Lithium batteries

1. An electrochemical cell comprising:

(a) a solid lithium anode;

(b) a solid cathode comprising an electroactive sulfur-containing material; and

(c) a non-aqueous electrolyte interposed between the anode and the cathode wherein the electrolyte comprises:

(i) one or more lithium salts;

(ii) one or more non-aqueous solvents; and

(iii) one or more capacity-enhancing reactive components;

wherein said capacity-enhancing reactive components comprise an electron transfer mediator selected from the group consisting of the mediator of the formula:

and the mediator of the formula:

wherein:

Z is the same or different at each occurrence and is selected from the group consisting of O, S, Se, and NR 5 , where R 5 is alkyl, aryl, or substituted derivatives thereof;

R is the same or different at each occurrence and is selected from the group consisting of alkyl, aryl, F, Cl, CF 3 , CF 3 SO 2 , and N(R 6 ) 2 , where R 6 is alkyl, aryl, or substituted derivatives thereof;

Y is —C═C— or

t is an integer from 0 to 4; and

u is an integer from 1 to 6.

2. The cell of claim 1 , wherein said electron transfer mediator is present in the amount of 0.2% to 25% by weight of said electrolyte.

3. The cell of claim 1 , wherein said electron transfer mediator has an oxidation-reduction potential less than 2.2 V.

4. The cell of claim 1 , wherein said electron transfer mediator has an oxidation-reduction potential in the range of 1.5 V to about 2.0 V.

5. The cell of claim 1 , wherein said one or more capacity-enhancing reactive components increase the discharge capacity of the first charge-discharge cycle of the cell by greater than 10%.

6. The cell of claim 1 , wherein said one or more capacity-enhancing reactive components increase the total discharge capacities of 30 charge-discharge cycles of the cell by greater than 10%.

7. The cell of claim 1 , wherein said one or more capacity-enhancing reactive components increase the total discharge capacities of 30 charge-discharge cycles of the cell by greater than 30%.

8. The cell of claim 1 , wherein said one or more non-aqueous solvents are selected from the group consisting of ethers, cyclic ethers, polyethers, dioxolanes, sulfones, and sulfolanes.

9. The cell of claim 1 , wherein said one or more lithium salts are selected from the group consisting of LiBr, LiI, LiSCN, LiBF 4 , LiPF 6 , LiAsF 6 , LiSO 3 CF 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , (LiS x ) z R, and Li 2 S x , where x is an integer from 1 to 20, z is an integer from 1 to 3, and R is an organic group.

10. The cell of claim 1 , wherein said electroactive sulfur-containing material comprises elemental sulfur.

11. The cell of claim 1 , wherein the electroactive sulfur-containing material comprises greater than 75% by weight of sulfur.

12. The cell of claim 1 , wherein the lithium anode is selected from the group consisting of lithium metal, lithium-aluminum alloys, lithium-tin alloys, lithium-intercalated carbons, and lithium-intercalated graphites.

13. The cell of claim 1 , wherein the cell has an energy density greater than 1000 Wh/Kg.

14. The cell of claim 1 , wherein the cell is a secondary electrochemical cell.

15. The cell of claim 1 , wherein the cell is a primary electrochemical cell.

16. A method of making an electrochemical cell comprising the steps of:

(a) providing a solid lithium anode;

(b) providing a solid cathode comprising an electroactive sulfur-containing material; and

(c) interposing a non-aqueous electrolyte between the anode and the cathode, wherein the electrolyte comprises:

(i) one or more lithium salts;

(ii) one or more non-aqueous solvents; and

(iii) one or more capacity-enhancing reactive components;

wherein the capacity-enhancing reactive components comprise an electron transfer mediator selected from the group consisting of the mediator of the formula:

and the mediator of the formula:

wherein:

Z is the same or different at each occurrence and is selected from the group consisting of O, S, Se, and NR 5 , where R 5 is alkyl, aryl, or substituted derivatives thereof;

R is the same or different at each occurrence and is selected from the group consisting of alkyl, aryl, F, Cl, CF 3 , CF 3 SO 2 , and N(R 6 ) 2 , where R 6 is alkyl, aryl, or substituted derivatives thereof;

Y is —C═C— or

t is an integer from 0 to 4; and

u is an integer from 1 to 6.