Plasma process for purification of graphite

Abstract

A plasma process for purifying a graphite feed material is disclosed herein. The process comprises producing a plasma to bring a graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a purified graphite material. The gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1:4. The hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8.

Description

TITLEPLASMA PROCESS FOR PURIFICATION OF GRAPHITECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application 63 / 602,051 , filed November 22, 2023. The contents of the referenced application are incorporated into the present application by reference.BACKGROUND1. Field

[0002] This disclosure broadly relates to the field of thermal purification of graphite. More specifically, but not exclusively, the present disclosure relates to the purification of graphite using a plasma torch. Yet more specifically, the present disclosure relates to a process for the purification of graphite using a thermal plasma torch and a plasma gas comprising CO2 and a hydrocarbon. Furthermore, the present disclosure relates to a thermal plasma process for modifying the surface pH of graphite. The present disclosure also relates to plasma purified particulate graphite for use in lithium-ion batteries (LiBs).2. Related Art

[0003] The following discussion of the background art is only intended to facilitate an understanding of the process described herein.

[0004] Graphite is a polymorphic, crystalline form of carbon. It is formed as a result of the exposure of organic matter to high temperatures and pressures, a process called graphitization. Some graphite deposits are the result of both metamorphism and hydrothermal deposition. Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets.

[0005] Graphite is generally sourced from natural and synthetic sources, with natural graphite being the main source. Natural graphite (NG) is sourced from mines, whereas synthetic graphite may be obtained from petroleum coke. Natural graphite may be categorized as amorphous, microcrystalline, flake or vein graphite. Natural graphite may be sourced from several countries such as China (accounting for 60% of the worlds graphite production), India (accounting for 15% of the worlds graphite production), and Brazil (accounting for 7% of the worlds graphite production). Other countries include Turkey, North Korea, Canada, Mexico, Norway, Russia, and Zimbabwe.

[0006] The versatility of graphite, combined with its unique physical and chemical properties, make it uniquely suitable for a wide range of industrial applications, non-limiting examples of which include its use in the manufacture of welding rods, as a desulfurization agent, in foundry facings, in lubricating oils and greases, as brake linings, as a lubricant, in electrical devices such as electrodes, batteries (e.g., vanadium redox batteries), solar panels, in steel making, the manufacture of graphene, in fuel cells, as cores of nuclear reactors, in conductive coatings, in paints, in pencils, crucibles, refractories, friction products, carbon additives, arc lamps, brushes for electrical motors, hockey sticks, and golf clubs.

[0007] Graphite exhibits both metallic and non-metallic properties. To that effect, graphite features unique properties such as high thermal and electrical conductivity, a low coefficient of thermal expansion, exceptional thermal resistance, high thermal shock resistance, stiffness, strength, lubricity, and inertness. Synthetic graphite (SG) is used in applications requiring higher standards of purity, such as in lead batteries, making it more expensive relative to natural graphite.

[0008] A novel process for the purification of graphite that is of an environmentally cleaner design, and overcoming the technical and economic limitations of the existing commercial processes, is of commercial interest.SUMMARY

[0009] The present disclosure broadly relates to the thermal purification of graphite. More specifically, but not exclusively, the present disclosure relates to the purification of graphite using a plasma torch. Yet more specifically, the present disclosure relates to a process for the purification of graphite using a thermal plasma torch and a plasma gas comprising CO2 and a hydrocarbon. Furthermore, the present disclosure relates to a thermal plasma process for modifying the surface pH of graphite. The present disclosure also relates to plasma purified particulate graphite for use in lithium-ion batteries (LiBs).

[0010] In an aspect, the present disclosure relates to a process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a purified graphite material. In an embodiment of the present disclosure, the process further comprises cooling the purified graphite material to a temperature ranging from about 25°Cto about 500°C by injecting a quench gas. In an embodiment of the present disclosure, the process further comprises collecting the purified graphite material. In an embodiment of the present disclosure, the gas mixture is injected into the plasma. In an embodiment of the present disclosure, the gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. In an embodiment of the present disclosure, the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. In an embodiment of the present disclosure, the hydrocarbon is CH4. In an embodiment of the present disclosure, the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0011] In an aspect, the present disclosure relates to a process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the plasma to produce a purified graphite material. In an embodiment of the present disclosure, the process further comprises cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. In an embodiment of the present disclosure, the process further comprises collecting the purified graphite material. In an embodiment of the present disclosure, the plasma is produced using a gas mixture comprising CO2 and a hydrocarbon. In an embodiment of the present disclosure, the gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. In an embodiment of the present disclosure, the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. In an embodiment of the present disclosure, the hydrocarbon is CH4. In an embodiment of the present disclosure, the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0012] In an aspect, the present disclosure relates to a process for graphite purification, the process comprising: determining the impurity content of a graphite feed material to be purified; using process simulation and / or modeling software to model a plasma arc reaction for the graphite feed material to be purified and a purification agent comprising CO2 and a hydrocarbon; feeding the graphite feed material into a thermal plasma torch producing a purified graphite material. In an embodiment of the present disclosure, the process further comprises producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the purification agent comprising CO2 and a hydrocarbon producing thepurified graphite material; and cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. In an embodiment of the present disclosure, the process further comprises collecting the purified graphite material. In an embodiment of the present disclosure, the purification agent is injected into the plasma. In an embodiment of the present disclosure, the purification agent comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. In an embodiment of the present disclosure, the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. In an embodiment of the present disclosure, the hydrocarbon is CH4. In an embodiment of the present disclosure, the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0013] In an aspect, the present disclosure relates to a thermal plasma process for treating a particulate graphite feed material, the process comprising: producing a plasma to bring the particulate graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the particulate graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a plasma treated particulate graphite material; wherein the plasma treated particulate graphite material comprises an increased surface pH and / or a modified surface. In an embodiment of the present disclosure, the process further comprises cooling the plasma treated particulate graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. In an embodiment of the present disclosure, the process further comprises collecting the plasma treated particulate graphite material. In an embodiment of the present disclosure, the gas mixture is injected into the plasma. In an embodiment of the present disclosure, the gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. In an embodiment of the present disclosure, the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. In an embodiment of the present disclosure, the hydrocarbon is CH4. In an embodiment of the present disclosure, the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0014] In an aspect, the present disclosure relates to a graphite material purified by a thermal plasma process, the thermal plasma process comprising the use of a plasma produced using a gas mixture comprising CO2 and a hydrocarbon.

[0015] In an aspect, the present disclosure relates to a surface-pH modified graphite material produced by a thermal plasma process, the thermal plasma process comprising the use of a plasma produced using a gas mixture comprising CO2 and a hydrocarbon.

[0016] In an aspect, the present disclosure relates to a surface modified graphite material produced by a thermal plasma process, the thermal plasma process comprising the use of a plasma produced using a gas mixture comprising CO2 and a hydrocarbon.

[0017] In an aspect, the present disclosure relates to an electrode or electrochemical storage device comprising a graphite material purified by a thermal plasma process, the thermal plasma process comprising the use of a plasma produced using a gas mixture comprising CO2 and a hydrocarbon. In an embodiment of the present disclosure, the electrode or electrochemical storage device comprises lithium-ion batteries (LiBs).

[0018] Also disclosed in the context of the present disclosure are embodiments 1 to 74. Embodiment 1 is a process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a purified graphite material. Embodiment 2 is the process of embodiment 1 , further comprising cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. Embodiment 3 is the process of embodiment 1 or 2, further comprising collecting the purified graphite material. Embodiment 4 is the process of any one of embodiments 1 to 3, wherein reacting the graphite feed material with the gas mixture comprises injecting the gas mixture into the plasma. Embodiment 5 is the process of any one of embodiments 1 to 4, wherein the gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. Embodiment 6 is the process of any one of embodiments 1 to 5, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. Embodiment 7 is the process of embodiment 6, wherein the hydrocarbon is CH4. Embodiment 8 is the process of any one of embodiments 1 to 7, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs. Embodiment 9 is the process of any one of embodiments 1 to 8, wherein the plasma is produced using a readily ionizable working gas. Embodiment 10 is the process of embodiment 9, wherein the readily ionizable working gas comprises at least one of He, Ar and N2. Embodiment 11 is the process of any one of embodiments 1 to 10, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radio-frequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma. Embodiment 12 is the process of embodiment 11 , wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch. Embodiment 13is the process of embodiment 11 or 12, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation. Embodiment 14 is the process of embodiment 13, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis. Embodiment 15 is the process of any one of embodiments 1 to 14, further comprising adjusting a composition of the gas mixture based on postplasma mixture composition analysis. Embodiment 16 is the process of any one of embodiments 1 to 15, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis. Embodiment 17 is the process of any one of embodiments 1 to 16, further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns. Embodiment 18 is the process of any one of embodiments 1 to 17, wherein the purified graphite material comprises a purity in excess of 99 wt.% C.

[0019] Embodiment 19 is a process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the plasma to produce a purified graphite material. Embodiment 20 is the process of embodiment 19, further comprising cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. Embodiment 21 is the process of embodiment 19 or 20, further comprising collecting the purified graphite material. Embodiment 22 is the process of any one of embodiments 19 to 21 , wherein the plasma is produced using a gas mixture comprising CO2 and a hydrocarbon. Embodiment 23 is the process of any one of embodiments 19 to 22, wherein the gas mixture comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. Embodiment 24 is the process of any one of embodiments 19 to 23, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. Embodiment 25 is the process of embodiment 24, wherein the hydrocarbon is CH4. Embodiment 26 is the process of any one of embodiments 19 to 25, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs. Embodiment 27 is the process of any one of embodiments 19 to 26, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radio-frequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma. Embodiment 28 is the process of embodiment 27, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch. Embodiment 29 is the process of embodiment 27 or 28, wherein the DCthermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation. Embodiment 30 is the process of embodiment 29, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis. Embodiment 31 is the process of embodiment 22, further comprising adjusting a composition of the gas mixture based on post-plasma mixture composition analysis. Embodiment 32 is the process of embodiment 22, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis. Embodiment 33 is the process of any one of embodiments 19 to 32, further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns. Embodiment 34 is the process of any one of embodiments 19 to 33, wherein the purified graphite material comprises a purity in excess of 99 wt.% C. Embodiment 35 is the process of embodiment 2 or 20, wherein the quench gas comprises Ar.

[0020] Embodiment 36 is a process for graphite purification, the process comprising: determining the impurity content of a graphite feed material to be purified; using process simulation and / or modeling software to model a plasma arc reaction for the graphite feed material to be purified and a purification agent comprising CO2 and a hydrocarbon; and feeding the graphite feed material into a thermal plasma torch producing a purified graphite material. Embodiment 37 is the process of embodiment 36, further comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the purification agent comprising CO2 and a hydrocarbon producing the purified graphite material; and cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. Embodiment 38 is the process of embodiment 36 or 37, further comprising collecting the purified graphite material. Embodiment 39 is the process of any one of embodiments 36 to 38, wherein reacting the graphite feed material with the purification agent comprising CO2 and a hydrocarbon comprises injecting the purification agent into the plasma. Embodiment 40 is the process of any one of embodiments 36 to 39, wherein the purification agent comprises a CO2 / hydrocarbon ratio ranging from about 2: 1 to about 1 :4. Embodiment 41 is the process of any one of embodiments 36 to 40, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. Embodiment 42 is the process of embodiment 41 , wherein the hydrocarbon is CH4. Embodiment 43 is the process of any one of embodiments 36 to 42, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs. Embodiment 44 is the process of embodiment 37, wherein theplasma is produced using a readily ionizable working gas. Embodiment 45 is the process of embodiment 44, wherein the readily ionizable working gas comprises at least one of He, Ar and N2. Embodiment 46 is the process of embodiment 37, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radio-frequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma. Embodiment 47 is the process of embodiment 46, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch. Embodiment 48 is the process of embodiment 46 or 47, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation. Embodiment 49 is the process of embodiment 48, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis. Embodiment 50 is the process of any one of embodiments 36 to 49, further comprising adjusting a composition of the purification agent based on post-plasma mixture composition analysis. Embodiment 51 is the process of any one of embodiments 36 to 50, further comprising adjusting a rate of injection of the purification agent based on post-plasma mixture composition analysis. Embodiment 52 is the process of any one of embodiments 36 to 51 , further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns. Embodiment 53 is the process of any one of embodiments 36 to 52, wherein the purified graphite material comprises a purity in excess of 99 wt.% C.

[0021] Embodiment 54 is a thermal plasma process for treating a particulate graphite feed material, the process comprising: producing a plasma to bring the particulate graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the particulate graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a plasma treated particulate graphite material; wherein the plasma treated particulate graphite material comprises an increased surface pH and / or a modified surface. Embodiment 55 is the process of embodiment 54, further comprising cooling the plasma treated particulate graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas. Embodiment 56 is the process of embodiment 54 or 55, further comprising collecting the plasma treated particulate graphite material. Embodiment 57 is the process of any one of embodiments 54 to 56, wherein reacting the particulate graphite feed material with the gas mixture comprises injecting the gas mixture into the plasma. Embodiment 58 is the process of any one of embodiments 54 to 57, wherein the gas mixture comprises a CO2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4. Embodiment 59 is the process of any one of embodiments 54 to 58, whereinthe hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8. Embodiment 60 is the process of embodiment 59, wherein the hydrocarbon is CH4. Embodiment 61 is the process of any one of embodiments 54 to 60, wherein the particulate graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs. Embodiment 62 is the process of any one of embodiments 54 to 61 , wherein the plasma is produced using a readily ionizable working gas. Embodiment 63 is the process of embodiment 62, wherein the readily ionizable working gas comprises at least one of He, Ar and N2. Embodiment 64 is the process of any one of embodiments 54 to 63, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radio-frequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma. Embodiment 65 is the process of embodiment 64, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch. Embodiment 66 is the process of embodiment 64 or 65, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation. Embodiment 67 is the process of embodiment 66, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis. Embodiment 68 is the process of any one of embodiments 54 to 67, further comprising adjusting a composition of the gas mixture based on postplasma mixture composition analysis. Embodiment 69 is the process of any one of embodiments 54 to 68, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis. Embodiment 70 is the process of any one of embodiments 54 to 69, further comprising milling the plasma treated particulate graphite material to a particle size ranging from about 1 to about 50 microns. Embodiment 71 is the process of any one of embodiments 54 to 70, wherein the plasma treated particulate graphite material comprises a purity in excess of 99 wt.% C.

[0022] Embodiment 72 is a graphite material obtained or obtainable by the process of any one of embodiments 1 to 71. Embodiment 73 is an electrode or electrochemical storage device comprising the particulate graphite material of embodiment 72. Embodiment 74 is the electrode or electrochemical storage device of embodiment 73, wherein the electrochemical storage device comprises a lithium-ion battery (LiBs).

[0023] The word “a” or “an” when used in conjunction with the term “comprising” in the claims and / or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one” unless the content clearly dictates otherwise. Similarly, the word “another” may mean at least a second or moreunless the content clearly dictates otherwise.

[0024] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0025] As used in this specification and claim(s), the word “consisting” and its derivatives, are intended to be close ended terms that specify the presence of stated features, elements, components, groups, integers, and / or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and / or steps.

[0026] The term “consisting essentially of’, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and / or steps as well as those that do not materially affect the basic and novel characteristic(s) of these features, elements, components, groups, integers, and / or steps.

[0027] The terms “about”, “substantially” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0028] The foregoing and other advantages and features of the present disclosure will become more apparent upon reading of the following non-restrictive detailed description of illustrative embodiments thereof, with reference to the accompanying drawings / figures. It should be understood, however, that the detailed description and the illustrative embodiments, while indicating specific embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this description.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0029] The following figures / drawings form part of the present specification and are included to further demonstrate certain aspects of the present specification. The present specification may be better understood by reference to one or more of thesefigures / drawings in combination with the detailed description. In the appended drawings / figures:

[0030] FIG. 1 - Illustration of an apparatus including a DC thermal plasma torch, in accordance with an embodiment of the present disclosure.

[0031] FIG. 2 - Illustration of a plasma reactor comprising an inlet (16), exhaust (17), thermocouple (18), view port (19), conical bed (20), air manifold (21), cooling water outlets (22, 23), cooling water inlets (24, 25), plasma gas inlet (26), and plasma torch (27), in accordance with an embodiment of the present disclosure.

[0032] FIG. 3 - Illustration of an X-ray diffractogram of a natural graphite sample before (bottom portion) and after (top portion) thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0033] FIG. 4 - Illustration of an SEM image of a natural graphite feed material (a) before and (b) after thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0034] FIG. 5 - Illustration of an SEM-EDS image of a natural graphite feed material (a) before and (b) after thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0035] FIG. 6 - Illustration of a mapping distribution of a natural graphite feed material before thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0036] FIG. 7 - Illustration of a mapping distribution of a natural graphite feed material after thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0037] FIG. 8 - Illustration of a TG analysis of a natural graphite feed material before and after thermal plasma treatment under an oxidizing atmosphere (left) and an argon atmosphere (right), in accordance with an embodiment of the present disclosure. The mass loss for the thermally treated graphite, under an oxidizing atmosphere, is due to graphite loss in the form of CO2. Under the same conditions, the mass loss for untreated material, is due to graphite loss in the form of CO2 as well as loss of impurities.

[0038] FIG. 9 - Illustration of a dTG analysis of a natural graphite feed material before and after thermal plasma treatment under an oxidizing atmosphere (left) and an argon atmosphere (right), in accordance with an embodiment of the present disclosure.

[0039] FIG. 10 - Illustration of a DSC analysis of a natural graphite feed material before and after thermal plasma treatment under an oxidizing atmosphere (left) and an argon atmosphere (right), in accordance with an embodiment of the present disclosure

[0040] FIG. 11 - Illustration of an XPS spectrum of a natural graphite feed material before (left) and after (right) thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0041] FIG. 12 - Illustration of an FTIR spectrum of a natural graphite feed material before (bottom portion) and after (top portion) thermal plasma treatment, in accordance with an embodiment of the present disclosure.

[0042] FIG. 13 - Illustration of the power variation over time for a plasma torch operating using a plasma gas having CO2 / CH4 ratio of 1 :1 and 2:1 respectively, in accordance with an embodiment of the present disclosure.

[0043] FIG. 14 - Illustration of the enthalpies of a CO2 / CH4 plasma torch (left), an argon plasma torch (bottom), and a nitrogen plasma torch (middle).DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0044] The present disclosure broadly relates to the thermal purification of graphite. More specifically, but not exclusively, the present disclosure relates to the purification of graphite using a plasma torch. Yet more specifically, the present disclosure relates to a process for the purification of graphite using a thermal plasma torch and a plasma gas comprising CO2 and a hydrocarbon. Furthermore, the present disclosure relates to a thermal plasma process for modifying the surface pH of graphite. Yet furthermore, the present disclosure relates to a thermal plasma process for modifying the surface of graphite. The present disclosure also relates to plasma purified particulate graphite for use in lithium-ion batteries (LiBs).

[0045] With reference to FIGs. 1 and 2, and in accordance with an embodiment of the present disclosure, illustrated therein are an apparatus including a DC thermal plasma torch, and a plasma reactor. The apparatus is equipped with a spouted bed reactor comprising a bottom cone in direct contact with the plasma where temperatures can advantageously exceed 2000°C. The walls of the reactor are cooled using cold water to avoid overheating and deformation of the reactor walls. The apparatus was further equipped with one or more filters to remove fine particulate material from the exit gasses. The plasma gas mixture was advantageously comprised of CO2 and a hydrocarbon. In an embodiment of the present disclosure, the plasma gas mixture comprises aCO2 / hydrocarbon ratio ranging from about 1 :1 to about 2:1. In an embodiment of the present disclosure, the hydrocarbon is at least one of CH4, C2H6, and C3H8. In an embodiment of the present disclosure, the hydrocarbon is CH4. Reducing the CO2 / CH4 ratio from 2:1 to 1 :1 ( / .e. increasing the amount of CH4 relative to CO2) increases the reducing power of the plasma gas. In further embodiments of the present disclosure, the current and voltage of the plasma torch were kept constant at 252 amps and 150 V respectively. The pressure within the torch was maintained close to atmospheric pressure or near 760 torr. The plasma gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for the deposition of a carbon layer on the cathode surface during operation. The purified graphite product was cooled using a flow of argon. In further embodiments of the present disclosure, the graphite containing feed material was subjected to plasma treatment for periods ranging from 10 to 45 minutes.

[0046] In an aspect, the present disclosure relates to a process for the purification of graphite using a DC thermal plasma torch and a plasma gas mixture comprising CO2 and a hydrocarbon. In embodiments of the present disclosure, the graphite comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0047] In an aspect, the present disclosure relates to a process for the purification of graphite using a DC thermal plasma torch and a plasma gas mixture comprising CO2 and a hydrocarbon. The use of a plasma gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for generating a plasma exhibiting high enthalpy and high thermal conductivity. Furthermore, a plasma gas mixture comprising CO2 advantageously provides for higher plasma power at lower gas flow rates relative to plasma gasses such as Ar or mixtures such as Ar / CFU. Yet furthermore, the use of a plasma gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for extending the life of the cathode by deposition of a carbon layer on the cathode surface during operation. The carbon layer protects the cathode from erosion. In an embodiment of the present disclosure, the source of the graphite comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0048] In an aspect, the present disclosure relates to a process for modifying the surface pH of graphite using a DC thermal plasma torch and a plasma gas mixture comprising CO2 and a hydrocarbon. The use of a plasma gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for generating a plasma exhibiting high enthalpy and high thermal conductivity. Furthermore, a plasma gas mixture comprising CO2 advantageously provides for higher plasma power at lower gas flow ratesrelative to plasma gasses such as Ar or mixtures such as Ar / CH4. Yet furthermore, the use of a plasma gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for extending the life of the cathode by deposition of a carbon layer on the cathode surface during operation. The carbon layer protects the cathode from erosion. In an embodiment of the present disclosure, the source of the graphite comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

[0049] In an aspect, the present disclosure relates to a process for the purification of graphite using a DC thermal plasma torch and a plasma gas mixture comprising CO2 and a hydrocarbon. In an embodiment of the present disclosure, the source of the graphite comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs. XRD and SEM were used to examine the graphite material before and after it has been subjected to thermal treatment using the DC thermal plasma torch. The results show that graphite can be advantageously purified using a DC thermal plasma torch. Moreover, XRD and SEM analyses of the graphite material after thermal treatment illustrate that thermal plasma treatment not only provides for the purification of the graphite material, but also provides for increasing the surface pH of the graphite material.

[0050] EXAMPLES

[0051] The following examples are included to demonstrate preferred embodiments of the disclosure. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the disclosure.

[0052] General Methods and Materials

[0053] CO2 (99%) and CH4 (99%) are used as the plasma gasses in the DC thermal plasma torch. Argon (99%) is used to cool down the experimental apparatus and reduced products. Natural graphite has been received from Nouveau Monde Graphite (NMG), Quebec, Canada. X-ray diffraction, using a X'Pert Pro MPD X-ray diffractometer from PANalytical, was performed on the graphite samples before and after thermal treatment toidentify the phases. The starting angle was 10°, and the final angle was 70°, with a gradient of 0.057min. Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), providing information on the elemental composition of the graphite material, was performed using a Hitachi S-4700 microscope equipped with a field-effect gun and cold cathode. Thermogravimetric analysis (TGA), providing information on the mass of the graphite sample as a function of temperature or time, was performed using a SETSYS Evolution 24 thermogravimetric analyzer from Setaram. The graphite sample was subjected to a controlled temperature program in a controlled atmosphere and pressure. Thermogravimetric analysis was also coupled with differential thermal analysis (DTA) such that thermal effects on the graphite material could be measured simultaneously. TGA determines decomposition / mass loss over a temperature range, whereas DTA determines endo- and exothermic event temperatures, and shows phase transitions. FTIR spectra were obtained using a SpectrumTM 3 FT-IR spectrometer from PerkinElmer. BET surface area analysis was performed using an ASAP 2020 analyzer from Micromeritics. An inert gas (e.g., N2) was continuously flowed over a solid graphite sample over a range of pressures to generate an adsorption isotherm. Alternatively, the graphite sample could also be suspended in a defined gaseous volume. The BET equation (Brunauer, Emmett, and Teller) was used to extract information on the specific surface area, while the BJH (Brunauer, Joyner, and Halenda) model was used to extract information on pore size, volume, and distribution (Brunauer, Joyner, and Halenda). X-ray photoelectron spectroscopy, providing information on the graphite sample’s surface chemistry, was performed using a Kratos Axis Ultra DLD X-ray Photoelectron Spectrometer. XPS further provides information on the elemental composition as well as the chemical and electronic state of the atoms within the graphite sample. Overall, XPS provides quantitative elemental and chemical / oxidation state information from the outermost few nanometers (surface) of a solid material.

[0054] XRD Analysis

[0055] The natural graphite feed material was analyzed before and after thermal plasma treatment. With reference to FIG. 3, natural graphite contains some impurities such as aluminum silicate. Following the thermal plasma treatment, pure graphite was obtained.

[0056] SEM Analysis

[0057] With reference to FIG. 4, SEM analysis of the natural graphite feed material before (a) and after (b) thermal plasma treatment revealed that surface modifications hadtaken place. Prior to thermal plasma treatment, the shape of the natural graphite particles was irregular and exhibited distinct layering on their surface. Some impurity content could also be observed on the surface. The shape of the graphite particles remained generally unchanged following thermal plasma treatment, which appears indicative that the effects of the thermal plasma treatment may be limited to the surface while not affecting the particles per se. The “surface cleaning” effect is corroborated by the substantial absence of impurities following thermal plasma treatment. This observation is substantiated by the results obtained following XRD analysis, which indicated the removal of impurities form the particles’ surface.

[0058] SEM-EDS Analysis

[0059] With reference to FIG. 5, the elemental composition of natural graphite before (a) and after (b) thermal plasma treatment was determined by SEM-EDS analysis. The results are further illustrated in Table 1. The carbon content was determined to have increased from 95.45% to 99.82%, indicative of a purification effect. To that effect, the respective content of O, Al, Si and S, elements typically associated with impurity content, was determined to have been advantageously reduced.

[0060] Table 1 : Elemental analysis of natural graphite before and after thermal plasma treatment.

[0061] With reference to FIG. 6, an elemental mapping distribution (C, O, Al, Si, S) of a natural graphite sample before thermal plasma treatment is illustrated. The mapping illustrates that the graphite sample comprises impurities, such as represented by the oxygen, aluminum, silicon and sulfur content.

[0062] With reference to FIG. 7, an elemental mapping distribution (C, O, Al, Si, S) of a natural graphite sample after thermal plasma treatment is illustrated. The mapping illustrates that substantially all of the impurities have been removed following thermal plasma treatment. The remaining oxygen content is substantially the result of some residual mineral inclusion products.

[0063] TGA-DTA Analysis

[0064] Thermogravimetric analysis coupled with differential thermal analysis (dTG) illustrates a difference in the behavior of the natural graphite sample before and after thermal treatment. With reference to FIGs. 8 and 9, the natural graphite sample before thermal treatment, under an oxidizing air atmosphere (oxygen content of about 20-21 %) shows a mass loss starting at about 600-650°C and continuing until the final temperature was reached (-2% / min starting at about 800°C). The observed reactions, between 600- 800°C, are of an endothermic nature, while some exothermic reactions are observed at temperatures above 800°C. Under an argon atmosphere, the graphite mass loss is significantly reduced, with a maximum of 91.5% of the mass remaining when the final temperature was reached. The mass loss starts at about 600°C and remains constant at 0.1 % / min until about 1000°C where a second slope is observed with a loss of 0.15% / min. This mass loss under an oxidizing atmosphere is largely due to the reaction of the graphite with oxygen, which leads to the release of CO2.

[0065] With reference to FIGs. 8 and 9, the natural graphite sample following thermal treatment, under an oxidizing air atmosphere, shows a mass loss of about 1.5% between 500-650°C. The observed reactions, between 500-650°C, are of an endothermic nature, while some exothermic reactions are observed at temperatures above 650°C. Under an argon atmosphere, the graphite mass loss is largely insignificant (about 0.5% when the final temperature was reached). To that effect, a mass gain of about 0.5% was observed between 100-950°C. This mass loss under an oxidizing atmosphere is due to the reaction of the graphite with oxygen, which leads to the release of CO2.

[0066] DSC Analysis

[0067] Differential Scanning Calorimetry (DSC) provides an indication of how the physical properties of the natural graphite sample change with temperature over time. It is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature. With reference to FIG. 10, the DSC curves of a natural graphite sample before and after thermal treatment, under an oxidizing air atmosphere and an inert argon atmosphere, show different behaviors. Heating was started at room temperature up to 1300°C, at a heating rate of 10°C / min. An endothermic peak was observed at 600°C corresponding to CO and CO2 release, Moreover, some minor exothermic peaks were observed between 800°C and 1000°C.

[0068] BET surface area analysis

[0069] The natural graphite sample’s surface (before and after thermal plasma treatment) was analyzed using an ASAP 2020 analyzer from Micromeritics (Table 2). To generate an adsorption isotherm, the sample is exposed to a gas, typically nitrogen, at a variety of pressures. The BET equation (Brunauer, Emmett, and Teller) was used to extract information on the specific surface area, while the BJH model was used to extract information on pore size, volume, and distribution (Brunauer, Joyner, and Halenda). BET analysis shows that the specific surface area of the natural graphite sample was decreased by 0.8026 m2 / g following thermal plasma treatment relative to the natural graphite sample before treatment. The decreased surface area may be a result of a decrease in the pore size caused by the thermal plasma treatment.

[0070] Table 2: Natural graphite surface area before and after thermal plasma treatment.

[0071] Surface pH measurement

[0072] Surface pH analysis reveals that the thermal plasma treatment has the effect of raising the pH (Table 3). To that effect, the thermal plasma treatment does not cause any damage to the natural graphite particles’ surface, but merely eliminates impurities that impact the surface’s pH, or causes certain functional group transformations into less acidic moieties. These changes may also influence the surface oxidation level of the graphite particles. The main effects of the thermal plasma treatment are thus a decreased surface area and removal of impurities from the particles’ surface.

[0073] Table 3: Surface pH variation of natural graphite before and after thermal plasma treatment.

[0074] XPS Analysis

[0075] X-ray photoelectron spectroscopy (XPS) provides information on the graphite sample’s surface chemistry as well as information regarding its elemental / chemical composition. With reference to FIG. 11 , the scans were performed between 1400 eV and 0 eV for both the natural graphite feed material before and after thermal plasma treatment. The predominant element for the natural graphite sample before and after thermal plasma treatment is a Cisemission at 285 eV accompanied by a CKLL Auger emission at 1250 eV. Furthermore, a small Oispeak at 540 eV and an OKLL Auger emission at 1000 eV is observed. The Oispeak at 540 eV is smaller for the graphite material following thermal plasma treatment, indicative of a purification effect. The natural graphite feed material prior to thermal plasma treatment contained surface impurities such as Fe, Si, and Al. These impurities appear to have been substantially eliminated following thermal plasma treatment. Finally, the atomic percentage of carbon in the natural graphite feed material prior to thermal plasma treatment was 81 .5%. Importantly, the carbon atomic percentage increases to values in excess of 95% following plasma thermal treatment, further corroborating the purification effect imparted by the plasma thermal treatment.

[0076] FTIR Analysis

[0077] The natural graphite feed material was analyzed, before and after thermal plasma treatment, using a SpectrumTM 3 FT-IR spectrometer from PerkinElmer. With reference to FIG. 12, the natural graphite feed material, before thermal plasma treatment, exhibits signals at 3450, 3000, 1800, 1650, 1400, and 1054 cm'1due to -OH, C-H, C=O, C-OH, and C-O stretching vibrations respectively. Following thermal plasma treatment, the spectrum is dominated by an -OH stretching vibration at 3450 cm'1and a less important C-H stretching vibration at around 3000 cm'1. These changes are indicative of significant modifications at the natural graphite’s surface, such as purification effects and / or chemical functional group transformations, following thermal plasma treatment. The chemical functional group transformations may very well account for the observed pH variations for graphite particles’ surface.

[0078] Effect of CO2 / CH4 Gas Ratio

[0079] At ambient pressure, a plasma having a CO2 / CH4 ratio of 1 :1 may be more stable than one having a CO2 / CH4 ratio of 2:1. This is surmised to be due, at least in part, to the latter's potential to produce a hotter, more reactive plasma with a greater concentration of reactive species. FIG. 13 illustrates the power variation over time in a spouted bed reactor.

[0080] Enthalpy

[0081] The use of a gas mixture comprising CO2 and a hydrocarbon such as CH4 advantageously provides for generating a plasma exhibiting high enthalpy and high thermal conductivity. FIG. 14 illustrates the enthalpies of a CO2 / CH4 plasma torch, an argon plasma torch, and a nitrogen plasma torch. The plasma enthalpy reveals a system's heat content. As a result, the thermodynamic properties of a plasma arc are affected by the particle density, the plasma gases, and the degree of ionization. The presence of a high electron density plasma makes the environment more energetic and reactive, allowing the plasma arc to create a rich region for chemical species activation.

[0082] EXAMPLE 1 - Purification of Natural Graphite

[0083] A sample of natural graphite (400 g) provided by Nouveau Monde Graphite (NMG), Quebec, Canada was used in this Example. The sample had a particle size of 20- 50 mesh. A steady plasma arc exhibiting high enthalpy and thermal conductivity was generated using a 50 kW DC thermal plasma torch and the two greenhouse gases carbon dioxide (CO2) and methane (CH4). Thermocouples were used to monitor the inlet and outlet temperatures of the reactor in order to maintain a desired temperature gradient for the graphite material. The experimental apparatus (FIGs. 1 and 2) was equipped with a spouted bed reactor comprising a bottom cone in direct contact with the plasma. The 50 kW DC thermal plasma torch’s power was modulated by adjusting the CO2 / CH4 gas ratio to 55:45. The current and voltage of the plasma torch were kept constant at 252 amps and 150 V respectively. In an embodiment of the present disclosure, the graphite material was heated for about 30 minutes. The pressure within the torch was maintained close to atmospheric pressure. The walls of the reactor are cooled using cold water and the purified graphite material was cooled using a flow of argon. Exit gases from the reactor were analyzed using a mass spectrometer. In an embodiment of the present disclosure, the thermally treated graphite material may be advantageously cooled by injecting a quench gas into the reactor. In a further embodiment of the present disclosure, the quench gas may be Ar.

[0084] All of the processes disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the processes of this disclosure have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the processes and in the steps or in the sequence of steps of the processes described herein without departing from the concept, spirit, and scope of the disclosure. More specifically, it will be apparent thatcertain process parameters and / or reagents which are chemically related may be substituted for the reagents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the disclosure as defined by the appended claims.

Claims

CLAIMS1. A process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a purified graphite material.

2. The process of claim 1 , further comprising cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas.

3. The process of claim 1 or 2, further comprising collecting the purified graphite material.

4. The process of any one of claims 1 to 3, wherein reacting the graphite feed material with the gas mixture comprises injecting the gas mixture into the plasma.

5. The process of any one of claims 1 to 4, wherein the gas mixture comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4.

6. The process of any one of claims 1 to 5, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8.

7. The process of claim 6, wherein the hydrocarbon is CH4.

8. The process of any one of claims 1 to 7, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

9. The process of any one of claims 1 to 8, wherein the plasma is produced using a readily ionizable working gas.

10. The process of claim 9, wherein the readily ionizable working gas comprises at least one of He, Ar and N2.

11. The process of any one of claims 1 to 10, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radiofrequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma.

12. The process of claim 11 , wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch.

13. The process of claim 11 or 12, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation.

14. The process of claim 13, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis.

15. The process of any one of claims 1 to 14, further comprising adjusting a composition of the gas mixture based on post-plasma mixture composition analysis.

16. The process of any one of claims 1 to 15, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis.

17. The process of any one of claims 1 to 16, further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns.

18. The process of any one of claims 1 to 17, wherein the purified graphite material comprises a purity in excess of 99 wt.% C.

19. A process for purifying a graphite feed material, the process comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the plasma to produce a purified graphite material.

20. The process of claim 19, further comprising cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas.

21. The process of claim 19 or 20, further comprising collecting the purified graphite material.

22. The process of any one of claims 19 to 21 , wherein the plasma is produced using a gas mixture comprising CO2 and a hydrocarbon.

23. The process of any one of claims 19 to 22, wherein the gas mixture comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4.

24. The process of any one of claims 19 to 23, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8.

25. The process of claim 24, wherein the hydrocarbon is CH4.

26. The process of any one of claims 19 to 25, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

27. The process of any one of claims 19 to 26, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radiofrequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma.

28. The process of claim 27, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch.

29. The process of claim 27 or 28, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation.

30. The process of claim 29, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis.

31. The process of claim 22, further comprising adjusting a composition of the gas mixture based on post-plasma mixture composition analysis.

32. The process of claim 22, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis.

33. The process of any one of claims 19 to 32, further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns.

34. The process of any one of claims 19 to 33, wherein the purified graphite material comprises a purity in excess of 99 wt.% C.

35. The process of claim 2 or 20, wherein the quench gas comprises Ar.

36. A process for graphite purification, the process comprising: determining the impurity content of a graphite feed material to be purified;using process simulation and / or modeling software to model a plasma arc reaction for the graphite feed material to be purified and a purification agent comprising CO2 and a hydrocarbon; and feeding the graphite feed material into a thermal plasma torch producing a purified graphite material.

37. The process of claim 36, further comprising: producing a plasma to bring the graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; reacting the graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with the purification agent comprising CO2 and a hydrocarbon producing the purified graphite material; and cooling the purified graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas.

38. The process of claim 36 or 37, further comprising collecting the purified graphite material.

39. The process of any one of claims 36 to 38, wherein reacting the graphite feed material with the purification agent comprising CO2 and a hydrocarbon comprises injecting the purification agent into the plasma.

40. The process of any one of claims 36 to 39, wherein the purification agent comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4.

41. The process of any one of claims 36 to 40, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8.

42. The process of claim 41 , wherein the hydrocarbon is CH4.

43. The process of any one of claims 36 to 42, wherein the graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

44. The process of claim 37 wherein the plasma is produced using a readily ionizable working gas.

45. The process of claim 44, wherein the readily ionizable working gas comprises at least one of He, Ar and N2.

46. The process of claims 37, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radio-frequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma.

47. The process of claim 46, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch.

48. The process of claim 46 or 47, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation.

49. The process of claim 48, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis.

50. The process of any one of claims 36 to 49, further comprising adjusting a composition of the purification agent based on post-plasma mixture composition analysis.

51. The process of any one of claims 36 to 50, further comprising adjusting a rate of injection of the purification agent based on post-plasma mixture composition analysis.

52. The process of any one of claims 36 to 51, further comprising milling the purified graphite material to a particle size ranging from about 1 to about 50 microns.

53. The process of any one of claims 36 to 52, wherein the purified graphite material comprises a purity in excess of 99 wt.% C.

54. A thermal plasma process for treating a particulate graphite feed material, the process comprising: producing a plasma to bring the particulate graphite feed material to a reaction temperature ranging from about 500°C to about 5000°C; and reacting the particulate graphite feed material at the reaction temperature ranging from about 500°C to about 5000°C with a gas mixture comprising CO2 and a hydrocarbon to produce a plasma treated particulate graphite material; wherein the plasma treated particulate graphite material comprises an increased surface pH and / or a modified surface.

55. The process of claim 54, further comprising cooling the plasma treated particulate graphite material to a temperature ranging from about 25°C to about 500°C by injecting a quench gas.

56. The process of claim 54 or 55, further comprising collecting the plasma treated particulate graphite material.

57. The process of any one of claims 54 to 56, wherein reacting the particulate graphite feed material with the gas mixture comprises injecting the gas mixture into the plasma.

58. The process of any one of claims 54 to 57, wherein the gas mixture comprises a CC>2 / hydrocarbon ratio ranging from about 2:1 to about 1 :4.

59. The process of any one of claims 54 to 58, wherein the hydrocarbon is at least one of natural gas, CH4, C2H6, and C3H8.

60. The process of claim 59, wherein the hydrocarbon is CH4.

61. The process of any one of claims 54 to 60, wherein the particulate graphite feed material comprises natural graphite, synthetic graphite, mined natural flake graphite (NFG) or graphite recovered from spent LiBs.

62. The process of any one of claims 54 to 61 , wherein the plasma is produced using a readily ionizable working gas.

63. The process of claim 62, wherein the readily ionizable working gas comprises at least one of He, Ar and N2.

64. The process of any one of claims 54 to 63, wherein the plasma is produced using a DC thermal plasma torch, an alternating current (AC) thermal plasma torch, a radiofrequency (RF) thermal plasma torch, an induction thermal plasma torch, or a microwave plasma.

65. The process of claim 64, wherein the DC thermal plasma torch is a transferred arc plasma torch or a non-transferred arc plasma torch.

66. The process of claim 64 or 65, wherein the DC thermal plasma torch comprises an anode and a cathode, and wherein a carbon layer is deposited on the cathode surface during operation.

67. The process of claim 66, further comprising adjusting the electric current through the cathode and anode based on post-plasma mixture composition analysis.

68. The process of any one of claims 54 to 67, further comprising adjusting a composition of the gas mixture based on post-plasma mixture composition analysis.

69. The process of any one of claims 54 to 68, further comprising adjusting a rate of injection of the gas mixture based on post-plasma mixture composition analysis.

70. The process of any one of claims 54 to 69, further comprising milling the plasma treated particulate graphite material to a particle size ranging from about 1 to about 50 microns.

71. The process of any one of claims 54 to 70, wherein the plasma treated particulate graphite material comprises a purity in excess of 99 wt.% C.

72. A graphite material obtained or obtainable by the process of any one of claims 1 to 71.

73. An electrode or electrochemical storage device comprising the particulate graphite material of claim 72.

74. The electrode or electrochemical storage device of claim 73, wherein the electrochemical storage device comprises a lithium-ion battery (LiBs).

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