Silicon-containing pitch-based composite powder, and methods for producing and using the same.

Abstract

The composite powder can be formed by blending silicon particles with petroleum pitch under grinding conditions. The composite powder may contain up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and optionally up to 80% by mass of graphite particles, relative to the total mass of the composite powder. The silicon particles are dispersed in a matrix containing petroleum pitch, which contains multiple pitch particles. The composite powder can then be converted into a carbon matrix containing amorphous carbon by heating the petroleum pitch at a temperature of about 700°C to about 1800°C in an environment containing less than about 0.1 mol% oxygen.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 508,389, filed on June 15, 2023, the disclosure of which is incorporated herein by reference in its entirety. This disclosure relates to composite powders, more particularly, composite powders containing or derived from petroleum pitch.

Background Art

[0002] Batteries, including lithium - ion batteries, are commonly used in portable electronic devices, electric vehicles, and general energy storage. Lithium - ion batteries are commonly used for such applications because of their high energy storage density and high power output. A lithium - ion battery cell includes a cathode and an anode. The cathode is made from a lithium compound (e.g., lithium cobalt oxide, lithium nickel manganese cobalt oxide), and the anode is conventionally made from natural or synthetic graphite materials. One limitation of lithium - ion batteries is that graphite materials typically have a rather limited energy storage capacity for charge, and the theoretical weight charge capacity in a commercially realized lithium - ion battery is typically up to 372 mAh / g. The energy storage capacity can be increased by incorporating an electrochemically active material into the graphite material. However, volume expansion and contraction during charge and discharge cycles can cause mechanical degradation of the electrode, especially when an electrochemically active material is added and the storage capacity is increased. One suitable precursor for graphite materials used to form anodes in lithium-ion batteries is petroleum pitch. Petroleum pitch is a carbon-rich, viscoelastic material derived from petroleum, possessing properties similar to thermoplastic polymers. Petroleum pitch can be used as a precursor material for producing many consumer and industrial carbon products, such as carbon fibers, graphite, binder pitch, and impregnated pitch. Beyond battery applications, the main markets for petroleum pitch and its derived carbon products include, but are not limited to, high-performance and general-purpose carbon fibers, refractories, carbon / carbon composites, synthetic graphite and graphite components, binder and impregnated pitch for electrodes, binder and impregnated aluminum-produced anodes and cathodes, impregnated pitch for electric arc steelmaking furnace electrodes, carbon foam for heat transfer and sound absorption applications, roofing products, lubricants, and consumer products (e.g., cosmetics).

[0003] Limiting the volume expansion of the electrochemical active material is the most common approach to minimizing mechanical decomposition at the anode. This can be achieved by three means: (1) coating the electrochemical active material, typically with a carbon-based material, to improve its mechanical integrity; (2) mixing the electrochemical active material with graphite while preparing the anode slurry; or (3) using smaller active material particles. Relying on any one of these approaches will not produce a competitive anode with a high cycle life, and typically, combining all three approaches is the common practice for best results. However, current approaches still cannot push the total amount of electrochemical active material at the anode beyond the resulting gravimetric charge capacity of 500 mAh / g. This limitation is a result of both insufficient dispersion of the active material particles in the graphite in the slurry and insufficient mechanical properties of the coating. The latter requires preparing a masterbatch by mixing an electrochemical active material with up to 70% by mass of a coating / matrix material, and then adding the masterbatch to a slurry to prepare up to 30% by mass of an anodic active material. [Overview of the Initiative]

[0004] In various embodiments, the present disclosure provides a composite powder comprising up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and up to about 80% by mass of graphite, wherein the silicon and graphite particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch comprises a plurality of pitch particles. In some or other various embodiments, the Disclosure provides compositions comprising up to about 60% by mass of silicon particles dispersed in a carbon matrix, relative to the total mass of the composition, wherein the carbon matrix comprises amorphous carbon. In various other embodiments, the method of the present disclosure comprises the steps of forming a blend comprising up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and up to about 80% by mass of graphite, based on the total mass of the blend, and processing the blend under grinding conditions to form a composite powder, wherein the silicon and graphite particles are dispersed in a matrix comprising petroleum pitch, and the petroleum pitch comprises a plurality of pitch particles. The characteristics and other attributes of the disclosed compositions and methods herein, as well as their advantageous uses and / or applications, will become apparent from the subsequent detailed description. The accompanying drawings are provided for the assistance of those skilled in the art in creating and using the subject matter of this specification. The following drawings are included to illustrate certain aspects of the disclosure and should not be viewed as exclusive. The disclosed subject matter can be modified, altered, combined, and equivalent in form and function by those skilled in the art, and in which there is an interest of the disclosure. [Brief explanation of the drawing]

[0005] [Figure 1A] This is a diagram of a composite powder having silicon particles dispersed between pitch particles. [Figure 1B] This is a diagram of a composite powder containing silicon particles within pitch particles. [Figure 1C] This is a diagram of a composite powder having silicon particles both inside and between pitch particles. [Figure 2A] These are SEM-BSE (scanning electron microscope-backscattered electron) images of the illustrative composite powder sample produced according to the drying blending procedure of this disclosure. [Figure 2B] These are SEM-BSE (scanning electron microscope-backscattered electron) images of the illustrative composite powder sample produced according to the drying blending procedure of this disclosure. [Figure 2C] These are SEM-BSE (scanning electron microscope-backscattered electron) images of the illustrative composite powder sample produced according to the drying blending procedure of this disclosure. [Figure 3] This is a powder XRD (X-ray diffraction) plot of an illustrative composite powder sample produced according to the drying blending procedure of this disclosure and carbonized at various temperatures. [Modes for carrying out the invention]

[0006] This disclosure relates to composite powders containing, or derived from, petroleum pitch. It should be understood that the terms “pitch” and “petroleum pitch” are used interchangeably in this specification. Furthermore, it should be understood that “pitch particles” as described herein include petroleum pitch. This disclosure provides for the readily available use of composite powders containing petroleum pitch, silicon, and graphite for battery anodes and for which the carbonization or graphitization can be readily processed into other carbon-based structures. It should be recognized that silicon oxide forms can be used as substitutes for pure silicon. The composite powders may contain natural or synthetic graphite and silicon in nanoparticle form, thereby providing several advantages for battery anodes and other applications. Silicon in nanoparticle form (silicon nanoparticles) may include previously produced nanoparticle forms blended with petroleum pitch, or, more advantageously, the nanoparticle form may be produced in situ when a silicon source is blended with petroleum pitch. As used herein, the term “nanoparticle form” refers to any size range of less than about 1000 nm, preferably less than about 500 nm, more preferably less than about 200 nm, or less than about 100 nm. By incorporating silicon into petroleum pitch to form a composite powder, and then carbonizing it, silicon can increase energy density (e.g., theoretical gravimetric charging capacity up to approximately 3600 mAh / g), enabling improved performance, for example, in battery anodes. Furthermore, incorporating silicon into composite powders in the form of nanoparticles can achieve remarkable improvements in performance regarding stability during volume expansion and contraction. While not bound by theory or mechanism, the improved performance and mechanical stability during charge and discharge cycles are thought to be due to the silicon's resistance to re-expansion and contraction in the nanoparticle form. The easy dispersion of silicon within the pitch may also play a role in this.

[0007] Advantageously, the composite powders of this disclosure can be prepared under continuous blending and pulverization conditions, with or without first melting or softening the petroleum pitch. When the petroleum pitch is heated above its softening temperature, the blending process may be referred to as a melt blend. Above the softening temperature, the pitch particles become more malleable, thereby allowing silicon particles to be embedded on the outer surface of the pitch particles, or to be mixed within the pitch particles so that the pitch particles can be further deformed and reshaped. At temperatures below the softening temperature, the blending process may be referred to as a dry blend. Below the softening temperature, the pitch particles remain hard, and the silicon particles remain on the outside of the pitch particles. In both the melt blend and dry blend cases, the blending process may be carried out continuously in a screw mill extruder or a similar extruder type, and the resulting product can be obtained directly as a composite powder without the need for further grinding. Optionally, the composite powder may be sieved to the desired particle size if necessary. The extruder can facilitate the formation of reduced particle sizes in both the petroleum pitch and the silicon particles incorporated therein, while also facilitating their close blending to form a composite powder. Optionally, under dry blending conditions, a continuous grinding process may be generated in a cooled (e.g., about -10°C to about 5°C) extruder to maintain the petroleum pitch in a hardened state and to limit potential chemical decomposition. In this disclosure, the term “cold blend” is used to refer to a dry blending process carried out below room temperature (23°C) and below the softening temperature of the components being blended. It should be recognized that the blending of petroleum pitch, silicon, and graphite can be carried out in a single step via dry or melt blending, thereby improving the mechanical stability of the final anode composite powder as a result of good dispersion among the three components. Furthermore, blending in a single step process combines the coatings of both silicon and graphite in one step, which is an advantage from a processing standpoint.When the composite powder is produced under such dry blending conditions, the close blend of petroleum pitch particles and silicon particles can be further heated after dry blending at a temperature below the softening temperature of petroleum pitch (e.g., about 200°C to about 450°C, or about 200°C to about 300°C, or about 300°C to about 450°C) to adhere or immobilize the silicon particles on the outer surface of the pitch particles (e.g., through complete or partial embedding of silicon particles on the surface of the pitch particles), while the overall composition remains in a well-dispersed powder form. Since the onset of softening usually occurs about 50°C to 100°C below the actual softening temperature, some of the embedding of silicon particles on the outer surface of the pitch particles may occur within the aforementioned temperature range. Some crosslinking of petroleum pitch may also occur under these heating conditions in a low-oxygen environment containing about 1 mol% to about 20 mol% oxygen, if heating is carried out. Heating in an environment with low oxygen content (less than approximately 0.1 mol%) may result in minimal or no crosslinking. When silicon particles are attached or immobilized on the outer surface of pitch particles, the interior of the pitch particles may remain devoid of silicon particles. In contrast, the melt blending process can result in the dispersion of at least some of the silicon particles throughout the interior of the pitch particles, rather than the silicon particles being confined to the gaps between the pitch particles. However, some silicon particles may still remain outside the pitch particles during the melt blending process.

[0008] The oxidation of at least some of the petroleum pitch and / or silicon particles may occur under the heating conditions used to fix the silicon particles. Partial oxidation of the pitch particles can improve the mechanical integrity of the composite powder through at least partial crosslinking of the petroleum pitch. Furthermore, partial oxidation can reduce the time required to stabilize the petroleum pitch through oxidative crosslinking before carbonization of the composite powder when fixing or immobilizing the silicon particles. The accompanying oxidation of the silicon particles is not considered problematic because any silicon oxide that takes shape during its fixing or immobilization can be reverted to elemental silicon under the conditions used for subsequent carbonization or graphitization of the composite powder.

[0009] The composite powders of this disclosure may comprise silicon or silicon dioxide (SiO2) particles, preferably silicon or silicon dioxide nanoparticles, and, in some cases, graphite particles blended with petroleum pitch, wherein the silicon or silicon dioxide particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch comprises a plurality of pitch particles. The silicon particles and silicon dioxide particles may be used interchangeably when forming the composite powders according to this disclosure, since the silicon dioxide may revert to elemental silicon during the subsequent carbonization or graphitization of the composite powder under the conditions used. Unless otherwise specified herein, the term “silicon particles” and its grammatical variations refer primarily to any particulate material containing elemental silicon or one or more silicon compounds, preferably silicon oxide, e.g., silicon dioxide. Therefore, any mention of silicon or silicon particles herein is understood to equally refer to silicon oxide, e.g., silicon dioxide. Furthermore, the use of the term “silicon dioxide” herein should be understood to include other silicon oxides. Other silicon species can similarly exist in silicon particles.

[0010] The form of the composite powder may vary depending on whether the silicon particles are combined with petroleum pitch under molten blending conditions, dry blending conditions, or a combination thereof. In the dry blending process, the silicon particles may be dispersed in the composite powder by being located between pitch particles, for example, in the void spaces between pitch particles. Figure 1A is a diagram of composite powder 100A showing silicon particles 102 dispersed between pitch particles 104 in void spaces 106. In contrast, the molten blending process can produce a composite powder in which at least some of the silicon particles are dispersed inside the pitch particles, and optionally some of the silicon particles are exposed on the surface of the pitch particles. Figure 1B is a diagram of composite powder 100B showing silicon particles 102 inside pitch particles 104, in this case the void spaces 106 are not occupied (as depicted in Figure 1B), or some of the silicon particles 102 are also present in the void spaces 106 and / or embedded on the outer surface of the pitch particles 104 (Figure 1C). Optionally, further drying blending of the composite powder 100B having silicon particles 102 may be performed to fill at least a portion (not shown) of the void spaces 106. Figure 1C is a diagram of the composite powder 100C showing silicon particles 102 inside the pitch particles 104 and in the void spaces 106, which are filled either during the melt blending process or during a further drying blending process after the melt blending process. Although the pitch particles 104 and silicon particles 102 are shown as circular and individually of the same size in Figures 1A-1C, it should be recognized that the particle shapes may be irregular and various particle sizes may be present in both the silicon particles 102 and the pitch particles 104.

[0011] More specifically, each composite powder may contain, with respect to the total mass of the composite powder, up to about 50% by mass of silicon particles or up to about 30% by mass of silicon particles, and about 15% to about 95% by mass of petroleum pitch, and up to about 80% by mass of graphite particles, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains a plurality of pitch particles. In non-limiting examples, each composite powder may contain silicon particles in amounts ranging from about 1% to about 30% by mass, or about 5% to about 30% by mass, or about 10% to about 30% by mass, or about 5% to about 20% by mass, or about 5% to about 15% by mass, or about 10% to about 20% by mass, or about 10% to about 25% by mass, or about 9% to about 15% by mass. In some, or other non-limiting, composite powders may contain petroleum pitch in amounts ranging from about 25% to about 95% by mass, or about 30% to about 80% by mass, or about 40% to about 75% by mass, or about 15% to about 70% by mass, or about 30% to about 50% by mass, or about 50% to about 70% by mass, or about 70% to about 90% by mass, or about 85% to about 95% by mass, based on the total mass of each composite powder. In some, or other non-limiting, composite powders may contain graphite particles in amounts ranging from about 1% to about 80% by mass, or about 1% to about 10% by mass, or about 10% to about 75% by mass, or about 15% to about 70% by mass, or about 30% to about 50% by mass, or about 50% to about 70% by mass, or about 70% to about 80% by mass, or about 50% to about 80% by mass, based on the total mass of each composite powder.

[0012] The petroleum pitch used in this disclosure may be obtained from any source or process, provided that the petroleum pitch does not contain any components that may be detrimental to the intended use after carbonization of the composite powder. In some examples, at least the majority of the petroleum pitch may consist of mesophase pitch. Mesophase pitch is an anisotropic pitch containing a composite mixture of aromatic molecules that are at least partially aligned and fuse with the liquid crystal phase. The degree of crystallinity can improve mechanical integrity. Further carbonization may result in a highly aligned structure that promotes improved conductivity, for example, in battery applications. In non-limiting examples, the petroleum pitch used herein may each have a mesophase pitch content of about 50% by mass or more, or about 60% by mass or more, or about 70% by mass or more, or about 80% by mass or more, or about 90% by mass or more, or about 95% by mass or more, or about 99% by mass or more, or about 99.9% by mass or more, for example, about 50% to about 90% by mass, or about 60% to about 80% by mass, or about 80% to about 90% by mass, or about 85% to about 99% by mass, or about 90% to about 99% by mass, or about 90% to about 99% by mass, or about 80% to about 99.9% by mass, or about 90% to about 99.9% by mass, or about 95% to about 99.9% by mass, or even 100% by mass.

[0013] The silicon particles used in this disclosure may include elemental silicon, silicon dioxide, or any combination thereof. The silicon particles used in this disclosure may be obtained from any source or process, provided that the silicon particles do not contain any components that may be harmful to the intended use. Depending on the source and whether elemental silicon or silicon dioxide is present in the silicon particles, the impurity content of the silicon particles may be about 5% by mass or less, or about 2% by mass or less, or about 1% by mass or less, or about 0.5% by mass or less, or about 0.1% by mass or less, or about 0.01% by mass or less, or about 0.001% by mass or less, or even about 0.00001% by mass or less. Similarly, depending on whether the silicon particles contain elemental silicon and / or silicon dioxide, and sources of silicon and / or silicon dioxide, the silicon particles may have a silicon content of about 25% to about 99.9999% by mass, or about 40% to about 99.9999% by mass, or about 45% to about 99.9999% by mass, or about 50% to about 99.9999% by mass, or about 90% to about 99.9999% by mass, or about 95% to about 99.9999% by mass, relative to the mass of the silicon particles. In some examples, if the silicon particles substantially contain elemental silicon, the remainder of the mass of the silicon particles may contain silicon dioxide. In embodiments, graphite includes natural and / or synthetic graphite. In embodiments, graphite includes a range of sizes from 1 μm to 200 μm. In this embodiment, the graphite contains 50% to 100% graphitization.

[0014] When blended with petroleum pitch, silicon particles can have any suitable size and any suitable particle size distribution so as to be dispersed in the carbon matrix formed after carbonization. For example, silicon particles blended with petroleum pitch may have a D50 of about 200 nm or less or about 300 nm or less, and a D90 of about 1000 nm or less or about 1200 nm or less. As used herein, the term "D50" refers to a diameter in which 50% of the sample (by volume unless otherwise specified) consists of particles having a diameter less than the aforementioned diameter. As used herein, the term "D90" refers to a diameter in which 90% of the sample (by volume unless otherwise specified) consists of particles having a diameter less than the aforementioned diameter. The example particle size distribution of silicon particles may include D50 particles of approximately 10 nm to 300 nm, or approximately 50 nm to 250 nm, or approximately 100 nm to 200 nm, or approximately 1 nm to 200 nm, and / or D90 particles of approximately 10 nm to 1200 nm, or approximately 10 nm to 1000 nm, or approximately 10 nm to 900 nm, or approximately 700 nm to 1100 nm.

[0015] In some or other instances, at least the majority of the silicon particles present in the composite powder may have sizes ranging from about 25 nm to about 200 nm, or about 50 nm to about 150 nm, or about 50 nm to about 100 nm, or about 50 nm to about 75 nm, or about 75 nm to about 100 nm, or about 75 nm to about 125 nm, or about 125 nm to about 175 nm. It should be noted that silicon particles may undergo size reduction under the grinding and micronization conditions used to produce the composite powders as further described herein, so silicon particles larger than 200 nm may be used to produce the composite powders disclosed herein. For example, before processing the blend of petroleum pitch and silicon particles under the grinding conditions used to produce the composite powders disclosed herein, the silicon particles may have sizes up to about 500 nm.

[0016] The composite powders of this disclosure may further contain graphite, which may be introduced when silicon particles are mixed with petroleum pitch to form the composite powder, or the graphite may be mixed with the composite powder at a later stage. In non-limiting examples, the composite powders may contain graphite in amounts ranging from about 0.1% to about 85% by mass, or about 0.1% to about 60% by mass, or about 5% to about 60% by mass, or about 5% to about 20% by mass, or about 20% to about 40% by mass, or about 30% to about 60% by mass, or about 5% to about 20% by mass, or about 20% to about 40% by mass, based on the total mass of the composite powder. If present, the graphite may further define the matrix containing petroleum pitch. That is, silicon particles (elemental silicon or silicon oxide) may be dispersed in a matrix containing petroleum pitch and graphite, and both petroleum pitch and graphite are in the form of particles. Natural or synthetic graphite, including graphite-like materials such as synthetic graphite derived from coke, may be used in connection with the foregoing. Graphite may be delivered in any suitable powder form. The composite powders of this disclosure may have particle sizes ranging from about 1 μm to about 50 μm, or about 5 μm to about 50 μm, or about 1 μm to about 25 μm, or about 5 μm to about 25 μm, or about 10 μm to about 30 μm. That is, the composite powders may contain at least petroleum pitch particles within the aforementioned size ranges. Silicon particles and graphite particles (if present) may be within the same or smaller size range as the petroleum pitch particles. Preferably, the silicon particles may be smaller than the petroleum pitch particles and within the nanoparticle size range, as discussed above.

[0017] The above composite powder can serve as a precursor composite material for forming a carbon composite material in which petroleum pitch is pyrolyzed (carbonized) to form a carbon matrix containing amorphous carbon and / or graphite. Amorphous carbon can be formed by exposing petroleum pitch to a temperature ranging from about 700 °C to about 1800 °C, or from about 900 °C to about 1800 °C, or from about 900 °C to about 1500 °C, or from about 1000 °C to about 1500 °C, or from about 900 °C to about 1400 °C in an oxygen-free or very low-oxygen environment (e.g., an oxygen content of about 0.1 mol% or less), preferably in the presence of an inert gas environment. Graphite can also be formed by heating at a higher temperature ranging from about 2000 °C to about 3400 °C or from about 2500 °C to about 3400 °C, again in an oxygen-free or very low-oxygen environment, preferably in the presence of an inert gas environment. Amorphous carbon can be spectroscopically distinguished from graphite by, for example, powder X-ray diffraction as recognized by those skilled in the art. Amorphous carbon further lacks long-range molecular order, while graphite is a covalent crystal defined by sheets of sp 2 hybridized carbon atoms. Preferably, upon carbonization to amorphous carbon, the resulting composition can be suitable for forming an anode for a battery, for example, a lithium-ion battery.

[0018] A small amount of mass loss can occur when the composite powder is carbonized to form a carbon matrix. Without being limited by theory or mechanism, the mass loss is thought to be due to various reactions of petroleum pitch that form gaseous products. Such reactions can include, for example, dehydrogenation, polymerization with loss of side chains and / or hydrogen generation, condensation of aromatic rings, and decomposition of oxygen-containing groups. The gaseous products can include, for example, carbon monoxide, carbon dioxide, water vapor, hydrocarbon vapor, methane, etc. Up to about 20 mass% of the petroleum pitch can undergo mass loss due to such reactions during carbonization. Preferably, the amount of mass loss is about 10 mass% or less, or about 5 mass% or less, or about 2 mass% or less. Such mass loss occurring during carbonization can increase the resulting carbon matrix with a corresponding filling amount of silicon up to about 60 mass% of such total mass.

[0019] Prior to carbonization, the composite powder of this disclosure may be heated at a temperature below the softening point of petroleum pitch, preferably in a low-oxygen environment (0.1 mol% to 20 mol% oxygen). Heating in this manner may help improve the mechanical integrity of the composite powder through at least partial crosslinking of petroleum pitch. Such heating may also aid in the adhesion of silicon particles within the matrix defined by petroleum pitch (e.g., on the outer surface of the pitch particles), for example, by at least partially embedding silicon particles on the outer surface of the petroleum pitch particles defining the matrix. In non-limiting examples, heating may be carried out at temperatures above room temperature and below about 500°C, or below about 400°C, or below about 300°C, or below about 200°C, for example, within the range of about 200°C to about 450°C, or about 200°C to about 300°C, or about 200°C to about 250°C, or about 300°C to about 450°C. The actual temperature may be selected considering the softening temperature of petroleum pitch. In some cases, a low-oxygen environment may have oxygen concentrations ranging from approximately 1 mol% to approximately 20 mol%, or approximately 1 mol% to approximately 15 mol%, or approximately 1 mol% to approximately 10 mol%, or approximately 1 mol% to approximately 5 mol%. Such heating below the softening temperature of petroleum pitch in the presence of a low-oxygen environment can induce a crosslinking reaction, thereby stabilizing the petroleum pitch and, preferably, raising the softening temperature before carbonization.

[0020] After carbonization achieved by heating petroleum pitch in the composite powder to a suitable temperature, the composition produced from the composite powder may contain up to about 60% by mass of silicon (elemental silicon or silicon dioxide) particles dispersed in a carbon matrix, the carbon matrix arising from the carbonization of the pitch. Depending on the carbonization conditions, the carbon matrix may contain amorphous carbon, graphite, or any combination thereof. Preferably, the carbon matrix may contain amorphous carbon, or may be essentially composed of it. Preferably, the carbon matrix may remain mainly in particulate form, although solidification of small amounts of particles may occur when the composite powder is carbonized. In a non-limiting example, the composite powder can be heated at a temperature ranging from about 700°C to about 1800°C, or from about 900°C to about 1800°C, or from about 900°C to about 1500°C, or from about 900°C to about 1400°C, or from about 1000°C to about 1500°C. Such temperatures can form a carbon matrix containing amorphous carbon, which may involve silicon carbide formation at high temperatures above about 1500°C. In some or other examples, the petroleum pitch can be converted to graphite by heating the composite powder (or the carbon matrix resulting from the carbonization of the composite powder) at from about 2000°C to about 3500°C, or from about 2000°C to about 3400°C, or from about 2500°C to about 3400°C, or from about 2500°C to about 3000°C, or from about 3000°C to about 3400°C, or from about 2800°C to about 3200°C. A graphitization catalyst can be present as needed, especially to promote graphitization at low temperatures within these ranges. The heating to promote graphitization can be carried out in an oxygen-free or very low oxygen environment containing up to about 0.1 mol% oxygen, preferably in the presence of an inert gas.

[0021] The dry blending method for making the compositions described herein enables single-step processing of the materials to form a precursor composite material having a powder form, thereby ensuring an appropriate particle size and proper dispersion of the silicon particles therein. The precursor composite material obtained by dry blending, preferably low-temperature blending, can further achieve a satisfactory dispersion of the silicon particles while maintaining a relatively low temperature, in a manner that limits undesirable oxidation, by combining a plurality of silicon particles, petroleum pitch, and optional graphite. Combining the components of the precursor composite material by the foregoing methods can include milling, extrusion, grinding, etc., or any combination thereof. In non-limiting examples, the composite powders disclosed herein may be formed by milling or grinding suitable petroleum pitch, suitable silicon, and graphite particles during a milling or grinding process, preferably carried out in a continuous milling or grinding process, more preferably in a screw mill extruder. While not theoretically bound, the milling or grinding may suitably combine the silicon, graphite particles, and petroleum pitch in a well-dispersed state, further reducing the particle size of individual components within the composite powder (e.g., silicon particles, petroleum pitch, optional graphite, etc.). Therefore, the silicon particles introduced into the screw mill extruder do not necessarily have to be within the final size range present in the composite powder. For example, the silicon particles introduced into the screw mill extruder may be up to about 10 μm, or up to about 5 μm, or up to about 1 μm, or up to about 500 nm, and may undergo size reduction to within the above size range in the composite powder. The screw mill may be of any size and configuration suitable for achieving favorable dispersion of silicon particles within petroleum pitch and for achieving a desired reduction in size. It should be recognized that the composite powder may also be produced by related processes, such as discontinuous (batch) processes, e.g., ball or sand milling.

[0022] Accordingly, the method of the present disclosure may include the steps of forming a blend containing up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and optionally about 0.1% to about 85% by mass of graphite, relative to the total mass of each blend, and processing the blend under grinding conditions to form the composite powders discussed in more detail above. Under grinding conditions (dry blending conditions), the silicon particles become dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains a plurality of pitch particles. Preferably, the grinding conditions may include the use of an extruder such as a screw mill extruder, where the composite powder is formed under continuous extrusion conditions. Extrusion may be carried out under dry blending conditions below the softening temperature of petroleum pitch. Preferably, the composite powder is formed under dry blending conditions, which can reduce energy consumption compared to a melt blending process. In some examples, dry blending in an extruder may be carried out by cooling the extruder temperature to below room temperature, for example, to about -10°C to about 5°C, or about -10°C to about 0°C, or about -5°C to about 5°C, or about -5°C to about 0°C, when processing the blend to form the composite powder. Discontinuous grinding processes, such as ball or sand milling, may be carried out in the same manner at temperatures below room temperature. As indicated above, such dry blending processes may result in the dispersion of silicon particles between pitch particles, for example, in the void spaces between pitch particles.

[0023] Alternatively, the composite powders of the present disclosure may be formed under melt-blending conditions above the softening temperature of petroleum pitch. Such a melt-blending process may be carried out above the softening temperature of petroleum pitch under continuous grinding conditions in a screw mill extruder, or in a batch process using ball or sand milling, thereby reducing the size of the silicon particles and causing at least some of the silicon particles to be incorporated into the petroleum pitch. Subsequently, the petroleum pitch is cooled below its softening temperature, followed by grinding, which grinds the petroleum pitch into particulate matter, dispersing all or most of the silicon particles within the pitch particles. Depending on the melt-blending conditions, at least some of the silicon particles may remain in the interstitial spaces between the pitch particles and / or be partially embedded at least within the outer surface of the pitch particles. It should be recognized that combined grinding processes are also envisioned in this disclosure. For example, two or more extruders may be used sequentially to achieve a desired particle size or degree of blend, and / or two or more extruders may be used in parallel to increase throughput. In some or other examples, when producing the composite powders described herein, a ball or jet milling process may follow the extrusion process, and vice versa. In yet another example, a dry blending process may follow a melt blending process to produce a composite powder having silicon particles dispersed both within and between the pitch particles.

[0024] Embodiments disclosed herein include: A. Composite powder. The composite powder contains silicon particles up to approximately 50% by mass relative to the total mass of the composite powder, petroleum pitch from approximately 15% to approximately 95% by mass relative to the total mass of the composite powder, and graphite particles up to approximately 80% by mass relative to the total mass of the composite powder. The silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains multiple pitch particles. B. Composition obtained from composite powder. The composition contains up to about 60% by mass of silicon particles dispersed in a carbon and graphite matrix relative to the total mass of the composition, the silicon particles being dispersed in the carbon and graphite matrix, and the carbon matrix containing amorphous carbon. B1. A battery anode containing composition B. B2. Lithium-ion battery including anode for B1 battery. C. Method for producing a composite powder. The method comprises the steps of forming a blend containing up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and up to about 80% by mass of graphite particles, relative to the total mass of the blend, and processing the blend under grinding conditions to form a composite powder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains multiple pitch particles. D. A melt blending method for producing a composite powder. The method comprises the steps of forming a blend containing up to about 50% by mass of silicon particles, about 15% to about 95% by mass of petroleum pitch, and up to 80% by mass of graphite particles relative to the total mass of the blend; processing the blend under grinding conditions above the softening temperature of petroleum pitch, and forming a composite powder after cooling; and obtaining the composite powder from the outlet of a screw mill extruder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains a plurality of pitch particles having silicon particles dispersed therein. Optionally, at least some of the silicon particles may remain outside the pitch particles.

[0025] Embodiments A to D may have one or more of the following additional elements in any combination. Element 1: Petroleum pitch contains approximately 50% or more by mass of mesophase pitch. Element 1A: Petroleum pitch contains approximately 80% or more by mass of mesophase pitch. Element 2: The composite powder further contains approximately 0.1% to 85% by mass of graphite relative to the total mass of the composite powder, and the matrix further contains graphite. Element 2A: The composition further comprises about 0.1% to about 85% by mass of graphite relative to the total mass of the composition, and the carbon matrix further comprises graphite. Element 3: Silicon particles are dispersed in the gaps between pitch particles. Element 4: At least some of the silicon particles are embedded on the outer surface of the pitch particles. Element 5: At least the vast majority of silicon particles are located inside pitch particles.

[0026] Element 6: Pitch particles have a particle size ranging from approximately 1 μm to approximately 25 μm. Element 6A: The pitch particles have a particle size ranging from approximately 5 μm to approximately 25 μm. Element 7: At least the vast majority of silicon particles have a size ranging from approximately 50 nm to approximately 200 nm. Element 8: The composite powder contains approximately 2% to 30% by mass of silicon particles. Element 9: The composition is produced by a process comprising the steps of obtaining a composite powder of A, and heating petroleum pitch in an environment optionally containing about 0.1 mol% or less of oxygen at a temperature sufficient to form a carbon matrix, wherein the carbon matrix is ​​in particulate form. Element 10: The temperature ranges from approximately 700°C to approximately 1800°C. Element 11: The step of processing the blend under grinding conditions includes the steps of mixing the blend in a screw mill extruder under dry blending conditions and obtaining a composite powder from the outlet of the screw mill extruder.

[0027] Element 12: Dry blending conditions are carried out below the softening temperature of petroleum pitch. Element 13: The screw mill extruder is cooled to a temperature of approximately -10°C to approximately 5°C when processing the blend. Element 14: The step of processing the blend under grinding conditions includes the step of ball-milling the blend. Element 15: The silicon particles have a size of up to approximately 500 nm before processing the blend under grinding conditions, and the size of the silicon particles ranges from approximately 50 nm to approximately 200 nm after processing the blend under grinding conditions. Element 16: The method further comprises the step of heating the composite powder at a temperature ranging from approximately 200°C to approximately 450°C. Element 17: The method further comprises the step of at least partially carbonizing the composite powder at a temperature ranging from about 700°C to about 1800°C in an environment containing less than about 0.1 mol% oxygen. Element 18: The step of processing the blend under grinding conditions includes the steps of mixing the blend in a screw mill extruder under molten blend conditions above the softening temperature of petroleum pitch, cooling the blend after mixing, and obtaining a composite powder from the outlet of the screw mill extruder.

[0028] As a non-limiting example, exemplary combinations applicable to A-C include, but are not limited to, 1 and 2 or 2A; 1 and 3; 1, 3 and 4; 1 and 5; 1 and 6; 1 and 7; 1 and 8; 3 and 4; 3 and 6; 3 and 7; 3 and 8; 3, 4 and 6; 3, 4 and 7; 3, 4 and 8; 5 and 6; 5 and 7; 5 and 8; and 7 and 8. With respect to C, any one of 1-8 may be further combined with any one or more of 9-17. Additional exemplary combinations applicable to C include, but are not limited to, any of the aforementioned combinations further combined with 9; 9 and 10; 11; 11 and 12; 11 and 13; 14; 15; 16; 17; or 18. Further additional exemplary combinations applicable to C include, but are not limited to, 11 and 12; 11 and 13; 11 and 15; 11 and 16; 11 and 17; 14 and 15; 14 and 16; 14 and 17; 15 and 16; 15 and 17; 16 and 17; 15 and 18; 16 and 18; and 17 and 18.

[0029] Additional embodiments disclosed herein include those defined by the following non-limiting sections. Section 1. A composite powder comprising silicon particles up to approximately 50% by mass relative to the total mass of the composite powder, petroleum pitch from approximately 15% to approximately 95% by mass relative to the total mass of the composite powder, and graphite particles up to approximately 80% by mass relative to the total mass of the composite powder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains multiple pitch particles. Section 2. Petroleum pitch is a composite powder of Section 1, containing approximately 50% or more by mass of mesophase pitch. Section 3. A composite powder according to Section 1 or 2, further containing approximately 0.1% to approximately 85% by mass of graphite relative to the total mass of the composite powder, and the matrix further containing graphite. Section 4. Silicon particles are dispersed in the interstitial spaces between pitch particles, in one of the composite powders described in Sections 1-3.

[0030] Section 5. A composite powder of any one of Sections 1-4, wherein at least some silicon particles are embedded on the outer surface of pitch particles. Section 6. A composite powder of any one of sections 1-3, in which at least the majority of silicon particles are located inside pitch particles. Section 7. Pitch particles are composite powders of any one of the components described in Sections 1 to 6, with particle sizes ranging from approximately 1 μm to approximately 25 μm. Section 8. A composite powder consisting of at least the majority of silicon particles, ranging in size from approximately 50 nm to approximately 200 nm, from any one of the components described in Sections 1 to 7. Section 9. The composite powder is one of the composite powders described in Sections 1 to 8, containing approximately 2% to 30% by mass of silicon particles. Section 10. A composition comprising silicon particles dispersed in a carbon matrix at a concentration of up to approximately 60% by mass relative to the total mass of the composition, wherein the carbon matrix comprises amorphous carbon. Section 11. The composition of Section 10, further comprising about 0.1% to about 85% by mass of graphite relative to the total mass of the composition, and the carbon matrix further comprising graphite. Section 12. The composition of Section 10 or 11, which is produced by a process comprising the steps of obtaining a composite powder from any one of Sections 1 to 9, and heating petroleum pitch to a temperature sufficient to form a carbon matrix in an environment containing about 0.1 mol% or less of oxygen.

[0031] Section 13. The composition described in Section 12, with a temperature ranging from approximately 700°C to approximately 1800°C. Section 14: The carbon matrix is ​​in particulate form, and is one of the compositions described in Sections 10-13. A battery anode comprising any one of the compositions described in Section 15.10 to 14. Lithium-ion battery, including anodes for the battery as described in Sections 16 and 15. Section 17. A method comprising the steps of forming a blend containing silicon particles up to about 50% by mass, petroleum pitch from about 15% to about 95% by mass, and graphite particles up to about 80% by mass, relative to the total mass of the blend, and processing the blend under grinding conditions to form a composite powder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains a plurality of pitch particles. Section 18. The method of Section 17, wherein the step of processing the blend under grinding conditions includes the steps of mixing the blend in a screw mill extruder under dry blending conditions and obtaining a composite powder from the outlet of the screw mill extruder. Section 19. Dry blending conditions are carried out below the softening temperature of petroleum pitch, according to the method in Section 18. Section 20. The screw mill extruder is cooled to a temperature of approximately -10°C to approximately 5°C when processing the blend, according to the method of Section 18 or 19.

[0032] Section 21. The step of processing the blend under grinding conditions includes the step of ball-milling the blend, as in the method of Section 17. Section 22. The method of Section 17, wherein the step of processing the blend under grinding conditions includes the steps of mixing the blend in a screw mill extruder under molten blend conditions above the softening temperature of petroleum pitch, cooling the blend after mixing, and obtaining a composite powder from the outlet of the screw mill extruder. Section 23. Petroleum pitch is a method of any one of sections 16 to 22, containing approximately 50% by mass or more of mesophase pitch. Section 24. The blend further contains approximately 0.1% to approximately 85% by mass of graphite relative to the total mass of the blend, and the matrix further contains graphite, according to any one method of Sections 16 to 23. Section 25. Pitch particles have a particle size ranging from approximately 1 μm to approximately 25 μm, using one of the methods described in Sections 16 to 24.

[0033] Section 26. The silicon particles have a size of up to approximately 500 nm before processing the blend under grinding conditions, and the size of the silicon particles after processing the blend under grinding conditions ranges from approximately 50 nm to approximately 200 nm, according to one of the methods in Sections 16 to 25. Section 27. The composite powder contains approximately 2% to 30% by mass of silicon particles, prepared using one of the methods described in Sections 16 to 26. Section 28. Any one of the methods described in Sections 16 to 27, further comprising the step of heating the composite powder at a temperature ranging from approximately 200°C to approximately 450°C in an environment containing approximately 0.1 mol% to approximately 20 mol% oxygen. Section 29. Any one of the methods described in Sections 16 to 28, further comprising the step of at least partially carbonizing the composite powder at a temperature ranging from approximately 700°C to approximately 1800°C in an environment containing approximately 0.1 mol% or less of oxygen. To facilitate a better understanding of the embodiments of this disclosure, the following examples of preferred or representative embodiments are provided. The following examples should not be read in any way as limiting or defining the scope of the invention. [Examples]

[0034] Composite powder samples were prepared by blending neat petroleum pitch, silicon or silicon dioxide (SiO2) particles with a diameter of approximately 500 nm, and optionally graphite, in a screw mill extruder under dry blend or melt blend conditions. The detailed compositions of samples E1 to E6 are shown in Table 1 below. Dry blends (samples E1 to E3) were carried out using an extruder cooled to a range of -5°C to 5°C at an extruder rotation speed of 300 rpm. Melt blends (samples E4 to E9) were carried out at over 280°C at the same rotation speed. After obtaining the resulting composite powder, the sample was placed inside a furnace and further heated to a temperature of 200°C to 300°C, below the softening point of petroleum pitch, to fix the silicon particles in the pitch matrix and to at least partially react oxygen with the petroleum pitch. Comparative samples without petroleum pitch (samples C1 and C2) were ground into fine powder using a ball and / or jet mill to obtain D50, similar to the experimental composite powder. The silicon-containing composite powder was processed with graphite in an appropriate ratio using a ball / jet mill to prepare comparative graphite-pitch-silicon samples (samples E4 and E5). The silicon-containing composite powder was added to a graphite and anode slurry to prepare comparative graphite-pitch-silicon samples (E10 and E11).

[0035] [Table 1]

[0036] Cross-sectional SEM-BSE (scanning electron microscope-backscattered electron) images of samples E1-E3 are shown in Figures 2A-2C. Uniform dispersion of silicon in the resulting composite powder was achieved with a packing amount of up to 30% by mass. Bright spots in the SEM-BSE images are Si particles. The composite powder was subsequently carbonized at temperatures of 900°C, 1100°C, 1200°C, and 1500°C. The degree of silicon carbide formation was tracked using powder X-ray diffraction (XRD), as shown in Figure 3. The patterns and peak positions of the samples heated at 900°C and 1200°C suggest the continued presence of elemental silicon. At 1500°C, the 26° peak became more prominent, indicating carbon formed from pitch, and new peaks at 36°, 41.5°, 60°, and 72° are thought to indicate the formation of silicon carbide. Selected samples, carbonized to 1100°C, were formed into half-cell coin batteries where the carbonized sample formed the anode and the counter electrode contained lithium. The batteries were operated for 5 cycles at a charge level of 0.1C. The discharge capacity and initial Coulomb efficiency (ICE) are shown in Table 2 below.

[0037] [Table 2] As shown, the samples formed from silicon-containing composite powders exhibited improved battery capacity exceeding that theoretically predicted for pure carbon-based active materials, as demonstrated in the comparative samples. The initial Columbic efficiencies (ICE) of both the experimental and comparative samples were all relatively high, remaining above 75%.

[0038] All documents described herein, including any priority documents and / or test procedures, are incorporated herein by reference to the extent that they do not contradict the text, for the purposes of all authority on which such practice is permitted. As is evident from the summary and specific embodiments described herein, the forms of this disclosure are illustrative and described, but can be modified in various ways without departing from the spirit and scope of this disclosure. Therefore, it is not intended that this disclosure will be limited by such modifications. For example, the compositions described herein do not have to include any components or compositions not expressly listed or disclosed herein. No method does not have to include any steps not listed or disclosed herein. Similarly, the term “comprising” is to be considered synonymous with the term “including.” Whenever a transitional phrase “including” precedes a method, composition, element or group of elements, it is understood that the inventors also envision the same composition or group of elements preceded by transitional phrases such as “essentially consisting of,” “consisting of,” “selected from a group consisting of,” or “is,” and vice versa.

[0039] Unless otherwise indicated, all numbers used in this specification and related claims to express raw materials, properties, such as molecular weight, reaction conditions, etc., should be understood in all examples to be modified by the term “approximately.” Therefore, unless otherwise indicated, the numerical parameters expressed in the following specification and appended claims are approximations that may vary depending on the desired properties to be obtained by one or more embodiments described herein. Each numerical parameter should be interpreted, at least in light of the reported number of significant figures and by applying common rounding techniques, not as an attempt to limit the application of the doctrine of equivalents to the claims.

[0040] Whenever a numerical range with lower and upper limits is disclosed, all numbers that fall within that range and the ranges in which any of them are included are specifically disclosed. More specifically, any range values ​​disclosed herein (in the form of "about a to about b" or equivalently "about a to b (from approximately a to b)" or equivalently "about a to b (from approximately ab)") should be understood to specify all numbers and ranges that are encompassed within a broader range of values. Furthermore, terms in the claims have plain and ordinary meanings unless otherwise explicitly and obviously defined by the patent holder. In addition, the indefinite articles "a" or "an" used in the claims are defined herein to mean one or more of the elements they introduce.

[0041] One or more illustrative embodiments are presented herein. Not all features of the physical implementation are described or shown in this application for clarity. It is understood that in developing the physical embodiments of the Disclosure, numerous implementation-specific decisions, such as implementation and compliance with ever-changing system-related, business-related, government-related, and other constraints, must be made to achieve the developer's goals. While the developer's efforts may be time-consuming, such efforts are still routine work for those skilled in the art and are of interest to the Disclosure. Accordingly, this disclosure is well adapted to obtain the purposes and benefits mentioned herein, as well as its unique characteristics. Since this disclosure can be modified and practiced in different but equivalent ways that are obvious to those skilled in the art, the detailed embodiments disclosed herein are merely illustrative and have the benefit of teaching herein. Furthermore, no limitation to the details of construction or design herein is intended beyond those described in the following claims. Accordingly, it is evident that the detailed illustrative embodiments disclosed herein can be changed, combined, or modified, and all such variations are considered to be within the scope and spirit of this disclosure. The embodiments disclosed herein as illustrations may preferably be practiced without any elements not specifically disclosed herein, and / or any optional elements disclosed herein.

Claims

1. A composite powder comprising up to approximately 50% by mass of silicon particles relative to the total mass of the composite powder, and approximately 15% to approximately 95% by mass of petroleum pitch relative to the total mass of the composite powder, and may also comprising up to approximately 80% by mass of graphite particles relative to the total mass of the composite powder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains multiple pitch particles.

2. The composite powder according to claim 1, wherein the petroleum pitch contains approximately 50% by mass or more of mesophase pitch.

3. The composite powder according to claim 1, further comprising about 0.1% to about 85% by mass of graphite relative to the total mass of the composite powder, wherein the matrix further comprises graphite.

4. The composite powder according to claim 1, wherein silicon particles are dispersed in the interstitial spaces between pitch particles.

5. The composite powder according to claim 4, wherein at least a portion of the silicon particles are embedded on the outer surface of the pitch particles.

6. The composite powder according to claim 1, wherein at least the majority of silicon particles are located inside the pitch particles.

7. The composite powder according to claim 1, wherein the pitch particles have a particle size ranging from about 1 μm to about 25 μm.

8. The composite powder according to claim 1, wherein at least the majority of the silicon particles have a size ranging from about 50 nm to about 200 nm.

9. The composite powder according to claim 1, wherein the composite powder contains about 2% by mass to about 30% by mass of silicon particles.

10. A composition comprising silicon particles up to about 60% by mass dispersed in a carbon and graphite matrix, relative to the total mass of the composition, wherein the carbon matrix contains amorphous carbon with a degree of graphitization of up to 60%.

11. The composition further contains approximately 0.1% to approximately 85% by mass of graphite relative to the total mass of the composition. The composition according to claim 10, wherein the carbon matrix further comprises graphite.

12. The composition is A composite powder comprising up to approximately 50% by mass of silicon particles relative to the total mass of the composite powder, and approximately 15% to approximately 95% by mass of petroleum pitch relative to the total mass of the composite powder, and possibly up to approximately 80% by mass of graphite particles relative to the total mass of the composite powder, wherein the silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains multiple pitch particles, a step of obtaining a composite powder, The step of heating the composite powder to a temperature sufficient to form a carbon matrix in an environment containing approximately 0.1 mol% or less of oxygen. The composition according to claim 10, produced by a process including the following:

13. The composition according to claim 12, wherein the temperature ranges from approximately 700°C to approximately 1800°C.

14. The composition according to claim 10, wherein the carbon matrix is ​​in the form of particles.

15. A battery electrode comprising the composition described in claim 10.

16. A lithium-ion battery comprising the battery electrode described in claim 15.

17. A step of forming a blend containing up to approximately 50% by mass of silicon particles and approximately 15% to approximately 95% by mass of petroleum pitch, and which may also contain up to 80% by mass of graphite particles, based on the total mass of the blend. A method comprising the step of reducing the average particle size of a blend to form a composite powder, wherein silicon particles are dispersed in a matrix containing petroleum pitch, and the petroleum pitch contains a plurality of pitch particles.

18. The method according to claim 17, wherein the blend further comprises a graphitizing catalyst.

19. The method according to claim 17, wherein the step of reducing the average particle size of the blend includes the step of mixing the blend in a screw mill extruder under dry blending conditions, and the step of obtaining a composite powder from the outlet of the screw mill extruder.

20. The method according to claim 18, wherein the drying blending conditions are performed below the softening temperature of petroleum pitch.

21. The method according to claim 18, wherein the screw mill extruder is cooled to a temperature of about -10°C to about 5°C when processing the blend.

22. The method according to claim 17, wherein the step of reducing the average particle size of the blend includes the step of ball-milling or jet-milling the blend.

23. The method according to claim 17, wherein the step of reducing the average particle size of the blend includes the steps of mixing the blend in a screw mill extruder under molten blend conditions above the softening temperature of petroleum pitch, cooling the blend after mixing, and obtaining a composite powder from the outlet of the screw mill extruder.

24. The method according to claim 17, wherein the petroleum pitch contains approximately 50% by mass or more of mesophase pitch.

25. The blend further contains approximately 0.1% to 85% by mass of graphite relative to the total mass of the blend. The method according to claim 17, wherein the matrix further comprises graphite.

26. The method according to claim 17, wherein the pitch particles have a particle size ranging from about 1 μm to about 25 μm.

27. The method according to claim 17, wherein the silicon particles have a size up to about 500 nm before the step of reducing the average particle size of the blend, and a size ranging from about 50 nm to about 200 nm after the step of reducing the average particle size of the blend.

28. The method according to claim 17, wherein the composite powder contains about 2% by mass to about 30% by mass of silicon particles.

29. The method according to claim 17, further comprising the step of heating the composite powder at a temperature ranging from about 200°C to about 450°C in an environment containing about 0.1 mol% to about 20 mol% oxygen.

30. The method according to claim 17, further comprising the step of at least partially carbonizing a composite powder at a temperature ranging from about 700°C to about 1800°C in an environment containing about 0.1 mol% or less of oxygen, thereby at least partially converting petroleum pitch to carbon with a degree of graphitization of up to 60%.

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