Method of manufacturing a particulate transition metal carbonate material

Abstract

A method of manufacturing a particulate transition metal carbonate material. A transition metal precursor salt in a liquid vehicle is mixed with a carbonate salt and / or a bicarbonate salt, and a preci

Description

BACKGROUND Lithium-ion secondary batteries are the leading battery technology currently used in applications from small personal devices to electric vehicles. Lithium-ion batteries are favoured for their high energy density and long cycle life, among other benefits. They contain a plurality of lithium-ion secondary cells, which is one example of an alkali metal ion secondary cell. Electrochemically active materials used within the electrodes of lithium-ion secondary cells are often manufactured by a process which includes an initial precipitation reaction to form a metal-containing particulate precursor compound, such as a mixed transition metal hydroxide compound. Such metal-containing particulate precursor compounds are precipitated from solution before being collected and subjected to further processes, such as calcination. It is important to be able to control the particle size and morphology of the precipitated precursor compounds, since this will feed into the particle size and morphology of the final electrochemically active material within the electrode. Poor particle size and / or poor morphology may result in active materials with poor electrochemical properties, such as poor capacity, energy density or rate capability. The particle size and morphology of the precipitated precursor compounds is however very difficult to control during precipitation. It is in particular very challenging to control the initial stages of precipitation, which can lead to uncontrolled growth or agglomeration of the particles as they form and begin to grow. Typically this results in particles with a wide particle size distribution and a rough surface. The result is a final material with a low density, which is detrimental to the energy density of the electrode. SUMMARY The present inventors have developed a method which can enable the preparation of particles of transition metal carbonate material which are small and have very low levels of agglomeration and high circularity. As such, they can be very useful as seed particles during a subsequent precipitation reaction. Accordingly, in a first aspect, the present invention provides a method of manufacturing a particulate transition metal carbonate material, the method comprising: mixing a transition metal precursor salt with a second salt in a liquid vehicle, wherein the second salt is selected from one or more of a carbonate salt and a bicarbonate salt; and carrying out a precipitation reaction to form a slurry of the particulate transition metal carbonate material in the liquid vehicle; wherein the particulate transition metal carbonate particulate material has a volumetric median particle diameter (Dv50) of from 0.2 to 10.0 pm. The particles have a small Dv50 of from 0.2 to 10.0 pm, and by virtue of the manufacturing method used to prepare them they have very low levels of agglomeration and high circularity. These properties mean that they can be very useful as seed particles during a subsequent precipitation reaction, because it can be easier to control the subsequent precipitation onto the seeds and the precipitated precursor compounds which form around the seeds have size and morphology which is predictable and controllable. The particulate transition metal carbonate material prepared by the method of the first aspect may also be useful for other purposes. Due to the small size, spherical morphology and lack of agglomeration, the particulate transition metal carbonate material may find use in the direct preparation of an electrochemically active material, without the need for further precipitation onto the material, especially for high-rate applications. For example, the material may be mixed with a lithium source and calcined to form an oxide useful as an electrochemically active material. A second aspect of the invention is a particulate transition metal carbonate material for use as seed particles during a precipitation reaction, obtained or obtainable by a method according to the first aspect. A third aspect of the invention is a method of manufacturing a particulate precursor material, the method comprising: providing a suspension of seed particles in a liquid vehicle; initiating a precipitation reaction involving one or more transition metal sources in the liquid vehicle in the presence of the seed particles; and allowing the precipitation reaction to proceed within a precipitation reaction vessel containing a reaction mixture comprising the suspension of seed particles, to form the particulate precursor material by precipitation onto the surface of the seed particles. A fourth aspect of the invention is a particulate transition metal carbonate material obtained or obtainable by the method according to the third aspect. In some embodiments, particles of the material comprise a core-shell structure comprising a core region derived from a particulate transition metal carbonate seed particle manufactured by a method according to the first aspect, and a shell region derived from a layer of transition metal carbonate precipitate deposited onto the core region by precipitation onto the seed particle. A fifth aspect of the invention is a method of manufacturing a particulate electrochemically active material, comprising: manufacturing the particulate precursor material by the method according to the third aspect; and calcining the particulate precursor material along with an alkali metal source to prepare the particulate electrochemically active material. By manufacturing a particulate precursor to an electrochemically active material (e.g. a carbonate or hydroxide precursor material which is subsequently calcined to form an electrochemically active material, e.g. oxide material) by precipitating the material of the particulate precursor onto seed particles, it may be possible to more closely control the particle size and morphology of the final particulate precursor material. In the absence of seed particles in the reaction mixture, particulate precursor material may form comprising particles which are non-uniform in size, with an unpredictable final particle size and significantly non-spherical morphology. However the use of seed particles may provide one or more of (a) predictable final particle size, (b) more uniform particle sizes, and (c) more spherical morphology of the particulate precursor material. A sixth aspect of the invention is a particulate precursor material obtained or obtainable by a method according to the fifth aspect. A seventh aspect of the invention is a method of manufacturing a particulate electrochemically active material, comprising manufacturing the particulate precursor material by the method according to the fifth aspect; and calcining the particulate precursor material along with an alkali metal source to prepare the particulate electrochemically active material. FURTHER OPTIONS AND PREFERENCES The method according to the first aspect comprises mixing a transition metal precursor salt with a second salt in a liquid vehicle, wherein the second salt is selected from one or more of a carbonate salt and a bicarbonate salt. In some embodiments, the transition metal precursor salt comprises or consists of one or more of transition metal sulfate salts, transition metal nitrate salts, transition metal oxalate salts and transition metal acetate salts. In some embodiments, the transition metal precursor salt comprises or consists of a transition metal sulfate salt. The identity of the transition metal or transition metals within the transition metal precursor salt is not particularly limited. If the particulate transition metal carbonate material is later used as a seed particle for the precipitation of a metal-containing particulate precursor compound, the seed particle itself will generally make up a very small proportion of the mass of the metal-containing particulate precursor compound. For example, a 1.5 pm seed particle will contribute less than 1 % to the final composition of an 8 pm diameter precursor compound particle which is formed by precipitation onto the seed particle. So, the impact of the composition of the seed particle on the final composition of subsequently precipitated precursors is low, and in theory any composition of seed particle may be used as a seed to precipitate any composition of precursor particle. For example, the seed particle may have a first composition, and the precursor particle precipitated onto the seed particle may have a second, different composition. However, as explained in more detail below, the inventors have discovered that the choice of transition metal or transition metals within the transition metal precursor salt can be used to influence certain aspects of the size and morphology of the seed particle itself, and as such can be used as a tool to control the size and morphology of the particulate transition metal carbonate material. In some embodiments, the transition metal precursor salt consists of a single transition metal salt species. It has been found that using a single species of transition metal salt within the transition metal precursor salt leads to a particulate transition metal carbonate material with a smaller Dv50 particle size. As such, it may be desirable to use a single species of transition metal salt in embodiments where a smaller Dv50 particle size for the particulate transition metal carbonate material is desired. In some embodiments, the transition metal precursor salt consists of two or more distinct transition metal salt species. It has been found that, when two or more distinct species of transition metal salt are present within the transition metal precursor salt, this leads to a particulate transition metal carbonate material with a larger Dv50 particle size than when a single species of transition metal salt is present. As such, it may be desirable to use two or more distinct species of transition metal salt in embodiments where a larger Dv50 particle size for the particulate transition metal carbonate material is desired. In some embodiments, the transition metal precursor salt consists of two distinct transition metal salt species. The use of two distinct transition metal salt species will provide a Dv50 particle size for the particulate transition metal carbonate material slightly larger than when a single species of transition metal salt is present, which may be desirable in some embodiments. In some embodiments, the transition metal precursor salt consists of more than two distinct transition metal salt species. The use of more than two distinct transition metal salt species will provide a Dv50 particle size for the particulate transition metal carbonate material slightly larger than when two distinct species of transition metal salt are present, which may be desirable in some embodiments. For example, the transition metal precursor salt may consist of three distinct transition metal salt species. The use of three distinct transition metal salt species will provide a Dv50 particle size for the particulate transition metal carbonate material slightly larger than when two distinct species of transition metal salt are present, which may be desirable in some embodiments. It is therefore possible to choose the number of distinct species of transition metal salt within the transition metal precursor salt depending on the desired particle size of the particulate transition metal carbonate material. In some embodiments, the transition metal precursor salt comprises or consists of one or more of an iron salt, a manganese salt, a nickel salt, and a cobalt salt. In some embodiments, the transition metal precursor salt consists of a manganese salt. In some embodiments, the transition metal precursor salt consists of an iron salt. In some embodiments, the transition metal precursor salt consists of a nickel salt. In some embodiments, the transition metal precursor salt consists of a cobalt salt. In some embodiments, the transition metal precursor salt consists of a manganese salt and a nickel salt. In some embodiments, the transition metal precursor salt consists of a manganese salt and an iron salt. In some embodiments, the transition metal precursor salt consists of a manganese salt, an iron salt, a nickel salt and a cobalt salt. In some embodiments, the transition metal precursor salt consists of a manganese salt, a nickel salt, and a cobalt salt. In some embodiments, the second salt has a solubility in water of at least 90 g / L at 20 °C, for example at least 100 g / L, at least 120 g / L, at least 140 g / L, at least 160 g / L, at least 180 g / L, at least 200 g / L, at least 210 g / L or at least 215 g / L. In some embodiments, the second salt has a solubility in water of from 90 g / L to 250 g / L at 20 °C, for example from 100 g / L to 250 g / L, from 120 g / L to 250 g / L, from 140 g / L to 250 g / L, from 160 g / L to 250 g / L, from 180 g / L to 250 g / L, from 200 g / L to 250 g / L or from 200 g / L to 220 g / L. In some embodiments, the second salt consists of either a carbonate salt or a bicarbonate salt. In some embodiments, the second salt comprises or consists of a bicarbonate salt. In some embodiments, the second salt consists of a single species of bicarbonate salt. In some embodiments therefore, the transition metal precursor salt is mixed with a bicarbonate salt. In some embodiments, the bicarbonate salt comprises or consists of one or more of ammonium bicarbonate and sodium bicarbonate. In some embodiments, the bicarbonate salt comprises or consists of ammonium bicarbonate. Ammonium bicarbonate results in particulate transition metal carbonate material having a particularly desirable particle size distribution with low agglomeration and a narrow distribution. In some embodiments, the precipitation reaction is performed at a temperature within the range 15 to 80 °C, for example 15 to 70 °C, 15 to 60 °C, 15 to 55 °C, 15 to 50 °C, 15 to 45 °C, 15 to 40 °C, 15 to 35 °C, 15 to 30 °C, 15 to 25 °C or 20 to 25 °C, or at room temperature. In some embodiments, the liquid vehicle consists of water. In some embodiments, the liquid vehicle consists of water, and the transition metal precursor salt and second salt are dissolved in the water before the precipitation reaction. In some embodiments, the molar ratio of the transition metal precursor salt to the second salt is from 1:2 to 1:80, for example from 1:2 to 1:70, from 1:2 to 1:60, from 1:2 to 1:50, from 1:2 to 1:40, from 1:2 to 1:30, from 1:2 to 1:20, from 1:4 to 1:80, from 1:4 to 1:50 or from 1:4 to 1:20. Particularly good results are observed when the molar ratio of the transition metal precursor salt to the second salt is from 1:4 to 1:45, for example from 1:4 to 1:20, from 1:8 to 1:45, for example from 1:10 to 1:40, from 1:15 to 1:40, from 1:20 to 1:40, from 1:25 to 1:40, from 1:30 to 1:40, or about 1:33. Such molar ratios have been observed to lead to particularly spherical particles with high circularity, a narrow particle size distribution and few agglomerates. The transition metal precursor salt with a second salt may be mixed in the liquid vehicle by different methods. For example, the transition metal precursor salt and the second salt, both in powder form, may be added to water to form an aqueous solution or suspension. In other embodiments, an aqueous solution of the second salt may be provided and the transition metal precursor salt in solid form may be added to the aqueous solution of the second salt. In some embodiments, an aqueous solution of the transition metal precursor salt may be provided and the second salt in solid form may be added to the aqueous solution of the transition metal precursor salt. It has been found that mixing an aqueous solution of the transition metal precursor salt with the second salt in solid (powder) form produces a product material with fewer agglomerates, smaller particle size and higher particle circularity. In some embodiments, separate aqueous solutions of the transition metal precursor salt and the second salt may be prepared before being mixed together to form a mixed aqueous solution as a reaction mixture. Such embodiments have been shown to produce a product material with the lowest proportion of agglomerates, and optimal particle size and circularity. In some embodiments, the method comprises: preparing a first solution of the one or more transition metal precursor salts in water, wherein the total concentration of the one or more transition metal precursor salts in the first solution is from 0.8 M to 3.5 M, for example from 0.8 M to 2.0 M; preparing a second solution of the second salt in water, wherein the total concentration of the second salt in the second solution is from 2.0 M to 4.0 M; and combining the first solution with the second solution such that the molar ratio of the transition metal precursor salt to the second salt is from 1:2 to 1:80, for example from 1:4 to 1:20. In some embodiments, the total concentration of the one or more transition metal precursor salts in the first solution is from 0.8 M to 1.5 M, for example from 0.8 M to 1.2 M, or about 1.0 M. In some embodiments, the total concentration of the second salt in the second solution is from 2.0 M to 3.5 M, for example from 2.0 M to 3.0 M, from 2.0 M to 2.5 M, or about 2.2 M. In some embodiments, mixing the first solution with the second solution is such that the molar ratio of the transition metal precursor salt to the second salt is from 1:2 to 1:70, for example from 1:2 to 1:60, from 1:2 to 1:50, from 1:2 to 1:40, from 1:2 to 1:30, from 1:2 to 1:20, from 1:4 to 1:80, from 1:4 to 1:50 or from 1:4 to 1:20. In some embodiments, the total concentration of the one or more transition metal precursor salts in the first solution is from 0.8 M to 1.2 M; the total concentration of the second salt in the second solution is from 2.0 M to 2.5 M; and mixing the first solution with the second solution is such that the molar ratio of the transition metal precursor salt to the second salt is from 1:4 to 1:40. Such concentrations and ratios have been observed to lead to particularly spherical particles with high circularity, a narrow particle size distribution and few agglomerates. In some embodiments, the total concentration of the one or more transition metal precursor salts in the first solution is about 1.0 M; the total concentration of the second salt in the second solution is about 2.2 M; and mixing the first solution with the second solution is such that the molar ratio of the transition metal precursor salt to the second salt is about 1:33. Such concentrations and ratios have been observed to lead to particularly spherical particles with high circularity, a narrow particle size distribution and few agglomerates. In some embodiments, after combining the first and second solution, the combined solution is left to react without any mixing, stirring or agitation. In some embodiments, after combining the first and second solution, the combined solution is mixed or stirred. In some embodiments, after combining the first and second solution, the combined solution is subjected to sonication at ultrasound frequencies. In some embodiments, sonication is caried out for a period of from 2 to 30 minutes, optionally 2 to 10 minutes. In some embodiments, sonication is performed at a temperature within the range 15 to 30 °C, optionally 20 to 25 °C. In some embodiments, sonication is performed within a round-bottom reaction vessel. In some embodiments, the precipitation reaction is carried out under sonication at ultrasound frequencies, or under stirring. In some embodiments, the precipitation reaction is carried out under sonication at ultrasound frequencies. The UP400St Powerful Ultrasonicator from Hielscher is one example of a suitable sonicator. In some embodiments, the amplitude range for the sonication is from 20 to 75 % and the pulse range is from 30 to 100 %. Performing the precipitation under ultrasonic sonication has been found to provide highly spherical particles, with a circularity of at least 50%, for example at least 60% or at least 70%, along with a small Dv50 particle size. In some embodiments, the precipitation reaction under sonication is caried out for a period of from 2 to 30 minutes, for example from 2 to 10 minutes. In some embodiments, the precipitation reaction under sonication is performed at a temperature of from 15 to 36 °C, for example from 15 to 30 °C or from 20 to 25 °C. In some embodiments, the precipitation reaction under sonication is performed within a round-bottom reaction vessel. In some embodiments, the precipitation reaction is carried out under stirring. In some embodiments, the stirring is at a rate of from 150 rpm to 5000 rpm, for example from 500 rpm to 5000 rpm or from 500 rpm to 2000 rpm. The particulate transition metal carbonate particulate material which is formed by the method of the first aspect has a volumetric median particle diameter (Dv50) of from 0.2 to 10.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 7.0 pm, for example less than 6.8 pm, less than 6.6 pm, less than 6.4 pm, less than 6.2 pm, less than 6.0 pm, less than 5.8 pm, less than 5.6 pm, less than 5.4 pm, less than 5.2 pm or less than 5.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of from 0.2 to 9.5 pm, for example from 0.2 to 9.0 pm, from 0.2 to 8.5 pm, from 0.2 to 8.0 pm, from 0.2 to 7.5 pm, from 0.2 to 7.0 pm, from 0.2 to 6.5 pm, from 0.2 to 6.0 pm, from 0.2 to 5.5 pm, or from 0.2 to 5.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of from 0.5 to 10.0 pm, for example from 1.0 to 10.0 pm, from 1.5 to 10.0 pm, from 2.0 to 10.0 pm, from 2.5 to 10.0 pm, from 2.5 to 8.0 pm, from 2.5 to 7.0 pm, from 3.0 to 7.0 pm, from 4.0 to 7.0 pm or from 5.0 to 7.0 pm. Dv50 is the volumetric median particle size. In other words, it represents the particle size in microns which splits the volume distribution of that population of particles in half, with 50 vol% of the particles having a particle size below that value and 50 vol% having a particle size above that value. The skilled person will appreciate that the volume median particle size Dv50 can be measured using a Malvern Mastersizer 3000 using the light scattering method set out in ASTM B822-20, applying the Mie scattering theory. The process of the invention may allow a material to be formed with a more uniform particle size distribution due to the reduced number of agglomerates and more predictable particle size and morphology. This uniformity may be characterised by the span of the distribution, defined as (Dv90 - Dv1O) / Dv5o. Dv50 is as defined above. Dv90 represents the particle size in microns which splits the volume distribution of that population of particles such that 90 vol% of the particles have a particle size below that value and 10 vol% have a particle size above that value. DvlO represents the particle size in microns which splits the volume distribution of that population of particles such that 10 vol% of the particles have a particle size below that value and 90 vol% have a particle size above that value. Dv10 and Dv50 may be measured by the same ASTM B822-20 method as Dv50. When the span is closer to zero, the particle size distribution of the material is more uniform. The particulate transition metal carbonate material may have a span ((Dv90 - DV10) / Dvso) of less than 1.5, for example less than 1.4, less than 1.3, less than 1.25, or less than 1.22. In some embodiments, the particulate transition metal carbonate material may have a span of less than 1.1, for example less than 1.06, less than 1.0, less than 0.95, less than 0.90, less than 0.85, less than 0.80, less than 0.75, less than 0.70, less than 0.65, less than 0.60, or less than 0.58. The particulate transition metal carbonate material have a span of from 0.5 to 1.5, for example from 0.5 to 1.4, from 0.5 to 1.3, from 0.5 to 1.25, from 0.5 to 1.22, from 0.5 to 1.1, from 0.5 to 0.95, from 0.5 to 0.9, from 0.5 to 0.85 or from 0.5 to 0.7. In some embodiments, the particulate transition metal carbonate material has a DvlO of from 0.5 to 3.0 pm, for example from 0.5 to 2.5 pm, from 0.5 to 2.0 pm, from 0.5 to 1.9 pm, from 0.5 to 1.8 pm, or from 0.5 to 1.75 pm. In some embodiments, the particulate transition metal carbonate material has a Dv90 of from 1.7 to 10.0 pm, for example from 1.7 to 6.0 pm, from 1.8 to 5.5 pm, from 2.0 to 5.0 pm, from 2.0 to 4.5 pm, or from 2.0 to 3.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of from 0.5 to 10.0 pm, a DvlO of from 0.5 to 3.0 pm, and a Dv90 of from 1.7 to 10.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of from 1.0 to 10.0 pm, a DvlO of from 0.5 to 2.5 pm, and a Dv90 of from 1.7 to 6.0 pm. In some embodiments, the particulate transition metal carbonate material has a Dv50 of from 5.0 to 7.0 pm, a DvlO of from 0.5 to 1.75 pm, and a Dv90 of from 2.0 to 3.0 pm. In some embodiments, the particulate transition metal carbonate material has a circularity of at least 50 %, for example at least 55 %, at least 60 %, at least 65 %, at least 70 %, at least 75 % or at least 80 %. Circularity is a quantification of how similar to a circle the shape of a particle is when a 2-dimensional image of particles within the material is analysed. A perfect circle has a circularity of 1, or 100% when expressed as a percentage. As particles become less circular their measured circularity will decrease. Circularity can be determined by static image analysis of a sample of the material by a static image analyser, such as a Malvern Panalytical Morphologi 4, using the method and calculation in ISO9276-6. To determine the circularity of a material, a sample of the material is analysed using the static image analyser, the circularity of all particles within the frame of the image is determined and then a mean average circularity value is calculated. The method of the invention enables particles of surprisingly high circularity to be obtained, which facilitates the subsequent manufacture of precursors with very good morphology by precipitation onto the particles. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 7 pm and a circularity of at least 50%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 7 pm and a circularity of at least 60%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 7 pm and a circularity of at least 70%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 7 pm and a circularity of at least 80%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 6 pm and a circularity of at least 50%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 6 pm and a circularity of at least 60%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 6 pm and a circularity of at least 70%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 6 pm and a circularity of at least 80%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 5 pm and a circularity of at least 50%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 5 pm and a circularity of at least 60%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 5 pm and a circularity of at least 70%. In some embodiments, the particulate transition metal carbonate material has a Dv50 of less than 5 pm and a circularity of at least 80%. The particulate transition metal carbonate material may have a span of less than 1.5 and a circularity of at least 50%. The particulate transition metal carbonate material may have a span of less than 1.5, a Dv50 of less than 7 pm and a circularity of at least 50%. In some embodiments, the particulate transition metal carbonate material has one or more of: (a) a volumetric median particle diameter (Dv50) of from 0.5 to 3.5 pm, for example from 0.5 to 1.6 pm; and (b) a circularity of at least 70 %. In some embodiments, the particulate transition metal carbonate material comprises less than 10 % agglomerates, based on the total weight of particulate transition metal carbonate material, for example less than 9 %, less than 8 %, less than 7 %, less than 6 %, less than 5 %, or less than 4 % agglomerates. The percentage agglomerates represents a number% (i.e. the number of agglomerated particles as a proportion of the total number of particles in the population) and is determined using Morphologi software. The particulate transition metal carbonate material comprises at least one transition metal element and carbonate. The particulate transition metal carbonate material may consist of at least one transition metal element and carbonate. However in some embodiments the particulate transition metal carbonate material may contain further cationic species and / or further anionic species. The particulate transition metal carbonate material may contain a mixture of carbonate and one or more further anionic species, for example hydroxide and / or oxide. The particulate transition metal carbonate material may therefore be a transition metal mixed carbonate hydroxide material in some embodiments (transition metal hydroxycarbonate, containing hydroxide and carbonate anions). In other embodiments, the particulate transition metal carbonate material may be a transition metal hydroxy-oxy-carbonate (containing hydroxide, oxide and carbonate anions). In other embodiments, the particulate transition metal carbonate material may be a transition metal oxy-carbonate (containing oxide and hydroxide anions). In some embodiments, the particulate transition metal carbonate material comprises or consists of one or more of an iron carbonate, a manganese carbonate, a nickel carbonate, and a cobalt carbonate. In some embodiments, the particulate transition metal carbonate material is a mixed transition metal carbonate comprising two or more of iron, manganese, nickel and cobalt. In some embodiments, the particulate transition metal carbonate material consists of manganese carbonate. In some embodiments, the particulate transition metal carbonate material consists of iron carbonate. In some embodiments, the particulate transition metal carbonate material consists of manganese nickel carbonate. In some embodiments, the particulate transition metal carbonate material consists of manganese nickel cobalt carbonate. In some embodiments, the particulate transition metal carbonate material has a composition according to Formula I: MnxC OyNizF ePMqCCh Formula I wherein 0<x< 1.0; 0<y< 1.0; 0<z< 1.0; 0<p< 1.0; M is one or more elements selected from Ca, K, Na, Ti and Mg; 0 <q <1.0; and x + y + z + p = 1.0. In some embodiments, x = 1.0. In some embodiments, y = 1.0. In some embodiments, z = 1.0. In some embodiments, p = 1.0. In some embodiments, q = 0. In some embodiments, at least two of x, y, z and p are non-zero and at least one of x, y, z and p is zero. In some embodiments, at least three of x, y, z and p are non-zero and one of x, y, z and p is zero. In some embodiments, at least two of x, y, z, p and q are non-zero and at least one of x, y, z, p and q is zero. In some embodiments, at least three of x, y, z and p are non-zero and one of x, y, z and p is zero. In some embodiments, at least two of x, y, z and p are non-zero; at least one of x, y, z and p is zero; and q is zero. In some embodiments, at least three of x, y, z and p are non-zero; one of x, y, z and p is zero; and q is zero. In some embodiments, 0<x< 1.0; 0<y< 1.0; z = 0; q = 0; and p = 0. In some embodiments, 0<x< 1.0; 0<z< 1.0; y = 0; q = 0; and p = 0. In some embodiments, 0<x< 1.0; 0 <y <1.0; 0<z< 1.0; q = 0; and p = 0. In some embodiments, 0<x< 1.0; y = 0; z = 0; q = 0; and 0<p< 1.0. In some embodiments, 0<x< 1.0; 0<y< 1.0; 0<z< 1.0; q = 0; and 0 <p <1.0. In some embodiments, the method further comprises isolating the particulate transition metal carbonate material from the reaction mixture after precipitation, for example by filtering and optionally washing and drying the particulate transition metal carbonate material. In some embodiments, the method comprises tuning the volumetric median particle diameter (Dv50) of the particulate transition metal carbonate material by controlling one or more of: (a) the number of different transition metal element species within the transition metal precursor salt; and (b) the molar ratio of the bicarbonate salt to the transition metal precursor salt in the liquid vehicle. In some embodiments, the method comprises tuning the volumetric median particle diameter (Dv50) of the particulate transition metal carbonate material by controlling the number of different transition metal element species within the transition metal precursor salt. As explained above, it has been found that a greater number of distinct transition metal species within the transition metal precursor salt leads to a larger Dv50 particle size for the particulate transition metal carbonate material. Hence the Dv50 can be tuned to be higher, by controlling the number of different transition metal element species within the transition metal precursor salt to be greater, the Dv50 can be tuned to be lower, by controlling the number of different transition metal element species within the transition metal precursor salt to be lesser. In some embodiments, the method comprises tuning the volumetric median particle diameter (Dv50) of the particulate transition metal carbonate material by controlling the molar ratio of the bicarbonate salt to the transition metal precursor salt in the liquid vehicle. A second aspect of the invention is a particulate transition metal carbonate material for use as seed particles during a precipitation reaction, obtained or obtainable by a method according to the first aspect. A third aspect of the invention is a method of manufacturing a particulate precursor material, the method comprising: providing a suspension of seed particles in a liquid vehicle; initiating a precipitation reaction involving one or more transition metal sources in the liquid vehicle in the presence of the seed particles; and allowing the precipitation reaction to proceed within a precipitation reaction vessel containing a reaction mixture comprising the suspension of seed particles, to form the particulate precursor material by precipitation onto the surface of the seed particles. In some embodiments, the seed particles may consist of a precipitate formed in a mother liquor during an earlier precipitation. The liquid vehicle may comprise at least a portion of the mother liquor. In some embodiments, the step of providing a suspension of seed particles in a liquid vehicle may comprise: performing a preliminary precipitation reaction to form a precipitate comprising the seed particles; and transferring at least some of the seed particles into the liquid vehicle. A fourth aspect of the invention is a particulate transition metal carbonate material obtained or obtainable by the method according to the third aspect. In some embodiments of the fourth aspect, particles of the material comprise a core-shell structure comprising a core region derived from a particulate transition metal carbonate seed particle manufactured by a method according to the first aspect, and a shell region derived from a layer of transition metal carbonate precipitate deposited onto the core region by precipitation onto the seed particle. A fifth aspect of the invention is a method of manufacturing a particulate electrochemically active material, comprising: manufacturing the particulate precursor material by the method according to the third aspect; and calcining the particulate precursor material along with an alkali metal source to prepare the particulate electrochemically active material. The particulate precursor material (also referred to herein as simply “precursor”) is a particulate material which may be converted by further downstream processing steps into an electrochemically active material, e.g. a positive active material (cathode material) or a negative active material (anode material). The precursor may be a particulate material which, when subjected to mixing with an alkali metal (e.g. Li) source and a calcination process, forms the electrochemically active material. In some embodiments, the seed particles have a volumetric median particle diameter (Dv50) of at least 0.1 pm. The seed particles may have a Dv50 of at least 0.12 pm, for example at least 0.14 pm, at least 0.16 pm, at least 0.18 pm, at least 0.20 gm, at least 0.22 gm, at least 0.24 gm, at least 0.26 gm or at least 0.28 gm. In some embodiments, the seed particles have a volumetric median particle diameter (Dv50) of at least 2 pm. Without wishing to be bound by theory, seed particles having a Dv50 of at least 2 gm may be less vulnerable to agglomeration and as a result the final precursor particle size may be predicted more reliably based on the seed particle size. As such, in some embodiments, the seed particles have a Dv50 of at least 2 pm, for example at least 2.5 pm, at least 3.0 pm, at least 3.1 pm, at least 3.2 pm, at least 3.3 pm, at least 3.4 pm, at least 3.5 pm, at least 4.0 pm, at least 4.5 pm, at least 5.0 pm, at least 5.5 gm, at least 6.0 pm, at least 6.5 pm, at least 7.0 gm, at least 7.5 pm or at least 8.0 pm. In some embodiments, the seed particles have a volumetric median particle diameter (Dv50) of from 0.1 pm to 20 pm. The seed particles may have a Dv50 of from 0.15 pm to 20 gm, for example from 0.20 pm to 20 pm, from 0.20 pm to 15 pm, from 0.20 pm to 12 pm, from 0.25 pm to 12 gm, from 0.25 pm to 10 gm, or from 0.25 pm to 9 pm. In some embodiments, the seed particles have a volumetric median particle diameter (Dv50) of from 3.0 pm to 20 pm. The seed particles may have a Dv50 of from 5.0 pm to 20 gm, for example from 5.5 pm to 20 pm, from 6.0 pm to 15 pm, from 6.0 pm to 12 pm, from 6.5 pm to 12 pm, from 7.0 gm to 10 pm, or from 8 pm to 20 pm. Such sizes may provide the benefit of more predictable final particle size for the reasons described above. In some embodiments, the seed particles have a span ((Dv90 - DvlO) / Dvso) of less than 1.5, for example less than 1.4, less than 1.3, less than 1.25, or less than 1.22. In some embodiments, the seed particles may have a span of less than 1.1, for example less than 1.06, less than 1.0, less than 0.95, less than 0.90, less than 0.85, less than 0.80, less than 0.75, less than 0.70, less than 0.65, less than 0.60, or less than 0.58. Span is as defined above. Providing a span for the seed particles within the above ranges may help provide particulate precursor material with a narrower particle size distribution and therefore a more homogeneous and predictable particle size. The seed particles may comprise any suitable material or mixtures of materials. The seed particles may comprise or consist of the particulate transition metal carbonate material according to the first aspect, however they are not limited to such material. As explained above, a seed particle used in the precipitation of a precursor will generally make up a very small proportion of the mass of the precursor. For example, a 1.5 pm seed particle will contribute less than 1 % to the final composition of an 8 pm diameter precursor particle which is formed by precipitation onto the seed particle. So, the impact of the composition of the seed particle on the final composition of subsequently precipitated precursors is low, and in theory any composition of seed particle may be used as a seed to precipitate any composition of precursor. For example, the seed particle may have a first composition, and the precursor precipitated onto the seed particle may have a second, different composition. Tn some embodiments, the seed particles comprise or consist of a synthetic material. In some embodiments, the seed particles comprise or consist of an inorganic material. In some embodiments, the seed particles comprise or consist of an inorganic synthetic material. In some embodiments, the seed particles comprise or consist of (a) an inorganic compound, or (b) a polymer. In some embodiments, the seed particles comprise or consist of (a) a transition metal compound, or (b) a polymer. The seed particles may comprise or consist of an inorganic compound, for example a ceramic material. The seed particles may comprise or consist of an inorganic compound comprising one or more metal elements. The seed particles may comprise or consist of an inorganic compound comprising one or more transition metal elements. The seed particles may comprise or consist of an inorganic compound selected from oxides, carbonates, hydroxides, carbides, phosphates, and inorganic carbon materials. Without wishing to be bound by theory, it is believed that such inorganic compound seed particles (e.g. inorganic compounds comprising one or more transition metal elements) may be less likely to agglomerate before or during the precipitation reaction, thereby leading to a particulate precursor with improved morphology and uniformity of particle size. Such particulate precursors may then be used to manufacture electrochemically active materials with improved electrochemical properties due to the improved morphology and uniformity of particle size of the electrochemically active material. In some embodiments, the seed particles comprise a transition metal carbonate material. In some embodiments, the seed particles comprise one or more of Mn, Ni, Co, Fe, Ca, K, Na, Ti and Mg. In some embodiments, the seed particles comprise one or more of Mn, Ni, Co and Fe. In some embodiments, the seed particles comprise one or more of Mn, Ni, Co and Fe; and optionally one or more of Ca, K, Na, Ti and Mg. In some embodiments, the seed particles comprise a single transition metal species selected from Mn, Ni, Co and Fe. In some embodiments, the seed particles comprise two or more distinct transition metal species selected from Mn, Ni, Co and Fe. In some embodiments, the seed particles comprise two or more distinct transition metal species selected from Mn, Ni and Co. In some embodiments, the seed particles comprise or consist of a polymer or copolymer. In some embodiments, the seed particles comprise or consist of a synthetic polymer or copolymer. In some embodiments, the seed particles comprise or consist of a hydrocarbon polymer or copolymer. In some embodiments, the seed particles comprise or consist of polystyrene or a derivative thereof. In some embodiments, the seed particles comprise or consist of polystyrene. The method of the fifth aspect comprises performing a precipitation reaction between the one or more transition metal sources in the presence of the seed particles in the reaction mixture within the precipitation reaction vessel. The reaction mixture may comprise a slurry of the seed particles in a liquid vehicle. The liquid vehicle may comprise water. The one or more transition metal sources may each independently be selected from transition metal sulfate salts, transition metal nitrate salts and transition metal acetate salts. The one or more transition metal sources may each independently be selected from transition metal sulfate salts. The one or more transition metal sources may each independently comprise one or more transition metal elements selected from Mn, Ni, Co and Fe. The one or more transition metal sources may each independently comprise one or more transition metal sulfate compounds selected from Mn, Ni, Co and Fe sulfate. In some embodiments, the concentration of seed particles within the reaction mixture at the start of the precipitation reaction is from 0.5 g / L to 90 g / L. In some embodiments, the concentration of seed particles within the reaction mixture at the start the precipitation reaction is from 0.5 g / L to 80 g / L, for example from 0.5 g / L to 70 g / L, from 0.5 g / L to 60 g / L, from 0.6 g / L to 50 g / L, from 0.8 g / L to 50 g / L or from 1.0 g / L to 50 g / L. This concentration is calculated by taking the total mass of seed particles contained within the precipitation reaction and dividing this by the total volume of the reaction mixture liquid within the reaction vessel. For example, if there is 5 L of reaction mixture and 20 g of seed particles are present, the concentration of seed particles is 4 g / L. The use of such a concentration of seed particles may provide a final particulate precursor with good particle size and morphology. The concentration of seed particles may also be used to influence the final particulate precursor material particle size. Without wishing to be bound by theory, it is believed that a lower concentration of seed particles in the reaction mixture leads to larger final particulate precursor particle size, because the same quantity of precipitate becomes deposited onto fewer seed particles. By contrast, when the concentration of seed particles is higher, then (all other variables being kept the same), the final particulate precursor particle size is smaller, since the same quantity of precipitate becomes deposited onto a greater number of seed particles, such that each individual particle grows more slowly and reaches a smaller ultimate particle size. As such, it is possible to tune the volumetric median particle diameter (Dv50) of the particulate precursor to be manufactured by controlling the concentration of the seed particles (e.g. by selecting a specific concentration of seed particle for preparing a particulate precursor with a desired Dv50). By controlling the concentration of seed particles to be lower, the resultant Dv50 of the particulate precursor to be manufactured will be higher. By controlling the concentration of seed particles to be higher, the resultant Dv50 of the particulate precursor to be manufactured will be lower. So, where it is desired to prepare relatively small particulate precursor particles, a higher concentration of seed particles can be provided in the reaction mixture for the precipitation, and where it is desired to prepare relatively large particulate precursor particles, a lower concentration of seed particles can be provided in the reaction mixture for the precipitation. Other factors which may influence the resultant Dv50 of the particulate precursor to be manufactured include the Dv50 of the seed particles used and the precipitation reaction time. A larger Dv50 of seed particles used, all other variables being kept the same, would be expected to lead to a correspondingly larger Dv50 of the particulate precursor after precipitation, since the core region of the final particle on which the layer of precipitate is deposited will be larger. A longer precipitation time would also be expected to lead to a larger Dv50 of the particulate precursor after precipitation, since a greater quantity of precipitate will be deposited onto the seed particles and subsequent growing precursor particles as the reaction progresses. In some embodiments, the method comprises tuning the volumetric median particle diameter (Dv50) of the particulate precursor to be manufactured by controlling one or more of: (a) the volumetric median particle diameter (Dv50) of the seed particles; (b) the concentration of seed particles within the reaction mixture; and (c) the precipitation reaction time. In some embodiments, the method comprises increasing the volumetric median particle diameter (Dv50) of the particulate precursor to be manufactured by doing one or more of: (a) increasing the volumetric median particle diameter (Dv50) of the seed particles; (b) decreasing the concentration of seed particles within the reaction mixture; and (c) increasing the precipitation reaction time. In some embodiments, the method comprises decreasing the volumetric median particle diameter (Dv50) of the particulate precursor to be manufactured by doing one or more of (a) decreasing the volumetric median particle diameter (Dv50) of the seed particles; (b) increasing the concentration of seed particles within the reaction mixture; and (c) decreasing the precipitation reaction time. In some embodiments, the seed particles are present within an initial heel solution within the precipitation reaction vessel (i.e. the initial volume of liquid which is added to the empty reaction, and into which further reagents are fed to initiate and / or sustain the precipitation reaction), or a suspension comprising the seed particles is added to the precipitation reaction vessel. In some embodiments, the method comprises in-line feeding of the seeds as a slurry into the reactor, i.e. feeding a slurry comprising the seeds into the reactor either before, after or in simultaneously with the feeding of one or more further reagents. In some embodiments, the precipitation reaction comprises reacting a transition metal sulfate solution with a hydroxide, carbonate or bicarbonate source. In some embodiments, the precipitation reaction comprises reacting a transition metal sulfate solution with a hydroxide, carbonate or bicarbonate source in the presence of a base. In some embodiments, the precipitation reaction comprises reacting a transition metal sulfate solution with a hydroxide, carbonate or bicarbonate source in the presence of ammonium hydroxide. The precipitation reaction vessel may be any suitable vessel for performing the precipitation reaction. The vessel may contain a stirrer or agitator. The vessel may comprise a means to heat the reaction mixture. In some embodiments, the precipitation reaction vessel is a stirred tank reactor. Stirring the reaction mixture during the reaction may assist in ensuring a more homogeneous particle size for the particulate precursor. The seed particles may have a Dv50 of from 0.2 to 10.0 pm. In some embodiments, the seed particles have a Dv50 of less than 7.0 pm, for example less than 6.8 pm, less than 6.6 pm, less than 6.4 pm, less than 6.2 pm, less than 6.0 pm, less than 5.8 pm, less than 5.6 pm, less than 5.4 pm, less than 5.2 pm or less than 5.0 pm. The seed particles may have a Dv50 of from 0.2 to 9.5 pm, for example from 0.2 to 9.0 pm, from 0.2 to 8.5 pm, from 0.2 to 8.0 pm, from 0.2 to 7.5 pm, from 0.2 to 7.0 pm, from 0.2 to 6.5 pm, from 0.2 to 6.0 pm, from 0.2 to 5.5 pm, or from 0.2 to 5.0 pm. The seed particles may have a Dv50 of from 0.5 to 10.0 pm, for example from 1.0 to 10.0 pm, from 1.5 to 10.0 pm, from 2.0 to 10.0 pm, from 2.5 to 10.0 pm, from 2.5 to 8.0 pm, from 2.5 to 7.0 pm, from 3.0 to 7.0 pm, from 4.0 to 7.0 pm or from 5.0 to 7.0 pm. In some embodiments, the seed particles have a circularity of at least 50 %, for example at least 55 %, at least 60 %, at least 65 %, at least 70 %, at least 75 % or at least 80 %. In some embodiments, the seed particles have a Dv50 of less than 7 pm and a circularity of at least 50%. In some embodiments, the seed particles have a Dv50 of less than 7 pm and a circularity of at least 60%. In some embodiments, the seed particles have a Dv50 of less than 7 pm and a circularity of at least 70%. In some embodiments, the seed particles have a Dv50 of less than 7 pm and a circularity of at least 80%. In some embodiments, the seed particles have a Dv50 of less than 6 pm and a circularity of at least 50%. In some embodiments, the seed particles have a Dv50 of less than 6 pm and a circularity of at least 60%. In some embodiments, the seed particles have a Dv50 of less than 6 pm and a circularity of at least 70%. In some embodiments, the seed particles have a Dv50 of less than 6 pm and a circularity of at least 80%. In some embodiments, the seed particles have a Dv50 of less than 5 pm and a circularity of at least 50%. In some embodiments, the seed particles have a Dv50 of less than 5 pm and a circularity of at least 60%. In some embodiments, the seed particles have a Dv50 of less than 5 pm and a circularity of at least 70%. In some embodiments, the seed particles have a Dv50 of less than 5 pm and a circularity of at least 80%. In some embodiments, the seed particles have one or more of: (a) a volumetric median particle diameter (Dv50) of from 0.5 to 3.5 pm, for example from 0.5 to 1.6 pm; and (b) a circularity of at least 50 %. In some embodiments, the seed particles comprise less than 10 % agglomerates, based on the total weight of seed particles, for example less than 9 %, less than 8 %, less than 7 %, less than 6 %, less than 5 %, or less than 4 % agglomerates. In some embodiments, particles of the particulate precursor material comprise a core-shell structure comprising a core region derived from a seed particles, and a shell region derived from a layer of precipitate deposited onto the core region by precipitation onto the seed particles. In some embodiments, the method further comprises isolating the particulate precursor material from the reaction mixture after precipitation onto the seed particles, for example by filtering and optionally washing the particulate precursor material. A sixth aspect of the invention is a particulate precursor material obtained or obtainable by a method according to the fifth aspect. A seventh aspect of the invention is a method of manufacturing a particulate electrochemically active material, comprising manufacturing the particulate precursor material by the method according to the fifth aspect; and calcining the particulate precursor material in the presence of an alkali metal source (e.g. Li source) to prepare the particulate electrochemically active material. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an SEM image of a particulate transition metal carbonate material. Figure 2 is an SEM image of a particulate transition metal carbonate material. Figure 3 is an SEM image of a particulate transition metal carbonate material. Figure 4 is an optical image of a particulate transition metal carbonate material. Figure 5 is an optical image of a particulate transition metal carbonate material. Figure 6 is an SEM image of a particulate transition metal carbonate material. Figure 7 is (a) an SEM image of a particulate transition metal carbonate material formed using a static precipitation method; and (b) a chart of the sphericity distribution of the material. Figure 8 is (a) an SEM image of a particulate transition metal carbonate material formed using a static precipitation method after calcination; (b) an SEM image of another particulate transition metal carbonate material formed using a static precipitation method and (c) a chart of the sphericity distribution of the material shown in (b). Figure 9 is a graph showing the growth of a mixed transition metal carbonate precipitate on mixed transition metal carbonate seeds added to the reactor in different amounts. Figure 10 shows SEM images of the particles grown from seeds after calcination in Example 11. Figure 11 is a graph showing the growth of a mixed transition metal carbonate precipitate on mixed transition metal carbonate seeds added to the reactor in different amounts. Figure 12 shows SEM images of the particles grown from seeds in Example 12. Figure 13 is a graph showing the growth of a mixed transition metal carbonate precipitate on manganese carbonate seeds added to the reactor in different amounts. Figure 14 is an SEM image of the particles grown from seeds in Example 13. Figure 15 shows SEM images of products of (a) seeded, and (b) non-seeded precipitation reactions. Figure 16 shows XRD patterns for products of (a) seeded and (b) non-seeded precipitation reactions. Figure 17 shows a plot of charge-discharge curves for products of seeded and non-seeded precipitation reactions. Figure 18 shows SEM images of products of (a) seeded, and (b) non-seeded precipitation reactions; and charts of the sphericity distribution of those (c) seeded and (d) non-seeded materials. Figure 19 shows XRD patterns for products of (a) seeded and (b) non-seeded precipitation reactions. Figure 20 shows a plot of charge-discharge curves for products of seeded and non-seeded precipitation reactions. Figure 21 shows SEM images of products of (a) seeded, and (b) non-seeded precipitation reactions; and charts of the sphericity distribution of those (c) seeded and (d) non-seeded materials. Figure 22 shows XRD patterns for products of (a) seeded and (b) non-seeded precipitation reactions. Figure 23 shows a plot of charge-discharge curves for products of seeded and non-seeded precipitation reactions. Figure 24 is a cell voltage v capacity plot showing the electrochemical performance of materials prepared from seeds according to the methods of the invention and comparative materials prepared in the absence of seeds. Figure 25 is a cell voltage v capacity plot showing the electrochemical performance of materials prepared from seeds according to the methods of the invention and comparative materials prepared in the absence of seeds. EXAMPLES &DETAILED DESCRIPTION Example 1 - Preparation of manganese carbonate seeds with stirring A 1.0 M aqueous solution of manganese sulfate was mixed with a 2.2 M aqueous solution of ammonium bicarbonate at 50 °C in a conical flask. 500 mL of 2.2 M aqueous solution of ammonium bicarbonate was added to 250 mL of 1.0 M aqueous solution of manganese sulfate. The mixture was stirred at 500 rpm using a magnetic stirrer bar. The reaction was allowed to proceed for 30 minutes under stirring, after which time it was considered complete. A precipitate formed during the reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The Dv50 was 1.6 pm. An SEM image of the particulate material is shown in Figure 1. The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. Example 2 - Preparation of manganese nickel carbonate seeds with stirring A 2L mixed transition metal solution of total concentration 1.0 M was prepared by adding 177.1272 g of Ni(SO4) and 224.1205 g of Mn(SO4) to 2 L of water. 250 mL of the mixed metal sulfate solution was mixed with 500 mL of a 2.2 M aqueous solution of ammonium bicarbonate at 50 °C in a conical flask. The mixture was stirred at 500 rpm using a magnetic stirrer bar. The reaction was allowed to proceed for 30 minutes, after which time it was considered complete. A precipitate formed during the reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The Dv50 was 2.5 um. An SEM image of the particulate material is shown in Figure 2. The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. Example 3 - Preparation of manganese nickel cobalt carbonate seeds with stirring A 2 L mixed transition metal solution of total concentration 2.0 M was prepared by adding Ni(SO4), Mn(SO4) and Co(SO4) to 2 L of water. 250 mL of the mixed metal sulfate solution was mixed with 500 mL of a 2.2 M aqueous solution of ammonium bicarbonate at 50 °C in a conical flask. The mixture was stirred at 500 rpm using a magnetic stirrer bar. The reaction was allowed to proceed for 30 minutes, after which time it was considered complete. A precipitate formed during the reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The Dv50 was 3.1 pm. An SEM image of the particulate material is shown in Figure 3. The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. The Dv50 particle sizes of the products of Examples 1-3 are summarised in Table 1: Table 1 Example Sulfate solution Dv50 / pm 1 Mn 1.6 2 Mn, Ni 2.5 3 Mn, Ni, Co 3.1 It is evident that it is possible to increase the Dv50 of the particulate transition metal carbonate product material in a controlled manner by adjusting the number of distinct transition metal species in the transition metal salt solution used as starting material. Example 4 - Preparation of manganese carbonate seeds with sonication A 1.0 M aqueous solution of manganese sulfate was provided in a round-bottom flask. The solution was sonicated using a UP400St Powerful Ultrasonicator from Hielscher using two different sonotrode horns. During sonication, a 2.2 M aqueous solution of ammonium bicarbonate was added at room temperature. The volume ratio of the manganese sulfate solution to the ammonium bicarbonate solution was 1:10. The total volume of the reaction mixture was 100 mL. Two different sonotrode horns were tested, an s24d3 which has a maximum operating volume of 100 mL, and a H14 which has a maximum operating volume of 1000 mL. It was ensured that the total volume of reaction mixture was within these limits when each was used. The reaction was observed to progress quickly with the formation of a precipitate visible in the solution. After 3 minutes the reaction was considered complete. A precipitate formed during the reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The Dv50 was 1.4 pm. An optical image of the particulate material is shown in Figure 4. The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. The circularity of the particles was calculated using static image analysis with a Malvern Panalytical Morphologi 4 instrument and found to be 75%. The proportion of agglomerates in the material was determined to be 3%. Example 5 - Scaled-up preparation of manganese carbonate seeds with sonication The method of Example 4 was repeated, except that the total volume of the reaction mixture was 1000 mL. A precipitate formed during the reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The Dv50 was 1.5 um. An optical image of the particulate material is shown in Figure 5. The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. The circularity of the particles was calculated using static image analysis with a Malvern Panalytical Morphologi 4 instrument and found to be 74%. The proportion of agglomerates in the material was determined to be 3%. Examples 4 and 5 show that the use of ultrasound sonication during the precipitation reaction can facilitate a very fast reaction and also provides a particulate material product with small Dv50, very low agglomerate content and high circularity. Example 6 - Preparation of seeds using ultrasonic bath or ultrasonic probe Manganese carbonate seeds, manganese nickel carbonate seeds, and manganese nickel cobalt carbonate seeds were prepared using sonication by two different methods - either an ultrasonic bath (UB) or an ultrasonic probe (UP). The results are shown in Table 2. In each of the beaker reactions a 0.5 M metal sulphate solution was mixed with a 2.2 M aqueous solution of ammonium bicarbonate in volume ratios such that the molar ratios shown in Table 2 were achieved. In the round-bottomed flask (RBF) reactions a 0.5 M metal sulphate solution was mixed with a 2.2 M aqueous 5 solution of ammonium bicarbonate. Table 2 Reactrion vessel Molar ratio of TM sulfate to NH4HCO3 DvlO / uni Dv50 / gm Dv90 / gm Span Mn seeds (UB) Beaker 1:4 1.1 1.7 2.3 0.706 Beaker 1:40 1.0 1.7 2.3 0.765 Mn seeds (UP) Beaker 1:4 1.0 1.6 2.1 0.688 Beaker 1:40 1.0 1.6 2.2 0.750 (Ni, Mn) seeds (UB) Beaker 1:4 0.8 1.3 1.8 0.769 Beaker 1:40 1.1 1.8 2.9 1.000 (Ni, Mn) seeds (UP) Beaker 1:4 0.8 1.2 1.8 0.833 Beaker 1:40 1.1 1.6 2.5 0.875 (Ni, Mn, Co) seeds (UB) Beaker 1:4 0.8 1.3 2.0 0.923 Beaker 1:40 1.1 1.9 2.8 0.895 (Ni, Mn, Co) seeds (UP) Beaker 1:4 0.8 1.2 1.8 0.833 Beaker 1:40 1.1 1.6 2.1 0.625 Mn seeds (UP-s24d3) RBF 1:20 1.1 1.4 1.9 0.571 Mn seeds (UP - H14) RBF 1:20 1.0 1.5 1.9 0.600 In the UB method, ultrasonic waves propagate throughout the entire reaction mixture and the shape of the reaction vessel is not thought to be of great importance. In the UP method, ultrasonic waves emanate from the tip of the probe which is immersed in the reaction mixture. It was found that a round-bottomed flask helped to eliminate ultrasound deadzones within the solution during the UP method, improving the uniformity of the particle size (i.e. reducing the Span value). This was the case for both sonotrode horns tested (s24d3 andH14). Example 7 - Investigation of the effect of reagent ratios on material properties A 2 L mixed transition metal solution of total concentration 1.0 M was prepared by adding Ni(SO4) and Mn(SO4) to 2 L of water. A 2.2 M aqueous solution of ammonium bicarbonate was also prepared. The mixed metal solution and ammonium bicarbonate solution were mixed together at 50 °C in beakers at various volume ratios. Each mixture was stirred at 500 rpm using a magnetic stirrer bar. The reaction was allowed to proceed for 30 minutes, after which time it was considered complete. A precipitate formed during each reaction was collected by filtration and the Dv50 particle size was determined using a Malvern Mastersizer 3000. The ratios used are shown in Table 3 below along with the measured Dv50 for each reaction: Table 3 Molar ratio NH4HCO3:TMSO4 Product Dv50 / gm Mixture A 2.2:1 5.6 Mixture B 22:1 2.5 Mixture C 33:1 2.4 Mixture D 44:1 2.2 SEM images of the particulate materials are shown in Figure 6(a)-(d) (products from mixtures A-D respectively). The 2.2:1 molar ratio (Mixture A) of starting solutions led to a relatively large particle size and particles with a rough surface and some agglomeration visible. A 22:1 molar ratio (Mixture B) provided particles with visibly improved properties, having a smaller particle size, a smoother surface and less agglomeration. A 33:1 molar ratio (Mixture C) improved the properties of the particles further, with the material having an even smaller particle size than those prepared from Mixture B, a very narrow particle size distribution and particles which were highly spherical with a smooth surface. Mixture D (44:1 molar ratio) reduced the particle size further and also resulted in spherical smooth particles, but the particle size distribution was more disperse than for the particles produced from Mixture C. Although all particles formed could find use as seeds in subsequent precipitation, the optimal molar ratio appears to be 33:1, producing a narrow particle size distribution with a small Dv50 and highly smooth and spherical particles. Example 8 Investigation of optimal reagent ratios for different seed compositions using a static precipitation method Precipitation reactions were performed using a static method (without any stirring of the reaction mixture). Manganese sulphate, and / or nickel sulphate and / or cobalt sulphate were mixed to form a 1.0 M mixed metal sulphate solution. The mixed metal sulphate solution was mixed with a 2.2 M aqueous solution of ammonium bicarbonate at room temperature in a beaker. The molar ratio of the sulphate solution to the ammonium bicarbonate solution was comprised between 1:4 and 1:50. The mixture was left overnight, without any stirring, without any ultrasound, and at ambient temperature without any heating. A precipitate formed during the reaction was collected by filtration. An SEM image of the particulate carbonate material is shown in Figure 7(a). A chart of the sphericity of the material is shown in Figure 7(b). The particles were observed to be spherical or near-spherical with a very low proportion of agglomerates. Manganese carbonate seeds, nickel manganese carbonate seeds, and further nickel cobalt manganese carbonate seeds were then prepared in the same way. Table 4 below shows details of the reactions and the properties of the seed particles formed: Table 4 Molar ratio of TM sulfate to DvlO / pm Dv50 / urn Dv90 / pin Span Mn seeds 1:40 1.2 2.2 2.7 0.682 (Ni, Mn) seeds 1:4 1.3 2.8 4.7 1.214 1:10 1.6 3.8 5.2 0.947 1:20 1.6 2.9 3.5 0.655 1:40 1.3 3.0 3.6 0.767 1:50 1.2 2.6 3.5 0.885 (Ni, Mn, Co) seeds 1:4 1.4 3.5 5.1 1.057 1:10 1.7 4.0 5.3 0.900 1:20 1.9 3.4 4.6 0.794 1:40 1.9 3.4 4.2 0.676 The Ni, Mn, Co carbonate material formed using the 1:4 ratio of reagents from Table 4 was calcined to produce an oxide material. An SEM image of the particulate oxide material is shown in Figure 8(a). The particles were observed to be spherical or near-spherical with 5 a very low proportion of agglomerates. An SEM image of the particulate Ni, Mn carbonate material formed using the 1:20 ratio of reagents from Table 4 is shown in Figure 8(b). A chart of the sphericity of the material is shown in Figure 8(c). The particles were observed to be spherical or near-spherical with a 10 very low proportion of agglomerates. Example 9 - Investigation of the use of powder reagents with stirring The method of Example 1 was repeated, except that one or more of the reagents were provided in powder form. The same molar ratio of NH4HCOs:MnSO4 was used for all 15 reactions (22:1 molar ratio). After combining the mixtures were stirred at 500 rpm using a magnetic stirrer bar. The nature of the reagents used is set out in Table 5: Table 5 NH4HCO3 properties MnSO4 properties Mixture E 2.2 M aqueous solution Powder, dried overnight at 80 °C and sieved with mesh size 125 pm Mixture F 2.2 M aqueous solution Powder, dried overnight under vacuum and sieved with mesh size 125 pm Mixture G 2.2 M aqueous solution Powder, dried overnight at 80 °C and mixed using Resodyn mixer Mixture H Powder, ground in pestle and mortar 1.0 M aqueous solution Mixture I Powder Powder After the reactions had completed, the particulate product was filtered and analysed. The products from Mixtures E-I were labelled Samples E-I respectively. The properties of Samples E-I are set out in Table 6: Table 6 Particle circularity / % Agglomerate content / % Sample E 33 19 Sample F 35 22 Sample G 27 15 Sample H 53 19 Sample I 44 27 The Samples all had reasonable circularity and reasonably low agglomerate content, but the circularity and agglomerate content of the earlier Examples (mixing of two solutions) 10 were better. It is evident that Sample H had relatively low agglomerate content and high circularity, which seems to arise from the use of NH4HCO3 in powder form added to a solution of MnSO4. Samples E, F and G, prepared by adding MnSO4 in powder form to a solution of 15 NH4HCO3, had less desirable properties in terms of circularity and agglomerate content. Providing both reagents in powder form (Sample I) resulted in a larger proportion of agglomerates in the material. Example 10 - Investigation of the use of powder reagents with sonication Example 9 was repeated, except that after combining the reagents, Mixtures E, F, G and I were sonicated using a UP400St Powerful Ultrasonicator from Hielscher instead of stirring (Mixture El was not repeated in this Example). After the reactions had completed, the particulate product was filtered and analysed. The products from sonicated Mixtures E, F, G and I were labelled Samples J-M respectively. A further Sample N was prepared by mixing pre-made solutions of NH4HCO3 and MnSO4, with the same molar ratio. The properties of the Samples are set out in Table 7: Table 7 Particle circularity / % Agglomerate content / % Sample J 52 12 Sample K 60 13 Sample L 58 15 Sample M 45 12 Sample N 64 5.8 Circularity was determined by static image analysis of the samples with a Malvem Panalytical Morphologi 4, using the method and calculation in ISO9276-6. Agglomerate % content was also determined using image analysis with the Malvern Panalytical Morphologi 4. When comparing like for like, it is evident that the Samples of Example 10 have better circularity and lower agglomerate content than those of Example 9. The use of ultrasonic sonication can therefore be used to improve material properties regardless of the physical form of the reagents. Sample N (solution-solution) had the best circularity and agglomerate content. The other Samples had quite similar results to one another in terms of circularity and agglomerate content, although Sample M (powder-powder) had the lowest circularity value. Example 11 - Use of MnNiCo seeds in a precipitation reaction The material prepared in Example 3 (Dv50 = 3.1 pm, TAP density 1.32 g cm'3) was used as seeds on which to precipitate a transition metal carbonate material from a reaction mixture in which a precipitation reaction was taking place. Different amounts of the mixed transition metal carbonate seeds were added to the reactor heel (the total reactor heel volume was 350 mL). Three different precipitation reactions were performed using the following amounts of seeds, as shown in Table 8: Table 8 Reaction (MnNiCo) seeds total mass / g 9A 15 9B 30 9C 45 For each of the three seed masses, the reaction was run for a variety of reaction times (30, 60, 120, 180 and 240 mins) and the Dv50 particle size of the resultant transition metal carbonate particles was determined. The results are shown in Figure 9. Two trends are apparent: (1) as the mass of seeds added at the start of the reaction decreases, the Dv50 of the resultant transition metal carbonate particles increases (at a given reaction time); and (2) as the reaction time increases, the Dv50 of the resultant transition metal carbonate particles increases (at a given seed mass). The precursor carbonate materials were then mixed with a lithium source and calcined to produce an electrochemically active oxide material. SEM images of the oxides were obtained. Figure 10 shows SEM images of the resultant oxide particles formed by precipitation onto the seeds of Example 3 and subsequent calcination. Figure 10(a) shows an image of a calcined product of the particle obtained in Reaction 9A (15g of seed). It can be seen that the outer layer of deposited material is thick, leading to the observed larger overall particle size after the precipitation. Figure 10(b) shows an image of a calcined product of the particle obtained in Reaction 9B (30g of seed). It can be seen that the outer layer of deposited material is slightly thinner than in Reaction 9A, leading to an intermediate particle size after the precipitation. Figure 10(c) shows an image of a calcined product of the particle obtained in Reaction 9C (45g of seed). It can be seen that the outer layer of deposited material is thin, leading to the observed smaller overall particle size after the precipitation. A clear core-shell structure of the final particles can be seen in the SEM images of Figure 10, along with clear evidence of highly spherical particles of a homogeneous particle size distribution. The final Dv50 and TAP density of the calcined oxide particles made by calcining the products of Reactions 9A, 9B and 9C is set out in Table 9: Table 9 Reaction Oxide final Dv50 / pm Oxide TAP density / g cm 3 9A 6.3 1.5693 9B 5.7 1.5308 9C 4.6 1.4193 Example 12 - Use of MnNi seeds in a precipitation reaction The material prepared in Example 2 (Dv50 = 2.5 pm, TAP density 1.34 g cm'3) was used as seeds on which to precipitate a transition metal carbonate material from a reaction mixture in which a precipitation reaction was taking place. Other than the seeds used, the procedure was the same as for Example 11. Four different precipitation reactions were performed using the following amounts of seeds, as shown in Table 10: Table 10 Reaction (MnNi) seeds total mass / g 10A 5 10B 15 10C 30 10D 45 For each of the four seed masses, the reaction was run for a variety of reaction times (30, 60, 120, 180 and 240 mins) and the Dv50 particle size of the resultant transition metal carbonate particles was determined. The results are shown in Figure 11. The same general trends as discussed above for Example 11 are apparent. The precursor carbonate materials were then mixed with a lithium source and calcined to produce an electrochemically active oxide material. SEM images of the oxides were obtained. Figure 12 shows SEM images of the resultant transition metal oxide particles formed by precipitation onto the seeds of Example 2 and subsequent calcination. Figure 12(a) shows an image of a calcined product of the particles obtained in Reaction 12 (5g of seed). Figure 12(b) shows an image of a calcined product of the particles obtained in Reaction 10B (15g of seed). Figure 12(c) shows an image of a calcined product of the particles obtained in Reaction 10C (30g of seed). Figure 12(d) shows an image of a calcined product of the particles obtained in Reaction 10C (45g of seed). In each of the SEM images of Figure 12, smooth near-spherical (or “potato-like”) particles are evident with relatively homogeneous particle size distribution. The final Dv50 and TAP density of the transition metal oxide material particles (precursor) made in Reactions 10A, 10B, 10C and 10D is set out in Table 11: Table 11 Reaction Oxide final Dv50 / uni Oxide TAP density / g cm 3 10A 7.7 1.5853 10B 6.6 1.5793 10C 5.8 1.4717 10D 4.4 1.4038 Example 13 - Use of Mn seeds in a precipitation reaction The material prepared in Example 1 (Dv50 = 1.6 pm, TAP density 1.23 g cm'3) was used as seeds on which to precipitate a transition metal carbonate material from a reaction mixture in which a precipitation reaction was taking place. Other than the seeds used, the procedure was the same as for Example 11. Four different precipitation reactions were performed using the following amounts of seeds, as shown in Table 12: Table 12 Reaction (Mn) seeds total mass / g 11A 5 11B 15 11C 30 11D 45 For each of the four seed masses, the reaction was run for a variety of reaction times (30, 60, 120, 180 and 240 mins) and the Dv50 particle size of the resultant transition metal carbonate particles was determined. The results are shown in Figure 13. The same general trends as discussed above for Example 11 are apparent. The precursor carbonate materials were then mixed with a lithium source and calcined to produce an electrochemically active oxide material. SEM images of the oxides were obtained. Figure 14 shows an image of oxide particles obtained in Reaction 1 IB and subsequent calcination (15g of seed). The final Dv50 and TAP density of the transition metal oxide material particles made in Reactions 11A, 1 IB, 1 IC and 1 ID is set out in Table 13: Tnhle 13 J J J Reaction Oxide final Dv50 / gm Oxide TAP density 1 _3 g cm J HA 7.6 1.5501 11B 5.6 1.3931 11C 4.4 1.3087 HD 3.4 1.2486 Example 14 - Comparison of seeded versus non-seeded nickel manganese precipitation reactions Both seeded and non-seeded precipitation reactions were performed to compare the product properties. In each case, a 2 M solution of nickel manganese sulfate was used. The reaction conditions were as follows: Table 14 Seeded reaction Non-seeded reaction Reactor type Stirred tank Stirred tank Seed mass 15g N / A Reaction time lOh 6 h Calcination Calcination temperature Ti 500 °C 500 °C Calcination temperature T2 900 °C 900 °C Figure 15 shows SEM images of the products of the seeded and non-seeded reactions respectively. It is evident that the product of the seeded reaction has a more spherical morphology with a more uniform particle size distribution and fewer agglomerates. 15 The properties of the products were as follows: Table 15 Seeded reaction Non-seeded reaction NiMn carbonate precipitate TAP density / g cm 3 1.6010 1.2351 NiMn calcined oxide TAP density / g cm 3 1.9199 1.3031 NiMn carbonate precipitate DvlO / pm 7.3 4.59 NiMn carbonate precipitate Dv50 / pm 9.2 6.9 NiMn carbonate precipitate Dv90 / pm 11.6 10.4 NiMn carbonate precipitate Span 0.462 0.842 Figure 16 (a) and (b) shows XRD patterns for the two materials resulting from the seeded and non-seeded reactions respectively. Figure 17 shows charge-discharge cycle plots for the two oxide materials resulting from the seeded and non-seeded reactions and subsequent calcinations. It is evident that the material from the seeded reaction has a higher specific capacity than the material from the non-seeded reaction. Example 15 - Comparison of seeded versus non-seeded nickel manganese cobalt precipitation reactions, 15 g seed Both seeded and non-seeded precipitation reactions were performed to compare the product properties. In the seeded reaction, a 3.5 M solution of nickel manganese cobalt sulfate was used. In the non-seeded reaction, a 2 M solution of nickel manganese cobalt sulfate was used, hence why the reaction time was increased. The reaction conditions were as follows: Table 16 Seeded reaction Non-seeded reaction Reactor type Stirred tank Stirred tank Seed mass 15 g N / A Reaction time 10 h 23 h Calcination Calcination temperature Ti 500 °C 500 °C Calcination temperature T2 900 °C 900 °C Figure 18 (a) and (b) show SEM images of the products of the seeded and non-seeded reactions respectively. It is evident that the product of the seeded reaction has a more spherical morphology with a more uniform particle size distribution and fewer 5 agglomerates. This is also evident from the sphericity distributions for the seeded and nonseeded products in Figures 18(c) and (d) respectively. The properties of the products were as follows: 10 Table 17 Seeded reaction Non-seeded reaction NiMnCo carbonate precipitate TAP density / g cm3 1.7493 1.5618 NiMnCo calcined oxide TAP density / g cm 3 1.9660 1.7168 NiMnCo carbonate precipitate Dv10 / pm 6.2 6.1 NiMnCo carbonate precipitate Dv50 / pm 8.9 9.0 NiMnCo carbonate precipitate Dv90 / pm 12.6 13.3 NiMnCo carbonate precipitate Span 0.718 0.808 Figure 19 (a) and (b) show XRD patterns for the two materials resulting from the seeded and non-seeded reactions respectively. Figure 20 shows charge-discharge cycle plots for the two oxide materials resulting from the seeded and non-seeded reactions and subsequent calcinations. It is evident that the material from the seeded reaction has a higher specific capacity than the material from the non-seeded reaction. Example 16 - Comparison of seeded versus non-seeded nickel manganese cobalt precipitation reactions, 25g seed Both seeded and non-seeded precipitation reactions were performed to compare the product properties. In the seeded reaction, a 2 M solution of nickel manganese cobalt sulfate was used. In the non-seeded reaction, a 3.5 M solution of nickel manganese cobalt sulfate was used. The reaction conditions were as follows: Table 18 Seeded reaction Non-seeded reaction Reactor type Stirred tank Stirred tank Seed mass 25 g N / A Reaction time lOh 23 h Calcination Calcination temperature Ti 500 °C 500 °C Calcination temperature T2 900 °C 900 °C Figure 21 (a) and (b) show SEM images of the products of the seeded and non-seeded reactions respectively. It is evident that the product of the seeded reaction has a more spherical morphology with a more uniform particle size distribution and fewer agglomerates. This is also evident from the sphericity distributions for the seeded and nonseeded products in Figures 21(c) and (d) respectively. The properties of the products were as follows: Table 19 Seeded reaction Non-seeded reaction NiMnCo carbonate precipitate TAP density / g cm 1.6889 1.5618 NiMnCo calcined oxide TAP density / g cm 3 1.7758 1.7168 NiMnCo carbonate precipitate Dv10 / pm 7.0 6.1 NiMnCo carbonate precipitate Dv50 / pm 9.0 9.0 NiMnCo carbonate precipitate Dv90 / pm 11.7 13.3 NiMnCo carbonate precipitate Span 0.518 0.808 Figure 22(a) and (b) show XRD patterns for the two materials resulting from the seeded and non-seeded reactions respectively. 5 Figure 23 shows charge-discharge cycle plots for the two oxide materials resulting from the seeded and non-seeded reactions and subsequent calcinations. It is evident that the material from the seeded reaction has a higher specific capacity than the material from the non-seeded reaction. 10 Example 17 - Use of large MnNiCo seeds in a precipitation reaction Ni(SO4).6H2O, Mn(SO4).H2O and Co(SO4).6H2O were dissolved in deionised water up to a final volume of 5000 mL (3665.3 g of water needed), to form Solution A (3.5 M concentration). 15 Na2COs was dissolved in deionised water to form Solution B (3.5 M concentration). 74.99 g of a 28 wt% ammonia solution (NFEOH) was dissolved in 300.5 g of deionised water to form Solution C (5.6 wt% ammonium hydroxide solution). A 5000 mL stirred tank reactor was filled with 500 mL deionised water, which was heated up to 55 °C and stirred at 500 rpm with a 90 mm PBT impeller. Once the temperature of the water had stabilised, coprecipitation was starting by adding Solution A at a rate of roughly 2.2 g / min addition. The pH was controlled to pH 7.5 by the addition of Solution B. Solution C was fed to the reactor to allow precipitation to occur. The particle size distribution of the formed precipitate was measured regularly throughout the precipitation and the results are set out in Table 20: Table 20 Time / min DviO Dv50 dv9o Span 5 6.14 11.0 19.0 1.164 15 3.39 9.27 18.0 1.572 30 2.88 7.89 16.6 1.743 60 2.72 6.46 14.5 1.817 120 3.02 5.96 11.8 1.478 180 3.30 6.14 11.4 1.323 300 3.76 6.55 11.2 1.141 1260 5.55 8.60 13.3 0.896 1380 5.67 8.68 13.2 0.867 Without wishing to be bound by theory, it is believed that for around the first 1-2 hours of the reaction many carbonate seeds are formed in the form of chelates that are agglomerated, hence the relatively large D50 early in the reaction. For around the first 1-2 hours these agglomerates then de-agglomerate and begin to grow as precipitated carbonate compounds, hence the gradual increase in size from 2 hours onwards. After 23 hours of reaction the Dv50 particle size had reached approximately 8.7 pm with a span less than 1.0, and the reaction was stopped by halting the feeds to the reactor and cooling the reactor. The solids content of the resultant slurry was roughly 0.172 g / mL for a total yield of approximately 860 g of powder within the 5L of slurry. These particles were used as seeds on which to precipitate a transition metal carbonate material from a reaction mixture in which a precipitation reaction was taking place, using the following method. The equation mentioned in Example 18 below was used establish the mass of seeds required. A good start point was 86 g, as this was the content of a 500 mL bottle of pre-prepared slurry. The amount of seeds can be adjusted by adding or removing some of the slurry. An advantage of this method is that the starting heel containing any mass of seeds (up to 172g) dispersed in motherliquor could be prepared without the need for filtration / drying etc. With a pre-prepared heel the growth reaction was performed as follows: Solution A - 3.5M mixed transition metal sulphate Solution B - 3.5M Na2CCh solution. Solution C - 5.6wt% (3.217 M) ammonium hydroxide solution. A 5000 mL stirred tank reactor was filled with 500 mL of pre-prepared heel containing the desired mass of seeds dispersed in motherliquor from a previous reaction (see above). The heel was heated up to 55 °C and stirred at 500 rpm with a 90 mm PBT impeller. pH should be at 7.5. Once the temperature of the heel was stabilised, coprecipitation is starting by adding Solution A The pH was controlled to pH 7.5 by the addition of Solution B. The particle size distribution of the formed precipitate was measured regularly throughout the precipitation and grew from reaction initiation onwards. After 23 hours the reactor was full, addition of feeds was stopped, the particle size (Dv50) depended on the quantity of seeds at the start of the reaction. The total yield was approximately 860g + starting mass of seeds, of powder within the 5L of slurry. Details of the reaction and results are set out in Table 21: Table 21 Reaction (MnNiCo) seeds total mass / g Precursor final Dv50 / uni Precursor TAP density / g cm 3 13A 43 20.9 1.73 13B 86 17.5 1.70 13C 172 14.0 1.77 Example 18 - Comparison of final particle Dv50 with predicted Dv50 The following equation was formulated as a way to predict the final Dv50 particle size after precipitation based on the seed Dv50 particle size, along with other parameters of the precipitation reaction. Eq. 1 In Eq. 1: D50t = Dv50 at time t D5Oo = Dv50 of seed particles (i.e. at time 0) t = reaction time in minutes = transition metal solution feed rate in g / min p= crystal density of the particles in g / cm3 q = reaction atom economy (with respect to metal feed) n = number of seed particles p (the crystal density of the particles) could not be directly measured, so was estimated by dividing the TAP density by the average packing efficiency (0.635) of spheres. The number of particles n was calculated by [(mass of seeds) / (particle density) / (seed 5 volume)]. Table 22 summarises the results of the various reactions performed along with the actual Dv50 of the final particles and the Dv50 predicted according to the model established by Eq. 1. Table 22 Reaction Seed Dv50 / inn Seeds total mass / g Precursor final Dv50 / uni Eq. 1 predicted Dv50 for precursor / uni Standard deviation 9A 3.1 15 7.1 5.6 1.06 9B 3.1 30 6.5 4.7 1.27 9C 3.1 45 5.1 4.4 0.49 10A 2.5 5 8.5 6.3 1.55 10B 2.5 15 7.4 4.6 1.98 10C 2.5 30 6.7 3.9 1.98 10D 2.5 45 5.0 3.6 0.99 HA 1.6 5 8.4 4.1 3.04 11B 1.6 15 6.2 3.0 2.26 11C 1.6 30 4.8 2.6 1.55 HD 1.6 45 3.6 2.4 0.85 13A 8.7 43* 20.9 22.14 0.88 13B 8.7 86* 17.5 17.90 0.28 13C 8.7 172* 14.0 14.70 0.49 * Mass estimated from volume of seeds From Table 22 it is evident that the reliability of the Eq. 1 model in predicting ultimate particle size is higher for larger initial seed particle size (for example greater than 3 pm, or greater than 5 pm). Thus by using seeds having such sizes, the final Dv50 of the precursor may be accurately predicted and controlled to within a tight tolerance. Without wishing to be bound by theory, smaller seed particles may be more vulnerable to agglomeration effects leading to greater inaccuracy in predicting the final precursor Dv50 after precipitation. Example 19 - Electrochemical testing The precursor made in Reaction 11A (Example 13) was calcined to prepare an electrochemically active oxide material, and was tested to determine its electrochemical properties, alongside an analogous material made in exactly the same way except without the presence of any seed particles in the reactor at the start of the precipitation reaction. Coin cells were made containing the electrochemically active oxide material and the comparative electrochemically active oxide material, and cycled at C / 10. The results are shown in Figure 24, with the product from the seeded precipitation giving rise to the traces marked “B” and the product from the non-seeded precipitation giving rise to the traces marked “A”. Improved electrochemical performance is evident for the electrochemically active oxide material prepared from the Example 13 precursor - the discharge capacity is higher (around 260-270 mAh g'1) than that of the comparative material made from a precursor manufactured without seeds (around 240-250 mAh g'1). To determine whether such improvements in electrochemical performance would also be present for materials prepared from large seeds, the same test was performed on an electrochemically active oxide material which was prepared by calcining the precursor made in Reaction 13 A (Example 17), and an analogous material made in exactly the same way except without the presence of any seed particles in the reactor at the start of the precipitation reaction. The results are shown in Figure 25. Improved electrochemical performance is evident for the electrochemically active oxide material prepared from the Example 17 precursor (traces marked with line “B” in Figure 25) - the discharge capacity is higher (around 270-280 mAh ) than that of the comparative material made from a precursor manufactured 5 without seeds (traces marked with line “A” in Figure 25, around 260-270 mAh g'1).

Claims

1. A method of manufacturing a particulate transition metal carbonate material, the method comprising:mixing a transition metal precursor salt with a second salt in a liquid vehicle, wherein the second salt is selected from one or more of a carbonate salt and a bicarbonate salt; andcarrying out a precipitation reaction to form a slurry of the particulate transition metal carbonate material in the liquid vehicle;wherein the particulate transition metal carbonate particulate material has a volumetric median particle diameter (Dv50) of from 0.2 to 10.0 pm.

2. The method according to claim 1, wherein the transition metal precursor salt comprises or consists of a transition metal sulfate salt.

3. The method according to claim 1 or 2, wherein the second salt has a solubility in water of at least 90 g / L at 20 °C.

4. The method according to any one of the preceding claims, wherein the second salt comprises or consists of ammonium bicarbonate.

5. The method according to any one of the preceding claims, wherein the precipitation reaction is performed at a temperature within the range 15 to 50 °C.

6. The method according to any one of the preceding claims, wherein the liquid vehicle is water, and the transition metal precursor salt and the second salt are dissolved in the water before the precipitation reaction.

7. The method according to any one of the preceding claims, wherein the molar ratio of the second salt to the transition metal precursor salt is from 4:1 to 80:1.

8. The method according to any one of the preceding claims, comprisingpreparing a first solution of the one or more transition metal precursor salts in water, wherein the total concentration of the one or more transition metal precursor salts in the first solution is from 1.0 M to 3.5 M;preparing a second solution of the second salt in water, wherein the total concentration of the second salt in the second solution is from 2.0 M to 4.0 M;and combining the first solution with the second solution at a molar ratio of first: second solutions of from 1:4 to 1:20 to initiate the precipitation reaction.

9. The method according to any one of the preceding claims, wherein the transition metal precursor salt consists of a single transition metal salt species.

10. The method according to any one of the preceding claims, wherein the transition metal precursor salt comprises or consists of one or more of a manganese salt, a nickel salt, a cobalt salt and an iron salt.

11. The method according to any one of the preceding claims, wherein the transition metal precursor salt consists of a manganese salt.

12. The method according to any one of the preceding claims, wherein the particulate transition metal carbonate material has one or more of:(a) a volumetric median particle diameter (Dv50) of from 0.5 to 3.5 pm, for example from 1.6 to 3 pm; and(b) a circularity of at least 50 %.

13. The method according to any one of the preceding claims, wherein the particulate transition metal carbonate material comprises less than 10 wt% agglomerates, based on the total weight of particulate transition metal carbonate material.

14. The method according to any one of the preceding claims, wherein the precipitation reaction is carried out under sonication at ultrasound frequencies, or under stirring.

15. The method according to claim 14, wherein the precipitation reaction under sonication is caried out for a period of from 2 to 30 minutes, optionally 2 to 10 minutes.

16. The method according to claim 14 or 15, wherein the precipitation reaction under sonication is performed at a temperature within the range 15 to 30 °C, optionally 20 to 25 °C.

17. The method according to any one of claims 14 to 16, wherein the precipitation reaction under sonication is performed within a round-bottom reaction vessel.

18. The method according to any one of the preceding claims, further comprising isolating the particulate transition metal carbonate material from the reaction mixture after precipitation, for example by filtering and optionally washing the particulate transition metal carbonate material.

19. The method according to any one of the preceding claims, wherein the method comprises tuning the volumetric median particle diameter (Dv50) of the particulate transition metal carbonate material by controlling one or more of:(a) the number of different transition metal element species within the transition metal precursor salt; and(b) the molar ratio of the second salt to the transition metal precursor salt in the liquid vehicle.

20. A particulate transition metal carbonate material for use as seed particles during a precipitation reaction, obtained or obtainable by a method according to any one of claims 1 to 19.

21. A method of precipitating a transition metal carbonate material onto seed particles, the method comprising:providing a slurry of transition metal carbonate seed particles manufactured by a method according to any one of claims 1 to 19; andperforming a precipitation reaction within the slurry such that a precipitate of transition metal carbonate material is deposited and builds up on the surface of the seed particles.5 22. A particulate transition metal carbonate material obtained or obtainable by themethod according to claim 21;wherein particles of the material comprise a core-shell structure comprising a core region derived from a particulate transition metal carbonate seed particle manufactured by a method according to any one of claims 1 to 19, and a shell region derived from a layer of 10 transition metal carbonate precipitate deposited onto the core region by precipitation onto the seed particle.

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