Lithium metal anode modified by double-layer ordered vertical mesoporous thin film, preparation method and application thereof

Abstract

The present invention discloses a metal lithium anode modified with a double-layer ordered vertical mesoporous thin film, a preparation method thereof, and an application. The metal lithium anode modified with the double-layer ordered vertical mesoporous thin film includes a macroporous single-layer ordered vertical mesoporous thin film, a microporous single-layer ordered vertical mesoporous thin film, and a metal lithium layer that are sequentially stacked. By sequentially arranging the microporous single-layer ordered vertical mesoporous thin film and the macroporous single-layer ordered vertical mesoporous thin film on the surface of the metal lithium layer, the present invention can regulate the lithium ion transport behavior during the charge and discharge process of the lithium anode, guide uniform lithium deposition, effectively inhibit the growth of lithium dendrites, solve the problem of lithium dendrite growth in metal lithium deposition in the prior art, thereby significantly increasing the cycle stability and greatly improving the safety of the metal lithium anode during use.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium metal batteries, and particularly to a lithium metal negative electrode modified with a double-layer ordered vertical mesoporous thin film, a preparation method thereof, and an application thereof. Background Art

[0002] China's demand for the development of new energy is increasing, which puts forward higher requirements for the energy density and safety of rechargeable batteries such as portable electronic devices and electric vehicles. Lithium metal has a high theoretical specific capacity (3860 mAh g -1 ) and the lowest negative electrode electrochemical potential (-3.04 V, hydrogen standard potential), and thus has received extensive attention as a negative electrode material for high-energy density batteries. However, the commercial development of lithium metal batteries still faces challenges in terms of cycle stability and safety. This is mainly because the side reactions between highly reactive lithium metal and the electrolyte continuously consume lithium metal and the electrolyte, resulting in a decrease in Coulomb efficiency and poor cycle stability; the uneven lithium deposition at the lithium metal interface causes dendrite growth, and even penetrates the separator to connect to the positive electrode, causing an internal short circuit of the battery and resulting in safety accidents.

[0003] Therefore, providing a method that can achieve uniform distribution and deposition of lithium ions at the interface of the lithium metal negative electrode is of great significance for improving the cycle stability of lithium metal batteries. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, and propose a lithium metal negative electrode modified with a double-layer ordered vertical mesoporous thin film, a preparation method thereof, and an application thereof, so as to solve the technical problem that the uneven distribution and deposition of lithium ions at the interface of the lithium metal negative electrode in the prior art lead to poor cycle stability of the battery.

[0005] The first aspect of the present invention provides a lithium metal negative electrode modified with a double-layer ordered vertical mesoporous thin film, which includes a macroporous single-layer ordered vertical mesoporous thin film, a microporous single-layer ordered vertical mesoporous thin film, and a lithium metal layer stacked in sequence.

[0006] The second aspect of the present invention provides a preparation method of a lithium metal negative electrode modified with a double-layer ordered vertical mesoporous thin film, including the following steps:

[0007] Obtain a macroporous single-layer ordered vertical mesoporous thin film and a microporous single-layer ordered vertical mesoporous thin film respectively;

[0008] Attach the microporous single-layer ordered vertical mesoporous thin film to the surface of the lithium metal layer, so that the macroporous single-layer ordered vertical mesoporous thin film is located on the side of the microporous single-layer ordered vertical mesoporous thin film away from the lithium metal layer, and obtain a lithium metal negative electrode modified with a double-layer ordered vertical mesoporous thin film.

[0009] The third aspect of the present invention provides an application of a metal lithium anode modified with a double-layer ordered vertical mesoporous film, and the metal lithium anode modified with the double-layer ordered vertical mesoporous film is used for preparing a lithium metal battery.

[0010] Compared with the prior art, the beneficial effects of the present invention include:

[0011] By sequentially arranging a small-pore single-layer ordered vertical mesoporous film and a large-pore single-layer ordered vertical mesoporous film on the surface of the metal lithium layer, the present invention can regulate the lithium ion transport behavior of the lithium anode during charge and discharge, guide uniform lithium deposition, effectively inhibit the growth of lithium dendrites, solve the problem of lithium dendrite growth in metal lithium deposition in the prior art, thereby significantly increasing the cycle stability and greatly improving the safety of the metal lithium anode during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic structural diagram of an embodiment of the metal lithium anode modified with the double-layer ordered vertical mesoporous film of the present invention;

[0013] Figure 2 is a Coulomb efficiency diagram of a lithium copper battery made of the lithium anode modified with the double-layer ordered vertical mesoporous film in Example 1 of the present invention;

[0014] Figure 3 is a Coulomb efficiency diagram of a lithium copper battery made of a double-layer ordered vertical mesoporous film with small pore diameters in Comparative Example 1 of the present invention;

[0015] Figure 4 is a Coulomb efficiency diagram of a lithium copper battery made of a double-layer ordered vertical mesoporous film with large pore diameters in Comparative Example 2 of the present invention;

[0016] Figure 5 is a Coulomb efficiency diagram of a lithium copper battery made of the lithium anode modified with the double-layer ordered vertical mesoporous film in Comparative Example 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, 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 and are not used to limit the present invention.

[0018] Please refer to Figure 1 , the first aspect of the present invention provides a metal lithium anode modified with a double-layer ordered vertical mesoporous film, including a large-pore single-layer ordered vertical mesoporous film, a small-pore single-layer ordered vertical mesoporous film and a metal lithium layer which are sequentially stacked.

[0019] In the present invention, the single-layer ordered vertical mesoporous film refers to a mesoporous film with a uniform pore size distribution and ordered vertical pore channels.

[0020] In the present invention, a small-pore single-layer ordered vertical mesoporous thin film and a large-pore single-layer ordered vertical mesoporous thin film are sequentially laminated on the surface of the lithium metal layer, successfully constructing a lithium negative electrode interface modification material with a uniform pore size distribution, an ordered vertical arrangement of pore channels, and pore-to-pore penetration, which can achieve a uniform distribution and deposition of lithium ions, effectively inhibit the growth of lithium dendrites, and significantly improve the cycle stability of the lithium metal battery.

[0021] In the present invention, the material of the above-mentioned double-layer ordered vertical mesoporous thin film is selected from metal oxides, non-metal oxides, high molecular compounds, etc., and the present invention does not limit this, and those skilled in the art can select according to the actual situation. For example, the metal oxide can be alumina, the non-metal oxide can be silica, and the high molecular compound can be porous polyolefin, etc.

[0022] The second aspect of the present invention provides a preparation method of a metal lithium negative electrode modified with a double-layer ordered vertical mesoporous thin film, comprising the following steps:

[0023] S1. Obtain a large-pore single-layer ordered vertical mesoporous thin film and a small-pore single-layer ordered vertical mesoporous thin film respectively;

[0024] S2. Attach the small-pore single-layer ordered vertical mesoporous thin film to the surface of the lithium metal layer, and make the large-pore single-layer ordered vertical mesoporous thin film located on the side away from the lithium metal layer of the small-pore single-layer ordered vertical mesoporous thin film to obtain a metal lithium negative electrode modified with a double-layer ordered vertical mesoporous thin film.

[0025] The present invention first prepares two kinds of single-layer ordered vertical mesoporous thin films with different pore sizes, and assembles them into a double-layer ordered vertical mesoporous thin film according to a specific order to modify the negative electrode of the lithium metal battery, obtaining a metal lithium negative electrode modified with a double-layer ordered vertical mesoporous thin film. This method is simple and easy to implement.

[0026] In some specific embodiments of the present invention, the materials of the above-mentioned large-pore single-layer ordered vertical mesoporous thin film and small-pore single-layer ordered vertical mesoporous thin film are silica, and the large-pore single-layer ordered vertical mesoporous thin film and small-pore single-layer ordered vertical mesoporous thin film are obtained through the following steps:

[0027] Cetyltrimethylammonium bromide (CTAB), tetraethyl orthosilicate (TEOS), and ammonia water are dispersed into a mixed solution A made of deionized water and absolute ethanol, stirred evenly, then indium tin oxide (ITO) glass is added for reaction, and then washed and dried. Then, the template agent is removed by washing with an ethanol solution containing hydrochloric acid, and finally, the film is separated from the ITO glass by soaking in a nitric acid solution to obtain a single-layer ordered vertical mesoporous thin film.

[0028] Further, in the mixed solution A, the volume ratio of deionized water to absolute ethanol is 1:(1 - 3), further 3:7; the concentration of CTAB in the mixed solution A is 0.001 - 0.002 g / ml, further 0.0016 g / ml; the dosage ratio of CTAB, TEOS to ammonia water is (0.01 - 0.02) g:(0.005 - 0.01) ml:1 μl, further 0.08 g:0.04 ml:5 μl, the reaction temperature is 60 - 100 °C, and the reaction time is 12 - 72 h; in the ethanol solution containing hydrochloric acid, the concentration of hydrochloric acid is 0.05 - 0.2 M, further 0.1 M; the concentration of the nitric acid solution is 2 M - 10 M, further 8 M.

[0029] Further, before the reaction, the indium tin oxide glass is ultrasonically cleaned with acetone and absolute ethanol respectively.

[0030] In this process, by adjusting the process parameters, a variety of single-layer ordered vertical mesoporous films with different pore sizes can be obtained.

[0031] The third aspect of the present invention provides an application of a metal lithium negative electrode modified with a double-layer ordered vertical mesoporous film, and the metal lithium negative electrode modified with the double-layer ordered vertical mesoporous film is used for preparing a lithium metal battery.

[0032] In some specific embodiments of the present invention, the macroporous single-layer ordered vertical mesoporous film and the microporous single-layer ordered vertical mesoporous film are laminated and assembled into the lithium metal battery through the assembly process of the lithium metal battery. The specific steps include: attaching the microporous single-layer ordered vertical mesoporous film to the surface of the lithium negative electrode, then attaching the macroporous single-layer ordered vertical mesoporous film to the surface of the microporous single-layer ordered vertical mesoporous film, then dropping the electrolyte, then placing the separator on the surface of the macroporous single-layer ordered vertical mesoporous film and continuing to drop the electrolyte, and finally placing the positive electrode plate, and obtaining the lithium metal battery after pressing. Further, the pressure is 30 - 60 MPa, more preferably 50 MPa, and the pressure holding time is 1 - 5 s; during the process of dropping the electrolyte, the amount dropped each time is 10 - 20 μl.

[0033] In the following examples and comparative examples of the present invention, unless otherwise specified, the summary of some raw materials is as follows: the mass fraction of CTAB is 99%, the mass fraction of TEOS is 99%, and the mass fraction of ammonia water is 20% - 30%.

[0034] Example 1

[0035] A preparation method of a metal lithium negative electrode modified with a double-layer ordered vertical mesoporous film includes the following steps:

[0036] (1) Preparation of small-hole single-layer ordered vertical mesoporous thin film: ITO glass was ultrasonically cleaned with acetone and absolute ethanol for 20 min respectively; 15 ml of deionized water and 35 ml of absolute ethanol were added to a beaker, and then 0.08 g of CTAB, 0.04 ml of TEOS and 5 μl of ammonia water were added in sequence. The solution was stirred with a magnetic stirrer for ten minutes until it became clear. Then the ITO substrate was placed flat at the bottom of the beaker with the ITO-coated side facing up. Then the beaker was placed in a water bath at 60 °C for 72 h; after the water bath ended, the glass substrate was taken out, rinsed 3 times with deionized water, and finally rinsed once with absolute ethanol. Then the substrate was placed in an oven with the oven temperature set at 100 °C and the drying time of 8 h; after drying, the glass substrate was taken out, placed in an ethanol solution of 0.1 M HCl, stirred for ten minutes, rinsed with deionized water, and the above operations were repeated three times. Finally, it was placed in an oven with the temperature set at 100 °C and the drying time set at 8 h; the dried glass substrate was placed in an 8 M nitric acid solution and soaked at room temperature for 8 h. There was a layer of thin film floating on the upper layer of the solution. Then the thin film was fished out and washed three times with deionized water to obtain a small-hole single-layer ordered vertical mesoporous thin film;

[0037] (2) Preparation of large-hole single-layer ordered vertical mesoporous thin film: The difference from step (1) is only that the 60 °C water bath is changed to a 100 °C oil bath;

[0038] (3) The small-hole single-layer ordered vertical mesoporous thin film was attached to the surface of the lithium negative electrode, and then the large-hole single-layer ordered vertical mesoporous thin film was attached to the surface of the small-hole single-layer ordered vertical mesoporous thin film. Then 20 μl of electrolyte was added dropwise. Then a separator was placed on the surface of the large-hole single-layer ordered vertical mesoporous thin film, and 20 μl of electrolyte was added continuously. Finally, the positive electrode plate was placed and pressed at 50 MPa for 1 s under a packaging machine to obtain a lithium metal battery. Among them, the electrolyte is a mixed solution of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) (volume ratio of 1:1) containing 1 wt% LiNO3; the separator is Celgard 2300; the positive electrode plate is a copper foil with a diameter of 12 mm.

[0039] Comparative Example 1

[0040] Repeat step (1) of Example 1 twice to prepare two small-hole single-layer ordered vertical mesoporous thin films, and apply them to the negative electrode interface through the same assembly process as in step (3) of the example.

[0041] Comparative Example 2

[0042] Repeat step (2) of Example 1 twice to prepare two large-hole single-layer ordered vertical mesoporous thin films, and apply them to the negative electrode interface through the same assembly process as in step (3) of the example.

[0043] Comparative Example 3

[0044] The difference between Comparative Example 3 and Example 1 is only that in step (3), the laying order of the macroporous and microporous films is different: that is, during battery assembly, the macroporous single-layer ordered vertical mesoporous film is attached to the lithium metal surface, and the microporous single-layer ordered vertical mesoporous film is attached to the side of the macroporous single-layer ordered vertical mesoporous film surface away from the lithium metal, and the same assembly process as in step (3) of the example is applied to the negative electrode interface.

[0045] Test group

[0046] Through the lithium metal battery assembly technology, the modified lithium metal negative electrodes prepared in Example 1 and Comparative Examples 1-3 above were made into different button batteries, and then the performance of different batteries was tested in the Blue Electric CT2001A test system. The test results are shown in Figures 2 - 5 and Table 1. Among them, the test conditions are as follows: The Coulomb efficiency was tested using the Blue Electric CT2001A, and the test conditions were to discharge at a current of 0.5 mA·cm -2 for 2 h, and then charge at a constant current with the same current. The cut-off condition was that the charging voltage reached 1 V.

[0047] Table 1

[0048] Initial cycle Coulomb efficiency / % 35th cycle Coulomb efficiency / % Example 1 95.84 97.03 Comparative Example 1 95.80 86.02 Comparative Example 2 95.82 84.04 Comparative Example 3 92.77 72.09

[0049] The Coulomb efficiency refers to the ratio of the battery discharge capacity to the charging capacity in the same cycle. A high Coulomb efficiency means a lower capacity attenuation during battery cycling. The slower the capacity attenuation rate, the higher the battery capacity can be maintained for a longer time, which corresponds to a long cycle life. Please refer to Figures 2 - 5 and Table 1. The Coulomb efficiency of the lithium-copper battery in Example 1 of the present invention has significantly better stability. The initial Coulomb efficiency is 95.84%, and after 35 cycles, the Coulomb efficiency slightly increases to 97.03%; Figure 3 and 4 (Comparative Example 1, Comparative Example 2) also have relatively high initial Coulomb efficiencies (95.80% and 95.82%), but the downward trend of the Coulomb efficiency increases significantly after 20 cycles; Figure 5 (Comparative Example 3) drops sharply from 92.77% at the beginning to 72.09% after 35 cycles. It can be seen that the examples of the present invention not only have a high Coulomb efficiency, but also show stable performance in terms of cycle stability, indicating that the interface modification of the lithium metal negative electrode with the double-layer ordered vertical mesoporous film stacked in a specific order in the present invention has obvious effects, which is beneficial to improving the Coulomb efficiency and cycle stability of the battery.

[0050] The specific embodiments of the present invention described above do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A lithium metal anode modified with a double-layer ordered vertical mesoporous thin film, characterized in that, It includes a macroporous single-layer ordered vertical mesoporous thin film, a microporous single-layer ordered vertical mesoporous thin film, and a lithium metal layer that are sequentially stacked; wherein, the materials of the macroporous single-layer ordered vertical mesoporous thin film and the microporous single-layer ordered vertical mesoporous thin film are silicon dioxide.

2. The metal lithium anode modified by the double-layer ordered vertical mesoporous film according to claim 1, wherein The macroporous single-layer ordered vertical mesoporous thin film and the microporous single-layer ordered vertical mesoporous thin film are obtained through the following steps: Cetyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia water are dispersed into a mixed solution A made of deionized water and absolute ethanol. After stirring evenly, indium tin oxide glass is added for reaction. Subsequently, it is washed and dried, then the template agent is removed by washing with an ethanol solution containing hydrochloric acid, and finally, the thin film is separated from the ITO glass by soaking in a nitric acid solution to obtain a single-layer ordered vertical mesoporous thin film.

3. The metal lithium anode modified with the double-layer ordered vertical mesoporous film according to claim 2, characterized in that, The concentration of cetyltrimethylammonium bromide in the mixed solution A is 0.001 - 0.002 g / ml, and the dosage ratio of cetyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia water is (0.01 - 0.02) g : (0.005 - 0.01) ml : 1 μl.

4. The lithium metal anode modified with the bilayer ordered vertical mesoporous thin film according to claim 2, characterized in that, The reaction temperature is 60 - 100 °C, and the reaction time is 12 - 72 h.

5. The lithium metal anode modified with the bilayer ordered vertical mesoporous film according to claim 2, wherein, In the mixed solution A, the volume ratio of deionized water to absolute ethanol is 1 : (1 - 3). In the ethanol solution containing hydrochloric acid, the concentration of hydrochloric acid is 0.05 - 0.2 M, and the concentration of the nitric acid solution is 2 M - 10 M.

6. A method for preparing a lithium metal anode modified with a double-layer ordered vertical mesoporous thin film as described in any one of claims 1-5, characterized in that, It includes the following steps: Obtain a macroporous single-layer ordered vertical mesoporous thin film and a microporous single-layer ordered vertical mesoporous thin film respectively; Attach the microporous single-layer ordered vertical mesoporous thin film to the surface of the lithium metal layer, and make the macroporous single-layer ordered vertical mesoporous thin film located on the side of the microporous single-layer ordered vertical mesoporous thin film away from the lithium metal layer to obtain a lithium metal negative electrode modified with a bilayer ordered vertical mesoporous thin film.

7. Use of a lithium metal anode modified with a bilayer ordered vertical mesoporous thin film as described in any one of claims 1-5, characterized in that, The lithium metal negative electrode modified with the bilayer ordered vertical mesoporous thin film is applied to the preparation of a lithium metal battery.

8. Use of the lithium metal anode modified with the double-layer ordered vertical mesoporous thin film according to claim 7, characterized in that, The macroporous single-layer ordered vertical mesoporous thin film and the microporous single-layer ordered vertical mesoporous thin film are stacked and assembled into a lithium metal battery through the assembly process of the lithium metal battery.

9. Use of the metal lithium negative electrode modified by the double-layer ordered vertical mesoporous film according to claim 7, characterized in that, The steps of stacking and assembling the macroporous single-layer ordered vertical mesoporous thin film and the microporous single-layer ordered vertical mesoporous thin film into a lithium metal battery through the assembly process of the lithium metal battery include: Attach the microporous single-layer ordered vertical mesoporous thin film to the surface of the lithium negative electrode, then attach the macroporous single-layer ordered vertical mesoporous thin film to the surface of the microporous single-layer ordered vertical mesoporous thin film. Subsequently, drop the electrolyte, then place a separator on the surface of the macroporous single-layer ordered vertical mesoporous thin film, and continue to drop the electrolyte. Finally, place the positive electrode plate, and a lithium metal battery is obtained after pressing.

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