JP2003092141A - Electrochemical device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing for an electrochemical device having sufficient electrolyte holding capacity, a solid electrolyte with high perfor mance, easy to manufacture, and having a high auto safety function even in abnormal state. SOLUTION: In a manufacturing method of an electrochemical device having a positive electrode and a negative electrode formed to face each other, a solid electrolyte layer placed between the positive electrode and the negative electrode, and a separator layer disposed between at least the positive electrode or the negative electrode and the solid electrolyte layer, matrix resin forming the solid electrolyte layer is formed by a wet phase separation method. The electrochemical device is provided thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety mechanism for an electrochemical device such as a lithium ion secondary battery and an electric double layer capacitor, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the development of portable devices has been remarkable, and one of the driving forces thereof is that high energy batteries such as lithium ion secondary batteries make a great contribution. At present, the market for lithium secondary ion batteries exceeds 300 billion a year, and it is expected that various mobile devices will continue to develop in the future, and the progress in battery manufacturing technology will be required accordingly.

Such a lithium ion secondary battery is usually composed of a positive electrode, a liquid or solid electrolyte layer, and a negative electrode. This positive and negative electrode material is obtained by mixing a positive electrode active material and a negative electrode active material with a conductive auxiliary agent and a binder and applying the mixture on a current collector. In such a lithium-ion secondary battery, there is a demand for higher energy density of the battery as a development trend, and development of a thin battery is progressing as a measure for that.

As a method of obtaining such a thin and lightweight battery, there is a polymer battery in which the electrolyte portion, which was a solution, is made into a solid state so as to make the battery thinner. This technology is already known technology such as USP 5418091, but
In recent years, the characteristics have been improved, and the battery characteristics have been improved to the extent that they cannot be compared with when the technology was first disclosed.

There are various types of batteries using such solid electrolytes, which are roughly classified into the following three types.

(1) Type using lithium ion conduction in polymer polymer as electrolyte (2) Type using lithium ion conduction in plasticized polymer polymer as electrolyte (3) Plasticizing with organic solvent and plasticizer as electrolyte Type using lithium ion conduction in polymerized polymer, solvent component belonging to (3) among these, organic polymer component,
Batteries that have been gelled (solidified) by mixing an electrolyte salt have characteristics comparable to solution batteries and are being put to practical use.

As a typical example of a method for producing a gelled solid-state battery of the type (3), for example, USP52
There is a method for manufacturing a battery described in 96318, USP 5418091. This is to prepare a solid polyvinylidene fluoride solid electrolyte medium, join it with the positive and negative electrodes, extract the plasticizer from the whole battery body, and inject the electrolyte solution to gel the whole. It is a thing.

By gelling the entire battery body in this manner, the liberated electrolytic solution does not exist inside the battery. Therefore, it can be said that the configuration is completely different from that of the conventional solution type battery. Furthermore, this patent US
According to the contents disclosed in P5296318 and USP 5418091, the battery characteristics are also excellent.

However, when the above-mentioned solid gelled electrolyte is used, no problem occurs during normal use, but in abnormal times, for example, during overcharge and heating test, the rapid current cutoff due to the dissolution of the resin does not sufficiently function. . This resulted in thermal runaway, which could result in rupture and ignition.

In order to solve such a problem, for example, Japanese Unexamined Patent Publication No. 2001-43897 discusses a method of using a solid electrolyte and a shutdown separator in combination. However, in order to manufacture the battery described in this publication, a gel electrolyte must be prepared by forming a gel electrolyte on the positive electrode and the negative electrode in advance and then facing the positive and negative electrodes with the separator sandwiched therebetween. However,
Since the gel electrolyte has to be handled in a dry atmosphere, the subsequent manufacturing process needs to be performed in a dry atmosphere, which makes the manufacturing process very difficult.

Further, in order to form a solid electrolyte, a matrix polymer is applied, dried, and an electrolytic solution is poured therein to form a solid electrolyte. At this time, the matrix polymer, the separator and the electrode are sufficiently electrolyzed. It is necessary to impregnate the liquid. For this reason, the matrix polymer must have sufficiently open fine pores for holding the electrolyte, but the conventional manufacturing method cannot provide sufficient openings, and as a result, impregnation and holding of the electrolyte are not sufficient. However, since the opening was not sufficient, only a solid electrolyte having a low Li ion conductivity was obtained.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an electrochemical device which has a solid electrolyte having a sufficient electrolyte holding ability and excellent performance and is easy to manufacture. .

It is another object of the present invention to provide a method for manufacturing an electrochemical device having an excellent self-safety function even in the case of an abnormality.

[0014]

That is, the above object is achieved by the following constitution of the present invention. (1) A positive electrode and a negative electrode are formed to face each other, a solid electrolyte layer is provided between the positive electrode and the negative electrode, and a separator is provided at least between the positive electrode or the negative electrode and the solid electrolyte layer. A method of manufacturing an electrochemical device having a layer, wherein the matrix resin forming the solid electrolyte is formed by a wet phase separation method. (2) The method for manufacturing an electrochemical device according to (1), wherein the separator is a shutdown separator that blocks ionic conduction between the electrode and the solid electrolyte layer at a predetermined temperature or higher. (3) The method for producing an electrochemical device according to (1) or (2), wherein the Gurley value of the separator is 150 or less. (4) The method for producing an electrochemical device according to any one of (1) to (3) above, wherein the matrix resin is a PVDF homopolymer. (5) The method for manufacturing an electrochemical device according to any one of (1) to (4) above, wherein the electrochemical device is a lithium secondary battery. (6) An electrochemical device obtained by the method according to any one of (1) to (5) above.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing an electrochemical device of the present invention, a positive electrode and a negative electrode are formed so as to face each other, and a solid electrolyte layer is provided between the positive electrode and the negative electrode, which is the positive electrode or the negative electrode. An electrode, a method of manufacturing an electrochemical device having a separator layer between the solid electrolyte layer,
The solid electrolyte is formed by a wet phase separation method.

As described above, by forming and disposing the matrix resin on at least one of the positive electrode, the negative electrode, and the separator layer by the wet phase separation method, safety and
An electrochemical device having excellent electrical characteristics can be obtained.

In the electrochemical device of the present invention, the second layer having an electrolyte retaining function is interposed on the positive electrode side or the negative electrode side of the solid electrolyte. This second layer preferably blocks ionic conduction between the electrode and the solid electrolyte layer at a certain temperature or higher. That is, in a normal state, this second layer does not greatly contribute to the deterioration of the ionic conductivity, but when the battery falls into an abnormal state such as overcharge or internal short circuit, the ionic conductivity is blocked by the conventional solid state. It is possible to prevent thermal runaway, which is a drawback of the electrolyte electrolyte. Specifically, if it is a polyolefin based fine porous film having a porosity within a predetermined range, it can be melted at a certain temperature or higher to block the pores and block the ionic conduction.

When polyvinylidene fluoride, which is a gel component of the separator, is applied normally, the pores of the separator are blocked and it is difficult to maintain good battery characteristics. Therefore, it is necessary to create pores in the gel component to be coated.

In this case, pores can be formed in the solid electrolyte membrane by mixing an inorganic filler such as silica or alumina with the gel component and coating the mixture, but the adhesion with the polyolefin separator is not sufficient. However, handling problems occur when batteries are used.

Such a problem can be solved by applying the gel by the wet phase separation method. The wet phase separation method is a method of coagulating a film-forming stock solution in a solvent for phase separation. The advantages of forming a gel component by this method include the following. 1) It is possible to form a film having a high porosity of 60 to 70%. 2) The solvent of the film-forming stock solution is also extracted from the portion that permeates the pores of the polyolefin separator to form pores, and the pores of the polyolefin separator are not blocked. 3) Since the gel component applied to the front and back of the polyolefin separator has a structure in which the pores of the polyolefin separator are connected to each other, the adhesion between the polyolefin separator and the gel component is good.

From the above facts, it is preferable that the pore diameter of the polyolefin separator is larger. However, when the pore size is large, the shutdown characteristic of the separator is deteriorated and the number of short circuits of the battery is increased. Therefore, the pore diameter of the polyolefin separator is 0.05 to
0.3 μm is preferable, and 0.1 to 0.2 is more preferable.
μm.

If the porosity of the separator is too large, the strength of the separator will be weakened and internal short circuit of the battery will occur frequently, and if it is too small, the conductivity will be lowered by ions and the characteristics will be deteriorated. Occurs. Therefore, the porosity is preferably 30 to 70%, more preferably 40 to 60%.

The porosity of the separator can be evaluated by the time required for a certain amount of gas to pass through the substrate (Gurley value). Generally, when the Gurley value is small, the pore diameter is large and the porosity is high. The substrate Gurley value (the time required for 100 cc of air to pass through the substrate) is preferably 200 s or less, more preferably 150 s or less.

If the thickness of the gel component to be coated is too thick, the gel component will be easily peeled off from the substrate, which will be disadvantageous in terms of volume, and will lead to an increase in internal resistance of the battery. If it is too thin, uneven coating will appear. Since the liquid retaining property of the electrolytic solution is uneven, 0.5-10 μm on one side, particularly 1-5 μm is preferable.

Further, the film strength may be improved by incorporating inorganic particles such as silica and alumina in the stock solution for film formation.

The matrix resin constituting the solid electrolyte includes (1) polyalkylene oxide such as polyethylene oxide and polypropylene oxide, (2) copolymer of ethylene oxide and acrylate, (3) copolymerization of ethylene oxide and glycyl ether. Coalescing, (4)
Copolymer of ethylene oxide, glycyl ether and allyl glycyl ether, (5) polyacrylate (6) polyacrylonitrile (7) polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-3 fluoride Ethylene Copolymer, Vinylidene Fluoride-Hexafluoropropylene Fluororubber, Vinylidene Fluoride "Tetrafluoroethylene-
Hexafluoropropylene fluororubber and other fluoropolymers can be used.

Among these resins, polyvinylidene fluoride (PVDF), polyethylene oxide, polyacrylonitrile and the like are preferable, and polyvinylidene fluoride homopolymer is particularly preferable. The PVDF homopolymer has a wide redox window, is electrochemically stable, and has excellent long-term stability.

The solid electrolyte matrix resin used in the present invention is formed by the following wet phase separation method.

The wet phase separation method is a method in which phase separation is performed in a solution in film formation by a solution casting method. That is, a polymer to be a microporous film is dissolved in a solvent in which the polymer can be dissolved, and the obtained film-forming stock solution is uniformly applied on a support such as a metal or plastic film to form a film. After that, a film-forming undiluted solution cast into a film is introduced into a solution called a coagulation bath to cause phase separation to obtain a microporous film. The coating solution for film formation may be applied in a coagulation bath. In the present invention, the above support may be used as a separator. By using the separator as the support, the manufacturing process can be further simplified.

The content of the resin component in the stock solution for film formation is as follows.
0.5 to 10% by mass, particularly 1 to 5% by mass is preferable. When the content of the resin component is too large, the gel film becomes thicker and is easily peeled from the substrate.

The separator sheet forming the separator has a constituent material of one or more kinds of polyolefins such as polyethylene and polypropylene (in the case of two or more kinds, there is a laminated product of two or more layers of film),
Examples thereof include polyesters such as polyethylene terephthalate, thermoplastic fluororesins such as ethylene-tetrafluoroethylene copolymer, and celluloses. The form of the sheet is such that the air permeability measured by the method specified in JIS-P8117 is about 5 to 2000 seconds / 100 cc, and the thickness is 5 to 100.
Examples include microporous film of about μm, woven fabric, and non-woven fabric.

In the present invention, it is particularly preferable to use a so-called shutdown separator as the separator. By using the shutdown separator, as the temperature inside the electrochemical device rises, the fine pores of the separator are closed, conduction of ions is suppressed, current is suppressed, and thermal runaway can be prevented. Examples of such a shutdown separator include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDP) described in Japanese Patent No. 2642206.
E) A separator made of a synthetic resin film having at least one kind of fine pores, containing 1% by weight or more of ultrahigh molecular weight polyethylene having a weight average molecular weight of 7 × 10 5 or more described in JP-A-2520316, Made of a microporous membrane composed of polyethylene composition with an average molecular weight / number average molecular weight of 10 to 300, thickness of 0.1 to 25 μm, porosity of 40
A method for producing a lithium battery separator having an average through-hole diameter of 0.001 to 0.1 μm and a breaking strength of 10 mm width of 0.5 kg or more, wherein the polyethylene composition is an aliphatic hydrocarbon or a cyclic hydrocarbon. Alternatively, the solution is heated and dissolved in a non-volatile solvent composed of a mineral oil fraction to form a uniform solution, and the solution is extruded through a die to form a gel-like sheet. After removing the non-volatile solvent, the solution is stretched at least uniaxially by a factor of 2 or more. Examples thereof include a lithium battery separator and the like.

By using a solid electrolyte for such a separator, it is possible to obtain a high-performance electrochemical device having both the characteristics of the separator and the characteristics of the solid electrolyte. That is, the adhesiveness with the electrode is improved, and the film strength can be maintained, and an electrochemical device excellent in environmental change and mechanical strength can be obtained. In particular, by using a solid electrolyte formed by a wet phase separation method and a shutdown separator in the manufacturing process, a device with high safety and good electric characteristics can be obtained.

As another form, a particle layer that does not swell with respect to an organic solvent-based material and melts at a certain temperature may be provided in the solid electrolyte layer or on the surface of the layer.

The coating method of the matrix resin is not particularly limited, and a known coating method can be used. Specifically, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method and the like are used. At this time, for the purpose of improving the adhesion between the separator and the matrix resin, an additive such as a surfactant which improves surface wettability may be used.

Thereafter, if necessary, rolling treatment may be carried out by a flat plate press, a calender roll or the like.

After the matrix resin is formed by the phase separation method, it may be heated and dried at an optimum temperature.

After the drying step, the matrix resin may be heat-bonded to the separator sheet by heat treatment. The heating temperature at this time varies depending on the matrix resin used, but is specifically about 100 to 120 ° C.

The gel electrolyte sheet precursor thus obtained is sandwiched between a positive electrode and a negative electrode and laminated to form a laminated body. After putting this laminated body in an exterior body such as an aluminum laminated film, an electrolytic solution is injected to impregnate the matrix resin. In such gelling treatment in the subsequent step, it is necessary to provide the matrix resin with sufficient openings as described above.

Finally, the outer package is sealed and hot pressed to obtain a solid electrolyte electrochemical device.

The structure of the electrochemical device of the present invention can be applied to both a wound type structure and a laminated type structure. In the case of the laminated type structure, a positive electrode, a negative electrode, a solid electrolyte layer and a separator layer are used. Since it has a structure of sequentially laminating, it does not require the film strength required for the winding type,
The mechanical constraints on the material for the separator are reduced.

The electrochemical element used in the electrochemical device of the present invention is not limited to a battery such as a lithium secondary battery, and a capacitor having a similar structure to this may be used.

<Lithium Secondary Battery> The structure of the lithium secondary battery is not particularly limited, but is usually composed of a positive electrode, a negative electrode and a solid electrolyte / separator, and is applied to a laminated battery, a wound battery or the like.

The electrode to be combined with the solid polymer electrolyte may be appropriately selected and used from those known as electrodes for lithium secondary batteries, preferably an electrode active material, a gel electrolyte and, if necessary, a conductive auxiliary agent. Is used.

For the negative electrode, a negative electrode active material such as carbon material, lithium metal, lithium alloy or oxide material is used, and for the positive electrode, oxide or carbon material capable of intercalating / deintercalating lithium ions. It is preferable to use a positive electrode active material such as By using such an electrode, a lithium secondary battery having good characteristics can be obtained.

The carbon material used as the electrode active material may be appropriately selected from, for example, mesocarbon microbeads (MCMB), natural or artificial graphite, resin-fired carbon material, carbon black, carbon fiber and the like. These are used as powder. Of these, graphite is preferable, and its average particle diameter is preferably 1 to 30 μm, and particularly preferably 5 to 25 μm. If the average particle size is too small, the charge / discharge cycle life tends to be short, and the capacity variation (individual difference) tends to increase. If the average particle size is too large, the variation in capacity becomes extremely large and the average capacity becomes small. When the average particle diameter is large, the variation in capacity is considered to be due to the variation in the contact between graphite and the current collector and the contact between graphite.

Lithium ion is an intercalating day
Intercalatable oxides include lithium
Complex oxides are preferred, for example LiCoO 2.₂, LiM
n₂O _Four, LiNiO₂, LiV₂O_FourAnd so on.
The average particle size of these oxide powders is about 1-40 μm
Is preferred.

A conductive auxiliary agent is added to the electrode, if necessary. Examples of the conductive aid include graphite, carbon black, carbon fibers, metals such as nickel, aluminum, copper, silver and the like, and graphite and carbon black are particularly preferable.

The electrode composition of the positive electrode is preferably in the range of active material: conductivity assistant: binder = 80 to 94: 2 to 8: 2 to 18 by mass ratio, and in the negative electrode, the active material: conductivity aid is in mass ratio. Agent: Binder = The range of 70 to 97:00 to 25: 3 to 10 is preferable.

As the binder, a thermoplastic elastomer resin such as a fluororesin, a polyolefin resin, a styrene resin, an acrylic resin, or a rubber resin such as fluororubber can be used. Specific examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyacrylonitrile, nitrile rubber, polybutadiene, butylene rubber, polystyrene, styrene-butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, carboxymethyl cellulose and the like.

In the production of electrodes, first, an active material and, if necessary, a conductive auxiliary agent are dispersed in a binder solution to prepare a coating solution.

Then, the electrode coating solution is applied to the current collector. The means for applying is not particularly limited and may be appropriately determined depending on the material and shape of the current collector. Generally, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method and the like are used.
Then, if necessary, rolling treatment is performed by a flat plate press, a calendar roll, or the like.

The current collector may be appropriately selected from ordinary current collectors depending on the shape of the device used by the battery, the method of arranging the current collector in the case, and the like. Generally, aluminum or the like is used for the positive electrode and copper, nickel or the like is used for the negative electrode.
A metal foil, a metal mesh, or the like is usually used as the current collector. Although the metal mesh has a smaller contact resistance with the electrode than the metal foil, the metal foil can also obtain a sufficiently small contact resistance.

Then, the solvent is evaporated to produce an electrode. The coating thickness is preferably about 50 to 400 μm.

Such a positive electrode, a solid electrolyte / separator, and a negative electrode are laminated in this order and pressure-bonded to obtain a battery body.

The electrolytic solution with which the solid electrolyte / separator is impregnated generally comprises an electrolyte salt and a solvent. Examples of the electrolyte salt include LiBF ₄ , LiPF ₆ , LiAsF ₆ ,
LiSO ₃ CF ₃ , LiClO ₄ , LiN (SO ₂ CF
₃ ) Lithium salts such as ₂ can be applied.

The solvent of the electrolytic solution is not particularly limited as long as it has good compatibility with the above-mentioned solid polymer electrolyte and electrolyte salt, but polar organic compounds which do not decompose even in a high operating voltage in a lithium battery or the like. Solvents such as ethylene carbonate (EC), propylene carbonate (P
C), butylene carbonate, dimethyl carbonate (DMC), carbonates such as diethyl carbonate and ethyl methyl carbonate, tetrahydrofuran (T
HF), cyclic ethers such as 2-methyltetrahydrofuran, cyclic ethers such as 1,3-dioxolane and 4-methyldioxolane, lactones such as γ-butyrolactone, and sulfolane are preferably used. 3-Methylsulfolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, ethyl diglyme and the like may be used.

The concentration of the electrolyte salt when considering that the solvent and the electrolyte salt constitute the electrolyte solution is preferably 0.3 to 5 mol.
l / l. Usually, the highest ionic conductivity is shown around 0.8 to 1.5 mol / l.

<Electric Double Layer Capacitor> The structure of the electric double layer capacitor used in the present invention is not particularly limited, but usually, a pair of polarizable electrodes are arranged through a solid electrolyte / separator, and the polarizable electrode and the solid state are arranged. An insulating gasket is preferably arranged around the electrolyte / separator. Such an electric double layer capacitor may be of what is called a paper type, a laminated type or the like.

As the polarizable electrode, activated carbon, activated carbon fiber or the like is used as a conductive active material, and a fluororesin, a fluororubber or the like is added as a binder thereto. And it is preferable to use what formed this mixture in the sheet-like electrode. The amount of the binder is about 5 to 15% by mass. A gel electrolyte may be used as the binder.

The current collector used for the polarizable electrode is platinum,
It may be conductive rubber such as conductive butyl rubber, may be formed by thermal spraying of a metal such as aluminum or nickel, and a metal mesh may be attached to one surface of the electrode layer.

In the electric double layer capacitor, the polarizable electrode as described above and the solid electrolyte / separator are combined.

As the electrolyte salt, (C ₂ H ₅ ) ₄ NBF can be used.
₄ , (C ₂ H ₅ ) ₃ CH ₃ NBF ₄ , (C ₂ H ₅ ) ₄ PBF
₄ etc.

The non-aqueous solvent used in the electrolytic solution may be any of various known ones, such as propylene carbonate, ethylene carbonate and γ- which are electrochemically stable non-aqueous solvents.
Butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, sulfolane alone or a mixed solvent is preferable.

The concentration of the electrolyte in such a non-aqueous solvent electrolyte solution may be 0.1 to 3 mol / l.

When the composition of the polymer solid electrolyte is represented by resin / electrolyte, the ratio of the electrolyte is preferably 40 to 90 mass% from the viewpoint of the strength of the membrane and the ionic conductivity.

As the insulating gasket, an insulator such as polypropylene or butyl rubber may be used.

The outer bag is composed of a laminate film in which a polyolefin resin layer such as polypropylene or polyethylene as a heat adhesive resin layer or a heat resistant polyester resin layer is laminated on both surfaces of a metal layer such as aluminum. . The outer bag is formed in a bag shape in which one side is opened by previously heat-bonding two laminated films to each other on the heat-adhesive resin layers on the end faces of the three sides to form a first seal portion. Alternatively, a single laminated film may be folded back and the end faces of both sides may be heat-bonded to form a seal portion to form a bag shape.

The laminate film has a laminated structure of a thermoadhesive resin layer / polyester resin layer / metal foil / polyester resin layer from the interior side in order to secure insulation between the metal foil forming the laminate film and the lead-out terminal. It is preferable to use a laminated film. By using such a laminated film, the polyester resin layer having a high melting point remains without being melted at the time of heat bonding, so that a separation distance between the lead-out terminal and the metal foil of the outer bag can be secured and insulation can be secured. Therefore, the thickness of the polyester resin layer of the laminated film is preferably about 5 to 100 μm.

[0070]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 LiCoO 2 as a positive electrode active material
₂ (90 parts by mass), carbon black (6 parts by mass) as a conduction aid, and PVDF, Kynar761A (4 parts by mass) as a binder were mixed to make a positive electrode mixture, and N-methyl-2-pyrrolidone was used as a solvent. And dispersed into a slurry. The obtained slurry was applied onto an Al foil as a current collector and dried to obtain a positive electrode.

Artificial graphite powder (90 parts by mass) as a negative electrode active material and PVDF, Kynar761A (10 parts by mass) as a binder were dispersed with N-methyl-2-pyrrolidone to form a slurry. This slurry was applied onto a Cu foil, which is a negative electrode current collector, and dried to obtain a negative electrode.

As the electrolytic solution, a non-aqueous electrolytic solution was prepared in which ethylene carbonate (30 parts by volume) and diethyl carbonate (70 parts by volume) were used as a mixed solvent, and LiPF ₆ was used as a solute at a ratio of 1 mol dm ⁻³ .

The following were used as solid electrolyte components. Matrix polymer: Kynar761A Polyolefin film: Asahi Kasei Polyethylene (P
E) H6022 25 μm film forming stock solution: 2% by mass-Kynar761A / NMP (N-methyl-
2-pyrrolidone) + 1% by mass L-77 (Nippon Unicar Co., Ltd.)
Manufacture) The above-mentioned polyolefin film was immersed in a film-forming stock solution, and then the dipped product was squeezed with a roll to remove excess film-forming stock solution. By pouring the sheet into water, the polymer in the undiluted solution for film formation was gelled in a porous state on the polyolefin film.

The gel electrolyte sheet obtained here is sandwiched between a positive electrode and a negative electrode to be laminated, and the laminate is put in an aluminum laminate film, then impregnated with an electrolytic solution, hermetically sealed and subjected to heat pressing at 80 ° C. A solid electrolyte lithium battery was produced.

<Example 2> In the preparation of the gel electrolyte sheet in Example 1, the polymer concentration of the stock solution for film formation was set to 1% by mass. A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

<Example 3> In the preparation of the gel electrolyte sheet in Example 1, the polymer concentration of the stock solution for film formation was set to 3% by mass. A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

<Example 4> In the preparation of the gel electrolyte sheet in Example 1, the polymer concentration of the stock solution for film formation was set to 5% by mass. A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

<Example 5> In the preparation of the gel electrolyte sheet in Example 1, a gel electrolyte sheet was prepared by using K835 made by Celgard as a polyolefin film.
A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

Comparative Example 1 In the preparation of the gel electrolyte sheet in Example 1, a gel electrolyte sheet was prepared by using K848 manufactured by Celgard for the polyolefin film.
A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

<Comparative Example 2> In the preparation of the gel electrolyte sheet in Example 1, a gel electrolyte sheet was prepared by using 2720 manufactured by Celgard as the polyolefin film.
A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

<Comparative Example 3> In the preparation of the gel electrolyte sheet in Example 1, a gel electrolyte sheet was prepared by using E16MMS manufactured by Tonen Kagaku as the polyolefin film. A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

The batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to a charge / discharge cycle test at 23 ° C. with a constant current of 0 and 5 A at a charge end voltage of 4 and 2 V and a discharge end voltage of 3.0 V. It was The results of the cycle test are shown in FIG. 1, the thickness of the gel electrolyte layer of the gel electrolyte sheets prepared on the polyolefin films in Examples and Comparative Examples is shown in Table 1, and the separator Gurley value is shown in Table 2. 2 and 3 show SEM photographs of the surface state observed before and after PVdF coating in Example 1, respectively.

[0084]

[Table 1]

[0085]

[Table 2]

As shown in FIG. 1, Examples 1 to 5 showed good cycle characteristics, whereas Comparative Examples could not obtain good cycle characteristics. Further, as is clear from FIGS. 2 and 3, it can be seen that the surface of the separator after PVdF coating is covered with a matrix resin having micropores that are sufficiently open. As shown in Table 1, the thickness of the gel electrolyte layer formed on each polyolefin film was almost dependent on the polymer concentration of the stock solution for film formation, and there was no great difference between the examples and the comparative examples. Table 2 shows the Gurley value of each polyolefin film used in Examples and Comparative Examples. The H6022 manufactured by Asahi Kasei and K835 manufactured by Celgard of the example in which good cycle characteristics were obtained were 90 and 110, which were small values as compared with the comparative example. Further, the reason why the cycle characteristics are good in Examples and poor in Comparative Examples is inferred from the above results, in the large Gurley value polyolefin film used in Comparative Examples, when the gel electrolyte layer is formed on the film. In addition, it is considered that the pore diameter is small and the gel component causes clogging, which causes a nonuniform difference in the conductivity of Li ions.

Table 3 shows the results of the heating test at 150 ° C. for 30 minutes and the results of the 6V-1A overcharge test.

[0088]

[Table 3]

Since the gel electrolyte-coated polyolefin separator is used in both Examples and Comparative Examples, when the battery temperature exceeds the melting point of polyethylene, the separator melts,
The conduction of Li ions was blocked, and the test could be safely completed.

Comparative Example 4 In Example 1, 40 parts by mass of dimethylacetamide and 40 parts of dioxane were used as the stock solution for film formation.
A gel electrolyte layer was formed on the polyolefin film with 20 parts by mass of polyvinylidene fluoride and 80 parts by mass of dioxane as the gelling bath and 20 parts by mass of water. A laminated solid electrolyte lithium battery was produced in the same manner as in Example 1 except for the above.

Since the method described in Japanese Patent Application Laid-Open No. 11-276298 differs from the method of preparation, the polyolefin film and the gel electrolyte layer were peeled off during winding.
In addition, it is considered that the gel electrolyte layer becomes thicker because the polymer concentration of the stock solution for film formation is 10 times higher. According to the method described in JP-A-11-276298,
Since it is necessary to form a self-supporting film, it is necessary to have a certain thickness, but in the present invention, since the gel electrolyte layer is formed on the substrate, the film strength is not so necessary.

Comparative Example 5 A gel electrolyte layer of SiO ₂ / PVDF = 85/15 (mass ratio) was coated on a polyolefin film with a bar coater to prepare it.
The film thickness after drying was about 10 μm on each side. An attempt was made to make a battery in the same manner as in Example 1, but because the adhesion between the polyolefin film and the gel electrolyte layer was not sufficient,
The battery could not be prepared because peeling occurred at the interface between the polyolefin film and the gel electrolyte layer during battery preparation.

From the above results, it is understood that by forming the gel electrolyte layer on the polyolefin film by the wet phase separation method, a battery having good battery characteristics and excellent safety can be prepared.

[0094]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to provide a method of manufacturing an electrochemical device which has a solid electrolyte having a sufficient electrolyte holding ability and excellent performance, and which is easy to manufacture. .

Further, it is possible to provide a method of manufacturing an electrochemical device having an excellent self-safety function even in the case of an abnormality.

[Brief description of drawings]

FIG. 1 is a graph showing a comparison of charge / discharge cycle characteristics of solid electrolyte batteries prepared by using respective solid electrolyte layers.

FIG. 2 is a drawing-substitute SEM photograph for observing the surface state of a separator film before PVdF coating in Example 1.

FIG. 3 is a drawing-substitute SEM photograph in which the surface state of the separator film after PVdF coating in Example 1 was observed.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Maruyama             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 5H021 CC00 EE04 HH00 HH02                 5H029 AJ12 AK03 AL06 AM03 AM04                       AM05 AM16 BJ02 BJ27 DJ04                       DJ09 EJ12

Claims (6)

[Claims] 1. A positive electrode and a negative electrode are formed to face each other, and a solid electrolyte layer is provided between the positive electrode and the negative electrode, and at least between the positive electrode or the negative electrode and the solid electrolyte layer. A method of manufacturing an electrochemical device having a separator layer on the inner surface thereof, wherein the matrix resin forming the solid electrolyte is formed by a wet phase separation method. 2. The method for producing an electrochemical device according to claim 1, wherein the separator is a shutdown separator that blocks ionic conduction between the electrode and the solid electrolyte layer at a predetermined temperature or higher. 3. The Gurley value of the separator is 200 s
The method for producing an electrochemical device according to claim 1 or 2, wherein: 4. The method for manufacturing an electrochemical device according to claim 1, wherein the matrix resin is a PVDF homopolymer. 5. The method for manufacturing an electrochemical device according to claim 1, wherein the electrochemical device is a lithium secondary battery. 6. An electrochemical device obtained by the method according to claim 1.