Patent ID: 8715856
Filing Date: 2014-05-06
Classification: H01M,Y02E,Y02T

Abstract:
1. A secondary battery comprising a cathode, an anode, a membrane and an electrolyte, wherein the cathode comprises a mixture of a first cathode material defined below and a second cathode material selected from the group consisting of a second-(a) cathode material defined below and a second-(b) cathode material defined below, and a combination thereof, wherein a mix ratio of the two cathode materials (first cathode material: second cathode material) is 50:50 to 90:10, and the membrane is an organic/inorganic composite porous membrane comprising (a) a polyolefin-based membrane substrate and (b) an active layer in which one or more areas selected from the group consisting of the surface of the substrate and a portion of pores present in the substrate are coated with a mixture of inorganic particles and a binder polymer, wherein the active layer has a structure in which the inorganic particles are interconnected and fixed through the binder polymer, and porous structures are formed by the interstitial volume between the inorganic particles, said first cathode material comprising a cathode material represented by Formula 1 below: wherein 0.8≦x≦1.2, 0≦z≦0.3, 1.8≦t≦4.2, (0.8-m-z)≦y≦(2.2-m-z), 0≦m≦0.3, A is at least one selected from Mg and Ca, and D is at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta; Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Au, Ag, Zn, Cd, Hg, B, Al, Ga, In, TI, C, Si, Ge, Sn, Pb, N, P, As, Sb and Bi; said second-(a) cathode material comprising a cathode material represented by Foimula 2a below: wherein 0.05≦a≦0.4, 0.1≦b≦0.4, 0.4<1-a-b<0.7, 0.95≦x≦1.05, 1.9<x+y<2.3; and said second-(b) cathode material comprising a cathode material which contains a transition metal mixture of Ni, Mn and Co, has an average oxidation number of all transition metals except for lithium, larger than +3 and satisfies Equations 2b and 2c below: wherein m(Ni)/m(Mn) is a molar ratio of nickel to manganese and (Ni