Flake Metal Lithium Powder and Preparing Method of the Same

Abstract

The present disclosure discloses flake metal lithium powder and a preparing method thereof; by ultrasonically pulverizing the metal lithium placed in a low-viscosity inert organic resolvent using a vacuum ultrasonic pulverization method, a micrometer scale flake metal lithium powder is prepared. The metal lithium powder may be used as an anode material for a lithium cell or lithium ion cell. The present method has advantages of high product purity, simple operation, low processing temperature, low cost, high efficiency, and less demanding on equipment, etc., and has a high prospect of being applied to mass production of metal lithium powder.

Claims

1. A metal lithium powder, wherein a morphology of the metal lithium powder is a flake structure.

2. The metal lithium powder according to claim 1, wherein the metal lithium powder has a thickness and the thickness of the metal lithium powder is 1300 m, with a width-to-thickness ratio being 240.

3. A method of preparing a metal lithium powder, comprising: a) placing metal lithium into an inert organic solvent, hermetically sealing, and vacuum-pumping; b) performing ultrasonic processing at a temperature lower than a lithium melting point; and c) filtering and drying the processing liquid to obtain flake metal lithium powder, wherein a morphology of the metal lithium powder is a flake structure.

4. The method of preparing the metal lithium according to claim 3, wherein the metal lithium in step a) is a lithium foil, a lithium strip, or a lithium wire, with a thickness or diameter being less than 1 mm.

5. The method of preparing the flake metal lithium powder according to claim 3, wherein the metal lithium has a mass percentage and the mass percentage of the metal lithium in the organic solvent in step a) is 0.0130%.

6. The method of preparing the flake metal lithium powder according to claim 3, wherein the organic solvent has a viscosity and the viscosity of the organic solvent in step a) is 100 mPa.Math.s.

7. The method of preparing the flake metal lithium powder according to claim 3, wherein the vacuum pumping operation has a vacuum degree, and the vacuum degree of the vacuum-pumping operation in step a) is 0.01 MPa.

8. The method of preparing the flake metal lithium powder according to claim 3, wherein a duration of the ultrasonic processing in step b) is 1120 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a scanning electron microscope (SEM) image of metal lithium powder prepared according to embodiment 1 of the present disclosure;

[0022] FIG. 2 is an X-ray diffraction (XRD) pattern of the metal lithium powder prepared according to embodiment 1 of the present disclosure;

[0023] FIG. 3 is a discharge profile of the metal lithium powder prepared according to embodiment 1 of the present disclosure;

[0024] FIG. 4 is an X-ray diffraction (XRD) pattern of the metal lithium powder prepared according to control example 1;

[0025] FIG. 5 is a discharge profile of the metal lithium powder prepared according to control example 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0026] Hereinafter, the present disclosure will be described in further detail with reference to specific embodiments in combination with FIGS. 15, but the protection scope of the present disclosure is not limited thereto.

Embodiment 1

[0027] Placing a 5 g battery-grade lithium foil (with a thickness of 0.05 mm) into a 200 ml plastic bottle loaded with 45 g cyclohexane; vacuum-pumping to 0.06 MPa, hermetically sealing, processing for 15 min in a 100 W ultrasonic instrument at a processing temperature of 60 C., filtering and vacuum drying, and then obtaining metal lithium powder. FIG. 1 is an SEM image of the prepared metal lithium powder. It may be seen from the image that the lithium powder is in a flake structure, with a thickness of 1050 m, a width of 100300 m, and a width-to-thickness ratio of approximately 630. FIG. 2 is a typical XRD pattern of the prepared metal lithium powder, showing that it is a pure phase of Li, without other impurity phases.

[0028] Rolling the metal lithium powder on a Cu foil as a working electrode, and with the metal lithium plate as a counter electrode, a 1 mol/L LiPF.sub.6 EC/DMC (with a volume ratio being 1:1) as the electrolyte, a Cellgard 2400 as the separator, to make a 2032-type coin cell. Testing the galvanostatic charging/ discharging performance of the cell using Wuhan LAND cell testing system (LAND CT2001A).

[0029] FIG. 3 is a discharge profile of the metal lithium powder anode prepared according to embodiment 1 of the present disclosure. The discharge capacity of the metal lithium powder may reach 3307 mAh/g, 85.7% of its theoretical lithium discharge capacity (3860 mAh/g). The result shows that the flake metal lithium powder may be used as an anode material for a lithium cell or a lithium ion cell.

Embodiment 2

[0030] Placing a 0.5 g battery-grade lithium foil (with a thickness of 0.05 mm) into a 50 ml plastic bottle loaded with 9.5 g dimethyl carbonate; vacuum-pumping to 0.06 MPa, hermetically sealing, processing for 5 min in a 100 W ultrasonic instrument at a processing temperature of 60 C., filtering and vacuum drying to remove the solvent, and then obtaining metal lithium powder. The resulting lithium powder is in a flake structure, with a thickness of 550 m, a width of 50200 m, and a width-to-thickness ratio of approximately 440. The result shows that this kind of the inert solvent has an impact on the lithium powder size and the pulverization efficiency.

Embodiment 3

[0031] Placing a 10 g battery-grade lithium strip (with a thickness of 0.5 mm) into a 200 g 1,3-dioxolane; vacuum-pumping to 0.06 MPa, hermetically sealing, processing for 3 min in a 600 W ultrasonic instrument, filtering and vacuum drying to remove the solvent, and then obtaining metal lithium powder. The resulting lithium powder is in a flake structure, with a thickness of 350 m, a width of 30150 m, and a width-to-thickness ratio of approximately 350. The result shows that the power of the ultrasonic pulverizer has a significant impact on the efficiency of pulverizing the lithium powder.

Embodiment 4

[0032] Rolling 0.5 g lithium grains (with a thickness of 2 mm) into thin-sheet with a thickness of about 0.2 mm; placing the thin sheet into a 50 ml plastic bottle loaded with 9.5 g dimethyl carbonate; vacuum-pumping to 0.06 MPa and hermetically sealing, processing for 5 min in a 100 W ultrasonic instrument at a processing temperature of 60 C., filtering and vacuum drying to remove the solvent, and then obtaining flake metal lithium powder. If lithium grains of this size are pulverized under the same condition without being thinned through mechanical rolling, even the processing duration is prolonged to 120 min, it is still hard to produce lithium powder. The result shows that the size of metal lithium before pulverization also has a significant impact on the efficiency of pulverizing the lithium powder.

Control Example 1

[0033] Placing a 5 g battery-grade lithium foil (with a thickness of 0.05 mm) into a 200 ml plastic bottle loaded with 45 g cyclohexane; filling argon to protect and hermetically seal, processing for 15 min in a 100 W ultrasonic instrument at a processing temperature of 60 C., filtering and vacuum drying, and then obtaining metal lithium powder. The resulting metal lithium powder has an effect approximate to the vacuum ultrasonic pulverization. However, it may be clearly seen from the XRD pattern (FIG. 4) that besides the phase of Li, it also includes the impurity of LiOH. Production of the LiOH might be caused by reaction of the active lithium powder with trace water and dissolved oxygen or other substance in the organic resolvent.

[0034] Making a 2032-type coin cell using the prepared metal lithium powder in control example 1 according to the scheme in Embodiment 1 and the cell performance was evaluated by the discharge test under the same condition. The discharge capacity of the metal lithium powder may reach 2829 mAh/g, 73.3% of its theoretical discharge capacity (3860 mAh/g). It may be seen that production of the LiOH impurity phase apparently reduces the discharge capacity of the metal lithium.

Control Example 2

[0035] Placing a 0.5 g battery-grade lithium foil (with a thickness of 0.05 mm) into a 50 ml plastic bottle loaded with 9.5 g dimethyl silicon oil with a viscosity of 1000 mPa.Math.s; vacuum-pumping to 0.06 MPa, hermetically sealing, processing for 120 min in a 100 W ultrasonic instrument at a processing temperature of 60 C.; the lithium foil substantially has no change. The result shows that the viscosity of the organic resolvent has a significant impact on the metal lithium pulverization effect.

[0036] The above description of the preferred embodiments of the present disclosure is not intended to limit the present disclosure. Those skilled in the art may make some modifications based on the present disclosure, which should all fall into the scope defined by the appended claims of the present disclosure without departing from the spirit of the present disclosure.