Electrolyte for secondary battery and lithium secondary battery including the same

1. A lithium secondary battery comprising an electrolyte and an electrode assembly comprising a cathode, an anode, and a polymer membrane disposed between the cathode and the anode, the electrode assembly being accommodated in a battery case,

wherein the cathode comprises a spinel-structure lithium metal oxide represented by Formula (2) below:

Li x Ni y Mn 2−y O 4   (2)

wherein 0.9≦x≦1.2 and 0.4≦y≦0.5,

the anode comprises a lithium metal oxide represented by Formula (4) below:

Li a Ti b O 4   (4)

wherein 0.5≦a≦3 and 1≦b≦2.5, and,

wherein the electrolyte comprises a non-aqueous solvent and a lithium salt, in which the non-aqueous solvent comprises a cyclic carbonate and a linear solvent, wherein an amount of the cyclic carbonate in the non-aqueous solvent is in a range of 1 wt % to 30 wt % based on a total weight of the non-aqueous solvent, and wherein an amount of the linear solvent in the non-aqueous solvent is in a range of 70 wt % to 99 wt % based upon the total weight of the non-aqueous solvent,

wherein the linear solvent is a linear carbonate,

wherein the linear carbonate is dimethyl carbonate (DMC), and

wherein the cyclic carbonate is ethylene carbonate (EC).

2. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide is LiNi 0.5 Mn 1.5 O 4 or LiNi 0.4 Mn 6 O 4 .

3. The lithium secondary battery according to claim 1 , wherein the lithium metal oxide is Li 1.33 Ti 1.67 O 4 or LiTi 2 O 4 .

4. The lithium secondary battery according to claim 1 , wherein the lithium secondary battery is a lithium ion battery.

5. The lithium secondary battery according to claim 1 , wherein the lithium secondary battery is a lithium ion polymer battery.

6. The lithium secondary battery according to claim 1 , wherein the lithium secondary battery has a capacity retention ratio in a range of 90% to 100% after 200 charge/discharge cycles at 3 C-rate.