CN112635728B - Graphene composite lithium-rich manganese-based positive electrode material, reconstruction preparation method thereof and lithium ion battery - Google Patents

Graphene composite lithium-rich manganese-based positive electrode material, reconstruction preparation method thereof and lithium ion battery Download PDF

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CN112635728B
CN112635728B CN202011485125.XA CN202011485125A CN112635728B CN 112635728 B CN112635728 B CN 112635728B CN 202011485125 A CN202011485125 A CN 202011485125A CN 112635728 B CN112635728 B CN 112635728B
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lithium
graphene
rich manganese
positive electrode
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CN112635728A (en
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顾庆文
赛喜雅勒图
王雪莹
刘兆平
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Ningbo Fuli Battery Material Technology Co ltd
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Ningbo Fuli Battery Material Technology Co ltd
Ningbo Institute of Material Technology and Engineering of CAS
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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
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • H01M4/62—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
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a graphene composite lithium-rich manganese-based positive electrode material which comprises lithium-rich manganese-based secondary particles, an outer graphene layer compounded on the surfaces of the lithium-rich manganese-based secondary particles and an outer oxide layer compounded on the surfaces of the outer graphene layer; the lithium-rich manganese-based secondary particles are formed by stacking lithium-rich manganese-based primary particle composite materials; the lithium-manganese-rich primary particle composite material comprises lithium-manganese-rich primary particles, an inner graphene layer compounded on the surface of the lithium-manganese-rich primary particles and an inner oxide layer compounded on the surface of the inner graphene layer. The anode material provided by the invention can prevent the material from generating side reaction with electrolyte under high voltage, greatly improve the conductivity of the lithium-rich manganese-based anode material, and has good inhibition effect on voltage attenuation caused by material structure transformation in the process of utilizing the lattice oxygen activity of the lithium-rich manganese-based anode material, thereby providing a good solution for the application of the material in a high-energy density power lithium ion battery.

Description

Graphene composite lithium-rich manganese-based positive electrode material, reconstruction preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium-rich manganese-based cathode materials, and relates to a graphene composite lithium-rich manganese-based cathode material, a preparation method thereof and a lithium ion battery, in particular to a graphene composite lithium-rich manganese-based cathode material, a reconstruction preparation method thereof and a lithium ion battery.
Background
The lithium ion battery is taken as a secondary battery, is already mature and commercialized to be applied to the fields of small power batteries such as 3C electronic products, mobile power supplies, electric tools, electric bicycles and the like, the used anode material mainly comprises lithium iron phosphate, lithium manganate, lithium cobaltate, ternary materials and the like, and the actual specific capacity of the lithium ion battery is lower than 200 mA.h/g. With the change of global energy patterns and the supply limitation of nickel-cobalt-manganese resources, lithium-rich manganese-based cathode materials with high specific capacity (>250mA · h/g) and low cost have attracted extensive attention of researchers, and are expected to be commercialized as cathode materials of next-generation power batteries, such as Hybrid Electric Vehicles (HEVs) or pure Electric Vehicles (EVs).
The existing method for synthesizing the lithium-rich manganese-based ternary material mainly comprises a high-temperature solid phase method, a sol-gel method, a hydrothermal synthesis method, a coprecipitation method and the like. The coprecipitation method is most widely applied to liquid-phase chemical synthesis of powder materials, the effective components in the product can be uniformly mixed at atomic and molecular levels, the equipment is simple, and the operation is easy. However, the lithium-rich material has poor rate capability and has the problems of voltage attenuation, capacity attenuation, gas generation and the like in the circulating process, so that the large-scale use of the lithium-rich material is limited.
To address the poor rate capability of materials, various approaches have been attempted, including: element doping, hollow core-shell structures, oxide coating, carbon coating, etc., with carbon coating being the most commercially viable method. The problems of voltage attenuation, capacity attenuation, gas generation and the like in the circulating process are mainly that the material has structural transformation in the charging and discharging process and CEI irregular proliferation in the circulating process, so that powder on a pole piece falls off, and the electrolyte is consumed quickly under high voltage. The cycle performance of the material is seriously influenced.
However, the problem of high-voltage electrolyte and the problem of lack of battery system matching research at the present stage cannot be effectively solved, and the conductivity of the pure doped modified material is poor, so that the rate performance and the cycle performance are poor, conductive carbon needs to be additionally added to increase the conductivity, and the simple carbon coating has no good inhibition effect on voltage attenuation caused by material structure transformation. Meanwhile, carbon coating causes poor rate performance of the material due to poor crystallization performance of amorphous carbon, and common carbon coating can have obvious cracking after long circulation, so that vacancy lithium precipitation is easy to cause, and the battery fails suddenly.
Therefore, how to find a more suitable method to solve the above problems and better improve the performance of the lithium-rich manganese-based cathode material is one of the focuses of researchers in the field on improving the application prospects of lithium-rich manganese-based materials.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a graphene composite lithium-rich manganese-based positive electrode material, a preparation method thereof, and a lithium ion battery, and in particular, a graphene composite lithium-rich manganese-based positive electrode material reconstruction preparation method. The graphene composite lithium-rich manganese-based positive electrode material provided by the invention has better conductivity and cycle performance, simple process, mild and easily-controlled conditions and high production efficiency, and is more favorable for popularization and application of industrial mass production.
The invention provides a graphene composite lithium-rich manganese-based positive electrode material which comprises lithium-rich manganese-based secondary particles, an outer graphene layer compounded on the surfaces of the lithium-rich manganese-based secondary particles and an outer oxide layer compounded on the surfaces of the outer graphene layer;
the lithium-rich manganese-based secondary particles are formed by stacking lithium-rich manganese-based primary particle composite materials;
the lithium-manganese-rich primary particle composite material comprises lithium-manganese-rich primary particles, an inner graphene layer compounded on the surface of the lithium-manganese-rich primary particles and an inner oxide layer compounded on the surface of the inner graphene layer.
Preferably, the particle size of the lithium-rich manganese-based secondary particles is 3-30 μm;
the thickness of the graphene layer is 0.7-30 nm;
the sheet diameter of graphene in the graphene layer is 3-20 microns;
the number of layers of graphene in the graphene layer is 1-10.
Preferably, the mass content of the outer graphene layer in the cathode material is 1-15%;
the mass content of the inner graphene layer in the anode material is 1-15%;
the particle size of the lithium-rich manganese-based primary particles is 0.5-5 mu m;
the thickness of the oxide layer is 10-100 nm.
Preferably, the oxide layer comprises a metal oxide layer;
the metal element in the metal oxide comprises one or more of Zr, Mg, Ti, Nb, Y and Zn;
the mass content of the outer metal oxide layer in the composite material is 0.01-5%;
the mass content of the inner metal oxide layer in the composite material is 0.01-5%.
Preferably, the surface area of the graphene composite lithium-rich manganese-based positive electrode material is 1-10 m2/g；
The graphene composite lithium-rich manganese-based positive electrode material is spherical-like particles;
the chemical formula of the lithium-rich manganese-based material is Li1+αMnxNiyCozO2，
Wherein, 0< alpha <1, 0.5 < x <1, 0.1< y <0.5, 0< z < 0.3;
the graphene composite lithium-rich manganese-based positive electrode material is a positive electrode material for a lithium ion battery.
The invention provides a preparation method of a graphene composite lithium-rich manganese-based positive electrode material, which comprises the following steps:
1) crushing the lithium-rich manganese-based material to obtain primary particles of the lithium-rich manganese-based material;
2) mixing the lithium-rich manganese-based material primary particles obtained in the step with graphene dispersion liquid, then adding a soluble metal salt solution, mixing again, and performing spray granulation and drying to obtain a lithium-rich manganese-based secondary particle composite material intermediate;
3) and calcining the lithium-rich manganese-based secondary particle composite material intermediate obtained in the step, then continuously mixing the calcined intermediate with a soluble metal salt solution, and then calcining again to obtain the graphene composite lithium-rich manganese-based positive electrode material.
Preferably, the mass concentration of graphene in the graphene dispersion liquid is 0.5-5%;
the graphene dispersion liquid is obtained by dispersing graphene, a dispersing agent and water;
the dispersing agent comprises one or more of polyvinylpyrrolidone, xanthan gum and sodium carboxymethyl cellulose;
the mass ratio of the graphene to the dispersing agent is preferably (2-8): 1;
the dispersed revolution number is 1200-1350 rpm;
the dispersing time is 2-4 h.
Preferably, the pH value of the graphene dispersion liquid is 8-9.5;
the lithium-rich manganese-based material is a lithium-rich manganese-based material treated by a gas-solid phase interface method;
the soluble metal salt comprises one or more of nitrate, chloride and sulfate;
the concentration of the soluble metal salt solution is 0.5-4 mol/L;
the remixing time is 2-8 h;
the rotation speed of the remixing is 200-1000 rpm.
Preferably, the temperature of the spray granulation drying is 120-200 ℃;
the speed of spray granulation drying is 5-30L/hr;
the spray granulation drying step further comprises a water washing step;
the heating rates of the calcination and the re-calcination are respectively 3-15 ℃/min;
the calcining temperature and the re-calcining temperature are respectively 280-650 ℃;
and the heat preservation time of the calcination and the re-calcination is 2-16 h respectively.
The invention also provides a lithium ion battery, and the positive electrode comprises the graphene composite lithium-rich manganese-based positive electrode material prepared by the preparation method of any one of the above technical schemes.
The invention provides a graphene composite lithium-rich manganese-based positive electrode material which comprises lithium-rich manganese-based secondary particles, an outer graphene layer compounded on the surfaces of the lithium-rich manganese-based secondary particles and an outer oxide layer compounded on the surfaces of the outer graphene layer; the lithium-rich manganese-based secondary particles are formed by stacking lithium-rich manganese-based primary particle composite materials; the lithium-manganese-rich primary particle composite material comprises lithium-manganese-rich primary particles, an inner graphene layer compounded on the surface of the lithium-manganese-rich primary particles and an inner oxide layer compounded on the surface of the inner graphene layer. Compared with the prior art, the graphene lithium-rich manganese-based positive electrode composite material provided by the invention has a specific structure and is a multi-layer coating cluster structure. The positive electrode composite material can well inhibit voltage attenuation caused by material structure transformation of the lithium-rich manganese-based positive electrode material in the process of utilizing lattice oxygen activity. Meanwhile, the graphene also solves the problems that the rate performance of the material is poor due to poor crystallization performance of amorphous carbon in the traditional carbon coating, the common carbon coating has obvious cracking condition after long circulation, so that vacancy lithium precipitation is easy to cause, the battery fails suddenly, moreover, the common amorphous carbon has more functional groups, gas production or CEI growth is easy to occur in the charging and discharging process, so that the electrolyte consumption is fast, and the like, and the problems that the rate cycle performance of the material is improved, and the voltage attenuation in the material cycle process is inhibited, and the like are solved.
According to the invention, the secondary granulation and coating composite technology is utilized, graphene is effectively and uniformly coated on the surface of the lithium-rich manganese-based positive electrode material, and graphene and oxide coatings are finally formed on the surface of the primary particles and the surface of the secondary spheres of the lithium-rich material by combining with the oxide surface coatings, so that the barrier material and electrolyte have side reactions under high voltage, the conductivity of the lithium-rich manganese-based positive electrode material is greatly improved, and the high-strength graphene is used as carbon coating, and the barrier material can well inhibit the voltage attenuation caused by the material structure transformation of the lithium-rich manganese-based positive electrode material in the process of utilizing the lattice oxygen activity. Meanwhile, the graphene also solves the problems that the traditional carbon coating has poor material rate capability due to poor crystallization performance of amorphous carbon, the common carbon coating has obvious cracking condition after long circulation, so that vacancy lithium precipitation is easy to cause, the battery fails suddenly, moreover, the common amorphous carbon has more functional groups, gas production or SEI growth is easy to occur in the charging and discharging process, so that the electrolyte consumption is fast, and the like, improves the rate cycle performance of the material, inhibits the voltage attenuation in the material circulation process, and the like, and provides a good solution for the application of the lithium-rich manganese-based anode material to the anode material of the high-energy-density power lithium ion battery. And the process is simple, the conditions are mild and easy to control, the production efficiency is high, and the popularization and application of industrial mass production are facilitated.
The experimental result shows that the graphene composite lithium-rich manganese-based cathode material has excellent electrochemical performance, the cycling stability of the material is greatly improved, particularly the rate performance of the material is obviously improved, and the voltage attenuation is also inhibited.
Drawings
Fig. 1 is a schematic structural diagram of a graphene composite lithium-rich manganese-based positive electrode material provided by the invention;
fig. 2 is a schematic flow chart of a preparation process of the graphene composite lithium-rich manganese-based positive electrode material provided by the invention;
fig. 3 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention;
fig. 4 is an XRD diffractogram of the graphene composite lithium-rich manganese-based positive electrode material prepared in embodiments 1 to 4 of the present invention;
fig. 5 is a charge-discharge electrochemical curve of the graphene composite lithium-rich manganese-based positive electrode material obtained in example 1 of the present invention at different rates;
fig. 6 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based positive electrode material prepared in example 2 of the present invention;
fig. 7 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based positive electrode material prepared in example 3 of the present invention;
fig. 8 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based positive electrode material prepared in example 4 of the present invention.
Detailed Description
For a further understanding of the invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are included merely to further illustrate the features and advantages of the invention and are not intended to limit the invention to the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All of the starting materials of the present invention are not particularly limited in their purity, and the present invention preferably employs purity requirements that are conventional in the art of analytically pure or solid oxide fuel cell manufacture.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
The process used in the invention belongs to the field of general abbreviation, the specific steps and general parameters of each abbreviation are clear and definite in the related field, and the technicians in the field can realize the process by the general method according to the abbreviation.
The invention provides a graphene composite lithium-rich manganese-based positive electrode material which comprises lithium-rich manganese-based secondary particles, an outer graphene layer compounded on the surfaces of the lithium-rich manganese-based secondary particles and an outer oxide layer compounded on the surfaces of the outer graphene layer;
the lithium-rich manganese-based secondary particles are formed by stacking lithium-rich manganese-based primary particle composite materials;
the lithium-manganese-rich primary particle composite material comprises lithium-manganese-rich primary particles, an inner graphene layer compounded on the surface of the lithium-manganese-rich primary particles and an inner oxide layer compounded on the surface of the inner graphene layer.
In the invention, the primary particles of the lithium-rich manganese-based material can reach the hundred nanometer level. The particle size of the lithium-rich manganese-based material primary particles is preferably 0.5-5 μm, more preferably 1-4 μm, and more preferably 2-3 μm. The particle size in the present invention is preferably the D50 particle size.
In the invention, the lithium-rich manganese-based primary particle composite material preferably has a core-shell structure.
In the present invention, the lithium-rich manganese-based material secondary particles are micron-sized particles. The particle size of the lithium-rich manganese-based secondary particles is preferably 3-30 μm, more preferably 8-25 μm, and more preferably 13-20 μm.
In the invention, the thickness of the graphene layer is preferably 0.7-30 nm, more preferably 5-25 nm, and more preferably 10-20 nm.
In the invention, the sheet diameter of graphene in the graphene layer is preferably 3-20 μm, more preferably 5-18 μm, more preferably 7-16 μm, more preferably 9-14 μm, and more preferably 11-12 μm.
In the invention, the number of graphene layers in the graphene layer is preferably 1-10, more preferably 3-8, and more preferably 5-6, and the graphene layer can be prepared by an intercalation stripping method, an oxidation stripping method, a mechanical stripping method, or the like.
The parameters of the graphene layers not only meet the preferable parameter conditions of the outer graphene layer, but also meet the preferable parameter conditions of the inner graphene layer, and the outer graphene layer and the inner graphene layer can be respectively and independently selected from the parameter conditions, so that the detailed description is omitted. The graphene has physical characteristics of high electric conductivity, high heat conductivity, flexibility, high hardness and the like, the theoretical gram capacitance of the graphene also reaches 744mAh/g, and the graphene is modified to use the high-strength graphene as carbon coating, so that the expansion and the SEI irregular growth can be effectively inhibited, and the electric conductivity and the cycling stability of the battery are further improved.
In the present invention, the mass content of the outer graphene layer in the positive electrode material is preferably 1% to 15%, more preferably 4% to 12%, and still more preferably 7% to 9%.
In the present invention, the thickness of the oxide layer is preferably 10 to 100nm, more preferably 30 to 80nm, and still more preferably 50 to 60 nm.
In the present invention, the oxide layer preferably includes a metal oxide layer.
In the present invention, the metal element in the metal oxide preferably includes one or more of Zr, Mg, Ti, Nb, Y, and Zn, and more preferably Zr, Mg, Ti, Nb, Y, or Zn.
The parameters of the metal oxide layer not only meet the preferable parameter conditions of the outer metal oxide layer, but also meet the preferable parameter conditions of the inner metal oxide layer.
In the present invention, the mass content of the outer metal oxide layer in the composite material is preferably 0.01% to 5%, more preferably 1% to 4%, and still more preferably 2% to 3%.
In the present invention, the content of the inner metal oxide layer in the composite material is preferably 0.01% to 5%, more preferably 1% to 4%, and still more preferably 2% to 3% by mass.
In the invention, the surface area of the graphene composite lithium-rich manganese-based positive electrode material is preferably 1-10 m2(ii)/g, more preferably 3 to 8m2A concentration of 5 to 6m2/g。
In the invention, the graphene composite lithium-rich manganese-based cathode material is preferably spherical-like particles.
In the present invention, the chemical formula of the lithium-rich manganese-based material is preferably Li1+αMnxNiyCozO2Wherein, 0<α<1, more preferably 0.2 to 0.8, and still more preferably 0.4 to 0.6. Wherein x is more than or equal to 0.5<1, more preferably 0.6 to 0.9, and still more preferably 0.7 to 0.8. Wherein, 0.1<y<0.5, more preferably 0.15 to 0.45, more preferably 0.2 to 0.4, and more preferably 0.25 to 0.35. Wherein, 0<z<0.3, more preferably 0.05 to 0.25, and still more preferably 0.1 to 0.2.
In the invention, the graphene composite lithium-rich manganese-based positive electrode material preferably has a core-shell structure. In the invention, the graphene composite lithium-rich manganese-based cathode material is preferably a cathode material for a lithium ion battery.
The graphene composite lithium-rich manganese-based positive electrode material provided by the invention takes a lithium-rich material as a substrate, the lithium-rich material is a spherical-like material with micron-sized secondary particles formed by stacking primary particles in a hundred-nanometer manner, and the graphene and the metal oxide are respectively and uniformly compounded on the surfaces of the primary particles and the secondary particles of the lithium-rich material. The graphene lithium-rich manganese-based positive electrode composite material provided by the invention is a multi-layer coating cluster structure, and can well inhibit voltage attenuation caused by material structure transformation in the process of utilizing lattice oxygen activity of the lithium-rich manganese-based positive electrode material. Meanwhile, the graphene also solves the problems that the rate performance of the material is poor due to poor crystallization performance of amorphous carbon in the traditional carbon coating, the common carbon coating has obvious cracking condition after long circulation, so that vacancy lithium precipitation is easy to cause, the battery fails suddenly, moreover, the common amorphous carbon has more functional groups, gas production or CEI growth is easy to occur in the charging and discharging process, so that the electrolyte consumption is fast, and the like, and the problems that the rate cycle performance of the material is improved, and the voltage attenuation in the material cycle process is inhibited, and the like are solved.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a graphene composite lithium-rich manganese-based positive electrode material provided by the invention.
The invention provides a preparation method of a graphene composite lithium-rich manganese-based positive electrode material, which comprises the following steps:
1) crushing the lithium-rich manganese-based material to obtain primary particles of the lithium-rich manganese-based material;
2) mixing the lithium-rich manganese-based material primary particles obtained in the step with graphene dispersion liquid, then adding a soluble metal salt solution, mixing again, and performing spray granulation and drying to obtain a lithium-rich manganese-based secondary particle composite material intermediate;
3) and calcining the lithium-rich manganese-based secondary particle composite material intermediate obtained in the step, then continuously mixing the calcined intermediate with a soluble metal salt solution, and then calcining again to obtain the graphene composite lithium-rich manganese-based positive electrode material.
The selection and proportion of the raw materials and other preferred principles of the invention are consistent with those of the graphene composite lithium-rich manganese-based positive electrode material unless otherwise noted, and are not repeated herein.
Firstly, crushing the lithium-rich manganese-based material to obtain primary particles of the lithium-rich manganese-based material.
The invention has no particular limitation on the source of the lithium-rich manganese-based material in principle, and the lithium-rich manganese-based material can be prepared or purchased by a preparation method known by the technical personnel in the field, and the technical personnel in the field can select and adjust the material according to the actual preparation condition, the product requirement and the quality requirement, the invention is a complete and refined integral preparation scheme, and the electrochemical performance of the lithium-rich manganese-based positive electrode material is better improved, and the preparation method of the lithium-rich manganese-based positive electrode material can specifically comprise the following steps:
a) mixing a nickel-containing compound, a cobalt-containing compound and a manganese-containing compound with water to obtain a mixed solution;
b) adding the mixed solution, a precipitator and a complexing agent into a coprecipitation reaction kettle through a metering pump, and performing coprecipitation reaction by controlling the temperature, the stirring speed and the reaction pH value of the reaction kettle to obtain a nickel-cobalt-manganese precursor solution, wherein the nickel-cobalt-manganese precursor is represented by a general formula (I);
the chemical formula of the lithium-rich manganese-based material is Li1+αMnxNiyCozO2Formula (I);
wherein, 0< alpha <1, 0.5 < x <1, 0.1< y <0.5, 0< z < 0.3;
c) and (3) mixing a lithium source with the nickel-cobalt-manganese precursor in a solid phase manner, and sintering at a high temperature to obtain the original material of the lithium-rich manganese-based positive electrode material.
In the invention, the lithium-rich manganese-based material is preferably a lithium-rich manganese-based material treated by a gas-solid phase interface method.
The specific steps of the gas-solid phase interface method for processing the lithium-rich manganese-based material are not particularly limited, and the corresponding steps and parameters of the gas-solid phase interface method, which are well known to those skilled in the art, can be selected and adjusted by those skilled in the art according to actual preparation conditions, product requirements and quality requirements, and the specific steps of the gas-solid phase interface method are preferred, refer to the related steps in the prior patent application "CN 104466157B".
In the present invention, the pulverization method includes one or more of sand milling, air flow pulverization, mechanical mill pulverization, and high energy ball milling.
In the invention, the primary particles of the lithium-rich manganese-based material can reach the hundred nanometer level. The particle size of the lithium-rich manganese-based material primary particles is preferably 0.5-5 μm, more preferably 1-4 μm, and more preferably 2-3 μm. The particle size in the present invention is preferably the D50 particle size.
And then mixing the lithium-rich manganese-based material primary particles obtained in the step with graphene dispersion liquid, adding a soluble metal salt solution, mixing again, and performing spray granulation and drying to obtain a lithium-rich manganese-based secondary particle composite material intermediate.
In the invention, the pH value of the graphene dispersion liquid is preferably 8-9.5, more preferably 8.3-9.1, and more preferably 8.6-8.8.
In the present invention, the mass concentration of graphene in the graphene dispersion liquid is preferably 0.5% to 5%, more preferably 1% to 4%, and still more preferably 2% to 3%.
In the present invention, the graphene dispersion liquid is preferably obtained by dispersing graphene, a dispersant and water.
In the present invention, the dispersant preferably includes one or more of polyvinylpyrrolidone, xanthan gum, and sodium carboxymethyl cellulose, and more preferably polyvinylpyrrolidone, xanthan gum, or sodium carboxymethyl cellulose.
In the invention, the mass ratio of the graphene to the dispersing agent is preferably (2-8): 1, more preferably (3-7): 1, more preferably (4-6): 1.
in the present invention, the number of revolutions of the dispersion is preferably 1200 to 1350rpm, more preferably 1230 to 1320rpm, and more preferably 1260 to 1290 rpm.
In the invention, the dispersing time is preferably 2-4 h, more preferably 2.4-3.6 h, and more preferably 2.8-3.2 h.
The graphene is dispersed through high shear force, and the uniformity of dispersion is further ensured through the proportion of the dispersing agent and the zero potential point of the solution.
In the present invention, the soluble metal salt preferably includes one or more of nitrate, chloride and sulfate, more preferably nitrate, chloride or sulfate.
In the invention, the concentration of the soluble metal salt solution is preferably 0.5-4 mol/L, more preferably 1-3.5 mol/L, more preferably 1.5-3 mol/L, and more preferably 2-2.5 mol/L.
In the present invention, the remixing means includes, but is not limited to, stirring. In the invention, the proportion of the graphene can be regulated and controlled by regulating and controlling the proportion of the solution A and the solution B, and the mass of the graphene in the mixed solution is preferably 2-30% of that of the lithium-rich manganese-based cathode material, and more preferably 5-25%.
In the invention, the time for remixing is preferably 2-8 h, more preferably 3-7 h, and more preferably 4-6 h.
In the present invention, the rotation speed of the remixing is preferably 200 to 1000rpm, more preferably 300 to 900rpm, more preferably 400 to 800rpm, and more preferably 500 to 700 rpm.
In the invention, the temperature of the spray granulation drying is preferably 120-200 ℃, more preferably 130-190 ℃, more preferably 140-180 ℃, and more preferably 150-170 ℃.
In the present invention, the speed of the spray granulation drying is preferably 5 to 30L/hr, more preferably 10 to 25L/hr, and still more preferably 15 to 20L/hr.
In the present invention, the spray granulation drying preferably includes a water washing step.
The invention can adjust the particle size and aperture of the composite material through drying temperature and time, and proper pore space and controllable particle size and pore structure can reduce the consumption of adhesive and solvent when in application, and can be more effectively matched in the battery anode. Further washing with water and secondary calcining to obtain the graphene composite lithium-rich manganese-based positive electrode material
And finally, calcining the intermediate of the lithium-rich manganese-based secondary particle composite material obtained in the step, continuously mixing the intermediate with a soluble metal salt solution, and then calcining again to obtain the graphene composite lithium-rich manganese-based positive electrode material.
In the invention, the heating rate of the calcination is preferably 3-15 ℃/min, more preferably 5-13 ℃/min, and more preferably 7-11 ℃/min.
In the invention, the calcination temperature is preferably 280-650 ℃, more preferably 330-600 ℃, more preferably 380-550 ℃, and more preferably 430-500 ℃.
In the invention, the calcination heat preservation time is preferably 2-16 h, more preferably 5-12 h, and more preferably 8-9 h.
In the present invention, the calcination atmosphere is preferably air. The graphene composite material can control the graphene composite proportion in the composite material through the heating rate and the highest temperature.
In the present invention, the means of continuing the mixing includes, but is not limited to, stirring.
In the invention, the time for continuously mixing is preferably 2-8 h, more preferably 3-7 h, and more preferably 4-6 h.
In the invention, the rotation speed of the continuous mixing is preferably 200-1000 rpm, more preferably 300-900 rpm, more preferably 400-800 rpm, and more preferably 500-700 rpm.
In the invention, the temperature rise rate of the re-calcination is preferably 3-15 ℃/min, more preferably 5-13 ℃/min, and more preferably 7-11 ℃/min.
In the invention, the temperature of the secondary calcination is preferably 280-650 ℃, more preferably 330-600 ℃, more preferably 380-550 ℃, and more preferably 430-500 ℃.
In the invention, the heat preservation time of the re-calcination is preferably 2-16 h, more preferably 5-12 h, and more preferably 8-9 h.
In the present invention, the atmosphere of the re-calcination is preferably air. The graphene composite material can control the graphene composite proportion in the composite material through the heating rate and the highest temperature.
The invention is a complete and refined integral preparation scheme, and better improves the electrochemical performance of the lithium-rich manganese-based anode material, and the preparation method of the graphene composite lithium-rich manganese-based anode material can specifically comprise the following steps:
d) processing the original material of the lithium-rich manganese-based anode material prepared in the previous step by a gas-solid interface to obtain a primary material of the lithium-rich manganese-based anode material,
e) crushing the primary lithium-rich manganese-based positive electrode material subjected to gas-solid interface treatment to obtain a small-particle lithium-rich manganese-based positive electrode material with D50 of about 1-5 microns;
f) dispersing graphene and a dispersing agent in water in the solution system to obtain a solution A; mixing the small-particle lithium-rich manganese-based positive electrode material with the solution A, and then coating the surface of a liquid phase; preparing solution system B solution containing metal M, wherein the coating material contains M which is one or two or more of Zr, Mg, Ti, Nb, Y and Zn;
g) and mixing the solution A with the solution B, and performing spray granulation and drying to obtain the intermediate of the graphene/lithium-rich manganese-based positive electrode material composite material.
h) The material is further washed and calcined, the liquid phase surface is coated again, washed again and calcined again to obtain the finished product graphene composite lithium-rich manganese-based positive electrode material
Referring to fig. 2, fig. 2 is a schematic view of a preparation process of the graphene composite lithium-rich manganese-based positive electrode material provided by the invention.
The invention effectively and uniformly coats the graphene on the surfaces of the primary particles and the secondary particles of the lithium-rich manganese-based positive electrode material by using a liquid phase-drying granulation composite technology to form a carbon coating with high-strength graphene, meanwhile, the surface metal oxide coating which is grown in situ on the surfaces of the primary particles and the secondary particles again effectively solves the problems of poor rate capability of the material caused by poor crystallization performance of amorphous carbon in the traditional carbon coating, moreover, the common carbon coating has more amorphous carbon functional groups, is easy to generate gas or SEI growth in the charging and discharging process, causes the problem of fast electrolyte consumption and the like, the problems of improving the multiplying power cycle performance of the material, inhibiting the voltage attenuation in the material cycle process and the like are solved, and a good solution is provided for the application of the lithium-rich manganese-based anode material to the anode material of the high-energy-density power lithium ion battery. Through the preparation method, the problem of dispersion uniformity of the added graphene is solved, and the reconstruction structure is effectively utilized to reduce the overlapping effect of the graphene.
The invention provides a lithium ion battery, and the positive electrode preferably comprises the graphene composite lithium-rich manganese-based positive electrode material prepared by the preparation method in any one of the above technical schemes or the graphene composite lithium-rich manganese-based positive electrode material prepared by the preparation method in any one of the above technical schemes.
The invention provides a graphene composite lithium-rich manganese-based positive electrode material, a reconstruction preparation method thereof and a lithium ion battery. According to the invention, graphene and metal oxide coatings are formed on the surfaces of the primary particles and the surfaces of the secondary spheres of the lithium-rich material, and the problems of low conductivity, poor cycle stability, voltage attenuation and gas generation of the lithium-rich material in the battery cycle process are solved by the graphene composite reconstruction lithium-rich material technology.
According to the invention, the secondary granulation and coating composite technology is utilized, graphene is effectively and uniformly coated on the surface of the lithium-rich manganese-based positive electrode material, and graphene and oxide coatings are finally formed on the surface of the primary particles and the surface of the secondary spheres of the lithium-rich material by combining with the oxide surface coatings, so that the barrier material and electrolyte have side reactions under high voltage, the conductivity of the lithium-rich manganese-based positive electrode material is greatly improved, and the high-strength graphene is used as carbon coating, and the barrier material can well inhibit the voltage attenuation caused by the material structure transformation of the lithium-rich manganese-based positive electrode material in the process of utilizing the lattice oxygen activity. Meanwhile, the graphene also solves the problems that the traditional carbon coating has poor material rate capability due to poor crystallization performance of amorphous carbon, the common carbon coating has obvious cracking condition after long circulation, so that vacancy lithium precipitation is easy to cause, the battery fails suddenly, moreover, the common amorphous carbon has more functional groups, gas production or SEI growth is easy to occur in the charging and discharging process, so that the electrolyte consumption is fast, and the like, improves the rate cycle performance of the material, inhibits the voltage attenuation in the material circulation process, and the like, and provides a good solution for the application of the lithium-rich manganese-based anode material to the anode material of the high-energy-density power lithium ion battery. And the process is simple, the conditions are mild and easy to control, the production efficiency is high, and the popularization and application of industrial mass production are facilitated.
The experimental result shows that the graphene composite lithium-rich manganese-based cathode material has excellent electrochemical performance, the cycling stability of the material is greatly improved, particularly the rate performance of the material is obviously improved, and the voltage attenuation is also inhibited.
For further illustration of the present invention, the following will describe in detail a graphene composite lithium-rich manganese-based cathode material, a preparation method thereof, and a lithium ion battery provided by the present invention with reference to examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, which are only for further illustration of the features and advantages of the present invention, but not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
The graphene composite lithium-rich manganese-based positive electrode material comprises the following steps of;
(1) preparation of quasi-spherical lithium-rich manganese-based positive electrode material precursor Ni by coprecipitation method0.25Co0.15Mn0.6CO3Washing and drying the precursor, mixing lithium and sintering to obtain the lithium-rich manganese-based positive electrode material Li (Li)0.5Ni0.25Co0.15Mn0.6)O2；
(2) Crushing the lithium-rich manganese-based anode material by airflow to obtain a crushed small-particle lithium-rich manganese-based anode material,
(3) dispersing graphene (the average sheet diameter of the graphene is 12 microns, the average layer number is 5 layers) in water, adding polyvinylpyrrolidone as a dispersing agent (the mass ratio of the graphene to the dispersing agent is 10:3), dispersing the graphene at a high speed of 1200rpm for 3 hours, and mixing the graphene with the lithium-rich manganese-based positive electrode material small particles to obtain a solution A, wherein the pH value of the solution A is 11.
(4) And (3) performing aqueous liquid phase surface alumina coating on the lithium-rich manganese-based positive electrode material solution A containing graphene to obtain a solution B.
(5) Uniformly mixing the solution A and the solution B, and then carrying out spray granulation and drying at 120 ℃; the drying speed was 5L/hr.
(6) And (3) calcining the dried product at high temperature in the air at the heating rate of 12 ℃/min, at the calcining temperature of 400 ℃ and for the calcining heat preservation time of 4hr to obtain the secondary spherical graphene lithium-rich manganese-based cathode material composite material.
(7) And coating the graphene lithium-rich manganese-based cathode material composite material with aqueous liquid phase surface alumina again, and calcining at high temperature in air again at the heating rate of 12 ℃/min and the calcining temperature of 400 ℃ for 4hr to obtain the finished graphene lithium-rich manganese-based cathode material composite material.
The graphene composite lithium-rich manganese-based positive electrode material prepared in the embodiment 1 of the invention is characterized.
Referring to fig. 3, fig. 3 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based cathode material prepared in example 1 of the present invention.
When the graphene lithium-rich manganese-based positive electrode material composite material obtained in example 1 is analyzed by X-ray diffraction, it is found that the graphene lithium-rich manganese-based positive electrode material composite material has a diffraction peak which is obvious near 26.5 °.
Referring to fig. 4, fig. 4 is an XRD diffractogram of the graphene composite lithium-rich manganese-based positive electrode material prepared in embodiments 1 to 4 of the present invention.
The electrochemical performance of the graphene composite lithium-rich manganese-based positive electrode material prepared in the embodiment 1 of the invention is detected.
Referring to fig. 5, fig. 5 is a charge-discharge electrochemical curve of the graphene composite lithium-rich manganese-based positive electrode material obtained in example 1 of the present invention under different multiplying factors.
The result shows that the positive electrode material is tested by a half cell, the first circle of 0.1C discharge capacity reaches 225mAh/g, the 0.5C multiplying power discharge gram capacity reaches 216mAh/g, the 1C multiplying power discharge gram capacity reaches 210mAh/g, and the 5C multiplying power reaches 186 mAh/g.
Example 2
The graphene composite lithium-rich manganese-based positive electrode material comprises the following steps of;
(1) preparation of quasi-spherical lithium-rich manganese-based positive electrode material precursor Ni by coprecipitation method0.16Co0.16Mn0.68CO3Washing and drying the precursor, mixing lithium and sintering to obtain the lithium-rich manganese-based positive electrode material Li (Li)0.2Ni0.16Co0.16Mn0.68)O2；
(2) Crushing the lithium-rich manganese-based anode material by airflow to obtain a crushed small-particle lithium-rich manganese-based anode material,
(3) dispersing graphene (the average sheet diameter of the graphene is 8 microns, the average layer number is 4 layers) in water, adding xanthan gum dispersing agent as dispersing agent (the mass ratio of the graphene to the dispersing agent is 10:5), dispersing the graphene at a high speed of 1200rpm for 3 hours, and mixing the graphene with the lithium-rich manganese-based positive electrode material small particles to obtain solution A, wherein the pH value of the solution A is 10.8.
(4) And (3) performing aqueous liquid phase surface alumina coating on the lithium-rich manganese-based positive electrode material solution A containing graphene to obtain a solution B.
(5) Uniformly mixing the solution A and the solution B, and then carrying out spray granulation and drying at 120 ℃; the drying speed was 5L/hr.
(6) And (3) calcining the dried product at high temperature in the air at the heating rate of 12 ℃/min, the calcining temperature of 450 ℃ and the calcining heat preservation time of 4hr to obtain the secondary spherical graphene lithium-rich manganese-based cathode material composite material.
(7) And coating the graphene lithium-rich manganese-based cathode material composite material with aqueous liquid phase surface alumina again, and calcining at high temperature in air again at the heating rate of 12 ℃/min and the calcining temperature of 450 ℃ for 4hr to obtain the finished graphene lithium-rich manganese-based cathode material composite material.
The graphene composite lithium-rich manganese-based positive electrode material prepared in embodiment 2 of the invention is characterized.
Referring to fig. 6, fig. 6 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based cathode material prepared in example 2 of the present invention.
When the graphene lithium-rich manganese-based positive electrode material composite material obtained in example 2 is analyzed by X-ray diffraction, it is found that the graphene lithium-rich manganese-based positive electrode material composite material has a diffraction peak which is obvious near 26.5 °.
Referring to fig. 4, fig. 4 is an XRD diffractogram of the graphene composite lithium-rich manganese-based positive electrode material prepared in embodiments 1 to 4 of the present invention.
The electrochemical performance of the graphene composite lithium-rich manganese-based positive electrode material prepared in the embodiment 2 of the invention is detected.
The result shows that the positive electrode material is tested by a half cell, the first circle of 0.1C discharge capacity reaches 255mAh/g, the 0.5C multiplying power discharge gram capacity reaches 236mAh/g, the 1C multiplying power discharge gram capacity reaches 230mAh/g, and the 5C multiplying power reaches 205 mAh/g.
Example 3
The graphene composite lithium-rich manganese-based positive electrode material comprises the following steps of;
(1) preparation of quasi-spherical lithium-rich manganese-based positive electrode material precursor Ni by coprecipitation method0.25Co0.25Mn0.5CO3Washing and drying the precursor, mixing lithium and sintering to obtain the lithium-rich manganese-based positive electrode material Li (Li)0.08 Ni0.25Co0.25Mn0.5)O2；
(2) Crushing the lithium-rich manganese-based anode material by airflow to obtain a crushed small-particle lithium-rich manganese-based anode material,
(3) dispersing graphene (the average sheet diameter of the graphene is 12 microns, the average layer number is 3 layers) in water, adding xanthan gum dispersing agent as dispersing agent (the mass ratio of the graphene to the dispersing agent is 10:5), dispersing the graphene at a high speed of 1200rpm for 3 hours, and mixing the graphene with the lithium-rich manganese-based positive electrode material small particles to obtain solution A, wherein the pH value of the solution A is 10.75.
(4) And (3) performing aqueous liquid phase surface alumina coating on the lithium-rich manganese-based positive electrode material solution A containing graphene to obtain a solution B.
(5) Uniformly mixing the solution A and the solution B, and then carrying out spray granulation and drying at 120 ℃; the drying speed was 5L/hr.
(6) And (3) calcining the dried product at high temperature in the air at the heating rate of 12 ℃/min, the calcining temperature of 550 ℃ and the calcining heat preservation time of 4hr to obtain the secondary spherical graphene lithium-rich manganese-based cathode material composite material.
(7) And coating the graphene lithium-rich manganese-based cathode material composite material with aqueous liquid phase surface alumina again, and calcining at high temperature in air again at the heating rate of 12 ℃/min and the calcining temperature of 550 ℃ for 4hr to obtain the finished graphene lithium-rich manganese-based cathode material composite material.
Referring to fig. 7, fig. 7 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based cathode material prepared in example 3 of the present invention.
When the graphene lithium-rich manganese-based positive electrode material composite material obtained in example 3 is analyzed by X-ray diffraction, it is found that the graphene lithium-rich manganese-based positive electrode material composite material has a significant diffraction peak near 26.5 °.
Referring to fig. 4, fig. 4 is an XRD diffractogram of the graphene composite lithium-rich manganese-based positive electrode material prepared in embodiments 1 to 4 of the present invention.
The electrochemical performance of the graphene composite lithium-rich manganese-based positive electrode material prepared in the embodiment 3 of the invention is detected.
The result shows that the first circle of the positive electrode material is tested by a half cell, the 0.1C discharge capacity reaches 265mAh/g, the 0.5C multiplying power discharge gram capacity reaches 253mAh/g, the 1C multiplying power discharge gram capacity reaches 236mAh/g, and the 5C multiplying power can reach 212 mAh/g.
Example 4
The graphene composite lithium-rich manganese-based positive electrode material comprises the following steps of;
(1) preparation of quasi-spherical lithium-rich manganese-based positive electrode material precursor Ni by coprecipitation method0.25Co0.25Mn0.5CO3Washing and drying the precursor, mixing lithium and sintering to obtain the lithium-rich manganese-based positive electrode material Li (Li)0.08 Ni0.25Co0.25Mn0.5)O2；
(2) Crushing the lithium-rich manganese-based positive electrode material by airflow to obtain a crushed small-particle lithium-rich manganese-based positive electrode material;
(3) dispersing graphene (the average sheet diameter of the graphene is 12 microns, the average layer number is 7 layers) in water, adding xanthan gum dispersing agent as dispersing agent (the mass ratio of the graphene to the dispersing agent is 10:5), dispersing the graphene at a high speed of 1200rpm for 3 hours, and mixing the graphene with the lithium-rich manganese-based positive electrode material small particles to obtain solution A, wherein the pH value of the solution A is 10.95.
(4) And (3) performing aqueous liquid phase surface alumina coating on the lithium-rich manganese-based positive electrode material solution A containing graphene to obtain a solution B.
(5) Uniformly mixing the solution A and the solution B, and then carrying out spray granulation and drying at 120 ℃; the drying speed was 5L/hr.
(6) And (3) calcining the dried product at high temperature in the air, wherein the heating rate is 12 ℃/min, the calcining temperature is 550 ℃, and the calcining heat preservation time is 4hr, so that the graphene-coated lithium-rich manganese-based cathode material composite material with 18% of the surface of the secondary sphere is obtained.
(7) And coating the graphene lithium-rich manganese-based cathode material composite material with aqueous liquid phase surface alumina again, and calcining at high temperature in air again at the heating rate of 12 ℃/min and the calcining temperature of 550 ℃ for 4hr to obtain the finished graphene lithium-rich manganese-based cathode material composite material.
Referring to fig. 8, fig. 8 is an SEM scanning electron microscope image of the graphene composite lithium-rich manganese-based cathode material prepared in example 4 of the present invention.
When the graphene lithium-rich manganese-based positive electrode material composite material obtained in example 4 is analyzed by X-ray diffraction, it is found that the graphene lithium-rich manganese-based positive electrode material composite material has a diffraction peak which is obvious near 26.5 °.
Referring to fig. 4, fig. 4 is an XRD diffractogram of the graphene composite lithium-rich manganese-based positive electrode material prepared in embodiments 1 to 4 of the present invention.
The electrochemical performance of the graphene composite lithium-rich manganese-based positive electrode material prepared in the embodiment 4 of the invention is detected.
The result shows that the positive electrode material is tested by a half cell, the first circle of 0.1C discharge capacity reaches 235mAh/g, the 0.5C multiplying power discharge gram capacity reaches 206mAh/g, the 1C multiplying power discharge gram capacity reaches 195mAh/g, and the 5C multiplying power reaches 185 mAh/g.
The graphene composite lithium-rich manganese-based cathode material, the reconstruction preparation method thereof, and the lithium ion battery provided by the present invention are described in detail above, and the principle and the embodiment of the present invention are explained herein by applying specific examples, and the description of the above examples is only used to help understanding the method and the core idea of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including making and using any device or system, and implementing any method in combination. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (10)

1. The graphene composite lithium-manganese-rich-based positive electrode material is characterized by comprising lithium-manganese-rich-based secondary particles, an outer graphene layer compounded on the surface of the lithium-manganese-rich-based secondary particles and an outer metal oxide layer compounded on the surface of the outer graphene layer;
the lithium-rich manganese-based secondary particles are formed by stacking lithium-rich manganese-based primary particle composite materials;
the lithium-manganese-rich primary particle composite material comprises lithium-manganese-rich primary particles, an inner graphene layer compounded on the surface of the lithium-manganese-rich primary particles and an inner metal oxide layer compounded on the surface of the inner graphene layer.
2. The graphene composite lithium-rich manganese-based positive electrode material according to claim 1, wherein the lithium-rich manganese-based secondary particles have a particle size of 3 to 30 μm;
the thickness of the graphene layer is 0.7-30 nm;
the sheet diameter of graphene in the graphene layer is 3-20 microns;
the number of layers of graphene in the graphene layer is 1-10.
3. The graphene composite lithium-rich manganese-based positive electrode material as claimed in claim 1, wherein the mass content of the outer graphene layer in the positive electrode material is 1-15%;
the mass content of the inner graphene layer in the anode material is 1-15%;
the particle size of the lithium-rich manganese-based primary particles is 0.5-5 mu m;
the thickness of the oxide layer is 10-100 nm.
4. The graphene composite lithium-rich manganese-based positive electrode material according to claim 1, wherein in the outer metal oxide layer, the metal elements in the metal oxide include one or more of Zr, Mg, Ti, Nb, Y, and Zn;
in the inner metal oxide layer, the metal elements in the metal oxide include one or more of Zr, Mg, Ti, Nb, Y and Zn;
the mass content of the outer metal oxide layer in the composite material is 0.01-5%;
the mass content of the inner metal oxide layer in the composite material is 0.01-5%.
5. The graphene composite lithium-rich manganese-based positive electrode material as claimed in claim 1, wherein the surface area of the graphene composite lithium-rich manganese-based positive electrode material is 1-10 m2/g；
The graphene composite lithium-rich manganese-based positive electrode material is spherical-like particles;
the chemical formula of the lithium-rich manganese-based material is Li1+αMnxNiyCozO2，
Wherein, 0< alpha <1, 0.5 < x <1, 0.1< y <0.5, 0< z < 0.3;
the graphene composite lithium-rich manganese-based positive electrode material is a positive electrode material for a lithium ion battery.
6. A preparation method of a graphene composite lithium-rich manganese-based positive electrode material is characterized by comprising the following steps:
1) crushing the lithium-rich manganese-based material to obtain primary particles of the lithium-rich manganese-based material;
2) mixing the lithium-rich manganese-based material primary particles obtained in the step with graphene dispersion liquid, then adding a soluble metal salt solution, mixing again, and performing spray granulation and drying to obtain a lithium-rich manganese-based secondary particle composite material intermediate;
3) and calcining the lithium-rich manganese-based secondary particle composite material intermediate obtained in the step, then continuously mixing the calcined intermediate with a soluble metal salt solution, and then calcining again to obtain the graphene composite lithium-rich manganese-based positive electrode material.
7. The preparation method according to claim 6, wherein the mass concentration of graphene in the graphene dispersion liquid is 0.5-5%;
the graphene dispersion liquid is obtained by dispersing graphene, a dispersing agent and water;
the dispersing agent comprises one or more of polyvinylpyrrolidone, xanthan gum and sodium carboxymethyl cellulose;
the mass ratio of the graphene to the dispersing agent is preferably (2-8): 1;
the dispersed revolution number is 1200-1350 rpm;
the dispersing time is 2-4 h.
8. The preparation method according to claim 6, wherein the graphene dispersion liquid has a pH value of 8 to 9.5;
the lithium-rich manganese-based material is a lithium-rich manganese-based material treated by a gas-solid phase interface method;
in the step 2), the soluble metal salt comprises one or more of nitrate, chloride and sulfate;
in the step 2), the concentration of the soluble metal salt solution is 0.5-4 mol/L;
in the step 3), the soluble metal salt comprises one or more of nitrate, chloride and sulfate;
in the step 3), the concentration of the soluble metal salt solution is 0.5-4 mol/L;
the remixing time is 2-8 h;
the rotation speed of the remixing is 200-1000 rpm.
9. The preparation method according to claim 6, wherein the temperature of the spray granulation drying is 120-200 ℃;
the speed of spray granulation drying is 5-30L/hr;
the spray granulation drying step further comprises a water washing step;
the heating rates of the calcination and the re-calcination are respectively 3-15 ℃/min;
the calcining temperature and the re-calcining temperature are respectively 280-650 ℃;
and the heat preservation time of the calcination and the re-calcination is 2-16 h respectively.
10. A lithium ion battery, wherein the positive electrode comprises the graphene composite lithium-rich manganese-based positive electrode material as defined in any one of claims 1 to 5 or the graphene composite lithium-rich manganese-based positive electrode material prepared by the preparation method as defined in any one of claims 6 to 9.
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