Lithium secondary battery

Patent metadata

Field	Value
Publication number	US-12087941-B2
Application number	US-202017292793-A
Country	US
Kind code	B2
Filing date	Jan 16, 2020
Priority date	Jan 16, 2019
Publication date	Sep 10, 2024
Grant date	Sep 10, 2024

Abstract

A lithium secondary battery, specifically, a lithium secondary battery. By specifically adjusting the porosity (%) and the mass of sulfur per unit area (mg/cm 2 ) of a positive electrode active material layer including a sulfur-carbon composite, the initial battery discharge capacity is improved, and thus a high energy density can be achieved.

First claim

The invention claimed is:

1. A lithium secondary battery comprising:
a positive electrode comprising a positive electrode active material layer;
a negative electrode;
a separator; and
an electrolyte liquid,
wherein the lithium secondary battery has an ED factor value represented by the following Mathematical Formula 1 of 850 or greater and 10,000 or less:

ED
⁢

factor

=

V
×
SC
⁢

factor
×

C
D

[

Mathematical
⁢

Formula
⁢

1

]

in Mathematical Formula 1, V is a discharge nominal voltage (V) for Li/Li + , D is a density (g/cm 3 ) of the electrolyte liquid, C is a discharge capacity (mAh/g) of the lithium secondary battery when discharging at a 0.1 C rate, and the SC factor is represented by the following Mathematical Formula 2, the SC factor being 0.45 or greater and 4.5 or less:

SC
⁢

factor

=

α
×

L
P

[

Mathematical
⁢

Formula
⁢

2

]

in Mathematical Formula 2, P is porosity (%) of the positive electrode active material layer, L is a mass of sulfur per unit area (mg/cm 2 ) of the positive electrode active material layer, and α is 10, wherein the SC factor defines the relationship between α, P, and L;
and
further wherein the positive electrode comprises a sulfur-carbon composite comprising a carbon material satisfying a condition of an AC factor represented by the following Mathematical Formula 3 being 100 or greater and 1,000 or less:
AC factor=0.1×specific area(m 2 /g)+2×conductivity(S/cm@2000 kgf)  [Mathematical Formula 3]

in Mathematical Formula 3, specific area is a specific surface area of the carbon material, and conductivity is electrical conductivity obtained by converting a powder resistance value measured while applying a pressure of 2000 kgf to the carbon material to conductivity,
wherein the electrolyte liquid comprises a solvent and a lithium salt, and the solvent comprises a first solvent in which a DV 2 factor value represented by the following Mathematical Formula 4 is 0.1 or greater and 1.75 or less and a second solvent that is a fluorinated ether-based solvent:

DV
2

⁢

factor

=

γ
×

μ
DV

[

Mathematical
⁢

Formula
⁢

4

]

in Mathematical Formula 4,
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 μ, γ, and DV, and
wherein the positive electrode comprises a dot-type carbon material.

2. The lithium secondary battery of claim 1 , wherein the carbon material has a specific surface area of 100 m 2 /g to 4500 m 2 /g.

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

4. The lithium secondary battery of claim 1 , wherein electrical conductivity obtained by converting a powder resistance value measured while applying a pressure of 2000 kgf to the carbon material to conductivity is from 10 S/cm to 100 S/cm.

5. The lithium secondary battery of claim 1 , wherein the dot-type carbon material comprises one or more selected from the group consisting of carbon black, ketjen black, denka black, acetylene black, channel black, furnace black, lamp black and thermal black.

6. The lithium secondary battery of claim 1 , wherein the first solvent comprises one or more selected from the group consisting of propionitrile, dimethylacetamide, dimethylformamide, gamma-butyrolactone, triethylamine and 1-iodopropane.

7. The lithium secondary battery of claim 1 , wherein the second solvent comprises one or more selected from the group consisting of 1H, 1H,2′H,3H-decafluorodipropyl ether, difluoromethyl 2,2,2-trifluoroethyl ether, 1,2,2,2-tetrafluoroethyl trifluoromethyl ether, 1,1,2,3,3,3-hexafluoropropyl difluoromethyl ether, pentafluoroethyl 2,2,2-trifluoroethyl ether and 1H, 1H,2′H-perfluorodipropyl ether.

8. The lithium secondary battery of claim 1 , wherein the first solvent is present in the solvent in an amount of 1% by weight to 50% by weight based on a total weight of the solvent.

9. The lithium secondary battery of claim 1 , wherein the second solvent is present in the solvent in an amount of 50% by weight to 99% by weight based on a total weight of the solvent.

10. The lithium secondary battery of claim 1 , wherein the first solvent and the second solvent are present in the solvent in a weight ratio of 3:7 to 1:9.

11. The lithium secondary battery of claim 1 , wherein, in the lithium secondary battery, an NS factor value represented by the following Mathematical Formula 5 is 3.5 or less:

NS
⁢

factor

=

Assignees

• Lg Energy Solution Ltd

Inventors

• Cho Eunkyung
• Park Intae
• Song Myeongjun
• Kim Ilto
• Cho Hyunah

Classifications

• H01M2300/0037

  Mixture of solvents · CPC title

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title

• H01M2004/028

  Positive electrodes · CPC title

• H01M2004/021

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

• H01M10/0525

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