TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The lithium-free oxide has an X-ray diffraction peak at 35.5 plus minus 2 degrees 2 theta for a peak corresponding to a (311) crystal face, when measured using copper-K alpha radiation, and a full width at half maximum of the X-ray diffraction peak corresponding to the (311) crystal face is less than 0.3 degrees 2 theta , preferably 0.22-0.27 degrees 2 theta . In the electrode active material, a ratio of an intensity of an X-ray diffraction peak corresponding to a (440) crystal face to an intensity of an X-ray diffraction peak corresponding to a (311) crystal face is greater than or equal to 0.3, a ratio of an intensity of an X-ray diffraction peak corresponding to a (511) crystal face to an intensity of an X-ray diffraction peak corresponding to a (400) crystal face is greater than or equal to 0.25, a ratio of an intensity of an X-ray diffraction peak corresponding to a (511) crystal face to an intensity of an X-ray diffraction peak corresponding to a (440) crystal face is greater than or equal to 0.5, a content of the lithium-free oxide is less than or equal to 10 wt.%, and a thickness of the surface treatment layer is 1 Angstrom to 1 mu m. The lithium-free oxide is of formula (A1aM1a2O4), which is at least one tin magnesium oxide (SnMg2O4), tin zinc oxide (SnZn2O4), magnesium aluminum oxide (MgAl2O4), copper aluminum oxide (CuAl2O4), nickel aluminum oxide (NiAl2O4) (all preferred), molybdenum aluminum oxide (MoAl2O4), zinc aluminum oxide (ZnAl2O4), zinc vanadium oxide (ZnV2O4), titanium manganese oxide (TiMn2O4), zinc manganese oxide (ZnMn2O4), magnesium gallium oxide (MgGa2O4), zinc gallium oxide (ZnGa2O4), calcium gallium oxide (CaGa2O4), titanium magnesium oxide (TiMg2O4), vanadium magnesium oxide (VMg2O4), magnesium vanadium oxide (MgV2O4), iron vanadium oxide (FeV2O4), zinc vanadium oxide (ZnV2O4), magnesium chromium oxide (MgCr2O4), manganese chromium oxide (MnCr2O4), iron chromium oxide (FeCr2O4), cobalt chromium oxide (CoCr2O4), nickel chromium oxide (NiCr2O4), copper chromium oxide (CuCr2O4), zinc chromium oxide (ZnCr2O4), cadmium chromium oxide (CdCr2O4), zinc manganese oxide (ZnMn2O4), magnesium iron oxide (MgFe2O4), titanium iron oxide (TiFe2O4), manganese iron oxide (MnFe2O4), cobalt iron oxide (CoFe2O4), nickel iron oxide (NiFe2O4), copper iron oxide (CuFe2O4), zinc iron oxide (ZnFe2O4), cadmium iron oxide (CdFe2O4), aluminum iron oxide (AlFe2O4), lead iron oxide (PbFe2O4), magnesium cobalt oxide (MgCo2O4), titanium cobalt oxide (TiCo2O4), zinc cobalt oxide (ZnCo2O4), tin cobalt oxide (SnCo2O4), iron nickel oxide (FeNi2O4), germanium nickel oxide (GeNi2O4), magnesium rhodium oxide (MgRh2O4), zinc rhodium oxide (ZnRh2O4), titanium zinc oxide (TiZn2O4), strontium aluminum oxide (SrAl2O4), chromium aluminum oxide (CrAl2O4), molybdenum aluminum oxide (MoAl2O4), iron aluminum oxide (FeAl2O4), cobalt aluminum oxide (CoAl2O4), magnesium gallium oxide (MgGa2O4), zinc gallium oxide (ZnGa2O4), magnesium indium oxide (MgIn2O4), calcium indium oxide (CaIn2O4), iron indium oxide (FeIn2O4), cobalt indium oxide (CoIn2O4), nickel indium oxide (NiIn2O4), cadmium indium oxide (CdIn2O4), and mercury indium oxide (HgIn2O4). The core comprises at least one lithium compounds of formula: (Li(LiaM2a1-a)O2+d) and (Li(LibM2acM3ae)O2+d); or (LixCo1-yM4ayO2-q)X1aq), LixCo1-y-zNiyM4azO2-q)X1aq), LixMn2-yM4ayO4-q)X1aq), LixCo2-yM4ayO4-q)X1aq) and LixM2ayM4aPO4-qX1aq); or (Li2M5aO3)p-(LiM2aO2)1-p) and (Li2M5aO3)r-(LiM2aO2)s-(Li1+dM6a2-wO4)t); or at least one silicon, tin, aluminum, germanium, lead, bismuth, antimony, a silicon alloy of formula (Si-Y1a), antimony alloy of formula (Sn-Y1a), lithium titanium oxide, vanadium oxide, lithium vanadium oxide, tin oxide, silicon oxide of formula (SiOj), natural graphite, artificial graphite, soft carbon, hard carbon, mesophase pitch carbide and sintered coke.A1a = at least one Sn, Mg, Mo, Cu, Zn, Ti, Ni, Ca, Fe, V, Pb, Co, Ge, Cd, Hg, Sr, Mn, Al, W or Be;M1a = at least one Mg, Zn, Al, V, Mn, Ga, Cr, Fe, Rh, Ni, In, Co or Mn, where A1a is different from M1a;a, b = greater than 0 to less than 1;b+c+e = 1;e = greater than 0 to less than 0.1;d = 0-0.1;M2a, M6a = at least one Ti, V Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr or B;M3a = at least one Mo, W, Ir, Ni or Mg;x = 0.9-1.1;y = 0-0.9;z = 0-0.5;(1-y-z) = greater than 0;q = 0-2;M4a = at least one Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, Cr, Fe, Mg, Sr, V and rare-earth element;X1a = O, F, S or P;p, r, s, and t = greater than 1 to less than 1;r+s+t = 1;w = 0-0.33;M5a = at least one Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, Cr, Fe, Mg, Sr, V and a rare-earth element;j = greater than 0 to less than 2; andY1a = at least one Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P,As, Sb, Bi, S, Se, Te, and Po.Preferred Method: The dry process comprises a method comprising a planetary ball mill method, a low-speed ball mill method, a high-speed ball mill method, a hybridization method, and a mechanofusion method. The method further comprises heat treating after the forming the surface treatment layer with the dry process to heat treat the surface layer on the core. In the method, a content of the lithium-free oxide is less than or equal to 10 wt.% based on a total weight of the mixture. The lithium-free oxide is prepared by a method comprising: preparing a mixture by milling a lithium-free oxide precursor; and sintering the mixture to prepare a sintered product. The sintering step is performed at 700-1500 degrees C for 12-72 hours. EXAMPLE - Tin oxide and zinc oxide were mixed at a mole ratio of 1:2, and then milled at 300-500 rpm for 5 hours in a planetary ball mill. The obtained product was sintered at 1200 degrees C for 48 hours in air, to obtain tin zinc oxide (SnZn2O4) having a spinel structure, followed by grinding the tin zinc oxide with a paint shaker for 1 hour, to obtain tin zinc oxide nanoparticles with a diameter of 100 nm. Then 3 pts. wt. tin zinc oxide nanoparticles and 97 pts. wt. lithium nickel manganese oxide (LiNi0.5Mn1.5O4) powder with an average particle diameter of 10 mu m were mixed. The obtained mixture was put into a dry type surface treatment device and treated at 6000 rpm for 5 minutes, to obtain cathode active material of which the surface treatment layer including tin zinc oxide was formed on lithium nickel manganese oxide core.