Lithium recovery from lithium salts dissolved in ionic liquids

Abstract

Described herein are methods for recovering lithium metal, lithium hydride, or lithium hydroxide from lithium salts by dissolving the lithium salt in ionic liquids and applying a current to the solution.

What is claimed: 
     
         1 . A method for recovering lithium, comprising:
 combining a lithium salt and a nonaqueous acid to form a composition comprising the lithium salt and the nonaqueous acid, wherein the lithium salt and the nonaqueous acid are combined in water and then dehydrated prior to adding the ionic liquid;   adding an ionic liquid to the composition to form an ionic liquid composition; and   applying a potential to the ionic liquid composition to deposit lithium onto an electrode.   
     
     
         2 . The method of  claim 1 , wherein the ionic liquid composition is sparged with an inert gas to remove water and CO 2  from the ionic liquid composition. 
     
     
         3 . The method of claim  3 , where the inert gas is selected from argon, helium, neon, krypton, and xenon. 
     
     
         4 . The method of  claim 1 , wherein the lithium salt is Li 2 CO 3 , LiCl, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , or LiCF 3 SO 3 , or combinations thereof. 
     
     
         5 . The method of  claim 1 , wherein the lithium concentration in the ionic liquid comprises about 0.1 M, 0.25 M, 0.5 M, 0.75 M, 1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M, 4.0 M, 4.5 M, 5.0 M, 5.5 M, 6.0 M, 6.5 M, or 7.0 M. 
     
     
         6 . The method of  claim 1 , wherein the anion of the ionic liquid and the anion of the nonaqueous acid comprise the same anionic moiety. 
     
     
         7 . The method of  claim 1 , wherein the nonaqueous acid is n-bis(trifluoromethanesulfonylimide) acid (HTFSI). 
     
     
         8 . The method of  claim 1 , wherein the ionic liquid comprises an n-bis(trifluoromethanesulfonylimide) (TFSI) anion. 
     
     
         9 . The method of  claim 1 , wherein the ionic liquid comprises a cation that does not undergo reductive decomposition at a potential between −2.5 and −4.5 V. 
     
     
         10 . The method of  claim 1 , wherein the ionic liquid comprises a cation selected from the group consisting of alkyl-substituted or unsubstituted ammonium cations; alkyl-substituted or unsubstituted piperidinium cations; or alkyl-substituted or unsubstituted pyrrolidinium cations. 
     
     
         11 . The method of  claim 1 , wherein the ionic liquid comprises a cation selected from the group consisting of a tetraalkylammonium cation, a dialkylpiperidinium cation, and a dialkylpyrrolidinium cation. 
     
     
         12 . The method of  claim 1 , wherein the ionic liquid comprises a cation selected from the group consisting of a butyltrimethylammonium cation; a 1-methyl-1-propylpiperidinium cation, and a 1-methyl-1-propylpyrrolidinium cation. 
     
     
         13 . The method of  claim 1 , wherein the applied potential is between −3.2 and −4.0 volts. 
     
     
         14 . The method of  claim 1 , wherein the applied potential is pulsed. 
     
     
         15 . The method of  claim 1 , wherein the applied potential is constant. 
     
     
         16 . The method of  claim 1 , wherein the lithium is deposited as lithium metal, lithium hydride, or lithium hydroxide. 
     
     
         17 . The method of  claim 1 , wherein the electrode comprises carbon or gold.