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EP-4737525-A1 - COMPOSITION IN POWDER FORM BASED ON FLUORINATED POLYMER

EP4737525A1EP 4737525 A1EP4737525 A1EP 4737525A1EP-4737525-A1

Abstract

The present invention relates to a composition, preferably in powder form, comprising a polymer P1 comprising recurring units derived from vinylidene fluoride and recurring units derived from a monomer M1 selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoroethylene, 1,2-difluoroethylene and perfluoroalkyle vinyl ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), a monomer of formula CF 2 =CFOCF 2 CF(CF 3 )OCF 2 CF 2 X wherein X is SO 2 F, CO 2 H, CH 2 OH, CH 2 OCN or CH 2 OPO 3 H; a monomer of formula CF 2 =CFOCF 2 CF 2 SO 2 F; a monomer of formula F(CF 2 )nCH 2 OCF=CF 2 wherein n is 1, 2, 3, 4 or 5; a monomer of formula R 1 CH 2 OCF=CF 2 wherein R 1 is hydrogen atom or F(CF 2 )m and m is 1, 2, 3 or 4; a monomer of formula R 2 OCF=CH 2 wherein R 2 is F(CF 2 )p et p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropene, hexafluoroisobutylene, perfluorobutylethylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or mixture thereof; characterized in that the particles of said polymer P1 have a Dv99 size distribution lower than 89 microns and a DvlO size distribution greater than 1.5 microns and in that said polymer P1 has a melting temperature Tm greater than 163.04 - 1.9628*x ; wherein x is the weight content of said fluorinated monomer M1 expressed as percent based on the total weight of said polymer P1 ; the melting temperature being measured by DSC according to the ASTM E794-06 (2018) standard test method.

Inventors

  • Beaume, François
  • FANG, Mingyuan
  • PETERSON, BRIAN
  • CHEUNG, PATRICIA

Assignees

  • ARKEMA FRANCE

Dates

Publication Date
20260506
Application Date
20241105

Claims (13)

  1. Composition in powder form comprising a polymer P1 comprising recurring units derived from vinylidene fluoride and recurring units derived from a monomer M1 selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoroethylene, 1,2-difluoroethylene and perfluoroalkyle vinyl ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), a monomer of formula CF 2 =CFOCF 2 CF(CF 3 )OCF 2 CF 2 X wherein X is SO 2 F, CO 2 H, CH 2 OH, CH 2 OCN or CH 2 OPO 3 H; a monomer of formula CF 2 =CFOCF 2 CF 2 SO 2 F; a monomer of formula F(CF 2 )nCH 2 OCF=CF 2 wherein n is 1, 2, 3, 4 or 5; a monomer of formula R 1 CH 2 OCF=CF 2 wherein R 1 is hydrogen atom or F(CF 2 )m and m is 1, 2, 3 or 4; a monomer of formula R 2 OCF=CH 2 wherein R 2 is F(CF 2 )p et p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropene, hexafluoroisobutylene, perfluorobutylethylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or mixture thereof; characterized in that the particles of said polymer P1 have a Dv99 size distribution lower than 89 microns and a DvlO size distribution greater than 1.5 microns and in that said polymer P1 has a melting temperature Tm greater than 163.04 - 1.9628*x ; wherein x is the weight content of said fluorinated monomer M1 expressed as percent based on the total weight of said polymer P1; the melting temperature being measured by DSC according to the ASTM E794-06 (2018) standard test method.
  2. A composition according to the preceding claim characterized in that said monomer M1 is hexafluoropropylene.
  3. A composition according to any one of the preceding claims characterized in that the mass content of said monomer M1 in said polymer P1 is between 1% and 16% based on the total weight of said polymer P1.
  4. A composition according to any one of the preceding claims characterized in that said polymer P1 has a melting temperature Tm greater than 164.04 - 1.9628*x, advantageously greater than 165.04 - 1.9628*x, preferably greater than 166.04 - 1.9628*x, in particular greater than 167.04 - 1.9628*x.
  5. A composition according to any one of the preceding claims characterized in that the melt viscosity of said polymer P1 ranges from 16 to 50 kP at 230°C and a shear rate of 100 s-1 measured according to ASTM D3835.
  6. A composition according to any one of the preceding claims characterized in that said polymer P1 comprises a functional group selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolics, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, or phosphonic.
  7. Composition according to any one of the preceding claims characterized in that said polymer P1 further comprises recurring units derived from a monomer M2 of formula R 1 R 2 C=C(R 3 )((X 1 ) p C(O)R 4 ) wherein the substituents R 1 , R 2 and R 3 are independently selected from the group consisting of H, CO 2 H et C 1 -C 5 alkyl ; R 4 is selected from the group consisting of -NHC(CH 3 ) 2 CH 2 C(O)CH 3 and -OR 5 wherein R 5 is selected from the group consisting of H and C 1 -C 18 alkyl optionally substituted by one or more functional groups -OH, -CO 2 H, -SO 3 H, -PO 3 H, -OC(O)R 6 , -C(O)O-R 6 or a heterocycle having five or six membered ring comprising at least one nitrogen atom in the backbone ; R 6 being selected from the group consisting of C 1 -C 6 alkyl and C 6 -C 12 aryl optionally substituted by one or more functional groups -OH, -CO 2 H, -SO 3 H, -PO 3 H ; p is 0 or 1; X 1 is selected from the group consisting of -[-C(O)OC(R 7 )(R 8 )C(R 9 )(R 10 )-] w1 - and C 1 -C 10 alkyl optionally substituted by one or more functional groups -OH, -CO 2 H or ester(s) ; w1 is an integer of from 1 to 50, advantageously from 1 to 25, preferably from 1 to 10, in particular from 1 to 5 ; R 7 , R 8 , R 9 , R 10 are independently from each other and independently for each unit w1 selected from the group consisting of H and C 1 -C 5 alkyl.
  8. A composition according to any one of the preceding claims characterized in that the particles of said polymer P1 have a distribution of size Dv90 lower than 50 microns.
  9. A composition according to any one of the preceding claims characterized in that the mass ratio between the extractible and the content of said monomer M1 in said polymer P1, both expressed as a percentage, is lower than 2.0.
  10. A composition according to any preceding claim characterized in that said polymer P1 is free of fluorosurfactants.
  11. Separator for electrochemical device comprising the composition according to any one of the preceding claims 1 to 10.
  12. Separator according to the previous claim wherein the separator comprises a porous support, a coating layer CL disposed on the support and an adhesive layer AL disposed on said coating layer CL; said adhesive layer AL being constituted of the composition according to any one of the preceding claims 1 to 10.
  13. Li-ion secondary battery comprising a negative electrode, a positive electrode and a separator, wherein said separator is according to the preceding claim.

Description

Technical field The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of Li-ion type. More specifically, the invention relates to a composition suitable for use as a coating in a separator. Background of the invention The market for separators for electrochemical devices is dominated by the use of polyolefins (e.g. Celgard® or Hipore®) produced by extrusion and/or stretching via dry or wet processes. Separators must have low thicknesses, optimal affinity for the electrolyte and sufficient mechanical and temperature strength. Among the most interesting alternatives to polyolefins, polymers with a better affinity vis-à-vis standard electrolytes have been proposed, in order to reduce the internal resistances of the system, such as poly(methylmethacrylate) (PMMA), poly(vinylidene fluoride) (PVDF) and poly(vinylidene-hexafluoropropene-fluoride) (P(VDF-co-HFP)). Poly(vinylidene fluoride) (PVDF) and its derivatives are of interest as the main constituent material of the separator and also as a polyolefin separator coating, for their electrochemical stability, and for their high dielectric constant which promotes ion dissociation and therefore conductivity. Copolymer P(VDF-co-HFP) (copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP)) has a crystallinity lower than PVDF. Therefore, the interest of these copolymers of P (VDF-co-HFP) is that they promote conductivity. The main evaluation criteria for a separator coating are the adhesion and the ionic conductivity or the swelling. Ionic conductivity represents the migration of Li ions through the separator and its coating, thanks to porosity. In the aqueous coating, this porosity corresponds to the interstices between the solid particles that make up the coating: polymer particles (from latex or powder redispersed in water) and / or ceramics. In the solvent coating, this porosity is created by the phase inversion (exposure to moisture of the acetone coating, for example) necessary before or during drying; Without phase reversal, a simple evaporation of the solvent forms a continuous non-porous coating. Gurley air permeability is used as an early indication of ion conduction. Beyond the air permeability of the initial coated separator, other aspects can affect ionic conductivity: the interaction with the electrolyte (favorable when a slight swelling of the polymer improves the wettability/affinity for the electrolyte, unfavorable when too much swelling of the polymer leads to reduce/clog the pores), the effect of pressing or lamination (reduces / clogs the pores). Dry adhesion is measured after assembly, by pressing or lamination, of the separator coated with an electrode. This adhesion increases with temperature and pressure applied post-coating. However, it is desirable to use gentle pressing/laminating conditions: reduced pressure to avoid/limit pore closure and thus minimize the impact on ionic conductivity, moderate temperature to limit energy consumption and maintain high line speed/productivity. There is always a need to develop new separator coatings that are easily implemented and have a good compromise between adhesion and low swelling. This is particularly the case for waterborne coatings prepared from polymer powder redispersed in water that are used for the preparation of a separator allowing good dry adhesion to the electrode at low pressing temperatures (including room temperature). Pressing at low temperatures during cell assembly has several advantages: temperature reached faster (line speed) and more quickly uniform in the thickness of the assembly (allows thicker assembly, line speed), reduced energy consumption. The invention therefore aims to remedy at least one of the disadvantages of the prior art, namely to provide a polymeric coating for separator capable of preventing swelling or dissolution in one (s) electrolyte solvent, while maintaining good adhesion properties to the electrode at low pressing temperature. Summary of the invention In a first aspect, the present invention provides a composition in powder form comprising a polymer P1 comprising recurring units derived from vinylidene fluoride and recurring units derived from a monomer M1 selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoroethylene, 1,2-difluoroethylene and perfluoroalkyle vinyl ethers, perfluoro(1,3-dioxole), perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), a monomer of formula CF2=CFOCF2CF(CF3)OCF2CF2X wherein X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; a monomer of formula CF2=CFOCF2CF2SO2F; a monomer of formula F(CF2)nCH2OCF=CF2 wherein n is 1, 2, 3, 4 or 5; a monomer of formula R1CH2OCF=CF2 wherein R1 is hydrogen atom or F(CF2)m and m is 1, 2, 3 or 4; a monomer of formula R2OCF=CH2 wherein R2 is F(CF2)p et p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluor