Polyacrylonitrile gel membranes

Abstract

The present invention pertains to a process for the manufacture of a polymer electrolyte membrane comprising a polyacrylonitrile-based polymer and to uses of said electrolyte membrane in various applications, particularly in electrochemical applications.

Description

1 SSPI 2024 / 029Polyacrylonitrile Gel MembranesCross-reference to related applications

[0001] This application claims priority to European application No. 24315487.9 filed on October 18, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0002] The present invention pertains to a process for the manufacture of a gel polymer membrane comprising a polyacrylonitrile-based polymer and to uses of said membrane in various applications, particularly in electrochemical devices.Background Art

[0003] Polyacrylonitrile (PAN) has different advantages that makes this polymer suitable for the manufacturing of polymer electrolyte membranes, such as good fire resistance (Akashi et al., Electrochimica Acta, Vol. 43, Nos10-11, p1193-1197, 1998) and also good electrochemical stability at high voltages (A. Nagai, Chapter 6 “Lithium Ion Batteries, Sciences et Technologies”, 2009- Springer).

[0004] The manufacturing of polymer electrolyte membranes comprising PAN are usually based on processes that include dissolution of PAN in a solvent, followed by a step of forming a film. As an example, US12040444 discloses a method for preparing a polymer electrolyte for solid state batteries comprising polyacrylonitrile, said method comprising the dissolution of PAN in DMF, followed by spraying the solution onto a selected receiving surface using electrostatic spinning technique to obtain a flexible thin film.

[0005] Gel polymer membrane based on PAN are also known in the art, for example from CN 107959049, which describes the manufacturing a membrane by a solvent-based process, followed by impregnation of the membrane with an electrolyte.

[0006] The Applicant has unexpectedly discovered that by selecting certain PAN- based copolymers, it is possible to obtain transparent gel membranes by a process in the absence of toxic and polluting solvents, thus eliminating cost and safety and environmental concerns related to handling of large volumes of said solvents. The PAN-based gel membranes of the present invention can2 SSPI 2024 / 029 suitably incorporate ionic species, thus can be used in the manufacture of electrolyte polymers endowed with very good ionic conductivity.Summary of invention

[0007] It is thus an object of the present invention a process for manufacturing gel polymer membrane [gel polymer membrane (GPM)], said process comprising the following steps:(i) dispersing at least one PAN-based polymer [polymer (P)], wherein said polymer (P) comprises: recurring units derived from acrylonitrile (AN), and recurring units derived from at least one hydrogenated vinyl monomer[monomer (HM)] of formula (III):wherein:Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, andRx is a C1-C20 hydrocarbon moiety comprising at least one protic functional group [group (FX)], into a liquid medium [medium (L)], thus providing a composition [composition (C)];(ii) depositing the composition (C) obtained in step i) onto a support, to obtain a layer of composition (C);(iii) subjecting the layer of composition (C) obtained in step ii) to a heating treatment.

[0008] A second object of the present invention pertains to the gel polymer membrane [gel polymer membrane (GPM)] obtainable by the process of the invention.

[0009] In a further object, the present invention provides a process for manufacturing an ionic conductive gel polymer electrolyte membrane [gel polymer electrolyte membrane (GPE)], said process comprising the following steps:(i) dispersing at least one PAN-based polymer [polymer (P)], wherein said polymer (P) comprises: recurring units derived from acrylonitrile (AN), and3 SSPI 2024 / 029 recurring units derived from at least one hydrogenated vinyl monomer [monomer (HM)], said monomer (HM) comprising at least one protic functional group [group (FX)] into a liquid medium [medium (L)] that comprises at least one metal salt (MS), thus providing a composition [composition (C)];(ii) depositing the composition (C) obtained in step i) onto a support, to obtain a layer of composition (C);(iii) subjecting the layer of composition (C) obtained in step ii) to a heating treatment.

[0010] A further object of the present invention pertains to the gel polymer electrolyte membrane [gel polymer electrolyte membrane (GPE)] obtainable by the process of the invention.Description of embodiments

[0011] The polymer (P)

[0012] The polymer (P) is typically obtainable by polymerization of acrylonitrile (AN) with at least one hydrogenated vinyl monomer (HM).

[0013] By the term “hydrogenated vinyl monomer [monomer (HM)]” it is hereby intended to denote an ethylenically unsaturated monomer comprising at least one hydrogen atom.

[0014] The term “at least one hydrogenated vinyl monomer” is understood to mean that the polymer (P) may comprise recurring units derived from one or more than one hydrogenated vinyl monomers. In the rest of the text, the expression “hydrogenated vinyl monomers” is understood, for the purposes of the present invention, both in the plural and the singular, that is to say that they denote both one or more than one hydrogenated vinyl monomers as defined below.

[0015] The at least one hydrogenated vinyl monomer (HM) is a compound of formula (I):wherein:Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, andRx is a C1-C20 hydrocarbon moiety comprising at least one protic functional group [group (FX)].4 SSPI 2024 / 029

[0016] Rx may further contain other functional groups different from group (FX) and may include heteroatoms.

[0017] The protic functional group is a functional group that contains hydrogen atoms capable of being donated ad protons (H+) in chemical reactions. That protic functional group is preferably selected from the group consisting of hydroxyl group, sulfonic acid group, phosphonic acid group, phosphoric acid group, and carboxylic acid group. Among them, carboxylic acid group is preferred.

[0018] Also, the protic functional group includes the ones in which the group becomes the respective salts. The cations forming these salts can include arbitrary metal cations, NR4+(R is an arbitrary organic group) and the like. Specific examples of preferable metal cation include cations such as Li, Na, K, Rh, Mg, Ca, Sr. Among them, cations of Na, K, and Li which are inexpensive and easily capable of proton substitution are preferably used.

[0019] The polymer (P) typically comprises from 0.05 % by moles to 20.0 % by moles of recurring units derived from the at least one monomer (HM), the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

[0020] Non limitative examples of monomers (HM) include, notably, methacrylic acid (MAA), itaconic acid (ITA), hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate, acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS).

[0021] Determination of average mole percentage of monomer (HM) recurring units in polymer (P) can be performed by any suitable method, used alone or in combination. Mention can be notably made of acid-base titration methods, well suited e.g. for the determination of the carboxylic groups content, of FT-IR methods, of NMR methods, adequate for the quantification of monomers (HM) comprising aliphatic hydrogen atoms in side chains, of weight balance based on total fed monomer (HM) and unreacted residual monomer (HM) during polymer (P) manufacture.

[0022] The polymer (P) is preferably semi-crystalline. The term “semi-crystalline” is hereby intended to denote a polymer that is partially crystalline (organized in definite and regular order) and partially amorphous (random distribution).

[0023] The molecular weight (MW) of the polymer (P) suitable for use according to the described process may be within the range of 50 to 5000 kg / mole, typically 90 to 1000 kg / mole, more typically 100 to 500 kg / mole.

[0024] The polymer (P) preferably comprises, more preferably consists of:5 SSPI 2024 / 029(a) at least 80% by moles, preferably at least 85% by moles, more preferably at least 95% by moles of acrylonitrile (AN); and

[0025] (b) from 0.05% to 20% by moles, preferably from 0.2% to 10% by moles, more preferably from 0.3% to 5% by moles of at least one monomer (HM) of formula (I) as defined above, the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

[0026] The polymer (P) is typically obtainable by emulsion polymerization, suspension polymerization or solution polymerization, according to methods known to the person skilled in the art.

[0027] The polymer (P) is typically in the form of powder.

[0028] The average particle size (D50) of the polymer (P) powder is conveniently lower than 1000 microns, most preferably lower than 500 microns, even more preferably lower than 150 microns. The particle size (D50) of the polymer (P) powder is suitably higher than 1 micron, preferably higher than 5 microns, more preferably higher than 10 microns. The particle size analysis of the powder can be carried out using laser diffraction according to the ISO 13320 norm. D50 designates the particle diameter where half the population lies below this value and half lies above.

[0029] The liquid medium (L)

[0030] For the purpose of the present invention, by the term “liquid medium [medium (L)]” it is hereby intended to denote a composition comprising one or more organic substances in the liquid state at 20°C under atmospheric pressure.

[0031] According to some embodiments of the present invention, said medium (L) is preferably selected from organic carbonates.

[0032] According to a first embodiment of the invention, said medium (L) comprises at least one organic carbonate as the only medium (L).

[0033] Non-limiting examples of suitable organic carbonates include, notably, ethylene carbonate, propylene carbonate, mixtures of ethylene carbonate and propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl-methyl carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate and mixtures thereof.

[0034] The medium (L) in composition (C) may further comprise one or more additives.

[0035] Should one or more additives be present in the liquid medium, non-limitative examples of suitable additives include, notably, those which are soluble in the liquid medium.6 SSPI 2024 / 029

[0036] The concentration of polymer (P) in the medium (L) of composition (C) is comprised between 2 and 30 % by weight.

[0037] The concentration of polymer (P) in the medium (L) of composition (C) is advantageously lower than 30%, preferably lower than 25% by weight.

[0038] The concentration of polymer (P) in the medium (L) of composition (C) is advantageously higher than 2%, preferably higher than 5% by weight.

[0039] The medium (L) in composition (C) may comprise at least one metal salt (MS). By the term “metal salt (MS)”, it is hereby intended to denote a metal salt comprising electrically conductive ions.

[0040] The metal salt (MS)

[0041] A variety of metal salts may be employed as metal salts (MS). Metal salts which are stable and soluble in the chosen liquid medium (L) are generally used.

[0042] Non-limitative examples of suitable metal salts (MS) include, notably, Mel, Me(PF6)n, Me(BF4)n, Me(CIO4)n, Me(bis(oxalato)borate)n("Me(BOB)n"), MeCF3SO3, Me[N(CF3SO2)2]n, Me[N(C2F5SO2)2]n, Me[N(CF3SO2)(RFSO2)]nwith RF being C2Fs, C4F9, CF3OCF2CF2, Me(AsFe)n, Me[C(CF3SO2)3]n, Me2Sn, wherein Me is a metal, preferably a transition metal, an alkaline metal or an alkaline-earth metal, more preferably Me being Li, Na, K, Cs, and n is the valence of said metal, typically n being 1 or 2.

[0043] Preferred metal salts (MS) are selected from the followings: Lil, LiPFe, LiBF4, LiCIO4, lithium bis(oxalato)borate ("LiBOB"), LiCF3SO3, LiN(CF3SO2)2(“LiTFSI”), LiN(C2F5SO2)2, M[N(CF3SO2)(RFSO2)]nwith RF being C2F5, C4F9, CF3OCF2CF2, LiAsFe, LiC(CF3SO2)3, Li2Snand combinations thereof.

[0044] The amount of metal salt (MS) in the medium (L) of composition (C) is advantageously comprised between 1 and 15 % by weight, preferably between 2 and 10 % by weight.

[0045] The process

[0046] In step (i) of the process, polymer (P) is dispersed in the medium (L) to provide a composition (C).

[0047] The applicant has surprisingly found that certain PAN-based polymers, when dispersed in a liquid medium (L) provide compositions (C) that can be suitably processed in the form of a film by a convenient and very efficient process.

[0048] The viscosity of the composition (C) may be adjusted in step (i) of the process by selecting the proper concentration of polymer (P) in medium (L).

[0049] In step (i) of the process, polymer (P) is added to medium (L) and stirred at room temperature, thus at a temperature comprised between 10°C and 30°C.7 SSPI 2024 / 029

[0050] Stirring is continued for a period of from 5 minutes to 60 minutes.

[0051] Polymer (P) in the form of powder can be added to liquid medium (L) in a single charge.

[0052] Alternatively, a portion of polymer (P) can be added to medium (L) and dissolved by stirring at 60-90°C to provide a modified liquid medium (ML), and then the remaining amount of polymer (P) can be added to obtain composition (C). The portion of polymer (P) that can be added to medium (L) is an amount of about 1% to 2% of the total amount of polymer (P). In this way, the viscosity of the composition (C) can be more easily adjusted.

[0053] In step (ii) of the process, the composition (C) obtained in step (i) is deposited onto a support, to provide a layer of composition (C).

[0054] The support can be made of an inert material, notably glass or a metal sheet.

[0055] When the layer of composition (C) is deposited onto an inert support, a selfstanding membrane can be obtained at the end of the process.

[0056] When the gel polymer membrane is used in the manufacture of electrochemical devices, such as smart windows, the layer of composition (C) can be deposited directly onto an already formed electrode.

[0057] The method for depositing composition (C) onto the surface of a support involves using a coating or film-forming device. Preferred coating or filmforming devices include rod coaters, roll coaters, flexible coaters, curtain coaters, and gravure coaters. More preferably, a rigid blade shearing device (typically known in industrial terms as a doctor blade) is used. This provides a continuous and fast film forming process.

[0058] Step (ii) of the process is carried out at room temperature, thus at a temperature comprised between 10°C and 30°C. The viscosity of composition (C) is conveniently such that no heating or addition of any solvent is required to spread the composition on the support.

[0059] The layer of composition (C) has preferably a thickness comprised in the range between 3 and 1000 microns, more preferably between 10 and 500 microns, even more preferably between 20 and 100 microns.

[0060] The layer of composition (C) obtained in step (ii) is then subjected to a heating treatment in step (iii), said treatment comprising increasing the temperature to reach a temperature not higher than 90°C.

[0061] The increase in temperature can occur linearly (eg, continuously increasing the temperature) or can occur in a stepwise manner (eg, increasing the temperature by a certain amount after a certain amount of time). The duration of the heating treatment, and the time between subsequent stepwise8 SSPI 2024 / 029 increases in temperature may correspond to the amount of time required to obtain a transparent gel polymer membrane.

[0062] The resulting membrane is thus advantageously free of traces of any solvents, unlike the films of the prior art, because no solvents are added to composition (C), and no traces of them may remain after heating, even if heating is advantageously carried out at relatively low temperature.

[0063] The residual solvent when used could be detrimental to the well performance of the electrochemical device. The solvent could interact with the components of the device leading to a shortening of the lifetime of the same. This is an important advantage of the process of the present invention.

[0064] In a further aspect, thus, the present invention provides a gel polymer membrane (GPM) obtainable by the process defined above.

[0065] In a preferred embodiment of the invention, the liquid medium (L) comprises at least one metal salt (MS). The Applicant has surprisingly discovered that in the presence of the metal salt (MS) in liquid (L), the viscosity of the compositions is reduced, and agglomerates are not formed, thus improving the processability and the homogeneity of the resulting film.

[0066] The membrane obtained by the process of the invention wherein the liquid medium (L) comprises at least one metal salt (MS) has a good ionic conductivity and is endowed with good mechanical properties, and it is thus is particularly suitable for use as gel polymer electrolyte membrane in electrochemical devices.

[0067] Thus, the present invention provides a process for manufacturing an ionic conductive gel polymer membrane [gel polymer electrolyte membrane (GPE)], said process comprising the following steps:(i) dispersing at least one PAN-based polymer [polymer (P)], wherein said polymer (P) comprises: recurring units derived from acrylonitrile (AN), and recurring units derived from at least one hydrogenated vinyl monomer [monomer (HM)], said monomer (HM) comprising at least one protic functional group [group (FX)] into a liquid medium [medium (L)] that comprises at least one metal salt (MS), thus providing a composition [composition (C)];(ii) depositing the composition (C) obtained in step i) onto a support, to obtain a layer of composition (C);(iii) subjecting the layer of composition (C) obtained in step ii) to a heating treatment.9 SSPI 2024 / 029

[0068] The same details provided above with regard to GPM and process steps (i) to (iii) for manufacturing GPM apply respectively to GME and the process steps (i) to (iii) for manufacturing GPE.

[0069] In a further aspect, thus, the present invention provides a gel polymer electrolyte membrane (GPE) obtainable by the process defined above.

[0070] In still a further aspect, the present invention provides an electrochemical device comprising a gel polymer membrane (GPM) or a gel polymer electrolyte membrane (GPE) obtained by the processes of the present invention.

[0071] Non-limitative examples of suitable electrochemical devices include, notably, secondary batteries, supercapacitors, smart windows and hybrid lithium ion capacitors.

[0072] The gel polymer membrane (GPM) of the present invention is particularly suitable for use in wire-shaped supercapacitor with carbon nanotube yarns, such as those described in M. Serrapede et al. Carbon 213 (2023) 118283.

[0073] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0074] The invention will be now described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.Experimental section

[0075] Raw materials

[0076] Polymer (Comp-1): AN (100% by moles). Mw: 150000 g / mol; commercially available from Sigma Aldrich.

[0077] Polymer (Comp-2): AN / Methyl acrylate (6 % by moles); commercially available from Sigma Aldrich.

[0078] LiTFSI: bis(trifluoromethanesulfonyl)imide lithium salt.

[0079] Medium (L-1): solution of LiTFSI (0.4 mol / L) in ethylene carbonate (EC) / propylene carbonate (PC) (1 / 1 by weight).

[0080] Medium (L-2): solution of LiTFSI (0.13 mol / L) in ethylene carbonate (EC) / propylene carbonate (PC) (1 / 1 by weight).

[0081] Medium (S-F): ethylene carbonate (EC) / propylene carbonate (PC) (1 / 1 by weight).10 SSPI 2024 / 029

[0082] Modified liquid medium (ML): solution of LiTFSI (0.4 mol / L) in ethylene carbonate (EC) I propylene carbonate (PC) (1 / 1 by weight) including 1% by weight of polymer (P-2).

[0083] CMC / SBR: mixture of styrene butadiene rubber and sodium carboxyl methyl cellulose.

[0084] CNTy: carbon nanotube yarn consisting of three bundles of CNT fibers twisted together, commercially available as GALVORN CNT-HS YARN from DexMat.

[0085] Preparation of Polymer (P-1) and Polymer (P-2)

[0086] In the continuous polymerization process for producing Polymer (P-1) and Polymer (P-2) an aqueous suspension free radical method was employed. The reaction took place in a one-gallon continuous stirred tank reactor. Each ingredient, including both monomers and initiator system, was fed independently and continuously via a peristaltic pump to the bottom of the reactor through a feed tube. Oxalic acid was used to control the pH of the solution.

[0087] The polymerization conditions for preparing polymer (P-1) are reported in table 1.Table 1

[0088] The polymerization conditions for preparing polymer (P-2) are reported in table 2.Table 211 SSPI 2024 / 029

[0089] The reactor was maintained at 55°C. As the polymer formed, it rose to the top and flowed out through an overflow slot before being collected in a separate vessel where the reaction is quenched to prevent further polymerization. The redox initiator system utilized included various ammonium and ferrous sulfates and sulfites. Acrylonitrile was the only component introduced in its pure form; all other components, including the comonomer, were dissolved in deionized water to ensure a steady supply via peristaltic pump. The comonomer content in the polymers was 0.4% by weight for ITA in polymer (P-1) and 1.4% by weight for MAA in polymer (P-2). After reaching steady state, polymer was collected in powder form at approximately 0.4 kg / hr.

[0090] Polymer (P-1) and polymer (P-2) were obtained:Polymer (P-1): AN / ITA (0.4% by moles). Mw : 133000 g / mol from GPC, D50=27 micronsPolymer (P-2): AN / MAA (1.4% by moles). Mw: 170000 g / mol from GPC, D50=37 microns.

[0091] Example 1 : Preparation of membranes

[0092] Polymer powders of each of polymer (Comp-1), polymer (Comp-2), polymer (P-1) and polymer (P-2) were dispersed in a liquid medium as detailed in table 3 and stirred for 30 minutes at room temperature. Then, with the Doctor Blade a membrane of about 20 to 40 microns was obtained from each composition onto an aluminum sheet. The membrane was brought at 60°C for 30 minutes and then placed at 90°C for ten minutes.

[0093] Determination of the viscosity of the polymer-liquid medium composition.

[0094] The viscosity of the compositions of polymer (P-1) and of polymer (P-2) in different liquid mediums at room temperature, as obtained before the formation of the membrane, was evaluated.12 SSPI 2024 / 029

[0001] A simple viscosity test of the compositions was conducted using a graduated glass plate, clean and dry, inclined at 60° with respect to the plane. A drop for each compositions was made to flow for a length of 5 cm and timed. The results are shown in Table 3.Table 3

[0095] From the tests it is clear that the viscosity is i) inversely proportional to the amount of dissolved salt and ii) the final viscosity can be tailored by dissolving a part of the polymer at 90° C before dispersion at RT (ML).

[0096] The viscosity of the compositions comprising Polymer (Comp-1) or Polymer (Comp-2) and either liquid medium (L-1) at different concentration or (L-2) can not be measured because of the formation of agglomerates (lumps of polymer and the liquid medium) immediately or right after some minutes of contact of the Polymer and the liquid medium. Therefore no measurement of viscosity is possible.

[0097] For a practical use it is preferred to have a dispersion with a viscosity (according to the above method) not more than 20 minutes.

[0098] Determination of the ionic conductivity of the polymer membrane.

[0099] The bulk resistance of the gel polymer electrolyte membranes obtained in example 1 was measured in EL- Cells, with stainless steel blocking electrodes. The VMP e3 potentiostat was used to perform the impedance spectroscopy.

[0100] The ionic resistance was determined by performing linear fitting in the nyquist plot between 500,000 and 70 Hz.

[0101] The point of contact between the resulting line and the axis of the real impedance defined the bulk resistance value.13 SSPI 2024 / 029

[0102] The ionic conductivity o was obtained using the following equation: dwherein d is the thickness of the film, Rb the bulk resistance and S is the area of the stainless steel electrode.

[0103] The results are shown in Table 4.Table 4

[0104] The results show that the compositions according to the invention, comprising a PAN-based polymer (P) and a liquid medium (L) comprising at least one metal salt (MS), allow to obtain transparent membranes endowed with good ionic conductivity.

[0105] Example 2. Preparation of a smart window.

[0106] A first electrode was prepared as follows: an electrochromic layer WO3, was prepared according to the procedure described in Solar Energy Materials and Solar Cells Volume 68, Issues 3-4, June 2001 , Pages 279-293.

[0107] The xerogel obtained was casted on a glass coated with FTO (Fluorine doped tin oxide). Three layers of xerogel were deposited on the coated glass and after every event the glass was treated at 300°C until the film became transparent. The thickness of the WO3 layer obtained was about 250 nm.

[0108] A second electrode was prepared as follows: on a glass coated with FTO, gold was sputtered, slightly changing the surface of the glass without affecting the transparency.

[0109] A membrane obtained from a composition comprising polymer (P-2) and medium (ML) (concentration of polymer (P-2) in ML=12% wt) was used as electrolyte layer: the composition was coated on the WO3 electrode (thickness14 SSPI 2024 / 029 of the layer = 300 um); the coated electrode was heated at a temperature of 90°C for two minutes until a transparent membrane was obtained on the electrode. Then, the second electrode was made in contact with the membrane and the system was cooled down to obtain a solid conductive membrane between the two electrodes. The adhesion towards both electrodes was very high, with no need of a sealant for sealing the device.

[0110] The smart window obtained as above detailed was tested during continuous cycling between -4 V (where the window is colored in blue) and +2.25 V (where the window is highly transparent).

[0111] In Table 5, the data of transmittance was measured at 550 nm, at different times with zero electrical charge are reported.Table 5

[0112] Example 3 - Manufacturing of a Hybrid Lithium Ion Capacitor

[0113] A full coin cell (CR2032) was assembled, the cell comprising, in order:1. Bottom cap15 SSPI 2024 / 0292. Graphite electrode (95% Graphite Actilion GHDR; 5% CMC / SBR in water prepared by roll to roll on copper (Mass Loading 3.7 mg cm'2) with a piece of Li metal to carry on graphite pre-lithiation3. Membrane prepared as follows:A dispersion of 12% polymer P-2 in Medium (L-1) was casted with doctor blade on both anode and cathode electrodes, then baked at 90° for 10 minutes. The electrodes were piled to assemble a cell without any further separator. A drop of Medium (L-1) was added to make sure a piece of lithium could entirely dissolve as sacrificial anode material to pre-intercalate graphite. The ionic conductivity of the membrane was about 2 mS / cm with an approximate thickness of 300 microns.4. Activated carbon electrode (85% activated carbon; 10% Carbon Black; 5% CMC / SBR in water prepared by roll to roll on aluminium (Mass Loading 3.4 mg cm-2))5. Spacer (stainless steel)6. Spring (stainless steel)7. Top cap

[0114] The cell was galvanostatically cycled at 50 mA g-1and Specific Capacitance was evaluated. The voltage window was limited to 2.6 V to 3.8 V. The results are shown in Table 6.Table 6

[0115] The data show that the device properly worked and that the capacitance increased with time. The increasing specific capacitance is monitored with respect to the activated carbon material because the capacitive response comes mainly from the activated carbon polarization. The value is greater than standard symmetrical supercapacitors assembled with activated carbon16 SSPI 2024 / 029 electrodes, implying the correct functioning of the hybrid architecture. The increasing trend with cycle number indicates the device is still activating to a steady state capacitance.

[0116] Example 4. Preparation of a wire-shaped supercapacitor.

[0117] A wire-shaped supercapacitor was assembled with two CNTy arranged parallel on a plane, at a constant distance of approximately 1 mm.

[0118] A composition comprising polymer (P-2) and medium (ML) (concentration of polymer (P-2) in ML=12% wt) was poured onto the yarns, incorporating them and then solidified on a hotplate at 90°C. The excess solid electrolyte was removed, obtaining a thread-like device.

[0119] The device was then characterized with a VMP3 potentiostat which shows that the device works very well. The potential window of the device was scanned from 0.2V to 3.0V, using the cyclic voltammetry technique. During these measurements, an almost constant Coulombic efficiency was observed at a scan rate of 1mV / s. The specific capacitance measured of the device reaches 1.79 mF / cm at 1mV / s with an energy density of 2.6x10-6 Wh / cm. The maximum power density recorded is 0.21 mW / h

Claims

17 SSPI 2024 / 029Claims1. A process for manufacturing a gel polymer membrane [gel polymer membrane (GPM)], said process comprising the following steps:(i) dispersing at least one PAN-based polymer [polymer (P)], wherein said polymer (P) comprises: recurring units derived from acrylonitrile (AN), and recurring units derived from at least one hydrogenated vinyl monomer[monomer (HM)] of formula (I):wherein:Ri, R2 and R3, equal to or different from each other, are independently selected from a hydrogen atom, a C1-C3 hydrocarbon group and Rx, andRx is a C1-C20 hydrocarbon moiety comprising at least one functional group [group (FX)] selected from the group consisting of hydroxyl group and ionic group into a liquid medium [medium (L)], thus providing a composition [composition (C)], wherein said medium (L) is a composition comprising one or more organic substances in the liquid state at 20°C under atmospheric pressure;(ii) depositing the composition (C) obtained in step (i) onto a support, to obtain a layer of composition (C);(iii) subjecting the layer of composition (C) obtained in step (ii) to a heating treatment.

2. The process according to claim 1 , wherein the protic functional group is selected from the group consisting of hydroxyl group, sulfonic acid group, phosphonic acid group, phosphoric acid group, and carboxylic acid group.

3. The process according to anyone of claims 1 or 2, wherein the polymer (P) preferably comprises, more preferably consists of:(a) at least 80% by moles, preferably at least 85% by moles, more preferably at least 95% by moles of acrylonitrile (AN); and18 SSPI 2024 / 029(b) from 0.1% to 20% by moles, preferably from 0.2% to 10% by moles, more preferably from 0.3% to 5% by moles of at least one monomer (HM) of formula (I), the aforementioned percentages by moles being referred to the total moles of recurring units of polymer (P).

4. The process according to anyone of the preceding claims, wherein the concentration of polymer (P) in the medium (L) of composition (C) is comprised between 3 and 30% by weight.

5. The process according to anyone of the preceding claims, wherein in step (i) polymer (P) is added to medium (L) and stirred at a temperature comprised between 10°C and 30°C.

6. The process according to anyone of the preceding claims, wherein the layer of composition (C) obtained in step (ii) has a thickness comprised in the range between 10 and 100 microns.

7. The process according to anyone of the preceding claims, wherein the heating treatment in step (iii) comprises increasing the temperature to a temperature not higher than 90°C.

8. The process according to anyone of the preceding claims, wherein the liquid medium [medium (L)] comprises at least one metal salt (MS).

9. The process according to claim 9, wherein the metal salt (MS) is selected from the group consisting of Lil, LiPFe, LiBF4, LiCIC i, lithium bis(oxalato)borate ("LiBOB"), UCF3SO3, LiN(CF3SO2)2(“LiTFSI”), LiN(C2F5SO2)2, M[N(CF3SO2)(RFSO2)]nwith RF being C2FS, C4F9, CF3OCF2CF2, LiAsFe, LiC(CF3SO2)3, Li2Snand combinations thereof.

10. The process according to anyone of claims 8 or 9, wherein the amount of metal salt (MS) in the medium (L) of composition (C) is comprised between 1 and 15 % by weight.

11. A gel polymer membrane [gel polymer membrane (GPM)] obtainable by the process according to anyone of claims 1 to 7.

12. A gel polymer electrolyte membrane [gel polymer electrolyte membrane (GPE)] obtainable by the process according to anyone of claims 8 to 10.19 SSPI 2024 / 02913. An electrochemical device comprising a gel polymer membrane (GPM) according to claim 11 and / or a gel polymer electrolyte (GPE) according to claim 12.

14. The electrochemical devices according to claim 13, which is selected from the group consisting of secondary batteries, supercapacitors, smart windows and hybrid lithium ion capacitors.

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