A composite material, process for producing the same, and uses thereof

Abstract

The present disclosure pertains to a composite material. Moreover, the present disclosure provides a process for the synthesis of a composite material comprising a Si based phase, a SiOx based phase, a SiC based phase, and a C based phase, using a silicon source, a carbon source, and a reducing agent. The invention also relates to the use of said composite material.

Description

A COMPOSITE MATERIAL, PROCESS FOR PRODUCING THE SAME,AND USES THEREOFFIELD OF THE INVENTION

[0001] The present disclosure pertains to a composite material. Moreover, the present disclosure provides a process for the synthesis of a composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase, using a silicon source, a carbon source, and a reducing agent. The invention also relates to the use of said composite material.BACKGROUND OF THE INVENTION

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the present invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Silicon and carbon are highly applicable, abundant materials. Their composites are also useful in many sectors.

[0004] The earth abundant forms of silicon and carbon are silica (SiO2) and graphite. Both being chemically robust, synthesis of a composite from these basic forms is not easy and generally involves chemical and high temperature processing. SiO2is required to be reduced to SiOxor other soluble forms and graphite is required to be chemically exfoliated. Conducting these processes separately and then combining the materials in a further step limits the set of composites that can be formed and increases the number of process stages and energy inputs.

[0005] Generally, composites of silica, silicon, and carbon are synthesized in multiple steps which include individual synthesis of silica, silicon, and carbon and their compound form(s), and then the final step includes combining these materials together in a high temperature process. Such individual synthesis increases the number of steps and consequently the complexity and energy involved.

[0006] Patent publication CN107611416A uses lamellar carbon / graphite / carbon nanotubes (CNTs) as carbonaceous material, i.e. a preformed / synthetic carbon source. Waste glass and a commercial carbon source are mixed by wet ball-milling and dried to form forexample SiCMCNT. SiCMCNT is then mixed with Mg and undergoes magnesiothermic reduction to form Si / SiOx / CNT. However, this process takes several steps.

[0007] The process that we propose is a facile pyrolytic process wherein reactive radicals may be generated in situ in a single step pyrolytic method. The process utilises agricultural waste and / or bio-waste which makes it an economically viable, energy saving process.

[0008] Since each form of agricultural or bio-waste may provide a different form of carbon, the process of the present invention can generate novel outcomes in terms of composition and morphology which would not be expected with synthetic and pre-selected forms.

[0009] Therefore, herein we disclose a process that can utilize both agricultural and biowaste, converting the same into a functional composite material, which makes the process commercially as well as environmentally sustainable, boosting the circular economy.OBJECTS OF THE INVENTION

[0010] Objects of the present invention are to provide a composite material, a process for the manufacture of the composite material and an energy storage device comprising the composite material produced by a method as disclosed herein.SUMMARY OF THE INVENTION

[0011] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0012] In a first aspect, the present invention provides a process of manufacturing a composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase, wherein the process comprises the following steps in order:(a) providing a mixture comprising a silicon source, a carbon source and a reducing agent,(b) grinding the mixture,(c) pyrolyzing the mixture under an inert atmosphere to obtain an impure composite material, and(d) washing the impure composite material with an acid, wherein the silicon source comprises a silicate glass and / or a silicic acid, and wherein the carbon source comprises agricultural waste and / or bio-waste.

[0013] It has surprisingly been established that a composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase can be conveniently prepared utilising the process of the present invention.

[0014] In the context of the present invention, where a phase is said to be “based on” a particular material or materials, this means that the phase predominantly consists of the corresponding said material or materials, which means typically that it comprises at least about 50 at.% of said material or materials.

[0015] Preferably the composite material comprises a plurality of each of a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase.

[0016] Preferably the Si based phase consists essentially of, more preferably consists of Si. Preferably the SiOxbased phase consists essentially of, more preferably consists of SiOx. Preferably the SiC based phase also comprises oxygen, preferably in trace amounts. Preferably said oxygen is present as an inclusion. Preferably the SiC based phase consists essentially of, more preferably consists of SiC and oxygen. Preferably the C based phase consists essentially of, more preferably consists of C.

[0017] Preferably, with regard to the composite material, x = 0.01-2.

[0018] Preferably the silicon source is a silicate glass and / or a silicic acid. Preferably the silicate glass is selected from soda-lime-silica glass and / or borosilicate glass. The silicate glass may preferably comprise 55-75% SiC , more preferably 60-70% SiCU, most preferably 63-67% SiC>2. Preferably the silicate glass in in the form of glass flakes. Urban waste in the form of glass can be a good source for obtaining silicon and can also provide the benefit of natural dopant incorporation into the composite.

[0019] Preferably the silicic acid is selected from one or more of orthosilicic acid, metasilicic acid, pyrosilicic acid, disilicic acid and derivatives. Preferably the silicic acid is orthosilicic acid. Preferably the silicic acid is in aqueous form. When the silicon source comprises or is a silicic acid, preferably the silicic acid is prepared by reacting a silicate glass with a base. Preferably the base is selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and NH3.

[0020] In the context of the present invention a “derivative” is a chemical substance related structurally to another chemical substance and theoretically derivable from it.

[0021] Preferably the carbon source is agricultural waste and / or bio-waste.

[0022] In the context of the present invention, agricultural waste includes crop residues (e.g. stalks, stems, leaves, husks e.g. rice husks, com stover and other parts of harvested plants thatremain after the primary crop is collected), unused or spoiled crops (e.g. crops that are not harvested due to spoilage, damage, or overproduction, e.g. cotton, grass), animal waste (e.g. carcasses, manure and bedding materials from livestock such as cows, pigs, chickens, and other farm animals), packaging materials (e.g. materials used in agricultural packaging such as cardboard, paper, plastics, and biodegradable materials), processing by-products (e.g. waste generated during the processing of agricultural products, such as bagasse e.g. from sugarcane and sorghum, nut shells e.g. walnut shells and powder from such shells, oil cake from seeds, pomace from fruit processing or milling by-products), horticultural waste (e.g. trimmings, prunings, and plant waste from horticultural activities like gardening and landscaping), aquacultural waste (e.g. waste materials produced from fish farming or aquaculture practices, including uneaten feed and organic matter, seaweed, algae, kelp), wood and timber waste (e.g. waste generated from forestry practices, such as sawdust, bark, wood chips and lignin), harvest and post-harvest losses (e.g. losses that occur during harvesting, transportation, and storage of agricultural products, contributing to waste).

[0023] In the context of the present invention, bio-waste includes biodegradable garden and park waste, food and kitchen waste from households, offices, restaurants, wholesale, canteens, caterers and retail premises and comparable waste from food processing plants in accordance with Directive 2008 / 98 / EC of the European Parliament and of the Council of 19 November 2008 on waste. The purpose of using agricultural waste and / or bio-waste derived carbon precursors is to achieve process controllable morphology and a commercially scalable and economically viable process. Such waste can be used in the as received form, or pre- processed physically or chemically depending on the desired final result.

[0024] Preferably the molar ratio of silicon comprised in the silicon source : carbon comprised in the carbon source is from 1: 10 to 2: 1, more preferably from 1:5 to 1: 1, even more preferably from 1 :2 to 1: 1.

[0025] Preferably the molar ratio of silicon comprised in the silicon source : reducing agent is from 1:20 to 1: 1, more preferably from 1:5 to 1: 1.5, even more preferably from 1:2.5 to 1: 1.7. Preferably the molar ratio of carbon comprised in the carbon source : reducing agent is from l: 10 to 1.5: 1, more preferably from 1:5 to 1.2: 1, even more preferably from 1: 1.5 to 1: 1.

[0026] The “reducing agent” used herein means a substance capable of reducing the higher oxidation states of silicon, e.g. Si4+to a lower state. Preferably the reducing agent is selected from one or more of potassium, calcium, barium, sodium, magnesium, aluminium, zinc,lithium, NaH, LiH, LiAlH4, CaH2, formic acid, oxalic acid, sulfite compounds and derivatives. More preferably the reducing agent is magnesium.

[0027] In one embodiment of the present disclosure, when Mg is the reducing agent, it is preferred that Mg is used in the form of powder comprising particles that have a z-average diameter in accordance with ISO 22412:2017 of 10 nm to 75 micrometer, more preferably from 10 nm to 10 micrometer.

[0028] In some preferred embodiments the mixture of step (a) also comprises a salt. Preferably the salt is selected from one or more of sodium chloride, potassium chloride, calcium chloride, sodium bisulfate, copper sulfate, magnesium sulfate, potassium iodide, potassium permanganate, sodium acetate, calcium acetate and derivatives. In an embodiment the mixture of step (a) may consist of the silicon source, the carbon source, the reducing agent and the salt.

[0029] In an alternative embodiment the mixture of step (a) may consist of the silicon source, the carbon source and the reducing agent.

[0030] Preferably the salt is mixed with the reducing agent prior to contacting either the silicon source or the carbon source. Preferably the salt and the reducing agent are ground together, more preferably ball milled together, prior to contacting either the silicon source or the carbon source. Preferably the grinding, more preferably ball milling, of the salt and the reducing agent is effected at 150-600 rpm, more preferably at 200-500 rpm, even more preferably at 250-500 rpm. Preferably the salt and the reducing agent are ground together, more preferably ball milled together, for at least 1 hr, more preferably at least 2 hr, even more preferably at least 3 hr, most preferably at least 4 hr, but preferably at most 24 hr, more preferably at most 10 hr, even more preferably at most 6 hr.

[0031] In some preferred embodiments the silicon source and the carbon source are mixed together before contacting the reducing agent and the salt if present. In some preferred embodiments the silicon source and the carbon source are ground together, more preferably ball milled together, before contacting the reducing agent and the salt if present. Preferably the grinding, more preferably ball milling, of the silicon source and the carbon source is effected at 150 - 600 rpm, more preferably at 200 - 500 rpm, even more preferably at 250- 500 rpm. Preferably the silicon source and the carbon source are ground together, more preferably ball milled together, for at least 1 hr, more preferably at least 2 hr, even more preferably at least 3 hr, most preferably at least 4 hr, but preferably at most 24 hr, more preferably at most 10 hr, even more preferably at most 6 hr.

[0032] In an alternative embodiment both the silicon source and the carbon source are ground, preferably ball milled, individually and then mixed together before contacting the reducing agent and the salt if present.

[0033] In another alternative embodiment, neither the silicon source nor the carbon source are ground before contacting the reducing agent and the salt if present.

[0034] Preferably the grinding of step (b) is effected via ball milling. Preferably the grinding, more preferably the ball milling, of step (b) is effected at 150-600 rpm, more preferably at 200-500 rpm, even more preferably at 250-500 rpm. Preferably the ball milling of step (b) is effected for at least 1 hr, more preferably at least 2 hr, even more preferably at least 3 hr, most preferably at least 4 hr, but preferably at most 24 hr, more preferably at most 10 hr, even more preferably at most 6 hr.

[0035] For the ball milling described herein, preferably the material to ball weight ratio is from l: l to 1:20, more preferably from 1:2 to 1: 15, even more preferably from 1:5 to 1: 10.

[0036] Preferably the pyrolysis of step (c) is effected at 400 - 1000 °C, more preferably 600 - 900 °C, even more preferably 700 - 800 °C. Preferably the pyrolysis of step (c) is effected for 1-15 hr, more preferably for 1-10 hr, even more preferably for 1-5 hr, most preferably for 2-4 hr. Preferably, in addition to the durations of the preceding sentence, the pyrolysis of step (c) further comprises a temperature ramp period. Preferably the temperature ramp period has a ramp rate of 1-20 °C / min, more preferably of 2-10 °C / min, even more preferably of 2-5 °C / min. Preferably the inert atmosphere of step (c) is an argon, helium, neon, argon, krypton, xenon, nitrogen and / or radon atmosphere, more preferably argon.

[0037] Preferably, after step (c) and before step (d), the impure composite material is washed with water, more preferably distilled water. Preferably the impure composite material is completely submerged in distilled water. Preferably the impure composite material is washed with distilled water for at least 10 min, more preferably for at least 30 min, even more preferably for at least 1 hr. Preferably the impure composite material is stirred during said washing with distilled water.

[0038] Preferably the acid used in step (d) is selected from one or more of hydrochloric acid, sulfuric acid, citric acid, nitric acid, carbonic acid, hydrofluoric acid, phosphoric acid, oxalic acid, boric acid, perchloric acid and acetic acid. More preferably the acid used in step (d) is hydrochloric acid. Preferably the acid is in the form of an aqueous solution. Preferably the acid has a concentration of 0.5-10 M, more preferably of 1-5 M, even more preferably 2-5 M. Preferably the impure composite material is completely submerged in the acid. Preferablythe impure composite material is washed with the acid for at least 10 min, more preferably for at least 30 min, even more preferably for at least 1 hr. Preferably the impure composite material is stirred during said washing with the acid.

[0039] In some preferred embodiments the process further comprises, after step (d), further washing the composite material with a second acid. Preferably the second acid comprises a mixture of acids. Preferably the second acid is a mixture of hydrochloric acid and acetic acid.

[0040] In some embodiments, the process further comprises drying the composite material.

[0041] In some preferred embodiments the mixture of step (a) also comprises a dopant precursor e.g. an amide such as urea or thiourea and / or an amine such as melamine or dopamine. The use of such precursors allows for kinetic in situ dopant incorporation during the composite formation. Given the diversity of the silicon and carbon sources, reducing agents and dopant precursors our synthetic concept enables a high degree of tuneability of the end product and its applicable properties such as morphology. Preferably the composite material comprises a plurality of particles, a plurality of aggregates and / or a plurality of layer stacks. Preferably at least one, more preferably each, particle, aggregate and / or layer stack comprises a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase, preferably comprises a plurality of each of said phases. Preferably each particle comprises a Si based core. Preferably the Si core directly contacts an overlying SiOxbased phase. Preferably the Si based core is chemically bonded to the SiOxbased phase. Preferably the SiOxbased phase comprises a layer based on SiOx. Preferably the SiOxbased phase directly contacts an overlying SiC based phase. Preferably the SiOxbased phase is chemically bonded to the SiC based phase. Preferably the SiC based phase comprises a layer based on SiC. Preferably the SiC based phase directly contacts an overlying C based phase. Preferably the SiC based phase is chemically bonded to the C based phase. Preferably the C based phase comprises a layer based on C.

[0042] Preferably the composite material comprises a plurality of particles that have a z- average diameter in accordance with ISO 22412:2017 of at least about 1 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm, 2500 nm, 3000 nm, 4000 nm, 5000 nm, 6000 nm, 7000 nm, 8000 nm, or at least 9000 nm. In some embodiments, the particles may have a z-average diameter in accordance with ISO 22412:2017 of less than 10,000 nm, 9000 nm, 8000 nm, 7000 nm, 6000 nm, 5000 nm, 4500 nm, 4000 nm, 3500 nm, 3000 nm, 2500 nm, 2000 nm, 1900 nm, 1800 nm, 1700nm, 1600 nm, 1500 nm, 1400 nm, 1300 nm, 1200 nm, 1100 nm, 1000 nm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 250 nm, or less than 100 nm. The z-average diameter of said particles can range from any of the minimum values described above to any of the maximum values described above, for example from 1 nm to 10,000 nm, 2 to 200 nm, 50 nm to 5,000 nm, 100 nm to 2500 nm, 200 nm to 2000 nm, or 500 nm to 1000 nm.

[0043] Preferably the Si phase is at least partially, preferably completely, crystalline.

[0044] Preferably the composite material comprises one or more dopant such as nitrogen and / or sulfur. More preferably the C phase of the composite material comprises one or more dopant.

[0045] In a second aspect, the present invention provides a composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase as manufactured according to the process of the first aspect.

[0046] In a third aspect, the present invention provides an energy storage device comprising a composite material according to the second aspect or as manufactured according to the first aspect. Preferably the energy storage device is an electric battery, more preferably a lithium- ion battery. Preferably the composite material is arranged to act as a negative electrode material of the electric battery. In some embodiments the electrodes can be used in half-cells and / or full-cells.

[0047] In a fourth aspect, the present invention provides the use of the composite material according to the second aspect or as manufactured according to the first aspect as a negative electrode material of an electric battery.

[0048] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.BRIEF DESCRIPTION OF DRAWINGS

[0049] Characteristics and advantages of the subject matter as disclosed in the present disclosure will become clearer from the detailed description of an embodiment thereof, with reference to the attached drawing, given purely by way of an example, in which:

[0050] FIG. 1: XRD of magnesiothermic reduction and co-pyrolysis of ball -milled glass flakes and bagasse with percentage of bagasse used shown.

[0051] FIG. 2: HR-TEM (a-c) and STEM image (d) of magnesiothermic reduction and copyrolysis of ball -milled glass flakes and bagasse with Si- 5wt% Bagasse.

[0052] FIG. 3: TEM of magnesiothermic reduction and co-pyrolysis of ball -milled glass flakes and bagasse with Si-10 % Bagasse

[0053] FIG. 4: Raman spectra of magnesiothermic reduction and co-pyrolysis of ball-milled glass flakes and bagasse.

[0054] FIG. 5: XRD of magnesiothermic reduction of Si(OH)4and co-pyrolysis of bagasse.

[0055] FIG. 6: Thermogravimetric analysis (TGA) of sample B as prepared by the Examples provided hereunder.

[0056] FIG. 7: HRTEM images of Sample B as prepared by the Examples provided hereunder.

[0057] FIG. 8: (a), (b) SEM images, (c) elemental mapping, and (d) ED AX of Sample B as prepared by the Examples provided hereunder.

[0058] FIG. 9: Raman spectra of Sample B as prepared by the Examples provided hereunder.

[0059] FIG. 10: XRD of magnesiothermic reduction Si(OH)4and co-pyrolysis of the walnut shell.

[0060] FIG. 11: (a) and (b) SEM images; (c) and (d) ED AX of magnesiothermic reduction Si(OH)4and co pyrolysis of walnut shell.

[0061] FIG. 12: XRD of magnesiothermic reduction of glass flakes (SiCh) and Si(OH)4along with co-pyrolysis of bagasse.

[0062] FIG. 13: Raman of magnesiothermic reduction of SiO2and Si(OH)4and co-pyrolysis of bagasse.

[0063] FIG. 14: XRD of magnesiothermic reduction and co-pyrolysis of Si(OH)4with bagasse and walnut shell.

[0064] FIG. 15: SEM of magnesiothermic reduction and co-pyrolysis of Si(OH)4with bagasse (a-b) and walnut shell (c-d).

[0065] FIG. 16: a) Rate performance of Si-5% Bagasse and b) Cycling stability of Si-5% Bagasse in the voltage window 0.01-2V.

[0066] FIG. 17: a) Rate performance of Si-5%Bagasse and b) Cycling stability of Si-5% Bagasse in the voltage window 0.01-1.5V.DETAILED DESCRIPTION OF THE INVENTION

[0067] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; onthe contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0068] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0069] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0070] In some embodiments, numbers have been used for quantifying weight percentages, angles, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0071] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0072] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise.Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0073] Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of’ or “consists essentially of’ means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

[0074] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. In the discussion of the invention herein, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

[0075] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0076] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group forreasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.

[0077] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.

[0078] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0079] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.While a particular form of the invention has been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention.When the reducing agent is magnesium, the reaction between the reducing agent and the starting SiO powder can be assumed as follows:But during the reduction of Si(OH)4there is a high possibility of the oxidization of Magnesium at high temperatures as in the following reactions:The other possible reaction that might occur is the formation of Magnesium silicates SiO ■ + 2 Mg(0H )2- ► Mg .SiO 4 + H . (4)However, the formation of SiC is explained by the following equation given below:

[0080] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art tomake and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.EXAMPLES

[0081] The present disclosure is further explained in the form of following examples. However, it is to be understood that the foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

[0082] Example 1: Converting glass flakes to composite material via magnesiothermic reduction and co-pyrolysis of bagasseStarting Material: Glass flakes (65%-SiC>2)Pyrolysed Material: bagasseThe required quantities of NaCl and magnesium powders (see the table below) were milled together for 4 hrs at 300 rpm using a planetary ball mill and 20 mm-sized agate balls. The required amounts of glass flakes and bagasse (see the table below) were then added and the mixture was milled again for 2 hrs at 350 rpm. For any given step of milling, the ratio of balls to total weight of reagents was maintained as 8: 1. The resulting mixture of powders was pyrolysed in the presence of Ar at 750 °C for 2 hrs with a ramp rate of 2° / min. The pyrolysed powder obtained was greenish-grey coloured. To remove excess salt, the powder was subjected to washing with distilled water. Subsequently, it was washed with 50 ml of 3M HC1 (aq) to remove MgO, followed by a mixture of 2M HC1 (aq) / 25% acetic acid to remove magnesium silicate impurities. Finally, the resultant powder was dried.The quantity of bagasse in the mixture of glass flakes and bagasse was varied from 5 wt.% bagasse to 23 wt.%. The XRD patterns of the products after the magnesiothermic reductionare shown in FIG. 1. All the diffraction patterns exhibit the peaks at 20 = 28.7°, 47.4°, 56.2° 69.1° and 76.4° which correspond to (111), (220), (311), (400), (331) planes of cSi (JCPDS no:- 00-027-1402) respectively. In the samples where bagasse was introduced during the reduction process peaks centered at 20= 35.6° and 60° have emerged which belong to (111) and (220) planes of SiC (JCPDS no.: 01-089-2223). In addition to this as the percentage of bagasse is increased there is a gradual increase in the intensity of the broad peak between 20 = 20°- 28° which is assigned to the presence of amorphous carbonaceous and SiOxspecies as we can expect the Si©2 peak at 26° and 22° respectively. The co-pyrolysis and reduction procedure produced polyphasic materials from the glass flakes and bagasse confirming the presence of cubic crystalline phases of both Si and SiC.High-resolution transmission electron microscope (HRTEM) characterization in FIG. 2 (a-c) displayed that the surfaces of the particles were coated by a thin layer of amorphous carbon suggesting the formation of carbon-coated layers on the surface of the silicon particles. The STEM image (FIG. 2d) clearly shows the presence and a homogenous distribution of carbonaceous species in the matrix of Si, SiC, and SiOx.In FIG. 3(b), 0.235 nm corresponds to SiC plane. The HRTEM image (FIG. 3c inset) verified Si crystallinity that exhibited the lattice fringe with 0.31 nm spacing corresponding to the Si (111) orientation. The results are in common with the X-ray diffraction results. The HR-TEM thus confirms the embedment of Si nanodomains in the amorphous SiOx, SiC, and carbonaceous species forming a Si / SiOx / SiC / C composite.The reduced products were further analysed by Raman spectroscopy (FIG. 4) to study the nature of silicon and the type of carbon formed. The Raman-active transverse optical phonon mode for bulk c-Si is at 521 cm'1, which red-shifts in c-Si nanostructures to 516 cm'1due to phonon confinement. The Raman spectrum also displays two main peaks at ~1360 and ~1600 cm'1, denoted as D band and G band as per the general conception. D band at 1333 cm'1arises from the defects present within the lattices, G band at 1580 cm'1due to the inplane vibration mode from the corresponding E2gphonons of sp2hybridized carbon atoms. These two bands indicate that the carbon coating layer contains two kinds of carbon. The intensity of the two peaks increases with the increase in the content of bagasse. The results are in good agreement with the X-Ray diffraction where the peak for the amorphous carbon increases with the increase in bagasse content. Finally, in the Raman spectrum, we also observed a band at ~960 cm'1, which was assigned to the longitudinal optical phonon mode of 3C-SiC.Table 1: CHNS analysis of magnesiothermic reduction and co-pyrolysis of bagasse.CHNS analysis shows that there is less than 10% carbon present in each sample.

[0083] Example 2: Converting Si(OH)4to composite material via magnesiothermic reduction and co-pyrolysis of bagasseStarting Material: Si(OH)4Pyrolysed material: bagasseSamples were synthesized with the following compositions targeted:1. Sample (A): 60% C and 40% Si2. Sample (B): 30% C and 70% SiInitially 5 g of NaCl and 2.77 g of magnesium powder were milled together for 4 hrs at 300 rpm using a planetary ball mill and 20 mm-sized agate balls. To this mixture 5.4 g of Si(OH)4and 8.57 g of bagasse were added and the mixture was milled again for 2 hrs at 350 rpm. For any given step of milling the ratio of balls to total weight of reagents was maintained as 8: 1. The resulting mixture of powders was pyrolysed in the presence of Ar at 750 °C for 3 hrs with a ramp rate of 2° / min. The pyrolysed mixture was subjected to washing with distilled water. Subsequently, 50 ml of 3M HC1 (aq) was used to remove MgO and then a mixture of 2M HC1 (aq) and 25% acetic acid was used to remove magnesium silicate impurities. Finally, the resulting powder was dried and named Sample A. For the preparation of Sample B, all the other reagent quantities except bagasse were the same. The bagasse quantity that was used for sample B was 4.30 g.Magnesiothermic reduction of Si(OH)4and co-pyrolysis of bagasse shows similar X-ray diffraction (FIG. 5) to the material of Example 1. The presence of cubic silicon is confirmed by the presence of peaks at 20 = 28.7°, 47.4°, 56.2° corresponding to (111), (220), (311) planes. Within the samples studied for Example 2, the intensities of the peaks corresponding to silicon increase with the increase in the precursor amount of silicon. The presence of SiC is confirmed with the presence of peaks at 20= 35.6° and 60°. However, the broad peak between 20 = 20- 28° is quite high as compared to silicon peaks which can be attributed to the presence of SiOx and carbonaceous species.The findings of TGA (FIG. 6) state 20.7% carbon is present in the sample B; explaining the higher intensity of the broad peak between 20 = 20- 28° in XRD.The HR-TEM images (FIG. 7a) shows a distinct lattice spacing of Si (0.31 nm) and SiC (0.231 nm). The image also shows an extremely fine (> Inm thickness) carbon coating along the edges. A clear boundary exists between the crystalline silicon and amorphous carbon as indicated by the arrows. The figure confirms the formation of a Si / SiOx / SiC / C composite. The FIG. 7b is another HRTEM image in the support of formation of highly crystalline silicon embedded in the SiC / C matrix.SEM image (FIG. 8a) shows formation of micron sized aggregates of the composite. On further magnification (FIG. 8b) the individual particles less than 200 nm size are seen. Elemental analysis of the micron-sized particle seen in FIG. 8c was done by EDAX analysis and the data reflect the relative composition of C, O and Si.The presence of both phases (Si and SiC) was reconfirmed using Raman spectroscopy, which is capable of unveiling the hybrid formation of SiC polytopes in the composite and defining the type of carbon formation. The Raman spectrum of the composite (FIG. 9) comprises of intense band corresponding to crystalline Si (at ~516 cm'1) and a weak band of SiC centered at 960 cm'1. Additionally, the Raman spectra also contain distinct bands centered at 1350 cm'1and 1597 cm'1assigned to D and G bands respectively. The presence of D band in the spectrum confirms the formation of graphitic fraction in the composite.

[0084] Example 3: Converting Si(OH)4to composite material via magnesiothermic reduction and co-pyrolysis of walnut shellStarting Material: Si(OH)4Pyrolysed material: walnut shellInitially, 10 g of NaCl and 3.5 g of magnesium powder were ball milled together for 4 hrs at 300 rpm using a planetary ball mill and 20 mm sized agate balls. To this mixture was added 4 g of Si(OH)4and 24 g of walnut shell powder and the resultant mixture was milled again for 6 hrs at 350 rpm. For any given step of milling the ratio of balls to total weight of reagents was maintained as (8: 1). The resulting mixture of powders was pyrolysed in the presence of Ar at 750 °C with a ramp rate of 2° / min for 3 hrs. The pyrolysed mixture was subjected to washing with distilled water. Subsequently, 50 ml of 3M HC1 (aq) was used to remove MgO and then a mixture of 2M HC1 (aq) and 25% acetic acid was used to remove magnesium silicate impurities. Finally, the resultant powder was dried.FIG. 10 shows X-ray diffraction (XRD) of magnesiothermically reduced Si(OH)4and copyrolysis of walnut shell. The diffraction pattern is similar to those reported in the earlier examples. The presence of cubic silicon is confirmed by the presence of peaks at 20 = 28.7°, 47.4°, 56.2° corresponding to (111), (220), (311) planes. The formation of SiC is confirmed by the presence of sharp peaks at 2 0 = 35.5° and 60.2° both of the peaks are associated with shoulder peaks at 2 0 = 34.7° and 59.5° which are other planes of SiC.The SEM shows a peculiar formation of carbonaceous material, much like dense sheets in FIG. 11 (a). Upon further magnification the individual aggregates become visible and range from 150 -300 nm sizes. However, there is no great distinction between the location of silicon, carbon and SiC across the sample. This implies that the elemental distribution in the sample is uniform. But in some areas porosity to a certain extent is observed which may arise from the formation of defects during the procedure.The XRD patterns of Examples 1& 2 (FIG. 12) are similar in terms of the 20 values for cubic silicon and SiC. The intensities of the peaks corresponding to silicon are visibly less in Example 2 as compared to Example 1. Apart from this the intensities of the peaks for SiC at 35.6 and the broad peak between 20 = 20- 28° are quite high in example 2. This may be due to the formation of higher percentages of SiC and carbonaceous species upon the change of silicon precursor.The higher percentage of SiC formation may be based on the complex interplay of the thermodynamics involved, the chemical environment and the evolution of other species formed during the reaction.By Raman spectroscopy (FIG. 13), we can confirm the formation of cubic silicon (516 cm'" in both samples. The formation of SiC is confirmed by the presence of a peak at 960 cm'1. However, the peak intensity is higher in sample 2 pertaining to the higher formation of SiC. The results are in good agreement with the XRD results. The Raman spectrum also displays two main peaks at ~ 1360 and ~1600 cm'1, denoted as D band and G band for both samples. ID / IG ratio for example 1 is 0.87 while for example 2 is 0.79 based on the intensities of the D band and G band.

[0085] Example 4: Comparison of Examples 2 and 3The XRD patterns of Examples 2 & 3 (FIG. 14), which use different carbon precursors, are similar in terms of the 20 values for cubic silicon and SiC. The formation SiC peaks is quite interesting in the two samples. The bagasse-based sample i.e. Example 2 shows a broad hump at 20 = 35.6°. On the contrary, in the walnut shell-based sample i.e. Example 3, a sharp peakfor SiC is observed at 20 = 35.5° along with a shoulder peak at 20 = 34.7°. The other SiC peak centered at 20 = 60.2° is difficult to detect for Example 3 but appears to be a sharp peak. These findings are indicative of the highly crystalline nature of SiC in the walnut shell based sample.The SEM image (FIG. 15a) for example 2 i.e. bagasse-based sample shows formation of micron-sized aggregates of the composite. On further magnification (FIG. 15b) individual particles of less than 200 nm in size are seen and are generally shape-specific i.e. spherical. In the case of example 3, layered and dense structures are observed along with smaller particles (FIG. 15c). Further magnifying the particles, they do not appear to be shape-specific and are bigger than 200 nm in size.

[0086] Example 5: Example of the application of the prepared composite:The electrochemical properties were investigated of example 1 for a battery technology application. The electrochemical properties of the prepared Si / 5%Bagasse sample were examined by preparing half cells against lithium metal foil using coin-cell CR2032 (i.e. a Li- ion battery with Composite material as an anode material). Half cells were investigated using IM LiPFe in EC: DMC as an electrolyte and Whatman glass fibre battery separators.The electrode composition was kept as 50% active material, 30% conducting carbon (Super P) and 20% PVDF as a binder. The electrode coatings were prepared on 12micrometre copper foil. The slurry composition used was 50:30:20 and NMP as a solvent. The slurry was coated on copper foil using doctor blade technique to obtain uniform electrodes. The loading was kept constant at 3-4 mg / cm2. IM LiPF6in EC:DMC (1: 1 v / v) with 10% FEC as an additive was used as the electrolyte. Galvanostatic charge-discharge and rate performance were investigated in the voltage window of a) 0.01-2 V (FIG. 16) and b) 0.01-1.5 V (FIG. 17).The one-pot synthesized Si with 5%Bagasse shows excellent rate capability and cyclic stability delivering around 802 mAh / g discharge capacity at 100 mA / g current density in the voltage window 0.01 - IN.

[0087] Various modifications and variations of the described assays, techniques and various means disclosed herein to implement the assays / methods in accordance with the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the describedmodes for carrying out the invention that are obvious to those skilled in the relevant fields are intended to be within the scope of the following claims.

Claims

We Claim:

1. A process of manufacturing a composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase, wherein the process comprises the following steps in order:(a) providing a mixture comprising a silicon source, a carbon source and a reducing agent,(b) grinding the mixture,(c) pyrolyzing the mixture under an inert atmosphere to obtain an impure composite material, and(d) washing the impure composite material with an acid, wherein the silicon source comprises a silicate glass and / or a silicic acid, and wherein the carbon source comprises agricultural waste and / or bio-waste.

2. The process according to claim 1, wherein the composite material comprises a plurality of each of a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase.

3. The process according to claim 1 or claim 2, wherein the Si based phase consists essentially of, preferably consists of Si; and / or wherein the SiOxbased phase consists essentially of, preferably consists of SiOx; and / or wherein the SiC based phase consists essentially of, preferably consists of SiC and oxygen; and / or wherein the C based phase consists essentially of, preferably consists of C.

4. The process according to any preceding claim, wherein the silicon source is a silicate glass and / or a silicic acid, preferably wherein the silicate glass is in the form of glass flakes.

5. The process according to any preceding claim, wherein the silicic acid is selected from one or more of orthosilicic acid, metasilicic acid, pyrosilicic acid, disilicic acid and derivatives thereof, preferably the silicic acid is orthosilicic acid.

6. The process according to any preceding claim, wherein the molar ratio of silicon comprised in the silicon source : carbon comprised in the carbon source is from 1: 10 to 2: 1, preferably from 1 :5 to 1: 1, more preferably from 1 :2 to 1: 1.

7. The process according to any preceding claim, wherein the molar ratio of silicon comprised in the silicon source : reducing agent is from 1:20 to 1: 1, preferably from 1:5 to 1: 1.5, more preferably from 1:2.5 to 1: 1.7; and / or wherein the molar ratio of carbon comprised in the carbon source : reducing agent is from 1 : 10 to 1.5: 1, preferably from 1:5 to 1.2: 1, more preferably from 1 : 1.5 to 1: 1.

8. The process according to any preceding claim, wherein the reducing agent is selected from one or more of potassium, calcium, barium, sodium, magnesium, aluminium, zinc, lithium, NaH, LiH, LiAlH4, CaH2, formic acid, oxalic acid, sulfite compounds and derivatives thereof, preferably the reducing agent is magnesium.

9. The process according to any preceding claim, wherein, when Mg is the reducing agent, the Mg is used in the form of powder comprising particles that have a z-average diameter in accordance with ISO 22412:2017 of 10 nm to 75 micrometer, preferably from 10 nm to 10 micrometer.

10. The process according to any preceding claim, wherein the mixture of step (a) also comprises a salt, preferably the salt is selected from one or more of sodium chloride, potassium chloride, calcium chloride, sodium bisulfate, copper sulfate, magnesium sulfate, potassium iodide, potassium permanganate, sodium acetate, calcium acetate and derivatives thereof.

11. The process according to claim 10, wherein the mixture of step (a) consists of the silicon source, the carbon source, the reducing agent and the salt.

12. The process according to claim 10 or claim 11, wherein the salt is mixed with the reducing agent prior to contacting either the silicon source or the carbon source, preferably the salt and the reducing agent are ground together, more preferably ball milled together, prior to contacting either the silicon source or the carbon source.

13. The process according to any preceding claim, wherein the silicon source and the carbon source are mixed together before contacting the reducing agent and the salt if present, preferably the silicon source and the carbon source are ground together, more preferably ball milled together, before contacting the reducing agent and the salt if present.

14. The process according to any preceding claim, wherein the grinding of step (b) is effected via ball milling, preferably effected at 150-600 rpm, more preferably at 200-500 rpm, even more preferably at 250-500 rpm.

15. The process according to any preceding claim, wherein the pyrolysis of step (c) is effected at 400 - 1000 °C, preferably 600 - 900 °C, more preferably 700 - 800 °C.

16. The process according to any preceding claim, wherein, after step (c) and before step (d), the impure composite material is washed with water, preferably distilled water.

17. The process according to any preceding claim, wherein the acid used in step (d) is selected from one or more of hydrochloric acid, sulfuric acid, citric acid, nitric acid, carbonic acid, hydrofluoric acid, phosphoric acid, oxalic acid, boric acid, perchloric acid and acetic acid, preferably the acid used in step (d) is hydrochloric acid.

18. The process according to any preceding claim, wherein the process further comprises, after step (d), further washing the composite material with a second acid, preferably the second acid comprises a mixture of acids, more preferably a mixture of hydrochloric acid and acetic acid.

19. The process according to any preceding claim, wherein the mixture of step (a) also comprises a dopant precursor e.g. an amide such as urea or thiourea and / or an amine such as melamine or dopamine.

20. The process according to any preceding claim, wherein the composite material comprises a plurality of particles, a plurality of aggregates and / or a plurality of layer stacks.

21. The process according to claim 20, wherein each particle comprises a Si based core, preferably the Si based core directly contacts an overlying SiOxbased phase, more preferably the Si based core is chemically bonded to the SiOxbased phase.

22. The process according to claim 21, wherein the SiOxbased phase directly contacts an overlying SiC based phase, preferably the SiC based phase directly contacts an overlying C based phase.

23. The process according to any of claims 20 to 22, wherein the composite material comprises a plurality of particles that have a z-average diameter in accordance with ISO 22412:2017 of from 1 nm to 10,000 nm, preferably 50 nm to 5,000 nm, more preferably 100 nm to 2500 nm, even more preferably 200 nm to 2000 nm, most preferably 500 nm to 1000 nm.

24. The process according to any preceding claim, wherein the Si based phase is at least partially, preferably completely, crystalline.

25. The process according to any preceding claim, wherein the composite material comprises one or more dopant such as nitrogen and / or sulfur, preferably the C phase of the composite material comprises one or more dopant.

26. A composite material comprising a Si based phase, a SiOxbased phase, a SiC based phase, and a C based phase as manufactured according to any preceding claim.

27. An energy storage device comprising a composite material according to claim 26 or as manufactured according to any of claims 1 to 25.

28. The energy storage device according to claim 27, wherein the energy storage device is an electric battery, preferably a lithium-ion battery.

29. Use of the composite material according to claim 26 or as manufactured according to any of claims 1 to 25 as a negative electrode material of an electric battery.

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