JP2015144036A - Electrode active material, electrode, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which has good cycle characteristics, and has large energy density and high output, and causes little reduction in capacity after repetition of charge and discharge.SOLUTION: An electrode active material comprises, as a matrix, an organic compound including a rubeanic acid expressed by the following general formula (I) or (II) in a constitutional unit. In the formulas, "n" is an integer of 1 to 20; and Rto Reach represent a hydrogen atom, a halogen atom, or a predetermined substituent group, such as a hydroxyl group, an alkyl group with 1-3 carbon atoms, an amino group, a phenyl group, a cyclohexyl group, or a sulfo group. The organic compound has an anisotropic particle form.

Description

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

  With the expansion of the market for portable electronic devices such as mobile phones, notebook computers, and digital cameras, secondary batteries that have a high energy density and are capable of high output as a cordless power source for these electronic devices are expected.

  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 have a high energy density and are becoming widespread as in-vehicle batteries.

  By the way, among the constituent elements of the secondary battery, the electrode active material is a substance that directly contributes to the battery electrode reaction such as the charge reaction and the 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 charging and discharging of the battery. To do. 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 an insertion reaction and a desorption reaction of lithium ions with respect to these electrode active materials are used. Charging / discharging.

  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 above-described lithium ion secondary battery, the migration 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 becomes the rate-determining rate. As a result, there is a limit to shortening the charging time.

  In addition, since this type of lithium ion secondary battery uses an electrode reaction of a transition metal having a large molecular weight, there is a limit in capacity density, and thus there is a limit in increasing output.

  Therefore, in order to solve such problems, research and development of secondary batteries using organic radical compounds, organic sulfur compounds, and quinone compounds as electrode active materials have been actively conducted in recent years.

  For example, Patent Document 1 is known as a prior art document using an organic radical compound as an electrode active material.

  Patent Document 1 discloses 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.

  In the organic radical compound, the unpaired electrons that react are localized in the radical atom, so that the concentration of the reaction site can be increased, and thus a high-capacity secondary battery can be realized. Further, since the reaction rate of radicals is high, it is considered that the charging time can be completed in a short time by performing charging / discharging utilizing a redox reaction of a stable radical.

  And in this patent document 1, the Example using a highly stable nitroxyl radical as a radical is described, for example, the electrode layer containing a nitronyl nitroxide compound is used as a positive electrode, and lithium bonding copper foil is used as a negative electrode. When a secondary battery was produced and repeatedly charged and discharged, it was confirmed that charging and discharging were possible over 10 cycles.

  Patent Documents 2 and 3 are known as prior art documents using an organic sulfur compound as an electrode active material.

  Patent Document 2 discloses a novel organic sulfur compound as a positive electrode material having an S—S bond in a charged state and an S—S bond being cleaved during discharge of the positive electrode to form an organic sulfur metal salt having a metal ion. Metal-sulfur battery cells have been proposed.

  In Patent Document 2, a disulfide-based organic compound represented by the general formula (1 ′) (hereinafter referred to as “disulfide compound”) is used as the organic sulfur compound.

R-S-S-R (1 ')
Here, R represents an aliphatic organic group or an aromatic organic group, and each includes the same or different cases.

  The disulfide compound can undergo a two-electron reaction, and the S—S bond is cleaved in a reduced state (discharge state), thereby forming an organic thiolate (R—S—). This organic thiolate forms an S—S bond in the oxidized state (charged state) and is restored to the disulfide compound represented by the general formula (1 ′). That is, since the disulfide compound forms an S—S bond having a small binding energy, a reversible redox reaction occurs using the bond and cleavage by the reaction, and thus charge and discharge can be performed.

Patent Document 3 discloses the following formula (2 ′):
-(NH-CS-CS-NH) (2 ')
A battery electrode comprising rubeanic acid or a rubeanic acid polymer that has a structural unit represented by the formula (II) and can be bonded to lithium ions has been proposed.

  The rubeanic acid or rubeanic acid polymer containing the dithione structure represented by the general formula (2 ′) binds to lithium ions during reduction, and releases the bound lithium ions during oxidation. Charging / discharging can be performed by utilizing such a reversible oxidation-reduction reaction of rubeanic acid or rubeanic acid polymer.

  In Patent Document 3, when rubeanic acid is used as a positive electrode active material, a two-electron reaction is possible, and a secondary battery having a capacity density of 400 Ah / kg at room temperature is obtained.

  Patent Document 4 is known as a prior art document using a quinone compound as an electrode active material.

  Patent Document 4 proposes an electrode active material containing a specific phenanthrenequinone compound having two quinone groups in the ortho-positional relationship.

  The specific phenanthrenequinone compound described in Patent Document 4 can cause a two-electron reaction peculiar to the quinone compound between the mobile carrier and a reversible oxidation-reduction reaction. Furthermore, the specific phenanthrenequinone compound is oligomerized or polymerized to achieve insolubilization in an organic solvent without causing a decrease in the number of reaction electrons due to repulsion between electrons. Patent Document 4 shows that the phenanthrenequinone dimer exhibits two oxidation-reduction voltages (around 2.9 V and around 2.5 V), and the initial discharge capacity reaches 200 Ah / kg.

JP 2004-207249 A (paragraph numbers [0278] to [0282]) US Pat. No. 4,833,048 (Claim 1, column 5, line 20 to column 28) JP 2008-147015 A (Claim 1, paragraph number [0011], FIG. 3, FIG. 5) JP 2008-222559 A (Claim 4, paragraph numbers [0027] and [0033], FIGS. 1 and 3)

  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 as in 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 Patent Document 2, a low-molecular disulfide compound in which two electrons are involved is used. However, since it repeatedly binds and cleaves with other molecules along with the charge / discharge reaction, it lacks stability, and charge / discharge reaction is not performed. If it is repeated, the capacity may decrease.

  In Patent Document 3, a rubeanic acid compound containing a dithione structure is used to cause a two-electron reaction. However, when a polymer compound such as a rubeanic acid polymer is used, an intermolecular interaction in the rubeanic acid polymer is performed. As a result of the large action and hindering the movement of ions, a sufficient reaction rate could not be obtained. For this reason, it took a long time to charge. In addition, since the movement of ions is hindered as described above, the proportion of active materials that can be effectively used is reduced, and thus it has been difficult to realize a secondary battery having a desired high output.

  Patent Document 4 uses a phenanthrenequinone compound having two quinone groups in the ortho-positional position as an electrode active material, and thus is excellent in stability, but is synthesized because it is a condensed ring compound. Difficult and capacity density is small.

  Thus, conventionally, even when organic compounds such as organic radical compounds, disulfide compounds, and rubeanic acid are used as electrode active materials, it is difficult to achieve both multi-electron reaction and stability against charge / discharge cycles. At present, an electrode active material having a large energy density, high output, good cycle characteristics and long life has not been realized.

  The present invention has been made in view of such circumstances, and an electrode active material having a large energy density, high output, and good cycle characteristics with little decrease in capacity even after repeated charge and discharge, and using this electrode active material It is an object of the present invention to provide an electrode and a secondary battery.

Conjugated dithione (-CS-CS-) in rubeanic acid has good reactivity with cations such as Li ⁺ .

  Therefore, the present inventors conducted extensive research on an organic compound containing a rubeanic acid structure containing a conjugated dithione in a structural unit, and found that the organic compound having the rubeanic acid structure has an anisotropic particle shape. As a result, it was found that the charge / discharge reaction is stabilized, whereby an electrode active material having good cycle characteristics and a high capacity density can be obtained.

  The present invention has been made based on such knowledge, 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, The organic compound is mainly composed of an organic compound containing a rubeanic acid structure in a structural unit, and the organic compound has an anisotropic particle shape.

  In the electrode active material of the present invention, it is preferable that the particle shape has a ratio a / b of a major axis a to a minor axis b of 1.5 or more.

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

  Is preferably represented by:

Here, in the formula, R _{1 to} R ₄ are a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group. Represents at least one selected from a group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, and R _{1 to} R ₄ include the same case and are connected to each other to be saturated or The case where an unsaturated ring is formed is included.

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

  It is also preferable that

In the formula, n represents an integer of 1 to 20, and R ₅ and R ₆ are a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted group. At least one selected from the group consisting of an amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, R ₅ and R ₆ are the same Including the case where they are linked to each other to form a saturated or unsaturated ring.

  The electrode according to the present invention is characterized by containing the above-described electrode active material and conductive material.

  The secondary battery according to the present invention is characterized in that the electrode active material described above 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.

  Furthermore, the secondary battery according to the present invention has a positive electrode, a negative electrode, and an electrolyte, and the positive electrode contains the electrode active material described above.

  According to the electrode active material of the present invention, an electrode active material used as an active material of a secondary battery that repeats charge and discharge by a battery electrode reaction, mainly comprising an organic compound containing a rubeanic acid structure in a structural unit In addition, since the organic compound has an anisotropic particle shape, a stable charge / discharge reaction can be performed, and an electrode active material having good cycle characteristics can be obtained.

In addition, the rubeanic acid structure contains conjugated dithione that is electrochemically active and highly reactive with cations such as Li ⁺ , and many electrons of two or more electrons are involved in the reaction. Therefore, charge / discharge efficiency is good and high capacity density can be achieved. As a result, it is possible to obtain an electrode active material having a large energy density and improved stability during charging and discharging.

  In addition, according to the electrode of the present invention, since it contains any of the electrode active materials and conductive materials described above, the charge / discharge efficiency is good, the battery can be charged in a short time, and the output is increased. Can be obtained.

  Furthermore, according to the secondary battery of the present invention, any one of the electrode active materials described above is included in at least one of reaction starting materials, products, and intermediate products in the discharge reaction of the battery electrode reaction. High energy density, quick charge, discharge at high output, rechargeable battery with good cycle characteristics with little capacity degradation even after repeated charge and discharge, and long battery life with stable battery characteristics It becomes.

  In addition, since the electrode active material is mainly composed of the above-described organic compound, it is possible to obtain a secondary battery that has a low environmental load and is also safe.

It is sectional drawing which shows one Embodiment of the coin-type battery as a secondary battery which concerns on this invention. 2 is a SEM image of rubeanic acid particles obtained in Example 1. It is a SEM image of the rubeanic acid particle obtained by the comparative example.

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

  The electrode active material of the present invention is mainly composed of an organic compound containing a rubeanic acid structure in a structural unit.

The rubeanic acid structure contains conjugated dithione (—CS—CS—) in the molecule, and this conjugated dithione is electrochemically active and rich in reactivity with cations such as Li ⁺ .

  The chemical reaction formula (A) shows an example of a charge / discharge reaction expected when the organic compound containing the rubeanic acid structure is used as an electrode active material and Li is used as a cation of an electrolyte salt.

That is, the organic compound of the present invention is considered to generate a complex salt with the battery electrode reaction, and two electrons are involved in the reaction during charging and discharging, and the conjugated dithione moiety contained in the rubeanic acid structure binds to Li ⁺ during reduction. And release Li ⁺ during oxidation.

And as mentioned above, conjugated dithione in the rubeanic acid structure is electrochemically active and rich in reactivity with cations such as Li ⁺ , and more than two electrons react with the structure having a small molecular weight. Therefore, the charge / discharge efficiency is good and the capacity density can be increased.

  Furthermore, in the present embodiment, the organic compound has an anisotropic particle shape, which improves the stability during charging and discharging, and an electrode active material having a large energy density can be obtained.

  That is, when the organic compound has an anisotropic particle shape, the contact area between the organic compound particles, which are the main components of the electrode active material, and between the conductive material and the organic compound particles contained in the electrode is increased. The discharge reaction proceeds more smoothly. Therefore, it is possible to obtain an electrode active material with further improved charge / discharge efficiency and better cycle characteristics, thereby obtaining an electrode active material with high energy density and improved stability during charge / discharge.

  If the shape of such an organic compound has an anisotropic particle shape, the particle diameter and the ratio a / b of the major axis a to the minor axis b are not particularly limited, but the average particle diameter Is preferably about 1 to 3 μm in terms of yen. The ratio a / b is also preferably 1.5 or more, and is preferably 1.8 or more, particularly preferably 2.5 or more, from the viewpoint of further stabilizing the cycle characteristics.

  In addition, as long as it has an anisotropic particle shape, the shape is not particularly limited, but a rod shape is preferable.

  And the organic compound which has rubeanic acid in a structural unit can be represented by the following general formula (1) or the following general formula (2), for example.

Here, in the general formula (1), R _{1 to} R ₄ are a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted amino group, a substituted or 1 represents at least one selected from an unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, and R _{1 to} R ₄ include the same case and are linked to each other To form a saturated or unsaturated ring.

In the formula, n represents an integer of 1 to 20, and R ₅ and R ₆ are a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted group. At least one selected from the group consisting of an amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, R ₅ and R ₆ are the same Including the case where they are linked to each other to form a saturated or unsaturated ring.

  And as an organic compound which belongs to the category of General formula (1), the organic compound shown to following chemical formula (1a)-(1q) can be mentioned, for example.

  Moreover, as an organic compound which belongs to the category of General formula (2), the organic compound shown to following Chemical formula (2a), (2b) can be mentioned, for example.

  Although the molecular weight of the organic compound which comprises the said electrode active material is not specifically limited, When a molecular weight becomes small too much, there exists a possibility that it may melt | dissolve easily in electrolyte. On the other hand, since the appearance of the effect desired by the present invention depends on the conjugated dithione portion of the rubeanic acid structure, when the portion other than the conjugated dithione increases, the capacity that can be stored per unit mass, that is, the capacity density decreases. Therefore, it is preferable to set the molecular weight of the organic compound in consideration of these.

  In addition, when using the polymer of the organic compound mentioned above, molecular weight and molecular weight distribution are not specifically limited.

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

  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 that constitutes the positive electrode current collector, a positive electrode 4 in which a mixture containing a positive electrode active material (electrode active material) and a conductive agent (conductive material) is formed 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 stainless steel foil or a copper foil overlaid with a lithium metal foil, or a lithium foil occlusion material such as graphite or hard carbon applied to a 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 organic compound containing a rubeanic acid structure in a structural unit is prepared. The organic compound is sufficiently pulverized using a pulverizer such as a ball mill, and the average particle diameter is preferably 1 to 3 μm in terms of a circle, and the ratio a / b between the major axis a and the minor axis b is 1.5. The above organic compound particles are prepared.

  Next, the organic compound particles are mixed with a conductive agent and a binder, and a solvent is added to form a slurry. The slurry is applied onto the positive electrode current collector by an arbitrary coating method and dried. Form.

  Here, the conductive 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, carbon nanotube, and carbon nanohorn, polyaniline, and polypyrrole. , Conductive polymers such as polythiophene, polyacetylene, and polyacene can be used. Further, two or more kinds of conductive agents can be mixed and used. In addition, as for the content rate in the positive electrode 4 of a electrically conductive 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 solvent, the compounding ratio of the organic compound and the solvent, the kind of additive and the amount of the additive, and the like 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.

Incidentally, the electrolyte 9 interposed between the negative electrode 6, which is a counter electrode of the positive electrode 4 and the positive electrode 4 performs a charge carrier transport between the electrodes, but as such a electrolyte 9, at room temperature for 10 ^{- 5} -10 -1 can be used which has an ionic conductivity of S ^{/ cm,} for example, it can be used an electrolytic solution dissolved in an organic solvent electrolyte salt.

Here, as the electrolyte salt, for example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ 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 can be a solid electrolyte, an ionic liquid in which a cation and an anion are combined, a symmetric glycol diether such as glymes, a chain sulfone, or the like.

  Examples of the polymer compound used for the solid electrolyte include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-monofluoroethylene copolymer, and 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 Acrylic nitrile polymers such as formic acid copolymer, acrylonitrile-vinyl acetate copolymer, polyethylene oxide, ethylene oxide-propylene oxide copolymer, and polymers of these acrylates and methacrylates. Can do. Further, these polymer compounds containing an electrolytic solution in a gel form can be used as the electrolyte 9 or only a polymer compound containing an electrolyte salt can be used as it is for the electrolyte 9.

Examples of the ionic liquid include cations such as 2-ethylimidazolium, 3-propylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, and 1,3-dimethylimidazolium. Imidazolium, diethylmethylammonium, tetrabutylammonium, cyclohexyltrimethylammonium, methyltri-n-octylammonium, triethyl (2-methoxyethoxymethyl) ammonium, benzyldimethyltetradecylammonium, benzyltrimethylammonium, and other alkylpyridinium, Dialkylpyrrolidinium, tetraalkylphosphonium, trialkylsulfonium, and the like can be used, and the anion can be Cl ⁻ , Br ⁻ , I ⁻ or the like. Rogenide anions, BF ₄ ⁻ , B (CN) ₄ ⁻ , B (C ₂ O ₄ ) ₂ ^{− and} other boride anions, (CN) ₂ N ⁻ , [N (CF ₃ ) ₂ ] ⁻ , [N ( SO ₂ CF _{3) 2]} ^- amide anion or anion, such as, RSO ₃ ^- (R represents an aliphatic hydrocarbon group or an aromatic hydrocarbon group similar or _{^{less), RSO 4 -., R}} f SO 3 - ( R ^f represents a fluorinated halogenated hydrocarbon group, the same applies hereinafter), sulfate anions such as R ^f SO ₄ ^— or sulfonate anions, R ^f ₂ P (O) O ⁻ , PF ₆ ⁻ , R ^f ₃ ^- PF ₃ phosphate anion, such as; SbF ₆ like antimony anions, other lactate, nitrate ions, can be used trifluoroacetate and the like.

  Moreover, methyltriglyme, ethyltriglyme, butyltriglyme, methyltetraglyme, ethyltetraglyme, butyltetraglyme, etc. can be used as glymes.

  Furthermore, as the chain sulfone, 2- (ethylsulfonyl) propane, 2- (ethylsulfonyl) butane, or the like can be used.

  Thus, since the electrode of the present invention contains the above-described electrode active material and conductive material, the charge / discharge efficiency is good, the battery can be charged in a short time, and the output can be increased.

  In addition, 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 in the charged state, the discharged state, or the state in the middle thereof. The electrode active material is contained in at least one of a reaction starting material in a discharge reaction (a material that causes a chemical reaction in a battery electrode reaction), a product (a material resulting from a chemical reaction), and an intermediate product. . As a result, it has a high energy density, can be charged quickly, can be discharged at high output, has a good cycle characteristic with little capacity decrease even after repeated charge and discharge, and realizes a long-life secondary battery with stable battery characteristics. It becomes possible to do.

  And in this Embodiment, since the secondary battery is comprised using the said electrode active material, the energy density is large and the secondary battery excellent in the stability of charging / discharging can be obtained.

  In addition, since the electrode active material is mainly composed of an organic compound, it is possible to obtain a secondary battery that has a low environmental load and is also safe.

  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 (1a) to (1q), (2a), and (2b) are also examples of the organic compound that is the main component of the electrode active material, and the present invention is not limited thereto. That is, if it is an organic compound containing a rubean structure as shown in the general formulas (1) and (2) in the structural unit, the same battery electrode reaction as in the chemical reaction formula (A) proceeds, so energy It becomes possible to obtain a desired secondary battery having a high density and good cycle characteristics with improved charge / discharge reaction stability.

  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.

  Moreover, in this Embodiment, although the electrode active material was used for the positive electrode active material, it is also useful to use for a negative electrode active material.

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

  In addition, the Example shown below is an example and this invention is not limited to the following Example.

[Production of secondary battery]
Rubeanic acid represented by the chemical formula (1a) was prepared.

  The rubeanic acid was pulverized for 168 hours with a pot-type ball mill to obtain rubeanic acid particles. And when the particle size of the rubeanic acid particle was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle size was 2 μm in terms of a circle.

  Further, this rubeanic acid particle was imaged at a magnification of 30,000 using a scanning electron microscope (hereinafter referred to as “SEM”).

  FIG. 2 is an SEM image of rubeanic acid particles.

  As shown in the SEM image of FIG. 2, it was found that rubeanic acid has an anisotropic particle shape. And from this SEM image, when rubeanic acid particle | grains were measured, it turned out that ratio a / b of the major axis a and the minor axis b is 3 or more.

Next, 1 g of the rubeanic acid particles, 800 mg of graphite powder, and 200 mg of polytetrafluoroethylene as a binder are weighed, kneaded while uniformly mixing, then press-molded, and a sheet having a thickness of about 150 μm. A shaped member was obtained. Thereafter, the sheet-like member was dried in vacuum at 70 ° C. for 1 hour, and then punched into a circle having a diameter of 12 mm to produce a positive electrode containing a mixture for active material. Next, the positive electrode was impregnated with the electrolytic solution, and the electrolytic solution was infiltrated into the voids in the positive electrode. Here, as the electrolytic solution, a mixed solution containing methyltetraglyme (electrolyte) and LiN (CF ₃ SO ₂ ) ₂ (electrolyte salt) in equimolar amounts was used.

  Next, this positive electrode was placed on a positive electrode current collector, and a separator having a thickness of 20 μm made of a polypropylene porous film impregnated with the electrolytic solution was further laminated on the positive electrode, and further a stainless steel current collector plate The negative electrode which stuck lithium on both surfaces was laminated | stacked on the separator. Then, a metal spring is placed on the current collector, and the negative electrode case is joined to the positive electrode case in a state where the gasket is arranged on the periphery, and the outer case is sealed by a caulking machine, and the active material is used as the positive electrode active material. A sealed coin type battery having metallic lithium as a mixture and a negative electrode active material was produced.

[Confirmation of secondary battery operation]
The coin-type 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 with a constant current of 0.1 mA until it reached 1.5 V. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.33 mAh having a voltage flat portion at a charge / discharge voltage of 2.1 V.

  And the capacity density per mass of the active material calculated from the discharge capacity was 440 Ah / kg, and it was found that this compound is a high capacity density electrode active material suitable for a high energy density battery.

  Then, charging / discharging was repeated 100 cycles in the range of 1.5-4.2V. As a result, the discharge capacity after 100 cycles was 0.32 mAh (initial capacity: 97% of 0.33 mAh), and it was found that the discharge capacity was excellent.

[Production of secondary battery]
The rubeanic acid used in Example 1 was pulverized with a planetary ball mill for 24 hours to obtain rubeanic acid particles. And when the particle diameter of this rubeanic acid particle was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle diameter was 1.2 micrometers in conversion of a circle.

  Further, as in Example 1, the rubeanic acid particles were imaged by SEM and observed, and it was confirmed that the ratio a / b of the major axis a to the minor axis b had an anisotropic particle shape of 3 or more. .

  Then, using this rubeanic acid, a sealed coin-type battery was produced by the same method and procedure as in Example 1.

[Confirmation of secondary battery operation]
The coin-type 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 with a constant current of 0.1 mA until it reached 1.5 V. As a result, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.48 mAh having a voltage flat portion at a charge / discharge voltage of 2.1 V.

  Moreover, the capacity density per mass of the active material calculated from the discharge capacity was 640 Ah / kg, and it was found that this compound is a high capacity density electrode active material suitable for a high energy density battery.

  Then, charging / discharging was repeated 100 cycles in the range of 1.5-4.2V. As a result, the discharge capacity after repeating 100 cycles was 80% or more of the initial capacity, and it was found that the cycle characteristics were good and the stability was excellent.

[Production of secondary battery]
N, N′-dimethyldithiooxamide represented by the chemical formula (1b) was prepared.

  N, N′-dimethyldithiooxamide was pulverized for 168 hours with a pot-type ball mill to obtain N, N′-dimethyldithiooxamide particles. And when the particle size was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle size was 2 μm in terms of a circle.

  Further, as in Example 1, the N, N′-dimethyldithiooxamide particles were imaged with an SEM and observed, and as a result, anisotropic particles having a ratio a / b of the major axis a to the minor axis b of 3 or more. It was confirmed to have a shape.

  A coin-type battery was produced in the same manner as in Example 1, except that N, N′-dimethyldithiooxamide particles were used in place of the rubeanic acid particles of Example 1.

[Confirmation of secondary battery operation]
The coin-type battery 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, this battery was confirmed to be a secondary battery having a discharge capacity of 0.31 mAh having a flat voltage portion at a charge / discharge voltage of 2.2 V.

  The capacity density per mass of the active material calculated from the discharge capacity was 400 Ah / kg, and it was found that this compound is a high capacity density electrode active material suitable for a high energy density battery.

  Then, charging / discharging was repeated 100 cycles in the range of 1.5-4.2V. As a result, the discharge capacity after repeating 100 cycles was 80% or more of the initial capacity, and it was confirmed that the discharge capacity was excellent.

[Production of secondary battery]
N, N′-bis (2-hydroxyethyl) dithiooxamide represented by the chemical formula (1n) was prepared.

  N, N′-bis (2-hydroxyethyl) dithiooxamide was pulverized in a pot-type ball mill for 168 hours to obtain N, N ′-(2-hydroxyethyl) dithiooxamide particles. And when the particle size was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle size was 3 μm in terms of a circle.

  Further, as in Example 1, the N, N′-dimethyldithiooxamide particles were imaged with an SEM and observed, and as a result, anisotropic particles having a ratio a / b of the major axis a to the minor axis b of 3 or more. It was confirmed to have a shape.

  And it replaced with the rubeanic acid particle | grains of Example 1, and produced the coin-type battery by the method similar to Example 1 except having used N, N'-bis (2-hydroxyethyl) dithiooxamide particle | grains.

[Confirmation of secondary battery operation]
The coin-type battery 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 this battery was a secondary battery having a discharge capacity of 0.24 mAh having a voltage flat portion at a charge / discharge voltage of 2.2V.

  The capacity density per mass of the active material calculated from the discharge capacity was 290 Ah / kg, confirming that this compound is a high capacity density electrode active material suitable for high energy density batteries.

  Then, charging / discharging was repeated 100 cycles in the range of 1.5-4.2V. As a result, the discharge capacity after repeating 100 cycles was 80% or more of the initial capacity, and it was confirmed that the discharge capacity was excellent.

[Production of secondary battery]
(2-Piperidinyl) -2-thioxoethanethioamide represented by the chemical formula (1q) was prepared.

  (2-Piperidinyl) -2-thioxoethanethioamide was ground in a pot-mounted ball mill for 168 hours to obtain (2-piperidinyl) -2-thioxoethanethioamide particles. And when the particle size was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle size was 3 μm in terms of a circle.

  Further, as in Example 1, the (2-piperidinyl) -2-thioxoethanethioamide particles were imaged with an SEM and observed, and the ratio a / b of the major axis a to the minor axis b was 3 or more. It confirmed that it had a typical particle shape.

  A coin-type battery was produced in the same manner as in Example 1 except that (2-piperidinyl) -2-thioxoethanethioamide particles were used in place of the rubeanic acid particles of Example 1.

[Confirmation of secondary battery operation]
The coin-type battery 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 this battery was a secondary battery having a discharge capacity of 0.28 mAh having a flat voltage portion at a charge / discharge voltage of 2.2V.

  The capacity density per mass of the active material calculated from the discharge capacity was 320 Ah / kg, and it was confirmed that this compound is a high capacity density electrode active material suitable for a high energy density battery.

  Then, charging / discharging was repeated 100 cycles in the range of 1.5-4.2V. As a result, the discharge capacity after repeating 100 cycles was 80% or more of the initial capacity, and it was confirmed that the discharge capacity was excellent.

Comparative example

[Production of secondary battery]
The rubeanic acid prepared in Example 1 was purified by sublimation to obtain rubeanic acid particles. And when the particle size of rubeanic acid particle was measured using the laser diffraction type particle size distribution measuring apparatus, the average particle size was 150 micrometers in terms of a circle.

  In addition, this rubeanic acid particle was imaged at a magnification of 3000 times using SEM.

  FIG. 3 is an SEM image of rubeanic acid particles.

  As shown in FIG. 3, it was found that the rubeanic acid particles do not show the elongated anisotropic shape as in Example 1, have a large particle size, and a shape close to a substantially rectangular parallelepiped shape.

  A coin-type battery was produced in the same manner as in Example 1 except that the rubeanic acid particles were used.

[Confirmation of secondary battery operation]
The coin-type battery 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, this battery was confirmed to be a secondary battery having a discharge capacity of 0.33 mAh having a voltage flat portion at a charge / discharge voltage of 2.1 V.

  The capacity density per mass of the active material calculated from the discharge capacity was 440 Ah / kg, confirming that this compound is a high capacity density electrode active material suitable for a high energy density battery.

  However, after 100 cycles of charge and discharge were repeated in the range of 1.5 to 4.2 V, the discharge capacity after 100 cycles was less than 80% of the initial capacity, and each secondary battery of Examples 1 to 5 It was found that the stability was inferior.

  Even when the charge / discharge reaction is repeated, the secondary battery can be realized with low capacity reduction, excellent cycle characteristics with excellent stability, high energy density, and high output.

4 Positive electrode 6 Negative electrode 9 Electrolyte

Claims (7)

An electrode active material used as an active material of a secondary battery that repeats charging and discharging by a battery electrode reaction,
While mainly composed of an organic compound containing a rubeanic acid structure in the structural unit,
An electrode active material, wherein the organic compound has an anisotropic particle shape.   2. The electrode active material according to claim 1, wherein the particle shape has a ratio a / b of a major axis “a” to a minor axis “b” of 1.5 or more. The organic compound has the general formula
[Wherein R _{1 to} R ₄ are a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group. Represents at least one selected from a group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, and R _{1 to} R ₄ include the same case and are connected to each other to be saturated or This includes the case of forming an unsaturated ring. ]
The electrode active material according to claim 1, wherein the electrode active material is represented by: The organic compound has the general formula
[Wherein, n represents an integer of 1 to 20, R ₅ and R ₆ represent a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, a substituted or unsubstituted group. At least one selected from the group consisting of an amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group, and a substituted or unsubstituted sulfo group, R ₅ and R ₆ are the same Including the case where they are linked to each other to form a saturated or unsaturated ring. ]
The electrode active material according to claim 1, wherein the electrode active material is represented by:   An electrode comprising the electrode active material according to any one of claims 1 to 4 and a conductive material.   The electrode active material according to any one of claims 1 to 4 is included in any one of a reaction starting material, a product, and an intermediate product in at least a discharge reaction of a battery electrode reaction. Next battery.   A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode contains the electrode active material according to any one of claims 1 to 4.