Electrolyte for secondary battery and lithium secondary battery including the same

1. A lithium secondary battery, comprising:

an electrode assembly comprising a cathode, an anode, and a polymer membrane disposed between the cathode and the anode, and an electrolyte,

wherein the cathode comprises a spinel-structure lithium metal oxide represented by Formula (1) below:

Li x M y Mn 2-y O 4-z A z   (1)

wherein 0.9≦x≦1.2, 0<y<2, and 0≦z≦0.2;

M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi, and A is at least one monovalent or divalent anion,

wherein 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,

wherein the electrolyte comprises:

a non-aqueous solvent, and a lithium salt,

wherein the non-aqueous solvent comprises an anion receptor, a cyclic carbonate, and a linear solvent,

wherein an amount of the cyclic carbonate is in a range of 1 wt % to 30 wt % based on a total weight of the non-aqueous solvent,

where in the anion receptor is a silylborate-based compound, and

wherein an amount of the anion receptor is in a range of 0.1 wt % to 0.5 wt % based on a total weight of the electrolyte,

wherein the linear solvent is a mixture of EMC and DMC.

2. The lithium secondary battery according to claim 1 , wherein the cyclic carbonate is one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), and combinations thereof.

3. The lithium secondary battery according to claim 2 , wherein the cyclic carbonate is EC.

4. The lithium secondary battery according to claim 1 , wherein the silylborate-based compound is trialkylsilyl borate or tris(trialkylsilyl)borate.

5. The lithium secondary battery according to claim 1 , wherein the silylborate-based compound is trimethylsilyl borate or tris(trimethylsilyl)borate.

6. The lithium secondary battery according to claim 1 , further comprising:

a battery case to accommodate the electrode assembly.

7. The lithium secondary battery according to claim 1 , wherein the spinel-structure lithium metal oxide of Formula (1) is 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.

8. The lithium secondary battery according to claim 7 , wherein the lithium metal oxide is LiNi 0.5 Mn 1.5 O 4 or LiNi 0.4 Mn 1.6 O 4 .

9. 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 .

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

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

12. The lithium secondary battery according to claim 1 , wherein the lithium secondary battery has a capacity retention ratio of 90% or higher after 200charge/discharge cycles at 3 C.