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, whichis likely when using standard dry 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.SUMMARY OF THE INVENTION

[0009] In a first aspect there is provided a process for fabricating a composite, the process comprising:mixing a PTFE solid, a cathode active material, and a conductive carbon material in a solvent, wherein the solids content within the solvent is 80 wt.% or below; applying mixing energy to distribute the PTFE solid, cathode active material, and conductive carbon material amongst each other;removing the mixing energy; andremoving solvent from the mixture.

[0010] The composite fabricated in the process of the first aspect may be suitable for use in a dry electrode coating process.Cathode Active Materials

[0011] 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. In the present invention, the active material is a cathode active material (CAM).

[0012] 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.

[0013] 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.

[0014] The cathode active material may be lithium-active or sodium active material.

[0015] Suitably, the cathode active material is selected from any of the cathode active materials described herein. The cathode active material may comprise a blend of multiple active materials, or just a single active material.

[0016] 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.

[0017] Suitably, the cathode active material is selected from one or more of NMC, NCA, LNMO, LFP, LMFP. More suitably, the cathode active material is selected from one or more of LTO, NMC, NCA or LFP. 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.

[0018] Suitably, the cathode active material may comprise an NMC cathode material with Ni content between 50% and 99%, as a mole fraction of all transition metals.

[0019] Suitably, the cathode active material may be a water sensitive cathode active material, e.g. a cathode material with nickel content (as a mole fraction of all transition metals) above 80% and below 99%.

[0020] Suitably, the cathode active material has a particle size (e.g. a d90 particle size) from 0.1 to 40 pm. More suitably, the cathode active material has a d90 particle size from 0.2 to 30 pm. Most suitably, the cathode active material has a d90 particle size from 1 to 30 pm. Conductive Carbon Materials

[0021] 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.

[0022] 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. Graphene (i.e. pristine graphene) can be considered to be a conductive carbon material and a 2D layered material.

[0023] The conductive carbon material is selected from any of the carbon materials described herein.

[0024] Suitably, the conductive carbon material comprises one or more of carbon black, acetylene black, ketjen black, graphite, carbon fibre, carbon nanofibers, carbon nanotubes, and graphene (e.g. pristine graphene), or other hard carbons. More suitably, the conductive carbon material comprises one or more of pristine graphene, carbon black, carbon nanotubes or carbon nanofibres. More suitably, the conductive carbon material comprises carbon black and optionally a high aspect ratio carbon-based material (e.g. graphene, carbon nanotubes).

[0025] In certain embodiments, the conductive carbon material may comprise only carbon black.

[0026] In certain embodiments, the conductive carbon material may comprise one or more of pristine graphene, carbon black, or carbon nanotubes (e.g. single wall carbon nanotubes). Preferably, 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.

[0027] 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.

[0028] 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.

[0029] A wide range of particle sizes of the conductive carbon material may be utilised, for example prior to formation of the composite, the conductive carbon material may have a d90 from 0.005 pm and 10 pm.

[0030] Suitably, the conductive carbon material has a primary particle size of from 5 nm to 200 nm. More suitably, the conductive carbon material has a primary particle size of from 10 nm to 75 nm.Polymeric Binder Material

[0031] Polymeric binder material(s) comprised within a battery is present to primarily adhere the electrode film to a substrate such as a current collector. The composites of the present invention comprise at least polytetrafluoroethylene (PTFE) as a binder.

[0032] In certain preferred embodiments, PTFE is the only polymeric binder used in the processes and composites of the present invention.

[0033] In other embodiments, the composites may also comprise one or more additional binders. The additional binder(s) may be present in an amount of from 5 to 50 wt.%, based on the total weight of the polymeric binder materials present.

[0034] The one or more additional binder material(s) may be or comprise a non-fibrillating binder.

[0035] Suitably, the one or more additional binder material(s) is selected from-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), 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). More suitably, the additional binder material is PVDF.

[0036] The inventors have advantageously identified that it is possible to mix solid PTFE, conductive carbon material and the cathode active material in one or more organic solvents, where the mixing results in the formation of an intimate composite of the three components. This can be done by both avoiding dry mixing processes, which can be difficult to control; and also by avoiding the use of large amounts water as a solvent, which can cause damage to certain cathode active materials such as NMC with nickel content above 80%.

[0037] Suitably, the PTFE solid used in the process of the invention may comprise a coating to make it more readily compositable with the conductive carbon material and the cathode active material. The coating may be a surfactant of emulsifier, preferably a surfactant. A coated PTFE solid as described herein may be referred to as a surface modified PTFE.

[0038] The PTFE solid may be in a powder or particulate form.

[0039] Suitably, the PTFE solid has a primary particle size from 100 to 1000 nm. More suitably, the PTFE solid has primary particle size from 100 to 500 nm. Most suitably, the PTFE solid has a primary particle size from 200 to 300nm.

[0040] In one embodiment, the PTFE solid (e.g. surface modified PTFE) is prepared by pretreating pure PTFE polymer with a coating prior to the process of the first aspect. Such treatment may involve adding a coating onto the individual particles of the PTFE.

[0041] In another embodiment, the surface modified PTFE solid is prepared by freeze drying a PTFE suspension comprising colloidal PTFE particles suspended in water.

[0042] Suitably, the surface modified PTFE solid has a primary particle size from 100 to 1000 nm. More suitably, the surface modified PTFE solid has primary particle size from 100 to 500 nm. Most suitably, the surface modified PTFE solid has a primary particle size from 200 to 300nm.

[0043] Suitably, the PTFE suspension comprises from 20 to 80 wt.% solids; preferably from 50 to 70 wt.% solids.

[0044] In a preferred embodiment, the surface modified PTFE comprises a one or more surfactants. The one or more surfactants may be coated onto individual particles of PTFE. The surfactant may be any of those described herein.

[0045] In certain embodiments, the surface modified PTFE comprises one or more surfactants in an amount of 0.01 to 10.0 wt.%, preferably from 0.1 to 6.0 wt.%, more preferably from 0.2 to 4.0 wt.%, based on the total weight of the surface modified PTFE.

[0046] The surface modified PTFE may also comprise some small amount of water, for example if being prepared by freeze drying. Suitably, the surface modified PTFE may comprise from 0 to 4.0 wt.% water, more suitably from 0.1 to 3.0 wt.% water, most suitably from 0.2 to 1.0 wt.% water based on the total weight of the surface modified PTFE.

[0047] The water present in the surface modified PTFE may be present within the surfactant or emulsifier coating.

[0048] In a preferred embodiment, the surface modified PTFE comprises PTFE particles, one or more surfactants, and water.

[0049] Suitably, the surface modified PTFE comprises PTFE particles, and:one or more surfactants in an amount of 0.01 to 10.0 wt.%; andwater in an amount of 0 to 4.0 wt.%;based on the total weight of the surface modified PTFE.

[0050] More suitably, the surface modified PTFE comprises PTFE particles, and:one or more surfactants in an amount of 0.1 to 6.0 wt.%; andwater in an amount of 0.1 to 3.0 wt.%;based on the total weight of the surface modified PTFE.

[0051] More suitably, the surface modified PTFE comprises PTFE particles, and:one or more surfactants in an amount of 0.2 to 4.0 wt.%; andwater in an amount of 0.2 to 1.0 wt.%;based on the total weight of the surface modified PTFE.

[0052] In other embodiments, the PTFE solid is pure PTFE.Further Features of Process

[0053] Suitably, in the process of the first aspect, the weight ratio of total polymeric binder: cathode active material: conductive carbon material is 0.2 - 3.0: 94.0 - 99.0: 0.2 - 3.0.

[0054] Suitably, in the process of the invention, the cathode active material is present in an amount of from 94.0 to 99.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material (e.g. PTFE or a combination of PTFE and one or more additional binders) present, more suitably from 95.0 to 99.0 wt.%, most suitably from 95.0 to 98.5 wt.% (e.g. 97.2 to 97.8 wt.%).

[0055] Suitably, in the process of the invention, the conductive carbon material is present in a total amount of from 0.5 to 3.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material (e.g. PTFE or a combination of PTFE and one or more additional binders) present, more suitably from 0.6 to 2.5 wt.%, most suitably from 0.7 to 2.3 wt.%,.

[0056] Suitably, the total amount of polymeric binder present is from 0.2 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material (e.g. PTFE or a combination of PTFE and one or more additional binders) present, more suitably from 0.5 to 3.0 wt.%, most suitably from 1.0 to 2.5 wt.%.

[0057] Suitably, in processes of the invention, the cathode active material is present in an amount of from 94.0 to 99.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 96.0 to 98.5 wt.%, most suitably from 97.0 to 98.0 wt.% (e.g. 97.2 to 97.8 wt.%).

[0058] Suitably, in processes of the invention, the conductive carbon material is present in a total amount of from 0.5 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 0.6 to 2.0 wt.%, most suitably from 0.7 to 1.5 wt.% (e.g. 0.8 to 1.2 wt.%).

[0059] Suitably, in processes of the invention, the total amount of polymeric binder material present is from 0.2 to 4.0 wt.%, based on the total dry weight of the cathode active material,the conductive carbon material, and total polymeric binder material present, more suitably from 0.5 to 3.0 wt.%, most suitably from 1.0 to 2.0 wt.%.

[0060] In an embodiment of the processes of the invention:the cathode active material is present in an amount of from 97.0 to 98.0 wt.%; the conductive carbon material is present in a total amount of from 0.7 to 1.5 wt.%; and the total amount of polymeric binder material present is from 1.0 to 2.0 wt.%; based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present.

[0061] In an embodiment of the processes of the invention:the cathode active material is present in an amount of from 97.2 to 97.8 wt.%; the conductive carbon material is present in a total amount of from 0.8 to 1.2 wt.%; and the total amount of polymeric binder material present is from 1.2 to 1.8 wt.%; based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present.

[0062] If one or more additional binder(s) are used, they may be present in an amount of from 5 to 50 wt.%, based on the total weight of the polymeric binder materials present.

[0063] Suitably, the composite formed by the process of the first aspect is in the form of solid cohesive agglomerated particles, for example a powder particulate material.

[0064] The powder may be formed into a moudable dough. The powder or dough may be processed into a film.

[0065] Suitably, the application of mixing energy comprises high shear mixing (above 105s’1), low shear mixing (at speeds of 105s-1or below) and / or planetary mixing.

[0066] Suitably, the process is performed at a temperature of from -20°C to 90°C.

[0067] The application of mixing energy may comprise any suitable mixing technique known in the art, for example or any of the methods disclosed herein. Suitably, the application of mixing energy may comprise one or more of high shear mixing, high shear rotor-stator mixing, one or more of sonication, paddle, bar, or blade stirring, stirring, planetary mixing or shear mixing.

[0068] The application of mixing energy may be provided by mixing at a shear rate of from 5000-500000 s-1, more suitably from 10000-200000 s’1, or more suitably 60000-100000 s-1(e.g. 80000 s-1).

[0069] Suitably, during the mixing step the solids content of the solvent is above 20 wt.% and below 80 wt.%. Suitably the solids content of the solvent during the mixing step is from 25 wt.% to 75 wt.%.

[0070] Suitably, the viscosity of the solvent during application of the mixing energy is less than 50 Pa.s. The viscosity during application of the mixing energy is measured while the PTFE, cathode active material, and conductive carbon material and optional further binders are present in the solvent.

[0071] Suitably, the solvent is a non-aqueous solvent. The solvent may be selected from a polar protic solvent which is not water. Suitably, the solvent is a polar organic solvent.

[0072] Suitably, the solvent is one in which PTFE, the conductive carbon material and the cathode active material are insoluble (or substantially insoluble) at 25°C.

[0073] Suitably, the solvent has a dielectric constant of from 2 to 50. More suitably, the solvent has a dielectric constant of from 2.5 to 35.

[0074] The solvent may be selected from one or more of methanol, ethanol, iso-propanol, dimethyl carbonate, diethyl carbonate, butyl acetate, 2-butoxyethyl acetate, heptyl butyrate, n-butyl acetate, tert-butyl acetate, propylene carbonate, iso-amyl acetate, hexyl acetate, heptyl acetate, triacetine, dimethyl isosorbite, tert-butyl methyl ether (TBME), 2-butoxyethyl acetate, ethyl diglycol carbonate, benzyl benzoate or dimethyl adipate. More suitably, the solvent is selected from one or more of 2-butoxyethyl acetate, heptyl butyrate, iso-propanol, ethanol, methanol, n-butyl acetate, iso-amyl acetate, dimethyl carbonate, diethyl carbonate, tert-butyl methyl ether (TBME), tert-butyl acetate, hexyl acetate. More suitably, the solvent is selected from one or more of methanol, dimethyl carbonate or iso-propanol. Most suitably, the solvent is selected from one or more of iso-propanol, or dimethyl carbonate.

[0075] Suitably, the process of the invention is performed under anhydrous conditions.

[0076] The process of the invention may be performed in an inert atmosphere, e.g. a nitrogen atmosphere.

[0077] Suitably, the mixing of components is performed under anhydrous conditions, e.g. in a nitrogen atmosphere.

[0078] The mixing will be performed in a suitable vessel.

[0079] In some embodiments, the cathode active material and conductive carbon material may be first subjected to mixing energy in the solvent, before addition of the PTFE. The mixture of the solid components (i.e. cathode active material, conductive carbon material, PTFE and optional further binder(s)), will then continue.

[0080] Suitably, if one or more additional polymeric binders are to be incorporated into the composite, they may be added before addition of the surface modified PTFE to the mixture.For example, the one or more additional polymeric binders may be subjected to mixing energy at the same time as the cathode active material and the conductive carbon material.

[0081] Following composite formation, the solvent will be removed. The solvent may be removed by one or more methods known in the art. Suitably, at least 95 wt.% of the solvent is removed. More suitably, at least 98 wt.% of the solvent is removed. More suitably, at least 99 wt.% of the solvent is removed.

[0082] The composite may be washed with one or more solvents to aid removal of noncomposited material and any residual PTFE coating.

[0083] Suitably, the solvent is removed by one or more of by filtration, centrifugation, decantation, and / or drying. More suitably, the solvent is removed by a one or more of decantation, filtration and / or drying.

[0084] If drying is used to remove some solvent, it may be performed at a temperature of 40 to 60°C. The drying may be performed in a vacuum oven.

[0085] Suitably, the filtration step is performed under anhydrous conditions.

[0086] Suitably, the decantation and / or filtration step removes some residual PTFE coating (e.g. surfactant or emulsifier) that is not retained in the composite material and also coating which is present in the solvent that would otherwise be present in the composite material upon drying of the mixture.

[0087] Suitably, the composite formed by the process of the first aspect has a d90 particle size of from 5 microns to 500 microns.

[0088] Suitably, the composite formed by the process of the first aspect has a d90 particle size greater than the d90 particle size of the cathode active material.

[0089] In some embodiments, following the removal of the solvent, the composite (e.g. composite powder) is applied into a calendar nip gap to form a continuous film.

[0090] Following removal of the solvent, the composite material may comprise less than 2.0 wt.% of solvent. More suitably, the composite material may comprise less than 1.0 wt.% of solvent. Most suitably, the composite material may comprise less than 0.5 wt.% of solvent.

[0091] The present invention allows for greater control of the degree of fibrilillation of the PTFE than exclusively dry compositing processes. For example, in some stages of the process the PTFE is not subjected to conditions which will impart significant fibrillation such as high temperature and high shear. In other stages, the PTFE may be subjected to conditions which cause some fibrillation to occur.

[0092] If desired, the process of the present invention allows a composite to be prepared without significantly fibrillating the PTFE material. Thus, in some embodiments, the PTFE is not subjected to conditions which will impart significant fibrillation during the whole course of the process.

[0093] Suitably, in some embodiments the PTFE is not subjected to shear higher than 105s-1over the course of the process or at some stages of the process. More suitably, in such embodiments the PTFE is not subjected to shear higher than 104s-1over the course of the process or at some stages of the process.

[0094] In other embodiments, the PTFE may be subjected to shear higher than 104s-1or 105s-1at some stages of the process.

[0095] Suitably, the PTFE is not subjected to temperatures above 19°C during the course of the process or at some stages of the process. For example, some parts of the process relating to PTFE, or the whole of the process, may be performed at temperatures from -20°C to 15°C, suitably -5°C to 5°C, more suitably 0°C to 5°C. By way of example, the PTFE while present in a solvent may be kept below 19°C, then following removal of the solvent might be heated above this temperature.

[0096] While fibrillation of the PTFE may be minimised, in some embodiments a certain degree of fibrillation is desirable. Thus, the PTFE may be exposed to shear higher than 104s-1(or 105s-1) and / or temperatures above 19°C during some of the process.

[0097] Mixing may be performed before and after addition of the PTFE solid (e.g. the surface modified PTFE) to the solvent, to ensure uniform distribution of the component materials.

[0098] Following composite formation, mixing may be continued for some time to ensure all of the PTFE has formed a composite with the other composite components. The mixing may then be ceased to allow the formed composite to be separated from the solvent mixture. Composites of the Invention

[0099] In a second aspect, there is provided a composite obtained by, obtainable by, or directly obtained by the process according to the first aspect.

[0100] In a third aspect, there is provided a composite comprising PTFE, a cathode active material, and a conductive carbon material.

[0101] The composites of the present invention may be used to fabricate electrode films, particularly cathode films. The composites find particular use in dry electrode coating processes, e.g. cathode coating processes.

[0102] As described herein, the composites comprise a cathode active material, a conductive carbon material and PTFE. These materials, together with any further additives, can be collectively defined as electrode film components or electrode component materials.

[0103] In some embodiments, the composites may comprise a one or more additional binder material(s). The one or more additional binder material(s) may be present in an amount of from 5 to 50 wt.%, based on the total weight of the binder materials present.

[0104] Suitably, the one or more additional binder material(s) is selected from-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), 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). More suitably, the additional binder material is PVDF.

[0105] In some embodiments, the PTFE in the composite is substantially non-fibrillated.

[0106] In some embodiments, the PTFE in the composite is less fibrillated than PTFE in a composite prepared by exclusively dry mixing processes. This may be determined by comparing observing SEMs of formed composites.

[0107] Suitably, the composite further comprises trace amounts of a surfactant, e.g. 0.001 to 0.2%, more suitably 0.005 to 0.1wt.%, based on the total dry weight of the composite material.

[0108] Suitably the surfactant is any of those defined herein, e.g. branched alcohol ethoxylates or branched secondary alcohol ethoxylates..

[0109] 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.

[0110] Suitably, in the composites of the invention, the cathode active material is present in an amount of from 94.0 to 99.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 95.0 to 98.0 wt.%, most suitably from 95.0 to 97.0 wt.%.

[0111] Suitably, in the composites of the invention, the conductive carbon material is present in a total amount of from 0.5 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 1.0 to 3.0 wt.%, most suitably from 1.5 to 2.5 wt.%.

[0112] Suitably, in other composites of the invention, the conductive carbon material is present in a total amount of from 0.5 to 3.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material (e.g. PTFE or a combination of PTFE and one or more additional binders) present, more suitably from 0.6 to 2.5 wt.%, most suitably from 0.7 to 2.3 wt.%.

[0113] Suitably, in the composites of the invention, the total amount of polymeric binder material present is from 0.2 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 0.5 to 3.0 wt.%, most suitably from 1.0 to 2.5 wt.%.

[0114] Suitably, in other composites of the invention, the cathode active material is present in an amount of from 94.0 to 99.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 96.0 to 98.5 wt.%, most suitably from 97.0 to 98.0 wt.% (e.g. 97.2 to 97.8 wt.%).

[0115] Suitably, in other composites of the invention, the conductive carbon material is present in a total amount of from 0.5 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 0.6 to 2.0 wt.%, most suitably from 0.7 to 1.5 wt.% (e.g. 0.8 to 1.2 wt.%).

[0116] Suitably, in other composites of the invention, the total amount of polymeric binder material present is from 0.2 to 4.0 wt.%, based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present, more suitably from 0.5 to 3.0 wt.%, most suitably from 1.0 to 2.0 wt.%.

[0117] In an embodiment of the composites of the invention:the cathode active material is present in an amount of from 97.0 to 98.0 wt.%; the conductive carbon material is present in a total amount of from 0.7 to 1.5 wt.%; and the total amount of polymeric binder material present is from 1.0 to 2.0 wt.%; based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present.

[0118] In an embodiment of the composites of the invention:the cathode active material is present in an amount of from 97.2 to 97.8 wt.%;the conductive carbon material is present in a total amount of from 0.8 to 1.2 wt.%; and the total amount of polymeric binder material present is from 1.2 to 1.8 wt.%; based on the total dry weight of the cathode active material, the conductive carbon material, and total polymeric binder material present.

[0119] Suitably, the cathode active material is selected from any of the cathode active materials described herein. The cathode active material may comprise a blend of multiple active materials, or just a single active material.

[0120] The composites of the present invention, e.g. those formed in the process of the first aspect, may be in the form of a solid cohesive agglomerated particles, for example a powder particulate material. The powder may be formed into a moudable dough.

[0121] Suitably, the composite powder can be used in a dry electrode coating process. Cathode utilising composites of the invention

[0122] In fourth aspect there is provided a cathode comprising:a) a metallic substrate;b) a film comprising the composite material according to the second or third aspect.

[0123] Advantageously, in some non-limiting embodiments, 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.

[0124] In a fifth aspect, there is provided a process for fabricating a cathode, the process comprising:i) fabricating or providing a composite material according to the second or third aspect; ii) forming the composite material into a film; andiii) coating the film onto a metal substrate.

[0125] In a sixth aspect, the invention also provides a cathode, obtained by, obtainable by or directly obtained by the process defined herein.

[0126] Suitably, the metallic substrate in the fourth and fifth aspect is a current collector, preferably an aluminium current collector.

[0127] Suitably, the film in the fourth and fifth aspect has a thickness of 30 to 300 microns, more suitably from 60 microns to 200 microns.

[0128] 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.

[0129] In some embodiments, the process of fabricating a cathode material, the metal substrate is substantially free of any primer during the coating of the film.

[0130] In other embodiments, the process of fabricating a cathode material, a primer is present on the metal substrate.

[0131] The composite material may be coated onto the metal substrate (e.g. an aluminum current collector) by dry coating processes, e.g. calendaring.Batteries utilising composites of the invention

[0132] In a seventh aspect, there is provided a battery comprising a cathode as defined herein. Suitably, the battery is a lithium ion battery.

[0133] 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.

[0134] Advantageously, the batteries comprising a composite of the invention may not need a primer layer between the electrode film and the current collector.

[0135] Suitably, the battery is a lithium ion battery.Preparation of Surface Modified PTFE solid

[0136] In an eighth aspect, there is provided a process for preparation of a surface modified PTFE solid, the process comprising:i) providing a PTFE suspension comprising colloidal PTFE particles suspended in water;ii) freeze drying the colloidal suspension comprising PTFE to remove at least 96 wt.% of the water from the PTFE suspension, thereby providing a surface modified PTFE solid.

[0137] Suitably, the surface modified is in the form of a particulate material.

[0138] Suitably, the PTFE suspension comprises 40 to 80 wt.% solids; preferably from 50 to 70 wt.% solids.

[0139] Suitably, the PTFE colloidal suspension further comprises one or more surfactant. The surfactant may be any of those described elsewhere herein, e.g. branched alcohol ethoxylates or branched secondary alcohol ethoxylates.

[0140] Suitably, at least 97 wt.% of the water in the PTFE suspension is removed, more suitably at least 98 wt.%.

[0141] In a ninth aspect, there is provided a PTFE solid suitable for use in an organic solventbased compositing process (i.e. a compositing process which is substantially free from water). The PTFE solid may be a surface modified PTFE as defined herein. The surface modificationmay be a surfactant coating on the PTFE particles. Suitably, the surfactant coating is not covalently attached to the PTFE particles.

[0142] In a tenth aspect, there is provided a surface modified PTFE solid obtained by, obtainable by, or directly obtained by, the process of the eighth aspect.

[0143] Suitably, the surface modified PTFE according to the ninth or tenth aspect, or produced by the process of the eighth aspect, comprises a coating to make it more readily compositable with the conductive carbon material and the cathode active material. The coating may be a surfactant of emulsifier, preferably a surfactant.

[0144] Advantageously, preparing a surface modified PTFE solid by freeze drying does not result in significant fibrillation of the PTFE material.

[0145] Suitably, the surface modified PTFE solid has a primary particle size from 100 to 1000 nm. More suitably, the surface modified PTFE solid has primary particle size from 100 to 500 nm. Most suitably, the surface modified PTFE solid has a primary particle size from 200 to 300nm.

[0146] 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.

[0147] The surface modified PTFE may be further characterised after suspending in isopropanol, wherein it may have a particle size of from 5 to 200 pm.

[0148] In an eleventh aspect, there is provided the use of a surface modified PTFE solid according to the ninth or tenth aspect, in the preparation of a composite. Suitably, the composite is a composite of the second or third aspect.

[0149] The surface modified PTFE solid of the ninth or tenth aspect may be used in the process of the first aspect.Surfactants

[0150] As mentioned herein, the PTFE solid may comprise a surfactant coating on its surface. This may be prepared by freeze drying a stabilised colloidal suspension of PTFE, or by mixing pure PTFE with a surfactant separately. The colloidal suspension of PTFE may suitably also comprise a surfactant in the suspension to stabilise the PTFE particles.

[0151] The surfactant (either as a coating or present in the colloidal PTFE suspension) may be selected from a number of surfactants known in the art, for example those described inW02015071055 and WO2015116754 the entirety of which is incorporated herein by reference.

[0152] Suitably, the surfactant is selected from hydrocarbon surfactants, i.e. the surfactant is non-fluorinated. The surfactant may be non-ionic or anionic.

[0153] The surfactant may have the general formula:wherein:Ri represents a linear or branched aliphatic hydrocarbon group having at least 6 carbon atoms, preferably from 8 to 18 carbon atoms,R2 represents an alkylene unit having 3 or 4 carbon atoms,R3 represents hydrogen, a (1 -3C)alkyl group, or a (1-3C)hydroxyalkyl group, n has a value of from 0 to 40,m has a value of from 0 to 40,and the sum of n+m is at least 2.

[0154] 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.

[0155] 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 phenyl-formaldehyde condensate, polyoxyethylene alkyl ether phosphate and the like. Particularly preferable are polyoxyethylene alkyl ethers and polyoxyethylene alkyl esters.

[0156] 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).

[0157] Suitable nonionic hydrocarbon surfactants include octyl phenol ethoxylates such as the Triton® X series supplied by Dow Chemical Company:X15 (n~1.5)X45 (n~4.5)X100 (n~10)

[0158] 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:OHTergitol®TMN-6 (n ~ 8)TMN-10 (n~ 11)TMN-100 (n~ 10)

[0159] 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.

[0160] Yet another useful group of suitable nonionic hydrocarbon surfactants are difunctional block copolymers supplied as Pluronic® R series from BASF, such as:Pluronic® R31R1 (m~26, n~8)17R2 (m~14, n~9)10R5 (m~8, n~22)25R4 (m~22, n~23)

[0161] Another group of suitable nonionic hydrocarbon surfactants are tridecyl alcohol alkoxylates supplied as Iconol® TDA series from BASF Corporation.TDA-6 (n = 6)TDA-9 (n = 9)TDA-10 (n = 10)

[0162] 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.

[0163] As described herein, a surface modified PTFE solid may be prepared by freeze drying a commercially available colloidal suspension of PTFE in water.

[0164] A wide range of PTFE suspensions are known in the art, and typically comprises PTFE stabilised by one or more surfactants. Without wishing to be bound by theory, it is thought that freeze drying removes water from the PTFE suspensions while retaining the surfactant, leaving it uniformly distributed throughout the remaining PTFE solid.

[0165] 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.

[0166] In a preferred embodiment, the surfactant has a structure according to one of the formulas below:wherein n is an integer between 4 and 15. Preferably, n is an integer between 6 and 14.Detailed Description of the Invention

[0167] In the present invention, the interaction between particles which form the composite (i.e. the CAM, CCM and PTFE solid) is stronger than the interaction between those same particles and the solvent. This allows the formation of a composite which can be separated from the solvent by methods such as filtration.

[0168] If the particle- particle interactions are stronger than the solvent-particle interactions, the composited product can easily be separated from the liquid by mechanical means (e.g. filtration, or decantation). More specifically, if the particle- particle interactions are stronger than the solvent-particle interactions, the smaller particles (e.g. PTFE, conductive carbon) will adhere to the cathode active material (CAM) rather than be dispersed separately from theCAM in the solvent phase. If the particle-solvent interactions are stronger than particle-particle interactions, then a composite will not form and it will be difficult to remove the particles from the solvent.

[0169] If the force of repulsion between the particles is higher than the forces of attraction, the solvent will be more difficult to remove mechanically (e.g. through filtration or sedimentation of the solid product).

[0170] If the solids content of the solvent in the process of the first aspect is too high after addition of all the components (i.e. the PTFE, cathode active material, and conductive carbon material and optional further binders), then during application of mixing energy (e.g. shear force) to the mixture of PTFE, cathode active material, and conductive carbon material, it may result in a mixture with substantially solid characteristics, e.g. a viscosity above 50 Pa.s. If the viscosity is too high, the mixture may separate from vessel walls during mixing, making control of temperature very difficult.

[0171] Homogeneous contact between the mixture (e.g. of the CAM, CCM and PTFE) and solid surfaces inside the mixing vessel, such as the walls of the vessel, is advantageous for good mixing efficiency and good temperature control. A lower viscosity mixture is much more pumpable, making it possible to use high speed rotor-stator mixers, facile transfer between and within mixing vessels. This helps to achieve high-efficiency scaling to 1000s of kilograms of product.AWhere viscosity is defined at a shear rate of 10 Hz.Particular Embodiments of the Invention

[0172] 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 binder(s) are present in the following relative amounts:Active Material Conductive Carbon Binder ContentMaterial94.0 - 99.0% wt.% 0.2 - 3.0% wt.% 0.2 - 3.0 wt.%

[0173] 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 binder(s) are present in the following relative amounts:Active Material Conductive Carbon Binder ContentMaterial94.5 - 98.0% wt.% 0.5 - 3.0% wt.% 0.2 - 3.0 wt.%

[0174] 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 binder(s) are present in the following relative amounts:Active Material Conductive Carbon Binder ContentMaterial95.0 - 97.0 wt.% 1.0 - 2.5 wt.% 0.5 - 2.5 wt.%

[0175] 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 binder(s) are present in the following relative amounts:Active Material Conductive Carbon Binder ContentMaterial95.5 - 96.5 wt.% 1.8 - 2.2 wt.% 1.8 -2.2 wt.%

[0176] 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 and polymeric binder(s):Active Material Conductive Carbon Binder ContentMaterial96 wt.% 2 wt.% 2 wt.%

[0177] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial94.0 - 99.0% wt.% 0.2 - 3.0% wt.% 0.2 - 3.0 wt.%

[0178] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial94.5 - 98.0% wt.% 0.5 - 3.0% wt.% 0.2 - 3.0 wt.%

[0179] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial95.0 - 97.0 wt.% 1.0 - 2.5 wt.% 0.5 - 2.5 wt.%

[0180] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial95.5 - 96.5 wt.% 1.8 - 2.2 wt.% 1.8 -2.2 wt.%

[0181] 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 and PTFE:Active Material Conductive Carbon PTFE ContentMaterial96 wt.% 2 wt.% 2 wt.%

[0182] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial97.0 - 98.0 wt.% 0.7 - 1.5 wt.% 1.0 -2.0 wt.%

[0183] 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 PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE ContentMaterial97.2 - 97.8 wt.% 0.8 - 1.2 wt.% 1.2 - 1.8 wt.%

[0184] 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 and PTFE:Active Material Conductive Carbon PTFE ContentMaterial97.5 wt.% 1 wt.% 1.5 wt.%

[0185] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 94.0 - 99.0% wt.% 0.2 - 3.0% wt.% 0.1 - 1.5 wt.% 0.1 - 1.5% wt.%

[0186] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 94.5 - 98.0% wt.% 0.5 - 3.0% wt.% 0.1 - 1.5 wt.% 0.1 - 1.5 wt.%

[0187] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 95.0 - 97.0 wt.% 1.0 - 2.5 wt.% 0.25 - 1.25 wt.% 0.25 - 1.25 wt.%

[0188] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material PolymericBinder(s)95.5 - 96.5 wt.% 1.8 - 2.2 wt.% 0.9 - 1.1 wt.% 0.9 - 1.1 wt.%

[0189] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 96 wt.% 2 wt.% 1 wt.% 1 wt.%

[0190] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 97.2 - 97.8 wt.% 0.8 - 1.2 wt.% 0.6 - 1.4 wt.% 0.3 - 0.9 wt.%

[0191] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 97.2 - 97.8 wt.% 0.8 - 1.2 wt.% 0.8 - 1.2 wt.% 0.3 - 0.6 wt.%

[0192] 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, additional polymeric binder and PTFE are present in the following relative amounts:Active Material Conductive Carbon PTFE Additional Material Polymeric Binder(s) 97.5 wt.% 1 wt.% 0.75 wt.% 0.75 wt.%

[0193] Suitably, in the above discussed embodiments, the additional polymeric binder is PVDF.

[0194] In an embodiment of the composites, electrodes and processes of the invention, and the composites of the invention:a. the conductive carbon material comprises carbon black and optionally at least one of carbon nanotubes and graphene; andb. the cathode active material is NMC.Freeze-Drying

[0195] As is discussed here, the PTFE solid used in the first aspect may be prepared by freeze-drying a commercially available colloidal suspension of PTFE in water. Water can be removed from a PTFE suspension by the freeze-drying process. The suspension is first frozen at low temperature, e.g. < -30°C. (for example via immersion in N2(l)), immersion into IPA / CC>2(2) slurries, or via a conventional refrigeration).

[0196] Freeze-drying can be achieved at the laboratory scale in 100-500ml volumes, on suspensions contained in glass vessels that can be attached to a vacuum system. Freeze drying can also be achieved at larger scale.

[0197] The freeze-dry equipment provides a cooled condenser (<-40°C) and a vacuum system. The frozen suspensions are exposed to a dynamic continuous vacuum. The frozen ice-water content of the suspension is sublimed from the remaining solid, gradually, as it returns to room temperature (with or without heated assistance).

[0198] This can be achieved at the laboratory scale using standard freeze drying equipment such as the LyoDry bench top pro.Exemplary Embodiment of the Invention

[0199] In a particular embodiment, the process of the first aspect comprises:1) Freeze-drying an aqueous colloid of PTFE particles to remove substantially all of the water from the colloid;2) Suspending dry solids of cathode active material and conductive carbon material in a nonaqueous solvent at a solids content below 80 wt% and above 20 wt%; 3) Applying shear force to the mixture, such that the cathode active material and conductive carbon material material are intimately mixed;4) Adding the freeze-dried PTFE solids into the mixture;5) Applying a further shear force to the solids;6) Stopping shear force;7) Removing solvent by decantation or filtration of the solid materials; and8) Drying the remaining mixture to remove the solvent.

[0200] It is expected that at step 3 above, cathode active material (e.g. NMC) and conductive carbon material (e.g. carbon black) will be non-covalently attached to each other, such that they will settle out of the liquid together, and the carbons would not be suspended by the liquid.BRIEF DESCRIPTION OF THE DRAWINGS

[0201] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:Figure 1 shows SEM images of a composite powder made in Example 2 at magnification of 500x, 1000x and 3000x.Figure 2 shows SEM images of a composite powder made in Example 2 at magnification of 5000x, 10,000x and 30,000x.Figure 3 a and b shows SEM images characterising powder products formed in Example 3.Figure 4 shows a film formed using the composite product of Example 4.Figure 5 shows backscatter mode SEM showing NMC (white) in a network of carbon and binder (dark grey) in Example 4Figure 6 shows EDX study of product formed in Example 4. The study confirms the identity of the light regions to be NMC (Ni, O) and the dark grey regions to be CB / PTFE (C, F). The F scan shows some small response from the NMC particles due to the overlap between the Mn and F signals in the EDX scan.Figure 7 shows SEM images characterising powder products formed in Example 6 Figure 8 shows SEM images characterising powder products formed in Example 7 Figure 9 shows particle size distribution of the composite material powder of Example 7Figure 10 shows Supernatant samples taken from NMC / CB interaction (step 4.2) after (left) 30 minutes and (right) 60 minutes. Both samples visually appear crystal clear. Figure 11 shows Supernatant samples taken from freeze-dried Daikin PTFE / CB interaction (step 3.2) after (left) 30 minutes, (middle) 60 minutes and (right) 2.5 hours. All samples visually appear visually dark.Figure 12 shows Supernatant samples taken from Daikin F104 PTFE / CB interaction (step 8.2) after (left) 30 minutes, (middle) 60 minutes and (right) 2.5 hours. All samples visually appear visually dark.Figure 13 shows an SEM image of interaction between NMC and CB (step 4).Figure 14 shows PSD data from KY181, the NMC CAM used in the examples described herein.Figure 15 shows a plot of discharge rate capability of a composite formed in Example 3 in a lithium half-cell versus a wet benchmark.Figure 16 shows a plot of discharge rate capabilityof a composite formed in Example 6 in a lithium half-cell versus a wet benchmark.Figure 17 shows a plot of discharge rate capability of a composite formed in Example 7 in a lithium half-cell versus a wet benchmark.DETAILED DESCRIPTION

[0202] The present invention allows for composites suitable for fabricating into cathode films to be prepared without the need for dry mixing processes. Electrode component 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.

[0203] In addition, the use of solvent based processes can mean that less dust can escape into the atmosphere while preparing the electrode composite material. This can allow for safer working environment in the preparation of electrode films.

[0204] 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.

[0205] 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, MoS2and hexagonal boron nitride. Typically, a 2D material will comprise from 1-10 molecular layers.

[0206] 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’.

[0207] The term ‘few-layered particle’ means a particle which is so thin that may exhibit different properties than the same compound when in bulk. Not all of the properties of the compound will differ between a few-layered particle and a bulk compound, but one or more properties are likely to be different. A more convenient definition would be that the term ‘few layered’ refers to a crystal that is from 2 to 9 atomic or molecular layers thick in cross-section (e.g. 2 to 5 layers thick). Crystals of graphene, for example, which have more than 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 thecase of the transition metal dichalcogenides (e.g. MoS2and 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.

[0208] 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.

[0209] 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 graphitelike structure or as a diamond-like structure in which the boron and nitrogen atoms are tetrahedral orientated.

[0210] 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.

[0211] 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, MoS2, TaS2, PtTe2, Te2.

[0212] A layer of graphene consists of a sheet of sp2-hybridized carbon atoms. Each carbon atom is covalently bonded to three neighbouring carbon atoms to form a ‘honeycomb’ network of tessellated hexagons. Carbon nanostructures which have more than 10 graphene layers (i.e. 10 atomic layers; 3.5 nm) generally exhibit properties more similar to graphite than to mono-layer graphene. Thus, throughout this specification, the term graphene is intended to mean a carbon nanostructure with up to 10 graphene layers (for example, where 90% of the graphene flakes have a thickness of 2 to 7 layers or where 90% of the graphene flakes have a thickness of 3 to 10 layers). Graphene is the ‘ultimate’ 2D material as it is defined by having one carbon atom thickness layer / sheet, which is a structural unit of graphite.

[0213] 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 inGraphene 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 1(D), to the G peak Raman intensity, referred to as 1(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 l(D) / l(G) ratio, the greater the distance between defects, thus, the amount of disorder is lower. In addition to this, the full width at half maximum (FWHM) of D, G, 2D (also referred to as G’), D’ peaks can be used to evaluate the level of disorder as discussed in E. H. Martins Ferreira et al. 2010, “Evolution of the Raman spectra from single-, few-, and many-layer graphene with increasing disorder”, PHYSICAL REVIEW B. If FWHM of D, G, 2D (also referred to as G’), and D’ Raman peaks at a laser excitation wavelength of 514.5 nm (2.41 eV), are reaching values lower than 20 cm-1, 20 cm-1, 35 cm-1, and 10 cm-1 respectively, then the distance between zero dimensional pointlike defects is expected to be greater than approximately 4 nm.

[0214] The composites formed by the method of the present invention which comprise graphene may have an l(D) / l(G) ratio of less than 0.75, less than 0.6 or preferably less than 0.5, at a laser excitation wavelength of 532 nm (2.33 eV). Thus, the composites formed by the method of the present invention may have an I (D) / l (G) ratio of from 0.01 to 0.75, 0.02 to 0.65 or 0.04 to 0.55, at a laser excitation wavelength of 532 nm (2.33 eV). Given the distance between defects is greater than approximately 4 nm and a laser excitation wavelength of 532 nm (2.33 eV); an I (D) / I(G) ratio less than 1 indicates that the defects are greater than 9.5 nm apart.

[0215] It is also possible to assess the nature of the graphene defects using Raman spectroscopy. In general, defects in graphene are considered to be anything that breaks the symmetry of the infinite carbon hexagonal lattice. This therefore includes edges, vacancies and changes in carbon-hybridization (e.g. sp2into sp3). An sp3defect is due to an additional atom being present out-of-plane of the graphene layer resulting in an sp3hybridized carbon atom or atoms. A vacancy defect is due to one or more missing atoms of a 2D material layer. An edge defect is due to a graphene sheet not being infinitely large and therefore having an edge.

[0216] 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 typicallyhave an I (D) / I(G) ratio of above 0.8 or FWHM of D, G, 2D (in some literature called G’) peaks values higher than 70, 70, 150 cm-1respectively. Conversely, partially oxidised graphene oxide has fewer oxygen atoms compared to graphene oxide but has not undergone harsh reduction processes like reduced graphene oxide. Thus, more of the hexagonal structure is maintained, meaning fewer sp3and vacancy defects. The number of defects can be assessed by measuring the I (D) / l (G) ratio or FWHM of peaks as discussed above.

[0217] 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.

[0218] The ratio of the intensity of the Raman D peak, referred to as I (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.

[0219] The graphene containing composites of the present invention may have a FWHM-(G) (Full Width at Half Maximum of the graphene Raman G peak of a raman spectra) of lower than 70 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Preferably, the FWHM-(G) will be lower than 60 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). More preferably, the FWHM-G will be lower than 50 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Even more preferably, the FWHM-(G) will be lower than 40 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV). Most preferably, the FWHM-(G-) will be lower than 30 cm-1at a laser excitation wavelength of 514.5 nm (2.41 eV).

[0220] 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 excitation wavelength of 514.5 nm (2.41 eV). More preferably, the FWHM-(2D) will be lower than 60 cm’1at a laser excitation wavelength of 514.5 nm (2.41 eV). Even 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.

[0221] 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% ofthe 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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] The term “high shear” relates to mixing at a rate greater than of 105s’1. An example of high shear mixing is an I KA T25 rotor-stator lab mixer at a speed of 10,000 RPM.

[0226] The term “low shear” relates to mixing at a rate of 105s-1or less, preferably 104s-1.

[0227] Particle size measurements may be performed using methods known in the art or the methods described herein.

[0228] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0229] 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 anymethod 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.

[0230] 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.EXAMPLES

[0231] The invention will now be described with reference to the following non-limiting examples.

[0232] The following protocol may be used to form freestanding films, unless described otherwise.Following the method described in WO2025062155A1: The powder was rolled out into a sheet using a rolling pin. After a film was formed, the film was repeatedly i) folded in half, ii) rotated through 90 degrees, and iii) rolled again. Folding in half was not strictly necessary if the electrode appeared homogeneous. Smaller diameter rollers were used during rolling if thinning was not occurring. Steps i-iii were repeated until the desired loading (e.g. 200 GSM) was reached.Freestanding films may be calendered onto current collector foil with or without a primer layer. Generally, a suitable primer layer will reduce electronic interfacial resistance between the current collector and film, and it may also improve mechanical attachment of the film to the current collector.Wet Benchmark Preparation and Cell Testing:

[0233] In all examples where electrochemical testing was conducted, the following protocol was used for testing electrodes at 200 GSM (20 mg / cm2) loading. A ‘wet benchmark’ was produced using standard techniques for processing NMP slurries.

[0234] Dissolution of PVDF and pre-dispersion of conductive carbon additives in a 1:1 ratio in NMP solvent was carried out using a thinky mixer. 45 minutes mixing at 2000 RPM facilitated a homogenous stock solution of NMP, PVDF binder and conductive carbon additives with a solid content of 5%.

[0235] The active material, an NMC811, was added to the above stock solution in quantities to achieve a ratio of 96wt% cathode active material, 2 wt% PVDF binder and 2wt% conductive carbon additive. NMP was then added to this mixture to bring the total solids to liquids ratio to 70:30. This slurry precursor was then mixed at 2000 rpm for 60 minutes in a thinky.

[0236] The viscosity of the slurry was checked every 20 minutes to ensure it remained within ideal electrode coating limits. This viscosity before coating was measured between 2 and 4 Pa.s at a sheer rate of 10.

[0237] The electrode slurry was then coated on 15 pm aluminum foil using a draw down coater and doctor blade, setting the blade gap to yield a final dry film of loading 20 mg / cm2. The coated electrode was dried for 12 hours at 120 °C under a vacuum of 50 mbar.

[0238] The resulting electrode was calandered down to a target density of 3.3 g / cc.

[0239] From this coating lithium half cell coin cells were prepared for electrochemical testing. A 12 micron polyethylene electrode separator and 1 M LiPF6 in 1:1 ethylene carbonate and dimethyl carbonate, with 2 wt% vinylene carbonate electrolyte were used for half cell assembly in addition to an 18 mm lithium metal disk.

[0240] Charge and discharge rates during initial electrochemical formation of the half cells were conducted at 0.1 C. Rate testing of half cells was then conducted over a range of discharge C-rates: 0.2C, 0.5C, 1 C, 2C, 3C, 4C and 5C. With a final 0.2 C recovery cycle check. A voltage cutoff of 2.75 V to 4.3 V was enforced on discharge and charge respectively for all steps.

[0241] The following examples were tested in this manner:o Example 3 (a plot of discharge rate vs cycle number is shown in Figure 15) o Example 6 (a plot of discharge rate vs cycle number is shown in Figure 16) o Example 7 (a plot of discharge rate vs cycle number is shown in Figure 17) Example 1 - Freeze Drying of PTFE Suspension

[0242] 100ml of Sigma-Aldrich 60% wt. PTFE aqueous suspension (665800, Sigma-Aldrich) is poured into a 250ml round bottom flask. The flask is then carefully immersed in liquid nitrogen for a period of 5-10mins. Care is taken here to avoid excess liquid nitrogen boil off. The flash is regularly inspected to confirm that all the suspension has frozen, both visually, by agitation, and by ice crystallisation sounds.

[0243] The LyoDry bench top pro freeze-dryer is turned on and its condenser is cooled down to -40°C. the freeze-dryer vacuum is turned on and a vacuum of <0.2mbar is reached.

[0244] The flask containing the frozen suspension is attached to the LyoDry equipment with conventional vacuum attachments.

[0245] The connected flask is then carefully opened to the freeze-drying equipment and the resulting vacuum is monitored as function of time.

[0246] Freeze-drying of the flasks contents is continued until the vacuum has reached ~ 0.06mbar (in this case it was reached in 14hrs without heating of the frozen suspension).

[0247] The flask containing the freeze-dried PTFE is removed to a fridge and the material recovered from the flask by tapping out.

[0248] The freeze-drying equipment is warmed to RT and the removed water is removed via the drain valve.

[0249] The remaining water in the freeze-dried PTFE is verified via TGA and Karl-Fisher equipment to be in the range 0.2-0.4 wt. %.Example 2 - Preparation of Composite

[0250] PTFE is prepared beforehand by freeze-drying an aqueous dispersion (665800, Sigma-Aldrich) as explained in Example 1.

[0251] 2 g Super P carbon black is dispersed in 80 g isopropyl alcohol using an IKA T25 equipped with an 18 G ST tool, running at 10,000 RPM for 15 minutes. Temperature is kept stable by keeping the vessel in a bath of approx. 150 ml of water at room temperature (i.e. 20-25°C).

[0252] 40 ml of this mixture is added into a second vessel. 48 g of NMC (KY181, from Targray) is added, then a further 60 ml isopropyl alcohol, then 1 g of the pre-prepared PTFE.

[0253] The mixture is dispersed for a further 5 minutes at 10,000 RPM, remaining in the water bath for temperature stability.

[0254] The beaker is added to an ice bath to settle for 30 minutes under N2 blanketing.

[0255] The mixture is filtered and the solids are washed with I PA.

[0256] The collected solids are left to dry under N2 blanketing at room temperature for 10 minutes.

[0257] The solids are then dried for 24h in a vacuum oven at 50°C.

[0258] SEM images of the formed composite powder are shown in Figures 1 and 2.Example 3

[0259] Step 1: 2.064 g CB (C65, Imerys) and 80 g dimethyl carbonate (Sigma-Aldrich) were added into a 140 ml beaker. High shear mixing (15k RPM) was applied using an IKA Ultra-Terrax T25 mixer, for 15 minutes.

[0260] Step 2: The following was then added into a fresh 140 ml beaker. Throughout step 2 the beaker was immersed in a water bath at ambient temperature (22 degrees Celsius)

[0261] Components were added in the following order:• 1 / 4 of the solvent mixture from step 1 (approx. 20 ml of solvent mixture, or enough to yield approx. 0.5 g CB)• 48.77 g NMC.• 40 ml DMC

[0262] Mixing at 10k RPM begins. Quickly, the following are added:• 20 ml further DMC added• 0.765 g PTFE is added, as prepared in example 1

[0263] Mixing continues for a total of 3 minutes in this step 2.

[0264] Step 3: Leave the mixture to settle for 15 minutes under nitrogen.

[0265] Step 4: The supernatant appeared transparent. The supernatant was removed, and the settled material was transferred into a Gooch funnel using approx. 50 ml to wash out the beaker into the funnel.

[0266] Step 5: The black product was filtered under a nitrogen blanket. Filtration was performed until the surface of the filter cake was dry to the eye, then left to dry on the filter for a further 10 minutes. Product was transferred to a vacuum oven to dry under vacuum for 24h at 50 degrees Celsius. Figure 3 shows SEM images of the powder product formed.

[0267] The powder product was rolled into an electrode. The product was rolled by hand using the following method also described in WO2025062155A1. The dough formed was rolled out into a sheet using a rolling pin. After a film was formed, the film was repeatedly i) folded in half, ii) rotated through 90 degrees, and iii) rolled again. Folding in half was not strictly necessary if the electrode appeared homogeneous. Smaller diameter rollers were used during rolling if thinning was not occurring.Example 4

[0268] Step 1: PTFE in isopropyl alcohol was prepared by mixing 1g PTFE (Daikin F107) in 10 ml IPA using an IKA Ultra-Terrax T25 mixer. Conditions used: 5k RPM, ice bath around mixing vessel, 2 minutes of mixing. This made a cloudy solvent mixture, and was set aside.

[0269] Step 2: 1.03 g CB (C65, Imerys) and 35 g isopropyl alcohol (IPA) were added into a 80 ml beaker. The carbon was stirred briefly with a spatula to ensure good wetting. High shear mixing at 10k RPM was applied using an I KA Ultra-Terrax T25 mixer, for 15 minutes. A good vortex was formed, and no clumps were visible in the liquid.

[0270] Step 3: The solvent mixture formed in step 2 was equipped with a magnetic stirrer and transferred to a magnetic stirring plate to be mixed at 900 RPM. 48.17 g of NMC (KY181, Targray) was added in portions to the beaker, followed by the PTFE solvent mixture from Step 1. The mixture was left stirring for 10 minutes at room temperature (22 degrees Celsius) while flowing nitrogen gently over the surface of the solvent mixture in the beaker.

[0271] Step 4: The mixture was transferred to a 2L beaker along with 400 ml IPA. The mixture was stirred at 550 RPM with a magnetic stirrer bar for 10 minutes, maintaining a flow of nitrogen gently over the surface of the solvent mixture in the beaker.

[0272] Step 5: The mixture was left to settle in an ice bath for 30 minutes. After this settling, some of the supernatant was collected in a 5 ml vial and found to be pale grey, almost clear.

[0273] Step 6: The supernatant was decanted, and vacuum filtration was performed using a large Gooch (sintered glass) filter. Sludge-like material was observed at the bottom of the beaker before transfer into the filter, indicating composite formation. On the filter, 5x 20 ml IPA portions were used to wash the product. A flow of nitrogen was provided over the filter. The composite material was left to dry on the filter for 10 minutes.

[0274] Step 7: The composite material was transferred to a crystalliser dish and dried in a vacuum oven at 50 degrees Celsius for 24h.

[0275] The composite product formed by this process was characterised.

[0276] The powder product was rolled into an electrode. The product was rolled by hand using the following method also described in WO2025062155A1. The dough formed was rolled out into a sheet using a rolling pin. Figure 4 shows a picture of the formed film. After a film was formed, the film was repeatedly i) folded in half, ii) rotated through 90 degrees, and iii) rolled again. Folding in half was not strictly necessary if the electrode appeared homogeneous. This process was performed until an areal loading of 200 grams per square centimetre was reached. Smaller diameter rollers were used during rolling if thinning was not occurring.

[0277] SEM in backscatter mode was performed on the product (Figure 5). The results showed a composite product of NMC particles interspersed with carbon / binder structures.

[0278] EDX mapping was performed on the sample to confirm identity of the materials observed in the backscattering SEM study. Images are shown in Figure 6. The EDX mappingstudy confirmed the identity of the light regions to be NMC (Ni, O) and the dark grey regions to be CB / PTFE (C, F). The F scan shows some small response from the NMC particles due to the overlap between the Mn and F signals in the EDX scan.Example 5 - Interaction of NMC and CB with freeze dried PTFE and pure PTFE

[0279] This example investigates the interaction between the individual components. E.g carbon with CAM, carbon with PTFE. Pure PTFE and freeze dried PTFE was used.Freeze Dried PTFE

[0280] Step 1: 1.50 g CB (C65, Imerys) and 73.52 g IPA (Fisher Scientific) were added to a 150 mL beaker (beaker 1A). High shear mixing (10k RPM) was applied using an IKA Ultra-Terrax T25 mixer, for 15 minutes. Throughout step 1 the beaker was immersed in a water bath at ambient temperature (22 degrees Celsius)

[0281] Step 2: The produced solvent mixture was split equally across three 100 mL beakers, ~33 mL per beaker (beaker 1B, 1C, 1D).CB + Freeze Dried DAIKIN

[0282] Step 3.1: 0.76 g freeze-dried PTFE (Daikin, D-210C) was added to beaker 1B. High shear mixing (10k RPM) was applied for 5 minutes. Throughout step 3.1, the beaker was immersed in a water bath at ambient temperature

[0283] Step 3.2: The solvent mixture was left to settle for 2.5 hours under nitrogen at room temperature. Samples of the supernatant were taken after 30 minutes, 1 hour and 2.5 hours. Throughout this period, the solvent mixture remained visually pitch black (see Figure 11). CB + NMC

[0284] Step 4.1: 48.75 g NMC (KY181, Targray) was added to beaker 1C. High shear mixing (10k RPM) was applied for 15 minutes. Throughout step 4.1, the beaker was immersed in a water bath at ambient temperature.

[0285] Step 4.2: The solvent mixture was left to settle for 1 hour under nitrogen at room temperature. Samples of the supernatant were taken after 30 minutes and 1 hour of settling. Within 30 minutes, a transparent supernatant was seen (Figure 10). Minimal changes were seen between 30 minutes and 1 hour of settling.

[0286] Step 4.3: After 1 hour, the supernatant was removed and the settled material was transferred into a Gooch funnel. Approximately 30 mL to wash out the beaker into the funnel.

[0287] Step 4.4: The black product was filtered under a nitrogen blanket. Filtration was performed until the surface of the filter cake was dry to the eye, then left to dry on the filter for a further 10 minutes.Pure PTFE

[0288] Step 6: 1.50 g CB (C65, Imerys) and 73.52 g IPA (Fisher Scientific) were added to a fresh 150 mL beaker (beaker 1F). High shear mixing (10k RPM) was applied for 15 minutes. Throughout step 6, the beaker was immersed in a water bath at ambient temperature

[0289] Step 7: 1 / 3 of the solvent mixture produced in step 7 (~33 mL) was decanted into a fresh 100 mL beaker (beaker 1G)CB + F104 PTFE

[0290] Step 8.1: 0.75 g PTFE (Daikin, F104) was added to beaker 1G. High shear mixing (10k RPM) was applied for 5 minutes. Throughout step 8.1, the beaker was immersed in a water bath at ambient temperature

[0291] Step 8.2: The solvent mixture was left to settle for 2.5 hours under nitrogen at room temperature. Samples of the supernatant were taken after 30 minutes, 1 hour and 2.5 hours. Throughout this time, the solvent mixture remained pitch black (see Figure 12).Example 6

[0292] Step 1: 1.27 g CB (C65, Imerys) and 61.73 g IPA were added into a 150 ml beaker. High shear mixing (15k RPM) was applied using an I KA Ultra-Terrax T25 mixer, for 15 minutes.

[0293] Step 2: The following was then added into a fresh 100 ml beaker:1 / 2 of the solvent mixture from step 1 (this 1 / 2 yielded approx. 40 ml slurry of CB / IPA) - 48.78 g NMC.0.65 g PTFE as prepared in example 1.- 30 ml IPA

[0294] Step 3: The mixture was mixed in the T25 mixer for 5 minutes at 10k RPM. A water bath at room temperature (22 degrees Celsius) was used to avoid excessive temperature rise. The temperature inside the mixture should reach elevated temperature (e.g. 28 degrees Celsius). The mixture was left to settle for 30 minutes under nitrogen.

[0295] Step 4: The supernatant appeared transparent. A small vial of supernatant (approx.5 ml) was removed, and the liquid appeared nearly completely transparent. The rest of the supernatant was not removed, and the mixture was transferred into a Gooch funnel using approx. 30 ml to help wash out the beaker into the funnel.

[0296] Step 5: The black product was vacuum filtered under a nitrogen blanket. Filtration was performed until the surface of the filter cake was dry to the eye. Product was transferredto a vacuum oven to dry overnight at 50 degrees Celsius. Figure 7 shows an SEM image of the formed powder.Example 7

[0297] Step 1: 1.52 g CB (C65, Imerys) and 73.5 g I PA were added into a 150 ml beaker. High shear mixing (15k RPM) was applied using an I KA Ultra-Terrax T25 mixer, for 15 minutes.

[0298] Step 2: The following was then added into a fresh 100 ml beaker:1 / 3 of the solvent mixture from step 1 (this 1 / 3 yielded approx. 30 ml slurry)- 48.78 g NMC (KY181, Targray).0.78 g PTFE as prepared in example 1.- 30 ml IPA

[0299] Step 3: The mixture was mixed in the T25 mixer for 5 minutes at 10k RPM. The temperature should reach around 28 degrees Celsius. Leave the mixture to settle for 30 minutes under nitrogen.

[0300] Step 4: The supernatant appeared transparent. The supernatant was removed, and the settled material was transferred into a Gooch funnel using approx. 50 ml to wash out the beaker into the funnel.

[0301] Step 5: The black product was filtered under a nitrogen blanket. Filtration was performed until the surface of the filter cake was dry to the eye. Product was transferred to a vacuum oven to dry overnight at 50 degrees Celsius. Figure 8 shows an SEM image of the formed powder.

[0302] Particle Size Distribution was tested using a Mastersizer 3000 with a liquid dispersion attachment (Figure 9). Measurements recorded over 15 minutes are plotted on top of each other to produce the trace in the figures. The liquid dispersing attachment was set to 1500 RPM to disperse the powder.

[0303] Particle size distribution data of the source NMC KY181 was collected using the following method.1. With MeOH used as dispersant liquid, mixer RPM set to 2500 RPM in the liquid cell2. Powder added gradually until -12% obscuration reached3. Once 12% obscuration reached, 50 measurements are taken, spaced over 15 minutes.4. Each measurement was plotted on the graph. Plots are shown in Figure 14.5. The peaks highlighted with a vertical line are from the measurement done at the end of the 15 minutes of measurement.

[0304] Particle size distribution data of the product from Step 5 was collected using the following method:.1. With IPA used as dispersant liquid, mixer RPM set to 1500 RPM in the liquid cell 2. Powder added gradually until 19% obscuration reached3. Once 12% obscuration reached, 50 measurements are taken, spaced over 15 minutes.4. Each measurement plotted on the graph, traces are shown in varying shades of grey. Plots are shown in Figure 9.5. The peaks highlighted with a vertical line are from the measurement done at the end of the 15 minutes of measurement.

[0305] The product was rolled by hand using the following method also described in WO2025062155A1. The dough formed was rolled out into a sheet using a rolling pin. After a film was formed, the film was repeatedly i) folded in half, ii) rotated through 90 degrees, and iii) rolled again. Folding in half was not strictly necessary if the electrode appeared homogeneous. This process was performed until an areal loading of 200 grams per square centimetre was reached. Smaller diameter rollers were used during rolling if thinning was not occurring.

Claims

CLAIMS1. A process for fabricating a composite, the process comprising:mixing a PTFE solid, a cathode active material, and a conductive carbon material in a solvent, wherein the solids content within the solvent is 80 wt.% or below; applying mixing energy to distribute the PTFE solid, cathode active material, and conductive carbon material amongst each other;removing the mixing energy; andremoving solvent from the mixture.

2. The process of claim 1, wherein following the removal of the solvent, the composite is applied into a calendar nip gap to form a continuous film.

3. The process according to claim 1 or claim 2, wherein the weight ratio of PTFE: cathode active material: conductive carbon material is 0.2 - 3.0: 94.0 - 99.0: 0.2 - 3.0 (e.g.0.2 - 3.0: 94.0 - 99.0: 0.5 - 3.0).

4. The process according to any one of the preceding claims, wherein the viscosity of the solvent is less than 50 Pa.s during application of the mixing energy.

5. The process according to any one of the preceding claims, wherein the cathode active material is selected from one or more of NMC, NCA, LNMO, LFP and LMFP.

6. The process according to any one of the preceding claims, wherein the cathode active material has a particle size from 0.1 to 40 μm.

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

8. The process according to any one of the preceding claims, wherein the conductive carbon material has a primary particle size of from 5 nm to 200 nm.

9. The process according to any one of the preceding claims, wherein the application of mixing energy comprises high shear mixing, one or more of sonication, paddle, bar, or blade stirring, stirring, planetary mixing or shear mixing.

10. The process according to any one of the preceding claims, wherein the solvent is a non-aqueous solvent;optionally wherein the solvent is selected from one or more of methanol, ethanol, isopropanol, dimethyl carbonate, diethyl carbonate, butyl acetate, 2-butoxyethyl acetate, heptyl butyrate, n-butyl acetate, tert-butyl acetate, propylene carbonate, iso-amyl acetate, hexyl acetate, heptyl acetate, triacetine, dimethyl isosorbite, tert-butyl methyl ether (TBME)tert-butyl methyl ether, 2-butoxyethyl acetate, ethyl diglycol carbonate, benzyl benzoate or dimethyl adipate;further optionally wherein the solvent is selected from one or more of 2-butoxyethyl acetate, heptyl butyrate, iso-propanol, ethanol, methanol, n-butyl acetate, iso-amyl acetate, dimethyl carbonate, diethyl carbonate, tert-butyl methyl ether (TBME), tertbutyl acetate, hexyl acetate;11. The process according to any one of the preceding claims, wherein the solvent is selected from one or more of iso-propanol, or dimethyl carbonate.

12. The process according to any one of the preceding claims, wherein the process is performed under anhydrous conditions.

13. The process according to any one of the preceding claims, wherein the solvent is removed by one or more of by filtration, centrifugation, decantation, and / or drying.

14. The process according to any one of the preceding claims, wherein the PTFE solid has a primary particle size 100 to 1000 nm.

15. The process according to any one of the preceding claims, wherein the PTFE solid comprises a surfactant coating;optionally wherein the surfactant is a non-fluorinated surfactant;further optionally wherein the surfactant is a non-ionic surfactant.

16. The process according to claim 15, wherein the surfactant is selected from branched alcohol ethoxylates or branched secondary alcohol ethoxylates.

17. The process according to any one of the preceding claims, wherein the PTFE solid comprises from 0 to 4.0 wt.% water, preferably from 0 to 3.0 wt.% water, more preferably from 0 to 2.0 wt.% water.

18. The process according to any one of the preceding claims, wherein the PTFE solid is prepared by freeze drying a PTFE suspension comprising colloidal PTFE particles suspended in water.

19. The process according to claim 18, wherein the PTFE colloidal suspension further comprises a surfactant; optionally wherein the surfactant is as defined in claim 14 or 15.

20. A process to prepare a surface modified PTFE solid, the process comprising:i) providing a PTFE suspension comprising colloidal PTFE particles suspended in water;ii) freeze drying the colloidal suspension comprising PTFE to remove at least 96 wt.% of the water from the PTFE suspension.

21. A process according to claim 20, wherein the PTFE suspension comprises 40 to 80 wt.% solids; preferably from 50 to 70 wt.% solids.

22. A process according to claim 20 or 21, wherein the PTFE suspension comprises one or more surfactant.

23. A process according to claim 22, wherein the PTFE suspension comprises one or more surfactants.wherein the one or more surfactants is a non-ionic surfactant;optionally wherein the surfactant is selected from branched alcohol ethoxylates or branched secondary alcohol ethoxylates.

24. A surface modified PTFE solid obtained by, obtainable by, or directly obtained by, the process according to any one of claims 20 to 23.

25. A surface modified PTFE solid suitable for use in an organic solvent-based compositing process.

26. The use of a surface modified PTFE according to claim 24 or 25 in the preparation of an electrode composite.

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