Electrochemical cell

1. An electrochemical cell comprising:

a cathode, wherein the cathode comprises a cathode formulation comprising a cathode active material, a conductive carbon filler, and a binder, wherein the cathode formulation is disposed on a cathode current collector;

an anode, wherein the anode comprises at least one lithium metal foil disposed on an anode current collector;

a header comprising a stepped header comprising a first step and a second step, and a first opening, a second opening, and a third opening, wherein

an upper surface of the first step is disposed directly on a lower surface of the header and an upper surface of the second step is disposed directly on a lower surface of the first step,

the first opening has a length extending from an upper surface of the header, through a thickness of the header and a thickness of the first step, and to a bottom surface of the first step,

the first opening in the first step is configured for a ball seal,

the second opening and the third opening each have a length extending from an upper surface of the header, through the thickness of the header, the thickness of the first step, and a thickness of the second step, and to a bottom surface of the second step, wherein a first terminal pin for connection to a cathode tab portion extends through the length of the second opening and a second terminal pin for connection to an anode tab portion extends through the length of the third opening, and

the second opening and the third opening in the second step are configured for a glass seal; and

an electrolyte, wherein the electrolyte comprises a lithium salt in a mixed solvent;

wherein the electrochemical cell has an internal volume including an electrode, a separator, an electrolyte volume, and a void volume, and the electrolyte volume is in the range of 38 percent to 46 percent of the internal volume, and

wherein the electrochemical cell has a swelling percentage of less than or equal to about 2 percent.

2. The electrochemical cell of claim 1 , wherein the cathode active material is CF x , conductive carbon filler is carbon black, and binder is polytetrafluoroethylene in a ratio of about 90:6:4.

3. The electrochemical cell of claim 1 , wherein the cathode active material is blended with the binder and the conductive carbon filler to form a pellet, and the pellet is disposed on the cathode current collector.

4. The electrochemical cell of claim 1 , wherein the cathode current collector comprises perforations.

5. The electrochemical cell of claim 4 , wherein the perforations comprise large circles and small circles and wherein the average diameter for the large circles is about 2.4 mm and the average diameter for the small circles is about 1.9 mm.

6. The electrochemical cell of claim 4 , wherein a ratio of area comprising the perforations to a whole area of the cathode current collector is about 0.6.

7. The electrochemical cell of claim 1 , wherein the cathode current collector has a thickness of about 0.6 to 0.8 mm.

8. The electrochemical cell of claim 1 , wherein the cathode current collector is coated with conductive carbon.

9. The electrochemical cell of claim 8 , wherein the conductive carbon coating has a thickness of about 0.080 mm.

10. The electrochemical cell of claim 1 , wherein the anode current collector comprises perforations, wherein the perforations comprise a diamond shape, a circle, an oval, a rectangle, a star, a triangle, and combinations thereof.

11. The electrochemical cell of claim 10 , wherein ratio of a perforated area to a total area of the anode current collector is about 0.6.

12. The electrochemical cell of claim 1 , wherein the anode current collector has a thickness of about 0.050 mm.

13. The electrochemical cell of claim 1 , wherein a ratio of an amount of electrolyte to an amount of cathode active material is in a range of about 0.7 to 1.1.

14. The electrochemical cell of claim 1 , wherein a ratio of an amount of electrolyte to an amount of cathode active material is 0.93.

15. The electrochemical cell of claim 1 , wherein the first step has a thickness of about 1.1 mm and the second step has a thickness of about 1.5 mm.

16. The electrochemical cell of claim 1 , wherein the lithium salt is present in an amount in a range of about 0.8 moles per liter to about 1.2 moles per liter based on a total volume of the solvent in the electrolyte.

17. An implantable device comprising:

the electrochemical cell of claim 1 , wherein

a ratio of an amount of electrolyte to an amount of cathode active material is about 0.93.

18. The electrochemical cell of claim 1 , wherein the electrolyte volume is in the range of about 40 percent to about 44 percent of the internal volume.

19. The electrochemical cell of claim 1 , wherein the electrolyte volume is in the range of about 41 percent to about 43 percent of the internal volume.

20. The electrochemical cell of claim 1 , wherein the electrolyte volume is about 42 percent of the internal volume.

21. The electrochemical cell of claim 1 , wherein the void volume is in the range of about 3 percent to about 9 percent of the internal volume.

22. The electrochemical cell of claim 1 , wherein the void volume is in the range of about 4 percent to about 8 percent of the internal volume.

23. The electrochemical cell of claim 1 , wherein the void volume is in the range of about 5 percent to about 7 percent of the internal volume.

24. The electrochemical cell of claim 1 , wherein the void volume is about 6 percent of the internal volume.

25. The electrochemical cell of claim 1 , wherein the length of the first step is less than a length of the header, and a length of the second step is less than a length of the first step.

26. The electrochemical cell of claim 1 , wherein the entire upper surface of the first step is disposed directly on the lower surface of the header and the entire upper surface of the second step is disposed directly on a lower surface of the first step.