AQUEOUS BASED POLYMERS FOR SILICON ANODES
Systems and methods utilizing aqueous-based polymer binders for silicon-dominant anodes may include an electrode coating layer on a current collector, where the electrode coating layer is formed from silicon and a water soluble polymer and may comprise one or more of the following materials: pH modifiers, viscosity modifiers, strengthening additives, surfactants and anti-foaming agents. The electrode coating layer may include more than 70% silicon and the anode may be in a lithium ion battery.
1 . A battery electrode, the electrode comprising:
an electrode coating layer on a current collector, the electrode coating layer comprising silicon, aqueous-based polyamide-imide (PAI), and aqueous-based polyvinyl alcohol (PVA),
wherein the aqueous-based PAI and the aqueous-based PVA are pyrolyzed into carbon during making of the electrode, and wherein a silicon to pyrolyzed carbon ratio of the electrode is approximately 9 to 1, and
wherein a ratio of the aqueous-based PAI to the aqueous-based PVA in the pyrolyzed carbon is greater than one.
2 . The electrode according to claim 1 , wherein an amount of the aqueous-based PVA modifies a viscosity of the electrode coating layer.
3 . The electrode according to claim 1 , wherein the aqueous-based PAI has a carbon yield upon pyrolysis of greater than about 30% and the aqueous-based PVA has a lower carbon yield upon pyrolysis than the aqueous-based PAI.
4 . The electrode according to claim 1 , wherein the electrode yields a thickness of less than approximately 85 um including the current collector.
5 . The electrode according to claim 1 , wherein the electrode active material coating yields a porosity of approximately 45-55%.
6 . The electrode according to claim 1 , wherein the electrode coating layer further comprises one or more surfactants.
7 . The electrode according to claim 6 , wherein the one or more surfactants when present comprise less than about 1% of the electrode coating layer.
8 . The electrode according to claim 1 , wherein the electrode is in electrical and physical contact with an electrolyte, the electrolyte comprising a liquid, solid, or gel.
9 . The electrode according to claim 8 , wherein the battery electrode is in a lithium ion battery.
10 . A method of forming an electrode, the method comprising:
creating an electrode coating layer from an electrode slurry comprising silicon, aqueous-based polyamide-imide (PAI), and aqueous-based polyvinyl alcohol (PVA), wherein adjusting an amount of the aqueous-based PVA modifies a viscosity of the electrode coating layer;
fabricating a battery electrode by coating the slurry on a current collector; and
pyrolyzing the aqueous-based PAI or the aqueous-based PVA of the electrode coating layer into pyrolytic carbon;
wherein the aqueous-based PAI has a carbon yield upon pyrolysis of greater than about 30%,
wherein a silicon to pyrolyzed carbon ratio of the electrode is approximately 9 to 1 following pyrolysis of the PAI and/or PVA, and
wherein a ratio of the aqueous-based PAI to the aqueous-based PVA in the pyrolyzed carbon is greater than one.
11 . The method according to claim 10 , wherein the aqueous-based PVA has a lower pyrolytic carbon yield than the aqueous-based PAI.
12 . The method according to claim 11 , wherein the aqueous-based PVA contributes less than approximately 30% of the pyrolytic carbon of the electrode coating layer.
13 . The method according to claim 10 , wherein the concentration of components yields a slurry with a viscosity greater than 1500 cP.
14 . The method according to claim 13 , wherein the concentration of components yields a slurry with a pH of approximately 7.
15 . The method according to claim 10 , further comprising creating the electrode coating layer by adding one or more surfactants.
16 . The method according to claim 15 , wherein the one or more surfactants when present comprise less than about 1% of the electrode coating layer.
17 . The method according to claim 10 , further comprising contacting the electrode with an electrolyte, the electrolyte comprising a liquid, solid, or gel.
18 . The method according to claim 17 , wherein the battery electrode is in a lithium ion battery.
19 . The method according to claim 10 , wherein the electrode is defined by a resistance of less than 5 ohms.
20 . The method according to claim 10 , wherein a ratio of the aqueous-based PAI and the aqueous-based PVA is approximately 60:40, the PVA contributing approximately 25% of the pyrolytic carbon.