Composition and method for producing said composition

Abstract

This composition contains (I) a compound represented by general formula (I) and (II) a compound represented by general formula (II). The compound (II) content is 0.01 to 2.0 parts by mass in a total of 100 parts by mass of compound (I) plus compound (II).

Description

Composition, and method for producing the composition

[0001] This disclosure relates to compositions containing difluorophosphates and methods for producing said compositions.

[0002] Difluorophosphates are used in a variety of applications, and in recent years, they have been particularly developed as electrolyte additives for lithium-ion batteries.

[0003] Patent Document 1 describes that adding lithium difluorophosphate to the electrolyte improves the capacity during high-temperature storage tests due to the effect of a film formed at the electrode interface. Patent Document 2 discloses a method for synthesizing difluorophosphate salts by reacting a difluorophosphate ester with a lithium salt.

[0004] Japanese Patent Publication No. 11-67270, International Publication No. 2021 / 025107

[0005] Difluorophosphates are highly hygroscopic and readily decompose upon contact with moisture to produce hydrofluoric acid (HF), indicating that there was room for improvement in their hydrolysis resistance (storage stability).

[0006] The inventors of the present invention have found that hydrolysis resistance (storage stability) is improved by including a predetermined amount of monofluorophosphate ester salt together with difluorophosphate, and have completed the present invention. That is, the present invention can be described as follows.

[0007] [1] A composition containing (I) a compound represented by the following general formula (I) and (II) a compound represented by the following general formula (II), wherein the composition contains 0.01 parts by mass or more and 2.0 parts by mass or less of compound (II) in a total of 100 parts by mass of compound (I) and compound (II). (In general formula (I), M ＋ (This represents alkali metal ions.) (In general formula (II), M ＋ represents an alkali metal ion. R represents an organic group selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, and aralkyl groups.) [2] M in the above general formula (I) and the above general formula (II) ＋The composition according to [1], which is a lithium ion or a sodium ion. [3] The composition according to [1] or [2], wherein R in the general formula (II) is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. [4] Reacting a compound (i) represented by the following general formula (i) and a compound (ii) represented by the following general formula (ii) with an alkali metal salt compound, (In the general formula (i), R represents an organic group selected from a linear or branched alkyl group having 1 to 15 carbon atoms, a linear or branched alkenyl group having 2 to 15 carbon atoms, a linear or branched alkynyl group having 2 to 15 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, and an aralkyl group having 7 to 15 carbon atoms.) (In the general formula (ii), R has the same meaning as in the general formula (i), and a plurality of Rs may be the same or different.) A method for producing the composition, comprising a step of obtaining a composition containing a compound (I) represented by the following general formula (I) and a compound (II) represented by the following general formula (II), (In the general formula (I), M ＋ represents an alkali metal ion.) (In the general formula (II), M ＋ represents an alkali metal ion. R has the same meaning as in the general formula (i).) In the above step, a method for producing a composition, wherein the compound (ii) is contained in an amount of 10.0% by mass or less in a total of 100% by mass of the compound (i) and the compound (ii). [5] A method for producing a composition, comprising a step of mixing a compound (I) represented by the following general formula (I) and a compound (II) represented by the following general formula (II), (In the general formula (I), M ＋ represents an alkali metal ion.) (In the general formula (II), M ＋represents an alkali metal ion. R represents an organic group selected from an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, and an aralkyl group.) In the above step, a method for producing a composition, wherein the compound (II) is contained in an amount of 0.01 parts by mass or more and 2.0 parts by mass or less in a total of 100 parts by mass of the compound (I) and the compound (II). [6] M in the general formula (I) and the general formula (II) ＋ is a lithium ion or a sodium ion, and is the method for producing the composition according to [4] or [5]. [7] R in the general formula (II) is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms, and is the method for producing the composition according to any one of [4] to [6].

[0008] According to the present invention, a composition excellent in storage stability of fluorophosphate and a method for producing the composition can be provided.

[0009] In the present specification, "~" is used to mean including the numerical values described before and after it as a lower limit value and an upper limit value.

[0010] Hereinafter, the present disclosure will be described in detail. However, the description of the constituent elements described below is an example of an embodiment of the present disclosure, and is not limited to these specific contents.

[0011] 1. Regarding the composition The composition of the present disclosure includes (I) a compound represented by the following general formula (I), and (II) a compound represented by the following general formula (II). Hereinafter, each component will be described.

[0012] <Regarding the compound (I) represented by the general formula (I)> The compound (I) represented by the following general formula (I) (also referred to as "(I)") included in the composition of the present disclosure will be described.

[0013]

[0014] In the general formula (I), M ＋represents an alkali metal ion. The alkali metal ion is not particularly limited and includes lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, etc., with lithium ions or sodium ions being preferred. (I) As the compound, lithium difluorophosphate and sodium difluorophosphate are preferred.

[0015] <(II) Compounds represented by general formula (II)> The compounds represented by the following general formula (II) (also referred to as "(II)") that are included in the compositions of this disclosure will be described below.

[0016]

[0017] In general formula (II), M ＋ represents an alkali metal ion. The alkali metal ion is not particularly limited and includes lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, etc., with lithium ions or sodium ions being preferred.

[0018] In general formula (II), R represents an organic group selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. Any hydrogen atom of the organic group represented by R may be substituted with a halogen atom. Examples of halogen atoms include fluorine, chlorine, bromine, or iodine atoms, with fluorine being preferred. In this specification, even when a hydrogen atom is substituted with a halogen atom, the terms alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, and aralkyl group will be used. Furthermore, examples of organic groups for R in general formula (II) include those selected from linear or branched alkyl groups having 1 to 15 carbon atoms, linear or branched alkenyl groups having 2 to 15 carbon atoms, linear or branched alkynyl groups having 2 to 15 carbon atoms, cycloalkyl groups having 3 to 15 carbon atoms, aryl groups having 6 to 15 carbon atoms, and aralkyl groups having 7 to 15 carbon atoms.

[0019] Examples of linear alkyl groups having 1 to 15 carbon atoms or branched alkyl groups having 3 to 15 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, t-butyl group, n-pentyl group, n-hexyl group, and n-dodecyl group. C1 to 10 alkyl groups are preferred, and methyl group, ethyl group, n-propyl group, or i-propyl group are preferred.

[0020] Examples of linear alkenyl groups having 2 to 15 carbon atoms or branched alkenyl groups having 3 to 15 carbon atoms include vinyl group, 1-propenyl group, 2-propenyl group (allyl group), isopropenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 1-hexenyl group, 2-hexenyl group, 3-hexenyl group, 1-heptenyl group, 2-heptenyl group, 5-heptenyl group, 1-octenyl group, 3-octenyl group, 5-octenyl group, and dodecenyl group.

[0021] Examples of linear alkynyl groups having 2 to 15 carbon atoms or branched alkynyl groups having 3 to 15 carbon atoms include acetylenyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, 1-pentynyl group, 2-pentynyl group, 3-pentynyl group, 1-hexynyl group, 2-hexynyl group, 3-hexynyl group, 1-heptynyl group, 2-heptynyl group, 5-heptynyl group, 1-octinyl group, 3-octinyl group, and 5-octinyl group.

[0022] Examples of cycloalkyl groups having 3 to 15 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, methylcyclopentyl group, cyclohexyl group, methylcyclohexyl group, cyclooctyl group, and methylcyclooctyl group.

[0023] Examples of aryl groups having 6 to 15 carbon atoms include phenyl, tolyl, naphthyl, and anthracenyl groups. Examples of aralkyl groups having 7 to 15 carbon atoms include benzyl, phenethyl, and phenylethyl groups.

[0024] In this disclosure, R in general formula (II) is preferably a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. Examples of compound (II) include lithium ethyl monofluorophosphate and sodium ethyl monofluorophosphate.

[0025] The compositions of the present disclosure may contain compound (II) in an amount of 0.01 parts by mass or more and 2.0 parts by mass or less, preferably 0.02 parts by mass or more and 1.5 parts by mass or less, more preferably 0.03 parts by mass or more and 1.0 part by mass or less, even more preferably 0.04 parts by mass or more and 0.95 parts by mass or less, and particularly preferably 0.05 parts by mass or more, in an amount of 0.05 parts by mass or more, in an amount of 0.01 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.04 parts by mass or more, and particularly preferably 0.05 parts by mass or more, in an amount of1 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.04 parts by mass or more, and particularly preferably 0.05 parts by mass or more, in a total of 100 parts by mass of compound (I) and compound (II). The compositions of the present disclosure may contain compound (II) in an amount of 2.0 parts by mass or less, preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.95 parts by mass or less, and particularly preferably 0.90 parts by mass or less, in a total of 100 parts by mass of compound (I) and compound (II). By containing compound (II) together with compound (I) in the above amounts, the compositions of the present disclosure can suppress the hydrolysis of compound (I) (generation of hydrofluoric acid (HF)) and have excellent storage stability for compound (I).

[0026] Compound (I) undergoes accelerated hydrolysis under acidic conditions. The presence of compound (II), which exhibits weak basicity, in the above-mentioned amounts along with compound (I) traps the trace amounts of acidic hydrofluoric acid (HF) that are generated. This prevents acidic conditions from being established, suppressing the hydrolysis of compound (I) and improving its storage stability. On the other hand, if compound (II) is present in excess beyond the above range, the less stable compound (II) will easily decompose, creating acidic conditions, which is thought to accelerate the hydrolysis of compound (I) and reduce its storage stability.

[0027] Furthermore, the composition of this disclosure contains compound (II) in an amount of 0.01 parts by mass or more and 2.0 parts by mass or less in a total of 100 parts by mass of compound (I) and compound (II), and compound (I) is one selected from the group consisting of lithium difluorophosphate and sodium difluorophosphate, and compound (II) may be one selected from the group consisting of ethyllithium monofluorophosphate and ethylsodium monofluorophosphate. Furthermore, the composition of this disclosure contains compound (II) in an amount of 0.02 parts by mass or more and 1.5 parts by mass or less in a total of 100 parts by mass of compound (I) and compound (II), and compound (I) is one selected from the group consisting of lithium difluorophosphate and sodium difluorophosphate, and compound (II) may be one selected from the group consisting of ethyllithium monofluorophosphate and ethylsodium monofluorophosphate. Furthermore, the composition of this disclosure contains compound (II) in an amount of 0.03 parts by mass or more and 1.0 parts by mass or less in a total of 100 parts by mass of compound (I) and compound (II), and compound (I) is one selected from the group consisting of lithium difluorophosphate and sodium difluorophosphate, and compound (II) may be one selected from the group consisting of ethyllithium monofluorophosphate and ethylsodium monofluorophosphate. Furthermore, the composition of this disclosure contains compound (II) in an amount of 0.04 parts by mass or more and 0.95 parts by mass or less in a total of 100 parts by mass of compound (I) and compound (II), and compound (I) is one selected from the group consisting of lithium difluorophosphate and sodium difluorophosphate, and compound (II) may be one selected from the group consisting of ethyllithium monofluorophosphate and ethylsodium monofluorophosphate.Furthermore, the composition of this disclosure contains compound (II) in an amount of 0.05 parts by mass or more and 0.90 parts by mass or less in a total of 100 parts by mass of compound (I) and compound (II), and compound (I) may be one selected from the group consisting of lithium difluorophosphate and sodium difluorophosphate, and compound (II) may be one selected from the group consisting of ethyllithium monofluorophosphate and ethylsodium monofluorophosphate.

[0028] 2. Regarding the method for producing the composition, the method for producing the composition of this disclosure includes the step of reacting a compound (i) represented by the following general formula (i) and a compound (ii) represented by the following general formula (ii) with an alkali metal salt compound to obtain a composition containing a compound (I) represented by the following general formula (I) and a compound (II) represented by the following general formula (II). The method for producing the composition of this disclosure can be represented by the following reaction formula.

[0029]

[0030] In general formulas (i) and (ii), R is equivalent to the values ​​in general formulas (I) and (II) above. The multiple Rs in general formula (ii) may be the same or different.

[0031] Examples of alkali metal salt compounds include lithium salt compounds, sodium salt compounds, potassium salt compounds, rubidium salt compounds, and cesium salt compounds, with lithium salt compounds and sodium salt compounds being preferred.

[0032] Examples of lithium salt compounds include one or more selected from the group consisting of lithium chloride, lithium bromide, lithium fluoride, lithium carbonate, lithium acetate, lithium propionate, lithium iodide, lithium hydroxide, lithium bicarbonate, lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium metaphosphate, and lithium sulfate.

[0033] The lithium salt compound is preferably one or more selected from the group consisting of lithium chloride, lithium bromide, lithium fluoride, lithium carbonate, lithium acetate, and lithium propionate. More preferably, it is one or more selected from the group consisting of lithium chloride, lithium acetate, lithium carbonate, and lithium propionate, and even more preferably, it is one or more selected from lithium chloride and lithium acetate.

[0034] Examples of sodium salt compounds include one or more selected from the group consisting of sodium chloride, sodium bromide, sodium fluoride, sodium carbonate, sodium acetate, sodium propionate, sodium iodide, sodium hydroxide, sodium bicarbonate, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium metaphosphate, and sodium sulfate.

[0035] The sodium salt compound is preferably one or more selected from the group consisting of sodium chloride, sodium bromide, sodium fluoride, sodium carbonate, sodium acetate, sodium iodide, and sodium propionate. More preferably, it is one or more selected from the group consisting of sodium chloride, sodium acetate, sodium carbonate, and sodium iodide, and even more preferably, it is one or more selected from sodium chloride and sodium iodide.

[0036] In the method for producing the composition of the present disclosure, the (ii) compound may be included in the above step in an amount of 10.0% by mass or less, preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 6.0% by mass or less, in the total 100% by mass of the (i) compound and the (ii) compound. Furthermore, since hydrolysis of the (i) compound proceeds due to trace amounts of water present in the solvent and alkali metal salt compound, and the (II) compound is produced, the lower limit of the (ii) compound in the total 100% by mass of the (i) compound and the (ii) compound can be 0% by mass or more. In the method for producing the composition of the present disclosure, the composition of the present disclosure can be suitably obtained by including the (ii) compound in the above amount in the total 100% by mass of the (i) compound and the (ii) compound.

[0037] In the manufacturing method of this disclosure, a mixture of compound (i) and compound (ii) containing compound (ii) in the above amount can be used. This mixture can be obtained, for example, by reacting dichlorophosphate ester with potassium fluoride in a predetermined solvent such as acetonitrile, as shown in the reaction formula below. The resulting mixture can then be subjected to vacuum distillation, and the distillation fraction can be appropriately separated to obtain a mixture containing compound (ii) in the above amount.

[0038]

[0039] Alternatively, the mixture can be obtained by preparing compound (i) and compound (ii) and mixing them to the extent described above.

[0040] The step of reacting compounds (i) and (ii) of the present disclosure with an alkali metal salt compound can be carried out in a non-aqueous organic solvent. The non-aqueous organic solvent used in the production method of the present disclosure is not particularly limited, but it is preferably one or more selected from the group consisting of carbonate esters, linear esters (linear carboxylic acid esters), ethers, and ketones, as commercially available products with low water content are readily available.

[0041] Examples of carbonate esters include ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, propylene carbonate, and butylene carbonate, with ethylmethyl carbonate, dimethyl carbonate, or diethyl carbonate being preferred. Examples of chain esters include ethyl acetate, methyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate, with ethyl acetate being preferred. Examples of ethers include dimethoxyethane, dimethoxymethane, tetrahydrofuran, and diethyl ether, with dimethoxyethane being preferred. Examples of ketones include acetone, ethyl methyl ketone, and diethyl ketone, with acetone being preferred.

[0042] The above non-aqueous organic solvent is preferably one or more selected from the group consisting of carbonate esters, chain esters, and ketones, more preferably one or more selected from the group consisting of carbonate esters and chain esters, and from the viewpoint of obtaining a predetermined composition, it is even more preferably a carbonate ester, and particularly preferably ethylmethyl carbonate, dimethyl carbonate, or diethyl carbonate.

[0043] (Reaction Conditions) In the manufacturing method of the present disclosure, a non-aqueous organic solvent and an alkali metal salt compound are mixed in a reaction vessel, and while stirring the mixed solution, compound (i) and compound (ii) are added to react with the alkali metal salt compound. The charging ratio of the total molar amounts of compound (i) and compound (ii) to the molar amount of the alkali metal salt compound is preferably 1.0:0.7 to 1.0:1.5 in molar ratio, and more preferably 1.0:0.9 to 1.0:1.2. The time for adding compound (i) and compound (ii) to the mixed solution is about 30 minutes to 2 hours.

[0044] The reaction according to this disclosure is preferably carried out under stirring with an anchor. This prevents the resulting (I) compound from having small particle sizes, and ensures that the particle size is uniform within the range of 50 to 250 μm. This further suppresses the hydrolysis of (I) compound and provides superior storage stability. Furthermore, the rotation speed of the anchor can be approximately 100 rpm on a beaker scale.

[0045] Furthermore, the amount of non-aqueous organic solvent used in the above reaction is preferably such that the concentrations of compound (i) and compound (ii) in the non-aqueous organic solvent are 5% to 60% by mass. In addition, the reaction solution temperature in the above reaction is preferably -10 to 120°C, and more preferably 0 to 60°C.

[0046] In the manufacturing method of this disclosure, the reaction in which compound (i) and compound (ii) are reacted with an alkali metal salt compound in a non-aqueous organic solvent can be carried out under air or under an inert gas, but it is preferable to carry it out under the protection of an inert gas from the viewpoint of suppressing the generation of by-products by suppressing the increase in the amount of water in the reaction system. Specifically, carrying out the above reaction under the protection of an inert gas means that the raw materials, solvent and reaction vessel used are handled under an inert gas atmosphere. The inert gas is preferably one whose dew point is -40°C or lower. Nitrogen gas is a preferred example of the inert gas. After the reaction is complete, the reaction product (composition) can be obtained by filtration, vacuum drying, etc.

[0047] [Other Methods for Producing the Composition] In addition to the above-described method, the compositions of this disclosure may be produced by the following methods. A method for producing the compositions of this disclosure includes the step of mixing a compound (I) represented by the above-described general formula (I) with a compound (II) represented by the following general formula (II).

[0048] In the above step, compound (II) is mixed in a total of 100 parts by mass of compound (I) and compound (II) in an amount of 0.01 parts by mass or more and 2.0 parts by mass or less, preferably 0.02 parts by mass or more and 1.5 parts by mass or less, more preferably 0.03 parts by mass or more and 1.0 part by mass or less, even more preferably 0.04 parts by mass or more and 0.95 parts by mass or less, and particularly preferably 0.05 parts by mass or more. In the above step, compound (II) is mixed in a total of 100 parts by mass of compound (I) and compound (II) in an amount of 0.01 parts by mass or more, preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.04 parts by mass or more, and particularly preferably 0.05 parts by mass or more. In the above step, compound (II) is mixed with a total of 100 parts by mass of compound (I) and compound (II) in an amount of 2.0 parts by mass or less, preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.95 parts by mass or less, and particularly preferably 0.90 parts by mass or less. The mixing step is not particularly limited as long as compound (I) and compound (II) can be mixed, but it is preferable to mix them in the non-aqueous solvent.

[0049] 3. Uses of the Compositions The compositions of this disclosure can be used for a variety of purposes, including, for example, additive compositions for non-aqueous electrolytes, functional material intermediates, and pharmaceutical intermediates. Depending on the application, the compositions of this disclosure may contain solvents, additives, etc.

[0050] For example, when the composition of the present disclosure is used as an additive composition for a non-aqueous electrolyte, the non-aqueous electrolyte additive composition can be mixed with a solute, a non-aqueous organic solvent, and other additives in a conventionally known manner to produce a non-aqueous electrolyte.

[0051] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted as long as they do not impair the effects of the present invention.

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the table, "-" indicates that there is no data (not measured), and "N.D." indicates that it was not detected (measured but below the detection limit).

[0053] <Example a relating to lithium difluorophosphate> [Synthesis example a1-1] Ethyl difluorophosphate (POF ２ Synthesis of OEt) 1. Add 2000 mL of acetonitrile and 326 g (2.0 mol) of ethyl dichlorophosphate to a 5 L fluororesin reactor and stir thoroughly. After adding 697 g (12.0 mol) of potassium fluoride, stirring was continued for 12 hours at a liquid temperature of 25°C. １９ F-NMR confirmed that the resulting reaction solution contained the target product, ethyl difluorophosphate (POF). ２ OEt) is 90% by mass, potassium hexafluorophosphate (KPF) ６ ) contains 4% by mass, diethyl monofluorophosphate (POF(OEt) ２ It was confirmed that 6% by mass of ) was present. The reaction equation is shown below. After removing potassium chloride by filtration, the target product was obtained by vacuum distillation, separating it into each distillation fraction as shown in Table 1 below. Table 1 shows the molar percentage of the components contained in each distillation fraction. Note that distillation fraction Fr. 0 is the fraction from which acetonitrile was removed by distillation.

[0054] [Synthesis Example a1-2] Ethyl difluorophosphate (POF ２ Synthesis of OEt) 2. Add 2000 mL of acetonitrile and 326 g (2.0 mol) of ethyl dichlorophosphate to a 5 L fluoropolymer reactor and stir thoroughly. After adding 697 g (12.0 mol) of potassium fluoride, stirring was continued for 12 hours at a liquid temperature of 25°C. １９ F-NMR confirmed that the resulting reaction solution contained the target product, ethyl difluorophosphate (POF). ２ OEt) is 90% by mass, potassium hexafluorophosphate (KPF) ６ ) contains 4% by mass, diethyl monofluorophosphate (POF(OEt) ２It was confirmed that 6% by mass of ) was present. After removing potassium chloride by filtration, the target product (fraction) was obtained by vacuum distillation. Table 1 shows the mass percentages of the components contained in the target product (fraction).

[0055]

[0056] [Synthesis Examples a2-1 to a2-5, Synthesis Example a3] Lithium difluorophosphate (LiPO ２ F ２ Synthesis of ) 50 mL of ethyl methyl carbonate (EMC) and 2.1 g of anhydrous lithium chloride (50 mmol) were placed in a 100 mL glass reactor, and stirring was started using a stirring blade at an internal temperature of 40°C. Then, 6.5 g (50 mmol) of ethyl difluorophosphate from distillation fraction Fr. 1 obtained by the procedure of Synthesis Example a1-1 was added over 1 hour. After that, stirring was continued at an internal temperature of 40°C for 12 hours. After lowering the internal temperature to below 25°C, the precipitated solid was collected by filtration, and after drying under reduced pressure at 80°C, lithium difluorophosphate (LiPO) was obtained with a yield of 98% and purity of 99%. ２ F ２ A reaction product containing ) was obtained. The main impurity contained in the reaction product was ethyl lithium monofluorophosphate (LiPO4 ２ The solution consisted of 0.01% by mass of diethyl monofluorophosphate (POF(OEt)) and the solvent EMC (Synthesis Example a2-1). Furthermore, lithium difluorophosphate was synthesized in the same manner as above using the distillation fractions Fr. 2-5 obtained in Synthesis Example a1-1, and the fraction obtained in Synthesis Example a1-2 (Synthesis Examples a2-2 to a2-5, Synthesis Example a3). The reaction equation is shown below. Table 2 shows the "Diethyl monofluorophosphate (POF(OEt)) before reaction" contained in the distillation fraction. ２ ) Content (mass%) and "Post-reaction ethyl lithium monofluorophosphate (LiPO)" contained in the reaction product ２ This indicates the F(OEt) content (mass%). As shown in Table 2, diethyl monofluorophosphate (POF(OEt) ２ When lithium difluorophosphate is synthesized using a distillation fraction with a high content of ), ethyl lithium monofluorophosphate (LiPO) is produced as a byproduct. ２ The amount of F(OEt) increased.

[0057] [Synthesis Example a4] Lithium difluorophosphate (LiPO) ２ F ２ Synthesis of (alternative method): 15.2 g (100 mmol) of lithium hexafluoride phosphate, 50 ml of dimethyl carbonate, and hexamethyldisiloxane (TMS) are added to a 100 mL glass reactor. ２ O) 35.7 g (220 mmol) was added and the mixture was stirred at 60°C for 24 hours. After the reaction was complete, the precipitated solid was collected by filtration and dried under reduced pressure at 80°C to obtain lithium difluorophosphate (reaction product) with a yield of 88% and a purity of 99%. The reaction equation is shown below. From the obtained reaction product, ethyl lithium monofluorophosphate (LiPO) ２ F(OEt)) was not detected.

[0058]

[0059] [Synthesis Example a5] Ethyl lithium monofluorophosphate (LiPO ２ In a 300 mL round-bottom flask containing a stirring bar for synthesis of F(OEt), 33.7 g (58 mmol) of potassium fluoride and 150 g of acetonitrile were added, followed by the addition of 50.3 g (29 mmol) of diethyl chlorophosphate. The solution in the round-bottom flask was then heated under a nitrogen stream at 100°C for 7 hours under reflux while stirring. After the solution had cooled to room temperature, excess potassium fluoride and precipitated potassium chloride were removed by suction filtration. The solvent in the filtrate obtained using an evaporator was removed by distillation to obtain 42 g of the target product, diethyl monofluorophosphate, a pale yellow transparent liquid. In a 100 mL round-bottom flask containing a stirring bar, 1.1 g (26 mmol) of lithium chloride and 20.0 g (128 mmol) of the aforementioned diethyl monofluorophosphate were added. The mixture was heated under a nitrogen stream at 120°C for 1.5 hours. After the reaction solution had cooled to room temperature, the precipitate in the reaction solution was filtered off by suction filtration to obtain a white solid. The product was dried at 130°C under a nitrogen atmosphere to obtain 3.0 g of the target product, ethyllithium monofluorophosphate.

[0060] <Examples a1-1 to a1-4, Comparative Examples a1-1 to a1-3> 5 g each of the lithium difluorophosphate compositions from Examples a1-1 to a1-4 (synthesis Examples a2-1 to a2-4) and Comparative Examples a1-1 to a1-3 (synthesis Example a2-5, Synthesis Example a3, Synthesis Example a4) were accurately weighed and placed into polyethylene bags (manufactured by Seinitchi Co., Ltd., product name: Unipack model number A-4) with a thickness of 40 μm and a size of 50 mm x 70 mm. The bags were then sealed by heat sealing the zipper portion. They were stored for 7 days under conditions of 25°C and 65% humidity (accelerated test). The amount of hydrogen fluoride in the lithium difluorophosphate composition after storage was measured. １９ The analysis was performed using F-NMR. The results are shown in Table 3.

[0061]

[0062] <Examples a2-1 to a2-3, Comparative Examples a2-1 to a2-2> Lithium difluorophosphate (LiPO) obtained in Synthesis Example a4 ２ F ２ ) compared to the ethyl lithium monofluorophosphate (LiPO) obtained in synthesis example a5 ２ A lithium difluorophosphate composition was prepared by adding F(OEt)) in the amount shown in Table 4. The obtained lithium difluorophosphate composition was tested in the same manner as above and stored for 7 days under conditions of 25°C and 65% humidity (accelerated test). The amount of hydrogen fluoride in the lithium difluorophosphate composition after storage was determined. １９ The analysis was performed using F-NMR. The results are shown in Table 4.

[0063]

[0064] From the results shown in Tables 3 and 4, lithium difluorophosphate (LiPO) ２ F ２ ) and ethyl lithium monofluorophosphate (LiPO ２ It was found that the hydrolysis of lithium difluorophosphate is suppressed and storage stability is excellent when ethyl lithium monofluorophosphate is included in a range of 0.01 parts by mass to 2.0 parts by mass per 100 parts by mass of F(OEt)). Furthermore, as shown in Table 3, ethyl difluorophosphate (POF) synthesized according to conventional methods such as synthesis example a1-2 was also found.２ Using OEt) lithium difluorophosphate (LiPO) ２ F ２ When ) is synthesized (synthesis example a3), as shown in Comparative Example a1-2, ethyl lithium monofluorophosphate (LiPO) ２ It was found that the presence of 2.1 parts by mass of F(OEt) accelerates the hydrolysis of lithium difluorophosphate, leading to a decrease in storage stability.

[0065] <Example b relating to sodium difluorophosphate> [Synthesis example b1-1] Ethyl difluorophosphate (POF ２ Synthesis of OEt) is carried out in the same manner as in synthesis example a1-1, as described in Table 1: ethyl difluorophosphate (POF ２ Each distillation fraction containing OEt was obtained.

[0066] [Synthesis example b1-2] Ethyl difluorophosphate (POF ２ Synthesis of OEt) 2 The target product (fraction) shown in Table 1 was obtained in the same manner as in Synthesis Example a1-2.

[0067] [Synthesis Examples b2-1 to b2-4, Synthesis Example b3] Sodium difluorophosphate (NaPO ２ F ２ Synthesis of sodium difluorophosphate (NaPO4) 10 mL of ethyl methyl carbonate (EMC) and 1.5 g (10 mmol) of sodium iodide were placed in a 50 mL glass reactor, and stirring was started at an internal temperature of 25°C. 1.3 g (10 mmol) of ethyl difluorophosphate from distillation fraction Fr. 1 obtained in synthesis example b1-1 was added over 1 hour. Stirring was then continued at an internal temperature of 25°C for 12 hours. After the reaction was complete, the precipitated solid was collected by filtration and dried under reduced pressure at 80°C to obtain sodium difluorophosphate (NaPO4) with a yield of 98% and purity of 99%. ２ F ２ A reaction product containing ) was obtained. The main impurity contained in the reaction product was sodium ethyl monofluorophosphate (NaPO ２The solution consisted of 0.01% by mass of diethyl monofluorophosphate (POF(OEt)) and the solvent EMC (Synthesis Example b2-1). Furthermore, sodium difluorophosphate was synthesized in the same manner as above using the distillation fractions Fr. 2, 3, and 5 obtained in Synthesis Example b1-1, and the fraction obtained in Synthesis Example b1-2 (Synthesis Examples b2-2 to b2-4, Synthesis Example b3). The reaction equation is shown below. Table 5 shows the "Diethyl monofluorophosphate (POF(OEt)) before reaction" contained in the distillation fraction. ２ ) Content (mass%) and "Ethyl sodium monofluorophosphate (NaPO) after reaction" contained in the reaction product ２ This indicates the F(OEt) content (mass%). As shown in Table 5, diethyl monofluorophosphate (POF(OEt) ２ When sodium difluorophosphate is synthesized using a distillation fraction with a high content of ), ethyl sodium monofluorophosphate (NaPO) is produced as a byproduct. ２ The amount of F(OEt) increased.

[0068] [Synthesis example b4] Sodium difluorophosphate (NaPO ２ F ２ Synthesis of (alternative method): 16.8 g (100 mmol) of sodium hexafluoride phosphate, 50 ml of dimethyl carbonate, and hexamethyldisiloxane (TMS) are added to a 100 mL glass reactor. ２ O) 35.7 g (220 mmol) was added and the mixture was stirred at 60°C for 24 hours. After the reaction was complete, the precipitated solid was collected by filtration and dried under reduced pressure at 80°C to obtain sodium difluorophosphate (reaction product) with a yield of 88% and a purity of 99%. The reaction equation is shown below. From the obtained reaction product, ethyl sodium monofluorophosphate (NaPO) ２ F(OEt)) was not detected.

[0069]

[0070] <Examples b1-1 to b1-3, Comparative Examples b1-1 to b1-3> 5 g each of the sodium difluorophosphate compositions from Examples b1-1 to b1-3 (synthesis examples b2-1 to b2-3) and Comparative Examples b1-1 to b1-3 (synthesis example b2-4, synthesis example b3, synthesis example b4) were accurately weighed and placed in polyethylene bags (manufactured by Seinitchi Co., Ltd., product name: Unipack model number A-4) with a thickness of 40 μm and a size of 50 mm x 70 mm. The bags were then sealed by heat sealing the zipper portion. They were stored for 7 days under conditions of 25°C and 65% humidity (accelerated test). The amount of hydrogen fluoride in the sodium difluorophosphate composition after storage was measured. １９ The analysis was performed using F-NMR. The results are shown in Table 6.

[0071]

[0072] From the results shown in Table 6, sodium difluorophosphate (NaPO) ２ F ２ ) and sodium monofluorophosphate (NaPO ２ It was found that the hydrolysis of sodium difluorophosphate is suppressed and storage stability is excellent when sodium ethyl monofluorophosphate is included in an amount of 0.01 parts by mass to 2.0 parts by mass per 100 parts by mass of F(OEt)). Furthermore, as shown in Table 6, ethyl difluorophosphate (POF) synthesized according to conventional methods such as synthesis example b1-2 was also found. ２ Using OEt), sodium difluorophosphate (NaPO) ２ F ２ When ) is synthesized (synthesis example b3), as shown in comparative example b1-2, ethyl sodium monofluorophosphate (NaPO ２ It was found that the presence of 2.6 parts by mass of F(OEt) accelerates the hydrolysis of sodium difluorophosphate, leading to a decrease in storage stability.

[0073] This application claims priority based on Japanese Patent Application No. 2025-010913, filed on 24 January 2025, and incorporates all of its disclosures herein.

Claims

1. A composition containing (I) a compound represented by the following general formula (I) and (II) a compound represented by the following general formula (II), wherein the composition contains 0.01 to 2.0 parts by mass of the compound (II) in a total of 100 parts by mass of the compound (I) and the compound (II). (In general formula (I), M ＋ represents an alkali metal ion.) (In general formula (II), M ＋ represents an alkali metal ion. R represents an organic group selected from an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, and an aralkyl group.) 2. M in the above general formula (I) and the above general formula (II) ＋ The composition according to claim 1, wherein is a lithium ion or a sodium ion.

3. The composition according to claim 1 or 2, wherein R in the general formula (II) is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms.

4. Compound (i) represented by the following general formula (i) and compound (ii) represented by the following general formula (ii) are reacted with an alkali metal salt compound. (In general formula (i), R represents an organic group selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, and aralkyl groups.) (In general formula (ii), R is synonymous with general formula (i), and multiple Rs may be the same or different.) A method for producing the composition, comprising the step of obtaining a composition comprising a compound (I) represented by the following general formula (I) and a compound (II) represented by the following general formula (II), (In general formula (I), M ＋ (This represents alkali metal ions.) (In general formula (II), M ＋ (where R represents an alkali metal ion, and R is synonymous with general formula (i).) A method for producing a composition, wherein in the above step, compound (ii) is contained in an amount of 10.0% by mass or less of compound (ii) in the total of 100% by mass of compound (i) and compound (ii).

5. A method for producing a composition, comprising the step of mixing compound (I) represented by the following general formula (I) and compound (II) represented by the following general formula (II), (In general formula (I), M ＋ (This represents alkali metal ions.) (In general formula (II), M ＋ (wherein R represents an alkali metal ion, R represents an organic group selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, and aralkyl groups.) A method for producing a composition, wherein in the above step, the composition contains 0.01 parts by mass or more and 2.0 parts by mass or less of compound (II) in a total of 100 parts by mass of compound (I) and compound (II).

6. M in the above general formula (I) and the above general formula (II) ＋ A method for producing the composition according to claim 4 or 5, wherein is a lithium ion or a sodium ion.

7. A method for producing the composition according to any one of claims 4 to 6, wherein R in the general formula (II) is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms.

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