JP6857444B2 - Method for manufacturing electrodes for non-aqueous secondary batteries, non-aqueous secondary batteries and electrodes for non-aqueous secondary batteries - Google Patents

Description

The present invention relates to electrodes for non-aqueous secondary batteries and non-aqueous secondary batteries.

Conventionally, a graphite negative electrode is known as a negative electrode for a lithium secondary battery. However, since the lithium storage potential of the carbon negative electrode is close to the lithium potential ( ^{about 0 to 0.2 V based on Li +} / Li), lithium metal is likely to be deposited on the carbon surface during lithium storage. Therefore, the present inventors have formed a skeleton in which an alkali metal element is coordinated with an organic skeleton layer containing an aromatic compound which is a dicarboxylic acid anion having two or more aromatic ring structures and oxygen contained in the carboxylic acid anion. It has been proposed to use a layered structure having an alkali metal element layer to be formed as an electrode active material for an electrode for a non-aqueous secondary battery (for example, Patent Document 1). Since the electrode for a non-aqueous secondary battery of Patent Document 1 uses an electrode active material in which lithium ions are occluded and released at a ^{higher potential (about 0.8 to 1.0 V based on Li + / Li) than the graphite negative electrode.} During lithium occlusion, lithium metal is less likely to precipitate than the graphite negative electrode.

Patent No. 5348170

However, the electrode for a non-aqueous secondary battery of Patent Document 1 may have low water resistance. In addition, if the potential becomes too low (for example ^{, 0.5 V or less based on Li +} / Li), the electrochemical characteristics may change, such as a change in the potential-capacity curve. Therefore, it has the same electrochemical characteristics as the electrode for non-aqueous secondary batteries of Patent Document 1, is difficult to dissolve in water, and has electrochemical characteristics even when exposed to a low potential of 0 V based on ^{Li + / Li.} An electrode for a non-aqueous secondary battery with a small change in the above has been desired.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an electrode for a non-aqueous secondary battery which is water-insoluble and has high reduction resistance.

In earnest research to achieve the above-mentioned object, the present inventors used an aromatic compound having two or more carboxylic acid anion portions, and arranged an alkaline earth metal element in oxygen contained in the carboxylic acid anion portion. The structure was prepared by arranging. As a result, they have found that the structure is difficult to dissolve in water and that the change in electrochemical properties is small even when exposed to a low potential of 0 V on the basis of ^{Li + / Li, and have completed the present invention.}

That is, the electrode for a non-aqueous secondary battery of the present invention is
An alkali that forms a skeleton by coordinating an alkaline earth metal element with oxygen contained in an organic skeleton layer containing an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions. It is provided with a layered structure having an earth metal element layer as an electrode active material.

Further, the non-aqueous secondary battery of the present invention is provided with the above-mentioned electrode for the non-aqueous secondary battery.

INDUSTRIAL APPLICABILITY The present invention can provide an electrode for a non-aqueous secondary battery that is water-insoluble and has high reduction resistance. The reason why such an effect can be obtained is that, for example, the crystal structure of the layered structure used for the electrode is more stable, it is difficult to dissolve in water, and the crystal structure does not easily change even when exposed to a low potential. It is inferred that.

Explanatory drawing which shows an example of the structure of the layered structure of this invention. The schematic diagram which shows an example of the non-aqueous secondary battery 20. X-ray diffraction measurement result of the layered structure of Example 1. The charge / discharge curve of Example 1.

The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, and an ion conduction medium interposed between the positive electrode and the negative electrode. In this non-aqueous secondary battery, for example, a positive electrode having a positive electrode active material that occludes and releases an alkali metal, a negative electrode having a negative electrode active material that occludes and releases an alkali metal, and an alkali interposed between the positive electrode and the negative electrode. It may be provided with an ion conduction medium for conducting metal ions. The non-aqueous secondary battery of the present invention includes the layered structure of the present invention as an electrode active material on at least one of a negative electrode and a positive electrode. In the layered structure of the present invention, an organic skeleton layer containing an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions, and an alkaline earth metal element are arranged in oxygen contained in the carboxylic acid anion portion. It has an alkaline earth metal element layer that forms a skeleton. The layered structure of the present invention is preferably a negative electrode active material. Further, the alkali metal occluded and released by charging and discharging can be, for example, any one or more of Li, Na, K and the like. Here, for convenience of explanation, a non-aqueous secondary battery in which the layered structure is used as the negative electrode active material and the alkali metal occluded and released by charging and discharging is Li will be mainly described below.

The negative electrode includes the layered structure of the present invention as an electrode active material. FIG. 1 is an explanatory diagram showing an example of the structure of the layered structure of the present invention. This layered structure has an organic skeleton layer and an alkaline earth metal element layer. 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.

The organic skeleton layer contains an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions. The aromatic ring structure may include one aromatic ring or may include two or more aromatic rings. The aromatic ring structure having two or more aromatic rings may be, for example, an aromatic polycyclic compound in which two or more aromatic rings such as biphenyl are bonded, or two or more aromatic rings such as naphthalene, anthracene, and pyrene. May be a condensed polycyclic compound obtained by condensing. The aromatic ring constituting the aromatic ring structure 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 1 or more and 5 or less. When the number of aromatic rings is 1 or more, it is easy to form a layered structure, and the crystal structure is easily stabilized. When the number of aromatic rings is 5 or less, the energy density can be further increased. The organic skeleton layer may have two or more carboxylic acid anion portions, but preferably has an even number of carboxylic acid anion portions, and more preferably a dicarboxylic acid anion having two carboxylic acid anion portions. .. Further, it is preferable that the organic skeleton layer contains, for example, an aromatic compound in which two of the carboxylic acid anion portions are bonded at diagonal positions of the aromatic ring structure. That is, it is preferable that the organic skeleton layer contains an aromatic compound in which one and the other of the carboxylic acid anion portions are bonded at diagonal positions of the aromatic ring structure. In this way, the crystal structure can be easily stabilized, for example, a layered structure can be easily formed by the organic skeleton layer and the alkaline earth metal element layer. The diagonal position to which the carboxylic acid anion portion is bonded may be the position farthest from the bonding position of one carboxylic acid anion portion to the bonding position of the other carboxylic acid anion portion. For example, the aromatic ring structure is naphthalene. If so, the 2nd and 6th places are listed, and if it is pyrene, the 2nd and 7th places are listed.

The organic skeleton layer may be composed of an aromatic compound containing a structure represented by the general formula (1). However, R may have the above aromatic ring structure having one or more aromatic rings. Specifically, the organic skeleton layer may include any one or more aromatic compounds of the following formulas (2) to (4). However, in the formulas (2) to (4), it is preferable that n is an integer of 1 or more and 5 or less, and m is an integer of 0 or more and 3 or less. When n is 1 or more and 5 or less, the size of the organic skeleton layer is suitable, and the charge / discharge capacity can be further increased. Further, when m is 0 or more and 3 or less, the size of the organic skeleton layer is suitable, and the charge / discharge capacity can be further increased. In the formulas (2) to (4), these aromatic compounds may have a substituent and a hetero atom in their structure. 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. For example, the organic skeleton layer may include any one or more aromatic compounds of the following formulas (5) to (11).

As shown in FIG. 1, for example, the alkaline earth metal element layer forms a skeleton in which the alkaline earth metal element is coordinated with oxygen contained in the carboxylic acid anion portion. The alkaline earth metal element may be at least one of Ca and Mg, of which Ca is preferable. With Ca, it is easier to make a layered structure. Since the alkaline earth metal element contained in the alkaline earth metal element layer forms the skeleton of the layered structure, it is presumed that it is not involved in the ion movement associated with charging and discharging. As shown in FIG. 1, the layered structure thus constructed is formed of an organic skeleton layer and a Ca layer (alkaline earth metal element layer) existing between the organic skeleton layers. There is. Further, in the energy storage mechanism, it is considered that the organic skeleton layer of the layered structure functions as a redox (e ⁻ ) site and the Ca layer ^{functions as an ion (for example, Li +} ) occlusion site.

More specifically, in the layered structure of the present invention, the organic skeleton layer is composed of an aromatic compound containing a terephthalic acid structure, and the alkaline earth metal element contained in the alkaline earth metal element layer is Ca. It is more preferable that it is the one shown in (12).

The layered structure of the present invention has a structure of the following formula (13) in which oxygen in three different carboxylic acid anion portions, four water molecules, and an alkaline earth metal element form a seven coordination. Is structurally stable and is preferable. Layered structure of formula (13), 2 or more carboxylic acid anion moiety attached to an aromatic ring structure R and an aromatic ring structure R (-COO ^-) and organic framework layer containing an aromatic compound having a, its It has an alkaline earth metal element layer in which an alkaline earth metal element M coordinates with oxygen contained in the carboxylic acid anion portion to form a skeleton. This layered structure has two or more aromatic ring structures as R, and two or more of the plurality of Rs may be the same, or one or more may be different. Further, this layered structure has two or more alkaline earth metal elements as M, and two or more of the plurality of Ms may be the same, or one or more may be different. The alkaline earth metal element M may be independently coordinated with the carboxylic acid anion portion, or may be added to the oxygen contained in the carboxylic acid anion portion as an alkaline earth metal salt formed with a salt of Mg, Li, Na or the like. It may be coordinated. As described above, it is preferable to have a structure in which the organic skeleton layer is bonded by the alkaline earth metal element.

The layered structure of the present invention may have a BET specific surface area of 1 m ² / g or less. Such a material is preferable because it can suppress the irreversible volume due to the reductive decomposition of the electrolytic solution. The BET specific surface area is ^{more preferably 1 m 2} / g or more and 10 m ² / g or less.

The layered structure of the present invention can occlude and release alkali metals, and can be used as an electrode active material that occludes and releases alkali metals.

For the negative electrode, for example, a negative electrode active material composed of a layered structure, a conductive material, and a binder are mixed, and an appropriate solvent is added to form a paste-like negative electrode mixture, which is applied and dried on the surface of the current collector. , If necessary, it may be formed by compression to increase the electrode density. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the negative electrode, and for example, graphite such as natural graphite (scaly graphite, scaly graphite) or artificial graphite, acetylene black, carbon black, etc. One or a mixture of one or more of Ketjen black, carbon whisker, graphite coke, carbon fiber, metal (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 binder plays a role of binding the active material particles and the conductive material particles, and is, for example, a fluororesin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluororubber, or polypropylene. Thermoplastic resins such as polyethylene, ethylene-propylene-diemmer (EPDM), sulfonated EPDM, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used. Examples of the solvent for dispersing the negative electrode active material, the conductive material, and the binder include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-. Organic solvents such as dimethylaminopropylamine, ethylene oxide and tetrahydrofuran can be used. Further, a dispersant, a thickener or the like may be added to water, and the active material may be slurried with a latex such as SBR. 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 kinds. Examples of the coating method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape. As the 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, a material 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 negative electrode 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.

For the positive electrode, for example, a positive electrode active material, a conductive material, and a binder are mixed, and an appropriate solvent is added to form a paste-like positive electrode mixture, which is applied and dried on the surface of the current collector, and if necessary. It may be formed by compression in order to increase the electrode density. 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 , Li (1-a)} MnO ₂ (0 <a <1, etc., the same applies hereinafter), Li _(1-a) Mn. Lithium manganese composite oxides such as ₂ O _{4 , lithium cobalt composite oxides such as Li (1-a)} CoO ₂ , lithium nickel composite oxides such as Li _(1-a) NiO ₂ , lithium such as LiV ₂ O ₃ Vanadium composite oxides, transition metal oxides such as _{V 2} O _{5 and the like can be used.} Of these, lithium transition metal composite oxides, such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , and LiV ₂ O ₃ , are preferred. Further, as the conductive material, the binder, the solvent and the like used for the positive electrode, those exemplified for the negative electrode can be used. The current collector of the positive electrode includes aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, etc., as well as aluminum for the purpose of improving adhesiveness, conductivity and oxidation resistance. A surface of copper or the like treated with carbon, nickel, titanium, silver or the like can be used. For these, it is also possible to oxidize the surface. The shape of the current collector can be the same as that of the negative electrode.

As the ion conduction medium, a non-aqueous electrolytic solution containing a supporting salt, a non-aqueous gel electrolytic solution, or the like can be used. Examples of the solvent for the non-aqueous electrolytic solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes and the like, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, and methyl-t. Chain carbonates such as -butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, methyl formate, methyl acetate, ethyl acetate, Chain esters such as methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, diethoxyethane, nitriles such as acetonitrile and benzonitrile, furans such as tetrahydrofuran and methyl tetrahydrofuran, sulfolane, tetramethylsulfolane and the like. Examples thereof include sulfolanes, dioxolanes such as 1,3-dioxolane and methyldioxolane. Of these, a combination of cyclic carbonates and chain carbonates is preferable. According to this combination, not only the cycle characteristics that express the battery characteristics by repeated charging and discharging are excellent, but also the viscosity of the electrolytic solution, the electric capacity of the obtained battery, the battery output, etc. can be balanced. it can. It is considered that the cyclic carbonates have a relatively high relative permittivity and increase the dielectric constant of the electrolytic solution, and the chain carbonates suppress the viscosity of the electrolytic solution.

Supporting salts include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF _{6 , LiAlF 4} , LiSCN, LiClO. ₄ , LiCl, LiF, LiBr, LiI, LiAlCl _{4 and the} like. Of these, from the group consisting _{of inorganic salts such as LiPF 6} , LiBF ₄ , LiAsF ₆ , and LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) _3. It is preferable to use one selected salt or a combination of two or more salts from the viewpoint of electrical characteristics. The concentration of this electrolyte salt in the non-aqueous electrolyte 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 mol / L or less. When the concentration of the electrolyte salt is 0.1 mol / L or more, a sufficient current density can be obtained, and when the concentration of the electrolyte salt 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.

Further, instead of the liquid ion conductive medium, a solid ion conductive polymer can be used as the ion conductive medium. As the ionic conductive polymer, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinylpyrrolidone, polyvinylidene fluoride and a supporting salt can be used. Further, an ionic conductive polymer and a non-aqueous electrolyte solution can be used in combination. Further, as the ion conductive medium, in addition to the ion conductive polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, an inorganic solid powder bound by an organic binder, or the like can be used.

The non-aqueous secondary battery of the present invention 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 a non-aqueous secondary battery. For example, a polymer non-woven fabric such as a polypropylene non-woven fabric or a polyphenylene sulfide non-woven fabric, or a thin olefin resin such as polyethylene or polypropylene is used. Examples include microporous membranes. These may be used alone or in combination of two or more.

The shape of the non-aqueous secondary battery of the present invention 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 view showing an example of the non-aqueous secondary battery 20 of the present invention. The non-aqueous secondary battery 20 has a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and provided at the bottom of the battery case 21, and a separator 24 with respect to the positive electrode 22 having a negative electrode active material. A negative electrode 23 provided at a position facing each other, 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. It has. In this non-aqueous secondary battery 20, the space between the positive electrode 22 and the negative electrode 23 is filled with the ion conduction medium 27. At least one of the positive electrode 22 and the negative electrode 23 has an organic skeleton layer containing an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions, and an alkaline earth metal element in oxygen contained in the carboxylic acid anion portion. It contains a layered structure having an alkaline earth metal element layer which is coordinated to form a skeleton as an electrode active material.

INDUSTRIAL APPLICABILITY The present invention can provide an electrode for a non-aqueous secondary battery that is water-insoluble and has high reduction resistance. Further, for example, since the layered structure of the present invention is water-insoluble, electrodes can be formed by water-based coating, and since the layered structure of the present invention has high reducing property, 0.5 V or less based on ^{Li + / Li, etc.} The electrochemical properties do not change when exposed to the low potential of. Further, when used for the negative electrode, the charge / discharge potential shows a range of 0.5 V or more and 1.0 V based on the lithium metal, so that it is possible to suppress a significant decrease in energy density due to a decrease in the operating voltage of the battery, while lithium. Metal precipitation can also be suppressed. Further, when used for a negative electrode, a high discharge capacity equivalent to that of the electrode for a non-aqueous secondary battery of Patent Document 1 can be obtained. In this layered structure, it is presumed that the organic skeleton layer functions as a redox site and a lithium ion occlusion site.

It goes without saying that the present invention 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 invention.

For example, in the above-described embodiment, the non-aqueous secondary battery has been described, but the electrode may be a non-aqueous secondary battery.

Hereinafter, an example in which the non-aqueous secondary battery of the present invention is specifically produced will be described as an example. It goes without saying that the present invention is not limited to the following examples, and can be carried out in various embodiments as long as it belongs to the technical scope of the present invention.

[Example 1]
A calcium terephthalate salt (see formula (12)) as a layered structure was synthesized as follows. Terephthalic acid (0.1 mol) and calcium hydroxide (0.1 mol) were dispersed in 200 mL of water and heated and stirred in a water bath at 80 ° C. for 4 hours to obtain crystals of calcium terephthalic acid. The crystals were filtered off and air dried at room temperature.

[Comparative Example 1]
Lithium terephthalate as a layered structure was synthesized as follows. To a solution prepared by dissolving 0.01525 mol of LiOH · H ₂ O in 50 mL of methanol, 0.00694 mol of terephthalic acid was added, and the mixture was stirred at room temperature. Immediately after the addition of terephthalic acid, the solution was completely dissolved, but after stirring for about 20 minutes, crystals began to precipitate. When stirring was continued for one day and night, the precipitated crystals grew and exhibited columnar crystals having a length of about 10 μm. After evaporating methanol, vacuum drying was performed at 120 ° C. to obtain a lithium terephthalate salt.

[Comparative Example 2]
A lithium 2,6-naphthalenedicarboxylic acid salt as a layered structure was synthesized as follows. _{To a solution prepared by dissolving 0.01525 mol of LiOH · H 2} O in 50 mL of methanol was added 0.00694 mol of 2,6-naphthalenedicarboxylic acid, and the mixture was stirred at room temperature. Immediately after the addition of 2,6-naphthalenedicarboxylic acid, the solution was completely dissolved, but after stirring for about 20 minutes, crystals began to precipitate. When stirring was continued for one day and night, the precipitated crystals grew and exhibited columnar crystals having a length of about 10 μm. After evaporating methanol, vacuum drying was performed at 120 ° C. to obtain a lithium 2,6-naphthalenedicarboxylic acid salt.

[X-ray diffraction measurement]
Powder X-ray diffraction measurement of the layered structures of Example 1 and Comparative Examples 1 and 2 was performed. The measurement was performed using a CuKα ray (wavelength 1.54051 Å) as radiation and using an X-ray diffractometer (RINT2200 manufactured by Rigaku). For the measurement, a graphite single crystal monochromator was used to monochromate the X-rays, the applied voltage was set to 40 kV, the current was set to 30 mA, and the scanning speed was 4 ° / min, and the angle range was 2θ = 10 ° to 60 °. I went there. FIG. 3 is an X-ray diffraction measurement result of the layered structure of Example 1. As shown in FIG. 3, in Example 1, peaks corresponding to the 110,011,130,200,21,190 planes clearly appear when the monoclinic crystals belonging to _{the space group P2 1 / c are assumed.} Therefore, it was inferred that the layered structure composed of the Ca layer and the organic skeleton layer shown in FIG. 1 was formed. Further, since Example 1 is _{a monoclinic crystal belonging to the space group P2 1} / c, oxygen and four water molecules of three different carboxylic acid anion portions and an alkaline earth metal element are seven. It is a structure that forms a coordination, and it is speculated that the interaction by the π-electron conjugated cloud is working in the part of the organic skeleton.

For example, in Crystal Growth & Design, Vol. 8, No. 2, 2008, pp685-689, even the calcium salt of 2,6-naphthalenedicarboxylic acid is a monoclinic type belonging to the _{space group P2 1 / c.} It has been clarified that the Ca layer and the organic skeleton layer form a layered structure.

[Measurement of structure solubility in water]
While stirring 100 mL of ion-exchange distilled water whose temperature was adjusted to 25 ° C. with a stirrer, about 0.1 g to 1.0 g of the structures of Example 1 and Comparative Examples 1 and 2 was added, and the dissolved state was visually confirmed. .. If it did not dissolve, it was confirmed that it did not dissolve even 2 hours after the addition. In this way, the amount of dissolution was measured and the solubility was determined. The structure of Example 1 (calcium terephthalate) was not dissolved in water, but the structure of Comparative Example 1 (lithium terephthalate) and the structure of Comparative Example 2 (lithium 2,6-naphthalenedicarboxylic acid). ) Was dissolved in water, and the solubility thereof was about 10% by mass.

[Measurement of potential-capacity curve during lithium occlusion / detachment]
The layered structure of Example 1 (calcium terephthalate), the layered structure of Comparative Example 1 (lithium terephthalate), and the layered structure of Comparative Example 2 (lithium 2,6-naphthalenedicarboxylic acid) are activated. Used as a substance. After mixing 70% by mass of active material, 15% by mass of carbon black as a conductive auxiliary agent, 15% by mass of PVdF as a binder, and a small amount of NMP as a dispersion medium, it is applied to the Cu foil of the current collector foil, dried, and pressed. The densification was performed to obtain an electrode.

A coin cell was produced using the obtained electrode as a working electrode and a lithium metal as the counter electrode. _{As the electrolytic solution, LiPF 6} is set to 1 M in a mixed solvent (EC: DMC: EMC = 30: 40: 30% by volume) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). The non-aqueous electrolyte solution added to was used. A microporous polypropylene membrane was used as the separator.

The coin cell is subjected to constant current discharge / constant current charging for 5 cycles at room temperature with a potential window of 0.5-1.5 V and a current of 20 mA / g (active material weight), and after measuring the charge / discharge capacity and average potential, the potential window is used. A constant current discharge / constant current charge was carried out for one cycle at 0-1.5 V and a current of 20 mA / g per active material weight (active material weight), and it was examined whether or not the charge / discharge curve changed. FIG. 4 shows the charge / discharge curve of Example 1. In the first 5 cycles, the charge / discharge characteristics of both Example 1 and Comparative Examples 1 and 2 were similar. From this, it was inferred that in the layered structure of Example 1, lithium was occluded and released in the vicinity of the inorganic layer (Ca layer) by redox in the organic skeleton layer.

Table 1 summarizes the experimental results. From Table 1, it was found that all the active materials of Example 1 and Comparative Examples 1 and 2 showed high volumes. Further, it was found that the average potential of all the active materials of Example 1 and Comparative Examples 1 and 2 was higher than that of the carbon negative electrode, and lithium metal was less likely to precipitate. On the other hand, when the lithium salt was used as in Comparative Examples 1 and 2, the charge / discharge curve was changed by the reduction to 0 V, whereas when the calcium salt was used as in Example 1, the charge / discharge curve was changed. The discharge curve did not change. It is presumed that this is because the crystal structure of the lithium salt changed (destroyed), whereas that of the calcium salt had high reduction resistance and the crystal structure did not change. The reason why the crystal structure does not change with the calcium salt is that the coordination bond between the metal and oxygen and the hydrogen bond between hydrogen and oxygen form a strong bond and stabilize the crystal structure. it is conceivable that. The lithium salt used in Comparative Examples 1 and 2 was dissolved in water in an amount of about 10% by mass, whereas the calcium salt used in Example 1 was not dissolved in water. From the above, it was confirmed that the calcium terephthalate salt used in Example 1 can be used as a novel negative electrode active material having high capacity, medium potential, high reduction resistance, and water insolubility.

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

20 non-aqueous secondary battery, 21 battery case, 22 positive electrode, 23 negative electrode, 24 separator, 25 gasket, 26 sealing plate, 27 ion conductive medium.

Claims (7)

An alkali that forms a skeleton by coordinating an alkaline earth metal element with oxygen contained in an organic skeleton layer containing an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions. It is a calcium terephthalate having an earth metal element layer, and 110,011,130,200,211 when a monooblique crystal belonging to the _{space group P2 1 / c is assumed in powder X-ray diffraction measurement.} , An electrode for non-aqueous secondary batteries equipped with a layered structure in which a peak corresponding to 190 planes appears as an electrode active material. The electrode for a non-aqueous secondary battery according to claim 1, wherein the layered structure has a peak corresponding to the 211th surface higher than the peak corresponding to the 190th surface. The electrode for a non-aqueous secondary battery according to claim 1 or 2, wherein the layered structure is a negative electrode active material capable of storing and releasing an alkali metal. A non-aqueous secondary battery comprising the electrode for a non-aqueous secondary battery according to any one of claims 1 to 3. The non-aqueous secondary battery according to claim 4, wherein the electrode for the non-aqueous secondary battery is a negative electrode. The non-aqueous secondary battery according to claim 4 or 5, further comprising an ion conduction medium that conducts alkali metal ions. An alkali that forms a skeleton by coordinating an alkaline earth metal element with oxygen contained in an organic skeleton layer containing an aromatic compound having an aromatic ring structure and two or more carboxylic acid anion portions. A method for manufacturing an electrode for a non-aqueous secondary battery, which comprises a layered structure having an earth metal element layer as an electrode active material.
A step of obtaining a calcium terephthalate salt which is the layered structure by using terephthalic acid and calcium hydroxide is included.
A method for manufacturing electrodes for non-aqueous secondary batteries.

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