Lithium secondary battery of improved rate capability

Abstract

Disclosed is a lithium secondary battery with improved rate characteristics. More particularly, disclosed is a lithium secondary battery including a cathode, an anode, a separator disposed between the cathode and the anode, and an electrolyte, wherein the electrolyte includes a mixed solvent of a cyclic carbonate-based material and a propionate-based material, the cathode includes a lithium manganese composite oxide represented by Formula 1 below as a cathode active material, and the anode includes a lithium metal oxide represented by Formula 2 below as an anode active material:LixMyMn2−yO4−zAz  (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,LiaM′bO4−xAc  (2)wherein M′ is at least one element selected from the group consisting of Ti, Cu, Pb, Sb, Zn, Fe, In, Al, and Zr; 0.1≦a≦4 and 0.2≦b≦4 wherein a and b are determined according to oxidation number of M′; 0≦c<0.2 wherein c is determined according to oxidation number of A; and A is at least one monovalent or divalent anion.

Description

TECHNICAL FIELD[0001]The present invention relates to a lithium secondary battery with improved rate characteristics. More specifically, the present invention relates to a lithium secondary battery including a cathode, an anode, a separator disposed between the cathode and the anode, and an electrolyte, wherein the electrolyte includes a mixed solvent of a cyclic carbonate-based material and a propionate-based material, the cathode includes a lithium manganese composite oxide having a particular formula as a cathode active material, and the anode includes a lithium metal oxide having a particular formula as an anode active material.BACKGROUND ART[0002]As mobile device technology continues to develop and demand therefor continues to increase, demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential, have long cycle lifespan, and have a low self-discha...

AI Technical Summary

Benefits of technology

The present invention provides a lithium secondary battery that uses a mixed solvent of a cyclic carbonate-based material and a propionate-based material in the electrolyte. This electrolyte has desired effects, such as improved lifespan and rate characteristics, without causing problems in terms of anode protective film formation and elution of components of the cathode active material. The use of a small amount of the cyclic carbonate-based material and a propionate-based material in the electrolyte can also reduce the decomposition of the electrolyte and improve the stability of the battery.

Problems solved by technology

However, lithium secondary batteries have high operating potentials and thus high energy may instantaneously flow therein.

Accordingly, when a lithium secondary battery is overcharged to 4.2 V or higher, the electrolyte starts to decompose, and when the temperature of the electrolyte increases, the electrolyte may readily reach an ignition point, which results in high possibility of combustion.

In particular, among lithium manganese composite oxides, spinel-structure lithium nickel manganese composite oxides having formula LixNiyMn2−yO4, where y=0.01 to 0.6, which are used as active materials for high-voltage applications since they have an average voltage of 4.7 V, reach oxidation potential of an electrolyte and thus the electrolyte is oxidized, resulting in generation of by-products such as gas and the like, which deteriorates secondary battery safety.