Electrode manufacturing technology

Abstract

The present application relates to an electrode comprising a redox-active material and a low- dimensional carbon material. At least around 70% of the surface of the electrode comprises at least one layer comprising the low-dimensional carbon material. The electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

Description

[0001] ELECTRODE MANUFACTURING TECHNOLOGY

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to electrodes comprising a redox-active material and a lowdimensional carbon material, and methods for forming such electrodes.

[0004] BACKGROUND

[0005] Electrodes are essential components of batteries. However, many common electrodes and their methods of manufacture suffer from a range of issues.

[0006] For example, standard electrode manufacturing processes use N-methyl-2-pyrollidine (NMP) as a solvent. Solvents generally need to be evaporated off towards the end of the manufacturing process, which adds time and energy costs. Moreover, NMP is toxic and so extra steps / equipment to recover and contain evaporated NMP are necessary when this is used as a solvent. NMP is also combustible, which gives rise to safety issues.

[0007] In addition, many conventional electrodes comprise binders (e.g. polymeric binders), which add to the mass and volume of the electrodes. The capacity of the electrodes can be limited if a binder is selected which is not redox-active or electronically conductive.

[0008] Standard electrode manufacturing processes commonly require high temperatures to adhere the electrode components into a mechanically stable electrode. These make the overall processes energy-intensive, and also run the risk of thermally damaging the electrode materials.

[0009] It would be desirable to produce an electrode and a method for forming an electrode which reduce the need for, for example, solvents and high temperatures, and / or which give rise to improved capacity and / or reduced charge transfer resistance. It would also be desirable to obviate, mitigate and / or ameliorate one or more deficiencies in known electrodes and / or methods for forming electrodes, whether identified herein or otherwise.

[0010] SUMMARY

[0011] According to a first aspect of the present disclosure, there is provided an electrode comprising a redox-active material and a low-dimensional carbon material, wherein: at least around 70% of the surface of the electrode comprises at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0012] According to a second aspect, there is provided a battery comprising one or more electrodes as described above.

[0013] According to a third aspect, there is provided a method for forming an electrode, wherein the method comprises: preparing an agglomeration comprising a redox-active material and at least one layer comprising a low-dimensional carbon material; and pressing the agglomeration to form an electrode, wherein: at least around 70% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0014] According to a fourth aspect, there is provided an apparatus suitable for carrying out the method described herein.

[0015] Other optional and preferred features of the apparatus and method of the present invention are set out below in the detailed description and follow in the claims.

[0016] DEFINITIONS

[0017] The following definitions apply for terms used herein. In the event that any term is not specifically defined here or otherwise, the standard meaning in the present technical field prevails. This standard meaning may bear in mind definitions provided in common general knowledge (e.g. standard textbooks) in the present technical field. Usefully, for example, chemical terms may be interpreted in accordance with the IUPAC Gold Book Version 3.0.1 .

[0018] The term “at least one” is synonymous with “one or more”, e.g. one, two, three, four, five, six, or more.

[0019] As used herein, the terms “around”, “about” or “substantially” generally encompass or refer to a range of values that one skilled in the art would consider equivalent to the recited values (e.g. having the same function or result, and / or achieved substantially in the same way). Suitably, where the term “about” is used in relation to a numerical value, it can represent (in increasing order of preference) a 10%, 5%, 2%, 1% or 0% deviation from that value. The term “low-dimensional carbon material” is one of the art. For the avoidance of any doubt, low-dimensional carbon materials are materials comprising carbon, particles of which have at least one spatial dimension on the nanoscale, e.g. about 0.1 to 1000 nm, about 0.5 to 500 nm, about 1 to 250 nm or about 5 to 100 nm. Low-dimensional carbon materials may comprise other chemical elements besides carbon, such as oxygen.

[0020] The term “zero-dimensional carbon material” as used herein refers to carbon materials comprising particles that have three spatial dimensions on the nanoscale, e.g. buckminsterfullerene and carbon black.

[0021] The term “one-dimensional carbon material” as used herein refers to carbon materials comprising particles that have only two spatial dimensions on the nanoscale, e.g. carbon nanofibres, carbon fibres and carbon nanotubes. Such materials may comprise acicular, needle-like or tubular particles.

[0022] The term “two-dimensional carbon material” as used herein refers to carbon materials comprising particles that have only one spatial dimension on the nanoscale, e.g. graphene oxide, graphene, holey graphene, graphite oxide, graphyne and graphenylene. Such materials may comprise flakes or flat particles.

[0023] The term “redox-active material” is one of the art. For the avoidance of any doubt, redox-active materials are materials able to undergo a redox process. In a redox process, the oxidation state of a component of a redox-active material changes, e.g. through loss / gain of electrons or atom transfer. For example, lithium cobalt oxide is a redox-active material in which the oxidation state of cobalt can be changed (e.g. by deintercalation of lithium).

[0024] The term “cathode material” is one of the art. For the avoidance of any doubt, cathode materials are redox-active materials suitable for use as cathodes, e.g. containing atoms / ions (such as lithium or sodium) that can be reversibly deintercalated from the cathode material.

[0025] The term “anode material” is one of the art. For the avoidance of any doubt, anode materials are redox-active materials suitable for use as anodes, e.g. containing cavities into which atoms / ions (such as lithium or sodium) can be reversibly intercalated.

[0026] Where the amount of a first component of an electrode is expressed relative to the amount of a second component of the electrode as a wt%, based on the total weights of the first component and second component in the electrode, this may be calculated as follows: weiqht of first component wt% = - - - . , . - - - — - - X 100% . total weight of irst and second components By way of example, an electrode may comprise 4.5 g of low-dimensional carbon material and 5.5 g of redox-active material. Said electrode therefore comprises 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0027] For the avoidance of any doubt, this parameter is not dependent on the amounts of other components in the electrode. For example, the electrode described in the previous paragraph may comprise no further components. It may alternatively comprise 10 g of further components. In both cases, the electrode comprises 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0028] Where, alternatively, the amount of a particular component of an electrode is expressed as a wt%, based on the total weight of the electrode, this may be calculated as follows:

[0029] Where a % of the surface of an electrode is said to comprise a layer, this may be calculated as follows: external surface area of layer

[0030] % = - : - : - — - 44 - — X 100% . total external sur ace area of electrode

[0031] For example, the surface of an electrode may comprise a layer of low-dimensional carbon material, the layer having an external surface area of 7 cm2. The total external surface area of the electrode (including the surface area occupied by the layer) may be 10 cm2. Therefore, 70% of the surface of the electrode comprises the layer of low-dimensional carbon material.

[0032] The term “layer” as used herein refers to a material / agglomeration in which one spatial dimension is significantly smaller than each of the other two spatial dimensions, e.g. 60% smaller, 70% smaller, 80% smaller, 85% smaller, 90% smaller, 91% smaller, 92% smaller, 93% smaller, 94% smaller, 95% smaller, 96% smaller, 97% smaller, 98% smaller or 99% smaller.

[0033] Where the “thickness” of a layer is recited, this can be understood to refer to the smallest spatial dimension of the layer. For example, a layer may have the dimensions 10 cm by 10 cm by 1 cm. The thickness of said layer is therefore 1 cm.

[0034] The term “interconnected layers” as used herein refers to layers that are permanently or temporarily attached to one another. Such attachment can occur, for example, via covalent bonding, ionic bonding, hydrogen bonding, dipole-dipole interactions, van der Waals interactions, mechanical bonding, hydrophobic / hydrophilic interactions and the like. Such attachment may result from compression of layers.

[0035] Where the term “at least” is applied to ratios, this should be interpreted as referring to the fact that the first number in the ratio is the number shown or is larger than the number shown, and / or the second number in the ratio is the number shown or is correspondingly smaller than the number shown. For example, an electrode described as comprising a first layer and a second layer with a thickness ratio of “at least around 0.1 :1” means that a ratio described as such may have values such as 0.1 :1 , 0.2:1 or 0.1 :0.9.

[0036] The converse of the above is true when the term “at most” is applied to ratios.

[0037] The term “porous and / or permeable to gases” as used herein refers to materials through which gases may pass. This encompasses materials which may require external interference (e.g. application of pressure) in order to allow passage of gases through the material.

[0038] The capacity of an electrode represents the number of electrons which may be transferred to / from the electrode during charge / discharge. Capacity may be expressed absolutely (units of A h), per unit mass (units of A h g1) or per unit volume (units of A h nr3).

[0039] The term “binder” as used herein refers to a substance which is typically added to an electrode to adhere the components of the electrode together.

[0040] The term “redox-active”, as used herein in the context of binders, refers to binders that are able to undergo a redox process (as defined above) under normal electrode / battery conditions. Conversely, the term “redox-inactive”, as used herein in the context of binders, refers to binders that are unable to undergo a redox process under normal electrode / battery conditions.

[0041] The term “electronically conducting”, as used herein in the context of binders, means a binder substantially allows the flow of electrical current through itself. For example, an electronically conducting binder may have an electronic conductivity of at least around 1 S crrr1. Conversely, the term “electronically insulating”, as used herein in the context of binders, means a binder is substantially resistant to the flow of electrical current through itself. For example, an electronically insulating binder may have an electronic conductivity of at most around 0.5 S crrr1.

[0042] The term “adhesion-enhancing”, as used herein in the context of binders, refers to binders that improve / promote adhesion within an electrode (i.e. the ability of the electrode to stick / hold together and stick / hold to the current collector, and not mechanically disintegrate) by being present within the electrode. The term “flexibility-enhancing”, as used herein in the context of binders, refers to binders that improve / promote the flexibility of an electrode (i.e. the ability of the electrode to bend / deform without breaking) by being present within the electrode.

[0043] The term “agglomeration” as used herein refers to a collection of material which is not necessarily bound together, e.g. an agglomeration may be in the form of a powder. For completeness, agglomerations can comprise materials which are bound together.

[0044] The term “average particle size” is suitably a number average and determined using dynamic light scattering (e.g. with a Malvern Zetasizer Nano ZS90), such as in accordance with ISO 22412:2017.

[0045] The terms “average particle diameter” and “average particle length” refer to a number average determined with scanning electron microscopy (e.g. Zeiss Merlin - Analytical), transmission electron microscopy (e.g. JEOL 3000F), and X-ray computed tomography (e.g. Zeiss Xradia 810 Ultra).

[0046] Some materials have a primary particle size and a secondary particle size. The term “primary particle size” as used herein refers to the as-produced particle size of a material before the material is used in a method for forming an electrode. The term “secondary particle size” as used herein refers to the particle size of a material after the material is used in a method for forming an electrode. The secondary particle size is generally larger than the primary particle size, e.g. due to compression of the material.

[0047] The terms “surface-treated”, “surface-treating” and the like, as used herein in the context of current collectors, refer to the application / deposition of a substance (e.g. carbon or a metal) on a surface (e.g. a first face and / or a second face) of a current collector.

[0048] BRIEF DESCRIPTION OF THE FIGURES

[0049] Fig. 1 : Schematic diagram of an electrode in accordance with the disclosure;

[0050] Fig. 2: Scanning electron microscopy (SEM) images of the surface of the low-dimensional carbon material layer of two electrodes in accordance with the disclosure;

[0051] Fig. 3 : SEM and energy dispersive spectroscopy (EDS) images of the cross-section of an electrode in accordance with the disclosure;

[0052] Fig. 4: SEM images of the cross-section of another electrode in accordance with the disclosure; Fig. 5: Comparative galvanostatic charge and discharge curves of an electrode in accordance with the disclosure and a conventional electrode;

[0053] Fig. 6: Comparative electrochemical impedance spectroscopy (EIS) measurements of an electrode in accordance with the disclosure and a conventional electrode; and

[0054] Fig. 7 : Schematic diagram of a method of manufacturing electrodes in accordance with the disclosure.

[0055] DETAILED DESCRIPTION

[0056] According to a first aspect of the present disclosure, there is provided an electrode comprising a redox-active material and a low-dimensional carbon material, wherein: at least around 70% of the surface of the electrode comprises at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0057] It has been found that the at least one layer comprising the low-dimensional carbon material holds the redox-active material in place, having an enveloping / sandwiching effect. This reduces the need for non-redox active and / or electronically insulating materials (e.g. redox-inactive and / or electronically insulating binders) in the electrode, whilst maintaining good mechanical stability and properties.

[0058] The at least one layer comprising the low-dimensional carbon material also acts as a highly electrically and ionically conductive interface (e.g. between the redox-active material and a current collector, and / or between the redox-active material and an electrolyte), having a low charge transfer resistance. Without wishing to be bound by theory, it is believed that this low resistance gives rise to a high capacity and allows fast charging of the electrode.

[0059] Limiting the proportion of low-dimensional carbon material present in the electrode (e.g. to around 45 wt%, based on the total weights of low-dimensional carbon material and redox-active material in the electrode) improves the capacity of the electrode relative to electrodes having higher proportions of low-dimensional carbon material. This is because low-dimensional carbon materials, in comparison to redox-active materials, tend to contribute less to energy storage and storage of ions.

[0060] At least around 75% of the surface of the electrode may comprise the at least one layer comprising the low-dimensional carbon material, optionally at least around 80%, optionally at least around 85%, optionally at least around 90%, optionally at least around 95%, optionally at least around 99%.

[0061] Higher surface coverage is favourable, since this allows for more contact between the highly conducting low-dimensional carbon material and, for example, other components of batteries (e.g. a current collector and / or an electrolyte).

[0062] The electrode may comprise, based on the total weights of low-dimensional carbon material and redox-active material in the electrode: at least around 0.1 wt% low-dimensional carbon material, optionally at least around 0.5 wt%, optionally at least around 1 wt%, optionally at least around 1 .5 wt%, optionally at least around 2 wt%, optionally at least around 3 wt%; and / or at most around 40 wt% low-dimensional carbon material, optionally at most around 30 wt%, optionally at most around 20 wt%, optionally at most around 10 wt%, optionally at most around 8 wt%, optionally at most around 6 wt%, optionally at most around 5 wt%; and / or around 0.1 to 40 wt% low-dimensional carbon material, optionally around 0.1 to 30 wt%, optionally around 0.5 to 20 wt%, optionally around 1 to 10 wt%, optionally around 1 .5 to 8 wt%, optionally around 2 to 6 wt%, optionally around 3 to 5 wt%, optionally around 4 wt%.

[0063] The low-dimensional carbon material may be substantially porous and / or permeable to gases (e.g. air or argon). It has been found that low-dimensional carbon materials having this property allow the electrode to be compressed to a higher density, which can contribute, for example, to mechanical stability and volumetric capacity. Without wishing to be bound by theory, it is believed that this higher density results from the facile escape of otherwise-trapped gas molecules during preparation of the electrode.

[0064] The low-dimensional carbon material may be a zero-, one- or two-dimensional carbon material, optionally a flaked, flat, tubular or needle-like carbon material.

[0065] It has been found that, for example, one-dimensional carbon materials can form an interconnected network which has good mechanical stability. Similarly, two-dimensional carbon materials can form an interconnected layer which also has good mechanical stability.

[0066] The low-dimensional carbon material may be selected from graphene oxide, graphene, holey graphene, graphite oxide, carbon nanofibres, carbon fibres, carbon nanotubes, graphyne and graphenylene.

[0067] The low-dimensional carbon material may be selected from:

[0068] (a) graphene oxide, graphene, holey graphene and graphite oxide, optionally having an average particle size of around 0.01 to 10 pm; (b) carbon nanotubes, optionally having an average particle length of 0.01 to 5 pm and / or an average particle diameter of around 1 to 500 nm;

[0069] (c) carbon nanofibres, optionally having an average particle length of around 1 to 200 pm and / or an average particle diameter of around 0.05 to 10 pm; or

[0070] (d) carbon fibres, optionally having an average particle length of around 5 to 500 pm and / or an average particle diameter of around 1 to 20 pm.

[0071] It has been found that electrodes comprising low-dimensional carbon materials having these particle sizes have particularly good mechanical strength. For example, without wishing to be bound by theory, it is believed that carbon nanotubes, carbon nanofibres and carbon fibres having the particle lengths and diameters given in (b) to (d) above form highly interconnected networks.

[0072] The electrode may comprise at least two layers comprising the low-dimensional carbon material.

[0073] The electrode may comprise a first layer, a second layer and a third layer; wherein: the first layer comprises the low-dimensional carbon material; the second layer comprises the redox-active material; the third layer comprises the low-dimensional carbon material; and the second layer is disposed between the first layer and third layer.

[0074] Such an electrode is particularly straightforward to manufacture, as the electrode can be formed by simply pressing the first layer, second layer and third layer in a top-to-bottom arrangement.

[0075] The first layer and the second layer may have a thickness ratio of: at least around 5xio6:1 , optionally at least around 1 xw5:1 , optionally at least around 1 xio4:1 , optionally at least around 1 xw3:1 , optionally at least around 0.01 :1 , optionally at least around 0.1 :1 ; and / or at most around 30:1 , optionally at most around 10:1 , optionally at most around 5:1 , optionally at most around 3:1 , optionally at most around 2:1 , optionally at most around 1 :1 ; and / or around 5xio6:1 to 30:1 , optionally around 1 xio5:1 to 10:1 , optionally around 1 xio4:1 to 5:1 , optionally around 1 xio3:1 to 3:1 , optionally around 0.01 :1 to 2:1 , optionally around 0.1 :1 to 1 :1.

[0076] The third layer may have a thickness within around 10% of the thickness of the first layer, optionally within around 8%, optionally within around 6%, optionally within around 4%, optionally within around 2%.

[0077] The at least one layer comprising the low-dimensional carbon material may have a thickness of: at least around 1 nm, optionally at least around 10 nm, optionally at least around 20 nm, optionally at least around 50 nm; and / or at most around 100,000 nm, optionally at most around 50,000 nm, optionally at most around 10,000 nm, optionally at most around 5000 nm; and / or around 1 to 100,000 nm, optionally around 1 to 50,000 nm, optionally around 1 to 10,000 nm, optionally around 1 to 5000 nm.

[0078] It has been found that layers having thicknesses in these ranges are particularly effective at enveloping the electrode and providing good mechanical stability, whilst allowing good electronic and ionic conductivity.

[0079] The second layer, when present, may have a thickness of: at least around 1 pm, optionally at least around 5 pm, optionally at least around 10 pm, optionally at least around 20 pm, optionally at least around 50 pm; and / or at most around 10,000 pm, optionally at most around 7500 pm, optionally at most around 5000 pm, optionally at most around 2500 pm, optionally at most around 1000 pm; and / or around 1 to 10,000 pm, optionally around 5 to 7500 pm, optionally around 10 to 5000 pm, optionally around 20 to 2500 pm, optionally around 50 to 1000 pm.

[0080] It has been found that the higher the thickness of the second layer (comprising the redox-active material), the higher the energy storage. However, as the thickness increases, electrical conductivity and ion diffusivity decrease, so the increase in energy storage is not linearly proportional to the layer thickness. It has been found that the thickness ranges above provide a good balance between these factors.

[0081] The redox-active material may be a cathode material, optionally selected from:

[0082] (a) metal oxides, optionally layered metal oxides (e.g. lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium manganese nickel oxide (e.g. lithium-rich Li1 2Mno 5Nio2O2) and lithium nickel cobalt aluminium oxide), spinels (e.g. lithium manganese oxide), and disordered rock salts (e.g. Li1 25Nbo 25Mno 5O2); preferably lithium nickel manganese cobalt oxide (e.g.

[0083] LiNixMnyCoz02, x+y+z = 1); and

[0084] (b) polyanion compounds (e.g. lithium iron phosphate).

[0085] The cathode material may have an average primary particle size of around 1 to 500 nm and / or an average secondary particle size of around 1 to 300 pm.

[0086] The redox-active material may be an anode material, optionally selected from graphite, silicon, silicon oxides, Li4TisOi2, hard carbon and soft carbon.

[0087] The anode material may have an average particle size of around 0.01 to 300 pm. The electrode may have a capacity of at least around 10 mA-h-g1, optionally at least around 200 mA-h-g1, optionally at least around 400 mA-h-g1, optionally at least around 600 mA-h-g1, optionally at least around 800 mA-h-g1, optionally at least around 1000 mA-h-g1.

[0088] Electrodes having a higher capacity per unit mass are particularly desirable in batteries for small, portable devices such as smartphones, since these electrodes have a higher energy density and thus provide a longer battery life.

[0089] The electrode may have a resistance of at most around 1000 Q cm2, optionally at most around 200 Q cm2, optionally at most around 150 Q cm2, optionally at most around 100 Q cm2, optionally at most around 50 Q cm2, optionally at most around 1 Q cm2.

[0090] Electrodes having a lower resistance store more (useful) energy and can be charged more quickly, which is useful for batteries in devices where fast charging is desirable (such as smartphones and electric vehicles).

[0091] The electrode may comprise, based on the total weight of the electrode, at most around 5 wt% binder, optionally at most around 4 wt% binder, optionally at most around 3 wt% binder, optionally at most around 2 wt% binder, optionally at most around 1 wt% binder, optionally at most around 0.5 wt% binder, optionally at most around 0.1 wt% binder, optionally at most around 0.01 wt% binder.

[0092] The electrode may comprise, based on the total weight of the electrode, at most around 8 wt% redox-inactive and / or electronically insulating binder, optionally at most around 7 wt%, optionally at most around 6 wt%, optionally at most around 5 wt%, optionally at most around 4 wt%, optionally at most around 3 wt%, optionally at most around 2 wt%, optionally at most around 1 wt%, optionally at most around 0.5 wt%, optionally at most around 0.1 wt%, optionally at most around 0.01 wt%.

[0093] In some implementations, the electrode does not comprise a redox-inactive binder and / or does not comprise an electronically insulating binder.

[0094] In some implementations, the electrode does not comprise a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene).

[0095] In some implementations, the electrode comprises one or more redox-active and / or electronically conducting binders. Optionally, said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxyl methyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole- based binders, polylactic acid-based binders and chitosan-based binders.

[0096] In some implementations, the electrode comprises one or more adhesion-enhancing and / or flexibility-enhancing binders. Optionally, said one or more adhesion-enhancing and / or flexibilityenhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol- based binders and methacrylic-based binders.

[0097] Electrodes comprising minimal or no electronically insulating binder exhibit higher capacities, since binders tend not to be redox-active and thus tend not to contribute to the transfer of electrons from / to the electrode.

[0098] The electrode may be positioned adjacent to a current collector. The current collector may comprise a metal, optionally aluminium, copper or stainless steel), optionally wherein:

[0099] (a) the redox-active material is a cathode material and the current collector comprises aluminium; or

[0100] (b) the redox-active material is an anode material and the current collector comprises copper.

[0101] The current collector may have been surface-treated, optionally with carbon (optionally a lowdimensional carbon material) and / or a metal (optionally silver and / or manganese).

[0102] The current collector may have a thickness of around 3 nm to 1 mm.

[0103] According to a second aspect of the present disclosure, there is provided a battery comprising one or more electrodes as described above.

[0104] The battery may have a pouch cell configuration, a cylindrical cell configuration, a prismatic cell configuration or a coin cell configuration.

[0105] According to a third aspect, there is provided a method for forming an electrode, wherein the method comprises: preparing an agglomeration comprising a redox-active material and at least one layer comprising a low-dimensional carbon material; and pressing the agglomeration to form an electrode, wherein: at least around 70% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0106] It has been found that pressing said agglomeration gives rise to an electrode in which the at least one layer comprising the low-dimensional carbon material strongly envelopes / sandwiches the redox-active material, as discussed above in relation to the first aspect.

[0107] At least around 75% of the surface of the electrode may comprise the at least one layer comprising the low-dimensional carbon material, optionally at least around 80%, optionally at least around 85%, optionally at least around 90%, optionally at least around 95%, optionally at least around 99%.

[0108] The electrode may comprise at most around 40 wt% low-dimensional carbon material, optionally at most around 35 wt% low-dimensional carbon material, optionally at most around 30 wt% lowdimensional carbon material, optionally at most around 25 wt% low-dimensional carbon material, optionally at most around 20 wt% low-dimensional carbon material, optionally at most around 15 wt% low-dimensional carbon material, optionally at most around 10 wt% low-dimensional carbon material.

[0109] Said preparing an agglomeration may comprise: preparing a first layer, wherein said first layer comprises the low-dimensional carbon material, placing a second layer on the first layer, wherein said second layer comprises the redoxactive material, and placing a third layer on the second layer, wherein said third layer comprises the lowdimensional carbon material.

[0110] Said pressing the agglomeration may comprise pressing the first layer, second layer and third layer.

[0111] As discussed above in relation to the first aspect, forming an electrode in this way is a particularly straightforward process since (for example) the first layer, second layer and third layer can simply be arranged on top of each other before being pressed from above.

[0112] Said pressing may be at a temperature of: at most around 250°C, optionally at most around 200°C, optionally at most around 150°C, optionally at most around 100°C, optionally at most around 50°C, optionally at most around 40°C, optionally at most around 30°C; and / or around -50 to 250°C, optionally around -30 to 200°C, optionally around -20 to 150°C, optionally around -10 to 100°C, optionally around 0 to 50°C, optionally around 10 to 40°C, optionally around 20 to 30°C.

[0113] Limiting the temperature at which pressing is performed reduces the energy demand of the method for forming an electrode. The method described herein is particularly favourable in this regard since it can be performed without any external heating, e.g. at room temperature.

[0114] Said pressing may comprise calendering; optionally at a calendering speed of around 0.01 to

[0115] 2 m s1, wherein “calendering speed” refers to the speed at which a material is passed through a calendering apparatus. Calendering is a particularly effective way of pressing the agglomeration in an industrial context as this can apply an approximately constant pressure to a feedstock comprising the agglomeration (e.g. on a conveyor belt).

[0116] Said calendering may comprise asymmetric calendering, optionally wherein a first roller operates at around 0.1 to 0.5 m s1and a second roller operates at around 0.8 to 1 .3 m s1.

[0117] The at least one layer comprising the low-dimensional carbon material may be substantially porous and / or permeable to gases (e.g. air or argon).

[0118] The method may further comprise expelling a gas (e.g. air or argon) from the redox-active material through one or more of the at least one layer comprising the low-dimensional carbon material. As described above in relation to the first aspect, expelling a gas through the at least one layer comprising the low-dimensional carbon material produces an electrode with a higher density.

[0119] Said pressing may comprise use of a pressure of: at least around 0.5 MPa, optionally at least around 1 MPa, optionally at least around

[0120] 3 MPa, optionally at least around 5 MPa, optionally at least around 7 MPa, optionally at least around 9 MPa, optionally at least around 10 MPa; and / or at most around 1000 MPa, optionally at most around 800 MPa, optionally at most around 600 MPa, optionally at most around 400 MPa, optionally at most around 300 MPa, optionally at most around 200 MPa, optionally at most around 100 MPa; and / or around 0.5 to 1000 MPa, optionally around 1 to 800 MPa, optionally around 3 to 600 MPa, optionally around 5 to 400 MPa, optionally around 7 to 300 MPa, optionally around 9 to 200 MPa, optionally around 10 to 100 MPa.

[0121] It has been found that pressures in these ranges produce particularly mechanically stable electrodes. Without wishing to be bound by theory, it is believed that such pressures give rise to strong binding interactions between the low-dimensional carbon material and the redox-active material.

[0122] After said pressing, the at least one layer comprising the low-dimensional carbon material (e.g. the first layer and third layer) may have a thickness of: at least around 50 nm; and / or at most around 30,000 nm, optionally at most around 20,000 nm, optionally at most around 10,000 nm, optionally at most around 5000 nm; and / or around 50 to 30,000 nm, optionally around 50 to 20,000 nm, optionally around 50 to 10,000 nm, optionally around 50 to 5000 nm.

[0123] After said pressing, the second layer, when present, may have a thickness of: at least around 1 pm, optionally at least around 2 pm, optionally at least around 3 pm, optionally at least around 4 pm, optionally at least around 5 pm; and / or at most around 10,000 pm, optionally at most around 7500 pm, optionally at most around 5000 pm, optionally at most around 2500 pm, optionally at most around 1000 pm; and / or around 1 to 10,000 pm, optionally around 2 to 7500 pm, optionally around 3 to 5000 pm, optionally around 4 to 2500 pm, optionally around 5 to 1000 pm.

[0124] In some implementations, the method does not comprise the use of a solvent (e.g. N-methyl-2- pyrrolidone or water). The use of a solvent in methods for forming electrodes is unfavourable, as extra method steps / equipment are needed to evaporate off the solvent. For toxic solvents such as N-methyl-2-pyrrolidone, further extra method steps / equipment are needed to contain the evaporated solvent safely.

[0125] In some implementations, the method does not comprise the use of a redox-inactive binder and / or does not comprise the use of an electronically insulating binder.

[0126] In some implementations, the method does not comprise the use of a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene).

[0127] In some implementations, the method comprises the use of one or more redox-active and / or electronically conducting binders. Optionally, said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole-based binders, polylactic acid-based binders and chitosan-based binders.

[0128] In some implementations, the method comprises the use of one or more adhesion-enhancing and / or flexibility-enhancing binders. Optionally, said one or more adhesion-enhancing and / or flexibility-enhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol- based binders and methacrylic-based binders.

[0129] The method may further comprise placing one or more of the at least one layer comprising the low-dimensional carbon material (e.g. the first layer) on a current collector, optionally wherein the current collector comprises a metal (e.g. aluminium, copper or stainless steel).

[0130] The current collector may comprise a first face and a second face, and the method may comprise placing one or more of the at least one layer comprising the low-dimensional carbon material (e.g. the first layer) on each of the first face and the second face. It will be understood that such a method will give rise to a current collector which comprises on each of its faces an electrode according to the present disclosure.

[0131] The method may comprise surface-treating the current collector (optionally prior to said placing one or more of the at least one layer comprising the low-dimensional carbon material), optionally with carbon (optionally a low-dimensional carbon material) and / or a metal (optionally silver and / or manganese).

[0132] The electrode may be or have been formed using a method as described above.

[0133] According to a fourth aspect, there is provided an apparatus suitable for carrying out the method described herein. The apparatus preferably comprises a means for supplying powder, a means for creating layers of powder, and a means for compressing the layers of powder. The apparatus may comprise:

[0134] (a) one or more powder feeders, optionally comprising a vibrating mechanism (e.g. an electromagnetic vibrating mechanism); and / or

[0135] (b) a conveyor belt; and / or

[0136] (c) a compression device, optionally comprising one or more calender rollers.

[0137] The apparatus may also comprise an imaging device for in-line observation, optionally a camera. Optionally, the apparatus further comprises a means for processing analysis of images produced by the imaging device. Such an apparatus is particularly effective because this permits in-line imaging, analysis and quality control of electrodes as they are being manufactured.

[0138] Optionally, the apparatus further comprises in-line electronic open-loop or closed-loop control for processing of the electrode. Optionally, the apparatus is configured to simulate mechanical compression. Optionally, the apparatus is further configured to predict optimal electrode porosity, electrode microstructure, battery performance, and / or manufacturing parameters, based on images produced by the imaging device. EXAMPLES

[0139] Example 1: Preparation of electrodes

[0140] Electrodes according to the disclosure were formed by preparing a first layer (of low-dimensional carbon material), placing a second layer (of redox-active material) on the first layer, placing a third layer (of low-dimensional carbon material) on the second layer and then pressing the three layers. Fig. 1 is a schematic diagram of such an electrode.

[0141] Exemplary electrode compositions are outlined below.

[0142] Electrode ID Low-dimensional carbon material Redox-active material

[0143] 1 Carbon fibres LiNi06Mn02Co02O2

[0144] 2 Graphite oxide LiNi06Mn02Co02O2

[0145] 3 Carbon fibres LiNi08Mn01Co01O2

[0146] 4 Graphite oxide LiNi08Mn01Co01O2

[0147] 5 Carbon fibres Si

[0148] 6 Graphite oxide Si

[0149] 7 Carbon fibres SiOx

[0150] 8 Graphite oxide SiOx

[0151] Example 2: Structural analysis of electrodes using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS)

[0152] Small pieces of the electrodes (around 1 cm x 0.5 cm) were cut and then stuck onto titanium blades. Ar+ion etching was then used to prepare cross-sections of the electrodes for SEM and EDS analysis.

[0153] Fig. 2 contains SEM images of the surface of the low-dimensional carbon material layer of two electrodes according to Example 1 . Fig. 2(a) shows the carbon fibre layer of electrode 1 , and Fig. 2(b) shows the graphite oxide layer of electrode 2.

[0154] Fig. 3(a) to (d) are SEM images of the cross-section of electrode 2. Fig. 3(a) shows the top graphite oxide layer and the middle LiNi06Mn02Co02O2 layer. Fig. 3(b) shows the middle LiNi06Mn02Co02O2 layer and the bottom graphite oxide layer. Fig. 3(c) is a magnified version of Fig. 3(a), showing the two-dimensional structure of the graphite oxide layer. Fig. 3(d) is a magnified version of Fig. 3(b), showing the microstructure of the LiNi06Mn02Co02O2 layer. The tight packing in Fig. 3(c) and Fig. 3(d) indicates that the electrode has good structural stability, notably without the presence of any binders. Fig. 3(e) and (f) are EDS images of the cross-section of electrode 2. Fig. 3(e) indicates the position of carbon atoms, which are present only in the top and bottom layers of the electrode. Fig. 3(f) indicates the position of manganese ions, which are only present in the middle layer. These images show that the electrode has a distinct three-layered structure.

[0155] Fig. 4 contains SEM images of the cross-section of electrode 1 . Fig. 4(a) shows the bottom carbon fibre layer, indicating an interconnected network with good mechanical stability. Fig. 4(b) shows the middle LiNi06Mn02Co02O2 layer. Fig. 4(c) shows the interface between the carbon fibre layer and the LiNi06Mn02Co02O2 layer, showing that individual LiNi06Mn02Co02O2 particles are wrapped by the carbon fibres. This indicates strong adhesion and good mechanical stability.

[0156] Example 3: Electrochemical testing of electrodes

[0157] The electrochemical performance of electrode 6 (per Example 1 above) was tested versus a lithium metal anode, at around 25°C.

[0158] Fig. 5(a) compares galvanostatic charge and discharge curves of electrode 6 (labelled as “layered electrode”) and a like-for-like conventional electrode (carbon and silicon materials homogeneously mixed together), at a charge and discharge current of 250 mA g1. This shows that, at this current, electrode 6 exhibits a 57% higher capacity than the conventional electrode.

[0159] Fig. 5(b) similarly compares measured capacities of electrode 6 and the conventional electrode at increasing charge and discharge current. This shows that electrode 6 exhibits significantly higher capacities than the conventional electrode at all currents tested. An effect of this is that electrode 6 is well-suited for fast charging. Fig. 5(b) also compares measured capacities over 100 charge and discharge cycles at 250 mA g1, demonstrating that electrode 6 also exhibits higher capacities than the conventional electrode over long cycling.

[0160] Example 4: Measurement of the resistance of electrodes using electrochemical impedance spectroscopy (EIS)

[0161] Electrodes were formed in accordance with Example 1 above. These were then assembled into batteries having coin cell, pouch cell or prismatic cell configurations. The batteries contained one working electrode (formed in accordance with Example 1) and one reference electrode (e.g. lithium foil), separated by a polymer separator (e.g. polyethylene) or a glass fibre separator. The batteries were sealed and tested using EIS (frequency range 0.01 to 106Hz), at around 25°C.

[0162] Fig. 6 compares EIS measurements of electrode 6 (labelled as “layered electrode”) and a like-for- like conventional electrode, in a coin cell using a lithium metal reference electrode and a polyethylene and polypropylene separator. Fig. 6(a) shows EIS measurements of the cells at the as-made state, Fig. 6(b) after battery charging and Fig. 6(c) after battery discharging. In these figures, the diameter of the approximate semicircles represents the charge transfer resistance of the electrodes. The measurements show that electrode 6 consistently exhibits a charge transfer resistance around 2.7 to 3 times smaller than that of the conventional electrode, in the as-made state, after battery charging and after battery discharging. Without wishing to be bound by theory, this may partially explain the good energy storage performance and long charge / discharge cycling performance demonstrated in Fig. 5.

[0163] Example 5: Method of manufacturing electrodes

[0164] Fig. 7 illustrates a method suitable for manufacturing electrodes in accordance with Example 1 above. According to the illustrated method, powder feeders (which may, for example, comprise an electromagnetic vibrating mechanism) are used to spread sequential layers of low-dimensional carbon material, redox-active material and then further low-dimensional carbon material on metallic foil, which moves along a conveyor belt. These sequential layers can be built upon one another, and the layers are then pressed using calender rollers in a pressing, or compression step. The force exerted by the rollers adheres the layers together to form a sheet of electrode material. At the same time, gas is expelled during the compression step. This may be air or could be an inert gas, for example a noble gas such as argon (e.g. if working in a controlled atmosphere). The resulting sheet of electrode material can suitably be cut into smaller pieces to form electrodes of a range of sizes.

[0165] Such a method does not require solvents, binders or high temperatures to produce electrodes in accordance with the disclosure.

[0166] An example of a machine to conduct this method may comprise the powder feeders, a conveyor belt and a series of calender rollers. Preferably, the machine comprises at least two calender rollers. Preferably, the machine comprises at least three powder feeders. The powder feeders may comprise a vibration mechanism, which may be an electromagnetic vibrating mechanism. The powder feeders may be gravity feeders. The machine may also comprise one or more covers or may be situated within a containment unit to contain the metallic powders and limit the mixing or transfer of the powders into the surrounding atmosphere. The containment unit for machine may be supplied with an inert gas supply line.

[0167] In this example, the pressure applied by the calendering rollers during the pressing step is around 0.5 to 1000 MPa, most preferably around 10 to 100 MPa.

[0168] It has been found that pressures in these ranges produce particularly mechanically stable electrodes. Without wishing to be bound by theory, it is believed that such pressures give rise to strong binding interactions between the low-dimensional carbon material and the redox-active material.

[0169] This method and machine could be scaled up to a roll-to-roll continuous process. With larger equipment, a suitable throughput width could be 1 to 2 m, with a 0.01 to 2 m s1production rate.

[0170] The disclosure also comprises the following clauses, which may be claimed:

[0171] 1 . An electrode comprising a redox-active material and a low-dimensional carbon material, wherein: at least around 70% of the surface of the electrode comprises at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

[0172] 2. The electrode of clause 1 , wherein at least around 75% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material, optionally at least around 80%, optionally at least around 85%, optionally at least around 90%, optionally at least around 95%, optionally at least around 99%.

[0173] 3. The electrode of any preceding clause, wherein the electrode comprises, based on the total weights of low-dimensional carbon material and redox-active material in the electrode: at least around 0.1 wt% low-dimensional carbon material, optionally at least around 0.5 wt%, optionally at least around 1 wt%, optionally at least around 1 .5 wt%, optionally at least around 2 wt%, optionally at least around 3 wt%; and / or at most around 40 wt% low-dimensional carbon material, optionally at most around 30 wt%, optionally at most around 20 wt%, optionally at most around 10 wt%, optionally at most around 8 wt%, optionally at most around 6 wt%, optionally at most around 5 wt%; and / or around 0.1 to 40 wt% low-dimensional carbon material, optionally around 0.1 to 30 wt%, optionally around 0.5 to 20 wt%, optionally around 1 to 10 wt%, optionally around 1 .5 to 8 wt%, optionally around 2 to 6 wt%, optionally around 3 to 5 wt%, optionally around 4 wt%.

[0174] 4. The electrode of any preceding clause, wherein the low-dimensional carbon material is substantially porous and / or permeable to gases (e.g. air or argon). The electrode of any preceding clause, wherein the low-dimensional carbon material is a zero-, one- or two-dimensional carbon material, optionally a flaked, flat, tubular or needlelike carbon material. The electrode of any preceding clause, wherein the low-dimensional carbon material is selected from graphene oxide, graphene, holey graphene, graphite oxide, carbon nanofibres, carbon fibres, carbon nanotubes, graphyne and graphenylene. The electrode of any preceding clause, wherein the low-dimensional carbon material is selected from:

[0175] (a) graphene oxide, graphene, holey graphene and graphite oxide, optionally having an average particle size of around 0.01 to 10 pm;

[0176] (b) carbon nanotubes, optionally having an average particle length of 0.01 to 5 pm and / or an average particle diameter of around 1 to 500 nm;

[0177] (c) carbon nanofibres, optionally having an average particle length of around 1 to 200 pm and / or an average particle diameter of around 0.05 to 10 pm; or

[0178] (d) carbon fibres, optionally having an average particle length of around 5 to 500 pm and / or an average particle diameter of around 1 to 20 pm. The electrode of any preceding clause, comprising at least two layers comprising the lowdimensional carbon material. The electrode of clause 8, comprising a first layer, a second layer and a third layer; wherein: the first layer comprises the low-dimensional carbon material; the second layer comprises the redox-active material; the third layer comprises the low-dimensional carbon material; and the second layer is disposed between the first layer and third layer. The electrode of clause 9, wherein the first layer and the second layer have a thickness ratio of: at least around 5xi o6:1 , optionally at least around 1 xw5:1 , optionally at least around 1 xw4:1 , optionally at least around 1 xw3:1 , optionally at least around 0.01 :1 , optionally at least around 0.1 :1 ; and / or at most around 30:1 , optionally at most around 10:1 , optionally at most around 5:1 , optionally at most around 3:1 , optionally at most around 2:1 , optionally at most around 1 :1 ; and / or around 5xi o6:1 to 30:1 , optionally around 1 xi o5:1 to 10:1 , optionally around

[0179] 1 xi o4:1 to 5:1 , optionally around 1 xi o3:1 to 3:1 , optionally around 0.01 :1 to 2:1 , optionally around 0.1 :1 to 1 :1 . The electrode of clause 9 or 10, wherein the third layer has a thickness within around 10% of the thickness of the first layer, optionally within around 8%, optionally within around 6%, optionally within around 4%, optionally within around 2%. The electrode of any preceding clause, wherein the at least one layer comprising the lowdimensional carbon material has a thickness of: at least around 1 nm, optionally at least around 10 nm, optionally at least around 20 nm, optionally at least around 50 nm; and / or at most around 100,000 nm, optionally at most around 50,000 nm, optionally at most around 10,000 nm, optionally at most around 5000 nm; and / or around 1 to 100,000 nm, optionally around 1 to 50,000 nm, optionally around 1 to 10,000 nm, optionally around 1 to 5000 nm. The electrode of any one of clauses 9 to 12, wherein the second layer, when present, has a thickness of: at least around 1 pm, optionally at least around 5 pm, optionally at least around 10 pm, optionally at least around 20 pm, optionally at least around 50 pm; and / or at most around 10,000 pm, optionally at most around 7500 pm, optionally at most around 5000 pm, optionally at most around 2500 pm, optionally at most around 1000 pm; and / or around 1 to 10,000 pm, optionally around 5 to 7500 pm, optionally around 10 to 5000 pm, optionally around 20 to 2500 pm, optionally around 50 to 1000 pm. The electrode of any preceding clause, wherein the redox-active material is a cathode material, optionally selected from:

[0180] (a) metal oxides, optionally layered metal oxides (e.g. lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium manganese nickel oxide (e.g. lithium-rich ii 2Mno 6Nio 2O2) and lithium nickel cobalt aluminium oxide), spinels (e.g. lithium manganese oxide), and disordered rock salts (e.g. Li1 25Nbo 25Mno5O2); preferably lithium nickel manganese cobalt oxide (e.g. LiNixMnyCoz02, x+y+z = 1); and

[0181] (b) polyanion compounds (e.g. lithium iron phosphate). The electrode of clause 14, wherein the cathode material has an average primary particle size of around 1 to 500 nm and / or an average secondary particle size of around 1 to 300 pm. The electrode of any one of clauses 1 to 13, wherein the redox-active material is an anode material, optionally selected from graphite, silicon, silicon oxides, Li4TisOi2, hard carbon and soft carbon. The electrode of clause 16, wherein the anode material has an average particle size of around 0.01 to 300 pm. The electrode of any preceding clause, wherein the electrode has a capacity of at least around 10 mA-h-g1, optionally at least around 200 mA-h-g1, optionally at least around 400 mA-h-g1, optionally at least around 600 mA-h-g1, optionally at least around

[0182] 800 mA-h-g1, optionally at least around 1000 mA-h-g1. The electrode of any preceding clause, wherein the electrode has a resistance of at most around 1000 Q cm2, optionally at most around 200 Q cm2, optionally at most around 150 Q cm2, optionally at most around 100 Q cm2, optionally at most around 50 Q cm2, optionally at most around 1 Q cm2. The electrode of any preceding clause, wherein the electrode comprises, based on the total weight of the electrode, at most around 5 wt% binder, optionally at most around

[0183] 4 wt% binder, optionally at most around 3 wt% binder, optionally at most around 2 wt% binder, optionally at most around 1 wt% binder, optionally at most around 0.5 wt% binder, optionally at most around 0.1 wt% binder, optionally at most around 0.01 wt% binder. The electrode of any preceding clause, wherein the electrode comprises, based on the total weight of the electrode, at most around 8 wt% redox-inactive and / or electronically insulating binder, optionally at most around 7 wt%, optionally at most around 6 wt%, optionally at most around 5 wt%, optionally at most around 4 wt%, optionally at most around 3 wt%, optionally at most around 2 wt%, optionally at most around 1 wt%, optionally at most around 0.5 wt%, optionally at most around 0.1 wt%, optionally at most around 0.01 wt%. The electrode of any preceding clause, wherein the electrode does not comprise a redoxinactive binder and / or does not comprise an electronically insulating binder. The electrode of any preceding clause, wherein the electrode does not comprise a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene). The electrode of any one of clauses 1 to 22, wherein the electrode comprises one or more redox-active and / or electronically conducting binders, optionally wherein said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole-based binders, polylactic acid-based binders and chitosan-based binders. The electrode of any one of clauses 1 to 21 and 24, wherein the electrode comprises one or more adhesion-enhancing and / or flexibility-enhancing binders, optionally wherein said one or more adhesion-enhancing and / or flexibility-enhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol-based binders and methacrylic-based binders. The electrode of any preceding clause, wherein the electrode is positioned adjacent to a current collector, optionally wherein the current collector comprises a metal, optionally aluminium, copper or stainless steel), optionally wherein:

[0184] (a) the redox-active material is a cathode material and the current collector comprises aluminium; or

[0185] (b) the redox-active material is an anode material and the current collector comprises copper. The electrode of clause 26, wherein the current collector has been surface-treated, optionally with carbon (optionally a low-dimensional carbon material) and / or a metal (optionally silver and / or manganese). The electrode of clause 26 or 27, wherein the current collector has a thickness of around 3 nm to 1 mm. A battery comprising one or more electrodes as described in clauses 1 to 28. The battery of clause 29, wherein the battery has a pouch cell configuration, a cylindrical cell configuration, a prismatic cell configuration or a coin cell configuration. A method for forming an electrode, wherein the method comprises: preparing an agglomeration comprising a redox-active material and at least one layer comprising a low-dimensional carbon material; and pressing the agglomeration to form an electrode, wherein: at least around 70% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode. The method of clause 31 , wherein at least around 75% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material, optionally at least around 80%, optionally at least around 85%, optionally at least around 90%, optionally at least around 95%, optionally at least around 99%. The method of clause 31 or 32, wherein the electrode comprises at most around 40 wt% low-dimensional carbon material, optionally at most around 35 wt% low-dimensional carbon material, optionally at most around 30 wt% low-dimensional carbon material, optionally at most around 25 wt% low-dimensional carbon material, optionally at most around 20 wt% low-dimensional carbon material, optionally at most around 15 wt% lowdimensional carbon material, optionally at most around 10 wt% low-dimensional carbon material. The method of any one of clauses 31 to 33, wherein said preparing an agglomeration comprises: preparing a first layer, wherein said first layer comprises the low-dimensional carbon material, placing a second layer on the first layer, wherein said second layer comprises the redox-active material, and placing a third layer on the second layer, wherein said third layer comprises the low-dimensional carbon material; and wherein said pressing the agglomeration comprises pressing the first layer, second layer and third layer. The method of any one of clauses 31 to 34, wherein said pressing is at a temperature of: at most around 250°C, optionally at most around 200°C, optionally at most around 150°C, optionally at most around 100°C, optionally at most around 50°C, optionally at most around 40°C, optionally at most around 30°C; and / or around -50 to 250°C, optionally around -30 to 200°C, optionally around -20 to 150°C, optionally around -10 to 100°C, optionally around 0 to 50°C, optionally around 10 to 40°C, optionally around 20 to 30°C. The method of any one of clauses 31 to 35, wherein said pressing comprises calendering; optionally at a calendering speed of around 0.01 to 2 m s1, wherein “calendering speed” refers to the speed at which a material is passed through a calendering apparatus. The method of clause 36, wherein said calendering comprises asymmetric calendering, optionally wherein a first roller operates at around 0.1 to 0.5 m s1and a second roller operates at around 0.8 to 1 .3 m s1. The method of any one of clauses 31 to 37, wherein the at least one layer comprising the low-dimensional carbon material is substantially porous and / or permeable to gases (e.g. air or argon). The method of any one of clauses 31 to 38, further comprising expelling a gas (e.g. air or argon) from the redox-active material through one or more of the at least one layer comprising the low-dimensional carbon material. The method of any one of clauses 31 to 39, wherein said pressing comprises use of a pressure of: at least around 0.5 MPa, optionally at least around 1 MPa, optionally at least around 3 MPa, optionally at least around 5 MPa, optionally at least around 7 MPa, optionally at least around 9 MPa, optionally at least around 10 MPa; and / or at most around 1000 MPa, optionally at most around 800 MPa, optionally at most around 600 MPa, optionally at most around 400 MPa, optionally at most around

[0186] 300 MPa, optionally at most around 200 MPa, optionally at most around 100 MPa; and / or around 0.5 to 1000 MPa, optionally around 1 to 800 MPa, optionally around 3 to

[0187] 600 MPa, optionally around 5 to 400 MPa, optionally around 7 to 300 MPa, optionally around 9 to 200 MPa, optionally around 10 to 100 MPa. The method of any one of clauses 31 to 40, wherein, after said pressing, the at least one layer comprising the low-dimensional carbon material (e.g. the first layer and third layer according to clause 34) has a thickness of: at least around 50 nm; and / or at most around 30,000 nm, optionally at most around 20,000 nm, optionally at most around 10,000 nm, optionally at most around 5000 nm; and / or around 50 to 30,000 nm, optionally around 50 to 20,000 nm, optionally around 50 to 10,000 nm, optionally around 50 to 5000 nm. The method of any one of clauses 31 to 41 , wherein, after said pressing, the second layer, when present, has a thickness of: at least around 1 pm, optionally at least around 2 pm, optionally at least around 3 pm, optionally at least around 4 pm, optionally at least around 5 pm; and / or at most around 10,000 pm, optionally at most around 7500 pm, optionally at most around 5000 pm, optionally at most around 2500 pm, optionally at most around 1000 pm; and / or around 1 to 10,000 pm, optionally around 2 to 7500 pm, optionally around 3 to 5000 pm, optionally around 4 to 2500 pm, optionally around 5 to 1000 pm. The method of any one of clauses 31 to 42, wherein the method does not comprise the use of a solvent (e.g. N-methyl-2-pyrrolidone or water). The method of any one of clauses 31 to 43, wherein the method does not comprise the use of a redox-inactive binder and / or does not comprise the use of an electronically insulating binder. The method of any one of clauses 31 to 44, wherein the method does not comprise the use of a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene). The method of any one of clauses 31 to 44, wherein the method comprises the use of one or more redox-active and / or electronically conducting binders, optionally wherein said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole- based binders, polylactic acid-based binders and chitosan-based binders. The method of any one of clauses 31 to 43 and 46, wherein the method comprises the use of one or more adhesion-enhancing and / or flexibility-enhancing binders, optionally wherein said one or more adhesion-enhancing and / or flexibility-enhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxyl methyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol-based binders and methacrylic-based binders. The method of any one of clauses 31 to 47, further comprising placing one or more of the at least one layer comprising the low-dimensional carbon material (e.g. the first layer according to clause 34) on a current collector, optionally wherein the current collector comprises a metal (e.g. aluminium, copper or stainless steel). The method of clause 48, wherein the current collector comprises a first face and a second face, and wherein the method comprises placing one or more of the at least one layer comprising the low-dimensional carbon material (e.g. the first layer according to clause 34) on each of the first face and the second face.

[0188] 50. The method of clause 48 or 49, further comprising surface-treating the current collector (optionally prior to said placing one or more of the at least one layer comprising the lowdimensional carbon material), optionally with carbon (optionally a low-dimensional carbon material) and / or a metal (optionally silver and / or manganese)

[0189] 51 . The electrode of any one of clauses 1 to 28, wherein the electrode is or has been formed using the method of any one of clauses 31 to 50.

[0190] 52. An apparatus suitable for carrying out the method described herein.

[0191] 53. The apparatus of clause 52, comprising:

[0192] (a) one or more powder feeders, optionally comprising a vibrating mechanism (e.g. an electromagnetic vibrating mechanism); and / or

[0193] (b) a conveyor belt; and / or

[0194] (c) a compression device, optionally comprising one or more calender rollers.

[0195] 54. The apparatus of clause 52 or 53, comprising an imaging device for in-line observation, optionally a camera.

[0196] 55. The apparatus of clause 54, further comprising a means for processing analysis of images produced by the imaging device.

[0197] 56. The apparatus of clause 54 or 55, wherein the apparatus is configured to predict optimal electrode porosity, electrode microstructure, battery performance, and / or manufacturing parameters, based on images produced by the imaging device.

[0198] 57. The apparatus of any one of clauses 52 to 56, comprising in-line electronic open-loop or closed-loop control for processing of the electrode.

[0199] 58. The apparatus of any one of clauses 52 to 57, wherein the apparatus is configured to simulate mechanical compression.

[0200] Any listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or common general knowledge. All references disclosed herein are to be considered to be incorporated herein by reference. All features discussed herein in respect of any of the uses, methods or products relate to all other uses, methods or products mutatis mutandis.

[0201] Those skilled in the art will recognise or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. The scope of the present disclosure herein is not intended to be limited to the above description, but rather is as set forth in the appended claims. Those of ordinary skill in the art will appreciate that various changes and modifications to this description may be made without departing from the spirit or scope of the present disclosure.

Claims

CLAIMS1 . An electrode comprising a redox-active material and a low-dimensional carbon material, wherein: at least around 70% of the surface of the electrode comprises at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.

2. The electrode of claim 1 , wherein the electrode comprises, based on the total weights of low-dimensional carbon material and redox-active material in the electrode: at least around 0.1 wt% low-dimensional carbon material, optionally at least around 0.5 wt%, optionally at least around 1 wt%, optionally at least around 1 .5 wt%, optionally at least around 2 wt%, optionally at least around 3 wt%; and / or at most around 40 wt% low-dimensional carbon material, optionally at most around 30 wt%, optionally at most around 20 wt%, optionally at most around 10 wt%, optionally at most around 8 wt%, optionally at most around 6 wt%, optionally at most around 5 wt%; and / or around 0.1 to 40 wt% low-dimensional carbon material, optionally around 0.1 to 30 wt%, optionally around 0.5 to 20 wt%, optionally around 1 to 10 wt%, optionally around 1 .5 to 8 wt%, optionally around 2 to 6 wt%, optionally around 3 to 5 wt%, optionally around 4 wt%.

3. The electrode of any preceding claim, wherein the low-dimensional carbon material is substantially porous and / or permeable to gases (e.g. air or argon).

4. The electrode of any preceding claim, wherein the low-dimensional carbon material is a zero-, one- or two-dimensional carbon material, optionally a flaked, flat, tubular or needlelike carbon material.

5. The electrode of any preceding claim, wherein the low-dimensional carbon material is selected from graphene oxide, graphene, holey graphene, graphite oxide, carbon nanofibres, carbon fibres, carbon nanotubes, graphyne and graphenylene.

6. The electrode of any preceding claim, comprising at least two layers comprising the lowdimensional carbon material.

7. The electrode of claim 6, comprising a first layer, a second layer and a third layer; wherein:the first layer comprises the low-dimensional carbon material; the second layer comprises the redox-active material; the third layer comprises the low-dimensional carbon material; and the second layer is disposed between the first layer and third layer.

8. The electrode of any preceding claim, wherein the at least one layer comprising the lowdimensional carbon material has a thickness of: at least around 1 nm, optionally at least around 10 nm, optionally at least around 20 nm, optionally at least around 50 nm; and / or at most around 100,000 nm, optionally at most around 50,000 nm, optionally at most around 10,000 nm, optionally at most around 5000 nm; and / or around 1 to 100,000 nm, optionally around 1 to 50,000 nm, optionally around 1 to 10,000 nm, optionally around 1 to 5000 nm.

9. The electrode of claim 7 or 8, wherein the second layer, when present, has a thickness of: at least around 1 pm, optionally at least around 5 pm, optionally at least around 10 pm, optionally at least around 20 pm, optionally at least around 50 pm; and / or at most around 10,000 pm, optionally at most around 7500 pm, optionally at most around 5000 pm, optionally at most around 2500 pm, optionally at most around 1000 pm; and / or around 1 to 10,000 pm, optionally around 5 to 7500 pm, optionally around 10 to 5000 pm, optionally around 20 to 2500 pm, optionally around 50 to 1000 pm.

10. The electrode of any preceding claim, wherein the redox-active material is a cathode material, optionally selected from:(a) metal oxides, optionally layered metal oxides (e.g. lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium manganese nickel oxide (e.g. lithium-rich ii 2Mno 6Nio 2O2) and lithium nickel cobalt aluminium oxide), spinels (e.g. lithium manganese oxide), and disordered rock salts (e.g. Li1 25Nbo 25Mno5O2); preferably lithium nickel manganese cobalt oxide (e.g. LiNixMnyCoz02, x+y+z = 1); and(b) polyanion compounds (e.g. lithium iron phosphate).11 . The electrode of any one of claims 1 to 9, wherein the redox-active material is an anode material, optionally selected from graphite, silicon, silicon oxides, Li4TisOi2, hard carbon and soft carbon.

12. The electrode of any preceding claim, wherein the electrode has a capacity of at least around 10 mA-h-g1, optionally at least around 200 mA-h-g1, optionally at least around400 mA-h-g1, optionally at least around 600 mA-h-g1, optionally at least around 800 mA-h-g1, optionally at least around 1000 mA-h-g1.

13. The electrode of any preceding claim, wherein the electrode has a resistance of at most around 1000 Q cm2, optionally at most around 200 Q cm2, optionally at most around 150 Q'cm2, optionally at most around 100 Q cm2, optionally at most around 50 Q cm2, optionally at most around 1 Q cm2.

14. The electrode of any preceding claim, wherein the electrode does not comprise a redoxinactive binder and / or does not comprise an electronically insulating binder.

15. The electrode of any preceding claim, wherein the electrode does not comprise a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene).

16. The electrode of any one of claims 1 to 14, wherein the electrode comprises one or more redox-active and / or electronically conducting binders, optionally wherein said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole-based binders, polylactic acid-based binders and chitosan-based binders.

17. The electrode of any one of claims 1 to 13 and 16, wherein the electrode comprises one or more adhesion-enhancing and / or flexibility-enhancing binders, optionally wherein said one or more adhesion-enhancing and / or flexibility-enhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol-based binders and methacrylic-based binders.

18. A battery comprising one or more electrodes as described in claims 1 to 17.

19. The battery of claim 18, wherein the battery has a pouch cell configuration, a cylindrical cell configuration, a prismatic cell configuration or a coin cell configuration.

20. A method for forming an electrode, wherein the method comprises: preparing an agglomeration comprising a redox-active material and at least one layer comprising a low-dimensional carbon material; and pressing the agglomeration to form an electrode, wherein:at least around 70% of the surface of the electrode comprises the at least one layer comprising the low-dimensional carbon material; and the electrode comprises at most around 45 wt% low-dimensional carbon material, based on the total weights of low-dimensional carbon material and redox-active material in the electrode.21 . The method of claim 20, wherein said preparing an agglomeration comprises: preparing a first layer, wherein said first layer comprises the low-dimensional carbon material, placing a second layer on the first layer, wherein said second layer comprises the redox-active material, and placing a third layer on the second layer, wherein said third layer comprises the low-dimensional carbon material; and wherein said pressing the agglomeration comprises pressing the first layer, second layer and third layer.

22. The method of claim 20 or 21 , wherein said pressing is at a temperature of: at most around 250°C, optionally at most around 200°C, optionally at most around 150°C, optionally at most around 100°C, optionally at most around 50°C, optionally at most around 40°C, optionally at most around 30°C; and / or around -50 to 250°C, optionally around -30 to 200°C, optionally around -20 to 150°C, optionally around -10 to 100°C, optionally around 0 to 50°C, optionally around 10 to 40°C, optionally around 20 to 30°C.

23. The method of any one of claims 20 to 22, wherein said pressing comprises calendering; optionally at a calendering speed of around 0.01 to 2 m s1, wherein “calendering speed” refers to the speed at which a material is passed through a calendering apparatus.

24. The method of claim 23, wherein said calendering comprises asymmetric calendering, optionally wherein a first roller operates at around 0.1 to 0.5 m s1and a second roller operates at around 0.8 to 1 .3 m s1.

25. The method of any one of claims 20 to 24, wherein the at least one layer comprising the low-dimensional carbon material is substantially porous and / or permeable to gases (e.g. air or argon).

26. The method of any one of claims 20 to 25, further comprising expelling a gas (e.g. air or argon) from the redox-active material through one or more of the at least one layer comprising the low-dimensional carbon material.

27. The method of any one of claims 20 to 26, wherein said pressing comprises use of a pressure of: at least around 0.5 MPa, optionally at least around 1 MPa, optionally at least around 3 MPa, optionally at least around 5 MPa, optionally at least around 7 MPa, optionally at least around 9 MPa, optionally at least around 10 MPa; and / or at most around 1000 MPa, optionally at most around 800 MPa, optionally at most around 600 MPa, optionally at most around 400 MPa, optionally at most around300 MPa, optionally at most around 200 MPa, optionally at most around 100 MPa; and / or around 0.5 to 1000 MPa, optionally around 1 to 800 MPa, optionally around 3 to600 MPa, optionally around 5 to 400 MPa, optionally around 7 to 300 MPa, optionally around 9 to 200 MPa, optionally around 10 to 100 MPa.

28. The method of any one of claims 20 to 27, wherein the method does not comprise the use of a solvent (e.g. N-methyl-2-pyrrolidone or water).

29. The method of any one of claims 20 to 28, wherein the method does not comprise the use of a redox-inactive binder and / or does not comprise the use of an electronically insulating binder.

30. The method of any one of claims 20 to 29, wherein the method does not comprise the use of a binder (e.g. a polymeric binder such as polyvinylidene fluoride or polytetrafluoroethylene).31 . The method of any one of claims 20 to 29, wherein the method comprises the use of one or more redox-active and / or electronically conducting binders, optionally wherein said one or more redox-active and / or electronically conducting binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxylmethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, cellulose-based binders, polyaniline-based binders, polypyrrole- based binders, polylactic acid-based binders and chitosan-based binders.

32. The method of any one of claims 20 to 28 and 31 , wherein the method comprises the use of one or more adhesion-enhancing and / or flexibility-enhancing binders, optionally wherein said one or more adhesion-enhancing and / or flexibility-enhancing binders are independently selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxyl methyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), ethylene-based binders, polylactic acid-based binders, ethylene glycol-based binders and methacrylic-based binders.

33. The electrode of any one of claims 1 to 17, wherein the electrode is or has been formed using the method of any one of claims 20 to 32.

34. An apparatus suitable for carrying out the method described herein.

35. The apparatus of claim 34, comprising:(a) one or more powder feeders, optionally comprising a vibrating mechanism (e.g. an electromagnetic vibrating mechanism); and / or(b) a conveyor belt; and / or(c) a compression device, optionally comprising one or more calender rollers.

36. The apparatus of claim 34 or 35, comprising an imaging device for in-line observation, optionally a camera.

37. The apparatus of claim 36, further comprising a means for processing analysis of images produced by the imaging device.

38. The apparatus of claim 36 or 37, wherein the apparatus is configured to predict optimal electrode porosity, electrode microstructure, battery performance, and / or manufacturing parameters, based on images produced by the imaging device.

39. The apparatus of any one of claims 34 to 38, comprising in-line electronic open-loop or closed-loop control for processing of the electrode.

40. The apparatus of any one of claims 34 to 39, wherein the apparatus is configured to simulate mechanical compression.

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