Conductive agent, preparation method of conductive agent, pole piece and secondary battery

Abstract

The present application provides a conductive agent, a method for preparing the conductive agent, an electrode sheet and a secondary battery, and relates to the technical field of lithium batteries; wherein the conductive agent includes a carbon substrate, the surface of the carbon substrate has a target functional group, and the target functional group is bonded to the surface of the carbon substrate; the target functional group includes a first group, and the first group is used to capture transition metal ions. Without affecting the conductivity of the conductive agent itself and the electrical performance of the secondary battery, the present application utilizes the large specific surface area of ​​the carbon substrate to provide a larger setting area for the target functional group used to capture transition metal ions, thereby increasing the proportion of the target functional group in the conductive agent, and thereby improving the ability to capture transition metal ions using the conductive agent.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a conductive agent, a method for preparing the conductive agent, a pole piece and a secondary battery. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, no memory effect, good safety performance and environmental friendliness, and are widely used in electronic equipment, power storage stations, new energy vehicles, etc. However, as the number of cycles continues to increase, transition metal ions (such as nickel ions, manganese ions, etc.) in the positive electrode active materials of lithium-ion batteries will dissolve into the electrolyte, resulting in reduced cycle performance and safety performance of lithium-ion batteries.

[0003] At present, transition metal ions dissolved into the electrolyte are usually captured by coating the surface of the positive electrode active material or adding a transition metal complex to the positive electrode active material.

[0004] However, the surface coating method of the positive electrode active material will affect the embedding and extraction of lithium ions in the positive electrode active material, thereby causing a decrease in the electrical performance of the lithium-ion battery. Although the method of adding transition metal complexes to the positive electrode active material will not affect the embedding and extraction of lithium ions, the transition metal complexes added to the positive electrode active material are usually small molecular weight substances that are easily dissolved in the electrolyte, resulting in a decrease in the electrical performance of the lithium-ion battery. Summary of the invention

[0005] The embodiments of the present application provide a conductive agent, a method for preparing the conductive agent, an electrode sheet and a secondary battery to solve the problem in the related art that the process of capturing transition metal ions dissolved from the positive electrode active material affects the deintercalation process of lithium ions in the positive electrode active material, and the transition metal complex is easily dissolved in the electrolyte, thereby causing the electrical performance of the lithium ion battery to decrease.

[0006] In order to solve the above problems, the present application is implemented through the following technical solutions:

[0007] The present application proposes a conductive agent, which includes a carbon substrate, the surface of the carbon substrate has a target functional group, and the target functional group is bonded to the surface of the carbon substrate;

[0008] The target functional group includes a first group, and the first group is used to capture transition metal ions.

[0009] Furthermore, in the conductive agent, the target functional group further includes a second group, and the target functional group is bonded to a hydroxyl group on the surface of the carbon substrate via the second group.

[0010] Furthermore, in the conductive agent, the target functional group further includes a second group, and the conductive agent further includes a binder;

[0011] The binder is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group is bonded to the hydroxyl groups on the surface of the carbon substrate and / or the binder through the second group.

[0012] Furthermore, in the conductive agent, the binder includes at least one of acrylic, olefin and silane.

[0013] Furthermore, in the conductive agent, the second group includes at least one of a carboxyl group, an ester group, an isocyanate group and a halogen atom.

[0014] Furthermore, in the conductive agent, pores are provided in the carbon substrate, and the pores are used to capture the transition metal ions.

[0015] Furthermore, in the conductive agent, the size of the pores is 50 nm to 200 nm.

[0016] Furthermore, in the conductive agent, the first group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group and a pyrrole group.

[0017] Furthermore, in the conductive agent, the carbon substrate is any one of carbon black, carbon nanotubes, graphene, and carbon fiber.

[0018] The present application also provides a method for preparing a conductive agent, the method comprising:

[0019] providing a carbon substrate;

[0020] A target functional group donor having a target functional group is reacted with the carbon substrate to bond the target functional group to the surface of the carbon substrate to form a conductive agent; wherein the target functional group includes a first group for capturing transition metal ions.

[0021] Furthermore, in the method, the first group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group and a pyrrole group.

[0022] Furthermore, in the method, the target functional group donor further includes a second group; the step of reacting the target functional group donor having the target functional group with the carbon substrate so that the target functional group is bonded to the surface of the carbon substrate to form a conductive agent comprises:

[0023] The second group reacts with the hydroxyl groups on the surface of the carbon substrate, so that the target functional group is bonded with the hydroxyl groups on the surface of the carbon substrate to form a conductive agent.

[0024] Furthermore, in the method, the target functional group donor further includes a second group; the method further includes:

[0025] The binder donor and the second group react with the hydroxyl groups on the surface of the carbon substrate simultaneously, so that the adhesive provided by the binder donor bonds with the hydroxyl groups on the surface of the carbon substrate, and the target functional group bonds with the hydroxyl groups on the surface of the carbon substrate to form a conductive agent.

[0026] Furthermore, in the method, the target functional group donor further includes a second group; the method further includes:

[0027] reacting a binder donor with hydroxyl groups on the surface of the carbon substrate so that the adhesive provided by the binder donor is bonded to the hydroxyl groups on the surface of the carbon substrate to form a binder bonded to the hydroxyl groups on the surface of the carbon substrate;

[0028] The second group reacts with the binder to bond the target functional group to the binder to form a conductive agent.

[0029] Furthermore, in the method, the target functional group donor further includes a second group; the method further includes:

[0030] The second group of the first part of the target functional group donor and the binder donor are reacted with the hydroxyl groups on the surface of the carbon substrate at the same time, so that the adhesive provided by the binder donor is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group provided by the first part of the target functional group donor is bonded to the hydroxyl groups on the surface of the carbon substrate, forming the binder and the target functional group bonded to the hydroxyl groups on the surface of the carbon substrate;

[0031] The second group of the target functional group donor of the second part reacts with the binder, so that the target functional group provided by the target functional group donor of the second part is bonded with the binder to form a conductive agent.

[0032] Furthermore, in the method, the binder donor includes at least one of acrylic, olefin and silane.

[0033] Furthermore, in the method, providing the carbon substrate comprises:

[0034] Co-depositing a carbon source and pore-forming particles to prepare a carbon-based composite material; the carbon-based composite material includes a carbon substrate formed by the carbon source and pore-forming particles dispersed in the carbon substrate;

[0035] The pore-forming particles in the carbon-based composite material are removed to obtain a carbon substrate; the carbon substrate includes pores formed after the pore-forming particles are removed.

[0036] Furthermore, in the method described above, the Dv50 particle size of the pore-forming particles is 50 nm to 200 nm, and the Dv50 represents the particle size corresponding to when the cumulative volume distribution percentage of the pore-forming particles is equal to 50%.

[0037] Furthermore, in the method, the pore-forming particles are silicon dioxide particles; and removing the pore-forming particles from the carbon-based composite material to obtain a carbon substrate comprises:

[0038] The silicon dioxide particles in the carbon-based composite material are dissolved by hydrofluoric acid to obtain a carbon substrate.

[0039] The present application also provides a pole piece, the pole piece comprising a positive pole piece and / or a negative pole piece;

[0040] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a transition metal ion, and the positive electrode active material layer further comprises a conductive agent as described in any one of the above items;

[0041] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and at least one of the negative electrode active material layers further includes the conductive agent as described in any one of the above items.

[0042] Furthermore, in the pole piece, the conductive coating of the positive electrode current collector and / or the negative electrode current collector includes the conductive agent as described in any one of the above items.

[0043] The present application also provides a secondary battery, which includes the electrode sheet as described above.

[0044] The present application also provides an electric device, which includes the secondary battery as described above, and the secondary battery serves as a power supply for the electric device.

[0045] Compared with the prior art, this application has the following advantages:

[0046] The conductive agent provided in the embodiment of the present application includes a carbon substrate, and the surface of the carbon substrate has a target functional group. The surface of the carbon substrate is modified by the target functional group, and the first group in the target functional group can be used to capture the transition metal ions dissolved from the positive electrode active material, without affecting the embedding and extraction process of lithium ions in the positive electrode active material. In addition, the target functional group is bonded to the surface of the carbon substrate and is not easily dissolved into the electrolyte, thereby not causing the attenuation of the electrical performance of the secondary battery, thereby improving the electrical performance of the secondary battery.

[0047] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A flowchart of the steps of a method for preparing a conductive agent provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0050] The present invention provides a conductive agent, comprising a carbon substrate, the surface of the carbon substrate having a target functional group, the target functional group being bonded to the surface of the carbon substrate, wherein the target functional group comprises a first group, and the first group is used to capture transition metal ions.

[0051] In the present application, transition metal ions are transition metal ions introduced into the positive electrode active material during the manufacturing process. The first group is any functional group that can be complexed with the above transition metal ions, and the target functional group is an organic functional group containing the first group, and the first group includes at least one of a carboxyl group (-COOH), an amino group (-NH2), an ester group (-COO-), a nitro group (-NO2), pyridine and pyrrole.

[0052] The carbon substrate serves as the matrix of the conductive agent provided in the embodiment of the present application. The surface of the carbon substrate includes hydroxyl groups, and the carbon substrate can bond target functional groups on its surface through the hydroxyl groups.

[0053] Optionally, in some embodiments, the target functional group further includes a second group, and the target functional group is bonded to a hydroxyl group on the surface of the carbon substrate through the second group.

[0054] The second group is used to increase the binding force of the target functional group on the surface of the carbon substrate and improve the adsorption stability of the target functional group on the surface of the carbon substrate. The second group is any group that can bond with the hydroxyl group on the surface of the carbon substrate.

[0055] Optionally, the second group may include a carboxyl group, an ester group, an isocyanate group (-NCO) and a halogen atom (-X) in a halogenated hydrocarbon. In addition to increasing the bonding effect, the above functional groups also have delocalized lone electrons, which increase the conductivity of the carbon-based surface, so that the conductive agent provided by the present application can still have excellent conductivity after the surface is combined with the target functional group.

[0056] In the case where the conductive agent provided in the embodiment of the present application includes a carbon substrate and a target functional group grafted on the surface of the carbon substrate, the target functional group is grafted on the surface of the carbon substrate via a second group bonded to the hydroxyl group on the surface of the carbon substrate, and the conductive agent can utilize the first group of the target functional group grafted on the surface of the carbon substrate to capture transition metal ions dissolved from the positive electrode active material.

[0057] It should be noted that since the carbon substrate in the conductive agent has a large specific surface area, it can provide more bonding sites for the target functional groups, so that the conductive agent provided in the embodiment of the present application contains a large number of first groups for capturing transition metal ions, which is beneficial to the enrichment of transition metal ions on the surface of the conductive agent, thereby improving the ability and efficiency of the conductive agent provided in the embodiment of the present application to capture transition metal ions.

[0058] Optionally, in some embodiments, the target functional group further includes a second group, and the conductive agent further includes a binder; the binder is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group is bonded to the hydroxyl groups on the surface of the carbon substrate and / or the binder through the second group.

[0059] Among them, the binder is a binder commonly used in positive electrode active materials and negative electrode active materials in secondary batteries. When the binder is included in the conductive agent, the binder can be used to capture transition metal ions dissolved from the positive electrode active material and increase the adhesion of the conductive agent in the electrode sheet.

[0060] In the embodiments of the present application, the binder can be grafted onto the surface of the carbon substrate; the target functional group can be grafted onto the surface of the carbon substrate, or onto the polymer chain of the binder, or can be grafted onto the surface of the carbon substrate and onto the polymer chain of the binder at the same time, and the embodiments of the present application do not make specific limitations on this.

[0061] It can be understood that when the conductive agent provided in the embodiment of the present application includes a target functional group, a binder and a carbon substrate, the binder is bonded to the hydroxyl group on the surface of the carbon substrate and grafted to the surface of the carbon substrate. The conductive agent can simultaneously utilize the binder grafted to the surface of the carbon substrate and the first group of the target functional group to capture transition metal ions dissolved from the positive electrode active material, thereby improving the capture efficiency of the transition metal ions.

[0062] Specifically, in some embodiments, when the conductive agent provided in the embodiments of the present application includes a target functional group, a binder and a carbon substrate at the same time, the binder and the target functional group can be simultaneously grafted to the surface of the carbon substrate, and the proportion of the binder and the target functional group on the surface of the carbon substrate is determined according to the actual use requirements of the conductive agent, which is not limited in the embodiments of the present application.

[0063] In other embodiments, when the conductive agent provided in the embodiments of the present application includes a target functional group, a binder and a carbon substrate at the same time, the binder is directly grafted onto the surface of the carbon substrate, and the target functional group is grafted onto the polymer chain of the binder through a second group; wherein the target functional group can form a double bond by polymerizing with the polymer chain of the binder through the second group, thereby achieving grafting onto the polymer chain of the binder through the second group, increasing the bonding stability of the binder surface, and thereby improving the metal ion adsorption effect.

[0064] In some other embodiments, when the conductive agent provided in the embodiments of the present application includes a target functional group, a binder and a carbon substrate at the same time, the binder and part of the target functional groups can be grafted onto the surface of the carbon substrate at the same time, and another part of the target functional groups can be grafted onto the polymer chain of the binder through a second group.

[0065] In an embodiment of the present application, the conductive agent includes a target functional group, a binder and a carbon substrate; the target functional group also includes a second group; in the conductive agent, the binder is bonded to the hydroxyl groups on the surface of the carbon substrate; the target functional group is bonded to the hydroxyl groups on the surface of the carbon substrate and / or the hydroxyl groups in the binder through the second group, so that the conductive agent can simultaneously utilize the binder and the first group in the target functional group to capture transition metal ions, providing more complexation sites for transition metal ions, thereby improving the efficiency of capturing transition metal ions.

[0066] Optionally, in some embodiments, the binder includes at least one of acrylic, olefin, and silane.

[0067] Among them, acrylic acid can be acrylic acid (Acrylic acid, AA, CH2 = CHCOOH) monomer, or polyacrylic acid (Polyacrylic acid, PAA), acrylic acid polymers (Acrylic acid Polymers, (C3H4O2) n )wait.

[0068] Olefins may be olefin monomers, such as 1-butene (n-butene), 1-hexene (hexene), 1-octene (octene), methyl methacrylate (MMA), styrene, etc. Olefins may also be olefin polymers, such as polyethylene (PE), polypropylene (PP), polybutene (PB-D1), poly-4-methyl-1-pentene (PM-Mw), etc.

[0069] Silanes can be silane monomers, such as methyl chlorosilane, phenyl chlorosilane, vinyl chlorosilane, ethyl trichlorosilane, propyl trichlorosilane, chloropropyl trichlorosilane, and fluorosilicone monomer. Silanes can also be silane polymers, such as polydimethylsiloxane (PDMS), polydiphenylsiloxane, and polysilazane (PSZ).

[0070] Optionally, in some embodiments, in the conductive agent provided in the embodiments of the present application, pores are provided in the carbon substrate, and the pores are used to capture the transition metal ions.

[0071] The pores provided in the carbon substrate are nanoscale pores with physical adsorption effects. When the conductive agent includes pores, the conductive agent can adsorb transition metal ions dissolved from the positive electrode active material through the pores. In the embodiment of the present application, the conductive agent can simultaneously use the first group of the target functional group and the pores provided in the carbon substrate to adsorb transition metal ions dissolved from the positive electrode active material, thereby capturing the transition metal ions.

[0072] The surface of the carbon substrate may be etched by a steam etching process known to those skilled in the art to obtain holes disposed in the carbon substrate.

[0073] Optionally, in the case where pores are provided in the carbon substrate, the size of the pores is 50 nanometers (nm) to 200 nm, so as to achieve a good physical adsorption effect on transition metal ions; illustratively, the size of the pores can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm and 200 nm, or any two of the range values. In the present application, the test methods for the size of the pores in the carbon substrate include gas adsorption method or mercury injection method, and the test results of the two test methods are close and within an acceptable range.

[0074] Optionally, in some embodiments, the target functional group also includes a second group, and the conductive agent provided in the embodiments of the present application includes a carbon substrate and a target functional group, and holes are provided in the carbon substrate; in this scenario, the holes are provided in the carbon substrate, and the target functional group is grafted to the surface of the carbon substrate through the second group, and the conductive agent can simultaneously utilize the first group and the holes in the target functional group to capture transition metal ions, thereby improving the ability of the conductive agent to capture transition metal ions.

[0075] Optionally, in some embodiments, the conductive agent includes a target functional group, a binder and a carbon substrate, and a hole is provided in the carbon substrate; in the conductive agent, the binder is bonded to the hydroxyl group on the surface of the carbon substrate, and the target functional group is bonded to the hydroxyl group and / or the binder on the surface of the carbon substrate through the second group. In the embodiment of the present application, while the first group of the target functional group in the conductive agent and the binder are used to capture transition metal ions, more complexation sites are provided for transition metal ions, and the holes provided in the carbon substrate can also be used to physically adsorb transition metal ions, further improving the ability of the conductive agent to capture transition metal ions dissolved from the positive electrode active material.

[0076] Optionally, in some embodiments, the first group of the target functional group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group, and a pyrrole group.

[0077] Optionally, in some embodiments, the carbon substrate in the conductive agent can be any one of carbon black (e.g., conductive carbon black), carbon nanotubes (e.g., single-walled carbon nanotubes), graphene (e.g., single-layer graphene, multi-layer graphene), and carbon fiber (e.g., vapor-phase carbon fiber).

[0078] It can be understood that by using any one of carbon black, carbon nanotubes, graphene, and carbon fiber as the carbon substrate in the conductive agent, while ensuring the conductivity of the conductive agent, the larger specific surface area of ​​the carbon substrate can also be used to provide more bonding sites for the binder and / or target functional groups, so that the conductive agent provided in the embodiment of the present application contains a large amount of binder and / or target functional groups for capturing transition metal ions, which is beneficial to the enrichment of transition metal ions on the surface of the conductive agent, thereby improving the ability and efficiency of the conductive agent provided in the embodiment of the present application to capture transition metal ions.

[0079] Optionally, in some embodiments, the second group in the binder and / or the target functional group can achieve bonding with the hydroxyl groups on the surface of the carbon substrate by reacting with the hydroxyl groups on the surface of the carbon substrate to undergo esterification, silanol dehydration, etherification, isocyanate group reaction, etc.

[0080] Related technologies generally capture transition metal ions dissolved from positive electrode active materials in the following ways:

[0081] Method 1: A porous conductive polyamic acid dispersion containing an imidazole structure is prepared by an in-situ polymerization method, and a polyamic acid-coated lithium ion positive electrode active material with a porous conductive structure is prepared based on the porous conductive polyamic acid dispersion containing an imidazole structure. A porous conductive polyimide coating layer containing an imidazole structure is provided on the surface of the positive electrode active material to capture transition metal ions. However, the coating of the positive electrode active material will affect the embedding and extraction process of lithium ions during the charge and discharge cycle, thereby affecting the electrical performance of the lithium ion battery.

[0082] Method 2: Dissolve the manganese ion chelator in water, prepare a coating slurry with a binder, a dispersant, and an inorganic oxide, and apply the coating slurry to the surface of the lithium-ion battery separator to form a coating with transition metal ion adsorption function, which effectively absorbs the transition metal ions dissolved in the electrolyte. However, this method does not inhibit the dissolution of transition metal ions from the source, and some of the dissolved transition metal ions cannot be adsorbed, resulting in reduced stability of the lithium-ion battery.

[0083] Method 3: Add transition metal complexes to the positive electrode slurry, so that even if transition metal ions are dissolved in the positive electrode active material, they can be captured, thereby inhibiting the damage of transition metal ions to the negative electrode material, reducing the consumption of active lithium ions, and improving the cycle performance. However, the transition metal complexes added to the positive electrode active material are all small molecular weight substances, which are easily dissolved in the electrolyte, resulting in the attenuation of the electrical performance of the lithium-ion battery.

[0084] Method 4: By modifying polyvinylidene fluoride and using the modified polyvinylidene fluoride to capture transition metal ions dissolved from the positive electrode active material, the electrochemical performance of lithium-ion batteries can be improved. However, the amount of polyvinylidene fluoride added to lithium-ion batteries is small, and it is difficult to effectively capture more transition metal ions during the long-term charge and discharge cycle of lithium-ion batteries.

[0085] The conductive agent provided in the embodiment of the present application includes a carbon substrate, and the surface of the carbon substrate has a target functional group. The surface of the carbon substrate is modified by the target functional group, and the first group in the target functional group can be used to capture the transition metal ions dissolved from the positive electrode active material, without affecting the embedding and extraction process of lithium ions in the positive electrode active material. The target functional group can be bonded to the surface of the carbon substrate through the functional group and is not easily dissolved into the electrolyte, thereby not causing the attenuation of the electrical performance of the secondary battery. In addition, the embodiment of the present application utilizes the large specific surface area of ​​the carbon substrate to provide a larger setting area for the target functional group for capturing transition metal ions, thereby increasing the proportion of the target functional group in the conductive agent, providing more capture sites for long-term transition metal ion capture, and improving the ability and efficiency of the conductive agent to capture transition metal ions.

[0086] Furthermore, the conductive agent provided in the embodiment of the present application can be applied to the conductive coating of the positive active material, the negative active material and the current collector of the secondary battery, further improving the effect of capturing transition metal ions using the conductive agent provided in the embodiment of the present application. The embodiment of the present application modifies the carbon substrate by the target functional group, and can also improve the dispersion effect of the conductive agent in the conductive coating of the positive active material, the negative active material and the current collector, thereby improving the uniformity of the conductivity of the conductive coating of the material, the negative material and the current collector, and thus improving the electrical performance of the secondary battery.

[0087] The present application also provides a method for preparing a conductive agent, such as Figure 1 As shown, the method includes steps S101 to S102:

[0088] Step S101: providing a carbon substrate.

[0089] Step S102: reacting a target functional group donor having a target functional group with the carbon substrate so that the target functional group is bonded to the surface of the carbon substrate to form a conductive agent.

[0090] Wherein, the target functional group includes a first group for capturing transition metal ions.

[0091] In step S101, a secondary battery conductive agent known to those skilled in the art may be used as a carbon substrate, or a conductive agent known to those skilled in the art may be subjected to steam etching to obtain a carbon substrate provided with pores. It is understood that the pores are nanoscale pores with physical adsorption effects, and when the pores are provided in the carbon substrate, the conductive agent may adsorb transition metal ions dissolved from the positive electrode active material through the pores.

[0092] Specifically, under high-temperature steam conditions, part of the carbon atoms on the surface of the conductive agent known to those skilled in the art can be reacted with high-temperature steam to obtain a carbon substrate with pores.

[0093] In step S102, the reaction between the target functional group donor and the carbon substrate refers to the reaction between the second group of the target functional group in the target functional group donor and the hydroxyl group on the surface of the carbon substrate. The reaction between the second group of the target functional group and the hydroxyl group on the surface of the carbon substrate may include but is not limited to at least one of free radical polymerization, ultraviolet light-induced polymerization, irradiation reaction and esterification reaction.

[0094] Among them, the free radical polymerization reaction refers to the process of uniformly dispersing the target functional group donor and the carbon substrate under high-speed dispersion conditions, adding a free radical initiator, reacting at 40 degrees Celsius (℃) to 90 degrees Celsius for 0.1 hour (h) to 12 hours, adding ethanol for precipitation and washing, and the resulting precipitate is dried and crushed to form a conductive agent.

[0095] The ultraviolet light-initiated polymerization reaction refers to uniformly dispersing the target functional group donor and the carbon substrate under high-speed dispersion conditions, adding a photoinitiator, irradiating with light at about 250nm~420nm, reacting at 40℃~90℃ for 2h~12h, adding ethanol for precipitation and washing, and the obtained precipitate is dried and crushed to form a conductive agent.

[0096] The esterification reaction refers to uniformly dispersing the target functional group donor and the carbon substrate under high-speed dispersion conditions, adding a catalyst such as sulfuric acid, phosphoric acid or formic acid, reacting at 40°C to 120°C for 2h to 12h, adding ethanol for precipitation and washing, and the obtained precipitate is dried and crushed to form a conductive agent.

[0097] It can be understood that, when no pores are provided in the carbon substrate provided in step S101, the conductive agent formed in step S102 includes the target functional group and the carbon substrate without pores, and at this time, the conductive agent can use the first group in the target functional group to capture transition metal ions; when pores are provided in the carbon substrate provided in step S101, the conductive agent formed in step S102 includes the target functional group and the carbon substrate with pores, and at this time, the conductive agent can use the first group in the target functional group and the pores in the carbon substrate to capture transition metal ions.

[0098] In the embodiment of the present application, the target functional group includes a first group, and the first group is used to capture transition metal ions. The transition metal ions are transition metal ions added to the positive electrode active material of the secondary battery, and the transition metal ions may include but are not limited to: cobalt ions, nickel ions, manganese ions and aluminum ions.

[0099] The first group is any functional group that can complex with the above transition metal ions, and the target functional group is an organic functional group containing the first group. For example, the first group can be the -X group of a halogenated hydrocarbon, which has a strong electron affinity and a strong ability to form a complex with the transition metal ions; the first group can also be a hydroxyl group, which has a strong polarity and hydrophilicity and a strong ability to form a complex with the transition metal ions.

[0100] The carbon substrate serves as the matrix of the conductive agent formed in the embodiment of the present application. The surface of the carbon substrate includes hydroxyl groups, and the carbon substrate can be grafted with a binder or a target functional group on its surface through the hydroxyl groups.

[0101] Optionally, in some embodiments, the target functional group donor includes at least one of acrylic, olefinic, and silane, nitrogen-containing, pyridine, and pyrrole.

[0102] In the embodiment of the present application, the target functional group donor is a small molecule substance. In other words, the target functional group donor can be at least one of acrylic monomer, olefin monomer, silane monomer, ester, pyridine and pyrrole.

[0103] Optionally, in some embodiments, the first group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group, and a pyrrole group.

[0104] Optionally, in some embodiments, the target functional group donor further includes a second group; and the step S102 of reacting the target functional group donor having the target functional group with the carbon substrate so that the target functional group is bonded to the surface of the carbon substrate to form a conductive agent includes:

[0105] The second group reacts with the hydroxyl groups on the surface of the carbon substrate, so that the target functional group is bonded with the hydroxyl groups on the surface of the carbon substrate to form a conductive agent.

[0106] The reaction of the second group with the hydroxyl group on the surface of the carbon substrate refers to a process in which the second group of the target functional group donor and the hydroxyl group on the surface of the carbon substrate form a chemical bond by sharing electrons or transferring electrons.

[0107] Specifically, in the case where no pores are provided in the carbon substrate provided in step S101, the conductive agent formed in step S102 includes a carbon substrate without pores and a target functional group grafted on the surface of the carbon substrate, and the target functional group reacts with the hydroxyl group on the surface of the carbon substrate through the second group to be grafted on the surface of the carbon substrate, and the conductive agent can capture transition metal ions dissolved from the positive electrode active material using the first group of the target functional group grafted on the surface of the carbon substrate. In the case where pores are provided in the carbon substrate provided in step S101, the conductive agent formed in step S102 includes a carbon substrate with pores, a target functional group grafted on the surface of the carbon substrate, and the conductive agent can capture transition metal ions dissolved from the positive electrode active material using the first group of the target functional group grafted on the surface of the carbon substrate and the pores.

[0108] The second group is any group that can bond with the hydroxyl group on the surface of the carbon substrate; the second group may include but is not limited to a carboxyl group, an ester group, an isocyanate group, and a halogen atom in a halogenated hydrocarbon.

[0109] In some embodiments, the target functional group donor further comprises a second group; and the method further comprises:

[0110] The binder donor and the second group react with the hydroxyl groups on the surface of the carbon substrate simultaneously, so that the adhesive provided by the binder donor bonds with the hydroxyl groups on the surface of the carbon substrate, and the target functional group bonds with the hydroxyl groups on the surface of the carbon substrate to form a conductive agent.

[0111] Optionally, the binder donor includes at least one of acrylic, olefin and silane.

[0112] In an embodiment of the present application, the conductive agent includes a carbon substrate, a binder and a target functional group; wherein the binder donor reacts with the hydroxyl groups on the surface of the carbon substrate, and the target functional group donor also reacts with the hydroxyl groups on the surface of the carbon substrate through a second group, so that the binder and the target functional group provided by the binder donor are directly bonded to the surface of the carbon substrate.

[0113] Optionally, in some embodiments, the target functional group donor further includes a second group; and the method further includes steps A11 to A12:

[0114] Step A11: reacting a binder donor with hydroxyl groups on the surface of the carbon substrate, so that the adhesive provided by the binder donor bonds with the hydroxyl groups on the surface of the carbon substrate to form a binder bonded with the hydroxyl groups on the surface of the carbon substrate.

[0115] Step A12: reacting the second group with the binder to bond the target functional group to the binder to form a conductive agent.

[0116] In an embodiment of the present application, the conductive agent includes a carbon substrate, a binder and a target functional group; wherein the binder donor reacts with the hydroxyl group on the surface of the carbon substrate through step A11, and the target functional group donor reacts with the binder through the second group to form a conductive agent; the binder in the conductive agent is directly bonded to the surface of the carbon substrate, and the target functional group is indirectly bonded to the surface of the carbon substrate by bonding to the polymer chain of the binder.

[0117] The reaction of the second group with the binder can be specifically the reaction of the second group of the target functional group donor with the binder, and the target functional group in the conductive agent is bonded to the polymer chain of the binder through the second group to form a double bond.

[0118] Optionally, in some embodiments, the conductive agent further comprises a binder; the target functional group donor further comprises a second group; and the method further comprises steps A13 to A14:

[0119] Step A13, reacting the second group of the first part of the target functional group donor and the binder donor with the hydroxyl groups on the surface of the carbon substrate at the same time, so that the adhesive provided by the binder donor is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group provided by the first part of the target functional group donor is bonded to the hydroxyl groups on the surface of the carbon substrate, to form a binder bonded to the hydroxyl groups on the surface of the carbon substrate and a target functional group bonded to the hydroxyl groups on the surface of the carbon substrate.

[0120] Step A14: reacting the second group of the target functional group donor of the second part with the binder so that the target functional group provided by the target functional group donor of the second part is bonded with the binder to form a conductive agent.

[0121] In an embodiment of the present application, the conductive agent includes a carbon substrate, a binder and a target functional group; wherein, first, the binder donor and the first part of the target functional group donor are reacted with the hydroxyl groups on the surface of the carbon substrate at the same time through step A13 to form a binder bonded to the hydroxyl groups on the surface of the carbon substrate and a target functional group bonded to the hydroxyl groups on the surface of the carbon substrate; then, the second part of the target functional group donor is reacted with the binder on the surface of the carbon substrate through step A14 to form a conductive agent; the binder in the conductive agent is directly bonded to the surface of the carbon substrate, the target functional group provided by the first part of the target functional group donor in the conductive agent is bonded to the hydroxyl groups on the surface of the carbon substrate through the second group, and the target functional group provided by the second part of the target functional group donor in the conductive agent is bonded to the polymer chain of the binder through the second group to form a double bond, and is bonded to the polymer chain of the binder.

[0122] It should be noted that the target functional groups provided by the first part of the target functional group donor and the target functional groups provided by the second part of the target functional group donor together constitute the target functional groups in the conductive agent; in the embodiment of the present application, the dosage of the first part of the target functional group donor in step A13 and the dosage of the second part of the target functional group donor in step A14 can be determined according to actual needs, and the embodiment of the present application does not make specific limitations on this.

[0123] In addition, in the case where the carbon substrate provided in step S101 is provided with no pores, the conductive agent formed in step S102 includes a carbon substrate without pores, a binder and a target functional group, and the conductive agent can capture transition metal ions dissolved from the positive electrode active material using the binder and the target functional group. In the case where the carbon substrate provided in step S101 is provided with pores, the conductive agent formed in step S102 includes a carbon substrate with pores, a binder and a target functional group, and the conductive agent can simultaneously capture transition metal ions dissolved from the positive electrode active material using the binder, the target functional group and the pores, thereby improving the conductive agent's ability to capture transition metal ions.

[0124] Optionally, in some embodiments, the step S101 of providing a carbon substrate includes steps S1011 to S1012:

[0125] Step S1011, co-depositing a carbon source and pore-forming particles to prepare a carbon-based composite material; the carbon-based composite material includes a carbon substrate formed by the carbon source and pore-forming particles dispersed in the carbon substrate.

[0126] Step S1012: removing the pore-forming particles in the carbon-based composite material to obtain a carbon substrate; the carbon substrate includes pores formed after the pore-forming particles are removed.

[0127] In the embodiment of the present application, the carbon source may be at least one of kerosene, methane, acetylene, heavy oil, etc.; the pore-forming particles may be any one of silicon dioxide (SiO2) particles and aluminum hydroxide particles (Al(OH)3).

[0128] Specifically, in step S1011, the carbon source and silane can be sprayed into the tunnel furnace in a ratio of 10:1 to 100:1, the temperature is set at 1000°C to 2000°C, water vapor is continuously introduced during the reaction, and the carbon-based composite material is obtained after cooling.

[0129] Optionally, in some embodiments, the pore-forming particles are aluminum hydroxide particles, and in step S1012, the carbon-based composite material is heated to a first temperature to thermally decompose the aluminum hydroxide particles in the carbon-based composite material, thereby removing the pore-forming particles in the carbon-based composite material to obtain a carbon substrate. The first temperature is the temperature at which the aluminum hydroxide particles are thermally decomposed; illustratively, the first temperature may be 150°C to 200°C.

[0130] Optionally, in some embodiments, the pore-forming particles are silicon dioxide particles, and the step S1012 of removing the pore-forming particles in the carbon-based composite material to obtain the carbon substrate includes:

[0131] The silicon dioxide particles in the carbon-based composite material are dissolved by hydrofluoric acid to obtain a carbon substrate.

[0132] In an embodiment of the present application, when the pore-forming particles are silica particles, the carbon-based composite material can be immersed in a hydrofluoric acid solution with a concentration of 2wt.% to 15wt.% to remove the pore-forming particles in the carbon-based composite material to obtain a carbon substrate.

[0133] Optionally, in some embodiments, the Dv50 particle size of the pore-forming particles is 50nm to 200nm, so that after the pore-forming particles in the carbon-based composite material are removed by step S1012, holes of the same size as the particle size of the pore-forming particles are formed in the carbon-based composite material, thereby obtaining a carbon substrate provided with holes. Exemplarily, the Dv50 particle size of the pore-forming particles can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm and 200nm, or any two of the range values. Wherein, the Dv50 represents the particle size corresponding to when the volume cumulative distribution percentage of the pore-forming particles is equal to 50%.

[0134] In summary, the embodiment of the present application first provides a carbon substrate, and then reacts the target functional group donor with the carbon substrate to form a conductive agent, so that the conductive agent includes the target functional group and the carbon substrate, so as to utilize the first group in the target functional group to capture the transition metal ions dissolved from the positive electrode active material, thereby improving the ability and efficiency of the conductive agent to capture the transition metal ions.

[0135] An embodiment of the present application also provides an electrode sheet, which includes a positive electrode sheet and / or a negative electrode sheet; the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the positive electrode collector, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes transition metal ions, and the positive electrode active material layer also includes the conductive agent described in any of the above items; the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on the negative electrode collector, the negative electrode active material layer includes a negative electrode active material, and at least one of the negative electrode active material layers also includes the conductive agent described in any of the above items.

[0136] Optionally, in some embodiments, the conductive coating of the positive electrode current collector and / or the negative electrode current collector includes the conductive agent as described in any one of the above items.

[0137] An embodiment of the present application further provides a secondary battery, which includes the electrode sheet as described above.

[0138] In the embodiment of the present application, because the above-mentioned conductive agent includes a target functional group and a carbon substrate, the secondary battery can utilize the first group in the target functional group in the conductive agent to capture transition metal ions dissolved from the positive electrode active material during the charge and discharge cycle, thereby improving the ability and efficiency of the conductive agent to capture transition metal ions without causing attenuation of the electrical performance of the secondary battery; and the embodiment of the present application modifies the carbon substrate through the target functional group, and can also improve the dispersion effect of the conductive agent in the conductive coating of the positive electrode active material, the negative electrode material and the current collector, thereby improving the uniformity of the electrical conductivity of the conductive coating of the material, the negative electrode material and the current collector, and further improving the electrical performance of the secondary battery.

[0139] The secondary battery of the present application is prepared by a method known to those skilled in the art.

[0140] For example, in the case where the conductive agent is a conductive agent including a target functional group and a carbon substrate, the preparation method of the battery provided in the embodiment of the present application is:

[0141] The conductive agent prepared above is evenly mixed with lithium iron phosphate (LFP) positive electrode active material and binder polyvinylidene fluoride (PVDF) in a certain mass ratio, and then coated on aluminum foil to prepare a positive electrode sheet, and then it is made into a battery cell in sequence with the negative electrode and separator commonly used in the art by winding or lamination methods known in the art, and then the battery cell is placed in a battery shell, an electrolyte is added, and then it is sealed to obtain a secondary battery.

[0142] The present application also provides an electric device, which includes the secondary battery as described above, and the secondary battery serves as a power supply for the electric device.

[0143] The present application is described in detail below through examples.

[0144] Example 1

[0145] (1) Providing carbon substrate:

[0146] First, acetylene and silane are sprayed into a tunnel furnace at a ratio of 20:1, and reacted at 1500°C to prepare a carbon-based composite material; the carbon-based composite material includes a carbon substrate formed by acetylene and silicon dioxide particles dispersed in the carbon substrate; then, the carbon-based composite material is immersed in a 15wt.% concentration of hydrofluoric acid solution to remove the silicon dioxide particles in the carbon-based composite material to obtain a carbon substrate; the carbon substrate includes pores formed after the silicon dioxide particles are removed; wherein the particle size of the silicon dioxide particles is 100nm.

[0147] (2) Preparation of conductive agent:

[0148] First, the carbon substrate obtained in step (1) is dispersed in water, 1% vinyl silane is added, and the pH value is adjusted to 8-9. Then, acrylic acid monomer is added, and the reaction is carried out at 90° C. for 2 hours. After filtering, washing, and drying, a conductive agent is formed. The mass ratio of acrylic acid monomer to carbon substrate is 1%. Acrylic acid is used to provide target functional groups, and the target functional groups include carboxyl groups for capturing transition metal ions and ester groups generated after esterification of acrylic acid with the surface of the carbon substrate.

[0149] (3) Preparation of secondary batteries:

[0150] A slurry is prepared using LFP, PVDF and the conductive agent obtained in step (2) in a mass ratio of 97:1:2 and coated on the surface of the positive electrode current collector to form a pole sheet, and then rolled to form a positive electrode sheet;

[0151] A slurry is prepared by mixing graphite, conductive carbon black (Super P) known to those skilled in the art, sodium carboxymethyl cellulose (CMC) and styrene-butadiene copolymer (SBR) in a mass ratio of 96:2:1:1, and then coated on the surface of the negative electrode current collector and rolled to form a negative electrode sheet;

[0152] The positive and negative electrodes and the separator are sequentially made into a battery cell by winding or laminating methods known in the art, and then the battery cell is placed in a battery shell, an electrolyte is added, and then sealed to obtain a secondary battery.

[0153] Example 2

[0154] The difference between Example 2 and Example 1 is that in step (1), the particle size of the silicon dioxide particles is 50 nm.

[0155] Example 3

[0156] The difference between Example 3 and Example 1 is that in step (1), the particle size of the silicon dioxide particles is 200 nm.

[0157] Example 4

[0158] The difference between Example 4 and Example 1 is that in step (2):

[0159] First, the carboxyl groups in the polyacrylic acid are subjected to an esterification reaction with the hydroxyl groups on the surface of the carbon substrate obtained in step (1); the mass of the polyacrylic acid and the carbon substrate is 2%, the esterification reaction time is 4 hours, the pH value is adjusted to 5-6, and the reaction temperature is 110°C.

[0160] Example 5

[0161] The difference between Example 5 and Example 4 is that in step (2), first, the carbon substrate obtained in step (1) is dispersed in toluene, 1% 4-bromobenzyl isocyanate is added, the reaction is carried out at room temperature for 2 hours, and the pretreated conductive agent is obtained after centrifugation, washing and drying; then, the pretreated conductive agent is dispersed in tetrahydrofuran, 1% acrylic acid is added, the reaction is carried out at 70°C for 4 hours, and the conductive agent is obtained after centrifugation, washing and drying.

[0162] Example 6

[0163] The difference between Example 6 and Example 4 is that in step (2), first, the carboxyl groups in the polyacrylic acid are subjected to an esterification reaction with the hydroxyl groups on the surface of the carbon substrate obtained in step (1) to obtain a carbon substrate having a binder on its surface; the mass ratio of the polyacrylic acid to the carbon substrate is 1%, the esterification reaction time is 4 hours, the pH value is adjusted to 5-6, and the reaction temperature is 110°C; then, the carbon substrate having a binder on its surface is dispersed in toluene, 4-bromobenzyl isocyanate is added at a mass ratio of 1% of the carbon substrate, the reaction is carried out at room temperature for 2 hours, and the pretreated conductive agent is obtained after centrifugal washing and drying.

[0164] Example 7

[0165] The difference between Example 7 and Example 1 is that in step (1), conductive carbon black known to those skilled in the art is determined as the carbon substrate.

[0166] Example 8

[0167] The difference between Example 8 and Example 4 is that 1% 4-bromobenzyl isocyanate is added while the carboxyl groups in the polyacrylic acid are subjected to an esterification reaction with the hydroxyl groups on the surface of the carbon substrate obtained in step (1) to obtain a carbon substrate having a binder and target functional groups on the surface; the mass ratio of polyacrylic acid to the carbon substrate is 1%, the reaction time is 4 hours, the pH value is adjusted to 5-6, and the reaction temperature is 110°C; and the pretreated conductive agent is obtained after centrifugal washing and drying.

[0168] Example 9

[0169] The difference between Example 9 and Example 1 is that in step (3):

[0170] A slurry is prepared by using LFP, PVDF and conductive carbon black known to those skilled in the art in a mass ratio of 97:1:2 and coated on the surface of the positive electrode current collector to form a pole sheet, and then rolled to form a positive electrode sheet;

[0171] A slurry is prepared by using graphite, the conductive agent obtained in step (2), sodium carboxymethyl cellulose and styrene-butadiene copolymer in a mass ratio of 96:2:1:1, and then coated on the surface of the negative electrode current collector and rolled to form a negative electrode sheet.

[0172] Example 10

[0173] The difference between Example 10 and Example 1 is that in step (3):

[0174] A slurry is prepared by using graphite, the conductive agent obtained in step (2), sodium carboxymethyl cellulose and styrene-butadiene copolymer in a mass ratio of 96:2:1:1, and then coated on the surface of the negative electrode current collector and rolled to form a negative electrode sheet.

[0175] Embodiment 11

[0176] The difference between Example 11 and Example 10 is that in step (3), the conductive coatings of both the positive electrode collector and the negative electrode collector include the conductive agent obtained in step (2).

[0177] Comparative Example 1

[0178] The difference between Comparative Example 1 and Example 1 is that:

[0179] Excluding steps (1) and (2);

[0180] In step (3), a slurry is prepared using LFP, PVDF and conductive carbon black known to those skilled in the art in a mass ratio of 97:1:2 and coated on the surface of the positive electrode collector to form a pole sheet, which is then rolled to form a positive electrode sheet.

[0181] Sample performance test:

[0182] (1) High temperature cycle test

[0183] The lithium-ion battery was charged to 3.8V at 1C constant current at 60°C, then charged at constant voltage to a cutoff current of 0.05C, left to stand for 1h, and then discharged to 2.0V at 1C constant current, which was recorded as one charge and discharge cycle. The battery was then cycled 500 times under the above conditions. The capacity retention rate (%) of the lithium-ion battery after 500 cycles = (discharge capacity of the 500th cycle / discharge capacity of the first cycle) × 100%.

[0184] (2) High temperature storage test

[0185] The lithium-ion battery was charged at 60°C with a constant current and constant voltage of 1C to 3.8V, cut off at 0.05C, left to stand for 1h, and then discharged at a constant current of 1C to 2.0V. This discharge capacity was calculated as the initial capacity C0. The battery was transferred to a high-temperature test cabinet and stored at 60°C for 7 days. After storage, the test battery was taken out, left at room temperature for 10h, and then discharged at a constant current of 1C to 2.0V. This discharge capacity was calculated as the initial capacity C1. Capacity retention rate (%) = C1 / C0*100%.

[0186] (3) DC internal resistance (DCIR) test

[0187] DCIR was tested using a Xinwei battery test cabinet (equipment model: BTS-5V12A) with the following test methods: (1) charge and discharge at 25°C and 0.2C to calibrate the battery capacity; (2) charge to 50% SOC at 0.2C; (3) discharge at 2C for 30s, record the termination voltage and termination current of each process, and calculate DCIR. The results are listed in Table 1.

[0188] The secondary batteries prepared in each embodiment and comparative example 1 were subjected to cycle performance tests, capacity retention rate tests at different temperatures, and storage performance tests. The test data are shown in Table 1.

[0189] Table 1

[0190]

[0191] According to Table 1, the DC resistance of the secondary batteries prepared in Examples 1 to 11 is substantially the same as the DC internal resistance of the secondary batteries prepared in Comparative Example 1, with no deterioration tendency; and the capacity retention rate of the secondary batteries prepared in Examples 1 to 11 after 500 cycles at 60°C is improved by about 2.2% compared with the secondary batteries prepared in Comparative Example 1; the capacity retention rate of the secondary batteries prepared in Examples 1 to 11 after storage at 60°C for 7 days is improved by about 1.9% compared with the secondary batteries prepared in Comparative Example 1. The embodiments of the present application improve the cycle performance and storage performance of the secondary batteries while ensuring that the DC internal resistance of the secondary batteries does not deteriorate; it can be seen that the embodiments of the present application improve the ability and efficiency of the conductive agent to capture transition metal ions, thereby improving the electrical performance of the secondary batteries prepared based on the conductive agent provided in the embodiments of the present application.

[0192] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0193] The conductive agent, the preparation method of the conductive agent, the electrode and the secondary battery provided by the present application are introduced in detail above. The principle and implementation mode of the present application are explained in this article by using specific examples. The description of the above embodiments is only used to help understand the method and the core idea of ​​the present application. At the same time, for the general technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation mode and the scope of application. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A conductive agent, characterized in that: The conductive agent includes a carbon substrate, the surface of the carbon substrate has a target functional group, and the target functional group is bonded to the surface of the carbon substrate; The target functional group includes a first group, and the first group is used to capture transition metal ions; The target functional group further includes a second group, and the conductive agent further includes a binder; The binder is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group is bonded to the hydroxyl groups on the surface of the carbon substrate and the binder through the second group; The target functional group is bonded to the binder to form a double bond.

2. The conductive agent according to claim 1, characterized in that The binder includes at least one of acrylic, olefin and silane.

3. The conductive agent according to claim 1, characterized in that: The second group includes at least one of a carboxyl group, an amino group, an isocyanate group and a halogen atom.

4. The conductive agent according to claim 1, characterized in that: The carbon substrate is provided with holes, and the holes are used to capture the transition metal ions.

5. The conductive agent according to claim 4, characterized in that: The size of the pores is 50 nm to 200 nm.

6. The conductive agent according to any one of claims 1 to 4, characterized in that: The first group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group, and a pyrrole group.

7. The conductive agent according to any one of claims 1 to 4, characterized in that: The carbon substrate is any one of carbon black, carbon nanotubes, graphene and carbon fiber.

8. A method for preparing a conductive agent, characterized in that: The method comprises: providing a carbon substrate; reacting a target functional group donor having a target functional group with the carbon substrate so that the target functional group is bonded to the surface of the carbon substrate to form a conductive agent; wherein the target functional group includes a first group for capturing transition metal ions; The target functional group donor also includes a second group; The method further comprises: The second group of the first part of the target functional group donor and the binder donor are reacted with the hydroxyl groups on the surface of the carbon substrate at the same time, so that the adhesive provided by the binder donor is bonded to the hydroxyl groups on the surface of the carbon substrate, and the target functional group provided by the first part of the target functional group donor is bonded to the hydroxyl groups on the surface of the carbon substrate, forming the binder bonded to the hydroxyl groups on the surface of the carbon substrate and the target functional group bonded to the hydroxyl groups on the surface of the carbon substrate; reacting the second group of the target functional group donor of the second part with the binder so that the target functional group provided by the target functional group donor of the second part is bonded with the binder to form a conductive agent; The target functional group is bonded to the binder to form a double bond.

9. The method according to claim 8, characterized in that The first group includes at least one of a carboxyl group, an amino group, an ester group, a nitro group, a pyridine group, and a pyrrole group.

10. The method according to any one of claims 8 to 9, characterized in that: The binder donor includes at least one of acrylic, olefin and silane.

11. The method according to claim 8, characterized in that The provision of a carbon substrate comprises: Co-depositing a carbon source and pore-forming particles to prepare a carbon-based composite material; the carbon-based composite material includes a carbon substrate formed by the carbon source and pore-forming particles dispersed in the carbon substrate; The pore-forming particles in the carbon-based composite material are removed to obtain a carbon substrate; the carbon substrate includes pores formed after the pore-forming particles are removed.

12. The method according to claim 11, characterized in that The Dv50 particle size of the pore-forming particles is 50 nm to 200 nm, and the Dv50 represents the particle size corresponding to when the cumulative volume distribution percentage of the pore-forming particles is equal to 50%.

13. The method according to claim 11, characterized in that The pore-forming particles are silicon dioxide particles; and removing the pore-forming particles from the carbon-based composite material to obtain a carbon substrate comprises: The silicon dioxide particles in the carbon-based composite material are dissolved by hydrofluoric acid to obtain a carbon substrate.

14. A pole piece, characterized in that: The pole piece includes a positive pole piece and / or a negative pole piece; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a transition metal ion, and the positive electrode active material layer further comprises a conductive agent as claimed in any one of claims 1 to 7; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and at least one of the negative electrode active material layers further includes a conductive agent as claimed in any one of claims 1 to 7.

15. The pole piece according to claim 14, characterized in that: The conductive coating of the positive electrode current collector and / or the negative electrode current collector comprises the conductive agent according to any one of claims 1 to 7.

16. A secondary battery, characterized in that: The secondary battery comprises the pole piece according to any one of claims 14 to 15.

17. An electrical equipment, characterized in that: The electric device comprises the secondary battery as claimed in claim 16, and the secondary battery serves as a power supply for the electric device.

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