Composite lithium supplement agent, preparation method thereof and battery

Abstract

The invention relates to a composite lithium supplement agent, a preparation method thereof and a battery. The composite lithium supplement agent comprises an organic lithium supplement agent, MOF and Mxene, and the organic lithium supplement agent comprises a compound with a general formula of Li2CnOn (n is greater than or equal to 2) and / or a compound with a general formula of Li2CnOn + 2 (n is greater than or equal to 2); the MOF is synthesized from a transition metal element and a dicarboxylic acid ligand; carrying out complex reaction on the MOF and Mxene to generate a complex with a three-dimensional structure; and an organic lithium supplement agent is loaded on the complex. According to the composite lithium supplement agent provided by the invention, the problem of battery performance degradation caused by gas production of the organic lithium supplement agent can be effectively avoided, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a composite lithium supplement and a preparation method thereof, and a battery. Background Art

[0002] Due to the formation of SEI film during the first charge and discharge process of the battery, lithium ions will be irreversibly consumed, which will lead to a decrease in battery capacity and deterioration in cycle performance. Therefore, in order to increase the energy density of the battery, lithium replenishment materials are usually used to pre-replenish the battery.

[0003] There are two problems with traditional common lithium supplement materials. First, they require a high delithiation potential. The battery needs to be charged to a high potential before it can decompose, which places high demands on the device and production process. Second, after the lithium supplement is delithiated, inactive substances with low conductivity will remain inside the battery cell, which will affect the overall conductivity of the electrode. Compared with other lithium supplements, organic lithium supplements have the advantage of no residue. Therefore, people have gradually turned their attention to the research on organic lithium supplements. However, the current organic lithium supplements still have the following defects: large impedance, slow lithium ion release, and easy production of gases such as CO2 during the decomposition process. The production of gases will affect the battery's cycle and high-temperature performance. Summary of the invention

[0004] Based on this, in response to the above problems, the present application provides a composite lithium supplement and a preparation method thereof, and a battery to solve the above technical problems.

[0005] The first aspect of the present application provides a composite lithium supplement, including an organic lithium supplement, MOF and Mxene, wherein the organic lithium supplement includes a general formula of Li2C n O n (n≥2) and / or the general formula is Li2C n O n+2 (n ≥ 2) compounds;

[0006] MOFs are synthesized from transition metal elements and dicarboxylic acid ligands;

[0007] MOF and Mxene undergo a complexation reaction to generate a complex with a three-dimensional structure;

[0008] The organic lithium supplement is loaded on the complex.

[0009] In some embodiments, the mass ratio of the organic lithium supplement agent, Mxene and MOF is 1: (1.5-2): (1.5-2.2).

[0010] In some embodiments, Li2C n O n(n≥2) is cyclic, including at least one of the compounds of formula (I) to formula (IV),

[0011] , , , .

[0012] In some embodiments, Li2C n O n+2 (n≥2) is chain-shaped, and includes at least one of the compounds of formula (V) to formula (VII),

[0013] , , .

[0014] In some embodiments, the MOF includes one or more of MIL-53Cr, MIL-100 Cr, MIL-101 Cr, MIL-100 Fe, MIL-177-LT, MIL-177-HT, MIL-45Co, MIL-45 Fe, MIL-53AI, MIL-53 Sc, MIL-88 Sc, MIL-8, MIL-9, MIL-47, MIL-51, MIL-59, MIL-69, MIL-88, MIL-91, MIL-96, MIL-101, MIL-103, MIL-102, MIL-110, and MIL-125.

[0015] In some embodiments, the chemical formula of Mxene is M n+1 X n T m , wherein M is one or more of chromium, molybdenum, manganese, iron, cobalt, copper, aluminum, silver, nickel, palladium, platinum, ruthenium and the like, and n=1, 2 or 3; X is carbon or nitrogen; Tm is one or more of hydroxyl, -O-, and halogen groups.

[0016] The second aspect of the present application provides a method for preparing the composite lithium supplement agent described in the first aspect, comprising the following steps:

[0017] S1. Dissolve a monolayer of Mxene in water and stir at room temperature to obtain a colloidal solution with a mass fraction of 1% to 2%;

[0018] S2, adding an organic lithium supplement agent to the colloidal solution, stirring at 15° C. to 30° C., to obtain a first mixed solution;

[0019] S3, adding MOF to the first mixed solution, diluting, and ultrasonically stirring to obtain a second mixed solution, and vacuum freeze-drying the second mixed solution to obtain an organic lithium supplement agent-Mxene / MOF material, i.e., a composite lithium supplement agent;

[0020] Among them, the layer thickness of Mxene is 1nm~2nm, and the length and width of Mxene are both 0.5μm~1.5μm;

[0021] The mass ratio of organic lithium supplement, Mxene and MOF is 1: (1.5~2): (1.5~2.2).

[0022] In some embodiments, in step S1, the stirring treatment time at room temperature is 4 h to 8 h.

[0023] In some embodiments, in step S2, the stirring treatment time is 12 h to 24 h, and the stirring treatment rate is 500 r / min to 800 r / min.

[0024] In some embodiments, in step S3, the temperature of the ultrasonic stirring treatment is -5°C to 0°C, the ultrasonic power is 200KW to 300KW, and the time is 10min to 30min.

[0025] In some embodiments, in step S3, the vacuum degree of the vacuum freeze-drying process is 1.3 Pa ~ 13 Pa, and the temperature is -50 ° C ~ -10 ° C.

[0026] The third aspect of the present application provides a battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode and / or the separator comprises the composite lithium supplement provided in the first aspect above, or the composite lithium supplement prepared according to the preparation method provided in the second aspect above.

[0027] In some embodiments, the positive electrode includes a composite lithium supplement, and based on the mass of the positive electrode being 100%, the mass of the composite lithium supplement accounts for 2% to 10%.

[0028] In the present application, MOF and Mxene are added to the composite lithium supplement agent, wherein MOF and Mxene can achieve complexation through the functional groups on their respective surfaces to generate a complex with a three-dimensional structure, and the organic lithium supplement agent is loaded on the complex. Specifically, the metal cations on MOF and the anions on Mxene, such as hydroxyl and halogen ions, are complexed. On the one hand, the three-dimensional structure has a larger specific surface area and more conductive sites, so that the organic lithium supplement agent can be evenly dispersed on the positive electrode and / or the diaphragm, and at the same time, the impedance of the organic lithium supplement agent can be effectively reduced, and the lithium removal speed of the composite lithium supplement agent can be increased to achieve rapid lithium supplementation; on the other hand, it can also prevent Mxene or MOF from agglomerating.

[0029] In addition, the transition metal elements in MOF can catalyze the decomposition of organic lithium supplements. At the same time, MOF can also absorb gases such as CO2 produced by the decomposition of organic lithium supplements, which can effectively avoid the problem of battery performance degradation caused by gas production by organic lithium supplements and improve the battery's cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart of a method for preparing a composite lithium supplement in one embodiment of the present application. DETAILED DESCRIPTION

[0031] References to embodiments of the present application will now be provided in detail, one or more embodiments of which are described below. Each embodiment is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0032] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0033] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0034] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0035] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 100~150 nm means that the units of the left endpoint "100" and the right endpoint "150" are both nm (nanometers).

[0036] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0039] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0040] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] The first aspect of the present application provides a composite lithium supplement, including an organic lithium supplement, MOF and Mxene. The organic lithium supplement includes a general formula of Li2C n O n (n≥2) and / or the general formula is Li2C n O n+2 (n≥2) compounds. MOF is synthesized from different transition metal elements and dicarboxylic acid ligands such as succinic acid and glutaric acid. MOF and Mxene can undergo complexation reaction through the functional groups on their respective surfaces to form a complex with a three-dimensional structure. The organic lithium supplement is loaded on the complex.

[0042] In some embodiments, the mass ratio of the organic lithium supplement agent, Mxene and MOF is 1: (1.5-2): (1.5-2.2).

[0043] In some embodiments, Li2C n O n (n≥2) is cyclic, including at least one of the compounds of formula (I) to formula (IV),

[0044] , , , .

[0045] In some embodiments, Li2C n O n+2 (n≥2) is chain-shaped, and includes at least one of the compounds of formula (V) to formula (VII),

[0046] , , .

[0047] In some embodiments, the MOF includes one or more of MIL-53Cr, MIL-100 Cr, MIL-101 Cr, MIL-100 Fe, MIL-177-LT, MIL-177-HT, MIL-45Co, MIL-45 Fe, MIL-53AI, MIL-53 Sc, MIL-88 Sc, MIL-8, MIL-9, MIL-47, MIL-51, MIL-59, MIL-69, MIL-88, MIL-91, MIL-96, MIL-101, MIL-103, MIL-102, MIL-110, and MIL-125.

[0048] In some embodiments, the chemical formula of Mxene is M n+1 X n T m , wherein M is one or more of chromium, molybdenum, manganese, iron, cobalt, copper, aluminum, silver, nickel, palladium, platinum, ruthenium and the like, and n=1, 2 or 3; X is carbon or nitrogen; Tm is one or more of hydroxyl, -O-, and halogen groups.

[0049] In the present application, MOF and Mxene are added to the composite lithium supplement agent, wherein MOF and Mxene can achieve complexation through the functional groups on their respective surfaces to generate a complex with a three-dimensional structure, and the organic lithium supplement agent is loaded on the complex. Specifically, the metal cations on MOF and the anions on Mxene, such as hydroxyl and halogen ions, are complexed. On the one hand, the three-dimensional structure has a larger specific surface area and more conductive sites, so that the organic lithium supplement agent can be evenly dispersed on the positive electrode and / or the diaphragm, and at the same time, the impedance of the organic lithium supplement agent can be effectively reduced, and the lithium removal speed of the composite lithium supplement agent can be increased to achieve rapid lithium supplementation; on the other hand, it can also prevent Mxene or MOF from agglomerating.

[0050] In addition, the transition metal elements in MOF can catalyze the decomposition of organic lithium supplements. At the same time, MOF can also absorb gases such as CO2 produced by the decomposition of organic lithium supplements, which can effectively avoid the problem of battery performance degradation caused by gas production by organic lithium supplements and improve the battery's cycle performance.

[0051] like Figure 1 As shown, the second aspect of the present application provides a method for preparing the composite lithium supplement agent described in the first aspect, comprising the following steps:

[0052] S1. Dissolve a single layer of MXene in water and stir at room temperature to obtain a colloidal solution with a mass fraction of 1% to 2%.

[0053] S2. Adding an organic lithium supplement agent into the colloidal solution, stirring the solution at 15° C. to 30° C., to obtain a first mixed solution.

[0054] S3, adding MOF to the first mixed solution, diluting, and ultrasonically stirring to obtain a second mixed solution, and vacuum freeze-drying the second mixed solution to obtain an organic lithium supplement - Mxene / MOF material, that is, a composite lithium supplement.

[0055] In some embodiments, the layer thickness of Mxene is 1 nm to 2 nm, including but not limited to 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, and 2 nm.

[0056] In some embodiments, the length and width of Mxene are both 0.5 μm to 1.5 μm, including but not limited to 0.5 μm, 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, and 1.5 μm.

[0057] In some embodiments, the mass ratio of the organic lithium supplement agent, Mxene and MOF is 1: (1.5-2): (1.5-2.2).

[0058] In some embodiments, in the above step S1, the stirring treatment time at room temperature is 4 h to 8 h, including but not limited to 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, and 8 h.

[0059] In some embodiments, in the above step S2, the stirring treatment time is 12h~24h, including but not limited to 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 17h, 18h, 19h, 20h, 22h, and 24h.

[0060] In some embodiments, in the above step S2, the stirring process rate is 500 r / min to 800 r / min, including but not limited to 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, and 800 r / min.

[0061] In some embodiments, in the above step S3, the temperature of the ultrasonic stirring treatment is -5°C~0°C, including but not limited to -5°C, -4°C, -3°C, -2°C, -1°C, and 0°C.

[0062] In some embodiments, in the above step S3, the ultrasonic power of the ultrasonic stirring treatment is 200KW~300KW, including but not limited to 200KW, 220KW, 240KW, 260KW, 280KW, and 300KW.

[0063] In some embodiments, in the above step S3, the time of ultrasonic stirring treatment is 10 min to 30 min, including but not limited to 10 min, 15 min, 20 min, 25 min, and 30 min.

[0064] In some embodiments, in the above step S3, the vacuum degree of the vacuum freeze-drying treatment is 1.3Pa~13Pa, including but not limited to 1.3Pa, 2Pa, 3Pa, 4Pa, 5Pa, 6Pa, 7Pa, 8Pa, 9Pa, 10Pa, 11Pa, 12Pa, and 13Pa.

[0065] In some embodiments, in the above step S3, the temperature of the vacuum freeze-drying treatment is -50°C to -10°C, including but not limited to -50°C, -40°C, -30°C, -20°C, and -10°C.

[0066] It is understandable that there is no special limitation on the solvent used for dilution in step S3 in the present application. Without violating the inventive concept of the present application, any known solvent that can be used for dilution can be applied to the present application. The following is only used as an illustrative example, not a limitation on the scope of protection. The solvent used for dilution can be distilled water, deionized water, purified water, etc.

[0067] The third aspect of the present application provides a battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode and / or the separator comprises the composite lithium supplement provided in the first aspect above, or the composite lithium supplement prepared according to the preparation method provided in the second aspect above.

[0068] In some embodiments, the positive electrode includes a composite lithium supplement, and based on the mass of the positive electrode as 100%, the mass of the composite lithium supplement accounts for 2% to 10%, including but not limited to 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

[0069] In some embodiments, the positive electrode further includes a positive electrode active material, which is a compound capable of reversibly inserting and extracting lithium. The continuous oxidation decomposition voltage of the positive electrode active material is ≥4.5 V. Exemplarily, the positive electrode active material is lithium nickel manganese oxide.

[0070] In some embodiments, the positive electrode further includes a positive electrode binder, a positive electrode conductor, and a positive electrode current collector.

[0071] It is understood that the present application has no particular limitation on the positive electrode current collector, as long as it has conductivity and does not cause chemical changes in the solid-state battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, or a metal current collector with a surface treated with carbon or other substances can be used.

[0072] The positive electrode binder is mainly used to bind the positive electrode active material, positive electrode conductor and positive electrode current collector together. The positive electrode binder includes but is not limited to polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polycarbonate (PC), polyamide (PA), acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene oxide (PPO) and carboxymethyl cellulose (CMC). Further, the binder is polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0073] The positive electrode conductive agent is mainly used to assist and improve the conductivity in the secondary battery, and there is no particular restriction on it in the present application, as long as it has conductivity without causing chemical changes. Specifically, the positive electrode conductive agent may include graphite, such as natural graphite or artificial graphite; carbon materials, such as conductive carbon black (super P), acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders, such as fluorocarbon powders, aluminum powders and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives, and from the aspect of improving conductivity, the positive electrode conductive agent may preferably be carbon black.

[0074] In some embodiments, the positive electrode may be manufactured by coating a positive electrode slurry on a positive electrode current collector, followed by drying and roll-pressing, wherein the positive electrode slurry includes a solvent and a positive electrode active material and / or a positive electrode binder, a positive electrode conductor dissolved in the solvent.

[0075] The solvent may include an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount such that a preferred viscosity is obtained when the positive electrode active material is included and optionally includes a positive electrode binder, a positive electrode conductor, etc. For example, the amount of the solvent included in the positive electrode slurry may be such that the concentration of the solids including the positive electrode active material, and optionally including a positive electrode binder and a positive electrode conductor is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %.

[0076] In some of the embodiments, the positive electrode can be prepared by a dry method, that is, the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder are mixed, or the positive electrode active material and the positive electrode conductive agent are first mixed, and then the positive electrode binder is added. Under the action of high shear force, the binder is converted from a powder state to a fibrous state to bind the positive electrode active material and the positive electrode conductive agent together, and a positive electrode active layer is formed by rolling. Finally, the positive electrode active layer and the positive electrode current collector are rolled and compounded to obtain the positive electrode.

[0077] It is understood that in the present application, there is no particular limitation on the negative electrode, as long as it can function as the negative electrode of the battery under the premise of conforming to the overall inventive concept of the present application. The following is only exemplary, and the negative electrode includes a negative electrode current collector, a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0078] In some embodiments, the shape of the negative electrode current collector includes any one of a foil shape, a plate shape, or a grid shape;

[0079] Further, the negative electrode current collector includes but is not limited to any one of aluminum, copper, nickel or zinc; optionally, the negative electrode current collector is copper, such as copper foil;

[0080] Furthermore, the negative electrode current collector includes any one of aluminum, copper, nickel or zinc alloy.

[0081] In some embodiments, the negative electrode active material includes, but is not limited to, one or more of graphite, silicon, silicon oxygen, silicon carbon, lithium titanate, hard carbon, soft carbon, tin oxide, and titanium dioxide materials.

[0082] In some embodiments, the negative electrode conductive agent includes, but is not limited to, carbon-based materials, powdered nickel or other metal particles or conductive polymers. Carbon-based materials may include, for example, particles of carbon black, graphite, super-P, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly (3,4-ethylenedioxythiophene) polystyrene sulfonate, and the like.

[0083] In some embodiments, the negative electrode binder includes, but is not limited to, one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polycarbonate (PC), polyamide (PA), acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene oxide (PPO) and carboxymethyl cellulose (CMC). Further, the binder is polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

[0084] It is understandable that the method for preparing the battery is not particularly limited in the present application, and any known process method for preparing the battery can be applied to the present application without violating the inventive concept of the present application.

[0085] The present application will be further described below with reference to specific embodiments and comparative examples.

[0086] Example 1

[0087] Preparation of composite lithium supplement

[0088] The organic lithium supplement (Li2C2O4), MOF (MIL-53Cr) and Mxene (Cr3C2OH) were weighed in a mass ratio of 1:1.8:1.8. The chromium ions on MIL-53Cr and the OH functional groups on Cr3C2OH were complexed to form a three-dimensional structure.

[0089] S1. Dissolve a monolayer of Mxene in water and stir at room temperature for 6 hours to obtain a colloidal solution with a mass fraction of 1.5%; wherein the layer thickness of Mxene is 1.5 nm, and the length and width of Mxene are both 1 μm.

[0090] S2. Adding an organic lithium supplement to the Mxene solution, stirring for 18 hours at a temperature of 20° C. and a rotation speed of 600 r / min, to obtain a first mixed solution.

[0091] S3, adding MOF to the first mixed solution, diluting it with distilled water, and ultrasonically stirring it for 20 minutes to obtain a second mixed solution, and vacuum freeze-drying the second mixed solution to obtain a powdered organic lithium supplement - Mxene / MOF material, that is, a composite lithium supplement.

[0092] The ultrasonic stirring treatment was carried out in an ice bath at a temperature of 0°C and an ultrasonic power of 200KW; the vacuum freeze-drying treatment was carried out at a temperature of -20°C and a vacuum degree of 5Pa.

[0093] Preparation of positive electrode

[0094] The composite lithium supplement agent is added to the positive electrode slurry to prepare a mixed slurry. The mass ratio of the composite lithium supplement agent to the positive electrode material in the positive electrode slurry is 5:95. The positive electrode material includes positive electrode active material lithium nickel manganese oxide, positive electrode binder PVDF and positive electrode conductive agent super P (the mass ratio of positive electrode active material, positive electrode binder and positive electrode conductive agent is 94:3:3). The mixed slurry is coated on aluminum foil, dried, and rolled to obtain a positive electrode.

[0095] The negative electrode is a graphite negative electrode, the separator is a PE film, homemade, and the electrolyte is EC:DMC=1:1vol%.

[0096] Preparation of batteries

[0097] The positive electrode, the negative electrode and the separator are wound / stacked to form a battery core, the electrolyte is injected into the battery core, and the battery is prepared through vacuum packaging, standing and formation processes.

[0098] Example 2

[0099] The difference between this embodiment and embodiment 1 is that the mass ratios of the organic lithium supplement agent, Mxene and MOF are different.

[0100] Example 3

[0101] The difference between this embodiment and embodiment 1 is that the mass ratios of the organic lithium supplement agent, Mxene and MOF are different.

[0102] Example 4

[0103] The difference between this embodiment and embodiment 1 is that the mass ratios of the organic lithium supplement agent, Mxene and MOF are different.

[0104] Example 5

[0105] The difference between this embodiment and embodiment 1 is that the types of organic lithium supplement agent, Mxene and MOF are different.

[0106] Example 6

[0107] The difference between this embodiment and embodiment 1 is that the mass ratios of the organic lithium supplement agent, Mxene and MOF are different.

[0108] Comparative Example 1

[0109] The difference between Comparative Example 1 and Example 1 is that Mxene and MOF are not added to the positive electrode.

[0110] Comparative Example 2

[0111] The difference between Comparative Example 1 and Example 1 is that Mxene is not added to the positive electrode.

[0112] Comparative Example 3

[0113] The difference between Comparative Example 1 and Example 1 is that no MOF is added to the positive electrode.

[0114] Comparative Example 4

[0115] The difference between Comparative Example 1 and Example 1 is that no organic lithium supplement, Mxene and MOF are added to the positive electrode.

[0116] The test parameters of the embodiments and comparative examples are summarized in Table 1 below:

[0117]

[0118] Test Case

[0119] (1) Determination of cycle performance

[0120] The prepared battery was subjected to a cycle test. At a temperature of 45°C ± 2°C, the first step was to charge at 0.1C to a final voltage of 4.95V, a cut-off current of 0.05C, and stand for 30 minutes; the second step was to discharge at 0.1C to a final discharge voltage (3.5V), record the discharge capacity, and stand for 30 minutes; the first and second steps were cycled to test the cycle performance of the battery for 100 cycles. The test results are shown in Table 2.

[0121] (2) Battery thickness change test

[0122] After the battery was cycled 100 times, the thickness change rate of the battery was tested. The test results are shown in Table 2.

[0123] (3) Battery internal resistance test

[0124] After the battery was prepared using the above method, the internal resistance was measured using a voltage resistance meter. The test results are shown in Table 2.

[0125]

[0126] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A composite lithium supplement, characterized in that: It includes an organic lithium supplement agent, MOF and Mxene, wherein the organic lithium supplement agent includes a general formula of Li2C n O n (n≥2) and / or the general formula is Li2C n O n+2 (n ≥ 2) compounds; The MOF is synthesized from transition metal elements and dicarboxylic acid ligands; The MOF and the Mxene undergo a complexation reaction to generate a complex having a three-dimensional structure; The organic lithium supplement agent is supported on the complex.

2. The composite lithium supplement according to claim 1, characterized in that: The mass ratio of the organic lithium supplement agent, the Mxene and the MOF is 1: (1.5-2): (1.5-2.2).

3. The composite lithium supplement according to claim 1, characterized in that: The Li2C n O n (n≥2) is cyclic, including at least one of the compounds of formula (I) to formula (IV), 、 、 、 。 4. The composite lithium supplement according to claim 1, characterized in that: The Li2C n O n+2 (n≥2) is chain-shaped, and includes at least one of the compounds of formula (V) to formula (VII), 、 、 。 5. The composite lithium supplement according to claim 1, characterized in that: The MOF includes one or more of MIL-53Cr, MIL-100Cr, MIL-101 Cr, MIL-100 Fe, MIL-177-LT, MIL-177-HT, MIL-45Co, MIL-45 Fe, MIL-53AI, MIL-53 Sc, MIL-88 Sc, MIL-8, MIL-9, MIL-47, MIL-51, MIL-59, MIL-69, MIL-88, MIL-91, MIL-96, MIL-101, MIL-103, MIL-102, MIL-110, and MIL-125.

6. The composite lithium supplement according to claim 1, characterized in that: The chemical formula of Mxene is M n+1 X n T m , wherein M is one or more of chromium, molybdenum, manganese, iron, cobalt, copper, aluminum, silver, nickel, palladium, platinum, and ruthenium, and n=1, 2 or 3; X is carbon or nitrogen; and Tm is one or more of hydroxyl, -O-, and halogen groups.

7. A method for preparing the composite lithium supplement according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Dissolve a monolayer of Mxene in water and stir at room temperature to obtain a colloidal solution with a mass fraction of 1% to 2%; S2, adding an organic lithium supplement agent to the colloidal solution, stirring at 15° C. to 30° C., to obtain a first mixed solution; S3, adding MOF to the first mixed solution, diluting, and ultrasonically stirring to obtain a second mixed solution, and vacuum freeze-drying the second mixed solution to obtain an organic lithium supplement agent-Mxene / MOF material, i.e., a composite lithium supplement agent; The layer thickness of the Mxene is 1 nm to 2 nm, and the length and width of the Mxene are both 0.5 μm to 1.5 μm; The mass ratio of the organic lithium supplement agent, the Mxene and the MOF is 1: (1.5-2): (1.5-2.2).

8. The method for preparing the composite lithium supplement according to claim 7, characterized in that: In step S1, the stirring treatment time at room temperature is 4h~8h; And / or in step S2, the stirring treatment time is 12h~24h, and the stirring treatment rate is 500r / min~800r / min; And / or in step S3, the temperature of ultrasonic stirring treatment is -5°C to 0°C, the ultrasonic power is 200KW to 300KW, and the time is 10min to 30min; And / or in step S3, the vacuum degree of vacuum freeze-drying treatment is 1.3Pa~13Pa, and the temperature is -50℃~-10℃.

9. A battery, characterized in that: It comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode and / or the separator comprises the composite lithium supplement agent according to any one of claims 1 to 6, or the composite lithium supplement agent prepared according to the preparation method according to any one of claims 7 or 8.

10. The battery according to claim 9, characterized in that The positive electrode includes the composite lithium supplement agent, and based on the mass of the positive electrode being 100%, the mass of the composite lithium supplement agent accounts for 2% to 10%.

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