A submicron sized Si based powder having an average primary particle size between 20 nm and 200 nm, wherein the powder has a surface layer comprising SiO.sub.x, with 0<x<2, the surface layer having an average thickness between 0.5 nm and 10 nm, and wherein the powder has a total oxygen content equal or less than 3% by weight at room temperature. The method for making the powder comprises a step where a Si precursor is vaporized in a gas stream at high temperature, after which the gas stream is quenched to obtain Si particles, and the Si particles are quenched at low temperature in an oxygen containing gas.

A submicron sized Si based powder having an average primary particle size between 20 nm and 200 nm, wherein the powder has a surface layer comprising SiO.sub.x, with 0<x<2, the surface layer having an average thickness between 0.5 nm and 10 nm, and wherein the powder has a total oxygen content equal or less than 3% by weight at room temperature. The method for making the powder comprises a step where a Si precursor is vaporized in a gas stream at high temperature, after which the gas stream is quenched to obtain Si particles, and the Si particles are quenched at low temperature in an oxygen containing gas.

A silicon material can include particles with a size between about 10 nanometers and 10 micrometers, where the particles can be porous or nonporous, and a coating disposed on the particles, wherein a thickness of the coating can be between about 1 nm and 1 μm. The coating can optionally include a carbon coating, graphite coating, or a polymeric coating.

A composite powder for use in the negative electrode of a battery, whereby the composite powder comprises composite particles, whereby the composite particles comprise a matrix material and silicon, whereby the composite particles have a particle size distribution having a d10 and a d90, whereby over at least part of the size range from d10 to d90 the composite particles have a size-dependent silicon content. Preferably a finer fraction of the composite powder has an average particle size D1 and a silicon content S1 and a coarser fraction of the composite powder has an average particle size D2 and a silicon content S2, whereby a size dependence factor F is defined as follows F=(S2−S1)/(D2−D1), whereby the absolute value of the size dependence factor F is at least 0.04 wt % silicon/μm.

A potassium hexafluoromanganate is represented by General Formula: K.sub.2MnF.sub.6, and a diffuse reflectance with respect to light having a wavelength of 310 nm is 20% or more.

An amorphous silicon-carbon composite, a method for preparing the amorphous silicon-carbon composite using a pyrolysis method, a negative electrode for a lithium secondary battery, and a lithium secondary battery including the same.

A method for manufacturing predominantly amorphous silicon-containing particles includes a chemical compound of formula: Si.sub.(1−x)C.sub.x, where 0.005≤x<0.05. The particles, when subjected to XRD analysis applying unmonochromated CuKα radiation, exhibit one peak at around 28° and one peak at around 52°. Both peaks have a Full Width at Half Maximum of at least 5° when using Gaussian peak fitting. The method includes forming a homogeneous gas mixture of a first precursor gas of a silicon containing compound and at least one second precursor gas of a substitution element M containing compound, injecting the homogeneous gas mixture of the first and second precursor gases into a reactor space where the precursor gases are heated to a temperature in the range of from 700 to 900° C. so that the precursor gases react and form particles, and collecting and cooling the particles to a temperature in the range of from ambient temperature up to about 350° C. The relative amounts of the first and the second precursor gases are adapted such that the formed particles obtain an atomic ratio C: Si in the range of [0.005, 0.05).

A potassium hexafluoromanganate is represented by General Formula: K.sub.2MnF.sub.6, and a diffuse reflectance with respect to light having a wavelength of 550 nm is 60% or more.

Silicon-carbon composite materials and related processes are disclosed that overcome the challenges for providing amorphous nano-sized silicon entrained within porous carbon. Compared to other, inferior materials and processes described in the prior art, the materials and processes disclosed herein find superior utility in various applications, including energy storage devices such as lithium ion batteries.

A simple method for making low surface area alloy particles with high silicon content has been discovered. The method involves two ball milling steps in which silicon containing precursor particles undergo a first milling to render the elemental silicon present to have an average grain size less than 20 nm, followed by a second milling with incorporated binding metal particles (e.g. certain transition metals) that serve to bind the first milled particles together. Done appropriately, the two milling step method results in alloy particles with high silicon content and have relatively low surface area and large particle size. As such, the particles are desirable for use in anode electrodes in rechargeable lithium batteries.