JP2003017014A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sufficient current capacity for leads even in a small lightweight battery to reduce possibility of blower-out leads or fusion of a sheath case, and to prevent poor sealing or a sealing defect of the sheath case. SOLUTION: This battery 10 has basic battery elements each including a positive electrode, a negative electrode and an electrolyte interposed between them; the sheath case 6 enclosing the basic battery elements; and the leads 5 connected to the positive electrode and the negative electrode. The respective leads 5 are led to the outside of the sheath case 6 with maintaining a sealing state of the sheath case 6. A ratio X/Y is <=0.4, and Y is <=20 mm, wherein X is a total value of widths of the leads 5 led out of each side of the sheath case 6, and Y is a length of the side, while the lead 5 has a cross section capable of securing the allowable current corresponding to five times a discharging (charging) current value when making the battery 10 making a 1-hour-rate discharging (charging).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly to a battery configured such that a peripheral portion of an outer case is sealed in a state where leads connected to electrodes are taken out of the outer case. Regarding

[0002]

2. Description of the Related Art A battery generally has two types of electrodes, a positive electrode and a negative electrode, and a space between these electrodes is filled with an electrolyte. In such a battery, the chemical energy accumulated in the positive and negative electrode active materials is converted into electric energy through a chemical reaction that occurs via the electrolyte, and this electric energy is extracted to the outside and used as an electromotive force.

Since a pair of positive and negative electrodes and an electrolyte filling the space between the electrodes are basic elements constituting a battery,
In the following description, these are collectively referred to as "basic battery element".

In many cases, this basic battery element has a flat plate shape in which positive and negative electrodes are laminated with an electrolyte interposed between the electrodes. Then, the flat basic battery element is formed into a long length and wound, or a plurality of flat basic battery elements are formed and stacked to form a basic battery element. To be done.
Here, the capacity of the battery can be adjusted by appropriately selecting the number of windings and the number of layers of the basic battery element. The battery element thus formed is covered with an outer case, and when the battery element is a non-aqueous type, the outer case is sealed to prevent intrusion of water, and a final battery is manufactured.

The battery thus manufactured can be classified into two types, "primary battery" and "secondary battery", from the viewpoint of its function, and a battery that is used irreversibly by discharging only. A “primary battery” is called a “secondary battery” or a “storage battery”, which is a battery that can be used reversibly by repeating charging and discharging.

It is also possible to further classify the primary battery and the secondary battery according to the materials of positive and negative electrodes (positive and negative active materials) and electrolytes and their combinations.
For example, primary batteries are manganese batteries, alkaline manganese batteries, silver oxide batteries, mercury batteries, lithium batteries, hydrogen zinc batteries, etc., and secondary batteries are lead storage batteries, alkaline secondary batteries, nickel hydrogen batteries, lithium secondary batteries. , Zinc-halogen battery, redox flow battery, sodium-sulfur battery, etc., respectively.

Among them, a lithium secondary battery, which is a secondary battery using lithium as an electromotive substance, is expected to be able to have a significantly high capacity and a high energy density. Research and development as a power source are being promoted, and its applications are rapidly expanding. For example, laptop computer, mobile computer, mobile phone, handy terminal, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini disk, electric shaver, transceiver, electronic notebook, calculator, memory card, Portable recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, clocks, strobes, cameras, medical equipment (pacemakers, hearing aids,
This lithium secondary battery has already been used or is expected to be used in a wide range of fields such as shoulder-shoulder machines).

By the way, a battery constructed by enclosing and sealing the above-mentioned battery element in an outer case usually has leads electrically connected to the positive and negative electrodes, respectively. It is configured to be taken out of the outer case while maintaining the sealed state of the case.

For example, when a shape-variable case such as a laminate film is used for the outer case for the purpose of reducing the size and weight of the battery, such a battery has a battery element between two outer members to be the outer case. One sheet which is housed and leads from which the leads connected to the electrodes are taken out of the exterior case from the bonding surface of the exterior member to heat the peripheral portion of the exterior member under reduced pressure with heat, or to form an exterior case The outer packaging member is folded back into two pieces, the battery element is housed therebetween, and the lead is taken out from the bonding surface of the outer packaging member to the outside of the outer packaging case, and the peripheral portion of the outer packaging member is thermally sealed under reduced pressure. It is manufactured by a method such as.

In the battery thus manufactured, the internal pressure of the outer case is low, so that the outer case is pressed by the atmospheric pressure and contracts, and the battery element is tightly compressed and sealed in the outer case. It As a result, the energy density of the battery is increased, and it is possible to obtain sufficient performance even though the battery is small and lightweight.

[0011]

At present, batteries are required to have higher capacity and higher output as well as further miniaturization and weight reduction. For example, in the future, "Bl
It is expected that communication technology between wireless (no power cord) devices using protocols such as "uetooth" will develop, and batteries are expected to be used as a power source for such wireless devices. The wireless device is not limited to the form of a conventional mobile phone or a laptop computer, but is, for example, a pen type device, a wrist watch type device, an eyeglass type device, a belt type device, etc.
Various forms of wireless devices have been invented or already developed. With the liberalization of these forms, it is expected that wireless devices will become smaller and lighter in the future, but the batteries housed in them will naturally be required to be smaller and lighter. Further, as the data transfer speed between wireless devices increases, the power consumption of the devices also increases. Therefore, in addition to downsizing and weight reduction of batteries, higher capacity and higher output of batteries are also required.

However, it has been found that a new problem arises in the battery in fulfilling these requirements. That is, in the peripheral portion of the exterior member encapsulating the battery element, the portion where the lead is taken out is not sufficiently sealed, and the deterioration of the battery occurs due to the infiltration of water into the battery element. This problem will be described in detail below.

It is necessary for the above-mentioned battery lead to secure a constant allowable current in proportion to the battery capacity and battery output. If the allowable current of the lead is not sufficient, the heat generated by the lead when the battery has a large current causes the adhesive part between the exterior members to loosen, resulting in insufficient sealing, which may lead to moisture infiltration.
This is because the lead itself will be blown out at a higher current. In general, when the lead material is the same, the allowable current is proportional to the cross-sectional area of the lead. Therefore, the lead of the battery needs to have a cross-sectional area equal to or larger than a certain value in proportion to the capacity of the battery and the battery output in order to suppress the infiltration of water into the battery element.

On the other hand, as the size and weight of the battery have progressed as described above, and the energy density of the battery has risen accordingly, the allowable current required for the lead is relatively large compared to the volume of the battery. As a result, the ratio of the cross-sectional area of the lead to the area of each surface of the battery increases. Such a tendency causes a problem when the outer case is sealed.

That is, in general, at the side of the outer case where the lead to be taken out exists, since the peripheral portion of the outer member is bonded while the lead is sandwiched, the cross-sectional area of the lead sandwiched between the outer members is relatively large. If it is large, the area of the adhesive surface is correspondingly small, and the adhesive force between the exterior members is weakened, and sealing may not be performed properly (sealing failure).
Even if the sealing is completed, it is not sufficient, and it often peels off due to an external impact (insufficient sealing).
Therefore, as described above, when the ratio of the cross-sectional area of the lead to the area of each surface of the battery is relatively high, the possibility of such defective sealing or insufficient sealing also increases.

Many battery elements are non-aqueous, and the infiltration of water into the battery elements deteriorates the battery characteristics. Therefore,
It is essential to reliably seal the outer case and to shield the battery element from external moisture. In addition, defective sealing or insufficient sealing may lead to liquid leakage and the like, so that reliable sealing must be achieved in order to safely use the battery. Especially, as mentioned above, when batteries will be used in various small wireless devices in the future,
As it is expected that the battery will be used in environments with high impacts, the need to achieve reliable encapsulation in miniaturized and lightweight batteries is ever increasing.

The present invention has been made in view of the above problems. In other words, the object of the present invention is to ensure a sufficient permissible current in the leads even in a small and lightweight battery, and even if a large current flows, the leads may melt and the moisture may enter due to melting of the outer case. It is an object of the present invention to provide a battery capable of reliably sealing the outer case while preventing the intrusion of water due to poor sealing of the outer case and insufficient sealing while simultaneously reducing the property.

[0018]

Therefore, as a result of intensive studies, the inventors of the present invention have found that even in a small battery, the side of the outer case from which the lead is taken out can be provided while giving the lead a certain cross-sectional area. The inventors have found that the above problems can be effectively solved by controlling the ratio of the total width of the leads taken out from the lead and the length of the side so as to fall within a certain range, and have reached the present invention.

That is, the gist of the present invention is to provide a basic battery element having a set of positive and negative electrodes and an electrolyte interposed between the positive and negative electrodes, an outer case enclosing at least one of the basic battery elements, and the basic case. A battery having leads connected to the electrodes of a battery element, each of the leads being taken out of the outer case while maintaining the sealed state of the outer case, On the side of the outer case from which the lead is taken out, the ratio X of the total value X of the width of the lead taken out from the side and the length Y of the side.
/ Y is 0.4 or less, and the side length Y is 20 mm or less, and the lead has a discharge current value when the lead discharges the battery at a rate of 1 hour or The battery is characterized by having at least a cross-sectional area capable of ensuring an allowable current equivalent to five times the charging current value when charging for one hour.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. (1) Type of Battery The battery of the present invention comprises at least one basic battery element having a pair of positive and negative electrodes and an electrolyte interposed between the positive and negative electrodes. Here, the positive and negative electrodes store chemical energy that is a source of electromotive force of the battery, and at least one of them is usually formed by providing an active material layer on a current collector. In addition, a separator is usually provided between both electrodes in order to prevent a short circuit between both electrodes. The separator is usually formed of a porous insulating material. In this case, the electrolyte is present between both electrodes including the voids present in the electrodes and the voids of the separator, and both electrodes are insulated from each other by the separator, so that they can be energized through the electrolyte. Composed. In the battery having such a configuration, the chemical energy accumulated in the positive and negative electrode active materials is converted into electric energy through a chemical reaction generated through the electrolyte, and this electric energy is extracted to the outside and used as an electromotive force.

Further, leads are connected to the positive and negative electrodes of the basic battery element, respectively, and the basic battery element is enclosed in an outer case, and each of the leads is kept sealed in the outer case. Meanwhile, it is configured to be taken out of the outer case.

As described above, such a structure is adopted in many batteries, and therefore the application of the present invention is not particularly limited depending on the kind of battery. That is, regardless of whether the target battery is a “primary battery” or a “secondary battery”, or a manganese battery, an alkaline manganese battery, a silver oxide battery, a mercury battery, a lithium battery, a zinc-zinc battery, a lead-acid battery, an alkaline battery. Regardless of the classification of secondary battery, nickel hydrogen battery, lithium secondary battery, zinc halogen battery, redox flow battery, sodium sulfur battery, etc., it has the basic battery element of the above structure and has the above structure connected to electrodes. The present invention can be applied to any battery as long as each lead is taken out of the outer case while keeping the outer case sealed.

However, the battery of the present invention is preferably a secondary battery. Since rechargeable batteries are repeatedly charged and discharged in a secondary battery, a large current may flow in the leads, which may easily lead to melting of the leads and moisture infiltration due to melting of the outer case. ,
Deterioration of battery characteristics due to poor sealing or insufficient sealing of the outer case is likely to occur, and the effect obtained by applying the present invention becomes large.

In the following description, for the sake of convenience, a lithium secondary battery, which is presumed to be particularly effective due to the application of the present invention, will be described as an example among the above-mentioned various batteries. Of course, in spite of the following description, the present invention is not limited to the lithium secondary battery, and as long as it does not exceed the gist, it can be widely applied to various other types of batteries having the above-mentioned basic battery element. It is possible to apply.

(2) Battery Material FIG. 1 is a schematic perspective view showing the structure of a basic battery element used in a lithium secondary battery as an embodiment of the present invention. As shown in FIG. 1, a basic battery element 1 of a lithium secondary battery includes a positive electrode active material layer 2b on a surface of a positive electrode current collector 2a.
And a negative electrode current collector 3a.
Of the negative electrode (electrode) 3 provided with the negative electrode active material layer 3b on its surface, and the separator 4 interposed between the positive and negative electrodes 2 and 3. Tabs 2'and 3'for connecting lead terminals, which will be described later, are extended from the positive and negative electrode current collectors 2a and 3a. further,
An electrolyte (not shown) is impregnated in the voids existing in the positive and negative electrodes 2 and 3 and the voids in the separator 4. Less than,
The material of each part constituting the basic battery element 1 of the lithium secondary battery will be described.

(2-1) Electrode (Positive Electrode, Negative Electrode) FIG. 2 is a schematic perspective view showing the structure of the electrode (positive electrode / negative electrode) used in the lithium secondary battery as one embodiment of the present invention. is there. As shown in FIG. 2, the positive electrode 2 of the lithium secondary battery usually includes a positive electrode active material layer 2b on a positive electrode current collector 2a.
And a positive electrode active material layer 2b containing a positive electrode active material capable of inserting and extracting Li.

Examples of the positive electrode active material include lithium transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide and lithium manganese composite oxide, and L
Examples thereof include compounds capable of inserting and extracting lithium ions such as iFePO ₄ , and organic compounds such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts. Of course, two or more kinds of positive electrode active materials selected from the above may be used in combination. The particle size of these positive electrode active materials may be appropriately selected depending on the balance with other constituent elements of the battery, but from the viewpoint of improving battery characteristics such as initial efficiency and cycle characteristics, it is usually 1 to 100 μm, particularly Two
It is preferably set to -60 μm. In the present invention, it is preferable to use a lithium transition metal composite oxide as the positive electrode active material. When these positive electrode active materials are used, a large current may flow into the leads, so the effect of applying the present invention becomes large.

As with the positive electrode 2, as shown in FIG.
The negative electrode 3 of the lithium secondary battery usually has a configuration in which a negative electrode active material layer (negative electrode material layer) 3b is provided on the current collector 3a.
The negative electrode active material layer 3b contains a negative electrode active material capable of inserting and extracting Li. Examples of the negative electrode active material include graphite, coal-based coke, petroleum-based coke, carbide of coal-based pitch, carbide of petroleum-based pitch, or carbide of these pitches subjected to oxidation treatment, needle coke,
Pitch coke, a carbide such as phenol resin and crystalline cellulose, and the like, and a carbon material obtained by partially graphitizing them, a carbon-based active material such as furnace black, acetylene black, and pitch-based carbon fiber can be mentioned. These carbon-based active materials can be used in the form of a mixture with a metal, a salt thereof, an oxide, or a coating. Further, oxides or sulfates of silicon, tin, zinc, manganese, iron, nickel, etc., and further metallic lithium, Li-Al, Li-Bi-
Lithium alloys such as Cd and Li-Sn-Cd, lithium transition metal nitrides, and silicon can also be used. Of course, two or more kinds of negative electrode active materials selected from the above may be used in combination. The particle size of these negative electrode active materials is usually 1 to 50 μm.
m, preferably 2 to 30 μm. If it is too large or too small, battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics are deteriorated, which is not preferable.

Positive electrode active material layer 2b and negative electrode active material layer 3b
In order to bind the positive electrode active material and the negative electrode active material to the corresponding current collectors 2a and 3a, a binder may be further contained. When the binder is contained, the amount of the binder based on 100 parts by weight of the active material is usually 0.
The amount is 01 parts by weight or more, preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and usually 50 parts by weight or less, preferably 30 parts by weight or less, more preferably 15 parts by weight or less. If the amount of the binder is too small, it becomes difficult to form a strong electrode, and if the amount of the binder is too large, the energy density and the cycle characteristics may deteriorate.

As the binder, for example, polyethylene,
Alkane-based polymers such as polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polymers having rings such as polystyrene, polymethylstyrene, polyvinylpyridine and poly-N-vinylpyrrolidone; poly Acrylic derivative polymers such as methyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, ethyl polyacrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide; polyvinyl fluoride, polyvinylidene fluoride, poly Fluorine-based resins such as tetrafluoroethylene, CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol; polyvinyl chloride, Halogen-containing polymers Li vinylidene chloride; such a conductive polymer such as polyaniline, various polymers can be used. Further, a mixture of the above various polymers, a modified product, a derivative, a random copolymer,
Alternate copolymers, graft copolymers, block copolymers and the like can also be used. Furthermore, it is also possible to use an inorganic compound such as silicate or glass.

The weight average molecular weight of the binder is usually 1,000 or more, preferably 10,000 or more, more preferably 20,000 or more, and usually 5 million or less, preferably 100.
It is preferably 10,000 or less, more preferably 300,000 or less. If the weight average molecular weight is too low, the strength of the coating film decreases, which is not preferable, and if it is too high, the viscosity increases and it becomes difficult to form the active material layer.

Further, it is preferable to mix the positive and negative active material layers 2b and 3b with the same electrolyte as that used in the electrolyte layer described later in order to facilitate the movement of ions in the active material layer. The ratio of the electrolyte in the active material layers 2b and 3b is 10
It is preferably set to ˜50% by volume. The greater the amount of electrolyte mixed, the easier the migration of ions in the active material layers 2b and 3b, which is preferable in terms of rate characteristics. On the other hand, the smaller the amount of electrolyte, the higher the energy density.

Further, the positive electrode active material layer 2b and the negative electrode active material layer 3b may contain additives, such as conductive materials and reinforcing materials, which exhibit various functions, powders, fillers, etc., if necessary. good. The conductive material is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with the active material, but as a commonly used material, acetylene black, carbon black, carbon powder such as graphite, and various metals. Fibers, metal foils and the like can be mentioned. As the reinforcing material, various inorganic or organic spherical or fibrous fillers can be used.

Current collector 2 used for positive electrode 2 and negative electrode 3
As the material of a and 3a, usually, metals such as aluminum, copper, nickel, tin, stainless steel, alloys of these metals, and the like can be used. In this case, aluminum is usually used as the positive electrode current collector 2a, and the negative electrode current collector 3 is used.
Copper is usually used as a.

The thickness of each of the positive electrode 2 and the negative electrode 3 is usually 1 μm or more, preferably 10 μm or more, and usually 500 μm or less, preferably 200 μm or less. If it is too thick or too thin, battery performance such as battery capacity and rate characteristics tends to decrease.

Specifically, the positive and negative current collectors 2a,
The thickness of 3a is usually 1 to 50 μm, preferably 1 to 3 μm.
It is 0 μm. If it is too thin, the mechanical strength of the electrodes 2 and 3 becomes weak, which is not practical when it is constructed as a battery. On the other hand, if it is too thick, the battery becomes large and the space occupied in the device becomes large, which makes it difficult to reduce the size of the battery.

The thickness of the positive and negative active material layers 2b and 3b provided on the current collectors 2a and 3a is, as a lower limit, usually 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and most preferably. Is 80 μm or more, while the upper limit is usually 200 μm or less, preferably 150 μm or less. The thicker one is preferable in terms of capacity, while the thinner one is preferable in terms of rate characteristics. Therefore, the above range is derived from the balance of both conditions.

The planar shape of the electrodes 2 and 3 is not particularly limited, and may be any shape according to the shape and properties of the battery to be manufactured, selection of other components, and the like.
Generally, as shown in FIG. 1 and FIG. 2, it has a polygonal shape such as a rectangle and has tabs 2 ′, 3 ′ for connecting lead terminals extended from current collectors 2a, 3a. To be done. The lead terminal will be described later.

The shapes and areas of the positive electrode 2 and the negative electrode 3 may be the same, but may be different. Positive electrode 2 and negative electrode 3
In the case where the areas are different, it is preferable to make the area of the negative electrode larger than the area of the positive electrode. By making the area of the negative electrode larger than the area of the positive electrode, it is possible to effectively prevent a short circuit between both electrodes due to deposition of lithium on the surface of the negative electrode.

The method for producing the electrodes 2 and 3 is not particularly limited, but a long or flat current collector is provided because it is excellent in production cost and the effect of applying the present invention can be remarkably obtained. It is preferable that a plurality of electrodes having an arbitrary planar shape are cut from a long or flat electrode raw material (electrode raw material) formed by providing a positive or negative active material layer thereon.

Specifically, first, a long or flat current collector formed of a plate member, a mesh member, punching metal or the like is prepared, and a positive or negative active material layer is formed on at least one surface of the current collector. To form.

As a method of forming the active material layer on the current collector, for example, a powdery positive or negative active material is mixed with a solvent together with an additive such as a binder and a conductive material, and this is mixed with a ball mill or a sand mill. There is a method in which a dispersion paint prepared by using a biaxial kneader or the like is applied onto a current collector and dried. In this case, the type of solvent used is not particularly limited as long as it is inert to the active material and can dissolve the binder, and for example, a commonly used organic solvent such as N-methylpyrrolidone or Any of the inorganic solvents can be used.

Also, the active material is mixed with a binder and an additive such as a conductive material, and the active material layer is pressed or sprayed on the current collector in a state of being heated and softened to form an active material layer on the current collector. It can also be formed. Alternatively, the active material layer can be formed on the current collector by firing the active material alone on the current collector without mixing the binder.

Here, in order to increase the adhesive strength between the active material layer and the current collector, it is preferable to preliminarily roughen the surface of the current collector before applying the active material. Examples of such a surface roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. Examples of the mechanical polishing method include a method of polishing the surface of the current collector with a wire brush provided with abrasive cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a steel wire and the like.

Then, a plurality of electrodes having an arbitrary plane shape are cut from the long or flat electrode raw material (electrode raw material) prepared by the above method. The method of cutting the electrode is not particularly limited, and various methods can be selected according to the shape, size, production scale, production process, etc. of the electrode. Among them, as a commonly used cutting method, a method by rolling and a method by shearing can be mentioned, but from the viewpoint that burrs are unlikely to occur on the end surface of the cut electrode, the method by shearing is preferable to the method by rolling. .
Regardless of which cutting method is used, deterioration due to wear of the cutting edge can cause burrs on the cutting surface of the electrode. It is necessary to replace the cutting edge with a different one and always keep the cutting edge in a state of low wear. Further, in any of the cutting methods, the active material is removed to some extent during the cutting, so it is advisable to remove the removed active material by suction. If the active material that has fallen off is present on the cut electrode, a short circuit is likely to occur and the function of the separator may deteriorate.

When a basic battery element is laminated to form a battery element, the positive or negative active material layer is not provided on only one surface of the current collector, but the active material layer is provided on both surfaces of the current collector. May be provided. A battery with a large capacity can be obtained by creating an electrode having a positive active material layer on both sides of a current collector and an electrode having a negative active material layer on both sides and alternately stacking a plurality of electrodes with a separator interposed therebetween. Can be manufactured efficiently.

(2-2) Separator As the material used for the separator of the lithium secondary battery (see reference numeral 4 in FIG. 1), for example, polyolefins such as polyethylene and polypropylene, or a part of these hydrogen atoms or Examples thereof include porous membranes of polyolefins, polyacrylonitrile, polyaramid, and the like, all of which are substituted with fluorine atoms. From the viewpoint of chemical stability to an electrolyte and stability to an applied voltage, a polyolefin or a fluorine-substituted polyolefin is preferable, and specifically, polyethylene or polypropylene, a part or all of these hydrogen atoms is used. The thing etc. which were substituted by the fluorine atom can be mentioned. Among these, particularly preferable are polyolefins such as polyethylene and polypropylene, and polytetrafluoroethylene (P
TFE) and polyvinylidene fluoride, most preferably polyolefins such as polyethylene and polypropylene. Of course, these copolymers and mixtures can also be used.

The number average molecular weight of the resin used as the material of the separator is usually 10,000 or more, preferably 100,000 or more, and usually 10 million or less, preferably 3 million or less. If the molecular weight is too small, the mechanical strength of the separator will be insufficient and short circuits will tend to occur.
On the other hand, if the molecular weight is too large, it tends to be difficult to fill the voids of the porous membrane with the electrolyte, and the production efficiency of the battery is reduced, and the battery performance such as rate characteristics tends to be reduced. If the molecular weight is too large, film formation may be difficult in the method of mixing a plasticizer described below and then stretching.

The separator may be a porous film. Examples of such a material include a porous stretched film and a non-woven fabric. In the present invention, a stretched film produced by stretching is more preferable. Since the porous stretched film has more uniform resistance in the film than the nonwoven fabric, it is possible to suppress local deposition of lithium, that is, dendrite that causes a short circuit between electrodes.

The lower limit of the porosity of the separator is usually 30% or more, preferably 35% or more, and the upper limit thereof is usually 80% or less, preferably 75% or less, more preferably 72% or less. . If the porosity is too small, the film resistance increases and the rate characteristics deteriorate. In particular,
The capacity decreases when used at a high rate. On the other hand, if the porosity is too large, the mechanical strength of the membrane decreases, and as a result, a short circuit easily occurs when the shape of the battery element changes.

The average pore size of the pores present in the separator is
The upper limit is usually 1.0 μm or less, preferably 0.2 μm
m or less, more preferably 0.18 μm or less, most preferably 0.15 μm or less, and the lower limit is usually 0.01 μm or more, preferably 0.07 μm or more. If the pore size is too large, a short circuit is likely to occur, while if the pore size is too small, the membrane resistance tends to increase, and battery performance such as rate characteristics tends to deteriorate.

The upper limit of the thickness of the separator is usually 3
0 μm or less, preferably 20 μm or less, more preferably 18 μm or less, and the lower limit is usually 3 μm.
Or more, preferably 5 μm or more, more preferably 7 μm
That is all. If the film thickness is too small, self-discharge due to the mild short circuit phenomenon is likely to occur. On the other hand, if the film thickness is too large, not only the battery characteristics such as rate characteristics become insufficient, but also the volume energy density tends to decrease.

The heat shrinkage ratio of the separator at 100 ° C. is usually 10% or less, preferably 9% or less, and more preferably 7% or less in one direction. Here, the "heat shrinkage rate in one direction" means, for example, in a stretched film, the heat shrinkage rate in the stretching direction and the heat shrinkage rate in the direction perpendicular thereto. If the heat shrinkage rate is too large, a short circuit is more likely to occur at the end of the electrode due to heating during battery production or leaving in a high temperature environment.

The method of manufacturing the separator is not particularly limited, but it is preferably manufactured as follows, for example.
A resin having a number average molecular weight of about 10,000 to 10,000,000, preferably 100,000 to 3,000,000 is mixed with a plasticizer as a heterogeneous dispersion medium, and the mixture is kneaded and then formed into a sheet. After extracting the plasticizer from the formed film with a solvent, by going through a step of stretching in a longitudinal or lateral direction at a predetermined ratio, or both,
A desired separator can be obtained.

(2-3) Electrolyte The electrolyte layer of a lithium secondary battery is usually formed by using the above-mentioned separator as a support and impregnating it with an electrolyte. The electrolyte usually contains an electrolytic solution, and the electrolytic solution is usually formed by dissolving a solute and, if necessary, a desired additive in a non-aqueous solvent. Here, the electrolyte may be present not only between the positive electrode and the negative electrode including the voids of the separator but also in the voids in the positive electrode and the negative electrode. The presence of the electrolyte in the voids in the positive electrode and the negative electrode can increase the conductivity of Li ions.

The solute is not particularly limited and any conventionally known solute can be used, but a lithium salt is preferable. As the lithium salt, for example, LiClO ₄ , L
iAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C
₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN
(SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC
_{(SO 2 CF 3) 3,} LiSbF 6, LiSCN , and the like, can be used at least one or more of these. Among these, especially LiPF ₆ , LiC
lO ₄ is preferred. The content of these solutes in the electrolytic solution (the total amount of the solute and the non-aqueous solvent) is usually 0.5 to 2.
It is 5 mol / l.

Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate and vinylene carbonate, non-cyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, tetrahydrofuran, 2
One or a mixture of two or more of furans such as methyltetrahydrofuran, ethers such as dimethoxyethane, lactones such as γ-butyl lactone, sulfur compounds such as sulfolane, and nitriles such as acetonitrile. . Of these, a mixed solution of one or more selected from cyclic carbonates, acyclic carbonates and lactones is preferable.

In addition to the above-mentioned solute and non-aqueous solvent, the electrolytic solution is an additive (for example, a sulfur-containing compound, a phosphorus-containing compound, a nitrogen-containing compound, anhydrous compound) for ensuring safety and battery characteristics (for example, cycle characteristics). Carboxylic acids, etc.) may be further contained.

Further, from the viewpoint of improving the liquid retaining property of the electrolyte layer and preventing the short circuit between the electrodes more effectively, the electrolyte may further contain a polymer in addition to the electrolyte.
The polymer is not particularly limited as long as it can secure the liquid retaining property of the electrolyte layer to some extent, and examples thereof include an acrylic polymer such as polymethyl methacrylate, an alkylene oxide polymer having an alkylene oxide unit, and a polyfluoride. Examples thereof include fluoropolymers such as vinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer. Among these polymers, from the viewpoint of sufficiently securing the liquid retaining property of the electrolyte layer, a bond (crosslinking bond) bonded so as to bridge between any two atoms of a molecule composed of chain-bonded atoms. It is preferable to use a polymer having a) (in the present specification, this is referred to as a “crosslinkable polymer”).

Examples of the material forming the basic skeleton of the crosslinkable polymer include those produced by polycondensation of polyester, polyamide, polycarbonate, polyimide, etc., those produced by polyaddition such as polyurethane and polyurea, and polymethacryl Examples thereof include those produced by addition polymerization of acrylic polymers such as methyl acidate and polyvinyl polymers such as polyvinyl acetate and polyvinyl chloride.

In the present invention, it is preferable to impregnate the separator and then polymerize it. Therefore, it is preferable to use a polymer produced by addition polymerization, in which the polymerization is easily controlled and by-products are not generated during the polymerization. . Examples of such polymers include acrylic polymers. Acrylic polymers are preferable materials in terms of battery characteristics such as battery capacity, rate characteristics, and mechanical strength.

As the acrylic polymer, a polymer obtained by polymerizing a monomer having an acryloyl group is particularly preferable. The monomer having an acryloyl group is not particularly limited as long as it contains an acryloyl group, methyl acrylate, ethyl acrylate, butyl acrylate, acrylamide, 2-ethoxyethyl acrylate, diethylene glycol ethyl ether acrylate, Monoacrylates such as polyethylene glycol alkyl ether acrylate, polypropylene glycol alkyl ether acrylate, 2-cyanoethyl acrylate; 1,2-butanediol diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, neopentane Alkanediol diacrylates such as diol diacrylate and 1,6-hexanediol diacrylate; ethylene glycol diacrylate Polyethylene glycol diacrylates such as gypsum, diethylene glycol diacrylate, triethylene glycol diacrylate and tetraethylene glycol diacrylate; polypropylene such as propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate and tetrapropylene glycol diacrylate Glycol diacrylates;
Bisphenol F ethoxylate diacrylate, bisphenol F ethoxylate dimethacrylate, bisphenol A ethoxylate diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, isocyanuric acid ethoxylate triacrylate , Glycerol ethoxylate triacrylate, glycerol propoxylate triacrylate, pentaerythritol ethoxylate tetraacrylate, ditrimethylolpropane ethoxylate tetraacrylate, dipentaerythritol ethoxylate hexaacrylate and the like.

Of these, polyacrylate polymers having ethylene glycol units are particularly preferable from the viewpoint of lithium ion conductivity. In the present invention, a copolymer of the above monomer component and another monomer component can be used as the acrylic polymer. That is, as a monomer component, a monomer having another structure may coexist and be polymerized in addition to the above monomers. In particular, when a monomer having a group having an unsaturated double bond such as a methacryloyl group, a vinyl group or an allyl group is allowed to coexist,
The strength and liquid retention of the electrolyte layer may be improved. As such a monomer, compounds such as methyl methacrylate, methacrylamide, butadiene, acrylonitrile, styrene, vinyl acetate and vinyl chloride can be used.

When an acrylic polymer is used, the abundance of monomers having an acryloyl group is not particularly limited, but it is usually 50% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more. Is. A higher abundance ratio is advantageous in that the polymerization rate is faster and the productivity of the gel electrolyte can be increased.

The crosslinkable polymer has crosslinks. The cross-linking can be produced by causing a cross-linking reaction between polymers with a cross-linking agent. Further, it can be produced by using a monomer having a plurality of reaction points (hereinafter, may be referred to as a “polyfunctional monomer”) as a raw material of the polymer. The latter method is preferred.

When the crosslinkable polymer is produced by the latter method, a monomer having one reaction point (hereinafter sometimes referred to as "monofunctional monomer") can be used as a raw material in addition to the polyfunctional monomer. . When the polyfunctional monomer and the monofunctional monomer are used in combination, the equivalent ratio of the functional groups of the polyfunctional monomer is usually 10% or more, preferably 15% or more, more preferably 20% or more.

The most preferable method for producing the crosslinkable polymer is a method in which a polyfunctional monomer having a plurality of acryloyl groups is polymerized with a monofunctional monomer having one acryloyl group, if necessary.

The content of the polymer contained in the electrolyte is usually 80% by weight or less, preferably 50% by weight or less, more preferably 20% by weight or less, based on the total weight of the electrolyte. If the content of the polymer is too large, the concentration of the electrolytic solution is lowered, so that the ionic conductivity is lowered and the battery characteristics such as rate characteristics tend to be lowered. On the other hand, if the proportion of the polymer is too low, gel formation becomes difficult and the retention of the solvent decreases, which may cause fluidity or liquid leakage, and may not ensure the safety of the battery. Therefore, the content of the polymer in the electrolyte is usually 0.1% by weight.
The amount is preferably 1% by weight or more, more preferably 2% by weight or more, and most preferably 5% by weight or more.

The ratio of the polymer to the non-aqueous solvent is appropriately selected according to the molecular weight of the polymer, but is usually 0.
It is 1% by weight or more, preferably 1% by weight or more, usually 50% by weight or less, preferably 30% by weight or less. If the proportion of the polymer is too low, gel formation becomes difficult, and the electrolyte retention becomes poor, tending to cause problems of fluidity and liquid leakage. If the proportion of the polymer is too large, the viscosity becomes too high and handling becomes difficult, and the ion conductivity decreases due to the decrease in the concentration of the electrolytic solution, and the battery characteristics such as rate characteristics tend to deteriorate.

In the present invention, it is preferable to use a method of forming a polymer by filling the voids of the separator with the monomer containing the raw material of the polymer in the electrolyte and then polymerizing the monomer.

As a method for polymerizing these monomers, for example, a method using heat, ultraviolet rays, electron beams and the like can be mentioned. In the present invention, from the viewpoint of easiness in production, heating or ultraviolet ray irradiation is used. It is preferred to polymerize the monomers. In the case of thermal polymerization,
In order to allow the polymerization reaction to proceed effectively, a heat-sensitive polymerization initiator may be added to the impregnated electrolyte. Examples of usable thermal polymerization initiators include azo compounds such as azobisisobutyronitrile and dimethyl 2,2′-azobisinbutyrate, benzoyl peroxide, cumene hydroperoxide, t-butylperoxy-2-ethylhexano. Peroxides such as ates can be used, and those preferable in terms of reactivity, polarity, safety, etc. may be used alone or in combination. In order to obtain the polymer,
Of all the functional groups of the monomer, usually 30% or more is reacted, preferably 40% or more, 50%
It is more preferable to react the above.

(3) Structure of Battery FIG. 3 is a perspective view schematically showing the structure of a battery element used in a lithium secondary battery as an embodiment of the present invention, and FIGS. 4 (a) and 4 (b). [Fig. 4] is a perspective view schematically showing the structure of the lithium secondary battery of the present embodiment, Fig. 4 (a) is an exploded view of the battery, and Fig. 4 (b) is an assembled view of the battery. For example, in FIG.
As shown in FIGS. 4 (a) and 4 (b), a battery (lithium secondary battery) 10 to which the present invention is applied has a battery element 1 ′ formed from the above-described basic battery element 1 with one or more exteriors. It is configured by being housed in a predetermined exterior case 6 composed of members 6a and 6b. In addition, the positive electrode 2 included in the battery element 1 '
The lead 5 is connected to each of the tabs 2 ′ and 3 ′ of the negative electrode 3 and the lead 5 is taken out of the outer case 6, and the edge of the outer case 6 is sealed so that the outer case 6 is It is sealed.

The main form of the battery element 1'is as follows.
As shown in FIG. 4 (a), a stacked type in which a plurality of basic battery elements 1 formed in a flat plate shape are stacked, or as shown in FIGS. 5 (a) and 5 (b), a long basic battery element 1 is formed. A winding type can be mentioned. In addition, FIG.
(B) is a diagram schematically showing the configuration of a battery element 1'used in a lithium secondary battery as an embodiment of the present invention. As the winding type, as shown in FIG. 5B, a cylindrical winding type obtained by winding a long basic battery element 1 into a cylindrical shape as shown in FIG. An example is a flat-plate winding die wound into a flat plate.

When the battery element 1'has a laminated form,
The lower limit of the number of stacked basic battery elements 1 is usually 5 layers or more, preferably 8 layers or more, more preferably 10 layers or more, and the upper limit is usually 50 layers or less, preferably 30 layers.
It is not more than 25 layers, more preferably not more than 25 layers. When the number of layers is small, the overall capacity of the battery decreases, while
If the number of layers is too large, it becomes difficult to reduce the size and weight of the battery.

On the other hand, when the battery element 1'takes a winding type, the number of windings of the basic battery element 1 is usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 2 or more.
It is 0 or less, preferably 15 or less, and more preferably 10 or less. If the number of windings is small, the overall capacity of the battery is small, while if the number of windings is too large, it is difficult to reduce the size and weight of the battery.

The positive electrode 2 and the negative electrode 3 of each basic battery element 1
The area of the separator 4 inserted between the electrodes 2 and 3 is
From the viewpoint of ensuring safety to prevent a short circuit between them, it is preferable to make the area larger than the area of either or both of the positive electrode 2 and the negative electrode 3. The area ratio in this case is not particularly limited, but from the viewpoint of battery miniaturization and the thermal contraction of the separator, the area of the separator 4 is preferably 125% or less of the area of the positive electrode 2 or the negative electrode 3, 123 % Or less, more preferably 120% or less.
Most preferably, it is set to be not more than%. The “area of the separator” means the area of the separator 4 on the contact surface between the separator 4 and the positive electrode 2 or the negative electrode 3, and the “area of the positive electrode or the negative electrode” means the area of the positive electrode 2 or the negative electrode 3 on the contact surface. The area.

Even if the area of the separator 4 is larger than the area of the positive electrode 2 or the negative electrode 3, the separator 4 contracts due to the heat applied to the battery element 1 ′, and as a result, a short circuit easily occurs. Therefore, the greater the heat shrinkage rate of the separator 4, the larger the area of the separator 4 needs to be. In other words, the separator 4 having a small heat shrinkage rate.
The area can be made smaller, and as a result, the battery can be made smaller and lighter.

When the battery element 1'has a laminated type, one lead 5 is usually provided for each of the positive and negative electrodes of a plurality of basic battery elements, and the lead 5 is wound by the battery element 1 '. In the case of the circular type, one is connected to each of the positive electrode and the negative electrode of the basic battery element.

The lead material is not particularly limited as long as it is a material having conductivity and mechanical strength, but a metal is preferable, and an annealed metal excellent in strength and bending durability is particularly preferable. As the type of metal, aluminum,
Copper, nickel, SUS, etc. are mentioned. Particularly, in the case of a lithium secondary battery described later, aluminum is a preferred material for the positive electrode lead, and copper is a preferred material for the negative electrode lead. These metals may be used alone or an alloy containing a plurality of kinds of metals and other components may be used. Also, a plurality of layers formed of such a single metal or alloy may be laminated.

The shape of the lead is not particularly limited, but it is preferably formed in a flat plate shape or a substantially flat plate shape from the viewpoint of ensuring a sufficient allowable current and mechanical strength while miniaturizing the battery. The cross-sectional area and width of the portion taken out from the outer case will be described later.

On the other hand, the outer case 6 for housing the above-mentioned battery element 1'is not particularly limited, but a flexible outer case is preferable. Here, the flexible outer case means a shape-variable case having flexibility and flexibility. By accommodating the battery element 1'in such a flexible outer case 6 and sealing it in a decompressed state, the adhesion between the basic battery elements 1 and between the battery element 1'and the outer case 6 is improved. The battery 10 can be made smaller and lighter.

Specific examples of the flexible outer case include a bag made of a polymer film such as a vinyl bag, a vacuum packaging bag or a vacuum pack made of a polymer film,
A vacuum packaging bag or vacuum pack made of a laminated material of metal foil and polymer film, a can formed of plastic, sandwiched between plastic plates, welded and bonded around the periphery,
An example is a case fixed by fitting. Among these, from the viewpoint of air tightness and shape changeability, a vacuum packaging bag or vacuum pack made of a polymer film, or a vacuum packaging bag or vacuum pack made of a laminate material of a metal foil and a resin (polymer film). Is preferred.

Examples of the material of the outer case include plastics, polymer films, metal films, rubbers, thin metal plates, and laminated films having a gas barrier layer and a resin layer. Particularly preferred is a gas barrier layer. A laminated film having resin layers on both sides. If a laminate film is used as an outer case for a battery element, the effect of reducing the weight and size of the battery can be achieved, but in general, the mechanical strength such as rigidity is inferior to that of metal, etc. There is also a problem that the sealed portion of the outer case is easily peeled off due to an impact or the like. Therefore, sufficient sealing of the outer case is required, and the effect obtained by applying the present invention is great.

Here, an example of the constitution of the laminate film used for the outer case of the battery of the present invention is shown in FIG.
An explanation will be given using (c). As shown in FIG. 6A, as the laminate film 60, a gas barrier layer 61 having an inner protective layer 62 laminated on one surface thereof can be used.

The gas barrier layer 61 is for preventing the infiltration of moisture or maintaining the shape retention property.
A single metal such as iron, copper, nickel, titanium, molybdenum, or gold, an alloy such as stainless steel or hastelloy, or a metal oxide such as aluminum oxide can be used. In particular,
Aluminum, which is excellent in workability, is preferable. The gas barrier layer 61 can be formed using a metal foil, a metal vapor deposition film, a metal sputter, or the like.

The inner protective layer 62 is formed on the surface of the gas barrier layer 61 (FIG. 6 (a)-
It is provided on the lower surface in (c)) and enables the outer case to be sealed by heat sealing, protects the gas barrier layer 61 from external impact and erosion by the electrolyte, and protects the gas barrier layer 61 and the battery element. It is used to prevent contact with 1'and the like. As the inner protective layer 62, for example, a chemically resistant synthetic resin capable of sealing by heat sealing, such as polyethylene, polypropylene, modified polyolefin, ionomer, or ethylene-vinyl acetate copolymer, can be used. Among them, when a polymer or copolymer such as ethylene or propylene is used, there is a relatively high possibility that defective sealing or insufficient sealing will occur, and therefore the effect obtained by applying the present invention is also high. large.

Further, as shown in FIG. 6B, in addition to the gas barrier layer 61 and the inner protective layer 62, the other surface of the gas barrier layer 61 which is the outer side when the outer case is sealed (see FIG. 6).
The outer protective layer 6 is formed on the upper surface in (a) to (c).
It is also possible to use a laminated film 60 ′ which is further provided with 2 ′ and configured as a three-layer structure. This outer protective layer 6
2'is for protecting the gas barrier layer 61 from external impact and erosion, and like the inner protective layer 62, various synthetic resins can be used. Among them, polyethylene, polypropylene, modified polyolefin Resins having excellent chemical resistance and mechanical strength, such as ionomers, amorphous polyolefins, polyethylene terephthalate, and polyamides are desirable.

Further, as shown in FIG. 6 (c), a laminated film 60 "having adhesive layers 63 and 63 'provided between the gas barrier layer 61 and the inner protective layer 62 and the outer protective layer 62' is formed. As described above, in the present invention, it is preferable to use a laminated film having resin layers provided on both sides of the gas barrier layer, and therefore, the embodiments shown in FIGS. This is an example of a preferable one.

The thickness of the inner protective layer 62 is usually 100 μm.
m or less. If it exceeds this range, the sealing at the time of heat sealing may be insufficient. In addition, the heat sealing time required for reliable sealing becomes long, which may lead to a decrease in productivity. The film thickness is preferably 80 μm or less in view of the balance between the sealing and the mechanical strength of the outer case, and more preferably 50 μm or less in order to make the sealing stronger. However, if it is too thin, the mechanical strength is insufficient, so the film thickness is usually 10 μm or more.

The film thickness of the adhesive layers 63 and 63 'is usually 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less, while normally 0.001 μm or more,
Preferably 0.01 μm or more, more preferably 0.1 μm
It is m or more. If the film thickness is larger than this range, the outer case 6 may be insufficiently sealed or may be poorly sealed, whereas if the film thickness is smaller than this range, the gas barrier layer 61 and Adhesion between the inner protective layer 62 and the outer protective layer 62 ′ may be insufficient.

In the present invention, when a laminated film having resin layers on both sides of a gas barrier layer is used as the shape-variable case, the resin layer existing on the side enclosing the battery element has a film thickness of 100 μm. The following is preferable. If it exceeds this range, the sealing at the time of heat sealing may be insufficient. In addition, the heat sealing time required for reliable sealing becomes long, which may lead to a decrease in productivity. The film thickness is particularly preferably 80 μm or less in view of the balance between the sealing of the outer case and the mechanical strength, and most preferably 50 μm or less in order to make the sealing stronger. However, if it is too thin, the mechanical strength is insufficient, so the film thickness is usually 10 μm or more. A laminated film having resin layers provided on both sides of the gas barrier layer is shown in FIG.
In the case of having the form as in (c), the “film thickness of the resin layer existing on the side enclosing the battery element” means the adhesive layer 63.
And the inner protective layer 62.

The outer case 6 is molded using the above materials. The outer case 6 is formed by various methods such as vacuum forming, pressure forming, press forming, or the like of the sheet-shaped body of the above-mentioned material, or injection molding using the above-mentioned material directly. You can

The shape of the outer case 6 is not particularly limited, and various shapes can be used. 4 (a),
In FIG. 7B, the exterior case 6 configured by the exterior member 6a provided with the accommodating portion of the battery element 1 ′ formed of the concave portion and the flat exterior member 6b is shown as an example. As shown in (a), it may be configured to include a plurality of exterior members 6'a and 6'b, both of which are provided with a housing for the battery element 1 '. The housing portion of the battery element 1'can be formed by drawing or the like. Alternatively, as shown in FIG. 7B, a single exterior member 6 may be used. Of course, these other configurations can be adopted.

Further, even if a dedicated member having a shape for accommodating the battery element 1'is not used, as shown in FIG.
As shown in (b) respectively, it is also possible to sufficiently form the outer case 6 of the present invention by using one or two or more film-shaped shape-variable laminated films 6f by laminating them together.

As described above, the battery element 1 ′ is sealed in the outer case 6 in a reduced pressure state.
0 is preferable in terms of downsizing of the whole and improvement of adhesion between the basic battery element 1 and the outer case 6. In this case, when the flexible outer case 6 is used as described above, the difference between the pressure inside the outer case 6 and the atmospheric pressure becomes the force for pressing the battery element 1 ′ through the outer case 6. Above all, a laminate film 6 in which both sides of the gas barrier layer 61 are covered with an inner protective layer 62 and an outer protective layer 62 ′ made of a resin
0 ', and between the gas barrier layer 61 and the inner protective layer 62 and the outer protective layer 62', adhesive layers 63 and 63 ', respectively.
From the viewpoint of achieving downsizing and weight reduction of the battery 10, it is preferable to use a case made of the laminated film 60 ″ provided with the above as the outer case 6 and to hermetically house the battery element 1 ′ therein under a reduced pressure. preferable.

After sealing the peripheral portion of the outer case 6 and hermetically sealing the battery element 1 ′ under reduced pressure, the sealed peripheral portion of the outer case 6 is shaped according to the entire shape of the battery, if necessary. Battery is created. The external shape of the final battery 10 includes the shape of the outer case 6 used and the sealing shape,
Depending on whether or not the peripheral portion of the outer case 6 after sealing is shaped,
There are various shapes.

Specifically, for example, when the battery element 1'is a laminated type and the exterior member is attached so that the battery element 1'is inserted from above and below the substantially flat plate shape of the battery element 1 ',
The shape is not limited to the shape in which the sealing portion of the outer case 6 is left extended as shown in FIG. 4B, and is not limited to the side from which the lead 5 is taken out in the peripheral portion of the outer case 6 after sealing. 9A can be shaped into a shape that is folded back only once as shown in FIG. 9A or a shape that is folded back twice as shown in FIG. 9B. Further, as shown in FIG. 9C, the battery element 1 ′ is folded back from one side of the battery element 1 ′ having a substantially flat plate shape so as to wrap the battery element 1 ′ with a single exterior member, and the battery element 1 ′ has a substantially flat plate shape. It is also possible to seal the exterior member on the side opposite to.

Also, in the case where the battery element 1'is a wound type, as shown in FIG. 10 (a), the outer casing 6 may have a shape in which the sealing portion is left extended, and FIG. The sealing portion of the outer case 6 may be shaped as shown in FIG.

When the lead 5 is inserted and the outer case 6 is sealed, as shown in FIGS. 11A and 11B, between the surface of the lead 5 and the inner surface of the outer case 6. For the purpose of strengthening the sealing of the outer case 6, it is preferable to interpose the sealing material 9. Here, FIGS. 11A and 11B
11 is a diagram schematically showing the structure of a portion from which the lead of the lithium secondary battery according to the present invention is taken out.
11A is a side sectional view of the battery, and FIG. 11B is FIG. 11A.
FIG. 4 is a partial cross-sectional view of the cross section of the battery indicated by the dotted line in FIG.

Note that FIG. 11B shows the case where the outer case 6 has the three-layer structure of FIG. 6B. Further, in FIG. 11B, the inner protective layer 62 of the outer case 6 is
The bonding surface between them is shown by a dotted line. Actually, when the outer case 6 is sealed, the inner protective layers 62 are adhered to each other and the boundary cannot be confirmed. However, it is judged that the boundary line is helpful for understanding. Therefore, in FIG. 11B, the dotted line is shown for convenience.

As the sealing material 9, a thermoplastic resin is usually used so that the space between the surface of the lead 5 and the inner surface of the outer case 6 can be filled at the time of sealing. The thermoplastic resin is preferably a material that softens at 150 ° C. or higher and 250 ° C. or lower. A material that softens at a temperature lower than 150 ° C. may cause a problem in practical use of the battery. on the other hand,
A material that does not soften unless it is 250 ° C. or higher may be sealed at a considerably high temperature when sealing by heat sealing, so that the battery element may be damaged and the battery performance may be deteriorated. As the thermoplastic resin, usually,
Acid-modified polyolefin is used. The acid-modified polyolefin is preferably acid-modified polyethylene or acid-modified polypropylene, and particularly preferably carboxylic acid-modified polyethylene or carboxylic acid-modified polypropylene.

For convenience of mounting the battery, etc., the battery element 1'is enclosed in the flexible outer case 6 as described above, and molded into a preferable shape to prepare the battery 10,
If necessary, one or more of these batteries 10 may be used.
It can also be stored in a rigid outer case.

(4) Relationship between Lead Width and Battery Side Length The battery of the present invention has a lead (FIGS. 3 to 5 and FIGS. 7 to 1).
The outer case (see FIG. 4) is taken out.
(B), FIGS. 9 (a) to 9 (c), FIGS. 10 (a) and 10 (b), and reference numeral 6 in FIG. 11 (a)), and the total value X of the widths of the leads 5 to be taken out The ratio X / Y to the length Y of the side of the outer case 6 from which the lead 5 is taken out is
It is 0.4 or less, and the length Y of the side of the outer case 6 from which the lead 5 is taken out is 20 mm or less,
It is one of the features.

Here, "the side of the outer case 6 from which the lead 5 is taken out" means the lead out of the sealed outer edges of the outer case 6 when the outer case 6 is sealed with the lead 5 taken out. A portion where 5 is present and has a substantially line segment shape. The length Y of the “side of the outer case 6 from which the lead 5 is taken out” based on this definition
Is different depending on the form of the battery element, the connection form of the leads, the shape of the outer case and the battery, etc., various measurement methods are possible, but in order to ensure the clarity of the definition, the measurement of X and Y , Will be explained in more detail below.

First, when the battery element is a laminated type, the battery is often a flat plate having a substantially polygonal (mostly substantially rectangular) planar shape as a whole. Among the sides of the substantially polygonal shape having the planar shape, the side where the lead 5 is present in a state where the outer case 6 is sealed is referred to as "the outer case 6 from which the lead 5 is taken out.
And the length is Y. Even if the planar shape of the battery is not substantially polygonal, when the entire battery is formed in a flat plate shape, the planar shape is approximated to a polygonal shape so that the outer case 6 is sealed and the leads 5 are sealed. It is possible to determine the edge on which exists.

For example, FIG. 4B and FIGS. 9A to 9C.
Each of the batteries 10 shown in FIG. 1 has a substantially rectangular planar shape, and the leads 5 are taken out from one short side located on the front side of the drawing. Therefore, the length of the short side on the front side of the drawing may be measured and set as Y.

When the battery element is a wound type,
The entire shape of the battery is often a substantially flat plate or a substantially columnar shape. When the overall shape of the battery is a substantially flat plate shape, since the planar shape of the battery is generally a polygonal shape, as in the case where the battery element is a laminated type, among the sides of the substantially polygonal shape that is a planar shape The side where the lead 5 exists in the state where the outer case 6 is sealed is referred to as “the side of the outer case 6 from which the lead 5 is taken out”, and this length is Y. Even if the planar shape of the battery is not substantially polygonal, when the entire battery is formed in a flat plate shape, the planar shape may be approximated as a polygonal shape as in the case where the battery element is a stack type.

On the other hand, when the battery has a generally cylindrical shape as a whole, each lead 5 is taken out from a line segment corresponding to one diameter of the substantially circular side surface in one of the substantially circular side surfaces of the substantially cylindrical shape. At the same time, the outer case 6 is generally sealed on this line segment. Therefore, the line segment from which the lead 5 is taken out is defined as "the side of the outer case 6 from which the lead 5 is taken out", and this length is designated as Y.

For example, the battery 10 shown in FIGS. 10 (a) and 10 (b) has an overall cylindrical shape, and the lead 5 corresponds to one diameter of one substantially circular side surface located on the front side of the drawing. It is taken out from above the line segment. Therefore, it is sufficient to measure the length of one diameter of the circular side surface on the front side of this figure and set it as Y.

When the "side of the outer case 6 from which the lead 5 is taken out" is defined as described above, the length of the cross-sectional shape of the lead 5 on this side in the direction parallel to this side is defined as "lead 5". The width in the direction perpendicular to this side is referred to as the “thickness (thickness) of the lead 5”. Since the lead 5 is usually a long flat plate, its cross-sectional shape is flat and substantially rectangular. Then, generally, in the sealed portion of the outer case 6, the lead 5 is taken out from the outer case 6 in such a direction that the long side of the substantially rectangular cross-section is in contact with the surface of the outer case 6. Therefore, in many cases, the length of the long side of the substantially rectangular cross-sectional shape of the lead 5 is the "width of the lead 5," and the length of the short side is the "thickness (thickness) of the lead 5."

The number of leads 5 taken out from one side of the outer case 6 may be one or plural. For example, FIG. 4, FIGS. 9A to 9C and FIG.
In the example of the battery 10 shown in (a) and (b),
Two leads 5 respectively connected to the positive electrode and the negative electrode
Are taken out from the same side (front side in the figure) of the outer case 6, but the positive and negative leads 5 may be taken out from different sides of the outer case 6, and in this case, each side of the outer case 6 is taken out. Only one lead 5 can be taken out from the.

When a plurality of leads 5 are taken out from one side of the outer case 6, the widths of the leads 5 are obtained for each of the leads 5, and these are summed up. Of the total value X ”. For example, in FIG.
In the example of the battery 10 shown in FIGS. 9A to 9C and FIGS. 10A and 10B, the widths X1 and X of the leads 5 are provided.
2 is obtained, and the sum X1 + X2 of these values becomes the total value X of the width of the lead 5. On the other hand, when there is only one lead 5 taken out from one side of the outer case 6, the width of the lead 5 is directly set as the “total value X of the width of the lead 5”.

Regarding the total value X of the widths of the leads 5 taken out from the sides of the outer case 6 and the length Y of the sides of the outer case 6 taken out of the leads 5 defined as described above, Calculate the ratio X / Y. In the present invention, in order to ensure the sealing of the outer case 6, this ratio X /
The value of Y is usually 0.4 or less. Further, in order to secure the balance between the sealing of the outer case 6 and the mechanical strength of the leads 5, it is preferable that the value of this ratio X / Y is 0.3 or less, and the outer case 6 is more firmly bonded. Therefore, it is more preferable to set it to 0.2 or less. However, if the value of the ratio X / Y is made too small, the mechanical strength of the lead 5 becomes insufficient, so that the value of X / Y is usually 0.
1 or more.

If the thickness of the lead 5 is too thick, the outer case 6 will not be sufficiently sealed, so that the thickness is usually 100 μm or less. Further, from the viewpoint of ensuring both the sealing of the outer case 6 and the sufficient allowable current of the leads 5, 90 μm or less is preferable. However, if the thickness of the lead 5 is too thin, the strength becomes insufficient, and the above-mentioned sufficient allowable current cannot be ensured, so that it is usually 5 μm or more.

The length Y of the side of the outer case 6 from which the lead 5 is taken out is usually 20 mm or less. In the case of a small battery having a Y value of 20 mm or less, there is a high possibility that defective sealing or insufficient sealing will occur when the outer case 6 is sealed,
As a result, the effect obtained when the present invention is applied is increased. Above all, from the viewpoint of further downsizing the battery,
It is preferably 15 mm or less, and more preferably 10 mm or less. Furthermore, from the viewpoint of use in small-sized equipment such as eyeglass-type electric equipment (battery is stored in a frame), the thickness is particularly preferably 5 mm or less. But,
If the value of Y is made extremely small, it becomes extremely difficult to seal the outer case 6 with the lead 5 taken out.
The value of is usually 2 mm or more.

Further, in the present invention, the distance Z from the outer edge on the end point side of the lead 5 closest to each end point of the side of the outer case 6 from which the lead 5 is taken out to the end point of the side.
(For example, FIG. 4, FIG. 9 (a)-(c), and FIG.
In (a) and (b), it is preferable that the value of the ratio Z / Y of the distance Z to the length Y of the side be within a certain range when the distance Z is measured. .
The Z / Y ratio is usually 0.025 or more, preferably 0.05.
Or more, and usually 0.25 or less, preferably 0.
It is 2 or less. When the Z / Y ratio is smaller than the above range,
Water may penetrate due to insufficient sealing, or the exterior member may peel off due to insufficient mechanical strength at the battery end. On the other hand, if the Z / Y ratio is larger than the above range, it may be difficult to reduce the size of the battery.

(5) Lead Allowable Current In the battery of the present invention, the lead has a discharge current value when the battery is discharged at a rate of 1 hour or a charging current value when the battery is charged at a rate of 1 hour. It is characterized by having at least a cross-sectional area capable of ensuring a corresponding allowable current.

Here, the "discharge current value when the battery is discharged for one hour rate or the charge current value when the battery is charged for one hour rate" is a value corresponding to the battery capacity of the battery. For example, if the battery capacity is 800 mAh,
The above current value is 800 mA. In the following description, this “discharge current value when the battery is discharged for 1 hour rate or the charging current value when the battery is charged for 1 hour rate” is referred to as a unit of “1C”. In other words, the lead used in the battery of the present invention has a cross-sectional area capable of ensuring an allowable current equivalent to at least 5C.

Here, the lead has "at least a cross-sectional area capable of ensuring an allowable current equivalent to 5C" means 5C.
Even if the current of the above is continuously applied to the leads, the cross-sectional area that is equal to or larger than the cross-sectional area at which the sealing part on the side where the leads of the outer case are taken out will not be melted by heat or the leads themselves will be fused
Refers to what the lead has.

At present, the performance of the lithium secondary battery is being improved, and in most cases, the lithium secondary battery is discharged at a current of 1 C or less when used. However, old Nicad batteries, nickel-hydrogen batteries, etc. are generally subjected to rapid discharge with a larger current when used, and accordingly, it is possible to discharge with a larger current. Is designed to. For example, a nickel-cadmium battery is generally designed to sufficiently withstand discharge at a current value of 5C. The lithium secondary battery is expected to be used for small devices such as small electric devices and toys that require discharging with a large current as future applications, in addition to communication devices, which are currently the main applications.
Therefore, it is necessary to design the lithium secondary battery to withstand a charge / discharge current of at least 5C in the future. Further, a lead having a cross-sectional area capable of ensuring a permissible current smaller than 5 C also has a problem in that the mechanical strength of the lead is generally insufficient and handling becomes difficult as a result of the cross-sectional area becoming small.

At least the allowable current of the lead to be secured is usually 5 when the above "1C" is used as a reference.
Although it is C, 10 C is preferable, and 15 C is more preferable in order to make it a design capable of withstanding rapid charge and discharge of the battery. 20C is particularly preferable in that the battery can be used in a small power tool with a margin.

However, if the allowable current of the lead is too large, the cross-sectional area of the lead becomes large accordingly and the sealing of the lead may be insufficient. Therefore, as described above, the total width of the lead 5 is The ratio X / Y between the value X and the length Y of the side of the outer case from which these leads 5 are taken out is 0.
It is necessary to set the cross-sectional area of the lead within the range of 4 or less.

Since the cross-sectional area of such a lead depends on the capacity of the battery, the material and width of the lead, the ambient temperature, the kind of the heat-sealing resin of the aluminum laminate used for the outer case, etc., it is an accurate value. However, since the present invention is intended to prevent melting of the outer case and fusing of the leads, it is sufficient to calculate an approximate value that does not deviate from this meaning. Although the approximate value of the cross-sectional area of such a lead can be measured by various methods,
In the present invention, the measurement is performed according to the following procedure.

In the following, description will be given separately for the case where the lead material is (a) only copper and (b) other cases. In addition,
(B) In other cases, in addition to the case where the material of the lead is a single metal other than copper, the case where the material of the lead is an alloy, the case where the material of the single metal is mixed with another material, and The case where the leads are configured as a plurality of layers made of different materials (for example, the case where the metal material is subjected to the surface treatment) is widely included.

(A) When the Lead Material is Only Copper When the lead material is only copper, the allowable current is calculated by the following method according to the cross-sectional area of the lead.

(A-1) The lead cross-sectional area is 0.105.
In the case of mm ² or less, it is calculated based on the relationship between the cross-sectional area of the conductor (copper) and the allowable current in Table 1 below.

[Table 1] * "Build-up multilayer printed wiring board technology" (Author: Kiyoshi Takagi, Publisher: Nikkan Kogyo Shimbun, June 20, 2000)
Excerpt from Table 4.2 on page 40, partially revised.

In the original text, Table 1 above shows the measurement results of the permissible current in the environment of the temperature rise of 20 ° C. for the copper foils having the different widths and the thickness of 35 μm. From the results in Table 1 above, there is a correlation between the cross-sectional area of the copper foil and the measured value of the allowable current. Therefore, in the present invention, when the cross-sectional area of the lead is 0.105 mm ² or less, the above Table 1
The allowable current of the lead is obtained based on the correlation shown in.

(A-2) The lead cross-sectional area is 0.785.
allowable current of the case mm ² or more of the cross-sectional area of the case leads of 0.785mm ² or more, "Fundamentals of electrical and electronic" (written and edited by: Takahiro Miyata, publishing office: Science Book Publishing Corporation and Gijutsuhyoronsha ，
Use the data in "Table 2.1 Allowable current of insulated wire" on page 56 of May 5, 2001, 1st edition, 1st printing). That is, the data showing the relationship between the diameter of the copper wire and the permissible current shown in the above "Table 2.1" and the copper wire shown in the above "Table 2.1" have a substantially circular cross-sectional shape. That is, the cross-sectional area of the copper wire is obtained from the diameter of the copper wire, and this cross-sectional area and the allowable current value are used. However, the relationship between the copper wire diameter and the permissible current in "Table 2.1" above is, for example, "when the copper wire diameter is 1.0 mm or more and less than 1.2 mm, the permissible current is 16 A". Since the diameter of the copper wire has a certain width with respect to the value of the permissible current, the cross-sectional area of the copper wire is 1.0 mm, which is the smallest of the above widths. The calculated value was obtained.

The relationship between the cross-sectional area of the copper wire and the fusing current obtained as described above is shown in Table 2 below.

[Table 2] * "Basics of Electricity and Electronics" (Edited by Takahiro Miyata, Publisher:
Scientific Book Publishing Co., Ltd. and Technical Review Co., Ltd., published May 5, 2001, 1st edition, 1st edition) Excerpts from "Table 2.1 Insulated wire allowable current" on page 56

From the results in Table 2 above, there is still a correlation between the cross-sectional area of the copper wire and the measured value of the permissible current.
Therefore, in the present invention, the lead has a cross-sectional area of 0.785 m.
When it is m ² or more, the allowable current of the lead is determined based on the correlation shown in Table 2 above.

(A-3) The lead cross-sectional area is 0.105.
In the case of ˜0.785 mm ² , linear approximation is performed by the following formula 1 based on the data on the copper foil having the maximum cross-sectional area in Table 1 and the data on the copper wire having the minimum cross-sectional area in Table 2. Allowable current of lead [A] = Cross sectional area of lead [mm ² ] * 13.668 + 5.2648. ． ． Formula 1

The graph of FIG. 12 shows the correlation between the cross-sectional area of the lead and the allowable current when the material is only copper, which is determined according to the above (a-1) to (a-3). In other words, when the material of the lead is only copper, the allowable current of the lead can be estimated from the cross-sectional area of the lead based on the graph shown in FIG.

(B) When the material of the lead is other than copper The allowable current when the material of the lead is other than copper is determined as follows. First, the permissible current of the lead in the case where the material has the same cross-sectional area and only copper is calculated based on the criterion (a). Next, in view of the fact that the allowable current of a conductor is generally proportional to the square root of conductivity, calculate the square root of the ratio of the conductivity of the target material and the conductivity of copper for the case where the material is copper only. Multiply the permissible current obtained to obtain the permissible current according to the lead material.

Regarding the numerical values of the electric conductivity of various conductive materials, in the present invention, "Basics of Electricity and Electronics" (edited by Takahiro Miyata, Publisher: Kagaku Tosho Publishing Co., Ltd. and Technical Review Co., Ltd., 2001) 1st edition, 1st edition) issued on May 5th. According to Table 1.3 on page 24 of this document, for example, when the conductivity of standard annealed copper is 100%, the conductivity of aluminum is 64.1% and the conductivity of nickel is 25.2%. Therefore, the square root of the ratio between the conductivity of these materials and the conductivity of copper is 0.8 for aluminum and 0.5 for nickel. Therefore, by multiplying these values by the permissible current of the lead when the material has the same cross-sectional area and only copper, the permissible current when the material of the lead is aluminum or nickel is obtained.

Table 3 below shows a partial excerpt of Table 1.3 described on page 24 of the above document.

[Table 3]

The material of the lead may be a metal not listed in Table 3 above, an alloy containing a plurality of kinds of metals, a material obtained by mixing other materials with the metal, or a plurality of materials such as surface-treated leads. When the material is used, the resistivity of each material is first measured. Then, the resistivity of the standard annealed copper in Table 3 above is divided by the resistivity of each of the above materials, and the square root thereof may be multiplied by the permissible current when the material is copper only with the same cross-sectional area.

As described above, based on the criteria described in (a-1) to (a-3) and (b), the allowable current of the lead can be estimated from the cross-sectional area of the lead, and conversely the desired allowable current can be secured. It is possible to calculate the cross-sectional area of For example, when the capacity of the battery is 800 mAh and the material of the lead is copper, the cross-sectional area capable of ensuring an allowable current equivalent to 5 C (4000 mA) is 0.0525 mm ² .

The battery capacity can be measured, for example, by using the following charging / discharging procedure. First,
0.5C to 4.2V against uncharged battery
Constant current charging is performed at (2 hour rate), and the current value is C
Perform constant voltage charging at 4.2V until it reaches / 20,
This is a rechargeable battery. Then charge this rechargeable battery to 0.2
The battery was discharged until the current value of C (5 hour rate) reached 2.7 V, and the discharge capacity obtained during this discharge was measured and used as the battery capacity.

In the present invention, in order to avoid the influence of the fluctuation of the battery capacity due to the charging / discharging of the battery and to ensure the accuracy of the measured battery capacity, the above-mentioned charging / discharging procedure is used.
Specifically, the battery capacity value is measured according to the following method. First, the estimated battery capacity value P is calculated based on the weight of the positive electrode active material of the battery. Page 2 of "Lithium-ion Secondary Battery-Materials and Applications-" (Edited by Masayuki Yoshio, Akiya Ozawa, Publisher: Nikkan Kogyo Shimbun, January 27, 2000, 2nd edition, 1st edition) , The theoretical capacity of the positive electrode active material of the lithium-ion secondary battery is shown. From here, the battery capacity per unit weight of the positive electrode active material is 137 mAh / g when the positive electrode active material is LiCoO ₂ , and LiN
It can be seen that it is about 193 mAh / g in the case of iO ₂ and about 148 mAh / g in the case of LiMn ₂ O ₄ . Although these values actually vary somewhat depending on the raw material purity, manufacturing method, battery assembly method, charge / discharge conditions, etc., based on these values,
It is possible to estimate the battery capacity from the weight of the positive electrode active material of the battery.

Next, using the calculated estimated battery capacity value P as a reference, a constant current constant voltage charge of 0.5 C and a constant current discharge of 0.2 C are performed in accordance with the above-mentioned charging / discharging procedure. The discharge capacity is measured, and this is used as an approximate battery capacity value Q. Then, 0.5 C constant-current constant-voltage charging and 0.2 C constant-current discharging were performed once again in accordance with the above-mentioned charging / discharging procedure with the rough battery capacity value Q as a reference, and the discharge capacity obtained during this discharging was measured. do it,
This is determined as the value of the battery capacity. The procedure for measuring the battery capacity described above is performed in an environment of a temperature of 25 ° C. and a humidity of 50%.

For example, if the positive electrode active material contained in the battery is Li
If it is CoO ₂ and contains 2 g by weight, the estimated battery capacity value P is 2 * 137 = 274 mAh. As the 0.5C charge for the first time, 4.2V and 137 mA constant current / constant voltage charge is performed. The final current is 274/20 = 1
It is 3.7 mA. Next, 0.2 C constant current discharge (27
4/5 = 54.8 mA) is performed up to the final voltage of 2.7 V, and the discharge capacity obtained at this time is set to the approximate battery capacity value Q. If this value is 270 mAh, then 4.2
V is charged again at a constant current of 135 mA and a constant voltage of 0.5 mA. Final current is 270/20 = 13.5mA
And Then, a constant current discharge of 0.2 C (270/5 =
54 mA) to a final voltage of 2.7 V, and the discharge capacity obtained at this time is determined as the battery capacity.

(6) Others As described above, as an example of the lithium secondary battery in which the effect of the application of the present invention is expected to be remarkable, as described above,
Although the present invention has been specifically described, it goes without saying that the present invention is not limited to a lithium secondary battery, and various other structures having a structure in which the above-mentioned lead is taken out from an outer case can be used without departing from the scope of the invention. It can be widely applied to various types of batteries.

The use of the battery according to the present invention is not particularly limited, but it is not limited to laptop computers, mobile computers, mobile phones,
Handy terminal, mobile copy, mobile printer,
Headphone stereo, video movie, LCD TV,
Handy cleaner, portable CD, mini disk, electric shaver, transceiver, electronic organizer, calculator, memory card, portable recorder, radio, backup power supply, motor, lighting equipment, toys, game equipment,
Clocks, strobes, cameras, medical devices (pacemakers,
It can be used as a power source for hearing aids, shoulder massagers, etc.). Further, it is expected to be used as a power source for wireless devices (for example, pen type devices) using protocols such as “bluetooth” in the future.

[0144]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A laminated lithium secondary battery was assembled according to the following steps (a) to (e). There is one lead terminal connected to each of the positive and negative electrodes, and each has a width of 2.5 mm,
The thickness is 80 μm. The planar shape of the battery is substantially rectangular, and the positive and negative lead terminals are taken out from the same side of the battery (one short side of the rectangular shape which is the planar shape of the battery). Length of side of battery from which lead terminal is taken out (equal to length of side of outer case from which lead terminal is taken out. "Battery width"
Call. ) Is 17 mm, and the ratio of the total width X of the lead terminals to the width Y of the battery (hereinafter referred to as “X / Y ratio”) is (2.5
+2.5) /17=0.294. Battery capacity is 9
It was 6.8 mAh. The following steps (c)-
The work of (e) was carried out in an environment with lower humidity than the environment with a dew point of -45 ° C.

(A) Preparation of positive electrode Positive electrode active material LiCoO ₂ 90 parts Conductive material Acetylene black 5 parts Binder polyvinylidene fluoride 5 parts Solvent N-methylpyrrolidone 80 parts The above materials are mixed and stirred, and then coated and dried on one side of an aluminum foil (current collector) having a thickness of 20 μm, and then rolled. By press molding with a press, a positive electrode raw material having a positive electrode active material layer on one surface of the current collector was obtained. This positive electrode raw material was cut into a positive electrode. The basic shape of the positive electrode was a rectangle of 11 × 22 mm, and an aluminum foil was extended outside the short side of the positive electrode to provide a tab of 3 × 3 mm for connecting lead terminals.

(B) Preparation of Negative Electrode Negative Electrode Active Material Graphite 90 parts Binder polyvinylidene fluoride 10 parts Solvent N-methylpyrrolidone 100 parts The above materials were mixed and stirred, and a 10 μm thick copper foil (collector) was prepared.
It was coated and dried, and pressure-molded by a roll press to obtain a negative electrode raw material having a negative electrode active material layer on one surface of the current collector. This negative electrode raw material was cut into a negative electrode. The basic shape of the negative electrode is a 13 × 24 mm square, and a copper foil is extended outside the short side of the negative electrode to form a 3 × 3 mm lead terminal connection.
Tabs are provided.

(C) Preparation of Non-Aqueous Electrolyte before Curing LiPF ₆ 10.5 parts Ethylene carbonate 43.3 parts Propylene carbonate 39.2 parts Polyethylene glycol diacrylate 4.67 parts Polyethylene oxide triacrylate 2.33 parts Polymerization initiator 0.2 parts The above materials are mixed and stirred to obtain non-water before curing. An electrolytic solution (electrolyte) was obtained.

(D) Preparation of Separator A microporous polyethylene film having a thickness of 16 μ is formed in a size of 15 × 26 mm.
Was cut into a rectangular shape to prepare a separator.

(E) Assembly of Battery The positive electrode and the negative electrode obtained in the above-mentioned steps (a) and (b) were dried at 110 ° C. for 30 minutes using a dryer under the environment of dew point of −45 ° C. Dried in. The positive electrode and the negative electrode after drying, and the separator obtained in the step (d) are impregnated with the non-aqueous electrolyte before curing obtained in the step (c), and then each electrode active material sandwiches the separator. The positive electrode and the negative electrode were attached to the separator so as to face each other. Next, heat at 90 ° C for 10 minutes,
A basic battery element was made by curing the acrylate. The basic battery elements were alternately stacked so that the same poles were back to back to prepare a 20-layer laminated battery element. The tabs extending from each positive electrode and each negative electrode of this laminated battery element were collected respectively, and the positive electrode tabs had an aluminum lead terminal with a thickness of 80 μm and a width of 2.5 mm, and the negative electrode tabs had a thickness. Width of 80 μm 2.
5 mm copper lead terminals were each welded. Next, this laminated battery element was housed in an aluminum laminate film (exterior case), and in a state where each lead terminal was extended from one side of the aluminum laminate film, the aluminum laminate film was heat-sealed at 180 ° C. under vacuum ( Sealed). At that time, a thermoplastic resin sheet (acid-modified polyolefin) was interposed between the lead terminal and the inner resin portion of the aluminum laminate for the purpose of strengthening the sealing. Furthermore, by bending the seals on both sides of the battery without lead terminals along the side surface of the battery, a width of 17 mm and a length of 3
A 1 mm laminated lithium secondary battery was produced.

(F) Charge / Discharge Cycle Test A charge / discharge cycle test was performed on the battery manufactured according to the above steps (a) to (e) under an environment of a temperature of 25 ° C. and a humidity of 50%. After charging with a termination current of 4.84 mA using a constant current and constant voltage of 4.2 V and 48.4 mA, 9
The process of discharging to a final voltage of 2.7 V using a constant current of 6.8 mA was set as one charge / discharge cycle, and this charge / discharge cycle was repeated 400 times. This is a cycle test in which charging is 0.5 C and discharging is 1 C. The discharge capacity retention rate of the battery after the completion of 400 charge / discharge cycles (the ratio of the discharge capacity after the completion of 400 charge / discharge cycles to the discharge capacity at the initial cycle) was 82.1%.

Example 2 A wound lithium secondary battery was assembled according to the following steps (a) to (e). There is one lead terminal connected to each of the positive electrode and the negative electrode, and each has a width of 2 mm and a thickness of 30 μm. The three-dimensional shape of the battery is substantially flat, and the positive and negative lead terminals are line segments corresponding to one diameter of the substantially circular side surface on one side of the battery (one substantially circular side surface of the substantially cylindrical shape which is the three-dimensional shape of the battery). The outer case is sealed on the line segment.). Battery width (length of battery side from which lead terminals are taken out, as in Example 1)
Is 12 mm and the X / Y ratio is (2 + 2) /12=0.333.
Became. The battery capacity was 288 mAh. The operations of the following steps (c) to (e) were performed in an environment having a lower humidity than the environment having a dew point of -45 ° C.

(A) Preparation of positive electrode Positive electrode active material LiCoO ₂ 90 parts Conductive material Acetylene black 5 parts Binder polyvinylidene fluoride 5 parts Solvent N-methylpyrrolidone 80 parts The above materials are mixed and stirred, applied and dried on both sides of an aluminum foil having a thickness of 20 μm, and pressure-molded by a roll press. By doing so, a positive electrode raw material having positive electrode active material layers on both surfaces of the current collector was obtained. The basic shape is cut into 8x
A 900 mm strip-shaped positive electrode was produced. An aluminum lead terminal having a width of 2 mm and a thickness of 30 μm was welded to a portion of the short side of the positive electrode corresponding to the final winding, and a short-circuit prevention tape was attached to the welded portion.

(B) Preparation of Negative Electrode Negative Electrode Active Material Graphite 90 parts Binder polyvinylidene fluoride 10 parts Solvent N-methylpyrrolidone 100 parts The above materials are mixed and stirred, and a copper foil (collector) having a thickness of 10 μm is prepared.
Both surfaces were coated and dried, and pressure-molded by a roll press to obtain a negative electrode raw material having negative electrode active material layers on both sides of the current collector. This negative raw material is cut into a basic shape of 9 ×
A 1020 mm strip-shaped negative electrode was prepared. A copper lead terminal having a width of 2 mm and a thickness of 30 μm was welded to a portion of the short side of the negative electrode corresponding to the final winding, and a short-circuit prevention tape was attached to the welded portion.

(C) Preparation of Non-Aqueous Electrolytic Solution Before Curing The same materials as in Example 1 were mixed and stirred to obtain a non-aqueous electrolytic solution (electrolyte) before curing.

(D) Separation of separator A microporous polyethylene film having a thickness of 16 μm was cut into a strip having a width of 10 mm to prepare a separator.

(E) Assembly of Battery The positive electrode and the negative electrode obtained in the above-mentioned steps (a) and (b) were dried at 110 ° C. for 30 minutes using a drier under a dew point of −45 ° C. Dried in. The positive electrode and the negative electrode after drying, and the separator obtained in the step (d) are stacked so that the respective electrode active materials face each other with the separator sandwiched therebetween, wound by a winding machine, and then the winding end portion. Was fixed with tape. The wound body was impregnated with a non-aqueous electrolyte before curing to prepare a battery element. The produced battery element is housed in an aluminum laminate film (exterior case), and in a state where each lead terminal is extended from one side of the aluminum laminate film, the aluminum laminate film is sealed under vacuum. I did. At that time, the same thermoplastic resin sheet as that used in Example 1 was interposed between the lead terminal and the inner resin portion of the aluminum laminate for the purpose of strengthening the sealing. Then, 90 ℃, 1
Curing treatment was performed by heating for 0 minutes. Furthermore, a wound type lithium secondary battery having a width of 12 mm and a length of 52 mm was produced by bending the seal portions on both side surfaces of the battery having no lead terminal along the side surface of the battery.

(F) Charge / Discharge Cycle Test The battery prepared according to the above steps (a) to (e) was
Under the same conditions as in Example 1, a charge / discharge cycle test of 0.5 C charge and 1 C discharge was performed. The discharge capacity retention ratio of the battery after 400 charge / discharge cycles was calculated to be 8
It was 2.9%.

Example 3 The shape of the positive electrode was a strip of 4 × 900 mm, and the shape of the negative electrode was 5 ×.
1020 mm strip, the width of the separator is 6 mm, the width of each lead terminal connected to the positive electrode and the negative electrode is 1 mm,
A wound lithium secondary battery was assembled according to the conditions of Example 2 except that the thickness was set to 80 μm. Battery width is 7mm,
The X / Y ratio was (1 + 1) /7=0.286. The battery capacity was 144 mAh.

The manufactured battery was subjected to a charge / discharge cycle test of 0.5 C charge and 1 C discharge under the same conditions as in Example 1. The discharge capacity retention rate of the battery after 400 charge / discharge cycles was calculated and found to be 82.3%.

Comparative Example 1 The width of each lead terminal connected to the positive electrode and the negative electrode is 5 mm.
A laminated lithium secondary battery was assembled according to the conditions of Example 1 except that. The battery width was 17 mm, and the X / Y ratio was (5 + 5) /17=0.588. Battery capacity is 9
It was 6.8 mAh.

The battery thus produced was subjected to a charge / discharge cycle test of 0.5 C charge and 1 C discharge under the same conditions as in Example 1. The discharge capacity retention rate of the battery after the completion of 400 charge / discharge cycles was 60.5%. Further, when the battery was visually observed after 400 charge / discharge cycles, corrosion was observed near the roots of the lead terminals.

Comparative Example 2 The width of each lead terminal connected to the positive electrode and the negative electrode was 2 m.
A wound-type lithium secondary battery was assembled according to the conditions of Example 2 except that m and thickness were 9 μm. Battery width is 1
2 mm, the X / Y ratio was (5 + 5) /17=0.588. The battery capacity was 288 mAh.

The manufactured battery was subjected to a charge / discharge cycle test of 0.5 C charge and 1 C discharge under the same conditions as in Example 1. The discharge capacity retention rate of the battery after the completion of 400 charge / discharge cycles was 81.3%. However, disconnection of lead terminals often occurred during handling of the manufactured battery.

Estimation of Allowable Current of Lead Terminal With respect to the batteries produced in the above Examples 1 to 3 and Comparative Examples 1 and 2, the allowable current of the lead terminal was estimated.
The allowable current was estimated by the method described above based on Table 12. That is, for the positive electrode lead terminal made of Cu (copper), the allowable current was calculated from the cross-sectional area of the lead terminal with reference to Table 12. The lead terminal material is A
Regarding the negative electrode of l (aluminum), the allowable current when the material is Cu with the same cross-sectional area is calculated with reference to Table 12, and in view that the ratio of the conductivity of Al to Cu is 0.8. The allowable current when the material is Cu is 0.
It was multiplied by 8 and this was taken as the allowable current. Furthermore, Example 1
˜3 and the batteries of Comparative Examples 1 and 2, the ratio between the estimated allowable current of each positive and negative lead terminal and the battery capacity was obtained.

The estimated allowable current of the lead terminals and the ratio of the estimated allowable current to the battery capacity calculated for Examples 1 to 3 and Comparative Examples 1 and 2 are shown below together with the other values in each Example and Comparative Example. It shows in Table 4.

[Table 4]

In the analysis and comparison example 1, the ratio of the total width X of the lead terminals to the side length Y of the battery from which the lead terminals are taken out (X / Y ratio).
However, it did not fall within the value of 0.4 or less, which is a feature of the present invention. As a result, a defective sealing of the outer case occurred on the side of the battery from which the lead terminals were taken out, and water entered the inside of the outer case, resulting in deterioration of the battery performance as seen in a decrease in discharge capacity retention rate, and It is considered that corrosion of the lead root occurred due to the electrolyte flowing out of the outer case.

In Comparative Example 2, the X / Y ratio was within the value of 0.4 or less, and the lead terminals were thin, so that the deterioration of the battery performance due to the defective sealing of the outer case was observed. There wasn't. However, it is considered that the lead terminals were broken due to insufficient strength because the lead terminals were too thin. Further, when the ratio of the estimated allowable current of the lead terminal to the battery capacity is 5 or less and the lead terminal cannot secure the allowable current of 5C of the battery capacity, which is a feature of the present invention, the battery is quickly charged or discharged at a large current. It is thought that it cannot cope with.

On the other hand, in the batteries of Examples 1 to 3,
No deterioration in battery performance due to poor sealing of the outer case was observed, there was no problem in handling, and the estimated allowable current of the lead terminal was a sufficient value. That is, by applying the present invention, even in a small battery having a battery width of 20 mm or less, it is possible to prevent defective encapsulation of the outer case and insufficient encapsulation, and ensure a sufficient allowable current for the leads. Was proved.

[0170]

According to the battery of the present invention, the width of the lead taken out from the side and the length of the side are taken in the side of the outer case from which the lead is taken out while ensuring a constant cross-sectional area of the lead. Since the ratio is configured to fall within a certain range, it is possible to prevent defective sealing or insufficient sealing of the outer case and ensure reliable sealing even in small and lightweight batteries. At the same time, a sufficient permissible current is secured in the leads, and the risk of melting the leads or melting of the outer case is reduced even when a large current flows.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a configuration of a basic battery element used in a lithium secondary battery as an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a configuration of electrodes (positive electrode / negative electrode) used in the lithium secondary battery of the present embodiment.

FIG. 3 is a perspective view schematically showing the configuration of a laminated battery element used in the lithium secondary battery of this embodiment.

4A and 4B are perspective views each schematically showing the structure of the lithium secondary battery of the present embodiment.

5A and 5B are perspective views each schematically showing a configuration of a wound-type battery element used in the lithium secondary battery of the present embodiment.

6 (a), (b) and (c) are cross-sectional views schematically showing the layer structure of an outer case used in the lithium secondary battery of the present embodiment.

7A and 7B are exploded perspective views schematically showing the structure of the lithium secondary battery for explaining the structure of the outer case used in the lithium secondary battery of the present embodiment. It is a figure.

8A and 8B are exploded perspective views schematically showing the structure of the lithium secondary battery in order to explain the structure of the outer case used in the lithium secondary battery of the present embodiment. It is a figure.

9 (a), (b), and (c) are perspective views each schematically showing a configuration of a lithium secondary battery of the present embodiment using a laminated battery element.

10 (a) and 10 (b) are perspective views each schematically showing a configuration of a lithium secondary battery of the present embodiment using a wound type battery element.

11A and 11B are cross-sectional views each schematically showing a structure of a portion from which a lead terminal of the lithium secondary battery of the present embodiment is taken out.

FIG. 12 is a graph showing the correlation between the cross-sectional area of the lead and the allowable current of the lead when the material of the lead is only copper.

[Explanation of symbols]

1 Basic battery element 1'battery element 10 batteries 2 Positive electrode (electrode) 2a Positive electrode current collector 2b Positive electrode active material layer 2'positive tab 3 Negative electrode (electrode) 3a Negative electrode current collector 3b Negative electrode active material layer 3'negative tab 4 separator 5 leads 6 exterior case 6a, 6b, 6'a, 6'b Exterior member 60,60 ', 60 "Laminated film 61 Gas barrier layer 62 inner protective layer 62 'outer protective layer 63,63 'adhesive layer 9 Sealant

Continued front page    F-term (reference) 5H011 AA13 AA17 CC02 CC06 CC10                       DD13 EE04 FF04 GG09 HH02                       KK01                 5H022 AA09 AA18 AA19 BB12 CC03                       EE01 EE03 EE04                 5H029 AJ12 AJ15 AK01 AK03 AK16                       AL01 AL02 AL04 AL06 AL07                       AL08 AL11 AL12 AM02 AM03                       AM04 AM05 AM07 BJ02 BJ12                       BJ14 BJ15 CJ05 CJ06 CJ28                       DJ02 DJ05 EJ01 EJ12 HJ04                       HJ17

Claims (11)

[Claims] 1. A basic battery element having a pair of positive and negative electrodes and an electrolyte interposed between the positive and negative electrodes, an outer case enclosing at least one of the basic battery elements, and the electrodes of the basic battery element. A battery having leads connected to each other, each of which is configured to be taken out of the outer case while maintaining the sealed state of the outer case, wherein the outer case from which the leads are taken out On the side of the case, the ratio X / Y of the total value X of the widths of the leads taken out from the side and the length Y of the side is 0.4 or less, and the length Y of the side.
Is 20 mm or less, and the lead secures an allowable current equivalent to 5 times the discharge current value when the battery is discharged for 1 hour rate or the charging current value when the battery is charged for 1 hour rate. A battery having at least a possible cross-sectional area. 2. A ratio X / Y between a total value X of widths of the leads taken out from the side of the outer case and a length Y of the side is 0.3 or less. The battery according to 1. 3. The ratio Z / Y between the distance Z from the outer edge of the lead closest to each end point of the side on the end point side to the end point of the side and the length Y of the side is 0.025 or more 0. The battery according to claim 1 or 2, wherein the battery is 0.25 or less. 4. The battery according to claim 1, wherein the basic battery element is wound. 5. The battery according to claim 1, wherein a plurality of the basic battery elements are laminated. 6. The battery according to claim 1, wherein lithium is used as the electromotive substance. 7. The battery according to claim 1, wherein the outer case is a shape-variable case. 8. The battery according to claim 7, wherein the shape-variable case is a laminate film in which resin layers are provided on both sides of a gas barrier layer. 9. The film thickness of the resin layer existing on the side of the shape-variable case in which the basic battery element is enclosed is 100 μm.
Battery according to claim 8, characterized in that: 10. The sealing agent is present between the inner surface of the outer case and the surface of the lead at the side of the outer case from which the lead is taken out, according to claim 1 to 9. The battery according to any one of 1. 11. The battery according to claim 7, wherein the basic battery element is vacuum-sealed while being housed in the shape-variable case.