CN113574731A

CN113574731A - Metal-organic framework (MOF) coated composite separator for electrochemical devices and applications thereof

Info

Publication number: CN113574731A
Application number: CN202080010044.6A
Authority: CN
Inventors: 吉米·王; 沈力; 卢峰
Original assignee: Shantou Chenghai Brothers Fine Chemical Co ltd; Fortchel International Ltd
Current assignee: Shantou Chenghai Brothers Fine Chemical Co ltd; Fortchel International Ltd; Ford Cheer International Ltd
Priority date: 2019-03-25
Filing date: 2020-03-25
Publication date: 2021-10-29
Also published as: WO2020192678A1

Abstract

The present invention provides a composite separator and an electrochemical device, such as a battery, having the same. The composite membrane includes at least one metal-organic framework (MOF) composite layer, and at least one porous layer that serves as a mechanical support for the at least one MOF composite layer. The at least one MOF composite layer includes at least one MOF material defining a plurality of channels and at least one polymer. The at least one MOF material is a type of crystalline porous scaffold composed of metal clusters with organic ligands and is activated for a period of time and at a temperature such that the at least one MOF material includes unsaturated metal centers, open metal sites, and/or structural defects capable of complexing with anions in the electrolyte.

Description

Metal-organic framework (MOF) coated composite separator for electrochemical devices and applications thereof

Cross reference to related patent applications

This application claims priority and benefit of U.S. provisional patent application serial No. 62/823,193 filed on 3, 25, 2019.

This application is also a continuation-in-part application of U.S. patent application No. 16/822,343 filed on 18/3/2020, claiming priority and benefit from U.S. provisional patent application No. 62/821,539 filed on 21/3/2019.

This application is also a continuation-in-part application of U.S. patent application No. 16/787,247 filed on 11/2/2020, claiming priority and benefit from U.S. provisional patent application No. 62/803,725 filed on 11/2/2019.

This application, which is also a continuation-in-part application of U.S. patent application serial No. 16/369,031 filed on 3/29/2019, itself claims priority and benefit of U.S. provisional patent application serial nos. 62/650,580 and 62/650,623 filed on 30/3/2018.

This application is also a continuation-in-part application of U.S. patent application No. 15/888,223 filed on 5.2.2018, which claims priority and benefit of U.S. provisional patent application nos. 62/455,752 and 62/455,800 filed on 7.2.7.2017.

This application is also a continuation-in-part application of U.S. patent application serial No. 15/888,232 filed on 5.2.2018, claiming priority and benefit of U.S. provisional patent application serial nos. 62/455,752 and 62/455,800 filed on 7.2.7.2017.

Each of the above applications is incorporated by reference herein in its entirety.

Technical Field

The present invention relates generally to batteries, and more particularly, to metal-organic framework (MOF) coated composite separators for electrochemical devices, such as high safety, high energy and high power batteries, and applications thereof.

Background

The background description provided herein is for the purpose of generally presenting the context of the disclosure. The subject matter discussed in this background of the invention section should not be admitted to be prior art merely by virtue of its inclusion in this background of the invention section. Similarly, the problems mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be considered as having been previously recognized in the prior art. The subject matter in the background section merely represents different approaches which may themselves be inventions. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

As an electrolyte reservoir in the cell, the separator acts as an intermediate layer that mediates the transport of ions and prevents the flow of electrons. The structure and performance of the separator significantly affect the performance of the battery. Particularly for lithium ion batteries, commercial polyolefin-based separators have poor thermal stability, insufficient mechanical modulus to block lithium dendrites, and inability to raise Li of the electrolyte⁺Migration number problems, which can create safety hazards, limit energy and power performance, and shorten battery life.

Including ceramic particles, e.g. ZrO, in a polymer matrix₂、Al₂O₃h and SiO₂Ceramic coating of particles, e.g. in the United statesDisclosed in No. 6,432,586, has been applied to polyolefin-based separators, which partially alleviates the above problems. In particular, such ceramic coated separator exhibits improved thermal stability against thermal runaway, and improved ability to inhibit lithium dendrite growth. However, such ceramic coatings do not regulate the transport of ions in the electrolyte, resulting in batteries with low Li⁺Migration number (<0.4). Therefore, new functions are developed on the separator to achieve efficient Li⁺Conduction represents a promising approach for advanced battery separators.

Li⁺Transport number (defined as Li)⁺The ratio of conductivity to total ionic conductivity) plays a crucial role in controlling the electrochemical performance of the cell. Low Li for commercial electrolytes in polyolefin-based separators⁺Migration number (<0.4) can lead to concentration polarization, degradation of the electrolyte-electrode interface, reduced energy efficiency, increased side reactions, and increased joule heating, which can shorten cycle life, particularly under rapid charge/discharge conditions. In other words, the polyolefin-based separator is not suitable for advanced batteries such as lithium metal batteries, high power batteries having a rapid charging capability, and the like.

Accordingly, there exists a heretofore unaddressed need in the art to address the aforementioned deficiencies and inadequacies.

Disclosure of Invention

In one aspect, the present invention relates to a composite separator for an electrochemical device comprising at least one metal-organic framework (MOF) composite layer; and at least one porous layer that serves as a mechanical support for at least one MOF composite layer. The at least one MOF composite layer includes at least one metal-organic framework (MOF) material defining a plurality of channels and at least one polymer. The at least one MOF material is a type of crystalline porous scaffold composed of metal clusters with organic ligands and is activated for a period of time and at a temperature such that the at least one MOF material comprises unsaturated metal centers, open metal sites and/or structural defects capable of complexing with anions in the electrolyte.

In one embodiment, the at least one MOF composite layer is formed by coating a mixture of at least one MOF material and a polymer solution comprising at least one polymer dissolved in at least one solvent on the at least one porous layer.

In one embodiment, the coating comprises dip coating, slot-die coating, knife coating, spin coating, or electrospinning.

In one embodiment, at least one porous layer has pores that serve as a liquid electrolyte host for conducting ions and is an electronic insulator for preventing short circuits.

In one embodiment, the at least one porous layer comprises one or more polymers including polypropylene (PP), Polyethylene (PE), Glass Fiber (GF), cellulose, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), Polyimide (PI), Polyallylamine (PAH), polyurethane, Polyacrylonitrile (PAN), Polymethylmethacrylate (PMMA), polytetraethylene glycol diacrylate, copolymers thereof, or combinations thereof.

In one embodiment, the at least one MOF composite layer comprises a MOF material in an amount ranging from about 5-99 wt% and at least one polymer in an amount ranging from about 1-95 wt%.

In one embodiment, the CO is produced by calcining, supercritical CO₂Or other treatment to activate at least one MOF material.

In one embodiment, the at least one MOF material has a tunable ligand functionality and a tunable pore size, wherein the tunable ligand functionality is by chemical modification of a negatively charged ligand and the tunable pore size is a grafting of chemical groups in the ligand.

In one embodiment, the organic ligand includes benzene-1, 4-dicarboxylic acid (BDC), benzene-1, 3, 5-tricarboxylic acid (BTC), biphenyl-4, 4' -dicarboxylic acid (BPDC), or derivatives thereof, and the metal cluster includes magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), or zirconium (Zr).

In one embodiment, the at least one MOF material comprises HKUST-1, MIL-100-Al, MIL-100-Cr, MIL-100-Fe, UiO-66, UiO-67, PCN series, MOF-808, MOF-505, MOF-74, or a combination thereof.

In one embodiment, the at least one MOF material comprises a zirconium-containing MOF (Zr-MOF) or has the general formula Zr₆(μ3-O₄)(μ3-OH₄)(-COO)₈(OH)₄(H₂O)_nWherein n is an integer less than 10.

In one embodiment, the at least one polymer comprises polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), PVDF-tetrahydrofuran (PVDF-THF), PVDF-chlorotrifluoroethylene (PVDF-CTFE), poly (methyl methacrylate) (PMMA), Polyacrylonitrile (PAN), and polyethylene oxide (PEO), copolymers thereof, or combinations thereof.

In one embodiment, the at least one solvent comprises acetone, water, methanol, ethanol, acetic acid, Dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), Tetrahydrofuran (THF), or a combination thereof.

In another aspect, the present invention relates to an electrochemical device comprising a positive electrode, a negative electrode, an electrolyte disposed between the positive electrode and the negative electrode, and a separator disposed in the electrolyte. The electrolyte is a liquid electrolyte comprising a metal salt dissolved in a nonaqueous solvent. The membrane is a composite membrane as disclosed.

In one embodiment, the non-aqueous solvent comprises one or more of: ethylene Carbonate (EC), Propylene Carbonate (PC), Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Methyl Propyl Carbonate (MPC), Butyl Methyl Carbonate (BMC), Ethyl Propyl Carbonate (EPC), dipropyl carbonate (DPC), cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-1, 3-oxazolidin-2-one, gamma-butyrolactone, 1, 2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, methyl acetate, ethyl acetate, nitromethane, 1, 3-propanesultone, gamma-valerolactone, methyl isobutyrylacetate, ethyl 2-methoxyacetate, ethyl 2-ethoxyacetate, Diethyl oxalate, an ionic liquid, a chain ether compound including at least one of γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane, and diethyl ether, and a cyclic ether compound including at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, and dioxane.

In one embodiment, anions in the liquid electrolyte are spontaneously adsorbed and immobilized within the pore channels by the at least one MOF material, thereby releasing metal ions and allowing the metal ions to be transported with a higher metal ion transport number than that of the membrane without the at least one MOF material.

In one embodiment, the metal ion transport number is the ratio of the metal ion conductivity to the ionic conductivity, wherein the ionic conductivity is the sum of the metal ion conductivity and the anion conductivity.

In one embodiment, the liquid electrolyte in the composite separator has a metal ion transport number in the range of about 0.5 to 1.

In one embodiment, the metal salt comprises one or more of a lithium salt, a sodium salt, a magnesium salt, a zinc salt, and an aluminum salt.

In one embodiment, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl imide) (LiTFSI), lithium bis (trifluorosulfonyl imide), lithium trifluoromethanesulfonate, lithium fluoroalkylsulfonyl imide, lithium fluoroarylsulfonyl imide, lithium bis (oxalato) borate, lithium tris (trifluoromethylsulfonyl imide), lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, and lithium chloride.

In one embodiment, the sodium salt comprises sodium triflate, NaClO₄、NaPF₆、NaBF₄One or more of sodium bis (trifluoromethanesulfonyl) imide (I) (NaTFSI) and sodium bis (fluorosulfonyl) imide (I) (NaFSI).

In one embodiment, the magnesium salt comprises magnesium triflate, Mg (ClO)₄)₂、Mg(PF₆)₂、Mg(BF₄)₂Bis (trifluoromethanesulfonyl) magnesium (II) imide (Mg (TFSI))₂) And magnesium bis (fluorosulfonyl) imide (II) (Mg (FSI))₂) One or more of (a).

In one embodiment, the zinc salt comprises zinc trifluoromethanesulfonate, Zn (ClO)₄)₂、Zn(PF₆)₂、Zn(BF₄)₂Bis (trifluoromethanesulfonyl) imide zinc (II) (Zn (TFSI))₂) Bis (fluorosulfonyl) imide zinc (II) (Zn (FSI))₂) One or more of (a).

In one embodiment, the electrochemical device is a lithium battery, a sodium battery, a magnesium battery, or a zinc metal battery.

In one embodiment, for a lithium battery, the positive electrode comprises one or more of: LiCoO₂(LCO)、LiNiMnCoO₂₍NMC), lithium iron phosphate (LiFePO)₄) Lithium iron fluorophosphate (Li)₂FePO₄F) Over-lithiated layer-by-layer cathodes, spinel lithium manganese oxide (LiMn)₂O₄) Lithium cobalt oxide (LiCoO)₂)、LiNi_0.5Mn_1.5O₄Comprising LiNi_0.8Co_0.15Al_0.05O₂Or lithium nickel cobalt aluminum oxide, lithium vanadium oxide (LiV) of NCA₂O₅) And Li₂MSiO₄Wherein M consists of Co, Fe and/or Mn in a certain ratio; and the negative electrode comprises one or more of: lithium metal (Li), graphite, hard or soft carbon, graphene, carbon nanotubes, including Li₄Ti₅O₁₂And TiO₂Titanium oxide, silicon (Si), tin (Sn), germanium (Ge), silicon monoxide (SiO), silicon dioxide (SiO)₂) Tin oxide (SnO)₂) And a transition metal oxide including Fe₂O₃、Fe₃O₄、Co₃O₄And Mn_xO_yAt least one of (1).

In one embodiment, the positive electrode comprises NaMnO for a sodium battery₂、NaFePO₄And Na₃V₂(PO₄)₃One or more of, TiSe for magnesium battery₂、MgFePO₄F、MgCo₂O₄And V₂O₅Or for zinc batteriesgamma-MnO of₂、ZnMn₂O₄And ZnMnO₂One or more of (a).

These and other aspects of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, although variations and modifications therein may be effected without departing from the spirit and scope of the novel concepts of the invention.

Drawings

The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like elements of an embodiment.

Fig. 1 shows a schematic view of a composite diaphragm according to an embodiment of the invention.

Fig. 2 shows a schematic representation of a metal-organic framework with open metal sites and the ion conduction behavior of lithium ions and anions, respectively, according to an embodiment of the invention.

Fig. 3 shows a schematic representation of chemically modified ligands of the metal-organic framework and the ion conduction behavior of lithium ions and anions, respectively, according to an embodiment of the invention.

Figure 4 shows an X-ray diffraction pattern of a simulated zirconium terephthalate-based MOF (UiO-66), a synthetic UiO-66, and a coated UiO-66 on a polypropylene-based membrane (support membrane, denoted PP) in accordance with an embodiment of the present invention.

FIG. 5 shows a thermogravimetric analysis curve of UiO-66 in an air atmosphere according to an embodiment of the present invention.

Fig. 6 shows a scanning electron microscope image of a PP separator (support separator from Celgard).

FIG. 7 shows a scanning electron microscope image of a PP coated with UiO-66 according to an embodiment of the invention.

Fig. 8 shows the measurement results of the lithium ion transport number of the electrolyte in the support separator.

Fig. 9 shows the measurement results of the lithium ion transport number of the electrolyte in the composite separator with activated UiO-66 according to the embodiment of the present invention.

Fig. 10 shows the measurement results of the lithium ion transport number of the electrolyte in the composite separator with deactivated UiO-66.

Fig. 11 shows galvanostatic cycling for a Li symmetric battery using an electrolyte saturated PP separator and a composite separator, according to an embodiment of the invention.

Fig. 12 shows a full cell (LiNi) using an electrolyte-saturated supporting separator and a composite separator according to an embodiment of the present invention_1/3Co_1/3Mn_1/3O₂As the cathode and graphite as the anode).

Fig. 13 shows a full cell (LiNi) using an electrolyte saturated supporting separator and a composite separator according to an embodiment of the present invention_1/3Co_1/3Mn_1/3O₂As the cathode and graphite as the anode).

FIG. 14 shows a zirconium-based MOF (UiO-66-NH) with chemical modification on the ligand according to an embodiment of the invention₂) Illustrative drawings.

FIG. 15 shows zirconium-based MOF (UiO-66-NH) during corresponding chemical modification on a ligand according to an embodiment of the invention₂) X-ray diffraction pattern of (a).

FIG. 16 shows a synthesized UiO-66-NH according to an embodiment of the present invention₂Scanning electron microscope images of (a).

Fig. 17 shows a scanning electron microscope image of a microporous layer (support membrane from Celgard corporation).

FIG. 18 shows UiO-66-NH with modification according to an embodiment of the invention₂Scanning electron microscope images of the composite membrane of (1).

FIG. 19 shows UiO-66-NH with modification according to an embodiment of the invention₂Scanning electron microscope images of the composite membrane of (1).

FIG. 20 illustrates a modified UiO-66-NH layer in accordance with an embodiment of the present invention₂The result of measuring the transference number of lithium ions of the electrolyte in the composite separator of (1).

Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

The terms used in this specification generally have their ordinary meanings in the art, in the context of the invention, and in the specific context in which each term is used. Certain terms used to describe the invention are discussed below or elsewhere in the specification to provide additional guidance to the practitioner regarding the description of the invention. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no effect on the scope and meaning of the term; in the same context, the scope and meaning of a term is the same, whether or not it is highlighted. It should be understood that the same thing can be described in more than one way. Thus, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is there any special meaning to indicate whether a term is set forth or discussed in detail herein. Synonyms for certain terms are provided. Recitation of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only and in no way limits the scope and meaning of the invention or any exemplary terms. Also, the present invention is not limited to the various embodiments presented in this specification.

It should be understood that, as used in the description herein and throughout the claims that follow, the meaning of "a", "an", and "the" includes plural referents unless the context clearly dictates otherwise. In addition, it will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Furthermore, relative terms, such as "lower" or "bottom" and "upper" or "top," may be used herein to describe one element's relationship to another element, as illustrated. It will be understood that the relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. For example, if the device in one of the figures is turned over, elements described as being on the "lower" side of other elements would then be oriented on "upper" sides of the other elements. Thus, the exemplary term "lower" can encompass both an orientation of "lower" and "upper," depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as "below" or "beneath" other elements would then be oriented "above" the other elements. Thus, the exemplary terms "below" or "beneath" can encompass both an orientation of above and below.

It will be further understood that the terms "comprises" and/or "comprising", "includes" and/or "including" and/or "having", or "carrying" and/or "carrying", or "containing" and/or "containing", or "involving (involving)" and/or "involving (involving)", and the like, are open-ended, i.e. meant to include, but not limited to. When used in this disclosure, they specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used in this disclosure, "about," "approximately," or "substantially" generally means within 20%, preferably within 10%, and more preferably within 5% of a given value or range. The numerical values set forth herein are approximations that may vary depending upon the particular circumstances involved, and it is intended that the term "about", "approximately" or "substantially" may be inferred if not expressly stated.

As used in this disclosure, the phrase "at least one of A, B and C" should be interpreted as using a non-exclusive logical or to mean a logic (a or B or C). As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following description is merely illustrative in nature and is not intended to limit the invention, its application, or uses. The broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention includes particular examples, the true scope of the invention should not be so limited since other modifications will become apparent from the drawings, the specification and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. It should be understood that one or more steps of the method may be performed in a different order (or simultaneously) without altering the principles of the present invention.

In one aspect, the present invention relates to a metal-organic framework (MOF) -coated separator (composite separator) that can significantly enhance Li of commercial electrolytes⁺Migration number (>0.6), wherein the MOF is a porous, coordinated solid periodically built up from metal clusters and organic linkers, forming ordered porous scaffolds with various sizes. The MOFs disclosed herein contain unsaturated coordination sites, structural defects, or negatively charged moieties that can immobilize/repel anion movement and facilitate cation (lithium ion) conduction. At the same time, the use of MOF coated membranes in batteries provides other various benefits, including but not limited to: reduced concentration polarization, accelerated electrode reaction kinetics, reduced electrolyte decomposition, improved thermal stability, and the like.

The use of metal-organic frameworks in batteries has been reported. For example, an electrolyte membrane comprising a metal-organic framework, a polymer and an electrolyte is discussed in U.S. Pat. nos. 9,105,940 and 10,347,939, which disclose a crosslinking method for preparing a composite membrane by covalently bonding a metal-organic framework (e.g., carboxylic acid) with a polymer (e.g., amine). A solid polymer electrolyte comprising a metal-organic framework, a lithium salt and a lithium ion conducting polymer is disclosed in chinese patents CN103474696B and CN106532112A, wherein the benefits of adding the claimed metal-organic framework to the solid polymer electrolyte combine the effects of conventional ceramic particles. The claimed benefits of adding a metal-organic framework to a solid polymer electrolyte include: reduced polymer crystallinity, increased Li⁺Electrical conductivity, enhanced mechanical and thermal stability. Further, a solid lithium ion electrolyte comprising a metal-organic framework is disclosed in U.S. Pat. No. 9,525,190, which discloses a post-synthesis method by grafting an alkoxide onto the metal-organic framework. The metal centers in the claimed metal-organic framework are covered with a lithium compound (lithium alkoxide) and then soaked in a typical electrolyte. A coated metal-organic framework (NH) is disclosed₂-MIL-125(Ti) -a titanium terephthalate-based framework, particlesThe polyolefin-based separator of (1) is used for stabilizing a lithium-metal anode (Chemical Science, 2017,8, 4285). The benefit of incorporating MOF is through-NH₂Radical (in the ligand) with Li⁺The interaction between the ions enables uniform electrodeposition of lithium ions. Synthesis of zirconium-based MOF (UiO-66-NH) with cationic center by chemical modification of amine groups in ligands₂) Particles (Energy Storage Materials) (2019)). Then incorporating the modified positively charged particles into a polymer electrolyte to increase the lithium ion transport number by interaction between the cation center and the anion; and MOF-based separators are disclosed in lithium-sulfur battery applications (Natural Energy (Nature Energy) 1.7(2016):16094, < ACS Energy Letters > (ACS Energy Letters) > 2.10(2017): 2362-. The claimed benefit is to mitigate the transport of dissolved polysulfides by preventing their transport through the micropores of the MOF. Other claimed benefits report enhanced chemical adsorption of polysulfides in MOF-carbon nanotube composite membranes (energy storage materials 14(2018): 383-.

However, the present invention is significantly different from the above-described technique in the following respects: (1) the metal-organic framework described herein contains Open Metal Sites (OMS), which can be understood as coordinatively unsaturated metal sites, exposed metal sites, and the like. (2) MOFs with OMS directly with commercially available liquid electrolytes (e.g., based on LiPF)₆Electrolyte) in which OMS can spontaneously bind anions in the electrolyte (e.g., PF)₆ ^-) Forming a negatively charged ion channel and facilitating the transfer of lithium ions. (3) The coating of the separator with the MOF having OMS effectively increased Li of the electrolyte compared to commercial polyolefin-based separators⁺Transport number or Li⁺Electrical conductivity. (4) The metal-organic frameworks described herein can also be modified with negatively charged moieties to exclude/repel anion movement and allow efficient transport of cations, mimicking ion channels typically present in biological systems.

Specifically, in one aspect of the present invention, a composite separator for an electrochemical deviceComprises at least one MOF composite layer; and at least one porous layer that serves as a mechanical support for the at least one MOF composite layer. The at least one MOF composite layer comprises at least one metal-organic framework (MOF) material and at least one polymer defining a plurality of channels. The at least one MOF material is a type of crystalline porous scaffold constructed from metal clusters with organic ligands and is activated for a period of time and at a temperature such that the at least one MOF material comprises unsaturated metal centers, open metal sites and/or structural defects capable of complexing with anions in the electrolyte. In certain embodiments, at least one MOF material is formed by calcining, supercritical CO₂Or other treatment to activate.

In certain embodiments, the at least one MOF composite layer is formed by coating a mixture of at least one MOF material and a polymer solution comprising at least one polymer dissolved in at least one solvent on the at least one porous layer. In certain embodiments, the coating comprises dip coating, slot extrusion coating, knife coating, spin coating, or electrospinning.

In certain embodiments, at least one porous layer has pores that serve as a liquid electrolyte host for conducting ions and is an electronic insulator for preventing short circuits. In certain embodiments, the at least one porous layer comprises one or more polymers comprising polypropylene (PP), Polyethylene (PE), Glass Fiber (GF), cellulose, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), Polyimide (PI), Polyallylamine (PAH), polyurethane, Polyacrylonitrile (PAN), Polymethylmethacrylate (PMMA), polytetraethylene glycol diacrylate, copolymers thereof, or combinations thereof.

In certain embodiments, at least one MOF composite layer comprises a MOF material in an amount ranging from about 5-99 wt% and at least one polymer in an amount ranging from about 1-95 wt%.

In certain embodiments, the at least one MOF material has a tunable ligand functionality and a tunable pore size, wherein the tunable ligand functionality is by chemical modification of a negatively charged ligand and the tunable pore size is a grafting of chemical groups in the ligand.

In certain embodiments, the organic ligand comprises benzene-1, 4-dicarboxylic acid (BDC), benzene-1, 3, 5-tricarboxylic acid (BTC), biphenyl-4, 4' -dicarboxylic acid (BPDC), or derivatives thereof, and the metal cluster comprises magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), or zirconium (Zr).

In certain embodiments, the at least one MOF material comprises HKUST-1, MIL-100-Al, MIL-100-Cr, MIL-100-Fe, UiO-66, UiO-67, the PCN series, MOF-808, MOF-505, MOF-74, or a combination thereof.

In certain embodiments, the at least one MOF material comprises zirconium MOF (Zr-MOF) or has the general formula Zr₆(μ3-O₄)(μ3-OH₄)(-COO)₈(OH)₄(H₂O)_nWherein n is an integer less than 10.

In certain embodiments, the at least one polymer comprises polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), PVDF-tetrahydrofuran (PVDF-THF), PVDF-chlorotrifluoroethylene (PVDF-CTFE), poly (methyl methacrylate) (PMMA), Polyacrylonitrile (PAN), and polyethylene oxide (PEO), copolymers thereof, or combinations thereof.

In certain embodiments, the at least one solvent comprises acetone, water, methanol, ethanol, acetic acid, Dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), Tetrahydrofuran (THF), or a combination thereof.

In certain embodiments, the non-aqueous solvent comprises one or more of: ethylene Carbonate (EC), Propylene Carbonate (PC), Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Methyl Propyl Carbonate (MPC), Butyl Methyl Carbonate (BMC), Ethyl Propyl Carbonate (EPC), dipropyl carbonate (DPC), cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-1, 3-oxazolidin-2-one, gamma-butyrolactone, 1, 2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, methyl acetate, ethyl acetate, nitromethane, 1, 3-propanesultone, gamma-valerolactone, methyl isobutyrylacetate, ethyl 2-methoxyacetate, ethyl 2-ethoxyacetate, Diethyl oxalate, an ionic liquid, a chain ether compound including at least one of γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane, and diethyl ether, and a cyclic ether compound including at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, and dioxane.

In certain embodiments, anions in the liquid electrolyte are spontaneously adsorbed and immobilized within the pore channels by the at least one MOF material, thereby releasing metal ions and allowing the metal ions to be transported with a higher metal ion transport number than that of the membrane without the at least one MOF material.

In certain embodiments, the metal ion transport number is the ratio of metal ion conductivity to ionic conductivity. The ionic conductivity is the sum of the metal ionic conductivity and the anion conductivity.

In certain embodiments, the liquid electrolyte in the composite separator has a metal ion transport number in the range of about 0.5 to 1.

In certain embodiments, the metal salt comprises one or more of a lithium salt, a sodium salt, a magnesium salt, a zinc salt, and an aluminum salt.

In certain embodiments, the lithium salt comprises one or more of the following: lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl imide) (LiTFSI), lithium bis (trifluoromethylsulfonyl imide), lithium trifluoromethanesulfonate, lithium fluoroalkyl sulfonyl imide, lithium fluoroaryl sulfonyl imide, lithium bis (oxalato) borate, lithium tris (trifluoromethylsulfonyl imide) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, and lithium chloride.

In certain embodiments, the sodium salt comprises sodium triflate, NaClO₄、NaPF₆、NaBF₄One or more of sodium bis (trifluoromethanesulfonyl) imide (I) (NaTFSI) and sodium bis (fluorosulfonyl) imide (I) (NaFSI).

In certain embodiments, the magnesium salt comprises magnesium triflate, Mg (ClO)₄)₂、Mg(PF₆)₂、Mg(BF₄)₂Bis (trifluoromethanesulfonyl) magnesium (II) imide (Mg (TFSI))₂) And magnesium bis (fluorosulfonyl) imide (II) (Mg (FSI))₂) One or more of (a).

In certain embodiments, the zinc salt comprises zinc trifluoromethanesulfonate, Zn (ClO)₄)₂、Zn(PF₆)₂、Zn(BF₄)₂Bis (trifluoromethanesulfonyl) imide zinc (II) (Zn (TFSI))₂) Bis (fluorosulfonyl) imide zinc (II) (Zn (FSI))₂) One or more of (a).

In certain embodiments, the electrochemical device is a lithium battery, a sodium battery, a magnesium battery, or a zinc metal battery.

In certain embodiments, for a lithium battery, the positive electrode comprises one or more of: LiCoO₂(LCO)、LiNiMnCoO₂(NMC) and lithium iron phosphate (LiFePO)₄) Lithium iron fluorophosphate (Li)₂FePO₄F) Over-lithiated layer-by-layer cathodes, spinel lithium manganese oxide (LiMn)₂O₄) Lithium cobalt oxide (LiCoO)₂)、LiNi_0.5Mn_1.5O₄Comprising LiNi_0.8Co_0.15Al_0.05O₂Or lithium nickel cobalt aluminum oxide, lithium vanadium oxide (LiV) of NCA₂O₅) And Li₂MSiO₄Wherein M consists of Co, Fe and/or Mn in a certain ratio; and the negative electrode comprises one or more of: lithium metal (Li), graphite, hard or soft carbon, graphene, carbon nanotubes, including Li₄Ti₅O₁₂And TiO₂Titanium oxide, silicon (Si), tin (Sn), germanium (Ge), silicon monoxide (SiO), silicon dioxide (SiO)₂) Tin oxide (SnO)₂) And (2) processA transition metal oxide comprising Fe₂O₃、Fe₃O₄、Co₃O₄And Mn_xO_yAt least one of (1).

In one embodiment, the positive electrode comprises NaMnO for a sodium battery₂、NaFePO₄And Na₃V₂(PO₄)₃One or more of, TiSe for magnesium battery₂、MgFePO₄F、MgCo₂O₄And V₂O₅Or gamma-MnO for zinc cell₂、ZnMn₂O₄And ZnMnO₂One or more of (a).

Referring to fig. 1, a composite diaphragm according to one embodiment of the present invention is shown. The composite separator comprises a composite material layer 1 containing particles of a metal-organic framework (MOF) and a porous supporting separator layer 2. Preferably, the supporting separator layer 2 is a commercially available separator containing pores that serve as a bulk of the liquid electrolyte for conducting ions. Meanwhile, the supporting membrane layer 2 is an electronic insulator for preventing short circuit. The composite material layer 1 as a functional layer comprises particles of MOF 3 and a polymer matrix 4, wherein the MOF serves as a functional moiety for modulating the properties of the electrolyte and the polymer serves as an adhesive or mechanical matrix for adhering the MOF to the supporting membrane layer 2.

In certain embodiments, the supporting membrane layer 2 includes, but is not limited to, polypropylene (PP), Polyethylene (PE), Glass Fiber (GF), cellulose, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), Polyimide (PI), Polyallylamine (PAH), polyurethane, Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polytetraethylene glycol diacrylate, copolymers thereof, or combinations thereof.

MOF 3 is a class of crystalline porous scaffolds constructed from metal cluster nodes and organic ligands and represents a class of porous coordination solids with multifunctional structures and functional convertibility. In certain embodiments, particles of MOF 3 are constructed by periodically bridging inorganic metal clusters with organic ligands (linkers) forming windows 5 typically below 2 nanometers, whereas mesoporous MOFs can be prepared by isoreticular expansion of organic ligands (isoreticular expansion). Suitable ligands are preferably, but not limited to, benzene-1, 4-dicarboxylic acid (BDC), benzene-1, 3, 5-tricarboxylic acid (BTC), and derivatives thereof. Examples of various BDC-based ligand derivatives are given in table 2. Suitable metal clusters include, but are not limited to, magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), zirconium (Zr), and the like.

Table 1: selected MOFs for high performance composite membranes

Table 1 shows examples of MOFs, including their typical chemical formula, ligand structure and approximate pore size.

In certain embodiments, MIL-100 series MOF (M)₃O(BTC)₂OH·(H₂O)₂) Is formed by sharing a common mu₃M of-O³⁺(M ═ Al, Cr, Fe) octahedral trimer. Each M³⁺Bonded to the four oxygen atoms of a bidentate ligand dicarboxylate (BTC) and their linkage results in a mesoporous cage (C)

And

) The mesoporous cage can pass through a micropore window (

And

) And (4) entering. The corresponding ends in the octahedron are generally occupied by removable guest molecules.

In certain embodiments, UiO-66 bridges Zr by bridging it with a BDC linker (BDC ═ 1, 4-dicarboxylate)₆O₄(OH)₄Inorganic cluster acquisition。Zr₆Octahedra alternately composed of μ from BDC₃-O、μ₃-OH and O atoms coordinated, wherein₃the-OH may undergo dehydroxylation upon thermal activation to form distorted Zr₆O₆Node (hepta-coordinated Zr).

In certain embodiments, UiO-67 has the same topology as UiO-66, with enlarged channels due to the larger linker size of BPDC (BPDC ═ biphenyl-4, 4' -dicarboxylate). Both UiO 66 and UiO 67 contain two types of pore sizes, small tetrahedral pores and large octahedral pores. Other ligand derivatives are illustrated in table 2.

Table 2: zirconium-based MOFs with different functional ligands

Typically, MOFs are synthesized in the presence of a solvent (e.g., water) and a ligand, both of which coordinate to the metal center of the MOF. Removal of solvent molecules (e.g., under vacuum at elevated temperatures) disrupts solvent coordination from the MOFs, resulting in MOF scaffolds with unsaturated metal centers. The conditions for removing solvent molecules include a temperature range of about 200 ℃ to about 220 ℃ at a pressure of about 30 millitorr. This temperature range is suitable for removing any solvent, although it will be appreciated that higher boiling solvents may require longer drain times than lower boiling solvents. In one example, MOF materials in powder form are degassed or activated under vacuum at high/elevated temperatures (e.g., from about 200 ℃ to about 220 ℃) to remove adsorbed water molecules. Other solvent molecule removal methods may also be used in the practice of the present invention.

The polymer matrix 4 includes, for example, but is not limited to, polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), PVDF-tetrahydrofuran (PVDF-THF), PVDF-chlorotrifluoroethylene (PVDF-CTFE), poly (methyl methacrylate) (PMMA), Polyacrylonitrile (PAN), and polyethylene oxide (PEO).

In certain embodiments, MOF particles 3 are blended with a polymer matrix 4 and the resulting mixture is compounded with a supporting membrane layer 2. Composite membranes can be prepared by, but are not limited to, such coating, lamination, extrusion, and electrospinning processes. Suitable examples of coating include, but are not limited to, dip coating, slot extrusion coating, blade coating, and spin coating.

The structure of the composite membrane is not limited to the form of a single layer-by-layer structure as shown in fig. 1. In certain embodiments, the stacking order and number of layers 1 and 2 may be in any combination. For example, the MOF layer 1 may be present on the surface of the supporting membrane layer 2 or may be coated on the surface of the pores on the supporting membrane layer 2. In other examples, the MOF layer 1 may be filled with or interpenetrated with the supporting membrane layer 2.

In certain embodiments, the liquid electrolyte solvent comprises Ethylene Carbonate (EC), Propylene Carbonate (PC), Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), butylmethyl carbonate (BMC), ethylpropyl carbonate (EPC), dipropyl carbonate (DPC), cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-1, 3-oxazolidin-2-one, γ -butyrolactone, 1, 2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, methyl acetate, ethyl acetate, nitromethane, 1, 3-propanesultone, γ -valerolactone, methyl isobutyrylacetate, Ethyl 2-methoxyacetate, ethyl 2-ethoxyacetate, diethyl oxalate or ionic liquids, chain ether compounds (such as γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane and diethyl ether), cyclic ether compounds (such as tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane and dioxane), or mixtures of two or more of these solvents.

In certain embodiments, examples of suitable lithium salts include lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium dilithium (trifluoromethylsulfonyl imide) Lithium (LiTFSI), lithium bis (trifluoromethylsulfonyl imide), lithium trifluoromethanesulfonate, lithium fluoroalkylsulfonyl imide, lithium fluoroarylsulfonyl imide, lithium bis (oxalato borate), lithium tris (trifluoromethylsulfonyl imide) methide, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium chloride, or combinations thereof.

Referring to fig. 2, the features and functions of MOF particles in a composite membrane and electrolyte are shown, according to one embodiment of the invention. In this illustrative example, an Open Metal Site (OMS)6 in the MOF framework is defined as an unsaturated coordination site from the metal center, which can be obtained from the elimination of coordinating solvent or ligand on the metal site by heat treatment (or thermal activation). The unsaturated metal sites can bind to anionic species 7 in the electrolyte, providing highly mobile lithium ions 8 through the MOF pore channels.

Referring to fig. 3, another function of MOF particles in a composite membrane and electrolyte is shown, according to one embodiment of the invention. The negatively charged MOFs 9 achieved by the modified ligands repel the movement of anions 10, providing highly mobile lithium ions 11 and increased lithium ion transport numbers.

Advantages of ion conduction behavior exhibited in MOF channels include, but are not limited to: (1) high transference number of lithium ions; (2) mitigated concentration polarization; (3) improved reaction kinetics; (4) an affinity electrode-electrolyte interface; (5) inhibiting the formation of dendritic lithium; (6) an enhanced power density; (7) excellent durability at high rates; bargaining for improved thermal stability (8).

In certain embodiments, for lithium-based batteries, the positive electrode may be made of LiCoO₂(LCO), and the negative electrode may be formed of lithium metal (Li). Other examples of suitable positive electrodes include LiNiMnCoO₂(NMC) and lithium iron phosphate (LiFePO)₄) Lithium iron fluorophosphate (Li)₂FePO₄F) Overlithiated layer-by-layer cathodes, spinel lithium manganese oxides (LiMn)₂O₄) Lithium cobalt oxide (LiCoO)₂)、LiNi_0.5Mn_1.5O₄Lithium nickel cobalt aluminum oxide (e.g., LiNi)_0.8Co_0.15Al_0.05O₂Or NCA), lithium vanadium oxide (LiV)₂O₅)、Li₂MSiO₄(consisting of Co, Fe and/or Mn in any proportion), or can be sufficiently subject to lithium intercalation andany other suitable material that de-intercalates. Other examples of suitable negative electrodes include graphite, hard or soft carbon, graphene, carbon nanotubes, titanium oxide (Li)₄Ti₅O₁₂，TiO₂) Silicon (Si), tin (Sn), germanium (Ge), silicon monoxide (SiO), silicon dioxide (SiO)₂) Tin oxide (SnO)₂) Transition metal oxide (Fe)₂O₃、Fe₃O₄、Co₃O₄、Mn_xO_yEtc.) or any other suitable material that can undergo an intercalation, conversion or alloying reaction with lithium.

These and other aspects of the invention are further described in the following sections. Without intending to limit the scope of the invention, further exemplary implementations of the invention according to embodiments of the invention are given below. It should be noted that titles or subtitles may be used in the examples for convenience of a reader, which shall in no way limit the scope of the invention. Furthermore, certain theories are proposed and disclosed herein; however, they should not limit the scope of the invention, whether right or wrong, so long as the invention is practiced according to the present invention without regard to any particular theory or scheme of action.

Example 1

In the present illustrative example, the polymer matrix solution was prepared by dissolving about 1.4g of PVDF-HFP in about 20mL of acetone at about 50 ℃. An example of a MOF is UiO-66 by mixing ZrOCl₂·8H₂O and BDC were dissolved in N, N-dimethylformamide and then hydrothermally treated in an autoclave (about 120 ℃ for about 24 hours). The synthesized UO-66 particles are thermally activated at about 350 deg.C under dynamic vacuum for about 2-4 hours. About 2.1g of activated UiO-66 particles were homogeneously mixed with the polymer matrix solution by high shear stirring at about 50 ℃ for about 1-2 hours. A polypropylene-based microporous layer of about 30um (indicated as PP, Celgard corporation) was used as a support membrane. Dip coating the support membrane with a mixture containing UiO-66 produced an MOF coating of about 10um on the Celgard membrane.

Referring to fig. 4, the crystal structure of the synthesized and activated uo-66 (on the support membrane) particles was consistent with the simulated uo-66 structure, as confirmed by x-ray powder diffraction. As shown in fig. 5, thermogravimetric analysis of UiO-66 demonstrated the high thermal stability of MOFs, which do not decompose up to about 500 ℃ in an air atmosphere. Referring to fig. 6, a scanning electron microscope image of the original polypropylene microporous membrane is shown. The unmodified separator showed a porous morphology with a pore size of about 30 nm. Fig. 7 shows a composite separator in which the surface of the separator is coated with a particle layer containing UiO-66 particles and a PVDF-HFP polymer matrix.

Evaluation of Li of electrolytes in original support membranes and modified composite membranes by activated UiO-66 using conventional potentiostatic methods⁺The migration numbers, which are shown in fig. 8 and fig. 9, respectively. An exemplary electrolyte herein is about 1M LiPF in ethylene carbonate and diethyl carbonate (EC/DEC-50/50 volume ratio)₆. Li of electrolyte in composite separator⁺The mobility ratio was about 68% higher than that obtained from the original separator (about 0.62 to about 0.37), demonstrating the effect of UiO-66 in improving lithium ion conduction. Furthermore, the importance of the open metal sites in UiO-66 is emphasized in this example. Composite separator made from UiO-66 without activation in a similar manner, Li of electrolyte obtained from non-activated UiO-66 in modified composite separator⁺The transport number is given in fig. 10, and the value obtained of about 0.43 is close to about 0.37 from the original unmodified membrane, further demonstrating the importance of the open metal sites zr (iv) in fixing the anions in the channels of the MOF.

At about 0.5mA cm^-2The electrochemical stability of the electrolyte-absorbing composite separator to high-energy lithium metal was evaluated in the Li-symmetric cell of (a). As shown in fig. 11, the voltage of the cell using the composite separator showed a stable and small voltage at about 50mV, while the cell with the original PP separator showed a voltage increase with cycling up to about 400 hours. The electrochemical performance of the original separator and the composite separator (with the above-described UiO-66 coating) in the prototype cell are shown in fig. 12 and 13. As used herein, the term "LiNi" is used to include LiNi_1/3Co_1/3Mn_1/3O₂(NCM) cathode, graphite anode and about 1M LiPF in ethylene carbonate and diethyl carbonate₆Full cell device evaluation of electrolytes. The area loading of the active material was comparable to a commercial benchmark, with an NCM loading of about 20mg cm^-2Graphite about 10mg cm^-2. Fig. 12 shows that full cells using the original separator and the composite separator are at about 0.1C to 2C (1C ═ 160mA g^-1) Wherein the battery with the composite separator exhibits better rate performance than the battery using the original separator. At 2C, the cell with the composite separator retained 76% of its original capacity at 0.1C, while under the same conditions, the cell with the original separator retained about 62% of its original capacity. As shown in fig. 13, the long-term cycle stability of the full cell was evaluated at 1C (the first 5 cycles at 0.2C), and the cell with the composite separator exhibited a capacity retention rate of about 76% higher than that of the cell with the original separator after about 350 cycles, which was about 45%.

Example 2

This example covers the example shown in fig. 14, in which the lithium transference number of the electrolyte in the composite separator can be increased by modifying the ligand or adjusting the pore size. UiO-66-NH₂(denoted as UN) was synthesized according to published literature (chem. Commun.) 2013,49, 9449-9451. Referring to fig. 14, anionic functionalization of UN is shown, where the ligand (2-amino terephthalic acid) is sulfonated (denoted UN-SH) and lithiated (UN-SLi) to create anionic grafting groups, excluding transfer of anions across the separator. The synthesized UN granules were mixed with an excess of 1, 3-propanesultone in CHCl₃Mixing the above materials. After stirring at about 45 ℃ for 12 hours, a bright yellow solid was collected by centrifuge. CHCl for solid₃Washed three times and then dried at about 80 ℃ to obtain SO₃H-functionalized UN. Lithiation of UN-SH is performed by neutralizing UN-SH with dilute aqueous LiOH solution. The final UN-SLi was collected by filtration, washed three times with water and ethanol, respectively, and dried at about 80 ℃. The powder was further dried under vacuum at about 120 ℃ for activation prior to use in a battery. The crystal structures of UN, UN-SH, UN-SLi, all of which can be transposed to UiO-66-NH, were examined by x-ray diffraction (FIG. 15)₂On the simulated pattern.

By makingThe coating of UN-SLi was performed on a microporous polypropylene separator (designated PP, Celgard 2325) with a PVDF-HFP polymer matrix. About 0.4g of PVDF-HFP and 0.6g of UN-SLi were dispersed in 10mL of acetone. After stirring at about 60 ℃ for about 12 hours, PP films were dip-coated with the mixture and dried in air. This was repeated three times. After the coating process, the film was dried in vacuo at about 90 ℃ before use. Other suitable solvents may be used to dissolve the polymer matrix (PVDF-HFP), such as co-solvents of ethylene carbonate and dimethyl carbonate (denoted as EC/DMC). Typical scanning microscope images of UN, PP coated with UN-SLi by acetone, PP coated with UN-SLi by EC/DMC are shown in FIGS. 16-19, respectively. Commercial electrolytes from BASF (about 1M LiPF in ethylene carbonate and diethyl carbonate) were used₆) To evaluate ion conduction behavior in the composite membrane. Referring to FIG. 20, Li of electrolyte in (UN-SLi) coated PP⁺The transport number was about 0.74, indicating that the anionic MOFs in the composite membranes can repel and immobilize the movement of anions while facilitating the conduction of lithium ions.

In short, the above disclosed exemplary examples clearly show that the invention achieves, among other things, at least the following improvements to lithium batteries: increased lithium transfer number; improved overall lithium ion conductivity; reduced interfacial resistance between the electrolyte and the electrode (cathode or anode); enhanced electrode reaction kinetics; an electrochemical window for an improved lithium ion electrolyte; increased power output; improved cycle life; and improved thermal stability.

The foregoing description of exemplary embodiments of the invention has been presented for the purposes of illustration and description only and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

The embodiments were chosen and described in order to explain the principles of the invention and their practical applications, to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description and the exemplary embodiments described therein.

In describing the present invention, a number of references, including patents, patent applications, and various publications, are cited and discussed. Citation and/or discussion of such references is provided solely for purposes of illustrating the description of the invention and is not an admission that any such reference is "prior art" to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entirety and to the same extent as if each reference were individually incorporated by reference.

Claims

1. A composite separator for an electrochemical device, comprising:

at least one metal-organic framework (MOF) composite layer; and

at least one porous layer serving as a mechanical support for the at least one MOF composite material layer,

wherein the at least one MOF composite layer comprises at least one MOF material defining a plurality of channels and at least one polymer; and

wherein the at least one MOF material is a type of crystalline porous scaffold composed of metal clusters with organic ligands and is activated for a period of time and at a temperature such that the at least one MOF material comprises unsaturated metal centers, open metal sites and/or structural defects capable of complexing with anions in the electrolyte.

2. The composite membrane of claim 1, wherein the at least one MOF composite layer is formed by coating a mixture of the at least one MOF material and a polymer solution comprising the at least one polymer dissolved in at least one solvent on the at least one porous layer, wherein the coating comprises dip coating, slot-die coating, knife coating, spin coating, or electrospinning.

3. The composite separator according to claim 1, wherein the at least one porous layer has pores serving as a liquid electrolyte host for conducting ions, and is an electronic insulator for preventing short circuits.

4. The composite separator membrane of claim 3, wherein the at least one porous layer comprises one or more polymers comprising polypropylene (PP), Polyethylene (PE), Glass Fibers (GF), cellulose, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), Polyimide (PI), Polyallylamine (PAH), polyurethane, Polyacrylonitrile (PAN), Polymethylmethacrylate (PMMA), polytetraethylene glycol diacrylate, copolymers thereof, or combinations thereof.

5. The composite membrane of claim 1, wherein the at least one MOF composite layer comprises a MOF material in an amount ranging from about 5-99 wt% and at least one polymer in an amount ranging from about 1-95 wt%.

6. The composite membrane of claim 1, wherein the at least one MOF material has a tunable ligand functionality and a tunable pore size, wherein the tunable ligand functionality is a negatively charged ligand through chemical modification, and the tunable pore size is a grafting of chemical groups in the ligand.

7. The composite separator according to claim 1, wherein the organic ligand comprises benzene-1, 4-dicarboxylic acid (BDC), benzene-1, 3, 5-tricarboxylic acid (BTC), biphenyl-4, 4' -dicarboxylic acid (BPDC), or a derivative thereof, and the metal cluster comprises magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), or zirconium (Zr).

8. The composite membrane of claim 7, wherein the at least one MOF material comprises HKUST-1, MIL-100-Al, MIL-100-Cr, MIL-100-Fe, uo-66, uo-67, PCN series, MOF-808, MOF-505, MOF-74, or a combination thereof.

9. The composite separator membrane of claim 1, wherein the at least one polymer comprises polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), PVDF-tetrahydrofuran (PVDF-THF), PVDF-chlorotrifluoroethylene (PVDF-CTFE), poly (methyl methacrylate) (PMMA), Polyacrylonitrile (PAN), and polyethylene oxide (PEO), copolymers thereof, or combinations thereof.

10. An electrochemical device, comprising:

a positive electrode, a negative electrode, an electrolyte disposed between the positive electrode and the negative electrode, and a separator disposed in the electrolyte,

wherein the electrolyte is a liquid electrolyte comprising a metal salt dissolved in a non-aqueous solvent; and is

Wherein the membrane is a composite membrane according to any one of claims 1 to 9.

11. The electrochemical device of claim 10, wherein the non-aqueous solvent comprises one or more of: ethylene Carbonate (EC), Propylene Carbonate (PC), Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Methyl Propyl Carbonate (MPC), Butyl Methyl Carbonate (BMC), Ethyl Propyl Carbonate (EPC), dipropyl carbonate (DPC), cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-1, 3-oxazolidin-2-one, gamma-butyrolactone, 1, 2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, methyl acetate, ethyl acetate, nitromethane, 1, 3-propanesultone, gamma-valerolactone, methyl isobutyrylacetate, ethyl 2-methoxyacetate, ethyl 2-ethoxyacetate, Diethyl oxalate, an ionic liquid, a chain ether compound including at least one of γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane, and diethyl ether, and a cyclic ether compound including at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, and dioxane.

12. The electrochemical device of claim 10, wherein anions in the liquid electrolyte are spontaneously adsorbed and immobilized within the pore channels by the at least one MOF material, thereby releasing metal ions and allowing the metal ions to be transported at a higher metal ion transport number than that of a membrane without the at least one MOF material.

13. The electrochemical device of claim 12, wherein the metal ion transport number is a ratio of metal ion conductivity to ionic conductivity, wherein the ionic conductivity is a total value of the metal ion conductivity and anion conductivity, wherein the metal ion transport number of the liquid electrolyte in the composite separator is in a range of about 0.5-1.

14. The electrochemical device of claim 10, wherein the metal salt comprises one or more of a lithium salt, a sodium salt, a magnesium salt, a zinc salt, and an aluminum salt,

wherein the lithium salt comprises one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl imide) (LiTFSI), lithium bis (trifluoromethylsulfonyl imide), lithium trifluoromethanesulfonate, lithium fluoroalkylsulfonyl imide, lithium fluoroarylsulfonyl imide, lithium bis (oxalato borate), lithium tris (trifluoromethylsulfonyl imide), lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, and lithium chloride;

wherein the sodium salt comprises sodium trifluoromethanesulfonate, NaClO₄、NaPF₆、NaBF₄One or more of sodium bis (trifluoromethanesulfonyl) imide (I) (NaTFSI) and sodium bis (fluorosulfonyl) imide (I) (NaFSI);

wherein the magnesium salt comprises magnesium triflate, Mg (ClO)₄)₂、Mg(PF₆)₂、Mg(BF₄)₂Bis (trifluoromethanesulfonyl) magnesium (II) imide (Mg (TFSI))₂) And magnesium bis (fluorosulfonyl) imide (II) (Mg (FSI))₂) One or more of; and is

Wherein the zinc salt comprises zinc trifluoromethanesulfonate, Zn (ClO)₄)₂、Zn(PF₆)₂、Zn(BF₄)₂Bis (trifluoromethanesulfonyl) imide zinc (II) (Zn (TFSI))₂) Bis (fluorosulfonyl) imide zinc (II) (Zn (FSI))₂) One or more of (a).

15. The electrochemical device of claim 14, wherein the electrochemical device is a lithium battery, a sodium battery, a magnesium battery, or a zinc metal battery,

wherein for the lithium battery, the positive electrode comprises one or more of: LiCoO₂(LCO)、LiNiMnCoO₂(NMC) and lithium iron phosphate (LiFePO)₄) Lithium iron fluorophosphate (Li)₂FePO₄F) Over-lithiated layer-by-layer cathodes, spinel lithium manganese oxide (LiMn)₂O₄) Lithium cobalt oxide (LiCoO)₂)、LiNi_0.5Mn_1.5O₄Comprising LiNi_0.8Co_0.15Al _0.05O₂Or lithium nickel cobalt aluminum oxide, lithium vanadium oxide (LiV) of NCA₂O₅) And Li₂MSiO₄Wherein M consists of Co, Fe and/or Mn in a certain ratio; and wherein the negative electrode comprises one or more of: lithium metal (Li), graphite, hard or soft carbon, graphene, carbon nanotubes, including Li₄Ti₅O₁₂And TiO₂Titanium oxide, silicon (Si), tin (Sn), germanium (Ge), silicon monoxide (SiO), silicon dioxide (SiO)₂) Tin oxide (SnO)₂) And a transition metal oxide including Fe₂O₃、Fe₃O₄、Co₃O₄And Mn_xO_yAt least one of; and is

Wherein the positive electrode comprises NaMnO for a sodium battery₂、NaFePO₄And Na₃V₂(PO₄)₃One or more of, TiSe for magnesium battery₂、MgFePO₄F、MgCo₂O₄And V₂O₅One or more ofOr gamma-M nO for zinc cells₂、ZnMn₂O₄And ZnMnO₂One or more of (a).