Structured silicon anode
A silicon/lithium battery can be fabricated from a silicon substrate. This allows the battery to be produced as an integrated unit on a chip. The battery includes a silicon anode formed from sub-micron diameter pillars of silicon fabricated on an n-type silicon wafer. The battery also includes a cathode including lithium.
1. An energy storage device comprising:
an anode comprising an array of sub-micron silicon structures supported on a silicon substrate; and
a cathode comprising lithium, arranged to form a battery.
2. A device according to claim 1 wherein the anode is arranged to tolerate the conditions occasioned by the volume changes caused by charging/discharging of the battery.
3. A device according to claim 1 wherein the anode is arranged to maintain structural integrity throughout the cycling of the battery.
4. A device according to claim 1 wherein the anode is arranged to withstand repeated volume expansion associated with alloying during use of the battery.
5. A device according to claim 1 wherein the array of sub-micron silicon structures comprise an array of sub-micron silicon pillars.
6. A device according to claim 5 wherein the pillars have a surface area of about 4 FH/d times the substrate area wherein F is the surface fractional coverage, H is the height of the pillar and d is the diameter of the pillar.
7. A device according to claim 5 in which the sub-micron pillars do not exceed a fractional coverage of 0.5 of the substrate.
8. A device according to claim 5 wherein the pillars are 0.1 to 1.0 microns in diameter and 1 to 10 microns in height.
9. A device according to claim 5 wherein the pillars are approximately 0.3 microns in diameter and 6 microns in height.
10. A device according to claim 1 in which the substrate comprises n-type silicon.
11. A device according to claim 1 made on a wafer-bonded silicon-on-insulator substrate.
12. A battery including a silicon anode comprising: an array of sub-micron silicon pillars fabricated on a silicon substrate; and a lithium cathode, wherein a compound film is formed on the silicon pillars in a charging step.
13. A battery according to claim 12 wherein the film is a Zintl-Phase Compound.
14. A battery according to claim 12 wherein the compound film is deformable so as not to give rise to significant stress-induced cracking during the volume change in a charging or discharging step.
15. An electrode for a battery comprising sub-micron silicon pillars supported on a silicon substrate and arranged to form a battery with a lithium cathode and a lithium-based electrolyte.