# US 2015/0104705 A1 · Method of forming silicon > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0104705 A1 - Document ID: US20150104705A1 - Status: Published application - Kind: A1 - Application number: 14/403,478 - Filed: 2013-06-03 - Published: 2015-04-16 - Earliest claimed: 2012-06-01 - Assignees: Nexeon Limited - Applicants: Nexeon Limited - Inventors: Leigh Canham; Christopher Michael Friend; William James Macklin; Scott Brown - Web page: https://patentgrep.com/patent/US20150104705A1 ## CPC - H01M 4/134: Electrodes based on metals, Si or alloys - C01B 33/023: by reduction of silica or {free} silica-containing material - H01M 4/386: {Silicon or alloys based on silicon} - H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries - H01M 2004/027: {Negative electrodes} - Y02E 60/10: Energy storage using batteries - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A method of forming a particulate material comprising silicon, the method comprising the step of reducing a particulate starting material comprising silica-containing particles having an aspect ratio of at least 3:1 and a smallest dimension of less than 15 microns, or reducing a particulate starting material comprising silica-containing particles comprising a plurality of elongate structural elements, each elongate structural element having an aspect ratio of at least 3:1 and a smallest dimension of less than 15 microns. ## Claims ### Claim 1 A method of forming a particulate material comprising silicon, the method comprising the step of reducing a particulate starting material comprising silica-containing particles having an aspect ratio of at least 3:1 and a smallest dimension of less than 15 microns, or reducing a particulate starting material comprising silica-containing particles comprising a plurality of elongate structural elements, each elongate structural element having an aspect ratio of at least 3:1 and a smallest dimension of less than 15 microns. ### Claim 2 (depends on 1) A method according to claim 1 wherein the aspect ratio of the silica-containing particles or of the elongate structural elements is at least 5:1. ### Claim 3 (depends on 1, 2) A method according to claim 1 or 2 wherein the smallest dimension of the silica-containing particles or of the elongate structural elements is less than 10 microns. ### Claim 4 (depends on 1, 2, 3) A method according to claim 1, 2 or 3 wherein the smallest dimension of the silica-containing particles or of the elongate structural elements is less than 3 microns. ### Claim 5 A method according to any preceding claim wherein substantially all silica of the starting material is reduced. ### Claim 6 A method according to any preceding claim wherein the geometric surface area of the silicon material is substantially the same as the geometric surface area of the starting material. ### Claim 7 (depends on 1, 2, 3, 4) A method according to any of claims 1-4 wherein silica at a surface of the starting material particles is reduced and silica at a core of the starting material particles is not reduced. ### Claim 8 (depends on 7) A method according to claim 7wherein the silica at the core is selectively removed. ### Claim 9 (depends on 8) A method according to claim 8 wherein the silica at the core is selectively removed by exposure to HF. ### Claim 10 (depends on 8, 9) A method according to claim 8 or 9 wherein the particulate material comprising silicon formed following selective removal of silica is a flake having a hollow core, or a tube. ### Claim 11 (depends on 9) A method according to claim 9 wherein the geometric surface area of the material comprising silicon is greater than the geometric surface area of the starting material. ### Claim 12 A method according to any preceding claim wherein the shape of the particles of the material comprising silicon is substantially the same as the shape of the starting material particles. ### Claim 13 A method according to any preceding claim wherein the starting material is n- or p-doped. ### Claim 14 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12) A method according to any of claims 1-12 wherein the starting material is undoped. ### Claim 15 A method according to any preceding claim wherein the starting material particles have an open framework structure. ### Claim 16 A method according to any preceding claim wherein the starting material is reduced at a reaction temperature of no more than 750° C., optionally no more than 650° C. ### Claim 17 A method according to any preceding claim wherein the starting material is reduced by exposure to liquid metal or metal vapour. ### Claim 18 (depends on 17) A method according to claim 17 wherein the metal is magnesium or calcium. ### Claim 19 (depends on 17, 18) A method according to claim 17 or 18 wherein the reduction takes place in the presence of a thermal moderator, optionally a salt. ### Claim 20 (depends on 19) A method according to claim 19 wherein the thermal moderator is mixed with the starting material and a reducing agent. ### Claim 21 (depends on 19, 20) A method according to claim 19 or 20 wherein a layer of thermal moderator is in contact with the starting material. ### Claim 22 A method according to any preceding claim wherein the silica is reduced by exposure to a reducing composition that causes both reduction of the silica and doping of the silicon. ### Claim 23 A method according to any preceding claim comprising the further step of coating at least part of the surface of the material comprising silicon. ### Claim 24 (depends on 23) A method according to claim 23 wherein at least part of the surface of the material comprising silicon is coated with silicon oxide or carbon. ### Claim 25 A method according to any preceding claim wherein the starting material is formed by electrospinning silica. ### Claim 26 (depends on 25) A method according to claim 25 wherein the starting material is formed by electrospinning silica onto a patterned collector defining a shape for the starting material. ### Claim 27 (depends on 25, 26) A method according to claim 25 or 26 wherein silica is electrospun with a polymer. ### Claim 28 (depends on 25, 26) A method according to claim 25 or 26 wherein silica only is electrospun. ### Claim 29 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24) A method according to any of claims 1-24 wherein the starting material is biogenic silica. ### Claim 30 A method according to any preceding claim wherein the starting material has a substantially enclosed void volume and the smallest dimension is a thickness of a wall of the starting material enclosing the void volume. ### Claim 31 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29) A method according to any of claims 1-29 wherein the smallest dimension of the starting material is an external thickness of the starting material. ### Claim 32 A method according to any preceding claim wherein the material comprising silicon has a BET value that is the same as or less than a BET value of the starting material. ### Claim 33 A method according to any preceding claim wherein the material comprising silicon has a BET value of less than 100 m2/g. ### Claim 34 A method according to any preceding claim wherein the starting material is no more than 95% silica by weight. ### Claim 35 (depends on 34) A method according to claim 34 wherein the starting material is no more than 90% silica by weight. ### Claim 36 A method according to any preceding claim wherein the particulate material comprising silicon is treated to remove reaction by-products. ### Claim 37 (depends on 356) A method according to claim 356 wherein reaction by-products are removed by HCl treatment. ### Claim 38 A method according to any preceding claim wherein the particulate material comprising silicon is etched to form silicon pillars extending from a silicon core of the particulate material. ### Claim 39 (depends on 38) A method according to claim 38 wherein the particulate material comprising silicon is etched by metal-assisted chemical etching. ### Claim 40 A particulate material comprising silicon obtainable by a method according to any preceding claim. ### Claim 41 (depends on 40) An electrode comprising an active material of a material comprising silicon according to claim 40. ### Claim 42 An electrode according to claim4l, wherein the electrode further comprises a conductive current collector in electrical contact with the active material. ### Claim 43 (depends on 40) A slurry comprising a particulate material comprising silicon according to claim 40 and at least one solvent. ### Claim 44 (depends on 42, 43) A method of forming an electrode according to claim 42, the method comprising the step of depositing onto the conductive current collector a slurry according to claim 43, and evaporating the solvent. ### Claim 45 (depends on 41, 42) A rechargeable metal ion battery comprising an anode, the anode comprising an electrode according to claim 41 or 42 capable of inserting and releasing metal ions; a cathode formed from a metal-containing compound capable of releasing and reabsorbing the metal ions; and an electrolyte between the anode and the cathode. ### Claim 46 (depends on 45) A rechargeable metal ion battery according to claim 45 wherein the metal ion battery is a lithium ion battery. ### Claim 47 A method of forming a material comprising silicon comprising the steps of electrospinning a material comprising silica and reducing the electrospun material comprising silica. ### Claim 48 (depends on 47) A method according to claim 47 wherein the electrospun material comprising silica to be reduced comprises silica-containing particles having an aspect ratio of at least 3:1, optionally at least 5:1 and a smallest dimension of less than 15 microns, optionally less than 3 microns, or reducing a particulate starting material comprising silica-containing particles comprising a plurality of elongate structural elements, each elongate structural element having an aspect ratio of at least 3:1, optionally at least 5:1 and an smallest dimension of less than 15 microns, optionally less than 3 microns. ### Claim 49 A method of forming silicon comprising the step of reducing biogenic silica. ### Claim 50 (depends on 49) A method according to claim 49 wherein the electrospun silica to be reduced comprises silica-containing particles having an aspect ratio of at least 3:1, optionally at least 5:1 and an smallest dimension of less than 15 microns, optionally less than 3 microns, or reducing a particulate starting material comprising silica-containing particles comprising a plurality of elongate structural elements, each elongate structural element having an aspect ratio of at least 3:1, optionally at least 5:1 and an smallest dimension of less than 15 microns, optionally less than 3 microns. ### Claim 51 A method of forming a particulate material comprising silicon, the method comprising the step of reducing a particulate starting material comprising silica-containing particles wherein the particulate starting material is no more than 95% silica by weight. ### Claim 52 (depends on 51) A method according to claim 51 wherein the particulate starting material is no more than 90% silica by weight. ### Claim 53 A method of forming a particulate material comprising silicon, the method comprising the step of reducing a particulate starting material comprising silica-containing particles wherein the particulate material comprising silicon has a surface area per unit weight of less than 100 m2/g. ### Claim 54 (depends on 53) A method according to claim 53 wherein the particulate material comprising silicon has a surface area per unit weight of less than 50 m2/g. ### Claim 55 (depends on 53, 54) A method according to claim 53 or 54 wherein the particulate starting material comprises amorphous or nanocrystalline silica and the particulate material comprising silicon comprises microcrystalline or nanocrystalline silicon. ### Claim 56 (depends on 53, 54, 55) A method according to any one of claims 53 to 55 wherein the particulate starting material comprises silica with a softening temperature that is lower than the reaction temperature at which the starting material is reduced. ### Claim 57 A method of forming a particulate material comprising silicon, the method comprising the step of reducing a particulate starting material comprising silica-containing particles wherein the particulate starting material is in contact with a layer of a thermal moderator. ### Claim 58 A method of forming a particulate material comprising silicon, the method comprising the step of partially reducing silica of a particulate starting material comprising silica-containing particles, and treating the partially reduced silica to remove remaining starting material. ### Claim 59 (depends on 58) A method according to claim 58 wherein the remaining starting material is removed using HF. ### Claim 60 (depends on 58, 59) A method according to claim 58 or 59 wherein the remaining starting material is removed to form a hollow core in the particulate material comprising silicon. ### Claim 61 (depends on 60) A method according to claim 60 wherein the particulate material comprising silicon is a flake having a hollow core or a tube.