CN116565185A - Nano Si@C-G composite negative electrode material, preparation method and lithium ion battery - Google Patents
Nano Si@C-G composite negative electrode material, preparation method and lithium ion battery Download PDFInfo
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- CN116565185A CN116565185A CN202310459808.5A CN202310459808A CN116565185A CN 116565185 A CN116565185 A CN 116565185A CN 202310459808 A CN202310459808 A CN 202310459808A CN 116565185 A CN116565185 A CN 116565185A
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- 239000002131 composite material Substances 0.000 title claims abstract description 103
- 238000002360 preparation method Methods 0.000 title claims description 30
- 239000007773 negative electrode material Substances 0.000 title claims description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 12
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 141
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 104
- 239000010405 anode material Substances 0.000 claims abstract description 64
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- 238000000034 method Methods 0.000 claims abstract description 23
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- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 14
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Classifications
-
- 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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- 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
- H01M4/62—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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative 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 nano Si@C-G composite anode material which comprises nano silicon particles, amorphous carbon and graphene, wherein a three-dimensional ball cage-like graphene cage is formed by a microchip of the graphene, the nano silicon particles are dispersed in the interior and the surface of the graphene cage, and the nano silicon particles are connected with the graphene cage by taking the amorphous carbon as a carbon skeleton. According to the nano Si@C-G composite material provided by the invention, nano Si grows in situ in the graphene three-dimensional structure, the graphene three-dimensional structure can provide space for volume expansion of nano Si particles, meanwhile, the in-situ growth of amorphous carbon improves the conductivity and structural stability of the composite material, the volume expansion of the material in the charge and discharge process is greatly reduced, the contact surface between the nano Si and electrolyte is reduced by the coating of the graphene, the stability of an SEI film of the composite material is improved, the circulation efficiency and the circulation stability of the composite material are improved, and the improvement of the conductivity is beneficial to the exertion of the multiplying power performance of the composite material.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a nano Si@C-G composite negative electrode material, a preparation method and a lithium ion battery.
Background
Silicon-based composites are considered ideal choices for next generation lithium ion batteries because of their high theoretical capacity. However, the silicon-based composite material has large volume expansion, low cycle performance and low conductivity during charge and discharge, so that the silicon-based composite material has great application difficulty in a power battery.
At present, the research in this aspect is mostly simple compounding of nano silicon and graphene, as reported in application number 201410448751.X, nano Si and graphene liquid are required to be uniformly dispersed by utilizing a high-speed dispersion and ultrasonic technology and then are subjected to drying treatment, but the compounding effect is poor, the capacity and the first efficiency are lower, si is a commercially available product, the XRD peak of Si is higher, si grains are not firmly combined with graphene, the charge-discharge expansion is larger, and the cycling stability is poor.
The preparation process of the technical scheme disclosed in the Chinese patent with application number 201911017933.0 is complex, nano Si and graphene are required to be mixed liquid-solid by using a coupling agent, and then are subjected to centrifugation and cold drying treatment, but the composite effect is poor, and the capacity and the first efficiency are low. The technical scheme disclosed in the China patent with the application number of 202111603918.1 is complex in preparation process, impurities in the expanded graphite are difficult to remove, the expanded graphite is prepared by using the flake graphite, nano Si is deposited on the surface and the inside of the expanded graphite in a high-temperature furnace through silane, the deposition is uneven, the composite effect is poor, and the capacity and the first efficiency are low.
At present, most of the silicon-based composite materials are simply compounded with corresponding carbon bodies, an effective composite structure is not formed, the expansion of the materials in the charge and discharge processes is not effectively inhibited, and the cycle retention rate is low. Therefore, a novel technical scheme is needed to prepare a novel composite structure to improve the electrochemical and electrical properties of the material.
Disclosure of Invention
In view of the above, the technical problem to be solved by the invention is to provide a nano Si@C-G composite negative electrode material, a preparation method and a lithium ion battery.
The invention provides a nano Si@C-G composite anode material which comprises nano silicon particles, amorphous carbon and graphene, wherein a three-dimensional ball cage-like graphene cage is formed by a microchip of the graphene, the nano silicon particles are dispersed in the interior and the surface of the graphene cage, and the nano silicon particles are connected with the graphene cage by taking the amorphous carbon as a carbon skeleton.
Preferably, the size of the nano silicon particles is 0.2 nm-200 nm;
the amorphous carbon is coated on the surface of the nano silicon particles, and the coating thickness is 2-200 nm;
preferably, the nano silicon particles account for 30-60% of the negative electrode material by mass;
the mass ratio of nano Si, amorphous carbon and graphene in the nano Si@C-G composite anode material is 100:1 to 10:5 to 60.
Preferably, the nano Si@C-G composite anode material has a porous structure and a specific surface area of 2-8 m 2 And/g, the pore diameter is 10 nm-5 μm, and the particle diameter is 2-50 μm.
The invention also provides a preparation method of the nano Si@C-G composite material, which comprises the following steps:
a) Mixing a dispersing agent, an additive, a carbon source and graphene slurry, drying and granulating to obtain a graphene cage precursor;
b) Carrying out preliminary carbonization on the graphene cage precursor under a protective atmosphere condition, then reacting with silicon-containing gas under a vacuum condition, and then continuously introducing the silicon-containing gas to react to obtain nano Si@G particles;
c) And (3) carrying out carbon coating on the surface of the nano Si@G particles to obtain the nano Si@C-G composite anode material.
Preferably, in step a), the dispersant is selected from one or more of polyethylene glycol, polyacrylate alcohol, tween-60, tween-80, sodium dodecyl sulfate and sodium dodecyl sulfate;
the additive is one or more selected from polyacrylamide, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, melamine formaldehyde resin, acetic acid and lithium acetate;
the carbon source is selected from one or more of glucose, sucrose, maltodextrin, starch, asphalt powder, povidone and polyacrylic acid;
the flake diameter of graphene in the graphene slurry is 200 nm-20 mu m; the number of layers is 1-30
The mass ratio of the dispersing agent to the additive to the carbon source to the graphene slurry is 0.1-0.2:0-0.3:0.5-1:100;
the drying method comprises one or more of spray drying, stirring and evaporating, centrifugal drying, two-flow drying and flash drying.
Preferably, in the step B), the temperature of the preliminary carbonization is 700-1000 ℃ and the time is 1-2 h;
the pressure of the vacuum condition is 1 Pa to 100Pa;
the temperature of the reaction with the silicon-containing gas under the vacuum condition is 1000-1300 ℃ and the time is 1-5 h;
continuously introducing silicon-containing gas to react at the temperature of 1000-1300 ℃ for 5-24 hours, wherein the flow rate of the silicon-containing gas is 0.1-10L/min;
the silicon-containing gas is selected from one or more of monosilane, trisilane, dichlorosilane, trichlorosilane and tetrachlorosilane.
Preferably, in the step C), the carbon coating method includes a vapor deposition method, or a method of mixing nano si@g particles with a carbon source to sinter.
Preferably, the carbon source is selected from one or more of acetylene, methane, ethylene, propane, phenolic resin, asphalt powder, polyethylene, polyacrylic acid.
The invention also provides a lithium ion battery, which comprises the nano Si@C-G composite material or the nano Si@C-G composite material prepared by the preparation method.
Compared with the prior art, the invention provides a nano Si@C-G composite anode material, which comprises nano silicon particles, amorphous carbon and graphene, wherein the microchip of the graphene forms a three-dimensional ball cage-like graphene cage, the nano silicon particles are dispersed in the interior and the surface of the graphene cage, and the amorphous carbon is used as a carbon skeleton to connect the nano silicon particles with the graphene cage. According to the nano Si@C-G composite material provided by the invention, nano Si grows in situ in the graphene three-dimensional structure, the graphene three-dimensional structure can provide space for volume expansion of nano Si particles, meanwhile, the in-situ growth of amorphous carbon improves the conductivity and structural stability of the composite material, the volume expansion of the material in the charge and discharge process is greatly reduced, the contact surface between the nano Si and electrolyte is reduced by the coating of the graphene, the stability of an SEI film of the composite material is improved, the circulation efficiency and the circulation stability of the composite material are improved, and the improvement of the conductivity is beneficial to the exertion of the multiplying power performance of the composite material.
The experimental results show that: the nano Si@C-G composite material provided by the invention is assembled into a 2032 button battery, the first discharge capacity is 2150-3200 mAh/G, the first charge capacity is 1800-2800 mAh/G, and the charge-discharge efficiency is 83-88%.
Drawings
FIG. 1 is a schematic structural diagram of a nano Si@C-G composite material provided by an embodiment of the invention;
FIG. 2 is an SEM image of nano Si particles in a nano Si material product prepared in example 1 of the present invention;
FIG. 3 is an SEM image of a graphene cage precursor prepared in example 1;
FIG. 4 is an SEM image of a nano Si@C-G composite anode material prepared in example 1
FIG. 5 is a TEM image of the nano Si@C-G composite negative electrode material prepared in example 1;
FIG. 6 is an XRD pattern of the prepared nano Si@C-G composite negative electrode material product prepared in example 1;
FIG. 7 is a graph showing the particle size distribution of a nano Si@C-G composite anode material;
FIG. 8 is a graph showing the particle size distribution of the nano Si@C-G-X composite anode material;
FIG. 9 is a first charge-discharge diagram of the nano Si@C-G composite anode material and nano Si anode material, nano Si@C-G-X composite anode material electrode sheet prepared in example 1 and comparative example 1;
fig. 10 is a graph showing the buckling cycle performance of the nano si@c-G composite anode material and the nano Si anode material, nano si@c-G-X composite anode material electrode sheet prepared in example 1 and comparative example 1.
Detailed Description
The invention provides a nano Si@C-G composite anode material which comprises nano silicon particles, amorphous carbon and graphene, wherein a three-dimensional ball cage-like graphene cage is formed by a microchip of the graphene, the nano silicon particles are dispersed in the interior and the surface of the graphene cage, and the nano silicon particles are connected with the graphene cage by taking the amorphous carbon as a carbon skeleton.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a nano si@c-G composite material provided by an embodiment of the present invention, wherein 1 is a graphene microchip, 2 is nano Si particles, and 3 is amorphous carbon.
In the invention, nano Si particles 1 are in a cage-shaped structure wrapped by graphene microplates 2, a hole structure is arranged in the structure, and amorphous carbon 3 is connected between nano Si@C-G particles 1 and graphene sheets 2.
According to the invention, the three-dimensional structure of the nano Si@C-G composite anode material can provide space for volume expansion of nano Si particles in the charge and discharge process, the surface amorphous carbon coating layer can reduce the contact surface of the anode material and electrolyte, so that quick exchange of lithium ions at the contact surface is facilitated, the cycle stability is good, and the composite coating of graphene and amorphous carbon improves the electronic conductivity of the material.
The nano Si@C-G composite anode material provided by the invention is ellipsoidal or spheroidic.
Wherein the size of the nano silicon particles is 0.2 nm-200 nm, preferably 5-200 nm;
the amorphous carbon is coated on the surface of the nano silicon particles, and the coating thickness is 2-200 nm;
the nano silicon particles account for 30-60% of the negative electrode material by mass, preferably 30%, 40%, 50%, 60%, or any value between 30-60%;
the content of amorphous carbon in the composite anode material is 2 to 15%, preferably 2%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, or any value between 2 and 15%;
in the composite anode material, the content of the nano silicon particles is 30-60%, preferably 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value between 30-60%;
in the composite anode material, the graphene content is 8 to 30%, preferably 8%, 10%, 15%, 20%, 25%, 30%, or any value between 8 and 30%.
The mass ratio of nano Si particles, amorphous carbon and graphene in the nano Si@C-G composite anode material is 100:1 to 10:5 to 60, preferably 100:1:5, 100:10:60, 100:5:30, or 100:1 to 10: any value between 5 and 60.
The nano Si@C-G composite anode material has a porous structure and a specific surface area of 2-8 m 2 Preferably 2, 3, 4, 5, 6, 7, 8, or 2-8 m 2 The pore diameter is 10nm to 5. Mu.m, preferably 10, 50, 100, 200, 500, 1000, 2000, 5000nm, or 10nm to 5. Mu.m, more preferably 200nm to 5. Mu.m; the particle diameter is 2 μm to 50. Mu.m, preferably 2 μm to 40. Mu.m, more preferably 5 μm to 20. Mu.m.
According to the invention, the amorphous carbon-graphene composite structure is stable, and silicon carbon expansion can be effectively inhibited. And the amorphous carbon-graphene composite structure and amorphous carbon coating can improve the conductivity of silicon carbon, so that the rate performance of the battery is improved. The invention can control the proportion of nano Si grown in situ by chemical vapor phase, can more effectively regulate and control the framework composition between nano Si and graphene, and can better regulate and control the cathode material with better conductivity and better circularity.
The invention also provides a preparation method of the nano Si@C-G composite material, which comprises the following steps:
a) Mixing a dispersing agent, an additive, a carbon source and graphene slurry, drying and granulating to obtain a graphene cage precursor;
b) Carrying out preliminary carbonization on the graphene cage precursor under a protective atmosphere condition, then reacting with silicon-containing gas under a vacuum condition, and then continuously introducing the silicon-containing gas to react to obtain nano Si@G particles;
c) And (3) carrying out carbon coating on the surface of the nano Si@G particles to obtain the nano Si@C-G composite anode material.
Specifically, the preparation method comprises the steps of firstly mixing a dispersing agent, an additive, a carbon source and graphene slurry, and drying and granulating to obtain a graphene cage precursor.
Wherein the dispersing agent is one or more selected from polyethylene glycol, polyacrylate, tween-60, tween-80, sodium dodecyl sulfate and sodium dodecyl sulfate; the additive is one or more selected from polyacrylamide, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, melamine formaldehyde resin, acetic acid and lithium acetate; the carbon source is selected from one or more of glucose, sucrose, maltodextrin, starch, asphalt powder, povidone and polyacrylic acid.
In the present invention, the source of the raw material component used for the graphene slurry is not particularly limited, and may be generally commercially available.
The flake diameter of graphene in the graphene slurry is 200 nm-20 mu m; the number of layers is 1-30. The graphene can be prepared by an intercalation stripping method, an oxidation stripping method, a mechanical stripping method and the like.
The mass ratio of the dispersing agent to the additive to the carbon source to the graphene slurry is 0.1-0.2:0-0.3:0.5-1:100, preferably 0.1-0.2:0.1-0.3:0.5-1:100;
in the present invention, the drying method includes one or more of spray drying, stirring and evaporating, centrifugal drying, two-flow drying and flash drying.
And after the graphene cage precursor is obtained, carrying out preliminary carbonization on the graphene cage precursor under the condition of protective atmosphere to obtain a preliminary carbonized product. Wherein the temperature of the preliminary carbonization is 700-1000 ℃, preferably 700, 800, 900, 1000, or any value between 700-1000 ℃ for 1-2 hours.
Wherein the protective atmosphere condition is one or more selected from nitrogen, argon and helium.
Then, under the vacuum condition, introducing silicon-containing gas and protective gas into the reaction vessel to react with the primary carbonized product.
Wherein the pressure of the vacuum condition is 1 Pa to 100Pa;
the reaction temperature with the silicon-containing gas under vacuum is 1000-1300 ℃, preferably 1000, 1100, 1200, 1300, or any value between 1000-1300 ℃, for a time of 1-5 hours, preferably 1, 2, 3, 4, 5, or any value between 1-5 hours.
Continuously introducing silicon-containing gas into a reaction vessel for reaction after the reaction is finished, wherein the flow rate of the silicon-containing gas is 0.1-10L/min, preferably 0.1, 0.5, 1, 3, 5, 7, 10 or any value between 0.1 and 10L/min, the reaction temperature is 1000-1300 ℃, preferably 1000, 1100, 1200, 1300 or any value between 1000-1300 ℃ and the time is 5-24 h, preferably 5, 10, 15, 20, 24 or any value between 5-24 h;
wherein the silicon-containing gas is selected from one or more of monosilane, trisilane, dichlorosilane, trichlorosilane and tetrachlorosilane.
In the present invention, a protective gas is introduced while a silicon-containing gas is introduced. Wherein the protective gas is selected from one or more of nitrogen, argon and helium.
And after the nano Si@G particles are obtained, carbon coating is carried out on the surfaces of the nano Si@G particles.
In the invention, the carbon coating method comprises a vapor deposition method or a method of mixing nano Si@G particles with a carbon source for sintering.
The specific method for mixing nano Si@G particles with a carbon source for sintering comprises the following steps:
mixing and stirring a certain amount of nano Si@G material and a carbon source, drying, and carbonizing and sintering under an inert atmosphere.
Wherein the carbon source is selected from one or more of acetylene, methane, ethylene, propane, phenolic resin, asphalt powder, polyethylene and polyacrylic acid, and the sintering temperature is 600-900 ℃, preferably 600, 700, 800, 900 or any value between 600-900 ℃ for 1-6 h, preferably 1, 2, 3, 4, 5, 6 or any value between 1-6 h.
In the invention, nano Si particles grow in situ in the graphene cage through silane, the nano Si particles are uniformly dispersed in a cage-shaped structure wrapped by graphene sheets, amorphous carbon frameworks are supported in the structure, a hole structure is arranged in the particles, and amorphous carbon frameworks are connected between the nano Si particles and the graphene sheets to form a nano Si@C-G composite structure.
In the present invention, the vapor deposition method includes the steps of:
the obtained Si@G precursor is placed in an atmosphere furnace, and the temperature of the atmosphere furnace is raised to 600-700 ℃ under the protection atmosphere; uniformly introducing a certain amount of carbon source gas and shielding gas into the atmosphere furnace for 1-5 hours to obtain the Si@C-G composite anode material; after the reaction is completed, stopping introducing the carbon source gas, and continuously introducing the protective gas into the atmosphere furnace for cooling.
And finally, cooling, screening and removing iron to obtain the nano Si@C-G composite anode material.
In the invention, after the silicon-containing gas is introduced under the vacuum condition for reaction, the effect of continuously introducing the silicon-containing gas for reaction is to generate nano silicon active sites in the graphene cage, and the continuously introduced silicon-containing gas can continuously grow the nano silicon content required by the silicon active sites.
According to the nano Si@C-G composite negative electrode material provided by the invention, nano Si grows in situ in the graphene three-dimensional structure, the graphene three-dimensional structure can provide space for volume expansion of nano Si particles, meanwhile, the in-situ growth of amorphous carbon improves the conductivity and structural stability of the composite material, the volume expansion of the material in the charge and discharge process is greatly reduced, the contact surface between the nano Si and electrolyte is reduced by the coating of the graphene, the stability of an SEI film of the composite material is improved, the cycle efficiency and the cycle stability of the composite material are improved, and the improvement of the conductivity is beneficial to the play of the multiplying power performance of the composite material.
In order to further understand the present invention, the nano si@c-G composite negative electrode material, the preparation method and the lithium ion battery provided by the present invention are described below with reference to examples, and the scope of protection of the present invention is not limited by the following examples.
The graphene slurries in the following examples and comparative examples were purchased from Ningbo graphene innovation center Co., ltd.
Example 1
The embodiment provides a method for preparing a nano Si@C-G composite anode material for a secondary lithium ion battery, which comprises the following steps:
(1) The preparation process of the graphene cage precursor comprises the following steps:
uniformly mixing 100g of polyethylene glycol, 500g of povidone and 100kg of graphene slurry, and then performing spray drying to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so as to obtain the graphene cage precursor.
(2) The preparation process of the nano Si@G comprises the following steps:
(1) placing 5kg of graphene cage precursor into a vacuum furnace, introducing nitrogen, heating to 1000 ℃ per minute at 5 ℃ for preliminary carbonization, and preserving heat for 1h; stopping introducing the protective gas, vacuumizing the vacuum furnace to 10pa, introducing 500L of monosilane gas and argon, preserving heat for 2 hours at 1000 ℃, and continuously introducing the mixed gas of monosilane and trisilane of which the silicon-containing gas is in a volume ratio of 1:1, wherein the flow rate is 0.5L/min; the flow rate of the shielding gas is 0.5L/min, the gas is continuously introduced for 14 hours at the temperature of 1000 ℃, and the nano Si@G material is obtained through cooling, screening and deironing.
(2) Introducing protective gas into a vacuum furnace, heating to 1000 ℃ per minute at 5 ℃, vacuumizing to 10pa, continuously introducing 500L of silicon-containing gas and the protective gas, preserving heat for 2 hours, and continuously introducing two mixed gases of monosilane and trisilane in the volume ratio of 1:1, wherein the flow rate is 0.5L/min; the flow rate of the shielding gas is 0.5L/min, the gas is continuously introduced for 14 hours, and the nano Si material is obtained by cooling, sieving and deironing and is used as a comparison test material.
Wherein, the step (1) and the step (2) are two independent product preparation processes.
(3) The preparation process of the nano Si@C-G comprises the following steps:
7kg of nano Si@G material and 500g of asphalt powder are placed in a stirring fusion machine to be mixed, stirred and dried, and in the drying process, 1L of ethanol solution of phenolic resin is sprayed into the material, and the material is discharged from the stirring fusion machine after being dried. And (3) placing the materials in an atmosphere furnace, heating to 850 ℃ per minute under the protection of inert atmosphere, carbonizing and sintering at 5 ℃, preserving heat for 2 hours, cooling to room temperature, sieving, and removing iron to obtain the nano Si@C-G composite anode material.
Fig. 2 is an SEM image of nano Si particles in a nano Si material product prepared in example 1 of the present invention, and it can be seen from fig. 1 that the nano Si particles are spherical, have uniform particle size distribution, and have a particle size ranging from 5nm to 200nm.
FIG. 3 is an SEM image of a graphene cage precursor prepared in example 1, with pores on the surface and inside, the pores ranging in size from 200nm to 5 μm and the particle size D50 ranging from 5 μm to 20. Mu.m.
FIGS. 4 and 5 are SEM images and TEM images of the nano Si@C-G composite anode material prepared in example 1, wherein the nano Si@C-G composite anode material is in a sphere-like shape, the micrometer particles with irregular shapes with holes on the surface and the inside are 200 nm-5 μm, the particles are composed of nano particles and micrometer particles, the particle size is 5 μm-40 μm, graphene and amorphous carbon are coated on the inside and the surface of the particles, a layer of amorphous carbon is coated on the surface of nano Si, the thickness of C is 2-200 nm, the C content in the composite material is 15%, the Si content is 60%, and the G content is 25%.
Fig. 6 is an XRD pattern of a nano si@c-G composite negative electrode material product prepared in example 1 of the present invention, in which 2θ is a peak of graphene at 26.59 ° and 2θ is a characteristic peak of Si at 28.4 °, 47.3 °, 56.1 °.
Fig. 7 and 8 are respectively particle size distribution diagrams of the nano Si@C-G composite anode material and the nano Si@C-G-X composite anode material, wherein the particle size distribution of the nano Si@C-G composite anode material is narrower, the D50 is smaller, and the particles are more uniform.
Comparative example 1
This comparative example 1 provides a method of nano si@c-G-X composite negative electrode material for a secondary lithium ion battery.
Mixing 5kg of nano silicon with the granularity of 10-60 nm, 100G of polyethylene glycol, 500G of povidone and 100kg of graphene slurry uniformly, and then performing spray drying to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so as to obtain the Si@C-G-X precursor. (X is the code of the comparative example, which is different from the product prepared in the above example)
7kg of nano Si@C-G-X precursor material and 500G of asphalt powder are placed in a stirring fusion machine to be mixed, stirred and dried, and in the drying process, 1L of ethanol solution of phenolic resin is sprayed into the material, and the material is discharged from the stirring fusion machine after being dried. And (3) placing the materials in an atmosphere furnace, heating to 850 ℃ per minute under the protection of inert atmosphere, carbonizing and sintering at 5 ℃, preserving heat for 2 hours, cooling to room temperature, sieving, and removing iron to obtain the nano Si@C-G-X composite anode material.
Electrochemical performance tests were performed on the nano Si@C-G composite anode material, the nano Si@C-G-X composite anode material and the nano Si anode material prepared in the examples and the comparative examples.
2030 button cell fabrication and electrochemical performance testing were as follows:
the mass ratio of the composite anode material to the carbon black to the CMC+SBR is 80:10:10, the composite anode material to the carbon black are uniformly mixed, then CMC+SBR aqueous solution is added, the mixture is coated on a Cu foil, the mixture is dried in vacuum at 120 ℃ for 24 hours in a vacuum drying box, an electrode plate with the diameter of 1.6 cm is taken as a working electrode, a metal lithium plate is taken as a counter electrode, electrolyte is LiPF6/EC-DMC-EMC (volume ratio of 1:1:1), and a 2032 button cell is assembled in a glove box filled with Ar gas.
Fig. 9, 10 and table 1 show that the nano si@c-G composite anode material prepared in example 1 and comparative example 1 of the present invention has better initial efficiency, cycle stability and in-situ electrode sheet expansion index than the nano Si anode material, the nano si@c-G-X composite anode material electrode sheet initial charge-discharge map, cycle map and in-situ electrode sheet expansion index.
TABLE 1
The charging and discharging voltage range is 2.0-0.005V, the charging and discharging current of the first circle is 200mA/g (0.1C), and the charging and discharging current density after the first circle is 400mA/g (0.2C);
in-situ electrode sheet expansion tests were performed on the nano Si@C-G composite anode material, the nano Si@C-G-X composite anode material and the nano Si anode material prepared in the examples and the comparative examples. The preparation method comprises the steps of mixing a ternary positive electrode material, carbon black and PVDF (polyvinylidene fluoride) uniformly in a mass ratio of 80:10:10, adding a solvent NMP (N-methyl pyrrolidone), coating on an Al foil, vacuum drying at 120 ℃ for 24 hours in a vacuum drying box, taking a ternary positive electrode plate with a diameter of 1.6 cm as a counter electrode, assembling a negative electrode plate (the preparation method of the negative electrode plate is the same as that of a working electrode described above) and the ternary positive electrode plate into a button cell full battery, and testing thickness change of the electrode plate under charge-discharge expansion in an in-situ buckling expander, wherein the charge-discharge voltage range is 3-4.2V and the charge-discharge multiplying power of 1-3 circles is 0.1C.
Through testing, the nano Si@C-G composite anode material prepared in example 1 has a first discharge capacity of 2541mAh/G, a first charge capacity of 2115mAh/G, a charge-discharge efficiency of 83.2%, a delithiation capacity of 1811.1mAh/G under 0.2C rate, a delithiation capacity of 1651.3mAh/G under 0.5C rate, a delithiation capacity of 1402.1mAh/G under 1C rate, and a retention rate of 95% of 20 circles in 1C cycle;
the first discharge capacity of the nano Si@C-G-X composite anode material prepared in comparative example 1 is 1950mAh/G, the first charge capacity is 1560mAh/G, the charge and discharge efficiency is 80%, and the retention rate of 20 circles of 1C circulation is 80%;
the first discharge capacity of the nano Si anode material prepared in the embodiment 1 is 3366mAh/g, the first charge capacity is 2630mAh/g, and the charge-discharge efficiency is 78.1%.
The in-situ pole piece expansion rates of the nano Si@C-G composite anode materials 1, 2 and 3 circles are 26.38%, 9.57% and 8.72%, respectively, the in-situ pole piece expansion rates of the nano Si@C-G-X composite anode materials 1, 2 and 3 circles are 60%, 41.79% and 40.26%, respectively, and the in-situ pole piece expansion rates of the nano Si anode materials 1, 2 and 3 circles are 113.94%, 69.09% and 56.06% respectively.
Example 2
1) The preparation process of the graphene cage precursor comprises the following steps:
uniformly mixing 100g of polyethylene glycol, 100g of sodium carboxymethyl cellulose, 500g of povidone and 100kg of graphene slurry, and then performing spray drying to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so as to obtain the graphene cage precursor. The source of the raw material components used in the graphene slurry is not particularly limited, and may be generally commercially available.
(2) The preparation process of the nano Si@G comprises the following steps:
placing 5kg of graphene cage precursor into a vacuum furnace, introducing nitrogen, heating to 900 ℃ per minute at 5 ℃ for preliminary carbonization, and preserving heat for 1h; stopping introducing the protective gas, vacuumizing the vacuum furnace to 10pa, introducing 500L of monosilane gas and argon, preserving heat for 2 hours at 1100 ℃, and continuously introducing silicon-containing gas monosilane at the flow rate of 1L/min; the flow rate of the shielding gas is 1L/min, the gas is continuously introduced for 14 hours at 1100 ℃, and the nano Si@G is obtained through cooling, screening and deironing.
(3) The preparation process of the nano Si@C-G comprises the following steps:
7kg of nano Si@G material and 500g of asphalt powder are placed in a stirring fusion machine to be mixed, stirred and dried, and in the drying process, 1L of ethanol solution of phenolic resin is sprayed into the material, and the material is discharged from the stirring fusion machine after being dried. And (3) placing the materials in an atmosphere furnace, heating to 850 ℃ per minute under the protection of inert atmosphere, carbonizing and sintering at 5 ℃, preserving heat for 2 hours, cooling to room temperature, sieving, and removing iron to obtain the nano Si@C-G composite anode material.
Through testing, the first discharge capacity of the nano Si@C-G composite anode material is 2800mAh/G, the first charge capacity is 2422mAh/G, the charge and discharge efficiency is 86.5%, and the delithiation capacity is 2005.3mAh/G under the 0.2C multiplying power.
Example 3
1) The preparation process of the graphene cage precursor comprises the following steps:
uniformly mixing 100g of polyethylene glycol, 500g of povidone and 100kg of graphene slurry, and then performing spray drying to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so as to obtain the graphene cage precursor.
(2) The preparation process of the nano Si@G comprises the following steps:
placing 5kg of graphene cage precursor into a vacuum furnace, introducing nitrogen, heating to 900 ℃ per minute at 5 ℃ for preliminary carbonization, and preserving heat for 1h; stopping introducing the protective gas, vacuumizing the vacuum furnace to 10pa, continuously introducing 500L of tetrachlorosilane gas and argon, keeping the temperature at 1150 ℃ for 2 hours, and continuously introducing the tetrachlorosilane gas at the flow rate of 5L/min; the flow rate of the shielding gas is 5L/min, the gas is continuously introduced for 10 hours at 1150 ℃, and the nano Si@G is obtained through cooling, screening and deironing.
(3) The preparation process of the nano Si@C-G comprises the following steps:
7kg of nano Si@G material and 500g of asphalt powder are placed in a stirring fusion machine to be mixed, stirred and dried, and the materials are discharged from the stirring fusion machine after being uniformly mixed and dried. And (3) placing the materials in an atmosphere furnace, heating to 800 ℃ per minute at 5 ℃ under the protection of inert atmosphere, carbonizing and sintering, preserving heat for 2 hours, cooling to room temperature, sieving, and removing iron to obtain the nano Si@C-G composite anode material.
Through testing, the first discharge capacity of the nano Si@C-G composite anode material is 3050.1mAh/G, the first charge capacity is 2688.8mAh/G, the charge and discharge efficiency is 87.5%, and the lithium removal capacity at 0.2C multiplying power is 2122.7mAh/G.
Example 4
1) The preparation process of the graphene cage precursor comprises the following steps:
100g of polyacrylate, 500g of povidone and 100kg of graphene slurry are uniformly mixed, and then spray drying is carried out to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so that the graphene cage precursor is obtained.
(2) The preparation process of the nano Si@G comprises the following steps:
placing 5kg of graphene cage precursor into a vacuum furnace, introducing nitrogen, heating to 1000 ℃ per minute at 5 ℃ for preliminary carbonization, and preserving heat for 1h; stopping introducing the protective gas, vacuumizing the vacuum furnace to 10pa, introducing 500L of tetrachlorosilane gas and argon, preserving heat for 2 hours at 1300 ℃, and continuously introducing silicon-containing gas tetrachlorosilane at a flow rate of 2L/min; the flow rate of the shielding gas is 2L/min, the gas is continuously introduced for 15 hours at 1300 ℃, and the nano Si@G is obtained through cooling, screening and deironing.
(3) The preparation process of the nano Si@C-G comprises the following steps:
placing 7kg of nano Si@G material in an atmosphere furnace, and heating the atmosphere furnace to 600 ℃ under the protection of nitrogen; stopping introducing nitrogen, uniformly introducing 15L of acetylene gas into the atmosphere furnace for 1h, introducing 15L of nitrogen into the atmosphere furnace, heating the atmosphere furnace to 950 ℃, and preserving heat for 2h; uniformly introducing 20L of acetylene gas, stopping introducing nitrogen gas, and preserving heat for 3 hours; and then introducing nitrogen for protection, cooling to room temperature, sieving and removing iron to obtain the nano Si@C-G composite anode material.
Through testing, the first discharge capacity of the nano Si@C-G composite anode material is 2850.2mAh/G, the first charge capacity is 2508.2mAh/G, the charge and discharge efficiency is 88%, and the lithium removal capacity at 0.2C multiplying power is 2250.4mAh/G.
Example 5
1) The preparation process of the graphene cage precursor comprises the following steps:
and uniformly mixing 100g of polyacrylate, 500g of polyacrylic acid and 100kg of graphene slurry, and then performing spray drying to granulate, wherein the temperature of a drying air inlet is 220 ℃, and the temperature of an air outlet is 90 ℃, so as to obtain the graphene cage precursor. The source of the raw material components used in the graphene slurry is not particularly limited, and may be generally commercially available.
(2) The preparation process of the nano Si@G comprises the following steps:
placing 5kg of graphene cage precursor into a vacuum furnace, introducing nitrogen, heating to 900 ℃ per minute at 5 ℃ for preliminary carbonization, and preserving heat for 1h; stopping introducing the protective gas, vacuumizing the vacuum furnace to 10pa, introducing 500L of trichlorosilane and argon, preserving heat for 2 hours at 1200 ℃, and continuously introducing the silicon-containing gas of trichlorosilane, wherein the flow rate is 1L/min; the flow rate of the shielding gas is 1L/min, the gas is continuously introduced for 20 hours at 1200 ℃, and the nano Si@G is obtained through cooling, screening and deironing.
(3) The preparation process of the nano Si@C-G comprises the following steps:
placing 7kg of nano Si@G material in an atmosphere furnace, and heating the atmosphere furnace to 600 ℃ under the protection of nitrogen; stopping introducing nitrogen, uniformly introducing 10L of acetylene gas into the atmosphere furnace for 1h, introducing 20L of nitrogen into the atmosphere furnace, heating the atmosphere furnace to 850 ℃, and preserving heat for 2h; uniformly introducing 20L of acetylene gas, stopping introducing nitrogen gas, and preserving heat for 3 hours; and then introducing nitrogen for protection, cooling to room temperature, sieving and removing iron to obtain the nano Si@C-G composite anode material.
Through testing, the first discharge capacity of the nano Si@C-G composite anode material is 2400mAh/G, the first charge capacity is 2064mAh/G, the charge and discharge efficiency is 86%, and the lithium removal capacity is 1902mAh/G at 0.2C multiplying power.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The nano Si@C-G composite anode material is characterized by comprising nano silicon particles, amorphous carbon and graphene, wherein the microchip of the graphene forms a three-dimensional ball cage-like graphene cage, the nano silicon particles are dispersed in the interior and the surface of the graphene cage, and the amorphous carbon is used as a carbon skeleton to connect the nano silicon particles with the graphene cage.
2. The anode material according to claim 1, wherein the nano-silicon particles have a size of 0.2nm to 200nm;
the amorphous carbon is coated on the surface of the nano silicon particles, and the coating thickness is 2-200 nm.
3. The negative electrode material according to claim 1, wherein the nano silicon particles account for 30-60% by mass of the negative electrode material;
the mass ratio of nano Si, amorphous carbon and graphene in the nano Si@C-G composite anode material is 100:1 to 10:5 to 60.
4. The negative electrode material according to claim 1, wherein the nano si@c-G composite negative electrode material has a porous structure with a specific surface area of 2 to 8m 2 And/g, the pore diameter is 10 nm-5 μm, and the particle diameter is 2-50 μm.
5. A method for preparing the nano si@c-G composite material according to any one of claims 1 to 4, comprising the steps of:
a) Mixing a dispersing agent, an additive, a carbon source and graphene slurry, drying and granulating to obtain a graphene cage precursor;
b) Carrying out preliminary carbonization on the graphene cage precursor under a protective atmosphere condition, then reacting with silicon-containing gas under a vacuum condition, and then continuously introducing the silicon-containing gas to react to obtain nano Si@G particles;
c) And (3) carrying out carbon coating on the surface of the nano Si@G particles to obtain the nano Si@C-G composite anode material.
6. The method according to claim 5, wherein in the step A), the dispersant is one or more selected from the group consisting of polyethylene glycol, polypropylene alcohol, tween-60, tween-80, sodium dodecyl sulfate and sodium dodecyl sulfate;
the additive is one or more selected from polyacrylamide, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, melamine formaldehyde resin, acetic acid and lithium acetate;
the carbon source is selected from one or more of glucose, sucrose, maltodextrin, starch, asphalt powder, povidone and polyacrylic acid;
the flake diameter of graphene in the graphene slurry is 200 nm-20 mu m; the number of layers is 1-30
The mass ratio of the dispersing agent to the additive to the carbon source to the graphene slurry is 0.1-0.2:0-0.3:0.5-1:100;
the drying method comprises one or more of spray drying, stirring and evaporating, centrifugal drying, two-flow drying and flash drying.
7. The method according to claim 5, wherein in the step B), the preliminary carbonization is performed at a temperature of 700 to 1000 ℃ for a time of 1 to 2 hours;
the pressure of the vacuum condition is 1 Pa to 100Pa;
the temperature of the reaction with the silicon-containing gas under the vacuum condition is 1000-1300 ℃ and the time is 1-5 h;
continuously introducing silicon-containing gas to react at the temperature of 1000-1300 ℃ for 5-24 hours, wherein the flow rate of the silicon-containing gas is 0.1-10L/min;
the silicon-containing gas is selected from one or more of monosilane, trisilane, dichlorosilane, trichlorosilane and tetrachlorosilane.
8. The method according to claim 5, wherein in the step C), the carbon-coated method comprises a vapor deposition method or sintering nano si@g particles mixed with a carbon source.
9. The method according to claim 8, wherein the carbon source is one or more selected from acetylene, methane, ethylene, propane, phenol resin, pitch powder, polyethylene, and polyacrylic acid.
10. A lithium ion battery, characterized by comprising the nano si@c-G composite material according to any one of claims 1 to 4 or the nano si@c-G composite material prepared by the preparation method according to any one of claims 5 to 9.
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