CN116613296B - Silicon-carbon negative electrode material of lithium ion battery, and preparation method and application thereof - Google Patents

Silicon-carbon negative electrode material of lithium ion battery, and preparation method and application thereof Download PDF

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CN116613296B
CN116613296B CN202310771215.2A CN202310771215A CN116613296B CN 116613296 B CN116613296 B CN 116613296B CN 202310771215 A CN202310771215 A CN 202310771215A CN 116613296 B CN116613296 B CN 116613296B
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CN116613296A (en
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何睿
董瑞
边式
贺兴臣
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Wuhan Zhongke Advanced Material Technology Co Ltd
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    • H01M4/00—Electrodes
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    • H—ELECTRICITY
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    • 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
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    • 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
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract

The application relates to a silicon-carbon negative electrode material of a lithium ion battery, and a preparation method and application thereof. The preparation method of the silicon-carbon anode material of the lithium ion battery comprises the following steps: adding polyacrylic acid with molecular weight of 5000-500000 and lysine-heparin product into water, stirring at room temperature to obtain composite adhesive solution; sequentially adding conductive carbon black and a silicon-based material into the composite binder solution to obtain negative electrode slurry; adding a cross-linking agent into the negative electrode slurry, uniformly mixing, coating on a foil substrate, and then carrying out sectional drying under a vacuum condition to obtain the silicon-carbon negative electrode material. The lithium ion battery prepared from the silicon-carbon anode material has good cycling stability, and the maximum capacity can be kept at about 87% after 100 cycles.

Description

Silicon-carbon negative electrode material of lithium ion battery, and preparation method and application thereof
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a silicon-carbon negative electrode material of a lithium ion battery, and a preparation method and application thereof.
Background
With the popularization of electric automobiles, development of lithium ion batteries with high energy density is increasingly important. The theoretical capacity of the graphite anode material with the most widely commercialized application at present is only 372 mAh.g -1 The actual measurement capacity of the high-end graphite material reaches 365 mAh.g -1 The development requirements of high energy density lithium ion batteries cannot be further met.
Silicon has an ultra-high theoretical capacity of 4200mAh/g, exhibits excellent fast charge and reserve advantages, and is considered to be one of the most promising anode materials in high energy density lithium ion batteries. However, in the actual charge and discharge process, each silicon atom will combine 4.4 lithium atoms on average, which causes the silicon to expand in volume up to 300% in the fully lithium intercalation state, which is very easy to induce collapse of its own structure, resulting in pulverization of the electrode and irreversible consumption of the positive electrode intercalation lithium by the new stable solid electrolyte film (SEI), eventually leading to capacity dip and battery failure.
The polymer binder is one of the main components of the electrode, and can bond the active material and the conductive particles to the current collector, and is an effective means for improving the stability of the expanded negative electrode and reducing the reversible capacity loss. When the existing silicon-carbon negative electrode is manufactured, a polyacrylic acid binder is added, stirred into slurry, coated on a current collector and dried. For example, patent CN110148751a discloses a silicon-carbon negative electrode and a preparation method thereof, and the technology adopts a three-dimensional network polymer formed by condensing polyacrylic acid and sodium carboxymethyl cellulose as a binder to prepare the negative electrode, while the expansion of a silicon-carbon negative electrode active material is inhibited to a certain extent, the anchoring of the chemical bond is only limited to long-chain effect and steric hindrance to adhere to the binder, the problems of low dispersibility and insufficient binding force of the binder still exist, and the three-dimensional wrapping application after the material is introduced is suspected.
Based on the analysis, it is important to provide a preparation method of a silicon-carbon anode material with high bonding strength.
Disclosure of Invention
The embodiment of the application provides a preparation method of a silicon-carbon negative electrode material of a lithium ion battery, which aims to solve the problems of high expansion rate and low bonding strength of the existing silicon-carbon negative electrode material in the related technology.
In a first aspect, the present application provides a method for preparing a silicon-carbon negative electrode material of a lithium ion battery, including the following steps:
s101, adding polyacrylic acid with molecular weight of 5000-500000 and lysine-heparin product into water, and stirring at room temperature to obtain a composite binder solution;
s102, sequentially adding conductive carbon black and a silicon-based material into a composite binder solution to obtain negative electrode slurry;
and S103, adding a cross-linking agent into the negative electrode slurry, uniformly mixing, coating on a foil substrate, and then carrying out sectional drying under a vacuum condition to obtain the silicon-carbon negative electrode material.
In some embodiments, the lysine-heparin product is prepared by the following process: adding heparin into PBS buffer solution, stirring and dissolving to obtain heparin solution; adding carbodiimide and N-hydroxysuccinimide into PBS buffer solution, stirring and dissolving, and adding into heparin solution to obtain mixed solution; adding lysine into PBS buffer solution to obtain lysine solution; adding the lysine solution into the mixed solution, stirring, purifying, dialyzing by using a cellulose membrane, and freeze-drying to obtain a lysine-heparin product. In the above preparation process, the amino group of lysine and the carboxyl group of heparin are chemically bonded.
In some embodiments, the freeze drying process is performed with a gland type dryer, the temperature of the condensing chamber is set to-50 ℃ for 12 hours.
In some embodiments, the mass ratio of polyacrylic acid to lysine-heparin product is 80-70%: 20-30%.
In some embodiments, the cross-linking agent is selected from the group consisting of 4, 4-diaminodiphenylmethane, trimethylolpropane tris (3- (2-methylaziridinyl) propionate), diethyltetramethylimidazole, diethylenetriamine, and 1, 4-phenylenedioxazoline. The cross-linking agent has higher activity, and can react with carboxyl ring opening under the condition of room temperature to realize the cross-linking of the low molecular weight polyacrylic acid.
In some embodiments, the crosslinker is used in an amount of 0.5 to 5% by mass of the polyacrylic acid.
In some embodiments, the mass percentages of the raw materials for preparing the silicon-carbon anode material of the lithium ion battery are as follows: 5-25% of composite binder, 50-90% of silicon-based material and 5-20% of conductive carbon black.
In some embodiments, the silicon-based material is a silicon-carbon material having a silicon content of about 13% and a theoretical ratioThe capacity is about 650 mAh.g -1 。
In some embodiments, in step S103, the process of sectional drying is: drying at 15-30 deg.c for 60-300 min, drying at 60-80 deg.c for 10-20 min and final drying at 100-120 deg.c for 120-720 min. The drying process of the anode material is divided into three stages, wherein the initial stage is firstly carried out at room temperature to realize the low molecular weight polyacrylic acid post-crosslinking reaction; the anode material is heated and pre-dried in the middle stage, so that the evaporation of the solvent is ensured, and the rolling is ensured to be not stuck to a roller; and finally, the temperature is further increased to ensure complete drying, and the stage is mainly due to the fact that certain hydrophilic groups can be formed in the polymerization process of polyacrylic acid in the presence of a cross-linking agent, and terminal drying is carried out in order to ensure the water content standard of the anode material.
In some embodiments, the viscosity of the negative electrode slurry is 1300 to 3000cps; the solid content of the negative electrode slurry is 30-50%.
In some embodiments, the silicon carbon anode material has a loading of 3-8 mg/cm 2 After rolling, the thickness of the matrix material layer in the silicon-carbon anode material is 30-60 mu m.
In a second aspect, the application also provides a silicon-carbon anode material of the lithium ion battery, which is prepared by the preparation method.
In a third aspect, the application of the prepared silicon-carbon anode material in preparing lithium ion batteries is provided.
Lysine and heparin are added into small molecular weight polyacrylic acid as additives to form a composite adhesive, groups in the lysine interact with acid groups in polyacrylic acid (PAA) reversibly through hydrogen bonds to form a PAA-Lys-PAA crosslinking structure, and irreversible sliding of PAA chain segments is prevented; and the sulfonic group in heparin can realize a certain Li + Ion transport, facilitating overall electrochemical reaction transport; finally, introducing a cross-linking agent into the negative electrode slurry, and utilizing a post-cross-linking process to obtain the ultra-high molecular weight polyacrylic acid synergistic high-elasticity polymer composite adhesive through the self-cross-linking effect of the low molecular weight polyacrylic acid in the drying stage of the negative electrode material, thereby further effectively ensuring siliconThe structural integrity of the carbon cathode greatly improves the battery performance, effectively buffers the mechanical stress caused by the volume change of silicon, maintains the stability, and improves the overall cyclicity of the battery interface transfer film.
In order to ensure higher binding power, the molecular weight of the polyacrylic acid binder commonly used for the silicon-carbon negative electrode is larger (more than 400 w), and the high molecular weight can cause the problems of reduced pulping efficiency, poor overall dispersibility of the slurry and the like. In order to ensure the cohesive force of the polyacrylic acid binder, and simultaneously, the binder with low viscosity and high cohesive force is required to be displayed, so that a proper amount of crosslinking agent is added before slurry coating, in-situ crosslinking of the polyacrylic acid binder with low molecular weight can be realized in a subsequent drying process, a certain continuous linear connection structure is formed, and the cohesive strength of the silicon-carbon negative electrode material is improved. Meanwhile, a large number of hydrogen bond action points exist between the elastic additive lysine and the sulfonic acid group-containing heparin in a certain proportion under the action of physical crosslinking and the PAA unit structure, and the buffer effect can be further achieved in the silicon volume change process through reconstruction of the reversible hydrogen bonds of the PAA and the additive, so that the microcrack damage of the electrode structure is repaired, and the stable circulation of the electrode structure is maintained.
The beneficial effects that technical scheme that this application provided brought include:
(1) The cross-linking matrix of the low molecular weight polyacrylic acid serving as the binder improves the overall distribution uniformity of the conductive carbon black and the silicon carbon negative electrode in the negative electrode material, and solves the problems of poor dispersibility and high pulping cost in the preparation process of the ultra-high molecular weight polyacrylic acid binder slurry; the method ensures that the low molecular weight polyacrylic acid is subjected to in-situ crosslinking through a post-crosslinking technology to form a certain continuous linear high molecular weight connection, so that the overall bonding strength of the silicon-carbon anode material is improved;
(2) According to the method, a large number of hydrogen bond action points exist between the lysine-heparin product with a certain proportion and the polyacrylic acid unit structure under the action of physical crosslinking, and the reversible hydrogen bonds of PAA and Lys are rebuilt, so that a buffer effect can be further achieved in the silicon volume change process, and the circulation stability of the electrode structure is ensured; according to the method, the cross-linking of the ionic conduction sulfonic acid groups in the polyacrylic acid and the heparin is realized through acid-base interaction, so that excellent first-circle coulomb efficiency is obtained;
(3) The lithium ion battery prepared from the silicon-carbon anode material has good cycling stability, and the maximum capacity can be kept at about 87% after 100 cycles.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic view of the cycling stability of the lithium ion battery of example 1 of the present application.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.
The embodiment of the application provides a preparation method of a silicon-carbon negative electrode material of a lithium ion battery, which can solve the problem of high expansion rate of the existing silicon-carbon negative electrode material.
The preparation method of the lithium ion battery silicon-carbon anode material provided by the embodiment of the application comprises the following steps:
step S101, adding polyacrylic acid with molecular weight of 5000-500000 and lysine-heparin product into water, and stirring at room temperature to obtain a composite binder solution;
step S102, sequentially adding conductive carbon black and a silicon-based material into a composite binder solution to obtain negative electrode slurry;
and step S103, adding a cross-linking agent into the negative electrode slurry, uniformly mixing, coating on a foil substrate, and then carrying out sectional drying under a vacuum condition to obtain the silicon-carbon negative electrode material.
The mass percentages of the raw materials are as follows: 1.5 to 10 percent of composite binder, 70 to 90 percent of silicon-based material and 1.5 to 20 percent of conductive carbon black.
The lithium ion battery silicon-carbon anode material and the preparation method thereof provided by the application are described in detail below with reference to examples and comparative examples.
In the following examples and comparative examples, lysine-heparin product was prepared by:
(1) Adding 0.1g heparin into 100ml of LPBS buffer (pH=6.0), stirring to dissolve completely to obtain heparin solution;
(2) 0.3g of carbodiimide (EDCI) and 0.2. 0.2g N-hydroxysuccinimide (NHS) were dissolved in 10ml of bs buffer (ph=6.0), stirred until uniform, and then slowly added dropwise to a heparin solution to obtain a mixed solution;
(3) 0.08g of lysine was added to 10ml of buffer solution (ph=6.0) to obtain a lysine solution, the lysine solution was added dropwise to the mixed solution, stirred at room temperature for 9 hours, followed by purification, and dialysis twice in distilled water using a cellulose membrane, followed by drying at-50 ℃ for 12 hours to obtain a lysine-heparin product.
Example 1:
embodiment 1 provides a preparation method of a silicon-carbon anode material of a lithium ion battery, which comprises the following steps:
(1) 1.0g of PAA (mw=450,000) and 0.3g of lysine-heparin product were added to 13g of ultrapure water, and the mixture was magnetically stirred at room temperature for 24 hours to obtain a homogeneous and 10wt% mass fraction composite binder solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Uniformly mixing conductive carbon black and a composite binder solution according to a mass ratio of 80:10:10, and homogenizing for 30min at 2000r/min by adopting a double-planetary homogenizer to form uniform negative electrode slurry;
(3) Mixing 4, 4-diaminodiphenylmethane with ultrapure water according to a mass ratio of 1:1, adding 0.015g of 4, 4-diaminodiphenylmethane solution into the negative electrode slurry according to 1% of the mass of polyacrylic acid, uniformly stirring, coating the mixture on a copper foil, placing the copper foil at 25 ℃ for 2 hours with a scraper lattice number of 10-16 lattices, vacuum drying at 80 ℃ for 20 minutes, rolling the copper foil at 3-10 lattices, and heating the copper foil at 120 ℃ for 2 hours to obtain the silicon-carbon negative electrode plate.
The silicon-carbon negative electrode sheet prepared in example 1 was punched into a 12mm round sheet, and then transferred into a glove box, and assembled with a separator, a metallic lithium sheet, an electrolyte (LiPF 6 of 1mol/L, EC: DMC: dec=1:1:1, 1.0% vc) and the like into a button half cell. The results of the cyclic stability test of the button half cell are shown in fig. 1.
Example 2:
embodiment 2 provides a preparation method of a silicon-carbon anode material of a lithium ion battery, which comprises the following steps:
(1) 1.0g of PAA (mw=100,000) and 0.35g of lysine-heparin product were added to a certain amount of ultrapure water, and placed at room temperature, magnetically stirred for 24 hours, to obtain a homogeneous and 10wt% mass fraction composite binder solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Conductive carbon black, composite binder solution according to mass ratio 80: mixing uniformly at a ratio of 10:10, and homogenizing for 30min by adopting a double-planetary homogenizer at a speed of 2000r/min to form uniform cathode slurry;
(3) Mixing trimethylolpropane tri (3- (2-methyl aziridinyl) propionate) and water according to a mass ratio of 1:1, adding 0.030g of trimethylolpropane tri (3- (2-methyl aziridinyl) propionate) solution into the negative electrode slurry according to 2% of the mass of polyacrylic acid, uniformly stirring, coating the mixture on a copper foil, placing the copper foil at a temperature of between 10 and 16 grids at 25 ℃ for 2 hours, vacuum drying at 80 ℃ for 20 minutes, and heating the copper foil at 120 ℃ for 2 hours after rolling the copper foil to obtain the silicon-carbon negative electrode plate.
The silicon-carbon negative electrode sheet prepared in example 2 was punched into a 12mm round sheet, and then transferred into a glove box, and assembled with a separator, a metallic lithium sheet, an electrolyte (LiPF 6 of 1mol/L, EC: DMC: dec=1:1:1, 1.0% vc) and the like into a button half cell.
Example 3:
embodiment 3 provides a preparation method of a silicon-carbon anode material of a lithium ion battery, which comprises the following steps:
(1) 1.0g of PAA (mw=5000) and 0.3g of lysine-heparin product were added to a certain amount of ultrapure water, and the mixture was magnetically stirred at room temperature for 24 hours to obtain a homogeneous composite binder solution with a mass fraction of 10 wt%;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Uniformly mixing conductive carbon black and a composite binder solution according to a mass ratio of 85:6:9, and homogenizing for 30min at 2000r/min by adopting a double-planetary homogenizer to form uniform negative electrode slurry;
(3) And (3) mixing diethyl tetramethylimidazole and water according to a mass ratio of 1:1, adding 0.015g diethyl tetramethylimidazole solution into the negative electrode slurry according to 1% of the mass of polyacrylic acid, uniformly stirring, coating the mixture on a copper foil, placing the copper foil at a temperature of 25 ℃ for 2 hours, vacuum drying at 80 ℃ for 20 minutes, rolling the copper foil at 3-10 grids, and heating the copper foil at 120 ℃ for 2 hours to obtain the silicon-carbon negative electrode plate.
The silicon carbon negative electrode sheet of example 3 was punched into a 12mm round sheet, transferred into a glove box, and assembled with a separator, a metallic lithium sheet, an electrolyte (LiPF 6 of 1mol/L, EC: DMC: dec=1:1:1, 1.0% VC) and the like to form a button half cell.
Example 4:
embodiment 4 provides a preparation method of a silicon-carbon anode material of a lithium ion battery, which comprises the following steps:
(1) 1.0g of PAA (mw=450,000) and 0.35g of lysine-heparin product were added to a certain amount of ultrapure water, and the mixture was placed at room temperature and magnetically stirred for 24 hours to obtain a homogeneous and 10wt% mass fraction composite binder solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) GuideUniformly mixing the electric carbon black and the composite binder solution according to the mass ratio of 80:10:10, and homogenizing for 30min at 2000r/min by adopting a double-planetary homogenizer to form uniform negative electrode slurry;
(3) Mixing diethylenetriamine and water according to a mass ratio of 1:1, adding 0.0225g diethylenetriamine solution into the negative electrode slurry according to 1.5% of the mass of polyacrylic acid, uniformly stirring, coating the mixture on a copper foil, placing the mixture at 25 ℃ for 2 hours, vacuum drying at 80 ℃ for 20 minutes, and heating the mixture at 120 ℃ for 2 hours after rolling the mixture at 3-10 grids to obtain the silicon-carbon negative electrode plate.
The obtained silicon-carbon negative electrode plate is punched into a 12mm round electrode plate, and then transferred into a glove box, and assembled with a diaphragm, a metal lithium plate, electrolyte (LiPF 6 of 1mol/L, EC: DMC: DEC=1:1:1, 1.0% VC) and the like to form a button half cell.
Example 5:
embodiment 5 provides a preparation method of a silicon-carbon anode material of a lithium ion battery, which comprises the following steps:
(1) 1.0g of PAA (mw=450,000) and 0.3g of lysine-heparin product were added to a certain amount of ultrapure water, and the mixture was placed at room temperature and magnetically stirred for 24 hours to obtain a homogeneous and 10wt% mass fraction composite binder solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Uniformly mixing conductive carbon black and a composite binder solution according to a mass ratio of 75:19:6, and homogenizing for 30min at 2000r/min by adopting a double-planetary homogenizer to form uniform negative electrode slurry;
(3) 1, 4-phenylene bisoxazoline and water are mixed according to the mass ratio of 1:1, 0.0375g of 1, 4-phenylene bisoxazoline solution is added into the negative electrode slurry according to the mass ratio of 2.5 percent of polyacrylic acid, the mixture is uniformly stirred and then coated on a copper foil, the number of scraping grids is 10-16 grids, the mixture is placed at the temperature of 25 ℃ for 2 hours, then the mixture is dried at the temperature of 80 ℃ for 20 minutes in vacuum, and the mixture is heated to 120 ℃ for 2 hours after the mixture is rolled and then the mixture is dried to obtain the silicon-carbon negative electrode sheet.
And stamping the obtained silicon-carbon negative electrode plate into a 12mm round electrode plate, transferring the round electrode plate into a glove box, and assembling the round electrode plate, the diaphragm, the metal lithium plate, the electrolyte and the like into the button type half battery.
Comparative example 1:
comparative example 1 provides a method for preparing a silicon carbon anode material, comprising the following steps:
(1) 1.0g of PAA (mw=450,000) was added to a certain amount of ultrapure water, and the mixture was allowed to stand at room temperature with magnetic stirring for 24 hours to obtain a homogeneous and 10wt% polyacrylic acid solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Uniformly mixing conductive carbon black and polyacrylic acid solution according to the mass ratio of 80:10:10, and homogenizing for 30min at 2000r/min by adopting a double-planetary homogenizer to form uniform negative electrode slurry;
(3) Mixing 4, 4-diaminodiphenyl methane and water according to a mass ratio of 1:1, adding 0.015g of 4, 4-diaminodiphenyl methane solution into the negative electrode slurry according to 1% of the mass of polyacrylic acid, uniformly stirring, coating the mixture on a copper foil, placing the copper foil at a temperature of 25 ℃ for 2 hours with a scraper grid number of 10-16 grids, vacuum drying at 80 ℃ for 20 minutes, rolling the copper foil at 3-10 grids, and heating the copper foil at 120 ℃ for 2 hours to obtain the silicon-carbon negative electrode plate.
The obtained silicon-carbon negative electrode plate is punched into a 12mm round electrode plate, and then transferred into a glove box, and assembled with a diaphragm, a metal lithium plate, electrolyte (LiPF 6 of 1mol/L, EC: DMC: DEC=1:1:1, 1.0% VC) and the like to form a button half cell.
Comparative example 2:
comparative example 2 provides a method for preparing a silicon carbon anode material, comprising the following steps:
(1) 1.0g of PAA (mw=450,000) and 0.3g of lysine-heparin product were added to a certain amount of ultrapure water, and the mixture was placed at room temperature and magnetically stirred for 24 hours to obtain a homogeneous and 10wt% mass fraction composite binder solution;
(2) The silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Mixing the conductive carbon black and the compound binder solution uniformly according to the mass ratio of 80:10:10, and adopting a double-planetary refiner to mix the mixture with the mixture at a ratio of 2Homogenizing for 30min at 000r/min to form uniform anode slurry;
(3) And (3) coating the negative electrode slurry on a copper foil, placing the copper foil for 2 hours at the temperature of 25 ℃ with the number of scraping blades of 10-16 grids, vacuum drying for 20 minutes at the temperature of 80 ℃, rolling and heating to 120 ℃ for 2 hours after the rolling of 3-10 grids, and obtaining the silicon-carbon negative electrode plate.
The obtained silicon-carbon negative electrode plate is punched into a 12mm round electrode plate, and then transferred into a glove box, and assembled with a diaphragm, a metal lithium plate, electrolyte (LiPF 6 of 1mol/L, EC: DMC: DEC=1:1:1, 1.0% VC) and the like to form a button half cell.
Comparative example 3:
comparative example 3 provides a method for preparing a silicon carbon anode material, comprising the following steps:
adopting conventional negative electrode common binder CMC/SBR as binder, and adopting silicon-carbon material (model: MA-EN-AN-3D010I, silicon content about 13%, carbon content about 87%, theoretical specific capacity about 650 mAh.g) -1 ) Conductive carbon black, CMC/SBR (CMC to SBR application mass ratio of 1: 1) Uniformly mixing according to a mass ratio of 80:10:10 to form uniform negative electrode slurry; and (3) coating the negative electrode slurry on a copper foil, placing the copper foil for 2 hours at the temperature of 25 ℃ with the number of scraping blades of 10-16 grids, vacuum drying for 20 minutes at the temperature of 80 ℃, rolling and heating to 120 ℃ for 2 hours after the rolling of 3-10 grids, and obtaining the silicon-carbon negative electrode plate.
The obtained silicon-carbon negative electrode plate is punched into a 12mm round electrode plate, and then transferred into a glove box, and assembled with a diaphragm, a metal lithium plate, electrolyte (LiPF 6 of 1mol/L, EC: DMC: DEC=1:1:1, 1.0% VC) and the like to form a button half cell.
The assembled button half cells of example 1-example 5 and comparative example 1-comparative example 3 were subjected to constant current charge and discharge test on a New Wired battery tester with a voltage range of 0.01V-2.0V and a current density of 325mA-1g.
The specific detection results are shown in Table 1.
Table 1: cycling performance of button half cells of examples 1-5, comparative examples 1-3 at a current density of 325mA/g
Number of test turns Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Comparative example 2 Comparative example 3
1 635.6418 624.4667 621.2161 650.3827 631.0516 592.5973 584.1357 478.8319
2 625.1621 620.5869 604.4022 631.9686 623.6199 570.648 562.19 473.0773
3 626.8309 619.3566 592.3145 627.5883 618.6003 554.2141 547.4957 464.4485
4 620.0548 618.1699 596.6496 616.0726 612.6666 533.1838 527.2816 458.7432
5 613.6033 614.0709 586.1866 611.1971 607.5417 521.1885 508.8115 451.801
6 610.6982 605.1144 589.3711 609.1253 602.7458 509.2551 490.8809 444.0465
7 608.5159 602.5389 577.2556 604.5591 598.4387 489.672 471.7296 439.5226
21 605.8924 601.2354 560.3247 601.0406 595.1067 472.0917 456.1357 382.6984
43 600.2687 597.1611 541.5572 600.0951 587.8955 464.0189 418.0096 323.3849
62 586.5943 582.8822 523.2259 585.2923 576.329 436.2307 371.8379 302.2093
83 566.6664 556.7112 507.4413 555.2851 546.1964 430.7548 346.4606 298.7918
85 565.3809 554.5382 506.9862 551.3810 543.8157 430.4039 322.6531 297.9031
93 558.1224 543.7742 497.5602 544.4532 533.9905 424.7231 284.3005 295.7643
96 548.2505 540.0334 487.5605 542.0319 528.3713 423.1604 282.786 294.4457
97 548.3749 538.2898 486.6499 540.8850 528.888 422.5468 277.3405 294.3049
98 547.9469 535.3604 487.2072 540.138 527.6763 421.8631 276.4367 292.4387
99 546.8481 531.1539 486.1237 538.4318 526.1791 420.8019 276.2779 291.8711
100 546.0488 529.5389 479.0022 538.0944 526.1517 419.5973 274.1357 291.2823
As shown in Table 1, at a current density of 325mA/g, the capacity of the binder formed by compounding and post-crosslinking the lysine-heparin product and polyacrylic acid after 100 times is 546.0488mAh/g in the silicon-carbon negative electrode formed by the binder, while the capacity of the silicon-carbon negative electrode formed by the PAA binder which is not compounded by post-crosslinking is only 274.1357mAh/g, and the capacity of the silicon-carbon negative electrode formed by the most commonly used binder CMC/SBR is less than 300mAh/g, which indicates that the lithium ion battery prepared by the method has better cycle performance.
The peel strength was used to characterize the adhesion of the adhesive and the specific procedure was determined with reference to the GBT 2790-1995 Standard of 180 peel strength test method for Adhesives. The test equipment was a TSE101A tensile machine in which the pole piece had a peel width of 25mm and a peel displacement of 100mm. The test results are shown in Table 2.
Table 2: results of peel strength test of silicon carbon negative electrode sheets of example 1-example 5, comparative example 1-comparative example 3
Table 2 is a table of 180 ° peel strength test data for each negative electrode sheet at 25mm width. As shown in Table 2, the peel strength of the adhesive formed by compounding lysine-heparin product and PAA and post-crosslinking in the formed negative electrode plate is 2.12N/cm at maximum, while the peel strength of the negative electrode plate formed by the PAA adhesive which is not subjected to post-crosslinking compounding is only 0.92N/cm, and the strength of the silicon carbon electrode formed by the most commonly used adhesive CMC/SBR is 0.6N/cm, which indicates that the negative electrode plate obtained by the application shows better adhesive strength.
In the description of the present specification, reference to the terms "one embodiment/manner," "some embodiments/manner," "example," "a particular example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/manner or example is included in at least one embodiment/manner or example of the present application. In this specification, the schematic representations of the above terms are not necessarily for the same embodiment/manner or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/modes or examples described in this specification and the features of the various embodiments/modes or examples can be combined and combined by persons skilled in the art without contradiction.
It should be noted that in this application, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. In the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless explicitly specified otherwise.
The foregoing is merely a specific embodiment of the application to enable one skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. The preparation method of the silicon-carbon anode material of the lithium ion battery is characterized by comprising the following steps of:
s101, adding polyacrylic acid with molecular weight of 5000-500000 and lysine-heparin product into water, and stirring at room temperature to obtain a composite binder solution;
s102, sequentially adding conductive carbon black and a silicon-based material into a composite binder solution to obtain negative electrode slurry;
s103, adding a cross-linking agent into the negative electrode slurry, uniformly mixing, coating on a foil substrate, and then carrying out sectional drying under a vacuum condition to obtain a silicon-carbon negative electrode material;
wherein the lysine-heparin product is prepared by the following process: adding heparin into PBS buffer solution, stirring and dissolving to obtain heparin solution; adding carbodiimide and N-hydroxysuccinimide into PBS buffer solution, stirring and dissolving, and adding into heparin solution to obtain mixed solution; adding lysine into PBS buffer solution to obtain lysine solution; adding the lysine solution into the mixed solution, stirring, purifying, dialyzing by using a cellulose membrane, and freeze-drying to obtain a lysine-heparin product;
in step S103, the process of sectional drying is: drying at 15-30 deg.c for 60-300 min, drying at 60-80 deg.c for 10-20 min and final drying at 100-120 deg.c for 120-720 min.
2. The method for preparing the silicon-carbon anode material of the lithium ion battery according to claim 1, wherein the mass ratio of the polyacrylic acid to the lysine-heparin product is 80-70%: 20-30%.
3. The method for preparing the silicon-carbon negative electrode material of the lithium ion battery according to claim 1, wherein the cross-linking agent is selected from one or more of 4, 4-diaminodiphenylmethane, trimethylolpropane tris (3- (2-methylaziridinyl) propionate), diethyl tetramethylimidazole, diethylenetriamine and 1, 4-phenylene bisoxazoline.
4. The preparation method of the lithium ion battery silicon-carbon anode material according to claim 1, wherein the usage amount of the cross-linking agent is 0.5-5% of the mass of the polyacrylic acid.
5. The preparation method of the lithium ion battery silicon-carbon anode material according to claim 1, wherein the mass percentages of the raw materials for preparing the lithium ion battery silicon-carbon anode material are as follows: 1.5 to 10 percent of composite binder, 70 to 90 percent of silicon-based material and 1.5 to 20 percent of conductive carbon black.
6. The method for preparing a silicon-carbon negative electrode material of a lithium ion battery according to claim 1, wherein the silicon-based material is a silicon-carbon material.
7. A silicon-carbon negative electrode material of a lithium ion battery, which is characterized by being prepared by the preparation method of any one of claims 1-6.
8. Use of the silicon-carbon negative electrode material prepared by the preparation method of any one of claims 1 to 6 in the preparation of lithium ion batteries.
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