Lithium-sulfur secondary battery

Patent metadata

Field	Value
Publication number	US-12021224-B2
Application number	US-201917265346-A
Country	US
Kind code	B2
Filing date	Nov 18, 2019
Priority date	Nov 22, 2018
Publication date	Jun 25, 2024
Grant date	Jun 25, 2024

Abstract

A lithium-sulfur secondary battery is disclosed, and in particular, a lithium-sulfur secondary battery in which a positive electrode includes a sulfur-carbon composite including a microporous carbon material and sulfur, or a conductive additive including a carbon material having high specific surface area. By specifying conditions of the positive electrode and an electrolyte liquid, energy density may be enhanced compared to existing lithium-sulfur secondary batteries.

First claim

The invention claimed is:

1. A lithium-sulfur secondary battery comprising:
a positive electrode comprising a positive electrode active material layer;
a negative electrode;
a separator; and
an electrolyte liquid,
wherein the positive electrode active material layer comprises a sulfur-carbon composite comprising a microporous carbon material and sulfur;
wherein the sulfur of the sulfur-carbon composite is present in an amount of from 50% by weight to 90% by weight based on a total weight of the sulfur-carbon composite,
the positive electrode has an SC factor value represented by the following Mathematical Formula 1 of 0.45 or greater:

SC
⁢

⁢
factor

=

α
×

L
P

[

Mathematical
⁢

⁢
Formula
⁢

⁢
1

]

in Mathematical Formula 1,
P is porosity (%) of the positive electrode active material layer;
L is mass of sulfur (mg/cm 2 ) per unit area of the positive electrode active material layer; and
α is 10;
wherein the SC factor defines the relationship between α, P, and L; and
wherein the electrolyte liquid comprises a lithium salt, a first solvent having a DV 2 factor value represented by the following Mathematical Formula 2 of 1.75 or less, and a second solvent that is a fluorinated ether-based solvent:

DV
2

⁢

⁢
factor

=

γ
×

μ
DV

[

Mathematical
⁢

⁢
Formula
⁢

⁢
2

]

in Mathematical Formula 2,
DV is a dipole moment per unit volume (D·mol/L);
μ is viscosity of the solvent (cP, 25° C.); and
γ is 100,
wherein the DV 2 factor defines the relationship between γ, μ, and DV.

2. The lithium-sulfur secondary battery of claim 1 , wherein the microporous carbon material comprises pores having an average diameter of from 1 nm to 10 nm.

3. The lithium-sulfur secondary battery of claim 1 , wherein the microporous carbon material has a specific surface area of from 500 m 2 /g to 4500 m 2 /g.

4. The lithium-sulfur secondary battery of claim 1 , wherein the microporous carbon material has porosity of from 10% to 90%.

5. The lithium-sulfur secondary battery of claim 1 , wherein the microporous carbon material has a pore volume of from 0.8 cm 3 /g to 5 cm 3 /g.

6. The lithium sulfur secondary battery of claim 1 , wherein the positive electrode active material layer further comprises a conductive additive comprising a carbon material having high specific surface area.

7. The lithium-sulfur secondary battery of claim 6 , wherein the carbon material having high specific surface area has a specific surface area of from 100 m 2 /g to 500 m 2 /g.

8. The lithium-sulfur secondary battery of claim 6 , wherein the carbon material having high specific surface area comprises at least one selected from the group consisting of carbon nanotubes, graphene, carbon black, and carbon fiber.

9. The lithium sulfur secondary battery of claim 6 , wherein the carbon material having high specific surface area comprises a mixture of carbon nanotubes and grapheme in a weight ratio of from 0:10 to 10:0.

10. The lithium-sulfur secondary battery of claim 6 , wherein the carbon material having high specific surface area is present in an amount of from 0.01% by weight to 30% by weight based on a total weight of the positive electrode active material layer.

11. The lithium-sulfur secondary battery of claim 1 , wherein the first solvent has a DV 2 factor value of 1.5 or less.

12. The lithium-sulfur secondary battery of claim 1 , wherein the lithium-sulfur secondary battery has an NS factor value represented by the following Mathematical Formula of 15 or less:

NS
⁢

⁢
factor

=

DV
2

⁢

⁢
factor

SC
⁢

⁢
factor

[

Mathematical
⁢

⁢
Formula
⁢

⁢
3

]

in Mathematical Formula 3,
SC factor has the same value as defined in Mathematical Formula 1; and
DV 2 factor has the same value as defined in Mathematical Formula 2,
wherein the NS factor defines the relationship between DV 2 and SC.

Assignees

• Lg Chemical Ltd
• Lg Energy Solution Ltd

Inventors

• Lee Changhoon
• Yang Doo Kyung
• Park Intae

Classifications

• H01M2300/0037

  Mixture of solvents · CPC title

• H01M2004/028

  Positive electrodes · CPC title

• H01M2004/021

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

• H01M10/056

  characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title