Preparation of a crosslinked and plasticized polymer electrolyte

Abstract

Preparation of a crosslinked and plasticized polymer electrolyte The invention relates to a method for preparing a so-called quasi-solid electrolyte comprising at least the following steps: (i) providing a composition comprising at least one plasticizing agent; at least one polyalkylene carbonate having two free terminal hydroxyl functions and having an average molar mass Mw, less than or equal to 200,000 g.mol-1; at least one triisocyanate compound in a dihydroxylated polycarbonate(s) / triisocyanate(s) mass ratio of between 0.5 and 5; at least one alkali or alkaline-earth metal salt; at least one catalyst for the coupling reaction between a hydroxyl function and an isocyanate function; and optionally at least one inorganic filler; and (ii) crosslinking said composition, to form said quasi-solid electrolyte.It also concerns the quasi-solid electrolyte thus obtained, and its use in an electrochemical system, in particular in a lithium battery. Figure for the abstract: None.

Description

Title of the invention: Preparation of a crosslinked and plasticized polymer electrolyte Technical field

[0001] The present invention relates to the preparation of a novel quasi-solid polymer electrolyte, as well as to the quasi-solid polymer electrolyte thus obtained.

[0002] Such electrolytes can be used in various electrochemical systems or devices, in particular in rechargeable lithium batteries. Prior art

[0003] Conventionally, the operating principle of an electrochemical generator is based on the insertion and removal, also called "deinsertion", of an alkali metal ion or a proton, into and from the positive electrode, and the deposition or extraction of this ion, onto and from the negative electrode.

[0004] The main systems use the lithium cation as the transport ionic species. In the case of a lithium accumulator, for example, the lithium cation extracted from the positive electrode during the charging of the battery is deposited on the negative electrode, and conversely, it is extracted from the negative electrode to be intercalated in the positive electrode during the discharge.

[0005] The transport of the proton or the alkali or alkaline-earth cation, in particular the lithium cation, between the positive electrode and the negative electrode, is ensured by an ionic conductive electrolyte.

[0006] The formulation of the electrolyte used is essential for the performance of the electrochemical system, in particular when it is used at very low or very high temperatures. The ionic conductivity of the electrolyte determines in particular the efficiency of the electrochemical system since it affects the mobility of the ions between the positive and negative electrodes. Other parameters also play a role in the choice of the electrolyte used. These include its thermal, chemical or electrochemical stability within the electrochemical system, as well as economic, safety and environmental criteria, including in particular the toxicity of the electrolyte.

[0007] Lithium batteries, using solid-state electrolytes (also known as "SSE" for the English acronym "Solid-State Electrolyte"), are considered the next generation of energy storage devices. These solvent-free electrolytes make it possible, in particular, to achieve higher energy densities.

[0008] SSEs can be classified into three categories: inorganic solid electrolytes (also called "ISEs" for "Inorganic Solid Electrolytes"), electrolytes polymeric solids (also called "SPEs" for "Solid Polymer Electrolytes") and hybrid solid electrolytes (also called "HSEs" for "Hybrid Solid Electrolytes"). Particular attention is paid to SPEs and HSEs due to the high flexibility of these electrolytes, which allows their use in the development of batteries with reduced thickness and greater flexibility.

[0009] The most widespread SPEs and HSEs, particularly for lithium electrochemical devices, are based on polyethers, and more particularly poly(oxyethylene) (POE) and their derivatives, due to their low glass transition temperature (Tg), of the order of -60°C, compared to that of other polymers, and their ability to complex Li+ cations. However, since the coordination structure of POE is very stable, Li+ ions are less mobile and, consequently, POE-based electrolytes have limited performance in terms of ion transport number (t+) and ionic conductivity. Thus, for a solid polymer electrolyte based on POE, for example, the ionic transport number t+ generally oscillates between 0.1 and 0.2, knowing that we seek to get as close as possible to an ionic transport number of 1 to obtain a system within which the ions circulate perfectly.Furthermore, POE is crystalline over a wide temperature range (the crystallinity of pure POE is in the order of 75-80% at room temperature), which leads to a loss of ionic conductivity of the POE-based solid electrolyte below its melting temperature (about 60-65°C). Most POE-based SPEs are also associated with complex phase diagrams, with several phases present in wide temperature intervals, making the conductivity behavior unpredictable. The mechanical stability of POE is also insufficient at high temperatures (above 60°C) where it conducts ions well. Moreover, POE has a narrow electrochemical stability window (< 3.9 V vs. Li / Li+), making this type of SPEs suitable only for their implementation with low potential cathodes, such as LiFePO4 (LFP).

[0010] For these reasons, many alternative polymers have been developed in recent years, such as polycarbonates, polyesters, poly(arylene ether sulfone)s, polynitriles, polyalcohols and polyamines, etc.

[0011] Among them, poly(trimethylene carbonate) (PTMC) has emerged as an alternative material to POE, particularly interesting for forming solid polymer electrolytes, allowing access to a wide window of electrochemical stability (up to 4.5 V vs. Li / Li+), good thermal stability and a higher ion transport number (t+ of 0.75) than POE. These particularly advantageous properties are obtained thanks to an amorphous structure, flexible chain segments and a high dielectric constant, and make PTMC a polymeric material particularly promising for forming the new generation of solid polymer electrolytes.

[0012] Unfortunately, in general, polyalkylene carbonates, in particular PTMC, have relatively poor mechanical strength, which can lead, among other things, to finishing problems at high temperatures. Summary of the invention

[0013] The present invention aims to remedy the problem of poor mechanical strength of PTMC-based electrolytes, by proposing a new material based in particular on polyalkylene carbonate, in particular based on PTMC, combining excellent electrochemical properties and mechanical strength.

[0014] More particularly, the present invention relates to a process for preparing a so-called quasi-solid electrolyte comprising at least the following steps: (i) have a composition comprising: (a) at least one plasticizing agent chosen from linear or cyclic carbonates; linear or cyclic sulfones; fluorinated carbonates; dinitriles; lactones; liquid linear or cyclic polyethers; fluorinated polyethers; and mixtures thereof b) at least one polyalkylene carbonate having two free terminal hydroxyl functions (-OH), called dihydroxylated polycarbonate, and having an average molar mass Mw, less than or equal to 200,000 g.mol1; c) at least one triisocyanate compound; said dihydroxylated polycarbonate(s) and said triisocyanate compound(s) being used in a dihydroxylated polycarbonate(s) / triisocyanate(s) mass ratio of between 0.5 and 5; d) at least one alkali or alkaline-earth metal salt, called an ionic conductive salt, in particular a lithium salt; e) at least one catalyst for the coupling reaction between a hydroxyl function and an isocyanate function; and f) optionally at least one inorganic filler, in particular conductive of the alkali or alkaline-earth cation(s), more particularly an inorganic filler conductive of lithium ions; (ii) crosslinking said composition to form said quasi-solid electrolyte.

[0015] According to an alternative embodiment, said composition of step (i) may optionally be, prior to step (ii), implemented in the form of a layer on the surface of a substrate, in order to form a quasi-solid electrolyte film.

[0016] As detailed below, step (ii) advantageously makes it possible to form a crosslinked polymer network in which said plasticizing agent, called plasticizer, is trapped.

[0017] It is precisely with regard to the presence of the liquid plasticizer trapped in the crosslinked polymer network that the electrolyte is said to be quasi-solid.

[0018] Thus, within the meaning of the invention, by “quasi-solid electrolyte” is meant an electrolyte comprising at least one component in liquid form and a solid structure.

[0019] Advantageously, the quasi-solid electrolyte obtained according to the process of the invention comprises said plasticizer(s) as a component in liquid form and a crosslinked polymer network as a solid structure.

[0020] Certainly, the formation of solid electrolytes based on a crosslinked polymer network has already been proposed in particular in documents FR 2 781 932, FR 3 098 349 and Lin et al. (Journal of Energy Chemistry 52 (2021) 67-74).

[0021] Thus, FR 2 781 932 describes solid polymer electrolytes comprising at least one methacrylonitrile polymer made three-dimensional by crosslinking. FR 3 098 349 proposes for its part the formation of a solid polymer electrolyte film based on a crosslinked matrix based on copolymers formed from cyclic monomers of lactone and cyclic carbonate type, in the presence of a thermoreactive or photoreactive crosslinking organic molecule. As for the publication Lin et al., electrolytes based on block copolymers with three-dimensional networks formed by crosslinked copolymerization from polyethylene glycol having soft chain segments and hard segments of hexamethylene dii-isocyanate trimers are proposed. The electrolyte based on a polymer network has a structure having favorable mechanical resistance at 55 °C.However, none of these electrolytes are obtained by forming a crosslinked polymer network from a dihydroxylated polycarbonate and a triisocyanate compound, and even less in the presence of a plasticizing agent as required according to the invention.

[0022] Preferably, the quasi-solid electrolyte prepared by the process according to the invention is obtained from a polytrimethylene carbonate, denoted PTMC, bearing two hydroxy terminal functions, also called dihydroxylated PTMC, and poly(hexamethylene diisocyanate), denoted PHDI.

[0023] According to a particular embodiment, components b), c), d), e) and optionally f) of the composition of step (i) are formulated in said plasticizer(s). The plasticizer used in the composition of step (i) preferably acts as a solvent.

[0024] In particular, the process according to the invention does not use an additional solvent separate from said plasticizer(s).

[0025] The invention also relates to a quasi-solid electrolyte, in particular in the form of a quasi-solid electrolyte film, obtained by the method according to the invention.

[0026] According to an alternative embodiment, a quasi-solid electrolyte according to the invention consists of a component in liquid form and a solid structure.

[0027] In particular, the quasi-solid electrolyte may comprise one or more plasticizer(s), as defined previously, trapped in the crosslinked polymer network.

[0028] In particular, the quasi-solid electrolyte film comprises from 1% to 85% by mass of plasticizing agents chosen from ethylene carbonate, propylene carbonate, diethyl carbonate, sulfolane, and mixtures thereof, more particularly from 10% to 80% by mass, in particular from 40% to 70% by mass, relative to the total mass of said quasi-solid electrolyte.

[0029] In particular, the crosslinked polymer network of said quasi-solid electrolyte according to the invention represents from 15% to 99% by mass, in particular from 30% to 70% by mass, of the total mass of said quasi-solid electrolyte.

[0030] The quasi-solid electrolyte obtained according to the invention proves to be advantageous in several ways.

[0031] First of all, the crosslinking of at least one polyalkylene carbonate according to the invention, in particular a dihydroxylated polytrimethylene carbonate, by a triisocyanate compound according to the invention makes it possible to obtain an electrolyte based on a crosslinked matrix, also called a crosslinked polymer network, within which the polytrimethylene carbonate chains are crosslinked via urethane groups, called "crosslinking nodes". This matrix, fixed by crosslinking, forming the solid structure of the electrolyte advantageously makes it possible to overcome the problems of fineness at high temperatures encountered with PTMC-based electrolytes while exhibiting good flexibility.

[0032] The associated defect, namely a decrease in ionic conductivity compared to a non-crosslinked polycarbonate, which is all the more significant as the molar mass of the dihydroxylated polycarbonate is high, is advantageously overcome at least partially, or even totally, by the presence of the plasticizer required according to the invention, even for molar masses as high as 100 kg / mol.

[0033] Thus, the quasi-solid electrolyte according to the invention makes it possible to achieve an excellent compromise between ionic conductivity and mechanical strength, in particular at room temperature, for a wide range of molar masses of dihydroxylated polycarbonate.

[0034] Furthermore, the quasi-solid electrolyte obtained according to the invention has good performance in terms of ionic conductivity. Thus, it can advantageously have an ionic conductivity, measured at 60°C, greater than or equal to 107 S.cm ', in particular greater than or equal to 106 S.cm ', or even greater than or equal to 5.106 S.cm *. It can also have an ionic conductivity greater than the ionic conductivity of a non-crosslinked solid polymer electrolyte based on PTMC for temperatures below 50°C. Thus, its ionic conductivity, measured at 20°C, can be greater than or equal to 109 S.cm ', in particular greater than or equal to 108 S.cm1, or greater than or equal to 107 S.cm

[0035] Finally, the plasticizer being trapped in the polymer matrix, the quasi-solid electrolyte obtained according to the invention has a stability greater than that of the usual quasi-solid electrolytes (which ensures the safety of the energy storage devices comprising them).

[0036] An electrochemical system, in particular a lithium battery, comprising a quasi-solid electrolyte according to the invention, can also operate over a wide temperature range, preferably between -20°C and 90°C, in particular between -10°C and 80°C.

[0037] The quasi-solid electrolyte according to the invention can be implemented in numerous electrochemical systems, such as generators, in particular lithium batteries.

[0038] The invention thus relates, according to another of its aspects, to the use of a quasi-solid electrolyte according to the invention in an electrochemical system, in particular in a rechargeable battery, in particular a lithium battery, for example a lithium-ion or lithium-metal battery.

[0039] The invention relates in particular to an electrochemical element comprising a quasi-solid electrolyte according to the invention, said electrochemical element comprising more particularly a quasi-solid electrolyte film sandwiched between at least one positive electrode and one negative electrode.

[0040] It also relates to a battery module comprising a plurality of electrochemical elements according to the invention; as well as a battery, in particular a rechargeable battery, in particular a lithium battery, in particular a lithium-ion or lithium-metal battery, comprising an assembly of battery modules according to the invention.

[0041] Other characteristics, variants and advantages of the quasi-solid electrolytes according to the invention, and of their preparation, will emerge more clearly on reading the description, examples and figures which follow, given for illustrative and non-limiting purposes of the invention. Brief description of the drawings

[0042] [Fig.l] schematically presents an example of a method for preparing a quasi-solid electrolyte according to the invention, with (a) the solubilization of a dihydroxylated PTMC in a solution of LiTFSI in ethylene carbonate (EC), (b) the addition of poly(hexamethylene diisocyanate), and (c) the crosslinking reaction between a dihydroxylated PTMC and the poly(hexamethylene diisocyanate);

[0043] [Fig.2] shows the infrared spectrum of a quasi-solid polymer electrolyte according to the invention prepared in Example 1;

[0044] [Fig.3] shows, in a schematic manner, the structure of the button batteries put in work for conductivity tests according to example 2;

[0045] [Fig.4] shows the evolution of the ionic conductivity (in S.cm1) as a function of the temperature (1000 / T, T being expressed in degrees Kelvin), for a crosslinked solid electrolyte prepared in example 1 from a dihydroxylated PTMC of 4 kg.mol1 without plasticizer (outside the invention, named “R PTMC 4k without plasticizer”), for a crosslinked quasi-solid electrolyte prepared in example 1 from a dihydroxylated PTMC of 4 kg.mol1 with sulfolane (according to the invention, named “R PTMC 4k 60% IM LiTFSI solution in sulfolane”), or with ethylene carbonate (according to the invention, named “R PTMC 4k 60% IM LiTFSI solution in EC”); for a crosslinked solid electrolyte prepared in example 1 from a dihydroxylated PTMC of 100 kg.mol1 without plasticizer (outside the invention, named “R PTMC 100k without plasticizer”) and for a crosslinked quasi-solid electrolyte prepared in example 1 from a dihydroxylated PTMC of 100 kg.mol1 with ethylene carbonate (according to the invention, “named R PTMC 100k(abcr) 60% IM LiTFSI solution in EC”); and for a non-crosslinked polymer electrolyte prepared from a monohydroxylated PTMC of 10 kg.mol1 (outside the invention, named “non-crosslinked mono 10k PTMC”).

[0046] In the remainder of the text, the expressions “between ... and ...” and “ranging from ... to ...” and “varying from ... to ...” are equivalent and are intended to mean that the limits are included, unless otherwise stated. Detailed description

[0047] As indicated previously, the quasi-solid electrolyte is obtained from the crosslinking of at least one polyalkylene carbonate having two free terminal hydroxyl functions with at least one triisocyanate compound, in the presence of at least one plasticizing agent. Plasticizing agent

[0048] The invention uses at least one plasticizing agent chosen from linear or cyclic carbonates such as ethylene carbonate, propylene carbonate, diethyl carbonate or dimethylcarbonate; linear or cyclic sulfones such as sulfolane; fluorinated carbonates such as fluoroethylene carbonate; dinitriles such as succinonitrile; lactones such as γ-butyrolactone; liquid linear or cyclic polyethers; fluorinated polyethers; and mixtures thereof.

[0049] In particular, said plasticizing agent(s) are chosen from ethylene carbonate, propylene carbonate, diethyl carbonate and sulfolane, preferably from ethylene carbonate and sulfolane.

[0050] Preferably, the plasticizing agent can solubilize the polyalkylene glycol, the triisocyanate compound and the alkali or alkaline earth metal salt. Advantageously, the plasticizing agent makes it possible to both solubilize the precursor polymers of the poly(alkylene glycol) network and the poly(alkylene glycol) triisocyanate compound. crosslinked polymer, and to conduct ions after formation of the crosslinked polymer network.

[0051] In particular, the plasticizing agent may have a boiling point of at least 100°C, more particularly of at least 150°C, or even of at least 200°C. Polyalkylene carbonate

[0052] The invention uses at least one polyalkylene carbonate, also called poly(alkylene carbonate), having two free terminal hydroxyl functions (-OH).

[0053] In other words, the polyalkylene carbonate used according to the invention has the following structure:

[0054] HO-PC-OH, in which PC is a polyalkylene carbonate chain, in particular obtained, as described in the remainder of the text, by ring-opening polymerization of at least one cyclic carbonate monomer.

[0055] By "polyalkylene carbonate" is meant both homopolymers comprising a single type of alkylene carbonate units and copolymers comprising at least two different alkylene carbonate units.

[0056] Preferably, the polyalkylene carbonate is a homopolymer formed from identical alkylene carbonate units.

[0057] A polyalkylene carbonate, within the meaning of the invention, does not use any polymeric unit other than alkylene carbonate units. In particular, it does not contain any unit derived from lactone-type or methacrylonitrile-type monomers.

[0058] A polyalkylene carbonate used according to the invention, as defined above, is more simply referred to as “dihydroxylated polyalkylene carbonate” or “dihydroxylated polycarbonate”.

[0059] As indicated previously, the dihydroxylated polycarbonate used according to the invention has an average molar mass, denoted Mw, less than or equal to 200,000 g.mol '.

[0060] According to a preferred embodiment, the dihydroxylated polycarbonate used according to the invention has an average molar mass, denoted Mw, of between 2,000 and 100,000 g.mol *, preferably less than or equal to 10,000 g.mol ', in particular of between 4,000 and 10,000 g.mol A

[0061] According to another particular embodiment, the dihydroxylated polycarbonate used according to the invention may have an average molar mass, denoted Mw, of between 4,000 and 150,000 g.mol *, preferably greater than or equal to 10,000 g.mol *, in particular of between 10,000 and 150,000 g.mol *, or even between 50,000 and 120,000 g.mol A

[0062] The average molar mass, denoted Mw, can be measured by chromatography size exclusion (SEC). It can also be obtained from the 'H NMR analysis of the polyalkylene carbonate obtained.

[0063] Without wishing to be bound by theory, the average molar mass of the dihydroxylated polycarbonate conditions, at the end of the formation of the crosslinked network in step (ii) of the process of the invention, the inter-node distance between the crosslinking nodes established from the triisocyanate compound. Preferably, the length of the polyalkylene carbonate chains must make it possible to ensure both good flexibility of the chains, satisfactory ionic conductivity and good mechanical properties.

[0064] Preferably, the dihydroxylated polycarbonate used in the process of the invention has a polydispersity index, reflecting the good homogeneity of the chain lengths of the polycarbonate, less than or equal to 2, in particular less than or equal to 1.5.

[0065] The polydispersity index, noted PDI, is equal to the ratio of the weight-average molar mass Mw to the number-average molar mass Mn. The number-average molar mass can be determined by steric exclusion chromatography, possibly coupled with static light scattering.

[0066] Preferably, the dihydroxylated polycarbonate is obtained, prior to its use in the process of the invention, by ring-opening polymerization (also called "ROP" for "Ring-Opening Polymerization" in English terminology) of one or more cyclic carbonate monomers, in particular comprising from five to eight members.

[0067] The cyclic carbonate monomers may more particularly be of the following formula (I):

[0068] [Chem.2]

[0069] in which: m is an integer between 1 and 4, in particular between 1 and 3, in particular m is 1 or 2 and more particularly m is 2; x is an integer between 0 and 2m+2; and Ri, carried by one or more carbon atoms of the cycle, represent, independently of each other, substituents, in particular alkyl groups, in particular C1 to C5, linear or branched.

[0070] According to a particular embodiment, the cyclic carbonate monomer is chosen among trimethylene carbonate and its derivatives. In particular, the cyclic carbonate monomer is trimethylene carbonate.

[0071] According to a particularly preferred embodiment, the dihydroxylated polycarbonate used according to the invention is a dihydroxylated poly(trimethylene carbonate) (dihydroxylated PTMC), in particular obtained by ROP of trimethylene carbonate (TMC).

[0072] The ROP reaction for the synthesis of a polycarbonate according to the invention can be more particularly carried out in the presence of at least one organic molecule, called “initiator” or “primer”, carrying two hydroxyl functions (diol compound) and, optionally, in the presence of at least one catalyst for the polymerization reaction.

[0073] Said ROP initiator or primer may have a number-average molar mass ranging from 18 to 50,000 g.mol *, in particular from 60 to 10,000 g.mol '.

[0074] In particular, the initiator may be a compound of formula R;(-OH)2, in which R; represents a divalent non-reactive group, in particular an alkylene group, in particular C1 to C6, in particular C1 to C3, linear or branched.

[0075] Preferably, the initiator for the synthesis of a dihydroxylated polycarbonate according to the invention is ethylene glycol.

[0076] It is up to the person skilled in the art to adjust the polymerization conditions to obtain the desired dihydroxylated polycarbonate.

[0077] The use of said diol initiator of the ROP, in particular provided in a determined quantity, advantageously makes it possible to control the molar mass and the polydispersity of the synthesized polycarbonates. According to a particular embodiment, said cyclic carbonate monomer(s) and said diol initiator(s) are used in a monomer(s) / initiator(s) molar ratio of between 30 / 1 and 2000 / 1, in particular between 38 / 1 and 1000 / 1.

[0078] According to a particular embodiment, the synthesis by ROP can be carried out in the presence of a catalyst. A person skilled in the art is able to choose a suitable catalyst for the ROP reaction. Examples of catalysts include phosphorus compounds, for example diphenylphosphate (DPP), and metal-type compounds, such as tin diethylhexanoate (Sn(Oct)2).

[0079] The ROP synthesis of dihydroxylated polycarbonate can also be catalyzed by methane sulfonic acid (MSA), or even be carried out in the absence of catalyst and under microwave irradiation, as described in the applications filed under numbers FR 2 012 955 and FR 2 012 956.

[0080] The ROP reaction can be carried out at a temperature between 20 and 110°C, advantageously at a temperature less than or equal to 40°C.

[0081] It can be carried out in bulk (in the absence of solvent) or in a solvent medium. Advantageously, it is carried out in a solvent medium, in particular with stirring. The solvent medium can more particularly be formed from one or more solvent(s) apolar and aprotic, in particular chosen from toluene, dichloromethane, tetrahydrofuran and their mixtures.

[0082] At the end of the polymerization, the dihydroxylated polycarbonates can be subjected to one or more purification steps, in particular to remove the catalyst, for example by precipitation in one or more polar solvents, typically methanol or ethanol, and recovered by filtration and drying.

[0083] According to a particular embodiment, the dihydroxylated polycarbonate used according to the invention, obtained by ROP from a diol type initiator, HO-Rj-OH, for example ethylene glycol, is of formula (II):

[0084] [Chem.3] HO—(CH2)pi OH (II) in which: Ri represents the group derived from the diol initiator as defined previously, for example an ethylene group derived from ethylene glycol; pl is an integer ranging from 2 to 4, in particular pl is 3; ni is a positive integer, 2xnl corresponding to the average number of monomeric units derived from cyclic carbonate monomers, in particular 2xnl is between 30 and 2000, in particular between 30 and 1000, or even between 30 and 500.

[0085] By way of example, the dihydroxylated polycarbonate used according to the invention is a PTMC obtained by polymerization by ROP from TMC monomers, initiated by a diol, in particular by ethylene glycol, of the following formula (II'):

[0086] [Chem.4] in which R; and ni are as defined above.

[0087] Preferably, the dihydroxylated polycarbonate used according to the invention is a dihydroxylated PTMC with an average molar mass, denoted Mw, less than or equal to 200,000 g.mol '.

[0088] According to a preferred embodiment, the dihydroxylated polycarbonate used according to the invention is a dihydroxylated PTMC with an average molar mass of between 2,000 and 100,000 g.mol *, preferably between 4,000 and 10,000 g.mol '.

[0089] According to another particular embodiment, the dihydroxylated polycarbonate used according to the invention may be a dihydroxylated PTMC of average molar mass

[0090]

[0091]

[0092]

[0093] between 10,000 and 150,000 g.mol *, or even between 50,000 and 120,000 g.mol *. Triisocyanate compound For the purposes of the invention, the term “triisocyanate compound” means a compound comprising three reactive isocyanate functions. By “reactive” isocyanate function, we mean that the isocyanate function is capable of reacting with a hydroxyl function to form a urethane bond. The triisocyanate compound is more particularly an organic molecule carrying three reactive isocyanate functions, in particular of the following formula (III): [Chem. 5] (III)

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] in which B represents a trivalent organic spacer, preferably having a molar mass of between 200 g / mol and 50,000 g / mol. Preferably, B represents a trivalent organic spacer having a molar mass of between 200 g / mol and 50,000 g / mol, in particular between 250 g / mol and 10,000 g / mol and preferably between 290 g / mol and 1,000 g / mol. In particular, the triisocyanate compound may be of formula (III) in which B represents a trivalent hydrocarbon radical which may contain one or more heteroatoms, such as oxygen and / or nitrogen atoms. In particular, B may represent a trivalent aliphatic or alicyclic radical, preferably aliphatic, which may be interrupted by one or more heteroatoms, in particular by one or more nitrogen and / or oxygen atoms, and / or by a carbonyl group (C=O). The triisocyanate compound may be chosen from aliphatic, cycloaliphatic and / or aromatic triisocyanates. In particular, it can be chosen from: - triisocyanates obtained by reaction between a triol and an excess of diisocyanate, in particular those of formula [Chem. 6] CH,CH,-c[-CH^OC-NH-R '-NCO L "Il J 3 0 (Ilia) - triisocyanates with a biuret unit, in particular isocyanatobiurets of formula:

[0102] [Chem.7] II OCN-R '-NH-CNC-NH-R '-NCO The IO R' NCO (Illb)

[0103] - isocyanurates of formula:

[0104] [Chem.8] O OCN-R < A XR'~NCO NN I R' I NCO (IIIc) in which R' represent, independently of one another, a linear, branched or cyclic hydrocarbon radical, comprising from 2 to 30 carbon atoms, in particular a linear or branched, in particular linear, alkylene group, comprising from 2 to 30 carbon atoms, in particular from 4 to 15 carbon atoms, in particular from 4 to 10 carbon atoms, and more particularly from 4 to 8 carbon atoms.

[0105] Preferably, said triisocyanate compound is chosen from polyisocyanates with biuret units, in particular the isocyanatobiurets of formula (IIIb) described previously.

[0106] In other words, according to a particular embodiment, the triisocyanate compound may be of formula (III) above in which B represents a trivalent radical of the following formula:

[0107] [Chem.9] *—R'-NH—C--N--C—NH-R'--* He । H OR' O I where * represents a covalent bond to an isocyanate function and R' is as defined previously.

[0108] Preferably, R' represent, independently of one another, a linear or branched hydrocarbon radical, comprising from 2 to 30 carbon atoms, in particular an alkylene, linear or branched, in particular linear, comprising from 2 to 30 carbon atoms, in particular from 4 to 15 carbon atoms, in particular from 4 to 10 carbon atoms, and more particularly from 4 to 8 carbon atoms, for example in C6.

[0109] According to a particularly preferred embodiment, the triisocyanate compound is poly(hexamethylene diisocyanate), denoted PHDI, with the formula recalled below:

[0110] [Chem. 10]

[0111] Triisocyanate compounds, such as PHDI, may be synthesized by methods known to those skilled in the art or, alternatively, be commercially available.

[0112] According to a particularly preferred embodiment, the quasi-solid electrolyte according to the invention is formed from at least one dihydroxylated poly(trimethylene carbonate) in particular as defined previously; and poly(hexamethylene diisocyanate).

[0113] Preferably, as indicated above, said dihydroxylated polycarbonate(s), in particular PTMC, and said triisocyanate compound(s), in particular PHDI, are used in the composition in step (i), in a dihydroxylated polycarbonate(s) / triisocyanate(s) mass ratio of between 0.5 and 5, preferably between 1 and 2, and more preferably of approximately 1.5 / 1.

[0114] A dihydroxylated polycarbonate / triisocyanate mass ratio of 1.5 / 1 advantageously makes it possible to access in step (ii) a completely crosslinked quasi-solid electrolyte.

[0115] Precursor composition of the quasi-solid electrolyte Ionic salt

[0116] As indicated previously, the composition in step (i) from which a quasi-solid electrolyte according to the invention is formed comprises at least one alkali or alkaline-earth metal salt, also called “ionic conductive salt”, used to ensure the conduction of ions at the level of the polyalkylene carbonate chains.

[0117] In the context of the invention, the following terms are understood to mean: - “alkali metals”, the chemical elements of the first column of the periodic table of elements, and more particularly chosen from lithium, sodium, potassium, rubidium, cesium. Preferably, the alkali metal is lithium, sodium or potassium, and more preferably lithium; - “alkaline earth metals” means the chemical elements in the second column of the periodic table of elements, and more particularly chosen from beryllium, magnesium, calcium, strontium, barium, radium. Preferably, the alkaline earth metal is magnesium or calcium.

[0118] The salt of an alkali metal may be, for example, a lithium salt or a sodium salt; the salt of an alkaline earth metal may be, for example, a magnesium salt. In particular, the salt used is a lithium salt.

[0119] Examples of lithium salts include LiPF6, LiC104, LiBF4, LiAsF6, LiCF3SO3, LiN(C2F5SO2)2, lithium bis(trifluoromethylsulfonyl)imide LiN[SO2CF3 ]2 (known by the abbreviation LiTFSI), lithium bis(fluorosulfonyl)amide (known by the abbreviation LiFSI) LiN[SO2F]2, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (known by the abbreviation LiTDI), lithium bispentafluoroethylsulfonylimide (known by the abbreviation LiBETI), lithium bis(oxalato)borate (known by the abbreviation LiBOB) and lithium difluoro(oxalato)borate (known by the abbreviation LiFOB) and mixtures of these.

[0120] Preferably, the electrolyte comprises, as lithium salt, LiTFSI, LiTDI or LiFSI, preferably LiTFSI or LiFSI and more preferably LiTFSI.

[0121] It is up to the person skilled in the art to adjust the quantity of alkali or alkaline earth metal salts.

[0122] According to a particular embodiment, the quantities of dihydroxylated polycarbonate(s) and lithium salt(s) are adjusted so that the molar ratio between the carbonyl groups of the dihydroxylated polycarbonate relative to the lithium, noted [CO] / [Li+], is between 0.5 and 30, in particular between 5 and 15 and more particularly approximately 15. Catalyst for the crosslinking reaction

[0123] The composition in step (i) from which a quasi-solid electrolyte according to the invention is formed comprises at least one catalyst for the crosslinking of said dihydroxylated polycarbonate(s) by the triisocyanate compound, in other words a catalyst for the coupling reaction between a hydroxyl function and an isocyanate function.

[0124] Examples of such catalysts include tertiary amines such as l,4-diazabicyclo[2,2,2]octane (DABCO), l-azabicyclo[2.2.2]octane (quinuclidine), l,8-Diazabicyclo[5.4.0]undec-7-ene (DBU, CAS: 6674-22-2), l,5-diazabicyclo[4.3.0]non-5-ene (DBN, CAS: 3001-72-7), 3,3,6,9,9-pentamethyl-2,10-diazabicyclo[4,4,0]dec-l-ene, tin chloride, organometallic compounds such as metal acetonylacetates, organometallic tin compounds, calcium hexanoate, calcium 2-ethylhexanoate, calcium octanoate and calcium linoleate, dibutyltin dilaurate (DBTDL, CAS: 75-58-7), bismuth tris(2-ethylhexanoate) and zinc bis(2-ethylhexanoate), sulfonimides, such as bis(trifluoromethane)sulfonimide (TFMI, CAS: 82113-65-3), sulfonic acids, such as trifluoromethanesulfonic acid (triflic acid), p-toluenesulfonic acid (PTSA, CAS: 104-15-4) and methanesulfonic acid (MSA, CAS: 75-75-2), phosphate derivatives, such as diphenyl phosphate (DPP, CAS: 838-85-7).

[0125] Preferably, the catalyst is chosen from 1,4-diazabicyclo[2,2,2]octane (DABCO), l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), l,5-diazabicyclo[4.3.0]non-5-ene (DBN), dibutyltin dilaurate (DBTDL), bis(trifluoromethane), triflic acid, p-toluenesulfonic acid (PTSA), methanesulfonic acid (MSA) and diphenylphosphate (DPP).

[0126] According to a particular embodiment, the catalyst is dibutyltin dilaurate (DBTDL).

[0127] Said catalyst(s) may be used in an amount of 0.1% to 5% by mass, preferably 1% to 3% by mass, relative to the total mass of the composition. Conductive inorganic filler

[0128] According to a particular embodiment variant, the precursor composition of the quasi-solid electrolyte according to the invention makes it possible to form a solid structure of the hybrid solid electrolyte (HSE) type. According to this variant, the composition of step (i) further comprises at least one inorganic filler.

[0129] The inorganic fillers may be chosen from inorganic fillers which conduct the alkali or alkaline-earth cation(s), in particular which conduct lithium ions, non-conductive fillers which conduct the alkali or alkaline-earth cation(s), and mixtures thereof.

[0130] The lithium ion conductive fillers may be chosen, for example, from lithiated oxides, such as Li7La3Zr20i2 (LLZO) and Lio.33La0.56Ti03 (LLTO), Lii.3Alo.3Tii,7 (PO4)3 (LATP), etc.

[0131] It may also be a question of charges chosen from: - garnets, for example chosen from Li7La3Zr20i2, Li6La2BaTa20i2, etc.; - lithium phosphates, for example chosen from Li3PO4, LiPO3, etc.; - lithium borates, for example chosen from Li3BO3, etc.; - oxynitrides, for example chosen from Li3PO4 xN2x / 3, Li4SiO4 xN2x / 3, Li4GcO4 xN 2x / 3 with 0 <x<4 ou Li3BO3 xN2x / 3avec 0<x<3 ; - lithium compounds based on lithium and phosphorus oxynitride (called LiPON); - silicates, for example Li2Si2O5 - sulfides, for example argyrodite.

[0132] The non-conductive fillers of alkali or alkaline-earth cations can for example be chosen from alumina (A12O3), silica (SiO2), titanium dioxide (TiO2) etc.

[0133] Said inorganic filler(s), in particular ion-conducting fillers, may be used in a volume ratio of conductive filler(s) / dihydroxylated polycarbonate(s) of between 20 / 80 and 80 / 20, in particular between 20 / 80 and 60 / 40.

[0134] Preparation of the composition, precursor of the quasi-solid electrolyte

[0135] The composition in step (i) advantageously has good homogeneity, in particular homogeneous solubilization of said dihydroxylated polycarbonate(s), in particular PTMC, and of said triisocyanate compound(s), in particular PHDI, in said plasticizer(s).

[0136] According to a particular embodiment, the composition in step (i) is obtained via the following steps: (al) preparation of a solution, denoted “solution S”, comprising said dihydroxylated polycarbonate(s), said triisocyanate compound(s) and said ionic conductive salt(s), and optionally said inorganic filler(s), in particular conductive fillers, in said plasticizing agent(s); and (a2) adding to said solution said catalyst of the coupling reaction between a hydroxyl function and an isocyanate function.

[0137] Preferably, said solution S combines at least one dihydroxylated PTMC and PHDI.

[0138] Said plasticizing agent(s) may in particular be chosen from ethylene carbonate, sulfolane and their mixtures.

[0139] Preferably, said solution S comprises less than 1% by mass, in particular less than 0.1% by mass of additional solvent(s) distinct from said plasticizer(s), such as polar organic solvents, in particular acetonitrile, acetone, tetrahydrofuran and their mixtures, or even is devoid of additional solvent(s).

[0140] Solution S in step (al) advantageously has good homogeneity. For example, solution S can be obtained by stirring.

[0141] In particular, solution S is obtained by adding said triisocyanate compound(s) to a solution SI comprising said dihydroxylated polycarbonate(s) and said plasticizing agent(s), in particular chosen from ethylene carbonate, sulfolane and mixtures thereof. In particular, the triisocyanate compound is PHDI, and the dihydroxylated polycarbonate is a dihydroxylated PTMC. Preferably, solution S1 further comprises said ionic conducting salt(s).

[0142] Preferably, the SI solution is homogeneous. In particular, the SI solution comprises the dihydroxylated polycarbonate solubilized in said plasticizer(s).

[0143] In particular, the SI solution is prepared by mixing said dihydroxylated polycarbonate(s) with a solution of said ionic conductive salt(s) in said plasticizer(s). In particular, the concentration of ionic conductive salt(s) in said plasticizer(s) ranges from 0.1 mol / L to 4 mol / L, in particular from 0.5 to 2 mol / L.

[0144] Solution SI and / or solution S may preferably be prepared in an atmosphere formed at more than 90% of its mass, or even consisting of, a neutral gas, in particular argon.

[0145] Preferably, the composition of step (i) comprises less than 1% by mass, in in particular less than 0.1% by mass of additional solvent(s) distinct from said plasticizer(s), such as polar organic solvents, in particular acetonitrile, acetone, tetrahydrofuran and their mixtures, or even is devoid of additional solvent(s).

[0146] Said triisocyanate compound(s), in particular PHDI, may be used in said composition of step (i) in an amount of 10 to 50% by mass, in particular 15 to 40% by mass, relative to the total mass of the composition.

[0147] Said dihydroxylated polycarbonate(s), preferably dihydroxylated PTMC, may be used in said composition of step (i) in an amount of 10 to 90% by mass, in particular 20 to 70% by mass, relative to the total mass of the composition.

[0148] Said plasticizing agent(s) may be used in the composition of step (i) in an amount of at least 1% by mass, in particular from 1% to 80% by mass, more particularly from 10% to 70% by mass, in particular from 40% to 60% by mass, relative to the total mass of the composition.

[0149] In particular, the assembly consisting of the sum of said plasticizing agent(s) and said ionic conducting salt(s) represents at least 1% by mass, in particular from 1% to 85% by mass, more particularly from 10% to 80% by mass, in particular from 40% to 70% by mass, relative to the total mass of the composition.

[0150] In particular, the mass ratio of the sum of said triisocyanate compound(s) and said dihydroxylated polycarbonate(s) to the sum of said plasticizing agent(s) and said ionic conducting salt(s), denoted triisocyanate(s) + dihydroxylated polycarbonate(s) / plasticizer(s) + salt(s), may be between 10% and 80%, in particular between 40% and 70%, or even between 50% and 70%.

[0151] Alternatively, the assembly consisting of the sum of said plasticizing agent(s) and said ionic conducting salt(s) may represent at least 1% by mass, in particular from 1% to 85% by mass, more particularly from 10% to 80% by mass, in particular from 40% to 70% by mass, relative to the total mass of the other constituents of the composition.

[0152] According to a particular embodiment, the composition of step (i) may consist of said plasticizing agent(s), said dihydroxylated polycarbonate(s), said triisocyanate compound(s), said ionic conductive salt(s), said catalyst(s) and optionally at least one inorganic filler, in particular as described above. Formation of the quasi-solid electrolyte

[0153] As indicated previously, the formation of a quasi-solid electrolyte according to the invention involves the crosslinking of said composition of step (i), preferably previously placed in the form of a layer or film on the surface of a substrate.

[0154] Advantageously, the crosslinking in step (ii) is carried out under conditions making it possible to limit or even prevent the evaporation of said plasticizing agent(s).

[0155] In particular, step (ii) can be carried out by heating said composition to a temperature between 50 and 100°C, in particular between 50 and 70°C.

[0156] Crosslinking can be carried out in an oven, in particular under ambient air.

[0157] Preferably, heating is continued until optimal crosslinking is obtained. of said polyalkylene carbonate chains, preferably complete crosslinking.

[0158] By "complete crosslinking" is meant that all of the hydroxyl functions of the dihydroxylated polyalkylene carbonates present in the composition have reacted with the isocyanate functions of the triisocyanate compounds.

[0159] Generally speaking, the crosslinking time can be between 3 hours and 48 hours, in particular between 6 hours and 24 hours and more particularly between 10 hours and 14 hours.

[0160] As indicated previously, the quasi-solid electrolyte can be prepared in the form of an electrolyte film or membrane directly on the surface of a suitable substrate, in particular inert and flat.

[0161] In the context of this embodiment variant, the composition of step (i) is, prior to step (ii) of crosslinking, implemented in the form of a layer on the surface of a substrate.

[0162] The layer can for example be obtained by coating, for example using a doctor blade.

[0163] The substrate can be of various natures. It can be made of glass, alumina, aluminum, silicone, polyimide, polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), silicone or even polypropylene.

[0164] According to an alternative embodiment, the substrate may be one of the electrodes of the electrochemical system for which the quasi-solid electrolyte according to the invention is intended. For example, for the preparation of a quasi-solid electrolyte intended for a lithium battery, the substrate may be a lithiated electrode.

[0165] The quasi-solid electrolyte film may optionally be detached from the substrate to be implemented at the level of the electrochemical system for which it is intended, in particular transferred onto at least one electrode.

[0166] The quasi-solid electrolyte film may have, for example, a thickness of between 5 and 600 μm, in particular between 50 and 500 μm and more particularly between 100 and 400 μm. Electrochemical system

[0167] The quasi-solid electrolyte obtained according to the invention can advantageously be used as an electrolyte in an electrochemical system. The quasi-solid electrolyte can in particular be used in an electrochemical system under the same conditions as a solid electrolyte, i.e. an electrolyte excluding the presence of a component in liquid form. Advantageously, the quasi-solid electrolyte according to the invention can act as both a separator and an ionic conductor in an electrochemical element. In particular, said plasticizing agent(s) are trapped in a structure of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type.

[0168] The electrochemical system may be an electrochemical generator, converter or storage system. It may more particularly be a fuel cell, for example a primary or secondary battery, for example a lithium, sodium, magnesium, potassium or calcium battery; a flow battery (“redox flow battery” in English terminology); a lithium-air or lithium-sulfur accumulator.

[0169] According to a particular embodiment, the quasi-solid electrolyte is implemented in a rechargeable battery, in particular in a lithium battery, in particular a lithium-ion or lithium-metal battery.

[0170] In particular, the invention also relates, according to another of its aspects, to an electrode / electrolytic membrane assembly, comprising a quasi-solid electrolyte membrane according to the invention.

[0171] It also relates to an electrochemical element, also called an electrochemical generator or accumulator, comprising a quasi-solid electrolyte according to the invention.

[0172] An electrochemical element according to the invention generally comprises a quasi-solid electrolyte film sandwiched between at least one positive electrode and one negative electrode. The quasi-solid electrolyte film acts both as an ionic conductor and a separator between the positive and negative electrodes.

[0173] The positive electrode of a lithium or lithium-ion electrochemical element generally comprises, as electrochemically active material, lamellar compounds, such as LiCoO2, LiNiO2 and mixed Li(Ni, Co, Mn, A1)O2, or compounds of spinel structure of compositions close to LiMn2O4, lithium phosphates, in particular LiMnFePO4 or LiFePO4.

[0174] Advantageously, the positive electrode comprises, as electrochemically active material, LiNii / 3Mni / 3Coi / 3O2 (NCM cathodes) or LiCoO2, preferably LiNii / 3Mni / 3Coi / 3O2.

[0175] The negative electrode generally comprises, as electrochemically active material, lithium metal or lithium-based alloy in the case of primary accumulators, or intercalation materials such as graphite carbon, or lithium titanium oxide (Li4Ti50i2) or titanium and niobium oxide (TiNb2O7), in the case of accumulators based on lithium-ion technology.

[0176] An electrochemical element according to the invention may be more particularly intended for a battery, in particular a lithium battery. Typically, a battery comprises a plurality of electrochemical elements capable of being grouped together within the same enclosure. A battery may be divided into modules, each module being composed of a plurality of electrochemical elements connected together in series, in parallel, in parallel-series or in series-parallel, brought together within the same container forming the casing of the module. The battery is intended to supply electrical energy to an external application. A charging circuit is generally provided to which the battery may be connected to recharge the elements. A management system comprising measurement sensors and an electronic control circuit, more or less advanced depending on the applications, may be associated with the battery.

[0177] The invention also relates to a battery module, in particular for a rechargeable battery, in particular a lithium battery, comprising a plurality of electrochemical elements.

[0178] The electrochemical elements within a module are typically electrically connected, in series and / or in parallel. Each element may be equipped with devices necessary for electrical connection with the other elements of the module, for example in the form of metal strips (busbar), devices for measuring the operating parameters of the element (temperature, voltage, current) and possibly safety devices (valve, cover).

[0179] The invention also relates to a battery, in particular a lithium battery, containing an assembly of modules according to the invention, each module comprising several electrochemical elements according to the invention.

[0180] Advantageously, it may be a lithium-metal battery, comprising a lithium metal electrode Li° and an electrode comprising LiNii / 3Mni / 3Coi / 3O2 or LiCoO2, preferably LiNii / 3Mni / 3Coi / 3O2.

[0181] The invention will now be described by means of the following examples and figures, given of course for illustrative and non-limiting purposes of the invention. Example 1 Preparation of electrolytes

[0182] 1.1. Preparation of quasi-solid and solid electrolytes

[0183] 1.1.1. Preparation of quasi-solid electrolytes crosslinked with plasticizer (according to the invention)

[0184] A PTMC comprising two reactive hydroxyl functions (noted "PTMC bi"), with a molar mass of 4018 g.mol1 (approximately 4 kg.mol *), is previously synthesized by ROP from trimethylene carbonate, initiated by ethylene glycol and catalyzed by methanesulfonic acid.

[0185] In a glove box, under an atmosphere composed of argon, a 1 mol / L lithium salt solution (LiTFSI) is prepared in ethylene carbonate.

[0186] In this solution, kept in a glove box, 1.5 g of said PTMC bi is solubilized in 4.16 g of the previously prepared LiTFSI solution in ethylene carbonate, to obtain a solution, called "solution 1", whose ratio between the carbonyl groups of the polycarbonate relative to the lithium, noted [CO] / [Li+], is 15. This solution is stirred until a homogeneous solution is obtained.

[0187] Then, 1 g of poly(hexamethylene diisocyanate), noted PHDI, from Sigma Aldrich, is introduced into solution 1. The solution is stirred to obtain a homogeneous solution. This solution is called “solution S” thereafter.

[0188] A mass ratio of OH / NCO functions of 1.5 / 1 is respected so that all the functions react and the system is completely crosslinked.

[0189] Then, dibutyltin dilaurate (DBTDL) (Sigma Aldrich) is added at 2% by mass as a catalyst.

[0190] In order to shape the quasi-solid electrolyte film, the solution is then spread using a 300 μm high scraper on a coating table onto an inert, flat aluminum coating at a speed that limits the formation of air bubbles.

[0191] The whole is placed in an oven at 60°C. Crosslinking takes place for 12 hours.

[0192] The method implemented is illustrated in [Fig.l].

[0193] The same protocol is reproduced to prepare a quasi-solid electrolyte: - by replacing ethylene carbonate with sulfolane;

[0194] - by replacing said PTMC bi with a molar mass of 4018 g.mol1 with a PTMC di- hydroxylated with a molar mass of 100 kg.mol *, marketed by ABCR.

[0195] The films obtained are self-supporting.

[0196] 1.1.2. Preparation of crosslinked solid electrolytes without plasticizer (outside the invention)

[0197] In a glove box, under an atmosphere composed of argon, 1 g of poly(hexamethylene diisocyanate), noted PHDI, from Sigma Aldrich, is solubilized in 2 mL of acetonitrile.

[0198] The solution is stirred to obtain a first homogeneous solution.

[0199] 1.5 g of the PTMC bi described in example 1.1.1. and lithium salt (LiTFSI) with a ratio of polycarbonate carbonyl groups to lithium, noted [CO] / [Li+], of 15, are solubilized with 2 mL of acetonitrile.

[0200] This solution is heated to 80°C with stirring to obtain a second homogeneous solution.

[0201] A mass ratio of OH / NCO functions of 1.5 / 1 must be respected so that all the functions react and the system is completely crosslinked.

[0202] Once the solutions have been homogenized, the first solution is transferred into the second solution with stirring and the mixture is heated to 80°C so as to partially evaporate the solvent and thus concentrate the solution.

[0203] The solution is allowed to cool to room temperature, then dibutyltin dilaurate (DBTDL) (Sigma Aldrich) is added at a rate of 2% by mass as a catalyst.

[0204] The solution is then degassed under vacuum for 5 minutes in the cold.

[0205] In order to shape the solid electrolyte film, the solution is then spread using a 300 μm high scraper on a coating table onto an inert, flat aluminum coating.

[0206] The whole is placed in an oven at 80°C. Crosslinking takes place for 12 hours.

[0207] The same protocol is reproduced to prepare a crosslinked solid electrolyte, without plasticizer, from a dihydroxylated PTMC with a molar mass of 100 kg.mol *, marketed by ABCR.

[0208] 1.1.2. Preparation of non-crosslinked solid electrolytes (outside the invention)

[0209] For comparison, a non-crosslinked polymeric electrolyte is prepared from a mono-hydroxylated PTMC with a molar mass of 10 kg.mol *, synthesized by ROP from trimethylene carbonate, initiated by a mono-alcohol (3-phenylpropanol) and catalyzed by methane sulfonic acid. This non-crosslinked polymeric electrolyte does not contain a plasticizer.

[0210] 1.2. Characterization of the quasi-solid electrolyte crosslinked with plasticizer

[0211] The crosslinked quasi-solid electrolyte prepared as described in Example 1.1.1., from dihydroxylated PTMC with an average molar mass of 100 kg.mol1 in the presence of ethylene carbonate, is characterized by Fourier Transform Infrared Spectroscopy or FT-IR (for the English acronym “Fourier Transform InfraRed Spec-troscopy”), equipped with an attenuated total reflectance ATR (for the English acronym “Attenuated Total Reflectance”).

[0212] The IR spectrum ([Fig.2]) makes it possible to highlight the total disappearance of the N=C=O band (2250 cm1) of the starting poly(hexamethylene diisocyanate), which proves that all the isocyanate functions have reacted.

[0213] The presence of the C=O (1700 cm1) and C-O (1200 cm1) peaks comes from PTMC and ethylene carbonate. Example 2

[0214] Electrochemical properties of quasi-solid and solid electrolytes

[0215] Evaluation of ionic conductivity

[0216] The quasi-solid and solid electrolytes prepared in Example 1 are mounted in a button cell, 16 mm in diameter, between two stainless steel electrodes.

[0217] The diagram of the button cell assembly is shown in [Fig.3].

[0218] The ionic conductivity results are shown in [Fig.4].

[0219] Plasticized electrolytes crosslinked from dihydroxylated PTMC of molar mass low of the order of 4 kg / mol have higher conductivities than the unplasticized electrolyte crosslinked from the same PTMC. In the case of the electrolyte crosslinked from dihydroxylated PTMC with a molar mass of the order of 4 kg / mol, and plasticized with sulfolane, the conductivity is of the order of 105 S / cm at 80°C, close to that of uncrosslinked PTMC, and the conductivity is even higher than the conductivity of uncrosslinked PTMC at temperatures below 50°C. The presence of plasticizer in the crosslinked electrolyte therefore makes it possible both to improve the conductivity of the PTMC and to do away with a spacer or separator, unlike the unplasticized or uncrosslinked system.

[0220] In the case of crosslinking from a PTMC with a much higher molar mass of 100 kg.mol ', i.e. 25 times higher than the molar mass of the first PTMC, the conductivity is of the order of 109 S / cm at 80°C. With the addition of ethylene carbonate as a plasticizer, a clear increase in conductivity is observed, with a value of approximately 106 S / cm at 80°C.

Claims

Claims

1. Process for preparing a so-called quasi-solid electrolyte comprising at least the following steps: (i) providing a composition comprising: a) at least one plasticizing agent chosen from linear or cyclic carbonates; linear or cyclic sulfones; fluorinated carbonates; dinitriles; lactones; liquid linear or cyclic polyethers; fluorinated polyethers; and mixtures thereof; b) at least one polyalkylene carbonate having two free terminal hydroxyl functions (-OH), called dihydroxylated polycarbonate, and having an average molar mass Mw, less than or equal to 200,000 g.mol1; c) at least one triisocyanate compound; said dihydroxylated polycarbonate(s) and said triisocyanate compound(s) being used in a dihydroxylated polycarbonate(s) / triisocyanate(s) mass ratio of between 0.5 and 5; d) at least one alkali or alkaline-earth metal salt, called ion-conducting salt, in particular a lithium salt; e) at least one catalyst for the coupling reaction between a hydroxyl function and an isocyanate function; and f) optionally at least one inorganic filler, in particular a conductor of the alkali or alkaline-earth cation(s), more particularly an inorganic filler that conducts lithium ions; (ii) crosslinking said composition to form said quasi-solid electrolyte.

2. Method according to the preceding claim, in which said plasticizing agent(s) are used in the composition of step (i) in an amount of at least 1% by mass, in particular from 1% to 80% by mass, more particularly from 10% to 70% by mass, in particular from 40% to 60% by mass, relative to the total mass of the composition.

3. A method according to claim 1 or 2, wherein said plasticizing agent(s) are selected from ethylene carbonate, propylene carbonate, diethyl carbonate and sulfolane, preferably from ethylene carbonate and sulfolane.

4. A method according to any preceding claim, wherein said dihydroxylated polycarbonate has a molar mass

5. average, Mw, between 2,000 and 100,000 g.mol *, preferably less than or equal to 10,000 g.mol1 and more preferably between 4,000 and 10,000 g.mol *. A process according to any one of the preceding claims, wherein said dihydroxylated polycarbonate is previously obtained by ring-opening polymerization (ROP) of one or more five- to eight-membered cyclic carbonate monomers, in particular of formula (I)

6.

7. in which m is an integer between 1 and 4, in particular between 1 and 3, in particular m is 1 or 2 and more particularly m is 2; x is an integer between 0 and 2m+2; and Ri, carried by one or more carbon atoms of the cycle, represent, independently of each other, substituents, in particular alkyl groups, in particular C1 to C5, linear or branched; preferably said dihydroxylated polycarbonate is previously obtained by ROP of tri-methylene carbonate. Process according to the preceding claim, in which said polymerization is initiated by at least one organic molecule carrying two hydroxyl functions, in particular by a compound of formula R;(-OH) 2, in which R; represents a divalent non-reactive group, in particular an alkylene group, in particular C1 to C6, in particular C1 to C3, linear or branched; preferably by ethylene glycol. A method according to any preceding claim, wherein said dihydroxylated polycarbonate is of formula (II) HO--(CH2)pi---O'Y°--Ri O n1 OH n1 (II) in which: Ri is as defined in claim 6, in particular an ethylene group; pl is an integer ranging from 2 to 4, in particular pl is 3; and ni is a positive integer, 2xnl corresponding to the average number

8. of monomeric units derived from cyclic carbonate monomers, in particular 2xnl being between 30 and 2000, more particularly between 30 and 1000, or even between 30 and 500. A method according to any one of the preceding claims, wherein said triisocyanate compound is of the following formula (III):

9.

10.

11. (III) in which B represents a trivalent organic spacer, preferably having a molar mass of between 200 g / mol and 50,000 g / mol, in particular between 250 g / mol and 10,000 g / mol and preferably between 290 g / mol and 1,000 g / mol; preferably B is a trivalent hydrocarbon radical which may contain one or more heteroatoms, such as oxygen and / or nitrogen atoms, and more preferably B represents a trivalent radical of formula: *—R'-NH—C--N He I C—NH-R'--* II O where * represents a covalent bond to an isocyanate function and R' represent, independently of each other, a linear or branched hydrocarbon radical containing from 2 to 30 carbon atoms, in particular a linear or branched, in particular linear, alkylene group containing from 2 to 30 carbon atoms, in particular from 4 to 15 carbon atoms, in particular from 4 to 10 carbon atoms, and more particularly from 4 to 8 carbon atoms. A method according to any preceding claim, wherein said triisocyanate compound is poly(hexamethylene dii-isocyanate) (PHDI). Process according to any one of the preceding claims, in which the said dihydroxylated polycarbonate(s) and the said triisocyanate compound(s) are used in a dihydroxylated polycarbonate(s) / triisocyanate(s) mass ratio of between 1 and 2, and more preferably 1.5 / 1. A method according to any preceding claim, in wherein said ionically conductive salt is a lithium salt, in particular chosen from lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI) or lithium bis(fluorosulfonyl)amide (LiFSI), preferably LiTFSI or LiFSI; the quantities of dihydroxylated polycarbonate(s) and lithium salt(s) being preferably adjusted so that the molar ratio between the carbonyl groups of the polycarbonate relative to the lithium, noted [CO] / [Li+], is between 0.5 and 30, in particular between 5 and 15 and more particularly 15.

12. A process according to any one of the preceding claims, wherein said catalyst for the coupling reaction between a hydroxyl function and an isocyanate function is selected from l,4-diazabicyclo[2,2,2]octane (DABCO), l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), l,5-diazabicyclo[4.3.0]non-5-ene (DBN), dibutyltin dilaurate (DBTDL), bis(trifluoromethane), triflic acid, p-toluenesulfonic acid (PTSA), methanesulfonic acid (MSA) and diphenyl phosphate (DPP), in particular said catalyst is dibutyltin dilaurate (DBTDL).

13. Process according to any one of the preceding claims, in which said composition in step (i) is obtained via the following steps: (a1) preparation of a solution, denoted "solution S", comprising said dihydroxylated polycarbonate(s), said triisocyanate compound(s) and said ionic conductive salt(s), and optionally said inorganic filler(s), in particular conductive, in said plasticizing agent(s), in particular chosen from ethylene carbonate, sulfolane and their mixtures; and (a2) addition to said solution of said catalyst for the coupling reaction between a hydroxyl function and an isocyanate function.

14. Method according to the preceding claim, in which said solution S is obtained by adding said triisocyanate compound(s), preferably poly(hexamethylene diisocyanate), to a solution S1 comprising said dihydroxylated polycarbonate(s), preferably a poly(trimethylene carbonate) (PTMC), and said plasticizing agent(s), in particular chosen from ethylene carbonate, sulfolane and their mixtures, solution S1 preferably comprising said conductive salt(s). ionic.

15. Method according to any one of the preceding claims, in which said composition is, prior to step (ii), implemented in the form of a layer on the surface of a substrate, in particular by coating.

16. A method according to any one of the preceding claims, wherein step (ii) is carried out by heating the composition to a temperature between 50 and 100°C, in particular between 50 and 70°C.

17. Quasi-solid electrolyte obtained by a process as defined according to any one of claims 1 to 16, said quasi-solid electrolyte being in particular in the form of a film.

18. Quasi-solid electrolyte according to the preceding claim, said plasticizing agent(s) being trapped in a structure of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type,

19. An electrochemical element comprising a quasi-solid electrolyte as defined in claim 17 or 18, said electrochemical element comprising in particular a film of said quasi-solid electrolyte sandwiched between at least one positive electrode and one negative electrode.

20. Battery module comprising a plurality of electrochemical elements as defined in claims 19.

21. Battery comprising an assembly of modules as defined in claim 20, said battery being in particular a rechargeable battery, in particular a lithium battery, for example a lithium-ion or lithium-metal battery.

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