Method for manufacturing lithium ion battery

Abstract

The present invention provides a method for manufacturing a lithium ion battery, which includes (1) selecting a high-purity ethylene carbonate-containing composition containing 90 mass% or more of ethylene carbonate having a total content of formic acid and formate of 500 mass ppm or less, and (2) introducing the selected high-purity ethylene carbonate-containing composition as an electrolyte into a lithium ion battery.

Description

[0001] This application is a divisional application. The Chinese national application number of the application to which it is directed is 201880019317.6, the international application number is PCT / JP2018 / 011520, the application date is March 22, 2018, the date of entry into China is September 19, 2019, and the name of the invention is “Method for stabilizing a composition containing high-purity ethylene carbonate”. Technical Field

[0002] The present invention relates to a method for stabilizing a composition containing high-purity ethylene carbonate, a stabilized composition containing high-purity ethylene carbonate, a method for storing the composition, an electrolyte for a lithium ion battery, and the like. Background Art

[0003] Ethylene carbonate is widely used as solvent of various macromolecular compounds, reaction solvent of various chemical reactions, extraction solvent, foaming agent, lubricating stabilizer, surfactant, soil modification material etc. In addition, in recent years, its use in fields such as resist, resist stripping agent, pharmaceuticals is also expanding. Especially high-purity ethylene carbonate becomes an organic compound useful as electrolyte raw material of lithium ion secondary battery in industry due to its high dielectric constant characteristic. In addition, ethylene glycol that can be used in polyester raw material, antifreeze etc. can also be selectively produced by hydrolyzing ethylene carbonate.

[0004] As the manufacture method of ethylene carbonate, it is known that the reaction of ethylene oxide and carbonic acid gas can be manufactured.When carrying out this reaction, in the resultant after the reaction, except comprising the ethylene carbonate as the main product, also comprising byproducts of reaction such as glycols such as the catalyst used in the reaction, monoethylene glycol, diethylene glycol, and also comprising water, hydrolysis catalyst when being hydrolyzed.Therefore, in order to remove above-mentioned impurity, the purification (referring to patent documentation 1~3 etc.) of ethylene carbonate based on vacuum distillation, cooling crystallization method etc. is carried out.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 7-89905

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-51484

[0009] Patent Document 3: International Publication No. 2007 / 108213 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In addition, when ethylene carbonate is used as an electrolyte of a lithium ion battery for a long time, ethylene carbonate is modified due to an electrochemical reaction, and deposits or decomposition gases are generated on the electrode surface, and the deterioration of the lithium ion battery progresses. Specifically, it is believed that the deterioration of the lithium ion battery occurs through the following phenomena. The first is the irreversible exchange reaction of the solvent due to the change in the composition of the electrolyte, the second is the accumulation of reaction products on the electrode surface due to the increase in the resistance component, and the third is the increase in the internal pressure of the battery accompanied by the generation of gases such as hydrocarbons. In addition, the change in the composition of the electrolyte, the resulting changes in viscosity and density, etc., can also promote this deterioration.

[0012] On the other hand, in recent years, it is also required to provide high-purity ethylene carbonate, for example, purity is more than 90 mass % ethylene carbonate. But up to now, there is still no concern about the specific behavior of the trace components contained in the high-purity ethylene carbonate. But according to the research of the inventor, in unused high-purity ethylene carbonate (in the above example, the ethylene carbonate before being used as the electrolyte of the lithium ion battery), it is unexpectedly produced that the modification and composition change (hereinafter, sometimes referred to as "modification") of the time property are produced.

[0013] Therefore, elucidating the modification mechanism of unused ethylene carbonate and suppressing it are urgent issues not only from the perspective of simply providing high-quality ethylene carbonate but also from the perspective of maintaining high quality for a long period of time when the ethylene carbonate is used in various applications.

[0014] The present invention is accomplished in view of the above-mentioned problems, and the purpose of the first embodiment and the second embodiment is to provide a novel stabilization method for suppressing the modification over time of a composition containing high-purity ethylene carbonate. In addition, other purposes of the invention of the first embodiment and the second embodiment are to provide a stabilized composition containing high-purity ethylene carbonate, whose modification over time is suppressed, and a method for preserving the same, and an electrolyte for lithium ion batteries using the same, etc. In addition, the purpose of the third embodiment is to provide a stabilized composition containing high-purity ethylene carbonate, a method for preserving the same, and an electrolyte for lithium ion batteries using the same, etc. In addition, other purposes of the invention of the third embodiment are to provide a manufacturing method that can stably manufacture such a stabilized composition containing high-purity ethylene carbonate.

[0015] It should be noted that the present invention is not limited to the purpose described here, and when the effects brought about by the various structures shown in the specific embodiments described later and which cannot be obtained by the conventional technology are exerted, it can also be regarded as other purposes of the present invention.

[0016] Means for solving problems

[0017] The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have elucidated the modification mechanism in a composition containing high-purity ethylene carbonate, and have found that the above-mentioned problems can be solved by adjusting the composition to a specific composition, thereby completing the present invention.

[0018] That is, the first embodiment of the present invention provides various specific modes shown below.

[0019] [A1] A method for stabilizing a composition containing high-purity ethylene carbonate, wherein the stabilization method includes a step of adjusting the content (content ratio) of formic acid and its salts in the composition containing high-purity ethylene carbonate containing 90% by mass or more of ethylene carbonate to a total of 500 mass ppm or less.

[0020] [A2] The method for stabilizing a composition containing high-purity ethylene carbonate as described in [A1], further comprising the step of adjusting the content of iron oxide in the composition containing high-purity ethylene carbonate to less than 100 mass ppm.

[0021] [A3] The method for stabilizing a composition containing high-purity ethylene carbonate as described in [A1] or [A2], further comprising the step of adjusting the water content in the composition containing high-purity ethylene carbonate to less than 100 mass ppm.

[0022] [A4] The method for stabilizing a composition containing high-purity ethylene carbonate according to any one of [A1] to [A3], wherein the content of ethylene carbonate in the composition containing high-purity ethylene carbonate is 99.90% by mass or more.

[0023] [A5] A stabilized high-purity ethylene carbonate-containing composition, characterized in that it contains 90% by mass or more of ethylene carbonate and a total amount of 500 ppm by mass or less of formic acid and a salt thereof.

[0024] [A6] The stabilized high-purity ethylene carbonate-containing composition according to [A5], wherein the total content of the formic acid and its salt is 100 mass ppm or less.

[0025] [A7] The stabilized high-purity ethylene carbonate-containing composition according to [A5] or [A6], wherein the total content of the formic acid and its salt is 50 ppm by mass or less.

[0026] [A8] The stabilized high-purity ethylene carbonate-containing composition according to any one of [A5] to [A7], wherein the total content of the formic acid and its salt is 10 ppm by mass or less.

[0027] [A9] The stabilized high-purity ethylene carbonate-containing composition according to any one of [A5] to [A8], further comprising iron oxide, wherein the content of the iron oxide is less than 100 ppm by mass.

[0028] [A10] The stabilized high-purity ethylene carbonate-containing composition according to any one of [A5] to [A9], further comprising water, wherein the water content is less than 100 ppm by mass.

[0029] [A11] A method for storing a composition containing high-purity ethylene carbonate, characterized in that the composition containing high-purity ethylene carbonate described in any one of [A5] to [A10] is stored in a closed container or a sealed container.

[0030] [A12] An electrolyte for a lithium ion battery, characterized in that it comprises the composition containing high-purity ethylene carbonate described in any one of [A5] to [A10].

[0031] Here, in [A1] to [A4], the adjusting step preferably further includes the steps of measuring the total content of formic acid and its salt in the composition containing high-purity ethylene carbonate and selecting a composition having the total content of 500 mass ppm or less.

[0032] That is, the second embodiment of the present invention provides various specific aspects shown below.

[0033] [B1] A method for stabilizing a composition containing high-purity ethylene carbonate, characterized in that it includes a step of adjusting the content (content ratio) of 2-chloroethanol in the composition containing high-purity ethylene carbonate containing 90% by mass or more of ethylene carbonate to 500 mass ppm or less.

[0034] [B2] The method for stabilizing a composition containing high-purity ethylene carbonate as described in [B1], further comprising the step of adjusting the content of iron oxide in the composition containing high-purity ethylene carbonate to less than 200 mass ppm.

[0035] [B3] The method for stabilizing a composition containing high-purity ethylene carbonate as described in [B1] or [B2], further comprising the step of adjusting the water content in the composition containing high-purity ethylene carbonate to less than 200 mass ppm.

[0036] [B4] The method for stabilizing a composition containing high-purity ethylene carbonate according to any one of [B1] to [B3], wherein the content of ethylene carbonate in the composition containing high-purity ethylene carbonate is 99.90% by mass or more.

[0037] [B5] A stabilized high-purity ethylene carbonate-containing composition, characterized in that it contains 90% by mass or more of ethylene carbonate and 500 ppm by mass or less of 2-chloroethanol.

[0038] [B6] The stabilized high-purity ethylene carbonate-containing composition as described in [B5], wherein the content of the 2-chloroethanol is 100 ppm by mass or less.

[0039] [B7] The stabilized high-purity ethylene carbonate-containing composition described in [B5] or [B6], wherein the content of the 2-chloroethanol is 50 ppm by mass or less.

[0040] [B8] The stabilized high-purity ethylene carbonate-containing composition according to any one of [B5] to [B7], wherein the content of the 2-chloroethanol is 10 ppm by mass or less.

[0041] [B9] The stabilized high-purity ethylene carbonate-containing composition according to any one of [B5] to [B8], further comprising iron oxide, wherein the content of the iron oxide is less than 200 ppm by mass.

[0042] [B10] The stabilized high-purity ethylene carbonate-containing composition according to any one of [B5] to [9], further comprising water, wherein the water content is less than 200 ppm by mass.

[0043] [B11] A method for storing a composition containing high-purity ethylene carbonate, characterized in that the composition containing high-purity ethylene carbonate described in any one of [B5] to [B10] is stored in a closed container or a sealed container.

[0044] [B12] An electrolyte for a lithium ion battery, characterized in that it comprises the composition containing high-purity ethylene carbonate described in any one of [B5] to [B10].

[0045] Here, in [B1] to [B4], the adjusting step preferably further includes the steps of measuring the content of 2-chloroethanol in the composition containing high-purity ethylene carbonate and selecting a composition having the content of 500 mass ppm or less.

[0046] The third embodiment of the present invention provides various specific aspects shown below.

[0047] [C1] A stabilized composition containing high-purity ethylene carbonate, characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content (total content ratio) of the monoethylene glycol and the monoethylene glycol formate after 125 days at 50°C in a closed container or a sealed container is 3.0 area % or less in gas chromatography analysis.

[0048] [C2] A stabilized high-purity ethylene carbonate-containing composition, characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 2.0 area % or less in a gas chromatography analysis at 50°C for 100 days in a closed container or a sealed container.

[0049] [C3] A stabilized composition containing high-purity ethylene carbonate, characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 1.0 area % or less in a gas chromatography analysis at 50°C in a closed container or a sealed container after 50 days.

[0050] [C4] The stabilized high-purity ethylene carbonate-containing composition according to any one of [C1] to [C3], further comprising formic acid and a salt thereof, wherein the total content of the formic acid and the salt thereof is 500 ppm by mass or less.

[0051] [C5] The stabilized high-purity ethylene carbonate-containing composition according to any one of [C1] to [C4], further comprising 2-chloroethanol, wherein the content of the 2-chloroethanol is 500 ppm by mass or less.

[0052] [C6] The stabilized high-purity ethylene carbonate-containing composition according to any one of [C1] to [C5], further comprising iron oxide, wherein the content of the iron oxide is less than 200 ppm by mass.

[0053] [C7] The stabilized high-purity ethylene carbonate-containing composition according to any one of [C1] to [C6], further comprising water, wherein the water content is less than 200 ppm by mass.

[0054] [C8] A stabilized high-purity ethylene carbonate-containing composition as described in any one of [C1] to [C7], wherein the ethylene carbonate is a carbonated ethylene carbonate having a 2-chloroethanol concentration and a formic acid and a salt thereof content of less than 0.1 mass ppm, respectively.

[0055] [C9] A method for storing a composition containing high-purity ethylene carbonate, characterized in that the composition containing high-purity ethylene carbonate described in any one of [C1] to [C8] is stored in a closed container or a sealed container.

[0056] [C10] An electrolyte for a lithium ion battery, characterized in that it comprises the composition containing high-purity ethylene carbonate described in any one of [C1] to [C8].

[0057] [C11] A method for producing a composition containing high-purity ethylene carbonate, characterized in that it comprises the following steps: a reaction step of reacting ethylene oxide with carbon dioxide to obtain ethylene carbonate; and a step of adjusting the concentration of 2-chloroethanol and the content of formic acid and its salt in the obtained ethylene carbonate to less than 0.1 mass ppm, respectively.

[0058] [C12] A method for producing a composition containing high-purity ethylene carbonate as described in [C11], characterized in that the method obtains the following stabilized composition containing high-purity ethylene carbonate, which comprises 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 3.0 area % or less in a gas chromatography analysis at 50°C for 125 days in a closed container or a sealed container.

[0059] [C13] A method for producing a composition containing high-purity ethylene carbonate as described in [C11] or [C12], characterized in that the method obtains the following stabilized composition containing high-purity ethylene carbonate, wherein the composition contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 2.0 area % or less in a gas chromatography analysis at 50°C for 100 days in a closed container or a sealed container.

[0060] [C14] A method for producing a composition containing high-purity ethylene carbonate as described in any one of [C11] to [C13], characterized in that the method obtains the following stabilized composition containing high-purity ethylene carbonate, wherein the composition comprises 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 1.0 area % or less in a gas chromatography analysis at 50°C in a closed container or a sealed container for 50 days.

[0061] Here, among [C11] to [C14], it is preferred to obtain a composition containing high-purity ethylene carbonate having any one or more, preferably two or more, of the characteristics of [C4] to [C8] above.

[0062] [D] A method for producing a composition containing high-purity ethylene carbonate containing 90% by mass or more of ethylene carbonate, the method comprising the following steps.

[0063] (1) a reaction step of reacting ethylene oxide with carbon dioxide to obtain a composition containing ethylene carbonate,

[0064] (2) a step of measuring the total content (total content ratio) of formic acid and its salts or the content (content ratio) of 2-chloroethanol in the above-mentioned composition containing ethylene carbonate,

[0065] (3) A step of selecting a composition in which the total content of formic acid and its salts or the content of 2-chloroethanol is 500 ppm by mass or less.

[0066] Effects of the Invention

[0067] According to the first embodiment or the second embodiment of the present invention, a novel stabilization method for suppressing the time-dependent modification of a composition containing high-purity ethylene carbonate can be realized. In addition, according to the first embodiment or the second embodiment of the present invention, a stabilized composition containing high-purity ethylene carbonate whose time-dependent modification is suppressed, a method for preserving the composition, and an electrolyte for lithium ion batteries using the composition can also be realized.

[0068] According to the third embodiment of the present invention, it is possible to realize a stabilized composition containing high-purity ethylene carbonate, a method for preserving the composition, and an electrolyte for lithium ion batteries using the composition, etc., which has been suppressed in terms of time-dependent modification. It is also possible to realize a method for stably manufacturing such a stabilized composition containing high-purity ethylene carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a figure which shows the analysis result of Experimental Examples 1-2.

[0070] Figure 2 It is a figure which shows the analysis results of Experimental Examples 3-5.

[0071] Figure 3 It is a figure which shows the analysis results of Experimental Examples 6-9.

[0072] Figure 4 It is a figure which shows the analysis result of Experimental Examples 10-11. DETAILED DESCRIPTION

[0073] The following is a detailed description of the embodiments of the present invention. The following embodiments are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these. In addition, the present invention can be implemented by making any changes within the scope of the gist thereof. It should be noted that in this specification, when "~" is used and numerical values ​​or physical property values ​​are sandwiched before and after it to express, it is used as a range including the values ​​before and after it. For example, the marking of the numerical range of "1 to 100" includes both its lower limit "1" and the upper limit "100". In addition, the marking of other numerical ranges is the same. In this specification, "monoethylene glycol" is sometimes referred to as "ethylene glycol", and "monoethylene glycol formate" is sometimes referred to as "ethylene glycol formate".

[0074] [Method for stabilizing a composition containing high-purity ethylene carbonate and stabilized composition containing high-purity ethylene carbonate]

[0075] The stabilization method of the composition containing high-purity ethylene carbonate of the first embodiment is characterized in that the content of formic acid and its salt in the composition containing high-purity ethylene carbonate containing 90% by mass or more of ethylene carbonate is adjusted to a total of less than 500 mass ppm. In addition, the stabilized composition containing high-purity ethylene carbonate of the present embodiment is characterized in that it contains 90% by mass or more of ethylene carbonate and a total of less than 500 mass ppm of formic acid and its salt.

[0076] In addition, the stabilization method of the composition containing high-purity ethylene carbonate of the second embodiment is characterized in that the content of 2-chloroethanol in the composition containing high-purity ethylene carbonate containing 90% by mass or more of ethylene carbonate is adjusted to below 500% by mass. In addition, the stabilized composition containing high-purity ethylene carbonate of the present embodiment is characterized in that it comprises 90% by mass or more of ethylene carbonate and below 500% by mass of 2-chloroethanol.

[0077] In addition, the stabilized high-purity ethylene carbonate-containing composition of the third embodiment is characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 3.0 area % or less in a gas chromatography analysis at 50° C. for 125 days in a closed container or a sealed container.

[0078] In other words, the stabilized high-purity ethylene carbonate-containing composition of the present embodiment is characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 2.0 area % or less in a gas chromatography analysis at 50° C. for 100 days in a closed container or a sealed container.

[0079] In other words, the stabilized high-purity ethylene carbonate-containing composition of the present embodiment is characterized in that it contains 90% by mass or more of ethylene carbonate and monoethylene glycol and / or monoethylene glycol formate, and the total content of the monoethylene glycol and the monoethylene glycol formate is 1.0 area % or less in a gas chromatography analysis at 50° C. for 50 days in a closed container or a sealed container.

[0080] As mentioned above, as a method for producing ethylene carbonate, there is a known method of reacting ethylene oxide with carbon dioxide, and its practical application has progressed. In addition, it is known that formic acid and 2-chloroethanol may be contained in the known ethylene oxide as impurities in its production process, and formic acid as an impurity contained in the ethylene oxide may be mixed into a composition containing high-purity ethylene carbonate. However, up to now, there has been no concern about the specific behavior caused by formic acid and 2-chloroethanol contained in the composition containing high-purity ethylene carbonate.

[0081] In contrast, the inventors have found that formic acid and its salts contained in a composition containing high-purity ethylene carbonate unexpectedly function as a triggering substance for increasing the amount of formate such as monoethylene glycol (MEG) or ethylene glycol monoformate (sometimes collectively referred to as "by-product impurities") over time, and the quality of the composition containing high-purity ethylene carbonate decreases over time due to the increase in the by-product impurities. At the same time, it has also been newly discovered that the permissible amount of formic acid and its salts in the composition is present in order to maintain the high quality of the composition containing high-purity ethylene carbonate for a specified period of time.

[0082] The inventors have also found that the 2-chloroethanol contained in the composition containing high-purity ethylene carbonate unexpectedly functions as a trigger material for increasing the by-product impurities of formate such as monoethylene glycol (MEG) or ethylene glycol monoformate over time, and the quality of the composition containing high-purity ethylene carbonate decreases over time due to the increase of the by-product impurities. At the same time, it has also been newly found that the permissible amount of 2-chloroethanol exists in the composition from the aspect of maintaining the high quality of the composition containing high-purity ethylene carbonate for a prescribed period.

[0083] The inventors have further discovered that formic acid and its salts and 2-chloroethanol contained in the composition containing high-purity ethylene carbonate unexpectedly function as a trigger material for increasing the by-product impurities of formate esters such as monoethylene glycol (MEG) and ethylene glycol monoformate over time, and the quality of the composition containing high-purity ethylene carbonate decreases over time due to the increase of the by-product impurities. At the same time, it has also been newly discovered that the increase of the by-product impurities in the composition has an allowable increase rate from the aspect of maintaining the high quality of the composition containing high-purity ethylene carbonate for a prescribed period.

[0084] This is further explained in detail below.

[0085] (ethylene carbonate)

[0086] The content of ethylene carbonate in the composition containing high-purity ethylene carbonate of the first embodiment and the second embodiment is not particularly limited, and is generally 90.00 mass % or more, preferably 95.00 mass % or more, more preferably 99.00 mass % or more, further preferably 99.50 mass % or more, particularly preferably 99.90 mass % or more, most preferably 99.95 mass % or more, and then most preferably 99.99 mass % or more relative to the total amount of the composition containing high-purity ethylene carbonate. By making the content of ethylene carbonate be above the above-mentioned preferred lower limit, there is a tendency that the instability phenomenon caused by other impurities can be relatively reduced and the stabilization effect of the present invention can be relatively significant.

[0087] As the ethylene carbonate used herein, novel synthetic products and commercial products can be used without distinction, are not particularly limited, and are preferably obtained through the reaction process (hereinafter sometimes referred to as "carbonation reaction process") of obtaining the composition containing ethylene carbonate by reacting ethylene oxide with carbon dioxide and the purification process of purifying the composition containing ethylene carbonate and the ethylene carbonate (hereinafter sometimes referred to as "carbonation ethylene carbonate") obtained. In the carbonation ethylene carbonate obtained by this preparation method, a relatively large amount of formic acid and / or 2-chloroethanol may be contained as impurities, thereby when using this carbonation ethylene carbonate, there is a tendency to make the stabilization effect of the present invention relatively significant. In addition, during the above-mentioned carbonation reaction, it is more preferred to use the carbonation catalyst described later to obtain the composition containing ethylene carbonate.

[0088] Ethylene oxide is usually produced industrially by reacting ethylene with oxygen in the presence of a silver catalyst. The selectivity of ethylene to ethylene oxide is usually about 80%, and the remaining 20% ​​or so is completely oxidized to become carbon dioxide and water. Therefore, the ethylene oxide used in the raw material of industrially produced ethylene carbonate usually contains about 40% water. In addition, sometimes a part of ethylene carbonate is hydrolyzed to contain glycols such as monoethylene glycol and diethylene glycol.

[0089] The purity of the ethylene oxide used as a raw material is not particularly limited, and is usually 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more. In addition, the upper limit is not particularly limited, but from the perspectives of economy and ease of acquisition, it is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less.

[0090] The molar ratio of the raw materials in the carbonation reaction step (carbon dioxide / ethylene oxide) is not particularly limited, but is usually 0.5 or more. The upper limit of the molar ratio is also not particularly limited, but is usually 5 or less, preferably 3.0 or less.

[0091] The carbonation reaction process of ethylene oxide is usually carried out in the presence of a catalyst. The carbonation catalyst can be appropriately selected from known catalysts, and its type is not particularly limited. Specifically, alkali metal halides; alkaline earth metal halides; alkylamines; quaternary ammonium salts; organic tin; germanium; tellurium compounds; halogenated organic phosphonium salts and alkali metal carbonates, etc., can be cited, and there are no particular limitations on them. Among these, alkali metal halides and halogenated organic phosphonium salts are preferred. In addition, alkali metal carbonates are preferred from the aspect of easily suppressing the formation of by-products.

[0092] Specific examples of alkali metal halides include alkali metal iodides such as potassium iodide and alkali metal bromides such as potassium bromide. Here, as the alkali metal, potassium having high solubility is preferred. Specific examples of alkaline earth metal halides include alkaline earth metal iodides and alkaline earth metal bromides.

[0093] Specific examples of halogenated organic phosphonium salts include quaternary phosphonium iodides such as triphenylmethylphosphonium iodide, triphenylpropylphosphonium iodide, triphenylbenzylphosphonium iodide, and tributylmethylphosphonium iodide, and quaternary phosphonium bromides such as triphenylmethylphosphonium bromide, triphenylpropylphosphonium bromide, triphenylbenzylphosphonium bromide, and tributylmethylphosphonium bromide. Specific examples of alkali metal carbonates include potassium carbonate and the like.

[0094] The amount of the catalyst used in the carbonation reaction step is not particularly limited, and is preferably 1 / 1000 or more, more preferably 1 / 200 or more, relative to ethylene oxide in molar ratio. On the other hand, the upper limit is not particularly limited, and is preferably 1 / 20 or less, more preferably 1 / 50 or less. It should be noted that the carbonation catalyst can be used alone, and two or more can be used in any combination and ratio. Regarding the amount used when using two or more carbonation catalysts, it is preferred that the total amount is within the above range.

[0095] The temperature for the carbonation reaction step of ethylene oxide is not particularly limited, but is usually 70° C. or higher, preferably 100° C. or higher. On the other hand, the upper limit is usually 200° C. or lower, preferably 170° C. or lower. The reaction pressure is also not particularly limited, but is usually 0.6 MPa or higher, preferably 1.0 MPa or higher. And, on the other hand, the upper limit is usually 5.0 MPa or lower, preferably 3.0 MPa or lower.

[0096] The carbonation reaction process of ethylene oxide can be carried out using any device. The carbonation reaction process can be carried out in any manner of batch type and continuous supply type, and the continuous supply type is preferred industrially. Specifically, for example, a bubble tower with a liquid circulation conduit equipped with a heat exchanger and a circulation pump can be used, and the reaction solution in the tower is circulated through the liquid circulation conduit, thereby controlling the reaction temperature, and continuously supplying raw materials ethylene oxide, carbon dioxide and catalyst from the bottom of the tower to allow the reaction to proceed. In addition, it is also preferred to use a reactor equipped with a jet-type nozzle. When a bubble tower is used for reaction, from the aspect of reaction efficiency, it is preferred to arrange a tubular reactor after the bubble tower so that the unreacted ethylene oxide is further reacted.

[0097] In the carbonation ethylene carbonate obtained by this method, formic acid and its salt, 2-chloroethanol etc. as impurities can be contained in a large amount. These formic acid and its salt, 2-chloroethanol play the function of the trigger material that makes the by-product impurities such as monoethylene glycol or its formates increase over time, and the quality of the composition containing high-purity ethylene carbonate is reduced over time due to the increase of these by-product impurities. Therefore, it is preferred to further carry out the operation that the content of 2-chloroethanol and formic acid and its salt in the carbonation ethylene carbonate is reduced. At this time, the content of 2-chloroethanol and formic acid and its salt in the carbonation ethylene carbonate is not particularly limited, and it is preferably adjusted to be less than 0.1 mass ppm respectively. Here, the content of 2-chloroethanol and formic acid and its salt in the carbonation ethylene carbonate is the less the better, in view of the effect brought by the present invention, it is preferably 0ppm. However, since there are technical limitations (detection limit, lower limit of quantitation) in measuring devices for detecting, for example, formic acid and its salts, the contents of 2-chloroethanol and formic acid and its salts in carbonation-process ethylene carbonate are preferably less than the detection limit in these measuring devices.

[0098] The reduction of the content of 2-chloroethanol and formic acid and its salt can be carried out according to a conventional method, and its method is not particularly limited. As this reduction method, for example, separation methods based on recrystallization, crystallization, suspension washing extraction (suspension washing extraction), concentration, washing, dehydration, filtration, distillation, distillation removal, rectification, chromatography, cation exchange resin, alcohol adsorbent, etc. can be enumerated. In addition, the reduction of the content of 2-chloroethanol and formic acid and its salt can be carried out in the purification step described later.

[0099] In the purification process, the ethylene carbonate obtained by the carbonation reaction process is purified. Purification can be carried out by crystallization, distillation, etc. From the aspect of excellent energy efficiency, it is preferably purified by crystallization, and more preferably purified by countercurrent contact type crystallization. When utilizing the crystallization method to purify, ethylene carbonate crystals are usually made by cooling the reaction solution. For example, in the wall falling type crystallization method, by heating the crystallization after the cooling wall is separated out, it is melted and flows down, thus obtaining high-purity ethylene carbonate. In the countercurrent contact type crystallization method, the reaction solution is cooled, etc. to generate the crude crystal of ethylene carbonate, and then the crystal melt obtained by heating the crude crystal is contacted with the unmelted crystal, thus obtaining high-purity ethylene carbonate.

[0100] The crude crystals of ethylene carbonate can be separated out by adding a poor solvent in the reaction solution that has carried out the carbonation reaction, cooling the reaction solution that has carried out the carbonation reaction. Here, industrially, the crude crystals of ethylene carbonate are preferably separated out by cooling the reaction solution. And the crude crystals of ethylene carbonate can be taken out by carrying out solid-liquid separation with the liquid that comprises unreacted ethylene oxide or catalyst.

[0101] In the countercurrent contact type crystallization method, it is industrially preferred to allow crude ethylene carbonate crystals to descend from the upper part of a tower, melt the crude ethylene carbonate crystals at the bottom of the tower, extract a portion of the obtained molten liquid from the tower, and allow the remainder of the molten liquid to rise in the form of reflux liquid to countercurrently contact the descending crude ethylene carbonate crystals.

[0102] In the case of carrying out the hydrolysis reaction of ethylene carbonate, it is preferred to carry out the hydrolysis reaction in the presence of a known hydrolysis catalyst such as an alkali metal compound. As the hydrolysis catalyst, specifically, alkali metal compounds such as sodium and potassium can be mentioned. The alkali metal contained in the alkali metal compound is preferably potassium. In addition, as the alkali metal compound, hydroxides of alkali metals; carbonates and bicarbonates can be mentioned. Among these, as the hydrolysis catalyst, alkali metal compounds are preferred, and carbonates of alkali metals are more preferred. In the case of carrying out the carbonation reaction and the hydrolysis reaction at the same time, the amount of the hydrolysis catalyst is preferably present in an amount of 0.01 to 1.0 in a molar ratio relative to the carbonation catalyst. It should be noted that the hydrolysis catalyst can be used alone, and two or more kinds can also be used in any combination and ratio. Regarding the amount used when using two or more hydrolysis catalysts, it is preferred that the total amount is within the above range.

[0103] (Formic acid or its salt)

[0104] In the first embodiment, the formic acid that functions as a trigger substance may exist in a salt state. Examples of the salt of the formic acid that functions as a trigger substance include metal salts such as alkali metal salts and alkaline earth metal salts.

[0105] The content of formic acid and its salt in the composition containing high-purity ethylene carbonate of the present embodiment is to add up to less than 500 mass ppm, preferably to add up to less than 100 mass ppm, more preferably to add up to less than 50 mass ppm, and further preferably to add up to less than 10 mass ppm relative to the total amount of the composition containing high-purity ethylene carbonate.On the other hand, the lower limit of the total content of formic acid and its salt is not particularly limited, and in view of the effect brought by the present invention, 0ppm is its target.But in fact, due to the technical limitation (detection limit, detection possibility) of the assay device for detecting formic acid and its salt, therefore expect the improvement of analytical technology to verify the behavior when being less than the detection limit of the assay device.Therefore, when using gas chromatography as the assay device for detecting formic acid and its salt, it is preferably more than the detection limit of the assay device, more preferably to add up to more than 0.1 mass ppm, further preferably to add up to more than 0.5 mass ppm, and particularly preferably to add up to more than 1.0 mass ppm.

[0106] By making the total content of formic acid and its salts below the above-mentioned upper limit, the time-dependent increase of monoethylene glycol or its formate (monoethylene glycol monoformate, etc.) can be suppressed. It should be noted that the content of formic acid and its salts can be measured by gas chromatography. In addition, there is no particular restriction on the means for adjusting the total content of formic acid and its salts. For example, it can be adjusted by removing formic acid or its salts contained in the composition containing high-purity ethylene carbonate; adding formic acid or its salts relative to the composition containing high-purity ethylene carbonate; setting a reference value for the amount of formic acid and its salts and measuring the amount of formic acid and its salts, and not shipping if it exceeds the standard, etc. The adjustment may include the following steps: a step of measuring the total content of formic acid and its salts and a step of selecting a composition whose total content is below a specific amount.

[0107] (2-Chloroethanol)

[0108] The content of the 2-chloroethanol in the composition containing high-purity ethylene carbonate of the second embodiment is below 500 mass ppm, preferably below 100 mass ppm, more preferably below 50 mass ppm, further preferably below 10 mass ppm relative to the total amount of the composition containing high-purity ethylene carbonate.On the other hand, the lower limit of the content of 2-chloroethanol is not particularly limited, and in view of the effect brought by the present invention, 0ppm is its target.But, in fact, owing to there is technical limitation (detection limit, detection possibility) in the assay device for detecting 2-chloroethanol, therefore expect the raising of analytical technique to verify the behavior when being less than the detection limit of assay device.Therefore, when using gas chromatography as the assay device for detecting 2-chloroethanol, be preferably more than the detection limit of this assay device, more preferably more than 0.1 mass ppm, more preferably more than 0.5 mass ppm, particularly preferably more than 1.0 mass ppm.

[0109] By making the content of 2-chloroethanol below the above-mentioned upper limit, the time-dependent increase of monoethylene glycol or its formate (monoethylene glycol monoformate, etc.) can be suppressed. It should be noted that the content of 2-chloroethanol can be measured by gas chromatography. In addition, there is no particular restriction on the adjustment of the content of 2-chloroethanol, for example, it can be adjusted by removing the 2-chloroethanol contained in the composition containing high-purity ethylene carbonate; adding 2-chloroethanol relative to the composition containing high-purity ethylene carbonate; setting a reference value for 2-chloroethanol and measuring the amount of 2-chloroethanol, and not shipping if it exceeds the standard, etc. The removal of the triggering substance can be, for example, a separation method based on a cation exchange resin, an alcohol adsorbent, or distillation. The adjustment may include the following steps: a step of measuring the content of 2-chloroethanol and a step of selecting a composition whose total content is below a specific amount.

[0110] (monoethylene glycol and monoethylene glycol formate)

[0111] In the composition containing high-purity ethylene carbonate of the third embodiment, the contents of monoethylene glycol and monoethylene glycol formate increase over time due to the trigger substance, and the amount of increase varies depending on the storage period and storage temperature. Therefore, in this embodiment, the total content of monoethylene glycol and monoethylene glycol formate when a certain period of time has passed at 50° C. under a specified condition, i.e., in a sealed container or a sealed container, is specified.

[0112] Specifically, the total content of monoethylene glycol and monoethylene glycol formate at 50° C. after 125 days in a closed container or a sealed container is 3.0 area % or less, preferably 2.5 area % or less, more preferably 2.0 area % or less, further preferably 1.75 area % or less, and particularly preferably 1.5 area % or less in gas chromatography. The total content of monoethylene glycol and monoethylene glycol formate after 100 days is preferably 2.0 area % or less, more preferably 1.75 area % or less, further preferably 1.5 area % or less, and particularly preferably 1.25 area % or less in gas chromatography. Furthermore, the total content of monoethylene glycol and monoethylene glycol formate after 50 days is preferably 1.0 area % or less, more preferably 0.75 area % or less, further preferably 0.5 area % or less, and particularly preferably 0.25 area % or less in gas chromatography.

[0113] By setting the total content of monoethylene glycol and monoethylene glycol formate at 50° C. for a certain period to be below the above preferred upper limit, the quality reliability of the high-purity ethylene carbonate-containing composition exposed to various environments from production to distribution and use tends to be further ensured.

[0114] On the other hand, the lower limit of the total content of monoethylene glycol and monoethylene glycol formate at 50°C for a certain period of time in a closed container or a sealed container is not particularly limited, and in view of the effects of the present invention, 0 area % is the target. However, in practice, since there are technical limitations (detection limit, quantitative lower limit) in gas chromatography analysis, it is expected that the analysis technology will be improved to verify the behavior when it is less than the detection limit of the measuring device. Therefore, it is preferably above the detection limit of the gas chromatography analyzer, more preferably 0.001 area % or more, further preferably 0.01 area % or more, and particularly preferably 0.1 area % or more.

[0115] It should be noted that the adjustment of the total content of monoethylene glycol and monoethylene glycol formate is not particularly limited, and can be performed by, for example, removing formic acid or its salt, 2-chloroethanol, water or iron oxide contained in the composition containing high-purity ethylene carbonate, adding these components to the composition containing high-purity ethylene carbonate, etc. In addition, the starting date of the number of days elapsed is usually when high-purity ethylene carbonate is manufactured, but since the content of monoethylene glycol and monoethylene glycol formate tends to increase over time, even if the number of days elapsed from the time of manufacture is not strictly counted, as long as the total content of monoethylene glycol and monoethylene glycol formate after at least a specified number of days elapsed is less than the above-mentioned specified value, it can be judged that it corresponds to the present embodiment.

[0116] (Other ingredients)

[0117] The composition containing high-purity ethylene carbonate of the first embodiment to the third embodiment can further include iron oxide as an impurity. In this case, the content of iron oxide is preferably less than 200 mass ppm, more preferably less than 150 mass ppm, more preferably less than 100 mass ppm, and then preferably less than 50 mass ppm, and then preferably less than 25 mass ppm, and then preferably less than 10 mass ppm, and then preferably less than 5 mass ppm relative to the total amount of the composition containing high-purity ethylene carbonate. It should be noted that in this specification, iron oxide refers to the value obtained by inductively coupled plasma emission spectrometry (ICP / OES). When measuring the content of iron oxide in ethylene carbonate, for example, ethylene carbonate can be decomposed using acids such as nitric acid and sulfuric acid, and iron oxide is quantitatively measured by ICP / OES. In addition, the lower limit of the content of iron oxide is not particularly limited, and in view of the effect brought by the present invention, 0ppm is its target. However, in reality, similarly to the formic acid and its salts and 2-chloroethanol mentioned above, because the measuring device has a detection limit, it is preferably higher than the detection limit of inductively coupled plasma emission spectrometry, more preferably higher than 0.1 mass ppm, further preferably higher than 0.5 mass ppm, and particularly preferably higher than 1.0 mass ppm.

[0118] It should be noted that the iron oxide used as the object here is FeO, Fe2O3 and Fe3O4. In the case of containing formic acid or its salt or 2-chloroethanol and iron oxide, the increase of monoethylene glycol or its formate (monoethylene glycol monoformate, etc.) over time sometimes becomes significant. By adjusting the content of formic acid and its salt, 2-chloroethanol, the content of iron oxide is adjusted to be less than the above-mentioned preferred upper limit, which has a tendency to stably suppress the increase of monoethylene glycol or its formate over time. In addition, the adjustment of the content of iron oxide is not particularly limited, for example, it can be carried out by removing the iron oxide contained in the composition containing high-purity ethylene carbonate, adding iron oxide relative to the composition containing high-purity ethylene carbonate, etc.

[0119] The composition containing high-purity ethylene carbonate of the first embodiment to the third embodiment can further contain water as an impurity. In this case, in the first embodiment, relative to the total amount of the composition containing high-purity ethylene carbonate, the content of water is preferably less than 100 mass ppm, more preferably less than 50 mass ppm, more preferably less than 25 mass ppm, and particularly preferably less than 10 mass ppm. In the second embodiment to the third embodiment, relative to the total amount of the composition containing high-purity ethylene carbonate, the content of water is preferably less than 200 mass ppm, more preferably less than 100 mass ppm, more preferably less than 50 mass ppm, particularly preferably less than 25 mass ppm, and most preferably less than 10 mass ppm. It should be noted that in this specification, the content of water refers to the value obtained by measuring using a Karl Fischer moisture meter. In addition, the lower limit of the content of water is not particularly limited. In view of the effect of the present invention, 0ppm is its target. However, in reality, similarly to the formic acid or its salt, 2-chloroethanol, and iron oxide, the content is preferably greater than the detection limit of the Karl Fischer titrator, more preferably greater than 0.1 mass ppm, further preferably greater than 0.5 mass ppm, and particularly preferably greater than 1.0 mass ppm, because the measuring device has a detection limit.

[0120] In the case of containing both formic acid or its salt or 2-chloroethanol and water, the temporal increase of monoethylene glycol or its formate (monoethylene glycol monoformate, etc.) may become significant. By adjusting the content of the formic acid and its salt and 2-chloroethanol, the content of water is adjusted to be less than the above-mentioned preferred upper limit, and there is a tendency that the temporal increase of monoethylene glycol or its formate can be stably suppressed. In addition, the adjustment of the content of water is not particularly limited, and can be carried out, for example, by removing the water contained in the composition containing high-purity ethylene carbonate, adding water relative to the composition containing high-purity ethylene carbonate, etc.

[0121] The composition containing high-purity ethylene carbonate of the first embodiment to the third embodiment can be prepared by mixing the components, or by separating or removing the appropriate components therefrom after mixing the components so that the content of each component reaches a specified range. The method for separating the components is not particularly limited and can be selected according to the type of components. At this time, the content of formic acid and its salts or 2-chloroethanol can be adjusted to less than 500 mass ppm, and the content of iron oxide or water can be further adjusted to less than 100 mass ppm (in the first embodiment) and adjusted to less than 200 mass ppm (in the second and third embodiments) as needed.

[0122] In the first embodiment, the composition containing high-purity ethylene carbonate in which the content of formic acid and its salts and, if necessary, the content of iron oxide and water is adjusted to a predetermined ratio is thus obtained. By-product impurities such as monoethylene glycol (MEG) or its formate ester are unlikely to increase even over time, and the composition is excellent in storage stability, high purity, and high quality.

[0123] In addition, in the composition containing high-purity ethylene carbonate of the second embodiment in which the content of 2-chloroethanol and, if necessary, the content of iron oxide and water are adjusted to a predetermined ratio, by-product impurities such as monoethylene glycol (MEG) or its formate ester are unlikely to increase even over time, and the composition is excellent in storage stability, high purity, and high quality.

[0124] In addition, the high-purity ethylene carbonate-containing composition of the third embodiment having such a composition does not easily increase by-product impurities such as monoethylene glycol (MEG) or its formate even over time, and is a high-purity, high-quality composition with excellent storage stability.

[0125] [Method for storing a composition containing high-purity ethylene carbonate]

[0126] From the aspect that suppresses the by-product impurities that increase due to the moisture in the atmosphere, the composition that contains ethylene carbonate of the first embodiment~the 3rd embodiment is preferably preserved in the state that does not contact with air and water, specifically, is preferably stored in a closed container or a sealed container. In addition, more preferably preserve under low oxygen partial pressure atmospheres such as vacuum or inert gas (nitrogen, argon, helium) atmosphere and / or under low water vapor partial pressure atmosphere.

[0127] The storage temperature is not particularly limited, but is preferably 10 to 70° C., more preferably 10 to 60° C., and further preferably 10 to 55° C. When the storage temperature is within the above range, the effect of suppressing the temporal increase of by-product impurities such as monoethylene glycol (MEG) or its formate ester tends to be well exhibited.

[0128] A closed container or a sealed container including the composition containing ethylene carbonate according to the first to third embodiments is also one embodiment of the present invention.

[0129] [Method for producing a composition containing high-purity ethylene carbonate]

[0130] The high-purity ethylene carbonate-containing composition containing 90% by mass or more of ethylene carbonate according to the first to third embodiments can be produced by a method including the following steps.

[0131] (1) Reaction step of reacting ethylene oxide with carbon dioxide to obtain a composition containing ethylene carbonate

[0132] (2) A step of measuring the total content of formic acid and its salts or the content of 2-chloroethanol in the composition containing ethylene carbonate

[0133] (3) A step of selecting a composition having a total content of formic acid and its salts or a content of 2-chloroethanol of 500 ppm by mass or less

[0134] [Quality management method for composition containing high-purity ethylene carbonate]

[0135] The quality of the high-purity ethylene carbonate-containing composition containing 90% by mass or more of ethylene carbonate according to the first to third embodiments can be controlled by a method including the following steps.

[0136] (1) Step of reacting ethylene oxide with carbon dioxide to produce a composition containing ethylene carbonate

[0137] (2) A step of measuring the total content of formic acid and its salts or the content of 2-chloroethanol in the composition containing ethylene carbonate

[0138] (3) A step of selecting a composition having a total content of formic acid and its salts or a content of 2-chloroethanol of 500 ppm by mass or less

[0139] [Electrolyte for lithium-ion batteries]

[0140] The electrolyte for lithium ion batteries of the first embodiment to the third embodiment includes the above-mentioned composition containing high-purity ethylene carbonate. In the composition containing high-purity ethylene carbonate of this embodiment, since there are few by-product impurities such as monoethylene glycol (MEG) or its formate, and its increase over time is suppressed, when it is used in the electrolyte for lithium ion batteries, the unexpected performance degradation of the lithium ion battery caused by the by-product impurities can be suppressed, thereby maintaining the battery capacity and battery performance for a longer period of time, and realizing a lithium ion battery with high reliability during long-term use.

[0141] Furthermore, as the purpose of lithium ion batteries, it is expected that there will be not only small-sized purposes but also large-sized purposes, and further the demand for industrial batteries in the future is expected to grow day by day. Therefore, from the perspective of the need for higher-performance lithium ion batteries in the future, the composition containing high-purity ethylene carbonate of the present embodiment that can improve the reliability during long-term use can also be said to be very useful as a solvent for the electrolyte.

[0142] The electrolyte for lithium ion batteries can be composed of components known in the art, and there is no particular limitation on its mixed composition. For example, electrolytes for lithium ion batteries containing non-aqueous solvents such as lithium salts such as LiPF6 or LiBOB, saturated cyclic carbonates, linear carbonates, linear carboxylates, cyclic carboxylates, ether compounds, sulfone compounds, and various additives known in the art are available on the market. In particular, the above-mentioned composition containing high-purity ethylene carbonate is particularly preferably used as an additive or non-aqueous solvent for the electrolyte for lithium ion batteries.

[0143] Example

[0144] The following experimental examples are given to more specifically illustrate the content of the present invention, but the present invention is not limited by these experimental examples. It should be noted that the values ​​of various manufacturing conditions and evaluation results in the following experimental examples have the meaning of preferred values ​​as the upper or lower limits in the embodiments of the present invention, and the preferred range can be the range defined by combining the above-mentioned upper or lower limit values ​​with the values ​​of the following experimental examples or the values ​​of the experimental examples with each other.

[0145] [Experimental Example 1]

[0146] First, carbon dioxide, ethylene oxide, water, tributylmethylphosphonium iodide, and potassium carbonate are continuously supplied to a reactor, and the resulting reaction solution is purified by a countercurrent contact crystallization method and then subjected to solid-liquid separation, thereby obtaining high-purity ethylene carbonate with a purity of 99.999%, wherein formic acid and its salt, 2-chloroethanol, and iron oxide are less than the detection limit, respectively, and water contains about 5 mass ppm.

[0147] Next, 0.01 parts by mass of formic acid was added to 100 parts by mass of the obtained high-purity ethylene carbonate (100 parts by mass relative to the total amount of the composition) to prepare a composition containing high-purity ethylene carbonate of Experimental Example 1.

[0148] Thereafter, the obtained high-purity ethylene carbonate-containing composition was placed in a 20 mL glass vial, which was sealed, placed in an open cylinder, and then stored in a TABAI oven SPH-100 set at 50°C.

[0149] Afterwards, after the prescribed period from the beginning of preservation, the composition containing high-purity ethylene carbonate of 0.8mL is sampled from a glass vial, 0.2mL of acetonitrile is added, and a gas chromatography sample solution is prepared respectively. It should be noted that, when sampling, when confirming solid component, a PTFE disc filter of 0.2 μm is utilized to filter as required. Use the prepared sample solution, implement gas chromatographic analysis under the following conditions, calculate the area % of the peak equivalent to ethylene glycol and ethylene glycol monoformate.

[0150] [Analysis conditions]

[0151] Device: GC-2010plus manufactured by Shimadzu Corporation

[0152] Inlet temperature: 130℃

[0153] Injection volume: 1.0 μL

[0154] Column: Agilent DB-WAXetr 123-7364

[0155] Column temperature: After holding at 60°C for 2 minutes, the temperature was increased to 200°C at a rate of 20°C / min and held for 16 minutes, and then increased to 230°C at a rate of 20°C / min and held for 5 minutes

[0156] Carrier gas: Helium, flow rate 50cm / sec

[0157] Injection method: No split (1:20 split after 1 minute of injection)

[0158] Detector: Flame ionization detector (FID) 250°C

[0159] Post-treatment: For each measurement, drive out at INJ 230°C and COL 230°C for 5 minutes

[0160] Cleaning solvent: acetonitrile

[0161] Area calculation method: Area percentage method excluding acetonitrile peak

[0162] Detection limit: 7 mass ppm

[0163] [Experimental Example 2]

[0164] A composition containing high-purity ethylene carbonate of Experimental Example 2 was prepared in the same manner as in Experimental Example 1 except that the blending amount of formic acid was changed to 0.001 parts by mass (10 parts by mass relative to the total amount of the composition).

[0165] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate in Experimental Example 2 was used instead of the composition containing high-purity ethylene carbonate in Experimental Example 1.

[0166] [Experimental Example 3]

[0167] A composition containing high-purity ethylene carbonate of Experimental Example 3 was prepared in the same manner as in Experimental Example 1 except that 0.0001 parts by mass of water (1 ppm by mass relative to the total amount of the composition) was further added to 100 parts by mass of high-purity ethylene carbonate.

[0168] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 3 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0169] [Experimental Example 4]

[0170] A composition containing high-purity ethylene carbonate of Experimental Example 4 was prepared in the same manner as in Experimental Example 3 except that the blending amount of formic acid was changed to 0.001 parts by mass (10 parts by mass relative to the total amount of the composition).

[0171] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 4 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0172] [Experimental Example 5]

[0173] A composition containing high-purity ethylene carbonate of Experimental Example 5 was prepared in the same manner as in Experimental Example 3 except that the blending amount of formic acid was changed to 0.0001 parts by mass (1 ppm by mass with respect to the total amount of the composition).

[0174] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 5 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0175] [Experimental Example 6]

[0176] A composition containing high-purity ethylene carbonate of Experimental Example 6 was prepared in the same manner as in Experimental Example 1 except that 0.01 parts by mass of 2-chloroethanol (100 parts by mass relative to the total amount of the composition) was added instead of formic acid.

[0177] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 6 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0178] [Experimental Example 7]

[0179] The composition containing high-purity ethylene carbonate of Experimental Example 7 was prepared in the same manner as in Experimental Example 6, except that 0.001 mass part of water (10 mass ppm relative to the total amount of the composition) and 0.01 mass part of iron oxide (Fe3O4) (100 mass ppm relative to the total amount of the composition) were further added to 100 mass parts of high-purity ethylene carbonate.

[0180] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 7 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0181] [Experimental Example 8]

[0182] A composition containing high-purity ethylene carbonate of Experimental Example 8 was prepared in the same manner as in Experimental Example 7 except that the mixing amount of water was changed to 0.01 parts by mass (100 parts by mass relative to the total amount of the composition).

[0183] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 8 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0184] [Experimental Example 9]

[0185] A composition containing high-purity ethylene carbonate of Experimental Example 9 was prepared in the same manner as in Experimental Example 7 except that the blending amount of 2-chloroethanol was changed to 0.001 parts by mass (10 parts by mass relative to the total amount of the composition).

[0186] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 9 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0187] [Experimental Example 10]

[0188] A composition containing high-purity ethylene carbonate of Experimental Example 10 was prepared in the same manner as in Experimental Example 7 except that the blending amount of 2-chloroethanol was changed to 0.1 parts by mass (1000 parts by mass relative to the total amount of the composition).

[0189] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 10 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0190] [Experimental Example 11]

[0191] A composition containing high-purity ethylene carbonate of Experimental Example 11 was prepared in the same manner as in Experimental Example 8 except that the blending amount of 2-chloroethanol was changed to 0.1 parts by mass (1000 parts by mass relative to the total amount of the composition).

[0192] Furthermore, gas chromatography analysis was performed in the same manner as in Experimental Example 1, except that the composition containing high-purity ethylene carbonate of Experimental Example 11 was used instead of the composition containing high-purity ethylene carbonate of Experimental Example 1.

[0193] The results of each experimental example are shown in Tables 1 to 3 and Figures 1 to 4 middle.

[0194] In addition, formic acid, 2-chloroethanol, water, and iron oxide in Tables 1 to 3 indicate the amounts added to the high-purity ethylene carbonate of each experimental example before storage.

[0195] [Table 1]

[0196]

[0197] MEG: Ethylene glycol

[0198] MEG Monoformate: Ethylene glycol monoformate

[0199] [Table 2]

[0200]

[0201] MEG: Ethylene glycol

[0202] MEG Monoformate: Ethylene glycol monoformate

[0203] [Table 3]

[0204]

[0205] MEG: Ethylene glycol

[0206] MEG Monoformate: Ethylene glycol monoformate

[0207] Industrial Applicability

[0208] The composition containing high-purity ethylene carbonate of the present invention and the stabilization method thereof can be widely and effectively utilized in various applications such as solvents for various polymer compounds, reaction solvents for various chemical reactions, extraction solvents, foaming agents, lubricating stabilizers, surfactants, soil modifying materials, resists, resist stripping agents, pharmaceuticals, polyester raw materials, antifreeze solutions, etc., and can be particularly effectively utilized in electrolytes for lithium ion batteries.

Claims

1. A method for manufacturing a lithium ion battery, comprising the following steps: (1) selecting a high-purity ethylene carbonate-containing composition containing 90% by mass or more of ethylene carbonate, which has a total content of formic acid and formate of 500 mass ppm or less, and (2) Introducing the selected high-purity ethylene carbonate-containing composition as an electrolyte into a lithium-ion battery.

2. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) has a total content of the formic acid and the formate salt of 100 mass ppm or less.

3. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) has a total content of the formic acid and the formate salt of 50 mass ppm or less.

4. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) has a total content of the formic acid and the formate salt of 10 mass ppm or less.

5. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) further has a 2-chloroethanol content of 500 ppm by mass or less.

6. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) further has a 2-chloroethanol content of 100 ppm by mass or less.

7. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) further has a 2-chloroethanol content of 50 ppm by mass or less.

8. The method according to claim 1, wherein: The high-purity ethylene carbonate-containing composition selected in (1) further has a 2-chloroethanol content of 10 ppm by mass or less.

9. The method according to claim 1, wherein: The total content of the formic acid and the formate salt in the high-purity ethylene carbonate-containing composition is 0.1 mass ppm or more and 500 mass ppm or less.

Images