CN112886019A

CN112886019A - High-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material and preparation method and application thereof

Info

Publication number: CN112886019A
Application number: CN202110149567.5A
Authority: CN
Inventors: 冯金奎; 魏传亮
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2021-02-03
Filing date: 2021-02-03
Publication date: 2021-06-01
Anticipated expiration: 2041-02-03
Also published as: CN112886019B

Abstract

The invention relates to the technical field of electrode material preparation, in particular to a highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material and a preparation method and application thereof. The negative electrode material includes: MXene film, COF nanoparticles and metal lithium; the COF nanoparticles are dispersed in the MXene film, and the metal lithium is distributed in the MXene-COF three-dimensional current collector. The MXene‑COF current collector has a three-dimensional structure, which can encapsulate lithium metal, which can not only reduce the local current density to suppress the growth of lithium dendrites, but also alleviate the volume expansion effect of metal lithium anode during deposition/stripping.

Description

High-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of electrode material preparation, in particular to a high-stability three-dimensional MXene-COF-Li composite metallic lithium negative electrode material, a preparation method and application thereof, and more particularly relates to a method for stabilizing a metallic lithium negative electrode by using a three-dimensional self-supporting lithium-philic MXene-COF film as a metallic lithium current collector.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

The rapid development of new energy electric vehicles, intelligent electronic products and energy storage power grids urgently requires rechargeable secondary batteries with high energy density. Lithium metal batteries, which employ metallic lithium as a negative electrode material with extremely high energy density, are considered as one of candidates for next-generation energy storage batteries. The lithium metal negative electrode has a low density (0.534 g/cm)³) High theoretical specific capacity (3860mAh/g), low electrochemical potential (-3.040V), which are figuratively referred to as "holy-cup" and "ultimate negative electrode".

However, the metallic lithium negative electrode has many problems such as uncontrolled growth of lithium dendrites, a large volume expansion effect, an unstable Solid Electrolyte Interface (SEI), and the like. Dendritic lithium easily pierces a diaphragm, and then causes short circuit of a lithium metal battery, and causes safety accidents such as thermal runaway, fire, explosion and the like. And excessive volume expansion effects and unstable SEI can reduce the cycle life and stability of the lithium metal anode. These problems greatly hinder the application of metallic lithium negative electrodes in lithium metal batteries. The problem of solving the lithium metal cathode is the premise of realizing the large-scale application of the lithium metal battery with high energy density and high safety.

The inventor researches and discovers that although the prior art discloses some composite or supported metallic lithium negative electrode materials, the electrode cycling stability is poor and the charge-discharge capacity is low.

Disclosure of Invention

Aiming at the problems, the invention provides a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material and a preparation method thereof. The lithium metal cathode material with long service life, high stability, high charge and discharge capacity and high safety is prepared and applied to the high-energy-density lithium metal battery, and the lithium metal cathode material has important significance for the rapid development of new energy industries.

Specifically, the invention is realized by the following technical scheme:

the invention provides a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material, which comprises the following components in percentage by weight: MXene thin films, COF nanoparticles, and metallic lithium;

the COF nano particles are dispersed in an MXene film, and the metallic lithium is distributed in an MXene-COF three-dimensional current collector.

The invention provides a preparation method of a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material, which comprises the following steps:

mixing MXene and COF nano particles, performing suction filtration to obtain a three-dimensional flexible MXene-COF self-supporting film, and depositing metallic lithium on the three-dimensional flexible MXene-COF self-supporting film.

The third aspect of the invention provides an application of a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material in a lithium metal battery.

The invention provides a lithium metal battery, which comprises a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material.

One or more embodiments of the present invention have the following advantageous effects:

1) the metallic lithium is limited in a three-dimensional MXene-COF current collector with certain lithium affinity. MXene has good conductivity and ion conductivity, and can accelerate the electron and ion transmission rate of the electrode and accelerate electrochemical kinetics. The inherent lithium-philic functional group on MXene and the lithium-philic COF nano particles dispersed in the MXene film can be used as nucleating agents to induce uniform lithium ion flow and realize uniform and dendrite-free lithium deposition. The MXene-COF current collector has a three-dimensional structure, can wrap the lithium metal, can reduce local current density, inhibit the growth of lithium dendrites and can relieve the volume expansion effect of a lithium metal negative electrode in deposition/stripping. The obtained MXene-COF-Li composite metal lithium negative electrode has the advantages of good stability, high safety, long service life and the like.

2) The prepared MXene-COF-Li composite lithium metal cathode still keeps the coulombic efficiency above 99.5% when the battery is cycled for 200 weeks, the initial specific capacity of the prepared full battery is about 1200mAh/g, after the battery is cycled for 300 weeks under the multiplying power of 1C, the capacity retention rate of the MXene-COF-Li | S full battery is 73.8%, the capacity retention rate of the MXene-Li | S full battery is 19.3%, and the MXene-COF-Li | S full battery has smaller polarization phenomenon and larger specific discharge capacity than the MXene-Li | S full battery.

3) The invention adopts a simple vacuum filtration method, has simple and easy operation and uniform film formation. The invention adopts the electrodeposition method to prepare the composite metal lithium cathode, and has the advantages of high safety, controllable deposition amount and the like.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic flow chart of preparing a highly stable three-dimensional MXene-COF-Li composite lithium metal anode material in examples 1-15 of the present invention;

FIG. 2 is a scanning electron micrograph of COF-LZU1 of example 1 according to the present invention;

fig. 3 is a scanning electron microscope image of an MXene current collector in a comparative example of the present invention;

FIG. 4 is a scanning electron micrograph of MXene-COF current collector in example 1 of the present invention;

fig. 5 is a graph of deposition voltage versus capacity of lithium on an MXene current collector and an MXene-COF current collector in comparative example and example 1 of the present invention;

fig. 6 is a graph of coulombic efficiency of an MXene current collector and an MXene-COF current collector in comparative example and example 1 of the present invention;

FIG. 7 is a scanning electron microscope image of MXene-Li composite cathode in comparative example of the present invention, and the deposition current is 0.5mA/cm²The deposition capacity is 5mAh/cm²；

FIG. 8 is a scanning electron microscope image of the MXene-COF-Li composite cathode in example 1 of the present invention, with a deposition current of 0.5mA/cm²The deposition capacity is 5mAh/cm²；

FIG. 9 is a charge and discharge curve diagram of MXene-Li | S full cell and MXene-COF-Li | S full cell at 1C rate in comparative example and example 1 of the present invention;

fig. 10 is a cycle curve diagram of the MXene-Li | | | S full cell and the MXene-COF-Li | | | S full cell at 1C rate in the comparative example and example 1 of the present invention, where S refers to the vulcanized polyacrylonitrile positive electrode material.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Although the lithium metal negative electrode has a low density (0.534 g/cm)³) High theoretical specific capacity (3860mAh/g), low electrochemical potential (-3.040V) and the like. However, the lithium metal negative electrode has many problems such as uncontrolled growth of lithium dendrites, a large volume expansion effect, an unstable Solid Electrolyte Interface (SEI), and the like. Dendritic lithium easily pierces a diaphragm, and then causes short circuit of a lithium metal battery, and causes safety accidents such as thermal runaway, fire, explosion and the like. And excessive volume expansion effects and unstable SEI can reduce the cycle life and stability of the lithium metal anode. These problems greatly hinder the application of metallic lithium negative electrodes in lithium metal batteries. The problem of solving the lithium metal cathode is the premise of realizing the large-scale application of the lithium metal battery with high energy density and high safety.

The invention provides a high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material and a preparation method thereof. The lithium metal cathode material with long service life, high stability, high charge and discharge capacity and high safety is prepared and applied to the high-energy-density lithium metal battery, and the lithium metal cathode material has important significance for the rapid development of new energy industries.

Specifically, the invention is realized by the following technical scheme:

If the COF nano particles and the metallic lithium are directly and simply loaded on the MXene film, on one hand, the COF nano particles and the metallic lithium are mutually influenced in the deposition or loading process, and the good loading of the COF nano particles and the metallic lithium cannot be realized. On the other hand, COF nanoparticles and metallic lithium are distributed on the MXene film in a scattered manner, so that a continuous or regular lithium ion transmission path cannot be formed by the negative electrode material, and lithium dendrite is not controlled easily, and the volume stability is maintained.

Compared with the method that COF nano particles and metallic lithium are simply loaded on the MXene film directly, the COF nano particles are dispersed in the MXene film creatively, so that the COF nano particles and the MXene film generate certain physical adsorption effect, a better substrate is provided for lithium deposition, and a powerful basis is provided for a larger capacity and better cycle performance of the MXene-COF-Li composite metallic lithium negative electrode material.

In one or more embodiments of the invention, the MXene is selected from Ti₃C₂T_x、V₂CT_x、Ti₂NT_x；

Preferably, the MXene is selected from Ti₃C₂、Nb₄C₃、Ti₂C、Ta₄C₃、TiNbC、(V_0.5Cr_0.5)₃C₂、V₂C、Nb₂C、Ti₃CN、Ti₃C₂、Ti₂C、Ta₄C₃、TiNbC、(V_0.5Cr_0.5)₃C₂、V₂C、Nb₂C、Nb₄C₃Or Ti₃One or more of CN.

In one or more embodiments of the invention, the COF nanoparticles are selected from the group consisting of COF-LZU1, COF-42, and Tf-TAPA.

In one or more embodiments of the present invention, the COF nanoparticles account for 1% to 50% by mass of the MXene, preferably 5% to 33%, and further preferably 5%, 10%, or 33%.

One of the characteristics of the method of the invention is as follows: the metallic lithium is limited in a three-dimensional MXene-COF current collector with certain lithium affinity. MXene has good conductivity and ion conductivity, and can accelerate the electron and ion transmission rate of the electrode and accelerate electrochemical kinetics. Meanwhile, the inherent lithium-philic functional group on MXene and the lithium-philic COF nano particles dispersed in the MXene film can be used as nucleating agents to induce uniform lithium ion flow and realize uniform and dendrite-free lithium deposition. Compared with the cathode material which only uses MXene loaded lithium, the cathode material designed by the invention has more excellent battery capacity and cycle stability.

In addition, the MXene-COF current collector has a three-dimensional structure, and can wrap the metallic lithium, so that not only can the local current density be reduced, the growth of lithium dendrites be inhibited, but also the volume expansion effect of the metallic lithium negative electrode in deposition/stripping can be relieved. The obtained MXene-COF-Li composite metal lithium negative electrode has the advantages of good stability, high safety, long service life and the like.

In one or more embodiments of the present invention, MXene and COF nanoparticles are mixed in such a manner that the COF nanoparticles are added to an aqueous solution of MXene, stirred or sonicated;

preferably, the suction filtration adopts a vacuum filtration method;

preferably, the stirring or ultrasonic treatment time is 5-20min, preferably 10 min;

preferably, the suction filtration process further comprises a drying process of the three-dimensional flexible MXene-COF self-supporting film, and the drying process is carried out at the temperature of 50-80 ℃ for 10-15h, preferably at the temperature of 60 ℃ for 12 h.

In one or more embodiments of the invention, the deposition is by electrochemical deposition;

preferably, the electrolyte in the electrochemical deposition method is an ester electrolyte or an ether electrolyte;

preferably, the electrolyte is selected from the group consisting of LiTFSI-DOL/DME and LiPF₆-EC/DEC；

Preferably, the volume ratio of DOL to DME in the electrolyte LiTFSI-DOL/DME is 1: 1;

preferably, the electrolyte is LiPF₆-the volume ratio of EC and DME in EC/DEC is 1: 1;

preferably, the electrolyte concentration is 0.5-2mol/L, preferably 1 mol/L. The electrolyte concentration is too high, the deposited lithium is too much and is easy to peel off, and the electrolyte concentration is too low, so that the lithium deposition is incomplete, and the improvement of the battery capacity and the cycling stability are not facilitated.

Preferably, the electrochemical deposition current is 0.1-10mA/cm²Preferably 0.5 to 10mA/cm²；

Preferably, the electrochemical deposition capacity is 1-10mAh/cm²Preferably 5-8mAh/cm²。

In one or more embodiments of the invention, the MXene synthesis method is selected from the group consisting of acid etching, molten salt etching, electrochemical etching;

preferably, in the acid etching method, MAX phase powder is etched to obtain MXene aqueous solution;

preferably, the MAX phase powder is selected from Ti₃AlC₂、V₂AlC and Ti₂AlN；

Preferably, the acid in the acid etching process is selected from the group consisting of HF, LiF, HCl, and NH₄HF₂One or more of (a).

Preferably, the lithium metal battery is a high energy high density battery;

preferably, the lithium metal battery is a lithium metal half-battery or a lithium metal full-battery;

preferably, the lithium metal full cell is selected from MXene-COF-Li | | | S, MXene-COF-Li | | | LiFePO₄，MXene-COF-Li||LiCoO₂，MXene-COF-Li||LiMn₂O₄。

Preferably, the lithium metal battery is a high energy high density battery;

The invention effectively prolongs the cycle life and stability of the metal lithium cathode, is expected to improve the performance of the lithium metal battery, and is further widely applied to new energy electric vehicles, intelligent electronic products and energy storage power grids to promote the development and progress of the society.

The present invention is described in further detail below with reference to specific examples, which are intended to be illustrative of the invention and not limiting.

Example 1

The preparation and application of the high-stability three-dimensional MXene-COF-Li composite metal lithium negative electrode material comprise the following steps (figure 1):

(1) etching Ti by acid etching₃AlC₂Obtaining Ti from MAX phase powder₃C₂T_xMXene aqueous solution with concentration of 1 mg/mL.

(2) Taking trimesic aldehyde and p-phenylenediamine as raw materials and dioxane as a solvent to synthesize COF-LZU1 nano-particles (figure 2).

(3) COF-LZU1 nanoparticles with a mass of 1.5mg were added to 30mL of Ti₃C₂T_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

(4) And (3) carrying out suction filtration on the mixed solution in the step (3) to obtain the MXene-COF self-supporting film by using a vacuum suction filtration device, and drying at 60 ℃ for 12h (figure 4).

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm²(FIG. 8). The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

(6) MXene-COF-Li I S full cells are assembled by using CR2032 type button cells in 1M LiTFSI-DOL/DME (volume ratio 1:1) liquid electrolyte. The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a current collector (aluminum), a sulfur positive electrode, an MXene-COF-Li composite negative electrode, electrolyte and a diaphragm (PP).

Example 2

(1) etching V by acid etching₂AlC MAX phase powder to obtain V₂CT_xMXene aqueous solution with concentration of 1 mg/mL.

(2) Taking trimesic aldehyde and p-phenylenediamine as raw materials and dioxane as a solvent to synthesize COF-LZU1 nano particles.

(3) COF-LZU1 nanoparticles with a mass of 1.5mg were added to 30mL of V₂CT_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

(4) And (4) carrying out suction filtration on the mixed solution in the step (3) into an MXene-COF self-supporting film by using a vacuum suction filtration device, and drying at 60 ℃ for 12 h.

(5) Using CR2032 button cell in 1M LiTElectrochemical deposition of lithium is carried out in FSI-DOL/DME (volume ratio is 1:1) liquid electrolyte to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 3

(1) etching Ti by acid etching₂AlN MAX phase powder to obtain Ti₂NT_xMXene aqueous solution with concentration of 1 mg/mL.

(3) COF-LZU1 nanoparticles with a mass of 1.5mg were added to 30mL of Ti₂NT_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 4

(2) Taking trimesic aldehyde and 2, 5-diethoxyphthalhydrazide as raw materials and dioxane as a solvent to synthesize COF-42 nano-particles.

(3) COF-42 nanoparticles with a mass of 1.5mg were added to 30mL of Ti₃C₂T_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

Example 5

(2) Taking trimesic aldehyde and tri (4-aminophenyl) amine as raw materials, and dioxane as a solvent to synthesize the Tf-TAPA nano-particles.

(3) Tf-TAPA nanoparticles with a mass of 1.5mg were added to 30mL of Ti₃C₂T_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

Example 6

(3) COF-LZU1 nanoparticles with a mass of 3mg were addedTo 30mL of Ti₃C₂T_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

Example 7

(3) The COF-LZU1 nanoparticles with a mass of 10mg were added to 30mL of Ti₃C₂T_xAnd (3) carrying out ultrasonic treatment on the MXene aqueous solution for 10 minutes to obtain a uniformly mixed solution.

(5) Electrochemical deposition of lithium is carried out in liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio 1:1) by using CR2032 type button cell to obtain MXene-COF-Li compositeAnd (3) alloying the lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 8

(5) Using CR2032 button cell in 1M LiPF₆And electrochemically depositing lithium in an EC/DEC (volume ratio of 1:1) liquid electrolyte to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 9

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 5mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 10

(1) etching with acidEtching of Ti₃AlC₂Obtaining Ti from MAX phase powder₃C₂T_xMXene aqueous solution with concentration of 1 mg/mL.

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 10mA/cm²The deposition capacity is 5mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 11

(3) COF-LZU1 nanoparticles with a mass of 1.5mg were added to 30mL of Ti₃C₂T_xMXene aqueous solutionAnd carrying out ultrasonic treatment for 10 minutes to obtain a uniformly mixed solution.

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 8mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 12

(5) Electrochemical deposition of lithium is carried out in a liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio is 1:1) by using a CR2032 type button cell to obtain the MXene-COF-Li composite metal lithium negative electrode material. The deposition current was 0.5mA/cm²Deep and deepThe volume capacity is 10mAh/cm². The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene-COF current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

Example 13

(6) MXene-COF-Li II LiFePO is assembled by using CR2032 type button cell in 1M LiTFSI-DOL/DME (volume ratio 1:1) liquid electrolyte₄And (4) full cell. The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel) and a padSheet (stainless steel), current collector (aluminum), LiFePO₄The lithium ion battery comprises a positive electrode, an MXene-COF-Li composite negative electrode, an electrolyte and a diaphragm (PP).

Example 14

(6) Assembling MXene-COF-Li I LiCoO in liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio 1:1) by using CR2032 type button cell₂And (4) full cell. The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a current collector (aluminum) and LiCoO₂The lithium ion battery comprises a positive electrode, an MXene-COF-Li composite negative electrode, an electrolyte and a diaphragm (PP).

Example 15

(1) etching with acid etchingTi₃AlC₂Obtaining Ti from MAX phase powder₃C₂T_xMXene aqueous solution with concentration of 1 mg/mL.

(6) Assembling MXene-COF-Li | LiMn in liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio 1:1) by using CR2032 type button cell₂O₄And (4) full cell. The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a current collector (aluminum) and LiMn₂O₄The lithium ion battery comprises a positive electrode, an MXene-COF-Li composite negative electrode, an electrolyte and a diaphragm (PP).

Comparative example

The implementation of the comparative example mainly comprises the following steps:

(2) 30mL of MXene solution from (1) was suction filtered into MXene free-standing film using a vacuum filtration apparatus (FIG. 3) and baked at 60 ℃ for 12 h.

(3) Electrochemical deposition of lithium is carried out in liquid electrolyte of 1M LiTFSI-DOL/DME (volume ratio 1:1) by using CR2032 type button cell to obtain MXene-Li complexAnd (3) alloying the lithium negative electrode material. The deposition current was 0.5mA/cm²The deposition capacity is 5mAh/cm²(FIG. 7). The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), an MXene current collector, a lithium sheet negative electrode, electrolyte and a diaphragm (PP).

(6) MXene-Li I S full cell was assembled with CR2032 button cell in 1M LiTFSI-DOL/DME (1: 1 volume ratio) liquid electrolyte. The button cell structure comprises a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a current collector (aluminum), a sulfur positive electrode, an MXene-Li composite negative electrode, electrolyte and a diaphragm (PP).

Performance testing

(1) Taking the button cell assembled in example 1 as an example, the nucleation overpotential and the coulombic efficiency of MXene-COF current collector were evaluated by a charge and discharge device (Xinwei CT-4008). Meanwhile, as a comparison, the above-mentioned properties of the MXene current collector were also tested, and the results are shown in fig. 5 and 6, in which,

first, at a current density of 0.2mA/cm²Conditions of (a) testing the nucleation overpotential of lithium on the MXene and MXene-COF current collectors, the results are shown in fig. 5. Fig. 5 is a voltage-capacity curve of lithium deposition on an MXene current collector and an MXene-COF current collector. The nucleation overpotential of lithium on the MXene collector was 130.5mV and the nucleation overpotential of lithium on the MXene-COF collector was 73.5 mV. The above results show that the addition of COF nanoparticles can reduce the nucleation overpotential of lithium on the current collector.

Next, at a current density of 1.0mA/cm²The capacity is 1.0mAh/cm²The coulombic efficiency of lithium on the MXene current collector and the MXene-COF current collector was tested under the conditions and the results are shown in fig. 6. It can be seen that the MXene-COF current collector has a higher coulombic efficiency than the MXene current collector. The above results show that the addition of COF nanoparticles can improve coulombic efficiency.

Finally, the charge and discharge performance of the MXene-COF-Li | | S full cell and the MXene-Li | | S full cell were tested at a rate of 1C, and the results are shown in fig. 9 and 10. FIG. 9 shows the charge and discharge curves of MXene-COF-Li | S full cell and MXene-Li | S full cell at 1C rate. As can be seen, the MXene-COF-Li I S full cell has smaller polarization phenomenon and larger specific discharge capacity than the MXene-Li I S full cell. FIG. 10 shows the cycle curves of MXene-COF-Li | S full cell and MXene-Li | S full cell at 1C rate. As can be seen, the MXene-COF-Li | | | S full cell has better cycle performance than the MXene-Li | | | S full cell. After 300 cycles, the capacity retention rate of the MXene-COF-Li | | | S full cell is 73.8%, and the capacity retention rate of the MXene-Li | | | S full cell is 19.3%. The results show that the MXene-COF-Li composite negative electrode can enable the full battery to have better electrochemical performance.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. a highly stable three-dimensional MXene-COF-Li composite metal lithium negative material, is characterized in that, comprises: MXene film, COF nanoparticle and metallic lithium;

The COF nanoparticles are dispersed in the MXene film, and the metal lithium is distributed in the MXene-COF three-dimensional current collector.

2. The highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material according to claim 1, wherein the MXene is selected from Ti ₃ C ₂ T _x , V ₂ CT _x , and Ti ₂ NT _x ;

Preferably, the MXene is selected from Ti ₃ C ₂ , Nb ₄ C ₃ , Ti ₂ C, Ta ₄ C ₃ , TiNbC, (V _0.5 Cr _0.5 ) ₃ C ₂ , V ₂ C, Nb ₂ C, Ti ₃ CN One or more of , Ti ₃ C ₂ , Ti ₂ C, Ta ₄ C ₃ , TiNbC, (V _0.5 Cr _0.5 ) ₃ C ₂ , V ₂ C, Nb ₂ C, Nb ₄ C ₃ or Ti ₃ CN .

3. The highly stable three-dimensional MXene-COF-Li composite metal lithium anode material according to claim 1, wherein the COF nanoparticles are selected from COF-LZU1, COF-42 and Tf-TAPA.

4. The highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material according to claim 1, wherein the mass of the COF nanoparticles accounts for 1%-50% of the mass of the MXene, preferably 5%-33% , more preferably 5%, 10% or 33%.

5. The preparation method of the highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material according to any one of claims 1 to 4, characterized in that, comprising:

After mixing MXene and COF nanoparticles, a three-dimensional flexible MXene-COF self-supporting film was formed by suction filtration, and then metal lithium was deposited on the three-dimensional flexible MXene-COF self-supporting film.

6. The method for preparing a highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material according to claim 5, wherein the MXene and COF nanoparticles are mixed by adding the COF nanoparticles to the aqueous solution of MXene, stirring or sonication;

Preferably, the suction filtration adopts vacuum suction filtration;

Preferably, the stirring or ultrasonic treatment time is 5-20min, preferably 10min;

Preferably, after the suction filtration, the drying process of the three-dimensional flexible MXene-COF self-supporting film is further included, at 50-80° C. for 10-15 hours, preferably at 60° C. for 12 hours.

7. The preparation method of the highly stable three-dimensional MXene-COF-Li composite metal lithium anode material according to claim 5, wherein the deposition adopts an electrochemical deposition method;

Preferably, the electrolyte is selected from LiTFSI-DOL/DME and LiPF ₆ -EC/DEC;

Preferably, the volume ratio of DOL and DME in the electrolyte LiTFSI-DOL/DME is 1:1;

Preferably, the volume ratio of EC and DME in the electrolyte LiPF ₆ -EC/DEC is 1:1;

Preferably, the electrolyte concentration is 0.5-2 mol/L, preferably 1 mol/L;

Preferably, the electrochemical deposition current is 0.1-10 mA/cm ² , preferably 0.5-10 mA/cm ² ;

Preferably, the electrochemical deposition capacity is 1-10 mAh/cm ² , preferably 5-8 mAh/cm ² .

8. The method for preparing a highly stable three-dimensional MXene-COF-Li composite metal lithium anode material according to claim 5, wherein the MXene synthesis method is selected from the group consisting of acid etching, molten salt etching, electrochemical etching etch;

Preferably, in the acid etching method, the MAX phase powder is etched to obtain the MXene aqueous solution;

Preferably, the MAX phase powder is selected from Ti ₃ AlC ₂ , V ₂ AlC and Ti ₂ AlN;

Preferably, the acid in the acid etching method is selected from one or more of HF, LiF, HCl and NH ₄ HF ₂ .

9. Application of the highly stable three-dimensional MXene-COF-Li composite metal lithium anode material according to any one of claims 1 to 4 in lithium metal batteries;

Preferably, the lithium metal battery is a high-energy and high-density battery;

Preferably, the lithium metal battery is a lithium metal half battery or a lithium metal full battery;

Preferably, the lithium metal full battery is selected from MXene-COF-Li||S, MXene-COF-Li||LiFePO ₄ , MXene-COF-Li||LiCoO ₂ , MXene-COF-Li||LiMn ₂ O ₄ .

10. A lithium metal battery, comprising the highly stable three-dimensional MXene-COF-Li composite metal lithium negative electrode material according to any one of claims 1 to 4;