Process for graphene foam-protected anode active materials for lithium batteries

Patent metadata

Field	Value
Publication number	US-2017317336-A1
Application number	US-201715651528-A
Country	US
Kind code	A1
Filing date	Jul 17, 2017
Priority date	Aug 7, 2014
Publication date	Nov 2, 2017
Grant date	—

Abstract

A lithium-ion battery anode layer, comprising an anode active material embedded in pores of a solid graphene foam composed of multiple pores and pore walls, wherein (a) the pore walls contain a pristine graphene material having essentially no (less than 0.01%) non-carbon elements or a non-pristine graphene material having 0.01% to 5% by weight of non-carbon elements; (b) the anode active material is in an amount from 0.5% to 95% by weight based on the total weight of the graphene foam and the anode active material combined, and (c) some of the multiple pores are lodged with particles of the anode active material and other pores are particle-free, and the graphene foam is sufficiently elastic to accommodate volume expansion and shrinkage of the particles of the anode active material during a battery charge-discharge cycle to avoid expansion of the anode layer. Preferably, the solid graphene foam 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.

First claim

We claim:

1 . A process for producing an anode layer for a lithium ion battery, said process comprising:
(a) preparing a graphene dispersion having multiple particles of anode active material and multiple sheets of a starting graphene material dispersed in a liquid medium, wherein said starting graphene material comprises pristine graphene material or non-pristine graphene material, where non-pristine is defined as having a content of non-carbon elements greater than 2% by weight, and where said starting graphene material is selected from graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, and combinations thereof, and wherein said dispersion contains an optional blowing agent; (b) dispensing said graphene dispersion onto a surface of a supporting substrate to form a wet layer of graphene and anode active material mixture, wherein said dispensing procedure includes subjecting said graphene dispersion to an orientation-inducing stress; (c) partially or completely removing said liquid medium from the wet layer of graphene and anode active material to form a dried layer of mixture material; and (d) heat treating the dried layer of mixture material at a first heat treatment temperature selected from 80° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from said non-carbon elements or to activate said optional blowing agent for producing said pore-containing graphene foam anode layer.

2 . The process of claim 1 , further including a step of heat-treating the graphene foam anode layer at a second heat treatment temperature higher than said first heat treatment temperature for a length of time sufficient for obtaining a anode layer wherein said pore walls contain stacked graphene planes having an inter-plane spacing d 002 from 0.3354 nm to 0.36 nm and a content of non-carbon elements less than 2% by weight.

3 . The process of claim 1 , wherein said dispersion contains a blowing agent having a blowing agent-to-graphene weight ratio from 0.01/1.0 to 1.0/1.0.

4 . The process of claim 1 , wherein said blowing agent is a physical blowing agent, a chemical blowing agent, a mixture thereof, a dissolution-and-leaching agent, or a mechanically introduced blowing agent.

5 . The process of claim 1 , which is a roll-to-roll process wherein said steps (b) and (c) include feeding said supporting substrate from a feeder roller to a deposition zone, continuously or intermittently dispensing or depositing said graphene dispersion onto a surface of said supporting substrate to form said wet layer of graphene material thereon, drying said wet layer of graphene material to form the dried layer of graphene material, and collecting said dried layer of graphene material deposited on said supporting substrate on a collector roller

6 . The process of claim 1 , wherein said first heat treatment temperature is selected from 100° C. to 1,500° C.

7 . The process of claim 2 , wherein said second heat treatment temperature includes at least a temperature selected from (A) 300-1,500° C., (B) 1,500-2,100° C., and (C) 2,100-3,200° C.

8 . The process of claim 1 , wherein said step (d) of heat treating the dried layer of graphene material at a first heat treatment temperature is conducted under a compressive stress.

9 . The process of claim 1 , wherein said graphene dispersion contains a graphene oxide dispersion prepared by immersing a graphitic material in a powder or fibrous form in an oxidizing liquid in a reaction vessel at a reaction temperature for a length of time sufficient to obtain said graphene dispersion wherein said graphitic material is selected from natural graphite, artificial graphite, meso-phase carbon, meso-phase pitch, meso-carbon micro-bead, soft carbon, hard carbon, coke, carbon fiber, carbon nanofiber, carbon nanotube, or a combination thereof and wherein said graphene oxide has an oxygen content no less than 5% by weight.

10 . The process of claim 1 , wherein said anode active material is selected from the group consisting of: (a) silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti), nickel (Ni), cobalt (Co), and cadmium (Cd); (b) alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Ni, Co, or Cd with other elements; (c) oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Fe, Ni, Co, V, or Cd, and their mixtures, composites, or lithium-containing composites; (d) salts and hydroxides of Sn; (e) lithium titanate, lithium manganate, lithium aluminate, lithium-containing titanium oxide, lithium transition metal oxide; (f) prelithiated versions thereof; (g) particles of Li, Li alloy, or surface-stabilized Li; and (h) combinations thereof.

11 . The process of claim 1 , wherein said anode active material contains a prelithiated Si, prelithiated Ge, prelithiated Sn, prelithiated SnO x , prelithiated SiO x , prelithiated iron oxide, prelithiated VO 2 , prelithiated Co 3 O 4 , prelithiated Ni 3 O 4 , or a combination thereof, wherein 1<x<2.

12 . The process of claim 1 , wherein said anode active material is in a form of nanoparticle, nanowire, nanofiber, nanotube, nanosheet, nanobelt, nanoribbon, or nano-coating having a thickness or diameter less than 100 nm.

13 . The process of claim 1 , further comprising a lithium-conducting coating deposited onto said anode active material.

14 . The process of claim 1 , wherein said anode active material has a dimension less than 20 nm.

15 . The process of claim 1 , further comprising a carbon or graphite material in said dispersion, wherein said carbon or graphite material is in electronic contact with or deposited onto said anode active material.

16 . The process of claim 15 , wherein said carbon or graphite material is selected from 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.

17 . The process of claim 15 , further comprising a conductive protective coating, selected from a carbon material, electronically conductive polymer, conductive metal oxide, conductive metal coating, or a lithium-conducting material, which is deposited onto or wrapped around said active anode material.

18 . The process of claim 1 , wherein said graphene foam anode layer contains pristine graphene and said anode later has a density from 0.5 to 1.7 g/cm 3 or said pores have a pore size from 2 nm to 100 nm.

19 . A roll-to-roll process for producing a continuous-length sheet of the graphene foam anode layer of claim 1 , said process comprising:
(a) preparing a graphene dispersion having a graphene material and an anode active material dispersed in a liquid medium, wherein said dispersion contains a blowing agent; (b) continuously or intermittently dispensing and depositing said graphene dispersion onto a surface of a supporting substrate to form a wet layer of graphene-anode material mixture, wherein said supporting substrate is a continuous thin film supplied from a feeder roller and collected on a collector roller; (c) partially or completely removing said liquid medium from the wet layer of graphene-anode material mixture

Assignees

• Nanotek Instruments Inc

Inventors

• Zhamu Aruna
• Jang Bor Z

Classifications

• H01M10/052

  Li-accumulators · CPC title

• H01M4/1393

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

• H01M4/0471

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

• H01M4/133 Primary

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

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title