CN113745519A - Silicon-based negative electrode material with artificial SEI film and preparation method and application thereof - Google Patents

Silicon-based negative electrode material with artificial SEI film and preparation method and application thereof Download PDF

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CN113745519A
CN113745519A CN202111003432.4A CN202111003432A CN113745519A CN 113745519 A CN113745519 A CN 113745519A CN 202111003432 A CN202111003432 A CN 202111003432A CN 113745519 A CN113745519 A CN 113745519A
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silicon
agarose
negative electrode
electrode material
carbon
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CN113745519B (en
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谢英朋
冀亚娟
徐晓霞
刘蕾
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Eve Energy 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
    • H01M4/38—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
    • 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
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Abstract

The invention provides a silicon-based negative electrode material with an artificial SEI film, and a preparation method and application thereof, wherein the silicon-based negative electrode material comprises a silicon-based material and agarose coated on the surface of the silicon-based material, and the preparation method comprises the following steps: and mixing the silicon-based material and agarose, heating, and drying to obtain the silicon-based negative electrode material. The silicon-based material and the agarose in the silicon-based negative electrode material prepared by the invention have good associativity, the non-polar bond in the agarose improves the ionic conductivity, the polar group inhibits the growth of lithium dendrite, and the lithium ions consumed by the first charge and discharge are reduced, so that the silicon-based negative electrode material provided by the invention can reduce the irreversible capacity of a battery, and improve the first coulombic efficiency and the cycling stability of the battery.

Description

Silicon-based negative electrode material with artificial SEI film and preparation method and application thereof
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a silicon-based negative electrode material with an artificial SEI film, and a preparation method and application thereof.
Background
With the continuous expansion of the electronic product and electric automobile markets, people also put forward higher requirements on batteries, energy density is a key index for determining the endurance capacity of the batteries, wherein a negative electrode is one of important components of a battery material, and the reversible capacity of the negative electrode directly influences the energy density of the batteries. At present, graphite is used as a common negative electrode material in a lithium ion battery, the theoretical gram capacity of the graphite is only 372mAh/g, and the high-end graphite material in the market can reach 360-365mAh/g, so that the promotion space of the energy density of the corresponding lithium ion battery is quite limited.
Silicon-based materials have high theoretical gram capacity and low lithium removal potential, are environmentally friendly, abundant in reserves and low in cost, and have been widely concerned. However, the silicon-based material forms an SEI film on the surface of a negative electrode during the first charge and discharge process, and consumes active lithium, and in addition, the silicon-based material has huge volume expansion during the lithium intercalation and deintercalation process, so that the SEI film is cracked and grown, and more active lithium is lost, thereby greatly reducing the reversible capacity of the battery. Therefore, a large number of workers have treated silicon-based materials in an attempt to solve the problem of loss of active lithium during charge and discharge of the silicon-based materials.
CN110190245B discloses a preparation method of an artificial SEI film, wherein 0.5-5% of stable lithium salt is directly added into negative electrode slurry to be used as a coating layer of a negative electrode plate. The method is simple and easy to implement, can reduce lithium ions consumed by the SEI film, but the artificial SEI film is easy to crack due to negative electrode expansion in the circulation process, and reduces the circulation stability of the silicon-based material.
CN110178252A discloses a prelithiation method for secondary battery, which adopts a short circuit method to prelithiate silicon-based material, so as to reduce the lithium loss during the charging and discharging process of the battery, but most of the prelithiation layer obtained after the treatment is lithium silicon alloy or lithium silicate, which has poor toughness, and can crack along with the volume expansion of the silicon material during the charging and discharging process, thereby reducing the electrochemical performance of the silicon-based material.
CN105845894B discloses a method for pre-lithiation of a lithium ion battery negative electrode piece, which adopts an electrochemical method to pre-lithiate a silicon-based material to make up for the consumption of lithium ions in the process of SEI film formation, but forms a brittle layer on the surface of the silicon-based material, which is not beneficial to the cycling stability of the material; meanwhile, the method uses metal lithium in the pre-lithiation process, has great potential safety hazard and is not beneficial to large-scale production and use.
The silicon-based negative electrode materials reported above all have the problems of SEI film cracking and active lithium loss caused by silicon-based material expansion in the charging and discharging processes, and further influence the reversible capacity, the first coulombic efficiency and the cycling stability of the battery. Therefore, how to solve the above problems, preparing a silicon-based negative electrode material with better electrochemical performance has become a problem to be solved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a silicon-based negative electrode material with an artificial SEI film, and a preparation method and application thereof. According to the invention, the surface of the silicon-based material is coated with agarose to construct the artificial SEI film, so that lithium ions consumed by first charge and discharge can be reduced, and the artificial SEI film is not cracked in the expansion process. Meanwhile, the method is beneficial to improving the ionic conductivity, inhibiting the growth of Li dendritic crystals and further improving the first reversible capacity, the first coulombic efficiency and the cycling stability of the battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a silicon-based negative electrode material, and in particular provides a silicon-based negative electrode material with an artificial SEI film, wherein the silicon-based negative electrode material comprises a silicon-based material and agarose coated on the surface of the silicon-based material.
According to the invention, agarose with good flexibility is coated on the surface of the silicon-based material to play a role of an artificial SEI film, and the artificial SEI film is insoluble in organic solvents such as EC and DMC, so that the volume expansion of the silicon-based material in the circulation process can be relieved, and the stability of the artificial SEI film is improved. Meanwhile, agarose contains nonpolar bonds (-O-) and a large number of polar groups (-OH), wherein the nonpolar bonds (-O-) are favorable for improving the ionic conductivity, and the polar groups can effectively inhibit the growth of lithium dendrites and the side reaction between the lithium metal and electrolyte.
The silicon-based negative electrode material can reduce the irreversible capacity of the battery and improve the first coulombic efficiency and the cycling stability of the battery.
As a preferred technical scheme of the silicon-based negative electrode material, the agarose is carboxylated agarose.
The polar group carboxyl contained in the carboxylated agarose can inhibit the growth of lithium dendrite and the side reaction between the lithium metal and the electrolyte, and the safety performance of the battery is improved. Meanwhile, the carboxylated agarose is used as a linear polymer containing carboxyl, hydroxyl and ether bonds, strong acting force can be formed among molecules, the carboxylated agarose has good flexibility, and the carboxylated agarose is coated on the surface of a silicon-based material to be used as a buffer layer for silicon-based material expansion, so that the stability of the silicon-based negative electrode material in the electrochemical cycle process is ensured.
Preferably, the surface of the silicon-based material carries a group capable of bonding to a carboxyl group, which may be, for example, a hydroxyl group.
Preferably, the group capable of bonding to a carboxyl group is a hydroxyl group.
Carboxyl in the carboxylated agarose can form chemical bonds with groups (such as hydroxyl) on the surface of a silicon-based material, so that the bonding force of the carboxyl and the silicon-based material is greatly improved, the artificial SEI film cannot fall off in the lithium intercalation and deintercalation process, and the problem of the SEI film cracking and growing in the circulation process of the silicon oxide negative electrode is solved.
Preferably, the agarose has a thickness of 1-20nm, which may be, for example, 1nm, 2nm, 4nm, 8nm, 10nm, 12nm, 15nm, 18nm or 20 nm.
Preferably, the silicon-based material comprises a silicon carbon material and/or a silicon oxygen material, and may be, for example, a silicon carbon material, a silicon oxygen material, or a silicon carbon material and a silicon oxygen material.
Preferably, the silicon-based material is carbon-coated silica.
Preferably, the carbon-coated silica includes a silica core and a carbon layer coated on a surface of the silica core.
Preferably, the carbon layer has a thickness of 1-15nm, which may be, for example, 1nm, 2nm, 4nm, 8nm, 10nm, 12nm or 15 nm.
According to the invention, the carbon-coated silicon monoxide is adopted as the silicon-based material, so that the cycle performance of the silicon-based material can be further improved, and meanwhile, the silicon monoxide is environment-friendly, rich in reserves and low in cost, and is a silicon-based negative electrode material with excellent performance.
Preferably, the agarose content is 0.2-5%, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, preferably 0.5-3%, based on 100% by mass of the silicon-based anode material.
Preferably, the content of the silicon-based material is 90-99%, for example, 90%, 90.5%, 91%, 92%, 93%, 95%, 97%, 98.5% or 99%, preferably 93-98%, based on 100% by mass of the silicon-based anode material.
Preferably, the silicon-based negative electrode material comprises carbon-coated silica and agarose coated on the surface of the carbon-coated silica.
Preferably, the content ratio of the silicon oxide, the carbon layer and the agarose is (95-98): (0.5-3): (0.2-3) based on 100% of the mass of the silicon-based anode material, wherein, the selection range of the silicon oxide 95-98 can be 95, 95.5, 96, 96.5, 97, 97.5 or 98, the selection range of the carbon layer 0.5-3 can be 0.5, 1, 1.5, 2, 2.5 or 3, and the selection range of the agarose 0.2-3 can be 0.2, 0.5, 1, 1.5, 2, 2.5 or 3.
In a second aspect, the present invention provides a method for preparing a silicon-based anode material according to the first aspect, the method comprising the following steps:
and mixing and heating the silicon-based material and the agarose, and then drying to obtain the silicon-based negative electrode material.
The agarose has certain fluidity after being heated, can be uniformly coated on the surface of a silicon-based material and serves as an artificial SEI film, and the problem that the SEI film is cracked and grows in the circulation process of the silicon-based material is solved.
Preferably, the silicon-based material is carbon-coated silica.
The method for producing the carbon-coated silica of the present invention is not limited, and for example, the carbon-coated silica can be produced by the following method:
(1) uniformly mixing silicon powder and silicon dioxide powder, heating the mixture at the temperature of 700 ℃ and 1500 ℃ in an inert environment to generate silicon monoxide gas, cooling the silicon monoxide gas to obtain a silicon monoxide solid, and crushing the silicon monoxide solid to obtain silicon monoxide powder;
(2) and (2) introducing the silicon oxide powder obtained in the step (1) into a fluidized bed type atmosphere furnace, heating up to 550-1200 ℃ in an inert atmosphere, introducing a carbon source gas, preserving heat for 0.3-12h, then closing the carbon source gas, cooling to room temperature, and crushing to obtain carbon-coated silicon oxide.
Preferably, the molar ratio of the silicon powder to the silicon dioxide powder is (0.4-0.6): (0.6-0.4).
Preferably, the particle size D50 of the silicon powder is 5-15 μm.
Preferably, the particle size D50 of the silicon dioxide powder is 0.02-10 μm.
Preferably, the particle size D50 of the silicon oxide powder is 10-15 μm.
Preferably, the inert gas is any one of nitrogen, helium, argon or a combination of at least two thereof, and may be, for example, nitrogen, argon, helium or a combination of nitrogen and argon.
Preferably, the carbon source gas is any one or a combination of at least two of methane, acetylene, ethylene and ethane, and may be, for example, methane, acetylene, ethylene or a combination of methane and acetylene.
Preferably, the agarose is carboxylated agarose. The carboxylated agarose can be well dissolved in high-temperature water and uniformly coated on the surface of a silicon-based material, so that the coating effect is improved.
Preferably, the heating temperature is 60-80 ℃, for example, 60 ℃, 62 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃, preferably 65-75 ℃.
Preferably, the heating time is 9-12h, for example, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12 h.
Preferably, the heating is accompanied by stirring.
As a preferable technical scheme of the preparation method, the preparation method comprises the following steps:
adding a silicon-based material into water, performing ultrasonic dispersion until the silicon-based material is uniform, then adding agarose to obtain a mixed solution, and performing spray drying on the mixed solution to obtain the silicon-based negative electrode material.
According to the invention, the silica-based material is added into water for ultrasonic dispersion, and then the agarose is added, so that the silica-based material can be better coated by the agarose, and then spray drying is carried out.
Preferably, the inlet temperature of the spray drying is 120-.
Preferably, the outlet temperature of the spray drying is 60-90 ℃, for example 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ or 90 ℃.
As a further preferable technical scheme of the preparation method of the invention, the preparation method comprises the following steps:
adding a silicon-based material into water, performing ultrasonic dispersion until the silicon-based material is uniform, adding carboxylated agarose, heating and stirring at 60-80 ℃ for 9-12h, then performing spray drying, wherein the inlet temperature of the spray drying is 190 ℃ plus materials, the outlet temperature of the spray drying is 60-90 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
The silicon-based anode material prepared by the invention has uniform surface coating of the carboxylated agarose on the silicon-based material and strong binding force of the carboxylated agarose and the silicon-based material, solves the problem of SEI film breakage caused by huge expansion of the silicon-based material, and is simple in preparation method and easy to realize large-scale production.
In a third aspect, the present invention provides a lithium ion battery, where the lithium ion battery includes the silicon-based negative electrode material according to the first aspect.
The invention is not limited to the specific type of the lithium ion battery, and the lithium ion battery can be, for example, a liquid lithium ion battery, and generally, the liquid lithium ion battery includes a positive electrode, a negative electrode, an electrolyte and a diaphragm. The surface of the silicon-based negative electrode material is coated with the SEI film, so that the silicon-based negative electrode material can stably exist in an organic electrolyte solvent, and the damage of the co-intercalation of organic solvent molecules to an electrode material is prevented, so that the silicon-based negative electrode material can be applied to a liquid lithium ion battery, the cycle performance of the battery is improved, and the service life of the battery is prolonged.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the agarose with good flexibility is coated on the surface of the silicon-based material, so that the effect of an artificial SEI film is achieved, the volume expansion of the silicon-based material in the circulation process can be relieved, and the stability of the artificial SEI film is improved. Meanwhile, the ionic conductivity can be improved, the growth of lithium dendrite and side reaction between metal lithium and electrolyte are inhibited, the irreversible capacity of the battery can be reduced, and the first coulombic efficiency and the cycling stability of the battery are improved.
(2) The carboxylated agarose provided by the invention can further strengthen the effects of growth of lithium dendrites and inhibition of side reactions between lithium metal and electrolyte, has good flexibility, and can greatly improve the stability of an artificial SEI film; meanwhile, the silicon-based material with the surface provided with the group capable of being bonded with carboxyl is matched for use, so that the binding capacity between the silicon-based material and the carboxylated agarose is improved, the artificial SEI film is not fallen off in the lithium-intercalation and-deintercalation process, and the problem of the SEI film cracking and growing in the circulation process of the silicon-based negative electrode material is solved.
(3) The preparation method is simple and is easy to realize large-scale production.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-based negative electrode material according to an embodiment of the present invention, wherein the silicon oxide is 1-carboxylated agarose or 2-carbon-coated silica.
Fig. 2 is a schematic flow chart of a process for preparing a silicon-based anode material according to an embodiment of the invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The embodiment of the invention provides a silicon-based negative electrode material, which comprises a silicon-based material and agarose coated on the surface of the silicon-based material.
In some embodiments, the agarose is carboxylated agarose.
In some embodiments, the surface of the silicon-based material carries a group capable of bonding to a carboxyl group.
In some embodiments, the group capable of bonding to a carboxyl group is a hydroxyl group.
In some embodiments, the agarose is 1-20nm thick.
In some embodiments, the silicon-based material comprises a silicon carbon material and/or a silicon oxygen material.
In some embodiments, the silicon-based material is carbon-coated silica.
In some embodiments, the carbon-coated silica includes a silica core and a carbon layer coated on a surface of the silica core.
In some embodiments, the carbon layer has a thickness of 1 to 15 nm.
In some embodiments, the agarose content is 0.2-5%, preferably 0.5-3%, based on 100% by mass of the silicon-based anode material.
In some embodiments, the content of the silicon-based material is 90 to 99%, preferably 93 to 98%, based on 100% by mass of the silicon-based anode material.
In some embodiments, the silicon-based anode material comprises carbon-coated silica and agarose coating the surface of the carbon-coated silica.
In some embodiments, the ratio of the content of the silicon oxide, the carbon layer and the agarose is (95-98): (0.5-3): (0.2-3) based on 100% by mass of the silicon-based anode material.
In another embodiment, a method for preparing a silicon-based anode material is provided, and a flow diagram is shown in fig. 2, wherein the method includes steps S100-S200.
And S100, mixing the silicon-based material and the agarose, and heating.
In some embodiments, the silicon-based material is carbon-coated silica.
In some embodiments, the agarose is carboxylated agarose.
In some embodiments, the temperature of the heating is 60 to 80 ℃, preferably 65 to 75 ℃.
In some embodiments, the heating time is 9-12 hours.
In some embodiments, the heating is accompanied by stirring.
And S200, drying to obtain the silicon-based negative electrode material.
In some embodiments, the method for preparing the silicon-based anode material comprises the following steps:
adding a silicon-based material into water, performing ultrasonic dispersion until the silicon-based material is uniform, then adding agarose to obtain a mixed solution, and performing spray drying on the mixed solution to obtain the silicon-based negative electrode material;
in some embodiments, the inlet temperature of the spray drying is 120-;
in some embodiments, the outlet temperature of the spray drying is 60-90 ℃.
Example 1
The embodiment provides a silicon-based anode material, and the structural schematic diagram is shown in fig. 1, the silicon-based anode material comprises carbon-coated silica 1 and carboxylated agarose 2(HPBIO-KT523 carboxylated 4FF agarose) coated on the surface of the carbon-coated silica, wherein the thickness of a carbon layer on the surface of the silica is 1.2nm, and the thickness of the carboxylated agarose is 11 nm; the content ratio of the silicon oxide, the carbon layer and the carboxylated agarose is 97:0.7:2.3, wherein the mass of the silicon-based negative electrode material is 100%.
The embodiment also provides a preparation method of the silicon-based anode material, and the flow schematic diagram refers to fig. 2, and the preparation method comprises the following steps:
(1) uniformly mixing silicon powder and silicon dioxide powder according to a molar ratio of 0.4:0.5, heating to 1000 ℃ in a nitrogen environment to generate silicon monoxide gas, cooling to obtain a solid silicon oxide, crushing to obtain silicon oxide powder, introducing the silicon oxide powder into a fluidized bed type atmosphere furnace, heating to 900 ℃ in an inert atmosphere, introducing methane gas, keeping the temperature for 8 hours, closing the methane gas, cooling to room temperature, and crushing to obtain carbon-coated silicon oxide;
(2) adding carbon-coated silicon monoxide into water, performing ultrasonic dispersion until the silicon monoxide is uniform, adding carboxylated agarose, heating and stirring at 70 ℃ for 10 hours, then performing spray drying, wherein the inlet temperature of the spray drying is 150 ℃, the outlet temperature of the spray drying is 75 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
Example 2
The embodiment provides a silicon-based negative electrode material, which comprises carbon-coated silica and carboxylated agarose coated on the surface of the carbon-coated silica, wherein the thickness of a carbon layer on the surface of the silica is 1nm, and the thickness of the carboxylated agarose is 15 nm; the content ratio of the silicon oxide, the carbon layer and the carboxylated agarose is 96.5:0.5:3 by taking the mass of the silicon-based negative electrode material as 100%.
The preparation method of the silicon-based anode material comprises the following steps:
(1) uniformly mixing silicon powder and silicon dioxide powder according to a molar ratio of 0.4:0.5, heating to 950 ℃ in a nitrogen environment to generate silicon monoxide gas, cooling to obtain a solid silicon oxide, crushing to obtain silicon oxide powder, introducing the silicon oxide powder into a fluidized bed type atmosphere furnace, heating to 950 ℃ in an inert atmosphere, introducing acetylene gas, keeping the temperature for 6 hours, closing the acetylene gas, cooling to room temperature, and crushing to obtain carbon-coated silicon oxide;
(2) adding carbon-coated silicon monoxide into water, performing ultrasonic dispersion until the silicon monoxide is uniform, adding carboxylated agarose, heating and stirring at 60 ℃ for 12 hours, then performing spray drying, wherein the inlet temperature of the spray drying is 120 ℃, the outlet temperature of the spray drying is 60 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
Example 3
The embodiment provides a silicon-based negative electrode material, which comprises carbon-coated silica and carboxylated agarose coated on the surface of the carbon-coated silica, wherein the thickness of a carbon layer on the surface of the silica is 13nm, and the thickness of the carboxylated agarose is 1 nm; the content ratio of the silicon oxide, the carbon layer and the carboxylated agarose is 98:1.8:0.2 by taking the mass of the silicon-based negative electrode material as 100%.
The preparation method of the silicon-based anode material comprises the following steps:
(1) uniformly mixing silicon powder and silicon dioxide powder according to a molar ratio of 0.5:0.5, heating at 1100 ℃ in an argon environment to generate silicon monoxide gas, cooling to obtain a solid silicon oxide, crushing to obtain silicon oxide powder, introducing the silicon oxide powder into a fluidized bed type atmosphere furnace, heating at 1100 ℃ in an inert atmosphere, introducing ethylene gas, keeping the temperature for 10 hours, closing the ethylene gas, cooling to room temperature, and crushing to obtain carbon-coated silicon oxide;
(2) adding carbon-coated silicon monoxide into water, performing ultrasonic dispersion until the silicon monoxide is uniform, adding carboxylated agarose, heating and stirring at 80 ℃ for 9 hours, then performing spray drying, wherein the inlet temperature of the spray drying is 190 ℃, the outlet temperature of the spray drying is 90 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
Example 4
The embodiment provides a silicon-based anode material, which comprises silicon monoxide and carboxylated agarose coated on the surface of the silicon monoxide, wherein the thickness of the carboxylated agarose is 20 nm; the content ratio of the silicon oxide to the carboxylated agarose is 95:5 by taking the mass of the silicon-based negative electrode material as 100%.
The preparation method of the silicon-based anode material comprises the following steps:
(1) uniformly mixing silicon powder and silicon dioxide powder according to a molar ratio of 0.6:0.5, heating to 950 ℃ in a nitrogen environment to generate silicon monoxide gas, cooling to obtain a silicon monoxide solid, and crushing to obtain silicon monoxide;
(2) adding silicon monoxide into water, performing ultrasonic dispersion until the silicon monoxide is uniform, adding carboxylated agarose, heating and stirring at 70 ℃ for 10 hours, then performing spray drying, wherein the inlet temperature of the spray drying is 150 ℃, the outlet temperature of the spray drying is 75 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
Example 5
This example provides a silicon-based negative electrode material and a method for preparing the same, except that the carboxylated agarose is replaced by agarose, which is the same as in example 1.
Example 6
This example provides a silicon-based negative electrode material and a method for preparing the same as in example 1, except that the thickness of the carboxylated agarose was replaced by 0.5nm by replacing the ratio of the contents of the silica, the carbon layer, and the carboxylated agarose by 99.2:0.7: 0.1.
Example 7
This example provides a silicon-based negative electrode material and a method for preparing the same as in example 1, except that the thickness of the carboxylated agarose was replaced by 25nm by replacing the ratio of the contents of the silica, the carbon layer, and the carboxylated agarose by 93.3:0.7: 6.
Example 8
The embodiment provides a silicon-based negative electrode material and a preparation method thereof, the silicon-based negative electrode material is the same as that in the embodiment 1, and the preparation method comprises the following steps:
mixing carbon-coated silicon monoxide and carboxylated agarose, heating and stirring at 70 ℃ for 10 hours, then carrying out vacuum filtration, and finally collecting a dried product to obtain the silicon-based negative electrode material.
Comparative example 1
The comparative example provides a silicon-based negative electrode material and a preparation method thereof, and the materials are the same as those in example 1 except that the silicon-based negative electrode material does not contain carboxylated agarose.
Comparative example 2
This comparative example provides a silicon-based negative electrode material and a method for preparing the same as in example 1, except that carboxylated agarose was replaced with polyethylene oxide.
The electrochemical performance test is carried out on the silicon-based negative electrode materials provided by the embodiments 1-9 and the comparative examples 1-2, the pole piece comprises the silicon-based negative electrode material, conductive carbon black and polyacrylic acid binder, and the mass ratio of the silicon-based negative electrode material to the conductive carbon black is as follows: conductive carbon black: polyacrylic acid binder 92:4: 4. A CR2025 battery is prepared by taking a lithium sheet as a negative electrode, Celgard2400 as a diaphragm and 1mol/L LiPF6/EC + DMC + EMC (v/v is 1:1:1) as an electrolyte. The battery is subjected to constant-current charge-discharge test by adopting a Xinwei battery test system:
first reversible capacity and first coulombic efficiency test: at 25 ℃, the charge was made to 5mV at constant current and constant voltage at 0.1C, and then the discharge was made to 1.5V at 0.1C, and the test results are shown in table 1.
II, testing cycle performance: at 25 ℃, the charge was carried out to 5mV at a constant current and a constant voltage of 0.2C, and then the charge was discharged to 1.5V at 0.2C, and the charge and discharge cycle was carried out for 50 weeks, and the test results are shown in table 1.
TABLE 1
Figure BDA0003236390660000131
It can be known from the above examples 1-8 and comparative examples 1-2 that the silicon-based negative electrode material provided by the invention is formed by coating agarose on the surface of a silicon-based material, so that the lithium ions consumed by first charge and discharge can be reduced, and the artificial SEI film is not cracked in the expansion process. Meanwhile, the method is beneficial to improving the ionic conductivity, inhibiting the growth of Li dendritic crystals and further improving the first reversible capacity, the first coulombic efficiency and the cycling stability of the battery.
It can be known from the comparison between the example 1 and the example 5 that whether the agarose in the silicon-based negative electrode material contains carboxyl can affect the electrochemical performance of the negative electrode material, and the carboxyl contained in the carboxylated agarose can be combined with the hydroxyl on the silicon oxide to form a chemical bond, so that the binding force between the carboxyl and the hydroxyl is greatly improved, and the stability of the artificial SEI film is improved, therefore, the first coulombic efficiency in the example 1 is 80.5% and is higher than 77.2% of the coulombic efficiency of the battery in the example 5.
It can be known from the comparison between the embodiment 1 and the embodiments 6 to 7 that the content of agarose in the silicon-based negative electrode material affects the electrochemical performance of the negative electrode material, and when the content of agarose is too much, the inactive substances are too much, the lithium ion transmission path is increased, the polarization is increased, and the cycle performance is reduced, so that the capacity retention rate in the embodiment 7 is 89.5%, which is slightly lower than that in the embodiment 1; when the content of agarose is too small, the stability of the SEI film cannot be effectively improved, and the cycle performance of the battery is affected, so that the capacity retention rate in example 8 is 93.2%, which is slightly lower than that in example 1.
It can be known from the comparison between the example 1 and the example 8 that, when the silicon-based negative electrode material is prepared, the silicon-based material is ultrasonically dispersed in water and then mixed with the carboxylated agarose, so that the agarose is more uniformly coated on the surface of the silicon-based material, the structure of the negative electrode material is more stable, and after the ultrasonic treatment, the first coulombic efficiency of the example 1 is better than that of the example 9.
Compared with the comparative example 1, the carboxylated agarose in the silicon-based negative electrode material can improve the stability of the artificial SEI film, improve the ionic conductivity, reduce the irreversible capacity of the battery, and improve the first coulombic efficiency and the cycling stability of the battery, and the electrochemical performance of the silicon-based negative electrode material without the agarose in the comparative example 1 is poorer than that of the example 1 in a comprehensive manner.
It can be known from the comparison between example 1 and comparative example 2 that the kind of the coating layer on the surface of the silicon-based material affects the electrochemical performance of the negative electrode material, when polyethylene oxide is coated on the surface of the silicon-based material, the polyethylene oxide does not contain polar groups such as carboxyl groups, so that bonding with the silicon-based material cannot occur, the stability of the SEI film is ensured, and the growth of lithium dendrite cannot be inhibited, so that the effect of the present invention is achieved, and the electrochemical effect of comparative example 2 is generally inferior to that of example 1.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (10)

1. The silicon-based negative electrode material is characterized by comprising a silicon-based material and agarose coated on the surface of the silicon-based material.
2. The silicon-based anode material according to claim 1, wherein the agarose is carboxylated agarose;
preferably, the surface of the silicon-based material is provided with a group capable of bonding with a carboxyl group;
preferably, the group capable of bonding to a carboxyl group is a hydroxyl group;
preferably, the agarose has a thickness of 1-20 nm.
3. Silicon-based anode material according to claim 1 or 2, wherein the silicon-based material comprises a silicon carbon material and/or a silicon oxygen material;
preferably, the silicon-based material is carbon-coated silica;
preferably, the carbon-coated silicon oxide comprises a silicon oxide inner core and a carbon layer coated on the surface of the silicon oxide inner core;
preferably, the carbon layer has a thickness of 1-15 nm.
4. Silicon-based anode material according to any one of claims 1 to 3, wherein the agarose content is 0.2 to 5%, preferably 0.5 to 3%, based on 100% by mass of the silicon-based anode material;
preferably, the content of the silicon-based material is 90-99%, preferably 93-98% by mass of the silicon-based anode material.
5. The silicon-based anode material according to any one of claims 1 to 4, wherein the silicon-based anode material comprises carbon-coated silica and agarose coating the surface of the carbon-coated silica;
preferably, the content ratio of the silicon oxide, the carbon layer and the agarose is (95-98): (0.5-3): (0.2-3) based on 100% of the mass of the silicon-based anode material.
6. A preparation method of the silicon-based anode material according to any one of claims 1 to 5, wherein the preparation method comprises the following steps:
and mixing and heating the silicon-based material and the agarose, and then drying to obtain the silicon-based negative electrode material.
7. The method according to claim 6, wherein the silicon-based material is carbon-coated silica;
preferably, the agarose is carboxylated agarose;
preferably, the heating temperature is 60-80 ℃, preferably 65-75 ℃;
preferably, the heating time is 9-12 h;
preferably, the heating is accompanied by stirring.
8. The preparation method according to claim 6 or 7, wherein the preparation method of the silicon-based anode material comprises the following steps:
adding a silicon-based material into water, performing ultrasonic dispersion until the silicon-based material is uniform, then adding agarose to obtain a mixed solution, and performing spray drying on the mixed solution to obtain the silicon-based negative electrode material;
preferably, the inlet temperature of the spray drying is 120-190 ℃;
preferably, the outlet temperature of the spray drying is 60-90 ℃.
9. The method according to any one of claims 6 to 8, characterized in that it comprises the steps of:
adding a silicon-based material into water, performing ultrasonic dispersion until the silicon-based material is uniform, adding carboxylated agarose, heating and stirring at 60-80 ℃ for 9-12h, then performing spray drying, wherein the inlet temperature of the spray drying is 190 ℃ plus materials, the outlet temperature of the spray drying is 60-90 ℃, and finally collecting a dried product to obtain the silicon-based negative electrode material.
10. A lithium ion battery comprising the silicon-based negative electrode material according to any one of claims 1 to 5.
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