Directional coating diaphragm based on low reduction potential MOF, preparation method and application

Abstract

The invention discloses a coating diaphragm based on a low-reduction-potential MOF (Metal Organic Framework), a preparation method and application, and belongs to the field of new energy battery preparation. The coated diaphragm based on the low-reduction-potential MOF comprises a base film and an MOF coating which is coated on at least any surface of the base film and has the low reduction potential, and one side, coated with the MOF coating with low reduction potential, of the diaphragm is directionally close to the negative electrode of the electrochemical device. The MOF with low reduction potential is introduced to construct an electrochemically stable coating structure, and the coating is directionally close to the negative electrode side, so that the problems of capacity attenuation and safety caused by precipitation and deposition of a large amount of metal on the surface of the diaphragm are avoided; therefore, ion flow can be homogenized by virtue of the porous characteristic of the MOF material, dendritic crystal growth can be inhibited, and the stability of a diaphragm-negative electrode interface can be improved by virtue of the stable electrochemical property of the MOF material.

Description

Technical Field

[0001] This invention belongs to the field of batteries and relates to a MOF-coated separator, its preparation method and application. Background Technology

[0002] The separator is one of the key components of an ion battery, playing a crucial role in isolating electrons and conducting ions. To meet the evolving needs of batteries, separators have evolved from the first-generation polyolefin separators to coated or composite separators. These use a polyolefin membrane as the base membrane, coated with various functional coatings, such as inorganic ceramic material coatings (to improve thermal stability) and organic polymer coatings (to improve interfacial contact). With the application of metal-organic frameworks (MOFs) in the battery field, MOFs are also used as coating materials on the base membrane surface. Because MOFs have high porosity and large specific surface area, as coating materials, they can increase the separator's adsorption of electrolyte and mitigate the ion transport obstruction caused by separator thickening, as illustrated by patents (CN116073068A, CN116169434B).

[0003] However, not all MOF materials can be used as coating materials for coated separators. MOF materials need to meet the following requirements: 1) They need to have a large specific surface area and porosity to effectively adsorb electrolyte, increase the electrolyte retention of the separator, and wet the electrode interface; 2) They need to have a high thermal decomposition temperature to improve the thermal stability of the separator; 3) They need to have good chemical / electrochemical stability so that they will not easily undergo chemical / electrochemical reactions in the battery system, causing coating failure and affecting the performance of the battery system. Existing publicly available MOF-based coated separators basically take into account the first two requirements, namely the pore structure and thermal stability of MOF materials. However, the understanding of the chemical / electrochemical stability of MOF materials in battery systems is still insufficient, with technical blind spots and product defects. This is mainly manifested in the following ways: In some metal-based MOF materials, such as Cu-based MOF (Cu-MOF) and Fe-MOF, under the battery operating voltage window, metal ions in the MOF material gain electrons and deposit on the electrode surface, blocking carrier transport and reducing capacity; at the same time, their uneven deposition behavior can also cause metal dendrite growth, greatly increasing the risk of battery short circuit.

[0004] In summary, to better realize the potential of MOF materials in battery systems, it is necessary not only to utilize their porous structure but also to selectively design MOF coatings based on their chemical / electrochemical stability, thereby optimizing the technical route and improving product performance. Summary of the Invention

[0005] To address the shortcomings of existing MOF-based coated separators, which only utilize the porous structure of MOF materials without understanding their stability in electrochemical systems, this invention explores the stability of MOF materials in electrochemical systems and proposes a coated separator based on a low-reduction-potential MOF, its preparation method, and its application. The coated separator disclosed in this invention can prevent the deposition of metal ions from gaining electrons in the MOF material onto the negative electrode surface during charging, eliminating adverse factors that degrade product performance, such as capacity decay and dendrite growth.

[0006] In exploring the stability of MOF materials in electrochemical systems, the inventors discovered that commonly used Ag-MOF, Cu-MOF, and Fe-MOF materials, when applied as battery separator coatings, are prone to electrochemical reactions leading to coating failure. This is mainly because the metal centers of these MOF materials have high reduction potentials. For example, Ag-MOF (Ag... + / Ag = 0.7996 V vs SHE), Cu-MOF (Cu 2+ / Cu = 0.342 V vs SHE), Fe-MOF (Fe 3+ (Fe = -0.037 V vs SHE) Under current battery operating voltage windows, metal ions in these MOFs are easily reduced by gaining electrons, leading to metal deposition on the electrode surface. To address this, this invention enhances the electrochemical stability of the MOF by coating it with a metal-based MOF coating having a low reduction potential, thereby improving product performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0008] The present invention discloses a coated separator based on a low reduction potential MOF, wherein the coated separator based on a low reduction potential MOF includes at least a base film and a MOF coating coated on at least one surface of the base film, and the MOF coating has a low reduction potential.

[0009] Furthermore, the coated separator based on the low reduction potential MOF is an oriented coated separator; the oriented coated separator means that the separator is coated with the MOF coating on the surface at least close to the negative electrode side of the battery or electrochemical device.

[0010] Furthermore, the directional coated diaphragm is a single-sided coated diaphragm, and the coating on the single side is the MOF coating.

[0011] Furthermore, the directional coated diaphragm is a double-sided coated diaphragm, with one side coated with the MOF coating and the other side coated with other coatings, or both sides are coated with the MOF coating.

[0012] Furthermore, the other coatings are inorganic ceramic coatings, organic polymer coatings, or inorganic ceramic-organic polymer composite coatings.

[0013] Further, the low reduction potential refers to the electrode potential of the metal element in the MOF coating being less than -0.037 V vs SHE. Preferably, the MOF material is selected from one or more of Cr-MOF, Zn-MOF, Ti-MOF, Al-MOF, Ce-MOF, Mg-MOF, La-MOF, and MOFs based on alkali metals or alkaline earth metals. More preferably, it is selected from one or more of Zn-MOF, Al-MOF, Ce-MOF, Mg-MOF, La-MOF, and MOFs based on alkali metals or alkaline earth metals.

[0014] Furthermore, the base film is selected from one or more composite films selected from polyethylene film, polypropylene film, polyethylene-polypropylene composite film, polydimethylsiloxane film, polyethylene terephthalate film, polyamide film, polyimide film, glass fiber film, and nonwoven fabric.

[0015] Furthermore, the MOF coating contains MOF material and an adhesive; the adhesive is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene, polyvinyl alcohol, polyvinyl ethyl ether, polyethylene glycol, polyethylene terephthalate, polyethylene oxide, polypropylene, polyacrylonitrile, polymethyl methacrylate, polyimide, polyamide, polyamide-imide, sodium carboxymethyl cellulose, sodium alginate, chitosan, styrene-butadiene rubber, styrene-butadiene latex, and guar gum.

[0016] Furthermore, the method for preparing the coated diaphragm employs any one of the following: blade coating, roller coating, spray coating, spin coating, impregnation, pressure filtration, vacuum filtration, casting, and hot pressing.

[0017] Furthermore, the solvent used in the preparation method includes one or more of water, methanol, ethanol, isopropanol, ethyl acetate, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0018] Furthermore, the MOF-based coated separator is applied to an electrochemical device, which includes at least a positive electrode, a negative electrode, and the coated separator. The coated separator has a MOF coating on one side of its surface near the negative electrode of the electrochemical device, and the other side of the separator is near the positive electrode.

[0019] The beneficial effects of this invention are reflected in:

[0020] 1) The MOF materials used in existing MOF-based coated membranes are usually based on metal elements such as Fe, Cu, and Ag. These metal elements have high reduction potentials. During charging, these metal ions, such as Fe... 3+ Cu 2+ Ag + Metals, such as those with low reduction potential MOF materials, are easily deposited on the negative electrode surface, hindering carrier transport and causing a significant decrease in the capacity of the electrochemical device. This invention addresses this by using a directional coating membrane based on low reduction potential MOF materials. Because the metal elements in MOF materials have low potentials and are not easily reduced, their electrochemical properties are more stable, preventing metal deposition and avoiding performance degradation caused by metal deposition on the negative electrode surface. 2) The porous structure of MOF materials increases electrolyte retention and uniform ion flow, wetting the interface and inhibiting dendrite growth. 3) The MOF-based directional coating membrane preparation method of this invention is compatible with existing membrane coating processes, such as blade coating, roller coating, spray coating, spin coating, impregnation, pressure filtration, vacuum filtration, casting, and hot pressing. 4) The low reduction potential MOF-based coating and directional coating near the negative electrode proposed in this invention fill the technical gaps in existing MOF-coated membranes, providing important guidance for future MOF-based coated membrane selection and product development. Attached Figure Description

[0021] Figure 1 The stainless steel electrode surface morphology of the stainless steel battery assembled with the separator obtained in Example 1 before constant voltage charge-discharge cycle.

[0022] Figure 2 The stainless steel electrode surface morphology of the stainless steel battery assembled with the separator obtained in Example 1 after constant voltage charge-discharge cycle.

[0023] Figure 3 The stainless steel electrode surface morphology of the stainless steel battery assembled with the separator obtained in Example 2 before constant voltage charge-discharge cycle.

[0024] Figure 4 The stainless steel electrode surface morphology of the stainless steel battery assembled with the separator obtained in Example 2 after constant voltage charge-discharge cycle.

[0025] Figure 5 The surface morphology of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Comparative Example 1 before constant voltage charge-discharge cycle.

[0026] Figure 6 The surface morphology of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Comparative Example 1 after constant voltage charge-discharge cycle.

[0027] Figure 7 The aluminum element distribution on the surface of the stainless steel electrode sheet of the stainless steel battery assembled with the separator obtained in Example 1 before constant voltage charge-discharge cycle.

[0028] Figure 8 The aluminum element distribution on the surface of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Example 1 after constant voltage charge-discharge cycle.

[0029] Figure 9 The zinc element distribution on the surface of the stainless steel electrode sheet of the stainless steel battery with diaphragm assembly obtained in Example 2 before constant voltage charge-discharge cycle.

[0030] Figure 10 The zinc element distribution on the surface of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Example 2 after constant voltage charge-discharge cycle.

[0031] Figure 11 The copper element distribution on the surface of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Comparative Example 1 before constant voltage charge-discharge cycle.

[0032] Figure 12 The copper element distribution on the surface of the stainless steel electrode of the stainless steel battery assembled with the separator obtained in Comparative Example 1 after constant voltage charge-discharge cycle.

[0033] Figure 13 The cycle stability and coulombic efficiency of the battery assembled based on the separator obtained in Example 1 at 0.5C.

[0034] Figure 14 The cycling stability and coulombic efficiency of the battery assembled based on the separator obtained in Example 3 are shown at 0.5C, wherein an Al-MOF coating is applied to one side near the negative electrode side.

[0035] Figure 15 The cycling stability and coulombic efficiency of the battery assembled based on the separator obtained in Example 4 are shown at 0.5C, wherein the Al2O3 coating is close to the positive electrode side and the Al-MOF coating is close to the negative electrode side.

[0036] Figure 16 The cycling stability and coulombic efficiency of the battery assembled based on the separator obtained in Example 4 are shown at 0.5C, where the Al-MOF coating is close to the positive electrode side and the Al2O3 coating is close to the negative electrode side.

[0037] Figure 17 The cycling stability and coulombic efficiency of the battery assembled based on the separator obtained in Comparative Example 2 at 0.5C are shown. Detailed Implementation

[0038] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. All other content obtained by making several equivalent improvements and simple modifications to the present invention without departing from the spirit and essence of the present invention falls within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0039] The embodiments of this invention use a blade coating method as an example; other methods for preparing the MOF-based coated diaphragm are also within the scope of this invention. It should be noted that during the preparation of the MOF-based coated diaphragm of this invention, the MOF material and the coated diaphragm need to be dried. The drying temperature and drying time are not limited, and drying continues until constant weight is achieved. Preferably, the drying temperature is 60-150 °C, and the drying time is 1-12 h.

[0040] Example 1

[0041] 1) Place 162 g of MOF material MIL-53 (Al) in a vacuum oven, set the drying temperature to 120 ℃ and the drying time to 12 h to remove the moisture and other impurities adsorbed by the material.

[0042] 2) Mix the dried MIL-53 (Al) from step 1) with 18 g of polyvinylidene fluoride (PVDF), grind thoroughly and add 820 g of N-methylpyrrolidone, and sonicate to obtain a uniform slurry. The mass of the PVDF adhesive accounts for 10% of the total mass of the adhesive and aluminum-based MOF (MIL-53 (Al)).

[0043] 3) The MIL-53(Al) slurry obtained in step 2) is uniformly coated on one side of the surface of the commercial PP diaphragm Celgard-2500 (as the base membrane), and placed in a vacuum oven for drying. The drying temperature is set to 80 ℃, and the diaphragm is dried until constant weight (solvent is removed). The resulting diaphragm structure is MIL-53(Al) / PP, wherein the thickness of the MIL-53(Al) coating is 5 μm.

[0044] 4) Repeat steps 1)-3), coat the other side of the PP membrane, and dry the resulting membrane to obtain a double-sided coated membrane MIL-53(Al) / PP / MIL-53(Al).

[0045] Example 2

[0046] Replace MIL-53(Al) in Example 1 with ZIF-8 in Zn-MOF, and follow the same steps to obtain the coated diaphragm ZIF-8 / PP / ZIF-8.

[0047] Example 3

[0048] Repeat steps 1)-3) of Example 1 to obtain a single-sided coated diaphragm MIL-53(Al) / PP.

[0049] Example 4

[0050] 1) Place 162 g of MOF material MIL-53 (Al) in a vacuum oven, set the drying temperature to 120 ℃ and the drying time to 12 h to remove the moisture and other impurities adsorbed by the material.

[0051] 2) Mix the dried MIL-53 (Al) from step 1) with 18 g of polyvinylidene fluoride (PVDF), grind thoroughly and add 820 g of N-methylpyrrolidone, and sonicate to obtain a uniform slurry. The mass of the PVDF adhesive accounts for 10% of the total mass of the adhesive and aluminum-based MOF (MIL-53 (Al)).

[0052] 3) The MIL-53(Al) slurry obtained in step 2) is uniformly coated on one side of the surface of the commercial PP diaphragm Celgard-2500 (as the base membrane), and placed in a vacuum oven for drying. The drying temperature is set to 80 ℃, and the drying is continued until constant weight (solvent removal). The resulting diaphragm structure is MIL-53(Al) / PP.

[0053] 4) Place 285 g of alumina in a vacuum oven, set the drying temperature to 120 ℃, and the drying time to 12 hours to remove the moisture and other impurities adsorbed by the material.

[0054] 5) Mix the dried alumina from step 4) with 15 g of PVDF, grind thoroughly and add 700 g of N-methylpyrrolidone, and sonicate to obtain a uniform slurry. The mass of the PVDF binder accounts for 5% of the total mass of the binder and ceramic material.

[0055] 6) The alumina slurry obtained in step 5) is uniformly coated onto the other side of the MIL-53(Al) / PP composite membrane obtained in step 3), and then placed in a vacuum oven for drying. The drying temperature is set to 80 ℃, and the membrane is dried until constant weight (solvent is removed) to obtain a coated membrane structure of MIL-53(Al) / PP / Al2O3, wherein the thickness of the coating on each side is 5 μm.

[0056] Comparative Example 1

[0057] Replace MIL-53 (Al) with Cu-BTC (HKUST-1), and follow the same steps as in Example 1 to obtain a coated membrane Cu-BTC / PP / Cu-BTC.

[0058] Comparative Example 2

[0059] Replace MIL-53 (Al) with Fe-BDC (MIL-101), and follow the same steps as in Example 1 to obtain the coated membrane Fe-BDC / PP / Fe-BDC.

[0060] To test the electrochemical stability of the MOF coating on the separators in the above embodiments and comparative examples during charge-discharge cycles, constant voltage charge-discharge cycle tests were conducted. The MOF-based coated separators obtained in Examples 1, 2, and Comparative Example 1 were cut into circular pieces with a diameter of 19 mm, and then assembled with stainless steel electrodes and electrolyte (1 M LiPF6 in EC:DEC=7:3 vol.%) to form stainless steel symmetrical batteries. After standing for 8 h, constant voltage charge-discharge cycle tests were performed. The charge-discharge voltage was set to 3 V, the cutoff current to 1 mA, and the batteries were allowed to stand for 1 min between charge and discharge cycles. The batteries were charged and discharged 2000 times, and the surface morphology and chemical elemental composition of the stainless steel electrodes before and after charge-discharge were analyzed.

[0061] Figure 1 and Figure 2 The images shown are scanning electron microscope (SEM) images of the stainless steel electrodes of the battery assembled with the Al-MOF-coated separator obtained in Example 1 before and after 2000 constant-voltage charge-discharge cycles. The comparison reveals a slight deposition on the surface of the stainless steel electrodes after 2000 cycles. However, this deposition may originate from the dissolution and deposition of aluminum from the Al-MOF, or from other impurities introduced during the electrode surface or assembly process. Further analysis using chemical composition spectra, such as... Figure 7 and Figure 8 The aluminum element distribution on the stainless steel electrode surface of the stainless steel battery assembled with the separator obtained in Example 1 before and after constant voltage charge-discharge cycles were shown. It was found that, like before and after charge-discharge cycles, there was no significant aluminum enrichment on the stainless steel electrode surface, indicating that there was no or only very slight aluminum metal deposition on the electrode surface after charge-discharge cycles. Further quantitative analysis using EDS showed that the aluminum element content on the electrode surface before charge-discharge cycles in Example 1 was approximately 0.06 wt.%, and the aluminum element content after cycles was approximately 0.16 wt.%, indicating only very slight aluminum metal deposition, which can be ignored. Similarly, Figure 3 and Figure 4 The images shown are scanning electron microscope (SEM) images of the stainless steel electrodes of the battery assembled with the Zn-MOF-coated separator obtained in Example 2 before constant voltage charge-discharge cycles and after 2000 constant voltage charge-discharge cycles. A comparative analysis is provided. Figure 3 and Figure 4 It can be seen that after 2000 cycles, only slight metal deposition occurred on the electrode surface. This was confirmed by EDS analysis. Figure 9 and Figure 10The distribution of zinc on the surface of the stainless steel electrode was quantitatively analyzed. As shown in the figure, after 2000 cycles, the electrode surface showed no obvious zinc enrichment, similar to before the cycles. Further quantitative analysis by EDS showed that the zinc content on the electrode surface after 2000 cycles was about 2 wt.%. This is because the reduction potential of zinc is higher than that of aluminum. During the cycling process, Zn-MOF underwent slight structural decomposition, and the zinc deposition was slightly more than that of aluminum deposition in Example 1. However, considering the number of cycles of 2000, Zn-MOF still showed high electrochemical stability.

[0062] Figure 5 and Figure 6 The images shown are SEM images of the stainless steel electrodes of the battery assembled with the Cu-MOF-coated separator obtained in Comparative Example 1 before and after 2000 constant-voltage charge-discharge cycles. The comparison reveals severe deposition on the stainless steel electrode surface after 2000 charge-discharge cycles, almost completely covering the electrode surface. EDS analysis of the EDS spectra is as follows... Figure 11 and Figure 12 The images show the surface copper distribution on the stainless steel surface of the battery assembled with the Cu-MOF coated separator (Comparative Example 1) before and after 2000 constant-voltage charge-discharge cycles. Figure 11 and Figure 12 The comparison showed that after 2000 cycles, there was a very obvious enrichment of copper on the electrode surface, indicating that this area is a copper metal deposition area. EDS quantitative analysis showed that the copper content on the electrode surface was 0.19 wt.% before cycling and 20.11 wt.% after cycling, an increase of more than 100 times. This further confirms that due to the high reduction potential of copper, the Cu-MOF structure is unstable and easily decomposes during battery operation, resulting in the precipitation and deposition of Cu, which causes battery performance degradation.

[0063] The coated separators obtained in Examples 1, 3, 4, and Comparative Example 2 were assembled into batteries, and the resulting batteries were subjected to cycle stability tests. In Example 4, the Al-MOF coating on the coated separator was assembled using two methods: one near the positive electrode side and the other near the negative electrode side. The resulting battery configurations were LFP / / MIL-53(Al) / PP / MIL-53(Al) / / Li (Example 1), LFP / / PP / MIL-53(Al) / / Li (Example 3), LFP / / Al2O3 / PP / MIL-53(Al) / / Li (the Al-MOF coating assembly method in Example 4 with the coating near the negative electrode side), LFP / / MIL-53(Al) / PP / Al2O3 / / Li (the Al-MOF coating assembly method in Example 4 with the coating near the positive electrode side), and LFP / / MIL-101 / PP / MIL-101 / / Li (Comparative Example 2). The cycle stability results of these batteries were obtained by […]. Figure 13-17 As shown in the figure. Through comparison, it can be seen that the obtained battery structure LFP / / Al2O3 / PP / MIL-53(Al) / / Li has the best cycle stability, with a capacity retention of more than 95% after 1000 cycles (e.g., ...). Figure 15 This is because when the Al-MOF base coating is close to the negative electrode side, its high porosity and regular pore structure allow for uniform ion flow, ensuring uniform deposition and precipitation of lithium metal and suppressing lithium dendrite growth. Furthermore, Al-MOF exhibits good stability at low potentials, preventing structural decomposition that could lead to aluminum precipitation; while Al2O3 material is chemically inert, maintaining structural stability even at high-voltage positive electrodes, ensuring ion transport. The battery structure LFP / / MIL-53(Al) / PP / MIL-53(Al) / / Li retains more than 90% of its capacity after 1000 cycles. Figure 13 It also exhibited relatively good cycle stability, but... Figure 15The performance of the LFP / / Al2O3 / PP / MIL-53(Al) / / Li battery structure showed a slight decrease in cycle stability. This is mainly because, during long-term cycling, the Al-MOF on the positive electrode side may undergo slight structural decomposition due to the shuttle movement of large-sized ions or solvated ions in the electrolyte and the interaction between the positive electrode and the separator, affecting lithium-ion insertion / extraction. Therefore, under the premise of low-potential MOF oriented assembly on the negative electrode side, the positive electrode is more preferably an inorganic ceramic coating such as Al2O3, or a chemically inert organic polymer coating, or an inorganic ceramic-organic polymer composite coating. The subsequent battery cycle performance, from highest to lowest, was LFP / / PP / MIL-53(Al) / / Li, LFP / / MIL-53(Al) / PP / Al2O3 / / Li, and LFP / / MIL-101 / PP / MIL-101 / / Li, with a capacity retention of 74% after cycling. Figure 14 ), 54% Figure 16 ) and 10% Figure 17 Among them, the battery structure LFP / / PP / MIL-53(Al) / / Li, obtained by coating a separator on one side, achieved a capacity retention of approximately 74% after 1000 cycles, demonstrating good cycle stability. Figure 14 It should be noted that the battery capacity showed an upward trend after about 60 cycles. This is attributed to the high porosity of the MOF material, which gives the MOF coating the advantage of high liquid retention, allowing it to maintain interfacial wetting during cycling and promoting ion transport. The battery structure LFP / / MIL-53(Al) / PP / Al2O3 / / Li exhibited rapid capacity decay in some cycle cycles. Figure 16 This is caused by the formation of side reactions (such as dead lithium), indicating that the Al2O3 coating on the negative electrode side does not have the function of effectively suppressing side reactions. The capacity decay of the battery LFP / / MIL-101 / PP / MIL-101 / / Li obtained by Fe-MOF coated separator is severe, and a capacity drop occurs after about 150 cycles. Figure 17 This is because the high reduction potential of iron makes the Fe-MOF structure unstable. During cycling, the structure decomposes, and iron is deposited on the surface of the negative electrode, which hinders the insertion and extraction of lithium ions, resulting in a significant capacity decay.

[0064] In summary, the oriented coated separator based on a low-reduction-potential MOF of this invention exhibits excellent electrochemical stability. When oriented close to the negative electrode side, it can utilize its own regular pore structure to uniformly distribute ion flow and suppress dendrites, while its low potential prevents the precipitation and deposition of metal elements, avoiding capacity decay and extending the cycle life of the battery. The technology proposed in this invention fills the current technological gap in using MOF materials as separator coating materials, providing important application guidance for the product design and development of MOF-based coated separators. Furthermore, the preparation method disclosed in this invention is compatible with existing separator coating processes, featuring high feasibility and simple operation.

Claims

1. A coated membrane based on a low reduction potential MOF, characterized in that: The coated membrane based on a low reduction potential MOF includes at least a base film and a MOF coating formed on at least one surface of the base film; wherein the MOF coating has a low reduction potential; the low reduction potential refers to the electrode potential of the metal element of the MOF in the MOF coating being less than -0.037V vs SHE.

2. The coated membrane based on a low reduction potential MOF according to claim 1, characterized in that: The coated separator based on low reduction potential MOF is a directional coated separator; the directional coated separator means that the separator is coated with the MOF coating on at least one surface near the negative electrode of the battery or electrochemical device.

3. The coated membrane based on a low reduction potential MOF according to claim 2, characterized in that: The directional coated separator is a double-sided coated separator, and both sides are coated with the MOF coating; that is, the directional coated separator has the MOF coating formed on both the negative and positive electrodes of the battery or electrochemical device.

4. The coated membrane based on a low reduction potential MOF according to claim 2, characterized in that: The directional coated separator is a double-sided coated separator, with one side having the MOF coating and the other side having other coatings; that is, the directional coated separator has the MOF coating on the surface near the negative electrode of the battery or electrochemical device and other coatings on the surface near the positive electrode of the battery or electrochemical device.

5. A coated membrane based on a low reduction potential MOF according to claim 4, characterized in that: The other coatings are one or more of the following: inorganic ceramic coatings, organic polymer coatings, and inorganic ceramic-organic polymer composite coatings.

6. The coated membrane based on a low reduction potential MOF according to claim 1, characterized in that: The MOF material in the MOF coating is selected from one or more of Cr-MOF, Zn-MOF, Ti-MOF, Al-MOF, Ce-MOF, Mg-MOF, La-MOF, and MOFs based on alkali metals or alkaline earth metals.

7. A coated membrane based on a low reduction potential MOF according to claim 6, characterized in that: The MOF material in the MOF coating is selected from one or more of Zn-MOF, Al-MOF, Ce-MOF, Mg-MOF, La-MOF, and MOFs based on alkali metals or alkaline earth metals.

8. The coated membrane based on a low reduction potential MOF according to claim 1, characterized in that: The base film is selected from one or more composite films selected from polyethylene film, polypropylene film, polyethylene-polypropylene composite film, polydimethylsiloxane film, polyethylene terephthalate film, polyamide film, polyimide film, glass fiber film, and nonwoven fabric.

9. A coated diaphragm based on a low reduction potential MOF according to claim 1, characterized in that: The MOF coating contains MOF material and an adhesive; the adhesive is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene, polyvinyl alcohol, polyvinyl ethyl ether, polyethylene glycol, polyethylene terephthalate, polyethylene oxide, polypropylene, polyacrylonitrile, polymethyl methacrylate, polyimide, polyamide, polyamide-imide, sodium carboxymethyl cellulose, sodium alginate, chitosan, styrene-butadiene rubber, styrene-butadiene latex, and guar gum.

10. A method for preparing a coated membrane based on a low reduction potential MOF as described in any one of claims 1-9, characterized in that: The method is any one of the following: scraping, roller coating, spraying, spin coating, impregnation, pressure filtration, vacuum filtration, casting, and hot pressing.

11. An electrochemical device, characterized in that: The electrochemical device includes at least a positive electrode, a negative electrode, and a coated separator based on a low reduction potential MOF as described in any one of claims 1-9.

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