Description:PLEASE SEE THE ATTACHMENTS. , Claims:We Claim:
1. A method for preparing a reference standard solution of spent cathode material having a specific Li ion concentration (100), comprising:
a. homogenizing dry spent cathode material to provide a powdered cathode material, wherein the dry spent cathode material comprises a Li-based mixed metal oxide having Li and one or more elements (102);
b. performing elemental characterization of the powdered cathode material (104);
c. based on the elemental characterization, calculating an amount of the powdered cathode material required to provide the specific Li ion concentration in the reference standard solution of spent cathode material (106); and
d. digesting the calculated amount of the powdered cathode material with an acid at about 140-160°C for about 50-70 minutes to obtain the reference standard solution of spent cathode material having the specific Li ion concentration (108).

2. The method (100) as claimed in claim 1, wherein the one or more elements present in the Li-based mixed metal oxide are selected from Ni, Mn, Co, Al, Cu, Fe, and Mg.

3. The method (100) as claimed in claim 1or 2, wherein the elemental characterization of the powdered cathode material is performed by inductively coupled plasma optical emission spectroscopy (ICP-OES).

4. The method (100) as claimed in any one of claims 1 to 3, wherein the calculated amount of the powdered cathode material is digested with an acid at 150°C for about an hour.

5. The method (100) as claimed in any one of claims 1 to 4, wherein the acid is selected from hydrochloric acid, nitric acid, or any combination thereof.

6. The method (100) as claimed in any one of claims 1 to 5, wherein, after digestion, the solution of spent cathode material is cooled to 25°C followed by filtration and volume adjustment.

7. The method (100) as claimed in any one of claims 1 to 6, wherein the reference standard solution of spent cathode material has a Li ion concentration of 1000 ± 10 ppm.

8. The method (100) as claimed in any one of claims 1 to 7, wherein the reference standard solution of spent cathode material has a Ni ion concentration of 862 ± 10 ppm.

9. The method (100) as claimed in any one of claims 1 to 8, wherein the reference standard solution of spent cathode material has a Mn ion concentration of 2490 ± 10 ppm.

10. The method (100) as claimed in any one of claims 1 to 9, wherein the reference standard solution of spent cathode material has a Co ion concentration of 6503 ± 10 ppm.

11. The method (100) as claimed in any one of claims 1 to 10, wherein the reference standard solution provided by the method exhibits an uncertainty due to homogeneity (Uhome) within one-third of the targeted uncertainty (Utarget).

12. The method (100) as claimed in any one of claims 1 to 11, wherein the reference standard solution provided by the method exhibits an uncertainty of long-term stability (Ults) of about 0.65-0.75 for a period of 90 days.

13. The method (100) as claimed in any one of claims 1 to 12, wherein the reference standard solution provided by the method exhibits a calculated extended uncertainty of long-term stability (UltsFinal) of about 2.9 to 3.0 for a period of 365 days.

14. A reference standard solution of spent cathode material, comprising Li-based mixed metal oxide having Li and one or more elements, wherein the concentration of Li ions in the solution is 1000 ppm ± 10 ppm.

15. The reference standard solution as claimed in claim 14, wherein the one or more elements are selected from Ni, Mn, Co, Al, Cu, Fe, and Mg.

16. The reference standard solution as claimed in claim 14 or 15, wherein the concentration of Ni ions in the solution is 862 ± 10 ppm.

17. The reference standard solution as claimed in any one of claims 14 to 16, wherein the concentration of Mn ions in the solution is 2490 ± 10 ppm.

18. The reference standard solution as claimed in any one of claims 14 to 17, wherein the concentration of Co ions in the solution is 6503 ± 10 ppm.

19. The reference standard solution as claimed in any one of claims 14 to 18, wherein the solution exhibits an uncertainty due to homogeneity (Uhome) within one-third of the targeted uncertainty (Utarget).

20. The reference standard solution as claimed in any one of claims 14 to 19, wherein the solution exhibits an uncertainty of long-term stability (Ults) of about 0.65-0.75 for a period of 90 days.

21. The reference standard solution as claimed in any one of claims 14 to 20, wherein the solution exhibits a calculated extended uncertainty of long-term stability (UltsFinal) of about 2.9 to 3.0 for a period of 365 days.

22. A method for elemental quantification of a test cathode material in spent lithium batteries by inductively coupled plasma optical emission spectroscope (ICP-OES) or atomic absorption spectroscope (AAS) (200), comprising:
a. running the reference standard solution of spent cathode material as claimed in any one of claims 14 to 21 or the reference standard solution prepared by the method as claimed in any one of claims 1 to 13 on the ICP-OES or AAS (202);
b. running a sample of a test cathode material on the ICP-OES or AAS (204); and
c. performing elemental quantification of the test cathode material based on intensity of the sample of the test cathode material with respect to intensity of the reference standard solution (206).

23. The method (200) as claimed in claim 22, wherein the element quantified by the method is Li.

24. The method (200) as claimed in claim 22, wherein the element quantified by the method is selected from Li, Ni, Mn, Co, Al, Cu, Fe, and Mg.