A silicon negative electrode binder, silicon negative electrode material and preparation method thereof

Abstract

The invention discloses a binder for silicon negative electrode, and its raw materials include: triamine monomer, diamine monomer, dianhydride monomer, 2-(6-isocyanate hexamethyleneamide)-6-methyl-4-[H]-pyrimidone. The invention also discloses a silicon negative electrode material, and its raw materials include: silicon active material, conductive agent and binder. The invention also discloses a method for preparing the above-mentioned silicon negative electrode material, comprising the following steps: in an inert gas atmosphere, taking diamine monomer and dianhydride monomer to react in an organic solvent, then adding triamine monomer to continue the reaction, and then adding 2-(6-isocyanate hexamethyleneamide)-6-methyl-4-[H]-pyrimidone to continue the reaction to obtain a polyamic acid solution; then the polyamic acid solution, silicon active material, and conductive agent are mixed, applied to the surface of the current collector, dried, and imidized to obtain a silicon negative electrode material. The present invention has good bonding performance and toughness performance, and can effectively suppress the volume expansion of the silicon negative electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of binders, and in particular to a binder for silicon negative electrodes, a silicon negative electrode material and a preparation method thereof. Background Art

[0002] The performance of lithium-ion batteries is greatly dependent on the positive and negative active materials. In order to meet the requirements of various fields for high-energy and high-power lithium-ion batteries, researchers have invested a lot of energy in studying active materials, such as silicon, germanium and tin. Among them, silicon active materials stand out in the field of lithium-ion battery negative electrodes due to their advantages of low cost, high capacity and low potential. However, there is a defect that cannot be ignored in silicon negative electrode materials, that is, when silicon negative electrodes are embedded with lithium, their volume will expand, and its volume expansion can even reach 360% of the original volume, resulting in a significant reduction in battery performance, which seriously restricts the application of silicon negative electrodes. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a binder for silicon negative electrode, a silicon negative electrode material and a preparation method thereof. The present invention has good bonding performance and toughness performance, can effectively inhibit the volume expansion of the silicon negative electrode, and improve the electrical properties of the silicon negative electrode.

[0004] The invention provides a binder for silicon negative electrode, the raw materials of which include: triamine monomer, diamine monomer, dianhydride monomer and 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidone.

[0005] Preferably, the molar ratio of the triamine monomer, the diamine monomer, the dianhydride monomer, and 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidinone is 1:1:1.9-2.1:0.4-0.6.

[0006] Preferably, the triamine monomer is at least one of 1,3,5-tris(4-aminophenoxy)benzene and 1,3,5-tris(4-amino-2-trifluoromethylphenoxy)benzene.

[0007] Preferably, the diamine monomer is at least one of 2-(3-aminophenyl)-5-aminobenzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0008] The dianhydride monomer may be: 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, pyromellitic acid dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and the like.

[0009] The present invention also proposes a silicon negative electrode material, the raw materials of which include: silicon active material, conductive agent and binder, wherein the binder is the above-mentioned binder for silicon negative electrode.

[0010] Preferably, the weight ratio of the silicon active material, the conductive agent and the binder is 6-7:1.5-2:1.5-2.

[0011] The conductive agent may be conductive carbon black, acetylene black, Ketjen black, graphite, or the like.

[0012] The present invention also proposes a method for preparing the above-mentioned silicon negative electrode material, comprising the following steps: in an inert gas atmosphere, taking a diamine monomer and a dianhydride monomer to react in an organic solvent, then adding a triamine monomer to continue the reaction, and then adding 2-(6-isocyanate hexamethyleneamide)-6-methyl-4-[H]-pyrimidone to continue the reaction to obtain a polyamic acid solution; then mixing the polyamic acid solution, the silicon active material, and the conductive agent, coating them on the surface of the current collector, drying, and imidizing to obtain the silicon negative electrode material.

[0013] Preferably, the diamine monomer and the dianhydride monomer are reacted in an organic solvent at room temperature for 1-2 hours, and then the triamine monomer is added and the reaction is continued at room temperature for 1-2 hours.

[0014] Preferably, 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidinone is added and the reaction is continued at room temperature for 1-2 hours.

[0015] Preferably, the imidization procedure is: keeping warm at 140-160° C., 220-240° C., 260-280° C. for 0.5-1 h respectively.

[0016] Preferably, the solid content of the polyamic acid solution is 10-15 wt %.

[0017] The organic solvent may be N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide or the like.

[0018] Beneficial effects:

[0019] The invention sequentially copolymerizes a diamine monomer, a triamine monomer and a dianhydride monomer to form a network structure of polyamic acid, greatly improves the strength and toughness of the binder, and suppresses the problem of silicon volume expansion during charging and discharging; and adjusts the molar ratio of the diamine monomer, the triamine monomer and the dianhydride monomer so that a plurality of active amino groups remain in the polyamic acid, and then reacts with 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidone to introduce pyrimidone groups and amide groups, which can form multiple strong hydrogen bonds with silicon negative electrode materials, improve the bonding performance of the binder, adhere closely to the surface of the silicon active material, and effectively suppress the expansion of silicon volume; and the diamine monomer is selected from 2-(3-aminophenyl)-5-aminobenzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole, which can also form hydrogen bonds with the silicon negative electrode material, further improve the bonding performance of the binder, and suppress the silicon volume expansion. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in detail below through specific embodiments.

[0021] Example 1

[0022] A method for preparing a silicon negative electrode material comprises the following steps:

[0023] Under nitrogen protection, 10 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 19 mmol of 3,3',4,4'-benzophenonetetracarboxylic dianhydride were dissolved in N,N-dimethylacetamide, and the mixture was stirred and reacted at room temperature for 1 hour. Then, 10 mmol of 1,3,5-tris(4-aminophenoxy)benzene was added, and the mixture was stirred and reacted at room temperature for 2 hours. Then, 6 mmol of 2-(6-isocyanate hexylamineamide)-6-methyl-4-[H]-pyrimidone was added, and the mixture was stirred and reacted at room temperature for 2 hours. The solid content was adjusted to 10 wt% to obtain a polyamic acid solution.

[0024] Then, 20 g of polyamic acid solution, 6 g of nano-silicon active material, and 2 g of acetylene black were mixed, coated on the cleaned and dried copper foil surface, dried at 80°C for 24 h, and then imidized at 140°C, 220°C, and 260°C for 1 h respectively to obtain the silicon negative electrode material.

[0025] Example 2

[0026] A method for preparing a silicon negative electrode material comprises the following steps:

[0027] Under nitrogen protection, 10 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 21 mmol of 3,3',4,4'-benzophenonetetracarboxylic dianhydride were dissolved in N,N-dimethylacetamide, stirred and reacted at room temperature for 2 hours, and then 10 mmol of 1,3,5-tris(4-amino-2-trifluoromethylphenoxy)benzene was added, and the stirring reaction was continued at room temperature for 1 hour, and then 4 mmol of 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidone was added, and the stirring reaction was continued at room temperature for 1 hour, and the solid content was adjusted to 15wt% to obtain a polyamic acid solution;

[0028] Then, 10 g of polyamic acid solution, 7 g of nano-silicon active material, and 1.5 g of acetylene black were mixed, coated on the cleaned and dried copper foil surface, dried at 80°C for 24 h, and then imidized at 160°C, 240°C, and 280°C for 0.5 h, respectively, to obtain the silicon negative electrode material.

[0029] Example 3

[0030] A method for preparing a silicon negative electrode material comprises the following steps:

[0031] Under nitrogen protection, 10 mmol of 2-(3-aminophenyl)-5-aminobenzimidazole and 20 mmol of 3,3',4,4'-benzophenonetetracarboxylic dianhydride were dissolved in N,N-dimethylacetamide, and the mixture was stirred and reacted at room temperature for 1.5 h. Then, 10 mmol of 1,3,5-tris(4-aminophenoxy)benzene was added, and the mixture was stirred and reacted at room temperature for 1.5 h. Then, 5 mmol of 2-(6-isocyanate hexylamineamide)-6-methyl-4-[H]-pyrimidone was added, and the mixture was stirred and reacted at room temperature for 1.5 h. The solid content was adjusted to 10 wt % to obtain a polyamic acid solution.

[0032] Then, 15 g of polyamic acid solution, 6.5 g of nano-silicon active material and 2 g of acetylene black were mixed, coated on the cleaned and dried copper foil surface, dried at 80°C for 24 h, and then imidized at 150°C, 230°C and 270°C for 1 h respectively to obtain silicon negative electrode material.

[0033] Comparative Example 1

[0034] No 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidinone was added, and "20 mmol of 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride" was replaced with "25 mmol of 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride", and the rest was the same as in Example 3.

[0035] Comparative Example 2

[0036] The “2-(3-aminophenyl)-5-aminobenzimidazole” is replaced by “4,4′-diaminodiphenyl ether”, and the rest is the same as in Example 3.

[0037] Comparative Example 3

[0038] No 1,3,5-tris(4-aminophenoxy)benzene was added, and "10 mmol of 2-(3-aminophenyl)-5-aminobenzimidazole" was replaced with "40 mmol of 2-(3-aminophenyl)-5-aminobenzimidazole", and the rest was the same as in Example 3.

[0039] The silicon negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as negative electrodes, respectively, and lithium sheets were used as positive electrodes. A mixed solution of 1 mol / L LiPF6 in EC and EMC (v / v=1:1) was used as an electrolyte solution to assemble button-type batteries. The button-type batteries prepared in the above examples and comparative examples were subjected to charge and discharge tests, and the results are shown in Table 1.

[0040] Table 1 Test results

[0041]

[0042] It can be seen from Table 1 that the silicon negative electrode material of the present invention has a small expansion rate and good electrical properties.

[0043] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A binder for silicon negative electrode, characterized in that: The raw materials include: triamine monomer, diamine monomer, dianhydride monomer, 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidinone; The molar ratio of the triamine monomer, the diamine monomer, the dianhydride monomer, and 2-(6-isocyanate hexanamide)-6-methyl-4-[H]-pyrimidinone is 1:1:1.9-2.1:0.4-0.6; The triamine monomer is at least one of 1,3,5-tris(4-aminophenoxy)benzene and 1,3,5-tris(4-amino-2-trifluoromethylphenoxy)benzene; The diamine monomer is at least one of 2-(3-aminophenyl)-5-aminobenzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole; The dianhydride monomer is one of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, pyromellitic acid dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

2. A silicon negative electrode material, characterized in that: The raw materials include: silicon active material, conductive agent and binder, wherein the binder is the binder for silicon negative electrode as claimed in claim 1.

3. The silicon negative electrode material according to claim 2, characterized in that: The weight ratio of the silicon active material, the conductive agent and the binder is 6-7:1.5-2:1.5-2.

4. A method for preparing the silicon negative electrode material as claimed in claim 2 or 3, characterized in that: The method comprises the following steps: in an inert gas atmosphere, taking a diamine monomer and a dianhydride monomer to react in an organic solvent, then adding a triamine monomer to continue the reaction, and then adding 2-(6-isocyanate hexamethyleneamide)-6-methyl-4-[H]-pyrimidone to continue the reaction to obtain a polyamic acid solution; then mixing the polyamic acid solution, a silicon active material and a conductive agent, coating the mixture on the surface of a current collector, drying, and imidizing to obtain a silicon negative electrode material.

5. The method for preparing the silicon negative electrode material according to claim 4, characterized in that: The diamine monomer and the dianhydride monomer are reacted in an organic solvent at room temperature for 1-2 hours, and then the triamine monomer is added to continue the reaction at room temperature for 1-2 hours.

6. The method for preparing the silicon negative electrode material according to claim 4, characterized in that: Add 2-(6-isocyanate hexylamine amide)-6-methyl-4-[H]-pyrimidinone and continue the reaction at room temperature for 1-2 hours.

7. The method for preparing the silicon negative electrode material according to claim 4, characterized in that: The imidization procedure is: keep warm at 140-160°C, 220-240°C, and 260-280°C for 0.5-1h respectively.

8. The method for preparing the silicon negative electrode material according to claim 4, characterized in that: The solid content of the polyamic acid solution is 10-15wt%.

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