Polyacrylamide / sodium alginate composite binder as well as preparation method and application thereof

Abstract

The invention discloses a polyacrylamide / sodium alginate composite binder, which is prepared from the following raw materials in parts by weight: 10 parts of polyacrylamide, 3 to 5 parts of sodium alginate, 0.8 to 1 part of phytic acid and 0.5 to 0.7 part of cross-linking agent. The invention also discloses a preparation method of the polyacrylamide / sodium alginate composite binder, which comprises the following steps: uniformly mixing a polyacrylamide aqueous solution and a sodium alginate aqueous solution, adding phytic acid, uniformly mixing, adding a cross-linking agent, and uniformly mixing to obtain the polyacrylamide / sodium alginate composite binder for the negative electrode of the lithium battery. The invention also discloses an application of the polyacrylamide / sodium alginate composite binder in a negative electrode material. The binder disclosed by the invention has good bonding performance and mechanical performance, and can effectively inhibit volume expansion of a silicon material; and the problems that the silicon material is easy to crush and pulverize and the battery performance is greatly attenuated can be greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyacrylamide / sodium alginate composite binders, and in particular to a polyacrylamide / sodium alginate composite binder and a preparation method and application thereof. Background Art

[0002] In recent years, the pursuit of higher battery performance has been driving the scientific community to continuously improve the capacity of batteries, and many research focuses have focused on the development of positive and negative electrode materials. When the internal space of the battery is limited, using high-capacity negative electrode materials to match low-capacity positive electrode materials is a good way to increase the battery capacity. The theoretical specific capacity of silicon material can reach 4200mAh / g at high temperatures, and even at room temperature, its specific capacity is about 10 times higher than that of graphite negative electrode. It is a very promising negative electrode material that can greatly increase the capacity of the battery. However, due to the huge volume change of the silicon negative electrode during the operation of the battery, the silicon material may be broken and powdered, which in turn leads to the destruction of the electrode structure and causes a huge attenuation of battery performance. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a polyacrylamide / sodium alginate composite adhesive and its preparation method and application. The adhesive of the present invention has good bonding properties and mechanical properties and can effectively inhibit the volume expansion of silicon materials; it can greatly improve the problem that silicon materials are easily broken and powdered, and the battery performance is greatly attenuated.

[0004] The invention provides a polyacrylamide / sodium alginate composite adhesive. The raw materials thereof include, by weight, 10 parts of polyacrylamide, 3-5 parts of sodium alginate, 0.8-1 parts of phytic acid and 0.5-0.7 parts of a cross-linking agent.

[0005] Preferably, the crosslinking agent is a water-soluble calcium salt; more preferably calcium chloride.

[0006] The present invention also proposes a method for preparing the polyacrylamide / sodium alginate composite binder, comprising the following steps: mixing a polyacrylamide aqueous solution and a sodium alginate aqueous solution, then adding phytic acid and mixing, and then adding a cross-linking agent and mixing to obtain the polyacrylamide / sodium alginate composite binder for lithium battery negative electrode.

[0007] Preferably, the mass fraction of the polyacrylamide aqueous solution is 1-5wt%.

[0008] Preferably, the mass fraction of the sodium alginate aqueous solution is 0.5-1 wt %.

[0009] Preferably, phytic acid is added and stirred at 40-50° C. for 1-2 hours to mix well.

[0010] Preferably, a cross-linking agent is added and stirred at 40-50° C. for 0.5-1 h to mix well.

[0011] Preferably, after adding the cross-linking agent and mixing evenly, the solid content is adjusted to 4-6wt% to obtain a polyacrylamide / sodium alginate composite binder for lithium battery negative electrode.

[0012] The present invention also proposes the application of the polyacrylamide / sodium alginate composite binder in negative electrode materials.

[0013] The above-mentioned negative electrode material is lithium-ion battery silicon negative electrode material.

[0014] The present invention selects polyacrylamide and sodium alginate to cooperate with each other. The -NH2 in polyacrylamide and the -OH in sodium alginate can respectively form hydrogen bonds with the phosphate group of phytic acid to achieve chain crosslinking of polyacrylamide and sodium alginate, forming a three-dimensional network structure to improve the bonding performance and mechanical properties of the binder; then calcium salt is added to cooperate with sodium alginate and phytic acid to form a more complex network structure, thereby further improving the bonding performance and mechanical properties of the binder, thereby buffering the huge stress caused by the huge volume change of silicon during the charging and discharging process and maintaining the stability of the battery pole piece; and the remaining amide groups in polyacrylamide form reversible hydrogen bond crosslinking with the silicon negative electrode material, and the hydrogen bonds are repeatedly broken and formed during the charging and discharging process, so that the binder has self-repairing properties, further inhibiting the volume expansion of the silicon material; thereby greatly improving the problem that the silicon material is easily broken and pulverized and the battery performance is greatly attenuated. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is described in detail below through specific embodiments.

[0016] Example 1

[0017] A polyacrylamide / sodium alginate composite adhesive comprises the following raw materials by weight: 10 parts of polyacrylamide, 3 parts of sodium alginate, 1 part of phytic acid and 0.5 part of calcium chloride.

[0018] The preparation method of the polyacrylamide / sodium alginate composite binder comprises the following steps:

[0019] Polyacrylamide is dissolved in water to prepare a polyacrylamide aqueous solution with a mass fraction of 5 wt%;

[0020] Sodium alginate is dissolved in water to prepare a sodium alginate aqueous solution with a mass fraction of 0.5 wt%;

[0021] The polyacrylamide aqueous solution and the sodium alginate aqueous solution were mixed, and then a 1wt% phytic acid aqueous solution was added, and the mixture was stirred at 50°C for 1h, and then a 1wt% calcium chloride aqueous solution was added, and the mixture was stirred at 50°C for 0.5h, and then the solid content was adjusted to 6wt% to obtain a polyacrylamide / sodium alginate composite binder for lithium battery negative electrode.

[0022] Example 2

[0023] A polyacrylamide / sodium alginate composite adhesive comprises the following raw materials in parts by weight: 10 parts of polyacrylamide, 5 parts of sodium alginate, 0.8 parts of phytic acid and 0.7 parts of calcium chloride.

[0024] The preparation method of the polyacrylamide / sodium alginate composite binder comprises the following steps:

[0025] Polyacrylamide is dissolved in water to prepare a polyacrylamide aqueous solution with a mass fraction of 1 wt%;

[0026] Sodium alginate is dissolved in water to prepare a sodium alginate aqueous solution with a mass fraction of 1 wt%;

[0027] The polyacrylamide aqueous solution and the sodium alginate aqueous solution were mixed, and then a 1wt% phytic acid aqueous solution was added, and the mixture was stirred at 40°C for 2h, and then a 1wt% calcium chloride aqueous solution was added, and the mixture was stirred at 40°C for 1h, and then the solid content was adjusted to 4wt% to obtain a polyacrylamide / sodium alginate composite binder for lithium battery negative electrode.

[0028] Example 3

[0029] A polyacrylamide / sodium alginate composite adhesive comprises the following raw materials in parts by weight: 10 parts of polyacrylamide, 4 parts of sodium alginate, 0.9 parts of phytic acid and 0.6 parts of calcium chloride.

[0030] The preparation method of the polyacrylamide / sodium alginate composite binder comprises the following steps:

[0031] Polyacrylamide is dissolved in water to prepare a polyacrylamide aqueous solution with a mass fraction of 2 wt%;

[0032] Sodium alginate is dissolved in water to prepare a sodium alginate aqueous solution with a mass fraction of 0.8 wt %;

[0033] The polyacrylamide aqueous solution and the sodium alginate aqueous solution were mixed, and then a 1wt% phytic acid aqueous solution was added, and the mixture was stirred at 45°C for 1.5h, and then a 1wt% calcium chloride aqueous solution was added, and the mixture was stirred at 45°C for 0.5h, and then the solid content was adjusted to 5wt% to obtain a polyacrylamide / sodium alginate composite binder for lithium battery negative electrode.

[0034] Comparative Example 1

[0035] The binder does not contain phytic acid, and the rest is the same as in Example 3.

[0036] Comparative Example 2

[0037] The binder does not contain calcium chloride, and the rest is the same as in Example 3.

[0038] Comparative Example 3

[0039] The binder is a polyacrylamide aqueous solution with a solid content of 5 wt%.

[0040] Comparative Example 4

[0041] The binder is a sodium alginate aqueous solution with a solid content of 5 wt%.

[0042] Comparative Example 5

[0043] The binder is a sodium carboxymethyl cellulose aqueous solution with a solid content of 5 wt%.

[0044] Take the binders of Examples 1-3 and Comparative Examples 1-5, and prepare negative electrode sheets according to the same method (mix nano silicon, SuperP and binder to obtain negative electrode slurry, apply it to the surface of copper foil, and dry to obtain negative electrode sheets), and test the peeling force of the negative electrode sheets; and prepare lithium ion button batteries according to the same method (the electrolyte is 1 mol / L LiPF6 solution, and the solvent is EC:DMC=1:1v / v), and perform performance testing at a current density of 0.2C. The results are shown below.

[0045] Table 1 Test results

[0046]

[0047]

[0048] It can be seen from Table 1 that the binder of the present invention has good bonding properties. When used for silicon negative electrode materials, the lithium battery has good cycle performance, can buffer the huge stress caused by the huge volume change of silicon during the charging and discharging process, and maintain the stability of the battery electrode.

[0049] 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 polyacrylamide / sodium alginate composite binder, characterized in that: The raw materials include, by weight: 10 parts of polyacrylamide, 3-5 parts of sodium alginate, 0.8-1 parts of phytic acid, and 0.5-0.7 parts of a cross-linking agent.

2. The polyacrylamide / sodium alginate composite adhesive according to claim 1, characterized in that: The crosslinking agent is a water-soluble calcium salt.

3. A method for preparing the polyacrylamide / sodium alginate composite adhesive as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: mixing a polyacrylamide aqueous solution and a sodium alginate aqueous solution, then adding phytic acid and mixing, and then adding a cross-linking agent and mixing to obtain a polyacrylamide / sodium alginate composite binder for a lithium battery negative electrode.

4. The method for preparing the polyacrylamide / sodium alginate composite binder according to claim 3, characterized in that: The mass fraction of the polyacrylamide aqueous solution is 1-5wt%.

5. The method for preparing the polyacrylamide / sodium alginate composite binder according to claim 3 or 4, characterized in that: The mass fraction of the sodium alginate aqueous solution is 0.5-1wt%.

6. The method for preparing the polyacrylamide / sodium alginate composite binder according to any one of claims 3 to 5, characterized in that: Add phytic acid and stir at 40-50°C for 1-2 hours to mix well.

7. The method for preparing the polyacrylamide / sodium alginate composite binder according to any one of claims 3 to 6, characterized in that: Add the cross-linking agent and stir at 40-50°C for 0.5-1h to mix well.

8. The method for preparing the polyacrylamide / sodium alginate composite binder according to any one of claims 3 to 7, characterized in that: After adding the cross-linking agent and mixing evenly, the solid content is adjusted to 4-6wt% to obtain a polyacrylamide / sodium alginate composite binder for a lithium battery negative electrode.

9. Use of the polyacrylamide / sodium alginate composite binder as claimed in claim 1 or 2 in negative electrode materials.

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