Preparation method of composite water-soluble binder
By blending PEDOT with PSS and adding L-ascorbic acid and tannin, a composite water-soluble binder was prepared, which solved the problems of poor ion diffusion ability and insufficient water solubility in lithium-ion batteries, and achieved a stable three-dimensional conductive network and excellent bonding performance, which improved the electrochemical performance of lithium-ion batteries.
Patent Information
- Application Number
- CN202510414286.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-03
- Publication Date
- 2025-07-08
AI Technical Summary
As an electronic conductor, PEDOT has problems such as poor ion diffusion ability, poor elasticity and insufficient water solubility in lithium-ion batteries, which affects its cycle stability and application potential.
By blending PEDOT with PSS to form PEDOT:PSS, and adding L-ascorbic acid and tannin, a composite water-soluble binder is prepared to improve its linear structure and form a stable three-dimensional conductive network, enhancing bonding performance and conductivity.
It improves the electrochemical stability, self-healing and electron ion conductivity of lithium-ion batteries, enhances the bonding strength of the electrode sheet and the stability of the conductive network, and improves the coulomb efficiency and cycling performance of the battery.
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Figure BDA0005343459830000081
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of batteries, and specifically to a preparation method of a composite water-soluble binder. Background Art
[0002] Poly(3,4-ethylenedioxythiophene) (abbreviated as PEDOT) is an electronic conductor with a rigid conjugated backbone and has received research attention due to its application potential in LIBs (lithium-ion batteries). However, PEDOT has some limitations, such as poor ion diffusion ability and poor elasticity, which result in unsatisfactory performance in terms of cycle stability. In addition, PEDOT has poor water solubility, which limits its further development and application. To overcome these challenges, researchers have attempted to blend PEDOT with poly(4-styrenesulfonate) (PSS). PSS not only acts as a counterion for the positive charge ions of PEDOT but also as a soluble template for PEDOT, significantly improving the chemical stability and solubility of PEDOT in aqueous solutions. This combination forms a conductive polymer, poly(3,4-ethylenedioxythiophene)-poly(styrene-4-sulfonate) (abbreviated as PEDOT:PSS), which has excellent electrochemical stability, self-healing properties, and good electronic and ionic conductivity. Due to these excellent properties, PEDOT:PSS can be used as a dual-functional polymer binder with both adhesiveness and conductivity, thereby improving the electronic and ionic conductivity of active materials. However, the linear structure of PEDOT:PSS may not be sufficient to effectively alleviate the volume expansion problem during the charge and discharge process of the battery. Therefore, researchers have explored mixing it with other polymers to form a more stable conductive network, maintain the integrity of the electrode, and reduce the electrode impedance.
[0003] In summary, PEDOT has potential applications as an electronic conductor in lithium-ion batteries, but its inherent disadvantages are improved by blending with PSS to form PEDOT:PSS. As a multifunctional binder, PEDOT:PSS can enhance battery performance, but in practical applications, it may need to be combined with other polymers to enhance the stability of its structure and conductive network.
[0004] To overcome the defects of the prior art, the present invention provides a preparation method of a composite water-soluble binder. Summary of the Invention
[0005] The object of the present invention is to provide a preparation method of a composite water-soluble binder to solve the problems in the prior art.
[0006] To solve the above technical problems, the present invention provides the following technical solutions:
[0007] A preparation method of a composite water-soluble binder, comprising the following steps:
[0008] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; blend poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and then dissolve them in deionized water to obtain a conductive polymer solution; add the conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 - 15 min to remove oxygen in the solution, and then stir and react for 12 - 14 h under a nitrogen atmosphere to obtain an LAPE binder;
[0009] Step 2: Dissolve tannic acid in deionized water to obtain a tannic acid solution; add the LAPE binder to the tannic acid solution and stir and react at 25 - 30 °C to obtain a composite water-soluble binder.
[0010] Preferably, in Step 1, when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid to the conductive polymer is (0 - 2):1.
[0011] Preferably, in Step 1, the conductive polymer solution is 1.5 - 1.7%.
[0012] Preferably, in Step 2, when preparing the composite water-soluble binder, the reaction mass ratio of tannic acid to the LAPE binder is (1 - 3):1.
[0013] The positive electrode sheet prepared from the composite water-soluble binder includes the following steps: mix lithium iron phosphate, acetylene black, the composite water-soluble binder and deionized water, and stir well for 6 - 8 h to obtain a positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil and dry it at 110 - 120 °C for 12 - 14 h to obtain a positive electrode sheet; cut the positive electrode sheet to obtain a positive electrode sheet with a diameter of 12 mm, and finally dry the positive electrode sheet at 60 - 70 °C for later use.
[0014] Preferably, the reaction mass ratio of lithium iron phosphate, acetylene black, and the composite water-soluble binder is (17 - 19):2:1.
[0015] Advantages of the present invention:
[0016] L-ascorbic acid (L-Ascorbic Acid, abbreviated as LAA) is a natural and effective antioxidant and biological reducing agent, with the advantages of being non-toxic, harmless, and having no adverse side effects. In addition, L-ascorbic acid has rich active groups of hydroxyl groups, and the hydroxyl group, as a good acceptor / donor for forming hydrogen bonds, can form a rich hydrogen bond network to enhance the adhesion performance to the active material. In particular, the hydroxyl group of L-ascorbic acid is an alcoholic hydroxyl group, which is not only easy to form hydrogen bonds but also easy to form chemical bonds with acidic groups, thereby providing a stronger bonding force.
[0017] Tannic acid (TA) is a water-soluble natural polyphenol arranged in a dendritic pattern. Tannic acid has excellent biocompatibility and is often used as a precursor for forming multifunctional coatings, such as antifouling coatings, adhesive coatings, conformal coatings, etc. Similar to dopamine, tannic acid can be spontaneously coated on almost any surface at room temperature by a similar method. The large number of phenolic hydroxyl groups in tannic acid provide opportunities for tannic acid to form van der Waals bonds, hydrogen bonds, and coordination bonds with other substances, and the rich oxygen-containing functional groups can also store charges through the doping of Li + doping. By adding tannic acid, the linear structure of the conductive polymer can be improved, which can not only provide excellent conductivity, reduce the accumulation of small molecules, but also form a three-dimensional conductive network, providing sufficient channels for the transmission of lithium ions and improving the Coulomb efficiency.
[0018] In summary, in the present invention, L-ascorbic acid and / or tannic acid are added to a conductive polymer solution (a conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and dissolving them in deionized water), to obtain a composite water-soluble binder. The composite water-soluble binder prepared in the present invention can effectively improve the linear structure of the conductive polymer, form a stable three-dimensional conductive network, and at the same time improve the bonding performance, so it has broad application prospects in the field of battery technology. Specific Embodiments
[0019] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.
[0020] Source of raw materials:
[0021] Lithium iron phosphate, battery grade, provided by Zhangzhou Wanbao Energy; acetylene black, battery grade, provided by Tianjin Youmeng Chemical Industry; metallic lithium sheet, battery grade, provided by Tianjin Zhongneng Lithium Industry; polyvinylidene fluoride, HSV900 (Mw≈600,000), provided by Nanwu Laboratory; L-ascorbic acid, analytical pure (AR), provided by Sinopharm; conductive polymer (PEDOT:PSS), 1.5% in water, provided by Aladdin; tannic acid, analytical pure, provided by Aladdin.
[0022] Example 1: Preparation of electrode sheet using polyvinylidene fluoride binder
[0023] Step 1: Mix lithium iron phosphate, acetylene black, polyvinylidene fluoride binder and deionized water, and stir well for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode sheet; cut the positive electrode sheet to obtain a positive electrode sheet with a diameter of 12 mm, and finally dry the positive electrode sheet at 60 °C and transfer it to the glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black, and polyvinylidene fluoride binder is 17:2:1.
[0024] Example 2: When preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (0:1):
[0025] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain the LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (0:1); the conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and dissolving them in deionized water;
[0026] Step 3: Mix lithium iron phosphate, acetylene black, LAPE binder and deionized water, and stir well for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode sheet; cut the positive electrode sheet to obtain a positive electrode sheet with a diameter of 12 mm, and finally dry the positive electrode sheet at 60 °C and transfer it to the glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black, and LAPE binder is 17:2:1.
[0027] Example 3: When preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (1:1):
[0028] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain the LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (1:1); the conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and dissolving them in deionized water;
[0029] Step 3: Mix lithium iron phosphate, acetylene black, LAPE binder and deionized water, and stir well for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode sheet; cut the positive electrode sheet to obtain a positive electrode sheet with a diameter of 12 mm, and finally dry the positive electrode sheet at 60 °C and transfer it to a glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black and LAPE binder is 17:2:1.
[0030] Example 4: When preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (2:1): Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain the LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (2:1); the conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and dissolving them in deionized water.
[0031] Step 3: Mix lithium iron phosphate, acetylene black, LAPE binder and deionized water, and stir well for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode sheet; cut the positive electrode sheet to obtain a positive electrode sheet with a diameter of 12 mm, and finally dry the positive electrode sheet at 60 °C and transfer it to a glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black and LAPE binder is 17:2:1.
[0032] Example 5: When preparing the composite water-soluble binder, the reaction mass ratio of tannic acid and the LAPE binder is (1:1), and the rest is the same as in Example 3:
[0033] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain the LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and the conductive polymer is (1:1); the conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and dissolving them in deionized water.
[0034] Step 2: Dissolve tannic acid in deionized water to obtain a tannic acid solution; then add the LAPE binder to the tannic acid solution and stir and react at 25 °C to obtain the composite water-soluble binder; when preparing the composite water-soluble binder, the reaction mass ratio of tannic acid and the LAPE binder is (1:1);
[0035] Step 3: Mix lithium iron phosphate, acetylene black, composite water-soluble binder and deionized water, and stir thoroughly for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode plate; cut the positive electrode plate to obtain a positive electrode plate with a diameter of 12 mm, and finally dry the positive electrode plate at 60 °C and transfer it to the glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black and composite water-soluble binder is 17:2:1.
[0036] Example 6: When preparing the composite water-soluble binder, the reaction mass ratio of tannic acid and LAPE binder is (2:1), and the rest is the same as in Example 3:
[0037] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain the LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid and conductive polymer is (1:1); the conductive polymer solution is prepared by dissolving a blend of poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) in deionized water;
[0038] Step 2: Dissolve tannic acid in deionized water to obtain a tannic acid solution; then add the LAPE binder to the tannic acid solution and stir and react at 25 °C to obtain the composite water-soluble binder; when preparing the composite water-soluble binder, the reaction mass ratio of tannic acid and LAPE binder is (2:1);
[0039] Step 3: Mix lithium iron phosphate, acetylene black, composite water-soluble binder and deionized water, and stir thoroughly for 6 h to obtain the positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, and dry it at 110 °C for 12 h to obtain the positive electrode plate; cut the positive electrode plate to obtain a positive electrode plate with a diameter of 12 mm, and finally dry the positive electrode plate at 60 °C and transfer it to the glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black and composite water-soluble binder is 17:2:1.
[0040] Example 7: When preparing the composite water-soluble binder, the reaction mass ratio of tannic acid and LAPE binder is (3:1), and the rest is the same as in Example 3:
[0041] Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; then add a 1.5% conductive polymer solution to the L-ascorbic acid solution, and introduce nitrogen for 10 min to remove the oxygen in the solution, and then stir and react for 12 h under a nitrogen atmosphere to obtain an LAPE binder; when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid to the conductive polymer is (1:1); the conductive polymer solution is prepared by blending poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and then dissolving them in deionized water;
[0042] Step 2: Dissolve tannic acid in deionized water to obtain a tannic acid solution; then add the LAPE binder to the tannic acid solution and stir and react at 25 °C to obtain a composite water-soluble binder; when preparing the composite water-soluble binder, the reaction mass ratio of tannic acid to the LAPE binder is (3:1);
[0043] Step 3: Mix lithium iron phosphate, acetylene black, the composite water-soluble binder and deionized water, and stir well for 6 h to obtain a positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, dry it at 110 °C for 12 h to obtain a positive electrode plate; cut the positive electrode plate to obtain a positive electrode plate with a diameter of 12 mm, and finally dry the positive electrode plate at 60 °C and transfer it to a glove box for standby; the reaction mass ratio of lithium iron phosphate, acetylene black, and the composite water-soluble binder is 17:2:1.
[0044] Detection test:
[0045] Peeling force test: Use the positive electrode plate prepared by the present invention as a sample, and use a multi-functional tensile testing machine to perform a 180° peeling test on the sample to compare the bonding performance of different compound binders. First, cut the dried electrode plate into strips of 20 mm × 100 mm, paste 3M tape on the surface of the electrode plate, and perform a peeling strength test at a tensile speed of 40 mm / min.
[0046] Cycling performance test: Assemble the positive electrode plate prepared by the present invention into a battery, and then use a Neware battery tester to perform constant current charging and discharging on the battery at a current density of 1C at 25 °C within a voltage range of 2.5 V - 4.0 V.
[0047] Rate performance test: Assemble the positive electrode plate prepared by the present invention into a battery, and then use a Neware battery tester to perform cyclic constant current charging and discharging tests on the battery at a current density of 1C at 25 °C within a voltage range of 2.5 V - 4.0 V. (The current density at 1C is 170 mA·g -1 ) The results are as follows in the table:
[0048]
[0049] Conclusion: By comparison, it is found that the binder prepared in the present invention has more excellent peel strength compared to the commercial polyvinylidene fluoride binder in Example 1.
[0050] The change in the proportion of the modifier L-ascorbic acid added has an obvious effect on the bonding performance of the sample. When the mass ratio of the added amount of L-ascorbic acid to the conductive polymer is 1:1, its bonding performance is the best. Compared with the case where no L-ascorbic acid is added, the alcoholic hydroxyl groups contained in L-ascorbic acid can not only form a rich hydrogen bond network to enhance the adhesion performance to the active material, but also easily form chemical bonds with acidic groups, thereby providing a stronger bonding force. While compared with the case where the mass ratio of the added amount of L-ascorbic acid to the conductive polymer is 2:1, since L-ascorbic acid is a small molecule organic compound with a molecular weight of only 176. Although the -OH group of L-ascorbic acid can interact with the -SO3H group of the conductive polymer to enhance the bonding strength, excessive addition will lead to a decrease in the overall molecular weight, which will instead lead to a decrease in the bonding strength of the sample.
[0051] At a rate of 1C, when the added amount of L-ascorbic acid is 2, the discharge specific capacity of the battery in Example 4 is only 139 mAh·g -1 , even worse than that of Example 2 without added L-ascorbic acid and Example 1 with a commercial polyvinylidene fluoride binder (147 mAh·g -1 and 141 mAh·g -1 ) respectively. It can be obtained from this: when the added amount of L-ascorbic acid is 1 (Example 3), it has more excellent rate performance. The change in the discharge specific capacity between Example 2 and Example 3 in the LAPE series is not significant, indicating that the two are stable. And the discharge specific capacity of Example 3 is always higher than that of Example 2 because there is an interaction between the -OH group and the -SO3H group in Example 3, which provides a faster transmission channel for the lithium ions.
[0052] When the added amount of tannic acid is 1, it is found that its bonding strength is enhanced (9.77 N·m -1 ). However, when the added amount of tannic acid is increased to 2, it is found that its bonding strength (5.41 N·m -1 ) has decreased to a large extent. The reason for this result may be the excessive addition of tannic acid, resulting in the accumulation of small molecule compounds and affecting the bonding strength. To better illustrate this result, we continue to increase the added amount of tannic acid to 3, and at this time it is found that its bonding strength (4.26 N·m -1)Continue to decrease. Such results indicate that the addition of tannic acid is not the more the better. When the addition amount is 1, the most excellent bonding strength is achieved. From the results of the electrical cycle test, it is concluded that the addition of an appropriate amount of tannic acid improves the linear structure, not only has excellent electrical conductivity, reduces the accumulation of small molecules, but also constitutes a three-dimensional conductive network, providing sufficient channels for the transmission of lithium ions and improving the Coulomb efficiency.
[0053] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.
[0054] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A preparation method of a composite water-soluble binder, characterized in that: It includes the following steps: Step 1: Dissolve L-ascorbic acid in deionized water to obtain an L-ascorbic acid solution; blend poly(3,4-ethylenedioxythiophene) and poly(4-styrenesulfonate) and then dissolve them in deionized water to obtain a conductive polymer solution; add the conductive polymer solution to the L-ascorbic acid solution, introduce nitrogen for 10 - 15 min to remove oxygen in the solution, and then stir and react for 12 - 14 h under a nitrogen atmosphere to obtain an LAPE binder; Step 2: Dissolve tannic acid in deionized water to obtain a tannic acid solution; add the LAPE binder to the tannic acid solution and stir and react at 25 - 30 °C to obtain a composite water-soluble binder.
2. The preparation method of a composite water-soluble binder according to claim 1, characterized in that: In Step 1, when preparing the LAPE binder, the reaction mass ratio of L-ascorbic acid to the conductive polymer is (0 - 2):
1.
3. The preparation method of a composite water-soluble binder according to claim 1, characterized in that: In Step 1, the conductive polymer solution is 1.5 - 1.7%.
4. The preparation method of a composite water-soluble binder according to claim 1, wherein: In Step 2, when preparing the composite water-soluble binder, the reaction mass ratio of tannic acid to the LAPE binder is (1 - 3):
1.
5. A composite water-soluble binder, characterized in that, Prepared by the preparation method according to any one of claims 1 - 4.
6. A positive electrode sheet prepared from the composite water-soluble binder according to claim 5, characterized in that: It includes the following steps: Mix lithium iron phosphate, acetylene black, the composite water-soluble binder and deionized water, and stir well for 6 - 8 h to obtain a positive electrode slurry; coat the positive electrode slurry on the surface of aluminum foil, dry it at 110 - 120 °C for 12 - 14 h to obtain a positive electrode plate; cut the positive electrode plate to obtain a positive electrode plate with a diameter of 12 mm, and finally dry the positive electrode plate at 60 - 70 °C for later use.
7. The positive electrode sheet prepared from the composite water-soluble binder according to claim 6, characterized in that: The reaction mass ratio of lithium iron phosphate, acetylene black, and the composite water-soluble binder is (17 - 19):2:
1.
8. Application of the positive electrode plate according to any one of claims 6 - 7 in a battery.