Coated conductive agent for all-solid-state battery positive electrode and preparation method and application thereof

Abstract

The application discloses a coated conductive agent for a positive electrode of a full solid-state battery and a preparation method and application thereof, and belongs to the technical field of solid-state batteries. The coated conductive agent is obtained by coating a oxychloride electrolyte buffer layer on the surface of the conductive agent, and the oxychloride electrolyte is generated in situ by low-temperature melting reaction of a chloride electrolyte LiAlCl4 and a metal oxide Sb2O3. The prepared coated conductive agent has high electronic conductivity and ion conduction function, can effectively block the direct electronic contact between the conductive agent and the sulfide solid-state electrolyte, inhibit the interface side reaction, reduce the interface impedance, construct an electron-ion collaborative transmission network, and significantly improve the rate performance and cycle stability of the full solid-state battery. The application has the advantages of simple operation, strong controllability and suitability for large-scale preparation of high-energy-density full solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically, it relates to a coating conductive agent for the positive electrode of an all-solid-state battery, its preparation method and application. Background Technology

[0002] With the development of power batteries and energy storage technologies, all-solid-state lithium batteries have attracted widespread attention due to their advantages such as high safety, high energy density, and excellent cycle life. Sulfide solid electrolytes, with their high ionic conductivity at room temperature and good interfacial contact performance under relatively low forming pressure, have become one of the most promising solid electrolyte materials for all-solid-state batteries. However, sulfide solid electrolytes are prone to interfacial side reactions when in contact with high-voltage cathode materials, severely affecting the battery's cycle stability and rate performance.

[0003] On the one hand, sulfide electrolytes have a limited intrinsic oxidation decomposition potential. When they come into direct contact with cathode materials with operating voltages exceeding 4.2V (such as ternary materials, nickel-rich materials, spinel structures, etc.), their surfaces are prone to oxidation decomposition, generating an electrochemically inert phase, which leads to a gradual increase in interfacial impedance. In addition, the migration of transition metal ions on the surface of the cathode material can also catalyze electrolyte decomposition, further destabilizing the interfacial structure.

[0004] On the other hand, composite cathodes typically require the addition of conductive agents to establish an electron transport network. Commonly used conductive agents, such as conductive carbon (carbon black, acetylene black, carbon nanotubes, graphene, etc.), possess high electronic conductivity and high specific surface area. When the conductive agent comes into direct contact with the sulfide solid electrolyte, an electron leakage pathway is formed, allowing electrons to enter the sulfide electrolyte, which is supposed to be electrically insulating, thereby inducing accelerated oxidative decomposition reactions in the electrolyte. Defects on the surface of the conductive carbon material and its strong surface activity further promote the decomposition of the sulfide electrolyte, leading to a sharp increase in interfacial impedance, accelerated capacity decay, and reduced cycle life.

[0005] Current interface stabilization technologies mainly include surface coating of cathode materials, surface modification of solid electrolytes, or optimization of composite electrode ratios to reduce side reactions. However, these methods typically require complex preparation processes and are difficult to avoid direct contact between the conductive agent and the sulfide electrolyte. Especially during compaction molding, the conductive agent tends to distribute unevenly within the electrode, creating localized high electron density regions, making electron-induced decomposition of the sulfide electrolyte unavoidable. Furthermore, existing coating technologies struggle to simultaneously achieve uniform coverage, ion conductivity, and processing adaptability, thus failing to fundamentally solve the problem of conductive agents disrupting the interfacial stability of sulfide solid electrolytes.

[0006] Therefore, there is an urgent need to provide a new interface stabilization strategy. By coating the conductive agent itself with a coating, the conductive agent can maintain its electron transport capability while blocking direct electronic contact between the conductive agent and the sulfide solid electrolyte. This can effectively suppress the interfacial decomposition reaction of the sulfide electrolyte and improve the chemical and electrochemical stability of the solid-state battery. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a coated conductive agent for the positive electrode of all-solid-state batteries, its preparation method and application.

[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a mixing device for premixing to obtain buffer layer precursor; A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor and conductive agent obtained in step A1 are put into a mixing device and mixed evenly to obtain a conductive agent mixture; the conductive agent mixture is put into a reaction device for low-temperature melting reaction to obtain a coated conductive agent for the positive electrode of all-solid-state battery.

[0009] As a further technical solution, the ratio of the chloride electrolyte to the metal oxide is 1:0.2-0.27.

[0010] As a further technical solution, the mixing equipment is one of a high-energy ball mill, a grinder, a manual grinder, and a high-shear mixer.

[0011] As a further technical solution, the conductive agent is one of VGCF, CNT, CNF, graphene, and Super P.

[0012] As a further technical solution, the ratio of the buffer layer precursor to the conductive agent is 7-9:1-3.

[0013] As a further technical solution, the reaction equipment is one of a muffle furnace, a vacuum tube furnace, and a constant temperature oven.

[0014] As a further technical solution, the reaction environment of the low-temperature melting reaction is a vacuum environment, a nitrogen or argon atmosphere; the reaction conditions are heating to 200-250℃ at a heating rate of 2-5℃ / min, and holding for 1-3 hours.

[0015] This invention coats a conductive agent with a layer of chlorine oxide electrolyte exhibiting ionic conductivity through low-temperature melting. This allows the conductive agent to maintain good electronic conductivity while also possessing ion conduction capabilities, thereby constructing a continuous electron-ion synergistic transport network within the solid-state electrode. This significantly improves the interfacial contact between the conductive agent, solid electrolyte, and cathode particles, reduces interfacial impedance, and increases ion transport efficiency within the electrode. Furthermore, the chlorine oxide electrolyte layer coating the conductive agent effectively suppresses side reactions between the conductive agent, solid electrolyte, and high-potential electrode materials, enhancing interfacial chemical and structural stability. Consequently, it improves the rate performance, cycle performance, and overall electrochemical performance of solid-state batteries, making it suitable for the preparation and application of high-energy-density solid-state batteries.

[0016] The beneficial effects of this invention are: 1. This invention, while maintaining the original high electronic conductivity of the conductive agent, endows it with ion conduction function, and constructs a continuous electron-ion synergistic transport network inside the solid electrode; 2. This invention effectively blocks direct electronic contact between the conductive agent and the sulfide solid electrolyte, inhibits the electrolyte oxidation and decomposition reaction induced by the conductive agent, and reduces interfacial side reactions; 3. This invention significantly reduces interfacial impedance and improves ion transport efficiency in the electrode by improving the contact state between the conductive agent, solid electrolyte and positive electrode particles. 4. This invention uses a low-temperature melting reaction to form a buffer layer, making the coating structure more uniform and dense, thus avoiding the adverse effects of high-temperature treatment on material properties. Thanks to the above improvements, the rate performance, cycle stability and overall electrochemical performance of solid-state batteries can be significantly improved, making them of great application value in the field of high-energy-density solid-state batteries. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] According to the key process parameters of each embodiment shown in Table 1, a coated conductive agent for the positive electrode of an all-solid-state battery was prepared.

[0019] Table 1 Example 1 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a high-energy ball mill at a ratio of 1:0.25 for premixing to obtain the buffer layer precursor; namely 0.25-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.25-ClO) obtained in step A1 and VGCF were added into a high-energy ball mill at a ratio of 8:2 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a vacuum tube furnace for low-temperature melting reaction. The reaction was carried out in a vacuum environment, and the reaction conditions were heating to 250°C at a heating rate of 2°C / min and holding for 2 hours to obtain a coated conductive agent (i.e., VGCF / 0.25-ClO) for the positive electrode of all-solid-state batteries.

[0020] Example 2 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a grinder at a ratio of 1:0.20 for premixing to obtain the buffer layer precursor; namely 0.20-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.20-ClO) obtained in step A1 and CNT were added to a grinder in a ratio of 9:1 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a constant temperature oven for low-temperature melting reaction. The reaction was carried out under a nitrogen protective atmosphere and the reaction conditions were heating to 200℃ at a heating rate of 3℃ / min and holding for 1h to obtain a coated conductive agent (i.e., CNT / 0.20-ClO) for the positive electrode of an all-solid-state battery.

[0021] Example 3 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a high shear mixer at a ratio of 1:0.27 for premixing to obtain the buffer layer precursor, namely 0.27-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.27-ClO) obtained in step A1 and CNF were added to a high-shear mixer in a ratio of 7:3 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a muffle furnace for low-temperature melting reaction. The reaction was carried out under an argon protective atmosphere and the reaction conditions were: heating to 230°C at a heating rate of 5°C / min and holding for 3 hours to obtain a coated conductive agent (i.e., CNF / 0.27-ClO) for the positive electrode of an all-solid-state battery.

[0022] Example 4 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are placed in a manual mortar at a ratio of 1:0.25 and premixed to obtain the buffer layer precursor; namely 0.25-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.25-ClO) obtained in step A1 and graphene were added into a manual mortar at a ratio of 8:2 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a vacuum tube furnace for low-temperature melting reaction. The reaction was carried out in a vacuum environment, and the reaction conditions were heating to 220°C at a heating rate of 2°C / min and holding for 2 hours to obtain a coated conductive agent (i.e., graphene / 0.25-ClO) for the positive electrode of all-solid-state batteries.

[0023] Example 5 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a high-energy ball mill at a ratio of 1:0.20 for premixing to obtain the buffer layer precursor; namely 0.20-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.20-ClO) obtained in step A1 and SuperP were added to a high-energy ball mill at a ratio of 8:2 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a muffle furnace for low-temperature melting reaction. The reaction was carried out under an argon protective atmosphere. The reaction conditions were: heating to 250°C at a heating rate of 4°C / min and holding at that temperature for 1.5h to obtain a coated conductive agent (i.e., Super P / 0.20-ClO) for the positive electrode of an all-solid-state battery.

[0024] Example 6 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a grinder at a ratio of 1:0.27 for premixing to obtain the buffer layer precursor; namely 0.27-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.27-ClO) obtained in step A1 and VGCF were added into a grinder at a ratio of 9:1 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a constant temperature oven for low-temperature melting reaction. The reaction was carried out under a nitrogen protective atmosphere, with the reaction conditions being a heating rate of 3℃ / min, heating to 210℃, and holding at that temperature for 2h to obtain a coated conductive agent (i.e., VGCF / 0.27-ClO) for the positive electrode of an all-solid-state battery.

[0025] Example 7 A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery includes the following steps: A1. Preparation of buffer layer precursor: The raw materials of the buffer layer precursor, chloride electrolyte (LiAlCl4) and metal oxide (Sb2O3), are put into a high shear mixer at a ratio of 1:0.25 for premixing to obtain the buffer layer precursor; namely 0.25-ClO. A2. Preparation of the buffer layer coated conductive agent: The buffer layer precursor (0.25-ClO) obtained in step A1 and CNTs were added to a high-shear mixer at a ratio of 7:3 and mixed evenly to obtain a conductive agent mixture. The conductive agent mixture was placed in a vacuum tube furnace for low-temperature melting reaction. The reaction was carried out under an argon protective atmosphere and the reaction conditions were: heating to 240°C at a heating rate of 5°C / min and holding for 3 hours to obtain a coated conductive agent (i.e., CNT / 0.25-ClO) for the positive electrode of an all-solid-state battery.

[0026] Comparative Example 1 The difference between this comparative example and Example 1 is that in this comparative example, only the chloride electrolyte LiAlCl4 was placed in a high-energy ball mill for mixing, and the metal oxide Sb2O3 was not introduced to obtain the conductive agent.

[0027] Comparative Example 2 VGCF is used directly as a conductive agent.

[0028] Comparative Example 3 The difference between this comparative example and Example 1 is that in this comparative example, no low-temperature melting reaction treatment was performed to obtain the conductive agent.

[0029] Comparative Example 4 The difference between this comparative example and Example 1 is that in this comparative example, the melting reaction process is carried out by heating to 350°C at a heating rate of 5°C / min and holding at that temperature for 2 hours to obtain the conductive agent.

[0030] Comparative Example 5 The difference between this comparative example and Example 1 is that in this comparative example, the chloride electrolyte (LiAlCl4) and the metal oxide (Sb2O3) are fed in a ratio of 1:0.4 to obtain the conductive agent.

[0031] LiNi 0.8 Co 0.1 Mn 0.1 O2 and Li6PS5Cl were mixed with Examples 1 and Comparative Examples 1-5 in a ratio of 75:24.5:0.5 and ground for 30 minutes to obtain a positive electrode mixture. This mixture was used as a raw material to assemble solid-state batteries, and its performance was tested. The test results are shown in Table 2. Table 2 As shown in the table above, the battery assembled in the embodiments of the present invention has significantly higher performance than the comparative examples. The reasons are as follows: In Comparative Example 1, without the introduction of metal oxides, the single chloride electrolyte is difficult to form a stable chemical and structural transition layer between the positive electrode active material and the sulfide solid electrolyte; In Comparative Example 2, without coating the conductive agent, the conductive agent is directly exposed to the interface between the positive electrode active material and the solid electrolyte, which easily leads to interfacial side reactions; In Comparative Example 3, when only physical mixing is performed without undergoing a low-temperature melting reaction, the buffer layer precursor is difficult to form a continuous and dense coating structure on the surface of the conductive agent; In Comparative Examples 4 and 5, when high-temperature treatment is performed or the proportion of metal oxides exceeds a reasonable range, the structural stability and ion transport performance of the buffer layer are adversely affected. Therefore, the positive electrode mixtures obtained in the comparative examples are difficult to achieve ideal results in terms of interfacial compatibility, structural stability, and ion / electron co-transport.

[0032] In this embodiment of the invention, a specific proportion of metal oxides is introduced into the chloride electrolyte to construct a chloride oxide electrolyte buffer layer precursor, and a low-temperature melting reaction is used to coat the buffer layer in situ onto the surface of the conductive agent, thereby forming a stable and continuous coating structure.

[0033] This buffer layer is not a simple physical adhesion, but rather achieves structural rearrangement and interfacial bonding under controlled temperature conditions, enabling the conductive agent surface to simultaneously possess electronic conductivity and good ionic compatibility. Through synergistic control of the metal oxide doping ratio, the precursor-to-conductive agent ratio, and the reaction temperature range, the buffer layer maintains structural stability while avoiding the adverse effects of high-temperature treatment on material properties. It not only suppresses interfacial side reactions but also reduces interfacial impedance. Therefore, this invention has significant application value in the field of solid-state battery technology.

[0034] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery, characterized in that, Includes the following steps: A1. The raw materials of the buffer layer precursor, chloride electrolyte and metal oxide, are put into a mixing device for premixing to obtain the buffer layer precursor. A2. The buffer layer precursor and conductive agent obtained in step A1 are put into a mixing device and mixed evenly to obtain a conductive agent mixture; the conductive agent mixture is put into a reaction device for low-temperature melting reaction to obtain a coated conductive agent for the positive electrode of an all-solid-state battery.

2. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The ratio of the chloride electrolyte to the metal oxide is 1:0.2-0.

27.

3. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The mixing equipment is one of the following: a high-energy ball mill, a grinder, a manual grinder, and a high-shear mixer.

4. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The conductive agent is one of VGCF, CNT, CNF, graphene, and Super P.

5. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The ratio of the buffer layer precursor to the conductive agent is 7-9:1-3.

6. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The reaction equipment is one of a muffle furnace, a vacuum tube furnace, and a constant temperature oven.

7. The method for preparing a coated conductive agent for the positive electrode of an all-solid-state battery according to claim 1, characterized in that, The reaction environment for the low-temperature melting reaction is a vacuum environment, a nitrogen or argon atmosphere; the reaction conditions are a heating rate of 2-5℃ / min to 200-250℃, and a holding time of 1-3h.

8. A coating conductive agent for the positive electrode of an all-solid-state battery, characterized in that, Prepared according to the method according to any one of claims 1-7.

9. The application of the conductive agent prepared by the preparation method according to any one of claims 1-7 or the coating conductive agent for the positive electrode of an all-solid-state battery according to claim 8 in the field of solid-state battery technology.

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