Additive for lithium ion battery, and its application

Abstract

To provide an additive for a lithium ion battery, and its application.SOLUTION: An additive for a lithium ion battery contains the following raw materials by the following parts by weight: solvent for 40 to 70, a first polymer for 1 to 10, a second polymer for 5 to 15, a small-molecular organic amine for 10 to 20, and a stabilizer for 10 to 20. The first polymer includes at least one polar functional group that does not include nitrogen. The second polymer includes at least one polar functional group that includes nitrogen. The stabilizer is a hydrazine compound.EFFECT: The additive provided by the present application is used for a lithium ion battery, and can solve the problem that a thick electrode is broken easily and the diffusion of cathode particles is difficult.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to additives for lithium ion batteries and their applications. [Background technology]

[0002] With existing technology, an effective way to increase the energy density of lithium-ion batteries is to develop and design thick electrodes. However, thick electrodes have at least two problems: first, they are prone to cracking and have poor mechanical properties; and second, it is difficult to disperse nano-sized cathode particles. Summary of the Invention

[0003] Based on the above, there is a need for an additive that can solve the problems of thick electrodes being prone to cracking and difficult to disperse cathode particles.

[0004] The additive for lithium ion batteries, wherein the weight parts of the raw materials of the additive are as follows: 40 to 70 parts of a first solvent; 1 to 10 parts of a first polymer; 5 to 15 parts of a second polymer; 10 to 20 parts of a small molecular organic amine, It consists of 10 to 20 stabilizers. The first polymer is at least one of ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl alcohol copolymer, and methyl vinyl ether-maleic anhydride linear copolymer.

[0005] The second polymer is at least one of polyvinylpyrrolidone, hydrogenated nitrile rubber, polyacrylonitrile, polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer.

[0006] The stabilizer is a hydrazine compound.

[0007] The additive for lithium ion batteries provided by the present application can be used as a dispersant for conductive agents in lithium ion batteries. By adding the additive to the conductive agent, the dispersion performance of the conductive agent can be significantly improved, the viscosity and fineness of the conductive agent can be reduced, and the resistivity of the electrode plate can be reduced.

[0008] The lithium-ion battery additive provided by the present application is used in the kneading process of lithium-ion battery positive electrode mixtures to increase the viscosity and solid content of the slurry. The increased solid content reduces the amount of solvent evaporation and reduces the likelihood of cracking during the process of producing thick electrodes from the mixture slurry, thereby improving the mechanical properties of the thick electrodes. The additive can effectively promote the dispersion of cathode particles, while also improving the viscosity stability of the positive electrode mixture material and the coating uniformity.

[0009] The first solvent dissolves the remaining components of the additive and does not have any particular effect on other components, so a common organic solvent can be used, for example, N-methylpyrrolidone (NMP), dimethyl sulfoxide, or dimethylformamide. Preferably, the first solvent is N-methylpyrrolidone.

[0010] Some optional methods are also presented below, but these are not intended as additional restrictions on the overall technical solution above. As long as there is no technical or logical contradiction, each optional method can be combined individually or multiple optional methods can be combined with the overall technical solution above.

[0011] Optionally, the ingredients of the additives are in the following weight parts: 40 to 60 parts of a first solvent; 1 to 5 parts of a first polymer; 9 to 15 parts of a second polymer; 15 to 20 parts of a small molecular organic amine; It consists of 15 to 20 stabilizers.

[0012] Optionally, the ingredients of the additives are in the following weight parts: 56 parts of a first solvent; 1 to 5 parts of a first polymer; 9 to 15 parts of a second polymer; 15 to 20 parts of a small molecular organic amine; It consists of 15 to 20 stabilizers.

[0013] Optionally, the first polymer comprises at least one nitrogen-free polar functional group, the first polymer having a polyethylene backbone, and the nitrogen-free polar functional group is one of an aldehyde group, a hydroxyl group, a carbonyl group, and an acid anhydride.

[0014] The first polymer has a polyethylene main chain and contains polar functional groups such as hydroxyl groups, carboxyl groups, aldehyde groups, and carbonyl groups in the main chain or side chains. The polar functional groups allow the polymer to dissolve in a solvent such as NMP, and at the same time, the hydrophobic structure of the polyethylene in the main chain adsorbs to the surface of the positive electrode active material or conductive agent such as carbon nanotubes or carbon black, causing steric hindrance when the positive electrode mixture or conductive agent is dispersed. This prevents secondary aggregation of the positive electrode active material or conductive agent, maintains stable viscosity, and reduces the fineness of the slurry.

[0015] Optionally, the first polymer is at least one of ethyl cellulose (e.g., Ashland N7, Ashland N10), polyvinyl alcohol (e.g., Kuraray 3-98, Kuraray 5-98, Kuraray 11-98), polyvinyl butyral (PVB, e.g., Kuraray B30H, Kuraray B60H), ethylene-vinyl alcohol copolymer (e.g., Kuraray G176, Kuraray E105), and methyl vinyl ether-maleic anhydride linear copolymer (e.g., Vertellus ZeMac E60, Vertellus ZeMac E400).

[0016] Optionally, the second polymer is at least one of polyvinylpyrrolidone (PVP, e.g., BASF K17, BASF K30), hydrogenated nitrile rubber (e.g., Alanxeo 4307, Sannan ZNL3403), polyacrylonitrile, polypyrrole (weight average molecular weight 80,000 to 100,000), and styrene-acrylonitrile-acrylic acid linear copolymer (Nippon Techno UMG S210B).

[0017] The second polymer has a nitrogen-containing polar functional group, and the nitrogen contains an unshared electron pair, which can form a large π bond with the carbon atom of the lithium ion positive electrode material, providing good compatibility and an alkaline environment.

[0018] The first polymer and second polymer preferably have a molecular weight of 5,000 to 200,000. If the molecular weight is too small, they may decompose or dissolve in the electrolyte during the charge / discharge process of the lithium battery, resulting in gas generation and reduced performance. If the molecular weight is too large, they may become insoluble in the solvent or the dispersion viscosity of the mixture may increase, resulting in an inability to achieve a significant viscosity reduction effect. At least 5% of the mass of the first polymer and second polymer is dissolved in NMP, and the viscosity after dissolution is in the range of 10 to 1,000 mPa·s. It will be understood that the viscosity of a 5% by mass NMP solution of the first polymer at 25°C is in the range of 10 to 1,000 mPa·s, and the viscosity of a 5% by mass NMP solution of the second polymer at 25°C is in the range of 10 to 1,000 mPa·s.

[0019] Optionally, the small molecule organic amine is at least one of ethanolamine, isopropanolamine, isobutanolamine, triethanolamine, anhydrous piperazine, and guanidine carbonate.

[0020] The small molecule organic amines are used to adjust the pH value and provide an alkaline environment, and their high polarity allows them to form a better cover for the conductive agent, thereby improving the wettability of the conductive material and facilitating dispersion.

[0021] Optionally, the stabilizer is at least one of hydroxyethylhydrazine, hydrazine hydrate, and carbohydrazide. Preferably, the stabilizer is hydroxyethylhydrazine (CAS: 109-84-2). The stabilizer has a hydrazine structure and is strongly polar, providing an unshared electron pair, adsorbing to the surface of cathode particles or carbon particles of a lithium ion battery and increasing the polarity of the cathode particles or carbon particles, so that the particles are dispersed and stabilized in the first solvent without secondary aggregation.

[0022] Optionally, the ingredients of the additives are in the following weight parts: 56 parts of a first solvent; 1 to 5 parts ethyl cellulose, 5 to 10 parts of polyvinylpyrrolidone, 15 to 20 parts isobutanolamine, It consists of 15 to 20 parts of hydroxyethylhydrazine.

[0023] Optionally, the ingredients of the additives are in the following weight parts: 56 parts of a first solvent; 1 to 2 parts of an ethylene-vinyl alcohol copolymer; 1 to 2 parts polyvinyl butyral, 5 to 10 parts hydrogenated nitrile rubber; 15 to 20 parts isobutanolamine, It consists of 15 to 20 parts of hydroxyethylhydrazine.

[0024] Optionally, the ingredients of the additives are in the following weight parts: 56 parts of a first solvent; 1 to 5 parts of polyvinyl butyral; 10 to 15 parts polypyrrole, 10 to 15 parts isopropanolamine, It consists of 15 to 20 parts of hydroxyethylhydrazine.

[0025] Optionally, the method for preparing the additive comprises the steps of: dissolving a first polymer in a first solvent to obtain a first polymer solution; dissolving a second polymer in a first solvent to obtain a second polymer solution; uniformly mixing the small molecule organic amine, the stabilizer, the first polymer solution, and the second polymer solution at a temperature below 50°C to obtain the additive;

[0026] The first polymer and the second polymer may each be dissolved in a first solvent, i.e., the first solvent is divided into at least two parts, one of which is used to dissolve the first polymer and the other of which is used to dissolve the second polymer; the first polymer and the second polymer may be simultaneously dissolved in the first solvent, i.e., the first polymer and the second polymer are added simultaneously; or the first polymer and the second polymer may be sequentially dissolved in the first solvent, i.e., one polymer is first added and dissolved in the first solvent, and then the other polymer is added and dissolved. There are many different polymers to choose from for the first and second polymers. For polymers that require high-temperature dissolution (e.g., polyvinyl alcohol, ethylene-vinyl alcohol copolymer, methyl vinyl ether-maleic anhydride linear copolymer, hydrogenated nitrile rubber, polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer), dissolution should be performed at 80-100°C under nitrogen protection (dissolution time should be selected according to actual needs, e.g., 4-8 hours). Once dissolution is complete, the temperature should be reduced to below 50°C before mixing with the other components.

[0027] For polymers that do not require high-temperature dissolution (e.g., ethyl cellulose, polyvinylpyrrolidone, polyvinyl butyral), dissolve under nitrogen protection for 0.5 to 2 hours.

[0028] The components are mixed uniformly under stirring conditions, and the mixing time is 0.5 to 2 hours.

[0029] The present application also provides the application of the additive in a conductive agent.

[0030] The conductive agent includes a second solvent, a conductive material, and the additive, and the amount of the additive is 10 to 20% by mass of the conductive material.

[0031] The second solvent may be a common solvent for conductive agents, such as N-methylpyrrolidone (NMP) or dimethylformamide (DMF).

[0032] The conductive material is at least one of carbon nanotubes, graphene, carbon black, ketjen black, and nano carbon fiber (VGCF).

[0033] The fineness of the scraper for the conductive agent is 10 to 15 μm.

[0034] The conductive agent has a film resistivity of 14 to 16 mΩ·cm.

[0035] The conductive agent has a slurry viscosity of 400 to 550 mPa·s.

[0036] The present application also provides an application of the additive in a lithium ion battery positive electrode slurry.

[0037] The weight parts of the raw materials for the lithium ion battery positive electrode slurry are as follows: 100 parts lithium iron phosphate, 1 to 5 parts of a conductive agent; 1 to 5 parts PVDF adhesive; 0.1 to 0.5 parts of an additive; and 40 to 50 parts of a third solvent.

[0038] The second solvent is a component of the conductive agent, and the third solvent is a component of the lithium-ion battery positive electrode slurry. The first solvent, the second solvent, and the first solvent in the additive each have their own unique meanings. The same solvent can be used for all three, but different types of solvents can also be used.

[0039] The third solvent may be a common solvent for positive electrode slurries, such as N-methylpyrrolidone (NMP) or dimethylformamide (DMF).

[0040] The lithium ion battery positive electrode slurry has a viscosity of less than 12000 mPa·s after being left to stand for 24 hours.

[0041] The lithium ion battery positive electrode slurry has a viscosity of less than 12000 mPa·s and more than 9000 mPa·s after being left for 24 hours.

[0042] Unless otherwise specified in this application, viscosity refers to viscosity at 25°C.

[0043] The lithium ion battery cathode slurry has a solids content of greater than 65%.

[0044] The lithium ion battery positive electrode slurry has a solids content of more than 65% and less than 70%.

[0045] The addition of additives to the positive electrode mixture material of a lithium-ion battery effectively promotes the dispersion of the nanoscale lithium iron phosphate and the conductive agent, effectively reduces the viscosity of the positive electrode mixture material, and allows the solid content in the positive electrode mixture slurry to be increased by at least 6% at the same viscosity level, thereby improving efficiency, reducing consumption, improving the viscosity stability of the positive electrode mixture material, and improving coating uniformity.

[0046] The additives provided herein have at least the following beneficial effects: (1) Used as a dispersant in the dispersion process of conductive agents such as carbon nanotubes, graphene, and carbon black, the amount used is 10% to 20% of the mass of the conductive agent, which can significantly improve the dispersion of the conductive agent, reduce the viscosity of the conductive agent slurry, reduce the fineness of the conductive agent slurry, and reduce the resistivity of the conductive agent in the electrode plate. (2) During the kneading process of the lithium iron phosphate positive electrode mixture, after adding the PVDF solution and the conductive agent, an additive is added in an amount of 0.1 to 0.5% of the mass of the lithium iron phosphate positive electrode mixture, which significantly increases the solid content of the positive electrode mixture and reduces the viscosity of the mixture slurry. [Brief explanation of the drawings]

[0047] [Figure 1a] FIG. 1 is a diagram showing the fineness of the scraper when the additive prepared in Example 1 is applied to a conductive agent. [Figure 1b] FIG. 10 is a diagram showing the fineness of the scraper when the additive prepared in Example 2 is applied to a conductive agent. [Figure 1c] FIG. 10 is a diagram showing the fineness of the scraper when the additive prepared in Example 3 is applied to a conductive agent. [Figure 2a] FIG. 10 is a diagram showing the fineness of the scraper when the additive prepared in Comparative Example 1 is applied to a conductive agent. [Figure 2b] FIG. 10 is a diagram showing the fineness of the scraper when the additive prepared in Comparative Example 2 is applied to a conductive agent. [Figure 2c] FIG. 10 is a diagram showing the fineness of the scraper when the additive prepared in Comparative Example 3 is applied to a conductive agent. [Figure 3a] 1 is a graph showing the particle size test results when the additive prepared in Example 1 is applied to a conductive agent. [Figure 3b] 1 is a graph showing the particle size test results when the additive prepared in Example 2 is applied to a conductive agent. [Figure 3c] 1 is a graph showing the particle size test results when the additive prepared in Example 3 is applied to a conductive agent. [Figure 4a] 1 is a graph showing the particle size test results when the additive prepared in Comparative Example 1 is applied to a conductive agent. [Figure 4b] 10 is a graph showing the particle size test results when the additive prepared in Comparative Example 2 is applied to a conductive agent. [Figure 4c] 10 is a graph showing the particle size test results when the additive prepared in Comparative Example 3 is applied to a conductive agent. [Figure 5a]1 is an electrochemical performance test chart of a reference example. [Figure 5b] 1 is an electrochemical performance test chart in which the additive prepared in Example 1 is applied to a positive electrode mixture slurry. [Figure 6] This is an AC internal resistance (ACIR) test chart, with the horizontal axis representing the number of battery packs. [Figure 7] This is a battery voltage test chart, with the horizontal axis representing the number of battery packs. [Figure 8] This is a DC internal resistance (DCIR) test chart, with the horizontal axis representing the number of battery packs. DETAILED DESCRIPTION OF THE INVENTION

[0048] Hereinafter, the embodiments of the present application will be described in detail with reference to the accompanying drawings. Note that the following embodiments are merely examples of the present application and do not limit the technical scope of the present application. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present application without departing from the scope of the present application are also within the scope of the present application.

[0049] To better describe and illustrate the embodiments of the present application, reference may be made to one or more drawings; however, any additional details or examples used to illustrate the drawings should not be considered as limitations on the scope of any of the inventions, embodiments or preferred forms of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0051] Example 1 N-methylpyrrolidone (NMP) was used as the first solvent. 56 parts of NMP was weighed out, and 2.4 parts of ethyl cellulose (i.e., the first polymer, Ashland N7, with an 8% NMP solution viscosity of 50 cPs) was added to the first solvent under nitrogen protection at a high temperature of 100°C. After dissolving for 2 hours, the mixture was cooled to below 50°C, and 9.6 parts of polyvinylpyrrolidone (i.e., the second polymer, BASF K10, with an 8% NMP solution viscosity of 15 cPs) was added. After dissolving for 1 hour, 16 parts of isobutanolamine (i.e., a small molecular organic amine) and 16 parts of hydroxyethylhydrazine (i.e., a stabilizer) were added, and the mixture was stirred at a stirring speed of 1200 rpm for 1 hour to obtain an additive.

[0052] <Example 2> N-methylpyrrolidone (NMP) was used as a first solvent, and 56 parts of NMP were weighed out. 9.6 parts of hydrogenated nitrile rubber (i.e., the second polymer, Arlanxeo 4307, the viscosity of a 6% NMP solution of hydrogenated nitrile rubber is 800 cPs) was added to the first solvent at a high temperature of 80°C under nitrogen protection, and 1.2 parts of ethylene-vinyl alcohol copolymer (i.e., the first polymer, Kuraray G176, the viscosity of a 3% NMP solution of ethylene-vinyl alcohol copolymer was 800 cPs) was added. The viscosity is 100 cPs) is added and dissolved for 2 hours, then cooled to below 50°C, and then 1.2 parts of polyvinyl butyral (i.e., the first polymer, Kuraray B60H is used, and the viscosity of a 3% NMP solution of polyvinyl butyral is 20 cPs) is added and dissolved for 1 hour, and then 16 parts of isobutanolamine (i.e., a small molecular organic amine) and 16 parts of hydroxyethylhydrazine (i.e., a stabilizer) are added, and the mixture is stirred at a stirring speed of 1200 rpm for 1 hour to obtain an additive.

[0053] Example 3 N-methylpyrrolidone (NMP) was used as the first solvent. 50 parts of NMP was weighed and added to the first solvent at a high temperature of 80°C under nitrogen protection. 15 parts of polypyrrole (i.e., the second polymer, a 3% NMP solution of polypyrrole with a viscosity of 100 cPs) was added. After dissolving for 2 hours, the mixture was cooled to below 50°C, and then 2 parts of polyvinyl butyral (i.e., the first polymer, Kuraray B60H, a 3% NMP solution of polyvinyl butyral with a viscosity of 20 cPs) was added. After dissolving for 1 hour, 16 parts of isopropanolamine (i.e., a small organic amine) and 16 parts of hydroxyethylhydrazine (i.e., a stabilizer) were added. The mixture was stirred at a stirring speed of 1200 rpm for 1 hour to obtain the additive. Comparative Example 1: No polymer added

[0054] N-methylpyrrolidone (NMP) is used as the first solvent, 68 parts of NMP is weighed, 16 parts of isobutanolamine and 16 parts of hydroxyethylhydrazine are added, and the mixture is stirred at a stirring speed of 1200 rpm for 1 hour to obtain an additive.

[0055] Comparative Example 2: No organic amine or stabilizer added N-methylpyrrolidone (NMP) is used as the first solvent. 72 parts of NMP are weighed out, and 2.4 parts of ethyl cellulose (i.e., the first polymer, Ashland N7, with a viscosity of 50 cPs at 25°C of 8% ethyl cellulose in NMP) are added to the first solvent under nitrogen protection at a high temperature of 100°C. After dissolving for 2 hours, the mixture is cooled to below 50°C, and then 9.6 parts of polyvinylpyrrolidone (i.e., the second polymer, BASF K10, with a viscosity of 15 cPs at 25°C of 8% polyvinylpyrrolidone in NMP) are added and dissolved for 1 hour to obtain the additive.

[0056] Comparative Example 3: No stabilizer added N-methylpyrrolidone (NMP) was used as the first solvent. 56 parts of NMP was weighed out, and 2.4 parts of ethyl cellulose (i.e., a first polymer, Ashland N7, with a viscosity of 50 cPs at 25°C of 8% ethyl cellulose in NMP) was added to the first solvent under nitrogen protection at a high temperature of 100°C. After dissolving for 2 hours, the mixture was cooled to below 50°C. 9.6 parts of polyvinylpyrrolidone (i.e., a second polymer, BASF K10, with a viscosity of 15 cPs at 25°C of 8% polyvinylpyrrolidone in NMP) was added and dissolved for 1 hour. After dissolving for 1 hour, 32 parts of isopropanolamine was added and the mixture was stirred at a stirring speed of 1200 rpm for 1 hour to obtain an additive.

[0057] Application example 1: Application to conductive agents Weigh out 89.3 parts of N-methylpyrrolidone (NMP), add 6.7 parts of additives, mix uniformly, add 5 parts of 5-10 nm multi-walled carbon nanotubes, crush and disperse them at a shear rate of 15 m / s. After uniform dispersion, test the viscosity, scraper fineness, particle size, and film resistance. Table 1 shows the test results of applying the additives prepared in each example and comparative example to conductive agents. JPEG2025176676000002.jpg56170

[0058] As shown in Table 1, the viscosities of the conductive agent slurries to which the additives of Examples 1 to 3 have been added are smaller than those of the conductive agent slurries to which the additives of Comparative Examples 1 to 3 have been added.

[0059] The details of the fineness of the scrapers in Examples 1 to 3 are shown in Figures 1a to 1c, and the details of the fineness of the scrapers in Comparative Examples 1 to 3 are shown in Figures 2a to 2c. Combining the data in each figure with Table 1, it can be seen that the conductive agent slurries containing the additives in Examples 1 to 3 have smaller particle sizes.

[0060] As shown in Table 1, the resistivity of the conductive agent slurries to which the additives of Examples 1 to 3 were added was lower than that of the conductive agent slurries to which the additives of Comparative Examples 1 to 3 were added.

[0061] The conductive agent slurry has a lower viscosity, a smaller fineness, and a lower resistivity, which shows that the addition of the additive can effectively improve the dispersion performance of the conductive agent.

[0062] Application example 2: Application to positive electrode mixture A positive electrode mixture slurry was prepared in a ratio of lithium iron phosphate: carbon black: PVDF binder: additive: NMP = 97:1:2.5:0.2:43.67. After preparing the positive electrode mixture slurry, the viscosity, viscosity, and film resistance were tested initially and after leaving it for 2 hours, 4 hours, 8 hours, and 24 hours. The results are shown in Table 2. In Table 2, the reference example does not contain any additives. JPEG2025176676000003.jpg63170

[0063] The CV curves for the cathode mixture slurry prepared in the Reference Example are shown in Figure 5a, and the cathode mixture slurry prepared with the additive prepared in Example 1 are shown in Figure 5b. Electrochemical performance tests showed no significant difference between the case with the additive and the case without the additive. The additive remained stable without decomposition even at voltages above 4.5 V, with no obvious redox peaks. This indicates that the additive is stable in the battery, does not undergo side reactions, and can be used in high-voltage systems.

[0064] As shown in Table 2, after adding the additives prepared in each example, the viscosity of the positive electrode mixture slurry was significantly reduced and the resistivity of the diaphragm was slightly reduced. This indicates that the addition of additives reduces the viscosity of the positive electrode mixture, thereby actually increasing the content of active ingredients, reducing the amount of third solvent used, improving the firing efficiency of the electrode plate, and allowing the electrode to be thicker to prevent cracking. At the same time, the resistivity of the diaphragm was essentially the same as without the additives, indicating that the addition of additives does not affect the internal resistance of the battery. Although the additives are not conductive, they help to disperse the cathode and conductive agent, thereby improving overall battery performance.

[0065] Battery performance characterization A positive electrode mixture slurry is prepared according to the data shown in Table 3, and a battery cell is manufactured, and the AC internal resistance, platform voltage, and DC internal resistance are tested. JPEG2025176676000004.jpg46170280 The iron-lithium positive electrode mixture slurry ratio was lithium iron phosphate:carbon black:binder PVDF:NMP=97:1:2.5:43.67.

[0066] In Experiment 2, 0.2% of the additive prepared in Comparative Example 1 was added, i.e., the amount of the additive prepared in Comparative Example 1 was 0.2% of the mass of the lithium iron phosphate. Similarly, in Experiment 3, 0.03% of the additive prepared in Example 1 was added, i.e., the amount of the additive prepared in Example 1 was 0.03% of the mass of the lithium iron phosphate.

[0067] As shown in Table 3, the solid content in experiment 3 increased to 66.6%, and the slurry viscosity in experiment 3 decreased to 4010 MPa·s.

[0068] The three types of positive electrode mixture slurries prepared in Experiments 1, 2, and 3 did not show any obvious abnormalities such as particles or scratches from the electrode piece production process, nor were any abnormalities such as belt breaks or wrinkles from the rolling process observed.

[0069] As shown in FIG. 6, in Experiment 2, after the additive prepared in Comparative Example 1 was added, the AC internal resistance of the battery cell increased, and in Experiment 3, after the additive prepared in Example 1 was added, the AC internal resistance of the battery cell decreased by more than 30%.

[0070] As shown in Figure 7 , the platform voltage in Experiments 2 and 3 increased by approximately 5%, while the platform voltage in Experiment 1 was lower.

[0071] As shown in FIG. 8, after adding the additive prepared in Example 1 of Experiment 3, the internal resistance of the battery cell decreased by nearly 50%.

[0072] The test results of the standard charge-discharge energy retention rate (1P / 0.5P, 2P / 0.5P) of Experiments 1, 2, and 3 are shown in Tables 4 and 5. In Experiment 3, after adding the additive prepared in the example, the 0.5P voltage platform and 2P charge energy retention rate of the battery were significantly improved. JPEG2025176676000005.jpg103170 JPEG2025176676000006.jpg101170

[0073] The test results of the standard charge-discharge energy retention rate (1P / 0.5P, 2P / 0.5P) of Experiments 1, 2, and 3 are shown in Tables 6 and 7. In Experiment 3, after adding the additive prepared in the example, the battery platform voltage and the charge-discharge energy efficiency of 1P and 2P were significantly improved. JPEG2025176676000007.jpg103170 JPEG2025176676000008.jpg96170

[0074] As shown in Table 8, there is basically no difference in the high-temperature charge-discharge performance of the batteries in Experiment 1, Experiment 2, and Experiment 3. JPEG2025176676000009.jpg85170

[0075] The technical features of the above-described embodiments may be combined in any manner, but for the sake of simplicity, not all possible combinations of the technical features in the above-described embodiments are described; however, unless there is a contradiction in the combinations, all are deemed to be within the scope of this specification.

[0076] The above-mentioned embodiments only represent some embodiments of the present application, and although the descriptions thereof are relatively specific and detailed, they should not be construed as limiting the scope of the patent of the present invention. It should be noted that those skilled in the art can make some modifications and improvements without departing from the concept of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of this patent application should be determined by the appended claims.

Claims

1. An additive for a lithium ion battery, wherein the weight parts of raw materials of the additive are as follows: 40 to 70 parts of a first solvent; 1 to 10 parts of a first polymer; 5 to 15 parts of a second polymer; 10 to 20 parts of a small molecule organic amine; It consists of 10 to 20 stabilizers, the first polymer is at least one of ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl alcohol copolymer, and methyl vinyl ether-maleic anhydride linear copolymer; the second polymer is at least one of polyvinylpyrrolidone, hydrogenated nitrile rubber, polyacrylonitrile, polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer; The additive for lithium ion batteries is characterized in that the stabilizer is a hydrazine compound.

2. The weight parts of the raw materials of the additives are as follows: 56 parts of a first solvent; 1 to 5 parts of a first polymer; 9 to 15 parts of a second polymer; 15 to 20 parts of a small molecule organic amine; 2. The additive for lithium ion batteries according to claim 1, characterized in that it comprises 15 to 20 parts of a stabilizer.

3. 2. The additive for a lithium ion battery according to claim 1, wherein the small molecule organic amine is at least one of ethanolamine, isopropanolamine, isobutanolamine, triethanolamine, anhydrous piperazine, and guanidine carbonate.

4. 2. The additive for a lithium ion battery according to claim 1, wherein the stabilizer is at least one of hydroxyethylhydrazine, hydrazine hydrate, and carbohydrazide.

5. The preparation method of the additive includes the following steps: dissolving a first polymer in a first solvent to obtain a first polymer solution; dissolving a second polymer in a first solvent to obtain a second polymer solution; The additive for lithium ion batteries according to any one of claims 1 to 4, further comprising a step of uniformly mixing a small molecule organic amine, a stabilizer, a first polymer solution, and a second polymer solution at a temperature of less than 50°C to obtain the additive.

6. A conductive agent containing the additive according to any one of claims 1 to 4, a second solvent; and Conductive materials and A conductive agent comprising the additive according to any one of claims 1 to 4, wherein the amount of the additive added is 10 to 20% by mass of the conductive material.

7. The conductive agent of the additive according to claim 6, wherein the fineness of the scraper of the conductive agent is 10 to 15 μm, the film resistivity of the conductive agent is 14 to 16 mΩ cm, and the slurry viscosity of the conductive agent is 400 to 550 mPa s.

8. A lithium ion battery positive electrode slurry containing the additive according to any one of claims 1 to 4, wherein the weight parts of the raw materials are as follows: 100 parts of lithium iron phosphate, 1 to 5 parts of a conductive agent; 1 to 5 parts PVDF adhesive; 0.1 to 0.5 parts of the additive according to any one of claims 1 to 4; and 40 to 50 parts of a third solvent.

9. 9. The lithium ion battery cathode slurry of claim 8, wherein the solids content of the lithium ion battery cathode slurry is greater than 65%.

10. 9. The lithium ion battery positive electrode slurry according to claim 8, wherein the viscosity of the lithium ion battery positive electrode slurry after being left for 24 hours is less than 12,000 mPa·s.

Images