Salt composition for low-acetamide-containing electrolytes

Abstract

The present invention relates to a composition containing a salt composed of a sodium cation and an anion of formula (II): TIFF2025523138000008.tif28170[wherein R 1 and R 2 each independently represents a fluorine atom or a perfluoro group] and having an acetamide content of 0.1 to 1000 ppm by weight. The present invention also relates to a method for preparing this composition and an electrolyte containing the same.

Description

Technical Field

[0001] The present invention relates to a salt composition for an electrolyte for a sodium-ion battery, a preparation process thereof, and an electrochemical cell incorporating an electrolyte containing this composition.

Background Art

[0002] Lithium-ion (Li-ion) batteries are commonly used in electric vehicles, as well as mobile and portable devices.

[0003] Sodium-ion (Na-ion) batteries are environmentally friendly alternatives to Li-ion batteries.

[0004] Na-ion batteries include at least an anode, a cathode, an electrolyte, and preferably a separator. The electrolyte is generally formed from a sodium salt dissolved in a solvent (which can be a mixture of organic solvents) to achieve a good compromise between the viscosity and dielectric constant of the electrolyte.

[0005] The passivation layer formed during the first charge / discharge cycle of the battery is essential for the life of the battery. The passivation layer includes, in particular, the passivation of aluminum, which is generally a current collector used in the cathode, and the solid electrolyte interface (SEI), which is an inorganic polymer layer formed at the anode / electrolyte and cathode / electrolyte interfaces. The stability of these interfaces is a major issue in improving the life of the battery.

[0006] For prior art on Na-ion batteries, please refer to the following review articles: - Hwang et al., Sodium-ion batteries: present and future, in Chem.Soc.Rev., 46:3529-2614 (2017); - Chen et al., Readiness Level of Sodium-Ion Battery Technology: A Materials Review, in Adv.Sus.Sys., DOI: 10.1002 / adsu.201700153 (2018); - Eshetu et al., Electrolytes and Interphases in Sodium-Based Rechargeable Batteries: Recent Advances and Perspectives, in Adv.Energy Mater., 10:2000093 (2020).

[0007] In the latter, various electrolytes for sodium-ion batteries are presented. As possible electrolyte salts, NaFSI (sodium bis(fluorosulfonylimide)) is mentioned.

[0008] European Patent Application Publication No. 2578533 describes fluorosulfonylimide-type alkali metal salts (preferably lithium salts) having a sulfate ion content of less than 3000 ppm.

[0009] U.S. Patent No. 9,440,852 describes a NaFSI (sodium bis(fluorosulfonylimide)) salt having a purity of 99.5 wt% or more, free of water, and containing impurities of NaCl, NaF, and NaFSO3 at a content of 1000 ppm or less each.

[0010] Patent Gazette No. 6592380 discloses an electrolyte for a sodium-ion battery containing NaFSI and propylene carbonate (PC), with a specific ratio of PC to sodium.

[0011] European Patent Application Publication No. 3985775 teaches an electrolyte containing a sodium salt, a carbonate-type solvent, and an additive (alkylene carbonate or nitrile). The list of possible sodium salts includes NaFSI.

[0012] International Publication No. 2019 / 229359 describes a process for producing salts such as lithium bis(fluorosulfonyl)imide (LiFSI) from bis(fluorosulfonyl)imide (HFSI).

[0013] There is a need to provide a composition useful for preparing an electrolyte for a Na-ion battery, which has advantageous properties with respect to non-flammability, performance, and especially battery life and can be produced by a simple and inexpensive process.

Summary of the Invention

[0014] The present invention firstly relates to a composition comprising a salt consisting of a sodium cation and an anion of formula (II): TIFF2025523138000002.tif28170[wherein R 1 and R 2 each independently represents a fluorine atom or a perfluoro group] and having an acetamide content of 0.1 to 1000 ppm by weight.

[0015] In certain embodiments, the anion of formula (II) is a bis(fluorosulfonyl)imide anion or a bis(trifluoromethylsulfonyl)imide anion, preferably a bis(fluorosulfonyl)imide anion.

[0016] In certain embodiments, the acetamide content is 1 to 5000 ppm by weight, preferably 2 to 100 ppm by weight.

[0017] In certain embodiments, the salt is present in a weight content of 99.5% by weight or more, preferably 99.8% by weight or more, more preferably 99.9% by weight or more.

[0018] In certain embodiments, the composition comprises, by weight, - 0 to 500 ppm, preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm of water, - Cl at 0 to 50 ppm, preferably 0.5 to 20 ppm, more preferably 1 to 10 ppm - ions, - F at 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm - ions, - SO4 at 0 to 3000 ppm, preferably 0.5 to 500 ppm, more preferably 1 to 20 ppm 2- ions, - FSO3 at 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm - ions is also included.

[0019] The present invention also relates to - formula (I): TIFF2025523138000003.tif28170[wherein R 1 and R 2 each independently represents a fluorine atom or a perfluoro group] supplying a compound of, - reacting the compound of formula (I) with a sodium compound also relates to a process for preparing the above composition.

[0020] In certain embodiments, the sodium compound is NaCl or preferably a sodium base selected from NaH, NaOH, NaHCO3, Na2CO3, and Na(OAc), preferably Na2CO3.

[0021] In certain embodiments, the reaction is - in the presence of an organic solvent, preferably selected from nitrile, ester, ether, ketone, alcohol, carbonate, and combinations thereof, and / or - at a molar ratio of sodium compound / compound of formula (I) of 0.9 to 1.1, preferably 1 to 1.05, and / or - at a temperature of -5°C to 40°C, preferably 15°C to 25°C carried out.

[0022] In certain embodiments, the reaction is carried out in the presence of acetonitrile as an organic solvent.

[0023] In certain embodiments, the process - synthesizes the compound of formula (I), preferably by fluorination of a chlorinated compound and optionally by distillation and includes a step.

[0024] In certain embodiments, the process further - purifies the reaction mixture after the reaction, preferably by filtration and crystallization and includes a step.

[0025] In certain embodiments, crystallization is carried out in the presence of a non-solvent for the compound of formula (II), preferably selected from chlorinated solvents, aromatic solvents, alkanes, and combinations thereof.

[0026] The present invention also relates to an electrolyte comprising the above composition mixed with one or more solvents and optionally one or more additives.

[0027] In certain embodiments, the electrolyte further comprises an ionic liquid comprising FSI or TFSI anions preferably associated with an onium cation.

[0028] The present invention also relates to an electrochemical cell comprising a negative electrode, a positive electrode, and an electrolyte, wherein the electrolyte comprises the above composition.

[0029] In certain embodiments, the negative electrode comprises hard carbon and / or soft carbon as an electrochemically active material, and the positive electrode comprises a polyanion-based compound containing sodium.

[0030] The present invention also relates to a battery comprising at least one of the above-described electrochemical cells.

[0031] The present invention makes it possible to meet the above needs.

[0032] Advantageously, the composition of the present invention enables an improvement in the quality of the SEI in a sodium ion battery.

[0033] Advantageously, the composition of the present invention enables an improvement in the Coulomb efficiency after SEI formation and can improve the battery life (i.e., increase the number of cycles for maintaining at least 80% of the initial capacity of the battery).

[0034] Advantageously, a battery incorporating the composition of the present invention exhibits good performance even at high charge and discharge rates.

[0035] Advantageously, the composition of the present invention can be manufactured at a moderate cost, particularly without using expensive raw materials such as LiFSI or KFSI.

[0036] Advantageously, the purification of this composition is simplified.

[0037] Advantageously, raw materials having specific qualities, such as HFSI, are used to enable the easy obtainment of a high-performance level composition.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be described in more detail and non - limitatively in the following description.

[0039] Unless otherwise indicated, all percentages and ratios are percentages and ratios by weight, and all ratios between two amounts are weight ratios.

[0040] Composition containing salt The present invention relates first to a composition comprising at least one salt consisting of an anion of formula (II): TIFF2025523138000004.tif28170 and a sodium cation.

[0041] In formula (II), R 1 and R 2independently represents a fluorine atom or a perfluoro group, which preferably contains 1 to 8 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably is a trifluoromethyl group.

[0042] In some embodiments, there may be a plurality of anions of formula (II), but preferably only one anion of formula (II) is present. Preferably, the anion of formula (II) is a bis(fluorosulfonyl)imide anion (also referred to as the FSI anion); and / or a bis(trifluoromethylsulfonyl)imide anion (also referred to as the TFSI anion). Even more preferably, it is the FSI anion, in which case the salt is NaFSI.

[0043] It should be understood that throughout the following, a reference to the singular form of the anion of formula (II) can be taken to include a reference to the plural form of the anion of formula (II).

[0044] The composition according to the present invention may contain a salt (an anion of formula (II) and a sodium cation) in a content of preferably 99% by weight or more, more preferably 99.5% by weight or more, even more preferably 99.8% by weight or more, or even 99.9% by weight, based on the total weight of the composition. The salt content means the total of the content of the anion of formula (II) and the content of the sodium cation.

[0045] The composition according to the present invention may contain acetamide in a weight content of 1000 ppm or less; 500 ppm or less; 200 ppm or less; 100 ppm or less; 50 ppm or less; 20 ppm or less; 10 ppm or less.

[0046] The composition according to the present invention may particularly contain an acetamide content of 0.1 to 1000 weight ppm, preferably 1 to 500 weight ppm, more preferably 2 to 100 weight ppm.

[0047] The composition according to the present invention may particularly contain an acetamide content of 0.1 to 10 ppm by weight; 10 to 50 ppm by weight, 50 to 100 ppm by weight; 100 to 200 ppm by weight; 200 to 300 ppm by weight; 300 to 500 ppm by weight; 500 to 1000 ppm by weight.

[0048] The above acetamide content can, in particular, make it possible to obtain optimal performance of the composition when used in a Na-ion battery electrolyte.

[0049] The composition of the present invention may particularly contain one or more other anions and / or one or more other cations.

[0050] In certain embodiments, the composition optionally contains sulfamate ions (NH2SO3 - ) in a content of 3000 ppm or less, preferably 1000 ppm or less, more preferably 300 ppm or less. Sulfamate ions may be essentially absent or may be present in an amount of 0.1 ppm by weight or more, or 1 ppm by weight or more, or 10 ppm by weight or more. For example, the content of sulfamate ions can be 0 to 3000 ppm by weight, or 1 to 1000 ppm by weight, or 10 to 300 ppm by weight.

[0051] In certain embodiments, the composition optionally contains water in a content of 500 ppm by weight or less, preferably 200 ppm by weight or less, preferably 100 ppm by weight or less, and in some cases 50 ppm by weight or less. Water may be essentially absent or may be present in an amount of 0.1 ppm by weight or more, or 0.5 ppm by weight, or 1 ppm by weight. For example, the water content can be 0 to 500 ppm by weight, or 0.5 to 100 ppm by weight, or 1 to 50 ppm by weight.

[0052] In certain embodiments, the composition optionally contains Cl - ions in a content of 50 ppm by weight or less, preferably 20 ppm by weight or less, preferably 10 ppm by weight or less. Cl -Ions may essentially not exist, or may exist in an amount of 0.1 ppm by weight or more, or 0.5 ppm by weight, or 1 ppm by weight. For example, Cl - The ion content may be 0 to 50 ppm by weight, or 0.5 to 20 ppm by weight, or 1 to 10 ppm by weight.

[0053] In certain embodiments, the composition optionally contains F - ions in a content of 100 ppm by weight or less, preferably 50 ppm by weight or less, preferably 10 ppm by weight or less. F - Ions may essentially not exist, or may exist in an amount of 0.1 ppm by weight or more, or 0.5 ppm by weight or more, or 1 ppm by weight or more. For example, F - The ion content may be 0 to 100 ppm by weight, or 0.5 to 50 ppm by weight, or 1 to 10 ppm by weight.

[0054] In certain embodiments, the composition optionally contains SO4 2- ions in a content of 3000 ppm by weight or less, preferably 500 ppm by weight or less, preferably 100 ppm by weight or less, or even 20 ppm by weight or less. SO4 2- Ions may essentially not exist, or may exist in an amount of 0.1 ppm by weight or more, or 0.5 ppm by weight, or 1 ppm by weight. For example, SO4 2- The ion content may be 0 to 3000 ppm by weight, or 0.5 to 500 ppm by weight, or 1 to 20 ppm by weight.

[0055] In certain embodiments, the composition optionally contains FSO3 - ions in a content of 100 ppm by weight or less, preferably 50 ppm by weight or less, preferably 10 ppm by weight or less. FSO3 - Ions may essentially not exist, or may exist in an amount of 0.1 ppm by weight or more, or 0.5 ppm by weight, or 1 ppm by weight. For example, FSO3 - The ion content may be 0 to 100 ppm by weight, or 0.5 to 50 ppm by weight, or 1 to 10 ppm by weight.

[0056] The content of ions in the composition can be analyzed by ion chromatography and / or inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-AES), and / or X-ray fluorescence analysis (XRF).

[0057] The water content can be determined by Karl Fischer analysis.

[0058] Acetamide and FSO3 - The content of ions can be determined by nuclear magnetic resonance ( 19 F and 1 H).

[0059] General scheme for preparing the composition The composition can be prepared by a process comprising each step of - Optionally, synthesizing a compound of formula (I): TIFF2025523138000005.tif28170 - Reacting the compound of formula (I) with a sodium compound - Optionally, purifying the reaction mixture

[0060] In formula (I), R 1 and R 2 have the same meaning as in formula (II).

[0061] In particular, when R 1 =R 2= F, the compound of formula (I) is bis(fluorosulfonyl)imide or HFSI (which enables the obtaining of NaFSI).

[0062] In particular, when R 1 =R 2= CF3, the compound of formula (I) is bis(trifluoromethylsulfonyl)imide (which enables the obtaining of NaTFSI). ​

[0063] Synthesis of the compound of formula (I) The compound of formula (I) can be synthesized, in particular, by fluorination of a chlorinated compound. The chlorinated compound has the same structure as the compound of formula (I), except that R 1 and R 2 each independently represent a halogen atom (F or Cl) or a perhalogenated group (preferably containing 1 to 8 carbon atoms, more preferably 1 to 3 carbon atoms, even more preferably a trihalomethyl group, provided that the chlorinated compound contains at least one chlorine atom). Preferably, the chlorinated compound is of formula (I), and R 1 and R 2 each independently represent a chlorine atom or a perchlorinated group, which preferably contains 1 to 8 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably a trichloromethyl group.

[0064] In particular, the chlorinated compound may be (bis(chlorosulfonyl)imide), whereby HFSI can be obtained.

[0065] In particular, the chlorinated compound may be (bis(trichloromethylsulfonyl)imide), whereby bis(trifluoromethylsulfonyl)imide can be obtained.

[0066] Fluorination is carried out by contacting the chlorinated compound with a fluorinating agent selected from the group consisting of preferably HF (preferably anhydrous HF), KF, AsF3, BiF3, ZnF2, SnF2, PbF2, CuF2, and mixtures thereof, more preferably HF, and even more preferably anhydrous HF. "Anhydrous HF" is understood to mean HF containing less than 500 ppm of water, preferably less than 300 ppm of water, and preferably less than 200 ppm of water.

[0067] Fluorination is preferably carried out in at least one organic solvent SO1. The organic solvent SO1 preferably has a donor number between 1 and 70, advantageously between 5 and 65. The donor number of the solvent represents the value -ΔH, where ΔH is the enthalpy for the interaction of the solvent with antimony pentachloride (by the method described in Journal of Solution Chemistry, vol. 13, no. 9, 1984). Examples of the organic solvent SO1 include, in particular, esters, nitriles, dinitriles, ethers, diethers, amines, phosphines, and mixtures thereof.

[0068] Preferably, the organic solvent SO1 is selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, isobutyronitrile, glutaronitrile, dioxane, tetrahydrofuran, triethylamine, tripropylamine, diethylisopropylamine, pyridine, trimethylphosphine, triethylphosphine, diethylisopropylphosphine, and mixtures thereof. In particular, the organic solvent SO1 is dioxane.

[0069] Fluorination can be carried out at a temperature between 0 °C and the boiling point of the organic solvent SO1 (or a mixture of organic solvents SO1). Preferably, step b) can be carried out at a temperature between 5 °C and the boiling point of the organic solvent OS1 (or a mixture of organic solvents OS1), preferably between 20 °C and the boiling point of the organic solvent OS1 (or a mixture of organic solvents OS1).

[0070] Fluorination (preferably with anhydrous hydrofluoric acid) can be carried out at a pressure between 0 and 16 bar abs.

[0071] Fluorination can preferably be carried out by dissolving the chlorinated compound in the organic solvent SO1 or a mixture of organic solvents SO1 prior to the reaction with the fluorinating agent (preferably anhydrous HF).

[0072] The weight ratio of the chlorinated compound to the organic solvent SO1 or a mixture of organic solvents SO1 is preferably between 0.001 and 10, advantageously between 0.005 and 5.

[0073] According to one embodiment, the anhydrous HF is preferably introduced into the reaction medium in gaseous state.

[0074] The molar ratio of the fluorinating agent (preferably anhydrous HF) to the chlorinated compound is preferably between 1 and 10, advantageously between 1 and 5.

[0075] The reaction with the fluorinating agent (preferably anhydrous HF) can be carried out in a closed or open medium, and it is particularly preferred to carry it out in an open medium where HCl is released in gaseous form.

[0076] In the fluorination reaction, typically HCl is formed, and most of it can be degassed from the reaction medium (similar to the excess HF in the case where the fluorinating agent is HF) by entrainment (stripping) with, for example, a neutral gas (such as nitrogen, helium, or argon).

[0077] However, there may be residual HF and / or HCl dissolved in the reaction medium. In the case of HCl, at its operating pressure and temperature, since HCl is mainly in gaseous state, the amount is very small.

[0078] The composition obtained at the end of the fluorination reaction can be stored in an HF-resistant container.

[0079] The product obtained at the end of the fluorination reaction may contain HF (especially unreacted HF), a chlorinated compound, a solvent SO1 (such as dioxane), and optionally HCl, and / or optionally heavy compounds.

[0080] After the reaction, the compound of formula (I) can be purified, especially by means of one or more distillation steps.

[0081] According to one embodiment, the distillation step is - A first stream F1, preferably at the top of a distillation column, containing HF, optionally an organic solvent SO1, and / or optionally HCl, and being a gas or a liquid, the stream F1; - A second stream F2, preferably at the bottom of a distillation column, containing the compound of formula (I) and optionally heavy compounds, and preferably being a liquid, the stream F2 enables the formation and recovery of.

[0082] When the stream F2 contains heavy compounds, it is subjected to an additional distillation step in a second distillation column to - A stream F2-1, preferably at the top of a distillation column, containing the compound of formula (I), not containing heavy compounds, and preferably being a liquid, the stream F2-1, - A stream F2-2, preferably at the bottom of a distillation column, containing heavy compounds and the compound of formula (I), and containing less than 10% by weight, preferably less than 7% by weight, preferably less than 5% by weight of the compound of formula (I) contained in the composition obtained in step b), and preferably being a liquid, the stream F2-2 can be formed and recovered.

[0083] "Heavy compounds" are understood to mean organic compounds having a boiling point higher than that of the compound of formula (I). These can occur by the decomposition reaction of chlorinated compounds, for example, the formation of compounds such as FSO2NH2, and / or by the formation of oligomers by the decomposition reaction of the solvent.

[0084] According to one embodiment, the distillation step is - A first stream F'1, preferably at the top of a distillation column, containing HF, optionally an organic solvent SO1, and / or optionally HCl, and being a gas or a liquid, the stream F'1, - A second stream F'2, preferably recovered by side stream withdrawal, containing the compound of formula (I), and preferably being a liquid, the stream F'2, - A third stream F'3, preferably at the bottom of the distillation column, containing the heavy compound and the compound of formula (I) and containing less than 10% by weight, preferably less than 7% by weight, preferably less than 5% by weight of the compound of formula (II) contained in the composition obtained in step b), and preferably being liquid, the stream F'3 enables the formation and recovery of.

[0085] To carry out the side stream withdrawal, the distillation column can be provided with at least one tray.

[0086] The distillation step can be carried out at a pressure in the range of 0 to 5 bar abs, preferably 0 to 3 bar abs, preferably 0 to 2 bar abs, advantageously 0 to 1 bar abs.

[0087] The distillation step can be carried out with any conventional apparatus. This can be a distillation device including a distillation column, a boiler, and a condenser. The distillation column can be provided with at least one packing such as random packing and / or structured packing, and / or trays such as perforated trays, fixed valve trays, movable valve trays, bubble cap trays, or combinations thereof.

[0088] At the end of the purification, the compound of formula (I) can be recovered in high purity. Using the high-purity compound of formula (I) advantageously makes it possible to avoid complex subsequent purification steps and prepare a composition containing a high-purity salt.

[0089] Therefore, the product collected (and / or used in the reaction with the sodium compound) preferably contains at least 95% by weight, more preferably at least 98% by weight, at least 99% by weight, at least 99.5% by weight, or even at least 99.8% by weight of the compound of formula (I).

[0090] The product collected (and / or used in the reaction with the sodium compound) preferably has a sulfamic acid content of 5000 ppm by weight or less, preferably 4000 ppm by weight or less, 3000 ppm by weight or less, 2500 ppm by weight or less, or even 2000 ppm by weight or less. In some cases, sulfamic acid may be essentially absent or may be present at a content of at least 1 ppm by weight. The sulfamic acid content can in particular be 1 - 5000 ppm, 10 - 4000 ppm, 100 - 3000 ppm, or 500 - 2500 ppm by weight. It can be, for example, 1 - 10 ppm, 10 - 50 ppm, 50 - 100 ppm, 100 - 200 ppm, 200 - 500 ppm, 500 - 1000 ppm, 1000 - 2000 ppm, 2000 - 3000 ppm, 3000 - 4000 ppm, or 4000 - 5000 ppm by weight. The sulfamic acid content can be determined by ion chromatography (represented as NH2SO3 - ).

[0091] For ion chromatography measurements, in particular, a THERMO ICS - 5000 instrument can be used. This instrument has two analysis channels, one of which is dedicated to anion analysis, and - Supply of ultrapure water (18.2 MΩ) by a dual piston pump; - An automatic eluent generator (EGC); - A valve equipped with an injection loop (volume = 25 microliters); - A guard column (AG19, T = 35 °C) and a separator column (AS19, T = 20 °C); - A suppressor (AERS 62 mA); - A conductivity meter for detecting peaks consisting of.

[0092] The eluent used can be a KOH solution with a concentration of 25 mmol / L and can have a flow rate of 1 mL / min.

[0093] Reaction of the compound of formula (I) with a sodium compound The term "sodium compound" is understood to mean a compound containing sodium.

[0094] The reaction with the sodium compound can be an ion exchange reaction. In this case, the soda compound can be, in particular, NaCl.

[0095] Alternatively, the reaction may be an acid-base reaction, in which case the sodium compound is a sodium base.

[0096] The term "sodium base" is understood to mean a basic compound containing sodium.

[0097] The sodium base can be selected, in particular, from NaH, NaOH, NaHCO3, Na2CO3, Na(OAc) (sodium acetate), and mixtures thereof. Preferably, Na2CO3 is used.

[0098] The reaction can be carried out, in particular, in the presence of an organic solvent that enables the promotion of the recovery of the compound of formula (II). It is preferable to select a solvent in which the compound of formula (II) is soluble. The organic solvent can be selected, in particular, from nitriles (in particular, acetonitrile, propionitrile or butyronitrile), esters (in particular, methyl, ethyl, propyl, isopropyl, or butyl acetate), ethers (in particular, diethyl ether or methyl tert-butyl ether), ketones (in particular, acetone or methyl ethyl ketone), alcohols (in particular, methanol, ethanol or isopropanol), carbonates (in particular, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate), and mixtures thereof.

[0099] Preferably, the reaction is carried out in the presence of acetonitrile as the organic solvent.

[0100] The reaction can be carried out by pouring the compound of formula (I) into a dispersion of a sodium compound (e.g., a sodium base) in an organic solvent. The weight ratio of the solvent to the compound of formula (I) can be between 0.5 and 10, preferably between 1 and 4. The molar ratio of the sodium compound (Na equivalent) to the compound of formula (I) can be between 0.9 and 1.1, preferably between 1 and 1.05. The reaction temperature can be from -5°C to 40°C, preferably from 15°C to 25°C.

[0101] At the end of the reaction, the reaction mixture can be purified. The purification can include filtration, crystallization, and one or more washings; alternatively, preferably, crystallization and optionally one or more washings are carried out after filtration.

[0102] Crystallization can be carried out by evaporating the solvent, especially under vacuum or at atmospheric pressure, for example by batch evaporation, by continuous evaporation using a falling-film evaporator or a thin-film evaporator, or alternatively by a short-path wiped-film evaporator.

[0103] Preferably, crystallization is carried out by adding an organic solvent that is a non-solvent for the compound of formula (II). The compound of formula (II) can be present with a solids content of 50% or more, preferably 70% or more. The organic solvent can be selected especially from chlorinated solvents such as dichloromethane or dichloroethane, aromatic solvents such as toluene or xylene, or alkanes (linear, branched, or cyclic) such as pentane, cyclohexane, or heptane, and mixtures thereof. Crystallization can be carried out especially at a temperature between -15°C and 25°C.

[0104] Optionally, the product can be washed one or more times with the organic solvent described above especially with respect to crystallization. Preferably, the organic solvent used for (one or more) washings is the same as that used for crystallization.

[0105] Finally, the product can be dried, for example, in a vacuum oven.

[0106] The yield of the resulting compound of formula (II) can be more than 70 mol%, or more than 80 mol%, or more than 90 mol%, or even more than 95 mol% based on the reactant of formula (I).

[0107] The resulting product can be characterized by nuclear magnetic resonance, by Karl Fischer analysis for water content, and by ion chromatography for anion and cation contents.

[0108] Electrolyte The above composition can be included in an electrolyte. The electrolyte can contain the above salt in a weight ratio that can be 1% to 70%, preferably 3% to 50%, more preferably 5% to 30%.

[0109] The electrolyte is preferably non-aqueous. Therefore, water is not contained or is essentially not contained. The water content can be 0 to 500 weight ppm, preferably 0.5 to 100 weight ppm, more preferably 1 to 50 weight ppm.

[0110] The content of acetamide in the electrolyte can be 0.1 to 1000 ppm, preferably 1 to 500 ppm, more preferably 2 to 100 ppm.

[0111] The content of sulfamate ions in the electrolyte can be 0 to 3000 weight ppm, preferably 1 to 1000 weight ppm, more preferably 10 to 300 weight ppm.

[0112] The content of Cl - ions in the electrolyte can be 0 to 50 ppm, preferably 0.5 to 20 ppm, more preferably 1 to 10 ppm.

[0113] The content of F - ions in the electrolyte can be 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm.

[0114] SO4 in the electrolyte 2- The content of ions can be 0 to 3000 ppm, preferably 0.5 to 500 ppm, more preferably 1 to 20 ppm.

[0115] FSO3 in the electrolyte - The content of ions can be 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm.

[0116] In addition to the composition according to the present invention, the electrolyte can contain one or more other sodium salts, one or more solvents, and one or more additives.

[0117] The other sodium salts can be selected particularly from NaPF6, NaClO4, NaBF4, NaOTf (sodium triflate), NaBOB (sodium bis(oxalato)borate), NaDFOB (sodium difluoro(oxalato)borate), NaTDI (sodium 4,5-dicyano-2-trifluoromethylimidazolidate), and combinations thereof. When a plurality of sodium salts are used in combination, the total content of all sodium salts is preferably 1 wt% to 70 wt%, more preferably 3 wt% to 50 wt%, even more preferably 5 wt% to 30 wt%.

[0118] In certain embodiments, the electrolyte consists essentially of, or even consists of, the above-described composition (optionally in combination with one or more other sodium salts), (one or more) solvents, and (one or more) additives.

[0119] (One or more) solvents can be selected especially from ethers, especially dimethoxyethane (DME), diethylene glycol dimethyl ether (DEGDME), or tetraethylene glycol dimethyl ether (TEGDME); esters, especially ethyl acetate or methyl propionate; lactones, especially gamma-butyrolactone; nitriles, especially acetonitrile; sulfoxides, especially dimethyl sulfoxide; sulfones, especially sulfolane; carbonates; and combinations thereof.

[0120] Among carbonates, the (one or more) solvents can especially be C3-C6 alkyl carbonate solvents (especially cyclic and / or linear).

[0121] In certain embodiments, a mixture of at least two solvents is provided, namely a mixture of a cyclic C3-C6 alkyl carbonate solvent and a linear C3-C6 alkyl carbonate solvent.

[0122] As the cyclic C3-C6 alkyl carbonate, especially ethylene carbonate (EC), butylene carbonate (BC), or propylene carbonate (PC) can be used.

[0123] As the linear C3-C6 alkyl carbonate, especially dimethyl carbonate (DMC), diethyl carbonate (DEC) or ethyl methyl carbonate (EMC) can be used.

[0124] The additive can include a C2-C6 alkylene carbonate.

[0125] The additive can include a C1-C8 nitrile.

[0126] The additive can include a C2-C6 alkylene carbonate and a C1-C8 nitrile.

[0127] The C2-C6 alkylene carbonate can be cyclic or linear. For example, the C2-C6 alkylene carbonate can be vinylene carbonate.

[0128] C1 to C8 nitriles may contain at least two nitrile units. Preferably, the C1 to C8 nitriles have the general formula NC-(CH) n -CN, where n is an integer from 1 to 6, preferably 2, 3, or 4. The C1 to C8 nitriles can be selected from adiponitrile, succinonitrile, or glutaronitrile, with adiponitrile being preferred (n = 4).

[0129] The electrolyte may particularly contain 2 wt% to 10 wt% of (one or more) C2 to C6 alkylene carbonates.

[0130] The electrolyte may particularly contain 0.2 wt% to 5 wt% of (one or more) C1 to C8 nitriles.

[0131] As an additive, the electrolyte may also contain at least one fluorinated carbonate, such as FEC (fluoroethylene carbonate) or F2EC (difluoroethylene carbonate); or at least one phosphate, such as TMP (trimethyl phosphate), or phosphite, such as TMSPI (tris(trimethylsilyl) phosphite).

[0132] The electrolyte may also include an ionic liquid (in addition to the above-mentioned solvent and additives). An ionic liquid is a salt having a melting point of less than 100 °C, preferably less than room temperature (i.e., less than the temperature in the range of 15 °C to 35 °C). Therefore, "ionic liquid" is understood to mean a salt, i.e., an ionic compound containing at least one anion and one cation that exists in liquid form at a temperature of 100 °C. The possible ionic liquids include, in particular, those combined with FSI or TFSI as an anion and preferably an onium cation selected from the group consisting of quaternary ammonium ions, pyridinium ions, imidazolium ions, oxazolidinium ions, piperidinium ions, phosphonium ions, pyrrolidinium ions, sulfonium ions, oxonium ions, and mixtures thereof. The onium cation can be, in particular, trimethylpropylammonium, trimethylbutylammonium, trimethylhexylammonium, tributylmethylammonium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-butyl-1-methylpyrrolidinium, 1-propyl-3-methylpyrrolidinium, 1-butyl-1-methylpiperidinium, 1-methyl-1-propylpiperidinium, and methyl(triethyl)phosphonium.

[0133] Electrochemical cell and battery The present invention also relates to an electrochemical cell containing the above-mentioned electrolyte. The electrochemical cell also includes a negative electrode (or anode) and a positive electrode (or cathode).

[0134] The electrochemical cell can also include a separator impregnated with the electrolyte. The electrolyte wets the electrodes and the separator.

[0135] "Negative electrode" means an electrode that functions as an anode when the cell conducts current (i.e., during the discharge process) and functions as a cathode during the cell charging process.

[0136] The negative electrode typically includes an electrochemically active material (negative electrode material), optionally an electronically conductive material, and optionally a binder, and preferably includes a negative electrode material, an electronically conductive material, and a binder.

[0137] The term "positive electrode" means an electrode that functions as a cathode when the cell conducts current (i.e., during the discharge process) and as an anode when the cell is in the charging process.

[0138] The positive electrode typically includes an electrochemically active material (positive electrode material), optionally an electronically conductive material, and optionally a binder, and preferably includes a positive electrode material, an electronically conductive material, and a binder.

[0139] The term "electrochemically active material" is understood to mean a material into which ions can be reversibly inserted.

[0140] The term "electronically conductive material" is understood to mean a material that can conduct electrons.

[0141] Independently for each electrode, the electronically conductive material is preferably conductive carbon.

[0142] Conductive carbon ensures electronic conductivity and can be any carbon that exhibits essentially electronically conductive behavior, such as carbon nanoparticles, carbon black, graphite, Ketjen (registered trademark) carbon, Shawinigan carbon, graphene, carbon nanotubes, carbon fibers (e.g., vapor-grown carbon fibers or VGCF), non-powdery carbon obtained from carbonization of organic precursors, or a combination of two or more of these.

[0143] Independently for each electrode, the binder can be any polymer that ensures the mechanical integrity of the electrode.

[0144] The material of each electrode may also include a binder. Non-limiting examples of binders include linear, branched, and / or cross-linked polyether polymer binders (e.g., polymers based on poly(ethylene oxide) (PEO) or poly(propylene oxide) (PPO), or mixtures of these two (or EO / PO copolymers), optionally containing units that can be cross-linked), water-soluble binders (e.g., polyacrylic acid, CMC (carboxymethyl cellulose), SBR (styrene / butadiene rubber), NBR (acrylonitrile / butadiene rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), ACM (acrylic rubber), etc.), or fluororesin binders (e.g., PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), etc.), and combinations thereof.

[0145] Preferably, it can be polyacrylic acid, CMC (e.g., in combination with SBR), or PVDF.

[0146] The negative electrode material can be any carbon having different ratios of amorphous domains and graphite domains. This includes hard carbon and soft carbon. Hard carbon, unlike soft carbon, is a solid form of carbon that cannot be converted to graphite by heat treatment. As a result, during appropriate heat treatment, the amorphous domains of soft carbon are reorganized into graphite planes. Thus, soft carbon represents graphitizable non-graphite carbon having high electronic conductivity and a degree of graphitization and interlayer distance that can be adjusted by heat treatment.

[0147] Soft carbon may include, for example, soft carbon derived from pitch, carbon black, spherical carbon derived from mesitylene, or heteroatom-doped, partially carbonized aromatic hydrocarbons.

[0148] The negative electrode material can be any mixture of hard carbon and soft carbon and can be post-treated either by heat treatment or by chemical treatment using an acidic or alkaline medium.

[0149] The positive electrode material can preferably be a polyanion-based compound containing sodium. This includes, in particular, layered oxides. In certain embodiments, the polyanion-based compound has the formula NaM x O y (where x is preferably from 1 to 2 and y is preferably from 2 to 3), and can be, for example, NaMO2. In these two formulas, and all of the following formulas, M represents a metal or a mixture of metals.

[0150] Optionally, oxygen can be partially or completely, preferably partially, replaced by any other element, such as a halogen, preferably fluorine: for example, the corresponding material can have the formula NaM x O y-z F z , where z is from 0 to y, and x and y are preferably within the above ranges.

[0151] Optionally, oxygen can be partially or completely, preferably completely, replaced by sulfate, phosphate, or silicate, and optionally by another element, especially a halogen, preferably fluorine.

[0152] In particular, it can be a compound of the formula Na q M x (PO4) y F z (preferably, q = 1 to 4, x = 2 to 4, y = 2 to 4, z = 0 to 3), such as Na3V2(PO4)2F3. It can also be a compound of the formula Na q M x (SO4) y (preferably, q = 1 to 4, x = 1 to 4, y = 1 to 4), such as Na2Fe(SO4)2. It can also be the compound Na q M x (SiO4) y (preferably, q = 1 to 4, x = 1 to 2, y = 1 to 4), such as Na2FeSiO4.

[0153] The negative electrode can be supported, for example, on an aluminum foil.

[0154] The positive electrode can be supported, for example, on an aluminum foil.

[0155] In both cases, the aluminum foil can have a thickness of about 5 to 40 μm.

[0156] The aluminum may be chemically treated or may be provided with a specific coating such as a carbon coating.

[0157] The support (for example, an aluminum foil) can be coated with an ink or dispersion containing an active material (positive or negative), an electron conductive material (for example, conductive carbon), a binder, and a solvent.

[0158] The solvent can be water or an aqueous solution, or an organic solvent (for example, ethanol, N-methylmethylpyrrolidone, etc.) that guarantees a uniform mixing of the components and the possibility of coating the ink by a coating method such as a slot die or Comma Coater (registered trademark) apparatus. The viscosity of the solution can be adjusted by the dry mass ratio defined as the ratio of the total mass of the total solid mass (solid and liquid). When the binder is carboxymethyl cellulose or polyacrylic acid, it is preferable to use water or an aqueous solution. When the binder is polyvinylidene fluoride, it is preferable to use an organic solvent.

[0159] The separator may be a porous membrane, which functions as a barrier between the negative electrode and the positive electrode and is electronically insulating but ionically conductive.

[0160] The separator can contain or be based on polyolefin or cellulose. As the polyolefin, an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or a multilayer structure of the above polymers can be used. Alternatively, the separator may be made of glass fiber.

[0161] The present invention also relates to a battery comprising at least one, preferably two or more, of the above-described electrochemical cells. The electrochemical cells can be assembled in series and / or in parallel within the battery.

Examples

[0162] The following examples illustrate the invention without limiting it.

[0163] Example 1 175.7 g of sodium carbonate (1.66 mol) and 2100 g of acetonitrile are charged into a 4-liter reactor. While stirring, 600 g of molten HFSI (3.31 mol) is poured in over 2 hours while maintaining the temperature between 15 °C and 20 °C. After the addition is complete, the mixture is left to react at 20 °C for 4 hours. The pH of the solution becomes 6. The solution is filtered and then evaporated under vacuum at 40 °C using a rotary evaporator. Drying is completed in a vacuum oven. 652 g of NaFSI is obtained in the form of a white powder. The yield is 97%.

[0164] 19 F NMR analysis shows the presence of peaks corresponding to NaFSI.

[0165] 1 H NMR analysis shows the presence of acetamide at a content of 300 ppm.

[0166] Karl Fischer analysis shows that the water content is 10 ppm.

[0167] Analysis by ion chromatography is as follows: - NH2SO3 - =540 ppm - Cl - <5 ppm - F - =80 ppm - SO4 2- =1680 ppm - FSO3 - <5 ppm

[0168] Example 2 215.4 g of sodium carbonate (2.03 mol) and 5600 g of acetonitrile are charged into a 10-liter reactor. While stirring, 700 g of molten HFSI (3.87 mol) is poured in over 2 hours while maintaining the temperature between 15 °C and 20 °C. After the addition is complete, the mixture is left to react at 20 °C for 2 hours. The solution is filtered and then concentrated to a concentration of 75% using a short-path thin-film evaporator under vacuum. The concentrated solution thus obtained is poured into 2250 g of dichloromethane and left to stand at 5 °C overnight. Next, the solution is filtered, the precipitate is washed with dichloromethane, and dried on the filter at 40 °C under nitrogen. 715 g of NaFSI is obtained in the form of a white powder. The yield is 91%.

[0169] 19 19F NMR analysis shows the presence of peaks corresponding to NaFSI.

[0170] 1 1H NMR analysis shows the presence of acetamide at a content of 40 ppm.

[0171] Karl Fischer analysis shows that the water content is 50 ppm.

[0172] Analysis by ion chromatography is as follows: - NH2SO3 - =20 ppm - Cl - <5 ppm - F -<5 ppm - SO4 2- <5 ppm - FSO3 - <5 ppm

Claims

1. A composition comprising a salt composed of sodium cations and an anion of formula (II): [wherein, R １ and R ２ each independently represents a fluorine atom or a perfluoro group] The composition has an acetamide content of 0.1 to 1000 ppm by weight.

2. The composition according to claim 1, wherein the anion of formula (II) is a bis(fluorosulfonyl)imide anion or a bis(trifluoromethylsulfonyl)imide anion, preferably a bis(fluorosulfonyl)imide anion.

3. The composition according to claim 1 or 2, wherein the acetamide content is 1 to 500 ppm by weight, preferably 2 to 100 ppm by weight.

4. The composition according to any one of claims 1 to 3, wherein the salt is present in a weight content of 99.5% by weight or more, preferably 99.8% by weight or more, more preferably 99.9% by weight or more.

5. By weight, - 0 to 500 ppm, preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm of water, - Cl ions at 0 to 50 ppm, preferably 0.5 to 20 ppm, more preferably 1 to 10 ppm － ions - F ions at 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm － ions - SO ions at 0 to 3000 ppm, preferably 0.5 to 500 ppm, more preferably 1 to 20 ppm ４ ２－ ions - FSO of 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm ３ － ion The composition according to any one of claims 1 to 4, which also contains.

6. - Supplying a compound of formula (I): [wherein, R １ and R ２ each independently represents a fluorine atom or a perfluoro group] And - Reacting the compound of formula (I) with a sodium compound A method for preparing the composition according to any one of claims 1 to 5, which comprises.

7. The sodium compound is NaCl or preferably NaH, NaOH, NaHCO ３ , Na ２ CO ３ , and a sodium base selected from Na(OAc), preferably Na ２ CO ３ , the method according to claim 6.

8. The reaction is - Preferably in the presence of an organic solvent selected from nitriles, esters, ethers, ketones, alcohols, carbonates, and combinations thereof, and / or - At a molar ratio of sodium compound / compound of formula (I) of 0.9 to 1.1, preferably 1 to 1.05, and / or - At a temperature of -5°C to 40°C, preferably 15°C to 25°C The method according to claim 6 or 7, which is carried out.

9. The method according to any one of claims 6 to 8, wherein the reaction is carried out in the presence of acetonitrile as the organic solvent.

10. - A step of synthesizing the compound of formula (I), preferably by fluorination of a chlorinated compound and optionally by distillation The method according to any one of claims 6 to 9, which comprises.

11. - After the reaction, a step of purifying the reaction mixture, preferably by filtration and crystallization The method according to any one of claims 6 to 10, which further comprises.

12. The method according to claim 11, wherein the crystallization is preferably carried out in the presence of a non-solvent for the compound of formula (II), which is selected from chlorinated solvents, aromatic solvents, alkanes, and combinations thereof.

13. An electrolyte comprising the composition according to any one of claims 1 to 5, mixed with one or more solvents and optionally one or more additives.

14. The electrolyte according to claim 13, further comprising an ionic liquid containing FSI or TFSI anions preferably associated with an onium cation.

15. An electrochemical cell comprising a negative electrode, a positive electrode, and an electrolyte, wherein the electrolyte comprises the composition according to any one of claims 1 to 5.

16. The cell according to claim 15, wherein the negative electrode comprises hard carbon and / or soft carbon as an electrochemically active material, and the positive electrode comprises a polyanion-based compound containing sodium.

17. A battery comprising at least one electrochemical cell according to claim 15 or 16.

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