Sulfonated hetero-junction covalent organic framework filler, method of making and composite polymer solid state electrolyte
Patent Information
- Application Number
- CN202610762247.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-29
- Publication Date
- 2026-08-28
AI Technical Summary
[0004]本发明针对现有技术中聚合物固态电解质离子电导率低、锂离子迁移数小以及填料功能单一等问题，提供一种磺化异质结共价有机框架填料，其制备方法，以及包含该填料的复合聚合物固态电解质
（1）在COF基异质结的一侧组分中引入磺酸基团，利用其强吸电子能力促进锂盐解离，并通过静电作用有效固定阴离子；同时，异质结界面处由于两种COF组分的能带差异形成内建电场，为锂离子提供额外驱动力，显著降低界面迁移活化能。磺酸基团与界面电场的协同作用，可显著提高聚合物电解质的离子电导率、锂离子迁移数，有效抑制锂枝晶的生长。
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Figure CN122659290A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid electrolyte materials technology, specifically relating to a sulfonated heterojunction covalent organic framework filler for lithium-ion batteries, its preparation method, and a composite polymer solid electrolyte containing the filler. Background Technology
[0002] With the continuous improvement of the energy density of lithium-ion batteries and the increasingly stringent safety requirements, traditional liquid organic electrolytes are no longer sufficient to meet the needs of next-generation high-safety energy storage devices due to safety hazards such as leakage, combustion, and even explosion. Solid electrolytes, especially polymer solid electrolytes, have become a research hotspot due to their good flexibility, ease of processing and molding, and interfacial compatibility with electrodes. However, polymer-based solid electrolytes such as polyethylene oxide and polyvinylidene fluoride generally have low ionic conductivity at room temperature and low lithium-ion transference numbers, which severely limits their practical applications.
[0003] Adding inorganic or organic nanofillers to polymer matrices is an effective strategy to improve the aforementioned properties. Covalent organic frameworks (COFs), as porous crystalline materials with ordered pore structures, functionalizability, and excellent thermal stability, have been widely studied as fillers for polymer electrolytes in recent years. However, single-component COF fillers often only provide a single ion transport channel or mechanical reinforcement, making it difficult to simultaneously meet the requirements of high ionic conductivity, high lithium-ion transference number, and good interfacial compatibility. In particular, how to effectively dissociate lithium salts, immobilize anions, and simultaneously promote the rapid migration of lithium ions at the filler / polymer interface remains a challenge for current technology. Therefore, developing a novel COF-based filler with synergistic functions is of great significance for improving the overall electrochemical performance of composite polymer solid electrolytes. Summary of the Invention
[0004] This invention addresses the problems of low ionic conductivity, low lithium-ion transference number, and limited functionality of fillers in existing polymer solid electrolytes. It provides a sulfonated heterojunction covalent organic framework filler, its preparation method, and a composite polymer solid electrolyte containing this filler. By introducing sulfonic acid groups into the framework of one of the COF components and constructing a covalently linked heterostructure, this invention enables the filler to simultaneously possess multiple synergistic functions, including anion immobilization, rapid lithium-ion transport, and an interface-built-in electric field that promotes ion migration.
[0005] The present invention provides a sulfonated heterojunction covalent organic framework filler, the filler comprising a first covalent organic framework and a second covalent organic framework; the first covalent organic framework and the second covalent organic framework are interconnected by imine bonds to form a heterostructure; and the skeleton of the first covalent organic framework is covalently linked with sulfonic acid groups (-SO3H).
[0006] In a preferred embodiment, the first covalent organic framework is a two-dimensional covalent organic framework formed by the Schiff base condensation reaction of 2,4,6-tricarboxymethyl phloroglucinol (Tp) and 2,5-diaminobenzenesulfonic acid (Pa-SO3H), denoted as TpPa-SO3H; the second covalent organic framework is a two-dimensional covalent organic framework formed by the Schiff base condensation reaction of 2,4,6-tricarboxymethyl phloroglucinol (Tp) and 3,6-diaminopyridazine (Dz), denoted as TpDz.
[0007] In the aforementioned fillers, the densely distributed sulfonic acid groups in the first COF possess strong electron-withdrawing capabilities, effectively promoting the dissociation of lithium ions and anions in the lithium salt. Simultaneously, the sulfonic acid groups fix the anions through electrostatic interactions, thereby significantly increasing the lithium-ion transport number. Due to differences in chemical structure and band structure, the two COF components achieve band alignment at the imine-bonded heterojunction interface, generating a built-in electric field pointing from TpDz to TpPa-SO3H. This built-in electric field lowers the activation energy for lithium-ion migration at the interface, providing additional driving force and promoting rapid lithium-ion transport along the heterojunction interface.
[0008] This invention also provides a method for preparing the above-mentioned sulfonated heterojunction covalent organic framework filler, comprising the following steps: Step 1: Synthesize the first covalent organic framework with sulfonic acid groups covalently linked to its backbone; Step 2: Mix the first covalent organic framework with the monomer that forms the second covalent organic framework, and use a solvothermal method to cause the second covalent organic framework to grow in situ on the surface of the first covalent organic framework to form a covalently bonded heterostructure, thus obtaining the sulfonated heterojunction covalent organic framework filler.
[0009] In a preferred embodiment, step one specifically includes: dissolving 2,4,6-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid in a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:4, and adding benzaldehyde and an aqueous solution of acetic acid, reacting at 120°C for 72 hours to obtain a first covalent organic framework. Step two specifically includes: mixing the first covalent organic framework with 2,4,6-triformylphloroglucinol and 3,6-diaminopyridazine in a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:1, and adding an aqueous solution of acetic acid, reacting at 120°C for 72 hours to obtain the sulfonated heterojunction covalent organic framework filler.
[0010] In the above preparation method, a heterojunction interface is constructed through covalent epitaxial growth. The residual amino and aldehyde groups on the surface of the first COF undergo secondary condensation with the monomer of the second COF, ensuring the structural stability and chemical bonding strength of the heterojunction interface and avoiding the phase separation and increased interfacial resistance problems commonly found in physically mixed fillers. This method is mild, requires no expensive equipment, and is suitable for large-scale production.
[0011] The present invention further provides a composite polymer solid electrolyte comprising a polymer matrix, a lithium salt, and a sulfonated heterojunction covalent organic framework filler.
[0012] In a preferred embodiment, the polymer matrix is selected from at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile (PAN), or polymethyl methacrylate (PMMA); the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), or lithium hexafluorophosphate (LiPF6).
[0013] In a preferred embodiment, the polymer matrix comprises 100 parts by weight, the lithium salt comprises 60 to 120 parts by weight, and the sulfonated heterojunction covalent organic framework filler comprises 1 to 3 parts by weight.
[0014] In a preferred embodiment, the composite polymer solid electrolyte is a membrane prepared by solution casting. Specifically, the above components are dissolved in an organic solvent (such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), acetonitrile (ACN)), stirred until completely dissolved, and then formed into a membrane in a polytetrafluoroethylene mold using solution casting. The solvent is then removed by vacuum drying to obtain the composite polymer solid electrolyte membrane.
[0015] In the aforementioned composite polymer solid electrolyte, the sulfonated heterojunction COF filler exhibits good interfacial compatibility with polymer matrices such as polyvinylidene fluoride (PVDF) and PVDF-hexafluoropropylene copolymer, facilitating uniform dispersion. The synergistic effect of sulfonic acid groups and the interfacial electric field significantly improves the ionic conductivity and lithium-ion transference number of the polymer electrolyte, effectively suppressing lithium dendrite growth. Simultaneously, the ordered nanopores of the COF itself constitute a three-dimensional rapid lithium-ion transport network, resulting in significantly improved electrochemical performance of the composite polymer solid electrolyte at room temperature.
[0016] The above-mentioned composite polymer solid electrolyte has applications in lithium-ion batteries. Lithium-ion batteries containing this electrolyte exhibit high safety, high rate performance, and long cycle life.
[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Sulfonic acid groups are introduced into one component of the COF-based heterojunction to promote lithium salt dissociation by utilizing their strong electron-withdrawing ability and effectively fix anions through electrostatic interaction. At the same time, the built-in electric field formed at the heterojunction interface due to the band difference between the two COF components provides an additional driving force for lithium ions and significantly reduces the activation energy of interface migration. The synergistic effect of sulfonic acid groups and interface electric field can significantly improve the ionic conductivity and lithium ion transference number of the polymer electrolyte and effectively inhibit the growth of lithium dendrites.
[0018] (2) A heterojunction interface is constructed through covalent epitaxial growth. The amino and aldehyde groups remaining on the surface of the first COF undergo secondary condensation with the monomer of the second COF, ensuring the structural stability and chemical bonding strength of the heterojunction interface and avoiding the phase separation and increased interfacial resistance problems commonly found in physically mixed fillers. This covalently connected interface also ensures the continuous and rapid transport of lithium ions within the filler. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 A flowchart illustrating the preparation method of the sulfonated heterojunction covalent organic framework filler provided by the present invention.
[0020] Figure 2 The results show the ionic conductivity test results of the composite polymer solid electrolytes in Example 2 and Comparative Example 1 of this invention.
[0021] Figure 3 The results are the electrochemical window test results of the composite polymer solid electrolytes of Example 2 and Comparative Example 1 of this invention.
[0022] Figure 4 The results of the cycle stability test of the composite polymer solid electrolyte in Example 2 of this invention are shown. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. However, the scope of protection of this invention is not limited to the following embodiments.
[0024] Example 1: Preparation of sulfonated heterojunction COF filler (TpPa-SO3H / TpDz) like Figure 1As shown, this embodiment provides a method for preparing sulfonated heterojunction covalent organic framework fillers, as detailed below: Step S101: Synthesize the first covalent organic framework with sulfonic acid groups covalently linked to its backbone; 2,4,6-tricarboxymethyl phloroglucinol (Tp, 0.2 mmol) and 2,5-diaminobenzenesulfonic acid (Pa-SO3H, 0.3 mmol) were dissolved in a mixed solvent (5 mL) of mesitylene and 1,4-dioxane in a volume ratio of 1:4. Benzaldehyde (0.1 mL) and 3 M aqueous acetic acid (0.5 mL) were added. After ultrasonic dispersion for 10 minutes, the mixture was transferred to a pressure-resistant reaction tube and reacted in an oven at 120 °C for 72 hours. After the reaction, the product was washed by centrifugation with deionized water, acetone, and N,N-dimethylacetamide, respectively, and finally dried under vacuum at 60 °C for 24 hours to obtain the first covalent organic framework TpPa-SO3H.
[0025] In this step, a two-dimensional COF structure linked by imine bonds is formed through a Schiff base condensation reaction, with sulfonic acid groups covalently attached to the framework. These sulfonic acid groups effectively promote lithium salt dissociation and immobilize anions, providing a functional basis for the high lithium-ion transference number of the subsequent composite electrolyte.
[0026] Step S102: Mix the first covalent organic framework with the monomer that forms the second covalent organic framework, and use a solvothermal method to cause the second covalent organic framework to grow in situ on the surface of the first covalent organic framework to form a covalently bonded heterostructure, thereby obtaining the sulfonated heterojunction covalent organic framework filler. The prepared TpPa-SO3H powder (50 mg), Tp monomer (0.2 mmol), and Dz monomer (3,6-diaminopyridazine, 0.3 mmol) were mixed evenly and dissolved in a 1:1 mixture of trimethylbenzene and 1,4-dioxane (5 mL). 3 M acetic acid aqueous solution (0.5 mL) was added. The suspension was sonicated at 60 °C for 15 minutes to allow the monomer to be uniformly adsorbed onto the TpPa-SO3H surface. After three cycles of liquid nitrogen freezing, vacuuming, and thawing, the mixture was sealed and placed in a 120 °C oven for 72 hours. After the reaction, the mixture was filtered, washed successively with DMF, acetone, and methanol, then extracted with tetrahydrofuran for 24 hours, and finally vacuum dried at 60 °C for 24 hours to obtain the sulfonated heterojunction covalent organic framework filler, denoted as TpPa-SO3H / TpDz.
[0027] In this step, the amino and aldehyde groups remaining on the TpPa-SO3H surface undergo a secondary condensation reaction with the Tp and Dz monomers, forming a covalent heterojunction interface linked by imine bonds. This covalently linked interface structure is stable, preventing phase separation. Simultaneously, due to the band structure difference between TpPa-SO3H and TpDz, a built-in electric field is formed at the interface, pointing from TpDz to TpPa-SO3H. This built-in electric field provides an additional driving force for lithium ions, significantly reducing the activation energy for interface migration.
[0028] Example 2: Preparation of composite polymer solid electrolyte This embodiment provides a composite polymer solid electrolyte comprising the sulfonated heterojunction covalent organic framework filler described in Example 1 and its preparation method.
[0029] By weight: 100 parts of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), 100 parts of lithium bis(trifluoromethanesulfonylimide) (LiTFSI), and 2 parts of the TpPa-SO3H / TpDz filler prepared in Example 1 were taken. The above components were dissolved in N,N-dimethylformamide (DMF) to a solid content of 25 wt%, and stirred at room temperature for 12 hours until completely dissolved. The solution was poured into a polytetrafluoroethylene mold using a solution casting method and vacuum dried at 80°C for 24 hours to obtain a composite polymer solid electrolyte membrane with a thickness of approximately 70 μm.
[0030] In the prepared composite polymer solid electrolyte, the sulfonated heterojunction COF filler is uniformly dispersed in the polymer matrix. The sulfonic acid groups promote the dissociation of LiTFSI and immobilize TFSI. - Anions increase the lithium-ion transference number; the built-in electric field of the heterojunction guides Li... + Rapid migration along the filler surface and interface; simultaneously, the COF nanopores provide additional three-dimensional ion transport pathways. These synergistic effects enable this electrolyte to exhibit excellent electrochemical performance at room temperature.
[0031] Example 3: Performance Testing of Composite Polymer Solid Electrolytes The composite polymer solid electrolyte membrane prepared in Example 2 was subjected to performance testing.
[0032] (1) Ionic conductivity test: The ionic conductivity was measured to be 7.92 × 10⁻⁶ at room temperature (25℃) using the AC impedance method. -4 S / cm, significantly higher than the unfilled PVDF-HFP / LiTFSI system (Comparative Example 1: 2.9 × 10⁻⁶). -4 This is due to the sulfonic acid groups promoting lithium salt dissociation and the built-in electric field accelerating ion migration.
[0033] (2) Lithium-ion transport number test: The lithium-ion transport number (t) was measured using the AC impedance method and the chronoamperometry method.Li+ The value was 0.72, significantly higher than that of the pure polymer electrolyte (Comparative Example 1: 0.42). This indicates that the sulfonic acid groups effectively immobilized the anions, while the heterojunction interface promoted the directional migration of lithium ions.
[0034] (3) Electrochemical window test: Linear sweep voltammetry showed that the electrochemical stability window was 4.8 V (relative to Li / Li). + This meets the requirements for the use of high-voltage cathode materials.
[0035] (4) Cyclic stability: Assembled Li / electrolyte / Li symmetric cell, at 0.1 mA / cm 2 The electrolyte can cycle stably for more than 1300 hours at current density without short circuit, indicating that it effectively suppresses the growth of lithium dendrites.
[0036] Example 4: Assembly and Testing of Lithium-ion Batteries The composite polymer solid electrolyte membrane prepared in Example 2 was used to assemble a lithium-ion battery. The positive electrode was lithium iron phosphate (LiFePO4), and the negative electrode was a lithium metal sheet. Battery performance was tested at 25°C: the initial discharge specific capacity at 0.5C was 152 mAh / g, and the capacity retention after 100 cycles was 98%. Compared to the control battery without filler (which retained only 55% of its capacity after 100 cycles), the battery of this invention exhibits superior cycle stability.
[0037] Comparative Example To illustrate the beneficial effects of the present invention, comparative examples 1 to 4 were set up to compare with Example 2. The filler type, ionic conductivity and ion transference number of the composite polymer solid electrolyte are shown in Table 1.
[0038] Table 1. Experimental results of Example 2 and Comparative Examples 1-4 As shown in Table 1, the ionic conductivity and lithium-ion transference number of the comparative example are significantly lower than those of Example 2, demonstrating the synergistic effect of sulfonic acid groups and the covalent heterojunction interface.
[0039] Industrial applicability The sulfonated heterojunction covalent organic framework filler, its preparation method, and the composite polymer solid electrolyte provided by this invention can be applied to the manufacture of high-safety, high-energy-density lithium-ion batteries and have broad industrialization prospects.
[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A sulfonated heterojunction covalent organic framework filler, characterized in that, The filler includes a first covalent organic framework and a second covalent organic framework; the first covalent organic framework and the second covalent organic framework are interconnected by imine bonds to form a heterostructure; and the framework of the first covalent organic framework is covalently linked with sulfonic acid groups.
2. The sulfonated heterojunction covalent organic framework filler according to claim 1, characterized in that, The first covalent organic framework is a two-dimensional covalent organic framework formed by the Schiff base condensation reaction of 2,4,6-tricarboxymethyl phloroglucinol and 2,5-diaminobenzenesulfonic acid; the second covalent organic framework is a two-dimensional covalent organic framework formed by the Schiff base condensation reaction of 2,4,6-tricarboxymethyl phloroglucinol and 3,6-diaminopyridazine.
3. A method for preparing the sulfonated heterojunction covalent organic framework filler according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Synthesize the first covalent organic framework with sulfonic acid groups covalently linked to its backbone; Step 2: Mix the first covalent organic framework with the monomer that forms the second covalent organic framework, and use a solvothermal method to cause the second covalent organic framework to grow in situ on the surface of the first covalent organic framework to form a covalently bonded heterostructure, thus obtaining the sulfonated heterojunction covalent organic framework filler.
4. The preparation method according to claim 3, characterized in that, Step one specifically includes: dissolving 2,4,6-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid in a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:4, and adding benzaldehyde and an aqueous solution of acetic acid. The reaction is carried out at 120°C for 72 hours to obtain the first covalent organic framework. Step two specifically includes: mixing the first covalent organic framework with 2,4,6-triformylphloroglucinol and 3,6-diaminopyridazine in a mixed solvent of mesitylene and 1,4-dioxane in a volume ratio of 1:1, and adding an aqueous solution of acetic acid. The reaction is carried out at 120°C for 72 hours to obtain the sulfonated heterojunction covalent organic framework filler.
5. A composite polymer solid electrolyte, characterized in that, It comprises a polymer matrix, a lithium salt, and the sulfonated heterojunction covalent organic framework filler as described in claim 1 or 2.
6. The composite polymer solid electrolyte according to claim 5, characterized in that, The polymer matrix is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, or polymethyl methacrylate; the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, or lithium hexafluorophosphate.
7. The composite polymer solid electrolyte according to claim 5 or 6, characterized in that, The polymer matrix comprises 100 parts by weight, the lithium salt comprises 60 to 120 parts by weight, and the sulfonated heterojunction covalent organic framework filler comprises 1 to 3 parts by weight.
8. The composite polymer solid electrolyte according to any one of claims 5 to 7, characterized in that, The composite polymer solid electrolyte is a membrane prepared by solution casting.