Non-aqueous electrolyte solution for lithium secondary battery and lithium secondary battery including the same

1. A non-aqueous electrolyte solution for a lithium secondary battery, the non-aqueous electrolyte solution comprising:

an ionizable lithium salt,

an organic solvent, and

an additive,

wherein the additive is a mixed additive which includes lithium difluorophosphate, tertiary alkylbenzene represented by Formula 1, and tetra-vinyl silane in a weight ratio of 1:1 to 4:0.05 to 0.5, and

the additive is included in an amount of 2.5 wt % to 4.5 wt % based on a total weight of the non-aqueous electrolyte solution for a lithium secondary battery:

wherein, in Formula 1,

R 1 is a tertiary alkyl having 4 to 5 carbon atoms.

2. The non-aqueous electrolyte solution for a lithium secondary battery of claim 1 , wherein the organic solvent is a mixed solvent which includes at least two of ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, and ethylmethyl carbonate.

3. The non-aqueous electrolyte solution for a lithium secondary battery of claim 1 , wherein the weight ratio of the lithium difluorophosphate:the tertiary alkylbenzene represented by Formula 1:the tetra-vinyl silane is in a range of 1:1.5 to 4:0.1 to 0.2.

4. The non-aqueous electrolyte solution for a lithium secondary battery of claim 1 , wherein a concentration of the lithium difluorophosphate in the non-aqueous electrolyte solution for a lithium secondary battery is in a range of 1×10 −2 mol/kg to 0.5 mol/kg.

5. The non-aqueous electrolyte solution for a lithium secondary battery of claim 1 , wherein the additive is included in an amount of 2.5 wt % to 4.3 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

6. The non-aqueous electrolyte solution for a lithium secondary battery of claim 1 , further comprising at least one additive for forming a solid electrolyte interface (SEI) film which is selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfate (Esa), and propane sultone (PS).

7. The non-aqueous electrolyte solution for a lithium secondary battery of claim 6 , wherein the additive for forming an SEI is included in an amount of at least 0.1 wt % to 2 wt % based on a total weight of the non-aqueous electrolyte solution.

8. A lithium secondary battery which comprises a negative electrode including a negative electrode active material, a positive electrode including a positive electrode active material, and a non-aqueous electrolyte solution,

wherein the positive electrode active material comprises at least one of a compound represented by Formula 4 and a compound represented by Formula 5, and

the non-aqueous electrolyte solution comprises the non-aqueous electrolyte solution for a lithium secondary battery of claim 1 :

Li(Ni x Co y Mn z )O 2   [Formula 4]

wherein, in Formula 4,

0<x<1, 0<y<1, 0<z<1, and x+y+z=1, and

Li(Ni x1 Co y1 Mn z1 )O 4   [Formula 5]

wherein, in Formula 5,

0<x1<2, 0<y1<2, 0<z1<2, and x1+y1+z1=2.

9. The lithium secondary battery of claim 8 , wherein the positive electrode active material is selected from the group consisting of Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 , Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 , Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 , and Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 .

10. The lithium secondary battery of claim 8 , wherein the positive electrode active material further comprises a compound represented by Formula 6:

LiMnO 2 .  [Formula 6]

11. The lithium secondary battery of claim 10 , wherein the positive electrode active material comprises the compound represented by Formula 4 or 5 in an amount of 80 wt % to 99 wt % and the compound represented by Formula 6 in an amount of 1 wt % to 20 wt %.