WO2023005520A1 - 一种粘结剂及其制备方法和应用 - Google Patents

一种粘结剂及其制备方法和应用 Download PDF

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WO2023005520A1
WO2023005520A1 PCT/CN2022/100420 CN2022100420W WO2023005520A1 WO 2023005520 A1 WO2023005520 A1 WO 2023005520A1 CN 2022100420 W CN2022100420 W CN 2022100420W WO 2023005520 A1 WO2023005520 A1 WO 2023005520A1
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binder
polyethyleneimine
negative electrode
preparation
reaction
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PCT/CN2022/100420
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English (en)
French (fr)
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李峥
冯玉川
沈志鹏
陈凯
何泓材
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苏州清陶新能源科技有限公司
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Publication of WO2023005520A1 publication Critical patent/WO2023005520A1/zh

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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
    • 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
    • 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
    • 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

Definitions

  • silicon negative electrode has a high specific capacity for lithium intercalation and deintercalation
  • silicon brings serious expansion problems during charging and subsequent cycles.
  • the volume expansion after lithium intercalation is very large, and the volume will expand reversibly during the cycle. shrink.
  • Huge volume expansion and contraction will lead to a series of problems during the use of silicon materials, such as silicon particle breakage, material pulverization, falling off from the pole piece, and the new exposed surface will generate a solid electrolyte film (SEI film), which consumes the battery.
  • SEI film solid electrolyte film
  • the traditional method chooses to increase the amount of binder in the negative electrode sheet to enhance the bonding strength between the active material and the current collector to resist the expansion of the active material during charging and cycling.
  • the stress generated at the interface between them will inevitably lead to a decrease in the amount of active materials in the system, resulting in a decrease in the energy density of the battery, and on the other hand, it will also cause a decrease in the kinetic performance of the pole piece.
  • CN111509223A discloses a lithium ion battery positive electrode binder and a lithium ion battery positive electrode slurry, wherein the positive electrode binder comprises high molecular weight PVDF and medium molecular weight PVDF, and the weight ratio of high molecular weight PVDF and medium molecular weight PVDF is (6 ⁇ 8): (2 ⁇ 4); the positive electrode slurry of the lithium-ion battery includes a solid component and a solvent, and the solid component includes the above-mentioned positive electrode binder.
  • the binder of this application can overcome the physical gel problem of high molecular weight PVDF binder in the nano-lithium iron phosphate system, the slurry prepared by it has good stability, can meet the needs of production and coating processing, and the amount of PVDF is low , to further increase the proportion of lithium iron phosphate material, thereby increasing the energy density of the single cell.
  • PVDF is relatively rigid, and is combined with silicon particles through weak van der Waals force, making it difficult to maintain the volume change of silicon-based negative electrodes under long-term cycles.
  • CN110890545A discloses a PEDOT:PSS/CMC composite binder and its preparation method and application.
  • the composite binder includes cross-linked poly-3,4-ethylenedioxythiophene: polystyrene sulfonate/hydroxymethyl cellulose (PEDOT:PSS/CMC); its preparation raw materials include a mass ratio of (0.1 ⁇ 10): PEDOT:PSS and CMC of 1.
  • the functional groups in the binder can effectively bond with silicon, thereby improving the binding force with the silicon-based material.
  • CMC has high rigidity and low elongation at break (5% to 8%), and the rigid polymer binder cannot completely eliminate stress, so cracks tend to occur during repeated cycles, resulting in significant attenuation of battery specific capacity; and CMC During the coating and drying process of the silicon negative electrode as a binder, it is easy to cause cracking of the pole piece.
  • an organic solvent such as NMP will be added during the coating process.
  • the residue of the organic solvent will react with the electrolyte and affect the battery life. Performance has a certain impact; the production process of lithium batteries has key requirements for moisture control.
  • the baking process of pole pieces with CMC-SBR as binder takes a long time, which affects production capacity and consumes high energy.
  • CN112310403A synthesizes a novel silicon-oxygen negative electrode binder by reacting dopamine and polyethyleneimine. Introduce catechol groups into the backbone of polyethyleneimine to generate a polyamine-based polymer binder containing catechol groups, which can form strong hydrogen bonds or covalent bonds with silicon particles , can inhibit the volume expansion of the silicon negative electrode, significantly improve the rate performance and cycle performance of the silicon-oxygen negative electrode, and prolong the service life of the lithium-ion battery.
  • the pole pieces are prone to cracking during the drying process of the pole pieces, and the drying time required is long, which is not conducive to improving production efficiency.
  • the embodiment of the present application provides a binder and its preparation method and application.
  • the prepared binder is combined with silicon It has strong cohesive force, and it can improve the drying rate, crack resistance, rate performance and cycle performance of the pole piece when applied to the negative pole piece of lithium ion battery.
  • polyamine-based polymers containing catechol groups and unsaturated hydroxy fatty acid groups are generated binder.
  • polyethyleneimine is a rich amine-based polymer.
  • a catechol group is introduced into its structure, adding more new activities.
  • the hydroxyl group adds more active sites, which can form more hydrogen bonds or covalent bonds with silicon particles, thereby improving the adhesion to silicon and enhancing the adhesion between the current collector and the silicon negative electrode It improves the rate performance and stability of lithium-ion batteries;
  • the hyperbranched structure of polyethyleneimine has high elasticity, and the two groups introduced in its structure can further undergo polymerization reactions to improve its own deformation resistance Ability, which can absorb the expansion and contraction of silicon materials through stretching and stretching, can buffer the volume change of silicon-based particles, is beneficial to the integrity of the negative silicon electrode and the integrity of the surface SEI film, and can well solve the problem of the anode sheet in During the charging process of the battery, the problem of active material swelling and separation from the current collector is easy to occur; the hydrophobic group with a long unsaturated hydroxy fatty acid group has excellent flexibility and water resistance, and the introduction of this structure can improve the air drying process of the pole piece.
  • the ability to resist water droplets can increase the drying rate of the pole piece, increase the moisture resistance of the pole piece, and solve the problem of easy cracking of the silicon-oxygen negative electrode during the coating process.
  • the molecular structure of unsaturated hydroxy fatty acid contains active double bonds, carboxyl groups and hydroxyl groups, which can be cross-linked with dopamine to form a three-dimensional network structure, which can better withstand the volume change of silicon materials while enhancing the viscosity of the adhesive. .
  • the modified polyethyleneimine is obtained through grafting reaction of polyethyleneimine, dopamine and unsaturated hydroxy fatty acid.
  • the number of carbon atoms of the unsaturated hydroxy fatty acid is greater than or equal to 10; the unsaturated hydroxy fatty acid includes a hydroxyl group, a carbon-carbon double bond and a carboxyl group.
  • the unsaturated hydroxy fatty acid includes any one of ricinoleic acid, hydroxypalmitoleic acid, 2-hydroxyoleic acid, 5-hydroxyl-8-decenoic acid, and 10-hydroxyl-2-decenoic acid one or a combination of at least two.
  • the polyethyleneimine is hyperbranched polyethyleneimine. Compared with linear polyethyleneimine, hyperbranched polyethyleneimine is more suitable for the expanded silicon-based anode system.
  • the ratio of the amount of tertiary amino groups, secondary amino groups, and primary amino groups in the polyethyleneimine is 1:(0.5 ⁇ 2):(0.5 ⁇ 1.5), for example, it can be 1:0.8: 0.8, 1:1:0.8, 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 etc.
  • the molar percentage of the primary amino groups is 25-35%, for example, it can be 27%, 27.5%, 28%, 28.5% %, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33% or 34%, and specific point values between the above point values, limited by space and for the sake of brevity It is considered that the application is not intended to be an exhaustive recitation of the specific point values included in the stated ranges.
  • the method A includes: reacting polyethyleneimine, dopamine and unsaturated hydroxy fatty acid to obtain the binder;
  • the method B includes: (1) reacting polyethyleneimine with dopamine to obtain dopacic-modified polyethyleneimine; (2) combining the dopacic-modified polyethyleneimine obtained in step (1) with The unsaturated hydroxy fatty acid reacts to obtain the binder.
  • both the reaction of the method A and the reaction of the step (1) are carried out in the presence of an amidating reagent.
  • the amidating reagent includes 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, N-hydroxysuccinimide, O-benzotriazole-tetramethyluronium hexafluorophosphate, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate Any one or a combination of at least two.
  • the pH of the reaction of the method A and the reaction of the step (1) is determined according to the type of the amidation reagent, and this technical means is a conventional technical means in the field.
  • the substance for adjusting the pH includes any one or a combination of at least two of dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid, and this technical means is a conventional technical means in the field.
  • the amount of dopamine used is 0.5-1.5 mol, for example, 0.55 mol, 0.7 mol, 0.85 mol, 1.0 mol, 1.25 mol, 1.33mol or 1.45mol, and the specific point values between the above-mentioned point values, due to space limitation and for the sake of simplicity, this application will not exhaustively list the specific point values included in the range.
  • the amount of the unsaturated hydroxy fatty acid is 0.5-1.5 mol, such as 0.55 mol, 0.7 mol, 0.85 mol, 1.0 mol, 1.25 mol , 1.33mol or 1.45mol, and the specific point values between the above-mentioned point values, due to space limitations and for the sake of brevity, this application does not exhaustively list the specific point values included in the range.
  • reaction of method A is carried out in the presence of a solvent.
  • the solvent comprises methanol and/or ethanol.
  • the reaction temperature of the method A is 20-40°C, for example, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C or 39°C,
  • the specific point values between the above point values due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values included in the range.
  • the reaction time of the method A is 6-12 hours, for example, it can be 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 the specific point values between the above point values, due to space limitations and for the sake of simplicity, this application will not list them exhaustively The specific point value that the range includes.
  • reaction in step (2) is carried out in the presence of solvent N.
  • the solvent N is any one or a combination of at least two of methanol, ethanol, ether, acetone or ethyl acetate.
  • the reaction temperatures of the step (1) and step (2) are both 20°C to 40°C, such as 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C °C, 38 °C or 39 °C, and the specific point values between the above point values, due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values included in the range.
  • the total reaction time of step (1) and step (2) is 8-15h, for example, it can be 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h or 14.5h, and the specific point values between the above-mentioned point values, due to space limitations and for the sake of simplicity, this application will not exhaustively list the specific point values included in the range.
  • the mass percentage of the conductive agent in the lithium-ion battery negative electrode material is 1-3%, such as 1.1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8% Or 2.9%, and the specific point values between the above-mentioned point values, due to space limitations and for the sake of simplicity, this application will not exhaustively list the specific point values included in the range.
  • 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%, as well as specific point values between the above-mentioned point values, due to space limitations and for the sake of brevity, this application does not exhaustively list the specific point values included in the range.
  • the silicon-based active material includes any one or a combination of at least two of elemental silicon, silicon alloys, silicon-carbon compounds or silicon-oxygen compounds.
  • the conductive agent in the lithium-ion battery negative electrode material includes one or more of acetylene black, Ketjen black, carbon fiber, superconducting carbon black, carbon nanotubes, and graphene.
  • an embodiment of the present application provides a lithium-ion battery
  • the lithium-ion battery includes a negative pole piece, a positive pole piece, a diaphragm, and an electrolyte; the diaphragm is arranged between the positive pole piece and the negative pole piece;
  • the negative electrode sheet includes the lithium ion battery negative electrode material as described in the third aspect.
  • unsaturated hydroxy fatty acid and dopacic acid are used to graft and modify polyethyleneimine, and catechol groups and unsaturated hydroxy fatty acid groups are introduced into the structure of polyethyleneimine, so that the prepared The bonding force between the binder and silicon is strong, and the peeling strength reaches 15N/m; when the binder is used for the negative pole piece, the drying rate of the pole piece is improved, and it only needs 6h, and no cracking during coating; the application of the negative electrode sheet in lithium-ion batteries can improve the charge-discharge cycle performance of the battery, and the capacity retention rate of the battery is as high as 94% after 500 cycles of charge-discharge.
  • binding agent is the polymer of dopacic acid and ricinoleic acid modified graft polyethyleneimine;
  • the modification of described modified polyethyleneimine includes a combination of dopamine and ricinoleic acid.
  • the preparation method of the binder comprises the following steps: mixing 0.5 mol of dopacic acid, 0.5 mol of ricinoleic acid, polyethyleneimine, amidation reagent and methanol, reacting at room temperature for 9 hours, and purifying by dialysis to obtain the binder.
  • Mw 300000
  • the molar ratio of the total number of amino groups to dopamine 2:1, wherein the amount of tertiary amino groups, secondary amino groups, and primary amino groups in polyethyleneimine The ratio is 1:1:1.
  • the mass ratio of methanol to dopacic acid is 10:1; the amidation reagent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride dopacic acid (EDCI) and N- The combination of hydroxysuccinimide (NHS), the mass ratio of dopamine, EDCI and NHS is 1:1.1:1.2.
  • This embodiment also provides a lithium-ion battery and a preparation method thereof, wherein the lithium-ion battery includes a negative pole piece, a positive pole piece, a diaphragm, and an electrolyte; the diaphragm is arranged between the positive pole piece and the negative pole piece;
  • the negative electrode sheet includes a silicon-based active material, a conductive agent, and the binder provided in this embodiment.
  • the silicon-based active material is simple silicon, and the conductive agent is superconducting carbon black.
  • the silicon-based active material, conductive agent, and binder The weight ratio is 98:1:1.
  • the preparation method of this lithium ion battery comprises the steps:
  • Diaphragm selection select the one with a thickness of 15 ⁇ m
  • the preparation method of the binder comprises the following steps: mixing 0.5 mol of dopamine, polyethyleneimine, amidating agent and water, adjusting the pH of the solution to 5.5, stirring for 20 minutes, and reacting at room temperature for 5 hours to obtain dopacic acid modified polymer Polymers of ethyleneimine.
  • the amidation reagent is a combination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride dopamine hydrochloride (EDCI) and N-hydroxysuccinimide (NHS);
  • EDCI 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride dopamine hydrochloride
  • NHS N-hydroxysuccinimide
  • This embodiment provides a lithium-ion battery and a preparation method thereof.
  • the difference between the lithium-ion battery and Example 1 is that the binder in the negative electrode sheet is the binder provided in this example, and the conductive agent is The weight ratio of acetylene black, silicon-based active material, conductive agent and binder is 96:2.5:1.5.
  • the difference between the preparation method of the lithium-ion battery and Example 1 is that the weight ratio of silicon-based active material, conductive agent, and binder is 96:2.5:1.5 when preparing the negative electrode sheet, and acetylene black is used as the conductive agent.
  • This embodiment provides a binder and a preparation method thereof, the binder is a polymer of dopamine and hydroxypalmitoleic acid-modified grafted polyethyleneimine; the modification of the modified polyethyleneimine Sexual agents include a combination of dopamine and hydroxypalmitoleic acid;
  • HATU O-benzotriazole-tetramethyluronium hexafluorophosphate
  • NHS N-hydroxysuccinimide
  • This embodiment provides a lithium-ion battery and a preparation method thereof.
  • the difference between the lithium-ion battery and Embodiment 1 is that the binder in the negative electrode sheet is the binder provided in this embodiment, and the conductive agent is The weight ratio of Ketjen black, silicon-based active material, conductive agent and binder is 97:2:1.
  • the difference between the preparation method of the lithium-ion battery and Example 1 is that the conductive agent is Ketjen Black when preparing the negative electrode sheet, and the weight ratio of the silicon-based active material, conductive agent, and binder is 97:2:1 .
  • This embodiment provides an adhesive and its preparation method, which are the same as those in Embodiment 1.
  • This embodiment provides a lithium ion battery and a preparation method thereof.
  • the difference between the lithium ion battery and the embodiment 1 is that the weight ratio of silicon-based active material, conductive agent, and binder is 97:2.5:0.5.
  • the difference between the preparation method of the lithium-ion battery and Example 1 is that the weight ratio of silicon-based active material, conductive agent, and binder is 97:2.5:0.5 when preparing the negative electrode sheet.
  • This comparative example provides a kind of binding agent and preparation method thereof, described binding agent is the polymer binding agent obtained by dopacic acid modified grafting polyethyleneimine. Its preparation method is the same as that of Example 1, except that unsaturated hydroxy fatty acid is not added to the preparation system.
  • This comparative example provides a lithium-ion battery and a preparation method thereof, which differ from Example 1 in that the binder in the negative electrode sheet is an SBR/CMC binder, and the preparation method and implementation of the lithium-ion battery Example 1 is the same.
  • This comparative example provides a lithium-ion battery and a preparation method thereof, which differ from Example 1 in that the binder in the negative electrode sheet is a PVDF binder, and the preparation method of the lithium-ion battery is the same as in Example 1. The difference is that N-methylpyrrolidone (NMP) is used instead of water.
  • NMP N-methylpyrrolidone
  • the present application introduces dopamine and ricinoleic acid into the polyethyleneimine structure, and when the binder prepared is used in the negative electrode sheet, no organic solvent is needed to resist cracking, and the electrode sheet It only takes 5-9 hours to bake until the moisture is below 100ppm, and the adhesion to the silicon base is strong, and the peel strength reaches 13.6-15N/m; when the negative electrode sheet containing this binder is applied to a lithium-ion battery, The charge and discharge efficiency of the battery is improved, the first charge and discharge efficiency is as high as 88-90%, the 3C rate discharge performance at room temperature reaches 98-99%, and the capacity retention rate can still reach 92-94% after 500 cycles of cycle charge and discharge cycles. Excellent performance.
  • Example 1 to Example 4 From Example 1 to Example 4, it can be seen that after adding unsaturated hydroxy fatty acid to the system, the drying time of the pole piece is shorter, the flexibility of the pole piece is improved, and the prepared batteries all have good electrical properties.
  • the chemical performance, especially the cycle performance of the battery, is well improved, which shows that the binder of the present application can effectively improve the problem of electrochemical performance degradation caused by the expansion of silicon-based materials during charging and cycling. Comparing Example 1 and Example 4, it can be seen that the battery using the binder prepared by the present application has excellent electrochemical performance even if the amount of binder used is relatively small (only 0.5% in Example 4).
  • the structure of the binder lacks unsaturated hydroxy fatty acid groups (comparative example 1)
  • it is necessary to add an organic solvent to prevent cracking when it is applied to the negative electrode sheet, it is necessary to add an organic solvent to prevent cracking, the adhesive force decreases, and the peel strength is 12.7N/m.
  • the drying rate of the pole piece drops a lot, and the charge-discharge efficiency and cycle performance decrease when it is applied to a lithium-ion battery.
  • the binder is an SBR/CMC-based binder, it is easy to crack when used in the negative electrode sheet, and organic solvents need to be added, the drying rate is extremely low, the adhesion is poor, and the charge and discharge efficiency and cycle performance are low.
  • PVDF binder also has the problems of low drying rate, easy cracking, low charge and discharge efficiency and poor cycle performance when used in negative electrode sheets.

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Abstract

本文公布一种粘结剂及其制备方法和应用，所述粘结剂包括改性聚乙烯亚胺；所述改性聚乙烯亚胺的改性剂包括多巴酸和不饱和羟基脂肪酸的组合。该粘结剂的制备方法包括方法A或方法B；所述方法A包括：将聚乙烯亚胺、多巴酸以及不饱和羟基脂肪酸进行反应，得到所述粘结剂；所述方法B包括：(1)聚乙烯亚胺与多巴酸反应，得到多巴酸改性聚乙烯亚胺；(2)将步骤(1)得到的多巴酸改性聚乙烯亚胺与不饱和羟基脂肪酸反应，得到所述粘结剂。该粘结剂柔韧性好、与硅的粘结能力强，应用于锂离子电池负极极片时可提高极片的烘干速率、耐开裂性能、倍率性能和循环性能。

Description

一种粘结剂及其制备方法和应用 技术领域
本申请实施例涉及锂离子电池负极材料技术领域，例如一种粘结剂及其制备方法和应用。
背景技术
近年来，随着大众对环保的重视，锂电池作为新能源行业的佼佼者，被广泛应用于各种电子产品、电动汽车以及其他储能设备上。因此，人们对锂电池的能量密度的要求也越来越高，除阴极选用三元材料外，所使用的阳极的克容量也必须提高，具有较高克容量的阳极材料当属石墨材料和硅材料，硅作为可以与锂形成合金的一种材料，具有较低的脱锂平台，每个硅原子可以与4.4个锂原子形成合金，具有超高的理论比容量，比石墨负极高出一个数量级。虽然硅负极具有很高的脱嵌锂比容量，但是硅在充电及之后的循环过程中带来较为严重的膨胀问题，嵌锂之后的体积膨胀非常巨大，并且在循环过程中体积会可逆的膨胀收缩。巨大的体积膨胀收缩会导致硅材料在使用过程中一系列问题，例如导致硅颗粒破裂，材料粉化，从极片上脱落，新的裸露的表面会生成固态电解质膜(SEI膜)，消耗电池中有限的电解液和正极中的锂。
在电池中，粘结剂是维持电极结构的关键，粘结剂的选择对于增强硅基电极结构的稳定性实现长期循环具有更加重要的意义。粘结力弱的粘结剂无法保持硅活性材料之间的电接触活性，会导致电极首效偏低和后续比容量衰减，影响高能量密度电池性能的实现，粘结力弱的粘结剂也无法阻止在循环过程中由于硅材料的膨胀导致的极片脱模，从而影响电池的安全性和可靠性。
为了解决该问题，传统的方法选择加大负极极片中粘结剂的量来增强活性物质与集流体之间的粘结强度以抵抗充电及循环过程中活性材料的膨胀在活性材料与集流体之间的界面产生的应力，但势必会导致体系中活性物质的量下降，从而导致电池的能量密度减少，另一方面也会造成极片动力学性能的下降。
传统粘结剂中，常采用PVDF或CMC作为粘结剂。例如，CN111509223A公开了一种锂离子电池正极粘结剂和锂离子电池正极浆料，其中，正极粘结剂包含高分子量PVDF和中分子量PVDF，高分子量PVDF和中分子量PVDF的 重量比为(6～8):(2～4)；锂离子电池正极浆料包含固体成分和溶剂，固体成分包含上述正极粘结剂。该申请的粘结剂能克服高分子量PVDF粘结剂在纳米磷酸铁锂体系中的物理凝胶问题，其配制的浆料稳定性好，能够满足生产以及涂布加工的需求，而且PVDF用量低，进一步提高了磷酸铁锂材料的占比，从而提高了单体电芯的能量密度。但是PVDF刚性较大，通过较弱的范德华力与硅粒子结合，难以维持硅基负极长久循环下的体积变化。
此外，出于对环保的要求，粘结剂的溶剂最好选择安全、无毒的试剂，目前最好选择水作为粘结剂的试剂。CN110890545A公开了一种PEDOT:PSS/CMC复合粘结剂及其制备方法和应用。该复合粘结剂包括交联状态的聚3,4-乙烯二氧噻吩:聚苯乙烯磺酸盐/羟甲基纤维素(PEDOT:PSS/CMC)；其制备原料包括质量比为(0.1～10):1的PEDOT:PSS和CMC。用上述复合粘结剂制备锂离子电池硅基负极时，粘结剂中的官能团能与硅发生有效的键连，从而提高与硅基材料的结合力。虽然以CMC为粘结剂的硅负极的电极结构的完整性增强，但是也存在诸多问题。CMC刚性大、断裂伸长率低(5％～8％)，刚性聚合物粘结剂不能完全消除应力，因此在重复的循环过程中往往会产生裂缝，导致电池比容量衰减明显；而且以CMC为粘结剂的硅负极在涂布烘干过程中，容易造成极片开裂，为了改善开裂，涂布过程中会加入NMP等有机溶剂，有机溶剂的残留会与电解液发生反应从而对电池的性能产生一定的影响；锂电池的制作过程中对水分控制有着关键要求，为了控制水分以CMC-SBR为粘结剂的极片烘烤过程中耗时较久，影响产能且耗能较高。
为了改善传统的采用刚性大的聚合物做粘结剂所带来的问题，CN112310403A以多巴酸和聚乙烯亚胺反应合成新型硅氧负极粘结剂。在聚乙烯亚胺的骨架中引入儿茶酚基团，生成含有儿茶酚基团的多胺基的聚合物粘结剂，该粘结剂可以和硅颗粒形成强的氢键或共价键，可以抑制硅负极的体积膨胀，明显提高硅氧负极的倍率性能和循环性能，延长锂离子电池的使用寿命。但是由于使用水性体系，在极片烘干过程中，极片容易开裂，所需烘干时间较长，不利于提高生产效率。
因此，开发一种柔韧性好、与硅的粘结力强、提升极片的耐开裂以及烘干速率、提高负极的倍率性能和循环性能的负极粘结剂具有重要的实际意义。
发明内容
以下是对本文详细描述的主题的概述。本概述并非是为了限制权利要求的保护范围。
本申请实施例提供一种粘结剂及其制备方法和应用，通过将多巴酸以及不饱和羟基脂肪酸接枝到聚乙烯亚胺的分子结构中，从而使得制备出的粘结剂，与硅有较强的粘结力，应用于锂离子电池负极极片时可提高极片的烘干速率、耐开裂性能、倍率性能和循环性能。
第一方面，本申请实施例提供一种粘结剂，所述粘结剂包括改性聚乙烯亚胺；所述改性聚乙烯亚胺的改性剂包括多巴酸和不饱和羟基脂肪酸的组合。
本申请实施例中，通过在聚乙烯亚胺的骨架中引入儿茶酚基团和不饱和羟基脂肪酸基团，生成含有儿茶酚基团、不饱和羟基脂肪酸基团的多胺基的聚合物粘结剂。该粘结剂中，聚乙烯亚胺为富胺基聚合物，其和多巴酸、不饱和羟基脂肪酸反应后，在其结构中引入了儿茶酚基团，增加了更多的新的活性基团羟基，增加了更多的活性位点，可以和硅颗粒形成更多的氢键或共价键，从而提高对硅的粘结力，并且增强了集流体和硅负极之间的粘附性，提升了锂离子电池的倍率性能和稳定性；聚乙烯亚胺的超支化结构，具有较高的弹性，其结构中引入的两个基团可以进一步发生聚合反应而提高其自身的抗变形能力，其能通过伸缩延展来吸收硅材料的膨胀和收缩，可以缓冲硅基粒子的体积变化，有利于负极硅电极的完整性和表面SEI膜的完整性，可以很好地解决阳极极片在电池的充电过程中容易发生的活性材料膨胀脱离集流体的问题；不饱和羟基脂肪酸基团较长的疏水基团具有优异的柔韧性和耐水性，该结构的引入可以提高极片空气干燥过程中对水滴的抗御能力，可以提升极片的烘干速率，并且增加极片的耐湿性，并可以解决硅氧负极在涂布过程中的易开裂问题。而且不饱和羟基脂肪酸的分子结构中含有活性的双键、羧基和羟基，与多巴酸的发生交联形成三维网络结构，增强粘结剂粘性的同时，可以更好地承受硅材料的体积变换。
优选地，所述改性聚乙烯亚胺通过聚乙烯亚胺、多巴酸和不饱和羟基脂肪酸的接枝反应得到。
本申请实施例中，所述不饱和羟基脂肪酸的碳原子数大于等于10；所述不饱和羟基脂肪酸包含羟基、碳碳双键和羧基。
优选地，所述不饱和羟基脂肪酸包括蓖麻油酸、羟基棕榈油酸、2-羟基油酸、 5-羟基-8-十-碳烯酸、10-羟基-2-癸烯酸中的任意一种或至少两种的组合。
本申请中，所述聚乙烯亚胺为超支化聚乙烯亚胺。超支化聚乙烯亚胺与线性聚乙烯亚胺相比，更加适合膨胀的硅基负极体系。
本申请中，所述聚乙烯亚胺中叔胺基、仲胺基、伯胺基的物质的量的比为1:(0.5～2):(0.5～1.5)，例如可以为1:0.8:0.8、1:1:0.8、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或1:1:0.8等。
优选地，所述聚乙烯亚胺的重均分子量为10000～300000，例如可以为20000、50000、70000、100000、150000、170000、200000、250000、270000或290000，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，以所述聚乙烯亚胺中的胺基总量为100％计，所述伯胺基的摩尔百分含量为25～35％，例如可以为27％、27.5％、28％、28.5％、29％、29.5％、30％、30.5％、31％、31.5％、32％、32.5％、33％或34％，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
第二方面，本申请实施例提供一种如第一方面所述的粘结剂的制备方法，所述制备方法包括方法A或方法B；
所述方法A包括：将聚乙烯亚胺、多巴酸以及不饱和羟基脂肪酸进行反应，得到所述粘结剂；
所述方法B包括：(1)聚乙烯亚胺与多巴酸反应，得到多巴酸改性聚乙烯亚胺；(2)将步骤(1)得到的多巴酸改性聚乙烯亚胺与不饱和羟基脂肪酸反应，得到所述粘结剂。
本申请中，所述方法A的反应和所述步骤(1)的反应均在酰胺化试剂存在下进行。
优选地，所述酰胺化试剂包括1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐、N-羟基丁二酰亚胺、N-羟基琥珀酰亚胺、O-苯并三氮唑-四甲基脲六氟磷酸盐、2-(7-氮杂苯并三氮唑)-N,N,N',N'-四甲基脲六氟磷酸盐中的任意一种或至少两种的组合。
优选地，所述方法A的反应和所述步骤(1)的反应的PH根据所述酰胺化试剂的种类确定，该技术手段为本领域常规技术手段。
优选地，调节所述PH的物质包括稀盐酸、稀硫酸或稀硝酸中的任意一种或至少两种的组合，该技术手段为本领域常规技术手段。
优选地，以所述聚乙烯亚胺中的伯胺基为1mol计，所述多巴酸的用量为0.5～1.5mol，例如可以为0.55mol、0.7mol、0.85mol、1.0mol、1.25mol、1.33mol或1.45mol，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，以所述聚乙烯亚胺中的伯胺基为1mol计，所述不饱和羟基脂肪酸的用量为0.5～1.5mol，例如可以为0.55mol、0.7mol、0.85mol、1.0mol、1.25mol、1.33mol或1.45mol，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述方法A的反应在溶剂存在下进行。
优选地，所述溶剂包括甲醇和/或乙醇。
优选地，所述步骤(1)的反应在溶剂M存在下反应。
优选地，所述溶剂M为水、甲醇或乙醇中的任意一种或至少两种的组合。
优选地，所述方法A的反应的温度为20～40℃，例如可以为22℃、24℃、26℃、28℃、30℃、32℃、34℃、36℃、38℃或39℃，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述方法A的反应的时间为6～12h，例如可以为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或11.9h，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述步骤(2)的反应在溶剂N存在下反应。
优选地，所述溶剂N为甲醇、乙醇、乙醚、丙酮或乙酸乙酯中的任意一种或至少两种的组合。
优选地，所述步骤(1)和步骤(2)的反应的温度均为20～40℃，例如可以为22℃、24℃、26℃、28℃、30℃、32℃、34℃、36℃、38℃或39℃，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述步骤(1)和步骤(2)的反应的总时间为8～15h，例如可以 为8.5h、9h、9.5h、10h、10.5h、11h、11.5h、12h、12.5h、13h、13.5h、14h或14.5h，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述方法A的反应和所述步骤(2)的反应结束后均包括分离提纯。
优选地，所述分离提纯的方法包括透析法、共沉淀法或层析法中的任意一种。
第三方面，本申请实施例提供一种锂离子电池负极材料，所述锂离子电池负极材料包括负极活性物质、导电剂以及如第一方面所述的粘结剂；所述负极活性物质为硅基活性物质。
优选地，所述锂离子电池负极材料中负极活性物质的质量百分含量为94～98％，例如可以为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％或97.9％，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述锂离子电池负极材料中导电剂的质量百分含量为1～3％，如可以为1.1％、1.2％、1.5％、1.8％、2％、2.2％、2.5％、2.8％或2.9％，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述锂离子电池负极材料中粘结剂的质量百分含量为0.5～1.5％，如可以为0.6％、0.7％、0.8％、0.9％、1％、1.1％、1.2％、1.3％或1.4％，以及上述点值之间的具体点值，限于篇幅及出于简明的考虑，本申请不再穷尽列举所述范围包括的具体点值。
优选地，所述硅基活性物质包括单质硅、硅合金、硅碳化合物或硅氧化合物中的任意一种或至少两种的组合。
优选地，所述锂离子电池负极材料中导电剂包括乙炔黑、科琴黑、碳纤维、超导炭黑、碳纳米管、石墨烯中的一种或几种。
第四方面，本申请实施例提供一种锂离子电池，所述锂离子电池包括负极极片、正极极片、隔膜以及电解液；所述隔膜设置于正极极片和负极极片之间；所述负极极片包括如第三方面所述的锂离子电池负极材料。
相对于相关技术，本申请实施例具有以下有益效果：
本申请实施例采用不饱和羟基脂肪酸和多巴酸对聚乙烯亚胺进行接枝改性，将儿茶酚基团以及不饱和羟基脂肪酸基团引入到聚乙烯亚胺结构中，使得制备出的粘结剂与硅的粘结力较强，剥离强度达到15N/m；该粘结剂用于负极极片时，极片的烘干速率得到提高，极片烘烤至水分为100ppm时仅需6h，且涂布时不开裂；该负极极片应用于锂离子电池中可以提高电池的充放电循环性能，在电池充放电500周后，电池的容量保持率高达94％。
在阅读并理解了详细描述后，可以明白其他方面。
具体实施方式
下面通过具体实施方式来进一步说明本申请的技术方案。本领域技术人员应该明了，所述实施例仅仅是帮助理解本申请，不应视为对本申请的具体限制。
实施例1
本实施例提供一种粘结剂及其制备方法，所述粘结剂为多巴酸和蓖麻油酸改性接枝聚乙烯亚胺的聚合物；所述改性聚乙烯亚胺的改性剂包括多巴酸和蓖麻油酸的组合。
该粘结剂的制备方法包括如下：将0.5mol的多巴酸和0.5mol的蓖麻油酸及聚乙烯亚胺、酰胺化试剂与甲醇混合，室温下反应9h，通过透析法提纯，得到所述粘结剂。其中，按胺基总数与多巴酸摩尔比＝2:1加入聚乙烯亚胺(Mw＝300000)，其中聚乙烯亚胺中的叔胺基、仲胺基、伯胺基的物质的量之比为1:1:1。甲醇与多巴酸的质量之比为10:1；酰胺化试剂为1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐多巴酸(EDCI)和N-羟基琥珀酰亚胺(NHS)的组合，多巴酸、EDCI与NHS的质量比为1:1.1:1.2。
将得到的粘结剂进行傅立叶红外光谱测试，出峰位置分别为IR(KBr)υ：3450cm -1(-NH)，3050cm -1(Ar-H)，2970cm -1，2850cm -1(-CH 2-)，1680cm -1(-C＝C-)，1650cm -1(-C＝O)，1400-1600cm -1(Ar)，1350-1260cm -1(-OH)。
本实施例还提供一种锂离子电池及其制备方法，所述锂离子电池包括负极极片、正极极片、隔膜以及电解液；所述隔膜设置于正极极片和负极极片之间；所述负极极片包括硅基活性物质、导电剂以及本实施例提供的粘结剂，硅基活性物质为单质硅，导电剂为超导炭黑，硅基活性物质、导电剂、粘结剂的重量比为98:1:1。
该锂离子电池的制备方法包括如下步骤：
(1)正极极片制备：将三元镍材料、超导炭黑、聚偏氟乙烯粘结剂按重量比为93:4:3进行混合，然后加入N-甲基吡咯烷酮搅拌混合得到正极浆料，将正极浆料涂覆在铝箔上，先后经室温以及120℃干燥、冷压、分切得到正极极片；
(2)负极极片制备：将硅基活性物质、导电剂、粘结剂按重量比为98:1:1进行混合，加入去离子水搅拌混合得到负极浆料，将负极浆料涂覆在铜箔上，先后经室温以及120℃干燥，直至极片水分低于100ppm，然后冷压、分切得到负极极片；
(3)隔膜选择：选用厚度为15μm的；
(4)锂离子电池制备：
将步骤(1)得到的正极极片、聚乙烯/聚丙烯隔膜、步骤(2)得到的负极极片依次叠放，然后卷绕得到裸电芯；将裸电芯放入带有凹槽的铝塑膜内，进行注液、真空封装、静置、负压化成、二次补液、整形等工序，得到所述锂离子电池。
实施例2
本实施例提供一种粘结剂及其制备方法，所述粘结剂为多巴酸和蓖麻油酸改性接枝聚乙烯亚胺的聚合物；所述改性聚乙烯亚胺的改性剂包括多巴酸和蓖麻油酸的组合；
该粘结剂的制备方法包括如下：将0.5mol多巴酸、聚乙烯亚胺、酰胺化试剂和水混合，调节溶液PH为5.5，搅拌20min，室温下反应5h，得到多巴酸改性聚乙烯亚胺的聚合物。其中，酰胺化试剂为1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐多巴酸(EDCI)和N-羟基琥珀酰亚胺(NHS)的组合；多巴酸、EDCI与NHS的质量比为1:1.1:1.2；聚乙烯亚胺的中胺基总数与多巴酸的摩尔比为2:1；聚乙烯亚胺中叔胺基:伯胺基:仲胺基＝1:1:2。
将得到的多巴酸改性聚乙烯亚胺的聚合物上述聚合物和1mol蓖麻油酸加入到乙酸乙酯中，室温下反应5h，通过共沉淀法提纯，得到所述粘结剂。
对上述粘结剂进行红外表征，出峰位置分别为IR(KBr)υ：3450cm -1(-NH)，3050cm -1(Ar-H)，2970cm -1，2850cm -1(-CH 2-)，1680cm -1(-C＝C-)，1650cm -1(-C＝O)，1400-1600cm -1(Ar)，1350-1260cm -1(-OH)。
本实施例提供一种锂离子电池及其制备方法，所述锂离子电池与实施例1 的区别仅在于所述负极极片中的粘结剂为本实施例提供的粘结剂，导电剂为乙炔黑，硅基活性物质、导电剂、粘结剂的重量比为96:2.5:1.5。
所述锂离子电池的制备方法中与实施例1的区别仅在于在制备负极极片时硅基活性物质、导电剂、粘结剂的重量比为96:2.5:1.5，导电剂选用乙炔黑。
实施例3
本实施例提供一种粘结剂及其制备方法，所述粘结剂为多巴酸和羟基棕榈油酸改性接枝聚乙烯亚胺的聚合物；所述改性聚乙烯亚胺的改性剂包括多巴酸和羟基棕榈油酸的组合；
将1.5mol多巴酸、1.5mol羟基棕榈油酸、聚乙烯亚胺、酰胺化试剂以及甲醇混合，室温下反应8h，通过柱层析法提纯，得到所述粘结剂。其中，酰胺化试剂为O-苯并三氮唑-四甲基脲六氟磷酸盐(HATU)和N-羟基琥珀酰亚胺(NHS)的组合；多巴酸、EDCI与NHS的质量比为1:1.1:1.2；聚乙烯亚胺的中胺基总数与多巴酸的摩尔比为2:1；聚乙烯亚胺中叔胺基:伯胺基:仲胺基＝1:1:2。
将得到的粘结剂进行傅立叶红外光谱测试，出峰位置分别为IR(KBr)υ：3450cm -1(-NH)，3050cm -1(Ar-H)，2970，2850cm -1(-CH 2-)，1680cm -1(-C＝C-)，1650cm -1(-C＝O)，1400-1600cm -1(Ar)，1350-1260cm -1(-OH)。
本实施例提供一种锂离子电池及其制备方法，所述锂离子电池与实施例1的区别仅在于所述负极极片中的粘结剂为本实施例提供的粘结剂，导电剂为科琴黑，硅基活性物质、导电剂、粘结剂的重量比为97:2:1。
所述锂离子电池的制备方法中与实施例1的区别仅在于在制备负极极片时导电剂为科琴黑，硅基活性物质、导电剂、粘结剂的重量比为97:2:1。
实施例4
本实施例提供一种粘结剂及其制备方法，所述粘结剂及其制备方法与实施例1相同。
本实施例提供一种锂离子电池及其制备方法，所述锂离子电池与实施例1的区别仅在于：硅基活性物质、导电剂、粘结剂的重量比为97:2.5:0.5。
所述锂离子电池的制备方法中与实施例1的区别仅在于在制备负极极片时硅基活性物质、导电剂、粘结剂的重量比为97:2.5:0.5。
对比例1
本对比例提供一种粘结剂及其制备方法，所述粘结剂为多巴酸改性接枝聚 乙烯亚胺所得到的的聚合物粘结剂。其制备方法与实施例1相同，区别仅为制备体系中不加入不饱和羟基脂肪酸。
本对比例提供一种锂离子电池及其制备方法，其与实施例1的区别在于所述负极极片中的粘结剂为本实施例提供的粘结剂，制备方法与实施例1相同。
对比例2
本对比例提供一种锂离子电池及其制备方法，其与实施例1的区别在于所述负极极片中的粘结剂为SBR/CMC粘结剂，所述锂离子电池的制备方法与实施例1相同。
对比例3
本对比例提供一种锂离子电池及其制备方法，其与实施例1的区别在于所述负极极片中的粘结剂为PVDF粘结剂，所述锂离子电池的制备方法与实施例1的区别在于采用N-甲基吡咯烷酮(NMP)代替水。
性能测试：
(1)剥离强度测试：
1、将实施例1-4以及对比例1-3提供的负极极片，裁切为170×20mm；2、将裁切好的负极极片用双面胶贴于薄钢板的中间，端面平齐，薄钢板应事先用无尘纸擦拭干净，不留污渍和灰尘；3、用2kg重的压轮在极片表面来回辊压3次；4、将已粘贴固定极片的钢板插入测试仪的下夹内，垂直固定；将未贴胶的极片插入上夹内固定，使贴合在胶纸上的极片与上夹固定的极片成180°。固定好测试样品后，首先校准清零，设定测试宽度，极片剥离长度100mm，剥离速度为5cm/min，然后开始测试，得到剥离强度曲线及平均值。
(2)放电性能测试：将实施例1-4以及对比例1-3提供的锂离子电池进行放电性能测试，电流密度为0.1C；其中首次充放电效率为η＝(第一次放电比容量/第一次充电比容量)×100％。
(3)倍率性能测试:将实施例1-4以及对比例1-3提供的锂离子电池分别以0.1C、0.3C、0.5C、1C、3C、1C、0.5C、0.3C、0.1C的电流密度进行循环测试。
(4)耐开裂及烘干时间测试：将实施例1-4以及对比例1-3提供的涂覆负极浆料的铜箔放入80℃的烘箱内进行烘烤，直至水分低于100ppm。取出观察极片表面是否发生开裂并记录烘干所需的时间。
性能测试结果如表1所示：
表1
Figure PCTCN2022100420-appb-000001
根据表1的数据可知，本申请通过将多巴酸和蓖麻油酸引入到聚乙烯亚胺结构中，制备出的粘结剂用于负极极片时，无需添加有机溶剂耐开裂，将极片烘烤至水分为100ppm以下仅需5～9h，与硅基的粘合力较强，剥离强度达到13.6～15N/m；将包含该粘结剂的负极极片应用于锂离子电池中时，提高了电池的充放电效率，首次充放电效率高达88～90％，室温下3C倍率放电性能达到 98～99％，在循环充放电循环500周后容量保持率仍能达到92～94％，循环性能优异。
从实施例1到实施例4可以看出，在体系中加入不饱和羟基脂肪酸后，极片的烘干时间都较短，极片的柔韧性得到提高，同时所制备的电池都具有良好的电化学性能，尤其是电池的循环性能，得到很好的改善，这说明本申请的粘结剂可有效改善充电及循环过程中硅基材料的膨胀导致的电化学性能下降的问题。对比实施例1和实施例4，可以看出，使用本申请制备的粘结剂的电池，即使使用的粘结剂量比较少(实施例4中仅为0.5％)仍具有优异的电化学性能。
当粘结剂的结构中缺少不饱和羟基脂肪酸基团时(对比例1)，将其应用于负极极片时，需要添加有机溶剂防止开裂，粘合力下降，剥离强度为12.7N/m，极片的烘干速率下降较多，将其应用于锂离子电池中时充放电效率以及循环性能有所下降。当粘结剂为SBR/CMC系粘结剂时，用于负极极片时易开裂，需添加有机溶剂，烘干速率极低，粘合性较差，充放电效率以及循环性能较低。PVDF粘结剂也存在用于负极极片时，烘干速率低、易开裂以及充放电效率低以及循环性能较差的问题。
申请人声明，本申请通过上述实施例来说明本申请的粘结剂及其制备方法和应用，但本申请并不局限于上述实施例，即不意味着本申请必须依赖上述实施例才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (15)

  1. 一种粘结剂，其中，所述粘结剂包括改性聚乙烯亚胺；所述改性聚乙烯亚胺的改性剂包括多巴酸和不饱和羟基脂肪酸的组合。
  2. 根据权利要求1所述的粘结剂，其中，所述改性聚乙烯亚胺通过聚乙烯亚胺、多巴酸和不饱和羟基脂肪酸的接枝反应得到。
  3. 根据权利要求1或2所述的粘结剂，其中，所述不饱和羟基脂肪酸的碳原子数大于等于10；
  4. 根据权利要求1-3任一项所述的粘结剂，其中，所述不饱和羟基脂肪酸包括蓖麻油酸、羟基棕榈油酸、2-羟基油酸、5-羟基-8-十-碳烯酸、10-羟基-2-癸烯酸中的任意一种或至少两种的组合。
  5. 根据权利要求1-4任一项所述的粘结剂，其中，所述聚乙烯亚胺为超支化聚乙烯亚胺；
    优选地，所述聚乙烯亚胺中叔胺基、仲胺基、伯胺基的物质的量的比为1:(0.5～2):(0.5～1.5)；
    优选地，所述聚乙烯亚胺的重均分子量为10000～300000；
    优选地，以所述聚乙烯亚胺中的胺基总量为100％计，所述伯胺基的摩尔百分含量为25～35％。
  6. 一种如权利要求1-5任一项所述的粘结剂的制备方法，其包括方法A或方法B；
    所述方法A包括：将聚乙烯亚胺、多巴酸以及不饱和羟基脂肪酸进行反应，得到所述粘结剂；
    所述方法B包括：(1)聚乙烯亚胺与多巴酸反应，得到多巴酸改性聚乙烯亚胺；(2)将步骤(1)得到的多巴酸改性聚乙烯亚胺与不饱和羟基脂肪酸反应，得到所述粘结剂。
  7. 根据权利要求6所述的制备方法，其中，所述方法A的反应和所述步骤(1)的反应均在酰胺化试剂存在下进行。
  8. 根据权利要求7所述的制备方法，其中，所述酰胺化试剂包括1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐、N-羟基丁二酰亚胺、N-羟基琥珀酰亚胺、O-苯并三氮唑-四甲基脲六氟磷酸盐、2-(7-氮杂苯并三氮唑)-N,N,N',N'-四甲基脲六氟磷酸盐中的任意一种或至少两种的组合。
  9. 根据权利要求6-8任一项所述的制备方法，其中，以所述聚乙烯亚胺中 的伯胺基为1mol计，所述多巴酸的用量为0.5-1.5mol。
  10. 根据权利要求6-9任一项所述的制备方法，其中，以所述聚乙烯亚胺中的伯胺基为1mol计，所述不饱和羟基脂肪酸的用量为0.5～1.5mol。
  11. 根据权利要求6-10任一项所述的制备方法，其中，所述方法A的反应在溶剂存在下进行；
    优选地，所述溶剂包括甲醇和/或乙醇；
    优选地，所述方法A的反应的温度为20～40℃；
    优选地，所述方法A的反应的时间为6～12h。
  12. 根据权利要求6-10任一项所述的制备方法，其中，所述步骤(1)的反应在溶剂M存在下进行；
    优选地，所述溶剂M为水、甲醇或乙醇中的任意一种或至少两种的组合；
    优选地，所述步骤(2)的反应在溶剂N存在下反应；
    优选地，所述溶剂N为甲醇、乙醇、乙醚、丙酮或乙酸乙酯中的任意一种或至少两种的组合；
    优选地，所述步骤(1)和步骤(2)的反应的温度均为20～40℃；
    优选地，所述步骤(1)和步骤(2)的反应的总时间为8～15h。
  13. 根据权利要求6-12中任一项所述的制备方法，其中，所述方法A的反应和所述步骤(2)的反应结束后均包括分离提纯；
    优选地，所述分离提纯的方法包括透析法、共沉淀法或层析法中的任意一种。
  14. 一种锂离子电池负极材料，其中，所述锂离子电池负极材料包括负极活性物质、导电剂以及如权利要求1-5任一项所述的粘结剂；所述负极活性物质为硅基活性物质；
    所述锂离子电池负极材料中负极活性物质的质量百分含量为94～98％；
    所述锂离子电池负极材料中导电剂的质量百分含量为1～5％；
    所述锂离子电池负极材料中粘结剂的质量百分含量为0.5～1.5％；
    优选地，所述硅基活性物质包括单质硅、硅合金、硅碳化合物或硅氧化合物中的任意一种或至少两种的组合；
    优选地，所述导电剂包括乙炔黑、科琴黑、碳纤维、超导炭黑、碳纳米管、石墨烯中的一种或几种。
  15. 一种锂离子电池，其中，所述锂离子电池包括负极极片、正极极片、隔膜以及电解液；所述隔膜设置于正极极片和负极极片之间；所述负极极片包括如权利要求14所述的锂离子电池负极材料。
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