Composite core-shell particles

Patent metadata

Field	Value
Publication number	US-2018342732-A1
Application number	US-201715556717-A
Country	US
Kind code	A1
Filing date	Feb 14, 2017
Priority date	Feb 17, 2016
Publication date	Nov 29, 2018
Grant date	—

Abstract

The invention relates to composite core-shell particles wherein the core is a porous, carbon-based matrix which contains silicon particles enclosed in pores of the matrix; the pores containing the silicon particles have a diameter of ≥60 nm as determined by scanning electron microscopy (SEM); the shell can be obtained by carbonizing one or more carbon precursors selected from among the group comprising tars, pitches, hard carbon, soft carbon and hydrocarbons having 1 to 20 carbon atoms, resulting in a non-porous shell.

First claim

1 . Core-shell composite particles comprising a core and a shell, wherein the core is a porous, carbon-based matrix which contains silicon particles in which the silicon particles are enclosed in pores of the matrix and the pores containing silicon particles have a diameter of ≥60 nm, and
the shell is a nonporous shell obtainable by carbonization of one or more carbon precursors selected from the group consisting of tars, pitches, hard carbon, soft carbon and hydrocarbons having from 1 to 20 carbon atoms.

2 . Core-shell composite particles according to claim 1 , wherein the silicon particles have volume-weighted particle size distributions having diameter percentiles d 50 of ≥50 nm and ≤800 nm.

3 . Core-shell composite particles according to claim 1 , wherein a ratio of the diameter of the pores of the matrix containing silicon particles to a diameter of the silicon particles is ≥1.1 and ≤3.

4 . Core-shell composite particles according to claim 1 , wherein the matrix is based on carbon which is obtainable by carbonization of one or more carbon precursors selected from the group consisting of resorcinol-formaldehyde resin, lignin and polyacrylonitrile.

5 . Core-shell composite particles according to claim 1 , wherein the pores containing silicon particles are obtainable by firstly coating silicon particles with one or more sacrificial materials to provide coated silicon particles having a first coating and coating the coated silicon particles with a second coating comprising one or more carbon precursors and once again removing the first coating based on the sacrificial materials at a later point in time, resulting in the second coating based on the carbon precursors being converted before or during removal of the sacrificial materials into a matrix based on carbon.

6 . Core-shell composite particles according to claim 5 , wherein the sacrificial materials are inorganic or organic in nature, where inorganic sacrificial materials comprise oxides, carbonates, silicates, carbides, nitrides or sulphides of the elements silicon, magnesium, calcium, tin, zinc, titanium or nickel and
organic sacrificial materials are selected from the group consisting of polyethylene, polypropylene, polystyrene, polybutadiene, poly-tert-butoxystyrene, polyvinyl chloride, polyvinyl acetate, polymethacryl methacrylate, polyacrylic acid, polymethacrylate, polyvinyl stearate polyvinyl laurate and copolymers thereof; polyvinyl alcohol; alkylene glycol; polyalkylene oxide; gamma-butyrolactone; propylene carbonate; polyurethane; dimethylformamide, monoethanolamine and N-methyl-2-pyrrolidinone.

7 . Core-shell composite particles according to claim 1 , wherein any pores present in the shell are <10 nm.

8 . Core-shell composite particles according to claim 1 , wherein a proportion of the shell is from 5 to 20% by weight and/or a proportion of the core is from 80 to 95% by weight, where % by weight figures are based on a total weight of the core-shell composite particles and in each case add up to 100% by weight.

9 . Core-shell composite particles according to claim 1 , wherein the core-shell composite particles have volume-weighted particle size distributions having diameter percentiles d 50 of ≥1 μm and ≤1 mm.

10 . Core-shell composite particles according to claim 1 , wherein a change in diameter percentiles d 50 (volume-weighted particle size distribution) of the core-shell composite particles due to a compressive stress of 17 MPa is ≤15%, based on the diameter percentiles d 50 (volume-weighted particle size distribution) of the core-shell composite particles before the compressive stress.

11 . Core-shell composite particles according to claim 1 , wherein a change in diameter percentiles d 50 (volume-weighted particle size distribution) of the core-shell composite particles due to a shear stress (high-speed stirrer; 16 m/s; 30 min) is ≤15%, based on the diameter percentiles d 50 (volume-weighted particle size distribution) of the core-shell composite particles before the shear stress.

12 . A process for producing the core-shell composite particles of claim 1 comprising the steps:
1) coating of silicon particles with one or more sacrificial materials to provide a product of step 1),
2) coating of the product of step 1) with one or more carbon precursors to provide a product of step 2),
3) carbonization of the product of step 2), with the sacrificial materials being decomposed and liberated in this carbonization step or in a further step 3′) to form a porous composite,
4) coating of the resulting porous composite with one or more carbon precursors selected from the group consisting of tars, pitches, hard carbon, soft carbon and hydrocarbons having from 1 to 20 carbon atoms to provide a product of step 4),
6) carbonization of the product of step 4) and subsequently
7) optionally removal of undersize or oversize particles.

13 . (canceled)

14 . A lithium ion battery having a first electrode as a cathode, a second electrode as an anode, a membrane arranged between the two electrodes as a separator, two connections to the electrodes, a housing accommodating the above-mentioned parts and an electrolyte which contains lithium ions and with which the two electrodes are impregnated, with part of the two electrodes containing core-shell composite particles according to claim 1 .

15 . Core-shell composite particles according to claim 2 , wherein a ratio of the diameter of the pores of the matrix containing silicon particles to a diameter of the silicon particles is ≥1.1 and ≤3.

16 . Core-shell composite particles according to claim 15 , wherein the matrix is based on carbon which is obtainable by carbonization of one or more carbon precursors selected from the group consisting of resorcinol-formaldehyde resin, lignin and polyacrylonitrile.

17 . Core-shell composite particles according to claim 16 , wherein the pores containing silicon particles are obtainable by firstly coating silicon particles with one or more sacrificial materials to provide coated silicon particles having a first coating and coating the coated silicon particles with a second coating comprising one or more carbon precursors and once again removing the first coating based on the sacrificial materials at a later point in time, resulting in the second coating based on the carbon precursors being converted before or during removal of the sacrificial materials into a matrix based on carbon.

18 . Core-shell composite particles according to claim 17 , wherein the sacrificial materials are inorganic or organic in nature,
where inorganic sacrificial materials comprise oxides, carbonates, silicates, carbides, nitrides or sulphides of the elements silicon, magnesium, calcium, tin, zinc, titanium or nickel and organic sacrificial materials are selected from the group consisting of polyethylene, polypropylene, polystyrene, polybutadiene, poly-tert-butoxystyrene, polyvinyl chloride, polyvinyl acetate, polymethacryl methacrylate, polyacrylic acid, polymethacrylate, polyvinyl stearate polyvinyl laurate and copolymers thereof; polyvinyl alcohol; alkylene glycol; polyalkylene oxide; gamma-butyrolactone; propylene carbonate; polyurethane; dimethylformamide, monoethanolamine and N-methyl-2-pyrrolidinone.

19 . Core-shell composite particles according to claim 18 , wherein any pores present in the shell are <10 nm.

20 . Core-shell composite particles according to claim 19 , wherein a proportion of the shell is from 5 to 20% by weight and/or a proportion of the core is from 80 to 95% by w

Assignees

• Wacker Chemie Ag

Inventors

• Troegel Dennis
• Haufe Stefan

Classifications

• H01M4/587

  for inserting or intercalating light metals · CPC title

• H01M4/386

  Silicon or alloys based on silicon · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• C01B33/02

  Silicon (forming single crystals or homogeneous polycrystalline material with defined structure C30B) · CPC title

• C01B32/05

  Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30 · CPC title