KR102664172B1 - Recovery of nickel and cobalt from Li-ion batteries or their waste - Google Patents

Abstract

The present invention belongs to the field of pyrometallurgy and discloses a process and slag suitable for the recovery of Ni and Co from Li-ion batteries or their waste. The slag composition is defined as follows: 10% < MnO <40%; (CaO + 1.5*Li ₂ O) / Al ₂ O ₃ >0.3; CaO + 0.8*MnO + 0.8*Li ₂ O <60%; (CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0; Li ₂ O ≥ 1%; and Al ₂ O ₃ + SiO ₂ + CaO + Li ₂ O + MnO + FeO + MgO > 85%. This composition is particularly suited to limit or avoid corrosion in furnaces lined with magnesia-retaining refractory bricks.

Description

Recovery of nickel and cobalt from Li-ion batteries or their waste

The present invention belongs to the field of pyrometallurgy, and more specifically relates to the recovery of Ni and Co from Li-ion batteries or their waste.

In recent years, electric vehicles have seen unprecedented growth, driven by new legislation, particularly in Europe and China, designed to gradually reduce the _CO2 footprint of automotive vehicles and limit urban air pollution. This growth is expected to continue over the next several decades. The adoption of electric vehicles largely depends on the performance of the batteries used to store electrical energy. To achieve the highest energy density while keeping costs under control, rechargeable Li-ion batteries are currently the preferred choice. Many of these batteries contain cathodes based on the transition metals Ni, Mn, and Co, making them also known as NMC batteries. As the electric mobility market grows, the demand for these metals is also expected to increase significantly.

Demand for Ni and Co may even exceed global production capacity. Co is particularly important because it is produced today solely as a by-product of the Ni and Cu industries. The nickel market is significantly larger than the cobalt market. Most of Ni is given to the manufacture of stainless steel, where the purity of Ni is less important. However, high purity Ni and high purity Co metals or compounds are already in short supply. Therefore, considering the above, recovering Ni and Co from spent Li-ion batteries or their waste is an attractive proposition.

There are several known processes for recycling Li-ion batteries, in which nickel, cobalt and copper oxides are reduced to metals and concentrated into an alloy phase at high temperatures.

WO2017121663 describes a slag composition prepared in an industrial process and discloses the effect of MnO on slag viscosity and cobalt recovery. The main slag components described herein include CaO, SiO ₂ , Al ₂ O ₃ , Li ₂ O, and MnO (MnO ₂ ). The MnO-concentration in these disclosed slags is very low and the above teaching limits the amount of MnO in the slag. Elwert et al. [Phase composition of high lithium slags from the recycling of lithium-ion batteries: World of Metallurgy-ERZMETALL, vol. 65 (3), 2012, pp. 163-171, the phase composition of three different slags is analyzed with the aim of developing a possible slag beneficiation process for lithium recovery. Hu et al. [Recovery of Co, Ni, Mn, and Li from Li-ion batteries by smelting reduction-Part II: A pilot-scale demonstration: Journal of Power Sources, vol. 483, 2021, 229089] proposes a recycling process for Li-ion batteries, producing slag and alloys containing Ni, Co, and Mn by smelting with a fluxing agent at temperatures exceeding 1500°C. there is. Elwert and Hu both describe slag compositions with MnO-concentrations well below 10%.

On the other hand, modern Li-ion batteries typically contain increasing amounts of Mn. This makes the formation of slag with small amounts of Mn more difficult, either by diluting the Mn by adding large amounts of fluxing agent to direct more Mn to the alloy phase instead of the slag phase, or by requiring stronger reducing conditions for this process. Because you need to make a choice. The former option increases the consumption of fluxing agent and the total amount of slag obtained, while the latter option increases the complexity of any subsequent hydrometallurgical treatment of the alloy due to the higher Mn content. Both of these options will significantly reduce the economics of the process.

WO12140951, WO13080266 and WO20013294 propose a process for recycling Li-ion battery scrap to recover Ni and Co while fixing impurities such as Fe and P in the slag. Although it is stated that Mn may be a major component of the slag obtained, the preferred extent or specific effect of MnO in such slag is not specified. Additionally, WO12140951 and WO13080266 focus on low melting Fe-enriched slag.

Vest et al. [Friedrich Slag design for lithium recovery from spent batteries: Int. Work. Met. Interact., vol. 9 (93), 2010, pp. 93-106.] describes theoretical calculations of MnO-rich slag. 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 from recycling of Li-ion batteries is analyzed.

CN103924088 and EP3269832 describe a bath smelting process for spent batteries, producing Co and/or Ni containing alloys and SiO ₂ and MnO-enriched slag.

The slag composition according to the invention is not taught in any of the above prior arts.

Even where slags with relatively higher contents of MnO are disclosed, none of the above documents teach the process conditions and do not mention any effect of the resulting MnO-rich slag composition on the walls of the furnace. not. Typically, furnace walls are made of refractory bricks. The main composition of these bricks is magnesia. Examples are magnesia bricks (typically greater than 90% magnesia content) or magnesia-chrome bricks (typically 50% to 70% magnesia content). It has been observed that magnesia from the walls is dissolved by common slag during furnace operation, resulting in wear or corrosion of the furnace walls over time. This is a recurring problem that results in high maintenance costs because the furnace has to be shut down and the refractory bricks have to be replaced regularly. This problem becomes even more pronounced at higher operating temperatures, for example above 1550°C.

Therefore, the object of the present invention is to reduce Ni from Li-ion batteries by operating them with a dedicated MnO- and Li ₂ O-enriched slag system constructed in such a way that the magnesia-retaining refractory bricks are less prone to corrosion during operation, thereby simultaneously increasing the life of the furnace. and a method for recovering Co. The achieved wear reduction contributes significantly to the overall economics of the method.

According to a first embodiment, a method for recovery of Ni and Co from Li-ion batteries or their waste

- providing a furnace lined with magnesia-retaining refractory bricks;

- providing a charge comprising a slag former and Li-ion batteries or waste thereof; and

- smelting the charge under reducing conditions, thereby obtaining an alloy containing most of Ni and Co, and slag,

The slag is characterized by having a percent composition by mass according to:

10% < MnO < 40%;

(CaO + 1.5*Li ₂ O) / Al ₂ O ₃ >0.3;

CaO + 0.8*MnO + 0.8*Li ₂ O <60%;

(CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0;

Li ₂ O ≥ 1%; and

Al ₂ O ₃ + SiO ₂ + CaO + Li ₂ O + MnO + FeO + MgO > 85%.

“Slag former” means, for example, one or more of CaO, Al ₂ O ₃ and SiO ₂ . Other slag formers well known to those skilled in the art may also be present. The slag forming compounds can be added as is, or they can be obtained in situ from readily oxidized metals present in the charge, such as aluminum.

“Li-ion batteries or waste thereof” means, for example, new or spent Li-ion batteries, used or end-of-life batteries, production or battery scrap, electrode materials, or so-called “black mass ( refers to battery materials that have been preprocessed, such as after crushing or sorting, including "black mass". However, they will still contain significant amounts of Co and/or Ni.

“Majority” of an element or compound means more than 50% by weight of the corresponding amount present in the charge. It may also include ranges with lower values selected from 55%, 60%, 65%, 70%, and 75%, and upper values selected from 80%, 85%, 90%, 95%, and 100%.

The content of MnO in the slag plays an important role in the present invention. A minimum of approximately 10% of the slag is required to be effective in inhibiting MgO dissolution into the slag from the magnesia-retaining refractory bricks lining the furnace. It is desirable to have at least 15% MnO. Additionally, it is advantageous to have a MnO content of 10% to 40% in relatively small amounts of slag, because the volume reduction of the slag helps suppress MgO dissolution. On the other hand, by adding more fluxing agent, the total volume of slag increases and the percentage of MnO is diluted, the amount of MgO dissolved from the refractory brick increases, and thus has a negative effect.

Additionally, the upper limit of MnO in the slag is important because it helps keep the melting temperature of the slag sufficiently low. The slag containing up to 40% MnO according to the invention melts below 1500°C. In combination with the MnO amount, lower temperatures are advantageous to suppress MgO dissolution from magnesia-retaining refractory bricks. Amounts of MnO exceeding 40% are less desirable, as they increase the melting point of the slag above 1500° C., especially when the slag also contains relatively higher amounts of Al ₂ O ₃ , such as greater than 50%.

According to a further embodiment, the content of MnO in the slag is not more than 30%.

The percentage of Mn in the slag is normalized as “percent of MnO”. However, the exact oxidation state of Mn is not always well defined in these slags. Accordingly, manganese oxide (“MnO”) can also refer to a mixture of the single-species MnO and manganese dioxide MnO ₂ . However, the sharing of single-species MnO is estimated to be well in excess of 95%, especially under selected reduction reaction conditions.

MnO is typically green, while MnO ₂ is typically black-brown or black-gray, giving it its name “manganese black.” Green will only be visible if the single-species content is sufficiently high.

According to a further embodiment, the content of CaO in the slag is at least 15%, preferably at least 20%.

According to a further embodiment, the content of CaO in the slag is not more than 50%, preferably not more than 30%.

A minimum of 15% CaO ensures that the slag remains sufficiently fluid and can be easily handled. As Ca and Mg share similar chemical sites in the slag, higher amounts of CaO, such as 20% or more, are preferred because CaO helps inhibit dissolution of Mg from the magnesia-retaining refractory brick. Operating the process at the preferred upper limit of 30% CaO helps maintain the melt temperature of the slag below 1600°C. Too high amounts of CaO, such as more than 50%, should be avoided as they significantly increase the melting temperature of the slag.

Additionally, it was observed that, in addition to MnO and CaO, Li ₂ O also inhibits the dissolution of Mg from magnesia-retained refractory bricks, but increasing the amount of SiO ₂ has a negative effect. This is reflected in the equation (CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0. When recycling Li-ion batteries, the amount of Li ₂ O in the slag is expected to be significant.

According to a further embodiment, the content of Al ₂ O ₃ in the slag is <50%, preferably <40%, since too large amounts of Al ₂ O ₃ increase the melting point of the slag.

According to a further embodiment, the content of Fe in the slag is not more than 25%, preferably not more than 10%.

According to a further embodiment, the sum of Al ₂ O ₃ , SiO ₂ , CaO, Li ₂ O, MnO, FeO and MgO is at least 90%, preferably at least 95%.

According to a further embodiment, (CaO + 2*Li ₂ O + 0.4*MnO) / (SiO ₂ + 0.2*Al ₂ O ₃ ) is > 1.5.

Slag composition and operating temperature are important considerations for the processes described herein. The present invention provides compounds that protect the furnace walls (e.g. MnO, CaO, Li ₂ O) and compounds that have a negative effect on the furnace walls but are unavoidable (e.g. Al ₂ O ₃ from Al in the feed). A balance is achieved between compounds otherwise required (e.g. SiO ₂ needed to lower the melting point of the slag). Additionally, the slag composition domains enable suitable fluidity of the slag and minimal overheating of the slag at the desired operating temperature. It is desirable for the temperature to be as low as possible while remaining above the melting point of the alloy.

This balance is reflected not only in the proposed process conditions but also in the composition of the slag itself.

According to a further embodiment, the smelting step of 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, to ensure complete melting of the metallurgical charge. It is carried out at a high temperature of ℃. The lower limit is desirable to avoid even partial solidification of the resulting alloy and slag. The upper limit is desirable to avoid overheating of the slag. Higher temperatures promote the dissolution of Mg from magnesia-retaining refractory bricks. Therefore, lower temperatures are generally desirable for energy savings as well as wear reduction. Overheating of the slag has a negative effect on the dissolution of magnesia-retaining refractory bricks by the slag.

The stated ratios of CaO and Li ₂ O relative to Al ₂ O ₃ in the slag are such that the melting point of the slag is sufficiently low, preferably below 1700° C., more preferably below 1650° C., even more preferably below 1600° C., most preferably It helps keep the temperature below 1550℃.

Despite their beneficial effect on the life of magnesia-retaining refractory bricks, limiting the combined amounts of CaO, MnO and Li ₂ O in the slag when CaO + 0.8*MnO + 0.8*Li ₂ O exceeds 60%. It is equally relevant because the melting point of the slag becomes too high.

According to a further embodiment, the smelting step comprises the following further steps:

- Sampling the slag;

- Cooling the slag sample and evaluating its color; and

- if the slag sample is green, ending the smelting step; or

- If the slag sample is not green, adjust the pO ₂ -level to achieve stronger reducing conditions and then proceed with the smelting step.

“Slag sampling” means taking a small sample of slag and evaluating its color while the process continues under selected conditions.

Evaluation of color can be easily performed visually. Compared to chemical analysis of slag, monitoring color change provides a quick and efficient indicator that the slag contains a certain minimum percentage of MnO. As described in more detail below, the green slag was further observed to indicate that most of the Co contained in the feed was reduced and sent to the alloy. Without being bound by theory, in practice it is believed that the color change to green results from the reduction of MnO ₂ to MnO, as well as the reduction of typically darker oxides, for example Ni and Co.

Visual inspection is a quick and easy way to know whether process conditions need to be adjusted, optimized and/or shut down, which can save time and operating costs. Therefore, color identification is a reliable indicator of the progress of metallurgical operations.

As used herein, “green” is defined according to the ASTM D1535-14 (2018) standard as a color with hue, brightness, and saturation in the following ranges:

- Tints from 5GY to 5BG;

- Brightness: ≥3; and

- Saturation: ≥3.

An example of green is provided in the "Geological Rock-Color Chart with Genuine Munsell Color Chips" produced by Munsell Color in 2009.

Operating conditions are selected to oxidize most of the Mn to slag and reduce most of the Co and Ni to the alloy. To make the process most economical, preferably >90%, more preferably >95% and most preferably >98% of Co and Ni are collected in the alloy. The pO ₂ -levels of the present process are easily adjusted to reach these advantageous yields.

According to a further embodiment, the pO ₂ -level is 10 ^-7 > pO ₂ > 10 ^-12 , preferably pO ₂ < 10 ^-8 , more preferably pO ₂ < 10 ^-8.5 , most preferably pO ₂ It is adjusted to < 10 ^-9 .

Therefore, the preferred pO ₂ -levels of 10 ^-8 , 10 ^-8.5 and 10 ^-9 , as well as the limit of 10 ^-12 , represent stronger reducing conditions compared to the pO ₂ -level of 10 ^-7 .

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 black-gray or black-brown to green as the process progresses.

According to a further embodiment, the furnace is an electric furnace. Using an electric furnace or electric arc furnace (EAF) allows greater flexibility when higher operating temperatures are desired or required. Another advantage is that you can benefit from off-peak electricity pricing, or from electricity produced by green, clean sources, such as local wind farms.

According to a further embodiment, the Li-containing metallurgical slag comprises a percent composition by mass according to:

10% < MnO < 40%;

(CaO + 1.5*Li ₂ O) / Al ₂ O ₃ >0.3;

CaO + 0.8*MnO + 0.8*Li ₂ O <60%;

(CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0;

Li ₂ O ≥ 1%; and

Al ₂ O ₃ + SiO ₂ + CaO + Li ₂ O + MnO + FeO + MgO > 85%.

According to a further embodiment, the Li-containing metallurgical slag has a green color.

According to a further embodiment, the content of MnO in the Li-containing metallurgical slag is not more than 30%.

According to a further embodiment, the content of CaO in the Li-containing metallurgical slag is at least 15%, preferably at least 20%.

According to a further embodiment, the content of CaO in the Li-containing metallurgical slag is not more than 50%, preferably not more than 30%.

According to a further embodiment, the content of Al ₂ O ₃ in the Li-containing metallurgical slag is not more than 50%, preferably not more than 40%.

According to a further embodiment, the content of Fe in the Li-containing metallurgical slag is not more than 25%, preferably not more than 10%. In FeO-rich slags containing more than 10% FeO, each containing even more than 20% FeO, CoO also cannot be reduced to metallic Co without transferring relatively large amounts of metallic Fe to the alloy phase. This is less desirable as it significantly increases the cost of any hydrometallurgical subsequent processing of the resulting alloy.

According to a further embodiment, Li-containing metallurgical slag is used as a slag former in a pyrometallurgical recycling process. The metallurgical slag obtained contains CaO and SiO ₂ and can therefore be used as a slag former in new operations.

According to a further embodiment, Li-containing metallurgical slag is used as slag former in the process according to the first embodiment, partially or completely replacing the slag former in the step of providing a charge comprising the slag former. .

Reusing the metallurgical slag produced in a new operation allows greater flexibility in choosing operating conditions, such as the pO ₂ -level of the process. For example, when stronger oxidation conditions are used to send more Co and/or Ni to the slag, these valuable metals will not be lost, but rather will be recycled in a new operating cycle, where perhaps stronger reducing conditions will be used. More Co and/or Ni will be recovered.

When such metallurgical slag is reused as a slag former in a new process or as a starting slag for the same process, the incoming battery or its waste may contain additional amounts of compounds such as Al, Mn or Li that will eventually be in the slag after oxidation. It must be taken into account that it is possible. As a result, the respective amounts of Al ₂ O ₃ , MnO or Li ₂ O in the slag will increase. Although the amount of Li ₂ O is considered less important, the amount of Al ₂ O ₃ and MnO has a more direct effect on the melting temperature. In a further embodiment, the preferred upper limit for MnO is 30% to allow room for fresh MnO coming from fresh charge.

Due to the new compounds introduced, the metallurgical slag according to the invention can only be reused for a limited number of cycles. To determine whether the slag can be continuously reused, the slag composition should be analyzed and compared to the composition specifications described herein. Removing and reusing at least a portion of the metallurgical slag and diluting it with new slag formers is available as a viable long-term option.

As described above, the slag according to the invention helps to significantly inhibit the dissolution of MgO from the refractory brick. However, this cannot be completely avoided. This creates another positive side effect when recycling slag. Dissolved MgO from the refractory bricks (resulting from some MgO dissolution during the previous smelting process) accumulates in the slag, which, in combination with MnO, Li ₂ O and CaO, tends to inhibit further corrosion of the refractory bricks. This makes the reuse of the obtained slag particularly attractive.

The following examples are provided to further illustrate embodiments of the invention.

Example 1

The dissolution of MgO from the walls of magnesia-containing crucibles was measured when using several different slag compositions. Various compounds contained in Li-ion batteries or their waste, respectively their oxides such as FeO, Al ₂ O ₃ , Li ₂ O and MnO were melted together with CaO and SiO ₂ as fluxing agents in a 1 L MgO crucible. The total weight of added oxide was 1000 g. The ratios of FeO, Al ₂ O ₃ , Li ₂ O, and MnO were selected to represent the typical composition of a conventional Li-ion battery.

The crucible was gradually heated using an induction furnace at a heating rate of 150° C./hour. When the slag was completely melted, the crucible was maintained at a temperature of 1400°C, 1450°C, or 1500°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 obtained in this example.

Table 1: Composition of the obtained slag

The MgO concentration in the slag was relatively low (0.9% to 3.9%). These results indicate that the dissolution of MgO from the wall of the crucible was well inhibited under the selected conditions.

Experiments were performed with slag compositions without Ni, Co or Cu because the amounts of these metals in the final slag are typically very low and have essentially no effect on slag properties.

Comparative Example 2

The dissolution of MgO from the walls of magnesia-containing crucibles was measured when using different slag compositions. Various compounds contained in Li-ion batteries or their waste, respectively their oxides such as FeO, Al ₂ O ₃ , and MnO, were melted together with CaO and SiO ₂ as fluxing agents in a 1 L MgO crucible. The total weight of added oxide was 1000 g.

The crucible was gradually heated using an induction furnace at a heating rate of 150° C./hour. When the slag was completely melted, the crucible was kept at a temperature of 1400°C or 1450°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 obtained in this example.

Table 2: Composition of the obtained slag

Compared to the slags 1-1 to 1-3 used in Example 1, here the SiO ₂ content in the slag was adjusted higher, while the content of CaO, Li ₂ O and/or MnO was adjusted lower. The MgO concentration measured in the slag was relatively high (8.7% to 13.2%), indicating that a relatively large amount of MgO from the crucible was dissolved into each slag.

As in Example 1, the slag contained no Ni, Co or Cu.

Consideration of Example 1 and Example 2

The slag obtained in Example 1 contained less MgO than the slag obtained in Comparative Example 2. While no visible deterioration of the MgO crucible was observed under the conditions of Example 1, the crucible walls became thinner under the conditions of Example 2. As demonstrated in Example 1, slag containing relatively low concentrations of SiO ₂ and relatively high combined concentrations of Li ₂ O, CaO, and/or MnO inhibited MgO dissolution. More specifically, when the ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 2 or more, MgO dissolution into slag was efficiently suppressed.

Example 3

500 kg of spent rechargeable Li-ion batteries were fed into a 1 m diameter furnace newly lined with 200 mm chrome-magnesia refractory bricks. 80 kg of limestone and 20 kg of sand were added along with the Li-ion battery. The bath temperature was maintained between 1450°C and 1500°C, which was adequate to keep both slag and alloy sufficiently fluid for easy tapping and handling. Heat was supplied by oxidation of Al and C in the battery using immersed O ₂ injection. The injection rate was chosen to ensure strong reducing conditions, i.e. a pO ₂ of 10 ^-9 . Natural gas was added to compensate for heat loss in the furnace. After heating for 1 hour, the resulting alloy and slag were separated by tapping. Table 3 shows the input and production analysis of the process.

Table 3: Process input and output phases

During battery processing, no visible deterioration of the magnesia-retaining refractory bricks was observed. The concentration of MgO in the obtained slag was only 1.2%, equivalent to a loss of 2.3 kg of MgO from the refractory bricks, which is considered low. The ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 4.3. Therefore, this slag effectively suppressed wear of the furnace wall.

Comparative Example 4

500 kg of spent rechargeable Li-ion batteries were fed into a 1 m diameter furnace newly lined with 200 mm chrome-magnesia refractory bricks. 50 kg of limestone and 50 kg of sand were added along with the Li-ion battery. The bath temperature was maintained between 1450°C and 1500°C, which was adequate to keep both slag and alloy sufficiently fluid for easy tapping and handling. Heat was supplied by oxidation of Al and C in the battery using immersed O ₂ injection. The injection rate was chosen to ensure strong reducing conditions, i.e. a pO ₂ of 10 ^-9 . Natural gas was added to compensate for heat loss in the furnace. After heating for 1 hour, the resulting alloy and slag were separated by tapping. Table 4 shows the input and production analysis of the process.

Table 4: Process input and output phases

The concentration of MgO in the obtained slag was 9.0%, equivalent to a loss of 19.8 kg of MgO from the refractory bricks, resulting in significant wear of the furnace walls.

The ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 1.7.

Example 5

500 kg of spent rechargeable Li-ion batteries were fed into a 1 m diameter furnace newly lined with 200 mm chrome-magnesia refractory bricks. 50 kg of limestone and 50 kg of sand were added along with the Li-ion battery. The bath temperature was maintained between 1450°C and 1500°C, which was adequate to keep both slag and alloy sufficiently fluid for easy tapping and handling. Heat was supplied by oxidation of Al and C in the battery using immersed O ₂ injection. The injection rate was chosen to ensure strong reducing conditions, i.e. a pO ₂ of 10 ^-9 . Natural gas was added to compensate for heat loss in the furnace. After heating for 1 hour, the resulting alloy and slag were separated by tapping. Table 5 shows the input and production analysis of the process.

Table 5: Process input and output phases

The concentration of MgO in the obtained slag was 2.8%, equivalent to a loss of 7.4 kg of MgO from the refractory brick. The ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 2.8.

Consideration of Example 3, Example 4, and Example 5

In Example 3 and Comparative Example 4, batteries of the same amount and composition were supplied to the furnace with different proportions of limestone and sand. The resulting slag 3 contained a higher concentration of CaO and a lower concentration of SiO ₂ than slag 4.

The ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 4.3 in slag 3 and 1.7 in slag 4, respectively. Only 2.3 kg of MgO was dissolved in slag 3, while a significantly higher amount of 19.8 kg of MgO was dissolved in slag 4.

In Example 5, a battery was supplied to the furnace with higher concentrations of Mn and Li while maintaining the same proportions of limestone and sand as in Comparative Example 4. The resulting slag 5 contained higher concentrations of MnO and Li ₂ O than slag 4.

In slag 5, 7.4 kg of MgO was dissolved, while the ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 2.8. Therefore, this example demonstrates the beneficial effect of MnO and Li ₂ O in combination while all other reaction conditions remain the same.

As demonstrated in Examples 3 and 5, slags containing lower concentrations of SiO ₂ and higher combined concentrations of Li ₂ O, CaO, and MnO are better suited to inhibit MgO dissolution.

Example 6

500 kg of spent rechargeable Li-ion batteries were fed into a 1 m diameter furnace newly lined with 200 mm chrome-magnesia refractory bricks. 189 kg of slag from Example 3 was added along with the Li-ion battery. The bath temperature was maintained between 1450°C and 1500°C, which was adequate to keep both slag and alloy sufficiently fluid for easy tapping and handling. Heat was supplied by oxidation of Al and C in the battery using immersed O ₂ injection. The injection rate was chosen to ensure strong reducing conditions, i.e. a pO ₂ of 10 ^-9 . Natural gas was added to compensate for heat loss in the furnace. After heating for 1 hour, the resulting alloy and slag were separated by tapping. Table 6 shows the input and production analysis of the process.

Table 6: Process input and output phases

During battery processing, no visible deterioration of the magnesia-retaining refractory bricks was observed. The concentration of MgO in the resulting slag was only 1.2%, equivalent to a loss of 1.4 kg of MgO from the refractory brick, which is a much smaller decomposition than in Example 3. The ratio (CaO + 2Li ₂ O + 0.4MnO) / SiO ₂ was 6.8. Therefore, this slag effectively suppressed wear of the furnace walls made of magnesia-containing refractory bricks.

general conclusion

The metallurgical slag according to the invention is suitable for recovering valuable metals such as Ni and Co from Li-ion batteries or their waste while minimizing the decomposition of the magnesia-retaining refractory bricks of the furnace.

Claims (20)

A method for recovering Ni and Co from Li-ion batteries or their waste, comprising:
- providing a furnace lined with magnesia-retaining refractory bricks;
- providing a charge comprising a slag former and Li-ion batteries or waste thereof; and
- smelting the charge under reducing conditions, thereby obtaining an alloy containing most of Ni and Co, and slag
A method for recovery of Ni and Co from Li-ion batteries or waste thereof, characterized in that the slag has a percent composition by weight according to:
10% < MnO <40%;
(CaO + 1.5*Li ₂ O) / Al ₂ O ₃ >0.3;
CaO + 0.8*MnO + 0.8*Li ₂ O <60%;
(CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0;
Li ₂ O ≥ 1%; and
Al ₂ O ₃ + SiO ₂ + CaO + Li ₂ O + MnO + FeO + MgO > 85%. The method according to claim 1, wherein the content of MnO in the slag is greater than 10% and less than or equal to 30%. The method according to claim 1, wherein the content of CaO in the slag is 15% or more and 50% or less. The method according to claim 1, wherein the content of Al ₂ O ₃ in the slag is 50% or less. The method according to claim 1, wherein the Fe content in the slag is 25% or less. The method of claim 1, wherein the sum of Al ₂ O ₃ , SiO ₂ , CaO, Li ₂ O, MnO, FeO and MgO is 90% or more. The method of claim 1, wherein (CaO + 2*Li ₂ O + 0.4*MnO)/(SiO ₂ + 0.2*Al ₂ O ₃ ) is > 1.5. The process according to 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 to avoid overheating. The method of claim 1, wherein the smelting step comprises the following additional steps:
- Sampling the slag;
- Cooling the slag sample and evaluating its color; and
- if the slag sample is green, ending the smelting step; or
- If the slag sample is not green, adjust the pO ₂ -level to achieve stronger reduction conditions and then proceed with the smelting step. The method of claim 1, wherein the pO ₂ -level is adjusted to 10 ^-7 > pO ₂ > 10 ^-12 . The method of claim 9, wherein the color of the slag is green. The method of claim 1, wherein the furnace is an electric furnace. 2. The method of claim 1, wherein the Li-containing metallurgical slag partially or completely replaces the slag former in the step of providing a charge comprising the slag former, and the Li-containing metallurgical slag has a percent composition by weight according to: method:
10% < MnO <40%;
(CaO + 1.5*Li ₂ O) / Al ₂ O ₃ >0.3;
CaO + 0.8*MnO + 0.8*Li ₂ O <60%;
(CaO + 2*Li ₂ O + 0.4*MnO) / SiO ₂ ≥ 2.0;
Li ₂ O ≥ 1%; and
Al ₂ O ₃ + SiO ₂ + CaO + Li ₂ O + MnO + FeO + MgO > 85%. delete delete delete delete delete delete delete