Silicon-carbon composite anode for lithium-ion batteries
The present invention describes a silicon-carbon composite anode tor lithium-ion batteries comprising 40-80 weight % of silicon particles, 10-45 weight % of carbon, consisting of carbon black and graphite, and a combination of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SB.R) as a binder. The invention also comprises a method of manufacturing the anode and a Li-ion battery comprising the Si—C composite anode according to the present invention.
1. A silicon-carbon composite anode for lithium-ion batteries consisting of, based on the total mass of dry materials:
40-80 weight % of silicon particles with a D 50 particle size between 1-10 μm,
10-45 weight % of carbon, consisting of carbon black and graphite, wherein the amount of carbon black is 5-17.5 weight % and the amount of graphite is 5-30 weight %, and
a combination consisting of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as a binder wherein the amount of CMC and SBR as the binder is 7.5-30 weight % and the mass ratio CMC/SBR is from 0.8:1 to 1:0.8,
wherein lithium-ion batteries comprising said silicon-carbon composites allows >1200 cycles at cycling capacity of 600 mAh/g tot , or >1000 mAh/g Si .
2. The silicon-carbon composite anode according to claim 1 , comprising, based on the total mass of dry materials
50-70 weight % of silicon particles with the D 50 particle size between 1-10 μm,
12.5-17.5 weight % of carbon black
8.5-20 weight % of graphite, and
10-17.5 weight % of the combination of CMC and SBR as the binder.
3. The silicon-carbon composite anode according to claim 1 , comprising, based on the total mass of dry materials
50-70 weight % of silicon particles with the D 50 particle size between 1-10 μm,
12.5-17.5 weight % of carbon black
8.5-12.5 weight % of graphite, and
the combination of CMC and SBR as the binder in a mass ratio from 0.9:1 to 1:0.9.
4. The silicon-carbon composite anode according to claim 1 , wherein the silicon-carbon composite anode comprises a metal foil as a current collector.
5. The silicon-carbon composite anode according to claim 4 , wherein the thickness of the silicon-carbon composite material layer deposited on the metal foil current collector is 12.5-152.4 μm.
6. A method for preparing a silicon-carbon composite anode according to claim 1 , comprising the following steps:
providing CMC and SBR binders in an aqueous solvent,
weighting out desired quantities of silicon particles, carbon black and graphite with the D 50 particle size between 1-10 μm,
adding the said quantities of silicon particles, carbon black and graphite to the said binder solution forming a slurry,
dispersing the slurry by shear mixing or ball milling forming a homogenous paste,
tape-casting the paste on a current collector metal foil, and
drying the pasted film.
7. The method according to claim 6 , where the aqueous solvent is a buffer solution at pH 3.
8. The method according to claim 6 , where the current collector metal foil is prepared by cutting the metal foil, cleaning and drying prior to tape-casting the paste.
9. A lithium-ion battery comprising a cathode, an anode, current collectors, a non-aqueous liquid electrolyte and separator, wherein the anode is a silicon-carbon composite as defined in claim 1 .
10. The lithium-ion battery according to claim 9 , wherein the electrolyte comprises fluoroethylene carbonate (FEC) as an additive.
11. The lithium-ion battery according to claim 9 allowing >1000 cycles, at a capacity of 1000 mAh/g Si .
12. The lithium-ion battery according to claim 11 allowing >1200 cycles at a capacity of 1000 mAh/g Si .