An oxygen generating electrode includes: an oxide film having a perovskite structure; an organic film over the oxide film; and a conductive film electrically coupled to the organic film, wherein the organic film contains an amino acid having a side chain of negative polarity.

A cathode configured to use oxygen as a cathode active material includes: a porous film including a metal oxide, where a porosity of the porous film is about 50 volume percent to about 95 volume percent, based on a total volume of the porous film, and an amount of an organic component in the porous film is 0 to about 2 weight percent, based on a total weight of the porous film.

A solid electrolyte assembly is obtained by joining a solid electrolyte layer having oxide ion conductivity and containing lanthanum and a first electrode layer made of an oxide that is represented by ABO.sub.3−δ and has a cubic perovskite structure to each other, where A represents an alkaline-earth metal element, B represents a transition metal element, and δ represents a fraction that occurs depending on the valences and amounts of A, B, and O. The oxide contains lanthanum at a part of the A site, and an atom ratio of lanthanum to all the elements occupying the A site is 0.01 or greater and 0.80 or less.

A positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. The primary particles include a lithium-containing composite metal oxide. Inside the secondary particles, an electron conducting oxide is disposed at at least a part of a grain boundary between the primary particles. The electron conducting oxide has a perovskite structure.

The present invention provides a positive electrode active material for a secondary battery, the positive electrode active material including a lithium composite metal oxide particle represented by Formula 1 below, and a secondary battery including the same.
Li.sub.aNi.sub.1xyCo.sub.xM1.sub.yM2.sub.zM3.sub.wO.sub.2[Formula 1] In Formula 1, M1 is a metal element whose surface energy (E.sub.surf) calculated by Equation 1 below is 0.5 eV or higher, M2 is a metal element whose surface energy (E.sub.surf) calculated by Equation 1 below is 1.5 eV or higher and less than 0.5 eV, M3 is a metal element whose surface energy (E.sub.surf) calculated by Equation 1 below is less than 1.5 eV, and 1.0a1.5, 0<x0.5, 0<z0.05, 0.002w0.1, 0<x+y0.7. $\begin{array}{c}\begin{array}{c}{E}_{\mathrm{surf}}=E_{\mathrm{surf}2}-E_{\mathrm{surf}1}\\ =(E_{\mathrm{slab}}\end{array}\end{array}$

Disclosed herein are doped perovskite oxides. The doped perovskite oxides may be used as a cathode material in an electrochemical cell to electrochemically generate ammonia from N.sub.2. The doped perovskite oxides may be combined with nitride compounds, for instance iron nitride, to further increase the efficiency of the ammonia production.

An objective of the present invention is to provide a positive electrode active material that can inhibit the capacity changes associated with temperature variations, and an alkaline battery that contains this positive electrode active material. Aluminum and ytterbium are at least partially solid-dissolved in nickel hydroxide in the nickel composite hydroxide present in the positive electrode active material of the present invention.

A composition consisting essentially of a perovskite crystalline structure, the composition comprising: ions of a first metal M.sup.1 which occupies an A-site of the perovskite crystalline structure; ions of a second metal M.sup.2 which occupies a B-site of the perovskite crystalline structure, M.sup.2 having two oxidation states capable of forming a redox couple suitable for reversibly catalyzing an oxygen reduction reaction (ORR) and an oxygen evolution reaction (OER); ions of a third metal M.sup.3 at least a portion of which substitutes for M.sup.1 in the A-site of the perovskite crystalline structure, and at least a portion of which optionally also substitutes for M.sup.2 in the B-site of the perovskite crystalline structure, at least some of the atoms M.sup.3 having a different oxidation state to the atoms M.sup.1; and atoms of an element X, which is a chalcogen; wherein the metal ions M.sup.1, M.sup.2 and M.sup.3 are present in the atomic ratios (a) or (b): (a) 25 to 49.9 atomic % M.sup.1, 30 to 60 atomic % M.sup.2, and 5 to 45 atomic % M.sup.3; (b) 10 to 30 atomic % M.sup.1, 50.1 to 60 atomic % M.sup.2, and 25 to 45 atomic % M.sup.3; each expressed as a percentage of the total metal ions in the composition excluding oxygen; wherein the presence of the M.sup.3 ions causes a change in the oxidation state of some of the M.sup.2 ions in the structure, thereby creating the redox couple suitable for reversibly catalyzing the ORR and OER.

Provided are a method of preparing a positive electrode active material for a secondary battery, in which the positive electrode active material is uniformly doped with various doping elements without worrying about surface damage of the active material and characteristics degradation by including mixing a metal precursor for a positive electrode active material and a raw material including a doping element, in which an average particle diameter ratio is in a range of 5:1 to 2,000:1, using acoustic resonance to prepare a precursor doped with the doping element, and mixing the doped precursor with a lithium raw material and performing a heat treatment, and a positive electrode active material which has improved structure stability by being prepared by the above method and may improve battery characteristics, for example, capacity reduction may be minimized and cycle characteristics may be improved when used in the battery.

A perovskite material represented by Formula 1:

Li.sub.xA.sub.yM.sub.zO.sub.3-Formula 1 wherein in Formula 1, 0<x1, 0<y1, 0<x+y<1, 0<z1.5, 01, A is H, Na, K, Rb, Cs, Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, or a combination thereof, and M is Ni, Pd, Pb, Fe, Ir, Co, Rh, Mn, Cr, Ru, Re, Sn, V, Ge, W, Zr, Mo, Hf, U, Nb, Th, Ta, Bi, Li, H, Na, K, Rb, Cs, Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Mg, Al, Si, Sc, Zn, Ga, Ag, Cd, In, Sb, Pt, Au, or a combination thereof.