CN112457805B - Adhesive, preparation method thereof, silicon-carbon negative electrode material and lithium battery - Google Patents

Adhesive, preparation method thereof, silicon-carbon negative electrode material and lithium battery Download PDF

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CN112457805B
CN112457805B CN202011166582.2A CN202011166582A CN112457805B CN 112457805 B CN112457805 B CN 112457805B CN 202011166582 A CN202011166582 A CN 202011166582A CN 112457805 B CN112457805 B CN 112457805B
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adhesive
methoxyethoxy
ethyl ester
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宋江选
靳谧涵
虎琳琳
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Xian Jiaotong University
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J153/00—Adhesives based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
    • C09J153/005—Modified block copolymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
    • C08F293/005—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule using free radical "living" or "controlled" polymerisation, e.g. using a complexing agent
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08F8/00—Chemical modification by after-treatment
    • C08F8/12—Hydrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
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    • C08F2438/00—Living radical polymerisation
    • C08F2438/01—Atom Transfer Radical Polymerization [ATRP] or reverse ATRP
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention discloses a binding agent and a preparation method thereof, a silicon-carbon negative electrode material and a lithium battery, wherein the binding agent is a multi-block amphiphilic copolymer, organic unification of a hydrophobic polymer and a hydrophilic polymer is realized by copolymerizing polystyrene and polyacrylic acid in the binding agent and regulating and controlling the proportion of the polystyrene and the polyacrylic acid, and the prepared amphiphilic block copolymer binding agent can be uniformly dispersed and dissolved in water, so that the binding effect of a polystyrene block on carbon and the binding effect of a polyacrylic acid block on silicon are respectively exerted; the adhesive has the multifunctional characteristic that the styrene block can be bonded with silicon through hydrophobic interaction and pi-pi stacking action, the polyacrylic acid block can be bonded with silicon through hydrogen bond action, and the poly 2- (2-methoxyethoxy) ethyl ester block can promote lithium ion conduction.

Description

Adhesive, preparation method thereof, silicon-carbon negative electrode material and lithium battery
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of battery materials, and relates to a binder and a preparation method thereof, a silicon-carbon negative electrode material and a lithium battery.
[ background of the invention ]
Lithium ion batteries have been widely used in electric vehicles, 3C products, renewable energy sources, and energy storage devices of smart grids, but the energy density of current commercial lithium ion batteries has gradually failed to meet the requirement of large-scale energy storage, and further research and development of novel electrode materials with higher energy density are required.
The silicon negative electrode material has higher theoretical specific capacity and larger application potential. However, the silicon-carbon negative electrode can generate serious volume expansion in the charging and discharging processes, so that the electrode structure is damaged, the material is pulverized, and finally the battery capacity is attenuated. The silicon-carbon material combines the advantages of silicon and carbon, presents high specific capacity, ensures excellent mechanical property in the charging and discharging process, and has wide commercial prospect.
However, in terms of adhesives, there is currently little research on adhesives of silicon-carbon materials, and it is widely reported that pure silicon adhesives mostly achieve adhesion by establishing interaction with polar functional groups on the surface of pure silicon, for example, CN108417838 discloses a tetraborate ionomer adhesive that achieves adhesion by interaction between hydrocarbon groups contained in the adhesive and polar groups on the surface of silicon. Because the surface property of the silicon carbon material is different from that of pure silicon due to the introduction of carbon, the silicon surface is hydrophilic, and the carbon surface is hydrophobic, the adhesive suitable for the pure silicon material is not suitable for the silicon carbon material, so the adhesive suitable for the silicon carbon composite material is required to be further developed on the basis of the pure silicon adhesive.
[ summary of the invention ]
The present invention is directed to overcome the above disadvantages of the prior art, and provides a binder, a preparation method thereof, a silicon-carbon negative electrode material and a lithium battery, so as to solve the problem of the prior art that a binder suitable for a silicon-carbon negative electrode material is lacking.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
an adhesive, wherein the adhesive is polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid, and the molecular structural formula of the adhesive is as follows:
Figure BDA0002745993070000021
wherein: x: y: and z is 30: (50-70): (500-600), wherein x, y and z are natural numbers.
2. A method of making an adhesive comprising the steps of:
step 1, dissolving a macromolecular initiator with a styrene block and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide to form a reaction system A; removing oxygen in the reaction system A, then introducing nitrogen, adding a catalyst and a coordination agent, wherein the mixing ratio of 2- (2-methoxyethoxy) ethyl ester, the styrene block-containing macroinitiator, the catalyst and the coordination agent is (50-70): 1: (1-1.2): (1-1.2), generating a solution B after reaction; removing the copper catalyst in the solution B, precipitating in a mixed solution of ether and petroleum ether, and drying a precipitation product to constant weight to obtain a polystyrene-B-poly 2- (2-methoxyethoxy) ethyl ester diblock copolymer;
step 2, adding a polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester diblock copolymer and a tert-butyl acrylate monomer into butanone to form a reaction system C; removing oxygen in the reaction system C, then introducing nitrogen and adding a catalyst and a coordination agent, wherein the molar ratio of tert-butyl acrylate: initiator: catalyst: the mixing ratio of the complexing agent is (500-700): 1: (1-1.2): (1-1.2), reacting to generate a mixed solution D; removing the copper catalyst in the mixed solution D, precipitating in a mixed solution of methanol and water, and drying a precipitation product to constant weight to obtain a polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-poly (tert-butyl acrylate) triblock copolymer;
and 3, hydrolyzing the polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-poly tert-butyl acrylate to obtain a polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid triblock copolymer, and finishing the preparation of the adhesive.
The invention is further improved in that:
preferably, the catalyst in step 1 and step 2 is CuBr or CuCl; the complexing agent is dipyridine, pentamethyldiethylenetriamine or tris [2- (dimethylamino) ethyl ].
Preferably, in the step 1, the concentration of the 2- (2-methoxyethoxy) ethyl ester monomer in the reaction system A is 2-3 mol/L; in the step 2, the concentration of the tert-butyl acrylate monomer is 2-3 mol/L.
Preferably, in the step 1, the reaction temperature is 60-75 ℃, the reaction time is 4-6 hours, and a solution B is generated after the reaction; in the step 2, the reaction temperature is 60-75 ℃, and the reaction time is 8-12 hours.
Preferably, in step 1, the copper catalyst in the solution B is removed through a neutral alumina column; in step 2, the copper catalyst in the solution D is removed by a neutral alumina column.
Preferably, in step 3, the hydrolysis process is to dissolve polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-poly (tert-butyl acrylate) in dichloromethane to form a solution E, and mixing trifluoroacetic acid and dichloromethane to obtain a solution F. And under the ice bath condition, dropwise adding the solution F into the solution E, reacting to obtain a precipitate, dissolving the precipitate in water after reduced pressure evaporation, performing dialysis purification, and finally performing freeze drying on the dialyzed solution to obtain the polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-polyacrylic acid triblock copolymer.
Preferably, in step 3, the volume ratio of trifluoroacetic acid to dichloromethane in the solution F is 1: (1-2); and in the step 3, dropwise adding the solution F into the solution E, wherein the reaction time is more than 24 h.
The silicon-carbon negative electrode material comprises a current collector and silicon-carbon negative electrode slurry attached to the current collector, wherein the silicon-carbon negative electrode slurry comprises a silicon-carbon active material, a conductive additive and an adhesive, and the molar ratio of the silicon-carbon active material to the conductive additive to the adhesive is (60-95): (4.5-25): (0.5 to 15);
the adhesive is the adhesive.
A lithium battery comprising the silicon carbon negative electrode material of claim, the counter electrode being pure lithium.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses an adhesive, which is a multi-block amphiphilic copolymer, wherein organic unification of a hydrophobic polymer and a hydrophilic polymer is realized by copolymerizing polystyrene and polyacrylic acid and regulating and controlling the proportion of the polystyrene and the polyacrylic acid in the adhesive, and the prepared amphiphilic block copolymer adhesive can be uniformly dispersed and dissolved in water, so that the adhesion of a polystyrene block to carbon and the adhesion of a polyacrylic acid block to silicon are respectively exerted; the adhesive has the characteristic of multiple functions, the polystyrene block can be adhered with carbon through hydrophobic interaction and pi-pi stacking action, the polyacrylic acid block can be adhered with silicon through hydrogen bond action, the poly 2- (2-methoxyethoxy) ethyl ester block can promote lithium ion conduction, the impedance of a battery is reduced, the mechanical property of a polymer can be regulated and controlled, and the processability of a pole piece is improved. The adhesive realizes effective adhesion to the silicon-carbon cathode, and effectively improves the cycling stability of the silicon-carbon cathode. Meanwhile, the adhesive is water-soluble and environment-friendly.
The invention also discloses a preparation method of the adhesive, and in the preparation process, the adhesive is prepared by a three-step method, firstly PS-b-P (EO)2The preparation method comprises the following steps of preparing a triblock copolymer on the basis of a diblock copolymer, finally preparing a polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-polyacrylic acid) triblock copolymer through hydrolysis, wherein the whole preparation process adopts atom transfer living radical polymerization, the reaction process is easy to control, the preparation of the multi-block amphiphilic copolymer can be realized, and the polymer is endowed with the multifunctionality as an adhesive. Pure polystyrene can interact with carbon with a hydrophobic surface, but is insoluble in water and cannot be used as an aqueous binder. In the invention, organic unification of hydrophobic polymer and hydrophilic polymer is realized by copolymerizing polystyrene and polyacrylic acid and regulating and controlling the proportion of the polystyrene and the polyacrylic acid, and the prepared amphiphilic block copolymer adhesive can be uniformly dispersed and dissolved in water, thereby respectively exerting the adhesive action of polystyrene block to carbon and the adhesive action of polyacrylic acid block to silicon
The invention also discloses a silicon-carbon negative electrode material which comprises the binder, and the silicon-carbon negative electrode material shows good binding force when being applied to the silicon-carbon negative electrode, and the silicon-carbon negative electrode shows good electrochemical stability.
The invention also discloses a lithium battery which comprises the silicon-carbon negative electrode material, and the whole battery has good electrochemical stability in the application process.
[ description of the drawings ]
FIG. 1 is an infrared spectrum of a PSEA triblock polymer made according to example 3 of the present invention.
Fig. 2 is a graph comparing the peel strength of a silicon carbon negative electrode tab using the binder a3 of example 3 and the binder B1 of comparative example 1.
Fig. 3 is a graph comparing the cycle performance of a silicon carbon anode cell employing binder a3 in example 3 and binder B1 in comparative example 1.
[ detailed description ] embodiments
The invention is described in further detail below with reference to the accompanying drawings:
in the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention; the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; furthermore, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly and encompass, for example, both fixed and removable connections; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The invention discloses a binding agent for a silicon-carbon cathode material of a lithium ion battery and a preparation method thereof, wherein the binding agent polymer is polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-polyacrylic acid (PS-b-P (EO))2-b-PAA), a triblock copolymer (PSEA for short), in which b is the abbreviation of block, indicating a block copolymer. The adhesive is prepared by atom transfer living radical polymerization. The adhesive is water-soluble and environment-friendly, a polystyrene block can bond carbon through hydrophobic interaction and pi-pi stacking action, a poly (2-methoxyethoxy) ethyl ester) block can promote lithium ion conduction, and a polyacrylic acid block can bond silicon through hydrogen bond action. Three blocks have synergistic effect to ensure the silicon-carbon cathodeThe structural integrity in the circulation process improves the circulation stability of the lithium ion battery. The molecular structural formula of the compound is as follows:
Figure BDA0002745993070000061
wherein, the stoichiometric ratio of the polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid is styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid x y z 30: (50-70): (500-600).
The preparation method of the device is a polymerization method, is an atom transfer living radical polymerization method, and comprises the following steps:
step 1, polystyrene-b-Poly-2- (2-methoxyethoxy) ethyl ester diblock copolymer (PS-b-P (EO))2) The synthesis of (2): dissolving a polystyrene macroinitiator with a structural formula shown in a chemical formula (2) and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide to form a reaction system A, wherein the concentration of the 2- (2-methoxyethoxy) ethyl ester monomer is 2-3 mol/L; freezing with liquid nitrogen, extracting gas, and thawing for three times to remove oxygen, introducing nitrogen gas and adding catalyst and complexing agent, wherein the catalyst is CuBr or CuCl, and the complexing agent is bipyridine (bpy), Pentamethyldiethylenetriamine (PMTEDA) or tris [2- (dimethylamino) ethyl ] ethyl](ME6TREN); on a molar basis, 2- (2-methoxyethoxy) ethyl ester: initiator: catalyst: a complexing agent (50-70): 1: (1-1.2): (1 to 1.2) in which the initiator is 1, and represents the above-mentioned polymer containing 30 styrene groups, and the following examples represent the same; and (3) reacting at the temperature of 60-75 ℃ for 4-6 hours, and then quenching the reaction by using liquid nitrogen to enable the reaction to be completed quickly, so as to obtain a mixed solution B. Removing copper catalyst from the reacted mixed solution B by passing through a neutral alumina column, dripping the solution B into diethyl ether/petroleum ether mixed solution with ten times of volume to obtain precipitate, dissolving the precipitate in dichloromethane (dissolving), and dripping the solution into diethyl ether/petroleum ether mixed solution with ten times of volume to obtain the final productAfter precipitation, the above process was repeated 2 times, wherein the volume ratio of ethyl ether to petroleum ether was diethyl ether: petroleum ether (5-7): (3-5). Finally, the precipitated product is dried to constant weight at 40 ℃ to obtain PS-b-P (EO)2A diblock copolymer.
Figure BDA0002745993070000071
(2) Polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-poly (tert-butyl acrylate) triblock copolymer (PS-b-P (EO))2-synthesis of b-PtBA): the PS-b-P (EO) in the step (1)2The two-block copolymer is used as an initiator and dissolved in butanone together with a tert-butyl acrylate monomer to form a reaction system C, wherein the concentration of the tert-butyl acrylate monomer is 2-3 mol/L; the reaction system C was repeated three times with liquid nitrogen freeze-pump-thaw to remove oxygen, then charged with nitrogen and added with catalyst and complexing agent, in molar terms, tert-butyl acrylate: initiator: catalyst: (ii) a complexing agent of (500-700): 1: (1-1.2): (1-1.2) the initiator in the proportion is 1, and represents PS-b-P (EO) containing 30 styrene and 50-70 2- (2-methoxyethoxy) ethyl esters2Diblock copolymers, the following examples represent the same; reacting for 8-12 hours at 60-75 ℃ to ensure that tert-butyl acrylate can be copolymerized and blocked in PS-b-PEO2Then, the reaction was quenched with liquid nitrogen to give a mixed solution D. The reacted mixed solution D was passed through a neutral alumina column to remove the copper catalyst. Dropwise adding the solution B into a mixed solution of methanol and water with ten times of volume to obtain a precipitate, dissolving the precipitate in dichloromethane (dissolving), dropwise adding the solution into a mixed solution of methanol and water with ten times of volume to obtain a precipitate, and repeating the process for 2 times, wherein the volume ratio of methanol to water is methanol: water (3-5): (5-7). Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
The catalyst used in the step is preferably one of CuBr or CuCl, and the complexing agent is bipyridine (bpy) and Pentamethyldiethylenetriamine (PM)TEDA) or tris [2- (dimethylamino) ethyl](ME6TREN).
(3) Polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid triblock copolymer (PS-b-P (EO))2-b-PAA) synthesis: the PS-b-P (EO) in (2)2-b-PtBA triblock polymer dissolved in dichloromethane as solution E, and excess trifluoroacetic acid mixed with dichloromethane as solution F, wherein the volume ratio of trifluoroacetic acid to dichloromethane is 1: (1-2), slowly dripping the solution F into the solution E in an ice water bath to ensure the safety and controllability of the reaction, and reacting for more than 24 hours at room temperature to ensure the reaction to be more complete, wherein the solution is PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Removing excessive dichloromethane and trifluoroacetic acid by evaporation under reduced pressure, dissolving the precipitate in deionized water for dialysis purification, and freeze drying the dialyzed solution to obtain PS-b-P (EO)2-b-PAA triblock copolymer.
According to the invention, the PSEA triblock copolymer is prepared through atom transfer active radical polymerization, the reaction process is easy to control, the preparation of the multi-block copolymer can be realized, the polymer is endowed with the characteristic of multiple functions, the polystyrene block can be bonded with silicon through hydrophobic interaction and pi-pi stacking action, the polyacrylic acid block can be bonded with silicon through hydrogen bond action, and the poly 2- (2-methoxyethoxy) ethyl ester block can promote lithium ion conduction.
Based on the above functions, when the binder is applied to a silicon-carbon negative electrode, the binder can show better binding force to an electrode material and can improve the cycle stability of a battery.
The lithium ion battery silicon-carbon negative electrode comprises a current collector and silicon-carbon negative electrode slurry attached to the current collector; the silicon-carbon negative electrode slurry comprises a silicon-carbon active material, a conductive additive and a binder, and the mass ratio of the silicon-carbon negative electrode active material to the conductive additive is as follows: conductive additive: (ii) a binder (60-95): (4.5-25): (0.5 to 15); the silicon-carbon negative electrode active material comprises the following components in percentage by mass: carbon 2: 3, 1: 4 and 1: 32 kinds of the raw materials; the conductive additive comprises Super P, acetylene black and Ketjen black; the adhesive is the above-described PSEA triblock copolymer adhesive.
The adhesive can be used for preparing a silicon-carbon cathode of a lithium ion battery and the lithium ion battery containing the silicon-carbon cathode, and comprises the following steps:
(1) the preparation method comprises the following steps of (60-95): (4.5-25): (0.5-15), and uniformly dispersing the silicon carbide anode slurry in deionized water by ball milling to obtain uniformly mixed silicon carbide anode slurry.
(2) And (3) uniformly coating the slurry in the step (1) on a copper foil with the thickness of 12 microns by using an automatic coating machine, wherein the coating thickness is 120 microns, and then placing the copper foil in a vacuum drying oven to dry and remove the solvent. And cutting the silicon-carbon negative electrode plate into a silicon-carbon negative electrode plate with the diameter of 12 mm after drying.
(3) And (3) transferring the electrode plates prepared in the step (2) into a glove box filled with argon gas, and assembling into a 2032 button half cell. A pure lithium sheet was used as the counter electrode and a Celgard2325 polypropylene-polyethylene-polypropylene (PP-PE-PP) membrane was used as the separator. The electrolyte solution used was a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1: 1) containing 1M lithium hexafluorophosphate (LiPF6), and 10% volume fraction fluoroethylene carbonate (FEC) was added.
(4) And (3) standing the button cell assembled in the step (3) for 5 hours, and then cycling at a rate of 0.1C for one week in a voltage range of 0.01-2.00V, and then performing charge-discharge cycling at a rate of 0.3C. Wherein 1C is 950 mAh/g.
Example 1
(1) Dissolving 1.03g of polystyrene macroinitiator and 3g of 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide, freezing, pumping and thawing the reaction system by using liquid nitrogen for three times to remove oxygen, then introducing nitrogen and adding 0.05g of CuBr and 0.06g of PMDETA, wherein the molar ratio is 2- (2-methoxyethoxy) ethyl ester monomer: polystyrene macroinitiator: PMDETA: CuBr 50: 1: 1: 1, the concentration of the monomer is 2.5mol/L, and the reaction is quenched with liquid nitrogen after reacting for 4 hours at 60 ℃. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in ten volumes of a mixed solution of diethyl ether/petroleum ether (volume ratio: 1/1). Finally, the product of the precipitationDrying the extract at 40 deg.C to constant weight to obtain PS-b-P (EO)2A diblock copolymer.
(2) Collecting 0.913g of PS-b-P (EO) prepared in (1)2The diblock copolymer as initiator was dissolved in butanone along with 5g of t-butyl acrylate monomer (tBA), the reaction system was repeated three times with liquid nitrogen freeze-pump-thaw to remove oxygen, then nitrogen was charged and 0.011g of CuBr and 0.016g of PMDETA were added, the molar ratio was tBA: PS-b-P (EO)2: PMDETA: CuBr 500: 1: 1: 1, the concentration of the monomer is 2.5 mol/L; after 8 hours at 70 ℃ the reaction was quenched with liquid nitrogen. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in a ten-fold volume of a methanol/water (volume ratio: 1/1) mixed solution. Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
(3) Taking PS-b-P (EO) in (2)2-B-PtBA triblock is dissolved in dichloromethane to serve as a solution A, excess trifluoroacetic acid is mixed with dichloromethane to serve as a solution B, and then the solution B is slowly dripped into the solution A under the ice water bath. After 3 days at room temperature, PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Removing excessive dichloromethane and trifluoroacetic acid by rotary evaporation, dissolving precipitate in deionized water, dialyzing, purifying, and freeze drying to obtain PS-b-P (EO)2-b-PAA triblock copolymer as binder a1, with the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 50: 500.
preparing a silicon-carbon cathode of the lithium ion battery by using a binder A1 according to the method and assembling the silicon-carbon cathode into a lithium ion battery for testing performance, wherein the silicon-carbon cathode material, the conductive additive and the binder are mixed according to a mass ratio of 80: 10: 10, and the conductive additive is Super P.
Example 2
The preparation, reaction conditions and purification of the PSEA triblock copolymer were the same as in example 1, but the charge ratios were different, the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 50: 600 as adhesive a 2.
The adhesive A2 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Example 3
The preparation, reaction conditions and purification of the PSEA triblock copolymer were the same as in example 1, but the charge ratios were different, the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 60: 500 as adhesive a 3; FIG. 1 is an infrared spectrum of the PSEA triblock copolymer prepared in this example, from which it can be seen that 2923cm is in the spectrum of PS-1，2849cm-1The absorption peak at (A) corresponds to-CH2Antisymmetric stretching, symmetric stretching vibration of 1600cm-1，1580cm-1，1500cm-1，1450cm-1The absorption band at (b) corresponds to the ring vibration of the benzene ring;
diblock polymer PS-b-P (EO)2Has a spectrum of 1730cm-1The new absorption peak appeared nearby corresponds to the stretching vibration of-C ═ O, and is 1246cm-1，1105cm-1In the position corresponding to-C-O-C-antisymmetric stretching vibration of 1023cm-1Symmetric stretching vibration corresponding to-C-O-C-, proving PS-b-P (EO)2Successful synthesis of the compound;
triblock Polymer PS-b-P (EO)2-b-PtBA at 1366cm-1The new absorption peak appearing nearby corresponds to-CH3Symmetric stretching vibration, evidence of PS-b-P (EO)2Successful synthesis of b-PtBA;
hydrolyzed PS-b-P (EO)2The spectrum of the-b-PAA shows 3300-2500 cm-1Broad absorption peaks, corresponding to stretching vibrations of O-H and carboxyl groups, demonstrate successful hydrolysis of tert-butyl acrylate, i.e., PS-b-P (EO)2Successful synthesis of b-PAA.
The adhesive A3 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Example 4
The preparation, reaction conditions and purification of the PSEA triblock copolymer were the same as in example 1, but the charge ratios were different, the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 60: 600 as adhesive a 4.
The adhesive A4 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Example 5
The preparation, reaction conditions and purification of the PSEA triblock copolymer were the same as in example 1, but the charge ratios were different, the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 70: 500 as adhesive a 5.
The adhesive A5 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Example 6
The preparation, reaction conditions and purification of the PSEA triblock copolymer were the same as in example 1, but the charge ratios were different, the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 70: 600 as adhesive a 6.
The adhesive A6 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Comparative example 1
As per sodium hydroxy cellulose (CMC): styrene Butadiene Rubber (SBR) ═ 2: 3 to prepare an aqueous solution as a binder B1.
The adhesive B1 is used for preparing the silicon-carbon cathode of the lithium ion battery according to the method and assembling the silicon-carbon cathode into the lithium ion battery for testing performance.
Fig. 2 shows the results of the peel performance test of the binder a3 prepared in example 3 and comparative example 1, and the average peel strength of the binder of the present invention is 150N/m or more, which is higher than that of comparative example 1(100N/m), demonstrating that the binder has good adhesion to a silicon carbon anode.
Table 1 shows the charge-discharge cycle test results of lithium ion batteries manufactured by using silicon-carbon negative electrodes in each example of the present invention and comparative example:
TABLE 1
Numbering First week efficiency (%) Capacity maintenance Rate (%) after 200 weeks
Example 1 87.9 85.0
Example 2 87.6 85.2
Example 3 88.1 86.5
Example 4 87.5 86.2
Example 5 87.8 88.8
Example 6 87.2 87.9
Comparative example 1 84.6 7.7
From the results in table 1, referring to fig. 3, the first-cycle coulombic efficiencies of the silicon-carbon positive electrode binder provided by the present invention are all 87% or more, and the capacity retention rates after 200-cycle cycles are all 85% or more, but the first-cycle efficiencies of the comparative binders are about 84%, and the capacity retention rates after 200-cycle cycles are only 7.7%. Therefore, the adhesive provided by the invention obviously improves the cycle stability of the silicon-carbon negative electrode material.
Example 7
(1) Dissolving polystyrene macroinitiator and 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide, freezing, extracting and thawing the reaction system by liquid nitrogen for three times to remove oxygen, introducing nitrogen, adding CuCl and bpy, and adding the molar ratioIs 2- (2-methoxyethoxy) ethyl ester monomer: polystyrene macroinitiator: bpy: CuCl 50: 1: 1.1: 1.1, the concentration of the monomer is 2.8mol/L, and the reaction is quenched with liquid nitrogen after reacting for 4 hours at 75 ℃. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in ten volumes of a mixed solution of diethyl ether/petroleum ether (volume ratio: 1/1). Finally, the precipitated product is dried at 40 ℃ to constant weight to give PS-b-P (EO)2A diblock copolymer.
(2) Taking the PS-b-P (EO) prepared in the step (1)2The diblock copolymer as initiator and tert-butyl acrylate monomer (tBA) were dissolved in butanone together, the reaction system was repeated three times with liquid nitrogen freeze-pump-thaw to remove oxygen, then nitrogen was charged and CuCl and bpy were added in a molar ratio of tBA: PS-b-P (EO)2: bpy: CuCl 600: 1: 1.1: 1.1, the concentration of the monomer is 2.8 mol/L; after 9 hours at 75 ℃ the reaction was quenched with liquid nitrogen. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in a ten-fold volume of a methanol/water (volume ratio: 1/1) mixed solution. Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
(3) Taking PS-b-P (EO) in (2)2-B-PtBA triblock is dissolved in dichloromethane to serve as a solution A, excess trifluoroacetic acid is mixed with dichloromethane to serve as a solution B, and then the solution B is slowly dripped into the solution A under the ice water bath. After 3 days at room temperature, PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Removing excessive dichloromethane and trifluoroacetic acid by rotary evaporation, dissolving precipitate in deionized water, dialyzing, purifying, and freeze drying to obtain PS-b-P (EO)2-b-PAA triblock copolymer as binder a7, with the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 50: 600.
preparing a silicon-carbon cathode of the lithium ion battery by using a binder A7 according to the method and assembling the silicon-carbon cathode into a lithium ion battery for testing performance, wherein the silicon-carbon cathode material, the conductive additive and the binder are mixed according to a mass ratio of 95: 4.5: 0.5 mixing.
Example 8
(1) Dissolving a polystyrene macroinitiator and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide, carrying out freezing-air extraction-unfreezing on a reaction system by using liquid nitrogen for three times to remove oxygen, then introducing nitrogen, adding CuBr and PMDETA, and carrying out reaction according to the molar ratio of the 2- (2-methoxyethoxy) ethyl ester monomer: polystyrene macroinitiator: PMDETA: CuBr 60: 1: 1: 1, the concentration of the monomer is 2mol/L, and the reaction is quenched by liquid nitrogen after reacting for 4 hours at 65 ℃. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in ten volumes of a mixed solution of diethyl ether/petroleum ether (volume ratio: 1/1). Finally, the precipitated product is dried at 40 ℃ to constant weight to give PS-b-P (EO)2A diblock copolymer.
(2) Taking the PS-b-P (EO) prepared in the step (1)2The diblock copolymer as an initiator and tert-butyl acrylate monomer (tBA) are dissolved in butanone together, the reaction system is frozen by liquid nitrogen, pumped and unfrozen for three times to remove oxygen, then nitrogen is filled, CuBr and PMDETA are added, and the molar ratio is tBA: PS-b-P (EO)2: PMDETA: CuBr 600: 1: 1: 1, the concentration of the monomer is 2 mol/L; after reaction for 12 hours at 65 ℃ the reaction was quenched with liquid nitrogen. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in a ten-fold volume of a methanol/water (volume ratio: 1/1) mixed solution. Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
(3) Taking PS-b-P (EO) in (2)2Dissolving the-B-PtBA triblock copolymer in dichloromethane to obtain a solution A, mixing excessive trifluoroacetic acid with dichloromethane to obtain a solution B, and slowly dropwise adding the solution B into the solution A in an ice-water bath. After 3 days at room temperature, PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Excess dichloromethane and trifluoroacetic acid were removed by rotary evaporation, the precipitate was then dissolved in deionized water and the solution was evaporatedPurifying by dialysis, and freeze drying the dialyzed solution to obtain PS-b-P (EO)2-b-PAA triblock copolymer as binder A8, with the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 60: 600.
preparing a silicon-carbon cathode of the lithium ion battery by using a binder A8 according to the method, assembling the silicon-carbon cathode into a lithium ion battery to test performance, wherein the mass ratio of the silicon-carbon cathode material to the conductive additive to the binder is 70: 20: 10, and mixing.
Example 9
(1) Dissolving a polystyrene macroinitiator and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide, carrying out freezing-air extraction-unfreezing on a reaction system by using liquid nitrogen for three times to remove oxygen, then introducing nitrogen, adding CuCl and bpy, and adding the 2- (2-methoxyethoxy) ethyl ester monomer according to the molar ratio: polystyrene macroinitiator: bpy: CuCl 70: 1: 1.1: 1.1, the concentration of the monomer is 2.6mol/L, and the reaction is quenched with liquid nitrogen after 5 hours at 70 ℃. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in ten volumes of a mixed solution of diethyl ether/petroleum ether (volume ratio: 1/1). Finally, the precipitated product is dried at 40 ℃ to constant weight to give PS-b-P (EO)2A diblock copolymer.
(2) Taking the PS-b-P (EO) prepared in the step (1)2The diblock copolymer as initiator and tert-butyl acrylate monomer (tBA) were dissolved in butanone together, the reaction system was repeated three times with liquid nitrogen freeze-pump-thaw to remove oxygen, then nitrogen was charged and CuCl and bpy were added in a molar ratio of tBA: PS-b-P (EO)2: bpy: CuCl 500: 1: 1.1: 1.1, the concentration of the monomer is 2.6 mol/L; after 10 hours at 70 ℃ the reaction was quenched with liquid nitrogen. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in a ten-fold volume of a methanol/water (volume ratio: 1/1) mixed solution. Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
(3) Taking PS-b-P (EO) in (2)2Dissolving the-B-PtBA triblock copolymer in dichloromethane to obtain a solution A, mixing excessive trifluoroacetic acid with dichloromethane to obtain a solution B, and slowly dropwise adding the solution B into the solution A in an ice-water bath. After 3 days at room temperature, PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Removing excessive dichloromethane and trifluoroacetic acid by rotary evaporation, dissolving precipitate in deionized water, dialyzing, purifying, and freeze drying to obtain PS-b-P (EO)2-b-PAA triblock copolymer as binder a9, with the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 70: 500.
preparing a silicon-carbon cathode of the lithium ion battery by using a binder A9 according to the method, assembling the silicon-carbon cathode into a lithium ion battery to test performance, wherein the silicon-carbon cathode material, the conductive additive and the binder are mixed according to the mass ratio of 75: 15: 10, and mixing.
Example 10
(1) Dissolving a polystyrene macroinitiator and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide, carrying out freezing-air extraction-unfreezing on a reaction system by using liquid nitrogen for three times to remove oxygen, then introducing nitrogen, adding CuCl and bpy, and adding the 2- (2-methoxyethoxy) ethyl ester monomer according to the molar ratio: polystyrene macroinitiator: bpy: CuCl 70: 1: 1.2: 1.2, the concentration of the monomer is 2.3mol/L, and the reaction is quenched by liquid nitrogen after reacting for 6 hours at 70 ℃. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in ten volumes of a mixed solution of diethyl ether/petroleum ether (volume ratio: 1/1). Finally, the precipitated product is dried at 40 ℃ to constant weight to give PS-b-P (EO)2A diblock copolymer.
(2) Taking the PS-b-P (EO) prepared in the step (1)2The diblock copolymer as initiator and tert-butyl acrylate monomer (tBA) were dissolved in butanone together, the reaction system was repeated three times with liquid nitrogen freeze-pump-thaw to remove oxygen, then nitrogen was charged and CuCl and bpy were added in a molar ratio of tBA: PS-b-P (EO)2: bpy: CuCl 700: 1: 1.2: 1.2, the concentration of the monomer is 2.3 mol-L; after 11 hours at 70 ℃ the reaction was quenched with liquid nitrogen. The reacted mixed solution was passed through a neutral alumina column to remove the copper catalyst. The solution was then precipitated 3 times in a ten-fold volume of a methanol/water (volume ratio: 1/1) mixed solution. Finally, the precipitated product is dried at 60 ℃ to constant weight to give PS-b-P (EO)2-b-PtBA triblock copolymers.
(3) Taking PS-b-P (EO) in (2)2Dissolving the-B-PtBA triblock copolymer in dichloromethane to obtain a solution A, mixing excessive trifluoroacetic acid with dichloromethane to obtain a solution B, and slowly dropwise adding the solution B into the solution A in an ice-water bath. After 3 days at room temperature, PS-b-P (EO)2-b-PAA is precipitated from the solution as a hydrolysate. Removing excessive dichloromethane and trifluoroacetic acid by rotary evaporation, dissolving precipitate in deionized water, dialyzing, purifying, and freeze drying to obtain PS-b-P (EO)2-b-PAA triblock copolymer as binder a10, with the stoichiometric ratio of the three blocks being styrene: 2- (2-methoxyethoxy) ethyl ester: acrylic acid 30: 70: 700.
preparing a silicon-carbon cathode of the lithium ion battery by using a binder A10 according to the method and assembling the silicon-carbon cathode into a lithium ion battery for testing performance, wherein the silicon-carbon cathode material, the conductive additive and the binder are mixed according to the mass ratio of 85: 10: and 5, mixing.
The invention provides a silicon-carbon negative electrode material adhesive for a lithium ion battery and a preparation method thereof. A series of polystyrene-2-poly (2-methoxyethoxy) ethyl ester-polyacrylic acid triblock copolymers with different stoichiometric ratios are prepared by atom transfer radical polymerization with better controllability. The adhesive has the characteristics of multiple functions, wherein the polystyrene block can be adhered with carbon through hydrophobic interaction and pi-pi stacking action, the polyacrylic acid block can be adhered with silicon through hydrogen bond action, and the poly 2- (2-methoxyethoxy) ethyl ester block can promote lithium ion conduction. When applied in a silicon carbon negative electrode, the silicon carbon negative electrode shows good adhesive force and electrochemical stability. Finally, the adhesive is water-soluble, green and environment-friendly, the structure of the adhesive is easy to regulate and control, and the performance requirements of different silicon-carbon materials can be met.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. The adhesive is characterized by being polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid, and the molecular structural formula of the adhesive is as follows:
Figure FDA0002745993060000011
wherein: x: y: and z is 30: (50-70): (500-600), wherein x, y and z are natural numbers.
2. A method of preparing an adhesive, comprising the steps of:
step 1, dissolving a macromolecular initiator with a styrene block and a 2- (2-methoxyethoxy) ethyl ester monomer in N, N-dimethylformamide to form a reaction system A; removing oxygen in the reaction system A, then introducing nitrogen, adding a catalyst and a coordination agent, wherein the mixing ratio of 2- (2-methoxyethoxy) ethyl ester, the polystyrene block macromolecule initiator, the catalyst and the coordination agent is (50-70): 1: (1-1.2): (1-1.2), generating a solution B after reaction; removing the copper catalyst in the solution B, precipitating in a mixed solution of ether and petroleum ether, and drying a precipitation product to constant weight to obtain a polystyrene-B-poly 2- (2-methoxyethoxy) ethyl ester diblock copolymer;
step 2, adding a polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester diblock copolymer and a tert-butyl acrylate monomer into butanone to form a reaction system C; removing oxygen in the reaction system C, then introducing nitrogen and adding a catalyst and a coordination agent, wherein the molar ratio of tert-butyl acrylate: initiator: catalyst: the mixing ratio of the complexing agent is (500-700): 1: (1-1.2): (1-1.2), reacting to generate a mixed solution D; removing the copper catalyst in the mixed solution D, precipitating in a mixed solution of methanol and water, and drying a precipitation product to constant weight to obtain a polystyrene-b-poly (2-methoxyethoxy) ethyl ester-b-poly (tert-butyl acrylate) triblock copolymer;
and 3, hydrolyzing the polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-poly tert-butyl acrylate to obtain a polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid triblock copolymer, and finishing the preparation of the adhesive.
3. The method for preparing an adhesive according to claim 2, wherein the catalyst in step 1 and the catalyst in step 2 are both CuBr or CuCl; the complexing agent is dipyridine, pentamethyldiethylenetriamine or tris [2- (dimethylamino) ethyl ].
4. The method for preparing the adhesive according to claim 2, wherein in the step 1, the concentration of the 2- (2-methoxyethoxy) ethyl ester monomer in the reaction system A is 2-3 mol/L; in the step 2, the concentration of the tert-butyl acrylate monomer is 2-3 mol/L.
5. The method for preparing the adhesive according to claim 2, wherein in the step 1, the reaction temperature is 60-75 ℃, the reaction time is 4-6 hours, and a solution B is generated after the reaction; in the step 2, the reaction temperature is 60-75 ℃, and the reaction time is 8-12 hours.
6. The method of claim 2, wherein in step 1, the copper catalyst in the solution B is removed by a neutral alumina column; in step 2, the copper catalyst in the solution D is removed by a neutral alumina column.
7. The method for preparing an adhesive according to claim 2, wherein in the step 3, the hydrolysis process comprises dissolving polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-poly (tert-butyl acrylate) in dichloromethane to form a solution E, mixing trifluoroacetic acid and dichloromethane to form a solution F, dropwise adding the solution F into the solution E under an ice bath condition, reacting to obtain a precipitate, evaporating the precipitate under reduced pressure, dissolving the precipitate in water, dialyzing and purifying, and finally freeze-drying the dialyzed solution to obtain the polystyrene-b-poly 2- (2-methoxyethoxy) ethyl ester-b-polyacrylic acid triblock copolymer.
8. The method for preparing an adhesive according to claim 6, wherein in the step 3, the volume ratio of trifluoroacetic acid to dichloromethane in the solution F is 1: (1-2); and in the step 3, dropwise adding the solution F into the solution E, wherein the reaction time is more than 24 h.
9. The silicon-carbon negative electrode material is characterized by comprising a current collector and silicon-carbon negative electrode slurry attached to the current collector, wherein the silicon-carbon negative electrode slurry comprises a silicon-carbon active material, a conductive additive and an adhesive, and the molar ratio of the silicon-carbon active material to the conductive additive to the adhesive is (60-95): (4.5-25): (0.5 to 15);
the adhesive is the adhesive of claim 1.
10. A lithium battery comprising the silicon-carbon negative electrode material of claim 9, wherein the counter electrode is pure lithium.
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