JPH1167275A - Solid electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte secondary battery with improved safety and high energy density. SOLUTION: In manufacturing a battery, a plastic sheet 20 of a mutilayer structure having Al in its center is folded and bonded to form a cylindrical sheet 21, a battery power generating element 30 is introduced into the cylindrical sheet from one opening part 23, and both opening parts 22, 23 in its longitudinal direction are sealed to form the battery 40. Since a zone for forming a sealing part is reduced in the battery, the battery is miniaturized compared with a conventional one, and has high energy density. A solid electrolyte containing a foaming material is used in the battery. When abnormality has occurred in the battery, electrochemical reaction between the positive and negative electrodes is stopped by generation of decomposition gas out of the foaming material to improve safety for the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous secondary battery, and more particularly to a structure of a solid electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, there has been remarkable progress in miniaturization, thinning and weight reduction of electronic devices. Particularly in the OA field, the size and weight of electronic devices have been reduced from desktop types to laptop types and further to notebook types. I have. In addition, the field of new small electronic devices such as electronic notebooks and electronic still cameras has emerged. Further, in addition to the miniaturization of conventional hard disks and floppy disks, the development of memory cards, which are new memory media, has been promoted. In the wave of downsizing, thinning, and weight reduction of such electronic devices, high performance is also required for secondary batteries that support such electric power. Under such demands, development of lithium secondary batteries has rapidly progressed as a high energy density battery replacing lead storage batteries and nickel cadmium batteries.

[0003] Such a lithium secondary battery has a flammable non-aqueous electrolyte inside due to its characteristics. Since a lithium secondary battery is a high energy density battery, high safety is required for various failures (short circuit, overcharge, overdischarge, reverse charge, nailing, crushing, heating). When a failure such as a short circuit occurs in the battery, heating of the battery and an increase in the internal pressure of the battery generally occur, and in the worst case, a rupture of the liquid leaks. For this reason, lithium secondary batteries are usually provided with various safety mechanisms.

[0004] As a general safety mechanism, (1) a method of avoiding an abnormal mode by providing a safety circuit externally, and (2) providing a safety valve to the battery and, when the internal pressure of the battery rises beyond a certain level, to the outside. Gas release method, (3) Separate material that melts at lower temperature and cut off current at high temperature, (4) Cut off abnormally high current and current at high temperature by PTC, mechanical mechanism, etc. (JP-A-4-328278). However, it is not yet completely secure.

[0005]

In the development related to the safety of the battery, a battery using a solid electrolyte has recently attracted attention. The solid electrolyte is a battery that does not cause liquid leakage due to its characteristics and is less likely to cause a burst flame even in an abnormal mode of the battery. However, sufficient safety measures have not been taken for this as well.
Accordingly, an object of the present invention is to provide a high energy density solid electrolyte secondary battery with improved safety.

[0006]

The above object is achieved by the following constitution. That is, in a secondary battery having a laminated structure of at least a positive electrode current collector layer, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer, the electrolyte layer is a solid electrolyte, The above problem is solved by the foaming material being included in the electrolyte (claim 1).

[0007] The solid electrolyte secondary battery of the present invention preferably has the following configuration. That is, (1) the solid electrolyte:
It is a gel-like solid electrolyte obtained by dissolving at least a polymerizable compound in an electrolytic solution to cause a polymerization reaction (Claim 2), and (2) the polymerizable compound is an acrylate compound (Claim 2). Item 3), (3) The gas generated from the foamable material is CO ₂ or N ₂ (Claims 4 and 5), (4) The decomposition temperature of the foamable material is 100 ° C. to 200 ° C. it (claim 6), (5) the positive active active material constituting the material layer LiMn _2-n X n O
₄ [where X is group IIA, group IIIA, group IVA
Group, VA group, VIA group, VIIA group, VIII group, IB group, IIB
At least one element selected from the group consisting of Group III, Group IIIB, Group IVB and Group VB (0 ≦ n ≦ 1.0). (Claim 7) or (6) It is preferable that the electrolyte salt constituting the electrolyte layer is LiBF ₄ (Claim 8).

Further, the structure of the solid electrolyte secondary battery according to the present invention is preferably as follows. It is assumed that the battery power generation element is housed inside an exterior sheet having an A1 (aluminum) layer at least at the center and having a structure of three or more layers of plastic / A1 / plastic, and the opening of the exterior sheet is sealed. (Claim 9) The exterior sheet is processed into a cylindrical shape, a battery power generation element is housed inside, and an opening of the exterior sheet is sealed (claim 9). Item 10), one in which the two side surfaces of the cylindrical exterior sheet have a bellows structure (invention 11), one in which a current interruption mechanism is not provided (invention 12), and one in which a separator is provided (invention). Item 13), that the negative electrode active material layer contains at least a carbon material (Claim 14), or that the negative electrode active material layer is artificial graphite obtained by firing natural graphite and coke. (Claim 15) is preferable.

The foamable material is generally a material that decomposes under a certain condition and generates gas with the decomposition. By adding such a material into the solid electrolyte, if the battery abnormally generates heat due to a short circuit, etc., or if the voltage rises abnormally due to overcharging,
The foamable material decomposes and generates gas. As a result, the interface that electrochemically connects the positive electrode and the negative electrode is peeled off, and it is possible to prevent a further current from flowing. In other words, in the fixed electrolyte battery, when gas is generated from the electrolyte layer due to its structure, a portion where the gas is generated becomes hollow, so that an electrochemical reaction between the positive electrode and the negative electrode cannot be performed.
That is, it is possible to prevent a further current from flowing.

On the other hand, in a battery provided with an ordinary electrolytic solution, even if gas is generated, the gas is pushed out from the battery power generating element because the electrolyte layer is composed of a liquid, and the gas is generated by the gas generation. The above-mentioned effects are hardly obtained. In addition, the conventional battery using a liquid for the electrolyte layer is covered with a hard exterior (such as a stainless steel can), which also promotes the gas to be pushed out of the battery power generating element. This point solid electrolyte battery,
As will be described later, since the electrolyte layer does not flow unlike a liquid, it is not necessary to use a hard exterior, and a flexible exterior can be used. For this reason, it is possible to configure a battery in which gas is not pushed out from the battery power generating element.

[0011]

Embodiments of the present invention will be described below. The foamable material used in the present invention preferably satisfies the following requirements. (I) The gas can be released in a short time and its speed can be adjusted. (Ii) Decomposition temperature and decomposition potential can be controlled. (iii) The decomposition gas is not corrosive and harmless. (Iv) Disperse or dissolve easily. (V) The foaming material, decomposition residue, and decomposition gas have a low unpleasant odor and low contamination. (Vi) have no effect on other general characteristics. It is preferable that the foaming material (hereinafter, sometimes referred to as a foaming material) satisfies all the above requirements, but it can be used even if it does not.

More specifically, examples of the inorganic foaming material include carbonates (ammonium carbonate, ammonium hydrogen carbonate, lithium carbonate, etc.), ammonium nitrite, sodium borohydride, azides and the like. Organic foaming materials include azo-based azobisisobutyronitrile, azodicarbonamide, and barium azodicarboxylate; hydrazine-based diphenylsulfone disulfohydrazine, oxybis (benzenesulfohydrazine), trihydrazinotriazine, and allylbis (sulfo) Hydrazide); tolylenesulfonyl semicarbazide and oxybis (benzenesulfonyl semicarbazide) as semicarbazide; morpholylthiatriazole as triazole; dinitrosopentamethylenetetramine, dimethyldinitrosoterephthalamide and the like as N-nitroso.

Preferably, the gas generating gas is harmless and generates N ₂ or CO ₂ gas, lithium carbonate,
Sodium hydrogen carbonate, azo-based materials, and hydrazine-based materials are preferred. Further, the decomposition temperature is preferably out of the temperature range in which the battery is usually used.
It is preferable to select a temperature higher than 00 ° C. Specifically, 100 ° C to 200 ° C is preferable. Specifically, azodicarbonamide, diphenylsulfonedisulfohydrazine, oxybis (benzenesulfohydrazine), allylbis (sulfohydrazide), morpholylthiatriazole, dimethyldinitrosoterephthalamide and the like are preferable.

Examples of the solid electrolyte used in the present invention include, for example, AgCl, AgBr, AbI, and LiI in inorganic systems.
Metal halides such as RbAg ₄ I ₅ , RbAg ₄
I ₄ CN ion conductor and the like. Further, in the organic system, a complex in which an electrolyte solution containing a polymer matrix of polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, or the like is dissolved, or a cross-linked product thereof, low-molecular-weight polyethylene oxide, polyethylene imine, crown ether And a solid polymer electrolyte in which an ion dissociating group such as the above is grafted on the polymer main chain. Alternatively, a gel-like solid electrolyte having a structure in which an electrolyte solution is contained in a polymer matrix may be mentioned, but it is preferable to use a gel-like solid electrolyte having excellent ionic conductivity.

The gel-like solid electrolyte is composed of a high-molecular-weight polymer base material and a non-aqueous electrolyte, and is entirely composed of a homogeneous viscoelastic material. The viscoelastic solid electrolyte of the present invention has high ionic conductivity, low glass transition temperature (Tg), high temperature stability, easy workability, low creep characteristics and tackiness, and furthermore, while containing a large amount of electrolyte. It is excellent in liquid retention and shape retention.

The solid electrolyte of the present invention is greatly affected by the ionic conductivity at 25 ° C. according to the AC impedance method and the conductivity of the non-aqueous electrolyte solution which is a constituent element of the electrolyte, and does not exceed that. The conductivity hardly decreases even by solidification, and is usually 1/10 ⁴ to 1/1.
0 ² S / cm.

The elastic modulus of the solid electrolyte of the present invention measured by a dynamic viscoelasticity tester (MR-300 Solid Meter, Rheology Co., Ltd.) is usually 10 ⁶ dyne / cm ² or less, preferably 10 ² to 10 ^5. dyne / cm ² , more preferably 10 ³ to 10 ⁵ dyne / cm ² , and Tg of -3.
It is 0 ° C. or lower, and does not dissolve even at 100 ° C. The elongation is 20% or more, and has a resilience to stretching deformation without breaking up to about 400%. Also, 1
It does not break even when bent at 80 degrees.

The solid electrolyte of the present invention is a creep meter (RE-3305, Yamaden Corporation, plunger cross section 2c).
(m ² , load: 30 g), the change in strain over time was measured. As a result, the strain did not change with time and had low creep characteristics. Load 25g / c using creep meter
Even if the solid electrolyte is compressed at m ² , the electrolyte contained therein does not flow out. Further, the viscoelastic body exhibits high adhesiveness, and after the viscoelastic bodies are bonded to each other, even if the viscoelastic bodies are to be separated, the material is destroyed and does not peel off from the bonded surface.

The solid electrolyte of the present invention can be obtained by dissolving a polymerizable compound in a non-aqueous electrolyte and causing a polymerization reaction. In this case, the polymerizable compound is, in addition to thermopolymerizable,
It exhibits polymerizability with actinic rays such as light, ultraviolet rays, electron beams, γ rays, and X rays.

The polymerizable compound used in the present invention contains a hetero atom other than carbon, such as an oxygen atom, a nitrogen atom, and a sulfur atom, in the molecule. The solid electrolyte of the present invention can be obtained by dissolving the polymerizable compound containing a hetero atom in a non-aqueous electrolyte and causing a polymerization reaction. This solid electrolyte is preferably formed in an inert gas atmosphere. In this case, a solid electrolyte having excellent ionic conductivity and strength as compared with the case where the solid electrolyte is manufactured in the air can be obtained. In the obtained solid electrolyte, it is presumed that the heteroatom other than carbon promotes ionization of the electrolyte salt, improves the ionic conductivity of the solid electrolyte, and also has a function of improving the strength of the solid electrolyte.

The type of the polymerizable compound used in the present invention is not particularly limited, and includes those which produce a polymer by causing a polymerization reaction such as thermal polymerization and actinic ray polymerization. Preference is given to combinations of monofunctional and polyfunctional monomers which can be formed.
In particular, when a trifunctional monomer is used as the polyfunctional monomer, a crosslinked polymer matrix having higher ionic conductivity and sufficient strength and viscoelasticity as a solid electrolyte for an electrochemical device can be obtained. Hereinafter, the polymerizable compound used in the present invention will be specifically described.

Examples of the polymerizable compound include polyfunctional and polyfunctional (meth) acrylate monomers or prepolymers. In addition, (meth) acrylate in this specification means acrylate or methacrylate. Monofunctional acrylates include alkyl (meth) acrylates [methyl (meth) acrylate, butyl (meth) acrylate, trifluoroethyl (meth) acrylate
Alicyclic (meth) acrylate; hydroxyalkyl (meth) acrylate [hydroxyethyl acrylate, hydroxypropyl acrylate, etc.]; hydroxypolyoxyalkylene (oxyalkylene group preferably has 1 to 4 carbon atoms) (meth) Acrylates (hydroxypolyoxyethylene (meth) acrylate, hydroxypolyoxypropylene (meth) acrylate, etc.) and: Alkoxyalkyl (alkoxy group preferably has 1 to 4 carbon atoms) (meth) acrylate [methoxyethyl acrylate, ethoxyethyl acrylate Phenoxyethyl acrylate, etc.]. Preferred examples of the trifunctional or higher polyfunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, pentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.

Specific examples of other (meth) acrylates include, for example, methylethylene glycol (meth) acrylate, ethylethylene glycol (meth) acrylate, propylethylene glycol (meth) acrylate, phenylethylene glycol, ethoxydiethylene glycol acrylate, and methoxyethyl. Alkyl ethylene glycol (meth) acrylates such as acrylate, methoxydiethylene glycol methacrylate, methoxytriethylene glycol acrylate, methoxytriethylene glycol methacrylate, and methoxytetraethylene glycol methacrylate; alkyls such as ethylpropylene glycol acrylate, butylpropylene glycol acrylate, and methoxypropylene glycol acrylate Propylene glycol (meth) acrylate, others.

The (meth) acrylate may contain a heterocyclic group, such as oxygen, nitrogen,
It is a heterocyclic residue containing a hetero atom such as sulfur. The type of the heterocyclic group contained in the (meth) acrylate is not particularly limited, but for example, a furfuryl group,
Furfuryl (meth) having a tetrahydrofurfuryl group
Acrylate and tetrahydrofurfuryl (meth) acrylate are preferred. Other (meth) acrylates having a heterocyclic group include furfurylethylene glycol (meth) acrylate, tetrahydrofurfurylethylene glycol (meth) acrylate, furfurylpropylene glycol (meth) acrylate, and tetrahydrofurfurylpropylene glycol (meth) acrylate And alkylene glycol acrylates having a furfuryl group or a tetrahydrofurfuryl group.

The molecular weight of the (meth) acrylate compound and its prepolymer is usually less than 500, preferably 300 or less. In the case of a (meth) acrylate having a molecular weight of 500 or more, the non-aqueous solvent easily oozes out of the obtained solid electrolyte. The above (meth) acrylate compounds may be used alone or in combination of two or more. The use ratio of the (meth) acrylate compound is 50% by weight or less, preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the non-aqueous electrolyte.

Further, as the polyfunctional monomer, a polyfunctional unsaturated carboxylic acid ester is particularly preferred. By using the polyfunctional unsaturated carboxylic acid ester in combination, the elastic modulus,
An ideal solid electrolyte can be obtained with both ionic conductivity. Examples of the polyfunctional unsaturated carboxylic acid ester include a monomer or a prepolymer having two or more (meth) acryloyl groups, and in particular, a trifunctional unsaturated carboxylic acid ester having three (meth) acryloyl groups is It is most preferable in that it provides a solid electrolyte having excellent liquid retention, ionic conductivity, and strength.

Specific examples of the polyfunctional unsaturated carboxylic acid ester include ethylene glycol dimethacrylate,
Diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol diacrylate, EO-modified trimethylolpropane triacrylate, PO-modified trimethylolpropane triacrylate, butanediol ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

The polymerizable compound used in the present invention includes the monofunctional and polyfunctional (meth) acrylates described above.
In addition to the polyfunctional unsaturated carboxylic acid ester, a combination of a polyene and a polythiol may be used.

The electrolyte salt used in the present invention includes L
iClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ ,
LiBr, LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ )
_2, such as _{LiC (CF 3 SO 2) 3} , but include those commonly used in lithium batteries, the battery of 4V class, which will be described later, LiPF _6, LiBF from stability of the electrolyte
It is preferable to use ₄ . Further, from the viewpoint of battery safety, which is the object of the present invention, it is preferable to use LiBF ₄ . This is because LiPF ₆ is unstable to moisture and reacts with water to generate hydrogen fluoride. When the battery is destroyed, LiBF ₄ can exist more stably in the atmosphere. Because. The cost is Li
BF ₄ is less expensive.

Examples of the solvent constituting the electrolyte include ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane and dimethoxyethane; amides such as dimethylformamide and dimethylacetamide; acetonitrile and benzonitrile and the like. Nitriles; sulfur compounds such as dimethylsulfoxysulfolane; linear carbonates such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl isopropyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; However, the present invention is not limited thereto, and they may be used alone or as a mixture of two or more.

The positive electrode active material used in the present invention includes:
TiS ₂ , MoS ₂ , Co ₂ S ₆ , V ₂ O ₅ , Mn
Transition metal oxides such as O ₂ and CoO ₂ , transition metal chalcogen compounds, complexes of these with Li, and conductive polymers can be used. To increase the energy, a composite oxide having a layered structure represented by LiMo ₂ such as lithium cobalt oxide or lithium nickel oxide having an operating voltage of 4 V or a spinel structure represented by LiM ₂ O ₄ is used. It is preferable to use a composite oxide having the same.

Among them, particularly, spinel LiMn ₂ O
No. ₄ has a higher potential than conventional active materials, and is made from manganese oxide, which is abundant and inexpensive as a raw material, and is therefore promising as a positive electrode material. When LiMn ₂ O ₄ is used as the positive electrode, an initial discharge capacity of 100 to 120 mAh / g can be obtained. However, in order to solve the problem that the capacity decreases with charge / discharge cycles, LiMn ₂ O _{4 is} further added. it is preferable to use LiMn _2-n X _n O ₄ where a part of Mn atoms was replaced with another atom X in the positive electrode active material. In order to achieve both discharge capacity and cycle stability, spinel LiMn ₂ O ₄ and LiMn _2-n
It is further preferred to use a mixture of X _n O _4.

As the negative electrode material used in the battery of the present invention, lithium metal, an alloy of Li with a low melting point metal such as Pb, Bi, Sn and the like, a lithium alloy such as a Li-Al alloy, a carbon material and the like are used. Among them, carbon materials are most preferable, and examples thereof include (1) a synthetic polymer such as phenol and polyimide, and a natural polymer at 400 to 800 ° C.
(2) conductive carbon obtained by firing coal, pitch, synthetic polymer, or natural polymer in a reducing atmosphere at 800 to 1300 ° C. And (3) those obtained by calcining coke, pitch, synthetic polymer, and natural polymer at a temperature of 2000 ° C. or more in a reducing atmosphere, and graphite-based carbon bodies such as natural graphite.

Among the above, the carbon body of (3) is preferable, and the carbon body and natural graphite obtained by firing coke in a reducing atmosphere at 2500 ° C. or more have excellent potential flatness.
It has particularly favorable electrode properties. In a further preferred embodiment of the present invention, a composite anode of a carbon body and natural graphite obtained by firing coke in a reducing atmosphere at 2500 ° C. or higher is used. Although natural graphite has favorable characteristics in terms of potential flatness and current characteristics, general-purpose electrolytes conventionally used for non-aqueous electrolytes also have a problem of decomposing propylene carbonate as a solvent. A carbon body obtained by calcining coke in a reducing atmosphere at 2500 ° C. or higher has no disadvantages as described above, and has a feature that an electrolyte solvent can be easily selected.

On the other hand, by using a composite negative electrode of a carbon body and natural graphite obtained by firing coke in a reducing atmosphere at 2500 ° C. or more, natural graphite retains good potential flatness and current characteristics. Thus, a negative electrode without decomposition of the electrolyte can be manufactured. The carbon material is not limited to the natural graphite, and one type of carbon material may be used alone, or two or more types may be used in combination. The carbon body can be formed into a sheet by a wet papermaking method from the carbon body and the binder, or by a coating method using a coating material in which an appropriate binder is mixed with a carbon material. The electrode can be produced by supporting the sheeted carbon body on the current collector by a method such as adhesion or pressure bonding.

In the battery of the present invention, a separator can be used in combination. As a result, the mechanical strength of the solid electrolyte can be significantly improved, a safe battery with less short circuit inside the battery can be provided, and the electrolysis between the positive and negative electrodes can be performed more uniformly, and the cycle characteristics can be improved. An excellent battery can be manufactured.

As the separator, it is preferable to use a separator having a low resistance to the ion transfer of the electrolyte solution and having an excellent solution retention. Examples of such a separator include a glass fiber, a filter, a nonwoven fabric filter made of a polymer fiber such as polyester, Teflon, polyflon, polyethylene, and polypropylene, and a nonwoven filter using a mixture of the glass fiber and the polymer fiber. be able to. Further, since the battery of the present invention has a safety mechanism based on gas generation inside the battery, there is an advantage that the battery does not need to be provided with a current cut-off mechanism such as a PTC or the like provided outside or outside the battery.

As the exterior material for enclosing the battery power generating element of the present invention, basically any material can be used, but it is necessary to prevent the generated gas from escaping from the positive / negative electrode interface. In order to more efficiently cause the phenomenon of peeling off the positive and negative electrode interfaces, it is preferable to use a flexible exterior. As the exterior sheet, one containing at least A1 at the center and having a structure of three or more layers of plastic / A1 / plastic is particularly preferable to protect the battery power generation element from the atmosphere.

In order to further increase the energy density of the battery, it is preferable that the exterior sheet is processed into a cylindrical shape, which will be described with reference to the drawings.
FIG. 1 is a perspective view illustrating a method for manufacturing a solid electrolyte secondary battery according to the present invention in the order of steps, and FIG. 2 is a perspective view illustrating another example of the solid electrolyte secondary battery. 3 to 5 are front views showing various specific examples of an exterior sheet for producing a solid electrolyte secondary battery.

A method of manufacturing a solid electrolyte secondary battery will be described. A single plastic sheet 20 having a multilayer structure having at least a center A1 layer as shown in FIG. A cylindrical sheet 21 as shown in FIG. In FIG. 1A, 11,
13 is a plastic film, 12 is an aluminum foil,
Reference numerals 22 and 23 denote openings, and a strip-like portion indicated by a dotted line is an adhesive portion 24 between the plastic sheets.

Next, as shown in FIG. 1C, the battery power generating element 30 is introduced into the tubular sheet 21 through the opening 23, and the front and rear openings 22, 23 are sealed. The battery 40 shown in d) is formed. In FIG. 1C, reference numeral 31 denotes a positive terminal, and 32 denotes a negative terminal.
In the figures, 25 and 26 are the seal portions, and 41 is an exterior sheet.

In the conventional battery 50 shown in FIG. 7, sealing portions 52a and 52
b, 52c, and 52d, the battery of the present invention shown in FIG. 1D does not have a portion corresponding to the sealing portions 52a and 52b, so that a battery having a smaller size and higher energy density is formed. can do. In FIG. 1B, two openings (22, 23) are provided, but one opening may be provided. In FIG. 7, reference numeral 51 denotes an exterior material, 53 denotes a battery power generation element, 54 denotes a positive electrode terminal, and 55 denotes a negative electrode terminal.

The battery shown in FIG. 2 has a terminal portion led out from the battery power generating element 30 serving as a sealing portion. In this figure, reference numeral 31a denotes a positive electrode terminal exposed portion, and 32a denotes a negative electrode terminal exposed portion. According to such a structure, the terminal portion can be made smaller, which is effective for increasing the energy density of the battery. In addition, since the terminals are almost completely covered with the exterior sheet 41, the terminals are protected from physical impact, and there is no danger that the terminals may come into contact and short-circuit the battery.

FIGS. 3, 4 and 5 show the cylindrical sheet 21 respectively.
FIG. 5 is a front view showing specific examples different from each other;
FIG. Compared to the opening 22 of FIG. 3, that of FIGS. 4 and 5 is suitable for inserting a thicker battery power generating element. Although the shape and size of the opening are selected according to the thickness of the battery power generating element, FIGS.
Among them, the shape shown in FIG. 5 is the most preferable, and wrinkles are less likely to be formed on the outer sheet 41, and a thick battery power generating element can be more efficiently introduced.

The outer sheet 41 (tubular sheet) preferably has a low gas permeability and a low moisture permeability. Specifically, for example, as shown in FIG. Sheets can be used. More preferably, a heat-fusible plastic layer is preferably provided on the outermost layer (front and back) of the plastic sheet, so that processing into a cylindrical sheet and sealing of an opening can be performed by heat sealing (heat sealing). ).

[0046]

Next, the present invention will be described in more detail with reference to examples. Example 1 In a 3M HBF ₄ aqueous solution containing aniline, a stainless steel sheet 4 × 7 having a through-hole of 0.9 mmφ subjected to a blast treatment of 20 μm as a reaction electrode.
Using 5 cm (polymerized part), a polymerization reaction treatment was performed on both surfaces at 3 mA / cm ² . After washing the obtained stainless polyaniline electrode with running water, the solution was washed with 0.2N sulfuric acid at -0.4%.
The potential was applied to V vs SCE to perform a sufficient dedoping operation. This was reduced using a 20% hydrazine aqueous solution, washed and dried to obtain a polyaniline electrode (660 μm in thickness). In the same manner, two positive electrodes in which polyaniline was polymerized only on one side were produced. Except for the terminals of the three positive electrodes produced in this way, the entire active material layer was fixed with a cylindrical polypropylene pore filter so as to cover the entire active material layer.

Then, LiN (CF ₃ ) was added to a 7/3 (volume ratio) mixture of propylene carbonate and dimethoxyethane.
An electrolyte in which 1.95 M of SO ₂ ) ₂ and 0.05 M of LiBF ₄ were dissolved was 84.9%, 14.76% of ethoxydiethylene glycol acrylate, 0.23% of trimethylolpropane triacrylate, and 0.1% of benzoin isopropyl ether % Of a solution prepared by adding 0.01% of allyl bis (sulfohydrazide) as a foaming material to a solution mixed at a ratio of 0.1% was soaked in polyaniline, and irradiated with light in high-pressure mercury. The electrolyte was solidified, and the liquid did not exude even when pressure was applied. These were used as positive electrode members.

Carbon 4 calcined at 2500 ° C.
A coating solution consisting of 7.4 parts by weight, 5.2 parts by weight of polyvinylidene fluoride and 47.4 parts by weight of n-methylpyrrolidone was blasted with stainless steel (SUS
A negative electrode active material layer (4 × 7.5) having a thickness of 20 μm is applied on the current collector consisting of 304) and dried at 80 ° C.
cm) on both sides. After performing an operation of inserting lithium ions into carbon, the mixed solution was permeated and irradiated with light from a high-pressure mercury lamp to completely solidify the electrolytic solution. This is 2
A negative electrode member was prepared.

The positive electrode member and the negative electrode member were laminated so as to have a layer structure as shown in FIG. The positive terminal portions 1a, 5a, and 9a were electrically connected to the negative terminal portions 3a and 7a by welding, respectively, and the external lead terminals made of stainless steel were welded to the positive and negative electrodes, respectively. FIG. 6 is a perspective view showing a laminated structure of a power generating element, wherein 1, 5 and 9 are positive electrode members, 2, 4, 6 and 8 are separators, 3 and 7
Are negative electrode members, 1a, 5a and 9a are positive electrode terminal portions, 3a
And 7a are negative electrode terminals.

Separately from this, a 25 μm aluminum layer is formed at the center, and a thickness 5
A sheet provided with a modified polyethylene layer of 0 μm and processed into a cylindrical shape (FIG. 1b) was prepared. The secondary battery was completed by inserting the above laminate and heat sealing the opening under reduced pressure.

When this secondary battery was heated to 230 ° C., the battery expanded significantly. When the battery was disassembled and the interior was observed, the positive and negative electrode interfaces were peeled off, and it was predicted that the positive and negative electrode interfaces were peeled off due to gas generation. The dimensions of the battery, excluding the terminals before heating, were 4.4 × 9.0 cm.

Example 2 9.9 parts by weight of polyaniline, crystalline V ₂ O ₅ 23.1
Parts by weight, a coating solution consisting of 67 parts by weight of n-methylpyrrolidone was applied on a stainless steel positive electrode current collector also serving as a blasted exterior, and dried at 120 ° C.
A positive electrode active material having a thickness of 120 μm (both sides) and 60 μm (one side) was formed. The thickness of the negative electrode active material layer was 60 μm.
(Both sides). A battery was fabricated in the same manner as in Example 1 except for this, and when this battery was heated to 230 ° C., the same result as in Example 1 was obtained.

Comparative Example 1 A battery was produced in the same manner as in Example 1 except that the battery power generating element of Example 1 was vertically sandwiched between two exterior sheets and four sides were sealed. The vertical and horizontal dimensions of this battery are 5.5 × 9.0 cm
Which is larger than that of the first embodiment.

Example 3 A coating solution composed of 3.5 parts by weight of polyvinylidene fluoride (PVDF), 51.5 parts by weight of spinel type LiMn ₂ O _4, 8 parts by weight of conductive graphite, and 37 parts by weight of N-methylpyrrolidone was prepared. The same procedure as in Example 1 was carried out except that the composition of the electrolyte used in Example 1 at a ratio of 84.9% was 2M LiPF ₆ / ethylene carbonate: dimethyl carbonate (1: 1 volume ratio). A battery was manufactured.
When this battery was heated to 230 ° C., the same results as in Example 1 were obtained.

Example 4 A battery was fabricated in the same manner as in Example 3 except that LiPF ₆ used in Example 3 was replaced with LiBF ₄ . Replace this battery with 230
Upon heating to ℃, the same results as in Example 1 were obtained.

Example 5 A battery was produced in the same manner as in Example 2 except that the number of positive and negative electrodes was set to 7 for the positive electrode and 6 for the negative electrode, and that the exterior sheet had a bellows structure with five turns. Battery width is 4.5
cm. When this battery was heated to 230 ° C., the same results as in Example 1 were obtained.

Comparative Example 2 A battery was produced in the same manner as in Example 5, except that the outer sheet was folded twice. Battery width is 4.8
cm, which was larger than 5 turns, and wrinkled at the end (turned portion) of the exterior.

[0058]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) A secondary battery having a laminated structure of at least a positive electrode current collector layer, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer, wherein the electrolyte layer is a solid electrolyte, By including a foamable material in the solid electrolyte, the safety of the battery is ensured even when the battery is exposed to high temperatures.

(2) Claim 2 Since the solid electrolyte is a gel-like solid electrolyte obtained by dissolving at least a polymerizable compound in an electrolytic solution and performing a polymerization reaction, the ionic conductivity of the electrolyte is increased. I do.

(3) Claim 3 When the polymerizable compound is an acrylate compound, a solid electrolyte having excellent viscoelasticity and ionic conductivity can be provided.

(4) Claims 4 and 5 Since the gas generated from the foamable material is CO ₂ or N ₂ , there is no harm to the human body and no pollution to the environment.

(5) Claim 6 When the decomposition temperature of the foamable material is 100 ° C. to 200 ° C., gas is generated at a relatively high temperature as compared with the environment in which the battery is normally used. The battery can be used more safely than the generated foam material.

[0063] (6) active material for constituting claims 7 cathode active material layer is LiMn _2-n X n O ₄
, A battery having a higher energy density can be formed.

(7) Claim 8 Since the electrolyte salt constituting the electrolyte layer is LiBF ₄ ,
It is possible to provide an electrolyte salt that does not decompose and produce harmful substances even when the battery casing is broken.

(8) Claim 9 A battery element is housed inside an exterior sheet having at least the center of A1 and having a structure of three or more layers of plastic / A1 / plastic, and the opening of the exterior sheet is sealed. Since the battery is characterized in that the battery is stopped, the interface between the positive electrode and the negative electrode can be more reliably separated from the hard exterior material by gas generation. Also, a lightweight battery can be configured.

(9) In the tenth and eleventh aspects, the exterior sheet is processed into a cylindrical shape, the battery power generation element is housed inside, and the opening of the exterior sheet is sealed. According to the eleventh aspect, since the two side surfaces of the exterior sheet having a tubular structure have a bellows structure, it is possible to configure a battery having a high energy density.

(10) Claim 12 Since this battery does not have a current cutoff mechanism, the volume and weight of the battery can be reduced, and a battery with higher energy density can be constructed.

(11) Claim 13 Since the battery is provided with the separator, the safety of the battery is further improved.

(12) Since the negative electrode active material layer contains at least a carbon material,
It is possible to provide a negative electrode with improved safety for a metal negative electrode and excellent cycle characteristics.

(13) The negative electrode active material layer is made of artificial graphite obtained by calcining natural graphite and coke, thereby providing a negative electrode having no decomposition of a solvent and having excellent potential flatness and current characteristics. can do.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a method for manufacturing a solid electrolyte secondary battery according to the present invention in the order of steps.

FIG. 2 is a perspective view showing another example of the solid electrolyte secondary battery according to the present invention.

FIG. 3 is a front view illustrating an example of an exterior sheet.

FIG. 4 is a front view showing another example of the exterior sheet.

FIG. 5 is a front view showing still another example of the exterior sheet.

FIG. 6 is a perspective view showing a laminated structure of a power generation element constituting a solid electrolyte secondary battery according to an embodiment of the present invention.

FIG. 7 is a perspective view showing the structure of a conventional solid electrolyte secondary battery.

[Explanation of symbols]

 1,5,9 Positive electrode member 1a, 5a, 9a Positive terminal portion 2,4,6,8 Separator 3,7 Negative member 3a, 7a Negative terminal portion 11,13 Plastic film 12 Aluminum foil 20 Plastic sheet 21 Cylindrical sheet 22 , 23 Opening part 24 Adhesive part 25, 26 Seal part 30 Battery power generation element 31 Positive terminal 31a Exposed part 32 Negative terminal 32a Exposed part 40 Solid electrolyte secondary battery 41 Outer sheet 50 Battery 51 Outer material 52a to 52d Sealing part 53 Power generation Element 54 Positive terminal 55 Negative terminal

Claims (15)

[Claims] 1. A secondary battery having a laminated structure of at least a positive electrode current collector layer, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer, wherein the electrolyte layer is a solid electrolyte, A solid electrolyte secondary battery comprising a foamable material in a solid electrolyte. 2. The solid electrolyte according to claim 1, wherein the solid electrolyte is a gel-like solid electrolyte obtained by dissolving at least a polymerizable compound in an electrolytic solution to cause a polymerization reaction. Rechargeable battery. 3. The solid electrolyte secondary battery according to claim 2, wherein the polymerizable compound is an acrylate compound. 4. The gas generated from the foamable material is CO.
Solid electrolyte secondary battery according to claim 1, 2 or 3, characterized in that it is _2. 5. The gas generated from the foamable material is N ₂
The solid electrolyte secondary battery according to claim 1, wherein: 6. The decomposition temperature of the foamable material is 100 ° C. or more.
The solid electrolyte secondary battery according to claim 1, wherein the temperature is 200 ° C. 7. 7. The active material constituting the positive electrode active material layer is L
iMn is _2-n X n O ₄ (provided that, X is a Group IIA, III
Group A, Group IVA, Group VA, Group VIA, Group VIIA, Group VIII, I
At least one element selected from Group B, IIB, IIIB, IVB, and VB elements;
It is. The solid electrolyte secondary battery according to any one of claims 1 to 6, wherein 8. The electrolyte salt constituting the electrolyte layer is Li
Solid electrolyte secondary battery according to claim 7, characterized in that the BF _4. 9. A1 (aluminum) at least in the center
The battery power generation element is housed inside an exterior sheet having a layer and a structure of three or more layers of plastic / A1 / plastic, and an opening of the exterior sheet is sealed. 9. The solid electrolyte secondary battery according to any one of 1 to 8. 10. The solid electrolyte according to claim 9, wherein the exterior sheet is processed into a cylindrical shape, a battery power generation element is housed inside, and an opening of the exterior sheet is sealed. Rechargeable battery. 11. The solid electrolyte secondary battery according to claim 10, wherein two side surfaces of the cylindrical exterior sheet have a bellows structure. 12. The solid electrolyte secondary battery according to claim 1, wherein a current cutoff mechanism is not provided. 13. The solid electrolyte secondary battery according to claim 1, further comprising a separator. 14. The solid electrolyte secondary battery according to claim 1, wherein the negative electrode active material layer contains at least a carbon material. 15. The solid electrolyte secondary battery according to claim 14, wherein the negative electrode active material layer is artificial graphite obtained by firing natural graphite and coke.