JP2003303622A - Battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery of which the initial defective ratio is improved and the battery characteristics such as battery capacity and load property can be improved, and its manufacturing method. <P>SOLUTION: The battery comprises a wound electrode body 20 in which a positive electrode 21 and a negative electrode 22 are laminated and wound through an electrolyte 23 that contains a polymer material and an insulating particle 23a. Since the width of the electrolyte 23 is larger than the positive electrode 21 and the negative electrode 22 by 0.5 mm or more and 4 mm or less, the positive electrode 21 and the negative electrode 22 are completely covered, thereby, short circuit is prevented. It is desirable that the content of the insulating particle 23a is 6 volume % or more and 15 volume % or less. It is desirable that the average distance between the electrodes is 15 μm or more and 50 μm or less, and the average particle size of the insulating particle 23a is made 0.5 μm or more and 5 μm or less. In the manufacture, after the electrolyte 23 is formed, it is pressurized while heating, thereby, the internal resistance of the electrolyte 23 is reduced and the insulating particle 23a is dispersed in the electrolyte 23 uniformly. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery in which a pair of electrodes and an electrolyte interposed between the electrodes are wound, 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.

In this solid electrolyte battery, the positive electrode and the negative electrode are similar to those of a normal lithium ion battery, but as an electrolyte, for example, a polymer material such as a copolymer of polyvinylidene fluoride and hexafluoropropylene is used, and LiP is used.
A solution in which a lithium salt such as F ₆ is dissolved is used.
Such an electrolyte may be used as an all-solid-state electrolyte in which a solvent such as ethylene carbonate or propylene carbonate is not added, but may also be used as a gelled electrolyte that is plasticized by adding a solvent. In particular, the gel electrolyte can obtain a relatively high ionic conductivity at room temperature, and is regarded as a promising secondary battery in the future.

In such a solid electrolyte battery, the electrolyte may function as a separator in some cases. However, since the electrolyte is soft and softens when the temperature is raised, the distance between the electrodes becomes extremely short when the temperature rises, and capacity deterioration may occur due to repeated cycles or storage at high temperatures. there were.

Therefore, conventionally, attempts have been made to improve the mechanical strength by preventing the softening by adding a filler to the electrolyte to improve the high temperature storage characteristics and the cycle characteristics. As the filler, for example, various insulating particles are used, and examples thereof include oxides of silicon (Si), aluminum (Al) or titanium (Ti), ceramics such as zeolite, polymers such as polyolefin, nylon or polycarbonate. , Styrene-butadiene rubber and the like as a main material, and an example of using a powder obtained by molding this into a fibrous, spherical, rock-shaped or the like has been reported (for example, JP-A 2000-164254, JP-A 7-
237258, JP-A-10-116513, JP-A-2001-167795, and US Pat.
658,685, U.S. Pat. No. 5,460,904.
Gazette, US Pat. No. 5,720,780, etc.).

[0007]

However, the battery using the electrolyte to which the insulating particles are added has a big problem that the initial failure rate is high. This is often due to a short circuit. Generally, in a lithium ion battery, the negative electrode potential is near the potential at which lithium is deposited. For this reason, if there is an edge portion or the like where the current is concentrated, a lithium precipitation phenomenon occurs at that portion, and a short-circuit occurs due to the dendritic lithium deposition. As a measure to prevent this, the negative electrode is several meters longer than the positive electrode.
Although it is made to be large in the plane direction by about m, the defect rate cannot be suppressed even with such measures.

Unless short-circuited, the effect of preventing the capacity deterioration due to the addition of the filler is exhibited, but this time the initial capacity and load characteristics cannot be obtained. In particular, high performance in recent years
As a battery for multifunctional portable electronic devices, it has been a serious problem that load characteristics cannot be obtained.

The present invention has been made in view of the above problems, and an object thereof is to provide a battery and a manufacturing method thereof which can improve the initial failure rate and battery characteristics such as battery capacity and load characteristics. To provide.

[0010]

A first battery according to the present invention comprises a pair of electrodes and an electrolyte wound between the electrodes, and the electrolyte is a polymer material and insulating particles. In addition, the width of the electrolyte is larger than that of the electrode in the range of 0.5 mm or more and 4 mm or less.

The second battery according to the present invention comprises a pair of electrodes and an electrolyte wound between the electrodes, and the electrolyte contains a polymer material and insulating particles. The content is 6% by volume or more and 15% by volume or less.

The first method for manufacturing a battery according to the present invention is for manufacturing a battery in which a pair of electrodes and an electrolyte interposed between the electrodes are wound, and An electrolyte containing a polymer material and insulating particles,
This step includes a step of forming the electrolyte so that its width is larger than that of the electrode within a range of 0.5 mm or more and 4 mm or less, and a step of forming the electrolyte and then pressing the electrolyte while heating the electrolyte.

The second method for manufacturing a battery according to the present invention is for manufacturing a battery in which a pair of electrodes and an electrolyte interposed between the electrodes are wound, and A step of forming an electrolyte containing a polymer material and insulating particles and having a content of the insulating particles of 6% by volume or more and 15% by volume or less; and a step of forming the electrolyte and then applying pressure while heating the electrolyte. It includes.

In the first battery according to the present invention, the width of the electrolyte is larger than that of the electrode in the range of 0.5 mm or more and 4 mm or less, so that the end portion of the electrode is completely covered with the electrolyte containing the insulating particles. . Therefore, the burr at the electrode end portion that causes the short circuit is completely covered with the electrolyte, and the initial defect rate is improved.

In the second battery according to the present invention, since the content of the insulating particles in the electrolyte is 6% by volume or more and 15% by volume or less, the short circuit rate is reduced and the battery capacity is improved.

In the first and second manufacturing methods according to the present invention, the electrolyte is pressurized while being heated at a temperature of 50 ° C. or higher and 120 ° C. or lower. Therefore, the density of the insulating particles in the electrolyte is made uniform, and the short circuit is reduced.

[0017]

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 formed by laminating a positive electrode 21 and a negative electrode 22 with an electrolyte 23 in between and winding the layers. In the wound electrode body 20,
In order to prevent a short circuit due to the deposition of lithium, the width of the negative electrode 22 is wider than the width of the positive electrode 21 by several mm. Here, the width of the positive electrode 21 or the negative electrode 22 means the positive electrode 21.
Alternatively, it refers to the length in the direction perpendicular to the longitudinal direction of the negative electrode 22 (that is, the winding direction), and specifically means the width of the positive electrode mixture layer 21a or the negative electrode mixture layer 22a described later.

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 so as to substantially penetrate the spirally wound electrode body 20. The positive electrode collector 21a is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless foil.

The positive electrode mixture layer 21b is made of, for example, a positive electrode active material.
Positive electrode capable of inserting and extracting lithium as
It contains any one kind or two or more kinds of materials. Well
If necessary, conductive agents such as graphite, and polyfluoride
Vinylidene, styrene butadiene rubber, polymethacryl
Methyl acid, ethylene propylene diene monomer or
It may contain a binder such as a copolymer containing these.
Yes. Positive electrode material capable of inserting and extracting lithium
As the material, for example, TiS₂, MoS₂, FeS ₂，
NbSe₂, MnO₂Or V₂O_FiveSuch as lithium
Metal sulfides or oxides that do not contain, or
Contains lithium oxide, lithium sulfide or lithium
Intercalation compounds such as lithium-containing compounds or graphite
Rui or polymeric materials can be mentioned.

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 width of the negative electrode 22 described above is determined by the negative electrode mixture layer 22b.
Equivalent to the width of. That is, the width of the negative electrode mixture layer 22b is larger than the width of the positive electrode mixture layer 21b. The negative electrode current collector 22a has an exposed portion where the negative electrode mixture layer 22b is not provided at one end in the longitudinal direction, and the negative electrode lead wire 12 substantially penetrates the wound electrode body 20 at this exposed portion. It is installed so that The negative electrode current collector 22a is
For example, it is made of 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 as a negative electrode active material. If necessary, a conductive agent and a binder such as polyvinylidene fluoride, styrene butadiene rubber, polymethyl methacrylate, ethylene propylene diene monomer or a copolymer containing these may be contained.

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 they can obtain high charge / discharge capacity and good cycle characteristics. Particularly, graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density.

Specific examples of carbon materials 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.

Among them, 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 of titanium oxide, lithium titanate, iron oxide, ruthenium oxide, molybdenum oxide, or Li.
Examples of the polymer material include N _{3 and the} like, and examples of the polymer material include polyacetylene, polyaniline, polypyrrole and the like.

The electrolyte 23 contains a polymer material, a lithium salt as an electrolyte salt, and a solvent if necessary.

Examples of the polymer material include polyvinylidene fluoride and copolymers 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.

As the polymer material, for example, carboxymethyl cellulose, polyacrylonitrile and a copolymer of polyacrylonitrile can be used.
The copolymer monomers such as vinyl monomers are vinyl acetate, methyl methacrylate, butyl methacrylate, methyl acrylate, butyl acrylate, itaconic acid, hydrogenated methyl acrylate, hydrogenated ethyl acrylate, acrylamide, vinyl chloride, fluorine. Examples thereof include vinylidene chloride and 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.

These polymeric materials may be used either individually or in combination of two or more.

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.

As the solvent, various nonaqueous solvents conventionally used in nonaqueous electrolytic solutions can be used. Specifically, cyclic carbonic acid esters such as propylene carbonate, ethylene carbonate and butylene carbonate, chain esters such as dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate, or γ-
Examples include ethers such as butyrolactone, sulfolane, oxolane, 2-methyltetrahydrofuran, and 1,2-dimethoxyethane. In particular, from the viewpoint of oxidation stability, it is preferable to include carbonic acid ester.

The electrolyte 23 further includes, for example, alumina (A
The insulating particles 23a made of, for example, 1 ₂ O ₃ ) are included to improve the mechanical strength and prevent a short circuit. The content of the insulating particles 23a in the electrolyte 23 is preferably 6% by volume or more and 15% by volume or less. This is because if it is less than 6% by volume, short circuit cannot be prevented, and if it is more than 15% by volume, the capacity decreases.

FIG. 3 shows the relationship between the width of the electrolyte 23 and the widths of the positive electrode 21 and the negative electrode 22. Width W ₂₃ of the electrolyte 23 is preferably larger than the width W ₂₂ of width W ₂₁ and the anode 22 of the cathode 21. The end portions of the positive electrode 21 and the negative electrode 22 can be completely covered with the electrolyte 23 containing the insulating particles 23a, and the current is concentrated on the end portion of the positive electrode 21 or the portion of the negative electrode 22 facing the burr to deposit lithium. This is because a short circuit due to Specifically, the width W ₂₃ of the electrolyte ₂₃ is defined by the positive electrode 21 and the negative electrode 2
It is preferable that the longer width of the two, that is, the width W _{22 of the} negative electrode 22 in this case, is larger in the range of 0.5 mm or more and 4 mm or less. This is because if it is less than 0.5 mm, the ends of the positive electrode 21 and the negative electrode 22 cannot be completely covered, and if it exceeds 4 mm, the capacity decreases due to an increase in the portion that does not contribute to the battery reaction.

FIG. 4 is an enlarged view of a part of the positive electrode 21, the negative electrode 22 and the electrolyte 23 in order to explain the size of the insulating particles 23a and the thickness of the electrolyte 23. The average particle diameter of the insulating particles 23a is sufficiently large, and specifically,
It is preferably 0.5 μm or more. By improving the tortuosity of the electrolyte 23 and dispersing the current, it is possible to prevent the current from concentrating on the portion of the negative electrode 22 facing the edge portion of the positive electrode 21 and reduce the short-circuit rate. is there. In addition, when the particle size of the insulating particles 23a is small, the insulating particles 23a can be inserted into the positive electrode mixture layer 21b through the gap between the positive electrode active material particles 21c or the negative electrode active material particles 22c.
Alternatively, it is mixed into the negative electrode mixture layer 22b to form the positive electrode mixture layer 2
This is because the load characteristics are deteriorated due to clogging of the 1b or the negative electrode mixture layer 22b. On the other hand, insulating particles 2
If the average particle diameter of 3a is larger than 5 μm, the insulating particles 23
a is unevenly distributed in the electrolyte 23, and the insulating particles 23a
A short circuit is likely to occur in a portion where there is little.

When the average particle diameter of the insulating particles 23a is set in this way, the average inter-electrode distance C is preferably 15 μm or more and less than 50 μm in conjunction with this. When the average inter-electrode distance C is 50 μm or more, the positive electrode 2
This is because the resistance between the No. 1 and the negative electrode 22 increases, which may deteriorate the load characteristics. Further, when the average inter-electrode distance C is less than 15 μm, the short circuit due to the uneven distribution of the insulating particles 23a is likely to occur. Here, the average inter-electrode distance C is determined by the thicknesses of the positive electrode lead wire 11 and the negative electrode lead wire 12 and the exterior member 30.
The thicknesses of a and 30b are subtracted from the thickness of the battery, and the obtained value is divided by the number of repeated facings of the positive electrode 21 and the negative electrode 22 in the thickness direction, that is, the number of stacked layers. Half of total thickness and positive electrode 21
It is obtained by subtracting one half of the total thickness of the.

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

FIG. 5 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, a polymer material, an electrolyte salt, insulating particles 23a and, if necessary, a solvent are dispersed in a dispersion medium to prepare an electrolyte precursor, and the electrolyte precursor is put on the positive electrode 21 and the negative electrode. It is applied onto 22 and, if necessary, polymerization or the like is performed to volatilize the dispersion medium to form the electrolyte 23 (step S103). At this time, for example, it is preferable to apply the electrolyte precursor in a width wider than that of the positive electrode 21 and the negative electrode 22. The width of the electrolyte 23 is adjusted by, for example, volatilizing the dispersion medium, cutting the electrolyte 23, and arranging it, and removing the underlay. The content of the insulating particles 23a in the electrolyte 23 and the average particle size are
It is preferable to adjust it to fall within the above range. Further, the thickness of the electrolyte 23 is preferably adjusted so that the inter-electrode distance C when the positive electrode 21 and the negative electrode 22 are laminated and wound to form the wound electrode body 20 is in the above range.

After forming the electrolyte 23, for example, the positive electrode lead wire 11 is attached to the positive electrode current collector 21a, and
The negative electrode lead wire 12 is attached to the negative electrode current collector 22a. After that, for example, the positive electrode 21 and the negative electrode 22 are laminated via the electrolyte 23. After that, wind this laminated body,
The wound electrode body 20 is formed (step S104).

After forming the 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 brought into close contact with each other by heat fusion or the like (step S105). 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.

The spirally wound electrode body 20 is attached to the exterior members 30a and 30b.
Then, a hot press process is performed in which the electrolyte 23 is heated and pressed at a predetermined temperature (step S106).
As a result, the electrolyte 23 provided on the positive electrode 21 and the electrolyte 23 provided on the negative electrode 22 are integrated, and the interface resistance is reduced. Further, the insulating particles 23 a unevenly distributed near the surface of the electrolyte 23 are uniformly packed inside the electrolyte 23. The temperature of the hot pressing step is preferably such that the electrolyte 23 can be sufficiently softened and the lithium salt is not decomposed, and specifically, it is preferably in the range of 50 ° C. or higher and 120 ° C. or lower.

The hot pressing step is preferably performed after the wound electrode body 20 is sealed in the exterior members 30a and 30b. This is because, if the width of the electrolyte 23 is formed larger than that of the positive electrode 21 and the negative electrode 22, if the hot pressing step is performed before encapsulation, the softened electrolyte 23 reaches the pressing machine and the width of the electrolyte 23 changes. By the above, 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 occluded in the negative electrode mixture layer 22b via the electrolyte 23. Further, when discharged, lithium ions are released from the negative electrode mixture layer 22b and are occluded in the positive electrode mixture layer 21b via the electrolyte 23.

In the present embodiment, since the electrolyte 23 contains the insulating particles 23a in an amount of 6% by volume or more and 15% by volume or more, the short-circuit rate is improved and the capacity is improved. Further, since the width of the electrolyte 23 is larger than that of the positive electrode 21 and the negative electrode 22,
The positive electrode 21 and the negative electrode 22 are completely covered with the electrolyte 23 containing the insulating particles 23a, and the short circuit is more effectively prevented. Furthermore, since the average inter-electrode distance C is 15 μm or more and less than 50 μm and the average particle diameter of the insulating particles 23a is 0.5 μm or more and 5 μm or less, short circuit can be prevented more effectively and high load characteristics can be obtained. You can

As described above, according to the present embodiment, the content of the insulating particles 23a in the electrolyte 23 is set to 6% by volume or more and 15% by volume or less, so that the mechanical strength is improved and the short circuit is prevented. A high capacity can be obtained.

Since the width of the electrolyte 23 is formed larger than that of the positive electrode 21 and the negative electrode 22, the electrolyte 2 containing the insulating particles 23a at the ends of the positive electrode 21 and the negative electrode 22 is formed.
3 can be completely covered, and the occurrence of a short circuit at the end of the positive electrode 21 or the portion of the negative electrode 22 facing the burr can be prevented.

Furthermore, since the average inter-electrode distance C is 15 μm or more and less than 50 μm and the average particle diameter of the insulating particles 23a is 0.5 μm or more and 5 μm or less, occurrence of short circuit can be suppressed and load characteristics can be improved. it can.

As a method of preventing a short circuit, n
A method for solving the variation by using very fine insulating particles of m order has been proposed (Japanese Patent Laid-Open No. 7-23).
No. 7258), this method cannot obtain load characteristics. On the other hand, according to the present embodiment, it is possible to obtain the effect of improving the load characteristics while allowing the dispersion variation of the insulating particles.

In addition, since the hot pressing step of pressing the electrolyte 23 while heating it at a predetermined temperature is performed, the electrolyte 23 provided on the positive electrode 21 and the electrolyte 23 provided on the negative electrode 22 are integrated. The resistance at the interface can be reduced, the resistance inside the electrolyte 23 can be reduced, and the capacity is improved. Further, since the insulating particles 23a unevenly distributed near the surface of the electrolyte 23 can be uniformly packed inside the electrolyte 23, it is possible to prevent a short circuit due to the dispersion of the insulating particles 23a. .

[0062]

EXAMPLES Further, specific examples of the present invention will be described in detail by using the same reference numerals with reference to FIGS.

(Examples 1-1 to 1-3) First, a lithium-cobalt composite oxide (LiCo) was used as a positive electrode active material.
O ₂ ), the lithium-cobalt composite oxide 94
Parts by mass, and 3 parts by mass of carbon black which is a conductive agent,
A positive electrode mixture was prepared by mixing 3 parts by mass of polyvinylidene fluoride as a binder. Next, 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. ,
A positive electrode 21 was prepared by compression molding with a roll press to form a positive electrode material mixture layer 21b having a thickness of 50 μm.

Further, artificial graphite powder was prepared as a negative electrode active 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 the negative electrode current collector 22 made of a strip-shaped copper foil having a thickness of 20 μm
A uniform coating was applied to both surfaces of a, dried, and compression-molded by a roll press to form a negative electrode mixture layer 22b having a thickness of 50 μm, and the negative electrode 22 was produced.

Then, polyvinylidene fluoride and hexafluoropropylene copolymer, which are raw materials of the polymer material,
An electrolyte precursor was prepared by mixing LiPF ₆ , which is an electrolyte salt, and ethylene carbonate and propylene carbonate, which are solvents, with dimethyl carbonate, which is a dispersion medium. After that, the electrolyte precursor was applied on the positive electrode 21 and the negative electrode 22 with the same width as those by the casting method to volatilize dimethyl carbonate. At that time, the insulating particles 23 have an average particle diameter of 0.04 μm.
m alumina powder was used, and the addition amount was
In 1-3, the content of the insulating particles 23a in the electrolyte 23 was changed to the values shown in Table 1. Further, the coating amount of the electrolyte precursor was adjusted so that the average interelectrode distance was 50 μm. After forming the electrolyte 23, the positive electrode lead wire 11 was attached to the positive electrode collector 21a, and the negative electrode lead wire 12 was attached to the negative electrode collector 22a.

[0066]

[Table 1]

Positive electrode lead wire 11 and negative electrode lead wire 12
After attaching, the positive electrode 21 and the negative electrode 22 are laminated and wound, and the thickness is approximately 4 mm, the width is 35 mm, and the height is 62 mm.
The wound electrode body 20 was used. After that, the positive electrode lead wire 11
And while winding out the negative electrode lead wire 12 to the outside, the spirally wound electrode body 20 is covered with an exterior member 30a made of a laminate film,
30b was sealed under reduced pressure to obtain the secondary battery shown in FIGS. 1 and 2.

20 secondary batteries were prepared for each of Examples 1-1 to 1-3. Regarding the obtained secondary battery,
When the average inter-electrode distance was measured before the first charge, it was 50μ.
It was m. Note that this value was obtained as described in the embodiment. Specifically, the thicknesses of the positive electrode lead wire 11 and the negative electrode lead wire 12 (each 0.2 mm) and the thickness of the exterior members 30a and 30b (each 0.15 mm).
Is subtracted from the thickness (3.9 mm) of the battery, and the obtained value is divided by the number of repeated facing of the positive electrode 21 and the negative electrode 22 in the thickness direction, that is, the number of stacked layers (20), and from the obtained value, 2 of the total thickness (120 μm) of the negative electrode 22
1 and 2 of the total thickness of the positive electrode 21 (120 μm)
Subtracted 1 /.

As Comparative Examples 1-1 and 1-2 with respect to this example, the secondary battery was the same as this example except that the content of the insulating particles 23a was changed as shown in Table 1. Was produced.

Regarding the obtained secondary batteries of Examples 1-1 to 1-3 and Comparative examples 1-1 and 1-2, 4.2V to 3V
5 cycles of charging and discharging under the same conditions at the rated capacity (2
The discharge capacity at the cycle) and the short circuit rate were measured.
The obtained results are also shown in Table 1. The short-circuited ones were judged from the fact that the voltage becomes 0 when the circuit is open.

As can be seen from Table 1, the insulating particles 23a
Example 1 in which the content of is 6 vol% or more and 15 vol% or less
-1 to 1-3 have higher capacities and improved short-circuit rates than Comparative Example 1-1 in which the content of the insulating particles 23a is 4% by volume and Comparative Example 1-2 in which the content of the insulating particles 23a is 17% by volume. It had been. That is, it was found that when the content of the insulating particles 23a was 6% by volume or more and 15% by volume or more, short circuit was prevented and the capacity was improved.

Examples 2-1 to 2-6 Secondary batteries were produced in the same manner as in Example 1-2 except that the width of the electrolyte 23 was changed as shown in Table 2. . Electrolyte 23
The width of was changed by using an underlay of a glass plate when applying the electrolyte precursor, volatilizing dimethyl carbonate without removing the underlay, and cutting to a desired width. The width of the positive electrode 21 was 48 mm, and the width of the negative electrode 22 was 50 mm. The example 2-1 is under the same conditions as the example 1-2.

[0073]

[Table 2]

Each of the obtained secondary batteries of Examples 2-1 to 2-6 was charged and discharged for 5 cycles under the same conditions at 4.2V to 3V, and the rated capacity and the short circuit rate were measured. The obtained results are also shown in Table 2.

As can be seen from Table 2, according to Examples 2-2 to 2-6 in which the width of the electrolyte 23 was wider than that of the negative electrode 22, the short circuit rate could be improved and the rated capacity could be improved. In particular, in Examples 2-3 to 2-6, the short circuit rate was 0, and the short circuit due to the metal foil burr at the end of the positive electrode 21 could be completely prevented. Further, as the width of the electrolyte 23 was increased, the capacity increased, showed a maximum value, and then tended to decrease. That is, the width of the electrolyte 23 is set to the negative electrode 22.
It was found that short circuit can be prevented and the capacity can be increased by increasing the thickness in the range of 0.5 mm to 4 mm.

However, the rated capacity was still low, and was about 380 mAh with respect to the input capacity (550 mAh). It is presumed that the cause is the resistance in the electrolyte 23. That is, since the electrolyte 23 has almost no fluidity after casting, it is difficult to integrate the electrolyte 23 on the positive electrode 21 and the electrolyte 23 on the negative electrode 22, but especially when the insulating particles 23a are mixed. Has
It seems that there are many parts where the two are not integrated.

(Examples 3-1 to 3-6) Rolled electrode body 20
Example 2-2 except that a hot pressing step of pressing the electrolyte 23 while heating the electrolyte 23 at a predetermined temperature was performed after the secondary battery was manufactured by enclosing it in the exterior members 30a and 30b.
A secondary battery was produced in the same manner as in. The temperature of the hot pressing process was changed as shown in Table 3. In addition, Example 3-
1 is under the same conditions as in Example 2-4.

[0078]

[Table 3]

Each of the obtained secondary batteries of Examples 3-1 to 3-6 was charged and discharged for 5 cycles under the same conditions at 4.2V to 3V, and the rated capacity and the short circuit rate were measured. The obtained results are also shown in Table 3.

As can be seen from Table 3, according to Examples 3-2 to 3-6 in which the hot pressing process is performed, the rated capacity can be improved more than in the case of Rie 3-1 in which the hot pressing process is not performed. did it. Moreover, the rated capacity tended to increase as the hot-pressing temperature was increased, reached a maximum value, and then decreased. In particular, the temperature of the hot press process is 50 ° C to 12 ° C.
In Examples 3-3 to 3-5 in which the temperature is 0 ° C., the rated capacity is 50
It was able to be sufficiently increased to 0 mAh or more. this is,
By performing the hot pressing step, the electrolyte 2 on the positive electrode 21
3 and the electrolyte 23 on the negative electrode 22 are integrated to reduce the resistance of the interface, and the insulating particles 23a unevenly distributed in the vicinity of the surface of the electrolyte 23 are uniformly clogged inside the electrolyte 23, resulting in a short circuit. This is probably because the prevention effect was enhanced. That is, it was found that the capacity can be improved by performing the hot pressing step after forming the electrolyte 23, and a higher effect can be obtained by setting the temperature to 50 ° C. or higher and 120 ° C. or lower. .

(Examples 4-1 to 4-20) Insulating particles 2
A secondary battery was made in the same manner as in Example 3-4, except that the average particle diameter of 3a and the average distance between electrodes were changed as shown in Table 4. In addition, Example 4-1 is under the same conditions as Example 3-4.

[0082]

[Table 4]

Each of the obtained secondary batteries of Examples 4-1 to 4-20 was charged and discharged for 5 cycles under the same conditions at 4.2V to 3V, and the rated capacity and the short circuit rate were measured.
In addition, the load characteristics were measured by performing load discharge at a current value (3 C) at which the rated capacity was completely discharged in 20 minutes. The obtained results are also shown in Table 4.

As can be seen from Table 4, the larger the average particle size or the shorter the average distance between the electrodes, the more the load characteristics tended to improve, while the short-circuit rate tended to increase. Was given. That is, the average particle size is 0.5
It was found that if the average electrode distance is 15 μm or more and 50 μm or less and a short circuit does not occur, a very high load characteristic can be obtained.

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, the case where spherical particles are used as the insulating particles 23a has been described, but insulating particles having other shapes such as rock-like or fibrous may be used. When a fibrous material is used, the average particle diameter in the above-mentioned embodiments and examples corresponds to the fiber diameter. In addition, in the above embodiments and examples, the case where alumina is used as the insulating particles 23a has been described, but an insulating material other than alumina may be used. Examples thereof include oxides of Si or Ti, ceramics using Ca, etc., polymer materials such as zeolite, polyolefin, polytetrafluoroethylene, and polycarbonate, and derivatives or modified products thereof, or a mixture thereof.

Further, in the above-mentioned embodiment and example,
Although the polymer material, the electrolyte salt and the solvent have been specifically described with examples, other materials may be used.

Further, in the above-mentioned embodiment and examples,
Although the winding laminate type secondary battery using the exterior members 30a and 30b made of a laminate film has been described, the present invention can be similarly applied to the case of using another exterior member such as a can. Further, not only the secondary battery but also the primary battery can be applied.

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 metal 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.

[0089]

As described above, according to the battery described in any one of claims 1 to 3, the electrolyte is
Since the electrolyte is formed to have a width larger than that of the electrode by 0.5 mm or more and 4 mm or less as well as including the polymer material and the insulating particles, the electrolyte including the insulating particles completely covers the electrode, Short circuit due to metal foil burr in the extreme part is prevented. Therefore, the initial defect rate can be significantly reduced and the capacity can be improved.

In particular, according to the battery of claim 2, claim 4 or claim 5, the content of the insulating particles in the electrolyte is set to 6% by volume or more and 15% by volume or less, so that the mechanical strength is improved. It is possible to prevent short circuit and improve the capacity.

Particularly, according to the battery of claim 3 or 5, the average interelectrode distance is set to 15 μm or more and less than 50 μm, and the average particle diameter of the insulating particles is set to 0.5 μm or more and 5 μm or less. Therefore, it is possible to prevent a short circuit and improve load characteristics.

Further, according to the battery manufacturing method of the sixth or seventh aspect, since the step of pressurizing the electrolyte while heating is included, the resistance at the interface of the electrolyte is reduced and the inside of the electrolyte is reduced. The resistance can be reduced and the capacity is improved. In addition, the insulating particles can be uniformly packed inside the electrolyte, and a short circuit due to variations in the insulating particles can be prevented.

[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 plan view for explaining the relationship between the width of the electrolyte shown in FIG. 2 and the widths of the positive electrode and the negative electrode.

FIG. 4 is a cross-sectional view showing a positive electrode, a negative electrode, and a part of the electrolyte in an enlarged scale in order to explain the size of the insulating particles and the thickness of the electrolyte shown in FIG.

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

[Explanation of symbols]

DESCRIPTION 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, 21c ... Positive electrode active material particle, 22 ... Negative electrode, 22
a ... Negative electrode collector, 22b ... Negative electrode mixture layer, 22c ... Negative electrode active material particles, 23 ... Electrolyte, 23a ... Insulating particles, 30
a, 30b ... Exterior member, 31 ... Adhesive film

Continued front page    F-term (reference) 5H029 AJ02 AJ03 AJ06 AJ11 AJ12                       AK03 AL01 AL02 AL03 AL06                       AL07 AL11 AL16 AM03 AM04                       AM05 AM07 AM16 BJ02 BJ14                       CJ02 CJ03 CJ07 EJ04 EJ12                       HJ04 HJ05 HJ07

Claims (7)

[Claims] 1. A battery formed by winding a pair of electrodes and an electrolyte interposed therebetween, wherein the electrolyte contains a polymer material and insulating particles, and the width of the electrolyte is larger than that of the electrodes. Is 0.5 mm or more 4
A battery characterized by being formed large in a range of not more than mm. 2. The battery according to claim 1, wherein the content of the insulating particles in the electrolyte is 6% by volume or more and 15% by volume or less. 3. The average inter-electrode distance between the pair of electrodes is 15
The battery according to claim 1, wherein the battery has a size of not less than μm and less than 50 μm, and an average particle size of the insulating particles is not less than 0.5 μm and not more than 5 μm. 4. A battery formed by winding a pair of electrodes and an electrolyte interposed between the electrodes, wherein the electrolyte contains a polymer material and insulating particles, and the content of the insulating particles is 6 volumes. % To 15% by volume, a battery. 5. The average inter-electrode distance between the pair of electrodes is 15
The battery according to claim 4, wherein the battery has a size of not less than μm and less than 50 μm, and an average particle size of the insulating particles is not less than 0.5 μm and not more than 5 μm. 6. A method for producing a battery, which comprises winding a pair of electrodes and an electrolyte interposed therebetween, wherein an electrolyte containing a polymer material and insulating particles is formed between the pair of electrodes. The width of the electrolyte is 0.5 mm than the electrode
A method of manufacturing a battery, comprising: a step of increasing the size in the range of 4 mm or less; and a step of pressing the electrolyte while heating the electrolyte after forming the electrolyte. 7. A method for producing a battery, which comprises winding a pair of electrodes and an electrolyte interposed between the pair of electrodes, comprising a polymer material and insulating particles between the pair of electrodes, The content of particles is 6% by volume or more and 15% by volume
A method of manufacturing a battery, comprising the following steps of forming an electrolyte and, after forming the electrolyte, applying pressure while heating the electrolyte.