A positive electrode active material reduces an eluted lithium amount when used for a nonaqueous electrolyte secondary battery, and a nickel-manganese composite hydroxide as a precursor. A nickel-manganese composite hydroxide contains a secondary particle formed of a plurality of mutually flocculated primary particles and is represented by Formula (1): Ni.sub.x1Mn.sub.y1M.sub.z1(OH).sub.2+ (0.70x10.95, 0.05y10.30, x1+y1+z1=1.0, and 00.4 are satisfied; and M is at least one element selected from Co, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Fe, and W). The nickel-manganese composite hydroxide has a manganese-rich layer from a particle surface to a particle inner part of the secondary particle. The manganese-rich layer is represented by Formula (2): Ni.sub.x2Mn.sub.y2M.sub.z2(OH).sub.2+. The thickness of the manganese-rich layer is at least 5% and up to 20% of the radius of the secondary particle.

The present invention industrially provides: a non-aqueous electrolyte secondary battery having a high energy density and high cycling characteristics; a cathode active material for a non-aqueous electrolyte secondary battery having a high packing efficiency; and a nickel manganese containing composite hydroxide having a small particle size, a narrow particle size distribution, and a high sphericity. When producing the nickel manganese containing composite hydroxide by a crystallization reaction using material solution where metal compounds including nickel and manganese dissolve, a nucleation process is performed in a non-oxidizing atmosphere by stirring an aqueous solution for nucleation, that includes the quantity of the material solution corresponding to 0.6% to 5.0% of the whole amount of substance of metal element included in a metal compound used for the overall crystallization reaction.

Provided are a hydrotalcite substance composition having excellent dispersibility, and an additive using the hydrotalcite substance composition. The hydrotalcite substance composition of the present invention contains a hydrotalcite substance and a surface treatment agent containing an organic compound. The hydrotalcite substance is in a state in which at least part thereof is coated with the surface treatment agent. The amount of an extract to be extracted from the composition by hot toluene treatment is 1 wt % or less with respect to the composition, and the content of calcium in the extract is 500 ppm or less with respect to the weight of the composition.

A hydrotalcite is represented by formula (1):

(M.sup.2+).sub.1-X(M.sup.3+).sub.X(OH).sub.2(A.sup.n).sub.X/n.mH.sub.2O(1), wherein M.sup.2+ indicates a divalent metal, M.sup.3+ indicates a trivalent metal, A.sup.n indicates an n-valent anion, n indicates an integer of 1 to 6, 0.17x0.36, and 0m10. The hydrotalcite has (A) a lattice strain in the <003> direction is 310.sup.3 or less as measured using an X-ray diffraction method; (B) primary particles with an average width between 5 nm and 200 nm inclusive per a SEM method; and (C) a degree of monodispersity of 50% or greater (degree of monodispersity (%)=(average width of primary particles as measured using the SEM method/average width of secondary particles as measured using a dynamic light scattering method)100). A resin containing the hydrotalcite, a suspension containing the hydrotalcite and a method for producing the hydrotalcite are disclosed.

New layered double hydroxide materials useful as intermediates in the formation of catalysts are described, as well as methods of preparing the layered double hydroxides. Also described are catalysts suitable for catalysing the hydrogenation of CO.sub.2 to methanol, as well as methods for preparing the catalysts. The LDH-derived catalysts of the invention are active in the hydrogenation of CO.sub.2 to methanol, and show improved activity with respect to Cu/ZnO catalysts derived from copper-zinc hydroxycarbonate precursors.

A lithium-manganese composite oxide containing a lithium-iron-manganese composite oxide represented by the composition formula: Li.sub.1+xw(Fe.sub.yNi.sub.zMn.sub.1yz).sub.1xO.sub.2, where 0<x<, 0w<0.8, 0<y<1, 0<z<0.5, y+z<1, and 0<0.5, in which at least in a state of charge of a lithium ion battery using the lithium-manganese composite oxide as a positive-electrode active material, at least some of iron atoms are pentavalent.

To provide an inorganic solid material that has a hydrogen sulfide sustained releasability at ordinary temperature in the air atmosphere and is capable of being handled safely and a method for producing the same, and a method for generating hydrogen sulfide using the material. A layered double hydroxide having HS? and/or Sk2? (wherein k represents a positive integer) intercalated among layers (sulfide ion-containing LDH) is produced, and the sulfide ion-containing LDH is hermetically housed in a packaging material to provide a package. In generating hydrogen sulfide, the packaging material of the package is opened, and the sulfide ion-containing LDH is exposed to the air atmosphere to sustainably release hydrogen sulfide.

A layered double hydroxide is represented by the following formula (I): Ni.sup.2+.sub.1?(x+y+z)Fe.sup.3+.sub.xV.sup.3+.sub.yCo.sup.3+.sub.z(OH).sub.2A.sup.n?.sub.(x+y+z)/n.Math.mH.sub.2O . . . (I). In one embodiment, in the formula (I), (x+y+z) is from 0.2 to 0.5, x represents more than 0 and 0.3 or less, y represents from 0.04 to 0.49, and z represents more than 0 and 0.2 or less.

The present disclosure provides a universal preparation method for in-situ growth of a layered double hydroxide (LDH) layer on a substrate surface, and belongs to the technical field of material synthesis. In the present disclosure, an LDH protective layer is grown in situ on a surface of a substrate by means of electrodeposition combined with hydrothermal treatment. Specifically, a seed crystal layer of the LDH is formed on the substrate surface by the electrodeposition, and then obtained LDH seed crystals are crystallized and grown by Ostwald ripening through the hydrothermal treatment. In this way, the LDH protective layer is formed in which an interlayer anion is a nitrate. The protective layer protects the substrate against corrosion. Moreover, since the interlayer anion is the nitrate, the protective layer can be exchanged with other corrosion-inhibiting anions, and is modifiable.

A layered double hydroxide (LDH) material, methods for using the LDH material to catalyse the oxygen evolution reaction (OER) in a water-splitting process and methods for preparing the LDH material. The LDH material includes nickel, iron and chromium species and possesses a sheet-like morphology including at least one hole.