Non-aqueous electrolyte, secondary battery, and method for manufacturing the same

Abstract

This electrolytic solution contains a sulfonyl imide compound represented by general formula (1): LiN(R1SO2)(R2SO2) (where R1 and R2 are the same as or different from each other, and represent a fluorine atom, a C1-6 alkyl group, or a C1-6 fluoroalkyl group) as an electrolyte salt, and an electrolytic solution solvent, the electrolytic solution also being such that at least one of CO2, CO, HCO3 -, and CO3 2- is dissolved therein, the electrolytic solution solvent containing at least one selected from the group consisting of carbonate-based solvents, lactone-based solvents, ether-based solvents, nitrile-based solvents, and chain-form-ester-based solvents, and the total dissolved amount of at least one of CO2, CO, HCO3 -, and CO3 2- being 20 mass ppm or greater.

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte, a secondary battery, and a method for manufacturing the same.

Background Art

[0002] It has been reported that the battery characteristics are improved by injecting carbon dioxide (CO 2 ) into a battery using Li metal or carbon as a negative electrode material. The same has also been reported for secondary batteries using Si-based negative electrodes or Sn-based negative electrodes.

[0003] For example, in Patent Document 1, a non-aqueous secondary battery is proposed in which the non-aqueous electrolyte contains vinylene carbonate at 0.1% by weight or more in a state before the first charge after battery fabrication, and CO 2 is enclosed in the battery container. In this battery, by adding vinylene carbonate and enclosing CO 2 , improvements in both discharge storage characteristics and cycle characteristics are observed.

[0004] In Patent Document 2, a non-aqueous lithium-type energy storage device is proposed in which the non-aqueous electrolyte contains carbon dioxide at 10 μg / L or more and 5000 μg / L or less, and the positive electrode active material layer contains a lithium compound other than the active material at 1% by mass or more and 50% by mass or less. In this energy storage device, improvements in input / output characteristics, high-temperature durability, etc. are also observed even in the positive electrode containing the lithium compound.

[0005] Patent Document 3 proposes an electrolyte for a lithium-ion secondary battery containing a lithium imide salt, a room-temperature molten salt, and a high-vapor-pressure solvent. The room-temperature molten salt, also called an ionic liquid, contains a cation component and an anion component, is a salt that is in a molten state and has fluidity at room temperature, and is different from the organic solvents used in conventional lithium-ion secondary batteries. While this room-temperature molten salt can improve the safety of the battery, it is extremely difficult to impregnate the positive electrode, negative electrode, and separator. The high-vapor-pressure solvent is a solvent that is easily volatile and has a vapor pressure of 1 kPa or more at 20°C, and examples thereof include carbon dioxide, monohydric alcohols, ketones, nitriles, esters, chain carbonates, cyclic ethers, and chain ethers.

[0006] Patent Document 4 proposes a non-aqueous electrolyte secondary battery in which, in at least one of the positive and negative electrodes, the amount of carbon dioxide released when heated at 350°C for 1 minute is 0.1 ml or more and 10 ml or less per unit weight of the active material layer contained in the electrode. In this battery, carbon dioxide is contained as an impurity in the electrode (negative electrode).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] Incidentally, through previous studies, the inventors of the present application have found that a non-aqueous electrolyte containing a sulfonylimide compound such as lithium bis(fluorosulfonyl)imide as an electrolyte salt improves the high-temperature durability and battery performance such as charge-discharge cycles of a lithium-ion secondary battery.

[0009] However, in Patent Document 1, a non-aqueous electrolyte containing a sulfonylimide compound has not been studied. Further, in the battery described in Patent Document 1, since vinylene carbonate is contained in the non-aqueous electrolyte, there is also a problem that the DC resistance (DCR) and impedance of the battery increase, and the battery performance is not sufficient.

[0010] In the non-aqueous electrolyte described in Patent Document 2, when the electrolyte salt concentration is 1.2 mol / L, the dissolved amount of CO 2 is at most less than 5 ppm, so there is a possibility that the improvement effects such as input-output characteristics and high-temperature durability due to the dissolved CO 2 cannot be sufficiently obtained.

[0011] Patent Document 3 describes that the electrolyte can improve the initial capacity of the battery while containing a room-temperature molten salt and is easy to impregnate the positive electrode, negative electrode, and separator. However, when evaluating a battery using the electrolyte, the improvement effect due to containing the room-temperature molten salt is not sufficient, and there is a possibility that the battery performance may decrease instead.

[0012] In Patent Document 4, similar to Patent Document 1, a non-aqueous electrolyte containing a sulfonylimide compound has not been studied. Further, in Patent Document 4, although the amount of carbon dioxide contained in the electrode is adjusted by controlling the atmosphere during the production of the electrode, the carbon dioxide contained in the non-aqueous electrolyte and its amount have not been studied.

[0013] The present disclosure has been made in view of such points, and an object thereof is to provide a non-aqueous electrolyte capable of improving battery performance in a non-aqueous electrolyte containing a sulfonylimide compound, a secondary battery including the non-aqueous electrolyte, and a method for manufacturing the same.

Means for Solving the Problem

[0014] As a result of further studies, the inventors of the present application have found that a battery using a non-aqueous electrolyte containing a sulfonylimide compound has a larger self-discharge from a fully charged state than a battery using a non-aqueous electrolyte containing a lithium compound other than the sulfonylimide compound (for example, LiPF 6 LiBF 4 etc.) alone, and there is room for improvement in the storage characteristics of the battery. This finding was first discovered by the inventors of the present application, and the self-discharge of a battery using a non-aqueous electrolyte containing a sulfonylimide compound (especially lithium bis(fluorosulfonyl)imide) is not mentioned in Patent Documents 1 and 2 and other documents.

[0015] In Patent Document 4, it is described that the generation of a film is promoted and self-discharge is suppressed by the inclusion of carbon dioxide in the electrode. In this Patent Document 4, the rate of change in the thickness and the capacity retention rate of a battery (SOC 50% state) before and after storage, which is charged to 30% state at a 1C rate and then stored at 65°C for one month, are used as indicators of the amount of self-discharge during storage. However, in this indicator, the reaction between carbon dioxide physically adsorbed on the negative electrode and carbon dioxide present as a compound in the negative electrode and the negative electrode active material during battery storage is regarded as the self-discharge reaction. This is an evaluation of the durability of the electrolyte, and is different from the original indicator that regards the charge consumption in the state where there is no electrical load between the positive and negative electrodes as self-discharge.

[0016] In order to improve the storage characteristics and battery performance of the above-described battery, in this disclosed technology, in a non-aqueous electrolyte containing a sulfonylimide compound, vinylene carbonate or the like, which may increase the resistance of the battery, is not used, and the self-discharge of the battery is suppressed. The present disclosure is specifically as follows.

[0017] The non-aqueous electrolyte of the present disclosure has, as an electrolyte salt, the general formula (1): LiN(R 1 SO 2 )(R2 SO 2 ) (R 1 and R 2 each independently represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms. ) (1) comprising a sulfonylimide compound represented by the formula: and an electrolytic solution solvent, and containing at least one of carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - ), and carbonate ion (CO 3 2- ) dissolved therein, wherein the electrolytic solution solvent contains at least one selected from the group consisting of carbonate solvents, lactone solvents, ether solvents, nitrile solvents, and chain ester solvents, and the total dissolved amount of at least one of the carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - ), and carbonate ion (CO 3 2- ) is 20 mass ppm or more.

[0018] The method for producing a non-aqueous electrolytic solution according to the present disclosure is a method for producing a non-aqueous electrolytic solution containing a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolytic solution solvent, and containing at least one of carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - ), and carbonate ion (CO 3 2- ) dissolved therein, wherein the electrolytic solution solvent contains at least one selected from the group consisting of carbonate solvents, lactone solvents, ether solvents, nitrile solvents, and chain ester solvents, and the method includes a dissolving step of dissolving at least one of the carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - ), and carbonate ion (CO 3 2- ) into the non-aqueous electrolytic solution, and the dissolving step involves carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ion (HCO3 - ) and carbonate ions (CO 3 2- ) at least one kind of gas is pressurized into the non-aqueous electrolyte, a liquid contact step of bringing the gas into contact with the non-aqueous electrolyte, a bubbling step of blowing the gas into the non-aqueous electrolyte, and a replacement step of replacing the air in the sealed container containing the non-aqueous electrolyte with the gas, including at least one of them.

[0019] The secondary battery of the present disclosure is a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte includes a sulfonylimide compound represented by the general formula (1) as an electrolyte salt, and at least one selected from the group consisting of a carbonate solvent, a lactone solvent, an ether solvent, a nitrile solvent, and a chain ester solvent as an electrolyte solvent, and contains carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ions (HCO 3 - ) and carbonate ions (CO 3 2- ) at least one kind is dissolved, and the total dissolved amount of at least one kind of the carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ions (HCO 3 - ) and carbonate ions (CO 3 2- ) is 20 mass ppm or more.

[0020] The manufacturing method of the secondary battery of the present disclosure is a method for manufacturing a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte includes a sulfonylimide compound represented by the general formula (1) as an electrolyte salt, and at least one selected from the group consisting of a carbonate solvent, a lactone solvent, an ether solvent, a nitrile solvent, and a chain ester solvent as an electrolyte solvent, and contains carbon dioxide (CO 2 ), carbon monoxide (CO), hydrogen carbonate ions (HCO 3 - ) and carbonate ions (CO 3 2- ) at least one kind is dissolved, and the carbon dioxide (CO 2)), carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - )) and carbonate ion (CO 3 2- ) is used, in which the total dissolved amount of at least one of them is 20 mass ppm or more.

[0021] The method for manufacturing a secondary battery of the present disclosure is a method for manufacturing a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte includes a sulfonylimide compound represented by the general formula (1) as an electrolyte salt, and at least one selected from the group consisting of a carbonate solvent, a lactone solvent, an ether solvent, a nitrile solvent, and a chain ester solvent as an electrolyte solvent. Carbon dioxide (CO 2 ) is injected into the battery under an atmosphere.

[0022] The method for manufacturing a secondary battery of the present disclosure is a method for manufacturing a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte includes a sulfonylimide compound represented by the general formula (1) as an electrolyte salt, and at least one selected from the group consisting of a carbonate solvent, a lactone solvent, an ether solvent, a nitrile solvent, and a chain ester solvent as an electrolyte solvent. After injecting the non-aqueous electrolyte, the air in the battery is replaced with carbon dioxide (CO 2 ).

Advantages of the Invention

[0023] According to the present disclosure, it is possible to provide a non-aqueous electrolyte capable of improving battery performance, a secondary battery including the non-aqueous electrolyte, and a method for manufacturing the same in a non-aqueous electrolyte containing a sulfonylimide compound.

Brief Description of the Drawings

[0024]

Figure 1

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present disclosure will be described in detail. The following description of the preferred embodiments is merely illustrative in nature and is not at all intended to limit the present disclosure, its applications, or its uses.

[0026] <Non-aqueous Electrolyte and Method for Producing the Same> (Electrolyte Salt) The non-aqueous electrolyte according to this embodiment contains an electrolyte salt. The electrolyte salt has the general formula (1): [Chemical Formula 1] LiN(R 1 SO 2 )(R 2 SO 2 ) (1) and contains a sulfonylimide compound represented by the formula (hereinafter referred to as "sulfonylimide compound (1)", a fluorine-containing sulfonylimide salt).

[0027] In the general formula (1), R 1 and R 2 are the same or different (independent of each other) and represent a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.

[0028] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. Among the alkyl groups having 1 to 6 carbon atoms, a linear or branched alkyl group having 1 to 6 carbon atoms is preferred, and a linear alkyl group having 1 to 6 carbon atoms is more preferred.

[0029] Examples of the fluoroalkyl group having 1 to 6 carbon atoms include those in which some or all of the hydrogen atoms of the alkyl group having 1 to 6 carbon atoms are substituted with fluorine atoms. Examples of the fluoroalkyl group having 1 to 6 carbon atoms include fluoromethyl group, difluoromethyl group, trifluoromethyl group, fluoroethyl group, difluoroethyl group, trifluoroethyl group, pentafluoroethyl group, etc. In particular, the fluoroalkyl group may be a perfluoroalkyl group.

[0030] Substituent R 1 and R 2 are preferably a fluorine atom and a perfluoroalkyl group (for example, a perfluoroalkyl group having 1 to 6 carbon atoms such as trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, etc.), more preferably a fluorine atom, trifluoromethyl group and pentafluoroethyl group, even more preferably a fluorine atom and trifluoromethyl group, and still more preferably a fluorine atom. Note that substituent R 1 and R 2 may be the same or different from each other.

[0031] Examples of the sulfonylimide compound (1) include lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ), hereinafter also referred to as "LiFSI"), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF 2 SO 3 ) 2 ) 2, also referred to as "LiTFSI" hereinafter, include lithium (fluorosulfonyl)(methylsulfonyl)imide, lithium (fluorosulfonyl)(ethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(pentafluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(heptafluoropropylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium bis(heptafluoropropylsulfonyl)imide, and the like. The sulfonylimide compound (1) may be used alone or in combination of two or more. Further, as the sulfonylimide compound (1), a commercially available product may be used, or one obtained by synthesis by a conventionally known method may be used.

[0032] Among the sulfonylimide compounds (1), from the viewpoints of reducing the impedance and DCR of the battery and improving the low-temperature charge-discharge characteristics and charge-discharge cycle characteristics, LiN(FSO 2 ) 2 and LiN(CF 3 SO 2 ) 2 are preferable, and LiN(FSO 2 ) 2 is more preferable. In other words, among non-aqueous electrolytes, the sulfonylimide compound (1) preferably contains at least one of LiN(FSO 2 ) 2 and LiN(CF 3 SO 2 ) 2 , and those containing LiN(FSO 2 ) 2 are preferable.

[0033] The electrolyte salt may contain the sulfonylimide compound (1), but may also contain other electrolytes (electrolytes other than the sulfonylimide compound (1)). Examples of other electrolytes include imide salts and non-imide salts.

[0034] Examples of the imide salts include other fluorine-containing sulfonylimide salts different from the sulfonylimide compound (1) (hereinafter referred to as "other sulfonylimide compounds"). Examples of the other sulfonylimide compounds include non-lithium salts of the fluorine-containing sulfonylimides listed as the sulfonylimide compound (1) (for example, in the sulfonylimide compound (1), salts in which lithium (ions) are replaced with cations other than lithium ions). Examples of the salts in which lithium ions are replaced with other cations include alkali metal salts such as sodium salts, potassium salts, rubidium salts, and cesium salts; alkaline earth metal salts such as beryllium salts, magnesium salts, calcium salts, strontium salts, and barium salts; aluminum salts; ammonium salts; phosphonium salts; and the like. The other sulfonylimide compounds may be used alone or in combination of two or more. Further, as the other sulfonylimide compounds, commercially available products may be used, or those obtained by synthesis by a conventionally known method may be used.

[0035] Examples of the non-imide salts include salts of non-imide anions and cations (lithium ions and the cations exemplified above). Examples of the non-imide salts include the compound represented by the general formula (2): [Chemical Formula 2] LiPF a (C m F 2m+1 ) 6-a (a: 0 ≤ a ≤ 6, m: 1 ≤ m ≤ 4) (2) hereinafter referred to as "fluorophosphoric acid compound (2)", the compound represented by the general formula (3): [Chemical Formula 3] LiBF b (C n F 2n+1 ) 4-b (b: 0 ≤ b ≤ 4, n: 1 ≤ n ≤ 4) (3) hereinafter referred to as "fluoroboric acid compound (3)", lithium hexafluoroarsenate (LiAsF 6 ), LiSbF 6 , LiClO 4 , LiSCN, LiAlF 4 , CF 3 SO 3 Li, LiC[(CF3 SO 2 ) 3 )、LiN(NO 2 )、LiN[(CN) 2 and other lithium salts; non-lithium salts (for example, in these lithium salts, salts in which lithium (ions) are replaced with the exemplified cations (for example, NaBF 4 , NaPF 6 , NaPF 3 (CF 3 ) 3 etc.) etc. are included. The non-imidate salts may be used alone or in combination of two or more. Also, the non-imidate salts may be commercially available products or those obtained by synthesis by a conventionally known method.

[0036] Among other electrolytes, non-imidate salts are preferred from the viewpoints of ionic conductivity, cost, etc., and fluorophosphoric acid compounds (2), fluoroboric acid compounds (3), and LiAsF 6 are preferred, and fluorophosphoric acid compounds (2) are more preferred.

[0037] Examples of the fluorophosphoric acid compound (2) include LiPF 6 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (C 3 F 7 ) 3 , LiPF 3 (C 4 F 9 ) 3 etc. Among the fluorophosphoric acid compounds (2), LiPF 6 and LiPF 3 (C 2 F 5 ) 3 are preferred, and LiPF 6 is more preferred.

[0038] Examples of the fluoroboric acid compound (3) include LiBF 4 , LiBF(CF3 ) 3 , LiBF(C 2 F 5 ) 3 , LiBF(C 3 F 7 ) 3 and the like. Among the fluoroboric acid compounds (3), LiBF 4 , and LiBF(CF 3 ) 3 are preferred, and LiBF 4 is more preferred.

[0039] In addition, these electrolyte salts (sulfonylimide compound (1), other electrolytes, etc.) may exist (be contained) in the form of ions in the non-aqueous electrolyte.

[0040] From the viewpoints of reducing the impedance and DCR of the battery, and improving the low-temperature charge / discharge characteristics and charge / discharge cycle characteristics, the concentration of the sulfonylimide compound (1) in the non-aqueous electrolyte is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more, even more preferably 0.1 mol / L or more, still more preferably 0.2 mol / L or more, and even still more preferably 0.5 mol / L or more. Also, from the viewpoint of suppressing the deterioration of battery performance due to an increase in the viscosity of the electrolyte, the concentration is preferably 5 mol / L or less, more preferably 3 mol / L or less, and still more preferably 2 mol / L or less.

[0041] Here, as shown in FIG. 1, in a non-aqueous electrolyte containing the sulfonylimide compound (1), in the vibration spectrum, regarding the peak intensity derived from the organic solvent (electrolyte solvent described later) contained in the non-aqueous electrolyte, when the intensity of the original peak of this electrolyte solvent is Io and the intensity of the peak when the original peak of the electrolyte solvent shifts (hereinafter also referred to as "shift peak") is Is, as the concentration of the sulfonylimide compound (1) increases, the magnitude relationship between the two peak intensities changes from Is < Io to Is > Io. That is, in a non-aqueous electrolyte containing the sulfonylimide compound (1) at a high concentration (for example, 4 mol / L), in the vibration spectrum chart, the relationship between the two peak intensities is Is > Io.

[0042] The peak of the electrolyte solvent itself means the peak observed at the peak position (wavenumber) when only the electrolyte solvent is subjected to vibrational spectroscopic measurement. The value of the intensity Io of the peak of the electrolyte solvent itself and the value of the intensity Is of the shifted peak are the height or area from the baseline of each peak in the vibrational spectroscopy spectrum.

[0043] In the vibrational spectroscopy spectrum, when there are multiple peaks where the peak of the electrolyte solvent itself has shifted, the relationship between Is and Io may be determined based on the peak that is most easily judged for the relationship between Is and Io. Further, when the non-aqueous electrolyte contains multiple types of electrolyte solvents, the electrolyte solvent that is most easily judged for the relationship between Is and Io (the difference between Is and Io is the most prominent) is selected, and the relationship between Is and Io may be determined based on the peak intensity thereof. Further, when the peak shift amount is small and the peaks before and after the shift overlap and look like a gentle mountain, peak separation may be performed using known means, and the relationship between Is and Io may be determined.

[0044] Note that the existing environments in the non-aqueous electrolyte are different between the electrolyte solvent forming the cluster and the electrolyte solvent not involved in the formation of the cluster. Specifically, in the vibrational spectroscopic measurement, the peak derived from the electrolyte solvent forming the cluster is observed to shift to the high wavenumber side or the low wavenumber side from the wavenumber at which the peak derived from the electrolyte solvent not involved in the formation of the cluster (the peak of the electrolyte solvent itself) is observed. Therefore, the peak shifted to the high wavenumber side or the low wavenumber side from the peak of the electrolyte solvent itself corresponds to the peak derived from the electrolyte solvent forming the cluster.

[0045] Examples of the vibration spectrum include an IR spectrum or a Raman spectrum. Examples of the measurement method for IR measurement include transmission measurement methods such as the Nujol method and the liquid film method, and reflection measurement methods such as the ATR method. Regarding which of the IR spectrum and the Raman spectrum to select, in the vibration spectrum of the non-aqueous electrolyte, a spectrum in which the relationship between Is and Io can be easily judged may be selected. Note that the vibration spectrum measurement is preferably performed under conditions where the influence of moisture in the atmosphere can be reduced or ignored. Examples of the method for performing the measurement under such conditions include a method of performing IR measurement under low humidity or no humidity conditions such as a dry room or a glove box, and a method of performing Raman measurement with the non-aqueous electrolyte kept in a sealed container.

[0046] From the viewpoints of reducing the impedance and DCR of the battery and improving the low-temperature charge / discharge characteristics and charge / discharge cycle characteristics, the content of the sulfonylimide compound (1) in the non-aqueous electrolyte is preferably 10 mol% or more, more preferably 20 mol% or more, still more preferably 30 mol% or more, and particularly preferably 50 mol% or more based on 100 mol% of the total electrolyte salts contained in the non-aqueous electrolyte.

[0047] The salt composition of the electrolyte salt may be an electrolyte salt having a single salt composition of the sulfonylimide compound (1), or may be an electrolyte salt having a mixed salt composition containing the sulfonylimide compound (1) and other electrolytes. When using an electrolyte salt having a mixed salt composition, an electrolyte salt having a mixed salt composition containing the sulfonylimide compound (1) and the fluorophosphate compound (2) is preferable, and LiN(FSO 2 ) 2 and LiN(CF 3 SO 2 ) 2 At least one of and LiPF 6 and an electrolyte salt having a mixed salt composition containing them is more preferable, and an electrolyte salt having a mixed salt composition containing LiN(FSO 2 ) 2 and LiPF 6 is particularly preferable.

[0048] When using an electrolyte salt of a mixed salt composition containing a sulfonylimide compound (1) and other electrolytes, the concentration of each of the other electrolytes in the non-aqueous electrolyte is preferably 0.1 mol / L or more, more preferably 0.2 mol / L or more, still more preferably 0.5 mol / L or more, from the viewpoints of reducing the impedance and DCR of the battery, improving the low-temperature charge-discharge characteristics and charge-discharge cycle characteristics. Also, the concentration is preferably 1 mol / L or less, more preferably 0.6 mol / L or less, from the viewpoints of reducing the impedance and DCR of the battery, improving the low-temperature charge-discharge characteristics and charge-discharge cycle characteristics.

[0049] The total concentration of the electrolyte salt in the non-aqueous electrolyte is preferably 0.8 mol / L or more, more preferably 1.2 mol / L or more, from the viewpoints of reducing the impedance and DCR of the battery, improving the low-temperature charge-discharge characteristics and charge-discharge cycle characteristics. Also, the concentration is preferably 5 mol / L or less, more preferably 3 mol / L or less, still more preferably 2 mol / L or less, from the viewpoint of suppressing the deterioration of battery performance due to an increase in the viscosity of the electrolyte.

[0050] From the viewpoints of reducing the impedance and DCR of the battery, improving the low-temperature charge-discharge characteristics and charge-discharge cycle characteristics, it is preferable to increase the concentration of the sulfonylimide compound (1). The ratio of the sulfonylimide compound (1) to other electrolytes (the molar ratio of the sulfonylimide compound concentration to the other electrolyte concentration) is preferably 1:25 or more, more preferably 1:10 or more, even more preferably 1:8 or more, still more preferably 1:5 or more, even still more preferably 1:2 or more, particularly preferably 1:1 or more, and preferably 25:1 or less, more preferably 10:1 or less, even more preferably 5:1 or less, still more preferably 2:1 or less.

[0051] (CO 2 、CO, HCO 3 - and CO 3 2- of at least one kind) The non-aqueous electrolyte according to this embodiment contains a sulfonylimide compound (1) as an electrolyte salt and contains carbon dioxide (CO 2) Carbon monoxide (CO), hydrogen carbonate ion (HCO 3 - ) and carbonate ion (CO 3 2- ) of at least one kind (hereinafter also referred to as "CO 2 etc.") is dissolved.

[0052] As described above, the inventors of the present application have found that in a battery using a non-aqueous electrolyte containing the sulfonylimide compound (1), compared with a battery using a non-aqueous electrolyte containing the other electrolyte (LiPF 6 , LiBF 4 etc.) alone, the self-discharge from the fully charged state is large. More specifically, in a battery using a non-aqueous electrolyte containing the sulfonylimide compound (1), it has been found that the self-discharge increases depending on the concentration of the sulfonylimide compound (1). Then, as a result of intensive studies to solve the specific problems of the non-aqueous electrolyte containing the sulfonylimide compound (1), the inventors of the present application have found that even without using vinylene carbonate in the non-aqueous electrolyte, by dissolving CO 2 etc. in a non-aqueous electrolyte containing the sulfonylimide compound (1) in a predetermined amount or more, the self-discharge of the battery is suppressed. Further, as shown in the examples described later, the non-aqueous electrolyte containing the sulfonylimide compound (1) not only has the self-discharge further suppressed (excellent self-discharge suppression effect (storage characteristics)) due to the dissolution of CO 6 in the electrolyte compared with a non-aqueous electrolyte containing LiPF 2 alone, but also various battery performances such as a decrease in DCR and impedance of the battery, and an improvement in low-temperature charge and discharge characteristics and charge and discharge cycle characteristics are further improved.

[0053] In this specification, the dissolution of CO 2 etc. in the non-aqueous electrolyte containing the sulfonylimide compound (1) means intentionally dissolving CO 2 etc. in the non-aqueous electrolyte. For example, CO 2 etc. contained in the raw materials of the non-aqueous electrolyte such as the electrolyte solvent, or CO 2It does not exclude the dissolution of the like. In other words, the CO described later 2 and the like, the total dissolved amount thereof includes the intentionally dissolved CO 2 and the like, together with the CO 2 and the like in the raw material and the unavoidably dissolved CO 2 and the like may be included.

[0054] Incidentally, the form of CO 2 and the like dissolved in the non-aqueous electrolyte is not particularly limited, and CO 2 , CO, HCO 3 - and CO 3 2- may exist in at least one form of, may exist in any one form, or may exist in a plurality of forms.

[0055] The total dissolved amount of CO 2 and the like in the non-aqueous electrolyte is, for example, 20 mass ppm or more in terms of the electrolyte ratio, preferably 50 mass ppm or more, more preferably 100 mass ppm or more, still more preferably 150 mass ppm or more, even more preferably 200 mass ppm or more, and particularly preferably 250 mass ppm or more. The upper limit value of the total dissolved amount is not particularly limited, but is, for example, not more than the saturation concentration at 25°C. The total dissolved amount can be measured by the method described in the examples below, for example, gas chromatography or the like.

[0056] In this specification, the total dissolved amount of CO 2 and the like in the non-aqueous electrolyte means · In the preparation process of the non-aqueous electrolyte, after the preparation of the electrolyte (immediately), or after the aging period (for example, one week) for stabilizing the dissolved amount of CO 2 and the like, the total dissolved amount of CO 2 and the like in the electrolyte, or · In the manufacturing process of the secondary battery, after performing the battery aging process, for example, in a nitrogen atmosphere, the total dissolved amount of CO 2 and the like in the electrolyte extracted from the battery. The aging process includes, for example, the following processes and the conditions described in the examples below. (I) After injection of the electrolyte, after partial charging, it is heat-treated (stored) at 30 °C or higher for 6 hours or more within 28 days. After degassing and resealing, after confirming that there are no defects in the initial performance by charge and discharge, it is held at a charge depth of 50% for 1 week or more to confirm that there are no defects due to self-discharge. (II) A process similar to (I) except that heat treatment is not performed after partial charging. (III) A process similar to (I) except that degassing is not performed after heat treatment.

[0057] A method of dissolving CO etc. in a non-aqueous electrolyte containing the sulfonylimide compound (1) 2 Examples of the method of dissolving CO etc. include, for example, (A) a method of dissolving CO etc. in the non-aqueous electrolyte in the step of preparing the non-aqueous electrolyte; (B) a method of dissolving CO etc. in the non-aqueous electrolyte in the manufacturing process of the secondary battery. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte in the step of preparing the non-aqueous electrolyte include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte in the manufacturing process of the secondary battery include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc.

[0058] In the above-mentioned (A) method of dissolving CO etc. in the non-aqueous electrolyte in the step of preparing the non-aqueous electrolyte, in other words, it is a method of using a non-aqueous electrolyte containing the sulfonylimide compound (1) and in which CO etc. are dissolved in advance at 20 mass ppm or more (hereinafter also referred to as "CO etc. dissolved electrolyte" or "CO dissolved electrolyte"), and injecting the electrolyte into the secondary battery. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2 Examples of the method of dissolving CO etc. in the non-aqueous electrolyte (dissolving step) include, for example, a method of contacting a gas containing CO etc. with the non-aqueous electrolyte (liquid contact step), a method of blowing a gas containing CO etc. into the non-aqueous electrolyte (bubbling step), a method of stirring the non-aqueous electrolyte in a gas atmosphere containing CO etc. (stirring step), a method of contacting a gas containing high-pressure CO etc. with the non-aqueous electrolyte (a method of pressurizing the non-aqueous electrolyte with a gas containing CO etc., pressurizing step), a method of adding a substance that generates a gas containing CO etc. to the non-aqueous electrolyte (addition step), etc. 2Examples of substances that generate gases including the like are bicarbonates, carbonates, dry ice, and the like. Also, since CO 2 and the like can generally dissolve in the electrolyte solvent used in the non-aqueous electrolyte, the sulfonylimide compound (1) may be dissolved in the electrolyte solvent in which CO 2 and the like are previously dissolved to prepare a non-aqueous electrolyte. Note that, as a method for dissolving CO 2 and the like in the electrolyte solvent, the same method as described above can be used. As another method, a previously prepared non-aqueous electrolyte is placed in a sealed container so as to be about 1 / 10 of its volume, the inside of the container is made substantially vacuum, and then CO 2 and the like are filled, and this operation is repeated a plurality of times to replace the air inside the container with CO 2 and the like, and finally, a method of storing the container in a sealed state at a low temperature for several days (replacement step) and the like can be mentioned. The dissolution step may include at least one of the above-described steps, or a plurality of steps may be combined. Among the dissolution steps, it is preferable to include at least one of a pressurization step, a liquid contact step, a bubbling step, and a replacement step, more preferably to include at least one of a pressurization step, a liquid contact step, and a bubbling step, and even more preferably a pressurization step and a replacement step (a combination of a pressurization step and a replacement step may also be used).

[0059] Also, in the method of (A) above, from the viewpoint of controlling the total dissolved amount of CO 2 and the like in the non-aqueous electrolyte to be constant, the secondary battery may be assembled in a CO 2 atmosphere or an atmosphere containing CO 2 . Specifically, a step of injecting a non-aqueous electrolyte in which CO 2 and the like are previously dissolved into the battery, or a step after the injection may be performed in a CO 2 atmosphere or an atmosphere containing CO 2 . Further, after the injection of the electrolyte, it may be exposed to a high-pressure CO 2 atmosphere.

[0060] The CO 2 and the like dissolved electrolyte used in the method of (A) above is obtained by the method for producing a non-aqueous electrolyte according to this embodiment. This production method involves dissolving CO in a non-aqueous electrolyte containing a sulfonylimide compound (1)2 It includes a dissolving step including at least one of the above steps to dissolve 20 mass ppm or more of the like.

[0061] In the manufacturing process of the secondary battery (B), CO 2 and the like are dissolved. Examples of the method for dissolving CO 2 include, for example, a method of assembling a secondary battery in a CO 2 atmosphere and injecting a non-aqueous electrolyte into the battery (specifically, after making the inside of the battery case sealed on three sides substantially in a vacuum state, filling it with CO 2 and then injecting the non-aqueous electrolyte from the unsealed side and sealing it at normal pressure); after injecting the non-aqueous electrolyte into the secondary battery, replacing the air in the battery with CO 2 . Examples of the method for replacing the air in the battery with CO 2 include the same method as the method for replacing the air in the container with CO 2 . Specifically, after making the inside of the case filled with the non-aqueous electrolyte substantially in a vacuum state, the operation of filling it with CO 2 is repeated a plurality of times, so that the air in the case is replaced with CO

[0062] Since the total dissolved amount of CO 2 and the like in the non-aqueous electrolyte varies depending on the temperature of the non-aqueous electrolyte, it is preferably controlled at a constant temperature in the preparation process of the non-aqueous electrolyte and / or the manufacturing process of the secondary battery.

[0063] (Electrolyte solvent) The non-aqueous electrolyte may contain an electrolyte solvent. The electrolyte solvent is not particularly limited as long as it can dissolve and disperse the electrolyte salt. Examples of the electrolyte solvent include non-aqueous solvents, media such as polymers and polymer gels used in place of the electrolyte solvent, and any solvent generally used in batteries can be used.

[0064] As the non-aqueous solvent, a solvent having a high dielectric constant, high solubility of the electrolyte salt, a boiling point of 60 °C or higher, and a wide electrochemical stability range is preferable. More preferably, it is an organic solvent having a low water content. Examples of such organic solvents include ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane, 1,3-dioxolane; chain carbonate (carbonate) solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate, methyl phenyl carbonate; saturated cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, 2,3-dimethyl ethylene carbonate, 1,2-butylene carbonate, and erythritan carbonate; fluorine-containing cyclic carbonate solvents such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate, and trifluoropropylene carbonate; aromatic carboxylic acid ester solvents such as methyl benzoate and ethyl benzoate; lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; phosphate ester solvents such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, and triethyl phosphate; nitrile solvents such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, and isobutyronitrile; sulfur compound solvents such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane; aromatic nitrile solvents such as benzonitrile and tolunitrile; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 3-methyl-2-oxazolidinone; chain ester solvents such as ethyl acetate, butyl acetate, and propyl propionate. These solvents may be used alone or in combination of two or more.

[0065] Among electrolytic solution solvents, carbonate solvents such as chain carbonate solvents and saturated cyclic carbonate solvents, lactone solvents, ether solvents, nitrile solvents, and chain ester solvents are preferred, chain carbonate solvents, saturated cyclic carbonate solvents, and lactone solvents are more preferred, and chain carbonate solvents and saturated cyclic carbonate solvents are even more preferred. Specifically, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, and γ-valerolactone are preferred, and dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate are more preferred.

[0066] In addition, the electrolytic solution solvent may include, together with the various organic solvents described above, a solvent that is also referred to as an ionic liquid, contains a cation component and an anion component, and is in a molten state and has fluidity at room temperature. On the other hand, a non-aqueous electrolyte containing only an ionic liquid (that is, not containing the various organic solvents described above) is not preferable because the battery performance using the electrolyte deteriorates as described in the examples below. The ionic liquid is not particularly limited, and examples thereof include 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI), 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI), and room temperature molten salts described in JP-A-2018-170272 (Patent Document 3).

[0067] When using a polymer or a polymer gel instead of the electrolytic solution solvent, the following method may be adopted. That is, a method of dropping a solution in which an electrolyte salt is dissolved in a solvent onto a polymer formed by a conventionally known method to impregnate and support the electrolyte salt and a non-aqueous solvent; a method of melting and mixing a polymer and an electrolyte salt at a temperature equal to or higher than the melting point of the polymer and then forming a film and impregnating the film with a solvent (the above is a gel electrolyte); a method of mixing a non-aqueous electrolyte in which an electrolyte salt is previously dissolved in an organic solvent and a polymer and then forming a film of this by a casting method or a coating method and volatilizing the organic solvent; a method of melting, mixing, and molding a polymer and an electrolyte salt at a temperature equal to or higher than the melting point of the polymer (true polymer electrolyte); and the like.

[0068] Examples of polymers used in place of the electrolytic solution solvent include polyethylene oxide (PEO), which is a homopolymer or copolymer of an epoxy compound (ethylene oxide, propylene oxide, butylene oxide, allyl glycidyl ether, etc.), polyether-based polymers such as polypropylene oxide, methacrylic-based polymers such as polymethyl methacrylate (PMMA), nitrile-based polymers such as polyacrylonitrile (PAN), fluorine-based polymers such as polyvinylidene fluoride (PVdF), polyvinylidene fluoride - hexafluoropropylene, and copolymers thereof. These polymers may be used alone or in combination of two or more.

[0069] (Additive) The non-aqueous electrolyte is represented by the general formula (4): [Chemical formula 4] M 1 PO c F d (M 1 : alkali metal element, c: 1 ≤ c ≤ 3, d: 1 ≤ d ≤ 3) (4) a compound represented by the formula (hereinafter referred to as "fluorophosphoric acid compound (4)"), general formula (5): [Chemical formula 5] M 2 (FSO 3 ) e (M 2 : monovalent or divalent metal element, e: 1 or 2) a compound represented by the formula (5) (hereinafter referred to as "fluorosulfonic acid compound (5)") and general formula (6):

[0070] [Chemical formula]

[0071] (In general formula (6), M 3 : B or P, A f+ : metal ion, H or onium ion, f: 1 ≤ f ≤ 3, g: 1 ≤ g ≤ 3, h: g / f, i: 1 ≤ h ≤ 3, j: 0 ≤ j ≤ 4, k: 0 or 1, R 3: An alkylene group having 1 to 10 carbon atoms or a halogenated alkylene group having 1 to 10 carbon atoms, R 4 : F or a fluorinated alkyl group having 1 to 10 carbon atoms, T 1 , T 2 : Each independently represents O or S.) It may further contain at least one selected from the group consisting of compounds represented by (hereinafter also referred to as "fluorooxalato compound (6)"). These compounds (4), (5) and (6) may be used alone or in combination of two or more.

[0072] By adding at least one of the fluorophosphoric acid compound (4), the fluorosulfonic acid compound (5) and the fluorooxalato compound (6) to the non-aqueous electrolyte containing the sulfonylimide compound (1), various battery performances can be improved. Therefore, it is preferable that the electrolyte contains at least one of the compounds (4), (5) and (6). In addition, by adding at least one of the compounds (4), (5) and (6), although the self-discharge of the battery using the non-aqueous electrolyte containing the sulfonylimide compound (1) is suppressed, compared with the battery using the electrolyte containing LiPF 6 alone, the effect (degree) of self-discharge suppression is not sufficient and there is room for improvement. In this regard, the inventors of the present application have found that in the non-aqueous electrolyte containing the sulfonylimide compound (1), in addition to adding at least one of the compounds (4), (5) and (6), by dissolving CO 2 etc. (by using a combination of adding at least one of the compounds (4), (5) and (6) and dissolving CO 2 etc.), the self-discharge of the battery is further suppressed. It has also been found that various battery performances are further improved.

[0073] In the general formula (4), examples of the alkali metal element represented by M 1 include lithium, sodium, potassium, rubidium, cesium and the like. Among these, lithium is preferable.

[0074] Examples of the fluorophosphoric acid compound (4) include lithium monofluorophosphate (Li2 PO 3 F) Lithium difluorophosphate (LiPO 2 F 2 ) and the like. The fluorophosphoric acid compound (4) may be used alone or in combination of two or more. Among the fluorophosphoric acid compounds (4), LiPO 2 F 2 is preferred.

[0075] In the general formula (5), the monovalent metal element represented by M 2 is the same as the above-mentioned alkali metal element. Further, as the divalent metal element represented by M 2 , alkaline earth metal elements and the like can be mentioned. Examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, barium and the like. Among these, the monovalent metal element (alkali metal element) is preferred, and lithium is more preferred.

[0076] Examples of the fluorosulfonic acid compound (5) include lithium fluorosulfonate (LiFSO 3 ), sodium fluorosulfonate (NaFSO 3 ), potassium fluorosulfonate (KFSO 3 ), magnesium fluorosulfonate (Mg(FSO 3 )) 2 ) and the like. The fluorosulfonic acid compound (5) may be used alone or in combination of two or more. Among the fluorosulfonic acid compounds (5), LiFSO 3 is preferred.

[0077] In the general formula (6), M 3 represents B (boron) or P (phosphorus).

[0078] In the general formula (6), A f+represents a metal ion, H (hydrogen), or an onium ion. Examples of the metal ion include an alkali metal ion, an alkaline earth metal ion, a trivalent metal ion, etc. Examples of the alkali metal and alkaline earth metal are the same as those described above. Examples of the trivalent metal include boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), etc. Among the metal ions, Li + , Na + , Mg 2+ and Ca 2+ are preferred, and Li + is more preferred. Examples of the onium ion include chain quaternary ammonium such as tetraethylammonium, tetrabutylammonium, triethylmethylammonium, etc.; chain tertiary ammonium such as triethylammonium, tributylammonium, dibutylmethylammonium, dimethylethylammonium, etc.; imidazolium such as 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, etc.; pyrrolidinium such as N,N-dimethylpyrrolidinium, N-ethyl-N-methylpyrrolidinium, etc. Among these, chain quaternary ammonium and imidazolium are preferred, and chain quaternary ammonium is more preferred. That is, in the general formula (6), f, g, and h are preferably 1.

[0079] In the general formula (6), R 3 represents an alkylene group having 1 to 10 carbon atoms or a halogenated alkylene group having 1 to 10 carbon atoms. Examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, and these may be branched. Examples of the halogenated alkylene group having 1 to 10 carbon atoms include a group in which part or all of the hydrogens of the alkylene group having 1 to 10 carbon atoms are replaced by F, Cl, Br, or I (among them, F is preferred, for example, a fluoromethylene group, a fluoroethylene group, etc.). R 3Among them, an alkylene group having 1 to 4 carbon atoms and a fluorinated alkylene group having 1 to 4 carbon atoms are preferable, and an alkylene group having 1 to 2 carbon atoms and a fluorinated alkylene group having 1 to 2 carbon atoms are more preferable. k is 0 or 1. When k is 0, it represents a direct bond of the carbonyl group, and the compound of the general formula (6) becomes oxalate borate or oxalate phosphonium. It is preferable that k is 0.

[0080] In the general formula (6), R 4 represents F (fluorine) or a fluorinated alkyl group having 1 to 10 carbon atoms. Examples of the fluorinated alkyl group having 1 to 10 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a tetrafluoroethyl group, a perfluoroethyl group, a fluoropropyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluorooctyl group, and the like. Among R 4 , a fluorinated alkyl group having 1 to 2 carbon atoms and F are preferable, and F is more preferable.

[0081] In the general formula (6), T 1 and T 2 each independently (identically or differently) represent O (oxygen) or S (sulfur). From the viewpoint of availability, it is preferable that both T 1 and T 2 are O.

[0082] In the general formula (6), when M 3 is B (boron), i is preferably 1 or 2. When i is 1, j is 2, and it is more preferable that R 4 is F. When i is 2, j is 0. On the other hand, when M 3 is P (phosphorus), i is 1 to 3. When i is 1, j is 4. When i is 2, j is 2. When i is 3, j is 0.

[0083] Examples of the fluorooxalate compound (6) include difluorooxalate borate salt, bisoxalate borate salt, tetrafluorophosphonium salt, difluorobisoxalate phosphonium salt, and trisoxalate phosphonium salt. More specifically, lithium salts having an oxalic acid skeleton such as lithium bis(oxalato)borate (LiBOB), lithium difluorooxalato borate (LiDFOB), lithium difluorooxalato phosphanite (LIDFOP), lithium tetrafluorooxalato phosphate (LITFOP), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tris(oxalato)phosphate can be mentioned. The fluorooxalate compound (6) may be used alone or in combination of two or more. Among the fluorooxalate compounds (6), lithium difluorooxalato borate (LiDFOB) is preferred.

[0084] From the viewpoint of suppressing self-discharge of the battery and further improving battery performance, the content of the above additive in the non-aqueous electrolyte is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less.

[0085] (Other components) The non-aqueous electrolyte may contain other additives (additives different from the compounds (4), (5), and (6)) for the purpose of improving various characteristics of the lithium-ion secondary battery. Examples of other additives include carboxylic acid anhydrides such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, and phenylsuccinic anhydride; sulfur-containing compounds such as ethylene sulfite, 1,3-propanesultone, 1,4-butanesultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram monosulfide, and trimethylene glycol sulfate; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide; saturated hydrocarbon compounds such as heptane, octane, and cycloheptane; carbonate compounds such as fluoroethylene carbonate (FEC), trifluoropropylene carbonate, phenylethylene carbonate, and erythritol carbonate; sulfamic acid (amidosulfuric acid, H 3 NSO 3 ); sulfamates (alkali metal salts such as lithium salt, sodium salt, and potassium salt; alkaline earth metal salts such as calcium salt, strontium salt, and barium salt; other metal salts such as manganese salt, copper salt, zinc salt, iron salt, cobalt salt, and nickel salt; ammonium salt; guanidine salt, etc.). The other additives may be used alone or in combination of two or more.

[0086] The other additives are preferably used in the range of 0.1% by mass or more and 10% by mass or less, more preferably in the range of 0.2% by mass or more and 8% by mass or less, and even more preferably in the range of 0.3% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte. When the amount of the other additives used is too small, the effects derived from the other additives may be difficult to obtain. On the other hand, even if a large amount of the other additives is used, it is difficult to obtain an effect commensurate with the added amount, and there is a risk that the viscosity of the non-aqueous electrolyte will increase and the conductivity will decrease.

[0087] The non-aqueous electrolyte (CO 2 etc. dissolved electrolyte) configured as above is used, for example, in a battery (a battery having a charge / discharge mechanism), an electricity storage (electrochemical) device (or a material of an ion conductor constituting these), etc. Specifically, the electrolyte can be used, for example, as an electrolyte constituting a primary battery, a secondary battery (e.g., a lithium (ion) secondary battery), a fuel cell, an electrolytic capacitor, an electric double layer capacitor, a solar cell, an electrochromic display element, etc. Hereinafter, a battery (particularly a secondary battery) will be taken as an example for explanation.

[0088] <Secondary battery> The secondary battery according to this embodiment includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. In this secondary battery, the non-aqueous electrolyte contains a sulfonylimide compound (1) and CO 2 etc. dissolved at 20 mass ppm or more. In other words, the non-aqueous electrolyte contained in this secondary battery corresponds to the non-aqueous electrolyte (CO 2 etc. dissolved electrolyte) according to this embodiment.

[0089] (Positive electrode) The positive electrode includes a positive electrode current collector and a positive electrode mixture layer, the positive electrode mixture layer is formed on the positive electrode current collector, and is usually formed in a sheet shape.

[0090] Examples of the metal used for the positive electrode current collector include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. Among these, aluminum is preferred. Note that the shape and dimensions of the positive electrode current collector are not particularly limited.

[0091] The positive electrode mixture layer is formed of a positive electrode mixture (positive electrode composition). The positive electrode mixture contains a positive electrode active material, a conductive assistant, a binder, a solvent for dispersing these components, etc.

[0092] In the secondary battery according to this embodiment, the positive electrode (positive electrode mixture) preferably has the general formula (7): [Chemical formula 7] Li z Ni x Mny Co (1-x-y) O 2 (z: 0.9 ≤ z ≤ 1.1, x: 0.2 ≤ x < 1, y: 0 ≤ y ≤ 0.4, 0 < 1 - x - y ≤ 0.8) (7) A ternary cathode active material represented by the following (hereinafter referred to as "ternary cathode active material (7)") and a general formula (8): [Chemical formula 8] Li p Fe 1-r Q r (PO 4 ) p (Q: Mn or Ni, p: 0.9 ≤ p ≤ 1.1, r: 0 ≤ r ≤ 0.05) (8) contains at least one of the cathode active materials represented by the following (hereinafter referred to as "iron phosphate cathode active material (8)"). These cathode active materials may be used alone or in combination of two or more.

[0093] In a secondary battery including a cathode containing a ternary cathode active material (7) or an iron phosphate cathode active material (8) as a cathode active material, when a non-aqueous electrolyte containing a sulfonylimide compound (1) is used, it was found that the self-discharge from the fully charged state is larger compared to the case of using a non-aqueous electrolyte containing LiPF 6 alone. In this regard, the inventors of the present application have found that by dissolving CO 2 etc. in the non-aqueous electrolyte containing the sulfonylimide compound (1) (by using in combination with the dissolution of the ternary cathode active material (7) or the iron phosphate cathode active material (8) and CO 2 etc.), the self-discharge of the battery is further suppressed. It was also found that various battery performances are further improved.

[0094] Examples of the ternary cathode active material (7) include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.8 Co0.1 Mn 0.1 O 2 Examples include Mn, O, etc. The ternary cathode active material (7) may be used alone or in combination of two or more kinds.

[0095] Examples of the iron phosphate-based cathode active material (8) include compounds having an olivine structure such as LiFePO 4 、LiFe 0.995 Mn 0.005 PO 4 etc. The iron phosphate-based cathode active material (8) may be used alone or in combination of two or more kinds.

[0096] The cathode may contain at least one of the ternary cathode active material (7) and the iron phosphate-based cathode active material (8), but may also contain other cathode active materials (cathode active materials other than the ternary cathode active material (7) and the iron phosphate-based cathode active material (8)). As the other cathode active material, any material capable of occluding and releasing various ions (such as lithium ions and sodium ions) may be used. For example, cathode active materials used in conventionally known secondary batteries (such as lithium ion secondary batteries and sodium ion secondary batteries) can be used.

[0097] Examples of the cathode active material used in a lithium ion secondary battery include lithium cobaltate; lithium nickelate; lithium manganate; LiNi 1-v-w Co x Al y O 2 Transition metal oxides such as ternary oxides other than the ternary cathode active material (7) represented by (0 ≦ v ≦ 1, 0 ≦ w ≦ 1); compounds having an olivine structure such as LiAPO 4 (A = Mn, Ni, Co); solid solution materials incorporating a plurality of transition metals (electrochemically inert layered Li 2 MnO 3 and electrochemically active layered LiMO 2 (M = transition metals such as Co, Ni)); solid solutions of LiCo x Mn 1-x O 2 (0 ≦ x ≦ 1); LiNi x Mn 1-x O2 (0 ≦ x ≦ 1); Li 2 APO 4 Compounds having an olivine fluoride structure such as F(A = Fe, Mn, Ni, Co); sulfur, etc. can be used. These may be used alone or in combination of two or more kinds.

[0098] As the positive electrode active material used in a sodium ion secondary battery, for example, NaNiO 2 , NaCoO 2 , NaMnO 2 , NaVO 2 , NaFeO 2 , Na(Ni X Mn 1-X )O 2 (0 < X < 1), Na(Fe X Mn 1-X )O 2 (0 < X < 1), NaVPO 4 F, Na 2 FePO 4 F, Na 3 V 2 (PO 4 ) 3 etc. may be mentioned. These may be used alone or in combination of two or more kinds.

[0099] Among other positive electrode active materials, in particular, a positive electrode active material capable of occluding and releasing lithium ions may be preferably used. Such a positive electrode active material is used, for example, in a lithium ion secondary battery using a non-aqueous electrolyte. Such a non-aqueous system usually has a lower ionic conductivity than an aqueous system, but in the present disclosure, even in such a case, the discharge capacity can be improved efficiently.

[0100] The content of the positive electrode active material (total content when including a plurality of positive electrode active materials) is preferably 75% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, preferably 99% by mass or less, more preferably 98% by mass or less, still more preferably 95% by mass or less, based on 100% by mass of the total amount of the components contained in the positive electrode composite material, from the viewpoint of improving the output characteristics and electrical characteristics of the secondary battery.

[0101] The conductive additive is used to improve the output of the lithium-ion secondary battery. As the conductive additive, conductive carbon is mainly used. Examples of the conductive carbon include carbon black, fibrous carbon, graphite, etc. The conductive additives may be used alone or in combination of two or more kinds. Among the conductive additives, carbon black is preferred. Examples of the carbon black include ketjen black, acetylene black, etc. The content of the conductive additive in the non-volatile matter of the positive electrode composite is preferably 1 to 20% by mass, more preferably 1.5 to 10% by mass, from the viewpoint of improving the output characteristics and electrical characteristics of the lithium-ion secondary battery.

[0102] Examples of the binder include fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene; synthetic rubbers such as styrene-butadiene rubber and nitrile butadiene rubber; polyamide-based resins such as polyamideimide; polyolefin-based resins such as polyethylene and polypropylene; poly(meth)acrylic-based resins; polyacrylic acid; cellulose-based resins such as carboxymethyl cellulose; etc. The binders may be used alone or in combination of two or more kinds. Also, the binder may be in a state dissolved in a solvent or in a state dispersed in a solvent during use.

[0103] Examples of the solvent include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetonitrile, acetone, ethanol, ethyl acetate, water, etc. The solvents may be used alone or in combination of two or more kinds. The amount of the solvent used is not particularly limited and may be appropriately determined according to the manufacturing method and the materials used.

[0104] In the positive electrode composite material, as other components, if necessary, for example, non-fluorine-based polymers such as (meth)acrylic polymers, nitrile-based polymers, diene-based polymers, etc., fluorine-based polymers such as polytetrafluoroethylene, etc., polymers, anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, etc., emulsifiers; dispersants such as styrene-maleic acid copolymers, polyvinylpyrrolidone, etc., high molecular weight dispersants, thickeners such as carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), alkali-soluble type (meth)acrylic acid-(meth)acrylic acid ester copolymer, etc., preservatives, etc. may be contained. The content of other components in the non-volatile matter of the positive electrode composite material is preferably 0 to 15% by mass, more preferably 0 to 10% by mass.

[0105] The positive electrode composite material can be prepared, for example, by mixing a positive electrode active material, a conductive auxiliary agent, a binder, a solvent, and other components as necessary, and dispersing them using a bead mill, a ball mill, a stirring type mixer, etc.

[0106] The method for forming the positive electrode (coating method) is not particularly limited. For example, (1) a method of coating (and further drying) the positive electrode composite material on the positive electrode current collector by a conventional coating method (for example, doctor blade method, etc.), (2) a method of immersing (and further drying) the positive electrode current collector in the positive electrode composite material, (3) a method of joining a sheet formed of the positive electrode composite material to the positive electrode current collector (for example, joining through a conductive adhesive) and pressing (and further drying), (4) a method of applying or casting the positive electrode composite material added with a liquid lubricant on the positive electrode current collector, forming it into a desired shape, and then removing the liquid lubricant (and then stretching it in one or multiple axial directions), (5) a method of slurrying the positive electrode composite material (or the solid content forming the positive electrode composite material layer) with an electrolytic solution, transferring it to the current collector (positive electrode current collector) in a semi-solid state, and using it as an electrode (positive electrode) without drying, etc.

[0107] Note that the positive electrode composite material layer may be dried or pressed as necessary after formation or coating (application).

[0108] (Negative electrode) The negative electrode includes a negative electrode current collector and a negative electrode composite material layer. The negative electrode composite material layer is formed on the negative electrode current collector and is usually formed in a sheet shape.

[0109] Examples of the metal used for the negative electrode current collector include iron, copper, aluminum, nickel, stainless steel (SUS), titanium, tantalum, gold, platinum, etc. Among these, copper is preferred. Note that the shape and dimensions of the negative electrode current collector are not particularly limited.

[0110] The negative electrode composite material layer is formed from a negative electrode composite material (negative electrode composition). The negative electrode composite material contains a negative electrode active material, a conductive auxiliary agent, a binder, a solvent for dispersing these components, etc.

[0111] As the negative electrode active material, conventionally known negative electrode active materials used in various batteries (for example, lithium secondary batteries) etc. can be used, as long as they can occlude and release various ions (for example, lithium ions). Specific negative electrode active materials include carbon materials such as artificial graphite, natural graphite, etc., mesophase fired bodies made from coal, petroleum pitch, carbon materials such as non-graphitizable carbon, Si-based negative electrode materials such as Si, Si alloys, SiO, Sn-based negative electrode materials such as Sn alloys, lithium metal, lithium alloys such as lithium-aluminum alloys, etc. The negative electrode active materials may be used alone or in combination of two or more kinds.

[0112] The negative electrode composite material may further contain a conductive auxiliary agent (conductive substance), a binder, a solvent, etc. As the conductive auxiliary agent, binder, solvent, etc., the same components as described above can be used. Also, the usage ratio etc. are the same as described above.

[0113] As a method for manufacturing the negative electrode, the same method as the method for manufacturing the positive electrode may be adopted.

[0114] (Separator) The secondary battery may include a separator. The separator is disposed so as to separate the positive electrode and the negative electrode. There is no particular limitation on the separator, and in the present disclosure, any of the conventionally known separators can be used. Specific examples of the separator include a porous sheet made of a polymer capable of absorbing and holding an electrolytic solution (non-aqueous electrolytic solution) (for example, a polyolefin-based microporous separator, a cellulose-based separator, etc.), a non-woven fabric separator, a porous metal body, and the like.

[0115] Examples of the material of the porous sheet include polyethylene, polypropylene, and a laminate having a three-layer structure of polypropylene / polyethylene / polypropylene.

[0116] Examples of the material of the non-woven fabric separator include cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, aramid, glass, etc. Depending on the required mechanical strength, etc., the above-exemplified materials may be used alone or in combination of two or more.

[0117] (Battery exterior material) A battery element including a positive electrode, a negative electrode, and a non-aqueous electrolytic solution (and further a separator) is usually housed in a battery exterior material to protect the battery element from external impacts, environmental degradation, etc. during battery use. The material of the battery exterior material is not particularly limited, and any of the conventionally known exterior materials can be used.

[0118] The battery exterior material may be provided with an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, etc. as required to prevent an increase in pressure inside the battery and overcharge / discharge.

[0119] The shape of the battery (such as a lithium ion secondary battery) is not particularly limited, and any of the conventionally known shapes such as a cylindrical shape, a rectangular shape, a laminate shape, a coin shape, a large size, etc. can be used. Further, when used as a high voltage power supply (several 10 V to several 100 V) for mounting on an electric vehicle, a hybrid electric vehicle, etc., a battery module configured by connecting individual batteries in series can also be used.

[0120] The rated charging voltage of a secondary battery (such as a lithium-ion secondary battery) is not particularly limited. However, when the secondary battery includes a positive electrode mainly containing a ternary cathode active material (7), it may be 3.6 V or more, preferably 4.0 V or more, more preferably 4.1 V or more, and even more preferably 4.2 V or more. Also, when the secondary battery includes a positive electrode mainly containing an iron phosphate cathode active material (8), it may be 2.5 V or more, preferably 3.0 V or more, more preferably 3.2 V or more, and even more preferably 3.5 V or more. The higher the rated charging voltage, the higher the energy density can be increased. However, from the perspective of safety and the like, the rated charging voltage may be 4.6 V or less (for example, 4.5 V or less).

[0121] <Method for manufacturing a secondary battery> The secondary battery according to this embodiment can be easily manufactured, for example, by laminating a positive electrode and a negative electrode (with a separator interposed therebetween if necessary), placing the obtained laminate in a battery exterior material, injecting a non-aqueous electrolyte into the battery exterior material, and sealing it.

[0122] Here, in the method for manufacturing a secondary battery according to this embodiment, the non-aqueous electrolyte contained in the obtained secondary battery contains a sulfonylimide compound (1) and has CO 2 dissolved therein at 20 mass ppm or more. Therefore, as described above, (A) In the step of preparing the non-aqueous electrolyte, CO 2 and the like are dissolved in the non-aqueous electrolyte. Specifically, as the non-aqueous electrolyte, the non-aqueous electrolyte according to this embodiment (CO 2 dissolved electrolyte) is used, or (B) In the step of manufacturing the secondary battery, CO 2 and the like are dissolved in the non-aqueous electrolyte. Specifically, the non-aqueous electrolyte is injected into the battery under a CO 2 atmosphere, or the air inside the battery after injecting the non-aqueous electrolyte is replaced with CO 2 .

[0123] In addition, in the method for manufacturing a secondary battery according to this embodiment, at least one of a ternary cathode active material (7) and an iron phosphate cathode active material (8) may be used as the cathode.

[0124] According to the method for manufacturing a secondary battery configured as described above, a secondary battery including a non-aqueous electrolyte containing the sulfonylimide compound (1) and in which CO 2 and the like are dissolved and the total dissolved amount thereof is 20 mass ppm or more can be obtained. Preferably, a secondary battery including the non-aqueous electrolyte and a cathode including at least one of a ternary cathode active material (7) and an iron phosphate cathode active material (8) can be obtained.

Examples

[0125] Hereinafter, the present disclosure will be described based on examples. Note that the present disclosure is not limited to the following examples, and the following examples can be modified and changed based on the gist of the present disclosure, and they are not excluded from the scope of the present disclosure.

[0126] <Example 1 Series> (1-1) Preparation of non-aqueous electrolyte (reference electrolyte) As an electrolyte solvent, a mixed solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 (volume ratio) (manufactured by Kishida Chemical Co., Ltd., the same applies hereinafter), LiFSI (manufactured by Nippon Shokubai Co., Ltd., the same applies hereinafter) and LiPF 6 (manufactured by Stella Chemifa Corporation, the same applies hereinafter), an electrolyte salt having a mixed salt composition, or an electrolyte salt having a single salt composition containing only LiPF 6 alone was dissolved so as to have the concentrations shown in Table 1-1, respectively, to prepare a non-aqueous electrolyte (hereinafter also simply referred to as "electrolyte"). In addition, vinylene carbonate (VC) was further added to Comparative Electrolyte 1-2 so as to be 2% by mass. In the following description, a non-aqueous electrolyte in which CO 2 and the like are not intentionally dissolved is referred to as a "reference electrolyte". This reference electrolyte is obtained without going through a dissolution step (before the dissolution step), and CO 2 and the like in the raw materials and CO 2may also include the like. The obtained reference electrolyte solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte solution are shown in the "Reference Electrolyte Solution" column of Table 1-1.

[0127] Incidentally, the dissolved amount of CO 2 in the non-aqueous electrolyte solution was quantified by the following method using gas chromatography (apparatus: GC-2010 plus, manufactured by Shimadzu Corporation, column: Micropacked ST, manufactured by Shinwa Chemical Industries Co., Ltd.).

[0128] (Measurement conditions for gas chromatography) When measuring by gas chromatography, the non-aqueous electrolyte solution or the calibration gas was directly introduced into the gas chromatography apparatus in a state where the apparatus was purged with nitrogen (under a nitrogen atmosphere) so that air did not mix into the measurement system. The specific measurement conditions for gas chromatography are as follows.

[0129] · Column temperature program: Hold at 37°C (for 2.5 minutes from the start) ⇒ 37°C to 250°C (heating at 20°C / min) ⇒ 250°C to 270°C (heating at 15°C / min) ⇒ Hold at 270°C (for 5.42 minutes) · Vaporization chamber temperature: 130°C · Detector temperature: 300°C (BID) · Carrier gas: Helium (column flow rate 1.33 mL / min) · Injection volume: 1 μL (split method, split ratio: 5.0).

[0130] (Method for quantifying the dissolved amount of CO 2 ) CO 2 A plurality of types of standard helium gases with known CO 2 mixing ratios were analyzed under the same conditions as the above gas chromatography measurement conditions except that the above injection volume (1 μL) was changed to 1 mL. From the peak area of the obtained CO 2 gas, the CO 2A calibration curve showing the relationship with the peak area of the gas was created. Subsequently, the non-aqueous electrolytes obtained in each example were analyzed by gas chromatography. Finally, by the external standard method, the dissolved amount of CO 2 in each non-aqueous electrolyte was quantified.

[0131] (1-2) Preparation of a non-aqueous electrolyte in which CO 2 is dissolved (CO 2 dissolved electrolyte) (the method of (A), dissolution step: replacement step) Each electrolyte obtained in the above-mentioned "(1-1) Preparation of non-aqueous electrolyte (reference electrolyte)" was placed in a sealed bottle so as to be about 1 / 10 of the volume of the bottle. Subsequently, in a desiccator, the bottle was left standing with its opening facing upward, and then the inside of the desiccator was evacuated to 40 mmHg with a vacuum pump. Next, CO 2 was supplied and filled into the desiccator. This process was repeated 3 times to replace the air in the bottle with CO 2 . Thereafter, the bottle was sealed and stored in a refrigerator for 3 days to prepare a CO 2 dissolved electrolyte. The obtained CO 2 dissolved electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of "(A) CO 2 dissolved electrolyte" in Table 1-1.

[0132]

Table 1-1

[0133] (1-3) Fabrication of laminate battery 1-1 (Fabrication of the positive electrode) LiNi which is a ternary positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 O 2(Produced by Umicore, product number: MX7h), acetylene black (AB, produced by Denka Co., Ltd., product name: Denka Black (registered trademark)), graphite (produced by Nippon Graphite Industry Co., Ltd., product number: SP270), and polyvinylidene fluoride (PVdF, produced by Kuraray Co., Ltd., product number: KF1120) were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode composite slurry (positive electrode active material: AB:graphite:PVdF = 93:2:2:3 (solid content mass ratio)). Subsequently, the obtained positive electrode composite slurry was applied unilaterally to an aluminum foil (positive electrode current collector, produced by Nippon Foil Mfg. Co., Ltd., thickness 15 μm) with an applicator so that the coating weight after drying was 19.4 mg / cm 2 and dried on a hot plate at 110 °C for 10 minutes. Further, it was dried in a vacuum drying oven at 110 °C for 12 hours. Then, by pressure molding with a roll press until the density reached 3.1 g / cm 3 , a sheet-shaped (thickness 83 μm) positive electrode was obtained.

[0134] (Fabrication of negative electrode) Graphite (natural graphite (produced by Hitachi Chemical Co., Ltd., product number: SMG): artificial graphite (produced by TIMCAL, product number: SFG15) = 85:15 (solid content mass ratio)) as the negative electrode active material, styrene-butadiene rubber (SBR, binder), and carboxymethyl cellulose (CMC, binder) were dispersed in ultrapure water to prepare a negative electrode composite slurry (negative electrode active material: SBR:CMC = 97.3:1.5:1.2 (solid content mass ratio)). Subsequently, the obtained negative electrode composite slurry was applied unilaterally to a copper foil (negative electrode current collector, produced by Fukuda Metal Foil & Powder Co., Ltd., thickness 15 μm) with an applicator so that the coating weight after drying was 9.8 mg / cm 2 and dried on a hot plate at 80 °C for 10 minutes. Further, it was dried in a vacuum drying oven at 100 °C for 12 hours. Then, by pressure molding with a roll press until the density reached 1.3 g / cm 3 , a sheet-shaped (thickness 113 μm) negative electrode was obtained.

[0135] (Fabrication of laminated battery) The obtained positive electrode and negative electrode were each cut, the polarity lead-out leads were welded by ultrasonic waves, the positive electrode and negative electrode were opposed to each other via a 16-μm polyethylene (PE) separator, and three sides were sealed with a laminate exterior to fabricate a non-liquid-injected battery. Subsequently, 700 μL of each electrolyte solution shown in Table 1-1 or Table 1-2 was added from the unsealed side of the non-liquid-injected battery. After injecting the electrolyte solution, vacuum sealing was performed to fabricate a laminate battery (cell) 1-1 with a voltage of 4.2 V and a capacity of 30 mAh.

[0136] Using a charge-discharge test device (manufactured by Asuka Electronics Co., Ltd., product number: ACD-01, the same hereinafter), the cell 1-1 obtained above was subjected to constant current charging at 0.1 C (3 mA) for 4 hours at room temperature (25 °C, the same hereinafter), and then left at room temperature for 5 days. After leaving, constant current constant voltage (CCCV) charging was performed at 4.2 V and 0.5 C (15 mA) for 5 hours at room temperature. Thereafter, constant current discharging was performed at 0.2 C (6 mA) and a termination voltage of 2.75 V (discharge termination voltage) at room temperature, and the excess laminate was cracked and vacuum sealed to vent the gas in the cell 1-1. After venting the gas, the cell 1-1 was further subjected to constant current constant voltage charging under the same conditions as above, and then constant current discharging was performed at 1 C (30 mA) and a termination voltage of 2.75 V at room temperature. Partial charging was performed at 0.5 C (15 mA) for 1 hour at room temperature to set the state of charge (SOC) to 50%, and then it was held at room temperature for 2 weeks. The above was defined as the aging process of the cell.

[0137] (1-4) Fabrication of laminate battery 1-2 (method of (B) above) Using the same method as above, a non-liquid-injected battery was fabricated, and 700 μL of each electrolyte solution shown in Table 1-1 was added from the unsealed side of the non-liquid-injected battery. After injecting the electrolyte solution, the battery after injection was left stationary in a desiccator with its opening facing upward, and then the inside of the desiccator was evacuated to 40 mmHg with a vacuum pump. Next, CO 2 was supplied and filled. This process was repeated three times to replace the air in the battery with CO 2 , and then atmospheric pressure sealing was performed to fabricate a laminate battery (cell) 1-2 with a voltage of 4.2 V and a capacity of 30 mAh. Thereafter, the aging process of cell 1-2 was performed in the same procedure as cell 1-1.

[0138] Also, in the same manner as described above, after replacing the air in the battery filled with 700 μL of each electrolyte shown in Table 1-1 with CO 2 , atmospheric pressure sealing was performed. Then, it was stored at room temperature for 5 days, the laminate was cleaved in a nitrogen atmosphere, and the electrolyte replaced inside the cell was extracted. The extracted electrolyte replaced inside the cell was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of "(B) Electrolyte replaced inside the cell" in Table 1-1.

[0139] (1-5) Evaluation of the battery (Self-discharge) After aging, the cell was charged at a constant current and constant voltage with 1C (30 mA) at 4.2V and terminated with 0.02C (0.6 mA) at room temperature to a fully charged state, stored at 60 °C for 4 weeks, and the open circuit voltage (OCV: Open Circuit Voltage) of the cell before and after storage was measured. The results are shown in Table 1-2. Note that the smaller the degree of decrease in the OCV (measured value) after storage compared to the OCV (measured value) before storage (hereinafter, also simply referred to as "degree of OCV decrease"), the more the self-discharge of the battery is suppressed.

[0140] (Impedance) After aging, the cell was discharged at 0.2C (6 mA) to 2.75V at room temperature, then charged at a constant current of 4.2V and 1C (30 mA) for 30 minutes at room temperature to a state of charge (SOC) of 50%. Under the conditions of 25 °C or -30 °C, an impedance analyzer (manufactured by Bio Logic, product number: VSP-300) was used to measure the impedance from a frequency of 1 GHz to 10 mHz (25 °C) or 1 mHz (-30 °C). The real-axis resistance (interface resistance) was obtained from the frequency at which the arc of the obtained measured value diverges. The results are shown in Table 1-2. Note that the frequency at which the arc diverges means the frequency at which the imaginary-axis value reaches a minimum between 100 Hz and 0.01 Hz for the measurement at 25 °C, and the frequency at which the imaginary-axis value reaches a minimum between 10 Hz and 0.001 Hz for the measurement at -30 °C.

[0141] (DCR) The cells after aging were subjected to constant current constant voltage charging with a termination current of 0.02C (0.6 mA) at 4.2 V at 1C (30 mA) at room temperature, and the fully charged state (SOC 100%) or the state of charge (SOC) of 50% was set. Subsequently, after leaving it for 30 minutes from the fully charged state (SOC 100%) or the state of charge (SOC) of 50%, it was discharged at 6 mA for 10 seconds, then after leaving it for 30 minutes, it was discharged at 30 mA for 10 seconds, and further after leaving it for 30 minutes, it was discharged at 60 mA for 10 seconds. With each discharge current on the horizontal axis and the difference (ΔV) between the open circuit voltage at the start of discharge and after 10 seconds at each discharge current on the vertical axis, the slope of the I-V straight line was defined as the DCR of the cell. The results are shown in Table 1-2.

[0142] (Low temperature charge and discharge characteristics) The cells after impedance measurement were discharged at 0.2C (6 mA) to 2.75 V at 25°C, and then subjected to constant current constant voltage charging with a termination current of 0.02C (0.6 mA) at 4.2 V at 1C (30 mA) at 25°C. After leaving the charged cells at -20°C for 3 hours, the constant current discharge capacity with a termination voltage of 2.75 V at 1C (30 mA) at -20°C was measured. Subsequently, after leaving the cells at -20°C for 3 hours after measuring the constant current discharge capacity at -20°C, they were left at room temperature for 3 hours, and then subjected to constant current discharge with a termination voltage of 2.75 V at 0.2C (6 mA) at 25°C. After discharging the cells, they were left at -20°C for 3 hours, and then the constant current charge capacity with a termination voltage of 4.2 V at 1C (30 mA) at -20°C was measured. The results are shown in Table 1-2.

[0143] (Charge and discharge cycle characteristics) The cells after aging were subjected to a cycle test of a total of 300 cycles at 45°C under the following charge and discharge conditions (cycle conditions). The capacity retention rate after 300 cycles was calculated by the following formula (1): [Equation 1] Capacity retention rate (%) = (1C capacity at the 300th cycle / 1C capacity at the 1st cycle) × 100 (1) and was obtained based on this. The results are shown in Table 1-2.

[0144] (Cycle conditions) · Charge: Constant current constant voltage charging at 4.2 V at 1C (30 mA), termination at 0.02C (0.6 mA), 10-minute pause. ·Discharge: Constant current (CC) discharge at 1C (30 mA), termination at 2.75 V, 10-minute rest.

[0145]

Table 1-2

[0146] Based on Table 1-2, the results of obtaining the reduction rate of OCV are shown in Table 1-3. The reduction rate of OCV refers to the ratio (%) of the difference in OCV before and after storage in the reference electrolyte (reference electrolyte) to the difference in OCV before and after storage in the electrolyte having the same salt composition as the reference electrolyte and containing CO 2 dissolved therein or having the air inside the cell replaced with CO 2 by a method of dissolving CO 2 in the electrolyte. For example, the reduction rate of OCV in Example 1-1 is calculated by the following formula (2) using Comparative Example 1-1 as the reference electrolyte: [Equation 2] Reduction rate of OCV in Example 1-1 (%) = [{(OCV before storage in Example 1-1) - (OCV after storage in Example 1-1)} / {(OCV before storage in Comparative Example 1-1) - (OCV after storage in Comparative Example 1-1)}] × 100 (2) It should be noted that the smaller the value of the reduction rate of OCV, the more the self-discharge of the battery is suppressed, that is, the better the effect of suppressing self-discharge (the higher the effect (degree) of suppressing self-discharge).

[0147]

Table 1-3

[0148] (Self-discharge) From the results of Table 1-2, the batteries (Comparative Examples 1-1 to 1-3) using the electrolytes containing LiFSI (sulfonylimide compound (1)) have a large decrease in OCV after storage depending on the concentration (i.e., large self-discharge from the fully charged state), and also LiPF 6It was found that the degree of OCV decrease was large compared to the batteries (Comparative Examples 1-4 and 1-6) using the electrolyte containing it alone. Also, in these batteries, CO 2 was dissolved or the air inside the cell was replaced with CO 2 to dissolve CO 2 in the electrolyte, and it was found that the decrease in OCV was suppressed (i.e., self-discharge was suppressed).

[0149] Here, from the results in Table 1-3, all the batteries (each Example) using the electrolyte containing LiFSI had a smaller reduction rate of OCV compared to the batteries (Comparative Examples 1-5, 1-7, and 1-8) using the electrolyte not containing LiFSI. Thus, it was found that self-discharge was further suppressed. More specifically, each Example had an OCV after storage that was equal to or lower than that of Comparative Examples 1-5, 1-7, and 1-8 (in other words, the degree of OCV decrease (the "difference in OCV before and after storage" shown in Table 1-3) was equal to or greater), but the reduction rate of OCV was significantly lower. From this, it can be said that each Example has a higher effect of suppressing self-discharge due to the dissolution of CO 2 in the electrolyte compared to Comparative Examples 1-5, 1-7, and 1-8.

[0150] (Impedance) From the results in Table 1-2, all the batteries using the electrolyte with dissolved CO 2 had a significantly lower impedance compared to the batteries using the reference electrolyte without intentionally dissolving CO 2 (comparison between Comparative Example 1-1 and Examples 1-1, 1-4; comparison between Comparative Example 1-2 and Examples 1-2, 1-5; comparison between Comparative Example 1-3 and Examples 1-3, 1-6). The effect of this impedance reduction was particularly prominent at low temperatures. In Comparative Examples 1-6 to 1-8 where VC was added to the electrolyte, it was found that the impedance at low temperatures was extremely high regardless of the presence or absence of dissolved CO 2 .

[0151] (DCR) From the results in Table 1-2 2All the batteries using the electrolyte with dissolved 2 showed a significant decrease in DCR compared to the batteries using the reference electrolyte without intentionally dissolving 2 CO (the comparison target is the same as above). Since the effect of this DCR decrease was confirmed in both SOC100% and SOC50%, it suggests that this effect can be obtained regardless of the state of charge of the battery. In Comparative Examples 1-6 to 1-8 where VC was added to the electrolyte, it was found that the DCR was extremely high regardless of the presence or absence of dissolved

[0152] (Low-temperature charge and discharge characteristics) From the results in Table 1-2, all the batteries using the electrolyte with dissolved 2 showed an improvement in the charge and discharge capacity at low temperature compared to the batteries using the reference electrolyte without intentionally dissolving 2 CO (the comparison target is the same as above). In Comparative Examples 1-6 to 1-8 where VC was added to the electrolyte, it was found that the discharge capacity at low temperature was particularly low regardless of the presence or absence of dissolved 2 CO. This is considered to be because the impedance at low temperature is extremely high, as shown in the impedance measurement results.

[0153] (Charge and discharge cycle characteristics) From the results in Table 1-2, all the batteries using the electrolyte with dissolved 2 showed an improvement in the 300-cycle capacity retention rate compared to the batteries using the reference electrolyte without intentionally dissolving 2 CO (the comparison target is the same as above).

[0154] (1-6) Preparation of a non-aqueous electrolyte with dissolved 2 CO under pressurized conditions (CO 2 dissolved electrolyte) (the method in (A) above, dissolution process: pressurization process and replacement process) The electrolyte 1-3 (reference electrolyte) obtained in the above “(1-1) Preparation of non-aqueous electrolyte (reference electrolyte)” was put into a sealed bottle to an amount about 1 / 10 of the volume of the bottle. Subsequently, the bottle was placed in an autoclave so that its opening faced upward, and then pressurized to 0.3 MPa with CO 2 Next, the release valve was opened halfway to reduce the internal pressure of the autoclave to 0.15 MPa. This process was repeated three times to replace the air in the autoclave with CO 2 . After replacement, it was pressurized again to 0.3 MPa with CO 2 and allowed to stand for a predetermined time (refer to Table 1-4 below for the standing time at 0.3 MPa). The electrolyte after standing was taken out of the autoclave and further allowed to stand at 24 °C for 1 week in a sealed state. After standing for 1 week, a part of the electrolyte (Example 1-9) with a standing time of 15 minutes at 0.3 MPa was taken out and diluted 2 times (Example 1-8), 4 times (Example 1-7), or 10 times (Comparative Example 1-10) using the reference electrolyte. The obtained CO 2 dissolved electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte and the increase amount of the dissolved amount of CO 2 with respect to the reference electrolyte are shown in Table 1-4.

[0155] (1-7) Fabrication of laminated battery 1-1 A laminated battery (cell) 1-1 with a voltage of 4.2 V and a capacity of 30 mAh was fabricated by the same method as in the above “(1-3) Fabrication of laminated battery 1-1”, and then the aging process of cell 1-1 was carried out. The lamination was cleaved in a nitrogen atmosphere, and the electrolyte was extracted. The extracted electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the columns of “Dissolved amount of CO 2 after aging” in Table 1-4 and Table 1-5.

[0156] (1-8) Evaluation of battery (Impedance and self-discharge) The self-discharge (OCV) and impedance of the cells were measured by the same method as the above-mentioned “(1-5) Evaluation of batteries”. The results are shown in Table 1-4.

[0157]

Table 1-4

[0158] Based on Table 1-4, in the same manner as above, the results of obtaining the reduction rate of OCV are shown in Table 1-5.

[0159]

Table 1-5

[0160] Based on Table 1-4, the results of obtaining the decrease amount of the real-axis resistance (impedance reduction degree) with respect to the reference electrolyte are shown in Table 1-6. The decrease amount of the real-axis resistance with respect to the reference electrolyte is the value obtained by subtracting the real-axis resistance of the reference electrolyte (the electrolytes of Comparative Examples 1-9) at the same temperature from the real-axis resistance of the electrolyte of each example at each temperature.

[0161]

Table 1-6

[0162] (Self-discharge) From the results of Table 1-4, it was found that the cells (each example) using the electrolyte in which CO 2 was dissolved at 20 mass ppm or more in the non-aqueous electrolyte had a smaller decrease degree of OCV after storage and suppressed self-discharge of the cells compared with the cells (Comparative Examples 1-9) using the reference electrolyte (Electrolyte 1-3) in which CO 2 was dissolved at 1 mass ppm and the cells (Comparative Example 1-10) using the electrolyte in which CO 2 was dissolved at 11 mass ppm. Also, from the results of Table 1-5, the CO 2 dissolved amount and the CO 2As the increase in the dissolved amount became larger, the effect of self-discharge suppression increased. From this, CO 2 It was found that the dissolved amount and the effect of self-discharge suppression were in a proportional relationship.

[0163] (Impedance) From the results in Table 1-4, the batteries of each example had a lower impedance compared to the batteries of each comparative example. The effect of this impedance reduction was particularly remarkable at low temperatures. Also, from the results in Table 1-6, CO 2 The dissolved amount and CO with respect to the reference electrolyte 2 As the increase in the dissolved amount became larger, the amount of reduction in the real-axis resistance with respect to the reference electrolyte became larger, and the effect of impedance reduction increased. From this, CO 2 It was found that the dissolved amount and the effect of impedance reduction were in a proportional relationship.

[0164] (CO after aging 2 dissolved amount) From the results in Table 1-4, after performing the above aging process, the laminate was cleaved in a nitrogen atmosphere, and the CO extracted 2 in the dissolved electrolyte 2 of the dissolved amount (CO dissolved amount after aging 2 was reduced compared to the dissolved amount of CO in the dissolved electrolyte before the aging process (after electrolyte preparation), but it was found that it was 20 mass ppm or more in any of the examples. 2 in the dissolved electrolyte 2 of

[0165] (1-9) Consideration of Example 1 Series From the above results, in the non-aqueous electrolyte containing the sulfonylimide compound (1), even without using VC which may significantly increase the resistance of the battery, CO 2By dissolving the like in an amount of 20 mass ppm or more, it was confirmed that self-discharge of the battery using the electrolytic solution was suppressed. Further, it was confirmed that the battery using the nonaqueous electrolytic solution containing the sulfonylimide compound (1) was more suppressed in self-discharge (that is, excellent in the effect of suppressing self-discharge) as compared with the battery using the nonaqueous electrolytic solution not containing the sulfonylimide compound (1). Further, it was confirmed that the battery performance was improved in terms of reduction in the resistance (impedance, DCR) of the battery, improvement in low-temperature charge / discharge characteristics, charge / discharge cycle characteristics, and the like.

[0166] <Example 2 Series> (2-1) Preparation of nonaqueous electrolytic solution (reference electrolytic solution) Lithium difluorophosphate (LiPO 2 F 2 ) was further added to the electrolytic solution so as to have the content shown in Table 2-1 and dissolved, and a nonaqueous electrolytic solution was prepared in the same manner as in the above “(1-1) Preparation of nonaqueous electrolytic solution (reference electrolytic solution)”. The composition of the obtained electrolytic solution is shown in Table 2-1. The obtained reference electrolytic solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolytic solution are shown in the column of “reference electrolytic solution” in Table 2-1.

[0167] (2-2) Preparation of nonaqueous electrolytic solution (CO 2 -dissolved electrolytic solution) in which CO 2 is dissolved (method (A) above, dissolution step: substitution step) Using each of the electrolytic solutions obtained in the above “(2-1) Preparation of nonaqueous electrolytic solution (reference electrolytic solution)”, the above “(1-2) Preparation of nonaqueous electrolytic solution (CO 2 -dissolved electrolytic solution) in which CO 2 is dissolved (method (A) above, dissolution step: substitution step)”, a CO 2 -dissolved electrolytic solution was prepared in the same manner, and the electrolytic solution was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 -dissolved electrolytic solution are shown in the column of “(A) CO 2 -dissolved electrolytic solution” in Table 2-1.

[0168]

Table 2-1

[0169] (Fabrication of the (2-3) laminate battery 2-1) (Fabrication of the positive electrode) LiNi, which is a ternary positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (manufactured by Umicore, product number: MX7h), acetylene black (AB, manufactured by Denka Co., Ltd., product name: Denka Black (registered trademark)), graphite (manufactured by Nippon Graphite Industries Co., Ltd., product number: SP270), and polyvinylidene fluoride (PVdF, manufactured by Kuraray Co., Ltd., product number: KF1120) were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode composite slurry (positive electrode active material: AB: graphite: PVdF = 93:2:2:3 (solid content mass ratio)).

[0170] Subsequently, the obtained positive electrode composite slurry was applied unilaterally to an aluminum foil (positive electrode current collector, manufactured by Nippon Foil Mfg. Co., Ltd., thickness 15 μm) with an applicator so that the coating weight after drying was 19.8 mg / cm 2 and dried on a hot plate at 110 °C for 10 minutes. Further, it was dried in a vacuum drying oven at 110 °C for 12 hours. Then, by pressure molding with a roll press until the density reached 3.1 g / cm 3 a sheet-shaped (thickness 83 μm) positive electrode was obtained.

[0171] (Fabrication of the negative electrode) As the negative electrode active material, graphite (natural graphite manufactured by Hitachi Chemical Co., Ltd., product number: SMG), acetylene black (AB, manufactured by Denka Co., Ltd., product name: Denka Black (registered trademark)), styrene-butadiene rubber (SBR, binder), and carboxymethyl cellulose (CMC, binder) were dispersed in ultrapure water to prepare a negative electrode composite slurry (natural graphite: acetylene black: SBR: CMC = 96:2:1:1 (solid content mass ratio)).

[0172] Subsequently, the obtained negative electrode composite slurry was applied unilaterally to a copper foil (negative electrode current collector, manufactured by Fukuda Metal Foil & Powder Co., Ltd., thickness 15 μm) with an application weight after drying of 9.8 mg / cm 2 using an applicator so as to achieve this, and dried on a hot plate at 80°C for 10 minutes. Further, it was dried in a vacuum drying oven at 100°C for 12 hours. Thereafter, by pressure molding using a roll press until a density of 1.3 g / cm 3 was achieved, a sheet-like (thickness 113 μm) negative electrode was obtained.

[0173] (Fabrication of laminated battery) The obtained positive and negative electrodes were each cut, the polarity lead-out leads were welded by ultrasonic waves, the positive and negative electrodes were opposed to each other via a 25-μm polyethylene (PE) separator, and three sides were sealed with a laminated exterior to fabricate an unassembled battery. Subsequently, 500 μL of each electrolyte shown in Table 2-1 was added from the unsealed side of the unassembled battery. After injecting the electrolyte, vacuum sealing was performed to fabricate a laminated battery (cell) 2-1 with a voltage of 4.2 V and a capacity of 32 mAh.

[0174] The obtained cell 2-1 was subjected to constant current constant voltage charging at 0.5 C (16 mA) until 4.2 V at room temperature for 5 hours using a charge and discharge test device, and left for 5 days. After leaving, constant current discharge at 0.2 C (6.4 mA) until 2.75 V was performed at room temperature, the excess laminate was cracked, and vacuum sealing was performed to vent the gas inside cell 2-1. After venting the gas, cell 2-1 was charged again under the same conditions as above by constant current constant voltage charging, and then constant current discharge at 1 C (32 mA) until 2.75 V was performed at room temperature. Partial charging at 0.5 C (15 mA) for 1 hour was performed at room temperature to set the state of charge (SOC) to 50%, and then it was held at room temperature for 2 weeks. The above was defined as the cell aging process.

[0175] (Fabrication of laminated battery 2-2 (method (B) above)) Using the same method as described above, an un-injected electrolyte battery was fabricated. From the unsealed side of the un-injected electrolyte battery, 500 μL of each reference electrolyte shown in Table 2-1 was added. After injecting the electrolyte, the battery after injection was placed in a desiccator and allowed to stand with its opening facing upward. Then, the inside of the desiccator was evacuated to 40 mmHg with a vacuum pump. Next, CO 2 was supplied and filled into the desiccator. This process was repeated three times to replace the air inside the battery with CO 2 . After that, by performing atmospheric pressure sealing, a laminated battery (cell) 2-2 with a voltage of 4.2 V and a capacity of 35.8 mAh was fabricated. Then, following the same procedure as for cell 2-1, the aging process of cell 2-2 was carried out.

[0176] Also, using the same method as described above, after replacing the air inside the battery injected with 500 μL of each electrolyte shown in Table 2-1 with CO 2 , atmospheric pressure sealing was performed. Then, it was stored at room temperature for 5 days, the laminate was cracked in a nitrogen atmosphere, and the electrolyte replaced inside the cell was extracted. The extracted electrolyte replaced inside the cell was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of "(B) Electrolyte replaced inside the cell" in Table 2-1.

[0177] (2-5) Evaluation of the battery (Impedance, DCR, and low-temperature charge-discharge characteristics) Using the same method as described above, the impedance, DCR, and low-temperature (-20 °C) charge-discharge capacity of the cell were measured. The results are shown in Table 2-2.

[0178] (Self-discharge) The aged cell was charged at a constant current and constant voltage of 0.5C (16 mA) and 4.2 V at room temperature until termination at 0.02C (0.64 mA) to reach a fully charged state, then stored at 60 °C for 4 weeks, and the open circuit voltage (OCV) of the cell before and after storage was measured. The results are shown in Table 2-2.

[0179]

Table 2-2

[0180] Based on Table 2-2, the OCV reduction rate was calculated in the same manner as above, and the results are shown in Table 2-3.

[0181] [Table 2-3]

[0182] (Impedance) From the results in Table 2-2, the electrolyte 2 Dissolve CO in the air inside the cell. 2 By replacing 2 All batteries that use electrolytes containing dissolved CO 2 The impedance was lower than that of a battery using a reference electrolyte solution not containing dissolved therein (Comparative Example 2-1 vs. Examples 2-1 to 2-3 and 2-5; Comparative Example 2-2 vs. Examples 2-2 and 2-4). This effect of lowering the impedance is particularly noticeable at low temperatures.

[0183] (DCR) From the results in Table 2-2, CO 2 All batteries that use electrolytes containing dissolved CO 2 The DCR was significantly lower than that of the battery using the reference electrolyte without dissolved . (The comparison was the same as above.) This effect of lowering the DCR was confirmed at both SOC 100% and SOC 50%, suggesting that this effect can be obtained regardless of the battery's state of charge.

[0184] (Low temperature charge / discharge characteristics) From the results in Table 2-2, CO 2 All batteries that use electrolytes containing dissolved CO 2 Compared to a battery using a reference electrolyte that does not have CO dissolved therein, the charge / discharge capacity at low temperatures was improved (the comparison target is the same as above). This effect is due to the increase in the amount of CO dissolved in the electrolyte, as shown in the impedance measurement results. 2 This is believed to be due to a decrease in impedance at low temperatures due to dissolution.

[0185] (Self-discharge) From the results in Table 2-2, all the batteries using the electrolyte with dissolved CO 2 were found to have a smaller decrease in OCV after storage and suppressed self-discharge of the battery compared to the batteries using the reference electrolyte without intentionally dissolved CO 2 . (The comparison target is the same as above).

[0186] Also, the batteries using the reference electrolyte containing LiFSI and LiPO 2 F 2 but without intentionally dissolved CO 2 (Comparative Examples 2-1 and 2-2) had a larger decrease in OCV after storage compared to the batteries using the electrolyte containing LiPF 6 alone (without containing LiPO 2 F 2 and CO 2 ) (Comparative Example 2-3). This indicates that although the addition of LiPO 2 F 2 is known to improve various battery performances such as initial resistance reduction, in the electrolyte containing the sulfonylimide compound (1), a sufficient effect on suppressing the self-discharge of the battery cannot be obtained. In the electrolyte containing the sulfonylimide compound (1) having such specific problems, by dissolving CO 2 F 2 along with the addition of LiPO 2 , it was found that the decrease in OCV after storage was equal to or smaller than that of the electrolyte containing LiPF 6 alone, and an excellent effect of suppressing self-discharge was obtained.

[0187] Furthermore, from the results in Table 2-3, all the batteries using the electrolyte containing LiFSI and LiPO 2 F 2 and having dissolved CO 2 (each Example) had, in place of LiFSI, LiPF 6 alone (containing LiPO 2 F 2 and having dissolved CO 2Compared with the battery (Comparative Example 2-5) using the electrolytic solution in which [substance] was dissolved, since the reduction rate of OCV was small, it was found that self-discharge was further suppressed.

[0188] (2-6) CO under pressurized conditions 2 Non-aqueous electrolytic solution in which [substance] is dissolved (CO 2 Preparation of dissolved electrolytic solution) (the method of (A) above, dissolution process: pressurization process and replacement process) Except for using the electrolytic solution 2-1 (reference electrolytic solution) obtained in the above-mentioned “(2-1) Preparation of non-aqueous electrolytic solution (reference electrolytic solution)”, the above-mentioned “(1-6) CO under pressurized conditions 2 Non-aqueous electrolytic solution in which [substance] is dissolved (CO 2 Preparation of dissolved electrolytic solution) (the method described in the method of (A) above, dissolution process: pressurization process and replacement process), non-aqueous electrolytic solutions with various CO 2 dissolved amounts were prepared. The obtained CO 2 dissolved electrolytic solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolytic solution and the increase amount of the CO 2 dissolved amount with respect to the reference electrolytic solution are shown in Table 2-4.

[0189] (2-7) Fabrication of laminated battery 2-1 In the same manner as in the above-mentioned “(2-3) Fabrication of laminated battery 2-1”, after fabricating a laminated battery (cell) 2-1 with a voltage of 4.2 V and a capacity of 30 mAh, an aging process of cell 2-1 was performed. The laminate was cleaved in a nitrogen atmosphere, and the electrolytic solution was extracted. The extracted electrolytic solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolytic solution are shown in the columns of “Dissolved amount of CO after aging” in Tables 2-4 and 2-5. 2

[0190] (2-8) Evaluation of battery (Impedance and self-discharge) In the same manner as in the above-mentioned “(2-5) Evaluation of battery”, the self-discharge (OCV) and impedance of the cell were measured. The results are shown in Table 2-4.

[0191] ​

Table 2-4

[0192] Based on Table 2-4, in the same manner as described above, the results of obtaining the reduction rate of OCV are shown in Table 2-5.

[0193]

Table 2-5

[0194] Based on Table 2-4, in the same manner as described above, the results of obtaining the decrease amount of the real-axis resistance (impedance reduction degree) with respect to the reference electrolyte are shown in Table 2-6.

[0195]

Table 2-6

[0196] (Self-discharge) From the results of Table 2-4, for the batteries (each example) using the electrolyte in which CO 2 was dissolved at 20 mass ppm or more in the non-aqueous electrolyte, compared with the battery (Comparative Example 2-6) using the reference electrolyte (Electrolyte 2-1) in which CO 2 was dissolved at 2 mass ppm in the non-aqueous electrolyte without undergoing the dissolution process, it was found that the degree of decrease in OCV after storage was small and the self-discharge of the battery was suppressed. Also, from the results of Table 2-5, as the dissolved amount of CO 2 and the increase amount of the dissolved amount of CO 2 with respect to the reference electrolyte increased, the effect of self-discharge suppression increased. From this, it was found that the dissolved amount of CO 2 and the effect of self-discharge suppression were in a proportional relationship.

[0197] (Impedance) From the results of Table 2-4, the impedance of the batteries of each example decreased compared with the battery of Comparative Example 2-6. This effect of impedance reduction was particularly remarkable at low temperatures. Also, from the results of Table 2-6, CO 2Dissolved amount and CO with respect to the reference electrolyte 2 As the increase in the dissolved amount became larger, the effect of impedance reduction increased. From this, CO 2 It was found that the dissolved amount and the effect of impedance reduction were in a proportional relationship.

[0198] (CO after aging 2 dissolved amount) From the results in Table 2-4, after performing the above aging process, the laminate was cleaved in a nitrogen atmosphere, and the extracted CO 2 in the dissolved electrolyte 2 The dissolved amount of (CO dissolved amount after aging 2 was reduced compared to the dissolved amount of CO in the dissolved electrolyte before the aging process (after electrolyte preparation) 2 in the dissolved electrolyte 2 However, it was found that it was 20 mass ppm or more in any of the examples.

[0199] (2-6) Consideration of Example 2 series From the above results, in the non-aqueous electrolyte containing the sulfonylimide compound (1), regarding the self-discharge of the battery for which sufficient effects could not be obtained even with the addition of LiPO 2 F 2 a clear effect was confirmed by dissolving CO 2 etc. at 20 mass ppm or more. Also, due to the synergistic effect of the dissolution of CO 2 etc. and the addition of LiPO 2 F 2 it was confirmed that the battery performance was further improved in terms of reduction of battery resistance (impedance, DCR), improvement of low-temperature charge and discharge characteristics, charge and discharge cycle characteristics, etc.

[0200] <Example 3 series> (3-1) Preparation of non-aqueous electrolyte (reference electrolyte) LiPO 2 F 2 Instead of, lithium fluorosulfonate (LiFSO 3A non-aqueous electrolyte was prepared in the same manner as in the above “(2-1) Preparation of non-aqueous electrolyte (reference electrolyte)”, except that 2 was added to the electrolytic solution and dissolved. The composition of the obtained electrolytic solution is shown in Table 3-1. The obtained reference electrolytic solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO

[0201] in the electrolytic solution are shown in the “Reference Electrolyte” column of Table 3-1. 2 was dissolved in the non-aqueous electrolyte (CO 2 dissolved electrolytic solution) (method (A) above, dissolution step: replacement step) Using each of the electrolytic solutions obtained in the above “(3-1) Preparation of non-aqueous electrolyte (reference electrolyte)”, the above “(1-2) CO 2 was dissolved in the non-aqueous electrolyte (CO 2 dissolved electrolytic solution) (method (A) above, dissolution step: replacement step)”, a CO 2 dissolved electrolytic solution was prepared, and the electrolytic solution was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolytic solution are shown in the “(A) CO 2 dissolved electrolytic solution” column of Table 3-1.

[0202]

Table 3-1

[0203] (3-3) Fabrication of laminate battery 3-1 A laminate battery (cell) 3-1 with a voltage of 4.2 V and a capacity of 32 mAh was fabricated in the same manner as in the above “(2-3) Fabrication of laminate battery 2-1”, and then the aging process of cell 3-1 was performed.

[0204] (3-4) Fabrication of laminate battery 3-2 (method (B) above) A laminated battery (cell) 3-2 with a voltage of 4.2 V and a capacity of 32 mAh was fabricated by the same method as the above-mentioned “(2-4) Fabrication of the laminated battery 2-2 (method (B))”. After that, an aging process for the cell 3-2 was carried out in the same procedure as for the cell 3-1.

[0205] Also, the in-cell replacement electrolyte was analyzed by gas chromatography in the same manner as the above-mentioned “(2-4) Fabrication of the laminated battery 2-2 (method (B))”, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of “(B) In-cell replacement electrolyte” in Table 3-1.

[0206] (3-5) Evaluation of the battery (Impedance, low-temperature charge-discharge characteristics, and self-discharge) The impedance, low-temperature (-20 °C) charge-discharge capacity, and self-discharge (OCV) of the cell were measured by the same method as the above-mentioned “(2-5) Evaluation of the battery”. The results are shown in Table 3-2.

[0207]

Table 3-2

[0208] Based on Table 3-2, the reduction rate of OCV was obtained in the same manner as above, and the results are shown in Table 3-3.

[0209]

Table 3-3

[0210] (Impedance) From the results in Table 3-2, for all the batteries using the electrolyte with dissolved CO 2 or by the method of replacing the air inside the cell with CO 2 to dissolve CO 2 intentionally, CO 2The impedance decreased when compared with the battery using a reference electrolyte without dissolved [substance] (comparison between Comparative Example 3-1 and Examples 3-1 to 3-4). The effect of this impedance decrease is particularly remarkable at low temperatures.

[0211] (Low-temperature charge and discharge characteristics) From the results in Table 3-2, all of the batteries using the electrolyte with dissolved CO 2 showed an improvement in the charge and discharge capacity at low temperatures when compared with the batteries using a reference electrolyte without intentionally dissolved CO 2 (the same comparison targets as above). This effect is considered to be based on the decrease in impedance at low temperatures due to the dissolution of CO 2 and the like in the electrolyte as shown in the impedance measurement results.

[0212] (Self-discharge) From the results in Table 3-2, all of the batteries using the electrolyte with dissolved CO 2 showed a smaller decrease in OCV after storage and suppression of the self-discharge of the battery when compared with the batteries using a reference electrolyte without intentionally dissolved CO 2 (the same comparison targets as above). Also, from the results in Table 3-3, all of the batteries (each example) using the electrolyte containing LiFSI and LiFSO 3 and with dissolved CO 2 showed a smaller reduction rate of OCV and thus further suppression of self-discharge when compared with the battery (Comparative Example 3-4) using the electrolyte containing LiPF 6 alone (containing LiFSO 3 and with dissolved CO 2 ).

[0213] (3-6) Consideration of Example 3 series From the above results, in the non-aqueous electrolyte containing the sulfonylimide compound (1), even when further containing LiFSO 3 , a clear effect on the self-discharge of the battery was confirmed by dissolving 20 mass ppm or more of CO 2 and the like. Also, the dissolution of CO 2 and the like and the presence of LiFSO3 Due to the synergistic effect with the addition, it was confirmed that the battery performance was further improved in terms of reducing the battery resistance (impedance) and improving the low-temperature charge and discharge characteristics.

[0214] <Example 4 Series> (4-1) Preparation of non-aqueous electrolyte (reference electrolyte) LiPO 2 F 2 A non-aqueous electrolyte was prepared in the same manner as in the above "(2-1) Preparation of non-aqueous electrolyte (reference electrolyte)", except that lithium difluorooxalate borate (LiDFOB) was added to and dissolved in the electrolyte. The composition of the obtained electrolyte is shown in Table 4-1. The obtained reference electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the "Reference Electrolyte" column of Table 4-1.

[0215] (4-2) Preparation of non-aqueous electrolyte with dissolved CO 2 (CO 2 dissolved electrolyte) (Method (A), dissolution step: replacement step) Using each electrolyte obtained in the above "(4-1) Preparation of non-aqueous electrolyte (reference electrolyte)", in the same manner as in the above "(1-2) Preparation of non-aqueous electrolyte with dissolved CO 2 (CO 2 dissolved electrolyte) (Method (A), dissolution step: replacement step)", a CO 2 dissolved electrolyte was prepared, and the electrolyte was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolyte are shown in the "(A) CO 2 dissolved electrolyte" column of Table 4-1.

[0216]

Table 4-1

[0217] (4-3) Fabrication of laminated battery 4-1 After manufacturing a laminated battery (cell) 4-1 with a voltage of 4.2 V and a capacity of 35.8 mAh by the same method as in the above “Manufacture of (2-3) laminated battery 2-1”, an aging process for the cell 4-1 was performed.

[0218] (4-4) Manufacture of laminated battery 4-2 (method of (B) above) After manufacturing a laminated battery (cell) 4-2 with a voltage of 4.2 V and a capacity of 35.8 mAh by the same method as in the above “(2-4) Manufacture of laminated battery 2-2 (method of (B) above)”, an aging process for the cell 4-2 was performed in the same procedure as for the cell 4-1.

[0219] Also, the in-cell replacement electrolyte was analyzed by gas chromatography in the same method as in the above “(2-4) Manufacture of laminated battery 2-2 (method of (B) above)”, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of “(B) In-cell replacement electrolyte” in Table 4-1.

[0220] (4-5) Evaluation of battery (Impedance, low-temperature charge-discharge characteristics, and self-discharge) The impedance, low-temperature (-20°C) charge-discharge capacity, and self-discharge (OCV) of the cell were measured by the same method as in the above “(2-5) Evaluation of battery”. The results are shown in Table 4-2.

[0221]

Table 4-2

[0222] Based on Table 4-2, the results of obtaining the reduction rate of OCV in the same manner as above are shown in Table 4-3.

[0223]

Table 4-3

[0224] (Impedance) From the results in Table 4-2, CO 2 is dissolved in the electrolyte or the air inside the cell is CO2 By the method of replacing with, in any battery using an electrolytic solution in which CO 2 is dissolved, the impedance decreased compared to the battery using a reference electrolytic solution in which CO 2 is not intentionally dissolved (comparison between Comparative Example 4-1 and Examples 4-1 and 4-4). The effect of this impedance decrease is particularly remarkable at low temperatures.

[0225] (Low-temperature charge and discharge characteristics) From the results in Table 4-2, in any battery using an electrolytic solution in which CO 2 is dissolved, the charge and discharge capacity at low temperatures improved compared to the battery using a reference electrolytic solution in which CO 2 is not intentionally dissolved (the comparison target is the same as above). This effect is considered to be based on the decrease in impedance at low temperatures due to the dissolution of CO 2 in the electrolytic solution shown in the impedance measurement results.

[0226] (Self-discharge) From the results in Table 4-2, in any battery using an electrolytic solution in which CO 2 is dissolved, it was found that the degree of decrease in OCV after storage was small compared to the battery using a reference electrolytic solution in which CO 2 is not intentionally dissolved, and the self-discharge of the battery was suppressed (the comparison target is the same as above). Also, from the results in Table 4-3, in any battery using an electrolytic solution containing LiFSI and LiDFOB and in which CO 2 is dissolved (each example), compared to the battery using an electrolytic solution containing LiPF 6 alone (containing LiDFOB and in which CO 2 is dissolved) (Comparative Example 4-4), since the reduction rate of OCV was small, it was found that the self-discharge was further suppressed.

[0227] (4-6) Consideration of Example 4 series From the above results, in the non-aqueous electrolytic solution containing the sulfonylimide compound (1), even when further containing LiDFOB, CO 2By dissolving the like in an amount of 20 mass ppm or more, a clear effect on the self-discharge of the battery was confirmed. Also, due to the synergistic effect of the dissolution of CO 2 and the like and the addition of LiDFOB, it was confirmed that the battery performance was further improved in terms of reduction of battery resistance (impedance) and improvement of low-temperature charge-discharge characteristics.

[0228] <Example 5 Series> (5-1) Preparation of non-aqueous electrolyte (reference electrolyte) A non-aqueous electrolyte was prepared in the same manner as in the above-mentioned "(1-1) Preparation of non-aqueous electrolyte (reference electrolyte)". The composition of the obtained electrolyte is shown in Table 5-1. The obtained reference electrolyte was analyzed by gas chromatography, and the result of quantifying the dissolved amount of CO 2 in the electrolyte is shown in the "Reference Electrolyte" column of Table 5-1.

[0229] (5-2) Preparation of non-aqueous electrolyte (CO 2 dissolved electrolyte) in which CO 2 is dissolved (the method of (A) above, dissolution step: replacement step) Using each of the electrolytes obtained in the above-mentioned "(5-1) Preparation of non-aqueous electrolyte (reference electrolyte)", in the same manner as in the above-mentioned "(1-2) Preparation of non-aqueous electrolyte (CO 2 dissolved electrolyte) in which CO 2 is dissolved (the method of (A) above, dissolution step: replacement step)", a CO 2 dissolved electrolyte was prepared, and the electrolyte was analyzed by gas chromatography. The result of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolyte is shown in the "(A) CO 2 dissolved electrolyte" column of Table 5-1.

[0230]

Table 5-1

[0231] (5-3) Fabrication of laminate battery 5-1 A laminate battery (cell) 5-1 with a voltage of 4.2V and a capacity of 30 mAh was fabricated by the same method as “(1-3) Fabrication of the laminate battery 1-1” except that the ternary cathode active material (7) shown in each of the following experimental examples was used as the cathode active material. After that, the aging process of the cell 5-1 was carried out.

[0232] (5-4) Fabrication of the laminate battery 5-2 (the method of (B)) A laminate battery (cell) 5-2 with a voltage of 4.2V and a capacity of 30 mAh was fabricated by the same method as “(1-4) Fabrication of the laminate battery 1-2” except that the ternary cathode active material (7) shown in each of the following experimental examples was used as the cathode active material. After that, the aging process of the cell 5-2 was carried out.

[0233] Also, the in-cell replacement electrolyte was analyzed by gas chromatography in the same manner as “(1-4) Fabrication of the laminate battery 1-2”, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of “(B) In-cell replacement electrolyte” in Table 5-1.

[0234] (5-5) Evaluation of the battery [Experimental Example 1] In Experimental Example 1, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (manufactured by Umicore, product number: MX7h) was used.

[0235] (Impedance, low-temperature charge and discharge characteristics, and self-discharge) The impedance, DCR, and self-discharge (OCV) of the cell were measured by the same method as “(1-5) Evaluation of the battery”. The results are shown in Table 5-2.

[0236]

Table 5-2

[0237] Based on Table 5-2, the results of obtaining the reduction rate of OCV in the same manner as above are shown in Table 5-3.

[0238] [Table 5-3]

[0239] (Impedance) From the results in Table 5-2, the electrolyte 2 Dissolve CO in the air inside the cell. 2 By replacing 2 Any battery that uses an electrolyte containing dissolved CO 2 The impedance was significantly reduced compared to a battery using a reference electrolyte not containing dissolved therein (Comparative Example 5-2 vs. Examples 5-1 and 5-4; Comparative Example 5-3 vs. Examples 5-2 and 5-5; Comparative Example 5-4 vs. Examples 5-3 and 5-6). This effect of reducing impedance is particularly noticeable at low temperatures.

[0240] (DCR) From the results in Table 5-2, CO 2 Any battery that uses an electrolyte containing dissolved CO 2 The DCR was significantly lower than that of the battery using the reference electrolyte without dissolved . (The comparison was the same as above.) This effect of lowering the DCR was confirmed at both SOC 100% and SOC 50%, suggesting that this effect can be obtained regardless of the battery's state of charge.

[0241] (self-discharge) From the results in Table 5-2, LiFSI and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 In an electrolyte containing (ternary positive electrode active material (7)), CO 2 Dissolve CO in the air inside the cell. 2 By replacing it with CO 2 Any battery that uses an electrolyte containing dissolved CO 2Compared with the battery using a reference electrolyte without dissolved [substance], it was found that the degree of decrease in OCV after storage was small and the self-discharge of the battery was suppressed (the comparison target was the same as above). Also, in the batteries of Examples 5-1 to 5-6, although LiFSI was contained in the electrolyte, compared with the battery using an electrolyte containing LiPF 6 alone (Comparative Example 5-1), it was found that the degree of decrease in OCV after storage was equivalent or smaller, and an excellent self-discharge suppression effect was obtained. Furthermore, from the results in Table 5-3, it was found that in the electrolyte containing LiFSI and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , the reduction rate of OCV could be further reduced depending on the mixing ratio of LiFSI and LiPF 6 .

[0242] [Experimental Example 2] In Experimental Example 2, as the positive electrode active material, instead of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , commercially available LiNi 0.5 Co 0.2 Mn 0.3 O 2 was used. In the same manner as in Experimental Example 1, the impedance, DCR, and self-discharge (OCV) of the cell were measured. The results are shown in Table 5-4 respectively.

[0243]

Table 5-4

[0244] Based on Table 5-4, in the same manner as above, the results of obtaining the reduction rate of OCV are shown in Table 5-5.

[0245]

Table 5-5

[0246] From the results in Table 5-4 and Table 5-5, for the ternary positive electrode active material (7), LiNi 0.5Co 0.2 Mn 0.3 O 2 Even in Experimental Example 2 where it was changed to, the same results as in Experimental Example 1 were obtained.

[0247] [Experimental Example 3] In Experimental Example 3, as the positive electrode active material, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 was replaced with commercially available LiNi 0.6 Co 0.2 Mn 0.2 O 2 was used. In the same manner as in Experimental Example 1, the impedance, DCR, and self-discharge (OCV) of the cell were measured. The results are shown in Table 5-6 respectively.

[0248]

Table 5-6

[0249] Based on Table 5-6, in the same manner as above, the results of obtaining the reduction rate of OCV are shown in Table 5-7.

[0250]

Table 5-7

[0251] From the results of Table 5-6 and Table 5-7, even in Experimental Example 3 where the ternary system positive electrode active material (7) was changed to LiNi 0.6 Co 0.2 Mn 0.2 O 2 the same results as in Experimental Example 1 were obtained.

[0252] [Experimental Example 4] In Experimental Example 4, as the positive electrode active material, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 was replaced with commercially available LiNi 0.8 Co 0.1 Mn 0.1 O 2was used. In the same manner as in Experimental Example 1, the impedance, DCR, and self-discharge (OCV) of the cells were measured. The results are shown in Tables 5-8 respectively.

[0253]

Table 5-8

[0254] Based on Table 5-8, in the same manner as described above, the results of obtaining the reduction rate of OCV are shown in Table 5-9.

[0255]

Table 5-9

[0256] From the results of Tables 5-8 and 5-9, even in Experimental Example 3 where the ternary cathode active material (7) was changed to LiNi 0.8 Co 0.1 Mn 0.1 O 2 the same results as in Experimental Example 1 were obtained.

[0257] (5-6) Consideration of Example 5 Series From the above results, although the self-discharge of the battery provided with the non-aqueous electrolyte containing the sulfonylimide compound (1) and the cathode containing the ternary cathode active material (7) increases as the concentration of the sulfonylimide compound (1) increases, by dissolving CO 2 etc. at 20 mass ppm or more in the electrolyte, the self-discharge is suppressed, and it was confirmed that an effect of suppressing self-discharge superior to that of a battery using an electrolyte containing LiPF 6 alone is obtained. Also, it was confirmed that the resistance value (impedance, DCR) of the battery is significantly reduced.

[0258] <Example 6 Series> (6-1) Preparation of Non-aqueous Electrolyte (Reference Electrolyte) A single-salt composition containing only LiFSI or LiPF 6 and a composition of LiFSI and LiPF 6An electrolyte salt of a mixed salt composition containing is included in an electrolytic solution at the concentration described in Table 6-1, and lithium difluorophosphate (LiPO 2 F 2 ) was further added so as to have the content (concentration) described in Table 6-1. An aprotic electrolyte solution was prepared in the same manner as in the above “(2-1) Preparation of aprotic electrolyte solution (reference electrolyte solution)”. The composition of the obtained electrolyte solution is shown in Table 6-1. The obtained reference electrolyte solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte solution are shown in the “reference electrolyte solution” column of Table 6-1.

[0259] (6-2) Preparation of aprotic electrolyte solution in which CO 2 is dissolved (CO 2 dissolved electrolyte solution) (method (A) above, dissolution step: substitution step) Using each of the electrolyte solutions obtained in the above “(6-1) Preparation of aprotic electrolyte solution (reference electrolyte solution)”, the above “(1-2) Preparation of aprotic electrolyte solution in which CO 2 is dissolved (CO 2 dissolved electrolyte solution) (method (A) above, dissolution step: substitution step)”. In the same manner, a CO 2 dissolved electrolyte solution was prepared, and the electrolyte solution was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolyte solution are shown in the “(A) CO 2 dissolved electrolyte solution” column of Table 6-1.

[0260]

Table 6-1

[0261] (6-3) Fabrication of laminated battery 6-1 Instead of the ternary cathode active material (7) LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , a commercially available lithium iron phosphate-based cathode active material (8) LiFePO 4A laminate battery (cell) 6-1 with a voltage of 3.55 V and a capacity of 28.8 mAh was fabricated by the same method as the above-mentioned “(2-3) Fabrication of the laminate battery 2-1”, except that [the method] was used. After that, the aging process of the cell 6-1 was carried out.

[0262] (6-4) Fabrication of the laminate battery 6-2 (the method of (B) above) A laminate battery (cell) 6-2 with a voltage of 3.55 V and a capacity of 28.8 mAh was fabricated by the same method as the above-mentioned “(2-4) Fabrication of the laminate battery 2-2 (the method of (B) above)”. After that, the aging process of the cell 6-2 was carried out in the same procedure as that of the cell 6-1.

[0263] Also, the in-cell replacement electrolyte was analyzed by gas chromatography in the same method as the above-mentioned “(2-4) Fabrication of the laminate battery 2-2 (the method of (B) above)”, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of “(B) In-cell replacement electrolyte” in Table 6-1.

[0264] (6-5) Evaluation of the battery (Impedance and charge / discharge capacity at low temperature (-20°C)) The impedance and charge / discharge capacity at low temperature (-20°C) of the cell were measured by the same method as the above-mentioned “(2-5) Evaluation of the battery”. The results are shown in Table 6-2.

[0265] (Self-discharge) The aged cell was charged at a constant current and constant voltage of 0.5C (14.4 mA) and 3.55 V at room temperature until terminated at 0.02C (0.576 mA) to reach a fully charged state, and then stored at 60°C for 4 weeks. The open circuit voltage (OCV) of the cell before and after storage was measured. The results are shown in Table 6-2.

[0266]

Table 6-2

[0267] Based on Table 6-2, the results of obtaining the reduction rate of OCV in the same way as above are shown in Table 6-3.

[0268] [Table 6-3]

[0269] (Impedance) From the results in Table 6-2, the electrolyte 2 Dissolve CO in the air inside the cell. 2 By replacing 2 Any battery that uses an electrolyte containing dissolved CO 2 The impedance was lowered compared to a battery using a reference electrolyte not containing dissolved therein (Comparative Example 6-1 vs. Examples 6-1 and 6-3; Comparative Example 6-2 vs. Example 6-2; Comparative Example 6-3 vs. Example 6-4). This effect of lowering the impedance is particularly noticeable at low temperatures.

[0270] (Low temperature charge / discharge characteristics) From the results in Table 6-2, CO 2 Any battery that uses an electrolyte containing dissolved CO 2 Compared to a battery using a reference electrolyte that does not have CO dissolved therein, the charge / discharge capacity at low temperatures was improved (the comparison target is the same as above). This effect is due to the increase in the amount of CO dissolved in the electrolyte, as shown in the impedance measurement results. 2 This is thought to be due to a decrease in impedance at low temperatures due to dissolution.

[0271] (self-discharge) From the results in Table 6-2, CO 2 Any battery that uses an electrolyte containing dissolved CO 2 Compared to a battery using a reference electrolyte that did not have any dissolved therein, it was found that the decrease in OCV after storage was smaller, and the self-discharge of the battery was suppressed (comparison was the same as above).

[0272] In addition, from the results of Table 6-3, all of the batteries (each Example) using an electrolyte containing LiFSI were found to be equivalent to the LiPF 6Compared with the battery (Comparative Example 6-5) using the electrolyte containing [substance] alone, since the reduction rate of OCV is small, it was found that self-discharge is further suppressed. More specifically, each Example has an OCV after storage that is equal to or lower than that of Comparative Example 6-5 (in other words, the degree of decrease in OCV (the "difference in OCV before and after storage" shown in Table 6-3) is equal to or greater than that of Comparative Example 6-5), but the reduction rate of OCV is significantly lower. From this, it can be said that each Example has a higher effect of suppressing self-discharge due to the dissolution of CO 2 in the electrolyte than Comparative Example 6-5.

[0273] (6-6) Consideration of Example 6 Series From the above results, in a battery equipped with a non-aqueous electrolyte containing the sulfonylimide compound (1), even when the positive electrode of the battery is equipped with a lithium iron phosphate-based positive electrode active material (8) different from that equipped with a positive electrode containing a ternary positive electrode active material (7), the self-discharge of the battery is clearly confirmed to be suppressed by dissolving CO 2 etc. at 20 mass ppm or more. Also, due to the synergistic effect of the dissolution of CO 2 etc. and the addition of LiPO 2 F 2 , it was confirmed that the battery performance is further improved in terms of reducing the battery resistance (impedance) and improving the low-temperature charge and discharge characteristics.

[0274] Also, it was confirmed that the above effects can be obtained even in a non-aqueous electrolyte containing an electrolyte salt with a single salt composition using only the sulfonylimide compound (1).

[0275] <Example 7 Series> (7-1) Preparation of Non-aqueous Electrolyte (Reference Electrolyte) A non-aqueous electrolyte was prepared by dissolving an electrolyte salt with a single salt composition containing only LiFSI in dimethyl carbonate (DMC) (manufactured by Kishida Chemical Co., Ltd.) as the electrolyte solvent so as to have the concentration shown in Table 7-1. Also, in a mixed solvent with a composition of EC:EMC = 3:7 (volume ratio) as the electrolyte solvent, LiPF 6An electrolyte salt with a simple salt composition containing only was dissolved to a concentration shown in Table 7-1 to prepare a non-aqueous electrolyte. The composition of each obtained electrolyte is shown in Table 7-1. The obtained reference electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the "Reference Electrolyte" column of Table 7-1.

[0276] (7-2) Raman Spectroscopy Measurement of Non-aqueous Electrolyte Raman spectroscopy measurements were performed on DMC used as the electrolyte solvent, reference electrolyte 7-1 and electrolyte 7-1 shown in Table 7-1, and LiFSI powder using NRS-3100 (manufactured by JASCO Corporation). The results are shown in Figure 1. In Figure 1, the horizontal axis is the wave number (cm -1 ), and the vertical axis is the scattering intensity.

[0277] (Measurement Conditions for Raman Spectroscopy) · Instrument: JASCO RFT-6000 (manufactured by JASCO Corporation) · Laser wavelength: 1064 nm · Exposure time: 10 seconds × 5 times · Central wave number: 1450 cm -1 · Slit: φ0.05 mm · Attenuator: Open · Objective lens: 20 times · Data interval: 4 cm -1 · Smoothing process: Baseline correction (linear correction between 872 cm-1 and 1873 cm-1) · Smoothing process, simple moving average (convolution width: 5) · Measurement cell: Glass cell · The electrolyte was sealed in a glass cell under an inert gas atmosphere and used for measurement.

[0278] As shown in Figure 1, in the Raman spectrum of LiFSI powder ("LiFSI powder" in Figure 1), a characteristic peak derived from (FSO -1 ) 2 ) 2 of LiFSI was observed near 790 cm.

[0279] In the Raman spectrum of DMC ("DMC solvent" in Fig. 1), a characteristic peak (the original peak of DMC) derived from the stretching vibration of the double bond between C and O of DMC was observed near 910 cm -1 -1.

[0280] In the Raman spectrum of the reference electrolyte 7-1 (LiFSI concentration: 1.0 mol / L) ("1.0M" in Fig. 1), the original peak of DMC (peak intensity Io: 1.32) was observed near 910 cm -1 -1, and a characteristic peak (shifted peak, intensity Is: 0.345) derived from the stretching vibration of the double bond between C and O of DMC was observed near 950 cm -1 -1 on the high-frequency side of the original peak of DMC. The relationship between the intensities of the two peaks Is and Io was Is = 0.26×Io, that is, Is < Io.

[0281] In the Raman spectrum of the electrolyte 7-1 (LiFSI concentration: 4.0 mol / L) ("4.0M" in Fig. 1), the original peak of DMC (peak intensity Io: 0.11) was observed near 910 cm -1 -1, and a shifted peak (intensity Is: 0.55) was observed near 950 cm -1 -1 on the high-frequency side of the original peak of DMC. The relationship between the intensities of the two peaks Is and Io was Is = 5.0×Io, that is, Is > Io.

[0282] From the above, in the non-aqueous electrolyte containing LiFSI and DMC, with the increase in the LiFSI concentration, the peak derived from DMC shifts to the high-frequency side, so that while the intensity Io of the peak derived from DMC decreases, the intensity Is of the shifted peak increases. As a result, it was confirmed that the magnitude relationship between the intensities of the two peaks changes from Is < Io to Is > Io. That is, it was confirmed that the relationship between the intensities of the two peaks in the Raman spectrum of the non-aqueous electrolyte containing a high concentration of LiFSI is Is > Io.

[0283] (7-3) CO 2 dissolved non-aqueous electrolyte (CO2 Preparation of dissolved electrolyte (method (A), dissolution step: replacement step) Using each electrolyte obtained in the above “(7-1) Preparation of non-aqueous electrolyte (reference electrolyte)”, the above “(1-2) CO 2 dissolved non-aqueous electrolyte (CO 2 Preparation of dissolved electrolyte (method (A), dissolution step: replacement step)”, a CO 2 dissolved electrolyte was prepared, and the electrolyte was analyzed by gas chromatography. CO 2 The amount of CO dissolved in the dissolved electrolyte 2 is shown in the “(A) CO 2 dissolved electrolyte” column of Table 7-1.

[0284]

Table 7-1

[0285] (7-4) Fabrication of laminate battery 7-1 A laminate battery (cell) 7-1 with a voltage of 4.2 V and a capacity of 32 mAh was fabricated by the same method as the above “(2-3) Fabrication of laminate battery 2-1”, and then the aging process of cell 7-1 was carried out.

[0286] (7-5) Fabrication of laminate battery 7-2 (method (B)) A laminate battery (cell) 7-2 with a voltage of 4.2 V and a capacity of 32 mAh was fabricated by the same method as the above “(2-4) Fabrication of laminate battery 2-2 (method (B))”, and then the aging process of cell 7-2 was carried out in the same procedure as cell 7-1.

[0287] Also, the in-cell replacement electrolyte was analyzed by gas chromatography by the same method as the above “(2-4) Fabrication of laminate battery 2-2 (method (B))”, and the amount of CO 2 dissolved in the electrolyte is shown in the “(B) In-cell replacement electrolyte” column of Table 7-1.

[0288] (7-6) Evaluation of battery (Impedance) The impedance of the cell was measured by the same method as the above-mentioned “(2-5) Evaluation of battery”. The results are shown in Table 7-2.

[0289] (Self-discharge) The cells after aging were charged at a constant current and constant voltage with 0.5C (16 mA) at room temperature and 4.2V until terminated at 0.02C (0.64 mA) to reach a fully charged state, then stored at 60°C for 4 weeks, and the open circuit voltage (OCV) of the cells before and after storage was measured. The results are shown in Table 7-2.

[0290]

Table 7-2

[0291] Based on Table 7-2, the results of obtaining the reduction rate of OCV in the same manner as above are shown in Table 7-3.

[0292]

Table 7-3

[0293] (Impedance) From the results of Table 7-2, for all the batteries using the electrolyte with dissolved CO 2 or replacing the air inside the cell with CO 2 , the impedance decreased compared with the batteries using the reference electrolyte without intentionally dissolving CO 2 (comparison between Reference Example 7-1 and Examples 7-1, 7-2). The effect of this impedance reduction is particularly remarkable at low temperatures. 2

[0294] (Self-discharge) From the results of Table 7-2 and Table 7-3, for all the batteries using the electrolyte with dissolved CO 2 , they all 2Compared with the battery using the reference electrolyte without dissolved [substance], it was found that the degree of decrease in OCV after storage was small and the self-discharge of the battery was suppressed (comparison between Reference Example 7-1 and Examples 7-1 and 7-2).

[0295] (7-7) Consideration of Example 7 Series From the above results, in the non-aqueous electrolyte containing the sulfonylimide compound (1), even when the relationship between the two peak intensities in the Raman spectrum is Is > Io, when CO 2 or the like is dissolved at 20 mass ppm or more, a clear effect on the self-discharge of the battery was confirmed.

[0296] <Example 8 Series> (8-1) Preparation of Non-aqueous Electrolyte (Reference Electrolyte) As an electrolyte solvent, in a mixed solvent with a composition of EC:EMC = 3:7 (volume ratio), an electrolyte salt with a mixed salt composition containing LiFSI and LiPF 6 or an electrolyte salt with a single salt composition containing only LiPF 6 was dissolved to the concentrations shown in Table 8-1, and further 10 mass% of fluoroethylene carbonate (FEC, manufactured by Kishida Chemical Co., Ltd., the same below) was added to prepare a non-aqueous electrolyte. The composition of the obtained electrolyte is shown in Table 8-1. The obtained reference electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the "Reference Electrolyte" column of Table 8-1.

[0297] (8-2) Preparation of Non-aqueous Electrolyte with Dissolved CO 2 (CO 2 Dissolved Electrolyte) (Method (A) above, Dissolving Step: Substitution Step) Using each of the electrolytes obtained in the above "(8-1) Preparation of Non-aqueous Electrolyte (Reference Electrolyte)", in the same manner as in the above "(1-2) Preparation of Non-aqueous Electrolyte with Dissolved CO 2 (CO 2 Dissolved Electrolyte) (Method (A) above, Dissolving Step: Substitution Step)", CO 2The dissolved electrolyte was prepared and analyzed by gas chromatography. CO 2 CO in the dissolved electrolyte 2 The results of quantifying the dissolved amount of are shown in the column of "(A) CO 2 dissolved electrolyte" in Table 8-1.

[0298]

Table 8-1

[0299] (Preparation of coin-type lithium battery 8-1) (Preparation of Si-containing graphite composite sheet) Si-containing graphite (SiO: graphite = 10:90) as the active material, carbon black (manufactured by Denka Co., Ltd., product name: Denka Black) and carbon fiber (manufactured by Showa Denko K.K., product name: VGCF) as conductive aids, styrene-butadiene rubber (SBR, binder) and carboxymethyl cellulose (CMC, binder) were dispersed in ultrapure water to prepare an Si-containing graphite composite slurry (active material: conductive aid: SBR: CMC = 100:5:3:1 (solid content mass ratio)). Subsequently, the obtained composite slurry was applied unilaterally to a copper foil (current collector, manufactured by Fukuda Metal Foil & Powder Co., Ltd., thickness 15 μm) with an applicator so that the coating weight after drying was 7.2 mg / cm 2 and dried on a hot plate at 80 °C for 10 minutes. Further, it was dried in a vacuum drying oven at 100 °C for 12 hours. Then, it was pressure-molded by a roll press until the density reached 1.5 g / cm 3 to obtain an Si-containing graphite composite sheet with a thickness of 65 μm.

[0300] (Preparation of coin-type lithium battery) A coin-type lithium battery was assembled using parts for a CR2032 coin-type battery (manufactured by Takizawa Co., Ltd.). A negative electrode cap with a gasket, a wave washer, a spacer, and a lithium foil (φ14 mm, thickness 0.5 mm) (manufactured by Honjo Metal Co., Ltd.) were stacked in this order. Then, 25 μL of the non-aqueous electrolyte shown in Table 8-1 was dropped onto the lithium foil. After a PE separator was placed on the lithium foil, 25 μL of the non-aqueous electrolyte was again dropped onto the separator and impregnated. Then, a circularly punched (φ14 mm) Si-containing graphite composite material sheet prepared as described above was placed so as to face the lithium foil with the separator in between. The positive electrode case was placed on top of it, and the coin-type lithium battery 8-1 was manufactured by caulking with a caulking machine.

[0301] The coin-type lithium battery 8-1 obtained above was charged at a constant current (CC) of 0.1C (0.5 mA) for 4 hours at room temperature using a charge-discharge test device and left at room temperature for 5 days. After leaving, it was charged at a constant current and constant voltage (CCCV) of 0.01V and 0.1C (0.5 mA) at room temperature. At this time, the termination condition was a current value of 0.02C (0.1 mA). Then, it was discharged at a CC of 0.1C (0.5 mA) at room temperature. The termination condition was 1.5V. Next, the CCCV charge and CC discharge were repeated 4 more times. The charge-discharge was performed under the same conditions as above except that the current values during discharge were 0.2C (1.0 mA) for the first time, 1C (5 mA) for the second time, 2C (9.5 mA) for the third time, and 0.1C (0.5 mA) for the fourth time. A partial charge was performed at 0.1C (0.5 mA) for 5 hours at room temperature to set the state of charge (SOC) to 50%, and then it was held at room temperature for 2 weeks. The above was defined as the aging process of the coin-type lithium battery.

[0302] (8-4) Fabrication of coin-type lithium battery 8-2 (method of (B) above) Internal air is CO 2 The coin-type lithium battery 8-2 was fabricated and subjected to an aging process in the same manner as described above (fabrication of the coin-type lithium battery), except that the battery was fabricated in a glove box in which the air inside was replaced with CO

[0303] Also, in the same manner as above, CO 2After fabricating the battery in the glove box replaced with [replacement substance], it was stored at room temperature for 5 days, and then the coin-type lithium battery was disassembled in an argon atmosphere to extract the electrolyte. The extracted electrolyte was analyzed by gas chromatography to quantify the dissolved amount of CO 2 in the electrolyte. The quantification results are shown in the column of "(B) Electrolyte replaced inside the cell" in Table 8-1.

[0304] (8-5) Quantification of the dissolved amount of CO 2 after aging After the coin-type lithium batteries 8-1 and 8-2 after aging were subjected to constant current (CC) discharge at 1.5 V and 0.1 C (0.5 mA) at room temperature, they were disassembled in a glove box replaced with argon gas to extract the electrolyte. The extracted electrolyte was analyzed by gas chromatography to quantify the dissolved amount of CO 2 in the electrolyte. The quantification results are shown in the column of "Dissolved amount of CO 2 after aging" in Table 8-2.

[0305] (8-6) Evaluation of the battery (Self-discharge) After the coin-type lithium battery after aging was subjected to CC discharge at 1.5 V and 0.1 C (0.5 mA), it was subjected to constant current-constant voltage (CCCV) charging at 0.01 V and 0.1 C (0.5 mA) at room temperature to be fully charged. The charging capacity at this time was taken as the charging capacity before storage. The fully charged battery was stored at 60 °C for 4 weeks, and after the stored battery was allowed to cool at room temperature for 2 hours, it was subjected to CC discharge at 1.5 V and 0.1 C (0.5 mA), and the discharge capacity at this time was taken as the residual capacity. The results are shown in Table 8-2. Note that the smaller the difference between the charging capacity before storage and the residual capacity (hereinafter referred to as "self-discharge capacity" in the Example 8 series), the more the self-discharge of the battery is suppressed.

[0306] (Impedance) After aging, the cells were discharged to 1.5 V at 0.1 C (0.5 mA) at room temperature and then charged at a constant current of 0.5 C (2.5 mA) for 1 hour at room temperature to a state of charge (SOC) of 50%. The real-axis resistance (interface resistance) was determined in the same manner as described in the column of (Impedance) in the above "(1-5) Evaluation of Batteries". The results are shown in Table 8-2.

[0307]

Table 8-2

[0308] Based on Table 8-2, the results of calculating the reduction rate of self-discharge capacity are shown in Table 8-3. The reduction rate of self-discharge capacity refers to the ratio (%) of the difference in discharge capacity before and after storage in the reference electrolyte (reference electrolyte) to the difference in discharge capacity before and after storage in the electrolyte having the same salt composition as the reference electrolyte and containing dissolved CO 2 or having the air inside the battery replaced with CO 2 by a method of dissolving CO 2 in it. For example, the reduction rate of self-discharge capacity of Example 8-1 can be calculated by the following formula (3) using Comparative Example 8-2 as the reference electrolyte: [Equation 3] Reduction rate of self-discharge capacity of Example 8-1 (%) = [{(Discharge capacity before storage of Example 8-1) - (Discharge capacity after storage of Example 8-1)} / {(Discharge capacity before storage of Comparative Example 8-2) - (Discharge capacity after storage of Comparative Example 8-2)}] × 100 (3) It should be noted that the smaller the value of the reduction rate of self-discharge capacity, the more the self-discharge of the battery is suppressed, that is, the better the effect of suppressing self-discharge (the higher the effect (degree) of suppressing self-discharge).

[0309]

Table 8-3

[0310] (Impedance) From the results of Table 8-2, when CO 2 is dissolved in the electrolyte or the air inside the battery is replaced with CO2 By the method of replacing with, the batteries using the electrolytic solution in which CO 2 is dissolved all have significantly lower impedance compared to the batteries using the reference electrolytic solution in which CO 2 is not dissolved (comparison between Comparative Example 8-2 and Examples 8-1 and 8-4; comparison between Comparative Example 8-3 and Examples 8-2 and 8-5; comparison between Comparative Example 8-4 and Examples 8-3 and 8-6). The effect of this impedance reduction is particularly remarkable at low temperatures.

[0311] (Self-discharge) From the results in Table 8-3, it was found that by the method of dissolving CO 2 in the electrolytic solution or replacing the air inside the battery with CO 2 all the batteries using the electrolytic solution in which CO 2 is dissolved have a larger remaining capacity after storage and the self-discharge of the battery is suppressed compared to the batteries using the reference electrolytic solution in which CO 2 is not dissolved (the comparison objects are the same as above). Also, in the batteries of Examples 8-1 to 8-6, although LiFSI is contained in the electrolytic solution, compared to the battery using the electrolytic solution containing LiPF 6 alone (Comparative Example 8-1), it was found that the remaining capacity after storage is large and an excellent self-discharge suppression effect is obtained. Furthermore, from the results in Table 8-3, it was found that in the batteries containing LiFSI and the Si-containing graphite composite material, the reduction rate of the self-discharge capacity can be further reduced depending on the mixing ratio of LiFSI and LiPF 6 .

[0312] (8-7) Consideration of Example 8 Series From the above results, although the self-discharge increases as the concentration of the sulfonylimide compound (1) increases in the non-aqueous electrolytic solution containing the non-aqueous electrolytic solution containing the sulfonylimide compound (1) and the electrolytic solution solvent (EMC, chain carbonate ester) having a vapor pressure of 1 kPa or more at room temperature, and a battery comprising a battery electrode plate containing Si or its oxide and graphite, by further dissolving 20 ppm or more of CO 2 etc. in the electrolytic solution, self-discharge is suppressed, and LiPF 6It was confirmed that an effect of suppressing self-discharge superior to that of a battery using an electrolytic solution containing alone was obtained. Further, it was confirmed that the resistance value (impedance) of the battery was also significantly reduced.

[0313] <Example 9 Series> (9-1) Preparation of non-aqueous electrolytic solution (reference electrolytic solution) A non-aqueous electrolytic solution was prepared in the same manner as in the above “(1-1) Preparation of non-aqueous electrolytic solution (reference electrolytic solution)”, except that ethylene carbonate (EC) and / or propylene carbonate (PC) as an electrolytic solution solvent and at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and γ-butyrolactone (GBL) (all manufactured by Kishida Chemical Co., Ltd.) were used. The composition of the obtained electrolytic solution is shown in Table 9-1. The obtained reference electrolytic solution was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolytic solution are shown in the “Reference Electrolytic Solution” column of Table 9-1.

[0314] (9-2) Preparation of non-aqueous electrolytic solution (CO 2 dissolved electrolytic solution) in which CO 2 is dissolved (method (A) above, dissolution step: replacement step) Using each of the electrolytic solutions obtained in the above “(9-1) Preparation of non-aqueous electrolytic solution (reference electrolytic solution)”, the above “(1-2) CO 2 dissolved non-aqueous electrolytic solution (CO 2 dissolved electrolytic solution) Preparation (method (A) above, dissolution step: replacement step)”, a CO 2 dissolved electrolytic solution was prepared, and the electrolytic solution was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolytic solution are shown in the “(A) CO2 dissolved electrolytic solution” column of Table 9-1.

[0315]

Table 9-1

[0316] Fabrication of the laminated battery 9-1 After fabricating a laminated battery (cell) 9-1 with a voltage of 4.2 V and a capacity of 32 mAh by the same method as in the above-mentioned “(2-3) Fabrication of the laminated battery 2-1”, an aging process of the cell 9-1 was carried out.

[0317] (9-4) Fabrication of the laminated battery 9-2 (by the method of (B) above) After fabricating a laminated battery (cell) 9-2 with a voltage of 4.2 V and a capacity of 32 mAh by the same method as in the above-mentioned “(2-4) Fabrication of the laminated battery 2-2 (by the method of (B) above)”, an aging process of the cell 9-2 was carried out in the same procedure as that of the cell 9-1.

[0318] Also, the in-cell replacement electrolyte was analyzed by gas chromatography in the same method as in the above-mentioned “(2-4) Fabrication of the laminated battery 2-2 (by the method of (B) above)”, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the column of “(B) In-cell replacement electrolyte” in Table 9-1.

[0319] (9-5) Evaluation of the battery (Impedance, DCR, low-temperature charge-discharge characteristics, and self-discharge) The impedance, DCR, low-temperature (-20 °C) charge-discharge capacity, and self-discharge (OCV) of the cell were measured by the same method as in the above-mentioned “(1-5) Evaluation of the battery”. The results are shown in Table 9-2.

[0320]

Table 9-2

[0321] Based on Table 9-2, the results of obtaining the reduction rate of OCV in the same way as above are shown in Table 9-3.

[0322]

Table 9-3

[0323] (Impedance) From the results in Table 9-2, by dissolving CO 2 in the electrolyte or replacing the air inside the cell with CO 2 , all the batteries using the electrolyte with dissolved CO 2 showed a decrease in impedance compared to the batteries using the reference electrolyte without intentionally dissolving CO 2 (comparison between Comparative Example 9-1 and Examples 9-1, 9-6; Comparative Example 9-2 and Examples 9-2, 9-7; Comparative Example 9-3 and Examples 9-3, 9-8; Comparative Example 9-4 and Examples 9-4, 9-9; Comparative Example 9-5 and Examples 9-5, 9-10). The effect of this impedance decrease is particularly prominent at low temperatures.

[0324] (Low-temperature charge-discharge characteristics) From the results in Table 9-2, all the batteries using the electrolyte with dissolved CO 2 showed an improvement in charge-discharge capacity at low temperatures compared to the batteries using the reference electrolyte without intentionally dissolving CO 2 (the comparison is the same as above). This effect is considered to be based on the decrease in impedance at low temperatures due to the dissolution of CO 2 in the electrolyte as shown in the impedance measurement results.

[0325] (Self-discharge) From the results in Table 9-2, all the batteries using the electrolyte with dissolved CO 2 were found to have a smaller decrease in OCV after storage and suppressed self-discharge compared to the batteries using the reference electrolyte without intentionally dissolving CO 2 (the comparison targets are the same as above). Also, from the results in Table 9-3, all the batteries using the electrolyte containing LiFSI and dissolved CO 2 (each example) showed a smaller reduction rate of OCV compared to the battery using the electrolyte containing LiPF 6 alone instead of LiFSI (Comparative Example 9-6), indicating that self-discharge is further suppressed.

[0326] (9-6) Consideration of Example 9 series From the above results, even when the non-aqueous electrolyte contains a chain carbonate or lactone as the electrolyte solvent in the sulfonylimide compound (1), CO 2 and the like are dissolved at 20 ppm or more, and a clear effect on the self-discharge of the battery was confirmed.

[0327] <Example 10 Series> (10-1) Preparation of non-aqueous electrolyte (reference electrolyte) A non-aqueous electrolyte was prepared in the same manner as in the above “(1-1) Preparation of non-aqueous electrolyte (reference electrolyte)”, except that ethylene carbonate (EC) (manufactured by Kishida Chemical Co., Ltd.), ethyl methyl carbonate (EMC) (manufactured by Kishida Chemical Co., Ltd.), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) (manufactured by Nippon Shokubai Co., Ltd.), and 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI) (manufactured by Tokyo Chemical Industry Co., Ltd.) were used as the electrolyte solvents. The composition of the obtained electrolyte is shown in Table 10-1. The obtained reference electrolyte was analyzed by gas chromatography, and the results of quantifying the dissolved amount of CO 2 in the electrolyte are shown in the “Reference Electrolyte” column of Table 10-1.

[0328] (10-2) Preparation of non-aqueous electrolyte in which CO 2 is dissolved (CO 2 dissolved electrolyte) (method (A) above, dissolution step: substitution step) Using each electrolyte obtained in the above “(10-1) Preparation of non-aqueous electrolyte (reference electrolyte)”, the method for preparing a non-aqueous electrolyte in which CO 2 is dissolved (CO 2 dissolved electrolyte) (method (A) above, dissolution step: substitution step)” was used to prepare a CO 2 dissolved electrolyte, and the electrolyte was analyzed by gas chromatography. The results of quantifying the dissolved amount of CO 2 in the CO 2 dissolved electrolyte are shown in the “(A) CO 2 dissolved electrolyte” column of Table 10-1.

[0329]

Table 10-1

[0330] (Fabrication of the laminated battery 10-1) A laminated battery (cell) 10-1 with a voltage of 4.2 V and a capacity of 32 mAh was fabricated in the same manner as the above-mentioned “(2-3) Fabrication of the laminated battery 2-1”, except that six cellulose sheets with a thickness of 22 μm were stacked to form a separator.

[0331] (10-4) Evaluation of the battery (Initial discharge capacity) The cell 10-1 obtained above was subjected to constant current charging at 0.1 C (3 mA) for 4 hours at room temperature (25 °C, the same hereinafter) using a charge-discharge test apparatus, and then left at room temperature for 5 days. After leaving, the excess laminate was cracked and vacuum-sealed to remove the gas in the cell 10-1. After constant current constant voltage (CCCV) charging at 4.2 V and 0.5 C (15 mA) for 5 hours at room temperature, constant current discharge was performed at 0.2 C (6 mA) and 2.75 V cut-off (discharge cut-off voltage) at room temperature to evaluate the initial discharge capacity. The results are shown in Table 10-2.

[0332]

Table 10-2

[0333] (Initial discharge capacity) From the results in Table 10-2, it can be seen that the initial discharge capacity of all the batteries using the electrolytes without EC or EMC was significantly lower than that of the batteries using the electrolytes containing EC or EMC. This is also the case for the electrolytes with dissolved CO 2 , and since this difference is greater than the performance improvement of CO 2 described in Example series 1 to 9, it can be said that the battery performance has decreased overall. This phenomenon is considered to be due to the increase in the resistance of the electrolyte caused by the high viscosity of EMImFSI or P13FSI.

Claims

1. A non-aqueous electrolyte containing a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolytic solution solvent, and dissolving at least one of carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ). The sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ), ２ and The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less, The electrolyte solvent consists of only at least one selected from the group consisting of carbonate solvents, lactone solvents, and nitrile solvents, The total dissolved amount of at least one of the carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) is 20 mass ppm or more. Non-aqueous electrolyte solution. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ each independently represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

2. The sulfonylimide compound represented by the general formula (1) is LiN(CF ３ SO ２ ), ２ The non-aqueous electrolyte according to claim 1, comprising the same.

3. Regarding the peak intensity derived from the electrolyte solvent in the vibrational spectroscopic spectrum of the non-aqueous electrolyte, when the intensity of the peak of the electrolyte solvent itself is Io and the intensity of the peak when the peak is shifted is Is, Is > Io. The non-aqueous electrolyte according to Claim 1 or 2.

4. The electrolyte salt further contains at least one selected from the group consisting of a compound represented by the general formula (2), a compound represented by the general formula (3), and LiAsF ６ The non-aqueous electrolyte according to any one of claims 1 to 3. LiPF ａ (C ｍ F ２ｍ＋１ ) ６－ａ (a: 0 ≤ a ≤ 6, m: 1 ≤ m ≤ 4) (2) LiBF ｂ (C ｎ F ２ｎ+１ ) ４－ｂ (b: 0 ≤ b ≤ 4, n: 1 ≤ n ≤ 4) (3)

5. The non-aqueous electrolyte according to any one of Claims 1 to 4, further comprising at least one selected from the group consisting of a compound represented by the general formula (4), a compound represented by the general formula (5), and a compound represented by the general formula (6). M １ PO ｃ F ｄ (M １ : alkali metal element, c: 1 ≦ c ≦ 3, d: 1 ≦ d ≦ 3) (4) M ２ (FSO ３ ) ｅ (M ２ : monovalent or divalent metal element, e: 1 or 2) (5) 【Chemical 1】 (In the general formula (6), M ３ : B or P, A ｆ＋ : Metal ion, H or onium ion, f: 1 ≤ f ≤ 3, g: 1 ≤ g ≤ 3, h: g / f, i: 1 ≤ h ≤ 3, j: 0 ≤ j ≤ 4, k: 0 or 1, R ３ : An alkylene group having 1 to 10 carbon atoms or a halogenated alkylene group having 1 to 10 carbon atoms, R ４ : F or a fluorinated alkyl group having 1 to 10 carbon atoms, T １ , T ２ : Each independently represents O or S.)

6. A method for producing a non-aqueous electrolyte solution containing a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolyte solvent, and in which at least one of carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) is dissolved, The sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ), ２ and The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less, The electrolyte solvent consists of only at least one selected from the group consisting of carbonate solvents, lactone solvents, and nitrile solvents, The above carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) are provided with a dissolution step of dissolving at least one kind in a non-aqueous electrolyte solution, The dissolution step includes at least one of a pressurization step of pressurizing a gas containing at least one of carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) into a non-aqueous electrolyte, a liquid contact step of bringing the gas into contact with the non-aqueous electrolyte, a bubbling step of blowing the gas into the non-aqueous electrolyte, and a replacement step of replacing air in a sealed container containing the non-aqueous electrolyte with the gas, which is a method for producing a non-aqueous electrolyte. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ are the same or different and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

7. A secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, The non-aqueous electrolyte contains a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolyte solvent, and contains carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ), and at least one of them is dissolved. The total dissolved amount of at least one of carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) is 20 mass ppm or more. The sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ). ２ The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less. The electrolyte solvent consists of only at least one selected from the group consisting of carbonate solvents, lactone solvents, and nitrile solvents. A secondary battery. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ are the same or different and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

8. The secondary battery according to Claim 7, wherein the positive electrode contains at least one of a positive electrode active material represented by the general formula (7) and a positive electrode active material represented by the general formula (8). Li ｚ Ni ｘ Mn ｙ Co （１－ｘ－ｙ） O ２ (z: 0.9 ≤ z ≤ 1.1, x: 0.2 ≤ x < 1, y: 0 ≤ y ≤ 0.4, 0 < 1 - x - y ≤ 0.8) (7) Li ｐ Fe １－ｒ Q ｒ (PO ４ ) ｐ (Q: Mn or Ni, p: 0.9 ≦ p ≦ 1.1, r: 0 ≦ r ≦ 0.05) (8)

9. A method for manufacturing a secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, The non-aqueous electrolyte contains a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolyte solvent, and contains carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ), and at least one of them is dissolved. The total dissolved amount of at least one of the carbon dioxide (CO ２ ), carbon monoxide (CO), hydrogen carbonate ion (HCO ３ － ), and carbonate ion (CO ３ ２－ ) is 20 mass ppm or more. The sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ). ２ The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less. A method for manufacturing a secondary battery using a non-aqueous electrolyte composed of only at least one selected from the group consisting of a carbonate-based solvent, a lactone-based solvent, and a nitrile-based solvent is used. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ are the same or different and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

10. A method for manufacturing a secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, The non-aqueous electrolyte contains a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolyte solvent, and the sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ). ２ The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less, and the electrolyte solvent consists of only at least one selected from the group consisting of carbonate solvents, lactone solvents, and nitrile solvents. A method for manufacturing a secondary battery, comprising injecting the non-aqueous electrolyte into a battery in a carbon dioxide (CO ２ ) atmosphere. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ are the same or different and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

11. A method for manufacturing a secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, The non-aqueous electrolyte contains a sulfonylimide compound represented by the general formula (1) as an electrolyte salt and an electrolyte solvent, and the sulfonylimide compound represented by the general formula (1) contains LiN(FSO ２ ). ２ The concentration of the sulfonylimide compound represented by the general formula (1) in the non-aqueous electrolyte is 0.01 mol / L or more and 2 mol / L or less, and the electrolyte solvent consists of only at least one selected from the group consisting of carbonate solvents, lactone solvents, and nitrile solvents. A method for manufacturing a secondary battery, which replaces air in the battery with carbon dioxide (CO ２ ) after injecting the non-aqueous electrolyte solution. LiN(R １ SO ２ )(R ２ SO ２ )(R １ and R ２ are the same or different and each represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

12. The method for manufacturing a secondary battery according to any one of Claims 9 to 11, wherein at least one of a positive electrode active material represented by the general formula (7) and a positive electrode active material represented by the general formula (8) is used as the positive electrode. Li ｚ Ni ｘ Mn ｙ Co （１－ｘ－ｙ） O ２ (z: 0.9 ≤ z ≤ 1.1, x: 0.2 ≤ x < 1, y: 0 ≤ y ≤ 0.4, 0 < 1 - x - y ≤ 0.8) (7) Li ｐ Fe １－ｒ Q ｒ (PO ４ ) ｐ (Q: Mn or Ni, p: 0.9 ≦ p ≦ 1.1, r: 0 ≦ r ≦ 0.05) (8)

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