Method of manufacturing negative electrode for lithium secondary batteries

Patent metadata

Field	Value
Publication number	US-12027688-B2
Application number	US-201917252119-A
Country	US
Kind code	B2
Filing date	Oct 10, 2019
Priority date	Oct 10, 2018
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

A method of manufacturing a negative electrode for lithium secondary batteries. With the method, a negative electrode for lithium secondary batteries having excellent cycle performance may be manufactured by performing a process of compressing the negative electrode after pre-lithiation of the negative electrode so that the porosity of the negative electrode after the pre-lithiation is maintained within a certain range.

First claim

The invention claimed is:

1. A method of manufacturing a negative electrode for lithium secondary batteries, comprising:
manufacturing a negative electrode by forming a negative electrode active material layer on a negative electrode current collector, wherein the forming of the negative electrode active material layer comprises coating the negative electrode current collector with a negative electrode active material, and first compressing the negative electrode active material on the surface of the negative electrode current collector to form the negative electrode active material layer;
manufacturing a pre-lithiated negative electrode by impregnating the negative electrode with a pre-lithiation solution to perform a pre-lithiation process; and
second compressing the pre-lithiated negative electrode to adjust a porosity of the pre-lithiated negative electrode,
wherein the negative electrode active material comprises a silicon-based negative electrode active material and a carbon-based negative electrode active material,
wherein a weight ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material is 1:99 to 50:50,
wherein the porosity of the pre-lithiated negative electrode is in a range of 20% to 45%,
wherein the porosity is calculated by the following Equation 1:
Porosity (%)=[1−(Real Density/True Density)]×100  Equation 1

wherein real density is a density of the negative electrode active material layer comprising pores, and
true density is a solids density of the negative electrode active material layer without pores.

2. The method of claim 1 , wherein the porosity of the pre-lithiated negative electrode is in a range of 25% to 35%.

3. The method of claim 1 , wherein the pre-lithiation process comprises electrochemically charging the negative electrode using a lithium metal as a counter electrode after the negative electrode is impregnated with the pre-lithiation solution.

4. The method of claim 1 , wherein the impregnation is performed at a temperature of 10° C. to 200° C. for 2 hours to 48 hours.

5. The method of claim 3 , wherein the charging is performed to 5% to 35% of a charge capacity of the negative electrode at a current density of 0.1 mA/cm 2 to 10 mA/cm 2 .

6. The method of claim 1 , wherein the compression is performed at a linear pressure of 0.1 kN/cm to 30 kN/cm.

7. The method of claim 1 , wherein the pre-lithiation solution comprises a lithium salt and an organic solvent.

8. The method of claim 1 , wherein manufacturing of the pre-lithiated negative electrode comprises:
impregnating the negative electrode with the pre-lithiation solution to perform a pre-lithiation process; and
washing the negative electrode with an organic solvent.

9. The method of claim 8 , wherein washing is performed at a temperature of 10° C. to 200° C. for 1 minute to 3 hours using the organic solvent.

10. A method of manufacturing a lithium secondary battery comprising:
manufacturing a negative electrode as defined in claim 1 ;
manufacturing a positive electrode;
placing a separator between the negative electrode and the positive electrode; and
injecting an electrolyte solution into the lithium secondary battery.

11. The method of claim 1 , wherein the method consists of the steps of manufacturing the negative electrode, first compressing the negative electrode active material, manufacturing the pre-lithiated negative electrode, and second compressing the pre-lithiated negative electrode.

12. The method of claim 1 , wherein the step of first compressing the negative electrode active material and the step of second compressing the pre-lithiated negative electrode are performed before and after the step of manufacturing the pre-lithiated negative electrode, respectively.

13. The method of claim 1 , wherein the pre-lithiation solution comprises LiPF 6 dissolved to a concentration of 1 M in a solvent comprising ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed at a volume ratio of 3:7 and 2% by weight of fluoroethylene carbonate (FEC).

Assignees

• Lg Chemical Ltd
• Lg Energy Solution Ltd

Inventors

• Chae Oh Byong
• Woo Sang Wook
• Kim Ye Ri

Classifications

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/386

  Silicon or alloys based on silicon · CPC title

• H01M4/483

  for non-aqueous cells (H01M4/485 takes precedence) · CPC title

• H01M4/587

  for inserting or intercalating light metals · CPC title