Preparation method of water-based binder for lithium ion battery negative electrode material and water-based binder for lithium ion battery negative electrode material

Abstract

The application relates to the technical field of water-based adhesives, and particularly provides a preparation method of a water-based adhesive for a lithium ion battery negative electrode material and the water-based adhesive for the lithium ion battery negative electrode material. The preparation method of the water-based adhesive for the lithium ion battery negative electrode material comprises the following steps: adding first mixed monomers composed of a first monomer, a second monomer and a third monomer into water to perform a first polymerization reaction, then adding a surfactant and / or a protective colloid and mixing uniformly, and then adding second mixed monomers composed of a fourth monomer, a fifth monomer and a sixth monomer to perform a second polymerization reaction, and the water-based adhesive is obtained. The water-based adhesive has the characteristics of good dispersibility for negative electrode material active particles, high adhesion to a pole piece, high cohesion, good softness and low pole piece resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based adhesives, in particular to a preparation method of a water-based adhesive for a lithium ion battery negative electrode material and the water-based adhesive. BACKGROUND

[0002] The water-based adhesive is one of the key auxiliary materials for the lithium ion battery negative electrode material. The performance of the water-based adhesive has an important influence on the performance of the lithium ion battery, including the dispersibility and dispersion stability of the negative electrode material, the adhesion to the electrode sheet, the flexibility, the cohesive strength, and the influence on the low resistance of the battery cell. The effective components of the water-based adhesive usually include polyacrylic acid (PAA), polyvinyl alcohol (PVA), sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR), styrene-acrylate (SA), etc. The polyacrylic acid water-based adhesive has the characteristic of high adhesion, but the dispersibility and dispersion stability of the negative electrode material, the flexibility, and the low resistance of the battery cell still need to be improved. The prior art also proposes some improvement methods, such as using different monomer combinations and improving the polymerization method, but the inventors believe that further improvement is still needed. SUMMARY

[0003] In view of the deficiencies of the PAA water-based adhesive in the prior art, the present application provides a preparation method of a water-based adhesive for a lithium ion battery negative electrode material and the water-based adhesive.

[0004] The present application adopts the following technical solution:

[0005] The preparation method of the water-based adhesive for the lithium ion battery negative electrode material comprises: adding a first mixed monomer composed of a first monomer, a second monomer and a third monomer into water to perform a first polymerization reaction, then adding a surfactant and / or a protective colloid and mixing uniformly, and then adding a second mixed monomer composed of a fourth monomer, a fifth monomer and a sixth monomer to perform a second polymerization reaction, thereby obtaining the water-based adhesive.

[0006] The first monomer and the fourth monomer are independently selected from monomers with a general formula of CH2=CR 1 COOM, wherein R 1 is selected from H or C1-C4 alkyl, and M is selected from at least one of H, Na+, Li+ and K+;

[0007] The second monomer and the fifth monomer are independently selected from at least one or a combination of several soft monomers, or a combination of the soft monomers and acrylamide monomers, or are independently selected from acrylamide monomers;

[0008] The third monomer and the sixth monomer are independently selected from monomers with a general formula of R 2 CH=CHR 3CN, wherein R 2 is selected from H or methyl, R 3 is absent or at least one selected from C1-C4 alkylene.

[0009] Preferably, the first mixed monomer consists of 20-50% of the first monomer, 0-40% of the second monomer and 20-50% of the third monomer by weight of 100%.

[0010] Preferably, the second mixed monomer consists of 5-50% of the fourth monomer, 5-50% of the fifth monomer and 10-90% of the sixth monomer by weight of 100%.

[0011] Preferably, the weight ratio of the first mixed monomer and the second mixed monomer is 1:9-9:1.

[0012] Preferably, the conversion rate of the first mixed monomer reaches 70% and above after the first polymerization reaction.

[0013] Preferably, the weight percentage of the surfactant and / or the protective colloid in the second mixed monomer is 0-50%.

[0014] Preferably, the surfactant is selected from one or a combination of two or more of anionic surfactant and non-ionic surfactant.

[0015] Preferably, the protective colloid is selected from at least one of polyvinyl alcohol, carboxymethyl cellulose ether, hydroxyethyl cellulose ether, hydroxypropyl cellulose ether and polyvinyl pyrrolidone.

[0016] Preferably, the weight percentage of the aqueous binder is 3-60%.

[0017] An aqueous binder for a lithium ion battery negative electrode material is prepared by the preparation method of any one of the above embodiments.

[0018] In summary, the present application has the following beneficial effects:

[0019] 1. The aqueous binder of the present application is used for the dispersion of negative electrode material active particles and the adhesion to the pole piece, which has the characteristics of good dispersion of negative electrode material active particles, high adhesion to the pole piece, high cohesive strength, good softness and low pole piece resistance.

[0020] 2、The application has the following characteristics through the selection of acrylate monomers, the setting of monomer ratio and the adjustment of preparation process: (1) ensuring the interaction force between the pole piece and the current collector copper foil; (2) ensuring the interaction force with the hydrophobic negative electrode material such as graphite particles; (3) the existence of carboxyl brings the hydrogen bond interaction between the polymers, thereby ensuring the cohesion of the pole piece, and the high cohesion helps to maintain the stability of the structure during the battery cycle; (4) the existence of soft monomers improves the ability of the polymer chain itself to rotate freely, reduces the glass transition temperature, and the branched structure can further improve the flexibility of the high molecular chain compared with the linear structure, further reducing the hardness of the pole piece; (5) improving the compatibility with the electrolyte, while reducing the wrapping of the active particle surface, the alternating current impedance is lower, and the existence of more carboxyl groups in the polymer chain enhances the interface conduction capacity of lithium ions, fully exerting the advantages of low resistance of PAA polymer materials. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in detail below.

[0022] Throughout this specification, unless otherwise specifically indicated, the terms used herein are to be understood in the manner as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs. If there is a contradiction, the present specification takes precedence.

[0023] The present application proposes a preparation method of a water-based binder for lithium ion battery negative electrode material, comprising: adding a first mixed monomer composed of a first monomer, a second monomer and a third monomer to water to carry out a first polymerization reaction, then adding a surfactant and / or a protective colloid and mixing uniformly, and then adding a second mixed monomer composed of a fourth monomer, a fifth monomer and a sixth monomer to carry out a second polymerization reaction, thereby obtaining a water-based binder.

[0024] The first monomer and the fourth monomer are independently selected from monomers of the general formula CH2=CR 1 COOM, wherein R 1 is selected from H or C1-C4 alkyl, and M is selected from at least one of H, Na+, Li+ and K+; the first monomer and the fourth monomer have good hydrophilicity, and can provide certain hydrophilicity for the water-based binder. For example, the first monomer and the fourth monomer can be acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, etc.

[0025] The second monomer and the fifth monomer are independently selected from at least one or a combination of soft monomers, or a combination of the soft monomers and acrylamide monomers, or independently selected from acrylamide monomers. The second monomer and the fifth monomer each contain at least one soft monomer, which can be a single soft monomer or a combination of a soft monomer and a hard monomer (such as methyl methacrylate, ethyl methacrylate, acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, N-ethyl acrylamide, etc.), such as a weight ratio of 1:1 to 5:1 of the soft monomer to the hard monomer, or a single acrylamide monomer (such as N,N-dimethyl acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-diethyl acrylamide, etc.). The soft monomer can impart good flexibility to the second acrylate polymer. In the present application, the soft monomer refers to a homopolymer obtained by homopolymerization of the monomer, the glass transition temperature Tg of which is not more than 0°C, or further, the Tg is not more than -10°C. In the present application, the general formula of the soft monomer can be CH2=CHCOOR 4 , wherein R 4 is selected from C2-C18 alkyl or C2-C18 substituted alkyl; for example, the soft monomer can be butyl acrylate, octyl acrylate, iso-octyl acrylate, hexyl acrylate, lauryl acrylate, stearyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, glycidyl acrylate, etc. In the present application, the hard monomer is a concept relative to the soft monomer, which refers to a homopolymer obtained by homopolymerization of the monomer, the glass transition temperature Tg of which is not less than 0°C, or further, the Tg is more than 10°C. Further, in the present application, the second monomer can be a combination of the soft monomer and the acrylamide monomer at a weight ratio of 1:1 to 10:1, and the acrylamide monomer can be acrylamide, N,N-dimethyl acrylamide, N-methyl acrylamide, N-ethyl acrylamide, etc. Further, in the present application, the fifth monomer can be a single soft monomer or a combination of the soft monomer and the acrylate hard monomer at a weight ratio of 1:1 to 10:1, and the acrylate hard monomer can be methyl methacrylate, ethyl methacrylate, etc.

[0026] The third monomer and the sixth monomer are independently selected from monomers with a general formula of R 2 CH=CHR 3 CN, wherein R 2 is selected from H or methyl, and R 3 is absent or selected from at least one of C1-C4 alkylene. The third monomer and the sixth monomer have high polarity and can have good hydrophilic and hydrophobic properties in the aqueous adhesive. For example, the third monomer and the sixth monomer can be acrylonitrile, methacrylonitrile, 3-butenenitrile, etc., respectively.

[0027] The present application obtains acrylate polymers with different polymer segments by respectively polymerizing the first mixed monomers and the second mixed monomers, and after introducing a surfactant and / or a protective colloid, branched structures can be introduced into the acrylate polymer macromolecular chains, the branching degree of the acrylate polymer is improved, which is beneficial to improve the dispersibility of the active particles of the negative electrode material and the adhesion with the pole piece.

[0028] In a preferred embodiment of the present application, the first mixed monomers consist of 20-50% of the first monomers, 0-40% of the second monomers and 20-50% of the third monomers by weight of 100%.

[0029] Further, the first mixed monomers consist of 30-50% of the first monomers, 0-20% of the second monomers and 30-50% of the third monomers by weight of 100%. For example, the first mixed monomers can consist of 30% of the first monomers, 20% of the second monomers and 50% of the third monomers, or consist of 40% of the first monomers, 10% of the second monomers and 50% of the third monomers, or consist of 50% of the first monomers, 10% of the second monomers and 40% of the third monomers, etc., but are not limited to the above listed.

[0030] In a preferred embodiment of the present application, the second mixed monomers consist of 5-50% of the fourth monomers, 5-50% of the fifth monomers and 10-90% of the sixth monomers by weight of 100%. Further, the second mixed monomers consist of 10-50% of the fourth monomers, 10-30% of the fifth monomers and 30-70% of the sixth monomers by weight of 100%. For example, the second mixed monomers can consist of 10% of the fourth monomers, 10% of the fifth monomers and 80% of the sixth monomers, or consist of 20% of the fourth monomers, 30% of the fifth monomers and 50% of the sixth monomers, or consist of 40% of the fourth monomers, 20% of the fifth monomers and 40% of the sixth monomers, etc., but are not limited to the above listed.

[0031] In a preferred embodiment of the present application, the weight ratio of the first mixed monomers to the second mixed monomers is 1:9-9:1. For example, the weight ratio of the first mixed monomers to the second mixed monomers can be 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, etc., but are not limited to the above listed. Further, the weight ratio can be 6:1-1:6.

[0032] In one preferred embodiment of the present application, the conversion rate of the first mixed monomers reaches 70% or above after the first polymerization reaction. After the first polymerization, the conversion rate of the first mixed monomers is not less than 70%, and the residual first mixed monomers in the reaction system are less, which has little or no effect on the proportion of each monomer in the second mixed monomers added. Further, after the first polymerization, the conversion rate of the first mixed monomers is not less than 75%, or further, not less than 80%.

[0033] In one preferred embodiment of the present application, the weight percentage of the surfactant and / or protective colloid in the second mixed monomers is 0-50%. Specifically, the surfactant can be one or a combination of two or more of anionic surfactants and / or non-ionic surfactants, for example, the surfactant can be sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, AEO-3, AEO-9, AEO-15, Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60, Tween 80, etc., without particular limitation. Further, the weight percentage of the surfactant in the second mixed monomers can be 0.5-3%; specifically, the amount of the protective colloid can be 0.5-30wt% of the weight of the second mixed monomers, or further, the amount of the protective colloid can be 0.5-20% of the weight of the second mixed monomers, and the protective colloid can be polyvinyl alcohol PVA, polyvinyl pyrrolidone PVP, polyethylene glycol PEG, carboxymethyl cellulose ether, hydroxyethyl cellulose ether, hydroxypropyl cellulose ether, etc. Taking PVA as the protective colloid, the degree of hydrolysis can be 70-99%, or further, the degree of hydrolysis can be 80-95%. Further, the surfactant and / or protective colloid can be only the protective colloid, or a combination of the protective colloid and the surfactant in a weight ratio of 1-20:1.

[0034] In one preferred embodiment of the present application, the weight percentage of the aqueous binder is 3-60%, for example, the weight percentage can be 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0035] Another aspect of the present application provides a water-based binder for a lithium ion battery negative electrode material, which is prepared by the method described in any of the above embodiments. For example, the water-based binder for a lithium ion battery negative electrode material can be prepared by the following method: adding water into a reaction vessel and heating to a polymerization temperature, simultaneously dropping a first mixed monomer composed of the first monomer, the second monomer and the third monomer and a water-soluble initiator solution, performing a first polymerization reaction for 1-6 hours, continuing to react at a constant temperature for 0-8 hours after dropping is completed, then adding a surfactant and / or protective colloid, mixing uniformly, and then simultaneously dropping a second mixed monomer composed of the fourth monomer, the fifth monomer and the sixth monomer and a water-soluble initiator solution, performing a second polymerization reaction for 1-6 hours, continuing to react at a constant temperature for 0-6 hours after dropping is completed, to obtain the water-based binder. Alternatively, the water-based binder can be prepared by the following method: adding a first mixed monomer composed of the first monomer, the second monomer and the third monomer into a reaction vessel, adding an appropriate amount of water, heating to a polymerization temperature, dropping a water-soluble initiator solution, continuing to react at a constant temperature for 0-4 hours after dropping is completed, adding a surfactant and / or protective colloid, stirring and dissolving uniformly, adding a second mixed monomer composed of the third monomer, the fourth monomer and the fifth monomer, continuing to drop a water-soluble initiator solution, and reacting at a constant temperature for 2 hours after dropping is completed, then cooling, adjusting the pH to neutral, and adjusting the solid content by adding water.

[0036] The technical solutions of the present application are described in detail below in combination with examples and comparative examples. Unless otherwise specified, the parts in the following examples and comparative examples are all parts by weight.

[0037] Example 1

[0038] A first mixed monomer composed of 37 parts of methacrylic acid, 16 parts of n-butyl acrylate, 4 parts of acrylamide and 43 parts of acrylonitrile and 300 parts of water were added into a reaction vessel, heated to 72°C, and 10 parts of a 2wt% ammonium persulfate aqueous solution was dropped within 30 minutes, and the reaction was continued for 90 minutes after dropping was completed. The conversion rate of the first mixed monomer was 73% as measured by sampling. Then 5 parts of PVA 1792 was gradually added and stirred and dissolved, a second mixed monomer composed of 10 parts of methacrylic acid, 25 parts of n-butyl acrylate and 15 parts of acrylonitrile was added, and 50 parts of water was added, and the temperature was continued to be raised to 74°C, 10 parts of a 3wt% ammonium persulfate aqueous solution was dropped within 30 minutes, and the reaction was continued for 120 minutes after dropping was completed. The temperature was then lowered, the pH was adjusted to neutral, and the solid content was adjusted to 12wt% by adding water, to obtain the water-based binder.

[0039] Example 2

[0040] The difference between Example 2 and Example 1 is that in Example 1, the acrylamide in the first mixed monomer is replaced by an equal weight part of isooctyl acrylate. The remaining steps remain unchanged.

[0041] Example 3

[0042] Example 3 differs from Example 1 in that in Example 1, the second mixed monomer is adjusted from 25 parts of n-butyl acrylate to 15 parts, and from 15 parts of acrylonitrile to 25 parts. The remaining steps remain unchanged.

[0043] Example 4

[0044] Example 4 differs from Example 1 in that in Example 1, the first mixed monomer is composed of 40 parts of methacrylic acid, 9 parts of n-butyl acrylate, 3 parts of acrylamide, and 48 parts of acrylonitrile. The remaining steps remain unchanged.

[0045] Example 5

[0046] Example 5 differs from Example 1 in that in Example 1, the PVA1792 is adjusted from 5 parts to 10 parts, the second mixed monomer is adjusted to be composed of 20 parts of methacrylic acid, 50 parts of butyl acrylate, and 30 parts of acrylonitrile, and the aqueous ammonium persulfate solution with a concentration of 3wt% is adjusted from 10 parts to 15 parts. The remaining steps remain unchanged.

[0047] Example 6

[0048] Example 6 differs from Example 1 in that in Example 1, the PVA1792 is adjusted from 5 parts to 15 parts, the second mixed monomer is adjusted to be composed of 40 parts of methacrylic acid, 100 parts of n-butyl acrylate, and 60 parts of acrylonitrile, and the aqueous ammonium persulfate solution with a concentration of 3wt% is adjusted from 10 parts to 30 parts. The remaining steps remain unchanged.

[0049] Example 7

[0050] In a reaction vessel, 500 parts of water is added and warmed to 75°C, and a first mixed monomer composed of 40 parts of methacrylic acid, 9 parts of octyl acrylate, 3 parts of N,N-dimethyl acrylamide, and 48 parts of methacrylonitrile is added dropwise simultaneously with 10 parts of an aqueous ammonium persulfate solution with a concentration of 2wt%, dropwise for 3h, and then constant temperature reaction is continued for 3h, the conversion rate of the first mixed monomer is measured to be 81%, 6 parts of PVA1788 is gradually added and dissolved by stirring, and a second mixed monomer composed of 20 parts of methacrylic acid, 30 parts of n-butyl acrylate, and 50 parts of acrylonitrile is added dropwise simultaneously with 10 parts of an aqueous ammonium persulfate solution with a concentration of 5wt%, dropwise for 1h, and then constant temperature reaction is continued for 4h, the temperature is lowered, the pH is adjusted to be neutral, water is added to adjust the concentration to 15wt%, and an aqueous adhesive is obtained.

[0051] Example 8

[0052] Example 8 differs from Example 7 in that the first mixed monomer is adjusted to be composed of 40 parts of methacrylic acid, 6 parts of octyl acrylate, 6 parts of N,N-dimethyl acrylamide, and 48 parts of methacrylonitrile. The remaining steps remain unchanged.

[0053] Example 9

[0054] The difference between Example 9 and Example 7 is that the first mixed monomers are adjusted to consist of 40 parts of methacrylic acid, 9 parts of hydroxybutyl acrylate, 3 parts of N,N-dimethylacrylamide and 48 parts of methacrylonitrile. The remaining steps remain unchanged.

[0055] Example 10

[0056] The difference between Example 9 and Example 7 is that 6 parts of PVA1788 are replaced by a combination of 4 parts of PVA1788 and 2 parts of AEO-9. The remaining steps remain unchanged.

[0057] Comparative Example 1

[0058] A mixed monomer consisting of 37 parts of methacrylic acid, 16 parts of n-butyl acrylate, 4 parts of acrylamide and 43 parts of acrylonitrile and 300 parts of water are added to a reaction vessel, heated to 72°C, and 20 parts of a 2wt% aqueous ammonium persulfate solution are added dropwise over 30 minutes. After the dropwise addition is complete, the temperature is maintained for 4 hours, the temperature is lowered, the pH is adjusted to neutral, and water is added to adjust the solidification to 12wt%. An aqueous adhesive is obtained.

[0059] Comparative Example 2

[0060] 300 parts of water are added to a reaction vessel, heated to 90°C, and 5 parts of PVA1792 are gradually added and stirred to dissolve. The temperature is lowered to not more than 40°C, a mixed monomer consisting of 10 parts of methacrylic acid, 25 parts of n-butyl acrylate and 15 parts of acrylonitrile is added, the temperature is further increased to 74°C, and 12 parts of a 3wt% aqueous ammonium persulfate solution are added dropwise over 30 minutes. After the dropwise addition is complete, the temperature is maintained for 4 hours, the temperature is lowered, the pH is adjusted to neutral, and water is added to adjust the solidification to 12wt%. An aqueous adhesive is obtained.

[0061] Comparative Example 3

[0062] 350 parts of water are added to a reaction vessel, heated to 90°C, and 5 parts of PVA1792 are gradually added and stirred to dissolve. The temperature is lowered to not more than 40°C, a mixed monomer consisting of 47 parts of methacrylic acid, 41 parts of butyl acrylate, 4 parts of N,N-dimethylacrylamide and 58 parts of acrylonitrile is added, the temperature is further increased to 74°C, and 20 parts of a 3wt% aqueous ammonium persulfate solution are added dropwise over 30 minutes. After the dropwise addition is complete, the temperature is maintained for 4 hours, the temperature is lowered, the pH is adjusted to neutral, and water is added to adjust the solidification to 12wt%. An aqueous adhesive is obtained.

[0063] The components and parts of each monomer of Examples 1-10 and Comparative Examples 1-3 are shown in Table 1 below.

[0064] Table 1 / Parts

[0065]

[0066]

[0067] The preparation process of the performance test graphite negative electrode sheet is as follows: the water-based binder to be tested and 50% water are dispersed at 1000 rpm for 15 minutes, then the conductive agent SP conductive carbon black is added and wetted for 12 minutes, and then high-speed stirring is carried out at 1600 rpm for 120 minutes; then the negative electrode material S360-L2-H and the remaining 50% water are added and high-speed stirring is continued at 1600 rpm for 120 minutes. After dispersion is completed, the viscosity (23°C) is adjusted to be between 2500-2700 mPa·s, and the discharge is completed after filtration with a 150 mesh filter screen. The copper foil is placed on the coating machine, the doctor knife scale of the wet film preparation device is adjusted, the filtered slurry is evenly poured, and the air blowing is baked to dryness in an environment of 100°C. The specification is 12.5 cm x 5 cm, and the single-sided area density of the electrode sheet is 100-110 g / m 2 .

[0068] The electrode sheet peeling force test method is as follows: the cut electrode sheet is sent into a 35% RH constant temperature room for 30 minutes, the coating is outward, the copper foil is inward, two electrode sheets are pasted together, and the electrode sheet is rolled to 1.6 g / cm 3 in the electric roller press, and then placed for 30 minutes. During this period, five 12.5 x 5 cm stainless steel plates are selected, double-sided adhesive tape of the corresponding specification is pasted on the steel plates, the electrode sheet is pasted on the double-sided adhesive tape with the coating downward, a 2.5 cm wide masking tape is pasted on the copper foil, and the electrode sheet steel plate is rolled back and forth for one round with a certain pressure by the electric roller, and then the adhesion of the electrode sheet is tested by the electronic peeling machine. In the same way as above, the electrode sheet is pasted on the double-sided adhesive tape with the coating upward, and the cohesion of the electrode sheet can be tested.

[0069] The electrode sheet flexibility test method is as follows: a softness tester ITM-RRD01 is used for testing.

[0070] The test method of the swelling rate of the gel film electrolyte is as follows: the gel film without bubbles is trimmed, and then cut into a specification of about 1 x 4 cm, and then placed in a 105°C air drying oven for drying for 4 hours, weighed and recorded as M1, and then placed in a small bottle containing electrolyte (1 M LiPF6 in EC:DMC:EMC=1:1:1) for constant temperature soaking for 48 hours. After taking out, the surface electrolyte is wiped dry with filter paper, and the wiping and weighing process is controlled within 1 minute. Weighing M2, the gel film swelling rate is (M2-M1) / M1 x 100%.

[0071] The assembly sequence of the battery is as follows from bottom to top: negative shell - spring - gasket - lithium sheet - electrolyte - separator - electrolyte - electrode sheet - positive shell; the first coulombic efficiency and impedance test are as follows:

[0072] The first efficiency test is 0.1C, 0.005-1.5V charge-discharge; the impedance scan is from 100kHz to 0.1Hz.

[0073] The results are shown in Table 2 below.

[0074] Table 2

[0075]

[0076] From the results in Table 2, it can be seen that the aqueous binder for lithium ion battery negative electrode material of the application is used for the dispersion and bonding of active particles of the negative electrode material, and can obtain the characteristics of good comprehensive performance, such as adhesion, cohesion, electrode sheet softness, glue film swelling rate, low internal resistance and high first efficiency.

[0077] The specific embodiments are only an explanation of the application, and are not a limitation of the application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the application, they are protected by the patent law.

Claims

1. A process for the preparation of an aqueous binder for lithium-ion battery anode materials, characterized in that Comprising: adding a first mixed monomer composed of a first monomer, a second monomer and a third monomer to water to perform a first polymerization reaction, then adding a surfactant and / or a protective colloid and mixing uniformly, followed by adding a second mixed monomer composed of a fourth monomer, a fifth monomer and a sixth monomer to perform a second polymerization reaction, to obtain an aqueous adhesive; said first monomer and said fourth monomer are independently selected from monomers of the general formula CH2=CR 1 COOM, wherein R 1 is selected from H or C1-C4 alkyl, M is selected from at least one of H, Na + , Li + and K + ; the second monomer and the fifth monomer alone contain one or several combinations of soft monomers, or a combination of the soft monomers and acrylamide monomers, or are selected from acrylamide monomers alone; said third monomer and said sixth monomer are individually selected from the group consisting of monomers of the general formula R 2 CH=CHR 3 CN, wherein R 2 is selected from H or methyl, R 3 is absent or at least one selected from C1-C4 alkylene; the first mixed monomer consists of 20-50% of the first monomer, 0-40% of the second monomer and 20-50% of the third monomer by weight of 100%; the second mixed monomer consists of 5-50% of the fourth monomer, 5-50% of the fifth monomer and 10-90% of the sixth monomer by weight of 100%; the conversion rate of the first mixed monomer reaches 70% or above after the first polymerization reaction.

2. The production method according to claim 1, characterized by, the weight ratio of the first mixed monomer to the second mixed monomer is 1:9-9:

1.

3. The preparation method according to claim 1, characterized in that, the weight percentage of the surfactant and / or the protective colloid in the second mixed monomer is 0-50%.

4. The method of claim 1, wherein, the surfactant is selected from one or a combination of two or more of anionic surfactants and non-ionic surfactants.

5. The preparation method according to claim 1, characterized in that, the protective colloid is selected from at least one of polyvinyl alcohol, carboxymethyl cellulose ether, hydroxyethyl cellulose ether, hydroxypropyl cellulose ether and polyvinyl pyrrolidone.

6. The method of claim 1, wherein, the weight percentage of the aqueous adhesive is 3-60%.

7. An aqueous binder for a lithium-ion battery anode material, characterized in that, obtained by the preparation method of any one of claims 1-6.

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