A METHOD OF RECOVERING METALS FROM SPENT Li-ION BATTERIES

Abstract

The present invention relates to an improved process and method of recovering metals of value from used Lithium Ion batteries. More particularly, the invention provides a method for recovering cobalt and lithium along with other metals of value wherein the method majorly includes physical processes for separation, limiting the use of chemical for removing minor impurities. Majority of elements were separated by physical process instead of chemical process which gives the benefit of cost saving in chemical treatment of liquid and solid effluents. Chemicals are used to dissolve only minor impurities from electrolyte which lead to the process economically attractive. This makes the method of recovering metal values is environment friendly. The invention provides for a cost effective, economic and environmental friendly process for recovering metals of value.

Claims

1. A process for recovering valuable metals from spent lithium ion batteries comprising the steps of: a) shredding the lithium ion batteries into particles of a preferable size, in water, with water level well above the level of the batteries being shredded to obtain a slurry and shredded plastic and Teflon matrix; b) removing the plastic and Teflon matrix that floats on the water in step a); c) wet screening the slurry obtained in step a) through sieve of at least fifty mesh size to separate particles of varying sizes; wherein coarser particles containing copper, aluminum and protection circuit modules form screened slurry containing solids are retained by the sieve and collected, and finer particles containing lithium and cobalt are aggregated; d) filtering the lithium and cobalt containing aggregate of step c) through a filter press to obtain a wash liquor containing lithium and a residue containing cobalt, metal impurities and organic matrix; e) drying the residue of step d) and roasting the dried residue at 900 C. to obtain cobalt oxide; f) washing and filtering the cobalt oxide of step e) with dilute acid solution at pH range 2.0 to 3.0 to obtain pure cobalt oxide and filtrate; g) treating the wash liquor of step d) with saturated solution of soda ash at pH range 11 to 11.5 and temperature ranging from 80 to 120 C. for 3-6 hours to obtain lithium carbonate precipitate and supernatant.

2. The process for recovering metals of value as claimed in claim 1, wherein the preferable size of particles obtained through shredding is 10 mm.

3. The process for recovering metals of value as claimed in claim 1, wherein the coarser pieces of step c) are processed using magnetic separator to segregate magnetic part comprising protection circuit module from non magnetic part comprising copper and aluminum.

4. The process for recovering metals of value as claimed in claim 1, wherein the supernatant of step g) and the filtrate of step f) are subsequently mixed and processed using repetition of step d) to step g).

5. The process for recovering metals of value as claimed in claim 1, wherein the dilute acid solution is preferably hydrochloric acid solution.

6. The process for recovering metals of value as claimed in claim 1, wherein the cobalt oxide obtained in step f) has purity of 97% with cobalt content of more than 76%.

7. The process for recovering metals of value as claimed in claim 1, wherein the cobalt oxide obtained in step f) has metal impurity level below 2%.

8. The process for recovering metals of value as claimed in claim 1, wherein the lithium carbonate obtained in step g) has purity of 98% with lithium content of more than 18%.

9. The process for recovering metals of value as claimed in claim 1, wherein the lithium carbonate obtained in step g) has metal impurity level below 0.5%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] A complete understanding of the system and process of the present invention may be obtained by reference to the following drawings:

[0032] FIG. 1 elucidates the flow sheet of the process according to an embodiment of the invention.

[0033] FIG. 2 elucidates the X-ray diffraction pattern (XRD) of recovered cobalt oxide from spent lithium-ion battery.

[0034] FIG. 3 elucidates X-ray diffraction (XRD) pattern of pure lithium carbonate obtained from spent lithium-ion battery.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will now be described in detail hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.

[0036] FIG. 1 elucidates the process and method for recovering valuable metals from used Lithium ion batteries without substantial use of chemical solutions. The process majorly depends on physical separation of the metals without compromising on the quality of the recovered products and by-products. The process of the present invention comprises the following steps of: [0037] i) Wet shredding of batteries; [0038] ii) Floatation followed by wet sieving for the separation of metals, electrolyte and plastic/polymer matrix; [0039] iii) Filtration for the separation of mixed metal powder from lithium ion; [0040] iv) Enrichment of cobalt content in lithium free cobalt oxide by drying and roasting; [0041] v) Purification of cobalt oxide by dilute acid wash; [0042] vi) Magnetic separation for removal of printed circuit boards and steel from the copper and Aluminum matrix; and [0043] vii) Lithium recovery as lithium carbonate by precipitation of wash liquor of step (iii).

[0044] The two stages of washing of the mixed black powder resulted in satisfactory separation of cobalt and lithium. Lithium in the wash liquor was precipitated using saturated sodium carbonate solution, while cobalt and organic content in the residue were separated through roasting followed by magnetic separation. The major steps of process are described in details as follows: [0045] i) Wet shredding of spent batteries: In this step, spent LIBs are fed into a shredder in presence of water well above the battery level so that the water acts as a scrubbing agent as well as temperature controller. The wet shredding is carried at room temperature (305 C.). The shredder is designed in such a way to achieve a size after shredding of less than 10 mm. The shredder is preferably, a twin shaft shredder with a water spray system and shear type cutting is used. [0046] ii) Wet shredding is followed by floatation and sieving step. In this step, the shredder output slurry containing plastic/Teflon matrix floats on water and is removed. The slurry particles of size less than 300 microns are made to pass through a sieve (mesh size 50). The sieve retains metals like copper foils, aluminum casing and PCBs which are then collected. [0047] iii) Filtration for the separation of mixed metal powder from lithium ion: In this step slurry containing particles of size less than 300 microns is filtered through a filter press. The filtrate contains dissolved lithium ions. The residue or filter cake obtained upon filtration contains cobalt ions along with some metal impurities and organic matrix. [0048] iv) Enrichment of cobalt content in lithium free cobalt oxide by drying and roasting: In this step to remove organic matrix from the cake obtained in the step iii, the material is dried and then roasted above 900 C. The enrichment step requires high temperature exposure specifically to cobalt metal and that does not cause any harm to other metals. [0049] v) Purification of cobalt oxide by dilute acid wash: In this step the above roasted material is treated with dilute hydrochloric acid solution at pH between 2.0 to 3. [0050] vi) Magnetic separation for removal of PCBs, copper and Aluminum matrix: In this step, from the mixture of PCBs, Copper and Aluminum obtained from step (ii), PCBs are separated by using a magnetic separator. The magnetic part contains PCBs and non-magnetic part contains Copper and Aluminum. [0051] vii) Lithium recovery as lithium carbonate by precipitation of wash liquor of step (iii): In this step, the wash liquor obtained from step (iii) is treated with saturated solution of soda ash to increase the pH and maintain it between 11-11.5 at 90 to 100 C. for 4 hrs.

[0052] Accordingly, in most preferred embodiment of the present invention is proposed a process for recovering valuable metals from spent lithium ion batteries comprising the steps of: [0053] a) shredding the lithium ion batteries into particles of a preferable size, i.e. 10 mm, in water, with water level well above the level of the batteries being shredded to obtain a slurry and shredded plastic and Teflon matrix; [0054] b) removing the plastic and Teflon matrix that floats on the water in step a); [0055] c) wet screening the slurry obtained in step a) through sieve of at least fifty mesh size to separate particles of varying sizes; wherein coarser particles containing copper, aluminum and protection circuit boards form screened slurry containing solids are retained by the sieve and collected, and finer particles containing lithium and cobalt are aggregated; [0056] d) filtering the lithium and cobalt containing aggregate of step c) through a filter press to obtain a wash liquor containing lithium and a residue containing cobalt, metal impurities and organic matrix; [0057] e) drying the residue of step d) and roasting the dried residue at 900 C. to obtain cobalt oxide; [0058] f) washing and filtering the cobalt oxide of step e) with dilute hydrochloric acid solution at pH range 2.0 to 3.0 to obtain pure cobalt oxide and filtrate; [0059] g) treating the wash liquor of step d) with saturated solution of soda ash at pH range 11 to 11.5 and temperature ranging from 80 to 120 C. for 3-6 hours to obtain lithium carbonate precipitate and supernatant.

[0060] In further embodiment, the coarser pieces of step c) of the process are processed using magnetic separator to segregate magnetic part comprising protection circuit boards from non magnetic part comprising copper and aluminum.

[0061] In another embodiment, the proposed process provides cobalt oxide with purity of 97% with cobalt content of more than 76% and metal impurity level below 2%.

[0062] In another embodiment, the proposed process provides lithium carbonate with purity of 98% with lithium content of more than 18% and metal impurity level below 0.5%.

EXAMPLES

[0063] The invention will now be illustrated by the following non-limiting examples.

Example 1

[0064] A batch (Batch 1) of 10 kg spent mobile batteries (Samsung2100 mAh) was taken and processed as per the process specified in the present invention. Initially, wet shredding of spent batteries was done followed by floatation, resulting in removal of about 0.58 Kg of plastics and polymer materials. The materials are then sieved through 50 mesh wherein the mixture (about 2.32 Kg) of PCBs and metals like copper, aluminum are retained and collected.

[0065] The slurry containing particles of size less than 300 microns is subjected to filtration. Upon filtration, the cake weighing about 5.78 Kg (dry wt.) and filtrate (about 30 liters) containing dissolved lithium metals are obtained.

[0066] The mixture (about 2.32 Kg) of PCB, aluminum and copper was then magnetically separated that provides about 0.109 kg of PCB's for gold recovery process. The remaining amount (about 2.21 Kg) of mixture was subjected to density separation (using air) which leads to separation of aluminum (1.5 Kg) and copper (0.7 Kg) selectively.

[0067] The cake (5.78 Kg) obtained in the filtration step was roasted at 900 C. for at least 9 hours. After roasting, about 1.38 Kg residue is obtained, which was further purified by agitating it with dilute hydrochloric acid (pH 2-3) for 2 hrs followed by filtration and drying. The obtained purified cake contains about 1.35 Kg of pure cobalt oxide powder.

[0068] The filtrate (about 30 liters) was agitated with about 3.6 liters of saturated soda ash solution at 90-100 C. for at least 4 hours resulting in the precipitation of lithium as lithium carbonate. The precipitated slurry was filtered, washed with hot water and dried to get pure lithium carbonate (about 1.13 Kg).

Example 2

[0069] Another batch (Batch 2) of 10 kg spent mobile batteries (Samsung2600 mAh) was taken and processed. In the first step, the batteries were shredded in wet environment and subjected to floatation step that resulted in removal of about 0.85 Kg of plastics and polymer materials. These materials were sieved using 50 mesh size sieve wherein the mixture (about 3.37 Kg) of PCBs and metals like copper, aluminum are retained and collected.

[0070] The slurry containing particles of size less than 300 microns is subjected to filtration. Upon filtration, the cake weighing about 4.55 Kg (dry wt.) and filtrate (about 30 liters) containing dissolved lithium metals are obtained.

[0071] The mixture (about 3.37 Kg) of PCB and metals like copper, aluminum was then magnetically separated that provides about 0.109 kg of PCB's for gold recovery process. The remaining amount (about 3.26 Kg) of mixture was subjected to density separation (using air) which leads to separation of aluminum (1.68 Kg) and copper (0.7 Kg) selectively.

[0072] On the other hand, the cake (4.55 Kg) obtained after filtration step was roasted at 900 C. for 9 hours to get about 1.41 Kg of roasted powder. The obtained roasted powder was further purified by agitating it with dilute hydrochloric acid (pH 2-3) for 2 hrs followed by filtration and drying. The purified cake obtained from Batch 2 contains about 1.37 Kg of pure cobalt oxide powder.

[0073] The filtrate (about 30 liters) was agitated with about 3.6 liters of saturated soda ash solution at 90-100 C. for at least 4 hours resulting in the precipitation of lithium as lithium carbonate. The precipitated slurry was filtered, washed with hot water and dried to get pure lithium carbonate (about 1.04 Kg).

[0074] The products obtained in the above process were analyzed by MP-AES (microwave plasma-atomic emission spectra) and the analyses were presented in Table 1 and 2.

TABLE-US-00001 TABLE 1 Chemical analysis of cobalt oxide (%) Co Cu Li Pb Mn Al Ni Fe Zn 76.2 0.35 1.09 BDL BDL 0.31 BDL 0.19 BDL

TABLE-US-00002 TABLE 2 Chemical analysis of lithium carbonate (%) Li Cu Pb Mn Al Ni Fe Zn Co 18.68 BDL BDL BDL 0.1 BDL BDL BDL BDL

[0075] The X-ray diffraction (XRD) pattern of the same products (cobalt oxide and lithium carbonate) was characterized by using a powder diffractometer (Bruker, D8 Advance).

[0076] The major peaks at 20 values (36.86), (42.82) and (62.17) correspond to the hk1 values (111), (200) and (220), respectively are of Cobalt oxide (FIG. 2). It is a cubic type structure and the pattern is in good agreement with the JCPDS card No. 43-1004. The other two peaks at 20 values (18.21) and (18.34) are due to the traces amount of LiCoO2, which was again confirmed from the chemical analysis of the obtained cobalt oxide (Table 1).

[0077] Referring to FIG. 3, diffraction (XRD) pattern of pure lithium carbonate obtained from spent lithium-ion battery is elucidated. The major peaks at 20 values (21.32), (30.61), (31.80) and (36.95) corresponds to the hk1 values (110), (202), (002) and (311), respectively. The lithium carbonate has monoclinic type structure and the pattern was found in good agreement with the JCPDS card No. 22-1141.

[0078] The purity of the products obtained during the processes was analyzed by Microwave Plasma Atomic emission spectra (MP-AES). Purity of cobalt oxide obtained was around 97% and that of Lithium carbonate was found to be 98%.

[0079] The details of the process steps and quantity of recovered metals are summarized in the Table 3.

TABLE-US-00003 TABLE 3 Summary of the process Batch no Batch 1 Input Output Step No Process Material quantity unit Material quantity unit 1 Wet shredding Spent LIBs 10 Kg Shredded material 9.48 Kg (samsung-2100 mAh) 2 Floation Shredded material 9.48 Kg Polymeric 0.58 Kg Slurry (Al, Cu, PCB, 8.9 Kg black powder) 3 Wet sieving Slurry (Al, Cu, PCB, 8.9 Kg Mixture of Al, 2.32 Kg followed by black powder) Cu and PCB filtration Cake (dry Wt) 5.78 Kg Filtrate 30 Lt 4 Separation of Mixture of Al, 2.32 Kg Al and Cu 2.21 Kg Al, Cu and PCB by Cu and PCB PCB 0.109 Kg magnetic separator 5 Density separation Al and Cu 2.21 Kg Al 1.5 Kg of Al and Cu Cu 0.7 6 Roasting of cake Dry Cake 5.78 Kg Roasted powder 1.387 Kg 7 Purification Roasted powder 1.387 Kg Purified 1.35 Kg cobalt oxide 8 Lithium Filtrate 30 Lt Li.sub.2CO.sub.3 1.13 Kg precipitation Batch no Batch 2 Input Output Step No Material quantity unit Material quantity unit 1 Spent LIBs 10 Kg Shredded material 9.57 Kg (samsung-2600 mAh) 2 shredded 9.57 Kg Polymeric 0.85 Kg material Slurry (Al, Cu, PCB, 8.72 Kg black powder) 3 Slurry (Al, Cu, PCB, 8.72 Kg Mixture of Al, 3.37 Kg black powder) Cu and PCB Cake(dry Wt) 4.55 Kg Filtrate 30 Lt 4 Mixture of Al, 3.37 Kg Al and Cu 3.26 Kg Cu and PCB PCB 0.109 Kg 5 Al and Cu 3.26 Kg Al 1.68 Kg Cu 0.7 Kg 6 Dry Cake 4.55 Kg Roasted powder 1.411 Kg 7 Roasted powder 1.411 Kg Purified 1.37 Kg cobalt oxide 8 Filtrate 30 Lt Li.sub.2CO.sub.3 1.04 Kg