Electrolyte solution, and electrochemical device and secondary battery using same

Abstract

Provided are an electrolyte solution capable of improving the durability of an electrochemical device and reducing the rate of increase in resistance, and an electrochemical device and a secondary battery using the same. An electrolyte solution containing at least one compound represented by general formula (1). Rf1OLi (1) (Rf1 is a fluoroalkyl group having 1 to 5 carbon atoms).

Description

Technical Field

[0001] The present invention relates to an electrolyte, and an electrochemical device and a secondary battery using the same. Background Art

[0002] With the recent trend toward lighter and smaller electrical products, the demand for electrochemical devices such as secondary batteries has rapidly increased. Furthermore, as electrical products are being enhanced to higher performance and given previously unavailable functions, the demand for electrochemical devices that can withstand extended periods of use and under harsh conditions continues to grow.

[0003] It has been proposed that, by incorporating specific additives, an electrolyte solution can be obtained that has a high capacity retention rate even when an electrochemical device such as a lithium ion secondary battery is stored at high temperatures, suppresses elution from the positive electrode, and is less likely to generate gas (Patent Document 1).

[0004] Prior art literature Patent Literature Patent Document 1: International Publication No. 2019 / 003780 Summary of the Invention Technical problem to be solved by the invention An object of the present invention is to provide an electrolyte solution capable of improving the durability of an electrochemical device, reducing the resistance increase rate, and reducing the amount of metal deposition, as well as an electrochemical device and a secondary battery using the same.

[0005] Technical solutions to technical problems The present invention is an electrolyte solution containing at least one compound represented by the following general formula (1).

[0006] Rf 1 OLi (1) (Rf 1 is a fluorinated alkyl group having 1 to 5 carbon atoms. The Rf of the compound represented by the above general formula (1) 1 Any one of the following formulas (1a) to (1e) is preferred.

[0007] (1a) CF2HCF2 (1b) CF2HCF2CH2 (1c) CF3CHFCF2 (1d) CF3CF2CH2 (1e) HCF2CF2CF2CF2CH2 The content of the compound represented by the general formula (1) is preferably 0.0001 to 500 ppm based on the entire electrolyte solution.

[0008] More preferably, the compound represented by the following general formula (2) is contained.

[0009] Rf 2 OR 3 (2) (Rf 2 、Rf 3 are independently fluoroalkyl groups having 1 to 8 carbon atoms. The compound represented by the general formula (2) is preferably at least one selected from the group consisting of CF2HCF2CH2OCF2CF2H, CF2HCF2CH2OCF2CHFCF3, and CF3CF2CH2OCF2CF2H.

[0010] The content of the compound represented by the general formula (2) is preferably 0.01 to 80% by mass based on the entire electrolytic solution.

[0011] The content of the compound represented by the general formula (1) is preferably 0.00000001 to 11% by mass relative to the compound represented by the general formula (2).

[0012] The content of the compound represented by the general formula (2) is preferably 0.1 to 75% by mass relative to the entire electrolyte solution, and the content of the compound represented by the general formula (1) is preferably 0.000025 to 0.35% by mass relative to the compound represented by the general formula (2).

[0013] The compound represented by the above general formula (1) is preferably CF2HCF2CH2OLi.

[0014] The compound represented by the general formula (2) is preferably CF2HCF2CH2OCF2CF2H.

[0015] The present invention is also an electrochemical device comprising the above-mentioned electrolyte solution.

[0016] The present invention is also a secondary battery including the above-mentioned electrolyte solution.

[0017] The present invention is also a lithium ion secondary battery including the above-mentioned electrolyte solution.

[0018] Effects of the Invention The present invention can provide an electrolyte solution that can improve the durability of electrochemical devices, reduce the rate of resistance increase, and reduce the amount of metal deposition. In addition, electrochemical devices and secondary batteries using the electrolyte solution of the present invention have improved durability and reduced rate of resistance increase. DETAILED DESCRIPTION

[0019] Hereinafter, the present invention will be described in detail.

[0020] The electrolyte solution of the present invention contains at least one compound represented by the following general formula (1).

[0021] Rf 1 OLi (1) (Rf 1 is a fluorinated alkyl group having 1 to 5 carbon atoms. The present invention includes the specific alkali metal fluoroalkoxide in the electrolytic solution for an electrochemical device, thereby improving the durability of the electrochemical device, namely the cycle characteristics (for example, the capacity retention rate after cycling), and reducing the resistance increase rate and the amount of metal deposition in the electrochemical device.

[0022] (lithium fluoroalkoxide) The electrolyte solution of the present invention contains a compound represented by the following general formula (1).

[0023] Rf 1 OLi (1) (Rf 1 is a fluorinated alkyl group having 1 to 5 carbon atoms. The Rf of the compound represented by the above general formula (1) 1 Since it is advantageous in terms of oxidation resistance, any one of the following formulas (1a) to (1e) is preferred.

[0024] (1a) CF2HCF2 (1b) CF2HCF2CH2 (1c) CF3CHFCF2 (1d) CF3CF2CH2 (1e)CF2HCF2CF2CF2CH2 As the compound represented by the general formula (1), CF2HCF2CH2OLi is particularly preferred in terms of suppressing the resistance increase rate.

[0025] The content of the compound represented by the general formula (1) is preferably 0.0001 ppm to 500 ppm relative to the entire electrolyte solution. A content within this range is particularly excellent in suppressing the resistance increase rate.

[0026] The lower limit of the content of the compound represented by the general formula (1) is more preferably 0.01 ppm, further preferably 0.1 ppm, and particularly preferably 1 ppm. The upper limit of the content of the compound represented by the general formula (1) is more preferably 400 ppm, further preferably 300 ppm, and particularly preferably 100 ppm.

[0027] The compound represented by the above general formula (1) can be prepared by a known method. For example, by making a fluoroalcohol (Rf 1 OH) reacts with Li in the presence of a catalyst.

[0028] (Fluoroether) The electrolyte solution of the present invention preferably further contains a compound represented by the following general formula (2) (hereinafter sometimes referred to as fluoroether (2)).

[0029] Rf 2 OR 3 (2) (Rf 2 、Rf 3 are independently fluoroalkyl groups having 1 to 8 carbon atoms. By including the fluoroether (2), the flame retardancy of the electrolyte is improved, and the stability and safety at high temperature and high voltage are improved. In addition, the durability of the electrochemical device can be further improved, the resistance increase rate can be reduced, and the amount of metal precipitation can be reduced.

[0030] The fluoroalkyl group is a fluoroalkyl group having 1 to 8 carbon atoms. The fluoroalkyl group is preferably a fluoroalkyl group having 1 to 4 carbon atoms. Among them, a fluoroalkyl group having 2 to 3 carbon atoms is more preferred.

[0031] If the number of carbon atoms in the fluoroalkyl group is too small, the boiling point tends to be low. If the number of carbon atoms is too large, the solubility of the electrolyte salt decreases, which also begins to have an adverse effect on the compatibility with other solvents. In addition, due to the increase in viscosity, the rate characteristics tend to decrease. 2 The number of carbon atoms is 3 or 4, Rf 3 When the number of carbon atoms is 2 or 3, it is advantageous in that the boiling point and rate characteristics are excellent.

[0032] The fluorine content of the fluoroether (2) is preferably 40 to 75% by mass. A fluorine content within this range provides a particularly good balance between non-flammability and compatibility. Furthermore, it is also preferred from the perspective of good oxidation resistance and safety.

[0033] The lower limit of the fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass, while the upper limit is more preferably 70% by mass, further preferably 66% by mass.

[0034] The fluorine content of the fluoroether (2) is a value calculated from {(number of fluorine atoms×19) / molecular weight of the fluoroether (2)}×100 (%) based on the structural formula of the fluoroether (2).

[0035] As Rf 2, for example, CF3CF2CH2-, CF3CFHCF2-, HCF2CF2CF2-, HCF2CF2CH2-, CF3CF2CH2CH2-, CF3CFHCF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CF2CH2-, HCF2CF2CH2CH2-, HCF2CF(CF3)CH2-, etc. In addition, as Rf 3 For example, -CH2CF2CF3, -CF2CFHCF3, -CF2CF2CF2H, -CH2CF2CF2H, -CH2CH2CF2CF3, -CH2CF2CFHCF3, -CF2CF2CF2CF2H, -CH2CF2CF2CF2H, -CH2CH2CF2CF2H, -CH2CF(CF3)CF2H, -CF2CF2H, -CH2CF2H, -CH2CF3, -CF2CH3, etc. can be mentioned.

[0036] Specific examples of the fluoroether (2) include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, C6F 13 OCH3、C6F 13 OC2H5、C8F 17 OCH3、C8F 17 OC2H5, CF3CFHCF2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, HCF2CF2OCH2CH(CH3)2, etc.

[0037] As the fluoroether (2), from the viewpoint of being particularly advantageous in flame retardancy, at least one selected from the group consisting of CF2HCF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, and CF3CF2CH2OCF2CF2H is preferred.

[0038] Among them, CF2HCF2CH2OCF2CF2H is more preferred.

[0039] The content of the fluoroether (2) is preferably 0.01 to 80% by mass relative to the total electrolyte. Within this range, the electrolyte can be used as a good electrolyte. Specifically, if the content is increased, the amount of metal precipitated from the active material decreases, but the viscosity of the electrolyte increases, and the ion conductivity decreases, thereby tending to shorten the battery life.

[0040] The lower limit is preferably 0.1% by mass, more preferably 1% by mass, and the upper limit is preferably 75% by mass, more preferably 50% by mass.

[0041] The content of the compound represented by the general formula (1) is preferably 0.00000001 to 11% by mass relative to the compound represented by the general formula (2).

[0042] The lower limit is preferably 0.000025% by mass, more preferably 0.01% by mass, and particularly preferably 0.02% by mass. The upper limit is preferably 10% by mass, more preferably 1% by mass, further preferably 0.5% by mass, and particularly preferably 0.35% by mass.

[0043] The electrolytic solution of the present invention preferably contains a solvent.

[0044] The solvent preferably contains at least one selected from the group consisting of carbonates and carboxylates.

[0045] The carbonate esters may be cyclic carbonate esters or chain carbonate esters.

[0046] The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0047] Examples of the non-fluorinated cyclic carbonate include non-fluorinated saturated cyclic carbonates, preferably non-fluorinated saturated alkylene carbonates having an alkylene group having 2 to 6 carbon atoms, and more preferably non-fluorinated saturated alkylene carbonates having an alkylene group having 2 to 4 carbon atoms.

[0048] Among them, as the above-mentioned non-fluorinated saturated cyclic carbonate, from the viewpoint of high dielectric constant and suitable viscosity, it is preferably at least one selected from ethylene carbonate, propylene carbonate, cis-2,3-pentylene carbonate, cis-2,3-butylene carbonate, 2,3-pentylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,2-butylene carbonate and butylene carbonate.

[0049] The above-mentioned non-fluorinated saturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0050] When the non-fluorinated saturated cyclic carbonate is contained, the content of the non-fluorinated saturated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and even more preferably 15 to 50% by volume based on the solvent.

[0051] The fluorinated cyclic carbonate is a fluorine-containing cyclic carbonate. A solvent containing the fluorinated cyclic carbonate can be suitably used even at high voltage.

[0052] In this specification, "high voltage" refers to a voltage of 4.2 V or higher. The upper limit of "high voltage" is preferably 4.9 V.

[0053] The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0054] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically includes a compound represented by the following general formula (A): [Chemistry 1] (Where X 1 ~X 4 are the same or different and represent -H, -CH3, -C2H5, -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. 1 ~X 4 At least one of them is -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. ) The fluoroalkyl group mentioned above refers to -CF3, -CF2H, -CH2F, etc.

[0055] When the electrolyte solution of the present invention contains the fluorinated saturated cyclic carbonate, when the electrolyte solution is used in a high-voltage lithium-ion secondary battery or the like, the oxidation resistance of the electrolyte solution is improved, and stable and excellent charge and discharge characteristics can be obtained.

[0056] In addition, in this specification, an "ether bond" is a bond represented by -O-.

[0057] From the perspective of good dielectric constant and oxidation resistance, X 1 ~X 4 One or two of them are preferably -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond.

[0058] From the perspective of being able to expect a decrease in viscosity at low temperatures, an increase in flash point, and an improvement in the solubility of the electrolyte salt, X 1 ~X 4 Preferred are -H, -F, a fluoroalkyl group (a), a fluoroalkyl group having an ether bond (b), or a fluoroalkoxy group (c).

[0059] The fluoroalkyl group (a) is a group obtained by replacing at least one hydrogen atom of an alkyl group with a fluorine atom. The fluoroalkyl group (a) preferably has 1 to 20 carbon atoms, more preferably 1 to 17 carbon atoms, further preferably 1 to 7 carbon atoms, and particularly preferably 1 to 5 carbon atoms.

[0060] If the number of carbon atoms is too large, low-temperature characteristics may be reduced or the solubility of the electrolyte salt may be reduced. If the number of carbon atoms is too small, reduced solubility of the electrolyte salt, reduced discharge efficiency, and increased viscosity may be observed.

[0061] Among the fluoroalkyl groups (a), examples of the fluoroalkyl group having 1 carbon atom include CFH2-, CF2H-, and CF3-. In particular, CF2H- or CF3- is preferred in terms of high-temperature storage characteristics, and CF3- is most preferred.

[0062] The fluorine content of the fluoroalkyl (a), the fluoroalkyl (b) with ether bond and the fluoroalkoxy (c) in the above-mentioned fluorinated saturated cyclic carbonate is preferably more than 10 mass %. If the fluorine content is too low, then the effect of reducing the viscosity reduction under low temperature, the effect of the flash point increase may not be fully obtained. From this viewpoint, the above-mentioned fluorine content is more preferably more than 12 mass %, further preferably more than 15 mass %. The upper limit is usually 76 mass %.

[0063] The fluorine content of the fluoroalkyl group (a), the fluoroalkyl group having an ether bond (b), and the fluoroalkoxy group (c) is a value calculated from the structural formula of each group by {(number of fluorine atoms × 19) / formula weight of each group} × 100 (%).

[0064] Furthermore, from the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the fluorinated saturated cyclic carbonate as a whole is preferably 10% by mass or more, more preferably 15% by mass or more, with the upper limit usually being 76% by mass.

[0065] The fluorine content of the fluorinated saturated cyclic carbonate is a value calculated from the structural formula of the fluorinated saturated cyclic carbonate by {(number of fluorine atoms×19) / molecular weight of the fluorinated saturated cyclic carbonate}×100 (%).

[0066] Specific examples of the fluorinated saturated cyclic carbonate include the following.

[0067] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate wherein at least one of the groups is -F include: [Chemistry 2] These compounds have high withstand voltage and good solubility of electrolyte salts.

[0068] Among them, the fluorinated saturated cyclic carbonate is preferably any one of the following compounds.

[0069] [Chemistry 3] [Chemistry 4] Among these fluorinated saturated cyclic carbonates, more preferred are fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate, (3,3,3-trifluoropropylene carbonate), and 2,2,3,3,3-pentafluoropropylethylene carbonate.

[0070] The above-mentioned fluorinated cyclic carbonates may be used alone or in combination of two or more in any combination and ratio.

[0071] When the fluorinated cyclic carbonate is contained, the content of the fluorinated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and even more preferably 15 to 45% by volume relative to the solvent.

[0072] The aforementioned chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

[0073] Examples of the non-fluorinated chain carbonate include hydrocarbon chain carbonates such as CH3OCOOCH3 (dimethyl carbonate: DMC), CH3CH2OCOOCH2CH3 (diethyl carbonate: DEC), CH3CH2OCOOCH3 (ethyl methyl carbonate: EMC), CH3OCOOCH2CH2CH3 (methylpropyl carbonate), methyl butyl carbonate, ethylpropyl carbonate, ethyl butyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl isopropyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2-phenylphenyl carbonate, trans-2,3-pentylene carbonate, trans-2,3-butylene carbonate, and ethylphenyl carbonate. Among these, at least one selected from ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate is preferred.

[0074] The non-fluorinated chain carbonates may be used alone or in combination of two or more in any combination and ratio.

[0075] When the non-fluorinated chain carbonate is contained, the content of the non-fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 20 to 85% by volume, and even more preferably 30 to 80% by volume relative to the solvent.

[0076] The carboxylate ester may be a cyclic carboxylate ester or a chain carboxylate ester.

[0077] The cyclic carboxylate may be a non-fluorinated cyclic carboxylate or a fluorinated cyclic carboxylate.

[0078] Examples of the non-fluorinated cyclic carboxylic acid ester include non-fluorinated saturated cyclic carboxylic acid esters, and are preferably non-fluorinated saturated cyclic carboxylic acid esters having an alkylene group having 2 to 4 carbon atoms.

[0079] Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include: β -Propiolactone, c -Butyrolactone, e -caprolactone, -Valerolactone, α methyl- c Among them, from the viewpoint of improving the dissociation degree of lithium ions and improving the load characteristics, it is particularly preferred c -Butyrolactone, -valerolactone.

[0080] The above-mentioned non-fluorinated saturated cyclic carboxylic acid esters may be used alone or in combination of two or more in any combination and ratio.

[0081] When the non-fluorinated saturated cyclic carboxylic acid ester is contained, the content of the non-fluorinated saturated cyclic carboxylic acid ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, further preferably 1 to 60% by volume, particularly preferably 5 to 40% by volume, based on the solvent.

[0082] The chain carboxylate may be a non-fluorinated chain carboxylate or a fluorinated chain carboxylate. When the solvent contains the chain carboxylate, an increase in resistance of the electrolyte after high-temperature storage can be further suppressed.

[0083] The solvent preferably contains at least one selected from the group consisting of the cyclic carbonate, the chain carbonate, and the chain carboxylic acid ester. The cyclic carbonate is preferably a saturated cyclic carbonate.

[0084] The electrolyte solution containing the solvent of the above composition can further improve the high-temperature storage characteristics and cycle characteristics of the electrochemical device.

[0085] In the case where the above-mentioned solvent comprises the above-mentioned cyclic carbonate and at least one selected from the above-mentioned chain carbonate and the above-mentioned chain carboxylic acid ester, the above-mentioned cyclic carbonate and at least one selected from the above-mentioned chain carbonate and the above-mentioned chain carboxylic acid ester preferably comprise 10 to 100 volume %, more preferably comprise 30 to 100 volume %, further preferably comprise 50 to 100 volume %.

[0086] Under the situation that above-mentioned solvent comprises above-mentioned cyclic carbonate and at least 1 being selected from above-mentioned linear carbonate and above-mentioned linear carboxylic ester, as above-mentioned cyclic carbonate and at least 1 volume ratio being selected from above-mentioned linear carbonate and above-mentioned linear carboxylic ester, preferably 5 / 95~95 / 5, more preferably more than 10 / 90, further preferably more than 15 / 85, particularly preferably more than 20 / 80; More preferably below 90 / 10, further preferably below 60 / 40, particularly preferably below 50 / 50.

[0087] The solvent preferably further comprises at least one selected from the group consisting of the non-fluorinated saturated cyclic carbonate, the non-fluorinated chain carbonate, and the non-fluorinated chain carboxylic acid ester. The electrolyte solution containing the solvent of the above composition can be suitably used in electrochemical devices used at relatively low voltages.

[0088] In the case where the above-mentioned solvent comprises the above-mentioned non-fluorinated saturated cyclic carbonate and at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester, the above-mentioned non-fluorinated saturated cyclic carbonate and at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester preferably comprise 5 to 100 volume %, more preferably comprise 20 to 100 volume %, further preferably comprise 30 to 100 volume %.

[0089] In the case where the above-mentioned electrolyte comprises the above-mentioned non-fluorinated saturated cyclic carbonate and at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester, the volume ratio of the above-mentioned non-fluorinated saturated cyclic carbonate to at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester is preferably 5 / 95 to 95 / 5; more preferably 10 / 90 or more, further preferably 15 / 85 or more, particularly preferably 20 / 80 or more; more preferably 90 / 10 or less, further preferably 60 / 40 or less, particularly preferably 50 / 50 or less.

[0090] Above-mentioned solvent also preferably comprises at least one that is selected from above-mentioned fluorinated saturated cyclic carbonate, above-mentioned fluorinated chain carbonate and above-mentioned fluorinated chain carboxylic acid ester.The electrolytic solution that contains the solvent of above-mentioned composition not only can be suitably used in the electrochemical device that uses under lower voltage, also can be suitably used in the electrochemical device that uses under higher voltage.

[0091] The above-mentioned solvent is preferably a non-aqueous solvent, and the electrolyte of the present invention is preferably a non-aqueous electrolyte.

[0092] The content of the solvent in the electrolyte solution is preferably 70 to 99.999% by mass, more preferably 80% by mass or more, and more preferably 92% by mass or less.

[0093] The electrolyte solution of the present invention preferably further comprises an electrolyte salt (excluding the aforementioned compound (5)). As the electrolyte salt, in addition to alkali metal salts, ammonium salts, and metal salts other than alkali metal salts (e.g., light metal salts other than alkali metal salts), any salt that can be used in an electrolyte solution, such as a liquid salt (ionic liquid), an inorganic polymer salt, or an organic polymer salt, can be used.

[0094] Examples of electrolyte salts for electrochemical device electrolytes include the following compounds: MPF6, MBF4, MClO4, MAsF6, MB(C6H5)4, MCH3SO3, MCF3SO3, MAlCl4, M2SiF6, MCl, and MBr. (In the formula, M is at least one metal selected from Li, Na, and K, preferably one metal selected from Li, Na, and K, and more preferably Li or Na.) The use of these alkali metal salts can achieve excellent battery capacity, cycle characteristics, and storage characteristics. Among these, at least one selected from MPF6, MBF4, MClO4, and MAsF6 is preferred, with MPF6 being more preferred. Using these alkali metal salts can further reduce internal resistance, achieving even higher performance.

[0095] As the electrolyte salt of the electrolyte solution for lithium ion secondary batteries, a lithium salt is preferable.

[0096] As the lithium salt, any lithium salt can be used, and specifically, the following lithium salts can be mentioned. For example, LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, LiWF7, LiAsF6, LiAlCl4, LiI, LiBr, LiCl, LiB 10 Cl 10 , Li2SiF6, Li2PFO3, LiPO2F2 and other inorganic lithium salts; Lithium tungstates such as LiWOF5; Lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium salts having an S=O group, such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, lithium methyl sulfate, lithium ethyl sulfate (C2H5OSO3Li), and 2,2,2-trifluoroethyl lithium sulfate; Lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, bis(perfluoroethanesulfonyl imide) lithium, cyclic 1,2-perfluoroethanedisulfonyl imide lithium, cyclic 1,3-perfluoropropanedisulfonyl imide lithium, cyclic 1,2-ethanedisulfonyl imide lithium, cyclic 1,3-propanedisulfonyl imide lithium, cyclic 1,4-perfluorobutanedisulfonyl imide lithium, LiN(CF3SO2)(FSO2), LiN(CF3SO2)(C3F7SO2), LiN(CF3SO2)(C4F9SO2), and LiN(POF2)2; Lithium sulfamate compounds such as (CF3CH2)2NSO3Li, (CF3CH2)(CH3)NSO3Li, (CNCH2)2NSO3Li; Methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3; and Formula: LiPF a (C n F 2n＋1 ) 6-a (wherein a is an integer of 0 to 5, and n is an integer of 1 to 6) (for example, LiPF3(C2F5)3, LiPF3(CF3)3, LiPF3(iso-C3F7)3, LiPF5(iso-C3F7), LiPF4(CF3)2, LiPF4(C2F5)2), LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, etc., fluorine-containing organic lithium salts, LiSCN, LiB(CN)4, LiB(C6H5)4, Li2(C2O4), LiP(C2O4)3, Li2B 12 F b H 12-b (b is an integer from 0 to 3), etc.

[0097] Among them, from the viewpoint of having the effects of improving output characteristics, high-rate charge and discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanedisulfonyl imide lithium, cyclic 1,3-perfluoropropanedisulfonyl imide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. are particularly preferred, and the most preferred is at least one lithium salt selected from LiPF6, LiN(FSO2)2 and LiBF4.

[0098] These electrolyte salts can be used alone or in combination of two or more. When two or more are used in combination, preferred examples are the combination of LiPF6 and LiBF4, and the combination of LiPF6 and LiPO2F2, C2H5OSO3Li or FSO3Li, which have the effect of improving high-temperature storage characteristics, load characteristics, and cycle characteristics.

[0099] In this case, the amount of LiBF4, LiPO2F2, C2H5OSO3Li or FSO3Li contained in 100% by mass of the electrolyte as a whole is not limited and is arbitrary as long as the effects of the present invention are not significantly impaired. It is usually 0.01% by mass or more, preferably 0.1% by mass or more, and is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less, relative to the electrolyte of the present invention.

[0100] In addition, another example is the use of an inorganic lithium salt and an organic lithium salt, which has the effect of suppressing degradation caused by high-temperature storage. As an organic lithium salt, preferably CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanedisulfonyl imide lithium, cyclic 1,3-perfluoropropanedisulfonyl imide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. In this case, the ratio of the organic lithium salt to 100% by mass of the entire electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more; and preferably 30% by mass or less, particularly preferably 20% by mass or less.

[0101] The concentration of these electrolyte salts in the electrolyte is not particularly limited as long as it does not impair the effects of the present invention. From the perspective of keeping the conductivity of the electrolyte within a good range and ensuring good battery performance, the total molar concentration of lithium in the electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and even more preferably 0.5 mol / L or more; and preferably 3 mol / L or less, more preferably 2.5 mol / L or less, and even more preferably 2.0 mol / L or less.

[0102] If the total molar concentration of lithium is too low, the conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the viscosity may increase, resulting in a decrease in conductivity and a reduction in battery performance.

[0103] The electrolyte solution of the present invention may further contain a fluorinated saturated cyclic carbonate, an unsaturated cyclic carbonate, an overcharge preventer, and other known auxiliary agents as additives, thereby suppressing degradation of the characteristics of the electrochemical device.

[0104] The electrolyte of the present invention may further contain, as additives, ether compounds that are not fluoroethers represented by the above general formula (2), cyclic and chain carboxylates, nitrogen-containing compounds, boron-containing compounds, organic silicon-containing compounds, non-flammable (flame retardant) agents, surfactants, high dielectric additives, cycle characteristics and rate characteristics improvers, sulfone compounds, etc., within the range that does not impair the effects of the present invention.

[0105] As the ether compound, chain ethers having 2 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms are preferred.

[0106] Examples of the chain ether having 2 to 10 carbon atoms include dimethyl ether, diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol, diethylene glycol dimethyl ether, pentaethylene glycol, triethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol, tetraethylene glycol dimethyl ether, and diisopropyl ether.

[0107] Examples of cyclic ethers having 3 to 6 carbon atoms include 1,2-dioxane, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, trioxane, 2-methyl-1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-(trifluoroethyl)dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, and fluorinated compounds thereof. Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ethers are preferred due to their high solvating ability for lithium ions and improved ion dissociation. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred due to their low viscosity and high ion conductivity.

[0108] The electrolyte of the present invention preferably contains 5 to 200 ppm of hydrogen fluoride (HF). The inclusion of HF promotes film formation of the additive. If the HF content is too low, the ability to form a film on the negative electrode is reduced, and the characteristics of the electrochemical device tend to be reduced. In addition, if the HF content is too high, the oxidation resistance of the electrolyte tends to be reduced due to the influence of HF. Even if the electrolyte of the present invention contains HF within the above range, it does not reduce the high-temperature storage properties and capacity recovery rate of the electrochemical device.

[0109] The HF content is more preferably 10 ppm or more, further preferably 20 ppm or more. Furthermore, the HF content is more preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 50 ppm or less.

[0110] The HF content can be determined by neutralization titration.

[0111] The electrolyte solution of the present invention can be prepared by any method using the above-mentioned components.

[0112] The electrolyte solution of the present invention can be suitably used in electrochemical devices such as lithium ion secondary batteries, lithium ion capacitors, hybrid capacitors, and electric double layer capacitors. An electrochemical device including the electrolyte solution of the present invention is also one aspect of the present invention.

[0113] (Electrochemical Devices) The electrochemical device is not particularly limited and can be applied to conventionally known electrochemical devices. Specifically, the electrochemical device includes secondary batteries such as lithium-ion batteries, primary batteries such as lithium batteries, magnesium-ion batteries, free radical batteries, solar cells (particularly dye-sensitized solar cells), and fuel cells. Capacitors such as lithium-ion capacitors, hybrid capacitors, electrochemical capacitors, and electric double-layer capacitors; Various capacitors such as aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc. Electrochromic elements, electrochemical switching elements, various electrochemical sensors, etc.

[0114] Among them, since it has high capacity and high output, it can be suitably used also in secondary batteries in which a large volume change occurs due to the movement of a large amount of metal ions.

[0115] The secondary battery can have a known structure and typically comprises a positive electrode and a negative electrode capable of absorbing and releasing ions (eg, lithium ions), and the electrolyte of the present invention. A secondary battery comprising the electrolyte of the present invention is also one aspect of the present invention.

[0116] Hereinafter, a secondary battery including the electrolytic solution of the present invention will be described.

[0117] The present invention also relates to a lithium-ion secondary battery comprising the electrolyte of the present invention. The secondary battery preferably comprises a positive electrode, a negative electrode, and the electrolyte. A lithium-ion secondary battery comprising the electrolyte of the present invention is also one aspect of the present invention.

[0118] <Positive electrode> The positive electrode is preferably composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0119] As the above-mentioned positive electrode active material, there is no particular limitation as long as it is a substance that can electrochemically absorb and release alkali metal ions. For example, a substance containing an alkali metal and at least one transition metal is preferred. As specific examples, transition metal composite oxides containing alkali metals and transition metal phosphate compounds containing alkali metals can be mentioned. Among them, as the positive electrode active material, transition metal composite oxides containing alkali metals that generate high voltage are particularly preferred. As the above-mentioned alkali metal ions, lithium ions, sodium ions, potassium ions, etc. can be mentioned. In a preferred embodiment, the alkali metal ions can be lithium ions. That is, in this embodiment, the alkali metal ion secondary battery is a lithium ion secondary battery.

[0120] Examples of the alkali metal-containing transition metal composite oxide include Formula (3-1): MaMn 2-b M 1 b O4 (wherein, M is at least one metal selected from Li, Na and K; 0.9≤a; 0≤b≤1.5; M 1 A lithium-manganese spinel composite oxide represented by at least one metal selected from Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge); Formula (3-2): MNi 1-c M 2c O2 (wherein, M is at least one metal selected from Li, Na and K; 0≤c≤0.5; M 2 a lithium-nickel composite oxide represented by at least one metal selected from Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge); or Formula (3-3): MCo 1-d M 3 d O2 (wherein, M is at least one metal selected from Li, Na and K; 0≤d≤0.5; M 3 A lithium-cobalt composite oxide represented by at least one metal selected from Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge). Among the above, M is preferably a metal selected from Li, Na, and K, more preferably Li or Na, and even more preferably Li.

[0121] Among them, MCoO2, MMnO2, MNiO2, MMn2O4, MNiO2, and MMn2O4 are preferred from the viewpoint of providing a secondary battery with high energy density and high output. 0.8 Co 0.15 Al 0.05 O2, or MNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., preferably a compound represented by the following formula (3-4).

[0122] MNi h Co i Mn j M 5 k O2 (3-4) (wherein, M is at least one metal selected from Li, Na and K, M 5 represents at least one selected from the group consisting of Fe, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge, (h+i+j+k)=1.0, 0≤h≤1.0, 0≤i≤1.0, 0≤j≤1.5, and 0≤k≤0.2. Examples of materials for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, nickel, or their alloys; and carbon materials such as carbon cloth and carbon paper. Among these, metals are preferred, and aluminum or its alloys are particularly preferred.

[0123] The positive electrode can be manufactured according to conventional methods. For example, a method of adding a binder, a thickener, a conductive material, a solvent, etc. to the above-mentioned positive electrode active material to prepare a slurry of positive electrode mixture, applying the slurry on a current collector, and pressing after drying to achieve high density can be cited.

[0124] The density increase can be achieved by hand pressing, roller pressing, etc. The density of the positive electrode active material layer is preferably 1.5 g / cm 3 More than 2 g / cm 3 More preferably, 2.2 g / cm 3 More than, and preferably 5g / cm 3 Below, more preferably 4.5g / cm 3 Below, more preferably 4g / cm 3 If the value exceeds this range, the electrolyte permeability near the current collector / active material interface decreases, and the charge and discharge characteristics at high current density are particularly degraded, sometimes preventing high output. If the value falls below this range, the conductivity between the active materials decreases, the battery resistance increases, and sometimes preventing high output.

[0125] <Negative electrode> The negative electrode is preferably composed of a negative electrode active material layer and a current collector.

[0126] (Negative electrode active material) The negative electrode active material is not particularly limited, and examples thereof include materials selected from carbonaceous materials such as lithium metal, artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolysis vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon, silicon-containing compounds such as silicon and silicon alloys, Li4Ti5O 12 Among them, substances containing at least a portion of a carbonaceous material and silicon-containing compounds can be particularly preferably used.

[0127] The negative electrode active material layer can be prepared, for example, by mixing a binder and a solvent, then adding the negative electrode active material to the resulting mixture and further mixing, thereby preparing a slurry-like negative electrode mixture. The resulting negative electrode mixture is then evenly coated onto a current collector such as metal foil or metal mesh, dried, and pressed as needed to form a thin negative electrode active material layer on the current collector, thereby producing a thin film electrode. Alternatively, the negative electrode mixture can be prepared by first mixing the negative electrode active material and the binder, and then adding the solvent.

[0128] Examples of the current collector included in the negative electrode of the present invention include metal foils such as iron, stainless steel, copper, aluminum, nickel, and titanium, and carbon materials such as metal mesh, carbon cloth, and carbon paper. Among them, copper foil is preferred.

[0129] The negative electrode of the present invention can be suitably produced by applying the negative electrode mixture of the present invention to a current collector. After the negative electrode mixture is applied, the coating can be dried, optionally heat-treated, and the resulting dried coating can be pressed.

[0130] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, porous metal mesh, stamped metal, foamed metal, etc. can be mentioned, and in the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be mentioned. Among them, metal foil is preferred. It should be noted that the film can be formed into a mesh shape as appropriate. The thickness of the film is arbitrary, usually 1 m m or more, preferably 3 m m or more, more preferably 5 m m or more; and, usually 1 mm or less, preferably 100 m m or less, more preferably 50 m If the film is thinner than this range, the strength required as a current collector may be insufficient. On the other hand, if the film is thicker than this range, the handling properties may be impaired.

[0131] <Isolator> The secondary battery of the present invention preferably further includes a separator.

[0132] The material and shape of the separator are not particularly limited as long as they are stable in the electrolyte and have excellent liquid retention. Known materials and shapes can be used. Preferred separators are those made of materials that are stable in the electrolyte of the present invention, such as resins, glass fibers, inorganic materials, etc., and have excellent liquid retention, such as porous sheets or nonwoven fabrics.

[0133] Materials for the resin and glass fiber separators include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. Polypropylene / polyethylene double-layer membranes and polypropylene / polyethylene / polypropylene triple-layer membranes can be used alone or in any combination and ratio. For excellent electrolyte permeability and shutdown effects, the separators are preferably porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene.

[0134] The thickness of the spacer is arbitrary, usually 1 m m or more, preferably 5 m m or more, more preferably 8 m m or more; and, usually 50 m m or less, preferably 40 m m or less, more preferably 30 m If the separator is too thin outside the above range, the insulation or mechanical strength may be reduced. If it is too thick outside the above range, not only may the battery performance such as rate characteristics be reduced, but the energy density of the electrolyte battery as a whole may also be reduced.

[0135] Battery Design The electrode assembly may be either a stacked structure formed by sandwiching the aforementioned positive and negative plates with the aforementioned separator, or a spirally wound structure formed by sandwiching the aforementioned separator with the aforementioned positive and negative plates. The ratio of the volume of the electrode assembly to the internal volume of the battery (hereinafter referred to as the electrode assembly occupancy ratio) is typically 40% or greater, preferably 50% or greater, and typically 90% or less, preferably 80% or less.

[0136] The material of the outer casing is not particularly limited as long as it is stable with the electrolyte used. Specifically, metals such as nickel-plated steel, stainless steel, aluminum, aluminum alloys, and magnesium alloys, or laminated films of resin and aluminum foil can be used. For lightweighting purposes, aluminum or aluminum alloys and laminated films are preferably used.

[0137] The secondary battery of the present invention may have any shape, including cylindrical, rectangular, laminated, coin, and large shapes. The shape and configuration of the positive electrode, negative electrode, and separator may be varied depending on the shape of the battery.

[0138] Example Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[0139] In the following examples, unless otherwise specified, "parts" and "%" represent "parts by weight" and "% by weight", respectively.

[0140] The compounds (1-1) to (1-5) used are shown below.

[0141] (1-1) CF2HCF2CH2OLi (1-2) CF2HCF2CF2CF2CH2OLi (1-3) CF2HCF2OLi (1-4) CF3CHFCF2OLi (1-5) CF3CF2CH2OLi The compounds (2-1) to (2-3) used are shown below.

[0142] (2-1) CF2HCF2CH2OCF2CF2H (2-2) CF2HCF2CH2OCF2CHFCF3 (2-3) CF3CF2CH2OCF2CF2H (Example 1) [Preparation of electrolyte] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3 / 7, and LiPF 6 was added to the mixture at a concentration of 1.0 mol / L to prepare a basic electrolyte solution.

[0143] 0.001 ppm of compound (1-1) was added to the above-mentioned basic electrolyte solution and mixed to prepare a non-aqueous electrolyte solution.

[0144] [Production of positive electrode] 97 parts by mass of LiCoO2 as a positive electrode active material, 1.5 parts by mass of acetylene black as a conductive additive, and 1.5 parts by mass of polyvinylidene fluoride (8% by mass NMP solution) as a binder were added and mixed using a disperser to form a slurry. The obtained slurry was applied to a 20 mm thick sheet. m m aluminum foil was dried, rolled using a press, and then cut into a shape having a coated portion (positive electrode material layer) of 50 mm wide and 30 mm long and an uncoated portion of 5 mm wide and 9 mm long to prepare a positive electrode.

[0145] [Production of negative electrode] Silicon oxide powder (SiO) as the negative electrode active material was mixed with 94% by mass of graphite (mass ratio 10 / 90) and 6% by mass of polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) was added and mixed to form a slurry. The obtained slurry was applied to a 15 mm thick plate. m A negative electrode current collector made of a 1000-μm copper foil was prepared and dried, cut into a predetermined electrode size, and rolled using a roll press to produce a negative electrode having a negative electrode material layer formed on the negative electrode current collector.

[0146] [Battery Production] The negative electrode having the negative electrode material layer on one side was cut into a shape having a coated portion (negative electrode material layer) of 52 mm wide and 32 mm long and an uncoated portion of 5 mm wide and 9 mm long to prepare a negative electrode.

[0147] The positive electrode and the negative electrode are separated by a thickness of 20 mm microporous polyethylene film (separator) is placed to make the positive electrode and the negative electrode face each other, and the non-aqueous electrolyte obtained above is injected. After the non-aqueous electrolyte is fully impregnated into the separator, etc., it is sealed and pre-charged and aged to produce an aluminum laminate battery (lithium ion secondary battery).

[0148] (Measurement of battery characteristics) [Cycle characteristics] The obtained aluminum laminate battery was subjected to constant current-constant voltage charging (hereinafter referred to as CC / CV charging) at 60°C with a current equivalent to 0.2C (0.1C cut-off) to 4.2V, then discharged at a constant current of 0.2C to 2.5V, with this being considered one cycle, and three cycles were performed. Subsequently, at 45°C, CC / CV charging was performed with a current equivalent to 1.0C (0.1C cut-off) to 4.2V, followed by discharge at a constant current of 1.0C to 2.5V, with this being considered one cycle. The initial discharge capacity was determined from the discharge capacity. The cycle was repeated again, and the discharge capacity after 500 cycles was measured. The ratio of the discharge capacity after 500 cycles to the initial discharge capacity was determined and used as the capacity retention rate (%).

[0149] Capacity retention (%) = (discharge capacity after 500 cycles) ÷ (initial discharge capacity at 1.0C) × 100 The results are expressed as relative values with the result of Comparative Example 1 being set to 1.

[0150] [Resistance rise rate] The battery was charged to 50% SOC and then discharged at 1, 3, and 5C rates. The voltage drop (V) was measured. The resistance value was calculated from the slope of the obtained voltage and current values using the equation V = IR. The resistance values were measured before and after the cycle, and the resistance increase rate was calculated as {resistance value after 500 cycles ÷ resistance value before the cycle}.

[0151] The relative values are shown in Table 1 or Table 2, with the value of Comparative Example 1 or the value of Comparative Example 2 being set to 1.

[0152] The above SOC represents the state of charge, and SOC100% is the capacity when the battery is charged to 4.2 V. For example, SOC50% represents half the capacity of SOC100%.

[0153] (Determination of Metal Precipitation Amount) [Co content] After 500 cycles, the aluminum laminate battery was disassembled, the negative electrode was removed, and immersed in a 5% by mass nitric acid aqueous solution for 24 hours. After 24 hours, the filtrate was filtered and the Co content was calculated by ICP emission spectroscopy.

[0154] (Examples 2 to 25) As shown in Table 1, a non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the type and amount of the electrolyte additives were changed. Furthermore, a battery was fabricated and various evaluations were performed.

[0155] The results are shown in Table 1.

[0156] (Comparative Example 1) A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that no additive was used, and a battery was fabricated and various evaluations were performed.

[0157] The results are shown in Table 1.

[0158] [Table 1] (Examples 26 to 29) Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 2 / 98, and LiN(FSO2)2 (LiFSI) was added to the mixture at a concentration of 1.0 mol / L to prepare a basic electrolyte solution.

[0159] As shown in Table 2, the non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the type and amount of the electrolyte additives were changed. In addition, LiNi 0.6 Mn 0.2 Co 0.2 A battery was produced in the same manner as in Example 1 except that O 2 (NMC622) was used as the positive electrode active material, and the above-mentioned battery characteristics and the following evaluation of the amount of metal deposition were performed.

[0160] The results are shown in Table 2.

[0161] (Determination of Metal Precipitation Amount) [Mn content] After 500 cycles, the aluminum laminate battery was disassembled, the negative electrode was removed, and immersed in a 5% by mass nitric acid aqueous solution for 24 hours. After 24 hours, the filtrate was filtered and the Mn content was calculated by ICP emission spectroscopy.

[0162] (Comparative Example 2) A non-aqueous electrolyte was prepared in the same manner as in Example 26 except that no additive was used, and a battery was fabricated and various evaluations were performed.

[0163] The results are shown in Table 2.

[0164] [Table 2] From the Examples in Tables 1 and 2, it can be seen that the use of the electrolyte solutions obtained in the Examples improves the cycle characteristics of the secondary battery and reduces the resistance increase rate.

[0165] Industrial Applicability Electrochemical devices such as secondary batteries using the electrolyte solution of the present invention can be used as various power sources such as mobile power sources and automobile power sources.

Claims

1. An electrolyte, characterized in that: Contains at least one compound represented by the following general formula (1): Rf 1 OLi (1) In formula (1), Rf 1 It is a fluorinated alkyl group having 1 to 5 carbon atoms.

2. The electrolyte according to claim 1, wherein The Rf of the compound represented by the general formula (1) 1 is any one of the following formulas (1a) to (1e): (1a) CF2HCF2 (1b) CF2HCF2CH2 (1c) CF3CHFCF2 (1d) CF3CF2CH2 (1e)CF2HCF2CF2CF2CH2.

3. The electrolyte according to claim 1 or 2, wherein The content of the compound represented by the general formula (1) is 0.0001 to 500 ppm based on the entire electrolyte solution.

4. The electrolyte according to any one of claims 1 to 3, wherein The electrolyte further comprises a compound represented by the following general formula (2): Rf 2 ORf 3 (2) In formula (2), Rf 2 、Rf 3 Each is independently a fluorinated alkyl group having 1 to 8 carbon atoms.

5. The electrolyte according to claim 4, wherein The compound represented by the general formula (2) is at least one selected from the group consisting of CF2HCF2CH2OCF2CF2H, CF2HCF2CH2OCF2CHFCF3 and CF3CF2CH2OCF2CF2H.

6. The electrolyte according to claim 4 or 5, wherein The content of the compound represented by the general formula (2) is 0.01 to 80% by mass based on the entire electrolyte solution.

7. The electrolyte according to any one of claims 4 to 6, wherein The content of the compound represented by the general formula (1) is 0.00000001 to 11% by mass relative to the compound represented by the general formula (2).

8. The electrolyte according to any one of claims 4 to 7, wherein The content of the compound represented by the general formula (2) is 0.1 to 75% by mass relative to the entire electrolyte solution, and the content of the compound represented by the general formula (1) is 0.000025 to 0.35% by mass relative to the compound represented by the general formula (2).

9. The electrolyte solution according to any one of claims 1 to 8, wherein The compound represented by the general formula (1) is CF2HCF2CH2OLi.

10. The electrolyte solution according to any one of claims 4 to 9, wherein The compound represented by the general formula (2) is CF2HCF2CH2OCF2CF2H.

11. An electrochemical device, characterized in that: The electrolyte solution according to any one of claims 1 to 10 is provided.

12. A secondary battery, characterized in that: The electrolyte solution according to any one of claims 1 to 10 is provided.

13. A lithium ion secondary battery, characterized in that: The electrolyte solution according to any one of claims 1 to 10 is provided.

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