Solvent-free method for preparing salts of bis(fluorosulfonyl)imides

Abstract

The present disclosure relates to a process for preparing salts of bis(fluorosulfonyl)imides and alkali metal salts of bis(fluorosulfonyl)imides from said bis(fluorosulfonyl)imide salts. More specifically, the present invention provides a novel process for producing these salts of bis(fluorosulfonyl)imides that is operable on an industrial scale and for providing high purity bis(fluorosulfonyl)imide salts.

Description

[Technical Field]

[0001] The present invention relates to a process for preparing salts of bis(fluorosulfonyl)imides and a process for preparing alkali metal salts of bis(fluorosulfonyl)imides from the bis(fluorosulfonyl)imide salts. More specifically, the present invention provides a novel process for producing these salts of bis(fluorosulfonyl)imides that is operable on an industrial scale and for providing high-purity bis(fluorosulfonyl)imide salts. [Background technology]

[0002] Bis(fluorosulfonyl)imides and their salts, particularly the lithium salt of bis(fluorosulfonyl)imide (LiFSI), are useful compounds in a variety of technical fields.

[0003] The preparation of bis(fluorosulfonyl)imides and their salts has been described in the literature. Among the various techniques described, the majority use a fluorination reaction with a fluorinating agent in a solvent.

[0004] In particular, International Publication No. 2017 / 090877 A1 (CLS) describes a method for producing lithium bis(fluorosulfonyl)imide, which includes the steps of (1) reacting bis(chlorosulfonyl)imide with a fluorinating agent in a solvent, followed by treatment with an alkaline reagent to produce ammonium bis(fluorosulfonyl)imide, and (2) reacting the ammonium bis(fluorosulfonyl)imide with a lithium base. The solvent used in step (1) is selected from the group consisting of alkyl ketones such as acetone, methyl ethyl ketone, and methyl isopropyl ketone; alcohols such as methanol, absolute ethanol, 1-propanol, and isopropanol; alkyl nitriles such as acetonitrile and propionitrile; and ethers such as tetrahydrofuran and dialkoxyalkanes. The solvent is then removed by distillation and concentration under reduced pressure.

[0005] In International Publication No. 2012 / 117961A1 (Nippon Soda), the formula [II] Cl-CO2-NH-SO2-R 1 (R 1 is a fluoroalkyl group, a fluorine atom or a chlorine atom) and preferably a compound of the formula NHF(HF) p A method for preparing fluorosulfonylimide salts is described, which involves the reaction of compound [II] (where p is 0-10) with a fluorinating agent [III]. The reaction between compound [II] and compound [III] can be carried out in the presence or absence of a solvent. However, according to Examples 1 and 2, ammonium di(fluorosulfonyl)imide is prepared from di(chlorosulfonyl)imide in acetonitrile. The solvent is then removed by distillation under reduced pressure. In general, this patent application does not disclose a method for preparing fluorosulfonylimide salts in the absence of a solvent or in the presence of a solvent amount less than 5% by weight, based on the total weight of the reaction mixture.

[0006] Japanese Patent No. 2016145147 (Nippon Shokubai) relates to a method for obtaining a fluorosulfonylimide compound represented by formula (1) by reacting a compound represented by formula (2) with a compound represented by formula (3) in a stoichiometric amount of 1 to 3 equivalents per mole of the compound in the presence of a solvent in an amount of 0 to 4 times the mass of the compound: [ka] In the formula, R 1 is C 1~6 is a fluoroalkyl group, and R 6 is halogen or C 1~6 Fluoroalkyl group, Cat1 + and Cat2 + is a monovalent group, and p is an integer of 1 to 10.

[0007] Japanese Patent Publication No. 2014201453 (Nippon Shokubai) describes a method for producing an alkali metal salt of fluorosulfonylimide, which comprises the steps of synthesizing an alkali metal salt of fluorosulfonylimide in the presence of a reaction solvent containing at least one solvent selected from the group consisting of carbonate-based solvents, aliphatic ether-based solvents, ester-based solvents, amide-based solvents, nitro-based solvents, sulfur-based solvents, and nitrile-based solvents, and then concentrating the alkali metal salt solution of fluorosulfonylimide by distilling off the reaction solvent in the presence of at least one poor solvent for the alkali metal salt of fluorosulfonylimide selected from the group consisting of aromatic hydrocarbon-based solvents, aliphatic hydrocarbon-based solvents, and aromatic ether-based solvents, and the concentration step comprises the step of mixing the poor solvent with a reaction solution containing the reaction solvent and the alkali metal salt of fluorosulfonylimide.

[0008] As described in the literature, the preparation of bis(fluorosulfonyl)imides and their salts by fluorination is carried out in a solvent, such as an organic solvent, to disperse the reactants and allow them to react. However, such solvents must be removed after the reaction to obtain products of the highest possible purity that can be used for battery applications. The step of removing the solvent increases the complexity of the industrial process as well as its overall cost. In addition, since only anhydrous solvents with residual amounts of water in ppm amounts are actually used, the solvent must typically be treated to remove residual amounts of water before being used in such processes.

[0009] It is an object of the present invention to provide a simpler process for preparing salts of bis(fluorosulfonyl)imides which does not require distillation of the reaction solvent.

[0010] WO 2012 / 096371 A1 (Sumitomo Electric Industries) describes a method for producing KN(SO2F)2 by adding HN(SO2Cl)2 (liquid form) to KF (powder form) under dry, solvent-free conditions to form an intermediate product, which is then reacted with KF in an aqueous solvent. More precisely, according to the method described in this document, in a first step, one chlorine atom of HN(SO2Cl)2 is replaced with fluorine, resulting in the intermediate product, which is the alkali metal salt KN(SO2Cl)(SO2F), and in a second step, the other chlorine atom is replaced with fluorine, resulting in the alkali metal salt KN(SO2F)2. Since HN(SO2Cl)2 is converted into the alkali metal salt KN(SO2Cl)(SO2F) in this two-step process, water can be used in the second step, as water dissolves alkali metal fluorides.

[0011] According to this document, the first part of the reaction is carried out under dry, solvent-free conditions by dropping one reactant in liquid form onto the second reactant in powder form. This results in a paste-like intermediate product that is very difficult to handle industrially. Furthermore, the total conversion of HN(SO2Cl)2 to KN(SO2F)2 occurs in two steps with separate intermediate products, which adversely affects the yield of the reaction as well as the level of impurities in the final product.

[0012] The object of the present invention is to provide a bis(fluorosulfonyl)imide salt X1N(SO2F)2 (where X1 is K + , Na + or onium cations (e.g., NH4 + The present invention provides a method for preparing bis(fluorosulfonyl)imide salts, which is operable on an industrial scale and provides high-purity bis(fluorosulfonyl)imide salts. In particular, the method is carried out in the presence of a molten reaction product, such as molten KN(SOF) or molten NHN(SOF), and in the absence of a solvent (or in the presence of a very limited amount of solvent), which serves to disperse the reactants. Summary of the Invention

[0013] The present invention relates to a compound of formula (I): [F-(SO2)-N - -(SO2)-F] n X1 n+ (I) (In the formula, - X1 n+ is K + , Na + and an onium cation, - n is 1 and represents the valence of the cation, Formula (II): Cl-(SO2)-NH-(SO2)-Cl (II) Bis(chlorosulfonyl)imide or a salt thereof Formula (III): X1 n+ (F - ) n (HF) p (In the formula, - p varies between 0 and 10, The process is carried out in the absence of a solvent or in the presence of an amount of solvent of less than 5% by weight, based on the total weight of the reaction mixture, in a molten salt of the bis(fluorosulfonyl)imide of formula (I).

[0014] The present invention also provides a compound of formula (I): [F-(SO2)-N - -(SO2)-F] n X1 n+ (I) (In the formula, - X1 n+ is K + , Na + and an onium cation, - n is 1 and represents the valence of the cation, Such salts can be obtained by the process of the present invention, which is characterized in that the amount of solvent is less than 100 ppm, for example less than 50 ppm.

[0015] The present invention also provides a compound represented by formula (V) F-(SO2)-NX3-(SO2)-F (IV) 1. A process for preparing an alkali salt of a bis(fluorosulfonyl)imide of the formula: (a) preparing a salt of a bis(fluorosulfonyl)imide of formula (I) according to any one of claims 1 to 8; (b) reacting the salt bis(fluorosulfonyl)imide (I) obtained in step (a) with an alkaline agent consisting of a lithium salt or a cesium salt.

[0016] The present invention also provides a compound of formula (IV): F-(SO2)-NX3-(SO2)-F (IV) wherein X3 represents Li or Cs, preferably Li; and the use of such salts in battery electrolyte solutions. DETAILED DESCRIPTION OF THE INVENTION

[0017] In this application: - the expressions "between… and…" as well as "from… to…" etc. are to be understood as including limits; - any description, even if made in relation to a particular embodiment, is applicable to and interchangeable with other embodiments of the invention; - When an element or component is said to be included in and / or selected from a list of enumerated elements or components, in the relevant embodiments expressly contemplated herein, the element or component can be any one of the individually enumerated elements or components, or can be selected from a group consisting of any two or more of the explicitly enumerated elements or components; it is to be understood that any element or component enumerated in a list of elements or components can be omitted from such list; - Any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited range, as well as the endpoints of the range, and equivalents thereof.

[0018] A first object of the present invention is to provide a compound of formula (I): [F-(SO2)-N - -(SO2)-F] n X1 n+ (I) (In the formula, - X1 n+ is K + , Na + and an onium cation, preferably NH + and - n is 1 and represents the valence of the cation, Formula (II): Cl-(SO2)-NH-(SO2)-Cl (II) Bis(chlorosulfonyl)imide or a salt thereof Formula (III): X1 n+ (F - ) n (HF) p (In the formula, - p varies between 0 and 10, The process is carried out in the absence of a solvent or in the presence of an amount of solvent less than 5% by weight, based on the total weight of the reaction mixture, in a molten salt of the bis(fluorosulfonyl)imide of formula (I).

[0019] The salts (I) described herein are characterized by a low residual amount of solvent, advantageously an undetectable amount of solvent, which makes the salts (I) suitable for many applications, especially battery applications.

[0020] The process of the present invention is carried out in the melt in the absence of solvents and diluents. More precisely, the process is carried out in a molten salt of the bis(fluorosulfonyl)imide of formula (I), e.g., molten KN(SO2F)2 or molten NH4N(SO2F)2, which serves to disperse the reactants and allows reactants (II) and (III) to meet and react. Importantly, the process of the present invention is a solvent-free process. In other words, no solvent / diluent is added to the reaction mixture during the reaction, or only very small amounts of solvent / diluent are added. This is advantageous, firstly, because steps to remove solvents increase the complexity of industrial processes as well as their overall cost. Secondly, because only anhydrous solvents (characterized by residual amounts of water on the order of ppm) can be practically used, the solvent typically needs to be treated before being used in such processes.

[0021] In the context of the present invention, the term "solvent" is intended to mean a compound that exhibits the following three cumulative properties: 1 / it is present throughout the reaction and is optionally added during the process; 2 / it is unchanged during the process, in other words, it is unreactive with the reactants involved; and 3 / it must be removed at the end of the process if the reaction product is to be in its highly pure form. Examples of solvents that fall within this definition are given below. For clarity, the molten salts of the bis(fluorosulfonyl)imides of formula (I) used in the process of the present invention are not included in the above definition of "solvent."

[0022] According to one embodiment of the present invention, the process described herein is carried out in the presence of a very small amount of solvent, i.e., less than 5 wt.% of the solvent, based on the total weight of the reaction mixture. Preferably, according to this embodiment, the amount of solvent is less than 4 wt.%, less than 3 wt.%, less than 2 wt.%, less than 1 wt.%, less than 0.5 wt.%, less than 0.1 wt.%, less than 0.01 wt.%, or less than 0.001 wt.% of the solvent, based on the total weight of the reaction mixture. The total weight of the reaction mixture is obtained by adding up the weights of the reactants and the weight of the molten salt of the bis(fluorosulfonyl)imide of Formula (I).

[0023] Solvents typically used in such processes are well known and have been described extensively in the literature. Such solvents may be aprotic, for example polar aprotic solvents, cyclic and acyclic carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, cyclic and acyclic esters, such as gamma-butyrolactone, gamma-valerolactone, methyl formate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, isopropyl acetate, propyl propionate, butyl acetate, cyclic and acyclic ethers, such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, amide compounds, such as N,N-dimethylformamide, N-methyloxazolidinone, sulfoxide and sulfone compounds, such as sulfolane, 3-methylsulfolane, dimethyl sulfoxide, and cyano-, nitro-, chloro- or alkyl-substituted alkanes or aromatic hydrocarbons, such as acetonitrile, valeronitrile, adiponitrile, benzonitrile, nitromethane, nitrobenzene may be selected from the group consisting of:

[0024] Typically, the organic solvent used to carry out such a process may be selected from the group consisting of ethyl acetate, isopropyl acetate, butyl acetate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, valeronitrile and acetonitrile, for example as described in the documents listed in the Background section.

[0025] According to the process of the present invention, in order to be in a molten state (also called a liquid state), a certain amount of a salt of a bis(fluorosulfonyl)imide of formula (I), such as KN(SO2F)2 and NH4N(SO2F)2, is heated to its melting temperature Tm before the addition of the reactants (or reactants). (I) The reaction mixture is heated to a temperature above 1000 K. Next, reactants, which may be in powder or liquid form, are added to the reaction mixture and reacted to produce a salt of a bis(fluorosulfonyl)imide of formula (I), such as KN(SO2F)2 or NH4N(SO2F)2. This means that the amount of such reaction product (i.e., a salt of a bis(fluorosulfonyl)imide of formula (I)) increases over the reaction time. In other words, the molten reaction product is used to provide a medium for dispersing the reactants and allowing them to meet and react. Therefore, no solvent is required according to the present invention. This is advantageous because it significantly simplifies the overall production process, as such a solvent does not need to be removed after the reaction to obtain a high-purity bis(fluorosulfonyl)imide salt. This presents the additional advantage of not requiring an additional step of removing water instead of the solvent.

[0026] According to the present invention, bis(chlorosulfonyl)imide (II): Cl-(SO2)-NH-(SO2)-Cl (II) or a salt thereof of formula (III): X1 n+ (F - ) n (HF) p (III) (In the formula, X1 n+and n are as defined above, and p varies between 0 and 10, preferably 0).

[0027] According to the present invention, X1 n+ is K + , Na + or an onium cation, where onium cation has its ordinary meaning to one skilled in the art.

[0028] Examples of onium cations include phosphonium cations, oxonium cations, sulfonium cations, fluoronium cations, chloronium cations, bromonium cations, iodonium cations, selenonium cations, telluronium cations, arsonium cations, stibonium cations, bismutonium cations; iminium cations, diazenium cations, nitronium cations, diazonium cations, nitrosonium cations, hydrazonium cations, diazenium dications, diazonium dications, imidazolium cations, pyridinium cations, quaternary ammonium cations, tertiary ammonium cations, secondary ammonium cations, primary ammonium cations, ammonium NH4 + cations, piperidinium cations, pyrrolidinium cations, morpholinium cations, pyrazolium cations, guanidinium cations, isouronium cations and isothiuronium cations.

[0029] Among these, imidazolium cation, pyridinium cation, quaternary ammonium cation, tertiary ammonium cation, secondary ammonium cation, primary ammonium cation, ammonium NH4 + More preferred are the piperidinium cation, the pyrrolidinium cation, the morpholinium cation, the pyrazolium cation, the guanidinium cation, and the isouronium cation.

[0030] Examples of these types of onium cations include: imidazolium cations, such as the 1,3-dimethylimidazolium cation, the 1-ethyl-3-methylimidazolium cation, the 1-propyl-3-methylimidazolium cation, the 1-butyl-3-methylimidazolium cation, the 1-pentyl-3-methylimidazolium cation, the 1-hexyl-3-methylimidazolium cation, the 1-heptyl-3-methylimidazolium cation, the 1-octyl-3-methylimidazolium cation, the 1-decyl-3-methylimidazolium cation, the 1-tetradecyl-3-methylimidazolium cation, midazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-allyl-3-ethylimidazolium cation, 1-allyl-3-butylimidazolium cation, 1,3-diallylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-methylimidazolium cation, and 1-hexadecyl-2,3-methylimidazolium cation; pyridinium cations, such as the 1-ethylpyridinium cation, the 1-butylpyridinium cation, the 1-hexylpyridinium cation, the 1-octylpyridinium cation, the 1-ethyl-3-methylpyridinium cation, the 1-ethyl-3-hydroxymethylpyridinium cation, the 1-butyl-3-methylpyridinium cation, the 1-butyl-4-methylpyridinium cation, the 1-octyl-4-methylpyridinium cation, the 1-butyl-3,4-dimethylpyridinium cation, and the 1-butyl-3,5-dimethylpyridinium cation; quaternary ammonium cations, such as tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetrabutylammonium cation, tetraheptylammonium cation, tetrahexylammonium cation, tetraoctylammonium cation, triethylmethylammonium cation, propyltrimethylammonium cation, diethyl-2-methoxyethylmethylammonium cation, methyltrioctylammonium cation, cyclohexyltrimethylammonium cation, 2-hydroxyethyltrimethylammonium cation, trimethylphenylammonium cation, benzyltrimethylammonium cation, benzyltributylammonium cation, benzyltriethylammonium cation, dimethyldistearylammonium cation, diallyldimethylammonium cation, 2-methoxyethoxymethyltrimethylammonium cation, N-methoxytrimethylammonium cation, N-ethoxytrimethylammonium cation, N-propoxytrimethylammonium cation and tetrakis(pentafluoroethyl)ammonium cation; tertiary ammonium cations, such as trimethylammonium cation, triethylammonium cation, tributylammonium cation, diethylmethylammonium cation, dimethylethylammonium cation, dibutylmethylammonium cation, and 4-aza-1-azoniabicyclo[2.2.2]octane cation; secondary ammonium cations, such as dimethylammonium cation, diethylammonium cation, and dibutylammonium cation; primary ammonium cations, such as methylammonium cation, ethylammonium cation, butylammonium cation, hexylammonium cation, and octylammonium cation; - Ammonium cation NH4 + ; piperidinium cations, such as the 1-propyl-1-methylpiperidinium cation and the 1-(2-methoxyethyl)-1-methylpiperidinium cation; pyrrolidinium cations, such as the 1-propyl-1-methylpyrrolidinium cation, the 1-butyl-1-methylpyrrolidinium cation, the 1-hexyl-1-methylpyrrolidinium cation, and the 1-octyl-1-methylpyrrolidinium cation; morpholinium cations, such as the 4-propyl-4-methylmorpholinium cation and the 4-(2-methoxyethyl)-4-methylmorpholinium cation; pyrazolium cations, such as the 2-ethyl-1,3,5-trimethylpyrazolium cation, the 2-propyl-1,3,5-trimethylpyrazolium cation, the 2-butyl-1,3,5-trimethylpyrazolium cation, and the 2-hexyl-1,3,5-trimethylpyrazolium cation; guanidinium cations, such as the guanidinium cation and the 2-ethyl-1,1,3,3-tetramethylguanidinium cation; and - isouronium cations, such as 2-ethyl-1,1,3,3-tetramethylisouronium cation Examples include:

[0031] Quaternary ammonium cations, tertiary ammonium cations, secondary ammonium cations, primary ammonium cations, and ammonium cation NH4 + and especially those specifically recited in the above list are more preferred. Ammonium cation NH4 + is the most preferred onium cation.

[0032] One of the reactants (sometimes called raw materials) required in the process of the present invention is bis(chlorosulfonyl)imide of formula (Cl-SO)-NH(II), sometimes abbreviated as HCSI. HCSI is commercially available or can be prepared by known methods, for example: - by reacting chlorosulfonyl isocyanate ClSO2NCO with chlorosulfonic acid ClSO2OH; - by reacting cyanogen chloride CNCl with anhydrous sulfuric acid SO3 and with chlorosulfonic acid ClSO2OH; - by reacting sulfamic acid NH2SO2OH with thionyl chloride SOCl2 and chlorosulfonic acid ClSO2OH Manufactured.

[0033] Another reactant required in the process of the present invention is a fluorinating agent (III). It can be used in any form in the process of the present invention, for example, in powder form or liquid form. Fluorinating agents are commercially available, or they can be prepared by known methods.

[0034] In formula (III), p represents a real number from 0 to 10, preferably from 0 to 4, and more preferably p is an integer from 0 to 4. In some embodiments, p is equal to 0.

[0035] According to one embodiment, the fluorinating agent (III) has the formula (IIIa): KF(HF)p (IIIa) (where p is 0 or 1).

[0036] According to another embodiment, the fluorinating agent (III) has the formula (IIIb): NaF(HF)p (IIIb) (where p is 0 or 1).

[0037] According to another embodiment, the fluorinating agent (III) has the formula (IIIc): X2F(HF)p (IIIc) where X2 is an onium cation as defined above and p is 0 or 1.

[0038] According to a preferred embodiment, the fluorinating agent (III) has the formula (IIId): NH4F(HF)p (IIId) (wherein p varies from 0 to 10) According to this preferred embodiment, specific examples of fluorinating agent (IIId) include NH4F, NH4F.HF, NH4F.2HF, NH4F.3HF, and NH4F.4HF. A preferred fluorinating agent (IIId) is NH4F.

[0039] According to another preferred embodiment, the fluorinating agent (III) is anhydrous. The water content, as measured, for example, by Karl Fischer water titration performed in a glove box, can be preferably less than 5,000 ppm, more preferably less than 1,000 ppm, less than 500 ppm, less than 100 ppm, less than 50 ppm, or even less than 10 ppm.

[0040] In some embodiments, the stoichiometric amount (also called molar amount) of fluorinating agent (III) to bis(chlorosulfonyl)imide (II) is from 0.1:1 to 20:1, for example, from 1:1 to 10:1, or from 2:1 to 8:1.

[0041] In some embodiments, the stoichiometric amount of fluorinating agent (III) is 1 equivalent or more per mole of bis(chlorosulfonyl)imide (II), for example, between 1 and 10 equivalents per mole of bis(chlorosulfonyl)imide (II). Preferably, the stoichiometric amount of fluorinating agent (III) is between 2 and 8 equivalents per mole of bis(chlorosulfonyl)imide (II), or between 3 and 6 equivalents per mole of bis(chlorosulfonyl)imide (II). More preferably, the stoichiometric amount of fluorinating agent (III) is equal to 4±0.8 equivalents or 4±0.5 equivalents per mole of bis(chlorosulfonyl)imide (II).

[0042] The process of the present invention may be carried out in batch, semi-batch or continuous mode.

[0043] In some embodiments, the process is carried out in a continuous or semi-continuous manner, and includes the step of continuously or semi-continuously removing the salt of bis(fluorosulfonyl)imide (I) from the reaction mixture. In accordance with the present invention, reactants can be continuously added to the reaction mixture and the reaction product can be semi-continuously removed.

[0044] In some embodiments, the process of the present invention comprises: (i) The amount Q of the salt of bis(fluorosulfonyl)imide (I) is calculated based on the melting point Tm of the compound (I). (I) a step of heating to the above temperature Ta (°C) to produce a molten salt of bis(fluorosulfonyl)imide (I); (ii) adding a fluorinating agent (III) and a bis(chlorosulfonyl)imide (II) to a molten salt of the bis(fluorosulfonyl)imide (I).

[0045] The temperature Ta (°C) is the melting point Tm of the salt of bis(fluorosulfonyl)imide (I). (I) For example, Ta may be greater than or equal to Tm(I)+2°C, or Ta may be greater than or equal to Tm(I)+5°C.

[0046] One of the reactants, for example the fluorinating agent (III), can be predispersed in the reaction mixture before introducing the second reactant, for example the bis(chlorosulfonyl)imide (II).

[0047] According to these embodiments, step (ii) may for example be carried out by itself: (ii1) adding a fluorinating agent (III) to a molten salt of bis(fluorosulfonyl)imide (I); (ii2) optionally removing residual amounts of water or aqueous liquid from the fluorinating agent (III); (ii3) adding bis(chlorosulfonyl)imide (II) to the reaction mixture.

[0048] As explained above, the reactants may be in any form, such as solid or liquid. For example, the fluorinating agent (III) may be added to the molten compound (I) in a solid form, such as powder form. The bis(chlorosulfonyl)imide (II) may be in a liquid form, such as dropwise addition to the reaction mixture.

[0049] Advantageously, the fluorinating agent (III) is added to the molten salt of bis(fluorosulfonyl)imide (I), followed by optional step (ii2) to remove residual amounts of water (or aqueous liquid) that the agent (III) may contain. This optional step is advantageously carried out after the fluorinating agent has been added to the reaction mixture. As explained above, the reaction should be carried out so that residual water is as little as possible in order to obtain a very pure salt of bis(fluorosulfonyl)imide (II). However, it is almost impossible to completely remove all residual water from the fluorinating agent (III) (dryness limit due to moisture in the crystals). However, this is advantageously possible when the fluorinating agent (III), in particular NHF, is dispersed in the molten salt of bis(fluorosulfonyl)imide (I). This optional step significantly contributes to a very pure product at the end of the reaction.

[0050] Preferably, the optional step (ii2) can be carried out by distillation of water.

[0051] In step (ii3), bis(chlorosulfonyl)imide (II) can be heated to a temperature Tb (°C) in the range of 30 to 150°C before being added to the reaction mixture. The temperature Tb (°C) can be, for example, in the range of 35 to 125°C, or in the range of 40 to 100°C. According to a particular embodiment, bis(chlorosulfonyl)imide (II) is heated to a temperature Tb (°C) = Ta (°C) ± 10°C, for example, Ta (°C) ± 5°C. According to another embodiment, bis(chlorosulfonyl)imide (II) is heated to a temperature Tb (°C) ≦ Ta (°C) + 10°C, or Tb (°C) ≦ Ta (°C).

[0052] In some embodiments, step (ii) comprises adding the fluorinating agent (III) and the bis(chlorosulfonyl)imide (II) simultaneously to the molten onium salt of the bis(fluorosulfonyl)imide (I).

[0053] The addition of reactants (II) and (III) to the molten onium salt of bis(fluorosulfonyl)imide (I) can generally be carried out sequentially, gradually, or continuously, and, particularly when the process is carried out batchwise, the total amount of each reactant can be added to the reactor in increments, for example, several times.

[0054] For example, batch reactors, extruders, and kneaders can be used in the present invention. An acid-corrosion resistant material (e.g., PTFE) can be coated into (or lined with) the selected reactor.

[0055] Reference can be made to industrialized melt mixers or melt blenders.

[0056] The kneader used can include any known suitable kneader that can be heated above the melting point of salt (I) and allows the release of gas products. Suitable kneaders generally have one, or preferably at least two, rotating shafts parallel to each other, the main shaft having a region with kneading elements arranged on its outer surface. The kneader can have rotors operated at a rotation speed ranging from 5 to 50 rpm, particularly preferably from 7.5 to 40 rpm, and especially from 10 to 30 rpm. The advantage of the kneader used in the present invention is that the residence time can be substantially longer than in an extruder. Degassing is even more substantially easier and can be carried out to a greater extent, thus facilitating the release of gas products. Furthermore, the shear rates of the present invention can be more easily achieved in the kneader. Various feed systems for reactants can be used in continuously operated kneaders. Liquid metering can be used when molten reactants are required.

[0057] Some or all of the steps of the process according to the invention are advantageously carried out in equipment that can withstand the corrosion of the reaction medium. For this purpose, corrosion-resistant materials are selected for the parts that come into contact with the reaction medium, such as alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon, and tungsten sold under the Hastelloy® brand, or alloys of nickel, chromium, iron, and manganese with added copper and / or molybdenum sold under the names Inconel® or Monel™, more particularly Hastelloy C276 or Inconel 600, 625, or 718 alloys. Stainless steels, such as austenitic steels, more particularly 304, 304L, 316, or 316L stainless steels, may also be selected. Steels with a nickel content of at most 22% by weight, preferably between 6% and 20% by weight, and more preferably between 8% and 14% by weight, are used. 304 and 304L steels have a nickel content that varies between 8% and 12% by weight, while 316 and 316L steels have a nickel content that varies between 10% and 14% by weight. More particularly, 316L steel is chosen. Equipment made of or coated with polymer compounds that are resistant to the corrosion of the reaction medium can also be used. In particular, materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA (perfluoroalkyl resin) can be mentioned. Glass equipment can also be used. The use of equivalent materials would not be outside the scope of the present invention. Other materials that may be suitable for contact with the reaction medium can also be mentioned, including graphite derivatives. The material for the filter must be compatible with the medium used. Fluorinated polymers (PTFE, PFA), loaded fluorinated polymers (Viton, etc.) can be mentioned. TM ), as well as polyester (PET), polyurethane, polypropylene, polyethylene, cotton, and other compatible materials can be used.

[0058] The process of the present invention can be carried out at atmospheric pressure or under reduced pressure. Preferably, the process of the present invention is carried out under reduced pressure. Carrying out the reaction under reduced pressure is preferred because it facilitates the removal of chlorine atoms from the bis(chlorosulfonyl)imide of formula (II) during the process. There is no particular limit to the pressure that can be applied to the process. The process can be carried out, for example, at a pressure between 0.5 bar and 3 bar, for example, between 0.7 and 2.5 bar, or between 0.9 and 2 bar.

[0059] The process of the present invention can advantageously be carried out under an inert atmosphere to avoid contamination with moisture, for example under nitrogen.

[0060] The process of the present invention can be carried out at a temperature below 150° C., for example below 125° C., or below 100° C. The process of the present invention preferably is carried out at a temperature below the melting temperature (Tm) of the onium salts of bis(fluorosulfonyl)imides of formula (I), such as KN(SOF) and NHN(SOF). (I) The reaction can be carried out at a temperature between 100°C and 150°C.

[0061] The reaction time of the process of the present invention can be freely selected depending on, for example, the reactor used, the required reaction temperature, and the amount of reactants, and is preferably 1 to 12 hours, particularly preferably 1.5 to 10 hours or 2 to 9 hours.

[0062] The process can include a step of heating a quantity Q of a salt of bis(fluorosulfonyl)imide (I) so that the salt (I) is in a molten or substantially molten state. In some embodiments, this step includes heating the quantity Q of the salt of bis(fluorosulfonyl)imide (I) to its melting point Tm (I)The process consists in heating the mixture to a temperature Ta (°C) or higher to produce a molten salt of bis(fluorosulfonyl)imide (I). The amount Q0 of the molten salt of bis(fluorosulfonyl)imide (I), in other words, the minimum amount of molten product used to carry out the process, cannot be less than 20 wt% of the total weight of the reaction mixture when all reactive materials have been added. For example, such amount Q0 can be at least 30 wt%, at least 35 wt%, at least 40 wt%, at least 45 wt%, at least 50 wt%, at least 55 wt%, at least 60 wt%, at least 65 wt%, or at least 70 wt%. Such amount Q0 can be less than 95 wt%, less than 90 wt%, or less than 85 wt%. The total weight of the reaction mixture when all reactive materials have been added can be calculated by adding the weight of the molten salt of bis(fluorosulfonyl)imide (I) to the weight of all reactants required in the process. According to an embodiment, the amount Q0 is 50±10 wt% of the total weight of the reaction mixture when all reactive materials have been added.

[0063] It is advantageous in accordance with the present invention to select the reaction conditions so that at the end of the process the conversion C is at least 95%, particularly preferably at least 98%, in particular at least 99%. For the purposes of the present invention, the conversion C is the molar ratio of the reacted reactive groups, i.e., bis(chlorosulfonyl)imide (II) and the fluorinating agent (III). Surprisingly, it has been found that the conversion of reactants (II) and (III) is very high under the operating conditions described herein, despite the absence of any solvent or diluent.

[0064] In some preferred embodiments, the process is such that the conversion C is at least 95%, at least 98%, at least 99%, at least 99.5%, at least 99.9% or at least 99.99%.

[0065] The process of the present invention may further comprise cooling the reaction mixture to a temperature Tc (°C) below 80°C, for example below 60°C.

[0066] The process of the present invention preferably further comprises filtering the reaction mixture. The filtering step is intended to remove reaction by-products and / or impurities, such as X1Cl and / or X1HF2 (wherein X1 is K + , Na + or an onium cation as described above). When the fluorinating agent is, for example, NH4F, the reaction by-products and / or impurities can be NH4Cl and NH4HF2.

[0067] Filtration products (funnel, membrane, Nutsche filter or glass filter, dryer...) are preferably used for the filtration.

[0068] According to the present invention, a high-purity or substantially high-purity salt of bis(fluorosulfonyl)imide of formula (I) is obtained in molten form at the end of the reaction. The bis(fluorosulfonyl)imide of formula (I) can be maintained at a temperature such that it remains liquid, but it can be post-processed to obtain a powder form, for example, a crystallized form. The bis(fluorosulfonyl)imide of formula (I) obtained from the process of the present invention can be used in its molten or crystallized form. For example, the molten salt of bis(fluorosulfonyl)imide of formula (I) can be added to a lower temperature organic solvent, such as trifluoroethanol, and crystallized before further use. According to yet another embodiment, the salt (I) can be at least partially crystallized in the melt, which can then be extracted or reused / recycled in a new reaction cycle.

[0069] The process of the present invention also comprises the following reaction parameters: - the molar ratio of bis(chlorosulfonyl)imide (II) to fluorinating agent (III) in the reaction mixture, the number of moles of reactants in the reaction mixture, in particular the number of moles of bis(chlorosulfonyl)imide (II), the temperature of the reaction mixture (°C), - pressure (atm), the melt viscosity of the reaction mixture, or - the filling level of the reactor, e.g. the kneader The method may include the additional step of measuring and / or monitoring at least one of:

[0070] A second object of the present invention is to provide a compound of formula (I): [F-(SO2)-N - -(SO2)-F] n X1 n+ (I) (In the formula, - X1 n+ is K + , Na + and an onium cation, - n is 1 and represents the valence of the cation) is a salt of bis(fluorosulfonyl)imide.

[0071] Such salts (I) can advantageously be obtained by the process described above.

[0072] The salts of the bis(fluorosulfonyl)imides of formula (I) of the present invention may be, for example, in the molten state or in crystalline form.

[0073] According to the invention, the salt (I) is such that its average crystal length is advantageously at least 400 μm, for example at least 450 μm, at least 500 μm, at least 600 μm or even at least 700 μm. Prior art salts have an average length of about 300 μm, which means that the salt is not of crystalline type.

[0074] Advantageously, due to the fact that no solvent is used in the process of the present invention, such salts are highly pure or substantially highly pure, with no traces of solvent or very little residual solvent. This is advantageous because the solvent typically used to prepare salt (I) needs to be removed after the reaction to obtain the highest possible purity product. Indeed, only very pure products can be used for battery applications. In some preferred embodiments, the amount of solvent in the salt of bis(fluorosulfonyl)imide of formula (I) is less than 100 ppm, for example, less than 90 ppm, less than 80 ppm, less than 70 ppm, less than 60 ppm, less than 50 ppm, less than 40 ppm, less than 30 ppm, less than 20 ppm, less than 10 ppm, or even less than 1 ppm. This is an advantageous feature of the salts obtained by the process of the present invention. The residual solvent content can be determined by GC (alternatively, headspace GC).

[0075] The salts of the bis(fluorosulfonyl)imides of formula (I) described herein are represented by the formula (II): Cl-(SO2)-NH-(SO2)-Cl (II) Bis(chlorosulfonyl)imide or a salt thereof Formula (III): X1 n+ (F - ) n (HF) p (In the formula, and p varies between 0 and 10, preferably 0, The process is carried out in the absence of a solvent or in the presence of an amount of solvent less than 5% by weight, based on the total weight of the reaction mixture, in a molten salt of the bis(fluorosulfonyl)imide of formula (I).

[0076] Such salts of formula (I) can advantageously be obtained directly from the fluorination of the bis(chlorosulfonyl)imide of formula (II) without any additional purification or separation steps.

[0077] The salts of the bis(fluorosulfonyl)imides of formula (I) are preferably the following salts: F-(SO2)-NK-(SO2)-F (Ia), F-(SO2)-NNa-(SO2)-F (Ib), or F-(SO2)-NNH4-(SO2)-F (Ic) It is one of the following.

[0078] A filtration step can be used in addition to the above process to remove reaction by-products and / or impurities, such as X1 n+ Cl - and / or X1 n+ HF2 - (Wherein, X1 is K + , Na + or an onium cation as described above).

[0079] A preferred embodiment of the present invention is a compound of formula (Ic): F-(SO2)-NNH4-(SO2)-F (Ic) The object of the present invention is to provide a salt of ammonium bis(fluorosulfonyl)imide.

[0080] In this preferred embodiment, the salt is free of the following impurities: -NH4Cl, -NH4F, -NH4HF2, -NH4FSO3, -NH4SO3NH2, -NH4[N(SO3H)(SO2F)](OFSI), and / or -NH4[N(SO3H)2](OSI) It may contain at least one of:

[0081] Impurities such as NH4Cl and NH4HF2 may, for example, be present in salt (Ic) in residual amounts of less than 1,000 ppm, less than 500 ppm, less than 200 ppm or less than 100 ppm, preferably less than 90 ppm. Such impurities may be present in salt (Ic) in amounts greater than 1 ppm, for example greater than 5 ppm or greater than 10 ppm.

[0082] Impurities such as OFSI and OSI may, for example, be present in salt (Ic) in residual amounts of less than 1,000 ppm, less than 500 ppm, less than 400 ppm or less than 300 ppm, preferably less than 250 ppm or even less than 200 ppm. Such impurities may be present in salt (Ic) in amounts greater than 1 ppm, for example greater than 5 ppm or greater than 10 ppm.

[0083] The salt (I) of the invention also preferably has the following contents of chemical entities: Chloride (Cl) less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm - ) content; and / or Fluoride (F) less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm - ); and / or - less than 30,000 ppm, preferably less than 10,000 ppm, more preferably less than 5,000 ppm of sulfate (SO4 2- ) content; and / or an iron (Fe) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a chromium (Cr) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a nickel (Ni) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a zinc (Zn) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a copper (Cu) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a bismuth (Bi) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a sodium (Na+) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm; and / or - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm potassium (K + ) content At least one of the following is shown.

[0084] The fluoride and chloride content can be measured, for example, by argentometry using ion-selective electrodes (or ISEs). The sulfate content can alternatively be measured by ionic chromatography or by turbidimetry.

[0085] The elemental impurity content can be measured, for example, by ICP-AES (inductively coupled plasma), and more specifically, the Na content can be measured by AAS (atomic absorption spectroscopy).

[0086] A third object of the present invention is to provide a compound of formula (IV): F-(SO2)-NX3-(SO2)-F (IV) A method for preparing an alkali salt of a bis(fluorosulfonyl)imide of the formula: wherein X3 represents Li or Cs, preferably Li.

[0087] This method is (a) preparing a salt of a bis(fluorosulfonyl)imide of formula (I) as described above; (b) reacting the salt of bis(fluorosulfonyl)imide (I) with an alkaline agent consisting of a lithium salt or a cesium salt.

[0088] According to the present invention, as described above, a highly pure or substantially highly pure salt of the bis(fluorosulfonyl)imide of formula (I) can be obtained. This means that, according to an embodiment, step (b) can be carried out directly using the salt (I) obtained by step (a), for example, in a molten form, without any additional purification. Alternatively, the molten salt of the bis(fluorosulfonyl)imide of formula (I) can be added to an organic solvent, such as trifluoroethanol, which can be a coolant. In this case, it is expected that the salt (I) will crystallize before carrying out step (b). According to yet another embodiment, the salt (I) can be at least partially crystallized in the melt and then extracted or reused / recycled in a new reaction cycle.

[0089] A fourth object of the present invention is to provide a compound of formula (IV): F-(SO2)-NX3-(SO2)-F (IV) wherein X3 represents Li or Cs, preferably Li.

[0090] Such salts (IV) can preferably be obtained by the above process.

[0091] The salt (IV) of the invention also preferably has the following content of chemical entities: Chloride (Cl) less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm - ) content; and / or Fluoride (F) less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 1,000 ppm, more preferably less than 500 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 20 ppm - ); and / or - less than 30,000 ppm, preferably less than 10,000 ppm, more preferably less than 5,000 ppm of sulfate (SO4 2- ) content; and / or an iron (Fe) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a chromium (Cr) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a nickel (Ni) content of less than 1,000 ppm, preferably less than 800 ppm, more preferably less than 500 ppm; and / or a zinc (Zn) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a copper (Cu) content of less than 1,000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a bismuth (Bi) content of less than 1000 ppm, preferably less than 100 ppm, more preferably less than 10 ppm; and / or a sodium (Na+) content of less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm; and / or - less than 10,000 ppm, preferably less than 5,000 ppm, more preferably less than 500 ppm potassium (K + ) indicates at least one of the following.

[0092] A fifth object of the present invention is directed to the use of the salt of the bis(fluorosulfonyl)imide of formula (IV) in a battery electrolyte solution.

[0093] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference contradicts the statements of this application to the extent that the term may be unclear, the statements of this application shall control. [Example]

[0094] The present invention will now be described in more detail with reference to the following examples, the purpose of which is illustrative only and is not intended to limit the scope of the disclosure.

[0095] Example 1 Bis(fluorosulfonyl)imide ammonium salt formation

[0096] Under nitrogen, 63.5 g of NHF (1.71 mol, 4.4 eq relative to HCSI) was mixed with 250 g of NHFSI (1.26 mol) and stirred at 90°C for 1 hour. Liquid HCSI was then added to the reaction mixture at a rate of 40 g / h using a feed funnel with a heat belt, and continuously added up to 83.3 g (0.39 mol). Stirring was continued for 12 hours. The temperature of the reaction was continuously monitored and maintained below 100°C. The reaction mixture was then cooled to 60°C in 1 hour. 320 g of TFE was then added to the mixture. The solid was isolated by filtration. The filtrate was then cooled to 10°C in 2 hours. The crystals were isolated by filtration at 25°C and then washed with 160 g of fresh TFE. The solid was dried under vacuum at room temperature for 12 hours. The product was then analyzed. The conversion was 19 FNMR(FSI - ) was 87.6%.

[0097] Example 2 Formation of bis(fluorosulfonyl)imide lithium salt Under a nitrogen atmosphere, a solution of 6.9 g of NH4FSI (0.35 mmol) from Example 1 was prepared in 60 g of ethyl methyl carbonate (EMC). 14.6 g of solid LiOH.HO (0.35 mmol) was added to the vessel at room temperature over 10 minutes. After 1 hour of stirring, NH4 (as determined by NaOH titration) was obtained. +The conversion of the ions was more than 90%. The medium was concentrated a first time under reduced pressure (P=20 mbar, T=0° C.). 120 mL of EMC was added and concentrated a second time under the same conditions. The concentrated solution was dried under reduced pressure at 30° C. for 24 hours. 5 g of a viscous, transparent liquid was obtained. 19 F NMR analysis indicated a purity of greater than 99% by weight, with no other fluorinated species detected.

Claims

1. Formula (I): [F-(SO ２ )-N － -(SO ２ )-F] ｎ X １ ｎ＋ (I) (In the formula, -X １ ｎ＋ Is, K ＋ , Na ＋ and an onium cation, n is 1 and represents the valence of the said cation, Formula (II): Cl-(SO ２ )-NH-(SO ２ )-Cl (II) bis(chlorosulfonyl)imide or its salt, Formula (III): X １ ｎ＋ (F － ) ｎ (HF) ｐ (In the formula, - p varies between 0 and 10, The process is carried out in the absence of a solvent or in the presence of an amount of solvent less than 5% by weight, based on the total weight of the reaction mixture, in a molten salt of the bis(fluorosulfonyl)imide of formula (I).

2. 10. The process of claim 1 carried out under reduced pressure.

3. 3. The process according to claim 1 or 2, wherein the stoichiometric amount of fluorinating agent (III) is between 1 and 10 equivalents per mole of bis(chlorosulfonyl)imide (II).

4. (i) the amount Q of the salt of bis(fluorosulfonyl)imide (I) ０ The melting point Tm （Ｉ） to produce a molten salt of bis(fluorosulfonyl)imide (I); (ii) adding said fluorinating agent (III) and said bis(chlorosulfonyl)imide (II) to a molten salt of said bis(fluorosulfonyl)imide (I).

5. Step (ii) is (ii1) adding the fluorinating agent (III) to the molten salt of the bis(fluorosulfonyl)imide (I); (ii2) optionally removing residual amounts of water or aqueous liquid from said fluorinating agent (III); (ii3) adding said bis(chlorosulfonyl)imide (II) to the reaction mixture.

6. 6. The method of claim 5, comprising step (ii2) carried out by distillation of water.

7. When all the reactive materials have been added, the amount Q ０ is 20 wt.% or more of the total weight of the reaction mixture.

8. 3. The process according to claim 1 or 2, carried out at a temperature below 100°C.

9. 3. A compound of formula (I): [F-(SO ２ )-N － -(SO ２ )-F] ｎ X １ ｎ＋ (I) (In the formula, -X １ ｎ＋ Is, K ＋ , Na ＋ and an onium cation, n is 1 and represents the valence of the cation, The amount of solvent is less than 100 ppm.

10. 10. The salt of claim 9, wherein the amount of solvent is less than 50 ppm.

11. Formula (V) F-(SO ２ )-NX ３ -(SO ２ )-F (IV) (In the formula, X ３ represents Li or Cs, preferably Li), comprising the steps of: (a) preparing a salt of a bis(fluorosulfonyl)imide of formula (I) according to claim 1 or 2; (b) reacting the salt of bis(fluorosulfonyl)imide (I) obtained in step (a) with an alkaline agent consisting of a lithium salt or a cesium salt.

12. 12. The process according to claim 11, wherein step (b) is carried out in an organic reaction medium comprising at least one organic solvent, said organic solvent being selected from aprotic organic solvents, preferably from the group consisting of ethyl acetate, isopropyl acetate, butyl acetate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, valeronitrile and acetonitrile.

13. 12. A compound of formula (IV): obtainable by the process according to claim 11 : F-(SO ２ )-NX ３ -(SO ２ )-F (IV) (In the formula, X ３ represents Li or Cs, preferably Li.

14. 14. Use of the salt of a bis(fluorosulfonyl)imide of formula (IV) according to claim 13 in a battery electrolyte solution.