Cross-linker for the preparation of a new family of single ion conduction polymers for electrochemical devices and such polymers

Abstract

A specific cross-linker, an alkaline metal bis(styrenesulfonyl)imide monomer, is used in the synthesis of single ionic conductive copolymers that are non-fluorinated and non-PEO based. Such copolymers meet the security and costs requirements to be used as solid polymers electrolytes (SPE). They are promising alternatives to standard liquid electrolytes in alkaline metal-ion batteries because of their improved security and inflammability properties. The copolymers described are either polyvinylsulfonates or acrylate vinylsulfonate block-copolymers. Preferred acrylate monomers are methacrylates and preferred vinylsulfonates are styrene sulfonates. The copolymer is prepared by radical polymerization of the vinyl sulfonate and the cross-linker and optionally the acrylate, in particular radical photopolymerization using a functionalized bis(acyl)phosphane oxide (BAPO) as photoinitiator. Also described is the use of such copolymer as solid polymer electrolyte in a lithium ion battery.

Claims

1. A method for the production of a solid conducting polymer, comprising: copolymerizing a monomer mixture comprising a bis(styrylsulfonylimide) salt of formula (I) to form the solid conducting polymer having crosslinking units of the bis(styrylsulfonylimide) salt, ##STR00008## wherein M.sup.+ is Li.sup.+ or Na.sup.+, as cross linking monomer, with an alkaline metal vinyl sulfonate monomer and a radical initiator, wherein the radical initiator is selected from the group consisting of a photoinitiator, a thermal initiator and combinations thereof.

2. A method for the production of a solid polymer electrolyte, comprising: copolymerizing a monomer mixture comprising a bis(styrylsulfonylimide) salt of formula (I) to form a solid conducting polymer having crosslinking units of the bis(styrylsulfonylimide) salt, ##STR00009## wherein M.sup.+ is Li.sup.+ or Na.sup.+, and forming the solid polymer electrolyte from the solid conducting polymer, as cross linking monomer, with an alkaline metal vinyl sulfonate monomer and a radical initiator, wherein the radical initiator is selected from the group consisting of a photoinitiator, a thermal initiator and combinations thereof.

3. A solid single-ion conducting polymer produced by copolymerizing a bis(styrylsulfonylimide) salt of formula (I) as a cross linking monomer, with an alkaline metal vinyl sulfonate monomer and a radical initiator, wherein said radical initiator is selected from the group consisting of a photoinitiator, a thermal initiator and combinations thereof ##STR00010## wherein M.sup.+ is Li.sup.+ or Na.sup.+.

4. The solid single-ion conducting polymer of claim 3, wherein it is a solid polymer electrolyte.

5. The solid single-ion conducting polymer of claim 3, wherein the solid single-ion conducting polymer further comprises copolymerized units of an acrylate monomer.

6. The solid single-ion conducting polymer of claim 5, wherein said acrylate monomer is a methacrylate monomer.

7. The solid single-ion conducting polymer of claim 6, wherein said acrylate monomer is methylmethacrylate.

8. The solid single-ion conducting polymer of claim 3, wherein the vinyl sulfonate monomer is styrene sulfonic acid salt.

9. The solid single-ion conducting polymer of claim 3, wherein the radical initiator is a photoinitiator or a combination of photoinitiator with a thermal initiator.

10. The solid single-ion conducting polymer of claim 3, wherein the radical initiator comprises a photoinitiator selected from the group consisting of an α-hydroxyketone, a benzophenone, a benzil derivative, a thioxanthone, an acetylphosphane, an alkoxyamine and an alkoxyamine.

11. The solid single-ion conducting polymer of claim 10, wherein the photoinitiator contains a photoinitiator of the acylphosphane oxide type of formula (II) ##STR00011## wherein n is from 1 to 6, m is 1 or 2, X is oxygen or sulfur, R.sup.1 is —C(R.sup.4).sub.3, wherein if n=1, all R.sup.4 are independently from each other selected from the group consisting of H, aromatic groups, alkenyl groups and aliphatic groups, wherein the aliphatic groups can be unbranched or branched, non-substituted or substituted by one or more of the following groups: aromatic groups, heteroaromatic groups, heterocyclic groups, ethers (polyethyleneglycol or polyethylene oxide), selenides, hydroxyl, thiol, ketones, imines, carboxylic acid derivatives, sulfones, sulfoxides, sulfates, sulfonium, sulfimines, sulfoximine, sulfonamide, amine, ammonium salts, nitriles, nitro, amidines, carbamates, guanidinium, hydrazones, hydrazides, hydrazines, silanes, siloxanes, polysiloxanes, phosphonium, phosphinates, phosphine oxide or phosphate groups, if n>1, at least one R.sup.4 is a 2 to 6-valent substituent selected from the list described above, wherein the aforementioned alkyl can also comprise one, two or more of the afore mentioned groups within the chain, or be substituted once or more times with such groups, and wherein said groups are separated by at least one CH.sub.2-group R.sup.2 is an aryl group, and R.sup.3 is —C(R.sup.4).sub.3 as specified above for R.sup.1.

12. The solid single-ion conducting polymer of claim 11, wherein n is 1, 2, 3 or 4.

13. The solid single-ion conducting polymer of claim 12, wherein n is 1 or 2.

14. The solid single-ion conducting polymer of claim 11, wherein R.sup.2 is 2,4,6-trimethylphenyl (mesityl).

15. The solid single-ion conducting polymer of claim 11, wherein R.sup.2 is 2,6-dimethoxyphenyl.

16. The solid single-ion conducting polymer of claim 11, wherein the photoinitiator is suitable to generate two radicals.

17. The solid single-ion conducting polymer of claim 11, wherein the photoinitiator is of formula (II) and wherein n is 1, m is 2, X is O, R.sup.1 is —CH.sub.2—CH.sub.2(Z), Z is —(CH.sub.2).sub.n1—NMe.sub.3X′.sup.+, wherein n.sub.1 is from 1 to 4, and X′ is Cl, Br, or I Z is an ester —(CO)OR.sup.6 wherein R.sup.6 is an alkyl comprising within its chain or said alkyl chain being interrupted by one or more —O—, or carrying one or more siloxy groups, or carrying one or more ammonium salt groups, and R.sup.2 is a mesityl group or a 2,6-dimethoxyphenyl group, or n is 2, m is 2, R.sup.1 is —(CO)O—(CH.sub.2—CH.sub.2—O).sub.x—O(CO)— wherein x is in the range of 1 to 1000, R.sup.2 is a mesityl group or a 2,6-dimethoxyphenyl group.

18. The solid single-ion conducting polymer of claim 17, wherein n.sub.1 is from 1 to 3.

19. The solid single-ion conducting polymer of claim 17, wherein R.sup.7, R.sup.8 and R.sup.9 are C1 to C4 alkyl groups.

20. The solid single-ion conducting polymer of claim 17, wherein R.sup.2 is a mesityl group.

21. The solid single-ion conducting polymer of claim 17, wherein x is from 1 to 100.

22. The solid single-ion conducting polymer of claim 11, wherein the photoinitiator is one of ##STR00012## ##STR00013##

23. The solid single-ion conducting polymer of claim 8, wherein the ratio of alkaline metal styrylsulfonate:acrylate is from about 1:0 to about 1:4.

24. The solid single-ion conducting polymer of claim 23, wherein the ratio of alkaline metal styrylsulfonate:acrylate is 1:1.

25. The solid single-ion conducting polymer of claim 5, wherein the cross linking monomer is present in a ratio of up to 20 mole-% referred to the amount of acrylate and sulfonate monomers.

26. The solid single-ion conducting polymer of claim 11, wherein R.sup.1 is an alkyl group substituted by an ester group and wherein the ratio of acrylate:alkaline metal styrylsulfonate:cross-linking monomer is about 1:1:0.2 or wherein R.sup.1 is an aliphatic group substituted by an ammonium salt and wherein the ratio of acrylate:alkaline metal styrylsulfonate:cross-linking monomer is about 0:10:1.

27. The solid single-ion conducting polymer of claim 3, wherein the photoinitiator and/or the thermally induced initiator is present in an amount of about 1 mol % of total monomers.

28. A battery comprising an electrolyte in which the electrolyte comprises the solid single-ion conducting polymer of claim 3, and the battery is a lithium ion battery or a sodium ion battery.

29. A battery comprising the solid single-ion conducting polymer of claim 3 as an electrolyte.

30. A cathode or an anode wherein the solid single-ion conducting polymer of claim 3 is intimately mixed with a cathode or anode electroactive material and optionally graphene and/or conductive carbon or graphite.

31. A method for producing the battery according to claim 29, comprising coating a releasable support with an active electrode material and optionally one or more conductive fillers to form a cathode and then coating the cathode with the solid single-ion conducting polymer.

32. The solid single-ion conducting polymer of claim 17, wherein R.sup.6 is an alkyl comprising one or more siloxy groups bonded to a vanadate.

33. The solid single-ion conducting polymer of claim 17, wherein R.sup.6 comprises a plurality of polyethylene groups interrupted by one or more —O—, or one or more siloxy groups of formula —SiR.sup.7.sub.y(OR.sup.8).sub.3-y, wherein y is 0 from 3, or carrying one or more ammonium salt groups of formula —N(R.sup.9).sup.4+X′.sup.− wherein R.sup.7, R.sup.8 and R.sup.9 are alkyl groups.

34. A cathode or an anode wherein the solid single-ion conducting polymer of claim 3 is anchored to a cathode or anode electroactive material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. This description makes reference to the annexed drawings, wherein:

(2) FIG. 1: Synthesis of photoinitiator BAPO-Vanadate

(3) FIG. 2: .sup.31 P NMR of the photoinitiator linked to vanadate

(4) FIG. 3: SEM image of PMMA embedding the Li.sub.xH.sub.yV.sub.3O.sub.8 fibers resulted from a BAPO-vanadate polymerization

(5) FIG. 4: XRD pattern of the films polymer TBP-1 1a (prepared without LiDS) and 1 b (with 9 mM LiDS)

(6) FIG. 5: Particle size distribution of polymer TBP-1 in water

(7) FIG. 6: TGA (“A”) and DSC (“B”) curves for TBP-1

(8) FIG. 7: Temperature dependence of conductivity (plotted logarithmically) for the tri-block polymers (TBP-1 to TBP-5 and DBP-6) prepared using the BAPO-1, BAPO-6 respectively as photo-initiators.

(9) FIG. 8: SEM images of LFP composite cathode films (L1 and L2) before and after pressing

(10) FIG. 9: SEM images of vanadate composite cathode films (V1)

(11) FIG. 10: Cycle-life of the composite L1 using the polymer TBP-1a at 60° C. and 70° C. with a current of 20 mA/g (C/8).

(12) FIG. 11: Specific charge vs. cycle for composite L3

(13) FIG. 12: Potential vs. specific charge for composite V1 and V2

(14) FIG. 13: Specific charge vs. cycle for composite V1 and V2.

MODES FOR CARRYING OUT THE INVENTION

(15) As indicated above, the present invention relates to cross-linkers suitable in the synthesis of single ionic conductive copolymers that are non-fluorinated and non-PEO based. Such copolymers meet the security and costs requirements to be used as solid polymers electrolytes (SPE). They are promising alternatives to standard liquid electrolytes in the Li-ion batteries or Na-ion batteries because of their improved security and inflammability properties. The copolymers described are either polyvinylsulfonates or polyacrylates, in particular methacrylates such as polymethylmethacrylates (PMMA) functionalized with alkaline metal polyvinylsulfonyl like alkaline metal polysulfonylstyrene such as lithium polysulfonylstyrene (LiPSS) and crosslinked by the use of the inventive linker, i.e. the alkaline metal (like Li) bis(styrenesulfonyl)imide (MBSSI like LiBSSI) monomer. The copolymers of the present invention can be prepared by radical polymerization, in particular radical photopolymerization, preferably photopolymerization using a functionalized bis(acyl)phosphane oxide (BAPO) as photoinitiator. Such copolymers can be used as solid polymer electrolytes in lithium-ion or sodium-ion batteries.

Experimental Section

(16) 1) Commercial Starting Materials

(17) Lithium styrene sulfonate was purchased from Tosoh Europe B.V., The Netherlands (>94%) and was purified before usage by recrystallization from bis(2methoxyethyl) ether (DME) and dried under vacuum at 100° C. for 2 days.

(18) Methyl metacrylate (MMA) was purchased from Aldrich (>99%) and was distilled prior to use. Tetraethyleneglycol dimethyl ether (TEG) was purified by distillation and stored over molecular sieves.

(19) 2) Synthesis of the Cross Linker: Bis(Styrylsulfonylimide) Lithium Salt

(20) ##STR00006##

i) 4-vinylbenzenesulfonylchloride

(21) A solution of 4-vinylbenzenesulfonic acid sodium salt (7.2 g, 35 mmol, 1 eq) in dimethylformamide (DMF) (58 mL) was cooled to 0° C. before adding thionyl chloride (34.4 g, 21 mL, 289 mmol, 8.3 eq) dropwise. The thionylchloride was degassed but used without purification. After stirring for 12 h, the mixture was left at −4° C. overnight and then poured into ice-water (100 mL) and extracted with diethylether (3×50 mL). The solution was concentrated under reduced pressure affording a yellowish oil (4.4 g, 66%).

(22) .sup.1 H-NMR (500.2 MHz, CDCl.sub.3) δ=7.92 (d, J=8.0 Hz, 2H, CHAr), 7.56 (d, J=7.5 Hz, 2H, CHAr), 6.81 (m, 1H, CHolef), 5.92 (d, J=17.5 Hz, 1H, CHolef), 5.47 (d, J=11.0 Hz, 1H, CHolef) ppm.

(23) .sup.13C{.sup.1H}NMR (75.5 MHz, CDCl.sub.3): δ=144.9 (CH.sub.2═CH—C), 142.9 (CSO.sub.2Cl), 135.0 (CH.sub.2═CH), 127.6 (CHAr), 127.2 (CHAr), 119.5 (CH.sub.2) ppm.

ii) 4-Vinylbenzenesulfonylamide

(24) 4-vinylbenzenesulfonylchloride (2 g, 9.87 mmol, 1 equiv) was reacted for 2 h with aqueous ammonia solution (100 mL, (25% NH.sub.3)) and then extracted with ether, dried over MgSO.sub.4 and concentrated giving the sulfonamide as a white solid (1.11 g, 62%).

(25) Mp:141° C.

(26) .sup.1H-NMR (500.2 MHz, CDCl3): δ=7.95 (d, J=8.0 Hz, 2H, CHAr), 7.58 (d, J=8.5 Hz, 2H, CHAr), 6.75 (m, 1H, CHolef), 5.94 (d, J=17.5 Hz, 1H, CHolef), 5.50 (d, J=11.0 Hz, 1H, CHolef), 3.08 (s, 2H, NH.sub.2) ppm.

iii) Bis(styrylsulfonylimide) lithium Salt

(27) A mixture of 4-vinylbenzenesulfonylchloride (323 mg, 1.6 mmol, 1 eq), 4-vinylbenzenesulfonylamide (293 mg, 1.6 mmol, 1 eq) and LiH (77 mg, 3.2 mmol, 2 eq) in THF (5 mL) was stirred for 12 h under Ar at room temperature, then concentrated and washed with ether giving a white solid. The solid was recrystallized from MeOH affording 0.4 g, 71% yield.

(28) Mp: >250° C. dec.

(29) .sup.1H-NMR (500.2 MHz, D.sub.2O): δ=7.61 (m, 4H, CHAr), 7.46 (m, 4H, CHAr), 6.76 (m, 2H, CHolef), 5.91 (d, J=17.5 Hz, 2H, CHolef), 5.36 (d, J=11.0 Hz, 2H, CHolef).

(30) .sup.13C-NMR (75.5 MHz, D.sub.2O): δ=141.9 (CH.sub.2═CH—C), 138.9 (CSO.sub.2N), 135.4 (CH.sub.2═CH), 126.7 (CHAr), 125.8 (CHAr), 116.4 (CH.sub.2) ppm.

(31) .sup.7Li-MAS NMR δ=0 ppm

(32) ATR IR: λ.sup.−1 (cm.sup.−1)=1626 w, 1494 m, 1424 m, 1200 s, 1137 m, 1093 s, 989 s, 904 m, 839 s, 743 m.

(33) EA Calc: C, 54.0%; H, 4.0%. Found C, 53.4%; H, 4.1%.

3) Synthesis of bis(acyl)phosphane oxide (BAPO) photoinitiators

(34) The general synthesis of the different BAPOs is described in PCT/EP2013/070378 (WO 2014/053455), WO 2011/003772 and WO 2006/056541. For BAPO-1, see example 23 of WO 2014/053455, for BAPO-2, see example 12a of WO 2014/053455, for BAPO-3, see example 27 of WO 2014/053455. BAPO-4 was prepared using BAPO-2 and the protocol described in example 34 of WO 2011/003772 and BAPO-5 was prepared according to example 23 of WO 2014/053455, using polyethyleneglycol diacrylate Mn 6000 as starting material.

(35) BAPO-6 is soluble in water and the synthesis was performed as described for Example 1 in patent WO 2006/056541 using 3-Bromopropyltrimethylammonium bromide in ethanol for the alkylation of bisenolate Na[P(COMes)2].sub.XDME} (step d).

4) Synthesis of bis(acyl)phosphane oxide (BAPO) photoinitiator Linked to Vanadate and Polymerization of MMA

(36) A bis(acyl)phosphane oxide functionalized with a siloxane group (BAPO-2) was linked to a lithium oxohydroxide vanadate Li.sub.xH.sub.yV.sub.3O.sub.8 (wherein 2<x+y<6.8 and 0<x<4 and 0.5<y<6) (described within US20130157138 A1) (FIG. 1).

(37) The linking of the BAPO to the vanadate was carried out under argon atmosphere in a 100 mL Schlenk flask connected to a reflux condenser. To a suspension of Li.sub.xH.sub.yV.sub.3O.sub.8 (1 g) in THF (30 mL) was added BAPO-2 (0.05 g, 0.087 mmol) and the mixture refluxed during 4 h. After cooling down the mixture, the solid was filtered, washed, and sonicated two times for 1 min in THF (20 mL). The resulting greenish solid was dried under vacuum at 50° C. for 24 h affording 0.95 g. Analysis of the material was performed spectroscopically (MAS NMR) to confirm the presence of bis(acyl)phosphane)oxide photoactive group in the material (.sup.31P NMR) (FIG. 2).

5) Synthesis of PMMA by Radical Polymerization Using a Vanadate Linked Photoinitiator

(38) The photoinitiated polymerization of MMA was carried out in a 100 mL Schlenk under argon atmosphere. A suspension of the linked photoinitiator (0.95 g) in THF (30 mL) was prepared and the MMA (0.78 g, 7.8 mmol) added to the suspension. The mixture was stirred vigorously for 5 min before irradiation. The irradiation of the mixture was performed with a mercury UV lamp under vigorous stirring at room temperature during 1 h affording a gel. The greenish solid was suspended in 50 mL of THF sonicated and filtered. The sample was dried under vacuum affording 0.87 g of a greenish solid. The morphology of this solid was investigated by SEM analysis (FIG. 3).

6) Synthesis of the Copolymers (CP-1 to CP-6)

6a) Synthesis of Tri-Block Copolymers (TBP-1 to TBP-5)

(39) Reaction Path for the Synthesis of TBP-1:

(40) ##STR00007##

(41) The synthesis of the polymer TBP-1 (1 b) was carried out in a 100 mL Schlenk flask under argon atmosphere. The reactor was charged with lithium sulfonate styrene (4 mmol, 760 mg), lithium bis(styrenesulfonyl)imide (0.8 mmol, 284 mg) and distilled water (30 mL). Freshly distilled methyl methacrylate (MMA) (4 mmol, 400 mg, 430 μL) and photoinitiator BAPO-1 (R=CH.sub.2CH.sub.2CO(OCH.sub.2CH.sub.2).sub.2OEt) (0.08 mmol, 42 mg) dissolved in DME (dimethoxyethane) (5 mL) were slowly added under argon atmosphere to the stirred mixture. To the reaction mixture lithium dodecylsulfate (9 mM) was added. The emulsion was deoxygenated for 20 min prior to being irradiated at 22° C. with a middle pressure mercury UV lamp (254 nm) for 1 h while maintaining a vigorous stirring (1200 rpm) resulting in a white suspension.

(42) The polymer was isolated by removing solvent under vacuum (40 C.°, 20 mbar). The resulting white viscous residual was washed with isopropanol (2×5 mL) and tetrahydrofuran (2×5 mL). The recovered polymer was dried under vacuum overnight (25 C.°, 0.1 mbar) affording 945 mg (71% yield).

(43) Stable suspensions of the polymer were prepared by adding distilled water and 5% (w/w) tetraethyleneglycol dimethylether (TEG). TEG was added as plasticizer to avoid dense packing of the polymer.

(44) Synthesis of TBP-2 to TBP-5 was performed analogously.

6b) Synthesis of Polymer DBP-6

(45) For polymer TBP-6 a preferential ratio of lithium styrylsulfonate to cross linker is a 10:1 ratio with no acrylate or methacrylate employed. Except for this change and the fact that the BAPO-6 was added to the aqueous solution containing monomers, the procedure for TBP-1 was followed.

7) Preparation of Self-Standing Films of SPE from the Suspension of the TBP

(46) Self standing films of the polymer electrolyte were prepared by casting the TBP suspension within Teflon plates with 300-500 μm circular groves. These circular groves had the size of the electrolyte films required for conductivity and battery tests (Ø 15 and 17 mm). The polymers were initially dried at room temperature under Ar for 24 h; then at 50° C. under Ar during 4 days, and finally under vacuum at 50° C. for 24 h. The processing resulted in homogeneous self-standing films of 200-700 μm which were stored in a glove box for 2 days prior to use.

8) Characterization of Tri-Block Copolymers (TBP) (after Processing as Self-Standing Films)

8a) Methods Used

(47) NMR

(48) The MAS NMR experiments were performed using a Bruker Avance 400 MHz 9.4T spectrometer. The .sup.7Li MAS NMR spectra were recorded at 155.50 MHz using 1.0 s radiofrequency pulses, a recycle delay of 2.0 s, a number of transient of 600, and a spinning rate of 7.0 kHz.

(49) XRD

(50) Powder X-ray diffraction patterns were obtained on a STOE Stadi P diffractometer equipped with a germanium monochromator and CuK.sub.α1 radiation (operated at 40 kV, 35 mA).

(51) SEM

(52) Scanning electron microscopy (SEM) was performed on a Zeiss Gemini 1530 operated at 1 kV.

(53) TEM

(54) Transmission electron microscopy (TEM) was performed on a CM30ST (FEI; LaB6 cathode) and a TecnaiF30 microscope that were operated at 300 kV with a maximum point resolution of ca. 2 Å.

(55) Ionic Conductivity

(56) Impedance measurements were carried out in the frequency range of 500 kHz to 1 Hz using an excitation amplitude of 50 mV (VMP3, Biologic SAS, France). Discs of 17 mm diameter were cut from the electrolyte film and the samples were placed between two round stainless steel discs (1.8 cm.sup.2) and sealed for air and moisture protection with a temperature stable tape. From the obtained line the bulk resistance (R) was calculated selecting the minimum in the Nyquist plot between the electrolyte arc and the beginning of the interfacial arc. The bulk resistance R of the polymer is then used to calculate the conductivity (σ) according to Eq. 1, where d is the sample thickness and A the sample area measured between the steel discs. This methodology has been broadly described to measure the ionic conductivity of SPE at different temperatures.[11]

(57) $\begin{array}{cc}\sigma =\frac{d}{A*R}& \mathrm{Eq}.1\end{array}$

8b. Characterization of Tri-Block Copolymer TBP-1

(58) .sup.7Li MAS NMR δ=−0.5 ppm

(59) ATR IR: υ(cm.sup.−1)=2350 w, 1724 s, 1456 m, 1248 s, 1149 s, 1085 s, 1030 s, 985 m, 948 m, 892 m, 758 m, 638 s

(60) EA C, 52.8%; H, 4.0%; N, 0.7%.

(61) Using XRD-diffraction no clear crystallinity was found for TBP1, independently on the addition of surfactant (LiDS). Only a very broad signal in the 2θ range of 10°-25° was detected, suggesting that the polymer contains regions having ordered chains, but from the signal width, it can be stated that these ordered domains are very small or not well defined (FIG. 4).

(62) On the other hand, the addition of LiDS had an influence on the polymer particle size and distribution. The polymer prepared without LiDS exhibited inferior stability and suffered from particle sedimentation after few hours. Zeta size measurements of polymer suspensions containing LiDS (9 mM) showed a narrow distribution of the particles size around 41 nm (FIG. 5). The size distribution remained unchanged after 2 weeks aging, and was used for the preparation of composite films.

(63) The thermal stability of the polymers was evaluated by thermal gravimetric analysis (TGA). TBP1 was thermally stable up to 190° C., with negligible mass loss (1%). There was an increasing mass loss of 7.6% at 290° C. The melting behavior of the polymers was quantified using differential scanning calorimetry (DSC) and representative curves for the polymer 1a are represented in FIG. 6 showing an endothermic peak at 290° C.

(64) FIG. 7 shows the conductivity vs inverse of temperature (T.sup.−1) for TBP-1 and the analogous polymers (TBP2, TBP3, TBP4, TBP5 and DBP6) prepared using the different BAPO photoinitiators described above. A linear increase in conductivity indicates that the conductivity mechanism remained the same throughout the temperature range measured. The maximum conductivity of 0.14 mS/cm at 60° C. was reached for the polymer obtained using a polymeric siloxane containing BAPO (BAPO-4). This sample however exhibited a deviation from the linear increase on the plot of logarithmic conductivity vs T.sup.−1. This indicates a change of the conduction mechanism at higher temperature or the influence of a second conduction process. Chemical stability of the polymer films against lithium was tested by placing the film on freshly cut lithium in dry argon atmosphere. The interface polymer/Li remained unchanged after the polymer film was lifted in regular time intervals (up to 3 weeks).

9) Composite Cathode Preparation with TBP-1

9a) One step SPE/AM Composites Preparation

(65) In a first step the cathode active materials (AM), either carbon coated lithium iron phosphate (LFP) (2 μm, A1100, Alees, Taiwan) or lithium oxohydroxide vanadate Li.sub.xH.sub.yV.sub.3O.sub.8 (wherein 2<x+y<6.8 and 0<x<4 and 0.5<y<6) (described in US20130157138 A1) were premixed with carbon black conductive additive (Super-P, Timcal) and alternatively also with graphite (SFG6 or KS6, Timcal, Switzerland) in an agate ball mill (300 rpm, 2×10 minutes). Then an aqueous suspension of the polymer TBP-1 with a concentration of 0.16 g/ml was added. Depending on the solid content, some additional de-ionized water was added until suitable viscosity of the slurry had been achieved. Optimal solid content around 18% and 35% for preparation of LFP and vanadates composites (L1-L2 and V1-V2) respectively were used. To prevent strong foaming during ball milling and resulting holes in the cathode films, a minimum amount of tributyl phosphate (>99.0%, Fluka Chemie AG, Buchs, Switzerland) was added as anti-foaming agent. After ball milling for 2×30 minutes (300 rpm, with reversed rotation direction) an homogenous slurry was obtained. The weight percent of different composite compositions are shown in Table 1.

(66) TABLE-US-00001 TABLE 1 LFP or Li.sub.xH.sub.yV.sub.3O.sub.8 composites with different ratios. LFP LFP composite composite Li.sub.xH.sub.yV.sub.3O.sub.8 Li.sub.xH.sub.yV.sub.3O.sub.8 L1(%) L2(%) V1(%) V2(%) AM = 74 55 46 43 (LFP or Li.sub.xH.sub.yV.sub.3O.sub.8) Graphite 10 10 15 0 (SFG6) Super P 5 5 11 29 Polymer TBP-1 11 30 27 27

(67) The slurries were casted by doctor-blading on standard aluminum foil (15 μm). The films were dried for one hour at room temperature and an airflow, then for 12 h at 50° C. under an Argon atmosphere, and finally for at least 24 h at 50° C. under vacuum, resulting in 40-100 μm thick dry films. The films were pressed (15 tons, 5 min) to reduce voids in the film and improve contact between particles. The microstructures of the LFP based films are shown in FIG. 9 and the corresponding microstructure of the vanadate based films in FIG. 10.

9b) Two Steps SPE/AM Composites Preparation by Coating and Infiltration

(68) As an alternative way to prepare SPE/AM composites, a LFP-based cathode was first bar coated on an aluminum foil and then a SPE-solution was drop casted on the cathode.

(69) The coated cathode had a composition of 88% (LFP), 6% (KS6) and 4% (SuperP)). In order to assure adhesion to the aluminum foil 2% of sodium methyl cellulose (Na-CMC) was used as binder. Then a suspension of TBP1 in water (30% wt) was drop casted on the LFP-cathode. The composites cathodes were initially dried at room temperature under Ar for 24 h then at 50° C. under Ar during 24 h, and finally under vacuum (10 mbar) at 50° C. for 24 h. The resulting cathode composites (composite L3) were 100 μm thick and contain a load of 17.6 mg polymer/cm.sup.2 cathode film.

10) Battery Setup

(70) Electrochemical performance was tested in standard coin cells (CR2025, Renata, Switzerland). Lithium metal disk was used as anode. Disks of 13 mm diameter were subsequently cut from the composite cathode films.

(71) For the composites prepared by one step route (L1-L2 & V1-V2), a SPE disk (diameter 17 mm) from the self-standing SPE film TBP1 was placed between the anode and the cathode. The test cells were assembled in dry Ar atmosphere (<0.1 ppm H.sub.2O; <0.1 ppm O.sub.2). For galvanostatic experiments, a current of 20-25 mA/g was used (based on the active material). The LFP window potential was 3.0-3.9 V and for vanadium 1.6-4.2 V.

10a) Electrochemical Performance of LFP-Composites (One Step Synthesis)

(72) The cathode L1 (FIG. 10) showed capacities close to the theoretical value (152 Ah/kg in the first cycle at 60° C.), and was stable for the five cycles measured at this temperature when cycled with a current of 20 mA/g (C/8). After these five cycles, the cell was transferred to another measurement device for long term measurement and the temperature was increased to 70° C. At this temperature, the capacity first increases to 167 Ah/kg. After 20 cycles 144 Ah/kg were measured.

10b) Electrochemical Performance of LFP-Composites (Two Step Synthesis)

(73) In FIG. 11 the composite L3 (where the SPE was drop-casted, see 8b) had been galvanostatically cycled at 70° C. in the 3.0-3.9 V range with a current of 20 mA/g. In the first 6 cycles a slight overcapacity was observed and from the 7th cycle recharge efficiencies close to 100%. At C/8 rate, the performance of the cell still achieved capacities higher than 160 mA/g after the 20.sup.th cycle.

10c) Electrochemical Performance of Vanadate-Composites (One Step Synthesis)

(74) FIG. 12 displays the potential vs Li.sup.+/Li (V) versus specific charge (Ah/Kg) for the first cycles of batteries using cathode V1 and V2 at 70° C. In FIG. 13, the capacity in dependence on the cycle number is shown for both composites up to the 23.sup.th cycle. The cathode composite V1 exhibited capacities in the first cycle of 398 Ah/kg close to the theoretical value, which decreased to 148 Ah/Kg after the 23th cycle. The cathode composite V2 achieved capacities up to 419 Ah/kg in the first cycle, which slowly decreased to 150 Ah/Kg after the 23th cycle. Remarkably, the columbic efficiency of composite V2 (Super P and graphite) was improved when compared to V2 (only SuperP as carbon additive).

(75) While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

REFERENCES

(76) [1] Tollefson, J. Car industry: Charging up the future. Nature 2008, 456, 436. [2] a) Cheng, F., Liang, J., Tao, Z. & Chen, J. Functional materials for rechargeable batteries. Adv. Mater. 2011, 23, 1695. b) Armand, M. & Tarascon, J-M. Building better batteries. Nature 2008, 451, 652. [3] Bruce, P. G., Freunberger, S. A., Hardwick, L. J. & Tarascon, J-M. LiO2 and Li2S batteries with high energy storage. Nature Mater. 2012, 11, 19. [4] Hammami, A., Raymond, N. & Armand, M. Lithium-ion batteries: Runaway risk of forming toxic compounds. Nature 2003, 424, 635. [5] Murata, K., Izuchi, S. & Yoshihisa, Y. An overview of the research and development of solid polymer electrolyte batteries. Electrochim. Acta 2000, 45, 1501. [6] Bruce, P. G. & Vincent, C. A. Polymer electrolytes. J. Chem. Soc. Faraday Trans. 1993, 89, 3187. [7] Marzantowicz, M., Dygas, J. R., Krok, F., Florjaczyk, Z. & Zygad Monikowska, E. Influence of crystalline complexes on electrical properties of PEO:LiTFSI electrolyte. Electrochim. Acta 2007, 53, 1518. [8] a) Vaia, R. A., Vasudevan, S., Krawiec, W., Scanlon, L. G. & Giannelis, E. P. New polymer electrolyte nanocomposites: Melt intercalation of poly(ethylene oxide) in mica-type silicates. Adv. Mater. 1995, 7, 154. b) Wong, S. & Zax, D. B. What do NMR linewidths tell us? Dynamics of alkali cations in a PEO-based nanocomposite polymer electrolyte. Electrochim. Acta. 1997, 42, 3513. c) Bujdàk, J., Hackett, E. & Giannelis, E. P. Effect of layer charge on the intercalation of poly(ethylene oxide) in layered silicates: Implications on nanocomposite polymer electrolytes. Chem. Mater. 2000, 12, 2168. d) Capiglia, C., Mustarelli, P., Quartarone, E., Tomasi, C. & Magistris, A. Effects of nanoscale SiO2 on the thermal and transport properties of solvent-free, poly(ethylene oxide) (PEO)-based polymer electrolytes. Solid State Ion. 1999, 118, 73. e) Croce, F., Appetecchi, G. B., Persi, L. & Scrosati, B. Nanocomposite polymer electrolytes for lithium batteries. Nature 1998, 394, 456. f) Forsyth, M. et al. The effect of nano-particle TiO2 fillers on structure and transport in polymer electrolytes. Solid State Ion. 2002, 147, 203. [9] Aryanfar, A., rooks, P., Merinov, B. V., Goddard, W. A., Colussi, A. J., Hoffmann, M. R., J. Phys. Chem. Lett. 2014, 5, 1721. [10] Bonnet J. P., Bouchet, R., Aboulaich, A., Gigmes, D. Maria, S., Bertin, D., Armand, M. Phan, T., Meziani, R. Block copolymer including a polyanion based on a TFSI anion monomers: A battery electrolyte. WO2013034848. [11] Murata, K., Izuchi, S. & Yoshihisa, Y. An overview of the research and development of solid polymer electrolyte batteries. Electrochim. Acta 2000, 45, 1501.