Recycled battery composition

Abstract

A method of preparing a cathode active material composition involves combining a first cathode active material including recycled lithium 40 with a second cathode active material 41; wherein the ratio

Description

Field of Invention The present invention relates to a method of preparing a cathode active material composition that has a partial recycled content. The present invention also relates to a cathode active material composition per se, an electrical energy storage device comprising the composition, the use of the composition in preparing an electrical energy storage device and an apparatus for preparing a cathode active material composition. The present invention has particular, but not exclusive, application in the production of sustainable materials for use in batteries, including high performance batteries designed for electric vehicles, consumer batteries, and other battery energy storage solutions such as rechargeable industrial batteries with a capacity greater than 2 kWh, and LMT (light means of transport) batteries. Background to the invention Batteries, which are essential for a net-zero future, are highly dependent on critical metals, the extraction and supply of which inflict harm on society and the environment and are subject to geopolitical tensions. To reduce damage and secure supply, there are ambitious targets being set for end-of-life battery recycling and critical metal recovery. As a potential source of critical materials, recycling end of life batteries could help secure regional material supply. Recycling also typically results in reduced energy consumption and greenhouse gas emissions compared to primary production. However, there are significant challenges with recycling given the vast amount of battery feedstocks commercially available. There is also a perception that recycled materials may not preform to the same standard as fresh materials. Accordingly, the development of the field may become unsustainable without the development of alternative ways to prepare batteries in a more sustainable manner. The present invention aims to address this issue by providing a method of incorporating recycled content into battery materials, reducing the demand on the extraction of critical materials from virgin sources. This work aligns with UN’s Sustainability Development Goals such as to decrease consumption of critical raw materials, ensure sustainable production of critical raw materials, and to reduce the demands upon supply chain for critical elements. The invention also aims to provide an optimised recycled content based on a full circularity model and battery ready cathode active materials. Summary of Invention According to a first of the present disclosure, there is provided a method of preparing a cathode active material composition, the method comprising: combining a first cathode active material comprising recycled lithium with a second cathode active material to provide the cathode active material composition; wherein the combining comprises controlling the ratio of the first cathode active material to the second cathode active material such that the cathode active material composition comprises lithium with a recycled content of at least 6%. The term “recycled lithium” as used herein is intended to refer to lithium that has been extracted from a waste source and used in a material or composition, i.e. lithium that has not been obtained directly from mining or other primary extraction methods. The waste source may be, for example, a spent battery or a waste material generated during preparation of a battery. It will be appreciated that analogous definitions are intended for other recycled elements, such as “recycled cobalt”. As such “recycled lithium” and other recycled elements has a lower environmental impact. Preferably, the first cathode active material and second cathode active materials comprise corresponding chemical compositions. The term “corresponding compositions” as used herein in intended to refer to compositions with approximately the same chemical formula. Put another way the first cathode active material and second cathode active material have essentially the same chemical composition (or chemical formula). The chemical formula may vary to the degree that it does not make a fundamental difference to the overall chemical structure. For example, both the first cathode active material and the second cathode active material would be considered the same category of battery chemistry (e.g. both NMC 811, 532, or 622). The amount of each element may vary within the chemical formula within normal manufacturing tolerances. The amount of each element may vary within the chemical formula by up to 10%. To provide an example, if the chemical composition of the second cathode active material can expressed by the formula LiNi0.8Mn0.1Co0.1O2, the corresponding first cathode active material may be expressed by the formula Li(0.9toi.i)Ni(0.72to0.88)Mn(0.09to 0.11)CO(0.09 to 0.11)0(1.8 to 2.2). In preferred embodiments, the first cathode active material and second cathode active material have the same chemical composition (or same chemical formula), i.e. they have the same ratio of chemical elements. In some embodiments, the first cathode active material and second cathode active material have the same crystalline phase. The first cathode active material and second cathode active material may have a layered crystalline structure. The first cathode active material and second cathode active material may have an olivine, spinel, or rhombohedron structure. The first cathode active material and second cathode active material may have a structures arising from any NMC disordered or ordered solid solution phase. The term “recycled content” as used herein in intended to refer to the amount of a particular element that has been obtained from a waste source, such as a spent battery (e.g. end of life batteries) or a waste material generated during preparation of a battery (e.g. gigafactory scarp), compared to the total amount of that element in the composition. For example, if a material comprises 1g of lithium in total, and 0.06g of the lithium in the structure was derived from waste sources, the recycled content would be 6%. It will be appreciated that when comparing the same elements, the mass, molar, volume and atomic percentage are the same. The term “virgin or fresh materials” or “non-recycled content” refer to materials which have not been recycled. A virgin material may be any available cathode active material (without limitation) sourced commercially or non commercially, or otherwise prepared from non-recycled elements. Advantageously, the method provides an optimised method for producing a highly performing yet more sustainable cathode active material. The use of the recycled content reduces the demand on mining fresh feedstocks without being detrimental to the performance of the final battery. It may also provide a reduced carbon footprint compared to a cathode active material composed entirely of virgin or fresh materials. The method is designed to be suitable for larger scale manufacturing including refining of over one million tonnes a year by 2030, growing to nearly 20 million by 2040, enabling a broad distribution of sustainable (recycled) material in the market. The use of partial recycled content may also be beneficial over producing fully recycled materials because it may allow environmental benefits without the potential for significant increases in cost per unit. Of course, where the recycling methods are optimised such that recycled elements are cheaper and less resource intensive than fresh elements, incorporating a recycled content could also reduce the cost of the final cathode active material. Further, the use of controlled amounts and blending ratios of recycled content with non-recycled content means it is possible to specifically tailor the final recycled content for optimum performance of the battery. A blending ratio of the first and second cathode materials can be suitably adjusted according to electrochemical design variables considering the use of a battery to be manufactured safely. Safety can be optimised in relation to electrochemical characteristics of cathode materials required such as structural integrity, thermal stability, voltage of Gibbs Free Energy profiling. Lastly, by conducting the method of the present invention and, particularly embodiments involving the mixing two separate cathode active materials with corresponding compositions to provide a final cathode active material, it becomes possible to incorporate recycled content into a final cathode active material very quickly without causing bottle necks in the industry. For example, a material with a high concentration of recycled elements can be blended with a large volumes of fresh cathode active material to produce high yields of sustainable cathode materials, with at least a degree of recycled content, without requiring the introduction of recycled content into all cathode active material production process / plants. The number of specialist recycling centres can therefore be small while still providing high volumes of sustainable materials, leading to an overall more efficient industrial process and a broad distribution of recycled materials in the market. The use of two separate cathode active materials may also allow for the facile adjustment and precise control of the recycled content to meet a particular consumer demand and without recertification. The ratios can be tuned without having to change any processing conditions in the recycling plant. According a second aspect of the disclosure there is provided a cathode active material composition prepared according to the method of first aspect of the invention. According to a third aspect of the disclosure there is provided a cathode active material composition for an electrochemical storage device, such as a battery, wherein the cathode active material composition comprises lithium with a recycled content of at least 6%. The cathode active material composition according to the second or third aspects of the invention may be for use in batteries designed for electric vehicles, rechargeable industrial batteries with a capacity greater than 2 kWh, and / or LMT batteries. According to a fourth aspect of the disclosure there is provided a method of preparing an electrical energy storage device, such as a battery, comprising: preparing a slurry comprising of cathode active material composition according to the second or third aspect of the invention; coating the slurry onto a substrate, preferably a metal substrate (e.g. a metal foil), and drying the slurry to form a first electrode; assembling a cell comprising the first electrode, an electrolyte and a second electrode. Preferably, the method further comprises cutting and / or calendaring the coated substrate. Preferably drying the slurry comprises vacuum drying. Preferably, the method further comprises charging, sealing and / or aging of the cell. According to a fifth aspect of the disclosure there is provided an electrical energy storage device, such as a battery, comprising the cathode active material composition of the second or third aspects of the disclosure. According to a sixth aspect of the disclosure there is provided the use of the cathode active material composition of the second or third aspects of the disclosure in preparing an electrochemical energy storage device. According to a seventh aspect of the disclosure there is provided an apparatus for preparing a cathode active material composition, the apparatus comprising: an inlet configured to supply a first cathode active material comprising recycled lithium; an inlet configured to supply a second cathode active material, preferably wherein the first cathode active material and second cathode active materials comprise corresponding chemical compositions; a mixing chamber configured to uniformly distribute the first cathode active material and the second cathode active material to provide the cathode active material composition; and a control means for controlling the weight ratio of the first cathode active material to second cathode active material introduced into the mixing chamber such that the cathode active material composition comprises lithium with a recycled content of at least 6%. The apparatus may be for conducting the method of the first aspect of the invention and may include any features suitable for carrying out the steps of the method of embodiments of the first aspect of the invention. Detailed Description Embodiments of the various aspects will be described below. For the avoidance of doubt, it will be appreciated that features described in respect of one aspect may be combined with any features described in respect of another aspect and all such combinations are expressly considered and disclosed herein. Recycled Lithium As described above, in relation to the various aspects of the disclosure, the cathode active material composition comprises lithium with a recycled content of at least 6%. The cathode active material composition may comprise lithium with a recycled content of at least 10%. The cathode active material composition may comprise lithium with a recycled content of at least 12%. The cathode active material composition may comprise lithium with a recycled content of at least 15%. The cathode active material composition may comprise lithium with a recycled content of at least 20%. The cathode active material composition may comprise lithium with a recycled content of at least 40%. The cathode active material composition may comprise lithium with a recycled content of at least 60%. The cathode active material composition may comprise lithium with a recycled content of at least 80%. The cathode active material composition may comprise lithium with a recycled content of from 6% to 99%. The cathode active material composition may comprise lithium with a recycled content of from 6% to 80%. The cathode active material composition may comprise lithium with a recycled content of from 6% to 50%. The cathode active material composition may comprise lithium with a recycled content of from 12% to 99%. For example, the cathode active material composition may comprise lithium with a recycled content of from 12% to 80%. The cathode active material composition may comprise lithium with a recycled content of from 12% to 50%. The cathode active material composition may comprise lithium with a recycled content of from 20% to 50%. As described above in relation to the first aspect of the disclosure, the first cathode active material comprises recycled lithium. In some methods, at least 7% of the lithium in the first cathode active material is recycled lithium. In some methods, at least 10% of the lithium in the first cathode active material is recycled lithium. In some methods, at least 15% of the lithium in the first cathode active material is recycled lithium. In some methods, at least 20% of the lithium in the first cathode active material is recycled lithium. In some methods, at least 33% of the lithium in the first cathode active material may be recycled lithium. In some methods, at least 37.5% of the lithium in the first cathode active material is recycled lithium. In further methods, at least 45% of the lithium in the first cathode active material is recycled lithium. For example, at least 46% of the lithium in the first cathode active material may be recycled lithium. In some methods, at least 60% of the lithium in the first cathode active material is recycled lithium. In some methods, at least 80% of the lithium in the first cathode active material is recycled lithium. In some methods, all of the lithium in the first cathode active material is recycled lithium. In some methods, x% of the cathode active material composition is derived from the first cathode active material, where x is greater or equal to 16 and less than or equal to 85. In such methods, at least (6*100 / x) % of the lithium in the first cathode active material may be recycled lithium. In other such methods, at least (12*100 / x) % of the lithium in the first cathode active material may be recycled lithium. In other such methods, at least (20*100 / x) % of the lithium in the first cathode active material may be recycled lithium. In other such methods, at least (40*100 / x) % of the lithium in the first cathode active material may be recycled lithium. In other such methods, at least (60*100 / x) % of the lithium in the first cathode active material may be recycled lithium. In other methods, the weight ratio of the first cathode active material to second cathode active material is expressed by x:1, wherein 0.19 <x <6. In such methods, the percentage of the lithium in the first cathode active material that is recycled lithium may be expressed by y% wherein y is greater or equal to 6(x+1) / x. y may be greater or equal to 12(x+1) / x. y may be greater or equal to 20(x+1) / x. y may be greater or equal to 40(x+1) / x. y may greater or equal to 60(x+1) / x. Recycled Cobalt In methods of the first aspect of the disclosure, the first cathode active material further comprises recycled cobalt. In some methods, at least 18.5% of the cobalt within the first cathode active material is recycled cobalt. In some methods, at least 26.5% of the cobalt within the first cathode active material is recycled cobalt. In some methods, at least 40% of the cobalt within the first cathode active material is recycled cobalt. In some methods at least 60% of the cobalt within the first cathode active material is recycled cobalt. In some methods, at least 80% of the cobalt within the first cathode active material is recycled cobalt. In some methods, at least 90% of the cobalt within the first cathode active material is recycled cobalt. In some methods, at least 95% of the cobalt within the first cathode active material is recycled cobalt. For example, 95% to 100% of the cobalt within the first cathode active material may be recycled cobalt. In some methods, all of the cobalt in the first cathode active material is recycled cobalt. The first cathode active material may comprise a recycled lithium to recycled cobalt weight ratio of 0.15:1 to 1:1. The first cathode active material may comprise a recycled lithium to recycled cobalt weight ratio of 0.3:1 to 1:1. The first cathode active material may comprise a recycled lithium to recycled cobalt weight ratio of 0.3:1 to 0.5:1. Using a higher recycled content of cobalt compared to lithium is beneficial because cobalt is considered of higher environmental concern than lithium, is less abundant and has a higher resource spend per kg during primary extraction. The cathode active material composition of the various aspects of the present disclosure may comprise cobalt with a recycled content of at least 16%. The cathode active material composition may comprise cobalt with a recycled content of at least 26%. The cathode active material composition may comprise cobalt with a recycled content of at least 40%. The cathode active material composition may comprise cobalt with a recycled content of at least 60%. The cathode active material composition may comprise cobalt with a recycled content of at least 80%. The cathode active material composition may comprise cobalt with a recycled content of from 16% to 99%. The cathode active material composition may comprise cobalt with a recycled content of from 16% to 80%. The cathode active material composition may comprise cobalt with a recycled content of from 16% to 50%. The cathode active material composition may comprise cobalt with a recycled content of from 26% to 99%. For example, the cathode active material composition may comprise cobalt with a recycled content of from 26% to 80%. The cathode active material composition may comprise cobalt with a recycled content of from 26% to 50%. The cathode active material composition may comprise cobalt with a recycled content of from 40% to 60%. In some methods, x% of the cathode active material composition is derived from the first cathode active material, where x is greater or equal to 16 and less than or equal to 85. In such methods, at least (16*100 / x) % of the cobalt in the first cathode active material may be recycled cobalt. In other such methods, at least (26*100 / x) % of the cobalt in the first cathode active material may be recycled cobalt. In other such methods, at least (40*100 / x) % of the cobalt in the first cathode active material may be recycled cobalt. In other such methods, at least (60*100 / x) % of the cobalt in the first cathode active material may be recycled cobalt. In other such methods, at least (80*100 / x) % of the cobalt in the first cathode active material may be recycled cobalt. In other methods, the weight ratio of the first cathode active material to second cathode active material is expressed by x:1, wherein 0.19 <x <6. In such methods, the percentage of the cobalt in the first cathode active material that is recycled cobalt may be expressed by z% wherein z is greater or equal to 16(x+1) / x. z may be greater or equal to 26(x+1) / x. z may be greater or equal to 40(x+1) / x. z may be greater or equal to 60(x+1) / x. z may greater or equal to 80(x+1) / x. Recycled Nickel In methods of the first aspect of the disclosure, the first cathode active material further comprises recycled nickel. In some methods, at least 7% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 10% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 15% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 20% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 25% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 33% of the nickel in the first cathode active material may be recycled nickel. In some methods, at least 37.5% of the nickel in the first cathode active material is recycled nickel. In further methods, at least 45% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 60% of the nickel in the first cathode active material is recycled nickel. In some methods, at least 80% of the nickel in the first cathode active material is recycled nickel. In some methods, all of the nickel in the first cathode active material is recycled nickel. The first cathode active material may comprise a recycled lithium to recycled nickel weight ratio of 1:2 to 2:1. In methods where the first cathode active material comprise both nickel and cobalt, the first cathode active material may comprise a recycled nickel to recycled cobalt weight ratio of 0.3:1 to 1:1. The cathode active material composition of the various aspects of the present disclosure may comprise nickel with a recycled content of at least 6%. The cathode active material composition may comprise nickel with a recycled content of at least 10%. The cathode active material composition may comprise nickel with a recycled content of at least 12%. The cathode active material composition may comprise nickel with a recycled content of at least 15%. The cathode active material composition may comprise nickel with a recycled content of at least 20%. The cathode active material composition may comprise nickel with a recycled content of at least 40%. The cathode active material composition may comprise nickel with a recycled content of at least 60%. The cathode active material composition may comprise nickel with a recycled content of at least 80%. The cathode active material composition may comprise nickel with a recycled content of from 6% to 99%. The cathode active material composition may comprise nickel with a recycled content of from 6% to 80%. The cathode active material composition may comprise nickel with a recycled content of from 6% to 50%. The cathode active material composition may comprise nickel with a recycled content of from 15% to 99%. For example, the cathode active material composition may comprise nickel with a recycled content of from 15% to 80%. The cathode active material composition may comprise nickel with a recycled content of from 15% to 50%. The cathode active material composition may comprise nickel with a recycled content of from 20% to 50%. In some methods, x% of the cathode active material composition is derived from the first cathode active material, where x is greater or equal to 16 and less than or equal to 85. In such methods, at least (6*100 / x) % of the nickel in the first cathode active material may be recycled nickel. In other such methods, at least (15*100 / x) % of the nickel in the first cathode active material may be recycled nickel. In other such methods, at least (20*100 / x) % of the nickel in the first cathode active material may be recycled nickel. In other such methods, at least (40*100 / x) % of the nickel in the first cathode active material may be recycled nickel. In other such methods, at least (60*100 / x) % of the nickel in the first cathode active material may be recycled nickel. In other methods, the weight ratio of the first cathode active material to second cathode active material is expressed by x:1, wherein 0.19 <x <6. In such methods, the percentage of the nickel in the first cathode active material that is recycled nickel may be expressed by 5% wherein 5 is greater or equal to 6(x+1) / x. 5 may be greater or equal to 15(x+1) / x. 5 may be greater or equal to 20(x+1) / x. 6 may be greater or equal to 40(x+1) / x. 6 may greater or equal to 60(x+1) / x. Recycled Manganese In methods of the first aspect of the disclosure, the first cathode active material further comprises recycled manganese. In some methods, at least 7% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 10% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 15% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 20% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 33% of the manganese in the first cathode active material may be recycled manganese. In some methods, at least 37.5% of the manganese in the first cathode active material is recycled manganese. In further methods, at least 45% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 60% of the manganese in the first cathode active material is recycled manganese. In some methods, at least 80% of the manganese in the first cathode active material is recycled manganese. In some methods, all of the manganese in the first cathode active material is recycled manganese. The first cathode active material may comprise a recycled lithium to recycled manganese ratio of 1:2 to 2:1. In methods where the first cathode active material comprise both manganese and cobalt, the first cathode active material may comprise a recycled manganese to recycled cobalt ratio of 0.3:1 to 1:1. The cathode active material composition of the various aspects of the present disclosure may comprise manganese with a recycled content of at least 6%. The cathode active material composition may comprise manganese with a recycled content of at least 10%. The cathode active material composition may comprise manganese with a recycled content of at least 12%. The cathode active material composition may comprise manganese with a recycled content of at least 15%. The cathode active material composition may comprise n manganese with a recycled content of at least 20%. The cathode active material composition may comprise manganese with a recycled content of at least 40%. The cathode active material composition may comprise manganese with a recycled content of at least 60%. The cathode active material composition may comprise manganese with a recycled content of at least 80%. The cathode active material composition may comprise manganese with a recycled content of from 6% to 99%. The cathode active material composition may comprise manganese with a recycled content of from 6% to 80%. The cathode active material composition may comprise manganese with a recycled content of from 6% to 50%. The cathode active material composition may comprise manganese with a recycled content of from 15% to 99%. For example, the cathode active material composition may comprise manganese with a recycled content of from 15% to 80%. The cathode active material composition may comprise manganese with a recycled content of from 15% to 50%. The cathode active material composition may comprise manganese with a recycled content of from 20% to 50%. In some methods, x% of the cathode active material composition is derived from the first cathode active material, where x is greater or equal to 16 and less than or equal to 85. In such methods, at least (6*100 / x) % of the manganese in the first cathode active material may be recycled manganese. In other such methods, at least (15*100 / x) % of the manganese in the first cathode active material may be recycled manganese. In other such methods, at least (20*100 / x) % of the manganese in the first cathode active material may be recycled manganese. In other such methods, at least (40*100 / x) % of the manganese in the first cathode active material may be recycled manganese. In other such methods, at least (60*100 / x) % of the manganese in the first cathode active material may be recycled manganese. In other methods, the weight ratio of the first cathode active material to second cathode active material is expressed by x:1, wherein 0.19 <x <6. In such methods, the percentage of the manganese in the first cathode active material that is recycled manganese may be expressed by w % wherein co is greater or equal to 6(x+1) / x. co may be greater or equal to 15(x+1) / x. co may be greater or equal to 20(x+1) / x. co may be greater or equal to 40(x+1) / x. co may greater or equal to 60(x+1) / x. Chemical composition As mentioned above, in preferred embodiments, the first cathode active material and second cathode active materials comprise corresponding chemical compositions. In other embodiments, the first cathode active material and the second cathode active materials have different chemical compositions. The first cathode active material and the second cathode active materials have different or the same morphologies or structures. In some embodiments, the first cathode active material and the second cathode active materials may have the same chemical compositions but a different crystalline phase or structure. The chemical composition of the first cathode active materials, second cathode active material and / or the cathode active material composition may be selected from (separately or in any combination) a lithium nickel manganese cobalt oxide (NMC), a lithium nickel cobalt aluminium oxide (NCA), a lithium nickel manganese cobalt aluminium oxide (NMCA), a lithium nickel manganese oxide (LNMO), a lithium manganese nickel oxide, a lithium iron phosphate (LFP), and a lithium manganese iron phosphate (LMFP). Preferably the chemical composition is a lithium nickel manganese cobalt oxide (NMC) or a lithium iron phosphate (LFP). Most preferably the chemical composition is a lithium nickel manganese cobalt oxide (NMC). Such an NMC may include all variations of the NMC phase without limitation all NMC mix variations of metals such as NCM, CMN, CNM, MNC, MCN comprising different metal combinations of nickel and manganese The chemical composition may be expressed by the general formula LiNixMnyCoi-x-yO2, wherein 0 <x <1, and 0 <y <1, and x + y <1, and any approximations and / or intermediary ratios. In some embodiments, x = 0.9 and y = 0.05 (i.e. LiNi0.9Mn0.05Co0.05O2, NMC 955). In some embodiments, x = 0.8 and y = 0.1 (i.e. LiNi0.8Mn0.1Co0.1O2, NMC 811). In some embodiments, x = 0.7 and y = 0.2 (i.e. LiNi0.7Mn0.2Co0.1O2, NMC 721). In some embodiments, x = 0.6 and y = 0.2 (i.e. LiNi0.6Mn0.2Co0.2O2, NMC 622). In some embodiments, x = 0.5 and y = 0.3 (i.e. LiNi0.5Mn0.3Co0.2O2, NMC 532). Put another way, the chemical composition may be NMC811, NMC721, NMC622, NMC532, or NMC955. Other chemical compositions comprise NCA 90, NMCA90, NCA 84 and NMC 90, NMX 75. In embodiments where the first cathode active material and the second cathode active materials have different chemical compositions (including approximate and / or intermediary compositions), the cathode active material composition may be a mixed blend of chemical compositions of any of the aforementioned cathode active materials. For example, in some embodiments, the first cathode active material may be NMC combined with any of the available cathode active materials such as LFP, LMFP, NCA, NMCA, LCO, LMO, LTO, and particularly, any combinations of NMC and LFP. The first cathode active material could be any of binary, tertiary, quaternary, or pseudo systems and the second active cathode material may be any available cathode active material . In this respect it may be possible to optimise the amounts used of cathode active materials with different chemistries for battery ready cathode active materials complying with OEM requirements. Tailoring by selection or tweaking of different chemistries in mixtures or blends and their relative amounts can result in optimum battery parameters such as specific energy, specific power, lifespan, cost and performance. Combining the cathode active materials As described above, the method of the first aspect of the disclosure comprises combining a first cathode active material with a second cathode active material. Combining may comprise mixing in any agitator, typically, using agitated tanks with specific geometry agitator blades, such as ribbon agitators. These may be suitable for slurry blending. In some methods, the weight ratio of the first cathode active material to second cathode active material may be from 1:10 to 10:1. Preferably the weight ratio of the first cathode active material to second cathode active material is from 1:6 to 10:1. The weight ratio of the first cathode active material to second cathode active material may be from 1:6 to 5:1. The weight ratio of the first cathode active material to second cathode active material may be from 1:6 to 1:1. The weight ratio of the first cathode active material to second cathode active material may be from 1:6 to 1:2. In further methods, the weight ratio of the first cathode active material to second cathode active material is from 1:3 to 2:1. The weight ratio of the first cathode active material to second cathode active material is from 1:3 to 1:1. The weight ratio of the first cathode active material to second cathode active material is from 1:3 to 1:2. In some methods of the first aspect of the disclosure, combining the first cathode active material and the second active cathode material comprises uniformly distributing particles of the first cathode active material and second cathode active material in a mixer under low moisture conditions. For example, the dew point may be -70°C or below. The dew point may be -73°C or below. The dew point may be -90°C or below. Dew point can be routinely calculated based on the relative humidity and the air temperature. For example, the air temperature may be 25°C and the relative humidity may be 0.01% to provide a dew point of -73°C. These low moisture conditions are required to avoid hydrolytic breakdown of the cathode materials, particular cathodes with higher nickel contents. For example, higher nickel content cathodes tend to increase susceptibility to hydrolytic breakdown. NMC111 and NMC532 are broadly unreactive with atmospheric water and CO2. Meanwhile, NMC622 and NMC811 (and higher ratios) can react directly with atmospheric water and CO2, yielding nickel hydroxide, lithium carbonate and overall gellation, destroying the function layered structure, rendering the cathode material inert. The method of the first aspect of the invention may further comprise processing (e.g. milling) the first cathode active material so that the weight median (D50) particle diameter is within 95 - 105% of the weight median particle diameter of the second cathode active material, prior to combining the first cathode active material with the second cathode active material. Conforming the particle diameters ensure that the first and second cathode compositions are almost equivalent except for the recycled content of the lithium (and potential other elements) allowing them to be homogenously mixed and effectively converted into an electrochemical energy storage device. Second cathode active material Preferably the second cathode active material does not comprise recycled lithium. More preferably the second cathode active material does not comprise recycled lithium, recycled cobalt, recycled nickel, recycled manganese, and / or combinations thereof. The second cathode active may not comprise any recycled elements. Put another way, the second cathode active material may be a virgin cathode active material. The second cathode active material may consist of elements that have been freshly obtained, e.g. mined materials. The second cathode active material may be a commercially available cathode active material or non-commercial. Additional Cathode active materials In some embodiments, the method comprises combining the first cathode active material comprising recycled lithium with a second cathode active material and one or more further cathode active materials (e.g. a third, and potentially fourth, cathode active material) to provide the cathode active material composition. It will be appreciated that in such embodiments the amount of the first cathode active material is controlled to ensure that the cathode active material composition comprises lithium (and potentially other elements) with the desired recycled content (e.g. of at least 6%). The one or more further cathode active materials may have corresponding compositions but with different recycled content (e.g. a different recycled lithium content, or a different recycled content of elements such as cobalt, manganese and nickel). Alternatively, the one or more further cathode active materials may have different chemical compositions. In preferred embodiments, there are only the two cathode active materials. Put another way the method comprises combining exclusively a first cathode active material comprising recycled lithium with a second cathode active material to provide the cathode active material composition. Beneficial combinations &embodiments In some methods of the first aspect of the disclosure, 100 wt% of the cobalt in the first cathode active material is recycled cobalt, at least 37.5% of the lithium in the first cathode active material is recycled lithium and the weight ratio of the first cathode active material to second cathode active material is from 1:5.25 to 1:1. In some methods of the first aspect of the disclosure, 100 wt% of the cobalt in the first cathode active material is recycled cobalt, at least 37.5% of the lithium in the first cathode active material is recycled lithium, at least 37.5% of the nickel in the first cathode active material is recycled nickel and the weight ratio of the first cathode active material to second cathode active material is from 1:5.25 to 1:1. In some methods of the first aspect of the disclosure, 100 wt% of the cobalt in the first cathode active material is recycled cobalt, at least 46% of the lithium in the first cathode active material is recycled lithium, and the weight ratio of the first cathode active material to second cathode active material is from 1:2.85 to 1:1. In some methods of the first aspect of the disclosure, 100 wt% of the cobalt in the first cathode active material is recycled cobalt, at least 46% of the lithium in the first cathode active material is recycled lithium, at least 57.5% of the nickel in the first cathode active material is recycled nickel, and the weight ratio of the first cathode active material to second cathode active material is from 1:2.85 to 1:1. In some methods of the first aspect of the invention, all of the metallic (cationic) species in the first cathode active material have a recycled content of at least 5%, preferably at least 20%. In some methods of the first aspect of the invention, all of the (cationic) species in the first cathode active material have a recycled content of at least 40%. In some methods of the first aspect of the invention, all of the metallic (cationic) species in the first cathode active material have a recycled content of 100%. In some methods of the first aspect of the invention, cobalt, nickel, manganese are comprised within the first cathode active material and have a recycled content of at least 5%, preferably at least 20%. In some methods of the first aspect of the invention, cobalt, nickel, manganese are comprised within the first cathode active material and have a recycled content of at least 40%. In some methods of the first aspect of the invention, cobalt, nickel, manganese are comprised within the first cathode active material and have a recycled content of at least 100%. Additional Components In some embodiments, the first and / or second chemical composition may comprise additives, dopants and / or coatings. In some methods all of the additives, dopants and / or coatings in the first cathode active material have a recycled content of at least 5%, preferably at least 20%. In some methods of the first aspect of the invention, all of the additives, dopants and / or coatings in the first cathode active material have a recycled content of at least 40%. In some methods of the first aspect of the invention, all of the additives, dopants and / or coatings in the first cathode active material have a recycled content of 100%. Formation of first cathode active material In some methods of the first aspect of the invention, the first cathode active material is at least partially formed from used electrochemical energy storage devices, such as spent batteries, and / or from waste materials generated during preparation of electrochemical energy storage devices. Put another way, the recycled elements, e.g. recycled lithium, cobalt, nickel and / or manganese, may be derived from one or more electrochemical energy storage devices and / or one or more waste materials generated during preparation of electrochemical energy storage devices. The one or more electrochemical energy storage devices and / or one or more waste materials may comprise a mixture of different chemical compositions. For example, a mixed feed of batteries comprising different cathode materials, such as NMC 811, NMC532 and NMC622. The first cathode material with a single specific chemical composition may then be formed from said mixed feed. In some methods of the first aspect of the disclosure, the method further comprises forming the first cathode active material comprising the recycled lithium. It will be appreciated that other recycled elements may be present. Forming the first cathode active material may comprise: Separating chemical elements from a source material (e.g. one or more electrochemical energy storage devices, and / or from one or more waste materials generated during preparation of electrochemical energy storage devices), to provide an individual stream of lithium and (an) individual stream(s) of other metallic species (e.g. cationic species such as cobalt, manganese, and / or nickel); combining the individual streams in the ratio that corresponds to the chemical composition of the second cathode active material; Optionally introducing further lithium into the individual stream of lithium and / or the combined stream; Optionally introducing further metallic species (e.g. cobalt, manganese, and / or nickel) into the respective individual stream(s) of the other metallic species (e.g. cobalt, manganese, and / or nickel) and / or the combined stream; and processing the combined streams to form the first cathode active material. The method may comprise controlling the introduction of the further lithium such that the further lithium constitutes 5% to 90% of the total amount of the lithium and 10% to 95% of the lithium is recycled lithium. The method may comprise controlling the introduction of the further lithium such that the further lithium constitutes 5% to 67% of the total amount of the lithium and 33% to 95% of the lithium is recycled lithium. The method may comprise controlling the introduction of the further lithium such that the further lithium constitutes 5% to 24% of the total amount of the lithium and 46% to 95% of the lithium is recycled lithium. The other metallic species may comprise cobalt and the method may comprise controlling the introduction of further cobalt such that the further cobalt constitutes 1% to 80% of the total amount of the cobalt and 20% to 99% of the cobalt is recycled cobalt. The method may comprises controlling the introduction of further cobalt such that the further cobalt constitutes 1% to 10% of the total amount of the cobalt and 90% to 99% of the cobalt is recycled cobalt. The other metallic species may comprise cobalt and the method may not involve the introduction of the further cobalt, such that cobalt is 100% recycled cobalt. The other metallic species may comprise nickel and the method may comprise controlling the introduction of further nickel such that the further nickel constitutes 5% to 90% of the total amount of the nickel and 10% to 95% of the nickel is recycled nickel. The method may comprise controlling the introduction of the further nickel such that the further nickel constitutes 5% to 67% of the total amount of the nickel and 33% to 95% of the nickel is recycled nickel. The method may comprise controlling the introduction of the further nickel such that the further nickel constitutes 5% to 42.5% of the total amount of the nickel and 57.5% to 95% of the nickel is recycled nickel. The other metallic species may comprise manganese and the method may comprise controlling the introduction of further manganese such that the further manganese constitutes 5% to 90% of the total amount of the manganese and 10% to 95% of the manganese is recycled manganese. The method may comprise controlling the introduction of further manganese such that the further manganese constitutes 5% to 67% of the total amount of the manganese and 33% to 95% of the manganese is recycled manganese. The method may comprise controlling the introduction of the further manganese such that the further manganese constitutes 5% to 42.5% of the total amount of the manganese and 57.5% to 95% of the manganese is recycled manganese. In some methods processing the combined streams comprises co-precipitating and calcining the combined streams to form the first cathode active material. In some methods combining the individual streams may comprise combining one or more of the streams of other metallic (cationic) species (e.g. cobalt, manganese and / or nickel) in a predetermined ratio and precipitating out these metallic (cationic) species to form a cathode active material precursor precipitate. This may then be subsequently combined with the lithium stream. The other metallic (cationic) species may be precipitated as hydroxide and / or carbonates. By precipitating these metals out of solution together, they are much better mixed that would be the case were they to be mixed as solids. The precipitated metallic (cationic) species (e.g. Ni, Mn, Co carbonate) may be filtered, dried, and milled before undergoing a pre-calcining step before addition of the lithium stream. The combined materials including the lithium may then be processed (e.g. calcined at elevated temperatures in oxygen) to form the first cathode active material. The method may include one or more mixing, grinding, or milling steps. Whilst such steps may take place at any stage where it is desirable to break down solids into smaller pieces, this step will most likely be conducted after the cathode active material precursor precipitate has been dried, after it has been pre-calcined, and / or after it has been calcined. Any suitable mixing, grinding, or milling process may be used and the present invention is not particularly limited by the method used, for example, dry or wet planetary ball milling, rolling ball milling, high shear milling, air jet milling, and / or impact milling. The method may include one or more filtration steps. The filtration step may take place at any stage where it is desirable to separate a solid from a liquid. Any suitable filtration process may be used and the present invention is not particularly limited by the method used. Separating chemical elements As mentioned above, forming the first cathode active material may comprise separating chemical elements from a source material (e.g. one or more electrochemical energy storage devices, and / or from one or more waste materials generated during preparation of electrochemical energy storage devices), to provide an individual stream of lithium and (an) individual stream(s) of the other metallic species (e.g. cobalt and / or nickel). This section provides further details regarding this separation step. In this section, the other metallic species are collectively referred to as one or more target metals. Accordingly, the separation of the chemical elements from the source material to provide an individual stream of lithium and (an) individual stream(s) of the one or more target metals may comprise: a) contacting the source material with water and acid to leach one or more target metals from the source material to form a pregnant leach solution; b) monitoring one or more of: i) foaming, ii) the rate of change of concentration of one or more target metals in the pregnant leach solution, iii) the rate of change of pH, and iv) the initial concentration of one or more target metals to determine when to cease addition of acid such that all target metals have been solubilized and the pH is between 0 and 2.3; c) adding a reducing agent, preferably a peroxide, whilst maintaining the temperature of the pregnant leach solution at 85°C or less and monitoring one or more of: i) foaming, ii) the rate of change of concentration of one or more target metals in the pregnant leach solution, iii) the rate of change of pH, and iv) the initial concentration of one or more target metals in the source material; and the pH is between 1 and 2.3 to determine when to cease addition of reducing agent; d) adding a base to the pregnant leach solution to increase the pH of the pregnant leach solution to around 5 to 5.3 and providing an oxidizing agent to precipitate any intermediary metals or metal compounds, such as copper, aluminium, and iron, from the pregnant leach solution to form a depleted leach solution; e) performing a copper cementation reaction to remove copper from the depleted leach solution if copper is present; and f) recovering one or more target metals (i.e. individual streams of other metallic species) from the depleted leach solution to provide a lithium leach solution (i.e. an individual stream of lithium). Source materials, which preferably contain one or more of manganese, cobalt, nickel, and lithium, such as batteries, mixed hydroxide precipitates, or scrap from battery manufacturing often contain other materials or metals such as aluminium, iron, copper, graphite, and possibly even cadmium. It is desirable to separate these different materials from one another so that the valuable materials may be re-used to form useful materials. Useful materials may include precursors to active electrode materials, cathode or anode active materials for use in batteries, cathode or anode active materials for use in batteries, as well as materials for any other use, such as, for example, speciality and technical material manufacture such as alloys, coatings, composites, alloys, performance additives agrichemical, construction materials, fertilizers, electrical components, and pharmaceutical derivatives. It is possible to leach metals into solution by contacting them with acid. Although a wide variety of acids could be used, for example hydrochloric acid, nitric acid, perchloric acid, hydrobromic acid, organic acids, aqua regia, or mixtures of any thereof, it is preferable to use sulphuric acid due to its availability, price, and suitability for use in a material recovery plant. Preferably, the sulphuric acid is not concentrated sulphuric acid at the point of process. In other words, concentrated sulphuric acid is not what is in contact with the material from which metals are being leached, but dilute acid is instead what is in contact with the material from which metals are being leached. For example the sulphuric acid may be 70% (mass fraction) or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. In the present context, concentrated sulphuric acid is defined as being greater than 70% (mass fraction). Typical commercially available concentrated sulphuric acid is 96% (mass fraction). Where other acids are used, they will have different parameters for defining whether the acid is concentrated or not. For example, concentrated hydrochloric acid is typically around 20% (mass fraction) or greater. Concentrated typically is defined by the azeotropic minimum water concentration or maximum dissolved in water under reasonably safe manufacturing and transport conditions. The addition of concentrated sulphuric acid leads to the production of hydrogen fluoride gas from fluorinated compounds in the source material, is highly toxic, more volatile, more difficult to handle and more difficult to control in chemical reactions. The amount of acid at the beginning of the leaching step may be around 35%, 30%, 25%, 20%, 15%, 10% (all w / v%) of the acid. As the leaching progresses and uses up the acid, this will drop over time. Staged addition of further acid will at least partially replace any acid which has been used up in the reaction or otherwise lost. It will be appreciated that in step d), the metals may precipitate in metallic form, but not necessarily and may additionally or alternatively precipitate as a compound including the metal. In addition, in step d) some copper may precipitate from solution, although the majority of any copper is removed in a subsequent cementation reaction step. The above separation method includes adding water to the source material and then adding sulphuric acid to leach metals into solution. The addition of water assists in mitigating the amount of HF gas produced. Preferably there is more than 15% (w / v%) water in the various stages of the above method. The above method describes an aqueous method of leaching and recovery of materials from a source material. This leaching process generates gases which cause foaming or bubbling, which is indicative of the reaction proceeding. In particular, the reactions generate hydrogen gas which causes bubbling or foaming. Although an anti-foaming agent could be added, it is preferable for one not to be added as this will increase costs, introduce potential contaminants that will ultimately have to be removed, and would also prevent one way of determining when the reaction is complete since no foam would be generated. In steps in which gas is generated which can cause foaming or bubbling, physical countermeasures may be employed. For example, the solution may be recirculated and sprayed on the top of the solution to control the foaming or bubbling. Additionally or alternatively, one or more physical foam breakers, such as a beater or a centrifugal flail, positioned above a liquid line may be used to beat and break any foam on contact. The amount of acid added, preferably sulphuric acid, is preferably greater than the stoichiometric amount required to leach all of the metals from the source material. For example, the amount of sulphuric acid added may be 1.01, 1.02, 1.02, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, or 1.15 times the stoichiometric amount. In this way, there is just more than enough acid to leach any valuable metals from the source material, thereby ensuring maximum recovery of the metals. In addition, since it will be necessary to ultimately neutralise the acid, it is desirable to control the amount added in order to avoid unnecessary wastage of acid and neutralisation agent by adding too much acid above the stoichiometric amount. In solution, acid serves as the oxidant for any aluminium, copper, or iron in solution. In the presence of acid, peroxide is a reducing agent for manganese and cobalt oxides, which can then be neutralised by acid. For nickel oxide, the acid serves as a neutralisation agent. The combined acid demand, which is dependent on the chemistry and amount of any leachable species as well as the desired final pH, can be calculated or estimated based on the characteristics of the initial feedstock. By adding slightly more than the stoichiometric amount, it can be assured that all leachable species have been leached into solution. The above separation method includes monitoring the reaction by one or more of foaming, the rate of change of the concentration of one or more target metals in the pregnant leach solution, the rate of change of pH, and the initial concentration of one or more target metals to determine when to cease addition of acid such that all target metals have been solubilized and the pH of the solution is between 0 and 2.3. Since gases are produced when there is an ongoing reaction, monitoring of the foaming can be used to determine when acid addition can be stopped since hydrogen gas will no longer be formed once all of the metals have been leached into solution. Similarly, the method may include monitoring the concentration of one or more target metals, such as manganese, cobalt, nickel, lithium, aluminium, copper, or iron, in the pregnant leach solution since the concentration will increase as long as there is more of the target metal to be leached. Once there is a constant concentration of the metal, taking into account any additional liquid added which would dilute the concentration but not the overall mass of metal in solution, addition of the acid may be ceased. Similarly, since the reaction with any metals will destroy the acid, knowing the rate at which acid is being provided, it is possible to monitor the rate of the change in pH to determine when the acid is no longer being used up in leaching the metals into solution. Furthermore, it is possible to calculate, based on the initial concentration of one or more target metals, how much acid needs to be added and by monitoring the initial concentration of the one or more target metals in a batch, it is possible to ensure that the correct amount of acid is added to leach the metals from the material and to also provide a solution within the given pH range. The method requires that the pH of the pregnant leach solution is between 0 and 2.3 in order to ensure that solubilised metals in solution remain in solution. The above separation method further includes adding a reducing agent, such as a peroxide, preferably hydrogen peroxide or sodium peroxide. Additionally or alternatively, the reducing agent may be sulphur dioxide, or an organic acid, such as oxalic acid, or a mixture of any of the reducing agents mentioned to the pregnant leach solution. Perhaps unexpectedly, the peroxide acts as a reducing agent in this step. Similarly, the sulphur dioxide or organic acid are also selected to serve as reducing agents. The reducing agent is selected so as to be unreactive against the highly acidic environment whilst also limiting the amount of any new or additional metal content into solution. The method includes keeping the temperature at 85°C or less in order to reduce the amount of acid gas, specifically hydrogen fluoride, being produced as this is a dangerous gas and needs to be scrubbed from any waste gas. The method may include keeping the temperature at 75°C or less, 65°C or less, 60°C or less, 55°C or less, 50°C or less, 45°C or less, or less than 50°C. In addition, hydrogen peroxide is susceptible to decomposition at increased temperatures, so using temperatures greater than 85°C would cause the hydrogen peroxide to decompose into oxygen and water without having sufficient time to react and would therefore simply be wasted due to decomposition rather than chemical reaction. The total amount of peroxide added may be calculated as the stoichiometric amount plus a calculated excess. The amount of peroxide, or indeed other reducing agent, added may be 1.01, 1.02, 1.02, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, or 1.15 times the stoichiometric amount. It has been found that using a less than stoichiometric amount does not lead to any selectivity regarding target metals and instead causes a loss of efficiency. This step also includes monitoring one or more of foaming, the rate of change of the concentration of one or more target metals in the pregnant leach solution, the rate of change of pH, and the initial concentration of one or more target metals to determine when to cease addition of peroxide / reducing agent. Preferably, the reducing agent, preferably a peroxide, preferably hydrogen peroxide, is added to the solution until the rate of change of pH over time and / or the rate of change of the concentration of one or more target metals tends to a predetermined value, which is preferably zero which indicates that the reaction is complete. The pH must end up between 1 and 2.3 in order to ensure that the metals remains in solution. Acid may be added to control the pH as required. The acid and / or peroxide may be added steadily or in batches. The above separation method is primarily a batch process. The above separation method further includes adding a base subsequent to the completion of the addition of the reducing agent, preferably hydrogen peroxide. The base may be selected from one or more of sodium hydroxide, calcium hydroxide, calcium carbonate, calcium oxide, magnesium carbonate, magnesium oxide, magnesium hydroxide, nickel hydroxide, cobalt hydroxide, manganese hydroxide, lithium hydroxide, mixed hydroxide precipitate, or a combination thereof. Although sodium hydroxide can be used, the base is preferably not sodium hydroxide since this results in the formation of sodium sulphate. Sodium sulphate as a by-product has a number of disadvantages. Firstly, sodium sulphate is in sufficient supply and is a low value by-product since it is generated in excessive quantities in parallel industries, such as a by-product in the manufacture of nylon and this supply is sufficient to meet the needs of sodium sulphate in the washing powder and pulping agent industries, and so the demand of sodium sulphate in the marketplace is already easily met. With ever increasing rates of recycling of battery materials, the supply of sodium sulphate is set to increase further. In addition, sodium sulphate accumulation in the system throughout is hard and expensive to remove. The solubility of sodium sulphate in water is unusually dynamic in that it increases by around ten times as the temperature of water increases from around 0°C up to around 32°C. As the solubility of sodium sulphate is heavily dependent on temperature, having sodium sulphate dissolved in a solution within a recycling process causes issues since the temperature either needs to be controlled and kept above ambient temperature to avoid the sodium sulphate crystallising out of solution at an undetermined step in the process, which can cause blockage of filters, pumps, or pipework in a plant, or the process needs to include an additional step towards the beginning of the process in which a large volume of solution needs to be cooled to knock out the dissolved sodium sulphate, filtered, and then reheated in order for subsequent reactions to take place at an acceptable rate. Both of these options incur high additional costs, which are not offset due to the low value of the sodium sulphate product. As such, the above process seeks to avoid these problems by minimising the production of sodium sulphate. Calcium hydroxide, calcium oxide, and calcium carbonate as well as magnesium hydroxide, magnesium oxide, and magnesium carbonate are suitable as a base for a number of reasons. In addition to being a base, calcium will react with any available fluoride to form calcium fluoride, which are extremely poorly soluble in water and therefore is removed from solution. Magnesium fluoride is also poorly soluble in water, meaning that it can be removed from solution readily. In this way, the above separation method includes a fluorine mitigation or fluoride scrubbing step. This mitigates the risk of hydrogen fluoride gas being released and residual hydrofluoric acid remaining in solution, which is a large risk when battery materials are being recycled due to the presence of fluorinated compounds in batteries. In addition, calcium sulphate is only sparingly soluble in water, unlike sodium sulphate, and therefore is readily removed from solution, such as by filtering, and does not require such rigorous thermal control of the solution. Magnesium sulphate is also poorly soluble in water. Furthermore, calcium sulphate, also known as gypsum, is much more valuable than sodium sulphate. After removal of calcium sulphate from solution, the osmotic pressure of the solution is reduced and so the solution can be concentrated without the risk of precipitation. The above separation method may include one or more filtration steps whenever a solid material needs to be removed. Any known filtration method may be employed and the present invention is not particularly limited by any specific filtration method. For example, graphite may be filtered from solution after the initial leaching step. The nickel hydroxide, cobalt hydroxide, and manganese hydroxide, possibly as a mixed metal hydroxide, may be produced. These may be used as the individual streams of the elements but also may be recycled back into the process to adjust the pH of the pregnant leach solution to precipitate any intermediary metals or materials, such as copper, aluminium, or iron. As such, one or more of the lithium hydroxide, manganese hydroxide, cobalt hydroxide, and nickel hydroxide may be a recycle stream at least partially obtained from the depleted leach solution. An intermediary material or metal is a material or metal other than nickel, cobalt, manganese, and lithium which needs to be removed from solution at some stage of the process. This may include one or more transition group metals. The pH of the pregnant leach solution is adjusted to around 5 to around 5.3, which causes any solubilised iron and aluminium to precipitate out of solution. An oxidising agent, such as air, is provided to assist with precipitation of any aluminium or iron. The above separation method further includes a copper cementation, otherwise known as copper scrubbing, step to remove copper from the depleted leach solution if copper is present. Where the source material includes any batteries, such as battery manufacture scrap, it is likely that the solution will include copper. In a copper cementation process, a redox reaction between metallic iron and copper in solution results in copper metal precipitating out of solution. In particular, the exemplary reaction may be: Fe(s) + Cu2+ *Cu(s) + Fe2+ Fe2+ + O2 + H2O —► Fe(O)OH Indeed, any metal with a more negative standard electrode potential than copper may be used and the process is not limited to metallic iron. A copper cementation process usually includes an oxidiser, such as air, to oxidise iron, or other metal, in solution, which can precipitate out as iron (III) oxy-hydroxide. The precipitated copper and iron, or other metal used in the cementation step, can be separated from the solution and processed separately. The copper may be recovered by, for example, electrowinning. Following the copper cementation reaction, one or more target metal, such as one or more of manganese, cobalt, and nickel, may be recovered from the depleted leach solution to provide a lithium leach solution (i.e. to provide an individual stream of lithium). The recovered metals may form the individual streams of the other target metals such as manganese, cobalt, and / or nickel). The separation of manganese, cobalt, and nickel from solutions may be conducted by solvent extraction. The above separation method may further include precipitating sodium sulphate from the concentrated lithium leach solution, assuming that sodium sulphate is present in solution. This may be done by cooling the concentrated lithium leach solution. The concentrated lithium leach solution may be cooled to around 5°C or less, for example from around 2 to around 4°C. The leach solution may be cooled to from around 0°C to around 6°C, around 1°C to 5°C, or around 2°C to 4°C. The above separation method may further include concentrating the lithium leach solution to form a concentrated lithium leach solution. Since the solution from which the lithium leach solution is derived needed to have sufficient volume to leach and hold the metals from the source material, as the respective metals are selectively removed from the solution, leaving primarily lithium in solution, the concentration of metal ions is decreased. As such, it is advantageous to concentrate the lithium leach solution so that a smaller volume of liquid needs to be handled and a higher extraction efficiency may be accessed. The concentration may be achieved by any method and the invention is not particularly limited by the method selected. Reverse osmosis is one example of a suitable concentration method. The above separation method may further include precipitating lithium carbonate from the concentrated lithium leach solution. The method may include adding one or both of sodium carbonate and ammonium carbonate to the concentrated lithium leach solution. The addition of these carbonate is to convert lithium ions in solution into lithium carbonate. The method may further include precipitating lithium carbonate from the concentrated lithium leach solution. It will be appreciated that the lithium could be precipitated from the lithium leach solution without concentration. Whilst this would mean that there is a large volume of liquid from which to precipitate the lithium carbonate, this would avoid the concentration step, which may be advantageous in simplifying the process. As previously mentioned, the source material may be a mixture of materials from different sources rather than a single type of material. Battery factory waste is material which is used to produce batteries and include offcuts, scrap, batteries which have failed quality control, as well as any other materials containing useful battery materials. Indeed, the source material may be a mixed source material, with materials from different sources being processed together. A further advantage of the present invention is that it is able to accommodate different feedstocks with different metals and different concentrations of metals, in contrast to existing methods which are limited to only particular feedstocks and do not provide the same flexibility to handle a range of feedstocks. Indeed, feedstocks can be blended deliberately to match the incoming metal composition balance with a particular product mix and / or demand plan for the various commercial offtakes. For example NMC111 feedstocks can be recycled alongside other feedstocks which result in an output which has a desired chemistry, for example NMC811. The above separation method may further include, prior to step a), contacting shredded lithium-containing batteries and / or source material with a basic aqueous solution of an alkali metal salt or alkali earth metal salt. The separation method may include, prior to step a), brine discharging of the source material to dissipate any electrical charge. This may be achieved by submerging any batteries in a brine to electrically discharge them. The batteries may be dry shredded or wet shredded. Preferably the alkali metal salt or alkali earth metal salt is not a chloride. Preferably, the alkali metal is other than sodium. The source material may include materials which retain some electrical charge. By contacting the source materials with a basic solution of an alkali metal salt other than sodium chloride or indeed any other sodium salt, the charge may be dissipated. Preferably, the method does not include thermal discharge of the source material. Thermal discharge is where the material is heated up to a temperature, such as 300°C or higher for a time to remove any electric charge from the materials and / or to burn off certain materials, such as plastic or paper. It is undesirable to burn off materials such as plastic or paper. In addition, thermal discharging of the source material requires additional energy to be provided, which increases cost and also energy requirements. Other means of dissipation could be implemented, such as electrical load discharging where a battery is connected to an electrical load to drain the battery, or by puncturing the battery and immersing it in a conductive fluid, such as brine, preferably sodium-free and / or chlorine-free brine. The solution is preferably aqueous, but can comprise an organic solvent if required. In this way removal of any chloride ions which could otherwise act as a contaminant is not required and a corrosion risk within chemical plant infrastructure designed for sulphuric acid based processes is avoided. In addition, the solution is basic in order to avoid degradation of electrolytes which may be present as these are generally fluorinated compounds, such as LiPFe, lithium hexafluorophosphate, which can release hydrogen fluoride gas, which is extremely hazardous. LiPFe is generally stable, but is susceptible to hydrolysis in acidic media. In addition, it is preferable to avoid the use of sodium salts since these will ultimately become sodium sulphate, which has various undesirable qualities as detailed above. Preferably, chloride salts are avoided since this can attack certain grades of steel and would require a higher grade of steel to be used, which increases costs. Calcium salts are preferable since the calcium can react with any free fluoride to precipitate as calcium fluoride. The above separation method may further include recovering the basic aqueous solution after contacting the basic aqueous solution with the source material. By separating the basic aqueous solution and any remaining solids, the solids can be passed into step a), optionally after being washed, and the basic aqueous solution can be taken away for further processing, if required. The separation can be done by any suitable means, such as filtration or centrifugal separation. The above separation method may include separating out any metallic foils, binders, membranes, separators, or plastics from the basic aqueous solution. Preferably, the metallic foils or plastics are removed prior to step a) to minimise the amount of material which is being processed and to minimise the amount of aluminium which needs to be removed. Batteries include conductive foils, usually aluminium, and whilst these can be removed in step a) by dissolving them in acid, this increases the amount of acid required to leach the valuable battery metals from the source material, increases the amount of hydrogen H2 released during the leach process and also increases the amount of aluminium which subsequently needs to be precipitated from solution. As such, removing any foils ahead of the leaching step, is preferable. The foils may be removed by any known method, for example, eddy current, shaker table separation, sieving or filtration. Similarly, the source material may include various plastics, some of which may be readily removed by, for example, flotation, shaker table separation, sieving or filtration. Preferably, the plastics are moved by a method other than combustion or other thermal removal, such as evaporation or pyrolysis. The above separation method may include adding water in step a) to provide a solid loading within a predetermined range. Since the source material needs to be mixed and transferred, this can be made easier by adding water to allow the source material to move more freely. Water may be added to provide any desired solid loading, such as 10wt% (that is the solid makes up 10% of the total mass of a given volume of the mixture of the source material and water), 15wt%, 20wt%, 25wt%, 30wt% or 40wt%. A lower solid loading will make mixing and transfer easier, but will increase the volume of liquid which needs to be handled. The above separation method may further include, adding, in step a) acid in stages or steadily at a rate which controls foaming and spontaneous exothermic processes. The addition of acid, such as sulphuric acid, generates gas and foaming which needs to be kept in control. The reaction generates hydrogen gas, which must be diluted otherwise it results in a danger of explosion. In addition, the addition of sulphuric acid to water causes an increase in temperature, which also needs to be controlled to avoid overheating the solution, which can present a safety hazard and can also result in the generation of unwanted hydrogen fluoride gas. In addition, the addition of sulphuric acid to cathode metal oxides causes an increase in temperature, which also needs to be controlled to avoid overheating the solution, which can present a safety hazard and can also result in the generation of unwanted hydrogen fluoride gas. In addition, it is desirable to keep the temperature below around 85°C since in the next stage hydrogen peroxide will be added, which rapidly decomposes at elevated temperatures. The temperature may be at or below around 80 °C, 75°C, 70°C, 65°C, 60°C, 55°C, 50°C, 45°C, or less than 50 °C .The staged addition of sulphuric acid or the addition of sulphuric acid at a controlled rate avoids these issues. Furthermore, since the total amount of metals in the source material may not be known exactly, given that the method is able to accommodate a whole range of potential source materials, it is preferable to control the addition of sulphuric acid to provide sufficient time for any foaming to be observed to inform on the progress of the reaction. Similarly, controlled addition of sulphuric acid also allows for sampling of the leach solution to measure whether the concentration of one or more target metals is static, which indicates that all of the valuable battery materials have been leached into solution. In addition, it may take some time for the pH to stabilise and it is desirable that at the reasonable completion of the reaction the pH between about 0 and about 2.3 so that there is a slight excess of acid to ensure that all of the valuable battery metals have been leached and that the pH is below the pH at which certain metals begin to precipitate from solution. In step c), the temperature of the solution may be from about 40°C to about 85°C, from about 50°C to about 70°C, from about 55°C to about 65°C, or about 60°C, or about 55°C, or about 50°C, or about 45°C, or less than 50°C. These temperature ranges ensure that the peroxide does not decompose before it can react and also minimises the production of hydrogen fluoride gas. The above separation method may include stirring at any step. It will be appreciated that it is desirable to ensure that the solution and the source materials are mixed so that the process is as efficient as possible. The oxidizing agent in step d) may be oxygen, air, or peroxide, such as hydrogen peroxide. Preferably, the oxidizing agent is oxygen or air. The oxidizing agent may be added by any suitable means, but where it is a gas, it may be bubbled through the solution. The above separation method may include adding zinc to the depleted leach solution after step e) in order to precipitate cadmium from solution. Zinc powder may be used to precipitate cadmium (s) where ZnO is in solution as Zn2+. Cadmium may be a contaminant and, if present, it is desirable to remove this dangerous element from the process. The addition of zinc causes any cadmium to precipitate out of solution, from which it can be removed and disposed of safely. As mentioned, one, two or all of manganese, cobalt, and nickel may be recovered from the depleted leach solution via solvent extraction. Solvent extraction of these elements from solution is known in the art, and the present invention is not particularly limited by the way in which this is achieved. For example, manganese may be removed from solution using Di(2-ethylhexyl)phosphoric acid (DEHPA) and kerosene. Cobalt may be removed from solution using Cyanex 272™ and kerosene. The pH of the solution may be adjusted using an acid, such as sulphuric acid, and one, two, or all of sodium hydroxide, ammonium hydroxide, lithium hydroxide, nickel hydroxide, manganese hydroxide, or cobalt hydroxide, preferably wherein the nickel hydroxide, lithium hydroxide, cobalt hydroxide, and / or manganese hydroxide is a recycle stream at least partially obtained from the depleted leach solution. By using a recycle stream, it is possible to reduce the amount of additional chemicals which need to be used in the process. The pH may be selected such that greater than 50% of a target material is extracted in the solvent extraction step. The solubility of different metals depends on the pH and by adjusting the pH of a solution, it is possible to control which metal is preferably extracted. Nickel may be precipitated from the pregnant leach solution with a mixture of ammonium hydroxide, lithium hydroxide, and / or sodium hydroxide. Whilst it is desirable to minimise the amount of sodium being used in the method, nickel coordinates with ammonium hydroxide, so it is preferable to use ammonium hydroxide to precipitate out the nickel alongside one or both of sodium hydroxide and lithium hydroxide. Even so, some ammonium hydroxide can be used to reduce the amount of sodium being introduced. The pH of the depleted leach solution may be increased to about 7 to about 11, to about 8 to about 10, to about 8.5 to 9.5, or to about 9 to 9.5 in order to precipitate nickel. Brief Description of the Drawings Specific embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing in which corresponding reference symbols indicate corresponding parts, and in which: Figure 1 is a schematic flowsheet depicting various steps in the method of separating chemical elements from a source material for subsequent use in a first cathode active material; Figure 2 is a schematic flowsheet depicting various subsequent steps in the method of separating chemical elements from a source material for subsequent use in a first cathode active material; Figure 3 is a schematic flowsheet depicting various further subsequent steps in the method of separating chemical elements from a source material for subsequent use in a first cathode active material; Figure 4 is a schematic flowsheet depicting a method of preparing a first cathode active material. Figure 5 is a schematic flowsheet depicting an example method according to invention. Figure 6 shows X-ray diffraction data of a first cathode active material comprising recycled lithium, cobalt, nickel and manganese and a second cathode active material made from fresh / virgin sources and the right hand side depicts an expanded view of the same as the left hand side. Figure 1 depicts a first flowsheet depicting various steps in the method of separating chemical elements from a source material for subsequent use in a cathode active material. In the method, a source material 1 is provided and water 3 is combined the source material 1. The water is added in an amount calculated depending on the amount of course material as well as the desired solid loading. Acid 2, such as sulphuric acid, is also combined with the mixture of water 3 and source material 1 in order to begin leaching metals from the source material 1. This acid leaching step is preferably conducted at from around 40 to around 80°C, and may be conducted at less than 50°C. The initial leaching step is monitored to determine when the leaching is complete. The pH of the solution is from 0 to 2.3 to ensure that the metals are retained in solution. The monitoring is done by any one or more of the methods described herein. For example, since the reactions which leach metals into solution also generates gases, the foaming of the solution can be observed to determine when the reaction is complete. The acid vapours, which include any HF produced as well as any hydrogen gas produced are taken away for further processing. After the initial leaching step has been completed, as indicated by a cessation of foaming, the concentration of one or more metals being constant, the pH indicating that no more acid is being used up in chemical reactions, or a total calculated amount of acid being added, and wherein the pH is between 0 and 2.3, hydrogen peroxide is added to the solution until the reaction has reached completion and wherein the pH is between 1 and 2.3. Additional acid may optionally be added if the pH rises above 2.3 during the second stage of the leaching, namely the addition of the reducing agent, preferably hydrogen peroxide. The hydrogen peroxide may be 30% hydrogen peroxide, although other concentrations can also be used. The temperature is kept below 85°C in order to avoid premature decomposition of the hydrogen peroxide. A greater than stoichiometric amount of the sulphuric acid 2 and hydrogen peroxide 5 are added to ensure that all of the metals are leached into solution. In order to avoid unnecessary usage of chemicals, the amounts added are just over stoichiometric. In other words, the amount of acid / peroxide added is greater than the stoichiometric amount required to leach all of the target metals into solution. The sulphuric acid 2 and hydrogen peroxide 5 are preferably added either in batches or at a controlled rate, rather than all at once, in order to control the reaction. Once the metals are leached into solution, graphite 6 and any other remaining solids are filtered out of the solution. The graphite 6 is unaffected by the leaching step and so the graphite phase retains the morphology and particle size required to act as new anode material, such as greater than 5 microns, without requiring an energy intensive fusion process step to regrow crystallites. The solution is then neutralised through the addition of a base. The base may be provided as a fresh base from outside the process, or may be a recycle stream including a basic solution or compound from a later stage of the process. The pH of the solution is increased to around a pH of 4 to 6 at a temperature of from around 30 to around 60°C. This causes gypsum (if the base includes calcium), iron, and aluminium to precipitate out of solution, which can be filtered off 8. If calcium hydroxide is used as a base, this will also precipitate out, likely as calcium fluoride. Following the filtration step 8, there is a copper cementation step 9. The copper cementation step 9 removes any copper present in solution and is achieved by the addition of metallic iron and an oxidiser, such as air. This causes copper metal to precipitate from solution as well as iron oxides. The solids may be filtered out in step 10 and the copper may be separated and recovered by electrowinning. This forms depleted pregnant leach solution 11, which including any nickel, cobalt, manganese, and lithium, but has been depleted of any copper, iron, or aluminium as intermediary metals. As shown in Figure 2, the depleted pregnant leach solution 11 is then passed to a series of extraction steps 12, 13, 14 to selectively remove manganese, cobalt and nickel from solution. The solvent extraction of manganese takes place first in line with standard practice and includes the addition of sulphuric acid, a solvent extraction base, water, DEHPA, and kerosene. This creates a manganese-loaded DEHPA / kerosene stream 15 from which manganese sulphate 16 can be removed, which forms a stripped DEHPA / kerosene stream 17, which is recycled back in order to extract further amounts of manganese from the depleted pregnant leach solution 11. This step can be repeated as many times as required. Once the manganese has been stripped out, cobalt is then stripped out in another solvent extraction step 13. Cobalt is extracted in line with standard practice and includes the addition of sulphuric acid, solvent extraction base, water, and Cyanex 272™ and kerosene. Cyanex 272™ is a trimethylpentylphosphonic acid. This creates a cobalt loaded Cyanex™ / kerosene stream 18 from which cobalt sulphate 19 can be removed, which forms a stripped Cyanex™ / kerosene stream 20. The stripped Cyanex™ / kerosene stream 20 is recycled back in order to extract further amounts of cobalt from the depleted pregnant leach solution 11. This step can be repeated as many times as required. The solvents used in solvent extraction are highly recyclable and can be used multiple times without total replacement. Although some may be destroyed or lost, only a small amount will need to be added to replace any lost solvent. The solvent may be dearomatised so that any catalytic decomposition with the metal ions is minimised, thereby extending the lifespan of the solvent. Once the manganese and cobalt have been extracted, a nickel precipitation step 14 is conducted by including a base to adjust the pH of the depleted pregnant leach solution 11 to cause the nickel to be precipitated. The precipitated nickel is filtered in a filtration step 21 to form a lithium leach solution 22. As shown in Figure 3, the lithium leach solution 22 is concentrated in concentration step 23. This can be achieved by, for example, reverse osmosis. Any demineralised water 24 can be recycled into the process at any stage where water is required. Indeed, any process stream which yields a solid product and the liquid by-product is available for recycling into an earlier stage requiring water. Residual concentrations in solution can re-enter the process flow at the appropriate stage to allow for recovery based on the contaminant profile, which leads to increased net recovery rates. Any filtered solids may be washed with fractions of water from the process and washings may be recovered either to an earlier or a later stage of the process. Any aqueous stream may be concentrated, such as by reverse osmosis or evaporation, with the collected purified water being used again, thereby reducing the overall volume of process waste Concentration of the lithium leach solution 22 is optional. Prior to the concentration step 23, there may be a sodium sulphate precipitation step 25. The concentrated lithium leach solution is passed to a sodium sulphate precipitation step 25 in which any remaining sodium sulphate is precipitated out by cooling the concentrated lithium leach solution. Although depicted as following the lithium concentration step 23, additionally or alternatively, there may be a sodium sulphate precipitation step 25 before the concentration step 23. The sodium sulphate is filtered out in filtration step 26. Following on from sodium sulphate precipitation and filtration, the remaining solution is passed to a lithium carbonate precipitation step 27 in which carbonates are added to react with lithium in solution and cause it to precipitate out as lithium carbonate. The lithium carbonate is filtered out to provide a lithium carbonate product 28. The lithium carbonate 28 may be passed to a third party for conversion to lithium hydroxide or the process may include a further step of converting the lithium carbonate 28 to lithium hydroxide. A final depleted leach solution 29 now depleted of all target metals may be taken off for further processing. As shown in Figure 4, nickel hydroxide 30, manganese sulphate 16, and cobalt sulphate 19 are blended with water. Additional manganese, cobalt, and / or nickel from a fresh (non-recycled) source 50 may be added to adjust the recycled ratio of these metals and / or to conform to the required chemical composition of the second cathode active material. The blended materials are then co-precipitated in a co-precipitation step 31 by the addition of a carbonate precipitant 32 to form a cathode active material precursor precipitate 33. Following co-precipitation, the co-precipitate is filtered and dried in a filtration and drying step 34. The cathode active material precursor precipitate 33 may undergo milling. For example, dry or wet planetary ball milling, rolling ball milling, high shear milling, air jet milling, and / or impact milling The cathode active material precursor precipitate 33 is pre-calcined in a pre-calcination step 35 at a temperature of around 350 to 500°c in air or oxygen to oxidise the cathode active material precursor precipitate 33. The pre-calcination step 35 may take place for as long as required to oxidize the cathode active material precursor precipitate 33 to form NMC oxides and oxidise any residual carbon in the matrix 36. Following pre-calcination, the NMC oxides 36 are blended with recycled lithium hydroxide and fresh (non-recycled) lithium hydroxide 51 in a blending step 37 to form a lithium hydroxide / NMC oxide green body 38. The green body 38 is then calcined in a calcination step 39 to form a first cathode active material 40 comprising recycled nickel, cobalt, manganese and lithium with a specific chemical formula (e.g. NMC 811). Figure 5 shows the mixing of the first cathode active material 40 with a second cathode active material 41, having the same chemical composition (e.g. both NMC 811), which was produced from fresh (non-recycled) elements to provide a cathode active material composition with a predetermined partial recycled content 43. The mixing is conducted in a mixer 42 under low moisture conditions to avoid any structural change of the chemical composition. Prior to mixing the first active material may be processed (e.g. milled) to provide a particle distribution that is similar to that of the second cathode active material). The mixing may be performed in the presence of additional liquid phases and additives used to form a slurry which can then be applied to a substrate to from the cathode of a battery. 5 Figure 6 shows X-ray diffraction data of a NMC 622 cathode active material comprising recycled lithium, cobalt, nickel and manganese which had been washed with 0.5L of water (A); a NMC 622 cathode active material comprising recycled lithium, cobalt, nickel and manganese which had been washed with 3L of water (B); a commercially available NMC 622 cathode active material derived from virgin materials (C); and a 10 commercially available NMC 811 cathode active material derived from virgin materials (D). As can be seen the diffraction pattern and therefore the crystalline phase of the recycled cathode active material corresponds well with the commercially available material. The characteristic properties of recycled cathode active materials essentially mirror those of the characteristic properties of commercial CAM tested demonstrating 15 optimised processes controlling structural features in crystallinity and morphology.

Claims

:

1. A method of preparing a cathode active material composition, the method5 comprising:forming a first cathode active material comprising recycled lithium, cobalt, manganese, and nickel, wherein forming the first cathode active material comprises:separating chemical elements from one or more electrochemical energy storage devices, and / or from one or more materials generated 10 during preparation of electrochemical energy storage devices, to providean individual streams of lithium, cobalt, manganese and nickel;combining the individual streams;introducing further lithium into the individual stream of lithium and / or the combined stream and15 processing the combined streams to form the first cathode activeC\l material;andv— combining the first cathode active material with a second cathode activeQQ material comprising lithium, cobalt, manganese, and nickel, to provide the cathode20 active material composition;wherein the combining comprises controlling the weight ratio of the first cathode active material to the second cathode active material from 1:6 to 10:1 such that the cathode active material composition comprises lithium with a recycled content of at least 6% and comprises cobalt with a recycled content of at least 16%.

252. The method of claim 1 wherein at least 20% of the lithium in the first cathode active material is recycled lithium, preferably at least 37.5% of the lithium is recycled lithium.30 3. The method of claim 1 or 2 wherein the weight ratio of the first cathode activematerial to second cathode active material is from from 1:3 to 2:1.

4. The method of any preceding claim wherein the cathode active material composition comprises lithium with a recycled content of at least 12%.

355. The method of any preceding claim wherein the first cathode active material further comprises recycled cobalt, and wherein the cathode active material composition comprises cobalt with a recycled content of at least 26%.

6. The method of claim 5 wherein at least 40% of the cobalt within the first cathode active material is recycled cobalt, preferably from 80 to 100% of the cobalt is recycled cobalt.

7. The method of claims 5 or 6 wherein the first cathode active material comprises a recycled lithium to recycled cobalt ratio of 0.3:1 to 1:1.

8. The method of any preceding claim wherein x% of the cathode active material composition is derived from the first cathode active material, where x is greater or equal to 16 and less than or equal to 85, and wherein at least (6*100 / x) % of the lithium in the first cathode active material is recycled lithium.

9. The method of any preceding claim wherein the first cathode active material further comprises recycled nickel and the cathode active material composition comprises nickel with a recycled content of at least 6%, preferably 15%; optionally wherein at least 20% of the nickel within the first cathode active is recycled nickel.

10. The method of any preceding claim wherein all of the metallic species in the first cathode active material have a recycled content of at least 5%, preferably at least 20%, optionally a recycled content of 100%.

11. The method of claim 10, wherein the chemical composition is expressed by the general formula LiNixMnyCoi-x-yO2, wherein 0 <x <1, and 0 <y <1, and x + y <1; and wherein x = 0.9 and y = 0.05, x = 0.8 and y = 0.1, x = 0.7 and y=0.2, x = 0.6 and y = 0.2, or x = 0.5 and y = 0.3.

12. The method of claim 1, further comprising introducing further metallic species into the respective individual stream(s) of the cobalt, manganese and / or nickel, and / or introducing further metallic species into the combined stream.

13. The method of an claims 1 wherein the one or more electrochemical energy storage devices and / or one or more waste materials comprise a mixture of different chemical compositions.

14. The method of claim 1 further comprising controlling the introduction of the further lithium such that the further lithium constitutes 5% to 67% of the total amount of the lithium and 33% to 95% of the lithium is recycled lithium.

15. The method of claim 1 wherein processing the combined streams comprises co-precipitating and calcining the combined streams to form the first cathode active material.

16. The method of any preceding claim wherein combining the first cathode active material and the second active cathode material comprises uniformly distributing particles of the first cathode active material and second cathode active material in a mixer under low moisture conditions, preferably wherein the dew point is -70°C or below.

17. The method of any preceding claim further comprising processing (e.g. milling) the first cathode active material so that the weight median particle diameter (d50) is within 95 - 105% of the weight median particle diameter of the second cathode active material18. A method of preparing an electrical energy storage device, such as a battery, comprising:preparing a slurry comprising the cathode active material composition prepared according to claims 1 to 17;coating the slurry onto a substrate, preferably a metal substrate, and drying the slurry to form a first electrode;assembling a cell comprising the first electrode, an electrolyte and a second electrode.

19. An apparatus for preparing a cathode active material composition, the apparatus comprising:a unit configured to:1015separate the chemical elements from one or more electrochemical energy storage devices, and / or from one or more materials generated during preparation of electrochemical energy storage devices, to provide an individual streams of lithium, cobalt, manganese and nickel,combine the individual streams; andprocess the combined streams to form a first cathode active material;an inlet to the unit configured to supply further lithium into the individual stream of lithium and / or the combined stream;a mixing chamber;a first inlet to the mixing chamber configured to supply the first cathode active material comprising recycled lithium;a second inlet to the mixing chamber configured to supply a second cathode active material, wherein the first cathode active material and the second cathode active materials comprise lithium, manganese, cobalt and nickel and wherein the mixing chamber is configured to uniformly distribute the first cathode active material and the second cathode active material to provide the cathode active material composition; and a control means for controlling the weight ratio of the first cathode active material to second cathode active material introduced into the mixing chamber from 1:6 to 10:1 such that the cathode active material composition comprises lithium with a recycled content of at least 6% and comprises cobalt with a recycled content of at least 16%.

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