Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/24—Alkaline accumulators
  • H01M10/26—Selection of materials as electrolytes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C245/00—Compounds containing chains of at least two nitrogen atoms with at least one nitrogen-to-nitrogen multiple bond
  • C07C245/20—Diazonium compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/54—Electrolytes
  • H01G11/58—Liquid electrolytes
  • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0568—Liquid materials characterised by the solutes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/13—Energy storage using capacitors

Definitions

• Aryl diazonium salt and use in an electrolytic solution of an electrochemical generator Aryl diazonium salt and use in an electrolytic solution of an electrochemical generator
• the invention relates to a diazonium salt and its use in an electrolytic solution of an electrochemical generator.
• Electrochemical generators include accumulators and supercapacitors.
• An accumulator is defined as an energy storage system, using electrochemical reactions to store and restore electrical energy.
• Li-ion batteries generally use electrolytes based on organic solvents containing a dissolved lithium salt.
• a supercapacitor is an electrochemical capacitor for storing a quantity of energy via surface adsorption reactions of the electrode materials and for restoring a power density, intermediate between the batteries and the conventional electrolytic capacitors.
• Electrochemical generators in particular lithium-ion batteries, using aqueous electrolytes are, however, beginning to develop.
• An aqueous electrochemical accumulator is conventionally composed of a positive electrode and a negative electrode, a porous separator ensuring the electronic insulation between the electrodes, positive and negative, of a water-based electrolyte in which is dissolved one or more salts providing the ionic conductivity.
• the salts commonly used are, for example, H 2 SO 4 for lead accumulators, a KOH-LiOH-NaOH mixture for alkaline storage batteries and a lithium salt. such as LiNO 3 , Li 2 SO 4 , LiOH for lithium aqueous accumulators.
• the electrolyte impregnates all or part of the porosity of the electrodes and the separator.
• Each of the positive and negative electrodes is composed of an active material, positive and negative respectively, of an electronic conductor such as carbon black and carbon fibers, a thickener and a binder.
• An aqueous super capacitor is conventionally composed of two porous electrodes, integrating either high surface area activated carbon type compounds or transition metal oxides of the MnO 2 , RuO 2 , Li 4 Ti 5 O 12 , TiO 2 type , a porous separating membrane between the two electrodes, an aqueous electrolyte in which is dissolved one or more salts ensuring the ionic conductivity such as KOH, H 2 SO 4 , KNO 3 , LiNO 3 , NaSO 4 .
• the performance of the electrochemical generators may be affected by instability phenomena of the organic or aqueous liquid electrolyte during operation of the accumulator.
• the electrolyte must effectively withstand the operating voltage of the accumulator which is between 1, 9V and 5 V depending on the pair of electrodes used for organic electrolytes and between 1, 2V and 2V for aqueous electrolytes.
• the operating voltage of the accumulator which is between 1, 9V and 5 V depending on the pair of electrodes used for organic electrolytes and between 1, 2V and 2V for aqueous electrolytes.
• parasitic reactions of decomposition of the catalyzed electrolyte on the surface of the electrodes are observed.
• the window of thermodynamic stability of the water as a function of the pH is 1.23 V and considerably limits the choice of active materials for such an electrochemical generator.
• the electrochemical decomposition of the water In the absence of overvoltage phenomenon, the oxidation of the water on the positive electrode is observed for potentials located above the line represented by a broken line (at the top in FIG. observe the reduction of the water on the negative electrode for potentials located below the line represented by a dashed line (bottom in Figure 1). Overvoltage phenomena related to oxidation and water reduction are low on lithium insertion materials.
• JP-A-2000340256 and JP-A-2000077073 exploit electrode surges to control interfacial reactions.
• Another proposed solution consists of passivating at least one electrode of the lithium-ion accumulator in order to inhibit the degradation of the liquid electrolyte.
• the document US-A-20090155696 proposes to produce an insulating film on the electrode, by polymerization of a monomer present in the electrolyte of the accumulator.
• Another way is to form a protective layer on the surface of an electrode by grafting via an electrochemical process of the aromatic group an aryl diazonium salt for modifying or improving the physico-chemical properties of the electrode material.
• R is a substituent of the aryl group
• X is an anion such as a halide or BF 4 " ion
• C is carbon
• SC is a semiconductor
• M is a metal.
• the grafting by electrochemical reduction of the diazonium salt to the surface of the positive electrode Li] jV 3 0 8 takes place when a potential imposed on the electrode less than the reduction potential of the diazonium salt.
• the presence of an organic layer obtained by such a process does not limit the charge transfer of the electrode and strongly inhibits the decomposition of the catalyzed organic electrolyte on the surface of the electrode.
• the object of the invention is to propose an alternative to the known diazonium salt.
• Another object of the invention is to provide an improved electrolytic solution for an electrochemical generator, in particular overcoming the drawbacks of the prior art.
• the object of the invention is to provide an aqueous electrolyte solution for a lithium-ion battery which is stable up to a high operating voltage and has a larger stability window as a function of pH than aqueous electrolytic solutions.
• a lithium-ion battery of the prior art a lithium-ion battery of the prior art.
• FIG. 1 corresponds to a water stability diagram representing the nominal voltage of the water as a function of the pH as well as the insertion and de-insertion potentials of various active materials of lithium-ion battery electrode.
• FIG. 3 represents the superposition of three spectra obtained according to a Total Attenuated Reflection (ATR) method, of a sample of a diazonium salt according to the invention, denoted DS 3 , of a sample of a LiFePC electrode. covered with a passivation layer according to the invention, denoted D 1; and a comparative sample of a bare LiFePO 4 electrode , denoted D 0 .
• ATR Total Attenuated Reflection
• FIG. 4 represents the superposition of three infrared spectra obtained according to an ATR method, a sample of a diazonium salt, denoted S 2 , and two comparative samples, respectively, of the bare electrode D 0 and a electrode passivated with salt S 2 , denoted D 2 .
• FIG. 5 represents three cyclic voltammetry curves obtained for an electrochemical cell comprising, respectively, the electrode D 0 , ⁇ ) ⁇ and D 2 in an aqueous electrolyte L1NO3 5M. Description of particular embodiments.
• Initial electrolytic solution of an electrochemical generator is understood to mean an electrolytic solution present in the electrochemical generator before the first charge of this generator. Initial electrolytic solutions containing such salts are more stable than those of the prior art and contribute to improving the performance of the generator, in particular, a lithium-ion battery.
• the diazonium salt has the following general formula (1):
• n is an integer between 1 and 10, preferably between 1 and 4,
• X " represents a counterion of the diazonium cation chosen from halides, BF 4 " ,
• R 1 is selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic
• R 2 is selected from the group consisting of -CH 2 - an alkyl chain preferably comprising from 2 to 6 carbon atoms, linear or branched, cyclic or acyclic, preferably a methylene-, ethylene-, n-propylene-, iso-propylene-, n-butylene- tert-butylene, sec-butylene and n-pentylene,
• R 3 is selected from the group consisting of -CH 3 , an alkyl chain preferably comprising from 2 to 6 carbon atoms, linear or branched, cyclic or acyclic and a group of formula (2) below:
• a ' is an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted,
• R is selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, cyclic or acyclic, and
• A is identical to or different from A 'and represents an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted, with the exception of the group of formula (3 ), shown below, when R 3 is selected from the group consisting of -CH 3 , an alkyl chain, linear or branched, cyclic or acyclic:
• R 5 and 3 ⁇ 4 are identical or different and independently selected from the group consisting of -CH 3 , an alkyl group, linear or branched, cyclic or acyclic.
• aryl group an aromatic system having one or more aromatic rings, optionally substituted.
• a and / or A ' is an aryl group
• an aryl group comprising from 6 to 9 carbon atoms, for example a phenyl, tolyl, xylyl or trimethylphenyl group
• the diazonium function is carried on the aromatic ring of the aryl group.
• condensed polyaromatic group is meant a polycyclic aromatic system formed of several fused benzene rings.
• the diazonium function can be carried on any of the aromatic rings of the condensed polyaromatic group.
• a and / or A ' is a fused polyaromatic group
• a polyaromatic group comprising from 10 to 45 carbon atoms, optionally substituted with one or more groups selected from the group consisting of -H, -CH3, will preferably be chosen, a halide, a linear or branched alkyl chain comprising from 2 to 8 carbon atoms and, optionally, one or more heteroatoms chosen from O, S and N.
• the diazonium salt is free of hydroxyl functions so as to minimize the affinity of the diazonium salt with the water of the electrolytic solution, for example, by avoiding the creation of Van der Waals and / or hydrogen bonds.
• R ls R 2 and R 3 are advantageously free of hydroxyl functions in order to obtain a diazonium salt having a non-polar part A and A 'containing the aromatic hydrocarbon group and a polar portion, aprotic, consisting of a polyether chain.
• a and A ' may be identical or different and selected from phenyl, anthracenyl and naphthalenyl groups, optionally substituted, preferably with one or more groups selected from the group consisting of -H, -CH 3 , a halide, a linear or branched alkyl chain comprising 2 and 8 carbon atoms and, optionally, one or more heteroatoms chosen from O, S and N.
• the diazonium salt may advantageously be a bis-diazonium salt of formula (1) in which R 3 is a group of formula (2).
• the diazonium salt may, for example, be a bis-diazonium salt of the following general formula (4):
• n is an integer between 1 and 10, preferably between 1 and 4,
• n 0 or 1
• p is an integer between 1 and 5, advantageously equal to 2,
• X " and Y " are identical or different and represent, independently, a counter-ion of the diazonium cation chosen from halides, BF 4 ⁇ , N0 3 " , HSO 4 " , PF 6 “ , CH 3 COO ⁇ N (SO 2 CF 3 ) 2 " , CF 3 SO 3 " , CH 3 SO 3 CF 3 COO (CH 3 0) (H) PO 2 N (CN) 2 " , R 1 and R 4 are the same or different and independently selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic,
• R 7 and R 8 are identical or different and independently selected from the group consisting of -H, -CH 3 , a halide, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, optionally containing a or more heteroatoms, advantageously chosen from O, S and N.
• the bis-diazonium salt advantageously has a polyether chain which makes it possible to solvate the cations, in particular the Li + ions.
• the polyether chain is advantageously a poly (oxyethylene).
• m is preferably equal to 0 and p between 2 and 4, advantageously equal to 2.
• the polyether chain between the aromatic groups of A and A ' is preferably in the benzylic position.
• each of R 1 and R 4 represents, advantageously, a group -CH 2 -, respectively, in formulas (1) and (2).
• the polyether chain is advantageously in position relative to the diazonium functions.
• the diazonium salt has the following eneral formula (5):
• n is an integer between 1 and 10, preferably between 1 and 4,
• n 0 or 1
• p is an integer between 1 and 5, advantageously equal to 2,
• X " and Y " are identical or different and represent, independently, a counter-ion of the diazonium cation chosen from halides, BF 4 " , N0 3 “ , HSO 4 " , PF 6 ⁇ , CH 3 COO “ , N (SO 2 CF 3 ) 2 " , CF 3 SO 3 " , CH 3 SO 3 “ , CF 3 COC> -, (CH 3 0) (H) PO 2 " , N (CN) 2 R 1 and R 4 are identical or different and chosen independently from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic,
• R 7 and R 8 are identical or different and independently selected from the group consisting of -H, -CH 3 , a halide, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, optionally containing a or more heteroatoms, advantageously chosen from O, S and N.
• R 7 and R 8 are chosen so as to promote the stability of the diazonium functions.
• substitute aromatic rings with R 7 and R 8 groups methoxy or ethoxy, in the ortho- and / or meta position with respect to the diazonium functional groups.
• R 7 and R 8 may advantageously be identical and preferably represent a hydrogen atom.
• a bis-diazonium salt of formula (5) can be obtained according to a synthesis method comprising three steps.
• a first step consists in adding a polyether via one or two hydroxyl functions to nitro-bromomethylbenzene, preferably 4-nitro-1-bromomethylbenzene, according to the following reaction scheme (1):
• the reaction step (1) makes it possible to add the benzyl group of 4-nitro-1-bromomethylbenzene at each end of a dihydroxylated polyether via the two free hydroxyl functional groups of the polyether chain.
• a polyether chain having a nitrobenzene group at each of its ends By choosing different starting dihydroxy polyethers, that is to say by choosing the value of n, m and p appropriately, it is easy to vary the length and the nature of the polyether chain separating the two apolar aromatic rings located at ends of the polyether thus formed.
• nature is meant the hydrophilic / hydrophobic character of the polyether chain and its solvating character vis-à-vis the lithium.
• a second step consists in reducing the nitro group of the aromatic rings of the polyether obtained in an amino group, according to any known method, at the end of the first step.
• This step may, for example, be carried out by a conventional reduction using hydrazine, catalyzed by palladium carbonaceous, denoted Pd-C.
• a third step consists of a diazotization reaction according to any known process, which makes it possible to convert the two amino groups into diazonium groups.
• the diazotization reaction is carried out, for example, by adding tetrafluoroboric acid and isoamyl nitrite to the polyether diamine obtained in the second step described above. There is then obtained a bis-diazonium salt of general formula (5) in which X " represents the counterion tetrafluoroborate BF 4 " .
• Oxide Ag 2 0 and excess silver bromide AgBr product are removed by filtration or centrifugation in dichloromethane wherein the nitro compound is soluble. After purification on a silica column with a dichloromethane / methanol mixture, 7.5 g (0.0178 mol) of pure, dry bis (4-nitrobenzyl) -trioxyethylene are obtained with a yield of 74%.
• the resulting bis (4-diazoniumbenzyl) -trioxyethylene tetrafluoroborate salt is almost pure.
• the traces of possible impurities may possibly be eliminated by additional successive purification operations according to common practices in the field of chemical synthesis.
• a diazonium salt, denoted DS5 was also synthesized.
• diazonium salt whose diazonium function is in position on the aromatic hydrocarbon group of A and, optionally, of A '
• the subject of the invention is not limited to at this position. It can also be envisaged to produce a salt of diazonium whose diazonium function (s) are in the ortho- or meta- position according to a synthetic method similar to that described above, by choosing appropriate starting materials.
• An electrolytic solution comprising the diazonium salt described above may advantageously be used in a non-charged lithium-ion battery so as to form a passivation layer on an electrode of the lithium-ion battery, during the first charge.
• an electrode of a lithium-ion accumulator is passivated by electrochemical reduction of an initial electrolytic solution containing the diazonium salt described above.
• the lithium-ion accumulator comprises first and second electrodes isolated from each other by a separator.
• the separator may be a microporous film made of polyethylene or polypropylene, cellulose or polyvinylidene fluoride impregnated with an electrolytic solution.
• the first electrode is preferably constituted by a material chosen from metals and their alloys, carbon, semiconductors and lithium insertion materials.
• the first electrode constituting the negative electrode may, for example, be based on Li 4 Ti 5 0 12 , Li 3 Fe 2 (PO 4) 3 or TiO 2 , or a mixture of these materials and optionally supported by a copper strip .
• the second electrode constituting the positive electrode may, for example, be based on LiCoO 2 , LiMn 2 O 4 , LiFePO 4 , Li 3 V 2 (PO 4 ) 3 or other lamellar oxides such as LiNiCoA10 2 and its derivatives, and possibly supported by an aluminum strip.
• the following positive and negative electrode pairs may be mentioned: LiMn 2 O 4 / Li 3 Fe 2 (PO 4 ) 3 , LiCoO 2 / Li 4 Ti 5 O 12 , LiCoO 2 / LiTi 2 (PO 4 ) 3 , LiFePO 4 / Li 4 Ti 5 O 12 , Li 3 V 2 (PO 4 ) 3 / Li 4 Ti 5 O 12 .
• the first and second electrodes are separated by a final electrolytic solution.
• final electrolytic solution is meant the electrolytic solution present in the lithium-ion battery, after having made a first charge of the lithium-ion battery containing the initial electrolytic solution.
• the Lithium-Ion accumulator containing the initial electrolytic solution is unchanged, that is to say has not been subjected to any charge.
• the initial or final electrolyte solution is preferably an aqueous solution.
• the initial or final electrolytic solution advantageously comprises a salt whose cation is at least partly lithium ion Li + dissolved in a solvent or a mixture of solvents.
• the solvent is preferably an aqueous solvent.
• aqueous solvent is meant a solvent containing mainly water.
• the salt must, advantageously, withstand the operating voltage of the lithium-ion accumulator formed.
• the lithium salt can be, typically, lithium nitrate, LiNO 3 .
• the first electrode is covered by a passivation layer.
• the passivation layer is remarkable in that it comprises a compound consisting of the repetition of a unit of formula (7) according to:
• n is an integer between 1 and 10, preferably between 1 and 4,
• R 1 is selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic
• R 2 is selected from the group consisting of -CH 2 an alkyl chain preferably comprising from 2 to 6 carbon atoms, linear or branched, cyclic or acyclic, for example a methylene-ethylene-n-propylene-isopropylene-n-butylene group; -, tert-butylene-, sec-butylene- or n-pentylene-
• R 3 is selected from the group consisting of -CH 3 , an alkyl chain preferably comprising from 2 to 6 carbon atoms, linear or branched, cyclic or acyclic and a group of formula (8) below:
• a ' is an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted,
• R4 is selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, cyclic or acyclic, and
• A is identical to or different from A 'and represents an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted.
• a and / or A ' is an aryl group
• an aryl group comprising from 6 to 9 carbon atoms, for example a phenyl, tolyl, xylyl or trimethylphenyl group
• a and / or A ' is a condensed polyaromatic group
• a polyaromatic group comprising from 10 to 45 carbon atoms, optionally substituted by one or more groups selected from the group consisting of -H, will preferably be selected.
• the unit is devoid of hydroxyl functions to form a barrier at the entry of water and comprises at least one polyether chain promoting the interactions between the passivation film formed on the first electrode and the cation, preferably Li + , present in the the final electrolytic solution.
• the hatched portion corresponds to the surface of the electrode.
• the pattern is grafted onto the first electrode by the group A and when R 3 is a group of formula (8), by the two groups A and A '.
• the pattern is grafted to the material of the first electrode via an aromatic hydrocarbon ring of the group A and, when R 3 is a group of formula (8), by an aromatic hydrocarbon ring of each of the groups A and A ' the bond connecting the first electrode and the pattern being a C-aromatic / metal or C-aromatic / carbon covalent bond.
• the presence of a polyether chain has a solvating effect of lithium ions Li + important that promotes the passage of lithium ions through the passivation layer, to be inserted in the first electrode.
• the kinetics of the insertion and de-insertion reactions of the Li + ions in the material of the first electrode are not, therefore, significantly slowed down.
• the apolar aromatic rings of the units create a hydrophobic zone near the surface of the first electrode.
• This hydrophobic zone limits the approach of water or, advantageously, can prevent the water from reaching the first electrode.
• the water reduction reaction which affects, in particular, the performance of a lithium-ion battery with an aqueous electrolyte is then strongly limited or even completely suppressed, at the operating potential of the first electrode thanks to the presence of this layer of water. passivation.
• Polyether chains which are suitable for solvating the cations of the final electrolytic solution, for example Li + ions, will therefore preferably be chosen.
• R 1 and R 4 are identical and each of R 1 and R 4 may, for example, represent a group -CH 2 -, to obtain a polyether chain in benzyl position.
• the pattern may form a bridge structure on the surface of the first electrode.
• R 3 is, advantageously, a group of formula (8).
• the bridge structure on the surface of the first electrode makes it possible to orient the polar polyether chain, aprotic, towards the final electrolyte solution of the charged lithium-ion battery.
• a and A ' may be identical or different and chosen from phenyl, anthracenyl and naphthalenyl groups, optionally substituted, preferably, with one or more groups selected from the group consisting of -H, -CH 3 , a halide, a linear or branched alkyl chain comprising 2 and 8 carbon atoms and, optionally, one or more heteroatoms selected from O, S and N.
• the pattern of the passivation layer may advantageously be represented by the following eneral formula (9):
• n is an integer between 1 and 10, preferably between 1 and 4,
• n 0 or 1
• p is an integer between 1 and 5, advantageously equal to 2
• R 1 and R 4 are identical or different and independently selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic,
• R 7 and R 8 are identical or different and independently selected from the group consisting of -H, -CH 3 , a halide, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, optionally containing a or more heteroatoms advantageously chosen from O, S and N.
• the pattern of the passivation layer is represented by the following general formula (10):
• n is an integer between 1 and 10, preferably between 1 and 4,
• n 0 or 1
• p is an integer between 1 and 5, advantageously equal to 2,
• R 1 and R 4 are identical or different and independently selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 6 carbon atoms, linear or branched, cyclic or acyclic,
• R 7 and R 8 are identical or different and independently selected from the group consisting of -H, -CH 3 , a halide, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, optionally containing a or more heteroatoms advantageously chosen from O, S and N.
• R 7 and R 8 are preferably identical and represent a hydrogen atom, -H.
• a method for producing a lithium-ion battery comprises a step of forming, according to any known method, an electrochemical cell comprising the first and second electrodes separated by an initial electrolytic solution.
• the initial electrolytic solution comprises a diazonium salt free of hydroxyl functions and of the general formula (11) below: ⁇ - + N ⁇ N- Ri- A- (OR 2) n - OR 3
• n is an integer between 1 and 10, preferably between 1 and 4,
• X " represents a counterion of the diazonium cation chosen from halides, BF 4 " ,
• R 1 and R 2 are identical or different and independently selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 1 to 8 carbon atoms, linear or branched, cyclic or acyclic,
• R 3 is selected from the group consisting of -CH 3 , an alkyl chain comprising, preferably, from 2 to 8 carbon atoms, linear or branched, cyclic or acyclic and a group of formula (12) below: in which
• a ' is an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted
• R4 is selected from the group consisting of -CH 2 -, an alkyl chain preferably comprising from 2 to 8 carbon atoms, linear or branched, cyclic or acyclic, and
• A is identical to or different from A 'and represents an aromatic hydrocarbon group, mono or polycyclic, selected from the group consisting of phenyl, aryl groups, condensed polyaromatic groups, optionally substituted.
• a and / or A ' is an aryl group
• an aryl group comprising from 6 to 9 carbon atoms, for example a phenyl, tolyl, xylyl or trimethylphenyl group, will preferably be chosen.
• a and / or A ' is a condensed polyaromatic group
• a polyaromatic group comprising from 10 to 45 carbon atoms, optionally substituted by one or more groups selected from the group consisting of -H
• -CH3 a halide, an alkyl chain, linear or branched, comprising from 2 to 8 carbon atoms and, optionally, one or more heteroatoms selected from O, S and N.
• the first step of assembly of the Electrochemical cell advantageously makes it possible to produce an uncharged lithium-ion accumulator forming the electrochemical cell.
• the first electrode is preferably the negative electrode where the water reduction reaction takes place.
• the step of assembling the electrochemical cell is followed by a step of forming the passivation layer on the first electrode of the electrochemical cell, by electrochemical reduction of the initial electrolytic solution.
• the groups A and A 'are preferably chosen for their stability properties, in particular electrochemical properties, at the reduction potential of the diazonium salt.
• the aromatic hydrocarbon ring (s) of A and A 'are advantageously not substituted, to avoid steric hindrance problems that may affect the grafting efficiency of the diazonium salt on the first electrode.
• the electrochemical reduction step makes it possible to form in situ the passivation layer on the first electrode, during a first charge of the cell of the lithium-ion accumulator.
• the non-charged Lithium-on accumulator formed at the end of the first step of the process is subjected to an operating voltage during the first charge of the lithium-ion battery, according to any known method.
• the first charge allows both the insertion of lithium into the material of the first electrode and the reduction of the diazonium salt present in the initial electrolytic solution.
• the first charge carries out the grafting of at least one aromatic hydrocarbon ring of the group A and / or A 'of the diazonium salt of formula (11) on the first electrode.
• the diazonium salt is consumed during the first charge in proportion to the creation of the passivation layer on the first electrode.
• the step of forming the passivation layer preferably comprises the creation of a covalent bond of C-aryl / metal or C-aryl / carbon type between an aromatic hydrocarbon ring of the group A and the material of the first electrode. and an aromatic hydrocarbon ring of the group A 'and the material of the first electrode, when R 3 is a group of formula (8) in the unit constituting the passivation layer.
• the lithium-ion battery comprises the first electrode covered by the passivation layer described above and a final electrolytic solution separating the first and second electrodes. At the end of the first charge, all the diazonium salt has preferably been consumed and the final electrolyte solution is then free of the diazonium salt.
• the diazonium salt may advantageously be present in the initial electrolytic solution at a molar concentration of less than 0.5M, preferably of between 0.05M and 0.3M.
• Passivation of a passivated LiFePO 4 electrode by electrochemical reduction of an aqueous initial electrolytic solution was carried out by cyclic voltammetry.
• passivation means that the electrode is covered by a passivation layer as described above.
• the initial electrolytic solution consists of 10 ml of an aqueous solution of a LiNO 3 salt at a concentration of 5M and a bis (4-diazoniumbenzyl) -trioxyethylene tetrafluoroborate salt, denoted DS3, as synthesized in FIG. Example 1 at a concentration of 2mM.
• the LiFePO 4 electrode is made on a current collector according to any known method.
• an ink is constituted by a mixture of LiFePO 4 forming the insertion material, carbon forming a conductive additive and polymeric binders forming a binder.
• the ink is coated on a collector, for example nickel, and then dried to form the LiFePO 4 electrode.
• the LiFePO 4 electrode is then calendered and cut, for use in a conventional cyclic voltammetry circuit.
• the cyclic voltammetry was performed according to a conventional argon assembly with the initial electrolytic solution described above and three electrodes including the LiFePO 4 electrode as described above, denoted D 1? constituting a working electrode, a saturated calomel electrode constituting the reference electrode and a platinum wire, for the counter-electrode.
• D 2 is a passivated LiFePO 4 electrode according to the same operating procedure as above but with a 4-methoxybenzenediazonium tetrafluoroborate salt, denoted S 2 , marketed by Sigma-Aldrich, and the other, denoted D 0 , is a bare LiFePO 4 electrode, that is to say devoid of a passivation layer obtained according to the same protocol but without adding a diazonium salt in the initial electrolytic solution.
• S 2 4-methoxybenzenediazonium tetrafluoroborate salt
• D 0 is a bare LiFePO 4 electrode, that is to say devoid of a passivation layer obtained according to the same protocol but without adding a diazonium salt in the initial electrolytic solution.
• Infrared spectra were obtained after the voltammetry on the electrodes ⁇ ⁇ and D 2; to confirm the formation of the passivation layer by verifying that the diazonium DS3 and S 2 aryl salts have been grafted, respectively, Dj and D2.
• the IR spectra shown in FIG. 3 were obtained by a Total Attenuated Reflection method (denoted ATR) on the DS3 diazonium salt alone and on the D 0 electrodes and the du ⁇ spectrum analysis compared to the DS3 and D spectra.
• 0 shows, indeed, the disappearance of a peak located at 2200 cm -1 characteristic of the diazonium function (dashed arrow in FIG. 3) and the appearance of a peak at 1600 cm -1 characteristic of an aromatic ring. substituted by an alkyl chain (solid arrow in Figure 3).
• the electrodes Ci, C 2 , C 3 , C 4 , C 5 and C 6 were passivated according to the same operating procedure as for a LiFePO 4 electrode, respectively with S 2 , DS 2 , DS 3 , DS 5 , DS 6 and DS 7.
• the electrode C0 is the non-passivated electrode.
• the comparative tests show the improvement of the electrochemical stability of the aqueous electrolyte according to the invention.
• the results particularly interesting for C 5 with a high surge of 290mV and a low current.
• the aqueous electrolytic solution for an electrochemical generator, in particular for a lithium-ion battery, containing an aryl diazonium salt according to the invention is stable up to a high operating voltage.
• the presence of an aryl diazonium salt in the initial electrolytic solution makes it possible to widen the window of stability of the water as a function of the pH, by increasing in particular the reduction potential of the water.

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