Disclosed are a method for dissolving a single-particle titanite and a method for determining an age of a single-particle titanite by (uranium-thorium)/helium dating, relating to the technical field of mineral isotope chronometry. A dissolution method exclusive to the single-particle titanite is provided. In the method for determining the age of the single-particle titanite by (uranium-thorium)/helium dating, contents of uranium, thorium, and helium are obtained by measuring a same sample, which are then substituted into a (uranium-thorium)/helium age equation to directly obtain an age value.

The present invention provides a halogen-free MXene represented by the following formula (1), that has no halogen in its surface functional group by performing an etching process to generate MXene from a MAX Phase material, and after the etching process, performing an impurity removal treatment process of etching and removing impurities using a halogen-free etchant and a halogen-free post-treatment agent, respectively.

M.sub.n+1X.sub.nT.sub.x[Formula 1] wherein, M is a transition metal element selected from the group consisting of Sc, Ti, V, Cr, Mn, Y, Zr, Nb, Mo, Hf, and Ta, X is at least one of carbon and nitrogen, and n is an integer from 1 to 4, and T.sub.x is a functional group selected from the group consisting of oxygen, alkoxide of 1 to 5 carbon atoms, alkyl, carboxylate, hydroxide, hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide, sulfonate, thiol, and epoxide.

The invention discloses a preparation method of an anode material for lithium-ion batteries, comprising: dispersing tetrabutyl titanate in glycerol solvent and adding hexadecyl trimethyl ammonium bromide solution, adding tetramethylammonium hydroxide to adjust Ph; then adding ammonium fluoride solution, heating at 150-200 C. for 16h, the product was centrifuged, washed, and dried in vacuum to obtain titanium/nitrogen/fluorine-doped porous titanium dioxide; preparing the titanium/nitrogen/fluorine-doped porous titanium dioxide organic solution, and then adding lithium salt solution, then adding graphite, mixing uniformly, and spray drying to obtain porous lithium titanate-coated graphite composites; taking porous lithium titanate-coated graphite composites and ammonium fluoride, placing them in a tube furnace, heating them under the protection of argon, and then heating them up to carbonization. The invention can improve the first-time efficiency of graphite composites and their power performance.

A composite that includes a layered MXene comprising at least two layers, and an amount of a chalcogen confined between the at least two layers. An electrode that includes a composite that includes a layered MXene comprising at least two layers, and an amount of a chalcogen confined between the at least two layers. Power cells that include the composite. A method, comprising: with an intercalant spacer, effecting an increase in an interlayer spacing in a multilayered MXene composition; and effecting intercalation of a chalcogen into the interlayer spacing so as to confine the chalcogen between layers of the multilayered MXene composition, and optionally effecting removal of the intercalant spacer.

The solid electrolyte material consists essentially of Li, Ti, Al, M, and F. Here, M is at least one selected from the group consisting of Zr and Mg.

A negative electrode active material is provided for a lithium ion secondary battery. The negative electrode active battery is represented by a general formula: Li.sub.4Ti.sub.5O.sub.12xM.sub.x wherein the x satisfies 0<x<12, and the element M is an element having an electronegativity lower than that of oxygen.

An embodiment provides a composite positive electrode active material including: a positive electrode active material represented by Chemical Formula 1; and a coating layer on a surface of the positive electrode active material, the coating layer including a compound represented by Chemical Formula 2.

Chemical Formula 1 and Chemical Formula 2 are as described in the specification.

A coated active material of the present disclosure includes: a positive electrode active material; lithium carbonate present on a surface of the positive electrode active material; and a coating layer coating at least a portion of the surface of the positive electrode active material. The coating layer includes a lithium-containing fluoride. When a mass of the lithium carbonate present on the surface of the positive electrode active material is measured by neutralization titration, a proportion R1 of the mass of the lithium carbonate in a mass of the positive electrode active material is 0.43% or more and 1.4% or less.

An electrode material includes a particle group of a coated active material. The coated active material includes an active material and a coating layer coating at least a part of a surface of the active material and including a first solid electrolyte. The electrode material satisfies at least one of the following (i) to (iii). (i) A thickness Tc of the coating layer calculated by averaging median values in thickness distributions of a plurality of particles is 1.0 nm or more and 100.0 nm or less. (ii) A thickness Ta of the coating layer calculated by averaging average values in thickness distributions of a plurality of particles is 9.0 nm or more and 100.0 nm or less. (iii) A thickness Tq of the coating layer calculated by averaging first quartiles in thickness distributions of a plurality of particles is 2.5 nm or more and 50.0 nm or less.

A method for producing a fluoride of the present disclosure includes firing a mixture including a titanium oxide, an aluminum oxide, a raw material fluoride having composition different from that of the fluoride to be produced, and a lithium-containing compound in an inert gas atmosphere. The titanium oxide includes TiO.sub.2. The aluminum oxide includes Al.sub.2O.sub.3. The raw material fluoride includes NH.sub.4F. The lithium-containing compound includes at least one selected from the group consisting of lithium fluoride, lithium carbonate, and lithium nitrate.