composites

Abstract

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.

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] Traditional batteries, including 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. The two electrodes are separated by a porous separator, and the movement of lithium in a liquid electrolyte from the anode to the cathode is what drives a concurrent flow of electrons to deliver the battery’s power to external circuits. The reverse occurs on charging of the battery.

[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). Although existing primers are available, 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 of the component solids can occur if the carbons are not properly dispersed,which is likely when using standard mixing techniques. This can lead to uneven distribution of the components in the composite, 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 composite material suitable for use in a dry electrode coating process, the composite comprising a cathode active material, a conductive carbon material, a first polymeric binder and PTFE, wherein the individual particles of the cathode active material are attached to the conductive carbon material by the first polymeric binder, and further comprise PTFE particles on their surface.

[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 process for fabricating a composite suitable for use in a dry electrode coating process, the process comprising:contacting a PTFE suspension with a particulate material comprising a cathode active material, a conductive carbon material and a first polymeric binder; wherein the PTFE is in the form of a stable colloidal suspension; andcoagulating the PTFE in the presence of the particulate material to form a composite.

[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 a cathode activematerial, a first polymeric binder, a conductive carbon material and PTFE. 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 cathode 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 solid-state 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 cathode active material may be lithium-active or sodium active material.

[0022] The cathode 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 cathode active material is selected from:LTO (lithium titanates);NMC (Lithium nickel manganese cobalt oxides);NCA (Lithium nickel cobalt aluminium oxide);LFP (lithium iron phosphate); orSilicon.

[0024] More suitably, the cathode active material is selected from LTO, NMC, NCA or LFP.

[0025] Most suitably, the cathode 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.

[0026] Suitably, the active material may be coated or contain one or more dopants. For example, the active material may contain a layer of carbon on the surface of the particles.Binder Materials

[0027] The one or more binder material comprised within a battery are present to primarily adhere the electrode film to a substrate such as a current collector. Multiple binders are utilised in the present invention. The binders utilised in the present invention are preferably polymeric binders, for example flexible polymeric binders.

[0028] The composites of the present invention comprise a first polymeric binder as defined herein, and a second polymeric binder which is a polytetrafluoroethylene (PTFE) binder.

[0029] Suitably, in the processes of forming the composites of the present invention, the PTFE is in the form of a stable suspension. Suitably, the PTFE suspension is a PTFE latex or colloid (i.e. a stable suspension comprising the PTFE polymer dispersed in water).

[0030] Suitably, the PTFE suspension may comprise from 20 to 80 wt.% of PTFE in water, more suitably from 50 to 70 wt.%.

[0031] In the processes of forming the composites of the present invention, the PTFE suspension is coagulated to form solid PTFE polymer.

[0032] Suitably, the first polymeric binder is or comprises a non-fibrilizable binder.

[0033] 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, xanthan gum, locust bean gum, guar gum, 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), polystyrene, polyanthracene, poly-L-lactic acid, polyethylene, 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).

[0034] Suitably the first polymeric binder comprises a gum (e.g. xanthan gum, locust bean gum, guar gum, methyl cellulose, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC) or sodium carboxymethylcellulose (Na-CMC)), a hydrophilic polymer (e.g. polyvinyl alcohol or ethylene vinyl alcohol), a hydrophobic polymer (e.g. polyethylene), or a fluoropolymer (e.g. PVDF or PVDF-HFP).

[0035] In certain embodiments, the first polymeric binder is a non-fluorinated polymer.

[0036] Suitably the first polymeric binder comprises a gum, for example xanthan gum, locust bean gum, guar gum, methyl cellulose, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC) or sodium carboxymethylcellulose (Na-CMC).

[0037] Suitably the first polymeric binder comprises a hydrophilic polymer, for example polyvinyl alcohol or ethylene vinyl alcohol.

[0038] Most suitably, the first polymeric binder is PVDF.Conductive carbon material

[0039] The conductive carbon 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.

[0040] The conductive carbon material comprises at least one carbon-based conductive additive, and may include one or more “high aspect ratio” materials, such as a 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.

[0041] Preferred high aspect ratio materials include carbon nanotubes and two-dimensional (2D) layered materials, such as graphene-based materials and inorganic layered materials.

[0042] 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+1-xM3+x(OH)2An-x / n·m2(where M2+= Mg2+, Fe2+, Co2+, Ni2+, Zn2+, etc.; M3+= Al3+, Fe3+, Co3+, etc.; and A = (CO3)2-,Cl-, (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, α-Fe2O3, Nb2O5, Co3V2O8, Na1.08V3O8, etc.• Layered Cu Oxides.• Perovskite-type e.g. Methylammonium lead halide (CH3NH3Pbl3), Cesium lead halides (CsPbXs), Bi4Ti3O12, Ca2Ta2TiO10, etc.• Hydroxides, e.g. Ni(OH)2, Eu(OH)2, ZnAI-layered double hydroxide (LDH).• MXenes: Sc2C(OH)2, Sc2CO2, Ti2CO2, Titanium Carbide (Ti3C2).

[0043] 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.

[0044] 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 graphenewith an oxygen content less than 15 atom%. Suitably, the 2D material is graphene with a FWHM Raman peak of less than 60 cm-1.

[0045] Preferably, the conductive carbon material comprises one or more of carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanotubes, and graphene (e.g. pristine graphene), or other hard carbons. Preferably, the conductive carbon material comprises one or more of pristine graphene, carbon black, or carbon nanotubes.

[0046] Suitably, the conductive carbon material comprises one or more of pristine graphene, carbon black, or carbon nanotubes (e.g. single wall carbon nanotubes). More suitably, the conductive carbon material comprises a combination of carbon black and at least one of pristine graphene or carbon nanotubes. Most suitably, the conductive carbon material comprises carbon black and single wall carbon nanotubes.

[0047] In preferred embodiments, the conductive carbon material comprises at least one high aspect ratio carbon-based material, such as for example pristine graphene or carbon nanotubes (such as single walled carbon nanotubes). 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, or 4: 1 to 19: 1.

[0048] In a particular embodiment, the conductive carbon material comprises carbon black and single wall carbon nanotubes in a weight ratio of from 4: 1 to 19: 1, respectively.

[0049] In certain embodiments, the conductive carbon material may comprise only carbon black.Composites of the Present Invention

[0050] As discussed above, the present invention provides a composite comprising a cathode active material, a conductive carbon material, a first polymeric binder, and PTFE, wherein the individual particles of the cathode active material are attached to the conductive carbon material by the first polymeric binder, and further comprise PTFE particles on their surface.

[0051] Suitably, the PTFE serves to bind the smaller particles of the particulate material together.

[0052] Suitably, the composite material has a particle size of from 30 to 300 microns, more suitably from 40 to 275 microns, most suitably from 50 to 250 microns.

[0053] Suitably, the composite material comprises:the cathode active material in an amount of from 85 to 99.5 wt.%;the first polymeric binder is present in an amount of from 0.01 to 7.5 wt.%;the PTFE binder is present in an amount of from 0.01 to 7.5 wt.%;the conductive carbon material in an amount of from 0.01 to 15 wt.%;based upon the total dry weight of the composite material;

[0054] Suitably, the weight ratio of PTFE to first polymeric binder is from 0.5:1 to 2:1, e.g.0.5:1 to 1.5:1

[0055] Suitably, the first polymer binder, cathode active material and conductive carbon materials are selected from any of the materials described herein.

[0056] Suitably, the composites of the invention comprise a cathode active material in an amount of from 90.0 to 99.0 wt.%, based upon the total dry weight of the composite material, more suitably from 94.0 to 98.0 wt.%, or most suitably from 95.0 to 97.0 wt.%.

[0057] Suitably, the composites of the invention comprise a conductive carbon material in an amount of from 0.5 to 8 wt.%, based upon the total dry weight of the composite material, more suitably from 0.5 to 3.0 wt.%, or most suitably from 1.5 to 2.5 wt.%.

[0058] Suitably, the composites of the invention comprise a first polymeric binder in an amount of from 0.05 to 4.0 wt.%, based upon the total dry weight of the composite material, more suitably from 0.25 to 2.5 wt.%, or most suitably from 0.75 to 1.5 wt.%.

[0059] Suitably, the composites of the invention comprise PTFE in an amount of from 0.25 to 4.0 wt.%, based on the based upon the total dry weight of the composite material, more suitably from 0.5 to 2.0 wt.%, or most suitably from 0.75 to 1.5 wt.%,.

[0060] Suitably, the weight ratio of PTFE to first polymeric binder is from 0.2: 1 to 20: 1. For example, the weight ratio of PTFE to first polymeric binder may be 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 PTFE to first polymeric binder is 1:1.

[0061] The composites formed in the present invention may be in the form of a solid cohesive agglomerated particles, for example a powder particulate material. The powder may be formed into a dough. The powder or dough may be processed into a film.

[0062] Suitably, the composites have a particle size of from 30 to 300 microns. More suitably from 50 to 250 microns.

[0063] Suitably, the composites have a press density of from 2.0 to 4.0 g cm-3, more suitably from 2.5 to 3.8 g cm-3.

[0064] A film comprising (or consisting of) the composite of the invention may have a thickness of from 30 to 300 microns, more suitably from 60 microns to 200 microns.

[0065] The composites of the present invention may be utilised in dry coating processes to prepare electrodes.

[0066] Suitably, the composites of the present invention further comprise trace amounts of a surfactant, e.g. 0.001 to 0.2wt.%, more suitably 0.005 to 0.1wt.%, based on the total dry weight of the composite material.

[0067] Suitably the surfactant is any of those defined herein, e.g. branched alcohol ethoxylates or branched secondary alcohol ethoxylates.

[0068] Suitably, the surfactant has a structure according to one of the formulas below:wherein n is an integer from 4 to 15. Preferably, n is an integer from 6 to 14.Cathode utilising composites of the invention

[0069] As discussed herein, the invention provides a cathode comprising:a) a metallic substrate;b) a film comprising the composite material as defined herein.

[0070] 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.

[0071] Suitably, the metallic substrate is a current collector, preferably an aluminium current collector.

[0072] Suitably, the film has a thickness of 30 to 300 microns, more suitably from 60 microns to 200 micronsBatteries utilising composites of the invention

[0073] 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, counter electrode and electrolyte in a sealed container. The counter electrode may be an anode or a cathode as appropriate.

[0074] Advantageously, the batteries comprising a composite of the invention may not need a primer layer between the electrode film and the current collector.

[0075] Suitably, the battery is a lithium ion battery.Processes of the Present inventionPreparation of the Composite Material

[0076] As discussed herein, the invention provides a process for fabricating a composite material, the process comprising;contacting PTFE with a particulate material comprising a cathode active material, a conductive carbon material and a first polymeric binder; wherein the PTFE is in the form of a stable colloidal suspension; andcoagulating the PTFE in the presence of the particulate material to form a composite.

[0077] Suitably, the coagulation is not induced by shear aggregation.

[0078] Suitably, the PTFE is not subjected to conditions which will impart significant fibrilization such as high temperature and high shear. The degree of fibrilization will be possible to assess using imaging techniques such as SEM.

[0079] In the context of the present invention, “significant fibrillation” refers to fibrillation which is visible using SEM.

[0080] Advantageously, it is possible to prepare composites with no, or very little, fibrilization relative to composites formed by dry mixing processes. In such composites, PTFE fibrilization is not evident in composite after formation.

[0081] In some embodiments, the PTFE is not subjected to shear higher than 105s-1over the course of the process. Suitably, the PTFE is not subjected to shear higher than 104s-1over the course of the process.

[0082] In certain embodiments, the cathode active material is not subjected to shear higher than 105s-1over the course of the process. Suitably, the cathode active material is not subjected to shear higher than 104s-1over the course of the process.

[0083] Suitably, the PTFE is not subjected to temperatures above 19°C during the course of the process. For example, the process may be performed at temperatures from 0°C to 15°C, more suitably 0°C to 5°C.

[0084] Suitably, the PTFE is in the form of a stable colloidal suspension such as a latex suspension. Suitably the latex suspension is an aqueous suspension.

[0085] Suitably, the PTFE latex suspension comprises one or more a surfactant, for example Tergitol.

[0086] Suitably, the surfactant is selected from hydrocarbon surfactants, i.e. the surfactant is non-fluorinated. The surfactant may be non-ionic or anionic.

[0087] The surfactant may have the general formula:wherein:Ri represents a linear or branched aliphatic hydrocarbon group having at least 6 carbon atoms, preferably 8 to 18 carbon atoms,R2 represents an alkylene unit having 3 or 4 carbon atoms,Rs represents hydrogen, a (1 -3C)alkyl group, or a (1-3C)hydroxyalkyl group, n has a value of 0 to 40,m has a value of 0 to 40,and the sum of n+m is at least 2.

[0088] The surfactant may be selected from nonionic hydrocarbon surfactants. A nonionic hydrocarbon surfactant does not contain a charged group but has a hydrophobic portion that is often is a long chain hydrocarbon. The hydrophilic portion of the nonionic surfactant typically contains water soluble functionality such as a chain of ethylene ether derived from polymerization of ethylene oxide. Rather than this structure, some nonionic surfactants are block copolymers with polyalkylene oxide blocks of different types, e.g. polyethylene oxide and polypropylene oxide.

[0089] Nonionic hydrocarbon surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, glycerol esters, their derivatives and the like. More specifically examples of polyoxyethylene alkyl ethers are polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether and the like; examples of polyoxyethylene alkyl phenyl ethers are polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether and the like; examples of polyoxyethylene alkyl esters are polyethylene glycol monolaurylate, polyethylene glycol monooleate, polyethylene glycol monostearate and the like; examples of sorbitan alkyl esters are polyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate and the like; examples of polyoxyethylene sorbitan alkyl esters are polyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate and the like; and examples of glycerol esters are glycerol monomyristate, glycerol monostearate, glycerol monooleate and the like. Also examples of their derivatives are polyoxyethylene alkyl amine, polyoxyethylene alkyl phenylformaldehyde condensate, polyoxyethylene alkyl ether phosphate and the like. Particularly preferable are polyoxyethylene alkyl ethers and polyoxyethylene alkyl esters.

[0090] Examples of such ethers and esters are those that have an HLB value of 10 to 18. More particularly there are polyoxyethylene lauryl ether (EO: 5 to 20. EO stands for an ethylene oxide unit.), polyethylene glycol monostearate (EO: 10 to 55) and polyethylene glycol monooleate (EO: 6 to 10).

[0091] Suitable nonionic hydrocarbon surfactants include octyl phenol ethoxylates such as the Triton® X series supplied by Dow Chemical Company:

[0092] Preferred nonionic hydrocarbon surfactants are branched alcohol ethoxylates such as the Tergitol® 15-S series supplied by Dow Chemical Company and branched secondary alcohol ethoxylates such as the Tergitol® TMN series also supplied by Dow Chemical Company. The structures of the surfactants in the Tergitol® TMN series are described in WO2015081055 as follows:3HCCH — CHSOHTergitol®TMN-6 (n ~ 8)TMNT-10 (n ~ 11)TMN-100 (n~ 10)

[0093] Ethylene oxide / propylene oxide copolymers such as the Tergitol® L series surfactant supplied by Dow Chemical Company are also useful as nonionic surfactants in this invention.

[0094] Yet another useful group of suitable nonionic hydrocarbon surfactants are difunctional block copolymers supplied as Plutonic® R series from BASF, such as:AARAB R.31R. I {ii- A-0)RO ( Al- i-9)10R5 {ii-0, n-H)25 4 (ni-22,ii-2

[0095] Another group of suitable nonionic hydrocarbon surfactants are tridecyl alcohol alkoxylates supplied as Iconol® TDA series from BASF Corporation.H u H HleoisAlSTDA-A (« 6)IAAA0 = 11 - 10)

[0096] Non- ionic, non-fluorinated surfactants as described above can be prepared, for example, by ethoxylation / propoxylation of secondary alcohols. Non-ionic emulsifiers of the type as described above are also commercially available, for example under the trade designation TERGITOL TMN from Dow Chemical Company, for example TERGITOL TMN 6, TERGITOL TMN 10 and TERGITOL TMN 100X.

[0097] A wide range of PTFE suspensions are known in the art, and typically comprises PTFE stabilised by one or more surfactants.

[0098] Particularly preferred surfactants are branched alcohol ethoxylates or branched secondary alcohol ethoxylates. Such surfactants are available commercially, for example those in the TERGITOL TMN family.

[0099] In a preferred embodiment, the surfactant has a structure according to one of the formulas below:wherein n is an integer from 4 to 15. Preferably, n is an integer from 6 to 14.

[0100] Suitably, the first polymeric binder is a non-fibrilizable polymer. More suitably, the non-fibrilizable polymer is selected from PVDF, a gum (e.g. xanthan gum, locust bean gum, guar gum, carboxymethyl cellulose) or a hydrophilic polymer (e.g. polyvinyl alcohol or ethylene vinyl alcohol). Most suitably, the first polymeric binder is PVDF.

[0101] Suitably, the weight ratio of PTFE to first polymeric binder is from 0.2:1 to 20:1.

[0102] Suitably, in the process of the invention:the cathode active material is present in an amount of from 90.0 to 99.0 wt.%; the first polymeric binder is present in an amount of from 0.05 to 4.0 wt.%; and the conductive carbon material is present in an amount of from 0.05 to 8.0 wt.%; the PTFE is present in an amount of from 0.25 to 4.0 wt.%;based upon the total dry weight of the final composite material.

[0103] Suitably, the weight ratio of PTFE to first polymeric binder is from 0.5:1 to 2:1.

[0104] Suitably, in the process of the invention, the cathode active material is present in an amount of from 90.0 to 99.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder, more suitably from 94.0 to 98.0 wt.%, most suitably from 95.0 to 97.0 wt.%.

[0105] Suitably, in the process of the invention, the conductive carbon material is present in a total amount of from 0.05 to 8.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder, more suitably from 0.5 to 3.0 wt.%, most suitably from 1.5 to 2.5 wt.%,.

[0106] Suitably, in the process of the invention, the PTFE is present in an amount of from 0.25 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder, more suitably from 0.5 to 2.0 wt.%, most suitably from 0.75 to 1.5 wt.%.

[0107] Suitably, in the process of the invention, the first polymeric binder is present in an amount of from 0.05 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder, more suitably from 0.25 to 2.5 wt.%, or most suitably from 0.75 to 1.5 wt.%.

[0108] Suitably, the PTFE suspension is coagulated by contacting the PTFE suspension with a coagulating solvent system, wherein the coagulating solvent system comprises one or more antisolvents and / or coagulants which destabilise the PTFE suspension upon contact.

[0109] Examples of coagulants which may be comprised within the coagulating solvent system include acids such as acetic acid, oxalic acid, butanoic acid, phosphoric acid, or sulphuric acid. Suitably, the coagulating solvent system may comprise an aqueous acid solution.

[0110] Dispersants may also act as coagulants in the present invention. The dispersant may be deactivated during the process of the present invention by changing the process conditions, thereby allowing coagulation. Examples of dispersants are those available from BYK.

[0111] An acid or base can also be used as a coagulant by neutralising as appropriate. Some acids have complimentary reactant products such as borate salts which are stabilizing coatings in some cathode active materials.

[0112] Suitably, the coagulating solvent system comprises an antisolvent which destabilises the PTFE suspension, preferably isopropyl alcohol or methanol.

[0113] Suitably, the coagulating solvent system comprises one or more of an acid, base or salt which destabilises the PTFE suspension.

[0114] Suitably, the particulate material is dispersed in the coagulating solvent system prior to the PTFE suspension being contacted with the coagulating solvent system.

[0115] Thus, in certain embodiments the process comprises:i) dispersing the particulate material in the coagulating solvent system;ii) contacting the coagulating solvent system with the PTFE suspension, such that the PTFE suspension is destabilised and PTFE is coagulated in the presence of the particulate material to form a composite.

[0116] Once prepared, the composite material may be coated onto a metal substrate (e.g. an aluminum current collector) by dry coating processes, such as calendaring.

[0117] In certain embodiments of the present invention, the process comprises preparing a particulate material prior and subsequently coagulating the formed particulate material with the PTFE as described herein. For example, in some embodiments, the step of dispersing the particulate material in the coagulating solvent system comprises preparing the particulate material by steps ia to ic below:ia) providing a first dispersion comprising a dispersing solvent and the first polymeric binder dissolved therein; and the first dispersion further comprises a cathode active material and a conductive carbon material dispersed therein;ib) providing an antisolvent in which the first polymeric binder is substantially insoluble, and which will destabilise the PTFE suspension;ic) contacting the first dispersion with the antisolvent to form a solvent mixture, wherein the volume ratio of the dispersing solvent to the antisolvent is above 1:0.01 to below 1:10, e.g. above 1:1 and below 1:5;wherein contacting the first dispersion with the antisolvent results in the precipitation of first polymeric binder in the presence of the cathode active material and conductive carbon material to form a particulate material as defined herein, dispersed in the coagulating solvent system.

[0118] Advantageously, the antisolvent used to precipitate the first polymeric binder to form the particulate material may also be used to destabilise the PTFE suspension during the coagulation step. This means that the solvent mixture formed in the preparation of the particulate material may also be used as a coagulating solvent system. Particularly preferred antisolvents for this purpose include methanol and isopropyl alcohol, which can both precipitate polymers such as PVDF and destabilise a PTFE latex suspension.

[0119] In certain embodiments, the coagulating solvent system comprises an antisolvent which destabilises the PTFE suspension, and also comprises a solvent in which the first polymeric binder is soluble at 25°C.

[0120] Suitably, the volume ratio of the solvent in which the first polymeric binder is soluble to the antisolvent, is from above 1:0.01 and below 1:20, e.g. above 1:1: and below 1:5. The solvent in which the first polymeric binder is soluble may suitably be the same as the dispersing solvent defined above.

[0121] One or more further antisolvents may be added to the solvent mixture prior to contact with the PTFE suspension to adjust the coagulating solvent system.

[0122] Suitably, the antisolvent used to precipitate the first polymeric binder to form the particulate material is selected from dimethyl carbonate, methanol and isopropyl alcohol. More suitably, the antisolvent used to precipitate the first polymeric binder to form the particulate material is selected from methanol and isopropyl alcohol.

[0123] Suitably, during the preparation of the particulate material, the dispersing solvent is NMP.

[0124] Suitably, when the process also comprises the preparation of the particulate material prior to coagulation, the first polymeric binder is PVDF.

[0125] Suitably, when the process also comprises the preparation of the particulate material prior to coagulation, the first polymeric binder is PVDF and the dispersing solvent is NMP.

[0126] The PTFE suspension may be added to the coagulating solvent system. For example, the PTFE suspension may be added dropwise to the coagulating solvent system with stirring.

[0127] Suitably, the coagulating solvent system is mixed throughout the process to maintain uniform dispersion of the particulate material and composite as it is formed. The mixing may comprise sonication, stirring, planetary mixing, shear mixing, or any of the methods disclosed herein. Suitably, the mixing comprises high shear mixing (above 105s'1), low shear mixing (at speeds of 105s-1or below) and / or planetary mixing.

[0128] In a preferred embodiment, the particulate material is dispersed in the coagulating solvent system to achieve a homogenous dispersion of the particulate material prior to addition of the PTFE suspension. The mixing may comprise high shear mixing and / or low shear mixing.

[0129] Suitably, immediately prior to addition of the PTFE suspension, any high shear mixing is removed and the coagulating solvent system is mixed at lower shear, e.g. with stirring.

[0130] Suitably, following addition of the PTFE suspension to the coagulating solvent system, and before drying, the PTFE is not subjected to shear greater than 105s’1.

[0131] Suitably, following addition of the PTFE suspension to the coagulating solvent system, and before drying, the PTFE is not subjected to temperatures greater than 19°C.

[0132] It is understood that not subjecting PTFE to shear greater than 105s'1and temperatures greater than 19°C will minimise the level of fibrillation of the PTFE in the formed composite.

[0133] Following coagulation of the PTFE in the presence of the particulate material, the composite suitably has a particle size of from 30 to 300 microns, more suitably from 40 to 275 microns, most suitably from 50 to 250 microns.

[0134] As mentioned above, in some embodiments of the invention, the particulate material may be pre-prepared and dispersed in an appropriate solvent prior to coagulation. For example, the particulate material may be prepared and dried, or kept in a slurry dispersion.

[0135] In an exemplary embodiment of the invention, the process comprises;ia) providing a first dispersion comprising NMP and PVDF dissolved therein; the first dispersion further comprising a cathode active material and a conductive carbon material dispersed therein;ib) providing an antisolvent in which PVDF is substantially insoluble, and which will destabilise a PTFE suspension as described herein;ic) contacting the first dispersion with the antisolvent to form a coagulating solvent system, wherein the volume ratio of the dispersing solvent to the antisolvent is above 1:0.01 to below 1:10, e.g. above 1:1 and below 1:5; wherein contacting the first dispersion with the antisolvent results in the precipitation of first polymeric binder in the presence of the cathode active material and conductive carbon material to form a particulate material, dispersed in the coagulating solvent system;ii) contacting the coagulating solvent system with a PTFE latex, such that the PTFE latex is destabilised and PTFE coagulates in the presence of the particulate material to form a composite.

[0136] The formed composite material may be separated from the coagulating solvent system by filtration.

[0137] Suitably, substantially all of the PTFE and particulate material used in the process will be comprised within the formed composite material. However, should any of the individual components remain in a non-composited form, they may be separate from the solvent mixture, e.g. by filtration.Preparation of Cathodes

[0138] As discussed herein, the invention provides a process for fabricating a cathode, comprising:i) fabricating a composite material as described herein;ii) forming the composite material into a film;iii) coating the film onto a metal substrate.

[0139] In the processes of the invention, the cathode active material, conductive carbon material, first binder and second binder may be any of those described herein.

[0140] In the process of fabricating a cathode material, suitably the metal substrate is substantially free of any primer during the coating of the film.

[0141] The composite material may be coated onto the metal substrate (e.g. an aluminum current collector) by dry coating processes, e.g. calendaring.

[0142] The invention also provides a composite material, obtained by, obtainable by or directly obtained by the process defined herein.

[0143] The invention also provides a cathode, obtained by, obtainable by or directly obtained by the process defined herein.Particular Embodiments of the Invention

[0144] In an embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder85 - 99.5 wt.% 0.1 - 10 wt.% 0.1 - 5 wt.% 0.1 - 5% wt.%W145] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder90 - 99.5 wt.% 0.1 - 10 wt.% 0.5 - 2.5 wt.% 0.75 -2.5 wt.%

[0146] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder94 - 98.5% wt.% 0.5 - 6% wt.% 0.75 - 1.5 wt.% 0.75 - 1.5 wt.%W147] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder95 - 97 wt.% 1.5 - 2.5 wt.% 0.75 - 1.25 wt.% 0.75 - 1.25 wt.%

[0148] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder96 - 99.5 wt.% 0.05 - 2.5 wt.% 0.05 - 1.25 wt.% 0.3 - 1.6 wt.%

[0149] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder97 -99.5 wt.% 0.1 - 1.3wt.% 0.05- 0.8 wt.% 0.3 - 1.4 wt.%

[0150] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder97.6 -99 wt.% 0.1 - 1 wt.% 0.1 -0.6wt.% 0.3 -0.8 wt.%

[0151] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder95.5 - 96.5 wt.% 1.8 - 2.2 wt.% 0.9- 1.1 wt.% 0.9- 1.1 wt.%

[0152] In a specific embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material, first polymeric binder and PTFE are present in the following relative amounts:active material conductive carbon first polymeric PTFE material binder96 wt.% 2 wt.% 1 wt.% 1 wt.%

[0153] In an embodiment of the composites, electrodes and processes of the invention, and the composites of the invention:a. the first polymeric binder is PVDFb. the conductive carbon material comprises carbon black and at least one of carbon nanotubes and graphene; andc. the cathode active material is NMC.

[0154] In a further embodiment of the composites, electrodes and processes of the invention, and the composites of the invention, the cathode active material, conductive carbon material and polymeric binders are present in the following relative amounts:active material First conductive second PVDF) PTFE) e.g. NMC carbon material conductive(e.g. carbon carbonblack material(e.g. carbonnanotubes orgraphene)95.5 - 96.5 1.6 - 1.95 wt.% 0.05 - 0.25 0.9 - 1.1 wt.% 0.9 - 1.1 wt.% wt.% wt.%Particulate Material

[0155] The present invention also provides particulate materials as described herein, and processes for their production. Such particulate materials can be used to form composites as described herein.

[0156] Thus, in one aspect there is provided a particulate material comprising a cathode active material, a conductive carbon material and a first polymeric binder.

[0157] Suitably, the individual particles of the cathode active material are attached to the conductive carbon material by the first polymeric binder.

[0158] It will be appreciated that the particulate materials discussed herein are preliminary composites comprising the cathode active material, conductive carbon material and first binder. Smaller sized particulate materials can be bound together by PTFE in the processes of the present invention.

[0159] The particulate material used in the processes of the present invention may be prepared as part of a preliminary step in the process of the present invention, or a preprepared particulate material may be incorporated into the process of the present invention.

[0160] Suitably, the particulate material has a particle size of 150 microns or less.

[0161] Suitably, the particulate material has a particle size of from 10 to 150 microns. More suitably, the particulate material has a particle size of from 50 to 150 microns.

[0162] Suitably, greater than 50% of the volume of the particulate material has a particle size of from 10 and 150 microns.

[0163] In one aspect there is provided a process for preparing a particulate material, the process comprising:i. providing a first dispersion comprising a dispersing solvent and a polymeric binder dissolved therein;ii. providing an antisolvent in which the polymeric binder is substantially insoluble;wherein at least one of the first dispersion and the antisolvent comprises a cathode active material dispersed therein and at least one of the first dispersion and the antisolvent comprises a conductive carbon material dispersed therein;wherein:the cathode active material is present in an amount of from 80 to 99.5 wt.%;the conductive carbon 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 cathode active material, conductive carbon material and first polymeric binder;iii. contacting the first dispersion with the antisolvent to form a solvent 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 cathode active material and conductive carbon material to form a particulate material.

[0164] In the above discussed process, an intimate particulate material comprising a first polymeric binder, active material and conductive carbon material is formed within a solvent mixture. The solvent mixture comprises the particulate material in a mixture of the dispersing solvent and antisolvent.

[0165] In another aspect, there is provided a particulate material obtained by, obtainable by or directly obtained by the process for preparing a particulate material as described above.

[0166] 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.

[0167] Suitably, there is an excess of antisolvent relative to the dispersing solvent.

[0168] Advantageously, the solvent mixture comprising antisolvent used to precipitate the first polymeric binder may also be used to destabilise the PTFE suspension and coagulate the PTFE.

[0169] 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.

[0170] 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.

[0171] 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 cathode active material and conductive carbon material are also substantially insoluble in the antisolvent.

[0172] The antisolvent may comprise one or more of methanol, water, acetone or a mixture thereof. Suitably, the antisolvent is selected from methanol or isopropyl alcohol.

[0173] Suitably, substantially all of the electrode components added to the first dispersion will be comprised within the formed particulate material. However, should any of the individual components remain in a non-composited form, they may be separated from the solvent mixture, e.g. by filtration.

[0174] Suitably, the components are thoroughly mixed in the first dispersion, to achieve a homogenous distribution of the components prior to flocculation of the first polymeric binder.

[0175] Suitably, the components in the first dispersion and the antisolvent will typically be mixed thoroughly to ensure uniform dispersion of the active and conductive carbon material in the formed particulate material.

[0176] Following contacting of the antisolvent with the first dispersion, the solvent mixture will also be thoroughly mixed. The mixing may suitably comprise high shear mixing, e.g. above 105s-1, or low shear mixing or stirring at 300-600 rpm.

[0177] In certain embodiments, the first polymeric binder and the conductive carbon material are added to the dispersing solvent and mixed at high shear; the cathode active material is then added to the dispersing solvent and stirred at lower shear.

[0178] In certain embodiments, the antisolvent is added to the first dispersion with lower shear mixing.

[0179] 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 shearmixing, stirring and / or planetary mixing. Once formed, the particulate material may be mixed in the coagulating solvent system at low shear, e.g. stirring at 300-600 rpm.

[0180] The components of the particulate material 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.

[0181] Suitably, the conductive carbon material, active material and any further additives are added to the first dispersion. Dispersion of the first dispersion may suitably be performed after the addition of each component to form a homogenous slurry.

[0182] The mixing may be performed continuously throughout the preparation of the particulate material. Thus, the first dispersion may be subjected to shear energy (such as mixing, sonication etc.) throughout the preparation of the particulate material.

[0183] The preparation of the particulate materials is typically performed under low viscosity conditions, allowing for the incorporation of high surface area carbon materials (e.g. graphene, carbon nanotubes).

[0184] Suitably, the viscosity of the first dispersion is between 0.01 Pa s and 100 Pa s prior to contact with the antisolvent. More suitably, the viscosity of the first dispersion is between 0.1 Pa s and 50 Pa s prior to contact with the antisolvent. Even more suitably, the viscosity of the first dispersion prior to contact with the antisolvent is between 1 Pa s and 40 Pa s.

[0185] Suitably, the solids content of the first dispersion prior to contact with the antisolvent is between 50% and 96%. More suitably, the solids content of the first dispersion prior to contact with the antisolvent is between 60% and 94%. Even more suitably, the solids content of the first dispersion prior to contact with the antisolvent is between 70% and 90%

[0186] Suitably, the viscosity of the solvent mixture is less than or equal to 10 Pa s following addition of the antisolvent to the first dispersion.

[0187] Suitably, the viscosity of the solvent mixture is less than or equal to 10 Pa s immediately before PTFE is added.

[0188] Suitably, the particle size of the cathode active material prior to addition of the antisolvent has a d90 from 0.1 to 40 pm. More suitably, the d90 may be from 10 pm and 30 pm.

[0189] A wide range of particle sizes of the conductive carbon material may be utilised, for example prior to addition of the antisolvent, the conductive carbon material may have a d90 from 0.005 pm and 10 urn.

[0190] Suitably, the conductive carbon material has a primary particle size of from 5 nm to 200 nm.

[0191] The formed particulate material may be retained in the solvent mixture, which can subsequently be used to coagulate the PTFE suspension and form a composite. This allows for conversion of all component materials into a composite without the need to dry and separate the particulate material.

[0192] In alternative embodiments, once prepared, the particulate material may be dried, e.g. in a vacuum oven. For example, once the particulate material is formed within the solvent mixture, the process further comprises removing a portion of the dispersing solvent and / or antisolvent.

[0193] In certain embodiments, the process further comprises removing a substantially all of the antisolvent from the solvent mixture. In such embodiments, the process may also comprise removing at least a portion of the dispersing solvent from the solvent mixture.

[0194] In certain embodiments, the process further comprises removing at least a portion of the dispersing solvent from the solvent mixture.

[0195] In some embodiments, the process further comprises drying the solvent 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.

[0196] Suitably, the formed particulate material may be filtered to remove any unflocculated starting materials.

[0197] In some embodiments, the formed particulate material may be dried. The drying may be achieved through heating, for example in a vacuum oven.

[0198] In certain embodiments, substantially all of the dispersing solvent and antisolvent may be removed during the drying step.

[0199] 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.

[0200] The process may also comprise filtering the particulate material to remove any noncomposited materials, or materials with a particle size less than 10 microns.

[0201] Following drying, the particulate material may be redispersed in a different coagulating solvent system, which can then be used to coagulate the PTFE suspension. Dispersing Solvents

[0202] 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.

[0203] Suitably, the dispersing solvent is a solvent with a boiling point above 150°C.

[0204] 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 firstpolymeric binders within the dispersing solvent, conductive carbon materials, and active materials used in each specific example.

[0205] 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; furfual; eugenol; isoeugenol; levulinic acid; chloroform; 1,2-dischloromethane; toluene; methyl-t- butyl ether; methyl ethyl ketone; trichloroethylene; xylene; I PA; Water; Acetone; Methanol.

[0206] In preferred embodiments, the dispersing solvent is selected from NMP, DMSO, cyrene or mixtures thereof. Most suitably, the dispersing solvent is NMP.Antisolvents

[0207] 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 cathode active material and conductive carbon material together. Thus, the addition of an antisolvent results in the flocculation of the first polymeric binder, active and conductive carbon materials to form a composited particulate material in which the components are bound together. An advantage of applying first binder flocculation by antisolvent over other methods is relatively quick immobilisation, where the components within the particulate material might not have time for segregation.

[0208] 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 at the temperature of the process. The antisolvent or antisolvent mixture may be selected from any suitable solvent described herein. The preferred use of one solvent over another is dependent on the solubility or dispersibility of the first and / or second polymeric binders, conductive carbon materials, and active materials used in each specific example.

[0209] Suitably, the antisolvent is or comprises an aqueous soluble solvent (including water). More suitably, the antisolvent comprises one or more of methanol, I PA water, acetone, acetic acid, acetonitrile, a butanol, 2-butanone, t-butyl alcohol, chlorobenzene, chrloroform, cyclohexane, 1-2 dichloroethane, dimethyl ether, diethyl ether, dipropyl ether, DME, DMF, DMSO, 1,4-dioxane, ethanol, ethyl acetate, ethyl lactate, furfual, eugenol, isoeugenol, levulinic acid, ethylene glycol, diethylene glycol, bis(2-methoxyethyl) ether, glycerin, heptane, hexane, MTBE, methylene chloride, NMP, nitromethane, pentane, a propanol, pyridine, THF, toluene, a xylene, dimethyl carbonate, diethyl carbonate, propylenecarbonate, ethylene carbonate, trimethylene carbonate, diphenyl carbonate, or a mixture thereof. Most suitably, the antisolvent comprises methanol or I PA.

[0210] 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.

[0211] Preferably, the antisolvent is a solvent which will also destabilise a PTFE suspension, such as methanol or I PA or any suitable solvent described herein. The antisolvent, antisolvent mixture, or the solvent mixture resulting, at the point of contacting a PTFE suspension, will be selected to cause the PTFE particles in the PTFE suspension to coagulate.

[0212] In a particular embodiment, the dispersing solvent is NMP and the antisolvent is selected from methanol or I PA.

[0213] The preparation of the particulate material converts smaller sized individual materials (e.g. first polymeric binder, conductive carbon material, and cathode active material particles) into larger sized particulate material. For example, the average (mode) particle size of the cathode active material prior to precipitation of the binder may be less than 20 microns. This will typically increase to around 30 to 500 microns following formation of the particulate material comprising the binder, conductive carbon material, and active material particles. The particles of cathode active material are adhered to the conductive carbon material by the binder, resulting in an increase in particle size.Preparation of the Composite Material

[0214] In the processes described above, once a particulate material has been prepared, it can be contacted with the PTFE suspension as it coagulates. For example, as discussed herein, the PTFE suspension may be added to the solvent mixture comprising the particulate material. In such cases, the solvent mixture may also function as a coagulating solvent system.

[0215] Additional antisolvents or coagulants may be added to the solvent mixture prior to contact with the PTFE suspension.

[0216] Suitably, once the particulate material has been formed, it may be stirred in the coagulating solvent system under low shear for at least 20 minutes following addition of the antisolvent, prior to contact with the PTFE suspension.

[0217] In an alternative process, the particulate material may also be prepared, dried, and then redispersed in a non-coagulating solvent together with the PTFE suspension, a coagulant may then be added to the non-coagulating solvent to form a composite material.BRIEF DESCRIPTION OF THE FIGURES

[0218] Embodiments of the invention are further described hereinafter with reference to the accompanying figures, in which:Figure 1 (RHS) shows the as-coated / densified electrode on aluminium foil.Achieved with a one pass film formation step and a one pass lamination onto aluminium foil without primer, achieving an evenly loaded and densified electrode at approx. 200 GSM loading; (LHS) Figure shows the discharge rate performance compared to a solvent-cast control electrode produced with standard NMP / PVDF slurry cast techniques. Discharging was performed from 0.1C to 50, with 0.1C charges in between each discharge. Discharge currents were in order: 0.1C, 0.1C, 0.2C, 0.5C, 10, 20, 30, 40, 50. A final capacity retention check was performed at 0.20 (cycle number 10).Figure 2 shows the SEM images of the obtained composite as various resolutions from LHS: 3k, 5k, 10k and 30k magnifications. The images show the carbon dispersion in the composite, the NMC, and the binders PTFE / PVDF.Figure 3 shows SEM images show the coated electrode in cross-section obtained by cleaving the electrode. The images at 1k and 3k magnifications show the carbon dispersion and the binder mixing and fibrillation.DETAILED DESCRIPTION

[0219] The present invention allows for composites suitable for fabricating into cathode films to be prepared without the need for dry mixing processes. Particulate materials can be bound to PTFE using exclusively solvent based processes. This allows excellent control of the degree of fibrillation of the PTFE, which can be difficult to control during dry mixing processes.

[0220] In addition, the use of solvent based processes can mean that less dust can escape into the atmosphere while preparing the particulate material and / or subsequent electrode composite material. This can allow for safer working environment in the preparation of electrode films.DEFINITIONS

[0221] 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 carbon material) and / or partially / fully dissolved solid materials. Generally, the term “slurry” may be used interchangeably with the term “dispersion”. For example, in the context of the present invention, the “first dispersion” relates to a slurry mixture of a dispersing solvent, the dissolved first polymeric binder, cathode active material and conductive carbon material dispersed within the dispersing solvent.

[0222] 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 coarsefiltration or sedimentation. In the present invention, flocculation occurs by coagulation of the PTFE caused by the destabilising of the PTFE suspension.

[0223] In certain embodiments, flocculation is also utilised during the preparation of the particulate material by the precipitation of the first polymeric binder in the presence of the cathode active material and the conductive carbon material, prior to coagulation of the PTFE suspension.

[0224] The coagulation of the PTFE suspension results in agglomeration of PTFE solid particles, resulting in the formed composite having a larger particle size compared 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 coagulation is advantageous over simple high shear mixing of particulate materials and PTFE, 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).

[0225] Flocculated products are advantageous because solvents can be recycled efficiently, as the formed flocculated material is easily separated from the dispersion mixture during flocculation.

[0226] The term “primary particle” refers to the individual constituent particles present in a material. A number of primary particles may be present within a larger aggregate of the material, comprising loosely bonded primary particles. The primary particle size may be determined by observing SEM images of the material.

[0227] 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.

[0228] 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.

[0229] 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’.

[0230] 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 moreproperties 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 9 molecular 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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 orTe). 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. Exemplary TMDCs include NbSe2, WS2, M0S2, TaS2, PtTe2, Te2.

[0235] 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 tographite 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.

[0236] 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 I(D), to the G peak Raman intensity, referred to as I(G), indicates the amount of defects present within the graphene. This is referred to as the I(D) / I(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) / I(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 pointlike defects is expected to be greater than approximately 4 nm.

[0237] The composites formed by the method of the present invention which comprise graphene may have an I(D) / I(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 l(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.

[0238] 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 materiallayer. An edge defect is due to a graphene sheet not being infinitely large and therefore having an edge.

[0239] 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) / l (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) / I(G) ratio or FWHM of peaks as discussed above.

[0240] 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.

[0241] 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.

[0242] The graphene containting 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).

[0243] 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 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 excitationwavelength 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 more preferably, 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.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] The term “high shear” relates to mixing at a rate greater than of 105s-1. An example of high shear mixing is an IKA mixer (e.g. IKA T25 rotor-stator lab mixer) at a speed of 10,000 RPM.

[0249] The term “low shear” relates to mixing at a rate of 105s-1or less, preferably 104s-1. Examples of low shear mixing include magnetic stirring.

[0250] 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 notintended 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.

[0251] 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 the steps 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.

[0252] 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 1 - NMC dry coating hierarchical composite made with PVDF from NMP / MeOH mixing, followed by incorporation of PTFE latex.Composition: 96 NMC: 1 PVDF: 0.1 CNT: 1.9CB (1 PTFE)

[0253] An initial NMC / CB / CNT / PVDF composite suspension is made by adding MeOH to a slurry in NMP. Shortly after this precipitation, PTFE latex is added, with stirring, yielding a hierarchical composite. Control of shear of the PTFE has been found to be beneficial to the processing.Method1. 2.512g of PVDF (10% wt. in NMP) solution was added to a 250ml beaker. 0.962g of carbon black, and 12.603g of Tuball CNT dispersion (0.4wt.% SWCNTs, 2wt.% PVDF, in NMP), and 120ml of NMP were then added. This mixture was then sheared with an IKA at 10k rpm for 15 mins. A good mixing vortex formed with no lumps or clogged polymer resulting in a well dispersed suspension.2. The beaker was removed and then placed on a magnetic plate with stirrer set at 450rpm. 48.53g of NMC (KY181) was added slowly during stirring, and stirring wascontinued for 30 mins. A 2L beaker with 200ml of MeOH was set up with overhead stirring (775rpm) and cooled in a surrounding ice / water bath. The 250ml beaker of as prepared slurry and another 1 L of MeOH we coincidently poured into the overhead stirred 2L beaker.3. The stirring was maintained for a further 25mins. After 25mins 0.826g of PTFE aqueous suspension (665800, Sigma-Aldrich, 60% wt. PTFE, density 1.5gcm-3) was added to the vortex. The stirring was continued for a further 5 mins (the temperature of the liquid was recorded ad 0.08°C.4. After the total of 30mins stirring the beaker was left to settle for 30mins cooled, and a further 1.5hrs at room temperature. The supernatant was decanted and the solid was removed by filtration in a Gooch filter funnel (#3), the sample was washed with 5x63ml of MeOH. The filtration was performed under blanket of N2, with gentle breaking up of the solid cake. The solid was recovered and dried in a vacuum furnace at 50°C.

[0254] Figure 1 shows: (LHS) The Ragone cycling eChem plot shows that the dry coated composite achieves parity rate performance vs a wet-coated benchmark; (RHS) Picture of composite dry-coated directly via one pass calendering and transferring on to the Al-current collector, achieving an evenly loaded and densified electrode.

[0255] Figure 2 shows: SEM of the composite powder: showing the dispersion of carbons, binder and NMC in the composite.

[0256] Figure 3 shows: SEM images show cross-sectional SEM of the electrode showing the dispersion of binder and carbons with NMC in the composite is maintained in the electrode and that the coating process has resulted in significant fibrillation of the composite.

Claims

1. CLAIMS1. A process for fabricating a composite suitable for use in a dry electrode coating process, the process comprising:contacting PTFE with a particulate material comprising a cathode active material, a conductive carbon material and a first polymeric binder; wherein the PTFE is in the form of a stable colloidal suspension; andcoagulating the PTFE in the presence of the particulate material to form a composite.

2. A process according to claim 1, wherein the coagulation is not induced by shear aggregation.

3. A process according to claim 1 or claim 2, wherein the PTFE is not subjected to conditions which will impart significant fibrilization.

4. A process according to any one of the preceding claims, wherein the PTFE is not subjected to shear higher than 105s-1over the course of the process, preferably the PTFE is not subjected to shear higher than 104s-1over the course of the process.

5. A process according to any one of the preceding claims, wherein the PTFE is not subjected to temperatures above 19°C during the course of the process.

6. A process according to any one of the preceding claims, wherein the PTFE suspension is coagulated by contacting with a coagulating solvent system, wherein the coagulating solvent system comprises one or more antisolvents and / or materials which destabilise the PTFE suspension upon contact.

7. A process according to claim 6, wherein the coagulating solvent system comprises an antisolvent which destabilises the PTFE suspension, preferably isopropyl alcohol or methanol.

8. A process according to claim 6 or 7, wherein the coagulating solvent system comprises one or more of an acid, base or salt which destabilises the PTFE suspension.9 A process according to any one of claims 6 to 8, wherein the coagulating solvent system further comprises a solvent in which the first polymeric binder is soluble at 25°C, preferably NMP.

10. A process according to claim 9, wherein the volume ratio of the solvent in which first polymeric binder is soluble to the antisolvent is from above 1:1 and below 1:5.

11. A process according to any one of claims 6 to 10, which comprises;i) dispersing the particulate material in the coagulating solvent system;ii) contacting the coagulating solvent system with the PTFE suspension, such that the PTFE suspension is destabilised and PTFE is coagulated in the presence of the particulate material to form a composite.

12. A process according to claim 11, wherein step i) of the process comprises steps ia to ic:ia) providing a first dispersion comprising a dispersing solvent and the first polymeric binder dissolved therein; and the first dispersion further comprises a cathode active material and a conductive carbon material dispersed therein;ib) providing an antisolvent in which the first polymeric binder is substantially insoluble, and which will destabilise the PTFE suspension;ic) contacting the first dispersion with the antisolvent to form the coagulating solvent system, wherein the volume ratio of the dispersing solvent to the antisolvent is above wherein the volume ratio of the dispersing solvent to the antisolvent is above 1:0.01 to below 1:10, e.g. above 1:1 and below 1:5; wherein contacting the first dispersion with the antisolvent results in the precipitation of first polymeric binder in the presence of the cathode active material and conductive carbon material to form a particulate material as defined in claim 1 dispersed in the coagulating solvent system.

13. A process according to claim 11 or 12, wherein the particulate material is dispersed in the coagulating solvent system at high shear prior to coagulation with the PTFE.

14. A process according to any one of claims 11 to 13, wherein following addition of the PTFE suspension to the coagulating solvent system, the PTFE is not subjected to shear greater than 105s-1.

15. A process according to any one of claims 10 to 14, wherein following addition of the PTFE suspension to the coagulating solvent system, the PTFE is not subjected to temperatures greater than 19°C.

16. A process according any one of the preceding claims, wherein the first polymeric binder is a non-fibrilizable polymer,optionally wherein the non-fibrilizable polymer is selected from PVDF, a gum (e.g. xanthan gum, locust bean gum, guar gum, carboxymethyl cellulose) or a hydrophilic polymer (e.g. polyvinyl alcohol or ethylene vinyl alcohol).

17. A process according any one of the preceding claims, wherein the first polymeric binder is PVDF.

18. A process according to any one of the preceding claims, wherein the PTFE is in the form of a latex suspension.

19. A process according to claim 18, wherein the PTFE latex suspension comprises a surfactant, for example tergitol.

20. A process according any one of the preceding claims, wherein the cathode active material is present in an amount of from 90.0 to 99.0 wt.%, preferably from 94.0 to 98.0 wt.%, most preferably 95.0 to 97.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder.

21. A process according any one of the preceding claims, wherein the conductive carbon material is present in a total amount of from 0.05 to 8.0 wt.%, preferably from 0.5 to 3.0 wt.%, more preferably from 1.5 to 2.5 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder.

22. A process according any one of the preceding claims, wherein the PTFE is present in an amount of from 0.25 to 4.0 wt.%, preferably from 0.5 to 2.0 wt.%, more preferably from 0.75 to 1.5 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder.

23. A process according any one of the preceding claims, wherein the first polymeric binder is present in an amount of from 0.25 to 4.0 wt.%, preferably from 0.5 to 2.5 wt.%, more preferably from 0.75 to 1.5 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, first polymeric binder and PTFE binder.

24. A process 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. 910, 811, 622, 532, 111;• 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.

25. A process according to any one of the preceding claims, wherein the conductive carbon material comprises one or more materials selected from carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanotubes, graphene (e.g. pristine graphene), and other hard carbons;optionally wherein the conductive carbon material comprises one or more materials selected from pristine graphene, carbon black and carbon nanotubes;further optionally wherein the conductive carbon material comprises carbon black and single wall carbon nanotubes;further optionally wherein the conductive carbon material comprises carbon black and single wall carbon nanotubes in a weight ratio of 4: 1 to 19: 1.

26. A process according to any one of the preceding claims, wherein the particulate material has a particle size of 150 microns or less, preferably from 50 to 150 microns.

27. A process according to any one of the preceding claims, wherein following coagulation of the PTFE, the composite has a particle size of from 30 to 300 microns.

28. A composite material obtained by, obtainable by, or directly obtained by a process according to any one of claims 1 to 27.

29. A composite material suitable for use in a dry electrode coating process, the composite comprising a cathode active material, a conductive carbon material, a first polymeric binder and wherein the individual particles of the cathode active material are attached to the conductive carbon material by the first polymeric binder, and further comprise PTFE particles on their surface.

30. A composite according to claim 27 or 28, wherein the PTFE particles are substantially non-fibrillated.

31. A composite according any one of claims 27 to 30, wherein the cathode active material is present in an amount of from 90.0 to 99.0 wt.%, preferably from 94.0 to 98.0 wt.%, most preferably 95.0 to 97.0 wt.%, based upon the total dry weight of the composite material.

32. A composite according any one of claims 27 to 31, wherein the conductive carbon material is present in a total amount of from 0.05 to 8.0 wt.%, preferably from 0.5 to 3.0 wt.%, more preferably from 1.5 to 2.5 wt.%, based upon the total dry weight of the composite material.

33. A composite according any one of claims 27 to 32, wherein the first polymeric binder is present in an amount of from 0.05 to 4.0 wt.%, preferably from 0.25 to 2.5 wt.%, or more preferably from 0.75 to 1.5 wt.%, based upon the total dry weight of the composite material.

34. A composite according any one of claims 27 to 33, wherein the PTFE is present in an amount of from 0.25 to 4.0 wt.%, preferably from 0.5 to 2.0 wt.%, more preferably from 0.75 to 1.5 wt.%, based upon the total dry weight of the composite material.

35. A composite according any one of claims 27 to 34, wherein the conductive carbon material comprises carbon black and single wall carbon nanotubes.

36. A composite according any one of claims 27 to 35, wherein the cathode active material is selected from LTO, NMC, NCA or LFP.

37. A composite according any one of claims 27 to 36, wherein the first polymeric binder comprises a gum (e.g. xanthan gum, locust bean gum, guar gum, methyl cellulose, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC) or sodium carboxymethylcellulose (Na-CMC)), a hydrophilic polymer (e.g. polyvinyl alcohol or ethylene vinyl alcohol), a hydrophobic polymer (e.g. polyethylene), or a fluoropolymer (e.g. PVDF or PVDF-HFP); optionally wherein the first polymeric binder is PVDF.

38. A composite according any one of claims 27 to 37, comprising a surfactant in an amount of from 0.001 to 0.2 wt.% based on the total dry weight of the composite material.

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