JP2002280065A - Electrolyte and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte having superior chemical stability, and a battery using the same. SOLUTION: A rolled electrode 20 having a band positive electrode 21 and a negative electrode 22 rolled via a separator 23 is provided in a battery can 11. The separator 23 is impregnated with the electrolyte. The electrolyte contains a solvent and a lithium salt dissolved in the solvent and additionally contains as an additive a material having a CSC structure with carbon, sulfur and carbon bonded. The material having the CSC structure is 1-benzothiophene or the like. Thus, the chemical stability of the electrolyte can be improved and reversibility in electrode reaction can be improved. Therefore, battery properties including discharge capacity or change/discharge cycle property can be improved and higher energy density and longer service life can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolyte used for an electrochemical device such as a battery, and a battery using the same.

[0002]

2. Description of the Related Art In recent years, portable electronic devices typified by a camera-integrated VTR (video tape recorder), a cellular phone or a laptop computer have become widespread, and their miniaturization, weight reduction and continuous driving for a long time are strongly demanded. Have been. Along with this, demands for higher capacity and higher energy density of secondary batteries as those portable power sources are increasing.

As a secondary battery capable of obtaining a high energy density, for example, a lithium ion secondary battery using a material capable of inserting and extracting lithium (Li) such as a carbon material for a negative electrode, or There is a lithium ion secondary battery using lithium metal for the negative electrode. These secondary batteries are expected to provide a higher energy density than conventional non-aqueous electrolyte secondary batteries, such as lead batteries or nickel cadmium batteries.

[0004]

However, the voltage of a lithium battery or a lithium ion secondary battery is three times or more that of a battery using an aqueous electrolyte such as a nickel cadmium battery. There is a problem that the existing electrolyte is exposed to a strong oxidizing or reducing atmosphere. Therefore, when the chemical stability of the electrolyte is insufficient, the reversibility of the electrode reaction is impaired, and the energy density is reduced due to the reduction in charge and discharge efficiency,
Alternatively, the capacity may be significantly deteriorated due to repetition of the charge / discharge cycle.

[0005] These problems are not limited to the conventional lithium ion secondary battery or lithium secondary battery, but secondary batteries recently developed by the inventors for realizing a higher energy density, for example, The same applies to a secondary battery in which the capacity of the negative electrode is represented by the sum of a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium.

The present invention has been made in view of such problems, and an object of the present invention is to provide an electrolyte having excellent chemical stability and a battery using the same.

[0007]

The electrolyte according to the present invention comprises:
It contains a substance having a CSC structure in which carbon (C), sulfur (S), and carbon shown in Chemical formula 8 are bonded.

[0008]

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The battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the electrolyte contains a substance having a CSC structure in which carbon, sulfur and carbon are combined as shown in Chemical formula 9.

[0010]

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Another battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the capacity of the negative electrode is the sum of a capacity component due to absorption and desorption of light metal and a capacity component due to precipitation and dissolution of light metal. The electrolyte is represented by a CS in which carbon, sulfur, and carbon shown in Chemical Formula 10 are bonded.
It contains a substance having a C structure.

[0012]

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In the electrolyte according to the present invention, the C
Since a substance having an SC structure is included, chemical stability is improved.

The batteries according to the invention and other batteries are provided with the electrolyte according to the invention, so that the chemical stability of the electrolyte is improved, for example the reversibility of the electrode reaction is improved,
Discharge capacity or charge / discharge cycle characteristics are improved.

[0015]

Embodiments of the present invention will be described below in detail.

The electrolyte according to one embodiment of the present invention is configured to include, for example, an electrolyte salt and a solvent that dissolves the electrolyte salt. The electrolyte salt is for imparting ionic conductivity by dissociation. As the electrolyte salt,
Light metal salts and the like, specifically, lithium (L
i) Salt, sodium (Na) salt or potassium (K)
Alkali metal salts such as salts, or magnesium (Mg)
One or two or more salts or alkaline earth metal salts such as calcium (Ca) salts or aluminum (Al) salts are used depending on the purpose.

As the lithium salt, for example, Li
AsF ₆ , LiPF ₆ , LiBF ₄ , LiClO ₄ , L
iB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ S
O ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF
₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, LiBr and the like.
Species or a mixture of two or more species is used.

The content (concentration) of the electrolyte salt is preferably not more than 3.0 mol / kg with respect to the solvent.
More preferably, it is 5 mol / kg or more. This is because the ionic conductivity of the electrolytic solution can be increased within this range.

The solvent is composed of, for example, a non-aqueous solvent such as a liquid organic solvent. The liquid non-aqueous solvent is, for example, one composed of one or more non-aqueous compounds and having an intrinsic viscosity at 25 ° C. of 10.0 mPa · s or less. In addition, the intrinsic viscosity in a state where the electrolyte salt is dissolved is 1
It may be 0.0 m · Pa or less, and when a plurality of non-aqueous compounds are mixed to form a solvent, the intrinsic viscosity in the mixed state may be 10.0 m · Pa or less. As such a non-aqueous solvent, for example, a mixture of one or more substances represented by a cyclic carbonate or a chain carbonate is preferable.

Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran,
2-methyltetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-dioxolan, methyl acetate,
Methyl propionate, ethyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropyronitrile, N, N-dimethylformamide, N-
Methylpyrrolidinone, N-methyloxazolidinone,
N, N'-dimethylimidazolidinone, nitromethane,
Nitroethane, sulfolane, dimethyl sulfoxide,
Trimethyl phosphate and those obtained by substituting a part or all of the hydroxyl groups of these compounds with a fluorine group are exemplified.

In particular, when this electrolyte is used for a battery using a carbon material for the negative electrode, for example, ethylene carbonate, propylene carbonate, vinylene carbonate,
It is preferable to use at least one of dimethyl carbonate and ethyl methyl carbonate. This is because excellent capacity characteristics and charge / discharge cycle characteristics can be obtained.

This electrolyte is also used as an additive.
1 containing a substance having a CSC structure in which carbon, sulfur and carbon are bonded. Thereby, in this electrolyte, chemical stability can be improved.

[0023]

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The substance having the CSC structure includes CSC
A heterocyclic compound having a structure is preferable because a high effect can be obtained. Such substances include, for example,
And a thiophene represented by the structural formula shown in Chemical Formula 13;
1-benzothiophene represented by the structural formula shown in Chemical Formula 14, isonatothiophene represented by the structural formula shown in Chemical Formula 15, allylthiophene represented by the structural formula shown in Chemical Formula 16, and shown in Chemical Formula 17 Vinylene thiophene represented by the structural formula, alkylthiophene represented by the structural formula shown in Chemical formula 18, and the like can be given. Among them, 1-benzothiophene shown in Chemical formula 14 is particularly preferable since a higher improvement effect can be obtained. One of these substances having the CSC structure may be used alone, or two or more may be used in combination. When two or more kinds are used in combination, a synergistic property improving effect is also expected.

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

Embedded image (Wherein, C _n H _{2n + 1} is, n represents one or more optional alkyl groups is an integer.)

The content of the substance having the CSC structure is as follows:
It depends on the molecular structure of the substance having the CSC structure or the type of the electrode or the solvent.
It is preferably in the range of 5% by mass to 30% by mass, and more preferably in the range of 0.1% by mass to 20% by mass. This is because a higher improvement effect can be obtained within this range.

The electrolyte may be a so-called liquid electrolyte comprising these electrolyte salts, a liquid solvent and additives, but may further contain a polymer compound holding them, and form a gel. It may be. In this case, the type and amount of the polymer compound are preferably adjusted so that the ionic conductivity is 1 mS / cm or more at room temperature.

Examples of the high molecular compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, and polyphosphazene. , Polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, a polymer compound having a structure of polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable from the viewpoint of electrochemical stability.

Some of these high molecular compounds do not have ionic conductivity, but some of them can dissociate the electrolyte salt and act as a transfer medium for the dissociated ions. Good. However, the polymer salt that can dissociate the electrolyte salt and acts as a moving medium for the dissociated ions also functions as a solvent. Therefore, such a polymer compound is included in the solvent when defining the content of the electrolyte salt or the content of the substance having the CSC structure.

The amount of the polymer compound added to the electrolyte is
Usually, it is preferably in the range of 5% by mass to 50% by mass of the electrolytic solution, though it depends on the compatibility of both.

This electrolyte can be produced, for example, by dissolving an electrolyte salt in a solvent and then adding a substance having a CSC structure. In the case of forming a gel, for example, the electrolyte can be produced by mixing the electrolytic solution with a monomer which is a starting material of a polymer compound, and polymerizing the monomer.

As described above, according to the electrolyte according to the present embodiment, since the substance having the CSC structure is included,
Chemical stability can be improved. Therefore, if an electrochemical element such as a battery is formed using this electrolyte, its characteristics can be further improved.

Such an electrolyte is preferably used in, for example, the following secondary batteries. Here, an example of a secondary battery using lithium as an electrode reactive species will be described with reference to the drawings.

FIG. 1 shows a sectional structure of a secondary battery using the electrolyte according to the present embodiment. This secondary battery is a so-called jelly roll type,
A band-shaped positive electrode 21 is provided inside a substantially hollow cylindrical battery can 11.
And a negative electrode 22 having a wound electrode body 20 wound with a separator 23 interposed therebetween. The battery can 11 is made of, for example, nickel-plated iron, and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are respectively arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

At the open end of the battery can 11, a battery cover 14 is provided.
And a safety valve mechanism 15 provided inside the battery lid 14.
And Positive Temperature Coefficie
nt; PTC element) 16 and caulked via a gasket 17, and the battery can 11
The inside is closed. The battery cover 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery cover 14 via the thermal resistance element 16, and when the internal pressure of the battery becomes higher than a certain level due to an internal short circuit or external heating, the disk plate 15a is inverted. Then, the electrical connection between the battery cover 14 and the spirally wound electrode body 20 is cut off. Thermal resistance element 1
Reference numeral 6 denotes an element for limiting the current by increasing the resistance value when the temperature rises and preventing abnormal heat generation due to a large current, and is made of, for example, a barium titanate-based semiconductor ceramic. The gasket 17 is made of, for example, an insulating material, and its surface is coated with asphalt.

The wound electrode body 20 is wound around, for example, a center pin 24. Positive electrode 2 of wound electrode body 20
1 is connected to a positive electrode lead 25 made of aluminum or the like, and the negative electrode 22 is connected to a negative electrode lead 26 made of nickel or the like. The positive electrode lead 25 is electrically connected to the battery cover 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode mixture layer 21b is provided on both surfaces of a positive electrode current collector 21a having a pair of opposing surfaces. Although not shown, the positive electrode mixture layer 21b may be provided only on one side of the positive electrode current collector 21a. Positive electrode current collector 21a
Has a thickness of, for example, about 5 μm to 50 μm, and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer 21b has a thickness of, for example, 80 μm to 250 μm and includes a positive electrode material capable of inserting and extracting lithium as a light metal. When the positive electrode mixture layer 21b is provided on both surfaces of the positive electrode current collector 21a, the thickness of the positive electrode mixture layer 21b is the total thickness thereof.

As the positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound such as lithium oxide, lithium sulfide or an intercalation compound containing lithium is suitable. You may use it. In particular, to increase the energy density, a lithium composite oxide represented by the general formula Li _x MO ₂ or an intercalation compound containing lithium is preferable. In addition, M is preferably one or more transition metals. Specifically, cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), aluminum (Al), vanadium (V) and titanium ( At least one of Ti)
Species are preferred. x differs depending on the charge / discharge state of the battery, and is usually a value in the range of 0.05 ≦ x ≦ 1.10. In addition, LiM having a spinel type crystal structure is also used.
n ₂ O ₄ or LiF having an olivine type crystal structure
ePO _{4 is} also preferable because a high energy density can be obtained.

Incidentally, such a positive electrode material includes, for example, lithium carbonate, nitrate, oxide or hydroxide,
It is prepared by mixing and pulverizing a transition metal carbonate, nitrate, oxide or hydroxide to have a desired composition, followed by calcination in an oxygen atmosphere at a temperature in the range of 600 ° C to 1000 ° C. Is done.

The positive electrode mixture layer 21b also contains, for example, a conductive agent, and may further contain a binder if necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black and Ketjen black, and one or more of them are used in combination. Further, in addition to the carbon material, a metal material or a conductive polymer material may be used as long as the material has conductivity. Examples of the binder include synthetic rubbers such as styrene-butadiene rubber, fluorine rubber and ethylene propylene diene rubber, and polymer materials such as polyvinylidene fluoride, and one or more of them are mixed. Used as For example,
When the positive electrode 21 and the negative electrode 22 are wound as shown in FIG. 1, it is preferable to use a highly flexible styrene-butadiene-based rubber or a fluorine-based rubber as the binder.

The negative electrode 22 has, for example, a structure in which a negative electrode mixture layer 22b is provided on both surfaces of a negative electrode current collector 22a having a pair of opposing surfaces. Although not shown, the negative electrode mixture layer 22b may be provided only on one side of the negative electrode current collector 22a. The negative electrode current collector 22a is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil having good electrochemical stability, electric conductivity, and mechanical strength. In particular, copper foil is most preferable because it has high electric conductivity. The thickness of the negative electrode current collector 22a is preferably, for example, about 6 μm to 40 μm. 6μ
If the thickness is smaller than m, the mechanical strength is reduced, the anode current collector 22a is easily broken in the manufacturing process, and the production efficiency is reduced. The volume ratio becomes larger than necessary,
This is because it becomes difficult to increase the energy density.

The negative electrode mixture layer 22b is composed of one or more negative electrode materials capable of inserting and extracting lithium as a light metal. A binder similar to that of the agent layer 21b may be included. The thickness of the negative electrode mixture layer 22b is, for example, 8
0 μm to 250 μm. The thickness of the negative electrode mixture layer 2
When 2b is provided on both surfaces of the negative electrode current collector 22a, it is the total thickness thereof.

It should be noted that, in the present specification, the term "storage / release of light metal" means that light metal ions are electrochemically stored / released without losing their ionicity. This includes not only the case where the occluded light metal exists in a perfect ionic state but also the case where the occluded light metal exists in a state that cannot be said to be a perfect ionic state. Such cases include, for example, occlusion by electrochemical intercalation reaction of light metal ions with respect to graphite. Further, occlusion of light metals by forming an intermetallic compound or an alloy can also be mentioned.

Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon and graphitizable carbon. These carbon materials are preferable because a change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good charge and discharge cycle characteristics can be obtained. Particularly, graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density.

As the graphite, for example, the true density is 2.10
g / cm ³ or more, preferably 2.18 g / cm ³
The above is more preferable. In order to obtain such a true density, the C-axis crystallite thickness of the (002) plane must be 1
It is necessary to be 4.0 nm or more. Also, (00
2) The spacing between the surfaces is preferably less than 0.340 nm, and more preferably 0.335 nm or more and 0.337 nm or less.

The graphite may be natural graphite or artificial graphite.
In the case of artificial graphite, for example, it can be obtained by carbonizing an organic material, performing a high-temperature heat treatment, and pulverizing and classifying. The high-temperature heat treatment is performed by, for example, carbonizing at 300 ° C. to 700 ° C. in an inert gas stream such as nitrogen (N ₂ ) as necessary,
The temperature is raised from 900 ° C to 1500 ° C at a rate of 1 ° C to 100 ° C per minute, the temperature is maintained for about 0 hours to 30 hours, and calcined, and heated to 2000 ° C or more, preferably 2500 ° C or more. This is performed by maintaining the temperature for an appropriate time.

As the organic material used as a starting material, coal or pitch can be used. For the pitch, for example, tars obtained by pyrolyzing coal tar, ethylene bottom oil or crude oil at a high temperature, asphalt, etc. (vacuum distillation, normal pressure distillation or steam distillation), thermal polycondensation, extraction, Examples include those obtained by chemical polycondensation, those produced at the time of wood reflux, polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, and 3,5-dimethylphenol resin.
These coals or pitches have a maximum of 400
It exists as a liquid at about ℃, and aromatic rings are condensed and polycyclic by being held at that temperature, and it is in a laminated orientation state, and then becomes a solid carbon precursor at about 500 ° C. or higher, that is, semi-coke. (Liquid phase carbonization process).

Examples of the organic material include condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphen, and pentacene, and derivatives thereof (for example, carboxylic acids and carboxylic anhydrides of the above compounds). , Carboximides), or mixtures thereof. Further, condensed heterocyclic compounds such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine and derivatives thereof;
Alternatively, a mixture thereof can be used.

The pulverization may be performed before or after carbonization or calcination, or during the heating process before graphitization. In these cases, heat treatment for graphitization is finally performed in a powder state. However, to obtain graphite powder with high bulk density and high breaking strength, heat treatment is performed after molding the raw material,
It is preferable to pulverize and classify the obtained graphitized molded body.

For example, in the case of producing a graphitized molded body, coke as a filler and binder pitch as a molding agent or a sintering agent are mixed and molded. And the pitch impregnating step of impregnating the sintered body with the melted binder pitch is repeated several times, followed by heat treatment at a high temperature. The impregnated binder pitch is carbonized and graphitized in the above heat treatment process. By the way, in this case,
Since filler (coke) and binder pitch are used as raw materials, it is graphitized as a polycrystal, and since sulfur and nitrogen contained in the raw materials are generated as a gas during heat treatment, minute holes are formed in the passage. It is formed. Accordingly, the vacancies facilitate the progress of the insertion and extraction reaction of lithium, and also have the advantage of high industrial processing efficiency. In addition, as a raw material of the molded body, the moldability itself,
A filler having sinterability may be used. In this case, it is not necessary to use a binder pitch.

The non-graphitizable carbon has a (002) plane spacing of 0.37 nm or more and a true density of 1.70 g / cm.
With less than ^3, differential thermal analysis in air (Differen
Those which do not show an exothermic peak above 700 ° C. in tial thermal analysis (DTA) are preferred.

Such non-graphitizable carbon can be obtained, for example, by subjecting an organic material to a heat treatment at about 1200 ° C., followed by pulverization and classification. The heat treatment is, for example, 3
After carbonization at 00 ° C to 700 ° C (solid carbonization process),
The temperature is raised from 900 ° C. to 1300 ° C. at a rate of 1 ° C. to 100 ° C. per minute, and the temperature is maintained for about 0 to 30 hours. The pulverization may be performed before or after carbonization, or during the heating process.

As the organic material used as a starting material, for example, furfuryl alcohol or furfural polymer or copolymer, or furan resin which is a copolymer of these polymers and other resins can be used. . Also,
Phenol resin, acrylic resin, vinyl halide resin, polyimide resin, polyamide imide resin, polyamide resin, conjugated resin such as polyacetylene or polyparaphenylene, cellulose or derivatives thereof, coffee beans, bamboo, shellfish including chitosan, bacteria Biocelluloses utilizing the same can also be used. Furthermore, the atomic ratio H / of hydrogen atoms (H) and carbon atoms (C)
A compound in which a functional group containing oxygen (O) is introduced (so-called oxygen cross-linking) into petroleum pitch in which C is, for example, 0.6 to 0.8 can also be used.

The oxygen content of this compound is preferably at least 3%, more preferably at least 5% (see Japanese Patent Application Laid-Open No. 3-252553). The oxygen content affects the crystal structure of the carbon material, and at a higher content, the physical properties of the non-graphitizable carbon can be increased.
This is because the capacity of the negative electrode 22 can be improved.
Incidentally, petroleum pitch is, for example, coal tar, tar bottoms obtained by pyrolyzing ethylene bottom oil or crude oil at high temperature, or asphalt,
It is obtained by distillation (vacuum distillation, normal pressure distillation or steam distillation), thermal polycondensation, extraction or chemical polycondensation. Examples of the oxidative crosslinking method include nitric acid,
A wet method in which an aqueous solution of sulfuric acid, hypochlorous acid, or a mixed acid thereof is reacted with petroleum pitch, a dry method in which an oxidizing gas such as air or oxygen is reacted with petroleum pitch, or sulfur, ammonium nitrate, ammonium persulfate, A method of reacting a solid reagent such as ferric chloride with petroleum pitch can be used.

The organic material used as a starting material is not limited to these, and any other organic material may be used as long as it is an organic material that can be made non-graphitizable carbon through a solid phase carbonization process by oxygen crosslinking or the like.

As the non-graphitizable carbon, those produced using the above-mentioned organic materials as starting materials, as well as those described in
A compound containing phosphorus (P), oxygen and carbon as main components described in 37010 is also preferable because it shows the above-mentioned physical property parameters.

Examples of the negative electrode material capable of inserting and extracting lithium include a metal or a semiconductor capable of forming an alloy or a compound with lithium, or an alloy or a compound thereof. These are preferable because a high energy density can be obtained, and it is more preferable to use them together with a carbon material because a high energy density can be obtained and excellent cycle characteristics can be obtained.

As such a metal or semiconductor,
For example, tin (Sn), lead (Pb), aluminum (A
l), indium (In), silicon (Si), zinc (Z
n), antimony (Sb), bismuth (Bi), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr)
And yttrium (Y). These alloys or compounds, e.g., chemical formula Ma _s Mb _t
Li _u, or include those represented by the chemical formula Ma _p Mc _q Md _r. In these chemical formulas, Ma represents at least one of a metal element and a semiconductor element capable of forming an alloy or a compound with lithium; Mb represents at least one of a metal element and a semiconductor element other than lithium and Ma; Represents at least one kind of non-metallic element, and Md represents at least one kind of metallic element and semiconductor element other than Ma. Also, s, t, u,
The values of p, q and r are s> 0, t ≧ 0, u ≧
0, p> 0, q> 0, r ≧ 0.

Among them, a metal element or a semiconductor element of group 4B, or an alloy or compound thereof is preferable.
Particularly preferred are silicon or tin, or alloys or compounds thereof. These may be crystalline or amorphous.

For such an alloy or compound,
To give an example, LiAl, AlSb, CuMgS
b, SiB_Four, SiB₆, Mg_TwoSi, Mg_TwoSn, N
i_TwoSi, TiSi_Two, MoSi_Two, CoSi_Two, Ni
Si_Two, CaSi_Two, CrSi_Two, Cu_FiveSi, FeS
i_Two, MnSi_Two, NbSi_Two, TaSi_Two, VS
i _Two, WSi_Two, ZnSi_Two, SiC, Si_ThreeN_Four, S
i_TwoN_TwoO, SiO_v(0 <v ≦ 2), SnO_w(0 <
w ≦ 2), SnSiO_Three, LiSiO or LiSn
O and the like.

Examples of the negative electrode material capable of inserting and extracting lithium include other metal compounds and polymer materials. Examples of other metal compounds include oxides such as iron oxide, ruthenium oxide, and molybdenum oxide, and LiN _3. Examples of polymer materials include polyacetylene, polyaniline, and polypyrrole.

In this secondary battery, during the charging process, lithium metal starts to precipitate on the negative electrode 22 when the open circuit voltage (that is, the battery voltage) is lower than the overcharge voltage. That is, when the open circuit voltage is lower than the overcharge voltage, lithium metal is deposited on the negative electrode 22, and the capacity of the negative electrode 22 is based on the capacity component due to insertion and extraction of lithium and the capacity component due to deposition and dissolution of lithium metal. And the sum of Therefore, in this secondary battery, both the negative electrode material capable of inserting and extracting lithium and the lithium metal function as the negative electrode active material, and the negative electrode material capable of inserting and extracting lithium is the base material when the lithium metal is deposited. It has become.

The overcharge voltage refers to an open circuit voltage when the battery is overcharged. For example, one of the guidelines set by the Japan Storage Battery Association (Battery Manufacturers Association) is “lithium”. Guideline for Secondary Battery Safety Evaluation Standards ”(S
"Full charge" as defined and defined in BA G1101)
Refers to a voltage higher than the open circuit voltage of the battery. In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, the standard charging method, or the recommended charging method used to determine the nominal capacity of each battery. Specifically, in this secondary battery, for example, the battery is fully charged when the open circuit voltage is 4.2 V, and the negative electrode capable of inserting and extracting lithium in a part of the open circuit voltage in the range of 0 V or more and 4.2 V or less. Lithium metal is deposited on the surface of the material.

As a result, in this secondary battery, a high energy density can be obtained, and the cycle characteristics and the rapid charging characteristics can be improved. This is similar to a so-called lithium secondary battery using lithium metal or a lithium alloy for the negative electrode in that lithium metal is deposited on the negative electrode 22, but deposits lithium metal on a negative electrode material capable of inserting and extracting lithium. This is considered to be because the following advantages are obtained.

First, it is difficult to deposit lithium metal uniformly in a so-called lithium secondary battery, which causes deterioration of cycle characteristics. However, a negative electrode material capable of inserting and extracting lithium is generally used. In this secondary battery, lithium metal can be uniformly deposited because the surface area is large. Secondly, in a so-called lithium secondary battery, the volume change accompanying the precipitation and elution of lithium metal is large, which also causes deterioration of the cycle characteristics. In this secondary battery, a negative electrode capable of inserting and extracting lithium is used. The lithium metal precipitates also in the gaps between the particles of the material, so that the volume change is small. Third, in a so-called lithium secondary battery, the larger the amount of lithium metal deposited / dissolved, the greater the above problem. However, in this secondary battery, lithium is inserted / extracted by a negative electrode material capable of inserting / extracting lithium. Also contributes to the charge / discharge capacity, which means that the amount of lithium metal deposited and dissolved is small in spite of the large battery capacity. Fourth, in a so-called lithium secondary battery, when rapid charging is performed, lithium metal is more unevenly deposited, thereby further deteriorating the cycle characteristics. However, in this secondary battery, lithium is initially stored and charged. Since lithium is occluded in the detachable negative electrode material, rapid charging becomes possible.

In order to obtain these advantages more effectively, for example, the maximum deposition capacity of lithium metal deposited on the negative electrode 22 at the maximum voltage before the open circuit voltage becomes the overcharge voltage is determined as follows. It is preferable that the charge capacity is 0.05 times or more and 3.0 times or less the rechargeable negative electrode material. If the amount of lithium metal deposited is too large, a problem similar to that of a so-called lithium secondary battery occurs. If the amount is too small, the charge / discharge capacity cannot be sufficiently increased. Also, for example, the discharge capacity of the negative electrode material capable of inserting and extracting lithium is preferably 150 mAh / g or more. This is because the greater the ability to insert and extract lithium, the smaller the amount of lithium metal deposited. The charge capacity of the negative electrode material can be determined, for example, from the amount of electricity when a negative electrode using lithium metal as a counter electrode and the negative electrode material as a negative electrode active material is charged by a constant current / constant voltage method until the voltage becomes 0 V. The discharge capacity capacity of the negative electrode material is obtained, for example, from the quantity of electricity when the negative electrode is discharged until the potential of the negative electrode becomes 2.5 V over 10 hours or more by a constant current method.

The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene or polyethylene, or a porous film made of ceramic. The structure may be modified. Above all, a polyolefin porous film is preferable because it has an excellent short-circuit prevention effect and can improve battery safety by a shutdown effect. In particular, polyethylene is 100
Since the shutdown effect can be obtained in the range of not less than 160 ° C. and the electrochemical stability is excellent, it is preferable as the material forming the separator 23. In addition, polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

The porous film made of polyolefin is prepared, for example, by kneading a liquid low-volatile solvent in a molten state with a polyolefin composition in a molten state to obtain a uniform high-concentration solution of the polyolefin composition. Molded by
It is obtained by cooling into a gel-like sheet and stretching.

As the low volatile solvent, for example, nonane,
Low volatile aliphatic or cyclic hydrocarbons such as decane, decalin, p-xylene, undecane or liquid paraffin can be used. The mixing ratio of the polyolefin composition and the low-volatile solvent is 100% by mass of the total of both.
The content of the polyolefin composition is preferably from 10% by mass to 80% by mass, and more preferably from 15% by mass to 70% by mass. If the amount of the polyolefin composition is too small, swelling or neck-in becomes large at the die exit during molding, and sheet molding becomes difficult. on the other hand,
If the amount of the polyolefin composition is too large, it is difficult to prepare a uniform solution.

When a high-concentration solution of the polyolefin composition is molded with a die, in the case of a sheet die, the gap is preferably, for example, 0.1 mm or more and 5 mm or less. Further, the extrusion temperature is preferably from 140 ° C. to 250 ° C., and the extrusion speed is preferably from 2 cm / min to 30 cm / min.

The cooling is performed to at least the gelling temperature or lower. As a cooling method, a method of directly contacting with cold air, cooling water, or another cooling medium, a method of contacting with a roll cooled by a refrigerant, or the like can be used. The high-concentration solution of the polyolefin composition extruded from the die may be taken at a take-up ratio of 1 to 10 and preferably 1 to 5 before or during cooling. If the take-up ratio is too large, neck-in becomes large, and breakage tends to occur during stretching, which is not preferable.

The stretching of the gel-like sheet is preferably carried out by biaxial stretching, for example, by heating this gel-like sheet and employing a tenter method, a roll method, a rolling method or a combination thereof. At that time, either vertical or horizontal simultaneous stretching or sequential stretching may be used, but simultaneous secondary stretching is particularly preferable.
The stretching temperature is preferably equal to or lower than the temperature obtained by adding 10 ° C. to the melting point of the polyolefin composition, and more preferably equal to or higher than the crystal dispersion temperature and lower than the melting point. If the stretching temperature is too high, an effective molecular chain orientation due to stretching cannot be performed due to melting of the resin, which is not preferable.If the stretching temperature is too low, the softening of the resin becomes insufficient and the film breaks during stretching. This is because it is easy to perform stretching at a high magnification.

After stretching the gel-like sheet, it is preferable to wash the stretched film with a volatile solvent to remove the remaining low-volatile solvent. After washing, the stretched film is dried by heating or blowing, and the washing solvent is volatilized. As the cleaning solvent, for example, pentane, hexane,
A volatile substance such as a hydrocarbon such as hebutane, a chlorinated hydrocarbon such as methylene chloride or carbon tetrachloride, a fluorocarbon such as ethane trifluoride, or an ether such as diethyl ether or dioxane is used. The washing solvent is selected according to the low-volatile solvent used, and used alone or in combination. The washing can be performed by a method of immersing in a volatile solvent for extraction, a method of sprinkling with a volatile solvent, or a method of combining these. This washing is performed until the residual low-volatile solvent in the stretched film becomes less than 1 part by mass with respect to 100 parts by mass of the polyolefin composition.

The separator 23 is impregnated with the electrolyte according to the present embodiment. This electrolyte contains a lithium salt as an electrolyte salt. In the present embodiment, since the electrolyte contains a substance having a CSC structure, the chemical stability of the electrolyte is increased, the reversibility of the electrode reaction is improved, and the discharge capacity or charge / discharge cycle characteristics are improved. It can be improved.

This secondary battery can be manufactured, for example, as follows.

First, for example, a positive electrode mixture is prepared by mixing a positive electrode material capable of inserting and extracting lithium, a conductive agent, and a binder, and this positive electrode mixture is mixed with N-methyl-2-pyrrolidone or the like. To a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is applied to the positive electrode current collector 21a, the solvent is dried, and then compression-molded by a roll press or the like to form the positive electrode mixture layer 21b, and the positive electrode 21 is manufactured.

Next, for example, a negative electrode material is prepared by mixing a negative electrode material capable of inserting and extracting lithium and a binder, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone. To form a paste-like negative electrode mixture slurry.
The negative electrode mixture slurry is applied to the negative electrode current collector 22a, the solvent is dried, and then compression-molded by a roll press or the like to form the negative electrode mixture layer 22b, thereby producing the negative electrode 22.

Subsequently, the positive electrode lead 2 is connected to the positive electrode current collector 21a.
5 is attached by welding or the like.
The negative electrode lead 26 is attached to “a” by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound via the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 sandwiched between the pair of insulating plates 12 and 13 are housed inside the battery can 11. After housing the positive electrode 21 and the negative electrode 22 inside the battery can 11, an electrolyte is injected into the inside of the battery can 11,
3 impregnated. After that, the battery lid 14, the safety valve mechanism 15, and the thermal resistance element 16 are fixed to the open end of the battery can 11 by caulking via the gasket 17.

The positive electrode lead 25 and the negative electrode lead 2
After attaching 6, the electrolyte may be applied to the positive electrode mixture layer 21b and the negative electrode mixture layer 22b, and the positive electrode 21 and the negative electrode 22 may be wound via the separator 23. After that, as described above, it is stored inside the battery can 11,
The battery cover 14 is fixed. Thereby, the secondary battery shown in FIG. 1 is formed.

This secondary battery operates as follows.

In this secondary battery, when charged, lithium ions are released from the positive electrode mixture layer 21b, and the separator 2
First, the negative electrode mixture layer 22
The lithium contained in b is stored in a negative electrode material that can be inserted and extracted. When charging is further continued, in the state where the open circuit voltage is lower than the overcharge voltage, the charge capacity exceeds the charge capacity capacity of the negative electrode material capable of inserting and extracting lithium, and the surface of the negative electrode material capable of inserting and extracting lithium is charged. Lithium metal begins to precipitate. Thereafter, lithium metal continues to be deposited on the negative electrode 22 until charging is completed. As a result, the appearance of the negative electrode mixture layer 22b changes from black to golden, and further to white silver when, for example, a carbon material is used as the negative electrode material capable of inserting and extracting lithium.

Next, when discharging is performed, first, the lithium metal deposited on the negative electrode 22 is eluted as ions, and is passed through the electrolyte impregnated in the separator 23.
b. When the discharge is further continued, the negative electrode mixture layer 22
The lithium ions occluded in the negative electrode material capable of occluding and releasing lithium in b are released and occluded in the positive electrode mixture layer 21b via the electrolytic solution. Therefore, in this secondary battery, characteristics of both a so-called lithium secondary battery and a lithium ion secondary battery, that is, high energy density and good charge / discharge cycle characteristics can be obtained.

In particular, in the present embodiment, since the electrolyte contains a substance having a CSC structure, the chemical stability of the electrolyte is improved, the reversibility of the electrode reaction is improved, and the discharge capacity or charge / discharge cycle characteristics are improved. Is more improved.

As described above, according to the present embodiment, since the electrolyte contains the substance having the CSC structure, the chemical stability of the electrolyte can be improved, the reversibility of the electrode reaction can be improved, and the discharge can be improved. Battery characteristics such as capacity or charge / discharge cycle characteristics can be further improved. Therefore, higher energy density and longer life can be realized.

In the above description, the capacity of the negative electrode 22 depends on the capacity component due to insertion and extraction of lithium, and the capacity of lithium deposition / desorption.
The secondary battery represented by the sum of the capacity component due to dissolution has been described as an example, but the electrolyte according to the present embodiment can be similarly used for a secondary battery having another configuration.

As a secondary battery having another configuration, for example, a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium, or a capacity of the negative electrode in which lithium metal is deposited and deposited. A so-called lithium secondary battery represented by a capacity component due to dissolution is exemplified.
Lithium ion secondary batteries, for example, occlude lithium
The secondary battery has the same configuration as the above secondary battery except that the amount of the detachable negative electrode material is relatively larger than the positive electrode material, and lithium metal does not precipitate on the negative electrode during charging. Further, the lithium secondary battery has the same configuration as the above-described secondary battery except that, for example, the negative electrode is made of lithium metal or the like.

Therefore, the same effects as those of the above secondary battery can be obtained by using the electrolyte according to the present embodiment also in these secondary batteries. That is, the chemical stability of the electrolyte can be improved, and the reversibility of the electrode reaction can be improved. Therefore, the discharge capacity or the charge / discharge cycle characteristics can be further improved, and higher energy density and longer life can be realized.

[0094]

EXAMPLES Further, specific examples of the present invention will be described in detail. 1 and 2 in the following embodiment.
A jelly roll type secondary battery as shown in was manufactured.
Therefore, here, the description will be made with reference to FIGS.

(Examples 1 to 5) As Examples 1 to 5, the capacity of the negative electrode 22 is expressed by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium. A battery was made as follows.

First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) were mixed with Li ₂ CO ₃ : CoC
O ₃ was mixed at a ratio of 0.5: 1 (molar ratio) and calcined in air at 900 ° C. for 5 hours to obtain a lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode material. Next, this lithium-cobalt composite oxide was pulverized to obtain a powder having a cumulative 50% particle size of 15 μm obtained by a laser diffraction method, and used as a positive electrode material.

Subsequently, 95% by mass of the lithium-cobalt composite oxide powder and 5% by mass of lithium carbonate powder were mixed, and 94% by mass of the mixture was mixed with 3% by mass of Ketjen black as a conductive agent. The mixture was mixed with 3% by mass of polyvinylidene fluoride as an agent to prepare a positive electrode mixture. After preparing the positive electrode mixture, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, and the positive electrode current collector 2 made of a 20 μm-thick strip-shaped aluminum foil was used.
1a, uniformly coated on both sides, dried, and compression-molded with a roll press to form a positive electrode mixture layer 21b having a thickness of 174.
A positive electrode 21 of μm was produced. After that, the positive electrode current collector 21
A positive electrode lead 25 made of aluminum was attached to one end of a.

Granular artificial graphite powder was prepared as a negative electrode material capable of inserting and extracting lithium, and 90% by mass of this particulate artificial graphite powder and 10% by mass of polyvinylidene fluoride as a binder were mixed. The mixture was adjusted. Then
This negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a slurry, and then uniformly applied to both surfaces of a negative electrode current collector 22a made of a 15-μm-thick strip-shaped copper foil, dried and rolled. The negative electrode mixture layer 22b was formed by compression molding with a press, and the negative electrode 22 having a thickness of 130 μm was produced. After that, a negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22a. When the positive electrode 21 and the negative electrode 22 were manufactured, their thicknesses, that is, the amounts of the positive electrode material and the negative electrode material were adjusted so that lithium metal was deposited on the negative electrode 22 during charging.

After each of the positive electrode 21 and the negative electrode 22 was prepared, a separator 23 made of a stretched microporous polyethylene film having a thickness of 25 μm was prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 were laminated in this order. Was spirally wound many times to produce a wound electrode body 20.

After manufacturing the wound electrode body 20, the wound electrode body 20 is sandwiched between a pair of insulating plates 12 and 13, and the negative electrode lead 2 is formed.
6 was welded to the battery can 11, the positive electrode lead 25 was welded to the safety valve mechanism 15, and the spirally wound electrode body 20 was housed inside the nickel-plated iron battery can 11. After that, the electrolytic solution was injected into the battery can 11. The electrolyte solution contains 5% by mass of vinylene carbonate, 45% by mass of ethylene carbonate, and 50% by mass of dimethyl carbonate.
In a solvent obtained by mixing the above, LiPF ₆ as an electrolyte salt was dissolved at a content of 1.5 mol / kg with respect to the solvent, and 1-benzothiophene shown in Chemical formula 13 was further added as an additive. At that time, the content of 1-benzothiophene relative to the solvent was changed as shown in Table 1 in Examples 1 to 5. The injection amount of the electrolyte was 3.0 g.

[0101]

[Table 1]

After injecting the electrolytic solution into the inside of the battery can 11, the battery cover 14 was caulked to the battery can 11 via a gasket 17 coated with asphalt on the surface. A cylindrical secondary battery having a length of 65 mm was obtained.

The secondary batteries of Examples 1 to 5 were subjected to a charge / discharge test to determine a rated discharge capacity and a discharge capacity retention ratio. At that time, charging was performed at a constant current of 400 mA until the battery voltage reached 4.2 V, and then 4.2 V was applied.
The charging was performed until the total charging time reached 4 hours. The voltage between the positive electrode 21 and the negative electrode 22 immediately before the end of charging was 4.2 V, and the current value was 5 mA or less. On the other hand, discharging was performed at a constant current of 400 mA until the battery voltage reached 2.75 V. By the way, when charging and discharging are performed under the conditions shown here, a fully charged state and a completely discharged state are obtained. The rated discharge capacity is the discharge capacity at the second cycle, and the discharge capacity retention ratio is calculated as the ratio of the discharge capacity at the 100th cycle to the rated discharge capacity, that is, (discharge capacity at the 100th cycle / rated discharge capacity) × 100. did. Table 1 shows the obtained results.

Further, with respect to the secondary batteries of Examples 1 to 5,
Dismantle those one cycle charge and discharge was later allowed to fully charged again conducted under conditions described above, visually and ⁷ Li nuclear magnetic resonance spectroscopy, examined whether lithium metal in the negative electrode mixture layer 22b is deposited Was. Further, two cycles of charge and discharge were performed under the above-described conditions, and the completely discharged battery was disassembled, and similarly, it was examined whether or not lithium metal had precipitated on the negative electrode mixture layer 22b. Table 1 shows the obtained results.

As Comparative Example 1 for this example, except that 1-benzothiophene was not added to the electrolytic solution,
Other than that produced the secondary battery similarly to this Example. The secondary battery of Comparative Example 1 was also subjected to a charge / discharge test in the same manner as in the present example to check the rated discharge capacity, the discharge capacity retention rate, and the presence / absence of lithium metal deposition in the fully charged state and the completely discharged state. Was. The results are also shown in Table 1.

As shown in Table 1, in Examples 1 to 5 and Comparative Example 1, in the fully charged state, the negative electrode mixture layer 22b
A silver-white precipitate was observed, and a peak attributed to lithium metal was obtained by ⁷ Li nuclear magnetic resonance spectroscopy. That is, deposition of lithium metal was observed. In the fully charged state, a peak attributed to lithium ions was obtained by ⁷ Li nuclear magnetic resonance spectroscopy, and it was confirmed that lithium ions were occluded between graphite layers in the negative electrode mixture layer 22b. On the other hand, in the completely discharged state, the negative electrode mixture layer 2
2b had no black and silvery precipitate, and no peak attributed to lithium metal was observed by ⁷ Li nuclear magnetic resonance spectroscopy. Further, the peak attributed to lithium ions was slightly recognized. That is, it was confirmed that the capacity of the negative electrode 22 was represented by the sum of the capacity component due to deposition and dissolution of lithium metal and the capacity component due to occlusion and desorption of lithium ions.

Further, as can be seen from Table 1, 1
-According to Examples 1 to 5 with the addition of benzothiophene,
A higher rated discharge capacity and a higher discharge capacity retention ratio were obtained as compared with Comparative Example 1 in which no addition was made. That is, 1
-It was found that the addition of benzothiophene can improve the discharge capacity and charge / discharge cycle characteristics.

From the results of Examples 1 to 5, the rated discharge capacity and the discharge capacity retention rate tend to increase as the content of 1-benzothiophene increases, and to decrease after reaching the maximum value. Was. That is, it was found that a higher effect can be obtained when the content with respect to the solvent is in the range of 0.05% by mass or more and 30% by mass or less.

(Examples 6 to 10) As Examples 6 to 10, lithium ion secondary batteries in which the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium were produced. At that time, except that the thickness of the negative electrode 22 was 180 μm,
Others were the same as Examples 1-5. In addition, 1 for the solvent
-The content of benzothiophene is shown in Table 2 in Examples 6 to 10.
Was changed as shown in FIG. Further, as Comparative Example 2 with respect to the present example, a secondary battery was manufactured in the same manner as in the present example except that 1-benzothiophene was not added. The secondary batteries of Examples 6 to 10 and Comparative Example 2 were also subjected to a charge / discharge test in the same manner as in Example 1 to obtain a rated discharge capacity, a discharge capacity retention rate, and a lithium metal in a fully charged state and a completely discharged state. The presence or absence of precipitation was examined.
Table 2 shows the obtained results.

[0110]

[Table 2]

As shown in Table 2, in Examples 6 to 10 and Comparative Example 2, no silver-white precipitate was observed in a fully charged state, the color was golden, and the sample was analyzed by ⁷ Li nuclear magnetic resonance spectroscopy. No peak attributed to lithium metal was observed, and only a peak attributed to lithium ions was obtained.
On the other hand, in the completely discharged state, the color was black, and even by ⁷ Li nuclear magnetic resonance spectroscopy, no peak attributed to lithium metal was observed, and a slight peak attributed to lithium ion was observed. That is, the capacity of the negative electrode 22 is represented by the capacity due to insertion and extraction of lithium, and it was confirmed that Examples 6 to 10 and Comparative Example 2 were existing lithium ion secondary batteries.

Further, as can be seen from Table 2, 1
-According to Examples 6 to 10 in which benzothiophene was added, higher rated discharge capacities and discharge capacity retention ratios were obtained than in Comparative Examples 2 to 5 in comparison with Comparative Example 2 in which benzothiophene was not added. Was done. That is, it was found that the addition of 1-benzothiophene also improved the discharge capacity and charge / discharge cycle characteristics of the lithium ion secondary battery.

Also in Examples 6 to 10, the rated discharge capacity and the discharge capacity retention rate tended to increase as the content of 1-benzothiophene increased, and tended to decrease after reaching the maximum value. . That is, it was found that a higher effect can be obtained when the content with respect to the solvent is in the range of 0.05% by mass or more and 30% by mass or less.

Examples 11 to 20 As Examples 11 to 15, except that a gel electrolyte was used instead of the electrolytic solution, the capacity of the anode 22 was changed to lithium. A secondary battery represented by the sum of a capacity component due to occlusion and desorption of lithium and a capacity component due to precipitation and dissolution of lithium was produced. Further, as Examples 16 to 20, except that a gel electrolyte was used instead of the electrolytic solution, the other Examples 6 to 20 were used.
In the same manner as in 10, the capacity of the negative electrode 22 is
A lithium ion secondary battery represented by a capacity component due to detachment was manufactured.

At this time, as the gel electrolyte, a polymer in which a copolymer of 95% by mass of polyvinylidene fluoride and 5% by mass of polyhexafluoropropylene was used as a polymer compound and an electrolyte solution was combined with the polymer compound was used. In the electrolyte, a non-aqueous solvent in which 48% by mass of ethylene carbonate, 48% by mass of propylene carbonate, and 4% by mass of vinylene carbonate were mixed was added with 1.5 mol / k of LiPF ₆ as an electrolyte salt.
g, and 1-benzothiophene as an additive was further added as an additive. The content of 1-benzothiophene with respect to the solvent was determined in Examples 11 to 11.
20 was changed as shown in Table 3. The mixing ratio of the polymer compound and the electrolytic solution was 8% by mass of the polymer compound and 92% by mass of the electrolytic solution.

[0116]

[Table 3]

In this embodiment, the gel electrolyte is applied to both surfaces of the positive electrode 21 and the negative electrode 22 by a coating apparatus.
After coating with a thickness of μm, a separator 23 made of a stretched microporous polyethylene film having a thickness of 15 μm was prepared.

As Comparative Example 3 for Examples 11 to 15 and Comparative Example 4 for Examples 16 to 20, a secondary battery was fabricated in the same manner as in this example except that 1-benzothiophene was not added. Produced. For Examples 11 to 20 and Comparative Examples 3 and 4, a charge / discharge test was performed in the same manner as in Example 1, and the rated discharge capacity, the discharge capacity retention rate, and the deposition of lithium metal in the fully charged state and the completely discharged state were measured. The presence or absence was checked. Table 3 shows the obtained results.

As can be seen from Table 3, Examples 11 to 20
According to Comparative Example 1, as in Examples 1 to 10, a higher rated discharge capacity and a higher discharge capacity retention rate than in the comparative example were obtained. That is, it was found that a similar effect can be obtained in a secondary battery using a gel electrolyte instead of the electrolytic solution. Also, 1
Similarly, it was found that the content of benzothiophene is preferably in the range of 0.05% by mass to 30% by mass with respect to the solvent.

(Examples 21 to 23) A non-graphitizable carbon was used as the negative electrode material, and the thickness of the negative electrode mixture layer 22b was 136 μm.
m, and a secondary battery was fabricated in the same manner as in Example 1 except that the content of 1-benzothiophene relative to the solvent was changed as shown in Table 4. That is, a secondary battery in which the capacity of the anode 22 was represented by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium was manufactured. Further, as Comparative Example 5 for this example, a secondary battery was fabricated in the same manner as this example, except that 1-benzothiophene was not added. For Examples 21 to 23 and Comparative Example 5, a charge / discharge test was performed in the same manner as in Example 1 to determine the rated discharge capacity, the discharge capacity retention rate, and whether or not lithium metal was deposited in the fully charged state and the completely discharged state. Was examined. Table 4 shows the obtained results.

[0121]

[Table 4]

As can be seen from Table 4, Examples 22 to 24
According to Comparative Example 1, as in Examples 1 to 5, a higher rated discharge capacity and a higher capacity retention ratio were obtained than in Comparative Examples. That is, it was found that the discharge capacity and the charge / discharge cycle characteristics could be improved by adding 1-benzothiophene regardless of the type of the carbon material used as the negative electrode material capable of inserting and extracting lithium.

(Examples 24 to 26) A mixture of 60% by mass of artificial graphite and 30% by mass of silicon was used as the negative electrode material. The thickness of the negative electrode 22 was 116 μm, and the amount of 1-benzothiophene added to the solvent was Was changed as shown in Table 5, except that the secondary battery was manufactured in the same manner as in Example 1. In other words, the capacity of the negative electrode 22 depends on the capacity component due to insertion and extraction of lithium,
A secondary battery represented by the sum of a capacity component due to dissolution was produced. Further, as Comparative Example 6 with respect to the present embodiment, 1-
A secondary battery was fabricated in the same manner as in this example, except that benzothiophene was not added. Example 24-
26 and Comparative Example 6 were also subjected to a charge / discharge test in the same manner as in Example 1 to examine the rated discharge capacity, the discharge capacity retention ratio, and the presence or absence of lithium metal deposition in the fully charged state and the completely discharged state. Table 5 shows the obtained results.

[0124]

[Table 5]

As can be seen from Table 5, Examples 24 to 26 were used.
According to Comparative Example 1, as in Examples 1 to 5, a higher rated discharge capacity and a higher capacity retention ratio were obtained than in Comparative Examples. In other words, even when a metal or a semiconductor capable of forming an alloy or a compound with lithium as a negative electrode material, or an alloy or a compound thereof, is used, adding 1-benzothiophene
It was found that the discharge capacity and charge / discharge cycle characteristics could be improved.

In the above embodiment, the substance having the CSC structure has been described with specific examples. However, it is considered that the above-mentioned effects are caused by the CSC structure. Therefore, a similar result can be obtained even when a compound having another CSC structure is used.

Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and can be variously modified. For example, in the above embodiments and examples, a battery using lithium as an electrode reactive species has been described.
The present invention can be applied to a case where another light metal or an alloy containing a light metal is used, and the same effect can be obtained. In that case, a negative electrode material, a positive electrode material, a non-aqueous solvent, an electrolyte salt or the like capable of inserting and extracting a light metal is selected according to the light metal. However, it is preferable to use lithium or an alloy containing lithium as the light metal because voltage compatibility with lithium ion secondary batteries currently in practical use is high. When an alloy containing lithium is used as the light metal, a substance capable of forming an alloy with lithium exists in the electrolyte, and an alloy may be formed at the time of deposition. Possible substances are present and may form an alloy upon precipitation.

In the above embodiments and examples, a gel electrolyte which is one kind of an electrolyte or a solid electrolyte has been described. However, the present invention can be similarly applied to other electrolytes. Can be. Other electrolytes include:
For example, an organic solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, an inorganic solid electrolyte made of ionic conductive ceramics, ionic conductive glass or ionic crystal, or a mixture of these inorganic solid electrolyte and electrolyte Or a mixture of these inorganic solid electrolytes and a gel electrolyte or an organic solid electrolyte.

Further, in the above embodiments and examples, a cylindrical secondary battery having a wound structure has been described. However, the present invention relates to an elliptical or polygonal secondary battery having a wound structure. Alternatively, the present invention can be similarly applied to a secondary battery having a structure in which a positive electrode and a negative electrode are folded or stacked. In addition, the present invention can be applied to a secondary battery such as a coin type, a button type, and a card type.

Further, in the above embodiments and examples, the case where the electrolyte of the present invention is used for a secondary battery has been described. However, the present invention can be applied to other batteries such as a primary battery. Further, it can be used for other electrochemical devices such as a capacitor, a capacitor or an electrochromic device.

[0131]

As described above, according to any one of the first to seventh aspects of the present invention, the electrolyte contains a substance having a CSC structure in which carbon, sulfur and carbon are bonded. Chemical stability can be improved.

According to the battery of any one of claims 8 to 22, since the electrolyte of the present invention is used, the chemical stability of the electrolyte can be improved. Therefore, the reversibility of the electrode reaction is improved, and the battery characteristics such as the discharge capacity and the charge / discharge cycle characteristics are further improved, so that a higher energy density and a longer life can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a secondary battery according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of a wound electrode body in the secondary battery shown in FIG.

[Explanation of symbols]

11 ... battery can, 12, 13 ... insulating plate, 14 ... battery lid, 1
Reference numeral 5: safety valve mechanism, 15a: disk plate, 16: thermal resistance element, 17: gasket, 20: wound electrode body, 21: positive electrode, 21a: positive electrode current collector, 21b: positive electrode mixture layer, 22:
Negative electrode, 22a: negative electrode current collector, 22b: negative electrode mixture layer, 23
... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead

Claims (22)

[Claims] 1. An electrolyte comprising a substance having a CSC structure in which carbon (C), sulfur (S) and carbon shown in Chemical formula 1 are bonded. Embedded image 2. The electrolyte according to claim 1, wherein the substance having a CSC structure includes a heterocyclic compound. 3. The electrolyte according to claim 1, wherein the substance having a CSC structure includes a substance having a thiophene structure shown in Chemical Formula 2. Embedded image 4. The electrolyte according to claim 1, wherein the substance having the CSC structure includes 1-benzothiophene shown in Chemical formula 3. Embedded image 5. The composition according to claim 1, further comprising an electrolyte salt and a solvent, wherein a content of the substance having the CSC structure is in a range of 0.05% by mass or more and 30% by mass or less based on the solvent. The electrolyte according to claim 1. 6. The electrolyte according to claim 1, further comprising a lithium salt. 7. The electrolyte according to claim 1, further comprising a polymer compound. 8. A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the electrolyte includes a substance having a CSC structure in which carbon, sulfur, and carbon are combined as shown in Chemical Formula 4. Embedded image 9. A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the capacity of the negative electrode is represented by the sum of a capacity component due to occlusion and release of light metal and a capacity component due to deposition and dissolution of light metal. A battery characterized in that the electrolyte includes a substance having a CSC structure in which carbon, sulfur, and carbon are combined as shown in Chemical Formula 5. Embedded image 10. The battery according to claim 8, wherein the substance having the CSC structure includes a heterocyclic compound. 11. The substance having the CSC structure is
10. The battery according to claim 8, further comprising a substance having a thiophene structure described in (1). Embedded image 12. The substance having the CSC structure is
10. The battery according to claim 8, comprising 1-benzothiophene described in (1). Embedded image 13. The electrolyte further comprises an electrolyte salt and a solvent, wherein the content of the substance having the CSC structure is:
10. The composition according to claim 8, wherein the content is in the range of 0.05% by mass or more and 30% by mass or less based on the solvent.
The battery as described. 14. The battery according to claim 8, wherein the electrolyte further contains a lithium salt. 15. The battery according to claim 8, wherein the electrolyte further contains a polymer compound. 16. The battery according to claim 8, wherein the negative electrode includes a negative electrode material capable of inserting and extracting light metal. 17. The battery according to claim 8, wherein the negative electrode contains a carbon material. 18. The battery according to claim 8, wherein the negative electrode contains at least one member selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 19. The battery according to claim 8, wherein the negative electrode contains graphite. 20. The negative electrode according to claim 8, wherein the negative electrode includes at least one selected from the group consisting of metals, semiconductors, alloys and compounds capable of forming an alloy or a compound with the light metal. Item 10. The battery according to Item 9. 21. The negative electrode comprises tin (Sn), lead (P)
b), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium ( Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr) and yttrium (Y). The battery according to claim 9, wherein: 22. The battery according to claim 9, wherein the light metal includes lithium (Li).