CN113206213A - Silicon-based composite electrode and preparation method and application thereof - Google Patents

Silicon-based composite electrode and preparation method and application thereof Download PDF

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CN113206213A
CN113206213A CN202110473360.3A CN202110473360A CN113206213A CN 113206213 A CN113206213 A CN 113206213A CN 202110473360 A CN202110473360 A CN 202110473360A CN 113206213 A CN113206213 A CN 113206213A
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silicon
electrode
based composite
active material
composite electrode
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张军
傅儒生
刘兆平
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a silicon-based composite electrode and a preparation method and application thereof, wherein the silicon-based composite electrode comprises a copper foil; electrode slurry coated on the upper and lower surfaces of the copper foil; the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry; the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2; the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1. The invention adopts the aboveThe silicon-based composite electrode is used as the negative electrode of the lithium ion battery, so that the first coulombic efficiency of the battery can be improved; has high cycling stability.

Description

Silicon-based composite electrode and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrode preparation, and particularly relates to a silicon-based composite electrode and a preparation method and application thereof.
Background
In recent years, lithium ion batteries have been widely used in the markets of portable electronic products such as mobile phones, notebook computers, digital cameras, etc., but at present, commercial lithium ion batteries still cannot meet the requirements of high-power electric vehicles and large-scale electric vehiclesThe ever-increasing demand in the field of energy storage has driven extensive research into new negative electrode materials with high energy density. With the continuous improvement of energy density of lithium ion batteries, the traditional graphite cathode can not meet the design requirements of high specific energy lithium ion batteries. Silicon-based negative electrode has lower voltage (0.4V vs. Li/Li)+) And high theoretical specific capacity (4200mAh/g) has great application prospect in the negative electrode of the lithium ion battery.
However, the commercial application of silicon anode materials is also limited by several factors. One of the most significant problems is the significant volume change associated with silicon during high levels of lithium deintercalation (for Li)22Si5About 360% of alloy phase), which easily causes silicon particle cracking and pulverization phenomena, resulting in separation between silicon particles and a substrate, increased internal resistance of a battery, rapid decrease of capacity, and poor cycle performance. The pulverization phenomenon of the silicon negative electrode also affects the formation of a stable and uniform SEI film on the surface, and the continuous formation of a new SEI film continuously consumes lithium ions and electrolyte, resulting in rapid capacity fading. In addition, slow lithium diffusion kinetics in silicon negative electrode materials (diffusion coefficient 10)-14～10-13cm2S) and lower conductivity (10)-5～10-3S/cm) also significantly affects the rate capability and capacity utilization of silicon anodes.
Disclosure of Invention
In view of the above, the present invention provides a silicon-based composite electrode, and a preparation method and an application thereof, wherein a battery assembled by the silicon-based composite electrode has a high first coulombic efficiency.
The invention provides a silicon-based composite electrode, which comprises a copper foil;
electrode slurry coated on the upper and lower surfaces of the copper foil;
the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry;
the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2;
the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1.
Preferably, the mass ratio of the active material to the sodium carboxymethyl cellulose to the styrene-butadiene latex to the acetylene black is 78-83: 2.5-3.5: 6-8: 8-12.
Preferably, the graphene-coated SiOxThe content of the graphene in the graphene is more than 0 wt% and less than or equal to 30 wt%.
Preferably, the mass ratio of the active material, the sodium carboxymethyl cellulose, the styrene-butadiene latex and the acetylene black is 80:3:7: 10.
The invention provides a preparation method of the silicon-based composite electrode in the technical scheme, which comprises the following steps:
mixing an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black to obtain electrode slurry;
coating the electrode slurry on a copper foil, and drying to obtain an intermediate pole piece;
dissolving polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1 in acetonitrile to obtain a packaging material; and coating the packaging material on the surface of the middle pole piece, and drying to obtain the silicon-based composite electrode.
The invention provides a lithium ion battery, which comprises a silicon-based negative electrode, electrolyte and a positive electrode material;
the silicon-based cathode electrode is the silicon-based composite electrode in the technical scheme or the silicon-based composite electrode prepared by the preparation method in the technical scheme.
Preferably, the electrolyte is LIB-3003F electrolyte;
in the invention, the cathode material is a commonly used cathode material, such as a ternary material, lithium iron phosphate, lithium manganate and the like.
The invention provides a silicon-based composite electrode, which comprises a copper foil; electrode slurry coated on the upper and lower surfaces of the copper foil; the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry; the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2; the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1. According to the invention, the silicon-based composite electrode is used as the negative electrode of the lithium ion battery, so that the first coulombic efficiency of the battery can be improved; has high cycling stability.
Drawings
FIG. 1 is a graph showing capacity tests of lithium ion batteries prepared in example 1 of the present invention and comparative example 1;
fig. 2 is a graph showing coulombic efficiency and lithium intercalation capacity tests of lithium ion batteries prepared in example 1 of the present invention and comparative example 1;
fig. 3 is a graph showing coulombic efficiency and lithium intercalation capacity tests after 100 cycles under 1C of the lithium ion batteries prepared in example 1 and comparative example 1 of the present invention;
FIG. 4 is a graph showing capacity tests of lithium ion batteries prepared in example 2 of the present invention and comparative example 2;
fig. 5 is a graph showing coulombic efficiency and lithium intercalation capacity tests after 100 cycles under 1C of the lithium ion batteries prepared in example 2 and comparative example 2 of the present invention;
fig. 6 is a graph showing coulombic efficiency and lithium intercalation capacity tests after 100 cycles under 1C for the lithium ion batteries prepared in example 3 and comparative example 3 of the present invention;
FIG. 7 is a graph of capacity and coulombic efficiency at 0.2C, 0.5C,1C, 2C rate for lithium ion batteries prepared in example 4 of the present invention and comparative example 4;
fig. 8 is a graph of capacity and coulombic efficiency at 0.2C, 0.5C,1C, 2C rate for lithium ion batteries prepared in example 5 of the present invention and comparative example 5.
Detailed Description
The invention provides a silicon-based composite electrode, which comprises a copper foil;
electrode slurry coated on the upper and lower surfaces of the copper foil;
the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry;
the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2;
the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1. The lithium salt is preferably LiTFSI.
In a specific embodiment of the invention, the mass ratio of polyethylene oxide to lithium salt is 0.5:1, or 0.8:1, or 0.6: 1.
The active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2; in a specific embodiment, the active material is commercial SiOx(x ≈ 1); or commercial SiOxG (the content of graphene is 20%) (x ≈ 1); or commercial SiOx (x ≈ 1.5); or commercial SiOx (x ≈ 0.5); or commercial SiOx (x ≈ 2). The graphene-coated SiOxThe content of the graphene in the graphene is more than 0 wt% and less than or equal to 30 wt%. In a specific embodiment, the graphene-coated SiOxThe content of the graphene in the composite material is 20 percent.
The mass ratio of the active material to the sodium carboxymethyl cellulose to the styrene-butadiene latex to the acetylene black is 80:3:7: 10.
In the invention, the mass ratio of the electrode slurry to the packaging material is 1-4: 1. In a specific embodiment, the mass ratio of the electrode paste to the encapsulating material is 1.8: 1.
The invention provides a preparation method of the silicon-based composite electrode in the technical scheme, which comprises the following steps:
mixing an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black to obtain electrode slurry;
coating the electrode slurry on a copper foil, and drying to obtain an intermediate pole piece;
dissolving polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1 in acetonitrile to obtain a packaging material; and coating the packaging material on the surface of the middle pole piece, and drying to obtain the silicon-based composite electrode.
The method provided by the invention is simple and convenient to operate, and the electrode can be permeated into the whole electrode only by coating the surface of the electrode.
In the invention, the electrode slurry is dried after being coated on a copper foil, and the drying temperature is preferably 75-85 ℃, more preferably 80 ℃; the drying atmosphere is air; the drying time is preferably 110-130 min, and more preferably 120 min.
The invention provides a lithium ion battery, which comprises a silicon-based negative electrode, electrolyte and a positive electrode material;
the silicon-based cathode electrode is the silicon-based composite electrode in the technical scheme or the silicon-based composite electrode prepared by the preparation method in the technical scheme.
The lithium ion battery provided by the invention adopts the silicon-based composite electrode as a negative electrode, so that the first coulombic efficiency of the battery can be improved; has high cycling stability.
In the embodiment of the invention, the weight of the active material on the negative electrode plate is preferably 1.5-2.5 mg.
In order to further illustrate the present invention, the following examples are provided to describe a silicon-based composite electrode, its preparation method and application in detail, but they should not be construed as limiting the scope of the present invention.
Comparative example 1
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material is commercial SiOx(x ≈ 1)/G (graphene content 20%) (purchased from Ningbo Furi Battery materials science and technology, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg. (weight of active material: dried pole piece, then subtract the weight of copper foil, multiply by the weight percent of active material).
The prepared pole piece is used as a positive electrode, the Li piece is used as a negative electrode, and the electrolyte model is 3003F (commercial), so that the button battery 2032 is assembled for testing. The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.) at the test temperature of 50 ℃, and is charged and discharged at 0.05C, 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the lithium intercalation capacity and the first coulombic efficiency of the button cell at the multiplying power of 0.05C, the coulombic efficiency of the cell at the multiplying powers of 0.2C, 0.5C,1C and 2C and the stability of the cell circulating 100 cycles at the multiplying power of 1C are evaluated, as shown in figure 1, the experimental result shows that the first lithium intercalation capacity of the button cell prepared in the embodiment is mA1308 h/g and the first coulombic efficiency is 70.5% at the multiplying power of 0.05C. As shown in FIG. 2, the capacities of this example are 1302mAh/g, 1173mAh/g, 1076mAh/g, and 930mAh/g at 0.2C, 0.5C,1C, and 2C multiplying powers, respectively. As shown in fig. 3, the capacity retention ratio of the present embodiment after 100 cycles at 1C magnification is 87%.
Example 1
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available as SiOx/G (20% graphene content) (x. apprxeq.1) from Ningbo Furun Battery materials science and technology, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And placing the pole piece for later use. Dissolving polyoxyethylene and salt in certain proportion in acetonitrile; the mass ratio of polyethylene oxide to LiTFSI was 0.5. And (3) coating the prepared mixed solution of the polyoxyethylene and the salt on the prepared pole piece by using a scraper, wherein the mass ratio of the electrode slurry to the packaging material is 1.8:1, and standing and drying at normal temperature. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.) at the test temperature of 50 ℃, and is charged and discharged at 0.05C, 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the lithium intercalation capacity and the first coulombic efficiency of the button cell at the multiplying power of 0.05C, the coulombic efficiency of the button cell at the multiplying power of 0.2C, 0.5C,1C and 2C and the stability of the button cell circulating for 100 circles at the multiplying power of 1C are evaluated. As shown in fig. 1, the first lithium intercalation capacity of the button cell prepared in the embodiment is 1478mAh/g, which is improved by 170mAh/g compared with the lithium intercalation capacity of comparative example 1, and the first coulomb efficiency is 71.4%; the first coulombic efficiency was increased by 0.9% compared to comparative example 1. This shows that the lithium intercalation capacity and the first coulombic efficiency can be improved after adding polyoxyethylene and LiTFSI on the surface of the electrode. As shown in FIG. 2, the capacities of this example at 0.2C, 0.5C,1C and 2C rates are 1394mAh/g, 1356mAh/g, 1308mAh/g and 1216mAh/g, respectively. Compared with the comparative example 1, the alloy improves 92mAh/g, 183mAh/g, 232mAh/g and 286 mAh/g. This demonstrates that the rate capability can be improved after addition of polyethylene oxide and LiTFSI to the electrode surface. As shown in fig. 3, the capacity retention rate of the present example after 100 cycles at a rate of 1C was 91.3%, which is 4.3% higher than that of comparative example 1, and this shows that the cycle stability can be improved after adding polyethylene oxide and LiTFSI to the electrode surface.
Comparative example 2
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 1) and purchased from Ningbo Furun Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The prepared pole piece is used as a positive pole, the Li piece is used as a negative pole, and the electrolyte model is 3003F (commercial). Assembled into a button cell 2032 for testing. The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, the charge and discharge are carried out at 0.05C and 1C, the cut-off voltage is 0.005V-1.5V, then the lithium intercalation capacity and the first coulomb efficiency of the button cell under 0.05C multiplying power and the stability of 100 cycles under 1C multiplying power are evaluated, as shown in figure 4, the test result shows that the first lithium intercalation capacity of the button cell prepared in the comparative example 2 is 1608mAh/g, and the first coulomb efficiency is 72.5% when the multiplying power is 0.05C. As shown in fig. 5, the capacity retention rate of the present example is 23.2% after 100 cycles at a magnification of 1C.
Example 2
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material is commercial SiOx(x ≈ 1) from Ningbo Furi Battery materials science and technology, Inc. Coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and placing the pole piece in an air atmosphereAnd (5) baking for 2 h. And placing the pole piece for later use. Dissolving polyoxyethylene and salt in certain proportion in acetonitrile; the mass ratio of polyethylene oxide to LiTFSI was 0.5. And (3) coating the prepared mixed solution of the polyoxyethylene and the salt on the prepared pole piece by using a scraper, wherein the mass ratio of the electrode slurry to the packaging material is 1.8:1, and standing and drying at normal temperature. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, charging and discharging are carried out at 0.05C and 1C until the voltage is 0.005V-1.5V, and then the lithium insertion capacity and the first coulombic efficiency of the button cell under the multiplying factor of 0.05C and the stability of the button cell under the multiplying factor of 1C for 100 cycles are evaluated. As shown in fig. 4, the first lithium intercalation capacity of the button cell prepared in this example is 1674mAh/g, which is 66mAh/g higher than that of comparative example 2, the first coulombic efficiency is 73.4%, and the first coulombic efficiency is 0.9% higher than that of comparative example 2. This shows that the lithium intercalation capacity and the first coulombic efficiency can be improved after adding polyoxyethylene and LiTFSI on the surface of the electrode. As shown in fig. 5, the capacity retention rate of the present example was 64.4% at 1C rate and 41.2% higher than that of comparative example 2, which indicates that the addition of polyethylene oxide and LiTFSI to the electrode surface can improve the cycle stability.
Comparative example 3
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 1.5) and purchased from Ningbo Furi Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The prepared pole piece is used as a positive pole, the Li piece is used as a negative pole, and the electrolyte model is 3003F (commercial). Assembled into a button cell 2032 for testing. The button cell is tested on a Land tester (Wuhanxinnuo electronics Co., Ltd.) at the test temperature of 50 ℃, and is charged and discharged at 1C, the cut-off voltage is 0.005V-1.5V, and then the stability of the button cell in 100 cycles under the multiplying power of 1C is evaluated, as shown in FIG. 6, the experimental result shows that the capacity retention rate of the button cell in 100 cycles under the multiplying power of 1C is 31.4%.
Example 3
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 1.5) and purchased from Ningbo Furi Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And placing the pole piece for later use. Dissolving polyoxyethylene and salt in certain proportion in acetonitrile; the mass ratio of polyethylene oxide to LiTFSI was 0.5. And (3) coating the prepared mixed solution of the polyoxyethylene and the salt on the prepared pole piece by using a scraper, wherein the mass ratio of the electrode slurry to the packaging material is 1.8:1, and standing and drying at normal temperature. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The button cell is tested on a Land tester (Wuhanxinnuo electronics Co., Ltd.) at the test temperature of 50 ℃, and the button cell is charged and discharged at 1C until the voltage is 0.005V-1.5V, and then the stability of the button cell in 100 cycles under the multiplying power of 1C is evaluated. As shown in fig. 6, the capacity retention rate of the present example after 100 cycles at the rate of 1C is 56%, which is increased by 24.6% compared to that of comparative example 3, which shows that the cycling stability can be improved after adding polyethylene oxide and LiTFSI on the surface of the electrode.
Comparative example 4
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 0.5) and purchased from Ningbo Furi Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The prepared pole piece is used as a positive electrode, the Li piece is used as a negative electrode, and the electrolyte model is 3003F (commercial), so that the button battery 2032 is assembled for testing. The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, charging and discharging are carried out at 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the coulomb efficiency of the button cell under the multiplying power of 0.2C, 0.5C,1C and 2C is evaluated. As shown in FIG. 7, the capacity of this example is 2003mAh/g, 1846mAh/g, 1708mAh/g, 1504mAh/g at 0.2C, 0.5C,1C, 2C magnification, respectively.
Example 4
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 0.5) and purchased from Ningbo Furi Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And placing the pole piece for later use. Dissolving polyoxyethylene and salt in certain proportion in acetonitrile; the mass ratio of polyethylene oxide to LiTFSI was 0.8. And (3) coating the prepared mixed solution of the polyoxyethylene and the salt on the prepared pole piece by using a scraper, wherein the mass ratio of the electrode slurry to the packaging material is 1.8:1, and standing and drying at normal temperature. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, charging and discharging are carried out at 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the coulomb efficiency of the button cell under the multiplying power of 0.2C, 0.5C,1C and 2C is evaluated. As shown in FIG. 7, the capacity of this example is 2185mAh/g, 2121mAh/g, 2026mAh/g, 1751mAh/g at 0.2C, 0.5C,1C, 2C multiplying power, respectively. Compared with comparative example 4, the nano-particles are respectively improved by 182mAh/g, 275mAh/g, 318mAh/g and 247 mAh/g. This indicates that the rate performance can be improved after addition of polyethylene oxide and LiTFSI to the electrode surface.
Comparative example 5
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 2) and purchased from Ningbo Furun Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The prepared pole piece is used as a positive electrode, the Li piece is used as a negative electrode, and the electrolyte model is 3003F (commercial), so that the button battery 2032 is assembled for testing. The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, charging and discharging are carried out at 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the coulomb efficiency of the button cell under the multiplying power of 0.2C, 0.5C,1C and 2C is evaluated. As shown in fig. 8, the capacities of this embodiment at 0.2C, 0.5C,1C, and 2C magnifications are 1332mAh/g, 1175mAh/g, 1037mAh/g, and 833mAh/g, respectively.
Example 5
The electrode slurry was prepared in such a manner that m (active material), m (CMC, sodium carboxymethylcellulose), m (SBR, styrene-butadiene latex), and m (acetylene black) were 80:3:7: 10. The active material was commercially available SiOx (x ≈ 2) and purchased from Ningbo Furun Battery materials technologies, Inc. And coating the prepared slurry on a Cu foil, putting the coated pole piece into an oven at 80 ℃, and drying for 2h in an air atmosphere. And placing the pole piece for later use. Dissolving polyoxyethylene and salt in certain proportion in acetonitrile; the mass ratio of polyethylene oxide to LiTFSI was 0.6. And (3) coating the prepared mixed solution of the polyoxyethylene and the salt on the prepared pole piece by using a scraper, wherein the mass ratio of the electrode slurry to the packaging material is 1.8:1, and standing and drying at normal temperature. And cutting the dried pole piece into a wafer with the diameter of 14mm, wherein the mass of the active material is 1.5-2.5 mg.
The button cell is tested on a Land tester (Wuhanxinnuo electronic Co., Ltd.), the test temperature is 50 ℃, charging and discharging are carried out at 0.2C, 0.5C,1C and 2C until the voltage is 0.005V-1.5V, and then the coulomb efficiency of the button cell under the multiplying power of 0.2C, 0.5C,1C and 2C is evaluated. As shown in FIG. 8, the capacities of the present embodiment at 0.2C, 0.5C,1C and 2C multiplying powers are 1406mAh/g, 1342mAh/g, 1247mAh/g and 973mAh/g, respectively. Compared with comparative example 5, the nano-particles are respectively improved by 74mAh/g, 167mAh/g, 210mAh/g and 140 mAh/g. This indicates that the rate performance can be improved after addition of polyethylene oxide and LiTFSI to the electrode surface.
From the above embodiments, the present invention provides a silicon-based composite electrode, which includes a copper foil; electrode slurry coated on the upper and lower surfaces of the copper foil; the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry; the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2; the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1. According to the invention, the silicon-based composite electrode is used as the negative electrode of the lithium ion battery, so that the first coulombic efficiency of the battery can be improved; has high cycling stability.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (7)

1. A silicon-based composite electrode comprises a copper foil;
electrode slurry coated on the upper and lower surfaces of the copper foil;
the packaging material is coated on the surface of the electrode slurry and permeates into the electrode slurry;
the electrode slurry comprises an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black; the active material is selected from SiOxOr graphene coated SiOxThe value of x is 0.5-2;
the packaging material comprises polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1.
2. The silicon-based composite electrode according to claim 1, wherein the mass ratio of the active material, the sodium carboxymethyl cellulose, the styrene-butadiene latex and the acetylene black is 78-83: 2.5-3.5: 6-8: 8-12.
3. The silicon-based composite electrode of claim 1, wherein the graphene-coated SiOxThe content of the graphene in the graphene is more than 0 wt% and less than or equal to 30 wt%.
4. The silicon-based composite electrode according to claim 1, wherein the mass ratio of the active material, the sodium carboxymethyl cellulose, the styrene-butadiene latex and the acetylene black is 80:3:7: 10.
5. A method for preparing a silicon-based composite electrode according to any one of claims 1 to 4, comprising the following steps:
mixing an active material, sodium carboxymethyl cellulose, styrene-butadiene latex and acetylene black to obtain electrode slurry;
coating the electrode slurry on a copper foil, and drying to obtain an intermediate pole piece;
dissolving polyoxyethylene and lithium salt in a mass ratio of 0.5-0.8: 1 in acetonitrile to obtain a packaging material; and coating the packaging material on the surface of the middle pole piece, and drying to obtain the silicon-based composite electrode.
6. The lithium ion battery is characterized by comprising a silicon-based negative electrode, electrolyte and a positive electrode material;
the silicon-based negative electrode is the silicon-based composite electrode as defined in any one of claims 1 to 4 or the silicon-based composite electrode prepared by the preparation method as defined in claim 5.
7. The lithium ion battery of claim 6, wherein the electrolyte is LIB-3003F electrolyte.
CN202110473360.3A 2021-04-29 2021-04-29 Silicon-based composite electrode and preparation method and application thereof Pending CN113206213A (en)

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