JP2011228050A - Electrode active material and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode active material and a secondary battery having high energy density, high output and excellent cycle characteristic with small capacity drop even in repeating charge/discharge.SOLUTION: The electrode active material includes an organic compound comprising two or more unsaturated five-membered ring structure as a constitutional unit as expressed by general formulas (I) and (II). In formulas, n and q are integers of 2 to 50, p is an integer of 1 to 50 and R, R, Xand Xare optional substituent groups.

Description

  The present invention relates to an electrode active material and a secondary battery, and more particularly to an electrode active material using an organic compound, and a secondary battery that repeats charging and discharging using a battery electrode reaction of the electrode active material.

  With the expansion of the market for portable electronic devices such as mobile phones, notebook computers, and digital cameras, secondary batteries with high energy density and long life are expected as cordless power sources for these electronic devices.

  In response to such demands, secondary batteries have been developed that use an alkali metal ion such as lithium ion as a charge carrier and use an electrochemical reaction associated with the charge exchange. In particular, lithium ion secondary batteries having a high energy density are now widely used.

  Among the constituent elements of the secondary battery, the electrode active material is a substance that directly contributes to a battery electrode reaction such as a charge reaction and a discharge reaction, and has a central role of the secondary battery. That is, the battery electrode reaction is a reaction that occurs with the transfer of electrons by applying a voltage to an electrode active material that is electrically connected to an electrode disposed in the electrolyte, and proceeds during charge and discharge of the battery. . Therefore, as described above, the electrode active material has a central role of the secondary battery in terms of system.

  In the lithium ion secondary battery, a lithium-containing transition metal oxide is used as a positive electrode active material, a carbon material is used as a negative electrode active material, and lithium ion insertion reaction and desorption reaction with respect to these electrode active materials. Charging and discharging is performed using

  However, the lithium ion secondary battery has a problem that the rate of charge and discharge is limited because the movement of lithium ions in the positive electrode is rate-limiting. That is, in the lithium ion secondary battery described above, the movement rate of lithium ions in the transition metal oxide of the positive electrode is slower than that of the electrolyte and the negative electrode, and therefore the battery reaction rate at the positive electrode is rate-limiting and the charge / discharge rate is increased. As a result, there is a limit to increasing the output and shortening the charging time.

  Therefore, in order to solve such problems, in recent years, secondary batteries using an organic compound as a positive electrode active material have been proposed. Research and development of secondary batteries using organic radical compounds among these organic compounds are being actively conducted.

  For example, Patent Document 1 proposes an active material for a secondary battery using a nitroxyl radical compound, an oxy radical compound, and a nitrogen radical compound having a radical on a nitrogen atom.

  This Patent Document 1 describes an example using a highly stable nitroxyl radical or the like as a radical. For example, a secondary battery using an electrode layer containing a nitronyl nitroxide compound as a positive electrode and a lithium-bonded copper foil as a negative electrode. After repeatedly charging and discharging, it has been confirmed that charging and discharging is possible over 10 cycles.

  Patent Document 2 proposes an electrode active material containing a phenanthrenequinone compound having two ketone groups in the ortho position.

  In Patent Document 2, a positive electrode active material is formed with an electrode active material containing the phenanthrenequinone compound, and a negative electrode active material is formed with a graphite layer into which lithium ions are inserted to produce a coin-type battery. When a charge / discharge test was performed, it was described that a reversible charge / discharge reaction proceeded and no significant capacity deterioration was observed up to 5 cycles.

  Patent Document 3 proposes an electrode active material for an electricity storage device having a specific thiol structure.

  In Patent Document 3, a positive electrode active material is formed of an electrode active material having a specific thiol structure, and a negative electrode is formed of lithium metal to produce a coin battery. When a charge / discharge test was performed, a capacity density of 120 Ah / kg could be obtained, and it was described that there was no capacity deterioration after 50 cycles.

JP 2004-207249 A (paragraph numbers [0278] to [0282]) JP 2008-222559 A (paragraph numbers [0018], [0072] to [0076]) JP 2008-112630 A (Claim 1, paragraph numbers [0042] to [0048])

  However, in Patent Document 1, although an organic radical compound such as a nitroxyl radical compound is used as an electrode active material, the charge / discharge reaction is limited to a one-electron reaction involving only one electron. That is, in the case of an organic radical compound, when a multi-electron reaction involving two or more electrons is caused, the radical lacks stability and decomposes, and the radical disappears and the reversibility of the charge / discharge reaction is lost. . For this reason, the organic radical compound of Patent Document 1 must be limited to a one-electron reaction, and it is difficult to realize a multi-electron reaction that can be expected to have a high capacity.

  In addition, Patent Document 2 uses an electrode active material containing the phenanthrenequinone compound as a positive electrode active material, but is not yet practical because it is not sufficiently stable in redox state and lacks capacity. The current situation is that it has not been realized.

  Furthermore, Patent Document 3 uses an electrode active material containing a specific thiol structure as the positive electrode active material, but as in Patent Document 2, the stability in the redox state is not sufficient and the capacity is insufficient. As a result, it has not yet been put to practical use.

  As described above, in conventional secondary batteries such as Patent Documents 1 to 3, even if an organic radical compound, a phenanthrenequinone compound, or a compound having a specific thiol structure is used as an electrode active material, the capacity is increased by a multi-electron reaction. Therefore, it is difficult to achieve both stability with respect to the charge / discharge cycle, and therefore, it has not been possible to realize an electrode active material having a sufficiently high energy density, good output, good cycle characteristics, and long life. is there.

  The present invention has been made in view of such circumstances, and provides an electrode active material and a secondary battery that have high energy density, high output, and good cycle characteristics with little decrease in capacity even after repeated charge and discharge. For the purpose.

  The inventors of the present invention have intensively studied to obtain an organic compound that can be used as an active material of a secondary battery that repeats charging and discharging by a battery electrode reaction, and contain two or more unsaturated five-membered ring structures in a structural unit. The organic compound is capable of multi-electron reaction and has excellent oxidation-reduction reaction stability, and it has been found that a large amount of electricity can be charged with a small molecular weight.

  The present invention has been made based on such knowledge, and the electrode active material according to the present invention is an electrode active material used as an active material of a secondary battery that repeats charge and discharge by a battery electrode reaction. It is characterized by having an organic compound containing one or more unsaturated five-membered ring structures in the structural unit.

  Specifically, in the electrode active material of the present invention, the organic compound has the general formula

(In the formula, R ₁ and R ₂ are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, an aryl group, an aralkyl group, a cycloalkyl group, an alkoxyl group, an alkenyl group, an aryloxy group, Arylamino group, alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, formyl group, silyl group, boryl group, stannyl group, cyano group, nitro group, nitroso group, carboxyl group, alkoxycarbonyl group, and halogen atom At least any one of them, including a case where they are linked to each other to form a saturated or unsaturated ring, and X ₁ and X ₂ are CH ₂ , CF ₂ , O, S, SO ₂ , Se, and N—R ₃ (R ₃ represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, an aryl group, an aralkyl group, a cycloalkyl group, an alkyl group, Coxyl group, alkenyl group, aryloxy group, arylamino group, alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, silyl group, boryl group, stannyl group, cyano group, nitro group, nitroso group and halogen atom Including at least one kind of a saturated or unsaturated ring linked to each other.)
It is characterized by containing an unsaturated five-membered ring structure represented by:

  In the electrode active material of the present invention, the organic compound has the general formula

(However, n is an integer of 2 to 50.)
It is characterized by being expressed by.

  In the electrode active material of the present invention, the organic compound has the general formula

(However, p is an integer of 1-50, and q is an integer of 2-50.)
It is characterized by being expressed by.

  The electrode active material of the present invention is characterized in that the p is an even number.

  Furthermore, the electrode active material of the present invention is characterized in that the sum of p and q is an even number.

  In the secondary battery according to the present invention, any of the electrode active materials described above is included in at least one of a reaction starting material, a product, and an intermediate product in the discharge reaction of the battery electrode reaction. It is characterized by that.

  The secondary battery according to the present invention includes a positive electrode, a negative electrode, and an electrolyte, and the positive electrode includes the electrode active material.

  According to the electrode active material of the present invention, since it has an organic compound containing two or more unsaturated five-membered ring structures in a structural unit, it is possible to perform a multi-electron reaction and to be stable against a redox reaction. It is possible to obtain an electrode active material that is excellent in properties and has a low molecular weight and high capacity density and good cycle characteristics.

  According to the secondary battery of the present invention, since the electrode active material is included in at least one of a reaction starting material, a product, and an intermediate product in the discharge reaction of the battery electrode reaction, It is possible to achieve both stability with respect to the charge / discharge cycle, high energy density, high output, and a long-life secondary battery with good cycle characteristics with little reduction in capacity even after repeated charge / discharge.

It is sectional drawing which shows one Embodiment of the coin-type battery as a secondary battery which concerns on this invention.

  Next, an embodiment of the present invention will be described in detail.

  The electrode active material of the present invention has an organic compound containing two or more unsaturated five-membered ring structures in the structural unit. As a result, a multi-electron reaction of two or more electrons is possible, the stability of the oxidation-reduction reaction can be improved, and a secondary battery having a large energy density and excellent stability can be obtained.

  The unsaturated five-membered ring structure can be represented by the general formula (1).

Here, R ₁ and R ₂ are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, an aryl group, an aralkyl group, a cycloalkyl group, an alkoxyl group, an alkenyl group, an aryloxy group, and an arylamino group. , Alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, formyl group, silyl group, boryl group, stannyl group, cyano group, nitro group, nitroso group, carboxyl group, alkoxycarbonyl group, and halogen atom 1 type is shown and includes a case where they are linked to each other to form a saturated or unsaturated ring. X ₁ and X ₂ are CH ₂ , CF ₂ , O, S, SO ₂ , Se, and N—R ₃ (R ₃ is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, aryl Group, aralkyl group, cycloalkyl group, alkoxyl group, alkenyl group, aryloxy group, arylamino group, alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, silyl group, boryl group, stannyl group, cyano group, nitro group A group, a nitroso group, and a halogen atom.), Which are linked to each other to form a saturated or unsaturated ring.

In addition, the carbon number of R ₁ , R ₂ and R ₃ was set to 50 or less because when the carbon number of R ₁ , R ₂ and R ₃ exceeds 50, the molecular weight increases excessively and the capacity density decreases. It is because there is a possibility of inviting.

  And as an unsaturated five-membered ring structure included in the category of the said General formula (1), the substituent represented by chemical formula (1A)-(1E) can be mentioned, for example.

  And as an organic compound containing the said General formula (1), the substance shown by General formula (2) is mentioned, for example.

  Here, n is preferably an integer of 2 to 50. That is, when n is 1, it is difficult to generate a plurality of cations during the charge / discharge reaction, and there is a possibility that a multi-electron reaction does not occur. On the other hand, when n exceeds 50, the molecular weight increases excessively, which may cause a decrease in capacity density.

  And as an organic compound which belongs to the category of General formula (2), the organic compound shown to Chemical formula (2A)-(2J) which has a cyclic structure can be mentioned.

  Moreover, as an organic compound containing the said General formula (1), the substance shown by General formula (3) can also be mentioned.

  Here, p is preferably an integer of 1 to 50, and q is preferably an integer of 2 to 50. Note that the reason why p and q are set to 50 or less is that when p and q exceed 50, the molecular weight is excessively increased and the capacity density may be lowered. Further, q is an integer of 2 or more, as in the case of n described above (see general formula (2)), it is difficult to generate a plurality of cations during the charge / discharge reaction, and a multi-electron reaction does not occur. Because there is a fear.

  Further, at least p is preferably an even number, and more preferably, the total of p and q is an even number. This is because when at least p is an even number, more preferably, the total of p and q is an even number, the organic compound becomes a resonance structure and is stabilized.

  And as an organic compound which belongs to the category of the said General formula (3), Chemical formula (3A ')-(3P) which has an organic compound represented by Chemical formula (3A)-(3K) which has a cyclic | annular monoone structure, and cyclic dione structure An organic compound represented by ′) can be mentioned.

  The electrode active material is considered to generate cations by an electrochemical oxidation reaction.

  Chemical reaction formula (4) shows an example of the expected charge / discharge reaction of 2,3,4,5-tetrakis [1,3-dithiol-2-ylidene] cyclopentanone represented by chemical formula (3A). ing.

  Thus, one molecule of 2,3,4,5-tetrakis [1,3-dithiol-2-ylidene] cyclopentanone (I) reacts with four electrons to form a cation represented by (II). Therefore, the capacity density can be increased as compared with the case of the one-electron reaction.

  The molecular weight of the organic compound constituting the electrode active material is not particularly limited. However, when the portion other than the unsaturated five-membered ring structure increases, the capacity that can be stored per unit mass, that is, the capacity density decreases. When used as a polymer of an organic compound having an unsaturated five-membered ring structure in the structural unit, the molecular weight and molecular weight distribution are not particularly limited.

  Next, a secondary battery using the electrode active material will be described.

  FIG. 1 is a cross-sectional view showing a coin-type secondary battery as an embodiment of a secondary battery according to the present invention. In this embodiment, the electrode active material of the present invention is used as a positive electrode active material. ing.

  The battery can 1 has a positive electrode case 2 and a negative electrode case 3, and both the positive electrode case 2 and the negative electrode case 3 are formed in a disk-like thin plate shape. In the center of the bottom of the positive electrode case 2 constituting the positive electrode current collector, a positive electrode 4 in which an electrode active material is molded into a sheet shape is disposed. A separator 5 formed of a porous sheet or film such as a microporous film, a woven fabric, or a nonwoven fabric is laminated on the positive electrode 4, and a negative electrode 6 is laminated on the separator 5. As the negative electrode 6, for example, a copper foil laminated with a lithium metal foil or a lithium foil occlusion material such as graphite or hard carbon applied to the copper foil can be used. A negative electrode current collector 7 made of metal is laminated on the negative electrode 6, and a metal spring 8 is placed on the negative electrode current collector 7. The electrolyte 9 is filled in the internal space, and the negative electrode case 3 is fixed to the positive electrode case 2 against the urging force of the metal spring 8 and sealed with a gasket 10.

  Next, an example of a method for manufacturing the secondary battery will be described in detail.

  First, an electrode active material is formed into an electrode shape. For example, the electrode active material is mixed with a conductive auxiliary agent and a binder, and a solvent is added to form a slurry. The slurry is applied on the positive electrode current collector by an arbitrary coating method, and dried to obtain the positive electrode. Form.

  Here, the conductive auxiliary agent is not particularly limited, and examples thereof include carbonaceous fine particles such as graphite, carbon black, and acetylene black, carbon fibers such as vapor grown carbon fiber (VGCF), carbon nanotube, and carbon nanohorn. , Conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene can be used. Further, two or more kinds of conductive assistants can be mixed and used. In addition, as for the content rate in the positive electrode 4 of a conductive support agent, 10-80 mass% is desirable.

  Further, the binder is not particularly limited, and various resins such as polyethylene, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyethylene oxide, carboxymethylcellulose, and the like can be used.

  Further, the solvent is not particularly limited, and examples thereof include basic solvents such as dimethyl sulfoxide, dimethylformamide, 1-methyl-2-pyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, and γ-butyrolactone, acetonitrile, Nonaqueous solvents such as tetrahydrofuran, nitrobenzene, and acetone, protic solvents such as methanol and ethanol, water, and the like can be used.

  Moreover, the kind of organic solvent, the compounding ratio of the organic compound and the organic solvent, the kind of additive and the addition amount thereof can be arbitrarily set in consideration of the required characteristics and productivity of the secondary battery. Next, the positive electrode 4 is impregnated into the electrolyte 9 so that the electrolyte 9 is impregnated with the positive electrode 4, and then the positive electrode 4 at the bottom center of the positive electrode case 2 constituting the positive electrode current collector is placed. Next, the separator 5 impregnated with the electrolyte 9 is laminated on the positive electrode 4, the negative electrode 6 and the negative electrode current collector 7 are sequentially laminated, and then the electrolyte 9 is injected into the internal space. Then, a metal spring 8 is placed on the negative electrode current collector 7, and a gasket 10 is arranged on the periphery, and the negative electrode case 3 is fixed to the positive electrode case 2 with a caulking machine or the like, and the outer casing is sealed. A type secondary battery is produced.

The electrolyte 9 is interposed between the positive electrode (electrode active material) 4 and the negative electrode 6 which is the counter electrode, and transports charge carriers between the two electrodes. Those having an ionic conductivity of ⁻⁵ to 10 ⁻¹ S / cm can be used. For example, an electrolytic solution in which an electrolyte salt is dissolved in an organic solvent can be used.

Here, examples of the electrolyte salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiC ₂ F ₅ SO _3, Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ). ₂ N, Li (CF ₃ SO ₂ ) ₃ C, Li (C ₂ F ₅ SO ₂ ) ₃ C, or the like can be used.

  As the organic solvent, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, 1-methyl-2-pyrrolidone, etc. are used. be able to.

  The electrolyte 9 may be a solid electrolyte. Examples of the polymer compound used in the solid electrolyte include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-monofluoroethylene copolymer, fluoride Vinylidene fluoride polymers such as vinylidene-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and acrylonitrile-methyl methacrylate copolymer Polymer, acrylonitrile-methyl acrylate copolymer, acrylonitrile-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-methacrylic acid copolymer, acrylonitrile-acrylic acid copolymer Examples thereof include acrylonitrile polymers such as polymers, acrylonitrile-vinyl acetate copolymers, polyethylene oxide, ethylene oxide-propylene oxide copolymers, and polymers of these acrylates and methacrylates. Further, these polymer compounds containing an electrolytic solution in a gel form may be used as the electrolyte 9 or only a polymer compound containing an electrolyte salt may be used as the electrolyte 9 as it is.

  Since the electrode active material of the secondary battery is reversibly oxidized or reduced by charge and discharge, it has a different structure and state depending on the charged state, discharged state, or intermediate state. The active material is contained in at least one of a reaction starting material in the discharge reaction (a material that causes a chemical reaction in the battery electrode reaction), a product (a material resulting from the chemical reaction), and an intermediate product.

  As described above, according to this embodiment, since the secondary battery is configured using the electrode active material that undergoes multi-electron reaction, it is possible to obtain a secondary battery having a large energy density and excellent stability. it can.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible in the range which does not deviate from a summary. For example, the above-described chemical formulas (2A) to (2J), (3A) to (3K), and (3A ′) to (3P ′) are also examples of the organic compound that is the main component of the electrode active material. It is not limited to these. That is, if at least an unsaturated five-membered ring structure is contained in the structural unit, a battery electrode reaction substantially the same as in the chemical reaction formula (4) proceeds, the energy density is large, and the desired two-components excellent in stability are obtained. It is possible to obtain a secondary battery.

  In this embodiment, a coin-type secondary battery has been described. However, the battery shape is not particularly limited, and can be applied to a cylindrical shape, a square shape, a sheet shape, and the like. Also, the exterior method is not particularly limited, and a metal case, mold resin, aluminum laminate film, or the like may be used.

  In this embodiment, an organic compound having an unsaturated five-membered ring structure in the structural unit is used as the positive electrode active material, but it is also useful to use it as the negative electrode active material.

  Next, examples of the present invention will be specifically described.

(Synthesis of organic compounds)
According to the following synthesis scheme (A), 2,3,4,5-tetrakis [1,3-dithiol-2-ylidene] cyclopentanone (hereinafter referred to as “Compound A”) was synthesized.

That is, the compound (3A ₁ ) (4.62 g, 10.0 mmol) was dissolved in 150 mL of dichloromethane (CH ₂ Cl ₂ ), and N-bromosuccinimide (hereinafter referred to as “NBS”) (3.56 g, 20 mmol) was added. added. The reaction at room temperature for 2 hours, Compound (3A ₂₎ to produce 6.18 g. The yield was 100%.

_{Next, Ni [P (C 6 H} 5) 3] 2 Br 2 (595mg, 0.80mmol), (C 6 H 5) 3 P (423mg, 1.6mmol), Zn-Cu (1.31g, 20mmol ) Was dissolved in 80 mL of tetrahydrofuran (hereinafter referred to as “THF”) under an inert gas atmosphere to prepare a catalyst. Next, 80 mL of a THF solution of the compound (3A ₂ ) was added with stirring in a CO atmosphere, and the mixture was stirred for 6 hours to obtain 1.45 g of the compound (3A ₃ ).

Next, compound (3A ₃ ) (475 mg, 0.5 mmol) and LiBr · H ₂ O (2.10 g, 20 mmol) were added to 70 mL of hexamethylphosphoric triamide [(CH ₃ ) ₂ N] ₃ P═O) ( HMPA) and stirred with heating for 12 hours. The reaction solution was cooled to room temperature, poured into 200 mL of pure water, the precipitate was filtered off, and dried under reduced pressure to prepare a reddish brown compound (3A).

[Production of secondary battery]
The above composite A: 100 mg, graphite powder as a conductive auxiliary agent: 200 mg, and polytetrafluoroethylene resin as a binder: 100 mg were weighed and kneaded while mixing to obtain a mixture. It was. And this mixture was pressure-molded and the sheet-like member about 150 micrometers thick was produced.

Next, this sheet-like member was dried in a vacuum at 80 ° C. for 1 hour, and then punched into a circle having a diameter of 12 mm to produce a positive electrode (positive electrode active material) mainly composed of the composite A. Next, the positive electrode was impregnated with an electrolytic solution, and the electrolytic solution was infiltrated into voids in the positive electrode. As the electrolytic solution, an ethylene carbonate / diethyl carbonate mixed solution, which is an organic solvent containing LiPF ₆ (electrolyte salt) having a molar concentration of 1.0 mol / L, was used. The mixing ratio of ethylene carbonate / diethyl carbonate was ethylene carbonate: diethyl carbonate = 3: 7 in volume%.

  Next, this positive electrode was placed on a positive electrode current collector, a 20 μm thick separator made of a polypropylene porous film impregnated with the electrolytic solution was laminated on the positive electrode, and lithium was further applied to both sides of the copper foil. The pasted negative electrode was laminated on the separator.

  Next, after a negative electrode current collector made of Cu was laminated on the negative electrode, an electrolytic solution was injected into the internal space. Thereafter, a metal spring was placed on the negative electrode current collector, and the negative electrode case was joined to the positive electrode case in a state where a gasket was disposed on the periphery, and the outer casing was sealed with a caulking machine. Thus, a sealed coin-type battery having the composite A as the positive electrode active material and metal lithium as the negative electrode active material was produced.

[Confirmation of secondary battery operation]
The secondary battery produced as described above was charged with a constant current of 0.1 mA until the voltage reached 4.2 V, and then discharged to 1.5 V with a constant current of 0.1 mA. As a result, it was confirmed that the secondary battery had a voltage flat portion at two places where the charge / discharge voltage was 3.6 V and 3.2 V, and the discharge capacity was 0.2 mAh. When the capacity density per electrode active material was calculated from this capacity, it was 210 Ah / kg.

  On the other hand, the theoretical capacity density Q (Ah / kg) of the secondary battery is expressed by Equation (1).

  Here, Z is the number of electrons involved in the battery electrode reaction, and W is the molecular weight of the electrode active material.

  Since the molecular weight of the composite A is 484.8, when the number of electrons Z involved in the battery electrode reaction is 4, the theoretical capacity density is 221 Ah / kg from Equation (1). Therefore, it was confirmed that the composite A has a multi-electron reaction involving at least 4 electrons or more per structural unit.

  Thereafter, when the secondary battery was repeatedly charged and discharged in the range of 4.2 to 1.5 V, the initial capacity of 80% or more could be secured even after 10 cycles. That is, it was found that a secondary battery having excellent stability with little decrease in capacity can be obtained even when charging and discharging are repeated.

  In addition, a secondary battery manufactured in the same manner was charged at a constant current of 0.1 mA until the voltage reached 4.0 V, and then held while the voltage was applied, and discharged at a constant current of 0.1 mA after 168 hours. As a result, the discharge capacity decreased as compared with the case where the battery was discharged immediately after charging, but it was possible to maintain 80% or more. That is, a secondary battery excellent in stability with little self-discharge could be obtained.

(Synthesis of organic compounds)
Tetrakis [1,3-benzodithiol-2-ylidene] cyclopentanone (hereinafter referred to as “Compound B”) was synthesized according to the following synthesis scheme (B).

That is, the compound (3G ₁ ) (990 mg, 3.0 mmol) was dissolved in 120 mL of dichloromethane, and NBS (1.07 g, 6.0 mmol) was added. The reaction at room temperature for 2 hours, Compound (3G ₂₎ was prepared 1.30 g. The yield was 89%.

_{Next, Ni [P (C 6 H} 5) 3] 2 Br 2 (223mg, 0.30mmol), (C 6 H 5) 3 P (157mg, 0.60mmol), Zn-Cu (493mg, 7.6mmol ) Was dissolved in 40 mL of THF under an inert gas atmosphere to prepare a catalyst. Next, 20 mL of a THF solution of the compound (3G ₂ ) was added with stirring under a CO atmosphere, and the mixture was stirred for 6 hours to obtain 430 mg of a dark brown compound (3G).

[Production of secondary battery]
A secondary battery was produced in the same manner as in [Example 1] except that the composite B was used as a positive electrode active material.

[Confirmation of secondary battery operation]
The secondary battery produced as described above was charged with a constant current of 0.1 mA until the voltage reached 4.2 V, and then discharged to 1.5 V with a constant current of 0.1 mA. As a result, it was confirmed that the secondary battery had a voltage flat portion at two locations of charge / discharge voltages of 4.0 V and 3.3 V and a discharge capacity of 0.22 mAh. When the capacity density per electrode active material was calculated from this capacity, it was 150 Ah / kg.

  On the other hand, since the molecular weight of the composite B is 685.0, if the number of electrons Z involved in the battery electrode reaction is 4, the theoretical capacity density is 156 Ah / kg. Therefore, it was confirmed that the composite B has a multi-electron reaction involving at least 4 electrons or more per structural unit.

  Thereafter, when the secondary battery was repeatedly charged and discharged in the range of 4.2 to 1.5 V, the initial capacity of 80% or more could be secured even after 10 cycles. That is, it was found that a secondary battery having excellent stability with little decrease in capacity can be obtained even when charging and discharging are repeated.

  In addition, a secondary battery manufactured in the same manner was charged at a constant current of 0.1 mA until the voltage reached 4.0 V, and then held while the voltage was applied, and discharged at a constant current of 0.1 mA after 168 hours. As a result, the discharge capacity decreased as compared with the case where the battery was discharged immediately after charging, but it was possible to maintain 80% or more. That is, a secondary battery excellent in stability with little self-discharge could be obtained.

Comparative example

  A cyclopentanone manufactured by Kanto Chemical Co., Ltd. was dried under reduced pressure at 80 ° C. for 30 minutes to obtain an electrode active material.

[Production of secondary battery]
A secondary battery was produced in the same manner as in Example 1 except that cyclopentanone was used as the positive electrode active material.

[Confirmation of secondary battery operation]
The secondary battery manufactured as described above was charged with a constant current of 0.1 mA until the voltage reached 4.2 V, and then discharged with a constant current of 0.1 mA to 1.8 V. The voltage dropped without being present. Therefore, it turned out that it is not suitable as a secondary battery.

  A stable secondary battery with high energy density, high output, good cycle characteristics with little decrease in capacity even after repeated charge and discharge is realized.

4 Positive electrode 6 Negative electrode 9 Electrolyte

Claims (8)

An electrode active material used as an active material of a secondary battery that repeats charging and discharging by a battery electrode reaction,
An electrode active material comprising an organic compound containing two or more unsaturated five-membered ring structures in a structural unit. The organic compound has the general formula

(In the formula, R ₁ and R ₂ are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, an aryl group, an aralkyl group, a cycloalkyl group, an alkoxyl group, an alkenyl group, an aryloxy group, Arylamino group, alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, formyl group, silyl group, boryl group, stannyl group, cyano group, nitro group, nitroso group, carboxyl group, alkoxycarbonyl group, and halogen atom At least any one of them, including a case where they are linked to each other to form a saturated or unsaturated ring, and X ₁ and X ₂ are CH ₂ , CF ₂ , O, S, SO ₂ , Se, and N—R ₃ (R ₃ represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, an aryl group, an aralkyl group, a cycloalkyl group, an alkyl group, Coxyl group, alkenyl group, aryloxy group, arylamino group, alkylamino group, thioaryl group, thioalkyl group, heterocyclic group, silyl group, boryl group, stannyl group, cyano group, nitro group, nitroso group and halogen atom Including at least one kind of a saturated or unsaturated ring linked to each other.)
The electrode active material according to claim 1, which contains an unsaturated five-membered ring structure represented by the formula: The organic compound has the general formula

(However, n is an integer of 2 to 50.)
The electrode active material according to claim 2, wherein The organic compound has the general formula

(However, p is an integer of 1-50, and q is an integer of 2-50.)
The electrode active material according to claim 2, wherein   The electrode active material according to claim 4, wherein the p is an even number.   6. The electrode active material according to claim 4, wherein the sum of p and q is an even number.   The electrode active material according to any one of claims 1 to 6 is included in at least one of a reaction starting material, a product, and an intermediate product in a discharge reaction of the battery electrode reaction. Secondary battery.   The secondary battery according to claim 7, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes the electrode active material.

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