Ternary electrolyte

Abstract

The invention relates to a ternary electrolyte comprising between 30 and 60 wt.% of at least two selected from the following: a first polyethylene oxide (PEO) and / or a second PEO and optionally polyvinylidene fluoride (PVDF), relative to the total weight of the ternary electrolyte, mel1, where the PVDF is present at least when the ternary electrolyte does not comprise the first PEO, the first PEO having a first weight average molecular weight Mw1 of between 1 * 106 and 8 * 106 g / mol, the second PEO having a second weight average molecular weight Mw2 of between 0.2 * 106 and 0.7 * 106 g / mol, and the PVDF having a third weight average molecular weight Mw3 of between 0.1 * 106 and 1 * 106 g / mol; between 5 and 15 wt.% of a salt of an alkali metal and between 35 and 50 wt.% of an ionic liquid, relative to the mel1; and between 2.5 and 10 wt.% of an inorganic filler relative to the total weight of the other components in the ternary electrolyte, mel2.

Description

TERNARY ELECTROLYTE Technical field of the invention

[0001] The present invention relates to a ternary electrolyte, particularly a solid ternary electrolyte. The present invention also relates to a battery comprising said ternary electrolyte, and to a method for producing said ternary electrolyte. Technological background

[0002] Solid electrolytes have long been considered as alternatives to liquid electrolytes to address the safety issues of the latter. Based on the classification of components, solid electrolytes can be divided into three categories: inorganic electrolytes, organic electrolytes, and organic-inorganic electrolytes.

[0003] One of the advantages of organic solid electrolytes is their flexibility, which allows good contact at the electrode / electrolyte interface due to the flexible nature of the polymer chains. Among organic solid electrolytes, dry polymer electrolytes have attracted market interest.

[0004] Dry polymer electrolytes, also called binary electrolytes, comprise a polymer matrix in which a solid component, such as a lithium salt, is dissolved. Dissolving a lithium salt (or an alkali metal salt) in the polymer host leads to the formation of the solid solution and modifies the interaction of the salt with its host, while maintaining the flexibility of the polymer chains. However, this type of solid electrolyte has a rather low bulk ionic conductivity at room temperature (value between 10' 6 and 10' 4 S / cm).

[0005] Known solutions to improve ionic conductivity at room temperature include the addition of liquid plasticizers, solvents organic, and more particularly ionic liquids, thus obtaining an electrolyte called a ternary electrolyte.

[0006] WO2020 / 096632 discloses a ternary polymer electrolyte comprising a polymer, e.g., PEG-urethane-diepoxy, a lithium salt, e.g., LiTFSI or LiFSI, and a plasticizer, e.g., succinonitrile. The solid electrolyte can be used in Li-ion batteries (LIBs), and demonstrates an ionic conductivity of between 10' 8 and 10' 2 S / cm.

[0007] A disadvantage of using the disclosed plasticizers is that the manufacturing process for the ternary polymer electrolyte requires melting them in order to handle them. In addition, succinonitrile is a highly toxic component.

[0008] EP4320668 discloses a solid polymer electrolyte comprising between 20 and 70 wt% of a copolymer of vinylidene fluoride (VDF) and a VDF-compatible comonomer, between 10 and 80 wt% of a mixture of an ionic liquid and a plasticizer, and between 2 and 30 wt% of a lithium salt, e.g., LiTFSI or LiFSI. The solid electrolyte demonstrates an ionic conductivity of between 10' 5 and 5 * 10' 3 S / cm.

[0009] The plasticizer in this solid polymer electrolyte is a solvent in which the lithium salt is dissolved during the electrolyte manufacturing process. In other words, the manufacture of this electrolyte involves the use of a solvent, despite the environmental concerns associated with the use of such chemicals.

[0010] A disadvantage of the aforementioned solid polymer electrolytes is that their manufacture requires the use of very specific chemicals that must be synthesized, thus making these methods complex and expensive.

[0011] CN1 13851709 discloses a solid electrolyte having high ionic conductivity and uniform distribution of an inorganic filler, and a method for manufacturing the same. The method comprises preparing of a mixture comprising an inorganic filler - preferably an inorganic ceramic material, e.g., AI-LLZO, LLZTO, SiO2 or TiO2 - whose surface is modified, as well as a lithium salt and a first polymeric matrix of polyethylene oxide (PEO), followed by hot extrusion of the mixture. It is known in the art that this type of inorganic filler acts as an active inorganic filler, actively contributing to the mechanical strength as well as the ionic conductivity of the solid electrolyte by inhibiting the crystallization of the first polymeric matrix and at the same time providing additional ion transport channels on the polymer-inorganic filler interface. A solvent is used in the mixing step to facilitate the mixing. In the hot extrusion step, a polymer additive (e.g., polyvinylidene fluoride (PVDF) having a number average molecular weight of 1.1 * 10 6g / mol or an ionic liquid) may be added to improve the electrical conductivity, mechanical strength and high temperature and high voltage resistance of the manufactured solid electrolyte. The solid electrolyte comprises between 5 and 15% by weight of the first PEO polymer matrix having a number average molecular weight between 0.1 * 10 6 and 0.8 * 10 6 g / mol, between 2 and 60% by weight of the polymer additive and between 0.5 and 65% by weight of the inorganic filler.

[0012] CN112072172 discloses a solid polymer electrolyte comprising PEO having a weight average molecular weight (M w ) between 5 * 10 6 and 9 * 10 6 g / mol loaded with an active inorganic filler (e.g., LLZO or LLTO) and uniformly dispersed in polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) having a Mw of 0.4 * 10 6. The inorganic filler has high ionic conductivity at room temperature, contributing to and increasing the ionic conductivity of the dry polymer electrolyte. The method comprises preparing a suspension comprising dissolving the PEO in dimethylformamide, adding the inorganic filler and dissolving the PVDF-HFP in the suspension. Then the suspension is applied to the surface of a mold and dried, forming a solid polymer electrolyte film.

[0013] U S2013 / 224609 discloses an electrolyte comprising a lithium ion-conducting polymer, such as PEO or PVDF, and having an M w between 0.1 * 10 6 and 1 * 10 6g / mol, a lithium salt and an ionic liquid having a specific anion. For each mole of the conductive polymer there are 0.1 to 2 moles of the ionic liquid. The electrolyte optionally comprises a non-conductive inorganic filler, such as SiC>2, in an amount of between 0.1 and 20% by weight based on the total mass of the polymer, salt and ionic liquid. Taking into account the molecular weights of each component, the electrolyte comprises at least 99% by weight of the conductive polymer and less than 1% by weight of each of the lithium salt and ionic liquid. Summary of the invention

[0014] The invention aims in particular to overcome the various drawbacks of solid electrolytes and known manufacturing processes.

[0015] More specifically, one objective of the invention is to provide a ternary electrolyte, more specifically a solid ternary electrolyte, or, in other words, a solid ternary polymer electrolyte, having excellent ionic conductivity at room temperature. Another objective is to provide a flexible ternary electrolyte.

[0016] Another objective of the invention is to provide a method for manufacturing such a ternary (solid) electrolyte which allows the use of commercially available components, thus making the method less complex and less expensive compared to methods known in the prior art.

[0017] Another objective of the invention is to provide a method for manufacturing a ternary electrolyte which does not require the use of a solvent, thus reducing the environmental impact.

[0018] Another objective of the invention is to provide a method for manufacturing a ternary electrolyte which makes it possible to use components having low toxicity, or even negligible toxicity, thus reducing the environmental impact and health risks associated with the manufacturing process.

[0019] In the present disclosure, the term "an active inorganic filler" is used for inorganic fillers having high ionic conductivity, wherein high ionic conductivity is used for ionic conductivity equal to or greater than 10' 4S / cm at 25 °C. The term "active" in relation to such an inorganic filler means its ability to contribute significantly to the ionic conductivity of an electrolyte comprising this active inorganic filler. Particular examples of active inorganic fillers include lithium lanthanum zirconium oxide (Li?La3Zr20i2, abbreviation LLZO), aluminum-doped lithium lanthanum zirconium oxide (Li?-xAlxLa3Zr20i2, abbreviation AI-LLZO), lithium lanthanum zirconium tantalum oxide (Li6.4La3Zn.4Tao.6O12, abbreviation LLZTO) and lithium germanium phosphorus sulfide (LiioGeP2Si2, abbreviation LGPS). It follows that the term "an inactive inorganic filler" used in the present disclosure means an inorganic filler which is not an active inorganic filler, and which therefore has an ionic conductivity lower than I O' 4 S / cm at 25°C.

[0020] To this end, a first aspect of the present invention relates to a ternary electrolyte according to the appended claims.

[0021] The ternary electrolyte comprises between 30 and 60%, preferably between 35 and 55% by weight, more preferably between 40 and 50% by weight of one or more polymers, between 5 and 15% by weight, preferably between 6 and 14% by weight, more preferably between 7 and 13% of a salt of an alkali metal, and between 35 and 50% by weight, preferably between 37.5 and 47.5% by weight, more preferably between 40 and 45% of an ionic liquid, the percentage by weight of each component being expressed relative to the total weight of ternary electrolyte, m e n. Advantageously, the ternary electrolyte does not comprise a crosslinking agent. Advantageously, the ternary electrolyte does not comprise a solvent.

[0022] The ternary electrolyte further comprises between 2.5 and 10% by weight, preferably between 5 and 10% by weight, more preferably between 7.5 and 10% by weight of an inorganic filler, relative to the total weight of the other components in the ternary electrolyte, m e i2, in which m e n = m e i2 + rrich, where rrich is the weight of the inorganic charge in the ternary electrolyte, or m C h is between 0.025 * m e i2 and 0.10 * m e i2 and then m e n is between 1.025 * m e i2 and 1.1 * m e i2. The inventors surprisingly discovered that the presence of such a weight of an inorganic filler makes it possible to obtain a solid ternary electrolyte which is flexible.

[0023] The polymer(s) comprise a first polyethylene oxide (PEO) and / or a second PEO and optionally polyvinylidene fluoride (PVDF) with the PVDF present at least when the ternary electrolyte does not comprise the first PEO.

[0024] The first PEO has a first molecular weight Mwi between 0.75 * 10 6 and 10 * 10 6 g / mol, preferably between 1 * 10 6 and 8 * 10 6 g / mol, more preferably between 2 * 10 6 and 7 * 10 6 g / mol, for example between 4 * 10 6 and 6 * 10 6 g / mol.

[0025] The second PEO has a second molecular weight Mw2 between 0.2 * 10 6 and 0.7 * 10 6 g / mol, preferably between 0.3 * 10 6 and 0.6 * 10 6 g / mol, more preferably between 0.4 * 10 6 and 0.6 * 10 6 g / mol.

[0026] PDVF has a third molecular weight Mw3 between 0.1 * 10 6 and 1 * 10 6 g / mol, preferably between 0.2 * 10 6 and 0.8 * 10 6 g / mol, more preferably between 0.3 * 10 6 and 0.7 * 10 6 g / mol, for example between 0.4 * 10 6 and 0.6 * 10 6 g / mol.

[0027] In the present disclosure, the term "molecular weight" refers to a weight average molecular weight. In the literature it is known to use the abbreviation M w to indicate the weight average molecular weight, e.g. Molecular Structure and Dynamics (1980), ISBN: 9780080859989, 0080859984, pages 15-16, using Mw for the weight average molecular weight and M n for the number average molecular weight). Therefore, in the present disclosure, Mwi, Mw2 and Mw3 indicate a first, second and third weight average molecular weight, respectively.

[0028] Molecular weights (i.e. weight-average molecular weights) are measured by means known in the field of polymers, in particular by size exclusion chromatography (English: gel permeation chromatography, GPC).

[0029] Advantageously, if the electrolyte comprises the first PEO and the second PEO, the proportion by weight of the first PEO and the second PEO is between 5:1 and 1:5, preferably between 3:1 and 1:3, more preferably between 1:1 and 1:3.

[0030] Advantageously, if the electrolyte comprises PVDF, the proportion by weight of the PEO(s) and PVDF is between 5:1 and 1:5, preferably between 3:1 and 1:3, more preferably between 2:1 and 1:2, e.g. 1:1.

[0031] In the present disclosure, the term "PEO(s)" refers to the PEOs in a composition, for example the electrolyte or an electrolyte paste, i.e., the first PEO or the second PEO if the composition contains either the first PEO or the second PEO and not both, or the first PEO and the second PEO if the composition contains the first PEO and the second PEO.

[0032] Advantageously, the ternary electrolyte comprises at least two of the following three components (polymers): the first PEO, the second PEO and PVDF, each having the (weight average) molecular weight described above. In other words, the ternary electrolyte advantageously comprises the first PEO and the second PEO, or the first PEO and PVDF, or the second PEO and PVDF, or the first PEO, the second PEO and PVDF.

[0033] The inventors have surprisingly discovered that a ternary electrolyte comprising at least two of the three polymers exhibits good, or even excellent, mechanical properties in terms of stability, flexibility and mechanical strength, as well as high ionic conductivity at room temperature as well as at high temperature. This high ionic conductivity even surprisingly allows the use of a wider range of inorganic fillers and in particular inactive inorganic fillers (having an ionic conductivity of less than 10' 4S / cm at 25 °C). Unlike ternary electrolytes known from the prior art, the inorganic filler does not necessarily have to have high ionic conductivity (i.e., does not have to be an active inorganic filler) in order to result in an electrolyte with good ionic conductivity, particularly at room temperature. Furthermore, it has been noted that the inorganic filler content can be reduced compared to ternary electrolytes of the prior art, thus making it possible either to increase the proportion of one or more other components in the electrolyte for the same total weight, or to obtain a lighter electrolyte.

[0034] Without wishing to be bound by any particular theory, the inventors believe that the combination of PEO chain lengths (when both the first PEO and the second PEO are present) and the presence of PVDF polymer chains (if any) results in a degree of crystallization that is both high enough to provide mechanical stability and low enough to provide flexibility and sufficient ionic conductivity, both at ambient and elevated temperatures.

[0035] Advantageously, the alkali metal is lithium or sodium, preferably lithium. When the alkali metal is lithium, the lithium salt advantageously comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium bis(fluorosulfonyl)imide (LiFSI).

[0036] Advantageously, the ionic liquid comprises pyrrolidinium bis(trifluoromethylsulfonyl)imide (PynRTFSI) and / or pyrrolidinium bis(fluorosulfonyl)imide (PynRFSI).

[0037] Advantageously, the inorganic filler is therefore not an active inorganic filler, i.e. it is advantageously an inactive inorganic filler. Advantageously, the inorganic filler comprises a sepiolite modified with tocopherol. Advantageously, the tocopherol is Da-tocopherol polyethylene glycol succinate (TPGS) and the sepiolite modified with tocopherol is advantageously a sepiolite modified with Da-tocopherol polyethylene glycol succinate (TPGS-Sep). Advantageously, the ternary electrolyte does not comprise LLZO, AI-LLZO, LLZTO and LGPS as inorganic filler.

[0038] A second aspect of the present invention relates to a battery according to the appended claims.

[0039] The battery comprises the ternary electrolyte according to the first aspect of the present invention.

[0040] Advantageously, the battery is a secondary battery.

[0041] Advantageously, the (secondary) battery is of the Li-ion, Na-ion, Li-S, Li-metal polymer or Na-metal polymer type. Advantageously, when the battery is of the Li-ion or Li-metal polymer type, the alkali metal salt of the electrolyte is a lithium salt. Similarly, and also advantageously, when the battery is of the Na-ion or Na-metal polymer type, the alkali metal salt of the electrolyte is a sodium salt.

[0042] An advantage of the electrolytes according to the present disclosure is that they can be used as such, i.e. without requiring additional preparation steps, for assembling the battery. In particular, their high ionic conductivity at room temperature as well as at high temperatures precludes the need to bring them into contact with a solution of an alkali metal salt and a solvent before assembling the battery, and It also eliminates the need for protective layers. This reduces the complexity of battery assembly, as well as its cost and environmental impact.

[0043] A third aspect of the present invention relates to a method of manufacturing a ternary electrolyte according to the appended claims. The ternary electrolyte manufactured by the method is advantageously a ternary electrolyte according to the first aspect of the present invention.

[0044] The method comprises preparing an electrolyte paste and shaping said electrolyte paste to obtain the ternary electrolyte. Advantageously, the method according to the present disclosure does not require a solvent. In other words, the method is advantageously a solvent-free process, thereby reducing environmental impact, recycling costs and risks associated with volatile or toxic solvents.

[0045] The electrolyte paste includes - a first PEO and / or a second PEO and optionally PVDF with the PVDF present at least when the electrolyte paste does not comprise the first PEO, wherein the first PEO, the second PEO and the PVDF are as described above, - a salt of an alkali metal, as described above, - an ionic liquid, as described above, - an inorganic filler, as described above.

[0046] Advantageously, the electrolyte paste does not include a crosslinking agent. Advantageously, the electrolyte paste does not include a solvent.

[0047] The molar ratio of ethylene oxide (EO) units of the PEO(s) and alkali metal ions in the electrolyte paste is between 5:1 and 30:1, preferably between 7:1 and 28:1, more preferably between 10:1 and 25:1.

[0048] Advantageously, the electrolyte paste comprises at least two of the following three components (polymers): the first PEO, the second PEO and PVDF. In other words, the ternary electrolyte advantageously comprises the first PEO and the second PEO, or the first PEO and PVDF, or the second PEO and PVDF, or the first PEO, the second PEO and PVDF.

[0049] The inventors found that an electrolyte paste comprising at least two of the three polymers exhibits a highly homogeneous distribution of the other components—the alkali metal salt, the ionic liquid, and the inorganic filler—in the electrolyte paste without requiring the presence of a solvent. In addition, it was noted that the paste is easy to form despite the absence of a solvent. This is attributed to optimal rheology, including viscosity and melt flow rate. A ternary electrolyte with excellent component homogeneity and optimal porosity can then be manufactured.

[0050] Advantageously, when the ionic liquid present in the electrolyte paste comprises pyrrolidinium bis(trifluoromethylsulfonyl)imide (PyriRTFSI) and / or pyrrolidinium bis(fluorosulfonyl)imide (PynRFSI), the molar ratio of PynR units +and alkali metal ions in the electrolyte paste is between 1:1 and 5:1, preferably between 2:1 and 4:1, more preferably between 2.5:1 and 3.5:1.

[0051] A particular advantage of the ternary electrolyte according to the present disclosure and its manufacturing process is that it comprises components that are commercially available (off the shelf products), and therefore do not require their own synthesis upstream of the production (manufacturing) of the electrolyte itself. In addition, these commercially available products are not (very) expensive. This makes the manufacturing process less complex and less expensive. Another advantage is the absence of toxic products, such as certain solvents, crosslinking agents and plasticizers used in the prior art. Brief description of the figures

[0052] The purposes, advantages and features are demonstrated in the following figures, which are not limiting, and in which: - Figure 1A shows the morphology of the surface of an electrolyte according to the invention obtained by SEM, - Figure 1 B shows the morphology of the cross-section of the same electrolyte as Figure 1A, also obtained by SEM, - Figure 2 shows the chemical composition analyses for the elements F, Mg and O in the cross-section of the electrolyte of Figures 1 A and 1 B, obtained by EDX, - Figure 3 shows the oxidative and reductive potentials for three electrolytes according to the invention, - figure 4 shows the stability window in which there is no oxidation or reduction, for an electrolyte according to the invention, - Figure 5 shows the ionic conductivities for a reference electrolyte and four electrolytes according to the invention as a function of temperature. Detailed description of the invention

[0053] Advantageously, the ternary electrolyte comprises or substantially consists of between 30 and 60% by weight, preferably between 35 and 55% by weight, more preferably between 40 and 50% by weight of at least two of a first polyethylene oxide (PEO), a second PEO and polyvinylidene fluoride (PVDF), with the PVDF present at least when the ternary electrolyte does not comprise the first PEO, the weight percentage being expressed relative to the total weight of the ternary electrolyte, m e n.

[0054] The first PEO has a first molecular weight Mwi between 0.75 * 10 6 and 10 * 10 6 g / mol, preferably between 1 * 10 6 And 8 * 10 6g / mol, more preferably between 2 * 10 6 and 7 * 10 6 g / mol, for example between 4 * 10 6 and 6 * 10 6 g / mol.

[0055] The second PEO has a second molecular weight Mw2 between 0.2 * 10 6 and 0.7 * 10 6 g / mol, preferably between 0.3 * 10 6 and 0.6 * 10 6 g / mol, more preferably between 0.4 * 10 6 and 0.6 * 10 6 g / mol.

[0056] PDVF has a third molecular weight Mw3 between 0.1 * 10 6 and 1 * 10 6 g / mol, preferably between 0.2 * 10 6 and 0.8 * 10 6 g / mol, more preferably between 0.3 * 10 6 and 0.7 * 10 6 g / mol, for example between 0.4 * 10 6 and 0.6 * 10 6 g / mol.

[0057] The inventors surprisingly discovered that such a ternary electrolyte (i.e. comprising at least two PEO and / or PVDF polymers) exhibits optimal mechanical properties in terms of stability, flexibility and mechanical strength, as well as high ionic conductivity.

[0058] Advantageously, the ternary electrolyte comprises between 5 and 15% by weight, preferably between 6 and 14% by weight, more preferably between 7 and 13% by weight of a salt of an alkali metal, the percentage by weight being expressed relative to the total weight of the ternary electrolyte, m e n.

[0059] Advantageously, the ternary electrolyte comprises between 35 and 50% by weight, preferably between 37.5 and 47.5% by weight, more preferably between 40 and 45% by weight of an ionic liquid, the percentage by weight being expressed relative to the total weight of the ternary electrolyte, m e n.

[0060] The ternary electrolyte further comprises between 2.5 and 10% by weight, preferably between 5 and 10% by weight, more preferably between 7.5 and 10% by weight of an inorganic filler, relative to the total weight of the other components in the ternary electrolyte, m e i2, in which m e n = m e i2 + rrich, where rrich is the weight of the inorganic charge in the ternary electrolyte, or m C h is between 0.025 * m e i2 and 0.10 * m e i2 and then m e n is between 1.025 * m e i2 and 1, 1 * m e i2.

[0061] It goes without saying that the % by weight of the polymers (the PEO(s) and the optional PVDF), of the salt of an alkali metal and of the ionic liquid, relative to m e n, is chosen according to the amount of inorganic charge in the ternary electrolyte.

[0062] For example, if m e i2 is 100 g and the ternary electrolyte comprises 2.5% by weight of m e i2 of the inorganic filler, the ternary electrolyte comprises 2.5 g of the inorganic filler, and has a total weight, m e n , of 102.5 g. If the ternary electrolyte comprises 5% by weight of an alkali metal salt and 35% by weight of an ionic liquid, it comprises 5.125 g (5% of 102.5 g) of salt and 35.875 g (35% of 102.5 g) of ionic liquid, and 59 g of polymers (100 g - 5.125 g - 35.875 g), which represents a % by weight relative to men of 57.6% (59 / 102.5*100%).

[0063] For example, if m e i2 is 100 g and the ternary electrolyte comprises 10 wt% of m e i2 of the inorganic filler, the ternary electrolyte comprises 10 g of the inorganic filler, and has a total weight, m e n, of 110 g. If the ternary electrolyte comprises 5% by weight of a salt of an alkali metal and 35% by weight of an ionic liquid, it comprises 5.5 g (5% of 110 g) of salt and 38.5 g (35% of 110 g) of ionic liquid, and 56 g of polymers (100 g - 5.5 g - 38.5 g), which represents a % by weight relative to m e n of 50.9% (56 / 110*100%).

[0064] The weight percentage of each component of the ternary electrolyte is determined by means known in the art. In particular, it is measured by thermogravimetric analysis (TGA). By TGA, the mass change of the ternary electrolyte is analyzed as a function of temperature or time. Specifically for the ternary electrolytes of the present invention, the polymers (PEO and the optional PVDF) are quantified based on their mass loss upon thermal degradation over a specific temperature range. The ionic liquid is also identified by its mass loss at a temperature that is, generally speaking, somewhat higher than that of the polymers. The salt of an alkali metal that does not decompose thermally is typically evaluated from the solid residue remaining after removal of the other components.

[0065] Advantageously, the alkali metal of the salt of an alkali metal is lithium or sodium, preferably lithium. Advantageously, when the alkali metal is lithium, the salt is a lithium salt selected from the group comprising LiTFSI, LiFSI, LiBOB, LiPFe, LiBF4, LiCIC, LiAsFe, LiN(CF3SO2)2, LiC(CF3SO2)3, LiDFOB, LiF, LiCI, LiBr, LiI1, Li2SO4, LiNO3, Li3PO4, Li2CO3, LiOH, lithium acetate, lithium trifluoromethyl acetate, lithium oxalate.

[0066] The ternary electrolyte may contain one or more salts of an alkali metal. When the ternary electrolyte comprises two or more salts of an alkali metal, the alkali metal of each salt may be the same or different. For example, when the ternary electrolyte comprises two salts of an alkali metal, the salts may be LiTFSI and LiFSI, in which the alkali metal of both salts is then the same, being lithium.

[0067] Advantageously, the ionic liquid is selected from the group comprising PynRTFSI, PynRFSI, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI) and trihexyltetradecylphosphonium bis trifluoromethylsulfonyl amide. The solid ternary electrolyte may contain one or more ionic liquid(s), for example two, three or four ionic liquids. Non-limiting examples of mixtures of ionic liquids include a mixture of PynRTFSI and PynRFSI, a mixture of EMIFSI and PynRTFSI, or a mixture of EMIFSI and PynRFSI.

[0068] Advantageously, the inorganic filler provides mechanical stability to the electrolyte, while making the electrolyte flexible, i.e., it contributes to its mechanical stability and flexibility. The inventors have discovered that the ionic conductivity of the inorganic filler is not essential, i.e., it is not necessary for the inorganic filler to have an ionic conductivity considered high in the state of art (typically a value equal to or greater than 10' 4 S / cm at 25 °C). This is particularly the case when the ternary electrolyte comprises at least two of the first polyethylene oxide (PEO), the second PEO and PVDF, because the inventors have discovered that such an electrolyte has a high ionic conductivity independently of the composition and proportion (% by weight) of the inorganic filler.

[0069] Advantageously, the inorganic filler is an inactive inorganic filler, that is to say, it advantageously has an ionic conductivity of less than 10' 4 S / cm at 25 °C. Advantageously, the ternary electrolyte does not include an active inorganic filler, such as LLZO, AI-LLZO, LLZTO and LGPS.

[0070] Advantageously, the inorganic filler is selected from the group comprising modified sepiolites (sepiolite being a clay mineral), in particular sepiolites modified with tocopherol, e.g. sepiolite modified with Da-tocopherol polyethylene glycol succinate (TPGS-Sep) and other clay minerals such as e.g. natural montmorillonite and halloysite.

[0071] A particular example of the inorganic filler is TPGS-Sep. It is known that Da-tocopherol polyethylene glycol succinate (TPGS) and TPGS-Sep are often used as an antioxidant for PEO, in order to prevent degradation of PEO, the degradation including the formation of peroxides at the methylene groups. TPGS-Sep can be prepared by a method that is less complex than methods known in the prior art for modifying the surface of an inorganic filler. Advantageously, TPGS-Sep is prepared by mixing sepiolite with Da-tocopherol polyethylene glycol succinate, followed by filtering and drying.

[0072] It is also known that clay minerals, and in particular sepiolite modified with tocopherol, are capable of increasing the storage modulus of the ternary electrolyte. It has been found that the incorporation of a clay mineral as an inorganic filler improves the stiffness of polymers, allowing a greater degree of stress transfer at the interface resulting in higher polymer stiffness.

[0073] The solid ternary electrolyte may contain one or more inorganic fillers, for example two, three or four inorganic fillers.

[0074] Advantageously, the electrolyte according to the invention has an ionic conductivity equal to or above 2 * 10' 4 S / cm, preferably at least 2.5 * 10' 4 S / cm, more preferably at least 3 * 10' 4 S / cm at room temperature. Ionic conductivity is measured by impedance spectroscopy.

[0075] Advantageously, the electrolyte according to the invention has an ionic conductivity equal to or above 5 * 10' 4 S / cm, preferably at least 7.5 * 10' 4S / cm, more preferably at least 1 * 10' 3 S / cm at 50°C.

[0076] Advantageously, the electrolyte according to the invention has an ionic conductivity equal to or above 1 * 10' 3 S / cm, preferably at least 1.5 * 10' 3 S / cm, more preferably at least 2 * 10' 3 S / cm at 80°C.

[0077] The present disclosure also relates to methods of manufacturing ternary electrolytes, in particular those described above. The methods comprise preparing an electrolyte paste and shaping the same.

[0078] The electrolyte paste comprises or substantially consists of at least two of a first PEO, a second PEO and PVDF, with the PVDF present at least when the electrolyte paste does not comprise the first PEO, a salt of an alkali metal, an ionic liquid and an inorganic filler.

[0079] The first PEO, the second PEO and the PVDF have a weight average molecular weight as described above.

[0080] The salt of an alkali metal, the ionic liquid and the inorganic filler are as described above.

[0081] The electrolyte paste may contain one or more salts of an alkali metal. When the electrolyte paste comprises two or more salts of an alkali metal, the alkali metal of each salt may be the same or different. It goes without saying that if the electrolyte paste contains one or more salts of an alkali metal, then the ternary electrolyte obtained by the method according to the invention also contains this / these salt(s) of an alkali metal because the method according to the invention transforms the electrolyte paste into a ternary electrolyte, in which the ternary electrolyte advantageously has the form of a film.

[0082] The electrolyte paste may contain one or more ionic liquid(s). It goes without saying that if the electrolyte paste contains one or more ionic liquid(s), then the ternary electrolyte obtained by the process according to the invention also contains this / these ionic liquid(s).

[0083] The electrolyte paste may contain one or more inorganic filler(s). It goes without saying that if the electrolyte paste contains one or more inorganic filler(s), then the ternary electrolyte obtained by the process according to the invention also contains this / these inorganic filler(s).

[0084] Advantageously, the amounts of each component in the electrolyte paste are chosen according to the desired composition of the ternary electrolyte. More specifically, the electrolyte paste, once prepared, has the same composition as the ternary electrolyte obtained by the method of the present invention. In other words, to obtain 100 g of the ternary electrolyte, an electrolyte paste of also 100 g is advantageously prepared.

[0085] For example, if a ternary electrolyte comprising 100 g of polymers, alkali metal salt and ionic liquid (m e i2 is 100 g) and 10 g of inorganic filler (10% by weight of m e i2) is to produce a paste also comprising 100 g of polymers, salt of an alkali metal and ionic liquid and 10 g of inorganic filler is advantageously prepared.

[0086] It then follows that the weight percentages of each component of the electrode paste are advantageously the same as mentioned above for the ternary electrolyte.

[0087] In electrolyte paste, the weight and weight percentage of each component refer to the weights of each component before the preparation of the electrolyte paste, also called the "starting weight". The starting weight of each component is advantageously measured by a balance, and the weight percentage of each component is calculated based on the sum of the starting weights of the components.

[0088] Advantageously, the electrolyte paste is prepared by means known in the art, e.g. by mixing the components to obtain a homogeneous paste. An advantage of the method according to the invention is that the step of preparing the electrolyte paste can be carried out at room temperature. It is well understood that the preparation of the electrolyte paste can be accelerated by heating the components, e.g. by heating the container in which the paste is prepared. If heating is chosen, the inventors have discovered that a temperature slightly above room temperature is sufficient, e.g. a temperature between 30°C and 75°C.

[0089] According to a particular embodiment, the paste is prepared by mixing the inorganic filler(s) with the PEO(s) and - if present - the PVDF. Then, the salt(s) of an alkali metal is (are) added, while continuing to mix the composition, followed by the addition of the ionic liquid(s). It is also possible to add the salt(s) of an alkali metal and the ionic liquid(s) simultaneously to the mixture. The inventors have discovered that by adding the components in this order, it is easier to obtain a homogeneous electrolyte paste.

[0090] Optionally, the method further comprises a step of homogenizing the electrolyte paste before shaping it. This optional step makes it possible to increase the homogeneity of the electrolyte paste. It goes without saying that homogenization is not necessary if the paste prepared in the previous step demonstrates satisfactory homogeneity.

[0091] The homogenization operation of the electrolyte paste can be carried out by means known in the art. Advantageously, the paste is homogenized by heating the paste, for example to a temperature between 30°C and 120°C, preferably between 50°C and 90°C. Advantageously, the temperature is selected so as to remain below the degradation temperatures of the components of the electrolyte paste, in particular the degradation temperature of each PEO and - if present - of the PVDF, in order to avoid any degradation thereof.

[0092] Advantageously, the electrolyte paste is homogenized in an atmosphere having a pressure below ambient pressure, in other words under vacuum. Advantageously, the step of homogenizing the electrolyte paste is carried out under vacuum at a temperature between 30°C and 120°C, preferably between 50°C and 90°C.

[0093] Advantageously, the shaping of the electrolyte paste is carried out by means known in the art. A compatible means is in particular pressure shaping. Advantageously, the pressure shaping comprises a heating operation followed by a pressure operation and a cooling step.

[0094] Advantageously, the paste is heated to a temperature between 100°C and 200°C, preferably between 125°C and 175°C, for example between 140°C and 150°C.

[0095] Advantageously, the pressure is done by keeping the dough at the elevated temperature. Advantageously, the pressure comprises the application of a pressure of between 2 kN and 50 kN, preferably between 5 kN and 30 kN, more preferably between 10 kN and 25 kN, by example 15 kN or 20 kN. It goes without saying that the pressure depends on the composition of the paste, its viscosity, the temperature and the thickness and / or the form of electrolyte desired.

[0096] Advantageously, the cooling operation includes keeping the paste under pressure while cooling. Cooling hardens the paste, thus forming the electrolyte.

[0097] Another example of a compatible shaping method is extrusion. Advantageously, extrusion includes a heating operation to melt the paste, followed by an extrusion operation and a cooling operation.

[0098] Advantageously, the paste is heated to a temperature of between 125°C and 200°C, preferably between 130°C and 175°C, for example between 140°C and 150°C, in order to melt the electrolyte paste.

[0099] Advantageously, the extrusion operation is carried out using means and parameters known in the art.

[0100] Advantageously, the cooling operation includes maintaining the shape (e.g. in the mold) of the paste while cooling. Cooling hardens the paste, thus forming the electrolyte.

[0101] The method optionally comprises one or more heating and cooling steps after the shaping step. In other words, the ternary electrolyte obtained during the shaping step can be heated and cooled, one or more times. The inventors have discovered that such a heating and cooling step can increase the ionic conductivity of the ternary electrolyte. Advantageously, the ternary electrolyte can be heated to a temperature between 30°C and 100°C, preferably between 40°C and 80°C. Examples Example 1

[0102] Four electrolyte pastes having the compositions 1-4 shown in Table 1 were prepared, electrolyte 1 being a prior art ternary electrolyte and electrolytes 2-4 being ternary electrolytes according to the present invention. First, sepiolite modified with Da-tocopherol polyethylene glycol succinate (TPGS-Sep in Table 1) and - if present - a first PEO (PEO 1 ), a second PEO (PEO 2 ) and PVDF, each component in their respective amount, are mixed. For example, to obtain 100 g of electrolyte 4, a 100 g paste was prepared by mixing 11.5 g of PEO 1 , 11.5 g of PEO 2, 23.0 g of PVDF and 10.0 g of TPGS-Sep. Specifically, the first PEO - if present - was added to the TPGS-Sep, followed by the second PEO and - if present - the PVDF.

[0103] The first polyethylene oxide (PEO) has a molecular weight of 5 * 10 6 g / mol. The second PEO has a molecular weight of 0.6 * 106 g / mol. The molecular weight of PVDF was 0.534 * 10 6 g / mol.

[0104] Then, LiTFSi or LiFSI was added as the lithium salt, and PynRTFSI or PynRFSI was added as the ionic liquid (IL in Table 1), while continuing to mix the paste. For example, for 100 g of electrolyte 4, 7.8 g of LiTFSi and 46.0 g of ionic liquid were added to the mixture of the three polymers and TPGS-Sep. The mixture was then mixed until a homogeneous paste was obtained.

[0105] Once a homogeneous, pasty texture was obtained, the mixtures were homogenized by heating at 90 °C under vacuum for 48 h. The homogenized electrolyte pastes were then converted into electrolytes by heating them at 140 °C for 15 minutes and then pressing them at this temperature for 20 minutes under a pressure of 15 kN in order to shape them. The shaped pastes were then cooled while maintaining the pressure of 15 kN, which allows the pastes to harden to obtain the electrolytes in the form of discs. The electrolytes produced were in the form of a self-supporting, semi-transparent film.

[0106] A reference binary electrolyte was also made by mixing PEO 2 with LiTFSI in the relative amounts mentioned in Table 1 (“Reference” in Table 1). This electrolyte was made according to the same method of the four inventive electrolytes. Table 1: Composition of the electrolytes produced (in % by weight relative to the total weight of the ternary electrolyte)

[0107] The surface morphology and cross-sectional morphology of the electrolytes, chemical composition and homogeneity of the bulk and surface of the electrolytes were examined by scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDX).

[0108] Figure 1A shows the surface morphology of electrolyte 2, and Figure 1B shows the cross-section morphology of the same electrolyte 2 obtained by SEM. It is clear that the surface and cross-section demonstrate a very homogeneous morphology.

[0109] Figure 2 shows the chemical composition analyses for the elements F, Mg and O in the cross section of the same electrolyte 2, obtained by EDX. It is clear that their dispersion in the cross section is very homogeneous. Example 2

[0110] To measure the electrochemical stability window, two-electrode button cells were prepared with the four ternary electrolytes (electrodes 1-4 in Table 1). The electrodes were one lithium metal electrode and one stainless steel electrode. Each button cell—thus each electrolyte—was tested between two potential ranges: between the open circuit potential (OCP) and 50 mV (low potential range), and between OCP and 5.2 V (high potential range) at a rate of 1 mV / s using a Biology battery cycler.

[0111] Figure 3 shows the oxidative and reductive potentials for electrolytes 1, 3 and 4. The result for the button cell comprising electrolyte 2 (inventive) was very similar to the result for electrolyte 1 (prior art). It is clear that each ternary electrolyte starts to oxidize at a potential well above 3.2 V, a value often mentioned in the literature for conventional binary electrolytes based on PEO 2, such as the reference binary electrolyte of Table 1.

[0112] Figure 4 shows the stability window (in which there is no oxidation or reduction) for electrolyte 2, indicating stable behavior (neither oxidation nor reduction, or 0 mA current (Y axis of Figure 4)) between a potential of 0.8 V and 4.0 V. Example 3

[0113] To measure ionic conductivity, a symmetrical cell was fabricated with each ternary electrolyte in Table 1, as well as the reference binary electrolyte. The electrodes used were made of stainless steel. The evolution of the electrolyte resistance was monitored for two heating-cooling cycles during which the temperature was varied between 25 °C and 60 °C for the cell comprising the reference electrolyte, and between 25 °C and 80 °C for the cells comprising an inventive electrolyte. The electrochemical impedance spectra were recorded in a frequency range of 7.0 MHz to 50 mHz with a signal amplitude of 10 mV. The ionic conductivity is calculated by dividing the thickness of the electrolyte film by the product of the geometric surface area and the resistance of the electrolyte.

[0114] Figure 5 shows the ionic conductivities obtained. It is clear that the ionic conductivity at each temperature tested, and in particular at room temperature, of each ternary electrolyte greatly exceeds that of the reference system. It is also clear that at temperatures equal to or lower than 50 °C (“moderate or even low temperatures”), the ionic conductivity of the ternary electrolytes according to the invention (electrolytes 2, 3 and 4) is higher than that of the ternary electrolyte of the prior art (electrolyte 1). In other words, at moderate temperatures, the ternary electrolytes according to the invention exhibit the best ionic conductivity.

Claims

CLAIMS 1. A ternary electrolyte comprising - between 30 and 60% by weight of a first polyethylene oxide (PEO) and / or a second PEO and optionally polyvinylidene fluoride (PVDF), relative to the total weight of the ternary electrolyte, men, with PVDF present at least when the ternary electrolyte does not comprise the first PEO, said first PEO having a first weight average molecular weight Mwi, said second PEO having a second weight average molecular weight Mw2, and said PVDF having a third weight average molecular weight Mw3, - between 5 and 15% by weight of a salt of an alkali metal relative to m e n, and - between 35 and 50% by weight of an ionic liquid, relative to men, characterized in that Mwi is between 1 * 10 6 and 8 * 10 6 g / mol, Mw2 is between 0.2 * 10 6 and 0.7 * 10 6 g / mol and Mw3 is between 0.1 * 10 6and 1 * 10 6 g / mol, in that the ternary electrolyte further comprises between 2.5 and 10% by weight of an inorganic filler relative to the total weight of the other components in the ternary electrolyte, m e i2, and in that the ternary electrolyte comprises at least two of the following three components: the first PEO, the second PEO and the PVDF.

2. The ternary electrolyte according to claim 1, in which Mwi is between 2 * 10 6 and 7 * 10 6 g / mol.

3. The ternary electrolyte according to any one of the preceding claims, wherein Mw2 is between 0.3 * 10 6 and 0.6 * 10 6 g / mol.

4. The ternary electrolyte according to any one of the preceding claims, wherein Mw3 is between 0.3 * 10 6 and 0.7 * 10 6 g / mol.

5. The ternary electrolyte according to any one of the preceding claims, wherein the electrolyte comprises the first PEO and the second PEO, and wherein the weight proportion of the first PEO and the second PEO is between 5:1 and 1:

5.

6. The ternary electrolyte according to any one of the preceding claims, wherein the electrolyte comprises PVDF, and wherein the weight proportion of the PEO(s) and PVDF is between 5:1 and 1:

5.

7. The ternary electrolyte according to any one of the preceding claims, wherein the alkali metal salt comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium bis(fluorosulfonyl)imide (LiFSI).

8. The ternary electrolyte according to any one of the preceding claims, wherein the ionic liquid comprises pyrrolidinium bis(trifluoromethylsulfonyl)imide (PynRTFSI) and / or pyrrolidinium bis(fluorosulfonyl)imide (PynRFSI).

9. The ternary electrolyte according to any one of the preceding claims, wherein the inorganic filler comprises a sepiolite modified with tocopherol, preferably a sepiolite modified with Da-tocopherol polyethylene glycol succinate (TPGS-Sep).

10. A battery comprising the ternary electrolyte according to any one of the preceding claims.

11. The battery of claim 10, wherein the battery is a Li-ion, Na-ion or Li-metal polymer type battery.

12. Method for manufacturing a ternary electrolyte, comprising the steps of: - prepare an electrolyte paste comprising: • a first PEO and / or a second PEO and optionally PVDF with the PVDF present at least when the electrolyte paste does not comprise the first PEO, said first PEO having a first weight average molecular weight Mwi, said second PEO having a second weight average molecular weight Mw2, and said PVDF having a third weight average molecular weight Mw3, • a salt of an alkali metal, • an ionic liquid, and • an inorganic charge, - shaping the electrolyte paste to obtain the ternary electrolyte, characterized in that Mwi is between 1 * 10 6 and 8 * 10 6 g / mol, Mw2 is between 0.2 * 10 6 and 0.7 * 10 6 g / mol and Mw3 is between 0.1 * 10 6 and 1 * 10 6g / mol, in that the molar ratio of ethylene oxide (EO) units of the PEO(s) and alkali metal ions in the electrolyte paste is between 5:1 and 30:1, preferably between 10:1 and 25:1, and in that the ternary electrolyte comprises at least two of the following three components: the first PEO, the second PEO and PVDF.

13. The method of manufacturing a ternary electrolyte, wherein the electrolyte paste comprises between 30 and 60% by weight of at least two of said first PEO, said second PEO and said optional PVDF, between 5 and 15% by weight of said salt of an alkali metal and 35 and 50% by weight of said ionic liquid, all based on the weight of said electrolyte paste, and between 2.5 and 10% by weight of an inorganic filler based on the total weight of the other components in the paste.

14. The method of any one of claims 12 to 13, wherein the alkali metal salt comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium bis(fluorosulfonyl)imide (LiFSI).

15. The method of any one of claims 12 to 14, wherein the ionic liquid comprises pyrrolidinium bis(trifluoromethylsulfonyl)imide (PynRTFSI) and / or pyrrolidinium bis(fluorosulfonyl)imide (PynRFSI).

16. The method of claim 15, wherein the molar ratio of PynR units + and alkali metal ions in the electrolyte paste is between 1:1 and 5:1, preferably between 2:1 and 4:

1.

17. The method according to any one of claims 12 to 16, wherein the inorganic filler comprises a sepiolite modified with tocopherol, preferably a sepiolite modified with Da-tocopherol polyethylene glycol succinate (TPGS-Sep).

Images