CN114551813A - A metal lithium composite electrode, preparation method, application and battery - Google Patents

Abstract

The invention discloses a metal lithium composite electrode, a preparation method, application and a battery. The preparation method comprises the following steps: (1) performing ball milling dispersion on the two-dimensional transition metal nitride nanosheet powder, and then drying in vacuum; (2) uniformly spreading two-dimensional transition metal nitride nanosheet powder on the surface of a metal lithium foil, and rolling to obtain a composite sheet; (3) folding the composite sheet and then rolling; (4) and (4) repeating the step (3) repeatedly to obtain the composite electrode. The method provided by the invention can avoid the problems of 'lithium dendrite' and 'dead lithium' caused by uneven lithium deposition and stripping easily occurring on the surface of the lithium metal negative electrode, thereby improving the coulombic efficiency of the electrode and prolonging the cycle life of the electrode. The two-dimensional transition metal nitride has excellent lithium affinity, can induce the two-dimensional nucleation and growth of the metal lithium, and can provide a larger specific surface area for the deposition of the metal lithium, reduce the local current density and further inhibit the growth of the metal lithium dendritic crystal.

Description

A metal lithium composite electrode, preparation method, application and battery

technical field

The invention belongs to the technical field of metal lithium electrodes, and more particularly, relates to a metal lithium composite electrode, a preparation method, an application and a battery.

Background technique

Lithium-ion batteries are the main source of power for electric vehicles, electronic equipment, and drones, and it is imperative to continuously improve their energy density. Compared with the traditional lithium-ion battery anode material (graphite anode), metal lithium has a lower reduction potential (-3.04V, vs H ⁺ /H ₂ ) and a higher theoretical specific capacity (3860mAh g ^-1 ), which can Greatly improve the energy density of the battery. However, during the charging and discharging process of lithium metal, "lithium dendrites" and "dead lithium" are easily formed on the surface of lithium metal, resulting in low Coulomb efficiency, short battery cycle life, and even thermal runaway and explosion due to battery short circuit. . The above problems greatly limit the application of lithium metal anodes in high specific energy batteries. The construction of high-performance Li-metal composite electrodes is one of the important approaches to achieve uniform Li deposition/stripping behavior and suppress Li dendrite growth.

The commonly used framework materials for the preparation of lithium-containing composite electrodes mainly include carbon materials such as copper foam, nickel foam and carbon fiber. , it is usually necessary to modify the surface with a layer of lithophilic substances, such as Au, Ag, ZnO ₂ , SnO ₂ , etc. This additional operation not only increases the cost, but also makes the process cumbersome. In addition, in the process of compounding with metal lithium, two methods are generally used: molten immersion lithium or electrochemical deposition of lithium. In addition, the process is complicated, the former needs to be carried out at a higher temperature, and the latter needs to go through additional complicated battery loading and battery removal processes. Based on the above two points, designing novel lithiophilic frameworks and developing simpler composite methods are the keys to the application of high-performance metal-lithium composite electrodes.

The additive is pressed into the metal lithium sheet, and the use of rolling method to prepare the metal lithium negative electrode also has relevant reports (such as a preparation method of a layered composite for the negative electrode of a secondary metal lithium battery, Chinese invention patent CN 106654232 B), wherein, the additive is One or more of metal nanopowders, non-metallic nanopowders, layered structure compounds, and two-dimensional nanosheets; wherein the two-dimensional nanosheets are selected from reduced graphene oxide, graphene oxide, boron nitride nanosheets, disulfide One or more of molybdenum nanosheets, tungsten disulfide nanosheets, and Ti3C2 _{- MXene} nanosheets. Compared with the use of granular materials to prepare composite electrodes by rolling, the larger specific surface area of 2D materials can reduce the current density of lithium nucleation and inhibit the growth of lithium dendrites more effectively. The use of non-conductive 2D materials (graphene oxide, boron nitride, etc.) as additives can lead to sluggish reaction kinetics, Li ion aggregation, and induce uneven Li deposition. If the conductive material has poor lithophilicity (reduced graphene oxide), metallic lithium is more likely to be unevenly deposited on the upper surface of the material and grow lithium dendrites. For conductive two-dimensional materials with certain lithophilicity, only uniform nucleation can be achieved to a certain extent, but lithium dendrites are still easy to grow under high current and large capacity cycling conditions.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides a metal lithium composite electrode, a preparation method, an application and a battery, the purpose of which is to combine the transition metal nitride and the metal lithium sheet by a rolling method, and make full use of the transition metal Metal nitrides combine the advantages of large specific surface area, high electronic conductivity, strong lithiophilic properties, fast ion transport, and promotion of metal lithium epitaxial tile growth to achieve dendrite-free lithium deposition/stripping at high current and large capacity.

In order to achieve the above object, according to one aspect of the present invention, a preparation method of a metal lithium composite electrode is provided, comprising the following steps:

(1) vacuum drying the two-dimensional transition metal nitride nanosheet powder after ball milling or ultrasonic treatment;

(2) uniformly spreading the two-dimensional transition metal nitride nanosheet powder on the surface of the metal lithium foil, and rolling to obtain a composite sheet;

(3) rolling the composite sheet after folding;

(4) Step (3) is repeated to obtain a lithium composite electrode with a certain thickness.

Preferably, the pretreatment process in the step (1) is ball milling or ultrasonic treatment. The ball milling is specifically as follows: the ball milling time is 0.5-3h, the ball milling speed is 500-1500rpm, and the ball milling adopts ZrO particles with a diameter of _0.5-2mm . The specific parameters of ultrasonic treatment are: ultrasonic time is 0.5-2h, ultrasonic frequency is 40kHZ.

Preferably, the two-dimensional transition metal nitride nanosheet powder is two-dimensional molybdenum nitride nanosheet powder, two-dimensional titanium nitride nanosheet powder, two-dimensional vanadium nitride nanosheet powder, and two-dimensional chromium nitride nanosheet powder , two-dimensional zirconium nitride nanosheet powder, two-dimensional niobium nitride nanosheet powder, two-dimensional tantalum nitride nanosheet powder or two-dimensional tungsten nitride nanosheet powder.

Preferably, the thickness of the two-dimensional transition metal nitride nanosheet is 5-8 nm, and the two-dimensional plane average size of the two-dimensional transition metal nitride nanosheet powder is 0.5-10 μm.

Preferably, the mass ratio of the two-dimensional transition metal nitride nanosheet powder to the metal lithium foil is 0.6:1-1.2:1.

Preferably, the number of times of rolling is 2-12 times.

Preferably, the steps (2)-(4) are carried out under an Ar protective atmosphere.

Another aspect of the present invention provides a metal lithium composite electrode.

Another aspect of the present invention provides the application of the metal lithium composite electrode in the negative electrode of a lithium metal battery.

Yet another aspect of the present invention provides a lithium metal battery, including the metal lithium composite electrode.

In general, compared with the prior art, the above technical solutions conceived by the present invention can at least achieve the following beneficial effects.

(1) In the present invention, two-dimensional transition metal nitride nanosheets and lithium sheets are combined, and two-dimensional transition metal nitride is a lithiophilic material. In general, metal lithium and transition metal nitride (titanium nitride) , vanadium nitride, chromium nitride, molybdenum nitride, zirconium nitride, niobium nitride, tantalum nitride or tungsten nitride) through the mechanical rolling process at room temperature, the metal lithium easily reacts with the metal nitride surface, Li ₃ N and corresponding transition metals are generated, showing lithiophilic properties. Therefore, there is a strong binding ability between metallic lithium and transition metal nitrides, so that metallic lithium can be induced to uniformly nucleate on its surface, and then uniformly deposited. This can avoid the problem of a large number of "lithium dendrites" and "dead lithium" due to uneven lithium deposition and stripping on the surface of the lithium metal negative electrode, thereby improving the coulombic efficiency of the battery and prolonging the cycle life of the battery.

And two-dimensional transition metal nitrides have large specific surface area, high electronic conductivity and strong lithiophilic properties, which can reduce the effective current density, speed up the reaction kinetics, reduce the nucleation overpotential, and achieve uniform nucleation; in addition, the two-dimensional transition metal Nitride reacts with metallic lithium to produce Li ₃ N and corresponding transition metals with very good ionic conductivity. Li ₃ N can promote fast ion transport and achieve high rate performance. Transition metals also have strong interactions with Li. And there is a low lattice mismatch with lithium, which can induce the epitaxial growth of metal lithium, and then achieve high-capacity cycling performance.

(2) In the present invention, the two-dimensional transition metal nitride nanosheets are first subjected to ball milling or ultrasonic dispersion treatment to obtain monodisperse nanosheets.

(3) Compared with bulk materials, two-dimensional sheets can provide a larger specific surface area, thereby providing more lithium nucleation sites and promoting uniform lithium nucleation; at the same time, some special two-dimensional surfaces (such as MoN ( 002) crystal plane) can induce the epitaxial horizontal growth of metallic lithium on the plane, preventing the vertical growth of lithium dendrites from piercing the separator. On the other hand, 2D materials have a large surface area, which can reduce the nucleation current density and further suppress the growth of Li dendrites.

(4) The two-dimensional transition metal nitride nanosheets in the present invention are preferably two-dimensional molybdenum nitride, which has the advantage of abundant Mo ore resources in my country. In addition, the planar (002) crystal plane of the two-dimensional MoN can induce the parallel growth of metal lithium epitaxy .

(5) The present invention uses multiple physical operations of mechanical rolling/folding to prepare transition metal nitride nanosheets/metal lithium composite electrodes. The preparation method operates at room temperature, avoids the high-temperature melting process, is safer, and is more conducive to industrial production and application.

Description of drawings

1 is a schematic diagram of a method for preparing a metal lithium composite electrode provided in an embodiment of the present invention;

Figure 2 (a) is a schematic diagram of the deposition and stripping mechanism of metallic lithium on pure lithium electrodes, and Figure 2 (b) is a schematic diagram of the deposition and stripping mechanism of metallic lithium on two-dimensional molybdenum nitride nanosheets/lithium composite electrodes;

Figure 3 (a) is the TEM image of the two-dimensional molybdenum nitride nanosheets; Figure 3 (c) is the Mapping spectrum of the element Mo in the two-dimensional molybdenum nitride nanosheets; Figure 3 (d) The two-dimensional molybdenum nitride nanosheets Mapping image of element N in the nanosheet, (b) in 3 is the TEM image corresponding to the Mapping image;

Fig. 4(a) is the XPS pattern of the two-dimensional molybdenum nitride nanosheet Mo3d, and Fig. 4(b) is the XPS pattern of the two-dimensional molybdenum nitride nanosheet N1s;

(a) in Figure 5 is an optical photograph of the composite electrode prepared by Example 7, (b) in Figure 5 is a cross-sectional view of the SEM of the composite electrode, and (c) in Figure 5 is an SEM image of the upper surface of the composite electrode;

Figure 6 is the XRD comparison pattern of pure molybdenum nitride and composite electrodes, wherein MoN@Li is prepared by Example 7, and MoN is the two-dimensional molybdenum nitride nanosheet powder Li PDF#15-0401 used in Example 7 and MoN PDF#25-1367 are standard cards;

Figure 7(a) is the cycle performance diagram of the composite electrode assembled symmetric battery prepared by Example 7 under the condition of current 1mA/cm ^-2 and capacity 1mAh/cm ^-2 , and Figure 7(b) is current 1mA/cm ^-2 and cycle performance diagram under the condition of capacity 3mAh/cm ^-2 ;

Figure 8(a) is the SEM image after the cycle of the composite electrode MoN@Li assembled symmetric battery prepared in Example 7, and Figure 8(b) is the SEM image after the cycle of the pure Li electrode assembled symmetric battery;

9 is a performance diagram of a full battery assembled using the composite electrode prepared in Example 7 as the negative electrode and lithium iron phosphate as the positive electrode;

Fig. 10(a) is the SEM image of the negative electrode after the charge-discharge cycle of the composite electrode prepared in Example 7 with MoN@Li as the negative electrode and lithium iron phosphate as the positive electrode, and Fig. 10(b) is pure Li SEM image of the negative electrode after charge-discharge cycles of a full battery assembled with the electrode as the negative electrode and lithium iron phosphate as the positive electrode.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The present invention adopts the mechanical rolling method. First of all, the materials rolled together need to have good electronic conductivity. The introduction of materials with poor conductivity (boron nitride nanosheets, molybdenum disulfide and tungsten disulfide nanosheets, graphene oxide) into the electrode will cause Non-uniform charge accumulation on the electrode surface, which in turn induces non-uniform Li deposition; secondly, the material should have good lithiophilic properties to induce uniform nucleation of Li, while surface nucleation of materials with poor lithiophilicity such as graphene The overpotential is high, which in turn causes uneven deposition, resulting in lithium dendrites. Ti ₃ C _{2 -MXene} has excellent electronic conductivity, and its surface is rich in _lithiophilic functional groups such as -F and -OH, which can achieve uniform lithium deposition to a certain extent. The preparation process is complicated, and more harmful drugs such as HF need to be used. On the other hand, the amount of functional groups such as F and -OH on the surface is difficult to precisely control. The present invention uses two-dimensional MoN nanosheets, which have excellent electronic conductivity and good lithiophilic properties. Li reacts with MoN on the surface, and the products are metal Mo and Li ₃ N, wherein Li ₃ N has extremely high ionic The transfer rate can greatly promote the rapid transfer of lithium ions. The two-dimensional plane (002) crystal plane of MoN and the lattice mismatch between the metal Mo (100) crystal plane and metal lithium are small, which can induce planar epitaxy growth of metal lithium and effectively inhibit lithium dendrites; thus, compared to conventional materials such as Ti3C2 _{- MXene} , the introduction of 2D MoN in the present invention can induce uniform Li deposition to a greater extent, suppress Li dendrites, and achieve high capacity/high current long cycle. In addition, the network structure of metallic lithium and MoN prepared by rolling is stable, and the volume change of the electrode during the Li deposition and stripping process is small, which is more conducive to the realization of high rate and long cycle performance.

In the invention, the two-dimensional transition metal nitride nanosheet is used as the metal lithium deposition skeleton, and a composite electrode stacked with two-dimensional transition metal nitride nanosheet and lithium is prepared by a simple mechanical rolling method. The preparation process of the two-dimensional transition metal nitride nanosheet/metal lithium composite electrode is simple and easy to commercialize. Two-dimensional transition metal nitride nanosheet/metal lithium composite electrode is applied to metal lithium negative electrode, which can reduce the nucleation overpotential of metal lithium, induce uniform nucleation of metal lithium, and then realize dendrite-free lithium deposition, which is the commercial application of metal lithium provide a possibility.

In some embodiments, the preparation method of the metal lithium composite electrode provided by the present invention includes the following steps:

(1) Ball milling the two-dimensional transition metal nitride nanosheet powder and then vacuum drying;

(2) uniformly spreading the two-dimensional transition metal nitride nanosheet powder on the surface of the metal lithium foil, and rolling to obtain a composite sheet;

(3) rolling the composite sheet after folding;

(4) Repeat step (3), and then prepare a circular electrode sheet with a certain diameter.

The two-dimensional transition metal nitride nanosheet/metal lithium composite electrode prepared by the invention is a composite electrode in which the two-dimensional transition metal nitride nanosheet and the metal lithium are stacked layer by layer.

The present invention prepares a composite electrode in which two-dimensional transition metal nitride nanosheets and metal lithium layers are stacked by several simple mechanical rolling/folding/rolling methods. FIG. 1 is a flow chart of a method for preparing a composite electrode in which two-dimensional transition metal nitride nanosheets and metal lithium are stacked layer by layer according to an embodiment of the present invention, and two-dimensional molybdenum nitride nanosheets are used as an example.

As shown in Figure 2 (a) and (b), the deposition mechanism of metal lithium on different substrate materials is compared. The surface of metal lithium is prone to uneven lithium deposition, and a large number of lithium dendrites and dead lithium will be generated during continuous cycling. In the two-dimensional molybdenum nitride nanosheet/metal lithium composite electrode, metal lithium can be uniformly nucleated on the surface of the nanosheet and further spread on the surface of the nanosheet, thereby achieving uniform lithium deposition.

In some embodiments, the dosage ratio of two-dimensional molybdenum nitride nanosheets to metal lithium is 0.8:1.

In some embodiments, the rolling times of the two-dimensional molybdenum nitride nanosheets and the metal lithium in the rolling process is 2 times.

In this example, a two-dimensional molybdenum nitride nanosheet/metal lithium composite electrode is prepared by a mechanical rolling method.

Various examples are given below for detailed analysis and description of the technical solution of this embodiment.

For details of the preparation method of the two-dimensional molybdenum nitride nanosheet powder in the following examples, please refer to the patent document with the application number: CN202110079625.1, titled: a method for assisted preparation of two-dimensional transition metal nitride by decomposable alkali metal compounds.

Example 1

Step (1): Ball milling the two-dimensional molybdenum nitride nanosheet powder, and the ball milling conditions are: the ball milling time is 3h, the ball milling speed is 500rpm, and the ball milling adopts ZrO particles with a diameter of _2mm ; drying the two-dimensional molybdenum nitride nanosheets slices and transfer to the glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 2 times according to the mass ratio of 0.6:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 2

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 2 times according to the mass ratio of 0.8:1;

Step (3): firing into a circular electrode sheet with a diameter of 12mm.

Example 3

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 2 times according to the mass ratio of 1:1;

Step (3): firing into a circular electrode sheet with a diameter of 12mm.

Example 4

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 2 times according to the mass ratio of 1.2:1;

Step (3): firing into a circular electrode sheet with a diameter of 12mm.

Example 5

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 4 times according to the mass ratio of 1:1;

Step (3): firing into a circular electrode sheet with a diameter of 12mm.

Example 6

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 6 times according to the mass ratio of 1:1;

Step (3): firing into a circular electrode sheet with a diameter of 12mm.

Example 7

Step (1): ball-milling the two-dimensional molybdenum nitride nanosheet powder; drying the two-dimensional molybdenum nitride nanosheet, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional molybdenum nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 8

Step (1): ball milling the two-dimensional titanium nitride nanosheet powder; drying the two-dimensional titanium nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional titanium nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 9

Step (1): ball-milling the two-dimensional vanadium nitride nanosheet powder; drying the two-dimensional vanadium nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional vanadium nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 10

Step (1): ball-milling the two-dimensional chromium nitride nanosheet powder; drying the two-dimensional chromium nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional chromium nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 11

Step (1): ball-milling the two-dimensional zirconium nitride nanosheet powder; drying the two-dimensional zirconium nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional zirconium nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 12

Step (1): ball milling the two-dimensional niobium nitride nanosheet powder; drying the two-dimensional niobium nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional niobium nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 13

Step (1): ball-milling the two-dimensional tantalum nitride nanosheet powder; drying the two-dimensional tantalum nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional tantalum nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

Example 14

Step (1): ball-milling the two-dimensional tungsten nitride nanosheet powder; drying the two-dimensional tungsten nitride nanosheet powder, and transferring it to a glove box;

Step (2): rolling/folding the two-dimensional tungsten nitride nanosheet powder and metal lithium for 8 times according to the mass ratio of 1:1;

Step (3): Then prepare a circular electrode sheet with a diameter of 12 mm.

results and analysis

The XPS results of molybdenum nitride, the raw material used in the above examples 1-7, are shown in Figure 4 (a) and (b), the XRD pattern is shown in Figure 6, the TEM pattern and the Mapping pattern of each element are shown in Figure 3 (a)-(d) shown. XPS results and XRD results show that there are no other impurities in the used two-dimensional molybdenum nitride, and the material has high crystallinity. Molybdenum has good crystallinity.

In Example 7, the optical photograph and SEM of the finally prepared composite electrode are shown in (a)-(c) of FIG. 5 . The results show that the molybdenum nitride and metal lithium are stacked.

In Example 7, the XRD result of the finally prepared composite electrode is shown in FIG. 6 . The results show that the (002) peak intensity of molybdenum nitride and metal lithium is significantly weakened after rolling and compounding, indicating that molybdenum nitride and metal lithium are in a surface-to-surface state, and metal lithium grows two-dimensionally along the nanosheets.

(a)-(b) in FIG. 7 are the cycle performance diagrams of the symmetric battery assembled with the composite electrode prepared in Example 7. The results show that the cycle performance of pure metal lithium electrode is poor, and the voltage polarization is obvious, while the cycle performance of composite electrode is significantly improved, and the cycle performance is still improved under high current and large capacity.

(a) in FIG. 8 is the SEM image after the cycle of using the composite electrode prepared in Example 7 to assemble the symmetrical battery. Comparing the results of (b) in Figure 8, it is shown that lithium dendrites and dead lithium will form on the surface of pure metal lithium after a certain number of cycles, while the surface of the composite electrode is very smooth and no dendrites are generated.

9 is a performance diagram of a full battery assembled using the composite electrode prepared in Example 7 as the negative electrode and lithium iron phosphate as the positive electrode. The results show that, in the case of the same positive electrode material, the composite electrode as a negative electrode improves the battery capacity and cycle performance.

(a) in FIG. 10 is a SEM image of the negative electrode after the full battery cycle assembled using the composite electrode prepared in Example 7 as the negative electrode and lithium iron phosphate as the positive electrode. Comparing the results in (b) in Figure 10, there are no obvious dendrites and dead lithium on the surface of the composite negative electrode, but more dead lithium accumulates on the surface of the pure lithium sheet.

It is easily understood by those skilled in the art that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. a preparation method of metal lithium composite electrode, is characterized in that, comprises the following steps: (1) vacuum drying the two-dimensional transition metal nitride nanosheet powder after pretreatment; (2) uniformly spreading the two-dimensional transition metal nitride nanosheet powder on the surface of the metal lithium foil, and rolling to obtain a composite sheet; (3) rolling the composite sheet after folding; (4) Step (3) is repeated to obtain a composite electrode. 2 . The preparation method according to claim 1 , wherein the pretreatment process in the step (1) is ball milling or ultrasonic treatment. 3 . 3. The preparation method of claim 1, wherein the two-dimensional transition metal nitride nanosheet powder is two-dimensional molybdenum nitride nanosheet powder, two-dimensional titanium nitride nanosheet powder, two-dimensional nitride nanosheet powder Vanadium nanosheet powder, two-dimensional chromium nitride nanosheet powder, two-dimensional zirconium nitride nanosheet powder, two-dimensional niobium nitride nanosheet powder, two-dimensional tantalum nitride nanosheet powder or two-dimensional tungsten nitride nanosheet powder. 4. The preparation method according to any one of claims 1-3, wherein the two-dimensional transition metal nitride nanosheet powder has a thickness of 5-8 nm, and the two-dimensional transition metal nitride nanosheet powder has a thickness of 5-8 nm. The average size of the two-dimensional plane is 0.5-10 μm. 5 . The preparation method according to claim 1 , wherein the mass ratio of the two-dimensional transition metal nitride nanosheet powder to the metal lithium foil is 0.6:1-1.2:1. 6 . 6. The preparation method according to claim 1, wherein the number of times of rolling is 2-12 times. 7. The preparation method of claim 1, wherein the steps (2)-(4) are carried out in an Ar atmosphere. 8. The lithium metal composite electrode prepared by the method according to any one of claims 1-7. 9. The application of the metal lithium composite electrode as claimed in claim 8 in the negative electrode of lithium metal battery. 10 . A lithium metal battery, characterized by comprising the metal lithium composite electrode according to claim 8 . 11 .

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