Controlled porosity in electrodes
Porous electrodes in which the porosity has a low tortuosity are generally provided. In some embodiments, the porous electrodes can be designed to be filled with electrolyte and used in batteries, and can include low tortuosity in the primary direction of ion transport during charge and discharge of the battery. In some embodiments, the electrodes can have a high volume fraction of electrode active material (i.e., low porosity). The attributes outlined above can allow the electrodes to be fabricated with a higher energy density, higher capacity per unit area of electrode (mAh/cm 2 ), and greater thickness than comparable electrodes while still providing high utilization of the active material in the battery during use. Accordingly, the electrodes can be used to produce batteries with high energy densities, high power, or both compared to batteries using electrodes of conventional design with relatively highly tortuous pores.
1. An electrode, comprising:
a matrix material comprising high-tortuosity pores having tortuosities of at least 2; and
a plurality of low-tortuosity pores having tortuosities of less than 1.5 extending through the matrix material and from a first external geometric surface of the electrode to a second external geometric surface of the electrode, wherein:
the electrode has a total porosity of from 20% to 60%, and
the percentage of the total porosity that is occupied by the low-tortuosity pores is from 20% to 80%.
2. The electrode of claim 1 , wherein the electrode has a total porosity of from 29% to 39%, and the percentage of the total porosity that is occupied by the low-tortuosity pores is from 25% to 47%.
3. The electrode of claim 1 , wherein the low-tortuosity pores are substantially straight.
4. The electrode of claim 1 , wherein the first external geometric surface of the electrode is opposed to the second external geometric surface of the electrode.
5. The electrode of claim 1 , wherein the ratio of the thickness of the electrode to the mean pore spacing of the low-tortuosity pores within the electrode is at least 0.2.
6. The electrode of claim 1 , wherein the matrix material comprises an electrode active material.
7. The electrode of claim 6 , wherein the ratio of the thickness of the electrode to the mean pore spacing of the low-tortuosity pores within the electrode is at least 0.2.
8. The electrode of claim 1 , wherein the ratio of the average cross-sectional diameter of the low-tortuosity pores to the mean pore spacing of the low-tortuosity pores is from 0.05 to 1.0.
9. The electrode of claim 1 , wherein the electrode has a total porosity of from 29% to 39%.
10. The electrode of claim 1 , wherein the percentage of the total porosity that is occupied by the low-tortuosity pores is from 25% to 47%.
11. The electrode of claim 1 , wherein the matrix material comprises a ceramic.
12. The electrode of claim 1 , wherein the plurality of low-tortuosity pores have tortuosities of less than 1.2.
13. The electrode of claim 1 , wherein the plurality of low-tortuosity pores have tortuosities of less than 1.1.
14. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 3.
15. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 4.
16. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 5.
17. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 2 and up to 20.
18. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 3 and up to 20.
19. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 4 and up to 20.
20. The electrode of claim 1 , wherein the high-tortuosity pores have tortuosities of at least 5 and up to 20.