Electrode structure and method for making same
Electrode structures and methods for making the same are generally described. In certain embodiments, the electrode structures can include a plurality of particles, wherein the particles comprise indentations relative to their convex hulls. As the particles are moved proximate to or in contact with one another, the indentations of the particles can define pores between the particles. In addition, when particles comprising indentations relative to their convex hulls are moved relative to each other, the presence of the indentations can ensure that complete contact does not result between the particles (i.e., that there remains some space between the particles) and that void volume is maintained within the bulk of the assembly. Accordingly, electrodes comprising particles with indentations relative to their convex hulls can be configured to withstand the application of a force to the electrode while substantially maintaining electrode void volume (and, therefore, performance). Particles having indentations relative to their convex hulls also occupy a relatively small volume, compared to spheres or other particles including boundaries that fill substantially all of their convex hulls, allowing one to introduce a desired amount of void volume while reducing the percentage of volume within the electrode occupied by particulate material.
1. An electrode for use in an electrochemical cell, comprising:
an assembly of particles defining a porous support structure, wherein:
each particle in the assembly of particles has a geometric particle volume,
the assembly of particles has a total geometric particle volume defined by the sum of each of the individual geometric particle volumes,
each particle in the assembly of particles has a convex hull defining a convex hull volume, and
at least about 50% of the total geometric particle volume is made up of particles that have at least one indentation such that, for each such particle, the geometric particle volume is less than about 75% of the convex hull volume of the particle; and
an electrode active material substantially contained within pores of the porous support structure.
2. The electrode of claim 1 , wherein, when a compressive force defining a pressure of at least about 20 Newtons/cm 2 is applied to the electrode, the void volume of the porous support structure does not change by more than about 25% relative to the void volume of the porous support structure before the force was applied but under otherwise essentially identical conditions.
3. The electrode of claim 1 , wherein at least about 75% of the total geometric particle volume is made up of particles that are shaped such that, for each particle, the geometric practice volume is less than about 75% of the convex hull volume.
4. The electrode of claim 1 , wherein the electrode active material comprises sulfur.
5. The electrode of claim 4 , wherein the sulfur comprises elemental sulfur, polymeric sulfur, an inorganic sulfide, an inorganic polysulfide, an organic sulfide, an organic polysulfide, and/or a sulfur organic compound.
6. The electrode of claim 1 , wherein at least a portion of the particles comprise an electrically conductive material.
7. The electrode of claim 6 , wherein the electrically conductive material comprises carbon and/or a metal.
8. The electrode of claim 1 , 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 sum of each of the individual pore volumes; and
at least about 50% of the total pore volume is defined by pores having cross-sectional diameters of between about 0.1 micrometers and about 10 micrometers.
9. The electrode of claim 1 , wherein at least a portion of the particles within the assembly are adhered to another particle via a binder and/or at least a portion of the particles within the assembly are fused to another particle.
10. The electrode of claim 1 , wherein at least a portion of the particles are substantially in the shape of a spherical cap.
11. The electrode of claim 1 , wherein at least a portion of the particles comprise at least three valence points.
12. The electrode of claim 1 , wherein the porous support structure has a total porosity percentage of at least about 50%.
13. An electrochemical cell comprising the electrode of claim 1 .
14. The electrochemical cell of claim 13 , wherein the electrochemical cell comprises a second electrode comprising lithium.
15. The electrochemical cell of claim 14 , wherein the second electrode comprises lithium metal and/or a lithium alloy.