JP7272044B2 - Non-aqueous electrolyte, non-aqueous electrolyte storage element, water-solubilizing agent for non-aqueous electrolyte, and method for producing non-aqueous electrolyte - Google Patents

Description

The present invention relates to a non-aqueous electrolyte, a non-aqueous electrolyte storage element, a water-solubilizing agent for the non-aqueous electrolyte, and a method for producing the non-aqueous electrolyte.

Non-aqueous electrolyte secondary batteries, typified by lithium ion secondary batteries, are widely used in electronic devices such as personal computers, communication terminals, and automobiles because of their high energy density. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the electrodes. It is configured to be charged and discharged by Capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries.

Generally, the nonaqueous electrolyte of the nonaqueous electrolyte storage element includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. In this non-aqueous electrolyte, various solvents and additives are selected and used for performance improvement. For example, a non-aqueous electrolyte using a mixed solvent of a chain carbonate and a cyclic carbonate as a non-aqueous solvent is widely known (see Patent Documents 1 and 2).

JP 2016-207633 A JP 2011-009230 A

Non-aqueous electrolytes for power storage devices generally fall under Category 4 (flammable liquids) of hazardous materials under the Fire Defense Law. Due to the Fire Service Act regulations, hazardous materials exceeding the specified quantity in Japan cannot be stored at places other than storage facilities and cannot be handled at places other than manufacturing facilities, storage facilities and handling facilities. Of the dangerous goods, the specified quantity of non-water-soluble liquids and water-soluble liquids are different for Class 4 dangerous goods Class 1 petroleum, Class 2 petroleum, and Class 3 petroleum. twice that of water-soluble liquids. For example, ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC), which are non-aqueous electrolytes containing a mixed solvent of the chain carbonate and the cyclic carbonate, are mixed at a volume ratio of 30:10:60. The non-aqueous electrolyte obtained by mixing lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt so that the content of lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt is 1.2 mol / L in the mixed non-aqueous solvent is 1000 L. It corresponds to a non-aqueous liquid. Here, if the non-aqueous electrolyte corresponding to Class 2 petroleum is a water-soluble liquid, the specified quantity is 2000 L, and the double amount is stored at a place other than the storage place, and It is industrially useful because it can be handled at any location.

The present invention has been made based on the circumstances as described above, and an object of the present invention is to provide a non-aqueous electrolyte for a power storage device which is a water-soluble liquid, a method for producing such a non-aqueous electrolyte, and a method for producing such a non-aqueous electrolyte. An object of the present invention is to provide a non-aqueous electrolyte storage element having an electrolyte and a water-solubilizing agent for the non-aqueous electrolyte.

One aspect of the present invention, which has been made to solve the above problems, contains a non-aqueous solvent containing ethyl methyl carbonate, and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, A non-aqueous electrolyte (A) for a power storage device, wherein the ethyl methyl carbonate content in the non-aqueous solvent is 65% by volume or less.

Another aspect of the present invention is a non-aqueous electrolyte for a power storage device, which is a water-soluble liquid containing a non-aqueous solvent and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms ( B).

Another aspect of the present invention is a non-aqueous electrolyte storage element including the non-aqueous electrolyte (A) or the non-aqueous electrolyte (B).

Another aspect of the present invention is a water-solubilizing agent for a non-aqueous electrolyte containing a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms.

Another aspect of the present invention comprises mixing a non-aqueous solvent containing ethyl methyl carbonate and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, wherein the non-aqueous solvent A method for producing a non-aqueous electrolyte for a power storage device, wherein the content of the ethyl methyl carbonate in the battery is 65% by volume or less.

Another aspect of the present invention is to mix a non-aqueous solvent with a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. A method for producing a non-aqueous electrolyte.

The present invention provides a non-aqueous electrolyte that is a water-soluble liquid, a method for producing such a non-aqueous electrolyte, a non-aqueous electrolyte storage element comprising such a non-aqueous electrolyte, and a water-solubilizing agent for the non-aqueous electrolyte. can do.

FIG. 1 is an external perspective view showing a non-aqueous electrolyte storage element according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a power storage device configured by assembling a plurality of non-aqueous electrolyte power storage elements according to one embodiment of the present invention.

A non-aqueous electrolyte according to one aspect of the present invention contains a non-aqueous solvent containing ethyl methyl carbonate (EMC) and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, A non-aqueous electrolyte (A) for a power storage device, wherein the EMC content in the water solvent is 65% by volume or less.

The non-aqueous electrolyte (A) becomes a water-soluble liquid by having the above composition. Although the reason why the non-aqueous electrolyte (A) becomes a water-soluble liquid is not clear, the following reasons are presumed. A sulfonate anion having a fluorinated hydrocarbon group having 4 or more carbon atoms is an anion having a fluorinated hydrocarbon group that is a hydrophobic group and a sulfonic acid group that is a hydrophilic group. In particular, a fluorinated hydrocarbon group having 4 or more carbon atoms exhibits high hydrophobicity because it is fluorinated and has a large number of carbon atoms. In addition, the presence of the highly electron-withdrawing fluorinated hydrocarbon group increases the anionicity (dissociation with cations) of the sulfonic acid group. For this reason, it is presumed that the excellent surface activity of the salt having this sulfonate anion enhances the compatibility between the non-aqueous solvent and water. In addition, if the EMC content required for viscosity adjustment is too high, the water solubility tends to decrease. % or less, the water-solubility is enhanced and a water-soluble liquid is obtained. Moreover, since the non-aqueous electrolyte (A) is a water-soluble liquid, the specified quantity is large, which is industrially beneficial.

Further, the non-aqueous electrolyte (A) is useful as a non-aqueous electrolyte for electric storage elements for the following reasons. When chain carbonates and cyclic carbonates, which are widely used as non-aqueous solvents, are compared, cyclic carbonates, which have a high dielectric constant, are more water-soluble. Therefore, for example, a non-aqueous electrolyte composed only of cyclic carbonate may become a water-soluble liquid. However, a non-aqueous electrolyte that does not contain a chain carbonate has too high a viscosity and cannot exhibit good performance of an electric storage device. Among chain carbonates, dimethyl carbonate (DMC), which has the lowest number of carbon atoms, tends to have relatively high water solubility, and there is a possibility that increasing the content of DMC may result in a water-soluble liquid. However, DMC has poor oxidation resistance and is difficult to use as a non-aqueous electrolyte for a storage element operated at high voltage. On the other hand, chain carbonates with a large number of carbon atoms, such as diethyl carbonate (DEC), have high oxidation resistance but low water solubility. Therefore, the non-aqueous electrolyte (A) contains EMC as a chain carbonate for viscosity adjustment and the like from the viewpoint of the balance between oxidation resistance and water solubility. It functions usefully as an electrolyte. Furthermore, the non-aqueous electrolyte (A) is useful in that the addition of a salt having a sulfonate anion can reduce the initial resistance of the storage element.

A non-aqueous electrolyte according to another aspect of the present invention is a water-soluble liquid containing a non-aqueous solvent and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, for a power storage device. is a non-aqueous electrolyte (B). Since the non-aqueous electrolyte (B) is a water-soluble liquid, the specified quantity is large, which is industrially beneficial. Furthermore, the non-aqueous electrolyte (B) is useful in that the addition of a salt having a sulfonate anion can reduce the initial resistance of the storage element.

In addition, "water-soluble liquid" refers to the one corresponding to "water-soluble liquid" in Cabinet Order Appended Table 3 on Regulation of Hazardous Materials. In some cases, it means that the mixed liquid maintains a uniform appearance even after the flow stops. The government ordinance on the regulation of hazardous materials is a government ordinance enacted based on the provisions of the Fire Service Act. In the specification of the present application, "gently stirring with the same volume of pure water" means pouring 10 mL of pure water and 10 mL of non-aqueous electrolyte into a 50 mL beaker, using a stirring rod, rotating at 60 rpm, 20 It means to carry out by stirring twice. Moreover, "after the flow subsides" refers to the time after stirring, allowing to stand for 30 seconds or longer, and visually confirming that no flow is observed.

In the non-aqueous electrolyte (A) and the non-aqueous electrolyte (B), the content of DMC in the non-aqueous solvent is preferably 10% by volume or less. In this way, by reducing the content of DMC, which is inferior in oxidation resistance, the oxidation resistance of the non-aqueous electrolyte is increased, and it can be suitably used for high-voltage storage elements.

A non-aqueous electrolyte storage element according to an embodiment of the present invention is a non-aqueous electrolyte storage element (hereinafter also simply referred to as "storage element") including the non-aqueous electrolyte (A) or the non-aqueous electrolyte (B). be. Since the storage element uses a non-aqueous electrolyte that is a water-soluble liquid, the specified quantity is large, which is industrially beneficial.

It is preferable that the positive electrode potential at the end-of-charge voltage in normal use of the storage element is 4.3 V (vs. Li/Li ⁺ ) or more. Since the positive electrode potential at the charging end voltage during normal use is 4.3 V (vs. Li/Li ⁺ ) or more, the element functions as a high-voltage storage element. Further, the non-aqueous electrolyte according to one embodiment of the present invention is a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms without using DMC with low oxidation resistance. It has become. For this reason, the non-aqueous electrolyte according to one embodiment of the present invention can improve the oxidation resistance, and the electric storage element using such a non-aqueous electrolyte has a positive electrode potential at the charging end voltage during normal use of It works well even at 4.3 V (vs. Li/Li ⁺ ) or higher.

Here, the term "during normal use" refers to the case where the storage element is used under the charging conditions recommended or specified for the storage element, and when a charger for the storage element is prepared. refers to the case of using the storage device by applying the charger. For example, in a storage device using graphite as a negative electrode active material, the positive electrode potential is about 4.35 V (vs. Li/Li ⁺ ) when the final charging voltage is 4.25 V, although this depends on the design.

A water-solubilizing agent according to an embodiment of the present invention is a water-solubilizing agent for a non-aqueous electrolyte containing a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. According to the water-solubilizing agent, the salt having the sulfonate anion can enhance the water-solubility of the non-aqueous electrolyte. That is, for example, by adding the water-solubilizing agent to a predetermined non-aqueous electrolyte that is a non-aqueous liquid, a non-aqueous electrolyte that is a water-soluble liquid can be obtained.

A method for producing a non-aqueous electrolyte according to an embodiment of the present invention comprises mixing a non-aqueous solvent containing EMC with a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. and a method for producing a non-aqueous electrolyte for a power storage device, wherein the EMC content in the non-aqueous solvent is 65% by volume or less. According to the method for producing a non-aqueous electrolyte, a non-aqueous Electrolyte can be obtained.

A method for producing a non-aqueous electrolyte according to one embodiment of the present invention comprises mixing a non-aqueous solvent with a salt having a sulfonate anion having a fluorinated hydrocarbon group having 4 or more carbon atoms. A method for producing a liquid non-aqueous electrolyte for a power storage device. According to the method for producing a non-aqueous electrolyte, a non-aqueous electrolyte that is a water-soluble liquid can be obtained by using a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms.

Hereinafter, a non-aqueous electrolyte, a method for producing a non-aqueous electrolyte, a water-solubilizing agent for the non-aqueous electrolyte, and a non-aqueous electrolyte storage element according to one embodiment of the present invention will be described in detail.

<Non-aqueous electrolyte>
A non-aqueous electrolyte (A) according to one embodiment of the present invention is used as a non-aqueous electrolyte for a power storage device. The non-aqueous electrolyte (A) contains a non-aqueous solvent and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms.

(Non-aqueous solvent)
Non-aqueous solvents include EMC. EMC is one of chain carbonates and a low-viscosity solvent. Therefore, by using EMC as the non-aqueous solvent, the non-aqueous electrolyte (A) exhibits suitable viscosity and exhibits excellent characteristics as a non-aqueous electrolyte for a power storage element. In addition, by using EMC among chain carbonates, both oxidation resistance and water solubility of the non-aqueous electrolyte (A) can be achieved.

The upper limit of the EMC content in the non-aqueous solvent is 65% by volume, preferably 60% by volume. By setting the EMC content to the above upper limit or less, a non-aqueous electrolyte exhibiting good water solubility can be obtained. On the other hand, the lower limit of the EMC content in the non-aqueous solvent is not particularly limited, but is preferably 10% by volume, more preferably 30% by volume, and even more preferably 50% by volume. By setting the EMC content to the above lower limit or more, a non-aqueous electrolyte having suitable viscosity and the like can be obtained. For these reasons, the content of EMC in the non-aqueous solvent is preferably in the range of any one of the above lower limits or more and any one of the above upper limits or less.

The non-aqueous solvent may contain chain carbonates other than EMC. Other chain carbonates include DMC and DEC. However, from the viewpoint of oxidation resistance, the upper limit of the content of DMC in the non-aqueous solvent is preferably 10% by volume, more preferably 5% by volume, even more preferably 1% by volume, and substantially contains DMC. Even more preferably not.

In addition, from the viewpoint of water solubility, oxidation resistance, etc., the lower limit of the EMC content in the total chain carbonate is preferably 80% by volume, more preferably 90% by volume, further preferably 95% by volume, and 99% by volume. is more preferable, and it is particularly preferable that the chain carbonate is substantially only EMC.

The non-aqueous solvent preferably further contains a cyclic carbonate. The cyclic carbonate can enhance the water solubility of the non-aqueous electrolyte (A). The cyclic carbonate may be one in which some or all of the hydrogen atoms are substituted with substituents such as fluorine. Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC) and the like. As the cyclic carbonate, EC, PC and BC are preferred, EC and PC are more preferred, and EC and PC are more preferably used in combination.

The lower limit of the cyclic carbonate content in the non-aqueous solvent is preferably 20% by volume, more preferably 30% by volume, even more preferably 35% by volume, and even more preferably 40% by volume. By making the content of the cyclic carbonate equal to or higher than the above lower limit, the water solubility can be further enhanced. On the other hand, the upper limit of the content of the cyclic carbonate in the non-aqueous solvent is preferably 70% by volume, more preferably 50% by volume, in order to adjust the viscosity to an appropriate level. For these reasons, the content of the cyclic carbonate in the non-aqueous solvent is preferably within the range of any one of the above lower limits or more and any of the above upper limits or less.

The lower limit of the volume ratio of EC to the cyclic carbonate is preferably 50% by volume, more preferably 60% by volume. On the other hand, the upper limit of this content may be 100% by volume, preferably 90% by volume, and more preferably 80% by volume. Moreover, the volume ratio of EC to the cyclic carbonate is preferably in the range of any of the above lower limits or more and any of the above upper limits or less.

The lower limit of the volume ratio of PC to the cyclic carbonate may be 0% by volume, preferably 10% by volume, and more preferably 20% by volume. On the other hand, the upper limit of this content is preferably 50% by volume, more preferably 35% by volume. Moreover, the volume ratio of PC in the cyclic carbonate is preferably in the range of any one of the above lower limits or more and any one of the above upper limits or less.

The nonaqueous solvent may further contain a nonaqueous solvent other than the chain carbonate and the cyclic carbonate. Other non-aqueous solvents can include esters, ethers, amides, sulfones, lactones, nitriles, and the like. However, the lower limit of the total content of chain carbonate and cyclic carbonate in the non-aqueous solvent is preferably 90% by volume, more preferably 99% by volume. The lower limit of the total content of EMC and cyclic carbonate in the non-aqueous solvent is preferably 90% by volume, more preferably 99% by volume. Furthermore, the lower limit of the total content of EMC, EC and PC in the non-aqueous solvent is preferably 90% by volume, more preferably 99% by volume. In this way, the non-aqueous electrolyte having better water-solubility, viscosity, oxidation resistance, etc. can be obtained by using a composition with a small content of other non-aqueous solvents.

(Salt with sulfonate anion)
The salt having a sulfonate anion contained in the non-aqueous electrolyte (A) is not particularly limited as long as it is a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. The salt having a sulfonate anion is preferably a salt having a sulfonate anion consisting of one fluorinated hydrocarbon group and one sulfonate group ( _{--SO.sub.3.sup.-} ⁾ .

The hydrocarbon group constituting the fluorinated hydrocarbon group having 4 or more carbon atoms may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but an aliphatic hydrocarbon group is preferred. Examples of the aliphatic hydrocarbon group include aliphatic chain hydrocarbon groups such as alkyl groups, alkenyl groups and alkynyl groups, and aliphatic cyclic hydrocarbon groups such as cycloalkyl groups. A hydrogen group is preferred, and an alkyl group is more preferred. Moreover, although the upper limit of carbon number of a hydrocarbon group is not specifically limited, 16 is preferable and 10 is more preferable, for example. Lithium heptadecafluorooctanesulfonate, which has a fluorinated hydrocarbon group with 8 carbon atoms, is designated as a Class 1 Specified Chemical Substance under the Law Concerning the Examination and Regulation of Manufacture, etc. of Chemical Substances. cannot be used as intended. Therefore, from the viewpoint of industrial utility, the number of carbon atoms in the fluorinated hydrocarbon group is preferably other than 8, more preferably 7 or less.

The number of fluorine atoms in the fluorinated hydrocarbon group may be 1 or more, preferably 5 or more, more preferably 9 or more. Although the upper limit of the number of fluorine atoms is not particularly limited, for example, 33 is preferable, and 21 is more preferable. The fluorinated hydrocarbon group is particularly preferably a hydrocarbon group in which all hydrogen atoms are substituted with fluorine atoms, such as a perfluoroalkyl group.

Examples of cations constituting a salt having a sulfonate anion include alkali metal ions, alkaline earth metal ions, and ammonium ions. Alkali metal ions are preferred, and lithium ions, sodium ions, and potassium ions are more preferred. .

A preferred example of a salt having a sulfonate anion is a compound represented by _{CnF2n + 1SO3A} . In the above formula, n is an integer of 4 or more, preferably an integer of 4 or more and 10 or less, and more preferably an integer of 4 or more and 7 or less. A is an alkali metal, preferably lithium, sodium or potassium, more preferably lithium or potassium.

The lower limit of the content of the salt having a sulfonate anion in the non-aqueous electrolyte (A) is preferably 0.1% by mass, more preferably 0.5% by mass. By setting the content of the salt having a sulfonate anion to the above lower limit or more, the water solubility of the non-aqueous electrolyte (A) can be further enhanced. On the other hand, the upper limit of the content of the salt having a sulfonate anion may be, for example, 10% by mass, 6% by mass, or 3% by mass. For these reasons, the content of the salt having a sulfonate anion in the non-aqueous electrolyte (A) is preferably in the range of any one of the above lower limits and above any of the above upper limits. From the viewpoint of further reducing the initial resistance of the electric storage element, the content of the salt having a sulfonate anion may be less than 1% by mass.

(electrolyte salt)
The non-aqueous electrolyte (A) usually contains an electrolyte salt dissolved in a non-aqueous solvent. The electrolyte salt does not include a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. Examples of electrolyte salts include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts and the like, with lithium salts being preferred. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiPF ₂ (C ₂ O ₄ ) ₂ , LiClO ₄ , LiN(SO ₂ F) ₂ , LiSO ₃ CF ₃ , LiN ( _SO2CF3 ) ₂ , LiN( _{SO2C2F5 ) 2 ,} LiN( _{SO2CF3 ) ( SO2C4F9 ) ,} LiC( _{SO2CF3 ) 3} , LiC _{( SO2C2F 5} ) Lithium salts having a fluorohydrocarbon group such as ₃ can be mentioned.

Among the above lithium salts, inorganic lithium salts are preferred, and LiPF ₆ is more preferred.

The lower limit of the content of the electrolyte salt in the non-aqueous electrolyte (A) is preferably 0.1 mol/L, more preferably 0.5 mol/L, still more preferably 1 mol/L, and particularly preferably 1.2 mol/L. . On the other hand, the upper limit is not particularly limited, but is preferably 2.5 mol/L, more preferably 2 mol/L, and even more preferably 1.5 mol/L. The content of the electrolyte salt in the non-aqueous electrolyte (A) is preferably 0.1 mol/L or more and 2.5 mol/L or less, more preferably 0.5 mol/L or more and 2 mol/L or less.

To the non-aqueous electrolyte (A), a non-aqueous solvent, a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, and other components other than the electrolyte salt are added as additives. good too. Examples of such additives include various additives contained in general non-aqueous electrolytes for electric storage elements. Examples of the above additives include 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, 4,4′-bis(2,2-dioxo-1,3,2-dioxathiolane), and the like. Compounds having a cyclic sulfate structure, compounds having a sultone structure such as 1,3-propanesultone and 1,4-butanesultone, nitrile compounds such as succinonitrile, phosphorus such as lithium difluorophosphate and lithium tetrafluorooxalate phosphate boron-containing compounds such as boron-containing compounds, lithium bisoxalate borate, and the like. Among these, compounds having a cyclic sulfate structure and phosphorus-containing compounds are preferred.

When the non-aqueous electrolyte (A) contains the additive, the lower limit of the content is preferably 0.1% by mass, more preferably 0.5% by mass. On the other hand, the upper limit of this content is preferably 5% by mass, more preferably 2% by mass, and even more preferably 1% by mass in some cases.

<Non-aqueous electrolyte (B)>
A non-aqueous electrolyte (B) according to one embodiment of the present invention is used as a non-aqueous electrolyte for a power storage device. The non-aqueous electrolyte (B) is a water-soluble liquid containing a non-aqueous solvent and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms.

The composition of the non-aqueous electrolyte (B) is not particularly limited except that it contains a non-aqueous solvent and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. A preferred specific composition of the non-aqueous electrolyte (B) is the composition of the non-aqueous electrolyte (A) described above.

<Method for producing non-aqueous electrolyte>
A method for producing a non-aqueous electrolyte according to an embodiment of the present invention comprises mixing a non-aqueous solvent containing EMC with a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. and a method for producing a non-aqueous electrolyte for a power storage device, wherein the EMC content in the non-aqueous solvent is 65% by volume or less. A method for producing a non-aqueous electrolyte according to another embodiment of the present invention comprises mixing a non-aqueous solvent with a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. By such a manufacturing method, it is possible to obtain a non-aqueous electrolyte for a power storage device, which is a water-soluble liquid, such as the above-described non-aqueous electrolyte (A) and non-aqueous electrolyte (B).

Specific examples of the non-aqueous solvent and the salt having a sulfonate anion used in the production method are as described above as the embodiments of the non-aqueous electrolyte (A). The method for mixing the non-aqueous solvent and the salt having a sulfonate anion is not particularly limited, either, and conventionally known methods can be used. Further, during this mixing, other components than the non-aqueous solvent and the salt having the sulfonate anion may be added. A salt having a sulfonate anion may be mixed with a non-aqueous solvent to which other ingredients have been added. After mixing the non-aqueous solvent and the salt having a sulfonate anion, other components may be added to the mixture to form a non-aqueous electrolyte. The other component may be the electrolyte salt.

<Water-solubilizing agent for non-aqueous electrolyte>
A water-solubilizing agent according to an embodiment of the present invention is a water-solubilizing agent for a non-aqueous electrolyte containing a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. The water-solubilizing agent can be suitably used as an additive in the production of a non-aqueous electrolyte that is a water-soluble liquid.

Specific examples of the salt having a sulfonate anion contained in the water-solubilizing agent are the same as the salt having a sulfonate anion described above as the component of the non-aqueous electrolyte (A). The water-soluble agent may further contain a component other than the salt having a sulfonate anion, but may consist essentially of a salt having a sulfonate anion. The content of the salt having a sulfonate anion in the water-solubilizing agent may be 90% by mass or more and 100% by mass or less, or may be 99% by mass or more and 100% by mass or less.

<Non-aqueous electrolyte storage element>
A power storage device according to one embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. A secondary battery will be described below as an example of the storage element. The positive electrode and the negative electrode normally form an electrode assembly alternately stacked or wound with a separator interposed therebetween. This electrode assembly is housed in a container, and the container is filled with a non-aqueous electrolyte. A non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. Moreover, as a container, a known metal container, resin container, or the like, which is usually used as a container for a secondary battery, can be used.

(positive electrode)
The positive electrode has a positive electrode base material and a positive electrode active material layer disposed directly on the positive electrode base material or via an intermediate layer.

A positive electrode base material has electroconductivity. Having “conductivity” means having a volume resistivity of 10 ⁷ Ω·cm or less as measured in accordance with JIS-H-0505 (1975), and “non-conductivity” It means that the volume resistivity is more than 10 ⁷ Ω·cm. As the material for the positive electrode substrate, metals such as aluminum, titanium, tantalum and stainless steel, or alloys thereof are used. Among these, aluminum or an aluminum alloy is preferable from the viewpoint of potential resistance, high conductivity, and cost. Examples of positive electrode substrates include foils and deposited films, and foils are preferred from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode substrate. Examples of aluminum or aluminum alloy include A1085 and A3003 defined in JIS-H-4000 (2014).

The lower limit of the average thickness of the positive electrode substrate is preferably 5 μm, more preferably 10 μm. The upper limit of the average thickness of the positive electrode substrate is preferably 50 μm, more preferably 40 μm. By making the average thickness of the positive electrode base material equal to or more than the above lower limit, the strength of the positive electrode base material can be increased. By making the average thickness of the positive electrode substrate equal to or less than the above upper limit, the energy density per volume of the secondary battery can be increased. For these reasons, the average thickness of the positive electrode substrate is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less. "Average thickness" refers to the average thickness measured at ten arbitrary points. The same definition applies when using the "average thickness" for other members or the like.

The intermediate layer is a layer arranged between the positive electrode substrate and the positive electrode active material layer. The structure of the intermediate layer is not particularly limited, and includes, for example, a resin binder and conductive particles. The intermediate layer reduces the contact resistance between the positive electrode substrate and the positive electrode active material layer, for example, by containing conductive particles such as carbon particles.

The positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer is usually a layer formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture forming the positive electrode active material layer may contain arbitrary components such as a conductive agent, a binder, a thickener, and a filler, if necessary.

The positive electrode active material can be appropriately selected from known positive electrode active materials commonly used in lithium ion secondary batteries and the like. A material capable of intercalating and deintercalating lithium ions is usually used as the positive electrode active material. Examples thereof include lithium transition metal composite oxides having an α-NaFeO ₂ type crystal structure, lithium transition metal oxides having a spinel crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Li[Li _x Ni _{1 -x} ]O ₂ (0≦x<0.5), Li[Li _x Ni _γ Co _{(1− x-γ)} ]O ₂ (0≦x<0.5, 0<γ<1), Li[Li _x Ni _γ Mn _β Co _(1-x-γ-β ) ]O ₂ (0≦x<0.5, 0<γ<1) 5, 0<γ, 0<β, 0.5<γ+β<1), etc. Lithium transition metal oxides having a spinel crystal structure include Li _x Mn ₂ O ₄ , Li _x Ni _γ Mn _{(2 -γ)} O ₄ etc. Polyanion compounds include LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F etc. Chalcogen compounds include titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc. Atoms or polyanions in these materials may be partially substituted with atoms or anionic species of other elements. In the positive electrode active material layer, one kind of these positive electrode active materials may be used alone, or two or more kinds may be mixed and used.

The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By making the average particle size of the positive electrode active material equal to or more than the above lower limit, manufacturing or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. Here, the "average particle size" is based on the particle size distribution measured by a laser diffraction/scattering method for a diluted solution in which the particles are diluted with a solvent in accordance with JIS-Z-8825 (2013). Z-8819-2 (2001) means the value at which the volume-based integrated distribution calculated according to 50%.

A pulverizer, a classifier, or the like is used to obtain particles of a positive electrode active material or the like in a predetermined shape. Pulverization methods include, for example, methods using a mortar, ball mill, sand mill, vibrating ball mill, planetary ball mill, jet mill, counter jet mill, whirling jet mill, sieve, and the like. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane is allowed to coexist can also be used. As a classification method, a sieve, an air classifier, or the like is used as necessary, both dry and wet.

The lower limit of the content of the positive electrode active material in the positive electrode active material layer is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass. The upper limit of the content of the positive electrode active material is preferably 98% by mass, more preferably 96% by mass. By setting the content of the positive electrode active material within the above range, the electric capacity of the secondary battery can be increased.

The conductive agent is not particularly limited as long as it is a conductive material. Examples of such conductive agents include graphite; carbon blacks such as furnace black and acetylene black; metals; and conductive ceramics. The shape of the conductive agent may be powdery, fibrous, or the like. Among these, acetylene black is preferable from the viewpoint of electronic conductivity and coatability.

The lower limit of the content of the conductive agent in the positive electrode active material layer is preferably 1% by mass, more preferably 2% by mass. The upper limit of the content of the conductive agent is preferably 10% by mass, more preferably 5% by mass. By setting the content of the conductive agent within the above range, the electric capacity of the secondary battery can be increased. For these reasons, the content of the conductive agent is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 5% by mass or less.

Examples of binders include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, and polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, Elastomers such as styrene-butadiene rubber (SBR) and fluororubbers; polysaccharide polymers;

The lower limit of the binder content in the positive electrode active material layer is preferably 1% by mass, more preferably 2% by mass. The upper limit of the binder content is preferably 10% by mass, more preferably 5% by mass. By setting the content of the binder within the above range, the active material can be stably retained. For these reasons, the content of the binder is preferably 1% by mass or more and 10% by mass, more preferably 2% by mass or more and 5% by mass or less.

Examples of thickeners include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be previously deactivated by methylation or the like.

A filler is not specifically limited. Examples of fillers include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and alumina silicate.

The positive electrode active material layer contains typical nonmetallic elements such as B, N, P, F, Cl, Br, and I; typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, and Ge; , Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W, etc., as components other than the positive electrode active material, conductive agent, binder, thickener and filler. may

(negative electrode)
The negative electrode has a negative electrode substrate and a negative electrode active material layer disposed directly on the negative electrode substrate or via an intermediate layer. The structure of the intermediate layer of the negative electrode is not particularly limited, and may have the same structure as that of the intermediate layer of the positive electrode.

A negative electrode base material has electroconductivity. As the material of the negative electrode base material, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof are used. Among these, copper or a copper alloy is preferred. Examples of negative electrode substrates include foils and vapor deposition films, and foils are preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferable as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

The lower limit of the average thickness of the negative electrode substrate is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the negative electrode substrate is preferably 30 μm, more preferably 20 μm. By making the average thickness of the negative electrode base material equal to or greater than the above lower limit, the strength of the negative electrode base material can be increased. The energy density per volume of the secondary battery can be increased by setting the average thickness of the negative electrode substrate to the above upper limit or less. For these reasons, the average thickness of the negative electrode substrate is preferably 3 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less.

The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer is usually a layer formed from a so-called negative electrode mixture containing a negative electrode active material. The negative electrode mixture forming the negative electrode active material layer may contain optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary. Optional components such as a conductive agent, a binder, a thickener, and a filler may be the same as those used for the positive electrode active material layer.

The negative electrode active material can be appropriately selected from known negative electrode active materials commonly used in lithium ion secondary batteries and the like. A material capable of intercalating and deintercalating lithium ions is usually used as the negative electrode active material. Examples of the negative electrode active material include metal Li; metals or metalloids such as Si and Sn; metal oxides and metalloid oxides such as Si oxide, Ti oxide and Sn oxide; Li ₄ Ti ₅ O ₁₂ ; Titanium-containing oxides such as LiTiO _{2 and} TiNb ₂ O ₇ ; polyphosphate compounds; silicon carbide; carbon materials such as graphite and non-graphitizable carbon (easily graphitizable carbon or non-graphitizable carbon) be done. Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer, one type of these materials may be used alone, or two or more types may be mixed and used.

“Graphite” refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by X-ray diffraction before charging/discharging or in a discharged state of 0.33 nm or more and less than 0.34 nm. Graphite includes natural graphite and artificial graphite. Artificial graphite is preferable from the viewpoint that a material with stable physical properties can be obtained.

“Non-graphitic carbon” means a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by X-ray diffraction before charging/discharging or in a discharged state of 0.34 nm or more and 0.42 nm or less. say. The crystallite size Lc of non-graphitic carbon is typically between 0.80 and 2.0 nm. Non-graphitizable carbon includes non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch-derived materials, and alcohol-derived materials.

Here, the term “discharged state” refers to a state in which the open circuit voltage is 0.7 V or more in a single electrode battery using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and metal Li as a counter electrode. Since the potential of the metal Li counter electrode in the open circuit state is approximately equal to the oxidation-reduction potential of Li, the open-circuit voltage in the above monopolar battery is approximately the same as the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. . In other words, the open circuit voltage of 0.7 V or higher in the above monopolar battery means that lithium ions that can be inserted and extracted are sufficiently released from the carbon material that is the negative electrode active material during charging and discharging. .

The term “non-graphitizable carbon” refers to a carbon material having a d ₀₀₂ of 0.36 nm or more and 0.42 nm or less. The non-graphitizable carbon generally has a property of being difficult to form a graphite structure having a three-dimensional stacking regularity among non-graphitic carbons.

“Graphitizable carbon” refers to a carbon material having a d ₀₀₂ of 0.34 nm or more and less than 0.36 nm. Graphitizable carbon usually has the property of easily forming a graphite structure having a three-dimensional stacking regularity among non-graphitic carbons.

The average particle size of the negative electrode active material can be, for example, 1 μm or more and 100 μm or less. By making the average particle size of the negative electrode active material equal to or greater than the above lower limit, the production or handling of the negative electrode active material is facilitated. By making the average particle size of the negative electrode active material equal to or less than the above upper limit, the electron conductivity of the negative electrode active material layer is improved. A pulverizer, a classifier, or the like is used to obtain particles of the negative electrode active material in a predetermined shape. The pulverization method and the powder class method can be selected from, for example, the methods exemplified for the positive electrode.

The negative electrode active material layer contains typical nonmetallic elements such as B, N, P, F, Cl, Br, and I; typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, and Ge; , Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W and other transition metal elements other than negative electrode active materials, conductive agents, binders, thickeners and fillers. It may be contained as a component.

(separator)
As the material of the separator, for example, a woven fabric, a nonwoven fabric, a porous resin film, or the like is used. Among these, a porous resin film is preferred from the viewpoint of strength, and a non-woven fabric is preferred from the viewpoint of retention of a non-aqueous electrolyte. As the main component of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of strength, and polyimide, aramid, and the like are preferable from the viewpoint of oxidative decomposition resistance. Also, these resins may be combined.

An inorganic layer may be provided between the separator and the electrode (usually the positive electrode). This inorganic layer is a porous layer that is also called a heat-resistant layer or the like. A separator having an inorganic layer formed on one surface of a porous resin film can also be used. The inorganic layer is generally composed of inorganic particles and a binder, and may contain other components. As inorganic particles, Al ₂ O ₃ , SiO ₂ , aluminosilicate and the like are preferable.

(Non-aqueous electrolyte)
The non-aqueous electrolyte used in the secondary battery (power storage element) is the non-aqueous electrolyte (A) or the non-aqueous electrolyte (B) according to one embodiment of the present invention described above.

When the content of DMC in the non-aqueous solvent of the non-aqueous electrolyte is 10% by volume or less, the non-aqueous electrolyte has high oxidation resistance. Therefore, when the secondary battery (power storage element) includes such a non-aqueous electrolyte, the secondary battery can be used at a high operating voltage. For example, the positive electrode potential at the charging end voltage during normal use of the secondary battery may be, for example, 4.0 V (vs. Li/Li ⁺ ) or more, but may be 4.3 V (vs. Li/Li ⁺ ). The above is preferable. On the other hand, the upper limit of the positive electrode potential at the charge termination voltage during normal use is, for example, 5.2 V (vs. Li/Li ⁺ ), and may be 5.0 V (vs. Li/Li ⁺ ).

<Method for producing non-aqueous electrolyte storage element>
A non-aqueous electrolyte storage element according to one embodiment of the present invention can be manufactured by a known method. For example, the electric storage element is manufactured by manufacturing a positive electrode, manufacturing a negative electrode, laminating or winding the positive electrode and the negative electrode with a separator interposed therebetween to form an alternately superimposed electrode body, It can be manufactured by a manufacturing method comprising housing the (electrode body) in a container and injecting a non-aqueous electrolyte into the container. After these steps, a secondary battery (power storage element) can be obtained by sealing the inlet.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be implemented in various modified and improved modes in addition to the above-described modes. For example, the intermediate layer may not be provided in the positive electrode or negative electrode. Moreover, the positive electrode and the negative electrode of the non-aqueous electrolyte storage element may not have a definite layer structure. For example, the positive electrode may have a structure in which a positive electrode active material is supported on a mesh-shaped positive electrode base material.

Further, in the above embodiments, the non-aqueous electrolyte storage element is mainly a non-aqueous electrolyte secondary battery, but other non-aqueous electrolyte storage elements may be used. Other non-aqueous electrolyte storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like.

FIG. 1 shows a schematic diagram of a rectangular non-aqueous electrolyte storage element 1 (non-aqueous electrolyte secondary battery) that is one embodiment of the non-aqueous electrolyte storage element according to the present invention. In addition, the same figure is taken as the figure which saw through the inside of a container. In the non-aqueous electrolyte storage element 1 shown in FIG. 1, the electrode body 2 is accommodated in the container 3 . The electrode body 2 is formed by winding a positive electrode including a positive electrode mixture and a negative electrode including a negative electrode mixture with a separator interposed therebetween. The positive electrode is electrically connected to a positive terminal 4 via a positive lead 4', and the negative electrode is electrically connected to a negative terminal 5 via a negative lead 5'. Further, the container 3 is filled with a non-aqueous electrolyte according to one embodiment of the present invention.

The configuration of the non-aqueous electrolyte storage element according to the present invention is not particularly limited, and examples thereof include cylindrical batteries, prismatic batteries (rectangular batteries), flat batteries, and the like. The present invention can also be implemented as a power storage device including a plurality of non-aqueous electrolyte power storage elements described above. One embodiment of a power storage device is shown in FIG. In FIG. 2 , the power storage device 30 includes a plurality of power storage units 20 . Each power storage unit 20 includes a plurality of nonaqueous electrolyte power storage elements 1 . The power storage device 30 can be mounted as a power supply for automobiles such as electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV).

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

Abbreviations of non-aqueous solvents and salts having sulfonate anions used in Examples and Comparative Examples are shown below.
(Non-aqueous solvent)
EC: Ethylene carbonate PC: Propylene carbonate EMC: Ethyl methyl carbonate

(Salt having a sulfonate anion, etc.)
LiTFMS: lithium trifluoromethanesulfonate LiNFBS: lithium nonafluoro-1-butanesulfonate KNFBS: potassium nonafluoro-1-butanesulfonate LiPFOS: lithium heptadecafluoro-1-octane sulfonate HTMABr: hexyltrimethylammonium bromide NaBS: sodium 1-butanesulfonate PFHA: undecafluorohexanoic acid DMOSPAH: dimethyl(n-octyl)(3-sulfopropyl)ammonium hydroxide inner salt

[Example 1]
(Preparation of non-aqueous electrolyte)
Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was mixed in a non-aqueous solvent obtained by mixing EC, PC, and EMC at a volume ratio of 30:10:60 so that the content was 1.2 mol/L. A solution was prepared. This solution was mixed with LiNFBS as a salt having a sulfonate anion so as to have a content of 2% by mass to prepare a non-aqueous electrolyte.

[Examples 2 to 6, Comparative Examples 1 to 8]
The type and volume ratio of the non-aqueous solvent, the content of the electrolyte salt, and the type and content of the salt having a sulfonate anion (salt having a sulfonate anion or a substitute salt thereof) are as shown in Table 1. Non-aqueous electrolytes of Examples 2 to 6 and Comparative Examples 1 to 8 were obtained in the same manner as in Example 1 except for the above. "-" in the table indicates that the corresponding component was not used.

[Evaluation] (Evaluation of water solubility)
Each of the obtained non-aqueous electrolytes was evaluated for water solubility as follows. In an atmosphere of 1 atm and 20° C., 10 mL of pure water and 10 mL of nonaqueous electrolyte were poured into a 50 mL beaker and gently stirred. Specifically, using a stirring rod, the mixture was stirred 20 times at a rotational speed of 60 rpm. After stirring, the mixture was allowed to stand still for 30 seconds or more, and it was visually confirmed that no flow was observed. A mixture that maintained a uniform appearance after the flow stopped was evaluated as a water-soluble liquid, and a mixture that separated into two phases was evaluated as a non-water-soluble liquid. Table 1 shows the evaluation results.

As shown in Table 1 above, Comparative Example 1 containing no salt having a sulfonate anion, etc., and a comparison containing LiTFMS, which is a salt having a sulfonate anion having a fluorinated hydrocarbon group with 1 carbon number Each of the nonaqueous electrolytes of Example 2 and Comparative Examples 3 to 6 containing salts other than salts having a sulfonate anion were water-insoluble liquids. Furthermore, the non-aqueous electrolytes of Comparative Examples 7 and 8, in which the EMC content in the non-aqueous solvent exceeds 65% by volume, contain a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms. However, it was a water-insoluble liquid. On the other hand, in Examples 1 to 6, the EMC content in the non-aqueous solvent is 65% by volume or less, and the salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms is contained. The non-aqueous electrolyte became a water-soluble liquid.

[Example 7]
(Preparation of non-aqueous electrolyte)
Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was mixed in a non-aqueous solvent obtained by mixing EC, PC, and EMC at a volume ratio of 30:10:60 so that the content was 1.2 mol/L. A solution was prepared. This solution was mixed with LiNFBS as a salt having a sulfonate anion so as to have a content of 0.5% by mass to prepare a non-aqueous electrolyte.

(Preparation of positive electrode)
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , which is a lithium transition metal composite oxide having an α-NaFeO ₂ -type crystal structure, was used as the positive electrode active material. A positive electrode paste containing a positive electrode active material: acetylene black (AB): polyvinylidene fluoride (PVDF) at a mass ratio of 93:4:3 (in terms of solid matter) and using N-methylpyrrolidone (NMP) as a dispersion medium. was made. This positive electrode paste was applied to both sides of a strip-shaped aluminum foil as a positive electrode substrate and dried to remove NMP. After pressurizing this with a roller press to mold a positive electrode active material layer, it was dried under reduced pressure at 100° C. for 14 hours to remove moisture in the electrode plate. Thus, a positive electrode was obtained.

(Preparation of negative electrode)
Graphite was used as a negative electrode active material. A negative electrode paste containing negative electrode active material (graphite): styrene-butadiene rubber (SBR): carboxymethyl cellulose (CMC) at a mass ratio of 97:2:1 (in terms of solid content) and using water as a dispersion medium was prepared. . This negative electrode paste was applied to both sides of a strip-shaped copper foil current collector as a negative electrode substrate, and dried to remove water. After pressurizing this with a roller press to form a negative electrode active material layer, it was dried under reduced pressure at 100° C. for 12 hours to remove moisture in the electrode plate. Thus, a negative electrode was obtained.

(Preparation of non-aqueous electrolyte storage element)
A polyolefin microporous membrane coated with an inorganic layer was used as a separator. An electrode body was produced by laminating the positive electrode and the negative electrode with the separator interposed therebetween. This electrode body was housed in an aluminum rectangular container can, and a positive electrode terminal and a negative electrode terminal were attached. After the non-aqueous electrolyte was injected into the container (rectangular battery can), the container was sealed to obtain a non-aqueous electrolyte storage element (secondary battery) of Example 7.

[Examples 8 to 10, Comparative Example 9]
Each nonaqueous electrolyte and nonaqueous electrolyte power storage of Examples 8 to 10 and Comparative Example 9 were prepared in the same manner as in Example 7, except that the type and content of the salt having a sulfonate anion were as shown in Table 2. I got the device. In addition, "-" in the column of additive in the table indicates that the corresponding salt having a sulfonate anion was not used.

[Evaluation] (Initial charge/discharge and ACR measurement)
Initial charge/discharge was performed on each obtained non-aqueous electrolyte storage element under the following conditions. In the first cycle, the battery was charged at a constant current of 0.2C to 4.25V at 25°C and then constant voltage charge (CCCV) at 4.25V. The termination condition of charging was when the current value reached 0.02C. After that, the battery was discharged at a constant current of 0.2C to 2.75V at 25°C. In the second cycle, the battery was charged at a constant current of 1C to 4.25V at 25°C and then charged at a constant voltage of 4.25V. The termination condition of charging was when the current value reached 0.02C. After that, the battery was discharged at a constant current of 1C to 2.75V at 25°C. A rest period of 10 minutes was set after charging and after discharging for all cycles. After that, the battery was discharged at a constant current of 0.2C to 2.75V at 25°C.
An initial AC resistance (ACR) of 1 kHz was obtained for each non-aqueous electrolyte storage element after the initial charge/discharge. Table 2 shows the ACR of each non-aqueous electrolyte storage element as a relative value with the ACR of the non-aqueous electrolyte storage element of Comparative Example 9 as the reference (100%).

As shown in Table 2, by using a non-aqueous electrolyte containing a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms, it can be seen that the initial resistance of the storage element can be lowered. .

INDUSTRIAL APPLICABILITY The present invention can be applied to electronic devices such as personal computers and communication terminals, and non-aqueous electrolyte storage elements used as power sources for automobiles and the like.

1 non-aqueous electrolyte storage element 2 electrode body 3 container 4 positive electrode terminal 4' positive electrode lead 5 negative electrode terminal 5' negative electrode lead 20 storage unit 30 storage device

Claims (6)

A non-aqueous solvent containing ethyl methyl carbonate, and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms,
A non-aqueous electrolyte for a power storage device, wherein the ethyl methyl carbonate content in the non-aqueous solvent is 60 % by volume or less. 2. The non-aqueous electrolyte according to claim 1, wherein the content of dimethyl carbonate in said non-aqueous solvent is 10% by volume or less. A non-aqueous electrolyte storage element comprising the non-aqueous electrolyte according to claim 1 or 2 . 4. The non-aqueous electrolyte storage element according to claim 3 , wherein the positive electrode potential at the end-of-charge voltage during normal use is 4.3 V (vs. Li/Li ⁺ ) or more. Containing a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms,
An aqueous solution of a non-aqueous electrolyte used to be added to a non-aqueous electrolyte containing a non-aqueous solvent containing ethyl methyl carbonate and having a content of the ethyl methyl carbonate in the non-aqueous solvent of 60% by volume or less. sexual agent. Mixing a non-aqueous solvent containing ethyl methyl carbonate and a salt having a sulfonate anion having a fluorinated hydrocarbon group with 4 or more carbon atoms,
A method for producing a non-aqueous electrolyte for a power storage device, wherein the ethyl methyl carbonate content in the non-aqueous solvent is 60 % by volume or less.

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