FLUOROPOLYMER HYBRID COMPOSITE

Abstract

The invention pertains to a process for the manufacture of a polymer electrolyte based on a fluoropolymer hybrid organic/inorganic composite, to a polymer electrolyte obtained thereof and to uses of said polymer electrolyte and membranes obtained therefrom in various applications, especially in electrochemical and in photo-electrochemical applications.

Claims

1-15. (canceled)

16. A process for manufacturing a polymer electrolyte based on a fluoropolymer hybrid organic/inorganic composite, said process comprising the following steps: (i) providing a composition comprising a pre-gelled metal compound [compound (P-GM)] obtained by partially hydrolysing and/or polycondensing a metal compound [compound (M)] having formula:
X.sub.4-mAY.sub.m wherein m is an integer from 1 to 4, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group, X is a hydrocarbon group, optionally comprising one or more functional groups; in the presence of: an electrolyte solution [solution (ES)] comprising at least one metal salt [metal salt (S)] and a liquid medium [medium (L)]; at least one acid catalyst; and optionally, an aqueous medium [medium (A)]; said pre-gelled metal compound [compound (P-GM)] comprising one or more inorganic domains consisting of ═A—O—A═ bonds and one or more residual hydrolysable groups Y; and then (ii) reacting in the molten state at least a fraction of hydroxyl groups of a functional fluoropolymer comprising at least one hydroxyl group [polymer (F)] with at least a fraction of hydrolysable groups Y of said compound (P-GM), so as to obtain a polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite incorporating the electrolyte solution (ES).

17. The process according to claim 16, wherein the compound (M) is a functional compound (M) selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltrismethoxyethoxysilane of formula CH.sub.2═CHS.sub.4OC.sub.2H.sub.4OCH.sub.3).sub.3, 2-(3,4-epoxycyclohexylethyltrimethoxysilane) of formula: ##STR00017## glycidoxypropylmethyldiethoxysilane of formula: ##STR00018## glycidoxypropyltrimethoxysilane of formula: ##STR00019## methacryloxypropyltrimethoxysilane of formula: ##STR00020## aminoethylaminpropylmethyldimethoxysilane of formula: ##STR00021## aminoethylaminpropyltrimethoxysilane of formula:
H.sub.2NC.sub.2H.sub.4NHC.sub.3H.sub.6Si(OCH.sub.3).sub.3 3-aminopropyltriethoxysilane, 3-phenylaminopropyltrimethoxysilane, 3-chloroisobutyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, n-(3- acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, (3-acryloxypropyl)dimethylmethoxysilane, (3-acryloxypropyl)methyldimethoxysilane, 3-(n-allylamino)propyltrimethoxysilane, 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane, carboxyethylsilanetriol, and its sodium salts, triethoxysilylpropylmaleamic acid of formula: ##STR00022## 3-(trihydroxysilyl)-1-propane-sulphonic acid of formula HOSO.sub.2-CH.sub.2CH.sub.2CH.sub.2—Si(OH).sub.3, N-(trimethoxysilylpropyl)ethylene-diamine triacetic acid, and its sodium salts, 3-(triethoxysilyl)propylsuccinic anhydride of formula: ##STR00023## acetamidopropyltrimethoxysilane of formula H.sub.3C—C(O)NH—CH.sub.2CH.sub.2CH.sub.2—Si(OCH.sub.3).sub.3, alkanolamine titanates of formula Ti(A)X(OR)Y, wherein A is an amine-substitued alkoxy group, e.g. OCH.sub.2CH.sub.2NH.sub.2, R is an alkyl group, and x and y are integers such that x+y =4.

18. The process according to claim 16, wherein the compound (M) is a non-functional compound (M) selected from the group consisting of triethoxysilane, trimethoxysilane, tetramethyltitanate, tetraethyltitanate, tetra-n-propyltitanate, tetraisopropyltitanate, tetra-n-butyltitanate, tetra-isobutyl titanate, tetra-tert- butyl titanate, tetra-n-pentyltitanate, tetra-n-hexyltitanate, tetraisooctyltitanate, tetra-n-lauryl titanate, tetraethylzirconate, tetra-n-propylzirconate, tetraisopropylzirconate, tetra-n-butyl zirconate, tetra-sec-butyl zirconate, tetra- tert-butyl zirconate, tetra-n-pentyl zirconate, tetra-tert-pentyl zirconate, tetra- tert-hexyl zirconate, tetra-n-heptyl zirconate, tetra-n-octyl zirconate, tetra-n- stearyl zirconate.

19. The process according to claim 16, wherein the at least one metal salt (S) is selected from the group consisting of: MeI, Me(PF.sub.6).sub.n, Me(BF.sub.4).sub.n, Me(ClO.sub.4).sub.n, Me(bis(oxalato)borate).sub.n (“Me(BOB)n”), MeCF.sub.3 SO.sub.3, Me[N(CF.sub.3SO.sub.2).sub.2].sub.n, Me[N(C.sub.2F.sub.5 SO.sub.2).sub.2].sub.n, Me[N(CF.sub.3SO.sub.2)(RFSO.sub.2)].sub.n with RF being C.sub.2F.sub.5, C.sub.4F.sub.9, CF.sub.3OCF.sub.2CF.sub.2, Me(AsF.sub.6).sub.n, Me[C(CF.sub.3SO.sub.2).sub.3].sub.n, Me.sub.2Sn, wherein Me is a metal and n is the valence of said metal.

20. The process according to claim 19, wherein the metal salt (S) is selected from the group consisting of LiI, LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, lithium bis(oxalato)borate (“LiBOB”), LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.2).sub.2 (“LiTF SI”), LiN(C.sub.2F.sub.5SO.sub.2).sub.2, M[N(CF.sub.3SO.sub.2)(RFSO.sub.2)].sub.n with RF being C.sub.2F.sub.5, C.sub.4F.sub.9, CF.sub.3OCF.sub.2CF.sub.2, LiAsF.sub.6, LiC(CF.sub.3SO.sub.2).sub.3, Li.sub.2Sn and combinations thereof.

21. The process according to claim 16, wherein the medium (L) in the electrolyte solution (ES) comprises at least one ionic liquid (IL), wherein the anion of the ionic liquid (IL) is selected from the group consisting of: bis(trifluoromethylsulphonyl)imide of formula (SO.sub.2CF.sub.3).sub.2N.sup.−, hexafluorophosphate of formula PF.sub.6.sub.−, tetrafluoroborate of formula BF.sub.4.sub.−, and oxaloborate of formula: ##STR00024##

22. The process according to claim 16, wherein electrolyte solution (ES) consists of at least one ionic liquid (IL) and LiTFSI.

23. The process according to claim 16, wherein the acid catalyst is an organic acid.

24. The process according to claim 16, wherein the medium (A) consists of water and ethanol.

25. The process according to claim 16, wherein under step (ii) the polymer (F) comprises comprising recurring units derived from at least one fluorinated monomer and recurring units derived from at least one comonomer comprising at least one hydroxyl group [comonomer (MA)] having formula (I): ##STR00025## wherein each of R.sub.1, R.sub.2, R.sub.3, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group and ROH is a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group.

26. The process according to claim 16, wherein under step (ii) the polymer (F) comprises: (a) at least 60% by moles of vinylidene fluoride (VDF); (b) optionally, from 0.1% to 15% by moles of a fluorinated comonomer selected from chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures thereof; and (c) from 0.05% to 10% by moles of comonomer (MA) of formula (I) wherein each of R.sub.1, R.sub.2, R.sub.3, equal to or different from each other, is ##STR00026## independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group and ROH is a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group.

27. A composition comprising the pre-gelled metal compound [compound (P-GM)], said composition being obtained according to step (i) of the process of claim 16.

28. A process for the manufacture of a polymer electrolyte membrane comprising processing into a film the polymer electrolyte obtained by the process according to claim 16 through compression moulding or extrusion techniques.

29. A polymer electrolyte membrane obtainable by the process according to claim 28.

30. An electrochemical device comprising the polymer electrolyte membrane according to claim 29.

Description

EXAMPLE 1

Manufacture of the Polymer Electrolyte with Polymer FA

[0180] Step (i): preparation of pre-gelled metal compound [0181] In a 50 ml beaker equipped with a magnetic stirrer running at a moderated speed the following ingredients are introduced in sequence: [0182] ES: 13.68 g [0183] TEOS: 6.62 g [0184] water: 2.30 g (molar ratio TEOS:H.sub.2O=1:4) [0185] ethanol: 1.66 g (weight ratio TEOS:EtOH=4:1) [0186] citric acid: 0.089 g (1 wt.% of TEOS+H.sub.2O) [0187] Theoretical amount of SiO.sub.2 produced in each batch was 1.89 g (17.91% of the starting TEOS, water, ethanol components); the pre-gelled metal compound composition was maintained under vigorous stirring during all the process.

[0188] Step (ii) preparation of polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite: [0189] The solution obtained in step (i) and polymer FA (8.4 g) were introduced into the feeding hopper of a mini-extruder and melt blended using a co-rotating twin screw micro extruder DSM Xplore 15 ml Microcompounder. The micro extruder is formed by a divisible fluid tight mixing compartment containing two detachable, conical mixing screws. Residence time was fixed at 2 minutes. The screw speed was fixed at 50 rpm for the feed and 100 rpm for the mixing, respectively. The heating temperature was set at 180° C. At the end of the 2 minutes of mixing the material was extruded through the nozzle. [0190] The amounts of the components of the polymer electrolyte so obtained were as follows: [0191] SiO.sub.2: 8% by weight; [0192] polymer FA: 35% by weight; [0193] ES: 57% by weight.

EXAMPLE 2

Comparative: Manufacture of Fluoropolymer Hybrid Organic/Inorganic Composite with Polymer FA

[0194] A fluoropolymer hybrid organic/inorganic composite was prepared according to the process disclosed in WO 2014/067816, wherein polymer FA has been extruded and reacted with the metal compound in the absence of electrolyte solution, leading to a polymer FA/SiO.sub.2 composite 75/25% by weight. The composite was obtained in the form of pellets. 10.08 g of said pellets were charged into the feeding hopper of a mini-extruder with 13.92 g of ES and kept at 180° C. After 2 minutes the product was discharged. The product resulting from extrusion had some transparent parts and some opaque parts. The extrudate did not show much consistency of the melt.

EXAMPLE 3

Manufacture of the Polymer Electrolyte with Polymer FB

[0195] Step (i): preparation of pre-gelled metal compound [0196] Step (i) was carried out as described in example 1 above.

[0197] Step (ii) preparation of polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite: [0198] Step (ii) was carried out in a twin screw co-rotating intermeshing extruder (Leistritz 18 ZSE 18 HP having a screw diameter D of 18 mm and a screw length of 720 mm (40 D)). The extruder was equipped with a main feeder a second feeder and a degassing unit. The barrel was composed of eight temperature controlled zones and a cooled one (at the main feeder) that allow to set the desired temperature profile. The molten polymer went out from a die, composed of a flat profile of 3 mm thick and 15 mm length. The extrudate was cooled in air. [0199] The polymer FB was fed into the extruder from the main hopper. [0200] Simultaneously, the pre-gel obtained in step (i) was fed into the extruder through the secondary hopper positioned in the block zone 3 (from 270 to 360 mm). The screw profile for this step was composed of a region of conveying elements with a regular decrease of pitch (from zone 0 to 1), then a kneading block composed by three kneading elements and a reverse flow element (zone 2), then a long conveying zone (from zone 3 to 4); after this series of elements, five kneading blocks (from zone 5 to 6). Finally five conveying elements and a degassing unit were situated before the die exit (zone 6 to 8). The temperature profile used is reported in Table 1 here below. The extruder rotation speed was 350 rpm.

TABLE-US-00001 TABLE 1 Zone 1 2 3 4 5 6 7 8 Profile [° C.] 160 140 90 100 140 150 160 170

[0201] The material appear continuous, self-sustaining, with melt strength able to be pulled.

EXAMPLE 4

Manufacture of the Polymer Electrolyte with Polymer FB

[0202] Step (i): preparation of pre-gelled metal compound [0203] In a 50 ml beaker equipped with a magnetic stirrer running at a moderated speed the following ingredients are introduced in sequence: [0204] ES: 13.68 g [0205] TEOS: 6.62 g [0206] formic acid: 1.83 g (27 wt. % of TEOS) the pre-gelled metal compound composition was maintained under vigorous stirring during all the process.

[0207] Step (ii) preparation of polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite:

[0208] Step (ii) was carried out as in step (ii) of example 3. [0209] The amounts of the components of the polymer electrolyte so obtained were as follows: [0210] SiO.sub.2: 8% by weight; [0211] polymer FB: 35% by weight; [0212] ES: 57% by weight.

EXAMPLE 5

Manufacture of a Membrane

[0213] The extrudates obtained from the process as detailed under Examples 1, 2, 3 and 4 were processed by compression moulding in a hot compression moulding press at 150° C. of heating temperature and 10 MPa of pressure for 3 min obtaining 60×60×0.2 mm.sup.3 membrane specimens. Then the samples where maintained at 120° C. for 120 minutes as part of the post-treatment of the process.

EXAMPLE 6

Elemental Analysis of the Samples Obtained in Example 5

[0214] In Table 2 the elemental analysis of the samples obtained in Example 5 are reported:

TABLE-US-00002 TABLE 2 Atomic % Example 2 Element Theoretical Example 1 comparative Example 3 Example 4 C 40.6 42.23 43.44 43.18 42.35 42.27 43.19 43.30 40.73 O 14.3 13.31 14.94 11.88 70.79 12.22 13.24 12.23 11.78 12.88 F 33.1 39.09 35.66 37.03 40.99 36.63 39.75 40.62 39.88 Si 2.2 2.28 2.25 2.80 29.21 1.01 2.59 1.60 1.53 2.05 S 4.9 3.08 3.71 5.12 3.43 5.26 3.23 2.76 4.35

[0215] The polymer electrolyte of the invention gives a rather uniform membrane.

[0216] The atomic elements in the membrane are well distributed in the film. On the contrary, the sample obtained with the extrudate of comparative example 2 shows areas where some of the elements are not even present.

EXAMPLE 7

Ionic Conductivity of the Samples Obtained in Example 5

[0217] In Table 3 the ionic conductivity of the samples obtained in Example 5 is reported:

TABLE-US-00003 TABLE 3 Example Ionic conductivity (S/cm) at 25° C. 1 5.11E−05 2 comparative 3.10E−05 3 3.16E−04 4 2.72E−04

[0218] The polymer electrolytes according to the present invention show ionic conductivity that makes them suitable for use in battery applications, such as in separators in Li-ion batteries.

EXAMPLE 8

Manufacture of Membrane of Polymer Electrolyte Film With Polymer FB by Film Extrusion

[0219] Step (i): preparation of pre-gelled metal compound

[0220] Step (i) was carried out as described in example 1 above.

[0221] Step (ii) preparation of polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite:

[0222] Step (ii) was carried out as in example 3, but at the end of the reaction the molten polymer went out from a die, composed of a flat profile of 1 mm thick and 40 mm length. The extrudate film was stretched between two cylinders of diameter 100 mm and width 100 mm with a gap from 100-500 um. The extrudate was cooled in air.

EXAMPLE 9

Manufacture of Membrane of Polymer Electrolyte Film With Polymer FB by Film Extrusion

[0223] Step (i): preparation of pre-gelled metal compound

[0224] Step (i) was carried out as described in example 4 above.

[0225] Step (ii) preparation of polymer electrolyte comprising a fluoropolymer hybrid organic/inorganic composite:

[0226] Step (ii) was carried out as described in example 8.

EXAMPLE 10

Elemental Analysis of the Samples Obtained in Example 8 and 9

[0227] In Table 4 the elemental analysis of the samples obtained in Example 8 and 9 are reported:

TABLE-US-00004 TABLE 4 Atomic % Element Theoretical Example 8 Example 9 C 40.6 49.69 51.75 O 14.3 13.13 9.41 F 33.1 32.26 32.71 Si 2.2 3.53 2.30 S 4.9 4.39 3.83

[0228] The polymer electrolyte of the invention gives a rather uniform membrane. The atomic elements in the membrane are well distributed in the film.

EXAMPLE 11 IONIC CONDUCTIVITY OF THE SAMPLES OBTAINED IN EXAMPLE 8 AND 9

[0229] In Table 5 the ionic conductivity of the samples obtained in Example 8 and 9 is reported:

TABLE-US-00005 TABLE 5 example Ionic conductivity (S/cm) 8 7.40E−05 9 4.36E−04

[0230] The polymer electrolytes membranes according to the present invention show ionic conductivity that makes them suitable for use in battery applications, such as in separators in Li-ion batteries.