Specialized hyperbranched network polyacrylic acid resin for silicon-carbon negative electrode, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion battery adhesives, and particularly relates to a hyperbranched network polyacrylic acid resin special for silicon-carbon negative electrodes, a preparation method and application thereof. The hyperbranched network polyacrylic acid resin special for silicon-carbon negative electrodes comprises, by mass fraction, 3-10 parts of water-based acrylic acid resin, 4-10 parts of monomer A, 2-6 parts of monomer B, 2-6 parts of monomer C, 60-80 parts of solvent, 0.1-0.2 parts of chain extender, 1-8 parts of crosslinking agent and 0.5-1 part of silane coupling agent. The monomer A is an acrylic ester monomer, the monomer B is an acrylamide monomer, the monomer C is at least one selected from an allyl amine monomer and an acrylonitrile monomer, and the chain extender is at least one selected from dodecyl mercaptan and 2-mercaptoethanol. The polyacrylic acid resin has high viscosity and peeling strength, and the prepared lithium ion battery negative electrode material has high discharge specific capacity and cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery adhesives, and particularly relates to a hyperbranched network polyacrylic acid resin special for silicon-carbon negative electrodes, a preparation method and application thereof. BACKGROUND

[0002] In the preparation process of lithium ion batteries, active materials, conductive additives and current collectors cannot be directly bonded to metal electrodes, so adhesives are an important component of lithium ion battery electrodes. Although the adhesive is used in a small proportion in the preparation of electrodes, the adhesive will still significantly affect the electrochemical performance of the silicon-carbon negative electrode.

[0003] At present, common adhesives include polyvinylidene fluoride adhesives, carboxymethyl cellulose and styrene-butadiene rubber adhesives, and polyacrylic acid adhesives.

[0004] Although polyvinylidene fluoride adhesives have excellent electrochemical and chemical stability, their electronic and ionic conductivity is weak. At the same time, polyvinylidene fluoride adhesives realize bonding through intermolecular van der Waals forces and hydrogen bonds formed by C-F bonds on the main chain and other substances in the electrode. When they are applied to silicon-carbon negative electrodes, it is difficult to withstand the huge stress caused by volume expansion during the charging and discharging process of the silicon-carbon negative electrode, and the battery performance will also quickly decrease.

[0005] Compared with polyvinylidene fluoride adhesives, carboxymethyl cellulose and styrene-butadiene rubber adhesives have small modulus, high elasticity, strong adhesion and low electrolyte absorption. This good mechanical property improves the adhesion and capacity retention of the silicon anode. However, the bonding strength of such adhesives is relatively low, and in some high-energy density battery applications, it may not meet the requirements for the stability of the electrode structure. In addition, the thermal stability of these two adhesives needs to be improved, and they may decompose in a high-temperature environment, affecting the performance of the battery.

[0006] Polyacrylic adhesives have a wide range of applications due to their strong hydrogen bonding with active substances containing hydroxyl groups on the surface because of the high proportion of carboxylic acid. A negative electrode binder, a negative electrode sheet and a battery are disclosed in Chinese patent CN118879245A. The negative electrode binder includes a binder composition and a liquid metal material, the binder composition includes a polymer, the polymer includes carboxyl type structural units, hydroxyl type structural units, nitrile type structural units, and acrylate type structural units; the liquid metal material is a hydroxyl or carboxyl modified liquid metal material. The technical solution forms a new negative electrode binder by blending the hydroxyl or carboxyl modified liquid metal material with the binder composition containing carboxyl type structural units, hydroxyl type structural units, nitrile type structural units, and acrylate type structural units. The addition of the hydroxyl or carboxyl modified liquid metal greatly improves the electrical conductivity of the negative electrode binder, and the binder has a unique response mechanism to the current, which can balance the rigidity and flexibility of the binder and comprehensively improve the mechanical properties of the binder; greatly reduces the internal resistance of the battery and improves the capacity.

[0007] Chinese patent CN117106393A discloses a polyacrylic or polyacrylate aqueous binder, a preparation method and application thereof. The polyacrylic or polyacrylate aqueous binder is a polymer obtained by polymerizing monomers, the monomers including hard monomers, soft monomers and functional monomers.

[0008] The hard monomers are selected from one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate or styrene.

[0009] The soft monomers are selected from one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, vinyl versatate, tetrahydrofurfuryl acrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate or ethoxyethoxyethoxy acrylate.

[0010] The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, acetoacetoxyethyl methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, or a silane coupling agent.

[0011] The polyacrylic acid or polyacrylate aqueous binder has higher bonding force and better flexibility, but does not pay attention to the performance of lithium ion batteries. SUMMARY

[0012] The present application aims at the above-mentioned problems, and provides a hyperbranched network polyacrylic acid resin special for silicon-carbon negative electrodes, a preparation method and application thereof.

[0013] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0014] The present application provides a hyperbranched network polyacrylic acid resin special for silicon-carbon negative electrodes, by mass fraction, raw materials include 3-10 parts of an aqueous acrylic acid resin, 4-10 parts of monomer A, 2-6 parts of monomer B, 2-6 parts of monomer C, 60-80 parts of a solvent, 0.1-0.2 parts of a chain extender, 1-8 parts of a crosslinking agent, and 0.5-1 parts of a silane coupling agent.

[0015] The monomer A is an acrylate monomer.

[0016] The monomer B is an acrylamide monomer.

[0017] The monomer C is selected from at least one of an allyl amine monomer and an acrylonitrile monomer.

[0018] The chain extender is selected from at least one of dodecyl mercaptan and 2-mercaptoethanol.

[0019] In some preferred embodiments, the preparation raw materials of the aqueous acrylic acid resin include an acrylic monomer, a crosslinking monomer, and water.

[0020] Preferably, the acrylic monomer is selected from at least one of acrylic acid and methacrylic acid.

[0021] Preferably, the crosslinking monomer is selected from at least one of polyethylene glycol, ethylene glycol, hexanediol, pentanediol, beta-cyclodextrin, sorbitol, N,N-dihydroxyaniline, polyether amine, ethylenediamine, and polypropylene oxide glycol.

[0022] Preferably, the mass ratio of the acrylic monomer, the crosslinking monomer and the water is 12-20:1:30-60.

[0023] In some preferred embodiments, the acrylate monomer is selected from at least one of ethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, butyl acrylate and 2-ethylhexyl acrylate.

[0024] In some preferred embodiments, the acrylamide monomer comprises at least one of acrylamide, methacrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide and N,N-methylene acrylamide.

[0025] Further preferably, the acrylamide monomer is acrylamide.

[0026] In some preferred embodiments, the allyl amine monomer is selected from at least one of diallyl amine and triallyl amine.

[0027] In some preferred embodiments, the acrylonitrile monomer is selected from at least one of acrylonitrile, N-methyl acrylonitrile and N-propyl acrylonitrile, preferably acrylonitrile.

[0028] Preferably, the solvent is N,N dimethylformamide.

[0029] In some preferred embodiments, the crosslinking agent is selected from at least one of polyethylene glycol, ethylene glycol, hexylene glycol, ethanolamine, pentylene glycol, β-cyclodextrin, sorbitol, N,N-dihydroxyaniline, polyether amine and ethylenediamine.

[0030] Preferably, the weight average molecular weight of the polyethylene glycol is 1000-6000.

[0031] In some preferred embodiments, the silane coupling agent is selected from at least one of KH560 (γ-glycidoxypropyltrimethoxysilane) and KH550 (γ-aminopropyltriethoxysilane), preferably KH550.

[0032] The special hyperbranched network polyacrylic resin for silicon-carbon negative electrode further comprises an emulsifier mixture, an initiator and a neutralizing agent.

[0033] In some preferred embodiments, the emulsifier mixture is a mixture of an emulsifier and water; the emulsifier is selected from at least one of dodecyl phenol polyoxyethylene ether, dodecyl benzene sulfonic acid, octyl phenol polyoxyethylene ether and sodium dodecyl sulfonate.

[0034] Preferably, the mass fraction of the emulsifier mixture is 0.005-0.09.

[0035] Preferably, the mass fraction of the initiator is 0.1-0.7.

[0036] Preferably, the neutralizing agent is added in an amount to adjust the pH of the hyperbranched network polyacrylic acid resin for silicon-carbon negative electrodes to 7.

[0037] In some preferred embodiments, the initiator is at least one selected from the group consisting of ammonium persulfate, potassium persulfate, ammonium persulfate, sodium bisulfite, and hydrogen peroxide.

[0038] In some preferred embodiments, the neutralizing agent is at least one selected from the group consisting of aqueous sodium hydroxide solution, aqueous lithium hydroxide solution, aqueous sodium bicarbonate solution, aqueous lithium carbonate solution, and ammonia.

[0039] The second aspect of the present application provides a preparation method of the above-mentioned hyperbranched network polyacrylic acid resin for silicon-carbon negative electrodes, comprising the following steps:

[0040] (1) uniformly mix acrylic monomers, crosslinking monomers, and water, and stir to react to obtain an aqueous acrylic resin;

[0041] (2) mix an emulsifier mixture, monomer A, monomer B, monomer C, a solvent, and the aqueous acrylic resin, add a chain extender and an initiator, and react under nitrogen protection;

[0042] (3) continue to react after adding a crosslinking agent and a silane coupling agent after cooling, and then add a neutralizing agent to adjust the pH of the system to 7.

[0043] Preferably, the temperature of the stirring reaction in step (1) is 25-30℃, the stirring reaction time is 20-60 min, and the stirring reaction speed is 200-300 rpm.

[0044] Preferably, the reaction in step (2) includes two reaction stages, the first reaction stage has a temperature of 50-70℃ and a time of 1.5-2.5 h, and the second reaction stage has a reaction temperature of 70-85℃ and a time of 2.5-3.5 h.

[0045] Preferably, the temperature after cooling in step (3) is 40-60℃.

[0046] Preferably, the reaction time in step (3) is 30-60 min.

[0047] The third aspect of the present application provides an application of the above-mentioned hyperbranched network polyacrylic acid resin for silicon-carbon negative electrodes in silicon-carbon negative electrodes.

[0048] The fourth aspect of the present application provides a negative electrode slurry comprising the above-mentioned hyperbranched network polyacrylic acid resin for silicon-carbon negative electrodes.

[0049] The fifth aspect of the present application provides a silicon-carbon negative electrode sheet, comprising the above-mentioned negative electrode slurry.

[0050] The sixth aspect of the present application provides a lithium ion battery, comprising the above-mentioned silicon-carbon negative electrode sheet.

[0051] Compared with the prior art, the present application has the following beneficial effects:

[0052] (1) The present application uses specific water-based acrylic resin, monomer A, monomer B, monomer C, chain extender, crosslinking agent and silane coupling agent together, and each raw material is indispensable, to prepare a polyacrylic acid resin with alternating soft and hard arrangement and hyperbranched network structure, which has high viscosity and peel strength, and is used to prepare negative electrode material for lithium ion batteries, inhibits material expansion, increases the structural stability of the negative electrode material, and has high discharge specific capacity and cycle performance.

[0053] (2) In the process of preparing the polyacrylic acid resin, the water-based acrylic resin is prepared first, then monomer A, monomer B, monomer C and the water-based acrylic resin are used for free polymerization, then the chain length is controlled by adding a chain extender, and finally a crosslinking agent and a silane coupling agent are added for further crosslinking, so that the obtained polyacrylic acid resin has better peel strength and higher discharge specific capacity and cycle performance when used to prepare negative electrode material for lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The silicon-carbon negative electrode peel degree test chart prepared by using the product of Example 1 (modified binder) and Comparative Example 7 (traditional binder).

[0055] Figure 2 The cycle performance chart of the battery prepared by using the product of Example 1 (modified binder) and Comparative Example 7 (traditional binder). DETAILED DESCRIPTION

[0056] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific implementation schemes will be described in detail.

[0057] The present application will be further described below in combination with examples, but the present application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different requirements of specific use, and the implementation conditions indicated are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as they do not conflict with each other.

[0058] In the following examples and comparative examples, the raw materials used are commercially available or prepared by conventional methods in the art, unless otherwise specified.

[0059] Example 1

[0060] A hyperbranched network polyacrylic resin special for silicon-carbon negative electrode, the raw material composition is: 4 parts of water-based acrylic resin, 6 parts of butyl acrylate, 2 parts of acrylamide, 1 part of diallylamine, 2 parts of acrylonitrile, 0.1 part of dodecyl mercaptan, 1.5 parts of ethylenediamine, 0.7 parts of silane coupling agent KH550, 0.006 parts of emulsifier mixture, 0.15 parts of potassium persulfate, and 20wt% lithium carbonate aqueous solution is used to adjust pH to 7.

[0061] The preparation method of the emulsifier mixture is: dodecylphenol polyoxyethylene ether (CAS:9014-92-0) is mixed with water at a mass ratio of 1:300 at 50°C for 20min.

[0062] The preparation method of the hyperbranched network polyacrylic resin special for silicon-carbon negative electrode is:

[0063] (1) The polyethylene glycol 6000, acrylic acid and water are mixed uniformly at a mass ratio of 1:15:50, and the reaction is carried out at 25°C and a stirring speed of 200rpm for 30min to obtain the water-based acrylic resin;

[0064] (2) The emulsifier mixture, butyl acrylate, acrylamide, diallylamine, acrylonitrile and water-based acrylic resin are mixed, and dodecyl mercaptan (CAS:112-55-0) and potassium persulfate are added, and the temperature is first raised to 70°C for 1h and then raised to 80°C for 3.5h under nitrogen protection;

[0065] (3) After cooling to 40°C, ethylenediamine and silane coupling agent KH550 are added for continuous reaction for 30min, and after the reaction is completed, 20wt% lithium carbonate aqueous solution is added to adjust pH to 7.

[0066] Example 2

[0067] A hyperbranched network polyacrylic resin special for silicon-carbon negative electrode, the raw material composition is: 3 parts of water-based acrylic resin, 8 parts of hydroxyethyl acrylate, 1.2 parts of 2-ethylhexyl acrylate (CAS:103-11-7), 5 parts of acrylamide, 0.5 parts of triallylamine, 0.1 part of 2-mercaptoethanol (CAS:60-24-2), 4 parts of ethanolamine, 0.5 parts of silane coupling agent KH550, 0.01 parts of emulsifier mixture, 0.2 parts of potassium persulfate, and 15wt% sodium bicarbonate aqueous solution is used to adjust pH to 7.

[0068] The preparation method of the emulsifier mixture is: dodecylbenzenesulfonic acid is mixed with water at a mass ratio of 1:200 at 60°C for 30min.

[0069] The preparation method of the hyperbranched network polyacrylic resin special for silicon-carbon negative electrode is:

[0070] (1)Mix glucose, methacrylic acid and water uniformly in a mass ratio of 1:20:60, and react for 60 min at 25℃ with a stirring speed of 200 rpm to obtain an aqueous acrylic resin;

[0071] (2) Mix the emulsifier mixture, ethyl acrylate, 2-ethylhexyl acrylate, acrylamide, triallylamine and the aqueous acrylic resin, add 2-mercaptoethanol and ammonium persulfate, and first heat to 75℃ for 1.5 h under nitrogen protection, and then heat to 85℃ for 3 h;

[0072] (3) Cool to 40℃, add ethanolamine and silane coupling agent KH550 and continue to react for 30 min, and then add 15 wt% sodium bicarbonate aqueous solution to adjust the pH to 7.

[0073] Example 3

[0074] A hyperbranched network polyacrylic resin special for silicon-carbon negative electrodes, wherein the raw material composition comprises, by mass fraction, 6 parts of an aqueous acrylic resin, 10 parts of hydroxypropyl acrylate, 4 parts of acrylamide, 3 parts of acrylonitrile, 0.1 part of dodecyl mercaptan, 6 parts of sorbitol, 0.5 part of silane coupling agent KH550, 0.06 part of an emulsifier mixture, and 0.2 part of hydrogen peroxide; and the pH is adjusted to 7 by ammonia water.

[0075] The preparation method of the emulsifier mixture is as follows: mix dodecylphenol polyoxyethylene ether and water in a mass ratio of 1:250 at 60℃ for 30 min to obtain the emulsifier mixture.

[0076] The preparation method of the hyperbranched network polyacrylic resin special for silicon-carbon negative electrodes is as follows:

[0077] (1) Mix polyetheramine, acrylic acid and water uniformly in a mass ratio of 1:12:30, and react for 30 min at 25℃ with a stirring speed of 300 rpm to obtain an aqueous acrylic resin;

[0078] (2) Mix the emulsifier mixture, hydroxypropyl acrylate, acrylamide, acrylonitrile, N,N-dimethylformamide and the aqueous acrylic resin, add dodecyl mercaptan and hydrogen peroxide, and first heat to 70℃ for 2 h under nitrogen protection, and then heat to 87℃ for 4 h;

[0079] (3) Cool to 40℃, add sorbitol and silane coupling agent KH550 and continue to react for 40 min, and then add ammonia water to adjust the pH to 7.

[0080] Example 4

[0081] A special hyperbranched network polyacrylic resin for silicon-carbon negative electrode, the raw material composition is: 5 parts of water-based acrylic resin, 6 parts of hydroxypropyl acrylate, 5.5 parts of acrylamide, 2.2 parts of acrylonitrile, 0.15 parts of dodecyl mercaptan, 4 parts of sorbitol, 0.7 parts of silane coupling agent KH550, 0.04 parts of emulsifier mixture, 0.2 parts of hydrogen peroxide; adjust the pH to 7 with ammonia.

[0082] The preparation method of the emulsifier mixture is: mix octylphenol polyoxyethylene ether (CAS: 9036-19-5) with water at a mass ratio of 1:250 at 60°C for 30min.

[0083] The preparation method of the special hyperbranched network polyacrylic resin for silicon-carbon negative electrode is:

[0084] (1) Mix N,N-dihydroxyaniline, acrylic acid and water at a mass ratio of 1:12:30 uniformly, and react at 25°C under stirring at a speed of 300rpm for 20min to obtain a water-based acrylic resin;

[0085] (2) Mix the emulsifier mixture, hydroxypropyl acrylate, acrylamide, acrylonitrile, N,N dimethylformamide and the water-based acrylic resin, add dodecyl mercaptan and hydrogen peroxide, and first heat to 70°C under nitrogen protection for 2h, and then heat to 87°C for 4h;

[0086] (3) Cool to 40°C, add sorbitol and silane coupling agent KH550 and continue to react for 60min, and after the reaction is completed, add ammonia water to adjust the pH to 7.

[0087] Example 5

[0088] A special hyperbranched network polyacrylic resin for silicon-carbon negative electrode, the raw material composition is: 10 parts of water-based acrylic resin, 6 parts of hydroxypropyl acrylate, 6 parts of acrylamide, 3 parts of acrylonitrile, 0.2 parts of dodecyl mercaptan, 6 parts of sorbitol, 0.8 parts of silane coupling agent KH550, 0.04 parts of emulsifier mixture, 0.3 parts of hydrogen peroxide; adjust the pH to 7 with ammonia.

[0089] The preparation method of the emulsifier mixture is: mix octylphenol polyoxyethylene ether with water at a mass ratio of 1:250 at 60°C for 30min.

[0090] The preparation method of the special hyperbranched network polyacrylic resin for silicon-carbon negative electrode is:

[0091] (1) Mix pentaerythritol, acrylic acid and water at a mass ratio of 1:12:30 uniformly, and react at 25°C under stirring at a speed of 300rpm for 20min to obtain a water-based acrylic resin;

[0092] (2)Mix the emulsifier mixture, hydroxypropyl acrylate, acrylamide, acrylonitrile, N,N dimethylformamide and water-based acrylic resin, add dodecyl mercaptan and hydrogen peroxide, and first heat to 70°C under nitrogen protection for 2h, and then heat to 87°C for 4h;

[0093] (3) Cool to 40°C, add sorbitol and silane coupling agent KH550 and continue to react for 60min, and then add ammonia water to adjust the pH to 7 to obtain the product.

[0094] Comparative Example 1

[0095] The difference from Example 1 is that the diallylamine is replaced by an equal amount of ethylene glycol dimethacrylate; the rest are the same.

[0096] Comparative Example 2

[0097] The difference from Example 1 is that the diallylamine is replaced by an equal amount of acrylamide; the rest are the same.

[0098] Comparative Example 3

[0099] The difference from Example 1 is that the water-based acrylic resin is replaced by an equal amount of acrylic acid; the rest are the same.

[0100] Comparative Example 4

[0101] The difference from Example 1 is that the silane coupling agent KH550 is replaced by an equal amount of dimethyldimethoxysilane; the rest are the same.

[0102] Comparative Example 5

[0103] The difference from Example 1 is that a special hyperbranched network polyacrylic resin for silicon-carbon negative electrodes, by mass fraction, is composed of: water-based acrylic resin 4 parts, butyl acrylate 6 parts, acrylamide 2 parts, diallylamine 1 part, acrylonitrile 2 parts, dodecyl mercaptan 0.1 part, emulsifier mixture 0.006 part, potassium persulfate 0.15 part; 20wt% aqueous lithium carbonate solution is used to adjust the pH to 7.

[0104] The preparation method of the emulsifier mixture is: mix dodecylphenol polyoxyethylene ether (CAS: 9014-92-0) with water at a mass ratio of 1:300 at 50°C for 20min to obtain the emulsifier mixture.

[0105] The preparation method of the special hyperbranched network polyacrylic resin for silicon-carbon negative electrodes is:

[0106] (1) Mix polyethylene glycol 6000, acrylic acid and water at a mass ratio of 1:15:50, and react for 30min at 25°C under stirring at a speed of 200rpm to obtain a water-based acrylic resin;

[0107] (2) Mix the emulsifier mixture, butyl acrylate, acrylamide, diallylamine, acrylonitrile and aqueous acrylic resin, add dodecyl mercaptan (CAS: 112-55-0) and potassium persulfate, and first heat to 70°C for 1h under nitrogen protection, and then heat to 80°C for 3.5h;

[0108] (3) After the reaction is completed, add 20wt% aqueous lithium carbonate solution to adjust the pH to 7 to obtain the product.

[0109] Comparative Example 6

[0110] The difference from Example 1 is that the preparation method of the hyperbranched network polyacrylic resin special for silicon-carbon negative electrodes is as follows:

[0111] (1) Mix polyethylene glycol 6000, acrylic acid and water in a mass ratio of 1:15:50 uniformly, and react at 25°C under stirring at a speed of 200rpm for 30min to obtain an aqueous acrylic resin;

[0112] (2) Mix the emulsifier mixture, butyl acrylate, acrylamide, diallylamine, acrylonitrile, silane coupling agent and aqueous acrylic resin, add dodecyl mercaptan and potassium persulfate, and first heat to 70°C for 1h under nitrogen protection, and then heat to 80°C for 3.5h;

[0113] (3) Cool to 40°C, add ethylenediamine and continue to react for 30min, and then add 20wt% aqueous lithium carbonate solution to adjust the pH to 7 to obtain the product; the rest is the same.

[0114] Comparative Example 7

[0115] Mix acrylic acid and deionized water in a mass ratio of 1:9 uniformly, add 0.01% sodium persulfate, and react at 70°C for 12h. After cooling, add lithium carbonate to adjust the pH to 7.

[0116] Test Example 1

[0117] The viscosities of the products of Examples and Comparative Examples were determined by a viscometer at a temperature of 25°C, and the results are shown in Table 1.

[0118] Test Example 2

[0119] Mix silicon-carbon, conductive carbon black and the product of Example or Comparative Example in a mass ratio of 8:1:1 to obtain a negative electrode slurry, coat the negative electrode slurry on the surface of a copper foil, and place it in a vacuum drying oven at 120°C to dry overnight, roll it, and form a negative electrode with a surface density of 4mg / cm 2 , and a compacted density of 1.77g / cm 3The electrode sheet was subjected to peel strength test: the electrode sheet of fixed size was pasted (3M glue) on the surface of the gauge, and stretched in the direction of 180°, and the average stress in the 20-80 mm stroke was recorded. The results are shown in Table 1. The peel degree test results of Example 1 and Comparative Example 7 are shown in the following figure: Figure 1

[0120] Table 1

[0121] Viscosity mPa.s Peel strength N / mm Example 1 50000 14 Example 2 40000 12 Example 3 80000 15 Example 4 50000 14 Example 5 100000 16 Comparative Example 1 20000 6.7 Comparative Example 2 40000 7.2 Comparative Example 3 80000 6.8 Comparative Example 4 80000 7.7 Comparative Example 5 60000 7.9 Comparative Example 6 50000 8.2 Comparative Example 7 45000 10.1

[0122] As can be seen from Table 1, the hyperbranched network polyacrylic acid resin obtained in Examples 1-5 has high viscosity and high peel strength, and the peel strength is 12-16 N / mm.

[0123] In Comparative Example 1, the diallylamine is replaced by the same mass of ethylene glycol dimethacrylate, and the viscosity of the hyperbranched network polyacrylic acid resin obtained is significantly reduced, and the peel strength is also significantly reduced. In Comparative Example 2, the diallylamine is replaced by the same mass of acrylamide, and the viscosity of the hyperbranched network polyacrylic acid resin obtained is the same as that of Example 2, but the peel strength is significantly reduced. In Comparative Example 3, the water-based acrylic resin is replaced by the same mass of acrylic acid, and the viscosity of the hyperbranched network polyacrylic acid resin obtained is high, but the peel strength is significantly reduced. Comparative Examples 1-3 show that the balance between viscosity and peel strength cannot be achieved by simply reacting any monomer.

[0124] In Comparative Example 4, the silane coupling agent KH550 is replaced by the same mass of dimethyl dimethoxy silane. In Comparative Example 5, there is no crosslinking agent and silane coupling agent. In Comparative Example 6, the silane coupling agent is reacted in step (2), and the viscosity of the hyperbranched network polyacrylic acid resin obtained is high, but the peel strength is significantly reduced, indicating that the balance between viscosity and peel strength cannot be achieved by simply adding any silane coupling agent and any sequence of adding the silane coupling agent.

[0125] Comparative Example 7 is a traditional adhesive, and the viscosity and peel strength are not as good as those of the hyperbranched network polyacrylic acid resin of Examples 1-5.

[0126] Test Example 3

[0127] In an argon glove box, a coin cell was assembled:

[0128] Counter electrode: lithium metal sheet;

[0129] Working electrode: the electrode sheet of Test Example 2;

[0130] Separator: Celgard2325;

[0131] ​Electrolyte: 1 mol / L LiPF6 (solvent is a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1);

[0132] Battery casing: CR2032 button battery casing;

[0133] The following tests were performed on the button battery:

[0134] (1) Charge and discharge performance: The charge and discharge current density is 0.1A / g and the voltage charge and discharge range is 0.01~3V in the Blue Electric test program.

[0135] (2) Cycling performance: In the Blue Electric test procedure, the charge / discharge current density was 0.2 A / g, the voltage charge / discharge range was 0.01–3 V, and the number of cycles was 200. The results are shown in Table 2; the performance results of Example 1 and Comparative Example 7 after 500 cycles are as follows: Figure 2 As shown.

[0136] Table 2

[0137]

[0138]

[0139] As shown in Table 2, the button batteries assembled using the hyperbranched network polyacrylic resin of Examples 1-5 have good initial charge-discharge performance and still have a specific capacity higher than 970 mA h / g after 200 cycles at 0.2 A / g. However, the button batteries assembled using the hyperbranched network polyacrylic resin of Comparative Examples 1-6 and the conventional binder of Comparative Example 7 have good initial charge-discharge performance, but their specific capacity is lower than 680 mA h / g after 200 cycles at 0.2 A / g.

[0140] Depend on Figure 2 It can be seen that the button cell assembled using the hyperbranched network polyacrylic acid resin of Example 1 still has a specific capacity of more than 900 mA h / g after 500 cycles under 0.2 A / g conditions; while the button cell assembled using the conventional binder of Comparative Example 7 has a specific capacity of less than 500 mA h / g after 500 cycles under 0.2 A / g conditions.

[0141] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A hyperbranched network polyacrylic acid resin for silicon-carbon anodes, characterized in that, By weight, the raw materials consist of 3-10 parts of water-based acrylic resin, 4-10 parts of monomer A, 2-6 parts of monomer B, 2-6 parts of monomer C, 60-80 parts of solvent, 0.1-0.2 parts of chain extender, 1-8 parts of crosslinking agent, 0.5-1 part of silane coupling agent, 0.005-0.09 parts of emulsifier mixture, 0.1-0.7 parts of initiator, and neutralizer; The preparation method of the aforementioned hyperbranched network polyacrylic acid resin for silicon-carbon anodes includes the following steps: (1) The acrylic monomer, crosslinking monomer and water are mixed evenly and stirred to react to obtain waterborne acrylic resin; (2) Mix emulsifier mixture, monomer A, monomer B, monomer C, solvent and waterborne acrylic resin, add chain extender and initiator, and react under nitrogen protection; (3) Cool, add crosslinking agent and silane coupling agent to continue the reaction, and add neutralizing agent to adjust the pH of the system to 7 after the reaction is completed; The acrylic monomer is selected from at least one of acrylic acid and methacrylic acid; the crosslinking monomer is selected from at least one of polyethylene glycol, ethylene glycol, hexanediol, pentanediol, β-cyclodextrin, sorbitol, N,N-dihydroxyaniline, polyetheramine, ethylenediamine and polyoxypropylene glycol; The temperature of the stirring reaction in step (1) is 25-30℃, the stirring time is 20-60 min, and the stirring speed is 200-300 rpm. The monomer A is an acrylate monomer; the monomer B is an acrylamide monomer; and the monomer C is selected from at least one of allylamine monomers and acrylonitrile monomers. The chain extender is selected from at least one of dodecyl mercaptan and 2-mercaptoethanol; The crosslinking agent is selected from polyethylene glycol, ethylene glycol, hexanediol, ethanolamine, pentanediol, β-hydroxylamine, etc. Cyclodextrin, sorbitol, N,N At least one of dihydroxyaniline, polyetheramine and ethylenediamine; The silane coupling agent is selected from at least one of KH560 and KH550.

2. The hyperbranched network polyacrylic acid resin for silicon-carbon anodes according to claim 1, characterized in that, The acrylamide monomers include at least one of acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N,N-methyleneacrylamide; the allylamine monomers are selected from at least one of diallylamine and triallylamine; and the acrylonitrile monomers are selected from at least one of acrylonitrile, N-methylacrylonitrile, and N-propylacrylonitrile.

3. The hyperbranched network polyacrylic acid resin for silicon-carbon anodes according to claim 1, characterized in that, The reaction described in step (2) includes two reaction stages. The temperature of the first reaction stage is 50-70℃ and the time is 1.5-2.5h. The reaction temperature of the second reaction stage is 70-85℃ and the time is 2.5-3.5h.

4. The application of the hyperbranched network polyacrylic acid resin for silicon-carbon anodes as described in any one of claims 1-3 in silicon-carbon anodes.

5. A negative electrode slurry, characterized in that, Includes the hyperbranched network polyacrylic acid resin for silicon-carbon anodes as described in any one of claims 1-3.

6. A silicon-carbon negative electrode, characterized in that, Includes the negative electrode slurry as described in claim 5.

7. A lithium-ion battery, characterized in that, Including the silicon-carbon anode sheet as described in claim 6.

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