WO2024055154A1

WO2024055154A1 - Block polymer and preparation method therefor and use thereof, and composition

Info

Publication number: WO2024055154A1
Application number: PCT/CN2022/118450
Authority: WO
Inventors: 黄继春; 吴燕英; 王星会
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-09-13
Filing date: 2022-09-13
Publication date: 2024-03-21
Also published as: CN118661295A

Abstract

The present application relates to a block polymer. A cyano group, an ester group and a polyethylene oxide block are introduced into the block polymer, such that the block polymer not only has a relatively good dispersion effect when used as a dispersing agent, but also has the characteristic of being resistant to high voltages and does not decompose at 4.3 V or above, thereby being applicable to high-voltage systems. Therefore, using the block polymer in the present application as a positive electrode dispersing agent in a positive electrode slurry can improve the dispersion uniformity of the positive electrode slurry, thereby significantly reducing the diaphragm resistance of a positive electrode sheet, reducing the direct-current resistance (DCR) of a battery cell, inhibiting the growth of the DCR, increasing the charging voltage of the battery cell and enhancing the cycle performance of the battery cell. The present application also relates to a preparation method for and the use of a block polymer, and a composition, a positive electrode slurry, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electric device.

Description

A block polymer and its preparation method and use, composition

Technical field

This application relates to the technical field of secondary batteries, specifically a block polymer and its preparation method and use, composition, positive electrode slurry, positive electrode sheet, secondary battery, battery module, battery pack and electrical device.

Background technique

Lithium-ion batteries (LIBs) are widely used in consumer electronics and electric vehicles as well as energy storage applications due to their long cycle life, wide operating temperature range, and high energy and power density. In order to meet the demand of electric vehicle customers for longer driving range on a single charge, it is necessary to increase the energy density of electric vehicle batteries. One of the ways to increase energy density is to increase the charging voltage of the battery cell. At present, the maximum charging cut-off voltage of a commercial lithium-ion battery cell is 4.3V. To further increase the voltage to 4.5V, high-voltage-resistant ternary cathode materials, high-voltage-resistant electrolytes, and high-voltage-resistant dispersants are required. Currently, polyvinylpyrrolidone (PVP), a commonly used dispersant for lithium-ion battery cathode materials, has good dispersion effect, but it will decompose above 4.3V and is not suitable for high-voltage systems.

Therefore, it is necessary to provide a dispersant with good dispersion effect and high voltage resistance, which can reduce the diaphragm resistance of the positive electrode plate, reduce the DCR of the battery core, increase the charging voltage of the battery core, and enhance the cycle performance of the battery core.

Contents of the invention

In view of the problems existing in the background technology, this application provides a block polymer, which can be used as a dispersant, has good dispersion effect and can withstand high voltage, can reduce the diaphragm resistance of the positive electrode plate and reduce the DCR of the battery cell. , and increase the charging voltage of the battery core and enhance the cycle performance of the battery core.

The block polymer provided in the first aspect of the application includes polyolefin A blocks, polyolefin B blocks and polyethylene oxide blocks. The polyolefin A block contains cyano groups. The polyolefin B block is connected to the polyolefin A block, and the polyolefin B block contains an ester group. One end of the polyethylene oxide block is connected to the polyolefin A block or polyolefin B block through a connecting unit, and the other end is connected to the terminal group R ¹ . Wherein, the terminal group R ¹ is selected from the following groups: C ₁ -C ₂₀ alkyl, C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy; or phenyl, phenyl is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ alkoxy.

In the technical solutions of the embodiments of the present application, by introducing cyano groups, ester groups and polyethylene oxide blocks into the block polymer, not only the block polymer has a better dispersion effect when used as a dispersant, but also It has high voltage resistance characteristics and does not decompose above 4.3V, so it is suitable for high voltage systems. Therefore, using the block polymer of the present application as a cathode dispersant in the cathode slurry can improve the dispersion uniformity of the cathode slurry, thereby significantly reducing the diaphragm resistance of the cathode plate and reducing the DC resistance (DCR) of the battery core. ), inhibit the growth of DCR, increase the charging voltage of the battery core, and enhance the cycle performance of the battery core.

In some embodiments, according to the first aspect, a first example of the first aspect is proposed, the connection unit includes the following structural formula

Among them, R ² is hydrogen or C ₁ -C ₂₀ alkyl, and C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy; * indicates sites for attachment to other groups.

In this design, by optimizing the connecting units, it is beneficial to easily and stably connect the polyethylene oxide block and the polyolefin A block or polyolefin B block.

In some embodiments, according to the first aspect, a second example of the first aspect is provided, the block polymer has the structure of general formula I:

in,

Has a structure selected from:

*Indicates the site connected to other groups;

R ¹ and R ² are as defined above;

R ³ , R ⁴ , R ⁵ and R ⁶ are independently hydrogen, halogen or C ₁ -C ₂₀ alkyl, and C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy;

R ⁷ is C ₁ -C ₂₀ alkyl, and C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy;

L ₁ and L ₂ are independently absent from each other, or _are independently C ₁ _-C ₂₀ alkylene, which is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ alkoxy;

a, b and c are 10-5000 independently of each other.

In this design, optimizing the structure of the block polymer will help further improve the dispersion effect and high voltage resistance characteristics of the block polymer when used as a dispersant.

In some embodiments, according to the first aspect, a third example of the first aspect is provided, the block polymer has a structure of general formula I-1:

in,

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , L ₁ , L ₂ , a, b and c are as defined above.

In some embodiments, according to a fourth example of the first aspect, the block polymer has a weight average molecular weight of 10,000-300,000 Daltons.

In this design, by optimizing the weight average molecular weight of the block polymer, it is beneficial to provide more polar groups in a smaller amount of addition. These polar groups can be adsorbed on the surface of the cathode active material particles and improve the cathode activity. The dispersion of materials can reduce the diaphragm resistance, reduce the DC resistance (DCR) of the battery core, and improve the cycle performance of the battery core.

In some embodiments, according to the fifth example of the first aspect, the block polymer has a weight average molecular weight of 200,000-250,000 Daltons.

In this design, by optimizing the weight average molecular weight of the block polymer, the weight average molecular weight is distributed within a narrow range, which is conducive to further improving the dispersion effect when the block polymer is used as a dispersant.

In some embodiments, according to the first aspect, a sixth example of the first aspect is proposed, a:b:c=(0.8-1.2):(0.8-1.2):(0.8-1.2).

In this design, by optimizing the proportional relationship between the degrees of polymerization a, b and c, it is beneficial to achieve better dispersion effects.

In some embodiments, according to the first aspect, a seventh example of the first aspect is proposed, R ¹ is selected from the following groups: C ₁ -C ₁₂ alkyl, C ₁ -C ₁₂ alkyl is unsubstituted or selected Substituted with a substituent selected from: halogen, hydroxyl, or C ₁ -C ₁₂ alkoxy; or phenyl, phenyl being unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₁₂ alkyl or C ₁ -C ₁₂ alkoxy;

R ² is hydrogen or C ₁ -C ₁₂ alkyl, and C ₁ -C ₁₂ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₁₂ alkoxy;

R ³ , R ⁴ , R ⁵ and R ⁶ are independently hydrogen or C ₁ -C ₁₂ alkyl, and C ₁ -C ₁₂ alkyl is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl or C ₁ -C ₁₂ alkoxy;

R ⁷ is C ₁ -C ₁₂ alkyl, and C ₁ -C ₁₂ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₁₂ alkoxy;

L ₁ and L ₂ do not exist independently of each other.

In this design, by optimizing the groups R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , L ₁ and L ₂ , it is helpful to further improve the dispersion of the block polymer when used as a dispersant. effect and high voltage resistance characteristics.

In some embodiments, according to the first aspect, an eighth example of the first aspect is provided, and R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are all hydrogen.

In this design, by optimizing the groups R ² , R ³ , R ⁴ , R ⁵ and R ⁶ , it is helpful to further improve the dispersion effect and high voltage resistance characteristics of the block polymer when used as a dispersant.

In some embodiments, according to the first aspect, a ninth example of the first aspect is provided, the block polymer has amphiphilicity.

In this design, the block polymer has both hydrophilicity and lipophilicity, which is beneficial to further improving the dispersion effect when the block polymer is used as a dispersant.

A second aspect of the application provides a method for preparing block polymers, including the following steps:

Mix the ethylenically unsaturated monomer A containing a cyano group, an initiator, a chain transfer agent and a solvent, and polymerize the monomer A to obtain a solution A;

Add ethylenically unsaturated monomer B containing an ester group to solution A, and polymerize the system to obtain solution B;

Add substituted or unsubstituted acrylic acid to solution B, and react the system to obtain product 1;

Mix R ¹ O ^- Na ⁺ , ethylene oxide, initiator, chain transfer agent and solvent, and react the system to obtain product 2, in which R ¹ is selected from the following groups: C ₁ -C ₂₀ alkyl , C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy; or phenyl, phenyl is unsubstituted or substituted with a substituent selected from the following Base substitution: halogen, hydroxyl, C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ alkoxy;

Product 1 and product 2 are subjected to an esterification reaction to obtain a block polymer.

In the technical solution of the embodiment of the present application, the block polymer of the present application can be easily prepared using monomer A, monomer B, acrylic acid, R ¹ O ^- Na ⁺ and ethylene oxide as raw materials. The preparation method operates Simple, highly reproducible, and suitable for large-scale industrial production.

In some embodiments, according to the second aspect, a first example of the second aspect is proposed, and the monomer A has the following structure:

Monomer B has the following structure:

Substituted or unsubstituted acrylic acid has the following structure:

in,

R ² is hydrogen or C ₁ -C ₂₀ alkyl, and C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy;

L ₁ and L ₂ are independently absent from each other, or _are independently C ₁ _-C ₂₀ alkylene, which is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ alkoxy.

In this design, by optimizing monomer A, monomer B and groups R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , L ₁ and L ₂ , it is beneficial to further improve the dispersion of the block polymer. The dispersion effect and high voltage resistance characteristics when using the agent.

In some embodiments, according to the second aspect, a second example of the second aspect is proposed, the molar ratio of monomer A, monomer B and substituted or unsubstituted acrylic acid (15-30): (15-30): 1.

In this design, optimizing the molar ratio of monomer A, monomer B and acrylic acid will help improve the conversion rate of product 1.

In some embodiments, according to the second aspect, a third example of the second aspect is provided, the molar ratio of R ¹ O ^- Na ⁺ and ethylene oxide is 1: (80-120).

In this design, by optimizing the molar ratio of R ¹ O ^- Na ⁺ and ethylene oxide, it is beneficial to increase the conversion rate of product 2.

In some embodiments, according to the second aspect, a fourth example of the second aspect is proposed, the molar ratio of product 1 and product 2 is (0.8-1.2): (0.8-1.2).

In this design, optimizing the molar ratio of product 1 and product 2 will help improve the conversion rate of the block polymer.

In some embodiments, according to the second aspect, a fifth example of the second aspect is proposed. In the step of preparing solution A, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is performed in a protective atmosphere. . In the step of preparing solution B, the reaction temperature is 50-100°C and the reaction time is 1-10 h. In the step of preparing product 1, the reaction temperature is 50-100°C and the reaction time is 1-10h. In the step of preparing product 2, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is carried out in a protective atmosphere. Product 1 and product 2 react in the presence of an acidic catalyst, the reaction temperature is 60°C, and the reaction time is 6 hours.

In this design, by optimizing the reaction conditions of each step, it is beneficial to promote each step of the reaction to proceed quickly with a high conversion rate and increase the yield of the final product.

The third aspect of the present application provides the use of the block polymer described in the first aspect of the present application or the block polymer obtained by the preparation method described in the second aspect of the present application as a dispersant.

When used as a dispersant, the block polymer of the present application has good dispersion effect, high voltage resistance, and good electrochemical stability.

The fourth aspect of the present application provides a composition, including: the block polymer described in the first aspect of the present application or the block polymer obtained by the preparation method described in the second aspect of the present application; and a solvent.

In the technical solutions of the embodiments of the present application, since the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application is used, the composition of the present application is used as a dispersant. It has good dispersion effect and high voltage resistance. In addition, block polymers are mixed with solvents into compositions that facilitate pipeline transportation for large-scale applications.

The fifth aspect of the present application provides a cathode slurry, including the block polymer described in the first aspect of the present application or the block polymer obtained by the preparation method described in the second aspect of the present application.

In the technical solutions of the embodiments of the present application, since the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application is used, the cathode slurry of the present application has better The dispersion effect also has high voltage resistance characteristics.

In some embodiments, according to the fifth aspect and the first example of the fifth aspect, the mass proportion of the block polymer in the cathode slurry is 0.05%-2%.

In this design, optimizing the content of the block polymer in the cathode slurry will help improve the dispersion of the cathode active material, thereby reducing the diaphragm resistance, reducing the DCR of the cell and improving the cycle performance of the cell.

A sixth aspect of the present application provides a positive electrode sheet, including the block polymer described in the first aspect of the present application or the block polymer obtained by the preparation method described in the second aspect of the present application.

In the technical solutions of the embodiments of the present application, due to the use of the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application, the positive electrode sheet of the present application has a reduced film chip resistor.

A seventh aspect of the present application provides a secondary battery, including the positive electrode plate described in the sixth aspect of the present application.

In the technical solutions of the embodiments of the present application, due to the use of the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application, the secondary battery of the present application has reduced DCR. and improved cycle performance.

An eighth aspect of the present application provides a battery module, including the secondary battery described in the seventh aspect of the present application.

In the technical solutions of the embodiments of the present application, due to the use of the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application, the battery module of the present application has reduced DCR and Improved cycle performance.

A ninth aspect of the present application provides a battery pack, including the secondary battery of the seventh aspect of the present application or the battery module described in the eighth aspect of the present application.

In the technical solutions of the embodiments of the present application, due to the use of the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application, the battery pack of the present application has reduced DCR and Improved cycle performance.

A tenth aspect of the present application provides an electrical device, including at least one of the secondary battery described in the seventh aspect of the present application, the battery module described in the eighth aspect of the present application, and the battery pack described in the ninth aspect of the present application. A sort of.

In the technical solutions of the embodiments of the present application, due to the use of the block polymer of the first aspect of the present application or the block polymer obtained by the preparation method of the second aspect of the present application, the electrical device of the present application has reduced DCR. and improved cycle performance.

The above description is only an overview of the technical solutions of the present application. In order to have a clearer understanding of the technical means of the present application, they can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, Specific embodiments of the present application are listed below.

Description of drawings

Figure 1 is a CV curve of the block polymers of Examples 1, 2, 3 and 4 of the present application.

Figure 2 is a charge-discharge cycle curve diagram of the battery cells corresponding to Examples 1-4 and Comparative Example 1 of the present application.

Detailed ways

In order to make the invention purpose, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application and are not intended to limit the present application.

For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range. In addition, although not explicitly stated, every point or individual value between the endpoints of a range is included in the range. Thus, each point or single value may serve as a lower or upper limit on its own in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.

In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" are inclusive, and "multiple" in "one or more" means two or more (including two) .

The above summary of the present application is not intended to describe each disclosed embodiment or every implementation in the present application. The following description illustrates exemplary embodiments in more detail. At various points throughout this application, guidance is provided through a series of examples, which may be used in various combinations. In each instance, the enumerations are representative only and should not be construed as exhaustive.

Lithium-ion batteries are widely used in consumer electronics and electric vehicles as well as energy storage applications due to their long cycle life, wide operating temperature range, and high energy and power density. In order to meet the demand of electric vehicle customers for longer driving range on a single charge, it is necessary to increase the energy density of electric vehicle batteries. One of the ways to increase energy density is to increase the charging voltage of the battery cell. At present, the maximum charging cut-off voltage of a commercial lithium-ion battery cell is 4.3V. To further increase the voltage to 4.5V, high-voltage-resistant ternary cathode materials, high-voltage-resistant electrolytes, and high-voltage-resistant dispersants are required. Currently, polyvinylpyrrolidone (PVP), a commonly used dispersant for lithium-ion battery cathode materials, has good dispersion effect, but it will decompose above 4.3V and is not suitable for high-voltage systems. Therefore, it is necessary to provide a dispersant with high voltage resistance and good dispersion effect.

After in-depth research, the inventor designed a block polymer including cyano groups, ester groups and polyethylene oxide blocks. Among them, the cyano group has strong stability and good oxidation resistance. It can be adsorbed on the surface of the conductive agent, which can improve the high voltage resistance characteristics of the block polymer and the dispersion effect of the cathode material. The ester group can make the dispersant better Dissolved in the solvent, the polyethylene oxide block can improve the flexibility of the pole piece and also has a certain degree of dispersion. The block polymer can be used as a dispersant, has good dispersion effect and is resistant to high voltage, and does not decompose when used under high pressure.

The block polymer of the present application is used as a cathode dispersant in the cathode slurry. Since it has a good dispersion effect, it can improve the dispersion uniformity of the cathode slurry, thereby significantly reducing the membrane resistance of the cathode plate. Reduce the DCR of the battery core and inhibit the growth of DCR. In addition, because it does not decompose when used under high voltage, it can increase the charging voltage of the battery core and enhance the cycle performance of the battery core.

In addition, the block polymer of the present application has a wide range of applications and is suitable for ternary high-voltage systems, lithium-rich manganese-based systems, and 5V high-voltage lithium nickel manganate systems.

The technical solutions described in the embodiments of this application are applicable to block polymers, and are also applicable to the preparation process of block polymers, uses of block polymers, compositions containing block polymers, positive electrode slurries and positive electrode sheets, A secondary battery using a positive electrode plate, a battery module using a secondary battery, a battery pack using a secondary battery or a battery module, and an electric device using at least one of a secondary battery, a battery module, and a battery pack.

In a first aspect, according to some embodiments of the present application, the present application provides a block polymer including a polyolefin A block, a polyolefin B block and a polyethylene oxide block. The polyolefin A block contains cyano groups. The polyolefin B block is connected to the polyolefin A block, and the polyolefin B block contains an ester group. One end of the polyethylene oxide block is connected to the polyolefin A block or polyolefin B block through a connecting unit, and the other end is connected to the terminal group R ¹ . Wherein, the terminal group R ¹ is selected from the following groups: C ₁ -C ₂₀ alkyl, C ₁ -C ₂₀ alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C ₁ -C ₂₀ alkoxy; or phenyl, phenyl is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ alkoxy.

In this application, the connecting unit connects the polyethylene oxide block with the terminal group R ¹ to the polyolefin A block or the polyolefin B block, thereby realizing the introduction of the polyethylene oxide block and R ¹ . Improved dispersion of block polymers.

in,

Has a structure selected from:

* indicates the site of attachment to other groups;

R ¹ and R ² are as defined above;

a, b and c are 10-5000 independently of each other.

In this design, by optimizing the structure of the block polymer, it is beneficial to further improve the dispersion effect and high voltage resistance characteristics when the block polymer is used as a dispersant.

In some embodiments, L ₁ and L ₂ independently of each other can be C ₁ _-C ₁₂ alkylene, which is unsubstituted or substituted with a substituent selected from: _halogen , Hydroxy, C ₁ -C ₁₂ alkyl or C ₁ -C ₁₂ alkoxy. Alternatively, L ₁ and L ₂ independently of each other may be C ₁ _-C ₆ alkylene which is unsubstituted or substituted with a substituent selected _from : halogen, hydroxyl, C ₁ -C ₆ alkyl or C ₁ -C ₆ alkoxy. For example, C ₁ -C ₆ alkylene can be methylene-CH ₂ -, ethylene-CH ₂ CH ₂ -, propylene-CH ₂ CH ₂ CH ₂ -, butylene-CH ₂ CH ₂ CH ₂ CH ₂ -, pentylene-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -, or hexylene-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -.

In some specific embodiments, a, b and c may be 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600 independently of each other. , 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4 100 , 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900 or 5000. Alternatively, a, b and c may be 3000-5000 independently of each other.

in,

In this design, by optimizing the weight average molecular weight of the block polymer, it is beneficial to provide more polar groups in a smaller amount of addition. These polar groups can be adsorbed on the surface of the cathode active material particles and improve the cathode activity. The dispersion of materials reduces the diaphragm resistance, reduces the DC resistance (DCR) of the battery core, and improves the cycle performance of the battery core.

In some specific embodiments, the block polymer may have a weight average molecular weight of 10,000 Daltons, 15,000 Daltons, 20,000 Daltons, 25,000 Daltons, 30,000 Daltons, 35,000 Daltons, or 40,000 Daltons. Dayton, 45000 Dalton, 50000 Dalton, 55000 Dalton, 60000 Dalton, 65000 Dalton, 70000 Dalton, 75000 Dalton, 80000 Dalton, 85000 Dalton, 90000 Dalton Dayton, 95000 Dalton, 100000 Dalton, 105000 Dalton, 110000 Dalton, 115000 Dalton, 120000 Dalton, 125000 Dalton, 130000 Dalton, 135000 Dalton, 140000 Dalton Dayton, 145000 Dalton, 150000 Dalton, 155000 Dalton, 160000 Dalton, 165000 Dalton, 170000 Dalton, 175000 Dalton, 180000 Dalton, 185000 Dalton, 190000 Dalton Dayton, 195000 Dalton, 200000 Dalton, 205000 Dalton, 210000 Dalton, 215000 Dalton, 220000 Dalton, 225000 Dalton, 230000 Dalton, 235000 Dalton, 240000 Dalton Dayton, 245000 Dalton, 250000 Dalton, 255000 Dalton, 260000 Dalton, 265000 Dalton, 270000 Dalton, 275000 Dalton, 280000 Dalton, 285000 Dalton, 290000 Dalton Dayton, 295,000 Daltons or 300,000 Daltons.

In some specific embodiments, a:b:c=(0.9-1.1):(0.9-1.1):(0.9-1.1) or (0.95-1.05):(0.95-1.05):(0.95-1.05). Optionally, a:b:c=1:1:1.

L ₁ and L ₂ do not exist independently of each other.

In some embodiments, R ¹ is C ₁ -C ₁₂ alkyl, which is unsubstituted or substituted with a substituent selected from _: _halogen , hydroxyl, or C ₁ -C ₁₂ alkoxy. base. Alternatively, ^R1 may be methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl. These groups Unsubstituted or substituted by halogen, hydroxyl or C ₁ -C ₁₂ alkoxy. Alternatively, R ¹ may be a _C ₁ -C ₆ alkyl group that is unsubstituted or substituted with a substituent selected from: _halogen , hydroxyl or C ₁ -C ₆ alkoxy.

In some embodiments, R ¹ can be phenyl, which is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl, C ₁ -C ₁₂ alkyl, or C ₁ -C ₁₂ alkoxy. . Alternatively, R ¹ can be phenyl, which phenyl is unsubstituted or substituted with a substituent selected from halogen, hydroxyl, C ₁ -C ₆ alkyl or C ₁ -C ₆ alkoxy.

In some embodiments, R ² can be hydrogen or C ₁ -C ₆ alkyl, which is unsubstituted or substituted with a substituent selected _from : _halogen , hydroxyl or C ₁ -C ₆ alkoxy.

In some specific embodiments, R ³ , R ⁴ , R ⁵ and R ⁶ may independently be hydrogen or C ₁ -C ₆ alkyl, with C ₁ -C ₆ alkyl being unsubstituted or substituted selected from the following Base substitution: halogen, hydroxyl or C ₁ -C ₆ alkoxy.

In some embodiments, R ⁷ can be a C ₁ -C ₆ alkyl group that is unsubstituted or substituted with a substituent selected from _: _halogen , hydroxyl, or C ₁ -C ₆ alkyl. Oxygen group.

It should be noted that the above definitions or limitations for each group, connecting unit, a, b and c are also applicable to each group, connecting unit, a, b and c involved in the preparation method below.

Monomer B has the following structure:

Substituted or unsubstituted acrylic acid has the following structure:

in,

In some specific embodiments, monomer A may be substituted or unsubstituted acrylonitrile.

In some embodiments, monomer B may be a substituted or unsubstituted acrylate.

In some embodiments, according to the second aspect, a second example of the second aspect is proposed, the molar ratio of monomer A, monomer B and substituted or unsubstituted acrylic acid is (15-30): (15-30) :1.

In some specific embodiments, the molar ratio of monomer A, monomer B and substituted or unsubstituted acrylic acid can be 15:15:1, 16:16:1, 17:17:1, 18:18:1, 19:19:1, 20:20:1, 21:21:1, 22:22:1, 23:23:1, 24:24:1, 25:25:1, 26:26:1, 27: 27:1, 28:28:1, 29:29:1 or 30:30:1. Alternatively, the molar ratio of monomer A, monomer B and substituted or unsubstituted acrylic acid may be (15-25):(15-25):1 or (18-22):(18-22):1 .

In some specific embodiments, the molar ratio of R ¹ O ^- Na ⁺ and ethylene oxide can be 1:80, 1:85, 1:90, 1:95, 1:100, 1:105, 1:110 , 1:115 or 1:120. Alternatively, the molar ratio of R ¹ O ^- Na ⁺ and ethylene oxide may be 1:(90-110).

In some specific embodiments, the molar ratio of product 1 and product 2 can be 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1 :1.2. Alternatively, the molar ratio of product 1 and product 2 may be (0.9-1.1):(0.9-1.1).

In some embodiments, according to the second aspect, a fifth example of the second aspect is proposed. In the step of preparing solution A, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is performed in a protective atmosphere. . In the step of preparing solution B, the reaction temperature is 50-100°C and the reaction time is 1-10 h. In the step of preparing product 1, the reaction temperature is 50-100°C and the reaction time is 1-10 h. In the step of preparing product 2, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is carried out in a protective atmosphere. Product 1 and product 2 react in the presence of an acidic catalyst, the reaction temperature is 40-80°C, and the reaction time is 1-10 h.

In some specific embodiments, in the step of preparing solution A, the reaction temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C ℃. The reaction time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h. The protective atmosphere can be nitrogen or argon, etc.

In some specific embodiments, in the step of preparing solution B, the reaction temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C ℃. The reaction time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

In some specific embodiments, in the step of preparing product 1, the reaction temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C ℃. The reaction time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

In some specific embodiments, in the step of preparing product 2, the reaction temperature may be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C ℃. The reaction time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h. The protective atmosphere can be nitrogen or argon, etc.

In some specific embodiments, the reaction temperature of Product 1 and Product 2 may be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C. The reaction time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h. The acidic catalyst can be concentrated sulfuric acid, and the mass fraction of concentrated sulfuric acid can be more than 70%, for example, 70%, 75%, 80%, 85%, 90% or 98.3%.

Other initiators commonly used in polymerization reactions in this field are suitable for this application, and those skilled in the art can select them according to actual needs. In some embodiments, the initiator may include azobisisobutyronitrile (AIBN), azobisisoheptanitrile, hydrogen peroxide, ammonium persulfate, potassium persulfate, benzoyl peroxide, benzoyl peroxide One or more of the acyl tert-butyl esters.

Chain transfer agents commonly used in polymerization reactions in this field are suitable for this application, and those skilled in the art can select them according to actual needs. In some embodiments, the chain transfer agent may be the trithioester 2-(dodecyltrithiocarbonate)-2-isobutyric acid.

In some specific embodiments, the mass proportion of the block polymer in the cathode slurry can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9 %, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%. Alternatively, the mass proportion of the block polymer in the cathode slurry may be 0.05%-1.5% or 0.1%-1%.

In some embodiments, the secondary battery is a lithium-ion battery.

In some embodiments, a lithium-ion battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator.

The positive electrode sheet includes positive active material. The positive active material is at least one of the following materials: lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide or a composite of the above substances Material.

The negative electrode sheet includes negative active material. The negative active material is a commonly used negative electrode material, including but not limited to at least one of the following materials: graphite, soft carbon, hard carbon, non-carbon silicon-based materials, tin-based materials, lithium titanate (LTO), lithium metal wait.

The material of the separator can be nano-scale microporous polyolefin membrane, including polyethylene PE single-layer membrane, polypropylene PP single-layer membrane, PP/PE/PP multi-layer microporous membrane composed of PP and PE, and others for separation. Separators or non-woven fabrics coated on the positive and negative electrodes.

Electrolyte includes electrolyte and solvent.

In some embodiments, the electrolyte may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, and trifluoromethanesulfonate. At least one of lithium difluoride, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte optionally also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

Definitions and explanations of terms

The term "halogen" refers to F, Cl, Br or I.

The term "C ₁ -C ₂₀ alkyl" is understood to preferably mean a linear or branched saturated monovalent hydrocarbon radical having 1 to 20 carbon atoms, preferably a C ₁ -C ₁₂ alkyl group, more preferably a C ₁ -C ₆ alkyl. The term "C ₁ -C ₁₂ alkyl" is understood to preferably mean a straight-chain or branched saturated monovalent hydrocarbon radical having 1 to 12 carbon atoms. The term "C ₁ -C ₆ alkyl" is understood to mean preferably a direct or branched saturated monovalent hydrocarbon radical having 1, 2, 3, 4, 5 or 6 carbon atoms, for example methyl, ethyl, propyl , butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl base, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3- Dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl or their isomers. In particular, said groups have 1, 2, 3 or 4 carbon atoms ("C ₁ -C ₄ alkyl"), for example methyl, ethyl, propyl, butyl, isopropyl, isobutyl , sec-butyl, tert-butyl, more particularly, said groups have 1, 2 or 3 carbon atoms ("C ₁ -C ₃ alkyl"), such as methyl, ethyl, n-propyl or iso propyl.

The term "alkoxy" means an alkyl group bonded through an oxygen atom. The term "C ₁ -C ₂₀ alkoxy" is understood to mean preferably a straight-chain or branched alkyloxy group having 1 to 20 carbon atoms, preferably C ₁ -C ₁₂ alkoxy, more preferably C ₁ -C ₆ alkoxy. The term "C ₁ -C ₁₂ alkoxy" is understood to mean straight-chain or branched alkyloxy groups having 1 to 12 carbon atoms. The term "C ₁ -C ₆ alkoxy" is understood to mean straight-chain or branched alkyloxy radicals having 1 to 6 carbon atoms.

The term "C ₁ -C ₂₀ alkylene" is understood to preferably mean a linear or branched saturated divalent hydrocarbon radical having 1 to 20 carbon atoms, preferably a C ₁ -C ₁₂ alkylene group, more preferably a C ₁ -C ₆ alkylene. The term "C ₁ -C ₁₂ alkylene" is understood to preferably mean a straight-chain or branched saturated divalent hydrocarbon radical having 1 to 12 carbon atoms. The term "C ₁ -C ₆ alkylene" is understood to mean preferably a straight-chain or branched saturated divalent hydrocarbon radical having 1 to 6 carbon atoms, for example methylene-CH ₂ -, ethylene-CH ₂ CH _2- , propylene-CH ₂ CH ₂ CH ₂ -, butylene-CH ₂ CH ₂ CH ₂ CH ₂ -, etc.

The term "substituted" means that one or more hydrogens on the designated atom are replaced by the listed groups, provided that the normal valence of the designated atom in the present case is not exceeded and that the substitution forms a stable compound. Combinations of substituents and/or variables are permissible only if such combinations form stable compounds.

The present invention will be further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the invention and are not intended to limit the scope of the invention.

Preparation of block polymers

Example 1: Preparation of block polymer of formula I-1-1 (where a is 54, b is 54, and c is 54)

Dissolve the initiator azobisisobutyronitrile (AIBN), RAFT chain transfer reagent (trithioester 2-(dodecyl trithiocarbonate)-2-isobutyric acid) and acrylonitrile in 300 ml di Oxygen six rings. Among them, AIBN: RAFT: acrylonitrile = 1:2:54 (molar ratio). Under nitrogen protection, control the temperature to 60°C and stir for 1 hour. Then, CH ₂ CHCOOCH ₃ was added, where acrylonitrile: CH ₂ CHCOOCH ₃ =1:1 (molar ratio), and the reaction was continued for 6 hours at 60°C. After that, acrylic acid was added, where acrylic acid: acrylonitrile = 1:54 (molar ratio), and the reaction was continued for 6 hours at 60°C. After washing with water, filtering, and drying, product 1 was obtained with the following structural formula.

Add CH ₃ O ^- Na ⁺ and ethylene oxide to 300 mL of dioxane at a molar ratio of 1:54. Under nitrogen protection, control the temperature to 60°C, stir and react for about 1 hour, wash with water, filter and dry. Afterwards, product 2 was obtained, with the following structural formula.

Finally, product 2 is added to product 1. The molar ratio of product 2 to product 1 is 1:1. The esterification reaction is carried out at 110°C under the catalysis of 98.3% concentrated sulfuric acid with a mass fraction of 1:1. The amount of concentrated sulfuric acid used is product 2. About 3% by weight, after reacting for 1 hour, washing with water, filtering, and drying, the final product is obtained, as shown in formula I-1-1, where a is 54, b is 54, and c is 54.

Using hydrogen nuclear magnetic resonance spectroscopy, the a, b and c values are determined by calculating the peak areas of characteristic hydrogens within different polymer units in the block polymer molecules. Specific characterization information is as follows:

The molecular structure of the block polymer was measured on a Bruker AVANCE III 400 nuclear magnetic resonance instrument. The test temperature was 25°C, tetramethylsilane (TMS) was used as the internal standard, and the solvent used was deuterated chloroform (CDCl ₃ ).

Testing process: Dissolve 5 mg of block polymer sample in the above solvent and transfer it to the NMR tube. Inject 1 mL of sample to proceed with the test. After testing, the a, b and c values can be determined by calculating the peak areas of characteristic hydrogens in different polymer units in the block polymer molecules.

It has been determined that the weight average molecular weight of the block polymer of formula I-1-1 is 10,000 Daltons.

Use a British PL-220 gel permeation chromatograph (GPC) to test the weight average molecular weight. Vacuum-dry the resulting dispersant in a vacuum oven at 80°C for 12 hours. Dissolve 0.1g in 20mL of N-methylpyrrolidone and filter with a filter membrane with a pore size of 10 μm. , take 5 mL of it and test the weight average molecular weight through gel permeation chromatography. The detector used is differential refractive index detection, and the standard material is polystyrene.

Example 2: Preparation of block polymer of formula I-1-2 (where a is 540, b is 540, and c is 540)

Dissolve the initiator azobisisobutyronitrile (AIBN), RAFT chain transfer reagent (trithioester 2-(dodecyl trithiocarbonate)-2-isobutyric acid), and acrylonitrile in 300 mL di Oxygen six rings. Among them, AIBN: RAFT: acrylonitrile = 1:2:540 (molar ratio). Under nitrogen protection, control the temperature to 60°C and stir for 1 hour. Then, CH ₂ CHCOOCH ₃ was added, where acrylonitrile: CH ₂ CHCOOCH ₃ =1:1 (molar ratio), and the reaction was carried out for 6 hours. After that, acrylic acid was added, where acrylic acid: acrylonitrile = 1:540 (molar ratio), reacted for 6 hours, washed with water, filtered, and dried to obtain product 1, whose structural formula is as follows.

Add CH ₃ O ^- Na ⁺ and ethylene oxide to 300mL dioxane at a molar ratio of 1:540. Under nitrogen protection, control the temperature to 60°C, stir for about 1 hour, wash with water, filter, and dry. , to obtain product 2, whose structural formula is as follows.

Finally, product 2 is added to product 1. The molar ratio of product 2 to product 1 is 1:1. The esterification reaction is carried out at 110°C under the catalysis of 98.3% concentrated sulfuric acid with a mass fraction of 1:1. The amount of concentrated sulfuric acid used is product 2. About 3% by weight, after reacting for 1 hour, washing with water, filtering, and drying, the final product is obtained, as shown in formula I-1-2, where a is 540, b is 540, and c is 540.

It was determined that the weight average molecular weight of the block polymer of formula I-1-2 was 100,000 Daltons.

The determination methods of a, b and c and the test method of weight average molecular weight are the same as in Example 1.

Example 3: Preparation of block polymer of formula I-1-3 (where a is 1080, b is 1080, and c is 1080)

Dissolve the initiator azobisisobutyronitrile (AIBN), RAFT chain transfer reagent (trithioester 2-(dodecyl trithiocarbonate)-2-isobutyric acid) and acrylonitrile in 300 ml di Oxygen six rings. Among them, AIBN: RAFT: acrylonitrile = 1: 2: 1080 (molar ratio). Under nitrogen protection, control the temperature to 60°C and stir for 1 hour. Then, CH ₂ CHCOOCH ₃ was added, where acrylonitrile: CH ₂ CHCOOCH ₃ =1:1 (molar ratio), and the reaction was carried out for 6 hours. After that, acrylic acid was added, where acrylic acid: acrylonitrile = 1:1080 (molar ratio), reacted for 6 hours, washed with water, filtered, and dried to obtain product 1, whose structural formula is as follows.

Add CH ₃ O ^- Na ⁺ and ethylene oxide to 300mL dioxane at a molar ratio of 1:1080. Under nitrogen protection, control the temperature to 60°C, stir and react for about 1 hour, wash with water, filter, and dry. , to obtain product 2, whose structural formula is as follows.

Finally, product 2 is added to product 1. The molar ratio of product 2 to product 1 is 1:1. The esterification reaction is carried out at 110°C under the catalysis of 98.3% concentrated sulfuric acid with a mass fraction of 1:1. The amount of concentrated sulfuric acid used is product 2. About 3% by weight, after reacting for 1 hour, washing with water, filtering, and drying, the final product is obtained, as shown in formula I-1-3, where a is 1080, b is 1080, and c is 1080.

It has been determined that the weight average molecular weight of the block polymer of formula I-1-3 is 200,000 Daltons.

Example 4: Preparation of block polymer of formula I-1-4 (where a is 1350, b is 1350, and c is 1350)

Dissolve the initiator azobisisobutyronitrile (AIBN), RAFT chain transfer reagent (trithioester 2-(dodecyl trithiocarbonate)-2-isobutyric acid), and acrylonitrile in 300 mL di Oxygen six rings. Among them, AIBN: RAFT: acrylonitrile = 1: 2: 1350 (molar ratio). Under nitrogen protection, control the temperature to 60°C and stir for 1 hour. Then, CH ₂ CHCOOCH ₃ was added, where acrylonitrile: CH ₂ CHCOOCH ₃ =1:1 (molar ratio), and the reaction was carried out for 6 hours. After that, acrylic acid was added, where acrylic acid: acrylonitrile = 1:1350 (molar ratio), reacted for 6 hours, washed with water, filtered, and dried to obtain product 1, whose structural formula is as follows.

Add CH ₃ O ^- Na ⁺ and ethylene oxide to 300mL dioxane at a molar ratio of 1:1350. Under nitrogen protection, control the temperature to 60°C, stir and react for about 1 hour, wash with water, filter, and dry. , to obtain product 2, whose structural formula is as follows.

Finally, product 2 is added to product 1. The molar ratio of product 2 to product 1 is 1:1. The esterification reaction is carried out at 110°C under the catalysis of concentrated sulfuric acid with a mass fraction of 98.3%. The amount of concentrated sulfuric acid used is product 2. About 3% by weight, after reacting for 1 hour, wash with water, filter, and dry to obtain the final product, as shown in formula I-1-4, where a is 1350, b is 1350, and c is 1350.

It has been determined that the weight average molecular weight of the block polymer of formula I-1-4 is 250,000 Daltons.

Using the block polymer of Examples 1-4 as a dispersant, the cathode slurry was prepared according to the following general preparation method.

Preparing cathode slurry

The ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), binder polyvinylidene fluoride (PVDF), dispersant (i.e., the prepared block polymer) according to a certain weight ratio in N-methylpyrrolidone (NMP) solvent system, stir thoroughly and mix evenly, then test the viscosity. The viscosity is in the viscosity range of 3000-10000mPa·s suitable for coating at 12 rpm, and the cathode slurry is made.

Example 1-1

The dispersant is the block polymer prepared in Example 1.

The weight ratio of the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), binder polyvinylidene fluoride (PVDF), and dispersant is 96.9%: 2% :1%:0.1%.

Example 1-2

The dispersant is the block polymer prepared in Example 1.

The weight ratio of the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), binder polyvinylidene fluoride (PVDF), and dispersant is 96.7%: 2% :1%:0.3%.

Example 1-3

The dispersant is the block polymer prepared in Example 1.

The weight ratio of the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), binder polyvinylidene fluoride (PVDF), and dispersant is 96.5%: 2% :1%:0.5%.

Examples 1-4

The dispersant is the block polymer prepared in Example 1.

The weight ratio of the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), binder polyvinylidene fluoride (PVDF), and dispersant is 96%: 2% :1%:1%.

Example 2-1

The dispersant is the block polymer prepared in Example 2.

Example 2-2

The dispersant is the block polymer prepared in Example 2.

Example 2-3

The dispersant is the block polymer prepared in Example 2.

Example 2-4

The dispersant is the block polymer prepared in Example 2.

Example 3-1

The dispersant is the block polymer prepared in Example 3.

Example 3-2

The dispersant is the block polymer prepared in Example 3.

Example 3-3

The dispersant is the block polymer prepared in Example 3.

Example 3-4

The dispersant is the block polymer prepared in Example 3.

Example 4-1

The dispersant is the block polymer prepared in Example 4.

Example 4-2

The dispersant is the block polymer prepared in Example 4.

Example 4-3

The dispersant is the block polymer prepared in Example 4.

Example 4-4

The dispersant is the block polymer prepared in Example 4.

Comparative example 1

Proceed according to the method of Example 1-1, except that no dispersant, ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), and binder are used. The weight ratio of polyvinylidene fluoride (PVDF) is 97%:2%:1%.

Comparative example 2

Proceed according to the method of Example 3-1, except that the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), and binder polyvinylidene fluoride (PVDF), the weight ratio of dispersant is 96.98%: 2%: 1%: 0.02%.

Comparative example 3

Proceed according to the method of Example 3-1, except that the ternary positive electrode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), and binder polyvinylidene fluoride (PVDF), the weight ratio of dispersant is 94%: 2%: 1%: 3%.

Comparative example 4

The block polymer of formula I-1-3 was prepared according to the method of Example 3. The difference is that by reducing the amount of raw materials added, in the obtained block polymer, a is 27, b is 27, and c is 27, Specifically, AIBN: RAFT: acrylonitrile = 1: 2: 27 (molar ratio), acrylic acid: acrylonitrile = 1: 27 (molar ratio), CH ₃ O ^- Na ⁺ , and ethylene oxide molar ratio is 1: 27 Than join. It has been determined that the weight average molecular weight of the block polymer of formula I-1-3 is 5000 Daltons.

The obtained block polymer was used as a dispersant to prepare cathode slurry according to the above general preparation method, in which the ternary cathode active material NCM523 (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ), conductive agent SP (SP conductive carbon black), adhesive The weight ratio of the binder polyvinylidene fluoride (PVDF) and the dispersant is the same as in Example 3-1.

Comparative example 5

The block polymer of formula I-1-3 was prepared according to the method of Example 3. The difference is that the addition amount of raw materials is increased so that in the obtained block polymer, a is 2160, b is 2160, and c is 2160. Specifically Ground, AIBN: RAFT: acrylonitrile = 1: 2: 2160 (molar ratio), acrylic acid: acrylonitrile = 1: 2160 (molar ratio), CH ₃ O ^- Na ⁺ and ethylene oxide at a molar ratio of 1: 2160 join in. It has been determined that the weight average molecular weight of the block polymer of formula I-1-3 is 400,000 Daltons.

Utilize the positive electrode slurries of Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, 4-1 to 4-4 and Comparative Example 1-5, and prepare according to the following general Methods for preparing lithium-ion batteries.

Preparing lithium-ion batteries

1) Preparation of positive electrode plate

The prepared positive electrode slurry is coated on the aluminum foil through the coating equipment. After the coating is completed, the solvent NMP is dried in the coating machine oven, and then the positive electrode sheet is prepared through cold pressing, slitting and die-cutting processes.

2) Preparation of negative electrode sheet

95wt% negative active material (artificial graphite), 1.0wt% conductive agent (conductive carbon black), 2.0wt% binder (styrene-butadiene rubber (SBR)) and 2.0wt% thickener (carboxymethyl Cellulose sodium (CMC)) was mixed, added with deionized water, stirred, and dispersed to form a negative electrode slurry. Then, the negative electrode slurry is coated on the copper foil, and after both sides are completed, it is dried, cold pressed, cut, and sliced to prepare negative electrode sheets.

3) Preparation of battery

Stack the prepared positive electrode pieces, separators, and negative electrode pieces in order so that the isolation film is between the cathode and anode for isolation, and wind it at the same time to obtain a bare cell, which is then welded, packaged, and injected with electrolyte. Processes such as formation, exhaust, and final sealing are carried out to finally obtain a soft pack battery.

Block polymer performance testing

CV test (voltammetry test):

Use the Biologic VMP3 electrochemical workstation with a scan rate of 100mV/s and a scan voltage of 3.0-5.0V. After the test, export the original data for graphing to obtain the CV curve of the block polymer. The CV curves of the block polymers of Examples 1-4 are shown in Figure 1.

It can be seen from Figure 1 that Examples 1-4 have no obvious oxidation peak at a voltage of 3-5V, indicating that the dispersant is relatively stable within 5V and does not decompose.

Positive electrode piece performance test

Diaphragm resistance test:

Use Yuaneng Technology's PRCD1100 diaphragm resistance meter to cut the positive electrode into small pieces with a length > 60mm and a width > 30mm. Turn on the diaphragm resistance meter, adjust the pressure to 0.2-0.4MPa, manually turn the pneumatic switch upward, and use Clamp the pole piece with tweezers, put it into the probe, manually toggle the start switch down to start the test, and record the resistance data when the value is stable. The test results are shown in Table 1 below.

Battery performance test

DC impedance (DCR) test:

First, the battery core is fixed to obtain the capacity C0. Conditions for constant capacity: the battery core is left standing for 30 minutes at 25°C, discharged to 3.0V at 0.33C, charged with a constant current of 0.33C to 4.5V, charged with a constant voltage, and the cut-off current is 0.05 C, 0.33C is discharged to 3.0V, and the capacity C0 is obtained. The battery cell is left to stand for 30 minutes at 25°C, charged with a constant current of 0.33C0 to 4.5V, charged with a constant voltage, with a cut-off current of 0.05C0, left to stand for 5 minutes at 25°C, and discharged from 0.33C0 to 0.5C0, which is 50% SOC at this time. (That is, the battery capacity remains 50%), and then discharge at a rate of 2C0 for 30 seconds. The voltage of 2C0 before discharge is V1, and the voltage after 30 seconds of discharge is V2. The calculation formula of DCR is as follows: R=(V1-V2)/2C0 , the obtained value is the DCR at 50% SOC. The test results are shown in Table 1 below.

25℃0.33C charge and discharge cycle test:

First, the battery core is fixed to obtain the capacity C0. Conditions for constant capacity: the battery core is left standing for 30 minutes at 25°C, discharged to 3.0V at 0.33C, charged to 4.5V with a constant current of 0.33C, charged at a constant voltage, and the cut-off current is 0.05C. , 0.33C is discharged to 3.0V, and the capacity C0 is obtained.

The battery cell is left to stand for 30 minutes at 25°C, charged with constant current of 0.33C0 to 4.5V, charged with constant voltage, with a cut-off current of 0.05C0, left to stand for 5 minutes at 25°C, and discharged to 3.0V with 0.33C0. Repeat the above steps until the capacity decays. to 80% C0 cutoff. The charge and discharge cycle test results of the batteries corresponding to Examples 1-4 and Comparative Example 1 are shown in Figure 2.

Table 1

By comparing Example 1-1 and Comparative Example 1, it can be seen that the positive electrode slurry of Comparative Example 1 does not contain a dispersant, and the corresponding diaphragm resistance and DCR of the lithium ion battery are both higher than those of Example 1-1. of lithium-ion batteries. It can be seen that the addition of dispersant increases the dispersion uniformity of the cathode slurry and reduces the diaphragm resistance and DCR of lithium-ion batteries.

By comparing Example 3-1 with Comparative Examples 2 and 3, it can be seen that the amount of dispersant used in Comparative Example 2 is too small, and the amount of dispersant used in Comparative Example 3 is too large. The membranes of lithium ion batteries corresponding to Comparative Examples 2 and 3 The sheet resistance and DCR are both higher than that of the lithium ion battery corresponding to Example 3-1. It can be seen that if the dosage of the dispersant is too large or too small, it is not conducive to the uniform dispersion of the cathode slurry, thereby adversely affecting the diaphragm resistance and DCR of the lithium-ion battery.

By comparing Example 3-1 with Comparative Examples 4 and 5, it can be seen that the weight average molecular weight of the dispersant in Comparative Example 4 is too small, and the weight average molecular weight of the dispersant in Comparative Example 5 is too large. The diaphragm resistance and DCR of the lithium ion battery are both higher than that of the lithium ion battery corresponding to Example 3-1. It can be seen that if the weight average molecular weight of the dispersant is too large or too small, it is not conducive to the uniform dispersion of the cathode slurry, thereby adversely affecting the diaphragm resistance and DCR of the lithium-ion battery.

It can be seen from Figure 2 and Table 1 that the battery core corresponding to Comparative Example 1 does not have a dispersant added, and its structure is stable under a high voltage of 4.5V. After 500 cycles at room temperature, the capacity retention rate is still above 90%. The dispersant causes the cathode slurry to be dispersed unevenly, and the cathode sheet prepared from it has a higher diaphragm resistance and a higher DCR of the battery core. The capacity retention rate of the battery cores corresponding to Examples 1-4 after 500 cycles at room temperature is equivalent to that of the battery core corresponding to Comparative Example 1. This shows that the dispersant of the present application has a stable structure under a high voltage of 4.5V, does not decompose, and can High voltage resistance. At the same time, the cathode slurry prepared using the dispersant of the present application has a good dispersion effect, so the cathode sheet prepared therefrom has a small diaphragm resistance and a small DCR of the battery core. It can be seen that the dispersant of the present application has good dispersion effect and is resistant to high voltage. It can significantly reduce the diaphragm resistance of the positive electrode plate, reduce the DCR of the battery core, increase the charging voltage of the battery core, and enhance the cycle performance of the battery core.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention. All substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

A block polymer, characterized by including:

Polyolefin A block, the polyolefin A block contains a cyano group;

Polyolefin B block, the polyolefin B block is connected to the polyolefin A block, and the polyolefin B block contains an ester group;

Polyethylene oxide block, one end of the polyethylene oxide block is connected to the polyolefin A block or the polyolefin B block through a connecting unit, and the other end is connected to the terminal group R 1 , wherein , the terminal group R 1 is selected from the following groups:

C 1 -C 20 alkyl which is unsubstituted or substituted with a substituent selected from : halogen, hydroxyl or C 1 -C 20 alkoxy; or

Phenyl, said phenyl being unsubstituted or substituted with a substituent selected from halogen, hydroxyl, C 1 -C 20 alkyl or C 1 -C 20 alkoxy.
The block polymer according to claim 1, characterized in that the connecting unit includes the following structural formula
Wherein, R 2 is hydrogen or C 1 -C 20 alkyl, and the C 1 -C 20 alkyl is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C 1 -C 20 alkoxy; *Indicates the site of attachment to other groups.
The block polymer according to claim 2, characterized in that it has the structure of general formula I:

in,

Has a structure selected from:

*Indicates the site connected to other groups;

R 1 and R 2 are as defined in claim 2;

R 3 , R 4 , R 5 and R 6 are independently hydrogen, halogen or C 1 -C 20 alkyl which is unsubstituted or substituted with a substituent selected from: halogen , hydroxyl or C 1 -C 20 alkoxy;

R 7 is C 1 -C 20 alkyl, which is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C 1 -C 20 alkoxy;

L 1 and L 2 are independently absent from each other, or are independently C 1 -C 20 alkylene, which is unsubstituted or substituted with a substituent selected from the following: halogen, Hydroxy, C 1 -C 20 alkyl or C 1 -C 20 alkoxy;

a, b and c are 10-5000 independently of each other.
The block polymer according to claim 3, characterized in that it has the structure of general formula I-1:

in,

R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , L 1 , L 2 , a, b and c are as defined in claim 3.
The block polymer according to any one of claims 1-4, characterized in that the weight average molecular weight of the block polymer is 10,000-300,000 Daltons.
The block polymer according to claim 5, characterized in that the weight average molecular weight of the block polymer is 200,000-250,000 Daltons.
The block polymer according to claim 3 or 4, characterized in that a:b:c=(0.8-1.2):(0.8-1.2):(0.8-1.2).
The block polymer according to claim 3 or 4, characterized in that,

R 1 is selected from the following groups: C 1 -C 12 alkyl, which is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl or C 1 -C 12 alkoxy ; Or phenyl, the phenyl group is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl, C 1 -C 12 alkyl or C 1 -C 12 alkoxy;

R 2 is hydrogen or C 1 -C 12 alkyl, which is unsubstituted or substituted with a substituent selected from the following: halogen , hydroxyl or C 1 -C 12 alkoxy;

R 3 , R 4 , R 5 and R 6 are independently hydrogen or C 1 -C 12 alkyl, which is unsubstituted or substituted with a substituent selected from: halogen, hydroxyl or C 1 -C 12 alkoxy;

R 7 is C 1 -C 12 alkyl, which is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C 1 -C 12 alkoxy;

L 1 and L 2 do not exist independently of each other.
The block polymer according to claim 8, characterized in that R 2 , R 3 , R 4 , R 5 and R 6 are all hydrogen.
The block polymer according to any one of claims 1 to 4, characterized in that the block polymer has amphiphilicity.
A method for preparing block polymers, characterized by comprising the following steps:

Mix the ethylenically unsaturated monomer A containing a cyano group, an initiator, a chain transfer agent and a solvent, and polymerize the monomer A to obtain solution A;

Add the ethylenically unsaturated monomer B containing an ester group to the solution A, and polymerize the system to obtain solution B;

Add substituted or unsubstituted acrylic acid to the solution B, and react the system to obtain product 1;

Mix R 1 O - Na + , ethylene oxide, initiator, chain transfer agent and solvent, and react the system to obtain product 2, in which R 1 is phenyl or C 1 -C 20 alkyl, so The phenyl group is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl, C 1 -C 20 alkyl or C 1 -C 20 alkoxy; the C 1 -C 20 alkyl group is unsubstituted or Substituted with a substituent selected from: halogen, hydroxyl or C 1 -C 20 alkoxy;

The product 1 and the product 2 are subjected to an esterification reaction to obtain a block polymer.
The preparation method according to claim 11, characterized in that:

The monomer A has the following structure:

The monomer B has the following structure:

The substituted or unsubstituted acrylic acid has the following structure:

in,

R 2 is hydrogen or C 1 -C 20 alkyl, which is unsubstituted or substituted with a substituent selected from the following: halogen , hydroxyl or C 1 -C 20 alkoxy;

R 3 , R 4 , R 5 and R 6 are independently hydrogen, halogen or C 1 -C 20 alkyl which is unsubstituted or substituted with a substituent selected from: halogen , hydroxyl or C 1 -C 20 alkoxy;

R 7 is C 1 -C 20 alkyl, which is unsubstituted or substituted with a substituent selected from the following: halogen, hydroxyl or C 1 -C 20 alkoxy;

L 1 and L 2 are independently absent from each other, or are independently C 1 -C 20 alkylene, which is unsubstituted or substituted with a substituent selected from: halogen, Hydroxy, C 1 -C 20 alkyl or C 1 -C 20 alkoxy.
The preparation method according to claim 11 or 12, characterized in that the molar ratio of the monomer A, the monomer B and the substituted or unsubstituted acrylic acid is (15-30): (15-30 ):1.
The preparation method according to claim 11 or 12, characterized in that the molar ratio of R 1 O - Na + and ethylene oxide is 1: (80-120).
The preparation method according to claim 11 or 12, characterized in that the molar ratio of the product 1 and the product 2 is (0.8-1.2): (0.8-1.2).
The preparation method according to claim 11 or 12, characterized in that,

In the step of preparing the solution A, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is carried out in a protective atmosphere;

In the step of preparing solution B, the reaction temperature is 50-100°C and the reaction time is 1-10h;

In the step of preparing the product 1, the reaction temperature is 50-100°C, and the reaction time is 1-10h;

In the step of preparing the product 2, the reaction temperature is 50-100°C, the reaction time is 0.5-5h, and the reaction is carried out in a protective atmosphere;

The product 1 and the product 2 are reacted in the presence of an acidic catalyst, the reaction temperature is 40-80°C, and the reaction time is 1-10 h.
Use of the block polymer according to any one of claims 1 to 10 or the block polymer obtained by the preparation method according to any one of claims 11 to 16 as a dispersant.
A composition, characterized in that it includes: the block polymer described in any one of claims 1-10 or the block polymer obtained by the preparation method described in any one of claims 11-16; and solvents.
A positive electrode slurry, characterized in that it includes the block polymer described in any one of claims 1-10 or the block polymer obtained by the preparation method described in any one of claims 11-16.
The cathode slurry according to claim 19, wherein the mass proportion of the block polymer in the cathode slurry is 0.05%-2%.
A positive electrode sheet, characterized by comprising the block polymer described in any one of claims 1-10 or the block polymer obtained by the preparation method described in any one of claims 11-16.
A secondary battery, characterized in that it includes the positive electrode plate according to claim 21.
A battery module comprising the secondary battery according to claim 22.
A battery pack, characterized in that it includes the secondary battery according to claim 22 or the battery module according to claim 23.
An electrical device, characterized by comprising at least one of the secondary battery according to claim 22, the battery module according to claim 23, and the battery pack according to claim 24.