Lithium ion battery anode containing silicon nanowires grown in situ in pores of graphene foam and production process

Patent metadata

Field	Value
Publication number	US-9997784-B2
Application number	US-201615287078-A
Country	US
Kind code	B2
Filing date	Oct 6, 2016
Priority date	Oct 6, 2016
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A process for producing an anode layer, comprising: (a) dispersing catalyst metal-coated Si particles, graphene sheets, and an optional blowing agent in a liquid medium to form a graphene/Si dispersion; (b) dispensing and depositing the dispersion onto a supporting substrate to form a wet layer and removing the liquid medium from the wet layer to form a dried layer of graphene/Si mixture material; and (c) exposing the dried layer to a high temperature environment, from 300° C. to 2,000° C., to induce volatile gas molecules from graphene sheets or to activate the blowing agent for producing the graphene foam and, concurrently, to enable a catalyst metal-catalyzed growth of multiple Si nanowires emanated from Si particles as a feed material in pores of the foam to form the anode layer; wherein the Si nanowires have a diameter of 5-100 nm and a length-to-diameter aspect ratio of at least 5.

First claim

We claim:

1. A process for producing an anode or negative electrode for a lithium-ion battery, said anode comprising a solid graphene foam composed of multiple pores and pore walls and silicon (Si) nanowires residing in said pores, said process comprising:
(a) dispersing catalyst metal-coated Si particles, graphene sheets, and an optional blowing agent in a liquid medium to form a graphene/Si dispersion, wherein said Si particles have a particle diameter from 0.2 μm to 20 μm and said catalyst metal is in a form of nano particles having a diameter from 0.5 nm to 100 nm or a thin coating having a thickness from 1 nm to 100 nm deposited on surfaces of said Si particles and optionally on surfaces of graphene sheets, and wherein said Si particles contain pure Si having at least 99.9% by weight of Si element or a Si alloy or mixture having from 70% to 99.9% by weight of Si therein;
(b) dispensing and depositing said graphene/Si dispersion onto a surface of a supporting substrate to form a wet layer of graphene/Si mixture and partially or completely removing said liquid medium from the wet layer of graphene/Si mixture to form a dried layer of graphene/Si mixture material; and
(c) exposing said dried layer of graphene/Si mixture to a high temperature environment, including a temperature from 100° C. to 2,500° C., for a period of time sufficient to induce volatile gas molecules from said graphene sheets or to activate said blowing agent for producing said graphene foam and, concurrently, to enable a catalyst metal-catalyzed growth of multiple Si nanowires emanating from said Si particles as a feed material in pores of said graphene foam to form said anode electrode layer; wherein said Si nanowires have a diameter from 2 nm to 100 nm and a length-to-diameter aspect ratio of at least 5 and said Si nanowires are in an amount from 0.5% to 99% by weight based on the total weight of said graphene foam and said Si nanowires combined.

2. The process of claim 1 , wherein said graphene sheets contain a pristine graphene material having less than 0.01% by weight of non-carbon elements or a non-pristine graphene material having 0.01% to 50% by weight of non-carbon elements, wherein said non-pristine graphene is selected from the group consisting of graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, and combinations thereof.

3. The process of claim 1 , wherein surfaces of said graphene sheets are also deposited with said catalyst metal and Si nanowires are also grown and emanated from said graphene surfaces.

4. The process of claim 1 , wherein said dispensing and depositing procedure includes subjecting said graphene/silicon dispersion to an orientation-inducing stress.

5. The process of claim 1 , wherein some of said multiple pores are lodged with said Si nanowires and other pores are Si-free, and said graphene foam is sufficiently elastic to accommodate volume expansion and shrinkage of said Si nanowires during a battery charge-discharge cycle to avoid expansion of said anode layer.

6. The process of claim 1 , wherein said graphene sheets are selected from a single-layer sheet or few-layer platelet of pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene bromide, graphene iodide, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, or a combination thereof, wherein few layer is defined as less than 10 layers of graphene planes.

7. The process of claim 1 , wherein said Si particles have a diameter from 0.5 μm to 5 μm.

8. The process of claim 1 , wherein said catalyst metal-coated Si particles are produced by a step of depositing a catalyst metal on Si particle surfaces by a procedure of physical vapor deposition, chemical vapor deposition, sputtering, plasma deposition, laser ablation, plasma spraying, ultrasonic spraying, printing, electrochemical deposition, electrode plating, electrodeless plating, chemical plating, or a combination thereof.

9. The process of claim 1 , wherein said catalyst metal is selected from the group consisting of Cu, Ni, Co, Mn, Fe, Ti, Al, Ag, Au, Pt, Pd, or combinations thereof.

10. The process of claim 3 , wherein said catalyst metal is deposited on Si and graphene sheet surfaces by a procedure including (a) dissolving or dispersing a catalytic metal precursor in a liquid to form a precursor solution, (b) bringing said precursor solution in contact with surfaces of said graphene sheets and surfaces of said Si particles, (c) removing said liquid; and (d) chemically or thermally converting said catalytic metal precursor to said catalyst metal coating or nano particles.

11. The process of claim 10 , wherein said step (d) of chemically or thermally converting said catalytic metal precursor is conducted concurrently with the procedure (c) of exposing said dried layer of graphene/Si mixture to a high temperature environment.

12. The process of claim 10 , wherein said catalytic metal precursor is a salt or organo-metal molecule of a transition metal selected from the group consisting of Cu, Ni, Co, Mn, Fe, Ti, Al, and combinations thereof.

13. The process of claim 10 , wherein said catalytic metal precursor is selected from the group consisting of copper nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, iron nitrate, titanium nitrate, aluminum nitrate, copper acetate, nickel acetate, cobalt acetate, manganese acetate, iron acetate, titanium acetate, aluminum acetate, copper sulfate, nickel sulfate, cobalt sulfate, manganese sulfate, iron sulfate, titanium sulfate, aluminum sulfate, copper phosphate, nickel phosphate, cobalt phosphate, manganese phosphate, iron phosphate, titanium phosphate, aluminum phosphate, copper hydroxide, nickel hydroxide, cobalt hydroxide, manganese hydroxide, iron hydroxide, titanium hydroxide, aluminum hydroxide, copper carboxylate, nickel carboxylate, cobalt carboxylate, manganese carboxylate, iron carboxylate, titanium carboxylate, aluminum carboxylate, and combinations thereof.

14. The process of claim 1 , wherein said solid graphene foam, when measured alone without Si, has a density from 0.01 to 1.7 g/cm 3 , a specific surface area from 50 to 2,000 m 2 /g, a thermal conductivity of at least 100 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 1,000 S/cm per unit of specific gravity.

15. The process of claim 1 , wherein said Si nanowires have a diameter less than 20 nm.

16. The process of claim 1 , wherein said graphene foam further comprises a carbon or graphite material therein, wherein said carbon or graphite material is in electronic contact with or deposited onto said anode active material.

17. The process of claim 16 , wherein said carbon or graphite material is selected from the group consisting of polymeric carbon, amorphous carbon, chemical vapor deposition carbon, coal tar pitch, petroleum pitch, meso-phase pitch, carbon black, coke, acetylene black, activated carbon, fine expanded graphite particle with a dimension smaller than 100 nm, artificial graphite particle, natural graphite particle, and combinations thereof.

Assignees

• Nanotek Instruments Inc

Inventors

• Su Yu-Sheng
• Yin Jun
• Fang Qing
• Zhamu Aruna
• Jang Bor Z

Classifications

• H01M4/133

  Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/0416

  involving impregnation with a solution, dispersion, paste or dry powder (H01M4/0438 takes precedence) · CPC title

• H01M4/0471

  involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis · CPC title

• H01M2004/027

  Negative electrodes · CPC title