composites

Abstract

The present invention relates to composite materials and processes for forming said composite materials. Such composites can find use in electrode and battery applications. The invention also relates to cathodes comprising the composites.

Description

Composites

[0001] The present invention relates to composite materials and processes for forming said composite materials. Such composites may be fabricated into electrode films, particularly cathode electrode films. The invention also relates to composites obtained by the processes described herein.BACKGROUND

[0002] Lithium (Li) ion batteries, comprise an anode, a separator material with an electrolyte medium, and a cathode. The anode electrode of most commercially available Li ion batteries is a copper foil coated with a mixture of graphite powder and a polymer blend such as polyvinylidene difluoride (PVDF). The cathode generally comprises a mixture of lithium transition metal oxides, PVDF and carbon black coated onto an aluminum foil.

[0003] Li-ion batteries require two electrodes to function; a cathode to store lithium when the cell is discharged (or in a low-energy state) and an anode to store lithium when / as the cell is charged.

[0004] For commercial batteries, particulate anode and cathode materials are used, due to ease of manufacture and the necessity of pores within the electrode to facilitate electrolyte ingress to facilitate local transfer of lithium ions. These ‘active material’ particles are usually coated onto sheet metal ‘current collectors’ to support the active materials and to provide long-range electron transfer from the battery terminals to the whole battery. These current collector sheets are then arranged in spirals or stacks depending on the format of the battery, e.g. cylindrical, prismatic, or pouch.

[0005] To attach the particles to a current collector, a binder is usually required. Such a binder will generally be required to not inhibit transfer of lithium ions to the surface of active electrode particle, while also facilitating cohesion of the active materials to each other and to any conductive additives, and adhesion of the mixture to a current collector.

[0006] As well as a binder, a primer is usually needed to allow the electrode film to properly adhere to a current collector, especially when the electrode coating process is substantially free of solvent (Dry coating). Primers generally comprise a carbon / binder mixture coated in a thin layer (e.g. 1 micron thickness) onto the current collector foil. Although primer coated foil is available at commercial scale, they are often costly to include in a manufacturing process for Li-ion batteries.

[0007] Incorporation of high surface area conductive carbon materials into electrodes is desirable due to their favourable electronic properties. However, a potential disadvantage of known methods of making conductive carbon containing electrode composites is that separation (inhomogeneity) of the component solids can occur if the carbons are not properly dispersed, which is likely when using standard mixing techniques like dry blademixing. This can lead to uneven distribution of the components in the electrode, affecting the electrical performance.

[0008] The use of high surface area conductive carbon materials in electrode manufacturing also has safety issues in that the high surface area, small sized, powder materials can disperse in the air. Means to reduce the amount of high surface area carbon materials which are released into the air during electrode manufacture is highly desirable.

[0009] The present invention was devised with the foregoing in mind.SUMMARY OF THE INVENTION

[0010] In a first aspect there is provided a composite material for use as a cathode film, comprising: a) a particulate material comprising: i) a cathode active material; ii) a first polymeric binder; iii) a conductive material; wherein the first binder attaches the cathode active material to the conductive material; and the particulate material has a particle size of at least 1 micron; b) a second polymeric binder material which binds the particles of the particulate material together; wherein: the cathode active material is present in an amount of 85 to 99.5 wt.%; the first polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the second polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the conductive material in an amount of 0.01 to 15 wt.%; based upon the total weight of the composite material; and wherein the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1.

[0011] In another aspect there is provided a cathode comprising: a) a metallic substrate; b) a film comprising the composite material according to the first aspect.

[0012] In another aspect, there is provided a battery comprising a cathode as defined herein. Suitably, the battery is a lithium ion battery.

[0013] In another aspect there is provided a process for fabricating a composite material, the process comprising; i) preparing composite comprising a cathode active material, a first polymeric binder and a conductive material; wherein the first binder attaches the cathodeactive material to the conductive material; and the particulate material has a particle size of at least 1 micron; ii) mixing the particulate material with a second polymeric binder such that the individual particles of the particulate material are attached to one another by the second polymeric binder.

[0014] In another aspect, there is provided a composite obtained by, obtainable by, or directly obtained by the process defined herein.

[0015] In another aspect, there is provided a process for fabricating an electrode, comprising: i) fabricating a composite material as defined herein; ii) forming the composite material into a film; iii) coating the film onto a metal substrate.Electrode Film Components

[0016] The composites of the present invention may be used to fabricate electrode films, particularly cathode films. As described herein, the composites comprise an active material, a first polymeric binder, a second polymeric binder and a conductive material. These materials, together with any further additives, can be collectively defined as electrode film components.Active Material

[0017] The active material in the electrode film of a battery is required to store and release cations (typically lithium ions). The active material in the electrode film or composites of the invention may be any suitable active material known in the art. The choice of active material will suitably depend on whether the electrode film is to be used in an anode or a cathode.

[0018] In the present invention, the active material is a cathode active material.

[0019] The active material is capable of being intercalated by, reacted with, or alloying with ions in a reversible electrochemical reaction. The ions may be selected from one or more of lithium, sodium, potassium, aluminum, magnesium, calcium, beryllium, lead, or nickel ions. Suitably, the ions are lithium ions.

[0020] A reversible electrochemical reaction permits coupling and decoupling with ions, with an associated electron transfer to balance charges, where at least 40% of the ions are returnable from the active material in the opposing electrochemical reaction.

[0021] The active material may be lithium-active or sodium active material.

[0022] The active material may be selected from one or more of the following:• oxides, nitrides, carbides, sulfides, phosphides, and selenides of Silicon, Germanium, Antimony, Tin, Lead, Bismuth, Zinc, Aluminium, Titanium, Iron, Nickel, Manganese, Cobalt, or Cadmium, and their mixtures, or lithium-containing composites;• Lithium transition metal phosphates, e.g. lithium nickel phosphate, lithium cobalt nickel phosphate, lithium iron phosphate and lithium mixed- transition-metal phosphates;• lithium titanate, lithium manganate, lithium aluminate, lithium-containing titanium oxide; and• lithium transition metal oxides, such as:• NMC (lithium nickel manganese cobalt oxide) and its stoichiometric variants, e.g. 910, 811 , 622, 532, 111 ;• NCA (Lithium nickel cobalt aluminium oxide) and its stoichiometric variants.

[0023] Suitably, the active material is selected from:LTO (lithium titanates);NMC (Lithium nickel manganese cobalt oxides);NCA (Lithium nickel cobalt aluminium oxide);LFP (lithium iron phosphate); or Silicon.

[0024] Most suitably, the active material is NMC (lithium nickel manganese cobalt oxide). The NMC may be NMC 811 , NMC 910, NMC 622, NMC 532 or NMC 111 , particularly NMC 811 or NMC 622.Binder Materials

[0025] The binder material of a battery is present to primarily adhere the electrode film to a substrate such as a current collector. The binder materials utilised in the present invention are polymeric, and may be a flexible polymer. Suitably, the first and second binder materials are different to one another.

[0026] Suitably, the first polymeric binder comprises one or more of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyacrylic acid (PAA) and alkali metal salts thereof, modified polyacrylic acid (mPAA) and alkali metal salts thereof, methyl cellulose, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC), sodium carboxymethylcellulose (Na-CMC), polyvinylalcohol (PVA), alginates and alkali metal salts thereof, styrene-butadiene rubber (SBR), polyimide, polyethylene oxide (PEO), CMC / SBR mixtures, PAI (e.g. Torlon® AI-10), chitosan, chitosan sulfate ethylamide glycinamide (CSEG), polyvinylpyrrolidone (PVP), ammonium polyphosphate (APP),sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups (SPEEK- FSA-Li), Lithiated poly(perfluoroalkylsulfonyl)imide (PFSILi) ionene(s), poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) doped further as appropriate, poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic acid) (PFFOMB), poly(9,9- dioctylfluorene-co-fluorenone) (PFFO), ethylene vinyl alcohol (EVOH) and polyurethane (PU).

[0027] More suitably, the first polymeric binder is selected from PVDF, PU, EVOH, PVDF- HFP, chitosan and PEO.

[0028] Most suitably, the first polymeric binder is PVDF.

[0029] Suitably, the second polymeric binder is Polytetrafluoroethylene (PTFE).Conductive Material

[0030] The conductive material (also known as a conductive additive) plays an important role in the electrochemical performance of lithium ion batteries. Such materials construct a conductive percolation network to increase and keep the electronic conductivity of electrode, impacting the rate at which the battery can charge and discharge, as well as the voltage drop associated with the charge and discharge. In addition, conductive additives may play a role in absorbing and retaining electrolyte, ultimately helping to maintain an intimate contact between the lithium ions and active materials.

[0031] The conducting material may comprise one or more of a two-dimensional layered material or a carbon-based conductive additive. Preferably, the conductive material comprises a conductive carbon material.

[0032] Suitable carbon-based conductive additives include carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanotubes, graphene, and hard carbons. The one carbon-based conductive additive may include one or more “high aspect ratio” materials, such as carbon nanotubes or a two-dimensional (2D) layered material (either carbon based, or non-carbon based). Graphene (i.e. pristine graphene) can be considered to be a conductive carbon material and a 2D layered material.

[0033] Suitable two-dimensional (2D) layered materials include graphene-based materials and inorganic layered materials.

[0034] Exemplary two-dimensional (2D) layered materials include:• graphene, graphene oxide, reduced graphene oxide, functionalised graphene, partially oxidised graphene (i.e. graphene with an oxygen content less than 15% that has not been reduced from graphene oxide or preferably graphene with an oxygen content less than 10 atom% that has not been reduced from graphene oxide);• metal oxide nanosheets which are composed of sheets of edge / corner sharing MOe octahedra, (where M is a transition metal, and O is oxygen), where the sheets are separated by alkali metal cations, protons, water, solvent or any combination thereof;• metal double hydroxides which are composed of octahedral hydroxide layers of divalent and trivalent metal cations, where charge is balanced with anions between the layers, represented by the general formula M2+i-xM3+x(OH)2An‘x / nm / 72O (whereM2+= Mg2+, Fe2+, Co2+, Ni2+, Zn2+, etc.; M3+= Al3+, Fe3+, Co3+, etc.; and A = (CO3)2-,Ch, (NO3)-, (CIO4)-, etc.);• Phosphorenes (black phosphorus).• 2D Chalcogenides:• hexagonal boron nitride (hBN), fluorographene, boron carbon nitride (BCN), SiC, Si2BN, silicene, germanene, stanene, borophene, graphyne, plumbene;• transition metal dichalcogenides with the general stoichiometry MX2, where M is a transition metal atom and X is a chalcogen atom, (e.g. M0S2, WS2, MoTe2, MoSe2, WSe2 etc.);• any other layered 2D material consisting of less than 4 elements in a compound, less than 40 atoms in the primitive cell, covalently bonded in-plane and held out-of-plane by weak intermolecular forces;• Layered Semiconductors, e.g. GaSe, GaTe, InSe, Bi2Se3, etc;• 2D Oxides; for example, MnO2, WO3, TiO2, MoO3, V2O5, TaO3, RUO2, NaNbO3, a- Fe2O3, Nb20s, CO3V2OS, Nai.osVsOs, ©to.• Layered Cu Oxides.• Perovskite-type e.g. Methylammonium lead halide (CH3NH3Pbl3), Cesium lead halides (CsPbX3), Bi4Ti30i2, Ca2Ta2TiO , etc.• Hydroxides, e.g. Ni(OH)2, Eu(OH)2, ZnAI-layered double hydroxide (LDH).• MXenes: Sc2C(OH)2, SC2CO2, Ti2CO2, Titanium Carbide (Ti3C2).

[0035] Suitably, the 2D layered material is selected from graphene, partially oxidised graphene, (i.e. graphene with an oxygen content less than 15 atom%, or more preferably graphene with an oxygen content less than 10 atom% that has not been reduced from graphene oxide), halogenated graphene, hexagonal boron nitride (hBN), 2D metal oxides, 2D metal hydroxides, and transition metal dichalcogenides (e.g. M0S2, WS2, MoTe2, MoSe2). Surprisingly and advantageously, the present invention does not require any functionalisation of the 2D materials in order to form composites. Suitably, the 2D material is selected from graphene which has had less than 15% of its atoms covalently modified, or more preferably, graphene which has had less than 10% of its atoms covalently modified.

[0036] Suitably, the 2D material is selected from hBN, graphene or a transition metal dichalcogenide. Suitably, the 2D material is graphene (i.e. pristine graphene) or graphene with an oxygen content less than 15 atom%. Suitably, the 2D material is graphene with a FWHM Raman peak of less than 60 cm-1.

[0037] In certain preferred embodiments of the invention, the conductive material comprises one or more conductive carbon materials.

[0038] Suitable conductive carbon materials include for example carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanotubes, and graphene (e.g. pristine graphene), and hard carbons. Preferably, the conductive material comprises one or more of pristine graphene, carbon black, or carbon nanotubes. More preferably, the conductive material comprises one or more of pristine graphene, carbon black, or carbon nanotubes (e.g. single wall carbon nanotubes).

[0039] In preferred embodiments, the conductive material comprises at least one “high aspect ratio” conductive carbon material, such as for example pristine graphene or carbon nanotubes (such as single walled carbon nanotubes).

[0040] In preferred embodiments, the conductive material comprises carbon black and at least one “high aspect ratio” conductive carbon material, such as for example pristine graphene or carbon nanotubes (such as single walled carbon nanotubes).

[0041] In certain embodiments, the conductive material comprises a combination of carbon black and at least one of pristine graphene or carbon nanotubes. The carbon nanotubes may be single walled carbon nanotubes.

[0042] In certain embodiments, the ratio of carbon black to the high aspect ratio carbon material is from 0.1 :1 to 20:1, e.g. 1:1 to 20:1 or 10:1 to 20:1.Composites of the Present Invention

[0043] As discussed above, the present invention provides a composite comprising: a) a particulate material comprising: i) a cathode active material, ii) a first polymeric binder; iii) a conductive material; wherein the first binder attaches the cathode active material to the conductive material; and the particulate material has a particle size of at least 1 micron; b) a second polymeric binder material which binds the particles of the particulate material together; wherein: the cathode active material is present in an amount of 85 to 99.5 wt.%;the first polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the second polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the conductive material in an amount of 0.01 to 15 wt.%; based upon the total weight of the composite material; and wherein the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1.

[0044] Suitably, the binder, active and conductive materials are selected from any of the materials described herein.

[0045] Suitably, the composites of the invention comprise an active material in an amount of from 85 to 99.5 wt.%, more suitably from 85 to 99 wt.% or most suitably from 94 to 98.5 wt.%.

[0046] Suitably, the composites of the invention comprise a conductive material in an amount of from 0.1 to 5 wt.%, more suitably from 0.25 to 3 wt.%, most suitably from 0.5 to 1.5 wt.%.

[0047] Suitably, the composites of the invention comprise a first polymeric binder in an amount of from 0.1 to 5 wt.%, more suitably from 0.25 to 3 wt.%, most suitably from 0.5 to 1.5 wt.%.

[0048] Suitably, the composites of the invention comprise a second polymeric binder in an amount of 0.1 to 5 wt.%, more suitably from 0.25 to 3 wt.%, most suitably from 0.5 to 1.5 wt.%.

[0049] Suitably, the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1 ; more suitably from 0.67:1 to 1.5:1 ; or most suitably from 0.9:1 to 1.1 :1. In certain embodiments, the weight ratio of the first polymeric binder to second polymeric binder is 1 :1.

[0050] Suitably, the particulate material has a particle size of at least 10 microns.

[0051] Suitably, the particulate material has a d90 particle size of from 4 to 400 microns. More suitably, the particulate material has a d90 particle size of from 10 to 400 microns. Most suitably, the particulate material has a d90 particle size of from 10 to 200 microns.

[0052] The composites formed in the present invention will typically be in the form of a solid cohesive agglomerated particles, for example a powder or a second particulate material (larger in size than the particulate material used in the process to make the composite). The powder may be processed into a film.

[0053] The composites formed in the present invention may also be formed into a mouldable dough, which may subsequently be processed into a film. A film comprising (or consisting of) the composite of the invention may have a thickness of from 30 to 300 microns, more suitably from 50 microns to 200 microns (e.g. 60 to 200 microns).Cathode utilising composites of the invention

[0054] As discussed herein, the invention provides a cathode comprising: a) a metallic substrate; b) a film comprising the composite material as defined herein.

[0055] Advantageously, the cathodes comprising a composite of the invention may not need a primer layer between the electrode film and the current collector. Suitably, the film may be directly attached to the metallic substrate. More suitably, there is no primer layer between the metallic substrate and the film. Even more suitably, there is no embossing or roughening of the metallic substrate.

[0056] Suitably, the metallic substrate is a current collector, preferably an aluminium current collector.

[0057] Suitably, the film has a thickness of 30 to 300 microns, more suitably from 60 microns to 200 microns.Batteries utilising composites of the invention

[0058] Following the formation of a cathode comprising an electrode film coated onto a current collector, the method of the invention suitably further comprises assembling a battery comprising the current collector coated with the electrode film. Assembling a battery suitably comprises assembling the coated current collector with a separator, a counter electrode, and electrolyte in a sealed container. The counter electrode may be an anode or a cathode as appropriate.

[0059] Advantageously, the batteries comprising a composite of the invention may not need a primer layer between the electrode film and the current collector.

[0060] Suitably, the battery is a lithium ion battery.Processes of the Present invention

[0061] As discussed herein, the invention provides a process for fabricating a composite material, the process comprising; i) preparing particulate material comprising a cathode active material, a first polymeric binder and a conductive material; wherein the first polymeric binder attaches the cathode active material to the conductive carbon material; and the particulate material has a particle size of at least 1 micron; ii) mixing the particulate material with a second polymeric binder such that the individual particles of the particulate material are attached to one another by the second polymeric binder.

[0062] Suitably, in the process of the invention: the cathode active material is present in an amount of 85 to 99.5 wt.%; the first polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the second polymeric binder is present in an amount of 0.01 to 7.5 wt.%; and the conductive material in an amount of 0.01 to 15 wt.%; based upon the total weight of the composite material.

[0063] Suitably, the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1.

[0064] As discussed herein, the invention provides a process for fabricating a cathode, comprising: i) fabricating a composite material as defined herein; ii) forming the composite material into a film; iii) coating the film onto a metal substrate.

[0065] In the processes of the invention, the active material, conductive material, first binder and second binder may be any of those described herein.

[0066] In the process of fabricating a cathode material, suitably the metal substrate is substantially free of any primer during the coating of the film. By “substantially free of any primer” it is meant that no detectable level of primer is present on the metal substrate.

[0067] The composite material may be coated onto the metal substrate (e.g. an aluminum current collector) by dry coating processes, e.g. by calendering.

[0068] The invention also provides a composite material, obtained by, obtainable by or directly obtained by the process defined herein.

[0069] The invention also provides a cathode, obtained by, obtainable by or directly obtained by the process defined herein.Particular Embodiments of the Invention

[0070] In an embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0071] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0072] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0073] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0074] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0075] In a specific embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0076] In an embodiment of the composites, electrodes and processes of the invention, and the composites of the invention:1. the first polymeric binder is PVDF2. the second polymeric binder is PTFE3. the conductive material comprises carbon black and at least one one of carbon nanotubes and graphene:4. the active material is NMC.

[0077] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:

[0078] In another embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the active material, conductive material and polymeric binders are present in the following relative amounts:Preparation of the Particulate Material

[0079] The particulate materials of the present invention may be prepared by a number of methods known in the art. However, in certain embodiment, the particulate materials comprising an electrode active material, a first polymeric binder and a conductive material discussed herein may be prepared by a process comprising: i. providing a first dispersion comprising a dispersing solvent and a first polymeric binder dissolved therein; ii. providing an antisolvent in which the first polymeric binder is substantially insoluble; wherein at least one of the first dispersion and the antisolvent comprises an active material dispersed therein and at least one of the first dispersion and the antisolvent comprises a conductive material dispersed therein; wherein: the active material is present in an amount of from 80 to 99.5 wt.%; the conductive material is present in an amount of from 0.01 to 15 wt.%; the first polymeric binder material is present in an amount of from 0.01 to 15 wt.%; based upon the total weight of the active material, conductive material and first polymeric binder; iii. contacting the first dispersion with the antisolvent to form a suspension mixture, wherein the volume ratio of the dispersing solvent to the antisolvent is from 1 :1 to 1 :10; wherein contacting the first dispersion with the antisolvent results in the precipitation of the first polymeric binder in the presence of the active material and conductive material to form a particulate material.

[0080] It will be appreciated that the particulate materials discussed herein are preliminary composites comprising the active material, conductive material and first polymeric binder.

[0081] The process of preparing the particulate material is typically performed under low viscosity conditions, allowing the incorporation of high surface area carbon materials (e.g. graphene, carbon nanotubes) with high mixing efficiency.

[0082] In the processes of preparing the particulate material of the present invention, an intimate particulate material comprising a first polymeric binder, active material and conductive material is formed within a suspension mixture. Following formation of the particulate material, the suspension mixture comprises the particulate material in a mixture of the dispersing solvent and antisolvent.

[0083] Suitably, the volume ratio of the dispersing solvent to the antisolvent is from 1 : 1 to 1 :5, more suitably from 1 :1 to 1 :4. More suitably, the volume ratio of the dispersing solvent to the antisolvent is from 1 :1.5 to 1 :3.

[0084] Suitably, there is an excess of antisolvent relative to the dispersing solvent.

[0085] In the context of the present invention, the dispersing solvent is a solvent in which the first polymeric binder is at least partially soluble in at 25°C and 1atm pressure. Suitably, the dispersing solvent is a solvent in which the first polymeric binder is substantially soluble in at 25°C and 1atm pressure.

[0086] The dispersing solvent may be selected from NMP, DMSO, Gyrene or a combination thereof. Suitably, the dispersing solvent is NMP or DMSO. Most suitably, the dispersing solvent is NMP.

[0087] The antisolvent is a solvent in which the first polymeric binder is substantially insoluble (i.e. at least 1000 mass part of the solvent is required to dissolve 1 mass part of solute at standard operating temperatures (e.g. 25°C and 1atm pressure). Suitably, the active material and conductive material are also substantially insoluble in the antisolvent.

[0088] The antisolvent may comprise one or more of methanol, water, acetone or a mixture thereof. Suitably, the antisolvent is selected from methanol or a blend of water and acetone.

[0089] Suitably, the antisolvent comprises no more than 75 wt.% water. For example, if a blend of acetone and water is to be used as an antisolvent, it may comprise at least 25 wt.% of acetone.

[0090] The blend of water and acetone may comprise from 10 to 75% water. Suitably, the blend of water and acetone may comprise from 30 to 70% water. Most suitably, the blend of water and acetone may comprise from 40 to 60% water.

[0091] Suitably, the viscosity of the first dispersion is less than or equal than 1 Pa.s prior to contact with the antisolvent.

[0092] Suitably, the viscosity of the suspension mixture is less than or equal to 1 Pa.s following addition of the antisolvent to the first dispersion.

[0093] Suitably, the particle size of the active material prior to addition of the antisolvent has a d90 between 1 urn and 40 urn. More suitably, the d90 may be between 10 urn and 30 urn.

[0094] A wide range of particle sizes of the conductive material may be utilised, for example prior to addition of the antisolvent, the conductive material may have a d90 between 0.005 urn and 10 urn.

[0095] Suitably, once the particulate material is formed within the suspension mixture, the process further comprises removing a portion of the dispersing solvent and / or antisolvent.

[0096] In certain embodiments, the process further comprises removing a substantially all of the antisolvent from the suspension mixture. In such embodiments, the process may also comprise removing at least a portion of the dispersing solvent from the suspension mixture.

[0097] In certain embodiments, the process further comprises removing at least a portion of the dispersing solvent from the suspension mixture.

[0098] In some embodiments, the process further comprises drying the suspension mixture, thereby removing substantially all of the dispersing solvent and antisolvent to provide a dried particulate material. Following removal of the dispersing solvent and antisolvent, the dried particulate material may be in the form of a powder or particulate material.

[0099] The particulate material may suitably be dried. The drying may be achieved through heating, for example in a vacuum oven. In certain embodiments, substantially all of the dispersing solvent and antisolvent may be removed during the drying step. The dried particulate material may be processed into an electrode film (e.g. by coating onto a current collector) as described herein.

[0100] Suitably, the dispersing solvent and the antisolvent may be removed by a combination of different methods. The dispersing solvent and the antisolvent may be removed by filtration and / or decantation. The dispersing solvent and the antisolvent may also be removed by drying.

[0101] The process may also comprise filtering the particulate material to remove any noncomposited materials, or materials with a particle size less than 10 microns.Dispersing Solvents

[0102] In preferred embodiments, the first polymeric binders of the invention are fully dissolved in the dispersing solvent, prior to the formation of a particulate material.

[0103] Suitably, the dispersing solvent is a solvent with a boiling point above 150°C.

[0104] The dispersing solvent may be selected from any suitable solvent described herein. The preferred use of one solvent over another is dependent on the solubility of the first polymeric binders within the dispersing solvent, conducting materials, and active materials used in each specific example.

[0105] Suitably, the dispersing solvent is selected from Gyrene (Dihydrolevoglucosenone); DMSO (dimethylsulfoxide); NMP; butyl lactate; dimethyl isosorbide; triacetin; DMF; 1 ,2- dichlorobenzene; benzonitrile; pyridine; triethyl citrate; THF, cyclohexanone; cyclopentanone; olefins including pentane, hexane, cyclohexane, heptane, cyclooctane; ethyl acetate; ethyl lactate; furfural; eugenol; isoeugenol; levulinic acid; chloroform; 1,2- dischloromethane; toluene; methyl-t-butyl ether; methyl ethyl ketone; trichloroethylene; xylene; I PA; Water; Acetone; Methanol.

[0106] In preferred embodiments, the dispersing solvent is selected from NMP, DMSO, cyrene or mixtures thereof. Most suitably, the dispersing solvent is NMP.Antisolvents

[0107] The addition of antisolvent to the dispersing solvent will cause the precipitation of first polymeric binder from the dispersing solvent. The precipitation of the first polymeric binder causes the first polymeric binder particles to act as a flocculant which binds the active material and conductive material together. Thus, the addition of an antisolvent results in the flocculation of the first polymeric binder, active and conductive materials to form a composited particulate material in which the components are bound together. An advantage of applying first polymeric binder flocculation by antisolvent over other methods is relatively quick immobilisation, where the components within the particulate material might not have time for segregation.

[0108] Suitable antisolvents for a first polymeric binder material will depend upon the solubility profile of the first polymeric binder to be used. The first polymeric binder will typically be substantially insoluble in the antisolvent.

[0109] Suitably, the antisolvent is or comprises an aqueous soluble solvent (including water). More suitably, the antisolvent comprises one or more of methanol, water, acetone or a mixture thereof.

[0110] Suitably, if the first polymeric binder is PVDF, then water alone is not used to precipitate the first polymeric binder. Suitably, the antisolvent comprises no more than 75 wt.% water.

[0111] Suitably, the antisolvent is selected from methanol or a mixture of acetone and water. The ratio of water to acetone may be from 0.25:1 to 4:1 , more suitably from 0.5:1 to 2:1 , or most suitably from 0.75:1 to 1.25:1.

[0112] In a particular embodiment, the dispersing solvent is NMP and the antisolvent is selected from methanol or a mixture of acetone and water (e.g. a 0.25:1 to 4:1 , a 0.5:1 to 2:1 or a 0.75:1 to 1.25:1 ratio of water to acetone).Mixing of First Polymeric Binder, Active and Conductive Materials

[0113] The process of preparing the particulate material of the invention converts smaller sized individual materials (e.g. binder, conductive material, and active material particles) into larger sized particulate material. For example, the d90 particle size of the active material prior to precipitation of the binder will be less than 20 microns, which may increase by a factor of 2 or more (for example, to a d90 of 10-200 microns) following formation of the particulate material comprising the binder, conductive material, and active material particles.

[0114] Suitably, substantially all of the electrode components added to the first dispersion will be comprised within the final particulate material. However, should any of the individual components remain in a non-composited form, they may be removed from the suspension mixture, e.g. by filtration.

[0115] Suitably, the active material and conductive material are both present in the first dispersion prior to the formation of a particulate material by the addition of the antisolvent. Thus, the first dispersion suitably comprises the dispersing solvent, with the first polymeric binder dissolved therein, and the active material and conductive material dispersed therein.

[0116] Suitably, the components are thoroughly mixed in the solvent in which they are present, i.e. the antisolvent or the first dispersion, to achieve a homogenous distribution of the components.

[0117] Suitably, the components in the first dispersion and the antisolvent will typically be mixed thoroughly to ensure uniform dispersion of the active and conducting material in the formed particulate material.

[0118] Following contacting of the antisolvent with the first dispersion, the suspension mixture will also be thoroughly mixed.

[0119] The mixing will suitably be performed throughout the process of the invention to maintain a uniform distribution of the components.

[0120] The mixing may comprise one or more of sonication, stirring, planetary mixing, shear mixing, or any of the methods disclosed herein. Suitably, the mixing comprises shear mixing and / or planetary mixing.

[0121] The electrode components can be mixed in the dispersing solvent using standard mixing techniques known in the art, for example sonication, stirring, high shear homogenisation, blending, high pressure homogenisation. The first polymeric binder may be dissolved within the dispersing solvent before or after the addition of the remaining components.

[0122] Suitably, the conductive material, active material and any further additives are added to the first dispersion or antisolvent. Dispersion of the mixture in the respective solvent to form a homogenous slurry may suitably be performed after the addition of each component to the dispersing solvent or antisolvent.

[0123] The mixing may be performed continuously throughout the process. Thus, the slurry may be subjected to shear energy (such as mixing, sonication etc.) throughout the process of the invention.

[0124] Once prepared, the particulate material may be dried, e.g. in a vacuum oven.Preparation of the Composite Material

[0125] In the processes of the invention, once a particulate material has been prepared, it can be mixed with the second polymeric binder. Such mixing may involve mixing the dried particulate material and the second polymeric binder at high shear. The mixing may also be applied at elevated temperature.

[0126] Once prepared, the composite material may be coated onto a metal substrate (e.g. an aluminum current collector) by dry coating processes, such as calendering.BRIEF DESCRIPTION OF THE DRAWINGS

[0127] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:Figure 1 shows a schematic of the process to produce the particulate materials (dry powder) discussed herein.Figure 2 shows particle size distribution data for composite 1 .Figure 3 shows a comparison of airborne particles of composite powder 1 versus mixture 1.Figure 4 shows a comparison of Electrode 1 and Electrode 2 discharge rate performance, in Li-ion half-cells.Figure 5 shows particle size distribution data for composite 3.Figures 6A and 6B show SEM images of a particulate material (composite 3).Figure 7 shows a comparison of the peel strength of electrode 3 (top two rectangles) vs electrode 4 (bottom two rectangles).DETAILED DESCRIPTION

[0128] The present invention allows for high surface area carbon materials to be bound to an active material with a first polymeric binder. This reduces the total surface area of the materials which the second polymeric binder (e.g. PTFE) needs to bind to in order to maintain good adhesion to both the active material and current collector. This potentially allows for the electrode film to be applied to a current collector without a primer layer.

[0129] In addition, binding the high surface area carbon materials to the active material in a first processing step means that less dust can escape into the atmosphere while preparing the electrode composite material. This can allow for safer working environment in the preparation of electrode films.DEFINITIONS

[0130] The term “slurry” in the context of the invention is intended to mean a mixture comprising a liquid (e.g. dispersing solvent) and undissolved (active material and conductive material) and / or partially / fully dissolved solid materials. Generally, the term “slurry” may be used interchangeably with the term “dispersion” and also “suspension”. However, in the context of the present invention, the three terms are used to indicate the composition of slurries obtained different stages of the process:1 . The “first dispersion” relates to a slurry mixture of the dispersing solvent, the dissolved binder, and optionally further comprises an active material and / or a conductive material dispersed within the dispersing solvent.2. The “suspension” or “suspension mixture” relates to the mixture of antisolvent, dispersing solvent, and formed particulate material present following the precipitation of the binder in the presence of the active material and conductive material to form the particulate material.3. The “particulate material slurry” relates to a mixture comprising a solvent in which the binder material is at least partially soluble. Suitably, the particulate material slurry does not comprise any solvent in which the binder material is insoluble.

[0131] Without wishing to be bound by theory, it is thought that components of a composite of the invention (i.e. active, binder and conductive material) are attracted to each other if in the presence of polymers like PVDF as the polymers are precipitating.

[0132] Flocculation is an advantageous step to include in a process as it permits the utilization of large amounts of solvent without the need for significant liquid evaporation or otherwise physical means of obtaining a product, which instead may be filtered by coarse filtration or sedimentation. Given that it is often difficult to obtain a good dispersion of 2D materials in solvents, flocculation of a product will permit recycling of the large volume of solvent likely needed when scaling up the production of 2D- particulate material composites.

[0133] The interaction between the active material and the conductive material (in the presence of the precipitating polymer particles) results in an increase in the particle size of the composite relative to the particulate material. This arises due to the formation of ‘secondary particles’ (aggregates of composite material) in the dispersing solvent. Thus, the use of antisolvent precipitation is advantageous over simple high shear mixing of particulate materials and 2D materials, because larger, bound particles can be formed. These larger particles are beneficial for further processing steps, as larger particles are known to have more predictable properties than nano-sized particles (e.g. nano-sized particles can be difficult to stabilise).

[0134] In the methods described herein, the addition of an antisolvent to the binder in the dispersing solvent will induce the conductive material and the particulate material to flocculate and form a composite material. The binder will be included in an amount sufficient to induce aggregation. Without wishing to be bound by theory, it is thought that inducing flocculation in this manner results in improved interaction between the 2D material and the particulate. This will often result in an increase in particle size due to the interaction between 2D and particulate materials. This results in a more efficient process for making composites of 2D materials than previously demonstrated in the prior art. Before addition of the antisolvent, the particle size within dispersion is expected to be the size at which it was made, e.g. 1 urn particles and higher. Generally, only small, unflocculated, particles (e.g. less than 30 urn) are observed with the microscope before addition of the antisolvent. However, larger particles may be visible depending on the preparation method used to form the dispersion.

[0135] Flocculated products are advantageous because solvents can be recycled efficiently, as the formed flocculated material is easily separated from the dispersion mixture during flocculation. This also means that a relatively large amount of solvent can be used for the dispersion of the 2D material, which reduces the risk of aggregation of the 2D material with itself, and ensures a homogeneous mixture of the composite.

[0136] The term ‘two-dimensional material” (2D material) may mean a compound in a form which is so thin that it may exhibit different properties than the same compound when in bulk. Typically, two-dimensional inorganic compounds are in a form which is single- or few layers thick, i.e. up to 10 layers thick. A two-dimensional crystal of a layered material (e.g. an inorganic compound or graphene) is a single or few layered particles of that material.

[0137] It will be understood by a skilled person that a 2D material may be defined as a layered material with an in-plane modulus significantly higher than the shear modulus between the layers. Such materials include but not are restricted to, graphene, WS2, M0S2 and hexagonal boron nitride. Typically, a 2D material will comprise from 1-10 molecular layers.

[0138] 2D materials do exhibit thicknesses, however the dimensions of those thicknesses are significantly lower than the widths and lengths of these materials, thus the origin of the name ‘2D materials’.

[0139] The term ‘few-layered particle’ means a particle which is so thin that may exhibit different properties than the same compound when in bulk. Not all of the properties of the compound will differ between a few-layered particle and a bulk compound, but one or more properties are likely to be different. A more convenient definition would be that the term ‘few layered’ refers to a crystal that is from 2 to 9 atomic or molecular layers thick in cross-section (e.g. 2 to 5 layers thick). Crystals of graphene, for example, which have more than 9molecular layers (i.e. 10 atomic layers; 3.5 nm) generally exhibit properties more similar to graphite than to graphene. An atomic or molecular layer is the minimum thickness chemically possible for the compound. In the case of boron-nitride one molecular layer is a single atom thick. In the case of the transition metal dichalcogenides (e.g. M0S2 and WS2), a molecular layer is three atoms thick (one transition metal atom and two chalcogen atoms). Thus, few-layer crystals of 2D materials are generally less than 50 nm thick, depending on the compound and are preferably less than 20 nm thick, e.g. less than 10 or 5 nm thick. However, for current top-down production methods, such as ball-milling, shear mixing or liquid phase exfoliation, the final dispersion consists of distribution of thicknesses rather than the single defined one.

[0140] The term ‘inorganic layered compound’ refers to any compound made up of two or more elements which forms layered structures in which the bonding between atoms within the same layer is stronger than the bonding between atoms in different layers. Many examples of inorganic layered compounds have covalent bonds between the atoms within the layers but van der Waals bonding between the layers. The term ‘inorganic layered compound’ is not intended to encompass graphene.

[0141] Many inorganic compounds exist in a number of allotropic forms, some of which are layered and some of which are not. For example, boron nitride can exist in a layered graphite-like structure or as a diamond-like structure in which the boron and nitrogen atoms are tetrahedral orientated.

[0142] Examples of layered inorganic compounds to which the present invention can be applied include: hexagonal boron nitride (hBN), bismuth strontium calcium copper oxide (BSCCO), transition metal dichalcogenides (TMDCs), Sb2Tes, Bi2Tes and MnC>2.

[0143] TMDCs are structured such that each layer of the compound consists of three atomic planes: a layer of transition metal atoms (for example Mo, Ta, W etc.) sandwiched between two layers of chalcogen atoms (for example S, Se or Te). Thus, in one embodiment, the TMDC is a compound of one or more of Mo, Ta and Wwith one or more of S, Se and Te. There is strong covalent bonding between the atoms within each layer of the transition metal chalcogenide and predominantly weak Van der Waals bonding between adjacent layers. Exemplary TMDCs include NbSe2, WS2, M0S2, TaS2, PtTe2, VTe2.

[0144] A layer of graphene consists of a sheet of sp2-hybridized carbon atoms. Each carbon atom is covalently bonded to three neighbouring carbon atoms to form a ‘honeycomb’ network of tessellated hexagons. Carbon nanostructures which have more than 10 graphene layers (i.e. 10 atomic layers; 3.5 nm) generally exhibit properties more similar to graphite than to mono-layer graphene. Thus, throughout this specification, the term graphene is intended to mean a carbon nanostructure with up to 10 graphene layers (for example, where 90% of the graphene flakes have a thickness of 2 to 7 layers or where 90%of the graphene flakes have a thickness of 3 to 10 layers). Graphene is the ‘ultimate’ 2D material as it is defined by having one carbon atom thickness layer / sheet, which is a structural unit of graphite.

[0145] The level of graphene defects in a composite can be assessed using Raman spectroscopy in a manner similar to L. G. Cancado et al. 2011 , “Quantifying Defects in Graphene via Raman Spectroscopy at Different Excitation Energies”, Nano Letters, which is incorporated herein by reference. The ratio of the intensity of the observed D peak Raman intensity, referred to as l(D), to the G peak Raman intensity, referred to as l(G), indicates the amount of defects present within the graphene. This is referred to as the l(D) / l(G) ratio. The distance between defects is a measure of the amount of disorder. Given the distance between defects is greater than approximately 4 nm; the lower the I (D) / l (G) ratio, the greater the distance between defects, thus, the amount of disorder is lower. In addition to this, the full width at half maximum (FWHM) of D, G, 2D (also referred to as G’), D’ peaks can be used to evaluate the level of disorder as discussed in E. H. Martins Ferreira et al. 2010, “Evolution of the Raman spectra from single-, few-, and many-layer graphene with increasing disorder”, PHYSICAL REVIEW B. If FWHM of D, G, 2D (also referred to as G’), and D’ Raman peaks at a laser excitation wavelength of 514.5 nm (2.41 eV), are reaching values lower than 20 cm-1 , 20 cm-1 , 35 cm-1 , and 10 cm-1 respectively, then the distance between zero dimensional point-like defects is expected to be greater than approximately 4 nm.

[0146] The composites formed by the method of the present invention which comprise graphene may have an I (D) / l (G) ratio of less than 0.75, less than 0.6 or preferably less than 0.5, at a laser excitation wavelength of 532 nm (2.33 eV). Thus, the composites formed by the method of the present invention may have an I (D) / l (G) ratio of from 0.01 to 0.75, 0.02 to 0.65 or 0.04 to 0.55, at a laser excitation wavelength of 532 nm (2.33 eV). Given the distance between defects is greater than approximately 4 nm and a laser excitation wavelength of 532 nm (2.33 eV); an I (D) / l (G) ratio less than 1 indicates that the defects are greater than 9.5 nm apart.

[0147] It is also possible to assess the nature of the graphene defects using Raman spectroscopy. In general, defects in graphene are considered to be anything that breaks the symmetry of the infinite carbon hexagonal lattice. This therefore includes edges, vacancies and changes in carbon-hybridization (e.g. sp2into sp3). An sp3defect is due to an additional atom being present out-of-plane of the graphene layer resulting in an sp3hybridized carbon atom or atoms. A vacancy defect is due to one or more missing atoms of a 2D material layer. An edge defect is due to a graphene sheet not being infinitely large and therefore having an edge.

[0148] Partially oxidised graphene and pristine graphene can be distinguished from graphene oxide, functionalised graphene and reduced graphene oxide using Raman spectroscopy, as discussed herein. Graphene oxide and functionalised graphene contain high amounts of sp3defects. Reduced graphene oxide is formed from the reduction of graphene oxide with reducing agent or temperature treatment. Reduced graphene oxide also includes a large amount of vacancy defects, as a result of the removal of oxygen to leave holes in the hexagonal lattice. Thus, graphene oxide and reduced graphene oxide typically have an I (D) / I(G) ratio of above 0.8 or FWHM of D, G, 2D (in some literature called G’) peaks values higher than 70, 70, 150 cm-1respectively. Conversely, partially oxidised graphene oxide has fewer oxygen atoms compared to graphene oxide but has not undergone harsh reduction processes like reduced graphene oxide. Thus, more of the hexagonal structure is maintained, meaning fewer sp3and vacancy defects. The number of defects can be assessed by measuring the I (D) / l (G) ratio or FWHM of peaks as discussed above.

[0149] The presence of sp3defects and vacancy defects can have a detrimental impact on the usefulness of the final composite. Thus, it is desirable for the number of sp3and / or vacancy defects to be minimised.

[0150] The ratio of the intensity of the Raman D peak, referred to as l(D), to the Raman D’ peak, referred to as l(D’), signifies the type of defects present in the sample. This is referred to as the l(D) / l(D') ratio. A ratio less than approximately 3.5, at a laser excitation wavelength of 514.5 nm (2.41 eV) indicates contributions from edge defects dominate. A ratio of approximately 7 indicates the presence of vacancy defects and a ratio of approximately 13 or more suggests sp3 defects.

[0151] The graphene containing composites of the present invention may have a FWHM- (G) (Full Width at Half Maximum of the graphene Raman G peak of a raman spectra) of lower than 70 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Preferably, the FWHM-(G) will be lower than 60 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). More preferably, the FWHM-G will be lower than 50 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Even more preferably, the FWHM-(G) will be lower than 40 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Most preferably, the FWHM-(G-) will be lower than 30 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV).

[0152] The graphene containing composites of the present invention may have a FWHM- (2D) (Full Width at Half Maximum of the graphene Raman 2D peak) of the present invention graphene containing composites may be lower than 100 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Preferably, the FWHM-(2D) will be lower than 80 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). More preferably, the FWHM-(2D) will be lower than 60 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Even morepreferably, the FWHM-(2D) will be lower than 50 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). The graphene containing composites of the present invention may have an l(D) / l(D’) ratio of from 0.01 to 7, 0.01 to 4.5, 0.01 to 3.5 or preferably from 0.1 to 3.45 at a laser excitation wavelength of 532 nm (2.33 eV). Thus, the composites of the present invention will preferably have minimal sp3 defects and more preferably minimal vacancy defects.

[0153] Graphene oxide typically comprises a weight percentage of oxygen of above 15 wt.%. In the scope of the present invention, the term “partially oxidised graphene” can be interpreted as a graphene oxide which only comprises oxygen in an amount of up to 15% of the total weight of the graphene, e.g. 5 to 15 wt.%. Typically, partially oxidised graphene would include oxygen in an amount of up to 10% of the total weight of the graphene. As discussed above, the term “pristine graphene” refers to graphene which has not been chemically modified.

[0154] The processes described within may be performed with graphene that is not substantially chemically modified, i.e. pristine graphene. Usually, the quality of such graphene is achieved using liquid phase exfoliation method. However, some graphene production methods may introduce some degree of oxidation (below 15%), resulting in partially oxidised graphene, as a result of slight oxidation facilitating faster exfoliation. However, unlike previous work involving graphene oxide, this degree of oxidation does not necessarily increase the processability of the graphene, and preferably the partial degree of oxidation / the degree of defects is reduced to as low as possible to reduce the impact on the conductive properties of the final composite material.

[0155] A “graphene-based” material refers to a 2D layered material which comprises a hexagonal carbon skeleton, such as graphene, graphene oxide, reduced graphene oxide, functionalised graphene (e.g. fluorinated graphene). Thus, a material that is “not graphene based” refers to materials which could be termed as “inorganic layered compounds”. Thus, the term ‘inorganic compound’ refers to any compound made up of two or more elements which forms layered structures in which the bonding between atoms within the same layer is stronger than the bonding between atoms in different layers. Many examples of inorganic layered compounds have covalent bonds between the atoms within the layers but van der Waals bonding between the layers. The term ‘inorganic layered compound’ is not intended to encompass graphene or graphene derivatives.

[0156] Particular examples of non-graphene based layered inorganic compounds to which the present invention can be applied include:• Graphene-like materials, such as hexagonal boron nitride (hBN), fluorographene, boron carbon nitride (BCN), SiC, Si2BN, silicene, germanene, stanene, borophene, graphyne, plumbene.• Phosphorenes (black phosphorus).• 2D Chalcogenides:• Transition metal dichalcogenides (TMDCs) such as M0S2, WS2, MoSe2, WSe2.• Layered Semiconductors: GaSe, GaTe, InSe, Bi2Ses, etc.• 2D Oxides: MnO2, WO3, TiO2, MoOs, V2O5, TaOs, RUO2, NaNbOs, a-Fe2Os, Nb20s, CO3V2O8, Nai.osVsOs, etc.• Layered Cu Oxides.• Perovskite-type: Methylammonium lead halide (CHsNHsPbh), Cesium lead halides (CsPbX3), Bi4Ti30i2, Ca2Ta2TiOio, etc.• Hydroxides: Ni(OH)2, Eu(OH)2, ZnAI-layered double hydroxide (LDH).• MXenes: Sc2C(OH)2, SC2CO2, Ti2CO2, Titanium Carbide (TisC2).

[0157] Graphene-like materials have their lattice structure arranged as honeycomb and the atoms are held by sp2 or sp3 hybridization.

[0158] Phosphorene’s structure consists of sp3 hybridization of phosphorus atoms within a 2D plane. Defect-free phosphorene has nonzero band gap and high electron mobility.

[0159] Chalcogenides are materials containing one or more chalcogen elements (e.g. S, Se or Te) as a substantial constituent. TMDCs are structured such that each layer of the compound consists of three atomic planes: a layer of transition metal atoms (for example Mo, Ta, W) sandwiched between two layers of chalcogen atoms (for example S, Se or Te). Thus, in one embodiment, the TMDC is a compound of one or more of Mo, Ta and W with one or more of S, Se and Te. There is strong covalent bonding between the atoms within each layer of the transition metal chalcogenide and predominantly weak Van der Waals bonding between adjacent layers. TMDC can be semiconducting, metallic, and insulating. For instance, semiconducting dichalcogenides are MoTe2, WTe2, ZrS2, ZrSe2, and metallic dichalcogenides include NbSe2, NbS2, TaS2, TiS2, NiSe2.

[0160] 2D oxide compounds are all constituted of stacked negatively charged slabs, corner- and / or edge-shared MOe (M = Ti, Nb, Mn, Ta, W) octahedral units, and alkali metal cations (K+, Rb+, Cs+) occupying the inter- layer space. A common feature of these layered oxides is their cation-exchange property involving interlayer alkali metal ions.

[0161] The general formula of M2+M3+(OH) An-mH O (M2+= Mg2+, Fe2+, 1-x x2 x / n 2 Co2+, Ni2+, Zn2+, etc.; M3+ = Al3+, Fe3+, Co3+, etc.) is for layered double hydroxides (LDH). LDH consists of octahedral-brucite-like M(OH)2 layers and charge-balancing anions (An-), the host layer [M2+I-XM3+X(OH)2]X+is positively charged with a charge density determined by the molar fraction x (0.2 < x < 0.33) of M3+. In addition, a new family of layered rare-earth hydroxide [RE(OH)2.5XH20] [An-]o.5 / n (RE = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) was synthesized and characterized with positively charged layers of [RE3+(OH)2.5XH2O]05+and charge-balancing anions, An", (Cl , NO3, etc.) sandwiched between the layers.

[0162] 2D perovskites can be defined as (A’)mAn-i BnX3n+i , where A’ is cation (m = 1 or 2) which intercalates between the inorganic An-iBnX3n+i sheets (n - thickness of the inorganic layers).

[0163] Materials belonging to the MXene group are layered transition metal carbides and carbonitrides. The structure can be defined with the general formula of Mn+iXnTx, where M stands for early transition metal, X stands for carbon and / or nitrogen and Txstands for surface terminations (mostly =0, -OH or -F), and usually n is between 1 and 4. MXenes exhibit high electric conductivity (10000-1500 Scm-1) combined with hydrophilic surfaces that can be tuned with solvents. They are synthesized from ceramic precursor MAX phases by removing the single atomic layer "A" where M stands for Ti, Mo, W, Nb, Zr, Hf, V, Cr, Ta, Sc, A stands for Al, Si, and X stands for C, N.

[0164] TMDCs are structured such that each layer of the compound consists of three atomic planes: a layer of transition metal atoms (for example Mo, Ta, W) sandwiched between two layers of chalcogen atoms (for example S, Se orTe). Thus, in one embodiment, the TMDC is a compound of one or more of Mo, Ta and Wwith one or more of S, Se and Te. There is strong covalent bonding between the atoms within each layer of the transition metal chalcogenide and predominantly weak Van der Waals bonding between adjacent layers. Exemplary TMDCs include NbSe2, WS2, M0S2, TaS2, PtTe2 and VTe2.

[0165] The term “substantially insoluble” in the context of the present invention means that at least 1000 mass parts of solvent is required to dissolve 1 mass part of solute at standard operating temperatures (e.g. 25°C and 1atm pressure). The term “insoluble”, in the context of the present invention means that greater than 10000 mass parts of solvent is required to dissolve 1 mass part of solute.

[0166] The term ‘viscosity’ in the context of the present invention refers to the dynamic viscosity measured a shear rate of 10 s-1at a temperature of 20°C.

[0167] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0168] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of thesteps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0169] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.EXAMPLESExample 1Composite 1 (a particulate material as defined herein):Process of making Composite 1 (A Particulate Material as defined herein):

[0170] In this example, a 5kg batch of composite material with the recipe [96: 1.9: 0.1 : 2] [NMC, Super P, SWCNT, PVDF] was created. Figure 1 shows a schematic of the process to produce the particulate materials discussed herein.

[0171] The above amounts give the total material requirements for the run. The material was composited as per the steps below:PVDF Dissolution• 7.5wt% stock solution made up o 75g PVDF o 925g NMP (=900 ml) o = 1000g PVDF stock• Dissolved on roller mixer in 11 duran bottle overnight• Remaining 25g of PVDF contained in the CNT dispersionShearing / mixingComponent addition and homogenisation• 3L NMP added to Mixing Vessel prior to any solids addition• CNT dispersion added: o 1250g pre-weighed CNT dispersion poured into the mixing vessel• 15 minute shear at 6000 RPM applied to blend• Conductive additive and binder additions o 95g C-black added o 925g PVDF stock• 10 minute homogenisation @7000 RPM. Temperature not allowed to exceed 42°C• After homogenising, 4.8kg NMC added• Mixed for 15 minutes in mixing vessel at 200 RPM before adding 2 L of methanol to reduce viscosity, aiding transfer to the settling vessel. 10 mins further mixing in mixing vessel with this extra methanol before transfer to the settling vessel.• Further 30 minutes of mixing in the settling vesselPrecipitation / ageing• MeOH pumped directly into the settling vessel to begin precipitation with agitation on high. Methanol added slowly until total of 12.85L MeOH fed l.e. bring total volume to 18L (minus solids)■ Solids = check volume after decanting• Aged for 30 minutes (left mixing in vessel)‘Aging’ defined here as beginning when MeOH addition finishedSettling / initial washes• After aging, settle for 30 minutes• Remove supernatant• Repeat twice: o Add 101 MeOH while agitatingo Agitate for 2 minutes o Settle for 10 mins o Remove supernatant■ Solids layer settled down to 7 L• Added 3 L MeOH to aid transfer to filtration vessel.Filtration / Drying• T ransfer to filtration vessel• Vacuum through base filter• Washed with 5.5 L of MeOH using spray, followed by using vacuum to remove solvent through base filter. Repeat (3x total)• On last wash cycle, hold cake in vessel until dry.• Take solid samples to assess if all solvent has been removed (determined by low Loss On Drying)Particle size analysis of composite 1

[0172] Particle size data was collected using a Mastersizer 3000 using the following protocol:1. With methanol used as dispersant liquid, mixer RPM set to 2500 RPM in the liquid cell2. Powder added gradually until 12% obscuration reached3. Once 12% obscuration reached, 50 measurements are taken, spaced over 15 minutes.4. Each measurement plotted on the graph, traces are shown in varying shades of grey. Plots are shown in Figure 2.5. The peaks highlighted with a vertical line are from the measurement done at the end of the 15 minutes of measurement.Dustiness comparisonMixture 1 :

[0173] The airborne particle number concentration was measured in an Eirich EL1 mixer after agitation. A benchmark powder mixture (Mixture 1) was compared directly to Composite Powder 1. No premixing was performed on the benchmark powder mixture before testing. Testing comprised an agitation step at 1.3 m / s, a rest step of 1 minute, followed by an airborne nanoparticle number concentration measurement of the air inside the mixer for 10 minutes. A measurement of the air with a Condensation Particle Counter provided the data shown in Figure 3. As air was taken into the CPC machine, HEPA-filtered air was used to displace it in the vessel. In separate studies, even adding PVDF into the benchmark powder mixture did very little to impact the level of airborne particles. These studies showed that it was necessary to form a structure with the particulate material process described herein to reduce aerosolization of fine particles from the composition.Example 2Composite 2 (A Particulate Material as defined herein):Process of making Composite 2

[0174] Composition:96NMC: 1 ,9CB:0.1 CNT: 1 PVDF

[0175] Into a glass beaker PVDF binder solution in N-methyl pyrrolidone (2.5 g, 10 w / w %) was added followed by carbon black (0.95 g) and carbon nanotubes (12.5 g of a 0.4 wt% dispersion). Anhydrous N-methyl pyrrolidone (~ 236 mL) was added and subject to shearing process using an I KA T25 homogeniser at 10000 rpm for a time of 15 minutes. The dark solution was then stirred on magnetic plate maintaining a stirrer speed of 600 rpm under gentle blanket of inert gas. To this slurry NMC 811 (Targray) (48.5 g) was added continuing to stir at 600 rpm under gentle flow on inert gas. After this time Methanol (in ratio of 1 :2.5 mixture: methanol) was added dropwise continuing to stir at 450 rpm for 30 minutes.

[0176] The dark mixture was then left upon standing for 30 minutes.

[0177] The supernatant was decanted and the dark composite subjected to vacuum filtration using a Gooch funnel washing with ~ 65 mL (x5 times) of anhydrous MeOH and dried under a blanket of inert gas on the sintered glass filter for 10 minutes.

[0178] Finally, the composite was transferred into a glass crystalliser and dried into a vacuum oven at 50°C for 24h.Electrode 1 (a cathode as defined herein)Electrode 1 composition:Process of making Electrode 1• In a 200 ml Thinky AR-250 mixer pot, composite 2 and PTFE were mixed at 2000 rpm for 2.5 minutes.• When the pot is open, the contents were agitated with a spatula (to break up aggregates and increase surface area).• This process was repeated 6 times.• The dough formed was rolled out to the desired thickness using a rolling pin.• The film was placed on primer-free 1060 alloy aluminium foil, then sandwiched between two steel sheets.• The sheets were calendered at 80 degrees Celsius, gradually reducing the calender gap by 10 urn at a time until the desired thickness was obtained. Between each calendering step, the shims were rotated by 90 degrees.Example 3

[0179] Electrode 1 was assembled into a half-cell and compared to a wet electrode of the following composition.Electrode 2 composition:

[0180] Electrode 2 was made by the following method:1. Add CNTs, CB, & PVDF into a Thinky AR-250, where PVDF is in a pre-dissolved 10wt% solution in NMP2. Dry mix powders for 10 minutes at 2000 RPM3. Add NMC4. Mix powders for 15 minutes, interrupted by a 1 minute 1500RPM degassing step after 10 minutes5. Add in NMP, gradually, with a 1 minute 1500RPM degassing step after each step, mixing at:1. 88% solids content for 5 minutes2. 65% solids content for 5 minutes3. 60% solids content for 5 minutes6. Coat slurry onto primer-free 1060 aluminium foil, and dry at 80 degrees overnight under a vacuumExample 4Process of making Composite 3

[0181] Composition:96.5NMC:1.4CB:0.11CNT:0.8PVDF :0.8PTFE

[0182] Composite 3 was made in the same manner and at the same scale (~50 g) as Composite 2, but with the following differences:1. Material addition was changed to reflect the above composition (96.5NMC:1.4CB:0.11CNT:0.8PVDF:0.8PTFE).2. Methanol addition was increased to 700 ml, and it was combined with the NMP solution by simultaneous solution pouring into vessel undergoing stirring.3. The Gooch funnel washing was with 5x 25 ml portions of methanol.4. The yield of the process was about 46.2 g.

[0183] The particle size distribution obtained for the particulate material (composite 3) is shown in Figure 5. SEM images of this material are shown in Figures 6A and 6B.Electrode 3 (a cathode as defined herein)Electrode 1 composition:Process of making Electrode 3• In a 200 ml Thinky AR-250 mixer pot, 5 g of composite 3 and an appropriate balance of PTFE were mixed with the following steps. In between each step, thepot was opened, and a spoon was used to lightly break up, agitate, and knead the mixture. o Add powders into the pot, mix at 500 RPM for 30 seconds o Mix at 500 RPM for 30 seconds o Mix at 500 RPM for 30 seconds o Mix at 500 RPM for 30 seconds o Mix at 1000 RPM for 60 seconds o Mix at 1000 RPM for 60 seconds o Mix at 1000 RPM for 60 seconds o Mix at 1000 RPM for 60 seconds• The dough formed was rolled out into a sheet using a rolling pin. After a film was formed, the film was repeatedly i) folded in half, ii) rotated through 90 degrees, and iii) rolled again. Folding in half was not strictly necessary if the electrode appeared homogeneous. This process was performed until an areal loading of 200 grams per square centimetre was reached. Smaller diameter rollers were used during rolling if thinning was not occurring.• The film was placed on primer-free 1060 alloy aluminium foil, then placed between two steel shims.• The electrode film was laminated to the aluminium foil in a multi-step calendering process, where the calender rollers were held at 120 degrees Celsius. Calendering was performed 12 times, where the calender gap was reduced by ~10 urn every 4 passes until the desired densification was obtained (corresponding to a density of 3.3 g / cc). Between each calendering step, the shims were rotated by 90 degrees.Process of making Electrode 4• In a 200 ml Thinky AR-250 mixer pot, NMC (19.1g), and CB (0.4 g) were added. o Mixing was performed using the Thinky AR-250 at 2000 rpm for 2.5 minutes. o When the pot is open, the contents were agitated with a spatula (to break up aggregates and increase surface area). o The pot was cooled to room temperature before continuing.• The above mixing process was repeated 4 times.• 0.5 g PTFE was added to the mixture o Mixing was performed at 2000 RPM for 2.5 minutes o When the pot was opened after mixing, the dough was agitated to ensure good mass transfer and no isolated PTFE particles.• The above process was repeated 6 times.• The dough formed was rolled into a sheet using a rolling pin. Rolling was repeated by folding the sheet in half and repeating rolling at 90-degree angle until no inhomogeneities could be seen, and an areal loading of 200 grams per square metre was reached. Smaller diameter rollers were used during rolling if thinning was not occurring.• The film was placed on primer-free 1060 alloy aluminium foil, then sandwiched between two steel shims.• The sheets were calendered at 120 degrees Celsius, starting at 80 microns and gradually reducing the calender gap by 10 urn at a time until the desired thickness (corresponding to a density of 3.3 g / cc) was obtained. Between each calendering step, the shims were rotated by 90 degrees.Process of testing peel strengthPeel strength was tested by adhering a 25mm wide strip of electrode face-down to a support substrate, followed by measuring the force to pull the foil at a 180-degree angle to the surface. The force over the pull period is reported as a boxplot in figure 7. The top two rectangles are from electrode 3, while the bottom two rectangles are from electrode 4.Process of testing electrochemical performanceElectrodes were assembled into half cells against Li metal. Voltage range: 2.75-4.3 V. Electrolyte used: 1M LiPF6 in DEC: EC 50:50.Process of testing PSD for Composite 3Particle Size Distribution was tested using a Mastersizer 3000 with a liquid dispersion attachment. Measurements recorded over 15 minutes are plotted on top of each other to produce the trace in the figures. The liquid dispersing attachment was set to 1500 RPM to disperse the powder.

Claims

CLAIMS1 . A composite material for use as a cathode film, comprising: a) a particulate material comprising: i) a cathode active material, ii) a first polymeric binder; iii) a conductive material; wherein the first polymeric binder attaches the cathode active material to the conductive material; and the particulate material has a particle size of at least 1 micron; b) a second polymeric binder material which binds the particles of the particulate material together; wherein: the cathode active material is present in an amount of 85 to 99.5 wt.%; the first polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the second polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the conductive material in an amount of 0.01 to 15 wt.%; based upon the total weight of the composite material; and wherein the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1.

2. The composite material according to claim 1 , wherein the active material is present in an amount of from 85 to 99.5 wt.%, preferably from 90 to 99 wt.%, or more preferably from 94 to 98.5 wt.%.

3. The composite material according to claim 1 or claim 2, wherein the first polymeric binder is present in an amount of from 0.1 to 5 wt.%, preferably from 0.25 to 3 wt.%, more preferably from 0.5 to 1 .5 wt.%.

4. The composite material according to any one of the preceding claims, wherein the second polymeric binder is present in an amount of from 0.1 to 5 wt.%, preferably from 0.25 to 3 wt.%, or more preferably from 0.5 to 1 .5 wt.%.

5. The composite material according to any one of the preceding claims, wherein the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1 ; preferably from 0.67:1 to 1.5:1 ; more preferably from 0.9:1 to 1.1 :1 ; most preferably the weight ratio of the first polymeric binder to second polymeric binder is 1 :1.

6. The composite material according to any one of the preceding claims, wherein the conductive material is present in an amount of from 0.1 to 10 wt.%, preferably from 0.5 to 6 wt.%, more preferably from 1.0 to 2.5 wt.%.

7. The composite material according to any one of the preceding claims, wherein the cathode active material is selected from:• oxides, nitrides, carbides, sulfides, phosphides, and selenides of Silicon, Germanium, Antimony, Tin, Lead, Bismuth, Zinc, Aluminium, Titanium, Iron, Nickel, Manganese, Cobalt, or Cadmium, and their mixtures, or lithium- containing composites;• Lithium transition metal phosphates, e.g. lithium nickel phosphate, lithium cobalt nickel phosphate, lithium iron phosphate and lithium mixed-transition- metal phosphates;• lithium titanate, lithium manganate, lithium aluminate, lithium-containing titanium oxide; and• lithium transition metal oxides, such as:• NMC (lithium nickel manganese cobalt oxide) and its stoichiometric variants, e.g. NMC910, NMC811 , NMC622, NMC631 , NMC532, NMC111 ;• NCA (Lithium nickel cobalt aluminium oxide) and its stoichiometric variants; optionally wherein the cathode active material is selected from one or more of LTO, NMC, NCA, LFP, or silicon (e.g. 300 mesh silicon chunks); further optionally wherein the cathode active material is NMC, for example NMC 910, NMC 811 , NMC 622, NMC 532 or NMC 111.

8. The composite material according to any one of the preceding claims, wherein the first polymeric binder is selected from one or more of PVDF, PU, EVOH, PVDF-HFP, chitosan and PEO; optionally wherein the first polymeric binder is PVDF.

9. The composite material according to any one of the preceding claims, wherein the second polymeric binder is PTFE.

10. The composite material according to any one of the preceding claims, wherein the conductive material comprises a conductive carbon material.

11. The composite material according to any one of the preceding claims, wherein the conductive carbon material is selected from one or more of carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanotubes and graphene (e.g. pristine graphene), and other hard carbons.

12. The composite material according to any one of the preceding claims, wherein the conductive material comprises one or more of pristine graphene, carbon black, or carbon nanotubes (e.g. single wall carbon nanotubes).

13. The composite material according to any one of the preceding claims, wherein the particulate material has a particle size of between 4 and 400 microns; optionally wherein greater than 50% of the volume of the particulate material has a particle size of between 100 and 300 microns.

14. A cathode comprising: a) a metallic substrate; b) a film comprising the composite material according to any one of claims 1 to 13.

15. A cathode according to claim 14, wherein the film is directly attached to the metallic substrate.

16. A cathode according to claim 14 or 15, wherein there is no primer layer between the metallic substrate and the film.

17. A cathode according to any one of claims 14 to 16, wherein the metallic substrate is a current collector, preferably an aluminium current collector.

18. A cathode according to any one of claims 14 to 17, wherein the film has a thickness of between 30 microns and 300 microns; optionally the film has a thickness of between 60 microns and 200 microns.

19. A battery comprising a cathode according to any one of claims 14 to 18; optionally wherein the battery is a lithium ion battery.

20. A process for fabricating a composite material, the process comprising; i) preparing particulate material comprising a cathode active material, a first polymeric binder and a conductive material; wherein the first polymericbinder attaches the cathode active material to the conductive carbon material; and the particulate material has a particle size of at least 1 micron; ii) mixing the particulate material with a second polymeric binder such that the individual particles of the particulate material are attached to one another by the second polymeric binder.

21. The process according to claim 20, wherein: the cathode active material is present in an amount of 85 to 99.5 wt.%; the first polymeric binder is present in an amount of 0.01 to 7.5 wt.%; the second polymeric binder is present in an amount of 0.01 to 7.5 wt.%; and the conductive material in an amount of 0.01 to 15 wt.%; based upon the total weight of the composite material; optionally wherein the weight ratio of first polymeric binder to second polymeric binder is from 0.5:1 to 2:1.

22. A process for fabricating a cathode, comprising: i) fabricating a composite material as defined in claim 20 or 21 ; ii) forming the composite material into a film; iii) coating the film onto a metal substrate.

23. The process of claim 22, wherein the metal substrate is substantially free of any primer during the coating of the film.

24. A composite material, obtained by, obtainable by or directly obtained by the process according to claim 20 or 21.

25. A cathode, obtained by, obtainable by or directly obtained by the process according to claim 22 or 23.

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