INTERCONNECTED HOLLOW NANOSTRUCTURES CONTAINING HIGH CAPACITY ACTIVE MATERIALS FOR USE IN RECHARGEABLE BATTERIES

• US 20100330423A1
• Filed: 05/25/2010
• Published: 12/30/2010
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Amprius Technologies Incorporated (Amprius, Inc.)
• Original Assignee: Amprius, Inc.
• Inventors: Cui, Yi, Han, Song, Loveness, Ghyrn E.
• Granted Patent: US 8,450,012 B2
• Time in Patent Office: Days
• US Class Current: 429/220
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 2004/022 Electrodes made of one single microscopic fiber
• CPC Class Codes: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/0402 Methods of deposition of the material
• CPC Class Codes: H01M 4/043 involving compressing or compaction
• CPC Class Codes: H01M 4/0438 by electrochemical processing electroless electrochemical plating C23C18/54
• CPC Class Codes: H01M 4/0471 involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• CPC Class Codes: H01M 4/049 Manufacturing of an active layer by chemical means
• CPC Class Codes: H01M 4/0492 Chemical attack of the support material
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/38 of elements or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/387 Tin or alloys based on tin
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Provided are electrode layers for use in rechargeable batteries, such as lithium ion batteries, and related fabrication techniques. These electrode layers have interconnected hollow nanostructures that contain high capacity electrochemically active materials, such as silicon, tin, and germanium. In certain embodiments, a fabrication technique involves forming a nanoscale coating around multiple template structures and at least partially removing and/or shrinking these structures to form hollow cavities. These cavities provide space for the active materials of the nanostructures to swell into during battery cycling. This design helps to reduce the risk of pulverization and to maintain electrical contacts among the nanostructures. It also provides a very high surface area available ionic communication with the electrolyte. The nanostructures have nanoscale shells but may be substantially larger in other dimensions. Nanostructures can be interconnected during forming the nanoscale coating, when the coating formed around two nearby template structures overlap.

Claims

1. A method for preparing an electrode layer of interconnected hollow nanostructures containing a high capacity electrochemically active material, the method comprising:

receiving a template comprising template structures;

forming a nanoscale template coating of the high capacity material around the template structures; and

at least partially removing and/or shrinking the template to form the electrode layer of the interconnected hollow nanostructures comprising the high capacity active material.

2. The method of claim 1, wherein receiving the template comprises electrospinning a polymeric material to form template nanofibers having a length of at least about 5 micrometers.

3. The method of claim 1, wherein the template comprises one or more polymeric materials selected from the group consisting of poly-acrylic nitrides (PAN), nylons, polyethylenes, polyethylene oxides, polyethylene terephthalates, polystyrenes, and polyvinyls.

4. The method of claim 1, wherein the template is formed as a layer having a thickness of between about 10 micrometer and 150 micrometers and a porosity of between about 20% and 80%.

5. The method of claim 1, further comprising pre-treating the template by compressing the template, thermally stabilizing the template, and/or carbonizing the template.

6. The method of claim 5, wherein thermally stabilizing the template comprising heating the template in an argon atmosphere to between about 150°

C. and 250°

C. for at least about 2 hours.

7. The method of claim 1, further comprising forming a nanoscale substrate coating of the high capacity materials over a conductive substrate surface adjacent to the template, wherein the nanoscale template coating and the nanoscale substrate coating partially overlap to interconnect the conductive substrate and the interconnected hollow nanostructures.

8. The method of claim 1, wherein forming the nanoscale template coating of the high capacity materials around the template comprises:

an initial deposition stage performed at initial process conditions, wherein no substantial shape distortions of the template occur during the initial deposition stage; and

a bulk deposition stage performed at bulk process conditions that are different from the initial process conditions and configured to provide a higher deposition rate of the nanoscale template coating during the bulk deposition stage.

9. The method of claim 1, wherein at least some removal or shrinking of the template occurs during forming the nanoscale template coating of the high capacity material around the template structures.

10. The method of claim 1, wherein partially removing or shrinking the template comprises one or more operations selected from the group consisting of burning the template at a temperature of at least about 300°

C. in presence of an oxidant, chemical etching the template, and annealing the template.

11. The method of claim 1, further comprising forming a second coating over the interconnected hollow nanostructures, the second coating is configured to increase an electronic conductivity of the electrode layer, improve solid electrolyte interphase (SEI) characteristics of the electrode layer, and/or to limit structural changes of the interconnected hollow nanostructures.

12. An electrode layer for use in a rechargeable battery, the electrode layer comprising:

interconnected hollow nanostructures having an aspect ratio of at least about four, a length of at least about 5 micrometers, and a shell thickness of less than about 100 nanometers and containing a high capacity electrochemically active material,

wherein the interconnected hollow nanostructures form internal cavities that provide free space for the high capacity active material to swell into during cycling of the rechargeable battery.

13. The electrode layer of claim 12, wherein the internal cavities are substantially inaccessible to an electrolyte of the rechargeable battery.

14. The electrode layer of claim 12, wherein the electrode layer is configured to provide a stable energy capacity of at least about 2000 mAh/g after at least 100 cycles based on the weight of the high capacity electrochemically active material.

15. The electrode layer of claim 12, further comprising junction structures interconnecting two or more interconnected hollow nanostructures, said junction structures comprise one or more materials selected from the group consisting of the high capacity electrochemically active material, metal, and a polymeric binder.

16. The electrode layer of claim 15, further comprising a conductive substrate, wherein additional junction structures interconnect one or more interconnected hollow nanostructures and said conductive substrate.

17. The electrode layer of claim 12, wherein the high capacity electrochemically active material comprises one or more materials selected from the group consisting of silicon, tin, and germanium.

18. The electrode layer of claim 12, further comprising an outer layer substantially covering an outer surface of the interconnected hollow nanostructures, wherein the outer layer comprising one or more material selected from the group consisting of carbon, titanium, silicon, aluminum, and copper.

19. The electrode layer of claim 12, wherein the electrode layer has a porosity of between about 20% and 80%.

20. The electrode layer of claim 12, wherein the rechargeable battery is a lithium ion battery and the high capacity electrochemically active material is a negative active material.

21. A lithium ion battery comprising:

an electrode layer comprising;

interconnected hollow nanostructures having an aspect ratio of at least about four, a length of at least about 5 micrometers, and a shell thickness of less than about 100 nanometers and containing a high capacity electrochemically active material,

wherein the interconnected hollow nanostructures form internal cavities provide free space for the high capacity active material to swell into during cycling of the rechargeable battery.