An active material includes lithium, silicon, oxygen, a first element, a second element, and a third element as constituent elements. The first element includes boron, phosphorus, or both. The second element includes at least one of an alkali metal element, a transition element, or a typical element. The alkali metal element excludes lithium. The typical element excludes lithium, silicon, oxygen, boron, phosphorus, the alkali metal element, and an alkaline earth metal element. The third element includes the alkaline earth metal element.

The present invention refers to a stable sodium and iron silicate solution that has a weight ratio of SiO.sub.2 to Na.sub.2O from 1.5 to 2.5 and a total percentage of solids, expressed by the sum of SiO.sub.2 and Na.sub.2O, from 20% to 55%. Said solution also has a soluble iron content, expressed by Fe, from 0.1% to 7%, and a water content from 38% to 79.9%. The present invention also refers to the process for preparing said stable solution of sodium and iron silicate, which comprises the steps of: (a) providing a siliceous material containing iron; (b) submitting said siliceous material containing iron to a hydrothermal treatment with caustic soda under high temperature and controlled pressure; and (c) filtering said reacted solution to separate the reacted portion of the hydrothermal treatment from the unreacted portion. Additionally, the present invention refers to the uses of said stable sodium and iron silicate solution.

A process of obtaining powdered sodium silicate from sand tailings generated from iron ore processing addresses the production of raw materials used in the manufacturing of geopolymers to be employed mainly by the construction industry and in road paving. The utilization of this tailing reduces environmental impact generated by the disposal in large dams, as well as enabling addition of value to a tailing by obtaining a commercially applicable product.

The present invention relates to silicon coated metal microparticles in which at least a part of a surface of a metal microparticle composed of at least one of metal elements or metalloid elements is coated with silicon, wherein the silicon coated metal microparticles are a product obtained by a reduction treatment of silicon compound coated precursor microparticles in which at least a part of a surface of a precursor microparticle containing a precursor of the metal microparticles is coated with a silicon compound, or silicon doped precursor microparticles containing a precursor of the metal microparticles. Because it is possible particularly to strictly control a particle diameter of the silicon compound coated metal microparticle by controlling conditions of the reduction treatment, design of a more appropriate composition can become facilitated, compared with a conventional composition, in terms of diversified usages and desired properties of silicon compound coated metal microparticles.

A NaSICON-type solid-state electrolyte that contains Na as a conducting species, Zr, M, Si, P, and O, where M is at least one element selected from Mg, V, and Nb. The NaSICON-type solid-state electrolyte has a composition in which a molar ratio of M to Zr (M/Zr) is less than 0.2.

Provided are a lithium-doped silicon-based negative electrode active material, a method of producing the same, and a negative electrode and a lithium secondary battery including the same. According to an exemplary embodiment of the present invention, a method of producing a negative electrode active material for a secondary battery including: a) a metal doping process of mixing a silicon-based material and a metal precursor and performing a heat treatment to dope the silicon-based material with a metal; and b) an acid gas treatment process of treating the metal-doped silicon-based material in an acid gas atmosphere to remove residual metal may be provided.

The invention has for its object to use an evaporation-spray drying process thereby providing layered silicate powder granules, each one containing a flat particle having an opening or recess in its surface center. Each of the layered silicate powder granule contains a flat particle including a layered silicate formed by evaporation-spray drying and a rheology modifier for modifying the crystal edge face of the layered silicate and having an opening or recess in its surface center.

A negative electrode active material includes: particles of negative electrode active material, the particles of negative electrode active material contain particles of silicon compound containing a silicon compound (SiO.sub.x:0.5≤x≤1.6); the particles of silicon compound contain at least one kind or more of Li.sub.2SiO.sub.3 and Li.sub.4SiO.sub.4; the particles of negative electrode active material contain Li.sub.2CO.sub.3 and LiOH on a surface thereof; and a content of the Li.sub.2CO.sub.3 is 0.01% by mass or more and 5.00% by mass or less relative to a mass of the particles of negative electrode active material and a content of the LiOH is 0.01% by mass or more and 5.00% by mass or less relative to the mass of the particles of negative electrode active material. Thus a negative electrode active material is capable of improving initial charge/discharge characteristics and the cycle characteristics when used as a negative electrode active material of the secondary battery.

With an aim to provide an oxide particle with controlled color characteristics, the present invention provides a method for producing an oxide particle, wherein the color characteristics of the oxide particle are controlled by controlling a M-OH bond/M-O bond ratio, which is a ratio of a M-OH bond between an element (M) and a hydroxide group (OH) to a ratio of an M-O bond between the element (M) and oxygen (O), where the element (M) is one or plural different elements other than oxygen or hydrogen included in the oxide particle selected from metal oxide particles and semi-metal oxide particles. According to the present invention, by controlling the M-OH bond/M-O bond ratio of the metal oxide particle or the semi-metal oxide particle, the oxide particle with controlled color characteristics of any of reflectance, transmittance, molar absorption coefficient, hue, and saturation can be provided.

A silicon-oxygen composite anode material includes a kernel, a coating layer wrapped outside the kernel, and an intermediate layer located between the kernel and the coating layer. The intermediate layer includes the non-lithium silicate, and mass content of the non-lithium silicate in the intermediate layer progressively decreases from the intermediate layer to the kernel. The progressive decrease includes a gradient decrease from the intermediate layer to the kernel. The gradient decrease refers to that mass proportions on a circumference with a same distance from a center of the kernel are the same, and the mass proportion decreases gradually as the distance from the center of the kernel decreases. The non-lithium silicate is generated in situ at an outer layer of the kernel, and has a non-water-soluble, non-alkaline, or weak-alkaline dense structure.