Layered double hydroxides having a high surface area (at least 125 m.sup.2/g) and the formula (I)

[M.sup.z+.sub.1-xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n-).sub.a/n.sup.+bH.sub.2O.c(AMO-solvent)(I)

wherein M and M are different and each is a charged metal cation (and must be present), z=1 or 2; y=3 or 4, 0<x<0.9, b is 0 to 10, c=0 to 10, X is an anion, n is the charge on the anion, and a=z(1x)+xy2; AMO-solvent is aqueous miscible organic solvent, may be prepared by a method which comprises a) precipitating a layered double hydroxide having the formula

[M.sup.z+.sub.1-xM.sup.y+.sub.x(OH).sub.2].sup.a+(X.sup.n-).sub.a/n.sup.+bH.sub.2O wherein M, M, z, y, x, a, b and X are as defined above from a solution containing the cations of the metals M and M and the anion X.sup.n-; b) ageing the layered double hydroxide precipitate obtained in step a) in the original solution; c) collecting, then washing the layered double hydroxide precipitate; d) dispersing the wet layered double hydroxide in an AMO solvent so as to produce a slurry of the layered double hydroxide in the solvent; e) maintaining the dispersion obtained in step d); and f) recovering and drying the layered double hydroxide.

The high surface area products have low particle size and are particularly suitable for use as catalysts, catalyst supports, sorbents and coatings.

Separators, electrochemical cells and methods are provided, to improve operation of cells such as metal-ion batteries and fuel cells. Separators comprise a porous, ionically conductive film including layered double hydroxide(s) (LDHs), which are functional ceramic additives, removing potentially harmful anions from the electrolyte by incorporating them into the LDH structure of positively-charged sheets with intermediary anions. For example, anions which are electrolyte decomposition products or cathode dissolution products may be absorbed into the LDH to prevent them from causing damage to the cell and shortening the cell's life. LDHs may be incorporated in the separator structure, coated thereupon or otherwise associated therewith. Additional benefits include dimensional stability during thermal excursions, fire retardancy and impurity scavenging.

This invention is directed to regeneration of solutions comprising metal ions, and production of valuable hydroxide compounds. Specifically, the invention is related to regeneration of spent electrolyte solutions comprising metal ions (e.g. Al ions), such as electrolyte solutions used in metal/air batteries. The invention is further related to production of layered double hydroxides, and, optionally aluminum tri-hydroxide from aluminate.

A method of removing hydrogen sulfide from a subterranean geological formation includes injecting a drilling fluid suspension in the subterranean geological formation. The drilling fluid suspension has a pH of 10 or more and includes a layered triple hydroxide material, including manganese, cobalt, and iron, in an amount of 0.01 to 0.5 percent by weight of the drilling fluid suspension. The method further includes circulating the drilling fluid suspension in the subterranean geological formation and forming a water-based mud and scavenging the hydrogen sulfide from the subterranean geological formation by reacting the hydrogen sulfide with the layered triple hydroxide material in the water-based mud.

Exemplary layered double hydroxides (LDHs) may comprise a compound of formula Mg.sub.4yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01y1. Exemplary layered double hydroxide hydrogels (LDH-gels) may comprise a hydrogel and at least one LDH. Exemplary hydrogels may comprise polyethylene (glycol) diacrylate (PEGDA) or polyacrylamide (PAAm). Exemplary LDH-gels may comprise at least one LDH comprising a compound of formula Mg.sub.4yAlX.sub.y(OH).sub.2, wherein X is Mn.sup.+2, Cu.sup.+2, Zn.sup.+2, or Fe.sup.+2, and 0.01y1.

Provided is a water-swelling layered double hydroxide characterized by having an organic sulfonic acid anion (A.sup.) between layers, and by being represented by the below mentioned general formula (1): Q.sub.ZR(OH).sub.2(Z+1)(A.sup.).sub.(1y)(X.sup.n).sub.y/n.mH.sub.2O . . . (1). Here, Q is a divalent metal, R is a trivalent metal, A.sup. is an organic sulfonic acid anion, m is a real number greater than 0, and z is in the range of 1.8z4.2. X.sup.n is the n-valent anion remaining without A.sup. substitution, n is 1 or 2, y represents the remaining portion of X.sup.n, and 0y<0.4.

The present invention relates to a process A process for modifying a layered double hydroxide (LDH), the process comprising, a. providing a material comprising a layered double hydroxide of formula: [M.sup.z+.sub.1-xM.sup.y+.sub.x(OH).sub.2].sup.q+(X.sup.n).sub.q/n.bH.sub.2O wherein M and M are metal cations, z is 1 or 2, x is 0.1 to 1, b is 0 to 5, y is 3 or 4, X is an anion, n is 1 to 3 and q is determined by x, y and z, b. optionally washing the material at least once with a mixture of water and a mixing solvent miscible with water, and c. washing the material obtained in step a or b at least once with at least one first solvent, the first solvent being miscible with water and having a solvent polarity P

One embodiment of the present invention provides a positive electrode active material for a sodium secondary battery, including P2-type layered oxide particles and O3-type layered oxide particles, wherein in SEM-EDS mapping analysis, an atomic ratio (S3/S2) of a surface Na content (at %) (S3) of the O3-type layered oxide particles to a surface Na content (at %) (S2) of the P2-type layered oxide particles is 0.4 to 1.6.

The disclosure relates to a positive electrode active material. The positive electrode active material having a crystalline structure in which a transition metal layer containing nickel and a lithium layer are alternately arranged, wherein an a/b axial length ratio calculated by Rietveld analysis of a radiation XRD is 0.8 or more.

The positive electrode active material powder of the present disclosure is used in a lithium secondary battery. The positive electrode active material powder is a positive electrode active material powder of a lithium secondary battery including a plurality of particles composed of a lithium transition metal oxide having a layered crystal structure. The thickness of the transition metal layers included in the lithium transition metal oxide is 2.06 to 2.19 . The thickness is calculated by Rietveld analysis using the emission X-ray diffractogram profile of the particle.