NOVELTY - A silicon surface (303) of the material having silicon (301) is partially covered by elemental metal (305). Metal-assisted chemical etching of the silicon is carried out by exposing the covered surface to an etching composition to obtain processed etching silicon of material. The elemental metal for the metal-assisted chemical etching is formed by exposing the silicon surface to the etching composition having metal ions and the elemental metal is formed by reduction of the metal ions (a) or depositing the elemental metal directly onto the silicon surface (b).    USE - Etched silicon is used to form anode of rechargeable metal ion battery e.g. lithium ion battery (claimed). Uses include but are not limited to conducting or semiconducting components of electronic circuitry, filter, fuel cells, photovoltaic cell, sensor, capacitor, thermal batteries, microfluidic devices, gas or vapor sensors, and thermal or dielectric insulating devices.    ADVANTAGE - The etched silicon has excellent capacity and produces batteries with excellent charging/discharging cycle.    DETAILED DESCRIPTION - A silicon surface of the material having silicon is partially covered by the elemental metal. The metal-assisted chemical etching of the silicon is a carried out by exposing the partially covered silicon surface to an etching composition to obtain processed etching silicon of material comprising silicon. The elemental metal for the metal-assisted chemical etching is formed by exposing the silicon surface to the etching composition having metal ions which is free of hydrogen fluoride and the elemental metal is formed by reduction of the metal ions (a) or depositing the elemental metal directly onto the silicon surface (b). INDEPENDENT CLAIMS are included for the following:    (1) electrode;    (2) method of forming an electrode; and    (3) rechargeable metal ion battery which is the lithium ion battery.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of process using powdered silicon.    Silicon particles (301)    Silicon surface (303)    Elemental metal (305)    Pillars (307)