Polymer dispersant for sodium-ion battery cathode material, sodium-ion battery

Abstract

The application belongs to the technical field of sodium ion batteries, and particularly relates to a polymer dispersant of a positive electrode material of a sodium ion battery and a sodium ion battery, which comprises, by mass fraction, 10-40 parts of acrylonitrile-acrylate copolymer A, 50-85 parts of amine-containing condensation polymer B and 3-10 parts of small molecule carboxylic acid additive C; the polymer dispersant exists in the form of an N-methylpyrrolidone solution, has a solid content of 20-40 wt%, and the solid content is the sum of the mass of the acrylonitrile-acrylate copolymer A, the amine-containing condensation polymer B and the small molecule carboxylic acid additive C, which accounts for the percentage of the total weight of the polymer dispersant; the combination of the above components can effectively improve the solid content under the premise that the viscosity of the positive electrode main material remains unchanged, and is not prone to gelation, so as to facilitate subsequent coating and rolling, improve the compaction density of the sodium battery, and effectively improve the production efficiency of the sodium battery.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a polymer dispersant for sodium-ion battery cathode materials and sodium-ion batteries. Background Technology

[0002] Sodium batteries operate on a principle highly similar to lithium batteries, both relying on the "rocking chair" intercalation and deintercalation of ions between the positive and negative electrodes to achieve charging and discharging. However, in terms of material composition, sodium batteries utilize sodium, an element abundant in the Earth's crust (2.3%), to replace scarce lithium, directly determining their low-cost nature. The main cathode materials for sodium batteries currently fall into three major technical routes: layered transition metal oxides, polyanionic compounds, and Prussian blue analogues. Each of these materials has its advantages: layered oxides prioritize high energy density, polyanionic compounds emphasize long cycle life and high safety, and Prussian blue focuses on low cost. Currently, polyanionic compounds dominate the market. Industry forecasts predict that polyanionic compounds will account for nearly 80% of the market share by 2030. The key to the industrialization of polyanionic compounds (especially phosphate systems such as sodium iron phosphate (NFP) and sodium iron pyrophosphate (NFPP)) lies in their optimal balance between cost, lifespan, and safety, precisely meeting the most pressing needs of the current energy storage market. First, significant cost advantage: The polyanion battery system does not contain precious metals such as cobalt, and is mainly composed of iron and manganese, resulting in lower raw material costs. After large-scale mass production, the cell cost is expected to be more than 15% lower than that of lithium iron phosphate batteries, and in the long term, it may even be reduced to less than 70% of the latter. Second, superior cycle life: Thanks to the stable three-dimensional framework structure of NASICON and other materials, the volume deformation during sodium ion insertion and extraction is minimal, and the theoretical cycle life far exceeds 8,000 cycles. Third, safety and wide temperature range: The polyanion structure has extremely strong thermal stability, and it can still operate stably in extreme environments ranging from -40℃ to 80℃. The capacity retention rate at -20℃ exceeds 90% (lithium batteries are usually less than 70%), perfectly solving the low-temperature pain point of energy storage power stations and power batteries in northern regions.

[0003] The manufacturing process of sodium-ion batteries also encompasses classic steps such as slurry preparation, coating, rolling, winding / stacking, electrolyte injection, and formation. However, differences exist in the details due to material properties. For example, in the positive electrode slurry preparation stage, the main sodium-ion battery material is prone to gelation. Commonly used dispersants for lithium-ion batteries, such as phosphate esters, polyvinylpyrrolidone, and polyacrylic acid, are difficult to increase the slurry's solid content and also result in poor slurry stability. This necessitates the addition of a large amount of NMP solvent during production, severely impacting production efficiency and increasing costs. Based on this, researchers have designed some dispersants specifically for sodium-ion batteries. For instance, patent CN118684812A uses acrylate monomers, vinyl acetate monomers, and ethylene tert-carbonate monomers to prepare an acrylate copolymer via free radical polymerization, which is then used as a dispersant for the positive electrode slurry of sodium-ion batteries. Experiments have shown that this dispersant has strong alkali resistance, can exist stably in alkaline solutions without chemical bond breakage, and exhibits good steric hindrance to improve particle dispersion stability and good adhesion to the current collector. Patent CN117638039A proposes functional small molecule additives to solve the problem of easy gelation of sodium plasma. The anti-gelling agent includes glycolic acid, acetic acid, anhydrous oxalic acid, anhydrous citric acid, maleic anhydride, acetic anhydride and their sodium salts.

[0004] Currently, research on dispersants for sodium battery cathode materials is still in its early stages. Although the products reported in the above patents can improve the solid content and reduce the viscosity of the slurry to some extent, in practice, the solid content of cathode slurries (NFP, NFPP) can only reach 50-55%, which is still far behind the 65-70% of lithium iron phosphate and ternary lithium.

[0005] Therefore, overcoming the deficiency of insufficient solid content in sodium battery cathode NFP and NFPP materials is an urgent problem to be solved in this field.

[0006] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0007] This disclosure provides at least one polymer dispersant for sodium-ion battery cathode materials and a sodium-ion battery.

[0008] In a first aspect, embodiments of this disclosure provide a polymer dispersant for a sodium-ion battery cathode material, comprising, by weight parts: 10-40 parts of acrylonitrile-acrylate copolymer A, 50-85 parts of amine-containing condensate polymer B, and 3-10 parts of a small molecule carboxylic acid auxiliaries C; the polymer dispersant exists in the form of an N-methylpyrrolidone solution with a solid content of 20-40 wt%, wherein the solid content is the percentage of the sum of the masses of acrylonitrile-acrylate copolymer A, amine-containing condensate polymer B, and small molecule carboxylic acid auxiliaries C to the total weight of the polymer dispersant; the molecular structural formula of the acrylonitrile-acrylate copolymer A is shown below: ; Wherein, x, y, and z are the mass fractions of the structural unit in the acrylonitrile-acrylate copolymer A, with values ​​ranging from x = 0.3 to 0.9, y = 0.05 to 0.7, and z = 0.05 to 0.15; R1 and R2 each independently represent -H or -CH3, and R represents C1 to C2. 12 Alkyl groups; the molecular structural formula of the amine-containing polymer B is shown below: ; Wherein, p, q, r, and s are the mass fractions of the structural unit in the amine-containing condensate B, with values ​​ranging from p=0.4 to 0.7, q=0 to 0.3, r=0.1 to 0.2, and s=0.2 to 0.5, and n is the number of repetitions of the oxypropylene unit, and is an integer in the range of 5 to 12.

[0009] In one optional embodiment, the acrylonitrile-acrylate copolymer A has a weight-average molecular weight of 200,000 to 500,000 and a molecular weight distribution of less than 2.8.

[0010] In one optional embodiment, the preparation method of the acrylonitrile-acrylate copolymer A includes: adding water to a reactor, heating to 50-95°C, then adding an initiator, stirring until homogeneous, and slowly dripping a mixed solution composed of monomers and chain transfer agents into the reactor, maintaining the temperature after the dripping is completed; wherein the monomers include acrylonitrile, (meth)acrylate, and (meth)acrylic acid; after the reaction is completed, filtering the material in the reactor, collecting the polymer, washing it with ethanol, and placing it in a forced-air drying oven to remove the solvent, thereby obtaining the acrylonitrile-acrylate copolymer A.

[0011] In one alternative embodiment, the alkyl chain contained in the (meth)acrylate is selected from C1 to C2. 12The alkyl group; the initiator is a water-soluble initiator, including any one of hydrogen peroxide, ammonium persulfate, potassium persulfate, V-50, VA-044, and VA-061, and its amount is 0.1 to 2% of the total mass of the monomers in the reactants; the chain transfer agent is a mercapto compound, including any one of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, and dodecyl mercaptoethanol, and its amount is 0.01 to 0.2% of the total mass of the monomers.

[0012] In one optional embodiment, the weight-average molecular weight of the amine-containing condensate B is 1500 to 5000.

[0013] In one optional embodiment, the preparation method of the amine-containing condensate B includes: adding a condensation monomer to a reactor, heating to 90-120°C, then adding a catalyst and formaldehyde, stirring to react fully, cooling to 60-80°C, removing moisture under vacuum, and diluting with NMP solvent to obtain an NMP solution of the amine-containing condensate B; wherein the condensation monomer includes naphthalenesulfonic acid, melamine, and phenoxyethanol polyoxypropylene ether.

[0014] In one optional embodiment, the catalyst comprises any one of sulfuric acid, hydrochloric acid, methanesulfonic acid, phosphoric acid, p-toluenesulfonic acid, formic acid, acetic acid, and oxalic acid, and its amount is 1 to 2% of the total weight of the polycondensation monomers in the reactants; the amount of formaldehyde is 75 to 110% of the total molar amount of the polycondensation monomers in the reactants.

[0015] In one optional embodiment, the reaction raw materials in the preparation method of the amine-containing condensate B further include p-aminobenzenesulfonic acid.

[0016] In one optional embodiment, the small molecule carboxylic acid auxiliary agent C is any one or more of oxalic acid, malonic acid, succinic acid, adipic acid, salicylic acid, and lactic acid, mixed in any proportion.

[0017] Secondly, embodiments of this disclosure also provide a sodium-ion battery, including a positive electrode material, wherein the positive electrode material is doped with a polymer dispersant as described above; the amount of the polymer dispersant is 0.05 to 0.3% of the weight of the main material in the positive electrode material.

[0018] The beneficial effects of this invention are that the polymer dispersant of the sodium-ion battery positive electrode material, utilizing the carboxyl, nitrile, and ester groups abundant in the acrylonitrile-acrylate copolymer A, combined with its high molecular weight, can effectively adsorb onto the surface of the main particles of the sodium-ion battery positive electrode, forming a coating layer that is equivalent to modifying the strongly polar groups of the main particles of the positive electrode; the amine groups abundant in the amine-containing condensate B can further bridge with the strongly polar groups of the acrylonitrile-acrylate copolymer A, and are smoothly adsorbed onto the surface of the main positive electrode, and through its abundant benzene, naphthalene, polyoxypropylene segments and other steric hindrance groups, can effectively isolate... The aggregation and coagulation of multiple sodium battery particles imparts a lower viscosity to the sodium battery cathode slurry and maintains stable viscosity. The small molecule carboxylic acid additive C has a small molecular volume and is rich in carboxylic acids, which can synergistically interact with acrylonitrile-acrylate copolymer A, making the cathode material more tightly wrapped by polar groups such as carboxylic acids, which is more conducive to the dispersion effect of amine-containing condensate B. The combination of the above components can effectively increase the solid content without changing the viscosity of the cathode material, and it is not easy to gel, which facilitates subsequent coating and rolling, improves the compaction density of sodium batteries, and also effectively improves the production efficiency of sodium batteries.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0023] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0024] In this embodiment of the invention, the molecular weight of the polymer was determined using a Waters 1515 gel permeation chromatograph under the following conditions: Gel column: Agilent PLgel 5 μm MIXED-C, column temperature: 55 °C, mobile phase: NMP, mobile phase flow rate: 1.0 mL / min, detector: Waters 2414 differential refractive index detector; molecular weight standard: PMMA type GPC standard.

[0025] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] This disclosure provides a polymer dispersant for a sodium-ion battery cathode material, comprising, by weight: 10-40 parts of acrylonitrile-acrylate copolymer A, 50-85 parts of amine-containing condensate polymer B, and 3-10 parts of a small molecule carboxylic acid auxiliaries C; the polymer dispersant exists in the form of an N-methylpyrrolidone solution with a solid content of 20-40 wt%, wherein the solid content is the percentage of the sum of the masses of acrylonitrile-acrylate copolymer A, amine-containing condensate polymer B, and small molecule carboxylic acid auxiliaries C to the total weight of the polymer dispersant; the molecular structure of acrylonitrile-acrylate copolymer A is shown below: ; Wherein, x, y, and z are the mass fractions of the structural unit in the acrylonitrile-acrylate copolymer A, with values ​​ranging from x = 0.3 to 0.9, y = 0.05 to 0.7, and z = 0.05 to 0.15; R1 and R2 each independently represent -H or -CH3, and R represents C1 to C2. 12 Alkyl groups; the molecular structural formula of the amine-containing polymer B is shown below: ; Wherein, p, q, r, and s are the mass fractions of the structural unit in the amine-containing condensate B, with values ​​ranging from p=0.4 to 0.7, q=0 to 0.3, r=0.1 to 0.2, and s=0.2 to 0.5, and n is the number of repetitions of the oxypropylene unit, and is an integer in the range of 5 to 12.

[0027] In some embodiments, specifically, the acrylonitrile-acrylate copolymer A has a weight-average molecular weight of 200,000 to 500,000 and a molecular weight distribution of less than 2.8.

[0028] In some embodiments, the preparation method of the acrylonitrile-acrylate copolymer A specifically includes: adding water to a reactor, heating to 50-95°C, then adding an initiator, stirring until homogeneous, and slowly dripping a mixed solution composed of monomers and chain transfer agents into the reactor, maintaining the temperature after the dripping is completed; wherein the monomers include acrylonitrile, (meth)acrylate, and (meth)acrylic acid; after the reaction is completed, filtering the material in the reactor, collecting the polymer, washing it with ethanol, and placing it in a forced-air drying oven to remove the solvent, thereby obtaining the acrylonitrile-acrylate copolymer A.

[0029] In some embodiments, specifically, the alkyl chain contained in the (meth)acrylate is selected from C1 to C2. 12 The alkyl group; the initiator is a water-soluble initiator, including any one of hydrogen peroxide, ammonium persulfate, potassium persulfate, V-50, VA-044, and VA-061, and its amount is 0.1 to 2% of the total mass of the monomers in the reactants; the chain transfer agent is a mercapto compound, including any one of mercaptoacetic acid, mercaptoethanol, mercaptopropionic acid, and dodecyl mercaptoethanol, and its amount is 0.01 to 0.2% of the total mass of the monomers.

[0030] In some embodiments, specifically, the weight-average molecular weight of the amine-containing condensate B is 1500 to 5000.

[0031] In some embodiments, the specific method for preparing the amine-containing condensate B includes: adding a condensation monomer to a reactor, heating to 90-120°C, then adding a catalyst and formaldehyde, stirring to react fully, cooling to 60-80°C, removing moisture under vacuum, and diluting with NMP solvent to obtain an NMP solution of the amine-containing condensate B; wherein the condensation monomer includes naphthalenesulfonic acid, melamine, and phenoxyethanol polyoxypropylene ether.

[0032] In some embodiments, specifically, the catalyst includes any one of sulfuric acid, hydrochloric acid, methanesulfonic acid, phosphoric acid, p-toluenesulfonic acid, formic acid, acetic acid, and oxalic acid, and its amount is 1 to 2% of the total weight of the polycondensation monomers in the reactants; the amount of formaldehyde is 75 to 110% of the total molar amount of the polycondensation monomers in the reactants.

[0033] In some embodiments, specifically, the reaction raw materials in the preparation method of the amine-containing condensate B further include p-aminobenzenesulfonic acid.

[0034] In some embodiments, specifically, the small molecule carboxylic acid auxiliary agent C is any one or more of oxalic acid, malonic acid, succinic acid, adipic acid, salicylic acid, and lactic acid, mixed in any proportion.

[0035] Secondly, embodiments of this disclosure also provide a sodium-ion battery, including a positive electrode material, wherein the positive electrode material is doped with a polymer dispersant as described above; the amount of the polymer dispersant is 0.05 to 0.3% of the weight of the main material in the positive electrode material.

[0036] The preparation method of acrylonitrile-acrylate copolymer A is described below.

[0037] Synthesis Example A-1: ​​1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 93℃. Then, 6g of hydrogen peroxide initiator (30% by mass) was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 160g of acrylonitrile, 10g of butyl acrylate, 30g of acrylic acid, and 0.2g of mercaptoethanol was slowly added dropwise to the reaction flask over 2 hours. After the addition was completed, the mixture was kept at the same temperature for 2 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-1. The ratio of each structural unit was x=0.8, y=0.05, and z=0.15. The yield was determined to be 92% by weighing, and the weight-average molecular weight was 225,000 by GPC, with a molecular weight distribution coefficient of 2.4.

[0038] Synthesis Example A-2: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 80℃. Then, 2.4g of ammonium persulfate initiator was added, and after stirring for 5 minutes, a mixed solution consisting of 150g of acrylonitrile, 30g of butyl methacrylate, 20g of acrylic acid, and 0.4g of dodecyl mercaptan was slowly added dropwise to the reaction flask over 5 hours. After the addition was completed, the mixture was kept at the same temperature for 1 hour. The material was then filtered through a 250-mesh nylon filter cloth, the polymer was collected, washed twice with ethanol, and then placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-2. The ratio of each structural unit was x=0.75, y=0.15, and z=0.1. The yield was determined by weighing to be 88%, and the weight-average molecular weight was 271,000, with a molecular weight distribution coefficient of 2.7 determined by GPC.

[0039] Synthesis Example A-3: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 70℃. Then, 0.5g of potassium persulfate initiator was added, and after stirring for 5 minutes, a mixed solution consisting of 150g of acrylonitrile, 30g of butyl acrylate, 20g of methacrylic acid, and 0.4g of dodecyl mercaptan was slowly added dropwise to the reaction flask over 2 hours. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, the polymer was collected, washed twice with ethanol, and then placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-3. The ratio of each structural unit was x=0.75, y=0.15, and z=0.1. The yield was determined by weighing to be 84%, and the weight-average molecular weight was 426,000 by GPC, with a molecular weight distribution coefficient of 2.2.

[0040] Synthesis Example A-4: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 55°C. Then, 0.5g of VA-044 initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 160g of acrylonitrile, 30g of lauryl acrylate, 10g of acrylic acid, and 0.24g of mercaptopropionic acid was slowly added dropwise to the reaction flask over 3 hours. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50°C forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-4. The ratio of each structural unit was x=0.8, y=0.15, and z=0.1. The yield was determined to be 91% by weighing, and the weight-average molecular weight was 498,000 by GPC, with a molecular weight distribution coefficient of 1.9.

[0041] Synthesis Example A-5: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 65℃. Then, 3g of VA-044 initiator was added, and after stirring for 5 minutes, a mixed solution consisting of 100g acrylonitrile, 90g butyl acrylate, 10g acrylic acid, and 0.1g mercaptoethanol was slowly added dropwise to the reaction flask over 4 hours. After the addition was completed, the mixture was kept at the same temperature for 4 hours. The material was then filtered through a 250-mesh nylon filter cloth, the polymer was collected, washed twice with ethanol, and then placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-5. The ratio of each structural unit was x=0.5, y=0.45, and z=0.05. The yield was determined by weighing to be 94%, and the weight-average molecular weight was 331,000 by GPC, with a molecular weight distribution coefficient of 2.1.

[0042] Synthesis Example A-6: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 60℃. Then, 1g of potassium persulfate initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 140g of acrylonitrile, 30g of methyl acrylate, 18g of ethyl acrylate, 12g of acrylic acid, and 0.12g of mercaptoethanol was slowly added dropwise to the reaction flask over 1 hour. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-6. The ratio of each structural unit was x=0.7, y=0.24, and z=0.06. The yield was determined by weighing to be 78%, and the weight-average molecular weight was 441,000 by GPC, with a molecular weight distribution coefficient of 2.7.

[0043] Synthesis Example A-7: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 95℃. Then, 4g of ammonium persulfate initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 173g of acrylonitrile, 17g of methyl acrylate, 10g of acrylic acid, and 0.02g of mercaptoethanol was slowly added dropwise to the reaction flask over 1 hour. After the addition was completed, the mixture was kept at the same temperature for 2 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-7. The ratio of each structural unit was x=0.865, y=0.085, and z=0.05. The yield was determined by weighing to be 82%, and the weight-average molecular weight was 205,000 by GPC, with a molecular weight distribution coefficient of 1.8.

[0044] Synthesis Example A-8: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 50°C. Then, 4g of V-50 initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 60g acrylonitrile, 100g methyl acrylate, 20g isooctyl acrylate, 20g acrylic acid, and 0.05g mercaptoethanol was slowly added dropwise to the reaction flask over 5 hours. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50°C forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-8. The ratio of each structural unit was x=0.3, y=0.6, and z=0.1. The yield was determined to be 75% by weighing, and the weight-average molecular weight was 258,000 by GPC, with a molecular weight distribution coefficient of 2.0.

[0045] Synthesis Example A-9: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 60°C. Then, 2g of VA-061 initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 60g acrylonitrile, 100g methyl acrylate, 20g isooctyl acrylate, 20g acrylic acid, and 0.05g mercaptoethanol was slowly added dropwise to the reaction flask over 5 hours. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50°C forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-9. The ratio of each structural unit was x=0.3, y=0.6, and z=0.1. The yield was determined to be 75% by weighing, and the weight-average molecular weight was 258,000 by GPC, with a molecular weight distribution coefficient of 2.0.

[0046] Synthesis Example A-10: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 67°C. Then, 0.6g of potassium persulfate initiator was added, and the mixture was stirred for 5 minutes. A mixed solution consisting of 100g acrylonitrile, 10g ethyl acrylate, 80g isooctyl acrylate, 10g acrylic acid, and 0.1g mercaptoethanol was slowly added dropwise to the reaction flask over 1 hour. After the addition was complete, the mixture was kept at this temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50°C forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-10. The structural unit ratios were x=0.5, y=0.45, and z=0.05. The yield was determined to be 80% by weight, and the weight-average molecular weight was 300,000 by GPC, with a molecular weight distribution coefficient of 2.7.

[0047] Synthesis Example A-11: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 93℃. Then, 6g of hydrogen peroxide initiator (30% by mass) was added, and the mixture was stirred for 5 minutes. 30% of a mixed solution consisting of 160g acrylonitrile, 10g butyl acrylate, 30g acrylic acid, and 0.25g mercaptoethanol was added to the reaction flask to initiate the initial reaction. The remaining solution was slowly added dropwise over 2 hours, and the mixture was kept at this temperature for 2 hours after the addition was complete. The material was then filtered through a 250-mesh nylon filter cloth, and the polymer was collected. After washing twice with ethanol, the polymer was placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-11. The structural unit ratios were x=0.8, y=0.05, and z=0.15. The yield was determined to be 94% by weight, and the weight-average molecular weight was 273,000 by GPC, with a molecular weight distribution coefficient of 9.3. A-11 and A-1 have the same ratio and the molecular weight is within a suitable range, but the molecular weight distribution is different. The molecular weight distribution of A-11 is obviously too wide.

[0048] Synthesis Example A-12: 1000g of water was added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer, and the temperature was raised to 50℃. Then, 0.65g of VA-044 initiator was added, and after stirring for 5 minutes, a mixed solution consisting of 160g acrylonitrile, 30g lauryl acrylate, and 10g acrylic acid was slowly added dropwise to the reaction flask over 3 hours. After the addition was completed, the mixture was kept at the same temperature for 5 hours. The material was then filtered through a 250-mesh nylon filter cloth, the polymer was collected, washed twice with ethanol, and then placed in a 50℃ forced-air drying oven for 24 hours to obtain acrylonitrile-acrylate copolymer A-12. The proportions of its structural units were x=0.8, y=0.15, and z=0.05. The yield was determined to be 92% by weight, and the weight-average molecular weight was 1.204 million by GPC, with a molecular weight distribution coefficient of 2.5. A-12 had the same proportions and similar reaction conditions as A-4, but no chain transfer agent was added, resulting in a significantly larger molecular weight for A-12.

[0049] The preparation method of amine-containing condensate B is described below.

[0050] Synthesis Example B-1: 50g of naphthalenesulfonic acid, 5g of p-aminobenzenesulfonic acid, 10g of melamine, and 35g of phenoxyethanol polyoxypropylene ether (molecular weight 500) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 110℃, followed by the addition of 1g of concentrated sulfuric acid as a catalyst. Then, 27g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 3 hours, the temperature was lowered to 65℃, and the water was removed by vacuum. 204g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-1. The ratio of each structural unit was p=0.5, q=0.1, r=0.2, and s=0.35. The solid content was determined to be 35.1%, and the weight-average molecular weight was 1710 as determined by GPC.

[0051] Synthesis Example B-2: 50g of naphthalenesulfonic acid, 20g of melamine, and 30g of phenoxyethanol polyoxypropylene ether (molecular weight 500) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 110℃, followed by the addition of 2g of oxalic acid as a catalyst. Then, 30.5g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 3 hours, the temperature was lowered to 65℃, and the water was removed by vacuum. 207g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-2. The ratio of each structural unit was p=0.5, q=0, r=0.2, and s=0.3. The solid content was determined to be 34.4%, and the weight-average molecular weight was 2050 as determined by GPC.

[0052] Synthesis Example B-3: 40g of naphthalenesulfonic acid, 20g of melamine, and 40g of phenoxyethanol polyoxypropylene ether (molecular weight 600) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 120℃, followed by the addition of 1.5g of oxalic acid catalyst. Then, 29g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 4 hours, the temperature was lowered to 65℃, and the water was removed by vacuum. 205g of NMP solvent was added for dilution to obtain an NMP solution containing amine condensate B-3. The ratio of each structural unit was p=0.4, q=0, r=0.2, and s=0.4. The solid content was determined to be 35.5%, and the weight-average molecular weight was determined to be 2540 by GPC.

[0053] Synthesis Example B-4: 40g of naphthalenesulfonic acid, 10g of p-aminobenzenesulfonic acid, 20g of melamine, and 30g of phenoxyethanol polyoxypropylene ether (molecular weight 600) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 100℃, followed by the addition of 1.3g of phosphoric acid catalyst. Then, 34g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 4 hours, the temperature was lowered to 65℃, and the water was removed by vacuum. 209g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-4. The ratio of each structural unit was p=0.4, q=0.1, r=0.2, and s=0.3. The solid content was determined to be 35.5%, and the weight-average molecular weight was 2990 as determined by GPC.

[0054] Synthesis Example B-5: 45g of naphthalenesulfonic acid, 15g of p-aminobenzenesulfonic acid, 15g of melamine, and 25g of phenoxyethanol polyoxypropylene ether (molecular weight 800) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 95°C, followed by the addition of 2g of sulfuric acid as a catalyst. Then, 37g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 4 hours, the temperature was lowered to 65°C, and the water was removed by vacuum. 211g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-5. The ratio of each structural unit was p=0.45, q=0.15, r=0.15, and s=0.25. The solid content was determined to be 34.9%, and the weight-average molecular weight was determined to be 3310 by GPC.

[0055] Synthesis Example B-6: 65g of naphthalenesulfonic acid, 15g of melamine, and 20g of phenoxyethanol polyoxypropylene ether (molecular weight 800) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 120°C, followed by the addition of 2g of methanesulfonic acid as a catalyst. Then, 41g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 4 hours, the temperature was lowered to 65°C, and the water was removed by vacuum. 214g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-6. The structural unit ratios were p=0.65, q=0, r=0.15, and s=0.2. The solid content was determined to be 35.1%, and the weight-average molecular weight was 4040 as determined by GPC.

[0056] Synthesis Example B-7: 25g of naphthalenesulfonic acid, 15g of p-aminobenzenesulfonic acid, 20g of melamine, and 40g of phenoxyethanol polyoxypropylene ether (molecular weight 500) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 110°C, followed by the addition of 1g of concentrated sulfuric acid as a catalyst. Then, 27g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 3 hours, the temperature was lowered to 65°C, and the water was removed under vacuum. 204g of NMP solvent was added for dilution, yielding an NMP solution containing amine condensate B-7. The structural unit ratios were p=0.25, q=0.15, r=0.2, and s=0.4. The solid content was determined to be 35.6%, and the weight-average molecular weight was 2020 as determined by GPC. Synthesis Example B-7 is basically similar to B-1, except that the raw material ratios exceed the range described in this application.

[0057] Synthesis Example B-8: 50g of naphthalenesulfonic acid, 12.5g of p-aminobenzenesulfonic acid, and 37.5g of phenoxyethanol polyoxypropylene ether (molecular weight 600) were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The temperature was raised to 100℃, followed by the addition of 1.3g of phosphoric acid catalyst. Then, 34g of formaldehyde solution (37%) was added dropwise to the reaction flask over 10 minutes. After mechanical stirring for 4 hours, the temperature was lowered to 65℃, and the water was removed under vacuum. 209g of NMP solvent was added for dilution, yielding an NMP solution of amine-containing condensation polymer B-8. The structural unit ratios were p=0.5, q=0.125, r=0, and s=0.375. The solid content was determined to be 34.7%, and the weight-average molecular weight was 2790 as determined by GPC. Synthesis Example B-8 is basically similar to B-4, except that the melamine raw material was removed, and the melamine portion was increased by the other three condensation monomers according to their respective proportions.

[0058] The preparation method of the polymer dispersant for the sodium-ion battery cathode material described in this invention is introduced below.

[0059] In Example 1, 103g of NMP, 25g of A-1, 70g of B-1, and 5g of succinic acid were added to a four-necked reaction flask equipped with a thermometer and mechanical stirrer. The mixture was heated to 80°C and stirred to dissolve. Then, the water was removed by vacuuming at this temperature to obtain the polymer dispersant for the sodium-ion battery cathode material of the present invention. The solid content was measured to be 30.2%.

[0060] The preparation methods for Examples 2-15 are the same as those for Example 1, involving conventional compounding and dissolution. The specific preparation methods are recorded in the table below.

[0061] Table 1. Types and amounts of raw materials used in Examples 1-15

[0062] To more clearly demonstrate the performance advantages of the polymer dispersant for sodium-ion battery cathode materials described in this invention, 10 comparative examples are given below.

[0063] Comparative Example 1: Polyvinylpyrrolidone (weight average molecular weight 15000), purchased from Sinopharm Chemical Reagent Co., Ltd., is a commonly used polymer dispersant in the power battery industry.

[0064] Comparative Example 2: Polyacrylic acid (molecular weight 2000-5000), purchased from Adamas Chemical Reagent Company, is a commonly used polymer dispersant in the power battery industry.

[0065] Comparative Example 3: Alkylphenol polyoxyethylene ether (molecular weight 1000, purchased from Adamas Chemical Company) was used. P2O5 was added and stirred at 90°C for 5 hours. Then, a small amount of water was added for hydrolysis, followed by dilution with NMP and vacuum dehydration. This is a commonly used polymer dispersant in the lithium battery industry.

[0066] The preparation methods for Comparative Examples 4 to 10 are the same as those for the Examples, and are listed in the table below.

[0067] Table 2. Raw materials used in Comparative Examples 4–10

[0068] In the comparative examples in the table above, Comparative Example 4 is similar to Example 1, except that it uses A-11, whose proportion is outside the range of acrylonitrile-acrylate copolymer A described in this application. Comparative Example 5 is similar to Example 1, except that it uses B-7, whose proportion is outside the range of amine-containing polymer B described in this application. Comparative Example 6 is similar to Example 1, except that it does not contain small molecule carboxylic acid. Comparative Example 7 is similar to Example 1, except that it does not contain amine-containing polymer B. Comparative Example 8 is similar to Example 1, except that it does not contain acrylonitrile-acrylate copolymer A. Comparative Example 9 is similar to Example 6, except that it uses A-12, whose molecular weight exceeds the range of acrylonitrile-acrylate copolymer A described in this application. Comparative Example 10 is similar to Example 10, except that it uses B-8, whose condensation monomer does not contain melamine, and therefore does not meet the requirements of amine-containing polymer B described in this application.

[0069] The following describes in more detail the dispersion performance of the polymer dispersant for sodium-ion battery cathode materials described in this invention in sodium battery cathode materials through application examples.

[0070] Application Example 1 Table 3 verifies the dispersion of the NFP slurry by the polymer dispersant for the sodium-ion battery cathode material described in this invention. The slurry was prepared by mixing NFP main material, PVDF, SP, CNT, and dispersant in a ratio of 94.6:3:1.8:0.2:0.4, and then NMP solvent was added to achieve a solid content of 50-63%. After homogenization using a vacuum degassing machine for 4 hours, the viscosity of the slurry was tested. Simultaneously, the slurry was allowed to stand at room temperature for 24 hours, and its stability was monitored. The data show that, compared to the blank, Examples 1-15 showed a 13 percentage point increase in slurry solid content. The output viscosity was essentially the same for both, around 10,000 cp. However, the viscosity changes were smaller in Examples 1-15 at 12 hours and 24 hours, with the 24-hour viscosity increasing by approximately 30-80%, while the control sample increased by approximately 370%. This demonstrates that the polymer dispersant for the sodium-ion battery cathode material described in this invention has excellent dispersion effects on the NFP slurry, increasing the slurry solid content by 26% and exhibiting superior viscosity stability. Comparative Examples 1-3, using conventional PVP, PAA, and polyether phosphate dispersants, failed to effectively improve slurry viscosity. PAA, in particular, showed no dispersing effect, while PVP and polyether phosphate only improved solidification by about 1-2 percentage points. Comparative Examples 4, 5, 9, and 10, although using similar types of dispersants to the examples, did not meet the requirements of this application regarding acrylonitrile-acrylate copolymer A and amine-containing condensate B, resulting in significantly affected performance. The discharge viscosity increased by 50-200% compared to Examples 1-15, and viscosity stabilization was insufficient. Comparative Examples 6-8, without the addition of small-molecule carboxylic acid, amine-containing condensate B, and acrylonitrile-acrylate copolymer A, showed significantly deteriorated dispersibility, with Comparative Example 7 completely losing its dispersibility.

[0071] Table 3 Viscosity of NFP slurry

[0072] Application Example 2 Table 4 verifies the dispersion of the sodium-ion battery cathode material polymer dispersant of the present invention on the NFPP slurry. The slurry was prepared by mixing NFPP main material, PVDF, SP, CNT, and dispersant in a ratio of 95.0:2.4:2.0:0.2:0.4. As shown in the table below, the conclusions are consistent with those in Table 3, both demonstrating that the sodium-ion battery cathode material polymer dispersant of the present invention has excellent dispersion and excellent viscosity stability for the sodium battery slurry, which will not be elaborated further here.

[0073] Table 4 Viscosity of NFPP slurry

[0074] Application Example 3 Table 5 verifies the effect of the polymer dispersant of the sodium-ion battery cathode material described in this invention on the electrode compaction density and battery energy density. The prepared NFP slurry was coated onto electrodes, and after drying, the compaction density was tested. The electrodes were then assembled into 2032 coin cells, and the discharge specific capacity (mAh / g) at different rates (0.1C and 1C) was measured. The data show that Examples 1-15 exhibit significant advantages over the control sample in all three tests: compaction density, discharge specific capacity at 0.1C, and discharge specific capacity at 1C. This indicates that the polymer dispersant of the sodium-ion battery cathode material described in this invention can effectively increase the compaction density by 3-7%, thereby improving the energy density of the sodium battery.

[0075] Table 5. Electrode compaction density and corresponding battery discharge specific capacity

[0076] In summary, the polymer dispersant of this sodium-ion battery positive electrode material, along with the carboxyl, nitrile, and ester groups abundant in the acrylonitrile-acrylate copolymer A, and its high molecular weight, can effectively adsorb onto the surface of the main positive electrode particles, forming a coating layer that modifies the strongly polar groups of the main positive electrode particles. Furthermore, the amine groups abundant in the amine-containing condensate B can bridge with the strongly polar groups of the acrylonitrile-acrylate copolymer A, facilitating adsorption onto the surface of the main positive electrode material. Through its abundant benzene, naphthalene, and polyoxypropylene segments, it can effectively isolate multiple [elements / groups]. The aggregation and coagulation of sodium-ion battery particles endow the sodium-ion battery cathode slurry with a lower viscosity and maintains the slurry viscosity stability. The small molecule carboxylic acid additive C has a small molecular volume and is rich in carboxylic acids, which can synergistically interact with acrylonitrile-acrylate copolymer A, making the cathode material more tightly wrapped by polar groups such as carboxylic acids, which is more conducive to the dispersion effect of amine-containing condensate B. The combination of the above components can effectively increase the solid content without changing the viscosity of the cathode material, and it is not easy to gel, which facilitates subsequent coating and rolling, improves the compaction density of sodium batteries, and also effectively improves the production efficiency of sodium batteries.

[0077] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A polymer dispersant for a sodium-ion battery cathode material, characterized in that, Included by weight parts: Acrylonitrile-acrylate copolymer A 10-40 parts, amine-containing condensate B 50-85 parts, and small molecule carboxylic acid auxiliaries C 3-10 parts; The polymer dispersant exists in the form of an N-methylpyrrolidone solution with a solid content of 20-40 wt%. The solid content is the percentage of the total weight of the polymer dispersant, which is the sum of the masses of acrylonitrile-acrylate copolymer A, amine-containing condensate B, and small molecule carboxylic acid auxiliaries C. The molecular structure of the acrylonitrile-acrylate copolymer A is shown below: ； Wherein, x, y, and z are the mass fractions of the structural unit in the acrylonitrile-acrylate copolymer A, and their values ​​range from x=0.3 to 0.9, y=0.05 to 0.7, and z=0.05 to 0.15; R1 and R2 each independently represent -H or -CH3, and R represents C1 to C2. 12 Alkyl groups; The molecular structure of the amine-containing condensate B is shown below: ； Wherein, p, q, r, and s are the mass fractions of the structural unit in the amine-containing condensate B, with values ​​ranging from p=0.4 to 0.7, q=0 to 0.3, r=0.1 to 0.2, and s=0.2 to 0.5, and n is the number of repetitions of the oxypropylene unit, and is an integer in the range of 5 to 12.

2. The polymer dispersant for the sodium-ion battery cathode material as described in claim 1, characterized in that, The acrylonitrile-acrylate copolymer A has a weight-average molecular weight of 200,000 to 500,000 and a molecular weight distribution of less than 2.

8.

3. The polymer dispersant for the sodium-ion battery cathode material as described in claim 1, characterized in that, The preparation method of the acrylonitrile-acrylate copolymer A includes: Add water to the reactor and heat it to 50-95°C. Then add the initiator and stir until homogeneous. Slowly drip the mixed solution consisting of monomer and chain transfer agent into the reactor. After the dripping is completed, keep the temperature. The monomers include acrylonitrile, (meth)acrylate, and (meth)acrylic acid; After the reaction is complete, the material in the reactor is filtered, the polymer is collected, washed with ethanol, and then placed in a forced-air drying oven to remove the solvent, thus obtaining acrylonitrile-acrylate copolymer A.

4. The polymer dispersant for the sodium-ion battery cathode material as described in claim 3, characterized in that, The alkyl chain contained in the (meth)acrylate is selected from C1 to C2. 12 Alkyl groups; The initiator is a water-soluble initiator, including any one of hydrogen peroxide, ammonium persulfate, potassium persulfate, V-50, VA-044, and VA-061, and its amount is 0.1% to 2% of the total mass of the monomers in the reactants; The chain transfer agent is a thiol compound, including any one of thioglycolic acid, thioethanol, thiopropionic acid, and dodecyl mercaptohydric acid, and its amount is 0.01 to 0.2% of the total mass of the monomer.

5. The polymer dispersant for the sodium-ion battery cathode material as described in claim 1, characterized in that, The weight-average molecular weight of the amine-containing condensate B is 1500–5000.

6. The polymer dispersant for the sodium-ion battery cathode material as described in claim 1, characterized in that, The preparation method of the amine-containing condensate B includes: Add the condensation monomer to the reactor, heat to 90-120°C, then add the catalyst and formaldehyde, stir to react fully, cool to 60-80°C, remove water by vacuum, add NMP solvent to dilute, and obtain an NMP solution containing amine condensation polymer B. The condensation monomers include naphthalenesulfonic acid, melamine, and phenoxyethanol polyoxypropylene ether.

7. The polymer dispersant for the sodium-ion battery cathode material as described in claim 6, characterized in that, The catalyst includes any one of sulfuric acid, hydrochloric acid, methanesulfonic acid, phosphoric acid, p-toluenesulfonic acid, formic acid, acetic acid, and oxalic acid, and its amount is 1 to 2% of the total weight of the condensation monomers in the reactants; The amount of formaldehyde used is 75-110% of the total molar amount of condensation monomers in the reactants.

8. The polymer dispersant for the sodium-ion battery cathode material as described in claim 6, characterized in that, The reaction raw materials in the preparation method of the amine-containing condensate B also include p-aminobenzenesulfonic acid.

9. The polymer dispersant for the sodium-ion battery cathode material as described in claim 1, characterized in that, The small molecule carboxylic acid auxiliary agent C is any one or more of oxalic acid, malonic acid, succinic acid, adipic acid, salicylic acid, and lactic acid, mixed in any proportion.

10. A sodium-ion battery, characterized in that, The cathode material includes a polymer dispersant as described in any one of claims 1-9. The polymer dispersant has a solid content of 0.05 to 0.3% of the weight of the main material in the cathode material.

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