Preparation method and use of lithium ion battery binder

Abstract

A preparation method and use of a lithium ion battery binder, relating to the technical field of lithium ion battery materials. The method comprises the following steps: (1) dissolving 1,3,5-triaminobenzene and polyacrylic acid in deionized water, and uniformly stirring at room temperature to obtain a mixed solution; (2) enabling the mixed solution to stand still at the room temperature to complete a cross-linking reaction to obtain a hydrogel; and (3) carrying out vacuum filtration on the hydrogel obtained in step (2), and then drying under a vacuum condition to obtain a lithium ion battery binder. When the binder is applied to a silicon-based negative electrode material of a lithium ion battery, a good binding effect can be achieved with a small amount of usage of the binder, and the binder significantly improves the film-forming property of the material, and has the advantages that raw materials are cheap and easily available, a preparation method is simple, environmental friendliness is achieved, and no pollution is produced. A lithium ion secondary battery prepared by using the binder has the characteristics of high specific capacity of an active material, long cycle service life of the battery, etc.

Description

Preparation method and application of lithium ion battery binder Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery materials, and in particular relates to a preparation method and application of a lithium ion battery binder. Background Art

[0002] Silicon is an ideal negative electrode material for lithium-ion batteries. On the one hand, the theoretical specific capacity of silicon (4200mAh g -1 ) is much higher than graphite (372mAh g -1 On the other hand, silicon is abundant in the Earth's crust, providing an inexhaustible source of raw materials for the preparation of lithium-ion batteries. Therefore, silicon anodes for lithium-ion batteries will be a major energy source in the future. However, during the process of delithiation and intercalation, silicon undergoes drastic volume changes, which in turn causes the silicon particles to rupture and fall off, leading to the fragmentation and re-formation of the SEI film, ultimately resulting in significant electrolyte consumption. Furthermore, the SEI film reformation process increases the film thickness, thereby increasing the internal resistance of the silicon anode and affecting the performance of the lithium-ion battery. Fracture of the silicon anode can also damage its internal structure, thereby inhibiting the electrode's ability to transport lithium ions. Binders play a crucial role in silicon anodes. Binders can connect silicon particles and the current collector through hydrogen bonds, covalent bonds, and dipole forces, thereby increasing the cohesion of the silicon anode. This increased electrode cohesion helps mitigate the expansion and fragmentation of silicon particles, thereby reducing side reactions during operation. PVDF, as an oily binder, can be used in graphite anodes, but it cannot form a tight bond with silicon particles. Newly developed aqueous binders such as CMC, SA, and GG, due to their abundant polar groups, can form strong interactions with Si-OH groups, thereby mitigating silicon particle expansion. However, because these binders are long-chain organic compounds, they can aggregate within the electrode. This aggregation leads to uneven stress distribution within the silicon anode, making it susceptible to cracking and dislodging.

[0003] In order to solve the above problems, the present invention uses 1,3,5-triaminobenzene to connect multiple long-chain organic substances, alleviate stress unevenness, and improve the structural stability and cycle stability of the silicon negative electrode.

[0004] In view of this, the present invention proposes a method for preparing a lithium-ion battery binder to solve the problem of uneven stress of the silicon negative electrode caused by agglomeration of general binders.

[0005] Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, the present invention specifically proposes a method for preparing a lithium-ion battery binder, which uses 1,3,5-triaminobenzene to cross-link multiple polyacrylic acid molecules to form a macromolecular hydrogel. The obtained polymer binder has a stress dissipation effect, alleviates stress unevenness, and improves the structural stability and cycle stability of the silicon negative electrode.

[0007] To achieve the above object, the present invention provides a method for preparing a lithium ion battery binder, comprising the following steps:

[0008] (1) dissolving 1,3,5-triaminobenzene and polyacrylic acid (PAA) in deionized water and stirring at room temperature to obtain a mixed solution;

[0009] (2) allowing the mixture to stand at room temperature to complete the cross-linking reaction and obtain a hydrogel;

[0010] (3) vacuum filtering the hydrogel obtained in step (2), and then drying it under vacuum conditions to obtain a lithium ion battery binder.

[0011] Furthermore, the mass ratio of the 1,3,5-triaminobenzene to the polyacrylic acid is 0.02-3, and the concentration of the mixed solution is 50 g / L-100 g / L.

[0012] In order to achieve sufficient cross-linking of 1,3,5-triaminobenzene and polyacrylic acid, the standing time in step (2) is 6-16 hours. During the cross-linking process, due to the presence of -NH2 steric hindrance in 1,3,5-triaminobenzene, self-polymerization is difficult to occur, but the polyacrylic acid is linked to -NH2, thereby achieving a cross-linking reaction between 1,3,5-triaminobenzene and polyacrylic acid to form a macromolecular hydrogel.

[0013] Preferably, the drying temperature in step (4) is 80-100° C., and the drying time is 1-24 h.

[0014] Another object of the present invention is to provide a lithium-ion battery binder prepared by the method for use in a lithium battery silicon negative electrode. The lithium-ion battery binder is mixed with a silicon-based negative electrode material to prepare a lithium battery negative electrode sheet. The negative electrode sheet produced by mixing the macromolecular binder with the silicon-based negative electrode material exhibits silicon powder breakage during charge and discharge. However, because the silicon powder is bound to the macromolecular binder, even if the silicon powder breaks, it remains integrated with the binder molecules, preventing volume expansion and providing excellent mechanical and cycling stability for the silicon negative electrode.

[0015] Furthermore, the lithium-ion battery binder and the silicon-based negative electrode material are mixed in deionized water to form a negative electrode slurry, which is then coated on a copper foil, dried and sliced ​​to obtain a silicon negative electrode sheet. Beneficial effects:

[0016] (1) The present invention uses 1,3,5-triaminobenzene to cross-link multiple polyacrylic acid molecules to form a macromolecular hydrogel to obtain a polymer binder. The binder is used to prepare a silicon negative electrode to enhance the mechanical electrochemical properties between silicon nanoparticles and the binder, and has a stress dissipation effect, reduces stress unevenness, and improves the structural stability and cycle stability of the silicon negative electrode.

[0017] (2) The binder prepared by the present invention can achieve a good bonding effect with a small amount when applied to silicon-based lithium-ion battery negative electrode materials, and can significantly improve the film-forming properties of the material; when used as a binder for silicon negative electrode active materials to be assembled into lithium-ion secondary batteries, it has high cycle stability and exhibits good electrochemical properties, enabling the silicon negative electrode to achieve high mechanical strength and long cycle life (500 cycles).

[0018] (3) The present invention is simple to operate, has low production cost, requires simple equipment, and is easy to mass produce. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below with reference to specific embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0020] The preparation and testing process of the button half-cell of the present invention is as follows:

[0021] 2g of silicon-based anode material (10nm-60nm) was mixed with 0.05g-1g of the prepared binder in an aqueous solution and stirred to form a uniform anode slurry. This slurry was evenly coated on copper foil, then dried at 120°C, roll-pressed, and punched to produce a circular silicon anode sheet. After vacuum drying at 120°C, the sheet was placed in a glove box with a dry argon atmosphere (the H2O and O2 contents in the glove box were less than 0.1ppm) and paired with a metal lithium electrode to form a button-type half-cell. The electrolyte used was 1M lithium hexafluorophosphate (EC / DMC / EMC = 1:1:1 (v / v)), and the separator was polypropylene.

[0022] Example 1

[0023] (1) Dissolve 0.5 g of 1,3,5-triaminobenzene and 1 g of polyacrylic acid (PAA) in 20 mL of deionized water and stir at room temperature to obtain a mixed solution;

[0024] (2) the mixed solution was allowed to stand at room temperature for 12 h, and the amino groups and hydroxyl groups formed hydrogen bonds to complete the crosslinking reaction, thereby obtaining a hydrogel;

[0025] (3) vacuum filtering the hydrogel obtained in step (2) and rinsing with excess deionized water to remove excess impurities and by-products, and then drying the filter cake at 100° C. under vacuum conditions for 12 hours to remove excess moisture to obtain a lithium-ion battery binder.

[0026] Example 2

[0027] (1) Dissolve 0.5 g of 1,3,5-triaminobenzene and 4 g of polyacrylic acid (PAA) in 25 mL of deionized water and stir at room temperature to obtain a mixed solution;

[0028] (2) the mixed solution was allowed to stand at room temperature for 6 h, and the amino groups and hydroxyl groups formed hydrogen bonds to complete the crosslinking reaction, thereby obtaining a hydrogel;

[0029] (3) vacuum filtering the hydrogel obtained in step (2) and rinsing with excess deionized water to remove excess impurities and by-products, and then drying the filter cake at 80° C. under vacuum conditions for 24 hours to remove excess moisture to obtain a lithium-ion battery binder.

[0030] Example 3

[0031] (1) Dissolve 1.5 g of 1,3,5-triaminobenzene and 0.5 g of polyacrylic acid (PAA) in 30 mL of deionized water and stir at room temperature to obtain a mixed solution;

[0032] (2) the mixed solution was allowed to stand at room temperature for 16 h, and the amino groups and hydroxyl groups formed hydrogen bonds to complete the crosslinking reaction, thereby obtaining a hydrogel;

[0033] (3) vacuum filtering the hydrogel obtained in step (2) and rinsing with excess deionized water to remove excess impurities and by-products, and then drying the filter cake at 100° C. under vacuum conditions for 6 h to remove excess moisture to obtain a lithium ion battery binder.

[0034] Example 4

[0035] 0.05 g of the binder prepared in Example 1 was dissolved in 10 mL of deionized water, 2 g of silicon-based negative electrode material (commercially available, purchased from Zhejiang Xintie Metal Materials Co., Ltd.) was added and stirred evenly to form a negative electrode slurry. The slurry was then evenly coated on a copper foil, dried at 120 ° C, rolled, and punched to obtain a circular silicon negative electrode sheet. After vacuum drying at 120 ° C for 12 h, it was placed in an argon-filled glove box (the content of H2O and O2 in the glove box was less than 0.1 ppm), paired with a metal lithium electrode to assemble into a half-cell, the electrolyte used was 1 M lithium hexafluorophosphate (EC / DMC / EMC = 1:1:1 (v), and the diaphragm used was a polypropylene diaphragm.

[0036] Testing revealed that a lithium-ion half-cell prepared using the binder obtained in Example 1 achieved an initial reversible capacity of 3500 mAh / g at a 0.5C current, with no electrode dropout. Repeated testing revealed that the charge and discharge performance of lithium-ion half-cells prepared using the binders obtained in Examples 2-3 was comparable to that of Example 1.

[0037] Example 5

[0038] The silicon negative electrode sheet prepared in Example 4 was used, LiCoO2 was used as the positive electrode, 1M lithium hexafluorophosphate (EC / DMC / EMC=1:1:1 (v)) was used as the electrolyte, and a polypropylene separator was used as the separator to assemble a full battery. The performance test was carried out. The test results are shown in Table 1.

[0039] Example 6

[0040] The silicon negative electrode prepared in Example 4 was used, LiMn2O4 was used as the positive electrode, 1M lithium hexafluorophosphate (EC / DMC / EMC=1:1:1 (v)) was used as the electrolyte, and a polypropylene separator was used as the separator to assemble a full battery. The performance test was carried out. The test results are shown in Table 1.

[0041] Example 7

[0042] The silicon negative electrode sheet prepared in Example 4, LiNi 0.8 Co 0.1 Mn 0.1 O2 was used as the positive electrode, 1M lithium hexafluorophosphate (EC / DMC / EMC=1:1:1 (v)) was used as the electrolyte, and a polypropylene separator was used as the separator. A full battery was assembled and performance tested. The test results are shown in Table 1.

[0043] Example 8

[0044] The silicon negative electrode sheet prepared in Example 4 was used as the positive electrode, LiFePO4 was used as the electrolyte, 1M lithium hexafluorophosphate (EC / DMC / EMC=1:1:1 (v)), and a polypropylene separator was used as the separator to assemble a full battery. The performance test was carried out. The test results are shown in Table 1.

[0045] Comparative Examples 1-4

[0046] The silicon negative electrode sheet prepared by replacing the "binder" in Example 4 with PVDF binder was respectively 0.8 Co 0.1 Mn 0.1 O2 and LiFePO4 were used as positive electrodes to assemble a full battery and the performance was tested. The test results are shown in Table 1.

[0047] The electrolyte used was 1M lithium hexafluorophosphate (EC / DMC / EMC=1:1:1 (v)), and the separator used was a polypropylene separator.

[0048] Table 1 Charge and discharge performance parameters and cycle capacity retention rates of various batteries

[0049] As can be seen from Table 1, the lithium ion secondary battery assembled with the binder prepared by the method of the present invention has the characteristics of high capacity utilization of electroactive materials, long cycle life of the battery, and high discharge platform voltage.

[0050] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features therein according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a lithium ion battery binder, characterized in that: The steps include: (1) dissolving 1,3,5-triaminobenzene and polyacrylic acid in deionized water and stirring at room temperature to obtain a mixed solution; (2) allowing the mixed solution to stand at room temperature to complete the cross-linking reaction and obtain a hydrogel; (3) vacuum filtering the hydrogel obtained in step (2), and then drying it under vacuum conditions to obtain a lithium ion battery binder.

2. The method for preparing a lithium ion battery binder according to claim 1, characterized in that: The mass ratio of the 1,3,5-triaminobenzene to the polyacrylic acid is 0.02-3, and the concentration of the mixed solution is 50g / L-100g / L.

3. The method for preparing a lithium ion battery binder according to claim 1, characterized in that: The standing time in step (2) is 6-16 hours.

4. The method for preparing a lithium ion battery binder according to claim 1, characterized in that: The drying temperature in step (4) is 80-100° C. and the drying time is 1-24 hours.

5. Use of a lithium ion battery binder prepared by the method according to any one of claims 1 to 4 in a lithium battery silicon negative electrode, characterized in that: The lithium-ion battery binder and the silicon-based negative electrode material are mixed to prepare the negative electrode plate of the lithium battery.

6. The use according to claim 5, characterized in that: The lithium-ion battery binder and the silicon-based negative electrode material are mixed in deionized water to form a negative electrode slurry, which is then coated on a copper foil, dried and sliced ​​to obtain a silicon negative electrode sheet.

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