A leveling agent for conductive coating slurry for lithium batteries

Abstract

The present invention relates to a leveling agent for a conductive coating slurry for lithium electricity, belonging to the technical field of lithium batteries. The leveling agent is composed of the following components: 1.4-1.8wt% of an anti-foaming agent, 2.5-3.5wt% of a thickening agent, and 30-35wt% of a dispersing agent, and the remainder is a modified organic silicon main agent; the modified organic silicon main agent is a functional matrix, which is etherified by hydroxyethyl acrylate and trichloroethyl phosphate to form a phosphate compound with terminal acrylate, that is, a modifier, and then the acrylate structure in the modifier is subjected to silylation with hydrogen-containing silicone oil, and the modifier is grafted to the side chain of the silicone oil; the leveling agent is applied in lithium battery slurry to effectively improve the leveling performance, and at the same time significantly improve the bonding ability of the slurry with aluminum foil, which is conducive to maintaining the cycle stability of the lithium battery.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries, and in particular relates to a leveling agent for a conductive coating slurry for lithium batteries. Background Art

[0002] As a high-energy-density, environmentally friendly battery technology, lithium-ion batteries are increasingly being used in electric vehicles, energy storage systems, etc. As one of the core components of batteries, the performance of cathode slurry directly affects key indicators such as battery charge and discharge efficiency, cycle life, and safety.

[0003] The positive electrode slurry is mainly composed of active materials, conductive agents, binders and solvents. In order to improve the flow and coating properties of the positive electrode slurry on the current collecting substrate, a certain amount of leveling agent is generally compounded into the positive electrode slurry. The leveling agent is mainly organic silicon compounds, such as polyether modified siloxane, alkyl modified siloxane, etc. These leveling agents improve the coating properties of the positive electrode slurry to a certain extent. However, these leveling agents will interfere with the bonding effect of the binder, resulting in a decrease in the bonding strength between the active material and the current collecting substrate, thereby affecting the mechanical stability of the electrode. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the purpose of the present invention is to provide a leveling agent for a conductive coating slurry for lithium batteries.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A leveling agent for a conductive coating slurry for lithium batteries consists of the following components: 1.4-1.8wt% of an anti-foaming agent, 2.5-3.5wt% of a thickening agent, 30-35wt% of a dispersing agent, and the remainder is a modified organic silicon main agent.

[0007] Preferably, the anti-foaming auxiliary agent is selected from polyethylene glycol hexadecyl ether, which has good compatibility with the modified silicone main agent and good anti-foaming property.

[0008] Preferably, the thickening aid is selected from polymethylphenylsiloxane, which has good compatibility with the modified silicone main agent and is easy to disperse and adjust the viscosity of the leveling agent.

[0009] Preferably, the dispersing aid is selected from methyl isobutyl ketone, which has good solubility with each component and keeps the state of the leveling agent stable.

[0010] The modified organosilicon main agent is prepared by the following method:

[0011] Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 70-80°C, stirring is applied at 60-90 rpm, an etherification catalyst is slowly added, and the reaction is refluxed for 4.5-5.5 hours. After the reaction is completed, carbon tetrachloride is removed by rotary evaporation, the substrate is washed with water and separated by rotary evaporation, and vacuum dried to obtain a modifier;

[0012] Preferably, the etherification catalyst is selected from trifluoromethanesulfonic acid, which has a highly efficient catalytic effect on the etherification of halogenated hydrocarbons and alcohols.

[0013] Furthermore, the usage ratio of trichloroethyl phosphate, hydroxyethyl acrylate, etherification catalyst and carbon tetrachloride is 0.1 mol: 0.31-0.33 mol: 1.5-2 mL: 55-70 mL, and under the promotion of trifluoromethanesulfonic acid, hydroxyethyl acrylate and trichloroethyl phosphate are etherified to form a phosphate compound with terminal acrylate.

[0014] Step A2: Mix hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene, introduce dry nitrogen, heat to 80-95°C, stir at 120-180 rpm, add modifier and react for 2.5-3.5 hours, then pressurize with nitrogen to 3-4 bar, continue to heat to 110-120°C and continue to react for 1.5-2 hours, remove toluene after the reaction is completed, and obtain modified organosilicon main agent;

[0015] Preferably, the hydrosilylation catalyst is selected from bis(triphenylphosphine)nickel chloride, which has a good selective catalytic effect on the addition of acrylate and hydrosilylation, has a low cost, and is suitable for industrial production;

[0016] Furthermore, the amount ratio of hydrogen-containing silicone oil, modifier, hydrosilylation catalyst and anhydrous toluene is 100 g: 25-40 mmol: 0.1-0.15 g: 60-80 mL, and under the catalysis of bis(triphenylphosphine)nickel chloride, the acrylate structure in the modifier undergoes hydrosilylation with the hydrogen-containing silicone oil to graft the modifier to the side chain of the silicone oil;

[0017] Preferably, the hydrogen-containing silicone oil is a branched hydrogen-containing silicone oil, and the modifier grafting site is on the side chain, which has a more excellent lubrication and leveling effect, and at the same time, the adhesion to the slurry layer is better improved after curing.

[0018] Beneficial effects of the present invention:

[0019] The invention discloses a composite leveling agent, which is applied in lithium battery slurry to effectively improve the leveling performance, and at the same time significantly improve the bonding ability between the slurry and aluminum foil, which is beneficial to maintaining the cycle stability of the lithium battery; the leveling agent uses a modified organic silicon main agent developed independently as a functional matrix, which is formed by etherification of hydroxyethyl acrylate and trichloroethyl phosphate to form a phosphate compound with terminal acrylate, namely the modifier, and then the acrylate structure in the modifier is subjected to silylation with hydrogen-containing silicone oil to graft the modifier to the side chain of the silicone oil, the phosphate structure on the side chain of the modified organic silicon main agent molecule has better wettability to active materials than traditional organic silicon chains, and the phosphate modification of the side chain is beneficial to the modification of the organic silicon main agent. The silicone main agent molecules are dispersed between the active materials, and the phosphate structure and ether structure in the side chain modifier molecules form a chelate effect, so that the modified silicone main agent chelates and adheres to the surface of the active material after infiltration, forming a stable silicone lubricating film between the active materials, greatly improving the fluidity between the active materials, which is beneficial to the spreading and leveling of the slurry; during the coating and curing process, the residual chelating sites of the modified silicone main agent chelate with the aluminum foil substrate, and its terminal acrylates cross-link during the thermal curing process, forming mutual entanglement between the substrate and the active material, greatly improving the bonding performance of the coating and the substrate, making the coating have higher adhesion and better resistance to corrosion by electrolytes and solvents. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example 1, preparing a leveling agent for a conductive coating slurry for lithium batteries, the specific implementation process is as follows:

[0022] (1) Synthesis of modified silicone main agent

[0023] Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 80° C., stirring is applied at 90 rpm, and an etherification catalyst is slowly added. The addition time is controlled to be 1.5 hours, and the total reaction time of the etherification catalyst is 4.5 hours. Among them, trifluoromethanesulfonic acid is selected as the etherification catalyst, and the amount ratio of trichloroethyl phosphate, hydroxyethyl acrylate, trifluoromethanesulfonic acid and carbon tetrachloride is 0.1 mol: 0.33 mol: 2 mL: 70 mL. After the reaction is completed, carbon tetrachloride is removed by rotary evaporation. After cooling, water is added to the rotary evaporation substrate for washing, the aqueous phase is separated and vacuum dried to obtain a modifier.

[0024] Step A2: Take hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene and add them into a pressure autoclave to mix, introduce dry nitrogen, heat to 95°C, stir at 180rpm, add a modifier and react for 2.5h, then pressurize to 4bar with nitrogen, continue to heat to 120°C and continue to react for 1.5h, wherein the hydrogenated silicone oil is KF-99 branched hydrogenated silicone oil, the hydrosilylation catalyst is bis(triphenylphosphine)nickel chloride, the amount ratio of hydrogenated silicone oil, modifier bis(triphenylphosphine)nickel chloride and anhydrous toluene is 100g:40mmol:0.15g:80mL, release the pressure and remove toluene by rotary evaporation after the reaction to obtain a modified silicone main agent.

[0025] (2) Preparation of leveling agent

[0026] Ingredients: The raw materials are taken according to weight percentage, anti-foaming agent 1.4wt%, polyethylene glycol hexadecyl ether, industrial-grade raw material, is selected during the implementation process; thickening agent 2.5wt%, polymethylphenylsiloxane, model IOTA-255, is used during the implementation process; dispersing agent 30wt%, methyl isobutyl ketone, industrial-grade raw material, is selected during the implementation process; modified silicone main agent 66.1wt%, which is homemade in this embodiment.

[0027] Mixing: premix the anti-foaming agent and the dispersing agent, add the modified silicone main agent to the premix at a uniform speed under stirring at 60 rpm and mix for 10 minutes, then reduce the stirring rate to 30 rpm, add the thickening agent and continue mixing for 30 minutes to obtain a leveling agent for the conductive coating slurry for lithium batteries.

[0028] Example 2, preparing a leveling agent for a conductive coating slurry for lithium batteries, the specific implementation process is as follows:

[0029] (1) Synthesis of modified silicone main agent

[0030] Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 70° C., stirring is applied at 60 rpm, and an etherification catalyst is slowly added. The addition time is controlled to be 2 hours. The total reaction time of the etherification catalyst is 5.5 hours. Among them, trifluoromethanesulfonic acid is selected as the etherification catalyst, and the amount ratio of trichloroethyl phosphate, hydroxyethyl acrylate, trifluoromethanesulfonic acid and carbon tetrachloride is 0.1 mol: 0.31 mol: 1.5 mL: 55 mL. After the reaction is completed, carbon tetrachloride is removed by rotary evaporation. After cooling, water is added to the rotary evaporation substrate for washing, the aqueous phase is separated and vacuum dried to obtain a modifier.

[0031] Step A2: Take hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene and add them into a pressure autoclave to mix, introduce dry nitrogen, heat to 80°C, stir at 120rpm, add a modifier and react for 3.5h, then pressurize to 3bar with nitrogen, continue to heat to 110°C and continue to react for 2h, wherein the hydrogenated silicone oil is KF-99 branched hydrogenated silicone oil, the hydrosilylation catalyst is bis(triphenylphosphine)nickel chloride, the amount ratio of hydrogenated silicone oil, modifier bis(triphenylphosphine)nickel chloride and anhydrous toluene is 100g:25mmol:0.1g:60mL, release the pressure after the reaction, remove toluene by rotary evaporation, and obtain a modified silicone main agent.

[0032] (2) Preparation of leveling agent

[0033] Ingredients: The raw materials are taken according to weight percentage, anti-foaming agent 1.8wt%, polyethylene glycol hexadecyl ether, industrial-grade raw material, is selected during the implementation process; thickening agent 2.5wt%, polymethylphenylsiloxane, model IOTA-255, is used during the implementation process; dispersing agent 33wt%, methyl isobutyl ketone, industrial-grade raw material, is selected during the implementation process; modified silicone main agent 62.7wt%, which is homemade in this embodiment.

[0034] Mixing: premix the anti-foaming agent and the dispersing agent, add the modified silicone main agent to the premix at a uniform speed under stirring at 60 rpm and mix for 10 minutes, then reduce the stirring rate to 30 rpm, add the thickening agent and continue mixing for 30 minutes to obtain a leveling agent for the conductive coating slurry for lithium batteries.

[0035] Example 3, preparing a leveling agent for a conductive coating slurry for lithium batteries, the specific implementation process is as follows:

[0036] (1) Synthesis of modified silicone main agent

[0037] Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 75° C., stirring is applied at 90 rpm, and an etherification catalyst is slowly added. The addition time is controlled to be 1.8 hours. The total reaction time of the etherification catalyst is 5 hours. The etherification catalyst is trifluoromethanesulfonic acid, and the amount ratio of trichloroethyl phosphate, hydroxyethyl acrylate, trifluoromethanesulfonic acid and carbon tetrachloride is 0.1 mol: 0.33 mol: 1.8 mL: 65 mL. After the reaction is completed, carbon tetrachloride is removed by rotary evaporation. After cooling, water is added to the rotary evaporation substrate for washing, the aqueous phase is removed by separation, and vacuum drying is performed to obtain a modifier.

[0038] Step A2: Take hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene and add them into a pressure autoclave to mix, introduce dry nitrogen, heat to 85°C, stir at 150rpm, add a modifier and react for 3h, then pressurize with nitrogen to 3bar, continue to heat to 110°C and continue to react for 1.8h, wherein the hydrogenated silicone oil is KF-99 branched hydrogenated silicone oil, the hydrosilylation catalyst is bis(triphenylphosphine)nickel chloride, the amount ratio of hydrogenated silicone oil, modifier bis(triphenylphosphine)nickel chloride and anhydrous toluene is 100g:30mmol:0.12g:70mL, after the reaction is completed, the pressure is released and the toluene is removed by rotary evaporation to obtain a modified silicone main agent.

[0039] (2) Preparation of leveling agent

[0040] Ingredients: The raw materials are taken according to weight percentage, anti-foaming agent 1.4wt%, polyethylene glycol hexadecyl ether, industrial-grade raw material, is selected during the implementation process; thickening agent 3.5wt%, polymethylphenylsiloxane, model IOTA-255, is used during the implementation process; dispersing agent 35wt%, methyl isobutyl ketone, industrial-grade raw material, is selected during the implementation process; modified silicone main agent 60.1wt%, which is homemade in this embodiment.

[0041] Mixing: premix the anti-foaming agent and the dispersing agent, add the modified silicone main agent to the premix at a uniform speed under stirring at 60 rpm and mix for 10 minutes, then reduce the stirring rate to 30 rpm, add the thickening agent and continue mixing for 30 minutes to obtain a leveling agent for the conductive coating slurry for lithium batteries.

[0042] Example 4, preparing a leveling agent for a conductive coating slurry for lithium batteries, the specific implementation process is as follows:

[0043] (1) Synthesis of modified silicone main agent

[0044] Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 70° C., stirring is applied at 90 rpm, and an etherification catalyst is slowly added. The addition time is controlled to be 2 hours. The total reaction time of the etherification catalyst is 5.2 hours. Among them, trifluoromethanesulfonic acid is selected as the etherification catalyst, and the amount ratio of trichloroethyl phosphate, hydroxyethyl acrylate, trifluoromethanesulfonic acid and carbon tetrachloride is 0.1 mol: 0.32 mol: 1.8 mL: 60 mL. After the reaction is completed, carbon tetrachloride is removed by rotary evaporation. After cooling, water is added to the rotary evaporation substrate for washing, the aqueous phase is separated and vacuum dried to obtain a modifier.

[0045] Step A2: Take hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene and add them into a pressure autoclave to mix, introduce dry nitrogen, heat to 90°C, stir at 180rpm, add a modifier and react for 3.2h, then pressurize to 4bar with nitrogen, continue to heat to 120°C and continue to react for 1.6h, wherein the hydrogenated silicone oil is KF-99 branched hydrogenated silicone oil, the hydrosilylation catalyst is bis(triphenylphosphine)nickel chloride, the amount ratio of hydrogenated silicone oil, modifier bis(triphenylphosphine)nickel chloride and anhydrous toluene is 100g:35mmol:0.15g:75mL, release the pressure and remove toluene by rotary evaporation after the reaction is completed to obtain a modified silicone main agent.

[0046] (2) Preparation of leveling agent

[0047] Ingredients: The raw materials are taken according to weight percentage, anti-foaming agent 1.5wt%, polyethylene glycol hexadecyl ether, industrial-grade raw material, is selected during the implementation process; thickening agent 2.8wt%, polymethylphenylsiloxane, model IOTA-255, is used during the implementation process; dispersing agent 32wt%, methyl isobutyl ketone, industrial-grade raw material, is selected during the implementation process; modified silicone main agent 63.7wt%, which is homemade in this embodiment.

[0048] Mixing: premix the anti-foaming agent and the dispersing agent, add the modified silicone main agent to the premix at a uniform speed under stirring at 60 rpm and mix for 10 minutes, then reduce the stirring rate to 30 rpm, add the thickening agent and continue mixing for 30 minutes to obtain a leveling agent for the conductive coating slurry for lithium batteries.

[0049] Comparative Example

[0050] This comparative example is a commercially available positive electrode slurry leveling agent, model: WE-D7000.

[0051] In order to verify the performance of the leveling agent in lithium battery slurry, lithium iron phosphate active powder, acetylene black and polyvinylidene fluoride were premixed in a weight ratio of 8:1:1 as the base material, and then 20%wt of NMP of the base material and 1.5wt% of the base material were mixed and ground into slurry, and then the slurry was scraped on the surface of aluminum foil, and the scraping was controlled to be 30mg / cm 2 , and bake at 120°C for 10 hours to fully dry to obtain a positive electrode sheet;

[0052] Take the above positive electrode sheet, use a light section microscope to measure the ten-point height Rz and the arithmetic mean deviation Ra of the microscopic roughness of the slurry cured layer; use the hundred grid method to test the adhesion performance of the slurry cured layer and evaluate the adhesion level; take the above positive electrode sheet and soak it in 1.0M LiTFSI electrolyte and NMP solvent for 24 hours, then use nylon cloth to wipe it repeatedly 50 times, wash it with water and dry it again, and calculate the weight loss rate of the positive electrode sheet before and after wiping. The specific test results are shown in the following table:

[0053]

[0054] It can be seen from the test results in the above table that the Rz value of the leveling agent in the embodiment after being applied to the positive electrode slurry after curing is 2.17-3.05μm, and the Ra value is 0.51-0.96μm. Compared with the comparative example, the leveling agent in the embodiment has a good leveling promoting effect on the positive electrode slurry, and the slurry using the leveling agent in the embodiment has a higher adhesion grade after curing, and is resistant to wiping by the electrolyte and the solvent NMP.

[0055] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0056] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A leveling agent for a conductive coating slurry for lithium batteries, characterized in that: The invention is composed of the following components: 1.4-1.8wt% anti-foaming agent, 2.5-3.5wt% thickening agent and 30-35wt% dispersing agent, and the balance is modified organic silicon main agent; The modified organosilicon main agent is prepared by the following method: Step A1: trichloroethyl phosphate, hydroxyethyl acrylate and carbon tetrachloride are mixed, dry nitrogen is introduced, the temperature is raised to 70-80° C., the etherification catalyst is slowly added with stirring and refluxed for 4.5-5.5 hours, carbon tetrachloride is removed by rotary evaporation after the reaction is completed, the substrate is washed with water and separated, and vacuum dried to obtain a modifier, wherein the amount ratio of trichloroethyl phosphate, hydroxyethyl acrylate, etherification catalyst and carbon tetrachloride is 0.1 mol: 0.31-0.33 mol: 1.5-2 mL: 55-70 mL; Step A2: Mix hydrogenated silicone oil, hydrosilylation catalyst and anhydrous toluene, introduce dry nitrogen, heat to 80-95°C, stir and add modifier to react for 2.5-3.5h, then pressurize with nitrogen to 3-4bar, continue to heat to 110-120°C and continue to react for 1.5-2h, remove toluene after the reaction is completed, and obtain modified silicone main agent.

2. A leveling agent for a conductive coating slurry for lithium batteries according to claim 1, characterized in that: The etherification catalyst is trifluoromethanesulfonic acid.

3. The leveling agent for a conductive coating slurry for lithium batteries according to claim 1, characterized in that: The usage ratio of hydrogen-containing silicone oil, modifier, hydrosilylation catalyst and anhydrous toluene is 100 g: 25-40 mmol: 0.1-0.15 g: 60-80 mL.

4. The leveling agent for a conductive coating slurry for lithium batteries according to claim 3, characterized in that: Hydrogen-containing silicone oil is a branched-chain hydrogen-containing silicone oil.

5. The leveling agent for a conductive coating slurry for lithium batteries according to claim 3, characterized in that: The hydrosilylation catalyst is bis(triphenylphosphine)nickel chloride.

6. The leveling agent for a conductive coating slurry for lithium batteries according to claim 1, characterized in that: The anti-foaming agent is polyethylene glycol hexadecyl ether.

7. The leveling agent for a conductive coating slurry for lithium batteries according to claim 1, characterized in that: The thickening aid is polymethylphenylsiloxane.

8. The leveling agent for a conductive coating slurry for lithium batteries according to claim 1, characterized in that: The dispersing aid is methyl isobutyl ketone.

Images