EP4655836A1

EP4655836A1 - Polymer electrolyte, electrochemical cell and battery comprising said electrolyte, method of preparation and uses thereof

Info

Publication number: EP4655836A1
Application number: EP23782506.2A
Authority: EP
Inventors: María MARTÍNEZ-IBÁÑEZ; Michel Armand; Mikel ARRESE-IGOR; Leire MEABE; Lorena GARCÍA; Iñigo RAPOSO; Eduardo GIL; Vincent Giordani
Original assignee: Basquevolt SA
Current assignee: Basquevolt SA
Priority date: 2023-01-25
Filing date: 2023-09-28
Publication date: 2025-12-03
Also published as: WO2024156383A1; CN120604373A

Abstract

The present invention relates to a polymer electrolyte comprising: i. at least one polymer; ii. at least one sulfonamide; and iii. at least one lithium salt; being said electrolyte further characterized in that it does not comprise an organic carbonate. The polymer electrolyte of the invention is preferably found in gel form. The invention also relates to an electrochemical cell or battery comprising said polymer electrolyte. One remarkable advantage of the gel electrolyte is that, due to the lack of flammable liquids that are generally involved in liquid electrolytes (such as organic carbonates), it features improved thermal stability. The present invention also relates to a method for preparing the polymer electrolyte of the invention and to a method for preparing the electrochemical cell or battery comprising the polymer electrolyte of the invention.

Description

POLYMER ELECTROLYTE, ELECTROCHEMICAL CELL AND BATTERY COMPRISING SAID ELECTROLYTE, METHOD OF PREPARATION AND USES THEREOF.

FIELD OF THE INVENTION

The present invention relates to the field of polymeric electrolytes, particularly those in the form of a gel, for use in electrochemical cells or batteries. The present invention may find widespread application in energy storage and electronic devices.

BACKGROUND

Lithium metal batteries (LMBs) arguably represent an attractive technology for energy storage applications due to their high energy density and ultralow redox potential. Commercial batteries primarily use liquid electrolytes (LEs) as the ion-transport media owing to their high ionic conductivity and exceptional wettability with electrodes and separator. Typical liquid electrolytes are organic carbonates and ethers, such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), 1,2-dimethoxy ethane (DME), etc. However, liquid electrolytes may be associated to potential safety concerns and performance degradation originating from dendrite growth and cathode electrochemistry. The organic solvents of liquid electrolytes are generally flammable solvents that may cause combustion (or even explosion) due to short-circuit and thermal runaway resulting from the growth of Li dendrites. These issues have so far hindered a practical use of LMBs.

Solid electrolytes, such as those made of polymers, ceramics or their hybrids, and gel electrolytes might solve the above problems related to the use of liquid electrolytes, however their conductivity is lower than that of established liquid electrolytes.

Particularly, a way to address the low conductivity in gel polymer electrolytes (GPEs) is the introduction of an organic carbonate as liquid component or a plasticizer that can help dissociate the Li salt (or plasticize a polymeric component). While increasing the ionic conductivity and improving the charge/discharge capacity of an electrochemical cell, such organic carbonates might again affect the cell stability and safety. Thus, additional work is required for the design and fabrication of functional GPEs that enable them to develop safe and durable LMBs. In some work, thermal-stable polymers, such as fluorinated polymers, have been introduced to improve the thermal stability of GPEs (J.H. Baik, D.G. Kim, J.H. Lee, S. Kim, D.G Hong, J.C. Lee, J. Ind. Eng. Chem. 2018, 64, 453-460).

Another effective improvement involves the use of fire-resistance additives, which can inhibit exothermic reactions via chemical reactions (e.g. SiCL, AI2O3, etc.). On the other hand, the fire-resistance additives may be detrimental to ion-conducting pathways in GPEs, resulting in a decreased ionic conductivity. Several sulfonamides have been used as component of liquid electrolytes, however other organic carbonate are generally required to achieve stable electrochemical cycling.

Document EP3050872A1 relates to an electrolyte solution comprising a fluorinated sulfonamide according to the general formula R^SCL-NTURs as part of a solvent system and an electrolyte salt, however this document teaches that flammable carbonate solvents are essential to solve the corresponding technical problem (e.g., aluminum current collector corrosion) while maintaining high electrolyte conductivity (figure 1).

Dong, P. and co-workers have disclosed in Deep Eutectic solvent-based polymer electrolyte for solid-state lithium metal batteries Journal of Energy Chemistry 2022, 70, 363-372, a solid electrolyte comprising poly(ethylene)oxide, a lithium salt that is lithium bi s(trifluorom ethyl sulfonyl) (LiTFSI) and a non-fluorinated sulphonamide compound (DMMSA). The authors have found that the oxygen atoms of the sulphonamide compound allows decoupling the lithium cations from the ethylene oxide chains of the polymer, which improves the Li⁺ transference of the electrode.

Document CA 2197056 Al relates to an electrolyte composition comprising a non-fluorinated sulfonamide compound of formula R¹R²-SO2-NR³R⁴ wherein three of the R groups are methyl, the remaining group being ethyl, or, wherein one of the R groups is a methoxyethyl group and the remaining R groups are each independently a methyl or a ethyl group. The disclosed composition may also comprise an aprotic polymer and/or a lithium salt. Xue and co-workers disclose in “Ultra-high-voltage Ni-rich layered cathodes in practical Li metal batteries enabed by a sulfonamide-based electrolyte” Nature Energy 2021, vol. 6, 495-505 a liquid electrolyte composition, free of polymers, comprising LiTFSI as lithium salt and (N,N-dimethyl)trifluoromethylsulfonamide. Qiao L. and co-workers disclose in “Stable non-corrosive sulfommide salt for 4- V-class lithium metal batteries” Nature Materials 2022, vol. 21, 455-462 an electrolyte composition comprising a mixture of organic carbonates and lithium (difluoromethyl(trifluoromethyl)sulfonamide (LiDFTSI) as lithium salt.

Thus, there is a need in art to develop new electrolyte systems, particularly, gel electrolytes, which overcome the thermal stability issues of state-of-art liquid electrolytes and, at the same time, offer a viable electrochemical performance for widespread application.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a polymer electrolyte, preferably in the form of a polymer gel electrolyte, comprising sulfonamides, (co)polymers and lithium salts further characterized in that it does not comprise organic carbonates. The inventors have found that such electrolyte composition comprising a fluorinated sulfonamide maintains high discharge capacity and current efficiency after multiple charge/discharge cycles and, on top of that, advantageous properties, such as non-flammability and high stability with lithium metal, were found.

Thus, a first aspect of the invention refers to a polymer electrolyte comprising: i. at least one polymer; ii. at least one sulfonamide; and iii. at least one lithium salt; being said electrolyte further characterized in that it does not comprise an organic carbonate and wherein the at least one sulfonamide has general formula I:

R₂S 9

N-S-R R₃ ^Z i wherein

- R¹ is selected from F, a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), a C3-C12 cycloalkyl group with one or more fluorine atom(s) and a C6-C12 aryl group substituted with one or more fluorine atom(s), and - R² and R³ are independently selected from a linear or branched C1-C12 alkyl group which may be substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s), a C6-C12 aryl group which may be substituted with one or more fluorine atom(s), and -CH2CH2O- (CH₂CH₂O)_n-R, wherein R is H or a methyl group and n is an integer from 1 to 20, or R² and R³ may be combined with each other to form a nitrogen-containing aliphatic ring.

A second aspect of the invention refers to an electrochemical cell or battery comprising the polymer electrolyte of the invention as defined above.

A third aspect of the invention refers to a method for preparing the polymer electrolyte of the first aspect of the invention comprising the steps of:

(i) providing at least one lithium salt as defined in the first aspect of the invention;

(ii) providing and mixing at least one sulfonamide, as defined in the first aspect of the invention, with the at least one lithium salt of step (i);

(iii) adding at least one polymer to the mixture obtained in step (ii); and,

(iv) optionally, when the polymer electrolyte comprises at least one polymer with one or more cross-linkable functional groups, cross-linking the at least one polymer comprised in the mixture resulting from step (iii).

A further aspect of the invention refers to the use of the electrochemical cell or battery of the second aspect of the invention in electric motors; electric cars, including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or the like; electric carts, including electric bikes (E-bikes) and electric scooters (E- scooters); electric golf carts; and electric power storage systems.

Finally, a fifth aspect of the invention refers to a method for preparing the electrochemical cell or battery of the second aspect of the invention comprising the steps of:

(i) providing a cathode for an electrochemical cell or a battery;

(ii) providing an anode for an electrochemical cell or a battery;

(iii) providing the polymer electrolyte of the first aspect of the invention;

(iv) coating the surface of the cathode provided in step (i) and of the anode provided in step (ii) with the electrolyte provided in step (iii), being said surfaces of the cathode and anode optionally covered with a membrane, prior to coating with the electrolyte, in a manner that the electrolyte is arranged between the cathode and the anode such that lithium cations can flow from the cathode to the anode; and

(v) optionally, when the polymer electrolyte comprises at least one polymer with one or more cross-linkable functional groups, cross-linking the at least one polymer comprised in the polymer electrolyte.

DESCRIPTION OF THE FIGURES

Figure 1. Discharge specific capacity (filled black dots) and Coulombic efficiency (hollow black dots) vs. cycle number for the Li°||NMC622 cells at 40 °C.

Figure 2. Discharge specific capacity (filled black dots) and Coulombic efficiency (hollow black dots) vs. cycle number for the Li°||NMC622 cells at 25 °C.

DETAILED DESCRIPTION OF THE INVENTION

All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the art. Other more specific definitions for certain terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

Throughout the description and claims the word “comprises" and variations of the word, are not intended to exclude other technical features, additives, components or steps. Furthermore, the word “comprise” encompasses the cases of “consist of’ and “consists essentially of’. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention.

Throughout the description and claims, the terms “blend(s)” and “mixture(s)” will be used interchangeably.

For the purposes of the invention, any ranges given include both the lower and the upper end-points of the range. Ranges or values given, such as temperatures, times, molar ratio, volume ratio and the like, should be considered approximate when they are defined by the term “about” (i.e. with a 5% margin of variation around indicated point). As mentioned above, a first aspect of the invention refers to a polymer electrolyte, comprising: i. at least one polymer; ii. at least one sulfonamide; and iii. at least one lithium salt, being said polymer electrolyte further characterized in that it does not comprise an organic carbonate and wherein the at least one sulfonamide has general formula I:

R₂S 9

N-S-R R₃ ^Z i wherein

- R¹ is selected from F, a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), a C3-C12 cycloalkyl group with one or more fluorine atom(s) and a C6-C12 aryl group substituted with one or more fluorine atom(s), and

- R² and R³ are independently selected from a linear or branched C1-C12 alkyl group which may be substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s), a C6-C12 aryl group which may be substituted with one or more fluorine atom(s), and -CH2CH2O- (CH₂CH₂O)_n-R, wherein R is H or a methyl group and n is an integer from 1 to 20, or R² and R³ may be combined with each other to form a nitrogen-containing aliphatic ring.

The inventors have surprisingly found that a polymer electrolyte comprising polymer(s), sulfonamide(s) of formula I and lithium salt(s) but lacking organic carbonates is suitable for electrochemical applications (e.g. in lithium metal batteries) with the corresponding advantages of no flammability and stability with lithium metal.

In a preferred embodiment, the polymer electrolyte of the first aspect of the invention is in a gel form. In the context of the present invention, a gel polymer electrolyte is understood as a polymer network that is expanded or swelled throughout its whole volume by the presence of at least one sulfonamide and, optionally, of a plasticizer (that is not a carbonate).

More embodiments regarding the first aspect of the invention will be given below.

Polymer

In the context of the invention, the polymer comprised in the polymer electrolyte of the invention refers to a polymer material suitable for ions conduction, in particular lithium cations, via non-covalent interactions between the polymer chain and the ion. Suitable polymers for polymer electrolytes are known in the art and typically comprise a heteroatom such as O, N, S or P in the repeating unit of the polymer chain that is suitable for interacting with a lithium cation through a lone pair of the heteroatom.

The at least one polymer comprised in the polymer electrolyte, preferably a polymer gel electrolyte, may be a homopolymer, a copolymer or a mixture thereof. In a further embodiment, the polymer is in the form of a cross-linked polymer or in the form of a cross-linkable polymer composition. In a further embodiment, the polymer may comprise in its molecular formula one or more cross-linkable functional groups.

In a particular embodiment, the at least one polymer is selected from a polyalkylene oxide, such as polyethylene oxide (PEO) or polypropylene oxide (PPO); a polyalkylenimine, such as polyethyleneimine (PEI); a polyalkylene sulphide, such as polyethylene sulphide (PES); a poly(meth)acrylate, in particular a polyalkylacrylate or an alkyl ester thereof, such as polymethylmethacrylate (PMMA), poly(butyl acrylate) (PBA), poly(ethyl) acrylate (PEA), poly(cyanoethylacrylate) (PCEA), or blends thereof, or co-polymers thereof or cross-linked polymers thereof with trimethylolpropane triacrylate- (ETPTA) and/or pentaerythritol tetraacrylate (PETA); a polyethyleneglycol optionally comprising one or more cross-linkable groups, such as poly(ethyleneglycol), poly(ethyleneglycol) methacrylate (PEGMA), poly(ethyleneglycol)methyl ether methacrylate, poly(ethyleneglycol) dimethacrylate (PEGDMA) or blends thereof, or copolymers thereof or cross-linked polymers thereof; a polyphosphazene, such as poly[bis(2-(2-methoxyethoxy) ethoxy) phosphazene (MEEP); a polysiloxane, such as poly(dimethyl siloxane) (PDMS); polyvinyl alcohol (PVA); polyvinyl amine (PVAm); polyvinyl acetate (PVAc); a polyvinyl halide, such as polyvinyl chloride (PVC) or polyvinylidene difluoride (PVdF); polyvinylidene difluoride-hexafluropropylene (PVdF- HFP); polyacrylonitrile (PAN); poly(vinylpyrrolidone) (PVP); poly(2-vinylpyridine) (P2VP); poly(s-caprolactone) (PCL); a poly(maleimide), preferably poly(alkylenemaleimide), more preferably poly(ethylene-alt-maleimide) (PEaMI); polyaniline (PANI); chitosan (CS); or any blend or any copolymer or any cross-linked polymer thereof. As in any of the examples above, the polymer may comprise in its molecular formula at least one cross-linkable functional group, such as (meth)acrylate, epoxy, alkene, thiol, amino, hydroxyl and others cross-linkable functional groups known in the art.

Preferably, the at least one polymer is selected from: a polyethyleneglycol containing mono-, di-, tri-, and tetra-acrylates, such as poly(ethyleneglycol)methyl ether methacrylate, poly(ethyleneglycol) methacrylate (PEGMA) or poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; poly alkyl acrylates such as poly(butyl acrylate) (PBA), poly(ethyl acrylates) (PEA), poly(cyanoethyl acrylate) (PCEA); or any blend thereof, or any copolymer thereof or any cross-linked polymer thereof with trimethylolpropane triacrylate- (ETPTA) and/or pentaerythritol tetraacrylate (PETA).

More preferably, the at least one polymer is selected from the group consisting of poly(ethyleneglycol) methyl ether methacrylate, poly(ethyleneglycol) dimethacrylate (PEGDMA), or any blend, any copolymer or any cross-linked polymer thereof; a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate- (ETPTA) and/or pentaerythritol tetraacrylate (PETA). It is also contemplated that the polymer is a mixture of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), that is the mixture prior to cross-linking.

In a further embodiment of the first aspect of the invention, the polymer is selected from the group consisting of poly( ethyleneglycol) methyl ether methacrylate, poly(ethyleneglycol) dimethacrylate (PEGDMA), blends, co-polymers and cross-linked polymers thereof.

In a further embodiment of the first aspect of the invention, the polymer is selected from the group consisting of poly(ethyleneglycol) methyl ether methacrylate or a cross-linked polymer thereof, poly(ethyleneglycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, a cross-linked polymer of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA).

In a specific embodiment, the polymer electrolyte comprises two polymers, which may be homopolymers, copolymers or a mixture thereof and are selected from the lists above; preferably the two polymers are poly(ethyleneglycol)methyl ether methacrylate and polyethylene glycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof.

In a preferred embodiment of the first aspect of the invention, the polymer is selected from the group consisting of a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA); and a cross-linked polymer of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA).

Said at least one polymer preferably has a molecular weight of between 100 grams per mole and 10,000 grams per mole. More preferably, said at least one polymer has a molecular weight of between 250 grams per mole and 5,000 grams per mole. Even more preferably, said at least one polymer has a molecular weight of between 500 grams per mole and 1,000 grams per mole. It is contemplated in certain embodiments that the polymer is selected from the group consisting of poly(ethyleneglycol) methyl ether methacrylate and poly(ethyleneglycol) dimethacrylate (PEGDMA), the polymer having a molecular weight of between 500 grams per mole and 1,000 grams per mole; preferably of 500 or 550 grams per mole.

When the at least one polymer comprises in its molecular formula one or more crosslinkable groups, such as one or more cross-linkable acrylate groups, the polymer electrolyte, preferably a polymer gel electrolyte, further optionally comprises an initiator of free radical polymerization, such as azoisobutyronitrile (AIBN). Said initiator compound is preferably present in a weight amount corresponding to 0.1% to 1% of the weight of the polymer electrolyte composition; more preferably in a weight amount of 0.3% of the weight of the polymer electrolyte composition.

In a further embodiment of the first aspect of the invention, the polymer is a crosslinked polymer resulting from the further polymerization of a mixture of polymers comprising in its molecular formula at least one cross-linkable functional group, such as a crosslinked polymer resulting from the further free radical polymerization of a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA. In particular, the (meth)acrylate groups comprise C=C bonds in the (meth)acrylate moieties that may be subjected to further polymerization resulting in the crosslinking of the (meth)acrylate polymer chains.

In another embodiment, the polymer is a cross-linked polymer resulting from the polymerization of a mixture of monomers comprising in its molecular formula at least one cross-linkable functional group, such as a cross-linked polymer resulting from the free radical polymerization of a mixture of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA).

The crosslinking process is promoted by an initiator of free radical polymerization (such as AIBN) and heat (in the range of 50-100 °C, more preferably at about 70 °C). Thus, it is also contemplated in a further embodiment that the polymer is a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA) or a mixture of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), that is the mixture prior to cross-linking.

In a further embodiment, when the polymer is a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA) or a crosslinked polymer thereof, it is preferred that the weight ratio of poly(ethyleneglycol) methyl ether methacrylate to PEGDMA is of between 50: 1 and 1 : 1; more preferably of between 10: 1 and 2: 1; even more preferably of about 3: 1.

In another embodiment, when the polymer is a mixture of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), or a cross-linked polymer thereof, the weight ratio of butyl acrylate to trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA) is of between 50: 1 and 1 : 1; more preferably of between 10: 1 and 2: 1; even more preferably of about 3: 1.

Regardless of the chemical nature of the at least one polymer, its gravimetric content in the polymer electrolyte may vary from 5 to 85 wt.% compared to the total weight of the electrolyte composition, preferably from 8 to 60 wt.%, even more preferably from 8 to 20% wt.%. In a most preferred embodiment, the gravimetric content of at least one polymer is about 12 wt.% compared to the total weight of the electrolyte composition. In a specific embodiment of the first aspect of the invention, the polymer is selected from the group consisting of poly(ethyleneglycol)methyl ether methacrylate, polyethylene glycol) dimethacrylate (PEGDMA), blends, co-polymers and cross-linked polymers thereof; and:

- the polymer represents from 5% to 85% of the weight of the composition; preferably, the polymer represents from 8% to 60% of the weight of the composition; even more preferably, the polymer represents from 8% to 20% of the weight of the composition; and/or

- when the polymer is a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, it is preferred that the weight ratio of PEGMA to PEGDA is of between 50: 1 and 1 : 1; more preferably of between 10: 1 and 2: 1; even more preferably of about 3: 1.

Sulfonamide

The polymer electrolyte, preferably a polymer gel electrolyte, of the present invention comprises at least one sulfonamide. The term “sulfonamide” denotes an organic compound containing the core functional group >N-S(=O)2- where the N atom is attached to two more organic moieties and the S atom is attached to one more organic moiety. In a particular embodiment, the polymer electrolyte, preferably a polymer gel electrolyte, of the present invention comprises one sulfonamide; in another particular embodiment, it comprises two sulfonamides.

In the first aspect of the invention, the at least one sulfonamide has the following general formula I: wherein

R¹ is selected from F, a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), a C3-C12 cycloalkyl group substituted with one or more fluorine atom(s) and a C6-C12 aryl group substituted with one or more fluorine atom(s), and

R² and R³ are independently selected from a linear or branched C1-C12 alkyl group which may be substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s), a C6-C12 aryl group which may be substituted with one or more fluorine atom(s), and CH2CH2O- (CH₂CH₂O)_n-R, wherein R is H or a methyl group and n is an integer from 1 to 20; or R² and R³ may be combined with each other to form a nitrogen-containing aliphatic ring.

A “Ci-C 12 alkyl” as used herein refers to a branched or linear aliphatic carbon chain consisting of 1 to 12 carbon atoms. Illustrative examples of C1-C12 alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, etc. In preferred embodiments, the aliphatic chain may comprise less carbon atoms, for example 6 (“Ci-Ce alkyl”) or 3 (“C1-C3 alkyl”) carbon atoms. The alkyl chain may be partially or completely fluorinated (“perfluorinated”), meaning that at least one but not all hydrogen atoms of any C-H bond is replaced by a fluorine atom or that all hydrogen atoms of any C-H bond is replaced by a fluorine atom, respectively.

A “C2-C12 alkenyl” as used herein refers to linear or branched aliphatic groups having from 2 to 12 carbon atoms and having at least 1 double C=C bond. Such alkenyl groups include ethenyl (-CH=CH2), n-2-propenyl (allyl, -CH2CH=CH2) and the like.

A “C3-C12 cycloalkyl” as used herein refers to mono-, bi- or tricyclic hydrocarbyl groups having 3 to 12 carbon atoms. Typical C3-C12 cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, cyclodecyl.

A “C6-C12 aryl” as used herein refers to aromatic hydrocarbon rings that contain 6 to 12 carbon atoms, also as two fused rings, optionally substituted with alkyl groups as already defined above, such as phenyl, a-naphthyl, P-naphthyl, m-methylphenyl, p- trifluoromethylphenyl and the like.

More particularly, Ri is selected from F, a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), and a C3-C12 cycloalkyl group substituted with one or more fluorine atom(s). Preferably, Ri is selected from F, a linear C1-C12 alkyl group substituted with one or more fluorine atom(s), and a C3-C12 cycloalkyl group substituted with one or more fluorine atom(s).

In preferred embodiments, when Ri is selected from a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), and a C3-C12 cycloalkyl group, said substitution with the fluorine atom occurs at least on the carbon atom of Ri that is adjacent to the sulfur atom of the compound of formula (I).

Even more preferably Ri is F or a linear C1-C12 alkyl group substituted with one or more fluorine atom(s), and even more preferably F or a linear C1-C4 alkyl group substituted with one or more fluorine atom(s). In more preferred embodiments, Ri is F or CF3. In the most preferred embodiment Ri is F.

More particularly, R2 and R3 are independently selected from a linear or branched C1-C12 alkyl group which may be substituted with one or more fluorine atom(s) and a linear or branched C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s).

Preferably, R2 and R3 are independently selected from a linear C1-C12 alkyl group which may be substituted with one or more fluorine atom(s) and a linear C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s). Even more preferably, R2 and R3 are independently selected from a linear C1-C10 alkyl group, and most preferably R2 and R3 are independently selected from a linear C1-C4 alkyl group.

In an embodiment Ri and R2 are the same. In another embodiment, Ri and R2 are different. In the most preferred embodiment, Ri = R2 = CH3.

In a further embodiment, the at least one sulfonamide has the general formula I as shown above, wherein:

- Ri is selected from F, a linear C1-C12 alkyl group substituted with one or more fluorine atom(s), and a C3-C12 cycloalkyl group substituted with one or more fluorine atom(s); and

- R2 and R3 are independently selected from a linear C1-C12 alkyl group which may be substituted with one or more fluorine atom(s) and a linear C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s).

In a further embodiment, the at least one sulfonamide has the general formula I as shown above, wherein: - Ri is selected from F and a linear C1-C4 alkyl group substituted with one or more fluorine atom(s); and

- R₂ and R₃ are linear C1-C4 alkyl groups which may be substituted with one or more fluorine atom(s).

In a further embodiment, the at least one sulfonamide is selected from at least one of the following structures:

In a most preferred embodiment, the at least one sulfonamide is one wherein Ri is F and

R₂ = R₃ = CH₃.

In another most preferred embodiment, the at least one sulfonamide is one wherein Ri is CF₃ and R₂ = R₃ = CH₃.

The at least one sulfonamide is present in the polymer electrolyte, preferably a polymer gel electrolyte, in an amount that may vary from 5 to 85 wt.%, preferably from 5 to 80 wt.%, more preferably from 40 to 75 wt.%. Even more preferably, the at least one sulfonamide is present in the gel electrolyte in an amount of about 70 wt.%.

Lithium salt

The at least one lithium salt comprised in the polymer electrolyte, preferably a polymer gel electrolyte, may be an organic lithium salt, an inorganic lithium salt, or a combination thereof.

Specifically, the inorganic lithium salt may include, but is not limited to, LiCICU, LiNO₃, LiBF4, LiAsFe, LiPFe, LiBF₃Cl, and LiF. The organolithium salt may include, but is not limited to, LiN(SO2CF3)2, LiN(SO2CF3)(SO₂CF₂H), LiN(SO₂F)₂, LiN(SO₂CF3)(SO₂F), LiN(C₂F₅SO2)(SO₂F), LiB(C₂O₄)₂, LiBF₂(C₂O₄), LiC(SO₂CF₃)3, LiPF₃(C₂F₅)3, and LiCF₃SO₃.

In an embodiment, the at least one lithium salt is selected from LiC10₄, LiNCh, LiBF₄, LiAsF₆, LiPF₆, LiBF₃Cl, LiF, LiN(SO₂CF₃)2 (LiTFSI), LiN(SO₂CF3)(SO2CF₂H), LiN(SO₂F)₂ (LiF SI), LiN(SO2CF₃)(SO₂F), LiN(C₂F₅SO2)(SO₂F) LiB(C₂O₄)₂, LiBF2(C2O₄), LiC(SO2CF3)3, LiPF3(C2Fs)3, LiCFsSCh and a combination thereof.

In another embodiment, the at least one lithium salt is selected from LiN(SO2CF3)2, LiN(SO2CF₃)(SO2CF₂H), LiN(SO₂F)₂, LiN(SO₂CF3)(SO₂F), LiB(C₂O₄)₂, LiBF₂(C₂O₄), LiC(SO2CF3)3, LiPF3(C2Fs)3, LiCFsSCh, and LiNCF or a combination thereof.

In a preferred embodiment, the at least one lithium salt is an organic lithium salt, preferably selected LiN(SO₂CF3)(SO2CF₂H), LiB(C₂O₄)₂, LiN(SO₂F)₂, LiN(SO₂CF₃)2, LiN(SO2CF3)(SO2F), or a combination thereof.

In a preferred embodiment, only one lithium salt is comprised in the polymer electrolyte, preferably a polymer gel electrolyte. In a further embodiment, the lithium salt comprised in the polymer electrolyte, preferably a polymer gel electrolyte, is LiN(SO2CF3)(SO2CF2H), (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide, also abbreviated as LiDFTFSI.

In another preferred embodiment, the polymer electrolyte of the first aspect of the invention is one wherein said at least one lithium salt is a combination of a first lithium salt and a second lithium salt other than the first lithium salt that is suitable for lithium metal batteries, said first lithium salt being selected from the group consisting of LiN(SO2CF₃)(SO2CF₂H), LiN(SO₂CF3)(SO₂F), and LiN(C2F₅SO2)(SO₂F). Preferably, the first lithium salt is LiN(SO2CF3)(SO2CF2H). In said preferred embodiment, the second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluorob orate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2F5)(SO2F), a salt of formula LiB(C2O₄)2, a salt of formula LiBF2(C2O₄), a salt of formula LiC(SO2CF3)3, a salt of formula LiPFTCbF fi, a salt of formula LiCF^SCF and mixtures thereof. Preferably, the second lithium salt is selected from the group consisting of lithium tetrafluorob orate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, a salt of formula LiB(C2O₄)2, a salt of formula LiBF2(C2O₄), a salt of formula LiPFsfC F Js, a salt of formula LiCFsSOs and mixtures thereof. More preferably, the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4).

In another preferred embodiment, the polymer electrolyte of the first aspect of the invention is one wherein said at least one lithium salt is a combination of a first lithium salt and a second lithium salt other than the first lithium salt that is suitable for lithium metal batteries, said first lithium salt being LiN(SO2CF3)(SO2CF2H) and the second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2Fs)(SO2F), a salt of formula LiB(C2C>4)2, a salt of formula LiBF2(C2C>4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2Fs)3, a salt of formula LiCFsSCh and mixtures thereof.

In further embodiments, said second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2Fs)(SO2F), a salt of formula LiB(C2C>4)2, a salt of formula LiBF2(C2C>4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2Fs)3, a salt of formula LiCFsSCh and mixtures thereof.

Preferably, the second lithium salt is selected from the group consisting of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2C>4), a salt of formula LiPF^CbF fi, a salt of formula LiCF^SCF and mixtures thereof. More preferably, the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4). Even more preferably, the second lithium salt is a salt of formula LiB(C₂O₄)2

When the polymer electrolyte comprises a first lithium salt and a second lithium salt, as described above, the weight ratio of the first lithium salt to the second lithium salt is comprised from 1 : 1 to 4: 1 ; preferably it is comprised from 1 : 1 to 3 : 1 and more preferably it is comprised from 1 : 1 to 2: 1. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is of about 112:81. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is of about 114:82. In an even more preferred embodiment of the first aspect of the invention, the weight ratio of the first lithium salt to the second lithium salt is of about 95:51. The at least one lithium salt comprised in the polymer electrolyte, preferably a polymer gel electrolyte, may vary from 10 to 90 wt.% with respect to the total weight of the electrolyte, preferably from 10 to 50 wt.%, even more preferably from 10 to 30 wt.%, and even more preferably from 15% to 25% in weight of the composition. Most preferably, the at least one lithium salt comprised in the electrolyte is about 18 wt.% with respect to the total weight of the electrolyte.

Organic carbonate

As stated above, the polymer electrolyte, preferably a polymer gel electrolyte, of the invention is further characterized in that it does not comprise an organic carbonate. For the purpose of the invention, any carbonate O=C(-O )2 that contains an organic, cyclic or linear chain with at least C and H atoms has to be considered an organic carbonate and, therefore, is excluded from the polymer electrolyte, preferably a polymer gel electrolyte, of the invention. The organic carbonate is preferably a liquid at room temperature. As practical examples, the definition of organic carbonates includes, even though the list is non-limiting, cyclic alkylene carbonates (ethylene carbonate, propylene carbonate, butylene carbonate and the likes) and di(hydrocarbyl) carbonates, such as dialkyl carbonates, diaryl carbonates, alkyl aryl carbonates or mixtures thereof.

Substituted derivatives of the aforementioned organic carbonates are also excluded from the polymer electrolyte, preferably a polymer gel electrolyte, of this invention. One or more substituents may be present on the alkylene, alkyl or aryl moieties. Non-limiting examples of substituents include halogen, alkoxy, hydroxyl, nitrogen substituents, phosphorous substituents, sulphur substituents and similar moieties.

Plasticizer

In a particular embodiment, the polymer electrolyte of the first aspect of the invention further comprises a plasticizer. In the context of the invention, the term “plasticizer” refers to a substance suitable for softening a polymer, swelling a polymer and/or dissolving the lithium salts of the polymer electrolyte. As stated above, the polymer electrolyte of the invention is characterized in that it does not comprise a carbonate, thus the plasticizer cannot be a carbonate. Examples of plasticizers are known in the art and include, among others, organic solvents and compounds such as dimethoxy ethane (DME), 1,2- diethoxy ethane (DEE), 1,3 -dioxolane (DOL), di ethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), tetrahydropyran (TEIP), y-butyrolactone, tetrahydrofuran (THF), 2-methyltetrahydrofiiran, diethylether, methyltert-butyl ether, succinonitrile (SN), glutaronitrile (GN), adiponitrile (AN), N,N- dimethyl sulfamoyl fluoride (FSA), N,N-dimethyltrifhioromethane-sulfonamide (TFSA), and any mixtures thereof.

Further embodiments of the polymer electrolyte

In an embodiment of the invention, the polymer electrolyte, preferably a gel polymer electrolyte consists of i. two polymers in the form of blend, copolymer or cross-linked polymer thereof; ii. one sulfonamide; and iii. one lithium salt; being said electrolyte further characterized in that it does not comprise an organic carbonate.

In an embodiment, the gel electrolyte of the invention comprises: i. at least one polymer selected from:

- a polyalkylene oxide;

- a polyalkylenimine;

- a polyalkylene sulphide;

- a poly(meth)acrylate, or a cross-linked polymer thereof with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA);

- a polyethyleneglycol, optionally comprising one or more cross-linkable groups;

- a polyphosphazene;

- a polysiloxane;

- polyvinyl alcohol (PVA);

- polyvinyl amine (PVAm);

- polyvinyl acetate (PVAc);

- a polyvinyl halide;

- polyacrylonitrile (PAN);

- poly(vinylpyrrolidone) (PVP); - poly(2-vinylpyridine) (P2VP);

- poly(s-caprolactone) (PCL);

- a poly(maleimide);

- polyaniline (PANI);

- chitosan (CS); or

- any copolymer or any mixture or any cross-linked polymer thereof; ii. at least one sulfonamide with general formula:

, wherein

- R¹ is selected from F, a linear or branched C1-C12 alkyl group substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group substituted with one or more fluorine atom(s), a C3-C12 cycloalkyl group substituted with one or more fluorine atom(s) and a C6-C12 aryl group substituted with one or more fluorine atom(s), and

- R² and R³ are independently selected from a linear or branched C1-C12 alkyl group which may be substituted with one or more fluorine atom(s), a linear or branched C2-C12 alkenyl group which may be substituted with one or more fluorine atom(s), a C6-C12 aryl group which may be substituted with one or more fluorine atom(s), and CH2CH2O-(CH2CH2O)_n-R, wherein R is H or a methyl group and n is an integer from 1 to 20; or R² and R³ may be combined with each other to form a nitrogen-containing aliphatic ring; and iii. an organic or inorganic lithium salt selected from LiC10₄, LiNO₃, LiBF4, LiAsFe, LiPF₆, LiBF₃Cl, LiF, LiN(SO₂CF₃)₂, LiN(SO₂CF₃)(SO2CF₂H), LiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂F), LiN(C₂F₅SO2)(SO₂F), LiB(C₂O₄)₂, LiBF₂(C₂O₄), LiC(SO2CF₃)₃, LiPF₃(C2F5)₃, LiCF₃SO₃ or a combination thereof.

In a particular embodiment of the latter:

- the at least one polymer amounts from 5 to 85 wt.% compared to the total weight of the electrolyte composition, preferably from 8 to 60 wt.%, even more preferably from 8 to 20% wt.%, even more preferably to about 12 wt.% with respect to the total weight of the gel electrolyte; - the at least one sulfonamide represents from 5 to 85 wt.% with respect to the total weight of the electrolyte, preferably from 5 to 80 wt.% with respect to the total weight of the electrolyte, more preferably from 40 to 75 wt.% with respect to the total weight of the electrolyte; even more preferably, is about 70 wt.% with respect to the total weight of the electrolyte; and/or

- the at least one lithium salt amounts to from 10 to 90 wt.% with respect to the total weight of the electrolyte, preferably from 10 to 50 wt.% with respect to the total weight of the electrolyte, even more preferably from 10 to 30 wt.% with respect to the total weight of the electrolyte, even more preferably to about 18 wt.% with respect to the total weight of the electrolyte.

In further embodiments, the polymer electrolyte comprises: i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethyleneglycol) methacrylate (PEGMA), polyethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; and a poly alkyl acrylate such as poly(butyl acrylate) (PBA), poly(ethyl acrylates) (PEA), poly(cyanoethyl acrylate) (PCEA); or any blend thereof, or any copolymer thereof or any crosslinked polymer thereof with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA). ii. at least one sulfonamide of formula I

, wherein

- Ri is selected from F or a linear C1-C4 alkyl group substituted with one or more fluorine atom(s); and

- R2 and R3 are linear C1-C4 alkyl groups; and iii. at least an organic lithium salt selected from LiN(SO2CF3)(SO2CF2H), LiB(C₂O₄)2, LiN(SO₂F)₂, LiN(SO₂CF₃)2, LiN(SO₂CF3)(SO₂F) and a combination thereof; wherein preferably the lithium salt is LiN(SO2CF3)(SO2CF2H).

In further embodiments, the polymer electrolyte consists of i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; and a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA); ii. a sulfonamide of formula I

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. an organic lithium salt selected from LiN(SO2CF3)(SO2CF2H), LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF3)(SO2F) or a combination thereof; wherein preferably the lithium salt is LiN(SO2CF3)(SO2CF2H).

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. the at least one lithium salt is a combination of a first lithium salt and a second lithium salt other than the first lithium salt that is suitable for lithium metal batteries, said first lithium salt being selected from the group consisting of LiN(SO₂CF3)(SO2CF₂H), LiN(SO₂CF3)(SO₂F), and LiN(C2F₅SO2)(SO₂F); preferably, the first lithium salt is LiN(SO2CF3)(SO2CF2H). In further embodiments, the polymer electrolyte consists of: i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; and a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA); ii. a sulfonamide of formula I

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. the at least one lithium salt is a combination of a first lithium salt that is selected from the group consisting of LiN(SO2CF3)(SO2CF2H), LiN(SO2CF3)(SO2F), and LiN(C2F5SO2)(SO2F) and a second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2F5)(SO2F), a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2F5)3, a salt of formula LiCFsSCh and mixtures thereof; preferably, the frist lithium salt is LiN(SO2CF3)(SO2CF2H) and/or the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4).

In further embodiments, the polymer electrolyte consists of i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; ii. a sulfonamide of formula I

, wherein

Specifically, in the latter, the weight ratio between poly(ethyleneglycol)methyl ether methacrylate and PEGDMA is of between 50:1 and 1 : 1, more preferably of between 10: 1 and 2: 1, even more preferably of about 3: 1; yet more specifically, the weight ratio between polymer: sulfonamide: lithium salt is of about 70: 12: 18.

In further embodiments, the polymer electrolyte consists of: i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; ii. a sulfonamide of formula I

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. the at least one lithium salt is a combination of a first lithium salt and a second lithium salt other than the first lithium salt that is suitable for lithium metal batteries, said first lithium salt being selected from the group consisting of LiN(SO₂CF3)(SO2CF₂H), LiN(SO₂CF3)(SO₂F), and LiN(C2F₅SO2)(SO₂F); preferably, the first lithium salt is LiN(SO2CF3)(SO2CF2H).

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. the at least one lithium salt is a combination of a first lithium salt that is selected from the group consisting of LiN(SO2CF3)(SO2CF2H), LiN(SO2CF3)(SO2F), and LiN(C2FsSO2)(SO2F) and a second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2Fs)(SO2F), a salt of formula LiB(C2C>4)2, a salt of formula LiBF2(C2O4), a salt of formula LiC(SO2CF3)3, a salt of formula LiPF3(C2Fs)3, a salt of formula LiCFsSCh and mixtures thereof; preferably, the frist lithium salt is LiN(SO2CF3)(SO2CF2H) and/or the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4).

Electrochemical cell and battery

The polymer electrolyte, preferably a polymer gel electrolyte, of the first aspect of the invention is particularly useful in electrochemical devices such as electrochemical cells or batteries, particularly secondary electrochemical cells or batteries wherein the cell reactions are reversible. The second aspect of the invention thus relates to an electrochemical cell or a battery comprising the polymer electrolyte according to the first aspect of the invention. In a preferred embodiment, the second aspect of the invention relates to an electrochemical cell or a battery comprising the polymer electrolyte according to any, preferred or particular, embodiment of the first aspect of the invention defined above.

In a preferred embodiment, the second aspect of the invention relates to a lithium metal battery comprising the polymer electrolyte according to any embodiment of the first aspect of the invention defined above. A lithium metal battery is a battery characterized in that it comprises an anode consisting essentially of metallic lithium.

In a further preferred embodiment, the second aspect of the invention relates to a lithium metal battery comprising a cathode wherein the cathode material is selected from the group consisting of lithium manganese oxide, lithium nickel oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium copper oxide, lithium copper sulphide, lithium iron phosphate, lithium iron sulphide, lithium manganese iron phosphate and lithium nickel cobalt aluminium oxide. In a further preferred embodiment, the second aspect of the invention relates to a lithium metal battery comprising a cathode wherein the cathode material is lithium nickel manganese cobalt oxide such as LiNio.6Mno.2Coo.2O2 (NMC622). Specifically, the lithium nickel manganese cobalt oxide cathode may additionally contain other additives. In a particular embodiment the cathode comprises NMC622, a conductive carbon and a polymeric binder; preferably, the cathode consists of NMC622, carbon black as conductive carbon and polyvinylidene fluoride (PVdF) as a polymeric binder. It is preferred that the weight ratio between NMC622: conductive carbon: polymeric binder is 90:5:5.

In a further preferred embodiment, the second aspect of the invention relates to a lithium metal battery comprising a separator membrane, such as a polypropylene membrane, preferably microporous polypropylene, arranged between at least one electrode and the polymer electrolyte in such a configuration that lithium cations can flow across said membrane between the electrolyte and the surface of said at least one electrode. In specific embodiments, the separator membrane has a thickness of between 1 and 50 pm, preferably of between 15 and 35 pm, more preferably of about 25 pm. The porosity of the separator membrane may also vary between a certain range, particularly the average pore diameter is comprised between 0.001 and 0.100 pm, preferably between 0.020 and 0.080 pm, more preferably is about 0.064 pm. In a further preferred embodiment, the second aspect of the invention relates to lithium metal battery having a charge retention capacity of at least 70%; preferably of at least 75%; and more preferably, of at least 80%, after 100 charging cycles. In a particular embodiment, the first cycle was applied at a current of C/20, the 3 following cycles at a current of C/10, and the remaining cycles at C/5, at a temperature of 25 °C. In another embodiment, the voltage is comprised between 3.00 V and 4.25 V.

In a further preferred embodiment, the second aspect of the invention relates to a lithium metal battery wherein the cathode material is lithium nickel manganese cobalt oxide and the polymer electrolyte, preferably a polymer gel electrolyte, is one wherein:

- the at least one sulfonamide is F-S(O)2(CH3)2 and is comprised in the polymer electrolyte composition in an amount that may vary from 5 to 85 wt.% with respect to the total weight of the composition, preferably from 5 to 80 wt.%, more preferably from 40 to 75 wt.%; even more preferably, in an amount of about 70 wt.%;

- the at least one lithium salt is LiDFTFSI and is comprised in the polymer electrolyte composition in an amount from 10 to 90 wt.% with respect to the total weight of the electrolyte composition; preferably, in an amount from 10 to 30 wt.% with respect to the total weight of the electrolyte composition; even more preferably, in an amount of about 18 wt.% with respect to the total weight of the electrolyte composition; and/or

- the at least one polymer is selected from the group consisting of poly(ethyleneglycol) methyl ether methacrylate or a cross-linked polymer thereof, poly(ethyleneglycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, a cross-linked polymer of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA), a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA);

- the polymer represents from 5 to 85 wt.% with respect to the total weight of the electrolyte composition; preferably, the polymer represents from 8 to 60 wt.% with respect to the total weight of the electrolyte composition; more preferably, the polymer represents from 8 to 20 wt.% with respect to the total weight of the electrolyte composition; even more preferably, the polymer represents about 12 wt.% with respect to the total weight of the electrolyte composition and wherein:

- when the polymer is a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, or is T1 a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), it is preferred that their respective weight ratio is between 50: 1 and 1 : 1; more preferably of between 10: 1 and 2: 1; even more preferably of about 3:1; and/or

- when the polymer is selected from the group consisting of poly(ethyleneglycol) methyl ether methacrylate, poly(ethyleneglycol) dimethacrylate (PEGDMA), and copolymers, or mixtures thereof, or is a mixture of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), the polymer electrolyte composition further comprises an initiator of free radical polymerization, such as azoisobutyronitrile (AIBN).

- the at least one lithium salt is a combination of a first lithium salt that is LiN(SO2CF3)(SO2CF2H), and a second lithium salt that is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4); and said combination is comprised in the polymer electrolyte composition in an amount from 10 to 90 wt.% with respect to the total weight of the electrolyte composition; preferably, in an amount from 10 to 30 wt.% with respect to the total weight of the electrolyte composition; and/or

- when the polymer is a mixture of poly(ethyleneglycol) methyl ether methacrylate with poly(ethyleneglycol) dimethacrylate (PEGDMA) or a cross-linked polymer thereof, or is a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), it is preferred that their respective weight ratio is between 50: 1 and 1 : 1; more preferably of between 10: 1 and 2: 1; even more preferably of about 3:1; and/or

The electrochemical cell or battery of the invention may be applied to a variety of electronic devices which may include, but are not limited to: electric motors; electric cars, including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or the like; electric carts, including electric bikes (E-bikes) and electric scooters (E-scooters); electric golf carts; electric power storage systems; or the like.

Methods for preparing the polymer electrolyte and the electrochemical cell or battery comprising said electrolyte

As defined above, a third aspect of the invention relates to a method for the preparation of a polymer electrolyte, preferably a polymer gel electrolyte, according to the first aspect of the invention comprising the steps of:

(ii) mixing at least one sulfonamide as defined in the first aspect of the invention with the at least one lithium salt of step (i);

(iii) adding at least one polymer as defined above to the mixture obtained in step (ii); and,

(iv) optionally, when the polymer comprises one or more cross-linkable functional groups, cross-linking the polymer comprised in the mixture resulting from step (iii). All the steps of the method above may be performed by using the neat components of the polymer electrolyte (e.g. as neat solid or liquid) or, alternatively, said components may be dissolved in a solvent prior to performing a given step.

In preferred embodiments, steps (i) and (ii) are carried out by using the neat components (lithium salt and sulfonamide).

In another embodiment, step (iii) is carried out by firstly adding solvent to the mixture obtained from step (ii) and then adding the at least one polymer. In another embodiment, step (iii) is carried out by adding the neat at least one polymer to the mixture obtained from step (ii).

It is preferable that the mixture obtained from step (iii) is stirred for a certain time to ensure that a homogeneous solution is obtained (i.e. no suspended matter is present). The stirring is performed magnetically at 100 rpm, at 200 rpm, at 300 rpm, at 400 rpm, at 500 rpm, at 600 rpm, at 700 rpm, at 800 rpm, at 900 rpm, at 1000 rpm; preferably the stirring is performed in a range between 100 and 500 rpm, even more preferably at about 300 rpm. Additionally, the mixture from step (iii) is stirred for at least 5 min, at least 15 min, at least 30 min, at least 1 hour, at least 2 hours, at least 4 hours, at least 6 hours, at least 12 hours, at least 1 day; preferably, the mixture from step (iii) is stirred for 1 to 4 hours, more preferably for 2 hours.

All the steps of the method above are performed at a temperature comprised between 10 and 30 °C, preferably between 15 and 25 °C, even more preferably between 20 and 25 °C. Step (iv) is optionally carried out when the polymer comprises one or more cross-linkable functional groups, preferably such groups are carbon-carbon double bonds, more preferably carbon-carbon double bonds of (meth)acrylates. In particular, when the polymer for electrolyte is poly(ethyleneglycol) methyl ether methacrylate, poly(ethyleneglycol) dimethacrylate (PEGDMA), or blends or copolymers thereof, or a blend of butyl acrylate and trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), the optional cross-linking step (iv) is preferably carried out by free radical polymerization, said reaction being preferably initiated with azoisobutyronitrile (AIBN). It is preferred that, after addition of AIBN, the so-obtained mixture is stirred to ensure homogeneity of the solution. Other cross-linking reactions are known in the art and will become apparent to the skilled person. A method for preparing an electrochemical cell or a battery according to the second aspect of the invention is a further aspect of the invention. Said method will become apparent to the skilled person using common general knowledge. In a preferred embodiment, said method comprises the steps of:

(i) providing a cathode for an electrochemical cell or a battery;

(ii) providing an anode for an electrochemical cell or a battery;

(iii) providing a polymer electrolyte, preferably a gel polymer electrolyte, as defined in any preferred or particular embodiment of the first aspect of the invention;

(iv) coating the surface of the cathode provided in step (i) and of the anode provided in step (ii) with the electrolyte provided in step (iii), being said surfaces optionally covered with a membrane, prior to coating with the electrolyte, in a manner that the electrolyte is arranged between the cathode and the anode such that lithium cations can flow from the cathode to the anode; and

(v) optionally, when the polymer electrolyte comprises a polymer with one or more crosslinkable functional groups, cross-linking the polymer comprised in the polymer electrolyte.

In particular embodiment, the coating step (iv) is performed by casting techniques as known in the art. As stated above such surfaces may be covered with a membrane which acts as a separator; in case both the cathode and anode surfaces are covered with a membrane, such membrane can be the same or different for each surface. Preferably such membrane is a polymeric membrane separator, more preferably is a polypropylene membrane separator.

In preferred embodiments, the cross-linking step (v) is a free radical polymerization involving (meth)acrylate groups as cross-linkable functional groups. Preferably, said (meth)acrylate groups are comprised in a poly(ethyleneglycol) compound, such as in poly(ethyleneglycol) methyl ether methacrylate or in poly(ethyleneglycol) dimethacrylate (PEGDMA), or in an (meth)acrylate monomer, such as methyl ethyl or butyl acrylate, pentaerythritol tetraacrylate (PETA) or trimethylolpropane triacrylate (ETPTA). The cross-linking is initiated by a radical polymerization initiator, such as AIBN, under conditions of temperature, pressure and for a reaction time easily deducible by a skilled person. In a preferred embodiment, the crosslinking step is performed at 50 °C, at 60°C, at 70 °C, at 80 °C, at 90 °C or at 100 °C, preferably in the range from 50 to 100 °C, more preferably at about 70 °C. The reaction time for the crosslinking step would be known to a skilled person depending on the group that undergoes crosslinking; this time would be at least 1 hour, at least 2 hours, at least 4 hours, at least 6 hours, at least 8 hours, at least 10 hours, at least 12 hours, at least 24 hours; preferably, the reaction time would be approximately 12 hours,

Preferred materials for the preparation of the electrochemical cell or battery are as defined in the preferred and particular embodiments of the second aspect of the invention.

The optional cross-linking step (v) may be carried out before or after step (iv). It is however preferred that it is carried out after step (iv), as it favours a maximal contact surface between the electrolyte and the electrodes.

EXAMPLES

The following examples are intended to illustrate but not to limit the disclosed embodiments.

List of abbreviations

LiDFTFSL (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide lithium salt LiBOB: lithium bis(oxalato)borate

PEGDMA: poly(ethyleneglycol) dimethacrylate with Mn = 550 g/mol

AIBN: azoisobutyronitrile rpm: rounds per minute

RT : room temperature

Reagents and starting materials

The following chemicals were purchased from Sigma- Aldrich and pre-treated as follows: poly(ethylene glycol) methyl ether methacrylate (M_n 500), PEGDMA (M_n 550) and AIBN were dried at high vacuum and at room temperature.

Example 1 : Preparation of the electrolyte

Lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (LiDFTFSI) (161.40 mg) was added to a vial, then N,N-dimethylsulfamoyl fluoride (636.52 mg) was added and subsequently poly(ethylene glycol) methyl ether methacrylate (85.93 mg or 79.6 mL) (PEGMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) (29.15 mg or 26.5 mL) were added and the solution was left under stirring for approximately 2 hours at 300 rpm. After this time, the solution appeared homogeneous. Finally, azobisisobutyronitrile (AIBN) (0.69 mg) was added and the solution was stirred for another 10 minutes at 300 rpm. A gel electrolyte was obtained after heating the mixture at 70 °C during 12 h.

The final electrolyte composition is the following:

Example 2: Cathode and electrochemical cell

Cathode preparation: LiNio.6Mno.2Coo.2O2 (NMC622) (6.3 g) cathode was composed by 90 wt.% of NMC622, 5 wt.% of conductive carbon (Super C-65) (0.35 g), and 5 wt.% of polymeric binder (PVdF) (0.35 g). The slurry was made using N-methyl-2-pyrrolidone (NMP) as solvent (10 g) and, after homogenization of the dispersion, this was casted on a carbon-coated aluminum current collector. Finally, it was dried overnight at 80 °C under vacuum leading to an average loading of ca. 1.2-1.5 mAh cm^-2. The electrodes were punched with dimensions 12 mm diameter and subsequently dried again under vacuum at 50 °C before cell assembly.

Cell assembly, a coin cell was assembled in an Argon filled glovebox using NMC622 (12 mm diameter) electrodes as cathode, Celgard 2500 as separator and Li metal disk (China Energy Lithium, 14 mm diameter and 500 pm thickness) as anode. The previously prepared electrolyte mixture was casted on the separator and the cell was closed with a crimper. Then, the crosslinking process was applied by keeping the cell at 70 °C for 12 hours.

Example 3 : Electrochemical measurements

The cells were cycled galvanostatically between 2.8 V and 4.25 V vs. Li/Li+, using a

Maccor Battery Tester (Series 4000). The applied protocol was based on 3 cycles at a current of C/20, then constant cycling at C/10 (both charge and discharge) at 25 and 40 °C.

Figure 1 shows the discharge specific capacity and coulombic efficiency vs. cycle number for the Li°||NMC622 cells comprising the gel electrolyte of the invention at two different temperatures (40 °C and 25 °C). It is evident that the discharge specific capacity and coulombic efficiency are maintained for at least 70 cycles.

Claims

1.- A polymer electrolyte comprising: i. at least one polymer, ii. at least one sulfonamide, and iii. at least one lithium salt; being said polymer electrolyte further characterized in that it does not comprise an organic carbonate, and wherein the at least one sulfonamide has general formula I:

R₂S 9

N-S-R R₃ ^Z i wherein

2.- The polymer electrolyte according to claim 1, wherein the at least one polymer is selected from:

- a polyalkylene oxide;

- a polyalkylenimine;

- a polyalkylene sulphide;

- a polyethylene glycol optionally comprising one or more cross-linkable groups; - a poly(meth)acrylate or a cross-linked polymer thereof with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA);

- a polyphosphazene;

- a polysiloxane;

- polyvinyl alcohol (PVA),

- polyvinyl amine (PVAm);

- polyvinyl acetate (PVAc);

- a polyvinyl halide;

- a polyacrylonitrile (PAN);

- poly(vinylpyrrolidone) (PVP);

- poly(2-vinylpyridine) (P2VP);

- poly(s-caprolactone) (PCL);

- poly(maleimide);

- polyaniline (PANI);

- chitosan (CS); or

- any copolymer, any mixture or any cross-linked polymer thereof.

3.- The polymer electrolyte according to claims 1 or 2, wherein the at least one polymer is selected from polyethylene glycol) methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or blends, copolymers or any cross-linked polymer thereof; or from a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA), wherein the weight ratio between polyethylene glycol) methyl ether methacrylate and PEGDMA or between butyl acrylate and trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA) is of between 50:1 and 1:1, more preferably of between 10:1 and 2:1, even more preferably of about 3:1.

4.- The polymer electrolyte according to any of claims 1 to 3, wherein the at least one polymer amounts from 5 to 85 wt.% compared to the total weight of the electrolyte composition, preferably from 8 to 60 wt.%, even more preferably from 8 to 20% wt.%, even more preferably to about 12 wt.% with respect to the total weight of the electrolyte composition.

5.- The polymer electrolyte according to any of the preceding claims, wherein the at least one sulfonamide is one of formula I

, wherein

- Ri is selected from F and a linear C1-C4 alkyl group substituted with one or more fluorine atom(s); and

- R2 and R3 are linear C1-C12 alkyl groups which may be substituted with one or more fluorine atom(s).

6.- The polymer electrolyte according to any of the preceding claims, wherein the at least one sulfonamide represents from 5 to 85 wt.% of the weight of the electrolyte, preferably from 5 to 80 wt.% of the weight of the electrolyte, more preferably from 40 to 75 wt.% of the weight of the electrolyte; even more preferably, is about 70 wt.% of the weight of the electrolyte.

7.- The polymer electrolyte according to any of the preceding claims, wherein the at least one lithium salt is an organic or inorganic lithium salt selected from LiC10₄, LiNO₃, LiBF₄, LiAsF₆, LiPF₆, LiBF₃Cl, LiF, LiN(SO₂CF₃)₂, LiN(SO₂CF₃)(SO₂CF₂H), LiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂F), LiN(C₂F₅SO₂)(SO₂F), LiB(C₂O₄)₂, LiBF₂(C₂O₄), LiC(SO₂CF₃)₃, LiPF₃(C₂F5)₃, LiCF₃SO₃ and a combination thereof; preferably, the at least one lithium salt is selected from LiN(SO₂CF₃)(SO₂CF₂H), LiB(C₂O₄)₂, LiN(SO₂F)₂, LiN(SO₂CF₃)₂, LiN(SO₂CF₃)(SO₂F) and a combination thereof; more preferably, the at least one lithium salt is LiN(SO₂CF₃)(SO₂CF₂H).

8.- The polymer electrolyte according to any of the preceding claims, wherein the at least one lithium salt amounts to from 10 to 90 wt.%, preferably from 10 to 50 wt.%, even more preferably from 10 to 30 wt.%, even more preferably to about 18 wt.% with respect to the total weight of the polymer electrolyte.

9.- The polymer electrolyte according to any one of the preceding claims comprising: i. at least one polymer selected from poly(ethyleneglycol)methyl ether methacrylate, poly(ethylene glycol) dimethacrylate (PEGDMA), or any blend thereof, or any co-polymer thereof or any cross-linked polymer thereof; and a cross-linked polymer of butyl acrylate with trimethylolpropane triacrylate (ETPTA) and/or pentaerythritol tetraacrylate (PETA); ii. a sulfonamide of formula I

, wherein

- R2 and R3 are linear C1-C4 alkyl groups; and iii. an organic lithium salt selected from LiN(SO2CF3)(SO2CF2H), LiB(C2O4)2, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2CF3)(SO2F) and a combination thereof, more preferably the lithium salt is LiN(SO2CF3)(SO2CF2H); further characterized in that the polymer electrolyte is in gel form.

10.- The polymer electrolyte according to any one of claims 1 to 6 and 8 to 9 wherein said at least one lithium salt is a combination of a first lithium salt and a second lithium salt other than the first lithium salt that is suitable for lithium metal batteries, said first lithium salt being selected from the group consisting of LiN(SO2CF3)(SO2CF2H), LiN(SO₂CF3)(SO₂F), and LiN(C2F₅SO2)(SO₂F).

11.- The polymer electrolyte according to claim 10 wherein the first lithium salt is LiN(SO2CF3)(SO2CF₂H).

12.- The polymer electrolyte according to claim 10 or claim 11 wherein the second lithium salt is selected from the group consisting of lithium perchlorate, lithium nitrate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, lithium fluoride, lithium oxide, lithium peroxide, a salt of formula LiN(SO2CF3)2, a salt of formula LiN(SO2F)2, a salt of formula LiN(SO2CF3)(SO2F), a salt of formula LiN(SO2C2Fs)(SO2F), a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2O4), a salt of formula Li SChCFs a salt of formula LiPF3(C2Fs)3, a salt of formula LiCF^SCF and mixtures thereof.

13.- The polymer electrolyte according to claim 10 to 12 wherein the second lithium salt is selected from the group consisting of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium chlorotrifluoroborate, a salt of formula LiB(C2O4)2, a salt of formula LiBF2(C2C>4), a salt of formula LiPF3(C2Fs)3, a salt of formula LiCF^SCF and mixtures thereof.

14.- The polymer electrolyte according to any one of claims 10 to 13 wherein the second lithium salt is a salt of formula LiB(C2O4)2 or a salt of formula LiBF2(C2O4).

15.- The polymer electrolyte according to any one of claims 10 to 14 wherein the weight ratio of the first lithium salt to the second lithium salt is comprised from 1 : 1 to 2: 1.

16.- A method for preparing the polymer electrolyte of any of claims 1 to 15 comprising the steps of:

(i) providing at least one lithium salt;

(ii) mixing at least one sulfonamide with the at least one lithium salt of step (i);

(iii) adding at least one polymer to the mixture obtained in step (ii); and,

(iv) optionally, when the polymer comprises one or more cross-linkable functional groups, cross-linking the at least one polymer comprised in the mixture resulting from step (iii).

17.- An electrochemical cell or battery comprising the polymer electrolyte according to any of claims 1 to 15, a cathode, an anode, and, optionally, a separator.

18.- The electrochemical cell or battery according to claim 17 wherein:

- the cathode material comprises lithium nickel manganese cobalt oxide;

- the anode consists of metallic lithium; and

- the optional separator is a polypropylene membrane.

19.- Use of the electrochemical cell or battery according to claims 17 or 18 in electric motors; electric cars, including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), or the like; electric carts, including electric bikes (E-bikes) and electric scooters (E-scooters); electric golf carts; and electric power storage systems.

20.- A method for preparing an electrochemical cell or a battery according to claim 17 or 18, said method comprising the steps of:

(i) providing a cathode;

(ii) providing an anode;

(iii) providing a polymer electrolyte as defined in any of claims 1 to 14;

(iv) coating the surface of the cathode provided in step (i) and of the anode provided in step (ii) with the polymer electrolyte provided in step (iii), being said surfaces of the cathode and anode optionally covered with a membrane prior to coating with the electrolyte; in a manner that the electrolyte is arranged between the cathode and the anode; and