Three-dimensional metal lithium negative electrode as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium batteries, and particularly discloses a three-dimensional metal lithium negative electrode as well as a preparation method and application thereof. During preparation of the negative electrode, Kevlar fibers are taken as a raw material, and a mixed solution of dimethyl sulfoxide and potassium hydroxide is used for dispersing the Kevlar fibers to prepare a Kevlar fiber dispersion solution; carrying out suction filtration treatment on the Kevlar fiber dispersion liquid to obtain a Kevlar fiber thin film, pouring the conductive material solution onto a filter membrane by using the thin film as the filter membrane, filtering, and then cleaning the filter membrane to obtain a Kevlar fiber / conductive composite membrane; or uniformly mixing the Kevlar fiber dispersion liquid with the conductive material solution, and carrying out suction filtration treatment to obtain the Kevlar fiber / conductive composite membrane; and finally, electrically depositing metal lithium on the Kevlar fiber / conductive composite film to obtain the three-dimensional metal lithium negative electrode. Rich amide functional groups of the Kevlar fiber film of the negative electrode can effectively inhibit generation of lithium dendrites in the lithium ion intercalation / deintercalation process, the safety of the battery is improved, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a three-dimensional metal lithium negative electrode, a preparation method and application thereof. Background Art

[0002] The metallic lithium anode has a high theoretical specific capacity (3860 mAh / g) and the lowest redox potential (-3.04 V) among all anode materials for lithium-ion batteries. vs Standard hydrogen electrode), is widely regarded as the most promising negative electrode material for lithium batteries. However, the uncontrollable dendrite growth and unstable solid electrolyte interface (SEI) of metal lithium negative electrode during the charge and discharge process will lead to a series of problems such as rapid capacity decay, reduced coulombic efficiency and battery short circuit. As a host-free negative electrode material, the infinite volume expansion of lithium negative electrode during the cycle leads to the continuous rupture and repair of SEI film, which in turn leads to the growth of lithium dendrites and the formation of dead lithium. Structured metal lithium negative electrode can effectively regulate lithium ion diffusion and lithium deposition behavior, inhibit lithium dendrite growth, and effectively improve the performance of lithium metal batteries.

[0003] It has been found that using a three-dimensional skeleton to load lithium metal can inhibit the growth of lithium dendrites and effectively improve the stability of the lithium metal negative electrode. The present invention constructs a three-dimensional Kevlar fiber film and composites it with a conductive polymer to form a three-dimensional current collector that can be used for a lithium metal negative electrode. Summary of the invention

[0004] The present invention provides a three-dimensional metallic lithium negative electrode, a preparation method and application thereof. The three-dimensional metallic lithium negative electrode can not only improve the contact with the solid electrolyte and regulate the deposition of lithium metal, but also effectively inhibit the growth of lithium dendrites and improve the safety and life of the battery.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a three-dimensional metal lithium negative electrode comprises the following steps: S1, using Kevlar fiber as a raw material, dispersing it with a mixed solution of dimethyl sulfoxide and potassium hydroxide to prepare a Kevlar fiber dispersion; S2, the Kevlar fiber dispersion is filtered to obtain a Kevlar fiber film, the film is used as a filter membrane, the conductive material solution is poured onto the filter membrane for filtration, and the filter membrane is then cleaned to obtain a Kevlar fiber / conductive composite membrane; or the Kevlar fiber dispersion and the conductive material solution are evenly mixed, and filtered to obtain a Kevlar fiber / conductive composite membrane; S3. Electrodepositing metallic lithium onto the Kevlar fiber / conductive composite film to obtain a three-dimensional metallic lithium negative electrode.

[0006] Furthermore, before the Kevlar fibers are dispersed, they are cut to a length of 2-3 cm, cleaned to remove surface impurities, and dried for later use. During the cleaning process, water and anhydrous ethanol are used for ultrasonic washing to fully remove surface impurities and oil stains.

[0007] Furthermore, the conductive material is a Schiff base conductive polymer.

[0008] Furthermore, the mass ratio of Kevlar fiber to conductive material is 1:0.5-5.

[0009] Furthermore, the Schiff base conductive polymer is prepared and used immediately, and is specifically prepared by polymerization of an amine compound and an active carbonyl compound; wherein the amine compound is one or more of o-tolidine, 3, 3'-diaminobenzidine, 3, 4-diaminotoluene, and o-phenylenediamine; and the active carbonyl compound is terephthalaldehyde and / or trimesic acid. The polymerization time is 4 to 8 hours, preferably 5 hours.

[0010] Furthermore, the conductive material dispersion is prepared by mixing the conductive material with a hydrochloric acid solution.

[0011] Furthermore, in S3, Kevlar fiber / conductive composite film is used as a working electrode, and a metal lithium sheet is used as a working electrode and a counter electrode to carry out metal lithium electrodeposition to obtain a three-dimensional metal lithium negative electrode.

[0012] The invention also relates to a three-dimensional metallic lithium negative electrode obtained by adopting the preparation method.

[0013] The invention also relates to the application of the three-dimensional metal lithium negative electrode in a lithium ion battery.

[0014] The present invention has the following beneficial effects: The present invention adopts Kevlar fiber to prepare the negative electrode matrix. Compared with metal matrix or carbon fiber matrix, its production technology is mature and low-cost, and large-scale production can be achieved.

[0015] When Kevlar fiber is used as a negative electrode substrate, it needs to be first subjected to conductive modification treatment to prepare a Kevlar fiber / conductive composite film, so that lithium can be deposited on the Kevlar fiber / conductive composite support layer by electrodeposition in the later stage. The three-dimensional support skeleton of Kevlar fiber increases the contact area with metallic lithium and also increases the loading amount of metallic lithium in the skeleton. The Kevlar fiber film has abundant amide functional groups that can effectively inhibit the nucleation and growth of lithium dendrites during the insertion / extraction of lithium ions. The composite of conductive materials gives the three-dimensional Kevlar fiber conductive properties. More importantly, it can buffer the volume expansion of lithium, improve the contact between lithium and solid electrolyte, regulate the deposition of lithium metal, effectively inhibit the growth of lithium dendrites, and improve battery safety and life.

[0016] The metallic lithium in the present invention is electro-deposited onto the Kevlar fiber / conductive composite film. Compared with the two-layer structure of the SEI film formed by directly coating the surface of the lithium substrate with a Kevlar fiber dispersion, the metallic lithium can adhere to the three-dimensional Kevlar fiber network structure to coat the Kevlar fiber, and is more evenly dispersed and can participate in the reaction more fully. The present invention can reduce the amount of metallic lithium used, which helps to reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The material pole piece of the Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode prepared in Example 2 is a Li-Cu half-cell at a current density of 1 mA / cm 2 Lithium metal deposition 1 mAh / cm 2 Coulomb efficiency diagram under different conditions.

[0018] Figure 2 This is a charge and discharge curve diagram of the material electrode of the Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode prepared in Example 2 with different number of turns. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] Example 1 (1) Add 2 g potassium hydroxide to 500 mL dimethyl sulfoxide and stir until completely dissolved; (2) 0.5 g of Kevlar fiber was cut into small pieces of 2-3 cm, and ultrasonicated in water and anhydrous ethanol for 10 min respectively, and then vacuum dried at 60 °C for 12 h; (3) placing 0.5 g of the Kevlar fiber segment obtained in step (2) into (1) and stirring for 7 days to obtain a Kevlar fiber dispersion; (4) The Kevlar fiber dispersion is subjected to vacuum filtration to obtain a Kevlar fiber film; (5) Dissolve 0.21 g of o-tolidine completely in 20 mL of anhydrous ethanol; (6) Dissolve 0.16 g of trimesaldehyde completely in 20 mL of anhydrous ethanol; (7) Slowly add (6) into (5) and continue stirring for 5 hours; (8) Using a Kevlar fiber film as a filter membrane for vacuum filtration, directly subjecting the reacted (7) to vacuum filtration, and finally pouring 20 mL of anhydrous ethanol for washing, thereby obtaining a Kevlar fiber / Schiff base conductive polymer film; (9) Using Kevlar fiber / Schiff base conductive polymer film as the working electrode and metal lithium sheet as the working electrode and counter electrode, metal lithium is deposited onto the Kevlar fiber / Schiff base conductive polymer film to obtain a Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode.

[0021] Example 2 (1) Add 2 g potassium hydroxide to 500 mL dimethyl sulfoxide and stir until completely dissolved; (2) 0.5 g of Kevlar fiber was cut into small pieces of 2-3 cm, and ultrasonicated in water and anhydrous ethanol for 10 min respectively, and then vacuum dried at 60 °C for 12 h; (3) placing 0.5 g of the Kevlar fiber segment obtained in step (2) into (1) and stirring for 7 days to obtain a Kevlar fiber dispersion having a concentration of 1 mg / mL; (4) Dissolve 0.21 g of o-tolidine completely in 20 mL of anhydrous ethanol; (5) Dissolve 0.16 g of trimesaldehyde completely in 20 mL of anhydrous ethanol; (6) Slowly add (5) to (4) and continue stirring for 5 hours. After the reaction is completed, wash it three times with anhydrous ethanol and then centrifuge it to obtain a Schiff base conductive polymer. (7) dispersing 0.05 g of the Schiff base conductive polymer obtained in (6) in 10 mL of deionized water; (8) Add the Schiff base conductive polymer dispersion obtained in (7) to 50 mL of 1 mg / mL Kevlar fiber dispersion and stir for 1 hour; (9) The stirred (8) is vacuum filtered, and finally poured into 50 mL of deionized water for washing, thereby obtaining a Kevlar fiber / Schiff base conductive polymer film; (10) Using Kevlar fiber / Schiff base conductive polymer film as the working electrode and metal lithium sheet as the working electrode and counter electrode, metal lithium is deposited on the Kevlar fiber / Schiff base conductive polymer film to obtain a Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode.

[0022] Example 3 (1) Add 2 g potassium hydroxide to 500 mL dimethyl sulfoxide and stir until completely dissolved; (2) 0.5 g of Kevlar fiber was cut into small pieces of 2-3 cm, and ultrasonicated in water and anhydrous ethanol for 10 min respectively, and then vacuum dried at 60 °C for 12 h; (3) placing 0.5 g of the Kevlar fiber segment obtained in step (2) into (1) and stirring for 7 days to obtain a Kevlar fiber dispersion; (4) The Kevlar fiber dispersion is subjected to vacuum filtration to obtain a Kevlar fiber film; (5) Dissolve 0.21 g of o-tolidine completely in 20 mL of anhydrous ethanol; (6) Dissolve 0.13 g of terephthalaldehyde completely in 20 mL of anhydrous ethanol; (7) Slowly add (6) into (5) and continue stirring for 5 hours; (8) Using a Kevlar fiber film as a filter membrane for vacuum filtration, directly subjecting the reacted (6) to vacuum filtration, and finally pouring 20 mL of anhydrous ethanol for washing, thereby obtaining a Kevlar fiber / Schiff base conductive polymer film; (9) Using Kevlar fiber / Schiff base conductive polymer film as the working electrode and metal lithium sheet as the working electrode and counter electrode, metal lithium is deposited onto the Kevlar fiber / Schiff base conductive polymer film to obtain a Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode.

[0023] Example 4 (1) Add 2 g potassium hydroxide to 500 mL dimethyl sulfoxide and stir until completely dissolved; (2) 0.5 g of Kevlar fiber was cut into small pieces of 2-3 cm, and ultrasonicated in water and anhydrous ethanol for 10 min respectively, and then vacuum dried at 60 °C for 12 h; (3) 0.5 g of the Kevlar fiber segment obtained in step (2) was placed in (1) and stirred for 7 days to obtain a Kevlar fiber dispersion having a concentration of 1 mg / mL; (4) Dissolve 0.21 g of o-tolidine completely in 20 mL of anhydrous ethanol; (5) Dissolve 0.13 g of terephthalaldehyde completely in 20 mL of anhydrous ethanol; (6) Slowly add (5) to (4) and continue stirring for 5 hours. After the reaction is completed, wash it three times with anhydrous ethanol and then centrifuge it to obtain a Schiff base conductive polymer. (7) dispersing 0.05 g of the Schiff base conductive polymer obtained in (6) in 10 mL of deionized water; (8) Add the Schiff base conductive polymer dispersion obtained in (7) to 50 mL of 1 mg / mL Kevlar fiber dispersion and stir for 1 hour; (9) The stirred (8) is vacuum filtered, and finally poured into 50 mL of deionized water for washing, thereby obtaining a Kevlar fiber / Schiff base conductive polymer film; (10) Using Kevlar fiber / Schiff base conductive polymer film as the working electrode and metal lithium sheet as the working electrode and counter electrode, metal lithium is deposited on the Kevlar fiber / Schiff base conductive polymer film to obtain a Li-Kevlar fiber / Schiff base conductive polymer film composite lithium negative electrode.

[0024] The composite lithium negative electrode prepared in the above examples and comparative examples was combined with a battery-grade copper sheet to form a Li-Cu half-cell with a current density of 1 mA / cm 2 , the capacity parameter is 1mAh / cm 2 , the test results are shown in Table 1.

[0025] Example 5 Steps (1) to (3) are the same as in Example 2; (4) Add 2 mL of aniline to 50 mL of 1 mol / L hydrochloric acid solution and control the solution temperature at 5 °C; (5) Add 1.5 g of ammonium persulfate into 20 mL of deionized water; (6) Slowly adding (5) into (4), stirring continuously for 24 hours, controlling the temperature at 5°C, and filtering after the reaction to obtain polyaniline; (7) Dispersing 0.05 g of the polyaniline obtained in (6) in 10 mL of 1 mol / L hydrochloric acid solution; (8) Add the polyaniline dispersion obtained in (7) to 50 mL of 1 mg / mL Kevlar fiber dispersion and stir for 1 hour; (9) The stirred (8) is vacuum filtered, and finally poured into 50 mL of deionized water for washing to obtain a Kevlar fiber / polyaniline film; (10) Using Kevlar fiber / polyaniline film as the working electrode and metal lithium sheet as the working electrode and counter electrode, metal lithium is deposited on the Kevlar fiber / polyaniline film to obtain a Li-Kevlar fiber / polyaniline film composite lithium negative electrode.

[0026] Table 1 Test results of Li-Cu half-cells prepared in Example

[0027] Using Schiff base polymer as conductive material can significantly improve the battery life.

[0028] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a three-dimensional metallic lithium negative electrode, characterized in that: The following steps are involved: S1, using Kevlar fiber as a raw material, dispersing it with a mixed solution of dimethyl sulfoxide and potassium hydroxide to prepare a Kevlar fiber dispersion; S2, the Kevlar fiber dispersion is filtered to obtain a Kevlar fiber film, the film is used as a filter membrane, the conductive material solution is poured onto the filter membrane for filtration, and the filter membrane is then cleaned to obtain a Kevlar fiber / conductive composite membrane; or the Kevlar fiber dispersion and the conductive material solution are mixed evenly, and filtered to obtain a Kevlar fiber / conductive composite membrane; S3. Electrodepositing metallic lithium onto the Kevlar fiber / conductive composite film to obtain a three-dimensional metallic lithium negative electrode.

2. The preparation method according to claim 1, characterized in that: Before dispersing Kevlar fibers, cut them into 2-3 cm lengths, clean them to remove surface impurities, and dry them for later use.

3. The preparation method according to claim 2, characterized in that: The sheared Kevlar fibers were ultrasonically washed with water and anhydrous ethanol to remove surface impurities.

4. The preparation method according to claim 1, characterized in that: The conductive material is a Schiff base conductive polymer.

5. The preparation method according to claim 1, characterized in that: The mass ratio of Kevlar fiber to conductive material is 1:0.5~5.

6. The preparation method according to claim 4, characterized in that: The Schiff base conductive polymer is ready-to-use and is specifically prepared by polymerizing an amine compound and an active carbonyl compound; the amine compound is one or more of o-tolidine, 3, 3'-diaminobenzidine, 3, 4-diaminotoluene, and o-phenylenediamine; and the active carbonyl compound is terephthalaldehyde and / or trimesic acid.

7. The preparation method according to claim 4, characterized in that: The polymerization time is 4~8h.

8. The preparation method according to claim 1, characterized in that: In S3, Kevlar fiber / conductive composite film is used as the working electrode, and metal lithium sheet is used as the working electrode and counter electrode to carry out metal lithium electrodeposition to obtain a three-dimensional metal lithium negative electrode.

9. A three-dimensional metallic lithium negative electrode obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the three-dimensional metallic lithium negative electrode obtained by the preparation method according to any one of claims 1 to 8 or the three-dimensional metallic lithium negative electrode according to claim 9 in a lithium ion battery.

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