NOVELTY - Forming (M1) particulate material comprising silicon involves: reducing a particulate starting material comprising silica-containing particles having an aspect ratio of at least 5:1 and smallest dimension of less than 3 microns, or reducing particulate starting material comprising silica-containing particles comprising several elongate structural elements, each elongate structural element has an aspect ratio of at least 5:1 and smallest dimension of less than 3 microns. The smallest dimension of the starting material is an external thickness of the starting material.    USE - For forming particulate material comprising silicon which is used in forming electrode used in rechargeable metal ion battery selected from lithium ion battery (all claimed) used in portable electronic devices such as mobile telephones and laptops and in electric or hybrid electric vehicles; in flow cell batteries; in other energy storage devices such as fuel cells and thermal batteries; photovoltaic devices such as solar cells; filters; sensors; electrical and thermal capacitors; microfluidic devices; gas/vapor sensors; thermal or dielectric insulating devices; devices for controlling or modifying the transmission, absorption or reflectance of light or other forms of electromagnetic radiation; chromatography; and wound dressings.    ADVANTAGE - The method (M1) reduces all silica of the starting material. The method provide elongate silicon-comprising structures; is a high yielding method of forming structured particles containing elongate silicon-comprising structures as elements of the structured particles; is a sustainable method of forming elongate silicon-comprising structures on a large scale; forms elongate silicon-comprising structures with certain shape, form and dimensional characteristics that provide performance improvements.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a particulate material comprising silicon obtainable by the method (M1);    (2) an electrode comprising an active material of a material comprising silicon obtained by the method (M1);    (3) a slurry comprising the particulate material comprising silicon obtained by the method (M1) and at least one solvent;    (4) forming (M2) the electrode involving: depositing onto the conductive current collector, the slurry and evaporating the solvent;    (5) a rechargeable metal ion battery comprising an anode, where the anode comprises the electrode capable of inserting and releasing metal ions; cathode formed from a metal-containing compound capable of releasing and reabsorbing the metal ions; and electrolyte between the anode and the cathode;    (6) forming (M3) a material comprising silicon involving: electrospinning a material comprising silica and reducing the electrospun material comprising silica; and    (7) forming (M4) silicon involving: reducing biogenic silica.