CN113571709B - Adhesive, preparation method and application thereof - Google Patents
Adhesive, preparation method and application thereof Download PDFInfo
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- CN113571709B CN113571709B CN202110860499.3A CN202110860499A CN113571709B CN 113571709 B CN113571709 B CN 113571709B CN 202110860499 A CN202110860499 A CN 202110860499A CN 113571709 B CN113571709 B CN 113571709B
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- polyethyleneimine
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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
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/02—Polyamines
- C08G73/0206—Polyalkylene(poly)amines
- C08G73/0213—Preparatory process
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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 provides a binder and a preparation method and application thereof, wherein the binder comprises modified polyethyleneimine; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and unsaturated hydroxy fatty acid. The preparation method of the adhesive comprises a method A or a method B; the method A comprises the following steps: reacting polyethyleneimine, dopa acid and unsaturated hydroxy fatty acid to obtain the binder; the method B comprises the following steps: (1) reacting polyethyleneimine with dopa to obtain dopa acid modified polyethyleneimine; (2) reacting the dopa acid modified polyethyleneimine obtained in the step (1) with unsaturated hydroxy fatty acid to obtain the adhesive. The adhesive has good flexibility and strong adhesive capacity with silicon, and can improve the drying rate, the cracking resistance, the rate capability and the cycle performance of a pole piece when being applied to a lithium ion battery negative pole piece.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery cathode materials, and particularly relates to a binder and a preparation method and application thereof.
Background
In recent years, with the importance of the public on environmental protection, lithium batteries are outstanding in the new energy industry and widely applied to various electronic products, electric automobiles and other energy storage devices. Therefore, the requirement of people on the energy density of the lithium battery is higher and higher, the gram capacity of the used anode needs to be improved besides the cathode is made of a ternary material, the anode material with higher gram capacity belongs to a graphite material and a silicon material, silicon is used as a material capable of forming an alloy with lithium, a lower lithium removal platform is provided, each silicon atom can form an alloy with 4.4 lithium atoms, the ultrahigh theoretical specific capacity is higher than that of a graphite cathode by one order of magnitude. Although the silicon negative electrode has a high specific capacity for lithium intercalation and deintercalation, silicon causes a serious problem of expansion during charge and subsequent cycles, volume expansion after lithium intercalation is very large, and volume expansion and contraction during cycles are reversible. The huge volume expansion and contraction can cause a series of problems of the silicon material during the use process, such as silicon particle breakage, material pulverization, falling off from a pole piece, and generation of a solid electrolyte film (SEI film) on a new exposed surface, and consumption of lithium in the limited electrolyte and the positive electrode in the battery.
In the battery, the binder is the key for maintaining the electrode structure, and the selection of the binder has more important significance for enhancing the stability of the silicon-based electrode structure and realizing long-term circulation. The adhesive with weak adhesive force can not keep the electrical contact activity between silicon active materials, which can cause the first effect of an electrode to be lower and the subsequent specific capacity to be attenuated, thus influencing the realization of the performance of the high-energy density battery, and the adhesive with weak adhesive force can not prevent the demoulding of a pole piece caused by the expansion of a silicon material in the circulation process, thereby influencing the safety and the reliability of the battery.
In order to solve the problem, the traditional method selects to increase the amount of the binder in the negative pole piece to enhance the binding strength between the active material and the current collector so as to resist the stress generated by the expansion of the active material on the interface between the active material and the current collector in the charging and circulating processes, but the traditional method inevitably causes the amount of the active material in the system to be reduced, thereby causing the energy density of the battery to be reduced, and on the other hand, the dynamic performance of the pole piece to be reduced.
Among conventional binders, PVDF or CMC is often used as a binder. For example, CN111509223A discloses a lithium ion battery cathode binder and a lithium ion battery cathode slurry, wherein the cathode binder comprises high molecular weight PVDF and medium molecular weight PVDF, and the weight ratio of the high molecular weight PVDF to the medium molecular weight PVDF is (6-8): 2-4; the lithium ion battery positive electrode slurry contains a solid component and a solvent, and the solid component contains the positive electrode binder. The binder can overcome the physical gel problem of a high molecular weight PVDF binder in a nano lithium iron phosphate system, the prepared slurry has good stability, can meet the requirements of production and coating processing, and the dosage of PVDF is low, so that the proportion of a lithium iron phosphate material is further improved, and the energy density of a monomer battery core is improved. But PVDF is rigid and is bonded to silicon particles by weak van der waals force, and it is difficult to maintain the volume change of the silicon-based negative electrode under long cycle.
In addition, for the requirement of environmental protection, the solvent of the binder is preferably selected from safe and nontoxic reagents, and at present, water is preferably selected as the reagent of the binder. CN110890545A discloses a PEDOT PSS/CMC composite binder, a preparation method and application thereof. The composite binder comprises crosslinked poly 3, 4-ethylenedioxythiophene, polystyrene sulfonate/hydroxymethyl cellulose (PEDOT: PSS/CMC); the preparation raw materials comprise PEDOT, PSS and CMC in a mass ratio of (0.1-10) to 1. When the composite binder is used for preparing the silicon-based negative electrode of the lithium ion battery, functional groups in the binder can be effectively bonded with silicon, so that the binding force with a silicon-based material is improved. Although the integrity of the electrode structure of a silicon negative electrode using CMC as a binder is enhanced, there are also problems. CMC has high rigidity and low elongation at break (5-8 percent), and the rigid polymer binder can not completely eliminate stress, so cracks are often generated in the repeated circulation process, and the specific capacity attenuation of the battery is obvious; in addition, the silicon cathode taking CMC as a binder is easy to crack a pole piece in the coating and drying processes, NMP and other organic solvents are added in the coating process in order to improve the cracking, and the residue of the organic solvent reacts with electrolyte to generate certain influence on the performance of the battery; the manufacturing process of the lithium battery has a key requirement on moisture control, and in order to control moisture, the baking process of the pole piece taking CMC-SBR as the binder consumes a long time, so that the productivity is influenced and the energy consumption is high.
In order to solve the problems caused by the traditional method of using a polymer with high rigidity as a binder, CN112310403A synthesizes a novel silicon-oxygen negative electrode binder by reacting dopa acid with polyethyleneimine. The catechol group is introduced into a skeleton of polyethyleneimine to generate a polyamine polymer binder containing the catechol group, and the binder can form strong hydrogen bonds or covalent bonds with silicon particles, so that the volume expansion of a silicon cathode can be inhibited, the rate capability and the cycle performance of the silicon-oxygen cathode are obviously improved, and the service life of a lithium ion battery is prolonged. However, due to the use of the aqueous system, the pole piece is easy to crack in the pole piece drying process, the required drying time is long, and the improvement of the production efficiency is not facilitated.
Therefore, the development of the negative electrode binder which has good flexibility and strong binding power with silicon, improves the cracking resistance and drying rate of the pole piece, and improves the rate capability and cycle performance of the negative electrode has important practical significance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the adhesive, the preparation method and the application thereof, wherein the prepared adhesive has stronger adhesive force with silicon by grafting the dopa acid and the unsaturated hydroxy fatty acid into the molecular structure of the polyethyleneimine, and the drying rate, the cracking resistance, the rate capability and the cycle performance of a pole piece can be improved when the adhesive is applied to a lithium ion battery negative pole piece.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an adhesive comprising a modified polyethyleneimine; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and unsaturated hydroxy fatty acid.
In the invention, the polymer binder containing polyamine groups of catechol groups and unsaturated hydroxy fatty acid groups is generated by introducing the catechol groups and the unsaturated hydroxy fatty acid groups into the skeleton of polyethyleneimine. In the binder, polyethyleneimine is a rich amine group polymer, and after the reaction of polyethyleneimine with dopa acid and unsaturated hydroxy fatty acid, catechol groups are introduced into the structure of the binder, so that more new active group hydroxyl groups are added, more active sites are increased, and more hydrogen bonds or covalent bonds can be formed with silicon particles, so that the binding power to silicon is improved, the adhesion between a current collector and a silicon cathode is enhanced, and the rate capability and the stability of a lithium ion battery are improved; the hyperbranched structure of the polyethyleneimine has higher elasticity, two groups introduced into the structure can further generate polymerization reaction to improve the deformation resistance of the hyperbranched structure, and the hyperbranched structure can absorb the expansion and contraction of a silicon material through telescopic extension, can buffer the volume change of silicon-based particles, is beneficial to the integrity of a negative silicon electrode and the integrity of a surface SEI (solid electrolyte interphase) film, and can well solve the problem that an active material of an anode pole piece is easy to expand and separate from a current collector in the charging process of a battery; the longer hydrophobic group of unsaturated hydroxyl fatty acid group has excellent pliability and water proofness, and the introduction of this structure can improve the resistance ability to the water droplet among the pole piece air drying process, can promote the stoving speed of pole piece to increase the moisture resistance of pole piece, and can solve the easy cracking problem of silica negative pole in the coating process. And the molecular structure of the unsaturated hydroxy fatty acid contains active double bonds, carboxyl and hydroxyl, and the unsaturated hydroxy fatty acid and the dopa acid are crosslinked to form a three-dimensional network structure, so that the volume change of the silicon material can be better borne while the viscosity of the adhesive is enhanced.
Preferably, the modified polyethyleneimine is obtained by a grafting reaction of polyethyleneimine, dopa acid and unsaturated hydroxy fatty acid.
In the present invention, the number of carbon atoms of the unsaturated hydroxy fatty acid is 10 or more; the unsaturated hydroxy fatty acid comprises a hydroxyl group, a carbon-carbon double bond, and a carboxyl group.
Preferably, the unsaturated hydroxy fatty acid comprises any one of ricinoleic acid, hydroxypalmitoleic acid, 2-hydroxyoleic acid, 5-hydroxy-8-decaenoic acid, 10-hydroxy-2-decenoic acid, or a combination of at least two thereof.
In the invention, the polyethyleneimine is hyperbranched polyethyleneimine. Compared with linear polyethyleneimine, the hyperbranched polyethyleneimine is more suitable for expanded silicon-based negative electrode systems.
In the present invention, the amount ratio of the tertiary amino group, the secondary amino group, and the primary amino group in the polyethyleneimine is 1 (0.5 to 2) to (0.5 to 1.5), and may be, for example, 1:0.8:0.8, 1:1: 0.8:1, 1:1.5:0.8, 1:1.5:1, 1:1.2:0.8, 1:1.2:1.2, 1:1.5:1.5, 1:1.5:1, 1:0.8:1.8, or 1:1: 0.8.
Preferably, the weight average molecular weight of the polyethyleneimine is 10000 to 300000, and may be 20000, 50000, 70000, 100000, 150000, 170000, 200000, 250000, 270000 or 290000, for example, and specific values therebetween, for reasons of brevity and clarity, the invention is not exhaustive with the specific values included in the range.
Preferably, the molar percentage of the primary amine groups is 25 to 35% based on 100% of the total amine groups in the polyethyleneimine, and for example, the molar percentage may be 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, or 34%, and specific values therebetween are not intended to limit the disclosure and the conciseness, and the invention is not exhaustive list of the specific values included in the range.
In a second aspect, the present invention provides a method for preparing the binder according to the first aspect, the method comprising method a or method B;
the method A comprises the following steps: reacting polyethyleneimine, dopa acid and unsaturated hydroxy fatty acid to obtain the binder;
the method B comprises the following steps: (1) reacting polyethyleneimine with dopa to obtain dopa acid modified polyethyleneimine; (2) and (2) reacting the dopa acid modified polyethyleneimine obtained in the step (1) with unsaturated hydroxy fatty acid to obtain the adhesive.
In the present invention, the reaction of the method A and the reaction of the step (1) are both carried out in the presence of an amidation agent.
Preferably, the amidation reagent comprises any one of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, O-benzotriazole-tetramethylurea hexafluorophosphate and 2- (7-azabenzotriazole) -N, N, N ', N' -tetramethylurea hexafluorophosphate or the combination of at least two of the two.
Preferably, the pH of the reaction of the method A and the reaction of the step (1) is determined according to the kind of the amidation reagent, which is a means conventional in the art.
Preferably, the means for adjusting the PH comprises any one of dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid, or a combination of at least two thereof, as is conventional in the art.
Preferably, the amount of the dopa acid is 0.5 to 1.5mol, for example, 0.55mol, 0.7mol, 0.85mol, 1.0mol, 1.25mol, 1.33mol or 1.45mol based on 1mol of the primary amine groups in the polyethyleneimine, and the specific values therebetween are not exhaustive, and for the sake of brevity and brevity, the specific values included in the range are not limited to the specific values.
Preferably, the unsaturated hydroxy fatty acid is used in an amount of 0.5 to 1.5mol, for example, 0.55mol, 0.7mol, 0.85mol, 1.0mol, 1.25mol, 1.33mol or 1.45mol based on 1mol of the primary amine group in the polyethyleneimine, and specific values therebetween are not exhaustive for the invention and for brevity.
Preferably, the reaction of process a is carried out in the presence of a solvent.
Preferably, the solvent comprises methanol and/or ethanol.
Preferably, the reaction of step (1) is carried out in the presence of a solvent M.
Preferably, the solvent M is any one of water, methanol or ethanol or a combination of at least two thereof.
Preferably, the reaction temperature of the method a is 20 to 40 ℃, for example, 22 ℃, 24 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 34 ℃, 36 ℃, 38 ℃ or 39 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive.
Preferably, the reaction time of the method a is 6-12 h, for example, 6.4h, 6.8h, 7.2h, 7.6h, 8.2h, 8.4h, 8.6h, 8.8h, 9h, 9.2h, 9.4h, 9.6h, 9.8h, 9.9h, 10.2h, 10.8h, 11h, 11.7h or 11.9h, and specific point values between the above point values are limited by space and for brevity, the invention is not exhaustive and specific point values included in the range are not listed.
Preferably, the reaction of step (2) is carried out in the presence of a solvent N.
Preferably, the solvent N is any one of methanol, ethanol, diethyl ether, acetone or ethyl acetate or a combination of at least two of them.
Preferably, the temperature of the reaction of step (1) and step (2) is 20 to 40 ℃, for example, 22 ℃, 24 ℃, 26 ℃, 28 ℃, 30 ℃, 32 ℃, 34 ℃, 36 ℃, 38 ℃ or 39 ℃, and the specific values therebetween are limited by space and for simplicity, and the invention is not exhaustive.
Preferably, the total time of the reaction of step (1) and step (2) is 8-15 h, for example, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h or 14.5h, and the specific values between the above values are limited by space and for the sake of brevity, the invention is not exhaustive of the specific values included in the range.
Preferably, the reaction of the method A and the reaction of the step (2) comprise separation and purification after finishing the reaction.
Preferably, the method for separation and purification includes any one of dialysis, coprecipitation, or chromatography.
In a third aspect, the present invention provides a lithium ion battery negative electrode material, including a negative electrode active material, a conductive agent, and the binder according to the first aspect; the negative active material is a silicon-based active material.
Preferably, the mass percentage of the negative active material in the negative electrode material of the lithium ion battery is 94-98%, for example, 94.2%, 94.5%, 94.8%, 95%, 95.2%, 95.5%, 95.8%, 96%, 96.2%, 96.5%, 96.8%, 97%, 97.2%, 97.5%, 97.8% or 97.9%, and specific values between the above values are limited to space and for brevity, and the invention does not list the specific values included in the range.
Preferably, the content of the conductive agent in the lithium ion battery negative electrode material is 1 to 3% by mass, such as 1.1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8% or 2.9%, and specific values therebetween, which are limited by space and for simplicity, the present invention does not exhaustively enumerate specific values included in the range.
Preferably, the mass percentage of the binder in the lithium ion battery negative electrode material is 0.5-1.5%, such as 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, or 1.4%, and the specific values therebetween are not limited to the space and for brevity, and the invention is not exhaustive.
Preferably, the silicon-based active material comprises any one of elemental silicon, a silicon alloy, a silicon carbon compound or a silicon oxygen compound or a combination of at least two of the foregoing.
Preferably, the conductive agent in the lithium ion battery negative electrode material comprises one or more of acetylene black, ketjen black, carbon fibers, superconducting carbon black, carbon nanotubes and graphene.
In a fourth aspect, the present invention provides a lithium ion battery, which includes a negative electrode plate, a positive electrode plate, a diaphragm and an electrolyte; the diaphragm is arranged between the positive pole piece and the negative pole piece; the negative pole piece comprises the negative pole material of the lithium ion battery in the third aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, unsaturated hydroxy fatty acid and dopa acid are adopted to graft and modify polyethyleneimine, and catechol groups and unsaturated hydroxy fatty acid groups are introduced into a polyethyleneimine structure, so that the prepared adhesive has strong adhesion with silicon, and the peel strength reaches 15N/m; when the adhesive is used for a negative pole piece, the drying rate of the pole piece is improved, the drying time of the pole piece is only 6 hours when the pole piece is baked until the moisture content is 100ppm, and the pole piece is not cracked during coating; the negative pole piece is applied to the lithium ion battery, so that the charge-discharge cycle performance of the battery can be improved, and the capacity retention rate of the battery reaches 94% after the battery is charged and discharged for 500 weeks.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
Example 1
The embodiment provides a binder and a preparation method thereof, wherein the binder is a polymer of modified grafted polyethyleneimine of dopa and ricinoleic acid; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and ricinoleic acid.
The preparation method of the adhesive comprises the following steps: mixing 0.5mol of dopa acid, 0.5mol of ricinoleic acid, polyethyleneimine and amidation reagent with methanol, reacting at room temperature for 9h, and purifying by dialysis to obtain the binder. Wherein, polyethyleneimine (Mw 300000) is added according to the molar ratio of the total number of amine groups to the dopamine acid being 2:1, wherein the amount ratio of substances of tertiary amine groups, secondary amine groups and primary amine groups in the polyethyleneimine is 1:1: 1. The mass ratio of the methanol to the dopa acid is 10: 1; the amidation reagent is a combination of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride dopa acid (EDCI) and N-hydroxysuccinimide (NHS), and the mass ratio of the dopa acid, EDCI and NHS is 1:1.1: 1.2.
And carrying out Fourier infrared spectrum test on the obtained binder, wherein the peak positions are respectively IR (KBr) upsilon: 3450cm-1(-NH)，3050cm-1(Ar-H)，2970cm-1，2850cm-1(-CH2-)，1680cm-1(-C＝C-)，1650cm-1(-C＝O)，1400-1600cm-1(Ar)，1350-1260cm-1(-OH)。
The embodiment also provides a lithium ion battery and a preparation method thereof, wherein the lithium ion battery comprises a negative pole piece, a positive pole piece, a diaphragm and electrolyte; the diaphragm is arranged between the positive pole piece and the negative pole piece; the negative pole piece comprises a silicon-based active substance, a conductive agent and the binder provided by the embodiment, wherein the silicon-based active substance is simple substance silicon, the conductive agent is superconducting carbon black, and the weight ratio of the silicon-based active substance to the conductive agent to the binder is 98:1: 1.
The preparation method of the lithium ion battery comprises the following steps:
(1) preparing a positive pole piece: mixing a ternary nickel material, superconducting carbon black and a polyvinylidene fluoride binder according to a weight ratio of 93:4:3, adding N-methyl pyrrolidone, stirring and mixing to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil, and drying, cold pressing and slitting at room temperature and 120 ℃ in sequence to obtain a positive electrode piece;
(2) preparing a negative pole piece: mixing a silicon-based active substance, a conductive agent and a binder according to a weight ratio of 98:1:1, adding deionized water, stirring and mixing to obtain a negative electrode slurry, coating the negative electrode slurry on a copper foil, drying at room temperature and 120 ℃ in sequence until the water content of a pole piece is lower than 100ppm, and then cold-pressing and slitting to obtain a negative pole piece;
(3) selecting a diaphragm: selecting the material with the thickness of 15 mu m;
(4) preparing a lithium ion battery:
stacking the positive pole piece obtained in the step (1), the polyethylene/polypropylene diaphragm and the negative pole piece obtained in the step (2) in sequence, and then winding to obtain a bare cell; and (3) placing the bare cell into an aluminum plastic film with a groove, and performing the procedures of liquid injection, vacuum packaging, standing, negative pressure formation, secondary liquid supplement, shaping and the like to obtain the lithium ion battery.
Example 2
The embodiment provides a binder and a preparation method thereof, wherein the binder is a polymer of modified grafted polyethyleneimine of dopa acid and ricinoleic acid; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and ricinoleic acid;
the preparation method of the adhesive comprises the following steps: mixing 0.5mol of dopa acid, polyethyleneimine, amidation reagent and water, adjusting the pH of the solution to 5.5, stirring for 20min, and reacting for 5h at room temperature to obtain a polymer of dopa acid modified polyethyleneimine. Wherein the amidation agent is a combination of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride dopa acid (EDCI) and N-hydroxysuccinimide (NHS); the mass ratio of the dopa acid to the EDCI to the NHS is 1:1.1: 1.2; the molar ratio of the total number of amine groups in the polyethyleneimine to the dopa acid is 2: 1; the ratio of tertiary amine group to primary amine group to secondary amine group in polyethyleneimine is 1:1: 2.
Adding the obtained polymer of the dopa acid modified polyethyleneimine and 1mol of ricinoleic acid into ethyl acetate, reacting for 5 hours at room temperature, and purifying by a coprecipitation method to obtain the binder.
And (3) performing infrared characterization on the binder, wherein the peak positions are respectively IR (KBr) upsilon: 3450cm-1(-NH)，3050cm-1(Ar-H)，2970cm-1，2850cm-1(-CH2-)，1680cm-1(-C＝C-)，1650cm-1(-C＝O)，1400-1600cm-1(Ar)，1350-1260cm-1(-OH)。
The present embodiment provides a lithium ion battery and a method for manufacturing the same, where the lithium ion battery is different from that in embodiment 1 only in that the binder in the negative electrode tab is the binder provided in this embodiment, the conductive agent is acetylene black, and the weight ratio of the silicon-based active material, the conductive agent, and the binder is 96:2.5: 1.5.
The preparation method of the lithium ion battery is different from that of the embodiment 1 only in that the weight ratio of the silicon-based active material, the conductive agent and the binder is 96:2.5:1.5 when the negative pole piece is prepared, and the conductive agent is acetylene black.
Example 3
The embodiment provides a binder and a preparation method thereof, wherein the binder is a polymer of modified grafted polyethyleneimine of dopa and hydroxy palmitoleic acid; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and hydroxy palmitoleic acid;
mixing 1.5mol of dopa acid, 1.5mol of hydroxy palmitoleic acid, polyethyleneimine, an amidation reagent and methanol, reacting for 8 hours at room temperature, and purifying by column chromatography to obtain the binder. Wherein the amidation reagent is a combination of O-benzotriazole-tetramethyluronium Hexafluorophosphate (HATU) and N-hydroxysuccinimide (NHS); the mass ratio of the dopa acid to the EDCI to the NHS is 1:1.1: 1.2; the molar ratio of the total number of amine groups in the polyethyleneimine to the dopa acid is 2: 1; the ratio of tertiary amine group to primary amine group to secondary amine group in polyethyleneimine is 1:1: 2.
And carrying out Fourier infrared spectrum test on the obtained binder, wherein the peak positions are respectively IR (KBr) upsilon: 3450cm-1(-NH)，3050cm-1(Ar-H)，2970，2850cm-1(-CH2-)，1680cm-1(-C＝C-)，1650cm-1(-C＝O)，1400-1600cm-1(Ar)，1350-1260cm-1(-OH)。
The embodiment provides a lithium ion battery and a preparation method thereof, and the lithium ion battery is different from the lithium ion battery in embodiment 1 only in that the binder in the negative electrode plate is the binder provided in the embodiment, the conductive agent is ketjen black, and the weight ratio of the silicon-based active material to the conductive agent to the binder is 97:2: 1.
The lithium ion battery preparation method is different from the embodiment 1 only in that the conductive agent is Ketjen black when the negative electrode plate is prepared, and the weight ratio of the silicon-based active substance to the conductive agent to the binder is 97:2: 1.
Example 4
This example provides a binder and a method of preparing the same as example 1.
This example provides a lithium ion battery and a method for manufacturing the same, and the lithium ion battery is different from example 1 only in that: the weight ratio of the silicon-based active substance to the conductive agent to the binder is 97:2.5: 0.5.
The preparation method of the lithium ion battery is different from that of the embodiment 1 only in that the weight ratio of the silicon-based active material, the conductive agent and the binder is 97:2.5:0.5 when the negative pole piece is prepared.
Comparative example 1
The present comparative example provides a binder which is a polymer binder obtained by modifying grafted polyethyleneimine with dopa, and a method for preparing the same. The preparation method is the same as that of example 1, except that no unsaturated hydroxy fatty acid is added to the preparation system.
The present comparative example provides a lithium ion battery and a preparation method thereof, which is different from example 1 in that the binder in the negative electrode plate is the binder provided in this example, and the preparation method is the same as example 1.
Comparative example 2
The present comparative example provides a lithium ion battery and a preparation method thereof, which is different from example 1 in that the binder in the negative electrode plate is an SBR/CMC binder, and the preparation method of the lithium ion battery is the same as example 1.
Comparative example 3
The present comparative example provides a lithium ion battery and a method for manufacturing the same, which is different from example 1 in that the binder in the negative electrode sheet is PVDF binder, and the method for manufacturing the lithium ion battery is different from example 1 in that N-methylpyrrolidone (NMP) is used instead of water.
And (3) performance testing:
(1) and (3) testing the peel strength:
1. cutting the negative pole pieces provided in examples 1-4 and comparative examples 1-3 to 170 × 20 mm; 2. sticking the cut negative pole piece to the middle of a thin steel plate by using a double-sided adhesive tape, wherein the end face of the thin steel plate is flush, and the thin steel plate is wiped clean by using dust-free paper in advance without leaving stains and dust; 3. rolling the surface of the pole piece back and forth for 3 times by using a pressing wheel with the weight of 2 kg; 4. inserting the steel plate adhered with the fixed pole piece into a lower clamp of a tester, and vertically fixing; inserting the pole piece without adhesive into the upper clamp for fixing, and making the angle between the pole piece attached on the adhesive paper and the pole piece fixed by the upper clamp be 180 degrees. After the test sample is fixed, firstly calibrating and resetting, setting the test width, the stripping length of the pole piece is 100mm, the stripping speed is 5cm/min, and then starting the test to obtain a stripping strength curve and an average value.
(2) And (3) testing the discharge performance: the lithium ion batteries provided in examples 1 to 4 and comparative examples 1 to 3 were subjected to discharge performance testing, and the current density was 0.1C; wherein the first charge-discharge efficiency is η ═ (first discharge specific capacity/first charge specific capacity) × 100%.
(3) Rate performance test the lithium ion batteries provided in examples 1 to 4 and comparative examples 1 to 3 were subjected to cycle tests at current densities of 0.1C, 0.3C, 0.5C, 1C, 3C, 1C, 0.5C, 0.3C, 0.1C, respectively.
(4) And (3) testing cracking resistance and drying time: the negative electrode paste-coated copper foils provided in examples 1 to 4 and comparative examples 1 to 3 were put into an oven at 80 ℃ and baked until the moisture was less than 100 ppm. And taking out the pole piece to observe whether the surface of the pole piece cracks or not and recording the time required by drying.
The performance test results are shown in table 1:
TABLE 1
According to the data in the table 1, the dopa acid and the ricinoleic acid are introduced into the polyethyleneimine structure, when the prepared binder is used for a negative electrode plate, an organic solvent is not needed to be added, cracking resistance is achieved, the electrode plate is baked until the moisture content is below 100ppm for only 5-9 hours, the adhesive force with silicon base is strong, and the peel strength reaches 13.6-15N/m; when the negative pole piece containing the binder is applied to a lithium ion battery, the charge-discharge efficiency of the battery is improved, the first charge-discharge efficiency is up to 88-90%, the 3C rate discharge performance at room temperature is up to 98-99%, the capacity retention rate can still reach 92-94% after 500 cycles of cyclic charge-discharge, and the cycle performance is excellent.
From the embodiment 1 to the embodiment 4, it can be seen that after the unsaturated hydroxy fatty acid is added into the system, the drying time of the pole piece is short, the flexibility of the pole piece is improved, and meanwhile, the prepared battery has good electrochemical performance, especially the cycle performance of the battery is well improved, which indicates that the binder of the application can effectively improve the problem of electrochemical performance reduction caused by expansion of the silicon-based material in the charging and cycle processes. Comparing example 1 with example 4, it can be seen that the battery using the binder prepared according to the present invention has excellent electrochemical properties even though the binder is used in a relatively small amount (only 0.5% in example 4).
When the structure of the binder lacks unsaturated hydroxy fatty acid groups (comparative example 1), when the binder is applied to a negative pole piece, an organic solvent needs to be added to prevent cracking, the adhesive force is reduced, the peel strength is 12.7N/m, the drying rate of the pole piece is reduced more, and the charge-discharge efficiency and the cycle performance are reduced when the binder is applied to a lithium ion battery. When the binding agent is SBR/CMC binding agent, the binding agent is easy to crack when used for a negative pole piece, an organic solvent needs to be added, the drying speed is extremely low, the binding property is poor, and the charge-discharge efficiency and the cycle performance are low. The PVDF binder also has the problems of low drying rate, easy cracking, low charge-discharge efficiency and poor cycle performance when being used for a negative pole piece.
The applicant states that the invention is illustrated by the above examples of binders according to the invention and their preparation and use, but the invention is not limited to the above examples, i.e. it is not intended that the invention necessarily depends on the above examples for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (28)
1. The binder for the silicon-based negative electrode of the lithium ion battery is characterized by comprising modified polyethyleneimine; the modifier of the modified polyethyleneimine comprises a combination of dopa acid and unsaturated hydroxy fatty acid; the modified polyethyleneimine is obtained through a grafting reaction of polyethyleneimine, dopa acid and unsaturated hydroxy fatty acid.
2. The binder according to claim 1, wherein the unsaturated hydroxy fatty acid has 10 or more carbon atoms.
3. The binder of claim 2 wherein the unsaturated hydroxy fatty acid comprises any one or a combination of at least two of ricinoleic acid, hydroxypalmitoleic acid, 2-hydroxyoleic acid, 5-hydroxy-8-decaenoic acid, and 10-hydroxy-2-decenoic acid.
4. The binder of claim 1 wherein the polyethyleneimine is hyperbranched polyethyleneimine.
5. The binder as claimed in claim 4, wherein the amount of the tertiary amino group, the secondary amino group and the primary amino group in the polyethyleneimine is 1 (0.5-2) to (0.5-1.5).
6. The adhesive according to claim 4, wherein the weight average molecular weight of the polyethyleneimine is 10000 to 300000.
7. The adhesive according to claim 5, wherein the molar percentage of the primary amine groups is 25 to 35% based on 100% of the total amount of the amine groups in the polyethyleneimine.
8. A method of preparing the binder of any one of claims 1-7, wherein the method comprises method A or method B;
the method A comprises the following steps: carrying out grafting reaction on polyethyleneimine, dopa acid and unsaturated hydroxy fatty acid to obtain the binder;
the method B comprises the following steps: (1) performing grafting reaction on polyethyleneimine and dopa to obtain dopa acid modified polyethyleneimine; (2) and (2) carrying out grafting reaction on the dopa acid modified polyethyleneimine obtained in the step (1) and unsaturated hydroxy fatty acid to obtain the adhesive.
9. The process according to claim 8, wherein the reaction of the process A and the reaction of the step (1) are both carried out in the presence of an amidation agent.
10. The method of claim 9, wherein the amidation reagent comprises any one of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, O-benzotriazol-tetramethylurea hexafluorophosphate, 2- (7-azabenzotriazole) -N, N' -tetramethylurea hexafluorophosphate, or a combination of at least two thereof.
11. The method according to claim 8, wherein the amount of the dopamine is 0.5 to 1.5mol based on 1mol of the primary amine group in the polyethyleneimine.
12. The method according to claim 8, wherein the amount of the unsaturated hydroxy fatty acid is 0.5 to 1.5mol based on 1mol of the primary amine group in the polyethyleneimine.
13. The process according to claim 8, wherein the reaction of the process A is carried out in the presence of a solvent.
14. The method of claim 13, wherein the solvent comprises methanol and/or ethanol.
15. The process according to claim 8, wherein the reaction of step (1) is carried out in the presence of a solvent M.
16. The method according to claim 15, wherein the solvent M is any one of water, methanol, or ethanol, or a combination of at least two thereof.
17. The method according to claim 8, wherein the reaction temperature of the method A is 20 to 40 ℃.
18. The preparation method according to claim 8, wherein the reaction time of the method A is 6-12 h.
19. The method according to claim 8, wherein the reaction of step (2) is carried out in the presence of a solvent N.
20. The method according to claim 19, wherein the solvent N is any one of methanol, ethanol, diethyl ether, acetone or ethyl acetate or a combination of at least two of them.
21. The method according to claim 8, wherein the reaction temperature of the step (1) and the reaction temperature of the step (2) are both 20 to 40 ℃.
22. The preparation method according to claim 8, wherein the total time of the reaction of the step (1) and the step (2) is 8-15 h.
23. The method according to claim 8, wherein the reaction of the method A and the reaction of the step (2) comprise separation and purification after the reaction is completed.
24. The method of claim 23, wherein the separation and purification method comprises any one of dialysis, coprecipitation, and chromatography.
25. A lithium ion battery negative electrode material, characterized in that the lithium ion battery negative electrode material comprises a negative electrode active material, a conductive agent, and the binder according to any one of claims 1 to 7; the negative active material is a silicon-based active material;
the mass percentage of a negative active substance in the lithium ion battery negative material is 94-98%;
the mass percentage of the conductive agent in the lithium ion battery negative electrode material is 1-5%;
the mass percentage of the binder in the lithium ion battery negative electrode material is 0.5-1.5%.
26. The lithium ion battery anode material of claim 25, wherein the silicon-based active material comprises any one of elemental silicon, a silicon alloy, a silicon carbon compound, or a silicon oxygen compound, or a combination of at least two thereof.
27. The lithium ion battery negative electrode material of claim 25, wherein the conductive agent comprises one or more of acetylene black, ketjen black, carbon fiber, superconducting carbon black, carbon nanotubes, and graphene.
28. A lithium ion battery is characterized by comprising a negative pole piece, a positive pole piece, a diaphragm and electrolyte; the diaphragm is arranged between the positive pole piece and the negative pole piece; the negative electrode sheet comprises the lithium ion battery negative electrode material of any one of claims 25-27.
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| CN202110860499.3A CN113571709B (en) | 2021-07-28 | 2021-07-28 | Adhesive, preparation method and application thereof |
| PCT/CN2022/100420 WO2023005520A1 (en) | 2021-07-28 | 2022-06-22 | Binder, preparation method therefor, and use thereof |
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| CN114770687B (en) * | 2022-04-08 | 2023-03-28 | 山东摩登港家具有限公司 | High-temperature shaping method for solid wood board |
| CN117801735A (en) * | 2024-03-01 | 2024-04-02 | 广州昊毅新材料科技股份有限公司 | Low-temperature pressure-sensitive lithium battery negative electrode adhesive material and preparation method thereof |
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| EP2279299A1 (en) * | 2008-04-15 | 2011-02-02 | SAPPI Netherlands Services B.V. | Coating formulation for an offset paper and paper coated therewith |
| US11581543B2 (en) * | 2017-06-07 | 2023-02-14 | Kuraray Co., Ltd. | Binder composition for non-aqueous electrolyte batteries, and binder aqueous solution for non-aqueous electrolyte batteries, slurry composition for non-aqueous electrolyte batteries, electrode for non-aqueous electrolyte batteries and non aqueous electrolyte battery each utilizing same |
| CN111883774A (en) * | 2020-08-04 | 2020-11-03 | 中国地质大学（武汉） | Water-based binder for lithium ion battery, electrode plate and preparation method thereof |
| CN113571709B (en) * | 2021-07-28 | 2022-07-19 | 苏州清陶新能源科技有限公司 | Adhesive, preparation method and application thereof |
| CN113594465B (en) * | 2021-08-02 | 2023-02-28 | 苏州清陶新能源科技有限公司 | Negative electrode binder and preparation method and application thereof |
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