The present disclosure relates to a negative electrode active material to a lithium secondary battery, including: a carbon-based material; a silicon coating layer disposed on the carbon-based material: and a carbon coating layer disposed on the silicon coating layer, wherein the silicon coating layer includes silicon particles and a silicon-based amorphous matrix.

In a method for depositing a layer of amorphous hydrogenated silicon carbide (SiC:H), a gas mixture comprising a reactive gas to inert gas volume ratio of 1:12 to 2:3 is introduced into a reaction chamber of a plasma-enhanced chemical vapor deposition apparatus. The reactive gas has a ratio of Si of 50 to 60, C of 3 to 13, and H of 32 to 42 at %. The inert gas comprises i) a first inert gas selected from helium, neon and mixtures; and ii) a second inert gas selected from argon, krypton, xenon and mixtures. The reaction plasma is at a power frequency of 1-16 MHz at a power level of 100 W to 700 W. The resulting layer exhibits a refractive index of not less than 2.4 and a loss of not more than 180 dB/cm at an indicated wavelength within 800 to 900 nm.

In a method for depositing a layer of amorphous hydrogenated silicon carbide (SiC:H), a gas mixture comprising a reactive gas to inert gas volume ratio of 1:12 to 2:3 is introduced into a reaction chamber of a plasma-enhanced chemical vapor deposition apparatus. The reactive gas has a ratio of Si of 50 to 60, C of 3 to 13, and H of 32 to 42 at %. The inert gas comprises i) a first inert gas selected from helium, neon and mixtures; and ii) a second inert gas selected from argon, krypton, xenon and mixtures. The reaction plasma is at a power frequency of 1-16 MHz at a power level of 100 W to 700 W. The resulting layer exhibits a refractive index of not less than 2.4 and a loss of not more than 180 dB/cm at an indicated wavelength within 800 to 900 nm.

In an embodiment, a system includes a three-dimensional (3D) printer, a neutral feedstock, a p-doped feedstock, an n-doped feedstock, and a laser. The 3D printer includes a platen and an enclosure. The platen includes an inert metal. The enclosure includes an inert atmosphere. The neutral feedstock is configured to be deposited onto the platen. The neutral feedstock includes a halogenated solution and a nanoparticle having a negative electron affinity. The p-doped feedstock is configured to be deposited onto the platen. The p-doped feedstock includes a boronated compound introduced to the neutral feedstock. The n-doped feedstock is configured to be deposited onto the platen. The n-doped feedstock includes a phosphorous compound introduced to the neutral feedstock. The laser is configured to induce the nanoparticle to emit solvated electrons into the halogenated solution to form, by reduction, layers of a ceramic comprising a neutral layer, a p-doped layer, and an n-doped layer.

According to an exemplary embodiment of the present disclosure, a negative electrode active material includes metal-silicon-carbon based particles including a M.sub.aSi.sub.bC matrix, wherein M in the M.sub.aSi.sub.bC matrix is one or more selected from the group consisting of Li, Mg, Na, Ca, and Al, 0.3≤a≤1, and 1≤b≤2. Since at the time of charging and discharging a battery, formation of an irreversible phase may be minimized by the M.sub.aSi.sub.bC matrix, initial efficiency of the battery may be improved, and electrical conductivity, physical strength, and chemical stability may be improved, such that capacity and lifecycle characteristics of the battery may be improved.

A method of forming a high purity granular material, such as silicon carbide powder. Precursors are added to a reactor; at least part of a fiber is formed in the reactor from the precursors using chemical deposition interacting with said precursors; and the granular material is then formed from the fiber. In one aspect, the chemical deposition may include laser induced chemical vapor deposition. The granular material may be formed by grinding or milling the fiber into the granular material, e.g., ball milling the fiber. In one example, silicon carbide powder having greater than 90% beta crystalline phase purity and less than 0.25% oxygen contamination can be obtained.

A method of forming a high purity granular material, such as silicon carbide powder. Precursors are added to a reactor; at least part of a fiber is formed in the reactor from the precursors using chemical deposition interacting with said precursors; and the granular material is then formed from the fiber. In one aspect, the chemical deposition may include laser induced chemical vapor deposition. The granular material may be formed by grinding or milling the fiber into the granular material, e.g., ball milling the fiber. In one example, silicon carbide powder having greater than 90% beta crystalline phase purity and less than 0.25% oxygen contamination can be obtained.

A membrane sorbent is described, which comprises 1-6 wt % silicon carbide nanoparticles dispersed in a polymer matrix. The polymer matrix may comprise polysulfone and polyvinylpyrrolidone. The membrane sorbent is used for separating oil from a contaminated water mixture. The silicon carbide nanoparticles of the membrane sorbent may be made from rice husk ash.

A method for manufacturing a honeycomb structure containing silicon carbide, including blending a recycled raw material derived from a material constituting a first honeycomb structure containing silicon carbide in a process after firing as a part of an initial raw material for a second honeycomb structure containing silicon carbide, wherein the initial raw material comprises silicon carbide and metallic silicon; and the recycled raw material is a powder recovered from the material constituting the first honeycomb structure containing silicon carbide in the process after firing, and after the recovering, a particle size is adjusted so that a 10% diameter (D10) is 10 μm or more and a 50% diameter (D50) is 35 μm or less when a cumulative particle size distribution on a volume basis is measured by a laser diffraction/scattering method.

A method for manufacturing a honeycomb structure containing silicon carbide, including blending a recycled raw material derived from a material constituting a first honeycomb structure containing silicon carbide in a process after firing as a part of an initial raw material for a second honeycomb structure containing silicon carbide, wherein the initial raw material comprises silicon carbide and metallic silicon; and the recycled raw material is a powder recovered from the material constituting the first honeycomb structure containing silicon carbide in the process after firing, and after the recovering, a particle size is adjusted so that a 10% diameter (D10) is 10 μm or more and a 50% diameter (D50) is 35 μm or less when a cumulative particle size distribution on a volume basis is measured by a laser diffraction/scattering method.