BATTERY RECYCLING WITH ELECTROLYSIS OF THE LEACH TO REMOVE COPPER IMPURITIES

Abstract

The present disclosure relates to a process for the recovery of transition metals from batteries comprising treating a transition metal material with a leaching agent to yield a leach which contains dissolved copper impurities, and depositing the dissolved copper impurities as elemental copper on a particulate deposition cathode by electrolysis of an electrolyte containing the leach.

Claims

1-17. (canceled)

18. A process for the recovery of transition metals from batteries comprising (a) treating a transition metal material from batteries with a leaching agent to yield a leach, wherein the leach comprises dissolved copper impurities, and (b) depositing the dissolved copper impurities as elemental copper on a particulate deposition cathode by electrolysis of an electrolyte comprising the leach.

19. The process according to claim 18, wherein the deposition cathode has a particle size d50 ranging from 1 μm to 1000 μm.

20. The process according to claim 18, wherein the electrolyte comprises less than or equal to 4000 ppm of the copper impurities before the electrolysis.

21. The process according to claim 18, wherein the deposition cathode is made of copper and/or carbon.

22. The process according to claim 18, wherein an electrochemical potential is applied to the deposition cathode during the electrolysis ranging from −50 mV to −500 mV with respect to the electrochemical potential of copper.

23. The process according to claim 18, wherein the electrolyte has a pH from 4 to 8.

24. The process according to claim 18, wherein the transition metal material is obtained from mechanically treated battery scraps, or is obtained as metal alloy from smelting battery scrap.

25. The process according to claim 18, wherein the deposition cathode is obtained at least partially from the transition metal material.

26. The process according to claim 18, further comprising removing non-dissolved solids from the leach, wherein the non-dissolved solids are carbon particles, and feeding the carbon particles into step (b) as deposition cathode.

27. The process according to claim 18, further comprising precipitating the transition metal as mixed hydroxides or mixed carbonates.

28. The process according to any of claims 18, wherein the leaching agent is an inorganic or organic aqueous acid.

29. The process according to claim 18, further comprising adjusting the pH value of the leach to 2.5 to 8, and removing precipitates of phosphates, oxides, hydroxides, and/or oxyhydroxides by solid-liquid separation.

30. The process according to claim 18, wherein the deposition cathode is suspended in the electrolyte.

31. The process according to claim 30 wherein the concentration of the suspended deposition cathode in the electrolyte is from 0.01 wt % to 10 wt %.

32. The process according to claim 18, wherein the electrolyte is passed through the deposition cathode as a particulate filter-aid layer.

33. The process according to claim 32, wherein the electrolysis is performed in an electrochemical filter flow cell.

34. The process according to claim 18, wherein step (b) comprises applying a further electrochemical potential to the deposition cathode during the electrolysis and depositing dissolved nickel salts as elemental nickel on the particulate electrode and/or depositing dissolved cobalt salts as elemental cobalt on the particulate electrode.

Description

EXAMPLES

[0105] The metal impurities and phosphorous were determined by elemental analysis using ICP-OES (inductively coupled plasma—optical emission spectroscopy) or ICP-MS (inductively coupled plasma—mass spectrometry). Total carbon was determined with a thermal conductivity detector (CMD) after combustion. Fluorine was detected with an ion sensitive electrode (ISE) after combustion for total fluorine or after H.sub.3PO.sub.4 distillation for ionic fluoride.

Example 1—Washing

[0106] Mechanically treated battery scrap (500 g; particle size D50 about 20 μm) was used comprising [0107] 203 g spent cathode active material with 1/1/1 molar ratio of Ni/Co/Mn, and a 1/1 molar ratio of Li to the sum of Ni, Co, and Mn as determined by elemental analysis; [0108] 199 g of total carbon in the form of graphite and soot and residual lithium containing electrolyte; and [0109] 41 g of further impurities comprising Al (10.7 g), Cu (4.9 g), F (in total: 9.8 g), Fe (1.1 g), P (2.5 g), Zn (0.14 g), Mg (100 mg), Ca (100 mg) as detemined by elemental analysis.

[0110] 500 g of this battery scrap was slurried in 2 kg water and stirred vigorously for 30 minutes. Then the solids were separated by filtration and washed with 1 kg water. Solids were dried and then re-slurried in 400 g deionized water in a 2.5 L stirred batch reactor.

[0111] All impurity contents are given as weight percentages unless specifically noted otherwise, and refer to the total amount of mechanically treated battery scrap.

Example 2—Leaching

[0112] A mixture of 841 g H.sub.2SO.sub.4 (50% H.sub.2SO.sub.4 in water) and 130 g hydrogen peroxide (30% H.sub.2O.sub.2 in water) was added dropwise to the slurry of Example 1 under vigorous stirring. The temperature of the slurry was kept between 30 and 40° C. After completion of the addition, the resulting reaction mixture was stirred for another 30 min at 30° C., heated to 40° C. for 20 minutes followed by heating to 60° C. for 40 minutes hours and then cooled to ambient temperature. Solids were removed from the resultant slurry by suction filtration. The filter cake was washed with 135 g deionized water. The combined filtrates (1644 g) contained 49 g Ni, 33 g Co, 30 g Mn, 4.9 g Cu and 14.6 g Li (as determined by elemental analysis), corresponding to leaching efficiencies >90% for all 5 metals. The dried filter cake (349 g) contained graphite particles which were used in Example 6 for electrolysis.

Example 3—pH Adjustment

[0113] The pH value of 1350 g of the combined filtrates from Example 2 was adjusted to pH 6.0 by adding 495.5 g of a 4.5 molar caustic soda solution under stirring. Precipitate formation could be observed. After stirring for another 30 min the solids were removed by suction filtration. The obtained filtrate (2353 g) contains impurity levels of Al, Zn, Mg, Ca, and Fe below 25 ppm, and about 64 ppm of Cu.

Comparative Example 4—Massive Carbon Cathode

[0114] An undivided electrochemical cell employing a solid glassy carbon anode and glassy carbon cathode (18 cm.sup.2 geometric surface area each) and a Ag/AgCl reference electrode (KCl sat., 200 mV vs. NHE) was used and filled with 80 ml of electrolyte.

[0115] As electrolyte the filtrate obtained in Example 3 was used. Directly before its use following concentrations were analyzed: 9 ppm Al, 0.87% Co, traces of Cr, 64 ppm Cu, 1.2% Ni, and 0.1-1% inorganic fluoride. The solution had a pH of about 4-5. In order to avoid HF formation and therefore maintain a pH of >4 throughout the electrolysis, sodium acetate was added as buffer until the solution had a pH of 6.

[0116] Electrolysis was conducted potentiostatically in two steps at −50 mV vs. Ag/AgCl and −250 mV vs. Ag/AgCl. After having passed a charge of 14.7 Coulomb at a rate of 0.02 C/min the electrolysis was stopped. The mean rate of copper reduction was 1.1*10.sup.−7 mol/min.

[0117] The remaining solution was analyzed and the following composition was found: 9 ppm Al, 0.87% Co, traces of Cr, <1 ppm Cu and 1.3% Ni. Thus, Cu was selectively reduced.

Comparative Example 5—Massive Copper Cathode

[0118] The same electrochemical cell as described in the previous Example 5 was used. Instead of a glassy carbon cathode, a copper cathode (18 cm.sup.2 geometric surface area each) was employed.

[0119] As electrolyte the filtrate obtained in Example 3 was used. Directly before its use following concentrations were analyzed: 9 ppm Al, 0.85% Co, <1 ppm Cr, 60 ppm Cu, 1.2% Ni and 0.1-1% inorganic fluoride. The solution had a pH of about 4-5. Sodium acetate was added as buffer until the solution had a pH of 6.

[0120] Electrolysis was conducted potentiostatically at −250 mV vs. Ag/AgCl. After having passed a charge of 19.7 Coulomb at a rate of 0.02 C/min the electrolysis was stopped. The mean rate of copper reduction was 7.8*10.sup.−8 mol/min.

[0121] The remaining solution was analyzed and the following composition was found: 10 ppm Al, 0.90% Co, <1 ppm Cr, <1 ppm Cu and 1.3% Ni. Thus, Cu was selectively reduced.

Example 6—Massive Carbon Cathode with Graphite Particles

[0122] The filter cake produced in Example 2 (Leaching) contained graphite particles and was dispersed in water and filtered repeatedly until no more changes in the metal impurities was detected. After drying the graphite particles contained about 5% fluorine, 1.7% Al, 0.06% Co, 0.01% Cu, 0.02% Fe, 0.04% Mn and 0.06% Ni after washing and total carbon content of 78.5 wt %. The resulting graphite particles had a particle size of D10=6 μm, D50=16 μm, and D90=83 μm.

[0123] An undivided electrochemical cell with glassy carbon anode (5 cm.sup.2) and glassy carbon cathode (18 cm.sup.2) as was used and filled with 80 ml of electrolyte. In addition, graphite particles were added to obtain a solid content of 0.68 wt.-% as graphite. In order to maintain periodical contact of the graphite particles with the cathode allowing charging of the particles, the electrolyte was stirred at 500 rpm using a magnetic stirrer bar. Thus, the graphite particles remain suspended in the electrolyte.

[0124] As electrolyte the filtrate obtained in Example 3 was used. Directly before its use following concentrations were analyzed: 10 ppm Al, 0.88% Co, <1 ppm Cr, 70 ppm Cu and 1.3% Ni, and 0.1-1% inorganic fluoride. The solution had a pH of about 4-5. Sodium acetate was added as buffer until the solution had a pH of 6.

[0125] Electrolysis was conducted potentiostatically in two steps at −75 mV vs. Ag/AgCl and −250 mV vs. Ag/AgCl. After having passed a charge of 19.2 C at a rate of 0.037 C/min the electrolysis was stopped. The mean rate of Cu reduction was 2.0*10.sup.−7 mol/min. The remaining solution was analyzed and the following composition was found: 10 ppm Al, 0.85% Co, <1 ppm Cr, <1 ppm Cu and 1.2% Ni. Thus, Cu was completely reduced.

[0126] As can be seen from the rate of which the current passed through the cell at constant potential, the residence time for complete Cu reduction could greatly be reduced by introducing the graphite particles into the cell. Making use of the graphite particles also reduces cost in a second way as no fresh graphite particles like graphite powder would need to be employed.

Example 7—Filter Flow Cell with Graphite Particles

[0127] In another example an electrochemical filter flow cell following the principles described e.g. in U.S. Pat. No. 5,164,091 was used. Contrary to the cell described in U.S. Pat. No. 5,164,091, a horizontal orientation of the electrodes facing each other was chosen. The geometry of the whole electrochemical cell was cylindrical. Anode and cathode chamber were separated by a Nafion® 324 polymer electrolyte. As anode served an expanded Ti metal sheet coated with iridium and tantalum mixed oxides. The supporting electrolyte in the anode chamber was a saturated potassium sulfate solution.

[0128] A stainless steel mesh (20 cm.sup.2, 1.4571) served as conductive support to build up the filter cake of the graphite particles, which were isolated from the filter cake produced in Example 2 (Leaching) as described in Example 6. Prior to starting the electrolysis, about 3 g of that graphite particles were filtered onto the stainless steel support mesh forming a layer of about 5 mm thickness.

[0129] As electrolyte 80 ml of the filtrate obtained in Example 3 was used. Directly before its use following concentrations were analyzed: 0.7% Co, <1 ppm Cr, 37 ppm Cu, 0.96% Ni and 0.1-1% inorganic fluoride. The electrolyte was introduced to the cathode chamber with a backpressure of about 50 to 100 mbar. The solution had a pH of about 4-5. Sodium acetate was added as buffer until the solution had a pH of 6.

[0130] Electrolysis was conducted at −250 mV vs. Ag/AgCl. After having passed a charge of 10.9 C at a rate of 0.36 C/min the electrolysis was stopped. The mean rate of copper reduction was 1.5*10.sup.−6 mol/min. The electrolyzed solution was analyzed and the following composition was found: 0.7% Co, <1 ppm Cr, <1 ppm Cu and 0.96% Ni. Thus, Cu was completely reduced.

[0131] As can be seen from the rate of which the current passed through the cell at constant potential, the residence time for complete Cu reduction was greatly reduced by a factor of ten compared to the undivided electrochemical cell with suspended graphite particles mentioned above.