Core-shell composite particles for anode materials of lithium ion batteries

Patent metadata

Field	Value
Publication number	US-2020044241-A1
Application number	US-201716484029-A
Country	US
Kind code	A1
Filing date	Feb 7, 2017
Priority date	Feb 7, 2017
Publication date	Feb 6, 2020
Grant date	—

Abstract

The invention relates to core-shell composite particles, the core being a porous, carbon-based matrix containing silicon particles and the shell being non-porous and being obtainable by the carbonization of one or more carbon precursors, the silicon particles having average particle sizes of 1 to 15 μm.

First claim

1 . A core-shell composite particle, comprising:
a core of a porous, carbon-based matrix containing silicon particles, and a shell, which is nonporous and obtained by carbonization of one or more carbon precursors, wherein the silicon particles have average sizes d 50 of from 1.5 to 15 μm, wherein the average particle sizes d 50 of the silicon particles are determined in accordance with ISO 13320 by means of static laser light scattering using the Mie model and the measuring instrument Horiba LA 950 using ethanol as dispersing medium for the silicon particles, and wherein the core of the core-shell composite particles contain ≤1% by weight of conductive additives selected from the group consisting of graphite, carbon black, carbon nanotubes, fullerenes and graphene, based on the total weight of the core-shell composite particles.

2 . The core-shell composite particle of claim 1 , wherein the matrix is based on carbon which is obtained by carbonization of one or more carbon precursors selected from the group consisting of resorcinol-formaldehyde resin, phenol-formaldehyde resin, lignin and polyacrylonitrile.

3 . The core-shell composite particle of claim 1 , wherein one or more pores of the matrix contain silicon particles and the pores which contain silicon particles are obtained by silicon particles firstly being coated with one or more sacrificial materials and the resulting products being coated with one or more carbon precursors and the coating based on the sacrificial materials being removed again at a later point in time, with the coating based on the carbon precursors being converted into a matrix based on carbon before or during removal of the sacrificial materials.

4 . The core-shell composite particle of claim 3 , wherein the sacrificial materials are inorganic or organic in nature, wherein inorganic sacrificial materials comprise oxides, carbonates, carbides, nitrides or sulfides of the elements silicon, magnesium, calcium, tin, zinc, titanium or nickel, or silicates of the elements 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, polyvinyl alcohol, alkylene glycols, polyalkylene oxides, gamma-butyrolactone, propylene carbonate, polysaccharides, melamine resins and polyurethanes.

5 . The core-shell composite particle of claim 1 , wherein the matrix contains pores having an average diameter of from 50 nm to 22 μm, where the average diameters of the pores are determined by means of scanning electron microscopy and the average diameter is defined as the median.

6 . The core-shell composite particle of claim 1 , wherein the ratio of the diameters of the pores of the matrix which contain silicon particles to the diameters of the silicon particles is from 1.1 to 3, where the diameters are determined by means of scanning electron microscopy.

7 . The core-shell composite particle of claim 1 , wherein the shell is obtainable by carbonization of one or more carbon precursors selected from the group consisting of tars, pitches, polyacrylonitrile and hydrocarbons having from 1 to 20 carbon atoms.

8 . The core-shell composite particle of claim 1 , wherein any pores present in the shell are <10 nm, determined from the pore size distribution by the BJH method by means of gas adsorption in accordance with DIN 66134.

9 . A method for the production of core-shell composite particles of claim 1 , comprising:
1) a) coating silicon particles having average particle sizes d 50 of from 1.5 to 15 μm with one or more sacrificial materials and/or
b) mixing silicon particles having average particle sizes d 50 of from 1.5 to 15 μm with one or more sacrificial materials, where the average particle sizes d 50 of the silicon particles are determined in accordance with ISO 13320 by means of static laser light scattering using the Mie model and the measuring instrument Horiba LA 950 using ethanol as dispersing medium for the silicon particles,
2) coating the product from step 1) with one or more carbon precursors, 3) carbonizing the product from step 2), with the sacrificial materials being decomposed and liberated in this carbonization or in a further carbonizing step 4) to form a porous composite, 5) coating of the porous composite obtained in this way with one or more carbon precursors for the shell, and 6) carbonizing of the product from step 5).

10 . A lithium ion battery comprising:
a cathode, an anode, a separator, and an electrolyte, wherein the anode is based on an anode material which comprises one or more core-shell composite particles of claim 1 .

11 . The lithium ion battery of claim 10 ,
wherein the anode material in a fully charged lithium ion battery is only partially lithiated.

12 . The lithium ion battery of claim 11 ,
wherein the ratio of the lithium capacity of the anode to the lithium capacity of the cathode is ≥1.15.

13 . The lithium ion battery of claim 11 , wherein the anode in the fully charged lithium ion battery is charged with from 800 to 1500 mAh/g, based on the mass of the anode.

14 . The lithium ion battery of claim 11 , wherein the ratio of lithium atoms to silicon atoms in the anode material in the fully charged state of the lithium ion battery is ≤4.0.

15 . The lithium ion battery of claim 11 , wherein the capacity of the silicon of the anode material of the lithium ion battery is utilized to an extent of ≤80%, based on the maximum capacity of 4200 mAh per gram of silicon.

Assignees

• Wacker Chemie Ag

Inventors

• Gigler Peter
• Bernhard Rebecca
• STOHRER JüRGEN

Classifications

• H01M4/366 Primary

  as layered products · CPC title

• H01M4/134

  Electrodes based on metals, Si or alloys · CPC title

• H01M2010/4292

  Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode · CPC title

• H01M2004/021

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

• H01M4/1395

  of electrodes based on metals, Si or alloys · CPC title