Method for Manufacturing Vanadium Electrolyte

Abstract

A method for manufacturing a vanadium electrolyte is used to solve the problem that the expansive raw material and the additional reducing agent are used in the conventional method. The method comprises: preforming a reduction roasting reaction of ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) at a temperature of 700 C. to 900 C. for a time period of 1 hour to 4 hours to obtain a first vanadium-containing mixture. The first vanadium-containing mixture is dissolved in a first aqueous sulfuric acid solution to obtain the vanadium electrolyte. Accordingly, the manufacturing cost of the vanadium electrolyte is reduced, and the quality of the vanadium electrolyte is improved.

Claims

1. A method for manufacturing a vanadium electrolyte, comprising: carrying out a reduction roasting reaction of ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) at a temperature of from 700 C. to 900 C. for a time period of 1 hour to 4 hours, obtaining a vanadium-containing mixture; and dissolving the vanadium-containing mixture in an aqueous sulfuric acid solution to obtain the vanadium electrolyte.

2. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the reduction roasting is carried out at a temperature equal to or greater than 800 C.

3. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the reduction roasting is carried out for a time period of equal to or greater than 3 hours.

4. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the reduction roasting is carried out at a temperature of 850 C. for a time period of 3 hours.

5. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the aqueous sulfuric acid solution has a sulfuric acid concentration of from 3 M to 6 M.

6. The method for manufacturing the vanadium electrolyte as claimed in claim 5, wherein the aqueous sulfuric acid solution has a sulfuric acid concentration of equal to or greater than 4 M.

7. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the vanadium-containing mixture is dissolved in the aqueous sulfuric acid solution at a temperature of from 60 C. to 90 C.

8. The method for manufacturing the vanadium electrolyte as claimed in claim 7, wherein the vanadium-containing mixture is dissolved in the aqueous sulfuric acid solution at a temperature of equal to or greater than 80 C.

9. The method for manufacturing the vanadium electrolyte as claimed in claim 1, wherein the vanadium-containing mixture is dissolved in the aqueous sulfuric acid solution for a time period of from 1 hour to 5 hours.

10. The method for manufacturing the vanadium electrolyte as claimed in claim 9, wherein the vanadium-containing mixture is dissolved in the aqueous sulfuric acid solution for a time period of equal to or greater than 3 hours.

11. A method for manufacturing a vanadium electrolyte, comprising: carrying out a first reduction roasting reaction of ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) at a temperature of from 700 C. to 900 C. for a time period of from 1 hour to 4 hours, obtaining a first vanadium-containing mixture; dissolving the first vanadium-containing mixture in a first aqueous sulfuric acid solution, obtaining a first vanadium-containing solution; carrying out a second reduction roasting reaction of ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) at a temperature of from 500 C. to 700 C. for a time period of from 1 hour to 4 hours, obtaining a second vanadium-containing mixture; dissolving the second vanadium-containing mixture in a second aqueous sulfuric acid solution, obtaining a second vanadium-containing solution; and mixing the first vanadium-containing solution and the second vanadium-containing solution to obtain the vanadium electrolyte.

12. The method for manufacturing the vanadium electrolyte as claimed in claim 11, further comprising: measuring average valence of the vanadium ion of the first vanadium-containing solution and average valence of the vanadium ion of the second vanadium-containing solution to calculate a predetermined mixing ratio between the first vanadium-containing solution and the second vanadium-containing solution; and mixing the first vanadium-containing solution and the second vanadium-containing solution according to the predetermined mixing ratio to obtain the vanadium electrolyte.

13. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first reduction roasting reaction is carried out at a temperature of equal to or greater than 800 C.

14. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first reduction roasting reaction is carried out for a time period of equal to or greater than 3 hours.

15. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first reduction roasting reaction is carried out at a temperature of 850 C. for a time period of 3 hours.

16. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first aqueous sulfuric acid solution has a sulfuric acid concentration of from 3 M to 6 M.

17. The method for manufacturing the vanadium electrolyte as claimed in claim 16, wherein the first aqueous sulfuric acid solution has a sulfuric acid concentration of equal to or greater than 4 M.

18. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution at a temperature of from 60 C. to 90 C.

19. The method for manufacturing the vanadium electrolyte as claimed in claim 18, wherein the first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution at a temperature of equal to or greater than 80 C.

20. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution for a time period of from 1 hour to 5 hours.

21. The method for manufacturing the vanadium electrolyte as claimed in claim 20, wherein the first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution for a time period of equal to or greater than 3 hours.

22. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second reduction roasting reaction is carried out at a temperature of equal to or greater than 600 C.

23. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second reduction roasting reaction is carried out for a time period of equal to or greater than 2 hours.

24. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second reduction roasting reaction is carried out at a temperature of 650 C. for a time period of 2 hours.

25. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second aqueous sulfuric acid solution has a sulfuric acid concentration of from 3 M to 6 M.

26. The method for manufacturing the vanadium electrolyte as claimed in claim 25, wherein the second aqueous sulfuric acid solution has a sulfuric acid concentration of equal to or greater than 4 M.

27. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution at a temperature of from 60 C. to 90 C.

28. The method for manufacturing the vanadium electrolyte as claimed in claim 27, wherein the second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution at a temperature of equal to or greater than 80 C.

29. The method for manufacturing the vanadium electrolyte as claimed in claim 11, wherein the second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution for a time period of from 1 hour to 4 hours.

30. The method for manufacturing the vanadium electrolyte as claimed in claim 29, wherein the second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution for a time period of equal to or greater than 2 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0027] FIG. 1 depicts a flow chart of a method for manufacturing a vanadium electrolyte according to a first embodiment of the present invention.

[0028] FIG. 2 depicts a flow chart of a method for manufacturing a vanadium electrolyte according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring to FIG. 1, a method for manufacturing a vanadium electrolyte according to a first embodiment of the present invention can generally comprise a step of reduction roasting S1 and step of dissolving S2, whereby ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) as a raw material to produce a vanadium electrolyte. The vanadium electrolyte contains vanadium (III) ion (V.sup.3+), vanadium (IV) ion (V.sup.4+; in the form of vanadyl ion (VO.sup.2+)) and sulfate ion (SO.sub.4.sup.2). In the vanadium electrolyte, the molar ratio of vanadium (III) ion (V.sup.3+) and vanadium (IV) ion (V.sup.4+) is approximately between 1:1 and 1.1:1. In other words, vanadium ions contain 50-53% of vanadium (III) ion (V.sup.3+) and 47-50% of vanadium (IV) ion (V.sup.4+) in molar percentage. Moreover, in the vanadium electrolyte, the total concentration of vanadium (III) ion (V.sup.3+) and vanadium (IV) ion (V.sup.4+) is between 1.6 M and 1.8 M, and the concentration of the sulfate ion (SO.sub.4.sup.2) is between 2.5 M to 3 M.

[0030] Specifically, in the step of reduction roasting S1, ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) is placed in a reduction furnace. The oxygen concentration in the reduction furnace is close to 0%, and a reduction roasting reaction is carried out in an anaerobic environment. In the reduction roasting reaction, ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) is heated to generate vanadium (V) oxide (V.sub.2O.sub.5(s)) and ammonia gas (NH.sub.3(g)) as shown in chemical equation (I). Moreover, according to chemical equations (II) and (III), the generated ammonia gas (NH.sub.3(g)) can reduce vanadium (V) oxide (V.sub.2O.sub.5) to form vanadium (IV) oxide (V.sub.2O.sub.4(s)) and/or vanadium (III) oxide (V.sub.2O.sub.3(s)), and a vanadium-containing mixture can be obtained.

##STR00001##

[0031] In addition, by adjusting the parameters, the vanadium-containing mixture containing vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (III) oxide (V.sub.2O.sub.3) with a molar ratio of approximately 1:1 can be formed according to chemical equation (IV). In the first embodiment of the present invention, the reduction roasting reaction can be carried out at a temperature of from 700 C. to 900 C. for a time period of from 1 hour to 4 hours. Preferably, the reduction roasting reaction can be carried out at a temperature of equal to or greater than 800 C., or the reduction roasting reaction can be carried out for a time period of equal to or greater than 3 hours.

##STR00002##

[0032] In the step of dissolving S2, the vanadium-containing mixture can be dissolved in an aqueous sulfuric acid solution. The vanadium (IV) oxide (V.sub.2O.sub.4) and the vanadium (III) oxide (V.sub.2O.sub.3) in the vanadium-containing mixture are dissolved to form vanadium (IV) ion (V.sup.4+; in the form of vanadyl ion (VO.sup.2+)) and vanadium (III) ion (V.sup.3+) according to chemical equations (V) and (VI), respectively, and the vanadium electrolyte can be therefore obtained. At this time, since the vanadium-containing mixture contains vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (III) oxide (V.sub.2O.sub.3) with a molar ratio of approximately 1:1, a molar ratio of vanadium (IV) ion (V.sup.4+) and vanadium (III) ion (V.sup.3+) obtained by dissolving the vanadium-containing mixture is also approximately 1:1.

##STR00003##

[0033] In the first embodiment according to the present invention, in order to improve the solubility of the vanadium-containing mixture, the aqueous sulfuric acid solution can have a sulfuric acid concentration of from 3 M to 6 M, and the aqueous sulfuric acid solution can preferably have a sulfuric acid concentration of equal to or greater than 4 M. Moreover, the dissolving of the vanadium-containing mixture in the aqueous sulfuric acid solution can be carried out at a temperature of from 60 C. to 90 C., and the dissolving of the vanadium-containing mixture in the aqueous sulfuric acid solution can be preferably carried out at a temperature of equal to or greater than 80 C. Furthermore, the dissolving of the vanadium-containing mixture in the aqueous sulfuric acid solution can be carried out for a time period of from 1 hour to 5 hours, and the dissolving of the vanadium-containing mixture in the aqueous sulfuric acid solution can be preferably carried out for a time period of equal to or greater than 3 hours.

[0034] It is worthy to note that the reduction roasting reaction uses the ammonia gas (NH.sub.3(g)), which is generated by heating ammonium trioxovanadate (V) (NH.sub.4VO.sub.3), as the reducing agent, and the ammonia gas (NH.sub.3(g)) actually has poor reducing ability. Therefore, the parameters of the reduction roasting reaction may be difficult to control, and the average valence of the vanadium ion of the vanadium electrolyte obtained by the method for manufacturing the vanadium electrolyte according to the first embodiment of the present invention may easily deviate from the expected value. Accordingly, a method for manufacturing the vanadium electrolyte according to the second embodiment of the present invention can be preferably carried out. Referring to FIG. 2, the method for manufacturing the vanadium electrolyte according to the second embodiment of the present invention can comprise a step of preparing a first vanadium-containing solution S3, a step of preparing a second vanadium-containing solution S4 and a step of mixing S5. As such, a first vanadium-containing solution containing vanadium (III) ion (V.sup.3+) and a second vanadium-containing solution containing vanadium (IV) ion (V.sup.4+) can be respectively prepared by ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) as a raw material. Then, the first vanadium-containing solution and the second vanadium-containing solution can be mixed to produce the vanadium electrolyte.

[0035] The step of preparing the first vanadium-containing solution S3 can include a substep of first reduction roasting S31. In the substep of first reduction roasting S31, a first reduction roasting reaction can be carried out. Ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) is heated to generate a first vanadium-containing mixture containing vanadium (III) oxide (V.sub.2O.sub.3) according to chemical equations (I), (II) and (III). In the second embodiment of the present invention, the first reduction roasting reaction can be carried out at a temperature of from 700 C. to 900 C. for a time period of from 1 hour to 4 hours. Preferably, the first reduction roasting reaction can be carried out at a temperature of equal to or greater than 800 C., or the first reduction roasting reaction can be carried out for a time period of equal to or greater than 3 hours.

[0036] The step of preparing a first vanadium-containing solution S3 can include a substep of first dissolving S32. In the substep of first dissolving S32, the first vanadium-containing mixture can be dissolved in a first aqueous sulfuric acid solution. Vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (III) oxide (V.sub.2O.sub.3) in the first vanadium-containing mixture are dissolved to form vanadium (IV) ion (V.sup.4+; in the form of vanadyl ion (VO.sup.2+)) and vanadium (III) ion (V.sup.3+) according to chemical equations (V) and (VI), respectively, and the first vanadium-containing solution can be therefore obtained. In the second embodiment of the present invention, the first aqueous sulfuric acid solution can have a sulfuric acid concentration of from 3 M to 6 M, and the first aqueous sulfuric acid solution can have a sulfuric acid concentration of equal to or greater than 4 M. Moreover, the dissolving of the first vanadium-containing mixture in the first aqueous sulfuric acid solution can be carried out at a temperature of from 60 C. to 90 C., and the dissolving of the first vanadium-containing mixture in the first aqueous sulfuric acid solution can be preferably carried out at a temperature of equal to or greater than 80 C. Furthermore, the dissolving of the first vanadium-containing mixture in the first aqueous sulfuric acid solution can be carried out for a time period of from 1 hour to 5 hours, and the dissolving of the first vanadium-containing mixture in the first aqueous sulfuric acid solution can be preferably carried out for a time period of equal to or greater than 3 hours.

[0037] The step of preparing a second vanadium-containing solution S4 can include a substep of second reduction roasting S41. In the substep of second reduction roasting S41, a second reduction roasting reaction can be carried out. Ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) is heated to generate a second vanadium-containing mixture mainly composed of vanadium (IV) oxide (V.sub.2O.sub.4) according to chemical equations (I), (II) and (III). That is, in the second vanadium-containing mixture which includes vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (V) oxide (V.sub.2O.sub.5), the proportion of vanadium (IV) oxide (V.sub.2O.sub.4) is higher than the proportion of vanadium (V) oxide (V.sub.2O.sub.5), and in the second vanadium-containing mixture which includes vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (III) oxide (V.sub.2O.sub.3), the proportion of vanadium (IV) oxide (V.sub.2O.sub.4) is higher than the proportion of vanadium (III) oxide (V.sub.2O.sub.3). In the second embodiment of the present invention, the second reduction roasting reaction can be carried out at a temperature of from 500 C. to 700 C. for a time period of from 1 hour to 4 hours. Preferably, the second reduction roasting reaction can be carried out at a temperature of equal to or greater than 600 C., or the second reduction roasting reaction can be carried out for a time period of equal to or greater than 2 hours.

[0038] The step of preparing a second vanadium-containing solution S4 can further include a substep of second dissolving S42. In the substep of second dissolving S42, the second vanadium-containing mixture can be dissolved in a second aqueous sulfuric acid solution. Vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (V) oxide (V.sub.2O.sub.5) in the second vanadium-containing mixture are dissolved to form vanadium (IV) ion (V.sup.4+; in the form of vanadyl ion (VO.sup.2+)) and vanadium (V) ion (V.sup.5+; in the form on dioxovanadium (V) ion (VO.sub.2.sup.+)) according to chemical equations (V) and (VII), respectively. Alternatively, vanadium (IV) oxide (V.sub.2O.sub.4) and vanadium (III) oxide (V.sub.2O.sub.3) in the second vanadium-containing mixture are dissolved to form vanadium (IV) ion (V.sup.4+; in the form of vanadyl ion (VO.sup.2+)) and vanadium (III) ion (V.sup.3+) according to chemical equations (V) and (VI). The second vanadium-containing solution can be therefore obtained. In the second embodiment of the present invention, the second aqueous sulfuric acid solution can have a sulfuric acid concentration of from 3 M to 6 M, and the second aqueous sulfuric acid solution can have a sulfuric acid concentration of equal to or greater than 4 M. Moreover, the dissolving of the second vanadium-containing mixture in the second aqueous sulfuric acid solution can be carried out at a temperature of from 60 C. to 90 C., and the dissolving of the second vanadium-containing mixture in the second aqueous sulfuric acid solution can be preferably carried out at a temperature of equal to or greater than 80 C. Furthermore, the dissolving of the second vanadium-containing mixture in the second aqueous sulfuric acid solution can be carried out for a time period of from 1 hour to 4 hours, and the dissolving of the second vanadium-containing mixture in the second aqueous sulfuric acid solution can be preferably carried out for a time period of equal to or greater than 2 hours.

##STR00004##

[0039] After obtaining the first vanadium-containing solution and the second vanadium-containing solution, the step of mixing S5 can be carried out to obtain the vanadium electrolyte by mixing the first vanadium-containing solution and the second vanadium-containing solution.

[0040] In order to ensure the molar ratio of vanadium (III) ion (V.sup.3+) and vanadium (IV) ion (V.sup.4+) in the obtained vanadium electrolyte, average valence of the vanadium ion of the first vanadium-containing solution and average valence of the vanadium ion of the second vanadium-containing solution are preferably measured to calculate a predetermined mixing ratio between the first vanadium-containing solution and the second vanadium-containing solution. Finally, the vanadium electrolyte is obtained by mixing the first vanadium-containing solution and the second vanadium-containing solution according to the predetermined mixing ratio. For example, when the average valence of the vanadium ion of the first vanadium-containing solution is 3.0, and the average valence of the vanadium ion of the second vanadium-containing solution is 4.0, the first vanadium-containing solution and the second vanadium-containing solution can be mixed at a volume ratio of 1:1. When the average valence of the vanadium ion of the first vanadium-containing solution is 3.3, and the average valence of the vanadium ion of the second vanadium-containing solution is 4.1, the first vanadium-containing solution and the second vanadium-containing solution can be mixed at a volume ratio of 3:1. When the average valence of the vanadium ion of the first vanadium-containing solution is 3.1, and the average valence of the vanadium ion of the second vanadium-containing solution is 4.2, the first vanadium-containing solution and the second vanadium-containing solution can be mixed at a volume ratio of 7:4. Accordingly, the vanadium electrolyte with a molar ratio of vanadium (III) ion (V.sup.3+) and vanadium (IV) ion (V.sup.4+) being approximately 1:1 can be obtained. (That is, the average valence of the vanadium ion of the vanadium electrolyte is approximately 3.5).

[0041] To evaluate the vanadium electrolyte can be obtained according to the method for manufacturing the vanadium electrolyte, the following trials are carried out:

Trial (A).

[0042] In trial (A), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the first reduction roasting reaction is carried out at a temperature of from 700 C. to 900 C. for a time period of 3 hours. The obtained first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of 4 hours. Undissolved first vanadium-containing mixture is removed, and the molar percentages of vanadium (III) ion (V.sup.3+) vanadium (IV) ion (V.sup.4+; in the form of VO.sup.2+) and vanadium (V) ion (V.sup.5+; in the form on VO.sub.2.sup.+) in the obtained first vanadium-containing solution are calculated by redox titration.

TABLE-US-00001 TABLE 1 Molar percentage of V.sup.3+, VO.sup.2+ and VO.sub.2.sup.+ in the first Temperature of the vanadium-containing first reduction roasting solution Group reaction (V.sup.3+:VO.sup.2+:VO.sub.2.sup.+) A1 700 C. 5.0%:95.0%:0% A2 750 C. 18.0%:82.0%:0% A3 800 C. 63.0%:37.0%:0% A4 850 C. 65.0%:35.0%:0% A5 900 C. 69.0%:31.0%:0%

[0043] Referring to TABLE 1, by the first reduction roasting reaction carried out at a temperature of from 700 C. to 900 C. for a time period of 3 hours, ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) can be reduced to form vanadium (III) oxide (V.sub.2O.sub.3) (groups A1 to A5), among which the first reduction roasting reaction carried out at a temperature of from 800 C. to 900 C. for a time period of 3 hours shows a better result (groups A3 to A5, the major proportion of the vanadium-containing compounds in the obtained first vanadium-containing mixture is vanadium (III) oxide (V.sub.2O.sub.3)), and the first reduction roasting reaction carried out at a temperature of 850 C. for a time period of 3 hours shows the best result (group A4).

Trial (B).

[0044] In trial (B), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in the closed reduction furnace, and the first reduction roasting reaction at a temperature of 850 C. for a time period of from 1 hour to 4 hours. The obtained first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of 4 hours. Undissolved first vanadium-containing mixture is removed, and the molar percentages of vanadium (III) ion (V.sup.3+), vanadium (IV) ion (V.sup.4+; in the form of VO.sup.2+) and vanadium (V) ion (V.sup.5+; in the form on VO.sub.2.sup.+) in the obtained first vanadium-containing solution are calculated by redox titration.

TABLE-US-00002 TABLE 2 Molar percentage of V.sup.3+, VO.sup.2+ and VO.sub.2.sup.+ in the first Time period of the vanadium-containing first reduction roasting solution Group reaction (V.sup.3+:VO.sup.2+:VO.sub.2.sup.+) B1 1 hour.sup. 38.0%:62.0%:0% B2 2 hours 40.0%:60.0%:0% B3 3 hours 65.0%:35.0%:0% B4 4 hours 63.0%:37.0%:0%

[0045] Referring to TABLE 2, by the first reduction roasting reaction carried out at a temperature of 850 C. for a time period of from 1 hour to 4 hours, ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) can be reduced to form vanadium (III) oxide (V.sub.2O.sub.3) (groups B1 to B4), among which the first reduction roasting reaction carried out at a temperature of 850 C. for a time period of from 3 hours to 4 hours shows a better result (groups B3 to B4, the major proportion of the vanadium-containing compounds in the obtained first vanadium-containing mixture is vanadium (III) oxide (V.sub.2O.sub.3)), and the first reduction roasting reaction carried out at a temperature of 850 C. for a time period of 3 hours shows the best result (group B3).

Trial (C).

[0046] In trial (C), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the first reduction roasting reaction is carried out at a temperature of 850 C. for a time period of 3 hours. The obtained first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (3 M to 6 M) at a temperature of 80 C. for a time period of 4 hours. Undissolved first vanadium-containing mixture is collected, and the solubility of the first vanadium-containing mixture in the first aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00003 TABLE 3 Sulfuric acid concentration of the first aqueous sulfuric acid solution for dissolving the first Solubility of the first vanadium-containing vanadium-containing Group mixture mixture C1 3M 87.8% C2 4M 91.3% C3 5M 99.6% C4 6M 99.6%

[0047] Referring to TABLE 3, the first vanadium-containing mixture can be effectively dissolved in the first aqueous sulfuric acid solution with a sulfuric acid concentration of from 3 M to 6 M at a temperature of 80 C. for a time period of 4 hours (groups C1 to C4), among which the first vanadium-containing mixture shows a better solubility in the first aqueous sulfuric acid solution with a sulfuric acid concentration of from 4 M to 6 M (groups C2 to C4, the solubility of the first vanadium-containing mixture reaches equal to or greater than 90%), and the first vanadium-containing mixture shows the best solubility in the first aqueous sulfuric acid solution with a sulfuric acid concentration of from 5 M to 6 M (groups C3 to C4, the solubility of the first vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, the first aqueous sulfuric acid with a sulfuric acid concentration of 5 M shows the best result (group C3).

Trial (D).

[0048] In trial (D), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the first reduction roasting reaction is carried out at a temperature of 850 C. for a time period of 3 hours. The obtained first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (5 M) at a temperature of from 60 C. to 90 C. for a time period of 4 hours. Undissolved first vanadium-containing mixture is collected, and the solubility of the first vanadium-containing mixture in the first aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00004 TABLE 4 Temperature for dissolving the first Solubility of the first vanadium-containing vanadium-containing Group mixture mixture D1 60 C. 81.0% D2 70 C. 84.8% D3 80 C. 99.6% D4 90 C. 99.6%

[0049] Referring to TABLE 4, the first vanadium-containing mixture can be effectively dissolved in the first aqueous sulfuric acid solution with a sulfuric acid concentration of 5 M at a temperature of from 60 C. to 90 C. for a time period of 4 hours (groups D1 to D4), among which the first vanadium-containing mixture shows a better solubility at a temperature of from 80 C. to 90 C. (groups D3 to D4, the solubility of the first vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, 80 C. shows the best result (group D3).

Trial (E).

[0050] In trial (E), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the first reduction roasting reaction is carried out at a temperature of 850 C. for a time period of 3 hours. The obtained first vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of from 1 hour to 5 hours. Undissolved first vanadium-containing mixture is collected, and the solubility of the first vanadium-containing mixture in the first aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00005 TABLE 5 Time for dissolving the first Solubility of the first vanadium-containing vanadium-containing Group mixture mixture E1 1 hour.sup. 76.0% E2 2 hours 82.2% E3 3 hours 92.2% E4 4 hours 99.6% E5 5 hours 99.7%

[0051] Referring to TABLE 5, the first vanadium-containing mixture can be effectively dissolved in the first aqueous sulfuric acid solution with a sulfuric acid concentration of 5 M at a temperature of 80 C. for a time period of from 1 hour to 5 hours (groups E1 to E5), among which the first vanadium-containing mixture shows a better solubility for a time period of from 3 hours to 5 hours (groups E3 to E5, the solubility of the first vanadium-containing mixture reaches equal to or greater than 90%), and the first vanadium-containing mixture shows the best solubility for a time period of from 4 hours to 5 hours (groups E4 to E5, the solubility of the first vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, 4 hours show the best result (group E4).

Trial (F).

[0052] In trial (F), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the second reduction roasting reaction is carried out at a temperature of from 500 C. to 700 C. for time period of 2 hours. The obtained second vanadium-containing is dissolved in the second aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of 3 hours. Undissolved second vanadium-containing mixture is removed, and the molar percentages of vanadium (III) ion (V.sup.3+), vanadium (IV) ion (V.sup.4+; in the form of VO.sup.2+) and vanadium (V) ion (V.sup.5+; in the form on VO.sub.2.sup.+) in the obtained second vanadium-containing solution are calculated by redox titration.

TABLE-US-00006 TABLE 6 Molar percentage of V.sup.3+, VO.sup.2+ and VO.sub.2.sup.+ in the second Temperature of the vanadium-containing second reduction solution Group roasting reaction (V.sup.3+:VO.sup.2+:VO.sub.2.sup.+) F1 500 C. 0%:75.9%:24.1% F2 550 C. 0%:88.9%:11.1% F3 600 C. 0%:90.0%:10.0% F4 650 C. 0%:99.7%:0.3% F5 700 C. 8.8%:91.2%:0%

[0053] Referring to TABLE 6, by the second reduction roasting reaction carried out at a temperature of from 500 C. to 700 C. for a time period of 2 hours, ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) can be reduced to form vanadium (IV) oxide (V.sub.2O.sub.4), which is the highest proportion among all vanadium-containing compounds in the obtained second vanadium-containing mixture (groups F1 to F5), among which the second reduction roasting reaction carried out at a temperature of from 600 C. to 700 C. for a time period of 2 hours shows a better result (groups F3 to F5, the proportion of vanadium (IV) oxide (V.sub.2O.sub.4) reaches equal to or greater than 90%), and the second reduction roasting reaction carried out at a temperature of 650 C. for a time period of 2 hours shows the best result (group F4).

Trial (G).

[0054] In trial (G), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the second roasting reaction is carried out at a temperature of 650 C. for a time period of from 1 hour to 4 hours. The obtained second vanadium-containing is dissolved in the second aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of 3 hours. Undissolved second vanadium-containing mixture is removed, and the molar percentages of vanadium (III) ion (V.sup.3+), vanadium (IV) ion (V.sup.4+; in the form of VO.sup.2+) and vanadium (V) ion (V.sup.5+; in the form on VO.sub.2.sup.+) in the obtained second vanadium-containing solution are calculated by redox titration.

TABLE-US-00007 TABLE 7 Molar percentage of V.sup.3+, VO.sup.2+ and VO.sub.2.sup.+ in the second Time of the second vanadium-containing reduction roasting solution Group reaction (V.sup.3+:VO.sup.2+:VO.sub.2.sup.+) G1 1 hour.sup. 0%:85.9%:14.1% G2 2 hours 0%:99.7%:0.3% G3 3 hours 0%:99.2%:0.8% G4 4 hours 0%:99.4%:0.6%

[0055] Referring to TABLE 7, by the second reduction roasting reaction carried out at a temperature of 650 C. for a time period of from 1 hour to 4 hours ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) can be reduced to form vanadium (IV) oxide (V.sub.2O.sub.4), which is the highest proportion among all vanadium-containing compounds in the obtained second vanadium-containing mixture (groups G1 to G4), among which the second reduction roasting reaction carried out at a temperature of 650 C. for a time period of from 2 hours to 4 hours shows a better result (groups G2 to G4, the proportion of vanadium (IV) oxide (V.sub.2O.sub.4) reaches equal to or greater than 90%), and the second reduction roasting reaction carried out at a temperature of 650 C. for a time period of 2 hours shows the best result (group G2).

Trial (H).

[0056] In trial (H), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the second roasting reaction is carried out at a temperature of 650 C. for a time period of 2 hours. The obtained second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution (3 M to 6 M) at a temperature of 80 C. for a time period of 3 hours. Undissolved second vanadium-containing mixture is collected, and the solubility of the second vanadium-containing mixture in the second aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00008 TABLE 8 Sulfuric acid concentration of the second aqueous sulfuric acid solution for dissolving the Solubility of the second second vanadium-containing vanadium-containing Group mixture mixture H1 3M 85.8% H2 4M 95.8% H3 5M 99.8% H4 6M 99.9%

[0057] Referring to TABLE 8, the second vanadium-containing mixture can be effectively dissolved in the second aqueous sulfuric acid with a sulfuric acid concentration of from 3M to 6 M at a temperature of 80 C. for a time period of 4 hours (groups H1 to H4), among which the second vanadium-containing mixture shows a better solubility in the second aqueous sulfuric acid solution with a sulfuric acid concentration of from 4 M to 6 M (groups H2 to H4, the solubility of the second vanadium-containing mixture reaches equal to or greater than 90%), and the second vanadium-containing mixture shows the best solubility in the second aqueous sulfuric acid solution with a sulfuric acid concentration of from 5 M to 6 M (groups H3 to H4, the solubility of the second vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, the second aqueous sulfuric acid solution with a sulfuric acid concentration of 5 M shows the best result (group H3).

Trial (I).

[0058] In trial (I), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the second roasting reaction is carried out at a temperature of 650 C. for a time period of 2 hours. The obtained second vanadium-containing mixture is dissolved in the first aqueous sulfuric acid solution (5 M) at a temperature of from 60 C. to 90 C. for a time period of 3 hours. Undissolved second vanadium-containing mixture is collected, and the solubility of the second vanadium-containing mixture in the second aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00009 TABLE 9 Temperature for Solubility of the dissolving the second second vanadium-containing vanadium-containing Group mixture mixture I1 60 C. 90.5% I2 70 C. 95.8% I3 80 C. 99.8% I4 90 C. 99.8%

[0059] Referring to TABLE 9, the second vanadium-containing mixture can be effectively dissolved in the second aqueous sulfuric acid solution at a temperature of from 60 C. to 90 C. for a time period of 3 hours (groups I1 to I4), among which the second vanadium-containing mixture shows a better solubility at a temperature of from 80 C. to 90 C. (groups I3 to I4, the solubility of the second vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, 80 C. shows the best result (group I3).

Trial (J).

[0060] In trial (J), ammonium trioxovanadate (V) (NH.sub.4VO.sub.3; 1,000 grams) is placed in a closed reduction furnace, and the second roasting reaction is carried out at a temperature of 650 C. for a time period of 2 hours. The obtained second vanadium-containing mixture is dissolved in the second aqueous sulfuric acid solution (5 M) at a temperature of 80 C. for a time period of from 1 hour to 4 hours. Undissolved second vanadium-containing mixture is collected, and the solubility of the second vanadium-containing mixture in the second aqueous sulfuric acid solution is calculated, accordingly.

TABLE-US-00010 TABLE 10 Time for dissolving Solubility of the the second second vanadium-containing vanadium-containing Group mixture mixture J1 1 hour.sup. 86.6% J2 2 hours 93.2% J3 3 hours 99.8% J4 4 hours 99.9%

[0061] Referring to TABLE 10, the second vanadium-containing mixture can be effectively dissolved in the second aqueous sulfuric acid with a sulfuric acid concentration of 5 M at a temperature of 80 C. for a time period of from 1 hour to 4 hours (groups J1 to J5), among which the second vanadium-containing mixture shows a better solubility for a time period of from 2 hours to 4 hours (groups J2 to J4, the solubility of the second vanadium-containing mixture reaches equal to or greater than 90%), and the second vanadium-containing mixture shows the best solubility for a time period of from 3 hours to 4 hours (groups J3 to J4, the solubility of the second vanadium-containing mixture reaches equal to or greater than 99%). Taking the cost and error range into consideration, 3 hours show the best result (group J3).

Trial (K).

[0062] According to the results of aforementioned trials, in trial (K), the first vanadium-containing solution of group D3 (with 65.0% of vanadium (III) ion (V.sup.3+) and 35.0% of vanadium (IV) ion (V.sup.4+), and thus the average valence of the vanadium ion is 3.350) and the second vanadium-containing solution of group I3 (with 99.7% of vanadium (IV) ion (V.sup.4+) and 0.3% of vanadium (V) ion (V.sup.5+), and thus the average valence of the vanadium ion is 4.003) are used.

[0063] The second vanadium-containing solution of group I3 as the adjusting solution is added to 1,000 mL of the first vanadium-containing solution of group D3. After adding 298 mL of the second vanadium-containing solution of group I3, the obtained mixture has the average valence of the vanadium ion of approximately 3.5 by redox titration, indicating that the vanadium electrolyte with the molar ratio of vanadium (III) ion (V.sup.3+) and vanadium (IV) ion (V.sup.4+) of approximately 1:1 can be obtained by the method for manufacturing the vanadium electrolyte.

[0064] Accordingly, in the method for manufacturing the vanadium electrolyte according to the present invention, by the use of ammonium trioxovanadate (V) (NH.sub.4VO.sub.3), which is cheaper than vanadium (V) oxide (V.sub.2O.sub.5), vanadium (IV) oxide (V.sub.2O.sub.4) and/or vanadium (III) oxide (V.sub.2O.sub.3) can be formed by the reduction roasting reaction. Vanadium (IV) oxide (V.sub.2O.sub.4) and/or vanadium (III) oxide (V.sub.2O.sub.3) can be further dissolved in the aqueous sulfuric acid solution to form the vanadium electrolyte. As such, the manufacturing cost of the vanadium electrolyte can be reduced.

[0065] Moreover, in the method for manufacturing the vanadium electrolyte according to the present invention, vanadium (V) oxide (V.sub.2O.sub.5) formed by heating ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) can be reduced by ammonia gas (NH.sub.3(g)) formed by heating ammonium trioxovanadate (V) (NH.sub.4VO.sub.3) as the reducing agent, and thus, no additional reducing agent is required in the method for manufacturing the vanadium electrolyte according to the present invention. Therefore, it is possible to avoid the impurities caused by the addition of additional reducing agents, and thereby improving the quality of the vanadium electrolyte.

[0066] Although the invention has been described in detail with reference to its presently preferable embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.