JPH09120804A - Battery - Google Patents

Abstract

(57) [PROBLEMS] To provide a battery having excellent properties such as low moisture permeation, high energy density, no short-circuit at the non-mouth portion, and high sealing strength at the sealing portion. SOLUTION: In a battery constituted by packaging a power generation element including at least a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer in an outer packaging material, a glass fiber having a diameter of 4 μm or more and 50 μm or less is used as a sealing material. Are orthogonal to each other, and the amount of glass cloth is 4 cm / m per 1 m of one side of the glass cloth used.
A battery characterized by using a composite body in which an insulating heat-fusible resin is composited on a glass cloth of 10 cm / m or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a battery in which a power generation element is sealed with a heat-fusible resin.

[0002]

2. Description of the Related Art Recent advances in miniaturization, thinning and weight reduction of electronic equipment have been remarkable, and particularly active in the field of OA equipment. For example, word processors have been reduced in weight from desktops to laptops and notebooks. In addition, new small electronic devices such as electronic notebooks and electronic still cameras have appeared, and further development of memory cards, which are new memory media, is under way. In the wave of miniaturization, thinning, and weight reduction of such electronic devices, high performance is also required for secondary batteries that support such electric power. In such a demand, development of a lithium secondary battery as a high energy density battery replacing a lead battery or a nickel cadmium battery has been rapidly advanced. In addition, a thin battery called a paper battery, a thin flat battery, or a plate-shaped battery has been developed for the purpose of reducing the thickness. However, since the sealing area of a battery using a heat-fusible resin typified by a paper battery has a wide sealing area, improvement of the sealing technology and / or sealing material has become a major technical issue. In the conventionally known button-type or coin-type batteries, a method is used in which the outer plates of the both electrodes or the ends of the battery container are bent, and a gasket is sandwiched to seal them. According to this method, it is considered difficult to seal a rectangle other than a circle, for example, a rectangle, and the thickness limit is set to 1.0 mm. A method of sealing a square battery or an ultrathin battery having a thickness of 0.5 mm or less is performed by heating and pressing the peripheral portion of the exterior plate through a frame-shaped insulating heat-fusible resin. A scheme has been proposed.

As a heat-fusible resin suitable for this purpose, polyolefin resins, fluororesins and modified products thereof have been proposed (for example, JP-A-49-12823).
No. 2, No. 59-83340, No. 60-14753,
Nos. 60-160559 and 60-185359, etc.). However, in this case, since the above heat-fusible resin flows by heating and pressurization and becomes thin, the thickness of the sealing material is partially thinned, the insulating property is lowered, and the end portion of the exterior plate is There has been a problem that short circuits easily occur due to contact with each other. Further, since the area of the sealing portion is large and the material of the sealing body is plastic, there is a problem that the water permeation is large and the reliability of the non-aqueous battery is deteriorated. Regarding the former problem of short circuit, the following proposals have already been made. For example, a method in which a base material mainly composed of a polyolefin resin and a carboxyl group-containing polyolefin resin having a low melt viscosity are laminated on both surfaces of the base material to use a sealing material which is not easily deformed during heat bonding (Japanese Patent Laid-Open No. 60-220553)
No.), a method using a resin mixed with glass fiber (Japanese Patent Laid-Open No. 60-3852), and a substrate obtained by impregnating a woven or non-woven fabric made of glass fiber with a polyolefin resin has a low melt viscosity on both sides. A method of using a sealing material in which a carboxyl group-containing polyolefin resin is laminated (JP-A-62-5556).

However, in JP-A-60-3852, the heat and pressure applied to the heat-fusible resin (polyolefin) at the time of sealing causes the resin to soften and flow and be exposed to the outer peripheral portion of the battery, which may impair the appearance. , The upper and lower metal (one is the positive electrode and the other is the negative electrode) contact with each other by hitting the softened resin layer, and the glass fiber is mixed with the polyolefin-based resin only in order to prevent the battery from being short-circuited easily. No investigations have been made to maximize the energy density of the battery while maintaining the sealing function and defects due to changes in the sealing strength due to the difference in the mixed amount, and the problem of water permeation has not been mentioned at all. Further, in JP-A-62-5556, sealing strength and deformation are improved by using a carboxyl group-containing polyolefin resin having a lower melt viscosity than that of polyolefin. However, in the above invention, the amount of the carboxyl group-containing polyolefin resin used is as large as 50% or more of the cross-sectional area of the sealing material, which is disadvantageous in increasing the energy density of the battery and also in terms of moisture permeation. It will be a disadvantage.

[0005]

[Object] It is an object of the present invention to provide a battery having excellent properties such as low moisture permeation, high energy density, no short-circuit in the non-mouthed portion, and high sealing strength in the sealing portion. .

[0006]

[Structure] The sealing material used in the secondary battery of the present invention is basically composed of a resin component mainly composed of a polyolefin resin and a glass fiber component. The heat-fusible resin used for the sealing material is usually a polyolefin resin, particularly a polyolefin-based resin, because it is required to be a thermoplastic resin that withstands the organic solvent used as the solvent of the non-aqueous electrolyte and has good heat-welding property. A resin and a resin obtained by modifying the polyolefin resin are mainly used, and as the polyolefin resin, polyethylene and polypropylene resins are preferably used. Further, the polyolefin-based resin may be a mixture of polyolefin-based resins, or a mixture of a polyolefin-based resin and another resin. Further, the sealing body of the present invention contains glass fibers mixed with the polyolefin resin, which has a high melting point and a large mechanical strength and which can prevent the water permeable resin from flowing and deforming. However, the specific gravity of glass fiber is higher than that of resin, and if glass fiber is used for the sealing body, the energy density of the battery will naturally decrease. This becomes a particularly serious problem in the case of a battery called a thin battery or a plate battery in which the area of the sealing portion is relatively large. Therefore, the amount of the glass fiber used in the sealing material is preferably the smallest possible amount within the range satisfying the purpose of use of the glass fiber as described above. As a result of various studies on the amount and form of use of the glass fiber, the present inventors prefer a glass fiber in the form of cloth, and the amount is 1 side of the glass cloth.
The amount of glass fiber contained per m is 4 cm or more and 10c
It has been found that a sealing material formed by using a glass cloth of m or less can satisfy the purpose of using the glass fiber while keeping the energy density of the battery high. If the amount of glass fiber in the sealing material is more than 10 cm / m, the energy density is lowered due to the increase in weight of the fiber, which is not preferable. If it is less than 4 cm / m, the energy density can be kept high, but the purpose of using the glass fiber cannot be achieved.

The definition in the present invention that the amount of glass fiber contained per 1 m of one side of the glass cloth is 4 cm / m or more and 10 cm / m or less will be described below with reference to FIG. In FIG. 1, one side of the glass cloth (a =
Total length of glass fiber included per 1 m)

(Equation 1) Means 4 cm / m to 10 cm / m. Here, a ₁ , a ₂ , a ₃ ,. . . a _j is the diameter of each fiber. Also, the total length of this glass fiber

(Equation 2) Is more preferably 5 cm / m to 8 cm / m. Further, the glass cloth has glass fibers orthogonal to each other,
Moreover, the glass fiber having a diameter of 4 μm to 50 μm is preferable. In the present invention, the above-described object of the present invention can be achieved by using the glass fiber constituting the sealing material in the above-mentioned usage amount and shape such as glass cloth. That is, when randomly using glass fibers, for example, when using a non-woven fabric, in order to obtain the same effect of using the glass fibers as in the present invention, more glass fibers are required and the energy density of the battery is increased. Will lower it.

In order to impregnate the glass cloth used in the present invention with the polyolefin resin, for example, a method of spraying a powder of the polyolefin resin on the glass cloth and integrating the resin and the glass cloth by heat and pressure, or glass There is a method in which a polyolefin resin is extruded on a cloth by an extruder or the like and integrated.
In the method, as the polyolefin resin,
Modified polyolefin resins are preferred. As the modified polyolefin resin, for example, one having a melting point or a softening point lower than that of the base polyolefin resin by 10 to 30 ° C. or more is particularly preferable. These modified polyolefin resins are obtained, for example, by copolymerizing or graft-polymerizing an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid or maleic anhydride with an ethylene or propylene monomer. Is. The resin, in addition to the original heat-weldability and solvent resistance of the nonpolar polyolefin-based resin, the heat-weldability with the metal surface is further improved by the presence of the carboxyl group, so that the surface layer of the sealing material, particularly both You may form only a surface layer with the said modified polyolefin resin.

The compounding amount of the resin in the glass cloth as the substrate is preferably less than 50% to 20% or more of the cross-sectional area of the sealing material. If it is 50% or more, the fused state is good, but the amount used is too large, which lowers the energy density of the battery and is disadvantageous in terms of water permeability.
This is because the polyolefin mixed with glass fiber is
This is because the water permeability of the polyolefin resin is as low as a fraction of a few to a few tens of minutes as compared with a non-contaminated polyolefin. Therefore, it is preferable that the polyolefin resin is as small as possible in the range satisfying its function. When it is less than 20%, the polyolefin containing a carboxyl group is deformed by heat pressure and the polyolefin resin of the base material appears, so that uniform adhesive strength cannot be obtained.

The secondary battery of the present invention basically comprises a positive electrode, a negative electrode and an electrolyte. Examples of the positive electrode active material used in the present invention include transition metal chalcogen compounds, conductive polymers, carbon bodies and composites thereof. Specific examples of the transition metal chalcogen compound include V ₂
O ₅ , TiO ₂ , Cr ₃ O ₈ , MnO ₂ , MnO ₃ , Co
Oxides such as O ₂ and NiO ₂ , sulfides such as TiS ₂ and FeS, complex oxides of Li and Mn, Ni and Co, such as L
Examples include ixMn ₂ O ₄ , LixCoO ₂ , and LixNiO ₂ . Examples of the conductive polymer include polyaniline, polypyrrole, polythiophene, polyacetylene, polyazulene, polydiphenylbenzidine, polyvinylcarbazole, and derivatives of poly3alkylthiophene. The most preferable form of the positive electrode active material is a composite of an inorganic active material and a conductive polymer active material. According to this, since the conductive polymer also serves as a binder, a conductive agent, and an active material, it is possible to form a flexible electrode that does not impair the flexibility of a thin battery while maintaining a high energy density. Is possible. More specifically, the combination of polyaniline and crystalline V ₂ O ₅ has desirable properties. As the negative electrode material used in the battery of the present invention, lithium metal and carbonaceous material can be used, but the cycle characteristics,
From the viewpoint of safety, it is preferable to use a carbonaceous material.
Examples of carbonaceous negative electrode active materials include fired bodies of graphite, pitch coke, synthetic polymers and natural polymers.
A solid electrolyte is preferable as the electrolyte used in the present invention. By using the solid electrolyte, it is possible to prevent a decrease in sealing strength due to the electrolytic solution adhering to the sealing portion. This is because the electrolyte is in a solid state and flows like an electrolytic solution and does not adhere to the sealing portion. When the electrolytic solution adheres to the surface of the sealing resin, the adhesive strength is significantly reduced.

Examples of the solid electrolyte used in the present invention include metal halides such as AgCl, AgBr, AgI and LiI in an inorganic system, RbAg ₄ I ₅ and RbAg ₄ I ₄ CN.
Examples include ionic conductors. In organic systems, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, etc. are used as a polymer matrix to dissolve an electrolyte salt, or a cross-linked product thereof, low-molecular-weight polyethylene oxide, polyethyleneimine, crown ether, etc. The polymer solid electrolyte in which the ion dissociative group of is grafted to the polymer main chain can be mentioned. Alternatively, a gelled polymer solid electrolyte having a structure in which the high molecular weight polymer contains the electrolytic solution is used. The gelled polymer solid electrolyte is a solid electrolyte that is obtained by adding a polymerizable compound to an ordinary electrolytic solution and polymerizing the compound by heat or light. More specifically, those described in WO91 / 14294 are used. As a polymerizable compound, an acrylate (eg, methoxydiethylene glycol methacrylate, methoxydiethylene glycol diacrylate) -based compound is polymerized using a polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, methylbenzoyl formate, benzoin isopropyl ether, and electrolysis. This is to solidify the liquid.
Among such solid electrolytes, it is preferable to use a gel polymer solid electrolyte from the viewpoint of ionic conductivity and flexibility.
The electrolyte salt used for the gelled solid electrolyte is not particularly limited, but those which dissolve in a non-aqueous solvent and exhibit high ionic conductivity are used. Examples of such a cation include an alkali metal ion. As the anion, Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ ,
Examples thereof include BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , and CF ₃ SO ₃ ⁻ . Although an organic non-aqueous polar solvent is used as the electrolytic solution, an organic non-aqueous polar solvent that is aprotic and has a high dielectric constant is preferable. As a concrete example,
Examples thereof include, but are not limited to, propylene carbonate, γ-butyl lactone, dimethyl sulfoxide, dimethylformamide, acetonitrile, ethylene carbonate, dimethoxyethane and dichloroethane. The organic non-aqueous polar solvent may be used alone or in combination of two or more. The electrolyte concentration cannot be unconditionally specified because it varies depending on the type of positive electrode, electrolyte and organic non-aqueous polar solvent used, but it is usually in the range of 0.001 to 10 mol / liter. If oxygen or water is contained in the electrolyte or solvent, the performance of the battery may be deteriorated. Therefore, it is preferable to sufficiently purify the electrolyte or solvent according to a conventional method. A separator may be used in the battery of the present invention. As the separator, it is preferable to use a separator that has a low resistance to the movement of ions of the electrolyte solution and is excellent in retaining the solution. Examples of such a separator include a glass fiber, a filter, a non-woven fabric filter made of polymer fibers such as polyester, Teflon, polyflon, and polypropylene, and a non-woven fabric filter made by mixing glass fibers and these polymer fibers.

[0012]

【Example】

Examples 1 to 10 and Comparative Examples 1 to 4 Stainless steel sheet 4 × 7.5 cm (polymerization part) having a through hole of 0.9 mmφ which was blasted to 20 μm as a reaction electrode in a 3M HBF ₄ aqueous solution containing aniline. )
Was used to polymerize only one side at 3 mA / cm ² . After washing this stainless polyaniline electrode with running water, 0.2
The dedoping operation was performed sufficiently by applying a potential to −0.4 V vs SCE in N sulfuric acid. This was reduced using a 20% hydrazine aqueous solution, washed and dried to obtain a polyaniline electrode. S having a thickness of 50 μm and a size of 5.5 × 9 cm
US sheet, outer diameter 5.5 × 9 cm, inner diameter 4.1 × 7.
A thickness of 200 including a glass cloth (diameter 4 μm, fiber amount 6 cm / m) in which glass fibers have an opening of 6 cm and orthogonal to each other.
A polyethylene / glass fiber composite sheet of μm was fixed by heat fusion, and a polyaniline electrode was adhered to the center of the composite sheet using a conductive adhesive. Then add L to a 7/3 (volume ratio) mixture of propylene carbonate and dimethoxyethane.
A solution prepared by mixing an electrolyte solution in which iBF ₄ was dissolved in 3M at a ratio of 86.9%, ethoxydiethylene glycol acrylate 12.8%, trimethylolpropane triacrylate 0.2%, and benzoin isopropyl ether 0.1% was sufficiently added to polyaniline. Soaked. Further, the mixed solution was sufficiently impregnated to a thickness of 25 μm, 4.5 × 8.0 c
A polypropylene pore filter of m was laminated on the polyaniline and irradiated with light from a high pressure mercury lamp. The electrolyte was solidified, and the liquid did not exude even when pressure was applied. This was used as a positive electrode member. Size of negative electrode 4 × 7.
5μ, 100μm thick lithium foil 20μ thick
m, which was pressure-bonded to a 5.5 × 9 cm SUS foil was used. Then, the lithium surface is coated with the mixed solution,
Irradiation with a high-pressure mercury lamp completely solidified the electrolyte solution on the lithium surface. This was used as a negative electrode member. The positive electrode member and the negative electrode member were laminated, and the three sides were sealed with heat of 6.5 mm from the end while applying (holding down) pressure uniformly to the power generation element part. Then, the remaining side was sealed under reduced pressure to complete the battery.
Charge this battery to 7.5V at 7.5mA, 7.5mA
Was discharged to 3.7 V, the capacity was measured, and the energy density of the battery was calculated. Also, for the initial energy capacity,
After storage for 3 months at 25 ° C. and 90% humidity, the energy capacities after recharging were compared, and the effect of water permeation was evaluated in the form of capacity retention before and after the test. In the above example,
The amount of glass fiber and fiber diameter to be used, the type of insulating heat-fusible resin to be used, and the amount to be used were changed, and the results were shown in Tables 1 and 2.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

【effect】

1. The present invention provides a battery having excellent properties such as low moisture permeation, high energy density, no short-circuit in the non-mouthed portion, and high sealing strength in the sealing portion. 2. A battery having a sealed portion which is resistant to an organic solvent and has a good heat fusion property is provided. 3. In addition to the effect of the above item 2, a battery that can be sealed at a low temperature is provided. 4. Provided is a battery in which the sealing strength is prevented from being lowered due to the electrolytic solution adhering to the sealing portion.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the structure of a glass cloth used in the present invention in which glass fibers are orthogonal to each other.

[Explanation of symbols]

a ₁ diameter of glass fiber a ₂ diameter of glass fiber a ₃ diameter of glass fiber a _j diameter of glass fiber

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Toshiyuki Kabata 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Hiroyuki Ichiji 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Nobuo Katagiri 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Yoshiko Kurosawa 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Yoshitaka Hayashi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (4)

[Claims] 1. A battery constituted by packaging at least a power-generating element composed of at least a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer with an exterior material, wherein the glass fiber has a diameter of 4 μm or more and 50 μm or less as a sealing material. The fibers are orthogonal to each other, and the amount of glass cloth is 4 cm / m per 1 m of one side of the glass cloth used.
A battery characterized by using a composite body in which an insulating heat-fusible resin is composited on a glass cloth of 10 cm / m or less. 2. The battery according to claim 1, wherein the insulating heat-fusible resin of the sealing material is a polyolefin resin. 3. The battery according to claim 2, wherein the polyolefin resin in at least both surface layer portions of the sealing material is a modified polyolefin resin. 4. The battery according to claim 1, 2 or 3, wherein the electrolyte layer is composed of a solid electrolyte.