A multidimensional carbon network / polymer double-coated high-nickel ternary cathode material and its preparation method and application

Abstract

The present invention relates to a multidimensional carbon network / polymer dual-coated high-nickel ternary cathode material and its preparation method and application. The preparation method also includes: uniformly dispersing graphene, carbon nanotubes, and polymer A in an organic solvent in sequence to obtain a carbon coating solution of a multidimensional carbon network; adding the high-nickel ternary material to the carbon coating solution, uniformly dispersing the mixture to obtain a mixed slurry; heating the mixed slurry to evaporate the solvent, sealing and allowing it to stand, drying, grinding, and sintering to obtain a high-nickel ternary material coated with a multidimensional carbon network; adding the high-nickel ternary material coated with the multidimensional carbon network to a modified solution of an electron / lithium ion conducting polymer B, uniformly dispersing the mixture, and heating the mixture to evaporate the solvent to obtain a high-nickel ternary cathode material coated with a multidimensional carbon network / polymer dual-coated. The high-nickel ternary cathode material prepared by the present invention has a two-layer coating structure, which improves the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery electrode materials, and in particular to a multi-dimensional carbon network / polymer double-coated high-nickel ternary positive electrode material, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have excellent properties such as high specific energy, high discharge voltage, and good safety, and are widely used in portable devices, energy storage systems, and electric vehicles. Among all the components of lithium-ion batteries, the positive electrode material is one of the most critical components, which largely determines the overall energy density and cost of the battery system. Current industrial positive electrode materials can be divided into three categories according to their structure: layered (such as LiCoO2), spinel (such as LiMn2O4), and olivine (such as LiFePO4). In recent years, the ternary layered oxide LiNi x Co y Mn z O2(x+y+z=1) and LiNi x Co y Al z O2 (x+y+z=1) is rapidly developing as a cathode material for electric vehicle batteries. However, high-nickel ternary cathode materials present numerous challenges, including lithium-nickel intermixing, transition metal ion dissolution, poor thermal stability, excessive alkali content, and microcracks. Therefore, it is necessary to modify high-nickel ternary materials to improve their performance through a variety of methods, including surface coating and bulk doping, to address these current shortcomings.

[0003] At present, surface coating technology is the mainstream improvement method for improving the performance of high-nickel ternary materials. The improvements to high-nickel ternary materials mainly include: 1. The coating can effectively remove residual alkali on the surface of the material; 2. The coating layer prevents the aggravation of the "air sensitive effect" during storage; 3. Reduces the side reactions between the electrode material and the electrolyte; 4. Part of the coating layer can form a conductive / ion-conducting channel on the surface for rapid transmission, effectively alleviating the problem of difficulty in lithium ion diffusion on the surface.

[0004] Patent publication number CN105070888A discloses a ternary material coated with a coupled carbon nanotube-graphene composite three-dimensional network structure and its preparation method. This method couples graphene and carbon nanotubes by chemical bonding, then disperses them evenly with the ternary material by physical methods, and obtains a uniformly coated ternary product by sintering. However, this method uses a silane coupling agent to couple the graphene sheets with the carbon nanotubes, which does not promote uniform dispersion of the two, resulting in uneven three-dimensional network formation. The coupling affects the structure and position of the graphene and carbon nanotubes, resulting in poor material performance when the same amount of graphene is added, increasing production costs.

[0005] Patent publication number CN110429269A discloses a polymer-coated high-nickel ternary cathode material and its preparation method. This method involves copolymerizing the polymer monomers in a strongly acidic medium while simultaneously undergoing oxidative polymerization. A liquid-phase method is then used to coat the polymer layer, yielding a ternary material that meets the requirements. However, this method involves conducting the polymerization reaction in a strong acidic system, extensively washing the polymer during treatment, and heating the reaction medium to volatilize acidic gases, which pollutes the environment. Furthermore, the complex preparation method undoubtedly increases production costs and results in insufficient economic benefits.

[0006] The patent with publication number CN114005970A discloses a carbon / conductive polymer coated ternary cathode material and its preparation method. The method adopts a plasma treatment method to coat carbon on the ternary material, and hydroxylates it under alkaline conditions provided by ammonia water, and disperses the carbon-coated ternary cathode material with rich hydroxylation on the surface into the polymer modification liquid, thereby obtaining a ternary material that meets the requirements. However, the plasma-assisted chemical vapor deposition method used for carbon coating is relatively complicated, and the pH control in the actual ammonia treatment process in the hydroxylation treatment is relatively complicated. Moreover, the hydroxylation of the carbon layer will cause the hydroxyl groups to be unevenly distributed, resulting in uneven distribution of the bonded conductive polymer, affecting the electrical properties of the ternary material. Summary of the Invention

[0007] Based on this, it is necessary to address the problems existing in the prior art. The purpose of the present invention is to provide a high-nickel ternary positive electrode material with a multidimensional carbon network / polymer double coating, and a preparation method and application thereof. The high-nickel ternary positive electrode material has a two-layer coating structure of a multidimensional carbon network layer and a conductive / ion-conducting polymer layer. It not only improves the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process, but also the synergistic effect of the multidimensional carbon network layer and the conductive / ion-conducting polymer layer makes the high-nickel ternary positive electrode material have higher lithium ion conductivity, first discharge specific capacity and relatively stable cycle performance.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions.

[0009] The present invention proposes a method for preparing a multidimensional carbon network / polymer dual-coated high-nickel ternary cathode material, which comprises the following steps:

[0010] S1. Graphene, carbon nanotubes, and polymer A are uniformly dispersed in an organic solvent in sequence to obtain a carbon coating solution having a multidimensional carbon network; a high-nickel ternary material is added to the carbon coating solution and uniformly dispersed to obtain a mixed slurry; the mixed slurry is heated to evaporate the solvent, sealed and allowed to stand, dried, ground, and sintered to obtain a high-nickel ternary material coated with a multidimensional carbon network;

[0011] S2. Add the multidimensional carbon network-coated high-nickel ternary material to the modified solution of the electron-conducting / lithium-conducting polymer B, disperse it evenly, and heat it to evaporate the solvent to obtain a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material.

[0012] The high-nickel ternary positive electrode material prepared by the present invention has a two-layer coating structure of a multidimensional carbon network layer and a conductive / ion-conducting polymer layer, which not only improves the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process, but also the multidimensional carbon network layer and the conductive / ion-conducting polymer layer work synergistically, so that the high-nickel ternary positive electrode material has higher lithium ion conductivity, first discharge specific capacity and relatively stable cycle performance.

[0013] As a further improvement of the above scheme of the present invention, in step S1, the molecular weight of the polymer A is 2000-300000, and it is prepared by the following method: adding reaction monomer a, reaction monomer b, and initiator to an organic solvent, heating for reaction, and then precipitating, filtering, washing, and drying to obtain polymer A; wherein the reaction monomer a is a compound containing both a carbon-carbon double bond and a benzene ring, and the reaction monomer b is a compound containing a polar functional group carbon-carbon double bond, an alkynyl group, or a cyano group.

[0014] As a further improvement of the above solution of the present invention, the reaction monomer a is at least one of styrene, α-ethylstyrene, 5-phenyl-1-pentene, 2-allyl-1,4-xylene, and 1-vinylpyrene;

[0015] And / or, the reactive monomer b is at least one of acrylonitrile, propiolonitrile, divinyl acetylene, and methyl methacrylate;

[0016] And / or, the added amount of the initiator is 1-2% of the total mass of the reaction monomer a and the reaction monomer b, and the initiator is an oil-soluble initiator; preferably, the initiator is one of benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile.

[0017] As a further improvement of the above solution of the present invention, the heating reaction is carried out by stirring at 50-70° C. for 6-12 hours.

[0018] As a further improvement of the above solution of the present invention, in step S1, the mass ratio of graphene, carbon nanotubes, and polymer A is 1-1.5:1-2:1-3.5;

[0019] And / or, in step S1, the number of graphene nanosheet layers is 2-6;

[0020] And / or, in step S1, the particle size of the carbon nanotubes is 60-100 nm.

[0021] As a further improvement of the above solution of the present invention, in step S1, the molecular formula of the high nickel ternary material is LiNi x M 1-x O2, wherein: x ≥ 0.6, M is at least one of Co, Mn, Al, and Mg;

[0022] And / or, in step S1, the mass ratio of the high nickel ternary material to the solute of the carbon coating solution is 1:1-3;

[0023] And / or, in step S1, the sintering is carried out in an inert atmosphere in a tube furnace, heating the temperature to 500-900°C at a heating rate of 3°C / min, and keeping the temperature for 5-10 hours.

[0024] As a further improvement of the above solution of the present invention, in step S2, the electron-conducting / lithium-conducting polymer B includes component C and component D, and the volume ratio of component C to component D is 1:1, wherein: the component C is at least one of polyacetylene, polybisyne, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and polypyrrole, and the component D is at least one of lithium polyacrylate, lithium polymaleate, lithium poly(methyl vinyl ether-co-maleate), and lithium polymethacrylate;

[0025] And / or, in step S2, the modified solution of the electron-conducting / lithium-ion-conducting polymer B is formed by dissolving the electron-conducting / lithium-ion-conducting polymer B at a concentration of 0.005-0.05 g / mL in an organic solvent, and the solid content of the modified solution of the electron-conducting / lithium-ion-conducting polymer B is 2-4 wt%;

[0026] And / or, in step S2, the mass ratio of the multi-dimensional carbon network-coated high-nickel ternary material to the electron-conducting / lithium-conducting polymer B is 1:0.001-0.1.

[0027] As a further improvement of the above solution of the present invention, the organic solvent is one of N-methylpyrrolidone, acetone, ethanol, isopropanol, glycerol, methanol, dimethyl sulfoxide, and dimethylformamide;

[0028] And / or, the uniform dispersion is achieved by mechanical stirring, and the mechanical stirring is at least one of ultrasound, high-speed shear emulsification, and wet ball milling.

[0029] The present invention proposes a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material, which is prepared by the preparation method of the multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material as described above.

[0030] The present invention proposes an application of the multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material as described above in a lithium battery.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention combines two-dimensional graphene with one-dimensional carbon nanotubes to form a multi-dimensional carbon network structure, which is evenly coated on the surface of the high-nickel ternary material under the action of polymer A. Due to the special network structure of graphene and carbon nanotubes, the self-assembled multi-dimensional carbon network can provide an excellent fast transmission channel for the conduction of lithium ions and electrons, improve the electrical conductivity of the material, facilitate the rapid storage and transmission of lithium ions and electrons, reduce the polarization process, and improve the cycle performance.

[0033] 2. The electron-conducting / lithium-ion-conducting polymer B coating of the present invention has both electron-conducting and ion-conducting properties and can synergize with the multidimensional carbon network, thereby reducing the resistance to lithium removal / insertion of the high-nickel ternary positive electrode material during charge and discharge, thereby achieving the excellent characteristics of high capacity, high rate, and long cycle life. In addition, the polymer B coating layer is a cross-linked network structure formed by chemical bonding of multiple C=C groups, which effectively prevents the polymer coating from swelling and dissolving in the electrolyte, avoiding phase changes and particle cracking of the high-nickel ternary material. The polymer film can also effectively resist external intrusion, thereby improving the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process.

[0034] 3. The high-nickel ternary positive electrode material prepared by the present invention has a two-layer coating structure of a multidimensional carbon network layer and a conductive / ion-conducting polymer layer, which not only improves the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process, but also the multidimensional carbon network layer and the conductive / ion-conducting polymer layer work synergistically, so that the high-nickel ternary positive electrode material has higher lithium ion conductivity, first discharge specific capacity and relatively stable cycle performance.

[0035] 4. The coating in the present invention adopts liquid phase coating, which makes the coating layer more uniform. The liquid phase blending method has a simple process, easy operation, mild reaction conditions and easy control, is suitable for industrial production, and has good economic prospects.

[0036] 5. The present invention utilizes a simple free radical polymerization method to synthesize polymer A with the desired degree of polymerization. The benzene rings in the structure of polymer A can form strong interaction forces with graphene and carbon nanotubes, preventing the graphene sheets from agglomerating easily, enabling the two to be evenly dispersed in an organic solvent, and constructing a multidimensional conductive / ion-conducting network. On the other hand, the abundant polar functional groups can form a strong coordination effect with transition metal ions, ensuring that the multidimensional carbon network can be evenly coated, which is beneficial to the rapid storage and transmission of electrons and lithium ions in the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1Schematic diagram of the particle structure of a multi-dimensional carbon network / polymer double-coated high-nickel ternary cathode material proposed in the present invention;

[0038] Figure 2 This is a comparison chart of the cycle performance of button batteries assembled with high-nickel ternary positive electrode materials prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] This embodiment provides a multi-dimensional carbon network / polymer double-coated high nickel ternary positive electrode material, the particle structure of which is shown in FIG. Figure 1 As shown, the multidimensional carbon network layer 2 and the conductive / ion-conducting polymer layer 3 are sequentially coated on the outside of the high-nickel ternary material 1 to form a high-nickel ternary positive electrode material with a two-layer coating structure. This not only improves the structural stability and electrochemical performance of the high-nickel ternary material during the charge and discharge process, but also the multidimensional carbon network layer and the conductive / ion-conducting polymer layer work synergistically, so that the high-nickel ternary positive electrode material has higher lithium ion conductivity, first discharge specific capacity and relatively stable cycle performance.

[0042] The preparation method of the multi-dimensional carbon network / polymer double-coated high-nickel ternary positive electrode material of this embodiment includes the following two steps S1-S2.

[0043] S1. Uniformly disperse graphene, carbon nanotubes, and polymer A in an organic solvent in sequence to obtain a carbon coating liquid with a multidimensional carbon network; add a high-nickel ternary material to the carbon coating liquid, and disperse it uniformly to obtain a mixed slurry; heat the mixed slurry to evaporate the solvent, seal it, let it stand, dry, grind, and sinter it to obtain a high-nickel ternary material coated with a multidimensional carbon network.

[0044] In this embodiment, polymer A has a molecular weight of 2,000-300,000 and is prepared by the following method: adding reactive monomer a, reactive monomer b, and an initiator to an organic solvent, stirring and heating the mixture at 50-70°C for 6-12 hours, and then subjecting the mixture to precipitation, filtration, washing, and drying to obtain polymer A. Reactive monomer a is a compound containing both a carbon-carbon double bond and a benzene ring, preferably at least one of styrene, α-ethylstyrene, 5-phenyl-1-pentene, 2-allyl-1,4-dimethylbenzene, and 1-vinylpyrene; reactive monomer b is a compound containing a polar functional group, a carbon-carbon double bond, an alkynyl group, or a cyano group, preferably at least one of acrylonitrile, propiolonitrile, divinyl acetylene, and methyl methacrylate; and the initiator is added in an amount of 1-2% of the total mass of reactive monomer a and reactive monomer b. The initiator is an oil-soluble initiator, preferably one of benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptylonitrile.

[0045] In this embodiment, the mass ratio of graphene, carbon nanotubes, and polymer A is 1-1.5:1-2:1-3.5. The number of graphene nanosheets is 2-6. The particle size of the carbon nanotubes is 60-100 nm.

[0046] In this embodiment, the molecular formula of the high nickel ternary material is LiNi x M 1-x O2, wherein: x≥0.6, M is at least one of Co, Mn, Al, and Mg, and the mass ratio of the high-nickel ternary material to the solute of the carbon coating solution is 1:1-3.

[0047] The sintering in this embodiment is carried out in an inert atmosphere in a tube furnace by heating the temperature to 500-900° C. at a heating rate of 3° C. / min and keeping the temperature for 5-10 hours.

[0048] S2. The multidimensional carbon network-coated high-nickel ternary material prepared in step S1 is added to the modified solution of the electron-conducting / lithium-conducting polymer B, uniformly dispersed, and heated to evaporate the solvent to obtain a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material.

[0049] The coating in this embodiment adopts liquid phase coating, which makes the coating layer more uniform. The liquid phase blending method has a simple process, easy operation, mild reaction conditions and easy control, is suitable for industrial production, and has good economic prospects.

[0050] In this embodiment, polymer A with the desired degree of polymerization is synthesized using a simple free radical polymerization method. The benzene rings in the structure of polymer A can form strong interactive forces with graphene and carbon nanotubes, preventing easy agglomeration between graphene sheets and enabling the two to be evenly dispersed in organic solvents, thereby constructing a multidimensional conductive / ion-conducting network. On the other hand, the rich polar functional groups can form strong coordination effects with transition metal ions, ensuring that the multidimensional carbon network can be evenly coated, which is beneficial to the rapid storage and transmission of electrons and lithium ions in the material.

[0051] In this embodiment, the electron-conducting / lithium-ion-conducting polymer B includes component C and component D, and the volume ratio of component C to component D is 1:1. Component C is preferably at least one of polyacetylene, polydiyne, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and polypyrrole, and component D is preferably at least one of lithium polyacrylate, lithium polymaleate, lithium poly(methyl vinyl ether-co-maleate), and lithium polymethacrylate. The modified solution of the electron-conducting / lithium-ion-conducting polymer B is formed by dissolving the electron-conducting / lithium-ion-conducting polymer B at a concentration of 0.005-0.05 g / mL in an organic solvent, and the solid content of the modified solution of the electron-conducting / lithium-ion-conducting polymer B is 2-4 wt%.

[0052] In this embodiment, the mass ratio of the high nickel ternary material coated with the multi-dimensional carbon network to the electron-conducting / lithium-conducting polymer B is 1:0.001-0.1.

[0053] The organic solvent in this embodiment is one of N-methylpyrrolidone, acetone, ethanol, isopropyl alcohol, glycerol, methanol, dimethyl sulfoxide, and dimethylformamide. The uniform dispersion in this embodiment is achieved by mechanical stirring, which is at least one of ultrasound, high-speed shear emulsification, and wet ball milling.

[0054] Next, in order to facilitate understanding of the present invention, the present invention will be described in more detail below with reference to specific embodiments.

[0055] Example 1

[0056] This embodiment provides a multi-dimensional carbon network / polymer dual-coated high-nickel ternary cathode material, the preparation method of which includes the following steps:

[0057] S1. Preparation of poly(α-ethylstyrene-co-divinylene): α-ethylstyrene and divinylene were added to N-methylpyrrolidone in a mass ratio of 1:1, and 1% azobisisobutyronitrile was added. The mixture was heated to 65°C and stirred for 10 hours. The mixture was then precipitated, filtered, washed, and dried to obtain poly(α-ethylstyrene-co-divinylene) with a molecular weight of 15,000.

[0058] S2. Coating of multidimensional carbon network: Graphene, carbon nanotubes, and poly (α-ethylstyrene-co-divinyl acetylene) were uniformly dispersed in N-methylpyrrolidone in a mass ratio of 1:1:1, and ultrasonically stirred for 40 min until the mixture was uniform to obtain a carbon coating solution of multidimensional carbon network; LiNi 0.75 Co 0.15 Mn 0.10 O2 (abbreviated as Ni75) is added to the carbon coating liquid and ultrasonically stirred for 1 hour to obtain a mixed slurry; the mixed slurry is heated and stirred to evaporate the solvent, sealed and allowed to stand for 1 hour, and then dried at 90°C for 12 hours. After grinding, it is placed in a tubular furnace and heated to 600°C at a heating rate of 3°C / min in an inert atmosphere, and then kept warm for 5 hours for sintering. After natural cooling, it is ground to obtain a high-nickel ternary material Ni75@C coated with a graphene-carbon nanotube multidimensional network.

[0059] S3. Coating of polymer layer: Ni75@C was added to a mixed modified solution (solid content of 2%, prepared by mixing polyaniline and lithium polyacrylate in a volume ratio of 1:1), wherein the mass ratio of Ni75@C to the mixed modified solution was 1:0.05, and then ultrasonically stirred at 40°C for 2 hours until the solvent was completely evaporated, and then transferred to a 90°C oven for drying for 12 hours to obtain a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material Ni75@C@PANI / PAALi.

[0060] Example 2

[0061] This embodiment provides a multi-dimensional carbon network / polymer dual-coated high-nickel ternary cathode material, the preparation method of which includes the following steps:

[0062] S1. Preparation of poly(styrene-co-methyl methacrylate): Styrene and methyl methacrylate acetylene were added to dimethylformamide in a mass ratio of 1:1, and 1.2% of azobisisoheptanenitrile was added. The mixture was heated to 70°C and stirred for 6 hours. The mixture was then precipitated, filtered, washed, and dried to obtain poly(styrene-co-methyl methacrylate) with a molecular weight of 10,000.

[0063] S2. Coating of multidimensional carbon network: Graphene, carbon nanotubes, and poly(styrene-co-methyl methacrylate) were uniformly dispersed in dimethylformamide in a mass ratio of 1.5:1:1.2, and ultrasonically stirred for 40 min until the mixture was uniform to obtain a carbon coating solution of multidimensional carbon network; LiNi 0.75 Co 0.15 Mn 0.10O2 (abbreviated as Ni75) is added to the carbon coating liquid and ultrasonically stirred for 1 hour to obtain a mixed slurry; the mixed slurry is heated and stirred to evaporate the solvent, sealed and allowed to stand for 1 hour, and then dried at 90°C for 12 hours. After grinding, it is placed in a tubular furnace and heated to 700°C at a heating rate of 3°C / min in an inert atmosphere, and then kept warm for 7 hours for sintering. After natural cooling, it is ground to obtain a high-nickel ternary material Ni75@C coated with a graphene-carbon nanotube multidimensional network.

[0064] S3. Polymer coating: Ni75@C was added to a mixed modified solution (solid content of 3%, prepared by mixing polypyrrole and lithium polymaleate in a volume ratio of 1:1), wherein the mass ratio of Ni75@C to the mixed modified solution was 1:0.1, and then ultrasonically stirred at 40°C for 2h until the solvent was completely evaporated, and then transferred to a 90°C oven for drying for 12h to obtain a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material Ni75@C@PPy / PMALi.

[0065] Example 3

[0066] This embodiment provides a multi-dimensional carbon network / polymer dual-coated high-nickel ternary cathode material, the preparation method of which includes the following steps:

[0067] S1. Preparation of poly(1-vinylpyrene-co-acrylonitrile): 1-vinylpyrene and acrylonitrile were added to acetone in a mass ratio of 1:1, and 1% benzoyl peroxide was added. The mixture was heated to 65°C and stirred for 12 hours. The mixture was then precipitated, filtered, washed, and dried to obtain poly(1-vinylpyrene-co-acrylonitrile) with a molecular weight of 20,000.

[0068] S2. Coating of multidimensional carbon network: Graphene, carbon nanotubes, and poly (1-vinylpyrene-co-acrylonitrile) were uniformly dispersed in acetone in a mass ratio of 1:1.5:1.2, and high-speed shearing was performed at 3000 rpm for 20 min to obtain a carbon coating solution of multidimensional carbon network; LiNi 0.88 Co 0.07 Mn 0.05 O2 (abbreviated as Ni88) is added to the carbon coating liquid and dispersed evenly at a high-speed shearing speed of 5000 rpm for 30 minutes to obtain a mixed slurry; the mixed slurry is heated and stirred to evaporate the solvent, sealed and allowed to stand for 1 hour, and then dried at 90°C for 12 hours. After grinding, it is placed in a tubular furnace and heated to 650°C at a heating rate of 3°C / min in an inert atmosphere, and then kept warm for 8 hours for sintering. After natural cooling, it is ground to obtain a high-nickel ternary material Ni88@C coated with a graphene-carbon nanotube multidimensional network.

[0069] S3. Polymer coating: Ni88@C was added to a mixed modified solution (solid content of 2%, made by mixing polyaniline and lithium polymethacrylate in a volume ratio of 1:1), where the mass ratio of Ni75@C to the mixed modified solution was 1:0.005. Then, ultrasonic stirring was performed at 40°C for 2 hours until the solvent was completely evaporated, and then the mixture was transferred to a 90°C oven for drying for 12 hours to obtain a high nickel ternary positive electrode material with a multidimensional carbon network / polymer double coating.

[0070] Ni88@C@PANI / PMAALi.

[0071] Comparative Example 1

[0072] This comparative example adopts the same implementation method as Example 1, except that: this comparative example only coats Ni75 with a polymer layer, specifically comprising the following steps:

[0073] LiNi 0.75 Co 0.15 Mn 0.10 O2 (abbreviated as Ni75) is added to a mixed modified solution (solid content of 2%, made by mixing polyaniline and lithium polyacrylate in a volume ratio of 1:1), where the mass ratio of Ni75@C and the mixed modified solution is 1:0.05. Then, ultrasonic stirring is carried out at 40°C for 2 hours until the solvent is completely evaporated, and then the mixture is transferred to a 90°C oven for drying for 12 hours to obtain a multi-dimensional carbon network / polymer double-coated high-nickel ternary positive electrode material Ni75@PANI / PAALi.

[0074] Comparative Example 2

[0075] This comparative example adopts the same implementation method as Example 1, except that: this comparative example only coats Ni75 with a multidimensional carbon network, specifically comprising the following steps:

[0076] S1. Preparation of poly(α-ethylstyrene-co-divinylene): α-ethylstyrene and divinylene were added to N-methylpyrrolidone in a mass ratio of 1:1, and 1% azobisisobutyronitrile was added. The mixture was heated to 65°C and stirred for 12 hours. The mixture was then precipitated, filtered, washed, and dried to obtain poly(α-ethylstyrene-co-divinylene) with a molecular weight of 15,000.

[0077] S2. Coating of multidimensional carbon network: Graphene, carbon nanotubes, and poly (α-ethylstyrene-co-divinyl acetylene) were uniformly dispersed in N-methylpyrrolidone in a mass ratio of 1:1:1, and ultrasonically stirred for 40 min until the mixture was uniform to obtain a carbon coating solution of multidimensional carbon network; LiNi 0.75 Co 0.15 Mn0.10 O2 (abbreviated as Ni75) is added to the carbon coating liquid and ultrasonically stirred for 1 hour to obtain a mixed slurry; the mixed slurry is heated and stirred to evaporate the solvent, sealed and allowed to stand for 1 hour, and then dried at 90°C for 12 hours. After grinding, it is placed in a tubular furnace and heated to 600°C at a heating rate of 3°C / min in an inert atmosphere, and then kept warm for 5 hours for sintering. After natural cooling, it is ground to obtain a high-nickel ternary positive electrode material Ni75@C coated with a graphene-carbon nanotube multidimensional network.

[0078] Test Case

[0079] The high nickel ternary positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 were assembled into button batteries according to the following methods:

[0080] (1) Preparation of positive electrode sheet: Weigh the positive electrode material, conductive agent (acetylene black) and binder (PVDF) in a mass ratio of 90%:5%:5%; mix and grind the weighed ternary positive electrode material and acetylene black in an agate mortar for 30 minutes, then add N-methylpyrrolidone (NMP) that has fully reacted with PVDF and mix until the slurry becomes a viscous liquid with a certain fluidity. Transfer the mixed slurry evenly to aluminum foil, and evenly coat the sample with a coater with a thickness of 150μm. Then pre-sinter in air at 60℃ for 5 hours, then vacuumize and dry at 90℃ for 12 hours to remove water and organic matter from the coated sample, and cut the positive electrode sheet according to size for use;

[0081] (2) Assembly of button cells: lithium sheet is used as negative electrode, the prepared positive electrode sheet is used as positive electrode, and the electrolyte ratio is EC:DMC=1:1, and button cells are assembled.

[0082] The above button batteries were subjected to electrical performance tests: 100 cycles at 1C, and the test results are shown in Table 1 below.

[0083] Table 1 Electrical performance test results

[0084]

[0085]

[0086] As can be seen from the results in Table 1, the first discharge capacity and cycle stability of the button cells assembled with the high-nickel ternary positive electrode materials prepared in Examples 1-3 at 1C are both higher than those of the button cells assembled with the high-nickel ternary positive electrode materials prepared in Comparative Examples 1 and 2. This indicates that the multidimensional carbon network layer and the conductive / ion-conductive polymer layer of the high-nickel ternary positive electrode material prepared in the present invention have a synergistic effect, which improves the conductivity, discharge capacity and cycle stability of the material. On the other hand, the present invention allows the multidimensional carbon layer and the polymer layer to be evenly coated on the surface of the material, thereby protecting the material, isolating the material from contact with the electrolyte, reducing the occurrence of side reactions, and thereby improving the chemical structure stability of the material, thereby further improving the electrical properties of the material, and has broad application prospects in lithium-ion batteries and other aspects.

[0087] The button batteries prepared in Example 1 and Comparative Example 1 were subjected to a cycle test at 1C. The test results are shown in FIG. Figure 2 As shown. Figure 2 It can be seen that after 100 cycles, the capacity of the button battery assembled with the high-nickel ternary positive electrode material prepared in Example 1 decreases slowly. It can be seen that the capacity retention rate of the high-nickel ternary positive electrode material prepared in Example 1 is significantly higher than that of the high-nickel ternary positive electrode material prepared in Comparative Example 1, proving that the multidimensional carbon network layer and the conductive / ion-conductive polymer layer can improve the capacity retention rate of the material.

[0088] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material, characterized in that: It includes the following steps: S1. uniformly dispersing graphene, carbon nanotubes, and polymer A in an organic solvent in sequence to obtain a carbon coating solution of a multidimensional carbon network; A high-nickel ternary material is added to the carbon coating liquid and uniformly dispersed to obtain a mixed slurry; the mixed slurry is heated to evaporate the solvent, sealed and allowed to stand, dried, ground, and sintered to obtain a high-nickel ternary material coated with a multidimensional carbon network; the polymer A has a molecular weight of 2000-300000 and is prepared by the following method: reaction monomer a, reaction monomer b, and an initiator are added to an organic solvent, heated for reaction, and then precipitated, filtered, washed, and dried to obtain polymer A; the reaction monomer a is at least one of styrene, α-ethylstyrene, 5-phenyl-1-pentene, 2-allyl-1,4-xylene, and 1-vinylpyrene; the reaction monomer b is at least one of acrylonitrile, propiolonitrile, divinylacetylene, and methyl methacrylate; S2. The high-nickel ternary material coated with the multidimensional carbon network is added to the modified solution of the electron-conducting / lithium-ion-conducting polymer B, and after uniform dispersion, the solution is heated to evaporate the solvent to obtain a high-nickel ternary positive electrode material with a multidimensional carbon network / polymer double coating; the electron-conducting / lithium-ion-conducting polymer B includes component C and component D, and the volume ratio of component C to component D is 1:1, wherein: the component C is at least one of polyacetylene, polybisyne, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and polypyrrole, and the component D is at least one of lithium polyacrylate, lithium polymaleate, lithium poly(methyl vinyl ether copolymer maleate), and lithium polymethacrylate.

2. The method for preparing the multidimensional carbon network / polymer double-coated high nickel ternary cathode material according to claim 1, characterized in that: The added amount of the initiator is 1-2% of the total mass of the reaction monomer a and the reaction monomer b, and the initiator is one of benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile.

3. The method for preparing the multidimensional carbon network / polymer double-coated high nickel ternary cathode material according to claim 1, characterized in that: The heating reaction is carried out by stirring at 50-70° C. for 6-12 hours.

4. The method for preparing a multidimensional carbon network / polymer double-coated high nickel ternary cathode material according to claim 1, characterized in that: In step S1, the mass ratio of graphene, carbon nanotubes, and polymer A is 1-1.5:1-2:1-3.5; And / or, in step S1, the number of graphene nanosheet layers is 2-6; And / or, in step S1, the particle size of the carbon nanotubes is 60-100 nm.

5. The method for preparing a high nickel ternary cathode material with a multidimensional carbon network / polymer double coating according to claim 1, characterized in that: In step S1, the molecular formula of the high nickel ternary material is LiNi x M 1-x O2, wherein: x ≥ 0.6, M is at least one of Co, Mn, Al, and Mg; And / or, in step S1, the mass ratio of the high nickel ternary material to the solute of the carbon coating solution is 1:1-3; And / or, in step S1, the sintering is carried out in an inert atmosphere in a tube furnace, heating the temperature to 500-900°C at a heating rate of 3°C / min, and keeping the temperature for 5-10 hours.

6. The method for preparing a multidimensional carbon network / polymer double-coated high nickel ternary cathode material according to claim 1, characterized in that: In step S2, the modified solution of the electron-conducting / lithium-ion-conducting polymer B is formed by dissolving the electron-conducting / lithium-ion-conducting polymer B at a concentration of 0.005-0.05 g / mL in an organic solvent, and the solid content of the modified solution of the electron-conducting / lithium-ion-conducting polymer B is 2-4 wt %; And / or, in step S2, the mass ratio of the multi-dimensional carbon network-coated high-nickel ternary material to the electron-conducting / lithium-conducting polymer B is 1:0.001-0.

1.

7. The method for preparing a multidimensional carbon network / polymer double-coated high nickel ternary cathode material according to claim 1, characterized in that: The organic solvent is one of N-methylpyrrolidone, acetone, ethanol, isopropanol, glycerol, methanol, dimethyl sulfoxide, and dimethylformamide; And / or, the uniform dispersion is achieved by mechanical stirring, and the mechanical stirring is at least one of ultrasound, high-speed shear emulsification, and wet ball milling.

8. A multi-dimensional carbon network / polymer double-coated high nickel ternary cathode material, characterized in that: It is prepared by the preparation method of the multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material according to any one of claims 1 to 7.

9. Use of the multidimensional carbon network / polymer double-coated high-nickel ternary positive electrode material as claimed in claim 8 in a lithium battery.

Images