Redox shuttles for high voltage cathodes

1. An electrolyte comprising:

an alkali metal salt;

a polar aprotic solvent; and

a redox shuttle;

wherein:

the redox shuttle comprises an aromatic compound represented by Formula I, II, III, or IV:

wherein:

R 1 , R 2 , R 3 , and R 4 are independently H, a alkyl group, a phosphate group, or a polyether group; or R 1 and R 4 are individually an alkyl group, and R 2 and R 3 are H or F; or R 1 and R 3 are individually an alkyl group, and R 2 and R 4 are H or F; or R 1 and R 2 , or R 2 and R 3 ; or R 3 and R 4 join together to form a fused ring on the benzene ring;

X and Y are independently a group of Formula (A):

Z is a group of Formula (B):

R 5 and R 6 are independently H, F, Cl, Br, CN, NO 2 alkyl, a haloalkyl, phosphate, or polyether;

R 7 and R 8 are independently H, F, Cl, Br, CN, NO 2 , alkyl, alkoxy, haloalkyl, haloalkoxy, aryl, aryloxy, haloaryl, haloaryloxy, or polyether;

R 9 is H, F, Cl, Br, CN, NO 2 , alkyl, alkoxy, haloalkyl, haloalkoxy, aryl, aryloxy, haloaryl, haloaryloxy, or polyether;

n is an integer from 0 to 8; and

p is 0 or 1;

with the proviso that where n is 0, p is 0, and where n is from 1 to 8, p is 0 or 1;

and

the electrolyte is substantially non-aqueous.

2. The electrolyte of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 are independently H, a alkyl group, or a polyether group.

3. The electrolyte of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 are independently H, or a C 1 -C 4 alkyl group.

4. The electrolyte of claim 1 , wherein R 1 and R 4 are the same and are different from that of R 2 and R 3 .

5. The electrolyte of claim 1 , wherein R 1 and R 3 are the same and are different from that of R 2 and R 4 .

6. The electrolyte of claim 1 , wherein R 1 and R 4 are individually an alkyl group, and R 2 and R 3 are H.

7. The electrolyte of claim 1 , wherein R 1 and R 4 are individually methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, or tert-butyl.

8. The electrolyte of claim 1 , wherein R 1 and R 3 are individually an alkyl group, and R 2 and R 4 are H.

9. The electrolyte of claim 1 , wherein R 1 and R 3 are individually methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, or tert-butyl.

10. The electrolyte of claim 1 , where the redox shuttle comprises:

11. The electrolyte of claim 1 , wherein the redox shuttle has a redox potential of 4 to 5 V in the electrolyte.

12. The electrolyte of claim 1 , wherein the redox shuttle has two, three or four oxygen atoms.

13. The electrolyte of claim 1 , wherein a concentration of the redox shuttle in the electrolyte is from 0.0005 wt % to 50 wt %.

14. The electrolyte of claim 1 , wherein the alkali metal salt comprises a lithium salt.

15. The electrolyte of claim 14 , wherein the alkali metal salt comprises Li[(C 2 O 4 ) 2 B], Li(C 2 O 4 )BF 2 , LiClO 4 , LiBF 4 , LiAsF 6 , LiPF 6 , LiCF 3 SO 3 , Li(CF 3 SO 2 ) 2 N, Li(CF 3 SO 2 ) 3 C, LiN(SO 2 C 2 F 5 ) 2 , or a lithium alkyl fluorophosphate.

16. The electrolyte of claim 1 , wherein the polar aprotic solvent comprises ethylene carbonate, propylene carbonate, dimethyl carbonate; ethyl methyl carbonate; diethyl carbonate; methyl propyl carbonate; ethyl propyl carbonate; dipropyl carbonate; bis(trifluoroethyl)carbonate; bis(pentafluoropropyl)carbonate; trifluoroethyl methyl carbonate; pentafluoroethyl methyl carbonate; heptafluoropropyl methyl carbonate; perfluorobutyl methyl carbonate; trifluoroethyl ethyl carbonate; pentafluoroethyl ethyl carbonate; heptafluoropropyl ethyl carbonate; perfluorobutyl ethyl carbonate; fluorinated oligomers; dimethoxyethane; triglyme; dimethylvinylene carbonate; tetraethyleneglycol; dimethyl ether; polyethylene glycols; sulfones; or γ-butyrolactone.

17. An electrochemical device comprising

a cathode

an anode; and

an electrolyte comprising:

an alkali metal salt;

a polar aprotic solvent; and

a redox shuttle;

wherein:

the redox shuttle comprises an aromatic compound represented by Formula I, II, III, or IV:

wherein:

R 1 , R 2 , R 3 , and R 4 are independently H, a alkyl group, a phosphate group, or a polyether group; or R 1 and R 4 are individually an alkyl group, and R 2 and R 3 are H or F; or R 1 and R 3 are individually an alkyl group, and R 2 and R 4 are H or F; or R 1 and R 2 , or R 2 and R 3 ; or R 3 and R 4 join together to form a fused ring on the benzene ring;

X and Y are independently a group of Formula (A):

Z is a group of Formula (B):

R 5 and R 6 are independently H, F, Cl, Br, CN, NO 2 alkyl, a haloalkyl, phosphate, or polyether;

R 7 and R 8 are independently H, F, Cl, Br, CN, NO 2 , alkyl, alkoxy, haloalkyl, haloalkoxy, aryl, aryloxy, haloaryl, haloaryloxy, or polyether;

R 9 is H, F, Cl, Br, CN, NO 2 , alkyl, alkoxy, haloalkyl, haloalkoxy, aryl, aryloxy, haloaryl, haloaryloxy, or polyether;

n is an integer from 0 to 8; and

p is 0 or 1;

with the proviso that where n is 0, p is 0, and where n is from 1 to 8, p is 0 or 1; and

the electrolyte is substantially non-aqueous.

18. A compound which is: