Porous electroactive material

• US 9,871,248 B2
• Filed: 09/02/2011
• Issued: 01/16/2018
• Est. Priority Date: 09/03/2010
• Status: Active Grant

• Current Assignee: Nexeon Limited
• Original Assignee: Nexeon Limited
• Inventors: Rayner, Philip John, Loveridge, Melanie J.
• Primary Examiner(s): Merkling, Matthew J
• Application Number:
  US13/820,223
• Publication Number:
  US 20130216907A1
• Time in Patent Office: 2,328 Days
• Field of Search: 429208-246, 296231-6235
• CPC Class Codes: B22F 1/06 Metallic powder characterised by the shape of the particles nanosized particles B22F1/054
• CPC Class Codes: B22F 1/068 Flake-like particles
• CPC Class Codes: B22F 1/07 Metallic powder characterised by particles having a nanoscale microstructure nanosized particles B22F1/054
• CPC Class Codes: B22F 2304/10 Micron size particles, i.e. above 1 micrometer up to 500 micrometer
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 9/04 starting from solid material, e.g. by crushing, grinding or milling C22C1/1084 takes precedence; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C
• CPC Class Codes: C01B 33/02 Silicon forming single crystals or homogeneous polycrystalline material with defined structure C30B
• CPC Class Codes: C22C 1/08 Alloys with open or closed pores
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: H01M 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/0404 by coating on electrode collectors
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A composition including a plurality of electroactive porous particle fragments including silicon as an electroactive material is characterized in that each porous particle fragment includes a network of pores defined and separated by silicon containing walls. The network of pores suitably has a three dimensional arrangement of pores extending through the volume of the particle in which the pore openings are provided on two or more planes over the surface of the particle. The composition is useful as an electroactive material that is able to form an alloy with lithium and can be used in the fabrication of anodes for use in lithium ion secondary batteries. A method of fabricating the silicon containing porous particle fragments is also disclosed.

Claims

1. A composition comprising silicon-containing electroactive fractals derived from porous particles, each of said fractals having a volume and being selected from the group consisting of:

a fractal having a substantially irregular shape or surface morphology, the fractal being derived from a silicon material originally defining or bounding pores or a network of pores within the porous particle; and

a fractal having a substantially irregular shape or surface morphology, the fractal comprising a random or ordered network of linear, branched or layered elongate elements, the fractal being derived from a silicon material comprising a random or ordered network of linear, branched or layered elongate elements within the porous particle, wherein one or more discrete or interconnected voids or channels are defined between the elongate elements of the network,

wherein each of said fractals itself does not comprise pores, voids, channels, or a network of pores, voids or channels extending through the volume of the fractal;

wherein each of said fractals comprises at least one peak, trough, bump or ridge disposed over the surface thereof;

has a spiky appearance; and

/or has a ridged appearance;

wherein the composition optionally further comprises silicon-containing pore-containing fragments derived from porous particles, the pore-containing fragments comprising a network of pores, cavities and channels, which pores, cavities and channels are separated and defined by silicon-containing walls within the pore-containing fragment, and wherein fragments and fractals having an average pore wall thickness or an average fractal thickness in the range 50 nm to 2 μ

m comprise at least 50% of the volume of the fragments and fractals.

2. A composition according to claim 1, wherein the fractals have an average thickness in the range 0.05 to 2 μ

m.

3. A composition according to claim 1, wherein the silicon-containing fractals have an aspect ratio (length (largest diameter) to width (smallest diameter) of particle) in the range 2:

1 to 5;

1.

4. A composition according to claim 1, wherein at least 10 vol % of the fractals have a maximum overall dimension in the range 1 to 40 μ

m.

5. A composition according to claim 1, wherein the fractals comprise a fractal comprising at least one peak or ridge disposed over the surface thereof.

6. A composition according to claim 1, wherein the fractals comprise a fractal having a spiky appearance.

7. A composition according to claim 1, wherein the fractals comprise a fractal having a ridged appearance.

8. A composition according to claim 1, wherein the fractals have a BET surface area greater than 4 m²/g and less than 50 m²/g.

9. A composition according to claim 1, which further comprises one or more components selected from a binder, a conductive material and optionally a non-silicon-containing electroactive material.

10. A composition, comprising 5 to 40 wt % of the silicon-containing electroactive material according to claim 1 and 60 to 95 wt % of an electroactive carbon material.

11. A composition according to claim 1, which further comprises one or more further silicon-containing components selected from the group consisting of silicon-containing particles having a minimal or negligible porosity;

silicon-containing wires, nano-wires, fibres, rods, tubes, sheets, elongate bundles, substrate particles, scaffolds, ribbons and silicon-containing pillared particles.

12. A composition according to claim 1, wherein one or more of the silicon-containing fractals include a coating.

13. A composition according to claim 1, which is an electrode material.

14. A composition according to claim 1, which is in the form of a mat.

15. A method of making a composition according to claim 1, the method comprising providing silicon-containing whole porous particles having a porosity in the range 0.2 to 0.8 and an average pore wall thickness in the range 50 nm to 2 μ

m;

fragmenting the silicon-containing whole porous particles to provide the silicon-containing fractals; and

isolating the silicon-containing fractals.

16. A method according to claim 15, wherein the providing the silicon-containing whole porous particles comprises

forming a molten silicon aluminum alloy composition;

cooling the molten composition to give alloy particles; and

etching the alloy particles to provide the silicon-containing whole porous particles.

17. A method according to claim 16, wherein the molten composition is cooled at a rate of between 10² and 10⁵K/s.

18. A silicon-containing fragment prepared according to claim 16.

19. An electrode comprising a current collector and a composition according to claim 1.

20. An electrode according to claim 19, wherein the composition is in the form of a free standing felt or mat to which a current collector is connected.

21. An electrode according to claim 19, wherein the composition is in the form of a felt or mat having a mass per surface area of between 1 mg/cm² and 6 mg/cm² thereby to give a composite electrode having a thickness of from 10 to 100 μ

m.

22. A method of manufacturing an electrode according to claim 19 comprising the steps of forming a slurry of the composition according to claim 1 in a solvent, applying the slurry to a current collector and drying the product to remove the solvent.

23. A battery comprising a cathode, an anode comprising a composition according to claim 1 and an electrolyte.

24. A composition according to claim 1, wherein the composition further comprises silicon-containing pore-containing fragments derived from porous particles, the pore-containing fragments comprising a network of pores, cavities and channels, which pores, cavities and channels are separated and defined by silicon-containing walls within the pore-containing fragment.

25. A composition according to claim 24, wherein the ratio of the pore width to wall thickness in the pore-containing fragments is greater than 2.5:

1.

26. A composition according to claim 24, characterized in that the pore-containing fragments comprise pores having a width in the range 100 nm to 10 μ

m.

27. A composition according to claim 24, wherein the ratio of the total volume of the pores in the pore-containing fragments to the total volume of the fragment is in the range 0.2 to 0.9.

28. A composition according to claim 1, wherein the composition optionally further comprises silicon-containing pore-containing fragments derived from porous particles, the pore-containing fragments comprising a network of pores, cavities and channels, which pores, cavities and channels are separated and defined by silicon-containing walls within the pore-containing fragment, and wherein fragments and fractals having an average pore wall thickness or an average fractal thickness in the range 50 nm to 2 μ

m comprise at least 70% of the volume of the fragments and fractals.

29. A composition according to claim 1, wherein the composition optionally further comprises silicon-containing pore-containing fragments derived from porous particles, the pore-containing fragments comprising a network of pores, cavities and channels, which pores, cavities and channels are separated and defined by silicon-containing walls within the pore-containing fragment, and wherein fragments and fractals having an a maximum overall dimension in the range of 1 to 40 μ

m comprise at least 50% of the volume of the fragments and fractals.

30. A composition according to claim 1, which comprises 50 to 90% of an electroactive material by weight, wherein the electroactive material comprises from 40 to 100% of the silicon-containing fractals by weight.

31. A method for making a composition according to claim 1, the method comprising:

forming porous particles using a method comprising at least one of;

i) a sol-gel formation method;

ii) injecting gases into a cooling molten mass comprising the electroactive material or alloy thereof; and

iii) etching particles comprising the electroactive material or an alloy thereof;

fragmenting the silicon-containing whole porous particles to provide the silicon-containing electroactive fractals; and

isolating the silicon-containing electroactive fractals.

32. A method according to claim 31, wherein forming the porous particles comprises

forming a molten silicon aluminum alloy composition;

cooling the molten composition to give alloy particles; and

etching the alloy particles to provide silicon-containing whole porous particles having a porosity in the range 0.2 to 0.8 and an average pore wall thickness in the range 50 nm to 2 μ

m.

33. A method according to claim 31, wherein the silicon-containing porous particles are fragmented using one or more of milling, ultrasonication, high shear mixing and use of a pestle and mortar.

34. A composition according to claim 1, wherein each of said fractals comprises a linear or branched elongate element.

35. A composition according to claim 1, wherein

the fractal having a substantially irregular shape or surface morphology and being derived from the silicon material originally defining or bounding pores or a network of pores within the porous particle has an average thickness in the range 0.05 to 2 microns;

and

in the fractal having a substantially irregular shape or surface morphology, and comprising the random or ordered network of linear, branched or layered elongate elements, and being derived from the silicon material comprising a random or ordered network of linear, branched or layered elongate elements within the porous particle, the network of linear, branched or layered elongate elements has an average thickness in the range 0.05 to 2 microns.

38. The method of claim 15, further comprising forming the silicon-containing whole porous particles by a sol-gel method or by injecting gases into a molten mass.

39. The method of claim 15, further comprising forming the silicon-containing whole porous particles by etching silicon or a silicon alloy.

40. The method of claim 15, wherein the fragmenting is performed by one or more of milling, ultrasonication, high-shear mixing, or use of a mortar and pestle.

36. A composition comprising silicon-containing electroactive fractals, each of said fractals being selected from the group consisting of:

a fractal comprising a substantially irregular shape or surface morphology and an average thickness in the range 0.05 to 2 microns; and

a fractal comprising a network of linear, branched or layered elongate elements having an average thickness in the range 0.05 to 2 microns

wherein each of said fractals

itself does not comprise pores, channels or a network of pores or channels extending through the volume of the fractal; and

comprises at least one peak, trough, bump or ridge disposed over each surface thereof;

has a spiky appearance; and

/or has a ridged appearance; and

wherein at least 10 vol% of the fractals have a maximum overall dimension in the range 1 to 40 μ

m.

37. The composition of claim 36, wherein each of said fractals has an aspect ratio (length to width) in the range 2:

1 to 5;

1.