Abstract: A positive electrode for a lithium secondary battery includes a positive electrode collector, a first positive electrode active material layer formed on the positive electrode collector and includes a first positive electrode active material, and a second positive electrode active material layer formed on the first positive electrode active material layer and includes a second positive electrode active material. The first positive electrode active material and the second positive electrode active material include a lithium nickel-cobalt-based oxide in which an amount of nickel among total metallic components excluding lithium is 80 atm % or more, the first positive electrode active material has a molar ratio of nickel to cobalt of 18 or more, and the second positive electrode active material has a molar ratio of nickel to cobalt of less than 18.

Abstract: A positive electrode active material for a lithium secondary battery comprising lithium transition metal oxide particles having a core-shell structure which includes a core portion and a shell portion disposed on a surface of the core portion. Wherein, the average crystallite size of the core portion is smaller than an average crystallite size of the shell portion and an amount of nickel among total transition metals included in the core portion and the shell portion is 80 atm % or more. A positive electrode active material, which suppresses decomposition of an electrolyte solution and occurrence of micro cracks of the positive electrode active material during charge and discharge by forming an average crystallite size of a core portion of the high-nickel positive electrode active material smaller than an average crystallite size of a shell portion, and a method of preparing the same.

Abstract: Disclosed is herein an air hypocaust structure for cooling and/or heating dwellings. In winter, hot air is supplied into a space between an upper and a base plate constituting the air hypocaust structure to heat the dwelling according to a convection and a radiation mechanism. In summer, cold air is supplied to the space between the upper and base plate to cool the dwelling according to the convection mechanism. A plurality of support legs and guide plates are installed between the upper and base plate, and the support legs and guide plates may be integrally formed on the lower side of the upper plate or may be separately produced to be assembled with the upper plate. A hole is formed at a lower end of each of the support legs, and projections each having a sharp tip at an end thereof and corresponding in position to the support legs are formed on the upper side of the base plate.

Abstract: Disclosed is herein an air hypocaust structure for cooling and/or heating dwellings. In winter, hot air is supplied into a space between an upper and a base plate constituting the air hypocaust structure to heat the dwelling according to a convection and a radiation mechanism. In summer, cold air is supplied to the space between the upper and base plate to cool the dwelling according to the convection mechanism. A plurality of support legs and guide plates are installed between the upper and base plate, and the support legs and guide plates may be integrally formed on the lower side of the upper plate or may be separately produced to be assembled with the upper plate. A hole is formed at a lower end of each of the support legs, and projections each having a sharp tip at an end thereof and corresponding in position to the support legs are formed on the upper side of the base plate.