Surface modification of active material structures in battery electrodes

Patent metadata

Field	Value
Publication number	US-9252421-B1
Application number	US-201314057931-A
Country	US
Kind code	B1
Filing date	Oct 18, 2013
Priority date	Oct 18, 2013
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

Provided herein are methods of processing electrode active material structures for use in electrochemical cells or, more specifically, methods of forming surface layers on these structures. The structures are combined with a liquid to form a mixture. The mixture includes a surface reagent that chemically reacts and forms a surface layer covalently bound to the structures. The surface reagent may be a part of the initial liquid or added to the mixture after the liquid is combined with the structures. In some embodiments, the mixture may be processed to form a powder containing the structures with the surface layer thereon. Alternatively, the mixture may be deposited onto a current collecting substrate and dried to form an electrode layer. Furthermore, the liquid may be an electrolyte containing the surface reagent and a salt. The liquid soaks the previously arranged electrodes in order to contact the structures with the surface reagent.

First claim

What is claimed is:

1. A method of forming a surface layer on negative electrode active material structures for a lithium ion battery, the method comprising:
receiving the negative electrode active material structures, wherein the negative electrode active material structures are lithium titanium oxide; and
combining the negative electrode active material structures with a liquid to form a mixture,
adding a surface reagent into the mixture, wherein the surface reagent is an oxy-silane,
the oxy-silane forming the surface layer covalently bound to the negative electrode active material structures, wherein the oxy-silane covalently bonds with titanium oxides of the lithium titanium oxide,
the surface layer reducing reactivity of the negative electrode active material structures with respect to electrolyte components, and
wherein the mixture comprising the oxy-silane is a slurry, the oxy-silane bonding with the lithium titanium oxide in the slurry to form the surface layer, the surface layer comprising siloxane.

2. The method of claim 1 , wherein the negative electrode active material structures chemically react with the surface reagent, thereby forming the surface layer covalently bound to the negative electrode active material structures,
or the negative electrode active material structures catalyze a chemical reaction involving the surface reagent such that the chemical reaction forms the surface layer covalently bound to the negative electrode active material structures.

3. The method of claim 1 , wherein the slurry is configured for coating onto a current collecting substrate, and wherein the mixture further comprises a polymer binder selected from the group consisting of polyacrylonitrile, poly(methylmethacrylate), poly(vinyl chloride), polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropene, polyacrylic acid, styrene butadiene rubber, carboxymethylcellulose and copolymers thereof.

4. The method of claim 3 , further comprising coating the slurry onto the current collecting substrate and drying the slurry, thereby forming an electrode active material layer on the current collecting substrate.

5. The method of claim 1 , wherein the surface reagent comprises a trioxy-silane having a general formula of R—Si(OR′) 3 , wherein R is selected from the group consisting of (CH 2 ) X CH 3 , CH═CH 2 , (CH 2 ) X (CF 2 ) Y CF 3 , (CH 2 ) X Si(OCH 3 ) 3 , (CH 2 ) X (N 2 C 3 H 5 ), and (CH 2 ) X PO 3 , wherein X is from 0 to 15 and wherein Y is from 0 to 5.

6. The method of claim 5 , wherein R′ comprises (CH 2 ) Z CH 3 , and wherein Z is from 0 to 1.

7. The method of claim 1 , wherein the surface reagent comprises one or more materials selected from the group consisting of methyltrimethoxy-silane, and tridecafluorooctyltriethoxy-silane.

8. The method of claim 1 , wherein an amount of the surface reagent is between about 0.25% by weight and about 5% by weight relative to the negative electrode active material structures.

9. The method of claim 1 , wherein the mixture is operable as an electrolyte, and wherein the mixture comprises an electrolyte salt.

10. The method of claim 1 , wherein the mixture comprises water, and wherein the water catalyzes formation of the surface layer.

11. The method of claim 1 , further comprising outgassing the mixture comprising the negative electrode active material structures and the surface reagent.

12. The method of claim 1 , further comprising heating the mixture to a temperature of at least about 80° C.

13. A method of forming a surface layer on electrode active material structures for a lithium ion battery, the method comprising:
receiving the electrode active material structures, wherein the electrode active material structures are lithium titanium oxide;
combining the electrode active material structures with a liquid to form a slurry;
adding a surface reagent into the slurry, the surface reagent comprising methyltrimethoxy-silane, wherein the methyltrimethoxy-silane covalently bonds with titanium oxides of the lithium titanium oxide in the slurry to form a conformal monolayer surface bonded to the lithium titanium oxide;
coating the slurry onto a current collecting substrate; and
drying the slurry on a surface of the current collecting substrate, thereby forming an electrode active material layer,
wherein the electrode active material structures in the electrode active material layer comprise a surface layer covalently bound to the electrode active material structures, the surface layer formed from the surface reagent,
the surface layer reducing reactivity of the electrode active material structures with respect to electrolyte components.

14. A method of forming a surface layer on negative electrode active material structures for a lithium ion battery, the method comprising:
receiving the negative electrode active material structures, wherein the negative electrode active material structures are lithium titanium oxide;
combining the negative electrode active material structures with a liquid to form a slurry;
adding a surface reagent into the slurry, wherein the surface reagent is methyltrimethoxy-silane;
coating the slurry onto a current collecting substrate wherein the surface reagent reacts with hydroxide groups on the lithium titanium oxide negative electrode active material structures to covalently bond with titanium oxides;
drying the slurry on a surface of the current collecting substrate, thereby forming an electrode active material layer, wherein the negative electrode active material structures in the electrode active material layer comprise a surface layer containing siloxane, the surface layer covalently bound to the negative electrode active material structures; and
reducing reactivity of the negative electrode active material structures with respect to electrolyte components through the surface layer containing siloxane.

15. The method of claim 14 , further comprising compressing the slurry coating on the current collecting substrate to a density of 1.8 g/cm 3 before drying the slurry.

16. The method of claim 13 , wherein an amount of the surface reagent may be between 0.5% and 2% by weight relative to the electrode active material structures.

Assignees

• A123 Systems Llc

Inventors

• Erickson Michael
• Tikhonov Konstantin

Classifications

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• B05D5/12

  to obtain a coating with specific electrical properties · CPC title

• H01M4/139

  Processes of manufacture · CPC title

• H01M4/0492 Primary

  Chemical attack of the support material · CPC title

• H01M4/0404

  by coating on electrode collectors · CPC title