CN112786846B - Cathode material, preparation method thereof and lithium ion battery - Google Patents

Cathode material, preparation method thereof and lithium ion battery Download PDF

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CN112786846B
CN112786846B CN201911087435.3A CN201911087435A CN112786846B CN 112786846 B CN112786846 B CN 112786846B CN 201911087435 A CN201911087435 A CN 201911087435A CN 112786846 B CN112786846 B CN 112786846B
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positive electrode
gas
active material
conductive
electrode active
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CN112786846A (en
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吴治国
洪丽
张海林
张勍
邹美靓
李艳
白培锋
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Evergrande New Energy Technology Shenzhen Co Ltd
Shanghai Cenat New Energy Co Ltd
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Shanghai Cenat New Energy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive electrode material, which comprises the following components: the anode comprises an anode active material, a composite metal oxide layer coated on the surface of the anode active material, and a composite carbon material layer coated on the surface of the composite metal oxide layer; wherein the composite carbon material layer comprises: conductive graphite, chain-shaped conductive carbon black, a conductive reinforcing agent and a binder. The positive electrode material comprises a positive electrode active substance, the surface of which is sequentially coated with a composite metal oxide layer and a composite carbon material layer, wherein the composite metal oxide layer can greatly reduce chemical or electrochemical reaction between electrolyte and the positive electrode active substance and can improve the storage and cycle performance of the battery; the composite carbon material coating layer of the multi-layer and multi-structure conductive network is formed by the conductive graphite, the chain-shaped conductive carbon black, the conductive reinforcing agent and the binder, so that the conductive performance and the battery power performance of the anode material are improved.

Description

Cathode material, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive electrode material and a preparation method thereof, and a lithium ion battery using the positive electrode material.
Background
Lithium ion batteries are receiving more and more attention because of their advantages of high energy density, small self-discharge, good safety performance, long cycle life, high operating voltage, etc. At present, lithium ion batteries are widely used in electronic products such as mobile phones, notebook computers, digital cameras, etc., and gradually replace traditional batteries in the fields of aviation, navigation, aerospace and military communication equipment, and are more widely used in the technical field of electric automobiles in recent years.
The lithium ion battery comprises a positive electrode material, a negative electrode material, a diaphragm and electrolyte. At present, LiCoO is the main anode material 2 、LiMn 2 O 4 、LiNi 0.5 Mn 1.5 O 4 、Li(Ni x Co y Mn z )O 2 (x + y + z is 1), and the like, but all of them have different disadvantages, and the positive electrode material is one of the key factors for further development of the lithium ion battery. With the higher requirement of the new energy industry on the endurance mileage of vehicles, the existing anode material cannot meet the requirements of people on high specific capacity, high specific power, long cycle life and low cost of the lithium ion battery. In order to further improve the performance of the cathode material, a lot of research on the cathode material has been carried out by those skilled in the lithium battery field, and various coated cathode materials are usually prepared by a solid-phase method or a liquid-phase method, so as to carry out modified coating on the cathode material. Alternatively, LiFePO is coated with C and LSM or CuO 4 And the electrochemical performance of high multiplying power is improved.
Although the existing method can improve the electrochemical performance of the battery to a certain extent, along with the continuous development of the industry, people have higher and higher performance requirements on the battery, and the existing method for improving the electrochemical performance by modifying and coating the anode material cannot meet the requirements. In addition, the anode material is generally a lithium-insertion transition metal oxide or lithium iron phosphate, which belongs to semiconductors, so that the problems of poor electron conductivity and low mass specific capacity of the anode, and low capacity performance and low large-current discharge capacity caused by poor conductivity of the anode can not be improved.
Disclosure of Invention
The invention aims to provide a positive electrode material, and aims to solve the technical problems of poor conductivity, poor cycle stability and storage stability of the conventional positive electrode material, low capacity performance, low large-current discharge capacity and the like caused by poor conductivity.
The invention also aims to provide a preparation method of the cathode material.
It is yet another object of the present invention to provide a lithium ion battery.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
a positive electrode material comprising: the composite material comprises a positive electrode active material, a composite metal oxide layer coated on the surface of the positive electrode active material, and a composite carbon material layer coated on the surface of the composite metal oxide layer; wherein the composite carbon material layer includes: conductive graphite, chain-shaped conductive carbon black, a conductive reinforcing agent and a binder.
Preferably, the composite metal oxide layer includes: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide; and/or the presence of a gas in the gas,
the positive electrode active material is selected from: a nickel cobalt manganese ternary material or a nickel cobalt aluminum ternary material;
the conductivity enhancer includes: at least one of carbon nanotubes and carbon nanofibers; and/or the presence of a gas in the atmosphere,
the chain-like conductive carbon black comprises: long single chain type conductive carbon black and branched chain type conductive carbon black; and/or the presence of a gas in the gas,
the adhesive comprises: at least one of polyvinylidene fluoride, polyvinylpyrrolidone and styrene butadiene rubber.
The coating amount of the composite metal oxide layer on the surface of the positive active material is 1000-3000 ug/g; and/or the presence of a gas in the atmosphere,
the mass ratio of the total mass of the positive electrode active material and the composite metal oxide layer to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductive reinforcing agent and the binder is (90-95): (0.5-1.5): 1-2: (0.8-1.5): (1.2-2.5); and/or the presence of a gas in the gas,
the nickel-cobalt-manganese ternary material comprises: at least one of NCM111, NCM523, NCM622, NCM 811; and/or the presence of a gas in the gas,
the specific surface area of the conductive graphite is 50-100g/m 2 (ii) a And/or the presence of a gas in the gas,
the specific surface area of the branched chain type conductive carbon black is 100-300g/m 2 。
Correspondingly, the preparation method of the cathode material is carried out in a protective gas atmosphere with the ambient humidity of 1% -30%, and comprises the following steps:
obtaining a positive electrode active substance and a composite metal oxide, and coating the surface of the positive electrode active substance with the composite metal oxide to obtain a first positive electrode active material;
obtaining a composite carbon material, and mixing the composite carbon material and the first positive electrode active material to coat the surface of the first positive electrode active material with the composite carbon material to obtain a second positive electrode active material;
and obtaining a binder, and mixing and dispersing the binder and the second positive electrode active material to obtain a positive electrode material.
Preferably, the step of mixing the composite carbon material with the first positive electrode active material includes:
obtaining conductive graphite and long single-chain type conductive carbon black, and carrying out primary mixing treatment on the conductive graphite, the long single-chain type conductive carbon black and the first positive electrode active material to obtain a first mixture;
obtaining branched chain type conductive carbon black, and carrying out secondary mixing treatment on the branched chain type conductive carbon black and the first mixture to obtain a second mixture;
and obtaining a conductive reinforcing agent, and carrying out third mixing treatment on the conductive reinforcing agent and the second mixture to obtain the second positive electrode active material.
Preferably, the step of coating the composite metal oxide on the surface of the positive electrode active material includes: coating the composite metal oxide on the surface of the positive active material by adopting a wet coating process or a calcining process; and/or the presence of a gas in the atmosphere,
the step of mixing and dispersing the binder with the second positive electrode active material includes: dissolving the binder in a first organic solvent to form binder gel, and mixing and dispersing the binder gel with the second positive electrode active material to obtain a positive electrode material; and/or the presence of a gas in the atmosphere,
the method also comprises the following steps of: and adding a second organic solvent into the positive electrode material, and mixing again to obtain positive electrode slurry.
Preferably, the conditions of the first mixing process include: stirring for 15-30 min under the condition that the revolution speed is 5-20 rpm; and/or the presence of a gas in the atmosphere,
the conditions of the second mixing treatment comprise: stirring for 5-20 min under the condition that the revolution speed is 5-50 rpm; and/or the presence of a gas in the gas,
the conditions of the third mixing treatment include: stirring for 20-50 min under the conditions that the revolution speed is 5-10 rpm and the rotation speed is 250-400 rpm; and/or the presence of a gas in the gas,
the conditions of the mixing and dispersing treatment comprise: stirring for 100-150 min under the conditions that the revolution speed is 15-30 rpm and the rotation speed is 800-1500 rpm; and/or the presence of a gas in the gas,
the conditions for performing the mixing treatment again include: stirring for 100-150 min under the conditions that the revolution speed is 30-50 rpm and the rotation speed is 2000-3000 rpm.
Preferably, the solid content of the conductivity enhancer is not less than 85%, and the conductivity enhancer comprises: at least one of carbon nanotubes and carbon nanofibers; and/or the presence of a gas in the gas,
the coating amount of the composite metal oxide in the first positive electrode active material to the positive electrode active material is 1000-3000 ug/g; and/or the presence of a gas in the gas,
the mass ratio of the binder to the organic solvent in the binder gel is 1: (9-33), the viscosity of the adhesive gel is 500-3000 mpa.s; and/or the presence of a gas in the atmosphere,
in the positive electrode material, the mass ratio of the total mass of the positive electrode active substance and the composite metal oxide to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductive reinforcing agent and the binder is (90-95): 0.5-1.5): 1-2: (1-2): 0.8-1.5): (1.2-2.5); and/or the presence of a gas in the gas,
the content of the organic solvent in the anode material is 5-30%; and/or the presence of a gas in the gas,
the first organic solvent and the second organic solvent are each independently selected from: at least one of N-methyl pyrrolidone and acetone.
Preferably, the composite metal oxide includes: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide; and/or the presence of a gas in the gas,
the positive electrode active material is selected from: a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material; and/or the presence of a gas in the gas,
the adhesive comprises: at least one of polyvinylidene fluoride, polyvinylpyrrolidone and styrene butadiene rubber; and/or the presence of a gas in the gas,
the specific surface area of the conductive graphite is 50-100g/m 2 (ii) a And/or the presence of a gas in the gas,
the specific surface area of the branched chain type conductive carbon black is 100-300g/m 2 。
Correspondingly, the lithium ion battery comprises the cathode material or the cathode material prepared by the method.
The invention provides a positive electrode material, which comprises a positive electrode active substance, wherein the surface of the positive electrode active substance is sequentially coated with a composite metal oxide layer and a composite carbon material layer, and the composite carbon material layer comprises: on one hand, the composite metal oxide layer coated on the outer surface of the positive active material can greatly reduce the chemical or electrochemical reaction between the electrolyte and the positive active material, and can improve the storage and cycle performance of the battery; on the other hand, the composite carbon material layer coated on the surface of the metal oxide layer contains conductive graphite, chain-shaped conductive carbon black, a conductive reinforcing agent and a binder, and the binder enables conductive carbon materials in various different forms such as particles, chains and the like to form a multi-structure conductive network on the surface of the metal oxide layer, the multi-structure conductive network comprises a multi-branch conductive network and intermediate-state small conductive networks such as a dot network structure and the like between the multi-branch conductive network and the dot network to form the multi-structure and multi-layer conductive network, so that micro-current is converged to a main trunk of a branch chain from the tail end of each branch chain or the conductive carbon black point and converged to a current collector through the conductive reinforcing agent, the conductive performance of the positive electrode material is effectively improved, and the power performance of the battery is improved.
The preparation method of the anode material provided by the invention comprises the steps of firstly coating a composite metal oxide on the surface of an anode active substance under the atmosphere of protective gas with the ambient humidity of 1-30% to obtain a first anode active material; and finally, stably combining and coating the composite carbon material on the surface of the positive active material through a binder to form a composite carbon material coating layer with a multi-layer and multi-structure conductive network, so as to obtain the positive material with the surface sequentially coated with the composite metal oxide and the composite carbon material. The preparation method provided by the invention is simple in process, and the prepared cathode material is good in cycling stability, good in safety and excellent in conductivity due to the fact that the surface of the cathode material is sequentially coated with the composite metal oxide and the composite carbon material, and the power performance of the battery can be effectively improved.
The lithium ion battery provided by the invention comprises the positive electrode material which is formed by sequentially coating the positive electrode active material with the composite metal oxide layer and the composite carbon material layer, and the positive electrode material has the advantages of good cycle stability, high safety and excellent conductivity, so that the lithium ion battery has high power performance.
Drawings
Fig. 1 is a schematic structural diagram of a positive electrode material provided in an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a single positive electrode active particle in a positive electrode material provided in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art without making any creative effort in combination with the embodiments of the present invention belong to the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiment of the present invention may be a unit of mass known in the chemical industry field, such as μ g, mg, g, and kg.
As shown in fig. 1 and 2, an embodiment of the present invention provides a positive electrode material including: the composite material comprises a positive electrode active material, a composite metal oxide layer coated on the surface of the positive electrode active material, and a composite carbon material layer coated on the surface of the composite metal oxide layer; wherein the composite carbon material layer comprises: conductive graphite, chain-shaped conductive carbon black, a conductive reinforcing agent and a binder.
The positive electrode material provided by the embodiment of the invention comprises a positive electrode active substance with a surface sequentially coated with a composite metal oxide layer and a composite carbon material layer, wherein the composite carbon material layer comprises: on one hand, the composite metal oxide layer coated on the outer surface of the positive active material can greatly reduce the chemical or electrochemical reaction between the electrolyte and the positive active material, and can improve the storage and cycle performance of the battery; on the other hand, the composite carbon material layer coated on the surface of the metal oxide layer contains conductive graphite, chain-shaped conductive carbon black, a conductive reinforcing agent and a binder, and the binder enables conductive carbon materials in various different forms such as particles, chains and the like to form a multi-structure conductive network on the surface of the metal oxide layer, the multi-structure conductive network comprises a multi-branch conductive network and intermediate-state small conductive networks such as a dot network structure and the like between the multi-branch conductive network and the dot network to form the multi-structure and multi-layer conductive network, so that micro-current is converged to a main trunk of a branch chain from the tail end of each branch chain or the conductive carbon black point and converged to a current collector through the conductive reinforcing agent, the conductive performance of the positive electrode material is effectively improved, and the power performance of the battery is improved.
In some embodiments, the composite metal oxide layer coated on the surface of the positive active material includes: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide. According to the embodiment of the invention, at least two transition metal oxides of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide coated on the surface of the positive active material form a composite metal oxide layer, so that on one hand, the positive active material can be stably protected, and the positive active material is prevented from structural collapse; on the other hand, the electrochemical performance of the positive active material can be better improved, and the chemical or electrochemical reaction between the electrolyte and the positive active material is greatly reduced, so that the corrosion of the electrolyte to the positive active material is avoided, and the storage performance, the cycle performance, the safety performance and the like of the battery are improved. In some embodiments, the composite metal oxide layer coated on the surface of the positive active material includes cobalt oxide, aluminum oxide and titanium oxide, and the composite metal oxide layer formed by cobalt oxide, aluminum oxide and titanium oxide can stabilize and protect the positive active material better, and improve the stability and safety of the positive active material.
In some embodiments, the coating amount of the composite metal oxide layer on the surface of the positive active material is 1000-3000ug/g, and as the coating amount of the composite metal oxide layer increases, the composite metal oxide layer can protect the positive active material more strongly, and the side reaction between the electrolyte and the positive active material is less, but if the coating amount of the composite metal oxide layer is too large, the insertion and extraction of lithium ions on the surface of the positive active material can be affected, so that the charging and discharging and power performance of the battery can be affected; if the coating amount of the composite metal oxide layer is too small, the positive active material cannot be protected well, side reactions between the electrolyte and the positive active material increase, and the structure and performance of the positive active material are damaged.
In some embodiments, the composite carbon material layer coated on the surface of the composite metal oxide layer comprises dotted conductive graphite, chain conductive carbon black, a conductive reinforcing agent and the like, wherein the chain conductive carbon black comprises long single chain conductive carbon black and branched conductive carbon black; the conductive reinforcing agent includes a long chain carbon nanotube, a carbon nanofiber and the like. Chain conductive carbon blacks such as long single chain conductive carbon black, branched chain conductive carbon black and the like can form a staggered conductive network structure on the surface of the composite metal oxide layer, and the dotted conductive graphite can play a role of point-line connection in the conductive network structure, so that branches of the network structure are refined, and conductive network nodes are reinforced; the conductive reinforcing agents such as the long-chain carbon nanotubes and the carbon nanofibers can further wrap the conductive network structure in a winding manner, so that the formed composite carbon material wrapping layers are enriched and reinforced, the conductive carbon materials in different forms can wrap the surface of the composite metal oxide layer through the adhesive to form a multi-layer and multi-structure conductive network with points, lines and nets, and through the mutual synergistic effect of the conductive carbon materials, the composite conductive network structure with excellent conductive performance is formed on the surface of the positive active material, so that the conductive performance and the power performance of the positive active material are effectively improved. In some specific embodiments, the composite carbon material layer coated on the surface of the composite metal oxide layer comprises dot-shaped conductive graphite (KS-6), long single chain type conductive carbon black (Super-p), branched chain type conductive carbon black (Litx300) and a conductive reinforcing agent such as long chain type carbon nano tubes and carbon nano fibers.
In some embodiments, the conductive graphite in the composite carbon material layer has a specific surface area of 50 to 100g/m 2 . In some embodiments, the specific surface area of the branched conductive carbon black is 100-300g/m 2 . The conductive graphite and the branched chain type conductive carbon black adopted by the embodiment of the invention both have larger specific surface areas, are more favorable for forming a composite carbon material coating layer of a multi-layer and multi-structure conductive network, and improve the conductivity of the positive active material. If the specific surface of the conductive material is too small, the contact points of the conductive agent and the active material are fewer, and the conductivity is reduced for the conductive agent with the same quality; if the specific surface of the conductive material is too large, the particles of the conductive material are mutually adsorbed and agglomerated, and are difficult to disperse, so that the advantage of large specific surface is difficult to exert, and the large agglomerated particles in the positive electrode slurry are caused to influence the processes of coating of the positive electrode material, manufacturing of a pole piece and the like. In some embodiments, the specific surface area of the conductive graphite in the composite carbon material layer may be 50g/m 2 、60g/m 2 、70g/m 2 、80g/m 2 、90g/m 2 Or 100g/m 2 The specific surface area of the branched chain type conductive carbon black may be 100g/m 2 、150g/m 2 、200g/m 2 、250g/m 2 Or 300g/m 2 。
In some embodiments, the binder in the composite carbon material layer coated on the surface of the composite metal oxide layer comprises: the composite carbon material coating layer of the multi-level and multi-structure conductive network is formed on the surface of the composite metal oxide layer on the outer surface of the positive active material by adopting any one of the adhesives, namely the polyvinylidene fluoride, the polyvinylpyrrolidone and the styrene butadiene rubber, so that the conductivity of the positive active material is improved.
In some embodiments, the mass ratio of the total mass of the positive electrode active material and the composite metal oxide layer in the positive electrode active material of the present application to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductivity enhancer and the binder is (90-95): (0.5-1.5): (1-2): (0.8-1.5): (1.2-2.5). In the positive active material of the embodiment of the invention, the positive active material is a main active material of the lithium ion battery and provides lithium ions for the battery. The composite carbon material layer can provide electronic conductivity during charging and discharging, particularly large-current charging and discharging, and the composite carbon material layer can realize better conductivity with smaller proportion by taking a plurality of conductive materials such as conductive graphite, long single-chain conductive carbon black, branched-chain conductive carbon black, a conductive reinforcing agent and the like as the composite conductive agent, and can form a composite carbon material coating layer with a multi-layer and multi-structure conductive network on the surface of the composite metal oxide layer by the mass ratio to improve the conductivity of the positive active material. The binder has the function of binding the positive active material coated with the composite metal oxide and the composite carbon material together to form a stable composite carbon material coated network as a stable electrode part.
In some embodiments, the positive active material employed in the positive electrode material is selected from: nickel cobalt manganese ternary material or nickel cobalt aluminium ternary material, wherein, nickel cobalt manganese ternary material includes: at least one of NCM111, NCM523, NCM622 and NCM811, wherein the positive active materials can provide lithium ions for the battery and have better lithium ion intercalation and deintercalation performance.
In some embodiments, the positive electrode material comprises a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material positive electrode active substance, at least two composite metal oxide layers of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide coated on the surface of the positive electrode active substance, and a layer coated on the surface of the composite metal oxide layer and containing conductive graphite and long single-chain conductive carbon blackA composite carbon material layer of branched conductive carbon black, a conductive reinforcing agent and a binder; wherein the mass ratio of the total mass of the positive electrode active substance and the composite metal oxide layer to the conductive graphite, the long single chain type conductive carbon black, the branched chain type conductive carbon black, the conductive reinforcing agent and the binder is (90-95): (0.5-1.5): 1-2: (0.8-1.5): (1.2-2.5); the conductivity enhancer includes: at least one of carbon nanotubes and carbon nanofibers; the conductivity enhancer includes: at least one of carbon nanotubes and carbon nanofibers; the specific surface area of the conductive graphite is 50-100g/m 2 (ii) a The specific surface area of the branched chain type conductive carbon black is 100-300g/m 2 。
The positive electrode material provided by the embodiment of the invention can be prepared by the following method.
The embodiment of the invention also provides a preparation method of the cathode material, which is carried out in a protective gas atmosphere with the ambient humidity of 1% -30%, and comprises the following steps:
s10, obtaining a positive electrode active substance and a composite metal oxide, and coating the surface of the positive electrode active substance with the composite metal oxide to obtain a first positive electrode active material;
s20, obtaining a composite carbon material, mixing the composite carbon material with the first positive electrode active material, and coating the surface of the first positive electrode active material with the composite carbon material to obtain a second positive electrode active material;
s30, obtaining a binder, and mixing and dispersing the binder and the second positive electrode active material to obtain a positive electrode material.
According to the preparation method of the anode material provided by the embodiment of the invention, under the atmosphere of protective gas with the ambient humidity of 1% -30%, the surface of an anode active substance is coated with a composite metal oxide to obtain a first anode active material; and finally, stably combining and coating the composite carbon material on the surface of the positive active material through a binder to form a composite carbon material coating layer with a multi-layer and multi-structure conductive network, so as to obtain the positive material with the surface sequentially coated with the composite metal oxide and the composite carbon material. The preparation method provided by the embodiment of the invention has simple process, and the prepared cathode material has good cycling stability, good safety and excellent conductivity due to the fact that the surface of the cathode material is sequentially coated with the composite metal oxide and the composite carbon material, and can effectively improve the power performance of the battery.
Specifically, the preparation method of the cathode material provided by the embodiment of the invention is carried out under a protective gas atmosphere with an ambient humidity of 1% -30%, wherein the protective gas atmosphere includes but is not limited to at least one of nitrogen, argon and helium, and can effectively prevent active substances in the cathode material from being oxidized. In addition, the environment humidity of 1-30% can prevent the moisture absorption of the anode active substance with large specific surface area and the conductive carbon material from influencing the quality of the material; can also prevent LiOH and Li in the anode material 2 CO 3 The quality of the anode material is influenced by the excessive moisture caused by the strong hygroscopicity of residual alkali.
Specifically, in step S10, a positive electrode active material and a composite metal oxide are obtained, and the surface of the positive electrode active material is coated with the composite metal oxide, so as to obtain a first positive electrode active material. According to the embodiment of the invention, the composite metal oxide is coated on the surface of the positive active material, so that the positive active material can be stably protected, and the positive active material is prevented from collapsing; the electrochemical performance of the positive active material can be better improved, and the chemical or electrochemical reaction between the electrolyte and the positive active material is greatly reduced, so that the corrosion of the electrolyte to the positive active material is avoided, and the storage performance, the cycle performance and the safety performance of the battery are improved. In some embodiments, the composite metal oxide is coated on the surface of the positive active material by a wet coating process. In other embodiments, a precursor of the positive electrode active material is mixed with a plurality of metal salts or oxides, and then the metal oxides are coated on the surface of the positive electrode active material by high-temperature sintering to form a composite metal oxide layer. In some embodiments, the composite metal oxide comprises: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide.
In some embodiments, the coating amount of the composite metal oxide on the positive active material in the first positive active material is 1000-3000ug/g, the composite metal oxide layer can protect the positive active material more strongly with the increase of the coating amount of the composite metal oxide layer, the side reaction of the electrolyte and the positive active material is less, but if the coating amount of the composite metal oxide layer is too much, the intercalation and deintercalation of lithium ions on the surface of the positive active material can be affected, and thus the charge and discharge and power performance of the battery can be affected; if the coating amount of the composite metal oxide layer is too small, the positive active material cannot be protected well, side reactions between the electrolyte and the positive active material increase, and the structure and performance of the positive active material are damaged.
Specifically, in step S20, a composite carbon material is obtained, and the composite carbon material is mixed with the first positive electrode active material so that the surface of the first positive electrode active material is coated with the composite carbon material, thereby obtaining a second positive electrode active material. Wherein the step of mixing the composite carbon material with the first positive electrode active material includes:
s21, obtaining conductive graphite and long single-chain type conductive carbon black, and carrying out primary mixing treatment on the conductive graphite, the long single-chain type conductive carbon black and the first positive electrode active material to obtain a first mixture;
s22, obtaining branched chain type conductive carbon black, and carrying out secondary mixing treatment on the branched chain type conductive carbon black and the first mixture to obtain a second mixture;
s23, obtaining a conductive reinforcing agent, and carrying out third mixing treatment on the conductive reinforcing agent and the second mixture to obtain the second positive electrode active material.
According to the embodiment of the invention, the composite carbon material and the first positive electrode active material are mixed, so that the surface of the first positive electrode active material is coated with the composite carbon material. In step S21, the granular conductive graphite and the long single-chain conductive carbon black are fully and uniformly mixed with the first positive electrode active material, so that the conductive graphite and the long single-chain conductive carbon black are coated on the surface of the first positive electrode active material to form a dot-line network coating structure; then, the branched chain type conductive carbon black is added and fully and uniformly mixed through the step S22, so that the branched chain type conductive carbon black is further coated on a point-line-shaped network coating structure formed on the surface of the first anode material, and the coated composite carbon material network structure is more refined and abundant; and step S23, adding a conductive reinforcing agent, fully mixing, further forming a multi-branched intermediate state small conductive network on the coated composite carbon material network structure to form a multi-structure and multi-layer composite carbon material network coating structure, so that micro-current is collected onto the trunk channels of the branched chains from the tail ends of the branched chains or conductive graphite, and finally collected onto a current collector through the conductive reinforcing agent and the like, thereby improving the conductive performance and the power performance of the battery.
In some embodiments, the method comprises the steps of obtaining conductive graphite and long single-chain type conductive carbon black, and stirring the conductive graphite, the long single-chain type conductive carbon black and the first positive electrode active material for 15-30 min under the condition that the revolution speed is 5-20 rpm, so as to fully and uniformly mix the conductive graphite, the long single-chain type conductive carbon black and the first positive electrode active material, so that the conductive graphite and the long single-chain type conductive carbon black are coated on the surface of the first positive electrode active material through intermolecular force, and thus obtaining a first mixture.
In some embodiments, the branched chain type conductive carbon black is obtained, the branched chain type conductive carbon black and the first mixture are stirred for 5-20 min to be fully and uniformly mixed under the condition that the revolution speed is 5-50 rpm, so that the branched chain type conductive carbon black is coated on a network structure formed by coating conductive graphite and long single chain type conductive carbon black on the surface of the first positive electrode active material through intermolecular force, and a second mixture is obtained.
In some embodiments, a conductive reinforcing agent is obtained, and the conductive reinforcing agent and the second mixture are stirred for 20-50 min to be mixed uniformly under the conditions that the revolution speed is 5-10 rpm and the rotation speed is 250-400 rpm, so that the conductive reinforcing agent is further coated on a conductive network formed by the composite carbon material on the outer surface of the first positive electrode material through intermolecular force, and the second positive electrode active material is obtained.
In some embodiments, the conductivity enhancer has a solids content of not less than 85%, and the conductivity enhancer includes: the conductive reinforcing agent with high solid content can form a mud shape with the second mixture, so that the conductive reinforcing agent is better coated in a conductive network structure formed by a composite carbon material on the surface of the positive active material, wherein the carbon nano tube and the carbon nano fiber with high length-diameter ratio can not only form a better network structure on the surface of the positive active material, but also have excellent conductive performance, and can obviously improve the conductive performance of the positive active material, thereby improving the power performance of the battery.
In some embodiments, the conductive graphite has a specific surface area of 50 to 100g/m 2 . In some embodiments, the branched conductive carbon black has a specific surface area of 100-300g/m 2 . The conductive graphite and the branched chain type conductive carbon black adopted by the embodiment of the invention both have larger specific surface area, are more favorable for forming a composite carbon material coating layer of a multi-layer and multi-structure conductive network, and improve the conductivity of the positive active material.
In some embodiments, the positive active material is selected from: nickel cobalt manganese ternary material or nickel cobalt aluminium ternary material, wherein, nickel cobalt manganese ternary material includes: at least one of NCM111, NCM523, NCM622 and NCM811, wherein the positive active materials can provide lithium ions for the battery and have better lithium ion intercalation and deintercalation performance.
Specifically, in step S30, a binder is obtained, and the binder and the second positive electrode active material are mixed and dispersed to obtain a positive electrode material. According to the embodiment of the invention, the adhesive and the second positive electrode active material are fully mixed and dispersed, so that the adhesive permeates into the composite carbon material coating layer, and the composite carbon material is stably coated on the surface of the first positive electrode active material to form the stable positive electrode material.
In some embodiments, the step of mixing and dispersing the binder with the second positive electrode active material includes: and dissolving the binder in a first organic solvent to form binder gel, and mixing the binder gel with the second positive electrode active material for dispersion treatment to obtain the positive electrode material. According to the embodiment of the invention, the adhesive and a part of solvent are mixed to form the adhesive gel, and then the adhesive gel is mixed and dispersed with the second positive electrode active material, so that the adhesive gel can be better infiltrated into the composite carbon material coating layer in the second positive electrode active material, and the composite carbon material can be stably combined and coated on the surface of the first positive electrode material to form the positive electrode material. In this case, the positive electrode material contains a part of the organic solvent, and the coated positive electrode material powder can be obtained by further drying the organic solvent to remove the solvent; can also be directly used for standby, and the viscosity is adjusted to the actual requirement when the adhesive is used. Under the condition of high viscosity, when the stirrer is used for dispersing, the shearing force of the stirring slurry can more crush particles in the slurry; and under the condition of low viscosity, the shearing force of the stirring slurry only provides energy for the slurry to perform circular motion, particles can move around the stirring machine in a circular mode, but the particles are not easy to break, the slurry is easy to have particles, and the dispersing effect is not good. Therefore, the embodiment of the invention mixes the binder into gel and then mixes and disperses the gel with the second positive electrode active material, which is more favorable for uniform dispersion and obtains the positive electrode material with stable combination of the coating layer.
In some embodiments, the mass ratio of the binder to the organic solvent in the binder gel is 1: (9-33), the viscosity of the binder gel is 500-3000mpa.s, and the binder gel with the characteristics is not only beneficial to stably combining a coating layer on the surface of the positive electrode active material, but also beneficial to enabling the positive electrode active material coated in the positive electrode material to form uniformly dispersed colloid, so that the agglomeration among the positive electrode active materials is avoided, and the performance is not influenced. In some embodiments, the mass ratio of the binder to the organic solvent in the binder gel may be 1: 10. 1:15, 1:20, 1:25, or 1:30, and the viscosity of the binder gel may be 500mpa.s, 1000mpa.s, 1500mpa.s, 2000mpa.s, 2500mpa.s, or 3000 mpa.s.
In some embodiments, the binder comprises: the composite carbon material coating layer of the multi-level and multi-structure conductive network is formed on the surface of the composite metal oxide layer on the outer surface of the positive active material by adopting any one of the adhesives, namely the polyvinylidene fluoride, the polyvinylpyrrolidone and the styrene butadiene rubber, so that the conductivity of the positive active material is improved.
In some embodiments, the obtaining of the cathode material further includes: and adding a second organic solvent into the positive electrode material, and mixing again to obtain positive electrode slurry. In the embodiment of the invention, the second organic solvent can be added into the dried positive electrode material powder or the positive electrode material obtained after the positive electrode material powder and the binder gel are uniformly mixed, and the mixture is mixed again, so that the positive electrode material is adjusted into positive electrode slurry with any viscosity, and the positive electrode slurry can be directly used for manufacturing the positive electrode plate. In some embodiments, the mass percentage of the organic solvent in the positive electrode slurry is 5% to 30%, and the solvent proportion of the mass percentage enables the positive electrode slurry to have a better coating film forming property, so that the positive electrode slurry is not too thin to be coated due to too much solvent, and the positive electrode sheet manufacturing process is not affected due to too thick slurry due to too little solvent and being incapable of being coated uniformly.
In some embodiments, the first organic solvent and the second organic solvent are each independently selected from: the solvents have better dissolving and dispersing effects on the anode material and the binder, can disperse the anode material to form a uniform organic whole, and are favorable for preparing the anode sheet by coating anode slurry.
In some embodiments, in the positive electrode material, a mass ratio of a total mass of the positive electrode active material and the composite metal oxide to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductive reinforcing agent, and the binder is (90-95): (0.5-1.5): (1-2): (0.8-1.5): (1.2-2.5), the components of the mixture ratio have the best stable synergistic effect on the positive active material, provide the conductivity of the positive active material and further improve the power performance of the battery.
Correspondingly, the embodiment of the invention also provides a lithium ion battery, and the lithium ion battery comprises the cathode material or the cathode material prepared by the method.
The lithium ion battery provided by the embodiment of the invention comprises the positive electrode material which is formed by sequentially coating the positive electrode active material with the composite metal oxide layer and the composite carbon material layer, and the positive electrode material has the advantages of good cycle stability, high safety and excellent conductivity, so that the lithium ion battery provided by the embodiment of the invention has high power performance.
In order to clearly understand the details of the above implementation and operation of the present invention by those skilled in the art, and to obviously embody the advanced performance of the cathode material, the preparation method thereof and the lithium ion battery according to the embodiment of the present invention, the above technical solution is illustrated by a plurality of examples.
Example 1
A positive electrode material is prepared under the conditions of nitrogen atmosphere protection and 1% -30% of ambient humidity, and comprises the following preparation steps:
firstly, taking a certain amount of NCM111 dry powder, adding a certain amount of cobalt oxide, aluminum oxide and titanium oxide, uniformly mixing, and coating the NCM111 by adopting a wet coating process, wherein the coating amount is controlled at 1000-3000 ppm;
putting 93 parts of NCM111 dry powder coated by various metal oxides, 1 part of conductive graphite KS-6 and 1.5 parts of long single-chain conductive carbon black Super-p into a stirring tank, stirring for 20min at the revolution speed of 10rpm to ensure that the KS-6 and the Super-p are fully coated on the surface of the ternary material particles,
thirdly, adding 1.5 parts of branched chain type conductive carbon black LiTX300, and stirring for 10min at the revolution speed of 10rpm to ensure that the branched chain type conductive carbon black is sequentially coated on the outer surface of the ternary material particles;
adding 1.4 parts of a conductive reinforcing agent, preferably 85% carbon nano tubes in the embodiment, and stirring for 30min at revolution of 5rpm and rotation speed of 300rmp to form a solid-liquid mixture with high solid content, kneading so that the carbon nano tubes sequentially surround the outer surfaces of the ternary material particles coated by the conductive agent to form a muddy solid-liquid mixture which is muddy because the solid content of the added carbon nano tubes is high;
mixing polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) according to the proportion of 1:19, fully stirring until a glue is formed, adding 1.6 parts of PVDF glue into the pasty solid-liquid mixture, and stirring for 120min at the revolution speed of 20rpm and the rotation speed of 1000 rpm; then adding the residual solvent NMP, and stirring for 120min at the speed of revolution of 40rpm and rotation of 2500 rmp;
sixthly, performing high-speed centrifugal dispersion on the slurry by using high-speed centrifugal dispersion equipment, wherein the rotating speed is 8000-.
A lithium ion battery comprises the following preparation steps:
coating the positive electrode material, wherein the density of a coated single side is 90 g/square meter, the density of a double side is 180 g/square meter, and the coating speed is 10-50 m/min;
secondly, the coated pole piece is placed in a rolling machine for rolling, the rolling pressure is 30-60 tons, and the running speed is 20-50 m/min;
thirdly, the rolled pole piece is subjected to slitting and die cutting to prepare a positive pole piece;
and fourthly, assembling the prepared positive plate, a negative plate made of graphite or amorphous carbon and a polypropylene or polyethylene diaphragm to prepare a naked electric core, then filling the naked electric core into an aluminum plastic film, injecting electrolyte, and preparing the battery 1 through activation.
Example 2
A positive electrode material is prepared under the conditions of nitrogen atmosphere protection and 1% -30% of ambient humidity, and comprises the following preparation steps:
firstly, taking a certain amount of NCM111 dry powder, adding a certain amount of cobalt oxide, aluminum oxide and titanium oxide, uniformly mixing, and coating the NCM111 by adopting a wet coating process, wherein the coating amount is controlled at 1000-3000 ppm;
② putting 92.7 parts of NCM111 dry powder coated by various metal oxides, 1 part of conductive graphite KS-6 and 1.5 parts of long single-chain conductive carbon black Super-p into a stirring tank, stirring for 20min at the revolution speed of 10rpm to ensure that KS-6 and Super-p are fully coated on the surface of ternary material particles,
thirdly, adding 1.5 parts of branched chain type conductive carbon black LiTX300, and stirring for 10min at the revolution speed of 10rpm to ensure that the branched chain type conductive carbon black is sequentially coated on the outer surface of the ternary material particles;
adding 1.5 parts of a conductive reinforcing agent, preferably 85% carbon nano tubes in the embodiment, stirring for 30min at 5rpm revolution and 300rmp rotation speed to form a solid-liquid mixture with high solid content, and kneading so that the carbon nano tubes sequentially surround the outer surfaces of the ternary material particles coated by the conductive agent to form a muddy solid-liquid mixture which is muddy because the solid content of the added carbon nano tubes is high;
fifthly, mixing polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) according to the ratio of 2:23, fully stirring until a glue solution is formed, adding 1.8 parts of PVDF glue solution into the muddy solid-liquid mixture, and stirring for 120min at the revolution speed of 20rpm and the rotation speed of 1000 rpm; adding residual solvent NMP, stirring at revolution speed of 40rpm and rotation speed of 2500rmp for 120min,
sixthly, performing high-speed centrifugal dispersion on the slurry by using high-speed centrifugal dispersion equipment, wherein the rotating speed is 8000-.
A lithium ion battery comprises the following preparation steps:
coating the positive electrode material, wherein the density of a coated single side is 90 g/square meter, the density of a double side is 180 g/square meter, and the coating speed is 10-50 m/min;
secondly, the coated pole piece is placed in a rolling machine for rolling, the rolling pressure is 30-60 tons, and the running speed is 20-50 m/min;
thirdly, the rolled pole piece is subjected to slitting and die cutting to prepare the positive pole piece.
And fourthly, assembling the prepared positive plate, a negative plate made of graphite or amorphous carbon and a polypropylene or polyethylene diaphragm to prepare a naked battery cell, then filling the naked battery cell into an aluminum-plastic film, injecting electrolyte, and activating to prepare the battery 2.
Comparative example 1
A positive electrode material is prepared under the conditions of nitrogen atmosphere protection and 1% -30% of ambient humidity, and comprises the following preparation steps:
putting 92 parts of NCM111 dry powder (for better comparability with the embodiment 1 and the embodiment 2), 1 part of conductive graphite KS-6 and 4 parts of long single-chain type conductive carbon black Super-p into a stirring tank, and stirring for 20min at a revolution speed of 10rpm to ensure that KS-6 and SP are fully wrapped on the surface of ternary material particles to form a mixture of a positive electrode material and a conductive agent;
secondly, adding the PVDF glue solution into the mixture obtained in the second step, and stirring for 180min at a revolution speed of 20rpm and a self-transmission speed of 1000 rpm; then adding the residual solvent NMP, and stirring for 120min at the speed of revolution of 40rpm and rotation of 2500 rmp;
thirdly, high-speed dispersion, namely, carrying out high-speed centrifugal dispersion on the slurry by using high-speed centrifugal dispersion equipment, wherein the rotating speed is 8000rmp plus materials, the flow rate is 5-20L/min, then carrying out sieving and demagnetization, and sieving by using a sieve with 200 meshes of 150 plus materials, thereby obtaining the anode material;
a lithium ion battery comprises the following preparation steps:
coating the positive electrode material, wherein the density of a coated single side is 90 g/square meter, the density of a double side is 180 g/square meter, and the coating speed is 10-50 m/min;
secondly, the coated pole piece is placed in a rolling machine for rolling, the rolling pressure is 30-60 tons, and the running speed is 20-50 m/min;
thirdly, the rolled pole piece is subjected to slitting and die cutting to prepare the positive pole piece.
And fourthly, assembling the prepared positive plate, a negative plate made of graphite or amorphous carbon and a polypropylene or polyethylene diaphragm to prepare a naked electric core, then filling the naked electric core into an aluminum plastic film, injecting electrolyte, and preparing the battery 3 through activation.
Further, in order to verify the advancement of the lithium ion battery prepared from the cathode material in the embodiment of the present invention, the embodiment of the present invention performs a performance test.
Test example 1
The battery 1 prepared in example 1, the battery 2 prepared in example 2, and the battery 3 prepared in comparative example 3 were subjected to a cycle test and a high-temperature storage test:
as shown in table 1, the capacity retention rate of each battery after the first week, 500 th week, 1000 th week, and 1500 th week of the cycle is:
TABLE 1
Group of Week 1 Week 500 Week 1000 Week 1500
Example 1 100％ 97.1％ 94.3％ 92％
Example 2 100％ 94.9％ 91.4％ 89.6％
Comparative example 1 100％ 94.6％ 87.0％ 80.3％
As shown in table 2, which is a graph comparing high-temperature cycle performance, table 2 is a table of changes in remaining capacity and recovered capacity of battery 1, battery 2, and battery 3 stored at a high temperature of 60 ℃ at a 100% SOC for 7 days:
TABLE 2
Storage testing Example 1 Example 2 Comparative example 1
Residual capacity (%) 94.3％ 93.6％ 89.7％
Recovery capacity (%) 97.7％ 97.5％ 94.5％
As can be seen from the above test results, the batteries 1 and 2 prepared by using the positive electrode materials in which the surfaces of the positive electrode active materials are sequentially coated with the composite metal oxide layer and the composite carbon material layer in examples 1 and 2 of the present invention have better thermal stability and structural stability during the cycle process, compared to the battery 3 of the reference 1. As can be seen from table 1, the multiple different conductive agents form a multi-structure and multi-layer composite carbon material layer conductive network, so that the conductive performance is better, the capacity retention rate of the battery 1 after 1000 cycles is 94.3%, the capacity retention rate of the battery 2 after 1000 cycles is 91.4%, and the capacity retention rate of the battery 2 after 1000 cycles is only 87.0% compared to the battery 3 of the comparative example 1.
In addition, as can be seen from table 2, the batteries 1 and 2 prepared by using the positive electrode materials in which the surfaces of the positive electrode active materials are sequentially coated with the composite metal oxide layer and the composite carbon material layer in examples 1 and 2 of the present invention have better power performance. The residual capacity of the battery 1 after being stored for 7 days at the high temperature of 60 ℃ under the 100% SOC is 94.3%, and the recovery capacity is 97.7%; the remaining capacity of the battery 2 was 93.6%, and the recovery capacity was 97.5%. Whereas battery 3 of comparative example 1 had a residual capacity of only 89.7% and a recovered capacity of 94.5% under the same test conditions.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. A positive electrode material, comprising: the anode comprises an anode active material, a composite metal oxide layer coated on the surface of the anode active material, and a composite carbon material layer coated on the surface of the composite metal oxide layer; wherein the composite carbon material layer comprises: the conductive carbon comprises point conductive graphite, chain conductive carbon black, long chain conductive reinforcing agent and adhesive; the composite metal oxide layer includes: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide;
the coating amount of the composite metal oxide layer on the surface of the positive active material is 1000-3000 ug/g; the chain-like conductive carbon black comprises: long single chain type conductive carbon black and branched chain type conductive carbon black;
the specific surface area of the conductive graphite is 50-100g/m 2 (ii) a The specific surface area of the branched chain type conductive carbon black is 100-300g/m 2 。
2. The positive electrode material according to claim 1, wherein the positive electrode active material is selected from the group consisting of: a nickel cobalt manganese ternary material or a nickel cobalt aluminum ternary material; and/or the presence of a gas in the gas,
the conductivity enhancer includes: at least one of carbon nanotubes and carbon nanofibers; and/or the presence of a gas in the gas,
the adhesive comprises: at least one of polyvinylidene fluoride, polyvinylpyrrolidone and styrene butadiene rubber.
3. The positive electrode material as claimed in claim 2, wherein the mass ratio of the total mass of the positive electrode active material and the composite metal oxide layer to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductive reinforcing agent and the binder is (90-95): (0.5-1.5): (1-2): (0.8-1.5): (1.2-2.5); and/or the presence of a gas in the atmosphere,
the nickel-cobalt-manganese ternary material comprises: at least one of NCM111, NCM523, NCM622, and NCM 811.
4. The method for preparing the positive electrode material according to any one of claims 1 to 3, wherein the positive electrode material is prepared in a protective gas atmosphere with an ambient humidity of 1% to 30%, and comprises the following steps:
obtaining a positive electrode active substance and a composite metal oxide, and coating the surface of the positive electrode active substance with the composite metal oxide to obtain a first positive electrode active material;
obtaining a composite carbon material, and mixing the composite carbon material and the first positive electrode active material to coat the surface of the first positive electrode active material with the composite carbon material to obtain a second positive electrode active material;
and obtaining a binder, and mixing and dispersing the binder and the second positive electrode active material to obtain a positive electrode material.
5. The method for producing a positive electrode material according to claim 4, wherein the step of mixing the composite carbon material with the first positive electrode active material comprises:
obtaining conductive graphite and long single-chain type conductive carbon black, and carrying out primary mixing treatment on the conductive graphite, the long single-chain type conductive carbon black and the first positive electrode active material to obtain a first mixture;
obtaining branched chain type conductive carbon black, and carrying out secondary mixing treatment on the branched chain type conductive carbon black and the first mixture to obtain a second mixture;
and obtaining a conductive reinforcing agent, and carrying out third mixing treatment on the conductive reinforcing agent and the second mixture to obtain the second positive electrode active material.
6. The method for producing a positive electrode material according to claim 5, wherein the step of coating the surface of the positive electrode active material with the composite metal oxide comprises: coating the composite metal oxide on the surface of the positive active material by adopting a wet coating process or a calcining process; and/or the presence of a gas in the gas,
the step of mixing and dispersing the binder with the second positive electrode active material includes: dissolving the binder in a first organic solvent to form binder gel, and mixing and dispersing the binder gel with the second positive electrode active material to obtain a positive electrode material; and/or the presence of a gas in the gas,
the method also comprises the following steps of: and adding a second organic solvent into the positive electrode material, and mixing again to obtain positive electrode slurry.
7. The method for producing a positive electrode material according to claim 6, wherein the conditions of the first mixing treatment include: stirring for 15-30 min under the condition that the revolution speed is 5-20 rpm; and/or the presence of a gas in the atmosphere,
the conditions of the second mixing treatment include: stirring for 5-20 min under the condition that the revolution speed is 5-50 rpm; and/or the presence of a gas in the gas,
the conditions of the third mixing treatment include: stirring for 20-50 min under the conditions that the revolution speed is 5-10 rpm and the rotation speed is 250-400 rpm; and/or the presence of a gas in the atmosphere,
the conditions of the mixing and dispersing treatment include: stirring for 100-150 min under the conditions that the revolution speed is 15-30 rpm and the rotation speed is 800-1500 rpm; and/or the presence of a gas in the gas,
the conditions for performing the mixing treatment again include: stirring for 100-150 min under the conditions that the revolution speed is 30-50 rpm and the rotation speed is 2000-3000 rpm.
8. The method for preparing a positive electrode material according to any one of claims 6 to 7, wherein the solid content of the conductivity enhancer is not less than 85%, and the conductivity enhancer comprises: at least one of carbon nanotubes and carbon nanofibers; and/or the presence of a gas in the atmosphere,
the coating amount of the composite metal oxide in the first positive electrode active material to the positive electrode active material is 1000-3000 ug/g; and/or the presence of a gas in the gas,
the mass ratio of the binder to the organic solvent in the binder gel is 1: (9-33), the viscosity of the adhesive gel is 500-3000 mpa.s; and/or the presence of a gas in the gas,
in the positive electrode material, the mass ratio of the total mass of the positive electrode active substance and the composite metal oxide to the conductive graphite, the long single-chain conductive carbon black, the branched conductive carbon black, the conductive reinforcing agent and the binder is (90-95): 0.5-1.5): 1-2: (1-2): 0.8-1.5): (1.2-2.5); and/or the presence of a gas in the gas,
the first organic solvent and the second organic solvent are each independently selected from: at least one of N-methyl pyrrolidone and acetone.
9. The method for producing a positive electrode material according to claim 8, wherein the composite metal oxide comprises: at least two of cobalt oxide, aluminum oxide, titanium oxide and vanadium oxide; and/or the presence of a gas in the atmosphere,
the positive electrode active material is selected from: a nickel cobalt manganese ternary material or a nickel cobalt aluminum ternary material; and/or the presence of a gas in the atmosphere,
the adhesive comprises: at least one of polyvinylidene fluoride, polyvinylpyrrolidone and styrene butadiene rubber; and/or the presence of a gas in the gas,
the specific surface area of the conductive graphite is 50-100g/m 2 (ii) a And/or the presence of a gas in the gas,
the branchThe specific surface area of the chain type conductive carbon black is 100-300g/m 2 。
10. A lithium ion battery, characterized in that the lithium ion battery comprises the cathode material as claimed in any one of claims 1 to 3, or the cathode material prepared by the method as claimed in any one of claims 4 to 9.
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