CN116914112A - Silicon-based negative electrode material and preparation method thereof - Google Patents

Silicon-based negative electrode material and preparation method thereof Download PDF

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Publication number
CN116914112A
CN116914112A CN202310917101.4A CN202310917101A CN116914112A CN 116914112 A CN116914112 A CN 116914112A CN 202310917101 A CN202310917101 A CN 202310917101A CN 116914112 A CN116914112 A CN 116914112A
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silicon
deposition
carbon
anode material
porous carbon
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请求不公布姓名
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Suzhou Peiwa Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

Abstract

The invention discloses a silicon-based anode material and a preparation method thereof, wherein the silicon-based anode material comprises silicon-carbon composite particles, and the silicon-carbon composite particles are formed by taking a porous carbon skeleton as a matrix and depositing a gaseous silicon source and a gaseous carbon source alternately. The preparation method comprises the steps of putting a porous carbon skeleton into a deposition device, and carrying out at least one composite deposition on the porous carbon skeleton to form silicon-carbon composite particles, wherein the composite deposition comprises silicon deposition and carbon deposition which are sequentially carried out; wherein the silicon deposition comprises the steps of: diluting the gaseous silicon source by adopting a diluting gas to form a mixed gas; the mixed gas is put into a deposition device, the deposition temperature is controlled to be 350-600 ℃, and the deposition time is controlled to be 0.1-100 h, so that the thickness of a silicon layer deposited on the porous carbon skeleton is 0.1-20 nm. The silicon-based anode material and the preparation method thereof can inhibit volume expansion and prolong the cycle life of the battery while ensuring the capacitance.

Description

Silicon-based negative electrode material and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion battery production, in particular to a silicon-based negative electrode material and a preparation method thereof.
Background
Graphite is often adopted as a negative electrode material of the lithium ion battery, but the requirement of continuously improving the energy density of the lithium ion battery is hardly met because the current commercial graphite gram capacity is close to the theoretical limit (372 mAh/g). Based on this, many people in the industry are working on developing new anode materials, wherein the specific capacity of elemental silicon at normal temperature reaches 3850mAh/g, and the anode materials are very potential to become anode materials of next-generation lithium ion batteries.
However, silicon has serious volume expansion during lithium intercalation, which can reach 300% or more. While high volume expansion can present challenges to cell design on the one hand, and can cause the active material to drop from the current collector during cycling on the other hand, while the volume expansion can easily cause particle breakage and introduce new contact interfaces of electrode material and electrolyte, and growth of SEI (solid electrolyte interface film) on the new contact interfaces can consume a certain amount of electrolyte, thereby reducing cell cycle life.
Disclosure of Invention
In order to overcome the defects, the invention aims to provide a silicon-based anode material and a preparation method thereof, which can inhibit volume expansion and prolong the cycle life of a battery while ensuring the capacitance.
In order to achieve the above purpose, one of the technical schemes adopted by the invention is as follows: a silicon-based anode material comprises silicon-carbon composite particles, wherein the silicon-carbon composite particles are formed by taking a porous carbon skeleton as a matrix and depositing a gaseous silicon source and a gaseous carbon source alternately.
The silicon-based anode material has the beneficial effects that:
the porous carbon skeleton is used as a matrix, and the pores on the porous carbon skeleton can be used as a gaseous silicon source and a deposition space of the gaseous carbon source, so that the volume occupied by deposition is reduced to a certain extent; a silicon layer can be formed on the porous carbon skeleton through the deposition of a gaseous silicon source, so that the gram capacity of the silicon layer is convenient to use to improve the charge and discharge capacity of the battery; the carbon layer can be formed on the porous carbon skeleton through the deposition of the gaseous carbon layer, the deposited silicon layer can be coated by the carbon layer formed through the deposition through the alternate deposition of the gaseous silicon source and the gaseous carbon source, and the volume expansion of the silicon layer in the charge and discharge process is restrained through the surface coating of the carbon layer, so that the purpose of prolonging the cycle life of the battery is achieved.
Further, the composite particle also comprises an outer coating layer coated on the surface of the silicon-carbon composite particle. The coating of the surface of the silicon-carbon composite particles by the outer coating layer can play a role in isolation so as to inhibit the reactivity of the silicon-carbon composite particles.
Further, the specific surface area of the silicon-carbon composite particles is not more than 50m 2 And/g, wherein the median particle diameter is 1-30 mu m, and the mass ratio of silicon element is 10-80 wt%.
Further, the porous carbon skeleton comprises porous carbon obtained by pyrolysis of resin or biomass substrate at high temperature, the median particle diameter of the porous carbon is 1-20 μm, and the specific surface area is not less than 1000m 2 Per gram, pore volume is not less than 0.2cm 3 And/g, wherein the porosity is 40-90%. Wherein, the resin can be phenolic resin, and the biomass base material can be coconut shell carbon, rice hull carbon, bamboo carbon and the like.
Further, the pores of the porous carbon can be divided into micropores, mesopores and macropores according to the pore size, wherein the pore size of the micropores is smaller than 2nm, the pore size of the mesopores is between 2 and 50nm, and the pore size of the macropores is larger than 50nm.
The second technical scheme adopted by the invention is as follows: the preparation method of the silicon-based anode material comprises the steps of putting a porous carbon skeleton into a deposition device, and carrying out at least one composite deposition on the porous carbon skeleton to form silicon-carbon composite particles, wherein the composite deposition comprises silicon deposition and carbon deposition which are sequentially carried out; wherein the silicon deposition comprises the steps of:
diluting the gaseous silicon source by adopting a diluting gas to form a mixed gas;
the mixed gas is put into a deposition device, the deposition temperature is controlled to be 350-600 ℃, and the deposition time is controlled to be 0.1-100 h, so that the thickness of a silicon layer deposited on the porous carbon skeleton is 0.1-20 nm.
The preparation method of the invention has the beneficial effects that:
in the composite deposition, a silicon layer and a carbon layer can be formed in the pores in the porous carbon skeleton in sequence through the silicon deposition and the carbon deposition which are sequentially carried out, and the problem of volume expansion of the silicon layer in the charge and discharge process is restrained by utilizing the coating of the carbon layer on the silicon layer; when the multi-time composite deposition is adopted, a plurality of silicon layers and carbon layers which are alternately arranged can be formed in the pores of the porous carbon skeleton, so that the volume expansion of the silicon layers is restrained by the carbon layers while the energy density of the battery is improved by the silicon layers, and the purpose of prolonging the cycle life of the battery while ensuring the high capacity of the battery is achieved.
Further, the diluent gas comprises at least one of argon, helium, nitrogen and hydrogen. Argon, helium, nitrogen and hydrogen are used as diluent gases, so that the reaction of the diluent gases and the gaseous silicon source is avoided, the gaseous silicon source can be protected, and the probability of the gaseous silicon source contacting oxygen in the deposition process is reduced.
Further, carbon deposition includes feeding a gaseous carbon source into a deposition apparatus, and controlling a deposition temperature to 400-1200 ℃ and a deposition time to 0.1-100 h, so that a thickness of a carbon layer deposited on the porous carbon is between 0.1-20 nm.
Further, the number of composite depositions is not more than 10.
Further, after the composite deposition is finished, the silicon-carbon composite particles can be coated with a surface coating, wherein the surface coating comprises at least one of carbon source, aluminum oxide, titanium dioxide, zirconium dioxide, magnesium oxide, titanium nitride, lithium phosphorus oxygen nitrogen, lithium phosphate and lithium aluminate. By coating the surface of the silicon-carbon composite particles, on one hand, the isolation effect can be achieved, so that the reactivity of the silicon-carbon composite particles is reduced, and meanwhile, the purpose of improving the electronic conductivity or the ionic conductivity can be achieved by utilizing the performance of the coating.
Drawings
Fig. 1 is a first-cycle charge-discharge curve of a half cell according to example 2 of the present invention;
fig. 2 is a cycle chart of a half cell of example 2 of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making clear and defining the scope of the present invention. It should be noted that the following examples are provided for better understanding of the present invention, and are not limited to the preferred embodiments, but are not limited to the content and the protection scope of the present invention, and any product which is the same as or similar to the present invention and obtained by combining the present invention with other features of the prior art in the light of the present invention falls within the protection scope of the present invention.
It should be noted that in the description of the present specification, descriptions of terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Furthermore, the examples do not address specific experimental procedures or conditions, and may be performed according to the procedures or conditions of conventional experimental procedures described in the literature in this field. In the examples, the numerical ranges shown using "to" represent ranges including the numerical values described before and after "to" as the minimum value and the maximum value, respectively. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Examples
The silicon-based anode material comprises silicon-carbon composite particles, wherein the silicon-carbon composite particles are formed by taking a porous carbon skeleton as a matrix and depositing a gaseous silicon source and a gaseous carbon source alternately.
The porous carbon skeleton is used as a matrix, and the pores on the porous carbon skeleton can be used as a gaseous silicon source and a deposition space of the gaseous carbon source, so that the volume occupied by deposition is reduced to a certain extent; a silicon layer can be formed on the porous carbon skeleton through the deposition of a gaseous silicon source, so that the gram capacity of the silicon layer is convenient to use to improve the charge and discharge capacity of the battery; the carbon layer can be formed on the porous carbon skeleton through the deposition of the gaseous carbon layer, the deposited silicon layer can be coated by the carbon layer formed through the deposition through the alternate deposition of the gaseous silicon source and the gaseous carbon source, and the volume expansion of the silicon layer in the charge and discharge process is restrained through the surface coating of the carbon layer, so that the purpose of prolonging the cycle life of the battery is achieved.
In some embodiments, the surface of the silicon carbon composite particles is also coated with an outer coating. The coating of the outer coating layer comprises at least one of carbon source, aluminum oxide, titanium dioxide, zirconium dioxide, magnesium oxide, titanium nitride, lithium phosphorus oxygen nitrogen, lithium phosphate and lithium aluminate. By coating the surface of the silicon-carbon composite particles, on one hand, the isolation effect can be achieved, so that the reactivity of the silicon-carbon composite particles is reduced, and meanwhile, the purpose of improving the electronic conductivity or the ionic conductivity can be achieved by utilizing the performance of the coating.
In some embodiments, the properties of the silicon carbon composite particles are as follows:
(1) The specific surface area of the silicon-carbon composite particles is not more than 50m 2 And/g. Preferably, the specific surface area is not more than 30m 2 And/g. More preferably, the specific surface area is not more than 10m 2 /g。
(2) The mass ratio of the silicon element in the silicon-carbon composite particles is 10-80 wt%. Preferably, the mass ratio is 20 to 70wt%. More preferably, the mass ratio is 30 to 60wt%.
(3) The median particle diameter (D50) of the silicon-carbon composite particles is 1-30 mu m. Preferably, the median particle diameter (D50) is from 2 to 20. Mu.m. More preferably, the median particle diameter (D50) is from 5 to 12. Mu.m.
In some embodiments, the porous carbon skeleton has the following properties:
(1) The porous carbon skeleton is made of hard carbon, and can be obtained by pyrolyzing resin at high temperature or by properly treating biomass base material and then pyrolyzing the biomass base material at high temperature. Illustratively, the resin may be phenolic resin, and the biomass substrate may be coconut charcoal, rice hull charcoal, bamboo charcoal, etc.
(2) The porous carbon may be a pure carbon base or a composite carbon base doped with other elements in an appropriate amount. The other elements may be elements such as phosphorus and nitrogen which improve electrochemical performance.
(3) The porous carbon has a median particle diameter (D50) of 1 to 20 μm. Preferably, the median particle diameter (D50) is from 2 to 15. Mu.m. More preferably, the median particle diameter (D50) is 4 to 10. Mu.m.
(4) The specific surface area of the porous carbon is not less than 1000m 2 And/g. Preferably, the specific surface area is not less than 1500m 2 /g。
(5) The pores of the porous carbon can be divided into micropores, mesopores and macropores according to the pore size. Wherein the aperture of the micropore is smaller than 2nm, the aperture of the mesopore is 2-50 nm, and the aperture of the macropore is larger than 50nm.
(6) The pore volume of the porous carbon is not less than 0.2cm 3 And/g. Preferably, the pore volume is not less than 0.4cm 3 And/g. More preferably, the pore volume is not less than 0.6cm 3 /g。
(7) The porosity of the porous carbon is 40% -90%. Preferably, the porosity is 50% to 80%. More preferably, the porosity is 60% to 75%.
In the invention, the synthetic route of the silicon-based anode material is as follows: taking a porous carbon skeleton as a matrix, alternately performing silicon deposition and carbon deposition through a gas phase precursor to form silicon-carbon composite particles, and then performing surface coating to form an outer coating layer.
Based on the method, the invention also provides a preparation method of the silicon-based anode material, which comprises the steps of putting the porous carbon skeleton into deposition equipment, and carrying out at least one composite deposition on the porous carbon skeleton to form silicon-carbon composite particles, wherein the composite deposition comprises silicon deposition and carbon deposition which are sequentially carried out.
In the composite deposition, a silicon layer and a carbon layer can be formed in the pores in the porous carbon skeleton in sequence through the silicon deposition and the carbon deposition which are sequentially carried out, and the problem of volume expansion of the silicon layer in the charge and discharge process is restrained by utilizing the coating of the carbon layer on the silicon layer; when the multi-time composite deposition is adopted, a plurality of silicon layers and carbon layers which are alternately arranged can be formed in the pores of the porous carbon skeleton, so that the volume expansion of the silicon layers is restrained by the carbon layers while the energy density of the battery is improved by the silicon layers, and the purpose of prolonging the cycle life of the battery while ensuring the high capacity of the battery is achieved. It should be noted that the deposition apparatus may be a fluidized bed, a batch rotary furnace, a continuous rotary furnace, an atmosphere box furnace, or the like.
Specifically, the silicon deposition includes the steps of:
s1, diluting a gaseous silicon source (such as silane) by adopting a diluting gas to form a mixed gas; wherein the diluent gas comprises at least one of argon, helium, nitrogen and hydrogen. And the volume ratio of the gaseous silicon source to the diluent gas is between 99:1 and 1:99. Illustratively, the volume ratio of gaseous silicon source to diluent gas may be 90:10, 70:30, 50:50, 30:70, 1:90, etc.
S2, putting the mixed gas into a deposition device, controlling the deposition temperature to be 350-600 ℃ and the deposition time to be 0.1-100 h, so that the thickness of the silicon layer deposited on the porous carbon skeleton is 0.1-20 nm. Illustratively, the deposition temperature may be 350 ℃, 450 ℃, 550 ℃, etc., and the deposition time may be 0.1h, 1h, 5h, 10h, 50h, 100h, etc., with silicon layer thicknesses of 0.5nm, 1nm, 3nm, 5nm, 10nm, 15nm, 20nm, etc.
When carbon deposition is carried out, a silicon source valve on the deposition equipment is closed firstly so as to stop introducing gaseous silicon source; then opening a carbon source valve to introduce a gaseous carbon source, controlling the deposition temperature to be 400-1200 ℃ and the deposition time to be 0.1-100 h, so that the thickness of a carbon layer deposited on the porous carbon is 0.1-20 nm. Illustratively, the deposition temperature may be 400 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1200 ℃, etc., and the deposition time may be 0.1h, 1h, 5h, 10h, 50h, 100h, etc., with the carbon layer thickness being 0.5nm, 1nm, 2nm, 5nm, 10nm, 15nm, 20nm, etc.
It should be noted that carbon deposition is performed by pyrolysis of a gaseous carbon source in a non-oxidizing atmosphere, wherein the gaseous carbon source may be (1) a hydrocarbon (such as methane, ethylene, acetylene, etc.) in gaseous form at room temperature or a mixed gas obtained by diluting a gaseous hydrocarbon with a non-oxidizing gas, and the volume ratio of carbon element in the mixed gas is 3-80%; (2) A mixed gas of hydrocarbons (e.g., toluene, xylene) in liquid form at room temperature, carried under a non-oxidizing atmosphere.
In some embodiments, one silicon deposition and one carbon deposition are taken as one composite deposition, and the total number of composite depositions is 1-10 in practical application. Multiple layers of silicon layers and carbon layers which are alternately arranged can be formed in the pores of the porous carbon skeleton through multiple composite deposition, so that the deposition density is enhanced.
After the composite deposition is completed, the silicon-carbon composite particles can be subjected to surface coating to form an outer coating layer. The surface-coated coating comprises at least one of carbon source, aluminum oxide, titanium dioxide, zirconium dioxide, magnesium oxide, titanium nitride, lithium phosphorus oxynitride, lithium phosphate and lithium aluminate. By coating the surface of the silicon-carbon composite particles, on one hand, the isolation effect can be achieved, so that the reactivity of the silicon-carbon composite particles is reduced, and meanwhile, the purpose of improving the electronic conductivity or the ionic conductivity can be achieved by utilizing the performance of the coating.
Further, when the surface is coated with a carbon source, the carbon source may be a hydrocarbon (e.g., methane, ethylene, acetylene, etc.) in the form of a gas at room temperature, or a mixed gas of the above-mentioned gaseous hydrocarbon diluted with a non-oxidizing gas; the carbon source may also be a mixed gas of hydrocarbon compounds (e.g., toluene, xylene, etc.) in liquid form at room temperature, carried under a non-oxidizing gas. Wherein the non-oxidizing atmosphere comprises at least one of nitrogen, argon and helium. And in the mixed gas, the volume ratio of the carbon element is 30-100%.
Further, the surface coating temperature is 700-1200 ℃. Such as 700 deg.c, 800 deg.c, 900 deg.c, 1000 deg.c and 1200 deg.c. The thickness of the outer coating layer is 1-200 nm.
The invention also provides a preparation method of the lithium battery, which comprises the following steps:
s1, mixing the silicon-based anode material with a conductive additive (such as at least one of carbon black, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene and the like) and an adhesive (such as at least one of sodium alginate, polyacrylic acid (PAA), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium carboxymethylcellulose/styrene-butadiene rubber (CMC/SBR) and the like) to form slurry, and taking water as a dispersing agent; in addition, when the slurry is prepared, a mixer can be selected for mixing in order to uniformly mix the components;
s2, coating the slurry obtained in the step S1 on a copper foil current collector with the thickness of 4-15 mu m by using a coating machine, drying and rolling to obtain a negative electrode, and then cutting into a proper size for standby;
s3, preparing a positive electrode material: a slurry coating process similar to the above-described negative electrode was employed.
Wherein the positive electrode material comprises one or more of the following substances: (1) Lithium-containing transition metal oxides, e.g. LiNi x Co y Mn 1-x-y O 2 (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) illustratively, e.g. LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 ，LiNi 0.7 Co 0.1 Mn 0.2 O 2 ，LiNi 0.5 Co 0.2 Mn 0.3 O 2 Etc. (2) Polyanionic positive electrode materials, e.g. LiMPO 4 (M is Fe or/and Mn, etc.), for example, liFePO 4 ，LiFe 0.8 Mn 0.2 PO 4 Etc.
The positive electrode current collector is generally a foil formed by compounding aluminum, nickel, stainless steel, titanium, or the like or a metal and a nonmetal. As the coating dispersion solvent, a nonaqueous solvent such as N-methylpyrrolidone (NMP) or the like is used. The binder typically employs a fluoropolymer such as polyvinylidene fluoride (PVDF).
S4, assembling the anode, the diaphragm and the cathode into a battery, wherein the diaphragm is used for isolating the anode and the cathode, and micropores for transmitting lithium ions are formed in the middle of the diaphragm. The separator may be a polyethylene or polypropylene film.
And S5, adding electrolyte into the battery, and sealing to obtain the lithium battery. Wherein the electrolyte can be selected from:
(1) A nonaqueous electrolyte solution which is liquid at room temperature and contains a salt, wherein the electrolyte solution comprises an aprotic solvent and a lithium-containing electrolyte salt which is soluble in the aprotic solvent. Aprotic solvents include dimethyl carbonate (DMC), ethylene Carbonate (EC), carbonAt least one of diethyl acid (DEC), propylene Carbonate (PC), ethylene carbonate (VC), fluoroethylene carbonate (FEC), and ethylmethyl carbonate (EMC); the lithium-containing electrolyte salt includes lithium hexafluorophosphate (LiPF) 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorooxalato borate (LiODFB), lithium perchlorate (LiClO) 4 ) Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), and the like. The concentration of the electrolyte solution is preferably 0.8 to 2.0M, and in addition, 0.1 to 3wt% of a compound containing a carboxylic acid anhydride group, a compound containing a sultone (e.g., propylene sultone, propane sultone, etc.) having a sulfur element, or a compound containing a boron element may be added to the electrolyte solution to improve the chemical stability of the electrolyte solution and suppress decomposition thereof on the surface of the anode material.
(2) Comprises a part or all of solid electrolyte components such as organic solid electrolyte, oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte.
Example 1
Taking a median particle diameter (D50) of 9 μm and a specific surface area of 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 6 hours, and closing the silicon source valve. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 1.
Preparing a half cell: silicon-based anode material 1, single-walled carbon nanotubes (SCNTs), conductive carbon black (SP), polyacrylic acid (PAA) and sodium carboxymethylcellulose (CMC) are mixed together according to the proportion of 85:75:0.5:3:10:0.75, and water is used as a dispersing agent to prepare slurry. And coating the obtained slurry on a copper foil current collector, and sequentially drying, rolling and cutting to obtain the silicon-based negative plate. And assembling the button half cell in a glove box filled with argon, and taking a metal lithium sheet as a positive plate. Electrolyte is 1M LiPF 6 The electrolyte solvent is Ethylene Carbonate (EC): diethyl carbonate (DEC): carbonic acidEthyl methyl Ester (EMC) =1:1:1, and 5% fluoroethylene carbonate (FEC) additive was added.
Preparing a full battery: graphite/silicon-based anode material 1, single-walled carbon nanotubes (SCNTs), conductive carbon black (SP), polyacrylic acid (PAA), sodium carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) are mixed together according to the proportion of 94:0.1:2:1.4:1.2:1.3 and water is used as a dispersing agent to prepare slurry. And coating the obtained slurry on a copper foil current collector, and sequentially drying, rolling and cutting to obtain the negative plate. The active material in the positive pole piece adopts LiNi 0.8 Co 0.1 Al 0.05 O 2 (NCA), conductive carbon black (SP), multi-wall carbon nanotubes (MWCNTs) and a binder polyvinylidene fluoride (PVDF) are mixed according to the proportion of 95:1.5:0.5:3, and then the materials are dispersed into uniform slurry in N-methyl pyrrolidone (NMP) solution to be coated and dried to obtain the positive plate. Then the positive plate and the negative plate are assembled into a soft package battery with the capacity of 3Ah in a drying chamber, and the electrolyte is 1M LiPF 6 The electrolyte solvent was Ethylene Carbonate (EC): diethyl carbonate (DEC): methyl ethyl carbonate (EMC) =1:1:1, and 5% fluoroethylene carbonate (FEC) additive was added.
Example 2
This embodiment 2 differs from embodiment 1 in that: and adopting silicon and carbon composite deposition twice.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. Heating to 550deg.C, and introducing acetylene/nitrogen (C) 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, the charging time is 30min, and the carbon source valve is closed. Then cooling to 450 ℃, and charging Silane (SiH) again 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. After heating to 550 ℃, acetylene/nitrogen (C) was introduced 2 H 2 /N 2 ) The mixed gas comprises the following components in percentage by volume:8, the charging time is 30min. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 2.
A half cell and a full cell were prepared using the silicon-based anode material 2 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 3
This embodiment 3 differs from embodiment 1 in that: and adopting silicon and carbon composite deposition for three times.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 2 hours, and closing the silicon source valve. Heating to 550deg.C, and introducing acetylene/nitrogen (C) 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, the charging time is 20min, and the carbon source valve is closed. Then cooling to 450 ℃, and charging Silane (SiH) again 4 ) And (5) introducing the silicon source valve for 2 hours, and closing the silicon source valve. After heating to 550 ℃, acetylene/nitrogen (C) was introduced 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, the charging time is 20min, and the carbon source valve is closed. Cooling to 450 ℃, and introducing Silane (SiH) 4 ) And (5) introducing the silicon source valve for 2 hours, and closing the silicon source valve. After heating to 550 ℃, acetylene/nitrogen (C) was introduced 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, and the charging time is 20min. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 3.
A half cell and a full cell were prepared using the silicon-based anode material 3 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 4
This embodiment 4 differs from embodiment 1 in that: the porous carbon has a different median particle diameter, specific surface area and pore volume.
Specifically, a median particle diameter (D50) of 4 μm and a specific surface area of 1700m were taken 2 Per gram, pore volume of 0.73cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 6 hours, and closing the silicon source valve. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 4.
A half cell and a full cell were prepared using the silicon-based anode material 4 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 5
This embodiment 5 differs from embodiment 2 in that: the type of gaseous carbon source varies.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. Heating to 550 ℃, and introducing methane/nitrogen (CH) 4 /N 2 ) And (3) in the mixed gas, the volume ratio of methane to nitrogen is 2:8, the charging time is 30min, and the carbon source valve is closed. Then cooling to 450 ℃, and charging Silane (SiH) again 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. After heating to 550 ℃, methane/nitrogen (CH) 4 /N 2 ) And in the mixed gas, the volume ratio of methane to nitrogen is 2:8, and the charging time is 30min. Then the temperature is raised to 750 ℃ and methane (CH) is introduced at the temperature 4 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of methane is 3 hours, and finally obtaining the silicon-based anode material 5.
A half cell and a full cell were prepared using the silicon-based anode material 5 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 6
This embodiment 6 differs from embodiment 2 in that: the temperature of silicon deposition varies.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then the temperature is raised to 550 ℃ at a rate of 5 ℃/min, and Silane (SiH) is introduced at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. Acetylene/nitrogen (C) 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, the charging time is 30min, and the carbon source valve is closed. Silane (SiH) is again introduced 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. Acetylene/nitrogen (C) 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, and the charging time is 30min. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 6.
A half cell and a full cell were prepared using the silicon-based anode material 6 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 7
This embodiment 7 differs from embodiment 2 in that: the carbon coating temperature is different.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection.Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. Heating to 550deg.C, and introducing acetylene/nitrogen (C) 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, the charging time is 30min, and the carbon source valve is closed. Then cooling to 450 ℃, and charging Silane (SiH) again 4 ) And (5) introducing the silicon source valve for 3 hours, and closing the silicon source valve. After heating to 550 ℃, acetylene/nitrogen (C) was introduced 2 H 2 /N 2 ) And in the mixed gas, the volume ratio of acetylene to nitrogen is 2:8, and the charging time is 30min. Subsequently, the temperature was increased to 950℃and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 7.
A half cell and a full cell were prepared using the silicon-based anode material 7 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Example 8
This embodiment 8 differs from embodiment 1 in that: the time of silicon deposition varies.
Specifically, the median particle diameter (D50) was 9 μm and the specific surface area was 1600m 2 Per gram, pore volume of 0.62cm 3 And (3) per gram of porous carbon, placing the porous carbon in a rotary furnace, heating to 100 ℃, preserving heat for 30min in a vacuum state, and then introducing nitrogen for protection. Then heating to 450 ℃ at a rate of 5 ℃/min, and then introducing Silane (SiH) at a rate of 0.5L/min 4 ) And (5) the silicon source valve is closed after the silicon source valve is opened for 4 hours. Then the temperature is raised to 750 ℃ and acetylene (C) 2 H 2 ) And (3) coating carbon on the outer surface of the silicon-based anode material, wherein the introducing time of acetylene is 3 hours, and finally obtaining the silicon-based anode material 8.
A half cell and a full cell were prepared using the silicon-based anode material 8 as an anode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Comparative example 1
Adding vapor deposition nanometer silicon powder (with a median particle diameter D50 of 70 nm) into absolute ethyl alcohol, performing ultrasonic dispersion for 30min to form uniform suspension, then adding artificial graphite (with a median particle diameter D50 of 15 mu m) and asphalt, and stirring for 3h to form uniform slurry, wherein the mass of the asphalt accounts for 8% of the total mass of the artificial graphite and the nanometer silicon powder. And then spray drying the slurry, setting the air inlet temperature to 140 ℃ and the air outlet temperature to 110 ℃ to obtain a negative electrode precursor, then carrying out high-temperature treatment under nitrogen atmosphere, heating to 950 ℃ at a heating rate of 5 ℃/min, and preserving heat for 5 hours to obtain the silicon-based negative electrode material 9.
A half cell and a full cell were prepared using the silicon-based negative electrode material 9 as a negative electrode material, respectively, and the preparation methods of the half cell and the full cell were the same as in example 1.
Test examples
The half cells and the full cells prepared in examples 1 to 8 and comparative example 1 were subjected to battery performance tests, respectively, and the test results are shown in table 1. And taking example 2 as an example, a first-turn charge-discharge curve (as shown in fig. 1, wherein the abscissa represents specific capacity, unit mAh/g, the ordinate represents voltage, unit V) and a half-cell cycle diagram (as shown in fig. 2, wherein the abscissa represents cycle number, and the ordinate represents capacity retention (%)) are respectively drawn.
Table 1 battery performance test results
Table 1 illustrates:
(1) Half-cell: the voltage range is 0.005-1.5V, the current density is firstly 0.05C constant current to 0.05V when discharging, then 0.02C constant current is used for discharging to 0.005V, and the mixture is kept stand for 20min, and is charged to 1.5V with 0.05C constant current.
(2) Full cell: the silicon-based negative electrode material and the artificial graphite are compounded and coordinated to form a composite negative electrode with the lithium removal capacity of 600mAh/g, the voltage range is 2.7-4.3V, the assembled battery circulates for 3 circles at the rate of 0.05, and then the current density of the battery is 1C during the circulation.
(3) The specific surface area measurement method comprises the following steps: and measuring the adsorption quantity of the gas on the solid surface under different relative pressures, and obtaining the monomolecular layer adsorption quantity of the sample based on a BET formula.
(4) The method for testing the tap density of the material comprises the following steps: the test was performed using a Kang Da (Autotap) tap density tester.
(5) The electrode membrane expansion rate testing method comprises the following steps: the thickness of the electrode membrane was measured by SEM, and the expansion ratio of the electrode membrane was = ((thickness after completion of first lithium intercalation-initial thickness)/initial thickness) ×100%.
As can be seen from table 1:
comparative examples 1 to 8 and comparative example 1 show that: compared with comparative example 1, the volume expansion rate of the silicon-based anode materials of examples 1 to 8 after the first lithium intercalation is significantly reduced, which is because the silicon-based anode materials of examples 1 to 8 are coated with the silicon layer through the carbon layer during the preparation process, thereby effectively inhibiting the volume expansion of the silicon layer.
Comparative examples 1 to 3 show that: in example 1, carbon coating was directly performed after one silicon deposition, example 2 was performed after two silicon and carbon depositions, example 3 was performed after three silicon and carbon depositions, and from the results of the battery performance test, the cycle capacity retention rate was improved, the first lithium intercalation expansion rate was reduced, and the number of silicon and carbon depositions was increased, the first lithium intercalation expansion rate was decreased. The reason is that the integral deposition amount of silicon is ensured through multiple times of silicon and carbon deposition, and the thickness of a single silicon layer can be reduced due to the deposition time, so that the expansion rate of the single silicon layer is reduced, and when silicon and carbon are alternately deposited, the silicon layer can be laminated and coated at intervals through the carbon layer, so that the effect of inhibiting the volume expansion of the silicon layer is enhanced.
Comparative examples 1 and 8 show that: the silicon deposition time in example 1 was 6h, the silicon deposition time in example 8 was 4h, and the initial lithium intercalation expansion rate of example 8 was lower than that of example 1 from the battery performance test result, but the tap density of the material of example 8 and the initial lithium removal capacity of half battery were both lower than that of example 1. The reason for this is that the silicon deposition time has a certain influence on the deposition amount, and the longer the deposition time is, the larger the deposition amount is, and therefore, the reason for the lower expansion rate of the first lithium intercalation of example 8 is that the silicon deposition amount is smaller.
The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and to implement the same, but are not intended to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.

Claims (10)

1. The silicon-based anode material is characterized by comprising silicon-carbon composite particles, wherein the silicon-carbon composite particles are formed by taking a porous carbon skeleton as a matrix and depositing a gaseous silicon source and a gaseous carbon source alternately.
2. The silicon-based anode material according to claim 1, further comprising an outer coating layer coated on the surface of the silicon-carbon composite particles.
3. The silicon-based anode material according to claim 1, wherein the specific surface area of the silicon-carbon composite particles is not more than 50m 2 And/g, wherein the median particle diameter is 1-30 mu m, and the mass ratio of silicon element is 10-80 wt%.
4. The silicon-based anode material according to claim 1, wherein the porous carbon skeleton comprises porous carbon obtained by pyrolysis of a resin or biomass substrate at high temperature, the porous carbon having a median particle diameter of 1 to 20 μm and a specific surface area of not less than 1000m 2 Per gram, pore volume is not less than 0.2cm 3 And/g, wherein the porosity is 40-90%.
5. The silicon-based anode material according to claim 4, wherein: the pores of the porous carbon can be divided into micropores, mesopores and macropores according to the pore size, wherein the pore size of the micropores is smaller than 2nm, the pore size of the mesopores is between 2 and 50nm, and the pore size of the macropores is larger than 50nm.
6. The preparation method of the silicon-based anode material is characterized by comprising the steps of putting a porous carbon skeleton into a deposition device, and carrying out at least one composite deposition on the porous carbon skeleton to form silicon-carbon composite particles; the composite deposition comprises silicon deposition and carbon deposition which are sequentially carried out; wherein the silicon deposition comprises the steps of:
diluting the gaseous silicon source by adopting a diluting gas to form a mixed gas;
the mixed gas is put into a deposition device, the deposition temperature is controlled at 400-1200 ℃, and the deposition time is controlled at 0.1-100 h, so that the thickness of a silicon layer deposited on a porous carbon skeleton is between 0.1-20 nm.
7. The method for preparing a silicon-based anode material according to claim 6, wherein the diluent gas comprises at least one of argon, helium, nitrogen and hydrogen.
8. The method according to claim 6, wherein the carbon deposition comprises feeding a gaseous carbon source into a deposition apparatus, controlling the deposition temperature to 350-600 ℃ and the deposition time to 0.1-100 h, so that the thickness of the carbon layer deposited on the porous carbon skeleton is between 0.1-20 nm.
9. The method of claim 6, wherein the number of composite depositions is not more than 10.
10. The method for preparing a silicon-based anode material according to claim 6, wherein after the composite deposition is completed, the silicon-carbon composite particles can be further subjected to surface coating, and the surface-coated coating comprises at least one of carbon source, aluminum oxide, titanium dioxide, zirconium dioxide, magnesium oxide, titanium nitride, lithium phosphorus oxygen nitrogen, lithium phosphate and lithium aluminate.
CN202310917101.4A 2023-07-25 2023-07-25 Silicon-based negative electrode material and preparation method thereof Pending CN116914112A (en)

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