[Problem to be solved] To produce an SiO powder having a rounded spherical particulate shape and a small particle diameter; and further having a low degree of impurity contamination, efficiently and economically. [Solution] A mixture of Si and SiO.sub.2 as an SiO gas generation raw material 9 is loaded into a crucible 2. The mixture in the crucible 2 is heated under a reduced pressure so as to generate SiO gas. The generated SiO gas is accumulated on a deposition base 5 rotating on the crucible 2. When SiO deposit 10 accumulated on the deposition base 5 is scraped off with a blade 7, a tip of the blade 7 is separated from a surface of the deposition base 5, and in a state in which a portion of the SiO deposit 10 accumulated on the deposition base 5 is left on the deposition base 5, the remaining SiO deposit 10 is scraped off by the blade 7 and collected as an SiO powder 11.

Disclosed is a black powder comprising silica particles that contain carbon. Each of the silica particles is single-layered. The content of carbon contained in the surfaces of the silica particles measured by an X-ray photoelectron spectroscopy is 1% by mass or less.

To produce an SiO powder having a rounded spherical particulate shape and a small particle diameter; and further having a low degree of impurity contamination, efficiently and economically.

A mixture of Si and SiO.sub.2 as an SiO gas generation raw material 9 is loaded into a crucible 2. The mixture in the crucible 2 is heated under a reduced pressure so as to generate SiO gas. The generated SiO gas is accumulated on a deposition base 5 rotating on the crucible 2. When SiO deposit 10 accumulated on the deposition base 5 is scraped off with a blade 7, a tip of the blade 7 is separated from a surface of the deposition base 5, and in a state in which a portion of the SiO deposit 10 accumulated on the deposition base 5 is left on the deposition base 5, the remaining SiO deposit 10 is scraped off by the blade 7 and collected as an SiO powder 11.

A silicon material can include a silicon aggregate comprising a plurality of porous silicon nanoparticles welded together. The silicon aggregate can optionally have a polyhedral morphology. A method can include: receiving a plurality of porous silicon nanoparticles and cold welding the plurality of porous silicon nanoparticles into an aggregated silicon particle.

A negative active material and a rechargeable lithium battery including the same are provided. The negative active material includes a porous amorphous carbon matrix; and a silicon oxide doped with the metal capable of (e.g., for) undergoing (e.g., to undergo) reduction, wherein a porosity of the porous amorphous carbon matrix is about 5% to about 25%.

A negative electrode active material including negative electrode active material particles, wherein the negative electrode active material particles contain silicon compound particles containing a silicon compound, the silicon compound particles contain Li.sub.2SiO.sub.3, at least a part of a surface of the silicon compound particles is covered with a carbon layer, and a surface layer of the negative electrode active material particles contains a substance having a carboxylic acid structure. Provided by this configuration is a negative electrode active material capable of increasing battery capacity due to improved initial efficiency and capable of realizing satisfactory battery cycle characteristics.

The present application provides a method, a equipment and a system for producing a silicon-containing products by using a silicon sludge which is produced by a diamond wire cutting silicon material. The method of the present application mainly utilizes a high oxide layer on the surface of a silicon waste particle produced during diamond wire cutting. The characteristics are such that the surface oxide disproportionates with adjacent internal elemental silicon to form silicon monoxide to be removed in a vapor to achieve a physical chemical reaction with a metal, a halogen gas, a hydrogen halide gas or hydrogen to form a high value-added silicon-containing products. The process realizes the large-scale, high-efficiency, energy-saving, continuous and low-cost complete recycling of diamond-wire cutting silicon waste.