US-20260125271-A1 - METHODS AND APPARATUS OF PRODUCING SILICON NANOPARTICLES

US20260125271A1US 20260125271 A1US20260125271 A1US 20260125271A1US-20260125271-A1

Abstract

A method of producing porous silicon particles includes providing reactants including a silica precursor and a metal reducing agent to an interior cavity of a tube of a rotary tube furnace. The method includes rotating the tube to form a mixture of the reactants in the tube. The method includes performing a thermal treatment to the mixture to produce a reaction product including the porous silicon particles. The method includes collecting the reaction product from the rotary tube furnace. The steps of providing the reactants, rotating the tube, performing the thermal treatment, and collecting the reaction product are performed concurrently.

Inventors

Jake E. Entwistle
Andre M. Zeitoun

Assignees

Ionic Mineral Technologies, LLC

Dates

Publication Date: 20260507
Application Date: 20251219

Claims (20)

1 . A method of producing porous silicon particles, comprising: providing reactants comprising a silica precursor and a metal reducing agent to an interior cavity of a tube of a rotary tube furnace; rotating the tube to form a mixture of the reactants in the tube; performing a thermal treatment to the mixture to produce a reaction product comprising the porous silicon particles; and collecting the reaction product from the rotary tube furnace, wherein the steps of providing the reactants, rotating the tube, performing the thermal treatment, and collecting the reaction product are performed concurrently.
2 . The method of claim 1 , wherein the tube of the rotary tube furnace is configured to house a metallothermic reaction between the silica precursor and the metal reducing agent.
3 . The method of claim 1 , wherein performing the thermal treatment to the mixture includes performing a degassing process that includes heating the mixture to a degassing temperature.
4 . The method of claim 1 , wherein: the tube of the rotary tube furnace is configured to house a metallothermic reaction between the silica precursor and the metal reducing agent; the metallothermic reaction is configured to occur at a reaction temperature; performing the thermal treatment to the mixture includes performing a degassing process that includes heating the mixture to a degassing temperature; and the degassing temperature is less than the reaction temperature.
5 . The method of claim 1 , wherein: the tube of the rotary tube furnace is configured to house a metallothermic reaction between the silica precursor and the metal reducing agent; the metallothermic reaction is configured to occur at a reaction temperature; and performing the thermal treatment to the mixture includes heating the mixture to a removal temperature greater than the reaction temperature to remove reaction byproducts from the reaction product.
6 . The method of claim 1 , wherein performing the thermal treatment to the mixture to produce the reaction product includes cooling the reaction product.
7 . The method of claim 1 , wherein performing the thermal treatment to the mixture to produce the reaction product includes: heating the mixture to an initiating temperature; heating the mixture to a reaction temperature greater than the initiating temperature; and heating the mixture to a removal temperature greater than the reaction temperature.
8 . The method of claim 1 , wherein performing the thermal treatment to the mixture to produce the reaction product includes: heating the mixture to an initiating temperature in a first zone of the rotary tube furnace; heating the mixture to a reaction temperature greater than the initiating temperature in a second zone of the rotary tube furnace; and heating the mixture to a removal temperature greater than the reaction temperature in a third zone of the rotary tube furnace.
9 . The method of claim 1 , comprising: sintering the porous silicon particles in an inert atmosphere.
10 . The method of claim 1 , comprising: sintering the porous silicon particles subsequent to performing the thermal treatment to the mixture.
11 . The method of claim 1 , wherein the steps of providing the reactants, rotating the tube, performing the thermal treatment, and collecting the reaction product are performed concurrently to produce the porous silicon particles in a continuous manner.
12 . The method of claim 1 , wherein the reactants include a thermal moderator.
13 . The method of claim 1 , wherein the reactants include at least one of sodium chloride or magnesium chloride.
14 . The method of claim 1 , wherein the reactants include a salt.
15 . The method of claim 1 , wherein the metal reducing agent includes at least one of magnesium, aluminum, sodium, potassium, zinc, or lithium.
16 . The method of claim 1 , wherein: the tube comprises a first opening and a second opening; the reactants are configured to enter the tube through the first opening; and the reaction product is configured to exit the tube through the second opening.
17 . The method of claim 1 , wherein providing the reactants comprising the silica precursor includes: providing a sample including an aluminosilicate; performing a dehydration process on the sample; and performing a dealumination process to remove aluminum from the sample, resulting in the silica precursor.
18 . The method of claim 1 , wherein the silica precursor includes dealuminated halloysite.
19 . The method of claim 1 , wherein the mixture of the reactants includes the metal reducing agent and the silica precursor at a molar ratio of 1.5:1 to 2.5:1.
20 . The method of claim 1 , comprising: washing the reaction product in an acid bath.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation of U.S. patent application Ser. No. 18/241,068, filed Aug. 31, 2023, which claims the benefit of and priority to U.S. Provisional Patent Application 63/403,654, filed Sep. 2, 2022. These applications are hereby incorporated by reference herein in their entireties. FIELD OF DISCLOSURE The present disclosure is generally related to methods and apparatus of producing nanoparticles and specifically related to manufacturing porous silicon particles. BACKGROUND Porous silicon particles (alternatively referred to as “porous silicon nanoparticles,” “porous silicon nanostructures,” or “porous silicon nanotubes,” or more generally as “silicon particles” or “silicon crystallites” in the following disclosure) are a promising anode material for lithium-ion batteries (LIBs) with a theoretical capacity of about 3600 mAh/g, compared to the capacity of the conventional anode material graphite with a theoretical capacity of about 372 mAh/g. The significantly greater capacity of silicon may lead to higher energy density in LIBs. In addition, porous silicon particles have demonstrated other advantages including, for example, fast charging. Furthermore, porous silicon particles may also be utilized in other applications including, for example, hydrogen gas production, fuel cells, drug delivery, catalysis support, electronics, solar power, photoluminescence, photocatalysis, to name a few. However, during battery operation the reversible lithiation of silicon causes porous silicon particles to undergo repeated volume expansion and contraction. In some instances, such volume expansion may be up to three-times the porous silicon particles' original volume. This is in contrast to an expansion of about 10% its original volume for graphite. The repeated volume expansion and contraction leads to degradation of the silicon material's structure during cycling and decline in its reversible capacity. Existing implementations for mitigating porous silicon particles' degradation during lithiation in the LIB anode electrode include, for example, reducing the size of porous silicon particles to below a critical threshold and introducing pores in the porous silicon particles. At sizes less than the threshold (e.g., below about 150 nm), porous silicon particles generally do not pulverize upon expansion. Furthermore, a porous silicon particle may expand into its own pore volume, reducing the stress on the particle itself and any surrounding particles. Current technologies of producing porous silicon particles suitable for LIB applications include, for example, top-down chemical vapor deposition (CVD) of silicon-containing gases (e.g., silane) onto carbon-based materials or other substrates (e.g., copper foil). However, the production of silane gas is currently lacking in scale, which also impacts the scalable production of porous silicon particles to significantly affect industries utilizing such porous silicon particles (e.g., the LIB anode industry). In addition, the top-down CVD process forms porous silicon particles having sizes on the μm—rather than nm—scales, which are above the threshold particle size for porous silicon particles described above. Additionally, the CVD method requires a substrate to fuse silicon into or onto, resulting in a lower capacity silicon composite versus an ability to produce a 100% silicon nano particle with the maximum theoretical capacity. Other technologies for producing porous silicon particles include using a metallothermic reduction reaction in a top-down synthesis process. This method utilizes nanoscopic silica precursors and converts them into nanoscopic porous silicon particles in a reduction process. If done correctly, this reduction reaction takes place well below the melting point of both silicon and silica, therefore the nanoscopic structure can be maintained. Metallothermic reduction, however, is highly exothermic and therefore specific precautions are routinely taken to avoid a runaway reaction leading to potential destruction of nanoscopic structures and properties of the porous silicon particles. Many studies have implemented such reduction reaction in batch processes. However, such batch processes generally have three main drawbacks. Firstly, existing reaction vessels are generally designed to perform these reduction reactions at small scales (e.g., at a batch size of about 5 g), leading to a lower purity of the porous silicon particles, even though at small scales the overall exothermic energy can be kept low enough that it can be dissipated from the reaction vessels. Secondly, in a batch process, an upper reaction purity of silicon is usually determined by the reaction time, which ranges from one hour to ten hours, with six hours being the usual, lowering the efficiency of the production process. Thirdly, when the purity of the produced porous silicon particles is low, then (HF) acid is required to remove any unre