JP2003187871A - Cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell which enables improvement of cell characteristics as discharge capacity and cycle characteristic, and to provide a manufacturing method therefor. <P>SOLUTION: The cell has a wound electrode assembly 20 which is made by winding positive electrodes 21 and negative electrodes 22 via separators 23 and electrolytes 24 respectively in a laminated form. The electrolytes 24 include the first electrolyte layers 24a on positive electrode 21 sides and the second electrolyte layers 24b on negative electrode 22 sides, and the first electrolyte layers 24a and the second electrolyte layers 24b are disposed via separators 23, respectively. The first electrolyte layers 24a include the first electrolyte and the first electrolyte keepers, and the second electrolyte layers 24b include the second electrolyte and the second electrolyte keepers. The second electrolyte has vinylethylene carbonate or dimethoxyethane as addition agent, and so it has different chemical composition compared with the first electrolyte. Consequently, chemical stabilities of both the first electrolyte layers 24a and the second electrolyte layers 24b are improved, and the discharge capacity and the cycle characteristic of the cell are improved. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery including a positive electrode, a negative electrode, and an electrolyte interposed therebetween, and a method for manufacturing the battery.

[0002]

2. Description of the Related Art Recently, a camera-integrated VTR (videotape)
Many portable electronic devices such as recorders), mobile phones, and laptop computers have appeared, and their size and weight have been reduced. Along with this, research and development for improving the energy density of batteries, especially secondary batteries, have been actively promoted as portable power supplies for these electronic devices. Among them, the lithium ion secondary battery is highly expected because it can obtain a larger energy density than a lead battery or a nickel cadmium battery, which are conventional non-aqueous electrolyte secondary batteries.

Recently, in this lithium ion secondary battery, a so-called solid electrolyte battery using a solid or gel electrolyte has been proposed. This solid electrolyte battery is
Since there is no need to worry about liquid leakage and there is no need for a sealing structure such as a secondary battery that uses an electrolytic solution, a wound electrode body for the positive and negative electrodes is sealed with a moisture-proof laminated film. can do. Therefore, the solid electrolyte battery has advantages that it can be made lighter and thinner than a secondary battery using an electrolytic solution, and the energy density of the battery can be further improved.
Among them, the one using a gel electrolyte in which a polymer material is plasticized with an electrolytic solution can obtain a relatively high ionic conductivity at room temperature, and is considered as a promising secondary battery in the future.

LiPF ₆ is widely used as an electrolyte salt for the gel electrolyte because it has a relatively high conductivity and is stable in terms of potential. However, L
iPF ₆ is not satisfactory in thermal stability, and there is a problem that the cycle characteristics or storage characteristics of the battery are deteriorated. Such characteristic deterioration occurs even when a slight thermal decomposition of LiPF ₆ occurs in the electrolyte.

LiPF₆Conventional electrolyte salts other than
From LiBF_Four, LiCF₃SO ₃, LiClO_FourAh
Ruiha LiAsF₆Are also known. However, Li
BF _FourHas high thermal stability and oxidative stability, but conductivity
There was a problem of being low. LiCF₃SO₃Is thermally stable
Although it has high conductivity, it has low conductivity and oxidation stability, and it has a voltage of 4V or higher.
It is said that sufficient discharge characteristics cannot be obtained when charged at high voltage.
There was a problem. LiClO_FourAnd LiAsF₆Is derived
There was a problem that the electric power was high but the cycle characteristics were poor.

In recent years, LiN (CF ₃ SO ₂ )
₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO
₂ ) ₃ or LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO
₂ ) and others have relatively high conductivity and high thermal stability, and are expected as electrolyte salts. But,
Since these electrolyte salts are inferior in oxidation stability, there is a problem that sufficient cycle characteristics cannot be obtained when they are charged and discharged at a high voltage of 4 V or higher.

Therefore, the charging voltage of these electrolyte salts is 4
Under the present circumstances, when used in a lithium ion secondary battery exceeding V, good conductivity, cycle characteristics and storage characteristics cannot be realized at the same time. Therefore, in order to overcome such a problem, studies have so far been made such that an electrolyte salt is mixed and used, and various kinds of additives are added to an electrolytic solution.

[0008]

However, since it is difficult for any of the electrolyte salts and additives to exist stably in a very wide potential region of 4 V or more, it is possible to mix the electrolyte salts or add the additives on the negative electrode side. Even if a good effect is seen, decomposition or deterioration of the electrolyte occurs on the positive electrode side, and conversely, even if a good effect is seen on the positive electrode side, decomposition or deterioration of the electrolyte occurs on the negative electrode side. There was a problem. Therefore, a sufficiently satisfactory value has not yet been obtained for battery characteristics such as battery capacity or cycle characteristics.

These problems are not limited to the conventional lithium ion secondary battery, but a lithium secondary battery using a lithium metal for the negative electrode or a higher energy density can be realized by the present inventor. The same applies to a secondary battery developed in recent years, for example, a secondary battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to absorption and desorption of lithium and the capacity component due to precipitation and dissolution of lithium. In this secondary battery, a carbon material capable of inserting and extracting lithium is used for the negative electrode, and lithium is deposited on the surface of the carbon material during charging. It is expected that a larger discharge capacity than that of a conventional lithium ion secondary battery can be realized while improving capacity deterioration due to a large volume change of the negative electrode, which is a problem.

The present invention has been made in view of the above problems, and an object thereof is to provide a battery capable of improving battery characteristics such as battery capacity and cycle characteristics, and a manufacturing method thereof.

[0011]

A battery according to the present invention comprises a positive electrode and a negative electrode, and an electrolyte interposed therebetween, the electrolyte including an electrolytic solution and a holder, and the positive electrode side. And the negative electrode side have different chemical compositions.

The method for producing a battery according to the present invention is for producing a battery having a positive electrode and a negative electrode and an electrolyte interposed therebetween, which includes an electrolytic solution and a holding body, and includes a positive electrode side and a negative electrode. It includes a step of forming an electrolyte having a different chemical composition from the side.

In the battery according to the present invention, since the chemical composition of the electrolyte is different between the positive electrode side and the negative electrode side, the chemical stability of the electrolyte is improved on both the positive electrode side and the negative electrode side, and the battery capacity and cycle characteristics are improved. The characteristics are improved.

In the method of manufacturing a battery according to the present invention, an electrolyte having different chemical compositions on the positive electrode side and the negative electrode side is formed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an exploded view of the structure of a secondary battery according to an embodiment of the present invention. This secondary battery is
The spirally wound electrode body 20 to which the positive electrode lead wire 11 and the negative electrode lead wire 12 are attached is attached to the film-shaped exterior member 30a, 3
It is enclosed inside 0b.

Positive electrode lead wire 11 and negative electrode lead wire 12
Are led out from the inside of the exterior members 30a and 30b to the outside, for example, in the same direction, respectively. The positive electrode lead wire 11 and the negative electrode lead wire 12 are each made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni) or stainless steel,
Each is in the form of a thin plate or mesh.

The exterior members 30a and 30b are made of, for example, a rectangular laminated film obtained by laminating a nylon film, an aluminum foil and a polyethylene film in this order. The exterior members 30a and 30b are
For example, the polyethylene film side and the spirally wound electrode body 20 are disposed so as to face each other, and the respective outer edge portions are adhered to each other by fusion or an adhesive. Exterior member 30
a, 30b, positive electrode lead wire 11 and negative electrode lead wire 12
An adhesion film 31 for preventing the invasion of the outside air is inserted between and. The adhesion film 31 is made of a material having adhesion to the positive electrode lead wire 11 and the negative electrode lead wire 12. For example, when the positive electrode lead wire 11 and the negative electrode lead wire 12 are made of the above-mentioned metal material, It is preferably composed of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene or modified polypropylene.

The exterior members 30a and 30b may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-mentioned laminated film.

FIG. 2 shows I of the spirally wound electrode body 20 shown in FIG.
It shows a cross-sectional structure taken along line I-II. The spirally wound electrode body 20 is obtained by laminating a positive electrode 21 and a negative electrode 22 with a separator 23 and an electrolyte 24 in between and winding them.
The outermost peripheral portion is protected by a protective tape 25.

The positive electrode 21 is, for example, a positive electrode current collector 21a.
And a positive electrode mixture layer 21b provided on both surfaces or one surface of the positive electrode current collector 21a. Positive electrode current collector 21
a includes the positive electrode mixture layer 21 at one end in the longitudinal direction.
There is an exposed portion where b is not provided, and the positive electrode lead wire 11 is attached to this exposed portion. Positive electrode current collector 2
1a is composed of a metal foil such as an aluminum foil, a nickel foil, or a stainless foil.

The positive electrode mixture layer 21b contains, for example, one or more positive electrode materials capable of inserting and extracting lithium, which is a light metal, as a positive electrode active material, and if necessary, graphite And a binder such as polyvinylidene fluoride. Examples of the positive electrode material capable of inserting and extracting lithium include, for example, metal sulfides or oxides not containing lithium such as TiS ₂ , MoS ₂ , NbSe ₂ or V ₂ O ₅ , or lithium oxide, Examples thereof include a lithium-containing compound such as lithium sulfide or an intercalation compound containing lithium, or a polymer material.

Particularly, in order to increase the energy density, a lithium composite oxide represented by the general formula Li _x MIO ₂ or an intercalation compound containing lithium is preferable. In addition, M
I is one or more kinds of transition metals, for example, cobalt (C
At least one of o), nickel, manganese (Mn), iron (Fe), aluminum, vanadium (V) and titanium (Ti) is preferable. x varies depending on the charge / discharge state of the battery and is usually a value within the range of 0.05 ≦ x ≦ 1.10. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , Li _y Ni.
_z Co _1-z O ₂ (y and z differ depending on the charge / discharge state of the battery, and are usually values within the range of 0 <y <1, 0.7 <z <1.02) or LiMn ₂ O ₄ etc. Is mentioned. In addition, LiMIIPO having an olivine type crystal structure
Lithium phosphate compounds such as ₄ (MII is one or more kinds of transition metals) are also preferable because a high energy density can be obtained.

The negative electrode 22 is, for example, similar to the positive electrode 21,
It has a negative electrode current collector 22a and a negative electrode mixture layer 22b provided on both surfaces or one surface of the negative electrode current collector 22a. The negative electrode current collector 22a has an exposed portion where the negative electrode mixture layer 22b is not provided at one end portion in the longitudinal direction, and the negative electrode lead wire 12 is attached to this exposed portion. The negative electrode current collector 22a is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless foil.

The negative electrode mixture layer 22b contains, for example, one or more negative electrode materials capable of inserting and extracting lithium which is a light metal as a negative electrode active material. It may contain a binder such as vinylidene chloride. In the present specification, occlusion / desorption of light metal means that light metal ion is electrochemically occluded / desorbed without losing its ionicity. This includes not only the case where the occluded light metal exists in a perfect ionic state, but also the case where it exists in a state that cannot be said to be a perfect ionic state. Examples of cases corresponding to these include storage of light metal ions with respect to graphite by an electrochemical intercalation reaction. Further, occlusion of a light metal in an alloy containing an intermetallic compound, or occlusion of a light metal by forming an alloy can 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 the change in the crystal structure that occurs during charging / discharging is very small, a high charge / discharge capacity can be obtained, and good 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, the (002) plane spacing is 0.340n
Less than m, the true density is 2.18 g / cm ³
As described above, the (002) plane spacing is 0.335 nm or more.
It is more preferable if it is 337 nm or less. As the non-graphitizable carbon, for example, the interplanar spacing of the (002) plane is 0.
It has a true density of 37 nm or more and less than 1.70 g / cm ³ and has a differential thermal analysis in air.
Those which do not show an exothermic peak at 700 ° C. or higher in lysis; DTA) are preferable.

Specific examples of the carbon material include pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbons and carbon blacks. this house,
Coke includes pitch coke, needle coke, petroleum coke, and the like. An organic polymer compound fired body is a carbon material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature. Say.

Examples of the negative electrode material capable of inserting and extracting lithium include a simple substance, an alloy or a compound of a metal element or a semimetal element capable of forming an alloy with lithium. These are preferable because they can obtain a high energy density, and particularly when used together with a carbon material, it is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. In the present specification, the alloy includes not only an alloy composed of two or more kinds of metal elements but also an alloy composed of one or more kinds of metal elements and one or more kinds of metalloid elements. The texture may be a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a coexistence of two or more of them.

Examples of such metal elements or metalloid elements are tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi). ), Cadmium (C
d), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y)
Alternatively, hafnium (Hf) or the like can be used. As these alloys or compounds, for example, the chemical formula Ma _s M
Examples thereof include those represented by b _t Li _u or the chemical formula Map _p Mc _q Md _r . In these chemical formulas, Ma is at least one of metal elements and metalloid elements capable of forming an alloy with lithium, and Mb is at least one of metal elements and metalloid elements other than lithium and Ma.
Seed, Mc represents at least one kind of non-metal element, and Md represents at least one kind of metal element and metalloid element other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, and q>, respectively.
0 and r ≧ 0.

Of these, simple substances, alloys or compounds of 4B group metal elements or metalloid elements are preferable, and particularly preferable are silicon or tin, or alloys or compounds thereof. These may be crystalline or amorphous.

For such alloys or compounds,
Physically, for example, LiAl, AlSb, CuMgS
b, SiB_Four, SiB₆, Mg₂Si, Mg₂Sn, N
i₂Si, TiSi₂, MoSi₂, CoSi₂, Ni
Si₂, CaSi₂, CrSi₂, Cu_FiveSi, FeS
i₂, MnSi₂, NbSi₂, TaSi₂, VS
i ₂, WSi₂, ZnSi₂, SiC, Si₃N_Four, S
i₂N₂O, SiO_v(0 <v ≦ 2), SnO_w(0 <
w ≦ 2), SnSiO₃, LiSiO or LiSn
There is O etc.

As the negative electrode material capable of inserting and extracting lithium, other metal compounds or polymer materials can be further cited. Other metal compounds include oxides such as iron oxide, ruthenium oxide and molybdenum oxide, LiN _{3 and the} like, and polymer materials include polyacetylene, polyaniline, polypyrrole and the like.

Further, in this secondary battery, lithium metal begins to deposit on the negative electrode 22 at the time when the open circuit voltage (ie, battery voltage) is lower than the overcharge voltage in the course of charging. That is, lithium metal is deposited on the negative electrode 22 in a state where the open circuit voltage is lower than the overcharge voltage, and the capacity of the negative electrode 22 is the capacity component due to occlusion / desorption of lithium and the capacity component due to precipitation / dissolution of lithium metal. It is expressed as the sum of. Therefore, in this secondary battery, both the negative electrode material capable of absorbing and desorbing lithium and the lithium metal function as a negative electrode active material, and the negative electrode material capable of absorbing and desorbing lithium is a base material when lithium metal is deposited. Has become. As a result, in this secondary battery, it is possible to obtain a high energy density and improve the cycle characteristics and the quick charge characteristics.

The overcharge voltage refers to an open circuit voltage when the battery is in an overcharged state, and is one of the guidelines set by the Japan Storage Battery Industry Association (Battery Industry Association), for example, "lithium". Secondary Battery Safety Evaluation Standard Guidelines "(S
"Full charge" as described and defined in BAG 1101)
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 when the nominal capacity of each battery is obtained. Specifically, in this secondary battery, for example, a negative electrode that is fully charged when the open circuit voltage is 4.2 V and is capable of occluding and releasing lithium in a part within the range of the open circuit voltage of 0 V or more and 4.2 V or less. Lithium metal is deposited on the surface of the material.

The separator 23 is composed of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene or polyethylene, or a porous film made of ceramic, and two or more kinds of these porous films are laminated. It may have a structure.

The electrolyte 24 is a so-called gel in which an electrolytic solution is dispersed or held in a holder, and the separator 23 is used.
First electrolyte layer 24a located on the positive electrode 21 side through
And a second electrolyte layer 24b located on the negative electrode 22 side. The first electrolyte layer 24a contains a first electrolytic solution and a first holder, and the second electrolyte layer 24b contains a second electrolytic solution and a second holder. The ionic conductivity of the first electrolyte layer 24a and the second electrolyte layer 24b is preferably 1 mS / cm or more at room temperature.

The first holding member and the second holding member may be the same or different and are made of, for example, a polymer material. Examples of the polymer material include polyvinylidene fluoride and a copolymer of polyvinylidene fluoride, and examples of the copolymer monomer include hexafluoropropylene and tetrafluoroethylene. These polyvinylidene fluoride and its copolymers are preferable because high battery characteristics can be obtained, and among them, the copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.

In addition, as the polymer material, for example, polyacrylonitrile and a copolymer of polyacrylonitrile can be used. As the copolymer monomer, for example, vinyl monomer, vinyl acetate, methyl methacrylate, methacrylic acid can be used. Butyl, methyl acrylate, butyl acrylate, itaconic acid, hydrogenated methyl acrylate,
Examples thereof include hydrogenated ethyl acrylate, acrylamide, vinyl chloride, vinylidene fluoride or vinylidene chloride. In addition, acrylonitrile butadiene rubber, acrylonitrile butadiene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile vinyl chloride resin,
Acrylonitrile methacrylate resin or acrylonitrile acrylate resin may be used.

As the polymer material, for example, polyethylene oxide or a copolymer of polyethylene oxide may be used, and as the copolymerization monomer, polypropylene oxide, methyl methacrylate, butyl methacrylate, methyl acrylate or acryl is used. Butyl acid and the like can be mentioned. In addition, polyether-modified siloxane and its copolymer may be used.

The content of the first holding member and the content of the second holding member are 5% by mass to the first electrolytic solution or the second electrolytic solution in order to obtain a good gel state. It is preferably within the range of 50% by mass.

The first electrolytic solution and the second electrolytic solution contain, for example, a solvent such as a non-aqueous solvent, a lithium salt as an electrolyte salt dissolved in this solvent, and an additive. The first electrolytic solution and the second electrolytic solution are different in, for example, the content of the additive, and thus the chemical compositions are different. The term "different content" as used herein is a concept including a case where the content is zero, and a case where a plurality of substances are mixed and included, a part of the content is different. The solvent and the lithium salt may be the same or different. The first electrolytic solution and the second electrolytic solution have an intrinsic viscosity of 10.0 mP at 25 ° C.
Those having a.s or less are preferable. This is because high conductivity can be obtained.

As the solvent, various non-aqueous solvents conventionally used for non-aqueous electrolytes can be used. Specifically, cyclic carbonates such as propylene carbonate, ethylene carbonate and butylene carbonate, chain esters such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, or γ-
Examples include ethers such as butyrolactone, sulfolane, 2-methyltetrahydrofuran, and dimethoxyethane. In particular, from the viewpoint of oxidation stability, it is preferable to include carbonic acid ester.

As the lithium salt, for example, LiP
F ₆ , LiAsF ₆ , LiBF ₄ , LiClO ₄ , Li
_{B (C 6 H 5) 4} , LiCH 3 SO 3, LiCF 3 SO
₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO
₂ ) ₂ , LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ),
LiC (CF ₃ SO ₂ ) ₃ , LiC ₄ F ₉ SO ₃ , Li
AlCl ₄ , LiSiF ₆ , LiCl or LiBr
And any one of these or two or more thereof may be mixed and used. Among them, LiPF ₆ is preferable because high conductivity can be obtained.

The content (concentration) of the lithium salt in the electrolytic solution is in the range of 0.1 mol / l to 2.0 mol / l, or in the range of 0.1 mol / kg to 2.0 mol / kg. preferable. This is because good ionic conductivity can be obtained within these ranges.

As the additive, one kind or a mixture of two or more kinds is used according to the purpose. Examples thereof include vinyl ethylene carbonate and 1,2-dimethoxyethane. These vinyl ethylene carbonate or 1,2
On the negative electrode 22 side, -dimethoxyethane has a function of adsorbing to radical active points of the negative electrode 22 to form a film and suppressing reductive decomposition of the solvent. However, on the positive electrode 21 side, there is a problem that the internal resistance is increased by forming a coating film on the positive electrode 21 or that the positive electrode 21 is decomposed due to low oxidation stability. Therefore, the content of these is zero or less in the first electrolytic solution located on the side of the positive electrode 21, and is larger than that of the first electrolytic solution in the second electrolytic solution located on the side of the negative electrode 22. In addition, although vinyl ethylene carbonate and 1,2-dimethoxyethane may function as a solvent in some cases, in the present specification, the function described above is focused on and explained as an additive. Of course, at least a part of the added substances may contribute to the reaction as described above, and those not contributing to the reaction may function as a solvent.

Further, the difference in chemical composition between the first electrolytic solution and the second electrolytic solution becomes smaller as the charging / discharging cycle is repeated, but the above-mentioned additives and the like act strongly at the initial stage of charging / discharging. Therefore, it suffices that the chemical composition is different at the initial stage of charge / discharge.

The secondary battery having such a structure can be manufactured, for example, as follows.

FIG. 3 shows a method of manufacturing the secondary battery according to this embodiment. First, for example, a positive electrode material capable of inserting and extracting lithium, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, which is then dispersed in a solvent such as N-methylpyrrolidone to prepare a positive electrode mixture slurry. The positive electrode mixture slurry is applied to both sides or one side of the positive electrode current collector 21a, dried, and compression molded to form the positive electrode mixture layer 21b, and the positive electrode 21 is manufactured (step S101).

Next, for example, a negative electrode material capable of inserting and extracting lithium and a binder are mixed to prepare a negative electrode mixture,
After being dispersed in a solvent such as N-methylpyrrolidone to form a negative electrode mixture slurry, this negative electrode mixture slurry is applied to, for example, both surfaces or one surface of the negative electrode current collector 22a, dried, and compression molded to form a negative electrode mixture layer 22b. To form the negative electrode 22 (step S102).

Subsequently, for example, the positive electrode lead wire 11 is attached to the positive electrode current collector 21a, and the first electrolyte layer 24a is formed on the positive electrode mixture layer 21b, that is, on both surfaces or one surface of the positive electrode 21 (step S103). ). Further, the negative electrode lead wire 12 is attached to the negative electrode current collector 22a, and the second electrolyte layer 24b is formed on the negative electrode mixture layer 22b, that is, on both surfaces or one surface of the negative electrode 22 (step S104). At this time, the first electrolyte solution of the first electrolyte layer 24a and the second electrolyte solution of the second electrolyte layer 24b are different in chemical composition. Specifically, vinylethylene carbonate and 1,2-dimethoxyethane were not added as additives to the first electrolytic solution,
At least one of vinyl ethylene carbonate and 1,2-dimethoxyethane is added to the second electrolytic solution.

After the first electrolyte layer 24a and the second electrolyte layer 24b are formed, for example, the first electrolyte layer 24 is formed.
A and the second electrolyte layer 24b are opposed to each other via the separator 23, and the positive electrode 21 and the negative electrode 22 are laminated. After that, this laminated body is wound, and the protective tape 25 is put on the outermost peripheral portion.
Are bonded to form the spirally wound electrode body 20 (step S10).
5).

After forming the spirally wound electrode body 20, for example,
The spirally wound electrode body 20 is sandwiched between the exterior members 30a and 30b, and the outer edge portions of the exterior members 30a and 30b are tightly sealed by heat fusion or the like (step S106). At that time, the adhesion film 31 is inserted between the positive electrode lead wire 11 and the negative electrode lead wire 12 and the exterior members 30a and 30b. As a result, the secondary battery shown in FIGS. 1 and 2 is completed.

This secondary battery operates as follows.

In this secondary battery, when charged, lithium ions are desorbed from the positive electrode mixture layer 21b and are contained in the negative electrode mixture layer 22b via the first electrolyte layer 24a and the second electrolyte layer 24b. The stored lithium is stored in the negative electrode material that can store and release lithium. When the charging is further continued, the charge capacity exceeds the charge capacity of the negative electrode material capable of inserting and extracting lithium when the open circuit voltage is lower than the overcharge voltage.
Lithium metal begins to deposit on the surface of the negative electrode material capable of inserting and extracting lithium. After that, lithium metal continues to deposit on the negative electrode 22 until the charging is completed.

When discharging is performed, first, the lithium metal deposited on the negative electrode 22 is eluted as ions, and the lithium metal is deposited on the positive electrode mixture layer 21b through the second electrolyte layer 24b and the first electrolyte layer 24a. It is occluded. When the discharge is further continued, the lithium ions occluded in the negative electrode material capable of occluding and releasing lithium in the negative electrode mixture layer 22b are released, and the positive electrode mixture is passed through the second electrolyte layer 24b and the first electrolyte layer 24a. It is occluded in the agent layer 21b.

In the present embodiment, the first electrolyte layer 24a
The second electrolyte layer 24b and the second electrolyte layer 24b have different chemical compositions between the first electrolyte solution and the second electrolyte solution, and the chemical stability of the electrolyte 24 is high on both the positive electrode 21 side and the negative electrode 22 side. There is. Therefore, excellent characteristics such as battery capacity and cycle characteristics can be obtained.

As described above, according to this embodiment, the content of the additive in the first electrolyte solution contained in the first electrolyte layer 24a and the second electrolyte solution contained in the second electrolyte layer 24b is Since the chemical composition is changed so that the first electrolyte layer 24a and the second electrolyte layer 24b can be improved in chemical stability, battery characteristics such as battery capacity and cycle characteristics can be improved. Can be made.

In the above embodiment, the secondary battery in which the capacity of the negative electrode 22 is represented by the sum of the capacity component due to the occlusion / desorption of lithium and the capacity component due to the precipitation / dissolution of lithium is described as an example. However, also for the secondary battery having another configuration, the same effect can be obtained by configuring the electrolyte in the same manner as in the above embodiment.

As a secondary battery having another structure, 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 absorption / desorption of lithium, or the capacity of the negative electrode is deposited / deposited of lithium metal A so-called lithium secondary battery represented by a capacity component due to dissolution is included.
A lithium ion secondary battery, for example, absorbs lithium
Except for the fact that the amount of the removable negative electrode material is relatively large relative to the positive electrode material and lithium metal does not deposit on the negative electrode during charging, it has the same configuration as the above secondary battery,
It can be manufactured in a similar manner. In addition, the lithium secondary battery has the same configuration as the above secondary battery except that the negative electrode is made of, for example, lithium metal, and can be manufactured in the same manner.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Further, specific embodiments of the present invention will be described in detail with reference to FIGS.

Example 1 A secondary battery was produced in which the capacity of the negative electrode 22 is represented by the sum of the capacity component due to the occlusion / desorption of lithium and the capacity component due to the precipitation / dissolution of lithium.

First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) were mixed with Li ₂ CO ₃ : CoC.
O ₃ = 0.5: 1 (molar ratio) was mixed, and the mixture was baked in air at 900 ° C. for 5 hours to obtain a lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode material.
Next, 91 parts by mass of this lithium-cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Then, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone which is a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 21a made of a strip-shaped aluminum foil having a thickness of 20 μm and dried. Then, the positive electrode mixture layer 21b is formed by compression molding with a roll press to form the positive electrode 2
1 was produced.

Further, artificial graphite powder was prepared as a negative electrode material, and 90 parts by mass of this artificial graphite powder and 10 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Next, this negative electrode mixture is dispersed in N-methyl-2-pyrrolidone which is a solvent to prepare a negative electrode mixture slurry, and then a negative electrode current collector 22a made of a strip-shaped copper foil having a thickness of 15 μm.
Was uniformly applied to both surfaces of the above, dried, and compression-molded by a roll press machine to form a negative electrode mixture layer 22b, thereby producing a negative electrode 22. The area density ratio between the positive electrode 21 and the negative electrode 22 is determined as follows:
It was adjusted so as to be represented by the sum of the capacity component due to the precipitation and dissolution of lithium.

Then, the positive electrode lead wire 11 is attached to the positive electrode current collector 21a, and the first electrode is formed on the positive electrode mixture layer 21b.
First electrolyte layer 2 including a holder for the same and a first electrolytic solution
4a was formed. At that time, a copolymer obtained by block-copolymerizing polyvinylidene fluoride and hexafluoropropylene was used as the first support. In the first electrolytic solution, LiPF ₆ as an electrolyte salt was dissolved in a solvent in which ethylene carbonate and propylene carbonate were mixed at a mass ratio of ethylene carbonate: propylene carbonate = 1: 1 at a content of 0.6 mol / l. I used one. The amount of the first holder added was 12.5% by mass with respect to the first electrolytic solution.

The negative electrode lead wire 1 is attached to the negative electrode collector 22a.
2 was attached and a second electrolyte layer 24b containing a second holding body and a second electrolytic solution was formed on the negative electrode mixture layer 22b. At that time, the same second holder as the first holder is used, and the second electrolytic solution is obtained by adding 1,2-dimethoxyethane as an additive to the first electrolytic solution. I was there. The content of 1,2-dimethoxyethane in the second electrolytic solution was 2% by mass. The amount of the second holder added was 12.5% by mass with respect to the second electrolytic solution.

Subsequently, a separator 23 made of a microporous polyethylene film is prepared, and the separator 23, the positive electrode 21, the separator 23, and the negative electrode 22 are sequentially laminated and wound, and a protective tape 25 is adhered to the wound electrode body 20. And
After that, while winding out the positive electrode lead wire 11 and the negative electrode lead wire 12 to the outside, the spirally wound electrode body 20 is vacuum-enclosed in the exterior members 30a and 30b made of a laminate film.
And the secondary battery shown in FIG. 2 was obtained.

As Comparative Example 1 to this Example, 1,2-dimethoxyethane was not added to the second electrolytic solution, and the first electrolytic solution and the second electrolytic solution were the same except that A secondary battery was manufactured in the same manner as in this example. Further, as Comparative Example 2 with respect to this Example, the first electrolytic solution and the second electrolytic solution
1,2-dimethoxyethane was added at a content of 1% by mass to the electrolytic solution of Example 1 and the first electrolytic solution and the second electrolytic solution were the same, except that the same as in the present example. A secondary battery was produced.

A charging / discharging test was conducted on the obtained secondary batteries of Example 1 and Comparative Examples 1 and 2 to examine the initial discharge capacity and the discharge capacity at the 30th cycle. The initial discharge capacity is
It is the discharge capacity obtained in the first charge and discharge, and the charge and discharge was performed at a constant current and constant voltage of 1 A at 23 ° C. up to an upper limit of 4.2 V, and then a constant current of 200 mA was terminated at a final voltage of 3.0.
I went to V. The discharge capacity at the 30th cycle is the discharge capacity obtained at the 29th cycle (that is, the 30th cycle as a whole) after 29 cycles of charging and discharging after obtaining the initial discharge capacity. The charge and discharge at that time is up to a constant current and constant voltage charge of 1 A at 23 ° C.
After discharging up to 2V, a constant current discharge of 500mA was carried out up to a final voltage of 3.0V. The results obtained are shown in Table 1. In Table 1, the values of Example 1 and Comparative Example 2 are the same as those of Comparative Example 1.
Of the first discharge capacity and the discharge capacity at the 30th cycle of 100
Is a relative value when.

[0070]

[Table 1]

As can be seen from Table 1, in the present example in which only the second electrolytic solution contained 1,2-dimethoxyethane, both the first electrolytic solution and the second electrolytic solution were 1,2- Comparative Example 1 containing no dimethoxyethane, and 1, 2 for both
The initial discharge capacity and the discharge capacity at the 30th cycle were higher than those of Comparative Example 2 containing -dimethoxyethane. That is, if 1,2-dimethoxyethane is added only to the second electrolytic solution and the chemical compositions of the first electrolytic solution and the second electrolytic solution are different, the discharge capacity and the cycle characteristics are improved. I found out that

Example 2 A lithium ion secondary battery in which the capacity of the negative electrode 22 is represented by the capacity component due to insertion / extraction of lithium was produced. At that time, during the charging, the negative electrode 22
Cathode 21 and anode 22 to prevent lithium metal from being deposited on
The same as Example 1 except that the area density ratio was adjusted and vinyl ethylene carbonate was used as an additive instead of 1,2-dimethoxyethane.

Further, as Comparative Example 3 with respect to this embodiment,
Example 1 except that the first electrolytic solution and the second electrolytic solution were added at a content of 1% by mass of vinyl ethylene carbonate, and the first electrolytic solution and the second electrolytic solution were the same. A secondary battery was produced in the same manner as in.

A charging / discharging test was conducted on the obtained secondary batteries of Example 2 and Comparative Example 3 in the same manner as in Example 1,
The initial discharge capacity and the 30th cycle discharge capacity were determined. The obtained results are shown in Table 2 together with the results of Comparative Example 1. In Table 2, the values of Example 2 and Comparative Example 3 are relative values when the initial discharge capacity of Comparative Example 1 and the discharge capacity at the 30th cycle are 100.

[0075]

[Table 2]

As can be seen from Table 2, this example containing vinyl ethylene carbonate only in the second electrolytic solution was
Both the initial discharge capacity and the discharge capacity at the 30th cycle were higher than Comparative Example 1 in which both the first electrolytic solution and the second electrolytic solution did not contain nylethylene carbonate, and Comparative Example 2 in which both contained vinylethylene carbonate. It was That is, by adding vinyl ethylene carbonate only to the second electrolytic solution so that the first electrolytic solution and the second electrolytic solution have different chemical compositions, the discharge capacity and cycle characteristics can be improved. Do you get it.

In the above embodiment, the capacity of the negative electrode 22 is represented by the sum of the capacity component due to occlusion / desorption of lithium and the capacity component due to precipitation / dissolution of lithium. The case where vinylethylene carbonate is added to a lithium ion secondary battery in which ethane is added and the capacity of the negative electrode 22 is represented by a capacity component due to insertion / extraction of lithium has been exemplified. The effect can be obtained, and the same effect can be obtained by adding 1,2-dimethoxyethane and vinylethylene carbonate together.

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 various modifications can be made. For example, in the above-described embodiments and examples, the case of using a so-called gel electrolyte has been described, but the present invention can also be applied to the case of using another electrolyte including a holding body and an electrolytic solution. Other electrolytes include
For example, a polymer solid electrolyte obtained by swelling a polymer material serving as a support with an electrolytic solution can be used. At that time, as the polymer material, for example, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, or the like is used. Further, in the above-described second embodiment and Examples 2-1 to 2-5, the polymer material was used as the holder for description, but lithium nitride, lithium iodide or lithium hydroxide polycrystal, iodine An inorganic conductor such as a mixture of lithium iodide and dichromium trioxide or a mixture of lithium iodide, thylium sulfide and phosphorous disulfide may be used as the holding body, and a polymer material and an inorganic conductor are mixed. You may use it.

Further, in the above-mentioned embodiment and examples,
As additives, vinyl ethylene carbonate and 1,
At least one of 2-dimethoxyethane is used, but other substances may be used. In this case, as other compounds, not only those having a good function in the negative electrode such as vinylethylene carbonate and 1,2-dimethoxyethane, but also those having a good function in the positive electrode may be used. When a positive electrode having a good function is used, the content of them is larger in the first electrolyte layer than in the second electrolyte layer.

Further, in the above-mentioned embodiment and example,
Although the first electrolyte solution and the second electrolyte solution have different chemical compositions by the additive, for example, the chemical compositions may be different by the solvent or the electrolyte salt. In that case, the additive may or may not be contained, and the first electrolytic solution and the second electrolytic solution may have the same or different contents.

In addition, in the above-described embodiments and examples, the case where lithium is used as the light metal has been described, but other alkali metals such as sodium (Na) or potassium (K), or magnesium or calcium (Ca), etc. The present invention can be applied to the case of using the alkaline earth metal, or other light metal such as aluminum, lithium, or an alloy thereof, and similar effects can be obtained. At that time, 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 the voltage compatibility with the lithium ion secondary batteries currently in practical use is high. When an alloy containing lithium is used as the light metal, there is a substance capable of forming an alloy with lithium in the electrolyte, and an alloy may be formed during precipitation, or an alloy with lithium may be formed in the negative electrode. Possible materials are present and may form alloys during precipitation.

Furthermore, in the above-mentioned embodiments and examples, the winding laminate type secondary battery has been described.
The present invention can be similarly applied to a laminated laminate type secondary battery. In addition, the present invention can be applied to so-called cylindrical type, square type, coin type, button type and other secondary batteries. Further, not only the secondary battery but also the primary battery can be applied. At that time, as the positive electrode material, for example, TiS ₂ , MnO ₂ , graphite, FeS ₂ or the like may be used instead of the material described in the above embodiment.

[0083]

As described above, according to the battery according to any one of claims 1 to 10, since the chemical composition of the electrolytic solution is different between the positive electrode side and the negative electrode side, the electrolytic solution is different. The chemical stability of can be improved on both the positive electrode side and the negative electrode side, and battery characteristics such as battery capacity and cycle characteristics can be improved.

Further, according to the battery manufacturing method of any one of claims 11 to 13, since the electrolyte having different chemical compositions of the electrolytic solution is formed on the positive electrode side and the negative electrode side, The battery of the present invention can be easily realized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an exploded secondary battery according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of the spirally wound electrode body shown in FIG.

FIG. 3 is a flowchart showing a manufacturing process of the secondary battery shown in FIGS. 1 and 2.

[Explanation of symbols]

11 ... Positive electrode lead wire, 12 ... Negative electrode lead wire, 20 ... Winding electrode body, 21 ... Positive electrode, 21a ... Positive electrode collector, 21b ... Positive electrode mixture layer, 22 ... Negative electrode, 22a ... Negative electrode collector, 22b ...
Negative electrode mixture layer, 23 ... Separator, 24 ... Electrolyte, 24a
... first electrolyte, 24b ... second electrolyte, 25 ... protective tape, 30a, 30b ... exterior member, 31 ... adhesion film

Continued front page    F-term (reference) 5H029 AJ03 AJ05 AK02 AK03 AK05                       AK16 AL06 AL07 AL08 AL11                       AL16 AM03 AM04 AM05 AM07                       BJ04 BJ14 DJ09 EJ14                 5H050 AA07 AA08 BA18 CA02 CA07                       CA08 CA09 CA11 CA20 CB07                       CB08 CB09 CB11 CB20 CB22                       DA13 EA23 EA26 FA02 FA05

Claims (13)

[Claims] 1. A battery comprising a positive electrode and a negative electrode, and an electrolyte interposed between the positive electrode and the negative electrode, wherein the electrolyte includes an electrolytic solution and a holder, and has a chemical composition on the positive electrode side and the negative electrode side. Batteries characterized by different. 2. The electrolyte comprises a first electrolytic solution and a first electrolytic solution.
A first electrolyte layer that is located on the positive electrode side and that includes a second holding body, and a second electrolyte layer that is located on the negative electrode side that includes a second electrolytic solution and a second holding body. 2. The battery according to claim 1, wherein the electrolytic solution and the second electrolytic solution have different chemical compositions. 3. The battery according to claim 1, wherein the electrolytic solution contains a solvent, an electrolyte salt, and an additive, and the content of the additive is different between the positive electrode side and the negative electrode side. 4. The electrolytic solution contains at least one of vinyl ethylene carbonate and 1,2-dimethoxyethane as an additive, and the content of these is larger on the negative electrode side than on the positive electrode side. The battery according to claim 3, wherein the battery is a battery. 5. The electrolyte contains, as a support, at least one of polyvinylidene fluoride and a copolymer of polyvinylidene fluoride.
Battery described. 6. The battery according to claim 1, wherein the electrolyte contains a copolymer of vinylidene fluoride and hexafluoropropylene as a holder. 7. The battery according to claim 1, wherein the capacity of the negative electrode is represented by a sum of a capacity component due to occlusion and release of light metal and a capacity component due to precipitation and dissolution of light metal. 8. The negative electrode contains a negative electrode material capable of inserting and extracting a light metal.
Battery described. 9. The battery according to claim 8, wherein the negative electrode contains a carbon material. 10. The negative electrode comprises tin (Sn), lead (Pn)
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), zirconium (Zr), yttrium (Y) or hafnium (H).
The battery according to claim 8, comprising at least one selected from the group consisting of simple substances, alloys, and compounds of f). 11. A method of manufacturing a battery comprising a positive electrode and a negative electrode, and an electrolyte interposed therebetween, comprising an electrolytic solution and a holder, and having different chemical compositions on the positive electrode side and the negative electrode side. A method of manufacturing a battery, comprising the step of forming. 12. A step of forming a first electrolyte layer containing a first electrolytic solution and a first holding body on a positive electrode, and a second electrolytic solution having a chemical composition different from that of the first electrolytic solution on a negative electrode. And a step of forming a second electrolyte layer including a second holder, and a step of stacking a positive electrode and a negative electrode with the first electrolyte layer and the second electrolyte layer facing each other. The method for manufacturing a battery according to claim 11. 13. The method for producing a battery according to claim 12, wherein at least one of vinyl ethylene carbonate and 1,2-dimethoxyethane is added to the second electrolytic solution.