CN114156462A - Lithium ion battery electrode with nano-scale coating for improving performance of monocrystal-like anode material - Google Patents
Lithium ion battery electrode with nano-scale coating for improving performance of monocrystal-like anode material Download PDFInfo
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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
- H01M4/48—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
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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
- 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
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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
- H01M4/48—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
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- 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
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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
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Abstract
The invention belongs to the technical field related to lithium ion batteries, and particularly relates to a lithium ion battery electrode for improving the performance of a single crystal-like anode material by nano-scale coating. A lithium ion battery electrode capable of improving performance of a single-crystal-like anode material through nanoscale coating is characterized in that raw materials for preparing the electrode comprise a single-crystal-like anode material coated with nanoscale graphene, a conductive agent, a binder and a current collector. According to the invention, the nano-grade graphene is covered on the surface of the single-crystal-like anode material, and the coating amount and the coating thickness of the nano-grade graphene are controlled, so that the material structure is stabilized, the prepared battery material is beneficial to lower impedance, higher retention rate of 45 ℃ circulating capacity and higher retention rate of high-rate discharge capacity, and the comprehensive performance of the battery is optimized.
Description
Technical Field
The invention belongs to the technical field related to lithium ion batteries, and particularly relates to a lithium ion battery electrode for improving the performance of a single crystal-like anode material by nano-scale coating.
Background
With the development of the preparation technology of the lithium ion battery and the related materials thereof in recent years, the lithium ion battery undoubtedly replaces the nickel-hydrogen battery, the lead-acid battery and the like to become a new generation power supply with high technological content and the most extensive application, has the advantages of environmental protection, high energy density, good cycle performance, good safety performance and the like, is called as the most promising chemical power supply, and has become one of the most rapid and active areas of the global lithium ion battery in China. The positive electrode material of the lithium ion battery is one of the key factors determining the performance of the battery, and therefore, under the current situation, the development of the positive electrode material of the lithium ion battery with good thermal safety performance and cycle stability performance is urgent.
Graphene is used as a corrosion-resistant material with good conductivity, and is very suitable for being used as a coating material to carry out surface modification on a lithium ion positive electrode material. The strong oxidizing property of the anode material at the final charging stage causes oxygen release, and the graphene is tightly coated on the surface of the anode material to effectively inhibit the side reaction of the anode material, but the small-diameter graphene is unevenly dispersed on the surface of the anode material to generate an agglomeration phenomenon, so that the oxygen production cannot be inhibited. The invention relates to the application field of a single crystal-like anode material, and aims to inhibit oxygen loss side reaction by coating the single crystal-like anode material with nano-grade graphene, improve the performance of the single crystal-like anode material and prepare a high-performance lithium ion battery.
Disclosure of Invention
In order to solve the technical problems, the invention provides a lithium ion battery electrode with nano-scale coating for improving the performance of a single-crystal-like anode material, and the preparation raw materials of the electrode comprise the single-crystal-like anode material coated by nano-scale graphene, a conductive agent, a binder and a current collector.
As a preferred technical solution, the nano-scale graphene-coated single-crystal-like cathode material includes a single-crystal-like cathode material and a graphene sheet; the graphene sheet material is tightly coated on the surface of the mono-like anode material; the sheet diameter of the graphene sheet is 10 nm-1000 nm.
As a preferable technical scheme, the positive electrode material with the single crystal-like morphology is selected from LiCoO2、LiNixCoyMnzO2、LiNixCoyAlzO2One or more of; the LiNixCoyMnzO2Or LiNixCoyAlzO2Wherein x + y + z is 1, x is more than or equal to 0.2 and less than or equal to 0.95, y is more than or equal to 0.05 and less than or equal to 0.4, and z is more than or equal to 0.05 and less than or equal to 0.5; the crystal structure of the single crystal-like positive electrode material is a layered structure, belongs to an R-3m space group and is in a single crystal-like shape.
As a preferable technical scheme, the coating thickness of the graphene sheet on the surface of the single crystal-like positive electrode material is less than 10 nm.
As a preferred technical scheme, the particle size distribution of the nano-scale graphene-coated single-crystal-like positive electrode material is basically the same as that of the single-crystal-like positive electrode material; the difference value between the average particle size of the nano-grade graphene-coated single crystal-like positive electrode material and the average particle size of the single crystal-like positive electrode material is less than 1000 nm; preferably, the difference between the average particle size of the nano-graphene-coated single-crystal-like positive electrode material and the average particle size of the single-crystal-like positive electrode material is less than 700 nm; more preferably, the difference between the average particle size of the nano-graphene coated single crystal-like morphology cathode material and the average particle size of the single crystal-like morphology cathode material is less than 400 nm.
As a preferred technical scheme, in a particle size distribution diagram, the longest distance between the nano-scale graphene and the surface of the single crystal-like positive electrode material is less than 3 nm; preferably, the longest distance between the nano-scale graphene and the surface of the single crystal-like positive electrode material is 0 nm.
As a preferable technical scheme, in a laser raman spectrum, a D peak, a G peak, and a G 'peak of a coating region of the single crystal-like morphology cathode material coated with the nano-sized graphene completely correspond to a D peak, a G peak, and a G' peak of the nano-sized graphene, respectively.
As a preferable technical scheme, in an X-ray diffraction pattern, the positions and relative intensity distribution orders of diffraction peaks of the nano-scale graphene-coated single-crystal-like positive electrode material and the single-crystal-like positive electrode material are the same, and the integral shift angle of the diffraction peaks is less than 3 °.
As a preferred technical scheme, a TEM image of the nano-graphene coated single-crystal-like positive electrode material meets the requirement of figure 1; the SEM image satisfies that of FIG. 2; preferably, the included angle between the nano-scale graphene and the tangent line of the nano-scale graphene at the contact point of the single crystal-like morphology cathode material is less than 5 degrees; more preferably, the included angle between the nanoscale graphene and the tangent line of the nanoscale graphene at the contact point of the single-crystal-like morphology cathode material is 0 degrees.
The invention provides an application of the lithium ion battery electrode for improving the performance of the single-crystal-like anode material through nanoscale coating, and the lithium ion battery electrode for improving the performance of the single-crystal-like anode material through nanoscale coating is used for preparing a button cell.
Has the advantages that: the invention provides a lithium ion battery electrode with nano-scale coating and improved performance of a mono-like anode material, which is characterized in that graphene is uniformly dispersed among anode material particles through high-speed nano dispersion, and the graphene on the surface of an anode plays a role in fixing oxygen atoms on the surface of the material, so that the structure of the material is stabilized, and the cycle performance, especially the high-temperature cycle performance, of the material is improved; according to the invention, the nano-grade graphene covers the surface of the quasi-single crystal anode material, so that the prepared battery material has the advantages of smaller impedance, higher retention rate of 45 ℃ circulating capacity, higher retention rate of high-rate charge-discharge capacity, optimized comprehensive performance of the battery, and better performance than the battery material corresponding to the quasi-single crystal anode material.
Drawings
FIG. 1 is a TEM image of a nano-graphene coated single-crystal-like positive electrode material;
FIG. 2 is an SEM image of the nano-scale graphene coated single crystal-like morphology cathode material at a magnification of 40 k;
FIG. 3 is XRD (X-ray diffraction) spectrums of a mono-like morphology positive electrode material (I) coated by nano-scale graphene and a mono-like morphology positive electrode material (II);
fig. 4 is a particle size distribution diagram of a single crystal-like positive electrode material (a) and a single crystal-like positive electrode material (b) coated with nano-scale graphene;
fig. 5 is a raman surface scan image (a) of the nano-scale graphene coated single-crystal-like morphology cathode material and a raman spectrum (b) of the nano-scale graphene coated single-crystal-like morphology cathode material;
FIG. 6 is an electrochemical alternating current impedance spectrum of a mono-like morphology cathode material (I) and a nano-scale graphene-coated mono-like morphology cathode material (II);
FIG. 7 shows the 45 ℃ cycle capacity retention of the button cell described in example 1 (c) and comparative example 1 (c);
fig. 8 is the rate charge capacity retention of the button cell described in example 1 (c) and comparative example 1 (c);
fig. 9 is the rate discharge capacity retention of the button cell described in example 1 (c) and comparative example 1 (c);
FIG. 10 is a schematic structural diagram of a nano-graphene-coated single-crystal-like positive electrode material; wherein a is a schematic diagram that the nano-scale graphene sheet is tightly coated on the positive electrode material particles with the single crystal-like appearance; b is a schematic diagram of attaching graphene free or semi-free on positive electrode material particles in the traditional technology; 1. 3 represents a nano-scaled graphene sheet; 2. and 4 represents the positive electrode material particles with the single-crystal-like morphology.
Detailed Description
Unless otherwise indicated, implied from the context, or customary in the art, all parts and percentages herein are by weight and the testing and characterization methods used are synchronized with the filing date of the present application. To the extent that a definition of a particular term disclosed in the prior art is inconsistent with any definitions provided herein, the definition of the term provided herein controls.
The technical features of the technical solutions provided by the present invention are further clearly and completely described below with reference to the specific embodiments, and the scope of protection is not limited thereto.
The words "preferred", "preferably", "more preferred", and the like, in the present invention, refer to embodiments of the invention that may provide certain benefits, under certain circumstances. However, other embodiments may be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention. The sources of components not mentioned in the present invention are all commercially available.
In order to solve the technical problems, the invention provides a lithium ion battery electrode with nano-scale coating for improving the performance of a single-crystal-like anode material, and the preparation raw materials of the electrode comprise the single-crystal-like anode material coated by nano-scale graphene, a conductive agent, a binder and a current collector.
In some embodiments, the weight ratio of the nano-scale graphene-coated single-crystal-like morphology cathode material to the conductive agent to the binder is (90-98): (1-6): (1-6).
In some preferred embodiments, the weight ratio of the nanoscale graphene-coated single-crystal-like morphology cathode material to the conductive agent to the binder is (92-96): (2-5): (2-5).
In a more preferred embodiment, the weight ratio of the nanoscale graphene-coated single-crystal-like morphology cathode material to the conductive agent to the binder is 93: 3: 3.
nano-grade graphene-coated monocrystal-like positive electrode material
In some embodiments, the nano-scale graphene coated single crystal-like morphology cathode material comprises a single crystal-like morphology cathode material and graphene sheets; the graphene sheet material is tightly coated on the surface of the positive electrode material with the single crystal-like appearance.
(graphene sheet)
In some embodiments, the graphene sheets have a particle size of 10nm to 1000nm, preferably 25nm to 500 nm; more preferably 50nm to 150 nm.
(Single-crystal-like positive electrode material)
In some embodiments, the single crystal-like morphology cathode material is selected from LiCoO2、LiNixCoyMnzO2、LiNixCoyAlzO2One or more of; the LiNixCoyMnzO2Or LiNixCoyAlzO2Wherein x + y + z is 1, x is more than or equal to 0.2 and less than or equal to 0.95, y is more than or equal to 0.05 and less than or equal to 0.4, and z is more than or equal to 0.05 and less than or equal to 0.5; the crystal structure of the single crystal-like positive electrode material is a layered structure, belongs to an R-3m space group and presents a single crystal-like appearance.
The LiNixCoyMnzO2Is nickel cobalt manganese oxide; the LiNixCoyAlzO2Is nickel cobalt aluminum oxide.
The graphene sheet is in a close coating form on the surface of the positive electrode material crystal grain.
In some embodiments, the graphene sheet has a coating thickness of less than 10nm on the surface of the mono-like cathode material.
In some embodiments, the nanoscale graphene coated single-crystal-like cathode material has a particle size distribution that is substantially the same as the particle size distribution of the single-crystal-like cathode material; the difference value between the average particle size of the nano-scale graphene-coated single-crystal-like anode material and the average particle size of the single-crystal-like anode material is less than 1000 nm; preferably, the difference between the average particle size of the nano-scale graphene coated single-crystal-like cathode material and the average particle size of the single-crystal-like cathode material is less than 700 nm; more preferably, the difference between the average particle size of the nano-scale graphene coated single-crystal-like cathode material and the average particle size of the single-crystal-like cathode material is less than 400 nm.
The particle size is measured by a laser light scattering method, and is equivalent sphere volume distribution.
In some embodiments, the longest distance between the nanoscale graphene and the surface of the single-crystal-like positive electrode material in the particle size distribution diagram is less than 3 nm; preferably, the longest distance between the nano-scale graphene and the surface of the single crystal-like cathode material is 0 nm.
The grain surface of the single crystal-like positive electrode material tightly coated by the nano-grade graphene does not obviously increase the grain size, namely the grain size distribution results of the single crystal-like positive electrode material coated by the nano-grade graphene and the single crystal-like positive electrode material are basically consistent. The "particle size distribution is substantially the same" means that the particle size distribution of the nano-scale graphene-coated single crystal-like morphology cathode material is little or unchanged from that of the single crystal-like morphology cathode material, wherein the "little" means that the absolute value of the difference of the volume densities corresponding to the same particle size is less than 1%.
In some embodiments, in a laser raman spectrum, a D peak, a G peak, and a G 'peak of a coating region of the single crystal-like morphology cathode material coated with the nano-sized graphene completely correspond to a D peak, a G peak, and a G' peak of the nano-sized graphene, respectively; the ratio of the D peak, the G peak and the G 'peak Intensity of the graphene is 0.01-10 (D)/Intensity (G), and 0.01-10 (D)/Intensity (G'); preferably, the ratio of the D peak, the G peak and the G 'peak Intensity of the graphene is 0.01 ≦ Intensity (D)/Intensity (G) ≦ 5, 0.01 ≦ Intensity (D)/Intensity (G') ≦ 5; more preferably, the ratio of the D peak, the G peak and the G 'peak Intensity of the graphene is 0.01 ≦ Intensity (D)/Intensity (G) ≦ 1, 0.01 ≦ Intensity (D)/Intensity (G') ≦ 1; the non-coating region of the nano-scale graphene-coated single crystal-like cathode material has no D peak, G peak and G' peak.
In some embodiments, the diffraction peak positions and relative intensity distribution orders of the nano-scale graphene-coated single-crystal-like morphology cathode material and the single-crystal-like morphology cathode material are the same, and the overall shift angle of the diffraction peaks is less than 3 °.
The nano-scale graphene is coated on the surface of the crystal grain of the single crystal-like positive electrode material, and the bulk phase structure in the crystal grain is not influenced, namely the X-ray test results of the single crystal-like positive electrode material coated by the nano-scale graphene and the single crystal-like positive electrode material are basically consistent. The invention discloses a method for improving the overall deviation of diffraction peaks, which is characterized in that when the pattern of a nano-grade graphene-coated single-crystal-like positive electrode material is compared with the pattern peak shape of the single-crystal-like positive electrode material, the deviation phenomenon of a single peak does not exist.
In some embodiments, a TEM image of the nanoscale graphene coated single crystal-like morphology cathode material satisfies figure 1; the SEM image satisfies that of FIG. 2.
In TEM and SEM images of the nano-scale graphene-coated single-crystal-like positive electrode material, that is, the nano-scale graphene-coated single-crystal-like positive electrode material shown in fig. 1 and 2, the nano-scale graphene is in a close-fitting coating state on the surface of the crystal grain of the single-crystal-like positive electrode material.
The nano-scale graphene is in a close-fit coating state on the surface of the crystal grain of the anode material with the single crystal-like morphology, so that the included angle between the nano-scale graphene and the tangent line of the nano-scale graphene at the contact point of the nano-scale graphene and the anode material with the single crystal-like morphology is less than 5 degrees; preferably, the included angle between the nanoscale graphene and the tangent line of the nanoscale graphene at the contact point of the monocrystal-like cathode material is 0 degrees.
The nano-scale graphene is in a close-fit coating state on the surface of the crystal grain of the anode material with the single crystal-like appearance, and the longest distance between the nano-scale graphene and the surface of the anode material with the single crystal-like appearance is less than 3 nm; preferably, the longest distance between the nano-scale graphene and the surface of the single crystal-like positive electrode material is 0 nm.
As shown in fig. 10a, the nano-scale graphene can be tightly attached to the surface of the positive electrode material particles with the single-crystal-like morphology, the nano-scale graphene is tightly contacted with the positive electrode material particles with the single-crystal-like morphology without any gap, and the shortest distance between the nano-scale graphene and the surface of the positive electrode material with the single-crystal-like morphology is about 0; instead of the method shown in fig. 10b, in the conventional technology, the nano-graphene covers the surface of the single crystal-like positive electrode material, under the condition of the nano-graphene with the same area, the contact area or the covering area of the nano-graphene on the surface of the single crystal-like positive electrode material is smaller, a gap is formed between the nano-graphene and the surface of the single crystal-like positive electrode material, the longest distance between the nano-graphite and the surface of the single crystal-like positive electrode material is far greater than 3nm, the close attachment shown in fig. 10a is not achieved, and the range of the invention that the nano-graphene is in a covering state on the surface of the single crystal-like positive electrode material is not included.
Conductive agent
In some embodiments, the conductive agent is selected from one or more of carbon black, nanographite, acetylene black, graphene, and activated carbon.
In some preferred embodiments, the conductive agent is carbon black, and the invention is not particularly limited by the brand and manufacturer of the carbon black.
Binder
In some embodiments, the binder is selected from one or more of fluororubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymer.
In some preferred embodiments, the binder is polyvinylidene fluoride, and the invention is not particularly limited to the grade and manufacturer of polyvinylidene fluoride.
Current collector
In the invention, the current collector refers to a structure or a part for collecting current, and mainly refers to metal foils such as copper foil and aluminum foil on the lithium ion battery; the function of the current collector is to collect the current generated by the active materials of the battery so as to form a larger current output, therefore, the current collector should be in full contact with the active materials, and the internal resistance should be as small as possible.
In some embodiments, the current collector is a copper foil and/or an aluminum foil.
In some preferred embodiments, the current collector is an aluminum foil, and the thickness, width and manufacturer of the aluminum foil are not particularly limited.
In one embodiment, the method for preparing the lithium ion battery electrode with nanoscale coating for improving the performance of the single-crystal-like cathode material comprises the following steps:
(1) uniformly mixing an organic solvent, a graphene sheet and polyvinylidene fluoride to obtain a substance I;
(2) mixing the substance I obtained in the step (1), the positive electrode material with the single crystal-like morphology and the organic solvent, and stirring for 2-5 hours at the temperature of 30-50 ℃ to uniformly mix to obtain mixed slurry;
(3) drying the mixed slurry obtained in the step (2) to obtain a nano-graphene-coated monocrystal-like positive electrode material;
(4) and (4) mixing the nano-graphene-coated single crystal-like positive electrode material obtained in the step (3), a conductive agent and a binder, and coating the mixture on a current collector to prepare the positive electrode piece.
In one embodiment, the method for preparing the lithium ion battery electrode with nanoscale coating for improving the performance of the single-crystal-like cathode material comprises the following steps:
(1) uniformly mixing an organic solvent, a graphene sheet and polyvinylidene fluoride to obtain a substance I;
(2) mixing the substance I obtained in the step (1), the positive electrode material with the single crystal-like morphology and the organic solvent, and stirring for 4 hours at 40 ℃ to uniformly mix to obtain mixed slurry;
(3) drying the mixed slurry obtained in the step (2) to obtain a nano-graphene-coated monocrystal-like positive electrode material;
(4) and (4) mixing the nano-graphene-coated single crystal-like positive electrode material obtained in the step (3), a conductive agent and a binder, and coating the mixture on a current collector to prepare the positive electrode piece.
In some embodiments, the organic solvent is any one or combination of benzene, toluene, acetone, methyl ethyl ketone, N-methyl pyrrolidone, dimethylformamide.
In some preferred embodiments, the organic solvent is N-methylpyrrolidone.
In some embodiments, the graphene sheet material, the polyvinylidene fluoride and the single crystal-like positive electrode material are mixed according to a mass ratio of (0.001-0.05): (0.001-0.07): 1; preferably, the mass ratio of the graphene sheet material to the polyvinylidene fluoride to the single-crystal-like positive electrode material is (0.002-0.04): (0.003-0.05): 1; more preferably, the mass ratio of the graphene sheet material to the polyvinylidene fluoride to the mono-like morphology cathode material is 0.003: 0.004: 1.
in some embodiments, the viscosity of the mixed slurry is 100-2000cp (25 ℃).
In some preferred embodiments, the viscosity of the mixed slurry is 500-1000cp (25 ℃).
In some preferred embodiments, the viscosity of the mixed slurry is 800cp (25 ℃).
In some embodiments, the drying is selected from any one of heat drying, spray drying, freeze drying, vacuum spin drying, microwave drying, forced air drying, and drive drying.
In some preferred embodiments, the drying is by spray drying.
In some embodiments, the temperature of the air inlet is 350-500 ℃ and the temperature of the outlet is 120-300 ℃ during the spray drying process.
In some preferred embodiments, the temperature of the air inlet is 400 to 450 ℃ and the temperature of the outlet is 180 to 250 ℃ during the spray drying process.
In some more preferred embodiments, the air inlet temperature during the spray drying process is 420 ℃ and the outlet temperature is 215 ℃.
The invention provides an application of the lithium ion battery electrode for improving the performance of the single-crystal-like anode material through nanoscale coating, and the lithium ion battery electrode for improving the performance of the single-crystal-like anode material through nanoscale coating is used for preparing a button cell.
The button cell is also called a button cell, and refers to a cell with the external dimension like a small button, generally speaking, the diameter is larger, and the thickness is thinner (compared with a columnar cell such as a cell with No. 5 AA in the market); the button cell is classified from the appearance, and the same corresponding cell is classified into a cylindrical cell, a square cell and a special-shaped cell.
In some embodiments, the button cell is assembled by using metallic lithium or graphite as a negative electrode and the lithium ion battery electrode which is coated with the nano-scale coating and improves the performance of the single crystal-like positive electrode material as a positive electrode.
The present invention will be specifically described below by way of examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and that the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above disclosure are still within the scope of the present invention.
Examples
Example 1
the weight ratio of the nano-scale graphene-coated single crystal-like positive electrode material to the conductive agent to the binder is 93: 3: 3;
the nano-scale graphene-coated single crystal-like positive electrode material comprises a single crystal-like positive electrode material and a graphene sheet; the graphene sheet material is tightly coated on the surface of the positive electrode material with the single crystal-like appearance;
the graphene sheet is GRCP101S model graphene, purchased from tianjin exk kichen graphene science and technology limited;
the monocrystal-like positive electrode material is HYX6 type nickel cobalt lithium manganate, belongs to a ternary material, is in a monocrystal-like shape, has a D50 ═ 3.9 +/-1.0 mu m, and is purchased from Yao graphene energy storage materials science and technology ltd in Ningxia Han;
the coating thickness of the graphene sheet on the surface of the single-crystal-like anode material is less than 10 nm;
the particle size distribution diagram of the nano-scale graphene-coated single crystal-like morphology cathode material is shown in fig. 4-a; the particle size distribution diagram of the single crystal-like morphology cathode material is 4-b; the particle size distribution of the nano-grade graphene-coated single crystal-like positive electrode material is basically the same as that of the single crystal-like positive electrode material;
the laser Raman spectrum of the nano-scale graphene-coated single crystal-like positive electrode material is shown in FIG. 5; through a laser Raman (Raman) testing technology, nano-scale graphene in a coating area and a single crystal-like positive electrode material in a non-coating area can be distinguished, a red area is the nano-scale graphene (red area), and a blue area is the single crystal-like positive electrode material (blue area); the D peak, the G peak and the G 'peak of the coating region of the nano-grade graphene-coated single crystal-like positive electrode material completely correspond to the D peak, the G peak and the G' peak of the nano-grade graphene respectively; the non-coating region of the nano-scale graphene-coated single crystal-like positive electrode material is free of a D peak, a G peak and a G' peak;
the X-ray diffraction pattern of the nano-grade graphene-coated single-crystal-like positive electrode material is shown in a figure 3-I; the X-ray diffraction pattern of the single-crystal-like positive electrode material is shown in a figure 3-II; the diffraction peak positions and the relative intensity distribution orders of the nano-scale graphene-coated single crystal-like positive electrode material and the single crystal-like positive electrode material are the same, and the integral deviation angle of the diffraction peaks is almost 0 degree;
a TEM image of the nano-scale graphene coated single-crystal-like morphology cathode material is shown in FIG. 1; the SEM image of the nano-scale graphene-coated single crystal-like morphology cathode material is shown in FIG. 2; the included angle between the nano-scale graphene and the tangent line of the nano-scale graphene at the contact point of the single crystal-like positive electrode material is almost 0 degree; the longest distance between the nano-scale graphene and the surface of the single crystal-like positive electrode material is almost 0 nm;
the conductive agent is carbon black, which is purchased from SuperP of Imery company;
the binder is polyvinylidene fluoride, available from HSV900 of arkema;
the current collector was aluminum foil, available from the Yongjie company 1060-H18;
the preparation method of the lithium ion battery electrode for improving the performance of the monocrystal-like anode material by nano-scale coating comprises the following steps:
(1) uniformly mixing an organic solvent, a graphene sheet and polyvinylidene fluoride to obtain a substance I;
(2) mixing the substance I obtained in the step (1), the positive electrode material with the single crystal-like morphology and the organic solvent, and stirring for 4 hours at 40 ℃ to uniformly mix to obtain mixed slurry;
(3) drying the mixed slurry obtained in the step (2) to obtain a nano-graphene-coated monocrystal-like positive electrode material;
(4) mixing the nano-graphene-coated single-crystal-like positive electrode material obtained in the step (3), a conductive agent and a binder, and coating the mixture on a current collector to prepare a positive electrode piece;
the organic solvent is N-methyl pyrrolidone;
the mass ratio of the graphene sheet material to the polyvinylidene fluoride to the mono-like positive electrode material is 0.003: 0.0045: 1;
the polyvinylidene fluoride is available from battery grade PVDF 5130 from suwei corporation;
the viscosity of the mixed slurry was 800cp (25 ℃);
the drying mode is spray drying;
the temperature of the air inlet in the spray drying process is 420 ℃, and the temperature of the outlet is 215 ℃.
A button cell of a lithium ion battery electrode for improving the performance of a single-crystal-like anode material by nano-coating uses metal lithium or graphite as a cathode, the lithium ion battery electrode for improving the performance of the single-crystal-like anode material by nano-coating is used as an anode, and the lithium ion battery electrode for improving the performance of the single-crystal-like anode material by nano-coating is placed in a vacuum drying oven at 110 ℃ and dried for 4.5 hours for standby; rolling the pole piece on a rolling machine, and punching the rolled pole piece into a circular pole piece with a proper size; the cell assembly was carried out in a glove box filled with argon, the electrolyte of the electrolyte was 1M LiPF6, the solvent was EC: DEC: and (3) assembling the DMC as a button cell by a volume ratio of 1:1: 1.
Comparative example 1
The comparative example 1 provides a lithium ion battery electrode made of a single-crystal-like positive electrode material, and the preparation raw materials of the electrode comprise the single-crystal-like positive electrode material, a conductive agent, a binder and a current collector;
the weight ratio of the single crystal-like positive electrode material to the conductive agent to the binder is 93: 3: 3;
the monocrystal-like positive electrode material is HYX6 type nickel cobalt lithium manganate, belongs to a ternary material, is in a monocrystal-like shape, has a D50 ═ 3.9 +/-1.0 mu m, and is purchased from Yao graphene energy storage materials science and technology ltd in Ningxia Han;
the conductive agent is carbon black, which is purchased from SuperP of Imery company;
the binder is polyvinylidene fluoride, available from HSV900 of arkema;
the current collector was aluminum foil, available from Yongjie 1060-H18.
The preparation method of the lithium ion battery electrode made of the single-crystal-like anode material comprises the following steps:
(1) uniformly mixing an organic solvent and polyvinylidene fluoride to obtain a substance I;
(2) mixing the substance I obtained in the step (1), the positive electrode material with the single crystal-like morphology and the organic solvent, and stirring for 4 hours at 40 ℃ to uniformly mix to obtain mixed slurry;
(3) drying the mixed slurry obtained in the step (2); mixing the dried mixed slurry, a conductive agent and a binder, and coating the mixture on a current collector to prepare a positive pole piece;
the organic solvent is N-methyl pyrrolidone;
the mass ratio of the polyvinylidene fluoride to the single-crystal-like positive electrode material is 0.0045: 1;
the polyvinylidene fluoride is available from battery grade PVDF 5130 from suwei corporation;
the viscosity of the mixed slurry in the step (2) is 800cp (25 ℃);
the drying mode is spray drying;
the temperature of the air inlet in the spray drying process is 420 ℃, and the temperature of the outlet is 215 ℃.
A lithium ion battery electrode button cell of single crystal-like anode material, regard metallic lithium or graphite as the negative pole, regard lithium ion battery electrode of the above-mentioned single crystal-like anode material as the positive pole, put the lithium ion battery electrode of the single crystal-like anode material in the vacuum drying oven of 110 duC and oven dry for 4.5 hours for subsequent use; rolling the pole piece on a rolling machine, and punching the rolled pole piece into a circular pole piece with a proper size; the cell assembly was carried out in a glove box filled with argon, the electrolyte of the electrolyte was 1M LiPF6, the solvent was EC: DEC: and (3) assembling the DMC as a button cell by a volume ratio of 1:1: 1.
Performance evaluation
1. Transmission electron microscopy images: the nano graphene coated single crystal-like cathode material prepared in example 1 was subjected to TEM characterization, and the test results are shown in fig. 1.
Fig. 1 is a TEM image (transmission electron microscope image) of the nano graphene coated single crystal-like cathode material prepared by the present invention.
2. Scanning electron microscopy: the nano-scale graphene-coated single-crystal-like cathode material in example 1 is magnified by 40k times under a scanning electron microscope, and the test result is shown in fig. 2.
Fig. 2 is an SEM image (scanning electron microscope image) of the nanographene-coated single-crystal-like positive electrode material prepared by the present invention.
X-ray diffraction pattern: the quasi-single crystal positive electrode material (i) coated with the nano-scale graphene in the embodiment 1 and the quasi-single crystal positive electrode material (ii) are subjected to an X-ray diffraction test, and the test result is shown in fig. 3.
As can be seen from fig. 3, the nano graphene sheet is coated on the surface of the crystal grain of the single-crystal-like material, and the bulk phase structure in the crystal grain is not affected, that is, the X-ray test results of the nano graphene coated single-crystal-like cathode material and the single-crystal-like cathode material are substantially consistent.
4. The particle size distribution diagram is as follows: the particle size distribution analysis of the nano-scale graphene-coated single-crystal-like cathode material and the single-crystal-like cathode material in example 1 was performed, and the test results are shown in fig. 4.
As can be seen from fig. 4, the nano graphene sheet is coated on the surface of the crystal grain of the single crystal-like material, and the particle size of the crystal grain is not significantly increased, that is, the results of the particle size distribution of the nano graphene coated single crystal-like cathode material and the single crystal-like cathode material are substantially consistent.
5. And (3) laser Raman testing: the nano-graphene-coated single-crystal-like cathode material described in example 1 was subjected to a laser raman test, and the test result is shown in fig. 5.
As can be seen from fig. 5, the positive electrode material portion and the coating material portion can be distinguished by a laser Raman (Raman) test technique, and the measured characteristic peaks of the coating material completely correspond to the characteristic peaks D, G, and G' of graphene; and the ratio of the D peak, the G peak and the G' peak Intensity of the graphene is not less than 0.01 and not more than Intensity (D)/not more than 1, and not less than 0.01 and not more than Intensity (D)/not more than 1.
6. Measuring alternating current impedance: the electrochemical alternating-current impedance of the mono-like anode material battery (I) and the mono-like anode material battery coated by the nano-scale graphene (II) is tested at the room temperature of 25 ℃, and the experimental result is shown in figure 6.
As can be seen from fig. 6, the impedance of the quasi-single crystal positive electrode material battery coated with the nano-scale graphene is obviously reduced compared with that of the quasi-single crystal positive electrode material battery, and the improvement effect is very significant.
7. Battery capacity retention ratio: the quasi-single crystal positive electrode material battery coated by the nano-scale graphene in the embodiment 1 and the quasi-single crystal positive electrode material battery in the comparative example 1 are subjected to a button cell capacity retention rate test at 45 ℃, and the test result is shown in fig. 7.
As can be seen from fig. 7, the retention rate of the quasi-single crystal positive electrode material battery coated with the nano-graphene is higher than that of the quasi-single crystal positive electrode material battery at 45 ℃, and the nano-graphene is coated with a certain improvement effect.
8. Rate of charge capacity retention of button cell: the quasi-single crystal positive electrode material battery (II) coated with the nano-scale graphene in the embodiment 1 and the quasi-single crystal positive electrode material battery in the comparative example 1 are subjected to a rate capability test of a button cell (I) in charge capacity retention rate, and the test result is shown in fig. 8.
As can be seen from fig. 8, the rate of charge capacity retention of the quasi-single crystal positive electrode material battery coated with the nano-graphene is higher than that of the quasi-single crystal positive electrode material battery, and the rate of charge retention of the quasi-single crystal positive electrode material coated with the nano-graphene is higher, so that the improvement effect is very significant.
9. Rate discharge capacity retention rate of button cell: the quasi-single crystal positive electrode material battery (II) coated by the nano-scale graphene in the embodiment 1 and the quasi-single crystal positive electrode material battery in the comparative example 1 are subjected to a rate discharge capacity retention performance test of a button cell (I), and the test result is shown in a figure 9.
As can be seen from fig. 9, the rate of discharge capacity retention of the nano-graphene-coated single-crystal-like cathode material battery is higher than that of the single-crystal-like cathode material battery, and the rate of discharge retention of the nano-graphene-coated single-crystal-like cathode material battery is higher, so that the improvement effect is very significant.
The foregoing examples are merely illustrative and serve to explain some of the features of the method of the present invention. The appended claims are intended to claim as broad a scope as is contemplated, and the examples presented herein are merely illustrative of selected implementations in accordance with all possible combinations of examples. Accordingly, it is applicants' intention that the appended claims are not to be limited by the choice of examples illustrating features of the invention. Also, where numerical ranges are used in the claims, subranges therein are included, and variations in these ranges are also to be construed as possible being covered by the appended claims.
Claims (10)
1. The lithium ion battery electrode is characterized in that the preparation raw materials of the electrode comprise a nano-graphene-coated single-crystal-like positive electrode material, a conductive agent, a binder and a current collector.
2. The electrode of claim 1, wherein the nano-scale graphene coated single crystal-like morphology cathode material comprises a single crystal-like morphology cathode material and nano-scale graphene sheets; the nano-scale graphene sheet material is tightly coated on the surface of the single crystal-like positive electrode material; the sheet diameter of the nano-scale graphene sheet is 10 nm-1000 nm.
3. The electrode according to claim 2, wherein a TEM image of the nano-graphene coated single-crystal-like morphology cathode material satisfies the attached figure 1; the SEM image satisfies that of FIG. 2; preferably, the included angle between the nano-scale graphene and the tangent line of the nano-scale graphene at the contact point of the single crystal-like morphology cathode material is less than 5 degrees; more preferably, the included angle between the nanoscale graphene and the tangent line of the nanoscale graphene at the contact point of the single-crystal-like morphology cathode material is 0 degrees.
4. The electrode of claim 2, wherein the single crystal-like positive electrode material is selected from the group consisting of LiCoO2、LiNixCoyMnzO2、LiNixCoyAlzO2One or more of; the LiNixCoyMnzO2Or LiNixCoyAlzO2Wherein x + y + z is 1, x is more than or equal to 0.2 and less than or equal to 0.95, y is more than or equal to 0.05 and less than or equal to 0.4, and z is more than or equal to 0.05 and less than or equal to 0.5; the crystal structure of the single crystal-like positive electrode material is a layered structure, belongs to an R-3m space group and is in a single crystal-like shape.
5. The electrode of claim 2, wherein the graphene sheet is coated on the surface of the positive electrode material with the single crystal-like morphology to a thickness of less than 10 nm.
6. The electrode according to any one of claims 2 to 5, wherein the particle size distribution of the nano-scale graphene-coated single crystal-like morphology cathode material is substantially the same as that of the single crystal-like morphology cathode material; the difference value between the average particle size of the nano-grade graphene-coated single crystal-like positive electrode material and the average particle size of the single crystal-like positive electrode material is less than 1000 nm; preferably, the difference between the average particle size of the nano-graphene-coated single-crystal-like positive electrode material and the average particle size of the single-crystal-like positive electrode material is less than 700 nm; more preferably, the difference between the average particle size of the nano-graphene coated single crystal-like morphology cathode material and the average particle size of the single crystal-like morphology cathode material is less than 400 nm.
7. The electrode according to claim 6, wherein the longest distance between the nano-scale graphene and the surface of the positive electrode material with the single-crystal-like morphology is less than 3 nm; preferably, the longest distance between the nano-scale graphene and the surface of the single crystal-like positive electrode material is 0 nm.
8. The electrode according to any one of claims 2 to 5, wherein in a laser Raman spectrum, a D peak, a G peak and a G 'peak of a coating region of the nano-graphene-coated single crystal-like morphology cathode material completely correspond to the D peak, the G peak and the G' peak of nano-graphene respectively.
9. The electrode according to any one of claims 2 to 5, wherein in an X-ray diffraction pattern, the positions and relative intensity distribution orders of diffraction peaks of the nano-scale graphene-coated single-crystal-like morphology cathode material and the single-crystal-like morphology cathode material are the same, and the overall shift angle of the diffraction peaks is less than 3 degrees.
10. The application of the lithium ion battery electrode with the nanoscale coating for improving the performance of the single-crystal-like anode material is characterized in that the lithium ion battery electrode with the nanoscale coating for improving the performance of the single-crystal-like anode material is used for preparing a lithium ion battery.
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| CN112117460A (en) * | 2020-07-29 | 2020-12-22 | 宁夏汉尧石墨烯储能材料科技有限公司 | Lithium ion battery electrode containing micron-sized graphene-coated single crystal cathode material |
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| JP2017199670A (en) * | 2016-04-21 | 2017-11-02 | 東レ株式会社 | Positive electrode material for lithium ion battery, method for manufacturing the same, positive electrode for lithium ion battery, and lithium ion battery |
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