JPWO2014092128A1 - Power storage device - Google Patents

Abstract

A positive electrode containing a nitroxyl compound having a nitroxyl radical cation partial structure represented by the following formula (1) in an oxidized state and a nitroxyl radical partial structure represented by the following formula (2) in a reduced state; A negative electrode containing a carbon material that can be inserted and removed, and an electrolytic solution containing a lithium salt and an aprotic organic solvent, the positive electrode contains a lithium compound, and the nitroxyl compound is a nitroxyl compound. By dropping or pouring a raw material solution in which the conductive material is dissolved or swelled and in which the conductive material is dispersed or dissolved into a solution in which the nitroxyl compound and the conductive material are not dissolved or swelled, the conductive material is contained inside the nitroxyl compound. By being obtained as a precipitate taken in, it is combined with a conductive material. Power storage device is disclosed. According to the present invention, a high-output power storage device is provided.

Description

  The present invention relates to an electricity storage device including a positive electrode including a nitroxyl compound, a negative electrode including a material capable of reversibly inserting and removing lithium ions, and an electrolytic solution including an aprotic organic solvent in which a lithium salt is dissolved. .

  In recent years, portable electronic devices such as notebook computers and mobile phones have become multifunctional, including communication functions, video playback functions, and camera functions. A power storage device used in such portable electronic devices is required to have high energy density, high output characteristics, high safety, and high cycle stability.

  A lithium ion capacitor is known as an electricity storage device having high output and high cycle stability. Since electric charges are stored by an electrostatic mechanism using an electric double layer, the energy density is small but the output is high and the cycle stability is also high. Patent Document 1 proposes storing lithium ions in advance by a chemical method for the negative electrode in order to increase the energy density. However, a sufficient energy density is still not obtained.

  Patent Document 2 proposes a power storage device containing a nitroxyl compound in a positive electrode as a high power power storage device (hereinafter, this power storage device is referred to as an “organic radical battery”). This nitroxyl compound takes an oxoammonium cation partial structure in an oxidized state, takes a nitroxyl radical partial structure in a reduced state, and transfers electrons between the two states, and this reaction is used as an electrode reaction of a positive electrode. . Since this electrode reaction proceeds relatively quickly, a high output battery can be obtained, and the battery is safe without problems such as thermal runaway. Furthermore, in order to obtain sufficient energy density and cycle stability and to further increase the output, it has been studied to store lithium ions in the negative electrode in advance. For example, Patent Document 3 proposes a method of electrically contacting a negative electrode and a lithium metal foil as a method of storing lithium ions in the negative electrode in advance.

  On the other hand, Patent Document 4 describes a battery having particles containing, as an active material, an organic compound that generates a radical compound in at least one of an electrochemical oxidation reaction and a reduction reaction. It is described that the particles are integrated with an electron conductive material. Patent Document 5 describes an electricity storage device using a conductive material-containing radical material and containing a nitroxy radical compound in an electrode.

Japanese Patent Laid-Open No. 8-1007048 JP 2002-304996 A International Publication No. 2010/140512 JP 2002-298850 A JP 2007-213992 A

  As a method for storing lithium ions in the negative electrode, as described in Patent Document 3, a lithium metal foil is used when a method in which the negative electrode is electrically contacted with the lithium metal foil in an electricity storage device is used. As a result, the cost becomes high, and safety becomes a problem when lithium metal remains after lithium ions are stored in the negative electrode. Further, in the battery described in Patent Document 4, it is considered that lithium ions are released from the negative electrode, and the output of the battery is reduced. Moreover, in the manufacturing method of the electrically conductive material containing radical material of patent document 5, it is necessary to mix an electrically conductive material in the liquid phase immediately after synthesize | combining radical material.

  The present invention provides an electricity storage device that is inexpensive, safe, and has a high output by storing a sufficient amount of lithium ions in a negative electrode in advance.

  One embodiment of the present invention takes a nitroxyl cation partial structure represented by the following formula (1) in the oxidized state and a nitroxyl radical partial structure represented by the following formula (2) in the reduced state, and between the two states It has a positive electrode containing a nitroxyl compound that performs the reaction shown in the following reaction formula (A) for transferring and receiving electrons, an negative electrode, and an electrolytic solution containing an electrolyte salt and an organic solvent, and the positive electrode serves as a lithium ion supply source. The present invention relates to an electricity storage device comprising lithium manganate, lithium iron phosphate or lithium sulfide, wherein the nitroxyl compound forms a conductive material and a nitroxyl compound / conductive material composite.

  According to the embodiment of the present invention, it is possible to provide an electricity storage device that is inexpensive, safe, and has high output.

1 is a perspective view of a laminate type electricity storage device according to an embodiment of the present invention. It is sectional drawing of the lamination type electrical storage device by embodiment of this invention.

  Next, a preferred embodiment of the present invention will be described.

  An electricity storage device according to an embodiment of the present invention includes a positive electrode including the nitroxyl compound as a positive electrode active material, a negative electrode, and an electrolytic solution including an electrolyte salt and an organic solvent. A lithium compound such as lithium manganate is added to the positive electrode as a lithium ion supply source. By dropping or pouring a raw material solution in which the nitroxyl compound is dissolved or swollen and the conductive material is dispersed or dissolved into a solution in which the nitroxyl compound and the conductive material are not dissolved or swollen, the conductive material is It is preferable that the nitroxyl compound is combined with the conductive material by being obtained as a precipitate taken into the nitroxyl compound. The negative electrode can include a material capable of reversibly occluding and releasing lithium ions as a negative electrode active material, a lithium salt can be used as an electrolyte salt, and an aprotic solvent can be used as an organic solvent.

  In the technology of the present invention, an energy storage device can be produced at low cost by adding a lithium compound in the positive electrode instead of using metal lithium in the battery configuration, and the remaining of metal lithium cannot occur. Can be secured.

  Further, instead of simply mixing the nitroxyl compound and the conductive material, the output characteristics can be improved by incorporating the conductive material into the nitroxyl compound. This is a composite of a nitroxyl compound and a conductive material that suppresses re-doping of lithium ions by lithium manganate, lithium iron phosphate, lithium sulfide, etc., and suppresses the release of lithium ions from the carbon anode. It is thought that there is. Thereby, charging and discharging of the electricity storage device can be performed in a state where a sufficient amount of lithium ions is stored in advance in the negative electrode.

  The electricity storage device according to the present embodiment can extract electrochemically stored energy in the form of electric power, and can be applied to an electric capacity device such as a primary battery, a secondary battery, a capacitor and a capacitor.

  First, materials used for manufacturing the electrode will be described.

[1] Electrode Material [1-1] Positive Electrode Active Material As the positive electrode active material in the electricity storage device according to the embodiment of the present invention, the nitroxyl cation partial structure (N-oxo-ammonium represented by the formula (1) in the oxidized state is used. A nitroxyl compound having a cation partial structure) and a nitroxyl radical partial structure represented by the formula (2) in a reduced state is used. This nitroxyl compound can perform an oxidation-reduction reaction represented by the reaction formula (A) in which electrons are transferred between these two states. The electricity storage device according to the present embodiment uses this oxidation-reduction reaction as the electrode reaction of the positive electrode.

このニトロキシル化合物の構造としては特に限定されないが、電解液に対する溶解性の観点から、ニトロキシル高分子化合物であることが好ましい。

The structure of the nitroxyl compound is not particularly limited, but is preferably a nitroxyl polymer compound from the viewpoint of solubility in the electrolytic solution.

  The nitroxyl polymer compound is preferably a polymer containing a cyclic nitroxyl structure represented by the following formula (Ia) in the side chain in an oxidized state.

（式中、Ｒ^１〜Ｒ^４はそれぞれ独立に炭素数１〜４のアルキル基を表し、Ｘは５〜７員環を形成する２価の基を表す。但し、Ｘがポリマーの側鎖の一部を構成することにより、式（Ｉａ）で示される環状ニトロキシル構造がポリマーの一部となっている。）

(In the formula, R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms, and X represents a divalent group forming a 5- to 7-membered ring, provided that X represents a side chain of the polymer. (By constituting a part, the cyclic nitroxyl structure represented by the formula (Ia) becomes a part of the polymer.)

R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 4 carbon atoms, preferably an ethyl group or a methyl group, and particularly preferably a methyl group in terms of radical stability.

X is _{specifically, -CH 2 CH 2 -, -} CH 2 CH 2 CH 2 -, - CH 2 CH 2 CH 2 CH 2 -, - CH = CH -, - CH = CHCH 2 -, - CH ═CHCH ₂ CH ₂ —, —CH ₂ CH═CHCH ₂ —, in which non-adjacent —CH ₂ — may be replaced by —O—, —NH— or —S—, -CH = may be replaced by -N =. The hydrogen atom bonded to the atoms constituting the ring may be substituted with an alkyl group, a halogen atom, ═O, an ether group, an ester group, a cyano group, an amide group, or the like.

  Particularly preferred cyclic nitroxyl structures are 2,2,6,6-tetramethylpiperidinoxyl radical (or cation), 2,2,5,5-tetramethylpyrrolidinoxyl radical (or cation), 2,2 , 5,5-tetramethylpyrrolinoxyl radical (cation), 2,2,6,6-tetramethylpiperidinoxyl radical (or cation), 2,2,5,5-tetra A methylpyrrolidinoxyl radical (or cation) is more preferred.

The cyclic nitroxyl structure represented by the formula (Ia) is, as shown in the formula (Ib), a residue X ′ obtained by removing hydrogen from —CH ₂ —, —CH═ or —NH— constituting the ring member in X. Can be attached to the polymer.

ニトロキシル高分子化合物の主鎖として用いられるポリマーとしては特に制限はなく、式（Ｉａ）で示される環状ニトロキシル構造が側鎖に存在できるものであればよい。

The polymer used as the main chain of the nitroxyl polymer compound is not particularly limited as long as the cyclic nitroxyl structure represented by the formula (Ia) can be present in the side chain.

  Examples of the nitroxyl polymer compound include those obtained by adding a group of the formula (Ib) to a normal polymer, or those obtained by substituting some atoms or groups of the polymer with a group of the formula (Ib). The atoms constituting the cyclic structure of the formula (Ib) may be bonded to the polymer (main chain) via an appropriate divalent group in the middle instead of directly. For example, X ′ and the main chain atom of the polymer can be bonded via a divalent group such as an ester bond (—COO—) or an ether bond (—O—).

  As the polymer used as the main chain of the nitroxyl polymer compound, polyalkylene polymers such as polyethylene and polypropylene; poly (meth) acrylic acid; poly (meth) acrylamide polymers are excellent in electrochemical resistance. Poly (meth) acrylate polymers and polystyrene polymers are preferred.

  Among such nitroxyl polymer compounds, those having high stability and those represented by any of the following formulas (3) to (7) are preferable.

（式中、ｎは１以上の整数である。）

(In the formula, n is an integer of 1 or more.)

  The nitroxyl polymer compound represented by the formulas (3) to (5) has a 2,2,6,6-tetramethylpiperidinoxyl radical (or cation) in the side chain, and the formulas (6), (7 The nitroxyl polymer compound shown in (2) is a polymer compound having a 2,2,5,5-tetramethylpyrrolidinoxyl radical (or cation) in the side chain. These nitroxyl polymer compounds are compounds having a sterically hindered stable radical in the side chain of the polymer.

  The molecular weight of the nitroxyl polymer compound is preferably 1000 or more, and more preferably 10,000 or more, from the viewpoint of solubility in the electrolytic solution. A higher molecular weight is preferred, but one having an average molecular weight of 5 million or less can be used. The skeleton structure of the nitroxyl polymer compound may be any of a chain, a branch, and a network, and may be a structure crosslinked with a crosslinking agent.

  Moreover, although a nitroxyl polymer compound can be used independently, you may mix and use 2 or more types.

  In view of sufficiently obtaining the effect of adding the nitroxyl polymer compound, the content of the nitroxyl polymer compound in the positive electrode active material is preferably 50% by mass or more, and more preferably 80% by mass or more.

[1-2] Conductive Material Examples of the conductive material include carbonaceous fine particles such as graphite, carbon black, and acetylene black, carbon fibers such as carbon nanotubes, and carbon materials such as activated carbon, polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. The conductive polymer is mentioned.

[1-3] Nitroxyl Compound / Conductive Material Complex In the positive electrode according to the embodiment of the present invention, the nitroxyl compound that is the positive electrode active material and the conductive material form a complex. Below, the manufacturing method of the nitroxyl compound and the electroconductive material composite based on this invention which used the nitroxyl compound and the electroconductive material as main raw materials is demonstrated.

  In the method for producing a nitroxyl compound / conductive material composite of the present invention, a raw material solution in which a nitroxyl compound having a radical partial structure in a reduced state is dissolved or swollen and a conductive material is dispersed or dissolved is used as the nitroxyl compound. In this method, a precipitate composed of a nitroxyl compound and a conductive material is generated by dropping or pouring into a solution in which the conductive material does not dissolve or swell. Since the nitroxyl compound and the conductive material are as described above, other configurations will be described below.

  The solvent constituting the raw material solution needs to be a solvent capable of dissolving or swelling the nitroxyl compound described above. Since many carbon materials and inorganic materials are usually insoluble, the solvent does not necessarily dissolve the conductive material, but it must be dispersed. Specific examples of such a solvent include N-methylpyrrolidone, tetrahydrofuran, toluene, xylene and the like. Among these, N-methylpyrrolidone is preferable.

  In preparing the raw material solution, first, the polymer radical material is dissolved in a solvent capable of dissolving or swelling the polymer radical material. There, a conductive material is added and stirred. The amount of the conductive material to be added is adjusted in consideration of electronic conductivity and the like. However, when the nitroxyl compound is 100 parts by weight, it is preferably blended in the range of 1 part by weight to 200 parts by weight. Is 1 to 100 parts by weight, more preferably 1 to 40 parts by weight. This blending amount varies depending on the type of nitroxyl compound and the type of conductive material, but when the amount of conductive material is small, the conductivity of the obtained electrode becomes insufficient, and when too large, the nitroxyl compound Since the amount of the battery becomes relatively small, the capacity of the obtained battery becomes small.

  In the present application, “dissolution” of a nitroxyl compound includes not only literally dissolution, but also includes an aspect in which it is compatible with fluidity in a solvent, and “swelling” refers to general dissolution. In other words, it includes a mode in which a so-called swollen state is produced by acting with a solvent, and the conductive material is uniformly dispersed in the nitroxyl compound by mixing with the conductive material. In addition, the “dispersion” of the conductive material includes, for example, a mode in which an insoluble material is dispersed in a solvent such as a carbon material, and the “dissolution” of the conductive material is literally dissolved in the solvent. It is intended to include compatible aspects.

  As a device used for mixing the nitroxyl compound and the conductive material, a stirring / mixing device such as a homogenizer can be used. By mixing using such an apparatus, a slurry-like raw material solution in which the conductive material is uniformly dispersed in the solution in which the nitroxyl compound is dissolved or swollen is obtained.

  The raw material solution thus obtained is dropped or poured little by little into a solvent (poor solvent) in which the nitroxyl compound and the conductive material do not dissolve or swell. By doing so, the nitroxyl compound and the conductive material can be precipitated simultaneously. Examples of the solvent (poor solvent) in which the nitroxyl compound and the conductive material do not dissolve or swell include methanol, ethanol, dimethyl ether, ethyl methyl ether, diethyl ether, hexane, heptane and the like. Among these, methanol is preferable.

  The poor solvent is selected mainly in relation to the nitroxyl compound, and in the embodiment of the present invention, mainly methanol or the like is preferably used, but other solvents may be used as long as they function as a poor solvent. Note that the conductive material is generally not easily considered because it is difficult to dissolve in an organic solvent, but the conductive material needs to be a solvent that does not dissolve or swell.

  The raw material solution is dripped little by little into such a poor solvent, or a precipitate is produced by pouring, but the manner of dripping or pouring (the amount of dripping or the dropping speed, etc.) depends on the characteristics and form of the resulting precipitate. Adjusted accordingly. In particular, in the present invention, since it is desirable that the conductive material is obtained as a precipitate taken in a state of being uniformly dispersed inside the nitroxyl compound, it is desirable to drop or pour in such a manner.

  The obtained precipitate is collected by filtration or the like and dried to obtain a nitroxyl compound / conductive material composite. The obtained nitroxyl compound / conductive material composite may be pulverized by pulverization or the like.

  As described above, according to the method for producing a nitroxyl compound / conductive material composite of the present invention, a conductive material can be uniformly dispersed in a nitroxyl compound, and the nitroxyl compound / conductive material obtained by such a production method can be dispersed. Since the material composite is obtained as a precipitate in which the conductive material is taken into the interior of the nitroxyl compound, the obtained nitroxyl compound / conductive material composite can have good electronic conductivity. As a result, the transfer of electrons accompanying the oxidation / reduction of the nitroxyl compound becomes smooth through the conductive material, and charging / discharging with a large current becomes possible. The resulting nitroxyl compound / conductive material composite also has a high proportion of radical sites that can contribute to the charge / discharge reaction, so that it can be used as an electrode material for power storage devices with little decrease in voltage even when discharged with a large current. It can be preferably used.

[1-4] Lithium ion source A lithium ion source can be used to dope the negative electrode with lithium ions. As (the _{x, 0 <x <2)} Li X Mn 2 O 4 lithium ion source, Li X _MnO 2 (x is, 0 <x ≦ 1) lithium manganate such as, LiFePO ₄ (lithium iron phosphate ), Li ₂ S (lithium sulfide), Li _X CoO ₂ (x is 0 <x ≦ 1), Li _X NiO ₂ (x is 0 <x ≦ 1), Li _X FeO ₂ (x is 0 < x ≦ 1), lithium metal oxides such as Li _x V ₂ O ₅ (x is 0 <x <2), etc., and transitions such as Li, Mg, Al, or Co, Ti, Nb, Cr, etc. A material to which a metal is added or substituted may be used. Not only these lithium compounds are used alone, but also a mixture of a plurality of them can be used. Among these, lithium manganate, lithium iron phosphate, and lithium sulfide are preferably used. The weight of the lithium compound used is 0.5% or more and 80% or less, more preferably 1% or more and 40% or less, and further preferably 1% or more and 20% or less of the weight of the positive electrode active material.

[1-5] Negative Electrode Active Material As the negative electrode active material in the electricity storage device according to the present embodiment, a material capable of reversibly occluding and releasing lithium ions (a material capable of occluding and releasing lithium ions during charging and discharging during discharging) is used. Can do. As such a negative electrode active material, carbon materials such as metal oxides and graphite can be used. The shape of these materials is not particularly limited, and examples thereof include a thin film, a powdered product, a fiber, and a flake. Moreover, these negative electrode active materials can be used alone or in combination.

[1-6] Conductivity imparting agent When forming the positive electrode and the negative electrode, a conductivity imparting agent may be further added for the purpose of reducing impedance. Examples of the conductivity imparting agent include carbonaceous fine particles such as graphite, carbon black, and acetylene black, carbon fibers such as carbon nanotubes, carbon materials such as activated carbon, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. It is done.

[1-7] Binder A binder can also be used when forming the positive electrode and the negative electrode. By using the binder, it is possible to strengthen the connection between the active materials, between the active material and the conductivity imparting agent, and between the active material or the conductivity imparting agent and the current collector. Examples of such a binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, Examples thereof include resin binders such as polypropylene, polyethylene, polyimide, partially carboxylated cellulose, and various polyurethanes.

[1-8] Current Collector An electrode material containing a positive electrode active material or a negative electrode active material can be provided on the current collector. As the current collector, a foil, sheet, flat plate or the like made of nickel, aluminum, copper, aluminum alloy, stainless steel, carbon, or the like can be used.

[2] Basic structure of power storage device, constituent member, and method for manufacturing power storage device FIG. 1 is a perspective view of an example of a laminate type power storage device according to the present embodiment, and FIG. As shown in these drawings, the electricity storage device 107 has a laminated structure including a positive electrode 101, a negative electrode 102 facing the positive electrode, and a separator 105 sandwiched between the positive electrode and the negative electrode. The electrode lead 104 is drawn out to the outside of the exterior film 106. An electrolytic solution is injected into the electricity storage device. Below, the structural member and manufacturing method of an electrical storage device are demonstrated in detail.

[2-1] Positive Electrode The positive electrode 101 includes a positive electrode active material and a lithium ion supply source, and further includes a conductivity imparting agent and a binder as necessary, and is formed on one current collector 103. The positive electrode active material of this embodiment is combined with a conductive material.

[2-2] Negative Electrode The negative electrode 102 includes a negative electrode active material, and further includes a conductivity imparting agent and a binder as necessary, and is formed on the other current collector 103.

[2-3] Separator An insulating porous separator 105 is provided between the positive electrode 101 and the negative electrode 102 to insulate and separate them. As the separator 105, a porous resin film made of polyethylene, polypropylene, or the like, a cellulose film, a non-woven cloth, or the like can be used.

[2-4] Electrolytic Solution The electrolytic solution transports the charge carrier between the positive electrode and the negative electrode, and is impregnated in the positive electrode 101, the negative electrode 102, and the separator 105. As the electrolytic solution, one having an ion conductivity of 10 ⁻⁵ to 10 ⁻¹ S / cm at 20 ° C. can be used, and a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in an organic solvent is used. it can. As the solvent for the electrolytic solution, an aprotic organic solvent can be used.

Examples of the electrolyte salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ (hereinafter “LiTFSI”), LiN (C ₂ F ₅ SO ₂ ) ₂ (hereinafter “LiBETI”). ), Li (CF ₃ SO ₂ ) ₃ C, Li (C ₂ F ₅ SO ₂ ) ₃ C, or other ordinary electrolyte materials can be used.

  Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; γ-lactones such as γ-butyrolactone; cyclics such as tetrahydrofuran and dioxolane. Ethers; amides such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone and the like. As another organic solvent, it is preferable to mix at least one of a cyclic carbonate and a chain carbonate.

[2-5] Exterior Film An aluminum laminate film or the like can be used as the exterior film 106. Examples of the exterior body other than the exterior film include a metal case and a resin case. Examples of the outer shape of the electricity storage device include a cylindrical shape, a square shape, a coin shape, and a sheet shape.

[2-6] Production Example of Electricity Storage Device The electrode laminate is obtained by placing the positive electrode 101 on the exterior film 106 and overlapping the negative electrode 102 with the separator 105 interposed therebetween. The obtained electrode laminate is covered with an exterior film 106, and three sides including the electrode lead portion are heat-sealed. An electrolyte is injected into this and vacuum impregnated. After sufficiently impregnating and filling the gap between the electrode and the separator 105 with the electrolytic solution, the remaining four sides are heat-sealed under reduced pressure, whereby a laminate-type power storage device 107 is obtained.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Synthesis of PTMA)
Poly (2,2,6,6-tetramethylpiperidinoxyl methacrylate (PTMA), which is a nitroxyl polymer used in this example, was synthesized according to the method described in JP-A-2009-238612.

  That is, it synthesize | combined according to the following description.

  In a 100 ml eggplant flask equipped with a reflux tube, 20 g (0.089 mol) of 2,2,6,6-tetramethylpiperidine methacrylate monomer was placed and dissolved in 80 ml of dry tetrahydrofuran. Thereto was added 0.29 g (0.00187 mol) of azobisisobutyronitrile (AIBN) (monomer / AIBN = 50/1), and the mixture was stirred at 75 to 80 ° C. in an argon atmosphere. After reacting for 6 hours, it was allowed to cool to room temperature. The polymer was precipitated in hexane, separated by filtration, and dried under reduced pressure to obtain poly (2,2,6,6-tetramethylpiperidine methacrylate). Next, 10 g of the obtained poly (2,2,6,6-tetramethylpiperidine methacrylate) was dissolved in 100 ml of dry-treated dichloromethane. To this, 100 ml of a dichloromethane solution of 15.2 g (0.088 mol) of m-chloroperbenzoic acid was added dropwise over 1 hour with stirring at room temperature. After further stirring for 6 hours, the precipitated m-chlorobenzoic acid was removed by filtration, and the filtrate was washed with an aqueous sodium carbonate solution and water, and then dichloromethane was distilled off. The remaining solid was pulverized, and the resulting powder was washed with diethyl carbonate (DEC) and dried under reduced pressure to obtain poly (2,2,6,6-tetramethylpiperidinoxyl methacrylate) (PTMA). Obtained.

(Preparation of negative electrode)
13.5 g of graphite powder (particle size 6 μm), 1.35 g of polyvinylidene fluoride, 0.15 g of carbon black, and 30 g of N-methylpyrrolidone were mixed and stirred with a homogenizer to prepare a uniform slurry.

  This slurry was applied onto a copper mesh as a current collector, and then dried at 120 ° C. for 5 minutes. Furthermore, the thickness was adjusted with a roll press. This was cut into a 22 × 24 mm rectangle, and a nickel electrode lead was ultrasonically bonded. The thickness of the obtained negative electrode was 50 to 60 μm.

Example 1
As a positive electrode active material, 2.1 g of PTMA was dissolved in 12 ml of N-methylpyrrolidone. Here, a carbon material (manufactured by Showa Denko, trade name: VGCF-H / highly crystalline carbon nanofiber synthesized by vapor phase method, fiber diameter 150 nm, fiber length 10 to 20 μm, aspect ratio 10 to 500 as a conductive material here. 0.42 g was added and stirred with a homogenizer to obtain a slurry in which the conductive material was uniformly dispersed in N-methylpyrrolidone in which the positive electrode active material was dissolved. By adding this slurry to 1 L of methanol little by little while stirring, the nitroxyl compound / carbon material composite was precipitated. The precipitate was filtered, and further vacuum-dried at 60 ° C. for 8 hours with a vacuum dryer to obtain a solid of a nitroxyl compound / carbon material composite. This was ground in a mortar to make a powder.

  Next, 2.1 g of a nitroxyl compound / carbon material composite, 0.2 g of lithium manganate as a lithium ion source, 0.2 g of acetylene black as a conductivity-imparting agent, 0.24 g of carboxymethyl cellulose (CMC) as a binder, and poly 0.03 g of tetrafluoroethylene (PTFE) and 15 ml of water were mixed and stirred with a homogenizer to prepare a uniform slurry.

  This slurry was applied on an aluminum foil as a current collector, and then dried at 80 ° C. for 5 minutes. Furthermore, the thickness was adjusted with a roll press. This was cut into a 22 × 24 mm rectangle, and an aluminum electrode lead was ultrasonically bonded. The thickness of the obtained positive electrode was 140 to 150 μm.

A polypropylene porous film separator was sandwiched between the positive electrode and the negative electrode to obtain an electrode laminate. The electrode laminate was covered with aluminum laminate and three sides including the electrode lead portion were heat-sealed. A mixed electrolytic solution of ethylene carbonate / diethyl carbonate = 30/70 (v / v) containing a 1 mol / L LiPF ₆ supporting salt was injected into this, and the electrode was well impregnated. The remaining four sides were thermally fused under reduced pressure to produce a laminate type electricity storage device.

  After the electricity storage device is manufactured, the current is supplied until the voltage reaches 4.6 V at a constant current of 0.1 mA, and then the current is supplied until the voltage reaches 3 V at a constant current of 0.5 mA. Lithium ions were previously stored in the negative electrode.

(Example 2)
An electricity storage device was produced in the same manner as in Example 1 except that 0.2 g of lithium iron phosphate was used as the lithium ion supply source in the slurry.

  After the electricity storage device is manufactured, the current is supplied until the voltage reaches 4.0 V at a constant current of 0.1 mA, and then the current is supplied until the voltage reaches 3 V at a constant current of 0.5 mA. Lithium ions were previously stored in the negative electrode.

(Comparative Example 1)
1.75 g of PTMA, 0.2 g of lithium manganate as a lithium ion source, 0.35 g of VGCF-H and 0.2 g of acetylene black as a conductivity-imparting agent, 0.24 g of carboxymethyl cellulose (CMC) and polytetrafluoroethylene ( PTFE) 0.03 g and water 15 ml were mixed and stirred with a homogenizer to prepare a uniform slurry.

  This slurry was applied on an aluminum foil as a current collector, and then dried at 80 ° C. for 5 minutes. Furthermore, the thickness was adjusted with a roll press. This was cut into a 22 × 24 mm rectangle, and an aluminum electrode lead was ultrasonically bonded. The thickness of the obtained positive electrode was 140 to 150 μm.

A polypropylene porous film separator was sandwiched between the positive electrode and the negative electrode to obtain an electrode laminate. The electrode laminate was covered with aluminum laminate and three sides including the electrode lead portion were heat-sealed. A mixed electrolytic solution of ethylene carbonate / diethyl carbonate = 30/70 (v / v) containing a 1 mol / L LiPF ₆ supporting salt was injected into this, and the electrode was well impregnated. The remaining four sides were thermally fused under reduced pressure to produce a laminate type electricity storage device.

  After the electricity storage device is manufactured, the current is supplied until the voltage reaches 4.6 V at a constant current of 0.1 mA, and then the current is supplied until the voltage reaches 3 V at a constant current of 0.5 mA. Lithium ions were previously stored in the negative electrode.

(Comparative Example 2)
An electricity storage device was produced in the same manner as in Comparative Example 1 except that 0.2 g of lithium iron phosphate was used as a lithium ion supply source in the slurry.

  After the electricity storage device is manufactured, the current is supplied until the voltage reaches 4.0 V at a constant current of 0.1 mA, and then the current is supplied until the voltage reaches 3 V at a constant current of 0.5 mA. Lithium ions were previously stored in the negative electrode.

(Discharge measurement and results)
The power storage devices of Examples 1 and 2 and Comparative Examples 1 and 2 were charged at 20 ° C. with a constant current of 0.5 mA until the voltage reached 4 V, and then discharged with a constant current of 10 mA until 3 V was reached. The average voltage of the electricity storage device during discharge was determined.

  Table 1 shows the average voltage results. The average voltages of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were 3.43V, 3.42V, 3.30V, and 3.34V. This is a composite of a nitroxyl compound and a conductive material, which suppresses re-doping of lithium ions by lithium manganate or lithium iron phosphate and suppresses release of lithium ions from the carbon negative electrode. 1 and 2 are considered to be because charging and discharging were possible in a state where more lithium ions were stored in the negative electrode than in Comparative Examples 1 and 2.

(Output measurement and results)
The power storage devices of Examples 1 and 2 and Comparative Examples 1 and 2 were charged at 20 ° C. with a constant current of 0.5 mA until the voltage reached 4 V, and then discharged at 10 mA for 1 second. The battery was charged again at a constant current of 0.5 mA until the voltage reached 4 V, and then discharged at 20 mA for 1 second. This charging / discharging was repeated while changing the discharge current to 30, 40, ..., 1000 mA. The output was obtained by multiplying the discharge end voltage and the measured current. The largest output among the outputs at each discharge current was defined as the maximum output.

Table 2 shows the maximum output results. The maximum outputs of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were 157 mW / cm ² , 179 mW / cm ² , 43 mW / cm ² , and 78 mW / cm ² , respectively. Thus, the output characteristics were improved by combining the nitroxyl compound with the conductive material. Similar to the results of the discharge measurement, in Examples 1 and 2, compared to Comparative Examples 1 and 2, it is considered that charging and discharging were performed in a state where more lithium ions were stored in the negative electrode.

  According to the embodiment of the present invention, an electricity storage device having a sufficient output can be provided. Therefore, the power storage device according to the embodiment of the present invention is a power storage device for driving or auxiliary such as an electric vehicle or a hybrid electric vehicle, a power source for various portable electronic devices, a power storage device for various energy such as solar energy or wind power generation, or It can be applied to a storage power source for household appliances.

DESCRIPTION OF SYMBOLS 101 Positive electrode 102 Negative electrode 103 Current collector 104 Electrode lead 105 Separator 106 Exterior film 107 Laminate type electricity storage device

Claims (7)

A positive electrode containing a nitroxyl compound having a nitroxyl radical cation partial structure represented by the following formula (1) in an oxidized state and a nitroxyl radical partial structure represented by the following formula (2) in a reduced state; A negative electrode containing a carbon material that can be inserted and removed, an electrolyte solution containing a lithium salt and an aprotic organic solvent, the positive electrode contains a lithium compound, and the nitroxyl compound is a conductive material. An electricity storage device comprising a nitroxyl compound / conductive material composite.

  The nitroxyl compound / conductive material complex is prepared by dropping a raw material solution in which a nitroxyl compound is dissolved or swollen and a conductive material is dispersed or dissolved into a solution in which the nitroxyl compound and the conductive material are not dissolved or swollen. The nitroxyl compound is combined with the conductive material by pouring to obtain the conductive material as a precipitate taken into the nitroxyl compound. The electricity storage device described.   The power storage device according to claim 1, wherein the positive electrode includes a mixture of the nitroxyl compound / conductive material composite and a lithium compound.   The power storage device according to any one of claims 1 to 3, wherein the lithium compound is lithium manganate, lithium iron phosphate, or lithium sulfide.   5. The electricity storage device according to claim 1, wherein a weight of the lithium compound is 1% or more and 20% or less of a weight of the positive electrode active material.   The weight of the conductive material taken into the nitroxyl compound is 1 part by weight or more and 200 parts by weight or less when the nitroxyl compound is 100 parts by weight. The electricity storage device according to claim 1. A nitroxyl compound having a nitroxyl radical cation partial structure represented by the following formula (1) in the oxidized state and a nitroxyl radical partial structure represented by the following formula (2) in the reduced state is dissolved or swelled, and the conductive material is By dropping or pouring the dispersed or dissolved raw material solution into a solution in which the nitroxyl compound and the conductive material do not dissolve or swell, the conductive material is obtained as a precipitate taken into the nitroxyl compound. Thus, the nitroxyl compound / conductive material composite in which the nitroxyl compound is combined with the conductive material is mixed with the lithium compound.

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