CN112909229A

CN112909229A - Silver coating method of three-dimensional lithium-philic metal foam framework and preparation method of application of silver coating method in lithium metal negative electrode

Info

Publication number: CN112909229A
Application number: CN202110066476.5A
Authority: CN
Inventors: 孙福根; 吴鹿鹿; 江伟伟; 丁国彧; 李亚辉; 张婧; 叶承舟; 徐国军; 李晓敏; 岳之浩; 周浪
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2021-01-19
Filing date: 2021-01-19
Publication date: 2021-06-04

Abstract

The invention relates to the technical field of lithium metal battery electrode materials, in particular to a silver coating method for a three-dimensional lithophilic metal foam skeleton and a preparation method for its application in a lithium metal negative electrode. After ultrasonic degreasing and washing, the commercial metal foam is immersed in a certain solubility of silver nitrate solution for replacement reaction. After washing and drying, a silver-coated metal foam skeleton (Ag@M foam) is obtained. Then, the molten liquid lithium The metal was infused into the metal foam framework to obtain a novel silver-coated metal foam/lithium metal composite (Ag@M foam/Li). The prepared silver-coated three-dimensional lithiophilic metal foam framework and its lithium metal composite material are used in lithium metal secondary batteries, which can effectively improve the coulombic efficiency and cycle stability performance of the lithium metal battery.

Description

Silver coating method of three-dimensional lithium-philic metal foam framework and preparation method of application of silver coating method in lithium metal negative electrode

Technical Field

The invention relates to the technical field of lithium metal battery electrode materials, in particular to a silver coating method of a three-dimensional lithium-philic metal foam framework and a preparation method of the silver coating method in application of a lithium metal negative electrode.

Background

In recent years, the development of various portable electronic products, wearable devices, electric vehicles, and the like has accelerated the research and development of high energy density battery materials and devices. Lithium metal negative electrode, due to its extremely high theoretical specific capacity (3860mAh g)^-1) And the lowest operating potential (-3.04V vs H)⁺/H₂) And is referred to as a "holy cup" negative electrode of a lithium secondary battery. However, the current application of lithium metal anodes presents several significant drawbacks: (1) the electrodeposition process of the lithium metal of the negative electrode is inclined to generate dendritic lithium thermodynamically, and meanwhile, the uneven distribution of the surface electric field of the dendritic lithium promotes the uneven deposition of lithium ions and the disordered growth of lithium dendrites; (2) the growth of a large amount of lithium dendrites is easy to pierce a diaphragm, so that the internal short circuit and safety problems of the battery are caused; (3) the uneven dissolution of the lithium dendrites generates a large amount of dead lithium separated from the negative electrode, so that the metal lithium negative electrode is pulverized; (4) the above huge volume change of the lithium negative electrode causes that an SEI film can not stably cover the surface of the lithium negative electrode, the SEI film is continuously formed, the electrolyte is continuously consumed, and the coulombic efficiency and cycle of the battery are improvedThe ring life is reduced.

In order to further solve a series of problems of the current lithium metal negative electrode, many researches are continuously conducted on strategies such as electrolyte modification, artificial SEI film construction, surface modification of metal lithium and the like, but the methods are difficult to effectively utilize due to the problems of unclear principle, complex operation, single strategy and the like. In the current research field, constructing a three-dimensional porous current collector structure (copper foam, nickel foam, iron foam, carbon nanotube, carbon cloth, graphene, etc.) is considered to be one of the most effective methods for suppressing lithium dendrite, and because of the lithium-phobicity of the interface surface layer of many three-dimensional structural materials, loading a lithium-philic material on a three-dimensional porous current collector has been widely used for lithium metal negative electrodes in recent years. The three-dimensional metal foam is regarded as the best modified current collector due to the advantages of low cost, high specific surface area, easy modification of an interface and the like; in addition, nano silver is also commonly used as a lithium-philic modified material due to its high lithium-philic property and electrical conductivity, which can induce uniform deposition of lithium ions, thereby effectively inhibiting lithium dendrites.

Therefore, the Ag @ M foam with low cost, high specific surface and lithium affinity is prepared by a simple and easily-scaled method, and the Ag @ M foam is the most potential possibility for being used as a high-efficiency and stable lithium metal negative electrode carrier for commercial lithium metal negative electrodes.

Disclosure of Invention

The invention aims to solve the technical problem that a technical means which is simple in process, low in cost and easy for industrial production is provided, a silver nano layer with good lithium affinity is coated on the surface of commercial lithium-phobic metal foam, and the lithium cathode composite material for inducing lithium metal to be uniformly deposited is prepared and used for a lithium metal battery, so that the performances of the lithium metal battery, such as coulombic efficiency, cycling stability and the like, can be effectively improved.

In order to achieve the purpose, the invention provides a preparation method of a silver-coated copper foam/lithium metal composite negative electrode with a three-dimensional lithium-philic metal foam framework, wherein the preparation method of the metal composite negative electrode comprises the following steps:

(1) cutting commercial three-dimensional metal foam according to the size of an electrode slice, putting the cut commercial three-dimensional metal foam into 20-50mL of acetone or dilute sulfuric acid solution, ultrasonically degreasing for 10-20 min, cleaning with deionized water and absolute ethyl alcohol, and drying;

(2) immersing the metal foam electrode slice obtained after drying in the step (1) into AgNO₃Taking out the solution after a displacement reaction is carried out for 5-30 min, and cleaning the solution by using deionized water and absolute ethyl alcohol;

(3) placing the electrode slice modified and cleaned in the step (2) in a blast drying oven for drying, and then transferring the electrode slice to a vacuum drying oven for drying to obtain a silver-coated metal foam electrode;

(4) compressing the silver-coated metal foam electrode plate obtained in the step (3) to 100-500 microns, then placing the electrode plate into a glove box with the water oxygen value less than 0.5ppm, heating the metal lithium plate to 300-350 ℃ to a molten state, then immersing the silver-coated metal foam electrode plate into liquid lithium metal for pouring, and cooling to prepare the silver-coated metal foam/lithium metal composite negative electrode;

(5) manufacturing the clean raw material metal foam electrode in the step (1) and the silver-coated metal foam electrode in the step (3) into a button half cell by respectively taking a metal lithium sheet as a counter electrode, and measuring the coulomb efficiency of the button half cell;

(6) and (4) respectively manufacturing the silver-coated metal foam/lithium metal composite negative electrode prepared in the step (4) and a commercial metal lithium sheet into a lithium-lithium symmetrical battery, and measuring the cycling stability of the battery.

Preferably, AgNO in the step (2)₃The concentration of (b) is 0.001-0.1 mol/L.

Preferably, in the step (3), the drying condition in the forced air drying oven is 60-80 ℃ for 1-2 h, and the drying condition in the vacuum drying oven is 50-60 ℃ for 6-12 h.

Preferably, the silver-coated copper foam/lithium metal composite negative electrode is applied to the preparation of a lithium metal negative electrode.

Compared with the prior art, the invention has the beneficial effects that:

(1) coating a layer of uniform and rich nano-silver pine leaves on the surface of the lithium-phobic metal foam by a simple and easily-scaled chemical displacement reaction principle, so that the modified silver-coated metal foam has good lithium-philic performance;

(2) the nano silver layer can provide abundant nucleation sites for lithium ions and induce the uniform deposition of lithium metal, thereby playing a role in inhibiting lithium dendrites;

(3) the metal foam lithium negative electrode current collector coated with the silver layer has the advantages of high specific surface area and good lithium affinity, is beneficial to reducing local current density, effectively reduces nucleation overpotential of lithium ions, and guides uniform deposition of lithium, thereby inhibiting growth of dendritic crystals and improving the cycle stability of the lithium metal negative electrode.

Drawings

FIG. 1 is an SEM image of a commercial copper foam (Cu foam) used in the present invention;

FIG. 2 is an SEM image of a silver coated copper foam electrode (Ag @ Cu foam) prepared according to the present invention;

FIG. 3 shows the current collector (Ag @ Cu foam) of the silver-coated copper foam lithium metal negative electrode at 3mA/cm²Coulombic efficiency at current density;

FIG. 4 shows the prepared silver-coated copper foam/lithium metal composite negative electrode (Ag @ M foam/Li) at 1mA/cm²Voltage-time profile at current density;

FIG. 5 shows the resulting silver coated copper foam/lithium metal composite negative electrode (Ag @ M foam/Li) at 3mA/cm²Voltage-time profile at current density.

Detailed Description

The present invention will be further described with reference to examples.

Example 1

Cutting a commercial three-dimensional copper foam material with the thickness of 2.0mm into electrode plates (Cu foam) with the diameters of 14mm and 16mm, then putting the electrode plates into 30mL of acetone solution for ultrasonic degreasing for 10min, then washing the electrode plates for three times by using deionized water and absolute ethyl alcohol, and drying the electrode plates;

(2) immersing the copper foam electrode slice obtained after the previous step is dried into 0.02mol/L AgNO₃Taking out the solution after (replacement) reaction for 10min, and washing the solution by using deionized water and absolute ethyl alcohol;

(3) placing the electrode slice subjected to modification cleaning in the last step in a 60 ℃ blast drying oven for drying for 1h, and then transferring the electrode slice to a 60 ℃ vacuum drying oven for drying for 12h to obtain a silver-coated copper foam electrode (Ag @ Cu foam);

(4) compressing the obtained Ag @ Cu foam electrode plate to 300 mu m, then placing the electrode plate into a glove box with the water oxygen value less than 0.5ppm, heating the metal lithium plate to 300 ℃ to a molten state, then immersing the Ag @ Cu foam electrode plate into hot molten lithium, and cooling to obtain the silver-coated copper foam/lithium metal composite negative electrode (Ag @ Cu foam/Li).

(5) And (3) respectively taking a metal lithium sheet as a counter electrode to manufacture the clean raw material copper foam electrode (Cu foam) in the step (1) and the silver-coated copper foam electrode (Ag @ Cu foam) in the step (3) into a button half cell to measure the coulomb efficiency of the button half cell. At a current density of 3mA/cm²And the circulation capacity is 1mAh/cm²Under the condition, the Li | Ag @ Cu foam half-cell is assembled to test, and after 250 cycles, the ultra-high coulombic efficiency of 97.6 percent is still maintained.

(6) And (3) respectively manufacturing the silver-coated copper foam/lithium metal composite negative electrode (Ag @ Cu foam/Li) prepared in the step (4) and a commercial metal lithium sheet (bare Li) into a lithium-lithium symmetrical battery, and measuring the cycle stability of the battery. At a current density of 1mA/cm²、3mA/cm²And a circulation capacity of 1mAh/cm²Under the test conditions of (1), the Ag @ Cu foam/Li symmetrical battery still maintains extremely high cycling stability after 1000 hours and 600 hours of cycling respectively.

FIG. 1 is an SEM image of a commercial copper foam (Cu foam) used in the present invention, a is an overall topography of the commercial copper foam (Cu foam), b is a topography of a skeleton surface of the copper foam; FIG. 2 is an SEM image of a silver-coated copper foam electrode (Ag @ Cu foam) prepared by the invention, wherein a is an overall appearance image of the silver-coated copper foam electrode (Ag @ Cu foam), and b is an appearance image of a copper foam framework surface coated with a nano silver layer; FIG. 3 shows Li | Ag @ Cu foam and Li | Cu foam batteries assembled by the prepared silver-coated copper foam lithium metal negative electrode current collector (Ag @ Cu foam) and the original copper foam (Cu foam) at a current density of 3mA/cm²And the circulation capacity is 1mAh/cm²The results of coulombic efficiency test under the conditions are compared with a graph, and the Li | Ag @ Cu foam still maintains 97.6 percent of ultrahigh coulombic efficiency after 250 cycles; FIG. 4 shows the resulting silver coated copper foam/lithium metal composite negative electrode (Ag @ M foam/Li) with commercial goldBelongs to a lithium sheet (bare Li), and the manufactured lithium-lithium symmetrical battery has the current density of 1mA/cm²And the circulation capacity is 1mAh/cm²The voltage-time distribution diagram under the condition is that the Ag @ Cu foam/Li symmetrical battery keeps higher cycle stability after 1000 hours of charge-discharge cycle; FIG. 5 shows a lithium-lithium symmetric battery fabricated from the silver-coated copper foam/lithium metal composite negative electrode (Ag @ M foam/Li) and a commercial lithium metal sheet (bare Li) at a current density of 3mA/cm²And the circulation capacity is 1mAh/cm²The voltage-time distribution diagram under the condition is that the Ag @ Cufoam/Li symmetrical battery still maintains higher cycle stability after 600 hours of charge-discharge cycles.

Example 2

The difference from example 1 is: (2) immersing the copper foam electrode slice obtained after the previous step is dried into 0.005mol/L AgNO₃Taking out the solution after (replacement) reaction for 10min, and washing the solution by using deionized water and absolute ethyl alcohol; the rest is the same as in example 1.

The prepared silver-coated copper foam electrode (Ag @ Cu foam) has a non-uniform nano silver layer coated on the surface, and the reaction effect of 0.02mol/L of adaptive solution cannot be achieved, which shows that AgNO₃The concentration of (b) has a great influence on the effect of silver coating.

Example 3

The difference from example 1 is: (2) immersing the copper foam electrode slice obtained after the previous step is dried into 0.02mol/L AgNO₃Taking out the solution after (replacement) reaction for 5min, and washing the solution by using deionized water and absolute ethyl alcohol; the rest is the same as in example 1.

The prepared silver-coated copper foam electrode (Ag @ Cu foam) has the advantages that the silver nano layer coated on the surface is not uniform enough, the effect of 0.02mol/L adaptive solubility reaction for 10min is not achieved, and the reaction time has great influence on the silver coating effect

Example 4

The difference from example 1 is: the base material (three-dimensional copper foam metal Cufoam) used in the experiment was changed to a three-dimensional nickel foam (Ni foam) metal material, and the rest was the same as in example 1.

The silver coating effect in the experiment is far from the effect when the three-dimensional copper foam metal material is used, which shows that the matrix material used in the reaction has great influence on the silver coating effect.

Example 5

The difference from example 1 is: (1) a commercial three-dimensional copper foam material of 1.2mm thickness was cut into electrode pieces (Cu foam) of 14mm and 16mm in diameter, then placed in 30mL of an acetone solution for ultrasonic degreasing for 10min, washed three times with deionized water and absolute ethanol and dried, and the rest was the same as in example 1.

The prepared silver-coated copper foam electrode (Ag @ Cu foam) and the silver-coated copper foam/lithium metal composite negative electrode (Ag @ Cu foam/Li) cannot achieve the electrochemical performance effect obtained by using a commercial three-dimensional copper foam material with the thickness of 2mm, and the thickness of a base material has certain influence on the electrochemical application of the base material.

Claims

1. the preparation of the silver-coated copper foam/lithium metal composite negative electrode of a three-dimensional lithophilic metal foam skeleton, is characterized in that: the preparation of described metal composite negative electrode comprises the following steps:

(1) Cut the commercial three-dimensional metal foam according to the size of the electrode sheet, put it into 20-50 mL of acetone or dilute sulfuric acid solution, degrease it by ultrasonic for 10-20 min, and then wash it with deionized water and absolute ethanol and dry it to obtain the metal foam electrode;

(2) Immerse the metal foam electrode of step (1) in the AgNO ₃ solution, take it out after 5-30 min of replacement reaction, and wash with deionized water and absolute ethanol;

(3) placing the modified and cleaned electrode sheet in step (2) first in a blast drying oven to dry, and then transferring it to a vacuum drying oven for drying to obtain a silver-coated metal foam electrode;

(4) Compress the silver-coated metal foam electrode sheet obtained in step (3) to 100 μm～500 μm, then put it into a glove box with water oxygen value less than 0.5ppm, and heat the metal lithium sheet to 300℃～350℃ to a molten state, then immerse the silver-coated metal foam electrode sheet into liquid lithium metal for perfusion, and after cooling, prepare a silver-coated metal foam/lithium metal composite negative electrode;

(5) The metal foam electrode of step (1) and the metal foam electrode covered with silver in step (3) are respectively made into a button-type half-cell with a metal lithium sheet as the counter electrode, and the coulombic efficiency thereof is measured;

(6) The silver-coated metal foam/lithium metal composite negative electrode and commercial metal lithium sheet prepared in step (4) were respectively made into lithium-lithium symmetrical batteries, and their cycle stability performance was measured.

2 . The preparation of the metal composite negative electrode according to claim 1 , wherein the concentration of AgNO ₃ in the step (2) is 0.001-0.1 mol/L. 3 .

3. The preparation of the metal composite negative electrode according to claim 1, characterized in that: in the step (3), the drying conditions in the blast drying oven are drying at 60°C to 80°C for 1 to 2 hours, and in the vacuum drying oven The drying conditions are 50 ℃ ~ 60 ℃ drying 6 ~ 12h.

4. The silver-coated copper foam/lithium metal composite negative electrode according to claim 1, wherein the silver-coated copper foam/lithium metal composite negative electrode is used in the preparation of lithium metal negative electrode.