JPH09270252A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with almost no drop in battery capacity and low generation ratio of internal shoft-circuiting in production and use of the battery by covering a lead connected to a positive current collector and/or a negative current collector with a folded current collector. SOLUTION: As the electrolyte of a battery, the ordinary electrolyte can be used without specifically limiting. A lead 1 connected to a positive current connector and/or a negative current collector is necessary to be covered with a folded current collector 2. The connecting method of the lead 1 to the positive current collector and/or the negative current collector is not specifically limited, and the usual method can be applicable. The distance from the positive current collector and/or the end part of a negative material coating part 3 is preferable to be less than 30mm. If the distance exceeds 30mm, the filling amount of an electrode is reduced, resulting in decrease in battery capacity. The number of folding of the current collector for covering the lead 1 is not specifically limited, but folding less than 10 times is preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery having an electrode body in which a positive electrode, a negative electrode and a separator are spirally wound.

[0002]

2. Description of the Related Art In recent years, with the widespread use of portable devices such as video cameras, mobile phones, and notebook computers, there is an increasing demand for small, lightweight, high-capacity secondary batteries. Many of the secondary batteries currently used are nickel-cadmium batteries using an alkaline electrolyte.

More recently, a non-aqueous electrolyte secondary battery using a material capable of doping and undoping lithium ions, such as lithium metal, a lithium alloy, or a carbonaceous material such as coke or an organic fired material, as a negative electrode material has been developed. Development is also being actively pursued.

In such a non-aqueous electrolyte secondary battery, generally, for example, as shown in FIG.
An electrode body in which a separator is spirally wound is used.

According to such a spiral electrode body,
Since the band-shaped positive electrode and the band-shaped negative electrode have a relatively large area, the current per unit area is small even when a large current is applied to the secondary battery, and it is possible to use this secondary battery under heavy load. Become.

[0006]

However, the positive electrode,
A battery having an electrode body in which a negative electrode and a separator are spirally wound has a high occurrence rate of an internal short circuit during the production of the battery as represented by the production of the electrode body and during use of the battery. For this reason, there is a problem that the yield at the time of manufacturing the battery is low, and when an internal short circuit occurs during use of the battery, heat generation, rupture, and ignition occur, particularly since the non-aqueous electrolyte secondary battery has a higher energy density than the conventional battery. There is a risk of causing such.
One of the causes of the internal short circuit is that the separator arranged between the positive electrode and the negative electrode of the spiral electrode body is damaged at the connection portion of the positive electrode lead and / or the negative electrode lead. To prevent this, for example, an insulating tape is attached on the positive electrode lead and / or the negative electrode lead, or the positive electrode lead is attached to the inner surface of the positive electrode as described in JP-A-5-335008. Therefore, a proposal has been made to prevent the occurrence of an internal short circuit between the positive electrode lead and the negative electrode. However, in the former case, there is a problem that this pasting work is very complicated and the filling amount of the electrode is reduced by the thickness of the pasted tape, and in the latter case, the separator is damaged by the positive electrode lead. However, in order to prevent the internal short circuit from occurring, it is necessary to lengthen the uncoated portion of the positive electrode to which the positive electrode lead is connected, resulting in a problem that the filling amount of the electrode is reduced.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a battery which has a low incidence of internal short-circuiting during the production and use of the battery, with almost no reduction in battery capacity. .

[0008]

In order to achieve the above object, the present invention has the following arrangement.

[In a battery having an electrode body in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, the lead connected to the positive electrode current collector and / or the negative electrode current collector is folded back. A battery characterized by being covered by an electric body. "

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The positive electrode and the negative electrode in the present invention are produced by providing a positive electrode material or a negative electrode material on one side or both sides of a current collector.

The current collector of the present invention can be used in the form of metal such as foil, mesh, lath, etc., but these are not particularly limited.

The battery manufactured in the present invention is not particularly limited as long as it is a battery using an electrode body wound in a spiral shape, but as a battery for mounting on portable equipment requiring high energy density, a negative electrode is used. A battery using an alkali metal as a material and a secondary battery utilizing doping of a carbonaceous material with cations or anions are effective. In the case of these batteries, that is, in the case of a non-aqueous electrolyte secondary battery containing an alkali metal salt, a material in which a positive electrode material is doped with anions and a negative electrode material in which an alkali metal or cation is doped are used as electrode materials. Material will be used.

A schematic view of an example of the electrode body of the present invention is shown in FIG. In FIG. 2, 5 is a positive electrode lead, 6 is a negative electrode lead, and 7 is a spiral electrode body.

The positive electrode material in the present invention is not particularly limited, and known materials may be used. Examples of the carbonaceous material include carbon fiber, artificial or natural graphite powder, and carbon fluoride metal. Alternatively, an inorganic compound such as a metal oxide or an organic polymer compound can be used. When an inorganic compound such as a metal or a metal oxide is used, charge / discharge reaction occurs due to cation doping and dedoping. When an organic polymer compound is used, a charge / discharge reaction occurs due to anion doping and undoping. As described above, various charge / discharge reaction modes are adopted depending on the substance, and these are appropriately selected depending on the required characteristics of the battery.

Specific examples include transition metal oxides containing alkali metals, inorganic compounds such as transition metal chalcogens,
Examples of the positive electrode used in ordinary secondary batteries include conjugated polymers such as polyacetylene, polyparaphenylene, polyphenylenevinylene, polyaniline, polypyrrole, and polythiophene, crosslinked polymers having disulfide bonds, and thionyl chloride. Among these, in the case of a secondary battery using a non-aqueous electrolyte containing a lithium salt,
Transition metal oxides and transition metal chalcogens such as cobalt, nickel, manganese, molybdenum, vanadium, chromium, iron, copper, and titanium are preferably used.

In particular, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li
_y Ni _1-x Me _x O ₂ (indicates one of Me: Ti, V, Mn, Fe),
_{Li 1-xa A x Ni 1} -yb B y O 2 ( however, A is at least one alkali or alkaline earth metal element, B
Is at least one kind of transition metal element) has a high voltage,
It is most preferably used because of its large energy density. In particular, in Li _1-xa A _x Ni _1-yb B _y O ₂ ,
0 <x ≤ 0.1, 0 ≤ y ≤ 0.3, -0.1 ≤ a ≤ 0.1, -0.15
≦ b ≦ 0.15 (However, when A and B consist of two or more elements, x is the total number of moles of all transition metal elements except Ni, y is the alkali or alkaline earth metal except Li, y = In the case of 0, when A contains at least one kind of alkaline earth metal element), a positive electrode material having excellent characteristics can be obtained. Particularly preferred A is Mg, Sr,
Examples of B include Co and Fe. Although it is not particularly limited as the negative electrode material in the present invention, as the carbonaceous material, carbon fiber, artificial or natural graphite powder,
Inorganic compounds such as fluorinated carbon, metal or metal oxide, and organic polymer compounds can be used. The carbon fiber used here is not particularly limited, but generally is obtained by firing an organic substance. Specifically, PAN-based carbon fiber obtained from polyacrylonitrile (PAN), pitch-based carbon fiber obtained from pitch of coal or petroleum, cellulose-based carbon fiber obtained from cellulose, gas obtained from gas of low molecular weight organic substance Examples thereof include phase-grown carbon fibers, but in addition, carbon fibers obtained by firing polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, furfuryl alcohol, etc. are also preferably used. Among these carbon fibers, carbon fibers satisfying the characteristics are appropriately selected and used according to the characteristics of the electrode and the battery in which the carbon fibers are used. When the carbon fiber is used for a negative electrode of a secondary battery using a non-aqueous electrolyte containing an alkali metal salt, a PAN-based carbon fiber and a pitch-based carbon fiber are preferable. Among them, PAN-based carbon fibers are preferably used because alkali metal ions, particularly lithium ions, are preferably doped.

Although the diameter and length of the carbon fiber are not particularly limited, it is preferable to use the milled carbon fiber from the viewpoints of ease of coating with a coater and prevention of short circuit when tension is strengthened. Milled carbon fibers are those having a diameter of preferably 0.1 to 1000 μm, more preferably 3 to 10 μm, and an average length of preferably 5 μm or more and less than 1 mm, more preferably 7 μm or more and less than 100 μm. is there. When milled carbon fibers are used, it is more preferable to perform high-temperature heat treatment in advance to improve cycle characteristics.

By the way, when the positive electrode material and the negative electrode material, which are the electrode materials, are adhered to the current collector to produce the positive electrode sheet and the negative electrode sheet, any method may be used. After applying a liquid that has been dissolved or dispersed in a solvent together with a binder or conductive material, it is dried, or the active material is attached to a current collector using a conductive binder or a mixture of a conductive material and a binder. The attachment method is preferred.

The binder usable in the present invention may be either a thermoplastic resin or a thermosetting resin and is not particularly limited. Further, it can be used in the form of a solution or an emulsion. The amount of addition is usually 0.01 to 40% by weight in the electrode material. Specific examples of the binder include various epoxy resins, cellulose resins, organic fluorine-based polymers and copolymers, acrylic resins, organic chlorinated resins, polyamides, polyimides, and polycarbonates. Particularly, from the viewpoint of stability, organic fluorine-based polymers and copolymers are preferable, and among them, polytetrafluoroethylene, polyvinylidene fluoride, propylene hexafluoride polymer and copolymer are preferable examples.

Examples of the conductive material usable in the present invention include carbon materials and metal powders, and particularly preferable conductive materials include various carbon blacks. In order to improve the conductivity by adding a conductive material, the optimum particle size and addition amount should be experimentally determined according to the material, shape, particle size of the positive electrode and negative electrode active material, and the type and blending amount of the binder. Usually, fine particles having a primary particle size of 0.001 μm to 100 μm, more preferably 0.005 μm to 20 μm are used.
The addition amount is 0.5 to 30 wt%, more preferably
0.7 to 20 wt% is used. If the primary particle size is less than 0.001 μm, stable production may be difficult, and if it exceeds 100 μm, the effect of addition tends to be small. On the other hand, if the addition amount is less than 0.5 wt%, the effect of addition is small, and if it exceeds 30 wt%, the capacity per unit weight of the electrode tends to decrease.

The separator in the present invention may be an insulating porous film, woven fabric, non-woven fabric or the like, and for example, polyolefin, polyethylene, polypropylene, polytetrafluoroethylene, polyacetal or the like is used. The thickness of the separator is preferably 200 μm or less, more preferably 50 μm in order to reduce the internal resistance of the battery.
It is as follows.

The electrolytic solution in the present invention is not particularly limited, and a conventional electrolytic solution or the like can be used. For example, an acid or alkali aqueous solution, a non-aqueous solvent and the like can be mentioned. Among them, as the electrolytic solution of the secondary battery composed of the above-mentioned non-aqueous electrolytic solution containing an alkali metal salt, ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, Acetonitrile, N, N-
Dimethylformamide, dimethylsulfoxide, tetrahydrofuran, 1,3-dioxolane, methyl formate, sulfolane, thionyl chloride, 1,2-dimethoxyethane, diethylene carbonate and derivatives and mixtures thereof are preferably used. Examples of the electrolyte contained in the electrolytic solution include alkali metal, particularly lithium halide, perchlorate, thiocyanate, borofluoride, phosphorus fluoride, arsenic fluoride, aluminum fluoride, trifluoromethyl sulfate, and the like. It is preferably used.

In the present invention, the leads connected to the positive electrode current collector and / or the negative electrode current collector must be covered with the folded current collector as shown in FIG. . In FIG. 1, 1 is a lead, 2 is a current collector,
Reference numeral 3 indicates an electrode material application portion, and 4 indicates an insulating tape.

In the present invention, the method of connecting the lead to the positive electrode current collector and / or the negative electrode current collector is not particularly limited, and a known connection method can be used. Specific examples include resistance welding, ultrasonic welding, cold welding, and mechanical connection using rivets.

In the present invention, the distance from the end of the positive electrode current collector and / or the negative electrode material coating portion is preferably less than 30 mm. When it exceeds 30 mm, the filling amount of the electrode is reduced due to the influence of the length of the current collector from the end portion of the positive electrode material and / or negative electrode material coating portion to the positive electrode and / or negative electrode lead connection portion, and as a result, the battery capacity is reduced. Tends to decline. More preferably, it is less than 25 mm.

In the present invention, the method of folding the current collector to cover the leads and the folding width are not particularly limited, but it is preferably less than 10 times. If it is more than 10 times, the thickness of the lead portion is increased, so that the filling amount of the electrode is reduced, and as a result, the capacity tends to be reduced. More preferably, it is less than 5 times.

The number of times the current collector is folded back to cover the leads is not particularly limited, but is preferably 5 times or less. If it is more than 5 times, the thickness of the lead portion increases and the filling amount of the electrode decreases, resulting in a decrease in capacity.

The lead portion extending from the spirally wound electrode body is covered with an insulating tape or an insulating material such as a resin in order to prevent a short circuit due to contact with a battery can or the like. It may be covered.

According to the present invention, it is possible to provide a battery having a low occurrence rate of an internal short circuit during the production and use of the battery, with almost no decrease in the battery capacity.

[0030]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to these examples.

Example 1 80% by weight of LiCoO ₂ as a positive electrode active material, 5% by weight of acetylene black: “Denka Black” (manufactured by Denki Kagaku Kogyo KK) as a conductive material, and polyvinylidene fluoride as a binder:
"KF Polymer"# 1000 (Kureha Chemical Industry Co., Ltd.) 15wt%
Were mixed, and this mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry. Then, the slurry was uniformly applied to both surfaces of a 20 μm-thick aluminum foil as a current collector, dried, and then roll-pressed.
A positive electrode sheet was obtained.

Next, a PAN-based carbon fiber "Torayca" T-300 (manufactured by Toray Industries, Inc.) in a milled form was used as the negative electrode active material, and the same binder and conductive material as the positive electrode and the same proportion as the positive electrode were used. And the mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry. Then, this slurry was uniformly applied to both sides of a copper foil having a thickness of 10 μm as a current collector, dried, and then roll-pressed to obtain a negative electrode sheet.

Next, at a collector portion 10 mm away from the end portion of the positive electrode material coating portion inside the positive electrode sheet, a thickness of 100 μm and a width of 3 mm.
After performing ultrasonic welding using the aluminum plate of No. 2 as a lead, the lead was covered by folding the aluminum foil of the current collector twice twice with the lead attachment portion as the core, as shown in FIG. Next, after a 100 μm thick nickel plate is ultrasonically welded to the negative electrode sheet as a lead, the positive electrode sheet is placed inside with a porous polypropylene film “Celguard” # 2500 (Hoechst Celanese) as a separator. By stacking and winding in this way, a spiral electrode body was obtained. Similarly, a total of 100 electrode bodies were produced. The presence or absence of an internal short circuit was measured by measuring the internal resistance of this electrode body with a tester.

Next, the electrode body was loaded into a battery can having an internal volume of 5 cc, and 1% of propylene carbonate and dimethyl carbonate containing 1M-lithium phosphorus hexafluoride as an electrolytic solution were added.
A battery using one mixed solution was prepared. This battery was charged at a constant current and constant voltage with a charging current of 400 mA, a constant voltage value of 4.2 V, and a charging time of 2.5 hours, and a capacity test was performed at a discharge current of 200 mA and a discharge end voltage of 2.5 V. The results are shown in Table 1.

Comparative Example 1 A battery was manufactured in the same manner as in Example 1 except that the positive electrode lead was covered with the polyester adhesive tape 558A (manufactured by Nichiban Co., Ltd.). The results are shown in Table 1.

Comparative Example 2 A battery was prepared in the same manner as in Example 1 except that the positive electrode lead was not covered. The results are shown in Table 1.

Comparative Example 3 In Example 1, the positive electrode lead was welded to the current collector portion 30 mm away from the end of the positive electrode material application portion inside the positive electrode sheet,
A battery was produced in the same manner as in Example 1 except that the positive electrode lead was not covered. The results are shown in Table 1.

From the results shown in Table 1, in Example 1, Comparative Example 1 and Comparative Example 3, the number of internal short circuits was 2, 3, and 2, whereas in Comparative Example 2, 21 were generated. There is. From this, covering the positive electrode lead by some method,
It can be seen that it is effective to prevent the internal short circuit by lengthening the current collector from the end portion of the positive electrode material application portion to the positive electrode lead welding portion and eliminating the influence of the unevenness generated in the positive electrode lead and the positive electrode lead welding portion. Further, the capacities of Comparative Example 1 and Comparative Example 3 are lower than those of Example 1 and Comparative Example 2. This is because in the former case, the thickness of the adhesive tape covering the positive electrode lead has an effect, and in the latter case, the length of the current collector from the end of the positive electrode material application part to the positive electrode lead welding part has an effect on the electrode. This is because the filling amount was reduced and as a result, the capacity was reduced.

From these results, according to the present invention, the occurrence rate of internal short circuit during battery production and use is low, with almost no decrease in battery capacity.

[0040]

[Table 1]

[0041]

EFFECTS OF THE INVENTION According to the present invention, it is possible to manufacture a battery having a low occurrence rate of an internal short circuit during battery preparation and during use, with almost no decrease in battery capacity.

[Brief description of drawings]

FIG. 1 is an example of an electrode in which a lead is covered with a folded current collector.

FIG. 2 is an example of a spiral electrode body.

[Explanation of symbols]

 1 Lead 2 Current Collector 3 Electrode Material Application Section 4 Insulating Tape 5 Positive Electrode Lead 6 Negative Lead 7 Spiral Electrode

Claims (4)

[Claims] 1. A battery having an electrode body in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, wherein a lead connected to the positive electrode current collector and / or the negative electrode current collector is folded back. A battery characterized by being covered with a current collector. 2. The battery according to claim 1, wherein carbon fibers are used in the negative electrode. 3. The battery according to claim 2, wherein the carbon fiber is a polyacrylonitrile-based carbon fiber. 4. The battery according to claim 2, wherein the carbon fiber is a milled carbon fiber.