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US-20260128312-A1 - PROCESSING AID FOR FREESTANDING ELECTRODE FABRICATION

US20260128312A1US 20260128312 A1US20260128312 A1US 20260128312A1US-20260128312-A1

Abstract

This invention discloses a cathode film comprising: a graphite based processing aid, cathode active material, optionally a conductive carbon, and a fluoropolymer binder comprising PVDF and PTFE. The cathode film is free of residue solvent. The cathode film is made by a dry fabrication process.

Inventors

  • Ayda Rafie
  • Ramin Amin-Sanayei
  • KOUAKOU DESSALESSE AMANI
  • Robert J. Barsotti

Assignees

  • ARKEMA INC.

Dates

Publication Date
20260507
Application Date
20251229

Claims (20)

  1. 1 . A cathode film comprising: a processing aid, cathode active material, optionally a conductive carbon, and a fluoropolymer binder comprising PTFE, and wherein the cathode is free of solvent residue, and wherein the total binder amount is from 0.5 wt % to 10 wt % of the cathode film.
  2. 2 . The cathode film of claim 1 , further comprising PVDF as a component of the binder wherein the weight ratio of PVDF to PTFE in the cathode is 10:90 to 95:5
  3. 3 . The cathode film of claim 1 , wherein the processing aid has an ID/IG of less than 1.6.
  4. 4 . The cathode film of claim 1 , wherein the processing aid is a graphite-based processing aid.
  5. 5 . The cathode film of claim 1 , wherein the processing aid is selected from the group consisting of graphite powder, graphene, nano graphite, furnace black, acetylene black, carbon nanotubes (CNT), carbon nanofibers (CNF), fine graphite powder, vapor deposited graphite fibers, Ketjen carbon black and combinations thereof.
  6. 6 . The cathode film of claim 1 , wherein the processing aid has a number average particle size of less than 5 microns.
  7. 7 . The cathode film of claim 1 , wherein the processing aid is a flaked graphite having a number average particle size of less than 4.0 micrometers
  8. 8 . The cathode film of claim 1 , wherein the amount of processing aid is from 0.1 to 20 wt % based on the weight of the cathode film.
  9. 9 . The cathode film of claim 2 , wherein the PVDF is a homopolymer or vinylidene fluoride copolymer.
  10. 10 . The electrode of claim 2 , wherein the PVDF is a functionalized PVDF comprising a functional group.
  11. 11 . The cathode film of claim 10 , wherein the functional group is selected from the group consisting of a carboxylic group or salt or ester thereof, a phosphate, a sulfonate or a combination thereof.
  12. 12 . The cathode film of claim 10 , wherein the fluoropolymer binder comprising the PTFE and the functionalized PVDF is in the form of a scaffold.
  13. 13 . The cathode film of claim 1 , wherein the cathode film is freestanding.
  14. 14 . The cathode film of claim 1 , wherein the amount of fluoropolymer binder in the cathode film is from 0.5 weight % to 6 weight % based on weight of the cathode film.
  15. 15 . The cathode film of claim 1 , wherein the cathode film contains conductive carbon.
  16. 16 . An energy storage device comprising the cathode film of claim 1 , wherein the energy storage device is selected from the group consisting of a lithium-ion battery, a sodium-ion battery and a lithium sulfur battery.
  17. 17 . A method of fabricating a cathode film of an energy storage device, comprising: a) combining a processing aid, cathode active material, optionally conductive carbon, and PVDF to form a first mixture b) adding PTFE to the first mixture to form a second mixture; and c) subjecting the second mixture to a shearing process to form a dry cathode forming mixture comprising PVDF and PTFE; wherein no liquid is used in the process.
  18. 18 . The method of claim 17 , wherein the processing aid is selected from the group consisting of graphite powder, graphene, nano graphite, furnace black, acetylene black, carbon nanotubes (CNT), carbon nanofibers (CNF), fine graphite powder, vapor deposited graphite fibers, Ketjen carbon black and combinations thereof.
  19. 19 . The method of claim 17 , wherein the processing aid has a number average particle size of less than 5.0 micrometers.
  20. 20 . The method of claim 17 , wherein the amount of processing aid is from 0.1 to 20 wt % based on the weight of the cathode film.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation of PCT/US2025/047890 which claims priority to U.S. 63/698,661, which are herein incorporated by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This application was made with United States Government support under DE-EE0009109 awarded by the Department of Energy of the United States. The United States Government has certain rights in the invention. FIELD OF THE INVENTION The present invention relates generally to the field of energy storage devices. More particularly, the present invention relates to structures and methods for making dry binders and films for energy storage devices. BACKGROUND OF THE INVENTION The processing rate of electrodes is often much lower than that of solution cast process due to concerns with the electrode's quality as well as the desire to reduce any irregularities in the fabricated electrodes. The irregularities in an electrode can be generally classified into two groups: 1) surface irregularities or defects due to lack of uniform dispersion of binder(s) and/or active materials and 2) gross irregularities which occurs due to uneven material flow or lack of sufficient malleability during the calendering step. The first one should be addressed during the powder mixing which is controlled by the PVDF type, PVDF particle size, as well as the use of processing aid(s) in the formulation. The second one occurs mostly during the calendering of electrode where the presence of processing aid allows the electrode to be rolled into uniform thin sheets without breaking, which in turn allows fabrication of high-quality, uniform and irregularity-free electrodes. A proper processing aid should allow for faster processing rate by inducing malleability, reducing energy costs, and minimizing the occurrence of irregularities, hence reducing off-spec electrodes. However, many common processing aids are not compatible with the battery environment. On some occasions, PVDF powder has been used in the formulation of electrodes to improve its adhesion to the current collector. PVDF could also help with the PTFE particle dispersion within the electrode mixture prior to calendaring, however, it requires PVDF particle size to be in the nano size range, preferably less than 200 nm, to become an effective processing aid in making a uniform binder(s) dispersion during fabrication of the electrodes including cathode and anode. PVDF-based polymers are semi-crystalline polymers used for many different applications such as extrusion, injection molding, fiber spinning, extrusion blow molding, blown film, and scaffolds to form articles. PVDF scaffolds are generally made via electrospinning of polymer solutions which often requires using toxic and flammable solvents. Fabricating scaffolds without using any solvent/liquid is advantageous especially when they are free of any residual solvent. Tensile strength and flexibility of articles made using scaffolds are important parameters for the purpose of handling, processing, and durability. The tensile strength of the articles made using scaffolds depends on the strength and quality of the scaffold, for example, electrode tensile strength, thickness, flexibility and mechanical properties are important to ensure that the roll-to-roll process is feasible. The volume resistivity of the electrodes is also an important parameter where the resistance inside the cell is directly correlated to the electronic conductivity within the electrodes. As a result, an electrode having low resistivity exhibits improved power density, energy density, and longevity. The first cycle efficiency (FCE) in lithium-ion batteries (LIBs) and in Sodium-ion batteries (NIBs) refers to the percentage of charge that can be stored and then retrieved during the initial charging and discharging cycle. The FCE is an important parameter because the overall performance, especially cell capacity and longevity can significantly improve with FCE. Therefore, having a high FCE is very desirable. Surprisingly, it was found that adding graphite/graphite-based processing aids to the cathode formulation can ease processing and allowed fabrication of high-quality, high strength cathodes. In some embodiments, conductivity and quality of electrodes can be further improved by using PVDF having a primary particle size of less than 150 nm. The cathode can be freestanding or supported. DOI: 10.1002/ente.202200732 describes a solvent-free graphite anode using a PTFE and PVDF binder. Adding PVDF increased the first cycle efficiency and helped the integrity of electrode even after PTFE was electrochemically reduced and degraded in the first lithiation cycle. This article demonstrates that the free-standing electrode film was formed when the dry mixture was hot rolled at 160° C. The hot roll was needed because the described process failed to produce PVDF-PTFE scaffolds and consequently needed high temperature to melt or soften th