Cathodes for high voltage lithium-ion secondary battery and dry method for manufacture of same

Patent metadata

Field	Value
Publication number	US-2024379938-A1
Application number	US-202218690458-A
Country	US
Kind code	A1
Filing date	Sep 8, 2022
Priority date	Sep 9, 2021
Publication date	Nov 14, 2024
Grant date	—

Abstract

A cathode for a high voltage lithium-ion secondary battery is described, including: an electrode layer having an electrode composition containing cathode active particles, fluoropolymer binder and conductive carbon. The cathode active particles are high voltage lithium transition metal oxides, the fluoropolymer binder is a fibrillated tetrafluoroethylene polymer having high melt creep viscosity, and the conductive carbon is carbon fibers having a specific surface area of about 50 m 2 /g or less. The carbon fibers and the fluoropolymer binder form a conducting structural web electronically connecting the cathode active particles, enabling electronic conductivity through the electrode layer. The electrode layer is adhered to a current collector comprising aluminum having surface roughness and substantially no carbon surface coating other than the conductive carbon of the electrode layer. Further described is a dry binder process to fabricate such cathodes, and the utility of such cathodes in high voltage lithium-ion secondary batteries.

First claim

What is claimed is:

1 . A cathode for a high voltage lithium-ion secondary battery, comprising:
an electrode layer comprising an electrode composition comprising cathode active particles, fluoropolymer binder and conductive carbon, wherein: said cathode active particles comprise lithium transition metal oxide having an electrochemical potential versus Li/Li+ of at least about 4.5 V; said fluoropolymer binder is a tetrafluoroethylene polymer having a melt creep viscosity of at least about 1.8×10 11 poise; said fluoropolymer binder is fibrillated; said conductive carbon comprises carbon fibers having a specific surface area of about 50 m 2 /g or less, said carbon fibers and said fibrillated fluoropolymer binder forming a conducting structural web electronically connecting said cathode active particles so as to enable electronic conductivity through the electrode layer, and wherein; said electrode layer is adhered to a current collector comprising aluminum having surface roughness and substantially no carbon surface coating other than said conductive carbon of said electrode layer.

2 . The cathode of claim 1 , wherein said conducting structural web comprises at least one of:
A. a portion of said tetrafluoroethylene polymer and a portion of said carbon fibers in said web is combined in the form of conductive strands comprising a continuous tetrafluoroethylene polymer matrix and a plurality of carbon fibers, wherein said carbon fibers are embedded in and adhered to the tetrafluoroethylene polymer matrix comprising said strands, and wherein the longitudinal axis of said carbon fibers is substantially aligned with the longitudinal axis of said strands, and wherein said strands are randomly interwoven and interconnected throughout the volume between said cathode active particles, and are in contact with said cathode active particles; B. a portion of said tetrafluoroethylene polymer and a portion of said carbon fibers in said web is combined in the form of discontinuous randomly matted regions located adjacent and attached to said cathode active particles, wherein said carbon fibers are embedded in and adhered to the tetrafluoroethylene polymer comprising said regions; C. a portion of the tetrafluoroethylene polymer in said web is in the form of free tetrafluoroethylene polymer fibrils; D. a portion of the tetrafluoroethylene polymer in said web is in the form of a tetrafluoroethylene polymer coating layer covering a portion of the surface of some of said cathode active particles; and E. a portion of said carbon fibers in said web are free conductive carbon fibers; and wherein said conductive strands (A.), said discontinuous random matted regions (B.), said free fluoropolymer fibrils (C.), said tetrafluoroethylene polymer coating layers (D.), and said free conductive carbon fibers (E.) are randomly interconnected with one another throughout said electrode layer, and are in contact with the surface of said cathode active particles, thereby forming said conducting structural web electrically connecting and securing in place said cathode particles.

3 . The cathode of claim 1 , wherein said electrode composition contains from about 1 to about 10 weight percent conductive carbon, about 0.5 to about 5 weight percent fluoropolymer binder, and the remainder cathode active particles, based on the combined weight of said fluoropolymer binder, said cathode active particles, and said conductive carbon.

4 . The cathode of claim 1 , wherein said electrode composition contains from about 2 to about 7 weight percent conductive carbon, about 1 to about 3 weight percent fluoropolymer binder, and the remainder cathode active particles, based on the combined weight of said fluoropolymer binder, said cathode active particles, and said conductive carbon.

5 . The cathode of claim 1 , wherein said electrode composition contains about 5 weight percent conductive carbon, about 2 weight percent fluoropolymer binder, and the remainder cathode active particles, based on the combined weight of said fluoropolymer binder, said cathode active particles, and said conductive carbon.

6 . The cathode of claim 1 , wherein said carbon fibers have a length of from about 10 micrometers to about 200 micrometers.

7 . The cathode of claim 1 , wherein said conductive carbon has a specific surface area of about 40 m 2 /g or less.

8 . The cathode of claim 1 , wherein said conductive carbon has a specific surface area of about 30 m 2 /g or less.

9 . The cathode of claim 1 , wherein said conductive carbon has a specific surface area of about 20 m 2 /g or less.

10 . The cathode of claim 1 , wherein said electrode layer is substantially free from conductive carbon having a specific surface area greater than about 50 m 2 /g.

11 . The cathode of claim 7 , wherein said electrode layer is substantially free from conductive carbon having a specific surface area greater than about 40 m 2 /g.

12 . The cathode of claim 8 , wherein said electrode layer is substantially free from conductive carbon having a specific surface area greater than about 30 m 2 /g.

13 . The cathode of claim 9 , wherein said electrode layer is substantially free from conductive carbon having a specific surface area greater than about 20 m 2 /g.

14 . The composition of claim 1 , wherein said tetrafluoroethylene polymer has a melt creep viscosity of at least about 2.0×10 11 poise.

15 . The of claim 1 , wherein said tetrafluoroethylene polymer has a melt creep viscosity of at least about 3.0×10 11 poise.

16 . The of claim 1 , wherein said tetrafluoroethylene polymer has a melt creep viscosity of at least about 4.0×10 11 poise.

17 . The cathode of claim 1 , wherein said electrode layer is formed by a process free from solvent.

18 . The cathode of claim 1 , wherein said electrode layer is formed by dry mixing said cathode active particles, fluoropolymer binder and conductive carbon to form said electrode composition, and applying a shear force to said electrode composition in the absence of solvent to form said electrode layer.

19 . The cathode of claim 1 , wherein said conductive carbon fibers have a diameter of from about 0.1 micrometers to about 0.2 micrometers.

20 . The cathode of claim 1 , wherein said conductive carbon fibers comprise vapor grown carbon fibers (VGCF).

21 . The cathode of claim 1 , wherein said lithium transition metal oxide has an electrochemical potential versus Li/Li+ of at least about 4.6 V.

22 . The cathode of claim 1 , wherein said lithium transition metal oxide is selected from the group consisting of LiNi x Mn 2-x O 4 (LNMO) and Li 1.098 Mn 0.533 Ni 0.113 Co 0.13802 (Li-rich layered oxide (LRLO)).

23 . The cathode of claim 1 , wherein said lithium transition metal oxide is selected from the group consisting of LiNi 0.5 Mn 1.5 O 4 , LiNi 0.45 Mn 1.45 Cr 0.104 , LiCr 0.5 Mn 1.5 O 4 , LiCrMnO 4 , LiCu 0.5 Mn 1.5 O 4 , LiCoMnO 4 , LiFeMnO 4 , LiNiVO 4 , LiNiPO 4 , LiCoPO 4 and Li 2 CoPO 4 F.

24 . The cathode of claim 1 , wherein said fluoropolymer binder is fibrillated such that said electrode layer is self-supporting.

25 . The cathode of claim 1 , wherein the surface roughness of said aluminum current collector expressed as Sa (arithmetical mean height) is at least about 260 nm.

26 . The cathode of claim 1 , wherein the surface roughness of said aluminum current collector expressed as Sa (arithmetical mean

Assignees

• Chemours Co Fc Llc
• Univ California

Inventors

• Meng Ying Shirley
• Kountz Dennis J
• Gould Benjamin
• Li Weikang
• Sichler Allison
• Waters Crystal K
• Yao Weiliang
• Zhang Minghao

Classifications

• H01M2300/0037

  Mixture of solvents · CPC title

• H01M2300/0034

  Fluorinated solvents · CPC title

• H01M2004/028

  Positive electrodes · CPC title

• H01M2004/021

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

• H01M10/0569

  characterised by the solvents · CPC title