CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. national phase application based on PCT Application No. PCT/KR2018/000769, filed Jan. 17, 2018, which is based on Korean Application No. 10-2017-0055621, filed Apr. 28, 2017, the entire contents of all of which are hereby incorporated by reference.

TECHNICAL FIELD

An electrolyte for a lithium secondary battery and a lithium secondary battery including the same are related.

BACKGROUND ART

Lithium secondary batteries are attracting attention as power sources for various electronic devices because of high discharge voltage and high energy density.

As for positive active materials of lithium secondary batteries, a lithium-transition metal oxide having a structure capable of intercalating lithium ions such as LiCoO2, LiMn2O4, LiNi1-xCoxO2(0<x<1), and the like has been used.

As for negative active materials of lithium secondary batteries, various carbon-based materials such as artificial graphite, natural graphite, and hard carbon capable of intercalating and deintercalating lithium ions have been used.

As for electrolytes of lithium secondary batteries, an organic solvent in which a lithium salt is dissolved has been used.

The lithium secondary batteries have a high temperature problem, that is, gas generation and electrode resistance due to the reaction between the positive active material and the electrolyte, which are significantly increased at particularly high temperature, and in addition, the solid electrolyte interface (SEI) film formed on the negative active material surface is destroyed at high temperature, and by-products are continuously generated to accelerate an irreversible reaction of the battery, and this phenomenon causes problems with battery performance degradation and thickness expansion (swelling) due to gas at higher temperatures than room temperature.

DISCLOSURE

Technical Problem

An embodiment provides an electrolyte for a lithium secondary battery that may prevent problems of thickness expansion at high temperatures.

Another embodiment provides a lithium secondary battery including the electrolyte.

Technical Solution

According to an embodiment, an electrolyte for a lithium secondary battery includes a non-aqueous organic solvent; a lithium salt; and an additive represented by Chemical Formula 1.



In Chemical Formula 1,

Ra, Rb, Rc, and Rdare each independently a halogen, a substituted or unsubstituted alkyl group, or CnF2n+1(n is an integer of 1 to 5). The Ra, Rb, Rc, and Rdmay each independently be a substituted or unsubstituted alkyl group. Herein, the alkyl group may have a carbon number of 1 to 5.

An amount of the additive may be 0.1 wt % to 2 wt % based on a total weight of the electrolyte and may be 0.5 wt % to 2 wt % based on a total weight of the electrolyte.

Another embodiment of the present invention provides a lithium secondary battery including a negative electrode including a negative active material; a positive electrode including a positive active material; and the electrolyte.

Other embodiments are included in the following detailed description.

Advantageous Effects

An electrolyte for a lithium secondary battery according to an embodiment of the present invention may improve storage characteristics at a high temperature, particularly high temperature swelling characteristics.

