Doped lithium lanthanum zirconium oxide

Abstract

A reaction composition is disclosed for forming doped lithium lanthanum zirconium oxide, comprising one or more lithium, lanthanum and / or zirconium species for forming a doped lithium lanthanum zircon

Description

BACKGROUND OF THE INVENTION

[0001] The present disclosure relates to doped lithium lanthanum zirconium oxide.

[0002] The present invention concerns doped lithium lanthanum zirconium oxide. More particularly, but not exclusively, this invention concerns a method of making a doped lithium lanthanum zirconium oxide. The invention also concerns a doped lithium lanthanum zirconium oxide, a composition for forming a doped lithium lanthanum zirconium oxide and a two-part reaction mixture composition for forming a doped lithium lanthanum zirconium oxide.

[0003] Doped lithiated solid-state electrolyte materials are typically produced by solidstate synthesis. This typically requires extensive periods of heating at high temperature. Such methods are energy-intensive and may not be scalable to produce large amounts of material. Furthermore, in some cases, a significant amount of processing of the produced material has to be undertaken. It is known to use aqueous synthetic routes to produce doped lithiated solid-state electrolyte materials, but such known routes often produce harmful or unwanted waste products, such as ammonium oxalate or choline hydroxide. Such known routes sometimes use relatively unstable reagents or precursors, such as niobium pentachloride.

[0004] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of making a doped lithium lanthanum zirconium oxide (sometimes referred to herein as LLZO). SUMMARY OF THE INVENTION

[0005] According to a first aspect of the invention, there is provided a method of making a doped lithium lanthanum zirconium oxide, the method comprising: forming the doped lithium lanthanum zirconium oxide from a polyoxometalate. 10 1024

[0006] The applicant has found that it is possible to make doped lithium lanthanum zirconium oxide using polyoxometalates. Examples of such methods have been found to be effective, typically do not generate harmful waste products, and typically use precursors that are relatively stable.

[0007] The polyoxometalate optionally provides at least one, and optionally more than one, dopant. For the avoidance of doubt, one or more dopant may be provided by a source or sources other than the poly oxometalate.

[0008] Those skilled in the art will realise that the polyoxometalate structure is not preserved in the doped lithium lanthanum zirconium oxide (“LLZO”). The polyoxometalate has proved to be a suitable vehicle for supplying a dopant as part of a doped LLZO.

[0009] A dopant may be any suitable element other than lithium, lanthanum and zirconium and oxygen that is present in the doped lithium lanthanum zirconium oxide at more than a trace amount. For example, a dopant may be a metal or senu-metal (such as boron or tellurium). A dopant may be a halogen, for example. For example, some of the oxygen may be replaced by halogen. Such a doped material may comprise a lattice, optionally a crystalline lattice, with certain species occupying the lattice sites and certain species occupying sites between the lattice sites (the sites between the lattice sites often being known as “interstitial sites”). One or more dopants may optically occupy sites between the lattice sites and / or may occupy lattice sites. Optionally, one or more species for incorporation into the solid-state electrolyte material may comprise species for forming the lattice structure, therefore optionally for occupying lattice sites. The method optionally takes place in an aqueous liquid. For the avoidance of doubt, the method may comprise proving one or more dopants other than that or those that are provided by the polyoxometalate.

[0010] A polyoxometalate is a polyatomic ion, usually but not always an anion, that comprises three or more metal oxyanions linked together by shared oxygen atoms to form a closed 3-dimensional framework. The poly oxometalate optionally comprises a transition metal, a Group 13 species (e.g. boron (B), aluminium (Al), gallium (Ga), indium (In), or thallium (T1)), a Group 15 species ((e.g. arsenic (As), antimony (Sb) or bismuth (Bi))) or a 10 1024 Group 16 species ((e.g. selenium (Se) or tellurium (Te)). The poly oxometalate may comprise one or more of niobium, molybdenum, tungsten, tellurium, tantalum and aluminium. Each polyoxometalate ion comprises at least 3, optionally at least 4, optionally at least 5, optionally at least 6 and optionally at least 7 metal species. Each polyoxometalate ion may comprise no more than 300 metal species, optionally no more than 250, optionally no more than 200, optionally no more than 150, optionally no more than 100, optionally no more than 80, optionally no more than 60, optionally no more than 50, optionally no more than 40, optionally no more than 30, optionally no more than 20, optionally no more than 15, optionally no more than 14, optionally no more than 13, optionally no more than 12, optionally no more than 11, optionally no more than 10, optionally no more than 9, optionally no more than 8 and optionally no more than 7 metal species. For the avoidance of doubt, this is not the number of different metal species in the ion, but the total number of metal atoms / ions in the polyoxometalate ion.

[0011] The polyoxometalate may have a Keggin structure, a Lindqvist structure or an Anderson-Evans structure, for example.

[0012] Optionally, the polyoxometalate comprises one or more of Nb, Te, Al, Ga, Sb, W and Ta.

[0013] Optionally, the polyoxometalate may comprise one or more of [NbeOig]8', [MO7O24]6; [TeNb50i9]7; [TeW6O24]6; [Nb6-xWxOi9](8’x); where x is an integer from 1 to 5, [Nb3W30i9]5; [Nb3Ta30i9]-8,, [W1204o]8-, [Wi2O42]12- and f A113O4(OH)24]7

[0014] The method may comprise mixing at least two compositions, at least one of which comprises the polyoxometalate. At least one of the compositions optionally comprises a lanthanum species. At least one of the compositions optionally comprises a zirconium species. At least one of the compositions may optionally comprise one or more dopants not provided by the polyoxometalate.

[0015] The method may optionally comprise forming a composition (optionally a precipitate) comprising a lanthanum species, a zirconium species and one or more dopant species derived from a polyoxometalate, optionally in the absence of lithium species. As mentioned above, one or more dopant species may initially be provided as a 10 1024 polyoxometalate. The method may comprise forming said composition and subsequently contacting said composition with one or more lithium species.

[0016] Forming the composition (optionally a precipitate) comprising a lanthanum species, a zirconium species and one or more dopant species optionally takes place at a pH of at least 3.5, optionally at least 3.6, optionally at least 3.7, optionally at least 3.8, optionally at least 3.9, optionally at least 4.0. optionally at least 7, optionally at a pH of at least 8 and optionally at a pH of at least 9.

[0017] Forming the composition (optionally a precipitate) comprising a lanthanum species, a zirconium species and one or more dopant species derived from a polyoxometalate may comprise mixing at least two precursor compositions, at least one of which comprises the polyoxometalate. At least one of the precursor compositions optionally comprises a lanthanum species. At least one of the precursor compositions optionally comprises a zirconium species. At least one of the precursor compositions may optionally comprise one or more dopants not provided by the poly oxometalate. Optionally, at least one of the precursor compositions is in the form of a solution. Optionally, at least one of the precursor compositions is in the form of a suspension. Optionally, at least two of the precursor compositions are in the form of a solution. Optionally, at least one of the precursor compositions comprises a base, such as hydroxide, carbonate or hydrogen carbonate. Optionally, at least one of the precursor compositions comprises lanthanum and zirconium species, and optionally comprises one or more dopant, optionally from a polyoxometalate. Optionally, at least one of the precursor compositions comprises lanthanum and zirconium species, but no dopant, and another precursor composition comprises one or more dopant, optionally from a polyoxometalate. Optionally, at least one of the precursor compositions comprises lanthanum and zirconium species, and one or more dopant, and another precursor composition comprises one or more dopant, optionally from a polyoxometalate, and optionally base. Optionally, at least one of the precursor compositions comprises lanthanum and zirconium species, and one or more dopant, and another precursor composition comprises base, but no dopant. Optionally, one of the precursor compositions may be acidic. 10 1024

[0018] For example, a first precursor composition, optionally in the form of a solution may comprise one or more of Zr, La and optionally one or more dopant. The first precursor composition may optionally be acidic. A second precursor composition, optionally in the form of a solution but also optionally in the form of a suspension, may comprise one or more of: a base, one or more dopant and one or more of Zr and La. Such a dopant may optionally be provided as a polyoxometalate. The provision of two such precursor compositions which may be mixed to form a precipitate has provided to be an effective way of making a composition (for example, in the form of a precipitate) from which doped lithium lanthanum zirconium oxide can be made.

[0019] Optionally, a first precursor composition, optionally in the form of a solution may comprise one or more of Zr, La and optionally one or more dopant. The first precursor composition may optionally be acidic. A second precursor composition, optionally in the form of a solution but also optionally in the form of a suspension, may comprise one or more of: a base and one or more dopant, but not one or more of Zr and La. Such a dopant may optionally be provided as a polyoxometalate. The provision of two such precursor compositions which may be mixed to form a precipitate has provided to be an effective way of making a composition (for example, in the form of a precipitate) from which doped lithium lanthanum zirconium oxide can be made.

[0020] Optionally, a first precursor composition, optionally in the form of a solution may comprise one or more of Zr, La and optionally one or more dopant. Such a dopant may optionally be provided as a polyoxometalate. The first composition may optionally be acidic. A second precursor composition, optionally in the form of a solution but also optionally in the form of a suspension, may comprise a base, but not one or more dopant, nor one or more of Zr and La.. The provision of two such precursor compositions which may be mixed to form a precipitate has provided to be an effective way of making a composition (for example, in the form of a precipitate) from which doped lithium lanthanum zirconium oxide can be made.

[0021] The method comprises contacting a lithium species (optionally lithium ions) with said composition. The lithium ions may be provided by forming a solution comprising lithium ions (for example, by dissolving a lithium salt) and contacting said composition 10 1024 with said solution. Alternatively or additionally, the composition (for example, in the form of a precipitate) will be present in a liquid, and the method may comprise dissolving a lithium salt in said liquid to provide the lithium ions. The lithium salt may comprise any suitable lithium salt, such as lithium hydroxide, lithium nitrate, lithium halide or lithium acetate.

[0022] Milling (such as ball milling) may be used to contact a lithium species with said composition.

[0023] Freeze drying or spray drying may be used to contact a lithium species with said composition.

[0024] The method may comprise forming a precipitate comprising lithium. Forming a precipitate comprising lithium may take place subsequent to, or contemporaneous with, contacting a lithium species (optionally lithium ions) with a composition (optionally a solid and optionally a precipitate) comprising zirconium, lanthanum and one or more dopant species. Forming a precipitate comprising lithium may comprise providing a source of anions with which lithium may form an insoluble salt. For the avoidance of doubt, “providing” does not mean that the source of anions with which lithium may form an insoluble salt is added in a separate step. For example, the composition comprising zirconium, lanthanum and one or more dopant species may also comprise a source of anions with which lithium may form an insoluble salt.

[0025] Forming a precipitate comprising lithium may optionally comprise (i) contacting the composition (optionally comprising a solid and optionally comprising a precipitate) comprising zirconium, lanthanum and one or more dopant species with lithium ions, and subsequently providing a source of anions with which lithium may form an insoluble salt; (ii) forming a composition (optionally comprising a solid and optionally comprising a precipitate) comprising zirconium, lanthanum, one or more dopant species and a source of anions with which lithium may form an insoluble salt, and subsequently providing lithium ions; or (iii) contemporaneously contacting the composition (optionally comprising a solid and optionally comprising a precipitate) comprising zirconium, lanthanum and one of more dopant species with a source of anions with which lithium may form an insoluble salt and lithium ions; or (iv) contacting the composition (optionally comprising a solid and 10 1024 optionally comprising a precipitate) comprising zirconium, lanthanum and one or more dopant species with a source of anions with which lithium may form an insoluble salt and, and subsequently providing lithium ions. In certain circumstances, option (i) is preferred because this may lead to a greater yield of the desired product. Lithium ions may be provided by dissolving a soluble lithium salt in a liquid, such as the carrier liquid of said precipitate. Alternatively or additionally, lithium ions may be provided by providing a solution of lithium ions and contacting said solution with said precipitate.

[0026] The reference to an insoluble salt refers to the salt optionally being insoluble in aqueous solution, being sufficiently insoluble to precipitate from solution.

[0027] The source of anions with which lithium may form an insoluble salt may comprise a source of carbonate anions. Lithium carbonate is insoluble in many liquids, such as aqueous liquids. The source of carbonate anions may comprise one or more of carbonate ions, hydrogencarbonate ions and carbon dioxide. Carbon dioxide may be particularly effective because the solution from which the precipitate comprising lithium is removed is a solution of lithium carbonate, which may be reused without further purification. This therefore reduces the loss of lithium.

[0028] The method may comprise heating the precipitate comprising lithium to form the doped solid-state electrolyte material. Such heating may optionally comprise calcining the precipitate comprising lithium. In the present case, calcining comprises heating to provide a phase transition. Heating the precipitate comprising lithium to form the doped solid-state electrolyte material may optionally comprise heating the precipitate comprising lithium to a temperature of at least 500 °C, optionally at least 600 °C, optionally at least 700 °C, optionally at least 800 °C, optionally at least 900 °C and optionally at least 1000 °C. Heating the precipitate comprising lithium to form the doped solid-state electrolyte material may optionally comprise heating the precipitate comprising lithium to a temperature of no more than 1500 °C, optionally no more than 1400 °C, optionally no more than 1300 °C, optionally no more than 1200 °C, optionally no more than 1100 °C and optionally no more than 1000 °C. 10 1024

[0029] The method may comprise separating the precipitate comprising lithium from an ambient liquid, for example, using filtration and / or drying. For example, spray drying or freeze drying may be used.

[0030] The method may comprise drying the precipitate comprising lithium, optionally post-separation of the precipitate comprising lithium from an ambient liquid. Drying the precipitate comprising lithium may comprise heating the precipitate comprising lithium, optionally to a temperature of no more than 200 °C, optionally no more than 180 °C, optionally no more than 160 °C, optionally no more than 140 °C, optionally no more than 120 °C and optionally no more than 100 °C. Drying the precipitate comprising lithium may comprise heating the precipitate comprising lithium, optionally to a temperature of at least 60 °C, optionally at least 80 °C, optionally at least 100 °C and optionally at least 120 °C. Drying the precipitate comprising lithium may comprise exposing the precipitate comprising lithium to reduced pressures.

[0031] The doped lithiated solid-state electrolyte material may comprise LiALaBZr(.OD, where A=5.0-8.0, B=2.5-3.0, C=l.0-2.0 and D=ll-12. A is optionally at least 5.5 and at least 5.8. A is optionally no more than 7.0 and optionally no more than 6.8. B is optionally at least 2.5 and optionally at least 2.8. C is optionally at least 1.3 and optionally at least 1.4. C is optionally no more than 1.8. D is optionally 12. For the avoidance of doubt, the doped lithiated solid-state electrolyte material will comprise dopants m addition to the lithium, lanthanum, zirconium and oxygen.

[0032] The statements below in relation to the method of the first aspect of the present invention all pertain to doped lithium lanthanum zirconium oxide. The one or more dopant comprises one or more of an alkali metal, an alkaline earth metal, a transition metal (for example, a Group 4, 5 or 6 species), a Group 13 species, a Group 15 species, a Group 16 species, a rare earth species and a lanthanide..

[0033] The doped lithium lanthanum zirconium oxide may have a formula Li .La^Zr^O^X,,, where A=5.0-8.0, B=2.5-3.0, C=l.0-2.0, D=ll-12 andX is one or more dopants, and E is the total amount of dopant. E is optionally at least 0.01, optionally at least 0.05, optionally at least 0.1, optionally at least 0.15, optionally at least 0.2, optionally at 10 1024 least 0.25 and optionally at least 0.3. E is optionally no more than 1.0, optionally no more than 0.9, optionally no more than 0.8 and optionally no more than 0.75.

[0034] One or more dopant optionally comprises one or more of a transition metal, a Group 6 species, a Group 13 species, a Group 15 species and a Group 16 species.

[0035] One or more dopant optionally comprises one or more of an alkali metal, an alkaline earth metal, a Group 4 species, a Group 6 species, a lanthanide and a rare earth species.

[0036] One or more dopant optionally comprises one or more of a transition metal, a Group 6 species, a Group 13 species, a Group 15 species and a Group 16 species, and in addition one or more of an alkali metal, an alkaline earth metal, a Group 4 species, a Group 6 species, a lanthanide and a rare earth species.

[0037] Optionally, the doped lithium lanthanum zirconium oxide may have a formula LiALaBZrcOoXlEiX2E2, where A, B, C and D are defined above, and where XI represents one or more dopants, each comprising a transition metal (optionally a Group 4, 5 or 6 species) (optionally Ta and / or Nb, and / or a Group 6 species (optionally W and / or Mo)), a Group 13 species (optionally Ga and / or Al), a Group 15 species (optionally Sb) or a Group 16 species (optionally Te), El represents the total amount of such dopants, X2 represents one or more dopants, each of which not being a transition metal, a Group 13 species, a Group 15 species and a Group 16 species, and E2 representing the total amount of such dopants. El is optionally at least 0.01, optionally at least 0.05, optionally at least 0.1, optionally at least 0.15, optionally at least 0.2, optionally at least 0.25 and optionally at least 0.3. El is optionally no more than 0.8, optionally no more than 0.7 and optionally no more than 0.6. E2 is optionally at least 0.01, optionally at least 0.05, optionally at least 0.08, optionally at least 0.1 and optionally at least 0.2. E2 is optionally no more than 0.5, optionally no more than 0.4 and optionally no more than 0.3. X2 optionally represents one or more dopant, each comprising an alkali metal (optionally Rb), an alkaline earth metal (optionally selected from the group consisting of Ca, Ba, Mg and Sr), a lanthanide (optionally Ce) and a rare earth species (optionally Y and / or Sc). X2 optionally represents one or more dopant, each comprising an alkali metal, an alkaline earth metal, a lanthanide or a rare earth species.

[0038] For example, XI may represent one or more of Nb, Te, Al, Ga, Sb, W and Ta. 10 1024

[0039] For example, X2 may represent one or more of Hf, Ti, Sr, Ca, Ba, Mg, Ce, Sc, Y and Rb.

[0040] One or more dopant optionally comprises one or more of Mo, Nb, Te, Al, Ga, Sb, W and Ta. Such dopants have been found to be advantageous for LLZO materials.

[0041] One or more dopant optionally comprises one or more of Hf, Ti, Sr, Ca, Ba, Mg, Ce, Sc, Y and Rb. Such dopants may be advantageous for LLZO materials, optionally in combination with other dopants, such as one or more of Nb, Mo, Te, Al, Ga, Sb, W and Ta.

[0042] According to a second aspect of the invention, there is also provided a doped lithium lanthanum zirconium oxide made in accordance with the method of the first aspect of the present invention. The doped lithium lanthanum zirconium oxide of the second aspect of the present invention may comprise the features described above in relation to the method of the first aspect of the present invention.

[0043] In accordance with a third aspect of the present invention, there is provided a reaction composition for forming doped lithium lanthanum zirconium oxide, comprising:

[0044] one or more lithium, lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and at least one dopant provided as a polyoxometalate.

[0045] The applicant has discovered that providing one or more dopant as a polyoxometalate has proved to be advantageous. The reaction composition may optionally comprise one or more reaction and / or decomposition products of the polyoxometalate, such as one or more metal oxides.

[0046] The reaction composition of the third aspect of the present invention may comprise one or more of the features of the method of the first aspect of the present invention. For example, the reaction composition may comprise a source of anions with which lithium may form a precipitate. For example, the reaction composition may comprise a source of carbonate ions, such as carbonate ions, hydrogen carbonate ions or carbon dioxide.

[0047] Optionally, the reaction composition may comprise one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and optionally at least one dopant, optionally provided as a polyoxometalate, but not a lithium species for forming a doped lithium lanthanum zirconium oxide. The reaction composition may 10 1024 comprise a solid (optionally a precipitate) that optionally provides the one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide. In this connection, such a composition may be formed prior to the addition of lithium species. The reaction composition may optionally comprise one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and optionally at least one dopant, optionally provided as a polyoxometalate, and a lithium species.

[0048] The pH of the reaction composition may be at least 3.5, optionally at least 4.0, optionally at least 4.5 and optionally at least 5.0. The pH of the reaction composition may optionally be no more than 8.0, optionally no more than 7.5, optionally no more than 7.0, optionally no more than 6.5, optionally no more than 6.0, optionally no more than 5.5 and optionally no more than 5.0. This may be the case, for example, when the reaction composition comprises one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and optionally at least one dopant, optionally provided as a polyoxometalate, but no lithium species. The one or more dopants may be substantially as described above in relation to the method of the first aspect of the present invention.

[0049] The method of the first aspect of the present invention may be used to make the composition of the third aspect of the present invention. In this connection, the present invention may provide a method of making a reaction composition in accordance with the third aspect of the present invention, the method comprising mixing at least two compositions, at least one of which comprises a polyoxometalate, at least one of which comprises a lanthanum species and at least one of which comprises a zirconium species. The compositions may have one or more features as described above in relation to the method of the first aspect of the present invention.

[0050] In accordance with a fourth aspect of the present invention, there is provided a multi-part reaction composition for forming a doped lithium lanthanum zirconium oxide, comprising: a first part comprising one or more lithium, lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, optionally a base, and optionally a dopant provided as a poly oxometalate; 10 1024 optionally a second part comprising a base if the base is not provided in the first part, and a dopant provided as a polyoxometalate, if the poly oxometalate is not provided in the first part; and optionally a third part comprising lithium species (optionally lithium ion, optionally provided as a solution of lithium ions, if lithium species are not provided in the first or second parts).

[0051] The multi-part reaction composition may comprise those features described above in relation to the method of the first aspect of the present invention and / or the reaction composition of the third aspect of the present invention.

[0052] For example, the multi-part reaction composition for forming a doped lithium lanthanum zirconium oxide, may comprise:

[0053] a first part comprising one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide;

[0054] a second part comprising a base and a dopant provided as a polyoxometalate; and

[0055] a third part comprising lithium species (optionally lithium ion), provided as a solution of lithium ions.

[0056] It will, of course, be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

[0057] Embodiments of the present invention will now be described by way of example only. DETAILED DESCRIPTION

[0058] In the Examples below, the sources of the reagents used are as follows: ZrOCl2.8H2O: Thermo Scientific (RTM) A12342; La2O3: ACROS Organics (RTM) 199160010; La(NO3)3.6H2O: VWR 24958.238; 37% HC1: VWR 20252-335; Na2CO3: Tata; K2CO3: VWR 26724.360; Nb2O5: Alfa Aesar (RTM) 11365-35; Nb2O5.xH2O: CBMM; KOH: VWR 26668.365; K8[Nb60i9] :Nb2O5 or Nb2O5.xH2O was stirred in KOH solution at 90 - 180 °C until almost no further dissolution occurred, then any remaining solid was filtered off to leave a clear, pale-blue solution; LiOH.H2O: Alfa Aesar (RTM) 10 1024 43171-36; NH4HCO3: Merck (RTM) 1.01131.5000; (NH4)2Zr(OH)2(CO3)2 solution: Sigma Aldrich (RTM) 464597.250; (TBA)OH 40% solution : VWR 85738.180; 69% HN03: VWR 20425.322; (ZrO2)2 CO2 xH2O: Alfa Aesar (RTM) 43245.36; (NH4)6[Mo7O24].4H2O: VWR 21276.185; LiNO3: VWR 25029.268; Te(OH)6: Alfa Aesar (RTM) 14197.09; Na2WO4.2H2O: HC Starck; Cs2CO3: Supplied by Dakram; Ta2O5: Alfa Aesar (RTM) 14709.18; HfOCl2.8H2O: Alfa Aesar (RTM) 11833.14; T1OSO4 solution: Sigma Aldrich (RTM) 495379-1L; SrCl2.6H2O: Alfa Aesar (RTM) 12494.36; CaCl2.2H2O: ACROS Organics (RTM) 207780025; BaCl2.2H2O: VWR 21709.364; MgCl2.6H2O: Sigma Aldrich (RTM) M9272-500G; CeCl3.7H2O: Alfa Aesar (RTM) A12947.30; ScC13.6H2O: Alfa Aesar (RTM) 11218.03; YC13.6H2O: ACROS Organics (RTM) 199180500; A1(NO3)3.9H2O: Alfa Aesar (RTM) 12360.A1; (NH4)io[H2Wi2042].xH20: HC Starck; (NH4)6[H2Wi204o].xH20: HC Starck; CO2: Air Liquide; K8Ta6Oi9.16H2O -tantalum powder and KOH were heated together at 450 °C until a melt formed. The melt was then extracted into the minimum quantity of water to make a clear, colourless solution; ; Rb2CO3: Sigma Aldrich (RTM) 8.43858.0010; WO3.2H2O - was slowly added to a room temperature solution of 20% HC1, and left to stir for 4 hours. The yellow precipitate formed was filtered off and dried in air.

[0059] Example 1 - MC06-081 - Li6.4La3Zri.4Nbo.60i2

[0060] Solution A was prepared by dissolving 128.9 g 37% HO and 66.6 g ZrOCl2.8H2O in 200 ml DI water. Once fully dissolved, 71.1 g La2O3 was added and stirred to dissolve. The solution was diluted to 1.5 L with DI water.

[0061] Solution B was prepared by diluting 75.8 g of KsNbeOig solution (30.7% as K8Nb6Oi9.15H2O, 4.34% as KOH) to 500 ml with DI water, then adding 107.2 g K2CO3. The mixture was stirred until fully dissolved.

[0062] Solution A was added to Solution B at room temperature over the course of 1 hr. The mixture was aged for 40 minutes. The white precipitate formed was isolated by filtration and washed until the filtrate had a conductivity of <500 pS.

[0063] The cake was then resuspended in a solution of 64.8 g LiOH.H2O in 500 ml DI water and agitated until resuspended. A solution of 61.0 g NH4HCO3 in 300 ml DI water was added to the suspended cake over the course of 45 minutes. The suspension was then 10 1024 isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.6O12. The crystal structure was confirmed to be cubic via XRD analysis. No impurities were observed. This example demonstrates that the doped LLZO may be produced by forming a precipitate comprising lanthanum, zirconium and niobium, contacting that precipitate with lithium ions and then adding a source of carbonate ions, with no observable impurities. The niobium was provided as a polyoxometalate, in this case [NbeOi9]8'. Example 2 - CO02-104 - Li6.4La3Zn.4Nbo.6O12

[0064] 7.42 g of Nb20s XH2O was added into 16.87 g of 40% TBA-OH solution and diluted to 50 mL. TBA is (C4Hg)4N+. The suspension was heated under reflux at 100 °C for 5.5 hours before being cooled to room temperature. The remaining solid was removed via vacuum filtration, leaving a solution containing (TBA)6Nbio028.

[0065] Solution A was prepared by dissolving 12.7 g of 37% HC1 and 6.59 g of ZrOCb.SILO in 30 mL DI water. Once dissolved, 7.00 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL.

[0066] Composition B was prepared by diluting 74.13 g of (TBA)eNbio028 solution (3.28 % as (TBA)6Nbio028, 1.21 % as TBA-OH) to 100 mL with DI water. 8.54 g of Na^CO; was added and stirred to dissolve, causing a white precipitate to form.

[0067] Solution A was added to Composition B over the course of 1 hour. The resultant white precipitate was aged for one hour before being isolated and washed via vacuum filtration.

[0068] The cake was resuspended in 50 mL of DI water and 6.19 g of LiOH.H2O was added and dissolved. Separately, 5.83 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 10 hours. The material produced was pure cubic LLZO. This example demonstrates that the doped LLZO may be produced using a decaniobate, in this case [Nbio028]6-.

[0069] Example 3 - CO02-115A - Li6.4La3Zn.4Nbo.6O12 10 1024

[0070] Solution A was prepared by dissolving 12.7 g of 37% HC1 and 6.59 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 7.00 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL.

[0071] Solution B was prepared by diluting 8.66 g of KsNbeOig. 15H2O (19.4% as KsNbeOig. 15H2O, 0.87% as KOH) to 50 mL with DI water. 12.4 g of NH4HCO3 was added into the solution and stirred to dissolve. Note the use of hydrogen carbonate ions in solution B, compared to carbonate ions in Examples 1 and 2.

[0072] Solution A was added to solution B over the course of 1 hour. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[0073] The cake was resuspended in 50 mL of DI water and diluted to 100 mL. 6.19 g of Li0H.H20 was added and dissolved. Separately, 5.83 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was then calcined at 900 °C for 12 hours. The material produced was cubic LLZO with a small La2O3 and La2Zr2O7 impurity. It is suspected that the impurities are an artefact of poor mixing during the experiment. The niobium was provided as a polyoxometalate, in this case [NbsOw]8'.

[0074] Example 4 - MC07-058C - Li6.4La3Zn.4Nbo.6O12

[0075] Solution A was prepared by dissolving 12.2 g 37% HO and 6.32 g Z1OCI2.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2O3 was added and stirred to dissolve. The solution was diluted to 100 mL with DI water.

[0076] Composition B was prepared by diluting 9.35 g of KsNbeOio solution (21.3% as KxNbeOw. 15H2O, 3.87% as KOH) to 100 ml with DI water, then adding 3.86 g Na2COs and 4.08 g KOH. The mixture was stirred until fully dissolved. A precipitate slowly formed on standing. Note the use of both carbonate anions and potassium hydroxide in solution B.

[0077] Solution A was added to Composition B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation, then resuspended in a solution of 6.01 g LiOH.H2O in 40 ml DI water. The suspension was agitated until homogenous. A solution of 5.66 g NH4HCO3 in 28 ml DI water was added 10 1024 to the suspended cake over the course of 40 minutes. The solid was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.6O12. The crystal structure was confirmed to be cubic via XRD analysis. No impurities were formed. The niobium was provided as a polyoxometalate, in this case [Nb60i9]8-.

[0078] Example 5 - MC07-060C - Li6.4La3Zn.4Nbo.6O12

[0079] Solution A was prepared by dissolving 12.2 g 37% HC1 and 6.33 g ZrOCb 8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2O3 was added and stirred to dissolve. The solution was diluted to 100 mL with DI water.

[0080] Solution B was prepared by diluting 9.34 g of KsNbeOio solution (21.3% as KsNb6Oi9.15H2O, 3.87% as KOH) to 100 ml with DI water, then adding 8.19 g KOH. The mixture was stirred until fully dissolved. Note the use of potassium hydroxide in solution B.

[0081] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation, then resuspended in a solution of 6.01 g LiOH.H2O in 40 ml DI water. The suspension was agitated until homogenous. A solution of 5.66 g NH4HCO3 in 28 ml DI water was added to the suspended cake over the course of 40 minutes. The solid was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.6O12. The crystal structure was confirmed to be cubic via XRD analysis. No impurities were observed. The niobium was provided as a polyoxometalate, in this case [NbeOig]8'.

[0082] Example 6 - COO2-i22A-Li6.4La3Zr1.4Nbo.6O12

[0083] Solution A was prepared by diluting 3.73 g of 69% HNO3 with 4.85 mL of DI water to give a 30% solution. 6.24 g of [ZrO2J2.CO2.xH2O (40.37 % as ZrO2) was added to this and the slurry heated to 50 °C to dissolve the solid, resulting in a ZrO(NO3)2 solution. 18.6 g of La(NO3)3.6H2O was then dissolved in the solution with agitation. Note the use of zirconium and lanthanum nitrates. 10 1024

[0084] Solution B was prepared by diluting 7.89 g of KgNbeOio solution (21.3% as KsNb6Oi9.15H2O, 3.87% as KOH) to 50 mL with DI water. 8.31 g of Na2CO3 was then dissolved in the solution with agitation.

[0085] Solution A was added to solution B over the course of 1 hour at room temperature. The resultant white precipitate was isolated and washed via centriguation before being reslurried in 50 mL of DI water. 6.19 g of Li0H.H20 was dissolved in the slurry. Separately, 5.83 g of NH4HCO3 was dissolved in 27 mL of DI water with agitation. The NH4HCO3 solution was added into the slurry over the course of 40 minutes with agitation. The precipitate was the isolated by filtration before being dried in an oven at 110 °C. The dried solid was calcined at 900 °C for 12 hours. The crystal structure was confirmed to be cubic via XRD analysis with a small amount of La2Zr2O7 present. The niobium was provided as a poly oxometalate, in this case [NbeOw]8'.

[0086] Example 7 - MC07-066C Li6.4La3Zn.4Nbo.6O12

[0087] Solution A was prepared by dissolving 12.2 g 37% HC1 and 6.72 g La2O3 in 20 ml DI water. The solution was diluted to 100 mL with DI water.

[0088] Solution B was prepared by diluting 13.09 g ammonium zirconium carbonate solution (13.6% as Zr) to 100 ml with DI water, then adding 4.63 g K2CO3.. The mixture was stirred until fully dissolved, then 9.33 g of KsNbeOw solution (21.3% as KgNbeOig. 15H2O, 3.87% as KOH) was added. The solution remained clear and colourless. Note the use of ammonium zirconium carbonate in solution B.

[0089] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation, then resuspended in a solution of 6.01 g LiOHH2O in 40 ml DI water. The suspension was agitated until homogenous. A solution of 5.66 g NH4HCO3 in 28 ml DI water was added to the suspended cake over the course of 40 minutes. The solid was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.6O12. The crystal structure was confirmed to be cubic via XRD analysis, with a small amount of La2Zr2O7 impurity. The niobium was provided as a polyoxometalate, in this case [NbeOio]8' 10 1024

[0090] Example 8 - MC07-012A - Li6.4La3Zn.7Moo.3O12 '

[0091] Solution A was prepared by dissolving 12.2 g 37% HO and 7.68 g Z1OCI2.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2O3 was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[0092] Solution B was prepared by dissolving 9.44 g KOH and 0.73 g (NH4)eMo7O24.4H2O in 100 ml H2O. The mixture was stirred until fully dissolved.

[0093] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation.

[0094] The cake was then resuspended in a solution of 6.68 g Li NO? in 50 ml DI water and agitated until resuspended. The volume of the suspension was made to 100 ml. The suspension was frozen and freeze-dried. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.7Moo.3O12. The crystal structure was confirmed to be cubic via XRD analysis. This example demonstrates the incorporation of a Mo dopant instead of Nb, using a poly oxometalate anion, in this case [Mo?O24]6'.

[0095] Example 9 - MC07-025 - Li6.4La3Zri.48Nbo.43Teo.o90i2

[0096] K7[TeNbsOi9] was prepared by adding 0.32 g Te(OH)e to 8.53 g of a solution containing 1.35 g K^NK-Ow] and 0.07 g KOH. The suspension was made to M0 ml, then stirred and heated gently until a clear, colourless solution formed. The solution was allowed to cool then sealed in a vial for 3 days before use.

[0097] Solution A was prepared by dissolving 14.2 g 37% HC1 and 7.83 g ZrOC12.8H2O in 20 ml DI water. Once fully dissolved, 7.38 g La2O3 was added and stirred to dissolve. The solution was diluted to 100 ml with DI water.

[0098] Solution B was prepared by adding the entire quantity of solution of K / fTeNbsOw] as prepared above and 9.72 g Na2CO3 to 100 ml H2O and dissolving to a clear, colourless solution.

[0099] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation, then resuspended in a solution of 7.57 g LiOH.H2O in 90 ml DI water and agitated until resuspended. The suspension was 10 1024 made to 150 ml. A solution of 7.13 g NH4HCO3 in 33 ml DI water was added to the suspended cake over the course of 40 minutes. The suspension was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zri.4sNbo.43Teo.o90i2. The crystal structure was confirmed to be cubic via XRD analysis. La2Ch impurity was present, likely due to overcharge. The niobium and tellurium were provided as a polyoxometalate, in this case [TeNbsOio]7'.

[00100] Example 10 - MC07-027 - Li6.4La3Zn.7Wo.257Teo.o430i2

[00101] Na6[TeW6O24].22H2O was made as set-out herein. 5.00 g Na^WO^bbO and 0.60 g Te(OH)e were dissolved in H2O and the solution diluted to 100 ml. The pH was adjusted to 4.95 with 10% HC1. The solution was heated to ~90 °C until the solution volume was ~40 ml. The solution was left to cool and stand. Large crystals of Na6[TeWeO24] 22H2O were formed, which were recovered by decantation and dried in air.

[00102] Solution A was prepared by dissolving 12.2 g 37% HC1 and 7.68 g ZrOC12.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2O3 was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[00103] Solution B was prepared by dissolving 8.89 g Na2CO3 and 1.27 g Nag[TeW6O24].22H2O in 100 ml H2O to form a clear, colourless solution.

[00104] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation.

[00105] The cake was then resuspended in a solution of 6.67 g LiNCh in 90 ml DI water and agitated until resuspended. The suspension was made to 100 ml with H2O, then stirred for 30 minutes. The suspension was sieved to remove lumps, then frozen and freeze-dried. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zri.7Wo.257Teo.o430i2. The crystal structure was confirmed to be cubic via XRD analysis (small La2Zr2O7 impurity). The tungsten and tellurium were provided as a polyoxometalate, in this case [TeW6O24]6'.

[00106] Example 11 - MC07-028 - Li6.4La3Z1.6W0.2Nb0.2O12 10 1024

[00107] Nominal KsfNbsWsOig] was made as set-out herein. 25.58 g of a solution containing 4.04 g KsfNbeOw] and 0.22 g KOH was added to 80 ml H2O and heated to 60 °C. 5.52 g WO3.2H2O was added with a further 20 ml H2O The suspension was heated and stirred until the yellow colour faded to white turbidity. The mixture was cooled and stored. This mixture will contain Lindqvist ions of the general formula [Nb6-xWxOi9](8'x)', where x is between 0 and 5. The majority of the ions will have x = 2, 3 and 4.

[00108] Solution A was prepared by dissolving 12.2 g 37% HC1 and 7.23 g Z1OCI2.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2Os was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[00109] Composition B was prepared by dissolving 8.69 g Na2COs and 21.53 g of a solution nominally containing 1.22 gKsfNbsWsOig] in 80 ml H2O. The mixture was stirred until the Na2CO; fully dissolved - a slight turbidity remained from the KsfNbsWaOie].

[00110] Solution A was added to Composition B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation.

[00111] The cake was then resuspended in a solution of 6.67 g Li NO, in 90 ml DI water and agitated until resuspended. The volume of the suspension was made to 150 ml and stirred for 30 minutes. The suspension was sieved to remove lumps, then frozen and freeze-dried. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Z1.6W0.2Nb0.2O12. The crystal structure was confirmed to be cubic via XRD analysis, with a small amount of La2O3 impurity. The tungsten and niobium were provided as a polyoxometalate, in this case [NbsWsOw]5'. Example 12 - MC07-058B - Li6.4La3Zr1.4Tao.3Nbo.3O12

[00112] Nominal Cs8[Nb3.nTa2.89Oi9] was made by mixing 30.11 g CS2CO3, 7.71 g Ta2O; and 5.00 g Nb20s by hand, then heating to 900 °C for 10 hrs. The cooled melt was extracted with water to give a pale blue, slightly turbid solution of total mass 110.5 g. This mixture will contain Lindqvist ions of the general formula [Nb6-xTaxOi9]8', where x is between 0 and 6. The majority of the ions will have x = 2, 3 and 4. 10 1024

[00113] Solution A was prepared by dissolving 12.2 g 37% HC1 and 6.33 g ZrOC12.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g LaaOs was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[00114] Composition B was prepared by dissolving 23.26 g CS2CO3 and 12.12 g of a solution nominally containing 2.89 g Css[Nb3.iiTa2.890i9] and 1.56 g CS2CO3 in 90 ml H2O. The mixture was stirred until the CS2CO3 fully dissolved - a slight turbidity remained from the CssfNbsTasOig].

[00115] Solution A was added to Composition B at room temperature over the course of 1 hr. The white precipitate formed was isolated and washed by centrifugation, then resuspended in a solution of 6.01 g LiOH.H2O in 40 ml DI water and agitated until resuspended. The suspension was made to 100 ml. A solution of 5.66 g NH4HCO3 in 28 ml DI water was added to the suspended cake over the course of 40 minutes. The suspension was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.3Tao.3O12. The crystal structure was confirmed to be cubic via XRD analysis. No impurities were observed. The tantalum and niobium were provided as a polyoxometalate, in this case nominally [NbsTasOio]'8.

[00116] Example 13 - CO02-79B Preparation of Li6.4La3Zr1.3Nbo.6Hfo.1O12

[00117] Solution A was prepared by dissolving 13.2 g of 37% HO and 6.77 g of ZrOCb.SILO in 30 mL DI water. Once dissolved, 7.23 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.61 g of HfOCh. 8H2O was added and stirred to dissolve.

[00118] Solution B was prepared by diluting 7.45 g of KsNbeOio. 15H2O solution (19.4% as KsNbeOw. 15H2O, 0.87% as KOH) to 50 mL. 8.82 g of Na2CO3 added into the solution and stirred to dissolve.

[00119] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00120] The cake was resuspended in 50 mL of DI water and 5.83 g of LiOH.H2O was added and dissolved. Separately, 5.49 g of NH4HCO3 was dissolved in 27 mL of DI 10 1024 water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was cubic LLZO with a small amount of La2Os. The niobium was provided as a poly oxometalate, in this case [NbeOio]8'

[00121] Example 14 - CO02-82A - Preparation of Li6.4La3Zr1.3Nbo.6Tio.1O12

[00122] Solution A was prepared by dissolving 13.3 g of 37% HC1 and 6.39 g of Z1OCI2.8H2O in 30 mL DI water. Once dissolved, 7.34 g of La?©? was added and stirred to dissolve. The solution was then diluted to 150 mL and 1.60 g of TiOSO4 solution (15 wt% TiOSO4, 50 wt% H2SO4) was added and stirred to dissolve.

[00123] Solution B was prepared by diluting 9.08 g of KsNbeOw. 15H2O solution (19.4% as K8Nb6Oi9.15H2O, 0.87% as KOH) to 50 mL. 10.50 g of Na2CO3 added into the solution and stirred to dissolve.

[00124] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00125] The cake was resuspended in 50 mL of DI water and 5.90 g of LiOH.HiO was added and dissolved. Separately, 5.56 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was cubic LLZO with a small amount of La2Os. The niobium was provided as a poly oxometalate, in this case [NbeOis]8'

[00126] Example 15 - CO02-29 - Preparation of Li6.5La2.9Sro.1Zr1.4Nbo.6O12:

[00127] Solution A was prepared by dissolving 12.9 g of 37% HO and 6.88g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 7.10 g of La^O? was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.40 g of SrC12.6H2O was added and stirred to dissolve. 10 1024

[00128] Composition B was prepared by diluting 10.19 g of KsNbeOig. 15H2O solution (21.3% as KsNbeOw. 15H2O, 3.87% as KOH) to 50 mL with DI water. 8.34 g of Na2CO3 was added and stirred to dissolve, causing a white precipitate to form.

[00129] Solution A was added to Composition B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for one hour before being isolated and washed via vacuum filtration.

[00130] The cake was resuspended in 50 mL of DI water and 5.97 g of LiOH.H2O was added and dissolved. Separately, 5.41 g of NH4HCO3 was dissolved in 22 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 10 hours. The material produced was pure cubic LLZO. The niobium was provided as a polyoxometalate, in this case [NbeOw]8'.

[00131] Example 16 - CO02-33 - Preparation of Li6.5La2.9Cao.1Zn.4Nbo.6O12:

[00132] Solution A was prepared by dissolving 13.0 g of 37% HC1 and 7.02 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 7.14 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.22 g of CaC12.2H2O was added and stirred to dissolve.

[00133] Composition B was prepared by diluting 10.25 g of KgNbeOw. 15H2O solution (21.3% as K8Nb60i9.15H2O, 3.87% as KOH) to 50 mL with DI water. 8.39 g of Na2COs was added and stirred to dissolve, causing a white precipitate to form.

[00134] Solution A was added to Composition B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00135] The cake was resuspended m 50 mL of DI water and 6.00 g of LiOH.H2O was added and dissolved. Separately, 5.65 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 10 hours. The material produced was pure cubic LLZO. The niobium was provided as a polyoxometalate, in this case [NbeOw]8’. 10 1024

[00136] Example 17 - CO02-39 - Preparation of Li6.75La2.75Cao.25Zn.4Nbo.5O12:

[00137] Solution A was prepared by dissolving 12.5 g of 37% HO and 7.53 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 6.88 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.56 g of CaC12.2H2O was added and stirred to dissolve.

[00138] Composition B was prepared by diluting 8.68 g of K8Nb6Oi9.15H2O solution (21.3% as K8Nb60i9.l5H2O, 3.87% as KOH) to 50 mL with DI water. 8.70 g of Na2COs was added and stirred to dissolve, causing a white precipitate to form.

[00139] Solution A was added to Composition B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00140] The cake was resuspended in 50 mL of DI water and 6.25 g of LiOH H2O was added and dissolved. Separately, 5.89 g of NH4HCO3 was dissolved in 28 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 10 hours. The material produced was pure cubic LLZO. The niobium was provided as a polyoxometalate, in this case [NbeOw]8'.

[00141] Example 18 - CO02-47 - Preparation of Li6.5La2.9Bao.1Zn.4Nbo.6O12

[00142] Solution A was prepared by dissolving 12.8 g of 37% HC1 and 6.94 g of ZrOCh.8H2O in 30 mL DI water. Once dissolved, 7.05 g of La2Os was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.36 g of BaC12.2H2O was added and stirred to dissolve.

[00143] Composition B was prepared by diluting 11.11 g of K8Nb6Oi9.15H2O solution (19.4% as K8Nb6Oi9.15H2O, 0.87% as KOH) to 50 mL with DI water. 8.57 g of Na2CO3 was added and stirred to dissolve, causing a white precipitate to form.

[00144] Solution A was added to Composition B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration. 10 1024

[00145] The cake was resuspended in 50 mL of DI water and 5.95 g of Li0H.H20 was added and dissolved. Separately, 5.60 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 10 hours. The material produced was pure cubic LLZO. The niobium was provided as a polyoxometalate, in this case [NbeOio]8'.

[00146] Example 19 - CO02-76A - Preparation of Li6.5La2.9Mgo.1Zn.4Nbo.6O12

[00147] Solution A was prepared by dissolving 13.0 g of 37% HC1 and 6.95 g of ZrOCh.SEEO in 30 mL DI water. Once dissolved, 7.17 g of La?O? was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.31 g of MgC12.6H2O was added and stirred to dissolve.

[00148] Solution B was prepared by dissolving 8.77 g of MrCOs in 50 mL of DI water. 2.19 g of KgNbeOw.lSEEO was added into the solution and stirred to dissolve.

[00149] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00150] The cake was resuspended in 50 mL of DI water and 6.02 g of LiOH.H2O was added and dissolved. Separately, 5.77 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was cubic LLZO with a small amount of Li2CO3. The niobium was provided as a poly oxometalate, in this case [NbeOio]8'

[00151] Example 20 - CO02-76B - Preparation of Li6.5La2.9Ceo.1Zn.4Nbo.6Or2

[00152] Solution A was prepared by dissolving 12.8 g of 37% HC1 and 6.84 g of ZrOCh.SELO in 30 mL DI water. Once dissolved, 7.06 g of La2Os was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.56 g of CeC13.7H2O was added and stirred to dissolve. 10 1024

[00153] Solution B was prepared by dissolving 8.71 g of Na2CO3 in 50 mL of DI water. 2.16 g of KsNbeOw.ISJhO was added into the solution and stirred to dissolve.

[00154] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00155] The cake was resuspended in 50 mL of DI water and 5.88 g of LiOH.H2O was added and dissolved. Separately, 5.53 g of NH4HCO3 was dissolved in 26 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was pure cubic LLZO. The niobium was provided as a polyoxometalate, in this case [NbeOig]8'.

[00156] Example 21 - CO02-79C - Preparation of Li6.5La3Zr1.3Nbo.6Sco.1O12

[00157] Solution A was prepared by dissolving 13.4 g of 37% HO and 6.38 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 7.34 g of La2Os was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.39 g of SCCI3.6H2O was added and stirred to dissolve.

[00158] Solution B was prepared by diluting 9.08 g of KsNbeOid 5H2O solution (19.4% as KsNlWw. 15H2O, 0.87% as KOH) to 50 mL. 8.76 g of Na2CO3 added into the solution and stirred to dissolve.

[00159] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00160] The cake was resuspended in 50 mL of DI water and 5.97 g of LiOH.H2O was added and dissolved. Separately, 5.62 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was cubic LLZO with a small amount of La2Os. The niobium was provided as a poly oxometalate, in this case [NbeOw]8' 10 1024

[00161] Example 22 - CO02-82B - Preparation of Li6.4La2.9Y0.! Zn.4Nbo.6O12

[00162] Solution A was prepared by dissolving 12.9 g of 37% HO and 6.88 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 7.10 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 150 mL and 0.46 g of YCI3.6H2O was added and stirred to dissolve.

[00163] Solution B was prepared by diluting 9.09 g of KsNbeOw. 15H2O solution (19.4% as K8Nb60i9.15H2O, 0.87% as KOH) to 50 mL. 8.69 g of Na2CO3 added into the solution and stirred to dissolve.

[00164] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00165] The cake was resuspended in 50 mL of DI water and 5.91 g of LiOHH^ was added and dissolved. Separately, 5.56 g of NH4HCO3 was dissolved in 27 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was cubic LLZO. The niobium was provided as a poly oxometalate, in this case [NbeOw]8'.

[00166] Example 23 - MC07-018 - Li5.8Al0.4La3Zr2Oi2

[00167] [A1i3O4(OH)24](NO3)7 was prepared thus. 18.76 g A1(NO3)3.9H2O was dissolved in H2O to make a solution with volume 100 ml. The solution was heated to 50 °C, then 6.36 g Na2CO3 was added over the course of 70 minutes. The temperature was maintained at 50 °C until the solution was clear and colourless, then the solution was cooled to ambient. A solution of total mass 105.5 g was obtained.

[00168] Solution A was prepared by dissolving 11.60 g [Ali3O4(OH)i2](NO3)7 solution and 9.04 g ZrOC12.8H2O in 20 ml DI water. Once fully dissolved, 12.2 g 37% HC1 and 6.72 g La2O3 were added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O. 10 1024

[00169] Solution B was prepared by dissolving 9.70 g Na2COs in 100 ml H2O. The mixture was stirred until fully dissolved.

[00170] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation, then resuspended in a solution of 5.60 g LiOH.H2O in 50 ml DI water and agitated until resuspended. The volume of the suspension was made to 100 ml. A solution of 5.28 g NH4HCO3 in 30 ml DI water was added to the suspended cake over the course of 40 minutes. The suspension was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li5.sAlo.4La3Zr20i2. The crystal structure was confirmed to be cubic via XRD analysis. There was a minor LaAlOs impurity. The aluminium was provided as a polyoxometalate.

[00171] Example 24 - MC07-062C - Lie.4La3Zr1.7W0.3O12

[00172] Solution A was prepared by dissolving 4.3 g of 37% HC1 and 8.35 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 2.40 g of La2O3 was added and stirred to dissolve. The solution was then diluted to 100 mL.

[00173] Composition B was prepared by dissolving 5.19 g KOH in 100 ml H2O. 1.17 g (NH4)io[H2Wi2042].xH20 (89.1% as WO3) was added to form an off-white suspension.

[00174] Solution A was added to Composition B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation.

[00175] The cake was then resuspended in a solution of 18.29 g LiNCh in 40 ml DI water and agitated until resuspended. A solution of 18.29 g NH4HCO3 in 97 ml DI water was added to the suspended cake over the course of 40 minutes. The suspension was then isolated by filtration and dried at 110 °C. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.7W0.3O12. The crystal structure was confirmed to be cubic via XRD analysis, with a minor amount of La2O3 and Li2ZrO3 impurity. It is appreciated that the La charge is too low to be stoichiometric. It is suspected that this is because the L1HCO3 solution produced leaches a Zr and W out of the precipitate. The amount of La2O3 used 10 1024 was arrived at by essentially iterating to the appropriate value. The tungsten was provided as a polyoxometalate.

[00176] Example 25 - MC07-026 - Li6.4La3Zn.7W0.3O12 via [H2Wi2O40]6'

[00177] Solution A was prepared by dissolving 12.2 g 37% HO and 7.68 g ZrOC12.8H2O in 20 ml DI water. Once fully dissolved, 6.72 g La2O3 was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[00178] Solution B was prepared by dissolving 9.50 g KOH and 1.04 g (NH4)6[H2Wi204o].xH20 (91.5% as WO3) in 100 ml H2O forming a clear, colourless solution.

[00179] Solution A was added to Solution B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation.

[00180] The cake was then resuspended in a solution of 6.67 g LiNCL in 100 ml DI water and agitated until resuspended. The volume of the suspension was made to 150 ml. The suspension was frozen and freeze-dried. The dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.7W0.3On. The crystal structure was confirmed to be cubic via XRD analysis. There was a minor La2Zr2O? impurity. The tungsten was provided as a polyoxometalate

[00181] Example 26 - MC07-007B - Li6.4La3Zn.7W0.3O12

[00182] Solution A was prepared by dissolving 13.3 g 37% HO and 8.36 g ZrOCl2.8H2O in 20 ml DI water. Once fully dissolved, 7.34 g La2O3 was added and stirred to dissolve. Once dissolved, the solution was diluted to 100 ml with H2O.

[00183] Composition B was prepared by dissolving 9.97 g KOH and 1.17 g (NH4)io[H2Wi2042].xH20 (89.1% as WO3) in 100 ml H2O. A cloudy suspension formed due to the low solubility of (NH4)io[H2Wi2042].xH20.

[00184] Solution A was added to Composition B at room temperature over the course of 1 hr. The white precipitate formed was isolated by centrifugation.

[00185] The cake was then resuspended in a solution of 7.26 g LiNCh in 50 ml DI water and agitated until resuspended. The volume of the suspension was made to 100 ml. 10 1024 The suspension was frozen and freeze-dried. The dried solid was heated to 900 °C for 10 hrs to produce Lie.4La3Zr1.7W0.3O12. The crystal structure was confirmed to be cubic via XRD analysis. There was a minor La2Zr2O? impurity. The tungsten was provided as a polyoxometalate.

[00186] Example 27 - LTO2-i47-Li6.4La3Zr1.4Nbo.6O12

[00187] Solution A was prepared by dissolving 266.1 g 37% HC1 and 137.4 g Z1OCI2.8H2O in 775 ml DI water. Once fully dissolved, 146.6 g LajO? was added and stirred to dissolve.

[00188] Composition B was prepared by diluting 137.1 g of KsNbgOio solution (31.6% as K8NbeOi9.15H2O, 5.44% as KOH) to 860 ml with DI water, then adding 168.5 g Na2CO3. A white precipitate formed.

[00189] Solution A was added to Composition B at room temperature over the course of 1 hr. The mixture was aged for 1 hr. The white precipitate formed was isolated by filtration and washed until the filtrate had a conductivity of <800 pS.

[00190] The cake was then resuspended in a solution of 114.5 g LiOH.H2O in 850 ml DI water and agitated until resuspended. The total volume was made to 1750 ml. CO2 gas was sparged into the suspension for 75 minutes until the pH dropped to 11.50. The suspension was aged for approximately 45 minutes, with further CO2 added if the pH rose above 11.5. The suspension was then isolated by filtration and dried at 110 °C. A sample of the dried solid was heated to 900 °C for 10 hrs to produce Li6.4La3Zr1.4Nbo.6O12. The crystal structure was confirmed to be cubic via XRD analysis. There were no significant impurities. This method may be particularly effective because the solution from which the precipitate comprising lithium is removed is a solution of lithium carbonate, which may be reused without further purification. This therefore reduces the loss of lithium. The niobium was provided as a polyoxometalate. 10 1024

[00191] Example 28 - CO02-68 - Li6.4La3Zr1.4Tao.6O12

[00192] Solution A was prepared by dissolving 9.0 g of 37% HC1 and 4.63 g of ZrOCh.SHiO m 30 mL DI water. Once dissolved, 4.95 g of La^O? was added and stirred to dissolve. The solution was then diluted to 112 mL.

[00193] Solution B was prepared by dissolving 5.90 g of Na2CO3 in 50 mL of DI water. 1.92 g of KsTaeOiLI 6H2O was added and stirred to dissolve.

[00194] Solution A was added to solution B over the course of 1 hour and 40 minutes. The resultant white precipitate was aged for 1 hour before being isolated and washed via vacuum filtration.

[00195] The cake was resuspended in 50 mL of DI water and 4.46 g of LiOH.H2O was added and dissolved. Separately, 4.20 g of NH4HCO3 was dissolved in 20 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was the calcined at 900 °C for 12 hours. The material produced was pure cubic LLZO with a small amount of La2O3. Due to weighing errors in this Example, Ta was undercharged during this reaction which is the likely cause of impurities. The tantalum was provided as a polyoxometalate.

[00196] Example 29 - MC07-068A - Li6.65La2.875Rb0.125Zn.4Nb0.6O12:

[00197] 9.22 g KsNb6Oi9.15H2O was dissolved in 100 ml DI water to form a clear, colourless solution. 8.29 La(NO3)3 6H2O was dissolved in 50 ml DI water to form a clear, colourless solution. The lanthanum nitrate solution was added to the potassium hexaniobate solution over the course of 40 minutes, forming a thick white precipitate. The precipitate was washed and isolated by centrifugation, then resuspended in 15 ml DI water. 2.43 g Rb2CO3 was added and the suspension stirred until homogenous. The suspension was freeze dried, then calcined at 1000 °C for 10 hrs to form RbLaNb2O?. XRD analysis suggested the material was 80% pure, with the remaining material Rb2CO3.

[00198] Solution A was prepared by dissolving 9 ml of 36% HC1 and 6.33 g of ZrOC12.8H2O in 30 mL DI water. Once dissolved, 5.88 g of La?©? was added and stirred to dissolve. The solution was then diluted to 100 ml. 10 1024

[00199] Composition B was prepared by diluting 5.44 g of KsNbeOig. 15H2O solution (21.3% as KsNbeOw.ISJW, 3.87% as KOH) to 100 mL with DI water. 1.13 g RbLaNbiO? (80% pure, remaining material Rb2CO3) was added and stirred to form a homogenous suspension. 7.28 g of NazCO? was then added and stirred to dissolve, causing a white precipitate to form.

[00200] Solution A was added to Composition B over the course of 1 hour. The resultant white precipitate was isolated and washed via centrifugation.

[00201] The cake was resuspended in 40 mL of DI water and 6.18 g of LiOH.HzO was added and dissolved. Separately, 5.82 g of NH4HCO3 was dissolved in 28 mL of DI water and was added into the suspended cake over the course of 40 minutes. The white suspension was isolated via vacuum filtration and dried at 110 °C. The dried solid was then calcined at 900 °C for 10 hours. The crystal structure was confirmed to be cubic via XRD analysis. The niobium was provided as a polyoxometalate.

[00202] The effect of pH to which the non-lithiated precursor material was subjected was investigated. Solution A was prepared by dissolving 7.01 g of ZrOCl2.8H2O in 30 mL of DI water. 12.7 g of 37% HC1 was added into the solution before 7.01 g of LazOs was dissolved in the solution with agitation. The solution was then diluted to 150 mL with DI water.

[00203] Solution B was prepared by diluting 7.91 g of KsNbgOw solution (21.3% as KsNb60i9.15H2O, 3.87% as KOH) to 50 mL with DI water. 8.12 g of Na2CO3 was dissolved in the solution with agitation.

[00204] Solution A was added to solution B over the course of 1 hour at room temperature. The pH of the reaction was then adjusted to a desired value from 3.5 to 4.5 using 37% HO. Once a stable pH had been reached, the precipitate was isolated and washed via centrifugation before being resuspended in 50 mL of DI water.

[00205] 6.20 g of L1OH.H2O was dissolved in the slurry and the total volume of the slurry was made up to 100 mL with DI water. Separately, 5.84 g of NH4HCO3 was dissolved in 27 mL of DI water with agitiation. The NH4HCO3 solution was added into the slurry over the course of 40 minutes with agitation. The precipitate was isolated by 10 1024 filtration before being dried in an oven at 110 °C. The dried solid was calcined at 900 °C for 12 hours.

[00206] Cubic lithium lanthanum zirconium niobium oxide (LLZNO) was formed, without impurities, when the pH was 4.0, 4.2, 4.4 and 4.5. Cubic lithium lanthanum zirconium niobium oxide (LLZNO) was formed, with small amounts of impurities, when the pH was 3.6, 3.7. 3.8 and 3.9. No cubic LLZNO was formed when the pH was 3.5.

[00207] The Examples above describe many examples of embodiments of methods in accordance with first aspect of the present invention, and of doped LLZO in accordance with the second aspect of the present invention. The Examples above also describe many examples of embodiments of compositions in accordance with the third and fourth aspects of the present invention.

[00208] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[00209] The many Examples above demonstrate that lithiated solid-state electrolyte materials, such as lithium lanthanum zirconium oxide, may be doped with a wide variety of dopants. Those skilled in the art will realise that other dopants may be used.

[00210] Many of the Examples above demonstrate the use of many different types of polyoxometalates as a source of one or more dopants. Those skilled in the art will realise that other polyoxometalates may be used. Furthermore, not all dopants need be provided as polyoxometalates.

[00211] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to CM be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. 10 1024

Claims

1. A reaction composition for forming doped lithium lanthanum zirconium oxide, comprising:one or more lithium, lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and at least one dopant provided as a polyoxometalate.

2. A reaction composition according to claim 1 comprising a source of anions with which lithium may form an insoluble salt.

3. A reaction composition according to claim 2 comprising a source of carbonate ions.

4. A reaction composition according to claim 2 or claim 3, wherein the source of carbonate ions comprises hydrogencarbonate ions, carbonate ions, hydrogen carbonate ions or carbon dioxide.

5. A reaction composition according to any preceding claim comprising one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and at least one dopant provided as a polyoxometalate, but not a lithium species for forming a doped lithium lanthanum zirconium oxide.

6. A reaction composition according to any preceding claim comprising a precipitate comprising the one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, and at least one dopant, optionally being the at least one dopant provided as a polyoxometalate.

7. A reaction composition according to any of claims 1 to 4 and claim 6, comprising the one or more lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, the at least one dopant provided as a polyoxometalate, and the one or more lithium species for forming a doped lithium lanthanum zirconium oxide.

8. A reaction composition according to any preceding claim wherein the poly oxometalate comprises a transition metal, a Group 13 species, a Group 15 species or a Group 16 species.

9. A reaction composition according to any preceding claim comprising one or more further dopants comprising one or more of an alkali metal, an alkaline earth metal, a lanthanide and a rare earth species.

10. A reaction composition according to any preceding claim having a pH of at least 3.5.-se10 1024ll, a method of making a reaction composition according to any preceding claim, the method comprising mixing at least two compositions, at least one of which comprises a polyoxometalate, at least one of which comprises a zirconium species and at least one of which comprises a lanthanum species.

12. A multi-part reaction composition for forming a doped lithium lanthanum zirconium oxide, comprising:a first part comprising one or more lithium, lanthanum and / or zirconium species for forming a doped lithium lanthanum zirconium oxide, optionally a base, and optionally a dopant provided as a polyoxometalate; anda second part comprising a base if the base is not provided in the first part, and a dopant provided as a polyoxometalate, if the polyoxometalate is not provided in the first part; ora third part comprising a lithium species, optionally a solution of lithium ions, if lithium species are not provided in the first or second parts.

13. A method of making a doped lithium lanthanum zirconium oxide, the method comprising:forming the doped lithium lanthanum zirconium oxide from a polyoxometalate, wherein the method comprises forming a precipitate comprising lithium and heating the precipitate comprising lithium to form the doped lithium lanthanum zirconium oxide.

14. A method according to claim 13, wherein the polyoxometalate comprises a transition metal, a Group 13 species, a Group 15 species or a Group 16 species.

15. A method according to claim 13 or claim 14 wherein the polyoxometalate comprises one or more of Mo, Nb, Te, Al, Ga, Sb, W and Ta.

16. A method according to any of claims 13 to 15, comprising mixing at least two compositions, at least one of which comprises a polyoxometalate.

17. A method according to any of claims 13 to 16, comprising forming a solid (optionally a precipitate) comprising a lanthanum species, a zirconium species and a dopant species derived from a polyoxometalate.

18. A method according to claim 17 comprising contacting said precipitate with a solution comprising lithium ions, thereby forming the precipitate comprising lithium.