A novel titanate aqueous solution is provided that is capable of easily preparing titanate compounds composed of alkali metals or alkaline earth metals, wherein the titanate aqueous solution contains titanate ions and quaternary ammonium cations in water, and the titanate aqueous solution is characterized in that 30 g of the titanate aqueous solution (25° C.) adjusted to a concentration containing 9% by mass of titanium in terms of TiO.sub.2 is added with 30 mL of a sodium hydroxide aqueous solution (25° C.) having a concentration of 2.2% by mass while stirring to form a precipitate composed of Na.sub.2Ti.sub.3O.sub.7 hydrate, or has a transmittance at a wavelength of 360 nm being 50% or less.

According to one embodiment, a negative electrode is provided. The negative electrode includes a negative electrode active material-containing layer including a niobium titanium composite oxide and a sulfur-containing coating. Spectral data obtained by X-ray photoelectron spectroscopy on the surface of the negative electrode active material-containing layer includes a first peak with a peak top existing in the range of 208 eV to 210 eV and a second peak with a peak top existing in the range of 160 eV to 165 eV. The ratio (P2/P1) of the peak height P2 of the second peak to the peak height P1 of the first peak falls within the range of 0.05 to 2.

A mixed conductor represented by Formula 1:
A.sub.4+xM.sub.5-yM′.sub.yO.sub.12-δ,  Formula 1
wherein, in Formula 1, A is a monovalent cation, M is at least one of a divalent cation, a trivalent cation, or a tetravalent cation, M′ is at least one of a monovalent cation, a divalent cation, a trivalent cation, a tetravalent cation, a pentavalent cation, or a hexavalent cation, M and M′ are different from each other, and 0.3≤x<3, 0.01<y<2, and 0≤δ≤1 are satisfied.

An electrochemical energy storage device is provided. The device may include a solid-state anode layer. The device may comprise a solid-state electrolyte layer. Further, the device may comprise a solid-state cathode layer. At least two adjacent ones out of the solid-state anode layer, the solid-state electrolyte layer, and the solid-state cathode layer may form a solid-state single-crystal with varying chemical compositions between the related layers. The solid-state electrolyte layer may have an ionic conductivity at room temperature higher than 10.sup.−6 S/cm.

The present invention relates to a method for producing potassium titanate, and the present invention provides a method for producing potassium titanate which uses anatase-phased titanium dioxide to simplify the process by a hydrothermal method, and thus may improve economical efficiency and productivity, and in which the reaction temperature, the reaction time and the molar ratio of a precursor may be controlled to produce a high-purity potassium titanate whisker having a nano size of an uniform shape.

This document describes processes for preparing ceramics, especially lithium-based ceramics. The ceramics produced by this process and their use in electrochemical applications are also described as well as electrode materials, electrodes, electrolyte compositions, and electrochemical cells comprising them.

A solid electrolyte including: an oxide represented by Formula 1, Formula 2, Formula 3, or a combination thereof,

Li.sub.2+4xM1.sub.1−xO.sub.3  Formula 1

wherein, in Formula 1, M1 is hafnium, titanium, zirconium, or a combination thereof, and 0<x<1;

Li.sub.2−y(a−4)M1.sub.1−yM2.sup.a.sub.yO.sub.3  Formula 2

wherein, in Formula 2, M1 is hafnium, titanium, zirconium, or a combination thereof, M2 is at least one element having an oxidation number of a, and wherein a is an integer from 1 to 6, and 0<y<1; or

Li.sub.2−zM1O.sub.3−zX.sub.z  Formula 3

wherein, in Formula 3, M1 is hafnium, titanium, zirconium, or a combination thereof, X is a halogen, a pseudohalogen, or a combination thereof, and 0<z<2.

The present invention provides a lithium titanate powder for an electrode of an energy storage device, the lithium titanate powder comprising Li.sub.4Ti.sub.5O.sub.12 as a main component, having a specific surface area of 4 m.sup.2/g or more, and containing at least one localized element selected from the group consisting of boron (B), Ln (where Ln is at least one metal element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Hb, Er, Tm, Yb, Lu, Y, and Sc), and M1 (where M1 is at least one metal element selected from W and Mo), wherein boron (B), Ln, and M1 as the localized element are localized on or near surfaces of lithium titanate particles forming the lithium titanate powder.

The present invention relates to a lithium-titanium complex oxide used in an electrode active material. A preparation method of a lithium-titanium complex oxide according to the present invention comprises the steps of: preparing a slurry mixture in which a titanium oxide, lithium and zirconium are mixed; wet-milling the mixture using beads having a size of 0.30 mm or less to obtain a wet-milled mixture; spray drying the wet-milled mixture to obtain a spray dried mixture; and calcining the spray dried mixture.

This composite titanium oxide compound is a composite titanium oxide compound wherein primary particles of an alkali metal titanate compound and primary particles of an alkaline earth metal titanate compound are joined to form secondary particles. The secondary particles have an average particle size of 1 to 80 μm. When the concentration of elements in the secondary particles is analyzed, a region where the alkaline earth metal is detected covers 50% or more of the surface area in 3% or less of the total number of secondary particles.