US-12617688-B2 - Silicon carbide-containing material, precursor composition and preparation processes thereof

US12617688B2US 12617688 B2US12617688 B2US 12617688B2US-12617688-B2

Abstract

Disclosed is a method for manufacturing a precursor composition of a silicon carbide-containing material, wherein nanoscale silicon dioxide, in particular fumed silica, and nanoscale carbon, in particular carbon black, are mixed. Also disclosed are a precursor composition manufactured in this way, a method for manufacturing a silicon carbide-containing material from the precursor composition and a silicon carbide-containing material manufactured in this way.

Inventors

Siegmund Greulich-Weber

Assignees

The Yellow SiC Holding GmbH

Dates

Publication Date: 20260505
Application Date: 20221027
Priority Date: 20211030

Claims (11)

1 . A method of manufacturing a precursor composition for the manufacture of a silicon carbide-containing material, comprising: first mixing nanoscale silicon dioxide and nanoscale carbon to form a mixture having a desired mass ratio; subsequently adding a solvent to the mixture and mixing the mixture; and drying the mixture, wherein the desired mass ratio of carbon to silica is in the range from 2.4:1 to 3.1:1.
2 . The method of claim 1 , wherein the carbon in the nanoscale carbon is present in particles of a size of 5 to 100 nm.
3 . The method of claim 1 , wherein the nanoscale carbon is carbon black.
4 . The method of claim 1 , wherein the nanoscale carbon has a specific resistance of 5·10 −2 Ω·cm or less.
5 . The method of claim 1 , wherein a dopant or alloying material is added to the mixture.
6 . The method of claim 1 , wherein a solvent is further added to the mixture of nanoscale silicon dioxide and nanoscale carbon, and the mixture is dried at a temperature of no more than 700° C.
7 . The method of claim 6 , wherein the drying is carried out at a temperature of not more than 150° C. and a dried nanoscale precursor composition is obtained.
8 . The method of claim 6 , wherein the drying is carried out at a temperature of not more than 250° C. and a dried microscale precursor composition is obtained.
9 . A method of manufacturing a silicon carbide-containing material, wherein a precursor composition manufactured according to claim 1 is converted into the silicon carbide-containing material by heating.
10 . The method of claim 9 , wherein the conversion of the precursor composition into the silicon carbide-containing material is carried out in an additive manufacturing process with laser-induced selective synthetic crystallization.
11 . The method of claim 9 , wherein the silicon carbide-containing material is an electrode material of a battery electrode.

Description

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to silicon carbide-containing materials and their manufacturing, including precursor compositions for use in such manufacturing methods and methods of manufacturing such precursor compositions. Description of the Related Art In the well-known Degussa process, SiC is produced from a dry mixture of SiO2 and C by a carbothermal reaction. Specifically, silicon carbide is produced by carbothermal reduction from compounds containing silicon dioxide. In particular, sand, various silicas or silane hydrolysates can be used as a silicon dioxide-containing compound. Sugar or organic binder systems such as phenol resins are often used as a carbon-containing material for the carbothermal reduction. Typically, the silicon dioxide and the carbon-containing material are heated to temperatures of over 1,400° C. for this purpose. What is produced by use of particulate silicon dioxide is usually a silicon carbide layer or silicon carbide granulate. However, the Degussa process is not sufficiently effective in practice. The SiO2—C mixture used is loose and only allows the carbothermal reaction to SiC to proceed incompletely because the reactants are too far apart from each other. The reaction produces large quantities of CO and CO2, and the SiC produced contains remnants of excess Si. This is unsatisfactory in terms of quality, economy and ecology. Also known is the manufacturing of structures containing silicon carbide by use of additive manufacturing. For example, structures containing silicon carbide can be produced from precursors containing carbon and silicon by use of a powder bed process with laser-induced so-called selective synthetic crystallization. Selective synthetic crystallization is disclosed, for example, in DE 10 2017 110 362 A1 and DE 10 2015 105 085 A1. In this process, precursor granules based on silane hydrolysates and sugars and possibly other additives are used in the powder bed, which are selectively converted by laser beams into silicon carbides or silicon carbide alloys. The precursor granules are produced in a sol-gel process, for example by mixing a silicate, a sugar solution, alcohol and other additives to form a sol, and gelling it at around 70° C., followed by drying at around 200° C. and pyrolysis at around 1000° C. Electrodes, in particular anodes for lithium-ion batteries, can be made from nano- or microcrystalline or amorphous SiC. In order to improve battery efficiency, the aim is an increase of the surface area and a more efficient incorporation of lithium into the electrode material, for example by use of nano- or microstructured SiC. One example is nanostructured silicon carbide foams made of interconnected silicon carbide fibers that form an open-cell foam. Depending on the reaction conditions, in particular the temperature regime in a reactor, either isolated silicon carbide fibers or nano structured silicon carbide-containing foams can be obtained from suitable precursor materials. A method for the manufacturing of such electrode materials from a precursor granulate containing silane hydrolysates and sugar is disclosed in DE 10 2014 116 868 A1. The publication of German patent application DE 10 2017 114 243 A1 discloses a corresponding method for the manufacture of fibers and foams containing silicon carbide from liquid or gaseous precursors. However, the use of precursors that contain sugar as a carbon source has disadvantages. Although the use of sugar, in particular liquid sugar solutions, in the production of precursor granulates achieves good and intimate mixing with the silicon-containing starting material, the sugar then tends to release large quantities of gases during the decomposition reactions in the carbothermal reduction process due to its high hydrogen and oxygen content. Most of these gases are climate-damaging gases such as CO2 and methane. Associated therewith is also a certain waste of resources. The release of the gases also hinders additive manufacturing, which relies on the site-selective formation and deposition of the silicon carbide, which is made more difficult by the strong gas formation. In the neighbouring field of silicon nitride production, US 2020/0038955 A1 discloses a method in which silicon dioxide in the form of sand, in a nitrogen atmosphere and in the presence of a small amount of graphite in a powder bed, is converted by laser irradiation to silicon nitride and carbon monoxide. BRIEF SUMMARY OF THE INVENTION In view of the aforementioned prior art, it is an object of the invention to provide a silicon carbide-containing material and a manufacturing method therefor, as well as a precursor composition for use in such a manufacturing method, and a method for manufacturing the precursor composition, which are more efficient and allow more precise control of the properties of the silicon carbide-containing material produced. The solution to this object is achieved with the silicon