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

Abstract

The present invention lies in 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. The slag composition is defined according to:

10%<MnO<40%;

(CaO+1.5*Li.sub.2O)/Al.sub.2O.sub.3>0.3;

CaO+0.8*MnO+0.8*Li.sub.2O<60%;

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

Li.sub.2≥1%; and,

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

This composition is particularly adapted to limit or avoid the corrosion of furnaces lined with magnesia-bearing refractory bricks.

Claims

1. Process for the recovery of Ni and Co from Li-ion batteries or their waste, comprising the steps: providing a furnace lined with magnesia-bearing refractory bricks; providing a charge comprising slag formers, and Li-ion batteries or their waste; and, smelting the charge in reducing conditions, thereby obtaining an alloy containing the major part of the Ni and Co, and a slag; characterized in that the slag has a percent composition by weight according to:
10%<MnO<40%;
(CaO+1.5*Li.sub.2O)/Al.sub.2O.sub.3>0.3;
CaO+0.8*MnO+0.8*Li.sub.2O<60%;
(CaO+2*Li.sub.2O+0.4*MnO)/SiO.sub.2≥2.0;
Li.sub.2O≥1%; and,
Al.sub.2O.sub.3+SiO.sub.2+CaO+Li.sub.2O+MnO+FeO+MgO>85%.

2. Process according to claim 1, wherein the content of MnO in the slag is greater than 10% and less than or equal to 30%.

3. Process according to claim 1, wherein the content of CaO in the slag is greater than or equal to 15% and less than or equal to 50%.

4. Process according to claim 1, wherein the content of Al.sub.2O.sub.3 in the slag is less than or equal to 50%.

5. Process according to claim 1, wherein the content of Fe in the slag is less than or equal to 25%.

6. Process according to claim 1, wherein the sum of Al.sub.2O.sub.3, SiO.sub.2, CaO, Li.sub.2O, MnO, FeO and MgO is greater than or equal to 90%.

7. Process according to claim 1, wherein (CaO+2*Li.sub.2O+0.4*MnO)/(SiO.sub.2+0.2*Al.sub.2O.sub.3) is >1.5.

8. Process according to claim 1, wherein the step of smelting the charge is performed at a temperature of at least 1400° C. and at most 300° C. above the liquidus point of the slag, thereby avoiding overheating.

9. Process according to claim 1, the smelting step comprising the further steps: sampling the slag; cooling down the slag sample and assessing its color; and, in case the slag sample is green, terminating the smelting step; or, in case the slag sample is not green, proceeding with the smelting step after adjusting the pO.sub.2-level to achieve more reducing conditions.

10. Process according to claim 1, wherein the pO.sub.2—level is adjusted to 10.sup.−7>pO.sub.2>10.sup.−12.

11. Process according to claim 9, wherein the color of the slag is green.

12. Process according to claim 1, wherein the furnace is an electric furnace.

13. Li—containing metallurgical slag having a percent composition by weight according to:
10%<MnO<40%;
(CaO+1.5*Li.sub.2O)/Al.sub.2O.sub.3>0.3;
Ca0+0.8*MnO+0.8*Li.sub.2O<60%;
(CaO+2*Li.sub.2O+0.4*MnO)/SiO.sub.2≥2.0;
Li.sub.2O≥1%; and,
Al.sub.2O.sub.3+SiO.sub.2+CaO+Li.sub.2O+MnO+FeO+MgO>85%.

14. Li—containing metallurgical slag according to claim 13, wherein said slag has a green color.

15. Li—containing metallurgical slag according to claim 13, wherein the content of MnO in the slag is greater than 10% and less than or equal to 30%.

16. Li—containing metallurgical slag according to claim 13, wherein the content of Ca0 in the slag is greater than or equal to 15% and less than or equal to 50%.

17. Li—containing metallurgical slag according to claim 13, wherein the content of Al.sub.2O.sub.3 in the slag is less than or equal to 50%.

18. Li—containing metallurgical slag according to claim 13, wherein the content of Fe in the slag is less than or equal to 25%.

19. A slag former in a pyrometallurgical recycling process comprising the Li-containing metallurgical slag according to claim 13.

20. Process according to claim 1, wherein a Li—containing metallurgical slag partially or fully replaces slag formers in the step of providing a charge comprising slag formers, wherein the Li—containing metallurgical slag has a percent composition by weight according to:
10%<MnO<40%;
(CaO+1.5*Li.sub.2O)/Al.sub.2O.sub.3>0.3;
CaO+0.8*MnO+0.8*Li.sub.2O<60%;
(CaO+2*Li.sub.2O+0.4*MnO)/SiO.sub.2≥2.0;
Li.sub.2O≥1%; and,
Al.sub.2O.sub.3+SiO.sub.2+CaO+Li.sub.2O+MnO+FeO+MgO>85% .

Description

Example 1

[0072] The dissolution of MgO from the walls of magnesia-bearing 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.sub.2O.sub.3, Li.sub.2O and MnO, were melted together with CaO and SiO.sub.2 as fluxing agents in a 1 L MgO crucible. The total weight of added oxides was 1000 g. The ratio of FeO, Al.sub.2O.sub.3, Li.sub.2O, and MnO was chosen to represent a typical composition of existing Li-ion batteries.

[0073] The crucibles were gradually heated at heating rate of 150° C./h using an induction furnace. When the slags were fully molten, crucibles were kept at temperatures of 1400, 1450, or 1500° C. After 2 h of heating, molten slags were taken out of the crucibles, and quenched with water. Table 1 lists the composition of the obtained slags in this example.

TABLE-US-00001 TABLE 1 Composition of the obtained slags Condition Temp. Composition (%) (CaO + 2*Li2O + Slag ° C. SiO.sub.2 FeO Al.sub.2O.sub.3 CaO Li.sub.2O MgO MnO 0.4*MnO)/SiO2 1-1 1450 15.8 3.6 20.5 34.2 1.0 2.5 22.3 2.8 1-2 1450 19.7 1.6 18.7 19.7 2.9 2.3 35.3 2.0 1-3 1400 17.7 0.0 19.6 47.1 1.0 1.9 12.7 3.1 1-4 1400 23.8 0.0 19.8 24.7 19.8 1.1 10.8 2.9 1-5 1500 19.2 1.9 16.3 21.1 19.2 0.9 18.2 3.5 1-6 1500 18.6 0.9 8.8 10.6 29.4 1.4 28.4 4.3 1-7 1500 9.2 2.7 11.9 1.8 33.0 3.9 32.7 8.8

[0074] MgO concentrations in above slags were relatively low (from 0.9% to 3.9%). This result indicates that a dissolution of MgO from the wall of the crucible was well-suppressed under the chosen conditions.

[0075] The experiments were performed with slag compositions having no Ni, Co or Cu, since the amount of these metals in the final slags are typically very low and thus essentially do not influence the slag properties.

Comparative Example 2

[0076] The dissolution of MgO from the walls of magnesia-bearing 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.sub.2O.sub.3, and MnO, were melted together with CaO and SiO.sub.2 as fluxing agents, in a 1 L MgO crucible. The total weight of added oxides was 1000 g.

[0077] The crucibles were gradually heated at a heating rate of 150° C./h using an induction furnace. When the slags were fully molten, crucibles were kept at temperatures of 1400 or 1450° C. for 2 h. After 2 h of heating, molten slags were taken out of the crucibles, and quenched with water. Table 2 lists the composition of the obtained slags in this example.

TABLE-US-00002 TABLE 2 Composition of the obtained slags Condition Temp. Composition (%) (CaO + 2*Li2O + Slag ° C. SiO.sub.2 FeO Al.sub.2O.sub.3 CaO Li.sub.2O MgO MnO 0.4*MnO)/SiO2 2-1 1450 31.0 3.4 20.3 11.5 0.9 11.6 21.3 0.7 2-2 1450 27.1 1.3 16.1 9.3 2.5 13.2 30.4 1.0 2-3 1400 32.0 0.0 18.2 32.0 0.0 8.7 9.1 1.1

[0078] Compared to the slags 1-1 to 1-3 used in Example 1, here the SiO.sub.2 content in the slags was adjusted to be higher, while the content of CaO, Li.sub.2O and/or MnO was adjusted to be lower. Measured MgO concentrations in above slags were relatively high (from 8.7% to 13.2%), which indicates that relatively large quantities of MgO from the crucibles were dissolved in the respective slags. As with Example 1, the slags contained no Ni, Co or Cu.

Discussion of Examples 1 and 2

[0079] The slags obtained in Example 1 contained less MgO than the slags obtained in Comparative Example 2. No visible degradation of the MgO crucible was observed under the conditions of Example 1, whereas the crucible walls became thinner under the conditions of Example 2. Slags containing relatively low concentrations of SiO.sub.2 and relatively high combined concentrations of Li.sub.2O, CaO, and/or MnO suppressed the MgO dissolution, as demonstrated in Example 1. More specifically, the MgO dissolution into the slag was efficiently suppressed when the ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 2 or higher.

Example 3

[0080] 500 kg of spent rechargeable Li-ion batteries were fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 80 kg of limestone and 20 kg of sand were added together with the Li-ion batteries. A bath temperature of 1450-1500° C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the batteries, using submerged O.sub.2 injection. The injection rate was chosen to guarantee strongly reducing conditions, i.e. pO.sub.2 of 10.sup.−9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 3 shows the analyses of the input and output phases of the process.

TABLE-US-00003 TABLE 3 Input and output phases of the process Composition (%) Mass Al Li Mn (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) C MgO Input Batteries 500 26.3 7.0 12.3 3.5 — —  5.0  2.0 7.0 15 — Limestone 80 — — — — 4.8 53.3 — — — 11.4 — Silica 20 — — — — 100 — — — — — Output Alloy 243 54.3 14.1  25.0 5.5 — — — — 1.1 — — Slag 3 189  0.2 0.5  0.6 2.5 12.7 22.8 (25.1) (11.4) (22.0)  — 1.2

[0081] During processing batteries, no visible degradation of the magnesia-bearing refractory bricks was observed. Concentration of MgO in the obtained slag was only 1.2%, equivalent to 2.3 kg loss of MgO from the refractory bricks, which is considered low. The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 4.3. This slag thus efficiently suppressed the wear of the furnace walls.

Comparative Example 4

[0082] 500 kg of spent rechargeable Li-ion batteries were fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 50 kg of limestone and 50 kg of sand were added together with the Li-ion batteries. A bath temperature of 1450-1500° C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the batteries, using submerged O.sub.2 injection. The injection rate was chosen to guarantee strongly reducing conditions, i.e. pO.sub.2 of 10.sup.−9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 4 shows the analyses of the input and output phases of the process.

TABLE-US-00004 TABLE 4 Input and output phases of the process Composition (%) Mass Al Li Mn (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) C MgO Input Batteries 500 26.3 7.0 12.3 3.5 — —  5.0 2.0 7.0 15 — Limestone 50 — — — — 4.8 53.3 — — — 11.4 — Silica 50 — — — — 100 — — — — — Output Alloy 241 54.6 14.1  25.2 5.5 — — — — 0.6 — — Slag 4 220  0.1 0.4  0.5 2.1 23.7 12.3 (21.5) (9.8) (19.7)  — 9.0

[0083] The concentration of MgO in the obtained slag was 9.0%, equivalent to 19.8 kg loss of MgO from the refractory bricks and thus significant wear of the furnace walls. The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 1.7.

Example 5

[0084] 500 kg of spent rechargeable Li-ion batteries were fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 50 kg of limestone and 50 kg of sand were added together with the Li-ion batteries. A bath temperature of 1450-1500° C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the batteries, using submerged O.sub.2 injection.

[0085] The injection rate was chosen to guarantee strongly reducing conditions, i.e. pO.sub.2 of 10.sup.−9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 5 shows the analyses of the input and output phases of the process.

TABLE-US-00005 TABLE 5 Input and output phases of the process Composition (%) Mass Al Li Mn (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) C MgO Input Batteries 500 10.8 11.3 11.5 0.1 — —  6.0  4.4 9.9 25 — Limestone 50 — — — — 4.8 53.3 — — — 11.4 — Silica 50 — — — — 100 — — — — — Output Alloy 164 32.8 32.9 33.2 0.4 — — — — 0.8 — — Slag 5 259  0.1  1.2  0.9 0.2 20.1 10.4 (21.9) (18.2) (23.7)  — 2.8

[0086] The concentration of MgO in the obtained slag was 2.8%, equivalent to 7.4 kg loss of MgO from the refractory bricks. The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 2.8.

Discussion of Examples 3, 4, 5

[0087] In Examples 3 and Comparative Example 4, the same amount and composition of batteries were fed into the furnace, but with different ratios of limestone and sand. The resulting Slag 3 contained a higher concentration of CaO and a lower concentration of SiO.sub.2 than Slag 4.

[0088] The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.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.

[0089] In Example 5, batteries with a higher concentration of Mn and Li were fed into the furnace, while keeping the same ratio of limestone and sand as in Comparative Example 4. The resulting Slag 5 contained a higher concentration of MnO and Li.sub.2O than Slag 4.

[0090] The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 2.8, while 7.4 kg of MgO were dissolved in Slag 5. This example thus demonstrates the beneficial effect of MnO and Li.sub.2O combined, while all other reaction conditions are kept the same.

[0091] Slags containing lower concentrations of SiO.sub.2 and higher combined concentrations of Li.sub.2O, CaO, and MnO are more suitable to suppress the MgO dissolution, as demonstrated in Examples 3 and 5.

Example 6

[0092] 500 kg of spent rechargeable Li-ion batteries were fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 189 kg of slag produced in Example 3 was added together with the Li-ion batteries. A bath temperature of 1450-1500° C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the batteries, using submerged O.sub.2 injection. The injection rate was chosen to guarantee strongly reducing conditions, i.e. pO.sub.2 of 10.sup.−9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 6 shows the analyses of the input and output phases of the process.

TABLE-US-00006 TABLE 6 Input and output phases of the process Composition (%) Mass Al Li Mn (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) C MgO Input Batteries 500 26.3 7.0 12.3 3.5 — —  5.0  2.0 7.0 15 — Slag 189 0.2 0.5 0.6 2.5 12.7 22.8 (25.1) (11.4) (22.0) — 1.2 former Output Alloy 242 54.2 14.1 24.9 5.6 — — — — 1.1 — — Slag 6 308 0.2 0.5 0.7 2.8  7.8 14.0 (30.7) (14.0) (26.9) — 1.2

[0093] During processing batteries, no visible degradation of the magnesia-bearing refractory bricks was observed. Concentration of MgO in the produced slag was only 1.2%, equivalent to 1.4 kg loss of MgO from the refractory bricks, which is an even smaller degradation than in Example 3. The ratio (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 6.8. This slag thus efficiently suppressed the wear of the furnace wall made of magnesia-bearing refractory bricks.

[0094] General Conclusion

[0095] The metallurgical slags according to the present invention are suitable to recover valuable metals, such as Ni and Co, from Li-ion batteries or their waste, while minimizing degradation of the magnesia-bearing refractory bricks of the furnace.