JP6264157B2 - Nonaqueous secondary battery electrode and nonaqueous secondary battery - Google Patents

Description

  The present invention relates to an electrode for a non-aqueous secondary battery and a non-aqueous secondary battery.

  In recent years, it has been studied to use an organic electrode active material in an alkali metal ion battery. For example, it has been proposed to use disodium terephthalate as a negative electrode active material (see Non-Patent Document 1). In this battery, a negative electrode obtained by mixing 50% by mass of a negative electrode active material, 37.5% by mass of carbon black, and 12.5% by mass of carboxymethyl cellulose (CMC) is used.

Adv. Mater. 2012, 24, 3562-3567

  However, in the non-patent document 1, the charge / discharge characteristics may be low, for example, the irreversible capacity in the initial charge / discharge may be large or the capacity retention rate may be low when the charge / discharge cycle is repeated. For this reason, it has been desired to further improve the charge / discharge characteristics.

  The present invention has been made in order to solve such problems, and mainly provides an electrode for a non-aqueous secondary battery capable of further improving charge / discharge characteristics and a non-aqueous secondary battery including the same. Objective.

  As a result of diligent research to achieve the above-mentioned object, the present inventors have used a structure in which lithium is coordinated to oxygen contained in the carboxylic acid using an aromatic compound that is a dicarboxylic acid anion as an electrode active material. Then, it has been found that the charge / discharge characteristics can be improved. Furthermore, when an electrode was produced by adding a conductive material and 2% by mass or more and 8% by mass or less of carboxymethyl cellulose to this electrode active material, it was found that charge / discharge characteristics could be further improved, and the present invention was completed. It came.

That is, the electrode for a non-aqueous secondary battery of the present invention is
An organic skeleton layer containing an aromatic compound that is a dicarboxylic acid anion having two or more aromatic ring structures; and an alkali metal element layer in which an alkali metal element coordinates to oxygen contained in the carboxylic acid anion to form a skeleton. An electrode active material comprising a layered structure having
Conductive material;
A water-soluble polymer that is at least one of carboxymethylcellulose and polyvinyl alcohol;
The water-soluble polymer is contained in the range of 2% by mass or more and 8% by mass or less.

The non-aqueous secondary battery of the present invention is
The non-aqueous secondary battery electrode described above;
An ion conducting medium that conducts alkali metal ions;
It is equipped with.

  In the electrode for nonaqueous secondary batteries and the nonaqueous secondary battery of the present invention, charge / discharge characteristics can be further improved. The reason why such an effect can be obtained is assumed as follows. In other words, the layered structure that is an active material has a 4-coordination between the oxygen of the dicarboxylic acid and the alkali metal element (for example, lithium), is hardly soluble in the non-aqueous electrolyte, and is charged and discharged by maintaining the crystal structure. It is presumed that the stability of the cycle characteristics is further improved. In this layered structure, it is presumed that the organic skeleton layer functions as a redox site, and the alkali metal element layer functions as an occlusion site for alkali metal ions that are charged and discharged. In addition, the interaction between the layered structure, which is a dicarboxylic acid, and a water-soluble polymer having an —OR structure (where R is hydrogen, sodium, ammonium, etc.) allows the electrode materials to be uniformly mixed and adhered to each other. It is speculated that the electrode can be made. At this time, when the amount of the water-soluble polymer is 2.0% by mass or more, the electrode material is mixed more uniformly, and when the amount of the water-soluble polymer is 8.0% by mass or less, the electrode material has a certain degree of flexibility and the electrode material is In order to adhere more closely, it is guessed that a heterogeneous reaction etc. are suppressed and stability of a charge / discharge cycle characteristic is improved more.

Explanatory drawing which shows an example of the structure of a layered structure. FIG. 3 is a schematic diagram illustrating an example of a non-aqueous secondary battery 20. X-ray diffraction measurement results of dilithium 2,6-naphthalenedicarboxylate. The charge / discharge curve of Experimental Example 4. The charge / discharge curve of Experimental Example 12. The graph showing the relationship between the ratio of CMC and the maximum capacity. The graph showing the relationship between the ratio of CMC and initial efficiency. The graph showing the relationship between the ratio of CMC and a capacity maintenance rate.

  The electrode for a non-aqueous secondary battery of the present invention includes an electrode active material, a conductive material, and a water-soluble polymer.

An electrode active material forms 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 coordinates to oxygen contained in the carboxylic acid anion to form a skeleton. A layered structure having an alkali metal element layer. FIG. 1 is an explanatory view showing an example of the structure of such a layered structure. This layered structure includes an organic skeleton layer and an alkali metal element layer (Li layer). The layered structure is preferably formed in a layered form by the π-electron interaction of the aromatic compound, for example, those having a monoclinic crystal structure belonging to the space group P2 ₁ / c, Those having an orthorhombic crystal structure belonging to the space group Pbc2 ₁ are preferred because they are structurally stable. Among these, those having a monoclinic crystal structure belonging to the space group P2 ₁ / c are more preferable. When the alkali metal element layer contains lithium, it tends to have a monoclinic crystal structure belonging to the space group P2 ₁ / c, and when the alkali metal element layer contains sodium, the space group Pbc2 _It tends to have an orthorhombic crystal structure belonging to ₁ . It is preferable that the layered structure has a structure represented by the following formula (1) in which four oxygen atoms of different dicarboxylic acid anions and an alkali metal element form a four-coordination. However, in this formula (1), R has two or more aromatic ring structures, and two or more of a plurality of Rs may be the same or one or more may be different. A is an alkali metal element. Thus, it is preferable to have a structure in which the organic skeleton layer is bonded by an alkali metal element.

  The organic skeleton layer contains an aromatic compound that is a dicarboxylic acid anion having two or more aromatic ring structures. The two or more aromatic ring structures may be, for example, an aromatic polycyclic compound in which two or more aromatic rings such as biphenyl are bonded, or a condensed polycyclic compound in which two or more aromatic rings such as naphthalene, anthracene, and pyrene are condensed. It may be a ring compound. This aromatic ring may be a 5-membered ring, a 6-membered ring or an 8-membered ring, and a 6-membered ring is preferred. The aromatic ring is preferably 2 or more and 5 or less. When the aromatic ring is 2 or more, a layered structure is easily formed, and when the aromatic ring is 5 or less, the energy density can be further increased. This organic skeleton layer preferably contains an aromatic compound in which one of the dicarboxylic acid anions and the other of the carboxylic acid anions are bonded to diagonal positions of the aromatic ring structure. By doing so, it is easy to form a layered structure of the organic skeleton layer and the alkali metal element layer. The diagonal position to which the carboxylic acid is bonded may be the farthest position 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 naphthalene, 2, 6 In the case of pyrene, the 2nd and 7th positions are mentioned. This organic skeleton layer may be composed of an aromatic compound including a structure represented by the following formula (2). However, R may be the above aromatic ring structure having two or more aromatic ring structures. Specifically, this organic skeleton layer may include any one or more aromatic compounds of the following formulas (3) to (5). However, in the formulas (3) to (5), n is preferably an integer of 2 or more and 5 or less, and m is an integer of 0 or more and 3 or less. When n is 2 or more and 5 or less, the size of the organic skeleton layer is suitable, and the charge / discharge capacity can be further increased. Moreover, 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 (3) to (5), these aromatic compounds may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen of an 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, an acyl group Further, it may have an amide group or a hydroxyl group as a substituent, or may have a structure in which nitrogen, sulfur or oxygen is introduced instead of carbon of the aromatic compound.

As shown in FIG. 1, the alkali metal element layer has a skeleton formed by coordination of an alkali metal element with oxygen contained in the carboxylate anion. The alkali metal element may be any one or more of Li, Na, and K, and among these, Li is preferable. Since the alkali metal element contained in the alkali metal element layer forms a skeleton of the layered structure, it is presumed that the alkali metal element does not participate in the ion migration accompanying charge / discharge. As shown in FIG. 1, the layered structure thus configured is formed by an organic skeleton layer and a Li layer (alkali metal element layer) existing between the organic skeleton layers. In the energy storage mechanism, the organic skeleton layer of the layered structure is considered to function as a redox (e ⁻ ) site, while the Li layer functions as a Li ⁺ storage site. That is, this layered structure is considered to store and release energy as shown in the following formula (6). Furthermore, in this layered structure, a space where Li can enter may be formed in the organic skeleton layer, and Li can be occluded and released also in portions other than the alkali metal layer in Formula (6). It is assumed that the discharge capacity can be further increased.

  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. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, A mixture of one or more of carbon materials such as ketjen black, carbon whisker, needle coke, and carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability. The conductive material may be particulate or fibrous, but is preferably particulate. In general, organic electrode active materials have low conductivity, and thus a fibrous conductive material is often added to improve conductivity. However, the present invention does not require the use of such a fibrous conductive material. It is because the significance of applying is high. Note that the fibrous form means that a / c and a / b are both larger than 2 when the dimensions in the three orthogonal directions are a, b, c (a ≧ b ≧ c), for example. Also good. Further, the particulate form may be other than the fibrous form. For example, a / c and b / c are preferably 3 or less, more preferably 1.5 or less. More preferably, it is 1.2 or less.

  The water-soluble polymer is at least one of carboxymethyl cellulose and polyvinyl alcohol. The water-soluble polymer plays a role as a binder for connecting the active material particles and the conductive material particles. Carboxymethyl cellulose may be, for example, an inorganic salt having a carboxymethyl group terminated with sodium or calcium, or an ammonium salt having a carboxymethyl group terminated with ammonium.

  The electrode for a non-aqueous secondary battery contains the above-described water-soluble polymer in the range of 2% by mass to 8% by mass. When the water-soluble polymer is contained in the range of 2% by mass or more, the capacity retention rate can be further increased. Moreover, in the thing containing a water-soluble polymer in 8 mass% or less, the adhesiveness of electrode materials or an electrode material and a collector is high. Among these, what contains a water-soluble polymer in 7 mass% or less is preferable, and what contains in 6 mass% or less is more preferable. Moreover, it is preferable that the electrode for non-aqueous secondary batteries contains an electrode active material in 70 mass% or more and 90 mass% or less. In general, an electrode using an organic electrode active material has low conductivity, and it is necessary to improve the conductivity by adding a large amount of a conductive material. Therefore, the amount of the electrode active material is less than 70% by mass. In the invention, the electrode active material is preferable in that it can be increased to 70% by mass or more. In the case where the electrode active material is contained in the range of 90% by mass or less, the amount of the conductive material and the water-soluble polymer is not decreased too much, so that the functions of the conductive material and the water-soluble polymer can be sufficiently exhibited. Moreover, it is preferable that the electrode for non-aqueous secondary batteries contains a electrically conductive material in 5 to 15 mass%. If it is 5 mass% or more, sufficient electroconductivity can be given to an electrode and deterioration of a charge / discharge characteristic can be suppressed. Moreover, if it is 15 mass% or less, since an electrode active material and a water-soluble polymer do not decrease too much, the function of an electrode active material and a water-soluble polymer can fully be exhibited.

  The electrode for a non-aqueous secondary battery may further include a styrene-butadiene copolymer in addition to the electrode active material, the conductive material, and the water-soluble polymer. The styrene-butadiene copolymer plays a role as a binder that holds the active material particles and the conductive material particles together. A material containing a styrene-butadiene copolymer is preferable in that the active material particles can be bound more strongly. When a styrene butadiene copolymer is included, it is preferably included in a range of 8% by mass or less. If the amount is 8% by mass or less, the amount of the active material, the conductive material, and the water-soluble polymer does not decrease too much, so that the functions of the active material, the conductive material, and the water-soluble polymer can be sufficiently exhibited.

  Non-aqueous secondary battery electrodes are prepared by mixing, for example, an electrode active material, a conductive material, and a binder (water-soluble polymer or styrene-butadiene copolymer) and adding a suitable solvent to form a paste-like mixture. May be applied to the surface of the current collector and dried, and may be compressed to increase the electrode density as necessary. As a solvent for dispersing the electrode active material, the conductive material, and the binder, for example, water or alcohol can be used. Examples of the application 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. Current collectors include copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., for the purpose of improving adhesion, conductivity and reduction resistance. For example, the surface of copper or the like treated with carbon, nickel, titanium, silver, or the like can also be used. For these, the surface can be oxidized. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous, foam, and formed fiber group. The thickness of the current collector is, for example, 1 to 500 μm.

  The non-aqueous secondary battery of the present invention includes the above-described electrode for a non-aqueous secondary battery of the present invention and an ion conductive medium that conducts alkali metal ions. In this battery, the positive electrode and the negative electrode are preferably capable of occluding and releasing alkali metals. In the non-aqueous secondary battery of the present invention, the non-aqueous secondary battery electrode of the present invention described above may be a positive electrode or a negative electrode, but is preferably a negative electrode. That is, the layered structure described above is preferably a negative electrode active material. Further, the alkali metal occluded / released by charging / discharging may be different from the alkali metal element of the alkali metal element layer or may be the same, for example, any one or more of Li, Na, K, etc. It can be. Here, for convenience of explanation, the above-described electrode for a non-aqueous secondary battery according to the present invention is used as a negative electrode, the alkali metal element layer of the layered compound contains Li, and the alkali metal occluded / released by charge / discharge is Li. The non-aqueous secondary battery will be mainly described below.

The positive electrode of the non-aqueous secondary battery is, for example, a mixture of a positive electrode active material, a conductive material, and a binder, and an appropriate solvent added to form a paste-like positive electrode mixture on the surface of the current collector. However, it may be compressed to increase the electrode density as necessary. 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 , FeS ₂ , Li _(1-a) MnO ₂ (0 <a <1, etc., the same shall apply hereinafter), Li _(1-a) Mn Lithium manganese composite oxide such as ₂ O ₄ , lithium cobalt composite oxide such as Li _(1-a) CoO ₂ , lithium nickel composite oxide 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 preferable. 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 positive electrode. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, What mixed 1 type (s) or 2 or more types, such as ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability. The binder serves to bind the active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorine-containing resin such as fluorine rubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene-propylene-dienemer (EPDM), sulfonated EPDM, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used. Examples of the solvent for dispersing the positive electrode active material, the conductive material, and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, and N, N-dimethylaminopropyl. Organic solvents such as amine, ethylene oxide, and tetrahydrofuran can be used. Moreover, a dispersing agent, a thickener, etc. may be added to water, and an active material may be slurried with 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. Examples of the application 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. Current collectors include aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, and aluminum, copper, etc. for the purpose of improving adhesion, conductivity, and oxidation resistance. A surface treated with carbon, nickel, titanium, silver or the like can be used. For these, the surface can be oxidized. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded, lath, porous, foam, and formed fiber group. The thickness of the current collector is, for example, 1 to 500 μm.

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

The supporting salt contained in the nonaqueous secondary battery is, 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. Among these, from the group consisting of inorganic salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _3. It is preferable from the viewpoint of electrical characteristics to use a combination of one or two or more selected salts. This electrolyte salt preferably has a concentration in the non-aqueous electrolyte of 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 is 5 mol / L or less, the electrolytic solution can be made more stable. Moreover, you may add flame retardants, such as a phosphorus type and a halogen type, to this non-aqueous electrolyte.

  Further, instead of the liquid ion conducting medium, a solid ion conducting polymer may be used as the ion conducting medium. As the ion conductive polymer, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, and polyvinylidene fluoride and a supporting salt can be used. Further, an ion conductive polymer and a non-aqueous electrolyte can be used in combination. 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 as the ion conductive medium.

  The nonaqueous secondary battery may include a separator between the positive electrode and the negative electrode. The separator is not particularly limited as long as it is a composition that can withstand the range of use of the non-aqueous secondary battery. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a thin olefin resin such as polyethylene or polypropylene is thin. A microporous membrane is mentioned. These may be used alone or in combination.

  The shape of the non-aqueous secondary battery 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. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc. FIG. 2 is a schematic diagram illustrating an example of the non-aqueous secondary battery 20. The non-aqueous secondary battery 20 includes a cup-shaped battery case 21, a positive electrode 22 having a positive electrode active material and provided at a lower portion of the battery case 21, a negative electrode active material having a separator 24 with respect to the positive electrode 22. A negative electrode 23 provided at a position opposed to each other via a gasket, a gasket 25 formed of an insulating material, a sealing plate 26 disposed in an opening of the battery case 21 and sealing the battery case 21 via the gasket 25, It has. In the nonaqueous secondary battery 20, an ion conductive medium 27 in which an alkali metal salt (lithium salt) is dissolved is filled in a space between the positive electrode 22 and the negative electrode 23. The negative electrode 23 includes an aromatic compound that is a dicarboxylic acid anion having two or more aromatic ring structures, and one of the dicarboxylic acid anions and the other of the carboxylic acid anions are bonded to diagonal positions of the aromatic compound. A layered structure including an organic skeleton layer and an alkali metal element layer coordinated to oxygen contained in a carboxylate anion is included as a negative electrode active material. Further, in addition to the negative electrode active material, it contains a conductive material and a water-soluble polymer that is at least one of carboxymethyl cellulose and polyvinyl alcohol, and the content of the water-soluble polymer is in the range of 2 mass% to 8 mass%. is there.

  In the non-aqueous secondary battery described above, in the layered structure that is the active material, the oxygen of the dicarboxylic acid and the Li element form a 4-coordination, which is difficult to dissolve in the non-aqueous system, and is maintained by maintaining the crystal structure. It is presumed that the stability of the discharge cycle characteristics can be further improved. In this layered structure, it is presumed that the organic skeleton layer functions as a redox site, and the Li layer functions as a Li ion storage site. In addition, the electrode material is uniformly mixed and adhered by the interaction between the layered structure which is a dicarboxylic acid and a water-soluble polymer having an —OR structure (R is hydrogen, sodium, ammonium, etc.) It is assumed that it can be. At this time, since the water-soluble polymer is contained in the range of 2.0% by mass or more, it is considered that the electrode material is mixed more uniformly. In addition, since the water-soluble polymer is contained in the range of 8.0% by mass or less, the electrode material has a certain degree of flexibility, the electrode material is more closely adhered, the heterogeneous reaction is suppressed, and the stability of the charge / discharge cycle characteristics is further improved. It is assumed that it can be increased.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  Below, the example which produced the negative electrode for non-aqueous secondary batteries and the non-aqueous secondary battery concretely is demonstrated as an experiment example. Experimental examples 1 to 8 correspond to examples of the present invention, and experimental examples 9 to 12 correspond to comparative examples.

[Experimental Example 1]
(Synthesis of dilithium 2,6-naphthalenedicarboxylate)
For the synthesis of dilithium 2,6-naphthalenedicarboxylate (see formula (7)) as a layered structure (electrode active material), 2,6-naphthalenedicarboxylic acid and lithium hydroxide monohydrate (LiOH) are used as starting materials. • H ₂ O) was used. Methanol (100 mL) was added to lithium hydroxide monohydrate (0.556 g) and stirred. After the lithium hydroxide monohydrate was dissolved, 2,6-naphthalenedicarboxylic acid (1.0 g) was added and stirred for 1 hour. After stirring, the solvent was removed, and a white powder sample was synthesized by drying at 150 ° C. for 16 hours under vacuum.

(X-ray diffraction measurement)
Powder X-ray diffraction measurement of the synthesized dilithium 2,6-naphthalenedicarboxylate was performed. The measurement was performed using CuKα rays (wavelength 1.54051Å) as radiation and using an X-ray diffractometer (RINT2200 manufactured by Rigaku). In addition, the measurement was performed by using a graphite single crystal monochromator for monochromatic X-ray, setting the applied voltage to 40 kV and current 30 mA, and the angle range of 2θ = 10 ° to 90 ° at a scanning speed of 4 ° / min. I went there. FIG. 3 is a result of X-ray diffraction measurement of dilithium 2,6-naphthalenedicarboxylate. As shown in FIG. 3, dilithium 2,6-naphthalenedicarboxylate has (001), (111), (102), (112) when assuming a monoclinic crystal belonging to the space group P2 ₁ / c. Since the peak appeared clearly, it was guessed that the layered structure which consists of a lithium layer and an organic frame | skeleton layer shown in FIG. 1 was formed. In addition, since Experimental Example 1 is a monoclinic crystal belonging to the space group P2 ₁ / c, a structure in which oxygen and lithium of four different aromatic dicarboxylic acid molecules form a four-coordination, It is inferred that the interaction by the π-electron conjugated cloud works in the organic skeleton.

(Preparation of coated electrode)
73.9% by mass of the synthesized dilithium 2,6-naphthalenedicarboxylate, 13.0% by mass of carbon black (Tokai Carbon, TB5500 (diameter: about 50 nm)) as the particulate carbon conductive material, carboxy which is a water-soluble polymer Methyl cellulose (CMC) (manufactured by Daicel Finechem, CMC Daicel 1120) was mixed in an amount of 5.2% by mass, and styrene butadiene copolymer (SBR) (manufactured by Nippon Zeon, BM-400B) in a ratio of 7.8% by mass. An appropriate amount of water as a dispersant was added to and dispersed in the slurry to obtain a slurry-like composite material. This slurry-like mixture was uniformly applied to a 10 μm thick copper foil current collector and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was pressure-pressed and punched out to an area of 2.05 cm ² to prepare a disk-shaped electrode. Thereafter, drying was performed at 120 ° C. for 12 hours in an argon inert atmosphere.

(Preparation of bipolar evaluation cell)
Non-aqueous electrolysis by adding lithium hexafluorophosphate to 1 mol / L to a non-aqueous solvent in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate are mixed at a volume ratio of 30:40:30. A liquid was prepared. Using the electrode as a working electrode, a lithium metal foil (thickness: 300 μm) as a counter electrode, a separator (manufactured by Toray Tonen) impregnated with the non-aqueous electrolyte was sandwiched between the two electrodes to produce a bipolar evaluation cell.

(Charge / discharge test)
Using the above bipolar evaluation cell, reduction (discharge) was performed at 0.14 mA to 0.5 V in a temperature environment of 20 ° C., and then oxidation (charge) was performed at 0.14 mA to 2.0 V. In this charge / discharge operation, the first reduction capacity is Q (1st) red, the oxidation capacity is Q (1st) oxi, the 10th reduction capacity is Q (10th) red, and the oxidation capacity is Q (10th) oxi. . Then, the initial efficiency was calculated from the equation of (Q (1st) oxi / Q (1st) red) × 100. Further, the capacity retention rate after 10 cycles was calculated from the formula of (Q (10th) oxi / Q (1st) oxi) × 100. The maximum capacity was the maximum of the first to tenth oxidation capacities.

[Experiment 2]
In preparation of the coated electrode, 77.7% by mass of dilithium 2,6-naphthalenedicarboxylate, 13.7% by mass of carbon black, 5.5% by mass of CMC, and 3.2% by mass of SBR were used. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experiment 3]
In the preparation of the coated electrode, 78.7% by mass of dilithium 2,6-naphthalenedicarboxylate, 13.9% by mass of carbon black, 5.6% by mass of CMC, and 1.9% by mass of SBR. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental Example 4]
In preparation of the coated electrode, 79.8% by mass of dilithium 2,6-naphthalenedicarboxylate, 14.1% by mass of carbon black, 4.2% by mass of CMC, and 1.9% by mass of SBR were used. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental Example 5]
In preparation of the coated electrode, the dilithium 2,6-naphthalenedicarboxylate was 80.2% by mass, the carbon black was 14.2% by mass, the CMC was 5.7% by mass, and the SBR was 0.0% by mass. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental Example 6]
In the production of the coated electrode, dilithium 2,6-naphthalenedicarboxylate was 81.0% by mass, carbon black was 14.3% by mass, CMC was 2.9% by mass, and SBR was 1.9% by mass. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Example 7]
In the production of the coated electrode, 81.8% by mass of dilithium 2,6-naphthalenedicarboxylate, 11.2% by mass of carbon black, 4.5% by mass of CMC, and 2.6% by mass of SBR. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Example 8]
In preparation of the coated electrode, 84.7% by mass of dilithium 2,6-naphthalenedicarboxylate, 9.4% by mass of carbon black, 3.8% by mass of CMC, and 2.2% by mass of SBR were used. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental Example 9]
In the production of the coated electrode, 86.1% by mass of dilithium 2,6-naphthalenedicarboxylate, 9.7% by mass of carbon black, 1.9% by mass of CMC, and 1.3% by mass of SBR. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental Example 10]
In preparation of the coated electrode, except that the ratio of dilithium 2,6-naphthalenedicarboxylate was 83.3 mass%, carbon black was 14.7 mass%, CMC was 0 mass%, and SBR was 2.0 mass%. A cell was produced in the same manner as in Experimental Example 1, and a charge / discharge test was performed.

[Experimental Example 11]
In preparation of the coated electrode, 74.9% by mass of dilithium 2,6-naphthalenedicarboxylate, 13.2% by mass of carbon black, 8.8% by mass of CMC, and 3.0% by mass of SBR. A cell was prepared in the same manner as in Experimental Example 1 except that a charge / discharge test was performed.

[Experimental example 12]
In the production of the coated electrode, 66.7% by mass of dilithium 2,6-naphthalenedicarboxylate, 11.1% by mass of carbon black as a particulate carbon conductive material, fibrous carbon (vapor-grown carbon fiber, Showa Denko VGCF (diameter of about 150 nm, length of about 10 to 20 μm)), polyvinylidene fluoride as a binder at a ratio of 10% by mass, and N-methyl-2-pyrrolidone as a dispersant. A cell was prepared in the same manner as in Experimental Example 1 except that an appropriate amount was added and dispersed to obtain a slurry composite, and a charge / discharge test was performed.

[Results and discussion]
Table 1 shows the results of maximum capacity, initial efficiency, and capacity maintenance rate. 4 shows the charge / discharge curve of Experimental Example 4, and FIG. 5 shows the charge / discharge curve of Experimental Example 12. Further, FIGS. 6 to 8 are graphs showing the relationship between the ratio of CMC and the maximum capacity, initial efficiency, and capacity maintenance rate. From Table 1 and FIGS. 4 and 5, compared with Experimental Example 10 in which the CMC binder was not used, Experimental Example 11 in which the CMC binder was excessive, and Experimental Example 12 in which the PVdF binder was used. In Experimental Examples 1 to 8 in which the CMC binder was used at a ratio of 2% by mass or more and 8% by mass or less, it was found that all of the maximum capacity, the initial efficiency, and the capacity maintenance rate were excellent. In this regard, when the cross section of the electrode was observed with a scanning electron microscope (SEM), in Experimental Examples 1 to 8, the entire electrode mixture was blackish, and the active material, conductive material, and water-soluble polymer were uniformly mixed and collected. It was in close contact with the electrical body. On the other hand, in Experimental Example 10, a white portion and a black portion were mixed in the electrode mixture, and phase separation occurred. In Experimental Examples 11 and 12, many portions where the electrode mixture was not in close contact with the current collector were observed. Therefore, in Experimental Examples 1 to 8 using an appropriate amount of CMC-based binder, Experimental Example 10 using no CMC-based binder, Experimental Example 11 using an excessive amount of CMC-based binder, PVdF-based binder Since the effect of mixing the active material and the conductive material uniformly and intimately adhering to the current collector is higher than in Experimental Example 12 using the dressing material, it is possible to suppress the occurrence of a heterogeneous reaction in the electrode. It was inferred that the discharge characteristics could be further improved. 6 and 7 show that the maximum capacity and the initial efficiency can be increased if the CMC in the electrode is 8.0% by mass or less. Further, FIG. 8 indicates that the capacity retention ratio can be increased when the CMC in the electrode is 2.0 mass% or more and 8.0 mass% or less. In Experimental Example 9 in which CMC in the electrode is 1.9% by mass, the maximum capacity and initial efficiency are equivalent to those of Experimental Examples 1 to 8, but the capacity retention rate is 10% or more than Experimental Examples 1 to 8. The value was low. Therefore, it was found that the negative electrode proposed in this case exhibits a good expression capacity, initial efficiency, and capacity retention rate by including a water-soluble polymer in the range of 2% by mass to 8% by mass.

  In Experimental Examples 1 to 12, dilithium 2,6-naphthalenedicarboxylate (see formula (7)) was used as the electrode active material. However, from the description in Japanese Patent Application No. 2011-115093, the electrode active material is 4,4. It was guessed that what is represented by Formula (1), such as dilithium '-biphenyl dicarboxylate (refer Formula (8)), may be sufficient. In the example of Japanese Patent Application No. 2011-115093, although SBR is used as a binder, dilithium terephthalate (see formula (9)) or dilithium 2,3-naphthalenedicarboxylate (see formula (10)) is used. It has been confirmed that charge and discharge characteristics can be improved when dilithium 2,6-dicarboxylate or dilithium 4,4′-biphenyldicarboxylate is used.

  The present invention can be used in the field of the battery industry.

  20 Nonaqueous secondary battery, 21 Battery case, 22 Positive electrode, 23 Negative electrode, 24 Separator, 25 Gasket, 26 Sealing plate, 27 Ion conduction medium.

Claims (10)

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 coordinates to oxygen contained in the carboxylic acid anion of the dicarboxylic acid anions to form a skeleton An electrode active material comprising a layered structure having an alkali metal element layer
A particulate conductive material rather than a fiber ,
A water-soluble polymer that is at least one of carboxymethylcellulose and polyvinyl alcohol;
Wherein the said look-containing water-soluble polymer in the range of 8 wt% or more 2 wt%, the organic framework layer, provides the following equation (1) to any one or more of an aromatic compound of (3) An electrode for a non-aqueous secondary battery.
  The electrode for non-aqueous secondary batteries according to claim 1, comprising the electrode active material in a range of 70 mass% to 90 mass%.   The electrode for a nonaqueous secondary battery according to claim 1 or 2, comprising the conductive material in a range of 5 mass% to 15 mass%.   The electrode for nonaqueous secondary batteries according to any one of claims 1 to 3, further comprising a styrene-butadiene copolymer.   The electrode for non-aqueous secondary batteries according to claim 4, comprising the styrene-butadiene copolymer in an amount of 8% by mass or less. The layered structure is formed in a layer shape by π-electron interaction of the aromatic compound, and has a monoclinic crystal structure belonging to the space group P2 ₁ / c. The electrode for non-aqueous secondary batteries as described in the item. The organic framework layer comprises the aromatic one and the other of the carboxylate anion is bound to the diagonal positions of the aromatic ring of the dicarboxylic acid anion compound, any one of the claims 1-6 The electrode for non-aqueous secondary batteries as described in the item. Alkali metal element contained in the alkali metal element layers are Li, nonaqueous secondary battery electrode according to any one of claims 1-7. The electrode for a non-aqueous secondary battery according to any one of claims 1 to 8 , wherein the layered structure is a negative electrode active material. The electrode for a non-aqueous secondary battery according to any one of claims 1 to 9 ,
An ion conducting medium that conducts alkali metal ions;
A non-aqueous secondary battery comprising: