Electrochemically stable onium salts and electrolytes containing such for electrochemical capacitors

Abstract

Based on the discovery that the melting point and solubility of onium salts are affected by the asymmetry of the substitution on cation, and that the branched substituents effectively shield onium cations from electrochemical reduction, new onium salts are synthesized and high performance electrolytes based on these salts for electrochemical capacitor are provided. The composition of the new electrolyte comprises an onium salt or mixture of such onium salts dissolved in aprotic, non-aqueous solvents or mixture of such solvents. The electrolyte is able to perform at high rate of charge/discharge, at low ambient temperatures, and within wide operating voltage, due to the high solubility, low melting temperature, and the improved reduction stability of the new onium cations, respectively.

1 - 14 . (Cancelled)  
     
     
         15 . An Asymmetric onium salt comprising an onium cation and an anion, and wherein said onium cation is selected from the group consisting of onium cations having the structure (I):  
       
         
           
           
               
               
           
         
       
       wherein the central atom group X is selected from the following compounds of Lewis base nature: heterocyclic organic bases; nitrile (R′—CN); nitroso (R′—NO); nitro (R′—NO 2 ); carbon oxide (CO); azide (R′N 3 ); and R′ and R 1  are different and are substituents independently selected from the groups consisting of (a) C 1 ˜C 10  normal alkyl, (b) C 3 ˜C 10  branched alkyl, (c) C 6 ˜C 12  aryl, (d) C 7 ˜C 15  aralkyl, and (e) C 1 ˜C 10  normal or branched alkyls having functional groups selected from the group consisting of (i) 0˜2n+1 halogens, wherein n is the number of carbon atoms in the substituent, (ii) sulfone, (iii) ether linkage, and (iv) carbonic diester; an onium cation having the structure (II):  
       
         
           
           
               
               
           
         
       
       wherein Y is the central atom bearing the charge, and is an element selected from Groups 15 or 16 of The Periodic Table of the Elements, and R 2 , R 3 , and R 4  are selected from categories (a) through (e) as defined above and at least one of R 2 , R 3  and R 4  is different from the rest; and an onium cation having the structure (III):  
       
         
           
           
               
               
           
         
       
       wherein Z is the central atom bearing the charge, and is an element selected from Group 15 of the Periodic Table of the Elements, and R 5 , R 6 , R 7  and R 8  are selected from categories of (a) through (e) as defined above and at least one of R 5 , R 6 , R 7  and R 8  is different from the rest; and wherein said anion comprises an organic or inorganic anion which is selected from the group consisting of polyhaloaluminate (AlX 4   − , X=F, Cl, Br and I), triflate (CF 3 SO 3   − , Tf − ), bis(trifluoromethane sulfonyl)imide ((CF 3  SO 2 ) 2 N − , Im − ), bis(pentafluoroethane sulfonyl)imide ((C 2 F 5 SO 2 ) 2 N − ), perchlorate (ClO 4   − ), tetrafluoroborate (BF 4   − ), tris(trifluoromethanesulfonyl)methide ((CF 3 SO 2 ) 3 C − , Me − ), hexafluoroarsenate (AsF 6   − ), hexafluorophosphate (PF 6   − ), and mixtures thereof.  
     
     
         16 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium hexafluorophosphate.  
     
     
         17 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium tetrafluoroborate.  
     
     
         18 . The onium salt of  claim 15 , wherein said salt comprises tri (isopropyl)methylammonium hexafluorophosphate.  
     
     
         19 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium hexafluorophosphate.  
     
     
         20 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium hexafluorophosphate.  
     
     
         21 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(iso-propyl)ammonium hexafluorophosphate.  
     
     
         22 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(iso-propyl)ammonium bis(trifluoromethane sulfonyl)imide.  
     
     
         23 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(iso-propyl)ammonium triflate.  
     
     
         24 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium hexafluorophosphate.  
     
     
         25 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium hexafluorophosphate.  
     
     
         26 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium hexafluorophosphate.  
     
     
         27 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium hexafluorophosphate.  
     
     
         28 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium bis(trifluoromethanesulfonyl)imide.  
     
     
         29 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium triflate.  
     
     
         30 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium tetrafluoroborate.  
     
     
         31 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium hexafluoroarsenate.  
     
     
         32 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium hexafluoroantimonate.  
     
     
         33 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium bis(trifluoromethanesulfonyl)imide.  
     
     
         34 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium triflate.  
     
     
         35 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium hexafluoroarsenate.  
     
     
         36 . The onium salt of  claim 15 , wherein said salt comprises methyltripropylammonium hexafluoroantimonate.  
     
     
         37 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-propyl)methylammonium bis(trifluoromethanesulfonyl)imide.  
     
     
         38 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium triflate.  
     
     
         39 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium tetrafluoroborate.  
     
     
         40 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium hexafluoroarsenate.  
     
     
         41 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylammonium hexafluoroantimonate.  
     
     
         42 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium bis(trifluoromethanesulfonyl)imide.  
     
     
         43 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium triflate.  
     
     
         44 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium tetrafluoroborate.  
     
     
         45 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium hexafluoroarsenate.  
     
     
         46 . The onium salt of  claim 15 , wherein said salt comprises tri(n-butyl)methylammonium hexafluoroantimonate.  
     
     
         47 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium bis(trifluoromethanesulfonyl)imide.  
     
     
         48 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium triflate.  
     
     
         49 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium tetrafluoroborate.  
     
     
         50 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium hexafluoroarsenate.  
     
     
         51 . The onium salt of  claim 15 , wherein said salt comprises tri(iso-butyl)methylammonium hexafluoroantimonate.  
     
     
         52 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(iso-propyl)ammonium tetrafluoroborate.  
     
     
         53 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(isopropyl)ammonium hexafluoroarsenate.  
     
     
         54 . The onium salt of  claim 15 , wherein said salt comprises ethylmethyldi(isopropyl)ammonium hexafluoroantimonate.  
     
     
         55 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium bis(trifluoromethanesulfonyl)imide.  
     
     
         56 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium triflate.  
     
     
         57 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium tetrafluoroborate.  
     
     
         58 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium hexafluoroarsenate.  
     
     
         59 . The onium salt of  claim 15 , wherein said salt comprises ethyldimethylsulfonium hexafluoroantimonate.  
     
     
         60 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium bis(trifluoromethanesulfonyl)imide.  
     
     
         61 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium triflate.  
     
     
         62 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium tetrafluoroborate.  
     
     
         63 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium hexafluoroarsenate.  
     
     
         64 . The onium salt of  claim 15 , wherein said salt comprises triethylmethylphosphonium hexafluoroantimonate.  
     
     
         65 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide.  
     
     
         66 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium triflate.  
     
     
         67 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium tetrafluoroborate.  
     
     
         68 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium hexafluoroarsenate.  
     
     
         69 . The onium salt of  claim 15 , wherein said salt comprises tributylmethylphosphonium hexafluoroantimonate.  
     
     
         70 . An electrolyte solution comprising the onium salt of  claim 15  dissolved in a non-aqueous, aprotic solvent.  
     
     
         71 . The electrolyte solution of  claim 70 , wherein said solvent is selected from or is a mixture of the group consisting of: acetonitrile (AN), adipontrile (ADN), butylene carbonate (BC), γ-butyrolactone (γBL), diethylcarbonate (DEC), dimethylcarbonate (DMC), ethyl methylcarbonate (EMC), methyl-iso-propylcarbonate (MiPC), ethylene carbonate (EC), propylene carbonate (PC), chloroethylene carbonate (ClEC), fluoroethylene carbonate (FEC), dichloroethylene carbonate (Cl 2 EC), difluoroethylene carbonate (F 2 EC), perchloroethylene carbonate (Cl 4 EC), perfluoroethylene carbonate (F 4 EC), chloropropylene carbonate (ClPC), fluoropropylene carbonate (FPC), perchloropropylene carbonate (Cl 3 PC), perfluoroethylene carbonate (F 4 EC), dialkylsulfoxide (R—SO—R′), dialkylsulfone (R—SO 2 —R′), sulfolane, alkylsulfite (R—S(O)—OR′), α-disulfones (R—S 2 O 4 —R′), trialkylphosphate, phosphite, and aldehyde.