Preparation of a rigid supercapacitor electrode

Abstract

The present invention is directed to a process for producing an electrode, the process comprising: heating a feedstock comprising a particulate coal to a first temperature sufficient for carbonization, thereby forming a solid article on cooling; and activating the solid article to form an electrode comprising micropores on a surface, whereby activating comprises heating the solid article to a second temperature in a reactive atmosphere, or exposing the solid article to an electrical current when in contact with an electrolyte. Also disclosed herein are electrodes for supercapacitors, and a supercapacitor comprising an electrode of the present invention.

Description

PREPARATION OF A RIGID SUPERCAPACITOR ELECTRODEField

[0001] The present invention relates to the field of energy storage. In particular the present invention is directed to a supercapacitor electrode, a process for producing an electrode and use thereof. However, it will be appreciated that the invention is not limited to this particular field of use.Background

[0002] The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of the common general knowledge in the field.

[0003] As the world economy moves towards renewable sources of energy, and away from fossil energy sources, the use of thermal coal is expected to continue to decline. For instance, it is expected that up to 600 jobs may be lost per year in Australia over the next two decades with the decline in the thermal coal market. With this transition comes the need to be able to store renewable energy, given the fluctuating nature of current renewable energy technologies.

[0004] Supercapacitors (also known as ultracapacitors) are a form of stationary energy storage with higher capacitance values compared to other capacitors, but with lower voltage limits, essentially falling in the gap between electrolytic capacitors and rechargeable chemi cal -based batteries. Supercapacitors advantageously store more energy than capacitors and can accept and deliver charge much faster than rechargeable batteries. One known form of supercapacitor is electrostatic double-layer capacitors (EDLCs) which generally uses carbon electrodes to store energy in an electrostatic double layer at the interface between the electrode and the electrolyte. As energy storage occurs electrostatically (and not chemically as occurs in a rechargeable battery), supercapacitors are more robust and can withstand many more charge-recharge cycles compared to batteries. However, such supercapacitors are not currently considered a viable option as their current cost per Watt of stored energy is higher than lithium-ion rechargeable batteries. This cost is at least partially due to the manufacture of the carbon electrodes, whichare commonly carbon aerogels, carbon nanotubes, or activated carbon that is applied to a metal substrate. Such electrodes use highly engineered and / or expensive materials.

[0005] With less thermal coal being used for energy purposes, and with coal being a cheap source of carbon currently produced in significant quantities, there is an opportunity to examine ways of utilising coal as a readily-available carbon source in other materials or processes before mining capacity is reduced or lost. However, the use of coal in many advanced manufacturing processes is not straightforward and requires technical hurdles to be addressed.

[0006] Accordingly, there is a need for a cost-effective energy storage option for use with renewable energy sources.

[0007] It is an object of the present invention that at least one of the needs above is at least partially satisfied.

[0008] It is an object of the present invention to overcome or ameliorate one or more of the disadvantages of the prior art, or at least provide a useful alternativeSummary of Invention

[0009] The present invention aims to provide a cost-effective process for manufacturing carbonbased electrodes. In particular, the inventor has identified that coal represents a plentiful carbon source which is widely available, with developed infrastructure and industry for mining and processing coal already in place and has advantageously developed a process that results in the production of solid articles comprising coal that may find use in, for example, supercapacitors or other energy storage or electrical devices.

[0010] In a first aspect of the present disclosure, there is provided a process for producing an electrode, comprising:(a) providing a feedstock comprising a particulate coal;(b) heating the feedstock to a first temperature sufficient for carbonization, thereby forming a solid article on cooling; and(c) activating the solid article to form an electrode comprising micropores on a surface, whereby activating comprises heating the solid article to a second temperature in a reactiveatmosphere, or exposing the solid article to an electrical current when in contact with an electrolyte.

[0011] The process of the present disclosure, at step (b), may comprise heating the feedstock in a mould. The mould may be any suitable hollow container that provides the solid article with a defined shape following heating to the first temperature and then cooling. When a mould is used, step (b) may also comprise the step of packing the feedstock into the mould before heating by applying pressure to the feedstock. When a pressure is applied, it may be between about 1 and about 5 MPa, or it may be between about 2 and about 4 MPa, or is may be between about 2.5 and 3.5 MPa, or any suitable value between 1 and 5 MPa. Alternatively, the process of the present disclosure, at step (b), may comprise heating the feedstock in an extruder and extruding the heated feedstock before cooling to form a solid article.

[0012] In the process of the present disclosure, the particulate coal may have a preferred maximum particle diameter, so that the particulate coal can closely pack together, providing a robust solid article after heating. The particulate coal may preferably have a maximum particle diameter of about 2 mm. In other words, coal particles of about 2 mm or less are preferred, although larger particles may, in some embodiments, result in a suitable solid article.

[0013] Step (b) of the process of the first aspect includes heating the feedstock to a first temperature. The first temperature is any temperature sufficient for carbonization of the feedstock. This first temperature may be between about 800°C and about 1200°C, or it may be any suitable temperature or range between about 800°C and about 1200°C, such as between about 800°C and about 1000°C or between about 1000°C and about 1200°C. To allow the carbonization process to proceed to completion, or substantially to completion, the feedstock may be held at the first temperature for a period of time. Therefore, step (b) of the process of the first aspect may further comprise the step of maintaining the first temperature for between about 30 minutes and about 3 hours, or any suitable time between about 30 minutes and about 3 hours, such as between 1 and 3 hours, or between 45 minutes and 2 hours, for example.

[0014] Step (c) of the process of the first aspect defines an activating step that is carried out on the solid article formed after step (b). Step (c) also comprises a heating step to a second temperature. The second temperature may be between about 300°C and about 800°C or any suitable value or range between about 300°C and about 800°C, such as between about 300°Cand about 500°C or between about 500°C and about 800°C. Step (c) may also comprise the step of maintaining the second temperature for a period of time to ensure sufficient activating of the surface of the solid article to form an electrode. This period of time may be for between about 30 minutes and about 3 hours, or any suitable time between about 30 minutes and about 3 hours, such as between 1 and 3 hours, or between 45 minutes and 2 hours, for example.

[0015] The feedstock used in the process of the first aspect of the present disclosure comprises particulate coal. The particulate coal may be provided by a milling and / or crushing step, whereby any suitable milling and / or crushing device or apparatus may be used. The feedstock may also include additional components, depending on the features of the particulate coal being used in the process. Some particulate coals may be deficient in vitrinite, and so the feedstock may further comprise a binder additive. The binder additive may preferably also be sourced from coal. The binder additive may be selected from particulate coking coal and / or coal tar. It is an advantage of the present disclosure that polymeric binders common in the art are not required, and that all binder components used to form the electrodes of the present disclosure are sourced from coal, particulate coals may be deficient in inertinite, and so the feedstock may further comprise a filler additive. The filler additive may be non-coking coal. The feedstock of the process of the first aspect may further comprise at least one conductive additive. The at least one conductive additive may be selected from graphite, carbon black powder, graphene, carbon nanotubes, carbon nanowires, a transition metal or transition metal alloy, or any other suitable conductive material, or any combination thereof. Preferably, the conductive additive is also particulate. When any (or all) of a binder additive, a filler additive or at least conductive additive is added to the feedstock, step (a) of the process may additionally comprise a step of milling, grinding and / or blending the particulate coal with the binder additive or the filler additive and / or the at least one conductive additive.

[0016] In some embodiments, the feedstock may comprise, in weight %, between 0% and 100% non-coking coal, between 0% and 100% coking coal, and between 0% and 20% graphite. In some embodiments, the feedstock may comprise, in weight %, between 50% and 100% noncoking coal, between 0% and 40% coking coal, and between 0% and 20% graphite. In some embodiments, the feedstock may comprise, in weight %, between 0% and 40% non-coking coal, between 50% and 100% coking coal, and between 0% and 20% graphite. In preferred embodiments, the feedstock may comprise, in weight %, about 70% non-coking coal, about 20% coking coal, and about 10% graphite.

[0017] Optionally, a treating step may be carried out between steps (b) and (c) of the process of the first aspect. The treating step may preferably comprise applying a composition comprising an hydroxide salt to at least one surface of the solid article and heating to a temperature of between about 300°C and 900°C for a period of time between about 1 and about 3 hours.

[0018] The electrode formed after step (c) of the process of the first aspect may be suitable for use in a supercapacitor, or any other suitable electrical device or energy storage apparatus.

[0019] In a second aspect of the present disclosure, there is provided the electrode produced by the process of the first aspect.

[0020] In a third aspect of the present disclosure, there is provided an electrode for use in a supercapacitor, the electrode comprising: sintered particulate coal, and at least one surface that comprises micropores. The electrode of the second aspect may also be suitable for use in the third aspect.

[0021] The process of the first aspect produce an electrode with at least one microporous surface, such as the electrodes of the second or third aspects. The micropores have an average diameter of between about 0.1 and about 50 nm.

[0022] In a fourth aspect of the present disclosure, there is provided a use of the electrode of the second or third aspects.

[0023] In a fifth aspect of the present disclosure, there is provided a supercapacitor that comprises the electrode of the second or third aspects, an electrolyte, a separator, a current collector / connector, and a container.

[0024] The supercapacitor of the fifth aspect may be in any suitable arrangement. In some embodiments, the electrolyte comprises sodium chloride and / or sodium sulfate. In some embodiments, the separator comprises glass paper, or cellulose paper, or polypropylene. In some embodiments, the container is sealable.Brief Description of Drawings

[0025] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures.

[0026] Figure 1: (a) Mapping extrusion and direct casting behaviour by coal thermoplastic properties; (b) Example of tiles produced from direct casting with an initial sample mass of 35g whereby tiles lying next to moulds are examples of thinner tiles produced using 20g.

[0027] Figure 2: (a) Impact of activation time on specific mass loss for different coals; (b) Specific energy storage vs activation mass loss, wt% for tiles derived from black coal.

[0028] Figure 3: Test apparatus, whereby 1 is Grafoil electrical connectors; 2 is a glass filter paper separator; 3 is 0.5 M ISfeSCU electrolyte; and 4 is the heat-sealed polypropylene bag and bund container.

[0029] Figure 4: A plot of voltage and current over time for a charge / discharge cycle of a carbon electrode comprising Australian black coal.

[0030] Figure 5: Comparison of coal -based supercapacitors with other energy storage technologies.Definitions

[0031] The following definitions are provided to enable the skilled person to better understand the invention disclosed herein. These are intended to be general and are not intended to limit the scope of the invention to these terms or definitions alone. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the invention pertains.

[0032] As used herein, the term “comprising” means “including”. Variations of the word “comprising”, such as “comprise” and “comprises”, have correspondingly varied meanings. As used herein, the terms “including” and “comprising” are non-exclusive. As used herein, the terms “including” and “comprising” do not imply that the specified integer(s) represent a major part of the whole.

[0033] Where applicants have defined an invention or a portion thereof with an open-ended term such as “comprising”, it should be readily understood that (unless otherwise stated) the description should be interpreted to also describe such an invention using the terms “consisting essentially of’ or “consisting of.” In other words, with respect to the terms “comprising”, “consisting of’, and “consisting essentially of’, where one of these three terms are used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of’ or, alternatively, by “consisting essentially of’.

[0034] The transitional phrase “consisting of’ excludes any element, step, or ingredient not specified. If in the claim, such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of’ appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0035] The transitional phrase “consisting essentially of’ is used to define a composition, process or method that includes materials, steps, features, components, or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components, or elements do not materially affect the basic and novel character! stic(s) of the claimed invention. The term “consisting essentially of’ occupies a middle ground between "comprising" and “consisting of’.

[0036] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0037] Also, the indefinite articles “a” and “an” preceding an element or component of the invention are intended to be non-restrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

[0038] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”. The examples are not intended to limit the scope of the invention. In what follows, or where otherwise indicated, “%” will mean “weight %”, “ratio” will mean “weight ratio” and “parts” will mean “weight parts”.

[0039] The terms “predominantly” and “substantially” as used herein shall mean comprising more than 50% by weight, unless otherwise indicated.

[0040] As used herein, with reference to numbers in a range of numerals, the terms “about”, “approximately” and “substantially” are understood to refer to the range of -10% to +10% of the referenced number, preferably -5% to +5% of the referenced number, more preferably -1 % to + 1 % of the referenced number, most preferably -0.1 % to +0.1 % of the referenced number. Moreover, with reference to numerical ranges, these terms should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, from 8 to 10, and so forth.

[0041] As used herein, wt.% refers to the weight of a particular component relative to total weight of the referenced composition.Description of Embodiments

[0042] The following description conveys exemplary embodiments of the present invention in sufficient detail to enable those of ordinary skill in the art to practice the present invention. Features or limitations of the various embodiments described do not necessarily limit other embodiments of the present invention or the present invention as a whole. Hence, the following detailed description does not limit the scope of the present invention, which is defined only by the claims.

[0043] The present invention relates to a process for producing an electrode, especially a process for producing a carbon-based electrode that is suitable for use in a supercapacitor.

[0044] In particular, the inventor has developed a process for producing an electrode for use in an energy storage device, which advantageously uses a widely available, low cost carbonsource, but is also rigid and stable over many charge / discharge cycles. Broadly, the electrodes of the present invention are produced by sintering a feedstock comprising particulate coal to form a solid article, before heat treating at least one surface to increase the surface area, which has been associated with higher storage potential in supercapacitors. As will be described in more detail below and with reference to the Examples, the process of the present invention advantageously uses coal, especially particulate coal, which is widely available at low cost with substantial mining and processing infrastructure already in place, as a source of carbon to form carbonbased conductive electrodes. Advantageously, the electrodes produced by this process are rigid, self-supporting (i.e., does not require a metallic substrate) and can be produced in a range of shapes and sizes, so have utility in a wide range of energy storage devices.

[0045] In the context of the present invention, the term “electrode” refers to an electrically conductive material that is capable of, or suitable for, use as a cathode and / or an anode in an electrolytic cell, battery, capacitor or similar electrical apparatus. In this context, an “electrode” is used to make contact with a non-metallic part of a circuit, such as an electrolyte. Electrodes may be found in a range of devices, such as, for example, an electrolytic cell, a galvanic or voltaic cell, a rechargeable battery, a capacitor, or a supercapacitor. In one preferred, but nonlimiting, embodiment of the present invention, the electrode is suitable for use as either an anode (i.e., an electrode with a negative charge) or a cathode (i.e., an electrode with a positive charge), or both in an electrochemical cell, such as for example, a supercapacitor.

[0046] The electrode of the present invention is based on, or comprises, or contains, carbon. As the skilled person will appreciate, certain forms of carbon, especially crystalline allotropes or polymorphs of carbon (including, for instance, graphite and graphene) are conductors of electricity. Therefore, the electrode of the present invention advantageously comprises, or contains, or consists of, conductive forms of carbon.Feedstock

[0047] In a first step of the process described herein, a feedstock is provided. The feedstock comprises a source of carbon to form a carbon-based electrode. In an advantage of the present invention, the carbon source is coal, preferably particulate coal. Any of the major forms or ranks of coal may be suitable for use in the process of the present invention, although the skilled person would appreciate that, for some coal forms or ranks, additional binder may be required toproduce a rigid electrode via the process disclosed herein. The coal may be hard coal (also known as anthracite), black coal (also known as bituminous coal), subbituminous coal, or brown coal (also known as lignite), or any combination thereof. In some embodiments, the coal is black coal or brown coal, preferably black coal. It is expected that a suitably skilled person would easily be able to differentiate between coal types based on their general knowledge.

[0048] As used herein, the term “non-coking coal” represents ranks of coal with low relative fluidity, which generally have a relatively high proportion of inertinite (i.e., lower carbon content) compared to vitrinite. Ranks of “non-coking coal” as defined herein include thermal coals (such as lignite) and low-fluidity coking coals (such as thermal bituminous coal) that would not be suitable or desirable for coking processes. In contrast, the term “coking coal” as used herein represents ranks of coal with high relative fluidity (such as bituminous coking coal), which generally have a relatively high proportion of vitrinite (i.e., higher carbon content) compared to inertinite and are generally most suitable for use in a blast furnace. As the terms “coking coal” and “non-coking coal” are known terms in the art, it is expected that the skilled person would be able to adequately distinguish between a coking coal and a non-coking coal. Accordingly, the term “particulate coal” as used herein refers to any coal in particle form that comprises or consists of at least one type of coal, whether coking coal or non-coking coal. For example, the “particulate coal” of the present invention may, for example, consist of either a non-coking coal or a coking coal, or it may comprise a blend of two or more ranks of coal (e.g., a non-coking coal and a coking coal, or two non-coking coals, or two coking coals), so long as a suitable balance of fluid and non-fluid macerals are present to produce a solid article in the method of the present invention.

[0049] As the skilled person would appreciate, coal generally contains varying amount of vitrinite and inertinite, whereby the vitrinite represents the plasticisable portion of the coal and inertinite represents non-plasticisable matter. Coking coals or metallurgical coals with a relatively high proportion of vitrinite may be referred to herein as “high fluidity” or “fluid” coals, and likewise coals with lower amounts of vitrinite (and hence relatively more inertinite) may be referred to herein as “low fluidity” or “non-fluid” coals. As will be explained in more detail below and with reference to the Examples, and without being bound to any theory, the inventor understands that there is a compromise between the amount of vitrinite present that provides fluidity and allows for the binding of the particulate coal to form a solid article, and the amount of inertinite present that provides sites for activation of the electrode. Put differently,when a feedstock comprising particulate coal is heated, it is believed that vitrinite becomes fluid and so acts to bind the particulate coal together but is more resistant to activation via oxidation, and the inertinite is more susceptible to activation when located on the surface of the electrode but is not fluid (and therefore does not contribute to particulate binding). In this regard, a mixture or combination of coal types or ranks can be used to achieve a balance between vitrinite and inertinite. For example, particulate black coal with a relatively high fluidity may be suitable for forming an electrode of the present invention when used alone. In another example, a combination of a particulate brown or black coal (i.e., a thermal coal or a low fluidity coking coal) with relatively low fluidity may be used in conjunction with, or when mixed or blended with, a particulate coking coal with a high fluidity. In some other embodiments, a coal-derived binder such as coal tar may be blended with the particulate coal to from an electrode of the present invention. In other words, high fluidity coals (or components thereof) can be used as a binder material for coals with low, or insufficient, inherent fluidity to form an electrode of the present invention.

[0050] The coal may be treated before use in the present process. It may be treated by thermal, chemical or physical means, or any combination thereof. For example, it may be advantageous for the skilled person to extract the liquid or semi-liquid hydrocarbon by-product portion of the coal (commonly known as tar) which may be able to be sold (for example, for chemical uses), used as an energy source for the heating step(s) or added back with the coal in a controlled manner as a binder. The coal may also, or alternatively, by dried before use, to remove water and / or volatile hydrocarbons which may form voids in the material during heating, particularly if the coal comprises relatively high amounts of volatile components and / or water. The coal may also be treated to remove impurities, such as sulfur and nitrogen-containing compounds.

[0051] In a preferred embodiment of the present invention, the coal used in the process is particulate coal. By “particulate” it is meant that the coal is present as, or substantially as, particles. The coal may have a maximum particle diameter of about 2 mm or less. It may have a maximum particle diameter of less than 1.5 mm, or less than 1 mm, or less than 0.5 mm, or less than 0.4 mm, or less than 0.3 mm, or less than 0.2 mm, or less than 0.1 mm, or less than 0.01 mm. The particles may substantially comprise of particles with diameters of between about 0.01 mm and 2 mm, or between about 1 mm and 2 mm, or between about 0.1 mm and 0.75 mm, or between about 0.5 mm and about 1.5 mm, or between about 0.2 mm and 0.5 mm, or between about 0.4 and about 1 mm, or between about 0.75 mm and about 1.25 mm, or between about1.25 mm and about 1.95 mm, or between about 0.2 mm and about 1.8 mm, or any range therein. Therefore, the process of the present invention may include a step of crushing and / or milling the coal to a desired particle diameter or range of particle diameters. It may also comprise removing particles above a desired upper particle size limit, such as by sieving or some other suitable method. As the skilled person will appreciate, particulate coal is better able to be packed together and sintered in order to form a solid, rigid, article of the present invention, however the process may also be able to be optimised for coal that is larger in size (depending on the size of the electrode being produced). The particulate coal may also, in some embodiments, contribute to the topology of the electrode surface once produced by providing millimetre or submillimetre scale variations.

[0052] Preferably, a feedstock comprising particulate coal is provided for the process of the present invention. The feedstock may comprise, or consist of, or consist essentially of, or contain, the particulate coal described herein. In some embodiments, the feedstock is 100% particulate coking coal, or 100% particulate non-coking coal, in circumstances where the balance of fluid and non-fluid macerals (for example, vitrinite and inertinite) in a particular coking or non-coking coal source is sufficient to form a rigid electrode in the process of the present invention without addition of further binder (i.e., coking coal) or filler (i.e., non-coking coal).

[0053] In other embodiments, the feedstock may comprise additional components in addition to the particulate coal. The additional components may modify the behaviour of the feedstock during the production process. For example, in some embodiments, the additional components comprise material that is high in vitrinite (to supplement low fluidity or non-fluid particulate non-coking coal) such as coking coal to act as additional binder(s) during the electrode formation process. In such embodiments, the coking coal is usually added to a non-coking coal feedstock and is preferably also particulate. In some embodiments, coking coal is added to the non-coking coal in any amount up to about 40% of the mass of the feedstock, or up to about 35%, or up to about 30%, or up to about 25%, or up to 20%, or up to about 15%, or up to about 10%, or up to about 5% of the mass of the feedstock, or it may be added at between about 1% and 40%, or between about 5% and 35%, or between about 10% and about 30%, or between about 15% and 25%, or it may be added at about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40% by mass of the feedstock. However, as the skilled person would appreciate, the amount of high-fluidity coking coal required will be dependent on the features of the particulate coal being used and particularly whether additional “high fluidity” material is needed to form a solid article. In other embodiments, the additional components may be high in inertinite or other non-fluid carbon phases such as charcoal, non-coking coal or biochar (to supplement high fluidity or nonfluid particulate coals) to provide more robustness (i.e., higher mechanical strength) and activation sites to the electrode. In some embodiments, non-coking coal or other non-fluid filler material is added to the coking coal in any amount up to about 40% of the mass of the feedstock, or up to about 35%, or up to about 30%, or up to about 25%, or up to 20%, or up to about 15%, or up to about 10%, or up to about 5% of the mass of the feedstock, or it may be added at between about 1% and 40%, or between about 5% and 35%, or between about 10% and about 30%, or between about 15% and 25%, or it may be added at about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40% by mass of the feedstock.

[0054] In some other embodiments, the additional components may modify the features or activity of the produced electrode. For example, in some embodiments, the feedstock may optionally comprise conductive components that increase the conductivity of the electrode. The additional conductive components may comprise carbon. It may comprise graphite (for example, graphite powder or graphite flakes). It may comprise carbon black powder. It may comprise graphene (for example, carbon nanotubes or carbon nanowires). The additional components may also or alternatively comprise a metallic conductor, such as a transition metal or alloy thereof (for example, silver, gold, copper, iron, aluminium, cobalt, zinc, steel, brass, or bronze) in a particulate form. The additional conductive components added to the feedstock may be particulate. In some embodiments, the additional conductive components are added to the particulate coal in any amount up to about 20% of the mass of the feedstock, or up to about 15%, or up to about 10%, or up to about 5% of the mass of the feedstock, or it may be added at between about 1% and 20%, or between about 2% and 15%, or between about 5% and about 10%, or between about 3% and 12%, or it may be added at about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% by mass of the feedstock. Accordingly, in one embodiment of the present invention, the feedstock may comprise between 50% and 100% non-coking coal, between 0% and 100% coking coal, and between 0% and 20% graphite. In one specific embodiment, the feedstock may comprise about 70% non-coking coal, about 20% coking coal and about 10% graphite.

[0055] The components of the feedstock (for instance, the particulate coal and any additional components, if any) may be combined by any suitable means, for instance they may be milled and / or crushed together, or they may be combined in particulate form by mixing, tumbling or stirring together so as to distribute the components evenly, or substantially evenly, throughout the feedstock. In some preferred embodiments, the feedstock consists of only particulate components (that is, all components of the feedstock are particulate) or consists substantially of particulate components (that is, non-particulate components may be present at less than 1% w / w, or less than 0.5% w / w, or less than 0.1% w / w of the feedstock). Preferably, the particulate coal and any additional components that are present are mixed to form a homogenous, or substantially homogenous, mixture prior to any further steps of the process described herein.

[0056] Surprisingly, the process of the present invention does not require, as an additional component, a non-vitrinite binder. In other words, components that may bind the feedstock during or after heating, such as polymers (such as, for example polyvinylidene fluoride (PVDF), polyethylene, polypropylene and the like), gums (such as, for example, xanthan gum, gellan gum and the like), or organic solvents (such as, for example, N-methyl pyrrolidone (NMP), ethanol, methanol and the like) are not added to the feedstock before, during or after use in this process. It is anticipated that by using only materials or substances derived from coal, production costs may advantageously be minimised, as externally-sourced materials are not required.

[0057] The feedstock may comprise at least 50% vitrinite, or at least 60% vitrinite, or at least 70% vitrinite, or at least 75% vitrinite, or at least 80% vitrinite, or at least 90% vitrinite, or between about 50% and 90% vitrinite, or between about 60% and about 90% vitrinite, or between about 70% and 80% vitrinite, such as about 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95% vitrinite. The ratio of fluid (such as vitrinite) to non-fluid (such as inertinite, charcoal, biochar or graphite) components in the feedstock may be between about 1 : 1 and about 9.5: 1, or it may be between about 2: 1 and about 9: 1, or it may be between about 3 : 1 and about 8: 1, or it may be between about 4: 1 and about 7: 1, or it may be between about 5: 1 and 6: 1, or it may be between about 3.5: 1 and about 8.5:1, for example is may be about 1 : 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.5: 1, 4: 1, 4.5: 1, 5: 1, 5.5: 1, 6: 1, 6.5:1, 7: 1, 7.5: 1, 8: 1, 8.5: 1, 9: 1, or 9.5:1, or any suitable range therein.Heating Step

[0058] Once the feedstock has been provided, heat is then applied to the feedstock. In a first heating step, the feedstock is exposed to a first temperature that is sufficient for carbonization of the feedstock. By “carbonization”, it is meant that the carbon in the coal (and other components of the feedstock, if any) is concentrated (that is, a higher concentration of carbon may be found in the solid article formed after heating than may be found in the feedstock before heating). This concentration or carbonization of the feedstock may involve one or more of: the removal of water (i.e., dehydration); the removal of volatile compounds (i.e. volatilization); the reduction of any other organic compounds that are present in the feedstock; or isomerization of the carbon (to form a more electrically conductive isomer of carbon), as examples. The inventor has found that the carbonization of the feedstock and subsequent cooling leads to the feedstock becoming solid and robust, thereby forming a solid article, so long as the feedstock has a sufficient amount of fluid macerals (as discussed above). The temperature of the first heating step sufficient for carbonization of the feedstock may be between about 800 °C and about 1200 °C, or between about 900 °C and 1100 °C, or between about 850 °C and about 1000 °C, or at about 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150 or 1200°C, or any value or range therein. During the first heating step, the temperature may be increased at any suitable rate, such as between about 1 °C / minute and 50 °C / minute, or between about 1 and 50, or between about 10 and 40, or between about 15 and 30, or between about 20 and 25°C / minute, such as about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 °C / minute or any range therein, until the first temperature is reached. The heating may be at a constant heating rate (that is, the same or substantially the same heating rate is used during the entire first heating step) or the first heating step may be at variable or programmed heating rates (that is, more than one heating rate may be used during the heating step before the first temperature is reached, such as for example, a slower heating rate initially and a faster heating rate at the end, or vice versa). The more than one heating rates in a variable heating rate process may increase or decrease stepwise (that is, the heating rate is substantially held at a certain rate for a period of time, before a short transition period to another heating rate) or the heating rate may be constantly or continually increased or decreased over time. Once the first temperature is reached, the feedstock may be held at this first temperature for a suitable period of time to cause complete, or at least substantial, or at least partial, carbonization of the feedstock to thereby form a solid article. This period of time may be between about 30 minutes and about 120minutes, or it may be between about 45 minutes and about 90 minutes, or it may be between about 60 and 75 minutes, or it may be for about 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 minutes. It is expected that the optimal first temperature sufficient for carbonization and the heating rate may be optimizable by a skilled person depending on, at least partially, the composition of the feedstock.

[0059] The process of the present invention may operate in a batch mode or in a continuous mode. In an example of a batch mode, the feedstock described herein is provided and located in a mould. The mould is a hollow container designed so as to contain the feedstock during heating and provide the shape of the solid article. Any suitable shaped mould may be used, such as a cube, a cylinder, a sphere, an ellipsoid or a rectangular cuboid. As the skilled person would appreciate, the mould is of similar relative dimensions as the intended solid article to be produced, although it may be slightly larger to account for any shrinkage that may occur as volatile components of the feedstock are lost during heating. In some embodiments, the solid article may shrink or contract by up to 25% in any dimension, or it may shrink or contract by up to 20%, or by up to 15%, or by up to 10%, or by up to 5%, or by up to 1% in any dimension, or it may not shrink or contract at all. Any shrinkage or contraction of the solid article may be dependent on the feedstock components. The mould preferably is formed from a suitable refractory material that is resistant, or substantially resistant, to heat. The refractory material may also be resistant, or substantially resistant, to pressure. The refractory material may also be resistant, or substantially resistant, to chemical attack. An example of a suitable refractory material is 316 stainless steel, although it would be expected that a skilled person could optimise the mould material and design depending on the desired electrode to be produced.

[0060] As the skilled person would appreciate, the feedstock comprising particulate coal (and optionally other solid particles) may comprise voids between the particles when the feedstock is located in the mould. In other words, for some feedstock compositions, in order to form a solid article, the feedstock may need to be more closely packed together before and / or during the heating step. Accordingly, the step of locating the feedstock in the mould may also comprise pressing the feedstock into the mould. In some embodiments, the mould is overfilled, and then pressure is applied in at least one dimension to pack the feedstock into the mould. This applied pressure may be released before heating, or it may continue to be applied during the heating step. As the skilled person would appreciate, this packing step may evacuate air or other gasses from between the particles and other components of the feedstock and bring the particles intocloser arrangement (i.e., increase the density of the feedstock before heating), which would be expected to lead to improved binding of the feedstock and a more robust solid article (and, ultimately, electrode) with improved mechanical properties. The pressure may be applied by any suitable means, for example by use of a hydraulic press, a piston or a mechanical press. The load applied to the feedstock may be up to about 50 tons, or up to about 40 tons, or up to about 30 tons, or up to about 25 tons, or between about 5 and 50 tons, or between about 10 and 40 tons, or between about 20 and 25 tons or any range therein. The pressure applied to the feedstock may be up to about 500 MPa, or up to about 400 MPa, or up to about 350 MPa, or up to about 300 MPa, or up to about 250 MPa, or up to about 200 MPa, or up to about 150 MPa, or up to about 100 MPa, or up to about 50 MPa, or between about 0.5 and about 500 MPa, or between about 1 and about 400 MPa, or between about 2 and about 300 MPa, or between about 0.1 and about 1 MPa, or between about 2.5 and about 5 MPa, or between about 5 and about 25 MPa, or between about 10 and about 100 MPa, or between about 150 and about 300 MPa, or between about 200 and about 400 MPa, such as for instance about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 MPa or any range therein.The step of locating the feedstock in the mould may also comprise other techniques for increasing the density of the feedstock before heating, such as for instance, shaking (e.g., using a shaking table) or vibrating (e.g., using a vibrating table or an ultrasonicator) the feedstock located in the mould.

[0061] Alternatively, the process of the present invention may be carried out in a continuous mode. In an example of a continuous mode, the feedstock is located in an extruder (or the like), such as a single-screw extruder or a double-screw extruder, whereby feedstock can be continually added to one end of the extruder, and heated mixed feedstock can be extruded from the other end of the extruder. In such embodiments, the extruder heats the feedstock to partially fluidize or plasticize the feedstock, so that the heated feedstock can be extruded through a die. The extruder may also act to mix the particulate coal, and / or to crush coal to form particulate coal. The temperature in the extruder may be less than the carbonizing temperature, or it may be about the carbonizing temperature. If the extrusion temperature is less than the carbonizing temperature, a further heating step as described above will be required in order to carbonize the extruded material. The extruder die may be any shape or diameter that is desired which isoptimisable by the skilled person. The extruded feedstock may optionally then be further shaped or processed before heating to a carbonizing temperature.

[0062] The carbonizing heating step, and / or extrusion step (if any) may be carried out in air, or it may be carried out in an inert atmosphere (such as, for instance, an environment high in nitrogen, carbon dioxide, or a noble gas) or a reducing environment (such as, for instance, an environment high in hydrogen, carbon monoxide, or hydrogen sulfide) or some other nonoxidizing atmosphere. As the skilled person may appreciate, it may be preferable to protect the feedstock from oxygen during the first heating process, so as to avoid combustion or oxidation of the carbon in the feedstock. Further, as gases commonly evolve during the initial heating of coal, these may serve to further displace oxygen so as to reduce or minimise oxidation of the plasticised coal. Therefore, in embodiments where the first heating step is carried out in air, a mould (if used) may be fitted with a snug fitting mould cover (such as a steel plate or the like) that seals the feedstock from the atmosphere, thereby limiting the oxygen able to access the feedstock during heating. The use of a snug fitting cover may also provide additional compressive force during heating to assist the formation of the solid article. However, it is also possible to produce a solid article without use of a mould cover or for the mould to be airtight.

[0063] After the first heating step in completed, the heated feedstock is allowed to cool, preferably to room temperature (that is, between about 20 and 25 °C). Once cooled, the feedstock preferably will have formed a solid article. The solid article may be formed and cooled in the mould, or it may be shaped after extrusion and left to cool.Treatment Step

[0064] The cooled solid article of the heating step above forms the basis for the electrode of the present invention. As will be described in more detail below, the solid article obtained by the heating step described above is electrically conductive and may be used itself as a carbon electrode. Alternatively, the solid article may optionally be further treated in a treatment step before the electrode is used, for example in a supercapacitor, such as an EDLC. As the skilled person would appreciate, an electrode for use in an EDLC apparatus preferably has a high surface area on at least one face of the electrode, thereby increasing the size of the electrodeelectrolyte interface, leading to more electrostatic charge being held in the Helmholtz double layer that is formed at this interface and hence a higher energy storage capacity. Increasedsurface area is also beneficial in electrodes used in other energy storage devices, such as batteries, that may utilise or be capable of utilising a carbon electrode. The optional treatment step described herein is one example of a process that can increase the surface area of an electrode of the present invention.

[0065] Before carrying out the optional treatment step, the solid article may optionally be further processed, or it may be used in the shape that it is produced after the first heating step. The optional further processing step may comprise trimming the edges of the solid article (to produce well defined sides, edges and corners for use in a specific apparatus), and / or forming the solid article into 2, 3, 4, 5 or more pieces for treatment to form electrodes (that is, the solid article may be used to produce more than 1 electrode).

[0066] Once the solid article is prepared, it may be exposed to an optional treatment step. This treatment step, when used, comprises the application of a composition to at least one surface of the solid article. In one embodiment, the composition may be applied to 1, 2, 3, 4, 5 or 6 surfaces of a cuboid solid article. The composition may be a solid composition (e.g., in the form of a powder, a foil, a gel or the like), or it may be a liquid composition (e.g., a solution, an emulsion or the like), or it may be a combination of these states (e.g., a suspension, a paste or the like). The composition may be applied to the at least one surface by any suitable means, depending on the physical form of the composition. For example, it may be applied by spraying, brushing, dipping, rolling, painting, fixing, adhering or condensing the composition to the at least one surface. Any suitable apparatus for applying the composition to the at least one surface may be used.

[0067] The composition that may be applied to the solid article is preferably corrosive to at least a portion or component of the solid article surface or subsurface. By “corrosive”, it is meant that the composition is capable of reacting with, or consuming, compounds that are found in at least a portion of the surface on which the composition is applied. The composition may be acidic, or it may be alkaline. It may be highly acidic (that is, a pH less than 2) or it may be highly alkaline (that is, a pH greater than 12). An acidic composition may comprise a mineral acid (such as hydrochloric acid, nitric acid, sulphuric acid, phosphoric acid, boric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, chloric acid or perchloric acid). The acidic composition may contain a mineral acid at a concentration of at least 1%, or at least 2%, or at least 5%, or at least 10%, or at least 20%, or at least 25%, or at least 50% of thecomposition on a v / w or v / v basis (depending on the form of the composition). An alkaline composition may comprise a strong base, in particular a hydroxide salt of the Group I (alkali metals) or Group II (alkaline earth metals) elements. The alkaline composition may comprise lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, caesium hydroxide, calcium hydroxide, strontium hydroxide, or barium hydroxide. The alkaline composition may contain a Group I or Group II hydroxide salt at a concentration of at least 1%, or at least 2%, or at least 5%, or at least 10%, or at least 20%, or at least 25%, or at least 50% of the composition on a w / w or w / v basis (depending on the form of the composition).

[0068] Once the composition is applied to at least one surface of the solid article, a further heating step is carried out. Without being bound to theory, the inventor understands that the combination of an acidic or alkaline composition and heat accelerates the corrosion of the surface and forms a surface with microporosity and hence a higher surface area. Depending on the composition being used, the surface can also become oxidized, therefore being more electrostatically active or attractive to hydrated ions in the electrolyte during use as an electrode and / or in a supercapacitor. The further heating step may include heating the treated solid article to a temperature of between about 500°C and about 900°C, such as between about 500 and 750°C, or between about 600 and 800°C, or between about 700 and 850°C, or to a temperature of about 500, 550, 600, 650, 700, 750, 800, 850 or 900°C or any range therein. The temperature may be increased at any suitable rate, such as between about 1 °C / minute and 25 °C / minute, or between about 2 and 10, or between about 5 and 15, or between about 7 and 20°C / minute, such as about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 °C / minute or any range therein, until the further temperature is reached. The heating may be at a constant heating rate (that is, the same or substantially the same heating rate is used during the entire further heating step of the optional treatment step) or the heating during the optional treatment step may be at variable or programmed heating rates (that is, more than one heating rate may be used during this heating step before the further temperature is reached, such as for example, a slower heating rate initially and a faster heating rate at the end, or vice versa). The more than one heating rates in a variable heating rate process may increase or decrease stepwise (that is, the heating rate is substantially held at a certain rate for a period of time, before a short transition period to another heating rate) or the heating rate may be constantly increased or decreased over time. Once the further temperature is reached, it may be held at this temperature for between a period of time sufficient to form micropores on the treated surface. This period of time may between about 30 minutes and about 180 minutes, or it may be between about 45minutes and about 90 minutes, or it may be between about 60 and 75 minutes, or it may be between about 90 and 150 minutes, or it may be for about 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180 minutes. The first and second heating steps may be carried out in any suitable apparatus, such as an oven or the like.

[0069] In embodiments whereby an optional treatment step is carried out, the treated solid article is then cooled to a room temperature and may be optionally washed or cleaned before the next step is carried out.Activating Step

[0070] Before use in a supercapacitor or other electrical device, the solid article formed from the process described above (and optionally subjected to a treatment step as described above) may then be exposed to an activating step to form an electrode. Without being bound to any particular theory, it is anticipated that an activating step oxidizes carbon material at the surface of the electrode, which at least partially consumes the carbon and increases the microporosity of the surface, similar to the optional treatment step described above. As mentioned above, an increase in microporosity of the surface leads to an increase in surface area and can therefore provide the electrode with improved electrostatic properties. The extent of this activation step can also increase the electrical resistance of the electrode, for example by adding non- conductive oxide species to the surface of the electrode.

[0071] Before carrying out the activating step, the solid article may optionally be further processed, or it may be used in the shape that it is produced after the first heating step. The optional further processing step may comprise trimming the edges of the solid article (to produce well defined sides, edges and corners for use in a specific apparatus), and / or forming the solid article into 2, 3, 4, 5 or more pieces for treatment to form electrodes (that is, the solid article may be used to produce more than 1 electrode).

[0072] The activating step may comprise a separate heating step, whereby the electrode is heated to a second temperature in a reactive atmosphere. The second temperature is typically at a lower temperature than the carbonizing temperature or the optional treatment steps described above. As the skilled person would appreciate, the second temperature is dependent on the atmosphere in which the electrode is being heated at this activating step. The atmospheregenerally comprises at least one reactive gas. In some embodiments, the reactive gas may comprise at least one gas that is reactive at elevated temperatures, such as, for example, oxygen (O2), nitrogen (N2), ozone (O3), hydrogen (H2), carbon monoxide (CO), sulfur dioxide (SO2), oxidized nitrogen compounds (e.g., NO or NO2), water (H2O, in the form of steam) and volatile organic compounds, or any combination of two or more of these reactive gasses. In particular embodiments, mixtures of nitrogen and oxygen, or carbon dioxide (CO2) and nitrogen, or water vapor (i.e., steam) and nitrogen, may be preferred. In some embodiments, the atmosphere is air (which is typically a mixture of nitrogen, oxygen, argon, water vapor and other trace gasses). As the skilled person would appreciate, the degree or rate of surface treatment that results from heating the electrode in an atmosphere containing or comprising a reactive gas (or gasses) may be at least partially controlled by also adding a non-reactive gas, such as an inert gas (e.g., helium, neon, or argon). In other words, in some embodiments the reactive gas mixture contains, or comprises, at least a portion of at least one non-reactive gas. It is expected that the skilled person could optimise the gas, or mixture of gasses, for any given feedstock or electrode composition.

[0073] Temperatures used in the activating step will vary according to the reactive gas mixture used. As the skilled person would appreciate, oxygen-based processes (i.e., combustion) are exothermic and so will generate heat as the oxygen reacts with carbon in the solid article, whereas gasification processes that include reactions between the carbon and CO2 or water vapor are generally endothermic and require the addition of heat. Accordingly, the optimal second temperature will be dependent on, at least partially, the reactions occurring at the surface of the solid article during this activating step, with lower temperatures favoured for mixtures containing oxygen (resulting in exothermic reactions) and higher temperatures favoured for mixtures containing, for example, CO2 or H2O (resulting in endothermic reactions). In embodiments where the reactive gasses are primarily or substantially involved in exothermic reactions (where oxygen is a substantial component of the reactive gas mixture), the second temperature is between about 300 °C and 600 °C, or between about 350 °C and 450 °C, or between about 400 °C and 550 °C, or at a temperature of about 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 °C or any range therein. In other embodiments where the reactive gasses are primarily or substantially involved in endothermic reactions (i.e., CO2 or H2O), the second temperature is between about 500 °C and about 900 °C, or between about 550 °C and about 750 °C, or between about 650 °C and about 850 °C, or at a temperature of about 500, 510, 520, 530, 540, 550, 560, 570, 580, 590,600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780,790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, or 900 °C or any range therein. The temperature of this step may be held for a period of time between about 1 hour to about 3 hours (that is, between 60 and 180 minutes), such as for about 60, 65, 70, 75, 80, 85, 90, 95, 100, 105,110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175 or 180 minutes or any range therein. In some embodiments, the activating step includes two or more distinct heating steps. The inventor has found that, when electrodes of the present invention are heated in an oxygen-containing atmosphere, if temperatures of about 450 °C or more are sustained for a period of time, this can lead to the non-homogenous activation of the electrode surface. Without being bound to any particular theory, it is believed that the non-homogenous activation of the surface is due to, or is at least contributed by, the build-up of heat of combustion on the electrode surface. To ameliorate this effect, when an oxygen-containing reactive gas mixture is present in the atmosphere during heating, it may be beneficial to heat the electrodes in two or more heating cycles to a temperature below 450 °C, or between 300 °C and 450 °C, such as 425 °C, for a longer period of time, with a cooling step between both, or each, heating cycles. It is believed that sequential heating steps may provide a more homogenous surface treatment in an oxidizing atmosphere.

[0074] Alternatively, or as well, the optional activating step may comprise use of the electrodes as an anode and / or a cathode in an electrolysis cell to split water, whereby oxygen and carbon dioxide is produced at the anode and hydrogen is produced at the cathode. In such embodiments, it is understood that the anode is partially consumed using the principle of “carbon-assisted water electrolysis”, thereby increasing its microporosity. Switching the electrical polarity will cause the opposite electrode to become the anode and begin activating. In other words, carbon electrodes of the present invention may form either the anode or the cathode of any electrolysis cell, and switching the polarity of the cell will allow for two electrodes to be activated in the same cell. This electrolysis-based activating step may also advantageously act as a quality control step to ensure that the electrodes are robust, suitable for use in contact with an aqueous electrolyte and can withstand voltages of at least 1.23 V (the minimum voltage required to split water into hydrogen and oxygen gas) and overpotentials thereof. For instance, the electrolysis cell comprising electrodes of the present invention may be run at a voltage of between about 3 V and about 12 V, such as at between about 4 V and about 10 V, or between about 5 V and about 9 V, or between about 2.5 V and about 11.5 V, or at about 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5 or 12 V or any range therein. The electrolysis cell may be run for aperiod of time of between about 1 hour and about 3 hours (that is between 60 and 180 minutes), such as for about 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 1665, 170, 175 or 180 minutes or any range therein.

[0075] The activating step, particularly if a heating step is used, is expected to result in mass loss of the electrode. It is believed that this mass loss is due to further volatile components being lost, or some carbon being oxidized and lost as carbon dioxide, or some ash or other impurities being lost from the surface, or any combination thereof. In some embodiments, the activated electrode (that is, the electrode after the activating step and any optional treatment steps have been carried out) may have lost about 25 % of its mass, or about 20 %, or about 15 %, or about 10%, or about 5%, or about 2% or about 1% of its mass, compared to the initial pristine solid article following the first heating step. It is expected that the skilled person can monitor the degree or extent of the activating surface treatment by measuring the mass loss of the electrode during or following the activating heating and / or electrolysis step(s).

[0076] After the activating step, the solid article, comprising at least one surface with microporosity, thereby forms an electrode that is suitable for use in a supercapacitor or other electrical storage device. The micropores formed on at least one surface of the electrode have a diameter of between about 0.1 nm and about 2 nm (that is, on the nanoscale). For example, they may be between about 0.05 nm and about 0.5 nm, or between about 0.1 nm and about 0.75 nm, or between about 0.25 nm and about 1.25 nm, or between about 0.5 nm and about 1.8 nm, or between about 0.75 nm and about 1.5 nm, or between about 1 nm and 2nm, or may be about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2nm or any range therein. In some embodiments of the present invention, the at least one surface of the electrode of the present invention may also contain or comprise mesopores; that is, the activated surface or surfaces may have both micropores and mesopores. The mesopores, when present, have a diameter of between about 2 nm and about 50nm. For example, they may have a diameter of between about 2 nm and about 25 nm, or between about 5 nm and about 30 nm, or between about 10 nm and about 40 nm, or between about 25 nm and about 50nm, or they may be about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 46 or 50 nm or any range therein. In one preferred embodiment of the present invention, the electrode comprises one microporous surface for interacting with the electrolyte, which is supported by the untreated surfaces to provide bulk strength and conductivity to the electrode.Capacitor

[0077] In another aspect of the present invention, there is provided an electrode. Preferably, the electrode of the present invention is suitable for use in a supercapacitor, specifically an EDLC, however the invention is not intended to be limited to this use. In one embodiment, the electrode is produced, or obtained, or obtainable, from the process described above. In other embodiment, the electrode comprises: sintered particulate coal; and at least one surface that comprises micropores (whereby the micropores are as defined above).

[0078] Accordingly, in another aspect of the present invention, these is provided the use of an electrode as described herein in a supercapacitor. The supercapacitor may preferably be an EDLC apparatus, although as the skilled person may appreciate, the electrode may be used as a cathode and / or anode in other electrical devices or circuits.

[0079] Accordingly, in another aspect of the present invention, there is provided a supercapacitor apparatus. The supercapacitor may comprise: an electrode as described herein; an electrolyte; a separator; a current collector / connector; and a container.

[0080] The electrolyte of the sup er capacitor may be liquid. It may be aqueous (that is, it may comprise water) or it may be an organic liquid or an ionic liquid. As the skilled person would appreciate, a supercapacitor, especially an EDLC, works by holding an electrostatic charge at the surface of the electrode in an electrical double layer. Therefore, the ions or charge carriers of the electrolyte must be mobile (that is, they must be able to move through the electrolyte matrix towards the electrodes). In one preferred embodiment, the electrolyte is an aqueous solution of a salt. The salt may be any suitable salt that completely, or substantially, dissociates in water at a room temperature (that is, about 20 to 25 °C). It may be a neutral salt, an acidic salt or a basic salt. Non-limiting examples of suitable salts include, for instance, sodium chloride, potassium chloride, potassium bromide, magnesium chloride, sodium sulfate, potassium sulfate and sodium nitrate, for instance. The electrolyte may comprise 1, 2, 3, 4, 5 or more different salts dissolved together. The total concentration of the dissolved salt(s) may be at least about 0.1 M, or at least about 0.2 M, or at least about 0.5 M, or at least about 0.75 M, or at least about 1 M, or it may be between about 0.1 M and about 2 M, or between about 0.25 M and about 1 M, or between about 0.5 M and about 0.75 M, or it may be about 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35,1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95 or 2 M or any range therein. In one particular embodiment, the electrolyte is a 0.5M aqueous solution of sodium sulfate (ISfeSC ).

[0081] The separator of the supercapacitor may be any suitable material that stops the electrodes from coming into contact and short circuiting the cell yet is porous so as to allow movement of ions between electrodes. The separator must also be chemically inert and not react or interact with the electrolyte. The separator may be an ion-permeable membrane. It may comprise a polymer (such as, for example, a polyacrylonitrile, polypropylene, polyvinylidene fluoride (PVDF), polyethylene, or polyimide or derivatives thereof), and / or it may comprise a biopolymer (such as, for example, cellulose, lignin, alginate or derivatives thereof) and / or it may comprise a ceramic, and / or it may comprise a glass. In some preferrable embodiments, the separator may comprise coal-derived components such as feed coal, minerals, high-ash coal, coal ash, coal tar, or any other low-cost or waste material obtained from coal mining or processing. The separator may be woven, or it may be non-woven. For example, the separator may be a non-woven polyacrylonitrile or polyimide film, or it may be a woven material comprising paper (i.e., cellulose), glass or ceramic fibres, or it may comprise both (that is, it may be a composite material comprising a non-woven film that is reinforced with a woven fibre). The separator may be less than 1 mm in thickness, or it may be less than 0.5 mm, or less than 0.3 mm, or less than 0.25 mm, or less than 0.2 mm, or less than 0.1 mm, or less than 0.05 mm in thickness. The separator may be any suitable dimensions necessary to provide the above features and will be dependent on the overall cell design. In one embodiment, the separator may be a woven glass fibre filter paper.

[0082] The capacitor also comprises a current collector. The current collector (or current connector, to use an interchangeable term) may be any suitable material that electrically connects the electrodes of the supercapacitor to the terminals of the supercapacitor (which in turn are connected to a power source for charging and discharging the supercapacitor). In other words, the current collector is an electrically conductive material that is in electrical contact with the electrode. In some supercapacitor designs, the current collector may be flexible, or it may be rigid. In some embodiments, the current collector may be a foil comprising or consisting of a metal (such as, for example, aluminium foil, copper foil, brass foil, or nickel foil) or other conductive material (such as, for example, graphite, graphene or polyaniline) or any combination thereof (such as, for example, a composite material comprising a polymer matrix and a conductive nanopowder, fibre, web, wire, nanorods or flakes embedded therein). As theskilled person may be aware, the choice of material for the current collector may need to be selected depending on the other materials used in a particular supercapacitor to ensure that the current collector does not galvanically react when in electrical contact with any other metalbased material, such as the container or any metallic impurities that may be present in the electrodes. In one particular embodiment, a graphite foil (e.g., Grafoil) may be suitable. In other embodiments, conductive carbon pastes such as graphite / grease mixtures may be suitable. The current collector may be any suitable dimensions and may be dependent on the overall design of the supercapacitor. The current collector may be adhered or bound to the electrode in any suitable manner that maintains electrical contact, for instance it may be secured directly to a surface of the electrode by use of a fastener (such as a nail, staple, clip, band or tie or the like), or it may be secured indirectly by use of another material, such as a conductive adhesive (such as a glue or grease comprising a conductive substance, such as graphite powder, metal filings, or the like), or any combination thereof. In some embodiments, the current collector comprises the non-activated portion of the carbon electrode. Without being bound by theory, the inventor understands that the non-activated internal portion of the carbon electrode, which has not been reacted in either the optional treatment or the activating steps described above, is likely derived, or largely derived, or substantially derived, from the vitrinite portion of the original coal feedstock and so is inherently conductive. In this embodiment, the electrical charge is conducted from the electrolyte-wetted surface of the carbon, through its non-reacted core structure and up into the non-wetted portions of the device.

[0083] The container of the supercapacitor may be of any dimensions suitable to locate the components of the supercapacitor (specifically at least the electrodes, electrolyte, separator and current collector) therein and will be dependent on the intended use of the supercapacitor. For example, it is envisioned that the supercapacitor described herein may be suitable for use as a bulk energy storage device for use with a large renewable energy source (for example, a solar farm, wave energy harvester, or a wind turbine), or it may be suitable for use as an energy storage device for a household or industrial setting (such as a building with roof-mounted solar panels), or it may be suitable to power individual devices. The container may be at least partially open to the surrounding environment; however, the inventor prefers that the container is sealed to the surrounding environment to avoid corrosion of the components and loss of electrolyte volume. When sealed, the container may be airtight, or it may allow for the escape of gasses that may generate during use of the supercapacitor. The container may be made of any suitable material. It may be rigid, or it may be flexible. In some supercapacitor designs, the containermay be non-conductive. It may be a polymer (such as, for example, polyethylene, polypropylene, polyester terephthalate (PET), polyvinyl chloride (PVC), polycarbonate, acrylonitrile butadiene styrene (ABS) or polyamide). In other supercapacitor designs, the container may be conductive. It may be a metal (such as, for example, aluminium, brass, copper, steel, or stainless steel). As the skilled person would appreciate, when a metallic container is used, the design of the supercapacitor must ensure that the container does not short circuit the electrodes (e.g., by physical contact) or react with any of the components therein. In some embodiments, the container may comprise at least two layers, whereby the outer layer is a strong, rigid, conductive material (such as steel) and the inner layer is a non-conductive material that separates the electrically-conductive components (that is, the electrolyte, electrodes and current collector) from the conductive outer layer of the container. In some embodiments, the outer layer of the container may house 2, 3, 4, 5 or more separate supercapacitor cells, which are themselves contained within an inert container.Use

[0084] The supercapacitor, comprising the electrodes of the present invention, may be used to store electricity. In other words, the supercapacitor may be charged with excess electricity during a charge phase, which can then be discharged at a later time. In particular, the inventor envisions that the supercapacitor described herein may be particularly suited as a bulk energy storage device for use with a renewable energy source (such as a solar farm, a wind turbine, wave generator, or the like) which has a variable electricity generation profile, to thereby provide baseload renewable power, or to provide energy at peak usage times that may occur during a non-generation period of time (for example, during a night time peak for electricity usage, when solar-based technologies cannot generate power). The supercapacitor described herein advantageously can charge and discharge electricity quickly and is more stable over many charge / discharge cycles compared to chemical -based energy storage methods, making it particularly suitable for this use.

[0085] The energy density, or specific energy storage, of the supercapacitors described herein may be up to about 20 Watt hours per kg of electrode mass (Wh / kg) when fully charged, or it may be up to about 15 Wh / kg, or up to about 10 Wh / kg, or it may be between about 2 and 20 Wh / kg, or between about 5 and 15 Wh / kg, or between about 6 and 12 Wh / kg, or between about 8 and 10 Wh / kg, or between about 4 and 18 Wh / kg, or between about 12 and 17 Wh / kg, orabout 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 Wh / kg, or any range therein. The maximum charge that may be held by the supercapacitor described herein may be about 3.5 V, or about 3 V, or about 2.5 V, or about 2 V, or about 1.9 V, or to about 1.5 V, or about 1.23 V, or between about 0.5 V and about 3.5 V, or between about 1 V and about 2 V, or about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, or 3.5 V or any range therein. As the skilled person may appreciate, the electrical voltage is dependent on other design factors, including the electrolyte chosen for use in the cell.

[0086] The time to fully charge the supercapacitor may be less than about 5 hours, or it may be about 4 hours, or about 3 hours, or about 2 hours, or about 1 hour, or any time between about 1 hour and about 5 hours, or between about 2 hours and about 3 hours, such as about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 hours or any time or range therein. The time to fully discharge the supercapacitor may be less than about 2 hours, or less than 1 hour, or less than 30 minutes, or less than 15 minutes, or it may be between about 15 minutes and 2 hours, or between about 30 minutes and 1 hour, or between about 45 minutes and 1.5 hours, such as about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115 or 120 minutes or any time or range therein.

[0087] In one particular embodiment of the present invention, the inventor envisions the supercapacitor described herein, comprising the electrodes of the present invention, to be arranged within a 20-foot (about 6 m) shipping container as an outer container. Such an arrangement would be expected to require about 20 tonnes of coal and therefor have a capacity of about 0.1 MWh per shipping container. Multiple shipping containers could be arranged in parallel to provide bulk energy storage for renewable energy storage applications.Examples

[0088] The present invention is further described with reference to the further non-limiting examples.Example 1 — Electrode Formation Method

[0089] A process for producing a coal -based electrode suitable for use in a supercapacitor has been developed by the inventor. In an example of this process, powdered coal (with particles less than about 3 mm in diameter) are packed together in a rectangular mould and heated to acarbonizing temperature of between about 800 and 1000°C. Generally, it has been found that low-fluidity coals will form a single sintered carbon tile, whereas non-fluid coals do not form a single tile. However, the addition of fluid coals (such as coking coal) can be blended with a nonfluid coal to provide a sintered carbon tile. Examples of this can be found below.A. Selection o f Coals

[0090] A range of coals have been studied to determine the most suitable coals for sintering and producing electrodes of the present invention and the results are shown in Figure 1. These coal samples are described in Table 1 below.Table 1. Coal sample standard analyses

[0091] Figure 1(a) shows a “map” of coal quality based on thermoplastic coal properties “fluidity” and Crucible Swell Number (CSN). Coals of higher fluidity and CSN values were able to be extruded in a laboratory extrusion device using a heated piston under load. Figure 1(b) shows that coals with lower fluidity / CSN values showed sufficient fluid properties to be sintered together in a stainless steel mould. Higher fluidity coals (such as those suitable for extrusion) typically become too fluid and tend to swell out of the mould, destroying their electrode forming potential. However, these high-fluidity coals are potentially of use as a blend component for non-fluid coals.

[0092] Table 2 further summarises the physical properties of the formed carbon electrode materials from different coals (measured before any activation or treatment steps are applied). It is clear that different coals produce different electrode material properties, and combinations of coal feedstocks can be used to fine-tune the desired properties for desired electrodes. A skilledperson would also appreciate that higher densities often align with higher material strength, but not necessarily with activation potential.Table 2. Summary of directly cast tile physical measurements* Thick and thin tiles were mechanically teted but not e ectrically tested for energy storage.

[0093] Table 3 shows the measured energy storage potential for each coal -based carbon electrode material following activation by heating to a temperature at about 400 °C for between 30-180 minutes in an air atmosphere. In one example, coal sample 004 was further subjected to carbon-assisted water electrolysis for 1 or 8 hours (with regular swapping of electrical polarity) as this was the lowest-performing coal sample following activation in air. The results in Table 3 indicate that this final “in-situ” activation treatment resulted in an improved energy storage potential for coal sample 004. Further, Table 3 shows that the specific energy charged is proportional to the activation mass loss (in %) for samples up to at least 24.4 % mass loss.Table 3. Summary of supercapacitor testing* Note: standard testing performed at 1.8 V charging voltage with 2 hour charge / discharge cycles.** Note 2: 004 was selected for an in situ electrolysis experiment at 10 V for lhr and 8 hr to determine if further activation could improve its energy storage potential.B. Microporosity Treatment

[0094] Once a single tile is formed, the inventor has found that it is beneficial to introduce a microporous surface on the electrode. This microporosity is generated by oxidising in air at 400°C for between 30-180 minutes. Lower temperatures require longer holding times, whilst higher temperatures require shorter periods of time. Furthermore, each coal feed stock has a different reactivity to air, based on its rank (see Figure 2(a)). Figure 2(b) shows the impact of activation mass loss on the Energy Storage potential for a supercapacitor.Example 2 — Supercapacitor Test Cell

[0095] Coal-based tiles produced according to the method above were tested in a test cell. The tiles produced are about 3 mm thick, and weigh about 11-12 g each after activation at 400°C for 2 hours in air. In this test cell, Grafoil as used as the electrical collector, which was adhered to one face of each of the electrodes using a conductive paste of grease and graphite powder. The two electrodes were arranged in a polypropylene bag with a glass paper separator placed between the electrodes. The polypropylene bag was filled with an electrolyte containing a 0.5M aqueous solution of ISfeSCU. An image of this test cell can be seen as Figure 3.

[0096] Electrodes comprising 70 wt% semi-soft coking coal, 20 wt% metallurgical coking coal and 10 wt% graphite powder were tested in this cell. Current and voltage were measured over a 1-hour charge and 2-hour discharge cycles, as shown in Figure 4. As can be seen from this figure, charging and discharging occur rapidly.Example 3 — Cost Benefit

[0097] The use of coal as a cost-effective carbon source to produce electrodes for energy storage in supercapacitors has been considered from a cost-benefit perspective. Currently, the cost of stored energy in Australian dollars per kilowatt hour ($ / kWh) is approximately $825 / kWh for lithium-ion based batteries, and about $195 / kWh for pumped hydro (two of the most popular sources of stored energy in Australia).

[0098] However, as shown above, energy densities of between 2 and 5 Wh / kg are obtainable with the electrodes of the present invention. Figure 5 shows the cost for manufacturing coalbased supercapacitors. The following assumptions have been taken into account when preparing Figure 5: price of coal = $260 / tonne (price range is indicative of differences between Newcastle thermal coal and metallurgical coal); cost of processing = $380-885 / tonne of carbon (dependingon the yield of carbon after carbonization at 1000°C using grid electricity); energy density = 2-5 Wh / kg (the same as typical supercapacitors).

[0099] As can be seen from Figure 5, the range of $30-70 / kWh is indicative of the coal quality that might be used and the thermal processing options that might be required. This cost is also competitive with other forms of contemporary energy storage technologies such as lithium-ion batteries and pumped hydro. Notably, if energy density is increased, costs for carbon-based supercapacitors would be further reduced.[000100] This cost advantage of coal -based electrodes is enhanced by the sale of tar by-products from the coal. For instance, crude coal tar contains products such as benzol, naphtha, and anthracene oil which can sell for $800-1000 per tonne. In some instances, depending on the coal used, the cost of producing the electrode and installing as a supercapacitor may be completely offset by the cost return from selling crude coal tar.[000101] Therefore, it is evident that coal -based supercapacitors, such as those described herein, could provide cheap energy storage options compared to other options currently available.Example 4 - Scaling[000102] In order to provide bulk energy storage for renewable energy generation, energy storage in the range of MWh is required. It is envisioned that the supercapacitors described herein could be arranged within a 20-foot shipping container, which is estimated to require 20 tonnes of coal and provide about 100 kWh (i.e., 0.1 MWh).[000103] In one arrangement, 6000 supercapacitor containers (providing storage of up to 600 MWh) could be used as storage for a 100 MW solar farm, whereby the solar farm charges the supercapacitors during the day, and then releases the electricity into the grid during the evening peak (when spot electricity prices are generally higher than during the day). This would allow the operator to receive a better economic result and reduces that pay -back period for the capital expense of installation, compared to simply providing the electricity to the grid during times of lower demand. Further, installations such as solar farms and wind farms have additional land that is not otherwise utilised, and so having on-site storage (that is capable of many charge / discharge cycles and is capable of charging and discharging quickly) may be an attractive option for operators of such facilities.[000104] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms in particular features of any one of the various described examples may be provided in any combination in any of the other described examples. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows.

Claims

CLAIMS1. A process for producing an electrode, comprising:(a) providing a feedstock comprising a particulate coal;(b) heating the feedstock to a first temperature sufficient for carbonization, thereby forming a solid article on cooling; and(c) activating the solid article to form an electrode comprising micropores on a surface, whereby activating comprises heating the solid article to a second temperature in a reactive atmosphere, or exposing the solid article to an electrical current when in contact with an electrolyte.

2. The process of claim 1, wherein step (b) comprises heating the feedstock in a mould.

3. The process of claim 2, further comprising the step of packing the feedstock into the mould before heating by applying pressure to the feedstock.

4. The process of claim 3, wherein the pressure is between about 1 and about 5 MPa.

5. The process of claim 1, wherein step (b) comprises heating the feedstock in an extruder and extruding the heated feedstock before cooling.

6. The process of any one of claims 1 to 5, wherein the particulate coal has a maximum particle diameter of about 2 mm.

7. The process of any one of claims 1 to 6, wherein the first temperature sufficient for carbonization is between about 800°C and about 1200°C.

8. The process of claim 7, further comprising maintaining the first temperature for between about 30 minutes and about 3 hours.

9. The process of any one of claims 1 to 8, wherein the second temperature is between about 300°C and about 800°C.

10. The process of claim 9, further comprising maintaining the second temperature for between about 30 minutes and about 3 hours.

11. The process of any one of claims 1 to 10, wherein the particulate coal is provided by a milling and / or crushing step.

12. The process of any one of claims 1 to 11, wherein the feedstock further comprises a binder additive selected from particulate coking coal and / or coal tar.

13. The process of any one of claims 1 to 11, wherein the feedstock further comprises a particulate non-coking coal as a filler additive.

14. The process of any one of claims 1 to 13, wherein the feedstock further comprises at least one conductive additive, selected from graphite, carbon black powder, graphene, carbon nanotubes, carbon nanowires, a transition metal or transition metal alloy, or combinations thereof, wherein the conductive additive is particulate.

15. The process of any one of claims 11 to 14, wherein step (a) additionally comprises a step of milling, grinding and / or blending the particulate coal with the binder additive or the filler additive and / or the at least one conductive additive.

16. The process of any one of claims 1 to 15, wherein the feedstock comprises, in weight %:- between 0% and 100% non-coking coal;- between 0% and 100% coking coal; and- between 0% and 20% graphite.

17. The process of claim 16, wherein the feedstock consists of, in weight %:- about 70% non-coking coal;- about 20% coking coal; and- about 10% graphite.

18. The process of any one of claims 1 to 17, further comprising a treating step between step (b) and step (c).

19. The process of claim 18, whereby the treating step comprises applying a composition comprising an hydroxide salt to at least one surface of the solid article and heating to a temperature of between about 300°C and 900°C for a period of time between about 1 and about 3 hours.

20. The process of any one of claims 1 to 19, wherein the electrode is for use in a supercapacitor.

21. The electrode produced by the process of any one of claims 1-19.

22. An electrode for use in a supercapacitor, the electrode comprising: sintered particulate coal, and at least one surface that comprises micropores.

23. The process or electrode of any one of claims 1 to 22, wherein the micropores have an average diameter of between about 0.1 and about 50 nm.

24. Use of the electrode of any one of claims 21-23 in a supercapacitor.

25. A supercapacitor comprising: the electrode of any one claims 21-23, an electrolyte, a separator, a current collector / connector, and a container.

26. The supercapacitor of claim 25, wherein:- the electrolyte comprises sodium chloride and / or sodium sulfate; and / or- the separator comprises glass paper, or cellulose paper, or polypropylene; and / or- the container is sealable.

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