Method of preparing cathode for secondary battery

Patent metadata

Field	Value
Publication number	US-9991504-B2
Application number	US-201715404227-A
Country	US
Kind code	B2
Filing date	Jan 12, 2017
Priority date	Jan 18, 2016
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

Provided herein is a method for preparing a cathode electrode based on an aqueous slurry. The invention provides a cathode slurry comprising a cathode material especially high Ni ternary cathode material with improved water stability. The cathode material shows lower tendencies for pH change when applied in the aqueous slurry. The lower processing temperatures may avoid the undesirable decomposition of cathode material having high nickel and/or manganese content. In addition, the batteries having the electrodes prepared by the method disclosed herein show impressive energy retention. The capacity retention of the battery is not less than 60% of its initial capacity after 2 weeks of high temperature storage.

First claim

What is claimed is:

1. A method of preparing a cathode for a secondary battery, comprising the steps of:
1) dispersing a binder material and a conductive agent in an aqueous solvent to form a first suspension;
2) cooling the first suspension to a temperature from about −5° C. to about 15° C.;
3) adding a cathode active material into the first suspension to form a second suspension;
4) homogenizing the second suspension by a homogenizer at a temperature from about −5° C. to about 15° C. to obtain a homogenized slurry;
5) applying the homogenized slurry on a current collector to form a coated film on the current collector; and
6) drying the coated film on the current collector at a temperature from about 35° C. to about 65° C. to form the cathode,
wherein the aqueous solvent is water and wherein the total processing time for steps 5) and 6) is less than 5 minutes.

2. The method of claim 1 , wherein the binder material is selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymers, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resins, phenolic resins, epoxy resins, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, a salt of alginic acid, polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropene, and combinations thereof.

3. The method of claim 2 , wherein the salt of alginic acid comprises a cation selected from Na, Li, K, Ca, NH 4 , Mg, Al, or a combination thereof.

4. The method of claim 1 , wherein the conductive agent is selected from the group consisting of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon, and combinations thereof.

5. The method of claim 1 , wherein the aqueous solvent further comprises ethanol, isopropanaol, methanol, acetone, n-propanol, t-butanol, n-butanol, dimethyl ketone, methyl ethyl ketone, ethyl acetate, isopropyl acetate, propyl acetate, and combinations thereof.

6. The method of claim 1 , wherein the cathode active material is selected from the group consisting of Li 1+x Ni a Mn b Co c Al (1−a−b−c) O 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 , LiNi 0.4 Mn 0.4 Co 0.2 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.7 Mn 0.15 Co 0.15 O 2 , LiNi 0.8 Mn 0.1 C 0.1 O 2 , LiNi 0.92 Mn 0.4 Co 0.04 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 3 , and combinations thereof; wherein −0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1, and a+b+c≤1.

7. The method of claim 1 , wherein the cathode active material is selected from the group consisting of LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.7 Mn 0.15 Co 0.15 O 2 , LiNi 0.8 Mn 0.1 C 0.1 O 2 , LiNi 0.92 Mn 0.04 C 0.04 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 3 , and combinations thereof.

8. The method of claim 1 , wherein the cathode active material comprises or is a core-shell composite having a core and shell structure, wherein the core and the shell each independently comprise a lithium transition metal oxide selected from the group consisting of Li 1+x Ni a Mn b Co c Al (1−a−b−c) O 2 , LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 3 , LiCrO 2 , Li 4 Ti 5 O 12 , LiV 2 O 5 , LiTiS 2 , LiMoS 2 , and combinations thereof; wherein −0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1, and a+b+c≤1.

9. The method of claim 1 , wherein the second suspension is homogenized by a planetary stirring mixer, a stirring mixer, a blender, or an ultrasonicator.

10. The method of claim 1 , wherein the homogenization is performed under vacuum at a pressure from about 0.5 kPa to about 10 kPa.

11. The method of claim 1 , wherein the second suspension is homogenized for about 0.5 hour to about 6 hours.

12. The method of claim 1 , wherein the second suspension is homogenized for a time period of less than 3 hours, less than 2 hours, or less than 1 hour.

13. The method of claim 1 , wherein the viscosity of the homogenized slurry is from about 1,000 mPa·s to about 6,000 mPa·s.

14. The method of claim 1 , wherein the solid content of the homogenized slurry is from about 30% to about 60% by weight, based on the total weight of the homogenized slurry.

15. The method of claim 1 , wherein the homogenized slurry is applied on the current collector using a doctor blade coater, a slot-die coater, a transfer coater, or a spray coater.

16. The method of claim 1 , wherein the coated film is dried by a conveyor hot air drying oven, a conveyor resistance drying oven, a conveyor inductive drying oven, or a conveyor microwave drying oven.

17. The method of claim 1 , wherein the total processing time for steps 3)-6) is from about 2 hours to about 6 hours.

18. The method of claim 1 , wherein the total processing time for steps 3)-6) is less than 5 hours or less than 3 hours.

Assignees

• Grst Int Ltd

Inventors

• Ho Kam Piu
• Wang Ranshi
• Shen Peihua

Classifications

• H01M4/1397

  of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy · CPC title

• H01M4/0419

  involving spraying · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/0471

  involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis · CPC title

• H01M4/623

  fluorinated polymers · CPC title