A lead-free piezoelectric ceramic composition which includes a primary phase formed of an alkali niobate-based perovskite oxide represented by a compositional formula (A1.sub.aM1.sub.b).sub.c(Nb.sub.d1, Mn.sub.d2, M2.sub.d3)O.sub.3+e (in which element A1 represents at least one species among the alkali metals; element M1 represents at least one species among Ba, Ca, and Sr; element M2 represents at least one species of Ti and Zr; the following conditions: 0<a<1, 0<b<1, a+b=1, 0.80<c<1.10, 0<d1<1, 0<d2<1, 0<d3<1, and d1+d2+d3=1, are satisfied; and e represents a value showing the degree of deficiency or excess of oxygen) and which satisfies the condition: b/(d2+d3)>1.0.

A method for producing lithium manganese oxide that is a precursor of a lithium adsorbent under atmospheric pressure is provided. The method for producing a precursor of a lithium adsorbent comprises the following steps (1) to (3): (1) A 1.sup.st mixing step of mixing a manganese salt and alkali hydroxide, so as to obtain a 1.sup.st slurry containing manganese hydroxide; (2) a 2.sup.nd mixing step of adding lithium hydroxide to the 1.sup.st slurry and then mixing the mixture to obtain a 2.sup.nd slurry; and (3) an oxidation step of adding an oxidizing agent to the 2.sup.nd slurry, so as to obtain a precursor of a lithium adsorbent. The method for producing a precursor of a lithium adsorbent comprises these steps, so that a precursor of a lithium adsorbent can be produced under atmospheric pressure. Therefore, a precursor of a lithium adsorbent can be produced at a limited cost.

A method for producing manganese(II) sulfate monohydrate includes a pulverization and washing step of pulverizing and washing a manganese-containing by-product, a leaching step of leaching the pulverized manganese-containing by-product after the pulverization and washing step to produce a leachate, a neutralization step of neutralizing the leachate produced in the leaching step, an impurity removal step of removing impurities from the leachate neutralized in the neutralization step, a solvent extraction step of recovering manganese in the form of an aqueous solution of manganese sulfate from a process liquid subjected to the impurity removal step by using a solvent extraction method, and a crystallization step of producing manganese(II) sulfate monohydrate by evaporating and concentrating the aqueous solution of manganese sulfate produced in the solvent extraction step.

A compound containing Sn, Te and Mn, and further containing either one or both of Sb and Bi.

Provided are a positive electrode active material and a preparation method thereof, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric apparatus. The positive electrode active material includes a core including Li.sub.1+xM.sub.n1?yA.sub.yP.sub.1?z,R.sub.zO.sub.4, a first coating layer enveloping the core and containing a crystalline pyrophosphate Li.sub.aMP.sub.2O.sub.7 and/or Mb(P.sub.2O.sub.7).sub.e, a second coating layer enveloping the first coating layer and containing a crystalline oxide M.sub.dO.sub.e, and a third coating layer enveloping the second coating layer and containing carbon. The positive electrode active material of this application can reduce Li/Mn anti-site defects generated, reduce dissolving-out amount of manganese, lower the lattice change rate, increase the capacity of the secondary battery, and improve the cycling performance, high-temperature storage performance, and safety performance of the secondary battery.

A transition metal composite hydroxide can be used as a precursor to allow a lithium transition metal composite oxide having a small and highly uniform particle diameter to be obtained. A method also is provided for producing a transition metal composite hydroxide represented by a general formula (1) MxWsAt(OH)2+, coated with a compound containing the additive element, and serving as a precursor of a positive electrode active material for nonaqueous electrolyte secondary batteries. The method includes producing a composite hydroxide particle, forming nuclei, growing a formed nucleus; and forming a coating material containing a metal oxide or hydroxide on the surfaces of composite hydroxide particles obtained through the upstream step.

A transition metal composite hydroxide can be used as a precursor to allow a lithium transition metal composite oxide having a small and highly uniform particle diameter to be obtained. A method also is provided for producing a transition metal composite hydroxide represented by a general formula (1) MxWsAt(OH)2+, coated with a compound containing the additive element, and serving as a precursor of a positive electrode active material for nonaqueous electrolyte secondary batteries. The method includes producing a composite hydroxide particle, forming nuclei, growing a formed nucleus; and forming a coating material containing a metal oxide or hydroxide on the surfaces of composite hydroxide particles obtained through the upstream step.

A cathode composition for a sodium-ion battery. The cathode composition may have the formula NaCr.sub.1-xM.sub.xO.sub.2, where M is one or more metal elements, and x is greater than 0 and less than or equal to 0.5.

A nitrogen oxide (NOx) reduction catalyst that includes a transition metal tungstate having the formula: MWO.sub.4 wherein M is selected from the group consisting of Mn, Fe, Co, Ni, and Cu. The catalyst may be utilized in various environments including oxygen rich and oxygen deficient environments.

A nitrogen oxide (NOx) reduction catalyst that includes a transition metal tungstate having the formula: MWO.sub.4 wherein M is selected from the group consisting of Mn, Fe, Co, Ni, and Cu. The catalyst may be utilized in various environments including oxygen rich and oxygen deficient environments.