JP6175703B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and particularly to a non-aqueous electrolyte secondary battery using a deuterated active material.

  Along with the expansion of the market for mobile phones and portable electronic devices, there are increasing demands for higher energy density and higher output for batteries used in these devices. In order to meet these demands, secondary batteries using an alkali metal ion such as lithium ion as a charge carrier and utilizing an electrochemical reaction associated with charge exchange have been developed. In particular, lithium ion secondary batteries have a high energy density and are currently widely used.

  In such a lithium ion secondary battery, a lithium-containing transition metal oxide is used as a positive electrode active material, and a carbon material is used as a negative electrode active material. And charging / discharging of a battery is performed using the insertion reaction and elimination | desorption reaction of lithium ion with respect to these active materials. However, the energy density of the lithium ion secondary battery is approaching the theoretical limit, and it is difficult to further increase the energy density.

  In order to solve such problems, secondary batteries using an organic compound as a positive electrode active material have been recently proposed. Such secondary batteries include those using organic radical compounds, those using organic sulfur compounds, and quinone compounds, and these researches and developments are actively conducted.

  By the way, Patent Document 1 discloses a secondary battery active material 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 nitroxyl radical having high stability as a radical. Specifically, for example, when a secondary battery is created using an electrode layer containing a nitronyl nitroxide compound as a positive electrode and a lithium-bonded copper foil as a negative electrode and repeatedly charged and discharged, it can be charged and discharged over 10 cycles or more. Is disclosed.

In addition, since the organic sulfur compound forms an SS bond having a small binding energy, it can be charged and discharged by utilizing a bond and a cleavage by reaction. For example, Patent Document 2 and Non-Patent Document 1 disclose an electricity storage device using a disulfide compound represented by the following formula (A) as an electrode active material.
R-S-S-R (A)
(However, in the above formula (A), R represents an aliphatic organic group or an aromatic organic group, which may be the same or different.)

  This organic sulfur compound forms an organic thiolate (R-SH) by cleaving the S—S bond in the reduced state. And this organic thiolate is restored to an organic sulfur compound (R—S—S—R) by forming an S—S bond in an oxidized state. That is, charging / discharging can be performed by a reversible oxidation-reduction reaction of the organic disulfide compound.

Patent Document 3 discloses a power storage device including rubeanic acid or a rubeanic acid polymer that has a structural unit represented by the following formula (B) and can be bonded to lithium ions. Patent Document 3 shows that when rubeanic acid is used, a battery having a capacity density of 400 Ah / kg per mass of the active material is obtained.
-(NH-CS-CS-NH)-(B)

  By the way, since the enolate ion which is a reductant is stabilized by a conjugated system, an oxidation reduction reaction is reversible and can charge / discharge using this quinone compound. Patent Document 4 discloses a power storage device in which an electrode active material is obtained by oligomerizing or polymerizing a specific quinone compound having two quinone groups in the ortho-positional relationship, particularly a phenanthrenequinone compound. Specifically, it is described that the phenanthrenequinone dimer exhibits two redox voltages (around 2.9 V and 2.5 V), and the initial discharge capacity reaches 200 Ah / kg.

  Further, Patent Document 5 discloses an electrolytic solution containing a labeled carbonate compound such as deuteration, and it is shown that it can be used for analysis of the reaction and operation mechanism inside the battery. Further, Patent Document 6 discloses a method for generating deuterated ions by neutrino and increasing the power of the battery.

JP 2004-207249 A U.S. Pat. No. 4,833,048 JP 2008-147015 A JP 2008-222559 A JP 2007-084469 A JP 2007-157664 A

J. et al. Electrochem. Soc. Vol 136, p. 661-664 (1989)

  However, in Patent Documents 1 to 4 and Non-Patent Document 1 described above, organic radical compounds such as nitroxyl radical compounds and organic compounds such as disulfide compounds, rubeanic acid compounds, and phenanthrenequinone compounds are used as electrode active materials. However, there is a problem that the stability is not sufficient with a normal electrolyte solvent, and the capacity decreases when the charge / discharge cycle is repeated.

  On the other hand, in Patent Document 5, deuterated carbonate is used, but no description of the active material is recognized. Patent Document 6 describes an increase in power due to deuterium, but the charge / discharge reaction mechanism is different from that of an ordinary chemical battery.

  Thus, conventionally, the possibility of high capacity density batteries using organic compounds such as organic radical compounds, disulfide compounds, rubeanic acid, and quinones as electrode active materials has been proposed. At present, secondary batteries that are insufficient and have high energy density and good cycle characteristics have not been realized.

  The present invention has been made in view of the above circumstances, and is a non-aqueous electrolyte secondary battery having high energy density, high output, and good cycle characteristics with little capacity decrease even after repeated charge and discharge. The issue is to provide.

The present invention has the following configuration.
The invention according to claim 1 is a non-aqueous electrolyte secondary battery having a positive electrode containing an electrode active material and a negative electrode, and charging and discharging by an electrode reaction of the electrode active material,
In the non-aqueous electrolyte secondary battery, the electrode active material is a deuterium compound containing deuterium, which is a stable isotope of a hydrogen atom, at a concentration higher than the natural abundance ratio.

  The invention according to claim 2 is the nonaqueous electrolyte secondary battery according to claim 1, wherein the deuteride is an organic compound.

  The invention according to claim 3 is characterized in that the deuterium compound is contained in any of reaction starting materials, products and intermediate products in the electrode reaction of the electrode active material. It is a nonaqueous electrolyte secondary battery of description.

  The invention according to claim 4 is characterized in that the organic compound is at least one of a neutral radical compound, a compound having a rubeanic acid structure, and a compound having a conjugated diamine structure. It is a non-aqueous electrolyte secondary battery as described in above.

  The invention according to claim 5 is the non-aqueous electrolyte secondary battery according to claim 4, wherein the neutral radical compound is a nitroxyl radical-based stable radical compound.

なお、上記一般式（１）において、Ｒ_１及びＲ_２は、置換または非置換のイミノ基、置換または非置換のアルキレン基、もしくは置換または非置換のアリーレン基である。式中ｎは、１〜１００の整数、好ましくは１〜２０の整数である。 The invention according to claim 6 is the non-aqueous electrolyte secondary battery according to claim 4, wherein the compound having a rubeanic acid structure is represented by the following general formula (1).

In the general formula (1), R ₁ and R ₂ are a substituted or unsubstituted imino group, a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group. In the formula, n is an integer of 1 to 100, preferably an integer of 1 to 20.

なお、上記一般式（２）において、Ｒ_３及びＲ_４は、置換または非置換のアルキル基、置換または非置換のアルキレン基、置換または非置換のアリーレン基、置換または非置換のカルボニル基、置換または非置換のアシル基、置換または非置換のアルコキシカルボニル基、置換または非置換のエステル基、置換または非置換のエーテル基、置換または非置換のチオエーテル基、置換または非置換のアミン基、置換または非置換のアミド基、置換または非置換のスルホン基、置換または非置換のチオスルホニル基、置換または非置換のスルホンアミド基、置換または非置換のイミン基、置換または非置換のアゾ基、もしくはこれらの１以上の組み合わせからなる連結基である。
また、上記一般式（２）において、Ｘ_１〜Ｘ_４は、ハロゲン原子、ヒドロキシル基、ニトロ基、シアノ基、カルボキシル基、置換または非置換のアルキル基、置換または非置換のアルケニル基、置換または非置換のシクロアルキル基、置換または非置換の芳香族炭化水素基、置換または非置換の芳香族複素環基、置換または非置換のアラルキル基、置換または非置換のアミノ基、置換または非置換のアルコキシ基、置換または非置換のアリールオキシ基、置換または非置換のアルコキシカルボニル基、置換または非置換のアリールオキシカルボニル基、置換または非置換のアシル基、もしくは置換または非置換のアシルオキシ基であり、これらの置換基は置換基同士で環構造を形成していてもよい。 The invention according to claim 7 is the non-aqueous electrolyte secondary battery according to claim 4, wherein the compound having the conjugated diamine structure is represented by the following general formula (2).

In the general formula (2), R ₃ and R ₄ are a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, a substituted or unsubstituted carbonyl group, a substituted Or unsubstituted acyl group, substituted or unsubstituted alkoxycarbonyl group, substituted or unsubstituted ester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine group, substituted or Unsubstituted amide group, substituted or unsubstituted sulfone group, substituted or unsubstituted thiosulfonyl group, substituted or unsubstituted sulfonamido group, substituted or unsubstituted imine group, substituted or unsubstituted azo group, or these A linking group comprising a combination of one or more of the following.
In the general formula (2), X _{1 to} X ₄ are each a halogen atom, a hydroxyl group, a nitro group, a cyano group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, substituted or Unsubstituted cycloalkyl group, substituted or unsubstituted aromatic hydrocarbon group, substituted or unsubstituted aromatic heterocyclic group, substituted or unsubstituted aralkyl group, substituted or unsubstituted amino group, substituted or unsubstituted An alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted acyloxy group; These substituents may form a ring structure with the substituents.

  The non-aqueous electrolyte secondary battery of the present invention uses a deuterium compound containing deuterium, which is a stable isotope of hydrogen atoms, in a concentration higher than the natural abundance ratio as an electrode active material. The side reaction at the time can be suppressed. As a result, it is possible to provide a non-aqueous electrolyte secondary battery that has high energy density, high output, good cycle characteristics with little reduction in capacity even after repeated charge and discharge, and excellent stability.

FIG. 1 is a cross-sectional view showing an example of a lithium secondary battery according to an embodiment to which the present invention is applied. FIG. 2 is a diagram showing the results of GC-MS analysis, (A) shows the results for rubeanic acid, and (B) shows the results for deuterated rubeanic acid. FIG. 3 is a diagram showing a result of charging and discharging the secondary battery of Example 1. FIG. 4 is a diagram showing a result of charging and discharging the secondary battery of Comparative Example 1. FIG. 5 is a diagram showing the result of charging and discharging the secondary battery of Example 4. FIG. 6 is a diagram showing the results of EI-MS measurement. (A) shows the results of 5,10-dihydro-5,10-dimethylphenazine, (B) shows deuterated 5,10-dihydro-5, It is a figure which shows the result of 10-dimethylphenazine, respectively.

Hereinafter, a lithium secondary battery according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings together with an electrode active material used therefor.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

First, the configuration of a lithium secondary battery which is an embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view showing an example of a lithium secondary battery according to an embodiment to which the present invention is applied. As shown in FIG. 1, a lithium secondary battery (nonaqueous electrolyte secondary battery) 1 according to the present embodiment includes a positive electrode case 2 and a negative electrode case 3. Both the positive electrode case 2 and the negative electrode case 3 are formed in a disk-like thin plate shape, and constitute a coin-type lithium secondary battery.

  The positive electrode case 2 constitutes a positive electrode current collector, and a positive electrode 4 in which an electrode active material is molded into a sheet shape is disposed at the center of the bottom. On the positive electrode 4, a separator 5 formed of a porous sheet or film such as a microporous film, a woven fabric, or a nonwoven fabric is laminated. Further, 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. On the negative electrode 6, a negative electrode current collector 7 made of metal is laminated. Further, a metal spring 8 is placed on the negative electrode current collector 7.

  The negative electrode case 3 is fixed to the positive electrode case 2 against the urging force of the metal spring 8. A positive electrode 4, a separator 5, a negative electrode 6, and a negative electrode current collector 7 are stacked and placed in an internal space formed by fixing the positive electrode case 2 and the negative electrode case 3 together with an electrolyte 9. Is filled. Further, the gap between the positive electrode case 2 and the negative electrode case 3 forming the internal space is sealed with a gasket 10.

  That is, the lithium secondary battery 1 of the present embodiment is a non-aqueous electrolyte secondary battery that has a positive electrode 4 and a negative electrode 6 including an electrode active material, and is charged and discharged by an electrode reaction of the electrode active material. The lithium secondary battery 1 of the present embodiment is characterized in that the electrode active material is a deuterium compound containing deuterium, which is a stable isotope of hydrogen atoms, at a higher concentration than the natural abundance ratio.

Here, the deuterium compound is a compound in which part or all of hydrogen (H) in the molecule is deuterium ( ² H). This deuterium compound is present in a certain ratio even in the natural state. In this embodiment, a deuterium compound containing deuterium at a concentration higher than the natural abundance ratio (0.015%) is used as the electrode active material. More specifically, the deuteration rate in the molecule of the deuterium compound is preferably 1% or more, more preferably 10% or more, and further preferably 90% or more.

  As described above, since the electrode active material contains a deuterium compound, side reactions occurring in the process of charge / discharge reaction of the electrode active material can be suppressed, so that the lithium secondary battery 1 having excellent stability can be obtained. . In the lithium secondary battery 1 of the present embodiment, the electrode active material is not particularly limited, but such an effect is particularly remarkable when the electrode active material is an organic compound. On the other hand, even if the electrode active material is, for example, a lithium ion secondary battery using lithium oxide, if the electrode active material is a deuterium compound, it exerts the effect of suppressing side reactions at high temperatures and overcharge. can do.

  Moreover, since the electrode active material of a secondary battery is reversibly oxidized or reduced by charging / discharging, it is known to take a different structure and state depending on a charged state, a discharged state, or an intermediate state. Therefore, in the present embodiment, the electrode active material is any one of at least a reaction starting material in the discharge reaction (a material that causes a chemical reaction in the battery electrode reaction), a product (a material generated as a result of the chemical reaction), and an intermediate product. As long as it is included.

As described above, in the lithium secondary battery 1 of the present embodiment, the electrode active material is preferably a deuterated organic compound. The organic compound is not particularly limited, but is preferably at least one of a neutral radical compound, a compound having a rubeanic acid structure, and a compound having a conjugated diamine structure.
Specific examples of organic compounds that can be suitably used for the electrode active material are illustrated below, but are not limited thereto.

  As the neutral stable radical compound, a nitroxyl radical compound, a nitronyl nitroxyl radical compound, a ferdazyl radical compound, a thioaminyl radical compound, or the like can be used. Among these, a nitroxyl radical compound is particularly preferable from the viewpoint of charge / discharge stability.

Examples of the nitroxyl radical compound include compounds represented by the following chemical formulas (3) to (8). Note that some or all of the hydrogen in the chemical formulas (3) to (8) is deuterated. Moreover, in chemical formula (3)-(7), n is an integer of 1-100, Preferably it is an integer of 1-20. Further, in the chemical formula (8), R ₅ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, a substituted or unsubstituted carbonyl group, a substituted or unsubstituted group. Acyl group, substituted or unsubstituted alkoxycarbonyl group, substituted or unsubstituted ester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine group, substituted or unsubstituted amide A group, a substituted or unsubstituted sulfone group, a substituted or unsubstituted thiosulfonyl group, a substituted or unsubstituted sulfonamido group, a substituted or unsubstituted imine group, a substituted or unsubstituted azo group, or one or more thereof A linking group consisting of a combination.

なお、上記一般式（１）において、Ｒ_１及びＲ_２は、置換または非置換のイミノ基、置換または非置換のアルキレン基、もしくは置換または非置換のアリーレン基である。式中ｎは、１〜１００の整数、好ましくは１〜２０の整数である。 The compound having a rubeanic acid structure is represented by the following general formula (1).

In the general formula (1), R ₁ and R ₂ are a substituted or unsubstituted imino group, a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group. In the formula, n is an integer of 1 to 100, preferably an integer of 1 to 20.

  Examples of the compound having a rubeanic acid structure include compounds represented by the following chemical formulas (9) to (18). In addition, some or all of the hydrogen in the chemical formulas (9) to (18) is deuterated. Moreover, in chemical formula (10)-(18), n is an integer of 1-100, Preferably it is an integer of 1-20.

The compound having a conjugated diamine structure is represented by the following general formula (2).

In the general formula (2), R ₃ and R ₄ are a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, a substituted or unsubstituted carbonyl group, a substituted Or unsubstituted acyl group, substituted or unsubstituted alkoxycarbonyl group, substituted or unsubstituted ester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine group, substituted or Unsubstituted amide group, substituted or unsubstituted sulfone group, substituted or unsubstituted thiosulfonyl group, substituted or unsubstituted sulfonamido group, substituted or unsubstituted imine group, substituted or unsubstituted azo group, or these A linking group comprising a combination of one or more of the following.

In the general formula (2), X _{1 to} X ₄ are each a halogen atom, a hydroxyl group, a nitro group, a cyano group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, substituted or Unsubstituted cycloalkyl group, substituted or unsubstituted aromatic hydrocarbon group, substituted or unsubstituted aromatic heterocyclic group, substituted or unsubstituted aralkyl group, substituted or unsubstituted amino group, substituted or unsubstituted An alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted acyloxy group; These substituents may form a ring structure with the substituents.

  Examples of the compound having a conjugated diamine structure include compounds represented by the following chemical formulas (19) to (27). Note that part or all of the hydrogen in the chemical formulas (19) to (27) is deuterated. Moreover, in chemical formula (23)-(26), n is an integer of 1-100, Preferably it is an integer of 1-20.

  In the lithium secondary battery 1 of the present embodiment, the method for producing a deuteride that is an electrode active material is not particularly limited, and a common method as a method for producing a heavy mass compound, for example, a building A method of producing a combination of heavy mass compounds to be blocks, or a method of exchanging a predetermined element with a stable isotope element in the presence of a catalyst such as an acid, a base, or a metal can be used.

Next, the manufacturing method of the lithium secondary battery 1 of this embodiment is demonstrated.
First, the electrode active material described above is formed into an electrode shape. For example, an electrode active material is mixed with a conductive additive and a binder, an organic solvent is added to form a slurry, and the slurry is applied on the positive electrode current collector (positive electrode case 2) by an arbitrary coating method. The positive electrode 4 is formed by drying.

  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 a content rate in the positive electrode 4 of a conductive support agent, it is desirable to set it as 10-80 mass%.

  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 organic solvent constituting the slurry is not particularly limited, and examples thereof include dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, propylene carbonate, diethyl carbonate, dimethyl carbonate, γ-butyrolactone, acetonitrile, tetrahydrofuran, and nitrobenzene. An aprotic solvent such as acetone or a protic solvent such as methanol or ethanol can be used.

  Next, the positive electrode 4 is impregnated with the electrolyte 9 so as to penetrate the positive electrode 4, and then the positive electrode 4 is placed on the positive electrode current collector at the center of the bottom of the positive electrode case 2. 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 9, 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 externally sealed. Through the above steps, the coin-type ion secondary battery 1 shown in FIG. 1 is manufactured.

Here, the electrolyte 9 is interposed between the positive electrode (electrode active material) 4 and the negative electrode 6 that is a counter electrode, and transports charge carriers between the two electrodes. As such an electrolyte 9, what has the ion conductivity of 10 ^<-5 > ^-10 < ^-1 > S / cm at room temperature can be used, For example, the electrolyte solution which dissolved electrolyte salt in the organic solvent is used. be able to.

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 ) _3m, 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, N-methyl-2-pyrrolidone, etc. are used. be able to.

  In this embodiment, instead of the electrolytic solution obtained by dissolving the electrolyte salt in the organic solvent, an electrolytic solution obtained by dissolving or dissolving the electrolyte salt in the deuterated solvent may be used as the electrolyte 9.

As the deuterated solvent, a part or all of hydrogen (H) in the molecule is deuterated ( ² H), for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dimethoxyethane, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylsulfone, methylethylsulfone, methylisopropylsulfone, ethylisopropylsulfone, dimethylformamide, dimethylacetamide, 1-methyl-2-pyrrolidone and the like can be mentioned. Among these, from the viewpoint of stabilizing effect, in particular, carbonate carbonate such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and sulfolane, dimethyl sulfone, methyl ethyl sulfone, methyl isopropyl sulfone, ethyl isopropyl sulfone. Sulfones such as are preferred.

  The electrolyte 9 may be a solid electrolyte, an ionic liquid, a symmetric glycol diether such as glyme, 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 copolymers, acrylonitrile-vinyl acetate copolymers, and further, polyethylene oxide, ethylene oxide-propylene oxide copolymers, and polymers of these acrylates and methacrylates. be able to.

  In addition, 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 it is for the electrolyte 9. Also good.

Moreover, as a compound used for the ionic liquid which combined the cation and the anion, the cation is 2-ethylimidazolium, 3-propylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methyl. Imidazolium such as imidazolium and 1,3-dimethylimidazolium; diethylmethylammonium, tetrabutylammonium, cyclohexyltrimethylammonium, methyltri-n-octylammonium, triethyl (2-methoxyethoxymethyl) ammonium, benzyldimethyltetradecylammonium, Ammonium such as benzyltrimethylammonium; other alkylpyridinium, dialkylpyrrolidinium, tetraalkylphosphonium, trialkylsulfonium, etc. ON ^Cl -, ^Br -, I ^- halide anion such _{^{as; BF 4 -, B (CN}} ) 4 -, B (C 2 O 4) 2 - boride such ^{_{anions; (CN) 2 N -,}} [ Amide anion or imide anion such as N (CF ₃ ) ₂ ] ⁻ and [N (SO ₂ CF ₃ ) ₂ ] ^— ; RSO ₃ ⁻ (hereinafter, R represents an aliphatic hydrocarbon group or an aromatic hydrocarbon group) , RSO ₄ ⁻ , R ^f SO ₃ ⁻ (hereinafter, R ^f represents a fluorinated halogenated hydrocarbon group), R ^f SO ₄ ^{— and the} like, sulfate anion or sulfonate anion; R ^f ₂ P (O) SbF ₆ and antimony _{^{anion;; O -, PF 6 -}} -, R f 3 PF 3 and phosphate anions other, lactate, nitrate ions, is made of trifluoroacetate and the like can be used.

  As the rulimes, methyltriglyme, ethyltriglyme, butyltriglyme, methyltetraglyme, ethyltetraglyme, butyltetraglyme and the like can be used. Furthermore, as the chain sulfone, 2- (ethylsulfonyl) propane, 2- (ethylsulfonyl) butane, or the like can be used.

  By the way, the realization of a secondary battery having a high capacity density has been conventionally expected by using an organic compound as an electrode active material. However, when an organic compound is used as an electrode active material, a secondary battery having insufficient stability and good cycle characteristics has not been realized, for example, the organic compound is decomposed during a charge / discharge cycle.

  In general, in the decomposition process of organic compounds, the bond between carbon, nitrogen, etc. and hydrogen is cleaved by a change in external conditions such as light and heat, and further, a side reaction proceeds and decomposes from the produced intermediate. It is known. On the other hand, a compound in which part or all of hydrogen in the molecular structure of an organic compound is replaced with deuterium (that is, deuterium compound) has stronger bond strength with carbon, nitrogen, etc., and bond cleavage due to external factors. Is suppressed.

  Accordingly, the present inventors have found an effect (deuteration effect) that side reactions such as decomposition and polymerization are suppressed even in an electrode reaction when a deuterium compound is used as an electrode active material. As a result, a material that could not be conventionally used as an electrode material for a secondary battery because it is easily decomposed can be used as an electrode active material with improved stability as a compound. Moreover, the charge / discharge cycle can be further stabilized (durability improved) for materials already used as the electrode material of the secondary battery. The deuteration effect becomes more prominent when an organic compound is used as the electrode active material.

  As described above, according to the lithium secondary battery 1 of the present embodiment, a deuterium compound containing deuterium, which is a stable isotope of a hydrogen atom, at a higher concentration than the natural abundance ratio is used as an electrode active material. Therefore, decomposition of the electrode active material during charging / discharging can be suppressed. Therefore, a non-aqueous electrolyte secondary battery having a large energy density and excellent stability can be obtained.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the above-described chemical formulas are also examples of the organic compounds that are the main components of the electrode active material of the above-described embodiment, and the present invention is not limited thereto. That is, if the electrode active material is a heavy mass compound, it is considered that the characteristics of the present invention can be realized, so that a secondary battery having a large energy density and excellent stability can be obtained. Examples of such stable isotope elements include ² H, ¹³ C, ¹⁵ N, and ¹⁸ O.

  In the above embodiment, the coin-type ion secondary battery has been described. However, the battery shape is not particularly limited, and can be applied to a cylindrical type, a square type, a sheet type, 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.

  Furthermore, in the said embodiment, although the electrode active material of this invention was used for the positive electrode active material, it is also useful to use for a negative electrode active material.

A specific example is shown below.
Example 1
[Synthesis of organic compounds]
Deuterated rubeanic acid was synthesized according to the synthesis scheme shown in the following formula (28).

  Specifically, as shown in the above formula (28), rubeanic acid, deuterated water and deuterated ethanol were heated and reacted at 80 ° C., and the resulting solid was filtered to obtain deuterated rubeanic acid. Here, FIG. 2 (A) shows rubeanic acid, and FIG. 2 (B) shows the GC-MS analysis results of deuterated rubeanic acid. Further, the deuteration rate of deuterated rubeanic acid measured by GC-MS was 35 atom% D.

[Production of secondary battery]
300 mg of deuterated rubeanic acid synthesized above, 600 mg of graphite powder, and 100 mg of polytetrafluoroethylene resin binder were weighed out and kneaded while mixing uniformly. This mixture was pressure-molded to obtain a sheet having a thickness of about 150 μm. This was dried in a 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 rubeanic acid. Next, this positive electrode was impregnated with an electrolyte in which ethylene carbonate and diethyl carbonate containing 1M LiN (C ₂ F ₅ SO ₂ ) ₂ were mixed at a volume ratio of 3: 7. This electrode is placed on a positive electrode current collector, a 20 μm thick separator made of a polypropylene porous film impregnated with the electrolyte is laminated, and lithium is bonded to a stainless steel current collector as a negative electrode Were laminated. Then, a metal spring was placed on the current collector, and the negative electrode side member whose periphery was covered with a gasket was stacked, and the exterior was sealed with a caulking machine. Thus, a sealed coin-type secondary battery having deuterated rubeanic acid as the positive electrode active material and metallic lithium as the negative electrode active material was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged to 1.5 V with a constant current of 0.1 mA. FIG. 3 shows the result of charging and discharging the produced secondary battery. This secondary battery was confirmed to be a secondary battery with a discharge capacity of 0.6 mAh having a voltage flat portion at 2.4 V and 2.0 V.

  Thereafter, charging and discharging were further repeated in the range of 4.0 to 1.5V. As a result, the capacity density was 95% or more of the initial value per active material even after 20 cycles, and it was confirmed that the secondary battery had a long cycle life with little decrease in capacity even after repeated charge and discharge.

(Comparative Example 1)
[Production of secondary battery]
Except that the electrode active material was changed from deuterated rubeanic acid to normal rubeanic acid, the same method as in Example 1 was used, and a sealed coin-type coin made of rubeanic acid as the positive electrode active material and metallic lithium as the negative electrode active material was used. A secondary battery was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged to 1.5 V with a constant current of 0.1 mA. FIG. 4 shows the result of charging and discharging the produced secondary battery. This secondary battery was confirmed to be a secondary battery with a discharge capacity of 0.6 mAh having a flat voltage portion at 2.3 V and 2.0 V.

  However, when charging / discharging was repeated in the range of 4.0 to 1.5 V, the capacity density after 20 cycles was 95% or less of the initial per active material, and it was confirmed that the secondary battery had large cycle deterioration. .

(Example 2)
[Synthesis of organic compounds]
According to the synthesis scheme shown in the following formula (29), a condensate of deuterated rubeanic acid and deuterated adipic acid dichloride was synthesized.

  Specifically, as shown in the above formula (29), first, deuterated rubeanic acid was dissolved in an aqueous solution containing sodium deuteride. Subsequently, after cooling the whole to 0 degreeC, deuterated adipic acid dichloride aqueous solution was dripped, stirring vigorously. Stirring was continued for 1 hour to react deuterated rubeanic acid with deuterated adipic acid dichloride. The solid thus obtained was washed and dried to obtain a deuterated condensate of light brown rubeanic acid and adipic acid dichloride. Moreover, the deuteration rate of the deuterated product of the condensate of rubeanic acid and adipic acid dichloride measured by GC-MS was 50 atom% D.

[Production of secondary battery]
The electrode active material was rubeanic acid as the positive electrode active material and the metal as the negative electrode active material in the same manner as in Example 1 except that the deuterated product of deuterated rubeanic acid to the condensate of rubeanic acid and adipic acid dichloride was applied. A sealed coin-type secondary battery made of lithium was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged to 1.5 V with a constant current of 0.1 mA. As a result, it was confirmed that this secondary battery was a secondary battery with a discharge capacity of 0.6 mAh having voltage flat portions at 2.4 V and 2.0 V.

  Thereafter, charging and discharging were repeated in the range of 4.0 to 1.5V. As a result, the capacity density was 95% or more of the initial value per active material even after 20 cycles, and it was confirmed that the secondary battery had a long cycle life with little decrease in capacity even after repeated charge and discharge.

(Example 3)
[Synthesis of organic compounds]
Deuterated poly (2,2,6,6-tetramethylpiperidinoxymethacrylate) was synthesized according to the reaction scheme shown in the following formula (30). In addition, the raw material was synthesize | combined according to well-known literature (Unexamined-Japanese-Patent No. 2008-088117). In addition, a commercially available deuterated 4-hydroxy-2,2,6,6-tetramethylpiperidine (Isotech: no product number) and deuterated methyl methacrylate are transesterified to produce deuterated 2, 2,6,6-tetramethylpiperidine methacrylate was obtained.

Next, according to the reaction scheme shown in the following formula (31), deuterated 2,2,6,6-tetramethylpiperidine methacrylate is polymerized and oxidized to produce deuterated poly (2,2,6,6). -Tetramethylpiperidinoxymethacrylate) was obtained. Moreover, the deuteration rate of the product measured by GC-MS was 80 atom% D.

[Production of secondary battery]
Except for using a deuterated poly (2,2,6,6-tetramethylpiperidinoxymethacrylate) as the electrode active material, poly (2,2) was used as the positive electrode active material in the same manner as in Example 1 above. , 6,6-tetramethylpiperidinoxymethacrylate) and a sealed coin-type secondary battery made of metallic lithium as the negative electrode active material.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 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 with a discharge capacity of 0.1 mAh having a voltage flat portion at 3.60V.

  Then, charging / discharging was repeated in the range of 4.2-2.5V. As a result, the capacity density was 95% or more of the initial value per active material even after 20 cycles, and it was confirmed that the secondary battery had a long cycle life with little decrease in capacity even after repeated charge and discharge.

Example 4
Deuterated phenazine was synthesized according to the synthesis scheme shown in the following formula (32).

Specifically, as shown in the above formula (32), after putting phenazine in a reaction vessel of a microwave reactor together with heavy water, platinum-activated carbon (Pt: 5%), and aluminum (III) powder, about 200 Microwave irradiation was performed at ° C. After allowing to cool, the filtrate was concentrated after suction filtration with washing with acetonitrile. The deuterated phenazine obtained by concentration was purified by sublimation to obtain the desired product. The deuteration rate of deuterated phenazine calculated by ¹ HNMR was 96 atom% D.

[Production of secondary battery]
A sealed coin type consisting of deuterated phenazine as a positive electrode active material and metallic lithium as a negative electrode active material in the same manner as in Example 1 except that deuterated phenazine as a yellow powder was used as the electrode active material. A secondary battery was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged to 1.5 V with a constant current of 0.1 mA. The result is shown in FIG. As shown in FIG. 5, it was confirmed that this battery was a secondary battery having a discharge capacity of 0.2 mAh having a voltage flat portion at 2.0V.

  Then, charging / discharging was repeated in the range of 4.0-2.0V. As a result, the capacity density became 95% or more per active material even after 20 cycles, and the shuttle phenomenon observed with phenazine was further suppressed with deuterated phenazine. As described above, the secondary battery prepared using deuterated phenazine as the positive electrode active material can be stably charged and has a long cycle life with little decrease in capacity even after repeated charge and discharge. confirmed.

３）

(Example 5)
[Synthesis of organic compounds]
Deuterated 5,10-dihydro-5,10-dimethylphenazine was synthesized according to the synthesis scheme shown in the following formulas (33) and (34).

3)

  Specifically, as shown in the above formula (33), deuterated phenazine was added to deuterated ethanol in an argon stream, and sodium adithionate dissolved in heavy water was added dropwise thereto. After the reaction, suction filtration was performed, and 5,10-dihydrophenazine was taken out and dried under vacuum heating. Subsequently, as shown in the above formula (34), dehydrated tetrahydrofuran tetrahydrofuran was added to 5,10-dihydrophenazine and butyllithium was added dropwise under an argon atmosphere, and then deuterated iodomethane was added and stirred. Subsequently, silica column chromatography separation and purification were performed to obtain deuterated 5,10-dihydro-5,10-dimethylphenazine. The EI-MS measurement results are shown in FIG. The deuteration rate of deuterated 5,10-dihydro-5,10-dimethylphenazine calculated by EI-MS was 98 atom% D.

[Production of secondary battery]
In the same manner as in Example 1 except that deuterated 5,10-dihydro-5,10-dimethylphenazine, which is a yellow powder, was used as the electrode active material, deuterated 5,10- A sealed coin-type secondary battery made of dihydrophenazine and metallic lithium as a negative electrode active material was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 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 0.15 mAh having a voltage flat portion at 3.0 V and 3.5 A.

  Then, charging / discharging was repeated in the range of 4.2-2.5V. As a result, the capacity density is 95% or more of the initial active material after 20 cycles, and the deuterated 5,10-dihydro-5,10-dimethylphenazine suppresses the shuttle phenomenon observed with phenazine. It was. As described above, the secondary battery prepared using deuterated 5,10-dihydro-5,10-dimethylphenazine as the positive electrode active material can be stably charged, and has a small capacity reduction even after repeated charge and discharge. It was confirmed that the secondary battery had a long cycle life.

(Example 6)
[Synthesis of organic compounds]
A polymer of a deuterated dihydrophenazine dicarbonyl compound was synthesized according to a synthesis scheme shown in the following formula (35).

  Specifically, as shown in the above formula (35), after deuterated 5,10-dihydrophenazine and 4-dimethylaminopyridine were dissolved in dehydrated pyridine in an argon stream, dehydrated tetrahydrofuran and ogisaryl chloride were dissolved. Was added at 0 ° C., and the mixture was stirred at room temperature for 1 hour and then at 60 ° C. for 4 hours. After completion of the reaction, pyridine was removed, methanol was added, and the precipitated black powder was filtered to obtain a deuterated dihydrophenazine dicarbonyl compound polymer. The deuteration rate of the deuterated dihydrophenazine dicarbonyl compound polymer measured by GC-MS was 96 atom% D.

[Production of secondary battery]
A deuterated product of dihydrophenazine dicarbonyl compound polymer was used as the positive electrode active material in the same manner as in Example 1 except that a deuterated product of dihydrophenazine dicarbonyl compound polymer that was a black solid was used as the electrode active material. Then, a sealed coin-type secondary battery made of metallic lithium as a negative electrode active material was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 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 0.1 mAh having a voltage flat portion at 2.4 V and 2.6 A.

  Then, charging / discharging was repeated in the range of 4.2-2.5V. As a result, the capacity density was 95% or more of the initial value per active material even after 20 cycles, and it was confirmed that the secondary battery had a long cycle life with little decrease in capacity even after repeated charge and discharge.

(Example 7)
[Production of secondary battery]
In the same manner as in Example 1 except that commercially available deuterated ethylene carbonate (Isotech: product number 57301-9) and deuterated diethyl carbonate (Isotech: product number 76050-1) were used as the electrolyte. Then, a sealed coin-type secondary battery made of deuterated rubeanic acid as the positive electrode active material and metallic lithium as the negative electrode active material was produced.

[Confirmation of secondary battery operation]
The manufactured coin-type secondary battery was charged with a constant current of 0.1 mA until the voltage reached 4.0 V, and then discharged to 1.5 V with a constant current of 0.1 mA. This battery was confirmed to be a secondary battery having a discharge capacity of 0.6 mAh having a voltage flat portion at 2.4 V and 2.0 V.

  Thereafter, charging and discharging were repeated in the range of 4.0 to 1.5V. As a result, the capacity density was 95% or more of the initial value per active material even after 20 cycles, and it was confirmed that the secondary battery had a long cycle life with little decrease in capacity even after repeated charge and discharge.

1 Lithium secondary battery (non-aqueous electrolyte secondary battery)
2 Positive electrode case (positive electrode current collector)
3 Negative electrode case 4 Positive electrode 5 Separator 6 Negative electrode 7 Negative electrode current collector 8 Metal spring 9 Electrolyte 10 Gasket

Claims (6)

A non-aqueous electrolyte secondary battery having a positive electrode containing an electrode active material and a negative electrode, and charging and discharging by an electrode reaction of the electrode active material,
The electrode active material is a deuterated organic compound containing deuterium which is a stable isotope of a hydrogen atom so that a deuteration rate is 1% or more ,
A non-aqueous electrolyte secondary battery comprising at least one of a neutral radical compound, a compound having a rubeanic acid structure, and a compound having a conjugated diamine structure as the organic compound .   2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the deuterated organic compound has a deuteration rate of 10% or more. 3. The non-aqueous solution according to claim 1 , wherein the deuterated organic compound is included in any one of a reaction starting material, a product, and an intermediate product in an electrode reaction of the electrode active material. Electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the neutral radical compound is a nitroxyl radical compound. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the compound having a rubeanic acid structure is represented by the following general formula (1).

In the general formula (1), R ₁ and R ₂ are a substituted or unsubstituted imino group, a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group. Wherein n is an integer of 1 to 100. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the compound having a conjugated diamine structure is represented by the following general formula (2).

In the general formula (2), R ₃ and R ₄ are a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted arylene group, a substituted or unsubstituted carbonyl group, a substituted Or unsubstituted acyl group, substituted or unsubstituted alkoxycarbonyl group, substituted or unsubstituted ester group, substituted or unsubstituted ether group, substituted or unsubstituted thioether group, substituted or unsubstituted amine group, substituted or Unsubstituted amide group, substituted or unsubstituted sulfone group, substituted or unsubstituted thiosulfonyl group, substituted or unsubstituted sulfonamido group, substituted or unsubstituted imine group, substituted or unsubstituted azo group, or these A linking group comprising a combination of one or more of the following.
In the general formula (2), X _{1 to} X ₄ are each a halogen atom, a hydroxyl group, a nitro group, a cyano group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, substituted or Unsubstituted cycloalkyl group, substituted or unsubstituted aromatic hydrocarbon group, substituted or unsubstituted aromatic heterocyclic group, substituted or unsubstituted aralkyl group, substituted or unsubstituted amino group, substituted or unsubstituted An alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryloxycarbonyl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted acyloxy group; These substituents may form a ring structure with the substituents.

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