Structured silicon anode

• US 7,842,535 B2
• Filed: 03/04/2008
• Issued: 11/30/2010
• Est. Priority Date: 11/05/2002
• Status: Active Grant

• Current Assignee: Nexeon Limited
• Original Assignee: Nexeon Limited
• Inventors: Green, Mino
• Primary Examiner(s): Smith; Bradley K
• Assistant Examiner(s): Valentine; Jami M
• Application Number:
  US12/074,642
• Publication Number:
  US 20090001936A1
• Time in Patent Office: 1,001 Days
• Field of Search: 257 1- 5, 257/E29.002, 257/701, 257/810, 257/932, 438/95, 438/800, 438/900, 324/252, 428/52, 320/107, 977/948, 977/701, 977/810, 977/932, 429/52
• US Class Current: 438/95
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/1395 of electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 438/90 Bulk effect device making
• CPC Class Codes: Y10S 977/701 Integrated with dissimilar structures on a common substrate
• CPC Class Codes: Y10S 977/81 Of specified metal or metal alloy composition
• CPC Class Codes: Y10S 977/932 for electronic or optoelectronic application
• CPC Class Codes: Y10S 977/948 Energy storage/generating using nanostructure, e.g. fuel cell, battery
• CPC Class Codes: Y10T 29/49108 Electric battery cell making

Abstract

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 submicron diameter pillars of silicon fabricated on an n-type silicon wafer. The battery also includes a cathode including lithium.

Claims

1. A method of fabricating an energy storage device comprising the steps of:

forming an anode comprising an array of sub-micron silicon structures supported on a silicon substrate;

forming a cathode comprising lithium; and

arranging the anode and cathode in communication to form a battery.

2. A method of fabricating a device according to claim 1 in which the anode is arranged to tolerate the conditions occasioned by the volume changes caused by charging/discharging of the battery.

3. A method according to claim 1 in which the anode is arranged to maintain structural integrity throughout a cycling of the battery.

4. A method according to claim 1 in which the anode is arranged to withstand repeated volume expansion associated with alloying during use of the battery.

5. A method according to claim 1 wherein the step of forming the array of submicron silicon structures comprises forming an array of sub-micron silicon pillars.

6. A method according to claim 5 wherein the step of forming the pillars comprises forming pillars having 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 method according to claim 5 further comprising the step of arranging the sub-micron pillars to not exceed a fractional coverage of 0.5 of the substrate.

8. A method according to claim 5 wherein the step of forming the pillars comprises forming pillars which are 0.1 to 1.0 microns in diameter and 1 to 10 microns in height.

9. A method according to claim 5 wherein the step of forming the pillars comprises forming pillars which are approximately 0.3 microns in diameter and approximately 6 microns in height.

10. A method according to claim 1 wherein the sub-micron silicon structures are formed on a substrate comprising n-type silicon.

11. A method according to claim 1 comprising forming the energy storage device on a wafer-bonded silicon-on-insulator substrate.

16. A method according to claim 1 further comprising the steps of forming the sub-micron silicon structures on a silicon substrate, the steps comprising:

(a) depositing a thin film of cesium chloride onto a silicon based substrate;

(b) exposing the film to water vapour so that the film reorganizes into a distribution of hemispherical islands on the surface; and

(c) reactive ion etching the coated substrate, with the islands of cesium chloride acting as a resist so that the uncoated silicon is etched away leaving the sub-micron silicon structures on the surface of the substrate.

17. A method according to claim 1 wherein the step of forming the array of sub-micron structures supported on a silicon-based substrate, comprises:

(a) depositing a film of a soluble solid onto the silicon-based substrate;

(b) exposing the film to solvent vapour so that the film reorganises into an array of discrete hemispherical islands on the surface; and

(c) reactively ion etching the silicon-based substrate with the islands of highly soluble solid acting as a resist so that the exposed silicon-based substrate is etched away leaving sub-micron silicon structures corresponding to the islands.

12. A method of operating a battery, including a silicon anode comprising an array of sub-micron silicon pillars on a silicon substrate and a lithium cathode, the method comprising the step of forming a compound film on the silicon pillars during a charging step.

13. A method according to claim 12 wherein the film is a Zintl-Phase Compound.

14. A method according to claim 12 wherein the step of forming the compound film comprises forming a deformable compound film which does not to give rise to significant stress-induced cracking during the volume change in a charging or discharging step of the battery.

15. A method of fabricating an electrode to form a battery with a lithium cathode and a lithium-based electrolyte comprising forming sub-micron silicon pillars on a silicon substrate.