CN114497562B - Polyurethane binder, preparation method thereof and positive electrode of lithium battery - Google Patents

Polyurethane binder, preparation method thereof and positive electrode of lithium battery Download PDF

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CN114497562B
CN114497562B CN202111654252.2A CN202111654252A CN114497562B CN 114497562 B CN114497562 B CN 114497562B CN 202111654252 A CN202111654252 A CN 202111654252A CN 114497562 B CN114497562 B CN 114497562B
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parts
lithium
polyurethane binder
polyurethane
stirring
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CN114497562A (en
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萧景驰
张淑雅
崔庆实
黄泽熹
王杰
袁黎光
杨小牛
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Huangpu Institute of Materials
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Huangpu Institute of Materials
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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
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/028—Positive 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a polyurethane binder, which comprises 100-200 parts of isocyanate by weight; 200-300 parts of PTMEG; 10-20 parts of a catalyst; 5-50 parts of MOCA; BDO 5-50 parts; 15-30 parts of lithium salt; 300-800 parts of solvent. The invention also discloses a preparation method of the polyurethane binder and a lithium battery positive electrode prepared by adopting the polyurethane binder. The invention improves the electronic and ionic conductivity and prolongs the service life of the lithium battery; the raw materials are easy to obtain, the synthesis operation is simple, and the method is suitable for industrial production and application.

Description

Polyurethane binder, preparation method thereof and positive electrode of lithium battery
Technical Field
The invention relates to the field of binders for lithium batteries, in particular to a polyurethane binder, a preparation method thereof and a positive electrode of a lithium battery.
Background
The binder is a key component for preparing the positive electrode of the lithium battery, and the active substance and the conductive agent are firmly adhered to the current collector through the binder to prevent the current collector from falling off, so that the integrity and the structural stability of the electrode are maintained, and the mechanical stability of the pole piece and the utilization rate of the active substance are enhanced.
PVDF is currently the most popular lithium ion battery binder due to its excellent electrochemical and thermal stability, but it suffers from the following disadvantages: (1) poor electronic and ionic conductivity; (2) Is easily dissolved by electrolyte, resulting in poor adhesion of active materials on the current collector; (3) the mechanical property and elasticity are not ideal; (4) Lithium carbide is easy to form with metal lithium, so that the service life and the safety performance of the battery are affected; and (5) the humidity requirement on the environment is high during storage and use.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a polyurethane binder, which improves electronic and ionic conductivity and prolongs the service life of a lithium battery.
Another object of the present invention is to provide a method for preparing the above polyurethane binder.
It is still another object of the present invention to provide a positive electrode for a lithium battery.
The aim of the invention is achieved by the following technical scheme:
a polyurethane binder comprises, by weight
Preferably, the isocyanate is IPDI (isophorone diisocyanate).
Preferably, the catalyst is dibutyl tin dilaurate.
Preferably, the lithium salt is LITFSI.
Preferably, the solvent is NMP (N-methylpyrrolidone).
The preparation method of the polyurethane binder comprises the following steps:
(1) Under the protection of inert gas, PTMEG, MOCA, BDO is mixed and stirred at 105-110 ℃ for vacuum water removal;
(2) Adding solvent at 75-85 deg.c and stirring to disperse;
(3) Adding isocyanate in a dropwise manner, and stirring for dispersion;
(4) Adding a catalyst, adding lithium salt, stirring and dispersing to react to obtain the polyurethane binder.
Preferably, the stirring speed in the step (1) is 750-850 rpm; the time for vacuum water removal is 3.5-4.5 hours;
the stirring rotating speed in the step (2) is 750-850 rpm.
Preferably, the dropping in the step (3) is constant pressure dropping; the stirring rotating speed in the step (3) is 750-850 rpm.
Preferably, the stirring dispersion reaction in the step (4) specifically comprises:
and the reaction is dispersed for 2.5 to 3.5 hours at the rotating speed of 550 to 650.
A positive electrode of a lithium battery is prepared from an active substance, a conductive material and the polyurethane binder.
Preferably, the positive electrode of the lithium battery is prepared by the following method:
lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio (7-9): 1: (3-3.5) grinding for 25-35 minutes, coating on a metal foil by a scraper, vacuumizing and drying at 75-85 ℃ for 11-13 hours, compacting at 4.5-5.5 mpa, annealing at 45-55 ℃ for 22-25 hours, and cutting into pole pieces.
The principle of the invention is as follows:
the invention utilizes the phase separation structure of the soft and hard segments of polyurethane, and can provide a special lithium ion transmission channel through the special ether bond of PTMEG, so that the polyurethane binder has more lithium ion channels relative to PVDF; meanwhile, the coulomb efficiency of lithium ions can be effectively improved through the Cl element of MOCA, and the dielectric constant of the binder can be improved through carbamate bonds in polyurethane, so that the migration number of lithium ions can be effectively improved, and the positive electrode material has better electrochemical performance. In addition, the polyurethane material prepared by the invention has better crosslinking density and higher chemical resistance, so the polyurethane material has better adhesive property and solvent corrosion resistance.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) Compared with PVDF, the polyurethane binder provided by the invention has more lithium ion channels, the coulomb efficiency of lithium ions can be effectively improved through the Cl element of MOCA, the dielectric constant of the binder can be provided by carbamate bonds in polyurethane, the migration number of lithium ions can be effectively improved, and the positive electrode material has better electrochemical performance, so that the lithium ion battery adopting the binder provided by the invention has better electronic and ionic conductivity.
(2) The polyurethane binder has better corrosion resistance in electrolyte due to better crosslinking density and higher chemical resistance of the material.
(3) Compared with PVDF, the polyurethane adhesive has better adhesive property between anode material powder and adhesive force between the anode material powder and aluminum foil, so the polyurethane adhesive has good adhesive property.
(4) Compared with the monocomponent and the monocomponent weight of PVDF, the polyurethane material in the polyurethane binder has the tensile and bending properties of the soft segment and the hard segment, and the high modulus and high hardness properties of the hard segment content, so that the polyurethane material has more excellent mechanical properties.
(5) The polyurethane binder disclosed by the invention is easy to obtain raw materials, simple in synthesis operation and suitable for industrial production and application.
Drawings
Fig. 1 is a comparison of the results of the rate performance test of the lithium ion batteries prepared in example 1, comparative example 1 and comparative example 2 according to the present invention.
Fig. 2 is a comparison of the cycle performance test results of the lithium ion batteries prepared in example 1, comparative example 1, and comparative example 2 according to the present invention.
Fig. 3 is a comparison of impedance performance test results of the lithium ion batteries prepared in this example, comparative example 1, and comparative example 2.
Detailed Description
The present invention will be described in further detail with reference to examples, but embodiments of the present invention are not limited thereto.
Example 1
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 82 parts of isocyanate, 200 parts of PTMEG, 10 parts of a first chain extender, 16 parts of a second chain extender, 15 parts of lithium salt and 390 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane adhesive of the embodiment comprises the following steps:
(1) 200 parts of PTMEG, 10 parts of a first chain extender and 16 parts of a second chain extender are added under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) Reducing the temperature to 80 ℃, adding 390 parts of solvent into the material obtained in the step (1), and dispersing for 30 minutes at the speed of 800 rpm;
(3) 82 parts of isocyanate is added by a constant pressure dropwise adding method, dispersed for 30 minutes at a speed of 800rpm, 10 parts of catalyst is added by a dropwise adding method, 15 parts of lithium salt is added, and the dispersion reaction is carried out for 3 hours at a speed of 600rpm, so as to obtain the polyurethane binder.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
The comparison of the results of the rate performance tests of the lithium ion batteries prepared in this example, comparative example 1 (see below for specific preparation method) and comparative example 2 (see below for specific preparation method) shows that the lithium ion battery prepared in this example has higher rate performance and the assembled battery has smaller impedance, which benefits from the higher ionic conductivity and lithium ion migration number of the polyurethane material prepared in this example.
The results of the cycle performance test of the lithium ion batteries prepared in this example, comparative example 1 and comparative example 2 are compared with those of fig. 2, and it can be seen from the graph that the lithium ion battery prepared in this example has a higher cycle retention rate, which benefits from the higher corrosion resistance of the prepared polyurethane material in the electrolyte compared with PDVF, and more lithium ion migration number and chemical stability.
The impedance performance test results of the lithium ion batteries prepared in this example, comparative example 1 and comparative example 2 are compared with those of fig. 3, and it can be seen from the graph that the lithium ion battery prepared in this example has smaller battery impedance, which benefits from the higher adhesive performance and ionic conductivity performance of the prepared polyurethane material relative to PDVF.
Example 2
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 120 parts of isocyanate, 200 parts of PTMEG, 20 parts of a first chain extender, 24 parts of a second chain extender, 15 parts of lithium salt and 520 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
(1) The preparation method of the polyurethane binder comprises the following steps:
200 parts of PTMEG, 20 parts of a first chain extender and 24 parts of a second chain extender are added under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) Reducing the temperature to 80 ℃, adding 520 parts of solvent into the material obtained in the step (1), and dispersing for 30 minutes at the speed of 800 rpm;
(3) 120 parts of isocyanate is added by a constant pressure dropwise adding method, dispersed for 30 minutes at a speed of 800rpm, 10 parts of catalyst is added by a dropwise adding method, 15 parts of lithium salt is added, and the dispersion reaction is carried out for 3 hours at a speed of 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Example 3
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 160 parts of isocyanate, 200 parts of PTMEG, 30 parts of a first chain extender, 32 parts of a second chain extender, 15 parts of lithium salt and 650 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane adhesive of the embodiment comprises the following steps:
(1) 120 parts of PTMEG, 30 parts of a first chain extender and 32 parts of a second chain extender are added under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) Reducing the temperature to 80 ℃, adding 650 parts of solvent into the material obtained in the step (1), and dispersing for 30 minutes at the speed of 800 rpm;
(3) 160 parts of isocyanate is added by a constant pressure dropwise adding method, dispersed for 30 minutes at 800rpm, 10 parts of catalyst is added by dropwise adding method, 15 parts of lithium salt is added, and the dispersion reaction is carried out for 3 hours at 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Example 4
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 200 parts of isocyanate, 200 parts of PTMEG, 30 parts of a first chain extender, 30 parts of a second chain extender, 15 parts of lithium salt and 780 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane binder comprises the following steps:
(1) 200 parts of PTMEG, 30 parts of a first chain extender and 30 parts of a second chain extender are put under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) Reducing the temperature to 80 ℃, adding 780 parts of solvent into the material obtained in the step (1), and dispersing for 30 minutes at the speed of 800 rpm;
(3) 200 parts of isocyanate was added by a constant pressure dropping method, dispersed at 800rpm for 30 minutes, then 10 parts of catalyst was added dropwise, 15 parts of lithium salt was added, and then the dispersion reaction was carried out at 600rpm for 3 hours.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Example 5
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 82 parts of isocyanate, 200 parts of PTMEG, 18 parts of a first chain extender, 4 parts of a second chain extender, 15 parts of lithium salt and 420 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane adhesive of the embodiment comprises the following steps:
(1) 200 parts of PTMEG, 18 parts of a first chain extender and 4 parts of a second chain extender are added under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) The temperature is reduced to 80 ℃, 420 parts of solvent is added into the material obtained in the step (1), and the material is dispersed for 30 minutes at the speed of 800 rpm;
(3) 82 parts of isocyanate is added by a constant pressure dropwise addition method, dispersed for 30 minutes at 800rpm, 10 parts of catalyst is added by dropwise addition, 15 parts of lithium salt is added, and the dispersion reaction is carried out for 3 hours at 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Example 6
The polyurethane binder of the embodiment is prepared from the following raw materials in parts by weight: 82 parts of isocyanate, 200 parts of PTMEG, 4 parts of a first chain extender, 14 parts of a second chain extender, 15 parts of lithium salt and 370 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane binder comprises the following steps:
(1) 200 parts of PTMEG, 4 parts of a first chain extender and 14 parts of a second chain extender are added under the protection of nitrogen, and water is removed in vacuum for 4 hours at 110 ℃ at a rotation speed of 800 rpm.
(2) The temperature is reduced to 80 ℃, 340 parts of solvent is added into the material obtained in the step (1), and the material is dispersed for 30 minutes at the speed of 800 rpm;
(3) 82 parts of isocyanate are added by a constant pressure dropwise addition method, dispersed for 30 minutes at 800rpm, 10 parts of catalyst are added by a dropwise addition method, 15 parts of lithium salt are added, and the dispersion reaction is carried out for 3 hours at 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Comparative example 1
(1) Lithium iron phosphate, conductive carbon black, and PVDF according to 8:1:1 grinding for 30 min, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 h, compacting under 5mpa pressure, annealing at 50 ℃ for 24 h, and cutting into pole pieces with the diameter of 12 mm.
(2) And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this example are shown in table 3.
Comparative example 2
The polyurethane binder of the comparative example is prepared from the following raw materials in parts by weight: 82 parts of isocyanate, 200 parts of PTMEG, 30 parts of a first chain extender, 15 parts of lithium salt and 370 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the first chain extender is MOCA; the solvent was NMP and the lithium salt was LITFSI.
The preparation method of the polyurethane binder of the comparative example comprises the following steps:
(1) 200 parts of PTMEG and 30 parts of a first chain extender were charged under nitrogen protection, and water was removed in vacuo at 110℃and 800rpm for 4 hours.
(2) The temperature is reduced to 80 ℃, 380 parts of solvent is added into the material obtained in the step (1), and the material is dispersed for 30 minutes at the speed of 800 rpm;
(3) 82 parts of isocyanate are added by a constant pressure dropwise addition method, dispersed for 30 minutes at 800rpm, 10 parts of catalyst are added by a dropwise addition method, 15 parts of lithium salt are added, and the dispersion reaction is carried out for 3 hours at 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this comparative example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this comparative example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this comparative example are shown in table 3.
From the test results, the polyurethane binder prepared by using MOCA alone as the chain extender can form a very dense crosslinking system, and can block the migration of lithium ions, so that the conductivity of the lithium ions is reduced, and the rate performance and the cycle performance of the battery are affected.
Comparative example 3
The polyurethane binder of the comparative example is prepared from the following raw materials in parts by weight: 82 parts of isocyanate, 200 parts of PTMEG, 16 parts of a second chain extender, 15 parts of lithium salt and 370 parts of a solvent, wherein the isocyanate is IPDI; PTMEG polyol molecular weight 1000, available from Basoff; the catalyst is dibutyl tin dilaurate; the second chain extender was BDO, the solvent was NMP, and the lithium salt was LITFSI.
The preparation method of the polyurethane binder of the comparative example comprises the following steps:
(1) 200 parts of PTMEG and 16 parts of a second chain extender are charged under nitrogen protection, and water is removed in vacuo at 110℃and a rotation speed of 800rpm for 4 hours.
(2) The temperature is reduced to 80 ℃, 370 parts of solvent is added into the material obtained in the step (1), and the material is dispersed for 30 minutes at the speed of 800 rpm;
(3) 82 parts of isocyanate are added by a constant pressure dropwise addition method, dispersed for 30 minutes at 800rpm, 10 parts of catalyst are added by a dropwise addition method, 15 parts of lithium salt are added, and the dispersion reaction is carried out for 3 hours at 600 rpm.
After the materials are placed at room temperature, lithium iron phosphate, conductive carbon black and the polyurethane binder liquid are mixed according to the weight ratio of 8:1:3.3 grinding for 30 minutes, coating on aluminum foil by a scraper, vacuumizing and drying at 80 ℃ for 12 hours, compacting under 5mpa pressure, annealing at 50 ℃ for 24 hours, and cutting into pole pieces with the diameter of 12 mm.
And assembling the PP diaphragm, the ester electrolyte, the lithium iron phosphate positive plate (phi 12 mm) and the lithium plate (phi 15 mm) into the CR2025 button cell. This procedure was carried out in a glove box (H 2 O＜0.1ppm，O 2 < 0.1 ppm).
The results of the rate performance test of the lithium ion battery prepared in this comparative example are shown in table 1.
The results of the cycle performance test of the lithium ion battery prepared in this comparative example are shown in table 2.
The impedance performance test results of the lithium ion battery prepared in this comparative example are shown in table 3.
According to the test results, the polyurethane binder prepared by the chain extender simply by BDO can form a loose crosslinking system, so that the mechanical property of the polyurethane material is insufficient, the binder in the positive electrode material is easily corroded by electrolyte, the positive electrode material is easily fallen off, and the service life of the lithium ion battery is influenced.
TABLE 1
TABLE 2
TABLE 3 Table 3
The embodiments described above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the present invention should be made in the equivalent manner, and are included in the scope of the present invention.

Claims (10)

1. A polyurethane adhesive is characterized by comprising the following components in parts by weight
100-200 parts of isocyanate
200-300 parts of PTMEG
10-20 parts of catalyst
MOCA 5-50 parts
BDO 5-50 parts
15-30 parts of lithium salt
300-800 parts of a solvent.
2. The polyurethane binder of claim 1 wherein the isocyanate is IPDI.
3. The polyurethane adhesive of claim 1, wherein the catalyst is dibutyltin dilaurate.
4. The polyurethane binder of claim 1 wherein the lithium salt is LITFSI.
5. The polyurethane binder of claim 1 wherein the solvent is NMP.
6. The method for preparing the polyurethane adhesive according to any one of claims 1 to 5, which is characterized by comprising the following steps:
(1) Mixing PTMEG, MOCA, BDO under the protection of inert gas, stirring at 105-110 ℃, and vacuum dewatering;
(2) Adding a solvent at 75-85 ℃ and stirring for dispersion;
(3) Adding isocyanate in a dropwise manner, and stirring for dispersion;
(4) Adding a catalyst, adding lithium salt, stirring and dispersing to react to obtain the polyurethane binder.
7. The method for producing a polyurethane adhesive according to claim 6, wherein the stirring in the step (1) is carried out at a rotational speed of 750 to 850rpm; the time for vacuum dehydration is 3.5-4.5 hours;
and (3) stirring in the step (2) at a rotating speed of 750-850 rpm.
8. The method for producing a polyurethane adhesive according to claim 6, wherein the dropping in the step (3) is constant pressure dropping; and (3) stirring at 750-850 rpm.
9. The method for preparing a polyurethane adhesive according to claim 6, wherein the stirring dispersion reaction in the step (4) is specifically:
and (3) dispersing and reacting for 2.5-3.5 hours at a rotating speed of 550-650 rpm.
10. A positive electrode for a lithium battery, which is characterized by being prepared from an active substance, a conductive material and the polyurethane binder according to any one of claims 1 to 5.
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