Negative electrode slurry, method of preparing the same, and battery
Patent Information
- Application Number
- CN202611121713.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-27
- Publication Date
- 2026-09-04
AI Technical Summary
[0007]本申请的主要目的在于提供一种负极浆料及其制备方法和应用，以解决现有技术中的硫化物电解质与常用极性溶剂接触时反应剧烈，导致电解质活性降低，进而影响电池整体性能，以及硫化物体系中负极浆料中存在分散不均、稳定性不足等问题
[0039] This application first mixes a sulfide electrolyte, a conductive agent, a composite binder, and a first solvent system, and then ball-mills the mixture to obtain a conductive electrolyte solution. Next, a negative electrode active material and a second solvent system are added to the conductive electrolyte solution for slurry preparation to obtain a negative electrode slurry. In this application, a three-dimensional network structure is constructed using a composite binder. A compound solvent system consisting of a non-polar solvent and/or a low-polarity solvent is used as the first solvent system and the second solvent system, respectively. This results in a sulfide all-solid-state negative electrode slurry with high electrolyte activity, reduced interfacial side reactions, and uniform dispersion. Consequently, the negative electrode sheet prepared from this slurry exhibits good capacity retention in sulfide all-solid-state batteries.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This application relates to sulfide all-solid-state batteries, and more specifically, to a negative electrode slurry, its preparation method, and the battery. Background Technology
[0002] Solid-state lithium batteries are a new battery technology that uses a solid electrolyte to replace the liquid electrolyte in traditional lithium-ion batteries. In this technology, the solid electrolyte plays a crucial role in transporting lithium ions between the positive and negative electrodes, achieving efficient conversion and storage of electrochemical energy and chemical energy. Compared to traditional liquid electrolytes, solid-state electrolytes have significant advantages, including higher energy density, better safety, support for fast charging, and longer cycle life.
[0003] Currently, sulfide-based all-solid-state battery cathodes are mainly formed using dry or wet processes. However, compared to wet processes, dry processes have significant limitations, making large-scale mass production difficult and resulting in relatively thick films. Therefore, to accelerate the industrialization of sulfide-based all-solid-state batteries, wet processes have become an indispensable key technology for cathode film formation.
[0004] Compared to the traditional liquid lithium-ion batteries, which have developed mature and stable slurry mixing processes over a long period of time (such as dissolving PVDF binders with polar solvents such as NMP to achieve efficient dispersion of active materials, conductive agents and binders), the slurry mixing process of sulfide all-solid-state batteries faces new challenges. It requires the introduction of solid electrolytes to improve ion conductivity, and the traditional slurry mixing system that relies on polar solvents is no longer applicable.
[0005] Specifically, sulfide electrolytes (such as Li6PS5Cl) are chemically active and are prone to violent side reactions (such as sulfide decomposition and interface passivation) when in contact with commonly used polar solvents (such as NMP and water). This not only damages the ion conduction structure of the electrolyte itself, but also leads to the deterioration of the interfacial performance between the active material and the electrolyte, ultimately seriously affecting the overall performance of the battery (such as capacity decay and rate reduction).
[0006] In view of the above, this application is hereby submitted. Summary of the Invention
[0007] The main purpose of this application is to provide a negative electrode slurry, its preparation method and application, to solve the problems in the prior art where the reaction between sulfide electrolytes and commonly used polar solvents is violent, resulting in reduced electrolyte activity and thus affecting the overall performance of the battery, as well as the problems of uneven dispersion and insufficient stability in the negative electrode slurry in the sulfide system.
[0008] To achieve the above objectives, according to one aspect of this application, a method for preparing a negative electrode slurry is provided, the method comprising:
[0009] Step S1: The sulfide electrolyte, conductive agent, composite binder and first solvent system are mixed and ball-milled to obtain conductive electrolyte solution;
[0010] Step S2: Add the negative electrode active material and the second solvent system to the conductive electrolyte solution for slurry processing to obtain the negative electrode slurry;
[0011] The first solvent system and the second solvent system are each independently a compound solvent system of nonpolar solvent and / or low polar solvent.
[0012] Furthermore, the composite adhesive includes FKM, HNBR and POE-g-MA, and the mass ratio of the three is (2~4):(3~7):(1~3).
[0013] Furthermore, the first solvent system and the second solvent system are each independently a compound solvent system of the first organic solvent and the second organic solvent; wherein, the first organic solvent is selected from xylene, and the second organic solvent is selected from at least one of toluene, isoamyl isobutyrate, isobutyl isobutyrate, xylene, and n-heptane.
[0014] Furthermore, the volume ratio of the first organic solvent to the second organic solvent is (1~6):1.
[0015] Further, in step S1, the mass ratio of the sulfide electrolyte, the conductive agent, the composite binder and the first solvent system is (2~3):(0.1~0.5):(0.3~0.8):(5~10).
[0016] Furthermore, the conductive agent is selected from at least one of conductive carbon black, Ketjen black, carbon nanotubes, graphene, and acetylene black.
[0017] Furthermore, the conductive agent is a mixture of conductive carbon black and Ketjen black, and the mass ratio of the two is (1~5):1.
[0018] Further, step S1 includes: mixing the conductive agent, composite binder and first solvent system and performing a first-stage ball milling to obtain a first adhesive solution, and mixing the first adhesive solution with a sulfide electrolyte and performing a second-stage ball milling to obtain a conductive electrolyte adhesive solution.
[0019] Furthermore, the ball milling speed in the first stage is 300~500 rpm, and the ball milling time in the first stage is 30~90 min.
[0020] Furthermore, the ball milling speed in the second stage is 200~300 rpm, and the ball milling time in the second stage is 10~50 min.
[0021] Further, in step S2, the mass ratio of the conductive electrolyte solution, the negative electrode active material, and the second solvent system is (2~4):(4~6):(1~3).
[0022] Furthermore, the negative electrode active material is selected from at least one of nano-silicon, micron-silicon, porous silicon, silicon suboxide, porous carbon-coated silicon, and carbon nanotube composite silicon.
[0023] Further, step S2 includes:
[0024] Step S21: The conductive electrolyte solution is divided into a first conductive electrolyte solution, a second conductive electrolyte solution, and a third conductive electrolyte solution, and the mass ratio of the three is (25~35):(25~35):(30~50).
[0025] Step S22: The first conductive electrolyte solution is mixed with the negative electrode active material and granulated to obtain a granulated slurry.
[0026] Step S23: Mix the second conductive electrolyte solution with the granulation slurry and knead it to obtain a kneaded slurry.
[0027] Step S24: The third conductive electrolyte solution is mixed with the kneading slurry for dispersion treatment, and then mixed with the second solvent system for slurry treatment to obtain the negative electrode slurry.
[0028] Furthermore, in step S22, the solid content of the granulated slurry is 85~96wt%.
[0029] Furthermore, in step S23, the solid content of the kneaded slurry is 75~80wt%.
[0030] Furthermore, granulation, kneading, dispersion, and slurry preparation are all carried out in a dual planetary mixer.
[0031] Furthermore, the granulation process has a revolution speed of 30-40 rpm and a granulation time of 20-40 min.
[0032] Furthermore, the kneading process involves a revolution speed of 30-40 rpm and a kneading time of 20-40 minutes.
[0033] Furthermore, the orbital speed of the dispersion treatment is 30~40 rpm, the rotational speed is 2500~3500 rpm, and the dispersion treatment time is 80~100 min.
[0034] Furthermore, the revolution speed of the slurry mixing process is 30~40 rpm, the rotation speed is 3000~4000 rpm, and the slurry mixing time is 50~70 min.
[0035] Furthermore, the kneading process is carried out under vacuum conditions.
[0036] Furthermore, the vacuum degree of the kneading process is -80 to -99 kPa.
[0037] To achieve the above objectives, according to a second aspect of this application, a negative electrode slurry is provided, which is prepared according to the preparation method provided in the first aspect of this application. The negative electrode slurry has a solid content of 60-70 wt% and a viscosity of 2000-5000 mPa. . s.
[0038] According to a third aspect of this application, a battery is provided, the battery including a negative electrode sheet, the negative electrode sheet including a current collector and a negative electrode material layer attached to the surface of the current collector, the negative electrode material layer being prepared by a negative electrode slurry prepared by the preparation method provided in the first aspect of this application or by coating, drying and rolling a negative electrode slurry provided in the second aspect of this application.
[0039] This application first mixes a sulfide electrolyte, a conductive agent, a composite binder, and a first solvent system, and then ball-mills the mixture to obtain a conductive electrolyte solution. Next, a negative electrode active material and a second solvent system are added to the conductive electrolyte solution for slurry preparation to obtain a negative electrode slurry. In this application, a three-dimensional network structure is constructed using a composite binder. A compound solvent system consisting of a non-polar solvent and / or a low-polarity solvent is used as the first solvent system and the second solvent system, respectively. This results in a sulfide all-solid-state negative electrode slurry with high electrolyte activity, reduced interfacial side reactions, and uniform dispersion. Consequently, the negative electrode sheet prepared from this slurry exhibits good capacity retention in sulfide all-solid-state batteries. Detailed Implementation
[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.
[0041] As described in the background section of this application, existing technologies suffer from problems such as vigorous reactions between sulfide electrolytes and commonly used polar solvents, leading to reduced electrolyte activity and consequently affecting the overall battery performance, as well as uneven dispersion and insufficient stability in the negative electrode slurry within the sulfide system. To address these issues, this application provides a negative electrode slurry, its preparation method, and a battery.
[0042] In a first typical embodiment of this application, a method for preparing a negative electrode slurry is provided, comprising:
[0043] Step S1: The sulfide electrolyte, conductive agent, composite binder and first solvent system are mixed and ball-milled to obtain conductive electrolyte solution;
[0044] Step S2: Add the negative electrode active material and the second solvent system to the conductive electrolyte solution for slurry processing to obtain the negative electrode slurry;
[0045] The first solvent system and the second solvent system are each independently a compound solvent system of nonpolar solvent and / or low polar solvent.
[0046] This application first mixes a sulfide electrolyte, a conductive agent, a composite binder, and a first solvent system, and then ball-mills the mixture to obtain a conductive electrolyte solution. Next, a negative electrode active material and a second solvent system are added to the conductive electrolyte solution for slurry preparation to obtain a negative electrode slurry. By using a compound solvent system of non-polar solvents and / or low-polarity solvents as the first and second solvent systems, this application not only avoids violent reactions between the sulfide electrolyte and the solvent system that could lead to deterioration of interfacial properties, but also promotes the uniform and stable dispersion of the sulfide electrolyte in the solvent system. This results in a negative electrode sheet prepared from the negative electrode slurry exhibiting good capacity retention in sulfide all-solid-state batteries.
[0047] In some embodiments, the composite adhesive includes FKM (hexafluoropropylene-vinylidene fluoride copolymer, fluorine content approximately 66%, weight-average molecular weight 100,000-200,000 g / mol), HNBR (hydrogenated nitrile butadiene rubber, acrylonitrile content 18-36%, weight-average molecular weight 200,000-500,000 g / mol), and POE-g-MA (maleic anhydride-grafted polyolefin elastomer, maleic anhydride grafting rate 0.5-3%, weight-average molecular weight 100,000-150,000 g / mol), and the mass ratio of the three is (2-4):(3-7):(1-3). FKM (hexafluoropropylene-vinylidene fluoride copolymer) in the composite adhesive has good compatibility with non-polar solvents, HNBR (hydrogenated nitrile butadiene rubber) provides a rubber-like network, mechanical flexibility, and basic bond strength, and POE-g-MA (maleic anhydride-grafted polyolefin elastomer) acts as an interfacial compatibilizer, further enhancing the bonding effect of the composite adhesive. The synergistic effect of FKM (hexafluoropropylene-vinylidene fluoride copolymer), HNBR (hydrogenated nitrile butadiene rubber), and POE-g-MA (maleic anhydride-grafted polyolefin elastomer) in the composite binder helps to promote enhanced interfacial adhesion, comprehensively improving the density, uniform ductility, tear resistance, interfacial compatibility, and excellent electrochemical performance of the electrode. Specifically, the mass ratio of FKM, HNBR, and POE-g-MA is any value from 2:5:3, 2:6:2, 2:7:1, 3:4:3, 3:5:2, 3:6:1, 4:3:3, 4:5:1, or any range between two of these values.
[0048] The preparation method of the composite adhesive includes: dissolving HNBR (hydrogenated nitrile butadiene rubber, acrylonitrile content of 18-36%) in toluene to prepare a solution with a mass concentration of 8-12%, and stirring at room temperature for 2-4 hours until completely dissolved; dissolving FKM (hexafluoropropylene-vinylidene fluoride copolymer, fluorine content of 65-70%) in ethyl acetate to prepare a solution with a mass concentration of 5-8%, heating to 60℃ and stirring until clear; slowly adding the FKM-containing solution dropwise to the HNBR solution, and stirring continuously at 60℃ for 1 hour to obtain the final product. Add POE-g-MA (maleic anhydride-grafted polyolefin elastomer with a maleic anhydride grafting rate of 0.5-3%) to the blending liquid and stir at 50°C for 30 minutes until completely dissolved. By adding toluene or ethyl acetate, the mass ratio of toluene to ethyl acetate in the blending liquid is (80-90):(10-20) to obtain a composite adhesive. The solid content of the composite adhesive is 10-15%, and the mass ratio of FKM, HNBR and POE-g-MA is (2-4):(3-7):(1-3).
[0049] In some embodiments, the first solvent system and the second solvent system are each independently a compound solvent system of a first organic solvent and a second organic solvent, wherein the first organic solvent is selected from xylene, and the second organic solvent is selected from any one of toluene, isoamyl isobutyrate, isobutyl isobutyrate, xylene, and n-heptane. Using a compound solvent system to form the first solvent system and the second solvent system respectively facilitates further adjustment of the solvent evaporation rate and avoids coating defects caused by excessively high or low boiling points of a single solvent. During the drying process of the negative electrode slurry, the staged evaporation of the compound solvent system helps to form a uniform negative electrode active material coating, while also improving the uniform dispersion of each component in the slurry and reducing agglomeration.
[0050] To promote uniform dispersion of the components in the negative electrode slurry, in some embodiments, the volume ratio of the first organic solvent to the second organic solvent in the first solvent system and the second solvent system is (1~6):1, respectively. Specifically, the volume ratio of the first organic solvent to the second organic solvent is any value from 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, or any value between two of them.
[0051] In some embodiments, the mass ratio of the sulfide electrolyte, conductive agent, composite binder, and first solvent system is (2~3):(0.1~0.5):(0.3~0.8):(5~10), which not only improves the dispersion uniformity and stability of each component in the negative electrode slurry, but also facilitates the synergistic construction of the sulfide electrolyte and conductive network in the first solvent system. It should be noted that the mass of the composite binder is based on the solid mass of the composite binder.
[0052] In some specific embodiments, the sulfide electrolyte is a commonly used electrolyte in the art, including but not limited to Li6PS5Cl and Li7P3S. 11 Li6PS5Br, Li 10 GeP2S 12 Any one or more mixtures of Li2S-P2O5-P2S5.
[0053] In some specific embodiments, the conductive agent is a commonly used conductive agent in the art, including but not limited to any one or more mixtures of conductive carbon black, Ketjen black, carbon nanotubes, graphene, and acetylene black.
[0054] In some preferred embodiments, the conductive agent is a mixture of conductive carbon black and Ketjen black, with a mass ratio of (1~5):1. The high specific surface area of the conductive carbon black and the dendritic structure of Ketjen black can form a high-density, continuous, and stable electron conduction pathway, significantly improving the electron conductivity of the conductive electrolyte solution, while avoiding the problems of uneven dispersion or agglomeration caused by a single conductive agent due to its uniform particle size or morphology. Specifically, the mass ratio of conductive carbon black to Ketjen black is any value from 1:1, 2:1, 3:1, 4:1, 5:1, or any range between the two.
[0055] In some embodiments, step S1 includes a first-stage ball milling and a second-stage ball milling. In some specific embodiments, step S1 includes: mixing the conductive agent, composite binder, and a first solvent system for a first-stage ball milling to obtain a first adhesive solution; mixing the first adhesive solution with a sulfide electrolyte for a second-stage ball milling to obtain a conductive electrolyte adhesive solution. The conductive agent and composite binder are first ball-milled in the absence of a sulfide electrolyte to form a stable and uniform conductive network adhesive solution (first adhesive solution), which is more conducive to avoiding particle damage or interface passivation caused by local stress concentration of the sulfide electrolyte under high shear force. Subsequently, the first adhesive solution is mixed with the sulfide electrolyte for a second-stage ball milling, so that the electrolyte particles are mildly and uniformly coated and dispersed under the protection of the conductive network, significantly improving the structural stability and uniformity of the conductive electrolyte adhesive solution.
[0056] To further improve the efficiency of the first-stage ball milling and ensure that the conductive agent is fully wetted in the first solvent system to form a continuous conductive path, in some embodiments, the ball milling speed in the first stage is 300-500 rpm, and the ball milling time in the first stage is 30-90 min. Specifically, the ball milling speed in the first stage is any value or a range between 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 420 rpm, 450 rpm, and 500 rpm; the ball milling time in the first stage is any value or a range between 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, and 90 min.
[0057] To further improve the interfacial compatibility and electrochemical stability of the negative electrode slurry, in some embodiments, the ball milling speed in the second stage is 200-300 rpm, and the ball milling time in the second stage is 10-50 min. Specifically, the ball milling speed in the second stage is any value or a range between 200 rpm, 210 rpm, 220 rpm, 230 rpm, 250 rpm, 270 rpm, 280 rpm, and 300 rpm; the ball milling time in the second stage is any value or a range between 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, and 50 min.
[0058] In some embodiments, the mass ratio of the conductive electrolyte solution, the negative electrode active material, and the second solvent system is (2~4):(4~6):(1~3). The synergistic effect of the conductive electrolyte solution, the negative electrode active material, and the second solvent system can further regulate the rheological behavior and solid content distribution of the negative electrode slurry during the mixing process. This further avoids problems such as agglomeration and sedimentation caused by an excessively high proportion of negative electrode active material or excessive viscosity and uneven coating caused by insufficient solvent. As a result, the negative electrode slurry still has good dispersion stability in the environment of a compound solvent system with non-polar solvents and / or low-polarity solvents. Specifically, the mass ratio of the conductive electrolyte solution, the negative electrode active material, and the second solvent system is any value or a range between any two of the following: 2:4:1, 2:5:2, 2:6:3, 3:4:1, 3:5:2, 3:6:3, 4:4:1, 4:5:2, and 4:6:3.
[0059] To further enhance the high energy density of the negative electrode active material in the negative electrode slurry and ensure good compatibility and long-term stability with the sulfide electrolyte, in some specific embodiments, the negative electrode active material is selected from any one or more mixtures of nano-silicon, micron-silicon, porous silicon, silicon suboxide, porous carbon-coated silicon, and carbon nanotube composite silicon.
[0060] In some embodiments, step S2 includes: step S21, dividing the conductive electrolyte solution into a first conductive electrolyte solution, a second conductive electrolyte solution, and a third conductive electrolyte solution, wherein the mass ratio of the three is (25~35):(25~35):(30~50); step S22, mixing the first conductive electrolyte solution with the negative electrode active material and performing granulation treatment to obtain a granulated slurry; step S23, mixing the second conductive electrolyte solution with the granulated slurry and performing kneading treatment to obtain a kneaded slurry; step S24, mixing the third conductive electrolyte solution with the kneaded slurry and performing dispersion treatment, and then mixing it with the second solvent system for slurry mixing treatment to obtain a sulfide all-solid negative electrode slurry.
[0061] The conductive electrolyte solution is divided into three parts. The first conductive electrolyte solution is mixed with the negative electrode active material and granulated to form a granulated slurry. The second conductive electrolyte solution is mixed with the granulated slurry and kneaded to form a kneaded slurry. The third conductive electrolyte solution is mixed with the kneaded slurry and dispersed. Finally, the mixture is combined with a second solvent system to obtain the negative electrode slurry. This series of processes further enables the sulfide electrolyte and the negative electrode active material to gradually achieve interfacial wetting. Specifically, the first conductive electrolyte solution initially coats the negative electrode active material particles during the granulation stage, further improving the surface wettability of the negative electrode active material and inhibiting agglomeration. The second conductive electrolyte solution deeply fills the gaps between particles during the kneading stage, further removing air bubbles and strengthening the contact and adhesion between the sulfide electrolyte and the negative electrode active material. The third conductive electrolyte solution fully dissociates the remaining agglomerates during the dispersion stage, further constructing a continuous and uniform conductive transport network. Then, it is further mixed with the second solvent system to make the slurry more uniform, thereby giving the slurry better stability. Therefore, mixing the conductive electrolyte solution with the negative electrode active material in stages can further reduce the fineness of the negative electrode slurry, reduce coating defects, and enhance the interfacial bonding strength, thereby reducing problems such as uneven dispersion, residual air bubbles, and interfacial debonding. This provides a better preparation path for preparing sulfide all-solid-state batteries with better consistency and stability.
[0062] In some specific embodiments, the mass ratio of the first conductive electrolyte solution, the second conductive electrolyte solution, and the third conductive electrolyte solution is any value among 25:25:50, 30:30:40, and 35:35:30, or any range between two of them.
[0063] To further enhance the encapsulation of the negative electrode active material in the granulated slurry obtained from the granulation process by the sulfide electrolyte, in some embodiments, the solid content of the granulated slurry is 85-96 wt%. Specifically, the solid content of the granulated slurry is any value or a range between any two of 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, and 96 wt%.
[0064] To further facilitate better filling of the particle pores by the second conductive electrolyte solution during the kneading process, in some embodiments, the solid content of the kneading slurry is 75-80 wt%. Specifically, the solid content of the kneading slurry is any value from 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, or any value between two of these.
[0065] In some embodiments, granulation, kneading, dispersion and slurry mixing are all performed in a dual planetary mixer, which can further disperse the slurry at high linear speed and achieve better mixing effect.
[0066] To further improve the uniformity of the granulated slurry, in some embodiments, the granulation process has a revolution speed of 30-40 rpm and a granulation time of 20-40 min. Specifically, the granulation process revolution speed is any value or a range between 30 rpm, 31 rpm, 32 rpm, 33 rpm, 34 rpm, 35 rpm, 36 rpm, 37 rpm, 38 rpm, 39 rpm, and 40 rpm; the granulation time is any value or a range between 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 35 min, and 40 min.
[0067] To further improve the elimination of air bubbles during the kneading process, in some embodiments, the kneading speed is 30-40 rpm, and the kneading time is 20-40 min. Specifically, the kneading speed is any value or a range between 30 rpm, 31 rpm, 32 rpm, 33 rpm, 34 rpm, 35 rpm, 36 rpm, 37 rpm, 38 rpm, 39 rpm, and 40 rpm; the kneading time is any value or a range between 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 35 min, and 40 min.
[0068] In order to further improve the dispersion of the conductive electrolyte solution in the kneaded slurry, in some embodiments, the revolution speed of the dispersion treatment is 30~40 rpm, the rotation speed is 2500~3500 rpm, and the dispersion time is 80~100 min. Specifically, the orbital speed of the distributed processing is any value or a range between any two of the following: 30 rpm, 31 rpm, 32 rpm, 33 rpm, 34 rpm, 35 rpm, 36 rpm, 37 rpm, 38 rpm, 39 rpm, and 40 rpm; the rotational speed of the distributed processing is any value or a range between any two of the following: 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2900 rpm, 3000 rpm, 3100 rpm, 3200 rpm, 3300 rpm, 3400 rpm, and 3500 rpm; and the time of the distributed processing is any value or a range between any two of the following: 80 min, 82 min, 84 min, 86 min, 88 min, 90 min, 92 min, 94 min, 96 min, 98 min, and 100 min.
[0069] To further improve the efficiency of the mixing process between the dispersion slurry and the second solvent system, in some embodiments, the revolution speed of the mixing process is 30-40 rpm, the rotation speed is 3000-4000 rpm, and the mixing time is 50-70 min. Specifically, the revolution speed of the mixing process is any value or a range between any two of 30 rpm, 31 rpm, 32 rpm, 33 rpm, 34 rpm, 35 rpm, 36 rpm, 37 rpm, 38 rpm, 39 rpm, and 40 rpm; the rotation speed is any value or a range between any two of 3000 rpm, 3100 rpm, 3200 rpm, 3300 rpm, 3400 rpm, 3500 rpm, 3600 rpm, 3700 rpm, 3800 rpm, 3900 rpm, and 4000 rpm.
[0070] To further improve the mixing effect between the second conductive electrolyte solution and the granulation slurry, and to accelerate the replacement of air and solvent on the surfaces of the second conductive electrolyte solution and the granulation slurry, in some preferred embodiments, the kneading process is carried out under vacuum conditions, preferably with a vacuum degree of -80 to -99 kPa.
[0071] In a second typical embodiment of this application, a negative electrode slurry is provided, which is prepared according to the preparation method provided in the first typical embodiment of this application. The negative electrode slurry has a solid content of 60-70 wt% and a viscosity of 2000-5000 mPa. .Specifically, the solid content of the negative electrode slurry is any value or a range between 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, and 70wt%; the viscosity is 2000 mPa. . s, 2300mPa . s, 2600mPa . s, 2900mPa . s, 3000mPa . s, 3300mPa . s, 3500mPa . s, 3800mPa . s, 4000mPa . s, 4500mPa . s, 5000mPa . Any value in s or any range of values between the two.
[0072] In this application, the negative electrode slurry is prepared by first ball milling a mixture of sulfide electrolyte, conductive agent, composite binder, and a first solvent system to obtain a conductive electrolyte solution, and then adding the negative electrode active material and a second solvent system to the conductive electrolyte solution for slurry preparation. By using a compound solvent system of non-polar solvent and / or low-polarity solvent as the first and second solvent systems, this application not only avoids violent reactions between the sulfide electrolyte and the solvent system that could lead to deterioration of interfacial performance, but also promotes the uniform and stable dispersion of the sulfide electrolyte in the solvent system. This results in the negative electrode sheet prepared from the negative electrode slurry exhibiting good capacity retention in sulfide all-solid-state batteries.
[0073] In a third typical embodiment of this application, a battery is provided, which includes a negative electrode sheet. The negative electrode sheet includes a current collector and a negative electrode material layer attached to the surface of the current collector. The negative electrode material layer is prepared by coating, drying and rolling a negative electrode slurry prepared by the preparation method provided in the first typical embodiment or a negative electrode slurry provided in the second typical embodiment.
[0074] This application also provides a battery in which the negative electrode sheet is prepared by coating, drying and rolling a negative electrode slurry. The negative electrode slurry uses a compound solvent system of non-polar solvents and / or low-polar solvents as the solvent system. Through the synergistic interaction of the specific solvent system, negative electrode active material, composite binder and sulfide electrolyte, the sulfide electrolyte, conductive agent and negative electrode active material are ensured to achieve nanoscale uniform dispersion under high solid content conditions, forming a stable negative electrode slurry. The resulting negative electrode active material layer has a smooth surface, uniform active material loading and tight interfacial bonding, significantly reducing coating defect rate and internal resistance fluctuation. During battery cycling, this structure effectively alleviates stress accumulation caused by negative electrode volume expansion, inhibits electrolyte interface passivation and conductive network breakage, thereby extending battery cycle life. It is also compatible with dry or wet continuous production processes, providing a structurally reliable and performance-stable negative electrode slurry for high-yield and large-scale manufacturing of sulfide all-solid-state batteries.
[0075] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.
[0076] Example 1
[0077] This embodiment provides a negative electrode slurry, which includes the following steps:
[0078] (1) Dissolve HNBR (hydrogenated nitrile butadiene rubber) in toluene to prepare a 10% mass concentration solution and stir at room temperature for 3.5 h until completely dissolved; dissolve FKM (hexafluoropropylene-vinylidene fluoride copolymer) in ethyl acetate to prepare a 7% mass concentration solution, heat to 60°C and stir until clear, slowly add the FKM-containing solution to the HNBR solution, and continue stirring at 60°C for 1 h to obtain a blend, add POE-g-MA (maleic anhydride grafted polyolefin elastomer) to the blend, and stir at 50°C for 30 min until completely dissolved, and add toluene or ethyl acetate to make the mass ratio of toluene to ethyl acetate in the blend 85:15 to obtain a composite adhesive, wherein the solid content of the composite adhesive is 12% and the mass ratio of FKM, HNBR and POE-g-MA is 3:5:2.
[0079] (2) Conductive carbon black and Ketjen black are mixed in a mass ratio of 3:1 to obtain a conductive agent mixture. Xylene and toluene are mixed in a volume ratio of 4:1 to obtain a first solvent system. The preparation method of the second solvent system is the same as that of the first solvent system.
[0080] (3) First, the conductive agent mixture, composite binder and first solvent system are subjected to a first-stage ball milling to obtain a first adhesive solution. Then, the first adhesive solution is subjected to a second-stage ball milling with sulfide electrolyte (Li6PS5Cl) to obtain a conductive electrolyte adhesive solution. The mass ratio of Li6PS5Cl, conductive agent mixture, composite binder and first solvent system is 2.2:0.3:0.5:7; the ball milling speed in the first stage is 400 rpm and the ball milling time in the first stage is 60 min; the ball milling speed in the second stage is 250 rpm and the ball milling time in the second stage is 30 min.
[0081] (4) The conductive electrolyte solution is divided into a first conductive electrolyte solution, a second conductive electrolyte solution, and a third conductive electrolyte solution according to a mass ratio of 30:30:40. The first conductive electrolyte solution and the negative electrode active material were added to a double planetary stirrer and granulated at a revolution speed of 35 rpm for 30 min to obtain a granulated slurry with a solid content of 90 wt%. The second conductive electrolyte solution was added to the double planetary stirrer and kneaded with the granulated slurry at a revolution speed of 35 rpm for 30 min to obtain a kneaded slurry with a solid content of 78 wt% and a vacuum degree of -90 kPa. The third conductive electrolyte solution was added to the double planetary stirrer and mixed with the kneaded slurry for dispersion at a revolution speed of 35 rpm and a rotation speed of 3000 rpm for 90 min. Then, it was mixed with the second solvent system and slurryed at a revolution speed of 35 rpm and a rotation speed of 3500 rpm for 60 min to obtain the negative electrode slurry.
[0082] Example 2
[0083] The difference between this embodiment and embodiment 1 is that the mass ratio of FKM, HNBR and POE-g-MA in step (1) is 2:7:1.
[0084] Example 3
[0085] The difference between this embodiment and embodiment 1 is that the mass ratio of FKM, HNBR and POE-g-MA in step (1) is 4:3:3.
[0086] Example 4
[0087] The difference between this embodiment and embodiment 1 is that the volume ratio of xylene and toluene in step (2) is adjusted to 1:1.
[0088] Example 5
[0089] The difference between this embodiment and embodiment 1 is that the volume ratio of xylene and toluene in step (2) is adjusted to 6:1.
[0090] Example 6
[0091] The difference between this embodiment and embodiment 1 is that step (2) is adjusted to make the first solvent system a mixed solvent of xylene and isoamyl isobutyrate, and the volume ratio of the two is 5:1.
[0092] Example 7
[0093] The difference between this embodiment and embodiment 1 is that the volume ratio of xylene and toluene in step (2) is adjusted to 0.3:1.
[0094] Example 8
[0095] The difference between this embodiment and embodiment 1 is that the volume ratio of xylene and toluene in step (2) is adjusted to 8:1.
[0096] Example 9
[0097] The difference between this embodiment and embodiment 1 is that the mass ratio of Li6PS5Cl, conductive mixture, composite binder and mixed solvent in step (3) is adjusted to 2:0.1:0.3:5.
[0098] Example 10
[0099] The difference between this embodiment and embodiment 1 is that the mass ratio of Li6PS5Cl, conductive mixture, composite binder and mixed solvent in step (3) is adjusted to 3:0.5:0.8:10.
[0100] Example 11
[0101] The difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of the first conductive electrolyte solution, the second conductive electrolyte solution and the third conductive electrolyte solution is adjusted to 25:25:50.
[0102] Example 12
[0103] The difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of the first conductive electrolyte solution, the second conductive electrolyte solution and the third conductive electrolyte solution is adjusted to 35:35:30.
[0104] Example 13
[0105] The difference between this embodiment and embodiment 1 is that in step (4), the conductive electrolyte solution is not divided into portions, but is directly mixed with the negative electrode active material and the second solvent system to obtain the negative electrode slurry.
[0106] Example 14
[0107] The difference between this embodiment and embodiment 1 is that the kneading process is not performed in step (4).
[0108] Example 15
[0109] The difference between this embodiment and embodiment 1 is that the rotation speed of the dispersion process in step (4) is adjusted to 1500 rpm.
[0110] Example 16
[0111] The difference between this embodiment and embodiment 1 is that the kneading process in step (4) is carried out under normal pressure.
[0112] Example 17
[0113] The difference between this embodiment and embodiment 1 is that the second solvent system in the slurry treatment in step (4) is added in two parts, with the first addition being 75% of the total volume and the second addition being 25% of the total volume.
[0114] Example 18
[0115] The difference between this embodiment and embodiment 1 is that the mass ratio of FKM, HNBR and POE-g-MA in step (1) is 1:7:2.
[0116] Example 19
[0117] The difference between this embodiment and embodiment 1 is that the mass ratio of FKM, HNBR and POE-g-MA in step (1) is 3:2:5.
[0118] Comparative Example 1
[0119] The difference between this comparative example and Example 1 is that the composite adhesive in step (1) is polyvinylidene fluoride.
[0120] Comparative Example 2
[0121] The difference between this comparative example and Example 1 is that the first solvent system in step (2) is adjusted to be N-methylpyrrolidone.
[0122] Comparative Example 3
[0123] The difference between this comparative example and Example 1 is that the second solvent system in step (4) is adjusted to be N-methylpyrrolidone.
[0124] Comparative Example 4
[0125] The difference between this comparative example and Example 1 is that in step (2), the first solvent system is adjusted to be a mixture of N-methylpyrrolidone and toluene, and the volume ratio of the two is 4:1.
[0126] Comparative Example 5
[0127] The difference between this comparative example and Example 1 is that in step (4), the second solvent system is adjusted to be a mixture of N-methylpyrrolidone and toluene, and the volume ratio of the two is 4:1.
[0128] Experimental Example 1
[0129] The negative electrode slurries prepared in the above embodiments and comparative examples were tested for solid content, viscosity, and fineness.
[0130] The test method for the solid content of the slurry is as follows: take a certain amount of slurry, dry it to constant weight, and calculate the solid content by the ratio of the mass of solids after drying to the mass of slurry before drying.
[0131] The viscosity test method is as follows: at a temperature of 25℃, using an RV3# rotor at a speed of 12 rpm, with a torque control range of 30~90% (optimal 30~75%), the viscosity value of the slurry is measured using a rotational viscometer.
[0132] The fineness test method is as follows: using a scraper fineness gauge, scrape the sample under specified conditions and read the scale value when the particles first appear stripes.
[0133] The test results are shown in Table 1.
[0134] Table 1
[0135]
[0136] Experimental Example 2
[0137] The negative electrode slurry prepared in the above embodiments and comparative examples is coated, dried and rolled to prepare a negative electrode material layer. The negative electrode material layer and the sulfide electrolyte membrane are transferred to the negative electrode sheet by roll transfer. Then, it is assembled with the ternary positive electrode sheet into a soft pack to obtain a sulfide all-solid-state soft pack battery. The sulfide all-solid-state battery is assembled and its performance is tested.
[0138] The test method for coating defect rate is as follows: visually inspect the samples under a standard light source, record the defect type, quantity and size, and calculate the defect rate according to the proportion of defective samples to the total number of samples inspected or the proportion of the total defect area to the total area inspected.
[0139] The test method for cycle capacity retention rate is as follows: Under constant conditions, repeatedly charge and discharge, record the discharge capacity of each cycle, compare it with the initial capacity to calculate the retention rate, adopt the rate charge and discharge step, set the charge and discharge step to 0.33C charge and discharge, set 0.33C constant current charging to 4.25V and switch to constant voltage charging, set the cutoff current to 0.05C, let stand for 10min, discharge at 0.33C, and set the cutoff voltage to 2.5V.
[0140] The test results are shown in Table 2.
[0141] Table 2
[0142]
[0143] Comparing Examples 1-19 with Comparative Examples 1-5, it can be seen that the negative electrode slurry prepared in Examples 1-19 constructs a three-dimensional network structure through a composite binder. A compound solvent system of non-polar solvent and / or low-polar solvent is used as the first solvent system and the second solvent system, respectively. This results in a sulfide all-solid-state negative electrode slurry with high electrolyte activity, reduced interfacial side reactions, and uniform dispersion. Consequently, the negative electrode sheet prepared from the negative electrode slurry has good capacity retention in sulfide all-solid-state batteries. In Comparative Example 1, the negative electrode slurry prepared using conventional polyvinylidene fluoride as a binder exhibited poor dispersibility, a high coating defect rate, and poor capacity retention after 100 cycles. In Comparative Examples 2-3, the use of highly polar solvents easily led to side reactions and poor dispersibility of the sulfide electrolyte in the solvent, resulting in a high coating defect rate and low capacity retention of the sulfide all-solid-state battery. In Comparative Examples 4-5, the use of a mixture of highly polar and low polar solvents as the solvent system also easily led to side reactions and poor dispersibility of the sulfide electrolyte in the solvent, resulting in a high coating defect rate and low capacity retention of the sulfide all-solid-state battery.
[0144] As can be seen from the comparison between Examples 1-6, Examples 9-12, Examples 17 and Examples 7-8, the reasonable mixing ratio of the first organic solvent and the second organic solvent in the first solvent system and the second solvent system in Examples 1-6, Examples 9-12 and Examples 17 is beneficial to the preparation of a negative electrode slurry with high electrolyte activity, fewer interfacial side reactions and uniform dispersion, thereby enabling the negative electrode sheet prepared from the negative electrode slurry to have good capacity retention in sulfide all-solid-state batteries.
[0145] As can be seen from the comparison between Examples 1-6, Examples 9-12, Examples 17 and Examples 13, the negative electrode slurry prepared in Examples 1-6, Examples 9-12 and Examples 17 adopts the method of dividing the conductive electrolyte solution into portions, which can further reduce the fineness of the negative electrode slurry, reduce coating defects, and enhance the interfacial bonding strength. This reduces problems such as uneven dispersion, residual bubbles and interfacial debonding, and provides a better preparation path with better consistency and stability for the preparation of sulfide all-solid-state batteries.
[0146] Compared with Examples 1-6, 9-12, 17 and 14, it can be seen that the kneading process used in Examples 1-6, 9-12 and 17 can further eliminate air bubbles, enhance the interfacial bonding strength, and obtain a more uniform and stable negative slurry. As a result, the negative electrode sheet prepared from the negative electrode slurry has a lower coating defect rate and a better capacity retention rate in sulfide all-solid-state batteries.
[0147] Compared with Examples 1-6, 9-12, 17 and 15, it can be seen that the rotation speed of the negative electrode slurry prepared in Examples 1-6, 9-12 and 17 can further disperse the conductive electrolyte solution in the kneaded slurry, thus preparing a sulfide all-solid-state negative electrode slurry with high electrolyte activity, reduced interfacial side reactions and uniform dispersion. As a result, the negative electrode sheet prepared from the negative electrode slurry has a lower coating defect rate and a good capacity retention rate in sulfide all-solid-state batteries.
[0148] Compared with Examples 1-6, 9-12, 17 and 16, it can be seen that the kneading process performed under vacuum conditions in Examples 1-6, 9-12 and 17 can further improve the mixing effect of the second conductive electrolyte solution and the granulation slurry, accelerate the replacement of air and solvent on the surface of the second conductive electrolyte solution and the granulation slurry, and thus enable the negative electrode sheet prepared by the negative electrode slurry to have a lower coating defect rate and a good capacity retention rate in sulfide all-solid-state batteries.
[0149] As can be seen from the comparison of Examples 1-6, 9-12, 17 and 18-19, the reasonable mass ratio of FKM, HNBR and POE-g-MA in the composite binder used in Examples 1-6, 9-12 and 17 can help promote the synergistic effect of enhanced interfacial adhesion, comprehensively improve the density, uniform ductility, tear resistance, interfacial compatibility and excellent electrochemical performance of the electrode, and thus enable the negative electrode prepared by the negative electrode slurry to have a lower coating defect rate and good capacity retention in sulfide all-solid-state batteries.
[0150] As can be seen from the above description, the embodiments of this application achieve the following technical effects:
[0151] This application first mixes a sulfide electrolyte, a conductive agent, a composite binder, and a first solvent system, and then ball-mills the mixture to obtain a conductive electrolyte solution. Next, a negative electrode active material and a second solvent system are added to the conductive electrolyte solution for slurry preparation to obtain a negative electrode slurry. In this application, a three-dimensional network structure is constructed using a composite binder. A compound solvent system consisting of a non-polar solvent and / or a low-polarity solvent is used as the first solvent system and the second solvent system, respectively. This results in a sulfide all-solid-state negative electrode slurry with high electrolyte activity, reduced interfacial side reactions, and uniform dispersion. Consequently, the negative electrode sheet prepared from this slurry exhibits good capacity retention in sulfide all-solid-state batteries.
[0152] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for preparing a negative electrode slurry, characterized in that, The preparation method includes: Step S1: The sulfide electrolyte, conductive agent, composite binder and first solvent system are mixed and ball-milled to obtain conductive electrolyte solution; Step S2: Add the negative electrode active material and the second solvent system to the conductive electrolyte solution for slurry processing to obtain the negative electrode slurry; Wherein, the first solvent system and the second solvent system are each independently a compound solvent system of nonpolar solvent and / or low polar solvent.
2. The preparation method according to claim 1, characterized in that, In step S1, the composite adhesive includes FKM, HNBR and POE-g-MA, and the mass ratio of the three is (2~4):(3~7):(1~3).
3. The preparation method according to claim 1, characterized in that, The first solvent system and the second solvent system are each independently a compound solvent system of a first organic solvent and a second organic solvent; wherein, the first organic solvent is selected from xylene, and the second organic solvent is selected from at least one of toluene, isoamyl isobutyrate, isobutyl isobutyrate, xylene, and n-heptane; Preferably, the volume ratio of the first organic solvent to the second organic solvent is (1~6):
1.
4. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the sulfide electrolyte, the conductive agent, the composite binder, and the first solvent system is (2~3):(0.1~0.5):(0.3~0.8):(5~10). Preferably, the conductive agent is selected from at least one of conductive carbon black, Ketjen black, carbon nanotubes, graphene, and acetylene black; Preferably, the conductive agent is a mixture of conductive carbon black and Ketjen black, and the mass ratio of the two is (1~5):
1.
5. The preparation method according to any one of claims 1 to 4, characterized in that, Step S1 includes: mixing the conductive agent, the composite binder and the first solvent system and performing a first-stage ball milling to obtain a first adhesive solution; mixing the first adhesive solution with the sulfide electrolyte and performing a second-stage ball milling to obtain the conductive electrolyte adhesive solution. Preferably, the ball milling speed in the first stage is 300~500 rpm, and the ball milling time in the first stage is 30~90 min; Preferably, the ball milling speed in the second stage is 200~300 rpm, and the ball milling time in the second stage is 10~50 min.
6. The preparation method according to any one of claims 1 to 5, characterized in that, In step S2, the mass ratio of the conductive electrolyte solution, the negative electrode active material, and the second solvent system is (2~4):(4~6):(1~3). Preferably, the negative electrode active material is selected from at least one of nano-silicon, micron-silicon, porous silicon, silicon suboxide, porous carbon-coated silicon, and carbon nanotube composite silicon.
7. The preparation method according to claim 6, characterized in that, Step S2 includes: Step S21: The conductive electrolyte solution is divided into a first conductive electrolyte solution, a second conductive electrolyte solution, and a third conductive electrolyte solution, and the mass ratio of the three is (25~35):(25~35):(30~50). Step S22: The first conductive electrolyte solution is mixed with the negative electrode active material and granulated to obtain a granulated slurry. Step S23: Mix the second conductive electrolyte solution with the granulation slurry and knead it to obtain a kneaded slurry; Step S24: The third conductive electrolyte solution is mixed with the kneaded slurry for dispersion treatment, and then mixed with the second solvent system for slurry treatment to obtain the negative electrode slurry; Preferably, in step S22, the solid content of the granulated slurry is 85-96 wt%. Preferably, in step S23, the solid content of the kneaded slurry is 75~80wt%.
8. The preparation method according to claim 7, characterized in that, The granulation process, the kneading process, the dispersion process, and the slurry mixing process are all carried out in a dual planetary mixer; Preferably, the granulation process has a revolution speed of 30-40 rpm and a granulation time of 20-40 min; Preferably, the kneading process has a revolution speed of 30-40 rpm and a kneading process time of 20-40 min; Preferably, the revolution speed of the dispersion process is 30-40 rpm, the rotation speed is 2500-3500 rpm, and the dispersion process takes 80-100 minutes. Preferably, the revolution speed of the slurry mixing process is 30~40 rpm, the rotation speed is 3000~4000 rpm, and the slurry mixing time is 50~70 min; Preferably, the kneading process is carried out under vacuum conditions, and more preferably, the vacuum degree of the kneading process is -80~-99kPa.
9. A negative electrode slurry, characterized in that, The negative electrode slurry is prepared by the method according to any one of claims 1 to 8, wherein the solid content of the negative electrode slurry is 60-70 wt% and the viscosity is 2000-5000 mPa. . s.
10. A battery, characterized in that, The battery includes a negative electrode sheet, which includes a current collector and a negative electrode material layer attached to the surface of the current collector. The negative electrode material layer is prepared by coating, drying and rolling a negative electrode slurry prepared by any one of the preparation methods of claims 1 to 8 or a negative electrode slurry as described in claim 9.