Recovery of nickel and cobalt from black mass.

Abstract

The present invention belongs to the field of pyrometallurgy and discloses a process and a slag suitable for the recovery of Ni and Co from Li-ion batteries or their waste products, specifically black mass. The composition of the slag is 25% <MnO<70%; Al2O3+0.5MnO<45% SiO2> 5%; Li2O>1%; 0.5% <P2O5<10%; MnO+Li2O+Al2O3+CaO+SiO2+FeO+MgO+P2O5> 90%; and (CaO+2Li2O+0.4MnO) / SiO2 ≧2.0. This composition is particularly suitable for limiting or avoiding wear or corrosion in furnaces lined with magnesia-containing refractory bricks.

Description

[Technical Field]

[0001] The present invention belongs to the field of pyrometallurgy and relates to the recovery of Ni and Co from Li-ion batteries or their waste products, more particularly black mass. [Background technology]

[0002] Electric vehicles have seen unprecedented growth in recent years, driven in particular by new legislation in Europe and China aimed at gradually reducing CO2 emissions from vehicles and limiting urban air pollution. This growth is expected to continue over the coming decades. The adoption of electric vehicles is highly dependent on the performance of the batteries used to store electrical energy. To obtain the highest energy density while keeping costs down, rechargeable Li-ion batteries are the preferred choice. Many of these batteries contain cathodes based on the transition metals Ni, Mn, and Co, and are therefore also known as NMC batteries. As the electric vehicle market grows, the demand for these metals is expected to increase significantly.

[0003] Demand for Ni and Co may even exceed global production capacity. Co is particularly important because it is currently produced only as a by-product of the Ni and Cu industries. The nickel market is significantly larger than the cobalt market. Most Ni is used in the production of stainless steel, where the purity of the Ni is not very important. However, high-purity Ni and high-purity Co metals or compounds are already in short supply. Therefore, in view of the above, recovering Ni and Co from used Li-ion batteries or their waste is an attractive proposition, which is also known as the circular economy of batteries.

[0004] In particular, so-called "black mass" (BM) or "black matter" is a very interesting starting material for recycling. In the industry, the term black mass is frequently used, but the exact composition can vary greatly depending on the manufacturer or application. Typically, end-of-life batteries are disassembled and crushed, which may include separation of the housing material, metal foil, and / or anode. Sometimes, batteries are also pre-processed. The black mass resulting from such processes is usually characterized by a relatively low aluminum content compared to the processing of whole batteries. On the other hand, black mass contains significantly higher amounts of lithium, manganese, cobalt, and / or nickel.

[0005] Facilities for recycling batteries and battery waste often use hydrometallurgical processes to treat the black mass, resulting in salts or metal hydroxides. Pyrometallurgical refining processes are less common, whereas the combined hydro-pyro process of the present invention remains a rare exception.

[0006] In a known pyrometallurgical process for recycling Li-ion batteries, nickel, cobalt, and copper oxides are reduced to their respective metals in a furnace and concentrated into alloy phases at high temperatures. Other compounds, such as lithium and manganese, are oxidized to LiO and MnO and are contained in the slag.

[0007] Such high-temperature processes cause wear and corrosion of furnace walls over time. Typically, furnace walls are made of refractory bricks. The most commonly used bricks are magnesia-based. Typical magnesia bricks contain over 90% magnesia, while magnesia-chrome bricks contain 50-70%. Magnesia has been observed to dissolve with the common slag during furnace operation. This wear and corrosion is a recurring problem, resulting in high maintenance costs due to the need to periodically shut down the furnace and replace the refractory bricks. This problem is more pronounced at higher operating temperatures, such as above 1550°C. [Prior art documents] [Chartered documents]

[0008]

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Non-licensed literature

[0009] [Non-licensed document 1] Wittkowski, Specification of Manganese in a Synthetic Recycling Slag Relevant for Lithium Recycling from Lithium-Ion Batteries: Metals, Volume 11(2), 2021, Page 188 [Non-licensed document 2] Xiao He, Recovery of Valuable Metals from Spent Lithium-Ion Batteries by Smelting Reduction Process Based on MnO-SiO2-Al2O3 Slag System: J. Sustain. Metall., Volume 3, 2017, Pages 703~710 [Non-licensed document 3] Vest et al., Slag design for lithium recovery from spent batteries: Int. Work. Met. Interact., Vol. 9(93), 2010, pp. 93-106 [Non-patent document 4] Geological Rock-Color Chart with Genuine Munsell Color Chips Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, the object of the present invention is not only to provide an efficient process for recovering Ni and Co from Li-ion batteries or their waste (specifically black mass), but also to extend furnace life. This is achieved by working with a dedicated MnO and LiO rich system with a controlled composition designed to limit corrosion of magnesia-bearing refractory bricks.

[0011] WO 2017121663 describes slag compositions produced in industrial processes and discloses the effect of MnO on slag viscosity and cobalt recovery. The primary slag components described therein are CaO, SiO, AlO, LiO, and MnO or MnO. The MnO content in these disclosed slags is very low, and the teaching is to limit the amount of MnO in the slag.

[0012] (Speciation of Manganese in a Synthetic Recycling Slag Relevant for Lithium Recycling from Lithium-Ion Batteries: Metals, Vol. 11(2), 2021, p. 188) analyzes the phase composition of various Li-containing slags relevant for recycling Li-ion batteries. Black mass is not mentioned as a starting material. All reported slags are characterized by an MnO content significantly below that of the present invention.

[0013] On the other hand, more recent Li-ion batteries typically contain increasing amounts of Mn, which results in slag compositions with higher MnO content.

[0014] WO 12140951, WO 13080266, and WO 20013294 propose processes for recycling Li-ion battery scrap to recover Ni and Co and fix impurities such as Fe and P in a slag phase. It is mentioned that Mn may be a component of the resulting slag, but the preferred range or specific effect of MnO in such a slag is not mentioned.

[0015] Chinese Patent No. 103924088 and European Patent No. 3269832 describe a bath smelting process for waste batteries, producing alloys containing Co and / or Ni and slags rich in SiO2 and MeO. The Li content in such slags is not mentioned, nor are any effects of MnO or Li2O mentioned. Black mass is not mentioned as a starting material.

[0016] Chinese Patent No. 105838895 and Xiao et al. (Recovery of Valuable Metals from Spent Lithium-Ion Batteries by Smelting Reduction Process Based on MnO-SiO2-Al2O3 Slag System: J. Sustain. Metall., Vol. 3, 2017, pp. 703-710) describe the composition of slag produced by smelting Li-ion batteries and a leaching process for extracting Li and Mn from the resulting slag. Disclosed is a method for extracting lithium and manganese from a lithium-containing manganese-rich slag; specific slag properties are not discussed. Typical slags are rich in MnO, SiO2, and Al2O3, but in all given examples, the Li2O content is very low.

[0017] Vest et al. (Slag design for lithium recovery from spent batteries: Int. Work. Met. Interact., Vol. 9(93), 2010, pp. 93-106) present theoretical calculations for various slag systems, some of which are also MnO-rich. However, for lithium, the goal is to design a slag that shifts the Li distribution to its maximum concentration in the flue dust rather than the slag. Therefore, one of the desirable slag properties is a low LiO capacity / solubility.

[0018] EP 21176046 describes a pyrometallurgical recycling process for Li-ion batteries in which the batteries are fed into a smelting furnace equipped with underwater injection of O2-containing gas to reduce most of the Ni and Co. The resulting slag is treated in a second reduction smelting step to extract the remaining Ni and Co. This slag contains less than 20% MnO and higher amounts of Al2O3 (e.g., more than 20%, or even more than 30%). No mention is made of wear or corrosion of the furnace walls. [Means for solving the problem]

[0019] The present invention achieves a significant reduction in the wear of magnesia-containing refractory bricks in pyrometallurgical processes, which contributes to the overall economy of the current process. The following embodiments further illustrate the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] According to a first embodiment, a method for recovering Ni and Co from a Li-ion battery or a waste thereof includes the steps of: - providing a furnace lined with magnesia-containing refractory bricks; - providing a charge comprising a slag former and Li-ion batteries or waste batteries, the charge having an Al content of less than 8%; and - smelting the charge under reducing conditions, thereby obtaining an alloy containing a large proportion of Ni and Co, and a Li-containing slag, which slag twenty five% <MnO<70%; Al2O3+0.5MnO<45%; SiO2>5%; Li2O>1%; 0.5% <P2O5<10%; MnO+Li2O+Al2O3+CaO+SiO2+FeO+MgO+P2O5>90%; and (CaO+2Li2O+0.4MnO) / SiO2≧2.0 having a percentage composition by mass according to Includes.

[0021] "Slag former" means, for example, one or more of CaO, Al2O3, and SiO2. Other slag formers known to those skilled in the art may also be present. The slag-forming compounds may be added as is or may be obtained in situ from easily oxidized metals (e.g., aluminum) present in the charge.

[0022] "Furnace lined with magnesia-containing refractory bricks" means a metallurgical furnace at least partially lined with such bricks (especially in the area in contact with the slag).

[0023] While this process is suitable for the treatment of Li-ion batteries or their waste, other materials can also be included in the metallurgical charge. For example, mixed hydroxide precipitate (MHP) can be added; such products often contain useful concentrations of Co, Ni, and Mn, along with Mg. The Co and Ni are recovered in the alloy, while the Mn and Mg are included in the slag, where they play a useful role in protecting the lining. Combining battery materials with MHP also optimizes total energy consumption, because batteries tend to be exothermic, while MHP is endothermic during smelting. The total charge can advantageously contain up to 30% MHP by mass.

[0024] Compounds not derived from Li-ion batteries or their waste, excluding MHP, should preferably be limited to less than 25% of the total charge, more preferably less than 15%.

[0025] According to a further embodiment, the Li-ion battery or waste product thereof is black mass.

[0026] The term "black mass" is typically used in industry to describe intermediate products derived from Li-ion batteries or their waste products (e.g., new or discarded Li-ion batteries, used or end-of-life batteries, production scrap or battery scrap, electrode materials, or other preprocessed battery materials). Batteries are usually dismantled. This process separates, for example, Al, Fe, and Cu from the casing and cables. All these battery materials are then fragmented and sometimes preprocessed (e.g., by heat treatment to remove residual electrolyte or graphite), resulting in a powder or filter cake that can be further processed into briquettes or pellets. In the latter case, this may include mixing with other compounds not derived from Li-ion batteries or their waste products to produce briquettes or pellets.

[0027] The black mass should still contain significant amounts of Co and / or Ni to make the pyrometallurgical process economically attractive. The above-mentioned properties make black mass a preferred feed material for the described process.

[0028] A "major portion" of an element or compound means greater than 50% by weight of the corresponding amount present in the charge, and may also include a range having a lower limit selected from 55%, 60%, 65%, 70%, and 75% and an upper limit selected from 80%, 85%, 90%, 95%, and 100%.

[0029] According to a further embodiment, the content of MnO in the slag is greater than or equal to 30%, preferably greater than or equal to 40%.

[0030] The MnO content in the slag plays an important role in the present invention. A minimum of about 10% MnO is required in the slag to observe an inhibitory effect on MgO dissolution from the magnesia-containing refractory brick lining the furnace into the slag. A slag content of at least 25% MnO is sufficient to inhibit MgO dissolution. Preferably, the slag contains at least 30% MnO, and more preferably at least 40%. When starting with black mass as the process feedstock and minimizing the use of slag-forming agents to reduce costs and keep slag volume low, the amount of MnO in the slag is typically greater than 25%.

[0031] A MnO content of 25-70% combined with a relatively small amount of slag is effective because it inhibits MgO dissolution.

[0032] On the other hand, further addition of fluxing agent, thereby increasing the total amount of slag and diluting the proportion of MnO below 25%, gradually increases the amount of MgO dissolved from the refractory brick, thus causing adverse effects.

[0033] The upper limit of 70% MnO in the slag helps to keep the melting point of the slag low enough.

[0034] Mn in slags is represented by "MnO". In such slags, the exact oxidation state of Mn is not always clearly defined. Therefore, manganese oxide ("MnO") may correspond to a mixture of MnO monoxide and MnO dioxide. In particular, under selected reducing conditions, the proportion of MnO is expected to be well above 95%.

[0035] MnO is typically green, while MnO2 is typically dark brown or dark gray, hence the name "manganese black." Only when the content of a single species is high enough does the green color predominate.

[0036] The content of P2O5 in the slag is 0.5% <P2O5<10%である。

[0037] Phosphorus typically comes from the electrolyte in Li-ion batteries and is contained in the slag as P2O5.

[0038] Lithium iron phosphate (LFP) batteries typically contain more phosphorus than NMC batteries, but no cobalt or nickel. In industrial facilities, recyclers may have to deal with loads containing such LFP batteries mixed with NMC batteries, which contribute to the total phosphorus content in the slag.

[0039] According to a further embodiment, the content of Al2O3 in the slag is less than 30%. If the amount of Al2O3 is too high (for example, more than 30%, or even more than 40%), the melting point of the slag increases. Heating to higher temperatures is economically less attractive and increases refractory wear.

[0040] Black mass typically has only a small amount of Al2O3 added to the slag, a clear difference when starting with black mass instead of a full Li-ion battery, which is typically Al-rich due to the housing.

[0041] A slag composition conforming to the formula Al2O3 + 0.5MnO < 45% allows for a slag with a relatively high MnO content while limiting the amount of Al2O3.

[0042] According to a further embodiment, the slag has a percentage composition by mass according to Al2O3 + 0.5MnO < 30%. In this way, the amount of Al2O3 is further limited in slags with a relatively high MnO content, which is beneficial for the protection of the magnesia-containing refractory bricks.

[0043] According to a further embodiment, the content of CaO in the slag is less than or equal to 40%, preferably less than or equal to 30%.

[0044] CaO helps keep the slag sufficiently fluid so that it can be easily handled. CaO also helps inhibit the dissolution of MgO from the magnesia-containing refractory brick because Ca and Mg share similar chemical sites in the slag. Operating the process at a preferred upper limit of 30% CaO helps keep the slag melting point below 1600°C. However, excessively high amounts of CaO (e.g., above 40%) should be avoided because they increase the slag melting point.

[0045] On the other hand, increasing the amount of MnO allows the amount of CaO to be reduced due to similarities in inhibiting the dissolution of MgO from magnesia-containing refractory bricks.

[0046] According to a further embodiment, the slag former does not include CaO.

[0047] MnO-rich feedstocks also allow for the complete avoidance of CaO as a slag former, which opens the door to exploring slag systems other than the well-known ternary slag system Al2O3-CaO-SiO2 typically used in the prior art.

[0048] Since MnO in the slag plays a key role in this regard, the beneficial effects of the present invention will still be achieved without the use of CaO.

[0049] According to a further embodiment, the content of Li2O in the slag is greater than 3%, preferably greater than 6%.

[0050] It has further been observed that in addition to MnO and CaO, Li2O also inhibits the dissolution of Mg from magnesia-containing refractory bricks. When recycling Li-ion batteries, the amount of Li2O in the slag is expected to be significant.

[0051] In this context, "more than 3%" should be specifically understood as 3.1 or more, preferably 3.2 or more, 3.3 or more, 3.4 or more, particularly 3.5 or more, 4.0 or more, 4.5 or more, 5.0 or more, or 5.5 or more. Amounts greater than 3% allow for increased lithium value in the slag. However, since LiO also inhibits Mg dissolution, higher amounts, such as more than 6%, are preferred not only for economic reasons but also for their greater contribution to wear reduction. This is particularly true for amounts of 7% or more, 8% or more, 9% or more, or 10% or more.

[0052] SiO contributes to lowering the melting point of the slag, while an increased amount of SiO has a negative effect. Therefore, according to a further embodiment, the amount of SiO in the slag is less than 20%.

[0053] In a preferred embodiment, the slag composition conforms to the formula (CaO+2Li2O+0.4MnO) / SiO2 ≥ 2.0.

[0054] According to a further embodiment, the content of cobalt oxide in the slag is 0.05% <CoO<1%である。

[0055] Under the applied process conditions, most of the cobalt is contained in the alloy, and only a small portion remains in the slag. Typically, concentrations of less than 1% are obtained. Industrial Li-ion battery recycling does not produce a completely cobalt-free slag.

[0056] According to a further embodiment, the Fe content in the slag is 25% or less, preferably 10% or less. FeO-rich slags containing more than 10% FeO, and even more than 25% FeO, respectively, do not transfer a relatively large amount of metallic Fe to the alloy layer and do not allow the reduction of CoO to metallic Co. This significantly increases the cost of any subsequent hydrometallurgical processing of the resulting alloy and is therefore less desirable. Furthermore, Fe-containing slags at high temperatures are aggressive to magnesia-containing refractory bricks.

[0057] Therefore, according to a preferred embodiment, the content of Fe in the charge is 5% or less, which can be achieved, for example, by separating out Fe-containing housing materials or by keeping the amount of unnecessary lithium iron phosphate (LFP) batteries in the charge sufficiently low.

[0058] Slag composition and operating temperature are important considerations for the process described herein. The present invention achieves a balance between compounds that protect the furnace walls (e.g., MnO, CaO, LiO) and compounds that adversely affect the furnace walls. The slag composition range also allows for proper slag fluidity and minimal overheating of the slag at the desired operating temperature. The lowest possible temperature is preferred while still remaining above the melting point of the alloy.

[0059] This balance is reflected in the process conditions presented and also in the composition of the slag itself.

[0060] According to a further embodiment, the charge smelting step is carried out at a temperature of at least 1400°C and at most 300°C above the liquidus point of the slag, preferably at most 100°C above the liquidus point of the slag, to ensure complete dissolution of the metallurgical charge. This lower limit is preferred to avoid even partial solidification of the resulting alloy or slag. This upper limit is preferred to avoid overheating of the slag. Higher temperatures promote dissolution of Mg from the magnesia-containing refractory brick. Therefore, lower temperatures are generally preferred to reduce wear and save energy. Overheating of the slag adversely affects the dissolution of the magnesia-containing refractory brick by the slag.

[0061] Preferred operating temperatures are below 1700°C, more preferably below 1650°C, even more preferably below 1600°C, and most preferably below 1550°C.

[0062] According to a further embodiment, the smelting step comprises: - Sampling of the slag; - cooling the slag sample and evaluating its color; and - terminating the smelting process if the slag sample is green; or - If the slag sample is not green, adjust the pO2 level to achieve more reducing conditions before proceeding with the smelting process. Further includes:

[0063] "Sampling the slag" means taking a small sample of the slag while the process continues under selected conditions.

[0064] Color assessment can be easily performed visually. Monitoring the color change, in comparison with a chemical analysis of the slag, quickly and efficiently indicates that the slag contains a certain minimum percentage of MnO. As explained in more detail below, it has further been observed that the green color of the slag also indicates that a significant portion of the Co contained in the feedstock has been reduced into the alloy. Without being bound by theory, it is believed that the green color change results from the reduction of MnO to MnO, but also from the reduction of typical darker oxides of, for example, Fe, Ni, and Co.

[0065] Visual inspection is a quick and easy way to guide the process, which can save time and reduce operational costs.

[0066] In this context, "green" refers to a color whose hue, value, and saturation fall within the following ranges according to the ASTM D1535-14 (2018) standard: - 5GY~5BG hue; - Brightness: 3 or higher; and - Saturation: 3 or more is defined as the color where

[0067] An example of the green color is shown in the "Geological Rock-Color Chart with Genuine Munsell Color Chips," produced by Munsell Color in 2009.

[0068] The operating conditions are selected to oxidize most of the Mn to slag and reduce most of the Co and Ni to the alloy. Preferably, greater than 90% of the Co and Ni are recovered in the alloy, more preferably greater than 95% and most preferably greater than 98%. The pO2 level of the process is easily adjusted to reach these preferred yields.

[0069] According to a further embodiment, the pO2 level is 10 -7 >pO2>10 -12 Preferably, pO2 < 10 -8Preferably, pO2 < 10 -8.5 Most preferably pO2 < 10 -9 is adjusted to.

[0070] 10 -8 , 10 -8.5 , and 10 -9 A preferred pO2 level of 10 -12 This limit is actually 10 -7 This represents reducing conditions relative to pO2 levels and supports high reduction yields.

[0071] According to a further embodiment, the slag is green in color. During smelting of the charge under reducing conditions, the color of the slag typically changes from dark gray or dark brown to green as the process progresses.

[0072] According to a further embodiment, the furnace is an electric furnace. The use of an electric furnace or electric arc furnace (EAF) allows for greater flexibility when higher operating temperatures are desired or required. Another advantage is that it is possible to benefit from off-peak electricity prices or electricity generated by environmentally friendly green sources such as local wind farms.

[0073] A further embodiment is twenty five% <MnO<70%; Al2O3+0.5MnO<45% SiO2>5%; Li2O>3%; 0.5% <P2O5<10%; MnO+Li2O+Al2O3+CaO+SiO2+FeO+MgO+P2O5>90%; and (CaO+2Li2O+0.4MnO) / SiO2≧2.0 This invention describes a Li-containing metallurgical slag having a percent composition by mass according to:

[0074] A further embodiment describes a Li-bearing metallurgical slag, wherein the color of the slag is green. The green color indicates that the slag contains a certain minimum percentage of MnO, which is important for certain slag properties.

[0075] A further embodiment describes a Li-containing metallurgical slag, in which the MnO content in the slag is 30% or more, preferably 40% or more, the higher the amount, the more beneficial it is for protecting the furnace walls.

[0076] A further embodiment describes a Li-containing metallurgical slag, in which the content of Al2O3 in the slag is less than 30%. Limiting this amount to less than 30% is beneficial for achieving a lower melting point.

[0077] A further embodiment describes a Li-bearing metallurgical slag in which the CaO content is 40% or less, preferably 30% or less. Slags with relatively high MnO content (e.g., greater than 40% or even greater than 50%) allow for low to very low amounts of CaO. This includes slags that contain no CaO.

[0078] In all cases, the beneficial properties of the slag according to the invention, which protect the furnace walls from wear or corrosion due to dissolution of MgO from the magnesia-containing refractory bricks, respectively, are maintained.

[0079] A further embodiment describes a Li-bearing metallurgical slag, wherein the content of Fe in the slag is 25% or less, preferably 10% or less. If the slag is reused in a new pyrometallurgical operation, iron from the slag may migrate into the alloy, which is undesirable because it makes any subsequent hydrometallurgical processing of such alloys more complex and therefore expensive.

[0080] A further embodiment describes the use of Li-bearing metallurgical slag as a slag former in a pyrometallurgical recycling process. The resulting metallurgical slag contains one or more of MnO, Al2O3, CaO, and SiO2 and can therefore be used as a slag former in new operations.

[0081] A further embodiment describes the use of a Li-containing metallurgical slag as a slag former in the method according to the first embodiment, thereby partially or completely replacing the slag former in the step of preparing a charge comprising the slag former.

[0082] Reusing the produced metallurgical slag in new operations allows for greater flexibility in the selection of operating conditions (e.g., pO2 level of the process). For example, if more oxidizing conditions are used, thereby sending more Co and / or Ni to the slag, these valuable metals will be recovered in subsequent operating cycles; more reducing conditions can be used to recover more Co and / or Ni. Thus, a further embodiment describes a Li-containing metallurgical slag, where the slag further comprises cobalt.

[0083] When reusing this metallurgical slag as a slag former in a new process cycle, it should be considered that the input battery or its waste may contain additional amounts of compounds (e.g., Al, Mn, or Li) that will be included in the slag after oxidation. As a result, the amount of Al2O3, MnO, or Li2O in the slag will increase. In particular, Al2O3 directly affects the melting point, and therefore its accumulation in the slag needs to be monitored.

[0084] Due to the introduction of new compounds, metallurgical slag according to the present invention can only be reused for a limited number of cycles. To determine whether the slag can continue to be reused, the slag composition should be analyzed and compared to the compositional specifications set forth herein. Draining and reusing at least a portion of the metallurgical slag or diluting it with new slag formers is a viable long-term option.

[0085] As explained above, the slag of the present invention helps to significantly inhibit the dissolution of MgO from magnesia-containing refractory bricks. However, this cannot be completely avoided. This has another beneficial side effect when recycling the slag. Any MgO that accumulated in the slag during a previous smelting operation, along with MnO, LiO, and CaO, tends to inhibit further corrosion of the refractory bricks. This makes the reuse of the slag particularly attractive.

[0086] Further embodiments describe the use of Li-containing metallurgical slag in lithium recovery processes. Slag with a LiO content greater than 3% allows for increased value of the contained lithium, but higher amounts of LiO (e.g., greater than 6% or even greater than 8%) are preferred. Lithium recovery is particularly attractive when the slag is repeatedly reused, because LiO accumulates in the slag with each new cycle, easily reaching concentrations greater than 8%, 10%, 12%, or 14%.

[0087] Li-fuming is the preferred process for lithium recovery from such Li-bearing metallurgical slags because it guarantees high recovery rates. For this purpose, the use of alkali or alkaline earth chlorides (e.g., CaCl) is described in WO2020104164.

[0088] A further embodiment describes the use of Li-containing metallurgical slag in a cobalt recovery process. Reuse of the slag as a slag former in the process according to the first embodiment or in other battery recycling processes allows for the recovery of residual cobalt. This is interesting not only for economic reasons but also for environmental reasons.

[0089] The CaO in the slag should preferably be limited to less than 1%, more preferably less than 0.5%, to reduce the loss of this valuable metal and allow the slag, once no longer being reused, to be safely disposed of in landfills.

[0090] The following examples are provided to further illustrate embodiments of the present invention. Example 1

[0091] The dissolution of MgO from the walls of a magnesia-containing crucible was measured using several different slag compositions. Various compounds contained in Li-ion batteries or their waste (e.g., FeO, Al2O3, Li2O, MnO, and PO5) were melted in a 1 L MgO crucible with CaO and SiO2 as fluxes. The total amount of oxide added was 1000 g.

[0092] The crucible was gradually heated at a heating rate of 150°C / hour using an induction furnace. When the slag was completely melted, the crucible was maintained at a temperature of 1500 or 1650°C. After 2 hours of heating, the molten slag was removed from the crucible and quenched with water. Table 1 lists the composition of the slag produced in this example.

[0093] [Table 1]

[0094] The MgO concentration in the slag was relatively low, indicating that the dissolution of MgO from the crucible wall was sufficiently suppressed under the selected conditions.

[0095] (CaO+2Li2O+0.4MnO) / SiO2 was 2.9 for slag 1-1, 2.2 for slag 1-2, and 9.0 for slag 1-3.

[0096] This experiment was carried out with a slag composition that did not contain Ni, Co, or Cu because the amounts of these metals in the final slag are typically very low and therefore do not essentially affect the slag properties.

[0097] Comparative Example 2 The dissolution of MgO from the wall of a magnesia-containing crucible was measured using different slag compositions. Various compounds contained in Li-ion batteries or their waste (e.g., FeO, Al2O3, Li2O, MnO, and PO5) were melted in a 1 L MgO crucible with CaO and SiO2 as fluxes. The total amount of oxide added was 1000 g.

[0098] The crucible was gradually heated at a heating rate of 150°C / hour using an induction furnace. When the slag was completely melted, the crucible was maintained at a temperature of 1500°C for 2 hours. After 2 hours of heating, the molten slag was removed from the crucible and quenched with water. Table 2 lists the composition of the slag produced in this example.

[0099] [Table 2]

[0100] Compared to the slag used in Example 1, the MnO content in the slag in Comparative Example 2 was adjusted to less than 10%. (CaO + 2LiO + 0.4MnO) / SiO2 was 1.2 for Slag 2-1 and 1.1 for Slag 2-2. The measured MgO concentrations in the slags were relatively high (9.0%-15.7%), indicating that a relatively large amount of MgO was dissolved from the crucible into each slag. As in Example 1, the slags contained no Ni, Co, or Cu.

[0101] Considerations of Examples 1 and 2 The slag obtained in Example 1 contained less MgO than the slag obtained in Comparative Example 2. Under the conditions of Example 1, no visible deterioration of the MgO crucible was observed, but under the conditions of Comparative Example 2, the crucible wall became thinner. As demonstrated in Example 1, slag containing a relatively high concentration of MnO inhibited MgO dissolution. More specifically, when the MnO concentration was 25% or higher, MgO dissolution in the slag was effectively inhibited. Example 3

[0102] 500 kg of black mass was fed into a 1 m diameter furnace freshly lined with 200 mm chrome-magnesia refractory bricks. Slag produced in a previous smelting operation, with a composition according to Table 3, was added along with the black mass and reused as a slag former. A batch temperature of 1500-1550 °C was maintained, which was suitable to maintain sufficient fluidity of both the slag and alloy for easy tapping and handling. O2 injection in water was used to provide heat by oxidation of Al and C in the cells. The injection rate was adjusted to achieve strongly reducing conditions (i.e., 10 in this case). -9 The temperature was selected to achieve a pO2 of 1000 K. Natural gas was added to compensate for heat losses in the furnace. After 1 hour of heating, the produced alloy and slag were separated by tapping. During the process, a small amount of material was collected as smoke.

[0103] Table 3 shows the analysis of the input and output stages of this process.

[0104] [Table 3]

[0105] No visible deterioration of the magnesia-containing refractory bricks was observed during the battery treatment. The MgO concentration in the produced slag was only 1.4%, corresponding to a loss of 0.1 kg of MgO from the refractory bricks, which is a very small degradation as a result of the high MnO content in the slag. Therefore, this slag effectively inhibited the wear of the furnace walls made of magnesia-containing refractory bricks.

[0106] Overall conclusion The metallurgical slag according to the present invention is suitable for recovering valuable metals such as Ni and Co from Li-ion batteries or their waste, while minimizing the deterioration of the magnesia-containing refractory bricks in the furnace.

Claims

1. A method for recovering Ni and Co from a Li-ion battery or a waste thereof, comprising: - providing a furnace lined with magnesia-containing refractory bricks; - providing a charge comprising a slag former and Li-ion batteries or waste thereof, the charge having an Al content of less than 8%; and smelting said charge under reducing conditions, thereby obtaining an alloy containing a large proportion of Ni and Co, and a Li-containing slag, said slag comprising: 25%<MnO≦44.3%; Al ２ O ３ +0.5MnO<45% Yes ２ >5%; Li ２ O>1%; 0.5%<P ２ O ５ <10%; MnO + Li ２ O + Al ２ O ３ + CaO + SiO ２ + FeO + MgO + P ２ O ５ > 90%; and (CO+2L& ２ O+0.4MnO) / SiO ２ ≧2.0 having a percentage composition by mass according to A method comprising:

2. 2. The method of claim 1, wherein the content of MnO in the slag is 30% or more.

3. Al in the slag ２ O ３ The method according to claim 1 or 2, wherein the content of is less than 30%.

4. The method of claim 1 , wherein the Li-ion battery or waste thereof is black mass.

5. 2. The method of claim 1, wherein the content of CaO in the slag is 40% or less, or 30% or less.

6. Li in the slag ２ 2. The method of claim 1, wherein the O content is greater than 3%.

7. 2. The method according to claim 1, wherein the content of cobalt oxide in the slag is 0.05%<CoO<1%.

8. The method of claim 1 , wherein the content of Fe in the slag is 25% or less, or 10% or less.

9. 2. The method of claim 1, wherein the content of Fe in the charge is 5% or less.

10. 2. The method of claim 1, wherein the step of smelting the charge is carried out at a temperature of at least 1400°C and at most 300°C above the liquidus point of the slag, or at most 100°C above the liquidus point of the slag, thereby avoiding overheating.

11. The smelting step includes: - sampling the slag; - cooling the slag sample and assessing its color; and - terminating the smelting step if the slag sample is green; or If the slag sample is not green, increase the pO ２ After adjusting the level, proceed with the smelting step, thereby obtaining an alloy containing a majority of Ni and Co and a Li-containing slag. Further comprising: The green color has a hue, value, and saturation in the following ranges according to the ASTM D1535-14 (2018) standard: - 5GY to 5BG color shade; - brightness: 3 or more; and - Saturation: 3 or more is defined as a color where The method of claim 1.

12. The pO ２ Level: 10 －７ >pO ２ >10 －１２ to, or pO ２ <10 －８ to, or pO ２ <10 －８．５ to, or pO ２ <10 －９ The method of claim 11 , wherein the

13. 13. The method of claim 11 or 12, wherein the color of the slug is green.

14. The method of claim 1 , wherein the furnace is an electric furnace.

15. 25%<MnO≦44.3%; Al ２ O ３ +0.5MnO<45% Yes ２ >5%; Li ２ O>3%; 0.5%<P ２ O ５ <10%; MnO + Li ２ O + Al ２ O ３ + CaO + SiO ２ + FeO + MgO + P ２ O ５ > 90%; and (CO+2L& ２ O+0.4MnO) / SiO ２ ≧2.0 A Li-containing metallurgical slag having a percentage composition by mass according to

16. 16. The Li-containing metallurgical slag of claim 15, wherein the slag is green in color.

17. 17. The Li-containing metallurgical slag according to claim 15 or 16, wherein the content of MnO in the slag is 30% or more, or 40% or more.

18. Al in the slag ２ O ３ The Li-containing metallurgical slag according to claim 15 or 16, wherein the content of is less than 30%.

19. 17. The Li-containing metallurgical slag according to claim 15 or 16, wherein the CaO content in the slag is 40% or less, or 30% or less.

20. 17. The Li-containing metallurgical slag according to claim 15 or 16, wherein the content of Fe in the slag is 25% or less, or 10% or less.

21. 17. Use of the Li-containing metallurgical slag according to claim 15 or 16 as a slag former in a pyrometallurgical recycling process.

22. 17. Use of the Li-containing metallurgical slag of claim 15 or 16 as a slag former in the method of claim 1, thereby partially or completely replacing the slag former in the step of preparing a charge comprising the slag former.

23. 17. Use of the Li-containing metallurgical slag according to claim 15 or 16 in a lithium recovery process.

24. 17. The Li-containing metallurgical slag of claim 15 or 16, wherein the slag further comprises cobalt.

25. 25. Use of the metallurgical slag of claim 24 in a cobalt recovery process.

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