Electrolyte for lithium secondary batteries and lithium secondary battery including the same

#This application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/KR2013/010708, filed Nov. 22, 2013, which claims priority to Korean Patent Application No. 10-2012-0133275, filed Nov. 22, 2012, the disclosures of which are incorporated herein by reference.

#The present invention relates to an electrolyte for lithium secondary batteries and a lithium secondary battery including the same. More particularly, the present invention relates to an electrolyte for lithium secondary batteries including a lithium salt and a non-aqueous solvent, the electrolyte including 10 wt % to 90 wt % of an ester based solvent and 10 wt % to 90 wt % of a carbonate based solvent with respect to the total weight of a non-aqueous solvent, and a lithium secondary battery including the same.

#Demand for lithium secondary batteries as energy sources is rapidly increasing as mobile device technology continues to develop and demand therefor continues to increase. Recently, use of lithium secondary batteries as a power source of electric vehicles (EVs) and hybrid electric vehicles (HEVs) has been realized. Accordingly, research into secondary batteries, which may meet a variety of requirements, is being actively performed. In particular, there is high demand for lithium secondary batteries having high energy density, high discharge voltage, and output stability.

#The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which:

#FIG. 1 is a graph illustrating relative resistances of secondary batteries according to Experimental Example 1 of the present invention;

#FIG. 2 is a graph illustrating room-temperature output characteristics of secondary batteries according to Experimental Example 2 of the present invention; and

#Now, the present invention will be described in more detail with reference to the following examples. These examples are provided only for illustration of the present invention and should not be construed as limiting the scope and spirit of the present invention.

#88 wt % of Li(Ni0.4Mn0.3Co0.3)O2 as a cathode active material, 8.5 wt % of Super-P as a conductive material, and 3.5 wt % of PVdF as a binder were added to NMP to prepare a cathode mixture slurry. The resulting cathode mixture slurry was coated, dried, and pressed over one side of aluminum foil to prepare a cathode.

#95.8 wt % of Graphite as an anode active material, 1 wt % of Super-P as a conductive material, and 2.2 wt % of SBR as a binder, and 1 wt % of a thickener were added to H2O as a solvent to prepare an anode mixture slurry. The resulting anode mixture slurry was coated, dried, and pressed over one side of copper foil to prepare an anode.