A lithium ion battery negative electrode binder, a preparation method thereof and a negative electrode slurry

Abstract

The present application belongs to the field of polymer, and discloses a preparation method of lithium ion battery negative electrode binder. In an organic phase, monomers are used to carry out a precipitation polymerization reaction in the presence of an initiator, a dispersant and a crosslinking agent, so as to obtain the lithium ion battery negative electrode binder. Compared with an oily binder, the negative electrode binder of the present application is in the form of powder. In order to improve the water dispersibility of the binder, a certain hydrophobic group needs to be introduced between polymer molecular chains, so as to prevent the phenomenon that the polymer forms a dense hydration layer too quickly after contacting with water, thereby preventing water from further entering the interior of the polymer particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer, in particular to a lithium ion battery negative electrode binder, a preparation method thereof and a negative electrode slurry. BACKGROUND

[0002] Lithium ion batteries have high energy density, good safety performance, long cycle life and other advantages, which make them show broad application prospects in small portable electronic devices, large electric vehicles and other large energy storage systems. With the vigorous development of new energy industry, how to prolong the cycle stability, high energy density, high transmission rate, low cost and high safety of lithium ion batteries has become a research hotspot for many enterprises. The energy density of lithium ion batteries is affected by many factors. In addition to improving the specific capacity or proportion of active materials, the amount of non-active substances can also be indirectly increased to improve the energy density of the battery.

[0003] The binder is an important non-active material in lithium ion batteries, which mainly functions to bond active materials, conductive agents and current collectors, so that they have overall connectivity, maintain the integrity of the electrode during the cycle process, thereby reducing the ion transmission resistance of the electrode, and at the same time making the electrode sheet have good mechanical properties and processing properties to meet the needs of industrial production.

[0004] Carbon negative electrode materials include graphitized carbon and non-graphitized carbon. Among them, graphite has a theoretical capacity of 372mA·h / g, and is considered as an ideal negative electrode material in the current commercial application of lithium ion batteries due to its low charge-discharge voltage platform, high cycle stability and low cost. However, the graphite negative electrode is prone to pulverization during the cycle process, resulting in capacity attenuation. The main reason for this phenomenon is that the binder does not sufficiently inhibit the expansion of the negative electrode during charging and discharging, and has low mechanical strength.

[0005] Currently, the binder for the graphite negative electrode of lithium ion batteries is a mixture of sodium carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR). SBR is a water-based binder with good aging resistance and strong adhesion, but has poor dispersion effect. Adding too much SBR will cause large swelling. CMC is a chain-like water-based binder containing abundant carboxyl groups. CMC has thickening, bonding and suspending effects in aqueous solution, and is therefore widely used in the fields of ceramics, textiles, adhesives, etc. When used as a battery binder, CMC can disperse the negative electrode slurry, prevent slurry settlement and improve the peel strength of the electrode sheet. CMC is brittle, and its combination with SBR combines the advantages of both, resulting in an electrode sheet with good adhesion and flexibility.

[0006] CMC is a derivative of a natural polysaccharide, the molecular chain of which is connected by glycosidic bonds, and there is no chemical cross-linking between the molecular chains. The content of carboxylate is not high enough, which limits the bonding effect between CMC and foil and active substances. In terms of chemical stability, adhesion and thickening ability, it has been increasingly unable to meet the requirements of lithium ion battery high performance and high energy density trend for binder materials.

[0007] D1: CN110627945A discloses a long-chain unsaturated carboxylic acid or its derivative modified acrylate adhesive and its preparation method and application. A long-chain unsaturated carboxylic acid or its derivative is introduced into the molecular chain of the acrylate adhesive. The long-chain unsaturated carboxylic acid is an unsaturated carboxylic acid with a carbon chain length of not less than 12, and its derivative is a derived carboxylate, ester, amide, acyl halide or anhydride. The long-chain unsaturated carboxylic acid or its derivative, represented by oleic acid, ricinoleic acid or glyceride, is used as a modified monomer. The raw materials are simple and easy to obtain, and the cost is low. Under the premise of ensuring good modification effect, the raw material cost can be effectively controlled. The obtained lithium battery adhesive has high adhesion, electrolyte resistance, low water absorption and flexibility, and can well match the preparation requirements of lithium battery ceramic separator slurry, negative electrode slurry and positive electrode slurry.

[0008] D2: CN114335546A discloses a battery electrode binder and a battery electrode. The binder comprises a solvent, a modified polyvinyl alcohol, and a polyphenol compound. The modified polyvinyl alcohol is a product obtained by hydrolysis or alcoholysis after copolymerization of carboxylic acid vinyl ester and side chain containing hydroxyl acrylamide and long chain alkyl acrylate. The polyphenol compound contains a benzene ring structure, and the benzene ring structure contains two or more phenolic hydroxyl groups. The mass of the polyphenol compound is 5-30% of the modified polyvinyl alcohol. By modifying the polyvinyl alcohol and introducing functional structural units of side chain containing hydroxyl acrylamide and long chain alkyl acrylate, the prepared binder has stronger adhesion to silicon-based negative active material, stronger ability to inhibit volume expansion of silicon-based negative active material, and better uniform and stable dispersion ability of silicon-based negative active material. At the same time, the thermal stability of polyvinyl alcohol as a lithium ion battery binder is also improved.

[0009] D3: CN112002903A discloses an oily binder and its use, the oily binder includes at least one of oily polyacrylic acid, oily polyacrylate, oily styrene acrylate, oily polyacrylonitrile, oily polyacrylamide, oily polyimide and oily polyamide-imide, the molecular weight thereof is selected from 5W~200W;The above-mentioned oily binder is used to replace the traditional water-based binder for negative electrode slurry, effectively solves the problems of uneven dispersion, many coated particles, water-based binder floating and cold pressing sticky roller in water-based negative electrode slurry preparation;And compared with the traditional water-based binder, the battery obtained from the oily binder has the characteristics of low direct current resistance, good fast charging performance, small fast charging temperature rise, less side reaction and long cycle life of the battery;And compared with the oily polyvinylidene fluoride as the binder, the battery obtained from the oily binder has higher energy density.

[0010] The specification records: compared with the prior art, the present application has the following beneficial effects:

[0011] (1) The oily binder for negative electrode slurry of the present application uses the above-mentioned specific composition and molecular weight, compared with the traditional water-based binder, it can obviously improve the problems of uneven dispersion, many coated particles, binder floating and cold pressing sticky roller in the negative electrode slurry preparation process, and the direct current resistance of the obtained battery is low, the fast charging performance is good, the side reaction is less, and the cycle life of the battery is long;

[0012] (2) Compared with the traditional oily polyvinylidene fluoride, the oily binder for negative electrode slurry of the present application can form hydrogen bonds between the current collector copper foil during use, and the adhesion is obviously greater than that of polyvinylidene fluoride, so that the amount of the binder is obviously reduced, and the energy density of the obtained battery is improved.

[0013] The product of D1 is an emulsion; D2 and D3 are oil-soluble systems.

[0014] The above-mentioned adhesive system has the following problems:

[0015] 1. The above-mentioned literature does not indicate that it can be matched with SBR;

[0016] 2. The above-mentioned literature does not clearly indicate whether it can replace CMC.

[0017] The technical problem solved by the present application is: how to further improve the adhesion of the SBR-based adhesive, reduce the amount of the binder in the negative electrode, reduce the battery internal resistance and DCR, improve the battery rate performance, and improve the battery energy density. SUMMARY

[0018] The present application aims to provide a lithium ion battery negative electrode binder, the negative electrode binder of the present application is in powder form compared with oily binder, in order to improve the water dispersibility of the binder, a certain hydrophobic group needs to be introduced between the polymer molecular chains, to prevent the polymer from forming a dense hydration layer too quickly after contacting with water, thus preventing the phenomenon of further water entering the inside of the polymer particles from occurring;

[0019] More preferably, an amide group is used, on the one hand, it has strong hydrophilicity like the acrylic group, which can improve the dispersibility and adhesion, and on the other hand, it can effectively combine with SBR, cooperate with SBR, and improve the adhesion effect of the negative electrode.

[0020] Meanwhile, the present application also provides a preparation method of the negative electrode binder and a negative electrode.

[0021] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of a lithium ion battery negative electrode binder, in an organic phase, using monomers, under the conditions of initiator, dispersant and crosslinking agent, carrying out precipitation polymerization reaction to obtain the lithium ion battery negative electrode binder;

[0022] The monomers include first monomers and second monomers;

[0023] The first monomers are acrylic monomers, and the second monomers are long-chain alkyl (methyl) acrylate monomers; the long-chain alkyl is C12-C18 alkyl;

[0024] The weight ratio of the first monomers and the second monomers is 500-1000:1-10;

[0025] The crosslinking agent is equivalent to 0.3-1% of the total weight of the monomers.

[0026] In the above-mentioned preparation method of the lithium ion battery negative electrode binder, the monomers include first monomers, second monomers and third monomers, and the third monomers are acrylamide monomers;

[0027] The weight ratio of the first monomers, the second monomers and the third monomers is 500-1000:1-10:1-10.

[0028] In the above-mentioned preparation method of the lithium ion battery negative electrode binder, the weight ratio of the first monomers, the second monomers and the third monomers is 500-1000:5-10:1-5.

[0029] In the above-mentioned preparation method of the lithium ion battery negative electrode binder, the acrylic monomers are one or more of acrylic acid, methacrylic acid, maleic acid and itaconic acid;

[0030] The long chain alkyl (meth) acrylate monomer is one or more of lauryl methacrylate, myristyl methacrylate, stearyl methacrylate, and cetyl acrylate;

[0031] The acrylamide monomer is one or more of acrylamide, methacrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and N,N-dimethyl acrylamide.

[0032] In the preparation method of the lithium ion battery negative electrode binder, the dispersant is polyoxyethylene (30) dipolyhydroxystearate or Span-80.

[0033] The initiator is azobisisobutyronitrile or azobisisoheptyl nitrile.

[0034] The crosslinking agent is one or more of divinylbenzene, polyethylene glycol (200) bisacrylate, polyethylene glycol (400) bisacrylate, polyethylene glycol (600) bisacrylate, polyethylene glycol (200) bismethacrylate, polyethylene glycol (400) bismethacrylate, polyethylene glycol (600) bismethacrylate / N,N-methylene bisacrylamide, pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane tri(3-aziridinyl propionate), polyurethane acrylate, dipentaerythritol diacrylate, dipropylene glycol diacrylate, and ethoxylated (30) bisphenol A diacrylate.

[0035] In the preparation method of the lithium ion battery negative electrode binder, the dispersant is used in an amount of 0.5-2 wt% of the total amount of monomers.

[0036] The initiator is used in an amount of 0.1-3 wt% of the total amount of monomers.

[0037] In the preparation method of the lithium ion battery negative electrode binder, the organic solvent is one or more of cyclohexane, n-hexane, ethyl acetate, butyl acetate, and ethyl propionate.

[0038] The organic solvent is used in an amount of 1-2 times the total weight of monomers.

[0039] In the preparation method of the lithium ion battery negative electrode binder, the initiation temperature of the precipitation polymerization reaction is 65-75°C, and the reaction time is 2-4 h.

[0040] Meanwhile, the application also discloses a lithium ion battery negative electrode binder prepared by any of the above methods.

[0041] Finally, the application also discloses a negative electrode slurry, which comprises water and a main material, wherein the main material comprises 0.4-0.6 wt% of a neutralized lithium ion battery negative electrode binder, 1.2-1.8 wt% of conductive carbon black Super_P, 95-97 wt% of graphite, and 1.5-2.5 wt% of butadiene styrene rubber; and the solid content in the negative electrode slurry is 45-50%.

[0042] Compared with the prior art, the application has the following beneficial effects:

[0043] Compared with the prior art, the binder of the application is in the form of powder, and in order to improve the water dispersibility of the binder, a certain amount of hydrophobic groups is introduced into the polymer molecular chain to prevent the polymer from forming a dense hydration layer after being contacted with water, so that the phenomenon of preventing water from further entering the interior of the polymer particles is avoided.

[0044] Preferably, the amide group is used, which has strong hydrophilicity like the acrylic group, can improve the dispersibility and adhesion, and can be effectively combined with SBR to improve the adhesion effect of the negative electrode. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0046] First Embodiment

[0047] Embodiment 1

[0048] In a 1000 mL flask equipped with a glass conduit, a reflux condenser, a stirrer and a thermometer, 100 g of acrylic acid, 80 g of cyclohexane, 90 g of ethyl acetate, 0.4 g of polyoxyethylene (30) dimeric hydroxystearate, 0.94 g of sucrose allyl ether, 1.5 g of hexadecyl acrylate and 0.3 g of acrylamide were added, and the mixture was deoxygenated by nitrogen blowing for 0.5 h while being stirred and heated to 70 DEG C.

[0049] 0.6 g of peroxy bis (3, 5, 5-trimethylhexanoyl) was dissolved in 60 g of benzene, and the initiator was started to be added dropwise, and the dropwise adding time was 2 h.

[0050] After the dropwise adding was completed, the reaction was ended after 2 h of 75 DEG C heat preservation, and the mixture was filtered and vacuum dried at 90 DEG C overnight to obtain a white powder product.

[0051] Embodiment 2

[0052] The same as Example 1 except that the amount of acrylamide was 0.2 g.

[0053] Example 3

[0054] The same as Example 1 except that the amount of acrylamide was 0.5 g.

[0055] Example 4

[0056] The same as Example 1 except that the amount of sucrose allyl ether was 0.85 g and the amount of hexadecyl acrylate was 1.6 g.

[0057] Example 5

[0058] The same as Example 1 except that the amount of sucrose allyl ether was 0.75 g, the amount of acrylamide was 0.45 g, and the amount of hexadecyl acrylate was 1.3 g.

[0059] Example 6

[0060] The same as Example 1 except that the long-chain alkyl (meth) acrylate monomer was stearyl methacrylate and the amount was 1.5 g.

[0061] Example 7

[0062] The same as Example 1 except that the acrylamide monomer was methacrylamide and the amount was 0.3 g.

[0063] Example 8

[0064] The same as Example 1 except that the long-chain alkyl (meth) acrylate monomer was lauryl methacrylate and the amount was 1.5 g.

[0065] Example 9

[0066] Into a 1000 mL flask equipped with a glass conduit, reflux condenser, stirrer, thermometer, was charged 100 g of acrylic acid, 80 g of cyclohexane, 90 g of ethyl acetate, 0.4 g of polyoxyethylene (30) dimeric hydroxystearate, 0.94 g of sucrose allyl ether, and 1.5 g of hexadecyl acrylate, and the mixture was deoxidized by bubbling nitrogen gas for 0.5 h while being stirred and warmed to 70°C.

[0067] The initiator was started to be added dropwise after 0.6 g of bis (3, 5, 5-trimethylhexanoyl) peroxide was dissolved in 60 g of benzene, and the dropwise addition was performed for 2 h.

[0068] After the completion of the dropwise addition, the reaction was terminated after 2 h of incubation at 75°C, and the product was obtained as a white powder by suction filtration and vacuum drying at 90°C overnight.

[0069] Example 10

[0070] The same as example 1, except that the acrylic monomer is maleic acid.

[0071] Second part of comparative case

[0072] Comparative example 1

[0073] The same as example 1, except that the amount of hexadecyl acrylate is 2.5 g.

[0074] Comparative example 2

[0075] The same as example 1, except that the amount of hexadecyl acrylate is 0.05 g.

[0076] Comparative example 3

[0077] The same as example 1, except that the amount of sucrose allyl ether is 0.2 g.

[0078] Comparative example 4

[0079] The same as example 1, except that the amount of sucrose allyl ether is 1.2 g.

[0080] Preparation of negative electrode sheet 1:

[0081] Dissolve the powdered product prepared in the examples and comparative examples in water to form an aqueous dispersion with a slurry solid content of 0.5 wt% ;

[0082] Add 1.5 wt% conductive carbon black Super_P and stir for 1 h at a speed of 1000 rpm;

[0083] Add lye to adjust the ph to about 7-7.5 and continue stirring and dispersing;

[0084] Add 96 wt% graphite and continue stirring for 2-3 h at a speed of 1000-1500 rpm;

[0085] Add 2 wt% SBR binder and stir for 0.5 h at a speed of 400 rpm, and continue stirring until the slurry is uniform, has no particles, and has a certain flowability;

[0086] The overall solid content of the slurry is 45%;

[0087] Screen the slurry, coat, bake, roll, cut, and prepare the negative electrode sheet.

[0088] Third part of performance test

[0089] 3.1 Adhesive performance test

[0090] Viscosity test: take a proper amount of the powder product prepared in the examples and comparative examples, add water to form a solution with solid content of 0.4%, place in a 25°C thermostat for 3h, then test the viscosity of the aqueous solution with a BROOKFIELD digital viscometer, the rotor rotation speed is 20r / min.

[0091] Peeling force test: fix the stainless steel plate and the current collector on the two clamps of the universal material testing machine, cut the electrode tab (negative electrode prepared according to 3.2.1) into a small strip slightly longer than the double-sided tape, take 10cm 3M-VHB double-sided tape, one side is pasted on the surface of the electrode, and the other side is pasted on the stainless steel plate, then perform 180° peeling test at a speed of 10mm / min and a load of 10N, the force detected when the current collector and the powder are completely peeled apart is recorded automatically by the computer, and the average peeling force in the length direction is taken as the result, the unit is N / cm.

[0092] 3.2 Performance test of lithium ion battery

[0093] 3.2.1 Assembly of battery

[0094] ①Preparation of negative electrode:

[0095] (1) take the powder product prepared in the examples and comparative examples, dissolve in water according to the slurry solid content of 0.5wt% to form an aqueous dispersion;

[0096] (2) add 1.5wt% conductive carbon black Super_P, stir and disperse for 1h, the rotation speed is 1000rpm;

[0097] (3) add alkali solution to adjust the ph to about 7-7.5, continue to stir and disperse;

[0098] (4) add 96wt% graphite, continue to stir for 2-3h, the rotation speed is 1000-1500rpm;

[0099] (5) add 2wt% SBR as binder, stir for 0.5h, the rotation speed is 400rpm, continue to stir until the slurry is uniform, without particles, and has certain fluidity

[0100] (6) sieve the slurry, coat, bake, roll, cut, and prepare the negative electrode tab;

[0101] Among them, CMC+SBR in table 1 and table 2 represents the following negative electrode preparation process:

[0102] (1) take CMC, dissolve in water according to the slurry solid content of 0.5wt% to form an aqueous dispersion;

[0103] (2) add 1.5wt% conductive carbon black Super_P, stir and disperse for 1h, the rotation speed is 1000rpm;

[0104] (3) Add lye to adjust the pH to about 7-7.5, continue to stir and disperse;

[0105] (4) Add 96wt% graphite, continue to stir for 2-3h, at a speed of 1000-1500rpm;

[0106] (5) Add 2wt% SBR as a binder, stir for 0.5h at a speed of 400rpm, continue to stir until the slurry is uniform, without particles, and has a certain fluidity

[0107] (6) Sieve the slurry, coat, bake, roll, cut, and prepare the negative electrode sheet;

[0108] ②Battery assembly:

[0109] Battery winding is the process of stacking the electrode sheets together in the order of positive electrode-separator-negative electrode, and then winding into a battery cell through an automatic winding device. After the finished electrode sheet goes through the steps of packaging, liquid injection, formation, and aging, the next electrochemical performance test can be carried out.

[0110] The relevant test results are shown in Tables 1 and 2;

[0111] Table 1 Physical and chemical performance test results of examples and comparative examples

[0112]

[0113]

[0114] Table 2 Electrical performance test results of examples and comparative examples

[0115] Serial No. Initial DCR Example 1 29.49 Example 2 32.23 Example 3 30.66 Example 4 26.82 Example 5 26.14 Example 6 36.79 Example 7 34.50 Example 8 33.32 Example 9 35.90 Example 10 35.76 Comparative Example 1 33.60 Comparative Example 2 35.13 Comparative Example 3 26.34 Comparative Example 4 31.05 CMC + SBR 30.65

[0116] Fourth part of the result analysis

[0117] 1. As shown by the viscosity and peel force tests of Examples 1-3 and 9, the addition of acrylamide has little effect on the viscosity of the polymer, but has a large effect on the peel strength of the negative electrode slurry. The more acrylamide is used, the greater the peel strength is.

[0118] As shown by the internal resistance tests of Examples 1-3 and 9, when the amount of acrylamide is 0.3-0.4g, the internal resistance is in the best state. The possible reason is that although acrylamide can improve the dispersibility and the bonding force with SBR, the amide group may increase the internal resistance. Therefore, too much acrylamide leads to an increase in internal resistance, and too little acrylamide leads to a negative electrode flatness and uniformity that is not as good as that of more acrylamide. In combination, the amount of acrylamide is selected to be 0.3-0.4g for the best result.

[0119] 2. By comparing Example 1, Example 4, Example 5, Comparative Example 4, Comparative Example 3, it can be seen that as the amount of crosslinking agent increases, the viscosity gradually increases, and the peel strength is shown as Example 1 > Example 4 > Example 5 > Comparative Example 3 > Comparative Example 4, it can be seen that too much crosslinking agent reduces the peel strength, and the possible reason is that too large crosslinking density causes polyacrylate and SBR to be unable to mix well, and finally reduces the peel strength of SBR.

[0120] And the internal resistance is shown as Comparative Example 3 > Example 5 > Example 4 > Example 1 > Comparative Example 4, it can be seen that the smaller the crosslinking density, the better the performance of reducing the internal resistance.

[0121] 3. By Example 6-8, it can be seen that when different acrylamide monomers and different long-chain alkyl (meth) acrylate monomers are selected, there is no regular change in viscosity, peel strength and internal resistance.

[0122] 4. By Example 1, Comparative Examples 1 and 2, it can be seen that too little hydrophobic monomer causes the polyacrylate particle surface to easily hydrate, resulting in poor dispersion of the particles in the slurry, and finally the viscosity, peel strength and internal resistance are all less than Example 1; too much hydrophobic monomer increases the internal resistance of the polyacrylate particles, although the viscosity and peel strength are not affected by too much, but the significant increase in internal resistance will cause the product performance to be poor.

[0123] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

1. A method for preparing a lithium-ion battery negative electrode binder, characterized in that, In an organic phase, a monomer is used to carry out a precipitation polymerization reaction in the presence of an initiator, dispersant and crosslinking agent to obtain a lithium-ion battery negative electrode binder. The monomer includes a first monomer, a second monomer, and a third monomer, wherein the third monomer is an acrylamide monomer; The weight ratio of the first monomer, the second monomer, and the third monomer is 500-1000:1-10:1-10; The first monomer is an acrylic monomer, and the second monomer is a long-chain alkyl (meth)acrylate monomer; the long-chain alkyl group is a C12-C16 alkyl group; The crosslinking agent is equivalent to 0.3% to 1% of the total weight of the monomers; The crosslinking agent is sucrose allyl ether.

2. The method for preparing the lithium-ion battery negative electrode binder according to claim 1, characterized in that, The weight ratio of the first monomer, the second monomer, and the third monomer is 500-1000:5-10:1-5.

3. The method for preparing the lithium-ion battery negative electrode binder according to claim 1, characterized in that, The acrylic monomer is one or more of acrylic acid and methacrylic acid; The long-chain alkyl (meth)acrylate monomers are one or more of lauryl methacrylate, tetradecyl methacrylate, stearate methacrylate, and hexadecyl acrylate; The acrylamide monomer is one or more of acrylamide, methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and N,N-dimethylacrylamide.

4. The method for preparing the lithium-ion battery negative electrode binder according to claim 1, characterized in that, The dispersant is polyoxyethylene (30) dihydroxystearate or Span-80; The initiator is azobisisobutyronitrile, bis(3,5,5-trimethylhexanoyl) peroxide, or azobisisoheptanenitrile.

5. The method for preparing the lithium-ion battery negative electrode binder according to claim 4, characterized in that, The amount of the dispersant used is equivalent to 0.5 to 2 wt% of the total monomers; The amount of the initiator is equivalent to 0.1 to 3 wt% of the total monomer.

6. The method for preparing the lithium-ion battery negative electrode binder according to claim 1, characterized in that, The organic phase is one or more of cyclohexane, n-hexane, ethyl acetate, butyl acetate, and ethyl propionate; The amount of the organic phase used is equivalent to 1 to 2 times the total weight of the monomers.

7. The method for preparing the lithium-ion battery negative electrode binder according to claim 1, characterized in that, The initiation temperature of the precipitation polymerization reaction is 65–75°C; the reaction time is 2–4 h.

8. A lithium-ion battery negative electrode binder, characterized in that, It is prepared by any one of the methods described in claims 1-7.

9. A negative electrode slurry, characterized in that, The slurry comprises water and main materials, wherein the main materials include 0.4-0.6 wt% of neutralized lithium-ion battery negative electrode binder as described in claim 8, 1.2-1.8 wt% of conductive carbon black Super_P, 95-97 wt% of graphite, and 1.5-2.5 wt% of styrene-butadiene rubber; the solid content in the negative electrode slurry is 45-50%.

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