Electrochemical cells comprising porous structures comprising sulfur
The present invention relates to the use of porous structures comprising sulfur in electrochemical cells. Such materials may be useful, for example, in forming one or more electrodes in an electrochemical cell. For example, the systems and methods described herein may comprise the use of an electrode comprising a conductive porous support structure and a plurality of particles comprising sulfur (e.g., as an active species) substantially contained within the pores of the support structure. The inventors have unexpectedly discovered that, in some embodiments, the sizes of the pores within the porous support structure and/or the sizes of the particles within the pores can be tailored such that the contact between the electrolyte and the sulfur is enhanced, while the electrical conductivity and structural integrity of the electrode are maintained at sufficiently high levels to allow for effective operation of the cell. Also, the sizes of the pores within the porous support structures and/or the sizes of the particles within the pores can be selected such that any suitable ratio of sulfur to support material can be achieved while maintaining mechanical stability in the electrode. The inventors have also unexpectedly discovered that the use of porous support structures comprising certain materials (e.g., metals such as nickel) can lead to relatively large increases in cell performance. In some embodiments, methods for forming sulfur particles within pores of a porous support structure allow for a desired relationship between the particle size and pore size. The sizes of the pores within the porous support structure and/or the sizes of the particles within the pores can also be tailored such that the resulting electrode is able to withstand the application of an anisotropic force, while maintaining the structural integrity of the electrode.
1. An electrode for use in an electrochemical cell, comprising:
a polymeric porous support structure comprising a plurality of pores; and
an electrode active material comprising sulfur substantially contained within the pores of the polymeric porous support structure, wherein
each pore of the plurality of pores has a pore volume, and the plurality of pores has a total pore volume defined by the total of each of the individual pore volumes; and
at least about 50% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 micron and about 10 microns, and
the polymeric porous support structure comprises at least one of a polyvinyl alcohol, a phenolic resin, lithium polystyrenesulfonate, an epoxy, UHMWPE, PTFE, PVDF, a PTFE/vinyl copolymer, and co-polymers/block co-polymers of these.
2. An electrode for use in an electrochemical cell, comprising:
a polymeric porous support structure comprising a plurality of pores; and
an electrode active material comprising sulfur substantially contained within the pores of the polymeric porous support structure, wherein
the plurality of pores of the polymeric porous support structure together define a total pore volume, and at least about 50% of the total pore volume is defined by pores having cross-sectional diameters of between about 1 micron and about 10 microns, and
the polymeric porous support structure comprises at least one of a polyvinyl alcohol, a phenolic resin, lithium polystyrenesulfonate, an epoxy, UHMWPE, PTFE, PVDF, a PTFE/vinyl copolymer, and co-polymers/block co-polymers of these.
3. An electrode as in claim 2 , wherein the standard deviation of the maximum cross-sectional dimensions of particles comprising an electrode active material comprising sulfur is less than about 50% of the average cross-sectional diameter of the plurality of pores.
4. An electrode as in claim 1 , wherein the standard deviation of the cross-sectional diameters of the pores is less than about 50% of the average cross-sectional diameter of the plurality of pores.
5. An electrode as in claim 1 , wherein the porous support structure comprises an electrically conductive polymer.
6. An electrode as in claim 1 , wherein the porous support structure comprises an electrically conductive material in addition to the polymeric material.
7. An electrode as in claim 6 , wherein the porous support structure comprises an electrically conductive material embedded into the bulk of the polymeric material.
8. An electrode as in claim 6 , wherein an electrically conductive material is deposited within the pores of the porous support structure.
9. An electrode as in claim 6 , wherein the electrically conductive material comprises at least one of carbon and a metal.
10. An electrode as in claim 1 , wherein the sulfur comprises at least one of elemental sulfur, polymeric sulfur, inorganic sulfides, inorganic polysulfides, organic sulfides, organic polysulfides, and sulfur organic compounds.
11. An electrode as in claim 10 , wherein the sulfur comprises elemental sulfur.
12. An electrode as in claim 1 , wherein the electrode comprises at least about 20 wt % sulfur.
13. An electrode as in claim 1 , wherein the electrode active material occupies at least about 10% of the accessible pore volume of the porous support structure.
14. An electrode as in claim 1 , wherein the electrode has a void volume of at least about 1 cm 3 per gram of sulfur.
15. An electrode as in claim 1 , wherein an electrochemical cell comprising the electrode is capable of utilizing at least about 65% of the total sulfur in the cell through at least 1 charge and discharge cycles subsequent to a first charge and discharge cycle, wherein 100% utilization corresponds to 1672 mAh per gram of sulfur in the electrode.
16. An electrode as in claim 1 , wherein an electrochemical cell comprising the electrode is capable of utilizing at least about 65% of the total sulfur in the cell through at least 10 charge and discharge cycles subsequent to a first charge and discharge cycle, wherein 100% utilization corresponds to 1672 mAh per gram of sulfur in the electrode.
17. An electrode as in claim 1 , wherein an electrochemical cell comprising the electrode is capable of achieving a current density of at least about 100 mA per gram of sulfur in the electrode during at least one charge and discharge cycle subsequent to a first charge and discharge cycle.
18. An electrode as in claim 1 , wherein an electrochemical cell comprising the electrode is capable of achieving a current density of at least about 100 mA per gram of sulfur in the electrode during at least 10 charge and discharge cycles subsequent to a first charge and discharge cycle.
19. An electrode as in claim 1 , wherein the porous support structure comprises a porous continuous structure.
20. An electrode as in claim 19 , wherein the maximum cross-sectional dimension of the porous continuous structure within the electrode is at least about 50% of the maximum cross sectional dimension of the electrode.
21. An electrode as in claim 1 , wherein:
the electrode has an external surface area,
at least about 50% of the external surface area defines a uniform area with a first average concentration of sulfur, and
any continuous area that covers about 10% of the uniform area of the external surface includes a second average concentration of sulfur that varies by less than about 25% relative to the first average concentration of sulfur across the uniform area.
22. An electrode as in claim 1 , wherein:
the electrode has an external surface area,
at least about 50% of the external surface area defines a first, continuous area of essentially uniform sulfur distribution, and the first area has a first average concentration of sulfur, and
any continuous external surface area that covers about 10% of the first, continuous area of the external surface includes a second average concentration of sulfur that varies by less than about 25% relative to the first average concentration of sulfur across the uniform area.
23. An electrode as in claim 1 , wherein:
the electrode has a thickness and a cross-section substantially perpendicular to the thickness,
at least about 50% of the cross-section defines a uniform area with a first average concentration of sulfur, and
any continuous area that covers about 10% of the uniform area of the cross-section includes a second average concentration of sulfur that varies by less than about 25% relative to the first average concentration of sulfur across the uniform area.
24. An electrode as in claim 1 , wherein at least about 70% of the total volume occupied by particles comprising an electrode active material comprising sulfur is occupied by particles having maximum cross-sectional dimensions of between about 0.1 microns and about 10 microns.
25. An electrode as in claim 1 , wherein at least about 80% of the total volume occupied by particles comprising an electrode active material comprising sulfur is occupied by particles having maximum cross-sectional dimensions of between about 0.1 microns and about 10 microns.
26. An electrode as in claim 1 , wherein at least about 70% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 microns and about 10 microns.
27. An electrode as in claim 1 , wherein at least about 80% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 microns and about 10 microns.
28. An electrode as in claim 1 , wherein the electrode contains less than about 20 wt % binder.
29. An electrode as in claim 1 , wherein the ratio of the average maximum cross-sectional dimension of the particles of material within the porous support structure to the average cross-sectional diameter of the pores within the porous support structure is between about 0.001:1 and about 1:1.
30. An electrochemical cell comprising an electrode as in claim 1 and an electrolyte, wherein the ratio of electrolyte to sulfur, by mass, within the electrochemical cell is less than about 6:1.
31. An electrochemical cell as in claim 30 , wherein the ratio of electrolyte to sulfur, by mass, within the electrochemical cell is less than about 5:1.
32. An electrochemical cell as in claim 30 , wherein the ratio of electrolyte to sulfur, by mass, within the electrochemical cell is less than about 4:1.
33. An electrochemical cell as in claim 30 , wherein the ratio of electrolyte to sulfur, by mass, within the electrochemical cell is less than about 3:1.
34. An electrochemical cell as in claim 30 , wherein the ratio of electrolyte to sulfur, by mass, within the electrochemical cell is less than about 2:1.
35. An electrode as in claim 6 , wherein the porous support structure is at least partially coated with the electrically conductive material.
36. An electrode as in claim 1 , wherein at least about 50% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 micron and about 3 microns.
37. An electrode as in claim 1 , wherein at least about 70% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 micron and about 3 microns.
38. An electrode as in claim 1 , wherein at least about 80% of the total pore volume is occupied by pores having cross-sectional diameters of between about 1 micron and about 3 microns.
39. An electrode as in claim 1 , wherein the electrode contains less than about 1 wt % binder.
40. An electrode as in claim 1 , wherein the electrode contains less than about 0.1 wt % binder.
41. An electrode for use in an electrochemical cell, comprising:
a polymeric porous support structure comprising a plurality of pores; and
an electrode active material comprising sulfur substantially contained within the pores of the polymeric porous support structure, wherein
each pore of the plurality of pores has a pore volume, and the plurality of pores has a total pore volume defined by the total of each of the individual pore volumes;
at least about 50% of the total pore volume is occupied by pores having cross-sectional diameters of between about 0.1 microns and about 10 microns;
the polymeric porous support structure is at least partially coated with an electrically conductive material, the polymeric material of the porous support structure is electrically conductive, and/or the porous support structure comprises an electrically conductive material embedded into the bulk of the polymeric material; and
the polymeric porous support structure comprises at least one of a polyvinyl alcohol, a phenolic resin, lithium polystyrenesulfonate, an epoxy, UHMWPE, PTFE, PVDF, a PTFE/vinyl copolymer, and co-polymers/block co-polymers of these.
42. An electrode as in claim 41 , wherein the porous support structure comprises a porous continuous structure.
43. An electrode as in claim 41 , wherein the sulfur comprises elemental sulfur.
44. An electrode for use in an electrochemical cell, comprising:
a polymeric porous support structure comprising a plurality of pores, wherein the bulk of the porous support structure is polymeric; and
an electrode active material comprising sulfur substantially contained within the pores of the polymeric porous support structure, wherein
each pore of the plurality of pores has a pore volume, and the plurality of pores has a total pore volume defined by the total of each of the individual pore volumes;
at least about 50% of the total pore volume is occupied by pores having cross-sectional diameters of between about 0.1 microns and about 10 microns; and
the polymeric porous support structure comprises at least one of a polyvinyl alcohol, a phenolic resin, lithium polystyrenesulfonate, an epoxy, UHMWPE, PTFE, PVDF, a PTFE/vinyl copolymer, and co-polymers/block co-polymers of these.
45. An electrode as in claim 44 , wherein the porous support structure comprises a porous continuous structure.
46. An electrode as in claim 44 , wherein the sulfur comprises elemental sulfur.
47. An electrode as in claim 1 , wherein the polymeric porous support structure comprises polyvinyl alcohol.
48. An electrode as in claim 1 , wherein the polymeric porous support structure comprises an epoxy.
49. An electrode as in claim 2 , wherein the polymeric porous support structure comprises polyvinyl alcohol.
50. An electrode as in claim 2 , wherein the polymeric porous support structure comprises an epoxy.
51. An electrode as in claim 41 , wherein the polymeric porous support structure comprises polyvinyl alcohol.
52. An electrode as in claim 41 , wherein the polymeric porous support structure comprises an epoxy.
53. An electrode as in claim 44 , wherein the polymeric porous support structure comprises polyvinyl alcohol.
54. An electrode as in claim 44 , wherein the polymeric porous support structure comprises an epoxy.