Microstructured electrode structures
A structure for use in an energy storage device, the structure comprising a backbone system extending generally perpendicularly from a reference plane, and a population of microstructured anodically active material layers supported by the lateral surfaces of the backbones, each of the microstructured anodically active material layers having a void volume fraction of at least 0.1 and a thickness of at least 1 micrometer.
1. A secondary battery comprising carrier ions, a non-aqueous electrolyte and at least two electrochemical stacks in a stacked arrangement, the direction of stacking of the at least two electrochemical stacks relative to each other being in a direction that is orthogonal to a reference plane, the carrier ions being lithium, sodium or potassium ions, each of the electrochemical stacks comprising, in a stacked arrangement, cathode structures, current collectors, cathodically active material layers, separator layers, anode current collectors, and a population of microstructured anodically active material layers, the separator layers being disposed between the cathodically active material layers and the members of the population of anodically active material layers, the anode current collectors having an electrical conductance that is substantially greater than the electrical conductance of the microstructured anodically active material layers, the direction of stacking of the cathode current collectors, cathodically active material layers, separator layers, anode current collectors, and microstructured anodically active material layers within each of the at least two electrochemical stacks being parallel to the reference plane, the carrier ions having a direction of travel between the cathodically active material layers and the anodically active materials of each of the at least two electrochemical stacks that is generally parallel to the reference plane as the secondary battery is charged and discharged, the members of the population of microstructured anodically active material layers of each of the at least two electrochemical stacks having a height, H A , of at least 100 micrometers measured in a direction orthogonal to the reference plane, a front surface, a back surface, a thickness, T, measured from the front surface to the back surface, and a void volume fraction of at least 0.1, wherein the front and back surfaces are substantially perpendicular to the reference plane, the thickness, T, is at least 1 micrometer and measured in a direction parallel to the reference plane, and the microstructured anodically active material layers comprise a fibrous or a porous anodically active material, and wherein the lineal distance, D L , between at least two members of the population of microstructured anodically active material layers of each of the at least two electrochemical stacks, measured in a direction parallel to the reference plane, is greater than the maximum value of H A for the population within each such electrochemical stack.
2. The secondary battery of claim 1 wherein the carrier ions are lithium ions.
3. The secondary battery of claim 1 wherein the population comprises at least 20 members.
4. The secondary battery of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.
5. The secondary battery of claim 1 wherein each member of the population comprises silicon or an alloy thereof and has a thickness of about 1 to about 100 micrometers.
6. The secondary battery of claim 1 wherein for each member of the population H A is greater than T.
7. The secondary battery of claim 1 wherein each member of the population comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of about 1 to about 200 micrometers.
8. The secondary battery of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.
9. The secondary battery of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm, and the maximum value of H A for the population is less than 1,000 micrometers.
10. The secondary battery of claim 1 wherein the anode structures comprise an anode current collector, the cathode structures comprise a cathode current collector, and the anode current collector or the cathode current collector comprises an ionically permeable conductor layer.
11. The secondary battery of claim 1 wherein the anode structures comprise an anode current collector layer and the anode current collector layer is disposed between the anodically active material layer and a separator layer.
12. The secondary battery of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.
13. The secondary battery of claim 1 wherein a ratio of the electrical conductance of the anode current collector to the electrical conductance of the microstructured anodically active material layer is at least 100:1.
14. The secondary battery of claim 1 wherein a ratio of the electrical conductance of the anode current collector to the electrical conductance of the microstructured anodically active material layer is at least 500:1.
15. The secondary battery of claim 1 wherein the anode current collector comprises a porous layer of a metal or a metal alloy that does not form an intermetallic compound with lithium.
16. The secondary battery of claim 1 wherein the anode current collector comprises porous copper silicide or porous nickel silicide.
17. The secondary battery of claim 1 wherein the cathode current collectors, cathodically active material layers, separator layers, anode current collectors, and microstructured anodically active material layers are stacked in this order.
18. The secondary battery of claim 1 wherein the cathodically active material layers, cathode current collectors, separator layers, microstructured anodically active material layers and anode current collectors are stacked in this order.
19. The secondary battery of claim 1 wherein the lineal distance, D L , between at least two members of the population of microstructured anodically active material layers of each of the at least two electrochemical stacks, measured in a direction parallel to the reference plane, is greater than the maximum value of H A for the population within each such electrochemical stack, respectively, by a factor of at least 10.
20. The secondary battery of claim 1 wherein each of the electrochemical stacks additionally comprises anode backbones and the anode backbones comprise an anode current collector having an electrical conductivity of at least about 10 4 Siemens/cm.