Composite conductive agent and preparation method and application thereof
By using blends of one-dimensional and two-dimensional conductive agents with conductive polymers to form a three-dimensional conductive network in sulfide-based solid-state batteries, the problems of suboptimal ion and electron transport and interfacial reactions in sulfide-based solid-state batteries are solved, thereby improving the cycle performance and lifespan of the batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-27
AI Technical Summary
Sulfide-based solid-state batteries suffer from problems such as imperfect ion and electron transport paths, frequent interfacial chemical reactions, and poor interfacial mechanical integrity, leading to performance degradation.
A three-dimensional conductive network structure is formed by blending one-dimensional and two-dimensional conductive agents with conductive polymers, which enhances the interfacial stability between the electrode material and the sulfide electrolyte and constructs a good ion and electron transport channel.
It improves the cycle performance and rate performance of sulfide solid-state batteries, enhances interface stability and electrochemical performance, and extends battery life.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of solid-state batteries, in particular to a composite conductive agent, a preparation method and application thereof, and specifically to a composite conductive agent, a preparation method thereof and application in sulfide solid-state batteries, a positive electrode sheet and a solid-state battery. BACKGROUND
[0002] Currently developed lithium batteries mainly use liquid electrolyte, which contains a large amount of organic solvent, resulting in a large safety hazard of liquid lithium batteries. Using a solid electrolyte layer instead of a liquid electrolyte is expected to eliminate the safety hazard during use and better meet the future development needs of electric vehicles and large-scale energy storage fields. Sulfide electrolyte has both the high ionic conductivity of oxide electrolyte and the high processability of polymer electrolyte, so sulfide-based solid-state batteries have broad industrialization prospects.
[0003] However, the current sulfide-based solid-state batteries still have problems such as unsatisfactory ion and electron transmission path and transmission efficiency, and easy chemical reaction between sulfide electrolyte and electrode material: (1) The electrochemical stability window of sulfide electrolyte is relatively narrow, which is easily oxidized at the positive electrode interface and reduced at the negative electrode interface, generating an intermediate layer with low ionic conductivity, increasing the interface impedance, and producing SO2 gas. For example, when the sulfide electrolyte contacts with high-voltage positive electrode materials (such as LiCoO2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.), reaction products such as sulfates, phosphates, elemental sulfur, lithium polysulfide and sulfides will be generated at the interface. Conventional conductive agents (such as carbon additives) will accelerate the decomposition of sulfide electrolyte during charging. Even if a small amount of carbon additive is added, it will cause serious decomposition of the sulfide electrolyte at the electrolyte / carbon interface, forming a poor interface layer and hindering the transmission of lithium ions.
[0004] (2) Due to the chemical potential difference of Li + in the positive electrode and the sulfide electrolyte, a high-resistance Li + defect layer, i.e. space charge layer, will be formed. This space charge layer will hinder the transmission of lithium ions and increase the interface impedance. The interface chemical reaction will cause the physical contact between the positive electrode material and the sulfide electrolyte to deteriorate or cracks to form, further increasing the interface impedance. In the slurry process, the binder and conventional conductive agent will migrate and aggregate to the surface due to capillary action and diffusion, resulting in uneven distribution in the electrode structure and affecting the overall conductivity of the electrode.
[0005] (3) Lithium ion intercalation / deintercalation during charge / discharge process leads to continuous change (shrinkage and expansion) of electrode material lattice, which results in huge stress / strain at the solid-solid interface between sulfide electrolyte and electrode, destroys the mechanical integrity of the interface, increases the interface impedance and leads to battery performance degradation. Conventional conductive agents are difficult to form a uniform and dense interface layer to effectively isolate the electrolyte from the electrode material, resulting in part of the electrode material still exposed to the electrolyte, and chemical reaction occurs.
[0006] Therefore, it is desirable to provide a new conductive agent to solve the above problems. SUMMARY
[0007] In order to solve the above technical problems, the present application provides a composite conductive agent, a preparation method and application thereof.
[0008] In a first aspect, the present application provides a composite conductive agent, which comprises a blend of at least one of one-dimensional conductive agent and two-dimensional conductive agent and conductive polymer, and the mass ratio of the total mass of the one-dimensional conductive agent and the two-dimensional conductive agent to the mass of the conductive polymer is 1-4:7.
[0009] In the mass ratio of the total mass of the one-dimensional conductive agent and the two-dimensional conductive agent to the mass of the conductive polymer, the total mass of the one-dimensional conductive agent and the two-dimensional conductive agent refers to the total mass of the one-dimensional conductive agent and the two-dimensional conductive agent when the composite conductive agent comprises both the one-dimensional conductive agent and the two-dimensional conductive agent, the mass of the one-dimensional conductive agent when the composite conductive agent only comprises the one-dimensional conductive agent, and the mass of the two-dimensional conductive agent when the composite conductive agent only comprises the two-dimensional conductive agent.
[0010] As a preferred technical solution of the present application, the composite conductive agent comprises a blend of one-dimensional conductive agent and conductive polymer, and the mass ratio of the one-dimensional conductive agent to the conductive polymer is 1.5-3:7.
[0011] As a preferred technical solution of the present application, the composite conductive agent comprises a blend of two-dimensional conductive agent and conductive polymer, and the mass ratio of the two-dimensional conductive agent to the conductive polymer is 1-2:7.
[0012] As a preferred technical solution of the present application, the composite conductive agent comprises a blend of one-dimensional conductive agent, two-dimensional conductive agent and conductive polymer, and the mass ratio of the one-dimensional conductive agent, the two-dimensional conductive agent and the conductive polymer is (1.5-3):(0.5-1):7.
[0013] As a preferred technical solution of the present application, the one-dimensional conductive agent comprises any one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon fibers and metal nanowires.
[0014] As a preferred technical solution of the present application, the two-dimensional conductive agent is selected from graphene.
[0015] As a preferred technical solution of the present application, the conductive polymer is selected from polypyrrole.
[0016] As a preferred technical solution of the present application, the composite conductive agent further comprises a zero-dimensional conductive agent, and the mass ratio of the zero-dimensional conductive agent to the conductive polymer is 0.1-0.2:7.
[0017] As a preferred technical solution of the present application, the zero-dimensional conductive agent comprises Super-P and / or acetylene black.
[0018] In a second aspect, the present application provides a preparation method of the composite conductive agent of the first aspect, and the preparation method comprises: mixing the powders of raw materials in a solvent to obtain a composite conductive agent slurry, and drying to obtain the composite conductive agent.
[0019] As a preferred technical solution of the present application, the mass ratio of the total mass of the powders of raw materials to the mass of the solvent is (1-6):(30-60).
[0020] As a preferred technical solution of the present application, the solvent is selected from any one or more of ethanol or NMP.
[0021] As a preferred technical solution of the present application, the drying temperature is 95-105℃.
[0022] As a preferred technical solution of the present application, the drying time is 8-12 h.
[0023] In a third aspect, the present application provides an application of the composite conductive agent of the first aspect or the composite conductive agent prepared by the preparation method of the second aspect in a sulfide solid-state battery.
[0024] In a fourth aspect, the present application provides a positive electrode sheet, which comprises the composite conductive agent of the first aspect or the composite conductive agent prepared by the preparation method of the second aspect, and a positive electrode active material and a sulfide solid-state electrolyte.
[0025] As a preferred technical solution of the present application, the mass ratio of the positive electrode active material, the composite conductive agent and the sulfide solid-state electrolyte is (65-75):(2-8):(25-35).
[0026] As a preferred technical solution of the present application, the mass ratio of the positive electrode active material, the composite conductive agent and the sulfide solid-state electrolyte is 70:5:30.
[0027] In a fifth aspect, the present application provides a solid-state battery, which comprises the positive electrode sheet according to the fourth aspect.
[0028] Compared with the prior art, the technical scheme provided by the embodiments of the present application has the following advantages: The composite conductive agent provided by the present application can effectively improve the interface stability between the electrode material and the sulfide electrolyte, and the three-dimensional conductive network structure can be formed by compounding at least one of the one-dimensional conductive agent and the two-dimensional conductive agent with the conductive polymer, so as to have excellent conductivity and large specific surface area, thereby constructing good ion and electron transmission channels, reducing the ion and electron transmission resistance at the interface, improving the ion and electron transmission efficiency, and thus enabling the sulfide solid-state battery to have excellent cycle performance and rate performance. DETAILED DESCRIPTION
[0029] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the schemes of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.
[0030] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other different manners from those described herein; obviously, the embodiments described in the specification are only a part of the embodiments of the present application, and not all the embodiments.
[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present application belongs; the terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the present application.
[0032] The currently developed lithium battery mainly uses liquid electrolyte, which contains a large amount of organic solvent, resulting in a large safety hazard of the liquid lithium battery. Using a solid-state electrolyte layer to replace the liquid electrolyte is expected to eliminate the safety hazard in the use process, and is more in line with the future development needs of the electric vehicle and large-scale energy storage fields. The sulfide electrolyte has high ionic conductivity of the oxide electrolyte and high processing performance of the polymer electrolyte, and has broad industrialization prospects. However, the current sulfide-based solid-state battery still has problems such as unsatisfactory ion and electron transmission path and transmission efficiency, and easy chemical reaction between the sulfide electrolyte and the electrode material. Therefore, the embodiments of the present application provide a composite conductive agent and a preparation method and application thereof, specifically a composite conductive agent and a preparation method thereof and application thereof in a sulfide solid-state battery, a positive electrode sheet and a solid-state battery.
[0033] First, the present invention provides a composite conductive agent, comprising a blend of at least one of a one-dimensional conductive agent and a two-dimensional conductive agent with a conductive polymer, wherein the total mass ratio of the one-dimensional conductive agent and the two-dimensional conductive agent to the mass ratio of the conductive polymer is 1-4:7, for example, it can be 1:7, 1.5:7, 2:7, 2.5:7, 3:7, 3.5:7, 4:7, etc.
[0034] The composite conductive agent provided in this invention can effectively improve the interfacial stability between the electrode material and the sulfide electrolyte. Furthermore, at least one of the one-dimensional and two-dimensional conductive agents, when combined with a conductive polymer, can form a three-dimensional conductive network structure with excellent conductivity and a large specific surface area. This constructs good ion and electron transport channels, reduces ion and electron transport resistance at the interface, and improves ion and electron transport efficiency. Consequently, the sulfide solid-state battery using this agent exhibits excellent cycle performance and rate performance. Specifically: In solid-state batteries, stress may arise between the electrode material and the solid electrolyte due to the insertion and extraction of lithium ions, leading to changes in the material structure at the interface. The composite conductive agent provided in this invention comprises a blend of at least one of a one-dimensional and a two-dimensional conductive agent with a conductive polymer. The resulting composite structure exhibits good flexibility and viscoelasticity. The composite conductive agent penetrates deep into the interface between the electrode and the solid electrolyte, effectively buffering the volume changes of the electrode material during charge and discharge. This characteristic reduces stress concentration at the interface, decreases the formation and propagation of interface cracks, and prevents irreversible damage to the material structure at the interface during repeated charge and discharge, thereby significantly improving interface stability. Furthermore, the conductive polymer possesses good chemical stability and compatibility with sulfide electrolytes, reducing side reactions with the sulfide electrolyte and helping to maintain interface stability. This prevents chemical corrosion between the electrolyte and electrode materials. Compared to traditional conductive agents (such as carbon black or carbon nanotubes), the chemical inertness of the conductive polymer helps maintain long-term interface stability, thereby extending battery life. Therefore, the composite conductive agent provided by the embodiments of the present invention can effectively enhance the mechanical strength and chemical stability of the interface, enabling the solid-state battery to maintain good electrochemical performance after multiple charge-discharge cycles.
[0035] Simultaneously, at least one of the one-dimensional and two-dimensional conductive agents, when combined with a conductive polymer, can form a three-dimensional conductive network structure with excellent conductivity and a large specific surface area. This constructs excellent electron and ion transport channels, reduces ion and electron transport resistance at the interface, thereby lowering the internal resistance of the solid-state battery using it. This reduces energy loss during charging and discharging, improves the battery's energy conversion efficiency, and effectively enhances the battery's rate performance and lifespan, maintaining good performance even under high-rate charge and discharge conditions. Furthermore, the composite conductive agent provided in this invention can significantly improve the utilization rate of electrode materials, thereby increasing the battery's specific capacity and energy density. Therefore, the composite conductive agent provided in this invention significantly improves the electrochemical performance and lifespan of sulfide solid-state batteries by enhancing interfacial stability and optimizing ion and electron transport channels, solving problems such as unsatisfactory ion and electron transport paths and efficiencies, and the tendency for chemical reactions to occur between sulfide electrolytes and electrode materials.
[0036] In the phrase "ratio of the total mass of one-dimensional and two-dimensional conductive agents to the mass of the conductive polymer," the "total mass of one-dimensional and two-dimensional conductive agents" refers to the total mass of both the one-dimensional and two-dimensional conductive agents when the composite conductive agent includes both; the mass of the one-dimensional conductive agent when the composite conductive agent includes only one-dimensional conductive agents; and the mass of the two-dimensional conductive agent when the composite conductive agent includes only two-dimensional conductive agents. The embodiments of this invention limit the ratio of the total mass of the one-dimensional and two-dimensional conductive agents to the mass of the conductive polymer to the above range. If the amount of conductive polymer is too high, it is easy to form agglomerates locally, affecting electron transport; if the amount of conductive polymer is too low, it cannot form a complete coating on the surface of the conductive agent.
[0037] The composite conductive agent provided by the embodiments of the present invention includes a blend of at least one of one-dimensional and two-dimensional conductive agents with a conductive polymer, which can form a three-dimensional conductive network structure, thereby constructing a good ion and electron transport channel, reducing the ion and electron transport resistance at the interface, and improving the ion and electron transport efficiency. In contrast, the zero-dimensional conductive agent and the conductive polymer can only form point contact and cannot form a three-dimensional conductive network structure, resulting in poor conductivity.
[0038] In some embodiments of the present invention, the composite conductive agent includes a blend of a one-dimensional conductive agent and a conductive polymer, wherein the mass ratio of the one-dimensional conductive agent to the conductive polymer is 1.5-3:7, for example, 1.5:7, 2:7, 2.5:7, 3:7, etc.
[0039] In some embodiments of the present invention, the composite conductive agent includes a blend of a two-dimensional conductive agent and a conductive polymer, wherein the mass ratio of the two-dimensional conductive agent to the conductive polymer is 1-2:7, such as 1:7, 1.2:7, 1.4:7, 1.6:7, 1.8:7, 2:7, etc.
[0040] The embodiments of the present invention limit the mass ratio of one-dimensional or two-dimensional conductive agent to conductive polymer to be within the above range. If the amount of conductive polymer is too large, it is easy to form agglomerates locally, which affects the transmission of electrons. If the amount of conductive polymer is too small, it cannot form a complete coating on the surface of the conductive agent.
[0041] In some embodiments of the present invention, the composite conductive agent includes a blend of a one-dimensional conductive agent and a two-dimensional conductive agent with a conductive polymer, wherein the mass ratio of the one-dimensional conductive agent, the two-dimensional conductive agent and the conductive polymer is (1.5-3):(0.5-1):7, for example 1.5:1:7, 2:0.8:7, 2.5:0.6:7, 3:0.5:7, etc.
[0042] The composite conductive agent provided in this invention includes both one-dimensional and two-dimensional conductive agents, which can further enhance the conductive network structure, further shorten the ion diffusion path, and improve ion and electron transport efficiency. However, if too much two-dimensional conductive agent is used, it can easily lead to the stacking of two-dimensional conductive agent sheets, hindering the ion diffusion path and reducing the effective specific surface area.
[0043] In some embodiments of the present invention, the one-dimensional conductive agent includes any one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon fibers, and metal nanowires.
[0044] The embodiments of the present invention utilize the above-mentioned one-dimensional conductive agent and conductive polymer to form a three-dimensional conductive network structure, constructing continuous ion and electron conductive channels, thereby effectively reducing the tortuosity of charge transport and improving the efficiency of ion and electron transport.
[0045] In some embodiments of the present invention, the two-dimensional conductive agent is selected from graphene.
[0046] In some embodiments of the present invention, the conductive polymer is selected from polypyrrole.
[0047] The conductive polymer provided in this invention is selected from polypyrrole. Polypyrrole has excellent conductivity, thermal stability, mechanical strength and chemical stability, and can more effectively improve interface stability.
[0048] In some embodiments of the present invention, the composite conductive agent further includes a zero-dimensional conductive agent, and the mass ratio of the zero-dimensional conductive agent to the conductive polymer is 0.1-0.2:7, such as 0.1:7, 0.12:7, 0.14:7, 0.16:7, 0.18:7, 0.2:7, etc.
[0049] The composite conductive agent provided in this invention also includes a zero-dimensional conductive agent. When the mass ratio of the zero-dimensional conductive agent to the conductive polymer is within the above-mentioned range, it can further enhance the conductive network formed by at least one of the one-dimensional and two-dimensional conductive agents and the conductive polymer, further shorten the ion diffusion path, and improve the ion and electron transport efficiency. If too much zero-dimensional conductive agent is used, on the one hand, the conductivity of the zero-dimensional conductive agent is limited, and the effect improvement is limited; on the other hand, too much zero-dimensional conductive agent is prone to agglomeration, which leads to a decrease in performance.
[0050] In some embodiments of the present invention, the zero-dimensional conductive agent includes Super-P and / or acetylene black.
[0051] Accordingly, embodiments of the present invention provide a method for preparing a composite conductive agent, comprising: The raw material powders are mixed in a solvent to obtain a composite conductive agent slurry, which is then dried to obtain the composite conductive agent.
[0052] The preparation method provided by the embodiments of the present invention is simple in process, low in raw material cost, and high in cost performance, and has broad prospects for industrial application.
[0053] In some embodiments of the present invention, the ratio of the total mass of each raw material powder to the mass of the solvent is (1-6):(30-60), for example 1:30, 1:40, 1:50, 1:60, 2:30, 2:60, 3:30, 3:50, 3:60, 4:30, 4:60, 5:30, 5:60, 6:30, 6:60, etc.
[0054] In some embodiments of the present invention, the solvent is selected from any one or more of ethanol or NMP.
[0055] In some embodiments of the present invention, the drying temperature is 95-105°C, such as 95°C, 98°C, 100°C, 102°C, 105°C, etc.
[0056] In some embodiments of the present invention, the drying time is 8-12 h, for example 8 h, 9 h, 10 h, 11 h, 12 h, etc.
[0057] Accordingly, embodiments of the present invention provide the application of composite conductive agents or the prepared composite conductive agents in sulfide solid-state batteries.
[0058] Accordingly, embodiments of the present invention provide a positive electrode sheet, comprising a composite conductive agent provided in embodiments of the present invention or a composite conductive agent prepared therefrom, as well as a positive electrode active material and a sulfide solid electrolyte.
[0059] In some embodiments of the present invention, the positive electrode active material includes NCM, lithium iron phosphate, and lithium cobalt oxide, etc.
[0060] In some embodiments of the present invention, the sulfide solid electrolyte includes Li7P3S. 11 Li3PS4 and Li 10 GeP2S 12 Any one or more of the following.
[0061] In some embodiments of the present invention, the mass ratio of the positive electrode active material, the composite conductive agent and the sulfide solid electrolyte is (65-75):(2-8):(25-35), for example 75:2:25, 72:3:28, 70:5:30, 68:6:32, 65:8:35, etc.
[0062] When the amounts of positive electrode active material, composite conductive agent and sulfide solid electrolyte are within the above range, the interfacial stability between the electrode material and the sulfide electrolyte can be effectively improved, and a three-dimensional conductive network structure can be formed in the positive electrode sheet to build a good ion and electron transport channel, reduce the ion and electron transport resistance at the interface, and improve the ion and electron transport efficiency. As a result, the sulfide solid battery using it has excellent cycle performance and rate performance.
[0063] In some embodiments of the present invention, the mass ratio of the positive electrode active material, the composite conductive agent, and the sulfide solid electrolyte is 70:5:30.
[0064] Accordingly, embodiments of the present invention provide a solid-state battery, including the positive electrode sheet provided in embodiments of the present invention.
[0065] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0066] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with conventional techniques or conditions in the art, techniques or conditions described in the literature, or product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0067] This embodiment provides a method for preparing polypyrrole, comprising the following steps: Dissolve 10 mL of pyrrole in 1000 mL of ethanol solution, add 128 mL of 0.5 mol / L ammonium persulfate solution, react for 24 hours, filter, wash and dry to obtain the final product.
[0068] Example 1 This embodiment provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of multi-walled carbon nanotubes and polypyrrole, with a mass ratio of multi-walled carbon nanotubes to polypyrrole of 1.5:7. The preparation method includes the following steps: Multi-walled carbon nanotubes and polypyrrole were weighed at a mass ratio of 1.5:7 and placed in a container to obtain a mixed powder. Ethanol was added to make the mass ratio of the total mass of the mixed powder to the mass of ethanol 1:5. The mixture was ultrasonically dispersed at a power of 65 W and then magnetically stirred at a speed of 300 r / min to ensure uniform dispersion of the mixed powder, thus obtaining a composite conductive agent slurry. The composite conductive agent slurry was placed in a vacuum drying oven and dried at 95°C for 12 hours to obtain the composite conductive agent.
[0069] Example 2 This embodiment provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of multi-walled carbon nanotubes, polypyrrole, and Super-P, with a mass ratio of multi-walled carbon nanotubes, polypyrrole, and Super-P of 2:7:0.2. The preparation method includes the following steps: Multi-walled carbon nanotubes, polypyrrole, and Super-P were weighed in a container at a mass ratio of 2:7:0.2 to obtain a mixed powder. NMP was added to make the mass ratio of the total mass of the mixed powder to NMP 1:10. The mixture was ultrasonically dispersed at a power of 100 W and then magnetically stirred at a speed of 500 r / min to ensure uniform dispersion of the mixed powder, resulting in a composite conductive agent slurry. The composite conductive agent slurry was placed in a vacuum drying oven and dried at 100℃ for 10 hours to obtain the composite conductive agent.
[0070] Example 3 This embodiment provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of multi-walled carbon nanotubes, polypyrrole, and Super-P, with a mass ratio of 3:7:0.1 for the multi-walled carbon nanotubes, polypyrrole, and Super-P. The preparation method includes the following steps: Multi-walled carbon nanotubes, polypyrrole, and Super-P were weighed in a container at a mass ratio of 3:7:0.1 to obtain a mixed powder. Ethanol was added to make the total mass ratio of the mixed powder to NMP 1:30. The mixture was ultrasonically dispersed at a power of 150 W and then magnetically stirred at a speed of 600 r / min to ensure uniform dispersion of the mixed powder, resulting in a composite conductive agent slurry. The composite conductive agent slurry was placed in a vacuum drying oven and dried at 105℃ for 8 hours to obtain the composite conductive agent.
[0071] Example 4 This embodiment provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of single-walled carbon nanotubes, polypyrrole, acetylene black, and graphene, with a mass ratio of 2:7:0.2:0.8. The preparation method is the same as in Example 2.
[0072] Example 5 This embodiment provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of graphene and polypyrrole, with a mass ratio of graphene to polypyrrole of 1.5:7. The preparation method is the same as in Example 2.
[0073] Comparative Example 1 This comparative example provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of multi-walled carbon nanotubes, polypyrrole, and Super-P, with a mass ratio of multi-walled carbon nanotubes, polypyrrole, and Super-P of 2:10:0.2. The preparation method is the same as in Example 2.
[0074] Comparative Example 2 This comparative example provides a conductive agent, which is a multi-walled carbon nanotube.
[0075] Comparative Example 3 This comparative example provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of multi-walled carbon nanotubes and Super-P, with a mass ratio of multi-walled carbon nanotubes to Super-P of 2:0.2. The preparation method includes the following steps: Multi-walled carbon nanotubes and Super-P were weighed at a mass ratio of 2:0.2 and placed in a container to obtain a mixed powder. NMP was added to make the mass ratio of the total mass of the mixed powder to NMP 1:10. The mixture was ultrasonically dispersed at a power of 100 W and then magnetically stirred at a speed of 500 r / min to ensure uniform dispersion of the mixed powder, thus obtaining a composite conductive agent slurry. The composite conductive agent slurry was placed in a vacuum drying oven and dried at 95°C for 12 hours to obtain the composite conductive agent.
[0076] Comparative Example 4 This comparative example provides a composite conductive agent and its preparation method. The composite conductive agent includes a blend of Super-P and polypyrrole, with a mass ratio of Super-P to polypyrrole of 2:7. The preparation method is the same as in Example 2.
[0077] Application examples The conductive agents prepared in the examples and comparative examples were used to prepare positive electrode sheets and sulfide all-solid-state batteries, respectively. (1) The sulfide solid electrolyte Li7P3S 11 The powder is pressed into electrolyte sheets with a thickness of 0.5 cm, a pressure of 120-150 MPa, and a pressing time of 10-15 min; (2) The positive electrode active material NCM811 and the sulfide solid electrolyte Li7P3S are mixed in a mass ratio of 70:30:5. 11 The powder and the composite conductive agent prepared in the examples or comparative examples are mixed and spread on one side of the electrolyte sheet, and pressed at 80 MPa for 5 min to obtain the positive electrode layer. (3) A lithium-magnesium alloy with a magnesium content of 4% was placed on the other side of the electrolyte sheet and pressed under a pressure of 30MPa for 2 min to obtain a negative electrode layer, thus obtaining a sulfide all-solid-state battery.
[0078] It should be noted that the above-mentioned all-solid-state battery used for testing is only an example listed to determine the performance of the composite conductive agent. The present invention is not limited to this type of all-solid-state battery. The raw materials, proportions, parameters and processes of the positive electrode and negative electrode, as well as the sulfide solid electrolyte, can be replaced with other conventional raw materials, proportions, parameters and processes in the field to form a sulfide all-solid-state battery different from the one used for testing.
[0079] Performance testing The conductive agents of the examples and comparative examples were used to prepare positive electrode sheets and sulfide all-solid-state batteries according to the method described in the application examples. The AC impedance of the obtained sulfide all-solid-state batteries was then tested. On an electrochemical workstation, the frequency response signal of the all-solid-state battery system was analyzed by inputting signal interference in the frequency range of 0.1~1MHz, and the ionic conductivity of the all-solid-state battery was calculated.
[0080] The ionic conductivity results are shown in Table 1: Table 1
[0081] As can be seen from Table 1, compared with Examples 1 and 5 and Comparative Example 2, the composite conductive agent obtained by the present invention using polypyrrole combined with multi-walled carbon nanotubes or graphene can effectively improve the interface of sulfide solid electrolyte and increase ionic conductivity.
[0082] Compared with Examples 1, 5 and Comparative Example 4, the composite conductive agent obtained by the present invention using polypyrrole combined with multi-walled carbon nanotubes or graphene can form a three-dimensional conductive network structure and improve ionic conductivity compared with the composite conductive agent obtained by using polypyrrole combined with Super-P.
[0083] Compared with Example 2 and Comparative Example 1, excessive amounts of polypyrrole may lead to local agglomeration, resulting in a decrease in electronic conductivity.
[0084] Compared to Example 1, Example 2 demonstrates that the present invention, utilizing polypyrrole-composite multi-walled carbon nanotubes and SP, significantly improves the interface of sulfide solid electrolytes, reducing ohmic resistance and charge transfer resistance while increasing ionic conductivity. Furthermore, the addition of graphene in Example 4 forms a three-dimensional conductive network of points, lines, and surfaces, further enhancing ionic conductivity.
[0085] It should be noted that, in this document, 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.
[0086] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. 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 the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A composite conductive agent, characterized in that, The composite conductive agent comprises a blend of at least one of a one-dimensional conductive agent and a two-dimensional conductive agent with a conductive polymer, wherein the total mass ratio of the one-dimensional conductive agent and the two-dimensional conductive agent to the mass ratio of the conductive polymer is 1-4:
7.
2. The composite conductive agent according to claim 1, characterized in that, The composite conductive agent comprises a blend of a one-dimensional conductive agent and a conductive polymer, wherein the mass ratio of the one-dimensional conductive agent to the conductive polymer is 1.5-3:
7. Alternatively, the composite conductive agent may comprise a blend of a two-dimensional conductive agent and a conductive polymer, wherein the mass ratio of the two-dimensional conductive agent to the conductive polymer is 1-2:7; Alternatively, the composite conductive agent may comprise a blend of a one-dimensional conductive agent and a two-dimensional conductive agent with a conductive polymer, wherein the mass ratio of the one-dimensional conductive agent, the two-dimensional conductive agent, and the conductive polymer is (1.5-3):(0.5-1):
7.
3. The composite conductive agent according to claim 1 or 2, characterized in that, The one-dimensional conductive agent includes any one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon fibers, and metal nanowires. And / or, the two-dimensional conductive agent is selected from graphene; And / or, the conductive polymer is selected from polypyrrole.
4. The composite conductive agent according to claim 1 or 2, characterized in that, The composite conductive agent also includes a zero-dimensional conductive agent, wherein the mass ratio of the zero-dimensional conductive agent to the conductive polymer is 0.1-0.2:
7.
5. The composite conductive agent according to claim 4, characterized in that, The zero-dimensional conductive agent includes Super-P and / or acetylene black.
6. The method for preparing the composite conductive agent according to any one of claims 1-5, characterized in that, The preparation method includes: The raw material powders are mixed in a solvent to obtain a composite conductive agent slurry, which is then dried to obtain the composite conductive agent.
7. The preparation method according to claim 6, characterized in that, The ratio of the total mass of the raw material powders to the mass of the solvent is (1-6):(30-60); And / or, the solvent is selected from any one or more of ethanol or NMP; And / or, the drying temperature is 95-105°C; And / or, the drying time is 8-12 h.
8. The application of the composite conductive agent as described in any one of claims 1-5 or the composite conductive agent prepared by the preparation method described in claim 6 or 7 in sulfide solid-state batteries.
9. A positive electrode sheet, characterized in that, The positive electrode sheet includes the composite conductive agent as described in any one of claims 1-5 or the composite conductive agent prepared by the preparation method described in claim 6 or 7, as well as the positive electrode active material and the sulfide solid electrolyte.
10. A solid-state battery, characterized in that, The solid-state battery includes the positive electrode sheet as described in claim 9.