▎ 摘　　要

NOVELTY - A lithium secondary battery comprises cathode, anode, electrolyte, and separator, where cathode includes a cathode active material comprising a central portion (I) and a surface portion (II) in the order from an inside to an outside, and a conductive material comprising a carbon large surface area structure and a carbon small surface area structure. Central portion has a constant concentration region which has a radius of equal to or greater than 0.6 microm from the center of the cathode active material. USE - A lithium secondary battery for electric vehicle, hybrid electric vehicle, mobile phone, notebook, personal digital assistant (PDA), etc. ADVANTAGE - The lithium secondary battery has excellent stability and high low-temperature characteristic and high output characteristic. The cathode active material has a section where the transition metal has a difference in concentration from the central portion to the surface portion, maintaining high capacity, high energy density, and heat stability and simultaneously improving discharge capacity at a low temperature, such that the cathode active material may have excellent characteristics. The electrolyte impregnated in the electrode assembly may be a general aqueous or non-aqueous electrolyte capable of smoothly conducting lithium ions involved in charging and discharging of the battery and stably maintaining battery characteristics for a long period of time in conventional lithium secondary batteries. DETAILED DESCRIPTION - A lithium secondary battery comprises cathode, anode, electrolyte, and separator, where cathode includes a cathode active material comprising a central portion of formula LiM1x1M2y1M3z1Ow (I) and a surface portion of formula LiM1x2M2y2M3z2Ow (II) in the order from an inside to an outside, and a conductive material comprising a carbon large surface area structure and a carbon small surface area structure. Central portion has a constant concentration region in which each of M1 concentration and M3 concentration is constant in a direction from the center of the cathode active material to the surface portion, and constant concentration region has a radius of equal to or greater than 0.6 microm from the center of the cathode active material. Cathode active material comprises a concentration gradient region in which M1 concentration continuously decreases and M3 concentration continuously increases in a direction from the end of the constant concentration region to the surface portion. M1-M3=Ni, Co, Mn, Fe, Na, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, and/or B; x1, x2=0.75-9; y1, y2=0-0.2; z1, z2=0.01-0.2; w=0-3; x1+y1+z1=0-1; and x2+y2+z2=0-1, where x2less than or equal tox1, y1less than or equal toy2, and z1less than or equal toz2.