A positive electrode active material for a sodium secondary battery includes a sodium composite transition metal oxide represented by Formula 1 and having a P3 crystal structure, and a positive electrode and a sodium secondary battery which include the positive electrode active material.

Na.sub.x[Li.sub.aM.sub.1-a]O.sub.2[Formula 1]

wherein M is at least one transition metal, 0.64x0.7, and 0.01a0.1.

An object of the present invention is to provide ferrite particles for a filtering medium excellent in filtration ability having a small apparent density, capable of various properties maintained in the controllable state and filling a specified volume with a small amount, and a filtering medium made from the ferrite particles. In order to achieve the object, ferrite particles provided an outer shell structure containing Ti oxide for a filtering medium, and a filtering medium made from the ferrite particles are employed.

The present invention relates to H.sub.2S removal that may be contained in biogas or industrial process gases in concentrations of 35-15000 ppm. By means of nanoparticles of manganese ferrite MnxFe.sub.3-xO.sub.4 with x=0%, 0.1%, 0.3% and 0.5%, obtained by means of chemical co-precipitation from solutions of chlorides and at a temperature below 100 C. With surface area of 142-240 m.sup.2/g and particle size of 7-9 nm. And that is done through a set of components such as: pressure regulating valve, a flow meter, a piston flow rector, a pressure gauge, a three-way valve, a biogas measuring device, a gas scrubber and a burner biogas.

An object is to provide the ferrite particles used as a magnetic filler or a raw material for a molded product excellent in dispersibility as a powder and excellent in uniformity after molding and result the surface with small unevenness; and a method of manufacturing the particles. To achieve the object, MnMg ferrite particles having an average particle size of 1 to 2000 nm and having a spherical shape are employed. It is preferable that the ferrite particles are produced by a method including subjecting of a ferrite raw material obtained through preparation of a ferrite composition to flame-spraying in air for ferritization followed by rapid cooling for solidifying of the ferrite.

Provided are a positive active material for use in a sodium-ion battery, a method for preparing same, a positive electrode plate containing same, a sodium-ion battery, and an electrical device. The method for preparing a positive active material for use in a sodium-ion battery includes the following steps: mixing a positive active material for use in a sodium-ion battery with, and causing the positive active material to react with, a washing solution at a temperature of T1, and filtering and drying a product of the reaction to obtain a washed positive active material for use in a sodium-ion battery, where the washing solution is deionized water or an acidic solution with a pH value lower than 7.0, and 0 C.T1<20 C.

Thermochemical storage materials having the general formula A.sub.xA.sub.1-xB.sub.yB.sub.1-yO.sub.3-, where A=La, Sr, K, Ca, Ba, Y and B=Mn, Fe, Co, Ti, Ni, Cu, Zr, Al, Y, Cr, V, Nb, Mo, are disclosed. These materials have improved thermal storage energy density and reaction kinetics compared to previous materials. Concentrating solar power thermochemical systems and methods capable of storing heat energy by using these thermochemical storage materials are also disclosed.

The present invention is directed to a method for generating oxygen comprising providing at least one oxygen source, providing at least one ionic liquid, providing at least one metal oxide compound, wherein the oxygen source is a peroxide compound, the ionic liquid is in the liquid state at least in the temperature range from 10 C. to +50 C., and the metal oxide compound is an oxide of one single metal or of two or more different metals, said metal(s) being selected from the metals of groups 2 to 14 of the periodic table of the elements, and contacting the oxygen source, the ionic liquid, and the metal oxide compound.

A positive electrode active material for a sodium-ion secondary battery contains a compound of formula Na.sub.xMn.sub.1-y-zM.sub.yM.sub.zO.sub.2 or its hydrate. A cathode can contain the active material and rechargeable sodium-ion battery can contain such a cathode.

A carrier core material is represented by a composition formula M.sub.XFe.sub.3-XO.sub.4 (where M is at least one type of metal element selected from Mg, Mn, Ca, Ti, Cu, Zn and Ni, 0<X<1), in which part of M and/or Fe is substituted with Sr and formed of ferrite particles, and in the carrier core material, a Sr content is equal to or more than 2500 ppm but equal to or less than 12000 ppm, the amount of Sr eluted with pure water at a temperature of 25 C. is equal to or less than 50 ppm, an apparent density is equal to or more than 1.85 g/cm.sup.3 but equal to or less than 2.25 g/cm.sup.3 and magnetization .sub.1k when a magnetic field of 79.5810.sup.3 A/m (1000 oersteds) is applied is equal to or more than 63 Am.sup.2/kg but equal to or less than 75 Am.sup.2/kg.

A process for preparing a stable Group VIII Period 4 element (iron, cobalt, or nickel) B site and chlorine O site modified lithium manganese-based AB.sub.2O.sub.4 spinel cathode material is provided. The general formula of the B and O site modified lithium manganese-based AB.sub.2O.sub.4 spinel is LixMn.sub.2-yM.sub.yO.sub.4-z(Cl.sub.z) where M is Fe, Co or Ni. In addition, a Group VIII Period 4 element (iron, cobalt, or nickel) B site and chlorine O site modified lithium manganese-based AB.sub.2O.sub.4 spinel cathode material is provided. Furthermore, a lithium or lithium ion rechargeable electrochemical cell is provided, incorporating the Group VIII Period 4 element (iron, cobalt, or nickel) B site and chlorine O site modified lithium manganese-based AB.sub.2O.sub.4 spinel cathode material in a positive electrode.