Conductive network construction process method of solid-state battery

Abstract

The invention discloses a conductive network construction process method of a solid-state battery. The conductive network construction process method specifically comprises the following steps: S1, selecting and compounding a conductive agent; s2, preparing electrode slurry; the invention relates to the technical field of solid-state batteries. According to the conductive network construction process method of the solid-state battery, a continuous three-dimensional conductive network is formed in an electrode by optimizing conductive agent type compounding and a conductive network forming process, so that the overall conductivity of the electrode is greatly improved, the transmission path of electrons in the electrode is smoother, and the internal resistance of the electrode is reduced; due to the improvement of the conductivity of the electrode, the polarization phenomenon of the solid-state battery in the large-current charging and discharging process is obviously improved, and the internal resistance of the battery is reduced, so that the solid-state battery can bear larger charging and discharging current, and the rate capability of the battery is improved; the continuous and stable conductive network can effectively relieve the volume change and stress concentration of the electrode in the charging and discharging process.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and specifically to a process method for constructing a conductive network of a solid-state battery. Background Art

[0002] A solid-state battery is a battery that uses solid electrodes and a solid electrolyte. The negative electrode material of a solid-state battery can be a composite negative electrode of nanosilicon and graphite, the positive electrode can be lithium manganate, a lithium-rich manganese-based material, or a lithium-free positive electrode material, and the electrolyte is a solid electrolyte. The energy density can reach 300-450 watt-hours per kilogram. A solid-state battery uses a solid electrolyte to replace the electrolyte and separator of a traditional lithium-ion battery, making it safer, with a higher energy density and stronger cycle performance, becoming the main research and development direction for the next generation of power batteries. Solid electrolytes can be roughly divided into three categories: inorganic electrolytes, solid polymer electrolytes, and composite electrolytes. Due to the high power-to-weight ratio of solid-state batteries, they are ideal batteries for electric vehicles. The development of traditional solid-state batteries mainly follows four technical routes: polymer solid-state batteries, thin-film solid-state batteries, sulfide solid-state batteries, and oxide solid-state batteries. In solid-state ionics, a solid-state battery is a battery that uses solid electrodes and a solid electrolyte solution. Solid-state batteries generally have a lower power density and a higher energy density. Due to the high power-to-weight ratio of solid-state batteries, they are ideal batteries for electric vehicles.

[0003] In existing solid-state battery electrodes, the selection and combination of conductive agents are often not reasonable enough, resulting in difficulty in forming a continuous and stable conductive network inside the electrode. This hinders the transmission of electrons in the electrode, reducing the overall conductivity of the electrode. During high-rate charge and discharge processes, poor electron transmission will cause an increase in the internal resistance of the battery, generating more heat, thereby affecting the high-rate performance of the battery and limiting the high-current charge and discharge capacity of the battery. At the same time, an imperfect conductive network will also affect the structural stability of the electrode during charge and discharge, accelerating the pulverization and failure of the electrode material and reducing the cycle life of the battery. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a process method for constructing a conductive network of a solid-state battery, which solves the problems mentioned in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A process method for constructing a conductive network of a solid-state battery specifically includes the following steps:

[0006] S1. Selection and compounding of conductive agents: Select a variety of different types of conductive agents for compounding. Different types of conductive agents have different morphologies and conductive characteristics. By reasonable compounding, their synergistic effects can be exerted. The optimal compounding ratio of each conductive agent: The mass ratio of carbon black, carbon nanotubes, and graphene is (2-3):(1-2):(0.5-1);

[0007] S2. Electrode Slurry Preparation: Mix the cathode active material, conductive agent, and binder evenly in a certain proportion. The mass ratio of the active material, conductive agent, and binder is (80 - 90):(5 - 15):(5 - 10). Add the mixed materials to an organic solvent and use methods such as magnetic stirring or planetary ball milling to fully stir and disperse them, so that each component is evenly dispersed in the solvent to form a uniform electrode slurry;

[0008] S3. Conductive Network Formation Process: During the preparation of the electrode slurry, use high-speed stirring with a stirring speed of 1000 - 3000 r / min and a stirring time controlled within 2 - 6 h. At the same time, add an appropriate amount of dispersant to promote the uniform dispersion and mutual connection of the conductive agent in the electrode slurry. During the electrode coating process, use a special coating process to control the coating thickness and coating speed. Control the coating thickness to be 100 - 200 μm and the coating speed to be 3 - 8 m / min, so that the electrode slurry is evenly coated on the current collector. During the drying process, by controlling the drying temperature and drying time, make the solvent slowly volatilize to avoid the agglomeration and sedimentation of the conductive agent during drying, thus maintaining the continuity of the conductive network;

[0009] S4. Electrode Compaction and Heat Treatment: Compact the coated and dried electrode. The compaction pressure is 150 - 250 MPa and the compaction times are 1 - 3 times. The heat treatment temperature is 100 - 200 °C and the holding time is 2 - 6 h. Use equipment such as a roll press to control the compaction pressure and compaction times to make the electrode have an appropriate porosity and density. Appropriate compaction can improve the conductive performance and mechanical strength of the electrode, but excessive compaction will damage the structure of the conductive network. Conduct heat treatment on the compacted electrode and hold it at a certain temperature of 100 °C - 200 °C and in a certain atmosphere for a certain time, with the holding time being 2 - 6 h. Heat treatment can promote the interaction between various components inside the electrode, further optimize the structure of the conductive network, and improve the conductive ability and stability of the electrode.

[0010] Preferably, in S1, the conductive agent includes but is not limited to carbon black, carbon nanotubes, graphene, etc.

[0011] Preferably, in S2, the cathode active material is one of lithium iron phosphate and ternary materials, the binder is polyvinylidene fluoride, and the organic solvent is N-methylpyrrolidone.

[0012] Preferably, in S3, the dispersant is polyvinylpyrrolidone, the coating process uses one of knife coating or slot coating, and the current collector is aluminum foil or copper foil.

[0013] Preferably, in S4, the atmosphere is one of nitrogen or argon.

[0014] Beneficial effects

[0015] The present invention provides a process method for constructing a conductive network of a solid-state battery. Compared with the prior art, it has the following beneficial effects: The process method for constructing the conductive network of the solid-state battery specifically includes the following steps: S1, selection and compounding of conductive agents; S2, preparation of electrode slurry; S3, process for forming the conductive network; S4, electrode compaction and heat treatment; By optimizing the type compounding of conductive agents and the process for forming the conductive network, a continuous three-dimensional conductive network is formed inside the electrode, greatly improving the overall conductivity of the electrode, making the electron transmission path in the electrode smoother, reducing the internal resistance of the electrode, and being beneficial to improving the charge and discharge efficiency of the battery. Due to the improvement of the electrode conductivity, the polarization phenomenon during the high-current charge and discharge process of the solid-state battery is significantly improved, the internal resistance of the battery is reduced, so that it can withstand a larger charge and discharge current, improving the rate performance of the battery. The continuous and stable conductive network can effectively alleviate the volume change and stress concentration during the charge and discharge process of the electrode, reduce the pulverization and failure of the electrode material, and improve the structural stability of the electrode. At the same time, the good conductivity is also beneficial to the full reaction of the electrode material, improving the charge and discharge capacity retention rate of the battery and extending the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of the steps of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0018] Please refer to Figure 1 , the present invention provides three technical solutions: A process method for constructing a conductive network of a solid-state battery, specifically including the following embodiments:

[0019] Embodiment 1

[0020] S1, selection and compounding of conductive agents: Select a variety of different types of conductive agents for compounding. Different types of conductive agents have different morphologies and conductive characteristics. By reasonable compounding, their synergistic effects can be exerted. The optimal compounding ratio of each conductive agent: the mass ratio of carbon black, carbon nanotubes and graphene is 2.5:1.5:0.7;

[0021] S2. Electrode Slurry Preparation: Mix the positive active material, conductive agent, and binder evenly in a certain proportion. The mass ratio of the active material, conductive agent, and binder is 85:10:7. Add the mixed materials to an organic solvent and use methods such as magnetic stirring or planetary ball milling for sufficient stirring and dispersion to evenly disperse each component in the solvent and form a uniform electrode slurry;

[0022] S3. Conductive Network Formation Process: During the preparation of the electrode slurry, use high-speed stirring with a stirring speed of 2000 r / min and a stirring time controlled at 4 h. At the same time, add an appropriate amount of dispersant to promote the uniform dispersion and mutual connection of the conductive agent in the electrode slurry. During the electrode coating process, use a special coating process to control the coating thickness and coating speed. Control the coating thickness to be 150 μm and the coating speed to be 5 m / min to evenly coat the electrode slurry on the current collector. During the drying process, by controlling the drying temperature and drying time, make the solvent slowly volatilize to avoid agglomeration and sedimentation of the conductive agent during drying, thereby maintaining the continuity of the conductive network;

[0023] S4. Electrode Compaction and Heat Treatment: Compact the coated and dried electrode. The compaction pressure is 200 MPa and the number of compaction times is 2. The heat treatment temperature is 150 °C and the holding time is 4 h. Use equipment such as a roll press to control the compaction pressure and the number of compaction times to make the electrode have an appropriate porosity and density. Appropriate compaction can improve the conductive performance and mechanical strength of the electrode, but excessive compaction will damage the structure of the conductive network. Perform heat treatment on the compacted electrode and hold it at a certain temperature of 150 °C and in a certain atmosphere for a certain time, with the holding time being 4 h. Heat treatment can promote the interaction between various components inside the electrode, further optimize the structure of the conductive network, and improve the conductive ability and stability of the electrode.

[0024] Example Two

[0025] S1. Selection and Compound of Conductive Agent: Select multiple different types of conductive agents for compounding. Different types of conductive agents have different morphologies and conductive characteristics. By reasonable compounding, their synergistic effects can be exerted. The optimal compounding ratio of each conductive agent: the mass ratio of carbon black, carbon nanotubes, and graphene is 2:1:0.5;

[0026] S2. Electrode Slurry Preparation: Mix the positive active material, conductive agent, and binder evenly in a certain proportion. The mass ratio of the active material, conductive agent, and binder is 80:5:5. Add the mixed materials to an organic solvent and use methods such as magnetic stirring or planetary ball milling for sufficient stirring and dispersion to evenly disperse each component in the solvent and form a uniform electrode slurry;

[0027] S3. Conductive network formation process: During the preparation of the electrode paste, high-speed stirring is adopted, with a stirring speed of 1000 r / min and a stirring time controlled at 2 h. At the same time, an appropriate amount of dispersant is added to promote the uniform dispersion and mutual connection of the conductive agent in the electrode paste. During the electrode coating process, a special coating process is used to control the coating thickness and coating speed. The coating thickness is controlled at 100 μm and the coating speed is 3 m / min, so that the electrode paste is evenly coated on the current collector. During the drying process, by controlling the drying temperature and drying time, the solvent slowly volatilizes, avoiding the agglomeration and sedimentation of the conductive agent during drying, thus maintaining the continuity of the conductive network;

[0028] S4. Electrode compaction and heat treatment: The coated and dried electrode is subjected to compaction treatment. The compaction pressure is 150 MPa and the compaction times is 1 time. The heat treatment temperature is 100 °C and the holding time is 2 h. Equipment such as a roller press is used to control the compaction pressure and compaction times, so that the electrode has an appropriate porosity and density. Appropriate compaction can improve the conductive performance and mechanical strength of the electrode, but excessive compaction will damage the structure of the conductive network. The compacted electrode is subjected to heat treatment and held at a certain temperature of 100 °C and in a certain atmosphere for a certain time, and the holding time is 2 h. Heat treatment can promote the interaction between various components inside the electrode, further optimize the structure of the conductive network, and improve the conductive ability and stability of the electrode.

[0029] Example Three

[0030] S1. Selection and compounding of conductive agents: Multiple different types of conductive agents are selected for compounding. Different types of conductive agents have different morphologies and conductive characteristics. By reasonable compounding, their synergistic effects can be exerted. The optimal compounding ratio of each conductive agent: the mass ratio of carbon black, carbon nanotubes and graphene is 3:2:1;

[0031] S2. Preparation of electrode paste: The positive active material, conductive agent and binder are mixed evenly according to a certain ratio. The mass ratio of the active material, conductive agent and binder is 90:15:10. The mixed materials are added to an organic solvent, and methods such as magnetic stirring or planetary ball milling are used for sufficient stirring and dispersion to make each component evenly dispersed in the solvent to form a uniform electrode paste;

[0032] S3. Conductive network formation process: During the preparation of the electrode paste, high-speed stirring is used. The stirring speed is 3000 r / min, and the stirring time is controlled within 6 h. At the same time, an appropriate amount of dispersant is added to promote the uniform dispersion and mutual connection of the conductive agent in the electrode paste. During the electrode coating process, a special coating process is adopted to control the coating thickness and coating speed. The coating thickness is controlled at 200 μm, and the coating speed is 8 m / min, so that the electrode paste is evenly coated on the current collector. During the drying process, by controlling the drying temperature and drying time, the solvent slowly volatilizes, avoiding the agglomeration and sedimentation of the conductive agent during drying, thereby maintaining the continuity of the conductive network;

[0033] S4. Electrode compaction and heat treatment: The coated and dried electrode is subjected to compaction treatment. The compaction pressure is 250 MPa, and the compaction times are 3 times. The heat treatment temperature is 200 °C, and the holding time is 6 h. Equipment such as a roller press is used to control the compaction pressure and compaction times, so that the electrode has an appropriate porosity and density. Appropriate compaction can improve the conductive performance and mechanical strength of the electrode, but excessive compaction will damage the structure of the conductive network. The compacted electrode is subjected to heat treatment, held at a certain temperature of 200 °C and in a certain atmosphere for a certain time, and the holding time is 6 h. Heat treatment can promote the interaction between various components inside the electrode, further optimize the structure of the conductive network, and improve the conductive ability and stability of the electrode.

[0034] Meanwhile, the content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0035] Effect examples

[0036] The solid-state batteries provided by Examples 1-3 and the comparative example (conventional solid-state batteries on the market) are subjected to the following performance tests for capacity testing and cycle testing. The test results are shown in the following table:

[0037]

[0038] In summary, by optimizing the type compounding of conductive agents and the process of forming a conductive network, a continuous three-dimensional conductive network is formed inside the electrode, greatly improving the overall conductivity of the electrode. The electron transmission path in the electrode becomes smoother, reducing the internal resistance of the electrode, which is beneficial to improving the charge-discharge efficiency of the battery. Due to the improvement of the electrode conductivity, the polarization phenomenon during the high-current charge-discharge process of the solid-state battery is significantly improved, and the internal resistance of the battery is reduced, enabling it to withstand a larger charge-discharge current and improving the rate performance of the battery. The continuous and stable conductive network can effectively alleviate the volume change and stress concentration of the electrode during the charge-discharge process, reduce the pulverization and failure of the electrode material, and improve the structural stability of the electrode. At the same time, the good conductivity is also conducive to the full reaction of the electrode material, improving the charge-discharge capacity retention rate of the battery and extending the cycle life of the battery.

[0039] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0040] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process method for constructing a conductive network of a solid-state battery, characterized in that: Specifically, it includes the following steps: S1. Selection and compounding of conductive agents: Select multiple different types of conductive agents for compounding. Different types of conductive agents have different morphologies and conductive characteristics. By reasonable compounding, their synergistic effects can be exerted. The optimal compounding ratio of each conductive agent: the mass ratio of carbon black, carbon nanotubes and graphene is (2 - 3):(1 - 2):(0.5 - 1); S2. Preparation of electrode slurry: Mix the positive electrode active material, conductive agent and binder in a certain proportion evenly. The mass ratio of the active material, conductive agent and binder is (80 - 90):(5 - 15):(5 - 10). Add the mixed materials into an organic solvent, and use methods such as magnetic stirring or planetary ball milling to stir and disperse fully, so that each component is evenly dispersed in the solvent to form a uniform electrode slurry; S3. Process for forming conductive network: During the preparation of the electrode slurry, use high-speed stirring, the stirring speed is 1000 - 3000 r / min, and the stirring time is controlled within 2 - 6 h. At the same time, add an appropriate amount of dispersant to promote the uniform dispersion and mutual connection of the conductive agent in the electrode slurry. During the electrode coating process, use a special coating process to control the coating thickness and coating speed. Control the coating thickness to be 100 - 200 μm, and the coating speed to be 3 - 8 m / min, so that the electrode slurry is evenly coated on the current collector. During the drying process, by controlling the drying temperature and drying time, make the solvent volatilize slowly to avoid the agglomeration and sedimentation of the conductive agent during drying, thereby maintaining the continuity of the conductive network; S4. Electrode compaction and heat treatment: Compact the coated and dried electrode, the compaction pressure is 150 - 250 MPa, the compaction times are 1 - 3 times, the heat treatment temperature is 100 - 200 °C, and the heat preservation time is 2 - 6 h. Use equipment such as a roll press to control the compaction pressure and compaction times to make the electrode have an appropriate porosity and density. Appropriate compaction can improve the conductive performance and mechanical strength of the electrode, but excessive compaction will damage the structure of the conductive network. Conduct heat treatment on the compacted electrode, keep it at a certain temperature of 100 °C - 200 °C and in a certain atmosphere for a certain time, and the heat preservation time is 2 - 6 h. Heat treatment can promote the interaction between each component inside the electrode, further optimize the structure of the conductive network, and improve the conductive ability and stability of the electrode.

2. The conductive network construction process method of a solid-state battery according to claim 1, wherein: In the above S1, the conductive agents include but are not limited to carbon black, carbon nanotubes, graphene, etc.

3. A process method for constructing a conductive network of a solid-state battery according to claim 1, characterized in that: In the above S2, the positive electrode active material is one of lithium iron phosphate and ternary materials, the binder is polyvinylidene fluoride, and the organic solvent is N-methylpyrrolidone.

4. A process method for constructing a conductive network of a solid-state battery according to claim 1, characterized in that: In the above S3, the dispersant is polyvinylpyrrolidone, the coating process adopts one of blade coating or slot coating, and the current collector is aluminum foil or copper foil.

5. A process method for constructing a conductive network of a solid-state battery according to claim 1, characterized in that: In the above S4, the atmosphere is one of nitrogen or argon.

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