An aqueous adhesive, its preparation method and application

Abstract

The present invention provides an aqueous adhesive and its preparation method and application. The raw materials for preparing the aqueous adhesive include diisocyanate, polyol, a chain extender containing a disulfide bond, and lipoic acid cross-linked modified polyacrylic acid; the raw materials for preparing the lipoic acid cross-linked modified polyacrylic acid include acrylic acid monomers, acrylate monomers, lipoic acid compounds, and polyethylene glycol diacrylate. The aqueous adhesive provided in the present invention has excellent adhesive force and self-healing performance. The battery negative electrode made of the aqueous adhesive has a high peel strength, and the prepared lithium-ion battery has good electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesive materials, and particularly relates to an aqueous adhesive and a preparation method and application thereof. Background Art

[0002] With the expansion of the use of lithium-ion secondary batteries, the requirements for improving energy density, reliability, and durability are also continuously increasing. As one of the key components of lithium batteries, the performance of the electrode directly determines the battery efficiency and cycle life. Among them, the negative electrode is obtained by coating a slurry made of a carbon material and an adhesive on the surface of a negative electrode current collector such as a copper foil, drying, and then cutting it into an appropriate size. As an important raw material for preparing the electrode, the adhesive can bond the active substances to each other and between the active substance and the current collector, thereby playing a role in preventing the active substance from peeling off from the current collector, so as to ensure the structural stability of the entire electrode during the charge and discharge cycle, and ensure good electronic conduction paths and stable electrical properties during the use of the battery.

[0003] Currently commonly used aqueous negative electrode adhesives such as sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), etc. have a single structure and insufficient mechanical strength, and their service life far fails to meet the standards for negative electrode materials with high volume effects.

[0004] Therefore, it is necessary to develop an aqueous adhesive with high bonding strength and self-healing properties. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an aqueous adhesive and a preparation method and application thereof. The aqueous adhesive has excellent bonding strength and self-healing properties. The battery negative electrode made of the aqueous adhesive has a high peel strength, and the prepared lithium-ion battery has good electrochemical performance.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides an aqueous adhesive, and the preparation raw materials of the aqueous adhesive include diisocyanate, polyol, a chain extender containing a disulfide bond, and lipoic acid cross-linked modified polyacrylic acid;

[0008] The preparation raw materials of the lipoic acid cross-linked modified polyacrylic acid include acrylic acid monomers, acrylate monomers, lipoic acid compounds, and polyethylene glycol diacrylate.

[0009] In the present invention, the raw materials for preparing the water-based adhesive include diisocyanate, polyol, a chain extender containing a disulfide bond and thioctic acid cross-linked modified polyacrylic acid. The prepared water-based adhesive has a polyurethane-polyacrylic acid double network structure, wherein the functionalized blocks formed by the chain extender containing a disulfide bond and the thioctic acid compound can more effectively improve the mechanical properties of the water-based adhesive, increase elasticity and toughness, and also make it rich in strong dynamic bond effects and chemical bond interactions, thereby giving the water-based adhesive higher bonding strength and self-healing properties.

[0010] Compared with the traditional waterborne polyurethane adhesive, the present invention adopts a more compatible disulfide bond-containing chain extender to replace the carboxylate hydrophilic chain extender, thereby improving the problem that the polyurethane has strong cohesion and weak interaction with the negative electrode active material; and by introducing lipoic acid cross-linked modified polyacrylic acid, it is ensured that its network has strong rigidity and adhesion; the disulfide bond-containing chain extender can start melt polymerization when it reaches 70°C, and can react without adding an organic solvent, which can improve the problem that the use of carboxylate hydrophilic chain extenders in the preparation of traditional waterborne polyurethane adhesives requires the addition of organic solvents to assist the reaction, which is not conducive to environmental protection.

[0011] Preferably, the diisocyanate includes any one of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI) or toluene diisocyanate (TDI) or a combination of at least two thereof.

[0012] Preferably, the polyol comprises polyethylene glycol.

[0013] Preferably, the disulfide bond-containing chain extender comprises disulfide diol.

[0014] Preferably, the dithiodiol comprises 2,2'-dithiodiethanol and / or 4,4'-dithiodiylbis(2-methylphenol).

[0015] Preferably, the raw materials for preparing the aqueous adhesive include the following components in parts by weight: 40-60 parts (for example, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts or 58 parts, etc.) of diisocyanate, 60-100 parts (for example, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 95 parts, etc.) of polyol, 10-30 parts (for example, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts or 28 parts, etc.) of disulfide bond-containing chain extender and 30-70 parts (for example, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts or 65 parts, etc.) of thioctic acid cross-linked modified polyacrylic acid.

[0016] Preferably, the weight proportion of the disulfide bond-containing chain extender in the raw materials for preparing the water-based adhesive is 15 to 25 parts.

[0017] Preferably, the weight proportion of lipoic acid cross-linked modified polyacrylic acid in the raw materials for preparing the water-based adhesive is 40 to 60 parts.

[0018] Preferably, the raw materials for preparing the water-based adhesive further include a tin catalyst.

[0019] Preferably, the tin catalyst includes dibutyltin dilaurate.

[0020] Preferably, the weight portion of the tin catalyst in the raw materials for preparing the aqueous adhesive is 0-1 part (for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part or 0.9 part, etc.).

[0021] Preferably, the raw materials for preparing the water-based adhesive further include a neutralizer.

[0022] Preferably, the neutralizing agent comprises an amine neutralizing agent.

[0023] Preferably, the amine neutralizing agent includes triethylamine and / or N,N-dimethylethanolamine.

[0024] Preferably, the weight proportion of the amine neutralizing agent in the raw material for preparing the aqueous adhesive is 1 to 10 parts (eg, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts or 9 parts, etc.).

[0025] Preferably, the raw materials for preparing the aqueous adhesive further include water.

[0026] Preferably, the weight proportion of water in the raw material for preparing the aqueous adhesive is 150-250 parts (e.g., 160 parts, 170 parts, 180 parts, 190 parts, 200 parts, 210 parts, 220 parts, 230 parts or 240 parts, etc.).

[0027] Preferably, the raw materials for preparing the thioctic acid cross-linked modified polyacrylic acid include the following components in parts by weight: 30-50 parts (for example, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts or 48 parts, etc.) of acrylic acid monomers, 10-30 parts (for example, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts or 28 parts, etc.) of acrylate monomers, 30-50 parts (for example, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts or 48 parts, etc.) of thioctic acid compounds and 1-10 parts (for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts or 9 parts, etc.) of polyethylene glycol diacrylate.

[0028] Preferably, the weight proportion of lipoic acid compounds in the raw materials for preparing the lipoic acid cross-linked modified polyacrylic acid is 35-45 parts.

[0029] Preferably, the acrylic monomer includes acrylic acid and / or methacrylic acid.

[0030] Preferably, the acrylate monomer includes hydroxyethyl acrylate and / or 2-phenoxyethyl acrylate.

[0031] Preferably, the lipoic acid compound includes lipoic acid and / or lipoic acid derivatives.

[0032] Preferably, the lipoic acid derivative includes ethyl hydroxyphenol modified lipoic acid.

[0033] Preferably, the raw materials for preparing the lipoic acid crosslinked modified polyacrylic acid further include an ammonium catalyst.

[0034] Preferably, the ammonium catalyst includes ammonium persulfate.

[0035] Preferably, the weight part of the ammonium catalyst in the raw materials for preparing the lipoic acid crosslinked modified polyacrylic acid is 0-1 part (such as 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part or 0.9 part, etc.).

[0036] Preferably, the lipoic acid crosslinked modified polyacrylic acid is prepared by the following method: mixing the acrylic monomer, the acrylate monomer and the ammonium catalyst for the first reaction, adding the lipoic acid compound for the second reaction, and adding polyethylene glycol diacrylate for the third reaction to obtain the lipoic acid crosslinked modified polyacrylic acid.

[0037] In the present invention, the lipoic acid compound undergoes thermal ring-opening polymerization to form a lipoic acid compound segment and a crosslinked structure, and polyethylene glycol diacrylate is used for end-capping to inhibit its depolymerization and stabilize the structure.

[0038] Preferably, the temperature of the first reaction is 75-85 °C (such as 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C or 84 °C, etc.), and the time is 2-4 h (such as 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3.0 h, 3.2 h, 3.4 h, 3.6 h or 3.8 h, etc.).

[0039] Preferably, the temperature of the second reaction is 110-130 °C (such as 112 °C, 114 °C, 116 °C, 118 °C, 120 °C, 122 °C, 124 °C, 126 °C or 128 °C, etc.), and the time is 0.3-1 h (such as 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h or 0.9 h, etc.).

[0040] Preferably, the temperature of the third reaction is 110-130 °C (such as 112 °C, 114 °C, 116 °C, 118 °C, 120 °C, 122 °C, 124 °C, 126 °C or 128 °C, etc.), and the time is 0.3-1 h (such as 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h or 0.9 h, etc.).

[0041] In a second aspect, the present invention provides a method for preparing the aqueous adhesive as described in the first aspect, and the preparation method includes the following steps:

[0042] (1) Mix diisocyanate and polyol, and react to obtain product A.

[0043] (2) Mix product A obtained in step (1) and a chain extender containing a disulfide bond, and react to obtain product B.

[0044] (3) Mix product B obtained in step (2) and lipoic acid crosslinked modified polyacrylic acid, and react to obtain the aqueous adhesive.

[0045] The aqueous adhesive prepared by the preparation method in the present invention has high structural controllability, and the multi-block structure can better improve the bonding defects between the anode active materials through functional design, maintain the structural stability, and improve the problems such as insufficient lithium conduction and conductivity. It can be used for the bonding of high-energy density anode materials; adding lipoic acid crosslinked modified polyacrylic acid in step (3) for reaction can achieve chain extension and end capping.

[0046] Preferably, the mixing in step (1) further includes mixing with a tin-based catalyst.

[0047] Preferably, the reaction in step (1) is carried out under a nitrogen atmosphere.

[0048] Preferably, the temperature of the reaction in step (1) is 70-80 °C (such as 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C or 79 °C, etc.), and the time is 1.5-2.5 h (such as 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h or 2.4 h, etc.).

[0049] Preferably, the temperature of the reaction in step (2) is 70-80 °C (such as 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C or 79 °C, etc.), and the time is 1-1.5 h (such as 1.05 h, 1.1 h, 1.15 h, 1.2 h, 1.25 h, 1.3 h, 1.35 h, 1.4 h or 1.45 h, etc.).

[0050] Preferably, the temperature of the reaction in step (3) is 75-85 °C (such as 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C or 84 °C, etc.), and the time is 1.5-2.5 h (such as 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h or 2.4 h, etc.).

[0051] Preferably, after the reaction in step (3), it further includes the steps of adding a neutralizing agent for neutralization and adding water for emulsification.

[0052] Preferably, the temperature of the neutralization is 20-40 °C (such as 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, 36 °C or 38 °C, etc.), and the time is 0.2-1 h (0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h or 0.9 h, etc.).

[0053] In a third aspect, the present invention provides a battery negative electrode, which includes a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material includes a negative electrode active material, a conductive agent and the aqueous binder as described in the first aspect.

[0054] Preferably, the negative electrode active material includes a silicon-based negative electrode active material.

[0055] Preferably, the conductive agent includes conductive carbon black.

[0056] In a fourth aspect, the present invention provides a lithium-ion battery, which includes the battery negative electrode as described in the third aspect.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] In the present invention, the aqueous binder prepared by crosslinking and modifying polyacrylic acid with diisocyanate, polyol, a chain extender containing a disulfide bond and lipoic acid has excellent adhesive force and self-healing performance. The battery negative electrode made of the aqueous binder has a high peel strength, and the prepared lithium-ion battery has good electrochemical performance. Description of the Drawings

[0059] Figure 1 It is the infrared spectrum of the lipoic acid-crosslinked modified polyacrylic acid prepared in Example 1;

[0060] Figure 2 It is the infrared spectrum of Product A prepared in Example 1;

[0061] Figure 3 It is the infrared spectrum of Product B prepared in Example 1;

[0062] Figure 4IR spectrum of the aqueous adhesive prepared in Example 1;

[0063] Figure 5 IR spectrum of the polyacrylic acid prepared in Comparative Example 1. Detailed implementation manners

[0064] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0065] The sources of some components in the following examples and comparative examples are as follows:

[0066] Polyethylene glycol diacrylate: product number is P109708, manufacturer is Aladdin.

[0067] Example 1

[0068] This example provides an aqueous adhesive and its preparation method. The preparation raw materials of the aqueous adhesive include the following components by weight: 50 parts of diisocyanate (isophorone diisocyanate), 80 parts of polyol (polyethylene glycol 1000), 20 parts of chain extender containing disulfide bond (2,2'-dithiobisethanol), 50 parts of lipoic acid cross-linked modified polyacrylic acid, 0.5 part of tin catalyst (dibutyltin dilaurate), 5 parts of neutralizer (N,N-dimethylethanolamine), and 200 parts of water.

[0069] The above lipoic acid cross-linked modified polyacrylic acid is prepared by the following method: Mix 40 parts by weight of acrylic acid monomers (acrylic acid), 20 parts by weight of acrylate monomers (2-phenoxyethyl acrylate) with 0.5 part by weight of ammonium catalyst (ammonium persulfate), react at 80 °C for 3 h, add 40 parts by weight of lipoic acid compounds (lipoic acid), react at 120 °C for 0.5 h, and then add 5 parts by weight of polyethylene glycol diacrylate and react at 120 °C for 0.5 h to obtain the lipoic acid cross-linked modified polyacrylic acid.

[0070] The preparation method of the aqueous adhesive includes the following steps:

[0071] (1) Add diisocyanate, polyol and tin catalyst into a four-necked flask, and react at 70 °C for 2 h under a nitrogen atmosphere to obtain product A;

[0072] (2) Add the chain extender containing disulfide bond to the product A prepared in step (1) and react at 80 °C for 1 h to obtain product B;

[0073] (3) Add lipoic acid cross-linked modified polyacrylic acid to the product B obtained in step (2) and react at 80 °C for 2 h, then cool down to 30 °C, add a neutralizing agent and carry out a neutralization reaction for 0.2 h, and add water for emulsifying dispersion for 0.5 h under stirring at 1500 rpm to obtain the aqueous adhesive.

[0074] Example 2

[0075] This example provides an aqueous adhesive and a preparation method thereof. The raw materials for preparing the aqueous adhesive include the following components by weight: 40 parts of diisocyanate (dicyclohexylmethane diisocyanate), 70 parts of polyol (polyethylene glycol 1000), 15 parts of chain extender containing disulfide bond (2,2'-dithiobisethanol), 40 parts of lipoic acid cross-linked modified polyacrylic acid, 0.5 part of tin catalyst (dibutyltin dilaurate), 5 parts of neutralizing agent (N,N-dimethylethanolamine), and 200 parts of water.

[0076] The above lipoic acid cross-linked modified polyacrylic acid is prepared by the following method: Mix 30 parts by weight of acrylic acid monomers (acrylic acid), 30 parts by weight of acrylate monomers (2-phenoxyethyl acrylate) with 0.5 part by weight of ammonium catalyst (ammonium persulfate) and react at 85 °C for 3 h, add 40 parts by weight of lipoic acid compounds (lipoic acid) and react at 120 °C for 0.5 h, add 10 parts by weight of polyethylene glycol diacrylate and react at 120 °C for 0.5 h to obtain the lipoic acid cross-linked modified polyacrylic acid.

[0077] The preparation method of the aqueous adhesive includes the following steps:

[0078] (1) Add diisocyanate, polyol and tin catalyst into a four-necked flask, and react at 75 °C for 2 h under a nitrogen atmosphere to obtain product A;

[0079] (2) Add a chain extender containing a disulfide bond to the product A obtained in step (1) and react at 80 °C for 1.2 h to obtain product B;

[0080] (3) Add lipoic acid cross-linked modified polyacrylic acid to the product B obtained in step (2) and react at 70 °C for 2.5 h, then cool down to 30 °C, add a neutralizing agent and carry out a neutralization reaction for 0.2 h, and add water for emulsifying dispersion for 0.5 h under stirring at 1500 rpm to obtain the aqueous adhesive.

[0081] Example 3

[0082] This embodiment provides an aqueous adhesive and a preparation method thereof. The raw materials for preparing the aqueous adhesive include the following components in parts by weight: 40 parts of diisocyanate (toluene diisocyanate), 100 parts of polyol (polyethylene glycol 1000), 20 parts of chain extender containing disulfide bond (4,4'-dithiobis(2-methylphenol)), 40 parts of lipoic acid crosslinked modified polyacrylic acid, 0.5 part of tin catalyst (dibutyltin dilaurate), 5 parts of neutralizer (N,N-dimethylethanolamine), and 200 parts of water.

[0083] The above lipoic acid crosslinked modified polyacrylic acid is prepared by the following method: Mix 30 parts by weight of acrylic acid monomer (acrylic acid), 30 parts by weight of acrylate monomer (2-phenoxyethyl acrylate), and 0.5 part by weight of ammonium catalyst (ammonium persulfate), react at 75 °C for 3 h, add 35 parts by weight of lipoic acid compound (lipoic acid), react at 120 °C for 0.5 h, add 10 parts by weight of polyethylene glycol diacrylate, and react at 120 °C for 0.5 h to obtain the lipoic acid crosslinked modified polyacrylic acid.

[0084] The preparation method of the aqueous adhesive includes the following steps:

[0085] (1) Add diisocyanate, polyol, and tin catalyst into a four-necked flask, react at 80 °C for 2 h under a nitrogen atmosphere to obtain product A;

[0086] (2) Add the chain extender containing disulfide bond to the product A obtained in step (1), react at 80 °C for 1.5 h to obtain product B;

[0087] (3) Add lipoic acid crosslinked modified polyacrylic acid to the product B obtained in step (2), react at 85 °C for 1.5 h, then cool down to 30 °C, add a neutralizer for neutralization reaction for 0.2 h, and add water for emulsification dispersion for 0.5 h under stirring at 1500 rpm to obtain the aqueous adhesive.

[0088] Example 4

[0089] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Example 1 is only that the weight fraction of the chain extender containing disulfide bond (2,2'-dithiodiethanol) is adjusted to 30 parts, and other conditions are the same as those in Example 1.

[0090] Example 5

[0091] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Example 1 is only that the weight fraction of the chain extender containing disulfide bond (2,2'-dithiodiethanol) is adjusted to 10 parts, and other conditions are the same as those in Example 1.

[0092] Example 6

[0093] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that the weight part of lipoic acid crosslinked modified polyacrylic acid is adjusted to 70 parts, and other conditions are the same as those in Embodiment 1.

[0094] Embodiment 7

[0095] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that the weight part of lipoic acid crosslinked modified polyacrylic acid is adjusted to 30 parts, and other conditions are the same as those in Embodiment 1.

[0096] Embodiment 8

[0097] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that the weight part of lipoic acid compound (lipoic acid) in the preparation process of lipoic acid crosslinked modified polyacrylic acid is adjusted to 50 parts, and other conditions are the same as those in Embodiment 1.

[0098] Embodiment 9

[0099] This embodiment provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that the weight part of lipoic acid compound (lipoic acid) in the preparation process of lipoic acid crosslinked modified polyacrylic acid is adjusted to 30 parts, and other conditions are the same as those in Embodiment 1.

[0100] Comparative Example 1

[0101] This comparative example provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that in the preparation raw materials of the aqueous adhesive, lipoic acid crosslinked modified polyacrylic acid is replaced with polyacrylic acid of the same mass. The polyacrylic acid is prepared by the following method: 40 parts by weight of acrylic acid monomers (acrylic acid), 20 parts by weight of acrylate monomers (2-phenoxyethyl acrylate) and 0.5 part by weight of ammonium catalysts (ammonium persulfate) are mixed and reacted at 80 °C for 3 h, and 5 parts by weight of polyethylene glycol diacrylate is added and reacted at 120 °C for 1 h to obtain the polyacrylic acid, and other conditions are the same as those in Embodiment 1.

[0102] Comparative Example 2

[0103] This comparative example provides an aqueous adhesive and a preparation method thereof. The difference from Embodiment 1 is only that the chain extender containing disulfide bonds (2,2'-dithiobisethanol) is replaced with dihydroxymethylpropionic acid of the same mass. The preparation method of the aqueous adhesive includes the following steps:

[0104] (1) Add diisocyanate, polyol and tin catalyst into a four-necked flask, and react at 70 °C for 2 h under a nitrogen atmosphere to obtain product A;

[0105] (2) Add dimethylolpropionic acid and 20 parts by weight of N-methylpyrrolidone to the product A obtained in step (1), and react at 80 °C for 1 h to obtain product B;

[0106] (3) Add lipoic acid-crosslinked modified polyacrylic acid to the product B obtained in step (2), react at 80 °C for 2 h, then cool down to 30 °C, add a neutralizing agent for neutralization reaction for 0.5 h, and add water for emulsification and dispersion for 0.5 h under stirring at 1500 rpm to obtain the aqueous adhesive.

[0107] Other conditions are the same as those in Example 1.

[0108] Application Example 1

[0109] This application example provides a battery negative electrode, which includes a current collector (copper foil) and a negative electrode material coated on the surface of the current collector; the negative electrode material includes a negative electrode active material (silicon monoxide) with a mass ratio of 9:1:1, a conductive agent (conductive carbon black super P), and the aqueous adhesive provided in Example 1;

[0110] The battery negative electrode is prepared by the following method: Mix the negative electrode active material, the conductive agent, and the aqueous adhesive provided in Example 1, uniformly coat it on the surface of the current collector, with a coating thickness of 100 μm, and dry it to obtain the battery negative electrode.

[0111] Application Examples 2-9

[0112] Application Examples 2-9 respectively provide a battery negative electrode, the difference from Application Example 1 is only that the aqueous adhesive provided in Example 1 is respectively replaced with the aqueous adhesives provided in Examples 2-9 with the same mass, and other conditions are the same as those in Application Example 1.

[0113] Comparative Application Examples 1-2

[0114] Comparative Application Examples 1-2 respectively provide a battery negative electrode, the difference from Application Example 1 is only that the aqueous adhesive provided in Example 1 is respectively replaced with the aqueous adhesives provided in Comparative Examples 1-2 with the same mass, and other conditions are the same as those in Application Example 1.

[0115] Perform the following performance tests on the battery negative electrodes provided in the above Application Examples 1-9 and Comparative Application Examples 1-2.

[0116] (1) Peel strength: Peel the battery negative electrode with a 3M tape at 180° under a universal tensile machine. The width of the tested battery negative electrode is 18 mm, the peel length is 100 mm, and the peel speed is 50 mm / min to obtain a peel strength curve, and take the average value.

[0117] (2)Electrochemical performance: Assemble the battery negative electrode, electrolyte, and separator into a coin-type half-cell CR2032 for electrochemical performance testing;

[0118] The above-mentioned electrolyte is made by mixing LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC). The concentration of LiPF6 is 1 mol / L, and the volume ratio of ethylene carbonate to diethyl carbonate is 1:1;

[0119] The above-mentioned separator is a polypropylene separator;

[0120] Electrochemical performance testing: Test the cycle performance of the battery in a Neware charge-discharge system. After standing for 10 h at 25 °C, activate it at a small current density of 0.05 A / g for 3 cycles, and then perform constant current charge-discharge testing at a current density of 0.5 A / g to obtain the capacity at 100 cycles.

[0121] The test results are shown in Table 1 below:

[0122] Table 1

[0123]

[0124] As can be seen from the content of Table 1, the peel strength of the battery negative electrodes prepared in Application Examples 1-9 is ≥3.23 N, and the capacity of the coin-type half-cell CR2032 at 100 cycles is ≥502.46 mAh / g.

[0125] The number average molecular weight of the aqueous adhesive prepared in Example 1 was measured by gel permeation chromatography (GPC) to be 32156 g / mol, and the weight average molecular weight was 73513 g / mol.

[0126] Figure 1 is the infrared spectrum of lipoic acid cross-linked modified polyacrylic acid prepared in Example 1. Lipoic acid cross-linked modified polyacrylic acid shows a characteristic absorption peak of "-C-O-C-" at a wave number of 1142 cm -1 and a characteristic absorption peak of "C=O" at a wave number of 1724 cm -1 and a broad characteristic absorption peak of "-O-H" at a wave number of 3400 cm -1 , indicating the presence of ester groups and carboxyl groups; characteristic peaks of aromatic rings appear at 1600 cm -1 and 1640 cm -1 , indicating that 2-phenoxyethyl acrylate has successfully polymerized with other components. A characteristic absorption peak of "-C-S-" appears at a wave number of 670 cm -1 , indicating that lipoic acid has successfully reacted with other components.

[0127] Figure 2This is the infrared spectrum of product A obtained in Example 1. A characteristic absorption peak of "-NCO" appears at a wavenumber of 2200 cm -1 . After product A reacts with 2,2'-dithiobis(ethanol), the infrared spectrum of the resulting product B ( Figure 3 ) does not show the characteristic absorption peak of "-NCO" attributed to product A, indicating that product A and 2,2'-dithiobis(ethanol) have successfully reacted to form product B. Since the content of 2,2'-dithiobis(ethanol) is relatively low and the content of "-C-S-" is low, the Figure 3 does not show the "-C-S-" absorption peak.

[0128] Figure 4 This is the infrared spectrum of the aqueous adhesive obtained in Example 1. It contains the characteristic absorption peak of "-C-S-" of lipoic acid-crosslinked modified polyacrylic acid, and the characteristic absorption peak of "-C-O-C" is significantly enhanced, indicating successful reaction to form the aqueous adhesive. A broad characteristic peak appears at 3200 - 3500 cm -1 , indicating strong hydrogen bonding therein.

[0129] Figure 5 This is the infrared spectrum of polyacrylic acid obtained in Comparative Example 1, in which lipoic acid was not added for reaction and the "-C-S-" absorption peak did not appear.

[0130] Compared with Application Example 1, if the weight fraction of the chain extender containing disulfide bonds in the aqueous adhesive is too high (Application Example 4), the molecular weight of the pre-prepared product B is too large, resulting in a large hydrogen bond force in the polyurethane network, low adhesion of the prepared battery anode, and a decline in electrochemical performance. If the weight fraction of the chain extender containing disulfide bonds in the aqueous adhesive is too low (Application Example 5), the molecular weight of the pre-prepared product B is low, and the adhesion of the battery anode prepared with this aqueous adhesive is low, and the electrochemical performance declines. Thus, it can be seen that the aqueous adhesive prepared with the weight fraction of the chain extender containing disulfide bonds in the aqueous adhesive within a specific range has better performance.

[0131] Compared with Application Example 1, if the weight fraction of lipoic acid-crosslinked modified polyacrylic acid in the aqueous adhesive is too high (Application Example 6), the prepared battery anode is rigid and has poor elasticity, and the electrochemical performance declines. If the weight fraction of lipoic acid-crosslinked modified polyacrylic acid in the aqueous adhesive is too low (Application Example 7), the self-healing property of the prepared battery anode is poor, the rigidity is low, and the electrochemical performance declines. Thus, it can be seen that the aqueous adhesive prepared with the weight fraction of lipoic acid-crosslinked modified polyacrylic acid in the aqueous adhesive within a specific range has better performance.

[0132] Compared with Application Example 1, if the weight fraction of lipoic acid compounds (lipoic acid) is too high (Application Example 8) during the preparation of lipoic acid-crosslinked modified polyacrylic acid, the polymer network in the water-based adhesive lacks rigidity and is prone to deformation due to volume effects, resulting in a decline in the electrochemical performance of the prepared battery anode; if the weight fraction of lipoic acid compounds (lipoic acid) is too low (Application Example 9) during the preparation of lipoic acid-crosslinked modified polyacrylic acid, the self-healing performance is poor, the adhesion of the prepared battery anode is low, and the electrochemical performance declines; thus, it can be seen that the water-based adhesive prepared with the weight fraction of lipoic acid compounds within a specific range during the preparation of lipoic acid-crosslinked modified polyacrylic acid has better performance.

[0133] Compared with Application Example 1, if lipoic acid-crosslinked modified polyacrylic acid is replaced with polyacrylic acid (Comparative Application Example 1), the interaction between polyacrylic acid and polyurethane is low, resulting in a decline in the adhesion of the prepared battery anode and a significant decline in the electrochemical performance.

[0134] Compared with Application Example 1, if the chain extender containing disulfide bonds is replaced with dimethylolpropionic acid (Comparative Application Example 2), the adhesion of the prepared battery anode is low and the electrochemical performance declines.

[0135] The applicant declares that the present invention uses the above embodiments to illustrate the process method of the present invention, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A water-based adhesive, characterized in that: The raw materials for preparing the water-based adhesive include the following components by weight: 40-60 parts of diisocyanate, 60-100 parts of polyol, 10-30 parts of a chain extender containing a disulfide bond, and 30-70 parts of thioctic acid cross-linked modified polyacrylic acid; The polyol includes polyethylene glycol; The lipoic acid cross-linked modified polyacrylic acid is prepared by the following method: acrylic acid monomers, acrylic acid ester monomers and ammonium catalysts are mixed for a first reaction, lipoic acid compounds are added for a second reaction, and polyethylene glycol diacrylate is added for a third reaction to obtain the lipoic acid cross-linked modified polyacrylic acid; The lipoic acid compound is lipoic acid and / or ethylhydroxyphenol modified lipoic acid.

2. The water-based adhesive according to claim 1, characterized in that: The diisocyanate includes any one of isophorone diisocyanate, dicyclohexylmethane diisocyanate or toluene diisocyanate or a combination of at least two thereof; The disulfide bond-containing chain extender includes disulfide diol; The dithiodiol includes 2,2'-dithiodiethanol and / or 4,4'-dithiodiylbis(2-methylphenol).

3. The water-based adhesive according to claim 1, characterized in that: The raw materials for preparing the water-based adhesive also include a tin catalyst; The tin catalyst includes dibutyltin dilaurate; The weight portion of the tin catalyst in the raw materials for preparing the water-based adhesive is 0.1 to 1 part; The raw materials for preparing the water-based adhesive also include a neutralizing agent; The neutralizing agent includes an amine neutralizing agent; The amine neutralizing agent includes triethylamine and / or N,N-dimethylethanolamine; The weight proportion of the amine neutralizer in the raw material for preparing the water-based adhesive is 1 to 10 parts; The raw materials for preparing the water-based adhesive also include water; The weight proportion of water in the raw materials for preparing the water-based adhesive is 150 to 250 parts.

4. The water-based adhesive according to claim 1, characterized in that: The raw materials for preparing the lipoic acid cross-linked modified polyacrylic acid include the following components by weight: 30-50 parts of acrylic acid monomers, 10-30 parts of acrylate monomers, 30-50 parts of lipoic acid compounds and 1-10 parts of polyethylene glycol diacrylate; The acrylic monomers include acrylic acid and / or methacrylic acid; The acrylic acid ester monomers include hydroxyethyl acrylate and / or 2-phenoxyethyl acrylate; The raw materials for preparing the lipoic acid cross-linked modified polyacrylic acid also include an ammonium catalyst; The ammonium catalyst includes ammonium persulfate; The weight proportion of the ammonium catalyst in the raw materials for preparing the lipoic acid cross-linked modified polyacrylic acid is 0.1 to 1 part.

5. The water-based adhesive according to claim 1, characterized in that: The temperature of the first reaction is 75-85°C and the time is 2-4 h; The temperature of the second reaction is 110-130°C and the time is 0.3-1 h; The temperature of the third reaction is 110-130° C., and the time is 0.3-1 h.

6. A method for preparing a water-based adhesive according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) mixing diisocyanate and polyol, reacting to obtain product A; (2) mixing the product A obtained in step (1) and a disulfide bond-containing chain extender, and reacting them to obtain a product B; (3) The product B obtained in step (2) and thioctic acid cross-linked modified polyacrylic acid are mixed and reacted to obtain the water-based adhesive.

7. The preparation method according to claim 6, characterized in that: The mixing in step (1) further comprises mixing with the tin catalyst; The reaction in step (1) is carried out under a nitrogen atmosphere; The reaction temperature in step (1) is 70-80°C and the reaction time is 1.5-2.5 h; The reaction temperature in step (2) is 70-80°C and the reaction time is 1-1.5 h; The reaction temperature in step (3) is 75-85°C and the reaction time is 1.5-2.5 h; After the reaction in step (3), the steps of adding the neutralizing agent for neutralization and adding the water for emulsification are also included; The neutralization temperature is 20-40° C. and the time is 0.2-1 h.

8. A battery negative electrode, characterized in that: The battery negative electrode comprises a current collector and a negative electrode material coated on the surface of the current collector; the negative electrode material comprises a negative electrode active material, a conductive agent and an aqueous binder as claimed in any one of claims 1 to 5.

9. A lithium ion battery, characterized in that: The lithium-ion battery comprises the battery negative electrode as claimed in claim 8.

Images