MOFs-based flame-retardant diaphragm as well as preparation method and application thereof
By growing flame-retardant MOFs materials in situ on the secondary battery separator, the problem of thermal runaway caused by the flammability of the separator is solved, and high safety and excellent electrochemical performance are achieved.
Patent Information
- Application Number
- CN202510656644.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-07-08
AI Technical Summary
The existing secondary battery separator materials are flammable, resulting in battery thermal runaway safety problems have not been effectively solved.
Using MOFs-based flame retardant membranes, the thermal stability and ion transport performance of the membrane are improved by growing flame retardant MOFs materials in situ on a three-dimensional porous substrate, and using flame retardant agents and metal ions and organic ligands.
The MOFs-based flame retardant separator can quickly extinguish flames, inhibit dendrites' growth, improve the safety performance and electrochemical cycle stability of the battery, and improve the reversible specific capacity and electrochemical cycle stability of the battery.
Smart Images
Figure CN120280658A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of separator materials for secondary batteries, and relates to a MOFs-based flame-retardant separator and its preparation method and application. Background Art
[0002] With the continuous growth of global energy demand and the increasingly severe environmental problems, the development of efficient, low-cost and sustainable secondary battery energy storage technologies has become the key to alleviating the energy crisis and promoting the efficient utilization of renewable energy. As a key component of secondary batteries, the separator plays multiple roles of conducting the ion path and isolating the physical contact between the positive and negative electrodes, and its performance directly affects the safety performance and energy density of the battery. However, existing separator materials still face a series of challenges such as poor electrolyte wettability, uneven porosity distribution, low ionic conductivity, poor self-thermal stability and high flammability.
[0003] Currently, the separator materials in secondary batteries mainly focus on optimizing the electrochemical energy density of ion transport kinetics and strengthening the mechanical properties to inhibit dendrite penetration and cause battery short circuit. However, the safety problem that the separator is flammable and easily causes battery thermal runaway has not been solved. Therefore, the preparation of flame-retardant separators by simple and efficient methods has become an urgent need for high-safety secondary batteries. Summary of the Invention
[0004] In view of this, the purpose of the present invention is to solve the problem that the existing separator is flammable and easily causes battery thermal runaway, to provide a MOFs-based flame-retardant separator and its preparation method, and to apply the MOFs-based flame-retardant separator to the preparation of secondary batteries.
[0005] To achieve the above purpose, the present invention provides the following technical solutions:
[0006] 1. A MOFs-based flame-retardant separator, the flame-retardant separator comprising a three-dimensional porous substrate and a flame-retardant MOFs material formed on the surface of the substrate, the flame-retardant MOFs material being composed of a flame retardant, metal ions and an organic ligand.
[0007] 2. A preparation method of a MOFs-based flame-retardant separator, comprising the following steps:
[0008] Step S1: Immerse a three-dimensional porous substrate into a mixed solution containing a flame retardant and a metal salt to obtain a porous composite structure absorbing metal ions and a flame retardant;
[0009] Step S2: Immerse the porous composite structure absorbing the flame retardant and the metal salt into a conventional organic ligand solution to enable the in-situ uniform growth of a metal-organic framework (MOFs) with flame-retardant ability on its surface, and then dry it at room temperature to obtain the MOFs-based flame-retardant separator.
[0010] Preferably, the three-dimensional porous substrate described in step S1 is any one of bacterial cellulose membrane, polyacrylonitrile membrane, aramid membrane, alginate fiber membrane, polyimide membrane, polypropylene membrane, and ceramic fiber separator.
[0011] Preferably, the flame retardant described in step S1 is one or more of hexachlorocyclotriphosphazene, phytic acid, ammonium polyphosphate, or triphenyl phosphate, and the metal salt is any one or more of zinc salt, cobalt salt, iron salt, nickel salt, manganese salt, zirconium salt, aluminum salt, or copper salt. The solvent of the mixed solution is any one of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, or water. The organic ligand in step S2 is any one or more of 2-methylimidazole, imidazole, trimesic acid, terephthalic acid, 2-aminoterephthalic acid, or fumaric acid.
[0012] Preferably, the concentration of the flame retardant in the mixed solution is 1-100000 mmol / L, the concentration of the metal salt is 1-300000 mmol / L, and the concentration of the organic ligand solution is 1-300000 mmol / L.
[0013] More preferably, the concentration of the flame retardant in the mixed solution is 10-50000 mmol / L, the concentration of the metal salt is 10-50000 mmol / L, and the concentration of the organic ligand solution is 10-50000 mmol / L. Preferably, the thickness of the three-dimensional porous substrate is 10 μm-500 μm.
[0014] Preferably, in steps S1 and S2, the impregnation time is 0.1 h-720 h.
[0015] More preferably, the thickness of the three-dimensional porous substrate is 20-100 μm, and in steps S1 and S2, the impregnation time is 1-72 h.
[0016] 3. Application of the MOFs-based flame retardant separator in a metal-sulfur battery.
[0017] The beneficial effects of the present invention are as follows:
[0018] 1. The present invention discloses an MOFs-based flame retardant separator. The introduction of the flame retardant endows the separator with excellent thermal stability, enabling it to quickly extinguish the flame and prevent the continuation of combustion; the porous characteristics of the MOFs material itself can optimize the ion flux during the charge and discharge process of the battery, effectively inhibit dendrite growth, and eliminate potential safety hazards caused by battery short circuits; at the same time, the flame retardant and the metal ion center of the MOFs material have polarity, and can effectively anchor the active substances dissolved in the electrolyte through chemical adsorption to prevent their irreversible corrosion reaction with the negative electrode metal; at the same time, the metal ion center can promote the rapid conversion of intermediate soluble polysulfides, improving the reversible specific capacity and electrochemical cycle stability of the battery.
[0019] 2. The present invention discloses a preparation method of a MOFs-based flame-retardant separator, which anchors a flame retardant and MOFs on the surface of a fiber composite membrane by an in-situ construction method. The flame retardant forms new metal-organic coordination bonds with the metal ion centers in the MOFs and is uniformly and firmly compounded inside the MOFs material. The preparation method provided by the present invention is simple in operation, has a wide range of raw material sources and low prices, and is conducive to the industrial application of the MOFs-based flame-retardant separator.
[0020] 3. The MOFs-based flame-retardant separator disclosed by the present invention can effectively ensure the safety performance of secondary batteries and significantly improve their electrochemical performance, and has good application prospects.
[0021] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:
[0023] Figure 1 Optical picture of the ZIF-67-based bacterial cellulose composite flame-retardant separator prepared in Example 1;
[0024] Figure 2 SEM image and corresponding EDS element distribution pattern of the ZIF-67-based bacterial cellulose composite flame-retardant separator prepared in Example 1;
[0025] Figure 3 Raman spectrum of the ZIF-67-based bacterial cellulose composite flame-retardant separator prepared in Example 1;
[0026] Figure 4 XRD comparison chart of the ZIF-67 and bacterial cellulose composite separator prepared in Comparative Example 1;
[0027] Figure 5 SEM image of the ZIF-67 and bacterial cellulose composite separator prepared in Comparative Example 1;
[0028] Figure 6 Flame retardancy test results of Example 1 and Comparative Example 1;
[0029] Figure 7 Charge-discharge curve of the room-temperature sodium-sulfur battery in Example 2;
[0030] Figure 8For the cycling performance of the room-temperature sodium-sulfur battery in Example 2;
[0031] Figure 9 For the rate performance of the room-temperature sodium-sulfur battery in Example 2;
[0032] Figure 10 For the SEM image of the ZIF-8 / polyacrylonitrile composite flame-retardant separator prepared in Example 3. Detailed implementation manners
[0033] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.
[0034] Example 1
[0035] Prepare a ZIF-67-based bacterial cellulose composite flame-retardant separator. The specific preparation method is as follows:
[0036] (1) Immerse a commercial bacterial cellulose membrane in deionized water for 24 h, and freeze-dry the swollen bacterial cellulose membrane at -196 °C for 12 h using liquid nitrogen to obtain a fluffy bacterial cellulose membrane. Cut it into circular pieces with a diameter of 19 mm for later use;
[0037] (2) Immerse 40 mg of the bacterial cellulose circular pieces into 80 mL of a methanol solution containing 0.32 mol / L of Co(NO3)2·6H2O and 25 mg / mL of hexachlorocyclotriphosphazene for 12 h.
[0038] (3) Transfer the soaked bacterial cellulose circular pieces to a methanol solution containing 0.25 mol / L of 2-methylimidazole. After standing for 12 h, transfer the bacterial cellulose circular pieces to dry at room temperature to obtain the target product (ZIF-67-based bacterial cellulose flame-retardant separator).
[0039] Figure 1 For the optical picture of the ZIF-67-based bacterial cellulose composite flame-retardant separator prepared in Example 1.
[0040] Figure 2 For the SEM image and the corresponding EDS element distribution pattern of the ZIF-67-based bacterial cellulose composite flame-retardant separator prepared in Example 1. From Figure 2As can be seen, the ZIF-67 compounded with the flame retardant uniformly covers the surface of the fibers with a diameter of 5-10 nm in bacterial cellulose. As can be seen from the EDS diagram, the cobalt element from ZIF-67 and the chlorine, nitrogen, and phosphorus elements from the flame retardant hexachlorocyclotriphosphazene are uniformly distributed on the fiber surface, proving the successful compounding of the flame retardant in Example 1.
[0041] Figure 3 It is the Raman spectrum of the ZIF-67-based bacterial cellulose composite flame retardant separator prepared in Example 1. From Figure 3 As can be seen, in addition to forming a coordination bond with 2-methylimidazole, the cobalt ions in the MOFs material also form a new metal-organic coordination bond with the introduced flame retardant hexachlorocyclotriphosphazene.
[0042] Comparative Example 1
[0043] For the preparation method of Comparative Example 1, the commercial bacterial cellulose membrane was subjected to the same treatment steps as in Example 1, except that: in step S2, the hexachlorocyclotriphosphazene flame retardant was not added.
[0044] Figure 4 It is the XRD comparison diagram of the ZIF-67 and bacterial cellulose composite separator prepared in Comparative Example 1. From Figure 4 As can be seen, the characteristic peaks from ZIF-67 and bacterial cellulose are fully displayed in the ZIF-67 and bacterial cellulose composite separator, proving the successful in-situ growth of ZIF-67 on the surface of bacterial cellulose.
[0045] Figure 5 It is the SEM diagram of the ZIF-67 and bacterial cellulose composite separator prepared in Comparative Example 1. As can be seen from the figure, after ZIF-67 is loaded on the surface of bacterial cellulose, ZIF-67 still maintains its dodecahedron shape.
[0046] Performance Test
[0047] The separators described in Example 1 and Comparative Example 1 were ignited under an open flame condition to test their flame retardant performance. The specific test results are as Figure 6 shown.
[0048] From Figure 6 As can be known, the ZIF-67-based flame retardant separator compounded with the flame retardant in Example 1 can quickly extinguish the flame and prevent the continuation of combustion when encountering an open flame. In addition, even if the separator is ignited for the second time, it can still maintain its basic form and has excellent flame retardant performance. From the comparison of the separator morphology before and after ignition in Comparative Example 1, it can be seen that the ZIF-67 and bacterial cellulose composite separator burns and shrinks rapidly after ignition and does not have flame retardant performance. This shows that the introduction of the flame retardant makes the prepared separator have excellent flame retardant performance and solves the safety problem of battery thermal instability.
[0049] Example 2
[0050] The MOF-based flame-retardant separator material described in Example 1 was assembled into a room-temperature sodium-sulfur battery, and the cycle and rate performance were tested. The steps are as follows:
[0051] Using the MOF-based flame-retardant separator as the battery separator, sodium metal foil as the negative electrode, and 1 mol / L NaClO4 EC / PC (volume ratio 1:1) containing 5% FEC additive as the electrolyte, and paired with a sulfur positive electrode, a button battery was assembled in a glove box under an argon atmosphere in sequence. The assembled battery was subjected to constant current charge and discharge at a current rate of 0.5C (1C = 1675 mA h g -1 ), and after 100 cycles, its charge-discharge curve is as Figure 7 shown. As can be seen from Figure 7 , its reversible capacity reached 578.2 mA h g -1 , and the Coulomb efficiency was as high as 99.6%.
[0052] Figure 8 and Figure 9 are the cycle performance and rate performance of the room-temperature sodium-sulfur battery assembled with the MOF-based flame-retardant separator prepared in Example 1. As can be seen from Figure 8 , the room-temperature sodium-sulfur battery assembled with the MOF-based flame-retardant separator achieved excellent electrochemical cycle stability at a current density of 0.5C, showing an initial discharge capacity of 885.6 mA h g-1, and the capacity decay rate was only 0.059% after 1000 cycles. In addition, as can be seen from Figure 9 , the rate performance of the room-temperature sodium-sulfur battery assembled with the MOF-based flame-retardant separator prepared in Example 1 was also extremely outstanding, which was attributed to the strong capture of intermediate soluble polysulfides by the MOF-based flame-retardant separator and the effective promotion of its slow electrochemical reaction kinetics, fully demonstrating the positive role of this separator in improving the electrochemical performance of room-temperature sodium-sulfur batteries.
[0053] Example 3
[0054] Prepare a ZIF-8 / ZIF67 dual-MOF-based polyacrylonitrile fiber membrane composite flame-retardant separator. The specific preparation method is as follows:
[0055] (1) Add 1 g of polyacrylonitrile powder with a molecular weight of 130,000 to 1 mL of N,N-dimethylformamide solution, and stir until dissolved; transfer the mixed solution to an electrospinning instrument, with the nozzle 15 cm away from the receiver, add a voltage of 18 KV, and the receiver rotation speed of 60 rpm to obtain an electrospun polyacrylonitrile membrane with a thickness of 80 μm and a fiber diameter of 10 - 20 μm.
[0056] (2) The electrospun polyacrylonitrile membrane prepared above was kept at 180 °C in a muffle furnace for 30 min to stabilize the fiber structure (heating rate: 5 °C / min). After cooling to room temperature, the polyacrylonitrile membrane was cut into discs with a diameter of 19 mm for standby.
[0057] (3) The polyacrylonitrile discs in step (2) were immersed in 80 mL of a methanol solution containing 0.32 mol / L of Co(NO3)2·6H2O, 0.32 mol / L of Zn(NO3)2·6H2O, and 25 mg / mL of ammonium polyphosphate for 12 h.
[0058] (4) The immersed polyacrylonitrile membrane discs were transferred to 80 mL of a methanol solution containing 0.25 mol / L of 2-methylimidazole. After standing for 12 h, the polyacrylonitrile discs were transferred to dry at room temperature to obtain the target product (ZIF-8 / ZIF-67 dual-MOFs-based polyacrylonitrile composite flame-retardant separator).
[0059] Figure 10 is the SEM image of the ZIF-8 / ZIF-67 dual-MOFs-based polyacrylonitrile composite flame-retardant separator. As can be seen from Figure 10 , the polyhedral ZIF-8 and ZIF-67 separators are evenly distributed on the surface of the polyacrylonitrile fibers, proving the successful composite of the dual-MOFs material and the polyacrylonitrile membrane.
[0060] Example 4
[0061] To prepare a Cu-BTC-based bacterial cellulose composite flame-retardant separator, the specific preparation method is as follows:
[0062] (1) The commercial bacterial cellulose membrane was soaked in deionized water for 24 h, and the soaked bacterial cellulose membrane was freeze-dried at -196 °C with liquid nitrogen for 12 h to obtain a fluffy bacterial cellulose membrane, which was cut into discs with a diameter of 19 mm for standby.
[0063] (2) 40 mg of the bacterial cellulose discs were immersed in 80 mL of an N,N-dimethylformamide solution containing 0.32 mol / L of Co(NO3)2·3H2O and 25 mg / mL of phytic acid for 12 h.
[0064] (3) The immersed bacterial cellulose discs were transferred to an N,N-dimethylformamide solution containing 0.25 mol / L of trimesic acid. After standing for 12 h, the bacterial cellulose discs were transferred to dry at room temperature to obtain the target product (Cu-BTC-based bacterial cellulose composite flame-retardant separator).
[0065] The separator material prepared in this example also has the above-mentioned performance characteristics.
[0066] In summary, the present invention relates to a MOFs-based flame-retardant separator and its preparation method and application, belonging to the technical field of secondary battery separator preparation. By forming new metal-organic coordination bonds between flame retardant molecules and MOFs materials, the flame retardant molecules are uniformly and firmly introduced into the fiber composite membrane, constructing a MOFs-based flame-retardant separator with both high flame retardancy and stable ion transport characteristics. The coupling of flame retardant molecules endows traditional MOFs with excellent thermal stability and flame retardant properties, and the rich pore structure is conducive to the uniform distribution of ions, thus realizing the stable and uniform deposition / dissolution of metals. In addition, the efficient adsorption and catalytic effects of the flame retardant itself and the metal ion centers in the MOFs material on polysulfides effectively alleviate the shuttle effect, avoid the irreversible corrosion reaction between polysulfides and the negative electrode, and improve the chemical cycle stability of sulfur-based batteries. In addition, the flame-retardant separator material has the characteristics of low preparation cost, simple and safe operation, which is conducive to the industrial production and application of the flame-retardant separator.
[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.
Claims
1. A MOFs-based flame retardant separator, characterized in that, The flame-retardant separator includes a three-dimensional porous substrate and a flame-retardant MOFs material generated by the substrate. The flame-retardant MOFs material is composed of a flame retardant, metal ions, and an organic ligand.
2. A preparation method of a MOFs-based flame-retardant separator, characterized in that, It includes the following steps: Step S1: Immerse the three-dimensional porous substrate into a mixed solution containing a flame retardant and a metal salt to obtain a porous composite structure that has absorbed metal ions and the flame retardant. Step S2: Immerse the porous composite structure that has absorbed the flame retardant and the metal salt into a conventional organic ligand solution to enable the in-situ uniform growth of a metal-organic framework (MOFs) with flame-retardant ability on its surface, and then dry it at room temperature to obtain the MOFs-based flame-retardant separator.
3. The preparation method of a MOFs-based flame-retardant separator according to claim 2, wherein, The three-dimensional porous substrate in Step S1 is any one of a bacterial cellulose membrane, a polyacrylonitrile membrane, an aramid membrane, an alginate fiber membrane, a polyimide membrane, a polypropylene membrane, and a ceramic fiber separator.
4. The preparation method of a MOFs-based flame retardant separator according to claim 2, characterized in that, The flame retardant in Step S1 is one or more of hexachlorocyclotriphosphazene, phytic acid, ammonium polyphosphate, or triphenyl phosphate. The metal salt is any one or more of zinc salts, cobalt salts, iron salts, nickel salts, manganese salts, zirconium salts, aluminum salts, or copper salts. The solvent of the mixed solution is any one of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, or water. The conventional organic ligand in Step S2 is any one or more of 2-methylimidazole, imidazole, trimesic acid, terephthalic acid, 2-aminoterephthalic acid, or fumaric acid.
5. The preparation method of a MOFs-based flame retardant separator according to claim 2, wherein, The concentration of the flame retardant in the mixed solution is 1-100000 mmol / L, the concentration of the metal salt is 1-300000 mmol / L, and the concentration of the organic ligand solution is 1-300000 mmol / L.
6. The preparation method of a MOFs-based flame-retardant separator according to claim 5, wherein, The concentration of the flame retardant in the mixed solution is 10-50000 mmol / L, the concentration of the metal salt is 10-50000 mmol / L, and the concentration of the organic ligand solution is 10-50000 mmol / L.
7. The preparation method of an MOFs-based flame-retardant separator according to claim 2, characterized in that The thickness of the three-dimensional porous substrate is 10 μm to 500 μm.
8. The preparation method of a MOFs-based flame retardant separator according to claim 2, characterized in that, In Steps S1 and S2, the immersion time is 0.1 h-720 h.
9. The preparation method of a MOFs-based flame retardant separator according to claim 2, wherein, The thickness of the three-dimensional porous substrate is 20-100 μm. In Steps S1 and S2, the immersion time is 1-72 h.
10. Application of the MOFs-based flame-retardant separator described in Claim 1 in a secondary battery.