WO2023072106A1 - 一种粘结剂及含有该粘结剂的锂离子电池 - Google Patents

一种粘结剂及含有该粘结剂的锂离子电池 Download PDF

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WO2023072106A1
WO2023072106A1 PCT/CN2022/127483 CN2022127483W WO2023072106A1 WO 2023072106 A1 WO2023072106 A1 WO 2023072106A1 CN 2022127483 W CN2022127483 W CN 2022127483W WO 2023072106 A1 WO2023072106 A1 WO 2023072106A1
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binder
negative electrode
same
electrode sheet
lithium
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PCT/CN2022/127483
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English (en)
French (fr)
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储霖
李素丽
陈伟平
郭盼龙
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珠海冠宇电池股份有限公司
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J171/00—Adhesives based on polyethers obtained by reactions forming an ether link in the main chain; Adhesives based on derivatives of such polymers
    • C09J171/02—Polyalkylene oxides
    • 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
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
    • 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
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
    • C08G65/332—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof
    • C08G65/3324—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof cyclic
    • C08G65/3326—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing carboxyl groups, or halides, or esters thereof cyclic aromatic
    • 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
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/334—Polymers modified by chemical after-treatment with organic compounds containing sulfur
    • C08G65/3344—Polymers modified by chemical after-treatment with organic compounds containing sulfur containing oxygen in addition to sulfur
    • C08G65/3346—Polymers modified by chemical after-treatment with organic compounds containing sulfur containing oxygen in addition to sulfur having sulfur bound to carbon and oxygen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • C08G2170/00—Compositions for adhesives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • 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

  • the disclosure relates to a binder and a lithium-ion battery containing the binder, which belong to the technical field of lithium-ion batteries, and specifically belong to the technical field of lithium-ion battery negative electrode binders.
  • the charging and discharging process of lithium-ion batteries corresponds to the intercalation and deintercalation process of lithium ions between the layers of negative electrode materials (such as graphite) or silicon negative electrode materials.
  • negative electrode materials such as graphite
  • silicon negative electrode materials As the cycle period increases, the expansion of the negative electrode will gradually increase, which will lead to The reduction of the effective bonding network, such as the reduction of the effective bonding network between the active materials, the active material and the current collector, the reduction of the effective bonding network will also lead to the reduction of the conductive network inside the battery, and the final capacity retention of the battery will also drop.
  • the present disclosure provides a binder and a lithium battery containing the binder.
  • the binder is a polymer, the main chain of which is polyethylene glycol, and the two ends of the polymer chain contain catechol, and the two structural units make the binder have high ion conductivity and high viscosity. Consolidative advantages.
  • the present disclosure provides a binder comprising at least one polymer; wherein the polymer has a structure as shown in Formula 1:
  • R 3 and R 4 are the same or different, independently selected from H, alkyl, substituted alkyl or halogen, n is the number of repeating units; n is an integer of 20-1000;
  • the capping groups R1 and R2 at both ends are the same or different, independently selected from H or catechol groups shown in formula 2, and R1 and R2 are not H at the same time,
  • R 5 are the same or different, and are independently selected from at least one of alkyl, alkoxy, amino, aryl or halogen atoms;
  • n 0, 1, 2 or 3;
  • R is selected from alkylene or is absent
  • R 3 and R 4 are the same and both are H, then the main chain of the polymer is polyethylene glycol.
  • n is 20, 50, 100, 200, 500, 800, 1000.
  • n is an integer of 50-200.
  • R 1 and R 2 are the same or different, and are independently selected from one of H and groups having structures shown in formulas 2-1 to 2-8, and R 1 and R 2 is not H at the same time;
  • R 1 and R 2 are the same or different, and are independently selected from one of the groups having structures shown in Formulas 3-1 to 3-4, and R 1 and R 2 not both H:
  • the R 6 contains atoms or groups that can form hybrid orbitals, such as -O-, -S-, -NH-,
  • R 1 and R 2 are the same or different, and are independently selected from groups having structures shown in formulas 4-1 to 4-8, and R 1 and R 2 are not H at the same time :
  • the weight average molecular weight of the binder is 5 ⁇ 10 3 -1000 ⁇ 10 4 .
  • the glass transition temperature of the binder is -70°C to -40°C.
  • the ion conductivity of the binder is 10 -6 S ⁇ cm -1 to 10 -4 S ⁇ cm -1 .
  • the binder is a solution binder, such as a water-soluble binder; the solid content of the binder is 4wt%-25wt%.
  • the viscosity of the solution-type adhesive is 500-100000 mPa ⁇ s.
  • the present disclosure also provides a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the current collector, the negative electrode active layer contains a first binder, and the first binder is selected from the aforementioned binders.
  • the negative electrode active layer further contains a second binder.
  • the second binder is selected from at least one of SBR emulsion, styrene-acrylic emulsion and polyacrylic binder.
  • the total amount of the first binder and the second binder accounts for 0.5-5 wt% of the total solid mass in the negative electrode slurry.
  • total solid mass refers to the total mass of solid components in the negative electrode slurry after removing the solvent.
  • the first binder accounts for 10-90% of the total mass of the first binder and the second binder.
  • the present disclosure also provides a lithium-ion battery, the lithium-ion battery includes the above-mentioned binder; and/or the lithium-ion battery includes the above-mentioned negative electrode sheet.
  • the present disclosure provides a binder, a negative electrode sheet and a lithium ion battery containing the binder.
  • the main chain of the binder is a composite structure of polyethylene glycol and catechol at both ends of the polymer chain, so that the binder has the advantages of high ion conductivity and high cohesiveness respectively.
  • the negative electrode sheet containing the binder has higher ion conductivity and peeling strength.
  • the binder of the present disclosure is applied to lithium-ion batteries. Compared with lithium-ion batteries using conventional polymer binders, the lithium-ion batteries provided by the disclosure have a higher cycle capacity retention rate, lower cycle expansion rate, and higher rate of expansion. Better performance.
  • 1 is a schematic diagram of the binder transporting lithium ions of the present disclosure
  • FIG. 2 is a schematic diagram of a test device for the peel strength of the pole piece of the present disclosure
  • the present disclosure provides a binder comprising at least one polymer having a structure as shown in Formula 1:
  • R 3 and R 4 are the same or different, independently selected from H, alkyl, substituted alkyl or halogen, n is the number of repeating units; n is an integer of 20-1000;
  • the capping groups R1 and R2 at both ends are the same or different, independently selected from H or catechol groups shown in formula 2, and R1 and R2 are not H at the same time,
  • R 5 are the same or different, and are independently selected from at least one of alkyl, alkoxy, amino, aryl or halogen atoms;
  • n 0, 1, 2 or 3;
  • R 6 is an alkylene group or does not exist; wherein, the alkylene group is, for example, a C 1-6 alkylene group, for example, a methylene group, an ethylene group, a n-propylene group or an isopropylidene group, etc.;
  • R 3 and R 4 are the same and both are H, then the main chain of the polymer is polyethylene glycol.
  • n is 20, 50, 100, 200, 500, 800, 1000.
  • n is an integer of 50-200.
  • the main structure of the polymer has the characteristics of a low glass transition temperature, can be swollen in the electrolyte, has a certain flexibility, and can be bent and moved, and the oxygen atoms in the main structure can coordinate-decompose the lithium ions.
  • the role of coordination achieves the effect of transporting lithium ions, as shown in Figure 1A.
  • the end groups R1 and R2 contain a catechol structure, and the hydroxyl group on the benzene ring can form a hydrogen bond, so that the polymer containing this structure has strong adhesion and self-healing sex.
  • the polymer is used in the silicon negative electrode material.
  • the surface of the silicon negative electrode and the surface of the current collector contain a lot of hydroxyl groups.
  • the hydroxyl groups on the benzene ring can form hydrogen bonds with it, increasing the bonding strength of the entire negative electrode binder, as shown in Figure 1B shown.
  • R 1 and R 2 are the same or different, and are independently selected from, but not limited to, one of H, groups with structures shown in formulas 2-1 to 2-8, and R 1 and R 2 are not Also for H:
  • R 1 and R 2 are the same or different, and are independently selected from, but not limited to, one of H and groups having structures shown in formulas 3-1 to 3-4, and R 1 and R 2 not both H:
  • the R 6 contains atoms or groups that can form hybrid orbitals, such as -O-, -S-, -NH-,
  • R 1 and R 2 are the same or different, and are independently selected from, but not limited to, one of the groups having structures shown in formulas 4-1 to 4-8, and R 1 and R 2 are different from each other for H:
  • the weight average molecular weight of the binder is 5 ⁇ 10 3 to 1000 ⁇ 10 4 , such as 5 ⁇ 10 3 to 25 ⁇ 10 4 , for example 25 ⁇ 10 4 to 50 ⁇ 10 4 , 50 ⁇ 10 4 to 100 ⁇ 10 4 , 100 ⁇ 10 4 to 400 ⁇ 10 4 , 400 ⁇ 10 4 to 600 ⁇ 10 4 or 600 ⁇ 10 4 to 1000 ⁇ 10 4 , preferably 25 ⁇ 10 4 to 100 ⁇ 10 4 .
  • the glass transition temperature of the binder is -70°C to -40°C.
  • the ionic conductivity of the binder is 10 -6 S ⁇ cm -1 to 10 -4 S ⁇ cm -1 .
  • the binder is a solution-type binder, such as a water-soluble binder;
  • the solid content of the binder is 4wt% to 25wt%, exemplarily 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 25wt%;
  • the viscosity of the solution-type adhesive is 500-100000mPa ⁇ s, exemplarily 500mPa ⁇ s, 1500mPa ⁇ s, 2500mPa ⁇ s, 5000mPa ⁇ s, 7500mPa ⁇ s, 15000mPa ⁇ s s, 25000mPa ⁇ s, 35000mPa ⁇ s, 45000mPa ⁇ s, 55000mPa ⁇ s, 65000mPa ⁇ s, 75000mPa ⁇ s, 85000mPa ⁇ s, 95000mPa ⁇ s.
  • the present disclosure also provides a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the current collector, the negative electrode active layer contains a first binder, and the first binder is selected from the above binder.
  • the negative electrode current collector is selected from at least one of single-faced copper foil, double-faced copper foil, or porous copper foil.
  • the negative electrode active layer is provided by negative electrode slurry, and the negative electrode slurry contains the above-mentioned binder.
  • the first binder accounts for 0.5-5wt% of the total solid mass in the negative electrode slurry, preferably 0.8-2.5wt%, more preferably 1.5-2.5wt%.
  • the negative electrode slurry further includes a second binder.
  • the second binder is selected from at least one of SBR emulsion, styrene-acrylic emulsion and polyacrylic binder, such as polyacrylate.
  • the negative electrode slurry includes a first binder and a second binder.
  • the total amount of the first binder and the second binder accounts for 0.5-5wt%, preferably 0.8-2.5wt%, more preferably 1.5-2.5wt% of the total solid mass in the negative electrode slurry.
  • the first binder accounts for 10-90% of the total mass of the first binder and the second binder.
  • the negative electrode slurry further includes negative electrode active materials and/or additives.
  • the negative electrode active material is selected from at least one of artificial graphite, natural graphite, mesophase carbon spheres, lithium titanate, silicon oxide, nano silicon powder, silicon oxide and silicon carbon.
  • the additive includes a conductive agent and/or a dispersant.
  • the conductive agent is selected from at least one of graphite, carbon black, acetylene black, graphene and carbon nanotubes.
  • the dispersant is selected from sodium carboxymethylcellulose and/or lithium carboxymethylcellulose.
  • the conductive agent and/or dispersant used in the present disclosure is used in an amount known in the art.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the negative electrode current collector, and the negative electrode active layer contains at least the negative electrode active material and the first binder .
  • the present disclosure also provides a method for preparing the above-mentioned pole sheet, which includes the following steps: coating a negative electrode slurry containing the first binder on at least one side of the negative electrode current collector to prepare the negative electrode sheet.
  • the preparation method of the negative electrode sheet specifically includes the following steps:
  • Negative electrode active material such as artificial graphite 96wt%), conductive agent (such as carbon black 0.5wt%), dispersant (carboxymethylcellulose sodium 0.5wt%), the first binding agent (1.6wt%) %), SBR emulsion (1.4wt%) are mixed homogeneously, obtain negative electrode slurry;
  • the present disclosure also provides a lithium-ion battery, which includes the above-mentioned binder and/or the above-mentioned negative electrode sheet.
  • the lithium-ion battery further includes a positive electrode sheet, a separator, and an electrolyte; wherein, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one side of the current collector.
  • the positive current collector is selected from at least one of single-surface aluminum foil, double-surface aluminum foil or porous aluminum foil.
  • the positive electrode active layer is provided by positive electrode slurry.
  • the positive electrode slurry contains positive electrode active materials and/or additives.
  • the positive electrode active material is at least one selected from lithium iron phosphate, ternary positive electrode materials and lithium cobaltate.
  • the additive includes a conductive agent and/or a positive electrode binder.
  • the conductive agent is selected from at least one of graphite, carbon black, acetylene black, graphene and carbon nanotubes.
  • the positive electrode binder is selected from at least one of polyvinylidene fluoride (PVDF), polyacrylate and polyacrylic acid, preferably PVDF.
  • the positive electrode sheet is prepared through the following steps:
  • the mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder is not specifically limited, and the mass ratio commonly used in the technical field can be adopted.
  • the mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder may be 97.5:1.4:1.1; for example, the mass ratio of lithium cobaltate, carbon black, and PVDF is 97.5:1.4:1.1.
  • the lithium ion battery includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.
  • the positive electrode sheet, negative electrode sheet, and separator are assembled into a battery cell by winding or lamination, and then packaged with aluminum-plastic film, and then sequentially baked, injected with electrolyte, formed, and secondly sealed to obtain lithium ions. Battery.
  • the viscosities involved in the following examples and comparative examples are measured using a digital display rotational viscometer (Shanghai Sannuo NDJ-5S).
  • the glass transition temperature involved in the following examples and comparative examples is by differential scanning calorimeter (DSC), model is 910s (USA TA Instruments company), test obtains.
  • the ionic conductivity of the adhesive films in the following examples and comparative examples was tested as follows: the adhesive solution was spread on a polytetrafluoroethylene plate, and an adhesive film was obtained after drying. Shanghai Chenhua CHI660E electrochemical workstation was used to test the conductivity of the adhesive film at room temperature 25 °C. A stainless steel electrode is used as the working electrode, and another stainless steel electrode is used as the counter electrode and reference electrode; the test frequency is 1-10 6 Hz, and the amplitude is 10mV.
  • Positive electrode sheet disperse the positive electrode active material lithium cobaltate, binder PVDF and conductive carbon black in N-methylpyrrolidone, and obtain a uniformly dispersed positive electrode slurry after stirring, wherein the solid component includes 97.5wt% lithium cobaltate, 1.1wt% PVDF and 1.4wt% conductive carbon black, the solid content of the positive electrode slurry is 66.3wt%, and the viscosity is 20300mPa ⁇ s.
  • the positive electrode slurry was uniformly coated on both sides of the 9 ⁇ m aluminum foil, dried at 100-130°C for 4 hours, and compacted with a roller press to obtain a positive electrode sheet with a compacted density of 3.5-4.2 g/cm 3 .
  • negative electrode binder containing a polymer as shown in formula 1, wherein the main structure is the main chain of polyethylene glycol, R 1 and R 2 have the same structure, and the structures of R 1 and R 2 are shown in Table 1 As shown, the molecular weight is 403,000, the glass transition temperature is -51°C, and the ion conductivity is 4.5 ⁇ 10 -5 S ⁇ cm -1 ; the negative electrode binder is a solution type, the solvent is water, and the solid content is 6wt%. The viscosity is 5060mPa ⁇ s.
  • Preparation method Dissolve polyethylene glycol with a molecular weight of 400,000 in water, adjust the pH to 8-9 with sodium hydroxide, and drop Add the acetone solution in which 3,4-dimethoxybenzoyl chloride is dissolved, and stir to react for 6 hours. After the reaction, diethyl ether was added to precipitate the polymer, and the polymer was extracted by filtration. After the polymer was dried, it was dissolved in water again, dilute hydrochloric acid was added, and reacted at 50° C. for 1 h to obtain the target polymer.
  • Figure 3 is the infrared spectrogram of the target polymer.
  • negative electrode sheet Mix and disperse the above-mentioned binder, SBR emulsion, graphite, dispersant sodium carboxymethylcellulose (CMC), and conductive carbon black in deionized water to obtain negative electrode slurry.
  • the negative electrode slurry is uniformly coated on both sides of the 6 ⁇ m copper foil, dried at 70-100° C. for 5 hours, and compacted with a roller press, wherein the compacted density is 1.5-1.8 g/cm 3 to obtain the negative electrode sheet.
  • the negative electrode binder it contains a polymer as shown in formula 1, wherein the main structure is the main chain of polyethylene glycol, the structures of R1 and R2 are as shown in Table 1, the molecular weight is 34.5W, glass The transition temperature is -45°C, the ion conductivity is 4.2 ⁇ 10 -5 S ⁇ cm -1 ; the negative electrode binder is solution type, the solvent is water, the solid content is 8wt%, and the viscosity is 6070mPa ⁇ s.
  • Example 1 The polymer preparation method in this example is consistent with Example 1, except that 3,4-dimethoxybenzoyl chloride in Example 1 is replaced by 3,4-dimethoxybenzenesulfonyl chloride .
  • the negative electrode binder it contains a polymer as shown in formula 1, wherein the main structure is the main chain of polyethylene glycol, the structures of R1 and R2 are as shown in Table 1, the molecular weight is 55.4W, glass The transition temperature is -42°C, the ion conductivity is 4.6 ⁇ 10 -5 S ⁇ cm -1 ; the negative electrode binder is solution type, the solvent is water, the solid content is 7.5wt%, and the viscosity is 7280mPa ⁇ s.
  • Polymer preparation method The polymer preparation method in this example is consistent with Example 1, the difference is that the 3,4-dimethoxybenzoyl chloride in Example 1 is replaced by 3,4-dimethyl Oxybenzyl chloride.
  • the negative electrode binder it contains a polymer as shown in formula 1, wherein the main structure is the main chain of polyethylene glycol, the structures of R1 and R2 are as shown in Table 1, the molecular weight is 64.3W, glass The transformation temperature is -39°C, the ion conductivity is 3.8 ⁇ 10 -5 S ⁇ cm -1 ; the negative electrode binder is solution type, the solvent is water, the solid content is 11wt%, and the viscosity is 10800mPa ⁇ s.
  • Polymer preparation method The polymer preparation method in this example is consistent with Example 1, the difference is that the 3,4-dimethoxybenzoyl chloride in Example 1 is replaced by 3,4-dimethyl Oxybenzylidene Glycidyl Ether.
  • Negative electrode binder the same as in Example 1, the difference is that the negative electrode binder is polyethylene glycol with a molecular weight of 400,000, a glass transition temperature of -53°C, a viscosity of 4050mPa ⁇ s, and an ion conductivity of 4.3 ⁇ 10 -5 S ⁇ cm -1 .
  • Negative electrode binder the same as in Example 2, the difference is that the negative electrode binder is polyethylene glycol, the glass transition temperature is -48°C, the viscosity is 5140mPa ⁇ s, and the ion conductivity is 4.1 ⁇ 10 -5 S • cm ⁇ 1 .
  • Negative electrode binder the same as in Example 3, the difference is that the negative electrode binder is polyethylene glycol, the glass transition temperature is -44°C, the viscosity is 5890mPa ⁇ s, and the ion conductivity is 4.4 ⁇ 10 -5 S • cm ⁇ 1 .
  • Negative electrode binder the same as in Example 4, the difference is that the negative electrode binder is polyethylene glycol, the glass transition temperature is -43°C, the viscosity is 8600mPa ⁇ s, and the ion conductivity is 3.7 ⁇ 10 -5 S • cm ⁇ 1 .
  • Example 1 The negative electrode binder in Example 1 was replaced by the commercially available LA136D binder (catechol-free) from Indile Company, and the others were the same as in Example 1, wherein the ion conductivity of the negative electrode binder was 3.1 ⁇ 10 ⁇ 6 S ⁇ cm -1 ; solution viscosity is 15000mPa ⁇ s, molecular weight is 64W, glass transition temperature is 130°C.
  • embodiment 1-4 is compared with comparative example 5, although the peeling strength of comparative example 5 is high, because there is not the group (as shown in Figure 1A) that can conduct ions, its ionic conductivity is higher than that of embodiment 1-4. Compared with Comparative Examples 1-4, it is all lower, so each embodiment is better than Comparative Example 5. It can be seen that the binder disclosed in the present disclosure can well improve the cycle stability of the lithium-ion battery, suppress cycle expansion, and have better rate performance at the same time.

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Abstract

本发明公开了一种粘结剂及含有该粘结剂的锂离子电池，所述粘结剂包括至少一种聚合物；其中，所述聚合物具有如式1所示的结构。所述粘结剂利用主链为聚乙二醇、聚合物链两端含有邻苯二酚的复合结构，分别赋予粘结剂分子高离子电导和高粘结性。含有该粘结剂的负极片，具有较高的离子电导率和剥离强度。同时，本发明的粘结剂应用于锂离子电池中，对比使用常规聚合物粘结剂的锂离子电池，循环容量保持率更高、循环膨胀率更低、倍率性能更优异。

Description

一种粘结剂及含有该粘结剂的锂离子电池 技术领域
本公开涉及一种粘结剂及含有该粘结剂的锂离子电池，属于锂离子电池技术领域，具体属于锂离子电池负极粘结剂技术领域。
背景技术
锂离子电池充放电过程对应了负极材料(如石墨)层间或硅负极材料锂离子的嵌入和脱嵌过程，随着循环周期的增大，负极的膨胀也会逐渐增大，这将会导致有效的粘结网络的减少，如活性物质之间、活性物质与集流体之间的有效粘结网络减少，有效粘结网络减少也会导致电池内部的导电网络的减少，最终电池的容量保持率也将下降。
因此发明一种高粘附性、能有效抑制膨胀、提高离子电导率的粘结剂对电池的应用显得尤为重要。
发明内容
为了改善现有技术的不足，特别是现有技术中的常规的负极粘结剂粘结性不足和离子电导率低的问题，本公开提供了一种粘结剂及含有该粘结剂的锂离子电池。所述粘结剂为一种聚合物，该聚合物的主链为聚乙二醇、聚合物链两端含有邻苯二酚，两种结构单元使粘结剂具有高离子电导率和高粘结性的优点。
本公开提供一种粘结剂，所述粘结剂包括至少一种聚合物；其中，所述聚合物具有如式1所示的结构：
Figure PCTCN2022127483-appb-000001
式1中，R 3和R 4相同或不相同，彼此独立地选自H、烷基、取代烷基或卤素，n为重复单元数；n为20-1000的整数；
两端的封端基团R 1和R 2相同或不相同，彼此独立地选自H或如式2所示的邻苯二酚基，且R 1和R 2不同时为H，
Figure PCTCN2022127483-appb-000002
式2中，
R 5相同或不同、彼此独立地选自烷基、烷氧基、胺基、芳基或卤素原子中的至少一种；
m选自0、1、2或3；
R 6选自亚烷基或不存在；
R 7选自-C(＝O)-或-S(＝O)(＝O)-；
*表示连接端。
在一实例中，R 3和R 4相同，均为H，则所述聚合物的主链为聚乙二醇。
在一实例中，n为20、50、100、200、500、800、1000。优选n为50-200的整数。
在一实例中，式1中，R 1和R 2相同或不相同，彼此独立地选自H、具有式2-1～2-8所示结构的基团中的一种，且R 1和R 2不同时为H；
Figure PCTCN2022127483-appb-000003
在一实例中，式1中，R 1和R 2相同或不相同，彼此独立地选自具有式3-1～3-4所示结构的基团中的一种，且R 1和R 2不同时为H：
Figure PCTCN2022127483-appb-000004
在一实例中，式2中，所述R 6含有可以形成杂化轨道的原子或基团，例如-O-、-S-、-NH-、
Figure PCTCN2022127483-appb-000005
在一实例中，式1中，R 1和R 2相同或不相同，彼此独立地选自具有式4-1～4-8所示结构的基团，且R 1和R 2不同时为H：
Figure PCTCN2022127483-appb-000006
在一实例中，所述粘结剂的重均分子量为5×10 3～1000×10 4。
在一实例中，所述粘结剂的玻璃化转变温度为-70℃～-40℃。
在一实例中，所述粘结剂的离子电导率为10 -6S·cm -1～10 -4S·cm -1。
在一实例中，所述粘结剂为溶液型粘结剂，例如为水溶性粘结剂；所述粘结剂的固含量为4wt％～25wt％。
在一实例中，所述溶液型粘结剂的粘度为500～100000mPa·s。
本公开还提供一种负极片，所述负极片包括负极集流体和位于集流体至少一侧的负极活性层，所述负极活性层含有第一粘结剂，所述第一粘结剂选自上述的粘结剂。
在一实例中，所述负极活性层还含有第二粘结剂。
示例性地，所述第二粘结剂选自SBR乳液、苯丙乳液和聚丙烯酸类粘结剂中的至少一种。
在一实例中，所述第一粘结剂和第二粘结剂的总量占负极浆料中总固体质量的0.5-5wt％。其中，所述“总固体质量”是指负极浆料中去除溶剂后的固体组分的总质量。
在一实例中，所述第一粘结剂占第一粘结剂和第二粘结剂总质量的10～90％。
本公开还提供一种锂离子电池，所述锂离子电池包括上述的粘结剂；和/或所述锂离子电池包括上述的负极片。
有益效果：
本公开提供一种粘结剂和含有该粘结剂的负极片和锂离子电池。所述粘结剂的主链为聚乙二醇、聚合物链两端含有邻苯二酚的复合结构，分别使粘结剂具有高离子电导率和高粘结性的优点。使含有该粘结剂的负极片具有较高的离子电导率和剥离强度。同时，本公开的粘结剂应用于锂离子电池中，对比使用常规聚合物粘结剂的锂离子电池，本公开提供的锂离子电池的循环容量保持率更高、循环膨胀率更低、倍率性能更优异。
附图说明
图1为本公开的粘结剂传输锂离子的示意图；
图2为本公开的极片的剥离强度的测试装置示意图；
图3为制备例1的式1所示的聚合物的红外光谱图。
具体实施方式
[粘结剂]
本公开提供了一种粘结剂，所述粘结剂包括至少一种聚合物，所述聚合物具有如式1所示的结构：
Figure PCTCN2022127483-appb-000007
式1中，R 3和R 4相同或不相同，彼此独立地选自H、烷基、取代烷基或卤素，n为重复单元数；n为20-1000的整数；
两端的封端基团R 1和R 2相同或不相同，彼此独立地选自H或如式2所示的邻苯二酚基，且R 1和R 2不同时为H，
Figure PCTCN2022127483-appb-000008
式2中，
R 5相同或不同、彼此独立地选自烷基、烷氧基、胺基、芳基或卤素原子中的至少一种；
m选自0、1、2或3；
R 6为亚烷基或不存在；其中，所述亚烷基例如为C 1-6亚烷基，还例如为亚甲基、亚乙基、亚正丙基或亚异丙基等；
R 7选自-C(＝O)-或-S(＝O)(＝O)-；
*表示连接端。
在一实例中，R 3和R 4相同，均为H，则所述聚合物的主链为聚乙二醇。
在一实例中，n为20、50、100、200、500、800、1000。优选n为50-200的整数。
在一实例中，所述聚合物的主体结构具有玻璃化转变温度低的特点，在电解液中能够溶胀，具有一定柔性，可以弯曲移动，主体结构中的氧原子对锂离 子通过配位-解除配位的作用达到传输锂离子的效果，如图1A所示。
在一实例中，所述端基R 1和R 2中含有邻苯二酚的结构，苯环上的羟基，能够形成氢键，使得含有该结构的聚合物具有强的粘附性、自修复性。例如所述聚合物应用在硅负极材料中，硅负极表面以及集流体表面含有很多羟基，苯环上的羟基可以与之形成氢键后，增加整个负极粘结剂的粘结强度，如图1B所示。
示例性地，R 1和R 2相同或不相同，彼此独立地选自但不限于H、式2-1～2-8所示结构的基团中的一种，且R 1和R 2不同时为H：
Figure PCTCN2022127483-appb-000009
示例性地，R 1和R 2相同或不相同，彼此独立地选自但不限于H、具有式3-1～3-4所示结构的基团中的一种，且R 1和R 2不同时为H：
Figure PCTCN2022127483-appb-000010
在一个具体的实施方式中，所述R 6含有可以形成杂化轨道的原子或基团，例如-O-、-S-、-NH-、
Figure PCTCN2022127483-appb-000011
示例性地，R 1和R 2相同或不相同，彼此独立地选自但不限于具有式4-1～4-8所示结构的基团中的一种，且R 1和R 2不同时为H：
Figure PCTCN2022127483-appb-000012
在一个具体的实施方式中，所述粘结剂的重均分子量为5×10 3～1000×10 4，例如为5×10 3～25×10 4，还例如为25×10 4～50×10 4、50×10 4～100×10 4、100×10 4～400×10 4、400×10 4～600×10 4或600×10 4～1000×10 4，优选为25×10 4～100×10 4。
在一个具体的实施方式中，所述粘结剂的玻璃化转变温度为-70℃～-40℃。
在一个具体的实施方式中，所述粘结剂的离子电导率为10 -6S·cm -1～10 -4S·cm -1。
在一个具体的实施方式中，所述粘结剂为溶液型粘结剂，例如为水溶性粘结剂；所述粘结剂的固含量为4wt％～25wt％，示例性地为4wt％、6wt％、8wt％、10wt％、12wt％、14wt％、16wt％、18wt％、20wt％、22wt％、24wt％、25wt％；
在一个具体的实施方式中，所述溶液型粘结剂的粘度为500～100000mPa·s， 示例性地为500mPa·s、1500mPa·s、2500mPa·s、5000mPa·s、7500mPa·s、15000mPa·s、25000mPa·s、35000mPa·s、45000mPa·s、55000mPa·s、65000mPa·s、75000mPa·s、85000mPa·s、95000mPa·s。
[负极片]
本公开还提供一种负极片，所述负极片包括负极集流体和位于集流体至少一侧的负极活性层，所述负极活性层含有第一粘结剂，所述第一粘结剂选自上述粘结剂。
在一个具体的实施方式中，所述负极集流体选自单光面铜箔、双光面铜箔或多孔铜箔中的至少一种。
在一个具体的实施方式中，所述负极活性层由负极浆料提供，所述负极浆料中含有上述粘结剂。
在一个具体的实施方式中，所述第一粘结剂占所述负极浆料中总固体质量的0.5-5wt％，优选为0.8-2.5wt％，更优选为1.5-2.5wt％。
在一个具体的实施方式中，所述负极浆料中，还包括第二粘结剂。
优选地，所述第二粘结剂选自SBR乳液、苯丙乳液和聚丙烯酸类粘结剂中的至少一种，例如聚丙烯酸酯。
在一个具体的实施方式中，所述负极浆料中，包括第一粘结剂和第二粘结剂。优选地，所述第一粘结剂和第二粘结剂的总量占负极浆料中总固体质量的0.5-5wt％，优选为0.8-2.5wt％，更优选为1.5-2.5wt％。
进一步优选地，所述第一粘结剂占第一粘结剂和第二粘结剂的总质量的10～90％。
在一个具体的实施方式中，所述负极浆料中还包括负极活性物质和/或添加剂。
在一个具体的实施方式中，所述负极活性物质选自人造石墨、天然石墨、中间相碳球和钛酸锂、氧化硅、纳米硅粉、氧化亚硅和硅碳中的至少一种。
在一个具体的实施方式中，所述添加剂包括导电剂和/或分散剂。
优选地，所述导电剂选自石墨、炭黑、乙炔黑、石墨烯和碳纳米管中的至少一种。
优选地，所述分散剂选自羧甲基纤维素钠和/或羧甲基纤维素锂。
优选地，本公开中所述导电剂和/或分散剂的用量为本领域已知用量。
在一个具体的实施方式中，所述负极片包括负极集流体和位于所述负极集流体至少一个侧的负极活性层，所述负极活性层中至少含有负极活性物质和所述第一粘结剂。
本公开还提供上述极片的制备方法，包括如下步骤：在所述负极集流体至少一侧涂覆含有所述第一粘结剂的负极浆料制备得到所述负极片。
在一个具体的实施方式中，所述负极片的制备方法具体包括如下步骤：
(1)将负极活性物质(例如人造石墨96wt％)、导电剂(例如炭黑0.5wt％)、分散剂(羧甲基纤维素钠0.5wt％)、所述第一粘结剂(1.6wt％)、SBR乳液(1.4wt％)混合均匀，得到负极浆料；
(2)将所述负极浆料涂覆在负极集流体的一侧，烘烤后即得到所述负极极片。
[锂离子电池]
本公开还提供一种锂离子电池，所述锂离子电池包括上述粘结剂和/或上述负极片。
在一个具体的实施方式中，所述锂离子电池还包括正极片、隔膜和电解液；其中，所述正极片包括正极集流体和位于集流体至少一侧表面的正极活性层。
优选地，所述正极集流体选自单光面铝箔、双光面铝箔或多孔铝箔中的至少一种。
在一个具体的实施方式中，所述正极活性层由正极浆料提供。
优选地，所述正极浆料中含有正极活性物质和/或添加剂。
优选地，所述正极活性物质选自磷酸铁锂、三元正极材料和钴酸锂中的至少一种。
优选地，所述添加剂包括导电剂和/或正极粘结剂。示例性地，所述导电剂选自石墨、炭黑、乙炔黑、石墨烯和碳纳米管中的至少一种。示例性地，所述正极粘结剂选自聚偏氟乙烯(PVDF)、聚丙烯酸酯和聚丙烯酸中的至少一种，优选为PVDF。
在一实例中，所述正极片通过如下步骤制备得到：
(1)将正极活性物质、导电剂和正极粘结剂混合均匀，得到正极浆料；
(2)将所述正极浆料涂覆在正极集流体的一侧，烘烤后即得到正极极片。
本公开中，对正极活性物质、导电剂、正极粘结剂的质量比不做具体限定，可以采用本技术领域常用的质量比。例如，正极活性物质、导电剂和正极粘结剂的质量比可以为97.5:1.4:1.1；示例性地，钴酸锂、炭黑和PVDF的质量比为97.5:1.4:1.1。
在一实例中，所述锂离子电池包括正极片、隔膜、负极片和电解液。示例性地，将正极片、负极片和隔膜通过卷绕或者叠片组装成电芯，再通过铝塑膜进行封装，再依次经过烘烤、注入电解液、化成、二封工序即得到锂离子电池。
下文将结合具体实施例对本公开的技术方案做更进一步的详细说明。应当理解，下列实施例仅为示例性地说明和解释本公开，而不应被解释为对本公开保护范围的限制。凡基于本公开上述内容所实现的技术均涵盖在本公开旨在保护的范围内。
除非另有说明，以下实施例中使用的原料和试剂均为市售商品，或者可以通过已知方法制备。
下述实施例和对比例中涉及到的粘度是利用数显式旋转粘度计(上海三诺NDJ-5S)测量得到的。
下述实施例和对比例中涉及到的玻璃化转变温度是由差示扫描量热仪(DSC)，型号为910s(美国TA Instruments公司)，测试得到的。
下述实施例和对比例中的胶膜的离子电导率是按如下方法测试得到的：将粘结剂溶液铺展在聚四氟乙烯板上，干燥后得到粘结剂膜。采用上海辰华 CHI660E型电化学工作站测试粘结剂胶膜在常温25℃下的电导率。以不锈钢电极作为工作电极，另一片不锈钢电极做对电极和参比电极；测试频率为1～10 6Hz，振幅为10mV。根据得到的交流阻抗谱图得出粘结剂胶膜的电阻，离子电导率可根据以下公式计算得到：σ＝L/(RA)，A表示粘结剂膜的面积(cm 2)，L表示膜的厚度(cm)，其中R由EIS测出得到的欧姆阻抗。
实施例1
正极片：将正极活性物质钴酸锂、粘结剂PVDF和导电炭黑分散在N-甲基吡咯烷酮中，搅拌后得到均匀分散的正极浆料，其中固体成分包括97.5wt％的钴酸锂、1.1wt％的PVDF和1.4wt％的导电炭黑，正极浆料的固体含量为66.3wt％，粘度为20300mPa·s。将正极浆料均匀地涂覆在9μm铝箔两侧表面，经过100～130℃干燥4h，利用辊压机对其压实，压实密度为3.5～4.2g/cm 3，得到正极片。
负极片：
1、制备负极粘结剂：含有如式1所示的聚合物，其中，主体结构为聚乙二醇的主链，R 1和R 2的结构相同，R 1和R 2的结构如表1所示，分子量为40.3万，玻璃化转变温度为-51℃，离子电导率为4.5×10 -5S·cm -1；负极粘结剂为溶液型，溶剂为水，固含量为6wt％，粘度为5060mPa·s。
含有如式1所示的聚合物制备方法：将分子量为40万的聚乙二醇溶解于水中，用氢氧化钠调节pH至8～9范围内，在低温0～5℃范围内下，滴加溶解有3,4-二甲氧基苯甲酰氯的丙酮溶液，搅拌反应6小时。反应结束后，加入乙醚沉淀析出聚合物，过滤提出聚合物。聚合物干燥后再次溶解到水中，加入稀盐酸，50℃反应1h，得到目标聚合物。图3为目标聚合物的红外光谱图，从图中可以看出，在1200cm -1处有明显醚键特征峰，来源于聚乙二醇主链，1600cm -1和700cm -1处均为苯环的特征峰，而1730cm -1处为酯键特征峰，这证实了聚合物具有上述结构。
2、制备负极片：将上述粘结剂、SBR乳液、石墨、分散剂羧甲基纤维素钠(CMC)、导电炭黑混合分散于去离子水中，得到负极浆料，负极浆料的固含量为43.5wt％，粘度为4610mPa·s；其中固体成分包括96.5wt％石墨-氧化亚硅(石墨： 氧化亚硅＝9:1)、0.5wt％的CMC、0.5wt％导电炭黑、1.5wt％的粘结剂、1wt％SBR乳液。该负极浆料均匀地涂覆在6μm铜箔两侧表面，经过70～100℃干燥5h、辊压机压实，其中压实密度为1.5～1.8g/cm 3，得到负极片。
3、制备锂离子电池：将正极片、负极片焊极耳后，和隔膜(PP/PE/PP复合膜，厚度9μm，孔隙率为41％)卷绕成电芯，封装，然后注入电解液(碳酸二甲酯和碳酸亚乙酯体积比1:1的二元溶剂中包含1mol/L六氟磷酸锂，并添加10wt％碳酸氟代亚乙酯作为添加剂)，化成、热压、二封后得到锂离子电池。
实施例2
1、制备负极粘结剂：含有如式1所示的聚合物，其中，主体结构为聚乙二醇的主链，R 1和R 2的结构如表1所示，分子量为34.5W，玻璃化转变温度为-45℃，离子电导率为4.2×10 -5S·cm -1；负极粘结剂为溶液型，溶剂为水，固含量为8wt％，粘度为6070mPa·s。
本实施例中的聚合物制备方法与实施例1一致，不同之处在于，将实施例1中的3,4-二甲氧基苯甲酰氯替换为3,4-二甲氧基苯磺酰氯。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
实施例3
1、制备负极粘结剂：含有如式1所示的聚合物，其中，主体结构为聚乙二醇的主链，R 1和R 2的结构如表1所示，分子量为55.4W，玻璃化转变温度为-42℃，离子电导率为4.6×10 -5S·cm -1；负极粘结剂为溶液型，溶剂为水，固含量为7.5wt％，粘度为7280mPa·s。
聚合物制备方法：本实施例中的聚合物制备方法与实施例1一致，不同之处在于，将实施例1中的3,4-二甲氧基苯甲酰氯替换为3,4-二甲氧基苄基氯。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
实施例4
1、制备负极粘结剂：含有如式1所示的聚合物，其中，主体结构为聚乙二醇的主链，R 1和R 2的结构如表1所示，分子量为64.3W，玻璃化转变温度为-39℃，离子电导率为3.8×10 -5S·cm -1；负极粘结剂为溶液型，溶剂为水，固含量为11wt％，粘度为10800mPa·s。
聚合物制备方法：本实施例中的聚合物制备方法与实施例1一致，不同之处在于，将实施例1中的3,4-二甲氧基苯甲酰氯替换为3,4-二甲氧基苯亚甲基缩水甘油醚。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
对比例1
1、负极粘结剂：同实施例1，区别在于，负极粘结剂为聚乙二醇，分子量为40万，玻璃化转变温度为-53℃，粘度为4050mPa·s，离子电导率为4.3×10 -5S·cm -1。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
对比例2
1、负极粘结剂：同实施例2，区别在于，负极粘结剂为聚乙二醇，玻璃化转变温度为-48℃，粘度为5140mPa·s，离子电导率为4.1×10 -5S·cm -1。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
对比例3
1、负极粘结剂：同实施例3，区别在于，负极粘结剂为聚乙二醇，玻璃化转变温度为-44℃，粘度为5890mPa·s，离子电导率为4.4×10 -5S·cm -1。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
对比例4
1、负极粘结剂：同实施例4，区别在于，负极粘结剂为聚乙二醇，玻璃化转变温度为-43℃，粘度为8600mPa·s，离子电导率为3.7×10 -5S·cm -1。
2、制备负极片和锂离子电池：正极片、负极片及电池的制备方法同实施例1。
对比例5
采用商用茵地乐公司的LA136D粘结剂(不含邻苯二酚)替代实施例1中的负极粘结剂，其他同实施例1，其中负极粘结剂的离子电导率为3.1×10 -6S·cm -1；溶液粘度为15000mPa·s，分子量为64W，玻璃化转变温度为130℃。
测试例1
(1)上述实施例和对比例中涉及到的剥离强度是采用如下方法测试得到的：
将上述制备完成的负极片裁剪为20×100mm尺寸的测试试样，备用；将极片用双面胶粘接需要测试的那一面，并用压辊压实，使之与极片完全贴合；试样的双面胶的另外一面粘贴于不锈钢表面，将试样一端反向弯曲，弯曲角度为180°；采用高铁拉力机测试，将不锈钢一端固定于拉力机下方夹具，试样弯曲末端固定于上方夹具，调整试样角度，保证上下端位于垂直位置，然后以50mm/min的速度拉伸试样，直到负极浆料全部从基板剥离，记录过程中的位移和作用力，认为受力平衡时的力为极片的剥离强度，测试装置如图2所示，测试结果如表2所示。
(2)上述实施例和对比例中涉及到的容量保持率和膨胀率是采用如下方法测试得到的：
常温25℃下，以0.7C/0.5C充放电循环250次，计算250次后电池的容量保持率及电池的膨胀率，测试结果如表2所示。
(3)上述实施例和对比例中涉及到的倍率性能(倍率放电)是采用如下方法测试得到的：
将满电电池分别在0.2C/0.5C/1.0C/1.5C/2.0C放电至截止电压，计算容量保 持率(比0.2C放电的容量保持率)，即0.5C/0.2C，1.0C/0.2C，1.5C/0.2C，2C/0.2C的值，测试结果如表3所示。
表1 实施例中R 1和R 2结构式
Figure PCTCN2022127483-appb-000013
表2 实施例和对比例制备得到的电池的循环性能及负极片的剥离强度
组别 剥离强度(N/m) 容量保持率(％) 膨胀率(％)
实施例1 20.8 97.3 5.5
对比例1 15.6 92.1 8.6
实施例2 27.0 97.1 6.4
对比例2 12.5 90.9 8.8
实施例3 19.8 94.9 5.9
对比例3 13.5 90.7 9.2
实施例4 25.0 96.3 4.8
对比例4 16.6 90.4 6.8
对比例5 19.7 91.0 8.3
表3 实施例及对比例制备得到的电池的倍率性能
组别 0.5C/0.2C 1C/0.2C 1.5C/0.2C 2C/0.2C
实施例1 96.47％ 94.25％ 90.41％ 86.68％
对比例1 91.62％ 89.61％ 83.25％ 82.24％
实施例2 96.77％ 93.94％ 91.02％ 86.88％
对比例2 93.34％ 90.31％ 88.49％ 82.14％
实施例3 96.77％ 93.54％ 90.31％ 87.39％
对比例3 91.42％ 87.49％ 83.55％ 80.73％
实施例4 94.45％ 92.23％ 89.30％ 85.87％
对比例4 90.31％ 88.29％ 85.67％ 80.42％
对比例5 91.93％ 89.00％ 82.54％ 81.23％
从表2和表3可以看出，相比于对比例1-4，采用实施例1-4的粘结剂制备 的负极片剥离强度更高，由此证明了在粘结剂中引入了邻苯二酚的结构后，可以增加粘结剂的粘附作用。从电池的循环及倍率性能来看，实施例1-4比对比例1-4好，这归功于在粘结剂中引入邻苯二酚，能够在负极形成紧密的导电网络从而更利于电子的传输，也就使得在循环及大倍率电流作用下的电极的导电网络仍完好，所以循环过程中容量保持率更高，负极片膨胀更低，倍率性能也更优异。而实施例1-4与对比例5相比，尽管对比例5的剥离强度高，但由于没有可以导通离子的基团(如图1A所示)，其离子电导率比实施例1-4和对比例1-4相比都低，所以各实施例均比对比例5要好。由此可见，本公开的粘结剂能够很好的提升锂离子电池的循环稳定性，抑制循环膨胀，同时具有较佳的倍率性能。
以上对本公开示例性的实施方式进行了说明。但是，本申请的保护范围不拘囿于上述实施方式。本领域技术人员在本公开的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。

Claims (15)

  1. 一种粘结剂，所述粘结剂包括至少一种聚合物；其特征在于，所述聚合物具有如式1所示的结构：
    Figure PCTCN2022127483-appb-100001
    式1中，R 3和R 4相同或不相同，彼此独立地选自H、烷基、取代烷基或卤素，n为重复单元数；
    两端的封端基团R 1和R 2相同或不相同，彼此独立地选自H或如式2所示的邻苯二酚基，且R 1和R 2不同时为H，
    Figure PCTCN2022127483-appb-100002
    式2中，
    R 5相同或不同、彼此独立地选自烷基、烷氧基、胺基、芳基或卤素原子中的至少一种；
    m选自0、1、2或3；
    R 6选自亚烷基或不存在；
    R 7选自-C(＝O)-或-S(＝O)(＝O)-；
    *表示连接端。
  2. 根据权利要求1所述的粘合剂，其特征在于，所述R 1和R 2相同或不相同，彼此独立地选自H、具有式2-1～2-8所示结构的基团中的一种，且所述R 1和R 2不同 时为H；
    Figure PCTCN2022127483-appb-100003
  3. 根据权利要求1所述的粘结剂，其特征在于，所述R 1和R 2相同或不相同，彼此独立地选自具有式3-1～3-4所示结构的基团中的一种，且所述R 1和R 2不同时为H：
    Figure PCTCN2022127483-appb-100004
  4. 根据权利要求1所述的粘结剂，其特征在于，所述R 6为形成杂化轨道的原子或基团。
  5. 根据权利要求1所述的粘结剂，其特征在于，所述R 1和R 2相同或不相同，彼此独立地选自具有式4-1～4-8所示结构的基团，且所述R 1和R 2不同时为H：
    Figure PCTCN2022127483-appb-100005
  6. 根据权利要求1-5任一项所述的粘结剂，其特征在于，所述粘结剂的重均分子量为5×10 3～1000×10 4。
  7. 根据权利要求1-6任一项所述的粘结剂，其特征在于，所述粘结剂的玻璃化转变温度为-70℃～-40℃。
  8. 根据权利要求1-7任一项所述的粘结剂，其特征在于，所述粘结剂的离子电导率为10 -6S·cm -1～10 -4S·cm -1。
  9. 根据权利要求1-8任一项所述的粘结剂，其特征在于，所述粘结剂为溶液型粘结剂；
    优选地，所述粘结剂的固含量为4wt％～25wt％。
  10. 根据权利要求9所述的粘结剂，其特征在于，所述溶液型粘结剂的粘度为500～100000mPa·s。
  11. 一种负极片，其特征在于，所述负极片包括负极集流体和位于集流体至少一侧的负极活性层，所述负极活性层含有第一粘结剂，所述第一粘结剂选自权利要求1-10任一项所述的粘结剂。
  12. 根据权利要求11所述的负极片，其特征在于，所述负极活性层还含有第二粘结剂，所述第二粘结剂选自SBR乳液、苯丙乳液和聚丙烯酸类粘结剂中的至少一种。
  13. 根据权利要求11或12所述的负极片，其特征在于，所述第一粘结剂和第二粘结剂的总量占负极浆料中总固体质量的0.5-5wt％。
  14. 根据权利要求11-13任一项所述的负极片，其特征在于，所述第一粘结剂占第一粘结剂和第二粘结剂的总质量的10～90％。
  15. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1-10任一项所述的粘结剂，和/或包括权利要求11-14任一项所述的负极片。
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