Methods of preparing a composition

Abstract

A method of preparing a composition having the general formula AX where A = LieMf[c]d; [c] is a cation vacancy; M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof; 0

Description

B ACKGROUND Many currently available batteries use a lithium-containing composition in the electrodes, and as a consequence are known as lithium-ion batteries. Mechanochemistry relates to the use of mechanical energy to promote chemical reactions. Ball milling is a technique used in mechanochemistry. Lithium-containing compositions can be prepared by mechanochemical methods involving ball milling. SUMMARY According to a first aspect of the present invention, there is provided a method of preparing a composition, wherein the composition has the general formula: AX wherein: A = LieMf[c]d; [c] is a cation vacancy; M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof; 0 <d <0.5; 0 <e <1; 0 <f <1; and the sum of d, e and f is 1; and wherein: X = OpSqFiClk[a]m; [a] is an anion vacancy; 0<p<l;0<q<l;0<l<l;0<k<l;0<m< 0.5; and the sum of p, q, 1, k and m is 1; and wherein the method comprises: (a) (i) providing a precursor mixture comprising Li and M; wherein Li and M are provided in the form of at least one salt precursor selected from: lithium salt precursors, metal salt precursors, mixed metal salt precursors, phosphorus salt precursors and metalloid salt precursors; and (ii) providing at least one polar aprotic solvent; (b) ball milling the at least one polar aprotic solvent and the precursor mixture for a period of time. In some embodiments, the at least one metal salt precursor comprises one or more salts of Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, and / or Sn. In some embodiments, the at least one mixed metal salt precursor comprises two or more of Li, Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb and / or Sn. In some embodiments, the at least one metalloid salt precursor comprises Si and / or B. In some embodiments of the first aspect, the salt of the at least one lithium salt precursor, the at least one metal salt precursor, the at least one mixed metal salt precursor, the at least one phosphorus salt precursor and / or the at least one metalloid salt precursor is or comprises an oxide, a sulfide, a fluoride or a chloride. The metal of the at least one metal salt precursor and the at least one mixed metal salt precursor may be the same or different in each of the precursors. The salt of the at least one lithium salt precursor, the at least one metal salt precursor, the at least one mixed metal salt precursor, the at least one phosphorus salt precursor, the at least one silicon salt precursor and / or the at least one boron salt precursor may be the same or different in each of the precursors. In some embodiments of the first aspect, the method further comprises heating the precursor mixture provided at (a)(i) prior to providing the at least one polar aprotic solvent at (a)(ii). In such embodiments, the method of the first aspect comprises: (a) (i) providing a precursor mixture comprising Li and M; wherein Li and M are provided in the form of at least one salt precursor selected from: lithium salt precursors, metal salt precursors, mixed metal salt precursors, phosphorus salt precursors and metalloid salt precursors; heating the precursor mixture; and (ii) providing at least one polar aprotic solvent; (b) ball milling the at least one polar aprotic solvent and the precursor mixture for a period of time. In some embodiments of the first aspect, (i) at least one salt precursor is or comprises an oxide; and / or (ii) the method comprises delithiating the composition. When the method j comprises delithiation, 0 <e <1. Delithiation may be achieved by any method known in the art. In some embodiments, the method involves delithiation until the composition prepared has e = 0 i.e. complete delithiation may be achieved in some embodiments. In such embodiments, the space previously occupied by lithium cations may be cation vacancies, [c]. In some embodiments of the first aspect, M is Mn; 0 <e <0.65; and 0 <f <0.5. In some such embodiments, the composition can be expressed as the general formula: (y)LiMnO2.(l-y)Li2MnO3, wherein 0 <y <1. In such embodiments, the at least one mixed metal precursor comprises two mixed metal precursors. The mixed metal precursors are lithium manganese oxide precursors, LiMnO2 and Li2MnO3. These two mixed metal precursors are provided at step (a) of the method according to the first aspect in the proportions defined by y. In some embodiments of the first aspect, Li and M are provided in the form of precursors selected from: at least one lithium salt, at least one manganese salt, and at least one lithium-manganese mixed metal salt. In some such embodiments, the precursor mixture comprises Li2O and at least one of MmCh and Mn02, or the precursor mixture comprises LiMnO2 and Li2MnCh. According to a second aspect of the present invention, there is provided a method comprising: (a) providing at least one polar aprotic solvent; and providing a precursor mixture comprising or consisting of a precursor having the general formula AX; wherein: A = LieMf[c]d; [c] is a cation vacancy; M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof; 0 <d <0.5; 0 <e <1; 0 <f <1; and the sum of d, e and f is 1; and wherein: X = OPSqFiClk[a]m; [a] is an anion vacancy; 0<p<l;0<q<l;0<l<l;0<k<l;0<m< 0.5; and the sum of p, q, 1, k and m is 1; and wherein the precursor has a structure other than disordered rock salt structure and the composition has the same general formula as the precursor; and (b) ball milling the at least one polar aprotic solvent and the precursor mixture for a period of time. A solvent-free ball milling method analogous to the methods of the first and second aspects, but which does not include the step of providing at least one polar aprotic solvent at (a), can be used to prepare the same compositions as prepared in the first and second aspects disclosed herein. However, one common issue with this solvent-free method from the prior art is that the precursors (usually in powder form) can aggregate in a solid, compact mass, during ball milling. This process is also known as “caking”. When left unchecked, the caking of the precursors slows down or completely stops the reaction. One solution to this problem is to pause the ball milling and manually re-homogenise the precursors. This process is long, tedious and significantly slows down the synthesis process. In a typical solvent-free synthesis, re-homogenisation may need to be repeated after every 10 hours or so of ball milling. Each time, the sample has to be removed from the ball mill and manually re-homogenised before the ball milling can be restarted. As the total timeperiod required to obtain the desired composition is typically longer than 10 hours, manual re-homogenisation is required to achieve complete conversion of the precursors. The inventors have found that including at least one polar aprotic solvent at (a) of the method of the first and second aspects reduces or prevents caking. This means that a successful synthesis can be achieved in a single continuous ball milling cycle, without the need for re-homogenisation. This reduces the amount of user input required after starting the ball milling process. It may also reduce the overall time elapsed between starting ball milling at (b) and obtaining the composition. These mechanochemical syntheses require very high energy input. Providing additional components at step (a) of the method (such as a solvent) was expected to reduce the impact energy to the precursors in comparison to a solvent free method. Additionally, significant chemical interactions were expected to occur between the solvent and the salt precursors that would be detrimental to reaction of the precursors and / or formation of the final material. Therefore, achieving a successful synthesis with solvent present was an unexpected and surprising result. Without wishing to be bound by theory, the inventors hypothesised that, in the method disclosed herein, the polar aprotic nature of the solvent employed could be important in minimising such detrimental chemical interactions. Again, without wishing to be bound by theory, the inventors hypothesise that a polar solvent has a strong interaction with anionic species present on the particle surfaces, resulting in an effective “coating” of solvent on the particle surface during milling, reducing the occurrence of the fusing processes that ultimately lead to caking. Tn some embodiments of the first or the second aspect, M is Ti, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof. In some embodiments of the first or the second aspect, (i) k = 0; and / or (ii) p and / or q >0; and / or (iii) p >0; and / or (iv) 1 >0. When k = 0, the composition does not comprise Cl. When p and / or q >0, the composition comprises O and / or S. When p >0, the composition comprises O. When 1 >0, the composition comprises F. In some embodiments of the first or the second aspect, (i) 0 <e <1; and / or (ii) d and / or m = 0. In some embodiments of the first or the second aspect, M is Mn; 0 <e <0.65; 0 <f <0.5. In some such embodiments, M is Mn; e = 0.5+x and f = 0.5-x; and 0 <x <0.15. In some embodiments, q, 1 and k = 0. In such embodiments, the composition does not comprise S, F or Cl. In some embodiments, d and / or m = 0. In such embodiments, the composition does not comprise any cation vacancies and / or does not comprise any anion vacancies. In some embodiments, p >0 and optionally p = 1. In such embodiments, the composition comprises an oxide or is an oxide. In some embodiments of the first or the second aspect, the composition has a disordered rock salt (DRS) structure. In some embodiments, the method of the second aspect may be used to transform a precursor having a structure other than a disordered rock salt structure into a composition having a disordered rock salt structure. In some embodiments, the structure other than a disordered rock salt structure is a layered structure. In some embodiments of the first or the second aspect, the composition predominantly comprises a single phase. In some embodiments of the first or the second aspect, an X-ray diffraction pattern of the composition using a CuKa radiation source has a peak at a 29 value of at least one of, and optionally each of, (a) to (c): (a) 36.6° ± 2.0° (b) 43.0° ±2.0° (c) 61.8° ±2.0°. In some embodiments of the first or the second aspect, the period of time in (b) is 1 hour to 300 hours. The period of time for ball milling in the methods according to the first and second aspects corresponds to the total synthesis time, as there is no time spent rehomogenising the sample. In comparison, in a solvent-free method, the total synthesis time will include the time period for ball milling and additional time spent re-homogenising the sample between ball milling cycles. In some embodiments of the first or the second aspect, (i) 0 <e <1 and / or (ii) d and / or m = 0. When 0 <e <1, the composition comprises lithium. When d and / or m = 0, the composition does not comprise any cation vacancies and / or the composition does not comprise any anion vacancies. When d = 0, the composition does not comprise any cation vacancies. When m = 0, the composition does not comprise any anion vacancies In some embodiments of the first or the second aspect, the at least one polar aprotic solvent has a viscosity greater than or equal to 1 mPa.s (1 cp) at 25 °C. 1 mPa.s is equivalent to 1 cp. In some embodiments of the first or the second aspect, the method comprises separating the at least one polar aprotic solvent from the composition after ball milling. In some embodiments of the first or the second aspect, the at least one polar aprotic solvent comprises a polar aprotic organic solvent and / or a polar aprotic ionic liquid. In some such embodiments of the first or the second aspect, the polar aprotic organic solvent comprises one or more of: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, a phosphoester or a silyl ether. In some embodiments: the lactone is y-valerolactone and / or 8-valerolactone; and / or the sulfoxide is di methyl sulfoxi de (DMSO); and / or the sulfone is sulfolane; and / or the nitrile is benzonitrile; and / or the nitrate is nitrobenzene; and / or the cyanate is phenyl isocyanate; and / or the sulfonate ester is ethyl methanesulfonate; and / or the thiocyanate is phenyl isothiocyanate; and / or the phosphine is tributyl phosphene; and / or the phosphoester is trimethylphosphate; and / or the silyl ether is tetraethylorthosilicate. In some embodiments of the first or the second aspect, the polar aprotic organic solvent comprises one or more of: a lactone or a sulfoxide. In some such embodiments, the lactone is 5-valerolactone and / or the sulfoxide is DMSO. In some embodiments of the first or the second aspect, the polar aprotic ionic liquid comprises one or more of: an ammonium ionic liquid or phosphonium ionic liquid. In some embodiments of the first or the second aspect, the at least one polar aprotic solvent is provided in an amount from 0.5 ml to 2.5 ml for every 16 g of the precursor mixture provided at (a). In such embodiments, only a small amount of solvent is required relative to the amount of solid precursor. The inventors were surprised to find that such a small amount of solvent was sufficient prevent caking. According to a third aspect of the present invention, there is provided a composition obtainable by the method according to the first or the second aspect. Such compositions are useful as materials to be used in electrodes, electrochemical cells and electrochemical energy storage devices. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a powder XRD pattern of a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was dimethylsulfoxide (DMSO). Figure 2 is a scanning electron microscope (SEM) of a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was dimethylsulfoxide (DMSO). Figure 3 shows the results of galvanostatic testing between 4.8 - 2.0 V at 30°C carried out on half cells comprising a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was dimethyl sulfoxide (DMSO). Figure 4 is a powder XRD pattern of a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was 8-valerolactone (D VL). Figure 5 is a scanning electron microscope (SEM) of a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was 6-valerolactone (DVL). Figure 6 shows the results of galvanostatic testing between 4.8 - 2.0 V at 30°C carried out on half cells comprising a composition having a target formula Li1.1Mno.9O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was 6-valerolactone (DVL). Figure 7 is a powder XRD pattern of a composition having a target formula Li1.1Mno.7Tio.2O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was dimethylsulfoxide (DMSO). Figure 8 is a scanning electron microscope (SEM) of a composition having a target formula Li1.1Mno.7Tio.2O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was di methyl sulfoxi de (DMSO). Figure 9 shows the results of galvanostatic testing between 4.8 - 2.0 V at 30°C carried out on half cells comprising a composition having a target formula Li1.1Mno.7Tio.2O2. The composition was obtained by the method according to the first aspect disclosed herein and the polar aprotic solvent was dimethyl sulfoxide (DMSO). DETAILED DESCRIPTION Methods described herein usually employ ambient temperature of a typical laboratory, which is typically between 20 and 30°C, such as around 25°C, at atmospheric pressure, unless a different condition is defined herein or is more usually employed e g. for a particular apparatus. The methods of the first and second aspect may be described as mechanochemical synthesis methods because they use a mechanical method to cause a chemical reaction. The methods use a ball milling process to achieve the mechanochemical synthesis, and not only a mechanical mixing of precursors. Unless indicated otherwise, “%” refers to “weight %”. Similarly, “wt%” denotes “weight%”. Composition The first and second aspect provide methods of preparing a composition having the general formula AX. The following description of the composition applies equally to compositions obtainable by either of the first and second aspects. The composition may be described in terms of various different chemical and physical properties. The chemical structure of the composition may be described in terms of the general formula, AX. In some examples, the composition may additionally be described, for example, in terms of its crystal structure. In other words, the composition has a chemical formula given by the general formula AX and, in some embodiments, the composition may also have a particular crystal structure, such as a disordered rock salt structure. In the general formula AX, A is LieMf[c]d, wherein 0 <d <0.5; 0<e<l;0<f<l; and the sum of d, e and f is 1. As such, comprises M, wherein M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof. In some embodiments, M is Ti, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof. In some embodiments of the first or the second aspect, M is a transition metal selected from Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Nb or a combination thereof. In some embodiments of the first or the second aspect, M is a transition metal selected from Ti, Cr, Mn, Co, Ni, Mo, W, Nb or a combination thereof. In some embodiments, M is Mn. In some embodiments, M is a combination of metals. In some such embodiments, M is two or more selected from Mn, Ti, V and Fe. In some embodiments, M is Mn and Ti, or M is V and Fe. In some embodiments, A further comprises Li and / or cation vacancies [c]. In some embodiments, A comprises M and Li, and d=0. In such embodiments, the composition has no cation vacancies. In some embodiments, A comprises M and [c], and e=0. In such embodiments, the composition does not comprise Li. At its broadest, the method of the first aspect can be used to prepare compositions wherein 0 <e <1. As will be discussed later, in order to make a composition with e=0 by the method according to the first aspect, the method must further comprise delithiation. In contrast, the method according to the second aspect may be used to prepare compositions wherein 0 <e <1 without the need for delithiation. In some embodiments, A comprises M, Li and [c]. In such embodiments, the composition comprises M, Li and cation vacancies. In some embodiments, compositions of the first aspect may contain up to 20% [c] and / or up to 20% [a]. In some embodiments, such compositions may retain their original structure. In some embodiments, compositions of the first aspect may contain up to 18% [c], such as up to 15% [c], up to 12% [c] or up to 10% [c]. In some embodiments, compositions of the first aspect may contain up to 18% [a], such as up to 15% [a], up to 12% [a] or up to 10% [a]. In some embodiments, compositions of the first aspect may any combination of these ranges, for example up to 20% [a] and up to 10% [c], up to 10% [a] and up to 20% [c], up to 15% [a] and up to 15 [c], up to 12% [a] and up to 18% [c], or up to 10% [a] and up to 10% [c]. In some embodiments, e = 0. In some embodiments, e >0, such as 0.005 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.05 or more, 0.075 or more, 0.1 or more, 0.13 or more, or 0.15 or more such as 1 / 3 or more. In some embodiments, e is 0.25 or more, such as 0.27 or more, 0.3 or more, 0.33 or more, or 0.35 or more. In some embodiments, e is 2 / 3 or less, such as 0.65 or less, 0.63 or less, 0.6 or less, or 0.57 or less. Combinations of any of these values may be used to provide exemplary ranges for e. For example, e may be in the range of 0 <e <2 / 3, or 0 <e <0.63, or 0.005 <e <2 / 3, or 0.01 <e <0.63, or 0.015 <e <0.6, or 0.02 <e <0.65, or 0.025 <e <0.065, or 0.05 <e <0.6, or 0.075 <e <0.65, or 0.1 <e <0.63, or 0.13 <e <0.65, or 0.15 <e <0.63, or 0.25 <e <0.57, or 0.27 <e <0.65, or 0.3 <e <0.6, or 0.33 <e <0.65, or 0.35 <e <0.57. In some embodiments, 0.05 <e <2 / 3. In some embodiments, 0.25 <e <2 / 3. In some embodiments, 0.25 <e <0.6. In some embodiments, f =1. In some embodiments, f <1, such as 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.9 or less, 0.88 or less, or 0.85 or less. In some embodiments, f is 0.75 or less, such as 0.73 or less, 0.7 or less, 0.68 or less, or 0.65 or less. In some embodiments, f is 1 / 3 or more, such as 0.35 or more, 0.38 or more, 0.4 or more, or 0.43 or more. Combinations of any of these values may be used to provide exemplary ranges for f. For example, f may be in the range of 1 / 3 <f <1, or 1 / 3 <f <1, or 1 / 3 <f <0.99, or 1 / 3 <f <0.98, or 0.35 <f <1, or 0.35 <f< 0.97, or 0.35 <f< 0.96, or 0.38 <f <0.96, or 0.38 <f <0.95, or 0.38 <f <0.93, or 0.4 <f <1, 0.4 <f <0.95, 0.4 <f <0.9, 0.4 <f <0.88, 0.4 <f <0.85, 0.43 <f <1, or 0.43 <f <0.85, or 0.43 <f <0.75, or 1 / 3 <f <0.75, or 0.4 <f <0.73, or 1 / 3 <f <0.7, or 1 / 3 <f <0.68, or 0.38 <f <0.68, or 0.43 <f <0.68. In some embodiments, 1 / 3 <f <0.95. In some embodiments, 1 / 3 <f <0.75. In some embodiments, 0.4 <f <0.75. In some embodiments, the composition of the first aspect comprises a cation vacancy. In some embodiments, d = 0. Such embodiments do not have any cation vacancy. In some embodiments, d >0, such as at least 0.01, at least 0.02, at least 0.03, at least 0.04, at least 0.05, or at least 0.08. In some embodiments, d = 0.5. In some embodiments, d <0.5, such as up to 0.48, up to 0.45, up to 0.43 or up to 0.4. Combinations of any of these end-points may be combined to form a suitable range, such as 0 <d <0.5, 0 <d <0.5, 0 <d <0.5, 0.01 <d <0.48, 0.02 <d <0.45, 0.02 <d <0.43, 0.03 <d <0.43, 0.05 <d <0.48, 0.08 <d <0.45, or 0.08 <d <0.4. In the general formula AX, X is OPSqFiClk[a]m, wherein 0<p<l;0<q<l;0<l<l;0< k <1; 0 <m <0.5; and the sum of p, q, 1, k and m is 1. As such, X comprises at least one of O, S, F and Cl. Optionally, X comprises [a]. In some embodiments, X comprises O and / or F. In some embodiments, X comprises O. In some embodiments, X comprises O and does not comprise S, F or Cl. In some embodiments, X consists of O, or X consists of O and [a]. In some embodiments, X comprises O and F. In some embodiments, X comprises O and F, and does not comprise S, or Cl. In some embodiments, X consists of O and F, or X consists of O, F and [a]. In some embodiments, X consists of O and optionally [a]. In some embodiments, X consists of S and optionally [a]. In some embodiments, X consists of F and optionally [a]. In some embodiments, X consists of Cl and optionally [a]. In some embodiments, X consists of O and S and optionally [a]. In some embodiments, X consists of O and F and optionally [a]. In some embodiments, X consists of O and Cl and optionally [a]. In some embodiments, X consists of S and F and optionally [a]. In some embodiments, X consists of S and Cl and optionally [a]. In some embodiments, X consists of O, S and F and optionally [a]. In some embodiments, X consists of O, S and Cl and optionally [a]. In some embodiments, p = 0. In some embodiments, p >0, such as at least 0.01, at least 0.05, at least 0.1, at least 0.2 or at least 0.3. In some embodiments, p is 1. In some embodiments, p <1, such as 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, or 0.95 or less. Combinations of these end-points may be combined to form any suitable range. For example, 0<p<l, orO<p< 0.99, or 0.01 <p <0.99, or 0.05 <p <0.99, or 0.1 <p <0.98, or 0.2 <p <0.98, or 0.3 <p <0.95. In some embodiments, q = 0. In some embodiments, q >0 such as at least 0.01, at least 0.02, at least 0.03, at least 0.04 or at least 0.05. In some embodiments, q is 1. In some embodiments, q <1, such as 0.9 or less, 0.5 or less, 0.4 or less, 0.2 or less, or 0.1 or less. Combinations of these end-points may be combined to form any suitable range. For example, 0<q<l,or0<q< 0.9, or 0.01 <q <0.5, or 0.02 <q <0.4, or 0.03 <q <0.5, or 0.04 <q <0.2, or 0.05 <q <0.1. In some embodiments, 1 = 0. In some embodiments, 1 >0, such as at least 0.01, at least 0.02, at least 0.03, at least 0.04 or at least 0.05. In some embodiments, 1 is 1. In some embodiments, 1 <1, such as 0.9 or less, 0.5 or less, 0.4 or less, 0.2 or less, or 0.1 or less. Combinations of these end-points may be combined to form any suitable range. For example, 0 <1 <1, or 0 <1 <0.9, or 0.01 <1 <0.5, or 0.02 <1 <0.4, or 0.03 <1 <0.5, or 0.04 <1 <0.2, or 0.05 <1 <0.1. In some embodiments, k = 0. In some embodiments, k >0, such as at least 0.01, at least 0.02, at least 0.03, at least 0.04 or at least 0.05. In some embodiments, k is 1. In some embodiments, k <1, such as 0.9 or less, 0.5 or less, 0.4 or less, 0.2 or less, or 0.1 or less. Combinations of these end-points may be combined to form any suitable range. For example, 0<k<l,or0<k< 0.9, or 0.01 <k <0.5, or 0.02 <k <0.4, or 0.03 <k <0.5, or 0.04 <k< 0.2. or 0.05 <k <0.1. In some embodiments, the composition of the first aspect comprises an anion vacancy [a]. In some embodiments, m = 0. Such embodiments do not have any anion vacancy. In some embodiments, m >0, such as at least 0.01, at least 0.02, at least 0.03, at least 0.04, at least 0.05, or at least 0.08. In some embodiments, m = 0.5. In some embodiments, m <0.5, such as up to 0.48, up to 0.45, up to 0.43 or up to 0.4. Combinations of any of these end-points may be combined to form a suitable range, such as 0 <m <0.5, 0 <m <0.5, 0 <m <0.5, 0.01 <m <0.48, 0.02 <m <0.45, 0.02 <m <0.43, 0.03 <m <0.43, 0.05 <m <0.48, 0.08 <m <0.45, or 0.08 <m <0.4. In some embodiments, M is Mn; 0 <e <0.65; 0 <f <0.5; and 0 <d <0.5. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; 0.35 <e <0.65; 0.20 <f <0.50; and 0 <d <0.15. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; 0.40 <e <0.65; 0.25 <f <0.50; and 0 <d <0.10. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; 0.45 <e <0.65; 0.30 <f <0.50; and 0 <d <0.05. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; 0.5 <e <0.65; 0.35 <f <0.50; and d = 0. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; e = 0.55; f = 0.45; and d = 0. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; e = 0.55; f = 0.45; d = 0; and p = 1. In some embodiments, M is Mn. In some embodiments, M is Mn, e = 0.5+x and f = 0.5-x; wherein 0 <x <0.15. In such embodiments, A is (assuming no cation vacancies) Lio.5+xMno.5-x, wherein 0 <x <0.15. In some embodiments, 0.05 <x <0.15, or 0.085 <x <0.15, or 0.10 <x <0.15. In some embodiments, q, 1 and k = 0. In such embodiments, A is (assuming no cation vacancies) Lio.5+xMno.5-x, wherein 0 <x <0.15 and X does not comprise S, F or Cl. In some embodiments, p >0. In such embodiments, Ais (assuming no cation vacancies) Lio.s+xMno.s-x, wherein 0 <x <0.15 and X comprises an oxide. In some embodiments, p = 1. In such embodiments, X consists of an oxide and the composition may be written as follows (assuming no cation and anion vacancies): Lio.? xMno.s-xO, wherein 0 <x <0.15. In some embodiments, the composition has the general formula Lio.55Mno.45X, or Lio.6Mno.4X, or Lio.65Mno.35X. In some embodiments, the composition has the general formula Lio.55Mno.45O, or Lio.6Mno.4O, or Lio.65Mno.35O. In some embodiments, M is a combination of two metals, Ml and M2. The ratio of Ml :M2 in M can be any suitable ratio. In some embodiments, M is MlfiM2f2, wherein fl + 12 = f and M comprises no metals other than Ml and M2. The ratio of Ml to M2 may be expressed relative to f, for example by the value fl / f or the value f2 / f. For example, if the ratio of Ml to M2 in M is 1:1, fl / f = 0.5 and f2 / f = 0.5. If the ratio of Ml to M2 in M is 3:1, fl / f = 0.75 and f2 / f = 0.25. In some embodiments, 0.05 <fl / f <0.95, or 0.1 <fl / f <0.95; or 0.2 <fl / f <0.95; or 0.4 <fl / f <0.95; or 0.6 <fl / f <0.95. In some embodiments, 0.05 <f2 / f <0.95, or 0.1 <f2 / f <0.95; or 0.2 <f2 / f <0.95; or 0.4 <f2 / f <0.95; or 0.6 <f2 / f <0.95. In some embodiments, 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is a combination of Mn and Ti. The ratio of Mn:Ti in M can be any suitable ratio. In some embodiments, M is MnnTic, wherein fl + f2 = f and M comprises no metals other than Mn and Ti. The ratio of Mn to Ti may be expressed relative to f, for example by the value fl / f or the value f2 / f. For example, if the ratio of Mn to Ti in M is 1:1, fl / f = 0.5 and f2 / f = 0.5. If the ratio of Mn to Ti in M is 3:1, fl / f = 0.75 and f2 / f = 0.25. In some embodiments, 0.05 <fl / f <0.95, or 0.1 <fl / f <0.95; or 0.2 <fl / f <0.95; or 0.4 <fl / f <0.95; or 0.6 <fl / f <0.95. In some embodiments, 0.05 <f2 / f <0.95, or 0.1 <f2 / f <0.95; or 0.2 <f2 / f <0.95; or 0.4 <f2 / f <0.95; or 0.6 <f2 / f <0.95. In some embodiments, 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; 0 <e <0.65; 0 <f <0.5; and 0 <d <0.5. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; 0.35 <e <0.65; 0.20 <f <0.50; and 0 <d <0.15. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; 0.40 <e <0.65; 0.25 <f <0.50; and 0 <d <0.10. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; 0.45 <e <0.65; 0.30 <f <0.50; and 0 <d <0.05. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; 0.5 <e <0.65; 0.35 <f <0.50; and d = 0. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn and Ti; e = 0.55; f = 0.45; and d = 0. In some such embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, M is Mn; e = 0.55; f = 0.45; d = 0; and p = 1. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, M is Mn; e = 0.55; f = 0.45; d = 0; p = 1 and the ratio of Mn to Ti in M is 0.7:0.2. This ratio corresponds to fl / f = 0.78 (and f2 / f = 0.22). In such embodiments, the composition has the general formula Li1.1Mno.7Tio.2O2. In some embodiments, M is Mn and Ti, and p >0. In some embodiments, M is Mn and Ti, p >0, e = 0.5+x and f = 0.5-x; wherein 0 <x <0.15. In such embodiments, X comprises O and A is (assuming no cation vacancies) Lio.5+xMno.5-x, wherein 0 <x <0.15 and M is a combination of Mn and Ti. In some such embodiments, 0.5 <fl / f <0.95; 0.6 <fl / f <0.9, or 0.7 <fl / f <0.85. In some embodiments, q, 1 and k = 0. In such embodiments, X comprises O and optionally comprises [a]. In some embodiments, p >0.5, or p >0.7, or p >0.8, p >0.9, or p = 1. In some embodiments, the composition has the general formula (assuming no vacancies) Li1.1Mno.7Tio.2O2. In some embodiments, the composition has a face centred cubic (FCC) structure. In such embodiments, the composition has a space group Fm-3m. In some embodiments, the composition has a unit cell having a dimension (length) of at least a=b=c=4.10 A=0.41 nm, such as at least 0.411 nm (4.11 A), at least 0.412 nm (4.12 A), at least 0.415 nm (4.15 A), at least 0.420 nm (4.20 A), or at least 0.422 nm (4.22 A). In some embodiments, the composition has a unit cell dimension of no more than 0.435 nm (4.35 A), no more than 0.430 nm (4.30 A), no more than 0.429 nm (4.29 A), no more than 0.428 nm (4.28 A), no more than 0.420 nm (4.20 A), no more than 0.418 nm (4.18 A) or no more than 0.417 nm (4.17 A). Suitable combinations of these values may be used to provide exemplary ranges. For example, in some embodiments, the composition has a unit cell dimension of between 0.415 nm (4.15 A) to 0.430 nm (4.30 A), or between 0.418 nm (4.18 A) to 0.428 nm (4.28 A). In these embodiments, a=3=Y=90°. A skilled person will appreciate that disordered rock salt structures have a cubic unit cell size (i.e. a=b=c and 01=3= / =90°). In some embodiments, any structural disorder will be averaged across the unit cell dimension. The crystalline structure of the compositions may be assessed using XRD techniques. Typically, the compositions of the present invention are in the form of a powder, rather than single crystals, and so the crystalline structure of the compositions may be assessed using powder XRD techniques. Accordingly, where X-ray diffraction or XRD is used herein, it may generally refer to powder X-ray diffraction or powder XRD. The XRD pattern may be measured on any suitable diffractometer. Suitable diffractometers are typically used in reflection geometry. Suitable diffractometers may use CuKa radiation, with an x-ray wavelength of 0.154056 nm (1.54056 A). Suitable diffractometers may operate at 40 kV and 40 mA. A measurement range may be 30-75° 20. Analysis may be performed by any suitable means, such as with appropriate software. For example, a suitable diffractometer may be an Aeris Benchtop X-ray diffractometer equipped with a PIXcel detector. Any suitable sample preparation method may be used. In some embodiments, the XRD pattern shows a signature of a cubic phase associated with peaks at indicated positions. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 26 value of 36.6° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 36.6° ± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 36.6° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 36.6° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 43.0° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 43.0° ± 10°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 43.0° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 43.0° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 61.8° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 61.8° ± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 61.8° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has a peak at a 20 value of 61.8° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 2.0° and 43.0° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 1.0° and 43.0°± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 0.5° and 43.0° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 29 value of 36.6° ± 0.4° and 43.0° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 2.0° and 61.8° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 1.0° and 61.8° ± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 29 value of 36.6° ± 0.5° and 61.8° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 0.4° and 61.8° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 43.0° ± 2.0° and 61.8° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 43.0° ±1.0° and 61.8° ± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 43.0° ± 0.5° and 61.8° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 43.0° ± 0.4° and 61.8° ± 0.4°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 2.0°, 43.0° ± 2.0°, and 61.8° ± 2.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 1.0°, 43.0° ± 1.0°, and 61.8° ± 1.0°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 0.5°, 43.0° ± 0.5°, and 61.8° ± 0.5°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has peaks at a 20 value of 36.6° ± 0.4°, 43.0° ± 0.4°, and 61.8° ±0.4°. By “± 2.0°” we mean that the peaks describing the XRD pattern may differ by up to 2.0° 20 from the values mentioned. In some embodiments, one or more of the peaks, such as all of the peaks, may differ by up to 1.0° 20. In some embodiments, one or two of the peaks, may differ by up to 0.5° 20 from the mentioned values. In some embodiments, one or two of the peaks, may differ by up to 0.4° 20 from the mentioned values. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has three peaks at 26 = 36.8°, 43.1° and 62.2°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has three peaks at 26 = 36.3°, 42.1° and 61.2°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has three peaks at 26 = 36.8°, 42.8° and 62.2°. In some embodiments, an XRD pattern of the composition using a CuKa radiation source has an absence of peaks below a 26 value of 30°. In some embodiments, the characteristic XRD pattern has an absence of peaks below a 26 value of 31°, or below a 26 value of 32°, or below a 26 value of 33°, or below a 26 value of 34°, or below a 26 value of 35°. In some embodiments, the characteristic XRD pattern is substantially similar to, or the same as, the XRD pattern shown in any of Figures 1, 4 and 7. In some embodiments, the peaks of the characteristic peak XRD pattern with the range 30 to 70° 26 can be indexed to the Miller indices (a) (111); (b) (200) and (c) (220). In some embodiments, the composition predominantly comprises a single phase. In some embodiments, the composition of the first aspect contains a single phase. In some embodiments, the composition of the first aspect consists of a single phase. The single phase may be a disordered rock salt structure. A composition predominantly comprising, containing, or consisting of, a single phase may be characterised by an absence of other crystalline phases, such as remaining precursor materials. The absence of other crystalline phases such as remaining precursors may be confirmed by the absence of peaks below 30° 26 in the powder XRD pattern. As such, a composition predominantly comprising, containing, or consisting of, a single phase may be characterised by a powder XRD pattern without any peaks below 30° 26. In some embodiments, the electrochemical properties of the material may be measured. Such measurements may be carried out in a non-aqueous electrolyte containing a Li salt with a Li metal counter / reference electrode. Application of a positive / negative current may be applied and the resulting changes in potential vs Li metal recorded. These measurements may be measured using a cell, such as a coin type cell, assembled in an area containing inert gas, such as argon. Galvanostatic tests may be performed on an appropriate machine, such as a MACCOR, at a desired current density and within a desired voltage range, at any desired temperature and suitable pressure. A suitable pressure may be 101 kPa. Electrodes may be prepared according to any suitable method, and counter electrodes and electrolytes chosen appropriately. These measurements may permit understanding of the electronic structure within the material as a function of the Li content. The resulting voltage vs charge plots may be thought of as correlating to a measurement of the Fermi level within a material as a function of the Li content. These measurements can be used to infer how this material may perform in a practical Li ion cell. First Aspect In some embodiments of the first aspect, when more than one precursor is used, the salt (i.e. O, S, F or Cl) may be the same or different among the precursors. In some embodiments, at least one salt is an oxide. In some embodiments, at least one salt is a sulfide. In some embodiments, at least one salt is fluoride. In some embodiments, at least one salt is a chloride. In the first aspect, a mixture of salt precursors is provided. In compositions obtainable by the first aspect, 0 <e <1 and 0 <f <1. As such, said compositions comprise Li and M. It will be understood that the mixture of precursors must also comprise Li and M. The mixture of precursors can comprise any suitable combination of salts selected from lithium salts, metal salts, mixed metal salts and metalloid salts. As used herein, “lithium salt” refers to a salt comprising lithium and no other metals. For example, a lithium salt such as Li2O. As used herein, “metal salt” refers to a salt containing only one metal selected from Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, and Sn. For example, MnO. As used herein, “mixed metal salt” refers to a salt comprising two or more metals selected from Li, Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, and Sn. For example, a salt comprising Co and Fe, such as CoFe2O4. As used herein, “metalloid salt” refers to a salt containing Si and / or B. For example, a silicon salt such as SiO2. Suitable sources of lithium are lithium salts and mixed metals salts, wherein one of the two or more metals in the mixed metal salt is lithium. Suitable sources of M are metal salts, mixed metals salts and metalloid salts. In some embodiments, the precursor mixture comprises at least one lithium salt precursor and at least one metal salt precursor. In some embodiments, the precursor mixture comprises at least one mixed metal salt precursor. In some embodiments, the at least one lithium salt precursor is at least one of LhO, Li2S, LiF and LiCl. In some such embodiments, the at least one lithium salt precursor is at least one of Li2O and LiF. In some such embodiments, the at least one lithium salt precursor consists of Li2O and LiF. In some embodiments, the at least one lithium salt precursors comprises Li:O In some embodiments, the at least one lithium salt precursors consists of Li2O In some embodiments, the at least one mixed metal salt precursor comprises at least one lithium-containing mixed metal salt. In some embodiments, the lithium-containing mixed metal salt is selected from LiMnO2, Li2MnO3, LiNiMnCoO2 and Li2MnO2F. In some embodiments, the lithium-containing mixed metal salt is selected from LiMnO2 and Li2MnOs. In some embodiments, the at least one mixed metal salt precursor comprises LiMnO2 and Li2MnO3. In some embodiments, the at least one mixed metal salt precursor consists of LiMnO2 and Li2MnO3. When M is Ti or M is a combination comprising Ti, the at least one metal salt precursor comprises at least one titanium salt precursor. In some embodiments, the at least one metal salt precursor comprises one or more titanium precursors selected from: TiO, Ti2O3, TiO2, TiS, Ti2S3, TiS2, TiF2, TiFs, TiF4, TiCk, TiCh and TiCL. In some embodiments, the at least one metal salt precursor comprises one or more titanium precursors selected from: TiO, Ti20s and TiO2. In some embodiments, M is Ti or M is a combination comprising Ti, and the precursors comprise Li2O and TisCh. In some embodiments, M is Ti and the precursors consist of Li2O and InCh. When M is V or M is a combination comprising V, the at least one metal salt precursor comprises at least one vanadium precursor. In some such embodiments, the at least one metal salt precursor comprises one or more vanadium precursors selected from: V2O3, V2O4, V2O5, V2S3, V2S4, V2S5, VF3, VF4, VFs, VCI3, VC14 and VCh. In some embodiments, the at least one metal salt precursor comprises one or more vanadium precursors selected from: V2O3, V2O4 and V2O5. When M is Fe or M is a combination comprising Fe, the at least one metal salt precursor comprises at least one iron salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more iron salt precursors selected from: FeO, Fe2O3, FeS, Fe2S3, FeF2, FeF3, FeCh and FeCh. In some embodiments, the at least one metal salt precursor comprises one or more iron salt precursors selected from: FeO and Fe?O3. When M is Mn or M is a combination comprising Mn, Mn may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more manganese salt precursors selected from: MnO, Mn2O3, MnO2, MnS, Mn2S3, MnS2, MnF2, MnF3 MnCh, and MnCl3. In some such embodiments, the at least one metal salt precursor comprises one or more manganese salt precursors selected from: MnO, Mn2O3 and MnO2. In some embodiments, M is Mn and the at least one metal salt precursor comprises MmOs and Mn02. In some embodiments, M is Mn, the lithium salt precursor is Li2O and the at least one metal salt precursor comprises MmCh and MnO2. In some embodiments, the at least one mixed metal salt precursor comprises LiMnO2, Li2MnO3, LiNiMnCoO2 and Li2MnO2F. In some embodiments, the at least one mixed metal salt precursor comprises LiMnO2 and Li2MnO3. When M is Cr or M is a combination comprising Cr, Cr may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more chromium salt precursors selected from: CnCh, CrOs, &2S3, CrSs, CrFs, CrFe, CrCh and CrCk. In some such embodiments, the at least one metal salt precursor comprises one or more chromium salt precursors selected from: CnCh and CrOs. When M is Co or M is a combination comprising Co, Co may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more cobalt salt precursors selected from: CoO, CO3O4, CoS, C03S4, C0F2, C03F8, C0CI2 and C03CI8. In some such embodiments, the at least one metal salt precursor comprises one or more cobalt salt precursors selected from: CoO and CO3O4. When M is Ni or M is a combination comprising Ni, Ni may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more nickel salt precursors selected from: NiO, M2O3, NiO2, NiS, M2S3, NiSa, NiF2, NiFs NiCh, and NiCh. In some such embodiments, the at least one metal salt precursor comprises one or more nickel salt precursors selected from: NiO, NhCh and NiO2. When M is Mo or M is a combination comprising Mo, Mo may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more molybdenum salt precursors selected from: MoO2, MoOs, M0S2, M0S3, M0F4, MoFe, M0CI4 and MoCk In some such embodiments, the at least one metal salt precursor comprises one or more molybdenum salt precursors selected from: MoO2 and MoOs. When M is W or M is a combination comprising W, W may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more tungsten salt precursors selected from: WO2, WO3, WS2, WS3, WF4, WFe, WCI4 and WCk. In some such embodiments, the at least one metal salt precursor comprises one or more tungsten salt precursors selected from: WO2 and WO3. When M is Al or M is a combination comprising Al, Al may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more aluminium salt precursors selected from: AI2O3, AI2S3, AIF3 and AlCh. In some such embodiments, the at least one metal salt precursor comprises AI2O3. When M is Nb or M is a combination comprising Nb, Nb may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more niobium salt precursors selected from: NbO, NbO2, Nb2O5, NbS, NbS2, NbFs, NbF2, NbF4, Nb2S5, NbCh, NbClz and NbCk In some such embodiments, the at least one metal salt precursor comprises one or more niobium salt precursors selected from: NbO, NbO2, Nb20s. When M is Sn or M is a combination comprising Sn, Sn may be provided in the form of at least one metal salt precursor and / or at least one mixed metal salt precursor. In some such embodiments, the at least one metal salt precursor comprises one or more tin salt precursors selected from: SnO, SnO2, SnS, SnS2, SnF2, SnF4, SnCh, and SnCl4. In some such embodiments, the at least one metal salt precursor comprises one or more tin salt precursors selected from: SnO and SnO2. When M is P or M is a combination comprising P, P may be provided in the form of at least one phosphorus salt precursor. In some such embodiments, the precursor mixture comprises one or more phosphorus salt precursors selected from: P2O5 (also referred to as P4Oio), P4Oe, P2S5 (also referred to as P4Sio), P2S5, PFs and PCh. In some such embodiments, the precursor mixture comprises one or more phosphorus salt precursors selected from: P2O5 (also referred to as P4O10) and P4Oe When M is B or M is a combination comprising B, B may be provided in the form of at least one boron salt precursor. In some such embodiments, the precursor mixture comprises one or more boron salt precursors selected from: B2O3, BF3 and BCI3. In some such embodiments, the precursor mixture comprises a boron salt precursor which is B2O3. When M is Si or M is a combination comprising Si, Si may be provided in the form of at least one silicon salt precursor. In some such embodiments, the precursor mixture comprises one or more silicon salt precursors selected from: SiCh, SiF4 and SiCk In some such embodiments, the precursor mixture comprises a silicon salt precursor which is SiO2. In some embodiments, M is a combination comprising more than one of Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B and Sn. It will be understood that any combination of metal and / or mixed metal precursors may be used to achieve the desired combination of metals in M. It will also be understood that any proportion of metal and / or mixed metal precursors may be used to achieve the desired ratio of the more than one metal in M. In some embodiments, M comprises Ni, Mn, Co, Fe, Al or a combination thereof, and the at least one mixed metal salt precursor may comprise at least one of LiNiMnCoO2, CoFe2O4, CoAkCk and NiFe2O4. In some embodiments, M is a combination of Ni, Mn and Co and the at least one mixed metal salt precursor may be LiNiMnCoO2. In some embodiments, M is a combination of Co and Fe, and the at least one mixed metal salt precursor may be a cobalt-iron mixed metal salt. For example, CoFe2O4. In some embodiments, M is a combination of Co and Al, and the at least one mixed metal salt precursor may be a cobalt-aluminium mixed metal salt. For example, COAI2O4. In some embodiments, M is a combination of Ni and Fe, and the at least one mixed metal salt precursor may be an iron-nickel mixed metal salt. For example, NiFe2O4. In some embodiments, M is or comprises Mn and the precursor mixture comprises at least one precursor selected from: lithium salts, manganese salts and lithium-manganese mixed metal salts. In some embodiments, the precursor mixture comprises at least one lithium salt and at least one manganese salt. In some such embodiments, the at least one manganese salt is two manganese salts. In some embodiments, the lithium salt is Li2O. In some embodiments, the at least one manganese salt is selected from MmCh and MnCh. In some embodiments, M is Mn, and the precursors are Li2O, MmCh and Mn02. In some embodiments, the precursor mixture comprises at least one lithium-manganese mixed metal salt. In some embodiments, the at least one lithium-manganese mixed metal salt is selected from LiMnO? and Li2MnO3. In some embodiments, M is Mn, and the precursors are LiMnO2 and Li2MnO3. In some embodiments of the first aspect, M comprises Mn and Ti and the precursor mixture comprises at least one precursor selected from: lithium salts, manganese salts, titanium salts, lithium-manganese mixed metal salts and lithium-titanium mixed metal salts. In some embodiments, the lithium salt is Li2O, and / or the manganese salt is MmCh, and / or the titanium salt is TiO2, and / or the lithium-manganese mixed metal salt is one or both of LiMnO2 and Li2MnCh, and / or the lithium-titanium mixed metal salt is Li2TiO3. In some embodiments, M is Mn and Ti, and the precursors are Li2O, MmCh and TiO:. Second Aspect The second aspect of the invention provides a method of making a composition having the general formula AX, wherein precursor mixture comprising or consisting of a precursor having the general formula AX is provided. As with the composition, the precursor may also be described in terms of its chemical formula (i.e. general formula, AX) and its structure, such as its crystal structure. In the second aspect, the precursor has a structure other than a disordered rock salt structure and the composition may have a structure which is a disordered rock salt structure. In some embodiments, the structure other than a disordered rock salt structure is a layered structure. In some embodiments, the precursor has a layered structure, and the composition has a structure which is a disordered rock salt structure. It will be understood that the features of the general formula of the composition described herein apply equally to the general formula of the precursor. In other words, the precursor in the second aspect has the same chemical formula as the composition obtainable by the method of the second aspect (general formula, AX), but the precursor and the composition may have a different structure (e.g. crystal structure). Methods of making a precursor having the general formula AX and a structure other than a disordered rock salt structure are known in the art. Such a precursor may be made by solid state synthesis. For example, solid state synthesis may comprise providing suitable precursors, and said precursors may be fired at high temperature in a crucible for a period of time. For example, the temperature may be 700°C and the period of time may be several hours, or 12 h. In some embodiments of the second aspect, in both the composition having the general formula AX, and the precursor having the general formula AX and a structure other than a disordered rock salt structure, M is or comprises Mn. In some such embodiments, X comprises or consists of O. In some embodiments of the second aspect, in both the composition having the general formula AX, and the precursor having the general formula AX and a structure other than a disordered rock salt structure, M is or comprises Mn and Ti. In some such embodiments, X comprises or consists of O. Vacancies When d >0, the composition comprises cation vacancies, [c]. When m >0, the composition comprises anion vacancies, [a]. In some embodiments, the composition may comprise [c] and / or [a]. In some embodiments, anion vacancies, [a] may be introduced during preparation of the compositions, such as during a ball milling step discussed elsewhere herein. In some embodiments, anion vacancies [a] may be introduced during other stages e.g. during fast cooling (quenching) of the compositions following heating. In some embodiments, cation vacancies [c] may be introduced by delithiation, such as during use in a lithium-ion battery. In some embodiments, cation vacancies [c] may be introduced during preparation of the compositions, such as during a ball milling step discussed elsewhere herein. In some embodiments, vacancies [a] and [c] may be introduced by careful control of the starting materials. For example, if cation vacancies are desired, using a specific proportion of titanium salt precursor and lithium salt precursor may suitably be used in a method described elsewhere herein to introduce cation vacancies [c]. In some embodiments of the method of the first and second aspect, the method further comprises delithiating the composition obtained after step (b). In some embodiments, delithiating the composition comprises applying a potential difference to an electrode comprising a composition of the first aspect, so as to cause delithiation of the composition originally produced following step (b). In some embodiments, delithiation can be achieved using chemical means, such as with iodine. In some embodiments, the delithiating comprises reducing the amount of lithium in the composition. In some embodiments, the delithiating is carried out until e=0. In some embodiments, the delithiating is carried out until the amount of lithium is reduced, but e >0. Ball milling Step (b) of the methods according to the first and second aspects comprises ball milling the at least one polar aprotic solvent and the precursors for a period of time. Unless otherwise stated, the following description of the ball milling in step (b) applies equally to step (b) of the first and second aspects. In some embodiments, in step (b), the period of time is measured in hours (h). In some embodiments, in step (b), the period of time is at least 1 h, such as at least 3 h, at least 5 h, at least 7 h, or at least 10 h. In some embodiments, in step (b), the period of time is up to 300 h, such as up to 280 h, up to 250 h, up to 220 h, up to 200 h, or up to 150 h. Combinations of any of these values may be used to provide exemplary ranges for the period of time. For example, the period of time may be between 1 h and 300 h, between 3 h and 280 h, between 3 h and 250 h, between 7 h and 200 h, or between 10 h and 150 h. In some embodiments, in step (b), the period of time corresponds with a time at which no crystalline precursor peaks can be observed in a product of the ball milling, the crystalline precursor peaks being determined by taking an XRD pattern using a CuKa radiation source as described elsewhere herein. In some embodiments, the period of time is less than 100 h, or less than 90 h, or less than 80 h. In some embodiments, the period of time is between 1 and 100 h, or between 10 and 100 h, or between 40 and 80 h, or between 40 to 70 h. In some embodiments, the period of time is between 45 to 65h, or is about 60 h. For example, ball milling may be performed for a certain time, then paused, to form a single cycle. In some embodiments, the period of time may correspond to the total milling time taken for a particular number of such cycles, excluding any pauses. In some embodiments, there is no pause. In some embodiments, in step (b), the ball milling is carried out at a speed of 150 revolutions per minute (rpm) or more, such as 250 rpm or more, 350 rpm or more, 450 rpm or more, or 500 rpm or more such as 550 rpm. In some embodiments, in step (b), the ball milling is carried out at a speed of 1000 rpm or less, such as 950 rpm or less, 900 rpm or less, 850 rpm or less, or 800 rpm or less. Combinations of any of these values may be used to provide exemplary ranges for the ball milling speed. For example, ball milling may be carried out at a speed of between 150 rpm and 1000 rpm, or between 250 rpm and 950 rpm, or between 350 rpm and 900 rpm, or between 450 rpm and 850 rpm, or between 550 rpm and 800 rpm. In some embodiments, in step (b), a speed of the ball milling may be varied over the period of time. For example, ball milling may be carried out at 350 rpm for part of the period of time and increased to one or more higher speeds for the remainder of the period of time. In some embodiments, in step (b), a milling media is used to assist or cause the mechanochemical reaction. The milling media may comprise beads and / or balls. The milling media may be placed inside the ball mill to affect, cause or enhance the mechanochemical reaction. In some embodiments, the milling media has a diameter of 2-20 mm, such as between 3-10 mm, such as 4-7 mm. Any suitable known milling media may be used, for example yttrium stabilized ZrO2 (YSZ). In some embodiments of the first aspect, in step (b), a weight ratio of the precursors to the milling media is at least 1:1, such as at least 1:2, at least 1:4, at least 1:5, at least 1:6, or at least 1:7. The ratio refers to the sum of the weight of all of the precursors. Accordingly, in embodiments using, for example, one lithium salt precursor and two metal salt precursors, the ratio may refer to the sum of the weights of (the one lithium salt precursor + first metal salt precursor + second metal salt precursor). In some embodiments of the second aspect, in step (b), the weight ratio of the precursor having a structure other than a disordered rock salt structure to the milling media is up to 1:100, up to 1:50, up to 1:20, or up to 1:10. Combinations of any of these values may be used to provide exemplary ranges for the weight ratio. For example, the weight ratio may be 1:1 to 1:100, 1:2 to 1:100, 1:4 to 1:50, 1:5 to 1:20 or 1:7 to 1:10. In some embodiments, in step (b), the ball milling is carried out in a milling jar which is ZrO2, stainless steel, agate (SiCh), SiC, or WC. Such milling jars are considered to be capable of achieving the mechanochemical reaction while not causing unwanted contamination. In some embodiments, a hard and / or dense material is chosen for the jar material. In some embodiments, the milling jar is ZrO2 or stainless steel. In some embodiments, the milling jar is ZrO2. In some embodiments, the milling jar has a volume of at least 20 mL, at least 45 mL, at least 50 mL, at least 80 mL or at least 100 mL. In some embodiments, the milling jar has a volume or at least 250 mL or at least 500 mL. In some embodiments, a larger milling jar may allow a lower rpm to be used to achieve the mechanochemical synthesis. In some embodiments, variation of the ball milling conditions in step (b) may provide the compositions with one or more anion vacancies. In some embodiments, one or more anion vacancies can be introduced by considering aspects of the ball milling conditions of step (b) such as the period of time or speed of ball milling. In some embodiments, the amount of anion vacancies can be measured using TGA or XPS. In some embodiments, the amount of anion vacancies can be measured using TGA. In some such embodiments, the composition may be heated in air at any appropriate heating rate. In principle, any anion vacancies are filled by oxide anions from air during the heating process. Therefore, a mass increase recorded by the TGA in the region 0 to 450°C may be ascribed to the filling of anion vacancies, and thus the amount of vacant anion sites may be calculated. In some embodiments, the mass increase is the maximum mass increase, which may be identified by a peak position in that region. In some embodiments, other subsequent mass changes may be ascribed to thermal decomposition processes, such as mass changes occurring above 450°C or above 500°C. In some embodiments, the mass change is calculated from the peak position, or the largest mass change observed in the region 0 to 450°C. In some embodiments, the amount of anion vacancies that can be measured using TGA is the amount of oxygen anion vacancies. In some embodiments, induced oxygen deficiency may be calculated from TGA. In some embodiments, the calculation of induced oxygen deficiency may involve converting the wt% mass change to O2 (g), and using oxygen deficiency = (O2 mass x 2) / (mol[AX] x molecular mass [AX]). Corresponding calculations may be done for F, S and Cl. Polar Aprotic Solvent Step (a) of the method of the first and second aspects includes providing at least one polar aprotic solvent. The presence of at least one polar aprotic solvent during ball milling has been found to reduce or prevent caking. This description of the solvent applies equally to the methods of the first and second aspects. The polar aprotic solvent may be a polar aprotic organic solvent and / or a polar aprotic ionic liquid. In some embodiments, only one polar aprotic solvent is used. In some embodiments, more than one polar aprotic solvent is used. The skilled person will be aware of many known examples of polar aprotic solvents. The term “aprotic solvent” may be used to describe a solvent without labile hydrogen atoms. For example, solvents that do not contain any O-H or N-H bonds. The skilled person will be aware of solvents that are classed as aprotic. Kamlet-Taft solvent parameters a, p and 71* are a common system used to characterise and quantify solvent properties, where a is a measure of a solvent’s ability to act as hydrogen bond donor, p is a measure of a solvent’s ability to act as hydrogen bond acceptor, and 7t* is the polarisability of the solvent. These are described as “solvatochromic” parameters, as they are calculated by measuring the spectral shift in Xmax of indicator dyes when dissolved in the solvent of interest. 71*, P and a are calculated using the following equations: 7t* = (28.10 - Vmaxi) / 3.52 (Eq. 1) p = (0.984 Vmaxi +3.49 - Vmax2) / 2.759 (Eq. 2) a = (1.318vmaxi + 47.7 + Vmax3) / 5.47 (Eq. 3) To determine Vmaxi, A’A’-dimethyl-4-nitroaniline is added to the solvent of interest at a concentration between 0.03 mM to 0.05 mM in order to achieve a suitable UV-vis absorbance intensity. To determine Vmax2,4-nitroaniline is added to the solvent of interest at a concentration between 0.03 mM to 0.05 mM in order to achieve a suitable UV-vis absorbance intensity. The wavenumber of the highest wavelength UV-vis absorbance peak corresponds to the value Vmax2. To determine Vmax3, Reichardt’s dye (2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)phenolate) is added to the solvent of interest at a concentration of 0.1 mM. In each case, the wavelength of the maximum UV-vis absorbance peak corresponds to Xmax. Vmaxi, Vmax2 and Vmax3 are the wavenumber equivalent of Xmax, expressed in the unit KiloKaiser (KK), converted from wavelength in nm by: Vmax (KK) = 10,000 / Xmax(nm) This method is described in more detail in: M. J. Kamlet et al. The Journal of Organic Chemistry, 1983, 48 (17), 2877-2887. The values of a, P and 7t* parameters are documented for many common solvents. Table 1 shows Kamlet-Taft parameters for some common polar aprotic solvents. Table 1 a, P and it* for some common polar aprotic solvents. Values taken from M. J. Kamlet et al, The Journal of Organic Chemistry, 1983, 48 (17), 2877-2887. Solvent a p dimethyl sulfoxide (DMSO) 0.00 0.76 1.00 sulfolane 0.00 - 0.98 nitrobenzene 0.00 0.39 1.01 triethylphosphate 0.00 0.77 0.72 V,V-dimethylformamide (DMF) 0.00 0.69 0.88 V,V-dimethylacetamide (DMA) 0.00 0.76 0.88 A-methyl-2-pyrrolidinone (NMP) 0.00 0.77 0.92 Aprotic solvents may be characterised by a = 0, as they cannot donate hydrogen bonds. In some embodiments, the polar aprotic solvent may be characterised by a = 0. Polar solvents may be characterised by a high polarisability, 7i*. In some embodiments, the polar aprotic solvent may be characterised by a high polarisability. In some embodiments, the polar aprotic solvent may be characterised by 7t* >0.5, or rr* >0.6, or rc* >0.7, rr* >0.8,7t* >0.9. A solvent may also be characterised as non-polar or polar based on its dielectric constant. For example, non-polar solvents may be characterised by a dielectric constant at 25 °C of <5, medium polarity solvents may have a dielectric constant at 25 °C of about 5-20, and highly polar solvents may have a dielectric constant at 25 °C greater than or equal to 20. In some embodiments, the polar aprotic solvent has a dielectric constant at 25 °C of greater than or equal to about 20, or greater than or equal to about 25, or greater than or equal to about 30, or greater than or equal to about 35. The inventors have surprisingly found that using a solvent within a particular viscosity range can give improved results in the methods disclosed herein. Viscosity as referred to herein is dynamic viscosity. Dynamic viscosity can be measured, for example, in cp or mPa.s. 1 cp is equivalent to 1 mPa.s. In some examples, a solvent with a low viscosity may not reduce caking sufficiently and some manual homogenisation may be required during ball milling. In some examples, a solvent with a high viscosity may reduce the extent of conversion of the precursors in the mechanochemical reaction, reducing the yield or increasing the reaction time required. In some embodiments, the at least one polar aprotic solvent has a viscosity greater than 1 mPa.s (1 cp) at 25 °C, or >1.5 mPa.s (>1.5 cp) at 25 °C. In some embodiments, the at least one polar aprotic solvent has a viscosity between 1-4 mPa.s (1-4 cp) at 25 °C, or 1-3.5 mPa.s (1-3.5 cp) at 25 °C, or 1-3 mPa.s (1-3 cp) at 25 °C. In some embodiments, the at least one polar aprotic solvent has a viscosity between 1-2 mPa.s (1-2 cp) at 25 °C. In some embodiments, the polar aprotic organic solvent comprises one or more of: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, a phosphoester or a silyl ether. In some embodiments, the polar aprotic organic solvent comprises one or more of: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, or a phosphoester. In some embodiments, the polar aprotic organic solvent comprises one or more of: a lactone and a sulfoxide. In some such embodiments, the lactone is 8-valerolactone and / or the sulfoxide is DMSO. In some embodiments, the at least one polar aprotic organic solvent consists of a single polar aprotic organic solvent selected from: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, a phosphoester or a silyl ether. In some embodiments, the at least one polar aprotic organic solvent consists of a single polar aprotic organic solvent selected from: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, or a phosphoester. In some embodiments, the at least one polar aprotic organic solvent consists of a single polar aprotic organic solvent selected from: a lactone or a sulfoxide. In some such embodiments, the lactone is 8-valerol acton e or the sulfoxide is DMSO. In some embodiments, the polar aprotic ionic liquid comprises one or more of: an ammonium ionic liquid or a phosphonium ionic liquid. In some embodiments, one polar aprotic organic liquid is used. In some such embodiments, the polar aprotic organic liquid is an ammonium ionic liquid or a phosphonium ionic liquid. The inventors have found that just a small amount of solvent is required to reduce or prevent caking, for example, a ratio of less than or equal to 5 ml of solvent for every 16 g of precursor. The ratio refers to the total mass of all of the precursors in the precursor mixture to the total volume of solvents making up the at least one solvent. For example, in the first and the second aspect, when two solvents are used, the total volume of solvent in the ratio refers to the sum of the volumes of each solvent. In some embodiments, the at least one polar aprotic solvent may be provided in an amount less than or equal to 3.0 ml for every 16 g of the precursor mixture, or less than or equal to 2.0 ml. In some embodiments, the at least one polar aprotic solvent may be provided in an amount from 0.5 ml to 3.0 ml for every 16 g of the precursor mixture, 0.5 ml to 2.5 ml for every 16 g of the precursor mixture, 0.5 ml to 2.0 ml for every 16 g of the precursor mixture, or 1 ml to 1.5 ml for every 16 g of the precursor mixture. In some embodiments, the method further comprises separating the at least one polar aprotic solvent and the composition from the milling media after ball milling by any suitable method. For example, this may be achieved by sieving. In some embodiments, the method further comprises separating the at least one polar aprotic solvent from the composition after ball milling by any suitable known method. For example, this may be achieved by removing the solvent at a temperature above room temperature and / or under vacuum. For example, after ball milling, the mixture comprising the at least one polar aprotic solvent and the composition may be placed in a vacuum oven. In some embodiments, the temperature may be greater than or equal to 100 °C, or 110 °C, or 120 °C. In some embodiments, the vacuum oven is at a temperature of about 130 °C. In some embodiments, the vacuum pressure is less than 50 mbar, or less than 20 mbar, or less than 10 mbar, or less than 5 mbar, or about 1 mbar. In some embodiments, the vacuum pressure is about 1 mbar. In some embodiments, the temperature in the vacuum oven is about 130 °C and the pressure in the vacuum oven is about 1 mbar. EXAMPLES The present invention will now be described by way of examples, which are intended to be illustrative and not limiting on the present invention. The following compositions were synthesized using ball milling at around 700 rpm using magnesia stabilised zirconia (MgSZ) jars with 5 mm diameter yttria stabilised zirconia (YSZ) balls as the milling media. A 10:1 ratio by mass of the milling media to the precursors was used. The Milling was performed in a Fristch Pulversiette 7. Sampling was carried out every 10 h, and the milling was carried out in a cyclic manner with 75 mins milling with 15 mins break. XRD patterns were measured with an Aeris Benchtop X-ray diffractometer equipped with a PIXcel detector in reflection geometry using CuKa radiation, with an x-ray wavelength of 0.154056 nm (1.54056A), operating at 40 kV and 40 mA. The measurement range was 30-75° 20. SEM and EDX was performed on a Phenom XL G2 Desktop SEM from Thermofisher Scientific. For electrochemical testing, the prepared compositions were mixed inside a glovebox with a carbon conductive additive and PTFE as binder in a weight ratio of 80:10:10. The charge discharge curve was measured from a standard CR 2032 coin type cell assembled in an argon filled glove box (H2O content <Ippm). The charge-discharge cycle tests were performed at a current density of 30 mA / g cycled between 0.5 and 3 V vs. Li / Li+ on a MACCOR. AIM LiPFe solution obtained by dissolving in a mixture of EC and DMC in a volume ratio of 1:1 was used as electrolyte. Electrodes were prepared by combining the composition comprising lithium and titanium, acetylene black and PTFE in a weight ratio of 8:1:1 into a pellet. Metallic lithium was used as the counter electrode. The chargedischarge cycle tests were performed at 30°C (303 K) unless stated otherwise, and ambient pressure (101 kPa). Comparative Example The following comparative example describes the solvent-free process known in the prior art, wherein a mixture of dry precursors is subjected to ball milling. This differs from the methods disclosed herein, which comprise the step of providing at least one polar aprotic solvent. To target a composition of Li1.1Mno.9O2, an 80 mL magnesia stabilised zirconia (MgSZ) jar was filled with 150 g of yttria stabilised zirconia (YSZ) balls of 5 mm diameter. 15 g of the following precursors were added to the jar (on top of the balls) to achieve a 10:1 ball to powder ratio: LisO (2.7673 g), MmCh (9.3047 g), and MnO? (2.9279 g). Loading of the precursors was done in an argon filled glovebox, to ensure an inert environment. The jar was then sealed and removed from the glovebox for milling to be performed. The jar was milled at 700 rpm for 10 h (8 cycles of 75 min milling and 15 min break). The jar was returned to the glovebox for sampling of the material to check for caking. After 10 hours of ball milling, the sample in the jar was a mixture of milling media (i.e. the balls), non-caked (i.e. loose) powder and caked powder. Manual homogenisation was necessary to return the caked powder to a non-caked state before ball milling could be resumed. The homogenisation consisted of the following steps: 1. The balls and non-caked powder were removed from the jar. The balls were separated from the non-caked powder by sieving. 2. The caked powder was removed manually from the bottom of the jar using a knife and / or spatula. The caked powder was broken and detached in large chunks of agglomerated powder. 3. The chunks were ground into a fine powder using a pestle and mortar. 4. The non-caked powder from (1) was combined with the homogenised powder from (3) and mixed with the pestle and mortar. 5. Powder XRD of a sample of the powder showed that the desired composition had not yet been obtained and further ball milling was required. 6. The balls were re-introduced in the jar, followed by the powder. 7. The j ar was sealed again and removed from the glovebox. A total of 3Oh of ball milling was necessary to obtain the desired composition having a disordered rock salt (DRS) structure. Manual homogenisation as described in steps 1-7 above was required after lOh and 20h. Example 1 To target a composition of Li1.1Mno.9O2, an 80 mL magnesia stabilised zirconia (MgSZ) jar was filled with 160 g of yttria stabilised zirconia (YSZ) balls of 5 mm diameter. 1.2 mL of DMSO was measured using a micropipette and loaded in the jar along the sides and on top of the balls. 16 g of the following precursors were added to the jar (on top of the balls) to achieve a 10:1 ball to powder ratio: Li2O (2.9518 g), MmCh (9.9250 g), and Mn02 (3.1231 g)- Loading of the precursors was done in an argon filled glovebox, to ensure an inert environment. The jar was then sealed and removed from the glovebox for milling to be performed. The jar was milled at 700 rpm for 10 h (8 cycles of 75 min milling and 15 min break). The jar was returned to the glovebox for sampling of the material and ensure no caking was taking place. This process was repeated for a total of 60 h of ball milling. No caking was observed during the 60 h of ball milling and no manual homogenisation was required. After ball milling, the powder was collected by sieving and dried under vacuum (about 1 mbar) at 130°C for 18 h (overnight), to remove the DMSO. Figure 1 shows the powder XRD pattern of the composition. Three peaks were observed at 29 = 36.7950°, 43.1214° and 62.1780°. These peaks were indexed (h,k,l) as (1,1,1), (2,0,0), and (2,2,0), respectively. These peaks correspond to a cubic structure of the space group Fm-3m, also known as a disordered rock salt structure. Rietveld refinement analysis was used to calculate the FWHM and unit cell values. The FWHM was calculated to be 2.7777° 29. The unit cell length was calculated to be 0.42615 nm (4.2615 A). No evidence of crystalline precursors was observed. Figure 2 shows SEM images of the composition. These images indicate that the composition is a particulate material, i.e. a material made up of a plurality of discrete particles. The particles may comprise primary particles and / or secondary particles formed from the agglomeration of a plurality of primary particles. Powder electrodes were made to test electrochemical properties of the composition obtained by the disclosed method. The powder electrodes were made by making a mixture consisting of: an active material (in this case, the composition), carbon black and PTFE in the ratio 80:10:10, respectively. The mixture was pressed together in a pellet and assembled in a half cell in a coin cell format. Whatman glass fibre was used as the separator, lithium metal foil was used as the anode. The electrolyte consisted of IM LiPFe salt dissolved in a mixture of solvent EC / DMC in a ratio of 1:1. Galvanostatic testing (Figure 3) was performed on half cells between 4.8 2.0 V at 30°C and showed a capacity of first discharge of 188 mAh / g. Example 2 To target a composition of Li1.1Mno.9O2, an 80 mL magnesia stabilised zirconia (MgSZ) jar was filled with 160 g of yttria stabilised zirconia (YSZ) balls of 5 mm diameter. 1.5 mL of 8-valerolactone was measured using a micropipette and loaded in the jar along the sides and on top of the balls. 16 g of the following precursors were added to the jar (on top of the balls) to achieve a 10:1 ball to powder ratio: Li2O (2.9518 g), MmCh (9.9250 g), and Mn02 (3.1231g). Loading of the precursors was done in an argon filled glovebox, to ensure an inert environment. The jar was then sealed and removed from the glovebox for milling to be performed. The jar was milled at 700 rpm for 10 h (8 cycles of 75 min milling and 15 min break). The jar was returned to the glovebox for sampling of the material and ensure no caking was taking place. This process was repeated for a total of 60 h of ball milling. No caking was observed during the 60 h of ball milling and no manual homogenisation was required. After ball milling, the powder was collected by sieving and dried under vacuum (about 1 mbar) at 130°C for 18 h (overnight), to remove the 5-valerolactone. Figure 4 shows the powder XRD pattern of the composition. Three peaks were observed at 20 = 36.2738°, 42.1478° and 61.1773°. These peaks were indexed (h,k,l) as (1,1,1), (2,0,0), and (2,2,0), respectively. These peaks correspond to a cubic structure of the space group Fm-3m, also known as a disordered rock salt structure. Rietveld refinement analysis was used to calculate the FWHM and unit cell values. The FWHM was calculated to be 2.3842° 20. The unit cell length was calculated to be 0.4277 nm (4.277 A). No evidence of crystalline precursors was observed. Figure 5 shows SEM images of the composition. These images indicate that the composition is a particulate material, i.e. a material made up of a plurality of discrete particles. The particles may comprise primary particles and / or secondary particles formed from the agglomeration of a plurality of primary particles. Powder electrodes were made to test electrochemical properties of the composition obtained by the disclosed method. The powder electrodes were made by making a mixture consisting of: an active material (in this case, the composition), carbon black and PTFE in the ratio 80:10:10, respectively. The mixture was pressed together in a pellet and assembled in a half cell in a coin cell format. Whatman glass fibre was used as the separator, lithium metal foil was used as the anode. The electrolyte consisted of IM LiPFe salt dissolved in a mixture of solvent EC / DMC in a ratio of 1:1. Galvanostatic testing (Figure 6) was performed on half cells between 4.8 - 2.0 V at 30°C and showed a capacity of first discharge of 163 mAh / g. Example 3 To target a composition of Li1.1Mno.7Tio.2O2, an 80 mL magnesia stabilised zirconia (MgSZ) jar was filled with 160 g of yttria stabilised zirconia (YSZ) balls of 5 mm diameter. 1.2 mL of DMSO was measured using a micropipette and loaded in the jar along the sides and on top of the balls. 16 g of the following precursors were added to the jar (on top of the balls) to achieve a 10:1 ball to powder ratio: Li2O (2.9994 g), MmCh (10.0851 g) and TiO2 (2.9153 g). Loading of the precursors was done in an argon filled glovebox, to ensure an inert environment. The jar was then sealed and removed from the glovebox for milling to be performed. The jar was milled at 700 rpm for 10 h (8 cycles of 75 min milling and 15 min break). The jar was returned to the glovebox for sampling of the material and ensure no caking was taking place. This process was repeated for a total of 50 h of ball milling. No caking was observed during the 50 h of ball milling and no manual homogenisation was required. Figure 7 shows the powder XRD pattern of the composition. Three peaks were observed at 29 = 36.7574°, 42.7565° and 62.2355°. These peaks were indexed (h,k,l) as (1,1,1), (2,0,0), and (2,2,0), respectively. These peaks correspond to a cubic structure of the space group Fm-3m, also known as a disordered rock salt structure. Rietveld refinement analysis was used to calculate the FWHM and unit cell values. The FWHM was calculated to be 1.7883° 29. The unit cell length was calculated to be 0.42003 nm (4.2003 A). No evidence of crystalline precursors was observed. Figure 8 shows SEM images of the composition. These images indicate that the 5 composition is a particulate material, i.e. a material made up of a plurality of discrete particles. The particles may comprise primary particles and / or secondary particles formed from the agglomeration of a plurality of primary particles. Powder electrodes were made to test electrochemical properties of the composition 10 obtained by the disclosed method. The powder electrodes were made by making a mixture consisting of: an active material (in this case, the composition), carbon black and PTFE in the ratio 80:10:10, respectively. The mixture was pressed together in a pellet and assembled in a half cell in a coin cell format. Whatman glass fibre was used as the separator, lithium metal foil was used as the anode. The electrolyte consisted of IM LiPFo 15 salt dissolved in a mixture of solvent EC / DMC in a ratio of 1:1. Galvanostatic testing (Figure 9) was performed on half cells between 4.8 - 2.0 V at 30°C and showed a capacity of first discharge of 128 mAh / g.

Claims

1. A method of preparing a composition, wherein the composition has the general formula:AXwherein:A = LieMf[c]d;[c] is a cation vacancy;M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof;0 <d <0.5; 0 <e <1; 0 <f <1; and the sum of d, e and f is 1; and wherein:X = OpSqFiClk[a]m;[a] is an anion vacancy;0<p<l;0<q<l;0<l<l;0<k<l;0<m< 0.5; and the sum of p, q, 1, k and m is 1; andwherein the method comprises:(a) (i) providing a precursor mixture comprising Li and M;wherein Li and M are provided in the form of at least one salt precursor selected from: lithium salt precursors, metal salt precursors, mixed metal salt precursors, phosphorus salt precursors and metalloid salt precursors;(ii) providing at least one polar aprotic solvent; and(b) ball milling the at least one polar aprotic solvent and the precursor mixture for a period of time.

2. A method according to claim 1, wherein:(i) at least one salt precursor is or comprises an oxide; and / or(ii) the method comprises delithiating the composition; andwherein, after (ii), 0 <e <1.

3. The method according to any one of claims any of the preceding claims, wherein: M is Mn;0 <e <0.65; 0 <f <0.5.

4. The method according to any of the preceding claims, wherein:Li and M are provided in the form of precursors selected from: at least one lithium salt, at least one manganese salt, and at least one lithium-manganese mixed metal salt;optionally, wherein the precursor mixture comprises Li2O and at least one of M112O3 and MnOz, or the precursor mixture comprises LiMnO2 andLi2MnO3.

5. A method of preparing a composition, wherein the method comprises:(a) providing at least one polar aprotic solvent; andproviding a precursor mixture comprising or consisting of a precursor having the general formula AX;wherein:A = LieMf[c]a;[c] is a cation vacancy;M is Ti, V, Fe, Cr, Mn, Co, Ni, Mo, W, Al, Nb, P, Si, B, Sn or a combination thereof;0 <d <0.5; 0<e<l;0<f<l; and the sum of d, e and f is 1; and wherein:X = OPSqFiClk[a]m;[a] is an anion vacancy;0<p<l;0<q<l;0<l<l;0<k<l;0<m< 0.5; and the sum of p, q, 1, k and m is 1; andwherein the precursor has a structure other than disordered rock salt structure and the composition has the same general formula as the precursor; and(b) ball milling the at least one polar aprotic solvent and the precursor mixture for a period of time.

6. The method according to any one of the preceding claims, wherein:(i) k = 0; and / or(ii) p and / or q >0; and / or(iii) p >0; and / or(iv) 1 >0.

7. The method according to any one of the preceding claims, wherein:(i) 0 <e <1; and / or(ii) d and / or m = 0.

8. The method according to any one of the preceding claims, wherein: M is Mn;0 <e <0.65; 0<f<0.5.

9. The method according to claim 8, wherein q, 1 and k = 0.

10. The method according to any one of claims 8 or 9, wherein d and / or m = 0.

11. The method according to any one of claims 8 to 10, wherein p >0; optionally wherein p= 1.

12. The method according to any one of the preceding claims, wherein the composition has a disordered rock salt structure.

13. The method according to any one of the preceding claims, wherein the composition predominantly comprises a single phase.

14. A composition according to any one of the preceding claims, wherein an X-ray diffraction pattern of the composition using a CuKa radiation source has a peak at a 20 value of at least one of, and optionally each of, (a) to (c):(a) 36.6° ± 2.0°(b) 43.0° ±2.0°(c) 61.8° ±2.0°.

15. The method according to any one of the preceding claims, wherein the period of time in (b) is 1 hour to 300 hours.

16. The method according to any one of the preceding claims, wherein the at least one polar aprotic solvent has a viscosity greater than or equal to 1 mPa.s at 25 °C.

17. The method according to any one of the preceding claims, wherein the method comprises separating the at least one polar aprotic solvent from the composition after ball milling.

18. The method according to any one of the preceding claims, wherein the at least one polar aprotic solvent comprises a polar aprotic organic solvent and / or a polar aprotic ionic liquid.

19. The method according to claim 18, wherein the polar aprotic organic solvent comprises one or more of: a lactone, a sulfoxide, a sulfone, a nitrile, an ether, a nitrate, a cyanate, a sulfonate ester, a thiocyanate, a phosphine, a phosphoester or a silyl ether.

20. The method according to claim 19, wherein:the lactone is y-valerolactone and / or 5-valerolactone; and / orthe sulfoxide is dimethylsulfoxide (DMSO); and / orthe sulfone is sulfolane; and / orthe nitrile is benzonitrile; and / orthe nitrate is nitrobenzene; and / orthe cyanate is phenyl isocyanate; and / orthe sulfonate ester is ethyl methanesulfonate; and / orthe thiocyanate is phenyl isothiocyanate; and / orthe phosphine is tributyl phosphene; and / orthe phosphoester is trimethylphosphate; and / orthe silyl ether is tetraethylorthosilicate.

21. The method according to any one of claims 18 to 20, wherein the polar aprotic organic solvent comprises one or more of: a lactone or a sulfoxide.

22. The method according to claim 21, wherein the lactone is 8-valerolactone and / or the sulfoxide is DMSO.

23. The method according to claim 18, wherein the polar aprotic ionic liquid comprises one or more of: an ammonium ionic liquid or phosphonium ionic liquid.

24. The method of any one of the preceding claims, wherein the at least one polar aprotic 5 solvent is provided in an amount from 0.5 ml to 2.5 ml for every 16 g of the precursor mixture.

25. A composition obtainable by the method according to any one of the preceding claims.

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