Recovery of lithium from used lithium-ion batteries

Abstract

The disclosure relates to a method of recovering lithium from a used lithium-ion battery, the method comprising: obtaining from a used lithium-ion battery a mixture comprising a cathode active material and an anode material; combining the mixture with sucrose to form a roasting composition; heating the roasting composition so as to reduce the cathode active material; and subsequently leaching lithium from the roasting composition. The disclosure further relates to lithium products recovered according to the method and the use of sucrose as a reducing agent in roasting battery black mass materials.

Description

[0001] Recovery of lithium from used lithium-ion batteries

[0002] The present invention relates to the recovery of lithium from used lithium-ion batteries.

[0003] Lithium-ion batteries (LIBs) have become the predominant choice for energy storage solutions thanks to their relatively high energy density, low self-discharge, no memory effects, and good cycle life compared to other alternatives like lead-acid batteries and nickel metal hydride batteries. Current strategies for decarbonization and electrification are heavily reliant on LIBs, which has led the demand to increase from 30 GWh in 2011 to 492 GWh in 2021 and is predicted to reach 2-3.5 TWh by 2030. This massive increase of new LIBs will eventually lead to a higher number of spent LIBs as well, which will need to be collected and recycled efficiently to reduce the environmental impacts this hazardous waste could cause and to help lower the dependency on mined resources.

[0004] More than half of the total cost of LIBs is attributed to material expenses, with the majority of these materials categorised as critical and strategic raw materials according to the European Commission. These include lithium, cobalt, nickel, manganese, and bauxite (aluminium) in the cathode, and graphite and copper in the anode, which could see shortages in near future due to the increased demand from road transport electrification and limitations in domestic supply. As a result, battery manufacturers have been developing cheaper chemistries by substituting scarce and expensive materials, for example, lowering Co concentrations in favour of Ni in LiNi1-x-yMnxCoyO2(NMC) chemistries from NMC111 to NMC9.5.5, or opting for Co and Ni free chemistries like LiFePO4(LFP), where high energy densities are not the highest priority while also providing greater safety. Despite attempts to reduce dependence on critical raw materials, substituting lithium has proven challenging.

[0005] Industrially, LIBs are commonly recycled using hydrometallurgical methods or a combination of pyrometallurgical and hydrometallurgical processes. In pyrometallurgy, the spent LIBs are typically smelted at very high temperatures (1200-1500 °C) to form an alloy containing nickel, cobalt, and copper. This alloy can further undergo hydrometallurgicaltreatment to recover the metals separately. The advantages of this method are its versatility to treat a wide range of different cathode chemistries, there are no or less stringent requirements for pretreatments, and higher recycling capacities can be achieved when compared to hydrometallurgy. The main drawbacks with this method come from the loss of various materials, due to being used as fuel during the heat treatment - graphite, polymers, and other carbon-based materials, or lost in slag - Li, Mn, and Al. Other problems include high energy consumption and CO2 emissions. Although Li recovery has not been traditionally associated with pyrometallurgy, recovery of Li is possible through leaching of flue dust and / or slag. In hydrometallurgy, the metals are dissolved into an aqueous phase using a leaching agent and a reductant. The dissolved metals can be selectively separated by using solvent extraction, ion-exchange, or chromatographic separation, and finally recovered by using precipitation or evaporative crystallisation. This has the benefits of achieving high recovery efficiencies and purities and being theoretically able to recover all metals present in cathode material. The main disadvantages come from being less flexible on the different types of cathode chemistries that can be recycled together in a given process and needing additional pretreatment steps, such as discharging / deactivation, comminution, and separation to minimize the amount of impurities and to acquire black mass which mostly consists of the anode and cathode active materials. Li is also typically recovered at the last steps of the pathway, which results in significant material losses and lower purity of recovered material. Additional cons also include high chemical use and wastewater production and lower capacities compared to pyrometallurgy.

[0006] The typical industrial recycling pathways have been designed to recover the most expensive materials like cobalt, nickel, and copper. This has led to cheaper materials being discarded or downcycled after the recycling process, or to lower recovery efficiencies. Since the price of lithium and the concerns over its availability have increased in recent years, both academia and industry have started to investigate processes to efficiently recover lithium. New regulations in the EU will also require recyclers to recover at least 50% of lithium by 2028 and 80% by 2032.

[0007] To increase the Li recovery efficiency during recycling, one of the promising strategies is to recover Li first in the process. One popular way to do this is using a thermaltreatment to decompose or reduce the cathode active material into water-soluble Li salts, while the other metals remain as oxides or reduced metal. Different roasting methods include using carbothermic reduction, thermite reduction, nitration roasting, chlorine roasting, hydrogen roasting, and sulfation roasting. Compared to traditional pyrometallurgical methods like smelting, roasting is done at a much lower temperature (300-700 °C), however, it can still produce harmful emissions like Cl2, NOX, SOX, CO, CO2 and HF, which can damage the equipment and require further treatment to reduce their environmental impact.

[0008] However, in view of the large-scale demand for lithium, there remains a need to improve the efficiency of methods of recovering lithium from used lithium-ion batteries. The present invention arose from the desire to provide a method of recovering lithium from a used lithium-ion battery, with improved efficiency and low cost.

[0009] According to the present invention, there is provided a method of recovering lithium from a used lithium-ion battery, the method comprising:

[0010] (i) obtaining from a used lithium-ion battery a mixture comprising a cathode active material and an anode material;

[0011] (ii) combining the mixture with sucrose to form a roasting composition;

[0012] (iii) heating the roasting composition so as to reduce the cathode active material; and (iv) subsequently leaching lithium from the roasting composition.

[0013] The inventors of the present invention have developed the above method for recovering lithium from a lithium-ion material that allows for efficient reduction of the Li-containing cathode active material into water-soluble Li salts in a roasting process, without the need to isolate the cathode active material from the anode material prior to roasting. Accordingly, the method of the present invention allows for the efficient recovery of lithium from a battery black mass material, obtained directly from a used battery, without requiring additional pre-treatment steps to separate the cathode active material from the anode material. The overall efficiency of the recovery process is therefore significantly improved.In particular, the inventors of the present invention have surprisingly found that the use of sucrose as a reducing agent in roasting mixtures comprising cathode active material and anode material can provide high lithium leaching efficiencies, with relatively low roasting times and roasting temperatures. Overall, the efficiency of the lithium recovery process is significantly improved compared to known methods. For example, graphite serves as the material used in most commercially available anodes. However, graphite binds lithium to its structure when treated at elevated temperatures. This trapping of lithium within the anode material lowers the amount of lithium recoverable by subsequent leaching (i.e. reduces the efficiency of the lithium leaching process).

[0014] The present inventors have found that the use of sucrose as a reducing agent in the roasting process allows for the cathode active material to be roasted together with the anode material, whilst achieving a high lithium leaching efficiency by subsequent lithium leaching. In particular, the method had been found to mitigate trapping of lithium in the anode material, meaning that high lithium leaching efficiencies can be achieved. This provides a highly efficient lithium recovery process, in which many steps associated with separating and isolating components of the battery can be omitted, in particular separation of cathode and anode materials.

[0015] The method of the present invention also allows lithium contained within the anode material (which can, in some cases, be almost as much as in the cathode active material) to be recovered in the same leaching process as lithium contained within the cathode active material, whilst mitigating the trapping / binding of lithium by the anode material. Therefore, the overall efficiency of the process for recovering lithium from a used battery is significantly improved.

[0016] Still further, it has been found that the use of sucrose in the roasting process can provide high lithium leaching efficiencies, despite the presence of other impurities in a battery black mass material used in the roasting composition. For example, a black mass obtained from a used battery may contain impurities derived from components including current collectors (impurities such as Al and Cu), binders and electrolyte salts (impurities such as fluorine and phosphorus, which can form LiF and Li3PO4with very low solubilitiesin water and acids, thereby reducing Li recovery efficiency), and other materials such as Al2O3and AlOOH that may originate from various sources, such as residues from Al current collectors, casings and ceramically-covered separators. Accordingly, in embodiments of the present invention, the mixture of cathode active material and anode active material is in the form of a black mass derived directly from a used battery, which may therefore contain other components such as current collectors, binders, electrolytes and electrode coating materials. The black mass may be a concentrated mass of active cathode material and anode material obtained directly from a used lithium-ion battery using only mechanical treatment steps (such as physical removal of casing and / or separator materials, crushing or shredding of the remaining battery materials, and physical / mechanical separation of components, for example by sieving or magnetic separation) and / or drying steps to remove organics (such as organic electrolyte), without further purification steps (such as chemical or hydrometallurgical processing or calcination).

[0017] Moreover, the present invention is particularly beneficial, since sucrose is an inexpensive and widely available resource. Food grade sucrose can be used, for example. The method of the present invention therefore represents a highly cost effective and efficient process for the recovery of lithium from a lithium-ion battery.

[0018] Preferably, the roasting composition is heated to a target temperature and maintained at the target temperature for a predetermined period of time, so as to reduce the cathode active material. Heating of the roasting composition to the target temperature is preferably performed in a single heating step, with no prior heating of the roasting composition (that is, the combined mixture comprising cathode active material, anode material and sucrose). More particularly, the step of heating the roasting composition may comprise placing the roasting composition in a furnace, heating the furnace from a starting temperature to a target temperature in a single heating step, with no prior heating step performed on the roasting composition, and maintaining the furnace at the target temperature for a predetermined period of time, so as to reduce the cathode active material. The starting temperature is preferably less than 200 °C, more preferably less than 100 °C and most preferably less than 50°C. The starting temperature may be room temperature, for example. The furnace may be heated at a constant heating rate. Preferably, where theroasting composition and / or the furnace is maintained at the target temperature for a predetermined period of time so as to reduce the cathode active material, the roasting composition is cooled immediately after the step of maintaining the roasting composition and / or the furnace at the target temperature for the predetermined period of time, with no further heating steps prior to cooling.

[0019] In the step of heating the roasting composition, the roasting composition may be placed in a furnace and the furnace heated to a target temperature at a heating rate of 50 °C / min or less. In this regard, the present inventors have found that heating the roasting composition to a target temperature at a heating rate above this threshold reduces the lithium leaching efficiency of the process. This may be because at higher heating rates, sucrose decomposition occurs much faster (starting at approximately 250 °C) and the reduction of the cathode active material becomes a normal carbothermic reduction. In contrast, with lower heating rates, decomposition of sucrose generates additional intermediate products which promote reduction, increasing the efficiency of the process.

[0020] In embodiments of the present invention, the furnace may be heated to a target temperature at a heating rate of 100 °C / min or less, 90 °C / min or less, 80 °C / min or less, 70 °C / min or less, 60 °C / min or less, 50 °C / min or less or 45 °C / min or less.

[0021] The roasting composition may be heated to a target temperature and maintained at the target temperature for a period of 60 minutes or less, more preferably 30 minutes or less and most preferably 15 minutes or less. It has been found that the use of sucrose in the roasting process enables very fast reduction reactions, thereby reducing the required roasting time. The efficiency of the method as a whole is thereby improved.

[0022] The target temperature to which the roasting composition is not particularly critical, provided it is sufficient to cause reduction of the cathode active material. The roasting composition may be heated to a temperature in the range 300 °C to 700 °C, more preferably in the range 500 °C to 700 °C, and most preferably in the range 500 °C to 650 °C. For example, the roasting composition may be heated to a temperature of 300 °C or more, 350 °C or more, 400 °C or more, 450 °C or more, or 500 °C or more. The roasting compositionmay be heated to a temperature of up to 1000 °C, up to 900 °C, up to 800 °C, up to 700 °C, up to 650 °C, or up to 600 °C.

[0023] Determination of the temperature of the roasting composition during the heating step may be achieved by a variety of methods within the common general knowledge of the skilled person, dependant on the method of heating. For example, where the roasting composition is heated in a furnace, the internal temperature of the furnace at the position of the roasting composition within the furnace may be measured by use of a temperature probe inserted at or in proximity to the location of the roasting composition within the furnace.

[0024] In one particular embodiment, the step of heating the roasting composition so as to reduce the cathode active material comprises:

[0025] placing the roasting composition in a furnace;

[0026] heating the furnace from a starting temperature to a target temperature in a single heating step; and

[0027] maintaining the furnace at the target temperature for a predetermined period of time so as to reduce the cathode active material,

[0028] wherein the target temperature of the furnace is measured at a position internal to the furnace that is in proximity to the location of the roasting composition within the furnace. The target temperature of the furnace may be in the range 300 °C to 700 °C, more preferably in the range 500 °C to 700 °C, and most preferably in the range 500 °C to 650 °C.

[0029] In preferred embodiments, the roasting composition comprises a sucrose content in the range 5 to 25 wt% relative to the total weight of the roasting composition. It has been found that a sucrose content in this range is sufficient to yield high lithium leaching efficiencies of around 80 % or more. The roasting composition may comprise a sucrose content of 5 wt% or more or 10 wt% or more, relative to the total weight of the roasting composition.

[0030] The heating step may be carried out in an inert or anaerobic environment, for example under a flow of inert gas, such as argon or nitrogen.The anode material may comprise graphite.

[0031] The cathode active material may comprise at least one of a lithium cobalt oxide (LCO), a lithium nickel manganese cobalt oxide (NMC), lithium cobalt nickel aluminium oxide (NCA), lithium nickel dioxide (LNO), lithium manganese oxide (LMO), or any combination thereof.

[0032] Preferably, lithium is leached from the roasting composition using water, and most preferably using only water. In particular, lithium may be leached from the roasting composition without the use of acid. This allows for the selective leaching of lithium species (e.g. LiOH, Li2CO3), whilst other metal species (e.g. Co, Ni, Mn species) remain as solids for subsequent recovery.

[0033] Preferably, lithium is leached from the roasting composition using water at a temperature of 40 °C or above, and preferably using water at a temperature of 60 °C or less. Surprisingly, the present inventors have found that a water temperature of 40 °C or more during the water leaching step increases lithium leaching efficiency. This is in contrast to water leaching of a roasting composition comprising no sucrose, in which increasing the temperature of the water during leaching has been observed to decrease the lithium leaching efficiency.

[0034] Preferably, the mixture comprising the cathode active material and anode material is obtained by shredding or crushing the used lithium-ion battery. Preferably, the shredded / crushed material is sieved (in one or more steps) to remove particles having a dimension greater than 500 pm. Organic electrolyte may be removed from the mixture, for example by heating under vacuum at 120 °C for 2 to 4 hours. The present inventors have found that removal of the organic electrolyte helps to separate different fractions, which increases the yield of black mass after crushing and sieving, and increases the lithium leaching efficiency after roasting. The resulting material may be subsequently roasted with sucrose (steps (ii) and (iii)) without prior calcination to remove binders, separators or other organic fractions. In this regard, calcination in air (typically between 500 to 700 °C) isnormally carried out to remove organic fractions (particularly binders and separators). The present inventors have found that calcination in air can result in the loss of graphite and that the removal of binder materials also takes place during the roasting process. Accordingly, with the method of the present invention, it has been found that calcination steps prior to roasting can be omitted, whilst maintaining the efficiency of the overall process.

[0035] In a second aspect, the present invention provides a recovered lithium product obtainable by the method of the first aspect.

[0036] In a third aspect, the present invention provides the use of sucrose as a reducing agent in roasting a mixture of cathode active material and anode material obtained from a used lithium-ion battery, for the recovery of lithium from the mixture.

[0037] Detailed description

[0038] Using sucrose as a reducing agent during the roasting process is particularly beneficial, as it can act as a source of both hydrogen and carbon. In addition to that, intermediate products produced during the pyrolysis can also promote reduction, further increasing the efficiency of the process. A simplification of the possible reactions occurring during the roasting of lithium cobalt oxide (LCO) while using sucrose are the following:

[0039] 1. 2LiCoO2+ C ↔ Li2O + 2CoO + CO(g)

[0040] 2. 4LiCoO2+ C ↔ 2Li2O + 4CoO + CO2(g)

[0041] 3. 2LiCoO2+ CO(g) ↔ Li2O + 2CoO + CO2(g)

[0042] 4. 2CoO + C ↔ Co + CO2(g)

[0043] 5. CoO + C ↔ Co + CO(g)

[0044] 6. CoO + CO(g) ↔ Co + CO2(g)

[0045] 7

[0046]

[0047] 7. Li2O + CO2(g) ↔ Li2CO3

[0048] 8. 2LiCoO2+ H2(g) ↔ 2LiOH + 2CoO

[0049] 9. CoO + H2(g) ↔ Co + H2O

[0050] 10. 2LiOH + CO2(g) ↔ Li2CO3+ H2OThe presence of various reducing agents can reduce energy consumption for the process by lowering the required heating time and / or temperature. In addition to that, other side-products like biochar and -oil will also be produced. However, using organics such as biowaste or plastics as a reductant, depending on their origin, can introduce new impurities to the system which could affect the final yields and purities of the recovered metals.

[0051] With the method of the present invention, the inventors have found that the use of sucrose in the roasting of a battery black mass material allows for the recovery of lithium with a high lithium leaching efficiency, at relatively low roasting temperatures and short roasting times. In particular, the use of sucrose mitigates trapping of lithium in the anode material, leading to improved lithium leaching efficiencies.

[0052] By way of example, graphite anode material recovered from a used battery will also contain a significant amount of lithium. This lithium can normally be easily recovered with water leaching. In one experiment, a sample of graphite recovered from a used battery and isolated was leached with water at a solid to liquid ratio of 30 g / L at room temperature for 60 minutes. The lithium leaching efficiency was 99.3 %. However, it was found that roasting the graphite anode material significantly reduced the amount of recoverable lithium.

[0053] For example, in one experiment, a sample of graphite recovered from a used battery was first roasted at a temperature of 500 °C for 10 minutes under an atmosphere of Argon and subsequently leached with water at a solid to liquid ratio of 30 g / L at room temperature for 60 minutes. This resulted in a lithium leaching efficiency of 66.0 %, significantly lower than the leaching efficiency of the unroasted graphite anode material.

[0054] However, in a further experiment, the same graphite anode material was first mixed with sucrose (at a sucrose content of 15 wt% relative to the total weight of the mixture) and subsequently water leached with water at a solid to liquid ratio of 30 g / L at room temperature for 60 minutes. It was found that this increased the leaching efficiency to 73.1%, indicating that sucrose helps mitigate the trapping of lithium in graphite.Non-limiting embodiments of the invention will now be described, by way of example only, with reference to the following examples and the accompanying drawing in which:

[0055] Figure 1 is a schematic diagram of a reactor suitable for use in a method as described herein.

[0056] Examples

[0057] The use of sucrose as a reducing agent in roasting a battery black mass is illustrated in the following examples of methods for recovering lithium from a lithium-ion battery.

[0058] Examples 1 - 7

[0059] Each of Examples 1 to 7 described below was carried out using the general pretreatment, roasting and leaching steps described as follows. Specific conditions used for each Example is described thereafter.

[0060] Pre-treatment

[0061] Used lithium-ion batteries comprising lithium nickel manganese cobalt oxide (NMC622) cathodes and pure graphite anodes were first pretreated to recover a black mass for subsequent treatment. In the pre-treatment, casing materials were manually removed from the used lithium-ion batteries and the remaining materials were shredded using a commercial blender (power rating 1.5kW) for 3 minutes, before being dried in a vacuum oven at 100 to 150 °C for a period of 1 to 4 hours. The shredded components were then sieved to remove particles over 1000 pm, thus removing the majority of the casing and separator materials. After that, the battery mass was shredded a second time using a commercial blender (power rating 1.5kW) for 1 minute, and then sieved again to remove particles over 500 pm, representing the majority of the aluminium and copper from the current collector. The remaining fraction (particle size < 500 pm) contained cathode active material and anode material, with the majority of the casing, separator and current collector materials removed.Roasting

[0062] The black mass obtained by the pre-treatment method was mixed with an appropriate amount of sucrose (0 to 20 wt%) to form a roasting composition. 50 g of black mass was used for each experiment, with a total sample mass of up to 62.5g, depending on the amount of sucrose added. Mixing was achieved by milling to obtain a homogeneous mixture and to reduce the mean particle size of sucrose crystals. The milling conditions were 250 rpm, 3 x 5 min, 5 minutes breaks between each step. The exact mixing parameters can be adjusted according to the machine and milling ball size. Milling speed and time should be limited to avoid sucrose melting during mixing. The roasting composition was then heated in a tube furnace by heating the tube furnace to a target temperature of 500 to 650 °C at a heating rate of 20 °C / min. The roasting time (i.e. the time for which the tube furnace was maintained at the target temperature after reaching the target temperature) was varied from 5 to 60 minutes and sucrose dosage from 0 to 20 wt% of the total weight of the roasting composition. All roasting experiments were carried out in an oxygen-deficient environment.

[0063] Leaching

[0064] After roasting, the roasting composition was crushed or milled again before leaching with water to dissolve lithium. The leaching parameters used for all tests were 60 minutes leaching time, a solid to liquid ratio in the range 30 g / L to 100 g / L, at room temperature.

[0065] Leaching efficiency was calculated according to the following equation (1):

[0066] Li leaching efficiency(%) =

[0067] mLi in PLS+mLi in leach residue

[0068]

[0069] (1)

[0070] Where mu in PLS is the total mass off Li in the pregnant leach solution (PLS) and the mu in leach residue was the total mass of Li in the leach residue. To determine the Li mass in theleach residue, 2.5 g of leach residue was dissolved in 25 mL aqua regia (concentrated HNO3 + HCl, 1:4 ratio, 2 hours, 80 °C) for all experiments. Mass of Li was measured by Flame Atomic Absorption Spectroscopy (AAS).

[0071] After water leaching, the remaining residue consists of mainly transition metals, oxides, and graphite. This residue can then be dissolved in 2M sulphuric acid at room temperature without the need to add any other reductants to recover other metals, mainly Co, Mn, and Ni.

[0072] Example 1

[0073] Lithium was recovered from used lithium-ion batteries according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage in the range 0 to 20 wt% (relative to the total weight of the roasting composition). In the roasting step, the roasting composition was heated to a target temperature of 600 °C at a heating rate of 20 °C / min in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a period of 60 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio of 30 g / L. The results are shown in Table 1.

[0074] The results show that the addition of small amounts of sucrose to a battery black mass can significantly increase Li leaching efficiency of a roasted black mass material. Despite the presence of impurities present in the black mass, a Li leaching efficiency of almost 80 % was achieved at a sucrose dosage of only 5 wt%. The leaching efficiency increased significantly to 87.6% when the sucrose dosage was raised to 10 wt%. This shows that sucrose has a significant role in fully reducing the cathode active material and making Li recovery possible. When further increasing the sucrose dosage, the Li leaching efficiency decreased slightly, however, this change was within the error margin, so it was concluded that further increase in sucrose dosage showed no improvements and that 10 wt% was optimal for roasting.

[0075] Table 1Sucrose dosage (wt%) Li leaching efficiency (%) Example 1A 0 68.8

[0076] Example IB 5 79.5

[0077] Example 1C 10 87.6

[0078] Example ID 15 85.2

[0079] Example IE 20 85.4

[0080]

[0081] Example 2

[0082] Lithium was recovered from used lithium-ion batteries according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the roasting composition). In the roasting step, the roasting composition was heated to a target temperature in the range 500 to 650 °C at a heating rate of 20 °C / min in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a period of 60 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio of 30 g / L. The results are shown in Table 2.

[0083] The results show that high Li leaching efficiencies can be obtained at relatively low temperatures. In this regard, NMC cathode materials are known to require relatively high temperatures, since the presence of Mn makes the cathode active material more stable, requiring higher temperature for the reduction reaction. The use of sucrose has been found to allow relatively low temperatures to be used in the roasting step, improving the efficiency of the lithium recovery process. Leaching efficiency increased with temperature up to 600 °C but further raising the roasting temperature to 650 °C showed no further improvement. Thus, the use of sucrose allows a maximum Li leaching efficiency to be obtained at relatively low temperatures.

[0084] Table 2

[0085] Temperature °C Li leaching efficiency (%) Example 2 A 500 70.5

[0086] Example 2B 550 81.1

[0087]

[0088] Example 2C 600 85.2

[0089] Example 2D 650 85.5

[0090]

[0091] Example 3

[0092] Lithium was recovered from used lithium-ion batteries according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the roasting composition). In the roasting step, the roasting composition was heated to a target temperature of 600 °C at a heating rate of 20 °C / min in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a time period in the range 5 to 60 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio of 30 g / L. The results are shown in Table 3.

[0093] The results show that the use of sucrose allows very high Li leaching efficiencies to be obtained with relatively short roasting times. In particular, the optimum roasting time was found to be 15 minutes. The use of sucrose therefore provides a very efficient lithium recovery process.

[0094] Table 3

[0095] Roasting time (min) Li leaching efficiency (%) Example 3 A 5 87.0

[0096] Example 3B 10 85.9

[0097] Example 3C 15 87.6

[0098] Example 3D 30 85.8

[0099] Example 3E 60 84.3

[0100]

[0101] Example 4

[0102] Lithium was recovered from used lithium-ion batteries according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the roasting composition). In theroasting step, the roasting composition was heated to a target temperature of 600 °C at a heating rate of 20 °C / min in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a time period of 60 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio in the range 30 g / L to lOOg / L. The results are shown in Table 4

[0103] The results show that that Li leaching efficiency remained over 80% at double the solid to liquid ratio. It was therefore found that the use of sucrose in the roasting process allows for high Li leaching efficiencies to be obtained at relatively high solid to liquid ratios in the subsequent leaching process. The volume of water required to leach lithium is therefore reduced, improving the efficiency of the lithium recovery process as a whole.

[0104] Table 4

[0105] Solid to liquid ratio (g / L) Li leaching efficiency (%) Example 4 A 30 84.3

[0106] Example 4B 60 80.9

[0107] Example 4C 100 68.0

[0108]

[0109] Example 5

[0110] Lithium was recovered from used lithium-ion batteries according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the roasting composition). In the roasting step, the roasting composition was heated to a target temperature of 600 °C at a heating rate in the range 5 to 55 °C / min in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a time period of 15 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio of 30. The results are shown in Table 5.

[0111] The results show that heating rates up to 45 °C / min maintain a Li leaching efficiency of 80 % or more, whereas at 55 °C / min or above, the Li leaching efficiency falls below 80%. Additional experiments revealed that increasing the heating rate toapproximately 150 to 200 °C / min further reduced the Li leaching efficiency to values similar to those observed for roasting without sucrose (i.e. 0 wt% sucrose in the roasting composition). Accordingly, it was determined that roasting with sucrose was most effective at a heating rate up to about 50 °C / min, providing a lithium leaching efficiency of 80 % or more.

[0112] Table 5

[0113] Heating rate (°C / min) Li leaching efficiency (%) Example 5 A 5 86.6

[0114] Example 5B 10 87.6

[0115] Example 5C 20 86.5

[0116] Example 5D 30 86.4

[0117] Example 5E 45 80.0

[0118] Example 5F 55 77.8

[0119]

[0120] Example 6

[0121] Lithium was recovered from used lithium-ion batteries according to the method described above, except that the used lithium-ion batteries comprised lithium cobalt oxide (LCO) or lithium nickel cobalt aluminium oxides (NCA) cathodes. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the roasting composition). In the roasting step, the roasting composition was heated to a target temperature of 500 °C for LCO black mass, and to a target temperature of 600 °C for NCA black mass, at a heating rate of 20 °C / min. Both experiments were carried out in an inert (Ar) environment. Once at the target temperature, the roasting composition was maintained at the target temperature for a period of 15 minutes. Lithium was then leached from the roasting composition using water at a solid to liquid ratio of 30 g / L for 60 minutes. The results are shown in Table 6.Table 6

[0122] Cathode Li leaching efficiency (%) Example 6 A LCO 86.6

[0123] Example 6B NCA 83.5

[0124]

[0125] Example 7

[0126] Nickel, cobalt, and manganese were leached from the NMC622 black mass after lithium recovery according to the method described above. After pre-treatment, the battery black mass was mixed with sucrose at a sucrose dosage of 15 wt% (relative to the total weight of the composition). In the roasting step, the roasting composition was heated to a target temperature of 600 °C under inert gas (Ar) flow. Once at the target temperature, the roasting composition was maintained at the target temperature for a time period of 15 minutes. After roasting, lithium was leached from the roasting composition using water at a solid to liquid ratio of 30 g / L at room temperature for 60 minutes. After lithium leaching, the black mass was leached in a 2M sulphuric acid (H2SO4) solution at a solid to liquid ratio of 100 g / L at room temperature for 180 minutes to leach nickel, cobalt, and manganese left in the black mass. The results are shown in Table 7.

[0127] Table 7

[0128] Element Leaching efficiency (%)

[0129] Nickel 99.5

[0130] Cobalt 99.4

[0131] Manganese 99.6

[0132]

[0133] Example 8

[0134] To demonstrate the scalability of the method, lithium recovery was carried out on an industrial black mass mixture SI. The crushed black mass mixture contained a mixture of different cathode active materials. The elemental composition of the industrial black mass mixture SI used for upscaling experiments is given in Table 8. The non-leachablecomponent consists mainly of graphite, binder (PVDF), Al2O3, SiO2, and separator (polyester, PE / polypropylene, PP).

[0135] Table 8

[0136] Element / component SI (%)

[0137] Li 3.4-3.9

[0138] Co 17.0-20.8

[0139] Ni 5.1-6.3

[0140] Mn 2.6-3.1

[0141] Fe 0.2-0.3

[0142] Cu 2.6-2.9

[0143] Al 3.0-6.0

[0144] F 1.1

[0145] Si 0.1

[0146] Non-leachable 31.8-33.8

[0147] Moisture (water+electrolyte) 8.4

[0148]

[0149] Lithium recovery of S 1 was carried out using the same general roasting and leaching steps described above for Examples 1 to 7, except as indicated otherwise.

[0150] Roasting was carried out using a reactor (furnace) 1 as shown in the schematic diagram of Figure 1. Reactor 1 comprises a reactor vessel 10 having an inner vessel 12 in which the roasting is formed. Inner vessel 12 is provided to protect the reactor vessel 10 from corrosive gases (mostly HF) and to prevent contact between the roasted material and reactor vessel in the event of spillage. The reactor vessel 10 is surround by a heating element 14 and insulation 16. The interior of the reactor vessel 1 is closed by a reactor top 18, which comprises a gas inlet 19, a gas outlet 20 and a temperature probe 22 arranged to be inserted through the reactor top 18 into an interior space of the inner vessel 12. The reactor top 18 is engaged with and secured on the reactor vessel 12 by a bolted flange connection 24.For roasting of Example 8, the roasting composition was placed into an AI2O3 crucible, which in turn was placed into the inner vessel 12. A flow of protective gas (industrial grade N2) was passed through the inner vessel 12 through gas inlet 19 and gas outlet 20. Gaseous by-products of the reduction process were also released through gas outlet 20.

[0151] Heating element 14 was heated at a rate of 10 °C / min to a target temperature that was sufficient to bring the temperature of the inner vessel 12 near the centre point of the crucible (as measured by the temperature probe 22) to a target reaction temperature. For instance, in the present examples it was found that a target reaction temperature 630 °C near the centre point of the crucible could be achieved by heating the heating element 14 to a temperature of 720°C. It will be appreciated that the exact temperatures required will be dependent on the system used.

[0152] Sample SI (1 kg) was mixed with sucrose at a sucrose dosage in the range 0 to 10 wt% (relative to the total weight of the roasting composition). The total mass of the roasting composition was up to 1.11kg, depending on the amount of sucrose added. In the roasting step, the roasting composition was heated to a reaction temperature of approximately 630 °C by heating the heating element 14 of the reactor 1 to a target temperature of 720 °C at a heating rate of 10 °C / min, under a flow of N2 (100 CCM). Once the heating element reached the target temperature, the heating element was maintained at the target temperature for a period of about 40 minutes. The heating element was turned off to allow the reactor vessel 10 to cool. During cooling, the inner vessel 12 was lifted out of the heating area when the inner temperature reached about 200 °C or less to accelerate the cooling rate. During that process, the N2 flow was stopped and the inlet and outlet are removed. The roasted black mass was allowed to cool to room temperature before leaching with water.

[0153] After roasting, the roasting composition was leached using water to dissolve lithium. The leaching parameters used were: solid / liquid ratio 50 g / L, 15 minutes leaching time per leaching step, 1-2 leaching steps, 300 rpm mixing speed (using an overhead stirrer), deionised water, leaching temperature up to 60 °C. The temperature of thedeionised water used for leaching was varied between room temperature (22 °C) and 60 °C. In this regard, water was added to a container and heated to the target leaching temperature (as measured by temperature probe inserted into the water) before the roasting composition was added to the water for leaching. The temperature was maintained during each leaching 5 step. The results are shown in Table 9.

[0154] Table 9

[0155] Sucrose Temperature Li leaching Li leaching Total Li dosage (°C) efficiency, efficiency, leaching (wt%) step 1 (%) step 2 (%) efficiency (%) Example 8A 0 RT 62.0 - 62.0 Example 8B 0 40 57.8 - 57.8 Example 8C 5 RT 65.9 11.8 77.7 Example 8D 5 40 68.6 12.6 81.2 Example 8E 5 60 68.0 13.9 81.9 Example 8F 10 RT 65.1 - 65.1 Example 8G 10 40 70.5 - 70.5

[0156]

[0157] 0 The results showed an improvement in leaching efficiency by increasing the leaching temperature to 40 °C or more. This is understood to be due to sucrose decomposition products containing a significant amount of hydrogen, forming Li OH as a product of the lithium reduction. The solubility of LiOH increases with increasing temperature, which is opposite to Li₂CO₃. This was supported by that fact that the optimal 5 leaching temperature with no sucrose was room temperature, with a decrease in lithium leaching efficiency observed with increasing temperature to 40 °C, as lithium was mainly in the form of Li₂CO₃.

[0158] The results also showed an improvement in lithium leaching efficiency by addition 0 of sucrose to the roasting composition. Although the increase in lithium leaching efficiency was less pronounced than for the preceding examples, this may be due to the presence ofseparator materials in the black mass mixture, acting as an additional hydrocarbon reductant in the lithium reduction reaction. Nevertheless, the results show that the use of sucrose as a reducing agent is an effective means for enhancing lithium leaching efficiency from a roasted mixture of cathode and anode materials, without the need to first separate the cathode and anode materials.

[0159] The invention has been described above with reference to specific embodiments, given by way of example only. It will be appreciated that different arrangements of the system are possible, which fall within the scope of the appended claims.

[0160] All optional and preferred features and modifications of the described embodiments and dependent claims are usable in all aspects of the invention taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.

Claims

Claims1. A method of recovering lithium from a used lithium-ion battery, the method comprising:(i) obtaining from a used lithium-ion battery a mixture comprising a cathode active material and an anode material;(ii) combining the mixture with sucrose to form a roasting composition;(iii) heating the roasting composition so as to reduce the cathode active material; and (iv) subsequently leaching lithium from the roasting composition.

2. A method as claimed in claim 1, wherein in the step of heating the roasting composition comprises placing the roasting composition in a furnace, heating the furnace from a starting temperature to a target temperature in a single heating step, and maintaining the furnace at the target temperature for a predetermined period of time so as to reduce the cathode active material.

3. A method as claimed in claim 2, wherein the starting temperature is less than 100 °C.

4. A method as claimed in claim 2 or 3, wherein the roasting composition is cooled immediately after the step of maintaining the furnace at the target temperature for the predetermined period of time.

5. A method as claimed in any one of claims 1 to 4, wherein in the step of heating the roasting composition, the furnace is heated to a target temperature at a heating rate of 50 °C / min or less.

6. A method as claimed in any preceding claim, wherein the roasting composition is heated to a target temperature and maintained at the target temperature for a period of 60 minutes or less.

7. A method as claimed in any preceding claim, wherein the roasting composition is heated to a target temperature in the range 500 to 650 °C.

8. A method as claimed in any preceding claim, wherein the roasting composition comprises a sucrose content in the range 5 to 25 wt% relative to the total weight of the roasting composition.

9. A method as claimed in any preceding claim, wherein the roasting composition comprises a sucrose content in the range 5 to 20 wt% relative to the total weight of the roasting composition.

10. A method as claimed in any preceding claim, wherein the heating step is carried out in an inert or anaerobic environment.

11. A method as claimed in claim 10, wherein the heating step is carried out under an inert gas.

12. A method as claimed in any preceding claim, wherein the anode material comprises graphite.

13. A method as claimed in any preceding claim, wherein the cathode active material comprises at least one of a lithium cobalt oxide, a lithium nickel manganese cobalt oxide, a lithium cobalt nickel aluminium oxide, a lithium nickel dioxide, a lithium manganese oxide, or any combination thereof.

14. A method as claimed in any preceding claim, wherein lithium is leached from the roasting composition using water.

15. A method as claimed in claim 14, wherein lithium is leached from the roasting composition using water at a temperature of 40 °C or above.

16. A method as claimed in claim 14 or 15, wherein the lithium is leached from the roasting composition using water at a temperature of 60 °C or less.

17. A method as claimed in any preceding claim, wherein the mixture comprising the cathode active material and anode material is obtained by shredding or crushing the used lithium-ion battery.

18. A method as claimed in any preceding claim, wherein steps (ii) and (iii) are carried out without prior calcination of the mixture of cathode active material and anode material.

19. A recovered lithium product obtainable by the method as claimed in any preceding claim.

20. Use of sucrose as a reducing agent in roasting a mixture of cathode active material and anode material obtained from a used lithium-ion battery for the recovery of lithium.

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