CN112382756B - Cathode binder material with block structure side chain and preparation method thereof - Google Patents
Cathode binder material with block structure side chain and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the field of lithium ion battery materials, in particular to a negative electrode binder material with a block structure side chain, which is a polymer solution, wherein a polymer has a block structure side chain, and a preparation method thereof, and the preparation method comprises the following steps: (1) dissolving the modified water-soluble polymer in a solvent, and reacting the modified water-soluble polymer with an alkenyl monomer containing a polar group for 1-24 hours under the action of an initiator; (2) continuously adding an alkenyl monomer containing a polar group into the system, and continuously reacting for 1-24 h; (3) and adjusting the pH value of the polymer aqueous solution to obtain the novel negative electrode binder material. The side chain of the invention is a block structure, one end of the side chain contains a polar group, which enhances the bonding effect with a current collector and an active substance, and the other end of the side chain selects a flexible polymer to buffer the volume expansion of the active substance; the polar functional group is positioned on the outer side of the side chain, so that the adhesive effect is strong, the utilization rate of the group is high, the circulation stability is good, and the service life is long; and RAFT group modification is adopted, so that the molecular design capability is strong.
Description
Technical Field
The invention relates to the field of lithium ion battery materials, in particular to a negative electrode binder material with a block structure side chain and a preparation method thereof.
Background
With the continuous development of lithium ion batteries, high energy density lithium ion power batteries are the development direction in the future. Graphite is commonly used as a negative electrode material in commercial lithium ion batteries nowadays. The theoretical specific capacity of the graphite material is only 372mAh/g, and in comparison, the theoretical specific capacity of the pure silicon material is up to 4200mAh/g, so that the silicon-based material is expected to become a next-generation commercial negative electrode material. However, the silicon material has huge volume change along with the intercalation and deintercalation of lithium ions in the charging and discharging processes, which causes the crushing and pulverization of active particles, leads to the rapid attenuation of electrode capacity, and seriously affects the cycle performance of the battery. Therefore, it is important to develop an efficient binder for buffering the volume effect of the silicon material to realize the cycling stability of the silicon-based negative electrode.
At present, CMC and SBR are the most commonly used aqueous binders in the field of lithium ion batteries. When SBR is used as a binder, CMC must be added. CMC is used as a thickening agent to ensure the stability of slurry, but the viscosity of the CMC is poor, the bonding effect with silicon materials is weak, the problem of expansion of the silicon materials is difficult to bear in the charging and discharging processes, the bonding property is easy to remove, and the electrode cycle performance is not ideal. For silicon-based negative electrodes, most of the articles indicate that a binder rich in carboxyl groups is beneficial to improving the stability of the silicon negative electrode and helping to maintain the electrode capacity. When PAA with high carboxyl content is used as the binder, the material is in a glass state at normal temperature and shows brittle and hard characteristics, so that the phenomena of cracking, powder falling and the like are easily caused in the processing process of the pole piece, and the application of the PAA in the actual processing and production process is limited.
For example, under publication No. CN104277747A, "binder composition, method for preparing the same, and rechargeable lithium battery including the same", a binder composition based on a copolymer of an alkenyl monomer and a cyclic unsaturated anhydride monomer, a polyalkylene glycol, and polyacrylamide is proposed, the formed binder is a semi-interpenetrating network structure, has strong and tough characteristics, and has excellent flexibility, and can effectively control the expansion of an active material. However, the polymer obtained by the invention is brittle and is not beneficial to processing, and the network structure polymer is poor in dispersion performance of slurry when being used as a binder, and the binder is difficult to be completely dispersed on the surface of an active material during homogenizing to achieve uniform binding effect due to the limitation of a cross-linked network.
The publication No. CN106207184A discloses an aqueous binder for lithium ion batteries, a preparation method thereof and a lithium ion battery pole piece, and provides a novel binder system which comprises a modified polyvinyl alcohol dispersant, an acrylate monomer, an unsaturated carboxylic acid monomer, a vinyl hydrocarbon monomer and an optional other copolymerizable monomer copolymer. According to the invention, sulfonic group, carboxyl and amino are introduced into a polyvinyl alcohol molecular chain, so that the bonding strength of the adhesive can be improved, and the adhesive has high flexibility and is suitable for a silicon-based negative electrode adhesive. However, the thermal stability of the polyvinyl alcohol is poor, the dispersion effect on the slurry is limited, the hydroxyl content of the polyvinyl alcohol is high, and the proton hydrogen in the excessive hydroxyl is easy to react with the lithium hexafluorophosphate in the electrolyte, so that the side reaction of the electrolyte is caused, and the capacity of the battery is greatly reduced.
The publication number CN106866846A discloses a water-based binder for lithium ion batteries, a preparation method thereof and a lithium ion battery pole piece, and discloses a preparation method of the water-based binder, wherein a large amount of polar anion groups are introduced by chemically modifying hydroxyl groups in a water-soluble polymer repeating unit group, so that the improvement of the binding power by the polar action of a polymer and a current collector is facilitated; the hydroxyl is alkylated, so that a flexible side chain structure is introduced into a main chain, the flexibility of the polymer is improved, and the pole piece with good flexibility is prepared. However, the modification method adopts the traditional addition reaction, only homopolymer or random copolymer side chains can be introduced, and the molecular structure of the side chains is difficult to accurately control; meanwhile, the polar side chain is difficult to combine with active substances due to steric effect in the groups close to the main chain part in the actual use process, so that the utilization rate of the groups is low.
Disclosure of Invention
The invention aims to overcome the defects of poor dispersibility, short service life, difficult control of side chain structure and low radical utilization rate in the prior art, and provides a cathode binder material with a block structure side chain and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
the negative electrode binder material with the block structure side chain is characterized in that the binder material is a polymer solution, and the polymer has the block structure side chain, and is specifically a structure shown in a formula I or a formula II:
wherein, X1The radical being water containing hydroxy or carboxylA group of repeating units of a soluble polymer; x2The group is a repeating unit group of a water-soluble polymer containing an amino group; r1Is a C1-C2 linear alkylene group, branched alkylene group, alkylene group with a cyano group or alkylene group with an amino group; r2Alkylthio, alkyl, phenyl or benzyl of C4-C12; y is a repeating unit consisting of flexible monomers, and the monomers are selected from any one or the combination of at least two of an olefin monomer containing an ester group, an olefin monomer containing an amino group, an olefin monomer containing a hydroxyl group and a sulfonic alkenyl monomer; z is a repeating unit consisting of polar group-containing alkenyl monomers, and the monomers are selected from any one or the combination of at least two of ethylenically unsaturated carboxylic acid monomers, nitrile group-containing olefin monomers, amino group-containing olefin monomers, ester group-containing olefin monomers, acrylamide monomers, methacrylamide monomers and sulfonic group-containing alkenyl monomers; a. b and c are independently integers of 0-1000000.
The negative electrode binder material adopts a structure shown in a formula I and a structure shown in a formula II, wherein a, b and c can be independently selected as integers of 0-1000000, the specific numerical values are not limited, and a water-soluble polymer is used as a framework material to play a thickening role, so that the slurry is stabilized and prevented from settling; the invention has a side chain with a block structure, and one end of the side chain consists of a monomer unit containing a polar group so as to enhance the interaction of a polymer with a current collector and a negative electrode material, thereby improving the bonding property; the other end of the side chain is a flexible polymer chain and is used for buffering the volume expansion of the active substances, the overall flexibility and the processability of the polymer are improved, the battery pole piece with better flexibility can be prepared, and the polar functional group is positioned on the outer side of the side chain, so that the active substances can be grabbed to form good network structure buffering volume expansion, the bonding effect is strong, the group utilization rate is high, the circulation stability is good, and the service life is long.
Preferably, X is1The group is a repeating unit group from starch, vegetable gum, animal gum, cellulose, seaweed gum or polyvinyl alcohol materials; x2The group is a repeating unit group from chitosan or animal glue materials; and/or the solid content of the negative electrode binder material is 1-60%.
Preferably, the negative electrode binder material is prepared by taking a modified water-soluble polymer as a framework, sequentially adding monomers for graft polymerization and introducing a block structure side chain, and comprises the following steps:
(1) dissolving the modified water-soluble polymer in a solvent, and reacting the modified water-soluble polymer with a flexible monomer under the action of an initiator for 1-24 hours;
(2) continuously adding an alkenyl monomer containing a polar group into the system, and continuously reacting for 1-24 h;
(3) and after the polymerization reaction is finished, adjusting the pH value of the polymer aqueous solution to obtain the cathode binder material.
Preferably, in the step (1): the solvent is selected from one or combination of at least two of water, water solution containing alkaline substances, ethanol, methanol, tetrahydrofuran, dioxane, acetone or N-methylpyrrolidone; and/or the alkaline substance is any one or the combination of at least two of carbonate, silicate, acetate, sodium hydroxide, lithium hydroxide, methylamine, ammonia water, urea or pyridine.
Preferably, in the steps (1) and (2), the initiator is any one or combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, tert-butyl hydroperoxide, benzoyl peroxide, methyl ethyl ketone peroxide, potassium persulfate, ammonium persulfate, the combination of ammonium persulfate and sodium sulfite or the combination of potassium persulfate and ferrous chloride, and the addition amount of the initiator is 0.001-99% of the weight of the modified water-soluble polymer; and/or in the step (1), the flexible monomer is selected from one or a combination of at least two of an olefin monomer containing an ester group, an olefin monomer containing an amino group, an olefin monomer containing a hydroxyl group and a sulfonic acid group olefin monomer, and the addition amount of the flexible monomer is 0.1-500% of the mass of the modified water-soluble polymer; and/or in the step (2), the polar group-containing alkenyl monomer is selected from any one or a combination of at least two of an alkene unsaturated carboxylic acid monomer, a nitrile group-containing olefin monomer, an amino group-containing olefin monomer, an ester group-containing olefin monomer, an acrylamide monomer, a methacrylamide monomer and a sulfonic alkenyl monomer, and the addition amount of the polar group-containing alkenyl monomer is 0.1-500% of the mass of the modified water-soluble polymer.
Preferably, in the steps (1) and (2), the reaction temperature is 40-90 ℃; and/or in the step (3), the pH value of the polymer aqueous solution is 5-10, and the pH adjusting process is realized by alkali neutralization.
Preferably, the modified water-soluble polymer is prepared by reacting a water-soluble polymer with a RAFT reagent, and comprises the following steps:
a, stirring and dissolving a water-soluble polymer in a solvent, adding a RAFT reagent, and reacting for 0.5-48h under the action of a catalyst; and b, purifying the product after the reaction is finished to obtain the modified water-soluble polymer.
Hydroxyl in a water-soluble polymer repeating unit group is modified to introduce an RAFT group, a series of long side chains are obtained through RAFT polymerization, so that a growing free radical and a chain transfer agent are subjected to degeneration transfer, the concentration of the free radical is reduced, active free radical polymerization is realized, the bonding effect and flexibility of a bonding agent can be independently and efficiently freely regulated, the purpose of accurately regulating and controlling the density, the length and the molecular structure of the side chains is achieved, and the molecular design capability is strong; meanwhile, the RAFT group polymerization does not need to use expensive reagents, does not cause the situation that impurities or residual reagents are difficult to remove from a polymerization product, and has the advantages of narrow molecular weight distribution, low polymerization temperature and the like.
Preferably, in the step a: the water-soluble polymer is selected from one or combination of at least two of starch, vegetable gum, animal gum, cellulose, seaweed gum, chitosan or polyvinyl alcohol; the solvent is selected from any one or combination of at least two of water, aqueous solution containing alkaline substances, ethanol, methanol, tetrahydrofuran, dioxane, acetone or N-methylpyrrolidone, wherein the alkaline substances are selected from any one or combination of at least two of carbonate, silicate, acetate, sodium hydroxide, lithium hydroxide, methylamine, ammonia water, urea or pyridine; and/or the catalyst in the step a is selected from one or a combination of at least two of acids, salts, acid esters, metal oxides, carbonyl diimidazole, dimethylamino pyridine, N-methyl pyrrolidone, carbodiimides, succinimide and triazole, and the addition amount of the catalyst is 0.001-99% of the mass of the water-soluble polymer.
Preferably, the RAFT agent in step a has a general chemical structure:
wherein R is2Alkylthio, alkyl, phenyl or benzyl with the number of carbon atoms from four to twelve; r3Is isopropanoyl, acetoxy, 2-nitriloacetoxy or 2-aminoacetoxy, and/or the RAFT reagent is added in an amount of 0.01-100% of the water-soluble polymer.
Preferably, in the step a and the step b, the reaction temperature is 40-90 ℃; and/or the addition amount of the water-soluble polymer and the RAFT reagent accounts for 0.01-60% of the total mass of the reaction system.
In conclusion, the invention has the following beneficial effects: (1) the water-soluble polymer is used as a framework material to play a thickening role and is beneficial to stabilizing slurry and preventing sedimentation, the side chain is of a block structure, one end of the side chain is selected from the polymer containing polar groups to enhance the bonding effect between the side chain and a current collector and between the side chain and an active substance, and the other end of the side chain is selected from the flexible polymer to buffer the volume expansion of the active substance, so that the flexibility and the processability of the whole polymer are improved, and a battery pole piece with better flexibility can be prepared; (2) the polar functional group is positioned on the outer side of the side chain, so that active substances can be captured to form a good network structure to buffer volume expansion, the bonding effect is strong, the utilization rate of the group is high, the circulation stability is good, and the service life is long; (3) the RAFT group modification is adopted, so that the bonding effect and the flexibility of the adhesive can be independently and efficiently freely regulated and controlled, and the molecular design capability is strong.
Drawings
FIG. 1 is an SEM image of a pole piece prepared in example 1 of the invention.
Detailed Description
The invention is further described with reference to the following detailed description and accompanying drawings.
The present invention will be further described with reference to specific embodiments for the purpose of facilitating an understanding of technical means, characteristics of creation, objectives and functions realized by the present invention, but the following embodiments are only preferred embodiments of the present invention, and are not intended to be exhaustive. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative efforts belong to the protection scope of the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified, and materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1
(1) Stirring and dissolving 5 parts by weight of polyvinyl alcohol in 100 parts by weight of water, adding 3 parts by weight of RAFT reagent, and reacting for 12 hours at 60 ℃ under the action of 0.1 part by weight of phosphoric acid, wherein R2 of the RAFT reagent is decathio, and R3 of the RAFT reagent is isopropanoyl;
(2) after the reaction is finished, dewatering and drying to obtain a modified water-soluble polymer;
(3) dissolving 5 parts by weight of modified water-soluble polymer in 100 parts by weight of water, and reacting with 1 part by weight of methyl acrylate monomer at 80 ℃ for 8 hours under the action of 0.01 part by weight of potassium persulfate;
(4) continuously adding 1 weight part of acrylic monomer into the system, and continuously reacting for 12 hours;
(5) after the polymerization reaction was completed, the pH of the aqueous polymer solution was adjusted to 7 with lithium hydroxide to obtain a negative electrode binder material.
Example 2
(1) Dissolving 1 part by weight of chitosan in a mixed solvent of 70 parts by weight of water and 35 parts by weight of methanol by stirring, adding 0.5 part by weight of RAFT reagent, and reacting for 24 hours at 40 ℃ under the action of 0.4 part by weight of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.4 part by weight of N-hydroxysuccinimide, wherein R2 of the RAFT reagent is phenyl and R3 is 2-nitriloacetic acid group;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 1 weight part of modified water-soluble polymer in a mixed solvent of 60 weight parts of water and 20 weight parts of methanol, and reacting with 3 weight parts of butyl acrylate and 2 weight parts of methyl acrylate monomer at 60 ℃ for 8 hours under the action of 0.1 weight part of 4,4' -azobis (4-cyanopentanoic acid);
(4) continuously adding 3 parts by weight of acrylic monomer into the system, and continuously reacting for 12 hours;
(5) after the polymerization reaction was completed, the aqueous polymer solution was adjusted to pH 5 by carbonate to obtain a negative electrode binder material.
Example 3
(1) Stirring and dissolving 1 part by weight of sodium carboxymethylcellulose in 50 parts by weight of water, adding 0.5 part by weight of RAFT reagent, and reacting at 50 ℃ for 24 hours under the action of 0.1 part by weight of boric acid, wherein R2 of the RAFT reagent is benzyl, and R3 is 2-amino acetic acid group; (2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 1 part by weight of modified water-soluble polymer in a mixed solvent of 100 parts by weight of water and 10 parts by weight of ethanol, and reacting with 2 parts by weight of vinyl acetate monomer at 70 ℃ for 10 hours under the action of 0.2 part by weight of ammonium persulfate;
(4) continuously adding 3 parts by weight of itaconic acid monomer into the system, and continuously reacting for 12 hours;
(5) after the polymerization reaction was completed, the pH of the aqueous polymer solution was adjusted to 10 with lithium hydroxide to obtain a negative electrode binder material.
Example 4
(1) Stirring and dissolving 10 parts by weight of sodium alginate in a mixed solvent of 60 parts by weight of water and 10 parts by weight of dioxane, adding 7 parts by weight of RAFT reagent, and reacting at 70 ℃ for 16h under the action of 0.5 part by weight of alumina, wherein R2 of the RAFT reagent is octaalkyl, and R3 of the RAFT reagent is acetoxyl;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 3 parts by weight of modified water-soluble polymer in a mixed solvent of 80 parts by weight of water and 15 parts by weight of acetone, and reacting with 4 parts by weight of vinyl acetate and 0.5 part by weight of acrylic ester monomer under the action of 0.2 part by weight of potassium persulfate at 50 ℃ for 15 hours;
(4) continuously adding 3 parts by weight of methacrylic acid monomer into the system, and continuously reacting for 18 h;
(5) and after the polymerization reaction is finished, adjusting the pH value of the aqueous solution of the polymer to 7 by using sodium hydroxide to obtain the negative electrode binder material.
Example 5
(1) Stirring and dissolving 20 parts by weight of sodium alginate in a mixed solvent of 60 parts by weight of water and 10 parts by weight of dioxane, adding 7 parts by weight of RAFT reagent, and reacting at 90 ℃ for 16h under the action of 0.7 part by weight of alumina, wherein R2 of the RAFT reagent is octaalkyl, and R3 of the RAFT reagent is acetoxyl;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 2 parts by weight of modified water-soluble polymer in a mixed solvent of 80 parts by weight of water and 15 parts by weight of acetone, and reacting with 10 parts by weight of vinyl acetate and 8 parts by weight of acrylic acetate monomer under the action of 0.2 part by weight of potassium persulfate at 50 ℃ for 15 hours;
(4) continuously adding 5 parts by weight of methacrylic acid monomer into the system, and continuously reacting for 18 h;
(5) and after the polymerization reaction is finished, adjusting the pH value of the aqueous solution of the polymer to 10 by using sodium hydroxide to obtain the negative electrode binder material.
Example 6
(1) Stirring and dissolving 5 parts by weight of chitosan into a mixed solvent of 100 parts by weight of water and 35 parts by weight of methanol, adding 0.5 part by weight of RAFT reagent, and reacting for 24 hours at 40 ℃ under the action of 0.4 part by weight of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.4 part by weight of N-hydroxysuccinimide, wherein R2 of the RAFT reagent is phenyl and R3 is 2-nitriloacetic acid group;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 1 weight part of modified water-soluble polymer in a mixed solvent of 60 weight parts of water and 20 weight parts of methanol, and reacting with 3 weight parts of butyl acrylate and 2 weight parts of methyl acrylate monomer at 60 ℃ for 8 hours under the action of 0.5 weight part of 4,4' -azobis (4-cyanopentanoic acid);
(4) continuously adding 3 parts by weight of acrylic monomer into the system, and continuously reacting for 12 hours;
(5) and after the polymerization reaction is finished, adjusting the pH value of the polymer aqueous solution to 6 by using pyridine to obtain the negative electrode binder material.
Example 7
(1) Dissolving 1 part by weight of chitosan in a mixed solvent of 130 parts by weight of water and 65 parts by weight of methanol by stirring, adding 1 part by weight of RAFT reagent, and reacting for 48 hours at 40 ℃ under the action of 0.4 part by weight of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.4 part by weight of N-hydroxysuccinimide, wherein R2 of the RAFT reagent is phenyl and R3 is 2-nitriloacetic acid group;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 1 weight part of modified water-soluble polymer in a mixed solvent of 60 weight parts of water and 20 weight parts of methanol, and reacting with 3 weight parts of butyl acrylate and 2 weight parts of methyl acrylate monomer at 60 ℃ for 24 hours under the action of 0.99 weight part of 4,4' -azobis (4-cyanopentanoic acid);
(4) continuously adding 3 parts by weight of acrylic monomer into the system, and continuously reacting for 1 h;
(5) after the polymerization reaction was completed, the aqueous polymer solution was adjusted to pH 5 by carbonate to obtain a negative electrode binder material.
Example 8
(1) Dissolving 10 parts by weight of chitosan into a mixed solvent of 200 parts by weight of water and 70 parts by weight of methanol by stirring, adding 1 part by weight of RAFT reagent, and reacting for 0.5h at 90 ℃ under the action of 0.5 part by weight of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.49 part by weight of N-hydroxysuccinimide, wherein R2 of the RAFT reagent is phenyl and R3 is 2-nitriloacetic acid group;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 10 parts by weight of the modified water-soluble polymer in a mixed solvent of 500 parts by weight of water and 200 parts by weight of methanol, and reacting 0.005 part by weight of butyl acrylate and 0.005 part by weight of methyl acrylate monomer at 60 ℃ for 1h under the action of 0.0001 part by weight of 4,4' -azobis (4-cyanovaleric acid);
(4) continuously adding 0.01 weight part of acrylic monomer into the system, and continuously reacting for 24 hours;
(5) and after the polymerization reaction is finished, adjusting the pH value of the polymer aqueous solution to 8 by using pyridine to obtain the negative electrode binder material.
Example 9
(1) Dissolving 50 parts by weight of chitosan in a mixed solvent of 35 parts by weight of water and 15 parts by weight of methanol by stirring, adding 25 parts by weight of RAFT reagent, and reacting at 90 ℃ for 0.5h under the action of 0.00025 part by weight of boric acid, wherein R2 of the RAFT reagent is phenyl, and R3 of the RAFT reagent is 2-nitriloacetic acid group;
(2) removing the solvent after the reaction is finished and drying to obtain a modified water-soluble polymer;
(3) dissolving 0.1 weight part of modified water-soluble polymer in a mixed solvent of 60 weight parts of water and 40 weight parts of methanol, and reacting 0.3 weight part of butyl acrylate and 0.2 weight part of methyl acrylate monomer at 60 ℃ for 1h under the action of 0.099 weight part of 4,4' -azobis (4-cyanopentanoic acid);
(4) continuously adding 0.5 weight part of acrylic monomer into the system, and continuously reacting for 24 hours;
(5) and after the polymerization reaction is finished, adjusting the pH value of the polymer aqueous solution to 8 by using pyridine to obtain the negative electrode binder material.
Further, the negative electrode binder materials prepared in examples 1 to 4 were used for preparation of negative electrode sheets, assembly of button cells, and electrochemical performance testing. The method comprises the following specific steps: mixing the negative electrode binder material prepared in the examples 1 to 4 with a silica material, a graphite material, conductive carbon black and Styrene Butadiene Rubber (SBR) according to the mass ratio of 2:10:80:5:3, adding deionized water as a solvent, and stirring; uniformly stirring, uniformly coating on a copper foil current collector by using coating equipment, baking for 24 hours in a vacuum drying oven at 90 ℃, then uniformly pressing by using a roll machine, and finally preparing a circular pole piece with the diameter of 14mm by using a sheet punching machine; and then, a metal lithium sheet is taken as a counter electrode, a diaphragm is a polypropylene membrane (Celgard 2300), an electrolyte is a mixed solution of 1mol/L lithium hexafluorophosphate and vinyl carbonate and dimethyl carbonate in equal volume ratio, a 2025 button cell is assembled in a vacuum glove box filled with high-purity nitrogen, and electrochemical performance tests are carried out, wherein the test results are shown in Table 1. During testing, the charge and discharge cycles are carried out at 0.1C multiplying power (1C is calculated by 500 mAh/g), the voltage range is 0-1.5V, and the cycle times are 100 times. And disassembling the battery after the battery is circulated for 100 weeks to measure the expansion rate of the pole piece.
The performance test tables of the negative electrode binder materials prepared in examples 1 to 4 are shown in table 1.
TABLE 1 Performance test Table
As can be seen from the data in table 1, the negative electrode binder materials prepared in examples 1 to 4 all have high first coulombic efficiency and good cycle stability, and it is proved that the binder material can effectively alleviate the volume expansion of the active material, and avoid the structural damage caused by the volume effect of the active material, thereby greatly improving the cycle stability; in addition, the expansion rate in the material circulation process can also show that the adhesive material can effectively buffer the volume expansion of the pole piece, and the service life is prolonged.
Fig. 1 is an SEM image of the electrode sheet prepared in example 1, which shows that the active material and conductive carbon black are uniformly dispersed without significant agglomeration when the negative electrode binder is used.
Claims (10)
1. The negative electrode binder material with the block structure side chain is characterized in that the binder material is a polymer solution, and the polymer has the block structure side chain, and is specifically a structure shown in a formula I or a formula II:
wherein, X1The group is a repeating unit group of a water-soluble polymer containing hydroxyl or carboxyl; x2The group is a repeating unit group of a water-soluble polymer containing an amino group; r1Is a linear alkylene group having from C1 to C2, a branched alkylene group,Alkylene having a cyano group or alkylene having an amino group; r2Alkylthio, alkyl, phenyl or benzyl of C4-C12; y is a repeating unit consisting of flexible monomers, and the monomers are selected from any one or the combination of at least two of an olefin monomer containing an ester group, an olefin monomer containing an amino group, an olefin monomer containing a hydroxyl group and a sulfonic alkenyl monomer; z is a repeating unit consisting of polar group-containing alkenyl monomers, and the monomers are selected from any one or the combination of at least two of ethylenically unsaturated carboxylic acid monomers, nitrile group-containing olefin monomers, amino group-containing olefin monomers, ester group-containing olefin monomers, acrylamide monomers, methacrylamide monomers and sulfonic group-containing alkenyl monomers; a. b and c are independently integers of 0-1000000.
2. The anode binder material according to claim 1, wherein X is1The group is a repeating unit group from starch, vegetable gum, animal gum, cellulose, seaweed gum or polyvinyl alcohol materials; x2The group is a repeating unit group from chitosan or animal glue materials; and/or
The solid content of the negative electrode binder material is 1-60%.
3. The negative electrode binder material as claimed in any one of claims 1 to 2, wherein the negative electrode binder material is prepared by using a modified water-soluble polymer as a skeleton, sequentially adding monomers for graft polymerization, and introducing a block structure side chain, and comprises the following steps:
(1) dissolving the modified water-soluble polymer in a solvent, and reacting the modified water-soluble polymer with a flexible monomer under the action of an initiator for 1-24 hours;
(2) continuously adding an alkenyl monomer containing a polar group into the system, and continuously reacting for 1-24 h;
(3) and after the polymerization reaction is finished, adjusting the pH value of the polymer aqueous solution to obtain the cathode binder material.
4. The anode binder material according to claim 3, wherein in the step (1): the solvent is selected from one or combination of at least two of water, water solution containing alkaline substances, ethanol, methanol, tetrahydrofuran, dioxane, acetone or N-methylpyrrolidone; and/or
The alkaline substance is any one or combination of at least two of carbonate, silicate, acetate, sodium hydroxide, lithium hydroxide, methylamine, ammonia water, urea or pyridine.
5. The negative binder material of claim 3, wherein in the steps (1) and (2), the initiator is any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, tert-butyl hydroperoxide, benzoyl peroxide, methyl ethyl ketone peroxide, potassium persulfate, ammonium persulfate, a combination of ammonium persulfate and sodium sulfite or a combination of potassium persulfate and ferrous chloride, and the addition amount of the initiator is 0.001-99% of the weight of the modified water-soluble polymer; and/or
In the step (1), the flexible monomer is selected from one or a combination of at least two of an olefin monomer containing an ester group, an olefin monomer containing an amino group, an olefin monomer containing a hydroxyl group and a sulfonic acid group olefin monomer, and the addition amount of the flexible monomer is 0.1-500% of the mass of the modified water-soluble polymer; and/or
In the step (2), the polar group-containing alkenyl monomer is selected from any one or a combination of at least two of an ethylenically unsaturated carboxylic acid monomer, a nitrile group-containing olefin monomer, an amino group-containing olefin monomer, an ester group-containing olefin monomer, an acrylamide monomer, a methacrylamide monomer and a sulfonic acid alkenyl monomer, and the addition amount of the polar group-containing alkenyl monomer is 0.1-500% of the mass of the modified water-soluble polymer.
6. The negative binder material according to claim 4, wherein in the steps (1) and (2), the reaction temperature is 40-90 ℃; and/or
In the step (3), the pH of the aqueous polymer solution is adjusted to 5-10, and the pH adjustment process is realized by alkali neutralization.
7. The negative binder material of claim 4, wherein the modified water-soluble polymer is prepared by reacting a water-soluble polymer with a RAFT reagent, and comprises the following steps:
a, stirring and dissolving a water-soluble polymer in a solvent, adding a RAFT reagent, and reacting for 0.5-48h under the action of a catalyst;
and b, purifying the product after the reaction is finished to obtain the modified water-soluble polymer.
8. The anode binder material according to claim 7, wherein in step a: the water-soluble polymer is selected from one or combination of at least two of starch, vegetable gum, animal gum, cellulose, seaweed gum, chitosan or polyvinyl alcohol; and/or
The solvent is selected from any one or combination of at least two of water, aqueous solution containing alkaline substances, ethanol, methanol, tetrahydrofuran, dioxane, acetone or N-methylpyrrolidone, wherein the alkaline substances are selected from any one or combination of at least two of carbonate, silicate, acetate, sodium hydroxide, lithium hydroxide, methylamine, ammonia water, urea or pyridine; and/or
The catalyst in the step a is selected from any one or a combination of at least two of acids, salts, acid esters, metal oxides, carbonyldiimidazole, dimethylaminopyridine, N-methylpyrrolidone, carbodiimides, succinimide and triazole, and the addition amount of the catalyst is 0.001-99% of the mass of the water-soluble polymer.
9. The anode binder material of claim 7, wherein the RAFT agent in step a has a general chemical structure of:
wherein R is2Alkylthio, alkyl, phenyl or benzyl with the number of carbon atoms from four to twelve; r3Is isopropanoxy, acetoxy, 2-nitriloacetoxy or 2-aminoacetoxy, and/or
The RAFT agent is added in an amount of 0.01-100% by mass based on the mass of the water-soluble polymer.
10. The anode binder material according to claim 7, 8 or 9, wherein in the steps a and b, the reaction temperature is 40-90 ℃; and/or
The addition amount of the water-soluble polymer and the RAFT reagent accounts for 0.01-60% of the total mass of the reaction system.
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Effective date of registration: 20211119 Address after: No.855, Jianshe 2nd Road, Xiaoshan Economic and Technological Development Zone, Hangzhou City, Zhejiang Province Patentee after: Wanxiang A123 Co.,Ltd. Address before: No.855 Jianshe Er Road, Xiaoshan Economic and Technological Development Zone, Xiaoshan District, Hangzhou City, Zhejiang Province Patentee before: Wanxiang A123 Co.,Ltd. Patentee before: Wanxiang Group Co., Ltd |