JP2020136436A - Power storage device - Google Patents

Abstract

To further improve charge and discharge characteristics of a negative electrode using a layered structure.SOLUTION: A power storage device comprises: a positive electrode; a negative electrode including as a negative electrode active material, a layered structure comprising an organic skeleton layer including an aromatic dicarboxylic acid anion and an alkali metal element layer in which an alkali metal element coordinates with oxygen included in a carboxylic acid of the organic skeleton layer to form a skeleton; and an ion-conducting medium that includes at least lithium bis(fluorosulfonyl)imide (LiFSI) as supporting salt and that interposes between a positive electrode and a negative electrode to conduct lithium ions.SELECTED DRAWING: Figure 3

Description

This specification discloses a power storage device.

Conventionally, as a power storage device such as a lithium ion secondary battery, a device having a graphite negative electrode and using LiPF ₆ or lithium bis (fluorosulfonyl) imide (LiFSI) as a supporting salt in a non-aqueous electrolytic solution has been proposed (for example). , Non-Patent Document 1, etc.). In this lithium ion secondary battery, even if LiPF ₆ or lithium bis (fluorosulfonyl) imide (LiFSI) is used as the supporting salt, there is no big difference in the internal resistance of the cell. Further, as the power storage device, an organic skeleton layer containing an aromatic compound which is a dicarboxylic acid anion having two or more aromatic ring structures and an alkali metal element coordinate with oxygen contained in the carboxylic acid anion to form a skeleton. There has been proposed a layered structure having an alkali metal element layer and a negative electrode active material (see, for example, Patent Document 1). Although the layered structure as the negative electrode active material does not have conductivity, it is difficult to dissolve in a non-aqueous electrolytic solution, and by maintaining the crystal structure, the stability of charge / discharge cycle characteristics can be further enhanced.

Japanese Unexamined Patent Publication No. 2012-221754

Electrochimica. Acta. 259 (2018) 949-954

However, although the power storage device of Patent Document 1 described above can further improve the stability of charge / discharge cycle characteristics, it is still insufficient and the resistance of the negative electrode may be high, and it is required to reduce this resistance. Was being done. As described above, it has been required to enhance the charge / discharge characteristics of the electrode using the layered structure as the electrode active material.

The present disclosure has been made in view of such a problem, and an object of the present disclosure is to provide a power storage device capable of further enhancing the charge / discharge characteristics of a negative electrode using a layered structure.

As a result of diligent research to achieve the above-mentioned object, the present inventors further reduce IV resistance when a specific imide salt is added as a supporting salt when using a layered structure of an aromatic dicarboxylic acid metal salt. However, they have found that the discharge capacity can be further improved, and have completed the invention of the present disclosure.

That is, the power storage device of the present disclosure is
With the positive electrode
A layered structure including an organic skeleton layer containing an aromatic dicarboxylic acid anion and an alkali metal element layer in which an alkali metal element is coordinated with oxygen contained in the carboxylic acid of the organic skeleton layer to form a skeleton is used as a negative electrode active material. Including negative electrode and
An ionic conduction medium containing at least lithium bis (fluorosulfonyl) imide (LiFSI) as a supporting salt, interposed between the positive electrode and the negative electrode, and conducting lithium ions.
It is equipped with.

In the power storage device disclosed in the present specification, the charge / discharge characteristics can be further improved when the layered structure is used as the negative electrode active material. The reason why such an effect can be obtained is that, for example, when an ion conductive medium containing LiFSI is used for a negative electrode using a negative electrode active material of a layered structure, a low resistance film is formed at the interface between the negative electrode and the electrolytic solution. It is presumed that this is because of this.

Explanatory drawing which shows an example of the structure of the layered structure which has a biphenyl skeleton. Explanatory drawing which shows an example of the structure of the layered structure which has a naphthalene skeleton. Explanatory drawing which shows an example of a power storage device 20. XRD measurement results of the electrodes of Reference Examples 1 to 5. XRD measurement results of the electrodes of Reference Examples 6 to 9. (011) XRD measurement results of Reference Examples 6, 8 and 9 standardized in terms of plane. Evaluation results of electrode characteristics of the Bph layered structure of Experimental Examples 1 to 5, 9 and 11. Evaluation results of electrode characteristics of Naph layered structures of Experimental Examples 6 to 8, 10 and 12. The initial charge / discharge curves of Experimental Examples 1 to 5, 9 and 11. The initial charge / discharge curves of Experimental Examples 6 to 8, 10 and 12.

(Power storage device)
The power storage device of the present disclosure includes a positive electrode, a negative electrode, and an ion conduction medium. This power storage device may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, a lithium ion battery, or the like. This negative electrode contains a layered structure having an organic skeleton layer and an alkali metal element layer as a negative electrode active material. This negative electrode active material occludes and releases lithium ions, which are carriers. This negative electrode active material is a layered structure including an organic skeleton layer containing an aromatic dicarboxylic acid anion and an alkali metal element layer in which an alkali metal element is coordinated with oxygen contained in the carboxylic acid of the organic skeleton layer to form a skeleton. including. Further, the ion conduction medium is interposed between the positive electrode and the negative electrode and conducts lithium ions.

This layered structure may have an organic skeleton layer in which two or more aromatic ring structures are connected. It is structurally stable that this layered structure is formed in layers by the π-electron interaction of aromatic compounds and has a monoclinic crystal structure belonging to the space group P2 ₁ / c. Yes, preferred. This layered structure may have a structure represented by one or more of the formulas (1) to (3). However, in the formulas (1) to (3), a is an integer of 1 or more and 5 or less, b is an integer of 0 or more and 3 or less, and these aromatic compounds have substituents and heteros in this structure. It may have an atom. Specifically, instead of the hydrogen of the aromatic compound, a halogen, a chain or cyclic alkyl group, an aryl group, an alkenyl group, an alkoxy group, an aryloxy group, a sulfonyl group, an amino group, a cyano group, a carbonyl group and an acyl group. , An amide group or a hydroxyl group may be used as a substituent, or a structure in which nitrogen, sulfur or oxygen is introduced instead of the carbon of the aromatic compound may be used. More specifically, this layered structure may be an aromatic compound represented by the formulas (4) to (5). In the formulas (1) to (5), A is an alkali metal. Further, it is structurally stable that the layered structure has a structure of the following formula (6) in which four oxygens of different dicarboxylic acid anions and an alkali metal element form a tetracoordination. preferable. However, in this formula (6), R has two or more aromatic ring structures, and two or more of the plurality of Rs may be the same, or one or more may be different. Further, A is an alkali metal. As described above, it is preferable to have a structure in which the organic skeleton layer is bonded by the alkali metal element.

In this layered structure, when the organic skeleton layer has two or more aromatic ring structures, for example, it may be an aromatic polycyclic compound in which two or more aromatic rings such as biphenyl are bonded, or 2 such as naphthalene, anthracene, and pyrene. A condensed polycyclic compound obtained by condensing the above aromatic rings may be used. This aromatic ring may be a five-membered ring, a six-membered ring, or an eight-membered ring, and a six-membered ring is preferable. The aromatic ring is preferably 2 or more and 5 or less. When the number of aromatic rings is 2 or more, a layered structure is likely to be formed, and when the number of aromatic rings is 5 or less, the energy density can be further increased. This organic skeleton layer may have a structure in which one or more carboxy anions are bonded to an aromatic ring. The organic skeleton layer preferably contains an aromatic compound in which one and the other of the dicarboxylic acid anions are bonded at diagonal positions of the aromatic ring structure. The diagonal position to which the carboxylic acid is bonded may be the position farthest from the bonding position of one carboxylic acid to the bonding position of the other carboxylic acid. For example, if the aromatic ring structure is biphenyl, 4,4 'The place is listed, and if it is naphthalene, the second and sixth places are listed.

As shown in FIGS. 1 and 2, for example, the alkali metal element layer forms a skeleton in which the alkali metal element is coordinated with oxygen contained in the carboxylic acid anion. FIG. 1 is an explanatory diagram showing an example of the structure of a layered structure, using dilithium 4,4'-biphenyldicarboxylic acid as a specific example. FIG. 2 is an explanatory diagram showing an example of the structure of a layered structure, using dilithium 2,6-naphthalenedicarboxylic acid as a specific example. The alkali metal contained in the alkali metal element layer can be, for example, any one or more of Li, Na, K, and the like, but Li is preferable. The metal ions that are carriers of the power storage device and are occluded and released into the layered structure by charging and discharging may be different from or the same as the alkali metal elements contained in the alkali metal element layer, for example. , Li, Na, K, and the like, whichever is one or more. Further, since the alkali metal elements contained in the alkali metal element layer form the skeleton of the layered structure, it is presumed that they are not involved in the ion movement accompanying charge / discharge, that is, they are not stored and released during charge / discharge. .. As shown in FIGS. 1 and 2, the layered structure thus constructed is formed of an organic skeleton layer and a Li layer (alkali metal element layer) existing between the organic skeleton layers. There is. In the energy storage mechanism, organic framework layer of the layered structure redox (e ^-) while functioning as a site, the alkali metal element layer and functions as a storage site for the metal ion is a carrier (alkali metal ion adsorption site) Conceivable. The layered structure is preferably, for example, one or more of 2,6-naphthalenedicarboxylic acid alkali metal salt, 4,4'-biphenyldicarboxylic acid alkali metal salt and terephthalic acid alkali metal salt.

This layered structure may be prepared by a spray drying method in which a solution containing an aromatic dicarboxylic acid anion and an alkali metal cation is spray-dried. The spray drying may be performed by a spray dryer. The spray drying conditions may be appropriately adjusted depending on, for example, the scale of the apparatus and the amount of the electrode active material to be produced. The concentration of the aromatic dicarboxylic acid anion in the spray-dried preparation solution is preferably 0.1 mol / L or more, more preferably 0.2 mol / L or more. Further, the prepared solution preferably has a molar ratio B / A of 2.2 or more, which is the number of moles B (mol) of the alkali metal cation with respect to the number A (mol) of the aromatic dicarboxylic acid anion. By making the alkali metal cation excessive in this way, the resistance of the electrode for the power storage device can be further reduced, which is preferable. This molar ratio B / A may be 2.5 or more. Further, the molar ratio B / A may be 3.0 or less. The drying temperature is preferably in the range of 100 ° C. or higher and 250 ° C. or lower, for example. At 100 ° C. or higher, the solvent can be sufficiently removed, and at 250 ° C. or lower, energy consumption can be further reduced, which is preferable. The drying temperature is more preferably 120 ° C. or higher, 150 ° C. or higher, and more preferably 220 ° C. or lower. The amount of the supplied liquid may be in the range of 0.1 L / h or more and 2 L / h or less, for example, depending on the scale of production. The nozzle size for spraying the prepared solution may be, for example, in the range of 0.5 mm or more and 5 mm or less in diameter, although it depends on the scale of production.

The layered structure including the organic skeleton layer having a biphenyl skeleton has a hollow spherical structure formed by encapsulating a collection of flakes of the layered structure at the time of preparation by the spray drying method. This negative electrode is oriented on a predetermined crystal plane because the hollow spherical structure is crushed and a flaky layered structure is used. Even if the electrode for the power storage device shows a peak intensity ratio P (300) / P (111) of (300) to the peak intensity of (111) of 2.0 or more when the electrode is measured by X-ray diffraction. Good. That is, the peak intensity of (300) may be more than twice the peak intensity of (111). This strength ratio is more preferably 2.5 or more, and further preferably 3.0 or more. Further, this strength ratio may be 5.0 or less. In this range, the layer spacing of the layered structure is good, and the electrode resistance can be further reduced. Further, in this electrode for the power storage device, when the electrode is X-ray diffraction measured, the peak intensity ratio P (300) / P (011) of (300) to the peak intensity of (011) in the X-ray diffraction measurement is 2. It may indicate 0.0 or more. That is, the peak intensity of (300) may be more than twice the peak intensity of (011). This strength ratio is more preferably 2.5 or more, and further preferably 3.0 or more. Further, this strength ratio may be 5.0 or less. In this range, the layer spacing of the layered structure is good, and the electrode resistance can be further reduced. Further, when the electrode for the power storage device is X-ray diffraction measured, the peak intensity ratio P (100) / P (111) of (100) to the peak intensity of (111) in the X-ray diffraction measurement is 6. It may indicate 0.0 or more. That is, the peak intensity of (100) may be 6 times or more the peak intensity of (111). This strength ratio is more preferably 6.5 or more, and further preferably 6.6 or more. Further, this strength ratio may be 10.0 or less. In this range, the layer spacing of the layered structure is good, and the electrode resistance can be further reduced. Further, this electrode for a power storage device shows a peak intensity ratio P (100) / P (011) of (100) to the peak intensity of (011) of 5.0 or more when the electrode is measured by X-ray diffraction. May be. That is, the peak intensity of (100) may be 5 times or more the peak intensity of (011). This intensity ratio is more preferably 6.0 or more, and even more preferably 6.5 or more. Further, this strength ratio may be 10.0 or less. In this range, the layer spacing of the layered structure is good, and the electrode resistance can be further reduced. Further, this electrode for a power storage device shows a peak intensity ratio P (100) / P (300) of (100) to a peak intensity of (300) of 1.5 or more when the electrode is measured by X-ray diffraction. May be. That is, the peak intensity of (100) may be one or more times the peak intensity of (300). This strength ratio is more preferably 1.8 or more, and further preferably 2.0 or more. Further, this strength ratio may be 5.0 or less. In this range, the layer spacing of the layered structure is good, and the electrode resistance can be further reduced. Further, when the electrode for the power storage device is measured by X-ray diffraction, the electrode for the power storage device has a specific orientation in which small flakes of the active material existing inside the electrode are oriented in a specific manner. It shows a tendency that the peak intensity corresponding to is increased. Further, the electrode for the power storage device may have a smooth surface when the surface is observed with a scanning electron microscope. This electrode active material can be easily crushed to form an electrode in which flakes are highly dispersed, so that the electrode surface becomes smoother. The electrode for a power storage device satisfying this peak intensity ratio may particularly contain a 4,4'-biphenyldicarboxylic acid alkali metal salt.

Further, in a layered structure having an organic skeleton layer having a naphthalene skeleton, when produced by a spray drying method, the layered structure satisfies one or more of the following (1) to (3). Further, it is preferable that the negative electrode active material satisfies one or more of the following (4) to (8). In a layered structure having a naphthalene skeleton, the surface spacing of the (002) plane, (102) plane, (211) plane and (112) plane is the spacing based on the layered structure of the naphthalene skeleton and the naphthalene skeleton in the organic skeleton layer. Is. The surface spacing of the (200) plane is a spacing based on the organic skeleton layer between the alkali metal element layer and the alkali metal element layer. When the surface spacing is in the following range, it can be said that the layered structure has good crystallinity.
(1) The peak intensity ratio P (002) / P (011) of (002) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.25 or more.
(2) The peak intensity ratio P (102) / P (011) of (102) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.50 or more.
(3) The peak intensity ratio P (112) / P (011) of (112) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.60 or more.
(4) The surface spacing of the (002) plane (see FIG. 2A) in the X-ray diffraction measurement is preferably in the range of 0.42400 nm or more and 0.42700 nm or less, and preferably in the range of 0.42550 nm or more and 0.42650 nm or less. Is more preferable.
(5) The surface spacing of the (102) plane (see FIG. 2B) in the X-ray diffraction measurement is preferably in the range of 0.37000 nm or more and 0.37350 nm or less, and is in the range of 0.37250 nm or more and 0.37320 nm or less. Is more preferable.
(6) The surface spacing of the (112) plane (see FIG. 2C) in the X-ray diffraction measurement is preferably in the range of 0.30400 nm or more and 0.30600 nm or less, and preferably in the range of 0.30500 nm or more and 0.30580 nm or less. Is more preferable.
(7) The surface spacing of the (211) plane (see FIG. 2D) in the X-ray diffraction measurement is preferably in the range of 0.32250 nm or more and 0.32520 nm or less, and preferably in the range of 0.32408 nm or more and 0.32500 nm or less. Is more preferable.
(8) The surface spacing of the (200) plane (see FIG. 2E) in the X-ray diffraction measurement is preferably in the range of 0.50500 nm or more and 0.50900 nm or less, and is in the range of 0.50600 nm or more and 0.50800 nm or less. Is more preferable.

The peak intensity ratio P (002) / P (011) preferably shows 0.30 or more, and more preferably 0.32 or more. The peak intensity ratio P (111) / P (011) preferably shows 0.65 or more. The peak intensity ratio P (102) / P (011) preferably shows 0.60 or more, and more preferably 0.75 or more. The peak intensity ratio P (112) / P (011) preferably shows 0.65 or more, and more preferably 0.70 or more. Further, the peak intensity ratio P (110) / P (011) of (110) to the peak intensity of (011) in the X-ray diffraction measurement preferably shows 0.30 or less, and preferably 0.28 or less. Is more preferable, and it is further preferable to show 0.25 or less.

The negative electrode may be a current collector in which a negative electrode mixture containing the above-mentioned layered structure as a negative electrode active material, a binder, and a conductive material is formed. The negative electrode mixture may contain a water-soluble polymer as a binder. The water-soluble polymer may contain at least carboxymethyl cellulose (CMC) and may contain any one or more of polyvinyl alcohol (PVA), styrene-butadiene copolymer (SBR), and polyethylene oxide (PEO). The carboxymethyl cellulose may be, for example, an inorganic salt having a carboxymethyl group terminal such as sodium or calcium, or an ammonium salt having an ammonium carboxymethyl group terminal. This negative electrode mixture contains carboxymethyl cellulose in a range of 1.5% by mass or more and 3.5% by mass or less of the entire negative electrode active material, the conductive material, and the binder (hereinafter, also referred to as the entire mixture). Is preferable. When the amount of carboxymethyl cellulose is 1.5% by mass or more, the substance contained in the negative electrode mixture is sufficiently dispersed, and the electrode resistance can be further reduced. Further, when carboxymethyl cellulose is 3.5% by mass or less, the occurrence of electron path inhibition can be further suppressed, and the electrode resistance can be further reduced. In this range of CMC, the electrode capacitance can be further improved by further lowering the electrode resistance. Further, the negative electrode mixture may contain less than 2.0% by mass of carboxymethyl cellulose in the entire mixture. Alternatively, the negative electrode more preferably contains carboxymethyl cellulose in a range of 1.8% by mass or more and 2.5% by mass or less. In this range, the electrode resistance can be further reduced and the electrode capacitance can be further improved.

The water-soluble polymer containing CMC, PEO, etc. is preferably contained in the negative electrode in the range of 5% by mass or more and 12% by mass or less of the entire mixture. The polyethylene oxide preferably has a molecular weight of 500,000 or more, more preferably 1 million or more, and even more preferably 2 million or more. When this molecular weight is 500,000 or more, it performs a better function. This molecular weight may be in the range of 3 million or less. The polyethylene oxide is preferably contained in the electrode in the range of 8% by mass or less. The styrene-butadiene copolymer is preferably contained in the electrode in the range of 8% by mass or less. Polyvinyl alcohol (PVA) is preferably contained in the electrode in the range of 8% by mass or less. When it is 8% by mass or less, the amounts of the active material, the conductive material, and the water-soluble polymer are not too small, so that the functions of the active material, the conductive material, and the water-soluble polymer can be sufficiently exhibited. Further, the negative electrode may contain another binder in addition to or instead of the water-soluble polymer described above. Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF) and fluororubber, thermoplastic resins such as polypropylene and polyethylene, and ethylene-propylene-diene-monomer (EPDM). ) Rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) and the like may be used. These can be used alone or as a mixture of two or more.

The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance. For example, graphite such as natural graphite (scaly graphite, scaly graphite) or artificial graphite, acetylene black, carbon black, Ketjen A carbon material such as black, carbon whisker, needle coke, carbon fiber, or a mixture of one or more of metals (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, carbon black and acetylene black are preferable as the conductive material from the viewpoint of electron conductivity and coatability. The electrode for the power storage device preferably contains the conductive material in the range of 5% by mass or more and 25% by mass or less of the entire electrode mixture, and may be 10% by mass or more, or 15% by mass or more. When it is 5% by mass or more, the electrode can be provided with sufficient conductivity, and deterioration of charge / discharge characteristics can be suppressed. Further, if it is 25% by mass or less, the active material and the water-soluble polymer are not excessively reduced, so that the functions of the active material and the water-soluble polymer can be sufficiently exhibited.

The negative electrode preferably contains a larger amount of the negative electrode active material, and the negative electrode active material is preferably 65% by mass or more, more preferably 70% by mass or more, and 75% by mass or more in the entire negative electrode mixture. May be good. Further, the negative electrode active material may be in the range of 85% by mass or less or 75% by mass or less. When the negative electrode active material is contained in the range of 85% by mass or less, the amount of the conductive material or the water-soluble polymer does not become too small, so that the functions of the conductive material and the water-soluble polymer can be fully exhibited.

In the negative electrode, the negative electrode mixture is preferably formed into a current collector in the form of a paste or earth using a solvent. Water may be used as the solvent, and for example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N, N-dimethylaminopropylamine, ethylene oxide, etc. An organic solvent such as tetrahydrofuran may be used. Since a water-soluble polymer is used here, water is suitable. As a current collector, copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as for the purpose of improving adhesiveness, conductivity and reduction resistance. For example, one having a surface of copper or the like treated with carbon, nickel, titanium, silver or the like can also be used. Of these, it is more preferable that the current collector of the electrode for the power storage device is made of aluminum metal. That is, it is preferable that the layered structure is formed of an aluminum metal current collector. This is because aluminum is abundant and has excellent corrosion resistance. For these, it is also possible to oxidize the surface. Examples of the shape of the current collector include a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded body, a lath body, a porous body, a foam body, and a fiber group forming body. As the thickness of the current collector, for example, one having a thickness of 1 to 500 μm is used.

As the positive electrode, a known positive electrode used for a capacitor, a lithium ion capacitor, or the like may be used. The positive electrode may contain, for example, a carbon material as the positive electrode active material. The carbon material is not particularly limited, but for example, activated carbons, cokes, glassy carbons, graphites, graphitizable carbons, thermally decomposed carbons, carbon fibers, carbon nanotubes, etc. Examples include graphite. Of these, activated carbons showing a high specific surface area are preferable. Activated carbon as a carbon material preferably has a specific surface area of 1000 m ² / g or more, and more preferably 1500 m ² / g or more. When the specific surface area is 1000 m ² / g or more, the discharge capacity can be further increased. The specific surface area of this activated carbon is preferably 3000 m ² / g or less, and more preferably 2000 m ² / g or less, from the viewpoint of ease of production. It is considered that at the positive electrode, at least one of the anion and the cation contained in the ion conduction medium is adsorbed and desorbed to store electricity, but further, at least one of the anion and the cation contained in the ion conduction medium is inserted and desorbed. It may be used to store electricity.

Alternatively, the positive electrode may be a positive electrode used in a general lithium ion battery. In this case, as the positive electrode active material, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used. Specifically, transition metal sulfides such as TiS ₂ , TiS ₃ , MoS ₃ , and FeS _2, and the basic composition formula is Li _(1-x) MnO ₂ (0 <x <1, etc., the same applies hereinafter) and Li ₍₁ ). _-x) Lithium manganese composite oxide with Mn ₂ O _4, etc., Lithium cobalt composite oxide with basic composition formula as Li _(1-x) CoO _2, etc., basic composition formula as Li _(1-x) NiO _2, etc. Lithium-nickel composite oxide, the basic composition formula is Li _(1-x) Ni _a Co _b Mn _c O ₂ (a + b + c = 1) and Li _(1-x) Ni _a Co _b Mn _c O ₄ (a + b + c = 2) ) Etc., lithium nickel cobalt manganese composite oxide having a basic composition formula of LiV ₂ O ₃ or the like, transition metal oxide having a basic composition formula of V ₂ O ₅ or the like can be used. .. Further, the positive electrode active material may be lithium iron phosphate or the like. Of these, lithium transition metal composite oxides, such as LiCoO ₂ , LiNiO ₂ , and LiMnO ₂ , are preferred. The "basic composition formula" is intended to include other elements.

For the positive electrode, for example, the above-mentioned positive electrode active material, the conductive material, and the binder are mixed, and an appropriate solvent is added to form a paste-like positive electrode mixture, which is applied to the surface of the current collector, dried, and required. Therefore, it may be formed by compression in order to increase the electrode density. As the conductive material, the binder, the solvent, and the current collector used for the positive electrode, for example, those exemplified for the electrode for the power storage device can be appropriately used.

In this power storage device, the ion conduction medium may be, for example, a non-aqueous electrolyte solution containing a supporting salt (supporting electrolyte) and an organic solvent. The supporting salt contains at least lithium bis (fluorosulfonyl) imide (LiFSI). Further, the supporting salt may further contain a known lithium salt. As the lithium salt, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, Li (CF 3 SO 2) 2 N, LiN (C 2 F 5 SO 2) 2 and the like, Ya Among LiPF ₆ LiBF _{4 and the} like are preferable. The concentration of this supporting salt in the non-aqueous electrolytic solution is preferably 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less. When the concentration at which the supporting salt is dissolved is 0.1 mol / L or more, a sufficient current density can be obtained, and when the concentration is 5 mol / L or less, the electrolytic solution can be made more stable. Further, a flame retardant such as phosphorus or halogen may be added to this non-aqueous electrolytic solution. As the organic solvent, for example, an aprotic organic solvent can be used. Examples of such an organic solvent include cyclic carbonate, chain carbonate, cyclic ester, cyclic ether, chain ether and the like. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and the like. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and the like. Examples of the cyclic ester carbonate include gamma-butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran and the like. Examples of the chain ether include dimethoxyethane and ethylene glycol dimethyl ether. These may be used alone or in combination of two or more. In addition, as the non-aqueous electrolyte solution, a nitrile solvent such as acetonitrile or propylnitrile, an ionic liquid, a gel electrolyte, or the like may be used. Moreover, the ion conduction medium may be a solid electrolyte.

This power storage device may include a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the power storage device, and is, for example, a polymer non-woven fabric such as a polypropylene non-woven fabric or a polyphenylene sulfide non-woven fabric, or an olefin resin such as polyethylene or polypropylene. Examples include microporous films. These may be used alone or in combination.

The shape of the power storage device is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Further, it may be applied to a large-sized vehicle used for an electric vehicle or the like. FIG. 2 is a schematic diagram showing an example of the power storage device 20. The power storage device 20 has a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and provided at the lower part of the battery case 21, and a negative electrode active material with respect to the positive electrode 22 via a separator 24. A negative electrode 23 provided at an opposite position, a gasket 25 formed of an insulating material, and a sealing plate 26 disposed in the opening of the battery case 21 and sealing the battery case 21 via the gasket 25 are provided. There is. In the power storage device 20, the space between the positive electrode 22 and the negative electrode 23 is filled with the ion conduction medium 27. Further, the negative electrode 23 has the above-mentioned layered structure of the aromatic dicarboxylic acid metal salt as the negative electrode active material. Further, the ion conductive medium 27 contains lithium bis (fluorosulfonyl) imide (LiFSI) as a supporting salt.

In the power storage device described in detail above, in the device using the layered structure as the electrode active material, the charge / discharge characteristics can be further improved, for example, the IV resistance is further reduced and the electrode capacitance is further increased. The reason why such an effect can be obtained is that, for example, when an ion conductive medium containing LiFSI is used for a negative electrode using a negative electrode active material of a layered structure, a low resistance film is formed at the interface between the negative electrode and the electrolytic solution. It is presumed that this is because of this. When an ionic conduction medium containing LiFSI is used, the charge / discharge characteristics can be further improved even in a layered structure obtained by a solution mixing method in which an aromatic dicarboxylic acid and an alkali metal are dissolved and a solvent is removed. In the layered structure obtained by spray-drying a solution in which an aromatic dicarboxylic acid and an alkali metal are dissolved, the charge / discharge characteristics can be further improved. In particular, in a layered structure having a biphenyl skeleton, when spray-dried, it becomes hollow particles of the striped layered structure, which is easy to disintegrate, the aggregation of the layered structure is suppressed, and the primary particles are very large inside the electrode. It is presumed that a highly dispersed structure can be formed and the internal resistance can be reduced. Further, in a layered structure having a naphthalene skeleton, when spray-dried, the layered structure is formed in a state of having higher crystallinity, so that internal resistance is not performed without performing a step of increasing crystallinity such as firing an electrode. Etc. can be reduced.

It is needless to say that the present disclosure is not limited to the above-described embodiment, and can be implemented in various aspects as long as it belongs to the technical scope of the present disclosure.

Hereinafter, an example in which the power storage device of the present disclosure is specifically manufactured will be described. First, an example in which a layered structure is synthesized by a spray-drying method and a solution mixing method to prepare an electrode and evaluated will be described as a reference example.

[Reference example 1]
(Electrode active material: Synthesis of layered structure of dilithium 4,4'-biphenyldicarboxylic acid)
A layered structure was prepared by a spray-drying method. For the synthesis of dilithium 4,4'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid and lithium hydroxide monohydrate (LiOH · H ₂ O) were used as starting materials. Lithium hydroxide was added to water so as to have a concentration of 0.44 mol / L and stirred to prepare an aqueous solution. Then, the molar ratio B / A, which is the number of moles B (mol) of lithium hydroxide to the number A (mol) of 4,4'-biphenyldicarboxylic acid, is 2.2, that is, 4,4'. An aqueous solution was prepared so that the amount of −biphenyldicarboxylic acid was 0.20 mol / L. The prepared aqueous solution was spray-dried using a spray dryer (Mini Spray Dryer B-290, manufactured by Nippon Buch) to precipitate dilithium 4,4'-biphenyldicarboxylic acid. The nozzle diameter of the spray dryer used was 1.4 mm, the spray amount of the solution was 0.4 L / hour, and the drying temperature was 150 ° C. to synthesize lithium 4,4'-biphenyldicarboxylic acid.

(Electrode: Fabrication of 4,4'-dilithium biphenyldicarboxylic acid electrode)
79% by mass of lithium 4,4′-biphenyldicarboxylic acid produced by the above method, 14% by mass of carbon black (Tokai carbon, TB5500) as a particulate carbon conductive material, and polyvinyl alcohol (Gosenex, T-) which is a water-soluble polymer. 2.8% by mass of 330, Nippon Synthetic Chemistry) and 4.2% by mass of styrene-butadiene copolymer (Nippon Zeon, BM-400B) were mixed, and an appropriate amount of water was added and dispersed as a dispersant to form a slurry. It was used as a material. This slurry-like mixture was uniformly applied to a 10 μm-thick copper foil current collector so that the amount of the dilithium 4,4'-biphenyldicarboxylic acid dilithium active material per unit area was 3 mg / cm ^2, and dried by vacuum heating at 120 ° C. A coating sheet was prepared. Then, the coating sheet was pressure-pressed and punched into an area of 2 cm ² to prepare a disk-shaped electrode.

(Power storage device: Fabrication of bipolar evaluation cell)
1. The supporting electrolyte, lithium hexafluorophosphate, was added to a non-aqueous solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 30:40:30. A non-aqueous electrolyte solution was prepared by adding the mixture so as to be 0 mol / L. A separator (a separator) in which a dilithium 4,4'-biphenyldicarboxylic acid electrode produced by the above method is used as a working electrode and a lithium metal foil (thickness: 300 μm) is used as a counter electrode and both electrodes are impregnated with the non-aqueous electrolyte solution A bipolar evaluation cell was produced with Toray Tonen) in between.

[Reference Examples 2 to 4]
Reference Example 2 was treated in the same manner as in Reference Example 1 except that dilithium 4,4'-biphenyldicarboxylic acid was synthesized by a spray dryer and then vacuum dried at 120 ° C. An aqueous solution was prepared with the molar ratio of lithium hydroxide to 4,4'-biphenyldicarboxylic acid set to 2.5, and the same treatment as in Reference Example 1 was performed except that it was synthesized by a spray dryer. did. Further, Reference Example 4 was obtained by subjecting the same treatment as in Reference Example 3 except that lithium 4,4′-biphenyldicarboxylic acid was synthesized by a spray dryer and then vacuum dried at 120 ° C.

[Reference example 5]
A layered structure was prepared by a solution mixing method. Using 4,4'-biphenyldicarboxylic acid and lithium hydroxide monohydrate (LiOH · H ₂ O) as starting materials, add methanol (100 mL) to lithium hydroxide monohydrate (0.556 g) and stir. After that, 1.0 g of 4,4'-biphenyldicarboxylic acid was added, and the mixture was stirred for 1 hour. Then, after stirring, the solvent was removed, and the mixture was dried under vacuum at 150 ° C. for 16 hours to obtain lithium 4,4'-biphenyldicarboxylic acid as a white powder sample. Reference Example 5 was obtained by performing the same processing as in Reference Example 1 except that this was used.

[Reference Examples 6 and 7]
(Electrode active material: Synthesis of layered structure of dilithium 2,6-naphthalenedicarboxylic acid)
For the synthesis of dilithium 2,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and lithium hydroxide monohydrate (LiOH · H ₂ O) were used as starting materials. Lithium hydroxide was added to water so that 2,6-naphthalenedicarboxylic acid was 0.2 mol / L and lithium hydroxide was 0.44 mol / L, and the mixture was stirred to prepare a preparation solution (aqueous solution). This prepared solution was spray-dried using a spray dryer (Micromist spray dryer MDL-050, manufactured by Fujisaki Electric Co., Ltd.) to precipitate a powder of dilithium 2,6-naphthalenedicarboxylic acid. The spray amount (supply amount) of the prepared solution was 0.04 L / min, and the drying temperature was 200 ° C. As a recovery unit, a cyclone was arranged in series in the front stage and a bug filter was arranged in series in the rear stage, and the powder recovered in the front stage was designated as Reference Example 6 and the powder recovered in the rear stage was designated as Reference Example 7. Reference Example 7 was a finer powder than Reference Example 6.

[Reference Examples 8 and 9]
Using 2,6-naphthalenedicarboxylic acid and lithium hydroxide monohydrate as starting materials, add methanol (100 mL) to lithium hydroxide monohydrate (0.556 g), stir, and then 2,6-naphthalenedicarboxylic acid. Was added, and the mixture was stirred for 1 hour. After stirring, the solvent was removed, and the mixture was dried under vacuum at 150 ° C. for 16 hours to obtain a white powder sample of dilithium 2,6-naphthalenedicarboxylic acid (solution mixing method). The obtained white powder was heat-treated at 350 ° C. under Ar, and the obtained powder was used as Reference Example 8. Further, the powder before the heat treatment of Reference Example 8 was designated as Reference Example 9.

(X-ray diffraction measurement)
X-ray diffraction measurement of the electrode active material and the electrode of Reference Examples 1 to 5 was performed. The measurement was carried out using CuKα ray (wavelength 1.54051Å) as radiation and using an X-ray diffractometer (Ultima IV manufactured by Rigaku). For the measurement, a graphite single crystal monochrome meter was used for monochromatic X-rays, the applied voltage was set to 40 kV and the current was 30 mA, the scanning speed was 5 ° / min, and 2θ = 5 ° for the electrode active material. It was carried out in an angle range of about 60 °, and for the electrodes, it was carried out in an angle range of 2θ = 5 ° to 30 °. For Reference Examples 6 to 9, the same X-ray diffractometer was used, the applied voltage was set to 40 kV and the current was 40 mA, the scanning speed was 20 ° / min, and the angle range was 2θ = 5 ° to 60 °. It was.

(Evaluation of charge / discharge characteristics)
The capacity obtained by reducing the prepared bipolar evaluation cell to 0.5 V at 0.1 mA under a temperature environment of 20 ° C. was defined as the discharge capacity. Further, the capacity oxidized to 1.5 V at 0.1 mA thereafter was defined as the charge capacity. Further, using the obtained charge / discharge curve, the differential value of the charge / discharge curve was calculated with respect to the potential difference to obtain the differential curve. Further, the charge / discharge polarization was calculated from the peak difference between the two different internal resistance differential curves in this differential curve, and the IV resistance was calculated in consideration of the applied current. For the IV resistance, the charge / discharge curve of the second cycle was used.

(Results and discussion)
Table 1 shows the manufacturing methods of Reference Examples 1 to 5, the peak intensity ratio of the electrodes, and the IV resistance value. Further, FIG. 4 shows the XRD measurement results of the electrodes of Reference Examples 1 to 5. As shown in FIG. 4, in the electrodes of Reference Examples 1 to 4 containing the electrode active material prepared by the spray-drying method, a peak appeared at the same 2θ position as in the conventional solution mixing method. Regarding the peak intensity, the electrode produced by the spray-drying method showed a tendency to increase the peak intensity corresponding to the n00 surface. This indicates that the small flakes of the active material present inside the electrode have a specific orientation. In particular, in the electrodes of Reference Examples 1 to 4, the peak intensity of (300) is more than twice the peak intensity of (111) and (011) in the X-ray diffraction measurement, and the peak intensity of (100) is (100). It was found that the peak intensities of 111) and (011) were more than five times higher. Specifically, the peak intensity ratio P (300) / P (111) is 2.0 or more, P (300) / P (011) is 2.0 or more, and P (100) / P (111) is 6. 0 or more, P (100) / P (011) was 5.0 or more, and P (100) / P (300) was 1.5 or more. It was presumed that if any one or more of these peak intensity ratios was satisfied, it could be estimated that the active material was flaky and oriented. Further, as shown in Table 1, it was found that the IV resistance of the electrode prepared by the layered structure synthesized by the spray-drying method was further reduced as compared with the solution mixing method. Further, it was found that if the above peak intensity ratio is satisfied, the layered structure can be identified as being produced by the spray-drying method.

Table 2 shows the manufacturing methods of Reference Examples 6 to 9, (200) plane, (002) plane, (102) plane, (211) plane and (112) plane, with respect to the plane spacing (nm) and (011) plane. The peak intensity ratios of the 110) plane, the (002) plane, the (102) plane, the (211) plane, and the (112) plane are shown. FIG. 5 shows the XRD measurement results of the electrode active materials of Reference Examples 6 to 9. FIG. 6 shows the measurement results of Reference Examples 6, 8 and 9XRD standardized with the peak intensity of the (011) plane as 100. As shown in Table 2 and FIG. 5, the electrode active materials of the layered structure produced by the spray-drying method of Reference Examples 6 and 7 showed the same surface spacing and peak intensity ratio, and had the same crystal structure. Further, the layered structures of Reference Examples 6 and 7 have the same peak position as that of Reference Example 8 in which the layered structure prepared by the conventional solution mixing method is heat-treated at 350 ° C. in Ar, that is, the crystal structure is the same. I understand. In particular, in Reference Examples 6 to 8, unlike Reference Example 9, the peak positions on the (200) plane, the (102) plane, the (211) plane and the (112) plane were the same.

Further, in the XRD pattern of Reference Example 9 which has not been heat-treated and synthesized by the conventional solution mixing method, the peaks of the (102) and (112) planes marked with "*" are significantly different from those of Reference Example 8 which has been heat-treated. It was found that the crystals were highly crystallized by heat treatment. Further, it was found that the peak intensity ratios of Reference Examples 6 and 7 were higher than those of Reference Example 8 and the crystallinity was better. According to Reference Examples 6 and 7, the peak intensity ratio P (002) / P (011) is 0.25 or more, the peak intensity ratio P (111) / P (011) is 0.64 or more, and the peak intensity ratio P ( It was presumed that the crystal was good when either 102) / P (011) was 0.50 or more and the peak intensity ratio P (112) / P (011) was 0.60 or more. As described above, in Reference Examples 6 and 7 synthesized by the spray-drying method, it was found that the electrode active material having improved crystallinity without heat treatment can be synthesized in one step. Further, it was found that if the above peak intensity ratio is satisfied, the layered structure can be identified as being produced by the spray-drying method.

Next, a negative electrode is produced by changing the type and compounding ratio of the binder for the negative electrode, and the result of evaluation by changing the supporting salt of the electrolytic solution will be described as an experimental example. Experimental Examples 1 to 8 correspond to Examples, and Experimental Examples 9 to 12 correspond to Comparative Examples. Although the types of binders used in Experimental Examples 1 to 8 are different, the layered structure is the same, so that the X-ray diffraction of the negative electrode has the same results as in Reference Examples 1 to 4, 6 to 7. was gotten.

[Experimental Example 1]
(Preparation of 4,4'-dilithium biphenyldicarboxylic acid negative electrode)
72.7% by mass of dilithium 4,4'-biphenyldicarboxylate (Bph) produced by the spray-drying method, 18.2% by mass of carbon black (Tokai carbon, TB5500 (diameter about 50 nm)) as a conductive material, water-soluble. The polymer carboxymethyl cellulose (CMC) (Daicel Finechem, CMC Daicel 1120) is 2.7% by mass, polyethylene oxide (PEO) (molecular weight: 2 million) is 3.6% by mass, and styrene butadiene copolymer (Nippon Zeon, Japan Zeon, BM-400B) was weighed and mixed so as to be 2.7% by mass, and an appropriate amount of water was added and dispersed as a dispersant to obtain a slurry-like mixture. The amount of 4,4'-dilithium biphenyldicarboxylic acid active material per unit area was 2.5 mg / cm ² in a Cu (manufactured by Nippon Graphite) current collector with 10 μm thick copper foil and carbon deposited on this slurry-like mixture. A coating sheet was prepared by uniformly coating the coating sheet and drying it by heating. Then, the coating sheet was pressure-pressed and punched into an area of 10 cm ² to obtain a negative electrode. This was used as the negative electrode of Experimental Example 1.

(Preparation of bipolar evaluation cell)
Lithium bis (fluorosulfonyl) imide (LiFSI) is 1.1 mol / L in a solvent obtained by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a volume ratio of 30:40:30. A non-aqueous electrolyte solution was prepared by adding the above solution. The above 4,4'-dilithium biphenyldicarboxylic acid negative electrode is used as the working electrode, the lithium metal foil (thickness 300 μm) is used as the counter electrode, and a separator (manufactured by Toray Tonen) impregnated with the above non-aqueous electrolytic solution is sandwiched between both electrodes. A bipolar evaluation cell was prepared in.

(Evaluation of electrode capacitance and IV resistance)
Using this bipolar evaluation cell, the capacity was confirmed and the SOC was adjusted. The electrode capacitance was measured at 25 ° C. with a voltage range of 0.5 V to 1.5 V and a current value of 0.5 mA (corresponding to C / 10). Further, the differential curve (differential (dQ / dV curve)) of the potential change was obtained by differentiating the obtained charge / discharge curve with respect to the amount of electric charge. From the maximum value and the minimum value of the differential curve in the charging and discharging directions. The charge / discharge polarization was determined, and the IV resistance (Ω) was calculated using the test current.

[Experimental Examples 2-5]
Negative electrodes and bipolar evaluation cells of Experimental Examples 2 to 5 were prepared in the same manner as in Experimental Example 1 except that the compositions shown in Table 3 were blended. In the same manner as in Experimental Example 1, the electrode capacitance and IV resistance of Experimental Examples 2 to 5 were determined, respectively.

[Experimental Example 6]
(Preparation of dilithic negative electrode of 2,6-naphthalenedicarboxylic acid)
74.1% by mass of dilithium 2,6-naphthalenedicarboxylic acid (Naph) produced by the spray-drying method, 18.5% by mass of carbon black (Tokai Carbon, TB5500 (diameter about 50 nm)) as a conductive material, water-soluble polymer Polyvinyl alcohol (Gosenex, T-330, Nippon Synthetic Chemistry) was weighed and mixed so as to have a mass of 7.4% by mass, and an appropriate amount of water was added and dispersed as a dispersant to obtain a slurry-like mixture. Using this slurry-like mixture, a negative electrode and a bipolar evaluation cell produced under the same conditions as in Experimental Example 1 were designated as Experimental Example 6.

[Experimental Examples 7-8]
Negative electrodes and bipolar evaluation cells of Experimental Examples 7 to 8 were prepared in the same manner as in Experimental Example 6 except that the compositions shown in Table 3 were blended. In the same manner as in Experimental Example 1, the electrode capacitance and IV resistance of Experimental Examples 6 to 8 were determined, respectively.

[Experimental Examples 9-12]
Experimental Example 9 was treated in the same manner as in Experimental Example 1 except that the negative electrode of Experimental Example 1 was used and LiPF ₆ was used as the supporting salt. Experimental Example 10 was treated in the same manner as in Experimental Example 1 except that the negative electrode of Experimental Example 8 was used and LiPF ₆ was used as the supporting salt. The active material was prepared as shown in Table 3 using the negative electrode active material of the solution mixing method of Reference Example 5, and the same treatment as in Experimental Example 1 was performed except that LiPF ₆ was used as the supporting salt. And said. The active material was prepared as shown in Table 3 using the negative electrode active material of the solution mixing method of Reference Example 8, and the same treatment as in Experimental Example 6 was performed except that LiPF ₆ was used as the supporting salt. And said. Bipolar evaluation cells of Experimental Examples 9 to 12 were prepared, and the electrode capacitance and IV resistance of Experimental Examples 9 to 12 were determined in the same manner as in Experimental Example 1.

[Results and discussion]
Table 3 summarizes the active material types, electrode compounding ratios, and electrolytic solution compositions of Experimental Examples 1 to 12. Table 4 summarizes the types of active materials, the composition of the electrolytic solution, the IV resistance (Ω), and the electrode capacity (mAh / g) of Experimental Examples 1 to 12. FIG. 7 shows the evaluation results of the electrode characteristics of the Bph layered structures of Experimental Examples 1 to 5, 9 and 11, where FIG. 7A is the IV resistance (Ω) and FIG. 7B is the electrode capacitance (mAh / g). FIG. 8 shows the evaluation results of the electrode characteristics of the Naph layered structures of Experimental Examples 6 to 8, 10 and 12, where FIG. 8A is the IV resistance (Ω) and FIG. 8B is the electrode capacitance (mAh / g). 9 is an initial charge / discharge curve of Experimental Examples 1 to 5, 9 and 11, and FIGS. 9A to 9G are Experimental Examples 1 to 5, 9 and 11, respectively. 10A is an initial charge / discharge curve of Experimental Examples 6 to 8, 10 and 12, and FIGS. 10A to 10E are Experimental Examples 6 to 8, 10 and 12, respectively.

As shown in Table 4, Experimental Examples 11 and 12 using the layered structure prepared by the solution mixing method as the negative electrode active material and LiPF ₆ as the supporting salt showed a high IV resistance value and a low electrode capacitance value. showed that. In Experimental Examples 9 and 10 using the layered structure prepared by spray drying, improvements were made as compared with Experimental Examples 11 and 12, but the IV resistance and the electrode capacity were not yet sufficient. On the other hand, in Experimental Examples 1 to 8 in which the layered structure produced by the spray-drying method was used as the negative electrode active material and LiFSI was used as the supporting salt, lower IV resistance and higher electrode capacity were shown. Specifically, in Experimental Examples 1 to 5, the IV resistance was 90 Ω or less, more preferably 82 Ω or less, and the electrode capacitance was 195 mAh / g or more, more preferably 205 mAh / g or more. Further, in Experimental Examples 6 to 8, the IV resistance was 280 Ω or less, more preferably 270 Ω or less, and the electrode capacitance was 190 mAh / g or more, more preferably 200 mAh / g or more. For example, when a negative electrode containing graphite as a negative electrode active material is used as in Non-Patent Document 1, there is a difference in IV resistance and electrode capacity regardless of whether LiPF ₆ or LiFSI is used as the supporting salt. Absent. On the other hand, as in the present disclosure, it is clear that in a negative electrode containing a layered structure as a negative electrode active material, when LiFSI is used as a supporting salt for a non-aqueous electrolyte solution, the IV resistance is significantly reduced and the electrode capacity is improved. became. It was presumed that the reason for this was probably that when charging / discharging was performed using an electrolytic solution containing LiFSI, a low resistance film was formed at the interface between the electrolytic solution and the negative electrode. It was presumed that this film was formed not by the organic solvent of the electrolytic solution but by the supporting salt of the electrolytic solution. It was presumed that even when the electrolytic solution containing LiFSI was used for the negative electrodes of Experimental Examples 11 and 12, the IV resistance was lower and the electrode capacity was higher than that of Experimental Examples 11 and 12.

Further, it was presumed that the non-aqueous electrolyte solution preferably contained LiFSI at a concentration of 0.5 mol / L or more and 2.0 mol / L or less. Further, it was presumed that the negative electrode preferably contains a binder as a water-soluble polymer, particularly carboxymethyl cellulose in a range of 1.5% by mass or more and 3.5% by mass or less.

It goes without saying that the present disclosure is not limited to the above examples, and can be carried out in various aspects as long as it belongs to the technical scope of the present disclosure.

The present disclosure is available in the field of the battery industry.

20 power storage device, 21 battery case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 ion conductive medium.

Claims (8)

With the positive electrode
A layered structure including an organic skeleton layer containing an aromatic dicarboxylic acid anion and an alkali metal element layer in which an alkali metal element is coordinated with oxygen contained in the carboxylic acid of the organic skeleton layer to form a skeleton is used as a negative electrode active material. Including negative electrode and
An ionic conduction medium containing at least lithium bis (fluorosulfonyl) imide (LiFSI) as a supporting salt, interposed between the positive electrode and the negative electrode, and conducting lithium ions.
A power storage device equipped with. The storage according to claim 1, wherein the ion conduction medium is a non-aqueous electrolytic solution containing the supporting salt and an organic solvent, and contains the LiFSI at a concentration of 0.5 mol / L or more and 2.0 mol / L or less. device. The power storage device according to claim 1 or 2, wherein the negative electrode includes the layered structure having a structure represented by one or more of the formulas (1) to (3).
The power storage according to any one of claims 1 to 3, wherein the negative electrode includes the layered structure including the organic skeleton layer having a biphenyl skeleton and satisfies one or more of the following (1) to (5). device.
(1) The peak intensity ratio P (300) / P (111) of (300) to the peak intensity of (111) when the electrode for the power storage device is measured by X-ray diffraction is 2.0 or more.
(2) The peak intensity ratio P (300) / P (011) of (300) to the peak intensity of (011) in the X-ray diffraction measurement is 2.0 or more.
(3) The peak intensity ratio P (100) / P (111) of (100) to the peak intensity of (111) in the X-ray diffraction measurement is 6.0 or more.
(4) The peak intensity ratio P (100) / P (011) of (100) to the peak intensity of (011) in the X-ray diffraction measurement is 5.0 or more.
(5) The peak intensity ratio P (100) / P (300) of (100) to the peak intensity of (300) in the X-ray diffraction measurement is 1.5 or more. The power storage according to any one of claims 1 to 3, wherein the negative electrode includes the layered structure including the organic skeleton layer having a naphthalene skeleton, and satisfies one or more of the following (6) to (8). device.
(6) The peak intensity ratio P (002) / P (011) of (002) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.25 or more.
(7) The peak intensity ratio P (102) / P (011) of (102) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.50 or more.
(8) The peak intensity ratio P (112) / P (011) of (112) to the peak intensity of (011) in the X-ray diffraction measurement shows 0.60 or more. The negative electrode includes the layered structure including the organic skeleton layer having a naphthalene skeleton, and satisfies one or more of the following (9) to (13), according to any one of claims 1 to 3. Power storage device.
(9) The surface spacing of the (002) plane in the X-ray diffraction measurement is in the range of 0.42400 nm or more and 0.42700 nm or less.
(10) The surface spacing of the (102) plane in the X-ray diffraction measurement is in the range of 0.37000 nm or more and 0.37350 nm or less.
(11) The surface spacing of the (112) plane in the X-ray diffraction measurement is in the range of 0.30400 nm or more and 0.30600 nm or less.
(12) The surface spacing of the (211) plane in the X-ray diffraction measurement is in the range of 0.32250 nm or more and 0.32520 nm or less.
(13) The surface spacing of the (200) plane in the X-ray diffraction measurement is in the range of 0.50500 nm or more and 0.50900 nm or less. The power storage device according to any one of claims 1 to 6, wherein the negative electrode includes the layered structure including the alkali metal element layer having one or more of lithium, sodium and potassium. The negative electrode contains the negative electrode active material, a conductive material, and a water-soluble polymer as a negative electrode mixture, and 1.5% by mass or more and 3.5% by mass of carboxymethyl cellulose as the water-soluble polymer in the entire negative electrode mixture. The power storage device according to any one of claims 1 to 7, which comprises a range of% or less.