Additive for lithium-ion battery, and use thereof

Abstract

Disclosed in the present application are an additive for a lithium-ion battery, and the use thereof. The additive for a lithium-ion battery comprises the following raw materials in parts by weight: 40-70 parts of a first solvent, 1-10 parts of a first polymer, 5-15 parts of a second polymer, 10-20 parts of a small-molecule organic amine and 10-20 parts of a stabilizer, wherein the first polymer contains at least one nitrogen-free polar functional group; the second polymer contains at least one nitrogen-containing polar functional group; and the stabilizer is a hydrazine compound. The additive provided in the present application is used in a lithium-ion battery, and can solve the problems of a thick electrode being prone to cracking and positive electrode particles being difficult to disperse.

Description

An additive for lithium ion battery and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery, in particular to an additive for lithium ion battery and application thereof. BACKGROUND

[0002] In the prior art, an effective way to improve the energy density of lithium ion battery is to develop and design thick electrodes. TECHNICAL PROBLEM

[0003] However, thick electrodes at least have two problems, firstly, they are easy to crack and have poor mechanical properties; secondly, nanoscale positive electrode particles are difficult to disperse. TECHNICAL SOLUTION

[0004] Therefore, it is necessary to provide an additive to solve the problems of thick electrodes being easy to crack and positive electrode particles being difficult to disperse. An additive for lithium ion battery, the raw material weight parts of the additive are as follows:

[0005] 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;

[0006] The second polymer is at least one of polyvinylpyrrolidone, hydrogenated nitrile rubber, polyacrylonitrile, polypyrrole and styrene-acrylonitrile-acrylic acid copolymer;

[0007] The stabilizer is a hydrazine compound.

[0008] The additive for lithium ion battery provided by the present application can be used as a dispersant for lithium ion battery conductive agent. The addition of the additive to the conductive agent can significantly improve the dispersion performance of the conductive agent, reduce the viscosity and fineness of the conductive agent slurry, and reduce the resistivity of the electrode sheet.

[0009] The additive for lithium ion battery provided by the present application is applied to the positive electrode slurry mixing process of lithium ion battery, which can improve the viscosity and solid content of the slurry. Due to the increase of the solid content, the amount of the first solvent volatilized during the process of making thick electrodes from the slurry is small, and cracking is not easy to occur, thereby improving the mechanical properties of the thick electrodes. The additive can effectively promote the dispersion of positive electrode particles, and the viscosity stability of the positive electrode slurry material is better, and the coating uniformity is improved.

[0010] The first solvent dissolves the remaining components of the additive and has no other special effect. Commonly used organic first solvents can be used, for example, the first solvent is one of N-methyl pyrrolidone (NMP), dimethyl sulfoxide and dimethyl formamide. Preferably, the first solvent is N-methyl pyrrolidone.

[0011] The following also provides several optional ways, but not as an additional limitation on the above overall scheme, just a further supplement or preferred, without technical or logical contradictions, each optional way can be combined alone for the above overall scheme, but also can be combined among multiple optional ways.

[0012] Optionally, the raw material weight composition of the additive is as follows:

[0013] Optionally, the raw material weight composition of the additive is as follows:

[0014] The first polymer contains at least one nitrogen-free polar functional group, the first polymer is polyethylene as the main chain, and the nitrogen-free polar functional group is one of aldehyde group, hydroxyl group, carbonyl group, and acid anhydride.

[0015] The first polymer contains a polyethylene main chain and contains polar functional groups such as hydroxyl groups, carboxyl groups, aldehyde groups, and carbonyl groups on the main chain or side chain. Under the action of the polar functional groups, the polymer can be dissolved in a first solvent such as NMP. At the same time, the hydrophobic structure of the polyethylene main chain can be adsorbed on the surface of the positive active material or the conductive agent such as carbon nanotubes and carbon black. During the positive electrode slurry or conductive agent dispersion process, it can produce steric hindrance effect to prevent secondary agglomeration of the positive active material or the conductive agent, so as to maintain stable viscosity and reduce the fineness of the slurry.

[0016] Optionally, the first polymer is at least one of ethyl cellulose (for example, Ashland N7, Ashland N10), polyvinyl alcohol (for example, Kuraray 3-98; Kuraray 5-98; Kuraray 11-98), polyvinyl butyral (PVB, for example, Kuraray B30H; Kuraray B60H), ethylene-vinyl alcohol copolymer (for example, Kuraray G176; Kuraray E105), and methyl vinyl ether-maleic anhydride linear copolymer (for example, Vantico ZeMac E60, Vantico ZeMac E400).

[0017] Optionally, the second polymer is at least one of polyvinylpyrrolidone (PVP, for example, BASF K17, BASF K30), hydrogenated butyl nitrile rubber (for example, ArlanxeL 4307, Zeon ZNL3403), polyacrylonitrile (weight average molecular weight 80000-100000), polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer (for example, Japan UMGS210B).

[0018] The second polymer has a nitrogen-containing polar functional group, wherein the nitrogen contains a lone pair of electrons, and the carbon atoms in the lithium ion positive electrode material can form a large π bond, have good compatibility, and can provide an alkaline environment.

[0019] The first polymer and the second polymer preferably have a weight average molecular weight of 5000-200000; more preferably, the weight average molecular weight is 5000-50000. If the molecular weight is too small, decomposition may occur during charging and discharging of the lithium battery, or the polymer may dissolve in the electrolyte, resulting in gas production or performance degradation of the battery. If the molecular weight is too large, the polymer may not be soluble in the solvent, or the slurry dispersion viscosity may be too large, and the viscosity reduction effect may not be obvious.

[0020] The first polymer is dissolved in NMP, and the viscosity of a 5% first polymer NMP solution at 25°C is in the range of 10-1000 mPa·s. The second polymer is dissolved in NMP, and the viscosity of a 5% second polymer NMP solution at 25°C is in the range of 10-1000 mPa·s.

[0021] Optionally, the small molecule organic amine is at least one of diethylenediamine, ethanolamine, isopropanolamine, isobutanolamine, triethanolamine, anhydrous piperazine, and guanidine carbonate.

[0022] The small molecule organic amine is used to adjust the pH value, provide an alkaline environment, and has strong polarity, which can better wrap the conductive agent, so that the conductive material has better wettability and is easier to disperse.

[0023] Optionally, the stabilizer is at least one of hydroxyethyl hydrazine, hydrazine hydrate, and carbohydrazide. Preferably, the stabilizer is hydroxyethyl hydrazine (CAS: 109-84-2). The stabilizer has a diazene structure, has strong polarity, can provide a lone pair of electrons, and is adsorbed on the surface of the positive electrode particles or carbon particles of the lithium ion battery, increases the polarity of the positive electrode particles or carbon particles, disperses the particles, and stabilizes the particles in the first solvent without secondary agglomeration.

[0024] Optionally, the raw materials of the additive are composed of the following components by weight:

[0025] Optionally, the raw materials of the additive are composed of the following components by weight:

[0026] Optionally, the raw materials of the additive are composed of the following components by weight:

[0027] Optionally, the preparation method of the additive comprises the following steps:

[0028] The small molecule organic amine, the stabilizer, the first polymer solution, and the second polymer solution are uniformly mixed at a temperature below 50°C to obtain the additive. The first polymer solution and the second polymer solution are obtained by any of the following methods:

[0029] a) the first solvent is divided into two parts, one part dissolves the first polymer to obtain a first polymer solution, and the other part dissolves the second polymer to obtain a second polymer solution;

[0030] b) the first polymer and the second polymer are dissolved in the same first solvent in any order to obtain the first polymer solution and the second polymer solution.

[0031] For the case of dissolving in the same first solvent, the polymer added first is fully dissolved before the addition of the latter polymer.

[0032] Optionally, the preparation method of the additive comprises the following steps:

[0033] The first polymer is dissolved in the first solvent to obtain a first polymer solution;

[0034] The second polymer is dissolved in the first solvent to obtain a second polymer solution;

[0035] The small molecule organic amine, the stabilizer, the first polymer solution and the second polymer solution are mixed uniformly at a temperature below 50℃ to obtain the additive.

[0036] The first polymer and the second polymer have a plurality of different polymer options. For polymers that need to be dissolved at high temperature (for example, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, methyl vinyl ether-maleic anhydride linear copolymer, hydrogenated nitrile rubber, polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer), the dissolution is carried out at 80-100℃ under nitrogen protection (the dissolution time is selected according to actual needs, for example, 4-8h), and after the dissolution is completed, the temperature needs to be lowered to below 50℃ before mixing with other components.

[0037] For polymers that do not need to be dissolved at high temperature (for example, ethyl cellulose, polyvinyl pyrrolidone, polyvinyl butyral), the dissolution is carried out under nitrogen protection for 0.5-2h.

[0038] Each component is mixed uniformly under stirring for 0.5-2h.

[0039] The application also provides an application of the additive in a conductive agent.

[0040] A conductive agent comprises a second solvent, a conductive material and the additive, and the additive is added in an amount of 10-20% of the mass of the conductive material.

[0041] The second solvent can be N-methyl pyrrolidone (NMP), dimethylformamide (DMF) and other commonly used solvents for conductive agents.

[0042] The conductive material is at least one of carbon nanotubes, graphene, carbon black, ketjen black, and nano-carbon fiber (VGCF).

[0043] The slurry blade fineness of the conductive agent is 10-15 μm.

[0044] The sheet resistivity of the conductive agent is 14-16 mΩ·cm.

[0045] The slurry viscosity of the conductive agent is 400-550 mPa·s.

[0046] The application further provides a use of the additive in a lithium ion battery positive electrode slurry.

[0047] A lithium ion battery positive electrode slurry, the raw material weight parts are as follows:

[0048] The second solvent is a component of the conductive agent, the third solvent is a component of the lithium ion battery positive electrode slurry, and the first solvent, the second solvent and the third solvent each have a specific meaning, and the three can use the same solvent or different solvents.

[0049] The third solvent can be N-methyl pyrrolidone (NMP), dimethylformamide (DMF) and other commonly used solvents for positive electrode slurry.

[0050] The viscosity of the lithium ion battery positive electrode slurry is less than 12000 mPa·s after being placed for 24 hours.

[0051] The viscosity of the lithium ion battery positive electrode slurry is less than 12000 mPa·s and greater than 9000 mPa·s after being placed for 24 hours. In the present application, the viscosity refers to the viscosity at 25℃ unless otherwise specified.

[0052] The solid content of the lithium ion battery positive electrode slurry is greater than 65%.

[0053] The solid content of the lithium ion battery positive electrode slurry is greater than 65% and less than 70%. Beneficial effects

[0054] The addition of the additive to the lithium ion battery positive electrode slurry material can effectively promote the dispersion of the nano-scale lithium iron phosphate and the conductive agent, effectively reduce the viscosity of the positive electrode slurry material, and increase the solid content in the positive electrode slurry material by at least 6% under the same viscosity level, thereby improving the efficiency and reducing the consumption, preventing cracking, and improving the coating uniformity.

[0055] The additive provided by the present application has at least the following beneficial effects:

[0056] (1) In the process of dispersing conductive agent such as carbon nanotube, graphene and carbon black, the additive is used as dispersant, the amount of which is 10% to 20% of the mass of conductive agent, which can significantly improve the dispersion of conductive agent, reduce the viscosity of conductive agent slurry, the fineness of conductive agent slurry and the resistivity of the pole piece made of conductive agent;

[0057] (2) In the process of mixing slurry of lithium iron phosphate positive electrode, the additive is added after the addition of PVDF solution and conductive agent, the amount of which is 0.1-0.5% of the mass of lithium iron phosphate positive electrode, which can significantly improve the solid content of the mixed slurry of positive electrode and reduce the viscosity of the mixed slurry of positive electrode. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1a is a drawing of the blade fineness of the additive prepared in Example 1 applied to the conductive agent;

[0059] Figure 1b is a drawing of the blade fineness of the additive prepared in Example 2 applied to the conductive agent;

[0060] Figure 1c is a drawing of the blade fineness of the additive prepared in Example 3 applied to the conductive agent;

[0061] Figure 2a is a drawing of the blade fineness of the additive prepared in Comparative Example 1 applied to the conductive agent;

[0062] Figure 2b is a drawing of the blade fineness of the additive prepared in Comparative Example 2 applied to the conductive agent;

[0063] Figure 2c is a drawing of the blade fineness of the additive prepared in Comparative Example 3 applied to the conductive agent;

[0064] Figure 3a is a drawing of the particle size test results of the additive prepared in Example 1 applied to the conductive agent;

[0065] Figure 3b is a drawing of the particle size test results of the additive prepared in Example 2 applied to the conductive agent;

[0066] Figure 3c is a drawing of the particle size test results of the additive prepared in Example 3 applied to the conductive agent;

[0067] Figure 4a is a drawing of the particle size test results of the additive prepared in Comparative Example 1 applied to the conductive agent;

[0068] Figure 4b is a drawing of the particle size test results of the additive prepared in Comparative Example 2 applied to the conductive agent;

[0069] Figure 4c is a drawing of the particle size test results of the additive prepared in Comparative Example 3 applied to the conductive agent;

[0070] Figure 5a is a drawing of the electrochemical performance test of the reference example;

[0071] Figure 5b is a drawing of the electrochemical performance test of the additive prepared in Example 1 applied to the mixed slurry of positive electrode;

[0072] Figure 6 is an AC internal resistance (ACIR) test graph, in which the horizontal axis is the number of battery groups;

[0073] Figure 7 is a battery voltage test graph, in which the horizontal axis is the number of battery groups;

[0074] Figure 8 is a DC internal resistance (DCIR) test graph, in which the horizontal axis is the number of battery groups. Embodiments of the present application

[0075] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0076] In order to better describe and illustrate the embodiments of the present application, one or more drawings can be referred to, but additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the inventions, the presently described embodiments or the preferred modes of the present application.

[0077] 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 the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0078] Embodiment 1

[0079] N-methyl pyrrolidone (NMP) was used as the first solvent, 56 parts (by weight, the same for other raw materials) of NMP were weighed, and 2.4 parts of ethyl cellulose (i.e. the first polymer, specifically Ashland N7, the viscosity of which is 50 cPs, which is the viscosity of an NMP solution of 8% mass fraction ethyl cellulose at 25°C) was added in the first solvent under the condition of nitrogen protection at a temperature of 100°C. After continuous dissolution for 2 hours, the temperature was reduced to below 50°C, and then 9.6 parts of polyvinylpyrrolidone (i.e. the second polymer, specifically BASF K10, the viscosity of which is 15 cPs, which is the viscosity of an NMP solution of 8% mass fraction polyvinylpyrrolidone at 25°C) was added. After dissolution for 1 hour, 16 parts of isobutanolamine (i.e. small molecule organic amine) and 16 parts of hydroxyethyl hydrazine (i.e. stabilizer) were added, the stirring speed was 1200 rpm, and stirring was performed for 1 hour to obtain the additive.

[0080] Embodiment 2

[0081] N-methyl pyrrolidone (NMP) as the first solvent, 56 parts of NMP (weight parts, other raw materials are the same) were weighed, under the condition of 80°C temperature and nitrogen protection, 9.6 parts of hydrogenated butyl rubber (i.e. the second polymer, specifically using Arlanxeo 4307, the viscosity of the hydrogenated butyl rubber of this brand is 800 cPs, which is the viscosity of the NMP solution of 6% hydrogenated butyl rubber by mass fraction at 25°C) and 1.2 parts of ethylene-vinyl alcohol copolymer (i.e. the first polymer, specifically using Kolon G176, the viscosity of the ethylene-vinyl alcohol copolymer of this brand is 100 cPs, which is the viscosity of the NMP solution of 3% ethylene-vinyl alcohol copolymer by mass fraction at 25°C) were added in the first solvent, and dissolved for 2 hours, then the temperature was reduced to below 50°C, and then 1.2 parts of polyvinyl butyral (i.e. the first polymer, specifically using Kolon B60H, the viscosity of the polyvinyl butyral of this brand is 20 cPs, which is the viscosity of the NMP solution of 3% polyvinyl butyral by mass fraction at 25°C) was added, dissolved for 1 hour, then 16 parts of isobutanol amine (i.e. small molecule organic amine) and 16 parts of hydroxyethyl hydrazine (i.e. stabilizer) were added, the stirring speed was 1200 rmp, and stirring was performed for 1 hour to obtain the additive.

[0082] Example 3

[0083] N-methyl pyrrolidone (NMP) as the first solvent, 50 parts of NMP (weight parts, other raw materials are the same) were weighed, under the condition of 80°C temperature and nitrogen protection, 15 parts of polypyrrole (i.e. the second polymer, the viscosity of the polypyrrole is 100 cPs, which is the viscosity of the NMP solution of 3% polypyrrole by mass fraction at 25°C) was added in the first solvent. After dissolving for 2 hours, the temperature was reduced to below 50°C, and then 2 parts of polyvinyl butyral (i.e. the first polymer, specifically using Kolon B60H, the viscosity of the polyvinyl butyral of this brand is 20 cPs, which is the viscosity of the NMP solution of 3% polyvinyl butyral by mass fraction at 25°C) was added, dissolved for 1 hour, then 16 parts of isopropyl alcohol amine (i.e. small molecule organic amine) and 16 parts of hydroxyethyl hydrazine (i.e. stabilizer) were added, the stirring speed was 1200 rmp, and stirring was performed for 1 hour to obtain the additive.

[0084] Comparative Example 1 without adding polymer

[0085] N-methyl pyrrolidone (NMP) as the first solvent, 50 parts of NMP (weight parts, other raw materials are the same) were weighed, under the condition of 80°C temperature and nitrogen protection, 15 parts of polypyrrole (i.e. the second polymer, the viscosity of the polypyrrole is 100 cPs, which is the viscosity of the NMP solution of 3% polypyrrole by mass fraction at 25°C) was added in the first solvent. After dissolving for 2 hours, the temperature was reduced to below 50°C, and then 2 parts of polyvinyl butyral (i.e. the first polymer, specifically using Kolon B60H, the viscosity of the polyvinyl butyral of this brand is 20 cPs, which is the viscosity of the NMP solution of 3% polyvinyl butyral by mass fraction at 25°C) was added, dissolved for 1 hour, then 16 parts of isopropyl alcohol amine (i.e. small molecule organic amine) and 16 parts of hydroxyethyl hydrazine (i.e. stabilizer) were added, the stirring speed was 1200 rmp, and stirring was performed for 1 hour to obtain the additive.

[0086] Comparative Example 2 without adding organic amine and stabilizer

[0087] N-methyl pyrrolidone (NMP) as the solvent, 72 parts of NMP was weighed, under the condition of 100℃ temperature and nitrogen protection, 2.4 parts of ethyl cellulose (the same substance as in Example 1) was added into the solvent, dissolved for 2 hours, then cooled to below 50℃, 9.6 parts of polyvinyl pyrrolidone (the same substance as in Example 1) was added, dissolved for 1 hour, then the additive was obtained.

[0088] Comparative Example 3 without stabilizer

[0089] N-methyl pyrrolidone (NMP) as the solvent, 56 parts of NMP was weighed, under the condition of 100℃ temperature and nitrogen protection, 2.4 parts of ethyl cellulose (the same substance as in Example 1) was added into the solvent, dissolved for 2 hours, then cooled to below 50℃, 9.6 parts of polyvinyl pyrrolidone (the same substance as in Example 1) was added, dissolved for 1 hour, then 32 parts of isopropanolamine was added, stirring at 1200rmp for 1 hour, then the additive was obtained.

[0090] Application Example 1 in conductive agent

[0091] N-methyl pyrrolidone (NMP) 89.3 parts was weighed, 6.7 parts of the additive was added, mixed uniformly, then 5 parts of 5-10nm multi-walled carbon nanotubes was added, grinded and dispersed, the dispersion linear velocity was 15m / s, after uniform dispersion, the viscosity, doctor blade fineness, particle size and film resistance were tested. The test results of the additive prepared in each example and comparative example applied in conductive agent were shown in Table 1.

[0092] Table 1

[0093] As shown in Table 1, the viscosity of the conductive agent slurry added with the additive of Example 1-3 was smaller than that of the conductive agent slurry added with the additive of Comparative Example 1-3.

[0094] The doctor blade fineness diagrams of Example 1-3 were shown in Figure 1a-1c, and the doctor blade fineness diagrams of Comparative Example 1-3 were shown in Figure 2a-2c, combined with the figures and the data in Table 1, the fineness of the conductive agent slurry added with the additive of Example 1-3 was smaller.

[0095] As shown in Table 1, the resistivity of the conductive agent slurry added with the additive of Example 1-3 was smaller than that of the conductive agent slurry added with the additive of Comparative Example 1-3.

[0096] The smaller viscosity, smaller fineness and lower resistivity of the conductive agent slurry could prove that the addition of the additive could well improve the dispersion performance of the conductive agent.

[0097] Application Example 2 in positive electrode slurry

[0098] The positive electrode slurry was prepared according to the ratio of lithium iron phosphate: carbon black: binder PVDF: additive: NMP = 97: 1: 2.5: 0.2: 43.67. After the preparation of the positive electrode slurry, the viscosity of the initial, 2 hours, 4 hours, 8 hours, 24 hours was tested, and the viscosity and membrane resistance were tested, and the results are shown in Table 2.

[0099] In Table 2, no additive was added in the reference example.

[0100] Table 2

[0101] The CV curve of the positive electrode slurry prepared in the reference example is shown in Figure 5a, and the additive prepared in Example 1 is shown in Figure 5b. It can be seen that the addition of the additive has no obvious difference compared with the normal electrochemical performance test without the additive. The additive can remain stable without decomposition at a voltage above 4.5V, and there is no obvious redox peak, indicating that the additive is stable in the battery and will not have side reactions, and can be applied in high voltage system.

[0102] As shown in Table 2, after adding the additive prepared in each example, the viscosity of the positive electrode slurry is significantly reduced, and the membrane resistance rate is slightly decreased, indicating that by adding the additive, the viscosity of the positive electrode slurry can be reduced, so the effective ingredient content can be increased, the use amount of the third solvent can be reduced, the electrode baking efficiency can be improved, thick electrodes can be made, and electrode cracking can be prevented. At the same time, the membrane resistance rate is basically the same as that without adding the additive, indicating that the addition of the additive will not affect the internal resistance of the battery. Although the additive is not conductive, it can help the dispersion of the positive electrode and the conductive agent, and has an improvement effect on the overall battery performance.

[0103] Battery test performance characterization

[0104] The positive electrode slurry was prepared according to the data shown in Table 3, and the battery was prepared, and the AC resistance, platform voltage and DC resistance were tested.

[0105] Table 3

[0106] 280The weight ratio of lithium iron phosphate positive electrode slurry is: lithium phosphate: carbon black: binder PVDF: NMP = 97: 1: 2.5: 43.67.

[0107] In Experiment 2, 0.2% of the additive prepared in Comparative Example 1 was added, i.e. the addition amount of the additive prepared in Comparative Example 1 was 0.2% of the mass of lithium phosphate. Similarly, in Experiment 3, 0.03% of the additive prepared in Example 1 was added, i.e. the addition amount of the additive prepared in Example 1 was 0.03% of the mass of lithium phosphate.

[0108] Referring to Table 3, the solid content of Experiment Three is increased to 66.6%, and the slurry viscosity of Experiment Three is reduced to 4010 Mpa.s.

[0109] In the process of making the electrode sheet coating, the three kinds of positive electrode slurry prepared in Experiment One, Experiment Two and Experiment Three have no obvious abnormal phenomena such as particles and scratches, and no abnormality such as belt breakage and wrinkle during rolling.

[0110] Referring to Figure 6, after adding the additive prepared in Comparative Example 1 in Experiment Two, the AC internal resistance of the battery cell is increased, and after adding the additive prepared in Example 1 in Experiment Three, the AC internal resistance of the battery cell is reduced by more than 30%.

[0111] Referring to Figure 7, the capacity platform voltage of Experiment Two and Experiment Three is increased by about 5%, and the capacity platform voltage of Experiment One is lower.

[0112] Referring to Figure 8, after adding the additive prepared in Example 1 in Experiment Three, the DC internal resistance of the battery cell is reduced by nearly 50%.

[0113] The test results of the standard charge-discharge energy retention rate (1P / 0.5P; 2P / 0.5P) of Experiment One, Experiment Two and Experiment Three are shown in Table 4 and Table 5, and after adding the additive prepared in Example in Experiment Three, the 0.5P voltage platform and 2P charge energy retention rate of the battery are significantly improved.

[0114] Table 4

[0115] Table 5

[0116] The test results of the standard charge-discharge energy retention rate (1P / 0.5P; 2P / 0.5P) of Experiment One, Experiment Two and Experiment Three are shown in Table 6 and Table 7, and after adding the additive prepared in Example in Experiment Three, the platform voltage, 1P and 2P charge-discharge energy efficiency of the battery are significantly improved.

[0117] Table 6

[0118] Table 7

[0119] As shown in Table 8, the high-temperature charge-discharge performance of the batteries of Experiment One, Experiment Two and Experiment Three is basically the same.

[0120] Table 8

[0121] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0122] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. An additive for a lithium ion battery, characterized in that, The raw material weight parts composition of the additive is as follows: 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 polyvinyl pyrrolidone, hydrogenated nitrile rubber, polyacrylonitrile, polypyrrole, and styrene-acrylonitrile-acrylic acid copolymer. The stabilizer is at least one of hydrazine compounds.

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

3. The additive for a lithium-ion battery according to claim 1, wherein The stabilizer is at least one of hydroxyethyl hydrazine, hydrazine hydrate, and carbohydrazide.

4. The additive for a lithium ion battery according to claim 1, wherein The raw material weight parts composition of the additive is as follows:

5. The additive for a lithium-ion battery according to claim 1, wherein The raw material weight parts composition of the additive is as follows:

6. The additive for a lithium-ion battery according to claim 1, wherein The raw material weight parts composition of the additive is as follows:

7. The additive for a lithium-ion battery according to claim 1, wherein The method comprises the following steps: The small molecule organic amine, the stabilizer, the first polymer solution, and the second polymer solution are mixed uniformly at a temperature below 50℃ to obtain the additive. The first polymer solution and the second polymer solution are obtained by any of the following methods: a) The first solvent is divided into two parts, one part dissolving the first polymer to obtain the first polymer solution, and the other part dissolving the second polymer to obtain the second polymer solution; 8. The additive for a lithium-ion battery according to claim 7, wherein b) The first polymer and the second polymer are added in any order into the same first solvent for dissolution to obtain the first polymer solution and the second polymer solution. The small molecule organic amine, the stabilizer, the first polymer solution, and the second polymer solution are mixed uniformly under stirring, and the mixing time is 0.5-2h.

9. Use of the additive according to any one of claims 1-8 in a conductive agent.

10. Use of the additive according to any one of claims 1-8 in a lithium ion battery positive electrode slurry.

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