 are as follows: Figure 3 As shown, by Figure 3 It can be seen that the battery cell retains more than 95% of its capacity after 500 cycles of discharge, which is better than the industry average.

[0115] The cell test performance of Examples 1 to 8 and Comparative Examples 1 to 4 is as follows: Figure 4 As shown.

[0116] Example 4 was slightly inferior to Examples 1 to 3 because the mixing speed of the dry powder was too high. This was because the powder structure and morphology began to be destroyed and slight powder agglomeration occurred, but it was still better than Comparative Examples 1 to 4.

[0117] Example 5 performed slightly worse than Examples 1 to 3 due to the low kneading rate. This was because the powder was not fully wetted, which affected the stable colloidal network and impacted the electrochemical performance. However, it was still better than Comparative Examples 1 to 4.

[0118] Example 6 performed slightly worse than Examples 1 to 3 due to the excessively high kneading rate. This was because the binder molecular chains began to break and degrade, and the conductive agent network was damaged. However, it was still better than Comparative Examples 1 to 4.

[0119] Example 7 performed slightly worse than Examples 1 to 3 due to its low dilution rate. This was because the solvent was not dispersed evenly, some powders began to agglomerate, internal resistance increased, and rate performance decreased. However, it was still better than Comparative Examples 1 to 4.

[0120] Example 8 was slightly inferior to Examples 1 to 3 because the mixing speed of the dry powder was too high, the kneading rate was too low, and the dilution rate was too low. This was because the powder particles were damaged, the wetting effect was poor, the bonding network was uneven, and agglomeration occurred. However, it was still better than Comparative Examples 1 to 4.

[0121] In Comparative Example 1, because the deionized water was added to the slurry in four equal parts, there were defects such as insufficient swelling of the binder, poor uniform wetting effect, and easy stratification and sedimentation of the slurry.

[0122] Comparative Example 2 suffers from defects such as insufficient powder wetting, inadequate kneading and shearing, easy damage to the colloidal network, and easy stratification and sedimentation of the slurry due to the addition of deionized water in two stages: the first time in the dry mixture after dry mixing and the second time in the slurry after kneading.

[0123] In Comparative Example 3, since deionized water was not added when the first mixture was formed, and its amount was added together when the second mixture was formed, there were defects such as insufficient wetting of the powder surface, poor conductive network of each component, and local agglomeration.

[0124] Comparative Example 4 had all the deionized water added when the third mixture was formed, and no viscosity adjustment was performed. Therefore, it had defects such as unstable slurry viscosity and poor uniformity of coated electrode surface density.

[0125] In summary, by adding deionized water in batches at different proportions, adding 1%~1.5% deionized water during the dry powder mixing stage (forming the first mixture) can effectively reduce powder flying during the dry mixing process, preventing some powder from flying and sticking to the walls, thus avoiding inconsistencies in the proportions of the various components. Adding 20%~25% deionized water during the kneading stage (forming the second mixture) ensures sufficient wetting of the powder surface, uniform bonding between the components, and avoids uneven dispersion of the binder and localized enrichment. Good kneading also improves the consistency of the finished slurry's viscosity and solids content. During the dilution stage (forming the third mixture), adding 66%~75% deionized water, while reserving 3%~7.5% for subsequent viscosity adjustment (forming the silicon anode slurry), avoids excessively low viscosity caused by adding all the solvent at once, and reserves some solvent for viscosity adjustment, further improving the consistency of the slurry.

[0126] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0127] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0128] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0129] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for kneading silicon anode slurry, characterized in that, Includes the following steps: A first mixture is obtained by mixing a silicon-based active material, a binder, a conductive agent, and a first portion of water. The first mixture is kneaded together with the second portion of water to obtain the second mixture; The second mixture is mixed with the third portion of water to obtain the third mixture; The third mixture is mixed with the fourth part of water to obtain a silicon anode slurry; The mass ratio of the first part of water, the second part of water, the third part of water, and the fourth part of water is (1~1.5):(20~25):(66~75):(3~7.5). In the first mixture, the mass percentage of water in the first part is 0.4% to 0.6%.

2. The method for kneading silicon anode slurry as described in claim 1, characterized in that, The solid content of the silicon anode slurry is 45%~48%.

3. The method for kneading silicon anode slurry as described in claim 1, characterized in that, The viscosity of the silicon anode slurry is 3000 mPa·s to 6000 mPa·s.

4. The method for kneading silicon anode slurry as described in claim 1, characterized in that, In the silicon-based active material, silicon accounts for 28% to 35% of the mass.

5. The method for kneading silicon anode slurry as described in claim 1, characterized in that, In the silicon anode slurry, the mass ratio of silicon-based active material, binder, and conductive agent is (94~96):(3~5):(0.5~1.5).

6. The method for kneading silicon anode slurry as described in claim 1, characterized in that, The process of mixing silicon-based active material, binder, conductive agent, and a first portion of water to obtain a first mixture includes: The mixing speed is 15 rpm to 30 rpm; and / or, The dispersion rate of the mixture is 10 m / s to 20 m / s; and / or, Mixing time is 20-30 minutes.

7. The method for kneading silicon anode slurry as described in claim 1, characterized in that, In the process of kneading the first mixture with the second portion of water to obtain the second mixture, the rotor and blades move in opposite directions to form a cyclonic shearing mixture, wherein: The rotor speed is 10 m / s to 15 m / s; and / or, The impeller stirring speed is 15 rpm to 25 rpm; and / or, The mixing time is 30 min to 45 min.

8. The method for kneading silicon anode slurry as described in claim 1, characterized in that, The third mixture, obtained by mixing the second mixture with the third portion of water, is mixed using a shear dispersion method, wherein: Shear rate greater than or equal to 18 m / s; and / or, Mixing time is 20-30 minutes.

9. The method for kneading silicon anode slurry as described in claim 1, characterized in that, If the binder in the silicon anode slurry obtained by mixing the third mixture with the fourth portion of water contains styrene-butadiene rubber, then: The mixing rate is 6 m / s to 8 m / s; and / or, The mixing time is 15 min to 30 min.

10. The method for kneading silicon anode slurry as described in claim 1, characterized in that, If the binder in the silicon anode slurry obtained by mixing the third mixture with the fourth portion of water does not contain styrene-butadiene rubber, then: The mixing rate is 15 m / s to 20 m / s; and / or, The mixing time is 15 min to 30 min.

11. The method for kneading silicon anode slurry as described in claim 1, characterized in that: The silicon-based active material includes at least one of silicon nanoparticles, silicon-carbon composite materials, and silicon suboxide; and / or, The adhesive comprises at least one of polyacrylic acid, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyimide; and / or, The conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, and graphene.

12. The method for kneading silicon anode slurry as described in claim 1, characterized in that, The total time for the kneading process is less than or equal to 180 minutes.

13. A silicon anode paste, characterized in that, It is prepared by the silicon anode slurry kneading method as described in any one of claims 1 to 12.

14. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer is coated with the silicon negative electrode slurry as described in claim 13.

15. A secondary battery, characterized in that, It includes a positive electrode, a separator, and a negative electrode as described in claim 14.

16. The secondary battery as described in claim 15, characterized in that, The battery's energy density is greater than or equal to 340Wh / kg.

17. The secondary battery as described in claim 15, characterized in that, The battery's 3C rate discharge capacity is greater than or equal to 85%.

18. The secondary battery as described in claim 15, characterized in that, The battery retains a capacity of 93% or more after 500 cycles at 25°C.

19. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 15 to 18.

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