A salt composition for electrolytes with a low content of sulfamate ions

Abstract

The present invention relates to a composition comprising a salt consisting of a sodium cation and an anion of formula (II): TIFF2025523137000008.tif28170[wherein R 1 and R 2 each independently represents a fluorine atom or a perfluoro group] and having a sulfamic acid ion content of 0.1 to 3000 ppm by weight. The present invention also relates to a process for preparing this composition and an electrolyte containing this composition.

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 widely 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 generally include at least a negative electrode (anode), a positive electrode (cathode), an electrolyte, and preferably a separator. The electrolyte is generally formed from a sodium salt dissolved in a solvent (which may be a mixture of organic solvents) to achieve a good compromise between the viscosity and the 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 particularly includes 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 a fluorosulfonylimide-type alkali metal salt (preferably a lithium salt) 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, not containing water, and the impurities of NaCl, NaF, and NaFSO3 being present at a content of 1000 ppm or less, respectively.

[0010] Patent Publication 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 first relates to a composition comprising a salt consisting of a sodium cation and an anion of formula (II): TIFF2025523137000002.tif28170[wherein R 1 and R 2 each independently represents a fluorine atom or a perfluoro group] and having a sulfamic acid ion content of 0.1 to 3000 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 sulfamic acid ion content is 1 to 1000 ppm by weight, preferably 10 to 300 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, by weight, - Water in an amount of 0 to 500 ppm, preferably 0.5 to 100 ppm, more preferably 1 to 50 ppm, - Cl ions in an amount of 0 to 50 ppm, preferably 0.5 to 20 ppm, more preferably 1 to 10 ppm - ions, - F ions in an amount of 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm - ions, - SO4 ions in an amount of 0 to 3000 ppm, preferably 0.5 to 500 ppm, more preferably 1 to 20 ppm 2- ions, - FSO3 ions in an amount of 0 to 100 ppm, preferably 0.5 to 50 ppm, more preferably 1 to 10 ppm - ions are also included.

[0019] The present invention also relates to a process for preparing the above composition, - Formula (I): TIFF2025523137000003.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 is also related to a process comprising.

[0020] In certain embodiments, the compound of formula (I) has a sulfamic acid content of 1 to 5000 weight ppm, preferably 500 to 2500 weight ppm.

[0021] In certain embodiments, the sodium compound is NaCl or preferably a sodium base selected from NaH, NaOH, NaHCO3, Na2CO3, and Na(OAc), preferably Na2CO3.

[0022] In certain embodiments, 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 to 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 is carried out.

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

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

[0025] In certain embodiments, the 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 an FSI or TFSI anion preferably bound to 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 Na-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 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 such as HFSI having specific qualities are used so that a composition with a high performance level can be easily obtained.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be described in more detail and non-limiting manner 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 first relates to an anion of formula (II): Relates to a composition comprising at least one salt consisting of TIFF2025523137000004.tif28170 and sodium cations.

[0041] In formula (II), R 1 and R 2 each independently 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 multiple 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 called the FSI anion); and / or a bis(trifluoromethylsulfonyl)imide anion (also called the TFSI anion). Even more preferably, it is the FSI anion, in which case the salt is NaFSI.

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

[0044] The composition according to the present invention may contain the salt (the anion of formula (II) and sodium cations) 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 sodium cations.

[0045] The composition of the present invention may in particular contain one or more other anions and / or one or more other cations.

[0046] In particular, the composition according to the present invention contains sulfamate ions (NH2SO3 -) may be included in a weight content of 3000 ppm or less; 2000 ppm or less; 1000 ppm or less; 500 ppm or less; 300 ppm or less; 200 ppm or less; 100 ppm or less; 50 ppm or less; 20 ppm or less.

[0047] The composition according to the present invention may particularly include a sulfamic acid ion content of 0.1 to 3000 ppm by weight, preferably 0.5 to 3000 ppm by weight, more preferably 1 to 1000 ppm by weight, and even more preferably 10 to 300 ppm by weight.

[0048] The composition according to the present invention may particularly include a sulfamic acid ion 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; 1000 to 2000 ppm by weight; 2000 to 3000 ppm by weight.

[0049] The above sulfamic acid ion content can make it possible to obtain optimal performance of the composition, especially when used in a Na-ion battery electrolyte.

[0050] In certain embodiments, the composition optionally includes acetamide in a content of 1000 ppm or less, preferably 500 ppm or less, and more preferably 100 ppm or less. Acetamide 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 2 ppm by weight. For example, the acetamide content may be 0 to 1000 ppm by weight, preferably 1 to 500 ppm by weight, and more preferably 2 to 100 ppm by weight.

[0051] In certain embodiments, the composition optionally includes water in a content of 500 ppm by weight or less, preferably 200 ppm by weight or less, more 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 from 0 to 500 ppm by weight, or from 0.5 to 100 ppm by weight, or from 1 to 50 ppm by weight.

[0052] In certain embodiments, the composition optionally includes Cl - ions in a content of 50 ppm by weight or less, preferably 20 ppm by weight or less, more preferably 10 ppm by weight or less. Cl - ions 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 Cl - ion content can be from 0 to 50 ppm by weight, or from 0.5 to 20 ppm by weight, or from 1 to 10 ppm by weight.

[0053] In certain embodiments, the composition optionally includes F - ions in a content of 100 ppm by weight or less, preferably 50 ppm by weight or less, more preferably 10 ppm by weight or less. F - ions 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 more, or 1 ppm by weight or more. For example, the F - ion content can be from 0 to 100 ppm by weight, or from 0.5 to 50 ppm by weight, or from 1 to 10 ppm by weight.

[0054] In certain embodiments, the composition optionally includes SO4 2- ions in a content of 3000 ppm by weight or less, preferably 500 ppm by weight or less, more preferably 100 ppm by weight or less, or even 20 ppm by weight or less. SO4 2- ions 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 SO4 2-The content of the ion can 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 comprises 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 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, FSO3 - the content of ions can 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 - Optionally, a compound of formula (I): synthesizing TIFF2025523137000005.tif28170, - reacting the compound of formula (I) with a sodium compound, - Optionally, purifying the reaction mixture can be prepared by a process comprising each step of.

[0060] In formula (I), R1 and R 2 has the same meaning as in formula (II).

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

[0062] In particular, R 1 =R 2= in the case of 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 in particular be synthesized 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 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 independently represent a chlorine atom or a perchlorinated group, which preferably contains 1 to 8 carbon atoms, more preferably 1 to 3 carbon atoms, even more preferably a trichloromethyl group.

[0064] In particular, the chlorinated compound may be (bis(chlorosulfonyl)imide), which enables the obtaining of HFSI.

[0065] In particular, the chlorinated compound may be (bis(trichloromethylsulfonyl)imide), which enables the obtaining of bis(trifluoromethylsulfonyl)imide.

[0066] Fluorination is carried out by contacting a chlorinated compound with a fluorinating agent selected from the group consisting of 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 of the interaction between the solvent and 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] The organic solvent SO1 is preferably 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 SO1 (or a mixture of organic solvents SO1), preferably between 20 °C and the boiling point of the organic solvent SO1 (or a mixture of organic solvents SO1).

[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 an organic solvent SO1 or a mixture of organic solvents SO1 before the reaction with the fluorinating agent (preferably anhydrous HF).

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

[0073] According to one embodiment, anhydrous HF is preferably introduced into the reaction medium in a 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 medium or an open medium, and it is particularly preferred to carry out the reaction in an open medium where HCl is released in a gaseous state.

[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 stripping with, for example, an inert gas (such as nitrogen, helium, or argon).

[0077] However, there is a possibility that residual HF and / or residual HCl are dissolved in the reaction medium. In the case of HCl, at its operating pressure and temperature, since HCl is mainly in a 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 products obtained at the end of the fluorination reaction may contain HF (especially unreacted HF), chlorinated compounds, solvent SO1 (e.g., 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 - a first stream F1, preferably at the top of the distillation column, containing HF, optionally an organic solvent SO1, and / or optionally HCl, and being a gas or a liquid, stream F1; - a second stream F2, preferably at the bottom of the distillation column, containing the compound of formula (I) and optionally heavy compounds, preferably being a liquid, stream F2 allows for the formation and recovery of.

[0082] If 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 the distillation column, containing the compound of formula (I), not containing heavy compounds, preferably being a liquid, stream F2-1, - a stream F2-2, preferably at the bottom of the distillation column, containing heavy compounds and the compound of formula (I), with the compound of formula (I) contained in the composition obtained in step b) being less than 10% by weight, preferably less than 7% by weight, preferably less than 5% by weight, preferably being a liquid, stream F2-2 to form and recover.

[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 decomposition reactions of chlorinated compounds, for example, the formation of compounds such as FSO2NH2, and / or by the formation of oligomers by decomposition reactions of the solvent.

[0084] According to one embodiment, the distillation step is - a first stream F'1, preferably at the top of the distillation column, comprising 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, comprising 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, comprising a 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 a liquid, the stream F'3 to enable the formation and recovery of

[0085] To carry out the side stream withdrawal, the distillation column can comprise 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 conventional equipment. This can be a distillation device comprising a distillation column, a boiler, and a condenser. The distillation column can comprise 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 with high purity. Using the compound of formula (I) with high purity advantageously makes it possible to avoid complex subsequent purification steps and prepare a composition containing a high-purity salt.

[0089] Therefore, the collected product (and / or the product 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 collected product (and / or the product 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 from 1 to 5000 ppm, from 10 to 4000 ppm, from 100 to 3000 ppm, or from 500 to 2500 ppm by weight. It can be, for example, from 1 to 10 ppm, from 10 to 50 ppm, from 50 to 100 ppm, from 100 to 200 ppm, from 200 to 500 ppm, from 500 to 1000 ppm, from 1000 to 2000 ppm, from 2000 to 3000 ppm, from 3000 to 4000 ppm, or from 4000 to 5000 ppm by weight. The sulfamic acid content can be determined by ion chromatography (expressed 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, - Supply of ultrapure water (18.2 megohms) 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 It consists of

[0092] The eluent used may be a KOH solution with a concentration of 25 mmol / L and may 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 particularly NaCl.

[0095] Alternatively, the reaction can be an acid-base reaction. In this 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 particularly selected from NaH, NaOH, NaHCO3, Na2CO3, Na(OAc) (sodium acetate), and mixtures thereof. Preferably, Na2CO3 is used.

[0098] The reaction can be carried out particularly 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 particularly selected from nitriles (especially acetonitrile, propionitrile or butyronitrile), esters (especially methyl, ethyl, propyl, isopropyl, or butyl acetate), ethers (especially diethyl ether or methyl tert-butyl ether), ketones (especially acetone or methyl ethyl ketone), alcohols (especially methanol, ethanol or isopropanol), carbonates (especially dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate), and mixtures thereof.

[0099] Preferably, the reaction is carried out in the presence of acetonitrile as an 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 between -5°C and 40°C, preferably between 15°C and 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 particularly 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 particularly 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, particularly 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 content.

[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. Thus, water is not contained or is essentially free of water. 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 sulfamate ions in the electrolyte can be 0.1 to 3000 weight ppm, preferably 1 to 1000 weight ppm, more preferably 10 to 300 weight ppm.

[0111] The content of acetamide in the electrolyte can be 0 to 1000 weight ppm, preferably 1 to 500 weight ppm, more preferably 2 to 100 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 -The content of ions 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 (4,5-dicyano-2-trifluoromethylimidazolidone sodium), 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%, still more preferably 5 wt% to 30 wt%. 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.

[0118] (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.

[0119] Among carbonates, (one or more) solvents can be especially C3-C6 alkyl carbonate solvents (especially cyclic and / or linear).

[0120] In certain embodiments, a mixture of at least two solvents, namely a mixture of a cyclic C3-C6 alkyl carbonate solvent and a linear C3-C6 alkyl carbonate solvent, is provided.

[0121] As the cyclic C3-C6 alkyl carbonate, especially ethylene carbonate (EC), butylene carbonate (BC), or propylene carbonate (PC) can be used.

[0122] As the linear C3-C6 alkyl carbonate, especially dimethyl carbonate (DMC), diethyl carbonate (DEC) or ethyl methyl carbonate (EMC) can be used.

[0123] The additive can include a C2-C6 alkylene carbonate.

[0124] The additive can include a C1-C8 nitrile.

[0125] The additive can include a C2-C6 alkylene carbonate and a C1-C8 nitrile.

[0126] The C2-C6 alkylene carbonate can be cyclic or linear. For example, the C2-C6 alkylene carbonate can be vinylene carbonate.

[0127] C1-C8 nitriles may contain at least two nitrile units. Preferably, the C1-C8 nitrile has the general formula NC-(CH) n -CN, and n is an integer from 1 to 6, preferably 2, 3, or 4. The C1-C8 nitrile can be selected from adiponitrile, succinonitrile, or glutaronitrile, with adiponitrile being preferred (n = 4).

[0128] The electrolyte may particularly contain 2% to 10% by weight of (one or more) C2-C6 alkylene carbonates.

[0129] The electrolyte may particularly contain 0.2% to 5% by weight of (one or more) C1-C8 nitriles.

[0130] 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).

[0131] The electrolyte may also include an ionic liquid (in addition to the above 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 that combine FSI or TFSI as an anion with an onium cation preferably 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.

[0132] Electrochemical cell and battery The present invention also relates to an electrochemical cell containing the above-described electrolyte. The electrochemical cell also includes a negative electrode (or anode) and a positive electrode (or cathode).

[0133] The electrochemical cell can also include a separator impregnated with the electrolyte. The electrolyte wets the electrodes and the separator.

[0134] "Negative electrode" means an electrode that functions as an anode when the cell is discharging (i.e., during the discharge process) and functions as a cathode when the cell is charging.

[0135] 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.

[0136] The term "positive electrode" means an electrode that functions as a cathode when the cell is discharging (i.e., during the discharge process) and as an anode when the cell is in the charging process.

[0137] 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.

[0138] The term "electrochemically active material" is understood to mean a material into which ions can be reversibly inserted.

[0139] The term "electronically conductive material" is understood to mean a material that can conduct electrons.

[0140] Independently for each electrode, the electronically conductive material is preferably conductive carbon.

[0141] Conductive carbon ensures electronic conductivity and can be any carbon that essentially exhibits 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 the carbonization of organic precursors, or a combination of two or more of these.

[0142] Independently for each electrode, the binder can be any polymer that ensures the mechanical integrity of the electrode.

[0143] The material of each electrode can also contain 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.

[0144] Preferably, it can be polyacrylic acid, CMC (e.g., in combination with SBR), or PVDF.

[0145] The negative electrode material can be any carbon having amorphous domains and graphite domains in different ratios. 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.

[0146] Soft carbon can include, for example, soft carbon derived from pitch, carbon black, spherical carbon derived from mesitylene, or heteroatom-doped, partially carbonized aromatic hydrocarbons.

[0147] 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.

[0148] 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 the following formulas, M represents a metal or a mixture of metals.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] The negative electrode can be supported, for example, on an aluminum foil.

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

[0154] In either case, the aluminum foil can have a thickness of about 5 to 40 μm.

[0155] The aluminum can be chemically treated or may be provided with a specific coating such as a carbon coating.

[0156] The support (e.g., aluminum foil) can be coated with an ink or dispersion containing an active material (positive or negative), an electronically conductive material (e.g., conductive carbon), a binder, and a solvent.

[0157] The solvent can be water or an aqueous solution, or an organic solvent (e.g., 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) device. 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.

[0158] 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 ion-conductive.

[0159] 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.

[0160] The present invention also relates to a battery including 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

[0161] The following examples illustrate the invention without limiting it.

[0162] 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%.

[0163] 19 F NMR analysis shows the presence of peaks corresponding to NaFSI.

[0164] 1 H NMR analysis shows the presence of acetamide at a content of 300 ppm.

[0165] Karl Fischer analysis shows that the water content is 10 ppm.

[0166] Analysis by ion chromatography is as follows: - NH2SO3 - =540 ppm - Cl - <5 ppm - F - =80 ppm - SO4 2- =1680 ppm - FSO3 - <5 ppm

[0167] 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% in 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%.

[0168] 19 19F NMR analysis shows the presence of peaks corresponding to NaFSI.

[0169] 1 1H NMR analysis shows the presence of acetamide at a content of 40 ppm.

[0170] Karl Fischer analysis shows that the water content is 50 ppm.

[0171] 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 the following formula (II): [wherein, R １ and R ２ each independently represents a fluorine atom or a perfluoro group] and having a content of sulfamic acid ions of 0.1 to 3000 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 content of sulfamic acid ions is 1 to 1000 ppm by weight, preferably 10 to 300 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 method according to claim 6, wherein the compound of formula (I) has a sulfamic acid content of 1 to 5000 ppm by weight, preferably 500 to 2500 ppm by weight.

8. 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 or 7, wherein it is

9. 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 any one of claims 6 to 8, which is carried out.

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

12. The method according to claim 11, wherein 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.

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, preferably comprising an FSI or TFSI anion bound to 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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