WO2023026476A1 - Electrolyte solution for alkali metal secondary batteries, and alkali metal secondary battery - Google Patents

Electrolyte solution for alkali metal secondary batteries, and alkali metal secondary battery Download PDF

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WO2023026476A1
WO2023026476A1 PCT/JP2021/031540 JP2021031540W WO2023026476A1 WO 2023026476 A1 WO2023026476 A1 WO 2023026476A1 JP 2021031540 W JP2021031540 W JP 2021031540W WO 2023026476 A1 WO2023026476 A1 WO 2023026476A1
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alkali metal
electrolytic solution
alkaline earth
salt
secondary battery
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PCT/JP2021/031540
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French (fr)
Japanese (ja)
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哲 市坪
弘毅 李
将来 村山
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国立大学法人東北大学
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Publication of WO2023026476A1 publication Critical patent/WO2023026476A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/24—Alkaline accumulators
    • H01M10/26—Selection of materials as electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an electrolyte solution for alkali metal secondary batteries and an alkali metal secondary battery.
  • Lithium-ion secondary batteries are used as power sources for electronic devices such as smartphones and personal computers. Carbon materials such as graphite are widely used as negative electrode materials in lithium ion secondary batteries. The carbon material absorbs lithium ions during charging and releases them during discharging.
  • Non-Patent Document 1 As a method of suppressing the formation of dendrites, adding a predetermined salt to the electrolyte is being considered. For example, adding a magnesium salt to the electrolytic solution (Non-Patent Document 1) and adding a cesium salt or a rubidium salt to the electrolytic solution (Non-Patent Document 2) are being considered.
  • An object of the present invention is to provide a novel electrolyte solution for an alkali metal secondary battery that can suppress the generation of dendrites in an alkali metal secondary battery using an alkali metal such as lithium metal as a negative electrode material, and the electrolyte solution.
  • the present inventors have found that the surface of the negative electrode current collector of an alkali metal secondary battery is Alkali metal is deposited evenly on the surface, and the occurrence of dendrites is reduced, and the present invention has been completed. Accordingly, the present invention has the following aspects.
  • An electrolytic solution for an alkali metal secondary battery comprising a non-aqueous solvent, an alkali metal salt dissolved in the non-aqueous solvent, and an alkaline earth metal salt dissolved in the non-aqueous solvent.
  • the alkaline earth metal salt is an alkaline earth metal hexafluorophosphate, an alkaline earth metal perchlorate, an alkaline earth metal tetrafluoroborate, an alkaline earth metal trifluoromethanesulfonate, at least one salt selected from the group consisting of bis(trifluoromethylsulfonyl)imide alkaline earth metal salts, bis(trifluoromethylsulfonyl)amide alkaline earth metal salts, and bis(fluorosulfonyl)amide alkaline earth metal salts;
  • the electrolytic solution for an alkali metal secondary battery according to the above [1] or [2].
  • the alkali metal salt is an alkali metal hexafluorophosphate, an alkali metal perchlorate, an alkali metal tetrafluoroborate, an alkali metal trifluoromethanesulfonate, or an alkali metal bis(trifluoromethylsulfonyl)imide.
  • Salt bis(trifluoromethylsulfonyl)amide alkali metal salt, bis(fluorosulfonyl)amide alkali metal salt, which is at least one salt selected from the group consisting of [1] to [3] above alkali metal Electrolyte for secondary batteries.
  • an alkali metal secondary battery using an alkali metal such as lithium metal as a negative electrode material a novel electrolyte solution for an alkali metal secondary battery capable of suppressing the generation of dendrites, and the electrolyte solution It is possible to provide an alkali metal secondary battery using an alkali metal such as lithium metal as a negative electrode material.
  • FIG. 1 is a cross-sectional view of an alkali metal secondary battery according to one embodiment of the present invention
  • FIG. 2 shows Raman spectra of electrolyte solutions of Example 1 and Comparative Examples 1 and 3.
  • FIG. 2 shows Raman spectra of electrolyte solutions of Example 2 and Comparative Examples 2 and 3.
  • FIG. 2 is a cross-sectional view of a three-electrode cell used in the electrodeposition test of Examples. 1 shows the results of an electrodeposition test using the electrolytic solution of Example 1, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode.
  • 1 is a SEM photograph of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 1, where (a) is a plane photograph of the electrodeposit and (b) is a cross-sectional photograph of the electrodeposit. . It is the analysis result of Ca, F, and S by EDX of the cross section of the electrodeposit shown in FIG.9(b).
  • 1 is a SEM photograph of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 2, where (a) is a plane photograph of the electrodeposit, and (b) is a cross-sectional photograph of the electrodeposit. .
  • Fig. 11(b) shows the analysis results of Na, Ca, F, and S of the cross section of the electrodeposit by EDX.
  • FIG. 11(b) shows the analysis results of Na, Ca, F, and S of the cross section of the electrodeposit by EDX.
  • FIG. 3 is a cross-sectional view of a three-electrode cell used in cyclic voltammetry measurements in Examples.
  • 14(a) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Example 1
  • FIG. 14(b) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Comparative Example 1.
  • It is a voltammogram.
  • 15(a) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Example 2
  • FIG. 15(b) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Comparative Example 2.
  • FIG. 4 shows the results of a charge/discharge test of the coin-shaped half-cells obtained in Example 3 and Comparative Example 4.
  • FIG. Fig. 4 shows the results of an electrodeposition test using the electrolytic solution of Example 4, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode.
  • 4 is a SEM photograph of a plane of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 4.
  • FIG. 4 is a cyclic voltammogram of a three-electrode cell using the electrolytic solution of Example 4.
  • FIG. 1 is a cross-sectional view of an alkali metal secondary battery according to one embodiment of the present invention.
  • Alkali metal secondary battery 10 shown in FIG. The cathode 13 includes a cathode material layer 14 and a cathode current collector 15 .
  • Negative electrode 16 includes a negative electrode material layer 17 and a negative electrode current collector 18 .
  • electrons flow from the negative electrode 16 to the positive electrode 13 through the external circuit 19 , releasing alkali metal ions in the negative electrode material layer 17 into the electrolytic solution 12 .
  • the electrolytic solution 12 contains a nonaqueous solvent, an alkali metal salt, and an alkaline earth metal salt.
  • Alkaline earth metal salts include calcium salts, strontium salts and barium salts.
  • the alkali metal salt and alkaline earth metal salt are dissolved in a non-aqueous solvent.
  • Chain ethers, cyclic ethers, cyclic carbonates, chain carbonates, lactones, nitriles, sulfolane and the like can be used as non-aqueous solvents.
  • Glycol ethers can be used as chain ethers.
  • Glycol ethers are preferably symmetrical glycol ethers in which both terminal hydroxyl groups are substituted with the same substituents.
  • the substituent is preferably an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group and butyl group.
  • glycol ethers examples include monoglyme [ethylene glycol dimethyl ether], ethyl monoglyme [ethylene glycol diethyl ether], butyl monoglyme [ethylene glycol dibutyl ether], methyl diglyme [diethylene glycol dimethyl ether], ethyl diglyme [diethylene glycol diethyl ether].
  • Cyclic ethers include, for example, tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxofuran, 1,4-dioxane, 4-methyl-1,3-dioxolane, and 2-methyl-1,3-dioxolane. be able to.
  • THF tetrahydrofuran
  • 2-methyltetrahydrofuran 1,3-dioxofuran
  • 1,4-dioxane 1,4-dioxane
  • 4-methyl-1,3-dioxolane 4-methyl-1,3-dioxolane
  • 2-methyl-1,3-dioxolane 2-methyl-1,3-dioxolane.
  • cyclic carbonate ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate can be used.
  • chain carbonates dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, and dipropyl carbonate can be used.
  • lactone ⁇ -butyrolactone can be used.
  • Acetonitrile can be used as nitrile.
  • One of these nonaqueous solvents may be used alone, or two or more thereof may be used in combination. Also, in the non-aqueous solvent, some or all of the hydrogen atoms may be substituted with fluorine.
  • the alkali metal of the alkali metal salt contained in the electrolytic solution 12 may be the same as that of the negative electrode material layer 17 .
  • the alkali metal salt may include at least one of lithium metal salt and sodium metal salt.
  • lithium metal salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4 ) , lithium trifluoromethanesulfonate ( LiCF3SO3 ), bis Lithium (trifluoromethylsulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), Lithium bis(trifluoromethylsulfonyl)amide [Li(TFSA)], Lithium bis(fluorosulfonyl)amide [Li(FSA)] be able to.
  • LiPF6 lithium hexafluorophosphate
  • LiClO4 lithium perchlorate
  • LiBF4 lithium tetra
  • sodium metal salts include sodium hexafluorophosphate (NaPF 6 ), sodium perchlorate (NaClO 4 ), sodium tetrafluoroborate (NaBF 4 ), sodium trifluoromethanesulfonate (NaCF 3 SO 3 ).
  • sodium bis(trifluoromethylsulfonyl)imide NaNC2F6S2O4
  • sodium bis(trifluoromethylsulfonyl)amide [Na( TFSA )]
  • sodium bis(fluorosulfonyl ) amide [Na(FSA)] can be mentioned.
  • Examples of calcium salts contained in the electrolytic solution 12 include calcium hexafluorophosphate (Ca(PF 6 ) 2 ), calcium perchlorate (Ca(ClO 4 ) 2 ), calcium tetrafluoroborate (Ca(BF 4 ) 2 ), calcium trifluoromethanesulfonate (Ca( CF3SO3 ) 2 ) , calcium bis (trifluoromethylsulfonyl)imide (CaN( C2F6S2O4 ) 2 ) , calcium bis (trifluoromethylsulfonyl) Amide [Ca(TFSA) 2 ], calcium bis(fluorosulfonyl)amide [Ca(FSA) 2 ] may be mentioned.
  • Ca(PF 6 ) 2 calcium perchlorate
  • Ca(BF 4 ) 2 calcium tetrafluoroborate
  • Ca(BF 4 ) 2 calcium trifluoromethanesulfonate
  • the anion of the alkali metal salt and the anion of the calcium salt may be the same.
  • barium salts include barium hexafluorophosphate (Ba(PF 6 ) 2 ), barium perchlorate (Ba(ClO 4 ) 2 ), barium tetrafluoroborate (Ba(BF 4 ) 2 ), barium trifluoromethanesulfonate (Ba( CF3SO3 ) 2 ) , barium bis (trifluoromethylsulfonyl)imide ( Ba( NC2F6S2O4 ) 2 ) , barium bis(trifluoromethylsulfonyl)amide [ Ba(TFSA) 2 ], barium bis(fluorosulfonyl)amide [Ba(FSA) 2 ].
  • the anion of the alkali metal salt and the anion of the barium salt may be the same.
  • the concentration of the alkali metal salt contained in the electrolytic solution 12 may be in the range of 0.1 mol/L or more and 4.0 mol/L or less.
  • the concentration of the alkaline earth metal salt may be in the range of 0.1 mol/L or more and 4.0 mol/L or less.
  • the total concentration of the alkali metal salt and alkaline earth metal salt may be in the range of 0.2 mol/L or more and 5.0 mol/L or less.
  • the ratio of the alkali metal salt and the alkaline earth metal salt may be such that the amount of the alkaline earth metal salt per 1 mol of the alkali metal salt is in the range of 0.1 mol or more and 10 mol or less.
  • the positive electrode material layer 14 may contain a positive electrode active material, a conductive aid, and a binder.
  • a positive electrode active material is a material capable of intercalating and deintercalating alkali metal ions.
  • positive electrode active materials include layered oxides, spinel-type oxides, olivine-type phosphates, and silicates.
  • Examples of spinel-type oxides include MaMn 2 O 4 and Ma(Ni 0.5 Mn 1.5 )O 4 (Ma represents an alkali metal).
  • olivine-type phosphates examples include MaFePO 4 , MaMnPO 4 , MaNiPO 4 , MaCuPO 4 (Ma represents an alkali metal).
  • silicates examples include Ma 2 FeSiO 4 and Ma 2 MnSiO 4 (Ma represents an alkali metal).
  • a metal oxide containing no alkali metal such as V 2 O 5 or MnO 3
  • a single phase of sulfur or selenium, or a compound containing sulfur or selenium can be used. can.
  • a known conductive material that is used as a conductive aid for the positive electrode material layer of alkali metal secondary batteries such as carbon powder and metal fine powder
  • Carbon black such as acetylene black and ketjen black
  • the binder for example, a thermoplastic fluororesin such as polyvinylidene fluoride (PVDF), glass, or a known material used as a binder for the positive electrode material layer of an alkali metal secondary battery such as polyimide may be used. can be done.
  • the contents of the positive electrode active material, conductive material, and binder in the positive electrode material layer 14 are not particularly limited, but the content of the positive electrode active material is preferably in the range of 80% by mass or more and 98% by mass or less.
  • the content of the conductive material is preferably in the range of 1% by mass or more and 19% by mass or less, and the content of the binder is preferably in the range of 1% by mass or more and 19% by mass or less.
  • the material of the positive electrode current collector 15 is not particularly limited as long as it has conductivity.
  • materials that can be used for the positive electrode current collector 15 include aluminum, copper, platinum, carbon materials, molybdenum, and tungsten.
  • Examples of the shape of the positive electrode current collector 15 include plate-like, ribbon-like, foil-like, and wire-like shapes, but are not limited to these shapes.
  • the negative electrode material layer 17 contains an alkali metal.
  • the alkali metal may be at least one of lithium and sodium.
  • the negative electrode material layer 17 may be an alkali metal simple substance, or may be an alloy containing an alkali metal other than the alkali metal.
  • lithium alloys include Li--Al alloys, Li--Sn alloys, Li--Zn alloys, Li--Ag alloys, Li--In alloys, Li--Ge alloys, Li--Pb alloys and Li--Si alloys.
  • Examples of sodium alloys include Na--Pb alloys, Na--Sn alloys, and Na--Ge.
  • a metal that forms an alloy with an alkali metal may be used as the negative electrode material layer 17 .
  • Metals that form alloys with lithium include aluminum, tin, zinc, silver, indium, germanium, lead, and silicon. Examples of metals that form alloys with sodium include lead, tin, and germanium.
  • a metal forming an alloy with an alkali metal is used for the negative electrode material layer 17, a compound containing an alkali metal is used as the positive electrode active material.
  • the negative electrode current collector 18 is not particularly limited as long as it has conductivity. Examples of materials that can be used for the negative electrode current collector 18 include copper, platinum, carbon materials, molybdenum, and tungsten. Further, the negative electrode current collector 18 and the negative electrode material layer 17 may be integrated. Examples of the shape of the negative electrode current collector 18 include plate-like, ribbon-like, foil-like, and wire-like shapes, but are not limited to these shapes.
  • a separator may be placed between the positive electrode 13 and the negative electrode 16 .
  • a porous body such as a porous film, porous glass, or glass mesh may be used as the separator.
  • the shape of the alkali metal secondary battery 10 is not particularly limited, and may be a known shape adopted as the shape of an alkali metal secondary battery, such as a coin shape, a button shape, a sheet shape, a cylinder shape, a square shape, or the like. can be done.
  • the electrolytic solution 12 contains a non-aqueous solvent, and an alkali metal salt and an alkaline earth metal salt dissolved in the non-aqueous solvent. Therefore, the generation of dendrites in the negative electrode material layer 17 is suppressed. Therefore, the alkali metal secondary battery 10 can be stably used for a long period of time with a high capacity.
  • the electrolytic solution 12 can be advantageously used as an electrolytic solution for alkali metal secondary batteries.
  • Li(TFSA) lithium bis(trifluoromethylsulfonyl)amide
  • Ca(TFSA) 2 calcium bis(trifluoromethylsulfonyl)amide
  • Example 2 Na(TFSA)[sodium bis(trifluoromethylsulfonyl)amide] and Ca(TFSA) 2 were added to G3 and mixed to obtain a Na(TFSA) concentration of 0.5 mol/L and Ca(TFSA) An electrolytic solution having a concentration of 0.5 mol/L was prepared.
  • Li(TFSA) was added to G3 and mixed to prepare an electrolytic solution having a Li(TFSA) concentration of 0.5 mol/L.
  • the Raman spectrum of the electrolytic solution of Comparative Example 2 containing only Na (TFSA) shows a peak with a Raman shift of 870 nm ⁇ 1 derived from the bond between Na and G3.
  • a peak derived from the bond between Na and G3 and a peak derived from the bond between Ca and G3 were observed. shifted to the high frequency side.
  • the electrolytic solution of Example 2 like the electrolytic solution of Example 1, also differs from the electrolytic solution of Comparative Example 2 in the structure of solvation formed by Na, and furthermore, the structure of solvation formed by Ca is different from that of the electrolytic solution of Comparative Example 2. It is considered that the electrolytic solution of Comparative Example 3 is different.
  • FIG. 4 shows a cross-sectional view of the three-electrode cell used in the electrodeposition test.
  • the three-electrode cell 20 shown in FIG. 4 has a working electrode 31 , a counter electrode 32 and a reference electrode 33 .
  • the three-electrode cell 20 includes a first substrate 21, a second substrate 22 having a conical through hole 22a, a third substrate 23 having a through hole 23a, and a hollow container 24 having a flange portion 24a at the bottom. and a lid 25 of the container 24 .
  • the diameter of the through hole 23 a is larger than the outer diameter of the container 24 and smaller than the diameter of the flange portion 24 a of the container 24 .
  • the maximum diameter of the conical through-hole 22 a is smaller than the inner diameter of the container 24 .
  • the first substrate 21 , the second substrate 22 and the third substrate 23 are joined by bolts 26 .
  • the working electrode 31 is arranged between the first substrate 21 and the second substrate 22 .
  • the counter electrode 32 is supported by a counter electrode support member 34 fixed to the lid 25 of the container 24
  • the reference electrode 33 is supported by a reference electrode support member 35 fixed to the lid 25 of the container 24 .
  • An O-ring 27 is arranged between the working electrode 31 and the second substrate.
  • An O-ring 28 is arranged between the second substrate and the flange portion 24 a of the container 24 .
  • the diameter of the through hole 22a of the second substrate 22 on the side of the working electrode 31 was 1.13 cm (opening area 1 cm 2 ).
  • a copper foil was used for the working electrode 31 .
  • lithium is used when the sample electrolyte solution is prepared in Example 1 and Comparative Example 1, and sodium is used when it is prepared in Example 2 and Comparative Example 2.
  • calcium was used.
  • the electrodeposition test was conducted as follows. First, the electrolytic solution 12 of the sample was stored in the container 24 and the through hole 22a of the second substrate, the container 24 was covered, and the working electrode 31, the counter electrode 32, and the reference electrode 33 were brought into contact with the electrolytic solution 12. . Next, a voltage of 0.5 V was applied to the working electrode 31 with respect to the reference electrode 33, and electrodeposition was carried out until the charge amount of the reduction reaction reached 5 mAh.
  • FIG. 5 The results of the electrodeposition test using the electrolyte of Example 1 are shown in FIG. 5, and the results of the electrodeposition test using the electrolyte of Comparative Example 1 are shown in FIG. 5 and 6, (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. Comparing FIG. 5(a) with FIG. 6(a), the electrolytic solution in FIG. I know it's less. 5(b) and FIG. 6(b), the metal layer electrodeposited on the surface of the working electrode in FIG. 5(b) was electrodeposited on the surface of the working electrode in FIG. 6(b). Compared with the metal layer, the particle shape of the precipitated metal is more uniform, and the mixed amount of coarse metal particles is small.
  • FIG. 7 The results of the electrodeposition test using the electrolyte of Example 2 are shown in FIG. 7, and the results of the electrodeposition test using the electrolyte of Comparative Example 2 are shown in FIG. 7 and 8, (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. Comparing FIG. 7(a) and FIG. 8(a), the electrolytic solution in FIG. I know it's less. Further, when comparing FIG. 7(b) and FIG. 8(b), the deposited metal adheres to the surface of the working electrode in FIG. 7(b), whereas the action in FIG. It can be seen that almost no metal particles adhere to the surface of the pole.
  • FIG. 9 is a SEM photograph of the electrodeposit obtained in the electrodeposition test using the electrolytic solution of Example 1.
  • (a) is a plane photograph of the electrodeposit
  • (b) is a photograph of the electrodeposit. It is a cross-sectional photograph.
  • FIG. 10 shows the results of Ca, F, and S analysis by EDX of the cross section of the electrodeposit shown in FIG. 9(b). From the SEM photograph of FIG. 9, it was confirmed that the deposit was dense and no dendrite was generated. Moreover, it was confirmed from the EDX analysis results in FIG. 10 that the deposits contained Ca. In the electrodeposition test using the electrolytic solution of Comparative Example 3, no electrodeposit was observed on the copper foil surface, and F and S were detected along with Ca. Presumably, it is incorporated into the deposits.
  • FIG. 11 is a SEM photograph of the electrodeposit obtained in the electrodeposition test using the electrolytic solution of Example 2.
  • (a) is a plane photograph of the electrodeposit
  • (b) is a photograph of the electrodeposit. It is a cross-sectional photograph.
  • FIG. 12 shows the results of EDX analysis of Na, Ca, F, and S in the cross section of the electrodeposit shown in FIG. 11(b). From the SEM photograph of FIG. 11, it was confirmed that the deposit was dense and no dendrite was generated. From the EDX analysis results shown in FIG. 11, it was confirmed that the deposits contained Ca as well as Na. This Ca is considered to be incorporated into the deposit as Ca(TFSA) 2 . In the electrodeposition test using the electrolytic solution of Comparative Example 2, the electrodeposited matter did not adhere to the surface of the copper foil, so it is considered that Ca has the effect of improving the adhesion of the electrodeposited matter to the copper foil. be done.
  • a three-electrode cell 40 shown in FIG. 13 has a container 41 and a lid 42 .
  • the container 41 contains an electrolytic solution 43 , a working electrode (WE) 44 , a counter electrode (CE) 47 and a reference electrode (RE) 50 .
  • a working electrode (WE) 44 is connected to a lead wire 46 via a clip 45 fixed to the lid 42 .
  • a counter electrode (CE) 47 is connected to a lead wire 49 via a clip 48 fixed to the lid 42 .
  • a reference electrode (RE) 50 is connected to a lead wire 52 via a clip 51 fixed to the lid 42 .
  • a reference electrode (RE) 50 is Li and is immersed in a Li(TFSA)/G3 solution 53 having a concentration of 0.5 mol/L.
  • the Li(TFSA)/G3 solution 5 is separated from the electrolyte 43 by a ceramic filter 54 .
  • the results are shown in FIGS. 14 and 15.
  • FIG. 14 and 15 The results are shown in FIGS. 14 and 15.
  • FIG. 14(a) is a cyclic voltammogram of a three-electrode cell using the electrolytic solution prepared in Example 1 as the electrolytic solution 43
  • FIG. 14(b) shows the electrolytic solution prepared in Comparative Example 1.
  • 3 is a cyclic voltammogram of a 3-electrode cell.
  • the working electrode (WE) 44 and the counter electrode (CE) 47 used lithium. Comparing FIG. 14(a) and FIG. 14(b), it can be seen that the three-electrode cell using the electrolyte of Example 1 is 0 V compared to the three-electrode cell using the electrolyte of Comparative Example 1. , it can be seen that the current density on the low potential side decreases.
  • Li is electrodeposited on the surface of the copper foil (working electrode) on the low potential side from 0 V, it is considered that the electrodeposition of Li is suppressed in the three-electrode cell using the electrolytic solution of Example 1. This is probably because the electrolytic solution of Example 1 changed the structure of the solvation formed by Li due to the addition of Ca. Since it becomes difficult for Li to be electrodeposited, an overvoltage is applied to electrodeposit Li, the driving force for nucleation increases, and fine Li is electrodeposited. Therefore, as shown in the SEM photograph of FIG. 9, the electrodeposited layer (Li layer) is thought to be dense and have a flat surface.
  • FIG. 15(a) is a cyclic voltammogram of a three-electrode cell using the electrolytic solution prepared in Example 2 as the electrolytic solution
  • FIG. 15(b) shows the electrolytic solution prepared in Comparative Example 2.
  • 3 is a cyclic voltammogram of a 3-electrode cell. Sodium was used for the working electrode (WE) 44 and the counter electrode (CE) 47 . Comparing FIG. 15(a) and FIG. 15(b), as in the cases of Example 1 and Comparative Example 1, the three-electrode cell using the electrolytic solution of Example 2 has the electrolytic solution of Comparative Example 2.
  • Example 3 Two disc-shaped lithium metal plates (diameter: 16 mm, thickness: 100 ⁇ m) and a gas fiber separator (diameter: 25 mm, thickness: 50 ⁇ m) were prepared. A separator was placed between two lithium metal plates to obtain a laminate in which the lithium metal plate, the separator, and the lithium metal plate were laminated in this order. The obtained laminate and the electrolytic solution of Example 1 were placed in a coin-shaped battery case and sealed to prepare a coin-shaped half cell.
  • Li(TFSA) and Ba(TFSA) 2 barium bis(trifluoromethylsulfonyl)amide] were added to G3 and mixed to obtain a Li(TFSA) concentration of 0.5 mol/L and Ba(TFSA)
  • FIG. 17(a) is a photograph of the electrolytic solution after the electrodeposition test
  • (b) is a photograph of the surface of the working electrode
  • FIG. 18 is a SEM photograph of the plane of the electrodeposit obtained in the electrodeposition test. From the photograph of FIG. 17(a), it can be seen that the electrolytic solution of Example 4 has a small floating amount of electrodeposited metal. Further, from the photograph of FIG. 17(b), it can be seen that the particle shape of the metal electrodeposited on the surface of the working electrode is uniform, and the mixed amount of coarse metal particles is small. Further, from the SEM photograph of FIG. 18, it can be seen that the deposit was dense and no dendrite was generated.
  • FIG. 19 is a cyclic voltammogram of a three-electrode cell using the electrolytic solution of Example 4. From the results of FIG. 19, the three-electrode cell using the electrolytic solution of Example 4 starts from the second cycle, as in the case of the three-electrode cell using the electrolytic solution of Example 1, the current on the low potential side from 0 V It can be seen that the density is reduced. This is probably because the electrolytic solution of Example 4 changed the structure of solvation formed by Li due to the addition of Ba.

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Abstract

This electrolyte solution for alkali metal secondary batteries contains a nonaqueous solvent, an alkali metal salt that is dissolved in the nonaqueous solvent, and an alkaline earth metal salt that is dissolved in the nonaqueous solvent.

Description

アルカリ金属二次電池用電解液およびアルカリ金属二次電池Electrolyte for alkali metal secondary battery and alkali metal secondary battery
　本発明は、アルカリ金属二次電池用電解液およびアルカリ金属二次電池に関する。 The present invention relates to an electrolyte solution for alkali metal secondary batteries and an alkali metal secondary battery.
　リチウムイオン二次電池は、スマートフォンやパーソナルコンピューターなどの電子機器の電源として利用されている。リチウムイオン二次電池では、負極材料として黒鉛などの炭素材料が広く利用されている。炭素材料はリチウムイオンを、充電時に吸蔵し、放電時に放出する。 Lithium-ion secondary batteries are used as power sources for electronic devices such as smartphones and personal computers. Carbon materials such as graphite are widely used as negative electrode materials in lithium ion secondary batteries. The carbon material absorbs lithium ions during charging and releases them during discharging.
　電池の容量向上のため、負極材料に金属リチウムを用いることが検討されている。しかしながら、負極材料に金属リチウムを用いると、充放電を繰り返すことによって、負極の表面に、リチウムが樹枝状に析出したデンドライトを生成し、電池内で短絡するおそれがある。 In order to improve the capacity of batteries, the use of metallic lithium as a negative electrode material is being considered. However, when metallic lithium is used as the negative electrode material, dendrites in which lithium is deposited in a dendrite form are formed on the surface of the negative electrode by repeated charging and discharging, which may cause a short circuit in the battery.
　デンドライトの生成を抑える方法として、電解液に所定の塩を加えることが検討されている。例えば、電解液に、マグネシウム塩を加えること（非特許文献１）、電解液にセシウム塩やルビジウム塩を添加すること（非特許文献２）が検討されている。 As a method of suppressing the formation of dendrites, adding a predetermined salt to the electrolyte is being considered. For example, adding a magnesium salt to the electrolytic solution (Non-Patent Document 1) and adding a cesium salt or a rubidium salt to the electrolytic solution (Non-Patent Document 2) are being considered.
　本発明の目的は、リチウム金属などのアルカリ金属を負極材料として用いたアルカリ金属二次電池において、デンドライトの発生を抑制することができる新規なアルカリ金属二次電池用の電解液と、その電解液を用いたアルカリ金属二次電池を提供することにある。 An object of the present invention is to provide a novel electrolyte solution for an alkali metal secondary battery that can suppress the generation of dendrites in an alkali metal secondary battery using an alkali metal such as lithium metal as a negative electrode material, and the electrolyte solution. To provide an alkali metal secondary battery using
　本発明者らは、非水溶媒と、アルカリ金属塩とを含むアルカリ金属二次電池用電解液に、さらにアルカリ土類金属塩を加えることによって、アルカリ金属二次電池の負極集電体の表面にアルカリ金属が平坦に析出し、デンドライトの発生が低減することを見出して、本発明を完成させた。
　したがって、本発明は、下記の態様を有する。 The present inventors have found that the surface of the negative electrode current collector of an alkali metal secondary battery is Alkali metal is deposited evenly on the surface, and the occurrence of dendrites is reduced, and the present invention has been completed.
Accordingly, the present invention has the following aspects.
［１］非水溶媒と、前記非水溶媒に溶解したアルカリ金属塩と、前記非水溶媒に溶解したアルカリ土類金属塩と、を含む、アルカリ金属二次電池用電解液。
［２］前記アルカリ金属塩がリチウム金属塩およびナトリウム金属塩の少なくとも一方を含み、前記アルカリ土類金属塩がカルシウム金属塩およびバリウム金属塩の少なくとも一方を含む、前記［１］に記載のアルカリ金属二次電池用電解液。
［３］前記アルカリ土類金属塩が、ヘキサフルオロリン酸アルカリ土類金属塩、過塩素酸アルカリ土類金属塩、テトラフルオロホウ酸アルカリ土類金属塩、トリフルオロメタンスルホン酸アルカリ土類金属塩、ビス（トリフルオロメチルスルホニル）イミドアルカリ土類金属塩、ビス（トリフルオロメチルスルホニル）アミドアルカリ土類金属塩、ビス（フルオロスルホニル）アミドアルカリ土類金属塩からなる群より選ばれる少なくとも１つの塩である、前記［１］または［２］に記載のアルカリ金属二次電池用電解液。
［４］前記アルカリ金属塩が、ヘキサフルオロリン酸アルカリ金属塩、過塩素酸アルカリ金属塩、テトラフルオロホウ酸アルカリ金属塩、トリフルオロメタンスルホン酸アルカリ金属塩、ビス（トリフルオロメチルスルホニル）イミドアルカリ金属塩、ビス（トリフルオロメチルスルホニル）アミドアルカリ金属塩、ビス（フルオロスルホニル）アミドアルカリ金属塩からなる群より選ばれる少なくとも１つの塩である、前記［１］から［３］に記載のアルカリ金属二次電池用電解液。
［５］前記アルカリ金属塩のアニオンと前記アルカリ土類金属塩のアニオンが同じである、前記［１］から［４］に記載のアルカリ金属二次電池用電解液。
［６］前記非水溶媒が鎖状エーテルを含む、前記［１］から［５］に記載のアルカリ金属二次電池用電解液。 [1] An electrolytic solution for an alkali metal secondary battery, comprising a non-aqueous solvent, an alkali metal salt dissolved in the non-aqueous solvent, and an alkaline earth metal salt dissolved in the non-aqueous solvent.
[2] The alkali metal according to [1] above, wherein the alkali metal salt contains at least one of lithium metal salt and sodium metal salt, and the alkaline earth metal salt contains at least one of calcium metal salt and barium metal salt. Electrolyte for secondary batteries.
[3] The alkaline earth metal salt is an alkaline earth metal hexafluorophosphate, an alkaline earth metal perchlorate, an alkaline earth metal tetrafluoroborate, an alkaline earth metal trifluoromethanesulfonate, at least one salt selected from the group consisting of bis(trifluoromethylsulfonyl)imide alkaline earth metal salts, bis(trifluoromethylsulfonyl)amide alkaline earth metal salts, and bis(fluorosulfonyl)amide alkaline earth metal salts; The electrolytic solution for an alkali metal secondary battery according to the above [1] or [2].
[4] The alkali metal salt is an alkali metal hexafluorophosphate, an alkali metal perchlorate, an alkali metal tetrafluoroborate, an alkali metal trifluoromethanesulfonate, or an alkali metal bis(trifluoromethylsulfonyl)imide. Salt, bis(trifluoromethylsulfonyl)amide alkali metal salt, bis(fluorosulfonyl)amide alkali metal salt, which is at least one salt selected from the group consisting of [1] to [3] above alkali metal Electrolyte for secondary batteries.
[5] The electrolytic solution for an alkali metal secondary battery according to [1] to [4], wherein the anion of the alkali metal salt and the anion of the alkaline earth metal salt are the same.
[6] The electrolytic solution for an alkali metal secondary battery according to any one of [1] to [5], wherein the non-aqueous solvent contains a chain ether.
［７］前記［１］から［６］に記載のアルカリ金属二次電池用電解液と、アルカリ金属イオンの吸蔵および放出が可能な正極活物質を含む正極と、アルカリ金属を含む負極と、を備える、アルカリ金属二次電池。 [7] The electrolyte solution for an alkali metal secondary battery according to [1] to [6] above, a positive electrode containing a positive electrode active material capable of absorbing and releasing alkali metal ions, and a negative electrode containing an alkali metal Alkali metal secondary battery.
　本発明によれば、リチウム金属などのアルカリ金属を負極材料として用いたアルカリ金属二次電池において、デンドライトの発生を抑制することができる新規なアルカリ金属二次電池用の電解液と、その電解液を用いたアルカリ金属二次電池を提供することが可能となる。 According to the present invention, in an alkali metal secondary battery using an alkali metal such as lithium metal as a negative electrode material, a novel electrolyte solution for an alkali metal secondary battery capable of suppressing the generation of dendrites, and the electrolyte solution It is possible to provide an alkali metal secondary battery using
本発明の一実施形態に係るアルカリ金属二次電池の断面図である。1 is a cross-sectional view of an alkali metal secondary battery according to one embodiment of the present invention; FIG. 実施例１及び比較例１、３の電解液のラマンスペクトルである。2 shows Raman spectra of electrolyte solutions of Example 1 and Comparative Examples 1 and 3. FIG. 実施例２及び比較例２、３の電解液のラマンスペクトルである。2 shows Raman spectra of electrolyte solutions of Example 2 and Comparative Examples 2 and 3. FIG. 実施例の電析試験で使用した３極式セルの断面図である。FIG. 2 is a cross-sectional view of a three-electrode cell used in the electrodeposition test of Examples. 実施例１の電解液を用いた電析試験の結果であって、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。1 shows the results of an electrodeposition test using the electrolytic solution of Example 1, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. 比較例１の電解液を用いた電析試験の結果であって、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。2 shows the results of an electrodeposition test using the electrolytic solution of Comparative Example 1, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. 実施例２の電解液を用いた電析試験の結果であって、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。2 shows the results of an electrodeposition test using the electrolytic solution of Example 2, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. 比較例２の電解液を用いた電析試験の結果であって、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。It is the result of the electrodeposition test using the electrolytic solution of Comparative Example 2, (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. 実施例１の電解液を用いた電析試験で得られた電析物のＳＥＭ写真であり、（ａ）は電析物の平面写真であり、（ｂ）は電析物の断面写真である。BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a SEM photograph of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 1, where (a) is a plane photograph of the electrodeposit and (b) is a cross-sectional photograph of the electrodeposit. . 図９（ｂ）に示す電析物の断面のＥＤＸによるＣａ、Ｆ、Ｓの分析結果である。It is the analysis result of Ca, F, and S by EDX of the cross section of the electrodeposit shown in FIG.9(b). 実施例２の電解液を用いた電析試験で得られた電析物のＳＥＭ写真であり、（ａ）は電析物の平面写真であり、（ｂ）は電析物の断面写真である。1 is a SEM photograph of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 2, where (a) is a plane photograph of the electrodeposit, and (b) is a cross-sectional photograph of the electrodeposit. . 図１１（ｂ）に示す電析物の断面のＥＤＸによるＮａ、Ｃａ、Ｆ、Ｓの分析結果である。Fig. 11(b) shows the analysis results of Na, Ca, F, and S of the cross section of the electrodeposit by EDX. 実施例のサイクリックボルタンメトリーの測定で用いた３極式セルの断面図である。FIG. 3 is a cross-sectional view of a three-electrode cell used in cyclic voltammetry measurements in Examples. 図１４（ａ）は、実施例１の電解液を用いた３極式セルのサイクリックボルタモグラムであり、図１４（ｂ）は、比較例１の電解液を用いた３極式セルのサイクリックボルタモグラムである。14(a) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Example 1, and FIG. 14(b) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Comparative Example 1. It is a voltammogram. 図１５（ａ）は、実施例２の電解液を用いた３極式セルのサイクリックボルタモグラムであり、図１５（ｂ）は、比較例２の電解液を用いた３極式セルのサイクリックボルタモグラムである。15(a) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Example 2, and FIG. 15(b) is a cyclic voltammogram of a three-electrode cell using the electrolyte of Comparative Example 2. It is a voltammogram. 実施例３及び比較例４で得られたコイン型ハーフセルの充放電試験の結果である。4 shows the results of a charge/discharge test of the coin-shaped half-cells obtained in Example 3 and Comparative Example 4. FIG. 実施例４の電解液を用いた電析試験の結果であって、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。Fig. 4 shows the results of an electrodeposition test using the electrolytic solution of Example 4, in which (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. 実施例４の電解液を用いた電析試験で得られた電析物の平面のＳＥＭ写真である。4 is a SEM photograph of a plane of an electrodeposit obtained in an electrodeposition test using the electrolytic solution of Example 4. FIG. 実施例４の電解液を用いた３極式セルのサイクリックボルタモグラムである。4 is a cyclic voltammogram of a three-electrode cell using the electrolytic solution of Example 4. FIG.
　以下、本実施形態について、図面を適宜参照しながら詳細に説明する。以下の説明で用いる図面は、本発明の特徴をわかりやすくするために便宜上特徴となる部分を拡大して示している場合があり、各構成要素の寸法比率などは実際とは異なっていることがある。以下の説明において例示される材料、寸法等は一例であって、本発明はそれらに限定されるものではなく、その要旨を変更しない範囲で適宜変更して実施することが可能である。 Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the gist of the invention.
　図１は、本発明の一実施形態に係るアルカリ金属二次電池の断面図である。
　図１に示すアルカリ金属二次電池１０は、ケース１１と、ケース１１に収容されている電解液１２と、正極１３と、負極１６とを有する。正極は１３は、正極材料層１４と、正極集電体１５とを含む。負極１６は、負極材料層１７と、負極集電体１８とを含む。アルカリ金属二次電池１０では、充電時は、図１に示すように、外部回路１９を通って電子が正極１３から負極１６に流れ、電解液１２中のアルカリ金属イオンが負極材料層１７に吸蔵される。放電時は、外部回路１９を通って電子が負極１６から正極１３に流れ、負極材料層１７中のアルカリ金属イオンが電解液１２に放出される。 FIG. 1 is a cross-sectional view of an alkali metal secondary battery according to one embodiment of the present invention.
Alkali metal secondary battery 10 shown in FIG. The cathode 13 includes a cathode material layer 14 and a cathode current collector 15 . Negative electrode 16 includes a negative electrode material layer 17 and a negative electrode current collector 18 . In the alkali metal secondary battery 10, during charging, as shown in FIG. be done. During discharge, electrons flow from the negative electrode 16 to the positive electrode 13 through the external circuit 19 , releasing alkali metal ions in the negative electrode material layer 17 into the electrolytic solution 12 .
　電解液１２は、非水溶媒と、アルカリ金属塩と、アルカリ土類金属塩とを含む。アルカリ土類金属塩は、カルシウム塩、ストロンチウム塩、バリウム塩を含む。アルカリ金属塩とアルカリ土類金属塩は、非水溶媒に溶解されている。 The electrolytic solution 12 contains a nonaqueous solvent, an alkali metal salt, and an alkaline earth metal salt. Alkaline earth metal salts include calcium salts, strontium salts and barium salts. The alkali metal salt and alkaline earth metal salt are dissolved in a non-aqueous solvent.
　非水溶媒としては、鎖状エーテル、環状エーテル、環状カーボネート、鎖状カーボネート、ラクトン、ニトリル、スルホランなどを用いることができる。
　鎖状エーテルとしては、グリコールエーテル類を用いることができる。グリコールエーテル類は両側末端の水酸基が同一の置換基で置換された対称グリコールエーテルであることが好ましい。置換基は、メチル基、エチル基、プロピル基、ブチル基などの炭素数１～４のアルキル基であることが好ましい。グリコールエーテル類の例としては、モノグライム［エチレングリコールジメチルエーテル］、エチルモノグライム［エチレングリコールジエチルエーテル］、ブチルモノグライム［エチレングリコールジブチルエーテル］、メチルジグライム［ジエチレングリコールジメチルエーテル］、エチルジグライム［ジエチレングリコールジエチルエーテル］、ブチルジグライム［ジエチレングリコールジブチルエーテル］、メチルトリグライム［トリエチレングリコールジメチルエーテル］、エチルトリグライム［トリエチレングリコールジエチルエーテル］、ブチルトリグライム［トリエチレングリコールジエチルエーテル］、メチルテトラグライム［テトラエチレングリコールジメチルエーテル］、エチルテトラグライム［テトラエチレングリコールジエチルエーテル］、ブチルテトラグライム［テトラエチレングリコールジブチルエーテル］などのグライム化合物を挙げることができる。 Chain ethers, cyclic ethers, cyclic carbonates, chain carbonates, lactones, nitriles, sulfolane and the like can be used as non-aqueous solvents.
Glycol ethers can be used as chain ethers. Glycol ethers are preferably symmetrical glycol ethers in which both terminal hydroxyl groups are substituted with the same substituents. The substituent is preferably an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group and butyl group. Examples of glycol ethers include monoglyme [ethylene glycol dimethyl ether], ethyl monoglyme [ethylene glycol diethyl ether], butyl monoglyme [ethylene glycol dibutyl ether], methyl diglyme [diethylene glycol dimethyl ether], ethyl diglyme [diethylene glycol diethyl ether]. ], butyl diglyme [diethylene glycol dibutyl ether], methyl triglyme [triethylene glycol dimethyl ether], ethyl triglyme [triethylene glycol diethyl ether], butyl triglyme [triethylene glycol diethyl ether], methyl tetraglyme [tetraethylene glycol dimethyl ether], ethyl tetraglyme [tetraethylene glycol diethyl ether], and butyl tetraglyme [tetraethylene glycol dibutyl ether].
　環状エーテルとしては、例えば、テトラヒドロフラン（ＴＨＦ）、２－メチルテトラヒドロフラン、１，３－ジオキソフラン、１，４－ジオキサン、４－メチル－１，３－ジオキソラン、２－メチル－１，３－ジオキソランを用いることができる。 Cyclic ethers include, for example, tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxofuran, 1,4-dioxane, 4-methyl-1,3-dioxolane, and 2-methyl-1,3-dioxolane. be able to.
　環状カーボネートとしては、エチレンカーボネート、プロピレンカーボネート、１，２－ブチレンカーボネート、２，３－ブチレンカーボネート、１，２－ペンチレンカーボネート、２，３－ペンチレンカーボネートを用いることができる。鎖状カーボネートとしては、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、メチルプロピルカーボネート、エチルプロピルカーボネート、ジプロピルカーボネートを用いることができる。ラクトンとしては、γ－ブチロラクトンを用いることができる。ニトリルとしては、アセトニトリルを用いることができる。これら非水溶媒は１種を単独で使用してもよいし、２種以上を組合せて使用してもよい。また、非水溶媒は、水素の一部または全部がフッ素で置換されていてもよい。 As the cyclic carbonate, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate can be used. As chain carbonates, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, and dipropyl carbonate can be used. As the lactone, γ-butyrolactone can be used. Acetonitrile can be used as nitrile. One of these nonaqueous solvents may be used alone, or two or more thereof may be used in combination. Also, in the non-aqueous solvent, some or all of the hydrogen atoms may be substituted with fluorine.
　電解液１２に含まれるアルカリ金属塩のアルカリ金属は、負極材料層１７と同じであってもよい。アルカリ金属塩は、リチウム金属塩およびナトリウム金属塩の少なくとも一方を含んでいてもよい。
　リチウム金属塩の例としては、ヘキサフルオロリン酸リチウム（ＬｉＰＦ６）、過塩素酸リチウム（ＬｉＣｌＯ４）、テトラフルオロホウ酸リチウム（ＬｉＢＦ４）、トリフルオロメタンスルホン酸リチウム（ＬｉＣＦ３ＳＯ３）、ビス（トリフルオロメチルスルホニル）イミドリチウム（ＬｉＮ（ＣＦ３ＳＯ２）２）、リチウムビス（トリフルオロメチルスルホニル）アミド［Ｌｉ（ＴＦＳＡ）］、リチウムビス（フルオロスルホニル）アミド［Ｌｉ（ＦＳＡ）］を挙げることができる。また、ナトリウム金属塩の例としては、ヘキサフルオロリン酸ナトリウム（ＮａＰＦ６）、過塩素酸ナトリウム（ＮａＣｌＯ４）、テトラフルオロホウ酸ナトリウム（ＮａＢＦ４）、トリフルオロメタンスルホン酸ナトリウム（ＮａＣＦ３ＳＯ３）、ビス（トリフルオロメチルスルホニル）イミドナトリウム（ＮａＮＣ２Ｆ６Ｓ２Ｏ４）、ナトリウムビス（トリフルオロメチルスルホニル）アミド［Ｎａ（ＴＦＳＡ）］、ナトリウムビス（フルオロスルホニル）アミド［Ｎａ（ＦＳＡ）］を挙げることができる。 The alkali metal of the alkali metal salt contained in the electrolytic solution 12 may be the same as that of the negative electrode material layer 17 . The alkali metal salt may include at least one of lithium metal salt and sodium metal salt.
Examples of lithium metal salts include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4 ) , lithium trifluoromethanesulfonate ( LiCF3SO3 ), bis Lithium (trifluoromethylsulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), Lithium bis(trifluoromethylsulfonyl)amide [Li(TFSA)], Lithium bis(fluorosulfonyl)amide [Li(FSA)] be able to. Examples of sodium metal salts include sodium hexafluorophosphate (NaPF 6 ), sodium perchlorate (NaClO 4 ), sodium tetrafluoroborate (NaBF 4 ), sodium trifluoromethanesulfonate (NaCF 3 SO 3 ). , sodium bis(trifluoromethylsulfonyl)imide ( NaNC2F6S2O4 ), sodium bis(trifluoromethylsulfonyl)amide [Na( TFSA )], sodium bis(fluorosulfonyl ) amide [Na(FSA)] can be mentioned.
　電解液１２に含まれるカルシウム塩の例としては、ヘキサフルオロリン酸カルシウム（Ｃａ（ＰＦ６）２）、過塩素酸カルシウム（Ｃａ（ＣｌＯ４）２）、テトラフルオロホウ酸カルシウム（Ｃａ（ＢＦ４）２）、トリフルオロメタンスルホン酸カルシウム（Ｃａ（ＣＦ３ＳＯ３）２）、ビス（トリフルオロメチルスルホニル）イミドカルシウム（ＣａＮ（Ｃ２Ｆ６Ｓ２Ｏ４）２）、カルシウムビス（トリフルオロメチルスルホニル）アミド［Ｃａ（ＴＦＳＡ）２］、カルシウムビス（フルオロスルホニル）アミド［Ｃａ（ＦＳＡ）２］を挙げることができる。アルカリ金属塩のアニオンとカルシウム塩のアニオンは同じであってもよい。また、バリウム塩の例としては、ヘキサフルオロリン酸バリウム（Ｂａ（ＰＦ６）２）、過塩素酸バリウム（Ｂａ（ＣｌＯ４）２）、テトラフルオロホウ酸バリウム（Ｂａ（ＢＦ４）２）、トリフルオロメタンスルホン酸バリウム（Ｂａ（ＣＦ３ＳＯ３）２）、ビス（トリフルオロメチルスルホニル）イミドバリウム（Ｂａ（ＮＣ２Ｆ６Ｓ２Ｏ４）２）、バリウムビス（トリフルオロメチルスルホニル）アミド［Ｂａ（ＴＦＳＡ）２］、バリウムビス（フルオロスルホニル）アミド［Ｂａ（ＦＳＡ）２］を挙げることができる。アルカリ金属塩のアニオンとバリウム塩のアニオンは同じであってもよい。 Examples of calcium salts contained in the electrolytic solution 12 include calcium hexafluorophosphate (Ca(PF 6 ) 2 ), calcium perchlorate (Ca(ClO 4 ) 2 ), calcium tetrafluoroborate (Ca(BF 4 ) 2 ), calcium trifluoromethanesulfonate (Ca( CF3SO3 ) 2 ) , calcium bis (trifluoromethylsulfonyl)imide (CaN( C2F6S2O4 ) 2 ) , calcium bis (trifluoromethylsulfonyl) Amide [Ca(TFSA) 2 ], calcium bis(fluorosulfonyl)amide [Ca(FSA) 2 ] may be mentioned. The anion of the alkali metal salt and the anion of the calcium salt may be the same. Examples of barium salts include barium hexafluorophosphate (Ba(PF 6 ) 2 ), barium perchlorate (Ba(ClO 4 ) 2 ), barium tetrafluoroborate (Ba(BF 4 ) 2 ), barium trifluoromethanesulfonate (Ba( CF3SO3 ) 2 ) , barium bis (trifluoromethylsulfonyl)imide ( Ba( NC2F6S2O4 ) 2 ) , barium bis(trifluoromethylsulfonyl)amide [ Ba(TFSA) 2 ], barium bis(fluorosulfonyl)amide [Ba(FSA) 2 ]. The anion of the alkali metal salt and the anion of the barium salt may be the same.
　電解液１２に含まれるアルカリ金属塩の濃度は、０．１モル／Ｌ以上４．０モル／Ｌ以下の範囲内にあってもよい。アルカリ土類金属塩の濃度は、０．１モル／Ｌ以上４．０モル／Ｌ以下の範囲内にあってもよい。アルカリ金属塩とアルカリ土類金属塩の合計濃度は、０．２モル／Ｌ以上５．０モル／Ｌ以下の範囲内にあってもよい。アルカリ金属塩とアルカリ土類金属塩との割合は、１モルのアルカリ金属塩に対するアルカリ土類金属塩の量が０．１モル以上１０モル以下の範囲内となる割合であってもよい。 The concentration of the alkali metal salt contained in the electrolytic solution 12 may be in the range of 0.1 mol/L or more and 4.0 mol/L or less. The concentration of the alkaline earth metal salt may be in the range of 0.1 mol/L or more and 4.0 mol/L or less. The total concentration of the alkali metal salt and alkaline earth metal salt may be in the range of 0.2 mol/L or more and 5.0 mol/L or less. The ratio of the alkali metal salt and the alkaline earth metal salt may be such that the amount of the alkaline earth metal salt per 1 mol of the alkali metal salt is in the range of 0.1 mol or more and 10 mol or less.
　正極材料層１４と、正極活物質、導電助剤および結着剤を含んでいてもよい。
　正極活物質は、アルカリ金属イオンの吸蔵および放出が可能な材料である。正極活物質としては、例えば、層状酸化物、スピネル型酸化物、オリビン型リン酸塩、ケイ酸塩等が用いられる。層状酸化物の例としては、ＭａＣｏＯ２、ＭａＭｎＯ２、ＭａＮｉＯ２、Ｍａ（ＮｉｘＣｏｙＭｎｚ）Ｏ２（ｘ＋ｙ＋ｚ＝１）等を挙げることができる（Ｍａはアルカリ金属を表す。）。スピネル型酸化物の例としては、ＭａＭｎ２Ｏ４、Ｍａ（Ｎｉ０．５Ｍｎ１．５）Ｏ４等を挙げることができる（Ｍａはアルカリ金属を表す。）。オリビン型リン酸塩の例としては、ＭａＦｅＰＯ４、ＭａＭｎＰＯ４、ＭａＮｉＰＯ４、ＭａＣｕＰＯ４等を挙げることができる（Ｍａはアルカリ金属を表す。）。ケイ酸塩の例としては、Ｍａ２ＦｅＳｉＯ４、Ｍａ２ＭｎＳｉＯ４等を挙げることができる（Ｍａはアルカリ金属を表す。）。また、負極材料層１７がアルカリ金属を含む場合は、Ｖ２Ｏ５やＭｎＯ３などのアルカリ金属を含まない金属酸化物、硫黄やセレンの単相，あるいは硫黄やセレンを含む化合物を用いることができる。 The positive electrode material layer 14 may contain a positive electrode active material, a conductive aid, and a binder.
A positive electrode active material is a material capable of intercalating and deintercalating alkali metal ions. Examples of positive electrode active materials include layered oxides, spinel-type oxides, olivine-type phosphates, and silicates. Examples of layered oxides include MaCoO2 , MaMnO2 , MaNiO2 , Ma( NixCoyMnz ) O2 (x+y+z=1 ) , etc. (Ma represents an alkali metal). Examples of spinel-type oxides include MaMn 2 O 4 and Ma(Ni 0.5 Mn 1.5 )O 4 (Ma represents an alkali metal). Examples of olivine-type phosphates include MaFePO 4 , MaMnPO 4 , MaNiPO 4 , MaCuPO 4 (Ma represents an alkali metal). Examples of silicates include Ma 2 FeSiO 4 and Ma 2 MnSiO 4 (Ma represents an alkali metal). When the negative electrode material layer 17 contains an alkali metal, a metal oxide containing no alkali metal such as V 2 O 5 or MnO 3 , a single phase of sulfur or selenium, or a compound containing sulfur or selenium can be used. can.
　導電助剤としては、例えば、炭素粉体、金属微粉体などのアルカリ金属二次電池の正極材料層の導電助剤として利用されている公知の導電材を用いることができる。炭素粉体としては、アセチレンブラック、ケッチェンブラックなどのカーボンブラックを用いることかできる。結着剤としては、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）などの熱可塑性フッ素樹脂、ガラス、ポリイミドなどのアルカリ金属二次電池の正極材料層の結着剤として利用されている公知の材料を用いることができる。 As the conductive aid, for example, a known conductive material that is used as a conductive aid for the positive electrode material layer of alkali metal secondary batteries, such as carbon powder and metal fine powder, can be used. Carbon black such as acetylene black and ketjen black can be used as the carbon powder. As the binder, for example, a thermoplastic fluororesin such as polyvinylidene fluoride (PVDF), glass, or a known material used as a binder for the positive electrode material layer of an alkali metal secondary battery such as polyimide may be used. can be done.
　正極材料層１４の正極活物質、導電材および結着剤の含有量は特に制限はないが、正極活物質の含有量は８０質量％以上９８質量％以下の範囲内にあることが好ましい。導電材の含有量は１質量％以上１９質量％以下の範囲内にあることが好ましく、結着剤の含有量は１質量％以上１９質量％以下の範囲内にあることが好ましい。 The contents of the positive electrode active material, conductive material, and binder in the positive electrode material layer 14 are not particularly limited, but the content of the positive electrode active material is preferably in the range of 80% by mass or more and 98% by mass or less. The content of the conductive material is preferably in the range of 1% by mass or more and 19% by mass or less, and the content of the binder is preferably in the range of 1% by mass or more and 19% by mass or less.
　正極集電体１５の材料は、導電性を有するものであれば特に制限はない。正極集電体１５の材料としては、例えば、アルミニウム、銅、白金、炭素材料、モリブデン、タングステンを用いることができる。正極集電体１５の形状としては、例えば、板状、リボン状、箔体状、ワイヤー状などが挙げられるが、これらの形状に限定されるものではない。 The material of the positive electrode current collector 15 is not particularly limited as long as it has conductivity. Examples of materials that can be used for the positive electrode current collector 15 include aluminum, copper, platinum, carbon materials, molybdenum, and tungsten. Examples of the shape of the positive electrode current collector 15 include plate-like, ribbon-like, foil-like, and wire-like shapes, but are not limited to these shapes.
　負極材料層１７は、アルカリ金属を含む。アルカリ金属は、リチウムおよびナトリウムの少なくとも一方であってもよい。負極材料層１７は、アルカリ金属単体であってもよいし、アルカリ金属の他の金属を含む合金であってもよい。リチウム合金の例としては、Ｌｉ－Ａｌ合金、Ｌｉ－Ｓｎ合金、Ｌｉ－Ｚｎ合金、Ｌｉ－Ａｇ合金、Ｌｉ－Ｉｎ合金、Ｌｉ－Ｇｅ合金、Ｌｉ－Ｐｂ合金、Ｌｉ－Ｓｉ合金を挙げることができる。ナトリウム合金の例としては、Ｎａ－Ｐｂ合金、Ｎａ－Ｓｎ合金、Ｎａ－Ｇｅを挙げることができる。 The negative electrode material layer 17 contains an alkali metal. The alkali metal may be at least one of lithium and sodium. The negative electrode material layer 17 may be an alkali metal simple substance, or may be an alloy containing an alkali metal other than the alkali metal. Examples of lithium alloys include Li--Al alloys, Li--Sn alloys, Li--Zn alloys, Li--Ag alloys, Li--In alloys, Li--Ge alloys, Li--Pb alloys and Li--Si alloys. can. Examples of sodium alloys include Na--Pb alloys, Na--Sn alloys, and Na--Ge.
　負極材料層１７として、アルカリ金属と合金を形成する金属を用いてもよい。リチウムと合金を形成する金属としては、アルミニウム、スズ、亜鉛、銀、インジウム、ゲルマニウム、鉛、ケイ素を挙げることができる。ナトリウムと合金を形成する金属としては、鉛、スズ、ゲルマニウムを挙げることができる。負極材料層１７として、アルカリ金属と合金を形成する金属を用いる場合、正極活物質は、アルカリ金属を含む化合物を用いる。 A metal that forms an alloy with an alkali metal may be used as the negative electrode material layer 17 . Metals that form alloys with lithium include aluminum, tin, zinc, silver, indium, germanium, lead, and silicon. Examples of metals that form alloys with sodium include lead, tin, and germanium. When a metal forming an alloy with an alkali metal is used for the negative electrode material layer 17, a compound containing an alkali metal is used as the positive electrode active material.
　負極集電体１８は、導電性を有するものであれば特に制限はない。負極集電体１８の材料としては、例えば、銅、白金、炭素材料、モリブデン、タングステンを用いることができる。また、負極集電体１８と負極材料層１７とを一体としてもよい。負極集電体１８の形状としては、例えば、板状、リボン状、箔体状、ワイヤー状などが挙げられるが、これらの形状に限定されるものではない。 The negative electrode current collector 18 is not particularly limited as long as it has conductivity. Examples of materials that can be used for the negative electrode current collector 18 include copper, platinum, carbon materials, molybdenum, and tungsten. Further, the negative electrode current collector 18 and the negative electrode material layer 17 may be integrated. Examples of the shape of the negative electrode current collector 18 include plate-like, ribbon-like, foil-like, and wire-like shapes, but are not limited to these shapes.
　正極１３と負極１６との間にセパレータを配置してもよい。セパレータとしては、多孔質フィルム、多孔質ガラス、ガラスメッシュなどの多孔質体を用いてもよい。 A separator may be placed between the positive electrode 13 and the negative electrode 16 . A porous body such as a porous film, porous glass, or glass mesh may be used as the separator.
　アルカリ金属二次電池１０の形状としては特に制限はなく、コイン型、ボタン型、シート型、円筒型、角筒型などのアルカリ金属二次電池の形状として採用されている公知の形状とすることができる。 The shape of the alkali metal secondary battery 10 is not particularly limited, and may be a known shape adopted as the shape of an alkali metal secondary battery, such as a coin shape, a button shape, a sheet shape, a cylinder shape, a square shape, or the like. can be done.
　以上のような構成とされた本実施形態のアルカリ金属二次電池１０によれば、電解液１２が、非水溶媒と、この非水溶媒に溶解したアルカリ金属塩とアルカリ土類金属塩とを含むので、負極材料層１７へのデンドライトの発生が抑制される。このため、アルカリ金属二次電池１０は、高容量で長期間にわたって安定して使用することができる。また、電解液１２は、アルカリ金属二次電池用電解液として有利に利用することができる。 According to the alkali metal secondary battery 10 of the present embodiment configured as described above, the electrolytic solution 12 contains a non-aqueous solvent, and an alkali metal salt and an alkaline earth metal salt dissolved in the non-aqueous solvent. Therefore, the generation of dendrites in the negative electrode material layer 17 is suppressed. Therefore, the alkali metal secondary battery 10 can be stably used for a long period of time with a high capacity. In addition, the electrolytic solution 12 can be advantageously used as an electrolytic solution for alkali metal secondary batteries.
［実施例１］
　Ｌｉ（ＴＦＳＡ）［リチウムビス（トリフルオロメチルスルホニル）アミド］とＣａ（ＴＦＳＡ）２［カルシウムビス（トリフルオロメチルスルホニル）アミド］とをＧ３（メチルトリグライム）に加えて、混合して、Ｌｉ（ＴＦＳＡ）濃度が０．５モル／Ｌで、Ｃａ（ＴＦＳＡ）２濃度が０．５モル／Ｌの電解液を調製した。 [Example 1]
Li(TFSA) [lithium bis(trifluoromethylsulfonyl)amide] and Ca(TFSA) 2 [calcium bis(trifluoromethylsulfonyl)amide] are added to G3 (methyltriglyme) and mixed to form Li( An electrolytic solution having a TFSA) concentration of 0.5 mol/L and a Ca(TFSA) 2 concentration of 0.5 mol/L was prepared.
［実施例２］
　Ｎａ（ＴＦＳＡ）［ナトリウムビス（トリフルオロメチルスルホニル）アミド］とＣａ（ＴＦＳＡ）２とをＧ３に加えて、混合して、Ｎａ（ＴＦＳＡ）濃度が０．５モル／Ｌで、Ｃａ（ＴＦＳＡ）２濃度が０．５モル／Ｌの電解液を調製した。 [Example 2]
Na(TFSA)[sodium bis(trifluoromethylsulfonyl)amide] and Ca(TFSA) 2 were added to G3 and mixed to obtain a Na(TFSA) concentration of 0.5 mol/L and Ca(TFSA) An electrolytic solution having a concentration of 0.5 mol/L was prepared.
［比較例１］
　Ｌｉ（ＴＦＳＡ）をＧ３に加えて、混合して、Ｌｉ（ＴＦＳＡ）濃度が０．５モル／Ｌの電解液を調製した。 [Comparative Example 1]
Li(TFSA) was added to G3 and mixed to prepare an electrolytic solution having a Li(TFSA) concentration of 0.5 mol/L.
［比較例２］
　Ｎａ（ＴＦＳＡ）をＧ３に加えて、混合して、Ｎａ（ＴＦＳＡ）濃度が０．５モル／Ｌの電解液を調製した。 [Comparative Example 2]
Na(TFSA) was added to G3 and mixed to prepare an electrolytic solution having a Na(TFSA) concentration of 0.5 mol/L.
［比較例３］
　Ｃａ（ＴＦＳＡ）２をＧ３に加えて、混合して、Ｃａ（ＴＦＳＡ）２濃度が０．５モル／Ｌの電解液を調製した。 [Comparative Example 3]
Ca(TFSA) 2 was added to G3 and mixed to prepare an electrolytic solution having a Ca(TFSA) 2 concentration of 0.5 mol/L.
［評価結果］
（１）ラマンスペクトルの測定
　実施例１、２及び比較例１～３で調製した電解液のラマンスペクトルを測定した。
　図２は、実施例１及び比較例１、３の電解液のラマンスペクトルであり、図３は、実施例２及び比較例２、３の電解液のラマンスペクトルである。図２及び図３のラマンスペクトルにおいて、ラマンシフト７２０～７６０ｎｍ－１のピークは、ＴＦＳＡ［ビス（トリフルオロメチルスルホニル）アミド］アニオンの分子振動に由来する。
　図２に示すように、Ｌｉ（ＴＦＳＡ）のみを含む比較例１の電解液のラマンスペクトルでは、ＬｉとＧ３との結合に由来するラマンシフト８６９ｎｍ－１のピークが見られる。また、Ｃａ（ＴＦＳＡ）２のみを含む比較例３の電解液のラマンスペクトルでは、ＣａとＧ３との結合に由来するラマンシフト８７６ｎｍ－１のピークが見られる。これに対して、Ｌｉ（ＴＦＳＡ）とＣａ（ＴＦＳＡ）２を含む実施例１の電解液のラマンスペクトルでは、ＬｉとＧ３との結合に由来するピークとＣａとＧ３との結合に由来するピークが高周波側にシフトしている。このことから、実施例１の電解液は、Ｌｉが形成する溶媒和の構造が比較例１の電解液とは異なり、Ｃａが形成する溶媒和の構造が比較例３の電解液とは異なると考えられる。 [Evaluation results]
(1) Measurement of Raman Spectra Raman spectra of the electrolytic solutions prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were measured.
FIG. 2 shows Raman spectra of the electrolytes of Example 1 and Comparative Examples 1 and 3, and FIG. 3 shows Raman spectra of the electrolytes of Example 2 and Comparative Examples 2 and 3. FIG. In the Raman spectra of FIGS. 2 and 3, the peak at the Raman shift of 720-760 nm −1 originates from the molecular vibration of the TFSA [bis(trifluoromethylsulfonyl)amide] anion.
As shown in FIG. 2, in the Raman spectrum of the electrolytic solution of Comparative Example 1 containing only Li (TFSA), a peak with a Raman shift of 869 nm −1 derived from the bond between Li and G3 is observed. Also, in the Raman spectrum of the electrolytic solution of Comparative Example 3 containing only Ca(TFSA) 2 , a peak with a Raman shift of 876 nm −1 derived from the bond between Ca and G3 is observed. On the other hand, in the Raman spectrum of the electrolytic solution of Example 1 containing Li(TFSA) and Ca(TFSA) 2 , the peak derived from the bond between Li and G3 and the peak derived from the bond between Ca and G3 were observed. shifted to the high frequency side. From this, the electrolytic solution of Example 1 is different from the electrolytic solution of Comparative Example 1 in the solvation structure formed by Li, and the electrolytic solution of Comparative Example 3 is different in the structure of solvation formed by Ca. Conceivable.
　また、図３に示すように、Ｎａ（ＴＦＳＡ）のみを含む比較例２の電解液のラマンスペクトルでは、ＮａとＧ３との結合に由来するラマンシフト８７０ｎｍ－１のピークが見られる。これに対して、Ｎａ（ＴＦＳＡ）とＣａ（ＴＦＳＡ）２を含む実施例２の電解液のラマンスペクトルでは、ＮａとＧ３との結合に由来するピークとＣａとＧ３との結合に由来するピークが高周波側にシフトしている。よって、実施例２の電解液もまた、実施例１の電解液と同様に、Ｎａが形成する溶媒和の構造が比較例２の電解液とは異なり、さらにＣａが形成する溶媒和の構造が比較例３の電解液とは異なると考えられる。 Further, as shown in FIG. 3, the Raman spectrum of the electrolytic solution of Comparative Example 2 containing only Na (TFSA) shows a peak with a Raman shift of 870 nm −1 derived from the bond between Na and G3. On the other hand, in the Raman spectrum of the electrolytic solution of Example 2 containing Na(TFSA) and Ca(TFSA) 2 , a peak derived from the bond between Na and G3 and a peak derived from the bond between Ca and G3 were observed. shifted to the high frequency side. Therefore, the electrolytic solution of Example 2, like the electrolytic solution of Example 1, also differs from the electrolytic solution of Comparative Example 2 in the structure of solvation formed by Na, and furthermore, the structure of solvation formed by Ca is different from that of the electrolytic solution of Comparative Example 2. It is considered that the electrolytic solution of Comparative Example 3 is different.
（２）電析試験
　電析試験では、電解液中で銅箔（作用極）に金属を電析させ、電析した金属の状態を評価した。図４に、電析試験で用いた３極式セルの断面図を示す。
　図４に示す３極式セル２０は、作用極３１と対極３２と参照極３３とを有する。３極式セル２０は、第１基板２１と、円錐状の貫通孔２２ａを有する第２基板２２と、貫通孔２３ａを有する第３基板２３と、底部にフランジ部２４ａを備える中空状の容器２４と、容器２４の蓋２５と、を有する。貫通孔２３ａの直径は、容器２４の外径よりも大きく、容器２４のフランジ部２４ａの直径よりも小さい。円錐状の貫通孔２２ａの最大直径は、容器２４の内径よりも小さい。第１基板２１と、第２基板２２と、第３基板２３は、ボルト２６によって接合されている。作用極３１は、第１基板２１と第２基板２２との間に配置されている。対極３２は容器２４の蓋２５に固定された対極支持材３４に支持されていて、参照極３３は容器２４の蓋２５に固定された参照極支持材３５に支持されている。作用極３１と第２基板との間にはＯリング２７が配置されている。第２基板と容器２４のフランジ部２４ａの間にはＯリング２８が配置されている。第２基板２２の貫通孔２２ａの作用極３１側の直径は１．１３ｃｍ（開口の面積１ｃｍ２）とした。作用極３１は銅箔を用いた。対極３２及び参照極３３は、試料の電解液が実施例１及び比較例１で調製したものである場合はリチウムを用い、実施例２及び比較例２で調製したものである場合はナトリウムを用い、比較例３で調製したものである場合はカルシウムを用いた。 (2) Electrodeposition test In the electrodeposition test, a metal was electrodeposited on a copper foil (working electrode) in an electrolytic solution, and the state of the electrodeposited metal was evaluated. FIG. 4 shows a cross-sectional view of the three-electrode cell used in the electrodeposition test.
The three-electrode cell 20 shown in FIG. 4 has a working electrode 31 , a counter electrode 32 and a reference electrode 33 . The three-electrode cell 20 includes a first substrate 21, a second substrate 22 having a conical through hole 22a, a third substrate 23 having a through hole 23a, and a hollow container 24 having a flange portion 24a at the bottom. and a lid 25 of the container 24 . The diameter of the through hole 23 a is larger than the outer diameter of the container 24 and smaller than the diameter of the flange portion 24 a of the container 24 . The maximum diameter of the conical through-hole 22 a is smaller than the inner diameter of the container 24 . The first substrate 21 , the second substrate 22 and the third substrate 23 are joined by bolts 26 . The working electrode 31 is arranged between the first substrate 21 and the second substrate 22 . The counter electrode 32 is supported by a counter electrode support member 34 fixed to the lid 25 of the container 24 , and the reference electrode 33 is supported by a reference electrode support member 35 fixed to the lid 25 of the container 24 . An O-ring 27 is arranged between the working electrode 31 and the second substrate. An O-ring 28 is arranged between the second substrate and the flange portion 24 a of the container 24 . The diameter of the through hole 22a of the second substrate 22 on the side of the working electrode 31 was 1.13 cm (opening area 1 cm 2 ). A copper foil was used for the working electrode 31 . For the counter electrode 32 and the reference electrode 33, lithium is used when the sample electrolyte solution is prepared in Example 1 and Comparative Example 1, and sodium is used when it is prepared in Example 2 and Comparative Example 2. , and when prepared in Comparative Example 3, calcium was used.
　電析試験は、次のようにして行なった。
　先ず、試料の電解液１２を、容器２４と第２基板の貫通孔２２ａに貯留し、容器２４に蓋をして、電解液１２に、作用極３１と対極３２と参照極３３を接触させた。次いで、作用極３１は参照極３３に対して０．５Ｖの電圧を印加し、還元反応の電荷量が５ｍＡｈに達するまで電析を行った。 The electrodeposition test was conducted as follows.
First, the electrolytic solution 12 of the sample was stored in the container 24 and the through hole 22a of the second substrate, the container 24 was covered, and the working electrode 31, the counter electrode 32, and the reference electrode 33 were brought into contact with the electrolytic solution 12. . Next, a voltage of 0.5 V was applied to the working electrode 31 with respect to the reference electrode 33, and electrodeposition was carried out until the charge amount of the reduction reaction reached 5 mAh.
　図５に実施例１の電解液を用いた電析試験の結果を、図６に比較例１の電解液を用いた電析試験の結果を示す。図５及び図６において、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。
　図５（ａ）と図６（ａ）とを比較すると、図５（ａ）の電解液は、図６（ａ）の電解液と比較して、電析した金属（リチウム）の浮遊量が少ないことがわかる。また、図５（ｂ）と図６（ｂ）とを比較すると、図５（ｂ）の作用極の表面に電析した金属層は、図６（ｂ）の作用極の表面に電析した金属層と比較して、析出した金属の粒子形状が揃っており、粗大な金属粒子の混入量が少ないことがわかる。 The results of the electrodeposition test using the electrolyte of Example 1 are shown in FIG. 5, and the results of the electrodeposition test using the electrolyte of Comparative Example 1 are shown in FIG. 5 and 6, (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode.
Comparing FIG. 5(a) with FIG. 6(a), the electrolytic solution in FIG. I know it's less. 5(b) and FIG. 6(b), the metal layer electrodeposited on the surface of the working electrode in FIG. 5(b) was electrodeposited on the surface of the working electrode in FIG. 6(b). Compared with the metal layer, the particle shape of the precipitated metal is more uniform, and the mixed amount of coarse metal particles is small.
　図７に実施例２の電解液を用いた電析試験の結果を、図８に比較例２の電解液を用いた電析試験の結果を示す。図７及び図８において、（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。
　図７（ａ）と図８（ａ）とを比較すると、図７（ａ）の電解液は、図８（ａ）の電解液と比較して、電析した金属（ナトリウム）の浮遊量が少ないことがわかる。また、図７（ｂ）と図８（ｂ）とを比較すると、図７（ｂ）の作用極の表面には析出した金属が付着しているのに対して、図８（ｂ）の作用極の表面には金属粒子が殆ど付着していないことがわかる。 The results of the electrodeposition test using the electrolyte of Example 2 are shown in FIG. 7, and the results of the electrodeposition test using the electrolyte of Comparative Example 2 are shown in FIG. 7 and 8, (a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode.
Comparing FIG. 7(a) and FIG. 8(a), the electrolytic solution in FIG. I know it's less. Further, when comparing FIG. 7(b) and FIG. 8(b), the deposited metal adheres to the surface of the working electrode in FIG. 7(b), whereas the action in FIG. It can be seen that almost no metal particles adhere to the surface of the pole.
　なお、比較例３の電解液を用いた電析試験では、銅箔表面に電析物が見られなかった。この結果から、カルシウムはＧ３中では電析しないことが確認された。 In the electrodeposition test using the electrolytic solution of Comparative Example 3, no electrodeposit was found on the copper foil surface. From this result, it was confirmed that calcium was not deposited in G3.
　実施例１及び実施例２の電解液を用いた電析試験で電析した金属層を、ＳＥＭ－ＥＤＸ（走査型電子顕微鏡－エネルギー分散型Ｘ線分析装置）を用いて分析した。その結果を、図９～図１２に示す。 The metal layers electrodeposited in the electrodeposition test using the electrolytic solutions of Examples 1 and 2 were analyzed using SEM-EDX (scanning electron microscope-energy dispersive X-ray analyzer). The results are shown in FIGS. 9-12.
　図９は、実施例１の電解液を用いた電析試験で得られた電析物のＳＥＭ写真であり、（ａ）は電析物の平面写真であり、（ｂ）は電析物の断面写真である。また、図１０は、図９（ｂ）に示す電析物の断面のＥＤＸによるＣａ、Ｆ、Ｓの分析結果である。
　図９のＳＥＭ写真から、電析物は緻密であって、デンドライトが発生していないことが確認された。また、図１０のＥＤＸの分析結果から電析物はＣａが含むことが確認された。比較例３の電解液を用いた電析試験では、銅箔表面に電析物が見られなかったこと、Ｃａと共にＦとＳが検出されていることから、Ｃａは、Ｃａ（ＴＦＳＡ）２として電析物に取り込まれていると考えられる。 FIG. 9 is a SEM photograph of the electrodeposit obtained in the electrodeposition test using the electrolytic solution of Example 1. (a) is a plane photograph of the electrodeposit, and (b) is a photograph of the electrodeposit. It is a cross-sectional photograph. FIG. 10 shows the results of Ca, F, and S analysis by EDX of the cross section of the electrodeposit shown in FIG. 9(b).
From the SEM photograph of FIG. 9, it was confirmed that the deposit was dense and no dendrite was generated. Moreover, it was confirmed from the EDX analysis results in FIG. 10 that the deposits contained Ca. In the electrodeposition test using the electrolytic solution of Comparative Example 3, no electrodeposit was observed on the copper foil surface, and F and S were detected along with Ca. Presumably, it is incorporated into the deposits.
　図１１は、実施例２の電解液を用いた電析試験で得られた電析物のＳＥＭ写真であり、（ａ）は電析物の平面写真であり、（ｂ）は電析物の断面写真である。また、図１２は、図１１（ｂ）に示す電析物の断面のＥＤＸによるＮａ、Ｃａ、Ｆ、Ｓの分析結果である。
　図１１のＳＥＭ写真から、電析物は緻密であって、デンドライトが発生していないことが確認された。図１１のＥＤＸの分析結果から電析物は、Ｎａと共に、Ｃａが含むことが確認された。このＣａは、Ｃａ（ＴＦＳＡ）２として電析物に取り込まれていると考えられる。比較例２の電解液を用いた電析試験では、電析物が銅箔の表面に付着していなかったから、Ｃａは、電析物を銅箔との密着性を向上させる作用を有すると考えられる。 FIG. 11 is a SEM photograph of the electrodeposit obtained in the electrodeposition test using the electrolytic solution of Example 2. (a) is a plane photograph of the electrodeposit, and (b) is a photograph of the electrodeposit. It is a cross-sectional photograph. FIG. 12 shows the results of EDX analysis of Na, Ca, F, and S in the cross section of the electrodeposit shown in FIG. 11(b).
From the SEM photograph of FIG. 11, it was confirmed that the deposit was dense and no dendrite was generated. From the EDX analysis results shown in FIG. 11, it was confirmed that the deposits contained Ca as well as Na. This Ca is considered to be incorporated into the deposit as Ca(TFSA) 2 . In the electrodeposition test using the electrolytic solution of Comparative Example 2, the electrodeposited matter did not adhere to the surface of the copper foil, so it is considered that Ca has the effect of improving the adhesion of the electrodeposited matter to the copper foil. be done.
（２）サイクリックボルタンメトリー
　図１３に示す３極式セルを用いて、サイクリックボルタンメトリーを下記の条件で測定した。
　図１３に示す３極式セル４０は、容器４１と蓋４２とを有する。容器４１には、電解液４３と、作用極（ＷＥ）４４、対極（ＣＥ）４７、参照極（ＲＥ）５０が収容されている。作用極（ＷＥ）４４は、蓋４２に固定されたクリップ４５を介してリード線４６に接続されている。対極（ＣＥ）４７は、蓋４２に固定されたクリップ４８を介してリード線４９に接続されている。参照極（ＲＥ）５０は、蓋４２に固定されたクリップ５１を介してリード線５２に接続されている。参照極（ＲＥ）５０はＬｉであり、濃度が０．５モル／ＬのＬｉ（ＴＦＳＡ）／Ｇ３溶液５３に浸漬されている。Ｌｉ（ＴＦＳＡ）／Ｇ３溶液５電解液４３とはセラミックフィルター５４によって分離されている。その結果を、図１４～図１５に示す。 (2) Cyclic Voltammetry Cyclic voltammetry was measured using the three-electrode cell shown in FIG. 13 under the following conditions.
A three-electrode cell 40 shown in FIG. 13 has a container 41 and a lid 42 . The container 41 contains an electrolytic solution 43 , a working electrode (WE) 44 , a counter electrode (CE) 47 and a reference electrode (RE) 50 . A working electrode (WE) 44 is connected to a lead wire 46 via a clip 45 fixed to the lid 42 . A counter electrode (CE) 47 is connected to a lead wire 49 via a clip 48 fixed to the lid 42 . A reference electrode (RE) 50 is connected to a lead wire 52 via a clip 51 fixed to the lid 42 . A reference electrode (RE) 50 is Li and is immersed in a Li(TFSA)/G3 solution 53 having a concentration of 0.5 mol/L. The Li(TFSA)/G3 solution 5 is separated from the electrolyte 43 by a ceramic filter 54 . The results are shown in FIGS. 14 and 15. FIG.
（サイクリックボルタンメトリーの測定条件）
　走査範囲：－１．０Ｖ～＋１．０Ｖ
　操作速度：１０ｍＶｓ－１ (Measurement conditions for cyclic voltammetry)
Scan range: -1.0V to +1.0V
Operation speed: 10mVs -1
　図１４（ａ）は、電解液４３として実施例１で調製した電解液を用いた３極式セルのサイクリックボルタモグラムであり、図１４（ｂ）は、比較例１で調製した電解液を用いた３極式セルのサイクリックボルタモグラムである。作用極（ＷＥ）４４及び対極（ＣＥ）４７は、リチウムを用いた。
　図１４（ａ）と図１４（ｂ）とを比較すると、実施例１の電解液を用いた３極式セルは、比較例１の電解液を用いた３極式セルと比較して、０Ｖから低電位側の電流密度が低減することがわかる。Ｌｉは０Ｖから低電位側で、銅箔（作用極）の表面に電析することから、実施例１の電解液を用いた３極式セルはＬｉの電析が抑制されると考えられる。これは、実施例１の電解液は、Ｃａが添加されてＬｉが形成する溶媒和の構造が変わったことによると考えられる。Ｌｉが電析しにくくなったことにより、Ｌｉを電析させるのに過電圧が付与され、核生成駆動力が上昇し、微細なＬｉが電析する。このため、図９のＳＥＭ写真で示したように、電析層（Ｌｉ層）は緻密で、表面が平坦になると考えられる。 FIG. 14(a) is a cyclic voltammogram of a three-electrode cell using the electrolytic solution prepared in Example 1 as the electrolytic solution 43, and FIG. 14(b) shows the electrolytic solution prepared in Comparative Example 1. 3 is a cyclic voltammogram of a 3-electrode cell. The working electrode (WE) 44 and the counter electrode (CE) 47 used lithium.
Comparing FIG. 14(a) and FIG. 14(b), it can be seen that the three-electrode cell using the electrolyte of Example 1 is 0 V compared to the three-electrode cell using the electrolyte of Comparative Example 1. , it can be seen that the current density on the low potential side decreases. Since Li is electrodeposited on the surface of the copper foil (working electrode) on the low potential side from 0 V, it is considered that the electrodeposition of Li is suppressed in the three-electrode cell using the electrolytic solution of Example 1. This is probably because the electrolytic solution of Example 1 changed the structure of the solvation formed by Li due to the addition of Ca. Since it becomes difficult for Li to be electrodeposited, an overvoltage is applied to electrodeposit Li, the driving force for nucleation increases, and fine Li is electrodeposited. Therefore, as shown in the SEM photograph of FIG. 9, the electrodeposited layer (Li layer) is thought to be dense and have a flat surface.
　図１５（ａ）は、電解液として、実施例２で調製した電解液を用いた３極式セルのサイクリックボルタモグラムであり、図１５（ｂ）は、比較例２で調製した電解液を用いた３極式セルのサイクリックボルタモグラムである。作用極（ＷＥ）４４及び対極（ＣＥ）４７は、ナトリウムを用いた。
　図１５（ａ）と図１５（ｂ）とを比較すると、実施例１と比較例１の場合と同様に、実施例２の電解液を用いた３極式セルは、比較例２の電解液を用いた３極式セルと比較して、２サイクル目から０Ｖから低電位側の電流密度が低減することがわかる。Ｎａは０Ｖから低電位側で、銅箔（作用極）の表面に電析することから、実施例２の電解液を用いた３極式セルはＮａの電析が抑制されると考えられる。これは、実施例２の電解液は、Ｃａが添加されてＮａが形成する溶媒和の構造が変わったことによると考えられる。Ｎａが電析しにくくなったことにより、Ｎａを電析させるのに過電圧が付与され、核生成駆動力が上昇し、微細なＬｉが電析する。このため、実施例２の電解液を用いることによって、銅箔の表面に金属層（Ｎａ層）を形成することが可能となり、図１１のＳＥＭ写真で示したように、そのＮａ層は緻密で、表面が平坦になると考えられる。 FIG. 15(a) is a cyclic voltammogram of a three-electrode cell using the electrolytic solution prepared in Example 2 as the electrolytic solution, and FIG. 15(b) shows the electrolytic solution prepared in Comparative Example 2. 3 is a cyclic voltammogram of a 3-electrode cell. Sodium was used for the working electrode (WE) 44 and the counter electrode (CE) 47 .
Comparing FIG. 15(a) and FIG. 15(b), as in the cases of Example 1 and Comparative Example 1, the three-electrode cell using the electrolytic solution of Example 2 has the electrolytic solution of Comparative Example 2. It can be seen that the current density on the low potential side from 0 V is reduced from the second cycle as compared with the 3-electrode cell using . Since Na is electrodeposited on the surface of the copper foil (working electrode) on the low potential side from 0 V, it is considered that the electrodeposition of Na is suppressed in the three-electrode cell using the electrolytic solution of Example 2. This is probably because the electrolytic solution of Example 2 changed the structure of the solvation formed by Na due to the addition of Ca. Since the electrodeposition of Na becomes difficult, an overvoltage is applied to electrodeposit Na, the driving force for nucleation increases, and fine Li is electrodeposited. Therefore, by using the electrolytic solution of Example 2, it becomes possible to form a metal layer (Na layer) on the surface of the copper foil. As shown in the SEM photograph of FIG. 11, the Na layer is dense. , the surface is considered flat.
［実施例３］
　円板状のリチウム金属板（直径：１６ｍｍ、厚さ：１００μｍ）を２枚と、ガスファイバー製のセパレータ（直径：２５ｍｍ、厚さ：５０μｍ）を用意した。２枚のリチウム金属板の間にセパレータを配置して、リチウム金属板、セパレータ、リチウム金属板がこの順で積層した積層体を得た。得られた積層体と実施例１の電解液をコイン型電池ケースに収容し、封止して、コイン型のハーフセルを作製した。 [Example 3]
Two disc-shaped lithium metal plates (diameter: 16 mm, thickness: 100 μm) and a gas fiber separator (diameter: 25 mm, thickness: 50 μm) were prepared. A separator was placed between two lithium metal plates to obtain a laminate in which the lithium metal plate, the separator, and the lithium metal plate were laminated in this order. The obtained laminate and the electrolytic solution of Example 1 were placed in a coin-shaped battery case and sealed to prepare a coin-shaped half cell.
［比較例４］
　実施例１の電解液の代わりに、比較例１の電解液を用いたこと以外は、実施例３と同様にして、コイン型ハーフセルを作製した。 [Comparative Example 4]
A coin-type half-cell was produced in the same manner as in Example 3, except that the electrolytic solution of Comparative Example 1 was used instead of the electrolytic solution of Example 1.
［評価結果］
　コイン型ハーフセルを、リチウム金属板１ｃｍ２当たりの電流量で１ｍＡの定電流で２時間ずつのサイクルで充放電しながらコイン型ハーフセルの電圧を測定した。その結果を図１６に示す。
　図１６において、横軸は電流を流した時間であり、縦軸はコイン型ハーフセルの電圧である。図１６の結果から、１～６サイクル目までは、実施例１の電解液を用いた実施例３のコイン型ハーフセルは、比較例１の電解液を用いた比較例４のコイン型ハーフセルよりも電圧が高くなった。これは、実施例１の電解液を用いたことによって、Ｌｉの電析が抑制されたためである。また、比較例４のコイン型ハーフセルは、電圧がサイクルを繰り返す毎に上昇し、６サイクル目以降は、実施例３のコイン型ハーフセルよりも電圧が高くなった。これは、比較例４のハーフセルでは、電析物がリチウム基板から脱離してセパレータに巻き込まれて、部分的にＬｉイオンの伝導が難しくなり、内部抵抗が上昇したためであると考えられる。これに対して、実施例３のハーフセルは、６～２３サイクルまでは電圧の上昇が殆ど起こらなかった。これは、実施例３のハーフセルでは、電析物がリチウム基板の表面に密着し、電析物がセパレータに巻き込まれることが起こりにくく、また電析物が緻密で表面が平坦で、リチウム金属板の表面の電気抵抗が上昇しにくいたためであると考えられる。２３サイクル以後の電圧の上昇は電解液の分解による電極表面の不動態化に起因すると考えられる。 [Evaluation results]
The voltage of the coin-shaped half-cell was measured while charging and discharging the coin-shaped half-cell at a constant current of 1 mA per 1 cm 2 of lithium metal plate in cycles of 2 hours each. The results are shown in FIG.
In FIG. 16, the abscissa is the current flow time, and the ordinate is the voltage of the coin-type half-cell. From the results of FIG. 16, from the 1st to 6th cycles, the coin-shaped half-cell of Example 3 using the electrolytic solution of Example 1 was higher than the coin-shaped half-cell of Comparative Example 4 using the electrolytic solution of Comparative Example 1. voltage has increased. This is because the electrodeposition of Li was suppressed by using the electrolytic solution of Example 1. In the coin-shaped half-cell of Comparative Example 4, the voltage increased each time the cycle was repeated, and the voltage became higher than that of the coin-shaped half-cell of Example 3 after the sixth cycle. This is presumably because in the half cell of Comparative Example 4, the electrodeposits detached from the lithium substrate and were involved in the separator, partially making it difficult for Li ions to conduct and increasing the internal resistance. On the other hand, the half-cell of Example 3 showed almost no increase in voltage from 6 to 23 cycles. This is because, in the half-cell of Example 3, the electrodeposits adhered to the surface of the lithium substrate, the electrodeposits were less likely to be caught in the separator, and the electrodeposits were dense, had a flat surface, and the lithium metal plate It is considered that this is because the electrical resistance of the surface of the film is difficult to increase. It is considered that the increase in voltage after the 23rd cycle is due to the passivation of the electrode surface due to the decomposition of the electrolyte.
［実施例４］
　Ｌｉ（ＴＦＳＡ）とＢａ（ＴＦＳＡ）２［バリウムビス（トリフルオロメチルスルホニル）アミド］とをＧ３に加えて、混合して、Ｌｉ（ＴＦＳＡ）濃度が０．５モル／Ｌで、Ｂａ（ＴＦＳＡ）２濃度が０．５モル／Ｌの電解液を調製した。 [Example 4]
Li(TFSA) and Ba(TFSA) 2 [barium bis(trifluoromethylsulfonyl)amide] were added to G3 and mixed to obtain a Li(TFSA) concentration of 0.5 mol/L and Ba(TFSA) An electrolytic solution having a concentration of 0.5 mol/L was prepared.
　得られた電解液を用いて、実施例１と同様に、電析試験とサイクリックボルタンメトリーの測定を行った。その結果を図１７～図１９に示す。
　図１７の（ａ）は電析試験後の電解液の写真であり、（ｂ）は作用極の表面の写真である。図１８は、電析試験で得られた電析物の平面のＳＥＭ写真である。
　図１７（ａ）の写真から、実施例４の電解液は、電析した金属の浮遊量が少ないことがわかる。また、図１７（ｂ）の写真から、作用極の表面に電析した金属の粒子形状が揃っており、粗大な金属粒子の混入量が少ないことがわかる。さらに、図１８のＳＥＭ写真から、電析物は緻密であって、デンドライトが発生していないことがわかる。 Electrodeposition test and cyclic voltammetry measurement were performed in the same manner as in Example 1 using the obtained electrolytic solution. The results are shown in FIGS. 17-19.
FIG. 17(a) is a photograph of the electrolytic solution after the electrodeposition test, and (b) is a photograph of the surface of the working electrode. FIG. 18 is a SEM photograph of the plane of the electrodeposit obtained in the electrodeposition test.
From the photograph of FIG. 17(a), it can be seen that the electrolytic solution of Example 4 has a small floating amount of electrodeposited metal. Further, from the photograph of FIG. 17(b), it can be seen that the particle shape of the metal electrodeposited on the surface of the working electrode is uniform, and the mixed amount of coarse metal particles is small. Further, from the SEM photograph of FIG. 18, it can be seen that the deposit was dense and no dendrite was generated.
　図１９は、実施例４の電解液を用いた３極式セルのサイクリックボルタモグラムである。図１９の結果から、実施例４の電解液を用いた３極式セルは２サイクル目から、実施例１の電解液を用いた３極式セルの場合と同様に０Ｖから低電位側の電流密度が低減することがわかる。これは、実施例４の電解液は、Ｂａが添加されてＬｉが形成する溶媒和の構造が変わったことによると考えられる。 FIG. 19 is a cyclic voltammogram of a three-electrode cell using the electrolytic solution of Example 4. From the results of FIG. 19, the three-electrode cell using the electrolytic solution of Example 4 starts from the second cycle, as in the case of the three-electrode cell using the electrolytic solution of Example 1, the current on the low potential side from 0 V It can be seen that the density is reduced. This is probably because the electrolytic solution of Example 4 changed the structure of solvation formed by Li due to the addition of Ba.
　１０　アルカリ金属二次電池
　１１　ケース
　１２　電解液
　１３　正極
　１４　正極材料層
　１５　正極集電体
　１６　負極
　１７　負極材料層
　１８　負極集電体
　１９　外部回路
　２０　３極式セル
　２１　第１基板
　２２　第２基板
　２２ａ　貫通孔
　２３　第３基板
　２３ａ　貫通孔
　２４　容器
　２４ａ　フランジ部
　２５　蓋
　２６　ボルト
　２７、２８　Ｏリング
　３１　作用極
　３２　対極
　３３　参照極
　３４　対極支持材
　３５　参照極支持材
　４０　３極式セル
　４１　容器
　４２　蓋
　４３　電解液
　４４　作用極（ＷＥ）
　４５　クリップ
　４６　リード線
　４７　対極（ＣＥ）
　４８　クリップ
　４９　リード線
　５０　参照極（ＲＥ）
　５１　クリップ
　５２　リード線
　５３　Ｌｉ（ＴＦＳＡ）／Ｇ３溶液
　５４　セラミックフィルター REFERENCE SIGNS LIST 10 alkali metal secondary battery 11 case 12 electrolytic solution 13 positive electrode 14 positive electrode material layer 15 positive electrode current collector 16 negative electrode 17 negative electrode material layer 18 negative electrode current collector 19 external circuit 20 triode cell 21 first substrate 22 second substrate 22a Through-hole 23 Third substrate 23a Through-hole 24 Container 24a Flange 25 Lid 26 Bolt 27, 28 O-ring 31 Working electrode 32 Counter electrode 33 Reference electrode 34 Counter electrode support 35 Reference electrode support 40 Triode cell 41 Container 42 Lid 43 Electrolyte 44 Working electrode (WE)
45 clip 46 lead wire 47 counter electrode (CE)
48 clip 49 lead wire 50 reference electrode (RE)
51 clip 52 lead wire 53 Li(TFSA)/G3 solution 54 ceramic filter

Claims (7)

  1. 　非水溶媒と、
    　前記非水溶媒に溶解したアルカリ金属塩と、
    　前記非水溶媒に溶解したアルカリ土類金属塩と、を含む、アルカリ金属二次電池用電解液。     a non-aqueous solvent;
    an alkali metal salt dissolved in the non-aqueous solvent;
    and an alkaline earth metal salt dissolved in the non-aqueous solvent.
  2. 　前記アルカリ金属塩がリチウム金属塩およびナトリウム金属塩の少なくとも一方を含み、前記アルカリ土類金属塩がカルシウム金属塩およびバリウム金属塩の少なくとも一方を含む、請求項１に記載のアルカリ金属二次電池用電解液。 2. The alkali metal secondary battery according to claim 1, wherein said alkali metal salt contains at least one of lithium metal salt and sodium metal salt, and said alkaline earth metal salt contains at least one of calcium metal salt and barium metal salt. Electrolyte.
  3. 　前記アルカリ土類金属塩が、ヘキサフルオロリン酸アルカリ土類金属塩、過塩素酸アルカリ土類金属塩、テトラフルオロホウ酸アルカリ土類金属塩、トリフルオロメタンスルホン酸アルカリ土類金属塩、ビス（トリフルオロメチルスルホニル）イミドアルカリ土類金属、ビス（トリフルオロメチルスルホニル）アミドアルカリ土類金属塩、ビス（フルオロスルホニル）アミドアルカリ土類金属塩からなる群より選ばれる少なくとも１つの塩である、請求項１または２に記載のアルカリ金属二次電池用電解液。 The alkaline earth metal salts include alkaline earth metal hexafluorophosphate, alkaline earth metal perchlorate, alkaline earth metal tetrafluoroborate, alkaline earth metal trifluoromethanesulfonate, bis(tri It is at least one salt selected from the group consisting of fluoromethylsulfonyl)imide alkaline earth metal salts, bis(trifluoromethylsulfonyl)amide alkaline earth metal salts, and bis(fluorosulfonyl)amide alkaline earth metal salts. 3. The electrolytic solution for alkali metal secondary batteries according to 1 or 2.
  4. 　前記アルカリ金属塩が、ヘキサフルオロリン酸アルカリ金属塩、過塩素酸アルカリ金属塩、テトラフルオロホウ酸アルカリ金属塩、トリフルオロメタンスルホン酸アルカリ金属塩、ビス（トリフルオロメチルスルホニル）イミドアルカリ金属塩、ビス（トリフルオロメチルスルホニル）アミドアルカリ金属塩、ビス（フルオロスルホニル）アミドアルカリ金属塩からなる群より選ばれる少なくとも１つの塩である、請求項１から３のいずれか１項に記載のアルカリ金属二次電池用電解液。 The alkali metal salts are alkali metal hexafluorophosphate, alkali metal perchlorate, alkali metal tetrafluoroborate, alkali metal trifluoromethanesulfonate, bis(trifluoromethylsulfonyl)imide alkali metal salt, bis The alkali metal secondary according to any one of claims 1 to 3, which is at least one salt selected from the group consisting of (trifluoromethylsulfonyl)amide alkali metal salts and bis(fluorosulfonyl)amide alkali metal salts. Battery electrolyte.
  5. 　前記アルカリ金属塩のアニオンと前記アルカリ土類金属塩のアニオンが同じである、請求項１から４のいずれか１項に記載のアルカリ金属二次電池用電解液。 The electrolytic solution for an alkali metal secondary battery according to any one of claims 1 to 4, wherein the anion of the alkali metal salt and the anion of the alkaline earth metal salt are the same.
  6. 　前記非水溶媒が鎖状エーテルを含む、請求項１から５のいずれか１項に記載のアルカリ金属二次電池用電解液。 The electrolytic solution for an alkali metal secondary battery according to any one of claims 1 to 5, wherein the non-aqueous solvent contains a chain ether.
  7. 　請求項１から６のいずれか１項に記載のアルカリ金属二次電池用電解液と、
    　アルカリ金属イオンの吸蔵および放出が可能な正極活物質を含む正極と、
    　アルカリ金属を含む負極と、を備える、アルカリ金属二次電池。     The electrolytic solution for an alkali metal secondary battery according to any one of claims 1 to 6;
    a positive electrode containing a positive electrode active material capable of absorbing and releasing alkali metal ions;
    An alkali metal secondary battery, comprising: a negative electrode containing an alkali metal.
PCT/JP2021/031540 2021-08-27 2021-08-27 Electrolyte solution for alkali metal secondary batteries, and alkali metal secondary battery WO2023026476A1 (en)

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