SOLID ELECTROLYTE FOR LITHIUM BATTERIES

Abstract

The invention relates to a solid lithium battery electrolyte, comprising a polymer from the poly(alkylene carbonate) family and a lithium salt of formula (III): [Chem 2] (III).

Description

Title of the invention: SOLID ELECTROLYTE FOR LITHIUM BATTERIES technical field

[0001] The present invention falls within the field of lithium battery manufacturing.

[0002] More particularly, the present invention relates to an electrolyte comprising an organic salt and a polymer from the polycarbonate family, particularly suitable for use in an all-solid-state lithium battery. The invention also relates to a method for preparing such an electrolyte, as well as its use in an electrochemical cell for an all-solid-state lithium battery. Other objects of the invention relate to an electrochemical cell comprising the electrolyte according to the invention, and a lithium battery comprising such an electrochemical cell. Prior art

[0003] Lithium batteries, such as lithium-ion batteries, are increasingly used as a stand-alone power source, particularly in portable electronic equipment (such as mobile phones, laptops, and power tools), where they are gradually replacing nickel-cadmium (NiCd) and nickel-metal hydride (NiMH) batteries, and also in electric vehicles. They are also widely used to provide the power needed for new micro-applications, such as smart cards, sensors, and other electromechanical systems.

[0004] From a functional point of view, lithium-ion batteries operate on the principle of the intercalation-disintercalation of metallic ions within materials constituting the electrodes of the electrochemical cells of the battery, these materials being able to be described as (electrochemically) active materials.

[0005] More specifically, the reaction that produces current (i.e., when the battery is in discharge mode) involves the transfer, via an ionically conductive electrolyte, generally contained in a separator, of lithium cations from a negative electrode which intercalate into the acceptor network (or active material) of the positive electrode, while electrons from the reaction at the negative electrode supply the external circuit to which the positive and negative electrodes are connected.

[0006] Conventional ionically conductive electrolytes used in lithium batteries are liquid-type, composed of organic solvents in which lithium salts are dissolved. However, such liquid electrolytes suffer from safety problems due to their volatility, flammability and potential leakage risks.

[0007] One strategy to address these safety issues is to replace the liquid electrolytes used in batteries with solid materials. Batteries using solid-state electrolytes (or "SSEs") are commonly called "all-solid-state" batteries. This type of battery allows for higher energy densities than liquid-based battery technologies, through the use of metallic lithium electrodes, while also ensuring greater battery safety during operation. Furthermore, the solid electrolyte also acts as a separator within the battery: it prevents the electrodes from coming into physical contact.

[0008] The materials used in all-solid-state batteries can be inorganic materials such as oxides and sulfides (these are then referred to as "ISEs" for "Inorganic Solid Electrolytes"), or organic materials such as polymers (these are then referred to as "SPEs" for "Solid Polymer Electrolytes" or "HSEs" for "Hybrid Solid Electrolytes").

[0009] Solid polymer-based electrolytes, such as SPEs and HSEs, offer numerous advantages: they possess good interface properties with active materials, can adapt to changes in electrode volume, are lightweight, and allow for simpler processing methods, unlike inorganic materials. However, the ionic conductivity of current polymer-based electrolytes at room temperature, on the order of 10⁷ S.cm*, remains too low to be satisfactory.

[0010] More specifically, a solid polymer electrolyte is composed of a polymer matrix in which a lithium salt has been dissolved, and is free of liquid components, particularly liquid solvents (plasticizers). The composition of the ionically conductive electrolyte used in a battery has a significant impact on its performance. This performance is all the higher when the ionic conductivity of the electrolyte, which ensures the mobility of Li+ ions between the positive and negative electrodes, is itself high. The conduction of Li+ ions within the polymer can occur via two concurrent mechanisms: diffusion of ions under the effect of a concentration gradient, and complexation of Li+ ions assisted by the segmental mobility of the polymer chains.

[0011] The most common solid electrolytes of the SPE and HSE type, particularly for lithium batteries, are based on polyethers, and more specifically on poly(oxyethylene) (POE) and its derivatives. However, these electrolytes present Limited performance in terms of lithium ion transport number and ionic conductivity is linked to the ion coordination mechanism. As a result, many alternative polymers have been developed in recent years, such as polycarbonates, polyesters, poly(arylene ether sulfone)s, polynitriles, polyalcohols, and polyamines, etc. Among them, aliphatic polycarbonates, particularly poly(trimethylene carbonate) (PTMC) and its copolymers, have emerged as alternative host materials to POE, especially interesting for forming solid polymeric electrolytes, due to their highly amorphous structure, the flexibility of their chain segments, their high dielectric constant, their low toxicity, and their good mechanical properties.

[0012] It is also known that lithium salts containing anions that allow for strong delocalization of negative charges ensure good conduction of lithium ions within polymer electrolytes. Indeed, this strong delocalization weakens the ionic bond between the Li+ cation and its anion in order to maintain the mobility of the Li+ cation. Many lithium salts have thus been proposed in the prior art for the preparation of polymer electrolytes for lithium batteries, the most prominent of which is lithium bis(trifluoromethylsulfonyl)imidide (LiTFSI).

[0013] However, there still remains at present a need for a solid polymer-based electrolyte which has high ionic conductivity, enabling the formation of high-performance lithium batteries.

[0014] The present invention aims to provide such a polymer electrolyte.

[0015] Additional objectives of the invention are that this polymer electrolyte, in addition to its high ionic conductivity, meets in particular the safety, chemical stability and electrochemical stability criteria required for implementation within a lithium battery. Summary of the invention

[0016] It has now been discovered by the present inventors that these objectives are achieved by implementing, in a solid electrolyte, a specific combination of a particular polymer and lithium salt.

[0017] Thus, according to a first aspect, the present invention proposes an electrolyte, particularly suitable for use in an all-solid-state lithium battery, which comprises a lithium salt and a polymer having a repeating motif of formula (I):

[0018] [Chem.l] O ^■o'' b-"f N î v ;œ i. _3 (I)

[0019] in which m is equal to 0, 1 or 2, the lithium salt having the formula (III):

[0020] [Chem.2]

[0021] In particular embodiments of the invention, the molar ratio "lithium salt / carbonate groups of the polymer" [Li] / [CO3], in the electrolyte, is between 1 / 2 and 1 / 40.

[0022] Preferably, the formula repeat motif (I) is the only repeat motif of the polymer.

[0023] The polymer is, for example, a poly(trimethylene carbonate) (PTMC), the chain ends of which are preferably devoid of free hydroxyl groups. This polymer may thus, in particular, have the general formula (II):

[0024] [Chem.3] (II)

[0025] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, and X and Y, identical or different, each represent a group devoid of a free hydroxyl function, this group being preferably chosen from alkylaryls, optionally substituted, and alkanoates.

[0026] The polymer can in particular conform to the general formula (lia):

[0027] [Chem.4] (lia)

[0028] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, and Ar represents an aryl group, for example phenyl or naphthyl, optionally substituted.

[0029] The polymer preferably has a number-average molar mass between 1,000 g / mol and 10,000 g / mol.

[0030] The electrolyte according to the invention is preferably in solid form, in particular in the form of a film or a membrane.

[0031] An additional aspect of the invention is a method for preparing an electrolyte according to the invention, this method comprising a step of mixing the polymer and the lithium salt entering into the constitution of this electrolyte, as defined above and below.

[0032] Another aspect of the invention relates to the use of an electrolyte according to the invention in an electrochemical cell for lithium battery, in particular all-solid.

[0033] The invention also relates to an electrochemical cell for a lithium battery, comprising a positive electrode, a negative electrode and a solid electrolyte, this electrolyte being a solid electrolyte according to the invention, meeting one or more of the characteristics described above and below.

[0034] Another object of the invention is a lithium battery comprising at least one electrochemical cell according to the invention.

[0035] The features and advantages of the invention will become more apparent in the light of the following detailed description and implementation examples, which are by no means limiting, of the invention, with the support of Figures 1 to 5. Brief description of the drawings

[0036] [Fig.1] Fig.1 shows the 'H NMR spectrum of a PTMC in CDC13 (traces of dichloromethane).

[0037] [Fig.2] Fig.2 shows the *H NMR spectrum of an acetylated PTMC in CDC13.

[0038] [Fig. 3] Fig. 3 shows the curves obtained by calorimetry analysis differential scanning (10 K / min) for polymer electrolytes, respectively, PTMC / LiNPTFSI (according to the invention), and PTMC / LiTFSI (comparative example), the PTMC used being acetylated and having a number average molar mass of 2900 g / mol and each of the polymer electrolytes having a molar ratio [Li] / [CO3 ] = 1 / 15.

[0039] [Fig.4] Fig.4 shows the equivalent circuit used for data adaptation impedance for the determination by electrochemical impedance spectroscopy of the conductivity of polymer electrolytes.

[0040] [Fig. 5] Figure 5 shows the conductivity curves as a function of temperature, polymer electrolytes, respectively, PTMC / LiNPTFSI (according to the invention), and PTMC / LiTFSI (comparative example), the PTMC used being acetylated and having a number average molar mass of 2900 g / mol and each of the polymer electrolytes having a molar ratio [Li] / [CO3] = 1 / 15. DETAILED DESCRIPTION

[0041] Electrolyte composition

[0042] The electrolyte according to the invention comprises a lithium salt corresponding to the general formula (II) and at least one polymer comprising a formula repetition motif (I).

[0043] In the present description, the term polymer encompasses both polymers strictly speaking, that is to say comprising a single repeating motif, this motif corresponding to the general formula (I), and copolymers, comprising several different repeating motifs, at least one of which corresponds to the formula (I).

[0044] According to the present invention, at least one, preferably each, polymer entering into the composition of the electrolyte according to the invention comprises a repeating motif of formula (I):

[0045] [Chem.l] (I)

[0046] in which m is equal to 0, 1 or 2, and preferably equal to 1.

[0047] This repeating unit (also called the monomer unit) may be the only repeating unit of the polymer, the latter then belonging to the poly(alkylene carbonate) family, and preferably comprising from 10 to 100 repeats of the repeating unit of formula (I). Preferably, the polymer is a poly(trimethylene carbonate) (PTMC), m being equal to 1 in formula (I), this PTMC preferably comprising from 10 to 100 repeats of the repeating unit of formula (I).

[0048] Alternatively, the polymer entering into the composition of the electrolyte according to the invention may be a copolymer, comprising a monomer unit of formula (I), and at least one different monomer unit, for example of e-caprolactone, and / or several units of different formula (I), i.e. having different m values ​​from each other.

[0049] In the electrolyte composition according to the invention, the repeating motif polymer of formula (I) is combined with the lithium salt of formula (II), lithium N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide (LiNPTFSI). This lithium salt may have been obtained by any synthetic route whose development is within the scope of those skilled in the art, or by the process described below in this description.

[0050] Unexpectedly, the present inventors discovered that the electrolyte combining the two substances, LiNPTFSI and a repeating motif polymer of formula (I), exhibits a particularly high ionic conductivity. By way of example, the ionic conductivity of an electrolyte according to the invention, comprising poly(trimethylene carbonate) (PTMC) as the polymer and LiNPTFSI in solid form, was measured by the present inventors at a value of 1.9 x 10² mS·cm⁻¹ at 80°C, compared to 6.3 x 10³ mS·cm⁻¹ at the same temperature for a similar electrolyte composition, differing only in that the lithium salt it contains is not LiNPTFSI but the reference salt in the field, LiTFSI. More generally, regardless of temperature, the ionic conductivity of the PTMC - LiNPTFSI electrolyte according to the invention is about 3 times greater than the conductivity of the PTMC - LiTFSI composition.

[0051] We will not prejudge here the mechanisms underlying the achievement of such good performance, in terms of ionic conductivity, of the electrolyte according to the invention. It can be assumed that the following factors contribute to achieving this performance: - the specific structure of the anion in the constitution of the lithium salt, in which the anionic charge is strongly delocalized, leading to a weakening of the ionic bond between the Li+ cation and its anion, resulting in a high mobility of the Li+ cation; - and the properties of the PTMC polymer, in particular its high ion transport number (t+ = 0.75).

[0052] Nothing, however, suggested such high ionic conductivity for the electrolyte according to the invention, especially since LiNPTFSI itself has been described in the prior art, notably illustrated by the publication of Ladouceur et al., 2015, Journal of Power Sources, 293: 78-88, used in a liquid electrolyte composed of a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), as having a much lower ionic conductivity than LiTFSI. It is therefore particularly surprising that, in the context of a polymer electrolyte specifically comprising a polymer with a repeating formula motif (I), the conductivity performance of LiNPTFSI is superior, and even significantly superior, to that of LiTFSI.

[0053] The repeating pattern polymer(s) of formula (I) used in the composition of the electrolyte according to the invention belong to the family of aliphatic polycarbonates, more particularly poly(alkylene carbonate), and preferably poly(trimethylene carbonate) (PTMC). Polymers of the poly(trimethylene carbonate) family, used in a solid electrolyte for lithium batteries, offer in particular the advantages of providing access to a wide electrochemical stability window (up to 4.5 V vs. Li / Li+), and exhibiting good thermal stability as well as, as indicated above, a high ion transport number (t+ = 0.75).

[0054] In particular embodiments of the invention, at least one polymer with a repeating pattern of formula (I), in particular of the PTMC type, preferably all of these polymers contained in the electrolyte according to the invention, has a number average molar mass less than or equal to 10,000 g / mol, and preferably greater than or equal to 1,000 g / mol and preferably greater than or equal to 1,500 g / mol.

[0055] The number-average molar mass can, for example, be determined by size-exclusion chromatography, possibly coupled with static light scattering. This determination falls within the basic skills of a person skilled in the art.

[0056] In particular embodiments of the invention, the molar ratio "lithium salt of formula (III) / carbonate groups of the repeating motif polymer of formula (I)", preferably for each such polymer contained in the electrolyte, in particular polymer of the PTMC type, expressed as a molar ratio [Li] / [CO3], is between 1 / 2 and 1 / 40, preferably between 1 / 5 and 1 / 25, and for example equal to 1 / 15.

[0057] In particularly preferred embodiments of the invention, the repeating pattern polymer of formula (I), in particular PTMC, is devoid of free hydroxyl groups at chain ends.

[0058] The repeating pattern polymer of formula (I) then preferably has the general formula (II):

[0059] [Chem.3] O (II)

[0060] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, and X and Y, whether identical or different, each represent a group devoid of a free hydroxyl function.

[0061] The repeating pattern polymer of formula (I) has, for example, the general formula (II'):

[0062] [Chem.5] O (ID

[0063] in which n is an integer greater than or equal to 10, preferably between 10 and 100, and X and Y, identical or different, each represent a group devoid of a free hydroxyl function.

[0064] Depending on the method used to synthesize the polymer, in particular PTMC, X may be a group from a single hydroxyl function polymerization reaction initiator compound, for example 3-phenyl-l-propanol, or consist of a hydroxyl function protecting group.

[0065] Y can, for its part, consist of a protecting group of a hydroxyl function.

[0066] A protecting group for a hydroxyl function is understood to be any group used conventionally by itself to protect a hydroxyl function, that is, to mask its reactivity. This falls within the competence of a person skilled in the art. to be able to identify the protecting groups of hydroxyl functions that can be implemented within the framework of the invention. Examples of such protecting groups are listed in particular in Greene's book, "Protective groups in Organic Synthesis" (4th ed.), Wiley & Sons, 2006.

[0067] Each of the protecting groups of a hydroxyl function implemented according to the invention can for example be chosen from among the alkyl, acyl groups, in particular acetyl, benzyl, silyl, sulfonyl, alkoxy-alkyl, for example methoxymethyl, methoxyethoxymethyl or benzoxymethyl, etc.

[0068] X and / or Y can in particular be obtained by reaction of the polymer, in particular of PTMC, comprising free hydroxyl functions, with a compound selected from acyl chlorides, such as benzoyl chloride and acetyl chloride, acid anhydrides, such as acetic anhydride, and isocyanates, such as p-tolenesulfonyl isocyanate.

[0069] It is within the competence of a person skilled in the art to determine the reaction conditions enabling the protection of any free hydroxyl groups of the polymer, in particular of PTMC, according to the protecting group of a desired hydroxyl function.

[0070] Preferably, in the general formula (II) or (II'), X and Y, identical or different, are chosen from alkylaryls, optionally substituted, and alkanoates. X and Y, identical or different, may in particular be chosen from: - alkylaryls, possibly substituted, preferably at C8-C20, and preferably having an aliphatic hydrocarbon chain, for example at C2-C4, substituted, preferably at its end opposite its end linked to the repeating unit of the polymer, by an aryl group; preferably, this aryl group is then preferably at C6-C10, such as a phenyl or naphthyl group, and it may optionally be substituted, in particular by one or more alkyl, alkenyl and / or alkynyl groups, preferably each at C2-C4, for example by a vinyl group; As an example of such a substituted aryl group, we can cite the styryl group; - and C2-C6 alkanoates, such as acetate.

[0071] In particular embodiments of the invention, the repeating pattern polymer of formula (I) corresponds to the general formula (Ilb):

[0072] [Chem.6] (Ilb)

[0073] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, p is equal to 0, 1 or 2, preferably equal to 1, and Ar represents an optionally substituted aryl group.

[0074] The repeating pattern polymer of formula (I) has, for example, the general formula (Ilb'):

[0075] [Chem.7] OO (Ilb')

[0076] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, p is equal to 0, 1 or 2, preferably equal to 1, and Ar represents an optionally substituted aryl group.

[0077] In particular embodiments of the invention, the patterned polymer Repetition of formula (I) corresponds to the general formula (lia):

[0078] [Chem.4] (lia)

[0079] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, and Ar represents an optionally substituted aryl group.

[0080] The polymer with a repeating pattern of formula (I) has, for example, the formula general (lia'):

[0081] [Chem.8] ii (lia')

[0082] in which n is an integer greater than or equal to 10, preferably between 10 and 100, m is equal to 0, 1 or 2, preferably equal to 1, and Ar represents an optionally substituted aryl group.

[0083] In the formulas (lia), (lia'), (Ilb), (Ilb') above, Ar may in particular represent a C6-C10 aryl group, such as a phenyl or naphthyl group, this group optionally being substituted by one or more alkyl, alkenyl and / or alkynyl groups, preferably each in a C2-C4 position, for example by a vinyl group. An example of such a substituted aryl group is the styryl group.

[0084] A particular example of a repeating pattern polymer of general formula (I) that can be contained in the composition of the electrolyte according to the invention corresponds to the general formula (Ile):

[0085] [Chem.9] (Island)

[0086] in which n is an integer greater than or equal to 10, preferably between 10 and 100, and m is equal to 0, 1 or 2, preferably equal to 1, and, more specifically, to the general formula (Ile'):

[0087] [Chem. 10] (Island')

[0088] in which n is an integer greater than or equal to 10, preferably between 10 and 100.

[0089] The polymer(s) forming part of the electrolyte according to the invention may be crosslinked or non-crosslinked. In the configuration in which at least one of these polymers is in the crosslinked state, the lithium salt may have been combined with the polymer(s) before or after the crosslinking step.

[0090] The electrolyte composition according to the invention may further contain any conventional additive in itself in the field of lithium batteries, such as, for example, an inorganic charge conductive of the lithium salt cation in the electrolyte.

[0091] The electrolyte according to the invention is preferably in solid form, in particular in the form of a film or a membrane, which can be used directly within an electrochemical cell for a battery, as a solid electrolyte.

[0092] It preferably consists of a polymeric solid electrolyte (SPE) or a hybrid solid electrolyte (HSE).

[0093] In the present description, a solid electrolyte is understood, in a classical sense, as an electrolyte devoid of liquid components, and capable of acting, in an electrochemical cell, as both an ionic conductor and a separator, preventing the electrodes from coming into physical contact with each other.

[0094] Process for preparing the electrolyte

[0095] A method for preparing the electrolyte according to the invention comprises mixing the repeating pattern polymer of formula (I) and the lithium salt of formula (III).

[0096] This mixture can be prepared by solvent mixing, the lithium salt, the polymer(s), and any additives being brought into contact with each other in an organic solvent or a mixture of organic solvents, preferably aprotic and preferably polar, for example, tetrahydrofuran. The contact can be carried out at a temperature between 30 and 70°C, for example, around 50°C, for a duration of between 12 and 24 hours. It is preferably followed by an evaporation step of the solvent(s) used, in particular under reduced pressure, at a temperature ensuring this evaporation.

[0097] According to other embodiments of the invention, the mixture can be prepared by melting, in the absence of solvents. In such embodiments, the lithium salt, the polymer(s) and any additives are heated to a temperature above the glass transition temperature of each of the polymers, and mixed when each polymer is in a molten state, the mixture then preferably being cooled to induce solidification.

[0098] The process for preparing the electrolyte according to the invention may include a crosslinking step of at least one polymer contained in this electrolyte, this step being able to be carried out before, or after, the mixing of the lithium salt with the polymer(s).

[0099] The solid electrolyte according to the invention can be shaped into a film or membrane, which can be used directly within an electrochemical battery cell to form a solid electrolyte.

[0100] This shaping can be carried out at the end of the electrolyte preparation process, before the step of transitioning to the solid state, by depositing the electrolyte composition in the fluid state on the surface of a suitable substrate, preferably flat in shape, and then solidification.

[0101] By way of example, in embodiments where the electrolyte is formed by solvent extraction, deposition on the substrate surface can advantageously be carried out before the evaporation step of the solvent(s), for example by coating. In embodiments where the electrolyte is formed by melt extraction, deposition on the substrate surface can advantageously be carried out on the composition in its molten state, for example by extrusion, before the cooling step. All of these techniques are well known to those skilled in the art.

[0102] The substrate used is then chosen from among substrates made of materials that are chemically inert with respect to the components of the electrolyte, for example glass, silicone, polytetrafluoroethylene (PTFE), polypropylene, etc.

[0103] After solidification, the resulting film or membrane may or may not be detached from the substrate for its subsequent use.

[0104] The lithium salt LiNPTFSI used in the electrolyte according to the invention may have been previously prepared by any method that is conventional in itself for a person skilled in the art, for example by the process described in the aforementioned publication by Ladouceur et al.

[0105] The present inventors have, however, developed a particularly advantageous process for synthesizing this salt, in that it allows, in a few steps, the LiNPTFSI to be obtained with a high yield. Thus, one aspect of the invention relates to a process for preparing LiNPTFSI, of formula (III).

[0106] This process comprises successive steps of:

[0107] - preparation of (naphthalene-l-sulfonyl)trifluoromethylsulfonamide (NPTFSI), with general formula (IVb): [Chem. 11] o-—-.o

[0108]

[0109] (IVb) by reaction of naphthalen-l-sulfonyl chloride, of formula (IVc): [Chem. 12]

[0110] [YES] (IVc) with trifluoromethanesulfonamide, in the presence of a nucleophilic catalyst and a tertiary amine, - purification of the (naphthalene-l-sulfonyl)trifluoromethylsulfonamide thus obtained, - and contacting the (naphthalene-l-sulfonyl)trifluoromethylsulfonamide thus purified with lithium hydride LiH. The naphthalene-1-sulfonyl chloride of formula (IVb) above may have been obtained by any conventional method in itself. In particular embodiments of the invention, the process includes a preliminary step of preparing the naphthalene-1-sulfonyl chloride by chlorination of sodium 1-naphthalenesulfonate, by reaction with thionyl chloride of general formula (IVa):

[0112] [Chem. 13] SQjNa (IVa).

[0113] This chlorination reaction can be carried out in an aprotic solvent, preferably polar, such as dimethylformamide. It is preferably carried out at room temperature, i.e. between approximately 18 and 25 °C, and for a period of a few hours, in particular between 4 and 24 hours.

[0114] The process according to the invention preferably includes a step of separating the naphthalen-l-sulfonyl chloride thus obtained from the reaction medium, for example by precipitation in water and filtration, and preferably a step of purifying this compound, for example by sublimation after drying.

[0115] The step of preparing (naphthalene-l-sulfonyl)trifluoromethylsulfonamide (NPTFSI), of formula (IVc), from naphthalene-l-sulfonyl chloride of formula (IVb), is advantageously carried out by introducing the trifluoromethylsulfonamide motif onto the sulfonyl group of the latter by nucleophilic substitution. This reaction is carried out in the presence of a non-nucleophilic tertiary amine, such as triethylamine, 1,4-diazabicyclo[2.2.2]octane (DABCO) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and in the presence of a nucleophilic catalyst such as 4-dimethylaminopyridine (DMAP).

[0116] This reaction is preferably carried out in an aprotic solvent, preferably polar, such as acetonitrile. It is preferably carried out at room temperature, and for a period of a few hours, in particular between 12 and 30 hours.

[0117] The purification step of the (naphthalene-l-sulfonyl)trifluoromethylsulfonamide thus obtained can be carried out in any conventional manner. In particular, it can be carried out by concentrating the reaction medium, introducing the residue into ethyl acetate, and washing the organic phase with an acidic aqueous solution, for example, hydrochloric acid, and then, optionally, with a neutral aqueous solution, for example, a saturated sodium chloride solution. Optionally, the process according to the invention can then include steps of evaporating the organic phase, introducing it into an aprotic solvent, preferably polar, such as dichloromethane, and isolating the resulting (naphthalene-l-sulfonyl)trifluoromethylsulfonamide precipitate, preferably by filtration.

[0118] The final synthesis step of the process according to the invention, starting from (naphthalene-1-sulfonyl)trifluoromethylsulfonamide, is carried out by contacting this compound with lithium hydride. This contacting is preferably carried out in an aprotic solvent, preferably polar, such as tetrahydrofuran. It is preferably carried out at room temperature, and for a period of a few hours, in particular between 1 and 24 hours.

[0119] This final synthesis step is preferably followed by a purification step of the lithium salt of formula (III) obtained, for example by filtering the reaction medium so as to remove excess lithium hydride, preferably followed by a drying step.

[0120] The process for preparing lithium salt of formula (III) according to the invention, meeting one or more of the characteristics described above, advantageously allows obtaining this lithium salt in a simple manner, in only three synthesis steps, and with a high yield and a high level of purity.

[0121] The repeating motif polymer of general formula (I), in particular PTMC, can be obtained by any synthetic method known to those skilled in the art, for example by ring-opening polymerization of the corresponding alkylene carbonate, in particular trimethylene, in the presence of a polymerization reaction initiator, and optionally a catalyst such as diphenyl phosphate. Examples of such processes are described in particular in document FR 3130454, or below in this description.

[0122] Electrochemical cell

[0123] The electrolyte according to the invention can find application in various electrochemical systems, in particular in energy storage systems, especially all-solid-state lithium batteries.

[0124] Thus, the present invention also relates to the use of an electrolyte according to the invention for the manufacture of an electrochemical cell for a lithium battery, in particular an all-solid-state battery. The present invention is thus also expressed in terms of the use of an electrolyte according to the invention in an electrochemical cell for a lithium battery.

[0125] An additional object of the invention is an electrochemical cell for a lithium battery comprising a positive electrode, a negative electrode and a solid electrolyte according to the invention.

[0126] In the present description, the positive electrode is understood to be, in a classical sense, the electrode which acts as the cathode when the electrochemical cell is delivering current (i.e., when it is in the process of discharging) and which acts as the anode when the electrochemical cell is in the process of charging.

[0127] By negative electrode, we mean, also in a classical way in itself, the electrode which acts as an anode when the electrochemical cell delivers current (that is to say when it is in the process of discharging) and which acts as a cathode when the battery cell is in the process of charging.

[0128] The electrodes of the electrochemical cell according to the invention can be formed from any conventional material in itself for this type of application.

[0129] By way of example, for a lithium electrochemical cell: - the positive electrode may include, as electrochemically active material, lamellar compounds, such as LiCoO2, LiNiO2 and mixed Li(Ni,Co,Mn,Al)O2, or spinel structure compounds with compositions close to LiMn2O4, lithium phosphates, in particular LiMnFePO4 or LiFePO4, etc., - the negative electrode may include, as electrochemically active material, lithium metal or a lithium-based alloy, intercalation materials such as graphite, lithium titanium oxide (Li4Ti50i2), silicon, graphite / silicon composites, etc.

[0130] Each of the electrodes of the electrochemical cell can be associated with a current collector.

[0131] The solid electrolyte is preferably in the form of a film or membrane within the electrochemical cell according to the invention, sandwiched between the positive electrode and the negative electrode, this film or membrane also preferably acting as a separator between these electrodes.

[0132] Battery

[0133] Electrochemical cells according to the invention can be implemented within a lithium battery.

[0134] Thus, an object of the invention is a lithium battery, for example a lithium-ion or lithium-metal battery, comprising one, preferably several, electrochemical cells according to the invention, in which the electrolyte meets one or more of the characteristics defined above.

[0135] The battery according to the invention can be in any conventional form in itself, in particular have a planar type format, for example button cell type, a cylindrical format, in particular an AAA, AA, C, D or DD format, a wound or spiral format, a prismatic format, etc.

[0136] The following implementation examples are provided for illustrative purposes only and are in no way limiting of the invention. EXAMPLES

[0137] Materials and methods of characterization

[0138] Commercial reagents were used without further purification. Sodium 1-naphthalenesulfonate was purchased from Fisher Scientific. The other reagents and solvents were purchased from Sigma-Aldrich. The reactions were carried out under an inert atmosphere (argon), unless explicitly stated otherwise. The ¹³C, ¹¹H, and ¹³C NMR spectra were acquired on a Bruker NEO 400 MHz spectrometer equipped with a 5 mm BBO Smart Probe. The ¹³C and ¹³H NMR spectra were referenced to the solvent peak, while an internal standard, C6F6 (δ = 0 ppm), was used for the ¹¹F NMR. Fourier transform infrared (FT-IR) spectroscopy spectra were recorded with a PerkinElmer Spectrum Two® spectrometer. Mass spectrometry analyses were performed using an Agilent 6230 series LC-MS / TOF unit. CHNS elemental analyses were performed using an Elementar Unicube® organic elemental analyzer. Differential scanning calorimetry (DSC) analyses were performed with a Netzsch DSC 404 Fl Pegasus® calorimeter and 40 pL low-pressure aluminum crucibles, at 10 K / min under helium.

[0139] 1 / Example 1 - Synthesis of the LiNPTFSI

[0140] Lithium N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide (LiNPTFSI) is prepared by the following 3 steps.

[0141] 1.1 / Step 1 - Synthesis of naphthalen-l-sulfonyl chloride

[0142] The intermediate compound naphthalen-l-sulfonyl chloride, of formula (IVc):

[0143] [Chem. 14] o=è=o (IVc)

[0144] is prepared as follows.

[0145] In a three-necked flask under argon, thionyl chloride (15 mL, 199.6 mmol, 2.3 eq.) is added dropwise, with stirring, to a solution of sodium 1-naphthalenesulfonate (20 g, 86.9 mmol, 1 eq.) in anhydrous dimethylformamide (DMF) (80 mL) that has been previously cooled to 0°C. Once the addition is complete, the reaction mixture is allowed to return to room temperature and stirred for 18 hours. The The reaction mixture is then added dropwise to cold distilled water, and the resulting precipitate is filtered through a sintered slurry and dried under vacuum. The collected brown solid is purified by sublimation to give a white solid (17.656 g, Yield = 90%).

[0146] NMR 'H (400 MHz, CDC13): ô (ppm): 8.79 (d, 3 J = 8.8 Hz, 1H, H8), 8.36 (d, 3 J = 7.4 Hz, 1H, H2), 8.21 (d, 3 J = 8.2 Hz, 1H, H4), 8.00 (d, 3 J = 8.2 Hz, 1H, H5), 7.80 (ddd, 3 J = 7.4 Hz, 3 J = 8.8 Hz, 4 J = 1.4 Hz, 1H, H7), 7.68 (ddd, 3 J = 7.2 Hz, 3 J = 8.2 Hz, 4 J = 1.1 Hz, 1H, H6), 7.59 (dd, 3 J = 7.4 Hz, 3 J= 8.2 Hz, 1H, H3). (Assigned with a COSY spectrum) 13C{H] NMR (100 MHz, CDC13): ô (ppm): 139.6 (Cl), 137.1 (C4), 134.5 (CIO), 129.6 (C7), 129.5 (C2), 129.4 (C5), 127.9 (C6), 127.5 (C9), 124.2 (C8), 124.0 (C3). (Assigned with an HSQC spectrum) FT-IR (cm1): 3063 (vC H), 1590 (vc=c), 1560, 1506 (vc=c), 1361 (vs=o), 1172 (vs=o), 1138 (vs=o), 969, 866, 830, 803, 767(vc.H), 674, 624, 577, 506. Calculated for Ci0H7C1O2S: C 52.99, H 3.11, S 14.14%; Found: C 52.92, H 2.98, S 14.13%.

[0147] 1.2 / Step 2 - Synthesis of N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide

[0148] The intermediate compound N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide (NPTFSI), of formula (IVb):

[0149] [Chem. 15] (IVb)

[0150] is prepared as follows.

[0151] In a two-necked argon-filled flask, trifluoromethanesulfonamide (3.38 g, 22.1 mmol, 1 eq), anhydrous acetonitrile (35 mL), 4-dimethylaminopyridine (DMAP) (0.27 g, 2.21 mmol, 0.1 eq), and triethylamine (6.2 mL, 44.2 mmol, 2 eq) are introduced successively. A solution of naphthalen-1-sulfonyl chloride (5.0 g, 22.1 mmol, 1 eq) in anhydrous acetonitrile (20 mL) is then added dropwise to the reaction mixture with stirring at 0°C. Once the addition is complete, the reaction mixture is allowed to return to room temperature. and stirred for 17 hours. The reaction mixture is then concentrated under vacuum and resuspended in ethyl acetate. The organic phase is extracted three times with an aqueous HCl solution (IM) and once with a saturated NaCl solution. The organic phase is dried over MgSO4, filtered, and dried under vacuum. The crude reaction mixture is precipitated with dichloromethane to give, after filtration, a white solid (4.54 g, Yield = 61%).

[0152] 'H NMR (400 MHz, MeOD): ô (ppm): 8.82 (d, 3 J = 8.5 Hz, 1H, H8), 8.22 (dd, 3 J = 7.5 Hz, 4 J = 1.0 Hz, 1H, H2), 8.06 (d, 3 J = 8.1 Hz, 1H, H4), 7.95 (d, 3 J = 8.0 Hz, 1H, H5), 7.62 (ddd, 3 J = 6.9 Hz, 3 J = 8.5 Hz, 4 J = 1.4 Hz, 1H, H7), 7.57 (ddd, 3 J = 6.9 Hz, 3 J = 8.0 Hz, 4 J = 1.2 Hz, 1H, H6), 7.53 (dd, 3 J = 7.5 Hz, 3 J = 8.1 Hz, 1H, H3). (Assigned with a COSY spectrum) 13C{H] NMR (100 MHz, MeOD): δ (ppm): 140.8 (Cl), 135.7 (CIO), 134.1 (C4), 129.8 (C9), 129.5 (C5), 128.4 (C2), 128.1 (C7), 127.4 (C6), 127.2 (C8), 125.0 (C3), 121.5 (q,1 J cf = 322 Hz, Cl 1). (Assigned with an HSQC spectrum) 19F NMR (376 MHz, MeOD): δ (ppm): 85.4 (CF3) (internal standard C6F6) FT-IR (cm1): 3473-3550 (vN H), 3053 (vC H), 1700, 1633 (vN H), 1598 (vc=c), 1508 (vc^ ), 1320 (vs=o), 1182 (vs=o), 1116 (vs=o), 1056 (vC F), 766 (vC H), 675, 624, 583, 506. MS (ESI): m / z: [MH] = 338.0, [2(MH)+Na] = 699.0.

[0153] 1.3 / Step 3 - Synthesis of the N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide lithium

[0154] Lithium N-(l-naphthalenesulfonyl)trifluoromethylsulfonamide (LiNPTFSI), of formula (III):

[0155] [Chem. 16] (III)

[0156] is prepared as follows.

[0157] In a two-necked argon-filled flask, a solution of NPTFSI (2.8 g, 8.24 mmol, 1 eq.) in anhydrous tetrahydrofuran (THF) (10 mL) is added dropwise and With stirring, a suspension of lithium hydride (72.0 mg, 9.06 mmol, 1.1 eq.) in anhydrous THF (30 mL), previously prepared in a glove box and cooled to 0°C, was added. Once the addition was complete, the reaction mixture was allowed to return to room temperature and stirred for 19 hours. The reaction mixture was then filtered through a sintered filter to remove excess lithium hydride and subsequently dried under vacuum to yield a white solid corresponding to LiNPTFSI (2.60 g, Yield = 92%).

[0158] NMR 'H (400 MHz, MeOD): ô (ppm): 8.82 (d, 3 J = 8.3 Hz, 1H, H8), 8.22 (d, 3 J = 7.5 Hz, 1H, H2), 8.06 (d, 3 J = 8.2 Hz, 1H, H4), 7.95 (d, 3 J = 8.0 Hz, 1H, H5), 7.63 (dd, 3 J = 8.3 Hz, 3 J = 7.3 Hz, 1H, H7), 7.57 (dd, 3 J = 8.0 Hz, 3 J = 7.3 Hz, 1H, H6), 7.53 (dd, 3 J = 8.2 Hz, 3 J = 7.5 Hz, 1H, H3). 13C{H] NMR (100 MHz, MeOD): ô (ppm): 140.8 (Cl), 135.7 (CIO), 134.1 (C4), 129.8 (C9), 129.5 (C5), 128.4 (C2), 128.1 (C7), 127.4 (C6), 127.2 (C8), 125.0 (C3), 121.5 (q.7 Jcf = 322 Hz, Cil) 19F NMR (376 MHz, MeOD): ô (ppm): 85.5 (CF3) (internal standard C6F6) FT-IR (cm1): 3053 (vC H), 1598 (vc=c), 1508 (vc=c), 1308 (vs=o), 1186 (vs=o), 1123 (vs=o), 1068 (vc.F), 767 (vC H), 627, 582, 509.

[0159] 2 / Example 2 - Polymer Synthesis

[0160] Acetylated poly(trimethylene carbonate) (PTMC) is prepared according to the following 2 steps.

[0161] 2.1 / PTMC Synthesis

[0162] The PTMC, with the formula:

[0163] [Chem. 17] o

[0164] in which n is preferably between 10 and 100, is prepared as follows.

[0165] In a two-necked flask, trimethylene carbonate (25 g, 0.245 mol, 24.5 eq.), anhydrous dichloromethane (80 mL), and 3-phenyl-l-propanol (1.3 mL, 0.010 mol, 1 eq.) are added. A solution of diphenyl phosphate (1.96 g, 0.008 mol, 0.8 eq.) in dichloromethane (20 mL) is added to the reaction mixture while stirring. After 48 h at room temperature, the reaction mixture is neutralized with triethylamine (1.4 mL, 0.010 mol, 1 eq.). The reaction medium is concentrated under vacuum and the product obtained is precipitated in cold methanol and dried under vacuum at 60°C to give PTMC (26.3 g, 2800 g / mol, Yield = 98%).

[0166] The H-NMR spectrum of the polymer obtained is shown in [Fig. 1]. 'H NMR (400 MHz, CDC13): ô (ppm): 1.91 (q, 4H, H5, H8), 2.05 (q, 50H, H2), 2.71 (t, 2H, H9), 3.73 (t, 2H, H4), 4.15 (t, 2H, H7), 4.24 (t, 100H, Hl, H3), 4.29 (t, 2H, H6), 7.18-7.30 (m, 5H, H^).

[0167] 2.2 / Acetylation of PTMC

[0168] Acetylated PTMC, of ​​formula (Ile'):

[0169] [Chem. 10] (Island')

[0170] is prepared as follows.

[0171] In a two-necked flask under argon, acetyl chloride (1.3 mL, 17.7 mmol, 5 eq.) is added dropwise to a solution of PTMC (10 g, 3.53 mmol, 1 eq.) and triethylamine (2.5 mL, 17.7 mmol, 5 eq.) in dichloromethane (40 mL). After 18 h of reaction, the product is precipitated in cold methanol and dried under vacuum to give acetylated PTMC (9.52 g, Yield = 94%), with a number-average molar mass of 2900 g / mol.

[0172] The H-NMR spectrum of the polymer obtained is shown in [Fig.2].

[0173] 3 / Example 3 - Compositions of polymer electrolytes

[0174] 3.1 / Preparation of polymer electrolytes

[0175] a / PTMC / LiNPTFSI polymer electrolyte

[0176] The PTMC / LiNPTFSI polymer electrolyte according to the invention is prepared as follows.

[0177] In a glove box, PTMC (2900 g.mol1, 1.50 g, 0.52 mmol, 1 eq.), LiNPTFSI (0.318 g, 0.92 mmol, 1.76 eq.), and anhydrous THF (5 mL) are successively introduced into a bottle. The mixture is stirred at 50°C for 15 hours. The acetonitrile is then evaporated, and the electrolyte is dried at 80°C under vacuum for 96 hours. The electrolyte is stored in a glove box.

[0178] It has a molar ratio [Li] / [CO3] = 1 / 15.

[0179] b / PTMC / LiTFSI polymer electrolyte

[0180] The PTMC / LiTFSI electrolyte (comparative example) is prepared as follows.

[0181] In a glove box, acetylated PTMC (2900 g.mol1, 1.50 g, 0.52 mmol, 1 eq.), LiTFSI (0.264 g, 0.92 mmol, 1.76 eq.), and anhydrous THF (5 mL) are successively introduced into a flask. The mixture is placed under stirring at 50°C for 15H. The THF is then evaporated and the electrolyte is dried at 80°C under vacuum for 96H. The electrolyte is stored in a glove box.

[0182] It has a molar ratio [Li] / [CO3] = 1 / 15.

[0183] 3.2 / Analysis by differential scanning calorimetry

[0184] Polymer electrolytes are analyzed by differential scanning calorimetry (DSC).

[0185] The curves obtained are shown in [Fig. 3]. The following glass transition temperature values ​​can be deduced from them: - PTMC / LiNPTFSI: Tg = - 20.7°C, - PTMC / LiTFSI: Tg = - 14.5°C.

[0186] 3.3 / Conductivity measurement

[0187] The polymer electrolytes prepared above are inserted into button cells, in the form of symmetrical cells with locking stainless steel electrodes, within which they form a solid electrolyte. They are placed there as a thin film in the center of a polyethylene disc with an external diameter of 16 mm and an internal diameter of 10 mm, the assembly being held under pressure between the two disc-shaped stainless steel electrodes.

[0188] The button cells are then placed in an oven at 80°C. After 3 hours of equilibrium, electrochemical impedance spectroscopy (EIS) measurements are performed on a BioLogic VMP-300 potentiostat, between 80°C and 10°C, with temperatures decreasing in 10°C increments (2 hours of stabilization at each increment). Three button cells are prepared for each electrolyte.

[0189] The conductivity of the electrolyte is calculated using Equation (1):

[0190] [Math.l] S £7 = ---— SXJ?2 (1)

[0191] in which: o is the conductivity of the electrolyte (S / cm), e is the thickness of the electrolyte (cm), S is the surface area of ​​the electrolyte (cm2) and R2 is the resistance of the electrolyte (Q), after fitting the data with the equivalent circuit shown in [Fig.4]. In this figure, block 11 represents the resistance of the cables and the battery holder (“RI”), block 12 represents the contribution of the ionic conductivity of the material (“R2”) and element 13, connected in parallel with R2, represents the constant phase element or CPE (“Q2”).

[0192] The results obtained are shown in [Fig. 5]. It can be observed that the performance of the PTMC-LiNPTFSI polymer electrolyte according to the invention is superior compared to that of the PTMC-LiNPTFSI polymer electrolyte. Indeed, the conductivity measured during this study at 80°C was 1.9 x 10² mS·cm⁻¹ for the PTMC-LiNPTFSI polymer electrolyte system, while that of the PTMC-LiTFSI system was 6.3 x 10³ mS·cm⁻¹. Thus, the conductivity of the PTMC-LiNPTFSI system is on average more than three times greater than the conductivity of the PTMC-LiTFSI system, highlighting a synergy between PTMC and LiNPTFSI.

Claims

1. Demands Electrolyte comprising a lithium salt and a polymer having a repeating motif of formula (I): [Chem. 1] in which m is equal to 0, 1 or 2, characterized in that said lithium salt has the formula (III): [Chem 2] F

2.

3. Electrolyte according to claim 1, wherein the molar ratio "lithium salt / polymer carbonate groups" [Li] / [CO3] is between 1 / 2 and 1 / 40. Electrolyte according to claim 1 or 2, wherein said polymer has the general formula (II): [Chem. 3] in which n is an integer greater than or equal to 10, m is equal to 0, 1 or 2, and X and Y, identical or different, each represent a group devoid of a free hydroxyl function chosen from among the alkylaryls, optionally substituted, and the alkanoates.

4. Electrolyte according to claim 3, wherein said polymer corresponds to the general formula (lia): [Chem. 4] 0 0 AC Q- pQ- L ' Jn (lia) in which n is an integer greater than or equal to 10, m is equal to 0, 1 or 2, and Ar represents an optionally substituted aryl group.

5. Electrolyte according to any one of claims 1 to 4, wherein said polymer has a number-average molar mass of between 1,000 g / mol and 10,000 g / mol.

6. Electrolyte according to any one of claims 1 to 5, in solid form.

7. A method for preparing an electrolyte according to any one of claims 1 to 6, comprising a step of mixing said polymer and said lithium salt.

8. Use of an electrolyte according to any one of claims 1 to 6 in an electrochemical cell for a lithium battery.

9. Electrochemical cell for lithium battery comprising a positive electrode, a negative electrode and a solid electrolyte, characterized in that said electrolyte is an electrolyte according to claim 6.

10. Lithium battery comprising at least one electrochemical cell according to claim 9.

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