CN113036091A - Carbon-coated ternary positive pole piece and preparation method and application thereof - Google Patents

Carbon-coated ternary positive pole piece and preparation method and application thereof Download PDF

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CN113036091A
CN113036091A CN202110436684.XA CN202110436684A CN113036091A CN 113036091 A CN113036091 A CN 113036091A CN 202110436684 A CN202110436684 A CN 202110436684A CN 113036091 A CN113036091 A CN 113036091A
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carbon
ternary
positive electrode
ternary positive
pole piece
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朱呈岭
汪东煌
孙化雨
杨元婴
其他发明人请求不公开姓名
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Envision Power Technology Jiangsu Co Ltd
Envision Ruitai Power Technology Shanghai Co Ltd
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Envision Power Technology Jiangsu Co Ltd
Envision Ruitai Power Technology Shanghai 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/362—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
    • 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 carbon-coated ternary positive pole piece and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing the ternary material, a conductive agent, a binder and a solvent to obtain anode slurry; (2) coating the positive electrode slurry obtained in the step (1) on the surface of a current collector, and drying to obtain an uncoated ternary positive electrode piece; (3) coating a carbon material on the surface of the uncoated ternary positive pole piece in the step (2) in a magnetron sputtering mode to obtain the carbonA coated ternary positive electrode sheet; wherein the chemical formula of the ternary material is LiNixCoyMn1‑x‑yO2X is more than 0 and less than 1, and y is more than 0 and less than 1. According to the invention, the carbon coating can be carried out on the ternary material at room temperature by a magnetron sputtering method, so that the reduction and structural damage of the ternary material can be avoided, and in addition, the carbon coating can also effectively improve the cycle performance and thermal stability of the ternary cathode material and improve the rate capability of the material.

Description

Carbon-coated ternary positive pole piece and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a carbon-coated ternary positive pole piece, and a preparation method and application thereof.
Background
Ternary layered material LiNixCoyMn1-x-yO2By virtue of higher theoretical capacity and high reaction platform voltage, the ternary material becomes the first choice of a power battery system with high energy density, but as an automotive power battery, the ternary material also needs to improve the cycle performance and the rate capability, wherein the coating means can reduce the side reaction of the material in the battery cycle process, protect the material, and some functionalized coating materials can further improve the cycle performance and the rate capability of the material. Carbon coating is an important means for improving the conductivity of the material, and the carbon coating gradually becomes an important strategy for modifying the anode material due to the advantages of low cost, environmental friendliness and the like.
The carbon source selected by the existing carbon coating technology needs high-temperature carbonization treatment in inert atmosphere, but the ternary anode material, especially the high-nickel material, needs higher oxygen partial pressure in the synthesis process, and when the ternary material is subjected to heat treatment in high-temperature inert atmosphere, the ternary material can be reduced, so that the surface structure of the material is damaged, and the performance of the material is damaged.
CN103474628A discloses a preparation method of a carbon-coated ternary cathode material and the carbon-coated ternary cathode material, wherein the preparation method comprises the following steps: s1, preparing a ternary positive electrode material precursor by taking nickel salt, cobalt salt and manganese salt as raw materials; s2, preparing a conductive carbon dispersion system: dispersing conductive carbon in water containing an organic carbon source; s3, adding the ternary positive electrode material precursor and the lithium compound into the conductive carbon dispersion system, and uniformly mixing to obtain a mixture; s4, drying the mixture under a vacuum condition; and S5, carrying out high-temperature treatment on the dried mixture under a sealed condition or in an atmosphere protected by inert gas to obtain the carbon-coated ternary cathode material.
CN110429275A discloses a preparation method of a carbon-coated ternary cathode material and the carbon-coated ternary cathode material, wherein the preparation method of the carbon-coated ternary cathode material comprises the step of placing a dried ternary cathode material, an organic carbon source and an organic solvent compound under the condition of 240-350 ℃ for heat treatment.
Both of the above two documents require high temperature carbonization treatment, so the preparation conditions are harsh, and when the ternary material is subjected to heat treatment in a high temperature inert atmosphere, the ternary material is reduced, so that the surface structure of the material is damaged, and the performance of the material is damaged.
Therefore, it is a technical problem to be solved to avoid the reduction and structural damage of the ternary material in the carbon coating process and improve the cycle performance and thermal stability of the lithium ion battery.
Disclosure of Invention
The invention aims to provide a carbon-coated ternary positive pole piece and a preparation method and application thereof. According to the invention, the carbon coating can be carried out on the ternary material at room temperature by a magnetron sputtering method, so that the reduction and structural damage of the ternary material can be avoided, and in addition, the carbon coating can also effectively improve the cycle performance and thermal stability of the ternary cathode material and improve the rate capability of the material.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a preparation method of a carbon-coated ternary positive electrode plate, which comprises the following steps:
(1) mixing the ternary material, a conductive agent, a binder and a solvent to obtain anode slurry;
(2) coating the positive electrode slurry obtained in the step (1) on the surface of a current collector, and drying to obtain an uncoated ternary positive electrode piece;
(3) coating a carbon material on the surface of the uncoated ternary positive pole piece in the step (2) in a magnetron sputtering mode to obtain the carbon-coated ternary positive pole piece;
wherein the chemical formula of the ternary material is LiNixCoyMn1-x-y O 20 < x < 1, 0 < y < 1, for example, x may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., and y may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc.
According to the preparation method provided by the invention, the carbon coating of the anode plate can be realized at room temperature by a magnetron sputtering method, so that the reduction and structural damage of the ternary material can be avoided, the carbon material can be really coated on the ternary anode material, meanwhile, the carbon coating can reduce the direct contact area of the ternary anode material and the electrolyte, and the side reaction between the high-valence metal ions of the anode material and the electrolyte is inhibited, so that the cycle performance and the thermal stability of the ternary anode material are improved. In addition, the coated carbon layer can improve the electronic conductivity of the surface of the material and reduce the polarization phenomenon in the charging and discharging process, thereby improving the multiplying power performance of the material.
The conventional method for realizing carbon coating through high-temperature sintering has the defects that the high-temperature carbon coating needs to be carried out in an inert atmosphere, and the ternary material can be reduced, so that the surface structure of the material is damaged, and the performance of the material is damaged.
Preferably, the mass ratio of the ternary material, the conductive agent and the binder in the step (1) is (90-99): (0.2-7): 0.1-3, such as 97:2:1, 90:7:3 or 99:0.2: 0.8.
Preferably, the conductive agent in step (1) comprises any one of conductive carbon black, conductive carbon tubes, conductive graphite or carbon nanotubes or a combination of at least two of the foregoing.
Preferably, the binder in step (1) comprises any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride and carboxymethyl cellulose.
Preferably, the solvent of step (1) comprises N-methylpyrrolidone.
Preferably, the surface density of the uncoated ternary positive pole piece in the step (2) is 15-22 g/cm2E.g. 15g/cm2、16g/cm2、17g/cm2、18g/cm2、19g/cm2、20g/cm2、21g/cm2Or 22g/cm2And the like.
Preferably, the drying temperature in the step (2) is 90-120 ℃, for example, 90 ℃, 100 ℃, 110 ℃ or 120 ℃.
Preferably, the current collector of step (2) comprises aluminum foil
Preferably, the carbon material of step (3) comprises a pure carbon and/or nitrogen-doped carbon material.
Preferably, the carbon material is coated to a thickness of 3 to 200nm, such as 3nm, 5nm, 10nm, 20nm, 50nm, 80nm, 100nm, 120nm, 130nm, 150nm, 180nm, or 200 nm.
Preferably, the target for magnetron sputtering in step (3) comprises a graphite target.
Preferably, the magnetron sputtering method in the step (3) comprises the following steps:
and (3) placing the uncoated ternary positive pole piece in the step (2) into a magnetron sputtering cavity, vacuumizing, introducing protective gas, controlling current and voltage, and sputtering a carbon material on the surface of the uncoated ternary positive pole piece in the step (2) to form a carbon coating layer.
Preferably, after the carbon material is coated on the surface of the uncoated ternary positive pole piece in the step (2) in a magnetron sputtering manner, the pole piece is rolled.
Preferably, the vacuum degree of the cavity after vacuum pumping is 10-4～10-3Pa, e.g. 10-4Pa、2*10-4Pa、3*10- 4Pa、5*10-4Pa、8*10-4Pa or 10-3Pa, and the like.
Preferably, the protective gas comprises argon and/or nitrogen.
Preferably, the flow rate of argon gas is 25-35 sccm, such as 25sccm, 26sccm, 27sccm, 28sccm, 29sccm, 30sccm, 31sccm, 32sccm, 33sccm, 34sccm, or 35 sccm.
Preferably, the flow rate of the nitrogen gas is 0 to 15sccm, such as 0sccm, 1sccm, 3sccm, 5sccm, 10sccm, 12sccm, or 15 sccm.
Preferably, the current is 0.2-0.5A, such as 0.2A, 0.3A, 0.4A or 0.5A.
Preferably, the voltage is-450 to-550V, such as-450V, -480V, -500V, -530V or-550V, etc.
In the invention, the carbon coating layer is not uniform due to overlarge voltage in the magnetron sputtering process, and the carbon coating efficiency is low due to undersize voltage.
Preferably, the sputtering time of the magnetron sputtering is 5-30 min, such as 5min, 10min, 15min, 20min, 25min or 30min and the like
In the invention, the magnetron sputtering time is too short, so that the carbon coating layer is not uniform, and the carbon coating layer is too thick and the carbon coating efficiency is low.
As a preferred technical scheme, the preparation method of the carbon-coated ternary positive pole piece comprises the following steps:
(1) mixing a ternary material, a conductive agent, a binder and a solvent according to a mass ratio of (90-99) to (0.2-7) to (0.1-3) to obtain a positive electrode slurry;
(2) coating the positive electrode slurry obtained in the step (1) on the surface of a current collector, and drying at 90-120 ℃ to obtain the positive electrode slurry with the surface density of 15-22 g/cm2The uncoated ternary positive pole piece;
(3) placing the uncoated ternary positive pole piece in the step (2) into a magnetron sputtering cavity with the vacuum degree of 10 < -4 > -10 < -3 > Pa, introducing argon with the flow rate of 25-35 sccm and nitrogen with the flow rate of 0-15 sccm, and pre-sputtering for 5-30 min under the graphite target current with the bias voltage of-450V to-550V and the bias voltage of 0.2-0.5A to obtain the carbon-coated ternary positive pole material with the thickness of 10-20 nm;
wherein the chemical formula of the ternary material is LiNixCoyMn1-x-yO2，0＜x＜1，0＜y＜1。
In a second aspect, the invention provides a carbon-coated ternary positive electrode piece, which is prepared by the preparation method of the carbon-coated ternary positive electrode piece of the first aspect.
The carbon-coated ternary positive pole piece provided by the invention has a stable structure, and the carbon coating can reduce the direct contact area of the ternary positive pole material and the electrolyte and inhibit the side reaction between the high-valence metal ions of the positive pole material and the electrolyte, so that the cycle performance and the thermal stability of the ternary positive pole material are improved. In addition, the coated carbon layer can improve the electronic conductivity of the surface of the material and reduce the polarization phenomenon in the charging and discharging process, thereby improving the multiplying power performance of the material.
In a third aspect, the present invention further provides a lithium ion battery, which includes the carbon-coated ternary positive electrode sheet according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the carbon coating can be carried out on the ternary material at room temperature by a magnetron sputtering method, so that the reduction and structural damage of the ternary material can be avoided, the carbon coating can reduce the direct contact area of the ternary anode material and the electrolyte, and the side reaction between the high-valence metal ions of the anode material and the electrolyte is inhibited, thereby improving the cycle performance and the thermal stability of the ternary anode material. In addition, the coated carbon layer can improve the electronic conductivity of the surface of the material and reduce the polarization phenomenon in the charging and discharging process, thereby improving the rate capability of the material, and ensuring that the capacity retention rate of the battery can still reach 76% or more after the battery is charged and discharged for 100 cycles at 0.33C. Meanwhile, the preparation method provided by the invention is simple to operate, does not need high temperature and is easy for large-scale production.
Drawings
Fig. 1 is a graph comparing the cycle performance of the batteries provided in example 1 and comparative example 1.
FIG. 2 is a graph comparing the capacity retention rates at different rates of the batteries provided in example 2 and comparative example 1
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 20 nm.
The preparation method of the positive pole piece comprises the following steps:
(1) preparing single crystal ternary material LiNi0.55Co0.15Mn0.3O2Adding conductive carbon black (Super P), a conductive carbon tube (CNT) and polyvinylidene fluoride (PVDF) into a N-methyl pyrrolidone solvent (NMP) according to a mass ratio of 97:1:1:1, and stirring and mixing to obtain a slurry to obtain a positive electrode slurry;
(2) coating the anode slurry in the step (1) on an aluminum foil, then placing the aluminum foil in a vacuum oven, and drying the aluminum foil for 0.5 hour at the temperature of 100 ℃ to obtain the anode slurry with the surface density of 18g/cm2The uncoated ternary positive pole piece;
(3) putting the uncoated ternary positive pole piece obtained in the step (2) into a magnetron sputtering cavity, and vacuumizing the cavity to 10 DEG-4Introducing argon gas Pa, controlling the flow to be 25sccm, controlling the bias voltage to be-500V, controlling the carbon target current to be 0.3A, sputtering for 20min, coating carbon, and rolling the carbon-coated pole piece to compact the pole piece to 3.4g/cm3And obtaining the carbon-coated ternary positive pole piece.
Example 2
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 3 nm.
The preparation method of the positive pole piece comprises the following steps:
(1) preparing single crystal ternary material LiNi0.55Co0.15Mn0.3O2Adding conductive carbon black (Super P), a conductive carbon tube (CNT) and polyvinylidene fluoride (PVDF) into a N-methyl pyrrolidone solvent (NMP) according to a mass ratio of 97:1:1:1, and stirring and mixing to obtain a slurry to obtain a positive electrode slurry;
(2) coating the anode slurry in the step (1) on an aluminum foil, then placing the aluminum foil in a vacuum oven, and drying the aluminum foil for 2 hours at 90 DEG CWhen the surface density was obtained, it was 15g/cm2The uncoated ternary positive pole piece;
(3) putting the uncoated ternary positive pole piece obtained in the step (2) into a magnetron sputtering cavity, and vacuumizing the cavity to 10 DEG-3Introducing argon and nitrogen into the furnace Pa, controlling the flow of the argon to be 35sccm, controlling the flow of the nitrogen to be 10sccm, controlling the bias voltage to be-450V, controlling the carbon target current to be 0.2A, sputtering for 5min, coating carbon, rolling the carbon-coated pole piece, and compacting to be 3.4g/cm3And obtaining the carbon-coated ternary positive pole piece.
Example 3
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 200 nm.
The preparation method of the positive pole piece comprises the following steps:
(1) preparing single crystal ternary material LiNi0.65Co0.15Mn0.2O2Adding conductive carbon black (Super P), a conductive carbon tube (CNT) and polyvinylidene fluoride (PVDF) into a N-methyl pyrrolidone solvent (NMP) according to a mass ratio of 97:1:1:1, and stirring and mixing to obtain a slurry to obtain a positive electrode slurry;
(2) coating the anode slurry in the step (1) on an aluminum foil, then placing the aluminum foil in a vacuum oven, and drying the aluminum foil for 1 hour at 120 ℃ to obtain the anode slurry with the surface density of 22g/cm2The uncoated ternary positive pole piece;
(3) putting the uncoated ternary positive pole piece obtained in the step (2) into a magnetron sputtering cavity, and vacuumizing the cavity to 5 x 10-4Introducing argon and nitrogen into the furnace Pa, controlling the flow of the argon to be 30sccm, controlling the flow of the nitrogen to be 15sccm, controlling the bias voltage to be-550V, controlling the carbon target current to be 0.5A, sputtering for 30min, coating carbon, rolling the carbon-coated pole piece, and compacting to be 3.4g/cm3And obtaining the carbon-coated ternary positive pole piece.
Example 4
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 3 nm.
The difference between the preparation method of the positive electrode plate and the embodiment 1 is that the bias voltage in the step (3) of the embodiment is-400V.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 10 nm.
The difference between the preparation method of the positive electrode plate and the embodiment 1 is that the bias voltage in the step (3) of the embodiment is-600V.
The remaining preparation methods and parameters were in accordance with example 1.
Example 6
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 1.5 nm.
The difference between the preparation method of the positive electrode plate and the embodiment 1 is that the sputtering time in the step (3) of the embodiment is 2 min.
The remaining preparation methods and parameters were in accordance with example 1.
Example 7
The embodiment provides a carbon-coated ternary positive pole piece, and the thickness of the carbon coating is 8 nm.
The difference between the preparation method of the positive electrode plate and the embodiment 1 is that the sputtering time in the step (3) of the embodiment is 40 min.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
This comparative example provides a ternary positive pole piece.
The preparation method of the positive electrode plate is different from the embodiment in that the step of coating the carbon in the step (3) in the embodiment 1 is not performed in the comparative example.
The remaining preparation methods and parameters were in accordance with example 1.
As shown in fig. 1, after 100 cycles, the capacity retention rate of the carbon-coated pole piece in example 1 is about 89%, while the capacity retention rate of the carbon-uncoated pole piece in comparative example 1 is only about 74%, and the cycle performance of the carbon-coated pole piece is improved, as can be seen from fig. 2, fig. 2 is the capacity retention rate under different multiplying factors, and the multiplying factor of the carbon-coated pole piece in example 1 is obviously better than that of the uncoated pole piece in comparative example 1.
Comparative example 2
The ternary carbon coating material in the comparative example is high-temperature coating, and the preparation method comprises the following steps:
preparing single crystal ternary material LiNi0.55Co0.15Mn0.3O2Mixing the mixture with glucose according to a mass ratio of 95: 5, then calcining the mixture for 2 hours at 700 ℃ in an argon-coated atmosphere to obtain a carbon-coated ternary material, and then preparing a ternary material pole piece according to the steps (1) and (2) in the example 1
The positive electrode sheets provided in examples 1-7 and comparative examples 1-2 were assembled into button cells, and the electrical performance results are shown in table 1 at room temperature after 100 cycles of 0.33C charge and discharge cycles.
TABLE 1
Capacity retention (%)
Example 1 89％
Example 2 85％
Example 3 84％
Example 4 80％
Example 5 76％
Example 6 79％
Example 7 78％
Comparative example 1 74％
Comparative example 2 30％
From the data results of example 1 and examples 4 and 5, it is clear that too large voltage during magnetron sputtering leads to too thick carbon coating layer, while too small voltage leads to non-uniform carbon coating layer, and thus the efficiency is low.
From the data results of example 1 and examples 6 and 7, it is known that too short time in the magnetron sputtering process results in non-uniform coating of the carbon layer, and too long time results in too thick coating of the carbon layer, which affects the performance.
As is clear from the data results of example 1 and comparative example 1, the side reaction between the electrolyte and the ternary material was not suppressed without carbon coating, and the cycle performance was poor.
From the data results of example 1 and comparative example 2, it can be seen that the ternary material structure is destroyed and the cycle performance is very poor when the carbon coating is performed by conventional high temperature sintering.
In conclusion, the preparation method provided by the invention can be used for carbon coating by a magnetron sputtering method at room temperature, so that the reduction and the structural damage of the ternary material can be avoided, and in addition, the carbon coating can effectively improve the cycle performance and the thermal stability of the ternary cathode material and improve the rate capability of the material, so that the capacity retention rate of the battery can still reach 76% or more after 100 cycles of 0.33C charge-discharge cycle.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (10)

1. A preparation method of a carbon-coated ternary positive pole piece is characterized by comprising the following steps:
(1) mixing the ternary material, a conductive agent, a binder and a solvent to obtain anode slurry;
(2) coating the positive electrode slurry obtained in the step (1) on the surface of a current collector, and drying to obtain an uncoated ternary positive electrode piece;
(3) coating a carbon material on the surface of the uncoated ternary positive pole piece in the step (2) in a magnetron sputtering mode to obtain the carbon-coated ternary positive pole piece;
wherein the chemical formula of the ternary material is LiNixCoyMn1-x-yO2，0＜x＜1，0＜y＜1。
2. The method for preparing the carbon-coated ternary positive electrode plate as claimed in claim 1, wherein the mass ratio of the ternary material, the conductive agent and the binder in the step (1) is (90-99): (0.2-7): 0.1-3);
preferably, the conductive agent in step (1) comprises any one or a combination of at least two of conductive carbon black, conductive carbon tubes, conductive graphite or carbon nanotubes;
preferably, the binder of step (1) comprises any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride or carboxymethyl cellulose;
preferably, the solvent of step (1) comprises N-methylpyrrolidone.
3. The method for preparing the carbon-coated ternary positive electrode plate according to claim 1 or 2, wherein the surface density of the uncoated ternary positive electrode plate in the step (2)15 to 22g/cm2；
Preferably, the drying temperature in the step (2) is 90-120 ℃;
preferably, the current collector of step (2) comprises aluminum foil.
4. The method for preparing the carbon-coated ternary positive electrode sheet according to any one of claims 1 to 3, wherein the carbon material of the step (3) comprises a pure carbon and/or nitrogen-doped carbon material;
preferably, the carbon material coating thickness is 3-200 nm.
5. The method for preparing the carbon-coated ternary positive electrode piece according to any one of claims 1 to 4, wherein the target material for magnetron sputtering in the step (3) comprises a graphite target material.
6. The method for preparing the carbon-coated ternary positive electrode plate according to any one of claims 1 to 5, wherein the magnetron sputtering method in the step (3) comprises the following steps:
placing the uncoated ternary positive pole piece in the step (2) into a magnetron sputtering cavity, vacuumizing, introducing protective gas, controlling current and voltage, and sputtering a carbon material on the surface of the uncoated ternary positive pole piece in the step (2) to form a carbon coating layer;
preferably, after the carbon material is coated on the surface of the uncoated ternary positive pole piece in the step (2) in a magnetron sputtering manner, the pole piece is rolled.
7. The method for preparing the carbon-coated ternary positive electrode plate according to claim 6, wherein the degree of vacuum after the cavity is vacuumized is 10-4～10-3Pa；
Preferably, the protective gas comprises argon and/or nitrogen;
preferably, the introducing flow of the argon is 25-35 sccm;
preferably, the flow rate of the introduced nitrogen is 0-15 sccm;
preferably, the current is 0.2-0.5A;
preferably, the voltage is-450 to-550V;
preferably, the sputtering time of the magnetron sputtering is 5-30 min.
8. The method for preparing the carbon-coated ternary positive electrode sheet according to any one of claims 1 to 7, comprising the following steps:
(1) mixing a ternary material, a conductive agent, a binder and a solvent according to a mass ratio of (90-99) to (0.2-7) to (0.1-3) to obtain a positive electrode slurry;
(2) coating the positive electrode slurry obtained in the step (1) on the surface of a current collector, and drying at 90-120 ℃ to obtain the positive electrode slurry with the surface density of 15-22 g/cm2The uncoated ternary positive pole piece;
(3) putting the uncoated ternary positive pole piece obtained in the step (2) into a vacuum degree of 10-4～10-3Introducing argon gas with the flow rate of 25-35 sccm and nitrogen gas with the flow rate of 0-15 sccm into a Pa magnetron sputtering cavity, and pre-sputtering for 5-30 min under the graphite target current with the bias voltage of-450-550V and the bias voltage of 0.2-0.5A to obtain the carbon-coated ternary positive electrode material with the thickness of 10-20 nm;
wherein the chemical formula of the ternary material is LiNixCoyMn1-x-yO2，0＜x＜1，0＜y＜1。
9. A carbon-coated ternary positive electrode piece is characterized in that the ternary positive electrode piece is prepared by the preparation method of the carbon-coated ternary positive electrode piece according to any one of claims 1 to 8.
10. A lithium ion battery comprising the carbon-coated ternary positive electrode sheet of claim 9.
CN202110436684.XA 2021-04-22 2021-04-22 Carbon-coated ternary positive pole piece and preparation method and application thereof Pending CN113036091A (en)

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Application publication date: 20210625