OPTICAL FIBER FOR IN-SITU MEASUREMENT OF LITHIUM CONCENTRATION IN THE ELECTROLYTE OF A BATTERY, METHOD FOR PRODUCING THE OPTICAL FIBER AND ITS USE

Description

[0001] The present invention relates to an optical fiber functionalized by grafting onto at least a portion of its surface a plurality of first groups comprising a probe and by grafting, onto said at least a portion of its surface or onto the first groups, a plurality of second groups comprising an organic cation, as well as methods for obtaining it.

[0002] The present invention also relates to the uses of said optical fiber, in particular for measuring the lithium concentration, in particular for the in situ, or even in operando, measurement of the lithium concentration in the electrolyte of a battery.

[0003] The advantages of electrochemical propulsion in electric vehicles and the need for efficient large-scale energy storage, particularly in transportation, have led to a growing demand for high-performance batteries—namely, safe, efficient, and reliable batteries—in portable electronics and electric vehicles. The development of larger batteries with higher energy density and stricter safety requirements is therefore crucial.

[0004] In this context, Li-ion batteries have made considerable progress over the past few decades, particularly in issues ranging from thermal safety to cycling stability.

[0005] However, to reach the next level of Li-ion battery innovations, it is necessary to develop sensors that can be used to probe batteries in real time and in operando, to help optimize performance and more accurately determine cell health.

[0006] Conventional battery management systems, which typically rely on parameters such as current, voltage, and temperature, provide limited information about the chemical and physical processes occurring within the battery during operation. Understanding degradation processes and their evolution over time is also limited due to the complex nature of batteries. To improve the lifespan, safety, and reliability of current batteries and emerging battery technologies, more detailed information from the cells is required. In particular, it is important to know the local lithium ion concentration within the electrolyte of these batteries. This concentration varies during charge and discharge cycles, especially as the cell ages.The loss of active lithium through internal cell degradation processes, such as solid-electrolyte interface (SEI) growth, will result in a loss of performance. Many attempts have been made to observe lithium distributions in electrodes using techniques such as X-ray absorption near-threshold spectroscopy (XANES), nuclear magnetic resonance (NMR), X-ray diffraction, neutron scattering, particle-induced x-ray emission (PIGE / PIXE), Raman microspectroscopy, and hard X-ray photoelectron spectroscopy (HX-PES). However, these techniques do not allow direct measurement of the lithium concentration in the electrolyte. Furthermore, these techniques do not allow in situ or even in operando measurements, or even require disassembly of the battery to be analyzed. They are also very expensive.These are actually laboratory techniques that cannot be used for monitoring a battery pack in operation.

[0007] Document US 2021 / 122837 A1 discloses a fiber optic sensor for detecting at least one alkaline element in cationic form.

[0008] Probes, in particular based on an aryl or heteroaryl group substituted by at least two vicinal groups chosen from -OH and C 1 -C 3 alkoxy groups, are likely to be able to allow the measurement of the lithium concentration under the aforementioned conditions. However, the lithium concentration to be measured is often very high (of the order of 1 to 2M), and requires a high quantity of these probes for an effective measurement. However, these probes tend, when they do not complex the lithium, to self-condense, which leads to a reduction in the number of these probes, which is nevertheless critical as indicated above. Indeed, during the battery charge or discharge cycles, the lithium ions migrate towards the electrodes. The risk is that the chelating molecules are degraded (with in particular the formation of tars), and therefore to observe a reduction in sensitivity.

[0009] An objective of the invention is thus to provide a sensor making it possible to measure locally, in situ or even in operando, the lithium concentration at the heart of the battery, in the electrolyte, and in particular to provide real-time information that can be used by the battery management system (BMS). To this end, the sensor of the invention is stable in electrolytes, in particular in organic carbonates, and does not disrupt the operation of the battery.

[0010] Another objective of the invention is to provide a sensor which can be easily obtained from common materials (namely optical fibers).

[0011] Yet another objective of the invention is to provide a sensor that can easily be implemented in a simple, rapid and inexpensive method for measuring lithium concentration. This is a simple fluorescence measurement, which therefore meets the aforementioned criteria. Yet another objective of the invention is to provide a sensor that is stable over time and that can measure high lithium concentrations at any time.

[0012] In this context, the inventors have surprisingly identified that the presence of organic cations on the sensor makes it possible to protect the probes, in particular from self-condensation, and to stabilize them, while in no way hindering the measurement of the lithium concentration by the probes. Indeed, in the presence of lithium, the complex with the probe reforms to the detriment of the organic cation. The presence of grafted organic cations thus makes it possible to maintain the sensitivity of the lithium sensor over time.

[0013] Thus, according to a first aspect, the invention relates to an optical fiber carrying on at least part of its surface a plurality of groups A, and a plurality of groups B, the groups A carrying a group R being an aryl or heteroaryl group substituted by at least two vicinal groups chosen from -OH and C 1 -C 3 alkoxy groups, in particular -OMe, said vicinal groups being more particularly -OH, the groups B carrying a group R' being an organic cation.

[0014] The term "organic cation" refers in particular to an organic group carrying a positive charge. This may, for example, be a group containing a protonated N atom.

[0015] According to a particular embodiment, the counterion of the organic anion is PF 6 -< (hexafluorophosphate).

[0016] Unless otherwise indicated, when "group A" is mentioned, it is understood to mean group A, including group R (which is thus a substituent of group A). ​​The same applies to group B with group R'.

[0017] According to a particular embodiment, the plurality of groups A and the plurality of groups B are directly carried by said at least one part of its surface.

[0018] According to another particular embodiment, the groups A are substituted by at least one group B, in particular by a group B.

[0019] Said at least part of the surface is for example located at the end of the fiber, or along the fiber ( figure 1 ).

[0020] According to a particular embodiment, the group R is chosen from the following groups:

[0021] According to a particular embodiment, the group R' is chosen from quaternary ammoniums and heteroaromatic cations, in particular aza-heteroaromatic cations. The quaternary ammoniums are in particular the quaternary ammoniums of the following bases: aniline, phenylpyridine, quinoline, isoquinoline, pyrrole, indole and piperidine, these bases being optionally substituted by one or more substituents, for example C1-C3 alkyls, in particular a methyl.

[0022] According to a particular embodiment, the group R' is chosen from the following groups: in which: G -< represents a PF 6 -< anion, a triflimidate anion ([(CF 3 SO 2 ) 2 N] -< ) or a halogenated anion, for example Cl -< , G preferably being PF 6 -< ; R" represents a C1-C3 alkyl, in particular a methyl.

[0023] According to a more particular embodiment, the group R' is chosen from the following groups: in which: G -< represents a PF 6 -< anion, a triflimidate anion ([(CF 3 SO 2 ) 2 N] -< ) or a halogenated anion, for example Cl -< , G preferably being PF 6 -< .

[0024] According to a particular embodiment, the groups A and / or B are chains respectively carrying the group R or R', in particular in the terminal position, these chains being independently chosen from linear or branched alkyl or alkenyl chains, which are optionally interrupted by one or more atoms or groups chosen from -NH-, O, S, urea, urethane, amide, ester, arene diyls and heteroarene diyls.

[0025] According to a particular embodiment, the invention relates to an optical fiber as defined above carrying on at least part of its surface a plurality of groups of formula (I) and a plurality of groups of formula (I') following: in which: W, W', Y and Y' are independently selected from O and NH; i, i', j and j' are independently selected from 0 and 1; X represents a group of the following formula (II): X' represents a group of formula (II') following: in which: k and k' are independently chosen from 0 and 1; X a , X a ', X c and X c ' are independently chosen from: the groups X a1 being linear and branched C 1 -C 12 alkane diyls, in particular the groups of formula -(CH 2 ) n - with n from 1 to 12, or linear and branched C 2 -C 12 alkene diyls, the groups X a1 being in particular linear and branched C 1 -C 12 alkane diyls; the groups of formula -X a1 -NH-X a1 -, where X a1 is at each occurrence independently as defined above, in particular the groups of formula -(CH 2 ) n -NH-(CH 2 ) m - with n and m being independently from 1 to 12; groups of formula -X a1 -NHC(=O)-NH-X a1 - or -X a1 -NHC(=O)-NH-X a1 -NHC(=O)-NH-X a1 -, where X a1 is at each occurrence independently as defined above, in particular groups of formula -(CH 2 ) n -NHC(=O)-NH-(CH 2 ) m - with n and m being independently from 1 to 12;X b and X b ' are independently selected from: linear and branched C 1 -C 12 alkane diyls, in particular groups of formula - (CH 2 ) n - with n from 1 to 12, branched C 1 -C 12 alkane triyls, and linear and branched C 2 -C 12 alkene diyls, the groups X b and X b ' being in particular linear and branched C 1 -C 12 alkane diyls or triyls; optionally carrying, in particular in terminal position(s), at least one -(O-CH 2 -CH 2 ) p - or -(O-CH 2 -C(CH 3 )H) p - group, with p being an integer from 1 to 10; arene diyls and heteroarene diyls; X b being optionally substituted by a group A of the following formula (III): ; X c , Y, j, Z and R being as defined above or below, X b ' being optionally substituted by a group A of the following formula (III'): X c ', Y', j', Z' and R' being as defined above or below, Z and Z' being independently absent or selected from linear and branched C 1 -C 12 alkane diyls and linear and branched C 2 -C 12 alkene diyls, Z being in particular a linear C 2 alkane or alkene diyl, said group Z being optionally substituted by a -COOH group; R and R' are as defined above.

[0026] According to a particular embodiment, W and W', Y and Y', X and X', i and i', and / or j and j' are identical; W and W', Y and Y', X and X', i and i', and j and j' being identical.

[0027] According to a particular embodiment, the invention relates to an optical fiber as defined previously, in which: the groups of formula (I) are chosen from the groups of the following formula: and / or the groups of formula (I') are chosen from the groups of the following formula:

[0028] According to a particular embodiment, the invention relates to an optical fiber as defined above carrying on at least part of its surface a plurality of groups of the following formula (I): in which: W and Y are independently selected from O and NH; i and j are independently selected from 0 and 1; X represents a group of the following formula (II): in which: k is selected from 0 and 1; X a and X c are independently selected from: the groups X a1 being linear and branched C 1 -C 12 alkane diyls, in particular the groups of formula -(CH 2 ) n - with n from 1 to 12, or linear and branched C 2 -C 12 alkene diyls, the groups X a1 being in particular linear and branched C 1 -C 12 alkane diyls; the groups of formula -X a1 -NH-X a1 -, where X a1 is at each occurrence independently as defined above, in particular the groups of formula -(CH 2 ) n -NH-(CH 2 ) m - with n and m being independently from 1 to 12; groups of formula -X a1 -NHC(=O)-NH-X a1 - or -X a1 -NHC(=O)-NH-X a1 -NHC(=O)-NH-X a1 -, where X a1 is at each occurrence independently as defined above, in particular groups of formula -(CH 2 ) n -NHC(=O)-NH-(CH 2 ) m - with n and m being independently from 1 to 12;X b is chosen from: linear and branched C 1 -C 12 alkane diyls, in particular groups of formula - (CH 2 ) n - with n from 1 to 12, and branched C 1 -C 12 alkane triyls, and linear and branched C 2 -C 12 alkene diyls, the group X b being chosen in particular from linear and branched C 1 -C 12 alkane diyls or triyls; optionally carrying, in particular in terminal position(s), at least one group -(O-CH 2 -CH 2 ) p - or -(O-CH 2 -C(CH 3 )H) p -, with p being an integer from 1 to 10; arene diyls and heteroarene diyls; X b being optionally substituted by a group A of the following formula (III): ; X c , Y, j, Z and R being as defined above or below, Z is absent or selected from linear and branched C 1 -C 12 alkane diyls and linear and branched C 2 -C 12 alkene diyls, Z being in particular a linear C 2 alkane or alkene diyl, said group Z being optionally substituted by a -COOH group; R is an aryl or heteroaryl group substituted by at least two vicinal groups selected from -OH and C 1 -C 3 alkoxy groups, in particular -OMe, said vicinal groups being more particularly -OH, one of the atoms of the groups of formula (I) carrying a group B as defined above, this group B being in particular carried by an atom of the group X, in particular X b , of the groups of formula (I).

[0029] According to a particular embodiment, the invention relates to an optical fiber as defined above, in which the groups of formula (I) and the groups of formula (II) together form a group of the following formula:

[0030] According to a particular embodiment, (Y) j ZR is chosen from the following groups: and in particular among the following groups:

[0031] According to a particular embodiment, (Y') j' Z'R' is chosen from the following groups: in which: G -< represents a PF 6 -< anion, a triflimidate anion ([(CF 3 SO 2 ) 2 N] -< ) or a halogenated anion, for example Cl -< , G preferably being PF 6 -< ; R" represents a C1-C3 alkyl, in particular a methyl.

[0032] According to a particular embodiment, X b and / or X b ' are chosen from the following groups:

[0033] A and p being as defined previously.

[0034] According to a particular embodiment, the optical fiber according to the present invention is chosen from mineral optical fibers, in particular silica optical fibers, or optical fibers carrying an oxide layer chosen from TiO 2 , ZrO 2 , SnO 2 or HfO 2 , preferably modified by a compound comprising a phosphonic acid group as well as a primary amine, in particular a compound of formula (HO) 2 P(=O)-(CH 2 ) x NH 2 with x = 2, 3 or 4; organic optical fibers, in particular fibers made of or comprising polymethyl methacrylate (PMMA), optionally partially chlorinated polymethyl methacrylate, said polymethyl methacrylate optionally carrying carboxylic acid groups; and optical fibers carrying chains of functional oligomers, in particular chains of PVA, optionally partially acetylated.

[0035] According to a particular embodiment, the optical fiber according to the present invention is chosen from mineral optical fibers, in particular silica optical fibers, with i = 1 and W representing O, or optical fibers carrying an oxide layer chosen from TiO 2 , ZrO 2 , SnO 2 or HfO 2 , preferably modified by a compound comprising a phosphonic acid group as well as a primary amine, in particular a compound of formula (HO) 2 P(=O)-(CH 2 ) x NH 2 with x = 2, 3 or 4, with i = 1 and W representing N; organic optical fibers, in particular fibers made of or comprising polymethyl methacrylate (PMMA), optionally partially chlorinated polymethyl methacrylate, said polymethyl methacrylate optionally carrying carboxylic acid groups, with i = 0; and optical fibers carrying chains of functional oligomers, in particular chains of PVA, optionally partially acetylated, with i = 1 and W representing O.

[0036] According to a particular embodiment, the invention relates to an optical fiber as defined previously, which is solid or hollow, at least on said part of its surface.

[0037] The compounds of the present invention may be prepared by a number of methods well known to those skilled in the art, including, but not limited to, those described below, or by modifications of these methods by applying standard techniques known to those skilled in the art of organic synthesis. Suitable modifications and substitutions will be readily apparent and well known or may be readily obtained from the scientific literature by those skilled in the art. In particular, such methods may be found in RC Larock, Comprehensive Organic Transformations, Wiley-VCH Publishers, 1999.

[0038] All methods disclosed in association with the present invention may be carried out at any scale, including milligram, gram, multigram, kilogram, multikilogram, or commercial industrial scale.

[0039] It will be understood that the compounds of the present invention may contain one or more asymmetrically substituted carbon atoms and may be isolated in optically active or racemic forms. Thus, all chiral, diastereomeric, racemic, structural isomers are contemplated, unless the stereochemistry or specific isomeric form is specifically indicated. The manner of preparing and isolating these optically active forms is well known to those skilled in the art. For example, mixtures of stereoisomers can be separated by standard techniques including, but not limited to, resolution of racemic forms, classical chromatography, reverse and chiral phase chromatography, preferential salt formation, recrystallization and others, or by chiral synthesis, either from chiral starting materials or by targeted synthesis of the corresponding chiral centers.

[0040] The compounds of the present invention can be prepared by a variety of synthetic routes. The reagents and starting materials are commercially available, or readily synthesized by techniques well known to those skilled in the art. All substituents, unless otherwise indicated, are as defined above.

[0041] More particularly, the optical fibers of the invention, carrying a plurality of groups of formula (1), comprise the groups -NH-C(=O)-NH- (urea), -NH-C(=O)-O- or -OC(=O)-NH- (urethane), and / or -NH-C(=O)- or -C(=O)-NH- (amide).

[0042] The -NH-C(=O)-NH- group can be formed by any method well known to those skilled in the art, in particular by contacting a compound bearing an -NH 2 group (primary amine) with a compound bearing an -N=C=O group (isocyanate). This reaction can in particular be carried out in an anhydrous solvent, in particular an anhydrous aprotic solvent, for example dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), 1,4-dioxane, acetone. This reaction can be carried out at a temperature of 15 to 80°C, in particular 20 to 60°C, and / or for a period of 30 minutes to 24 hours, in particular 1 to 10 hours.

[0043] The -NH-C(=O)-O- or -OC(=O)-NH group may be formed by any method well known to those skilled in the art, in particular by bringing a compound bearing an -OH group (primary alcohol) into contact with a compound bearing an -N=C=O group (isocyanate), in particular in the presence of a catalyst, in particular chosen from triethylamine, 1,4-diazabicyclo[2,2,2]octane (DABCO), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), dibutyltin dilaurate (DBTDL), 1,8-diazabicylo[5,4,0]undec-7-ene (DBU), 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), di-isopropylethylamine (DIPEA), 4-dimethylaminopyridine (DMAP), 1,8-bis(dimethylamino)naphthalene (DMAN), for example triethylamine. This reaction can in particular be carried out in an anhydrous solvent, in particular an anhydrous aprotic solvent, for example dimethyl sulfoxide (DMSO).This reaction can be carried out at a temperature of 15 to 80°C, in particular 20 to 60°C, and / or for a time of 30 minutes to 24 hours, in particular 1 to 10 hours. When the -OH group is a silanol, in particular of an optical fiber of an optical fiber, this reaction can in particular be carried out at a temperature of 15 to 30°C, in particular 20 to 25°C, and / or for a time of 30 minutes to 2 hours, in particular 1 hour.

[0044] The NH-C(=O)- or -C(=O)-NH- group may be formed by any method well known to those skilled in the art, in particular by bringing a compound bearing a -COOH group (carboxylic acid) into contact with a compound bearing a -N=C=O group (isocyanate), in particular in the presence of a catalyst, in particular chosen from triethylamine, 1,4-diazabicyclo[2,2,2]octane (DABCO), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), dibutyltin dilaurate (DBTDL), 1,8-diazabicylo[5,4,0]undec-7-ene (DBU), 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), di-isopropylethylamine (DIPEA), 4-dimethylaminopyridine (DMAP), 1,8-bis(dimethylamino)naphthalene (DMAN), for example triethylamine. This reaction can in particular be carried out in an anhydrous solvent, in particular an anhydrous aprotic solvent, for example dimethyl sulfoxide (DMSO).This reaction can be carried out at a temperature of from 15 to 80°C, in particular from 20 to 60°C, and / or for a period of from 30 minutes to 24 hours, in particular from 1 to 10 hours.

[0045] According to another aspect, the invention also relates to a method for preparing an optical fiber as defined above, comprising the following step: (i) Contacting at least part of the surface of an optical fiber carrying -OH, -NH 2 or -COOH groups with: a compound (A) of the following formula: in which X, Y, j, Z and R are as defined above, and a compound (A') of the following formula: in which X', Y', j', Z' and R' are as defined previously.

[0046] By "optical fiber carrying -OH, -NH 2 or -COOH groups" is meant in particular that the optical fiber directly carries -OH, -NH 2 or -COOH groups on its surface, or that the fiber is functionalized by groups themselves carrying one or more -OH, -NH 2 or -COOH groups.

[0047] When the optical fiber carries -OH groups, i = 1 and W represents -O-.

[0048] When the optical fiber carries -NH2 groups, i = 1 and W represents -NH-.

[0049] When the optical fiber carries -COOH groups, i = 0.

[0050] According to a particular embodiment, the optical fiber according to the present invention is chosen from mineral optical fibers, in particular silica optical fibers, with i = 1 and W representing O, or optical fibers carrying an oxide layer chosen from TiO 2 , ZrO 2 , SnO 2 or HfO 2 , preferably modified by a compound comprising a phosphonic acid group as well as a primary amine, in particular a compound of formula (HO) 2 P(=O)-(CH 2 ) x NH 2 with x = 2, 3 or 4, with i = 1 and W representing N; organic optical fibers, in particular fibers made of or comprising polymethyl methacrylate (PMMA), optionally partially chlorinated polymethyl methacrylate, said polymethyl methacrylate optionally carrying carboxylic acid groups, with i = 0; and optical fibers carrying chains of functional oligomers, in particular chains of PVA, optionally partially acetylated, with i = 1 and W representing O.

[0051] According to another aspect, the invention also relates to a method for preparing an optical fiber as defined above, comprising, when W=W', i=i' and X=X', the following steps: (i') bringing at least part of the surface of an optical fiber carrying -OH, -NH 2 or -COOH groups into contact with a compound (B) of the following formula: [Chem 21] O=C=NXN=C=O (B), in which X is as defined previously, to obtain an optical fiber carrying on at least part of its surface a plurality of groups of the following formula (C): in which W, i and X are as defined previously, (ii') bringing the fiber obtained in the previous step (i') into contact with: a compound of the following formula (D): in which Z and R are as defined above, and in which Y' is: a -NH 2 group when j = 1 and Y is -NH-; a -OH group when j = 1 and Y is -O-; a -COOH group when j = 0; and a compound of the following formula (D'): in which Z' and R' are as defined above, and in which Y" is: a -NH 2 group when j' = 1 and Y' is -NH-; a -OH group when j' = 1 and Y' is -O-; a -COOH group when j' = 0.

[0052] By "optical fiber carrying -OH, -NH 2 or -COOH groups" is meant in particular that the optical fiber directly carries -OH, -NH 2 or -COOH groups on its surface, or that the fiber is functionalized by groups themselves carrying one or more -OH, -NH 2 or -COOH groups.

[0053] When the optical fiber carries -OH groups, i = 1 and W represents -O-.

[0054] When the optical fiber carries -NH2 groups, i = 1 and W represents -NH-.

[0055] When the optical fiber carries -COOH groups, i = 0.

[0056] The steps defined above are optionally carried out in the presence of a catalyst, in particular chosen from triethylamine, 1,4-diazabicyclo[2,2,2]octane (DABCO), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), dibutyltin dilaurate (DBTDL), 1,8-diazabicylo[5,4,0]undec-7-ene (DBU), 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), di-isopropylethylamine (DIPEA), 4-dimethylaminopyridine (DMAP), 1,8-bis(dimethylamino)naphthalene (DMAN), for example triethylamine, preferably when a urethane or amide group is formed.

[0057] The steps defined above are in particular carried out in an anhydrous solvent, in particular an anhydrous aprotic solvent, for example dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), 1,4-dioxane, acetone.

[0058] The steps defined above are in particular carried out at a temperature of 15 to 80°C, in particular 20 to 60°C, and / or for a duration of 30 minutes to 24 hours, in particular 1 to 10 hours.

[0059] According to a particular embodiment, the compounds of formula (A) and the compounds of formula (A') are, during step (i), brought into contact with said at least one part of the surface of an optical fiber simultaneously.

[0060] According to a particular embodiment, the compounds of formula (A) and the compounds of formula (A') are, in the context of step (i), in stoichiometric proportions.

[0061] According to a particular embodiment, a composition comprising the compounds of formula (A) and the compounds of formula (A'), in stoichiometric proportions, and optionally in addition, a solvent, is, during step (i), brought into contact with said at least one part of the surface of an optical fiber.

[0062] The compounds of formula (A), brought into contact with the compounds of formula (A'), in particular in stoichiometric proportions, form with the latter complexes (ionic intermediates) between the probe of a compound of formula (A) and the organic cation of a compound of formula (A').

[0063] These intermediate complexes are likely to allow the automatic positioning of the organic cation not far from the probe after grafting onto the optical fiber.

[0064] According to a particular embodiment, the compounds of formula (D) and the compounds of formula (D') are, during step (ii'), brought into contact with said at least one part of the surface of an optical fiber simultaneously.

[0065] According to a particular embodiment, the compounds of formula (D) and the compounds of formula (D') are, in the context of step (ii'), in stoichiometric proportions.

[0066] According to a particular embodiment, a composition comprising the compounds of formula (D) and the compounds of formula (D'), in stoichiometric proportions, and optionally in addition, a solvent, is, during step (ii'), brought into contact with said at least one part of the surface of an optical fiber.

[0067] According to another aspect, the invention also relates to a method for preparing an optical fiber as defined above, comprising the following steps: (i") bringing at least part of the surface of an optical fiber carrying -OH, -NH 2 or -COOH groups into contact with a compound (B) of the following formula: [Chem 25] O=C=NX a -N=C=O (B), in which X a is as defined previously, to obtain an optical fiber carrying on at least part of its surface a plurality of groups of the following formula (C): in which W, i and X a are as defined previously, (ii") bringing the fiber obtained in the previous step (i') into contact with: a compound of the following formula (D"): Where Q is NH 2 , OH or COOH, and X b is as defined previously, (iii") bringing the fiber obtained in the previous step (ii') into contact with: a compound of the following formula (III o): and a compound of formula (III o ') following: X c , X c ', Y, Y', j, j', Z, Z', R and R' being as defined above or below.

[0068] According to another aspect, the invention also relates to the use of an optical fiber as defined above, for measuring the concentration of a monovalent ion, in particular of an alkali metal ion, more particularly of lithium ion.

[0069] According to a particular embodiment, the present invention relates to a use as defined previously, for measuring the lithium ion concentration in a Li-ion battery, in particular within the electrolyte of said battery.

[0070] According to another aspect, the invention also relates to a method for measuring the concentration of a monovalent ion, in particular an alkali metal ion, more particularly lithium ion, comprising the following steps: (i) A step of bringing groups A and B carried by at least part of the surface of the optical fiber as defined previously into contact with the medium in which the monovalent ion concentration is to be measured; (ii) A step of excitation by transmission of light in said optical fiber; (iii) A step of measuring the fluorescence emitted and transmitted by said optical fiber.

[0071] According to a particular embodiment, in which the light of step (ii) is UV light or violet visible light, and in particular has a wavelength of from 350 to 450 nm.

[0072] The presence of one or more urea functions, in particular aliphatic or linked to aromatic or heteroaromatic cycles, urethane linked to aromatic or heteroaromatic cycles and / or amide linked to aromatic or heteroaromatic cycles, by virtue of their own fluorescence, makes it possible to generate a reference peak during fluorescence, insensitive to the presence or absence of lithium.

[0073] When said at least one part of the surface is for example located at the end of the fiber, the fluorescence measurement can be done by reflectance ( figure 1 , case 1).

[0074] When said at least part of the surface is for example located along the fiber, evanescent wave measurement points can be created. In this case, the measurement can be made by transmittance through the fiber, the excitation being sent to one end and the measurement being made at the other end. It is also possible to make a measurement by reflectance, but in this case, it is preferable to add a reflective deposit at the end of the fiber in order to maximize the reflectance ( figure 1 , case 2). Definitions

[0075] As used herein, the value ranges of "xy" or "from x to y" or "between x and y" include the bounds x and y as well as the integers between these bounds. For example, "1-5", or "from 1 to 5" or "between 1 and 5" denote the integers 1, 2, 3, 4 and 5. Preferred embodiments include each individual integer in the value range, as well as any subcombination of these integers. For example, preferred values ​​for "1-5" may include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, etc.

[0076] As used herein, the term "alkyl" means a straight or branched chain, especially straight, alkyl group having the number of carbon atoms indicated before said term, especially 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, etc. Thus, a term such as "C1-C3 alkyl" means an alkyl radical containing from 1 to 3 carbon atoms.

[0077] The same is true for the term "alkane".

[0078] By "diyl" is meant in particular a residue linked to two groups by a single bond between the residue and each of these two groups.

[0079] As used herein, the term "arene" means a mono- or bicyclic, substituted or unsubstituted, hydrocarbon aromatic ring system having 6 to 10 carbon atoms in the ring. Examples include benzene and naphthalene. Preferred arenes include unsubstituted or substituted benzene and naphthalene. Included within the definition of "arene" are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a cycloalkyl ring. Examples of such fused ring systems include, for example, indane, indene, and tetrahydronaphthalene.

[0080] As used herein, the term "heteroarene" means a cyclic aromatic system containing 5 to 10 carbon atoms in which one or more ring carbon atoms are replaced by at least one heteroatom such as -O-, -N- or -S-, particularly -N- and / or -O-. Examples of heteroarenes include pyrrole, furan, thiophene, pyrazole, imidazole, thiazole, isothiazole, isoxazole, oxazole, oxathiol, oxadiazole, triazole, oxatriazole, furazane, tetrazole, pyridine, pyrazine, pyrimidine, pyridazine, triazine, indole, isoindole, indazole, benzofuran, isobenzofuran, purine, quinazoline, quinoline, isoquinoline, benzoimidazole, benzothiazole, benzothiophene, thianaphthene, benzoxazole, benzisoxazole, cinnoline, phthalazine, naphthyridine and quinoxaline. Included in the definition of "heteroarene" are fused ring systems, including, for example, ring systems in which an aromatic ring is fused to a heterocycloalkyl ring.Examples of such fused ring systems include, for example, phthalamide, phthalic anhydride, indoline, isoindoline, tetrahydroisoquinoline, chromane, isochromane, chromene, and isochromene. FIGURES

[0081] There figure 1 corresponds to the fluorescence measurements using an optical fiber according to the invention as described in example 3. EXAMPLES

[0082] Example 1: Preparation of a functionalized silica optical fiber according to the invention The density of silanol groups on the surface of a glass can be estimated at 5 groups per square nm. It can also be estimated that generally, approximately 10% of these sites are likely to be grafted.

[0083] Thus, the concentration of the reagents to be used can be determined by knowing the section of the optical core of the glass fiber to be functionalized.

[0084] Generally, syntheses are carried out in anhydrous DMSO. Still generally, anything that is not grafted by a covalent bond is removed by rinsing in DMSO, then by rinsing in an ethylene carbonate / diethylene carbonate mixture. These rinses remove all impurities adsorbed on the surface of the optical fiber.

[0085] The hydroxylated surfaces were first dehydrated. This can be done, for example, at 150°C in anhydrous DMSO under argon sparging. 2 hours are generally sufficient to remove the water.

[0086] In addition, in 50 ml of anhydrous DMSO, 0.1 molar of 4-aminopyridine and then 0.1 molar of hexane diisocyanate are added. The reaction medium is left stirring for 3 hours at 50°C. At room temperature, 0.1 molar of a 1M solution of HCl in ethyl ether is added to form the pyridinium cation. The ethyl ether is evaporated at 50°C under a stream of argon.

[0087] Furthermore, in 50 ml of anhydrous DMSO, 0.1 molar of 3,4-dihydroxy-L-Phenylalanine is added, then 0.1 molar of hexane diisocyanate. The reaction medium is left stirring for 3 hours at 50°C.

[0088] Alternatively: in 50ml anhydrous DMSO, 0.1 molar of dopamine hydrochloride is added. The mixture is then transferred onto an inversion frit containing 1.5g of NaOH pearl (Alfa Aesar) previously dried for 5 hours under primary vacuum at 50°C and conditioned under argon. The solution is left for 5 minutes in contact with the sodium hydroxide and then filtered. The filtrate obtained contains, in the anhydrous DMSO, dopamine. The filtrate is stored away from light, then 0.08 molar of hexane diisocyanate is added. The reaction medium is then left stirring for 3 hours at 50°C; in 50ml of anhydrous DMSO, 0.1 molar of caffeic acid is added, then 0.1 molar of hexane diisocyanate and 0.01 molar of triethylamine. The reaction medium is then left stirring for 5 hours at 50°C.

[0089] Finally, 1 / 2 molar of the organic cation graft and 1 / 2 molar of a catechol graft are added in pure DMSO, before contacting with the surface prepared as indicated above to obtain the product of the invention.

[0090] Example 2: Preparation of another functionalized silica optical fiber according to the invention The hydroxylated surfaces of the optical fiber were first dehydrated. This can be done, for example, at 150°C in anhydrous DMSO under argon scavenging. 2 hours are generally sufficient to remove the water.

[0091] This fiber is soaked in 20 ml of a 0.1 M anhydrous DMSO solution of hexane diisocyanate, 1 ml of triethylamine is added to the anhydrous DMSO. The fiber is left in the reactive medium for 3 hours at 50°C. The grafted fiber is washed thoroughly with anhydrous DMSO to remove the ungrafted products.

[0092] The fiber is stored in anhydrous DMSO for the next step.

[0093] The grafted fiber is soaked in 20 ml of a 0.1 M solution of 1,3,5-triamine-2,4,6-triamine in anhydrous DMSO. The fiber is left in the reactive medium for 3 hours at 50 ° C. The grafted fiber is washed thoroughly with anhydrous DMSO to remove ungrafted products. The fiber is stored in anhydrous DMSO for the next step.

[0094] In parallel, a 0.1M solution of pyridinium cation in anhydrous DMSO was prepared (the description of the synthesis of the pyridinium cation is given in Example 1) and a 0.1M solution of caffeic acid carrying a reactive isocyanate in anhydrous DMSO (the description of the synthesis of caffeic acid carrying a reactive isocyanate is also given in Example 1). A mixture was made by taking 10 ml of each of the solutions. The fiber carrying a pendant melamine graft was immersed for 3 h at 50 ° C in the mixture.

[0095] The grafted fiber is washed thoroughly with anhydrous DMSO to remove ungrafted products.

[0096] Then it is washed again with a mixture of anhydrous organic carbonates and finally stored in this medium.

[0097] The fibers functionalized as follows were obtained according to this procedure: Example 3: Fluorescence measurements

[0098] Fluorescence measurements, emission spectrum and excitation spectrum, were recorded with a Horiba Jobin Yvon model Fluorolog-3 model FL3-22 spectrometer having the R928 Hamamatsu detector and a 450W Xenon lamp as excitation source.

[0099] The emission spectrum is obtained by exciting the sample with an absorbed wavelength, usually the absorption (or excitation) peak of maximum intensity. The emission monochromator scans the luminescence over a wavelength interval. The most important parameters are i) the excitation wavelength and ii) the slit width. The emission spectra were corrected for the spectral response of the monochromators and detector, using typical correction spectra provided by the manufacturer.

[0100] The excitation spectrum is measured by fixing the emission monochromator at a given emission wavelength (e.g., the one corresponding to the maximum of the emission spectrum). The excitation monochromator is then scanned in a given wavelength interval and the luminescence intensity corresponding to the monitored emission wavelength is measured. The most important parameters are i) the monitoring wavelength and ii) the slit width. The excitation spectra were corrected from 240 to 600 nm for the spectral distribution of the lamp intensity using a silicon photodiode reference detector.

[0101] To assess the sensor's sensitivity to lithium concentration, the emission and excitation spectra of the probe molecule in solution (EC+DEC) were measured. This is a reference measurement. Then, different concentrations of lithium in solution (EC+DEC+LiPF6) were added to the reference / initial solution and the emission and excitation spectra were recorded for each concentration.

[0102] For the dopamine-based probe, the emission spectrum was measured by exciting at a wavelength of 320 nm and with 1.5 mm slits for the emission spectrometer and 0.3 mm slits for the excitation spectrometer. The excitation spectrum was measured by monitoring at a wavelength of 360 nm and with 0.4 mm slits for the emission spectrometer and 0.8 mm slits for the excitation spectrometer.

[0103] For the melanin-based probe the emission spectrum was measured by exciting at a wavelength of 350 nm and with 1.5 mm slits for the emission spectrometer and 0.3 mm slits for the excitation spectrometer.

[0104] This example was obtained with optical fibers with grafting of probe molecules at the end of the fiber, for a measurement by reflectance, as presented in particular in figure 1 , case 1.

[0105] It is also possible to graft molecules along the fiber on areas where the cladding has been removed in order to create evanescent wave measurement points, as presented in particular in figure 1, case 2. In this case, the measurement is made by transmittance through the fiber. The excitation is sent to one end and the measurement is made at the other end. It is also possible in case 2 to make a measurement by reflectance, but in this case it is preferable to add a reflective deposit at the end of the fiber in order to maximize the reflectance.

Claims

1. An optical fiber carrying on at least part of its surface a plurality of groups A and a plurality of groups B, the groups A bearing a group R being an aryl or heteroaryl group substituted by at least two vicinal groups selected from -OH and C1-C3 alkoxy groups, in particular -OMe, said vicinal groups being more particularly -OH, the groups B bearing a group R' being an organic cation.

2. The optical fiber according to claim 1, wherein: - the plurality of groups A and the plurality of groups B are directly carried by said at least part of its surface; or - the groups A are substituted by at least one group B, in particular a group B.

3. The optical fiber according to any one of the preceding claims, wherein: - the group R is selected from the following groups: and / or - the group R' is chosen from quaternary ammoniums and heteroaromatic cations, in particular aza-heteroaromatic cations, the group R' being chosen in particular from the following groups: wherein: G- represents an anion PF6-, a triflimidate anion ([(CF3SO2)2N]-) or a halogenated anion, for example Cl-, G being preferably PF6-; R" represents a C1-C3 alkyl, in particular methyl.

4. The optical fiber according to any one of the preceding claims, wherein the groups A and / or B are chains bearing the group R or R' respectively, particularly in the terminal position, these chains being independently selected from linear or branched alkyl or alkenyl chains, which are optionally interrupted by one or more atoms or groups selected from -NH-, O, S, urea, urethane, amide, ester, arene diyls and heteroarene diyls.

5. The optical fiber according to any one of the preceding claims, wherein the groups (A) are of the following formula (I), and the groups (B) are of the following formula (I'): wherein: W, W', Y and Y' are independently selected from O and NH; i, i', j and j' are independently selected from 0 and 1; X represents a group of the following formula (II): X' represents a group of the following formula (II'): wherein: k and k' are independently selected from 0 and 1; Xa, Xa', Xc and Xc' are independently selected from: - the groups Xa1 being linear and branched C1-C12 alkanediyls, in particular the groups of the formula -(CH2)n- with n from 1 to 12, or linear and branched C2-C12 alkenediyls, the groups Xa1 being in particular linear and branched C1-C12 alkanediyls; - the groups of formula -Xa1-NH-Xa1-, wherein Xa1 is at each occurrence independently as defined above, in particular the groups of formula -(CH2)n-NH-(CH2)m- with n and m being independently from 1 to 12; - the groups of formula -Xa1-NHC(=O)-NH-Xa1- or -Xa1-NHC(=O)-NH-Xa1-NHC(=O)-NH-Xa1-, wherein Xa1 is at each occurrence independently as defined above, in particular groups of formula -(CH2)n-NHC(=O)-NH-(CH2)m- with n and m being independently from 1 to 12; Xb and Xb' are independently selected from: - the linear and branched C1-C12 alkanediyls, in particular groups of the formula -(CH2)n- with n from 1 to 12, branched C1-C12 alkanetriyls, and linear and branched C2-C12 alkenediyls, the groups Xb and Xb' being in particular linear and branched C1-C12 alkanediyls or triyls; optionally bearing, especially in terminal position(s), at least one -(O-CH2-CH2)p- or -(O-CH2-C(CH3)H)p- group, with p being an integer from 1 to 10; - the arene diyls and heteroarene diyls; Xb being optionally substituted by a group A of the following formula (III): Xc, Y, j, Z and R being as defined above or below, Xb' being optionally substituted by a group A of the following formula (III'): Xc', Y', j', Z' and R' being as defined above or below, Z and Z' being independently absent or selected from linear and branched C1-C12 alkane diyls and linear and branched C2-C12 alkene diyls, Z being in particular a linear C2 alkane or alkene diyl, said group Z being optionally substituted with a -COOH group; R and R' are as defined in claim 1, said optical fiber being in particular an optical fiber in which: - the groups of formula (I) are chosen from groups of the following formula : and / or the groups of formula (I') are chosen from groups of the following formula:

6. The optical fiber according to any one of the preceding claims, wherein the groups of formula (I) and the groups of formula (II) together form a group of the following formula: wherein: W and Y are independently selected from O and NH; i and j are independently selected from 0 and 1; X represents a group of the following formula (II): wherein: k is chosen from 0 and 1; Xa and Xc are independently selected from: - the groups Xa1 being linear and branched C1-C12 alkanediyls, in particular groups of the formula -(CH2)n- with n from 1 to 12, or linear and branched C2-C12 alkenediyls, the groups Xa1 being in particular linear and branched C1-C12 alkanediyls; - the groups of formula -Xa1-NH-Xa1-, wherein Xa1 is at each occurrence independently as defined above, in particular groups of formula -(CH2)n-NH-(CH2)m- with n and m being independently from 1 to 12; - the groups of formula -Xa1-NHC(=O)-NH-Xa1- or -Xa1-NHC(=O)-NH-Xa1-NHC(=O)-NH-Xa1-, wherein Xa1 is at each occurrence independently as defined above, in particular the groups of formula -(CH2)n-NHC(=O)-NH-(CH2)m- with n and m being independently from 1 to 12; Xb is selected from: - linear and branched C1-C12 alkanediyls, in particular groups of the formula -(CH2)n-with n from 1 to 12, branched C1-C12 alkanetriyls, and linear and branched C2-C12 alkenediyls, the groups Xb and Xb' being in particular linear and branched C1-C12 alkanediyls or triyls; optionally bearing, especially in terminal position(s), at least one -(O-CH2-CH2)p- or -(O-CH2-C(CH3)H)p- group, with p being an integer from 1 to 10; - the arene diyls and heteroarene diyls; Xb being optionally substituted by a group A of the following formula (III): Xc, Y, j, Z and R being as defined above or below, Z is absent or selected from linear and branched C1-C12 alkane diyls and linear and branched C2-C12 alkene diyls, Z being in particular a linear C2 alkane or alkene diyl, said group Z being optionally substituted by a -COOH group; R is an aryl or heteroaryl group substituted with at least two vicinal groups selected from -OH and the C1-C3 alkoxy groups, in particular -OMe, one of the atoms of the groups of formula (I) bearing a group B as defined in claim 1, this group B being in particular carried by an atom of group X, in particular Xb, of the groups of formula (I), said optical fiber being in particular an optical fiber wherein the groups of formula (I) and the groups of formula (II) together form a group of the following formula:

7. The optical fiber according to claim 5 or 6, wherein: - (Y)jZR is selected from the following groups: and in particular from the following groups and / or (Y')j'Z'R' is selected from the following groups: wherein: G' represents a PF6- anion, a triflimidate anion ([(CF3SO2)2N]-) or a halogenated anion, for example Cl-, G preferably being PF6-; R" represents C1-C3 alkyl, in particular methyl.

8. The optical fiber according to any one of claims 5 to 7, wherein Xb and / or Xb' are selected from the following groups: A and p being as defined in claim 5.

9. The optical fiber according to any one of the preceding claims, which is selected from inorganic optical fibers, in particular silica optical fibers, or optical fibers bearing an oxide layer selected from TiO2, ZrO2, SnO2 or HfO2, preferably modified with a compound comprising a phosphonic acid group as well as a primary amine, in particular a compound of formula (HO)2P(=O)-(CH2)xNH2 with x = 2, 3 or 4; the organic optical fibers, in particular fibers made of or comprising polymethyl methacrylate (PMMA), optionally partially chlorinated polymethyl methacrylate, said polymethyl methacrylate optionally carrying carboxylic acid groups; and optical fibers carrying functional oligomer chains, in particular PVA chains, optionally partially acetylated, said optical fiber being in particular selected from inorganic optical fibers, more particularly silica optical fibers, with i = 1 and W representing O, or optical fibers bearing an oxide layer selected from TiO2, ZrO2, SnO2 or HfO2, preferably modified with a compound comprising a phosphonic acid group as well as a primary amine, in particular a compound of formula (HO)2P(=O)-(CH2)xNH2 with x = 2, 3 or 4, with i = 1 and W representing N ; the organic optical fibers, in particular the fibers consisting of or comprising polymethyl methacrylate (PMMA), optionally partially chlorinated polymethyl methacrylate, said polymethyl methacrylate optionally carrying carboxylic acid groups, with i = 0; and optical fibers carrying functional oligomer chains, in particular PVA chains, optionally partially acetylated, with i = 1 and W representing O.

10. A method of preparing an optical fiber according to any one of the preceding claims, comprising the following step of: i) Contacting at least part of the surface of an optical fiber carrying groups of -OH, -NH2 ou -COOH, with: - a compound (A) of the following formula: wherein X, Y, j, Z and R are as defined in claim 1, and - a compound (A') of the following formula: wherein X', Y', j', Z' and R' are as defined in claim 1, or, when W=W', i=i' and X=X', the following steps: (i') contacting at least part of the surface of an optical fiber bearing groups -OH, -NH2 or -COOH, with a compound (B) of the following formula: [Chem 50]         O=C=N-X-N=C=O     (B), wherein X is as defined in claim 1, to obtain an optical fiber carrying on at least part of its surface a plurality of groups of the following formula (C): wherein W, i and X are as defined in claim 1, (ii') contacting the fiber obtained in the previous step (i') with: - a compound of the following formula (D): wherein Z and R are as defined in claim 1, and wherein Y' is: - a -NH2 group when j = 1 and Y is -NH-; - an -OH group when j = 1 and Y is -O-; - a -COOH group when j = 0; and - a compound of the following formula (D'): wherein Z' and R' are as defined in claim 1, and where Y" is : - an -NH2 group when j' = 1 and Y' is -NH-; - an -OH group when j' = 1 and Y' is -O-; - a -COOH group when j' = 0; or (i") contacting at least part of the surface of an optical fiber carrying -OH, -NH2 or - COOH groups, with a compound (B) of the following formula: [Chem 54]         O=C=N-Xa-N=C=O     (B), wherein Xa is as defined above, to obtain an optical fiber carrying on at least part of its surface a plurality of groups of the following formula (C): wherein W, i and Xa are as defined above, (ii") contacting the fiber obtained in the previous step (i') with: - a compound of the following formula (D"): where Q is NH2, OH or COOH, and Xb is as defined above, (iii") contacting the fiber obtained in the previous step (ii') with: - a compound of the following formula (IIIo): - and a compound of the following formula (IIIo') : Xc, Xc', Y, Y', j, j', Z, Z', R and R' being as defined above.

11. A use of an optical fiber according to any one of claims 1 to 9, for measuring the concentration of a monovalent ion, in particular an alkali metal ion, more particularly a lithium ion, in particular in a Li-ion battery, preferably within the electrolyte of said battery.

12. A method for measuring the concentration of a monovalent ion, in particular an alkali metal ion, more particularly a lithium ion, comprising the following steps: i) A step of contacting the groups A and B carried by at least part of the surface of the optical fiber according to any one of claims 1 to 9 with the medium in which the monovalent ion concentration is to be measured; ii) A step of excitation by transmission of light, in particular UV light of visible violet light, more particularly of wavelength between 350 and 450 nm, in said optical fiber; iii) A step for measuring the fluorescence emitted and transmitted by said optical fiber.