Carbon-based conductive agents with point-to-flake contact anchoring structures, preparation thereof and use in secondary batteries

Abstract

This invention belongs to the field of battery materials, specifically relating to a carbon-based conductive agent with a point-and-sheet contact anchoring structure, its preparation, and application. It comprises layered graphite with a porous structure, and acetylene black nanoparticles anchored on the surface and within the pore structure of the layered graphite. The preparation method of the material is as follows: layered graphite and a pore-forming agent are mixed and subjected to a pore-forming treatment at a temperature T1 of 800~1300℃ to obtain porous layered graphite; the porous layered graphite is then subjected to acetylene deposition treatment to obtain the carbon-based conductive agent with the point-and-sheet contact anchoring structure. The material of this invention exhibits a good fusion interface between the acetylene black and graphite, combining good liquid absorption, DCR (diffusion rate) performance, especially low-temperature DCR performance, and universal applicability to both positive and negative electrodes.

Description

Technical Field

[0001] This invention relates to the field of secondary battery materials, and more specifically to the field of conductive agents for secondary batteries. Background Technology

[0002] Commonly used conductive agents in lithium batteries include carbon black, conductive graphite, VGCF (vapor-grown carbon fiber), carbon nanotubes, and graphene. Conductive carbon black: It exists in chain or grape-like forms and has a high specific surface area. Carbon black can form point-to-point contact with active materials, which is beneficial for electrolyte adsorption and improving ionic conductivity. Adding about 3% is a cost-effective conductive material. Conductive graphite: It is a smaller-particle artificial graphite with more developed pores and specific surface area. It can form point-to-point contact with active materials, which is beneficial for improving the compaction density of electrode particles and increasing ionic and electronic conductivity. When used in the negative electrode, it can increase the negative electrode capacity.

[0003] In existing technologies, research on anode materials is extensive and the technology is relatively mature, but research on conductive agents is relatively scarce. Existing technologies mainly focus on simple composites of components such as carbon black and graphite. For example, Chinese patent document CN118173786A discloses a binary conductive agent composed of a hollow carbon shell and conductive carbon black. Chinese patent document CN115036510A discloses a graphene / carbon black composite conductive agent without added graphene. Chinese patent document CN116613314A discloses a carbon black conductive agent with an oil absorption value ≥200mL / 100g, a primary particle size of 35-45nm, and a BET surface area ≤100m² / g. Chinese patent document CN112768696A discloses an ultra-high conductivity electronic-grade graphene / CNT / carbon black conductive agent. Chinese patent document CN112542590A discloses an easily dispersible carbon black conductive agent, which includes carbon black and carboxymethyl cellulose grafted onto the surface of the carbon black. Chinese patent document CN107516740A discloses a carbon black and graphene powder composite conductive agent.

[0004] In summary, the variety of existing battery conductive agents is still relatively limited. The main issue is the simple compounding and mixing of existing conductive agents, which results in unsatisfactory performance and relatively simple characteristics. Most of them can only be matched with positive or negative electrode active materials alone, and it is difficult to achieve the characteristics of conductive agents that can be used for both positive and negative electrode active materials at the same time. Summary of the Invention

[0005] To address the shortcomings of existing battery conductive agents, this invention provides a carbon-based conductive agent with a patch contact anchoring structure, aiming to provide a conductive agent that has a patch contact anchoring structure and also has excellent electrochemical performance.

[0006] The second objective of this invention is to provide a method for preparing the carbon-based conductive agent of the dotted contact anchoring structure and its application in the preparation of secondary batteries.

[0007] A third objective of this invention is to provide a secondary battery comprising a carbon-based conductive agent with the aforementioned patch contact anchoring structure, as well as its electrodes and electrode materials.

[0008] To achieve better and more stable conductivity, and to better match the properties of the positive and negative electrode active materials, conductive agents used in lithium-ion batteries often need to possess morphologies that better match the active materials, the ability to construct high-strength conductive network structures, high specific surface area, high oil absorption value, high capacity, and high compaction properties. Commonly used conductive agents in lithium-ion batteries include conductive graphite, conductive carbon black, graphene, and carbon nanotubes. Conductive graphite and conductive carbon black are widely used due to their high cost-effectiveness. For example, conductive graphite KS6 and Super PLI conductive carbon black are widely used as conductive agents in the positive and negative electrode materials of lithium-ion batteries. KS-6 conductive agent is mainly equiaxed irregular spherical, which better matches the morphology of the positive electrode active material, but it has a low specific capacity of only 290 mAh / g, high irreversible capacity, low initial efficiency, and poor morphological compatibility with the negative electrode active material. Super PLI is a small-particle conductive carbon black that does not have lithium storage function and only serves a conductive function. For conductive carbon materials, a rich pore structure, high specific surface area, and high oil absorption value are necessary to facilitate the construction of a conductive network in the electrode and improve its solid-phase and liquid-phase conductivity. However, existing conductive carbon products in the industry cannot simultaneously meet the requirements of high capacity, high compaction, and high conductivity, nor can they simultaneously meet the requirements for the use of conductive agents in both positive and negative electrodes. To address this problem, this invention, after in-depth research, provides the following improvement: A carbon-based conductive agent with a point-and-sheet contact anchoring structure includes sheet graphite with a porous structure and acetylene black nanoparticles anchored on the surface of the sheet graphite and in the porous structure.

[0009] This invention provides a carbon-based conductive agent with a point-and-sheet contact anchoring structure. Based on the combination of composition and structure, it can solve the problems faced by conductive agents and can simultaneously possess the characteristics of morphology matching the positive and negative electrode active materials, high capacity, high compaction, high oil absorption value, and high conductivity. It can be widely used as a conductive agent for positive and negative electrodes of lithium batteries.

[0010] Preferably, the porous lamellar graphite has a specific surface area of ​​10~50 m². 2 / g, Dv50 is 1~6μm, acetylene black particle size is 20~300nm, and acetylene black mass fraction is 10~50wt%.

[0011] The present invention also provides a method for preparing the carbon-based conductive agent of the point-and-sheet contact anchoring structure, wherein sheet graphite and a pore-forming agent are mixed and subjected to pore-forming treatment at a temperature T1 to obtain porous sheet graphite; wherein the pore-forming agent is at least one of an alkaline component, a Lewis base component, an acidic component, and a Lewis acid component; and the temperature T1 is 800~1300℃. Porous sheet graphite is placed in a high-temperature reactor and heated. After the temperature rises to T2, an acetylene atmosphere is introduced to begin deposition. After the temperature continues to rise to T3, the deposition continues at this temperature. Acetylene carbon black nanoparticles are anchored and grown on the surface and in the pore structure of the porous sheet graphite to obtain the carbon-based conductive agent with the point-and-sheet contact anchoring structure. The temperature T2 is 800~900℃; the temperature T3 is 1700~2000℃; the weight ratio of acetylene to porous sheet graphite in the acetylene atmosphere is 15~30:100.

[0012] The requirements for conductive agents and active materials differ, as do their requirements for the physicochemical structure of the materials. For example, for carbon-based active materials, the key considerations are the stability and efficiency of ion intercalation and deintercalation. However, for conductive agents, the core considerations are the material's unit structure, oil absorption value, conductivity, and morphological compatibility with active materials. Conductive carbon black and graphite are well-known carbon-based conductive agents, but the compatibility of their physicochemical structures is not ideal. Even when combined, it is difficult to achieve synergistic effects, hindering the material's ability to function as both a positive and negative electrode. To address this preparation problem, this invention innovatively involves performing pore-forming treatment on graphite followed by acetylene vapor deposition. This, combined with the pore-forming and deposition processes, achieves synergy, enabling the preparation of a novel carbon-based conductive agent with a dot-pattern contact anchoring structure. Furthermore, the conductive agent prepared by this method possesses excellent properties such as morphology matching the positive and negative electrode active materials, high capacity, high compaction, high oil absorption value, and high conductivity. In addition, it also meets excellent low-temperature application requirements and can be widely used as a conductive agent for both positive and negative electrodes in lithium batteries.

[0013] In this invention, the sheet graphite can be any graphite material known in the battery field. For example, the sheet graphite is artificial graphite with a sulfur content ≤20ppm, an iron content ≤20ppm, and an ash content ≤0.5%.

[0014] In this invention, the Dv50 of the lamellar graphite is controlled to be 1~7μm before pore formation.

[0015] The research of this invention shows that optimizing the pore-forming method of graphite mainly involves the joint control of parameters such as the pore-forming agent and temperature, which helps to optimize its surface structure. This makes it easier to obtain a conductive agent with excellent bonding interface, excellent oil absorption, low-temperature conductivity and universality.

[0016] In this invention, the pore-forming agent includes one or more mixtures of KOH, KHCO3, NaHCO3, H3PO4, and ZnCl2; more preferably, at least one of KOH, KHCO3, and NaHCO3. In this invention, the preferred pore-forming agent unexpectedly further facilitates the preparation of conductive agents with the special dot-pattern characteristics described in this invention, while also possessing excellent performance, particularly low-temperature DCR performance.

[0017] In this invention, the weight ratio of sheet graphite to pore-forming agent is 1:1 to 3; more specifically, it can be 1:1.5 to 2.5.

[0018] In a preferred embodiment of the present invention, artificial graphite is pretreated in an atmosphere furnace under a carbon dioxide atmosphere at a temperature of 1000-1200°C; subsequently, a pore-forming process is performed. Research in this invention indicates that the preferred pretreatment, combined with the pore-forming process, helps to further construct porous graphite with physicochemical properties conducive to forming the point-surface anchoring structure, and further improves the effectiveness and versatility of the prepared material in conductive agent applications.

[0019] Preferably, the pretreatment time is 18~24h.

[0020] Preferably, the temperature (T1) during the pore-forming process is 850~1200℃.

[0021] Preferably, the heat preservation time at the pore-forming temperature is 3-5 hours.

[0022] Preferably, the pore-forming process is carried out under an inert atmosphere, and the system pressure during the pore-forming stage is controlled at a slightly positive pressure. This study shows that under the preferred process, it is possible to further induce acetylene deposition and improve interfacial bonding performance, thereby enhancing its performance and versatility as a conductive agent.

[0023] Preferably, the pressure of the micro-positive pressure is 0.15~0.25MPa.

[0024] Preferably, the BET of porous sheet graphite is 10~50m. 2 / g.

[0025] The acetylene atmosphere may also contain at least one of an inert gas and oxygen.

[0026] Preferably, the acetylene-containing atmosphere is a mixture of acetylene and oxygen, wherein the acetylene content is above 50 vol% and the oxygen content is below 5 vol% (e.g., 1-5 vol%). Research in this invention shows that incorporating a low oxygen content into the atmosphere can synergistically enhance the process, helping to further improve the performance of the conductive agent and its applicability to both positive and negative electrodes.

[0027] In this invention, the weight ratio of acetylene to porous sheet graphite is 15~25:100.

[0028] Preferably, the flow rate of the acetylene atmosphere is 100~200 ml / min.

[0029] Preferably, the deposition stage is carried out under positive pressure.

[0030] Preferably, the positive pressure is 0.15~0.25 MPa. Studies have shown that this preferred process is more conducive to the performance of the prepared material, especially its low-temperature DCR performance.

[0031] In this invention, the deposition reaction is initiated at temperature T2. This deposition reaction is an exothermic reaction. After the system is heated to temperature T3, it is maintained at this temperature until the deposition is completed.

[0032] The present invention also provides an application of the carbon-based conductive agent of the aforementioned spot contact anchoring structure, using it as a conductive agent for the preparation of secondary batteries.

[0033] Furthermore, it is used as a conductive agent in the preparation of electrodes for secondary batteries. The electrodes are positive and / or negative electrodes; considering the versatility of the prepared conductive agent, it can be both a positive and a negative electrode. In this invention, the conductive agent with these special characteristics, in addition to possessing excellent oil absorption and conductivity, especially low-temperature conductivity, unexpectedly exhibits high compatibility, simultaneously possessing the physicochemical characteristics of both positive and negative electrodes, improving the compatibility and synergy between the positive and negative electrodes, and improving the electrochemical performance of the prepared battery.

[0034] Furthermore, it is used as a conductive agent to mix with electrode active materials to obtain electrode materials for secondary batteries.

[0035] In this invention, the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0036] Preferably, the electrode is a positive electrode and / or a negative electrode.

[0037] In this invention, the carbon-based conductive agent described herein can be used as a conductive agent based on conventional principles and methods to prepare the required secondary battery and its electrodes and electrode materials.

[0038] The present invention also provides an electrode material for a secondary battery, comprising an electrode active material, a binder, and a conductive agent, characterized in that the conductive agent comprises a carbon-based conductive agent with a point-and-sheet contact anchoring structure as described in the present invention.

[0039] The electrode material of this invention, apart from containing the carbon-based conductive agent of the patch contact anchoring structure described in this invention, may have other conventional components and contents. For example, the content of the carbon-based conductive agent of the patch contact anchoring structure in the electrode material may be 1~10 wt.%, more specifically 1~5 wt.%.

[0040] The present invention also provides an electrode for a secondary battery, comprising a current collector and an electrode material composite thereon, wherein the electrode material is the carbon-based conductive agent containing the patch contact anchoring structure described in the present invention.

[0041] The electrode described in this invention can be a positive electrode and / or a negative electrode.

[0042] The present invention also provides a secondary battery comprising the electrodes described herein.

[0043] Beneficial effects This invention provides a carbon-based conductive agent with a patch-type contact anchoring structure, exhibiting excellent performance. Furthermore, this invention also provides a carbon-based conductive agent capable of preparing the patch-type contact anchoring structure, which, based on the combined graphite pore-forming-acetylene deposition process, further incorporates the combined control of the pore-forming and deposition processes. This induces a dotted distribution of acetylene black, improves its fusion interface with graphite, and enhances its liquid absorption and DCR performance, especially low-temperature DCR performance.

[0044] Furthermore, this invention also shows that pretreatment of graphite under a carbon dioxide atmosphere, and / or pore-forming treatment using alkali as a pore-forming agent, and / or pore-forming under micro-positive pressure, and / or deposition under a micro-oxygen acetylene atmosphere, and / or acetylene deposition under micro-positive pressure can further facilitate the induction of acetylene black deposition, improve its fusion interface with graphite, significantly improve the oil absorption value of the material, improve its DCR, and especially improve its low-temperature DCR. Attached Figure Description

[0045] Figure 1 This is an image of the conductive carbon product of Example 1.

[0046] Figure 2 This is an image of the conductive carbon product from Example 2. Detailed Implementation

[0047] To better understand the present invention, the following description, in conjunction with embodiments, further illustrates the present invention; however, the implementation of the present invention is not limited thereto.

[0048] A method for preparing a point-and-pattern contact anchoring structure conductive carbon material and a method for preparing conductive carbon material, comprising the following steps: A1. Pulverize artificial graphite to Dv50 = 1~7μm to obtain material M1; A2. Weigh the pore-forming agent according to a certain mass ratio with material M1, and then prepare the pore-forming agent into a solution; A3. Disperse material M1 into the pore-forming agent solution, stir evenly, and evaporate to dryness to obtain material M2; A4. Place material M2 in an atmosphere furnace and sinter it at a certain temperature. Cool it down and discharge it. Wash it with deionized water until it is neutral and dry it to obtain material M3. A5. Place material M3 in a CVD furnace, introduce inert gas to completely replace the air, then heat it to a certain temperature and introduce inert gas and acetylene gas. Control the acetylene flow rate, pressure and reaction temperature, cool down and discharge to obtain material M4. A6. Material M4 is placed in a VC high-speed mixer for depolymerization to obtain a point-and-piece contact anchoring structure conductive carbon material.

[0049] In this invention, during the acetylene deposition stage, the temperature range from T2 to T3 is heated by the self-exothermic process of acetylene deposition, and external heating can be used as an auxiliary method when necessary.

[0050] Example 1 A1. Pulverize artificial graphite to Dv50 = 5~7μm to obtain material M1; A2. Weigh out the pore-forming agent (potassium hydroxide) according to the mass ratio of material M1 to potassium hydroxide of 1:1.5, and then prepare the potassium hydroxide solution (potassium hydroxide concentration of 0.5~1M). A3. Disperse material M1 into potassium hydroxide solution, stir evenly, and evaporate to dryness to obtain material M2; A4. Place material M2 in an atmosphere furnace and heat it to temperature T1 (1100℃) at a rate of 5℃ / min under nitrogen protection. Hold the temperature for 5 hours, cool it down and discharge it. Then wash it with deionized water until it is neutral and dry it to obtain material M3. A5. Place material M3 in the CVD furnace, introduce nitrogen to completely replace the air in the furnace, then raise the temperature to T2 (850℃) at 5℃ / min, then introduce acetylene gas with a mass ratio of acetylene to material M3 of 20:100 and an acetylene flow rate of 200ml / min. Based on the self-exothermic method, raise the temperature until the reaction temperature reaches T3 (1800℃), maintain the furnace temperature at 1800℃ until the acetylene reaction is complete, then cool down and discharge to obtain material M4. A6. Place material M4 in a VC high-speed mixer at a linear speed of 30 m / s and stir for 30 min to obtain a point-and-piece contact anchoring structure conductive carbon material.

[0051] Example 2 Compared with Example 1, the only difference is that the pore-forming agent was changed, and the experimental groups were as follows: Group A: The pore-forming agent is zinc chloride; Group B: The pore-forming agent is aluminum chloride; All other operations and parameters are the same as in Example 1.

[0052] Example 3 Compared with Example 1, the only difference is that the raw material M1 in step A1 is preheated in a carbon dioxide atmosphere at 1100°C for 20 hours, then cooled and used as raw material for step A2 and subsequent processing; other operations and parameters are the same as in Example 1.

[0053] Example 4 Compared with Example 1, the only difference is that in step A4, nitrogen gas is used to pressurize the system during the pore-forming process, and the system is kept at a pressure of 0.15~0.2MPa. All other operations and parameters are the same as in Example 1.

[0054] Example 5 Compared with Example 1, the only difference is that in step A5, the acetylene atmosphere introduced is an acetylene atmosphere containing 2-3v% oxygen. All other operations and parameters are the same as in Example 1.

[0055] Example 6 Compared with Example 1, the only difference is that in step A5, during the deposition stage, an Ar atmosphere is added, and the system pressure is controlled at 0.2~0.25 MPa until the reaction is complete. Other operations and parameters are the same as in Example 1.

[0056] Example 7 Compared with Example 1, the only difference is that in step A1, the raw material M1 is preheated at 1100°C in a carbon dioxide atmosphere for 20 hours, then cooled and used as raw material for step A2 and subsequent processing; in step A5, the mass ratio of acetylene to material M3 is 25:100; the pressure of the system during the deposition stage is controlled at 0.2~0.25 MPa by adding nitrogen gas until the reaction is complete. Other operations and parameters are the same as in Example 1.

[0057] Example 8 A1. Pulverize artificial graphite to Dv50 = 3~5μm to obtain material M1; A2. Weigh out potassium hydroxide according to the mass ratio of material M1 to potassium hydroxide of 1:2.5, and then prepare potassium hydroxide solution. A3. Disperse material M1 into potassium hydroxide solution, stir evenly, and evaporate to dryness to obtain material M2; A4. Place material M2 in an atmosphere furnace and heat it to 1200℃ at a rate of 5℃ / min under nitrogen protection. Hold the temperature for 4 hours, cool it down and discharge it. Then wash it with deionized water until it is neutral and dry it to obtain material M3. A5. Place material M3 in the CVD furnace, introduce nitrogen to completely replace the air in the furnace, then raise the temperature to 900℃ at 5℃ / min, then introduce acetylene gas with a mass ratio of acetylene to material M3 of 25:100 and an acetylene flow rate of 180ml / min. When the reaction temperature reaches 1900℃, maintain the furnace temperature at 1900℃ until the acetylene reaction is complete, then cool down and discharge to obtain material M4. A6. Place material M4 in a VC high-speed mixer at a linear speed of 30 m / s and stir for 30 min to obtain a point-and-piece contact anchoring structure conductive carbon material.

[0058] Example 9 A1. Pulverize artificial graphite to Dv50 = 3~5μm to obtain material M1; A2. Weigh out potassium hydroxide according to the mass ratio of material M1 to potassium hydroxide of 1:1.5, and then prepare potassium hydroxide solution. A3. Disperse material M1 into potassium hydroxide solution, stir evenly, and evaporate to dryness to obtain material M2; A4. Place material M2 in an atmosphere furnace and heat it to 900℃ at a rate of 5℃ / min under nitrogen protection. Hold the temperature for 6 hours, cool it down and discharge it. Then wash it with deionized water until it is neutral and dry it to obtain material M3. A5. Place material M3 in the CVD furnace, introduce nitrogen to completely replace the air in the furnace, then raise the temperature to 850℃ at 5℃ / min, and then introduce acetylene gas. The mass ratio of acetylene to material M3 is 17:100, and the acetylene flow rate is 120ml / min. Wait for the reaction temperature to rise to 1800℃ and maintain the furnace temperature at 1800℃ until the acetylene reaction is complete. Cool down and discharge the material to obtain material M4. A6. Place material M4 in a VC high-speed mixer at a linear speed of 30 m / s and stir for 30 min to obtain a point-and-piece contact anchoring structure conductive carbon material.

[0059] Comparative Example 1 Compared with Example 1, the only difference is that in step A2, sodium chloride is used to replace the pore-forming agent, while other operations and parameters are the same as in Example 1.

[0060] Comparative Example 2 Compared with Example 1, the only difference is that the pore-forming process is not performed, that is, steps A2 and A3 are missing. M1 from step A1 is used as raw material to directly proceed to step A4 and subsequent processing. Other operations and parameters are the same as in Example 1.

[0061] Comparative Example 3 Compared with Example 1, the only difference is that in step A4, the temperature T1 is controlled at 700°C, while other operations and parameters are the same as in Example 1.

[0062] Comparative Example 4 Compared with Example 1, the only difference is that in step A5, the temperature T3 is controlled at 1300℃, while other operations and parameters are the same as in Example 1.

[0063] Comparative Example 5: Compared with Example 1, the only difference is that in step A5, methane is used instead of the acetylene, while other operations and parameters are the same as in Example 1.

[0064] Comparative Example 6 Compared with Example 1, the only difference is that in step A5, the mass ratio of acetylene to material M3 is 2:100, and other operations and parameters are the same as in Example 1.

[0065] Comparative Example 7 Compared with Example 1, the only difference is that in step A5, the mass ratio of acetylene to material M3 is 40:100, and other operations and parameters are the same as in Example 1.

[0066] Comparative Example 8 Compared with Example 1, the only difference is that porous graphite is prepared by step A4 of Example 1 and then physically mixed with commercial conductive carbon black, wherein the weights of graphite and conductive carbon black are the same as in Example 1.

[0067] The oil absorption value of the material was tested using an oil absorption value tester and the operating method of the new DABS carbon black oil absorption value tester.

[0068] The specific surface area of ​​the material was tested using a specific surface area analyzer according to GB / T 19587-2017 / ISO9277:2010, "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0069] The microstructure of the sample was tested using a scanning electron microscope.

[0070] Using conductive graphite KS6 from TIMCAL Corporation as the positive electrode conductive agent, and LFP as the positive electrode material in the comparative examples, soft-pack laminated full cells with a total capacity of approximately 700 mAh were fabricated. The positive electrode slurry formulation was LFP:PVDF:conductive agent (positive electrode conductive agent) = 96.0:2.0:2.0, and the negative electrode formulation was negative electrode active material:SP (negative electrode conductive agent):CMC:SBR = 95.3:1.0:1.2:2.5. The NP ratio of the full cell was 1.15. The DCR of the full cell was tested using a Landian testing system manufactured by Wuhan Landian Electronics Co., Ltd. DCR at 25°C: The battery was fully charged at 0.33C, then discharged at 0.33C to 50% SOC, and then discharged at 2C for 30 seconds. The DCR at 25°C was calculated. DCR of the battery at -20°C: The battery was fully charged at 0.33C in a 25°C environment, then discharged at 0.33C to 50% SOC, and then placed in a -20°C environment for 2 hours. After that, it was discharged at 0.36C for 30 seconds. The DCR of the battery at -20°C was calculated.

[0071] The conductive carbon products of Examples 1-9 and Comparative Examples 1-8 were tested respectively, and the test results are shown in Table 1.

[0072] Note: In (a), the conductive agent of the positive electrode is KS6, and the conductive agent of the negative electrode is SP.

[0073] In (b), the conductive agent used for both the positive and negative electrodes is the conductive agent prepared in Example 7.

[0074] In (c), it means that the conductive agent in the positive electrode is KS6 and the conductive agent in the negative electrode is the conductive agent prepared in Example 7.

[0075] Comparing Examples 1 and 2, it is evident that using alkali as a pore-forming agent, combined with the process of this invention, unexpectedly achieves a synergistic effect, improving the oil absorption of the conductive agent and the DCR, especially the low-temperature DCR. Furthermore, Examples 1, 3-7 demonstrate that pretreatment of graphite with carbon dioxide... This can further optimize the subsequent carbon black deposition effect, which helps to improve the performance of the prepared conductive agent. In addition, by using the methods described in Example 1, and / or creating pores under micro-positive pressure, and / or depositing under a micro-oxygen acetylene atmosphere, and / or depositing acetylene under micro-positive pressure, it is possible to further induce the deposition of acetylene black, improve its fusion interface with graphite, significantly improve the oil absorption value of the material, and improve its DCR, especially its low-temperature DCR.

[0076] Furthermore, as can be seen from Examples 7, 7(b), and 7(c), the conductive agent described in this invention has the combined compatibility of positive and negative electrodes. In particular, when the conductive agent described in this invention is used for both the positive and negative electrodes, synergy can be achieved to a certain extent, further enhancing the performance.

[0077] The above embodiments only illustrate several implementation methods of the present invention. The descriptions are relatively specific and detailed, but they should not be construed as allowing for various modifications and improvements to be made based on the concept of the present invention. These modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the claims used.

Claims

1. A carbon-based conductive agent with a dot-pattern contact anchoring structure, characterized in that, This includes sheet graphite with a porous structure, and acetylene carbon black nanoparticles anchored on the surface and in the porous structure of the sheet graphite. Preferably, the porous lamellar graphite has a specific surface area of ​​10~50 m². 2 / g, Dv50 is 1~6μm, acetylene black particle size is 50~300nm, and acetylene black mass fraction is 10~50wt%.

2. A method for preparing a carbon-based conductive agent with a dot-pattern contact anchoring structure as described in claim 1, characterized in that, Flake graphite and a pore-forming agent are mixed and kept at a temperature T1 to form pores, thereby obtaining porous flake graphite; the pore-forming agent is at least one of an alkaline component, a Lewis base component, an acidic component, and a Lewis acid component; the temperature T1 is 800~1300℃. Porous sheet graphite is placed in a high-temperature reactor and heated. After the temperature rises to T2, an acetylene atmosphere is introduced to begin deposition. After the temperature continues to rise to T3, the deposition continues at this temperature. Acetylene carbon black nanoparticles are anchored and grown on the surface and in the pore structure of the porous sheet graphite to obtain the carbon-based conductive agent with the point-and-sheet contact anchoring structure. The temperature T2 is 800~900℃; the temperature T3 is 1700~2000℃; the weight ratio of acetylene to porous sheet graphite in the acetylene atmosphere is 15~30:

100.

3. The method for preparing the carbon-based conductive agent with the dot-pattern contact anchoring structure as described in claim 2, characterized in that, The lamellar graphite is artificial graphite with a sulfur content ≤20ppm, an iron content ≤20ppm, and an ash content ≤0.5%. Preferably, the Dv50 of the lamellar graphite is controlled to be 1~7μm before pore formation.

4. The method for preparing the carbon-based conductive agent with the dot-pattern contact anchoring structure as described in claim 2, characterized in that, The pore-forming agent includes one or more mixtures of KOH, KHCO3, NaHCO3, H3PO4, and ZnCl2; Preferably, the weight ratio of sheet graphite to pore-forming agent is 1:1 to 3.

5. The method for preparing the carbon-based conductive agent with the dot-pattern contact anchoring structure as described in any one of claims 2 to 4, characterized in that, First, pre-pores are created in the artificial graphite using carbon dioxide at high temperature. The pulverized artificial graphite is placed in an atmosphere furnace and pretreated at 1000~1200℃ in a carbon dioxide atmosphere. Then, subsequent pore-creating treatment is carried out. Preferably, the pretreatment time is 18~24 hours; Preferably, the temperature T1 is 850~1200℃; Preferably, the heat preservation time at the hole-forming temperature is 3-5 hours; Preferably, the pore-forming process is carried out under an inert atmosphere, and the system pressure during the pore-forming stage is controlled to be slightly positive. Preferably, the pressure of the micro-positive pressure is 0.15~0.25MPa; Preferably, the BET of porous sheet graphite is 10~50m. 2 / g.

6. The method for preparing the carbon-based conductive agent with the dot-pattern contact anchoring structure as described in claim 2, characterized in that, The acetylene atmosphere may also contain at least one of an inert gas and oxygen. Preferably, the acetylene-containing atmosphere is a mixture of acetylene and oxygen, wherein the acetylene content is above 50% and the oxygen content is 1-5% (v / v). Preferably, the flow rate of the acetylene atmosphere is 100~200 ml / min; Preferably, the deposition stage is carried out under positive pressure; Preferably, the positive pressure is 0.15~0.25MPa.

7. The application of a carbon-based conductive agent with a patch contact anchoring structure as described in claim 1, or a carbon-based conductive agent with a patch contact anchoring structure prepared by the preparation method described in any one of claims 2 to 6, characterized in that, It is used as a conductive agent in the preparation of secondary batteries; Preferably, it is used as a conductive agent in the preparation of electrodes for secondary batteries; Preferably, it is used as a conductive agent to mix with electrode active materials to obtain electrode materials for secondary batteries; Preferably, the secondary battery is a lithium-ion battery or a sodium-ion battery; Preferably, the electrode is a positive electrode and / or a negative electrode.

8. An electrode material for a secondary battery, comprising an electrode active material, a binder, and a conductive agent, characterized in that, The conductive agent includes the carbon-based conductive agent with a patch contact anchoring structure as described in claim 1, or the carbon-based conductive agent with a patch contact anchoring structure prepared by the preparation method described in any one of claims 2 to 6.

9. An electrode for a secondary battery, comprising a current collector and an electrode material composited thereon, characterized in that, The electrode material is the electrode material as described in claim 8.

10. A secondary battery, characterized in that, Includes the electrode as described in claim 9.

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