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

• US 10,573,921 B2
• Filed: 12/02/2015
• Issued: 02/25/2020
• Est. Priority Date: 12/02/2014
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Kil, Eun Hye, Lee, Jin Kyu, Kim, Ki Tae, Yun, Hyung Ku, Han, Hyeaeun
• Primary Examiner(s): Lee, Sin J
• Application Number:
  US15/509,661
• Publication Number:
  US 20170288257A1
• Time in Patent Office: 1,546 Days
• Field of Search: None
• CPC Class Codes: C07C 69/22 having three or more carbon atoms in the acid moiety
• CPC Class Codes: C07D 317/36 Alkylene carbonates; Substituted alkylene carbonates
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/056 characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
• CPC Class Codes: H01M 10/0566 Liquid materials
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 2300/0037 Mixture of solvents
• CPC Class Codes: H01M 4/364 as mixtures
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/5825 Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

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.

Claims

1. An electrolyte for lithium secondary batteries, consisting of:

a non-aqueous solvent and a lithium salt,

wherein the non-aqueous solvent consists of;

25 to 45% by weight of a cyclic carbonate compound; and

55 to 75% 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 25 to 35% by weight, and the content of propyl propionate is 30 to 40% 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 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 4.5 cP and equal to or lower than 5.9 cP.

5. 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.

6. 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.

7. The lithium secondary battery according to claim 6, 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 Formul 1 and a compound represented by the following Formula 2:

Li_xMO_2-zA_z 

 

(1)

Li_aM′

(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.

8. The lithium secondary battery according to claim 7, 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_xCo_yM_1-yO_2-zA_z 

 

(3)

Li_aFe_1-bM′

_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.

9. The lithium secondary battery according to claim 8, wherein the compound represented by Formula 3 is LiCoO₂ and the compound represented by Formula 4 is LiFePO₄.

10. The lithium secondary according to claim 7, 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.

11. The lithium secondary battery according to claim 10, wherein the weight mix ratio of the compound of Formula 1 and the compound of Formula 2 is 70:

30 to 99;

1.

12. The lithium secondary battery according to claim 6, wherein the negative electrode comprises, as a negative electrode active material, a carbon-based material.

13. A battery pack comprising the lithium secondary battery according to claim 6 as a unit battery.

14. A device comprising the battery pack according to claim 13.

15. The device according to claim 14, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a system for storing power.