Polyurea binders

Abstract

A binder composition for use in a battery electrode comprises or consists of a polyurea polymer, such as a polyetherurea polymer. Also disclosed is a method of preparing a polyurea polymer for use in a binder composition for an electrode material, the method comprising reacting a diamine compound and methanol in the presence of a metal pincer complex and a base to form polyurea and hydrogen gas by dehydrogenative coupling.

Description

[0001] Polyurea binders

[0002] Field of the Invention

[0003] The present invention relates to polyurea compounds, e.g. polyetherurea compounds, suitable for use as binders for battery electrodes. In particular, but not exclusively, the invention relates to a binder composition comprising a polyetherurea for a battery electrode.

[0004] Background

[0005] There has been a huge increase in the global demand for energy due to a rise in population coupled with technological advancements such as the increased use of portable devices and the use of electric vehicles. Portable energy storage systems capable of storing energy, especially energy generated from renewable energy sources are a constant source of innovation. One example of such rechargeable energy storage systems is metal-ion batteries such as lithium-ion batteries (LIBs) and sodium-ion batteries.

[0006] LIBs provide high energy density, a relatively long lifespan of about two to three years, and good rate capabilities. They are also flexible, sustainable, and lightweight. The rechargeability of LIBs is dependent on insertion where Li+can be inserted into and extracted from the host structure without any modification to provide a good cycle life for the batteries. It should enable a large amount of Li+transport to maximise the capacity of the battery.

[0007] LIBs consist of a cathode (positive electrode), an anode (negative electrode), a current collector, and an electrolyte. Cathode materials are often lithium metal oxides whilst anodes are typically something like a graphitic carbon. An example of an electrolyte is a lithium salt that is dissolved in an organic solvent, for example lithium hexafluorophosphate (LiPFe). Upon charging, electrons move from the cathode to the anode through the electrolyte once the voltage is applied between both electrodes. When the electrons move in the reverse direction from the anode to the cathode through the electrolyte, the LIB is discharged.

[0008] A positive electrode is typically made of the following: active materials (e.g. LiFePCU (LFP)), binders, and conductive additives (such as conductive carbon) which are then dispersed in a solvent to obtain a viscous slurry. This may then be cast onto a current collector (aluminium foil) using a tape casting technique with a doctor blade.

[0009] 55652043-1 Binders maintain the structure of the different electrode materials and prevent the mechanical degradation of the electrodes due to the chemical and mechanical stress that occurs during the continuous charge / discharge process by acting as a glue. Binders increase the mechanical strength and electrochemical stability of the electrode and ensure electron and ion transport. They also improve the dispersion of the active material and maximise electrical contacts between electrode components and the current collector. Binders further aid the dispersion of other components in the solvent during the fabrication process, some can even increase the viscosity which enables a homogenous distribution.

[0010] Polymers can function as binders ensuring good adhesion and contact amongst the different components. The binding ability of polymers can depend on several properties of polymers such as their molar mass, the concentration of functional groups present, presence of side chains or branching. These factors further affect the following parameters: mechanical stability, tensile strength, flexibility, hardness, and adhesive strength.

[0011] These binders must be inert to the processes within the batteries along with the formations of the electrodes requiring high thermal, mechanical, chemical, and electrochemical stabilities. It should not react with the electrolyte, active material, or other components of the electrochemical reactions..

[0012] Examples of conventional binders include poly(vinylidene difluoride) (PVDF), carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR).

[0013] Poly(vinylidene difluoride) (PVDF) is currently the most commonly used binder for LIBs. This is due to its electrochemical stability and binding capability along with the ability to absorb the electrolyte for facile transport of Li+to the active material surface. However, PVDF requires the use of toxic and expensive organic solvents, such as N- methyl-2-pyrrolidone (NMP), which is environmentally unfriendly. Furthermore, PVDF has poor binding affinity to the electrode components because its binding mechanisms are primarily mechanical interlocking and weak van der Waals forces. PVDF is also electrically insulating and therefore requires a conductive additive for full functionality of the electrode.

[0014] The replacement of PVDF with aqueous binders is attractive as the slurry preparation can be done in water which makes the electrode preparation low-cost and environmentally friendly in comparison to the use of an organic solvent to prepare the slurry. Aqueous binders offer lower costs, no environmental detriment, and potential

[0015] 55652043-1 enhancement of the active material proportion in a cell due to the reduction in binder content.

[0016] Carboxymethylcellulose (CMC) is an aqueous linear-type binder consisting of natural cellulose which has been modified with carboxymethyl groups, making the material water-soluble. It is comparatively cheaper than PVDF and is easily disposed of through pyrolysis. CMC binds with its carboxylic groups to the surface of the substrates and can form strong hydrogen and covalent ester bonds rendering it suitable for compounds with surface hydroxyl groups.

[0017] Styrene-butadiene rubber (SBR) is a synthetic rubber made from the polymerisation reaction of styrene and butadiene. SBR exhibits strong binding force, high flexibility, and good heat resistance. Compared to PVDF, a smaller quantity of SBR provides higher binding ability, better mechanical properties, and a higher degree of flexibility. SBR is not often used by itself as a binder due to its poor adhesion resulting from low viscosity. Furthermore, SBR is insoluble in water and instead added as a nanoparticulate dispersion to the slurry containing CMC.

[0018] A combination of CMC / SBR binders has improved adhesion, enhanced cycle performance, dispersive capabilities, flexibility, elasticity, binding strength mechanical stability particularly when the electrode experiences volume expansion. Furthermore, this composite improved the rapid insertion / de-insertion of Li+.

[0019] Despite the technological advancements and development of aqueous binders, existing binders still face limitations, including limited compatibility between existing aqueous binders and certain electrode materials. Therefore, there is a need in the art for an aqueous binder that can offer advantageous properties for use in battery electrodes, and / or which is compatible with active materials that are efficient and sustainable.

[0020] It is an object of the invention to address and / or mitigate one or more problems associated with the prior art.

[0021] It is an object of the invention to provide an improve binder composition for use in battery electrodes, e.g. cathodes, for example in metal-ion batteries.

[0022] Definitions

[0023] "Alkyl" as used herein alone or as part of another group, refers to a linear or branched chain hydrocarbon containing from 1 to 20 carbon atoms, which can be referred to as a C1-C20 alkyl. Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n- pentyl, isopentyl, neopentyl, n-hexyl, 3-methyl hexyl, 2,2-dimethylpentyl, 2,3-

[0024] 55652043-1 dimethylpentyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and the like. "Lower alkyl" as used herein, is a subset of alkyl, and, in some embodiments, refers to a linear or branched chain hydrocarbon group containing from 1 to 4 carbon atoms. Representative examples of lower alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, and the like. The term "alkyl" or "lower alkyl" is intended to include both substituted and unsubstituted alkyl or lower alkyl unless otherwise indicated and these groups may be substituted with groups selected from halo, alkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, aryl, arylalkyl, heterocyclo, heterocycloalkyl, hydroxyl, alkoxy (thereby creating a polyalkoxy such as polyethylene glycol), alkenyloxy, alkynyloxy, haloalkoxy, cycloalkoxy, cycloalkylalkyloxy, aryloxy, arylalkyloxy, heterocyclooxy, heterocycloalkyloxy, mercapto, alkyl-S(O)m, haloalkyl-S(O)m, alkenyl- S(O)m, alkynyl-S(O)m, cycloalkyl-S(O)m, cycloalkylalkyl-S(O)m, aryl-S(O)m, arylalkyl- S(O)m, heterocyclo-S(O)m, heterocycloalkyl-S(O)m, amino, carboxy, alkylamino, alkenylamino, alkynylamino, haloalkylamino, cycloalkylamino, cycloalkylalkylamino, arylamino, arylalkylamino, heterocycloamino, heterocycloalkylamino, disubstituted- amino, acylamino, acyloxy, ester, amide, sulfonamide, urea, alkoxyacylamino, aminoacyloxy, nitro or cyano where m= 0, 1 , 2 or 3.

[0025] "Alkenyl" as used herein alone or as part of another group, refers to a linear or branched chain hydrocarbon containing from 1 to 20 carbon atoms (or in lower alkenyl 1 to 4 carbon atoms) that can include 1 to 8 double bonds in the normal chain, and can be referred to as a C1-C20 alkenyl. Representative examples of alkenyl include, but are not limited to, vinyl, 2-propenyl, 3-butenyl, 2-butenyl, 4-pentenyl, 3-pentenyl, 2-hexenyl, 3-hexenyl, 2,4-heptadiene, and the like. The term "alkenyl" or "lower alkenyl" is intended to include both substituted and unsubstituted alkenyl or lower alkenyl unless otherwise indicated and these groups may be substituted with groups as described in connection with alkyl and lower alkyl above.

[0026] "Alkynyl" as used herein alone or as part of another group, refers to a linear or branched chain hydrocarbon containing from 1 to 20 carbon atoms (or in lower alkynyl 1 to 4 carbon atoms) which include 1 triple bond in the normal chain, and can be referred to as a C1-C20 alkynyl. Representative examples of alkynyl include, but are not limited to, 2-propynyl, 3-butynyl, 2-butynyl, 4-pentynyl, 3-pentynyl, and the like. The term "alkynyl" or "lower alkynyl" is intended to include both substituted and unsubstituted alkynyl or lower alkynyl unless otherwise indicated and these groups may be substituted with the same groups as set forth in connection with alkyl and lower alkyl above.

[0027] 55652043-1 "Halo" as used herein refers to any suitable halogen, including -F, -Cl, -Br, and - I.

[0028] "Mercapto" as used herein refers to a -SH group.

[0029] "Azido" as used herein refers to a -N3 group.

[0030] "Cyano" as used herein refers to a -CN group.

[0031] "Hydroxyl" as used herein refers to an -OH group.

[0032] "Nitro" as used herein refers to a -NO2 group.

[0033] "Alkoxy" as used herein alone or as part of another group, refers to an alkyl or lower alkyl group, as defined herein (and thus including substituted versions such as polyalkoxy), appended to the parent molecular moiety through an oxy group, -O-. Representative examples of alkoxy include, but are not limited to, methoxy, ethoxy, propoxy, 2-propoxy, butoxy, tert-butoxy, pentyloxy, hexyloxy and the like.

[0034] "Acyl" as used herein alone or as part of another group refers to a -C(O)R radical, where R is any suitable substituent such as aryl, alkyl, alkenyl, alkynyl, cycloalkyl or other suitable substituent as described herein.

[0035] "Haloalkyl" as used herein alone or as part of another group, refers to at least one halogen, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein. Representative examples of haloalkyl include, but are not limited to, chloromethyl, 2-fluoroethyl, trifluoromethyl, pentafluoroethyl, 2-chloro-3- fluoropentyl, and the like.

[0036] "Alkylthio" as used herein alone or as part of another group, refers to an alkyl group, as defined herein, appended to the parent molecular moiety through a thio moiety, as defined herein. Representative examples of alkylthio include, but are not limited, methylthio, ethylthio, tert-butylthio, hexylthio, and the like.

[0037] "Cycloalkyl" as used herein alone or as part of another group, refers to a saturated or partially unsaturated cyclic hydrocarbon group containing from 1 to 20 carbon atoms (optionally with a carbon atom replaced in a heterocyclic group as discussed below). A cycloalkyl group may include 0, 1 , 2, or more double or triple bonds. Representative examples of cycloalkyl include, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclododecyl. These rings may optionally be substituted with additional substituents as described herein such as halo or lower alkyl. The term "cycloalkyl" is generic and intended to include heterocyclic groups as discussed below unless specified otherwise.

[0038] "Heterocyclic group" or “heterocyclo” as used herein alone or as part of another group, refers to an aliphatic (e.g., fully or partially saturated heterocyclo) or aromatic

[0039] 55652043-1 (e.g., heteroaryl) monocyclic- or a bicyclic-ring system. Monocyclic ring systems are exemplified by any 5- or 6-membered ring containing 1 , 2, 3, or 4 heteroatoms independently selected from oxygen, nitrogen and sulfur. The 5-membered ring has from 0-2 double bonds and the 6-membered ring has from 0-3 double bonds. Representative examples of monocyclic ring systems include, but are not limited to, azetidine, azepine, aziridine, diazepine, 1 ,3-dioxolane, dioxane, dithiane, furan, imidazole, imidazoline, imidazolidine, isothiazole, isothiazoline, isothiazolidine, isoxazole, isoxazoline, isoxazolidine, morpholine, oxadiazole, oxadiazoline, oxadiazolidine, oxazole, oxazoline, oxazolidine, piperazine, piperidine, pyran, pyrazine, pyrazole, pyrazoline, pyrazolidine, pyridine, pyrimidine, pyridazine, pyrrole, pyrroline, pyrrolidine, tetra hydrofuran, tetrahydrothiophene, tetrazine, tetrazole, thiadiazole, thiadiazoline, thiadiazolidine, thiazole, thiazoline, thiazolidine, thiophene, thiomorpholine, thiomorpholine sulfone, thiopyran, triazine, triazole, trithiane, and the like. Bicyclic ring systems are exemplified by any of the above monocyclic ring systems fused to an aryl group as defined herein, a cycloalkyl group as defined herein, or another monocyclic ring system as defined herein. Representative examples of bicyclic ring systems include but are not limited to, for example, benzimidazole, benzothiazole, benzothiadiazole, benzothiophene, benzoxadiazole, benzoxazole, benzofuran, benzopyran, benzothiopyran, benzodioxine, 1 ,3-benzodioxole, cinnoline, indazole, indole, indoline, indolizine, naphthyridine, isobenzofuran, isobenzothiophene, isoindole, isoindoline, isoquinoline, phthalazine, purine, pyranopyridine, quinoline, quinolizine, quinoxaline, quinazoline, tetrahydroisoquinoline, tetrahydroquinoline, thiopyranopyridine, and the like. These rings include quaternized derivatives thereof and may be optionally substituted with groups selected from halo, alkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, aryl, arylalkyl, heterocyclo, heterocycloalkyl, hydroxyl, alkoxy, alkenyloxy, alkynyloxy, haloalkoxy, cycloalkoxy, cycloalkylalkyloxy, aryloxy, arylalkyloxy, heterocyclooxy, heterocycloalkyloxy, mercapto, alkyl-S(O)m, haloalkyl-S(O)m, alkenyl-S(O)m, alkynyl- S(O)m, cycloalkyl-S(O)m, cycloalkylalkyl-S(O)m, aryl-S(O)m, arylalkyl-S(O)m, heterocyclo- S(O)m, heterocycloalkyl-S(O)m, amino, alkylamino, alkenylamino, alkynylamino, haloalkylamino, cycloalkylamino, cycloalkylalkylamino, arylamino, arylalkylamino, heterocycloamino, heterocycloalkylamino, disubstituted-amino, acylamino, acyloxy, ester, amide, sulfonamide, urea, alkoxyacylamino, aminoacyloxy, nitro or cyano where m = 0, 1 , 2 or 3.

[0040] "Aryl" as used herein alone or as part of another group, refers to a monocyclic, carbocyclic ring system or a bicyclic, carbocyclic fused ring system having one or more

[0041] 55652043-1 aromatic rings. Representative examples of aryl include, but are not limited to, azulenyl, indanyl, indenyl, naphthyl, phenyl, tetrahydronaphthyl, and the like. The term "aryl" is intended to include both substituted and unsubstituted aryl unless otherwise indicated and these groups may be substituted with the same groups as set forth in connection with alkyl and lower alkyl above.

[0042] "Arylalkyl" as used herein alone or as part of another group, refers to an aryl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein. Representative examples of arylalkyl include, but are not limited to, benzyl, 2-phenylethyl, 3-phenylpropyl, 2-naphth-2-ylethyl, and the like.

[0043] "Amino" as used herein means the radical -NH2.

[0044] "Alkylamino" as used herein alone or as part of another group means the radical -NHR, where R is an alkyl group.

[0045] "Ester" as used herein alone or as part of another group refers to a -C(O)OR radical, where R is any suitable substituent such as alkyl, cycloalkyl, alkenyl, alkynyl or aryl.

[0046] "Formyl" as used herein refers to a -C(O)H group.

[0047] "Carboxylic acid" as used herein refers to a -C(O)OH group.

[0048] "Sulfoxyl" as used herein refers to a compound of the formula -S(O)R, where R is any suitable substituent such as alkyl, cycloalkyl, alkenyl, alkynyl or aryl.

[0049] "Sulfonyl as used herein refers to a compound of the formula -S(O)(O)R, where R is any suitable substituent such as alkyl, cycloalkyl, alkenyl, alkynyl or aryl.

[0050] "Sulfonate" as used herein refers to a salt (e.g., a sodium (Na) salt) of a sulfonic acid and / or a compound of the formula -S(O)(O)OR, where R is any suitable substituent such as alkyl, cycloalkyl, alkenyl, alkynyl or aryl.

[0051] "Sulfonic acid as used herein refers to a compound of the formula -S(O)(O)OH.

[0052] "Amide" as used herein alone or as part of another group refers to a -C(O)NRaRb radical, where Raand Rb are any suitable substituent such as alkyl, cycloalkyl, alkenyl, alkynyl or aryl.

[0053] "Sulfonamide" as used herein alone or as part of another group refers to a - S(O)2NRaRb radical, where Raand Rb are any suitable substituent such as H, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroalkyl, or heteroaryl.

[0054] 55652043-1 The present invention is based on the finding that certain polyureas, such as polyetherureas, exhibit an advantageous combination of properties that makes them particularly suitable as binders in battery electrodes.

[0055] According to a first aspect, there is provided a binder composition for use in a battery electrode, the binder composition comprising or consisting of a polyurea polymer.

[0056] Preferably, the polyurea polymer may comprise or may consist of a polyetherurea polymer.

[0057] The binder composition may consist of the polyurea polymer. In other words, the polyurea polymer may be the only binder component in the battery electrode.

[0058] The binder composition may comprise the polyurea polymer, and at least one additional binder component. The additional binder component may comprise, for example, styrene-butadiene rubber (SBR).

[0059] Advantageously, the binder composition may be particularly suitable for use as a binder in an electrode material, e.g. in a battery electrode.

[0060] The binder composition may be particularly suitable for use as a binder in a cathode material, such as a metal-ion cathode material, e.g. a lithium-ion or a sodium- ion cathode material, e.g. a lithium iron phosphate cathode material.

[0061] The binder composition may be suitable for use as a binder in an anode material, such as a carbon-based anode material, for example in a sodium-ion battery.

[0062] Preferably, the polyetherurea polymer may comprise polyethylene glycol and / or polypropylene glycol units in its backbone. Without wishing to be bound by theory, it is believed that the provision of polar groups present in polyurea polymers may allow the redistribution of metal-ion flux such as Li-ion flux, resulting in a more uniform plating / stripping process. In addition, the provision of polyether units in the backbone of the polyurea may cause strong hydrogen bonds and / or polar interactions, which may help improve its solubility in water. Thus, it was discovered that polyetherurea polymers may exhibit an attractive combination of properties making them particularly suitable as binders in battery electrodes.

[0063] Typically, the polyurea, e.g. polyetherurea, may be prepared by dehydrogenative coupling of a diamine compound and methanol. For example, the polyurea, e.g.

[0064] 55652043-1 polyetherurea may be prepared by dehydrogenative coupling of a diamine compound and methanol in the presence of a metal pincer complex and a base to form polyurea and hydrogen gas.

[0065] The polyurea may be prepared according to a method as described in WO 2022 / 175693 (Kumar), the content of which is incorporated herein by reference in its entirety.

[0066] Thus, the polyurea, e.g. polyetherurea may be prepared by dehydrogenative coupling of a diamine compound and methanol, preferably a polyether diamine compound and methanol.

[0067] The polyether diamine may be a diamine of formula (I): R1HN-(CH2)m-W-(CH2)n-NHR2(I) wherein: each of R1and R2is independently H or a C1 to C4 hydrocarbyl group; each of m and n is independently an integer from 0 to 10, typically 0-3, e.g. 1-3; and

[0068] W is a polyether unit.

[0069] W may be a polyether unit of formula (II):

[0070] -[Q-O]r (II) where Q is a C2 to C24 alkylene group, a substituted C2 to C24 alkylene group, a C2 to C24 heteroalkylene group or a substituted C2 to C24 heteroalkylene group, a C2 to C24 aryl group or a substituted C2 to C24 aryl group; and

[0071] I is an integer from 1 to 140, typically from 2 to 35, e.g. from 2 to 20.

[0072] Typically, Q may be a C2 or a C3 alkyl.

[0073] Preferably, Q may be a C2 alkyl, e.g. ethylene.

[0074] Typically, each of R1and R2may be H.

[0075] Thus, in an embodiment, the polyether diamine may be a diamine of formula (la): H2N-(CH2)m-[CH2-CH2-O]i-(CH2)n-NH2(la) wherein: m is an integer from 0 to 10, typically 0-3, e.g. 1-3; n is an integer from 1 to 10, typically 1-3; and

[0076] I is an integer from 1 to 140, typically from 2 to 35, e.g. from 2 to 20.

[0077] 55652043-1 The polyether diamine may be a polyethyleneglycol diamine.

[0078] The polyether diamine may be a diamine of formula (lb): wherein n is an integer of about 10 to 50, typically about 33.

[0079] The polyether diamine of formula (lb) may have a number average molecular weight Mn of about 500 to 5000, e.g. about 1000 to 2000, e.g. about 1500.

[0080] The polyether diamine may be a diamine of formula (Ic). wherein n is an integer of about 100 to 200, typically about 135.

[0081] The polyether diamine of formula (Ic) may have a number average molecular weight Mn of about 1000 to 10000, e.g. about 2000 to 6000.

[0082] It will be appreciated that one or more end terminals, e.g. one or more amine end terminals, of the polyurea, may be modified, e.g. may be amidated.

[0083] For example, using a polyether diamine of formula (lb) as a starting material, the resulting polyetherurea may be a polyurea of formula (Illa), (lllb) or (I lie): wherein n is an integer of about 10 to 50, typically about 33; and m is an integer of about 2-10. wherein n is an integer of about 10 to 50, typically about 33; and m is an integer of about 2-10.

[0084] 55652043-1 wherein n is an integer of about 10 to 50, typically about 33; and m is an integer of about 2-10.

[0085] According to a second aspect, there is provided an electrode material, optionally a battery electrode, wherein the electrode material comprises a binder composition, the binder composition comprising or consisting of a polyurea polymer.

[0086] Preferably, the polyurea polymer may comprise or may consist of a polyetherurea polymer.

[0087] The polyurea polymer may be as described in the first aspect.

[0088] The electrode material may be a cathode material, such as a metal-ion cathode material, e.g. a lithium-ion or a sodium-ion cathode material, e.g. a lithium iron phosphate cathode material.

[0089] The electrode material may be an anode material, such as a carbon-based anode material, for example in a sodium-ion battery.

[0090] According to a third aspect, there is provided the use of a polyurea polymer in a binder composition for an electrode material, optionally in a battery electrode.

[0091] Preferably, the polyurea polymer may comprise or may consist of a polyetherurea polymer.

[0092] The polyurea polymer may be as described in the first aspect.

[0093] The electrode material may be a cathode material, such as a metal-ion cathode material, e.g. a lithium-ion or a sodium-ion cathode material, e.g. a lithium iron phosphate cathode material.

[0094] The electrode material may be an anode material, such as a carbon-based anode material, for example in a sodium-ion battery.

[0095] According to a fourth aspect, there is provided a method of preparing a polyurea polymer for use in a binder composition for an electrode material, the method comprising reacting a diamine compound and methanol in the presence of a metal pincer complex and a base to form polyurea and hydrogen gas by dehydrogenative coupling.

[0096] The method may be generally as described in WO 2022 / 175693 (Kumar), the content of which is incorporated herein by reference in its entirety.

[0097] 55652043-1 The diamine

[0098] The diamine may be a polyether diamine of formula (I): R1HN-(CH2)m-W-(CH2)n-NHR2(I) wherein: each of R1and R2is independently H or a C1 to C4 hydrocarbyl group; each of m and n is independently an integer from 0 to 10, typically 0-3, e.g. 1-3; and

[0099] W is a polyether unit.

[0100] W may be a polyether unit of formula (II):

[0101] -[Q-O]r (II) where Q is a C2 to C24 alkylene group, a substituted C2 to C24 alkylene group, a C2 to C24 heteroalkylene group or a substituted C2 to C24 heteroalkylene group, a C2 to C24 aryl group or a substituted C2 to C24 aryl group; and

[0102] I is an integer from 1 to 140, typically from 2 to 35, e.g. from 2 to 20.

[0103] Typically, Q may be a C2 or C3 alkyl.

[0104] Preferably, Q may be a C2 alkyl, e.g. ethylene.

[0105] Typically, each of R1and R2may be H.

[0106] Thus, in an embodiment, the polyether diamine may be a diamine of formula (la): H2N-(CH2)m-[CH2-CH2-O]i-(CH2)n-NH2(la) wherein: m is an integer from 0 to 10, typically 0-3, e.g. 1-3; n is an integer from 1 to 10, typically 1-3; and

[0107] I is an integer from 1 to 140, typically from 2 to 35, e.g. from 2 to 20.

[0108] The polyether diamine may be a polyethyleneglycol diamine.

[0109] The polyether diamine may be a diamine of formula (lb): wherein n is an integer of about 10 to 50, typically about 33.

[0110] 55652043-1 The polyether diamine of formula (lb) may have a number average molecular weight Mn of about 500 to 5000, e.g. about 1000 to 2000, e.g. about 1500.

[0111] The polyether diamine may be a diamine of formula (Ic). wherein n is an integer of about 100 to 200, typically about 135.

[0112] The polyether diamine of formula (Ic) may have a number average molecular weight Mn of about 1000 to 10000, e.g. about 2000 to 6000.

[0113] Metal pincer catalyst

[0114] The metal pincer catalyst is a ruthenium or manganese-based complex having a tridentate pincer ligand and has the general formula (II):

[0115] MXYZ’ L (II) where M is Ru or Mn

[0116] X is H or halo

[0117] Y is H, halo, CO, or borohydride,

[0118] Z’ is CO or PPhs and

[0119] L is a tridentate ligand with ANB donor sites in a meridional geometry, where each of A and B is independently chosen from P, N, O, S and N-heterocyclic carbenes.

[0120] According to certain embodiments, M may be Ru.

[0121] According to certain embodiments, the metal pincer catalyst may be selected from the following compounds:

[0122] The ruthenium pincer catalyst can be selected from compounds 1, 3 and 5.

[0123] Typically, the ruthenium pincer catalyst may be compound 1 (Ru-MACHO).

[0124] 55652043-1 According to certain embodiments, M may be Mn.

[0125] According to certain embodiments, the metal pincer catalyst may be compound 6 (Mn-MACHO).

[0126] The base

[0127] A base is typically present during the reaction. It is believed that the main role of the base is that of deprotonation of the N-H proton and removal of the chloride ligand to generate an active species (which is coordinatively unsaturated) that initiates the catalysis. A secondary role of the base could be to facilitate the release of H2 from the metal centre enabling the polymerisation process.

[0128] Suitable bases are known in the art. The base can be selected from the group comprising M, MH, MOH, MOR14, M2CO3, and MHCO3, where M is Li, Na, K, Cs, and M’3PO4 and ((CHshSi^NM’, where M’is Li, Na orK; and R14is a linear or branched C1 to C7 alkyl group or a substituted or unsubstituted aryl or aralkyl group. The alkyl group can be chosen from methyl, ethyl, isoporopyl and tert-butyl, e.g. Me, Et, 'Pr, ‘Bu. The aryl group can be phenyl, and the aralkyl group can be benzyl. The base can be KO‘Bu, NaO‘Bu, ((CH3)3Si)2NK, KH or KOH. Preferably, the base is KO‘Bu.

[0129] Advantageously, the base may be present in molar excess of the metal (e.g. ruthenium) pincer catalyst, i.e. the molar ratio of the base to the metal (e.g. ruthenium) pincer catalyst is greater than one. It has been found that a molar excess of base to metal (e.g. ruthenium) pincer catalyst can increase the yield of the polyurea. Preferably, the molar ratio of the base to the metal (e.g. ruthenium) pincer catalyst is greater than 2, greater than 2.5, greater than 3, greater than 3.5, or is equal to or greater than 4.

[0130] Solvent

[0131] The process of the invention can be carried out in the absence or in the presence of a solvent. When a solvent is present it can be an organic solvent, for example, a solvent chosen from toluene, THF, 1 ,4-dioxane, fluorobenzene, chlorobenzene, glyme, o-xylene, m-xylene, p-xylene, methanol, diglyme, anisole, DMSO, tert-butanol, mixtures and combinations thereof, and ionic liquids. The solvent can be chosen from toluene, THF, 1 ,4-dioxane, glyme, o-xylene, m-xylene, p-xylene, methanol, diglyme, anisole,

[0132] 55652043-1 DMSO, mixtures and combinations thereof. Preferred solvents include toluene, THF and 1 ,4-dioxane. Preferred mixtures and combinations include mixtures and combinations which include at least one of toluene, THF, and 1 ,4-dioxane. Preferred mixtures and combinations include toluene and THF, toluene and anisole, and toluene and DMSO. Ionic liquids can be of general formula R21R22R23N+X' (R21R22R23can be alkyl or cyclic groups or can together form a part of 5-7 membered ring; X can be halide e.g. F, Cl, Br, I or PF6).

[0133] The features described in relation to any aspect of the invention may equally apply to any other aspect and, merely for brevity, are not repeated. For example, features described in relation to compositions can apply in relation to methods, and vice versa.

[0134] The invention may be further described with reference to the following nonlimiting clauses:

[0135] Clause 1. A binder composition for use in a battery electrode, wherein the binder composition comprises or consists of a polyurea polymer.

[0136] Clause 2. A binder composition according to Clause 1 , wherein the polyurea polymer comprises or consists of a polyetherurea polymer.

[0137] Clause 3. A binder composition according to any preceding Clause, wherein the binder composition comprises at least one additional binder component.

[0138] Clause 4. A binder composition according to clause 3, wherein the additional binder component comprises styrene-butadiene rubber (SBR).

[0139] Clause 5. A binder composition according to any preceding Clause, wherein the polyetherurea polymer comprises polyethylene glycol and / or polypropylene glycol units in its backbone.

[0140] Clause 6. A binder composition according to any preceding Clause, wherein the polyurea is prepared by dehydrogenative coupling of a diamine compound and methanol.

[0141] Clause 7. A binder composition according to any preceding Clause, wherein the polyurea has the general formula (Illa), (I lib) or (I lie):

[0142] 55652043-1 wherein n is an integer of about 10 to 50, optionally about 33; and m is an integer of about 2-10, wherein n is an integer of about 10 to 50, optionally about 33; and m is an integer of about 2-10, wherein n is an integer of about 10 to 50, optionally about 33; and m is an integer of about 2-10.

[0143] Clause 8. An electrode material comprising a binder composition, wherein the binder composition comprises or consists of a polyurea polymer.

[0144] Clause 9. An electrode material according to Clause 8, wherein the electrode material comprises or is a battery electrode.

[0145] Clause 10. An electrode material according to Clause 8 or Clause 9, wherein the polyurea polymer comprises or consists of a polyetherurea polymer.

[0146] Clause 11. Use of a polyurea polymer in a binder composition for an electrode material.

[0147] Clause 12. Use of Clause 11 , wherein the electrode material is a battery electrode.

[0148] Clause 13. A method of preparing a polyurea polymer for use in a binder composition for an electrode material, the method comprising reacting a diamine compound and methanol in the presence of a metal pincer complex and a base to form polyurea and hydrogen gas by dehydrogenative coupling.

[0149] Clause 14. A method according to Clause 13, wherein the polyether diamine is a diamine of formula (I):

[0150] R1HN-(CH2)m-W-(CH2)n-NHR2(I) wherein: each of R1and R2is independently H or a C1 to C4 hydrocarbyl group;

[0151] 55652043-1 each of m and n is independently an integer from 0 to 10, typically 0-3, e.g. 1-3; and

[0152] W is a polyether unit.

[0153] Clause 15. A method according to Clause 13 or Clause 14, wherein the polyether diamine is a diamine of formula (la):

[0154] H2N-(CH2)m-[CH2-CH2-O]i-(CH2)n-NH2 (la) wherein: m is an integer from 0 to 10, optionally 1-3; n is an integer from 1 to 10, optionally 1-3; and

[0155] I is an integer from 1 to 140, optionally from 2 to 35.

[0156] Brief Description of Drawings

[0157] Embodiments of the invention are described with reference to the accompanying drawings, in which:

[0158] Figures 1-4 show comparative electrochemical data for CMC including coulombic efficiency with a 10 mA / g current density (Figure 1), potential vs specific capacity with a 10 mA / g current density (Figure 2), rate capability (Figure 3), and differential capacity with a 10 mA / g current density (Figure 4);

[0159] Figures 5-8 show comparative electrochemical data for CMC+SBR including coulombic efficiency with a 25 mA / g current density (Figure 5), potential vs specific capacity with a 25 mA / g current density (Figure 6), rate capability (Figure 7), and differential capacity with a 25 mA / g current density (Figure 8);

[0160] Figure 9 shows electrochemical data for embodiment MT19 including rate capability;

[0161] Figures 10-15 show electrochemical data for embodiment MT20 including coulombic efficiency with a 25 mA / g current density (Figure 10), coulombic efficiency with a 100 mA / g current density (Figure 11), potential vs specific capacity with a 25 mA / g current density (Figure 12), potential vs specific capacity with a 100 mA / g current density (Figure 13), differential capacity with a 25 mA / g current density (Figure 14) and differential capacity with a 100 mA / g current density (Figure 15);

[0162] Figures 16-19 show electrochemical data for embodiment MT22 including coulombic efficiency with a 10 mA / g current density (Figure 16), potential vs specific capacity with a 10 mA / g current (Figure 17), rate capability (Figure 18), and differential capacity with a 10 mA / g current density (Figure 19);

[0163] 55652043-1 Figures 20-22 show electrochemical data for embodiment MT23 including coulombic efficiency with a 100 mA / g current density (Figure 20), potential vs specific capacity with a 100 mA / g current (Figure 21), and differential capacity with a 100 mA / g current density (Figure 22);

[0164] Figures 23-25 show electrochemical data for embodiment MT24 including coulombic efficiency with a 100 mA / g current density (Figure 23), potential vs specific capacity with a 100 mA / g current (Figure 24), and differential capacity with a 100 mA / g current density (Figure 25);

[0165] Figures 26-28 show electrochemical data for embodiment MT22+SBR including coulombic efficiency with a 10 mA / g current density (Figure 26), potential vs specific capacity with a 10 mA / g current (Figure 27), and differential capacity with a 10 mA / g current density (Figure 28);

[0166] Figure 29 shows electrochemical data for embodiment MT23+SBR including rate capability;

[0167] Figure 30 shows electrochemical data for embodiment MT24+SBR including rate capability;

[0168] Figure 31 shows electrochemical data for PEG diamine 1500 including rate capability;

[0169] Figures 32-35 show comparative electrochemical data for starting material PEG diamine 1500 with 20 mol% base with SBR, including coulombic efficiency with a 100 mA / g current density (Figure 32), potential vs specific capacity with a 100 mA / g current (Figure 33), rate capability (Figure 34), and differential capacity with a 100 mA / g current density (Figure 35);

[0170] Figures 36-37 show electrochemical data for embodiment MT22 in a hard carbon I sodium half cell, including coulombic efficiency with a 50 mA / g current density (Figure 36), potential vs specific capacity with a 50 mA / g current (Figure 37);

[0171] Figures 38-39 show electrochemical data for embodiment MT22 + SBR in a hard carbon I sodium half cell, including coulombic efficiency with a 50 mA / g current density (Figure 38), potential vs specific capacity with a 50 mA / g current (Figure 39).

[0172] Detailed Description

[0173] In the present disclosure, reference is made to a number of terms, which have the meanings provided below, unless a context indicates to the contrary. The nomenclature used herein for defining compounds, in particular the compounds according to the invention, is in general based on the rules of the IIIPAC organisation for

[0174] 55652043-1 chemical compounds, specifically the “IIIPAC Compendium of Chemical Terminology (Gold Book)”. For the avoidance of doubt, if a rule of the IIIPAC organisation is in conflict with a definition provided herein, the definition herein is to prevail. Furthermore, if a compound structure is in conflict with the name provided for the structure, the structure is to prevail.

[0175] The term “comprising” or variants thereof is to be understood herein to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0176] The term “consisting” or variants thereof is to be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step or group of elements, integers or steps.

[0177] The term “about” herein, when qualifying a number or value, is used to refer to values that lie within ± 5% of the value specified. For example, if a temperature is specified to be about 5 to about 13 °C, temperatures of 4.75 to 13.65 °C are included.

[0178] Reference to physical states of matter (such as liquid or solid) refer to the matter’s state at 25 °C and atmospheric pressure unless the context dictates otherwise.

[0179] As explained above, the present inventors have discovered that certain polyurea compounds, such as polyetherurea compounds, exhibit an advantageous combination of properties that makes them particularly suitable as water-soluble binders in battery electrodes.

[0180] Experiments

[0181] All experiments were carried out under inert atmosphere of purified nitrogen using standard Schlenk techniques unless specified. Diamines, anhydrous methanol, and the catalyst (Ru-MACHO - illustrated by complex 1 below) were purchased from Sigma- Aldrich, Alfa Aesar, or TCI and used as received. Mn-MACHO complex was prepared using the method reported in the literature as described in the ACS Catal. 2017, 7, 3, 2022-2032.

[0182] 55652043-1 Dry solvents (toluene and THF) were provided by a PureSolv SPS-400-5 solvent purification system and degassed by Freeze- Pump-Thaw under nitrogen. Deuterated solvents including D2O and d6-DMSO were purchased from Sigma-Aldrich and used as received.

[0183] 1H, and13C{1 H} NMR experiments were carried out at 298 K using either a Bruker Avance II 500 (500 MHz1H, 125.8 MHz13C) with results being reported in ppm (5). NMR spectroscopy abbreviations: s, singlet; d, doublet; t, triplet; m, multiplet.1H and13C{1H} NMR spectroscopy were used to identify the carbonyl functionality as well as the repeating units present and possible end groups of the amine and formamide.

[0184] A known amount of internal standard of 1 ,1 -diphenylethylene was added along with a known amount of product to be dissolved in d6-DMSO to identify the indicated NMR yield of polyurea.

[0185] IR Spectroscopy was particularly useful in identifying the presence of the diagnostic C=O stretching frequency correlating to the urea linkage formed in the reaction. IR spectra were recorded on an Infrared Spectra (ATR-FTIR) Shimadzu IR Affinity-1 for analysis of a neat, solid sample of polyureas within a range of 400-4000 cm’ 1

[0186] Gel permeation chromatography (GPC) was performed on an Agilent 1260 Infinity II. Here, DMF was used as a mobile phase in combination with an Agilent PolerGel column (100-50,000 Da). Due to the sensitivities of the instrument, 2 mg / mL of product in DMF was needed. Calibration was performed using a polystyrene standard.

[0187] Thermal gravimetric analysis (TGA) was performed using a Redcroft STA-780 Series Thermal Analysis between 30 to 900°C at a heating rate of 10°C / min under a flow of nitrogen gas (25 mL / min). TGA is a method of thermal analysis which determines the change in mass of a sample with respect to temperature. This reflects physical and chemical reactions that may be taking place including absorption, desorption, decomposition, oxidation and reduction etc.69

[0188] Differential scanning calorimetry (DSC) analysis was performed using a Netzsch DSC204 between -70 to 295°C at a heating rate of 10°C / min under a flow of nitrogen gas (10 mL / min) after an initial heating / cooling cycle (25-120°C at 10°C / min with a 20- minute isothermal at 120°C) to eradicate the thermal history of the sample.

[0189] The polyureas were mixed with deionised water to make a solution in a 1 :45 ratio. This solution was then utilised in making slurries for binders where the ratio for the active material: binders: conductive carbon was in an 80:10:10 weight ratio. The LFP was

[0190] 55652043-1 supplied by AMTE Power (now Lionvolt) and used as received. The conductive carbon was purchased from Imerys and used as received. Some of the polyureas were mixed with SBR to make a composite so the binderwas in a 1 :1 ratio of polyurea:SBR emulating the industrially used CMC / SBR composites.

[0191] Before this, the conductive carbon and active material were ground for 15 minutes using a pestle and mortar and then added to the different binder solutions. The slurry was stirred overnight to ensure good homogeneity and cast onto a vacuum table using a doctor blade at 200 / zm onto aluminium foil. This cast was allowed to air dry for 30 minutes and the electrodes were punched out in 13 mm diameter circles.

[0192] The electrodes were then covered with Al foil which has a small hole in the lid and placed in a small antechamber of an M-Braun glovebox at 80°C under vacuum overnight to dry.

[0193] The coin cells were assembled in an M-Braun glovebox under an argon atmosphere. The order of assembly included a positive case, the electrode, a separator with eight drops of 1 M LiPFe in ethylene carbonate / dimethyl carbonate (1 :1) (BASF) electrolyte, lithium metal adhered on the spacer, current collector, a spring, then a negative case. This is then crimped using a hydraulic crimper (MTI) to make a coin cell.

[0194] Galvanostatic cycling was measured on a Biologic BCS-805 cycler and Neware BTS4000-5V10mA battery testing system, both at 30°C. The galvanostatic charge and discharge were performed with a potential range between 2.5 V and 4.2 V. The cycling performance was measured at four different current densities of 10, 25 and 100 mA / g for 200 cycles. The rate capabilities of the half-cells were tested at 25, 50, 75, 100, 250 and 500 mA / g. Due to time constraints and limited cell spaces, not all the cells could be cycled.

[0195] Dehydrogenative coupling of diamines and methanol

[0196] The generic protocol for the dehydrogenative coupling synthesis is as follows. Further detail of the synthesis for specific examples is described in more detail below in the Characterisation section.

[0197] The synthesis was performed using standard Schlenk line techniques.

[0198] PEG Diamine, Ru-MACHO catalyst, KO‘Bu base, toluene solvent, and methanol were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°C and stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) was added to aid precipitation and the reaction mixture was cooled to 5°C for 24 hours to afford a yellow solid. The crude

[0199] 55652043-1 product was collected by filtration, washed three times with hexane (ca. 3 * 10 mL) and dried under reduced pressure to afford the desired polyurea.

[0200] This product was soluble in water, diglyme, chloroform, and THF (tested for 5 mg / mL). The reactions were repeated using Mn-MACHO catalyst, THF as solvent, and / or different temperatures and time durations.

[0201] The reaction conditions were ultimately optimised using Ru-MACHO as the precatalyst, toluene, stirring at 150°C at 400 rpm for 24 hours. A summary of the various synthesized polyureas is provided in Table 1 , which shows the various parameters used for each synthesis.

[0202] 55652043-1 Table 1

[0203] Mol wt. of Amount of Isolated NMR

[0204] Temperature Solvent Catalyst KO‘Bu Methanol

[0205] Name Duration Solvent diamine diamine Catalyst yield yield

[0206] (°C) (mL) (mol%) (mol%) (mL)

[0207] (Mw) (mmol) (%) (%)

[0208] MT3 48 130 THF 2.0 1500 0.250 Ru-MACHO 2.5 5.0 0.4 90 0

[0209] MT5 48 130 Toluene 2.0 1500 0.250 Ru-MACHO 2.5 5.0 0.4 92 12

[0210] MT11 48 150 THF 0.5 1500 0.250 Mn-MACHO 10.0 20.0 0.1 52 32

[0211] MT 24 150 Toluene 0.5 230 0.412 Ru-MACHO 10.0 20.0 0.1 89 0

[0212] MT19 24 150 Toluene 0.5 2000 0.059 Ru-MACHO 10.0 20.0 0.1 63 70

[0213] MT20 24 150 Toluene 0.5 6000 0.017 Ru-MACHO 10.0 20.0 0.1 89 34

[0214] MT22 24 150 Toluene 0.5 1500 0.250 Ru-MACHO 10.0 20.0 0.1 60 49

[0215] MT23 24 150 Toluene 0.5 1500 0.250 Ru-MACHO 2.5 20.0 0.1 60 26

[0216] MT24 24 150 Toluene 0.5 1500 0.250 Ru-MACHO 20.0 40.0 0.1 72 25

[0217] Looking at MT22, MT23 and MT24, it was found that 10 mol% of Ru-MACHO and 20 mol% of base yields the highest yield of polyurea.

[0218] Although increased levels of base drive the dehydrogenation, due to the work-up of washing the product with hexane, it is likely that any excess base would not be removed and therefore the likely presence of potassium has a negative impact on the performance of the battery as will be discussed later. There is, therefore, a compromise to be met between the base loading to ensure that the efficient polymerisation process occurs but to also be conscious of the residual potassium affecting the electrochemical performance.

[0219] The reaction times were tested at 24 and 48 hours and it was found that there was no significant change in the molecular weight most likely due to the insolubility of the longer polymer chains or decomposition of the catalyst. The reaction was run at 150°C under a sealed system. The sealed system needed to be utilised due to the lack of yield and reaction conversion when conducted under an open vessel system, most likely due to the loss of methanol as it has a low boiling point of 64.7°C at 1 bar.

[0220] A manganese-based pincer complex (Mn-MACHO) was also been used for the synthesis of polyurea from diamines and methanol via the catalytic dehydrogenative coupling process. It was found that Mn-MACHO had an improved yield when using tetrahydrofuran (THF) as a solvent compared to toluene. However, from the experiments conducted in these tests, namely MT 11 and MT22, it was found that there was a higher conversion into polyurea when Ru-MACHO and toluene were used instead of Mn- MACHO and THF, although both options were viable.

[0221] As shown in Table 1 , it was observed that the starting polymeric PEG diamine had a significant effect on the NMR yield of polyurea and the resulting polymer chain length.

[0222] The three starting diamines tested here were SP1 SP2 and SP3 as shown below: wherein n is an integer of about 10 to 50, typically about 33, and SP1 has a number average molecular weight Mnof about 1500.

[0223] 55652043-1 wherein n is an integer of about 100 to 200, typically about 135, and SP2 has a number average molecular weight Mnof about 2000 or 6000. wherein SP3 has a number average molecular weight Mnof about 230.

[0224] Samples MT14, MT19, MT20 and MT22 illustrate the effect of the difference in the polymeric diamine, and the resulting yield of polyurea. When using polyoxypropylenediamine terminated Mn-230 (Jeffamine®), the reaction did not lead to the formation of a solid product as observed in the case of other diamines. The resulting product was also insoluble in water, which is believed to be due to the presence of the propyl group which reduces the packing in chains during polymerisation. It was found that the polyureas made with the PEG Diamine 1500 and PEG Diamine 2000 afforded the highest yields generating polyureas with Mnof approximately 10,900 to 12,800 Da, with approximately six to seven repeating units. However, when the starting diamine used was PEG Diamine 6000, although this resulted in a longer product with a chain length of approximately 16,800 Da, as the starting material is only 6000 Da, this is likely only an oligourea, with approximately 2.8 repeating units. This difference in yield could be due to the nucleophilicity of the terminal amines due to their proximity to the oxygen or due to the chain length and chance of interaction or a composite effect.

[0225] Having a concentrated solution with minimal solvent brings the amine end group of the PEG Diamine in contact with the formaldehyde yielding higher amounts of polyurea.

[0226] Optimisation studies showed that using an excess of methanol (-2.5 mmol of methanol with 0.25 mmol of PEG Diamine 1500) resulted in the highest yield of polyurea. This is hypothesised to be because of the low boiling point of methanol (~65°C) in comparison to the reaction temperature (150°C) which means that a significant amount of methanol will stay in the gaseous phase. Furthermore, this excess in methanol (9.9 equivalents) was advantageous for the reaction with diamines, ensuring a high yield.

[0227] 55652043-1 From the highest NMR yields of polyurea, it was determined that the following conditions were optimum for maximum conversion of diamine:

[0228] •Utilising Ru-MACHO as the pre-catalyst along with toluene as the solvent;

[0229] •Conducting the experiment at 150°C for 24 hours;

[0230] •Using a medium chain length of starting material;

[0231] •Utilising 10 mol% of Ru-MACHO and 20 mol% of base.

[0232] Characterisation

[0233] Details of the synthesis, and characterisation of several examples of the polyureas of Table 1 , as provided below.

[0234] MT19

[0235] Synthesis of MT19 followed Scheme 19 below:

[0236] Scheme 19

[0237] This experiment was performed using standard Schlenk line techniques.

[0238] PEG Diamine 2000 Mw (0.05915 mmol, 1.0 eq., 118.3 mg), Ru-MACHO (10 mol%, 0.1 eq., 3.6 mg), potassium tert-butoxide (20 mol%, 0.2 eq., 1.3 mg), toluene (0.5 mL) and methanol (0.1 mL, 9.9 eq.) were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°C and stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) is added to aid precipitation and the reaction mixture was cooled to 5°C for 24 hours to afford a yellow solid. The crude product was collected by filtration, washed three times with hexane (ca. 3 x 10 mL) and dried under reduced pressure to afford the desired polyurea (75.4 mg, 0.0372 mmol, 63%).

[0239] NMR:

[0240] 55652043-11H NMR 5 / 7(500.1 MHz, DMSO): 1.23 (s, 1.38 H, H-1), 3.13-3.16 (q, 6.36 H, H- 2,20), 3.23-3.26 (q, 3.16 H, H-9,13), 3.41 (s, 557.65 H, H-5,6,16,17), 3.51 (s, 466.09 H, H-3,8,14,19), 6.00 (t, 2.78 H, H-10,12), 8.06 (s, 1.00 H, H-21 , 23)

[0241] 13C{1H} NMR <5C(125.8 MHz, DMSO) 37.6 (C-2,9, 13,20), 70.3 (C- 3,5,6,8,14,16,17,19), 158.4 (C-11), 161.7 (C-11) 169.8 (C-22).

[0242] IR (FTIR) Vmax / cm-11095vs (C-0 stretching), 1242s, 1278s and 1342s (C-N stretching), 1463s (C-H bending), 1562m (N-H bending), 1620m (C=O stretching), 2885s (N-H stretching)

[0243] GPC Mn (g / mol): 12800 (D:1.4), 2400 (0:1.2)

[0244] MT20

[0245] Synthesis of MT20 followed Scheme 20 below:

[0246] Scheme 20

[0247] This experiment was performed using standard Schlenk line techniques.

[0248] PEG Diamine 6000 Mw (0.0167 mmol, 1.0 eq., 100.2 mg), Ru-MACHO (10 mol%, 0.1 eq., 1.0 mg), potassium tert-butoxide (20 mol%, 0.2 eq., 0.4 mg), toluene (0.5 mL) and methanol (0.1 mL, 9.9 eq.) were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°C and stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) is added to aid precipitation and the reaction mixture was cooled to 5°C for 24 hours to afford a yellow solid. The crude product was collected by filtration, washed three times with hexane (ca. 3 x 10 mL) and dried under reduced pressure to afford the desired polyurea (89.6 mg, 0.0149 mmol, 89%).

[0249] NMR

[0250] 55652043-11H NMR 5 / 7(500.1 MHz, DMSO): 1.23 (s, 6.56 H, H-1), 2.51 (m, 201.75 H, H- 2,9,13,20), 3.47 (s, 13812.48 H, H-5,6,16,17), 3.50 (s, 931.37 H, H-3,8,14,19), 5.99 (t, 1.65 H, H-10,12), 7.97 (s, 1.00 H, H-21 , 23)

[0251] IR (FTIR) Vmax / cm-11097vs (C-0 stretching), 1240s, 1278s and 1340s (C-N stretching), 1465s (C-H bending), 1570m (N-H bending), 1620m (C=O stretching), 2877s (N-H stretching)

[0252] GPC Mn (g / mol): 16800 (D:2.0)

[0253] MT22

[0254] Synthesis of MT22 followed Scheme 22 below:

[0255] Scheme 22

[0256] This experiment was performed using standard Schlenk line techniques.

[0257] PEG-diamine 1500 Mw (0.25 mmol, 1 eq., 375 mg), Ru-MACHO (10 mol%, 0.1 eq., 15.1758 mg), potassium tert-butoxide (20 mol%, 0.2 eq., 5.6106 mg), toluene (0.5 mL) and methanol (0.1 mL, 9.9 eq.) were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°C and stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) is added to aid precipitation and the reaction mixture cooled to 5°C for 24 hours to afford a yellow solid. The crude product was collected by filtration, washed three times with hexane (ca. 3 x 10 mL) and dried under reduced pressure to afford the desired polyurea.

[0258] NMR

[0259] 1H NMR 6H (500.1 MHz, DMSO): 1.24 (s, 1.26 H, H-24), 1.56-1.68 (m, 12.12 H, H-3,10,17), 2.17 (s, 0.21 H, H-25), 3.11-3.18 (m, 6.77 H, H-4,9,20), 3.51 (s, 1945.78 H, H-2,11 ,16), 5.82 (t, 2.28 H, H-12, 14), 8.00 (s, 1.00 H, H-26,28)

[0260] 55652043-113C{1H} NMR 8C (125.8 MHz, DMSO) 29.85 (C-3,10,17,24), 30.68 (C-2,11 ,16), 37.03 (C-25), 70.25 (C-4, 6, 7, 9, 18, 20, 21 , 23), 158.56 (C-13), 161.45 (C-13) 169.52 (C- 27).

[0261] IR (FTIR)vmax / crn-1 1093vs (C-N stretching), 1278s, 1342s, 1465s (C-H bending), 1560m (N-H bending), 1670m (C=O stretching), 2883s (N-H stretching)

[0262] GPC M„ (g / mol): 10900 (D:1.4), 1800 (0:1.2)

[0263] MT23

[0264] Synthesis of MT23 followed Scheme 23 below:

[0265] Scheme 23

[0266] This experiment was performed using standard Schlenk line techniques.

[0267] PEG Diamine 1500 Mw (0.25 mmol, 1.0 eq., 375 mg), Ru-MACHO (2.5 mol%, 0.025 eq., 3.8 mg), potassium tert-butoxide (20 mol%, 0.2 eq., 5.6 mg), toluene (0.5 mL) and methanol (0.1 mL, 9.9 eq.) were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°C and stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) is added to aid precipitation and the reaction mixture was cooled to 5°C for 24 hours to afford a yellow solid. The crude product was collected by filtration, washed three times with hexane (ca. 3 x 10 mL) and dried under reduced pressure to afford the desired polyurea (227.2 mg, 0.15 mmol, 60%).

[0268] NMR

[0269] 1H NMR 5 / 7(500.1 MHz, DMSO): 1.24 (s, 4.02 H, H-24), 1.56-1.69 (m, 37.30 H, H-3,10,17), 2.17 (s, 1.02 H, H-25), 3.11-3.19 (m, 16.99 H, H-4,9,20), 3.51 (s, 1456.92 H, H-2,11 ,16), 5.84 (t, 6.66 H, H-12, 14), 8.00 (s, 1.00 H, H-26,28)

[0270] 13C{1H} NMR <5C(125.8 MHz, DMSO) 29.9 (C-3,10,17,24), 30.7 (C-2,11 ,16), 37.0 (C-25), 70.3 (C-4, 6, 7, 9, 18, 20, 21 , 23), 158.6 (C-13), 161.5 (C-13) 169.5 (C-27).

[0271] 55652043-1 IR (FTIR) Vmax / cm'11091vs (C-0 stretching), 1240s, 1278s and 1342s (C-N stretching), 1465s (C-H bending), 1560m (N-H bending), 1670m (C=O stretching), 2883s (N-H stretching)

[0272] MT24

[0273] Synthesis of MT24 followed Scheme 24 below:

[0274] Scheme 24

[0275] This experiment was performed using standard Schlenk line techniques.

[0276] PEG Diamine 1500 Mw (0.25 mmol, 1.0 eq., 375 mg), Ru-MACHO (20 mol%, 0.2 eq., 30.4 mg), potassium tert-butoxide (40 mol%, 0.4 eq., 11.2 mg), toluene (0.5 mL) and methanol (0.1 mL, 9.9 eq.) were added to a J-Young Flask and sealed under Argon. This mixture was then heated to 150°Cand stirred at 400 rpm for 24 hours. After this time, the reaction was allowed to cool to room temperature. Hexane (approx. 20 mL) is added to aid precipitation and the reaction mixture was cooled to 5°C for 24 hours to afford a yellow solid. The crude product was collected by filtration, washed three times with hexane (ca. 3 * 10 mL) and dried under reduced pressure to afford the desired polyurea (275.8 mg, 0.18 mmol, 72%).

[0277] NMR

[0278] 1H NMR 5 / 7(500.1 MHz, DMSO): 1.24 (s, 2.91 H, H-24), 1.54-1.68 (m, 34.64 H, H-3,10,17), 2.18 (s, 1.08 H, H-25), 3.11-3.18 (m, 18.17 H, H-4,9,20), 3.51 (s, 1369.05 H, H-2,11 ,16), 5.82 (t, 6.45 H, H-12, 14), 7.99 (s, 1.00 H, H-26,28)

[0279] 13C{1H} NMR <5C(125.8 MHz, DMSO) 29.9 (C-3,10,17,24), 30.7 (C-2, 11 ,16), 37.0 (C-25), 70.3 (C-4, 6, 7, 9, 18, 20, 21 , 23), 158.6 (C-13), 169.5 (C-27).

[0280] IR (FTIR) VTnax / cm'11093vs (C-0 stretching), 1282s and 1344s (C-N stretching), 1471s (C-H bending), 1558m (N-H bending), 1654m (C=O stretching), 2899s (N-H stretching)

[0281] GPC Mn (g / mol): 12000 (D:1.7), 1500 (0:1.1)

[0282] 55652043-1 Electrochemical performance

[0283] Of the various polyureas that were made (see Table 1), five were pre-selected for electrochemical testing, and galvanostatic cycling was conducted to investigate the following effects:

[0284] •Impact of chain length of the starting material

[0285] •Loading of metal complex and base

[0286] •Impact of polyurea conversion and presence of starting material

[0287] •Effect of addition to SBR

[0288] •Comparison of polyurea against CMC

[0289] Table 2: Polyureas brought forward for galvanostatic cycling

[0290] Mnin the components column (e.g. 1500-6000 Da) corresponds to the starting material - polyetherdiamine as described above (SP1 , SP2), cat. = Ru-MACHO complex and base = KO‘Bu.

[0291] The electrochemical performance of the materials was investigated by galvanostatic cycling, involving the application of constant current under defined voltage ranges, in this case 2.5 to 4.2 V. Parameters such as Coulombic efficiency, charge and discharge capacities, rate capabilities, and differential capacity analysis (dQ / dV) were measured, and the results for these materials alone are shown in Figures 9-25. Galvanostatic cycling provides insights into the voltage and energy profiles of the materials under test.

[0292] The compositions included 80% active material (LFP), 10% conductive carbon, 10% polyurea binder.

[0293] 55652043-1 Coulombic efficiency

[0294] For cathode materials, the Coulombic efficiency refers to the ratio of the amount of reinserted Li+compared to that of the extracted Li+, it is the indication of the “released battery capacity” and is “the ratio of the discharge capacity after the full charge and the charging capacity of the same cycle”. Coulombic efficiency is an important factor for assessing the lifespan of batteries with respect to charge sustainability and is a method of observing the degradation of the capacity of the battery with ageing / cycling. It is typically less than 100% due to factors such as electrical discharge energy, resistance, side reactions, and electrode instability. Good retention in the discharge capacity and the Coulombic efficiency over the course of a cycling program is desirable as it indicates no degradation of the battery life.

[0295] Potential vs. Specific Capacity

[0296] The typical voltage profile features an oblique line and an approximate plateau. The specific capacity, provided by mAh / g is how much electricity can be delivered by the cell per one gram of material.

[0297] Rate Capabilities

[0298] Rate capabilities are measured by adjusting the current in a suitable range. As the current rate rises, the capacity will decrease due to the higher polarisation and kinetic limitations.

[0299] Differential capacity analysis dQ / dV is an effective measure to observe the ageing and polarization of batteries. It is calculated by differentiating the charge capacity against the voltage. The peaks on the dQ / dV curves graph which are caused by plateaus in the voltage profile correspond to the phase transition in the active material during the insertion and extraction of the Li+ions. The properties of the peak such as its position along the x-axis and the amplitude can be used to infer information regarding the battery polarization and its ageing. Deviations between the charge and discharge peak locations arise from polarisation and kinetic effects. As a higher current density is applied, peaks shift to higher voltages during the charging process and lower voltages during the discharge process due to polarisation effects. Furthermore, this increased current density means that the peaks tend to reduce in magnitude and resolution, becoming broader.

[0300] 55652043-1 In the case of LFP, there is generally a single peak as most of the change in capacity occurs across the single voltage plateau. This peak in the dQ / dV is caused by the transition from the de-inserted FePC to fully inserted LiFePC .

[0301] Impact of the presence of diamine starting material

[0302] From the characterisation data obtained from the various compounds made (see Table 1), there was evidence of residual starting material retained within the product. It was hypothesized that the starting material could have an effect on the electrochemical performance of the battery.

[0303] PEG Diamine 1500 as a starting material includes ether linkages making up the alkyl portion of the polymeric backbone contributing to its solubility in water. Rather than the urea functionality of the resulting polyurea, it instead includes terminal amine functional groups. These amine end groups are very weak hydrogen bond donors forming hydrogen bonds with water and are unable to form hydrogen bonds with other amines. Theoretically, the stronger degree of hydrogen bonding between the urea linkages compared to the amine and water increases the viscosity, subsequently increasing the adhesion and binding strength.

[0304] A comparison of the electrochemical performance of a mixture of PEG Diamine 1500 with NBR, and MT22 with NBR, is shown below in Table 3: and MT22 (1500 Mw, 10 mol% cat., 20 mol% base), both with SBR

[0305] 55652043-1 Comparing Figures 35 and 28, and it can be observed that the PEG diamine starting material has a significantly lower capacity and pronounced polarisation compared to that of the polyurea. Both plots have shown a slightly higher first charge capacity, likely due to oxidation of the electrolyte. In the starting material, the oxidation / reduction peaks occur at 3.48 / 3.38 V which has a difference of 0.10 V, indicating a much larger polarisation than that of the polyurea which has a polarisation of 0.06 V.

[0306] Comparing Figures 33 and 27, and it can be observed that the starting material has a lower capacity (about 92.36 mAh / g) compared to that of the polyurea. It is believed that this may be due to the detachment of the binder from the electrode when the starting material has inadequate adhesion to the electrode materials due to the lower degree of hydrogen bonding. There is pronounced sloping in Figure 32 in both the charge and discharge curves which is indicative of less well-defined phase transitions in the starting material potentially due to side reactions or the formation of a thicker SEI which can hinder reactions in later cycles.

[0307] This confirms that the polyurea is the positive contributor to the electrochemical performance and the presence of starting material is detrimental to the electrochemical performance, particularly with regards to the lowered capacity and higher polarisation.

[0308] Effect of polymeric diamine selection

[0309] Increased polymeric chain length was believed to be desirable due to its relationship with a higher viscosity, potentially leading to higher adhesion and stability and preventing sedimentation. Furthermore, polymeric binders with longer chain lengths are believed to provide increased binding sites for the active material.

[0310] The highest NMR yield of polyurea in terms of percentage was observed with medium length starting PEG diamine ranging from 1500 to 2000 Da, attributing this to the increased chances of interaction between the terminal amine groups of the diamines and methanol. Consequently, longer chain polymeric diamines of 6000 Da resulted in a lower NMR yield of polyurea. The resulting polyurea Mn values were 10,900 Da (from PEG Diamine 1500 Da) and 16,800 Da (from PEG Diamine 6000 Da). For the former, this indicates at least seven repeating units whilst for the latter, only 2.8 repeating units were estimated. The disparity suggests that the product of the longer chain diamine could be referred to as a dimer / trimer / oligourea rather than a polyurea, thus explain the lower NMR yield observed.

[0311] 55652043-1 mol% cat., 20 mol% base) and MT22 (1500 Mw, 10 mol% cat., 20 mol% base).

[0312] Comparing Figures 17 and 12, and it can be observed that both polyureas exhibit the characteristic plateaus in both charge and the discharge curves which indicate that the processes occurring are reversible and there is no discernible difference in the insertion / de-insertion mechanisms. There is a much higher first charge curve that is shown above in Figure 17, most likely due to oxidation or degradation of the electrolyte.

[0313] As shown above in Figures 17 and 12, LFP with MT22 binder (1500 Mw, 10 mol% cat., 20 mol% base) exhibits a maximum discharge capacity of 148.24 mAh / g and high capacity retention of 98.9% over 200 cycles at 10 mA / g in 2.5-4.2 V. Furthermore, it shows an extremely high Coulombic efficiency of -100% throughout the 200 cycles. This retention in the discharge capacity and the Coulombic efficiency throughout the cycling program is desirable as it indicates no degradation of the battery life. The same is observed in MT20 with a maximum discharge capacity of 138.21 mAh / g and an even higher capacity retention of 99.6% throughout 200 cycles.

[0314] MT22 polyurea (1500 Mw, 10 mol% cat., 20 mol% base) has a chain length of 10,900 Da (number of urea linkages: -7) and appears to have a higher first charge capacity due to the SEI formation resulting in the considerably lower initial Coulombic efficiency. Positively, there is not a significant detriment on the polarisation, as can be seen in the dQ / dV plots in Figures 19 and 14 - this is to be expected of the LFP and this has further demonstrated that polyurea as a binder does not detrimentally affect the polarisation. This shows that the polyurea binder is working effectively and maintaining the connectivity between the components.

[0315] From these graphs, the chain length of the polyurea does not appear to have a significant impact on the charge and discharge capacity or the Coulombic efficiency. Although this may be surprising, there are several factors as to why this could be the case. MT20 (6000 Mw, 10 mol% cat., 20 mol% base) (16,800 Da, number of urea linkages -2.5) was run at a higher current density which leads to lower capacities, and it

[0316] 55652043-1 also had a lower yield of polyurea. Therefore, it could also be the presence of a higher percentage of starting material which has shown to be detrimental to the electrochemical performance coupled with the higher current loading that has resulted in the lower capacity.

[0317] Loading of metal complex and base

[0318] Referring to Figures 20-22 relating to MT23 (1500 Mw, 2.5 mol% cat., 20 mol% base), with a lower NMR yield of polyurea of 26% and a slightly lower capacity than when using MT22 (1500 Mw, 10 mol% cat., 20 mol% base) which has a 49% NMR yield of polyurea. There is likely residual base, particularly potassium leftover that is interrupting the extraction / insertion mechanism during the charge / discharge process. There is significant polarisation occurring which is likely to be attributed to the kinetic limitations as shown below in the dQ / dV curve in Figure 22. The potassium could either be engaging in undesirable side reactions or disrupting the FePCU host structure or a composite effect. One reason for residual potassium is believed to be the workup method with hexane eliminating the catalyst, but not the base.

[0319] MT23 (1500 Mw, 2.5 mol% cat., 20 mol% base) still has well-defined peaks, albeit at a considerably lower capacity of 90.54 mAh / g compared to MT22 with peaks of 148.24 mAh / g. There is significant polarisation in MT23 (1500 Mw, 2.5 mol% cat., 20 mol% base) with the oxidation / reduction peaks located at 3.48 / 3.36 V, which shows a 0.12 V difference, which is double the polarisation compared to MT22 (1500 Mw, 10 mol% cat., 20 mol% base).

[0320] Referring now to Figures 23-25 relating to MT24, it can be seen that, for MT24 (1500 Mw, 20 mol% cat., 40 mol base), there is a significant decrease in the charge and discharge capacity compared to that of the MT23 (1500 Mw, 2.5 mol% cat., 20 mol% base). This is believed to be due to the presence of potassium which is interrupting the insertion / de-insertion mechanism. During charging, it exhibits a plateau indicating deinsertion is occurring. However, even from the first discharge cycle, it exhibits a steep gradient with no plateau which is indicative of the insertion mechanism being severely disrupted, to the extent it is not occurring. The absence of the plateau also indicates that this reaction is irreversible, and therefore, not rechargeable.

[0321] From the dQ / dV plot shown above in Figure 22 and Figure 25, there is a stark difference between MT23 (1500 Mw, 2.5 mol% cat., 20 mol% base) and MT24 (1500 Mw, 20 mol% cat., 40 mol% base). In the case of MT24 (1500 Mw, 20 mol% cat., 40

[0322] 55652043-1 mol% base), the charging peaks are significantly broader, with oxidation peaks occurring at 3.75-3.86 V, indicating disruption with the de-insertion process.

[0323] There is little to no evidence of the discharge peaks, agreeing with the above hypothesis that the insertion of Li+is being inhibited.

[0324] When examining the Coulombic efficiency (Figure 23) for MT24 (1500 Mw, 20 mol% cat., 40 mol% base) with considerably more catalyst, the Coulombic efficiency was mostly at 100% however with pronounced deviations which are indicative of the side reactions. There is a markedly lower specific capacity at 24.92 mAh / g which is hypothesised to be due to the presence of potassium and being exacerbated by the presence of the ruthenium.

[0325] Due to the large amount of catalyst, ruthenium is likely to be intertwined within the polymeric matrix and is so entangled that it is unable to be removed with the hexane upon work-up. In this case, there is likely to be both ruthenium and potassium present which is poisoning the cell performance causing the lower specific capacity.

[0326] Comparison of polyurea with CMC

[0327] Comparative electrochemical data for CMC is provided in Figures 1-4.

[0328] Table 5: Discharge capacities and Coulombic efficiencies of CMC and MT22 (1500 Mw, 10 mol% cat., 20 mol% base)

[0329] The polyurea has a higher overall specific capacity than the CMC. The polyurea also has a slightly higher reversible capacity as indicated by the lower cell polarisation which indicates a high degree of reversibility, rendering it effective for rechargeable applications.

[0330] Comparing Figures 2 and 17, and it can be observed that CMC has a maximum discharge capacity of 146.14 mAh / g but with a slightly lower capacity retention compared to that of the polyurea. The polyurea exhibits a maximum discharge capacity of 148.24 mAh / g and high capacity retention of 98.9% over 200 cycles at 10 mA / g in 2.5-4.2 V.

[0331] 55652043-1 Furthermore, it shows an extremely high Coulombic efficiency of -100% throughout the 200 cycles. This retention in the discharge capacity and the Coulombic efficiency throughout the cycling program is desirable as it indicates no degradation of the battery life. Although the CMC has a higher initial Coulombic efficiency, over time, the polyurea MT22 (1500 Mw, 10 mol% cat., 20 mol% base) exhibits higher Coulombic efficiency of 99% compared to CMC’s 97% indicating a longer cycle life. The CMC’s Coulombic efficiency of 97% is in accordance with that of the literature.

[0332] Comparing Figures 1 and 16, and it can be observed that CMC also exhibited premature cell failure, failing after 18 cycles compared to that of the 50 cycles thus far of the polyurea MT22.

[0333] The rate performances and differential capacity analysis, shown in Figures 3-4 and Figures 18-19, indicate similar charge and discharge capacities even at high current densities of 500 mA / g and the same polarisations of 0.05 V for both the polyurea and CMC. This comparable performance is immensely exciting as it has proven that the polyurea can act as an aqueous binder to the levels of CMC, even outperforming it in terms of higher specific capacity and Coulombic efficiency.

[0334] Addition of SBR

[0335] SBR is commonly added to CMC to form a composite that enhances the dispersive capabilities, flexibility, and binding strength.

[0336] It was hypothesised that the addition of SBR could confer similar properties to a material based on polyureas according to the present invention.

[0337] Testing was performed based on polyurea embodiment MT22 (see Figures 26- 28). mol% cat., 20 mol% base) without SBR and MT22 (1500 Mw, 10 mol% cat., 20 mol% base) with SBR

[0338] 55652043-1 Comparing Figures 17 and 27, and it can be observed that the first charge capacity is higher with pure polyurea, at 212.69 mAh / g however, there is a very consistent discharge capacity of 148.24 mAh / g and charge capacity for the subsequent cycles. Comparatively, the polyurea / SBR has slightly higher charge and discharge capacities with consistent discharge capacities throughout the cycles at 157.73 mAh / g. There is a considerably higher initial Coulombic efficiency, at 97% when incorporating the SBR with the polyurea which is likely due to the absence of electrolyte oxidation or formation of a thinner SEI which does not have detrimental effects on the insertion and de-insertion process in later cycles. In both samples, there is limited polarisation which once again exhibits that the polyurea cooperates and is a compatible binder with LFP.

[0339] Comparing Figures 16 and 26, and it can be observed that the polyurea / SBR composite had an enhanced Coulombic efficiency of 100% compared to that of the pure polyurea with a Coulombic efficiency of 99%. The polyurea / SBR had no presence of any side reactions that negatively impacted the insertion / de-insertion mechanism which is positive as the SBR has successfully enhanced the electrochemical performance as hypothesised through the additional mechanism of cross-linking alongside the hydrogen bonding of the polyurea.

[0340] With the addition of the SBR, the slurries had increased viscosity, which in turn has had the desired effect of increased adhesion and stability of the cast.

[0341] Referring now to Figures 19 and 28, and it can be observed that (see Figure 19) with the pure polyurea, the oxidation / reduction peaks occur at 3.44 / 3.39 V which has a difference of 0.05 V. Comparatively, as shown in Figure 28 with the polyurea / SBR composite, the oxidation / reduction peaks occur at 3.44 / 3.41 V indicating an even smaller polarisation of 0.03 V.

[0342] Use of binder in anodes

[0343] The potential for using the present materials as binders in anodes (not just cathodes) was further investigated. The present study is based on hard carbon anodes for use in sodium-ion batteries.

[0344] This investigation is illustrated in Figures 36-39.

[0345] 55652043-1 Figures 36-37 show electrochemical data for embodiment MT22 in a hard carbon I sodium half cell, including coulombic efficiency with a 50 mA / g current density (Figure 36), potential vs specific capacity with a 50 mA / g current (Figure 37);

[0346] Figures 38-39 show electrochemical data for embodiment MT22 + NBR in a hard carbon I sodium half cell, including coulombic efficiency with a 50 mA / g current density (Figure 38), potential vs specific capacity with a 50 mA / g current (Figure 39).

[0347] It can be seen from these figures that use of the polyurea as a binder provides hard carbon electrodes with high capacities and excellent cycling stability, which is further enhanced in combination with SBR.

[0348] It will be understood that the present embodiments are provided by way of example only, and that various modifications can be made to the present embodiments without departing from the scope of the invention.

[0349] 55652043-1

Claims

CLAIMS:

1. A binder composition for use in a battery electrode, wherein the binder composition comprises or consists of a polyurea polymer.

2. A binder composition according to claim 1, wherein the polyurea polymer comprises or consists of a polyetherurea polymer.

3. A binder composition according to any preceding claim, wherein the binder composition comprises at least one additional binder component.

4. A binder composition according to claim 3, wherein the additional binder component comprises styrene-butadiene rubber (SBR).

5. A binder composition according to any preceding claim, wherein the polyetherurea polymer comprises polyethylene glycol and / or polypropylene glycol units in its backbone.

6. A binder composition according to any preceding claim, wherein the polyurea is prepared by dehydrogenative coupling of a diamine compound and methanol.

7. A binder composition according to any preceding claim, wherein the polyurea has the general formula (Illa), (111 b) or (I I Ic):wherein n is an integer of about 10 to 50, optionally about 33; and m is an integer of about 2-10,wherein n is an integer of about 10 to 50, optionally about 33; and55652043-1m is an integer of about 2-10,wherein n is an integer of about 10 to 50, optionally about 33; and m is an integer of about 2-10.

8. An electrode material comprising a binder composition, wherein the binder composition comprises or consists of a polyurea polymer.

9. An electrode material according to claim 8, wherein the electrode material comprises or is a battery electrode.

10. An electrode material according to claim 8 or claim 9, wherein the polyurea polymer comprises or consists of a polyetherurea polymer.

11. Use of a polyurea polymer in a binder composition for an electrode material.

12. Use of claim 11, wherein the electrode material is a battery electrode.

13. A method of preparing a polyurea polymer for use in a binder composition for an electrode material, the method comprising reacting a diamine compound and methanol in the presence of a metal pincer complex and a base to form polyurea and hydrogen gas by dehydrogenative coupling.

14. A method according to claim 13, wherein the polyether diamine is a diamine of formula (I):R1HN-(CH2)m-W-(CH2)n-NHR2(I) wherein: each of R1and R2is independently H or a C1 to C4 hydrocarbyl group; each of m and n is independently an integer from 0 to 10, typically 0-3, e.g. 1-3; andW is a polyether unit.55652043-115. A method according to claim 13 or claim 14, wherein the polyether diamine is a diamine of formula (la):H2N-(CH2)m-[CH2-CH2-O]i-(CH2)n-NH2 (la) wherein: m is an integer from 0 to 10, optionally 1-3; n is an integer from 1 to 10, optionally 1-3; andI is an integer from 1 to 140, optionally from 2 to 35.55652043-1

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