Electrolyte for lithium secondary batteries with improved low temperature performance and lithium secondary battery including the same

Patent metadata

Field	Value
Publication number	US-11380932-B2
Application number	US-201916720300-A
Country	US
Kind code	B2
Filing date	Dec 19, 2019
Priority date	Dec 2, 2014
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

Disclosed are an electrolyte for lithium secondary batteries including 10 to 50% by weight of a cyclic carbonate compound, and 50 to 90% by weight of a linear ester compound, based on the total weight of a non-aqueous solvent, wherein a content of ethyl propionate of the linear ester compound is 20 to 60% by weight, based on the total weight of the non-aqueous solvent, and a lithium secondary battery including the electrolyte and exhibiting superior low-temperature characteristics.

First claim

The invention claimed is:

1. An electrolyte for lithium secondary batteries, consisting of:
a non-aqueous solvent, a lithium salt, and an additive that is selected from flame retardants, halogen-containing solvents, carbon dioxide gas, fluoro-ethylene carbonate (FEC), or propene sultone (PRS),
wherein the non-aqueous solvent consists of 10 to 50% by weight of a cyclic carbonate compound; and
50 to 90% by weight of a linear ester compound, the linear ester compound is a mixture of ethyl propionate and propyl propionate, and
the content of ethyl propionate is 20 to 40% by weight, and the content of propyl propionate is 30 to 50% by weight, based on the total weight of the non-aqueous solvent.

2. The electrolyte according to claim 1 , wherein the cyclic carbonate compound comprises at least one selected from the group consisting of ethylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, fluorethylene carbonate and vinylene carbonate.

3. The electrolyte according to claim 2 , wherein the cyclic carbonate compound comprises ethylene carbonate.

4. The electrolyte according to claim 1 , wherein the non-aqueous solvent consists of 20 to 50% by weight of a cyclic carbonate compound; and
50 to 80% by weight of a linear ester compound, the linear ester compound is a mixture of ethyl propionate and propyl propionate, and
the content of ethyl propionate is 20 to 40% by weight, and the content of propyl propionate is 30 to 40% by weight, based on the total weight of the non-aqueous solvent.

5. The electrolyte according to claim 1 , wherein, the electrolyte comprises 20 to 40% by weight of the cyclic carbonate compound and 60 to 80% by weight of the linear ester compound, based on the total weight of the non-aqueous solvent.

6. The electrolyte according to claim 1 , wherein the electrolyte has an ionic conductivity at −10° C. equal to or higher than 5.5 mS/cm and equal to or lower than 6.5 mS/cm and a viscosity at −10° C. equal to or higher than 4.5 cP and equal to or lower than 5.9 cP.

7. The electrolyte according to claim 1 , wherein, the electrolyte has an ionic conductivity at −10° C. equal to or higher than 5.5 mS/cm and equal to or lower than 6.0 mS/cm and a viscosity at −10° C. equal to or higher than 5.0 cP and equal to or lower than 5.9 cP.

8. The electrolyte according to claim 1 , wherein the additive is at least one selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, carbon tetrachloride and ethylene trifluoride, carbon dioxide gas, fluoro-ethylene carbonate (FEC), and propene sultone (PRS).

9. A lithium secondary battery comprising:
the electrolyte according to claim 1 ;
a positive electrode;
a negative electrode; and
a polymer membrane,
wherein an electrode assembly having a structure in which the polymer membrane is interposed between the positive electrode and the negative electrode is impregnated with the electrolyte and accommodated in a battery case.

10. The lithium secondary battery according to claim 9 , wherein the positive electrode comprises, as a positive electrode active material, at least one selected from the group consisting of a compound represented by the following Formula 1 and a compound represented by the following Formula 2:
Li x MO 2-z A z   (1)

Li a M′(PO 4-c )X c   (2)

wherein 0.9≤x≤1.2, 0≤z≤0.2, 0.5≤a≤1.5, 0≤c≤0.1;
M comprises at least one element selected from the group consisting of Co, Ni, Mn, Al, Mg, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi;
M′ comprises at least one element selected from the group consisting of Fe, Mn, Co, Ni, Cu, An, Mg, Cr, V, Mo, Ti, Al, Nb, B, and Ga;
A comprises at least one anion with a charge of −1 or −2; and
X comprises at least one element selected from F, S and N.

11. The lithium secondary battery according to claim 10 , wherein the compound represented by Formula 1 is represented by the following Formula 3 and the compound represented by Formula 2 is represented by the following Formula 4:
Li x Co y M 1-y O 2-z A z   (3)

Li a Fe 1-b M′ b (PO 4-c )X c   (4)

wherein 0.9≤x≤1.2, 0≤y≤1, 0≤z≤0.2, 0.5≤a≤1.5, 0≤b≤0.5, 0≤c≤0.1;
M comprises at least one element selected from the group consisting of Ni, Mn, Al, Mg, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi;
M′ comprises at least one element selected from the group consisting of Mn, Co, Ni, Cu, Zn, Mg, Cr, V, Mo, Ti, Al, Nb, B, and Ga;
A comprises at least one anion with a charge of −1 or −2; and
X comprises at least one element selected from F, S and N.

12. The lithium secondary battery according to claim 11 , wherein the compound represented by Formula 3 is LCoO 2 and the compound represented by Formula 4 is LiFePO 4 .

13. The lithium secondary battery according to claim 10 , wherein the positive electrode active material comprises the compound of Formula 1 and the compound of Formula 2, and a weight mix ratio of the compound of Formula 1 and the compound of Formula 2 is 60:40 to 99:1.

14. The lithium secondary battery according to claim 13 , wherein the weight mix ratio of the compound of Formula 1 and the compound of Formula 2 is 70:30 to 99:1.

15. The lithium secondary battery according to claim 9 , wherein the negative electrode comprises, as a negative electrode active material, a carbon-based material.

16. A battery pack comprising the lithium secondary battery according to claim 9 as a unit battery.

Assignees

• Lg Chemical Ltd
• Lg Energy Solution Ltd

Inventors

• Kil Eun Hye
• Lee Jin Kyu
• Kim Ki Tae
• Yun Hyung Ku
• Han Hyeaeun

Classifications

• H01M4/5825

  Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines · CPC title

• H01M10/0569

  characterised by the solvents · CPC title

• Y02T10/70

  Energy storage systems for electromobility, e.g. batteries · CPC title

• H01M10/056

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

• H01M2220/20

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