Composite material with MOF structure as well as preparation method and application of composite material

Abstract

The invention provides a composite material with an MOF structure as well as a preparation method and application thereof, the composite material comprises a main body material structure with oxygen vacancies coated with the MOF structure, the composite material is formed by in-situ growth of the MOF structure on a main body material with the oxygen vacancies, and the main body material with the oxygen vacancies is formed by in-situ growth of the MOF structure on the main body material with the oxygen vacancies. According to the MOF material, metal active sites capable of growing can be provided for the MOF structure, oxidizing gas generated by the battery under the extreme condition can be synergistically eliminated, the MOF material has Lewis acidity, the rate performance of the battery can be improved, reducing gas generated by the battery under the extreme condition can be adsorbed, and therefore the safety performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly relates to a composite material with a MOF structure, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium batteries have been widely used in energy storage systems, power batteries and other fields. The high-energy density cathode material is extremely easy to decompose and release oxygen at high temperatures, and further reacts with the anode and electrolyte to generate heat, ultimately leading to thermal runaway of the battery cell. On the anode side, after the SEI layer decomposes, the highly active lithium-inserted anode will react with the electrolyte to generate reducing gases such as hydrogen and alkynes. The diffusion of the reducing gases to the cathode side will reduce the stability of the cathode active material, resulting in oxygen evolution at a lower temperature, thereby reducing the safety performance of the battery cell. At present, most research focuses on solving the stability of the cathode active material and eliminating the active oxygen generated by its decomposition. There is no good solution to the problem of reduced stability of the cathode active material caused by the reducing gases generated by the reaction of the lithium-inserted anode and the electrolyte. Existing technologies are also difficult to simultaneously meet the rate performance and safety performance requirements of high-performance fast-charging lithium batteries. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the present application provides a composite material with a MOF structure. The composite material contains a MOF material grown in-situ on a host material containing oxygen vacancies, thereby obtaining a composite material of the MOF material and the host material containing oxygen vacancies. The material can effectively avoid the agglomeration of the MOF material during application, and ensure the safety of the battery while improving the rate performance of the battery.

[0004] The present application provides a composite material with a MOF structure, wherein the composite material contains a structure in which a MOF structure coats a host material with oxygen vacancies.

[0005] Preferably, for the above-mentioned composite material, the host material with oxygen vacancies is M1O z-x and, wherein z = a / 2, where a is the highest stable valence state of M1 in the oxide;

[0006] 0 < x < 0.5

[0007] M1 is selected from metal elements with an electronegativity greater than 1.1, preferably one or more of Al, Ti, Cr, Mn, Ni, Zn, W, Mo, Bi, Sn, and Ce;

[0008] and / or, the MOF structure is a MOF structure composed of M2 and an organic ligand, wherein M2 is selected from Zn 2+ 、Cu 2+ 、Ni 2+ 、Pd2+ 、Pt 2+ 、Ru 2+ 、Co 2+ 、Mg 2+ 、Zr 4+ 、Fe 2+ 、Mn 2+ and Al 3+ and one or more of the above.

[0009] Preferably, for the composite material described above, wherein, in the composite material, the content of the MOF structure is 2-10%.

[0010] Preferably, for any one of the above-mentioned composite materials, wherein the MOF structure grows in-situ on the surface of M1O z-x surface.

[0011] Preferably, for any one of the above-mentioned composite materials, wherein the organic ligand in the MOF structure is selected from organic ligands that form hydrogen bond interactions with reducing gases and / or organic ligands that form ion-dipole interactions with hydrogen ions;

[0012] Preferably, the organic ligand that forms hydrogen bond interactions with reducing gases is an alcohol organic ligand, a ketone organic ligand or a carboxylic acid organic ligand;

[0013] Preferably, the organic ligand that forms ion-dipole interactions with hydrogen ions is an aromatic organic ligand, a nitrogen-containing organic ligand, a carboxylic acid organic ligand or a phenolic hydroxyl organic ligand;

[0014] More preferably, the organic ligand is selected from one or more of trimesic acid, terephthalic acid, 2-aminoterephthalic acid and 2,5-dihydroxyterephthalic acid.

[0015] Preferably, for any one of the above-mentioned composite materials, wherein the D of the composite material 50 is 1000nm - 100nm, preferably 700nm - 200nm; and / or

[0016] the specific surface area of the composite material is 200m 2 / g - 20m 2 / g, preferably 150m 2 / g - 50m 2 / g.

[0017] This application provides a method for preparing a composite material with an MOF structure, comprising:

[0018] Treating the oxide to obtain a host material containing oxygen vacancies, and dispersing it in a solvent to obtain a dispersion;

[0019] Dissolve a metal salt and an organic ligand in a solvent to obtain a solution;

[0020] Mix the dispersion liquid and the solution and carry out a reaction to obtain the composite material.

[0021] The composite material may be a structure in which a MOF structure coats a host material structure having oxygen vacancies.

[0022] Preferably, for the method described above, wherein the oxide is selected from one or more of aluminum oxide, titanium oxide, chromium oxide, manganese oxide, nickel oxide, zinc oxide, tungsten oxide, molybdenum oxide, bismuth oxide, tin oxide and cerium oxide; and / or

[0023] The metal salt is a metal nitrate, a metal sulfate or a metal hydrochloride, preferably a metal nitrate, and further preferably selected from one or more of zinc nitrate, copper nitrate, nickel nitrate, palladium nitrate, platinum nitrate, ruthenium nitrate, cobalt nitrate, magnesium nitrate, iron nitrate, zirconium nitrate, manganese nitrate and aluminum nitrate; and / or

[0024] The solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol and deionized water.

[0025] Preferably, for any one of the methods described above, wherein the composite material is the composite material involved in any one of the above.

[0026] Preferably, for any one of the methods described above, wherein the reaction time is 12 - 24 h, and / or the reaction temperature is 50 - 150 °C.

[0027] The present application provides the use of the composite material described in any one of the above or the composite material prepared by the method described in any one of the above in a separator.

[0028] The present application provides a separator, which comprises the composite material described in any one of the above or the composite material prepared by the method described in any one of the above and a separator substrate.

[0029] The present application provides an electrode sheet, which is a positive electrode sheet or a negative electrode sheet containing the composite material described in any one of the above, or a positive electrode sheet or a negative electrode sheet containing the composite material prepared by the method described in any one of the above.

[0030] The present application provides a battery, which comprises the separator described above and / or the electrode sheet described above.

[0031] Effects of the Invention

[0032] The composite material described in this application is in-situ grown and compounded from a MOF material and a host material containing oxygen vacancies. The MOF material has a certain Lewis acidity. During the contact with the electrolyte, it promotes the dissociation of lithium salts and simultaneously fixes the anionic groups with large ionic radii, which is beneficial to improving the rate performance of the battery. At the same time, the MOF material has a large specific surface area and many metal active sites, providing a large accommodation space and binding sites for reducing gases such as hydrogen and alkynes generated at the negative electrode. In addition, the host material containing oxygen vacancies can not only provide metal active sites for the growth of MOF, but also cooperate to eliminate the oxidizing gases generated under extreme conditions of the battery, thereby improving the safety performance of the battery. The MOF material can improve the liquid retention rate and electrical properties of the separator. The composite material in this application can also avoid the agglomeration problem of the MOF material during application and reduce the use cost of the MOF material. The preparation process of this application does not need to change the current mainstream preparation processes of the separator and the MOF material, and has the advantages of high stability and low cost, and is suitable for large-scale applications. Detailed Embodiments

[0033] The following describes the present application in detail in conjunction with the described embodiments. Although specific embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be fully conveyed to those skilled in the art.

[0034] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended terms and should be interpreted as "including but not limited to". The following description of the specification is a preferred embodiment for implementing the present application, but the description is for the purpose of the general principles of the specification and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the scope defined by the appended claims.

[0035] The present application provides a composite material with a MOF structure, wherein the composite material contains a MOF structure coating a host material structure with oxygen vacancies; the composite material may also contain a separate MOF structure or a separate host material with oxygen vacancies or a mixture of the two; further preferably, the composite material is a MOF structure coating a host material structure with oxygen vacancies.

[0036] In some embodiments, the host material with oxygen vacancies is M1O z-x, where z = a / 2, a being the highest stable valence state of M1 in the oxide, and 0 < x < 0.5;

[0037] M1 is selected from metal elements with an electronegativity greater than 1.1, preferably one or more of Al, Ti, Cr, Mn, Ni, Zn, W, Mo, Bi, Sn, and Ce. Since the electronegativity of the metal elements in the material is relatively high, oxygen ions are likely to escape from the lattice, forming oxygen vacancies; and / or

[0038] The MOF structure is a MOF structure composed of M2 and an organic ligand, where M2 is preferably a metal ion with an electronegativity > 1, selected from 2+ Zn 2+ Cu 2+ Ni 2+ Pd 2+ Pt 2+ Ru 2+ Co 2+ Mg 4+ Zr 2+ Fe 2+ Mn 3+ and Al

[0039] In this application, the MOF structure is in-situ grown on the surface of the host material containing oxygen vacancies. The surface of the host material containing oxygen vacancies has abundant metal ion sites, which interact with the organic ligand in the MOF structure, enabling the rapid growth of the MOF material on the surface of the host material containing oxygen vacancies to obtain the above-mentioned composite material.

[0040] In some embodiments, in the composite material, the content of the MOF structure is 2 - 10%.

[0041] For example, in the composite material, the content of the MOF structure can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.; too high a content of the MOF material affects the fast charging and safety performance.

[0042] In some embodiments, the MOF structure is in-situ grown on the surface of M1O z-x , that is, on the surface of the host material containing oxygen vacancies.

[0043] The M1O z-x refers to the oxide material M1O z which forms an oxygen vacancy material due to the treatment under specific external conditions, causing the oxygen in the oxide lattice to detach and resulting in oxygen deficiency.

[0044] In this application, there is no limitation on the method for measuring oxygen vacancies, and it can be measured by conventional methods in the art, such as X-ray photoelectron spectroscopy, to determine the concentration and distribution of oxygen vacancies by measuring the electron energy levels on the surface of the material.

[0045] The host material containing oxygen vacancies described in this application can not only provide metal active sites for the growth of the MOF structure, but also cooperate to eliminate the oxidizing gases generated under extreme conditions of the battery.

[0046] The MOF structure of the composite material described in this application is easy to grow on the host material containing oxygen vacancies, and the specific surface area of the composite material is larger.

[0047] The MOF material in the composite material described in this application has certain Lewis acidity, can adsorb anions, promote the dissociation of lithium salts, and increase the ion transference number of the separator, thereby being beneficial to improving the rate performance of the battery;

[0048] Moreover, the MOF material has a large specific surface area, providing a large accommodation space for reducing gases such as hydrogen and alkynes generated at the negative electrode. In addition, the metal ions or organic ligands in the MOF material form interactions with the reducing gases, firmly fixing the reducing gases in the space, thereby improving the safety performance of the battery.

[0049] In this application, there is no limitation on the method for measuring the adsorption capacity of reducing gases such as hydrogen in the composite material, and it can be measured by conventional methods in the art.

[0050] In some embodiments, the organic ligand in the MOF structure is an organic ligand that forms a hydrogen bond interaction with reducing gases such as hydrogen, such as hydrogen, and / or an organic ligand that forms an ion-dipole interaction with hydrogen ions.

[0051] Preferably, the organic ligand that forms a hydrogen bond interaction with reducing gases such as hydrogen is an alcohol organic ligand, a ketone organic ligand, or a carboxylic acid organic ligand;

[0052] Preferably, the organic ligand that forms an ion-dipole interaction with hydrogen ions is an aromatic organic ligand, a nitrogen-containing organic ligand, a carboxylic acid organic ligand, or a phenolic hydroxyl organic ligand;

[0053] Further preferably, the organic ligand is selected from one or more of trimesic acid, terephthalic acid, 2-aminoterephthalic acid, and 2,5-dihydroxyterephthalic acid.

[0054] In some embodiments, the D of the composite material 50It is 1000 nm - 100 nm, such as 1000 nm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 400 nm, 300 nm, 200 nm, 100 nm, preferably 700 nm - 200 nm;

[0055] The specific surface area of the composite material is 200 m 2 / g - 20 m 2 / g, preferably 150 m 2 / g - 50 m 2 / g. 190 m 2 / g, 180 m 2 / g, 170 m 2 / g, 160 m 2 / g, 150 m 2 / g, 140 m 2 / g, 130 m 2 / g, 120 m 2 / g, 110 m 2 / g, 100 m 2 / g, 90 m 2 / g, 80 m 2 / g, 70 m 2 / g, 60 m 2 / g, 50 m 2 / g, 40 m 2 / g, 30 m 2 / g.

[0056] In this application, by treating the oxide material to prepare an oxide containing oxygen vacancies and growing a MOF material on its surface to form a composite material, the agglomeration of the MOF material can be avoided, and the production cost of using the MOF material can be greatly reduced while maintaining the performance of the separator and the battery.

[0057] The large specific surface area of the composite material obtained in this application indicates that in-situ growth of a MOF structural material on a host material containing oxygen vacancies can greatly increase the specific surface area of the composite material.

[0058] In this application, there is no limitation on the measurement method of the particle size and specific surface area of the composite material, and it can be measured by conventional methods in the art. For example, a laser particle size analyzer can be used to measure the composite material, so as to obtain the particle size and specific surface area of the composite material.

[0059] This application provides a method for preparing a composite material with a MOF structure, including:

[0060] Treat the oxide to obtain a host material containing oxygen vacancies and disperse it in a solvent to obtain a dispersion;

[0061] Dissolve a metal salt and an organic ligand in a solvent to obtain a solution;

[0062] Mix the dispersion liquid and the solution and carry out a reaction to obtain the composite material.

[0063] In the present application, there is no limitation on the method for treating an oxide to obtain a host material containing oxygen vacancies, and it can be prepared by a conventional method in the art. For example, it can be obtained by acid treatment or high-temperature reduction treatment. For example, the oxide material can be treated under a reducing atmosphere at a high temperature to obtain a host material containing oxygen vacancies. For example, it can be treated under a mixed atmosphere of argon and hydrogen at 1000 °C to obtain a host material containing oxygen vacancies.

[0064] In some embodiments, the oxide is selected from one or more of aluminum oxide, titanium oxide, chromium oxide, manganese oxide, nickel oxide, zinc oxide, tungsten oxide, molybdenum oxide, bismuth oxide, tin oxide, and cerium oxide; and / or the metal salt is a metal nitrate, a metal sulfate, or a metal hydrochloride, preferably a metal nitrite, and further preferably selected from one or more of zinc nitrate, copper nitrate, nickel nitrate, palladium nitrate, platinum nitrate, ruthenium nitrate, cobalt nitrate, magnesium nitrate, iron nitrate, zirconium nitrate, manganese nitrate, and aluminum nitrate.

[0065] In some embodiments, the solvent can be one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, methanol, ethanol, and deionized water. In some embodiments, the composite material is the composite material described in any one of the above.

[0066] In some embodiments, the reaction time is 12 - 24 h, and / or the reaction temperature is 50 - 150 °C.

[0067] For example, the reaction time can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, etc.; the reaction temperature is 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, etc.

[0068] The present application provides the composite material described in any one of the above or the composite material prepared by the method described in any one of the above, and its application in a separator.

[0069] The present application provides a separator, which comprises the composite material described in any one of the above or the composite material prepared by the method described in any one of the above and a separator substrate.

[0070] In this application, the separator substrate is a conventional separator substrate in the art. For example, it can be a polymer porous membrane such as polyethylene (PE), polypropylene (PP), polyimide (PI), etc., and a polymer porous membrane with a high-temperature resistant coating layer such as alumina or boehmite loaded on one or both sides.

[0071] In this application, a separator is obtained by preparing a composite material together with auxiliaries such as a dispersant, a thickener, a binder, and a wetting agent into a slurry and coating it on the separator substrate.

[0072] In this application, no limitation is imposed on the preparation method of the separator. It can be prepared by using a conventional method in the art. For example, it can be prepared by the following method:

[0073] (1) Mix and stir the composite material, the dispersant, and the solvent to obtain a dispersion;

[0074] (2) Add the thickener, the binder, and the wetting agent to the dispersion and stir to obtain a slurry;

[0075] (3) Coat the slurry on the surface of the separator substrate and dry to obtain the separator.

[0076] In this application, the thickness of the composite material coating is 0.1 - 10 μm. For example, the coating thickness can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0077] In this application, no limitation is imposed on the dispersant, the solvent, the thickener, the binder, and the wetting agent. They can be common dispersants, solvents, thickeners, binders, and wetting agents in the art. For example, the dispersant can be at least one of sodium polyacrylate, ammonium polyacrylate copolymer, polyvinylpyrrolidone, polyethylene glycol, and sodium hexametaphosphate;

[0078] The solvent can include aqueous or oil-based solvents, preferably at least one of water, ethanol, N-methylpyrrolidone, tetrahydrofuran, cyclohexane, petroleum ether, acetone, dimethylacetamide, and N,N-dimethylformamide;

[0079] The thickener can be at least one of sodium carboxymethyl cellulose, carboxyethyl cellulose, sodium alginate, polyvinylidene fluoride, polyacrylamide, and polyvinyl alcohol;

[0080] The binder may be selected from at least one of polymethacrylic acid, methyl methacrylate-butadiene rubber, styrene-acrylic emulsion, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane, or a copolymer formed by one or several monomers of methyl methacrylate and methacrylic acid, ethylacrylic acid, ethyl acrylate, ethyl methacrylate, propyl methacrylate, or butyl methacrylate;

[0081] The wetting agent may be selected from at least one of sodium perfluorooctanoate, nonylphenol, fluoroalkyl methoxy alcohol ether, polyoxyethylene alkylamine, sodium butylnaphthalenesulfonate, arylnaphthalenesulfonate, sodium dodecylbenzenesulfonate, or sodium alkyl sulfate.

[0082] This application provides a battery, which includes the separator described above.

[0083] In this application, the battery further includes an electrolyte, a positive electrode sheet, and a negative electrode sheet.

[0084] In this application, this application places no restrictions on the electrolyte, the positive electrode sheet, and the negative electrode sheet, and conventional electrolytes, positive electrode sheets, and negative electrode sheets in the art can be used.

[0085] For example, the electrolyte includes a lithium salt, an organic solvent, and an additive. The lithium salt may be at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), or lithium bis(difluoromethylsulfonyl)imide (LiFSI). The solvent may be at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or methyl propyl carbonate (MPC).

[0086] The positive electrode sheet may be one or more of lithium cobaltate, lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel manganate, and lithium-rich materials;

[0087] The negative electrode sheet may be one or more of graphite, hard carbon, silicon, molybdenum disulfide, lithium titanate, graphene, silicon carbide, and silicon monoxide.

[0088] Due to the composite material coated on the separator of the battery described in this application, the rate performance and safety performance can be improved.

[0089] Examples

[0090] This application generally and / or specifically describes the materials and test methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, that is, weight percentage. Reagents or instruments without indicating the manufacturer can all be obtained as conventional reagent products through commercial purchase.

[0091] Example 1

[0092] (1) Under a 10% argon-hydrogen mixed atmosphere, titanium oxide was kept at 1000 °C for 4 h to obtain titanium oxide particles with oxygen vacancies on the surface.

[0093] (2) The titanium oxide particles with metal ion active sites in step (1) were ball-milled and dispersed in 500 ml of DMF to obtain a titanium oxide dispersion. The solid content of titanium oxide with metal ion active sites was about 25%, and the particle size was 400 nm. Then, 0.02 mol of nickel nitrate and 0.02 mol of cobalt nitrate (the molar ratio of nickel nitrate to cobalt nitrate was 1:1) and 0.04 mol of 2-aminoterephthalic acid organic ligand were dissolved in 50 ml of DMF to obtain a solution.

[0094] (3) After mixing the two solutions in step (2) evenly, they were transferred into a reaction kettle and reacted at 100 °C for 24 h. After cooling to room temperature, they were taken out, centrifuged and dried to obtain 210 g of composite material. Among them, in the composite material, the MOF structure was 5%.

[0095] (4) The composite material, sodium polyacrylate, sodium carboxymethylcellulose, polymethacrylic acid and sodium perfluorooctanoate were pulped in a ratio of 100:0.3:1:5:0.4 and coated on a separator substrate to obtain a separator. The separator substrate was a polyethylene film with an alumina coating on one side. The thickness of the alumina coating was 2 μm, the thickness of the polyethylene film was 9 μm, and the thickness of the composite material coated on the uncoated side was 2 μm.

[0096] (5) The separator, the positive electrode Ni83, the negative electrode SiCO450 and the electrolyte (1 M LiPF6 in DMC:EC:EMC with a volume ratio of 1:1:1, the concentration was 1 M) were prepared into a battery according to the conventional method in the art.

[0097] Example 2

[0098] (1) Under a 10% argon-hydrogen mixed atmosphere, titanium oxide was kept at 1000 °C for 4 h to obtain titanium oxide particles with metal ion active sites on the surface.

[0099] (2) Disperse the titanium oxide particles with metal ion active sites in step (1) by ball milling in 500 ml of DMF to obtain a titanium oxide dispersion. The solid content of the titanium oxide with metal ion active sites is about 25%, and the particle size is 400 nm. Then dissolve 0.04 mol of nickel nitrate and 0.04 mol of 2-aminoterephthalic acid organic ligand in 50 ml of DMF to obtain a solution.

[0100] (3) After mixing the two solutions in step (2) evenly, transfer them to a reaction kettle, react at 100 °C for 24 h, and take them out after cooling to room temperature. After centrifugation and drying, a composite material is obtained, in which the MOF structure in the composite material is 5%.

[0101] (4)-(5) The operations are the same as those in (4)-(5) of Example 1.

[0102] Example 3

[0103] The difference between Example 3 and Example 1 is that the organic ligand used is terephthalic acid.

[0104] Example 4

[0105] The difference between Example 4 and Example 1 is that the content of the MOF structure is 2%.

[0106] Example 5

[0107] The difference between Example 5 and Example 1 is that the content of the MOF structure is 10%.

[0108] Example 6

[0109] The difference between Example 6 and Example 2 is that the organic ligand used is terephthalic acid.

[0110] Example 7

[0111] The difference between Example 7 and Example 1 is that cerium oxide is used to replace titanium oxide.

[0112] Example 8

[0113] The difference between Example 8 and Example 2 is that cobalt nitrate is used instead of nickel nitrate to prepare the composite material.

[0114] Comparative Example 1

[0115] (1) Under a 10% argon-hydrogen mixed atmosphere, keep titanium oxide at 1000 °C for 4 h to obtain titanium oxide particles with oxygen vacancies on the surface.

[0116] (2) Dissolve 0.02 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.04 mol of 2-aminoterephthalic acid organic ligand in 50 ml of DMF to obtain a solution. Transfer it to a reaction kettle and react at 100 °C for 24 h. After cooling to room temperature, take it out. After centrifugation, a bimetallic MOF material is obtained;

[0117] (3) Mix the titanium oxide with oxygen vacancies in step (1) and the MOF material in step (2) to obtain a mixture. Among them, the MOF material is 5% by mass percentage in the mixture;

[0118] (4) Pulp the mixture according to the methods in steps (4)-(5) of Example 1, coat it on the uncoated side with a thickness of 2 μm to obtain a separator, and assemble it into a battery.

[0119] Comparative Example 2

[0120] (1) Dissolve 0.2 mol of nickel nitrate, 0.2 mol of cobalt nitrate, and 0.4 mol of 2-aminoterephthalic acid organic ligand in 500 ml of DMF to obtain a solution. Transfer it to a reaction kettle and react at 100 °C for 24 h. After cooling to room temperature, take it out. After centrifugation, a bimetallic MOF material is obtained;

[0121] (2) Pulp the MOF material according to the methods in steps (4)-(5) of Example 1, coat it on the uncoated side with a thickness of 2 μm to obtain a separator, and assemble it into a battery.

[0122] Comparative Example 3

[0123] The difference between Comparative Example 3 and Comparative Example 2 is that: the MOF material is prepared by using terephthalic acid organic ligand.

[0124] Comparative Example 4

[0125] The difference between Comparative Example 4 and Comparative Example 2 is that: a single-metal MOF material is prepared by using nickel nitrate.

[0126] Comparative Example 5

[0127] (1) Under a 10% argon-hydrogen mixed atmosphere, keep titanium oxide at 1000 °C for 4 h to obtain titanium oxide particles with metal ion active sites on the surface.

[0128] (2) Ball-mill and disperse the titanium oxide particles in step (1) in 500 ml of DMF to obtain a titanium oxide dispersion. The solid content of titanium oxide with metal ion active sites is about 25%, the particle size is 400 nm. Pulp it and coat it to obtain a separator, and prepare a battery according to the methods in steps (4)-(5) of Example 1.

[0129] Comparative Example 6

[0130] Using untreated titanium oxide to make pulp, ball-milling and dispersing it in 500 ml of DMF to obtain a titanium oxide dispersion with a solid content of about 25% and a particle size of 400 nm.

[0131] And coating to obtain a separator, and preparing a battery according to the method of steps (4)-(5) in Example 1.

[0132] Comparative Example 7

[0133] The difference between Comparative Example 7 and Example 1 is that untreated titanium oxide is used to replace titanium oxide with oxygen vacancies to obtain a composite material, making pulp, coating to obtain a separator, and preparing a battery.

[0134] Experimental Example 1

[0135] The materials obtained in Examples 1-5, Comparative Example 1, and Comparative Examples 3-5 were analyzed and characterized using a laser particle size analyzer (Malvern 3000) and a specific surface area analyzer (Kubo-1200). The results are shown in Table 1. Among them, the test range of the laser particle size analyzer is 0.02 μm - 2000 μm, the detection angle is 0 - 135°, internal and external ultrasounds are used for particle dispersion, the external ultrasound intensity is 40 kHz, the ultrasound duration is 5 min, the internal ultrasound intensity is 15 kHz, the refractive index is 1 - 4%, and the pre-treatment for specific surface area testing is 3 h under the condition of 300 °C.

[0136] Table 1

[0137] Average particle size (μm) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 0.467 105.53 Example 2 0.462 103.56 Example 3 0.456 103.15 Example 4 0.436 50.83 Example 5 0.453 158.33 Comparative Example 1 0.538 48.31 Comparative Example 2 2.286 1645.63 Comparative Example 5 0.416 13.31 Comparative Example 6 0.424 12.56 Comparative Example 7 0.436 62.67

[0138] Comparing the examples with the comparative examples, it can be seen that the specific surface area of the composite material with in-situ grown MOF structure is larger. This is because the composite material doped with MOF has a reduced specific surface area of the overall composite material due to the aggregation between MOF materials caused by the high specific surface area of the MOF material. When the material is only MOF, the average particle size of the material increases significantly, indicating that the MOF material will aggregate. The specific surface area of the material with MOF coated on the surface has a significant increase, which depends on the characteristic of the large specific surface area of the MOF material.

[0139] Experimental Example 2

[0140] (1) Determination of hydrogen adsorption capacity

[0141] The hydrogen adsorption performance of the material was characterized by the gravimetric method using a Cahn-2000 type high-vacuum electronic balance. The experimental process is divided into 4 steps: sample weighing, sample vacuum thermal desorption, hydrogen purging, and adsorption testing. It is calculated according to the following formula, and the results are shown in Table 2. Among them, the hydrogen adsorption amount C refers to the ratio of the mass increment of the adsorbent after adsorbing hydrogen to the initial mass of the sample.

[0142]

[0143] where C is the hydrogen adsorption amount, %

[0144] m0 is the initial mass of the composite material, mg

[0145] m1 is the mass of the sample after hydrogen adsorption reaches equilibrium, mg

[0146] Table 2

[0147]

[0148]

[0149] It can be seen from Comparative Examples 2-6 that the MOF material with bimetallic ions has stronger hydrogen adsorption ability; the organic ligand will also affect the hydrogen adsorption ability of the MOF material, and the preferred organic ligand with nitrogen-containing groups can improve the hydrogen adsorption ability of the material; the oxide ceramic material basically does not have hydrogen adsorption ability.

[0150] Experimental Example 3 Determination of Ion Transference Number and Ionic Conductivity

[0151] (1) Determination of ion transference number

[0152] 1) Use a cutter to cut the separator into a sample with a φ16 mm circular piece and vacuum dry it at 60 °C for 12 h.

[0153] 2) In the glove box, clamp the separator between two lithium sheets and inject 90 μL of the conventional electrolyte in the art to assemble a coin cell.

[0154] 3) Let it stand for 6 h to ensure that the electrolyte completely wets the separator, and test the interfacial resistance R0 before battery polarization through an electrochemical workstation.

[0155] 4) After short-circuiting the battery with stainless steel tweezers, apply a small voltage (ΔV = 10 mV), polarize for 3 h for testing, and record the initial current I0 and the steady-state current I S .

[0156] 5) Test the interfacial resistance R of the battery after polarization through an electrochemical workstation S .

[0157] 6) The results are calculated according to the following formula, and the results are shown in Table 3.

[0158] t Li+ = I S (ΔV - I0R0) / I0(ΔV - I S R S ) In the formula:

[0159] t Li+ - Ion transference number, dimensionless

[0160] R0 - Interface resistance before polarization, unit: ohm (Ω)

[0161] I0 - Initial current, unit: milliampere (mA)

[0162] I S - Steady-state current, unit: milliampere (mA)

[0163] R S - Interface resistance after polarization, unit: ohm (Ω)

[0164] (2) Measurement of ionic conductivity

[0165] 1) Use a cutting machine to cut the separator into samples with a φ16mm circular shape, record the sample thickness d, and vacuum dry at 60 °C for 12 h.

[0166] 2) In the glove box, sandwich 1, 2, 3, and 4 separators between two stainless-steel gaskets respectively, and inject 90 μL of the conventional electrolyte in the art into each to assemble a button cell.

[0167] 3) Let it stand for 6 h to ensure that the electrolyte fully infiltrates the separator. Test the battery impedance through an electrochemical workstation, set the voltage to the open-circuit voltage, the frequency to 10 6 ~200 Hz, the perturbation voltage to 5 mV, and measure 4 impedance resistances R1, R2, R3, and R4 respectively.

[0168] 4) Calculate the results, and the obtained results are shown in Table 3.

[0169] Take the number of separator layers as the abscissa and the separator resistance as the ordinate, find the slope and linear fitting degree of the curve. When the linear fitting degree is greater than 0.99, the ionic conductivity of the separator is calculated according to the following formula. When the linear fitting degree is less than 0.99, re-testing is required.

[0170] R Ω =k * 1

[0171] Wherein:

[0172] R Ω - Resistance value of a 1-layer separator, unit: ohm (Ω);

[0173] k - Slope of the curve when the fitting degree is greater than 0.99.

[0174] δ = d / (R Ω * S)

[0175] Wherein:

[0176] δ - Ionic conductivity of the separator, unit: siemens per centimeter (S cm -1 );

[0177] The thickness of the d-1 layer separator, in micrometers (μm);

[0178] R Ω The resistance value of the -1 layer separator, in ohms (Ω);

[0179] S - The area of the stainless-steel gasket, in square centimeters (cm 2 ).

[0180] Table 3

[0181] <![CDATA[Ionic conductivity (mS cm -1 )]]> Ionic transference number Example 1 1.23 0.58 Example 2 1.13 0.54 Example 3 1.17 0.57 Example 4 0.75 0.51 Example 5 1.2 0.6 Example 6 1.1 0.55 Example 7 1.2 0.57 Example 8 1.14 0.54 Comparative Example 1 1.03 0.59 Comparative Example 2 1.72 0.75 Comparative Example 3 1.64 0.73 Comparative Example 4 1.43 0.67 Comparative Example 5 0.48 0.46 Comparative Example 6 0.46 0.42 Comparative Example 7 1.06 0.57

[0182] As can be seen from the above table, the MOF material is beneficial to improving the ionic conductivity and ion transference number of the coating film. In this application, in-situ growth of MOF on an oxide containing oxygen vacancies can greatly reduce the cost while maintaining the separator performance. For example, the MOF in-situ grown on the surface of the oxide containing oxygen vacancies in the examples also has the effect of improving the ionic conductivity and ion transference number of the coating film. Comparative Example 7 uses an oxide without oxygen vacancies for in-situ growth of the MOF material, and the ionic conductivity and ion transference number of the separator are relatively low. Therefore, the coated structure is an oxide containing oxygen vacancies, which is beneficial to the growth of MOF on the surface, and at the same time, the oxygen vacancy material is also beneficial to improving the conductivity and transference number.

[0183] Therefore, the in-situ growth of MOF material on the host material helps to improve the electrical performance of the separator.

[0184] Experimental Example 4

[0185] (1) Rate charge ratio test

[0186] a) Discharge the battery at a current of 0.33C to the battery discharge cut-off voltage at 23 ± 2°C and let it stand for 1 h;

[0187] b) Charge the battery at rates of 0.1C, 0.2C, 0.33C, 1C, 2C, and 3C to the material charge cut-off voltage and then discharge it at a constant current of 0.33 to the material discharge cut-off voltage, and cycle 4 times at the same rate;

[0188] c) Record the constant current charge ratio at different rates, and the results are shown in Table 4.

[0189] (2) Thermal box passing rate test

[0190] a) Discharge the battery at a constant current to the discharge cut-off voltage, charge it at a constant current to the full charge state, and then put the battery into the test chamber;

[0191] b) The test chamber is heated at a temperature rise rate of 5 °C / min. When the temperature inside the chamber reaches 140 ± 2 °C, it is kept constant for 1 h. Then, it is heated at a temperature rise rate of 5 °C / min again. When the temperature inside the chamber reaches 150 ± 2 °C, it is kept constant for 1 h. After that, it is heated at a temperature rise rate of 5 °C / min once more. When the temperature inside the chamber reaches 160 ± 2 °C, it is kept constant for 1 h.

[0192] c) If the battery does not catch fire or explode during the whole process, it is considered to pass. The results are shown in Table 4.

[0193] (3) Overcharge

[0194] The battery is discharged at a constant current until the discharge cut-off voltage. Then, it is charged at a constant current with the larger value of 3CA and three times the manufacturer-recommended charging current until the battery undergoes thermal runaway. Record the voltage value of the battery when thermal runaway starts to occur. The results are shown in Table 4.

[0195] Table 4

[0196]

[0197]

[0198] The electrical performance of the battery can intuitively reflect the performance of the separator in terms of safety and fast charging performance. It can be seen that the thermal box, rate performance, and overcharge SOC of the separator containing MOF materials have all been improved to a certain extent. Among them, the battery performance of the examples and comparative examples containing MOF materials has all been improved, indicating that the composite material containing MOF can improve the safety and fast charging performance of the battery. The main material in the composite material affects the performance of the separator, and the performance of the main material with oxygen vacancies is improved more significantly. Only blending and simple MOF structures have limited improvement in the safety and fast charging performance of the battery.

[0199] The above are only the preferred embodiments of the present application, and are not intended to limit the present application in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application without departing from the technical solution content of the present application still fall within the protection scope of the technical solution of the present application.

Claims

1. A composite material with a MOF structure, comprising a main material structure with oxygen vacancies encapsulated by a MOF structure.

2. The composite material according to claim 1, wherein The host material with oxygen vacancies is M1O z-x , wherein z=a / 2, wherein a is the highest stable valence state of the metal element M1 in the oxide; 0<x<0.5; and / or, M1 is selected from metal elements having an electronegativity greater than 1.1, preferably one or more of Al, Ti, Cr, Mn, Ni, Zn, W, Mo, Bi, Sn and Ce; And / or, the MOF structure is a MOF structure composed of M2 and an organic ligand, wherein M2 is selected from Zn 2+ , Cu 2+ 、Ni 2+ , Pd 2+ , Pt 2+ 、Ru 2+ 、Co 2+ Mg 2+ , Fe 2+ 、Zr 4+ , Mn 2+ and Al 3+ One or more of the following.

3. The composite material according to claim 1, wherein In the composite material, the content of the MOF structure is 2-10%.

4. The composite material according to claim 1 or 2, wherein: The MOF structure was in situ grown on M1O z-x surface.

5. The composite material according to any one of claims 1 to 3, wherein The organic ligands in the MOF structure are selected from organic ligands that form hydrogen bond interactions with reducing gases and / or organic ligands that form ion-dipole interactions with hydrogen ions; Preferably, the organic ligand that forms a hydrogen bond interaction with the reducing gas is an alcohol organic ligand, a ketone organic ligand or a carboxylic acid organic ligand; Preferably, the organic ligand that forms ion-dipole interaction with hydrogen ions is an aromatic organic ligand, a nitrogen-containing organic ligand, a carboxylic acid organic ligand or a phenolic hydroxyl organic ligand; More preferably, the organic ligand is selected from one or more of trimesic acid, terephthalic acid, 2-aminoterephthalic acid and 2,5-dihydroxyterephthalic acid.

6. The composite material according to any one of claims 1 to 4, wherein The D of the composite material 50 1000nm-100nm, preferably 700nm-200nm; and / or The specific surface area of ​​the composite material is 200 m 2 / g-20m 2 / g, preferably 150m 2 / g-50m 2 / g.

7. A method for preparing a composite material having a MOF structure, comprising: The oxide is processed to obtain a main material containing oxygen vacancies, and dispersed in a solvent to obtain a dispersion; Dissolving a metal salt and an organic ligand in a solvent to obtain a solution; The dispersion and the solution are mixed and reacted to obtain the composite material.

8. The method according to claim 7, wherein: The oxide is selected from one or more of aluminum oxide, titanium oxide, chromium oxide, manganese oxide, nickel oxide, zinc oxide, tungsten oxide, molybdenum oxide, bismuth oxide, tin oxide and cerium oxide; and / or The metal salt is a metal nitrate, a metal sulfate or a metal hydrochloride, preferably a metal nitrate, and further preferably one or more selected from zinc nitrate, copper nitrate, nickel nitrate, palladium nitrate, platinum nitrate, ruthenium nitrate, cobalt nitrate, magnesium nitrate, iron nitrate, zirconium nitrate, manganese nitrate and aluminum nitrate; and / or The solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol and deionized water.

9. The method according to any one of claims 7 to 8, wherein: The composite material is the composite material according to any one of claims 1 to 6.

10. The method according to any one of claims 7 to 9, wherein: The reaction time is 12-24h, and / or the reaction temperature is 50-150°C.

11. The composite material according to any one of claims 1 to 6 or the composite material prepared by the method according to any one of claims 7 to 10.

12. A separator comprising the composite material according to claim 11 and a separator substrate.

13. A pole piece, which is a positive pole piece or a negative pole piece comprising the composite material according to claim 11.

14. A lithium battery comprising the separator according to claim 12 and / or the pole piece according to claim 13.

Images