Substituted ramsdellite manganese dioxide (RMnO.sub.2) compounds are provided, where a portion of the Mn is replaced by at least one alternative cation, or a portion of the O is replaced by at least one alternative anion. Electrochemical cells incorporating substituted RMnO.sub.2 into the cathode, as well as methods of preparing the substituted RMnO.sub.2, are also provided.

A sintered pelletized catalyst precursor comprising iron oxides, including haematite, and Cr.sub.2O.sub.3 and optionally one or more of Al.sub.2O.sub.3, ZnO, MnO.sub.2, MgO, and/or CuO, the pelletized catalyst precursor having an iron oxide content of 60 wt % to 95 wt %, when expressed as Fe.sub.2O.sub.3, and a Cr(VI) content of less than 0.1 wt %, is physically stable on ignition or when subjected to a reducing gas sufficient to reduce the haematite to magnetite.

A sintered pelletized catalyst precursor comprising iron oxides, including haematite, and Cr.sub.2O.sub.3 and optionally one or more of Al.sub.2O.sub.3, ZnO, MnO.sub.2, MgO, and/or CuO, the pelletized catalyst precursor having an iron oxide content of 60 wt % to 95 wt %, when expressed as Fe.sub.2O.sub.3, and a Cr(VI) content of less than 0.1 wt %, is physically stable on ignition or when subjected to a reducing gas sufficient to reduce the haematite to magnetite.

Provided are a positive electrode active material for nonagueous secondary batteries, the material having a narrow particle-size distribution and a monodisperse property and being capable of increasing a battery capacity; an industrial production method thereof; and a nonaqueous secondary battery using the positive electrode active material and having excellent electrical characteristics. The positive electrode active material is represented by a general formula: Li.sub.1+uNi.sub.xCo.sub.yMn.sub.zM.sub.tO.sub.2+ (wherein, 0.05u0.95, x+y+z+t=1, 0x0.5, 0y0.5, 0.5z<0.8, 0t0.1, and M is an additive element and at least one element selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W), has an average particle diameter of 3 to 12 um, and has [(d.sub.90d.sub.10)/average particle diameter], an index indicating a scale of particle-size distribution, of 0.60 or less.

Provided are a positive electrode active material for nonagueous secondary batteries, the material having a narrow particle-size distribution and a monodisperse property and being capable of increasing a battery capacity; an industrial production method thereof; and a nonaqueous secondary battery using the positive electrode active material and having excellent electrical characteristics. The positive electrode active material is represented by a general formula: Li.sub.1+uNi.sub.xCo.sub.yMn.sub.zM.sub.tO.sub.2+ (wherein, 0.05u0.95, x+y+z+t=1, 0x0.5, 0y0.5, 0.5z<0.8, 0t0.1, and M is an additive element and at least one element selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W), has an average particle diameter of 3 to 12 um, and has [(d.sub.90d.sub.10)/average particle diameter], an index indicating a scale of particle-size distribution, of 0.60 or less.

A process of forming a coated cathode active material include preparing a cathode material precursor by co-precipitation; coating the cathode material precursor with an electrochemically inert coating material precursor by precipitation to form a coated cathode material precursor; lithiating the coated cathode material precursor with a lithium source material to form a lithiated coated cathode material precursor; and sintering the lithiated coated cathode material precursor to form a cathode active material coated with an electrochemically inert material.

A method of fabricating a metal oxide film includes sequentially laminating a carbon film and a metal oxide film including nano-sized metal oxide nanoparticles on a porous fuel membrane to form a preliminary composite structure and reducing the metal oxide film to form a composite structure by combusting the porous fuel membrane while applying a voltage to the preliminary composite structure.

A method of fabricating a metal oxide film includes sequentially laminating a carbon film and a metal oxide film including nano-sized metal oxide nanoparticles on a porous fuel membrane to form a preliminary composite structure and reducing the metal oxide film to form a composite structure by combusting the porous fuel membrane while applying a voltage to the preliminary composite structure.

A method for preparing a cathode active material is provided. The method for preparing a cathode active material can comprise the steps of: preparing a first metal oxide; preparing a second metal oxide having an oxygen ratio lower than that of the first metal oxide by heat treating the first metal oxide in a nitrogen-containing gas atmosphere; and preparing a lithium metal oxide by firing the second metal oxide and a lithium salt.

A respiratory protection filter includes filtration media. The filtration media includes an iron-doped manganese oxide material having an average pore size (BJH method) in a range from 1 to 4 nm and a surface area (BET) of at least 300 m.sup.2/g, or at least 350 m.sup.2/g, or at least 400 m.sup.2/g.