Hyperbranched polymer as well as preparation method and application thereof

Abstract

The invention discloses a hyperbranched polymer as well as a preparation method and application thereof, and particularly provides a hyperbranched polymer or a dispersant, which is characterized in that the hyperbranched polymer or the dispersant is prepared from a three-functionality carboxylic acid compound A and polyethyleneimine through an amidation reaction, the molar ratio of the three-functionality carboxylic acid compound A to the polyethyleneimine is (5-48): 1; wherein the trifunctional carboxylic acid compound A is selected from one or more of the following substances: citric acid, isocitric acid, 1, 3, 5-tricarboxylic acid pentane, 3-phosphoryl-1, 3, 5-pentane tricarboxylic acid, 1, 2, 3-benzene tricarboxylic acid, 1, 2, 4-benzene tricarboxylic acid, trimesic acid, 1, 3, 5-cyclohexane tricarboxylic acid, 1, 2, 4-butane tricarboxylic acid and 2-methylpropane tricarboxylic acid; the molecular weight of the polyethyleneimine is 500 to 5000 g / mol.

Description

Technical Field

[0001] The invention relates to a hyperbranched polymer and a preparation method and application thereof. Background Art

[0002] When the positive electrode of a lithium-ion battery is formed, lithium iron phosphate slurry needs to be coated on aluminum foil, so the properties of lithium iron phosphate slurry are directly related to the coating of the positive electrode. At present, the positive electrode slurry components of most domestic lithium-ion battery manufacturers are similar, mainly composed of lithium iron phosphate powder, conductive carbon black, adhesive and NMP.

[0003] In order to increase the capacity of the battery, it is usually achieved by increasing the proportion of electrode active materials in the positive electrode slurry, but this method will cause many problems in the processing process. Including the viscosity of the positive electrode slurry, or the viscosity changes rapidly over time, resulting in poor fluidity, which seriously affects the coating effect; in the preparation of the positive electrode slurry, it will be stirred and exhausted at a low speed, but there are often some dense bubbles that are difficult to eliminate, resulting in cracking during the coating and drying process; after drying, it will go through the rolling step. When pursuing a large compaction density, a large pressure rolling is required, which is easy to cause the particles to crack and then cause the pole piece to crack.

[0004] In response to the above problems, technicians in this field have conducted extensive research and have publicly reported some dispersants specifically used for lithium battery positive electrode slurries, such as polyvinyl pyrrolidone, phosphites, etc. However, the current positive electrode materials are quite diverse. For example, the main material of lithium iron phosphate varies in particle size, carbon coverage, element doping, etc., and the binder PVDF also has different processes such as suspension polymerization and emulsion polymerization. There are also factors such as the large differences in the processes and equipment used to prepare positive electrode slurries by different companies. Dispersants or additives with a single performance cannot adapt to a variety of positive electrode slurries, so compound positive electrode additives that can solve a variety of complex problems are urgently needed to be developed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defect of insufficient types of lithium battery positive electrode slurry dispersants in the prior art, and to provide a hyperbranched polymer that can reduce viscosity, increase slurry solid content, has excellent dispersibility, and can improve slurry viscosity and stability.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a hyperbranched polymer or dispersant, which is prepared by amidation reaction of a trifunctional carboxylic acid compound A and polyethyleneimine, wherein the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 5-48:1; wherein the trifunctional carboxylic acid compound A is a a and three carboxyl-substituted C 1-12 Alkyl or one or more Rb and three carboxyl-substituted C 6-14 Aryl; R a and R b They are independently OH or -P(=O)(OH)2; the average molecular weight of the polyethyleneimine is 500-5000 g / mol.

[0008] In some embodiments, the trifunctional carboxylic acid compound A is selected from one or more of the following substances: citric acid, isocitric acid, 1,3,5-tricarboxylic acid pentane, 3-phosphoryl-1,3,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, trimesic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 2-methylpropanetricarboxylic acid; such as citric acid, 1,3,5-tricarboxylic acid pentane, trimesic acid, 3-phosphoryl-1,3 ,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-tricarboxylic acid pentane and 1,2,3-tricarboxylic acid cyclohexane, one or two of them; for example, citric acid, 1,3,5-tricarboxylic acid pentane, trimesic acid, 3-phosphoryl-1,3,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-tricarboxylic acid pentane, 1,2,3-tricarboxylic acid cyclohexane, a combination of 1,2,4-benzenetricarboxylic acid and 1,3,5-cyclohexanetricarboxylic acid, or a combination of 1,2,3-benzenetricarboxylic acid and trimesic acid.

[0009] In some embodiments, the average molecular weight of the polyethyleneimine is (1500-5000) g / mol; for example, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 4000 g / mol or 5000 g / mol.

[0010] In some embodiments, the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is (23-45):1; for example, 23:1, 24:1, 29:1, 30:1, 32:1, 35:1, 38:1, 42:1 or 45:1.

[0011] In some embodiments, the hyperbranched polymer satisfies any of the following:

[0012] Scheme A: the trifunctional carboxylic acid compound A is citric acid, the average molecular weight of the polyethyleneimine is 5000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 30:1;

[0013] Scheme B: the trifunctional carboxylic acid compound A is 1,3,5-tricarboxylic acid pentane, the average molecular weight of the polyethyleneimine is 1500 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 23:1;

[0014] Scheme C: the trifunctional carboxylic acid compound A is trimesic acid, the average molecular weight of the polyethyleneimine is 2500 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 24:1;

[0015] Scheme D: the trifunctional carboxylic acid compound A is 3-phosphoryl-1,3,5-pentanetricarboxylic acid, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 35:1;

[0016] Scheme E: the trifunctional carboxylic acid compound A is 1,2,3-benzenetricarboxylic acid, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 38:1;

[0017] Scheme F: the trifunctional carboxylic acid compound A is 1,3,5-tricarboxylic acid pentane, the average molecular weight of the polyethyleneimine is 4000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 32:1;

[0018] Scheme G: the trifunctional carboxylic acid compound A is trimesic acid, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 29:1;

[0019] Scheme H: the trifunctional carboxylic acid compound A is 1,2,3-tricarboxylic acid cyclohexane, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 42:1;

[0020] Scheme I: the trifunctional carboxylic acid compound A is 1,2,4-benzenetricarboxylic acid and 1,3,5-cyclohexanetricarboxylic acid in a mass ratio of 25:7, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 45:1;

[0021] Scheme J: The trifunctional carboxylic acid compound A is 1,2,3-benzenetricarboxylic acid and trimesic acid in a mass ratio of 12:8, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 38:1.

[0022] In some embodiments, the hyperbranched polymer or dispersant is prepared by the following preparation method, which comprises the following steps: a) reacting the trifunctional carboxylic acid compound A with polyethyleneimine at a reaction temperature of 80 to 120° C. under low pressure in the presence of a solvent;

[0023] b) reacting at a temperature of 140 to 170° C. under normal pressure;

[0024] c) reacting at a reaction temperature of 140 to 170° C. under low pressure to obtain the target product;

[0025] The low pressure has a pressure of 0.070-0.096 MPa;

[0026] Normal pressure refers to the state where there is no additional change in pressure, and the pressure is close to the standard atmospheric pressure; such as 0.98 to 1.02 standard atmospheric pressure.

[0027] In some embodiments, a catalyst may be added in step a), and the catalyst is selected from one or more of dimethylaminopyridine, 4-pyrrolylpyridine, N,N-dicyclohexylcarbodiimide, diisopropylcarbodiimide, p-toluenesulfonic acid, triethylamine and 1-hydroxybenzotriazole, such as p-toluenesulfonic acid or triethylamine; the amount of the catalyst may be 0.5%-3% of the total mass of the trifunctional carboxylic acid compound A and polyethyleneimine; for example, 1%.

[0028] In some embodiments, in the preparation method, the solvent is N-methylpyrrolidone.

[0029] In some embodiments, in step a), the reaction temperature is 90-120°C; for example, 90°C, 100°C, 105°C, 110°C or 120°C.

[0030] In some embodiments, in step a), the low pressure has a pressure of -0.080 to -0.095 MPa.

[0031] In some embodiments, in step a), 0.5 to 5 hours; such as the reaction time is 1 to 4 hours; for example 1 hour, 2 hours, 3 hours or 4 hours.

[0032] In some embodiments, in step b), the reaction temperature is 150-160°C; for example, 150°C, 155°C or 160°C.

[0033] In some embodiments, in step b), 2 to 6 hours; such as the reaction time is 2 to 5 hours; for example 2 hours, 3 hours, 4 hours or 5 hours.

[0034] In some embodiments, in step c), the reaction temperature is 150-160°C; for example, 150°C, 155°C or 160°C.

[0035] In some embodiments, in step c), the low pressure has a pressure of -0.080 to -0.095 MPa.

[0036] In some embodiments, in step c), 2 to 6 hours; such as the reaction time is 2 to 4 hours; for example 2 hours, 3 hours or 4 hours.

[0037] In some embodiments, in the preparation method, the mass ratio of the solvent to the total mass of the trifunctional carboxylic acid compound A and polyethyleneimine is (0.8-1):1; for example, 1:1.

[0038] In some embodiments, the preparation method further comprises the following post-processing step: after the reaction is completed, the mixture is cooled to 80° C., and the solvent is added to adjust the solid content to 50%.

[0039] The present invention also provides a method for preparing a hyperbranched polymer or dispersant, characterized in that the hyperbranched polymer or dispersant is obtained by amidation reaction of a trifunctional carboxylic acid compound A and polyethyleneimine, wherein the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 5-48:1; wherein the trifunctional carboxylic acid compound A is a a and three carboxyl-substituted C 1-12 Alkyl or one or more R b and three carboxyl-substituted C 6-14 Aryl; R a and R b are independently OH or -P(=O)(OH)2; the average molecular weight of the polyethyleneimine is 500-5000 g / mol; preferably, the conditions and operation of the preparation method are as described in any of the previous items. The dispersant can be used in lithium battery positive electrode slurry.

[0040] The present invention also provides a use of any of the aforementioned hyperbranched polymers in the preparation of a dispersant; preferably, the dispersant is used in a positive electrode slurry for a lithium battery.

[0041] The present invention also provides a lithium battery positive electrode slurry, which includes the hyperbranched polymer as described in any of the preceding items or the dispersant as described in any of the preceding items; preferably, the mass percentage of the hyperbranched polymer or the dispersant in the lithium battery positive electrode slurry is 0.1-0.3%; for example 0.2%.

[0042] In some embodiments, the positive electrode slurry also includes the following components in proportion by mass: 93%-98% active material, 1%-4% conductive agent, and 1%-3% binder; the active material may be carbon-coated lithium iron phosphate, lithium manganese iron phosphate, or a mixture thereof; the conductive agent may be one or both of conductive carbon black and carbon nanotubes; the binder may be PVDF or carboxyl-modified PVDF.

[0043] The present invention also provides a lithium battery, which includes the lithium battery positive electrode slurry as described above.

[0044] In the present invention, the hyperbranched polymer refers to a mixture of a class of molecules, and the hyperbranched polymer prepared by a certain preparation method is a mixture of hyperbranched molecules with different branching degrees and the same structural units.

[0045] In the present invention, a negative pressure means that the actual pressure is lower than the atmospheric pressure, and the negative pressure is obtained by subtracting the standard atmospheric pressure from the actual pressure.

[0046] In the present invention, the dispersant refers to an agent that can have a dispersing effect, generally including molecules and solvents that can have a dispersing effect.

[0047] The positive and progressive effects of the present invention are:

[0048] 1. Stronger dispersing ability: The dispersant provided in the present application can effectively reduce the interaction force between molecules, improve the spatial isolation between particles, so that the active substances in the slurry can be evenly dispersed, avoid agglomeration, and reduce the precipitation of particles.

[0049] 2. Reduce slurry viscosity: The dispersant provided in this application can significantly improve the viscosity characteristics of the slurry at a lower addition amount, which helps to reduce equipment load and energy consumption during the production process.

[0050] 3. Improve slurry stability: The dispersant provided in this application can maintain the dispersibility of the slurry for a longer period of time, and the viscosity and rheology of the slurry will not change significantly even during storage. This helps to improve the controllability of the battery manufacturing process and ensure stable performance in long-term use.

[0051] 4. Adjustable average molecular weight and molar ratio: The dispersant provided in the present application can accurately control the performance of the dispersant by adjusting the molar ratio and average molecular weight of the trifunctional carboxylic acid compound to polyethyleneimine to meet the needs of different types of lithium battery positive electrode slurries.

[0052] 5. Diverse selection of trifunctional acids: Different trifunctional acids (such as citric acid, trimesic acid, etc.) can provide different dispersing effects. The patent shows the flexibility of the structure, which can be adjusted according to different application requirements.

[0053] 6. Increase solid content: The dispersant provided in the present application can also increase the solid content of the slurry, which has significant advantages for increasing the energy density of the battery and reducing the amount of solvent used in the slurry preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the infrared spectrum of the raw material citric acid in Example 1.

[0055] Figure 2 This is the infrared spectrum of the raw material polyethyleneimine in Example 1.

[0056] Figure 3 This is the infrared spectrum of the product of Example 1. DETAILED DESCRIPTION

[0057] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0058] In the following examples, the solvents mentioned are all N-methylpyrrolidone.

[0059] Polyethyleneimine (Manufacturer: Hesheng Chemical; Name: Lupasol FG; Batch No.: 20231107;)

[0060] Example 1

[0061] a) 17.4 g of citric acid (0.09 mol) and 15 g of polyethyleneimine with an average molecular weight of 5000 g / mol were dissolved in 32.4 g of N-methylpyrrolidone, the mixture was heated to 110° C., dehydrated under vacuum (pressure of −0.090 MPa) for 2 hours, and then returned to normal pressure;

[0062] b) the reaction temperature was raised to 150° C. and stirring was continued at this temperature for 4 hours;

[0063] c) maintaining vacuum conditions (pressure of -0.090 MPa) at 150° C. for dehydration reaction for 4 hours, cooling to 80° C. after the reaction, and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0064] Example 2

[0065] a) dissolving 25 g of 1,3,5-tricarboxylic acid pentane and 8 g of polyethyleneimine having an average molecular weight of 1500 g / mol in 33 g of N-methylpyrrolidone (NMP), heating to 100° C., dehydrating under vacuum conditions (pressure of −0.090 MPa) for 4 hours, and then returning to normal pressure;

[0066] b) raising the reaction temperature to 155° C. and stirring at this temperature for 3 hours;

[0067] c) After the reaction was completed, the vacuum condition (pressure was -0.090 MPa) was maintained at 160° C. for further dehydration for 3 hours, the mixture was cooled to 80° C., and the solvent was added to adjust the solid content to 50% to obtain the target product.

[0068] Example 3

[0069] a) 20 g of trimesic acid and 10 g of polyethyleneimine with an average molecular weight of 2500 g / mol were dissolved in 30 g of N-methylpyrrolidone (NMP), the temperature was raised to 120° C., and dehydrated under vacuum conditions (pressure of −0.085 MPa) for 3 hours, and then the pressure was restored to normal;

[0070] b) raising the reaction temperature to 150° C. and stirring at this temperature for 5 hours;

[0071] c) dehydrating at 155° C. under vacuum conditions (pressure of −0.090 MPa) for 4 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0072] Example 4

[0073] a) 30 g of 3-phosphoryl-1,3,5-pentanetricarboxylic acid and 6 g of polyethyleneimine with an average molecular weight of 2000 g / mol were dissolved in 36 g of N-methylpyrrolidone (NMP), the temperature was raised to 105° C., dehydrated under vacuum conditions (pressure of −0.095 MPa) for 1 hour, and then restored to normal pressure;

[0074] b) raising the reaction temperature to 160° C. and stirring at this temperature for 2 hours;

[0075] c) After the reaction was completed, the mixture was dehydrated at 150° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooled to 80° C., and then solvent was added to adjust the solid content to 50% to obtain the target product.

[0076] Example 5

[0077] a) 32 g of 1,2,3-benzenetricarboxylic acid and 8 g of polyethyleneimine with an average molecular weight of 2000 g / mol were dissolved in 40 g of N-methylpyrrolidone (NMP), the temperature was raised to 110° C., and dehydrated under vacuum conditions (pressure of −0.090 MPa) for 3 hours, and then restored to normal pressure;

[0078] b) raising the reaction temperature to 160° C. and stirring at this temperature for 3 hours;

[0079] c) After the reaction, dehydration was carried out at 160° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooled to 80° C., and then solvent was added to adjust the solid content to 50% to obtain the target product.

[0080] Example 6

[0081] a) dissolving 25 g of 1,3,5-tricarboxylic acid pentane and 15 g of polyethyleneimine having an average molecular weight of 4000 g / mol in 40 g of N-methylpyrrolidone (NMP), heating to 120° C., dehydrating under vacuum conditions (pressure of −0.080 MPa) for 3 hours, and then returning to normal pressure;

[0082] b) raising the reaction temperature to 150° C. and stirring at this temperature for 3 hours;

[0083] c) dehydrating at 160° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0084] Example 7

[0085] a) 20 g of trimesic acid and 10 g of polyethyleneimine with an average molecular weight of 3000 g / mol were dissolved in 30 g of N-methylpyrrolidone (NMP), and 0.3 g of p-toluenesulfonic acid was added. The mixture was heated to 90° C. and dehydrated under vacuum (pressure of −0.085 MPa) for 2 hours, and then restored to normal pressure;

[0086] b) raising the reaction temperature to 150° C. and stirring at this temperature for 4 hours;

[0087] c) dehydrating at 160° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0088] Example 8

[0089] a) 36 g of 1,2,3-tricarboxylic acid cyclohexane and 12 g of polyethyleneimine with an average molecular weight of 3000 g / mol were dissolved in 48 g of N-methylpyrrolidone (NMP), and 0.5 g of triethylamine was added. The mixture was heated to 90° C. and dehydrated under vacuum (pressure of −0.085 MPa) for 2 hours, and then restored to normal pressure;

[0090] b) raising the reaction temperature to 150° C. and stirring at this temperature for 4 hours;

[0091] c) dehydrating at 160° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0092] Example 9

[0093] a) 25 g of 1,2,4-benzenetricarboxylic acid and 7 g of 1,3,5-cyclohexanetricarboxylic acid and 10 g of polyethyleneimine with an average molecular weight of 3000 g / mol were dissolved in 42 g of N-methylpyrrolidone (NMP), the temperature was raised to 110° C., and dehydrated under vacuum conditions (pressure of −0.085 MPa) for 3 hours, and then restored to normal pressure;

[0094] b) raising the reaction temperature to 160° C. and stirring the reaction at this temperature for 4 hours;

[0095] c) dehydrating at 160° C. under vacuum conditions (pressure of −0.090 MPa) for 4 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0096] Example 10

[0097] a) 12 g of 1,2,3-benzenetricarboxylic acid and 8 g of trimesic acid and 5 g of polyethyleneimine with an average molecular weight of 2000 g / mol were dissolved in 25 g of N-methylpyrrolidone (NMP), the temperature was raised to 120° C., and dehydrated under vacuum conditions (pressure of 0.085 MPa) for 2 hours, and then restored to normal pressure;

[0098] b) raising the reaction temperature to 160° C. and stirring the reaction at this temperature for 4 hours;

[0099] c) dehydrating at 160° C. under vacuum conditions (pressure of −0.095 MPa) for 2 hours, cooling to 80° C., and then adding solvent to adjust the solid content to 50% to obtain the target product.

[0100] Embodiment 11

[0101] Raw materials and product structure verification and analysis:

[0102] The infrared spectra of the raw materials citric acid and polyethyleneimine in Example 1 are shown in Figure 1 and Figure 2 The infrared spectrum of the product is shown in Figure 3 . Figure 1-3 As shown in , the peak with a wave number of 1691.82 cm-1 in the product corresponds to the peak of 1708.25 cm-1 in the raw material citric acid, which corresponds to the stretching vibration peak of C=O in the carboxyl group. The red shift caused by the reduction of wave number is caused by the conjugation between the lone pair of electrons on the N on the -NH- in the amide bond formed in the product and the C=O bond, so the functional groups in the product are transformed from carboxylic acid groups and amino groups to amide groups. At the same time, the wave number of the raw material citric acid at 3000-2500 cm-1 is the stretching vibration of the -OH bond in the carboxyl group, and 1200-1300 cm-1 corresponds to the stretching vibration of the CO bond in the carboxyl group. The peak signal value in the comparison product in this wave number range is significantly weakened, which also shows that the content of carboxyl groups in the product is significantly reduced.

[0103] Additional specific data analysis:

[0104] 3400-3500cm -1 : The stretching vibration of hydroxyl (OH) indicates the presence of carboxyl (COOH) or water molecules.

[0105] 2960cm -1 and 2920cm -1 : The stretching vibrations of methyl (CH3) and methylene (CH2) groups indicate the presence of an alkane chain.

[0106] 1700cm -1 : The stretching vibration of the carbonyl group (C=O) indicates the presence of a carboxyl group (COOH).

[0107] 1650-1700cm -1 : The C=O stretching vibration of the amide bond (CONH) indicates that the amide polymer was successfully synthesized.

[0108] 1500-1600cm -1 :NH bending vibration and CN stretching vibration further confirmed the existence of amide bond.

[0109] 1400-1450cm -1 :CH deformation vibration indicates the presence of an alkane chain.

[0110] 1000-1300cm -1 :CO stretching vibration indicates the presence of carboxyl group (COOH).

[0111] Based on these characteristic absorption peaks, we determined that the amide polymer was successfully synthesized.

[0112] Application Examples

[0113] The hyperbranched dispersant solution of the above embodiment is applied to the positive electrode slurry formula, and the addition amount is 0.20% (solid) according to the total solid mass ratio of the formula. The components of the positive electrode slurry of the lithium battery and N-methylpyrrolidone (NMP) are wet homogenized using a planetary degassing machine to obtain the positive electrode slurry of the application example. The blank group is the positive electrode slurry obtained without adding any dispersant, and the amount of active material is adjusted to 97%. The proportion of each component of the positive electrode slurry is shown in Table 1, and the amount of all components of the positive electrode slurry is shown in Table 2.

[0114] Table 1 Amount of main components of positive electrode slurry

[0115]

[0116]

[0117] Table 2 Amount of each component of positive electrode slurry

[0118]

[0119]

[0120] Among them, PVDF is added in the form of 6wt% PVDF NMP glue, that is, 52.267g of glue is added, which contains 3.14g of PVDF. Among them, the dispersant is added in the form of a dispersant solution in the embodiment or the comparative example. For example, in slurry 1, 0.627g of a dispersant solution with a mass concentration of 50% containing a dispersant is added, which contains 0.3136g of dispersant. The solid content of the slurry means: the mass percentage of solids in the slurry. The solids in the positive electrode slurry of Table 2 include carbon-coated lithium iron phosphate, conductive agent, PVDF and the solid mass of the dispersant in the dispersant solution.

[0121] Effect Example

[0122] The performance of each slurry (blank slurry, slurry 1-10) in the application example was tested, including:

[0123] 1. Viscosity test

[0124] The viscosity test was carried out using a digital display rotational viscometer. After the sample was heated to a constant temperature of 25°C, a No. 64 rotor was used. The digital display data at 3 minutes of testing was the viscosity test data. The results are shown in Table 3:

[0125] 2. Slurry stability test

[0126] After the slurry was placed at room temperature for one week, the viscosity change was measured again. The results are shown in Table 3:

[0127] Table 3. Test results of positive electrode slurry viscosity and slurry stability

[0128] Slurry Discharge viscosity / mPa·s Viscosity after one week of storage / mPa·s Blank slurry 10860 20760 Slurry 1 9840 18520 Slurry 2 9260 16920 Slurry 3 8660 16360 Slurry 4 8890 17780 Slurry 5 7880 17720 Slurry 6 8460 16520 Slurry 7 7980 16280 Slurry 8 7440 16440 Slurry 9 7880 17800 Slurry 10 8280 18470

[0129] in conclusion

[0130] 1. From the tests in Tables 2 and 3, it can be seen that compared with the blank slurry, the solid content of slurries 1-10 is increased from 58% to 63%, but the viscosity is close to that of the blank slurry, indicating that the hyperbranched dispersant of the present invention can enable the slurry to maintain a considerable viscosity with a higher solid content. In other words, the hyperbranched dispersant of the present invention has a certain dispersing effect of reducing the viscosity and increasing the solid content of the slurry.

[0131] 2. As can be seen from Table 3, the discharge viscosity of the slurry (slurry 1-10) to which the hyperbranched dispersant of the present invention is added is less than that of the blank slurry, and the viscosity of the blank slurry changes greatly after being placed for one week, while the viscosity of the slurry (slurry 1-10) to which the hyperbranched dispersant of the present invention is added changes relatively little, indicating that the hyperbranched dispersant of the present invention has excellent dispersibility and helps to improve the long-term stability of the slurry.

[0132] 3. In summary, the dispersant provided by the present invention not only has excellent dispersing performance, but also can improve the viscosity and stability of the slurry while increasing the solid content of the slurry. It has important practical value in lithium battery slurry or other fields requiring a dispersant.

Claims

1. A hyperbranched polymer or dispersant, characterized in that It is prepared by amidation reaction of a trifunctional carboxylic acid compound A and polyethyleneimine, wherein the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 5-48:1; wherein the trifunctional carboxylic acid compound A is a and three carboxyl-substituted C 1-12 Alkyl or one or more R b and three carboxyl-substituted C 6-14 Aryl; R a and R b They are independently OH or -P(=O)(OH)2; the average molecular weight of the polyethyleneimine is 500-5000 g / mol.

2. The hyperbranched polymer or dispersant according to claim 1, characterized in that It meets one or more of the following conditions: (1) The trifunctional carboxylic acid compound A is selected from one or more of the following substances: citric acid, isocitric acid, 1,3,5-tricarboxylic acid pentane, 3-phosphoryl-1,3,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, trimesic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, and 2-methylpropanetricarboxylic acid; such as citric acid, 1,3,5-tricarboxylic acid pentane, trimesic acid, 3-phosphoryl-1,3,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, trimesic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, and 2-methylpropanetricarboxylic acid. One or two of pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-tricarboxylic acid pentane and 1,2,3-tricarboxylic acid cyclohexane; for example, a combination of citric acid, 1,3,5-tricarboxylic acid pentane, trimesic acid, 3-phosphoryl-1,3,5-pentanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,3,5-tricarboxylic acid pentane, 1,2,3-tricarboxylic acid cyclohexane, 1,2,4-benzenetricarboxylic acid and 1,3,5-cyclohexanetricarboxylic acid or a combination of 1,2,3-benzenetricarboxylic acid and trimesic acid; (2) The average molecular weight of the polyethyleneimine is (1500-5000) g / mol; for example, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 4000 g / mol or 5000 g / mol; (3) The molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is (23-45):1; for example, 23:1, 24:1, 29:1, 30:1, 32:1, 35:1, 38:1, 42:1 or 45:

1.

3. The hyperbranched polymer or dispersant according to claim 1, characterized in that It satisfies any of the following options: Scheme A: the trifunctional carboxylic acid compound A is citric acid, the average molecular weight of the polyethyleneimine is 5000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 30:1; Scheme B: the trifunctional carboxylic acid compound A is 1,3,5-tricarboxylic acid pentane, the average molecular weight of the polyethyleneimine is 1500 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 23:1; Scheme C: the trifunctional carboxylic acid compound A is trimesic acid, the average molecular weight of the polyethyleneimine is 2500 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 24:1; Scheme D: the trifunctional carboxylic acid compound A is 3-phosphoryl-1,3,5-pentanetricarboxylic acid, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 35:1; Scheme E: the trifunctional carboxylic acid compound A is 1,2,3-benzenetricarboxylic acid, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 38:1; Scheme F: the trifunctional carboxylic acid compound A is 1,3,5-tricarboxylic acid pentane, the average molecular weight of the polyethyleneimine is 4000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 32:1; Scheme G: the trifunctional carboxylic acid compound A is trimesic acid, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 29:1; Scheme H: the trifunctional carboxylic acid compound A is 1,2,3-tricarboxylic acid cyclohexane, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 42:1; Scheme I: the trifunctional carboxylic acid compound A is 1,2,4-benzenetricarboxylic acid and 1,3,5-cyclohexanetricarboxylic acid in a mass ratio of 25:7, the average molecular weight of the polyethyleneimine is 3000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 45:1; Scheme J: The trifunctional carboxylic acid compound A is 1,2,3-benzenetricarboxylic acid and trimesic acid in a mass ratio of 12:8, the average molecular weight of the polyethyleneimine is 2000 g / mol, and the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 38:

1.

4. The hyperbranched polymer or dispersant according to claim 1, characterized in that The preparation method comprises the following steps: a) reacting the trifunctional carboxylic acid compound A with polyethyleneimine at a reaction temperature of 80 to 120° C. under low pressure in the presence of a solvent; b) reacting at a temperature of 140 to 170° C. under normal pressure; c) reacting at a reaction temperature of 140 to 170° C. under low pressure to obtain the target product; The low pressure has a pressure of -0.070 to -0.096 MPa.

5. The hyperbranched polymer or dispersant according to claim 4, characterized in that Step a) is carried out in the presence of a catalyst, wherein the catalyst is selected from one or more of dimethylaminopyridine, 4-pyrrolylpyridine, N,N-dicyclohexylcarbodiimide, diisopropylcarbodiimide, p-toluenesulfonic acid, triethylamine and 1-hydroxybenzotriazole, such as p-toluenesulfonic acid or triethylamine; the amount of the catalyst can be 0.5%-3% of the total mass of the trifunctional carboxylic acid compound A and the polyethyleneimine; for example, 1%.

6. The hyperbranched polymer or dispersant according to claim 4, characterized in that In the preparation method, the solvent is N-methylpyrrolidone.

7. The hyperbranched polymer or dispersant according to claim 4, characterized in that The preparation method meets one or more of the following conditions: (1) In step a), the reaction temperature is 90-120°C; for example, 90°C, 100°C, 105°C, 110°C or 120°C; (2) In step a), the low pressure is -0.080 to -0.095 MPa; (3) In step a), the reaction time is 0.5 to 5 hours; such as 1 to 4 hours; for example, 1 hour, 2 hours, 3 hours or 4 hours; (4) In step b), the reaction temperature is 150-160°C; for example, 150°C, 155°C or 160°C; (5) In step b), the reaction time is 2 to 6 hours; such as 2 to 5 hours; for example 2 hours, 3 hours, 4 hours or 5 hours; (6) In step c), the reaction temperature is 150-160°C; for example, 150°C, 155°C or 160°C; (7) In step c), the low pressure is -0.080 to -0.095 MPa; (8) In step c), the reaction time is 2 to 6 hours; such as 2 to 4 hours; for example 2 hours, 3 hours or 4 hours; (9) In the preparation method, the mass ratio of the solvent to the total mass of the trifunctional carboxylic acid compound A and the polyethyleneimine is (0.8-1):1; for example, 1:1; (10) The preparation method further comprises the following post-treatment step: after the reaction is completed, the mixture is cooled to 80° C. and the solvent is added to adjust the solid content to 50%.

8. A method for preparing a hyperbranched polymer or dispersant, characterized in that: It is obtained by amidation reaction of a trifunctional carboxylic acid compound A and polyethyleneimine, wherein the molar ratio of the trifunctional carboxylic acid compound A to the polyethyleneimine is 5-48:1; wherein the trifunctional carboxylic acid compound A is a a and three carboxyl-substituted C 1-12 Alkyl or one or more R b and three carboxyl-substituted C 6-14 Aryl; R a and R b are independently OH, or -P(=O)(OH)2; the average molecular weight of the polyethyleneimine is 500-5000 g / mol; preferably, the conditions and operations of the preparation method are as described in any one of claims 2-7.

9. Use of a hyperbranched polymer as claimed in any one of claims 1 to 7 in the preparation of a dispersant; preferably, the dispersant is used in a positive electrode slurry for a lithium battery.

10. A positive electrode slurry for a lithium battery, characterized in that: It comprises a hyperbranched polymer or a dispersant as claimed in any one of claims 1 to 7; preferably, the mass percentage of the hyperbranched polymer or the dispersant in the positive electrode slurry of the lithium battery is 0.1-0.3%; for example, 0.2%; More preferably, the positive electrode slurry also includes the following components in proportion by mass: 93%-98% active material, 1%-4% conductive agent, and 1%-3% binder; the active material may be carbon-coated lithium iron phosphate, lithium manganese iron phosphate, or a mixture thereof; the conductive agent may be one or both of conductive carbon black and carbon nanotubes; the binder may be PVDF or carboxyl-modified PVDF.

11. A lithium battery, characterized in that: It includes the lithium battery positive electrode slurry as claimed in claim 10.

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