JP7342709B2 - Energy storage device - Google Patents

Description

A power storage device is disclosed herein.

Conventionally, one of the challenges of Li-ion batteries used as power storage devices is to make the electrolyte nonflammable. To solve this problem, secondary batteries using an aqueous solution as an electrolyte have been developed. In recent years, aqueous secondary batteries with operating voltages exceeding 2.0 V have been proposed (see, for example, Non-Patent Documents 1 and 2). In Non-Patent Document 1, LiMn ₂ O ₄ is used as a positive electrode active material, Mo ₆ S ₈ is used as a negative electrode active material, and an electrolyte in which Li(CF ₃ SO ₂ ) ₂ N (LiTFSA) is dissolved at a high concentration is used. , the operating voltage is 2.1V. Furthermore, in Non-Patent Document 2, the positive electrode active material is LiNi _0.5 Mn _1.5 O ₄ , the negative electrode active material is Li ₄ Ti ₅ O ₁₂ , and LiTFSA and Li(C ₂ F ₅ SO ₂ ) ₂ N(LiBETI) are used. It uses an electrolyte solution with a high concentration of 3:1, and is said to have an operating voltage of 3.0V. The electrolyte solution of Non-patent Documents 1 and 2 is a solution in which a compound serving as a supporting salt is dissolved in water at a high concentration, and the ratio of supporting salt to water is 1:4 to 1:2 in molar ratio (Patent Document (see 1). Furthermore, as an electrolyte for power storage devices, a non-flammable non-aqueous electrolyte containing LiTFSA as a supporting salt and a phosphoric acid compound as a solvent has been proposed (see, for example, Patent Document 2). This electrolytic solution is less likely to react with oxygen released from the positive electrode active material, and can further suppress heat generation in the electricity storage device.

Unexamined Japanese Patent Publication No. 2017-126500 JP2017-27923A

Science 20 Nov 2015:Vol.350,Issue6263,pp.938-943 Nature Energy 1, Article number: 16129 (2016)

However, some aqueous electrolytes operate at about 3 V, considering the oxidative decomposition potential and the reductive decomposition potential, but there has been a demand for an even higher operating voltage. In addition, electrolytes for power storage devices are required to have increased safety, such as non-flammability, and are also required to improve charging and discharging characteristics and further reduce irreversible capacity during charging and discharging. .

The present disclosure was made in view of such problems, and the main purpose of the present disclosure is to provide a power storage device that is safe and has improved charge/discharge characteristics.

After intensive research to achieve the above-mentioned purpose, the present inventors used an aqueous electrolyte on the positive electrode side, a non-flammable non-aqueous electrolyte on the negative electrode side, and installed a separation material between these electrolytes. It has been found that by not using the above, it is possible to further improve the charging and discharging characteristics, such as further increasing safety, further reducing the irreversible capacity of charging and discharging, and further suppressing the decrease in capacity. The invention to be disclosed has now been completed.

That is, the electricity storage device disclosed in this specification is
a positive electrode having a positive electrode active material;
an aqueous positive electrode electrolyte containing an amide compound and/or a sulfonic acid compound and water, which contacts the positive electrode and conducts carrier ions;
a negative electrode having a negative electrode active material;
A non-aqueous negative electrode electrolyte that contains an amide compound and/or a sulfonic acid compound and a fluorine-containing compound and is interposed between the negative electrode and the positive electrode electrolyte and conducts carrier ions,
A separation material having ion conductivity is not interposed between the positive electrode electrolyte and the negative electrode electrolyte.

The present disclosure can provide an electricity storage device that is safe and further improves charging and discharging characteristics, such as further reducing irreversible capacity. The reason why such an effect is obtained is considered to be, for example, as follows. In this electricity storage device, since an aqueous electrolyte is used on the positive electrode side, it is nonflammable, has better safety, has good ionic conductivity, and can further reduce irreversible capacity. Furthermore, since a non-flammable non-aqueous electrolyte containing fluorine is used on the negative electrode side, safety is better and ionic conductivity is better, and irreversible capacity can be further reduced. In addition, in this electricity storage device, the positive electrode electrolyte and the negative electrode electrolyte do not mix, and there is no separation material such as a separation membrane or solid electrolyte with ion conductivity interposed between them, resulting in a decrease in charge and discharge capacity. etc. can be further suppressed. Therefore, in this electricity storage device, the electrolytic solution is nonflammable and safe, and the difference between the charging capacity and the discharging capacity is smaller, and it is presumed that a decrease in the discharging capacity can be further suppressed.

FIG. 2 is a schematic diagram showing an example of a power storage device 20. FIG. 3 is an explanatory diagram showing a test cell 30. FIG. A photograph examining the compatibility between the positive electrode electrolyte and the negative electrode electrolyte in Experimental Example 1. Initial charge/discharge curve of Experimental Example 1. Initial charge/discharge curve of Experimental Example 3. Initial charge/discharge curve of Experimental Example 6. Initial charge/discharge curve of Experimental Example 8. FIG. 3 is a diagram showing the relationship between charge and discharge cycles and charge and discharge capacity in Experimental Example 1.

The electricity storage device of the present disclosure includes a positive electrode having a positive electrode active material, an aqueous positive electrode electrolyte that contacts the positive electrode and conducts carrier ions, a negative electrode having a negative electrode active material, and an aqueous positive electrode electrolyte that is interposed between the negative electrode and the positive electrode electrolyte. and a non-aqueous negative electrode electrolyte that conducts carrier ions. Here, examples of carrier ions serving as carriers of this electricity storage device include Group 1 ions and Group 2 ions. Examples of Group 1 ions include ions such as lithium, sodium, potassium, and cesium, and among these, lithium and sodium ions are preferred. Examples of Group 2 ions include beryllium ions, magnesium ions, calcium ions, and strontium ions. Examples of power storage devices include alkali metal secondary batteries including lithium secondary batteries, alkaline ion secondary batteries including lithium ion secondary batteries, hybrid capacitors, and air batteries. Here, for convenience of explanation, a lithium ion secondary battery using lithium ions as carrier ions will be mainly explained.

The positive electrode of the electricity storage device of the present disclosure is prepared by, for example, mixing a positive electrode active material, a conductive material, and a binding material, and adding an appropriate solvent to make a paste-like positive electrode material, which is then applied and dried on the surface of a current collector. , if necessary, it may be compressed and formed in order to increase the electrode density. As the positive electrode active material, it is preferable to use one having an oxidation-reduction potential within the range of 3.5 V or more and 4.9 V or less based on the Li reference potential. With such a positive electrode active material, the voltage of the electricity storage device can be further increased. The positive electrode active material may be, for example, a transition metal composite oxide containing Mn and further containing one or more of Co and Ni. Specifically, lithium manganese composite oxides whose basic composition formula is Li _x MnO ₂ (0≦x≦1.2, etc., the same applies hereinafter), Li _x Mn ₂ O ₄ , etc., and lithium manganese composite oxides whose basic composition formula is Li _x Ni _a Lithium nickel manganese composite oxide such as Mn _b O ₄ (a+b=2), the basic compositional formula of which is Li _x Ni _a Co _b Mn _c O ₂ (a≧0, b≧0, c≧0, a+b+c=1) A lithium nickel cobalt manganese composite oxide such as lithium nickel cobalt manganese composite oxide can be used. In addition, the positive electrode active material includes a lithium cobalt composite oxide having a basic composition formula such as Li _x CoO ₂ , a lithium nickel composite oxide having a basic composition formula such as Li _x NiO ₂ , and a lithium nickel composite oxide having a basic composition formula such as Li _x Ni _a Co _b It may also be a lithium nickel cobalt composite oxide such as O ₂ . Further, the positive electrode active material may be a lithium iron phosphate compound such as LiFePO ₄ . Note that the "basic compositional formula" may include other elements (for example, Al, Mg, Cr, etc.). Further, x in the above basic compositional formula may exceed 1, and a+b or a+b+c may exceed 1. Among these, positive electrode active materials include LiMn ₂ O ₄ , LiAl _0.1 Mn _1.9 O ₄ , LiCr _0.1 Mn _1.9 O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and the like. , LiNi _0.8 Co _0.2 O ₂ , LiFePO ₄ and the like are preferred.

The conductive material used for the positive electrode is not particularly limited as long as it is an electronically conductive material that does not adversely affect the battery performance of the positive electrode, and examples include graphite such as natural graphite (scaly graphite, flaky graphite), artificial graphite, acetylene black, etc. , carbon black, Ketjenblack, carbon whiskers, needle coke, carbon fibers, metals (copper, nickel, aluminum, silver, gold, etc.), or a mixture of two or more thereof can be used. Among these, carbon black and acetylene black are preferred as the conductive material from the viewpoint of electronic conductivity and coatability. The binder plays a role of binding the active material particles and the conductive material particles, and includes, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resin such as fluororubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), etc. can be used alone or as a mixture of two or more. Furthermore, an aqueous binder such as a cellulose binder or an aqueous dispersion of styrene-butadiene rubber (SBR) can also be used. Examples of the solvent for dispersing the positive electrode active material, conductive material, and binder include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, and N,N-dimethyl. Organic solvents such as aminopropylamine, ethylene oxide, and tetrahydrofuran can be used. Alternatively, the active material may be slurried with latex such as SBR by adding a dispersant, a thickener, etc. to water. As the thickener, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used alone or as a mixture of two or more. The ratio of the conductive material to the binder may be 3 to 25 parts by mass relative to 100 parts by mass of the conductive material. Application methods include, for example, roller coating using an applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. Any of these methods can be used to obtain an arbitrary thickness and shape. Current collectors include aluminum, titanium, stainless steel, nickel, iron, sintered carbon, conductive polymers, conductive glass, etc., as well as aluminum, copper, etc. for the purpose of improving adhesiveness, conductivity, and oxidation resistance. It is possible to use materials whose surfaces have been treated with carbon, nickel, titanium, silver, etc. It is also possible to oxidize the surface of these materials. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded material, lath material, porous material, foam material, and fiber group formed material. The thickness of the current collector used is, for example, 1 to 500 μm.

The positive electrode electrolyte is an aqueous electrolyte that comes into contact with the positive electrode. This positive electrode electrolyte contains an amide compound and/or a sulfonic acid compound and water. The amide compound may contain, for example, one or more of bis(trifluoromethanesulfonyl)amide (TFSA) anion and bis(fluorosulfonyl)amide (FSA) anion. The sulfonic acid compound may have two or more sulfonic acid groups at the end of the carbon chain. The sulfonic acid compound may include a propanedisulfonic acid (PDS) anion. Further, counter cations of amide compounds and sulfonic acid compounds include, for example, Group 1 cations such as lithium ions, sodium ions, and potassium ions, and Group 2 cations such as magnesium ions, calcium ions, and strontium ions. Among these, lithium is preferable as the counter cation. As the amide compound, LiTFSA, LiFSA, and PDSL are preferable. This positive electrode electrolyte may be one in which the concentration of the amide compound and/or sulfonic acid compound ranges from a dilute level to a saturated level. From the viewpoint of increasing the operating voltage, this positive electrode electrolyte is an aqueous solution in which an amide compound and/or a sulfonic acid compound is dissolved at a high concentration (for example, 5 mol/L or more, 10 mol/L or more, 20 mol/L or more). It is preferable. This positive electrode electrolyte preferably contains an amide compound and/or a sulfonic acid compound in a molar ratio of 1/3 to 1/2 to water. Use of such a concentrated aqueous electrolyte is preferable because the operating voltage of the electricity storage device can be made relatively high.

The negative electrode of the electricity storage device of the present disclosure may be formed by closely adhering a negative electrode active material and a current collector, or, for example, may be formed by mixing a negative electrode active material, a binder, and, if necessary, a conductive material. A paste-like negative electrode material may be formed by adding a suitable solvent to the surface of the current collector, and drying the paste, and compressing the paste to increase the electrode density if necessary. The negative electrode active material preferably has an oxidation-reduction potential within a range of 2.5 V or less, more preferably 1.5 V or less, still more preferably 1.0 V or less, based on Li reference potential. With the negative electrode active material within this range, the voltage of the electricity storage device can be further increased. Examples of the negative electrode active material include lithium, lithium alloys, inorganic compounds such as tin compounds, carbonaceous materials capable of intercalating and deintercalating lithium ions, composite oxides containing multiple elements, conductive polymers, and the like. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite have operating potentials close to those of metallic lithium, and can be charged and discharged at high operating voltages.When using lithium salts as supporting salts, they suppress self-discharge. In addition, it is preferable because irreversible capacity during charging can be reduced. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. As the binder, solvent, etc. used for the negative electrode, those exemplified for the positive electrode can be used. The current collector of the negative electrode is made of copper, nickel, stainless steel, titanium, aluminum, fired carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as materials with improved adhesiveness, conductivity, and reduction resistance. For this purpose, for example, copper or the like whose surface is treated with carbon, nickel, titanium, silver, etc. can also be used. It is also possible to oxidize the surface of these materials. The shape of the current collector can be similar to that of the positive electrode.

The negative electrode electrolyte is a nonaqueous electrolyte that is interposed between the negative electrode and the positive electrode electrolyte and conducts carrier ions. This negative electrode electrolyte contains an amide compound and/or a sulfonic acid compound and a fluorine-containing compound. For example, the fluorine-containing compound is preferably nonflammable, and more preferably has self-extinguishing properties that extinguish itself when ignited. The fluorine-containing compound is preferably, for example, a fluorinated phosphate ester compound or a fluorinated phosphate ester amide compound. The fluorine-containing compound includes, for example, tris(trifluoroethyl) phosphate as a fluorinated phosphate ester; TFEP or bis(trifluoroethyl)phenylmethylamide phosphate as a fluorinated phosphate ester amide; One or more of PNMePh, bis(trifluoroethyl)phenylpropylamide phosphate; PNPrPh, bis(trifluoroethyl)dipropylamide phosphate; PNPrPr, bis(trifluoroethyl)dimethylamide phosphate; and PNMeMe may be mentioned. These compounds are preferred because they are nonflammable and self-extinguishing. As the amide compound and sulfonic acid compound contained in the negative electrode electrolyte, those explained for the positive electrode electrolyte can be used as appropriate. This negative electrode electrolyte may be one in which the concentration of the amide compound and/or sulfonic acid compound ranges from a dilute level to a saturated level. From the viewpoint of increasing the operating voltage, this negative electrode electrolyte is a non-aqueous solution in which an amide compound and/or a sulfonic acid compound is dissolved at a high concentration (for example, 5 mol/L or more, 10 mol/L or more, 20 mol/L or more, etc.). It is preferable to do so. This negative electrode electrolyte preferably contains the amide compound in a molar ratio of 1/3.5 to 1/2.5 to the fluorine-containing compound. Use of such a concentrated non-aqueous electrolyte is preferable because the operating voltage of the electricity storage device can be made relatively high.

The positive electrode electrolyte and/or the negative electrode electrolyte may contain other supporting salts as carrier ion salts. Examples of this supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiSbF 6 , LiSiF ₆ , LiAlF ₄ , LiSCN, LiClO _{4 ,} LiCl, LiF, LiBr, LiI and LiAlCl ₄ . . The aqueous positive electrode electrolyte may have a potential window in the range of 1.7 V or more and 4.9 V or less at Li reference potential. The lower limit value of this potential window is preferably lower, and the upper limit value is preferably higher. When using this aqueous electrolyte, one or more of Li metal and graphite can be used as the negative electrode active material based on the lower limit potential of the potential window. The potential window of an aqueous electrolyte can be determined from the flat region of the curve by measuring a cyclic voltammogram of the aqueous electrolyte.

It is preferable that an additive containing a cation different from a carrier ion is added to the positive electrode electrolyte and/or the negative electrode electrolyte. Examples of this additive include those containing Mg, Ca, and Cs as cations. As this additive, one containing the same anion as the above-mentioned amide compound can be used. Specifically, MgTFSA, CaTFSA, CsTFSA, etc. may be mentioned. This additive may be contained, for example, in a molar ratio of 1.0 mol % or more, or 5.0 mol % or less with respect to the amide compound.

In the electricity storage device of the present disclosure, a separation material having ion conductivity is not interposed between the positive electrode electrolyte and the negative electrode electrolyte. Examples of the separation material include separation membranes and solid electrolytes that have ion conductivity and physically separate electrolytes. In this electricity storage device, since the aqueous positive electrode electrolyte and the non-aqueous negative electrode electrolyte are difficult to mix, there is no need to provide a physical separation material to separate the electrolyte, and charging due to decreases in ionic conductivity is not necessary. Decrease in discharge capacity can be suppressed. The separation membrane may be, for example, polyvinylidene fluoride (PVdF), a copolymer of PVdF and hexafluoropropylene (PVdF-HFP), polymethyl methacrylate (PMMA), or a copolymer of PMMA and acrylic polymer. Examples include resin films such as coalescence. Examples of solid electrolytes include general Li ₃ N, Li ₁₄ Zn(GeO ₄ ) ₄ called LISICON, sulfide Li _3.25 Ge _0.25 P _0.75 S ₄ , perovskite La _0.5 Li _0.5 TiO ₃ , ( La _2/3 Li _3x □ _1/3-2x ) TiO ₃ (□: atomic vacancy), garnet type Li ₇ La ₃ Zr ₂ O ₁₂ , NASICON type LiTi ₂ (PO ₄ ) ₃ , Li _1.3 M Examples include _0.3 Ti _1.7 (PO ₃ ) ₄ (M=Sc, Al). In addition, Li ₇ P ₃ S ₁₁ obtained from glass with a composition of 80Li ₂ S/20P ₂ S ₅ (mol%), which is a glass ceramic, and Li ₁₀ Ge ₂ PS, which is a sulfide-based substance with high conductivity. ₂ etc. can also be mentioned. Glass-based inorganic solid electrolytes include Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li ₄ SiO ₄ , Li ₂ S- P ₂ S ₅ , Li ₃ PO ₄ -Li ₄ SiO ₄ , Li ₃ BO ₄ -Li ₄ SiO ₄ , and Li ₂ O with SiO ₂ , GeO ₂ , B ₂ O ₃ and P ₂ O ₅ as glass-based substances. Examples include those used as network modifiers. In addition, as a thiolisicone solid electrolyte, Li ₂ S-GeS ₂ system, Li ₂ S-GeS ₂ -ZnS system, Li ₂ S-Ga ₂ S ₂ system, Li ₂ S-GeS ₂ -Ga ₂ S ₃ system, Li ₂ S -GeS ₂ -P ₂ S ₅ system, Li ₂ S-GeS ₂ -SbS ₅ system, Li ₂ S-GeS ₂ -Al ₂ S ₃ system, Li ₂ S-SiS ₂ system, Li ₂ S-P ₂ S ₅ Examples include Li ₂ S--Al ₂ S _3- based, LiS--SiS ₂ -Al ₂ S ₃ -based, Li ₂ S--SiS ₂ -P ₂ S ₅ -based, and the like.

The electricity storage device of the present disclosure may include a separator between the negative electrode and the positive electrode. This separator is a member that prevents direct contact between the positive electrode and the negative electrode, and unlike a separation material, it allows the electrolyte to pass through. The separator is not particularly limited as long as it has a composition that can withstand the usage range of power storage devices, but examples include polymeric nonwoven fabrics such as polypropylene nonwoven fabrics and polyphenylene sulfide nonwoven fabrics, and thin microporous materials made of olefin resins such as polyethylene and polypropylene. can be mentioned. Alternatively, filter paper may be used as a separator. These may be used alone or in combination.

In the electricity storage device of the present disclosure, the carrier ions may be alkali metal ions. Further, the negative electrode active material may be one or more of an alkali metal, an alkali metal alloy, and graphite. Further, the negative electrode electrolyte may be held in an absorbent material adjacent to the negative electrode. At this time, the positive electrode electrolyte may be held in a gap formed in the positive electrode. Alternatively, the electricity storage device may have a positive electrode electrolyte held in an absorbent material adjacent to the positive electrode. Further, the negative electrode electrolyte may be held in a gap formed in the negative electrode. In this electricity storage device, since the absorbent material is present between the positive electrode and the negative electrode, short circuits between the positive and negative electrodes can be further suppressed. Furthermore, since the potential of the negative electrode active material is low, the discharge voltage of the electricity storage device can be made higher. Furthermore, since the absorbent material suppresses the movement of the electrolyte solution, for example, even when the direction of the electricity storage device is changed, mixing of the electrolyte solution is further suppressed, which is preferable. Examples of the absorbent material include a member having voids through which the electrolytic solution can pass, such as a resin nonwoven separator and filter paper. This absorbent material may also be used as a separator.

The shape of this power storage device is not particularly limited, and examples thereof include a coin shape, a button shape, a sheet shape, a stacked type, a cylindrical shape, a flat shape, a square shape, and the like. Further, the present invention may be applied to large-sized vehicles used in electric vehicles and the like. FIG. 1 is a schematic diagram showing an example of a power storage device 20 disclosed in this specification. This electricity storage device 20 includes a negative electrode 21 , a negative electrolyte 24 , a positive electrode 25 , and a positive electrolyte 28 . In the electricity storage device 20, the negative electrode 21 includes a negative electrode active material 22 and a current collector 23 adjacent to the negative electrode active material 22. The positive electrode 25 includes a positive electrode active material 26 and a current collector 27 adjacent to the positive electrode active material 26. The negative electrode electrolyte 24 may be held on the negative electrode 21 by an absorbent material that absorbs the negative electrode electrolyte 24. Further, in FIG. 1, for convenience, it is assumed that the positive electrode electrolyte 28 is interposed between the negative electrode electrolyte 24 and the positive electrode 25, but the positive electrode electrolyte 28 may also be held in the gap of the positive electrode 25. good. The negative electrode electrolyte 24 is a non-aqueous negative electrode electrolyte containing an amide compound and/or a sulfonic acid compound and a fluorine-containing compound. The positive electrode electrolyte 28 is an aqueous electrolyte containing an amide compound and/or a sulfonic acid compound and water.

It is preferable that the irreversible capacity of the electricity storage device of the present disclosure, which is obtained by subtracting the discharge capacity from the charge capacity, is 16 mAh/g or less. This irreversible capacity is preferably smaller. Further, it is preferable that this electricity storage device exhibits a charge/discharge capacity ratio of 0.87 or more, which is obtained by dividing the discharge capacity by the charge capacity. This charge/discharge capacity ratio is preferably higher.

With the electricity storage device described in detail above, it is possible to provide an electricity storage device that is safe and further improves charging and discharging characteristics, such as further reducing irreversible capacity. The reason why such an effect is obtained is considered to be, for example, as follows. In this electricity storage device, since an aqueous electrolyte is used on the positive electrode side, it is nonflammable, has better safety, has good ionic conductivity, and can further reduce irreversible capacity. Furthermore, since a non-flammable non-aqueous electrolyte containing fluorine is used on the negative electrode side, safety is better and ionic conductivity is better, and irreversible capacity can be further reduced. In addition, in this electricity storage device, the positive electrode electrolyte and the negative electrode electrolyte do not mix, and there is no separation material such as a separation membrane or solid electrolyte with ion conductivity interposed between them, resulting in a decrease in charge and discharge capacity. etc. can be further suppressed. Therefore, in this electricity storage device, the electrolytic solution is nonflammable and safe, and the difference between the charging capacity and the discharging capacity is smaller, and a decrease in the discharging capacity can be further suppressed.

It goes without saying that the present disclosure is not limited to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

For example, in the embodiments described above, lithium was used as the main carrier, but the carrier is not particularly limited to this, and sodium or potassium may also be used. For example, although LiTFSA, LiFSA, and PDSL are mainly used in the positive electrode and negative electrode electrolytes, NaTFSA, NaFSA, PDSN (sodium propane disulfonate), etc. may also be used.

Below, an example in which the electricity storage device disclosed in this specification was specifically produced will be described as an experimental example. Note that Experimental Examples 1, 4, 6, and 8 correspond to Examples, and Experimental Examples 2, 3, 5, and 7 correspond to Comparative Examples.

[Experiment example 1]
The positive electrode was produced as follows. Spinel-type aluminum-substituted lithium manganese oxide (Li _1.1 Al _0.1 Mn _1.9 O ₄ manufactured by Sumitomo Mitsui Metal Mining), a conductive material (TB5500 manufactured by Tokai Carbon), and PVdF as a binder (#1320 manufactured by Kureha Chemical). were wet mixed with N-methylpyrrolidone (NMP). A kneader (Awatori Rentaro manufactured by Shinky Co., Ltd.) was used for mixing. This was coated on a 20 μm thick aluminum foil and vacuum dried at 150°C. Thereafter, it was punched out to a diameter of 14 mm and pressed to obtain a positive electrode. The thickness of the positive electrode composite material layer was 40 μm. Further, the final ratio of active material:conductive material:binder was 77:14:9 in terms of mass ratio. Further, the basis weight of the positive electrode active material was 6.55 mg/cm ² . The negative electrode used was a metal lithium (40 μm thick) punched out to a diameter of 14 mm. The positive electrode electrolyte was prepared by mixing lithium bis(trifluoromethanesulfonyl)amide (LiTFSA, manufactured by Kishida Chemical Co., Ltd.) and water in a molar ratio of 1:2.8 in an aqueous solution, and adding Mg (TFSA) in a molar ratio to LiTFSA. ) ₂ was added in an aqueous electrolyte solution in an amount of 3.5 mol %. 50 μL of this positive electrode electrolyte was impregnated into the gap of the positive electrode and held in the positive electrode. The negative electrode electrolyte is a non-aqueous mixture of lithium bis(fluoromethanesulfonyl)amide (LiFSA, manufactured by Kishida Chemical) and tris(trifluoroethyl) phosphate (TFEP, manufactured by Tosoh) in a molar ratio of 1:2.5. It was used as an electrolyte. A metal lithium negative electrode and a sheet of filter paper (manufactured by Kiriyama, 5C) were stacked together as a separator, and 200 μL of the negative electrode electrolyte was impregnated therein and retained. A test cell 30 was assembled by stacking this and a positive electrode impregnated with the above positive electrode electrolyte.

FIG. 2 is an explanatory diagram of the test cell 30. The test cell 30 includes a negative electrode 31 , a negative electrolyte 34 , a positive electrode 35 , and a positive electrolyte 38 . In the test cell 30, the negative electrode 31 includes a negative electrode active material 32 and a current collector 33 adjacent to the negative electrode active material 32. The positive electrode 35 includes a positive electrode active material 36 and a current collector 37 adjacent to the positive electrode active material 36. The negative electrode electrolyte 34 is held on the negative electrode 31 by an absorbent material (filter paper) that absorbs the negative electrode electrolyte 34 . Further, in FIG. 2, for convenience, it is assumed that the positive electrode electrolyte 38 is interposed between the negative electrode electrolyte 34 and the positive electrode 35, but the positive electrode electrolyte 38 may also be held in the gap of the positive electrode 35. good.

(compatibility of electrolyte)
FIG. 3 is a photograph in which the aqueous positive electrode electrolyte and the non-aqueous negative electrode electrolyte of Experimental Example 1 were placed in a container and their compatibility was examined. As shown in FIG. 3, it was confirmed that the positive electrode electrolyte and the negative electrode electrolyte were incompatible and maintained a separated state without intervening a separation membrane, solid electrolyte, or the like.

(Charge/discharge characteristics)
The charging and discharging characteristics of Experimental Example 1 were evaluated. In this evaluation, the battery was charged to 4.4V with a current of 0.04 mA/cm ² at 25° C., and then discharged to 2.9V with a current of 0.04 mA/cm ² . Table 1 summarizes the active materials, electrolytes, charge/discharge capacities, charge/discharge capacity ratios, and notes of the positive and negative electrodes of Experimental Examples 1 to 10. FIG. 4 is an initial charge/discharge curve of Experimental Example 1. The charge capacity and discharge capacity per positive electrode active material in the first cycle are 112 mAh/g and 98 mAh/g, respectively, and the irreversible capacity obtained by subtracting the discharge capacity from the charge capacity is as small as 14 mAh/g. The charge/discharge capacity ratio divided by capacity was as high as 0.875. Furthermore, in Experimental Example 1, the operating potential was as high as 4.2 V to 3.9 V, and it was revealed that the charge/discharge characteristics were high.

(Experiment example 2)
Other than using an aqueous solution in which LiTFSA and water were mixed at a molar ratio of 1:2.8 as the negative electrode electrolyte, 3.5 mol% of Mg(TFSA) ₂ was added in a molar ratio to LiTFSA. Experimental Example 2 was prepared in the same manner as Experimental Example 1. Experimental example 2 was produced using one solution of the positive electrode electrolyte of experimental example 1. A charge/discharge test was conducted in the same manner as in Experimental Example 1, but charging was not possible.

(Experiment example 3)
Experimental Example 3 was prepared in the same manner as Experimental Example 1 except that a non-aqueous electrolyte containing LiFSA and TFEP mixed at a molar ratio of 1:2.5 was used as the positive electrode electrolyte. Experimental example 3 was produced using one solution of the negative electrode electrolyte of experimental example 1. FIG. 5 is an initial charge/discharge curve of Experimental Example 3. When charging and discharging were performed in the same manner as in Example 1, the charging and discharging capacities per positive electrode active material in the first cycle were 114 mAh/g and 75 mAh/g, respectively, and the irreversible capacity was as large as 39 mAh/g. Further, the charge/discharge capacity ratio was 0.658, which was lower than that of Experimental Example 1. From the above, it was found that in Experimental Example 1, in which the aqueous positive electrode electrolyte and the non-aqueous non-flammable negative electrode electrolyte were brought into contact without a separation material, better charge/discharge characteristics were obtained.

(Experiment example 4)
Produced in the same manner as in Experimental Example 1 except that an aqueous electrolyte in which lithium propane disulfonate (PDSL, manufactured by Tosoh) and water were mixed and dissolved at a molar ratio of 1:14.6 was used as the positive electrode electrolyte. This was designated as Experimental Example 4. The charge/discharge test was conducted between 4.1V and 2.9V as in Experimental Example 1. The charging capacity and discharging capacity per positive electrode active material in the first cycle of Experimental Example 4 were 62 mAh/g and 55 mAh/g, respectively.Although the capacity was small, the irreversible capacity was 7 mAh/g, and the charge/discharge capacity ratio was 0. 887, showing good characteristics. It was inferred that amide compounds are better for the positive electrode electrolyte than sulfone compounds.

(Experiment example 5)
Experimental Example 5 was prepared in the same manner as Experimental Example 4, except that an aqueous electrolyte in which PDSL and water were mixed and dissolved at a molar ratio of 1:14.6 was used as the negative electrode electrolyte. Experimental example 5 was produced using one solution of the positive electrode electrolyte of experimental example 4. A charge/discharge test was conducted in the same manner as in Experimental Example 4, but charging was not possible.

(Experiment example 6)
Layered lithium nickel oxide (LiNi _0.8 Co _0.15 Al _0.05 O ₂ , Sakai Kagaku) was used as the positive electrode active material, and LiTFSA (Kishida Kagaku) and water were mixed as the positive electrode electrolyte at a molar ratio of 1:2.5. A non-aqueous non-flammable electrolyte in which LiFSA and bis(trifluoroethyl)phenylmethylamide phosphate (PNMePh, manufactured by Tosoh) were mixed and dissolved at a molar ratio of 1:3 as an aqueous electrolyte and a negative electrode electrolyte, respectively. Experimental Example 6 was prepared in the same manner as in Experimental Example 1 except that it was used. FIG. 6 is an initial charge/discharge curve of Experimental Example 6. The charge capacity and discharge capacity per positive electrode active material in the first cycle of Experimental Example 6 were 149 mAh/g and 134 mAh/g, respectively, the irreversible capacity was 15 mAh/g, and the charge/discharge capacity ratio was 0.899, which was a good result. The characteristics were shown.

(Experiment example 7)
Experimental Example 7 was prepared in the same manner as Experimental Example 6, except that a non-aqueous, non-flammable electrolyte in which LiFSA and PNMePh were mixed and dissolved at a molar ratio of 1:3 was used as the positive electrode electrolyte. Experimental Example 7 was produced using one solution of the negative electrode electrolyte of Experimental Example 6. The charge capacity and discharge capacity per positive electrode active material in the first cycle of Experimental Example 7 were 123 mAh/g and 106 mAh/g, respectively, the irreversible capacity was 17 mAh/g, and the charge/discharge capacity ratio was 0.862. It was found that Experimental Example 6 had a better charge/discharge capacity ratio and higher charge/discharge capacity than Experimental Example 7.

(Experiment example 8)
Experimental Example 8 was prepared in the same manner as Experimental Example 6 except that a lithium iron phosphate compound (LiFePO ₄ , manufactured by Nihon Kagaku Kogyo) was used as the positive electrode active material. Charging and discharging were performed between 3.7V and 2.8V. FIG. 7 is an initial charge/discharge curve of Experimental Example 8. The charge capacity and discharge capacity per positive electrode active material in the first cycle of Experimental Example 8 were 147 mAh/g and 141 mAh/g, respectively, the irreversible capacity was 6 mAh/g, and the charge/discharge capacity ratio was 0.959, which was a good result. The characteristics were shown.

(Experiment example 9)
Experimental Example 9 was prepared in the same manner as Experimental Example 8, except that a non-aqueous, non-flammable electrolyte in which LiFSA and PNMePh were mixed and dissolved at a molar ratio of 1:3 was used as the positive electrode electrolyte. The charging capacity and discharging capacity per positive electrode active material in the first cycle of Experimental Example 9 were 128 mAh/g and 92 mAh/g, respectively, the irreversible capacity was 36 mAh/g, the charge/discharge capacity ratio was 0.719, and the characteristics was low.

(Experiment example 10)
Experimental Example 10 was prepared in the same manner as Experimental Example 8 except that a 1 mm thick lithium ion conductive glass ceramic (LICGC (registered trademark), manufactured by OHARA) plate was provided between the positive electrode and the filter paper. The charge capacity and discharge capacity per positive electrode active material in the first cycle of Experimental Example 10 are 103 mAh/g and 94 mAh/g, respectively, the irreversible capacity is 9 mAh/g, and the charge/discharge capacity ratio is 0.913, which is good. However, the charge/discharge capacity was lower than that of Experimental Example 8. From the results of Experimental Example 10, it was found that when a solid electrolyte as a separation material was interposed between the positive electrode electrolyte and the negative electrode electrolyte, the discharge capacity was significantly reduced. For this reason, it has been found that it is preferable not to use a separation material between the positive electrode electrolyte and the negative electrode electrolyte.

(Charge/discharge cycle test)
The charge/discharge cycle characteristics of Experimental Example 1 were evaluated. The charge/discharge cycle characteristics were determined by performing 20 charge/discharge cycles using the test cell 30 of Experimental Example 1 as described above. FIG. 8 is a diagram showing the relationship between the number of cycles and the charge/discharge capacity in the charge/discharge cycle test of Experimental Example 1. In Experimental Example 1, an aqueous positive electrode electrolyte and a non-aqueous, non-flammable negative electrode electrolyte were made by contacting each other without a separating material. It was found that a discharge cycle could be performed. In addition, in Experimental Examples 4, 6, and 8 as well, it was presumed that the irreversible capacity was small and stable charge/discharge cycles could be performed. In addition, in Experimental Examples 1, 4, 6, and 8, it was found that even if charging and discharging were performed by changing the vertical direction, mixing of the electrolyte did not occur, and stable charging and discharging could be performed.

It goes without saying that the present disclosure is not limited to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

The power storage device disclosed herein can be used in the energy industry, for example, the battery industry.

20 electricity storage device, 21 negative electrode, 22 negative electrode active material, 23 current collector, 24 negative electrode electrolyte, 25 positive electrode, 26 positive electrode active material, 27 current collector, 28 positive electrode electrolyte, 30 test cell, 31 negative electrode, 32 negative electrode active substance, 33 current collector, 34 negative electrode electrolyte, 35 positive electrode, 36 positive electrode active material, 37 current collector, 38 positive electrode electrolyte.

Claims (7)

a positive electrode having a positive electrode active material;
an aqueous positive electrode electrolyte containing an amide compound and/or a sulfonic acid compound and water, which contacts the positive electrode and conducts carrier ions;
a negative electrode having a negative electrode active material;
A non-aqueous negative electrode electrolyte that contains an amide compound and/or a sulfonic acid compound and a fluorine-containing compound and is interposed between the negative electrode and the positive electrode electrolyte and conducts carrier ions,
The fluorine-containing compound is one or more of a fluorinated phosphate ester compound and a fluorinated phosphate ester amide compound,
The sulfonic acid compound has two or more sulfonic acid groups at the end of the carbon chain,
The amide compound contains one or more of a bis(trifluoromethanesulfonyl)amide (TFSA) anion and a bis(fluorosulfonyl)amide (FSA) anion,
An electricity storage device, wherein a separation material having ion conductivity and separating the positive electrode electrolyte and the negative electrode electrolyte is not interposed between the positive electrode electrolyte and the negative electrode electrolyte . The amide compound contains one or more of a bis(trifluoromethanesulfonyl)amide (TFSA) anion and a bis(fluorosulfonyl)amide (FSA) anion,
The electricity storage device according to claim 1, wherein the sulfonic acid compound includes a propanedisulfonic acid (PDS) anion. The electricity storage device according to claim 1 or 2, wherein the positive electrode electrolyte contains the amide compound and/or the sulfonic acid compound in a molar ratio of 1/3 or more and 1/2 or less with respect to water. The fluorine-containing compound is tris(trifluoroethyl) phosphate as a fluorinated phosphate ester; TFEP; or bis(trifluoroethyl)phenylmethylamide as a fluorinated phosphate ester amide; PNMePh, phosphorus; 1 or more of acid bis(trifluoroethyl) phenylpropylamide; PNPrPh; bis(trifluoroethyl) dipropyl phosphate; PNPrPr; bis(trifluoroethyl) dimethyl amide; PNMeMe; 3. The electricity storage device according to any one of 3. Any one of claims 1 to 4, wherein the negative electrode electrolyte contains the amide compound in a molar ratio of 1/3.5 to 1/2.5 to the fluorine-containing compound. The electricity storage device described in . the carrier ion is an alkali metal ion,
The negative electrode active material is one or more of an alkali metal, an alkali metal alloy, and graphite,
The negative electrode electrolyte is held on an absorbent material adjacent to the negative electrode ,
The electricity storage device according to any one of claims 1 to 5. The electricity storage device according to any one of claims 1 to 6, wherein the positive electrode electrolyte is held in a gap formed in the positive electrode.

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