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 is in the field of pyrometallurgy and relates to the recovery of Ni and Co from Li-ion batteries or their waste products, more specifically black mass. [Background technology]

[0002] Electric vehicles have shown unprecedented growth in recent years, and in particular, 2 This growth is driven by new legislation in Europe and China, aimed at gradually shedding loads and limiting air pollution in cities. This growth is expected to continue over the coming decades. The adoption of electric vehicles depends heavily on the performance of the batteries used to store the 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] The demand for Ni and Co may even exceed the world's production capacity. Co is particularly important because it is currently only produced as a by-product of the Ni and Cu industries. The nickel market is considerably larger than the cobalt market. Most of the Ni is used in the manufacture of stainless steels, where the purity of the Ni is not that important. However, high-purity Ni and high-purity Co metals or compounds are already in short supply. Therefore, in view of the above, recovery of 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, the 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 dismantled and crushed, which may include the separation of the housing material, the metal foil, and / or the anode. Sometimes the batteries are also pretreated. The black mass resulting from such a process is usually characterized by a relatively low aluminum content compared to the treatment of a complete battery. 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 for the treatment of black mass, resulting in salts or metal hydroxides. Pyrometallurgical refining processes are less common, whereas the combined dry-wet process according to the invention remains a rare exception.

[0006] In a known pyrometallurgical process for recycling Li-ion batteries, the oxides of nickel, cobalt, and copper in a furnace are reduced to their respective metals and concentrated into alloy phases at high temperatures. Other compounds, such as lithium and manganese, are reduced to Li 2 It is oxidized to O and MnO and is contained in the slag.

[0007] Carrying out such high temperature processes causes wear and corrosion of the furnace walls over time. Typically, the furnace walls are made of refractory bricks. The most commonly used bricks are magnesia based. Typical magnesia bricks contain more than 90% magnesia, while magnesia-chrome bricks contain 50-70%. It has been observed that magnesia dissolves with the prevailing slag during furnace operation. This wear or corrosion is a recurring problem, which results 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, e.g., above 1550°C.

Prior technical literature

[0008]

Patent Document 1

Patent document 2

Patent document 3

Patent document 4

Patent document 5

Patent document 6

Patent document 7

Patent document 8

Patent Document 9

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-Patent Document 3] Vest et al., Slag design for lithium recovery from spent batteries: Int. Work. Met. Interact., 9(93), 2010, 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] It is therefore an object of the present invention to provide an efficient process for recovering Ni and Co from Li-ion batteries or their waste (specifically black mass), as well as to extend furnace life. This is achieved by using a dedicated MnO and Li ion refractory material with a controlled composition designed to limit the corrosion of magnesia-bearing refractory bricks. 2 This is achieved by working with an O-rich system.

[0011] WO2017121663 describes slag compositions produced in an industrial process and discloses the effect of MnO on slag viscosity and cobalt recovery. The main slag components described therein are CaO, SiO 2 , Al 2 O 3 , Li 2 O, and MnO or MnO 2 The MnO content in these slags disclosed is very low and the teaching is to limit the amount of MnO in the slag.

[0012] In Wittkowski et al. (Speciation of Manganese in a Synthetic Recycling Slag Relevant for Lithium Recycling from Lithium-Ion Batteries: Metals, Vol. 11(2), 2021, p. 188) the phase composition of various Li-containing slags relevant for recycling Li-ion batteries is analyzed. Black mass is not mentioned as starting material. All reported slags are characterized by an MnO content significantly below that according to 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 the slag phase. It is stated that Mn may be a component of the resulting slag, but no preferred range or specific effect of MnO in such slag is stated.

[0015] Chinese Patent No. 103924088 and European Patent No. 3269832 describe a bath smelting process for waste batteries, which comprises an alloy containing Co and / or Ni and SiO 2 and MeO-rich slags are produced. The Li content in such slags is not stated, only MnO or Li 2 No effect of O is mentioned. Black mass is not mentioned as a starting material.

[0016] China Patent No. 105838895 and Xiao et al. (Recovery of Valuable Metals from Spent Lithium-Ion Batteries by Smelting Reduction Process Based on MnO-SiO 2 -Al 2 O 3 Slag System: J. Sustain. Metall., Vol. 3, 2017, pp. 703-710) describes 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, but the specific slag properties are not discussed. Typical slags contain MnO, SiO 2 , and Al 2 O 3 However, in all given examples, Li 2 The O 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 of 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 desired slag properties is to reduce the Li 2 The problem is that the capacity / solubility of O is low.

[0018] In European Patent No. 21176046, O was used to reduce most of the Ni and Co. 2 A pyrometallurgical recycling process for Li-ion batteries is described in which the batteries are fed into a smelting furnace equipped with underwater injection of the contained gas. The resulting slag is treated in a second reduction smelting step to extract the remaining Ni and Co. The slag contains less than 20% MnO and higher amounts of Al.2 O 3 (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 wear of magnesia-containing refractory bricks in pyrometallurgical processes, which contributes to the overall economics of the current process. The following embodiments further illustrate the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] According to the 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 materials thereof, the charge having an Al content of less than 8%; and - smelting the charge under reducing conditions, thereby obtaining an alloy containing mostly Ni and Co, and a Li-containing slag, which twenty five% <MnO<70%; Al 2 O 3 +0.5MnO<45%; SiO 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 (CaO+2Li 2 O+0.4MnO) / SiO 2 ≧2.0 having a percent composition by mass according to Includes.

[0021] "Slag forming agents" include, for example, CaO, Al 2 O 3 , and SiO 2 Other slag forming agents 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 areas in contact with the slag).

[0023] Although the 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 precipitates (MHP) can be added, and such products often contain useful concentrations of Co, Ni, and Mn, along with Mg. Co and Ni are recovered in the alloy, while Mn and Mg are included in the slag, where they play a useful role in protecting the lining. By combining battery materials with MHP, the total energy consumption is also optimized, since batteries tend to be exothermic, while MHP is endothermic during smelting. The total charge can advantageously contain up to 30% by weight of MHP.

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

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

[0026] The phrase "black mass" is typically used in industry to describe intermediate products (e.g. new or discarded Li-ion batteries, used or end-of-life batteries, production scrap or battery scrap, electrode materials or other pre-processed battery materials) originating from Li-ion batteries or their waste products. Batteries are usually dismantled. In this process, for example, Al, Fe, and Cu are separated from the casing and cables. All these battery materials are then fragmented and sometimes pre-processed (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 interesting. 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 ranges having lower limits selected from 55%, 60%, 65%, 70%, and 75% and upper limits 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 content of MnO in the slag plays an important role in the present invention. A minimum of about 10% MnO is required in the slag to observe the effect of inhibiting MgO dissolution from the magnesia-containing refractory bricks lining the furnace into the slag. At least 25% MnO in the slag is sufficient to inhibit MgO dissolution. It is preferred to have at least 30% MnO in the slag, more preferably at least 40%. When starting with black mass as the feed material in the process and using minimal slag formers to reduce costs and keep the slag volume low, the amount of MnO in the slag is typically greater than 25%.

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

[0032] In contrast, 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 a detrimental effect.

[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 as "MnO". In such slags, the exact oxidation state of Mn is not always clearly defined. Therefore, manganese oxide ("MnO") is divided into two groups: MnO monoxide and MnO dioxide. 2 In particular, under the selected reducing conditions, the proportion of MnO is expected to be well above 95%.

[0035] MnO is typically green, but 2 is typically dark brown or dark grey, hence the name "manganese black". Only when the content of a single species is high enough does the green colour predominate.

[0036] P in slag2 O 5 The content is 0.5% <P 2 O 5 <10%.

[0037] Phosphorus typically comes from the electrolyte in Li-ion batteries and is called P 2 O 5 is contained in the slag as

[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, Al in the slag 2 O 3 The content of Al is less than 30%. 2 O 3 If the amount of is too high (e.g., 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 contains trace amounts of Al 2 O 3 to the slag. This is a clear difference when starting from a black mass instead of a full Li-ion battery, which is typically Al-rich due to the enclosure.

[0041] Formula Al 2 O 3 The slag composition suitable for +0.5MnO<45% is Al 2 O 3 This allows for a slag with a relatively high MnO content while limiting the amount of MnO.

[0042] According to a further embodiment, the slag comprises Al 2 O 3+0.5MnO<30%. Thus, Al 2 O 3 The amount of is further limited in slags with a relatively high MnO content, which is beneficial for protecting 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 bricks since Ca and Mg share similar chemical sites in the slag. Operating the process at the 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 as it increases the slag melting point.

[0045] In contrast, 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 forming agent does not include CaO.

[0047] The MnO-rich feedstock also allows for the complete avoidance of CaO as a slag former, which is typically used in the known ternary slag systems Al 2 O 3 -CaO-SiO 2 This opens the door to exploring slag systems other than

[0048] Since MnO in the slag plays an important 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 Li in the slag 2 The O content is more than 3%, and preferably more than 6%.

[0050] In addition to MnO and CaO, Li 2 It has further been observed that O also inhibits the dissolution of Mg from magnesia-containing refractory bricks. When recycling Li-ion batteries, the Li 2 The amount of O is expected to be significant.

[0051] In this context, more than 3% should be understood specifically as 3.1 or more, preferably 3.2 or more, 3.3 or more, 3.4 or more, in particular 3.5 or more, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more. Amounts of more than 3% make it possible to increase the value of lithium in the slag. However, Li 2 O also inhibits Mg dissolution, so higher amounts such as more than 6% are preferred not only for economic reasons but also for their higher contribution to wear reduction, especially for amounts of 7% or more, 8% or more, 9% or more, 10% or more.

[0052] SiO 2 On the other hand, SiO 2 Therefore, according to a further embodiment, the amount of SiO in the slag is increased. 2 The amount of is less than 20%.

[0053] In a preferred embodiment, the slag composition is represented by the formula (CaO+2Li 2 O+0.4MnO) / SiO 2 ≧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 included in the alloy and only a small portion remains in the slag. Typically, concentrations below 1% are obtained. In industrial Li-ion battery recycling, completely cobalt-free slag is not obtained.

[0056] According to a further embodiment, the content of Fe in the slag is 25% or less, preferably 10% or less. FeO-rich slags containing more than 10% FeO, respectively more than 25% FeO, do not allow the reduction of CoO to metallic Co without transferring a relatively large amount of metallic Fe to the alloy layer. This significantly increases the cost of any hydrometallurgical subsequent processing of the resulting alloy and is therefore less desirable. Moreover, Fe-containing slags at high temperatures are aggressive towards magnesia-containing refractory bricks.

[0057] Thus, 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 provides compounds that protect the furnace walls (e.g., MnO, CaO, Li 2 A balance is achieved between the amount of slag (O) and compounds that adversely affect the furnace walls. The slag composition range also allows for proper fluidity of the slag 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 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, preferably at most 100° C. above the liquidus point of the slag, in order to ensure complete dissolution of the metallurgical charge. This lower limit is preferred to avoid even partial solidification of the alloy or slag produced. This upper limit is preferred to avoid overheating of the slag. At higher temperatures, dissolution of Mg from the magnesia-containing refractory bricks is promoted. Therefore, lower temperatures are generally preferred for wear reduction and energy savings. Overheating of the slag adversely affects the dissolution of the magnesia-containing refractory bricks by this 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 the slag; - cooling the slag sample and evaluating its color; and - terminating the smelting step if the slag sample is green; or - If the slag sample is not green, increase the pO to achieve more reducing conditions. 2 After adjusting the level, the smelting process is carried out. Further includes.

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

[0064] Color assessment may be easily performed visually. Monitoring the color change, in comparison to 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 color change to green indicates the reduction of MnO to MnO. 2 It is actually believed that the oxidation of the oxides results from the reduction of the oxides of Fe, Ni, and Co, but also from the reduction of the typically denser oxides of Fe, Ni, and Co, for example.

[0065] Visual inspection is a quick and easy way to conduct a process that can save time and reduce operational costs.

[0066] In this context, "green" refers to a color whose hue, value, and chroma 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 It is defined as a color that is.

[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 is recovered in the alloy, more preferably greater than 95% is recovered, and most preferably greater than 98% is recovered. The pO 2 Levels are easily adjusted to achieve these desired yields.

[0069] According to a further embodiment, pO 2 Level: 10 -7 >pO 2 >10-12 and preferably pO 2 <10 -8 More preferably, the pO 2 <10 -8.5 and most preferably pO 2 <10 -9 is adjusted to.

[0070] 10 -8 , 10 -8.5 , and 10 -9 The preferred pO 2 Level, and 10 -12 The limit is actually 10 -7 The pO 2 The results show reducing conditions compared to the levels and support high reduction yields.

[0071] According to a further embodiment, the color of the slag is green. 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 an 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 power plants.

[0073] A further embodiment comprises twenty five% <MnO<70%; Al 2 O 3 +0.5MnO<45% SiO 2 >5%; Li 2 O>3%; 0.5% <P 2 O 5 <10%; MnO+Li 2 O+Al 2 O 3 +CaO+SiO2 +FeO+MgO+P 2 O 5 >90%; and (CaO+2Li 2 O+0.4MnO) / SiO 2 ≧2.0 A Li-containing metallurgical slag having a percent composition by mass according to

[0074] A further embodiment describes a Li-bearing metallurgical slag, where the color of the slag is green, which 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 content of MnO is 30% or more, preferably 40% or more. The higher the amount, the more beneficial it is for the protection of the furnace walls.

[0076] A further embodiment is a Li-containing metallurgical slag, the Al in the slag being 2 O 3 The content of Li in Li-containing metallurgical slags is less than 30%. Limiting this amount to less than 30% is beneficial to achieve a lower melting point.

[0077] Further embodiments describe Li-bearing metallurgical slags, in which the CaO content is 40% or less, preferably 30% or less. Slags with relatively high amounts of MnO (e.g., more than 40% or even more than 50%) allow for low to very low amounts of CaO. This includes slags that do not contain CaO.

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

[0079] A further embodiment describes a Li-bearing metallurgical slag, in which the content of Fe in the slag is not more than 25%, preferably not more than 10%. If the slag is reused in a new pyrometallurgical operation, iron from the slag may migrate into the alloy, which is undesirable as it makes any hydrometallurgical downstream processing of such alloys more complicated and therefore more expensive.

[0080] A further embodiment describes the use of Li-containing metallurgical slag as a slag former in a pyrometallurgical recycling process. The resulting metallurgical slag contains MnO, Al 2 O 3 , CaO, and SiO 2 and therefore may be used as a slag former in the new operation.

[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] The generated metallurgical slag can be reused in new operations to reduce the operating conditions (e.g., pO of the process) 2 This allows for greater flexibility in the selection of the oxidation level (level of oxidation). 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 a subsequent work cycle, and more reducing conditions can be used to recover more Co and / or Ni. Thus, a further embodiment describes a Li-containing metallurgical slag, which further comprises cobalt.

[0083] If this metallurgical slag is to be reused as a slag former in a new process cycle, it should be taken into account 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.2 O 3 , MnO, or Li 2 The amount of O will increase. 2 O 3 has a direct effect on the melting point and therefore its buildup in the slag needs to be monitored.

[0084] Due to the input 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 with new slag formers are viable long-term options.

[0085] As explained above, the slag of the present invention helps to significantly reduce 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 has accumulated in the slag during a previous smelting operation will be dissolved in MnO, Li 2 Together with O and CaO, it tends to inhibit further corrosion of the refractory brick, making reuse of the slag particularly attractive.

[0086] Further embodiments describe the use of Li-containing metallurgical slag in lithium recovery processes. 2 Slag with an O content of more than 3% can increase the value of the lithium contained, but it also has a higher amount of LiO 2 (e.g., greater than 6%, or even greater than 8%). Lithium recovery is particularly attractive when the slag is repeatedly reused, because LiO 2 accumulates and can easily reach concentrations of more than 8%, more than 10%, more than 12%, or more than 14%.

[0087] Li-fuming is the preferred process for lithium recovery from such Li-bearing metallurgical slags, since it ensures high recovery rates. For this purpose, alkali or alkaline earth chlorides (e.g., CaCl 2 ) 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 the recovery of the remaining 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%, so that loss of this valuable metal is reduced and slag that is no longer being reused can be safely disposed of in landfills.

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

[0091] Using several different slag compositions, the dissolution of MgO from the walls of magnesia-containing crucibles was measured. Various compounds contained in Li-ion batteries or their waste, respectively, their oxides (e.g., FeO, Al 2 O 3 , Li 2 O, MnO, and P 2 O 5 )) in a 1 L MgO crucible with CaO and SiO 2 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 under the selected conditions, the dissolution of MgO from the crucible wall was sufficiently suppressed.

[0095] (CaO+2Li 2 O+0.4MnO) / SiO 2 was 2.9 for slug 1-1, 2.2 for slug 1-2, and 9.0 for slug 1-3.

[0096] This experiment was performed 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 Using different slag compositions, the dissolution of MgO from the walls of magnesia-containing crucibles was measured. Various compounds contained in Li-ion batteries or their waste, respectively, their oxides (e.g., FeO, Al 2 O 3 , Li 2 O, MnO, and P 2 O 5 )) in a 1 L MgO crucible with CaO and SiO 2 The total amount of oxide added was 1000 g.

[0098] The crucible was gradually heated at a heating rate of 150°C / hr 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 with the slag used in Example 1, in Comparative Example 2, the MnO content in the slag was adjusted to less than 10%. (CaO+2Li 2 O+0.4MnO) / SiO 2 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 from the crucible was dissolved 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. No visible deterioration of the MgO crucible was observed under the conditions of Example 1, but the crucible wall became thinner under the conditions of Comparative Example 2. 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 more, MgO dissolution in the slag was efficiently 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 with the black mass and reused as a slag former. A batch temperature of 1500-1550 °C was maintained, which is suitable to maintain sufficient fluidity of both the slag and alloy for ease of tapping and handling. O in water was added. 2 Injection was used to provide heat by oxidation of Al and C in the cell. The injection rate was adjusted to provide strong reducing conditions (i.e., 10 -9 pO 2 ) was selected. Natural gas was added to compensate for the heat loss 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 treatment of the batteries. The concentration of MgO in the produced slag was only 1.4%, which corresponds 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, the slag efficiently 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 deterioration of the magnesia-containing refractory bricks of the furnace.

Claims

1. A method for recovering Ni and Co from a Li-ion battery or a waste thereof, comprising 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 materials 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<70%; 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 percent composition by mass according to The method includes:

2. 2. The method according to 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. 4. The method according to claim 1, wherein the Li-ion battery or waste material thereof is black mass.

5. 5. The method according to claim 1, wherein the content of CaO in the slag is less than or equal to 40%, preferably less than or equal to 30%.

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

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

8. 8. The method according to any one of the preceding claims, wherein the content of Fe in the slag is less than or equal to 25%, preferably less than or equal to 10%.

9. 9. The method according to claim 1, wherein the content of Fe in the charge is less than or equal to 5%.

10. 10. The method according to any one of claims 1 to 9, 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, preferably 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 evaluating 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, proceeding with the smelting step. The method of claim 1 , further comprising:

12. The pO ２ Level: 10 －７ >pO ２ >10 －１２ and preferably pO ２ <10 －８ More preferably, the pO ２ <10 －８．５ and most preferably pO ２ <10 －９ The method according to claim 1 , wherein the concentration of the ion exchange resin is adjusted to

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

14. 14. The method according to any one of claims 1 to 13, wherein the furnace is an electric furnace.

15. 25%<MnO<70%; 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, preferably 40% or more.

18. Al in the slag ２ O ３ The Li-containing metallurgical slag according to any one of claims 15 to 17, wherein the content of is less than 30%.

19. 19. A Li-containing metallurgical slag according to any one of claims 15 to 18, wherein the content of CaO in the slag is not more than 40%, preferably not more than 30%.

20. 20. A Li-containing metallurgical slag according to any one of claims 15 to 19, wherein the content of Fe in the slag is not more than 25%, preferably not more than 10%.

21. 21. Use of the Li-containing metallurgical slag according to any one of claims 15 to 20 as a slag former in a pyrometallurgical recycling process.

22. 21. Use of a Li-containing metallurgical slag according to any one of claims 15 to 20 as a slag former in the method according to any one of claims 1 to 16, thereby partially or completely replacing the slag former in the step of preparing a charge comprising the slag former.

23. 21. Use of the Li-containing metallurgical slag according to any one of claims 15 to 20 in a lithium recovery process.

24. 21. The Li-containing metallurgical slag of any one of claims 15 to 20, wherein the slag further comprises cobalt.

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

Images