CN118315594A - A novel lithium metal negative electrode material and its preparation method and application - Google Patents

Abstract

The invention discloses a novel lithium metal anode material, a preparation method and application thereof, relates to the technical field of battery materials, and solves the technical problems that lithium dendrites are easy to form when lithium metal is used as an anode material, and the service life and safety of a battery are greatly influenced by volume change; the invention comprises silver nano particles, lithium sulfide, melamine and conductive carbon black, wherein the mass ratio of the silver nano particles to the lithium sulfide nano particles to the melamine to the conductive carbon black is (5-7): 1-2: 1; the novel lithium metal anode material provided by the invention can effectively inhibit the growth of lithium dendrites, relieve the stress generated in the charge and discharge process, improve the service life and safety of the battery, and simultaneously ensure the electrochemical dynamic performance of the lithium metal anode material.

Description

A novel lithium metal negative electrode material and its preparation method and application

Technical Field

The present invention relates to the technical field of battery materials, and in particular to a novel lithium metal negative electrode material and a preparation method and application thereof.

Background technique

Traditional lithium-ion batteries use graphite as the negative electrode material, but the theoretical specific capacity and energy density of graphite negative electrodes are low, which seriously limits its further application. Lithium metal has the advantages of extremely high theoretical specific capacity (3860mAh/g), the lowest redox potential (-3.04V relative to standard hydrogen electrode) and low density (0.534g/ ^cm3 ). Therefore, using lithium metal as the negative electrode material can greatly improve the energy density of lithium-ion batteries.

However, there are also some problems with lithium metal negative electrode materials during use. On the one hand, the electrochemical behavior of lithium ions during the charging and discharging process of lithium metal is uncontrolled, and lithium dendrites are easily formed, resulting in a decrease in cycle life. As the dendrites grow, they may even puncture the diaphragm, causing a short circuit and safety problems. On the other hand, the lithium metal negative electrode will produce a large volume change during the charging and discharging process, causing pressure to form inside the battery during the charging and discharging process, thereby affecting the battery life and safety.

Summary of the invention

The present invention aims to solve the technical problems that lithium metal as a negative electrode material is prone to form lithium dendrites and that the large volume change affects the battery life and safety. The present invention aims to provide a new type of lithium metal negative electrode material and its preparation method and application, which can effectively inhibit the growth of lithium dendrites, relieve the stress generated inside the charging and discharging process, improve the battery life and safety, and at the same time ensure the electrochemical kinetic performance of the lithium metal negative electrode material.

The present invention is achieved through the following technical solutions:

The first object of the present invention is to provide a novel lithium metal negative electrode material, comprising silver nanoparticles, lithium sulfide, melamine and conductive carbon black, wherein the mass ratio of the silver nanoparticles, lithium sulfide nanoparticles, melamine and conductive carbon black is (5~7):(1~2):(1~2):1.

The silver nanoparticles in the present invention have large surface energy and high lattice matching with lithium metal, and can induce lithium ions to electrochemically precipitate on the surface of the silver nanoparticles, thereby controlling the electrochemical behavior of lithium ions and inhibiting the growth of lithium dendrites; lithium sulfide has high lithium ion conductivity and can provide channels for the diffusion and migration of lithium ions; conductive carbon black is an electronic conductor and can provide channels for electronic transmission; melamine has high elasticity, which can better adapt to the volume change of lithium metal negative electrode materials during the charging and discharging process, relieve the stress generated inside the charging and discharging process, and improve the life and safety of the battery; on the other hand, the elasticity of melamine can ensure that lithium sulfide, conductive carbon black and silver nanoparticles always maintain stable contact during the charging and discharging process, thereby improving the electrochemical kinetic performance of the lithium metal negative electrode material.

As a further technical solution of the present invention, the mass ratio of the silver nanoparticles, lithium sulfide, melamine and conductive carbon black is 6:2:1:1.

As a further technical solution of the present invention, the lithium sulfide, melamine and conductive carbon black are nanoparticles.

The second object of the present invention is to provide a method for preparing a novel lithium metal negative electrode material, comprising the following steps:

(1) dissolving melamine in an organic solvent to obtain an organic solution containing melamine;

(2) mixing silver nanoparticles, lithium sulfide and conductive carbon black according to a mass ratio, and then stirring or grinding to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the organic solution containing melamine obtained in step (1), and then stirring or grinding the mixture to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the substrate and dried to form a thin film on the substrate, thereby obtaining a novel lithium metal negative electrode material.

As a further technical solution of the present invention, the dissolution conditions of melamine in step (1) are: dissolving melamine in a pyridine solution at a temperature of 70-90°C.

As a further technical solution of the present invention, the concentration of melamine in the pyridine solution is 1 mg/mL.

As a further technical solution of the present invention, the mass ratio of the silver nanoparticles, lithium sulfide, melamine and conductive carbon black is (5-7):(1-2):(1-2):1.

As a further technical solution of the present invention, in step (4), the drying process is: first drying at a temperature of 70-90°C for 20-28 hours, and then drying in a vacuum at a temperature of 70-90°C for 10-15 hours.

As a further technical solution of the present invention, the substrate is copper foil.

The third object of the present invention is to provide a new type of lithium metal negative electrode material for use in lithium metal solid-state batteries and lithium metal liquid batteries.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The silver nanoparticles in the present invention have large surface energy and high lattice matching with lithium metal, and can induce lithium ions to electrochemically precipitate on the surface of the silver nanoparticles, thereby controlling the electrochemical behavior of lithium ions and inhibiting the growth of lithium dendrites; lithium sulfide has high lithium ion conductivity and can provide channels for the diffusion and migration of lithium ions; conductive carbon black is an electronic conductor and can provide channels for electronic transmission; melamine has high elasticity, which can better adapt to the volume change of lithium metal negative electrode materials during the charging and discharging process, relieve the stress generated inside the charging and discharging process, and improve the life and safety of the battery; on the other hand, the elasticity of melamine can ensure that lithium sulfide, conductive carbon black and silver nanoparticles always maintain stable contact during the charging and discharging process, thereby improving the electrochemical kinetic performance of the lithium metal negative electrode material.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

FIG1 is a surface image of the negative electrode material composed of silver nanoparticles, lithium sulfide, melamine and conductive carbon black (referred to as Ag-Li ₂ SC-PM) in Example 1 after 10 cycles;

FIG2 is a surface image of a negative electrode material composed of lithium sulfide, conductive carbon black and melamine (referred to as Li ₂ SC-PM) without silver nanoparticles added after 10 cycles;

3 is a diagram of the coulombic efficiency of the negative electrode material (Ag-Li ₂ SC-PM) composed of silver nanoparticles, lithium sulfide, melamine and conductive carbon black in Example 1 at a current density of 5 mA/cm ² and an area capacity of 5 mAh/cm ² ;

FIG4 is a coulombic efficiency diagram of a negative electrode material (Li ₂ SC-PM) composed of lithium sulfide, melamine and conductive carbon black without adding silver nanoparticles at a current density of 5 mA/cm ² and an area capacity of 5 mAh/cm ² .

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

In the prior art, there are some problems with lithium metal negative electrode materials during use. The following problems exist: On the one hand, the electrochemical behavior of lithium ions in the process of charging and discharging lithium metal is uncontrolled, and lithium dendrites are easily formed, resulting in a decrease in cycle life. As the dendrites grow, they may even puncture the diaphragm, causing a short circuit and safety problems. On the other hand, the lithium metal negative electrode will produce a large volume change during the charging and discharging process, causing pressure to form inside the battery during the charging and discharging process, thereby affecting the life and safety of the battery. Based on the above defects of lithium metal negative electrode materials, the present invention now proposes a new type of lithium metal negative electrode material and its preparation method and application to solve these problems.

The following are specific embodiments of the present invention.

Example 1

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 100 mg of melamine nanoparticles in 100 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) mixing 600 mg of silver nanoparticles, 200 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles, and then stirring or grinding for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 80° C. for 24 hours to volatilize the pyridine solution, and then dried at 80° C. under vacuum for another 12 hours to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Example 2

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 200 mg of melamine nanoparticles in 200 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) mixing 600 mg of silver nanoparticles, 200 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles, and then stirring or grinding for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 80° C. for 24 hours to volatilize the pyridine solution, and then dried at 80° C. under vacuum for another 12 hours to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Example 3

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 100 mg of melamine nanoparticles in 100 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) mixing 700 mg of silver nanoparticles, 200 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles, and then stirring or grinding for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 80° C. for 24 hours to volatilize the pyridine solution, and then dried at 80° C. under vacuum for another 12 hours to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Example 4

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 100 mg of melamine nanoparticles in 100 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) mixing 700 mg of silver nanoparticles, 100 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles, and then stirring or grinding for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 90° C. for 20 h to volatilize the pyridine solution, and then dried at 90° C. for another 10 h under vacuum to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Example 5

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 100 mg of melamine nanoparticles in 100 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) 500 mg of silver nanoparticles, 100 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles are mixed, and then stirred or ground for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 70° C. for 28 hours to volatilize the pyridine solution, and then dried at 70° C. under vacuum for another 15 hours to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Example 6

This embodiment provides a method for preparing a novel lithium metal negative electrode material, comprising the following preparation steps:

(1) dissolving 200 mg of melamine nanoparticles in 200 mL of pyridine solution at 80° C. to obtain a pyridine solution with a melamine concentration of 1 mg/mL;

(2) 500 mg of silver nanoparticles, 200 mg of lithium sulfide nanoparticles and 100 mg of conductive carbon black nanoparticles are mixed, and then stirred or ground for a certain period of time to form a uniform mixture;

(3) adding the uniform mixture obtained in step (2) to the pyridine solution with a melamine concentration of 1 mg/mL obtained in step (1), and then stirring or grinding for 1 hour to obtain a uniform slurry;

(4) The slurry obtained in step (3) is evenly applied to the copper foil, and then dried at 70° C. for 28 hours to volatilize the pyridine solution, and then dried at 70° C. under vacuum for another 15 hours to obtain a uniform thin film on the copper foil;

(5) Cutting the film obtained in step (4) into an electrode shape to obtain a new type of lithium metal negative electrode material.

Comparative Example: The difference between this comparative example and Example 1 is that no silver nanoparticles are added in step (2), and the rest is the same as Example 1.

The following are the relevant performance test data of Example 1 and the comparative example.

FIG1 is a surface diagram of the negative electrode material composed of silver nanoparticles, lithium sulfide, melamine and conductive carbon black (Ag-Li ₂ SC-PM for short) in Example 1 after 10 cycles.

FIG. 2 is a surface image of a negative electrode material composed of lithium sulfide, conductive carbon black and melamine (referred to as Li ₂ SC-PM) without adding silver nanoparticles in a comparative example after 10 cycles.

From the comparison of Figures 1 and 2, it can be seen that after the same number of cycles, the surface dendrite phenomenon of the negative electrode material without silver nanoparticles is obvious, while the surface of the negative electrode material of the present invention has no obvious dendrite phenomenon. This is because the silver nanoparticles in the present invention have a large surface energy and a high lattice matching degree with lithium metal, which can induce lithium ions to electrochemically precipitate on the surface of the silver nanoparticles, thereby controlling the electrochemical behavior of lithium ions and inhibiting the growth of lithium dendrites.

3 is a graph of the coulombic efficiency of the negative electrode material (Ag-Li ₂ SC-PM) composed of silver nanoparticles, lithium sulfide, melamine and conductive carbon black in Example 1 at a current density of 5 mA/cm ² and an area capacity of 5 mAh/cm ² .

FIG4 is a coulombic efficiency diagram of a negative electrode material (Li ₂ SC-PM) composed of lithium sulfide, melamine and conductive carbon black without adding silver nanoparticles at a current density of 5 mA/cm ² and an area capacity of 5 mAh/cm ² .

From the comparison of Figure 3 and Figure 4, we can see that:

The comparative example does not add silver nanoparticles. In the first 5 cycles, the coulombic efficiency is low because of the consumption of lithium by the formation of the SEI film. The coulombic efficiency can be stabilized at about 97% later. After 140 cycles, the coulombic efficiency drops sharply. This is mainly because there are no nanosilver particles to induce lithium ion precipitation, thereby forming lithium dendrites, and generating "dead lithium" during the cycle, resulting in low coulombic efficiency. In the comparative example 1 of the present invention, silver nanoparticles are added. Except for the formation of the SEI film at the beginning, which leads to low coulombic efficiency, the coulombic efficiency is stabilized at about 98% later. It is not until 305 cycles that the coulombic efficiency drops. The coulombic efficiency is significantly better than that of the comparative example.

The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims (10)

1. A novel lithium metal negative electrode material, characterized in that it comprises silver nanoparticles, lithium sulfide, melamine and conductive carbon black, wherein the mass ratio of the silver nanoparticles, lithium sulfide nanoparticles, melamine and conductive carbon black is (5~7):(1~2):(1~2):1. 2. A novel lithium metal negative electrode material according to claim 1, characterized in that the mass ratio of the silver nanoparticles, lithium sulfide, melamine and conductive carbon black is 6:2:1:1. 3. The novel lithium metal negative electrode material according to claim 1, characterized in that the lithium sulfide, melamine and conductive carbon black are in the form of nanoparticles. 4. A method for preparing a novel lithium metal negative electrode material, characterized in that it comprises the following steps: (1) dissolving melamine in an organic solvent to obtain an organic solution containing melamine; (2) mixing silver nanoparticles, lithium sulfide and conductive carbon black according to a mass ratio, and then stirring or grinding to form a uniform mixture; (3) adding the uniform mixture obtained in step (2) to the organic solution containing melamine obtained in step (1), and then stirring or grinding the mixture to obtain a uniform slurry; (4) The slurry obtained in step (3) is evenly applied to the substrate and dried to form a thin film on the substrate, thereby obtaining a novel lithium metal negative electrode material. 5. The method for preparing a novel lithium metal negative electrode material according to claim 4, characterized in that the dissolution conditions of melamine in step (1) are: dissolving melamine in a pyridine solution at a temperature of 70-90°C. 6 . The method for preparing a novel lithium metal negative electrode material according to claim 5 , wherein the concentration of melamine in the pyridine solution is 1 mg/mL. 7. The method for preparing a novel lithium metal negative electrode material according to claim 4, characterized in that the mass ratio of the silver nanoparticles, lithium sulfide, melamine and conductive carbon black is (5-7): (1-2): (1-2): 1. 8. The method for preparing a novel lithium metal negative electrode material according to claim 4, characterized in that in step (4), the drying process is: first drying at a temperature of 70-90° C. for 20-28 hours, and then drying in a vacuum at a temperature of 70-90° C. for 10-15 hours. 9 . The method for preparing a novel lithium metal negative electrode material according to claim 4 , wherein the substrate is copper foil. 10. Use of the novel lithium metal negative electrode material according to any one of claims 1 to 3 or the novel lithium metal negative electrode material prepared by the preparation method according to any one of claims 4 to 9 in lithium metal solid-state batteries and lithium metal liquid batteries.